As one of the most promising cathode materials for sodium-ion batteries, sodium-ion layered oxide has the advantages of high capacity and low cost, which makes sodium-ion batteries have great application prospects in large-scale static energy storage. However, their commercial development has been limited due to poor electrochemical cycle stability and air stability. Compared with traditional polycrystalline layered oxides, single-crystalline layered oxides are characterized by high mechanical strength, low specific surface, and high taping density, and thus can effectively improve the cycling stability of layered oxides and enhance their comprehensive performance. The basic structure types of layered oxides of sodium-ion batteries are introduced in the paper.The synthesis methods of single-crystal layered oxides of sodium-ion batteries that have been reported so far are also reviewed and the advantages and disadvantages of various synthesis methods are analyzed. Besides, the improvement of single-crystal morphology on comprehensive performance is described and the research status of single-crystal layered oxides in sodium-ion batteries is presented with an outlook of the future development of single-crystal layered oxides for sodium-ion batteries.
Sodium metal has the advantages of abundant sources,low cost and uniform distribution,so sodium-ion batteries are considered to be one of the most promising large-scale energy storage systems.The cathode material in sodium-ion batteriesis a critical factor affecting both the electrochemical performance and production cost of the battery.Layered transition metal oxides have attracted significant attention because of their high energy density,simple synthesis method and environmental friendliness. This paper provides a comprehensive summary and review of the research on layered cathode materials from the perspective of their composition structure,phase transition mechanism,charge compensation mechanism,and modification strategies,which reveal the key factors limiting the improvement of the electrochemical performance of layered cathode materials,analyzing the effective means to inhibit phase transition process and the rational design to enhance the reversibility of anion redox reaction.Furthermore, this paper offers an outlook on future development trend.
In the context of addressing the energy crisis and realizing environmental sustainability, energy storage systems have received much attention. With the challenges posed by the rapid depletion of lithium resources and its uneven distribution, sodium-ion batteries (SIBs) with similar electrochemical properties have gradually become a research hotspot. Hard carbon (HC) materials have become one of the highly promising anode materials for SIBs due to their abundance of resources, cost-effectiveness and high carbon conversion. Coal-based hard carbon (CHC) has become one of the competitive materials in HC precursors due to its low cost and high carbon conversion. This article reviews recent research on the preparation strategies, optimization modifications, and electrochemical properties of coal-based hard carbon materials. Furthermore, we discuss the development prospects and research directions for coal-based hard carbon materials.
With the development of renewable energy sources,emerging energy storage systems have received a lot of attention. Sodium-on batteries have attracted extensive attention in the field of large-scale energy storage due to their abundant sources, safety,low cost,environmental friendliness and ease of use.The cathode materials of sodium-ion batteries affect the key properties of the battery such as energy density,cycling performance and multiplication characteristics.Currently,three cathode materials for sodium ion batteries have entered the industrialization horizon,namely layered transition metal oxides,polyanionic compounds and Prussian blue compounds.This paper summarizes the classification,properties,and research progress of main cathode materials for sodium-ion batteries,and anticipates the prospect of the potential research.
Zr4+-doped hollow spherical Na3V2（PO4）3 cathode material was prepared by spray drying method, and the influence of different Zr4+ doping levels （molar ratio of Zr4+ to Na3-x V2-x Zr x （PO4）3） on the material properties was investigated. Techniques such as X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and in-situ XRD were used to analyze the effects of Zr4+ doping on the structure and electrochemical performance of the material. It can be observed that Zr4+ doping enhanced the structural stability of the material, effectively inhibiting structural collapse and volume expansion during cycling. When the Zr4+ doping level was 0.15, Na2.85V1.85Zr0.15（PO4）3 （NVZP-15） demonstrated a discharge specific capacity of 76.5 mA?h/g at 15.0 C, with a capacity retention of 80.6% after 800 cycles at 10.0 C.
Sodium-ion batteries (SIBs) have garnered considerable attention as a viable option for large-scale energy storage,with O3-type layered transition metal oxides identified as one of the most promising cathode materials due to their superior specific capacity.However,the stability of these materials at elevated voltages remains a critical challenge,hindering their broader application.In this study,O3-NaNi1/3Fe1/3Mn1/3O2 was systematically characterized using scanning electron microscopy(SEM), transmission electron microscopy(TEM),and in-situ X-ray diffraction(XRD) to elucidate the relationship between microstructural evolution and electrochemical stability.The results reveal that phase transitions significantly impair Na? diffusion kinetics. Notably, the irreversible P3-O3' phase transition at high voltages above 4.1 V results in a reduction of the Na+ diffusion coefficient by at least five orders of magnitude,which is reflected by a substantial increase in internal resistance.Moreover,the O3' phase emerging during discharge triggers the formation of the P'3 phase,deviating it from the electrochemical pathway established during charging and thereby severely compromising the material’s cycling stability.
Cellulose, due to its abundance and propensity to form spherical structures, serves as an exceptional precursor for the synthesis of high-performance hard carbon materials used in sodium-ion batteries. This study explores the interplay between different cellulose types, their structural evolution during hydrothermal spherization, and the subsequent impact on the microcrystalline characteristics and electrochemical performance of the resulting hard carbon for sodium storage. The results observed that the crystallinity of various cellulose precursors-namely natural cellulose, α-cellulose, and microcrystalline cellulose-and their corresponding hard carbons are positively correlated. Among these, hard carbon derived from α-cellulose demonstrated superior attributes, including the highest closed pore volume and a balanced defect density, which contribute to its enhanced sodium storage capacity. Furthermore, the hydrothermal treatment of α-cellulose at 220 °C was optimized to achieve a spherical morphology, which significantly benefited both the capacity and rate performance of the hard carbon. The reversible capacities at current densities of 20 and 2 000 mA/g are 329.4 and 53.9 mA·h/g, respectively.
Transition metal sulfides are known for their high conductivity and theoretical lithium storage capacity,making them promising materials for phase change lithium storage.However,their cycling stability needs improvement.A simple electrostatic spinning method was used to prepare composites with in situ growth of cobalt-based zeolite imidazolite backbones(Co-ZIFs) on electrostatically spun fibers,and the stabilized structure of microzonated ZIFs was exploited to achieve spatially confined domains of metal particles in an N? heat treatment. Cobalt sulfide/carbon fiber composites (CoS/CFs) were then synthesized through a sulfidation reaction.X-ray diffraction (XRD) and Raman spectroscopy confirmed the uniform distribution of CoS particles on the carbon nanofibers.The optimized composite showed excellent lithium storage performance,maintaining a specific capacity of 584.5 mA·h/g after 250 cycles at a current density of 1 A/g.This demonstrates outstanding cycling stability and suggests promising applications in lithium storage.
