"Win‐Win" Modification of LiCoO2 Enables Stable and Long‐Life Cycling of Sulfide‐Based All Solid‐State Batteries

Interfacial side reactions and space charge layers between the oxide cathode material and the sulfide solid-state electrolytes (SSEs), moreover the structural crumble of the active material, seriously jeopardize the electrochemical performance for all-solid-state battery (ASSLBs). Cathodes surface coating and bulk doping are considered to be the most efficacious approaches that moderate the cathode/SSEs interface issues and brace the structure of cathode. Here, a one-step low-cost means is ingeniously designed to embellish LiCoO2 (LCO) with heterogeneous Li2TiO3/Li(TiMg)1/2O2 surface coating and bulk gradient Mg doping (denoted as LMT). When applied in Li10GeP2S12-based ASSLBs, the Li2TiO3 and Li(TiMg)1/2O2 coating layers can suppress interfacial side reactions and weaken space charge layer effect, respectively. On top of this, gradient Mg doping stabilizes the bulk structure to mitigate the formation of spinel-like phases during local overcharging caused by solid-solid contact. The LTM-LCO cathodes exhibits superb cycle performance with a capacity retention of 80% after 870 cycles. This killing-two-birds-with-one-stone strategy provides the possibility for large-scale commercial implementation of cathodes modification in sulfide based ASSLBs in the future.