Next Article in Journal / Special Issue
Studies on Incorporation of Mg in Zr-Based AB2 Metal Hydride Alloys
Previous Article in Journal
Lithium-Ion Battery Aspects on Fires in Electrified Vehicles on the Basis of Experimental Abuse Tests
Previous Article in Special Issue
Electrochemical Open-Circuit Voltage and Pressure-Concentration-Temperature Isotherm Comparison for Metal Hydride Alloys
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Batteries
Volume 2
Issue 2
10.3390/batteries2020010
batteries-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Review

Reviews on the U.S. Patents Regarding Nickel/Metal Hydride Batteries

by
Shiuan Chang
1,
Kwo-hsiung Young
2,3,*,
Jean Nei
3 and
Cristian Fierro
3
1
Department of Mechanical Engineering, Wayne State University, Detroit, MI 48202, USA
2
Department of Chemical Engineering and Materials Science, Wayne State University, Detroit, MI 48202, USA
3
BASF/Battery Materials–Ovonic, 2983 Waterview Drive, Rochester Hills, MI 48309, USA
*
Author to whom correspondence should be addressed.
Batteries 2016, 2(2), 10; https://doi.org/10.3390/batteries2020010
Submission received: 21 February 2016 / Revised: 22 March 2016 / Accepted: 31 March 2016 / Published: 12 April 2016
(This article belongs to the Special Issue Nickel Metal Hydride Batteries)
Browse Figures
Versions Notes

Abstract

:
U.S. patents filed on the topic of nickel/metal hydride (Ni/MH) batteries have been reviewed, starting from active materials, to electrode fabrication, cell assembly, multi-cell construction, system integration, application, and finally recovering and recycling. In each category, a general description about the principle and direction of development is given. Both the metal hydride (MH) alloy and nickel hydroxide as active materials in negative and positive electrodes, respectively, are reviewed extensively. Both thermal and battery management systems (BMSs) are also discussed.

Graphical Abstract

1. Introduction

The nickel/metal hydride (Ni/MH) battery is an essential electrochemical device for consumer, propulsion, and stationary energy storages. Since its commercial debut in the late 1980s, many researchers have worked diligently in the Ni/MH battery field. Their contributions were publicized through two routes: academic publications and patent applications. While there are several key reviews available on the former [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16], there is not one on the latter. Therefore, we have organized and summarized the patents related to Ni/MH battery technology in the current review and its companion—Reviews on the Japanese Patents Regarding Nickel/Metal Hydride Batteries [17].

2. Results

As shown in Figure 1, the current review is divided into six categories in the chronological order of technology development, which are active materials → electrode fabrication → cell assembly → multi-cell construction → system integration → application. Because of the extremely large number of U.S. patents on these subjects, we have selected and presented the most representative patents historically and technologically in the current review. More related U.S. patent documents can be found on each U.S. patent presented here.

2.1. Active Materials

The half-cell electrochemical reaction for the negative electrode is:
M + H2O + e− ⇄ MH + OH− (forward: charge, reverse: discharge)
where M is a hydrogen storage alloy capable of storing hydrogen reversibly and MH is the corresponding metal hydride (MH). During charge, applied voltage splits water into protons and hydroxide ions. Driven by the voltage and diffusion caused by the concentration difference, protons enter into the bulk of the alloy and then meet with electrons from the current collector, which is attached to a power supply. During discharge, protons at the alloy surface recombine with hydroxide ions in the electrolyte. Electrons are injected into the circuit load through the current collector in order to maintain charge neutrality in the negative electrode.
The counter reaction for the negative electrode is:
Ni(OH)2 + OH− ⇄ NiOOH + H2O + e− (forward: charge, reverse: discharge)
where Ni(OH)2 is the active material going through +2/+3 oxidation state change during the electrochemical reactions. During charge, protons deprived of Ni(OH)2 move to the surface of the positive electrode because of the applied voltage and recombine with hydroxide ions in the electrolyte. In order to maintain charge neutrality, electrons are injected into the power supply through the current collector. During discharge, water at the surface of the positive electrode splits into protons and hydroxide ions. Protons then enter into NiOOH and neutralize with electrons through the load to complete the circuit with the negative electrode. Shown in the net reaction Equation (3), charge/discharge reaction does not change the overall hydroxide concentration/pH value, which is different from the working principle of Ni/Cd battery Equation (4).
M + Ni(OH)2 ⇄ MH + NiOOH (forward: charge, reverse: discharge)
Cd(OH)2 + 2Ni(OH)2 ⇄ Cd + 2NiOOH + 2H2O (forward: charge, reverse: discharge)
Both the inventions and further developmental works of MH alloy and Ni(OH)2 are presented in the next two sections.

2.1.1. Metal Hydride Alloys in the Negative Electrode

Klaus Beccu contributed to the earliest patent using MH alloy as an active material in the negative electrode to construct a Ni/MH battery in 1970 [18]. The alloy used had a composition of Ti85Ni10Cu3V2 (in wt%), which was later expanded to any hydride of the third, fourth, or fifth group of transition metal (for example, Ti) [19]. Two types of MH alloys were used in the first commercialized Ni/MH batteries introduced in 1989. While Japanese companies such as Matsushita [20,21,22] (later changed its name to Panasonic), Toshiba [23], Sanyo [24,25], and Yuasa [26] used the misch metal-based (mixtures of light rare earth elements such as La, Ce, Pr, and Nd) AB5 MH alloy, the Ovonic Battery Company (OBC, Troy, MI, USA) chose the transitional metal-based AB2 MH alloy as the active material in the negative electrode. General properties of these two alloy families are listed in Table 1. The AB5 MH alloy eventually dominated the market due to the substantially lower price of misch metal since 2000.
Discovery of the hydrogen storage capability of the rare earth-based AB5 intermetallic alloy was accidental [27]. Guegen [28] filed the first patent using LaNi5 modified with Ti, Ca, Ba, Cr, and/or Cu with improved capacity as negative electrode material in 1978. In 1984, Willems et al. [29] filed a patent adding Co and/or Cu in LaNi5 to reduce the lattice expansion during hydride process and consequently extending the cycle life. Based on the idea of utilizing misch metal in AB5 for gaseous phase hydrogen storage originated by Osumi and his coworkers in 1979 [30] and 1983 [31], Kanda and Sato from Toshiba [32] filed a U.S. patent based on Mn, Al-modified misch metal-based AB5 MH alloy for Ni/MH battery in 1986. Subsequently, the Japanese companies filed many patents optimizing the AB5 formula (examples can be found in [17,33,34,35,36,37,38,39,40,41,42]) and finalized on using Co, Al, Mn, and Ni as the B-site elements. OBC also filed a patent for adding Zr or Si to extend the cycle life of Cu-containing AB5 MH alloy [43].
In the field of AB2 MH alloy, Gamo and his coworkers [44] from Matsushita filed a patent about its gaseous phase hydrogen storage application in 1979, and Sapru and her coworkers [45] at OBC filed the first patent for battery application in 1985. Since then, many patents have been filed on the AB2 MH alloys for electrochemical applications by OBC [46,47,48,49,50,51,52,53,54,55], Matsushita [56,57,58], and SAFT [59].
Other MH alloy families, including body-centered-cubic (BCC) solid solution [60,61,62], BCC-AB2 composite [63,64], Mg, Ni-based alloy [65,66,67,68], TiNi [69], and composite [70,71], were also proposed as negative electrode active materials; however, they were not commercialized. The only MH alloy that successfully succeeded AB2 and AB5 in commercialization is the A2B7 superlattice alloy [72,73,74,75,76]. Development works of the A2B7 MH alloy done in academia can be found in a previous review article [10]. Several non-conventional MH alloy fabrication processes, such as centrifugal casting [77], double-roller casting [78], melt-spin [34,79], gas atomization [80], strip casting [81,82], and a chemical process using misch metal oxide and/or hydroxide as raw material [83], have been patented as well, but only strip casting is used for mass production besides the conventional induction melting.
Besides patents on a specific alloy family, there are several patents that contribute across the board and independently of alloy selection. Sapru et al. [84] filed a patent about the advantage of increasing the degree of disorder in a multi-component MH alloy; as a result, the electrochemical performance is improved. Such material is disordered and characterized as a composite of amorphous, microcrystalline, and polycrystalline components lacking long-range compositional order and with three or more phases [85]. Another group of patents not confined to a specific alloy family addresses the structure designs of surface oxide, which is a catalyst for the electrochemical reaction [52,86,87,88] (Figure 2).

2.1.2. Nickel Hydroxide in the Positive Electrode

Soon after the Swedish inventor Waldemar Jungner filed a number of Swedish and German Patents on the concepts of Ni/Cd and Ni/Fe batteries in 1899 [89], a famous American inventor, Thomas A. Edison, filed several U.S. patents on Ni/Fe and Ni/Cd rechargeable batteries utilizing nickel hydroxide as active material in the positive electrode in 1901 [90,91]. The same chemistry, Ni(OH)2, has been used as a positive electrode active material for the entire alkaline battery family because of its high electrochemical reversibility, appropriate voltage (the highest among several options but lower than the oxygen gas evolution potential), and low cost. The original positive electrode used in Ni/MH batteries was inherited from those in Ni/Cd and Ni/Fe batteries [92,93,94,95]. The electrode is manufactured by first pasting filamentary Ni onto a substrate (such as perforated foil) and then “sintered” under a high temperature annealing furnace in a nitrogen/hydrogen atmosphere, where binders used in the pasting process are burned away to leave a conductive skeleton of nickel with a typical average pore size of about 30 μm [96]. Next, a chemical impregnation process is carried out to produce the active Ni(OH)2 by consecutively dipping the electrode between the Ni(NO3)2 and NaOH baths [97,98]. This kind of Ni(OH)2 electrode is the sintered type. A new pasted type of positive electrode using spherical Ni(OH)2 particles together with the CoO additive (for forming a CoOOH conductive network on the particle surface) was first patented by Oshitani and his coworkers in Yuasa in 1989 [26,99], and soon became the mainstream for Ni/MH battery due to its high volumetric and gravimetric energy densities. The spherical particle is originally produced by a two-step batch chemical precipitation process, which consists of ammonia complex formation and precipitation in two different reactors. Later on, Fierro and his coworkers at OBC [100] developed a continuous stirring single reactor process, and the smaller particles near the bottom of the reactor and the larger ones are separated by the centrifugal force from a bottom blade, leaving the container with an overflow (Figure 3). This method has been widely adopted in today’s modern manufacturing. The produced spherical Ni(OH)2 powder is then mixed with binders and pasted onto the Ni foam substrate to form the pasted type of positive electrode. The main advantage of using the pasted type of positive electrode is the increase in gravimetric energy density; however, rate-capability, cycle stability, and cost are sacrificed.
There are many patents modifying the basic Ni(OH)2 for performance improvement, such as increasing utilization rate by chemical modification through co-precipitation [25,101,102,103,104,105,106,107,108,109,110,111], promoting higher electron transfer per Ni atom by introducing the gamma phase with an oxidation state between +3 and +4 [112,113,114,115,116,117], alternating the microstructure by various process changes [118,119,120], and adding a conductive coating on the Ni(OH)2 core [121]. Moreover, OBC filed four patents regarding the incorporation of fine Ni fiber in the co-precipitation reactor for the purpose of increasing the native conductivity of Ni(OH)2 [122,123,124,125]. The crystalline size is an important indicator for the degree of disorder (density of stacking fault along the c-axis) of Ni(OH)2 and affects the electrochemical performance, and an evaluation method was patented by OBC [126]. In order to increase the conductivity or resistance to poisoning, a core-shell type of structure obtained by sequential precipitation or other coating methods was invented [108,124,125,127,128,129].

2.2. Electrode Fabrication

There are two electrodes in a typical Ni/MH battery, namely the negative and positive electrodes, and they are made of MH alloy and nickel hydroxide, respectively. During service (discharge), MH in the negative electrode is oxidized into metal, and therefore the negative electrode is also called an anode. Furthermore, the positive electrode can be termed a cathode since NiOOH is reduced to Ni(OH)2 during discharge.
Patents regarding electrode fabrications of both the anode and cathode, including component, substrate, and construction, are discussed in the following sections.

2.2.1. Negative Electrode (Anode)

The negative electrode in a commercial Ni/MH battery can be fabricated by any of the following methods: dry compaction, wet paste method, or dry paste method (Figure 4).
OBC filed a patent for its dry compaction manufacturing process in 1989 [130]. While the wet paste method was inherited from the conventional alkaline battery technology, negative electrode fabrication by dry pasting onto the Ni foam through brushing has gained popularity in just the last few years [131]. The pros and cons of each method are summarized in Table 2.
Expanded Ni substrate is typically used for the dry compaction method to reduce the burr that happens with the use of Ni mesh substrate. Ni-plated perforated steel (NPPS) plate [132] and Ni foam are commonly used for the wet paste and dry paste processes, respectively. Other types of substrates, such as porous Ni [133], porous Cu [134], welded Cu [135], cellular metal [136], and conductive ceramic [137], were also patented. Substrate-less electrode fabrication was also proposed, where the active material is first mixed with a conductive metal and subsequently forms the electrode without a substrate [138].
Additives such as carbon and metal powder can be added in the negative electrode to increase the conductivity [139]. Other additives such as rare earth oxides and GeO2 can be used to reduce the oxidation of the negative electrode [140,141]. Moreover, binders are required for the wet paste method, and many candidates were patented in the past [142,143,144]. Polyvinyl alcohol is the most popular binder material used in the negative electrode of Ni/MH battery.
In order to remove the passive oxide formed during powder fabrication and form a thin, porous, and electrochemically active oxide on the surface of MH alloy, activation is needed and can be executed at the powder or electrode level with acid [145] or alkaline [146] or in the sealed cell during formation. Furthermore, performing a controllable oxidation on MH alloy before fabricating it into electrode is preferred for the purpose of reducing the native oxide thickness [147,148]. Also, oxygen gas evolution during fast charge was found to be reduced by increasing the final surface roughness [149]. A surface fluorination process was invented for performance enhancement as well [150]. In terms of construction, an auxiliary negative electrode was added to reduce the cell pressure of button cell [151].

2.2.2. Positive Electrode (Cathode)

The most common type of positive electrode in today’s Ni/MH battery is the pasted type. Spherical Ni(OH)2 co-precipitated with one or more additional metal hydroxides (Co and Zn being the most common) is mixed with additives, binder, and solvent (water, methanol, or ethylene glycol) to form a paste. The paste is then applied to the Ni-foam substrate, calendared, and dried [152]. A continuous positive electrode fabrication method was patented by OBC in 1994 [97]. The active material in the tab area can be removed or avoided by water wash or ultrasonic cleaning, using a pre-taped foam substrate [153] or reduction by hot hydrogen [154]. Besides the commonly used Ni foam patented by Inco in 1990 [155], metal foil [156], metal mesh [157], Ni mesh/fabric/metal fiber composite [158], and Ni-plated porous Cu/Cu alloy skeleton [159] were also proposed as substrates. Both non-conducting [160] and conducting binders [161] can be used. Since the intrinsic conductivity of spherical particle is poor, a CoOOH conductive network on the surface has been indispensable since the beginning of spherical Ni(OH)2 application [99], an idea originated from its use in the sintered electrode [162]. Conversion from Co2+ to Co3+ is usually completed in the sealed cell during the formation process. Pre-oxidation of Co at the electrode level was also patented [163]. Modifications and improvements on the basic Co-compound additives were proposed [23,102,127,164,165,166,167,168,169]. Other additives such as Ca compound [170], Mn compound [171,172], Al compound [173], carbon [174], and silicate [175] were patented as well. For high temperature application, oxides of rare earth elements (Y2O3 and Yb2O3 being the most common) are added [176,177,178]. In today’s commercial Ni/MH battery, Y2O3 is a must additive in the positive electrode. Besides the pasting method, an electrodeless plating technique was proposed for applying the active material onto the substrate, but it is not commercialized [179,180].

2.3. Cell Assembly

Several key areas such as components (negative and positive electrodes, current collector, venting cap, case, electrolyte, and separator), construction type, design of capacity ratio, and formation process need to be considered in order to complete the cell assembly. The following sections summarize the patents concerning the aforementioned items.

