Batteries, Volume 4, Issue 3 (September 2018) – 18 articles

Flow batteries (also: redox batteries or redox flow batteries RFB) are briefly introduced as systems for conversion and storage of electrical energy into chemical energy and back. Their place in the wide range of systems and processes for energy conversion and storage is outlined. Acceleration of electrochemical charge transfer for vanadium-based redox systems desired for improved performance efficiency of these systems is reviewed in detail; relevant data pertaining to other redox systems are added when possibly meriting attention. An attempt is made to separate effects simply caused by enlarged electrochemically active surface area and true (specific) electrocatalytic activity. Because this requires proper definition of the experimental setup and careful examination of experimental results, electrochemical methods employed in the reviewed studies are described first. Full article

The commercialization of rechargeable alkaline zinc–air batteries (ZAB) requires advanced approaches to improve secondary zinc anode performance, which is hindered by the high corrosion and dissolution rate of zinc in this medium. Modified (with additives) alkaline electrolyte has been one of the most investigated options to reduce the high solubility of zinc. However, this strategy alone has not been fully successful in enhancing the cycle life of the battery. The combination of mitigation strategies into one joint approach, by using additives (ZnO, KF, K₂CO₃) in the base alkaline electrolyte and simultaneously preparing zinc electrodes that are based on ionomer (Nafion^®)-coated zinc particles, was implemented and evaluated. The joint use of electrolyte additives and ionomer coating was intended to regulate the exposition of Zn, deal with zincate solubility, minimize the shape change and dendrite formation, as well as reduce the hydrogen evolution rate. This strategy provided a beneficial joint protective efficiency of 87% thanks to decreasing the corrosion rate from 10.4 (blank) to 1.3 mg_Zn cm⁻¹·s⁻¹ for coated Zn in the modified electrolyte. Although the rate capability and capacity are limited, the ionomer-coated Zn particles extended the ZAB cycle life by about 50%, providing battery roundtrip efficiency above 55% after 270 h operation. Full article

Over the past few years, the use of 18650 form factor lithium-ion (Li-ion) cells have transitioned from primarily commercial applications to consumer/residential use. An evaluation of eight commercially available, circuit protected, 18650 form factor Li-ion cells were performed, with analysis focusing on a residential consumer evaluation of performance. As typical consumer cell usage occurs at a relatively low discharge rate, cells were evaluated between 4.2 V and 2.7 V at C/10, C/5, and C/2 discharge rates. The evaluated cells ranged from “high-cost” Panasonic, Hixon, Orbtronic, and EastValley cells to “low-cost” UltraFire (UF) and Eilong cells. Initial discharge comparisons revealed that no cells delivered their nameplate capacity, with a large overstatement of cell capacity occurring for low-cost cells. On average, high-cost cells delivered 92.5% of their advertised capacity, with low-cost cells delivering 20.6% at a C/10 rate. Basing consumer evaluation on a cost per unit capacity and/or cost per unit energy, even with this large overstatement in capacity, low-cost cells still offer an advantage over higher-cost alternatives. The average cost per amp-hour for each cell group ranged from $1.65 to $3.38 for the low-cost and high-cost cell groupings, respectively. Analysis of voltage profiles highlighted two chemistries used in cell production, coinciding with each cell grouping. Full article

Aqueous zinc ion batteries are considered to be one of the most promising battery types for stationary energy storage applications. Due to their aqueous electrolyte, they are inherently safe concerning flammability and environmentally friendly. In this work, the strong influence of the particle size of manganese sesquioxide on the performance of the battery is investigated. Ball milling was used to decrease the particle diameter. The resulting powders were used as active material for the cathodes, which were assembled in coin cells as full cells together with zinc foil anodes and aqueous electrolyte. It was shown that about one third of the original particle size can nearly triple the initial capacity when charged with constant current and constant end-of-charge voltage. Additionally, smaller particles were found to be responsible for the collapse of capacity at high current densities. By means of electrochemical impedance spectroscopy, it was shown that particle size also has a large impact on the internal resistance. Initially, the internal resistance of the cells with small particles was about half that of those with big particles, but became larger during cycling. This reveals accelerated aging processes when the reactive surface of the active material is increased by smaller particles. Full article

