t<sub>2</sub> occupancy as a descriptor for polysulfide conversion on spinel oxides.

Xie, Wen; Shen, Zihan; Xi, Shibo; Zhang, Longcheng; Tang, Kai; Ma, Zhenhui; Lu, Chichong; Xu, Zhichuan J · Nat Commun · 2025

basic_science · Level V

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Abstract

Transition metal oxides with partially filled d orbitals serve as effective polysulfide conversion catalysts in lithium-sulfur batteries. Nonetheless, a predictive descriptor to elucidate their structure-activity relationship is still lacking. To fill this gap, here we investigate the occupancy of t<sub>2</sub> orbitals as a possible descriptor for the polysulfide conversion activity of spinel oxides. The electrochemical characterizations reveal a volcano relationship between t<sub>2</sub> occupancy and the polysulfide conversion activity of spinel oxides. The theoretical calculations indicate that the t<sub>2</sub> occupancy effect is associated with the ability of tetrahedral cations to cleave S-S bonds and form Li-S bonds. As such, Mn<sub>0.5</sub>Co<sub>0.5</sub>Cr<sub>2</sub>O<sub>4</sub>, with an optimized average t<sub>2</sub> occupancy of 2.88, is designed and demonstrates promising polysulfide conversion activity among representative oxides. This work elucidates that t<sub>2</sub> occupancy serves as an effective descriptor for evaluating the polysulfide conversion activity of spinel oxides. With the catalytic mechanism proposed, the current study prompts further exploration of the application of t<sub>2</sub> occupancy as a descriptor for predicting the polysulfide conversion efficiency of other catalytic systems beyond the spinel structure.