Mechanistic Decomposition of Ion Transport in Amorphous Polymer Electrolytes via Molecular Dynamics

Understanding ion transport in polymer electrolytes is critical for designing next-generation energy storage systems. Molecular dynamics simulations offer complete atomistic information, but disentangling the contributions of distinct diffusion modes in cation transport remains a challenge. Here, we introduce a mathematical algorithm that decomposes the transport coefficient into a sum of interpretable diffusion mechanisms based on changes in local atomic environment. Applying this framework to a prototypical polymer electrolyte, we quantify the contributions of proposed transport modes. We identify a rare lithium diffusion mechanism associated with the disassembly of existing solvation environments which contributes an order of magnitude more to lithium transport properties per event than all other mechanisms. Finally, we characterize the spectrum of microscopic diffusion events, providing a detailed and quantitative understanding of ion transport in polymer electrolytes. Our approach offers a promising path toward a more quantitative and mechanistic understanding of ion transport in soft matter electrolytes.