LAUSR

Aqueous sodium-ion batteries (ASIB) offer many potential applications in large-scale power grids since they are inexpensive, safe, and environmentally friendly. Natrium superionic conductors (NASICON), especially carbon-coated Na3V2(PO4)3 (NVP), have attracted much attention due to the full use of their high ion migration speed. However, the poor cycle lifespan and capacity retention of NVP hinder its application in ASIB. Herein, a novel bimetal-doped Na3V1.3Fe0.5W0.2(PO4)3 (NV1.3Fe0.5W0.2P) cathode was designed and synthesized to achieve outstanding cycling stability (95% of initial capacity at 50th cycle). The electrochemical behavior and charge storage mechanism of NV1.3Fe0.5W0.2P are systematically investigated by various in-situ and ex-situ characterizations. The Fe and W codoping could stabilize the NASICON framework to suppress the attack of proton on the Na site in the aqueous electrolyte, thus resulting in excellent cycling stability. DFT calculations show that the vanadium is protected by bimetals. Moreover, an ASIB fabricated by NV1.3Fe0.5W0.2P cathode and Na1Ti2(PO4)3 anode delivers 64 mAh g-1 at room temperature, 95% capacity retention after 50 cycles (1 A g-1).