2.3.1. Cell Construction

There are five conventional designs of Ni/MH batteries, and a comparison among them can be found in Table 3. Moreover, a new pouch type of Ni/MH battery providing high energy density was recently proposed [181]. The cylindrical type of Ni/MH battery is the most common and mainly used to replace the disposable primary battery. While the typical cylindrical cell is made by winding the electrodes/separator spirally, a patent from Matsushita used the technique of layering hollow cylindrical electrodes in the form of concentric circles to increase the mutual facing area between the negative and positive electrodes [182]. Examples of prismatic Ni/MH batteries can be found in patents filed by Energy Conversion Devices Inc. (ECD) [183,184] and Toshiba [185,186,187] and show the most scalability up to 1 kWh. The typical prismatic cells are composed of a stack of electrodes with tabs welded together. Toyota filed a patent using a single piece of folded electrode stack (one separator and multiple positive and negative electrode) in a rectangular cell [188], similar to the design of GIGACELL developed by Kawasaki Heavy Industry [189]. The case and electrode assembly may not be in the same shape. For example, optimizing the amount of electrolyte by placing a spirally wound electrode assembly in a rectangular casing was proposed [190]. A flat wafer cell, similar in design to the coin cell [191], was patented with the use of conductive carbon-filled polymeric outer layers as electrode contacts [192,193].
While only separators are placed between the adjacent negative and positive electrodes in the typical Ni/MH cell construction, a special “bipolar” design (originated from its use for a lead-acid battery [194]) also uses a metal sheet as substrate for both electrodes (one side as negative electrode substrate and the other side as positive electrode substrate) (Figure 5). This design substantially reduces the contact resistance between adjacent cells [195,196,197,198]. Placing a hydrophobic layer between two adjacent negative electrodes to reduce the hydrogen pressure buildup in the cell is another special arrangement [199]. A monoblock of multi-cell assembly was designed to reduce the contact resistance and improve heat dissipation by integrating flow channels within, which allows the gas or liquid coolant to flow between adjacent cells [200]. A lightweight design where the electrode stacks are connected together in a honeycomb structure was also proposed [201].

2.3.2. Current Collector

Electrodes are connected to the terminals located outside of the cell casing through current collectors. Conventional consumer-type of Ni/MH battery (for application of up to 0.5C rate) uses a single Ni tab (or Ni-plated stainless steel (SS) tab) to collect the current from each electrode. The negative tab is stapled onto the negative electrode, and the positive tab is welded to the part of positive electrode without active material (tab area cleaned by ultrasonic cleaning or water jet). Cu was also proposed as the tab material [135]. Generally, the tab only connects to one side of the electrode: in a cylindrical cell, the positive tab is on the top and electrically connected to the safety valve, and the negative tab is on the bottom and grounded to the case; in a prismatic cell, both the positive and negative tabs are on the top. However, in a patent filed by Park, tabs on both sides of the electrode were proposed to reduce the impedance [202]. Usually, the tab is directly connected to the substrate, but there is also a patent suggesting the technique of folding the end of the electrode, which provides a coupling surface for the connection to the tab or terminal [203]. Matsushita [204,205,206], Sanyo [207], Yuasa [208], and Johnson Controls [209] patented special current collector designs for high-power cylindrical cells (for applications in power tool and hybrid electric vehicle (HEV)). Both laser welding [210] and electron beam welding [211] are popular techniques for welding multiple pieces of tabs together.

2.3.3. Other Components

Other components essential to the construction of Ni/MH battery include a safety vent, case, separator, and electrolyte. Most types of Ni/MH batteries require a safety vent to manage the extra pressure buildup during high-rate charge and also near the end of service life except a coin cell because of its special medical application requirement. The original safety vent designs were inherited from those available for the Ni/Cd battery. Through the years, companies such as ECD [212], Moltec [213], Sanyo [214], Toyota [215,216], and Johnson Controls [217,218,219] proposed a variety of improvements in the safety vent design. While the pressure limit in a cylindrical cell is around 350–400 psi, in a prismatic cell it is reduced to 100–120 psi because of the easy deformation of the case. Panasonic and Toyota together patented the idea of using a hydrogen-permeable case to release the overpressure within of the cell [220]. Another special case design with multiple ridges on the outside was also developed to improve the cooling performance and mechanical strength of the case [221].
Several different non-woven fabrics were proposed as separator materials previously [222,223,224,225,226,227,228,229], and the most commonly used is the grafted polypropylene/polyethylene type. Recently, a sulfonated separator [230] has become very popular for low self-discharge application since it can trap the nitrogen-containing compound in the cell, which is the main cause of the shutting effect that results in self-discharge [231]. A ceramic, polymer, or composite separator capable of conducting alkali ions was also proposed by Ceramatec [232,233], which can be used to eliminate the cross-contamination of ions leached out from the negative electrode onto the separator and positive electrode. Metal-organic framework, coordination polymer, or covalent-organic framework can serve as separator as well [234]. While most of the electrolyte works were performed in academia [235,236], there are several patents in the area of electrolytes for the Ni/MH battery. For example, Toshiba filed a patent for adding W- and Na-containing compounds to the electrolyte [237]. Certain separators can also serve as electrolytes, and they can be categorized into the gel/polymer and solid types. Electrolyte leakage can be reduced by the use of the gel/polymer type electrolyte. Motorola filed a patent with a KOH-dispersed polyvinyl alcohol or polyvinyl acetate polymer electrolyte [238]. Furthermore, Matsushita filed a patent on a gel electrolyte composed of a water absorbent polymer, a water repellent, and an aqueous alkaline solution [239]. In the solid-state battery field, silicon nitride [240], lithium nitride [241], halide [241], oxysalt [241], phosphorus sulfide [241], and oxide with a perovskite structure [242] were suggested. Among these, perovskite is the most promising. ABO3−δ perovskite, where A is a rare earth or alkaline earth element with a large radius and B is an element with a smaller radius, is capable of proton conduction. The structure of such an oxide, if prepared under proper conditions (e.g., acceptor-doped), is prone to a large density of oxygen vacancies. When it reacts with water, oxygen from water occupies the vacancy, and the remaining two protons are then attached to two separate oxygen ions, which creates a proton-conducting path. The proton conductivity depends on the vacancy density and also the distance between neighboring oxygen ions.

2.3.4. Cell Design

In a typical Ni/MH cell, an oversized negative electrode is needed to create an overcharge reservoir (OCR) and an overdischarge reservoir (ODR) (Figure 6) [243,244]. OCR is created to absorb the hydrogen gas produced during overcharge and also to provide a recombination center to react with the oxygen gas evolved from the positive electrode. ODR is created to prevent oxidation of the negative electrode during overdischarge (cell reversal). Typical negative-to-positive ratios (N/P) are around 1.2 for a high-capacity cell, 1.4–1.6 for a consumer cell, and 1.8–2.2 for a high-power cell [245]. Methodology for the N/P design can be found in several patents [245,246,247].
ODR does not exist when the battery is first built. Later on, ODR starts to increase due to oxidations of MH alloy (Equation (5)), Co(OH)2 (Equation (6)), separator, and other metal components in the cell.
3M + H2O → MO + 2M + H2 → MO + 2MH (assuming metal in +1 oxidation state)
Co(OH)2 + M → CoOOH + MH
With further cycling, ODR continues to grow and suppresses OCR, and finally the cell vents without the protection from OCR. Therefore, it is important to introduce a “pre-charge” to the positive electrode in order to compensate for the increase in ODR during formation when a low N/P is used [248,249].

2.3.5. Formation Process

After the cell is closed, a series of formation/activation is performed. The process is composed of two parts: a thermal activation and an electrochemical formation (Figure 7). Thermal activation dissolves the Co-compound additives in the positive electrode and also dissolves the native oxide formed on the surface of MH alloy during fabrication. Electrochemical formation applies several charge/discharge cycles to crack the MH alloy and create new and electrochemically active surfaces, and it also converts the dissolved Co into a CoOOH conductive network on the surface of Ni(OH)2. Various formation schemes have been patented [250,251,252,253,254], but they may need to be optimized to prevent cell venting. Also, it was shown that keeping a low state of charge (SOC) during battery routine operation helps ensure a long cycle life [251].

2.4. Multi-Cell Construction

The nominal voltage of a single Ni/MH cell is 1.2 V. In order to increase the voltage, several cells have to be connected in series to form a multi-cell module. For consumer use, a module composed of 4 (4.8 V) or 10 (12 V) cells is common. For the propulsion application, multiple modules are assembled together to form a pack. For example, the 1.3 kWh braking energy storage system for the Toyota 2010 HEV Prius (Generation IV) is composed of 168 cells in 28 modules, and each cell is a 6.5 Ah Ni/MH prismatic cell [255]. Patents regarding the module and pack constructions are reviewed in the following sections.

2.4.1. Module Assembly

A module can be made of a series of reparably individual cells with metal [184,256,257] or plastic cases [258], or it can be built with cells isolated by compartment dividers in a single case [259]. Inter-cell conduction is the subject of a number of patents [260,261]. Special module designs for cooling performance improvement include strategic placement of thermally conductive case material and negative electrodes [183] and adding coolant flow channels [262], heat exchanger [263,264], or cooling fins [265,266] between adjacent cells. A compressible two-plate spacer was designed to be placed between adjacent cells for module swelling reduction during operation [267]. For smaller applications in cellphones [268], portable power tools [269], and personal health devices [270], a multi-cell module is the final pack integrated with other system components.

2.4.2. Pack Assembly

When assembling several battery modules into a single pack, both the electrical interconnection between modules and integrity of the connectors are very important. While the former can be ensured by a dedicated welding methodology [271], the latter can be secured by strategically filling the gaps between modules with packaging material [272]. Thermal management of Ni/MH battery pack is also critical to achieve a long service life, which can be done by using either forced air [273,274] or a liquid coolant [275,276,277]. Moreover, the use of a heat sink is helpful to increase the thermal dissipation rate of the battery pack [278].

2.5. System Integration

For application of a larger energy storage system (for example, in EV), many sub-systems need to be integrated, such as a charging system, a battery management system (BMS), a protection system, and a thermal management system (TMS), to ensure a smooth and safe operation. Patents on these sub-systems are discussed in the following sections.

2.5.1. Charging System

For consumer application, a charger is a separate unit from the battery. In the early days, a different charger was needed for the Ni/MH battery but with a very similar design principle. Later charger hardware improvements made charging both Ni/Cd and Ni/MH batteries with the same charger possible. Numerous patents regarding the portable charger hardware design are available [279,280,281,282,283,284,285,286,287,288,289,290,291,292,293,294]. Most of the charging algorithms are composed of several different cut-off schemes, such as ΔT (temperature change), −ΔV (negative voltage change), dV/dt (voltage change with time), dT/dt (temperature change with time), maximum input, and Vt (terminal voltage) [295,296,297,298,299,300,301,302,303,304,305,306,307,308,309,310,311,312,313,314,315,316,317,318,319,320]. End-of-charge can also be detected by electronic circuit alone [321]. In order to fast charge, special hardware [322] and algorithms [323,324] are required. For application in EV, the charging unit is integrated into BMS and is a part of the system.

2.5.2. Battery Management System

When a large number of cells are used together, BMS is indispensable [325]. Even in a portable power tool, the SOC estimation of Ni/MH battery is necessary [326]. Due to its high abuse tolerance, BMS for Ni/MH battery system is much simpler than that for a Li-ion battery system. For example, voltage monitoring and SOC recording at the cell level in Ni/MH battery system are not necessary. Therefore, for Ni/MH battery systems used in vehicles, the main functions of BMS are monitoring charge/discharge [327,328,329,330,331,332] and voltage [333,334,335,336], estimating SOC [337,338,339,340,341,342,343,344] and state-of-health (SOH) [345,346,347,348,349,350,351], communicating with the on-board computer system, and handling emergencies. In order to obtain an accurate estimation, several methodologies, such as integral amp-hour [352,353,354], self-discharge calculation [355], calibration from voltage variation [356,357], and impedance measurement [358,359] are used in combination.

2.5.3. Protection System

Originated from the overcharge protection circuit invented for Ni/Cd battery [360,361,362,363,364], a similar design was patented for Ni/MH batteries [365,366]. Over-temperature protection [367] and under-voltage [368] circuitries for Ni/MH battery were previously patented. The design of putting a capacitor in parallel with the battery was also invented to offer an emergency power source [369,370,371]. The addition of a high-voltage connector was suggested for electrical shock prevention [372]. Finally, a venting system for automobiles equipped with Ni/MH battery system was proposed to release hydrogen from a strategic location [219].

2.5.4. Thermal Management System

Thermal dissipation for Ni/MH battery is performed either at the cell [184,256,257] or module level [189,262,263,265,266,373,374,375,376]. Compared to TMS for Li-ion battery pack, a much simpler TMS is needed for Ni/MH battery pack [373]. For example, the Ni/MH battery system equipped in Toyota HEV Prius requires only a three-speed 12 V DC blower [377], and its motor speed is determined by both the take-in air temperature and cell temperature. Furthermore, Toyota filed a patent regarding the design of cooling control in a battery pack [378].

2.6. Others

As the last part of this review, U.S. patents on the application and recycling of Ni/MH battery are presented.

2.6.1. Application

Key applications for Ni/MH battery are summarized in Table 4 [11]. For a consumer battery, a hybrid Ni/MH battery/capacitor device was patented by Motorola to handle pulse power communication [379,380]. Patents filed by OBC [381] and Delphi [382] described the use of Ni/MH batteries in HEV. Applications in uninterrupted power supply (UPS) [318,383] and grid [384,385,386] were also patented. A window construction combining Ni/MH battery and solar cell was proposed [387].

2.6.2. Revivification and Recycling

In order to reuse the battery pack, a refreshment method was proposed to replace or re-inject electrolyte into cells with bad performance [388]. At the stage where recovery is impossible, the Ni/MH battery is ready for recycling. Because of the high flammability of the negative electrode, rupturing the battery under anaerobic conditions and flooding the battery interior with CO2 in an anaerobic chamber is recommended [389]. Recycling can be performed at the component level by separating the MH alloy (AB2 [390] and AB5 [391]) and binder [392] or at the individual element level by aiming at rare-earth metals [393,394,395,396,397], Zr [395], Fe [396], Al [396], Co [396,397], and Ni [397,398].

3. Conclusions

U.S. patents on the Ni/MH battery have been reviewed and categorized. With close to 400 U.S. patents cited, this report summarizes the efforts to improve the performance and expand the applicability of Ni/MH batteries undertaken by scientists and engineers working in various companies; these can be used to study the principle and fabrication process systematically. By learning what has been patented previously, we can continue to explore uncharted territory in the science and engineering of Ni/MH batteries.

Acknowledgments

Shiuan Chang collected and organized the information. Kwo-hsiung Young and Cristian Fierro validated the information in the area of negative and positive electrodes, respectably. Jean Nei prepared the manuscript.

Author Contributions

All the authors made a significant contribution to the writing of this manuscript.

Conflicts of Interest

The authors declare no conflict of interest.

