Effects of Fe doping on the electrochemical performance of LiV 1− x Fe x PO 4 F/C ( x  = 0, 0.01, 0.02, 0.04) cathode materials for lithium‐ion batteries

The Fe‐doped LiVPO 4 F/C cathode material was synthesized by a one‐step solid‐state reaction method. The effects of Fe doping content on the structure and electrochemical performance of LiVPO 4 F/C were investigated. X‐ray diffraction (XRD) analyses demonstrated that the appropriate addition of Fe 3+ did not destroy the lattice structure of LiVPO 4 F/C. Scanning electron microscopy (SEM) showed that the surface of LiVPO 4 F/C is covered by a carbon film. The decreased grain size of the Fe‐doped LiVPO 4 F/C could shorten the ion transport path and thus improve the migration rate of lithium ions. X‐ray photoelectron spectroscopy (XPS) showed that the Fe ion exists in the Fe‐doped LiVPO 4 F/C as Fe 3+ ion. At the discharge rate of 1 C, the initial discharge capacity and capacity retention rate of the LiV 0.98 Fe 0.02 PO 4 F/C after 500 cycles were 123.5 mAh/g and 88.6%, respectively.