Currently, Li-ion cells are the preferred candidates as energy sources for existing portable applications and for those being developed. Thus, a proper characterization of Li-ion cells is required to optimize their use and their manufacturing process. In this study, the transport phenomena and electrochemical processes taking place in LiCoO₂-Li(NiMnCo)O₂/graphite (LCO-NMC/graphite) cells are identified from half-cell measurements by means of impedance spectroscopy. The results are calculated from current densities, instead of absolute values, for the future comparison of this data with other cells. In particular, impedance spectra are fitted to simple electrical models composed of an inductive part, serial resistance, and various RQ networks—the parallel combination of a resistor and a constant phase element—depending on the cell. Thus, the evolution of resistances, capacitances, and the characteristic frequencies of the various effects are tracked with the state-of-charge (SoC) at two aging levels. Concretely, two effects are identified at the impedance spectrum; one is clearly caused by the charge transfer at the positive electrode, whereas the other one is presumably caused by the transport of lithium ions across the solid electrolyte interphase (SEI) layer. Moreover, as the cells age, the characteristic frequency of the charge transfer is drastically reduced by a factor of around 70%. Full article

A novel chemical process has been developed to formulate injectable nickel ink for conductive film. This chemical method has the ability to remove the oxidation on nickel nano-particle surfaces during ink fabrication; the nickel ions, which are produced during chemical etching, will be reduced and bridged among original nano-nickel particles in the following thermal sintering process at 350 °C. X-ray diffraction results exhibit that the final nickel film has no significant composition change by this chemical method and that oxidation has been effectively removed. Scanning electron microscopy images show that this chemical process reduces nickel oxides into nickel and that the reduced nickel sticks on the original nickel particle surface acting as a “bridge” connecting each particle. So solid diffusion can be triggered easily among bridged nickel particles and sintered at relatively low temperatures. The resistivity of printed film is to $5\times {10}^{-6}\mathsf{\Omega }$ ∙m which is 71-times that of bulk nickel. The fabricated conductive nickel thin film has been applied on lithium ion batteries as a current collector for cathode and anode and shows good corrosion resistance and stability. Full article

The detailed study of the interplay between the physicochemical properties and the long-range charge migration mechanism of polymer electrolytes able to carry lithium ions is crucial in the development of next-generation lithium batteries. Glycerol exhibits a number of features (e.g., glass-forming behavior, low glass transition temperature, high flexibility of the backbone, and efficient coordination of lithium ions) that make it an appealing ion-conducting medium and a challenging building block in the preparation of new inorganic–organic polymer electrolytes. This work reports the preparation and the extensive investigation of a family of 11 electrolytes based on lithium glycerolate. The electrolytes have the formula C₃H₅(OH)_3−x(OLi)_x, where 0 ≤ x ≤ 1. The elemental composition is evaluated by inductively coupled plasma atomic emission spectroscopy. The structure and interactions are studied by vibrational spectroscopies (FT-IR and micro-Raman). The thermal properties are gauged by modulated differential scanning calorimetry and thermogravimetric analysis. Finally, insights on the long-range charge migration mechanism and glycerol relaxation events are investigated via broadband electrical spectroscopy. Results show that in these electrolytes, glycerolate acts as a large and flexible macro-anion, bestowing to the material single-ion conductivity (1.99 × 10⁻⁴ at 30 °C and 1.55 × 10⁻² S∙cm⁻¹ at 150 °C for x = 0.250). Full article

The effects of sulfuric acid concentration in VO²⁺ solutions were investigated via electrochemical methods and electron paramagnetic resonance. The viscosity of solutions containing 0.01 M VOSO₄ in 0.1–7.0 M H₂SO₄ was measured. Diffusion coefficients were independently measured via electrochemical methods and electron paramagnetic resonance (EPR), with excellent agreement between the techniques employed and literature values. Analysis of cyclic voltammograms suggest the oxidation of VO²⁺ to VO₂⁺ is quasi-reversible at high H₂SO₄ concentrations (>5 mol/L), and approaching irreversible at lower H₂SO₄ concentrations. Further analysis reveals a likely electrochemical/chemical (EC) mechanism where the H₂SO₄ facilitates the electrochemical step but hinders the chemical step. Fundamental insights of VO²⁺/H₂SO₄ solutions can lead to a more comprehensive understanding of the concentration effects in electrolyte solutions. Full article

