Preparation and Improvement of Electrochemical Performance of LiNi0.5Mn1.5O4 Cathode Materials In Situ Coated with AlPO4

In order to reduce the corrosion of LiNi0.5Mn1.5O4 by an electrolyte, an innovative method of in situ coating of AlPO4 was proposed in this paper, which effectively improved the high-temperature cycling performance of the electrode. The effects of AlPO4 coating with different mass fractions on the structure, morphology, and electrochemical properties of LiNi0.5Mn1.5O4 were investigated. Through analysis and testing, it is found that each coating amount has no obvious effect on the spinel structure of the material. When the coating content is 1.0%, the sample has higher capacity, better rate performance, and excellent cycle stability at a high temperature (55 °C). It is also found from the data of the alternating current impedance test that the Li+ diffusion of the material is the most favorable when the coating amount is 1.0%, and the capacity retention rate reaches about 90% after 50 cycles at a 1 C rate. The results show that compared with the traditional coating method, the AlPO4 coating layer of the LiNi0.5Mn1.5O4 material obtained by in situ coating is more uniform (the layer thickness is about 4.2 nm), which more effectively blocks the contact between the LiNi0.5Mn1.5O4 electrode and electrolyte, reduces the erosion of the electrolyte to LiNi0.5Mn1.5O4, inhibits the oxygen loss in the material, and is more conducive to lithium-ion diffusion.