Abbreviations

Ni/MHNickel/metal hydride
MHMetal hydride
OBCOvonic Battery Company
FCCFace-centered-cubic
1C/1C1C charge and discharge rates
DODDepth of discharge
BCCBody-centered-cubic
NPPSNi-plated perforated steel
ECDEnergy conversion devices
SSStainless steel
EVElectric vehicle
HEVHybrid electric vehicle
OCROvercharge reservoir
ODROverdischarge reservoir
N/PNegative-to-positive ratio
SOCState of charge
BMSBattery management system
TMSThermal management system
ΔTTemperature change
−ΔVNegative voltage change
dV/dtVoltage change with time
dT/dtTemperature change with time
VtTerminal voltage
SOHState of health
UPSUninterrupted power supply

References

  1. Sakai, T. Secondary Battery with Hydrogen Storage Alloys. In Hydrogen Storage Alloys—Fundamentals and Frontier Technology; Tamura, H., Ed.; NTS Inc.: Tokyo, Japan, 1998; p. 411. [Google Scholar]
  2. Osumi, Y. Suiso Kyuzou Goukin; Agune Co. Ltd.: Tokyo, Japan, 1999; pp. 473–507. [Google Scholar]
  3. Kleperis, J.; Wójcik, G.; Czerwinski, A.; Skowronski, J.; Kopczyk, M.; Beltowska-Brzezinska, M. Electrochemical behavior of metal hydride. J. Solid State Electrochem. 2001, 5, 229–249. [Google Scholar] [CrossRef]
  4. Feng, F.; Geng, M.; Northwood, D.O. Electrochemical behaviour of intermetallic-based metal hydrides used in Ni/metal hydride (MH) batteries: A review. Int. J. Hydrog. Energy 2001, 26, 725–734. [Google Scholar] [CrossRef]
  5. Hong, K. The development of hydrogen storage electrode alloys for nickel hydride batteries. J. Power Sources 2001, 96, 85–89. [Google Scholar] [CrossRef]
  6. Cuevas, F.; Joubert, J.M.; Latroche, M.; Percheron-Guégan, A. Intermetallic compounds as negative electrodes of Ni/MH batteries. Appl. Phys. A 2001, 72, 225–238. [Google Scholar] [CrossRef]
  7. Petrii, O.A.; Levin, E.E. Hydrogen-accumulating materials in electrochemical systems. Russ. J. Gen. Chem. 2007, 77, 790–796. [Google Scholar] [CrossRef]
  8. Zhao, X.; Ma, L. Recent progress in hydrogen storage alloys for nickel/metal hydride secondary batteries. Int. J. Hydrog. Energy 2009, 34, 4788–4796. [Google Scholar] [CrossRef]
  9. Liu, Y.; Pan, H.; Gao, M.; Wang, Q. Advanced hydrogen storage alloys for Ni/MH rechargeable batteries. J. Mater. Chem. 2011, 21, 4743–4755. [Google Scholar] [CrossRef]
  10. Young, K.; Nei, J. The current status of hydrogen storage alloy development for electrochemical applications. Materials 2013, 6, 4574–4608. [Google Scholar] [CrossRef]
  11. Young, K. Electrochemical Applications of Metal Hydrides. In Compendium of Hydrogen Energy; Barbir, F., Basile, A., Veziroğlu, T.N., Eds.; Woodhead Publishing Ltd.: Cambridge, UK, 2015; Volume 3, pp. 289–304. [Google Scholar]
  12. Oliva, P.; Leonardi, J.; Laurent, J.F.; Delmas, C.; Braconnier, J.J.; Figlarz, M.; Fievet, F.; Guibert, A.C. Review of the structure and the electrochemistry of nickel hydroxide and oxy-hydroxides. J. Power Sources 1982, 8, 229–255. [Google Scholar] [CrossRef]
  13. Barton, R.T.; Mitchell, P.J.; Hampson, N.A. The electrotechnology of the nickel positive electrode: A review of the recent literature. Surf. Coat. Technol. 1986, 28, 1–9. [Google Scholar] [CrossRef]
  14. Yuan, A.; Zhang, J.; Cao, C. Research progress of nickel hydroxide electrodes. Chin. J. Power Sources 2001, 25, 53–59. [Google Scholar]
  15. Vidotti, M.; Torresi, R.; Torresi, S.I. Nickel hydroxide modified electrodes: A review study concerning its structural and electrochemical properties aiming the application in electrocatalysis, electrochromism and secondary batteries. Quim. Nova 2010, 33, 2176–2186. [Google Scholar] [CrossRef]
  16. Hall, D.S.; Lockwood, D.J.; Bock, C.; McDougall, B.R. Nickel hydroxides and related materials: A review of their structures, synthesis and properties. Proceed. R. Soc. A Math. Phys. Eng. Sci. 2015, 471. [Google Scholar] [CrossRef] [PubMed]
  17. Ouchi, T.; Young, K.; Moghe, D. Reviews on the Japanese patent applications regarding nickel/metal hydride batteries. Batteries 2016, 2. [Google Scholar] [CrossRef]
  18. Beccu, K. Electrical Accumulator with a Metal Hydride Serving as the Cathodic Reactive Material Arranged in Suspension in the Electrolyte. U.S. Patent 3,520,728, 14 July 1970. [Google Scholar]
  19. Beccu, K. Accumulator Electrode with Capacity for Strong Hydrogen and Method of Manufacturing Said Electrode. U.S. Patent 3,669,745, 13 June 1972. [Google Scholar]
  20. Ikoma, M.; Kawano, H.; Matsumoto, I.; Yanagihara, N. Sealed Storage Battery and Method for Making Its Electrode. U.S. Patent 4,837,119, 6 June 1989. [Google Scholar]
  21. Ikoma, M.; Kawano, H.; Takahashi, O.; Matsumoto, I.; Ikeyama, M. Alkaline Storage Battery Using Hydrogen Absorbing Alloy. U.S. Patent 4,925,748, 15 May 1990. [Google Scholar]
  22. Ikoma, M.; Kawano, H.; Ito, Y.; Matsumoto, I. Sealed Type Nickel-Hydride Battery and Production Process Thereof. U.S. Patent 4,935,318, 19 June 1990. [Google Scholar]
  23. Hasebe, H.; Takeno, K.; Mitsuyasu, K.; Sato, Y.; Takahashi, H.; Hayashida, H.; Sawatari, I.; Ishiwa, K.; Hata, K.; Yoshida, K.; et al. Nickel-Metal Hydride Secondary Cell. U.S. Patent 5,032,475, 16 July 1991. [Google Scholar]
  24. Yamano, M.; Sakai, T.; Furukawa, N.; Murakami, S.; Matsumoto, T. Metal/Hydrogen Alkaline Storage Battery. U.S. Patent 4,636,445, 13 January 1987. [Google Scholar]
  25. Nakahori, S.; Honda, H. Method of Manufacturing Nickel Hydroxide Electrode for Alkaline Storage Cell. U.S. Patent 4,844,948, 4 July 1989. [Google Scholar]
  26. Oshitani, M.; Hasegawa, K.; Yufu, H. Alkaline Battery with a Nickel Electrode. U.S. Patent 4,985,318, 15 January 1991. [Google Scholar]
  27. Willems, J.J.G.; Buschow, K.H.J. From permanent magnets to rechargeable hydride electrodes. J. Less Comm. Met. 1987, 129, 13–30. [Google Scholar] [CrossRef]
  28. Born Guegen, A.P.; Achard, J.C.; Loriers, J.; Bonnemay, M.; Bronoёl, G.; Sarradin, J.; Schlapbach, L. Electrode Materials Based on Lanthanum and Nickel, and Electrochemical Uses of Such Materials. U.S. Patent 4,107,405, 15 August 1978. [Google Scholar]
  29. Willems, J.J.G.S.A.; van Beek, J.R.G.C.M.; Buschow, K.H.J. Electrochemical Cell Comprising Stable Hydride-Forming Material. U.S. Patent 4,487,817, 11 December 1984. [Google Scholar]
  30. Osumi, Y.; Suzuki, H.; Kato, A.; Nakane, M.; Miyake, Y. Alloy for Occlusion of Hydrogen. U.S. Patent 4,147,536, 3 April 1979. [Google Scholar]
  31. Osumi, Y.; Suzuki, H.; Kato, A.; Oguro, K.; Nakane, N. Alloy for Occlusion of Hydrogen. U.S. Patent 4,396,576, 2 August 1983. [Google Scholar]
  32. Kanda, M.; Sato, Y. Hermetically Sealed Metallic Oxide-Hydrogen Battery Using Hydrogen Storage Alloy. U.S. Patent 4,605,603, 12 August 1986. [Google Scholar]
  33. Mori, H.; Hasegawa, K.; Watada, M.; Oshitani, M. Metal Hydride Electrode. U.S. Patent 5,393,616, 28 February 1995. [Google Scholar]
  34. Hasebe, H.; Inada, S.; Isozaki, Y.; Inaba, T.; Sawa, T.; Horie, H.; Yagi, N.; Shizu, H.; Kanazawa, Y. Hydrogen-absorbing Alloy for Battery, Method of Manufacturing the Same, and Secondary Nickel-Metal Hydride Battery. U.S. Patent 5,843,372, 1 December 1998. [Google Scholar]
  35. Hirosawa, T.; Ikemachi, T. Hydrogen Storage Alloy Electrode and Manufacturing Method of the Same. U.S. Patent 5,766,792, 16 June 1998. [Google Scholar]
  36. Hazama, T. Hydrogen Absorbing Electrode for Use in Nickel-Metal Hydride Secondary Batteries. U.S. Patent 5,284,619, 8 February 1994. [Google Scholar]
  37. Lichtenberg, F. Alloys for Use as Active Material for the Negative Electrode of an Alkaline, Rechargeable Nickel-Metal Hydride Battery, and Process for Its Production. U.S. Patent 5,738,958, 14 April 1998. [Google Scholar]
  38. Ohyama, H.; Nakatsuji, K.; Kikuyama, S.; Dansui, Y. Negative Electrode Material for Nickel-Metal Hydride Battery and Treatment Method Thereof, and Nickel-Metal Hydride Battery. U.S. Patent 8,202,650, 19 June 2012. [Google Scholar]
  39. Kojima, Y.; Ikeda, H.; Furukawa, S.; Sugiyama, K.; Kobayashi, N. Hydrogen-Absorbing Alloy and Electrode for Nickel-Metal Hydride Secondary Batteries. U.S. Patent 8,377,374, 19 February 2013. [Google Scholar]
  40. Young, K.; Fetcenko, M.A.; Huang, B.; Chao, B. NdNi5 Alloys for Hydrogen Storage and Ni-MH Batteries. U.S. Patent 8,968,644, 3 March 2015. [Google Scholar]
  41. Ito, S.; Sakamoto, H. Nickel-Metal Hydride Battery. U.S. Patent 8,119,284, 21 February 2012. [Google Scholar]
  42. Lv, H. High-Temperature Ni-MH Battery and a Method for Making the Same. U.S. Patent 6,689,514, 10 February 2004. [Google Scholar]
  43. Fetcenko, M.A.; Young, K.; Ovshinsky, S.R.; Ouchi, T. Hydrogen Storage Alloys Having Improved Cycle Life and low Temperature Operating Characteristics. U.S. Patent 7,393,500, 1 July 2008. [Google Scholar]
  44. Gamo, T.; Moriwaki, Y.; Yamashita, T.; Fukuda, M. Method of Making a Hydrogen Storage Alloy and Product. U.S. Patent 4,144,103, 13 March 1979. [Google Scholar]
  45. Sapru, K.; Hong, K.; Fetcenko, M.A.; Venkatesan, S. Hydrogen Storage Materials and Methods of Sizing and Preparing the Same for Electrochemical Applications. U.S. Patent 4,551,400, 5 November 1985. [Google Scholar]
  46. Venkatesan, S.; Reichman, B.; Fetcenko, M.A. Enhanced Charge Retention Electrochemical Hydrogen Storage Alloys and an Enhanced Charge Retention Electrochemical Cell. U.S. Patent 4,728,586, 1 March 1988. [Google Scholar]
  47. Fetcenko, M.A.; Ovshinsky, S.R. Catalytic Hydrogen Storage Electrode Materials for Use in Electrochemical Cells and Electrochemical Cells Incorporating the Materials. U.S. Patent 5,104,617, 14 April 1992. [Google Scholar]
  48. Fetcenko, M.A.; Ovshinsky, S.R. Metastable Hydrogen Storage Alloy Material. U.S. Patent 5,135,589, 4 August 1992. [Google Scholar]
  49. Fetcenko, M.A.; Ovshinsky, S.R.; Kajita, K. Electrode Alloy Having Decreased Hydrogen Overpressure and/or Low Self-Discharge. U.S. Patent 5,238,756, 24 August 1993. [Google Scholar]
  50. Fetcenko, M.A.; Ovshinsky, S.R. Metal Hydride Cells Having Improved Cycle Life and Charge Retention. U.S. Patent 5,330,861, 19 July 1994. [Google Scholar]
  51. Ovshinsky, S.R.; Fetcenko, M.A. Electrochemical Hydrogen Storage Alloys and Batteries fabricated from These Alloys Having Significantly Improved Capacity. U.S. Patent 5,407,761, 18 April 1995. [Google Scholar]
  52. Fetcenko, M.A.; Ovshinsky, S.R.; Chao, B.S.; Reichman, B. Electrochemical Hydrogen Storage Alloys for Nickel Metal Hydride Batteries. U.S. Patent 5,536,591, 16 July 1996. [Google Scholar]
  53. Ovshinsky, S.R.; Fetcenko, M.A.; Im, J.S.; Young, K.; Chao, B.S.; Reichman, B. Hydrogen Storage Materials Having a High Density of Non-Conventional Useable Hydrogen Storing Sites. U.S. Patent 5,840,440, 24 November 1998. [Google Scholar]
  54. Fetcenko, M.A.; Young, K.; Ovshinsky, S.R.; Reichman, B.; Koch, J.; Mays, W. Modified Electrochemical Hydrogen Storage Alloy Having Increased Capacity, Rate Capability and Catalytic Activity. U.S. Patent 6,270,719, 7 August 2001. [Google Scholar]
  55. Fetcenko, M.A.; Young, K.; Fierro, C. Hydrogen Storage Battery and Methods for Making. U.S. Patent 6,593,024, 15 July 2003. [Google Scholar]
  56. Seri, H.; Yamamura, Y.; Tsuji, Y.; Moriwaki, Y.; Iwaki, T. Hydrogen Storage Alloy Electrodes. U.S. Patent 5,468,309, 21 November 1995. [Google Scholar]
  57. Tsuji, Y.; Yamamoto, O.; Yamamura, Y.; Seri, H.; Toyoguchi, Y. Hydrogen Storage Alloy and Electrode Therefrom. U.S. Patent 5,753,054, 19 May 1998. [Google Scholar]
  58. Izumi, Y.; Moriwaki, Y.; Yamashita, K.; Tokuhiro, T. Nickel-Metal Hydride Storage Battery and Alloy for Configuring Negative Electrode of the Same. U.S. Patent 5,962,156, 5 October 1999. [Google Scholar]
  59. Knosp, B.; Bouet, J.; Jordy, C.; Mimoun, M.; Gicquel, D. Hydridable Material for the Negative Electrode in a Nickel-Metal Hydride Storage Battery. U.S. Patent 5,626,987, 6 May 1997. [Google Scholar]
  60. Iba, H.; Akiba, E. Hydrogen-Absorbing Alloy. U.S. Patent 5,968,291, 19 October 1999. [Google Scholar]
  61. Iba, H.; Akiba, E. Hydrogen-Absorbing Alloy and Process for Preparing the Same. U.S. Patent 6,153,032, 28 November 2000. [Google Scholar]
  62. Nichimura, K.; Yano, M.; Nakamura, H.; Hamasaki, K.; Tokuda, M.; Itoh, Y. Nickel-Metal Hydride Storage Battery. U.S. Patent 6,632,567, 14 October 2003. [Google Scholar]
  63. Tsukahara, M.; Takahashi, K.; Mishima, T.; Isomura, A.; Sakai, T.; Miyamura, H.; Uehara, I. Hydrogen-Occluding Alloy and Hydrogen-Occluding Alloy Electrode. U.S. Patent 5,690,799, 25 November 1997. [Google Scholar]
  64. Tsukahara, M.; Takahashi, K.; Mishima, T.; Isomura, A.; Sakai, T.; Miyamura, H.; Uehara, I. Hydrogen-Occluding Alloy and Hydrogen-Occluding Alloy Electrode. U.S. Patent 5,776,626, 7 July 1998. [Google Scholar]
  65. Ovishinsky, S.R.; Fetcenko, M.A. Electrochemical Hydrogen Storage Alloys and Batteries Fabricated from Mg Containing Base Alloy. U.S. Patent 5,506,069 A, 9 April 1996. [Google Scholar]
  66. Ovishinsky, S.R.; Fetcenko, M.A.; Reichman, B.; Young, K.; Chao, B.; Im, J. Electrochemical Hydrogen Storage Alloys and Batteries Fabricated from Mg Containing Base Alloys. U.S. Patent 5,616,432 A, 1 April 1997. [Google Scholar]
  67. Fetcenki, M.A.; Young, K.; Ouchi, T.; Reinhout, M.; Ovshinsky, S.R. Mg-Ni Hydrogen Storage Composite Having High Storage Capacity and Excellent Room Temperature Kinetics. U.S. Patent 7,211,541, 1 May 2007. [Google Scholar]
