Effect of the morphology of Li–La–Zr–O solid electrolyte coating on the electrochemical performance of spinel LiMn1.95Ni0.05O3.98F0.02 cathode materials

Abstract

Lithium ion solid electrolyte Li₇La₃Zr₂O₁₂ (LLZO) coated LiMn_1.95Ni_0.05O_3.98F_0.02 cathode materials with controllable coating morphology were prepared via a sol–gel route and subsequently heat treated at different temperatures. The effect of the morphology of Li–La–Zr–O solid electrolyte coating on the electrochemical performance of spinel LiMn_1.95Ni_0.05O_3.98F_0.02 cathode materials was investigated by XRD, SEM, TEM and electrochemical tests. The results showed the coating did not change the spinel structure of LiMn_1.95Ni_0.05O_3.98F_0.02 cathode materials, as the atoms of coating material can only adhere to the surface of the octahedral grain rather than enter the spinel lattice. Heat annealing temperature has a significant effect on the microstructure of the LLZO coating layer. At a lower heat annealing temperature (400 °C), the coating forms a reticulation, whereas at the mid-temperature (600 °C), it exhibits a more uniform and continuous layer; moreover, when the heat treatment temperature increases to a high level (800 °C), the coating exists as discontinuous nanoparticles rather than as a layer. Among all coating forms, the continuous coating layer formed at 600 °C shows the best electrochemical performance.