Tailoring the Al distribution in secondary particles for optimizing the electrochemical performance of LiNi0.8Co0.1Mn0.1O2

Ni-rich materials, as one type of cathode materials for next-generation lithium-ion batteries, suffer from poor cycling stability due to severe structural degradation and surface deterioration. Lattice doping is an effective method to stabilize crystal structures, yet it has little effect on inhibiting surface side reactions. Herein, we demonstrate a strategy that can tailor the distribution of doping element Al in the entire secondary sphere in a controllable way to simultaneously stabilize the crystal structure and surface of the cathode material. The strategy takes advantage of the interdiffusion of elements at the solid-solid interface formed by aluminumcontaining species that uniformly cover the surface of the Ni0.8Co0.1Mn0.1(OH)2 precursor at a high temperature. The extent of Al doping in the materials can be properly regulated by the amount of aluminum-containing species to generate uniform doping, gradient doping, and gradient doping with a thin Al coating layer. As a result, the Al gradient-doped cathode material exhibits excellent capacity retention of 81.9% after 500 cycles at 2C, which is much higher than the capacity retention of 54.3% for the pristine counterpart.