Li⁺ Transport in Ethylene Carbonate Based Comb-Branched Solid Polymer Electrolyte: A Molecular Dynamics Simulation Study

Solid polymer electrolytes (SPEs) have the potential to resolve safety issues, be compatible with high-voltage cathode materials, and allow flexible designs of Li-ion batteries. Due to the limited Li+ transference number, a high degree of crystallinity at room temperature, and instability toward oxidation, polyether-based SPEs have been limited in batteries with the high-voltage cathodes and Li-metal anodes. Low ionic conductivity remains one of the biggest challenges for all types of SPE. Furthermore, the understanding of Li+ transport mechanisms and the related correlations with polymer structure are limited. In this study, extensive atomistic molecular dynamics simulations employ-ing polarizable force field were conducted for a series of poly(alkyl ethylene carbonate) comb-branched architectures doped with lithium bis(trifluoromethane)sulfonimide salt. By studying systems with systematic variance in the polymer structure, the Li+ transport mechanisms have been investigated through structural and dynamical correlations of cation local environments. The molecular-scale insights into the Li+ transport allow proposing principles for the design of comb-branched SPEs with improved conductivity.