Recent Advances and Prospects of Cathode Materials for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) receive significant attention for electrochemical energy storage and conversion owing to their wide availability and the low cost of Na resources. However, SIBs face challenges of low specific energy, short cycling life, and insufficient specific power, owing to the heavy mass and large radius of Na(+) ions. As an important component of SIBs, cathode materials have a significant effect on the SIB electrochemical performance. The most recent advances and prospects of inorganic and organic cathode materials are summarized here. Among current cathode materials, layered transition-metal oxides achieve high specific energies around 600 mW h g(-1) owing to their high specific capacities of 180-220 mA h g(-1) and their moderate operating potentials of 2.7-3.2 V (vs Na(+) /Na). Porous Na3 V2 (PO4 )3 /C nanomaterials exhibit excellent cycling performance with almost 100% retention over 1000 cycles owing to their robust structural framework. Recent emerging cathode materials, such as amorphous NaFePO4 and pteridine derivatives show interesting electrochemical properties and attractive prospects for application in SIBs. Future work should focus on strategies to enhance the overall performance of cathode materials in terms of specific energy, cycling life, and rate capability with cationic doping, anionic substitution, morphology fabrication, and electrolyte matching.