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

Lithium ion solid electrolyte Li7La3Zr2O12 (LLZO) coated LiMn1.95Ni0.05O3.98F0.02 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 LiMn1.95Ni0.05O3.98F0.02 cathode materials was investigated by XRD, SEM, TEM and electrochemical tests. The results showed the coating did not change the spinel structure of LiMn1.95Ni0.05O3.98F0.02 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.