  68. Ovshinsky, S.R.; Fetcenko, M.A.; Im, J.; Chao, B.; Reichman, B.; Young, K. Electrochemical Hydrogen Storage Alloys and Batteries Containing Heterogeneous Powder Particles. U.S. Patent 5,554,456, 10 September 1996. [Google Scholar]
  69. Ting, J.; Habel, U.; Peretti, M.W.; Eisen, W.B.; Young, R.; Chao, B.; Huang, B. Electrochemical Hydrogen Storage Alloys for Nickel Metal Hydride Batteries, Fuel Cells and Methods of Manufacturing Same. U.S. Patent 6,500,583, 31 December 2002. [Google Scholar]
  70. Komori, K.; Matsuda, H.; Toyoguchi, Y. Active Material for Hydrogen Storage Alloy Electrode and Method for Producing the Same. U.S. Patent 6,444,361, 3 September 2002. [Google Scholar]
  71. Arvidsson, J.; Carlström, R.; Hallén, H.; Löfgren, S. Powder Composition and Process for the Preparation Thereof. U.S. Patent 6,245,165, 12 June 2001. [Google Scholar]
  72. Hayashida, H.; Kitayama, H.; Yamamoto, M.; Inada, S.; Sakai, I.; Kono, T.; Yoshida, H.; Inaba, T.; Kanda, M. Nickel-Hydrogen Secondary Battery. U.S. Patent 6,200,705, 13 March 2001. [Google Scholar]
  73. Kakeya, T.; Kanemoto, M.; Kuzuhara, M.; Ozaki, T.; Watada, M.; Sakai, T. Hydrogen Storage Alloy, Hydrogen Storage Alloy Electrode, Secondary Battery, and Method for Producing Hydrogen Storage Alloy. U.S. Patent 8,343,660, 1 January 2013. [Google Scholar]
  74. Ozaki, T.; Sakai, T.; Kanemoto, M.; Kakeya, T.; Kuzuhara, M.; Watada, M. Hydrogen Absorbing Alloy, Production Method Thereof, and Secondary Battery. U.S. Patent 8,343,659, 1 January 2013. [Google Scholar]
  75. Kono, T.; Sakai, I.; Yoshida, H.; Inaba, T.; Yamamoto, M.; Takeno, S. Hydrogen-Absorbing Alloy, Electrode and Secondary Battery. U.S. Patent 6,214,492, 10 April 2001. [Google Scholar]
  76. Hayashida, H.; Yamamoto, M.; Kitayama, H.; Inada, S.; Sakai, I.; Kono, T.; Yoshida, H.; Inaba, T.; Kanda, M. Nickel-Hydrogen Secondary Battery. U.S. Patent 6,248,475, 19 June 2001. [Google Scholar]
  77. Hasebe, H.; Sori, N.; Arai, T. Nickel-Metal Hydride Secondary Cell, and Method of Manufacturing the Same, Hydrogen Absorbing Alloy Particles for Cell, Method of Manufacturing the Same. U.S. Patent 5,219,678, 15 June 1993. [Google Scholar]
  78. Inaba, T.; Sawa, T.; Inada, S.; Kawashima, F.; Sato, N.; Sakamoto, T.; Okamura, M.; Arai, T.; Hashimoto, K. Hydrogen-Absorbing Alloy for Battery and Secondary Nickel-Metal Hydride Battery. U.S. Patent 5,753,386, 19 May 1998. [Google Scholar]
  79. Ovshinsky, S.R.; Young, R.T.; Chao, B. Hydrogen Storage Alloys and Methods and Improved Nickel Metal Hydride Electrodes and Batteries Using Same. U.S. Patent 6,210,498, 3 April 2001. [Google Scholar]
  80. Chen, Y.; Cai, Y.; Yu, D.; Dai, X. Method and an Equipment for Producing Rapid Condensation Hydrogen Storage Alloy Powder. U.S. Patent 6,174,345, 16 January 2001. [Google Scholar]
  81. Yamamoto, K.; Miyake, Y.; Okada, C.; Kitazume, N. Method for Production of Rare Earth Metal-Nickel Hydrogen Occlusive Alloy Ingot. U.S. Patent 5,680,896, 28 October 1997. [Google Scholar]
  82. Sun, B.; Chen, X. Vacuum Induction Melting and Strip Casting Equipment for Rare Earth Permanent Magnetic Alloy. U.S. Patent 20140352909 A1, 4 December 2014. [Google Scholar]
  83. Shinya, N.; Sugahara, H.; Ishii, M. Process for Producing Hydrogen Absorbing Alloy Powder and Hydrogen Absorbing Alloy Electrode. U.S. Patent 6,284,066, 4 September 2001. [Google Scholar]
  84. Sapru, K.; Reichman, B.; Reger, A.; Ovshinsky, S.R. Rechargeable Battery and Electrode Used Therein. U.S. Patent 4,623,597, 18 November 1986. [Google Scholar]
  85. Ovshinsky, S.R.; Fetcenko, M.A. Electrochemical Hydrogen Storage Alloys and Batteries Fabricated These Alloys Having Significantly Improved Performance Characteristics. U.S. Patent 5,277,999, 11 January 1994. [Google Scholar]
  86. Fetcenko, M.A.; Young, K.; Ovshinsky, S.R.; Reichman, B.; Koch, J.; Mays, W. Modified Electrochemical Hydrogen Storage Alloy Having Increased Capacity, Rate Capability and Catalytic Activity. U.S. Patent 6,740,448, 25 May 2004. [Google Scholar]
  87. Fetcenko, M.A.; Ovshinsky, S.R.; Young, K.; Reichman, B.; Ouchi, T.; Koch, J.; Mays, W. Hydrogen Storage Alloys Having a High Porosity Surface Layer. U.S. Patent 6,830,725, 14 December 2004. [Google Scholar]
  88. Young, K.; Reichman, B.; Fetcenko, M.A. Metal Hydride Alloy with Catalyst Particles and Channels. U.S. Patent 8,877,378, 4 November 2014. [Google Scholar]
  89. Wikipedia. Nickel-Iron Battery. Available online: https://en.wikipedia.org/wiki/Nickel-iron_battery (accessed on 9 February 2016).
  90. Edison, T.A. Reversible Galvanic Battery. U.S. Patent 678722 A, 16 July 1901. [Google Scholar]
  91. Edison, T.A. Reversible Galvanic Battery. U.S. Patent 692507, 4 February 1902. [Google Scholar]
  92. Gutjahr, M.A.; Schmid, R.; Beccu, K.D. Method of Manufacturing Positive Nickel Hydroxide Electrodes. U.S. Patent 3,877,987 A, 15 April 1975. [Google Scholar]
  93. Gutjahr, M.A.; Schmid, R.; Beccu, K.D. Method of Manufacturing Positive Nickel Hydroxide Electrodes. U.S. Patent 3,926,671 A, 16 December 1975. [Google Scholar]
  94. Fritts, D.H.; Leonard, J.F. Method of Nickel Electrode Production. U.S. Patent 4,399,005, 16 August 1983. [Google Scholar]
  95. Fritts, D.H.; Leonard, J.F. Method for Fabricating Battery Plaque and Low Shear Nickel Electrode. U.S. Patent 4,628,593, 16 December 1986. [Google Scholar]
  96. Fetcenko, M.; Koch, J. Nickel-Metal Hydride Batteries. In Linden’s Handbook of Batteries, 4th ed.; Reddy, T.B., Ed.; McGraw-Hill: New York, NY, USA, 2011; p. 229. [Google Scholar]
  97. Ovshinsky, S.R.; Fetcenko, M.A.; Venkatesan, S.; Holland, A. Compositionally and Structurally Disordered Multiphase Nickel Hydroxide Positive Electrode for Alkaline Rechargeable Electrochemical Cells. U.S. Patent 5,344,728, 6 September 1994. [Google Scholar]
  98. Ovshinsky, S.R.; Fetcenko, M.A.; Venkatesan, S.; Holland, A. Compositionally and Structurally Disordered Multiphase Nickel Hydroxide Positive Electrode Containing Modifiers. U.S. Patent 5,948,564, 7 September 1999. [Google Scholar]
  99. Oshitani, M.; Yufu, H. Nickel Electrode for Alkaline Battery and Battery Using Said Nickel Electrode. U.S. Patent 4,844,999, 4 July 1989. [Google Scholar]
  100. Fierro, C.; Fetcenko, M.A.; Young, K.; Ovshinsky, S.R.; Sommers, B.; Harrison, C. Nickel Hydroxide Positive Electrode Material Exhibiting Improved Conductivity and Engineered Activation Energy. U.S. Patent 6,228,535, 8 May 2001. [Google Scholar]
  101. Watada, M.; Oshitani, M.; Onishi, M. Nickel Electrode for Alkaline Battery. U.S. Patent 5,366,831, 22 November 1994. [Google Scholar]
  102. Ohta, K.; Matsuda, H.; Ikoma, M.; Morishita, N.; Toyoguchi, Y. Nickel Positive Electrode for Alkaline Storage Battery and Sealed Nickel-Hydrogen Storage Battery Using Nickel Positive Electrode. U.S. Patent 5,571,636, 5 November 1996. [Google Scholar]
  103. Yamawaki, A.; Nakahori, S.; Tadokoro, M.; Hamamatsu, T.; Baba, Y. Nickel Electrode Active Material; a Nickel Electrode and a Nickel Alkali Storage Cell Using Such Nickel Electrode Active Material; and Production Methods of Such Material, Electrode, and Cell. U.S. Patent 5,629,111, 13 May 1997. [Google Scholar]
  104. Ovshinsky, S.R.; Fetcenko, M.A.; Venkatesan, S.; Holland, A. Compositionally and Structurally Disordered Multiphase Nickel Hydroxide Positive Electrode for Alkaline Rechargeable Electrochemical Cells. U.S. Patent 5,637,423, 10 June 1997. [Google Scholar]
  105. Ikoma, M.; Akutsu, N.; Enokido, M.; Yoshii, F.; Kaiya, H.; Tsuda, S. Nickel Hydroxide Active Material Powder and Nickel Positive Electrode and Alkali Storage Battery Using Them. U.S. Patent 5,700,596, 23 December 1997. [Google Scholar]
  106. Matsuda, H.; Okada, Y.; Ohta, K.; Toyoguchi, Y. Active Material and Positive Electrode for Alkaline Storage Battery. U.S. Patent 5,773,169, 30 June 1998. [Google Scholar]
  107. Joo, K.; Choi, J.; Choi, K.; Kim, G.; Lee, S. Active Material for Nickel Electrode and Nickel Electrode Having the Same. U.S. Patent 5,789,113, 4 August 1998. [Google Scholar]
  108. Corrigan, D.; Fierro, C.; Martin, F.J.; Ovshinsky, S.R.; Xu, L. Nickel Battery Electrode Having Multiple Composition Nickel Hydroxide Active Materials. U.S. Patent 5,861,225, 19 January 1999. [Google Scholar]
  109. Okada, Y.; Ohta, K.; Matsuda, H.; Toyoguchi, Y. Nickel Hydroxide Positive Electrode Active Material Having a Surface Layer Containing a Solid Solution Nickel Hydroxide With Manganese Incorporated Therein. U.S. Patent 6,066,416, 23 May 2000. [Google Scholar]
  110. Dansui, Y.; Kato, F.; Suzuki, K.; Yuasa, K. Nickel/Metal Hydride Storage Battery. U.S. Patent 6,074,785, 13 June 2000. [Google Scholar]
  111. Fierro, C.; Fetcenko, M.A.; Young, K.; Ovshinsky, S.R.; Sommers, B.; Harrison, C. Nickel Hydroxide Positive Electrode Material Exhibiting Improved Conductivity and Engineered Activation Energy. U.S. Patent 6,447,953, 10 September 2002. [Google Scholar]
  112. Jackovitz, J.F.; Pantier, E.A. Alkali Slurry Ozonation to Produce a High Capacity Nickel Battery Material. U.S. Patent 4,481,128, 6 November 1984. [Google Scholar]
  113. Ovshinsky, S.R.; Corrigan, D.; Venkatesan, S.; Young, R.; Fierro, C.; Fetcenko, M.A. Chemically and Compositionally Modified Solid Solution Disordered Multiphase Nickel Hydroxide Positive Electrode for Alkaline Rechargeable Electrochemical Cells. U.S. Patent 5,348,822, 20 September 1994. [Google Scholar]
  114. Ovshinsky, S.R.; Young, R.T. Nickel Metal Hydride Battery Containing a Modified Disordered Multiphase Nickel Aluminum Based Positive Electrode. U.S. Patent 5,567,549, 22 October 1996. [Google Scholar]
  115. Young, R.; Ovshinsky, S.R.; Xu, L. Beta to Gamma Phase Cycleable Electrochemically Active Nickel Hydroxide Material. U.S. Patent 5,905,003, 18 May 1999. [Google Scholar]
  116. Ovshinsky, S.R.; Young, R.T.; Xu, L.; Kumar, S. Active Nickel Hydroxide Material Having Controlled Water Content. U.S. Patent 6,019,955, 1 February 2000. [Google Scholar]
  117. Singh, D.B. Gamma NiOOH Nickel Electrodes. U.S. Patent 6,020,088, 1 February 2000. [Google Scholar]
  118. Aladjov, B. Battery-Grade Nickel Hydroxide and Method for Its Preparation. U.S. Patent 5,788,943, 4 August 1998. [Google Scholar]
  119. Olbrich, A.; Meese-Marktscheffel, J.; Stoller, V.; Erb, M.; Albrecht, S.; Gille, G.; Maikowske, G.; Schrumpf, F.; Schmoll, J.; Jahn, M. Nickel Hydroxide and Method for Producing Same. U.S. Patent 7,563,431, 21 July 2009. [Google Scholar]
  120. Kato, F.; Tanigawa, F.; Dansui, Y.; Yuasa, K. Positive Electrode Material for Alkaline Storage Battery, Method of Producing the Same, and Alkaline Storage Battery Using the Same. U.S. Patent 6,083,642, 4 July 2000. [Google Scholar]
  121. Junichi, I.; Yuri, K.; Tetsushi, M.; Toyoshi, I. Nickel Hydroxide Particles Having an α- or β-Cobalt Hydroxide Coating Layer for Use in Alkali Batteries and a Process for Producing the Nickel Hydroxide. U.S. Patent 6,040,007, 21 March 2000. [Google Scholar]
  122. Fetcenko, M.A.; Fierro, C.; Ovshinsky, S.R.; Sommers, B.; Reichman, B.; Young, K.; Mays, W. Composite Positive Electrode Material and Method for Making Same. U.S. Patent 6,177,213, 23 January 2001. [Google Scholar]
  123. Fetcenko, M.A.; Fierro, C.; Ovshinsky, S.R.; Sommers, B.; Reichman, B.; Young, K.; Mays, W. Composite Positive Electrode Material and Method for Making Same. U.S. Patent 6,348,285, 19 February 2002. [Google Scholar]
  124. Fetcenko, M.A.; Fierro, C.; Ovshinsky, S.R.; Sommers, B.; Reichman, B.; Young, K.; Mays, W. Composite Positive Electrode Material and Method for Making Same. U.S. Patent 6,548,209, 15 April 2003. [Google Scholar]
  125. Fetcenko, M.A.; Fierro, C.; Ovshinsky, S.R.; Sommers, B.; Reichman, B.; Young, K.; Mays, W. Composite Positive Electrode Material and Method for Making Same. U.S. Patent 6,569,566, 27 May 2003. [Google Scholar]
  126. Fierro, C.; Fetcenko, M.A.; Young, K.; Ovshinsky, S.R.; Sommers, B.; Harrison, C. Nickel Hydroxide Electrode Material With Improved Microstructure and Method for Making the Same. U.S. Patent 7,294,434, 13 November 2007. [Google Scholar]
  127. Ovshinsky, S.R.; Fetcenko, M.A.; Fierro, C.; Gifford, P.R.; Corrigan, D.A.; Benson, P.; Martin, F.J. Enhanced Nickel Hydroxide Positive Electrode Materials for Alkaline Rechargeable Electrochemical Cells. U.S. Patent 5,523,182, 4 June 1996. [Google Scholar]
  128. Fierro, C.; Fetcenko, M.A.; Ovshinsky, S.R.; Corrigan, D.A.; Sommers, B.; Zallen, A. Nickel Hydroxide Electrode Material and Method for Making the Same. U.S. Patent 6,416,903, 9 July 2002. [Google Scholar]
  129. Tokuda, M.; Ogasawara, T.; Yano, M.; Fujitani, S. Nickel Hydroxide Electrode for Alkaline Storage Battery and Alkaline Storage Battery. U.S. Patent 6,835,498, 28 December 2004. [Google Scholar]
  130. Wolff, M.; Nuss, M.A.; Fetcenko, M.A.; Lijoi, A.L. Method for the Continuous Fabrication of Hydrogen Storage Alloy Negative Electrodes. U.S. Patent 4,820,481, 11 April 1989. [Google Scholar]
  131. Wang, Y.; Li, W.; Sun, L.; Wang, S.; Wang, W.; Li, C.; Wang, J. Electrode of Charging Battery and Method and Equipment for Making Electrode. CN Patent 1,085,896, 29 May 2002. [Google Scholar]
  132. Hasebe, H.; Takeno, K.; Sato, Y.; Takahashi, H.; Hayashida, H.; Mitsuyasu, K.; Swatari, I. Nickel-Metal Hydride Secondary Cell. U.S. Patent 5,053,292, 1 October 1991. [Google Scholar]
