Low Concentration Electrolyte Enabling Cryogenic Lithium-Sulfur Batteries

Lithium-sulfur chemistry suffers from poor conversion reaction kinetics, causing low-capacity utilization of sulfur cathodes, particularly at cryogenic temperatures. Herein, based on low-cost and abundant commercial sulfur particles directly, a low concentration electrolyte (LCE, 0.1 m) is employed to accelerate lithium-sulfur conversion reaction at low temperatures, demonstrating a broad applicability of this approach. Compared to conventional concentration (1.0 m) electrolytes, the proposed LCE successfully enhances conversion kinetics from Li2S4 to Li2S and restrains shuttle effects of polysulfides, resulting in higher capacity utilizations and more stable cycle performance at 0 and -20 degrees C. Further interfacial chemistry analyses on cycled electrodes reveal that a hybrid surface layer dominated by organic species as well as some favorable inorganics is constructed in the LCE, demonstrating smaller surface layer resistance. In situ EIS measurements at 0 degrees C and CV tests reveal main differences of electrode kinetics in 0.1 and 1 m electrolytes, further explaining the differences in working mechanism of two electrolytes. These findings elucidate the roles of LCEs on realizing faster kinetics for cryogenic lithium-sulfur batteries and provide a simple, low-cost, and widely applicable pathway for achieving high-performance lithium-sulfur batteries under extreme conditions.

Automated summary

This study demonstrates that using a low concentration electrolyte can accelerate lithium-sulfur conversion reactions at low temperatures, leading to higher capacity utilization and more stable cycle performance. The interfacial analysis and battery tests show that the low concentration electrolyte can construct a more effective surface layer and suppress shuttle effects of polysulfides.