Refined Grain Enhancing Lithium-Ion Diffusion of LiFePO4 via Air Oxidation

LiFePO4 is a type of cathode material with good safety and long service life. However, the problems of the low Li ion diffusion rate and low electron conductivity limit the application of LiFePO4 in the field of electric vehicles. In this paper, FePO4 with different grain sizes was prepared via the air oxidation precipitation method and then sintered to prepare LiFePO4. The refined grain can shorten the diffusion distance of Li+, accelerate the diffusion of Li+, and improve the diffusion coefficient of Li+. The results show that LiFePO4 with a smaller grain size has better electrochemical performance. The discharge capacity of the first cycle is 151.3 mAh g−1 at 1 C, and the capacity retention rate is 95.04% after 230 cycles. Its rate performance is more outstanding, not only at 0.2 C, where the discharge capacity is as high as 155 mAh g−1, but also at 10 C, the capacity fade is less, and it can still reach 131 mAh g−1. The air oxidation precipitation method reduces the production cost, shortens the production process, and prepares FePO4 with small grains, which provides a reference for further improving the properties of precursors and LiFePO4.