Among the compounds of the olivine family, LiMPO₄ with M = Fe, Mn, Ni, or Co, only LiFePO₄ is currently used as the active element of positive electrodes in lithium-ion batteries. However, intensive research devoted to other elements of the family has recently been successful in significantly improving their electrochemical performance, so that some of them are now promising for application in the battery industry and outperform LiFePO₄ in terms of energy density, a key parameter for use in electric vehicles in particular. The purpose of this review is to acknowledge the current state of the art and the progress that has been made recently on all the elements of the family and their solid solutions. We also discuss the results from the perspective of their potential application in the industry of Li-ion batteries. Full article

In the majority of applications using lithium-ion batteries, batteries are exposed to some harmonic content apart from the main charging/discharging current. The understanding of the effects that alternating currents have on batteries requires specific characterization methods and accurate measurement equipment. The lack of commercial battery testers with high alternating current capability simultaneously to the ability of operating at frequencies above 200 Hz, led to the design of the presented experimental setup. Additionally, the experimental setup expands the state-of-the-art of lithium-ion batteries testers by incorporating relevant lithium-ion battery cell characterization routines, namely hybrid pulse power current, incremental capacity analysis and galvanic intermittent titration technique. In this paper the hardware and the measurement capabilities of the experimental setup are presented. Moreover, the measurements errors due to the setup’s instruments were analysed to ensure lithium-ion batteries cell characterization quality. Finally, this paper presents preliminary results of capacity fade tests where 28 Ah cells were cycled with and without the injection of 21 A alternating at 1 kHz. Up to 300 cycles, no significant fade in cell capacity may be measured, meaning that alternating currents may not be as harmful for lithium-ion batteries as considered so far. Full article

Due to the increasing demand for high-performance cells for mobile applications, the standards of the performance of active materials and the efficiency of cell production strategies are rising. One promising cell technology to fulfill the increasing requirements for actual and future applications are all solid-state batteries with pure lithium metal on the anode side. The outstanding electrochemical material advantages of lithium, with its high theoretical capacity of 3860 mAh/g and low density of 0.534 g/cm³, can only be taken advantage of in all solid-state batteries, since, in conventional liquid electrochemical systems, the lithium dissolves with each discharging cycle. Apart from the current low stability of all solid-state separators, challenges lie in the general processing, as well as the handling and separation, of lithium metal foils. Unfortunately, lithium metal anodes cannot be separated by conventional die cutting processes in large quantities. Due to its adhesive properties and toughness, mechanical cutting tools require intensive cleaning after each cut. The presented experiments show that remote laser cutting, as a contactless and wear-free method, has the potential to separate anodes in large numbers with high-quality cutting edges. Full article

X-ray photoelectron spectroscopy (XPS) is a key method for studying (electro-)chemical changes in metal-ion battery electrode materials. In a recent publication, we pointed out a conflict in binding energy (BE) scale referencing at alkali metal samples, which is manifested in systematic deviations of the BEs up to several eV due to a specific interaction between the highly reactive alkali metal in contact with non-conducting surrounding species. The consequences of this phenomenon for XPS data interpretation are discussed in the present manuscript. Investigations of phenomena at surface-electrolyte interphase regions for a wide range of materials for both lithium and sodium-based applications are explained, ranging from oxide-based cathode materials via alloys and carbon-based anodes including appropriate reference chemicals. Depending on material class and alkaline content, specific solutions are proposed for choosing the correct reference BE to accurately define the BE scale. In conclusion, the different approaches for the use of reference elements, such as aliphatic carbon, implanted noble gas or surface metals, partially lack practicability and can lead to misinterpretation for application in battery materials. Thus, this manuscript provides exemplary alternative solutions. Full article

Frequency-dependent capacitance C(ω) is a rapid and reliable method for the determination of the state-of-charge (SoC) of electrochemical storage devices. The state-of-the-art of SoC monitoring using impedance spectroscopy is reviewed, and complemented by original 1.5-year long-term electrical impedance measurements of several commercially available supercapacitors. It is found that the kinetics of the self-discharge of supercapacitors comprises at least two characteristic time constants in the range of days and months. The curvature of the Nyquist curve at frequencies above 10 Hz (charge transfer resistance) depends on the available electric charge as well, but it is of little use for applications. Lithium-ion batteries demonstrate a linear correlation between voltage and capacitance as long as overcharge and deep discharge are avoided. Full article

