2D-lamellar stacked Na3V2(PO4)2F3@RuO2 as a high-voltage, high-rate capability and long-term cycling cathode material for sodium ion batteries

Abstract

Uniform two-dimensional (2D)-lamellar stacked Na₃V₂(PO₄)₂F₃@RuO₂ has been successfully synthesized for the first time. As a cathode material for sodium ion batteries, it exhibits high-voltage efficiency with an 87.3% reversible capacity over 3.5 V. Furthermore, it shows high-rate capability with 115.8 mA h g⁻¹ at 20C, and a long-term cyclability with the reversible capacity maintained at 89.5 mA h g⁻¹ even after 1000 cycles. The electrochemical impedance spectroscopy result indicates that the charge transfer resistance decreases and the sodium-ion diffusion coefficient dramatically increases for Na₃V₂(PO₄)₂F₃@RuO₂ compared to Na₃V₂(PO₄)₂F₃. In addition, we have investigated the effect of HNO₃ concentration on the structure and electrochemical performance of Na₃V₂(PO₄)₂F₃. It is expected that this approach paves the way for designing cathode materials with outstanding performance.