Research Progresses on Flexible Sulfide Solid Electrolytes

Solid-state lithium batteries with solid electrolytes are expected to enhance the battery safety and energy density as one of the most promising next-generation batteries. Among various solid-state electrolytes, sulfide solid electrolyte is considered as promising candidate due to its ultra-high ionic conductivity. However, its large-scale production is restricted due to its fragility and difficulty in processing, which affects its application in solid-state batteries. Recent work indicates that the flexibility of solid electrolytes can be realized via introducing flexible polymers or supporting frameworks in solid electrolytes membranes, constituting a solution to the embrittlement challenge in large-scale and thin-film electrolyte preparations. Therefore, developing flexible solid electrolytes is one of the important strategies to promote the industrialization of solid-state batteries. This review introduced the physical/chemical properties and development of sulfide solid electrolytes, summarized the related research work on polymer self-supporting method and flexible skeleton-supporting method in the flexibility of solid electrolytes, and discussed the technical characteristics and advantages/disadvantages of wet/dry processes in the flexible sulfide solid electrolyte preparation, respectively. In addition, the future development aspects were also given to promote the practical application of solid-state lithium batteries.