Search Results (38)

Searching anode materials is an important task for the development of sodium-ion batteries. In this regard, bronze-phase titanium dioxide, TiO₂(B), has been considered as one of the promising materials, owing to its crystal structure with open channels and voids facilitating Na⁺ diffusion and storage. However, the electrochemical de-/sodiation mechanism of TiO₂(B) has not been clearly comprehended, and further experiments are required. Herein, in situ and ex situ observations by a combination of X-ray photoelectron spectroscopy, X-ray diffraction, Raman spectroscopy, gas chromatography–mass spectrometry was used to provide additional insights into the electrochemical reaction scenario of bronze-phase TiO₂ in Na-ion batteries. The findings reveal that de-/sodiation of TiO₂(B) occurs through a reversible intercalation reaction and without the involvement of the conversion reaction (no metallic titanium is formed and no oxygen is released). At the same time, upon the first Na⁺ uptake process, crystalline TiO₂(B) becomes partially amorphous, but is still driven by the Ti⁴⁺/Ti³⁺ redox couple. Importantly, TiO₂(B) has pseudocapacitive electrochemical behavior during de-/sodiation based on a quantitative analysis of the cyclic voltammetry data. The results obtained in this study complement existing insights into the sodium storage mechanisms of TiO₂(B) and provide useful knowledge for further improving its anode performance for SIBs application. Full article

The widespread adoption of sodium-ion batteries (SIBs) remains constrained by the inherent limitations of conventional anode materials, particularly their inadequate electronic conductivity, limited active sites, and pronounced structural degradation during cycling. To overcome these limitations, we propose a novel redox engineering approach to fabricate oxygen-vacancy-rich SnO₂ dots anchored on reduced graphene oxide (rGO), which are encapsulated within N-doped carbon nanofibers (denoted as ov-SnO₂/rGO@N-CNFs) through electrospinning and subsequent carbonization. The introduction of rich oxygen vacancies establishes additional sodium intercalation sites and enhances Na⁺ diffusion kinetics, while the conductive N-doped carbon network effectively facilitates charge transport and mitigates SnO₂ aggregation. Benefiting from the well-designed architecture, the hierarchical ov-SnO₂/rGO@N-CNFs electrode achieves remarkable reversible specific capacities of 351 mAh g⁻¹ after 100 cycles at 0.1 A g⁻¹ and 257.3 mAh g⁻¹ after 2000 cycles at 1.0 A g⁻¹ and maintains 177 mAh g⁻¹ even after 8000 cycles at 5.0 A g⁻¹, demonstrating exceptional long-term cycling stability and rate capability. This work offers a versatile design strategy for developing high-performance anode materials through synergistic interface engineering for SIBs. Full article

Na-layered Li-containing Mn-based cathodes (Na_xLi_yMn_1-yO₂, NLMOs) with additional Na⁺ storage ability resulting from the anionic redox reaction (ARR) hold great promise for sodium-ion batteries (NIBs). However, practical applications of NLMOs encounter challenges, such as migration of transition metal Mn, loss of lattice oxygen, and voltage decay during cycling. Here, we show that Cu plays an important role in enhancing the ARR via the reductive coupling mechanism (RCM). Results shows that a Cu²⁺/Fe³⁺ modified NLMO sample delivers a Na⁺ storage capacity as high as 174 mA h g⁻¹ at 0.2C, higher than that of a Zn²⁺/Fe³⁺ modified NLMO sample (130 mA h g⁻¹) and NLMO (154 mA h g⁻¹). Both in situ and ex situ characterization results indicate that the obvious improvement in the electrochemical performance of the Cu²⁺/Fe³⁺ modified NLMO is due to the additional overlaps between the Cu 3d and O 2p orbitals, which is beneficial for the RCM. As a result, the ARR is enhanced so as to increase the Na⁺ storage capacity. Full article

Layered transition metal oxide (LTMO) cathode materials for sodium-ion batteries (SIBs) have attracted extensive attention due to their unique structural stability and excellent electrochemical performance. However, their poor stability in air has significantly impeded their practical application, as exposure to moisture and carbon dioxide can lead to Na⁺ loss, phase transitions, and decreased electrochemical performance. This paper reviews the application of high-entropy strategies in sodium-ion LTMO cathode materials, focusing on the optimization of air stability and electrochemical performance through approaches including high-entropy cation regulation, P2/O3 dual-phase synergistic structures, and fluorine ion doping. Studies have shown that high-entropy design can effectively inhibit phase transitions, alleviate Jahn–Teller distortion, enhance oxygen framework stability, and markedly enhance the cycle life and rate performance of materials. Furthermore, future research directions are proposed, including the use of advanced characterization techniques to reveal failure mechanisms, the integration of machine learning to optimize material design, and the development of high-performance mixed-phase structures. High-entropy strategies provide new perspectives for the development of SIBs cathode materials with enhanced air stability, potentially promoting the practical application of SIBs in large-scale energy storage systems. Full article

