Enhanced cyclic stability of LiNi0.8Co0.1Mn0.1O2 (NCM811) by AlF3 coating via atomic layer deposition

LiNi0.8Co0.1Mn0.1O2 (NCM811) is a promising cathode material for lithium-ion batteries due to its high energy density and low cost. However, NCM811 suffers from poor cycling stability and storage sensitivity to air and moisture. This study introduces an AlF3 protective layer onto the surface of NCM811 (NCM811-AlF3) by atomic layer deposition (ALD). After the AlF3 layer protection, the initial capacity of the quasi-solid-state pouch cell with the NCM811 cathode was significantly increased from 148 to 180 mAh g−1. In addition, NCM811-AlF3 maintained a capacity of 167 mAh g−1, which exceeded that of pristine NCM811 (126 mAh g−1) after 500 cycles. This excellent electrochemical performance is attributed to the conformal AlF3 protective layer that prevents the NCM811 from coming into direct contact with the electrolyte. In addition, the AlF3 protective layer can prevent the Li/Ni mixture and Li loss during cycling by limiting the lattice expansion. Moreover, it can suppress the generation of residual alkali on the NCM811 surface during storage, improving the interfacial stability between NCM811 and the electrolytes. These results indicate that AlF3 protective layer by ALD can be an effective method for improving the performance of high-energy–density cathode materials.