Optimization of Fe/Mn Content Ratio of LiMn(1–x)FexPO4 Cathodes by Experiment and Calculation

Optimizing the Fe/Mn content ratio to obtain a balanced and satisfactory electrochemical performance is necessary. This research is carried out through the method of combining first-principles calculation and experiment. The calculated results show that the LiMn0.5Fe0.5PO4 cathode presents well-balanced structural stability and excellent charge transfer characteristics. The experimental results show that the increase of Mn content decreases the rate capability and cycle life of the cathode, which is attributed to the slowing of the electrochemical kinetics of the cathode by Mn atoms. The increase in Mn content improves the Li ion diffusion coefficient of the cathode due to the reduction of the Li ion de-embedding energy barrier. When the Fe/Mn ratio is 1, the LiMn0.5Fe0.5PO4 cathode exhibits the highest energy density of 534.7 Wh·kg-1 and the lowest redox voltage gap (174 mV) at a 0.1 C rate, along with the lowest redox voltage gap and well-balanced rate capability and cycling stability.