Na₂Ti₃O₇ (NTO), with low sodium insertion potential (~0.3 V vs. Na⁺/Na) and potential for high-energy-density batteries, is regarded as one of the most promising anode materials for sodium-ion batteries (SIBs). However, its practical application is hindered by poor electronic conductivity, sluggish Na⁺ (de)intercalation kinetics, and interfacial instability, leading to inferior cycling stability, low initial Coulombic efficiency, and poor rate capability. In this work, micron-sized rod-like NTO and Al-doped NTO (NTO-Al) samples were synthesized via a one-step high-temperature solid-state method. Al doping slightly reduced the size of NTO microrods while introducing oxygen vacancies and generating Ti³⁺, thereby enhancing electronic conductivity and reducing ionic diffusion resistance. H₂-TPR confirms that doping activates lattice oxygen and promotes its participation in the reaction. The optimized NTO-Al0.03 electrode delivered a significantly improved initial charge capacity of 147.4 mA h g⁻¹ at 0.5 C, surpassing pristine NTO (124.7 mA h g⁻¹). Moreover, it exhibited the best cycling stability (49.5% capacity retention after 100 cycles) and rate performance (36.3 mA h g⁻¹ at 2 C). Full article

Hard carbon anodes are promising for sodium-ion batteries due to their low cost and high reversible capacity. However, the long-term Na⁺ (de)intercalating process destroys the structure of the two-phase interface between the electrode and electrolyte, impairing cycling stability. In this paper, a few-layer graphene (FLG)-coated hard carbon fiber composite is constructed. A uniform graphene encapsulation is confirmed by synchrotron small-angle X-ray scattering and transmission electron microscopy technologies. Post-cycling observation reveals FLG participation in forming a hybrid solid electrolyte interphase (SEI). At a proper concentration, the FLG with a small specific surface area and pore size characteristics is well matched in the SEI. The FLG-integrated SEI not only mitigates volume expansion but also enhances ion conductivity through its oxygen-rich functional groups. As a result, the composite structure maintains 98.2% capacity retention after 100 cycles and reaches 164 mAh g⁻¹ at 1000 mA g⁻¹, compared to 97 mAh g⁻¹ for the pristine hard carbon. This work demonstrates that FLG coating simultaneously stabilizes the interfacial chemistry and improves the ion transport, offering a practical pathway to advance hard carbon anodes for high-performance sodium-ion batteries. Full article

The present study demonstrates, for the first time, the fundamental possibility of producing electrode materials for sodium-ion batteries through low-temperature carbothermic smelting of ilmenite concentrate fluxed with calcined soda and diatomite, followed by aqueous refining of titanium slag. The primary phase composition of the slag includes Na₂Ti₃O₇ (48.2%), Na_0.23TiO₂ (22.0%), Na₂TiSiO₅ (11%), and Na_0.67Al_0.1Mn_0.9O₂ (8.5%), which, upon hydrolysis, transform into a monophase titanium dioxide with intercalated sodium—Na_0.23TiO₂. Thermodynamic analysis of the heat effects of chemical reactions among raw materials and resulting products substantiates the role of silicon and sodium oxides, carbon, oxygen, and water in the formation of various electrode materials during carbothermic flux conversion and aqueous refining. Insights into the mechanisms of thermochemical formation and hydrothermal phase transformations offer a scientific basis for the development of intercalation systems from abundant and low-cost natural raw materials, bypassing the need for expensive precursor synthesis. Full article