  133. Yun, K.S.; Cho, B.W.; Cho, W.I.; Paik, C.H. Fabrication Method for Paste-Type Metal Hydride Electrode. U.S. Patent 5,682,592, 28 October 1997. [Google Scholar]
  134. Venkatesan, S.; Reichman, B.; Ovshinsky, S.R.; Prasad, B.; Corrigan, D.A. High Power Nickel-Metal Hydride Batteries and High Power Electrodes for Use Therein. U.S. Patent 5,856,047, 5 January 1999. [Google Scholar]
  135. Reichman, B.; Venkatesan, S.; Ovshinsky, S.R.; Fetcenko, M.A. Nickel-Metal Hydride Batteries Having High Power Electrodes and Low-Resistance Electrode Connections. U.S. Patent 5,851,698, 22 December 1998. [Google Scholar]
  136. Towsley, F.E. Method for Making Electrodes for Nickel-Metal Hydride Batteries. U.S. Patent 6,881,234, 19 April 2005. [Google Scholar]
  137. James, D.; Allison, D.B., II; Kelley, J.J.; Doe, J.B. Electrical Energy Devices. U.S. Patent 6,451,485, 17 September 2002. [Google Scholar]
  138. Moriwaki, Y.; Karanaka, S.; Iwasaki, M.; Yamasaki, Y.; Maeda, A. Hydrogen Storage Alloy Electrode, Battery Including the Same and Method for Producing the Both. U.S. Patent 6,610,445, 26 August 2003. [Google Scholar]
  139. Nakayama, S. Negative Electrode and Nickel-Metal Hydride Storage Battery Using the Same. U.S. Patent 7,534,529, 19 May 2009. [Google Scholar]
  140. Magari, Y.; Tanaka, T.; Akita, H.; Shinyama, K.; Funahashi, A.; Nohma, T. Nickel-Metal Hydride Storage Battery. U.S. Patent 6,924,062, 2 August 2005. [Google Scholar]
  141. Akita, H.; Tanaka, T.; Magari, Y.; Shinyama, K.; Funahashi, A.; Nohma, T. Nickel-Metal Hydride Storage Battery. U.S. Patent 6,926,998, 9 August 2005. [Google Scholar]
  142. Frye, B.; Pensabene, S.; Puglisi, V. Electrode Structure for Nickel Metal Hydride Cells. U.S. Patent 5,478,594, 26 December 1995. [Google Scholar]
  143. Kawase, H.; Morishita, S.; Towata, S.; Suzuki, K.; Abe, K. Sealed. U.S. Patent 5,948,563, 7 September 1999. [Google Scholar]
  144. Matsuura, Y.; Maeda, R.; Shinyama, K.; Tanaka, T.; Nohma, T.; Yonezu, I. Hydrogen Absorbing Alloy Electrode and Nickel-Metal Hydride Battery. U.S. Patent 6,475,671, 5 November 2002. [Google Scholar]
  145. Kuribayashi, Y.; Sugahara, H.; Ishii, M.; Shima, S. Hydrogen Absorbing Alloy Powder and Electrodes Formed of the Hydrogen Absorbing Alloy Powder. U.S. Patent 6,235,130, 22 May 2001. [Google Scholar]
  146. Ovshinsky, S.R.; Aladjov, B.; Venkatesan, S.; Dhar, S.K.; Hopper, T.; Fok, K. Method of Activating Hydrogen Storage Alloy Electrode. U.S. Patent 6,605,375, 12 August 2003. [Google Scholar]
  147. Young, K.; Fetcenko, M.A.; Ovshinsky, S.R. Hydrogen Storage Powder and Process for Preparing the Same. U.S. Patent 6,461,766, 8 October 2002. [Google Scholar]
  148. Noréus, D.; Zhou, Y. Method for Improving the Properties of Alloy Powders for NiMH Batteries. U.S. Patent 7,056,397, 6 June 2006. [Google Scholar]
  149. Okawa, T.; Murakami, T.; Aoki, K.; Usui, H. Nickel Metal Hydride Rechargeable Battery and Method for Manufacturing Negative Electrode Thereof. U.S. Patent 8,389,159, 5 March 2013. [Google Scholar]
  150. Matsuura, Y.; Nogami, M.; Maeda, R.; Shinyama, K.; Yonezu, I.; Nishio, K. Metal Hydride Alkaline Storage Cell and Manufacturing Method Thereof. U.S. Patent 6,852,447, 8 February 2005. [Google Scholar]
  151. Köhler, U.; Chen, G.; Lindner, J. Gastight, Sealed Metal Oxide/metal Hydride Storage Battery. U.S. Patent 5,639,569, 17 June 1997. [Google Scholar]
  152. Ferrando, W. Suspension Method of Impregnating Active Material into Composite Nickel Plaque. U.S. Patent 4,574,096, 4 March 1986. [Google Scholar]
  153. Amiel, O.; Belkhir, I.; Freluche, J.; Pineau, N.; Dupuy, C.; Babin, S. Non-Sintered Electrode With Three-Dimensional Support for a Secondary Electrochemical Cell Having an Alkaline Electrolyte. U.S. Patent 6,656,640, 2 December 2003. [Google Scholar]
  154. Pensabene, S.F.; Royalty, R.L. Electrode Having a Conductive Contact Area and Method of Making the Same. U.S. Patent 5,196,281, 23 March 1993. [Google Scholar]
  155. Babjak, J.; Ettel, V.A.; Paserin, V. Method of Forming Nickel Foam. U.S. Patent 4,957,543, 18 September 1990. [Google Scholar]
  156. Kawano, H.; Hayashi, T.; Matsumoto, I. Non-Sintered Type Nickel Electrode. U.S. Patent 5,824,435, 20 October 1998. [Google Scholar]
  157. Ohnishi, M.; Watada, M.; Oshitani, M. Nickel Electrode and Alkaline Battery Using the Same. U.S. Patent 5,200,282, 6 April 1993. [Google Scholar]
  158. Kobayashi, T. Nickel Electrode Plate for an Alkaline Storage Battery. U.S. Patent 5,677,088, 14 October 1997. [Google Scholar]
  159. Harada, K.; Ishii, M.; Watanabe, K.; Yamanaka, S. Process for Preparing Metallic Porous Body, Electrode Substrate for Battery and Process for Preparing the Same. U.S. Patent 5,640,669, 17 June 1997. [Google Scholar]
  160. Venkatesan, S.; Aladjov, B.; Fok, K.; Hopper, T.; Ovshinsky, S.R. Nickel Hydroxide Paste with Molasses Binder. U.S. Patent 6,818,348, 16 November 2004. [Google Scholar]
  161. Ovshinsky, S.R.; Aladjov, B.; Tekkanat, B.; Venkatesan, S.; Dhar, S.K. Active Electrode Composition With Conductive Polymeric Binder. U.S. Patent 7,238,446, 3 July 2007. [Google Scholar]
  162. Lee, W.W. Cobalt Treatment of Nickel Composite Electrode Surfaces. U.S. Patent 4,595,463, 17 June 1986. [Google Scholar]
  163. Geng, M.; Phillips, J.; Mohanta, S. Nickel Hydroxide Electrode for Rechargeable Batteries. U.S. Patent 8,048,566, 1 November 2011. [Google Scholar]
  164. Hyashi, K.; Tomioka, K.; Morishita, N.; Ikeyama, M.; Ikoma, M. Nickel Positive Electrode for Alkaline Rechargeable Batteries and Nickel Metal Hydride Cells. U.S. Patent 5,968,684, 19 October 1999. [Google Scholar]
  165. Seyama, Y.; Sasaki, H.; Murata, T. Positive Active Material for Alkaline Battery and Electrode Using the Same. U.S. Patent 6,251,538, 26 June 2001. [Google Scholar]
  166. Maeda, T.; Shinyama, K.; Matsuura, Y.; Nogami, M.; Yonezu, I.; Nishio, K. Nickel-Hydrogen Storage Battery. U.S. Patent 6,472,101, 29 October 2002. [Google Scholar]
  167. Miyamoto, K.; Bando, N. Active Material for Positive Electrode for Alkaline Secondary Cell and Method for Producing the Same, and Alkaline Secondary Cell Using the Active Material for Positive Electrode and Method for Producing the Same. U.S. Patent 6,528,209, 4 March 2003. [Google Scholar]
  168. Seyama, Y.; Sasaki, H.; Murata, T. Positive Active Material for Alkaline Battery and Electrode Using the Same. U.S. Patent 6,558,842, 6 May 2003. [Google Scholar]
  169. Sakamoto, H.; Ohkawa, K.; Yuasa, S. Alkali Battery Positive Electrode Active Material, Alkali Battery Positive Electrode, Alkali Battery, and Method for Manufacturing Alkali Battery Positive Electrode Active Material. Patent WO2006011430 A1, 2 February 2006. [Google Scholar]
  170. Pensabene, S.F.; Puglisi, V.J. Positive Nickel Electrode for Nickel Metal Hydride Cells. U.S. Patent 5,466,546, 14 November 1995. [Google Scholar]
  171. Nakayama, S.; Yuasa, K.; Kaiya, H. Nickel Positive Electrode Plate and Alkaline Storage Battery. U.S. Patent 6,803,148, 12 October 2004. [Google Scholar]
  172. Nakayama, S.; Yuasa, K.; Kaiya, H. Nickel Positive Electrode Plate and Alkaline Storage Battery. U.S. Patent 7,364,818, 29 April 2008. [Google Scholar]
  173. Bauerlein, P. Ni/Metal Hydride Secondary Element. U.S. Patent 6,881,519, 19 April 2005. [Google Scholar]
  174. Ovshinsky, S.R.; Corrigon, D.A.; Benson, P.; Fierro, C.A. Nickel Metal Hydride Battery Containing a Modified Disordered Multiphase Nickel Hydroxide Positive Electrode. U.S. Patent 5,569,563, 29 October 1996. [Google Scholar]
  175. Dansui, Y.; Suzuki, T.; Kasahara, H.; Yao, T. Nickel-Metal Hydride Secondary Battery Comprising a Compound Silicate. U.S. Patent 6,461,767, 8 October 2002. [Google Scholar]
  176. Maeda, A.; Kimiya, H.; Moriwaki, Y.; Matsumoto, I. Alkaline Storage Battery. U.S. Patent 6,338,917, 15 January 2002. [Google Scholar]
  177. Dansui, Y.; Suzuki, T.; Kasahara, H. Method of Preparing a Nickel Positive Electrode Active Material. U.S. Patent 7,147,676, 12 December 2006. [Google Scholar]
  178. Hayashi, K.; Tomioka, K.; Morishita, N.; Ikoma, M. Nickel Positive Electrode and Alkaline Storage Battery Using the Same. U.S. Patent 6,027,834, 22 February 2000. [Google Scholar]
  179. Klein, M. Method for Preparing Conductive Electrochemically Active Material. U.S. Patent 5,585,142, 17 December 1996. [Google Scholar]
  180. Klein, M. Method for Fabricating a Battery Electrode. U.S. Patent 5,611,823, 18 March 1997. [Google Scholar]
  181. Young, K.; Ng, K.Y.S.; Bendersky, L.A. A technical report of the robust affordable next generation energy storage system-BASF program. Batteries 2016, 2. [Google Scholar] [CrossRef]
  182. Yoshinaka, T.; Yamamoto, S.; Inagaki, T.; Nakamura, Y.; Tanigawa, F.; Kaiya, H.; Takeshima, H. Sealed Cylindrical Nickel-Metal Hydride Storage Battery. U.S. Patent 6,805,995, 19 October 2004. [Google Scholar]
  183. Ovshinsky, S.R.; Fetcenko, M.A.; Holland, A.; Dean, K.; Fillmore, D. Optimized Cell Pack for Large Sealed Nickel-Metal Hydride Batteries. U.S. Patent 5,558,950, 24 September 1996. [Google Scholar]
  184. Ovshinsky, S.R.; Corrigan, D.A.; Venkatesan, S.; Dhar, S.K.; Holland, A.; Fillmore, D.; Higley, L.; Gow, P.; Himmler, R.; Karditsas, N.; et al. Mechanical and Thermal Improvements in Metal Hydride Batteries, Battery Modules and Battery Packs. U.S. Patent 5,879,831, 9 March 1999. [Google Scholar]
  185. Kozawa, H.; Kojima, K.; Ono, T.; Yanagawa, H.; Kitazume, H.; Taguchi, K. Rectangular Nickel-Metal Hydride Secondary Cell. U.S. Patent 5,372,897, 13 December 1994. [Google Scholar]
  186. Kozawa, H.; Kojima, K.; Ono, T.; Yanagawa, H.; Kitazume, H.; Taguchi, K. Method of Making a Rectangular Nickel-Metal Hydride Secondary Cell. U.S. Patent 5,490,867, 13 February 1996. [Google Scholar]
  187. Kozawa, H.; Kojima, K.; Ono, T.; Yanagawa, H.; Kitazume, H.; Taguchi, K. Method of Manufacturing a Nickel-Metal Hydride Secondary Cell. U.S. Patent 5,537,733, 23 July 1996. [Google Scholar]
  188. Yuasa, S.; Morishita, N.; Taniguchi, A.; Ikoma, M. Rectangular Alkaline Storage Battery and Battery Module and Battery Pack Using the Same. U.S. Patent 20020022179 A1, 21 February 2002. [Google Scholar]
  189. Kawasaki Heavy Industries. Bipolar 3D Design Is the Secret to the High Capacity and Rapid Charge/Discharge of the GIGACELL. Available online: https://global.kawasaki.com/en/energy/solutions/battery_energy/about_gigacell/structure.html (accessed on 9 February 2016).
  190. Kato, F.; Tanigawa, F.; Yuasa, K. Nickel-Metal Hydride Storage Battery and Assembly of the Same. U.S. Patent 6,958,200, 25 October 2005. [Google Scholar]
  191. Sasaki, E.W.; Owens, B.B.; Passerini, S. Rechargeable Battery. U.S. Patent 6,265,100, 24 July 2001. [Google Scholar]
  192. Klein, M. Method of Making Electrodes for Bipolar Electrochemical Battery. U.S. Patent 5,478,363, 26 December 1995. [Google Scholar]
  193. Klein, M. Bipolar Electrochemical Battery of Stacked Wafer Cells. U.S. Patent 5,393,617, 28 February 1995. [Google Scholar]
  194. Mrotek, E.N.; Kao, W. Bipolar Battery and Method of Making Same. U.S. Patent 5,688,615, 18 November 1997. [Google Scholar]
  195. Fredriksson, L.; Puester, N. Bipolar Battery and Biplate Assembly. U.S. Patent 7,097,937, 29 August 2006. [Google Scholar]
  196. Fredriksson, L.; Puester, N.H. Bipolar Battery and a Method for Manufacturing a Bipolar Battery. U.S. Patent 7,258,949, 21 August 2007. [Google Scholar]
  197. Fredriksson, L.; Puester, N. Bipolar Battery and a Biplate Assembly. U.S. Patent 7,767,337, 3 August 2010. [Google Scholar]
  198. Puester, N.H.; Hock, D.; Fredriksson, L. Method for Manufacturing a Bipolar Battery with a Gasket. U.S. Patent 8,470,469, 25 June 2013. [Google Scholar]
  199. Benczur-Uermoessy, G. Gastight Prismatic Nickel-Metal Hydride Cell. U.S. Patent 7,205,065, 17 April 2007. [Google Scholar]
  200. Corrigan, D.A.; Gow, P.; Higley, L.R.; Muller, M.D.; Osgood, A.; Ovshinsky, S.R.; Payne, J.; Puttaiah, R. Monoblock Battery Assembly. U.S. Patent 6,255,015, 3 July 2001. [Google Scholar]
  201. Lyman, P.C. Battery. U.S. Patent 5,567,544, 22 October 1996. [Google Scholar]
  202. Park, Y. Secondary Battery. U.S. Patent 2013/0149579 A1, 13 June 2013. [Google Scholar]
  203. Fuhr, J.D.; Dougherty, T.J.; Dinkelman, J.P. Battery Cell. U.S. Patent 8,609,278, 17 December 2013. [Google Scholar]
  204. Hirano, F. Cylindrical Storage Battery. U.S. Patent 6,703,158, 9 March 2004. [Google Scholar]
  205. Hashimoto, T. Negative Electrode Current Collector, Negative Electrode Using the Same, and Non-Aqueous Electrolytic Secondary Cell. U.S. Patent 7,150,942, 19 December 2006. [Google Scholar]
  206. Nakamaru, H. Current Collector. U.S. Patent D522,965, 13 June 2006. [Google Scholar]
  207. Kometani, S.; Nagase, T.; Masuda, Y.; Asanuma, H.; Enishi, E.; Kondo, T. Collector Used for an Alkali Storage Battery. U.S. Patent 6,979,514, 27 December 2005. [Google Scholar]
  208. Mori, H.; Sakamoto, K.; Bandou, T.; Okabe, K. Nickel Metal-Hydride Battery. U.S. Patent 7,867,655, 11 January 2011. [Google Scholar]
  209. Fuhr, J.D.; Bowen, G.K.; Dinkleman, J.P.; Dougherty, T.J.; Tsutsui, W.; Bonin, C. Current Collector for An Electromechanical Cell. U.S. Patent 8,679,678, 25 March 2014. [Google Scholar]
