Zn-doping Na3+xV2-xZnx(PO4)2F3/C cathodes for sodium ion batteries

To enhance the electrochemical performance of NVPF, a dual modification strategy involving carbon coating and Zn doping is employed to fabricate Na_3+xV_2-xZn_x(PO₄)₂F₃/C (X=0.01, 0.03, 0.05, 0.07) composite cathodes for sodium-ion batteries. Among these, the Zn²⁺ doping ratio of x=0.03 (denoted as NVPF-Zn03) exhibited the best performance, significantly enhancing the structural stability of the NVPF cathode material during cycling and improving its cycle life under high-rate cycling conditions. Furthermore, it optimized the apparent diffusion kinetics during the oxidation-reduction process. The specific capacities of NVPF-Zn03 at current rates ranging from 0.1C to 10C were respectively 132.9, 134.6, 134.4, 128.6, 116.2, 85.3, and 55.1mAh·g^-1. Notably, after 1000 cycles at an ultra-high current rate of 10C, it still maintained a discharge capacity of 40.60mAh·g^-1, with a maximum capacity retention rate of 59.9%, significantly higher than that of the undoped sample. This study provides valuable guidance for the doping and modification of NVPF.