The imperative for sustainable energy has driven the demand for efficient energy storage systems that can harness renewable resources and store surplus energy for off-peak usage. Among the numerous advancements in energy storage technology, polymeric nanofibers have emerged as promising nanomaterials, offering high specific surface areas that facilitate increased charge storage and enhanced energy density, thereby improving electrochemical performance. This review delves into the pivotal role of nanofibers in determining the optimal functionality of energy storage systems. Electrospinning emerged as a facile and cost-effective method for generating nanofibers with customizable nanostructures, making it attractive for energy storage applications. Our comprehensive review article examines the latest developments in electrospun nanofibers for electrochemical storage devices, highlighting their use as separators and electrode materials. We provide an in-depth analysis of their application in various battery technologies, including supercapacitors, lithium-ion batteries, sodium-ion batteries, potassium-ion batteries, lithium–sulfur batteries, and lithium–oxygen batteries, with a focus on their electrochemical performance. Furthermore, we summarize the diverse fabrication techniques, optimization of key influencing factors, and environmental implications of nanofiber production and their properties. This review aims to offer an inclusive understanding of electrospinning’s role in advancing electrochemical energy storage, providing insights into the factors that drive the performance of these critical materials. Full article

Na−O₂ batteries are plagued by high cathodic oxygen reduction (ORR)/oxygen evolution (OER) overpotentials during discharging/charging. Herein, we constructed six carbide/nitride MXenes (M₂XO₂, M = Ti, Zr, and Hf, X = C, and N) and investigated their performance as cathodes for Na−O₂ batteries by first-principles calculations. M₂CO₂ MXenes have a pseudogap, showing semiconducting properties, while M₂NO₂ MXenes are conductive. The nucleophilic O on the M₂XO₂ surfaces prefers to bind with the Na atoms of Na_xO₂ intermediates to activate the Na−O bonds, improving the sodium deintercalation. For all M₂XO₂ MXenes, the OER overpotential is higher than the ORR overpotential, forming a performance bottleneck of Na−O₂ batteries. The overpotentials originate from the too-strong adsorption of Na_xO₂ on M₂XO₂ MXenes. Lowering the O p-band center of the M₂XO₂ MXenes can weaken the Na_xO₂ adsorption, thereby reducing the overpotential. Consequently, the overpotentials of the M₂CO₂ carbides are lower than those of the M₂NO₂ nitrides and further decrease with a decreasing M atomic number. The Ti₂CO₂ MXene shows extremely low ORR, OER, and total overpotentials (0.23, 0.32, and 0.55 V), suggesting a huge potential as cathodes in Na−O₂ batteries. Full article

Using biomass-derived hard carbon materials as anode materials for sodium-ion batteries has facilitated resource recycling and brought significant economic benefits. However, the main obstacles to the large-scale application of these materials are the low Coulombic efficiency and high irreversible capacity of hard carbon materials. This study used waste moso bamboo as a carbon source to prepare and pre-oxidize hard carbon through a stepped temperature sintering process. The introduction of oxygen atoms into the carbon layers has been shown to increase the spacing between the carbon layers, which facilitates the insertion of sodium-ions into them. Moreover, the presence of oxygen-containing groups increases the number of edge and vacancy defects in the carbon skeleton, thereby enhancing the actual capacity of the material. Studies have indicated that different pre-oxidation times have varying impacts on the electrochemical properties of hard carbon materials. This study used discarded moso bamboo as the raw material, and the optimal pre-oxidation duration of bamboo-based hard carbon was determined to be 4.5 h through a series of comparative experiments. A high-performance biomass-derived hard carbon material was prepared via a stepwise sintering process. It exhibited a specific capacity of 301.4 mAh·g⁻¹ at 0.1 C and a first-cycle Coulombic efficiency of 87%. Full article

Sodium-ion batteries (SIBs) hold significant promise in energy storage devices due to their low cost and abundant resources. Layered transition metal oxide cathodes (Na_xTMO₂, TM = Ni, Mn, Fe, etc.), owing to their high theoretical capacities and straightforward synthesis procedures, are emerging as the most promising cathode materials for SIBs. However, the practical application of the Na_xTMO₂ cathode is hindered by an unstable interface, causing rapid capacity decay. This work reviewed the critical factors affecting the interfacial stability and degradation mechanisms of Na_xTMO₂, including air sensitivity and the migration and dissolution of TM ions, which are compounded by the loss of lattice oxygen. Furthermore, the mainstream interface modification approaches for improving electrochemical performance are summarized, including element doping, surface engineering, electrolyte optimization, and so on. Finally, the future developmental directions of these layered Na_xTMO₂ cathodes are concluded. This review is meant to shed light on the design of superior cathodes for high-performance SIBs. Full article