Microbial fuel cells (MFCs) and microbial electrolysis cells (MECs) are promising bioelectrochemical systems (BESs) for simultaneous wastewater treatment and energy/resource recovery. Unlike conventional fuel cells that are based on stable chemical reactions, these BESs are sensitive to environmental and operating conditions, such as temperature, pH, external resistance, etc. Substrate type, electrode material, and reactor configuration are also important factors affecting power generation in MFCs and hydrogen production in MECs. In order to discuss the influence of these above factors on the performance of MFCs and MECs, this study analyzes published data via data synthesis and meta-analysis. The results revealed that domestic wastewater would be more suitable for treatment using MFCs or MECs, due to their lower toxicity for anode biofilms compared to swine wastewater and landfill leachate. The optimal temperature was 25–35 °C, optimal pH was 6–7, and optimal external resistance was 100–1000 Ω. Although systems using carbon cloth as the electrodes demonstrated better performance (due to carbon cloth’s large surface area for microbial growth), the high prices of this material and other existing carbonaceous materials make it inappropriate for practical applications. To scale up and commercialize MFCs and MECs in the future, enhanced system performance and stability are needed, and could be possibly achieved with improved system designs. Full article

Because of an increasing interest in NaSICON materials as electrolyte materials in all-solid state sodium batteries, their thermal expansion was investigated in this study. The thermal expansion coefficient (CTE) of the Al and Y-substituted NaSICON compositions Na_3+2xAl_xY_xZr_2−2xSi₂PO₁₂ with 0 ≤ x ≤ 0.3 was obtained by dilatometry and compared to the CTE derived from the lattice parameters using high-temperature X-ray diffraction. The difference in CTE obtained from techniques, the influence of sodium content and central metal cation on CTE, as well as other observations such as phase changes are described and rationalized. Full article

La³⁺ modification of Na₃V₂(PO₄)₂F₃ was performed by the direct mechanochemically assisted solid-state synthesis of the Na₃V_2−xLa_x(PO₄)₂F₃ compositions, and by the LaPO₄ coating of the as-prepared Na₃V₂(PO₄)₂F₃ via the precipitation method. It has been shown that no noticeable substitution of the V³⁺ ions by the La³⁺ ions occurs in the Na₃V₂(PO₄)₂F₃ structure under the synthesis conditions; meanwhile, the introduction of the La³⁺ ions into the reagent mixture leads to the formation of the LaPO₄ phase, and accordingly, an increase in the NaF/VPO₄ ratio. The latter results in the formation of the Na₃PO₄ and Na₃VF₆ surface impurity phases, which possess high ionic and electronic conductivity, respectively, and significantly enhances the electrical conductivity and the cycling performance of the composite cathode material both in Na and Li cells, while simple surface modification of Na₃V₂(PO₄)₂F₃ by LaPO₄ via precipitation does not. Full article

This paper presents various solutions for organizing an accumulator battery. It examines three different architectures: series-parallel, parallel-series and C3C architecture, which spread the cell output current flux to three other cells. Alternatively, to improve a several cell system reliability, it is possible to insert more cells than necessary and soliciting them less. Classical RAMS (Reliability, Availability, Maintainability, Safety) solutions can be deployed by adding redundant cells or by tolerating some cell failures. With more cells than necessary, it is also possible to choose active cells by a selection algorithm and place the others at rest. Each variant is simulated for the three architectures in order to determine the impact on battery-operative dependability, that is to say the duration of how long the battery complies specifications. To justify that the conventional RAMS solutions are not deployed to date, this article examines the influence on operative dependability. If the conventional variants allow to extend the moment before the battery stops to be operational, using an algorithm with a suitable optimization criterion further extend the battery mission time. Full article

Modularity-in-design of battery packs for electric vehicles (EVs) is crucial to offset their high manufacturing cost. However, inconsistencies in performance of EV battery packs can be introduced by various sources. Sources of variation affect their robustness. In this paper, parameter diagram, a value-based conceptual analysis approach, is applied to analyze these variations. Their interaction with customer requirements, i.e., ideal system output, are examined and critical engineering features for designing modular battery packs for EV applications are determined. Consequently, sources of variability, which have a detrimental effect on mass-producibility of EV battery packs, are identified and differentiated from the set of control factors. Theoretically, appropriate control level settings can minimize sensitivity of EV battery packs to the sources of variability. In view of this, strength of the relationship between ideal system response and various control factors is studied using a “house of quality” diagram. It is found that battery thermal management system and packaging architecture are the two most influential parameters having the largest effect on reliability of EV battery packs. More importantly, it is noted that heat transfer between adjacent battery modules cannot be eliminated. For successful implementation of modular architecture, it is, therefore, essential that mechanical modularity must be enabled via thermal modularity of EV battery packs. Full article