PTFE-derived carbon-coated Na3V2(PO4)2F3 cathode material for high-performance sodium ion battery

Na3V2(PO4)2F3 (NVPF) is considered to be a promising cathode for sodium-ion batteries (SIBs) due to its large theoretical capacity and high average operating voltage. However, the capacity is limited by its low intrinsic electronic conductivity and the inevitable fluorine loss during synthesis. Herein, carbon-coated NVPF composites were successfully synthesized using polytetrafluoroethylene (PTFE) as a carbon source and fluorine supplement agent. The NVP impurity in these carbon-coated NVPF composites was significantly reduced or eliminated. As a cathode material for SIBs, the optimized PTFE-derived carbon-coated NVPF exhibits excellent reversible ca-pacity, superior rate capability, and considerable long-term cycle stability. This simple and feasible modification strategy of using PTFE as a carbon source and fluorine supplement agent can also be extended to Na2FePO4F, LiVPO4F, K3V2(PO4)2F3, and other fluorine-containing polyanionic cathode materials.