Quantifying Single-Ion Transport in Percolated Ionic Aggregates of Polymer Melts

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Science

Background:

• Single-ion conducting polymers (ionomers) are crucial for next-generation battery electrolytes.
• Cation transport mechanisms are strongly influenced by nanoscale ion aggregation.
• Understanding these relationships is critical for optimizing battery performance.

Purpose of the Study:

• To investigate cation mobility in ionomer melts.
• To correlate cation diffusion with polymer architecture, permittivity, and ionic aggregate morphology.
• To elucidate the mechanisms governing cation transport in different aggregation states.

Main Methods:

• Coarse-grained molecular dynamics simulations were employed.
• Simulations analyzed ionomer melts under varying conditions.
• Cation diffusion coefficients were linked to ionic association lifetimes and aggregate structures.

Main Results:

• In systems with percolated ionic aggregates, cations diffuse through stepping motions along these pathways.
• Cation diffusivity in percolated systems correlates with the lifetimes of ion association.
• Predicting cation diffusivity in systems with isolated ionic aggregates requires additional time scales.

Conclusions:

• Cation transport mechanisms differ significantly between percolated and isolated ionic aggregates.
• The lifetime of ion association is a key predictor for diffusivity in percolated systems.
• Optimizing conductivity requires balancing Coulombic interaction strength for aggregate formation and ion dissociation.