Enhancing the performance of NaVPO4F cathode materials for sodium-ion batteries through graphite incorporation and polyethylene glycol 6000 modification

Abstract

NaVPO₄F has become a focal point in the realm of sodium-ion battery cathode materials owing to its robust structure, elevated voltage platform, and considerable theoretical capacity. Nonetheless, the limited conductivity of NaVPO₄F poses a challenge to its practical utilization. In this study, we introduce a straightforward one-step ball milling process to address this issue by creating NaVPO₄F/G (G stands for graphite) and enhancing electronic conductivity through the incorporation of polyethylene glycol 6000 (PEG6K). Graphite has the capability to enhance electrochemical properties and markedly enhance electronic conductivity. Furthermore, the incorporation of PEG6K can enhance the transport stability of sodium ions at the interface of sodium-ion batteries. After optimization, NaVPO₄F/G@P (P stands for PEG6K) delivers a high capacity of 128.5 mA h g⁻¹ at 0.2C and a high rate capacity of 105.0 mA h g⁻¹ at 10C, with a capacity retention rate of 116.0 mA h g⁻¹ after 200 cycles. Moreover, when coupled with a HC anode (HC as the negative electrode), the full cell still displays an outstanding performance of 76.0 mA h g⁻¹ at 20C. A simple approach is provided in our study that has the potential to significantly improve the performance of sodium-ion batteries.