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.

Exploration of the Unique Structural Chemistry of Sulfur Cathode for High‐Energy Rechargeable Beyond‐Li Batteries

“…Electrolyte plays an essential role in the kinetic reaction of metal-sulfur electrochemistry. [262][263][264][265] The ionic conductivity of the electrolyte enhances the facilitation of ions and electrons, with influence on the dissolution of soluble polysulfides into the bargain. [266,267] However, the degradation of electrolytes in a cell is inevitable due to the formation of insoluble polysulfides and solid electrolyte interface (SEI).…”

Recent Advancements on Biopolymer‐ Based Flexible Electrolytes for Next‐Gen Supercaps and Batteries: A Brief Sketch

“…Moreover, copious amount of elemental sulfur present in the earth with its non‐toxic and eco‐friendly trait marks itself as a potential choice to be employed in environment‐friendly ESD [98] . Restrains because of which up‐scaling the applications employing Li−S batteries [99] is not achievable quite easily include low electronic conductivity of sulfur and most importantly, the large volume expansion occurring during lithiation/de‐lithiation process which in‐turn reduces the capacity bringing about poorer rate performance along with a lower coulombic efficiency [100] . Another dreadful problem that limits the scale‐up of Li−S batteries [101] is the formation of polysulfides that evolve as intermediates in charge/discharge processes which gets easily dissolved in liquid electrolyte, subsequently getting reduced and deposited on lithium anode as Li 2 S 2 and Li 2 S leading to an irreversible loss of capacitance, also termed the “shuttle effect”.…”

Recent Advances in Emerging Non‐Lithium Metal–Sulfur Batteries: A Review

“…For instance, carbonaceous materials with various micro-nanostructures have been designed and constructed as sulfur hosts for non-lithium MSBs, thus resulting in good electrochemical performance. [29] In addition, myriads of efforts have been devoted to the exploration of new electrolytes, [30][31][32][33] modulation of metal anodes, [34][35][36] and modification of separators. [37][38][39] Strategies to mitigate the issues faced by metal anodes have been extensively reviewed, and as such, this review will refrain from reiterating this aspect of the field.…”