Chloride solid-state electrolytes for all-solid-state lithium batteries

Chloride solid-state electrolytes (SSEs) with wide electrochemical windows, high room-temperature ionic conductivity, and good stability towards air have attracted considerable attentions in building solid-state lithium batteries (SSLIBs). Here in this review, we summarized the progress of chloride SSEs, including history, advantages, categories, crystal structures, ion transportation, modification, application, and current limitations. The review began with a brief historical overview along with introducing the advantages of chloride SSEs, followed by summarizing the categorization and physicochemical properties of reported chloride SSEs such as crystal structure and transport mechanisms. We then discussed the synthesis method (solid phase & liquid phase) and modification approaches of chloride SSEs. The heterovalent metal atom, covalent metal atom, and non-metal atom substitution approaches were highlighted due to the improvement of ionic conductivity. Finally, we emphasized the battery application of chloride SSEs, especially with high-voltage LiCoO2 and ternary LiNixCoyMnzO2 cathodes. Through increasing the stability to anode and developing large-scale synthesis methods, chloride SSEs are expected to take important roles in the future SSLIBs market.