Graphene-Based Sulfur Cathodes and Dual Salt-Based Sparingly Solvating Electrolytes: A Perfect Marriage for High Performing, Safe, and Long Cycle Life Lithium-Sulfur Prototype Batteries

Abstract

The growing requirements for electrified applications entail exploring alternative battery systems. Lithium-sulfur batteries (LSBs) have emerged as a promising, cost-effective, and sustainable solution; however, their practical commercialization is impeded by several intrinsic challenges. With the aim of surpassing these challenges, the implementation of a holistic LSB concept is proposed. To this end, the effectiveness of coupling a high-performing 2D graphene-based sulfur cathode with a well-suited sparingly solvating electrolyte (SSE) is reported. The incorporation of bis(fluorosulfonyl)imide (LiFSI) salt to tune sulfolane and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropylether based SSE enables the formation of a robust and compact lithium fluoride-rich solid electrolyte interphase. Consequently, the lithium compatibility is improved, achieving a high Coulombic efficiency (CE) of 98.8% in the Li||Cu cells and enabling thin and dense lithium depositions. When combined with a high-performing 2D graphene-based sulfur cathode, a symbiotic effect is shown, leading to high discharge capacities, remarkable rate capability (2.5 mAh cm−2 at C/2), enhanced cell stability, and wide temperature applicability. Furthermore, the scalability of this strategy is successfully demonstrated by assembling high-performing monolayer prototype cells with a total capacity of 93 mAh, notable capacity retention of 70% after 100 cycles, and a high average CE of 99%.