Polymer-based electrolytes for all-solid-state lithium–sulfur batteries: from fundamental research to performance improvement

With the increasing demand for a higher energy density and a lower cost energy storage system, lithium–sulfur batteries have become one of the promising candidates to replace current Li-ion batteries. However, in liquid electrolyte systems, the lithium dendrite growth and the shuttle effect cause severe safety hazard as well as capacity decay, which hinders the commercialization of practical lithium–sulfur batteries. Polymer-based electrolytes provide a promising solution to these challenges. This type of electrolyte, including polymer and composite polymer electrolytes, demonstrates the capabilities to prevent polysulfide dissolution and suppress lithium dendrite growths, while ensuring good surface contact and high flame resistance. This review summarizes the most recent progress of polymer-based all-solid-state lithium–sulfur batteries (ASSLSB), which revealed mechanisms and challenges of electrolyte ionic conductivity, reaction mechanism, anode/electrolyte interface, and cathode/electrolyte interface. Based on these revealed principles, possible solutions to these challenges such as the addition of inorganic fillers, interface modification, utilization of different types of lithium salt and polymers are introduced. In addition, the state-of-the-art approaches with great performance improvement are highlighted in this review. Finally, we provide perspectives on research directions that can further the understanding and development of polymer-based ASSLSB.