Cooperative Transport of Lithium in Disordered Li10MP2S12 (M = Sn, Si) Electrolytes for Li-Ion Batteries

Disorder in sulfide solid-state electrolytes significantly impacts chemical bonding, affecting electrochemical properties and interface stability. Li10GeP2S12, a prominent sulfide electrolyte, is expensive and has limited interfacial stability, so substituting Ge with earth-abundant elements, such as Sn and Si, could be more practical. However, a thorough understanding of the kinetics and chemical bonding nature of Li in the Sn/Si-substituted systems is missing owing to the complexity associated with disordered sublattice in these materials. We use isothermal–isobaric ensemble Car–Parrinello molecular dynamics to evaluate configuration-dependent tracer and charged diffusivities and activation energies for lithium-ion migration in disordered configurations of Li10SiP2S12 (LSiPS) and Li10SnP2S12 (LSnPS) obtained using ensemble statistics. The study uses Li-ion probability density and maximally localized Wannier orbital analysis to determine how temperature and Sn and Si cations affect Li-ion migration. Our findings indicate that higher temperatures enhance Li-ion mobility by enabling more diffusion pathways. The disordered LSiPS and LSnPS electronic structure shows a Kohn–Sham band gap of 2.4 eV for LSiPS and 2 eV for LSnPS, of the most probable configuration across 500 configurations, suggesting a wider electrolyte window for LSiPS. Additionally, Wannier function visualizations demonstrated the significant impact of locality and temperature on the dynamic nature of bonding states of migrating Li ions.硫化物固态电解质中的无序结构会显著影响其化学键合特性，进而对电化学性能与界面稳定性造成负面影响。Li₁₀GeP₂S₁₂是一类高性能硫化物电解质，但存在成本高昂、界面稳定性不足的问题，因此用地壳储量丰富的锡（Sn）、硅（Si）等元素替代其中的Ge元素，有望获得更具实用性的电解质体系。然而，受限于这类材料亚晶格无序结构带来的复杂性，目前学界对锡/硅取代体系中锂离子的动力学行为与化学键合本质仍缺乏全面认知。本研究采用等温等压系综Car-Parrinello分子动力学（isothermal–isobaric ensemble Car–Parrinello molecular dynamics）方法，对通过系综统计得到的Li₁₀SiP₂S₁₂（LSiPS）与Li₁₀SnP₂S₁₂（LSnPS）无序结构，计算了构型依赖的示踪扩散系数、带电扩散系数以及锂离子迁移活化能。本研究通过锂离子概率密度分析与极大局域化万尼尔轨道（maximally localized Wannier orbital）分析，探究了温度与锡、硅阳离子对锂离子迁移行为的调控机制。研究结果表明，更高的温度可通过拓展锂离子的扩散通路，提升其迁移率。针对500个无序构型中的最可几构型进行电子结构分析，结果显示LSiPS的Kohn-Sham能带隙（Kohn–Sham band gap）为2.4 eV，LSnPS为2 eV，表明LSiPS拥有更宽的电解质稳定窗口。此外，万尼尔函数（Wannier function）可视化结果证实，局域性与温度对迁移锂离子的键合态动态特性具有显著影响。