锂硫电池WS2和WSe2填充行为的第一性原理研究
First-Principles Investigation of Anchoring Behavior of WS2 and WSe2 for Lithium-Sulfur Batteries
摘要：
锂硫（Li-S）电池的商业实现由于多硫化锂（LiPS）溶解到电解质中导致的容量快速衰减而受到阻碍。为了提高锂硫电池的效率和性能，过渡金属二硫属化合物被报道为有前途的锚定材料（AM），因为它们可以强烈地吸附并有效地抑制多硫化物物种的迁移。本文中，我们使用基于第一性原理的密度泛函理论（DFT）计算来研究AM如钨二硫属化物、WX 2（X=S和Se）与LiPS之间的相互作用。WS 2和WSe 2的LiPS结合行为非常相似。计算的LiPS物种的吸附能表明，WX 2具有中等的结合强度和结合促进通过电荷转移从多硫化物的AM。我们观察到在LiPS中的分子内Li-S键在其吸附到WX 2上时伸长，然而，LiPS的化学结构被保留而不分解。计算的态密度表明LiPS吸附的WX 2系统表现出半导体行为，与原始的WX 2相比具有略低的带隙。总的来说，我们的模拟结果提供了对WX 2作为AM的行为的详细了解，以抑制LiPS迁移，并为开发高性能Li-S电池铺平了道路。
英文摘要：
The commercial realization of lithium-sulfur (Li-S) batteries is obstructed because of rapid capacity fading due to lithium polysulfides (LiPSs) dissolution into the electrolyte. In order to enhance the efficiency and performance of the Li-S batteries, the transition metal dichalcogenides are reported as promising anchoring materials (AMs) as they could strongly adsorb and effectively suppress the migration of the polysulfides species. Herein, we used first-principles based density functional theory (DFT) calculations to investigate the interactions between AMs such as tungsten dichalcogenides, WX2 (X=S and Se) and the LiPSs. The LiPSs binding behavior of WS2 and WSe2 are found to be quite similar. The calculated adsorption energies of LiPS species indicate that the WX2 possesses moderate binding strength and the binding is facilitated via charge transfer from the polysulfides to the AM. We observe elongation of intramolecular Li-S bonds in LiPS upon their adsorption onto the WX2, however, chemical structures of LiPSs are preserved without decomposition. The calculated density of states indicates the LiPS adsorbed WX2 systems exhibits semiconducting behavior with a slightly lower bandgap compared to the pristine WX2. Overall, our simulation results provide detailed insight into the behavior of WX2 as AMs to suppress the LiPSs migration and henceforth paves the way towards the development of high-performance Li-S batteries.
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