In situ formed lithium ionic conductor thin film on the surface of high-crystal-layered LiCoO2 as a high-voltage cathode material

Abstract

The layered LiCoO₂ cathode plays a key role in high-energy-density lithium-ion batteries (LIBs), delivering a capacity of ∼185 mA h g⁻¹ at a high cut-off voltage of 4.5 V (vs. Li/Li⁺). However, its practical applications in high-voltage LIBs are limited by a severe side reaction and an irreversible structure transition during cycling. Herein, we report a facile surface coating technique to prepare the Li₄SiO₄-coated LiCoO₂ composite (LiCoO₂@Li₄SiO₄) to confront the issue of instability and increase the capacity of the LiCoO₂ cathode at 4.5 V. Notably, the LiCoO₂@Li₄SiO₄ electrode exhibits an exceptionally high initial discharge capacity (180.7 mA h g⁻¹ at 0.1 C), a significantly enhanced rate capability (147.2 mA h g⁻¹ at 5 C), and long-term cycling stability (capacity retention of 82.2% after 500 cycles at 2 C). The experimental results demonstrate that the Li₄SiO₄ coating could effectively reinforce the structural stability of the LiCoO₂@Li₄SiO₄ electrode during cycling. Furthermore, the density functional theory calculation results further confirm that the Li₄SiO₄ coating facilitates the rapid Li⁺ diffusion at the LiCoO₂@Li₄SiO₄ electrode. This work provides a potential strategy for interface engineering of the 4.5 V LiCoO₂ cathode for high-energy-density LIBs.