Unveiling Li-ions migration mechanism in Li6PS5Cl under applied constant potential: insights from classical molecular dynamics simulations

The elucidation of the multi-scale transport phenomena of lithium ions in solid electrolyte under working conditions poses huge challenges to both experimental and theoretical realms. High-resolution ab initio molecular dynamics simulations are severely limited by spatial and temporal scales, hindering direct comparisons with experimental observations under room temperature and applied electric potential. Herein, classical molecular dynamics simulations under constant potential are employed to unveil the migration mechanism of Li-ions in Li6PS5Cl (LPSC) confined by electrode interfaces considering realistic conditions. By sophisticated manipulation of anion compositions in LPSC electrolyte, it is observed that neighboring vacancies provide effective pathways for Li-ions migration and the coordination environments evolves progressively with increasing diffusion coefficient, while the conductivity exhibits a non-monotonic peak in Li5.3PS4.3Cl1.7. The semi-quantitative agreement with existing experimental results demonstrates the superiority of our constant potential solid electrolyte model, which we expect to provide atomistic understanding towards rational design of solid electrolyte.