Nb Doping Enhancing Structure Stability and High‐Temperature Electrochemical Performances of LiFe0.5Mn0.5PO₄ Cathode Material in Lithium‐Ion Batteries

The application of LiFe 1− y Mn y PO 4 (0 < y < 1) cathode materials with high voltage and high specific energy for lithium‐ion batteries is restrained by capacity decay, structure degradation, and low Li + /electronic conductivity, especially at high temperature. In this study, the Nb 5+ ‐doped olivine‐structured LiFe 0.5 Mn 0.5− x Nb x PO 4 (LFMP‐ x Nb, x = 0%, 0.5%, 1%, 2%, and 3%) are synthesized and characterized using X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, infrared spectroscopy, X‐ray photoelectron spectroscopy, and electrochemical techniques. The lattice parameters ( a , b , c , and V ), PO and TMO bond lengths, and particle size are reduced with Nb doping, and the structure stability, electronic/Li + transport rate, and electrochemical performances are improved. The preferred LFMP‐1%Nb sample delivers an initial discharge specific capacity of 160.57 mAh g −1 at 0.1 C with a coulombic efficiency of 91.38%, and a specific capacity of 91.23 mAh g −1 at 10 C, and a capacity retention rate of 78.71% with a residual capacity of 106.10 mAh g −1 after 1000 cycles at 1 C. Especially at 55 °C temperature, it can give a discharge specific capacity of 142.9 mAh g −1 and a capacity retention rate of 73.14% after 1000 cycles at 1 C.