Atomic-layer-deposited Ru-RuOx mixed protective layer for improving ionic-electronic conductivity of sintered LiCoO2 cathode in Li-ion batteries

Abstract

The use of high-density three-dimensional sintered (HTS) cathode plates is a promising approach for increasing the energy density of Li-ion batteries. However, their performances are limited by the absence of conducting agents and interfacial side reactions. In this study, a Ru-RuOx mixed protective layer (RRML) is conformally deposited on HTS-LiCoO2 (LCO) via atomic layer deposition and employed as a mixed ionic-electronic conducting protective layer. Physicochemical analyses reveal the formation of a Ru-RuOx solid solution at a 5 nm thickness without post-treatment. The full-cell evaluation demonstrates that the RRML-coated HTS-LCO electrode exhibits approximately twice the cycle life (80% capacity retention at 1 C) of the uncoated HTS-LCO. This study demonstrates that the RRML coating enables simultaneous ionic and electronic conduction and interfacial stabilization.