Recent progress in surface coating of layered LiNixCoyMnzO2 for lithium-ion batteries

•A comprehensive overview of various strategies for surface coating.•Unique classification from coating mechanisms: enhancing electronic, ionic conductivity.•Further insight into searching for future surface coating for layered NCM.

Layered LiNixCoyMnzO2 exhibits high capacity and energy density with low cost for lithium-ion batteries. However, the poor rate capability and strong capacity fading with prolonged cycles, which are mainly attributed to undesired side reactions at the interface between electrode and electrolyte, plague its practical applications. Surface coating is a facile and feasible strategy to address these problems. An ideal coating layer can prohibit these side reactions via acting like a physical protection barrier to avoid the direct contact with reactive electrolyte, leading to suppressed transition metals' dissolution, oxygen loss, phase transformation and safety issues. The ionic/electronic conductivity, structural and thermal stability can be manipulated by careful selection of coating materials. This work aims to overview the recent studies in surface coating of LiNixCoyMnzO2 from the perspective of improving the electronic or/and ionic conductivity. Also, current critical challenges and insight into future research outlooks are presented in detail.

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