A multiphase sodium vanadium phosphate cathode material for high-rate sodium-ion batteries

The unsatisfactory rate capability and poor cycling stability at high rate of sodium-ion batteries (SIBs) have impeded their practical applications. Herein, a Na3V2(PO4)3/Na3V3(PO4)4 multiphase cathode materials for high-rate and long cycling SIBs was successfully synthesized by regulation the stoichiometric ratio of raw materials. The combined experiment and simulation results show that the multiphase materials consisted of NASICON structural phase Na3V2(PO4)3 and layered structure phase Na3V3(PO4)4, possess abundant phase boundaries. Electrochemical experiments demonstrate that the multiphase materials maintain a remarkable reversible capacity of 69.0 mA h g−1 even at an ultrahigh current density of 100 C with a high capacity retention of 81.25 % even after 10,000 cycles. Na3V2(PO4)3/Na3V3(PO4)4 electrode exhibits a higher working voltage, superior rate capability and better cycling stability than Na3V2(PO4)3 electrode, which indicates that the introduction of second phase can be an effective strategy for the development of novel cathode materials for SIBs.