Enhanced rate and cyclability of a porous Na3V2(PO4)3 cathode using dimethyl ether as the electrolyte for application in sodium-ion batteries

Abstract

Sodium vanadium phosphate (NVP) is a potential cathode material for sodium-ion batteries, but its rate capability requires improvement. Herein, the electrode–electrolyte interface is modified using dimethyl ether (DME) electrolyte, such that the porous NVP cathode leads to ultrafast kinetics and ultra-long cycle life in comparison to those observed using conventional ethylene carbonate/propylene carbonate electrolytes. The rate capability and cycle life are the highest reported to date. The Na/NVP half-cell with DME affords good capacity (44 mA h g⁻¹ at 100 A g⁻¹; 854C) and stable ultra-long cycle life for 95 000 cycles with a negligible degradation rate (5.8 × 10⁻⁵ % per cycle at 50 A g⁻¹, i.e., 1.05 Na⁺ reversibly reacts with NVP within 4.5 s). The NVP full cell coupled with a Sn anode delivers a reversible capacity of 70 mA h g⁻¹ at 10 A g⁻¹ for 5000 cycles with 100% coulombic efficiency. After 5000 cycles, the energy density is 217 W h kg⁻¹ and the power density is 30 985 W kg⁻¹ (based on NVP mass). The DME electrolyte effectively modifies the interface for fast kinetics both as a half-cell and a full cell. This simple strategy can be extended to other battery systems to achieve fast kinetics.