Exploring nonlinear ion dynamics in polymer electrolytes from the perspective of hopping models

Area of Science:

• Materials Science
• Physical Chemistry
• Computational Chemistry

Background:

• Nonlinear ion transport in polymer electrolytes is crucial for understanding energy landscapes and transport mechanisms.
• Polymer electrolytes are key components in advanced energy storage devices.

Purpose of the Study:

• To investigate field-dependent ion dynamics in poly(ethylene oxide)/LiTFSI mixtures using molecular dynamics simulations.
• To analyze the electric-field dependence of current and ion diffusivities.
• To extract hopping distances and activation barriers in different electric field regimes.

Main Methods:

• Molecular dynamics simulations of poly(ethylene oxide)/LiTFSI mixtures.
• Analysis of field-dependent current and ion diffusivities (parallel and orthogonal).
• Comparison with analytically tractable hopping models in disordered energy landscapes.

Main Results:

• Nonlinear response in weak fields correlates with energetic disorder.
• Effective hopping distances and barrier heights were extracted in high fields.
• Hopping lengths align with structural analysis and show minimal salt concentration dependence.
• Activation barriers decrease linearly with increasing field, explaining unbounded ion motion.

Conclusions:

• Hopping models provide a consistent physical interpretation of ion dynamics across weak and high electric fields.
• The study demonstrates the utility of hopping models for quantifying nonlinear ion dynamics in polymer electrolytes.
• Findings contribute to the fundamental understanding of ion transport in materials for energy applications.