Crucial Challenges and Recent Optimization Progress of Metal–Sulfur Battery Electrolytes

Abstract

By virtue of environmental friendliness, low cost, and the high theoretical capacity of sulfur (1675 mAh/g), metal–sulfur batteries (MSBs), as promising next-generation rechargeable cells, have attracted ever-increasing attention from both academic and industrial fields. Despite good progress, however, thus far MSBs have been rarely able to bring their energy storage performance up to the needed levels of reliability due to challenging issues such as the shuttle effect of polysulfides, low utilization efficiency of the S, inferior cycling performance, and safety hazards. To tackle this, the rational optimization of the electrolyte, which tremendously affects the cycling stability, rate capability, lifespan, and safety of the investigated batteries, is considered to be one of the crucial directions to improve the performance of MSBs. Herein we outline the challenges and recent optimization progress on electrolytes in MSBs with Li, Na, Mg, Ca, K, and Al as metal anodes. The topics regarding the fundamentals of electrolyte optimization strategies and the possible solution to further performance improvement are highlighted. Finally, a perspective on further electrolyte development is presented. This discussion aims at gaining good insight into the rational design of electrolytes so as to boost the commercial process of MSB development.