STRATEGIES FOR POLYSULFIDE CONVERSION CATALYSIS ENHANCEMENTS IN LITHIUM-SULFUR BATTERIES

Abstract

The catalysis of polysulfide conversion reactions is an effective approach to improve the performance of lithium-sulfur batteries. While conventional wisdom emphasizes on the search for better catalysts, very few studies have considered the impact of battery operation on polysulfide catalysis, such as the difficulty of catalyzing solid S/Li2S, the limitations of single catalyst design, and gradual catalyst deactivation during battery cycling. This thesis aims to maximize the polysulfide catalysis outcome by introducing a mediator-assisted catalysis to circumvent the challenge of catalyzing solid S/Li2S; designing a co-catalyst system for stepwise catalysis to reduce as many rate-limiting steps in the overall catalysis as effectively possible; tuning the electrolyte with additives that can refresh the catalyst surface for a more sustained catalysis outcome; and finally combining the stepwise catalysis with a redox-matched mediator in a gelled sulfur cathode as an integrated system to simultaneously address these operational issues.