Selective TiO Nanolayer Coating by Polydopamine Modification for Highly Stable Ni-Rich Layered Oxides.

Ni-rich layered oxides are promising cathode materials for developing high-energy lithium-ion batteries. To overcome the major challenge of surface degradation, a TiO surface coating based on polydopamine (PDA) modification was investigated in this study. The PDA precoating layer had abundant OH catechol groups, which attracted Ti(OEt) molecules in ethanol solvent and contributed towards obtaining a uniform TiO nanolayer after calcination. Owing to the uniform coating of the TiO nanolayer, TiO -coated PDA-LiNi Co Mn O (TiO -PNCM) displayed an excellent electrochemical stability during cycling under high voltage (3.0-4.5 V vs. Li /Li), during which the cathode material undergoes a highly oxidative charge process. In addition, TiO -PNCM exhibited excellent cyclability at elevated temperature (60 °C) compared with the bare NCM. The surface degradation of the Ni-rich cathode material, which is accelerated under harsh cycling conditions, was effectively suppressed after the formation of an ultra-thin TiO coating layer.