Solid-state batteries require electrolytes that sustain high ionic conductivity under the mechanical environment of a functioning cell. Lattice strain, arising from stack pressure, thermal cycling, or lattice mismatch at interfaces, can either enhance or suppress Li+ transport in solid electrolytes, yet how it couples to the underlying diffusion mechanism remains poorly understood. Using Li3YCl6 halide superionic conductor, we address this with large-scale molecular dynamics simulations driven by an Atomic Cluster Expansion (ACE) machine learning interatomic potential trained on first-principles data. The ACE model faithfully reproduces experimental and \textit{ab initio} structural, mechanical, and transport properties of Li3YCl6. We find that Li+ diffusion in Li3YCl6 follows a two-regime Arrhenius behavior, crossing over at a critical temperature Tc from one-dimensional hopping at low temperature to three-dimensional cooperative diffusion at high temperature. Strain substantially modulates diffusivity: tensile strain enhances it while compressive strain suppresses it, yet leaves Tc invariant, indicating that strain tunes diffusion efficiency without reshaping the underlying transport framework. In each regime, the mechanistic origin differs: altered activation barriers dominate at low temperature, while modified pre-exponential factors become critical at high temperature. These results establish lattice strain as a design lever for ionic conductivity in Li3YCl6 solid-state electrolytes.
@article{arxiv.2605.05603,
title = {Strain-Dependent Ionic Transport in Li3YCl6 Solid Electrolytes},
author = {Wei-Fan Huang and Jin Dai and Jiahui Pan and Mingjian Wen},
journal= {arXiv preprint arXiv:2605.05603},
year = {2026}
}