An effective strategy to control thickness of Al2O3 coating layer on nickel-rich cathode materials

Controllable uniformity and thickness of the coating layer of oxides on the nickel-rich materials are extremely crucial for optimization of the performance of the materials, due to the poor electronic and ionic conductivity of oxides. In this work, an efficient coating approach is developed based on organic/water two-phase system. The Al2O3-coated LiNi0.8Co0.1Mn0.1O2 with uniform and controlled thickness of the coating layer can be prepared by adjusting the amount of water used in the organic/water mixture, where aluminum isopropoxide is hydrolyzed in water phase on the surface of the LiNi0.8Co0.1Mn0.1O2 spheres. It is demonstrated that the electrochemical performance of LiNi0.8Co0.1Mn0.1O2 strongly correlates to the thickness of the Al2O3 coating layer. With optimized thickness of the coating layer, the Al2O3-coated LiNi0.8Co0.1Mn0.1O2 can deliver a good initial discharge capacity of 191.3 mAh g−1, although the coated Al2O3 is electrochemically inactive. Importantly, a capacity retention of 95.42% can be achieved for the Al2O3-coated LiNi0.8Co0.1Mn0.1O2 upon 200 cycles at 1C, superior to that of 82.73% for the pristine counterpart. Those are ascribed to the protection effect of the coating layer to LiNi0.8Co0.1Mn0.1O2, to alleviate the side reactions at the electrode/electrolyte interface.