Unified Interplay of Chemical Bond and Solid‐State Kinetics in Lithium–Sulfur Batteries

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Abstract
It is proposed that the unified interplay between the chemical hardness of the Li–X (X = S, Se, and Te) bond and solid‐state conversion kinetics enables intrinsic reshaping of materials for fabricating high‐energy density lithium–sulfur batteries. This concept is evaluated using three cathode models: (i) Li2S, (ii) Se‐doped Li2S (Se‐Li2S), and (iii) Te‐doped Li2S (Te‐Li2S). Theoretical calculations reveal that the Li−X bond in the Se‐Li2S cathode shows low chemical hardness, and the chemical hardness decreases at a higher rate for the Te‐Li2S cathode. The local structural effect induces a decrease in the phase transition barrier during the solid‐state conversion reaction in the Se‐ and Te‐doped crystal phases, as revealed by electrochemical measurements and ex‐situ X‐ray photoelectron spectroscopy analysis. Investigation of the three sulfide‐based cathodes sheds light on the mechanism behind the kinetics of phase transition in the solid‐state conversion region, illuminating the intriguing concept of a local structure for harnessing the full potential of sulfur cathodes to achieve high‐energy‐density lithium–sulfur batteries.

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