Realizing superior cycling stability of Ni-Rich layered cathode by combination of grain boundary engineering and surface coating

Abstract

Ni-rich layered lithium transition metal oxides are promising cathode materials for the next generation high energy density lithium ion batteries. However, high Ni content leads to severe side reactions at cathode/electrolyte interface, coupled with mechanical disintegration significantly degrading the electrochemical performance and safety. Surface coating and grain boundary (GB) engineering can respectively protect surface layer and suppress cracking issue, but direct comparisons of the individual effect of the two methods at different cycling conditions has not been fully explored. Moreover, the two methods have never been coupled together previously, let alone their coupling effect. Herein, we take LiNi0·8Mn0·1Co0·1O2 as a model material and utilize atomic layer deposition coating and annealing protocol to demonstrate the individual and coupling effects of surface coating and GB engineering on cycling stability. GB engineering is found to be more effective than surface coating in enhancing cycling stability due to suppressed intergranular cracks. Promisingly, coupling GB engineering and surface coating, we can achieve superior cycle stability even upon high voltage cycling (91% retention after 200 cycles at 2.7–4.7 V), which demonstrates the importance to simultaneously alleviate surface degradation and bulk disintegration in design of advanced cathode materials.