Simultaneous Enhancement of Interfacial Stability and Kinetics of Single-Crystal LiNi_0.6Mn_0.2Co_0.2O₂ through Optimized Surface Coating and Doping

Abstract

Balancing interfacial stability and Li⁺ transfer kinetics through surface engineering is a key challenge in developing high-performance battery materials. Although conformal coating enabled by atomic layer deposition (ALD) has shown great promise in controlling impedance increase upon cycling by minimizing side reactions at the electrode-electrolyte interface, the coating layer itself usually exhibits poor Li⁺ conductivity and impedes surface charge transfer. In this work, we have shown that by carefully controlling postannealing temperature of an ultrathin ZrO₂ film prepared by ALD, Zr⁴⁺ surface doping could be achieved for Ni-rich layered oxides to accelerate the charge transfer yet provide sufficient protection. Using single-crystal LiNi_0.6Mn_0.2Co_0.2O₂ as a model material, we have shown that surface Zr⁴⁺ doping combined with ZrO₂ coating can enhance both the cycle performance and rate capability during high-voltage operation. Surface doping via controllable postannealing of ALD surface coating layer reveals an attractive path toward developing stable and Li⁺-conductive interfaces for single-crystal battery materials.