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

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.