  210. Shinohara, W.; Yamamoto, Y.; Hosokawa, H.; Yamauchi, Y. Method of Manufacturing Sealed Battery and Sealed Battery. U.S. Patent 6,843,811, 18 January 2005. [Google Scholar]
  211. Ling, P.T.P.; Ng, S.O.A. Prismatic Battery Cells, Batteries with Prismatic Battery Cells and Methods of Making Same. U.S. Patent 20060040176 A1, 23 February 2006. [Google Scholar]
  212. Dean, K.; Holland, A.; Ovshinsky, H.C.; Fetcenko, M.; Venkatesan, S.; Dhar, S. Hydrogen Containment Cover Assembly for Sealing the Cell Can of a Rechargeable Electrochemical Hydrogen Storage Cell. U.S. Patent 5,171,647, 15 December 1992. [Google Scholar]
  213. Pate, P.E. Electrochemical Cell Safety Vent. U.S. Patent 6,080,505, 27 June 2000. [Google Scholar]
  214. Sugita, N. Sealed Battery with Less Electrolyte Leakage. U.S. Patent 6,838,207, 4 January 2005. [Google Scholar]
  215. Komori, K.; Matsuura, T.; Hamada, S.; Eto, T.; Nakamura, Y. Nickel Metal Hydride Storage Battery With a Safety Valve for Relieving Excess Gas Pressure in the Battery When the Safety Valve Is Open, the Safety Valve Having a Hydrogen-Permeable Value Member for Allowing Hydrogen-Gas Leakage Therethrough When the Safety Valve Is Closed. U.S. Patent 7,758,994, 20 July 2010. [Google Scholar]
  216. Hamada, S.; Matsuura, T.; Eto, T.; Miyamoto, H. Nickel-Metal Hydride Storage Battery. U.S. Patent 7,807,282, 5 October 2010. [Google Scholar]
  217. Fuhr, J.D.; Trester, D.; Houchin-Miller, G.; Bonin, C.; Pacheco, A.C. Battery Module with Sealed Vent Chamber. U.S. Patent 8,999,538, 7 April 2015. [Google Scholar]
  218. Fuhr, J.D.; Tsutsui, W.; Houchin-Miller, G.P.; Bonin, C.M. Vent for Electrochemical Cell. U.S. Patent 8,945,740, 3 February 2015. [Google Scholar]
  219. Tyler, M.; Fuhr, J. Device for Aiding in the Fracture of a Vent of an Electrochemical Cell. U.S. Patent 9,105,902, 11 August 2015. [Google Scholar]
  220. Komori, K.; Ogata, Y.; Adachi, A.; Maekawa, K.; Fujioka, N. Nickel Metal Hydride Storage Battery. U.S. Patent 7,452,629, 18 November 2008. [Google Scholar]
  221. Hamada, S.; Eto, T. Sealed Rechargeable Battery and Battery Module. U.S. Patent 7,393,611, 1 July 2008. [Google Scholar]
  222. Kung, J.K. Battery Separator for Nickel/Metal Hydride Batteries. U.S. Patent 5,298,348, 29 March 1994. [Google Scholar]
  223. Senyarich, S.; Viaud, P. Storage Cell Having an Alkaline Electrolyte, in Particular a Storage Cell of Nickel-Cadmium or Nickel Metal Hydride. U.S. Patent 5,939,222, 17 August 1999. [Google Scholar]
  224. Whear, J.K.; Yaritz, J.G. Nonwoven Separator for a Nickel-Metal Hydride Battery. U.S. Patent 6,537,696, 25 March 2003. [Google Scholar]
  225. Tsukiashi, M.; Teraoka, H.; Hata, K.; Tajima, M. Battery Separator and Manufacturing Method Thereof, and Alkali Secondary Battery Having the Separator Incorporated Therein. U.S. Patent 6,623,809, 23 September 2003. [Google Scholar]
  226. Harada, Y.; Tanaka, T.; Magari, Y.; Shinyama, K.; Nohma, T.; Yonezu, I. Separator for Nickel-Metal Hydride Storage Battery and Nickel-Metal Hydride Storage Battery. U.S. Patent 7,052,800, 30 May 2006. [Google Scholar]
  227. Harada, Y.; Tanaka, T.; Shinyama, K.; Nohma, T.; Yonezu, I. Separator for Alkaline Secondary Battery, Method for Preparing the Same Alkaline Secondary Battery. U.S. Patent 6,790,562, 14 September 2004. [Google Scholar]
  228. Tsuji, Y.; Nakai, H.; Muraoka, Y. Nickel-Metal Hydride Storage Battery. U.S. Patent 7,435,511, 14 October 2008. [Google Scholar]
  229. Lim, H.S.; Arora, P. Separator Media for Electrochemical Cells. U.S. Patent 20140134498 A1, 15 May 2014. [Google Scholar]
  230. Sato, N.; Komori, K.; Morishita, N. Separator for Alkaline Storage Battery and Alkaline Storage Battery Using the Same. U.S. Patent 6,933,079, 23 August 2005. [Google Scholar]
  231. Young, K.; Yasuoka, S. Capacity degradation mechanisms in nickel/metal hydride batteries. Batteries 2016, 2. [Google Scholar] [CrossRef]
  232. Joshi, A.V.; Gordon, J.H.; Bhavaraju, S. Nickel-Metal Hydride Battery Using Alkali Ion Conducting Separator. U.S. Patent 8,012,621, 6 September 2011. [Google Scholar]
  233. Joshi, A.V.; Gordon, J.H.; Bhavaraju, S. Nickel-Metal Hydride/Hydrogen Hybrid Battery Using Alkali Ion Conducting Separator. U.S. Patent 9,209,445, 8 December 2015. [Google Scholar]
  234. Alkordi, M.H.; Eddaoudi, M. Electrode Separator. U.S. Patent 20130280611 A1, 24 October 2013. [Google Scholar]
  235. Yan, S.; Young, K.; Ng, K.Y.S. Effects of salt additives to the KOH electrolyte used in Ni/MH batteries. Batteries 2015, 1, 54–73. [Google Scholar] [CrossRef]
  236. Young, K.; Nei, J.; Rotarov, D. Studies in various hydroxides used as electrolyte in Ni/MH batteries. Batteries 2016. to be submitted for publication. [Google Scholar]
  237. Kitayama, H.; Hayashida, H.; Yamamoto, M.; Bando, N.; Miyamoto, K.; Suzuki, H. Nickel-Metal Hydride Secondary Battery. U.S. Patent 6,399,247, 4 June 2002. [Google Scholar]
  238. Anani, A.A.; Reichert, V.R.; Massaroni, K.M. Metal Hydride Electrochemical Cell Having a Polymer Electrolyte. U.S. Patent 5,541,019, 30 July 1996. [Google Scholar]
  239. Iwakura, C.; Furukawa, N.; Izumi, Y.; Moriwaki, Y. Nickel-Metal Hydride Storage Battery and Production Method Thereof. U.S. Patent 7,022,434, 4 April 2006. [Google Scholar]
  240. Ovshinsky, S.R.; Young, R. Solid State Battery Using a Hydrogenated Silicon Nitride Electrolyte. U.S. Patent 5,552,242, 3 September 1996. [Google Scholar]
  241. Nakamura, Y. Power Storage Device. U.S. Patent 7,803,486, 28 September 2010. [Google Scholar]
  242. Young, K.; Fetcenko, M.A. Low Cost, High Power, High Energy Density, Solid-State, Bipolar Metal Hydride Batteries. U.S. Patent 8,974,948, 10 March 2015. [Google Scholar]
  243. Van Deutekom, H.J.H. Rechargeable Electrochemical Cell. U.S. Patent 4,214,043, 22 July 1980. [Google Scholar]
  244. Van Deutekom, H.J.H. Rechargeable Electrochemical Cell. U.S. Patent 4,312,928, 26 January 1982. [Google Scholar]
  245. Ikezoe, M. Sealed Nickel-Metal Hydride Storage Cells and Hybrid Electric Having the Storage Cells. U.S. Patent 7,353,894, 8 April 2008. [Google Scholar]
  246. Takee, M.; Tadokoro, M.; Ise, T.; Yamawaki, A. Nickel-Metal Hydride Storage Cell Having a High Capacity and an Excellent Cycle Characteristic and Manufacturing. U.S. Patent 6,368,748, 9 April 2002. [Google Scholar]
  247. Berlureau, T.; Liska, J. Sealed Nickel-Metal Hydride Storage Cell. U.S. Patent 6,444,349, 3 September 2002. [Google Scholar]
  248. Onishi, M.; Fukunaga, H.; Isogai, M.; Nagai, R. Nickel Metal-Hydride Cell. U.S. Patent 6,593,031, 15 July 2003. [Google Scholar]
  249. Young, K.; Fierro, C.; Reichman, B.; Fetcenko, M.A.; Koch, J.; Zallen, A. Nickel Metal Hydride Battery Design. U.S. Patent 7,261,970, 28 August 2007. [Google Scholar]
  250. Hasebe, H.; Tsuruta, S.; Yoshida, H.; Yamamoto, M.; Kanno, K.; Ishitsuka, K.; Komiyama, K.; Oppata, H. Alkaline Secondary Battery Manufacturing Method, Alkaline Secondary Battery Positive Electrode, Alkaline Secondary Battery, and a Method of Manufacturing an Initially Charged Alkaline Secondary Battery. U.S. Patent 5,708,349, 13 January 1998. [Google Scholar]
  251. Nanamoto, K.; Umehara, Y. Method for Manufacturing Nickel-Metal-Hydride Battery. U.S. Patent 5,814,108, 29 September 1998. [Google Scholar]
  252. Singh, D.B. Method of Forming CoOOH and NiOOH in a NiMH Electrochemical Cell and An Electrochemical Cell Formed Thereby. U.S. Patent 6,270,535, 7 August 2001. [Google Scholar]
  253. Onishi, M.; Tomioka, K.; Fujioka, N.; Ikoma, M. Method for Producing a Nickel Metal-Hydride Storage Battery. U.S. Patent 6,669,742, 30 December 2003. [Google Scholar]
  254. Morishita, N.; Ito, S.; Seri, H. Nickel-Metal Hydride Rechargeable Battery. U.S. Patent 7,560,188, 14 July 2009. [Google Scholar]
  255. Toyota Prius Battery. Available online: http://www.toyotapriusbattery.com (accessed on 9 February 2016).
  256. Ovshinsky, S.R.; Corrigan, D.A.; Venkatesan, S.; Dhar, S.K.; Holland, A.; Fillmore, D.; Higley, L.; Gow, P.; Himmler, R.; Karditsas, N.; et al. Mechanical and Thermal Improvements in Metal Hydride Batteries, Battery Modules and Battery Packs. U.S. Patent 6,372,377, 16 April 2002. [Google Scholar]
  257. Ovshinsky, S.R.; Corrigan, D.A.; Venkatesan, S.; Dhar, S.K.; Holland, A.; Fillmore, D.; Higley, L.; Gow, P.; Himmler, R.; Karditsas, N.; et al. Mechanical and Thermal Improvements in Metal Hydride Batteries, Battery Modules and Battery Packs. U.S. Patent 6,878,485, 12 April 2005. [Google Scholar]
  258. Morishita, N.; Hamada, S.; Matsuda, H.; Ikoma, M. Cell and Module Battery of Sealed Nickel-Metal Hydride Storage. U.S. Patent 5,747,186, 5 May 1998. [Google Scholar]
  259. Hamada, S.; Kasahara, H.; Ito, S.; Ando, H.; Eto, T. Nickel-Metal Hydride Secondary Battery Module and Secondary Battery Module Manufacturing Method. U.S. Patent 8,785,014, 22 July 2014. [Google Scholar]
  260. Hamada, S.; Inoue, H.; Fujioka, N.; Ikoma, M. Battery Module. U.S. Patent 6,551,741, 22 April 2003. [Google Scholar]
  261. Muis, P. Interconnectors for a Battery Assembly. U.S. Patent 8,541,130, 24 September 2013. [Google Scholar]
  262. Yang, J.H. Battery Module of High Cooling Efficiency. U.S. Patent 7,955,726, 7 June 2011. [Google Scholar]
  263. Houchin-Miller, G.P.; Pacheco, A.C.; Wiegmann, M.; Joswig, R.; Hoh, M.; Balk, M.; Obasih, K. Battery System with Heat Exchanger. U.S. Patent 8,603,660, 10 December 2013. [Google Scholar]
  264. Houchin-Miller, G.P.; Pacheco, A.C.; Wiegmann, M.; Joswig, R.; Hoh, M.; Balk, M.; Obasih, K. Battery System with Heat Exchanger. U.S. Patent 9,225,045, 29 December 2015. [Google Scholar]
  265. Gadawski, T.J.; Payne, J. Battery Module and Method for Cooling the Battery Module. U.S. Patent 8,399,118 B2, 19 March 2013. [Google Scholar]
  266. Koetting, W.; Payne, J. Battery Module and Method for Cooling the Battery Module. U.S. Patent 8,399,119 B2, 19 March 2013. [Google Scholar]
  267. Shinyashiki, Y.; Fujiwara, M.; Maeda, H.; Funahashi, A. Method for Compressing Individual Cells in Battery Module. U.S. Patent 8,309,247, 13 November 2012. [Google Scholar]
  268. Chamberlain, C.P.; Lamb, D.; Lauby, W.J.; Voorheis, H.T. Compact, Shock Resistant Battery Pack. U.S. Patent 5,466,545, 14 November 1995. [Google Scholar]
  269. Wheeler, D.K.; Moores, R.G., Jr.; Walter, R.T. Battery Pack for Cordless Device. U.S. Patent 7,273,676, 25 September 2007. [Google Scholar]
  270. Adams, P.; Ellis, R.; Newton, J. Battery Pack Control Circuit for Handheld Battery Operated Device. U.S. Patent 8,548,633, 1 October 2013. [Google Scholar]
  271. Pyo, K.R. Battery Pack and Manufacturing Method for the Same. U.S. Patent 8,835,045, 16 September 2014. [Google Scholar]
  272. Shih, C.; Chang, C.; Yeh, S.; Liu, L.; Wu, S. Battery Pack. U.S. Patent 20130171492 A1, 4 July 2013. [Google Scholar]
  273. Mita, Y. Battery Module and Temperature-Controlling Apparatus for Battery. U.S. Patent 5,456,994, 10 October 1995. [Google Scholar]
  274. Inui, K.; Nakanishi, T. Battery Pack. U.S. Patent 6,504,342, 7 January 2003. [Google Scholar]
  275. Ogata, Y.; Hamada, S. Battery Pack Cooling Structure. U.S. Patent 6,709,783, 23 March 2004. [Google Scholar]
  276. Inui, K.; Etoh, T. Fluid-Cooled Battery Pack System. U.S. Patent 6,953,638, 11 October 2005. [Google Scholar]
  277. Ovshinsky, S.R.; Corrigan, D.A.; Venkatesan, S.; Dhar, S.K.; Holland, A.; Fillmore, D.; Higley, L.; Gow, P.; Himmler, R.; Karditsas, N.; et al. Mechanical and Thermal Improvements in Metal Hydride Batteries, Battery Modules and Battery Packs. U.S. Patent 7,217,473, 15 May 2007. [Google Scholar]
  278. Fuhr, J.D.; Houchin-Miller, G.P.; Swoyer, J.L.; Pacheco, A.C.; Zhang, X.; Obashih, K.M. Prismatic Electrochemical Cell. U.S. Patent 20130216872 A1, 22 August 2013. [Google Scholar]
  279. Yuen, T.K. Battery Charging Circuit for Charging NiMH and NiCd Batteries. U.S. Patent 5,489,836, 6 February 1996. [Google Scholar]
  280. Feldstein, R.S. NiCd/NiMH Battery Charger. U.S. Patent 5,523,668, 4 June 1996. [Google Scholar]
  281. McClure, M.S. Battery Monitoring and Charging Control Unit. U.S. Patent 5,563,496, 8 October 1996. [Google Scholar]
  282. Seong, H.; Im, S. Battery Charging Circuit with Charging Rate Control. U.S. Patent 5,698,963, 16 December 1997. [Google Scholar]
  283. Im, S.; Seoung, H.; Choi, B. Fast-Charging Device for Rechargeable Batteries. U.S. Patent 5,717,311, 10 February 1998. [Google Scholar]
  284. Cheon, K. Dual Battery Charging Device for Charging Nickel Metal-Hydride and Lithium-Ion Batteries. U.S. Patent 5,744,937, 28 April 1998. [Google Scholar]
  285. Gaza, B.S. Microcontrolled Battery Charger. U.S. Patent 5,764,030, 9 June 1998. [Google Scholar]
  286. Yeon, S. Charge Mode Control in a Battery Charger. U.S. Patent 5,821,736, 13 October 1998. [Google Scholar]
  287. Gaza, B.S. Microcontrolled Battery Charger. U.S. Patent 5,998,966, 7 December 1999. [Google Scholar]
  288. Yuen, T.K. Battery Charger. U.S. Patent 6,208,148, 27 March 2001. [Google Scholar]
  289. Tsenter, B. Battery Charger and Method of Charging Nickel Based Batteries. U.S. Patent 6,313,605, 6 November 2001. [Google Scholar]
  290. Gignac, R.G. Temperature/Voltage Controlled Battery Charging Circuit. U.S. Patent 6,707,273, 16 March 2004. [Google Scholar]
  291. Santana, G.L., Jr. Battery, Battery Charger, Electrical System and Method of Charging a Battery. U.S. Patent 6,924,620, 2 August 2005. [Google Scholar]
