【摘要】 锂硫电池（LSBs）具有超高的理论能量密度和低成本的阴极材料。然而，LSBs的循环使用会产生多硫化物（Li PSs），出现严重的“穿梭效应”，导致电池高度极化，电池性能受损，甚至产生安全问题，使得LSBs的应用仍然极具挑战性。本工作针对“穿梭效应”问题，利用结合能讨论了材料Cs₂F₅Li₃对Li₂S的吸附能力，即抑制其“穿梭”的能力。基于密度泛函理论的第一性原理方法，通过CASTEP软件对Cs₂F₅Li₃与Li₂S进行了模拟计算，得到Cs₂F₅Li₃对Li₂S的结合能为–2.53 e V。为了探究吸附的机理，计算分析了体相Cs₂F₅Li₃、体相Li₂S、Li₂S（100）、Cs₂F₅Li₃（001）以及Cs₂F₅Li₃（001）-Li₂S（100）的基本性质、电子结构和电荷转移。结果表明，结合能是由两切面结合后，F 2p和Li 1s2s、S 3p和Li 1s2s形成的离子键，S 3p和F 2p之间形成的共价键，与体系内键的弛豫交换能量提供。切面后，Cs₂F₅Li₃（001）比Cs₂F₅Li₃有更强的化学活性，Li₂S晶体由半导体性向金属性转变，Cs₂F₅Li₃（001）-Li₂S（100）体系金属性增加，导电性能更强，光电效应比Cs₂F₅Li₃（001）更强。吸附能计算结果表明Cs₂F₅Li₃能够抑制因Li₂S的扩散而带来的“穿梭效应”，有利于缓解Li₂S导致的LSBs反应动力学缓慢、活性低、电池容量下降等问题，对提高锂硫电池的性能具有较强的理论参考价值。更多还原

【Abstract】 Lithium-sulfur batteries（LSBs） have extremely high theoretical energy density and low-cost cathode materials. However, the recycling of LSBs will produce polysulfides（Li PSs）, which has a serious “shuttle effect”, resulting in highly polarized batteries, impaired battery performance, and even safety issues, and making the application of LSBs still extremely challenging. In this work, the binding energy of was used to discuss the absorption capacity of Cs₂F₅Li₃ to Li₂S, i.e., the ability to inhibit its “shuttle effect”. Based on the first-principles method of density functional theory, Cs₂F₅Li₃ and Li₂S were simulated by CASTEP software, and the binding energy of Cs₂F₅Li₃ to Li₂S is – 2.53 e V. In order to explore the mechanism of adsorption, the basic properties, electronic structures, and charge transfer of Cs₂F₅Li₃ and Li₂S bulk phases, Li₂S（100）, Cs₂F₅Li₃（001）, and Cs₂F₅Li₃（001）-Li₂S（100） were used for analysis. The results show that the binding energy is provided by the ionic bond between F 2p and Li 1s2s as well as S 3p and Li 1s2s, the covalent bond between S 3p and F 2p, and the relaxation exchange energy of the bonds in the system. After the section, Cs₂F₅Li₃（001） has stronger chemical activity than Cs₂F₅Li₃, and Li₂S crystal changes from semiconductor property to metallic property. The metallic property of Cs₂F₅Li₃（001）-Li₂S（100） system improves, electrical conductivity is stronger, and photoelectric effect is stronger than that of Cs₂F₅Li₃（001）. The adsorption energy calculation results show that Cs₂F₅Li₃ can inhibit the “shuttle effect” caused by the diffusion of Li₂S, which is conducive to alleviate the problems such as slow reaction kinetics, low activity, and reduced battery capacity caused by Li₂S, and it has a strong theoretical reference value for improving the performance of LSBs.更多还原