Structural and electronic transformations of lithium selenide during delithiation: A density functional theory study

초록

Lithium selenide (Li2Se) has emerged as a promising pre-lithiated additive for enhancing cathode performance in lithium-ion batteries. However, the fundamental understanding of how Li2Se functions in this role - particularly its structural and electronic transformations upon lithium removal - remains limited. This study aims to elucidate the mechanism of Li2Se as a pre-lithiated additive by systematically investigating its structural and electronic properties during delithiation using density functional theory calculations. Starting from the conventional Li2Se structure, modeled structures including Li7Sea, Li6Sea, LiaSea, and Li2Sea are generated and optimized. The results reveal significant structural modifications, with Li2Se maintaining a cubic structure at a high lithium content but exhibiting lattice distortions and volume changes as lithium is removed. The electronic properties also undergo notable changes, transitioning from semiconducting behavior in Li2Se to metallic character in the partially lithiated compounds. Density of states analysis highlights the dominant role of the selenide p-orbital near the band edges of Li2Se, which diminished upon lithium extraction. These findings provide fundamental insights into the relationship between the composition, crystal structure, and electronic properties of Li2Se and provide a foundation for optimizing its performance as a pre-lithiated additive in advanced lithium-ion batteries.

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