Solid‐State Li Ion Batteries with Oxide Solid Electrolytes: Progress and Perspective

Solid‐state batteries (SSBs), with desirable safety, high‐energy density, wide temperature tolerance, and simple packaging, are one of the most promising candidates for the next‐generation energy storage technologies. In SSBs, solid‐state electrolytes (SSEs) are the key components to enhance the safety concerns significantly with regard to the flammable organic liquid electrolytes in conventional Li‐ion batteries. To realize the practical SSBs, developing SSEs with high ionic conductivity, wide electrochemical window, and low interface resistance between electrode and electrolyte becomes essential. Among many solid electrolytes, the oxide inorganic SSEs demonstrate high ionic conductivity (10 −3 to 10 −4 S cm −1 ) and good chemical stability against Li metal, which probably hold great promise for high‐performance SSBs. Hence, this review summarizes the recent progress in understanding the oxide SSEs by addressing key issues in materials densification, stability, and electrochemical properties as a guidance to the flourishing SSBs. The critical issues of interface and the opportunities for oxide‐based SSBs are also discussed, where the key issues lie not only in the electrolyte material itself but also in regulating and ameliorating the electrolyte–electrode interface properties. This possibly paves the way to the future development of oxide‐based solid electrolytes and batteries.