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

Abstract

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.