Emerging sulfide-polymer composite solid electrolyte membranes

Sulfide solid electrolytes with an ultrahigh ionic conductivity are considered to be extremely promising alternatives to liquid electrolytes for next-generation lithium batteries. However, it is difficult to obtain a thin solid electrolyte layer with good mechanical properties due to the weak binding ability between their powder particles, which seriously limits the actual energy density of sulfide all-solid-state lithium batteries (ASSLBs). Fortunately, the preparation of sulfide-polymer composite solid electrolyte (SPCSE) membranes by introducing polymer effectively reduces the thickness of solid electrolytes and guarantees high mechanical properties. In this review, recent progress of SPCSE membranes for ASSLBs is summarized. The classification of components in SPCSE membranes is first introduced briefly. Then, the preparation methods of SPCSE membranes are categorized according to process characteristics, in which the challenges of different methods and their corresponding solutions are carefully reviewed. The energy densities of the full battery composed of SPCSE membranes are further given whenever available to help understanding the device-level performance. Finally, we discuss the potential challenges and research opportunities for SPCSE membranes to guide the future development of high-performance sulfide ASSLBs.