Exploring high-performance carbon anodes that are low-cost and easily accessible is the key to the commercialization of sodium-ion batteries. Producing carbon materials from bio by-products is an intriguing strategy for sodium-ion battery anode manufacture and for high-value utilization of biomass. Herein, a novel hard carbon (PPHC) was prepared via a facile pyrolysis process followed by acid treatment using biowaste pomegranate peel as the precursor. The morphology and structure of the PPHC were influenced by the carbonization temperature, as evidenced by physicochemical characterization. The PPHC pyrolyzed at 1100 °C showed expanded interlayer spacing and appropriate oxygen group content. When used as a sodium ion battery anode, the PPHC-1100 demonstrated a reversible capacity of up to 330 mAh g⁻¹, maintaining 174 mAh g⁻¹ at an increased current rate of 1 C. After 200 cycles at 0.5 C, the capacity delivered by PPHC-1100 was 175 mAh g⁻¹. The electrochemical behavior of PPHC electrodes was investigated, revealing that the PPHC-1100 possessed increased capacitive-controlled energy storage and improved ion transport properties, which explained its excellent electrochemical performance. This work underscores the feasibility of high-performance sodium-ion battery anodes derived from biowaste and provides insights into the sodium storage process in biomass-derived hard carbon. Full article

The main drawback of seawater batteries that use the aluminum (Al)–air system is their susceptibility to anode self-corrosion during the oxygen evolution reaction, which, in turn, affects their discharge performance. This study consist of an electrochemical investigation of pure Al, 6061 Al alloy, and both types coated with zinc as an anode in a 3.5% sodium chloride (NaCl) electrolyte. The electrolyte solution used for the deposition of zinc metal contained citrate, with and without EDTA as a complexing agent. Subsequently, the performance of the anode was tested in a seawater battery, using a carbon@MnO₂ cathode and a 3.5% NaCl electrolyte. The performance of Al–air batteries has been significantly enhanced by applying a process of electrodepositing zinc (Zn) with a citrate deposition electrolyte solution in both pure aluminum and alloy 6061. The performance of the battery was further enhanced by adding EDTA as a chelating agent to the citrate-based electrolyte solution. The Al–air battery with aluminum alloy 6061 with Zn electrodeposition with an additional EDTA as the anode, carbon@MnO₂ as the cathode, and NaCl 3.5% solution as the electrolyte has the highest battery performance, with a specific discharge capacity reaching 414.561 mAh.${\mathrm{g}}^{-1}$ and a specific energy density reaching 0.255 mWh.${\mathrm{g}}^{-1}$, with stable voltage at 0.55 V for 207 h. Full article

Nanostructured transition metal nitrides (TMNs) have been considered as a promising substitute for precious metal catalysts toward ORR due to their multi-electron orbitals, metallic properties, and low cost. To design TMN catalysts with high catalytic activity toward ORR, the intrinsic features of the influencing factor on the catalytic activity toward ORR of nanostructured TMNs need to be investigated. In this paper, titanium nitride (TiN), zirconium nitride (ZrN), and hafnium nitride (HfN) nanoparticles (NPs) are highly efficient and synthesized in one step by the direct current arc plasma. TiN, ZrN, and HfN NPs with an oxidation layer are applied as the catalysts of hybrid sodium–air batteries (HSABs). The effect of the composition and structural attributes of TMNs on ORR catalysis is defined as follows: (i) composition effect. With the increase in the oxygen content, the catalytic ORR capability of TMNs decreases progressively due to the reduction in oxygen adsorption capacity; (ii) structure effect. The redistribution of the density of states (DOS) of ZrN indicates higher ORR activity than TiN and HfN. HSABs with ZrN exhibit an excellent cyclic stability up to 137 cycles (about 140 h), an outstanding rate performance, and a specific capacity of 2817 mAh·g⁻¹ at 1.0 mA·cm⁻². Full article

Hard carbon is regarded as one of the greatest potential anode materials for sodium-ion batteries (SIBs) because of its affordable price and large layer spacing. However, its poor initial coulombic efficiency (ICE) and low specific capacity severely restrict its practical commercialization in SIBs. In this work, we successfully constructed abundant oxygen-containing functional groups in hard carbon by using pre-oxidation anthracite as the precursor combined with controlling the carbonization temperature. The oxygen-containing functional groups in hard carbon can increase the reversible Na⁺ adsorption in the slope region, and the closed micropores can be conducive to Na⁺ storage in the low-voltage platform region. As a result, the optimal sample exhibits a high initial reversible sodium storage capacity of 304 mAh g⁻¹ at 0.03 A g⁻¹, with an ICE of 67.29% and high capacitance retention of 95.17% after 100 cycles. This synergistic strategy can provide ideas for the design of high-performance SIB anode materials with the intent to regulate the oxygen content in the precursor. Full article