  292. Morgan, R. Rechargeable Batteries. U.S. Patent 7,459,882, 2 December 2008. [Google Scholar]
  293. Ishikawa, Y.; Okabayashi, H.; Sakai, M.; Kobayashi, M. Charging Apparatus. U.S. Patent 20130285600 A1, 31 October 2013. [Google Scholar]
  294. Guang, H.T.; Hua, L.W.; Wentink, R.F. Multiple Cell Battery Charger Configured With a Parallel Topology. U.S. Patent 8,860,372, 14 October 2014. [Google Scholar]
  295. Geodken, T.J. Battery Charger Having Variable-Magnitude Charging Current Source. U.S. Patent 5,166,596, 24 November 1992. [Google Scholar]
  296. Dias, D.R.; Mumper, E.W. Battery Charger Systems and Methods. U.S. Patent 5,488,284, 30 January 1996. [Google Scholar]
  297. Kamke, J.E. Apparatus and Method for Maintaining the Charge of a Battery. U.S. Patent 5,493,198, 20 February 1996. [Google Scholar]
  298. Hanselmann, D.; Mayer, B.; Nutz, K.; Weller, S. Charging Method for Storage Batteries. U.S. Patent 5,537,023, 16 July 1996. [Google Scholar]
  299. Takeda, T. Control Method and Control Apparatus for Secondary Battery Charging in Constant Current Charging Method. U.S. Patent 5,627,451, 6 May 1997. [Google Scholar]
  300. Sage, G.E. Pulse-Charge Battery Charger. U.S. Patent 5,633,574, 27 May 1997. [Google Scholar]
  301. Im, S.; Seoung, H.; Choi, B. Method and Apparatus for Detecting a Full-Charge Condition While Charging a Battery. U.S. Patent 5,691,624, 25 November 1997. [Google Scholar]
  302. Podrazhansky, Y.M.; Tsenter, B. Control and Termination of a Battery Charging Process. U.S. Patent 5,694,023, 2 December 1997. [Google Scholar]
  303. Kuno, H. Battery Charger and Method for Completing Charging at Designated Time. U.S. Patent 5,736,834, 7 April 1998. [Google Scholar]
  304. Lane, R.W. Method and Apparatus for Charging Batteries. U.S. Patent 5,739,672, 14 April 1998. [Google Scholar]
  305. Wieczorek, R. Method for Charging a Rechargeable Battery. U.S. Patent 5,773,956, 30 June 1998. [Google Scholar]
  306. Kwan, H.; Chen, Y.; Chu, C.; Chen, S.; Wang, C. Automatic Battery Charging System Using Lowest Charge Current Detection. U.S. Patent 5,844,398, 1 December 1998. [Google Scholar]
  307. Paryani, A.; Sando, Y. Refreshing Charge Control Method and Apparatus to Extend the Life of Batteries. U.S. Patent 6,011,380, 4 January 2000. [Google Scholar]
  308. Freiman, J.F. Temperature Compensated Voltage Limited Fast Charge of Nickel Cadmium and Nickel Metal Hydride Battery Packs. U.S. Patent 6,020,722, 1 February 2000. [Google Scholar]
  309. Hardie, J.O. Battery Charger. U.S. Patent 6,211,655, 3 April 2001. [Google Scholar]
  310. Pavlovic, V.S. Method and Apparatus for Charging Batteries Utilizing Heterogeneous Reaction Kinetics. U.S. Patent 6,495,992, 17 December 2002. [Google Scholar]
  311. Patino, J.; Fiske, J.D. Battery Charging Algorithm. U.S. Patent 6,731,096, 4 May 2004. [Google Scholar]
  312. Patino, J. Method and System for Battery State of Charge Estimation by Using Measured Changes in Voltage. U.S. Patent 7,098,666, 29 August 2006. [Google Scholar]
  313. Hoff, C.M.; Nelson, J.E. Controlling Re-Charge of a Nickel Metal-Hydride (NiMH) or Nickel Cadmium (NiCd) Battery. U.S. Patent 7,129,676 B2, 31 October 2006. [Google Scholar]
  314. Meng, C.; Daou, Y. Systems and Methods for Temperature-Dependent Battery Charging. U.S. Patent 7,615,969, 10 November 2009. [Google Scholar]
  315. Kung, S.; Shen, Y. Method for Charging Portable Electronic Device. U.S. Patent 7,772,807, 10 August 2010. [Google Scholar]
  316. Wong, K.P.; Ng, S.O.A.; Yeo, C.W. Method and System for Determining the SOC of a Rechargeable Battery. U.S. Patent 7,888,911, 15 February 2011. [Google Scholar]
  317. Kaplan, J.; Furlan, J.L.W.; Schaefer, P.R.; Bacho, E.V.; Chu, J.Y.H.; Lin, R.; Inman, R.T.; Orner, W. System and Method for Charging Rechargeable Batteries in a Digital Camera. U.S. Patent 8,259,221, 4 September 2012. [Google Scholar]
  318. Hoff, C.M.; Nelson, J.E. Method and System for Charging a NiMH or NiCd Battery. U.S. Patent 7,405,538, 29 July 2008. [Google Scholar]
  319. Esnard-Domerego, D.; Walley, J.; Wang, L. Sink Current Adaptation Based on Power Supply Detection. U.S. Patent 8,729,867, 20 May 2014. [Google Scholar]
  320. Yuen, T.K. Battery Charger. U.S. Patent 6,225,789, 1 May 2001. [Google Scholar]
  321. Uchida, Z. Quick Charge Control Apparatus and Control Method Thereof. U.S. Patent 5,200,690, 6 April 1993. [Google Scholar]
  322. Yau, K.W.; Li, Y.C.; Bai, L. Intelligent Serial Battery Charger. U.S. Patent 7,557,538, 7 July 2009. [Google Scholar]
  323. Nicolai, J. Method for the Fast Charging of a Battery and Integrated Circuit for the Implementation of This Method. U.S. Patent 5,612,607, 18 March 1997. [Google Scholar]
  324. Fernandez, J.M.; Coapstick, R.S. Method for Ultra-Rapidly Charging a Rechargeable Battery Using Multi-Mode Regulation in a Vehicular Recharging System. U.S. Patent 5,986,430, 16 November 1999. [Google Scholar]
  325. Young, K.; Wang, C.; Wang, L.Y.; Strunz, K. Electric Vehicle Battery Technologies. In Electric Vehicle Integration into Modern Power Networks; Garcia-Valle, R., Lopes, J.A.P., Eds.; Springer Science, Business Media: New York, NY, USA, 2013; pp. 15–56. [Google Scholar]
  326. Johnson, T.W.; Rosenbecker, J.J.; Meyer, G.D.; Zeiler, J.M.; Glasgow, K.L.; Zick, J.A.; Brozek, J.M.; Scheucher, K.F. Method and System for Battery Protection. U.S. Patent 9,112,248, 18 August 2015. [Google Scholar]
  327. Carrier, D.A.; Seman, A.E., Jr.; Howard, G.S.; Brotto, D.C.; Trinh, D.T.; Watts, F.S.; Choksi, S.S.; Zhang, Q.J. Battery Pack for Cordless Power Tools. U.S. Patent 7,728,553, 1 June 2010. [Google Scholar]
  328. Kim, S.; Song, J. Battery Management System, Method of Controlling the Same, and Energy Storage System Including the Battery Management System. U.S. Patent 8,806,240, 12 August 2014. [Google Scholar]
  329. Duncan, W.D.; Hyde, R.A.; Kare, J.T. Management of a Remote Electric Vehicle Traction Battery System. U.S. Patent 20140351107 A1, 27 November 2014. [Google Scholar]
  330. Lin, X.; Stefanopoulou, A.; Anderson, R.D.; Li, Y. Detection of Imbalance across Multiple Battery Cells Measured by the Same Voltage Sensor. U.S. Patent 20140361743 A1, 11 December 2014. [Google Scholar]
  331. Duncan, W.D.; Hyde, R.A.; Kare, J.T. Managed Electric Vehicle Traction Battery System. U.S. Patent 9,002,537, 7 April 2015. [Google Scholar]
  332. Phouc, D.V.; Wieczorek, R.; Zeising, E.; Hruska, L.W.; Taylor, A.H.; Friel, D.D.; Hull, M.P. Battery Pack Having a Processor Controlled Battery Operating System. U.S. Patent 5,691,621 A, 25 November 1997. [Google Scholar]
  333. Townsley, D.B.; Blanc, J.J. Circuit Offering Sequential Discharge and Simultaneous Charge for a Multiple Battery System and Method for Charging Multiple Batteries. U.S. Patent 5,666,006, 9 September 1997. [Google Scholar]
  334. Kadouchi, E.; Watanabe, Y.; Kinoshita, M.; Ito, N.; Takata, K. Monitoring Apparatus for a Series Assembly of Battery Modules. U.S. Patent 6,020,717, 1 February 2000. [Google Scholar]
  335. Hess, R.L.; Cooper, P.R.; Interiano, A.; Freiman, J.F. Battery Charge Monitor and Fuel Gauge. U.S. Patent 5,315,228, 24 May 1994. [Google Scholar]
  336. Wood, S.J.; Maubert, E.; Veglio, O. Cell Diagnostic System and Method. U.S. Patent 8,788,225, 22 July 2014. [Google Scholar]
  337. Rathmann, R. Battery Pack and a Method for Monitoring Remaining Capacity of a Battery Pack. U.S. Patent 5,955,869, 21 September 1999. [Google Scholar]
  338. Ying, R.Y. State of Charge Algorithm for a Battery. U.S. Patent 6,356,083, 12 March 2002. [Google Scholar]
  339. Kikuchi, Y. Battery Control System. U.S. Patent 6,600,293, 29 July 2003. [Google Scholar]
  340. Bockelmann, T.R.; Hope, M.E.; Zou, Z.; Kang, X. Battery Control System for Hybrid Vehicle and Method for Controlling a Hybrid Vehicle Battery. U.S. Patent 7,489,101, 10 February 2009. [Google Scholar]
  341. Melichar, R.J. Battery State of Charge Voltage Hysteresis Estimator. U.S. Patent 7,570,024, 4 August 2009. [Google Scholar]
  342. Fassnacht, J. Method for Regulating the State of Charge of an Energy Accumulator in a Vehicle Having a Hybrid Drive Unit. U.S. Patent 7,934,573, 3 May 2011. [Google Scholar]
  343. Izumi, J. Upper-Limit of State-of-Charge Estimating Device and Upper-Limit of State-of-Charge Estimating Method. U.S. Patent 8,912,761, 16 December 2014. [Google Scholar]
  344. Takahashi, K.; Nishi, Y.; Tomura, S.; Takemoto, T.; Haga, N.; Fuchimoto, T.; Sugimoto, T. Control System of Vehicle. U.S. Patent 8,498,766, 30 July 2013. [Google Scholar]
  345. Galbraith, R.E.; Gisi, J.M.; Norgaard, S.P.; Reetz, D.D.; Ziebarth, D.J. Method and Apparatus for Estimating the Service Life of a Battery. U.S. Patent 6,191,556, 20 February 2001. [Google Scholar]
  346. Galbraith, R.E.; Gisi, J.M.; Norgaard, S.P.; Reetz, D.D.; Ziebarth, D.J. Method and Apparatus for Estimating the Service Life of a Battery. U.S. Patent 6,271,647, 7 August 2001. [Google Scholar]
  347. Juncker, C.; Christensen, F.K. Battery Life Estimation. U.S. Patent 6,538,449, 25 March 2003. [Google Scholar]
  348. Singh, P.; Fennie, C., Jr.; Reisner, D.E. Method and System for Determining State-of-Health of a Nickel-Metal Hydride Battery Using an Intelligent System. U.S. Patent 7,051,008, 23 May 2006. [Google Scholar]
  349. Staton, K.L. Detecting an End of Life for a Battery Using a Difference between an Unloaded Battery Voltage and a Loaded Battery Voltage. U.S. Patent 8,410,783, 2 April 2013. [Google Scholar]
  350. Center, M.B. Method for Estimating Battery Life in a Hybrid Powertrain. U.S. Patent 8,204,702, 19 June 2012. [Google Scholar]
  351. Tsenter, B.J.; James, J.E. State of Health Recognition of Secondary Batteries. U.S. Patent 7,605,591, 20 October 2009. [Google Scholar]
  352. Interiano, A.; Hess, R.L.; Cooper, P.R.; Freiman, J.F. Battery Charge Monitor to Determine Fast Charge Termination. U.S. Patent 5,200,689, 6 April 1993. [Google Scholar]
  353. Van Phuoc, D.; Wieczorek, R.; Zeising, E.; Hruska, L.W.; Taylor, A.H.; Friel, D.D.; Hull, M.P. Battery Pack Having a Processor Controlled Battery Operating System. U.S. Patent 5,652,502 A, 29 July 1997. [Google Scholar]
  354. Tate, E.D., Jr.; Verbrugge, M.W.; Sarbacker, S.D. State of Charge Prediction Method and Apparatus for a Battery. U.S. Patent 6,441,586, 27 August 2002. [Google Scholar]
  355. Yao, T.; Kasahara, H.; Suzuki, T.; Masui, M.; Konishi, H. Method for Managing Back-up Power Source. U.S. Patent 6,097,176, 1 August 2000. [Google Scholar]
  356. Vebrugge, M.W.; Tate, E.D., Jr.; Sarbacker, S.D.; Koch, B.J. Quasi-Adaptive Method for Determining a Battery’s State of Charge. U.S. Patent 6,359,419 B1, 19 March 2002. [Google Scholar]
  357. Furukawa, T. Method for Estimating State of Charge of a Rechargeable Battery. U.S. Patent 8,000,915, 16 August 2011. [Google Scholar]
  358. Lee, J.; Lee, H.; Lee, J.; Lee, H.; Kim, D. Method for a Measuring Residual Capacity of a Ni/MH Cell. U.S. Patent 5,701,078, 23 December 1997. [Google Scholar]
  359. Kinoshita, T.; Miyazaki, H.; Emori, A.; Okoshi, T.; Hirasawa, T. Battery System, Battery Monitoring Method and Apparatus. U.S. Patent 7,173,397, 6 February 2007. [Google Scholar]
  360. Shinohara, S.; Takano, N. Battery Charger. U.S. Patent 5,444,353, 22 August 1995. [Google Scholar]
  361. Garrett, S.M.; Fernandez, J.M.; Patino, J. Ultrafast Rechargeable Battery Pack and Method of Charging Same. U.S. Patent 5,576,612, 19 November 1996. [Google Scholar]
  362. Van Phuoc, D.; Wieczorek, R.; Zeising, E.; Hruska, L.W.; Hull, M.P.; Taylor, A.H.; Friel, D.D. Battery Pack Having a Processor Controlled Battery Operating System. U.S. Patent 5,633,573 A, 27 May 1997. [Google Scholar]
  363. Tibbs, B.L. Recharging Method and Temperature-Responsive Overcharge Protection Circuit for a Rechargeable Battery Pack Having Two Terminals. U.S. Patent 5,708,350, 13 January 1998. [Google Scholar]
  364. McGrath, F.D.; Kellogg, N.D. Rechargeable Battery Having Overcharge Protection Circuit and Method of Charging Rechargeable Battery. U.S. Patent 5,939,865, 17 August 1999. [Google Scholar]
  365. Saeki, M.; Ozawa, H.; Tsukuni, T.; Takeda, Y. Protection Circuit and Battery Unit. U.S. Patent 6,051,955, 18 April 2000. [Google Scholar]
  366. Narita, I. Over Discharge Protection Circuit for a Rechargeable Battery. U.S. Patent 5,729,061, 17 March 1998. [Google Scholar]
  367. Gamboa, P. Method and Apparatus for Charging and Discharging a Rechargeable Battery. U.S. Patent 7,541,781, 2 June 2009. [Google Scholar]
  368. Johnson, T.W.; Rosenbecker, J.J.; Meyer, G.D.; Zeiler, J.M.; Glasgow, K.L.; Zick, J.Z.; Brozek, J.M.; Scheucher, K.F. Method and System for Battery Protection. U.S. Patent 7,589,500, 15 September 2009. [Google Scholar]
  369. Van Phuoc, D.; Wieczorek, R.; Zeising, E.; Hruska, L.W.; Taylor, A.H.; Friel, D.D.; Hull, M.P. Battery Pack Having a Processor Controlled Battery Operating System. U.S. Patent 5,646,508 A, 8 July 1997. [Google Scholar]
  370. Glonner, H.; Strobl, W.; Rump, R.; Mallog, J. Energy Storage System. U.S. Patent 7,591,331, 22 September 2009. [Google Scholar]
  371. Reis, A.; Whitmer, D.K.; Muthu, M.E.J.; Korutla, S.K. Integrated Energy Storage Unit. U.S. Patent 8,481,203, 9 July 2013. [Google Scholar]
