A new sodium vanadyl fluorophosphate as a high-rate and stable cathode for aqueous hybrid sodium–zinc batteries

Abstract

Herein, a facile solvothermal method is used to prepare a new polyanion-type sodium vanadyl fluorophosphate (Na_x(VO)₂(PO₄)_yF_z) for aqueous hybrid sodium–zinc batteries. The novel cathode delivers superior performance, which includes a high specific capacity of 87.2 mA h g⁻¹ at 0.05 A g⁻¹, good rate capability of 41.5 mA h g⁻¹ at 2 A g⁻¹, and high capacity retention. Based on ex situ XRD and XPS results, the Na⁺/Zn²⁺ co-insertion mechanism is proposed.