A high rate and stable electrode consisting of a Na3V2O2X(PO4)2F3−2X–rGO composite with a cellulose binder for sodium-ion batteries

Abstract

Sodium ion batteries are a promising alternative to conventional lithium-ion batteries, mostly for large scale energy storage applications. In this paper, we report sodium vanadium oxy-fluorophosphate as a cathode material for sodium-ion batteries with 8.0 wt% reduced graphene oxide (rGO), synthesized via solid state reaction followed by a hydrothermal method. The newly reported Na₃V₂O_2X(PO₄)₂F_3−2X–rGO (NVOPF–rGO) composite with a hydrophilic carboxymethyl cellulose sodium (CMC-Na) binder shows enhanced rate performance and highly stable cyclability; it delivers a stable reversible capacity of 108 mA h g⁻¹ in a sodium half-cell, and it exhibits 98% capacity retention at a 0.1C rate over 250 cycles. Furthermore, the as-prepared NVOPF–rGO composite exhibits discharge capacities of 98 mA h g⁻¹ and 64 mA h g⁻¹ at 0.2C and 2C rates, respectively, in a full-cell configuration with a NaTi₂(PO₄)₃–MWCNT (NTP–M) anode for 1000 cycles.