  372. Garascia, M.P.; Arena, A.P.; Wood, S.J. Battery System. U.S. Patent 8,235,732, 7 August 2012. [Google Scholar]
  373. Zhu, D.; Treharne, W.D. System and Method for Thermal Management of a Vehicle Power Source. U.S. Patent 7,683,582, 23 March 2010. [Google Scholar]
  374. Fuhr, J.D.; Obasih, K.; De Keuster, R.M.; Mack, R.; Houchin-Miller, G.P.; Patel, D. Battery Module Having a Cell Tray with Thermal Management Features. U.S. Patent 20140234687 A1, 21 August 2014. [Google Scholar]
  375. Hamada, S. Battery Pack. U.S. Patent 7,189,474, 13 March 2007. [Google Scholar]
  376. Wood, S.J.; Tiedemann, W.H. Battery System Including a Device Configured to Route Effluent Away from Battery Modules within the Battery System. U.S. Patent 7,846,572, 7 December 2010. [Google Scholar]
  377. Zolot, M.; Pesaran, A.A.; Mihalic, M. Thermal Evaluation of Toyota Prius Battery Pack; National Renewable Energy Laboratory: Golden, CO, USA, 2002.
  378. Murata, T. Power Source Apparatus. U.S. Patent 7,974,095, 5 July 2011. [Google Scholar]
  379. Thomas, G.; Moré, G. Hybrid Energy Storage System. U.S. Patent 5,587,250, 24 December 1996. [Google Scholar]
  380. Thomas, G.; Moré, G. Hybrid Energy Storage System. U.S. Patent 5,849,426, 15 December 1998. [Google Scholar]
  381. Kruger, D.D.; Young, G.; Moore, S.W. Method and Apparatus for Providing and Storing Power in a Vehicle. U.S. Patent 6,577,099, 10 June 2003. [Google Scholar]
  382. Ovshinsky, S.R.; Stempel, R.C. Very Low Emission Hybrid Electric Vehicle Incorporating an Integrated Propulsion System Including a Hydrogen Powered Internal Combustion Engine and a High Power Ni-MH Battery Pack. U.S. Patent 6,565,836, 20 May 2003. [Google Scholar]
  383. Lee, E. Energy Storage System and Method of Controlling the Same. U.S. Patent 9,041,354, 26 May 2015. [Google Scholar]
  384. Park, J.; Choi, J. Energy Storage System and Controlling Method of the Same. U.S. Patent 20130169064 A1, 4 July 2013. [Google Scholar]
  385. Yoo, H. Method of Measuring Voltage of Battery Pack and Energy Storage System Including the Battery Pack. U.S. Patent 2014/0035365 A1, 6 February 2014. [Google Scholar]
  386. Jung, Y. Battery Pack, Controlling Method of the Same, and Energy Storage System Including the Battery Pack. U.S. Patent 20140078632 A1, 20 March 2014. [Google Scholar]
  387. Pietrangelo, N.J.; Moran, T.J. Window Construction Combining NiMH Technology and Solar Power. U.S. Patent 20080236654 A1, 2 October 2008. [Google Scholar]
  388. Komori, K.; Fujioka, N.; Kimura, T.; Yamashita, H.; Takahashi, Y. Method for Recycling Battery Pack. U.S. Patent 6,936,371, 30 August 2005. [Google Scholar]
  389. Sloop, S.E. Recycling Batteries Having Basic Electrolytes. U.S. Patent 20130302223 A1, 14 November 2013. [Google Scholar]
  390. Smith, W.N.; Swoffer, S. Process for the Recovery of Metals from Used Nickel/metal Hydride Batteries. U.S. Patent 8,246,717 B1, 21 August 2012. [Google Scholar]
  391. Smith, W.N.; Swoffer, S. Process for the Recovery of AB5 Alloy from Used Nickel/metal Hydride Batteries. U.S. Patent 8,696,788, 15 April 2014. [Google Scholar]
  392. Prickett, O.G.; Czajkowski, R.; Citta, N.C.; Klein, M.R.; Huston, E.L.; Galbraith, P.W. Reclamation of Active Material From Metal Hydride Electrochemical Cells. U.S. Patent 6,180,278, 30 January 2001. [Google Scholar]
  393. Smith, W.N.; Swoffer, S. Process for the Recovery of Metals from Used Nickel/metal Hydride Batteries. U.S. Patent 8,252,085 B1, 28 August 2012. [Google Scholar]
  394. Jacobson, A.J.; Samarasekere, P. Methods and Systems for Recovering Rare Earth Elements. U.S. Patent 20140311294 A1, 23 October 2014. [Google Scholar]
  395. Burlingame, N.H.; Burlingame, S. Method for Recycling of Rare Earth and Zirconium Oxide Materials. U.S. Patent 8,940,256, 27 January 2015. [Google Scholar]
  396. Kleinsorgen, K.; KöHler, U.; Bouvier, A.; FöLzer, A. Process for the Recovery of Metals from Used Nickel/metal Hydride Storage Batteries. U.S. Patent 5,858,061, 12 January 1999. [Google Scholar]
  397. Kikuta, N.; Asano, S.; Takano, M. Method for Separating Nickel and Cobalt from Active Material Contained in Spent Nickel-Metal Hydride Battery. U.S. Patent 8,888,892, 18 November 2014. [Google Scholar]
  398. Kikuta, N.; Asano, S.; Takano, M. Method for Producing Nickel-Containing Acid Solution. U.S. Patent 8,974,754, 10 March 2015. [Google Scholar]
Batteries 02 00010 g001 1024
Figure 1. Content of this paper. MH: metal hydride.
Figure 1. Content of this paper. MH: metal hydride.
Batteries 02 00010 g001
Batteries 02 00010 g002 1024
Figure 2. Schematic diagrams of the evolution in MH alloy surface oxide from (a) metallic clusters and voids randomly distributed in the surface oxide to (b) metallic clusters and channels randomly distributed in the surface oxide and (c) metallic clusters only on the surface of channels.
Figure 2. Schematic diagrams of the evolution in MH alloy surface oxide from (a) metallic clusters and voids randomly distributed in the surface oxide to (b) metallic clusters and channels randomly distributed in the surface oxide and (c) metallic clusters only on the surface of channels.
Batteries 02 00010 g002
Batteries 02 00010 g003 1024
Figure 3. Schematic diagram of a continuous stirring tank reactor used to co-precipitate hydroxides of metals with similar solubilities, such as Co, Ni, and Zn. 1: Stainless-steel vessel; 2: mixer blade; 3: raw material inlet; 4: product overflow; and 5: product container.
Figure 3. Schematic diagram of a continuous stirring tank reactor used to co-precipitate hydroxides of metals with similar solubilities, such as Co, Ni, and Zn. 1: Stainless-steel vessel; 2: mixer blade; 3: raw material inlet; 4: product overflow; and 5: product container.
Batteries 02 00010 g003
Batteries 02 00010 g004 1024
Figure 4. Schematic diagrams of three commonly used nickel/metal hydride (Ni/MH) battery negative electrode fabrication methods: (a) dry compaction; (b) wet paste method; and (c) dry paste method.
Figure 4. Schematic diagrams of three commonly used nickel/metal hydride (Ni/MH) battery negative electrode fabrication methods: (a) dry compaction; (b) wet paste method; and (c) dry paste method.
Batteries 02 00010 g004
Batteries 02 00010 g005 1024
Figure 5. Schematic diagrams of (a) regular three cells in series; and (b) a bipolar design with three internal cells. +, −, S, and M denote the positive electrode, negative electrode, separator, and metal sheet, respectively.
Figure 5. Schematic diagrams of (a) regular three cells in series; and (b) a bipolar design with three internal cells. +, −, S, and M denote the positive electrode, negative electrode, separator, and metal sheet, respectively.
Batteries 02 00010 g005
Batteries 02 00010 g006 1024
Figure 6. Schematic diagrams demonstrating the positive-limit cell design in Ni/MH battery: (a) during regular operation (operating within the limit); (b) in the state of overcharge, where the oxygen gas evolved from the positive electrode recombines with the excess hydrogen stored in the negative electrode (OCR prevents hydrogen evolution from the negative electrode); and (c) in the state of overdischarge, where the hydrogen gas evolved from the positive electrode is stored in the negative electrode (ODR prevents oxygen gas evolution from the negative electrode). SOC: state of charge.
Figure 6. Schematic diagrams demonstrating the positive-limit cell design in Ni/MH battery: (a) during regular operation (operating within the limit); (b) in the state of overcharge, where the oxygen gas evolved from the positive electrode recombines with the excess hydrogen stored in the negative electrode (OCR prevents hydrogen evolution from the negative electrode); and (c) in the state of overdischarge, where the hydrogen gas evolved from the positive electrode is stored in the negative electrode (ODR prevents oxygen gas evolution from the negative electrode). SOC: state of charge.
Batteries 02 00010 g006
Batteries 02 00010 g007 1024
Figure 7. Schematic diagrams showing the formation process of Ni/MH battery: (a) before formation, where the MH alloy surface is covered with a thick native oxide; (b) after thermal activation, where a new catalytic oxide with metallic Ni embedded within is formed on the MH alloy surface, and bi-valent Co is dissolved; and (c) after electrochemical formation, where new surfaces are formed due to MH alloy cracking, and tri-valent Co conductive network is formed on the spherical particle surface in the positive electrode.
Figure 7. Schematic diagrams showing the formation process of Ni/MH battery: (a) before formation, where the MH alloy surface is covered with a thick native oxide; (b) after thermal activation, where a new catalytic oxide with metallic Ni embedded within is formed on the MH alloy surface, and bi-valent Co is dissolved; and (c) after electrochemical formation, where new surfaces are formed due to MH alloy cracking, and tri-valent Co conductive network is formed on the spherical particle surface in the positive electrode.
Batteries 02 00010 g007
Table
Table 1. Property comparison between the AB2 and AB5 MH alloy families. FCC, 1C/1C, and DOD denote face-centered-cubic, 1C charge and discharge rates, and depth of discharge, respectively.
Table 1. Property comparison between the AB2 and AB5 MH alloy families. FCC, 1C/1C, and DOD denote face-centered-cubic, 1C charge and discharge rates, and depth of discharge, respectively.
PropertyAB2 MH alloyAB5 MH alloy
Basic crystal structureHexagonal C14 and FCC C15Hexagonal CaCu5
Composition exampleTi12Zr21Ni38V10Cr5Mn12Co1.5Al0.5La10Ce5Pr0.5Nd1.5Ni60Co12Mn6Al5
Discharge capacity340–440 mAh·g−1300–330 mAh·g−1
High-rate dischargeabilityAcceptableExcellent
Cycle life (1C/1C, 100% DOD)8001200
Self-dischargeAcceptable (V-free alloy)Acceptable
High-temperature storageAcceptable due to leach-outBad due to surface passivation
ActivationModestEasy
Low temperatureGoodModest
Fabrication methodCasting, hydriding, and grindingCasting and grinding
Raw material costV is expensiveVolatile due to rare earth price fluctuation
Low-cost versionV and Co-free alloyPr, Nd, and Co-free alloy
Table
Table 2. Comparisons among three commonly used Ni/MH battery negative electrode fabrication methods. Both the dry compaction and dry paste method can be processed without a binder, and therefore the power density is higher from both cases compared to that from the wet paste method.
Table 2. Comparisons among three commonly used Ni/MH battery negative electrode fabrication methods. Both the dry compaction and dry paste method can be processed without a binder, and therefore the power density is higher from both cases compared to that from the wet paste method.
MethodsProsCons
Dry compaction
  • Higher power density
  • Lower cost and simple process
  • Difficult to control the thickness precisely
Wet paste method
  • Longer cycle life
  • Lower cost
  • Lower power density
  • Complicated process
Dry paste method
  • Simple process
  • Higher power density
  • Higher cost
Table
Table 3. Comparison among five common types of Ni/MH battery. SS: stainless steel. EV: electric vehicle; and HEV: hybrid electric vehicle.
Table 3. Comparison among five common types of Ni/MH battery. SS: stainless steel. EV: electric vehicle; and HEV: hybrid electric vehicle.
TypeDescriptionProsCons
Consumer
  • Cylindrical
  • SS case
  • Mass production
  • Compatible with other alkaline batteries
  • Size limitation
Stick
  • Prismatic
  • SS case
  • Mass production
  • Easy for integration
  • Higher cost
  • Lower energy density
EV
  • Prismatic
  • SS case
  • Large format (100 Ah)
  • Hand assembly
  • High cost
HEV
  • Prismatic
  • Plastic case
  • High-volume mass production
  • Lower pressure rating
  • Poor heat transfer
Coin
  • Button-shaped
  • SS case
  • High-volume mass production
  • Compact for medical application
  • No vent
  • Cannot be scaled up
Table
Table 4. Key applications for Ni/MH battery in the market. UPS: uninterrupted power supply.
Table 4. Key applications for Ni/MH battery in the market. UPS: uninterrupted power supply.
ApplicationExamplesMain CompetitorAdvantages over Competitor
ConsumerAA, AAA, cordless phone, shaver, power toolNi/Cd
  • Higher energy density
  • Environmentally safe
PropulsionEV, HEVLi-ion
  • Long service life
  • Excellent abuse tolerance
UPSCellphone communication hub, vending machineLead-acid
  • Higher energy density
  • Longer service life
  • Environmental safe
GridSolar and wind energy storage, voltage equalizerLead-acid
  • Higher energy density
  • Longer service life
  • Environmental safe
  • Higher instant charge acceptance

Share and Cite

MDPI and ACS Style

Chang, S.; Young, K.-h.; Nei, J.; Fierro, C. Reviews on the U.S. Patents Regarding Nickel/Metal Hydride Batteries. Batteries 2016, 2, 10. https://doi.org/10.3390/batteries2020010

AMA Style

Chang S, Young K-h, Nei J, Fierro C. Reviews on the U.S. Patents Regarding Nickel/Metal Hydride Batteries. Batteries. 2016; 2(2):10. https://doi.org/10.3390/batteries2020010

Chicago/Turabian Style

Chang, Shiuan, Kwo-hsiung Young, Jean Nei, and Cristian Fierro. 2016. "Reviews on the U.S. Patents Regarding Nickel/Metal Hydride Batteries" Batteries 2, no. 2: 10. https://doi.org/10.3390/batteries2020010

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop