Sulfide-based composite solid electrolyte films for all-solid-state batteries

Abstract All-solid-state batteries with non-flammable solid electrolytes offer enhanced safety features, and show the potential for achieving higher energy density by using lithium metal as the anode. Among various solid electrolytes, sulfides are favored for their high room-temperature ionic conductivity and low-temperature processing. However, making large-scale thin electrolyte films via pressing sulfide powder is still challenging. A polymer has recently been introduced as a binder or framework to obtain a flexible thin sulfide-based composite electrolyte film with high ionic conductivity. In this Review, we initially discuss the ionic transport mechanism of sulfide/polymer composite electrolyte films. Then, the preparation methods and the properties of sulfide-based composite electrolytes are introduced in detail, and the advantages and disadvantages of each method are also analyzed. We later discuss the application of composite electrolyte films in all-solid-state batteries. Finally, we provide a perspective on the future development direction of sulfide-based composite electrolyte films.