In-situ modification from surface to bulk for enhancing the performance of NCM811 cathode

LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode material has been widely applied mobile electronics products, electric vehicles, large-scale energy storage and so on. However, it is still necessary to develop a convenient strategy to resolve the challenges resulted from bulk (micro-stress, micro-cracks) to surface (side reactions) for advanced lithium-ion batteries. Herein, we develop a facile in-situ strategy to modify NCM811 with LiAlO2 coating on surface and Al doping in bulk. Especially, the LiAlO2 layer protect the active material from the erosion of air and electrolytes, while Al doping can effectively enlarge lattice spacing, restrain Li+/Ni2+ mixing, and reduces the microcracks within secondary particles. Two aspects significantly improve ambient tolerance, electrochemical performances and thermal stability over the bare counterpart. The optimized Al-modified NCM811 exhibits a discharge capacity of 197.3 mAh g-1 at 0.1 C, a well capability retention of 83.7% at 5.0 C, and a high capability retention of 92.1% after cycling at 1.0 C for 100 times. Furthermore, the exothermic temperatures increase from 271.3 ºC to 277.3 ºC, while the total heat generated from exothermic reactions reduce from 3985.0 J g-1 to 3078.0 J g-1.