第一性原理研究MS (M = Fe, Zn)的LiPSs催化性能

First-Principles Study on LiPSs Catalytic Performance of MS (M = Fe, Zn)

摘要: 锂硫电池因其高理论能量密度(2600 Wh kg⁻¹)、硫资源成本低和环境友好等优势，正成为极具前景的下一代储能技术。但其实际应用受到硫导电性差和中间体锂多硫化物(LiPSs)严重的穿梭效应双重限制。本文通过第一性原理计算，揭示了宽带隙半导体ZnS与金属性FeS在LiPSs催化功能上的失配。拥有优异化学锚定能力的ZnS因较高的决速步能垒陷入只捕不转的动力学僵局，而具备卓越电子传导与催化活性的FeS则受限于热力学吸附能力不足，难以实现高效的捕获。为了优化性能，我们构建了ZnS-FeS异质结，利用界面电子重构实现了功能的完美解耦与协同作用。结果显示，异质结在结处建立了多位点协同吸附，吸附能优于纯FeS和ZnS。异质结通过真空能级的显著下移，使得结处形成高效的内建电场(BIEF)，从而降低反应决速步能垒，促进对LiPSs的催化。

Abstract: Lithium-sulfur batteries, as a highly promising next-generation energy storage device, are concerned owing to their exceptional theoretical energy density (2600 Wh kg⁻¹), low cost of sulfur resources, and environmental friendliness. And its practical implementation is severely hindered by the poor electrical conductivity of sulfur and the detrimental “shuttle effect” of intermediate lithium polysulfides (LiPSs). In this paper, first-principles calculations are employed to understand the inherent functional mismatch between wide-bandgap semiconductor ZnS and metallic FeS. ZnS, which has excellent chemical anchoring ability, falls into a kinetic deadlock of “trapping without conversion” due to a high rate-determining step (RDS) energy barrier. And FeS, which holds excellent electronic conductivity and catalytic activity and insufficient thermodynamic adsorption, makes it difficult to achieve efficient polysulfide capture. To obtain better performance, we have constructed ZnS-FeS heterostructure that achieves perfect functional decoupling and synergy through interfacial electronic reconstruction. Results show that the heterostructure establishes a multi-site synergistic adsorption mode at the junction and yields stronger binding energies than that of single-component FeS and ZnS. The significant downward shift of vacuum level at the junction will induce a robust built-in electric field (BIEF), which effectively reduces the energy barrier of RDS and improves the catalysis of LiPSs.