Polysulfide Tandem Conversion for Lithium–Sulfur Batteries

Abstract

The electrocatalytic conversion of 16-electron multistep polysulfides is crucial for lithium–sulfur batteries, while it is hard to achieve compatibility between intricate sulfur reduction processes and appropriate catalysts. Herein, a tandem conversion strategy is reported to boost multi-step intermediate reactions of polysulfides transformation by designing an electrocatalyst featuring cobalt and zinc sites (Co/Zn), where the Zn serve as sites for the conversion of long-chain lithium polysulfides (LiPSs), promoting the transformation of S₈ to Li₂S₄; the Co sites accelerate the kinetics of the subsequent reduction of Li₂S₄. This tandem catalysis method not only enhances the conversion of the initial reactants but also provides additional support for the intermediates, thereby facilitating subsequent reactions to maximize capacity. Consequently, the cell utilizing this precise electrocatalyst delivers a high initial discharge-specific capacity of 1347.5 mAh g⁻¹ at a rate of 0.1 C, demonstrates outstanding rate performance (796.8 mAh g⁻¹ at 3 C), and excellent cycle stability with a capacity attenuation rate of 0.086% per cycle at 3.0 C. These results offer insights into the coordinated design of electrocatalysts for sulfur cathodes based on precise catalytic sites and complex multi-step conversion reactions.