Catalytic Activity of Co-X (X = S, P, O) and Its Dependency on Nanostructure/Chemical Composition in Lithium-Sulfur Batteries

Recently, cobalt-based polar materials with an unique catalytic behavior have been discovered and have shown promising electrochemical performance in lithium-sulfur (Li-S) batteries. However, there is lack of consensus on the relationship between catalytic activity and composition of different polar materials. Inconsistencies in morphologies, chemical compositions, and testing conditions lead to disparate results from laboratory to laboratory. To this end, we use zeolitic imidazolate frameworks (ZIF-67) nanosheets derived CoS2, CoP, and Co3O4 with nearly identical morphology and nanostructure to study the compositional effects on their catalytic activities and chemical absorption abilities. Combining with density functional theory calculations and electrochemical screening, we are able to confirm that CoS2 has the highest adsorption energy with polysulfides as well as the strongest catalytic activity toward polysulfides. We believe this work can inspire a more rational way to design efficient catalysts for Li-S batteries.