Enhanced Cathode Performance: Mixed Al₂O₃ and LiAlO₂ Coating of Li_1.2Ni_0.13Co_0.13Mn_0.54O₂

Li-rich, manganese-based cathode materials are attractive candidates for Li-ion batteries because of their excellent capacity, but poor rate and cycle performance have limited their commercial applications. Herein, Li-rich, manganese-based cathode materials were modified with aluminum isopropoxide as an aluminum source modifier using a sol-gel technique followed by a wet chemical method. To investigate the structure, morphology, electronic state, and elemental composition of both pristine- and surface-modified Li_1.2Ni_0.13Co_0.13Mn_0.54O₂, various characterizations were performed. Based on density functional theory simulations and the results of electrochemical tests, the surface of the modified cathode material was found to contain at least part of the LiAlO₂ phase. This was attributed to the aluminum isopropoxide reacting with a Li₂CO₃/LiOH byproduct on the material surface to form LiAlO₂ with a three-dimensional Li-ion channel structure. Electrochemical testing revealed that a 3 wt % aluminum isopropoxide coating of cathode materials exhibited excellent electrochemical performance. Furthermore, the initial Coulombic efficiency and discharge capacity at 0.1 C were up to 88.55% and 272.7 mAh g^-1, respectively. A final discharge capacity of 186.4 mAh g^-1 was achieved, corresponding to a capacity retention of 83.55% after 300 cycles at 0.5 C. This was attributed to LiAlO₂ partially accelerating the diffusion of Li ions and Al₂O₃ aiding the avoidance of side reactions in the mixed coating layer by partially protecting the structure.