Surface engineering for high voltage LiCoO2 in halide all-solid-state lithium-ion batteries

Abstract

All-solid-state lithium-ion batteries (ASSLIBs) have obtained more and more attention due to their inherent safety and high energy density. Halide solid electrolytes are one of the ideal candidates for ASSLIBs due to their high ionic conductivity, wide electrochemical window, and outstanding compatibility with oxide cathode materials. However, the contact interface issues between the oxide cathode and halide electrolyte and undesirable side-reaction under high voltage remain to be solved. Herein, we report an approach to stabilize the interface between high-voltage LiCoO₂ and Li₃InCl₆ solid electrolyte with a nanostructured Li₂SiO₃ coating using a simple sol-gel method. The Li₂SiO₃ coating layer with a similar layered structure to the LiCoO₂ shows an impressive ion conductivity. The uniform Li₂SiO₃ buffer layer between LiCoO₂ and Li₃InCl₆ suppresses the irreversible structural transition of the cathode active material and avoids interfacial by-product from the side-reaction at high voltage. Encouragingly, ASSLIBs with the Li₂SiO₃ coated LiCoO₂ displayed a high reversible discharge capacity of 193.4 mAh g⁻¹ and a superior capacity retention of 81 % after 250 cycles at 4.6 V.