Improved sodium storage properties of co-doped Na3V2(PO4)2F3@graphene as anode material for sodium ion batteries

In this paper, Co-doped Na3V2−xCox(PO4)2F3(x = 0,0.1,0.5,0.7) sodium ion battery anode material was prepared by one-step hydrothermal method, and Na3V1.5Co0.5(PO4)2F3 anode material coated with graphene was also prepared. It is confirmed that moderate Co2+ doping can improve the electrochemical performance of NVPF. Among all samples, Na3V1.5Co0.5(PO4)2F3@Graphene shows the best rate and cycle performance. It exhibits the highest specific capacity of 91.5 and 48.8 mAh/g at 1C, respectively when x = 0.5, after coating graphene, the charge-discharge specific capacities of 1C cycle are 128.2 mAh/g and 63.5 mAh/g for the first time, and 62.2 mAh/g and 45.1 mAh/g for 45 weeks.The performance results show that the excellent electrochemical performance of Na3V1.5Co0.5(PO4)2F3@Graphene can be attributed to the increase in electronic conductivity and ion diffusion coefficient.