Electronegative Co-WO₂ Interface with Li⁺ Pump Effects for Efficient Polysulfide Conversion in High-Performance Li-Sulfur Batteries.

Abstract

Catalyzing the polysulfide conversion process has become an effective paradigm for alleviating the shuttle effect and realizing reliable Li-S batteries. Although great improvements in designing highly active polysulfide catalysts have been achieved, the transfer of Li⁺ at the catalytic interface, which has a great influence on the reversible redox of sulfur, has not been addressed. Herein, we proposed the multimodal strategy of catalysts confers atomic Co active sites on WO₂, where the electronegative interfacial O atoms can act as Li⁺ pump and assist the rapid migration of Li⁺ in the electrolyte to polysulfide anchored at the Co sites during the discharge process and reduce oxidation energy barrier of Li₂S during the charge process, thus facilizing the lithiation/delithiation of polysulfides. Experimental and theoretical results reveal that more Li⁺ ions can be gathered around Co sites, and the length of Li-S bonds in Li₂S can be reduced in the Co-WO₂ catalysts, implying the efficient dual-direction conversion of polysulfides. Therefore, the cell assembled with Co-WO₂ exhibits long-term cycle stability (0.038% per cycle) at 1.0 C.