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

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.