The Importance of Morphology on Ion Transport in Single-Ion, Comb-Branched Copolymer Electrolytes: Experiments and Simulations

• Published in: Macromolecules Vol. 56; no. 7; pp. 2790 - 2800
• Main Authors: Kadulkar, Sanket, Brotherton, Zachary W., Lynch, Anna L., Pohlman, Gabriel, Zhang, Zidan, Torres, Rudy, Manthiram, Arumugam, Lynd, Nathaniel A., Truskett, Thomas M., Ganesan, Venkat
• Format: Journal Article
• Language: English
• Published: American Chemical Society 11-04-2023
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/acs.macromol.2c02500

Single-ion conducting polymer electrolytes (SICPEs) offer high lithium transference numbers and desirable physical properties while maintaining moderate conductivities. Bottlebrush and comb-branched copolymer electrolytes are a particular architecture that offer modularity and increased ion solvation. Despite this promise, the ion transport in these systems is poorly understood. In this report, we investigated lithium-ion transport in comb-branched SICPEs using a combination of experiments and atomistic simulations. A series of solvent-free SICPEs were synthesized by copolymerization of poly­(ethylene glycol) methyl ether acrylate (PEGMEA) with varying lithiated anionic groups in different ratios of the ionic species to the PEG side chain. Poly­(Lithium 3-[(trifluoromethane) sulfonamidosulfonyl]­propyl methacrylate-co-poly­(ethylene glycol methyl ether acrylate)) (p­(MPTFSI-co-PEGMEA) exhibited both highest ionic conductivity (on the order of 10–5 S/cm at room temperature) and degree of decoupling of ionic conductivity from polymer segmental dynamics. Simulations revealed that in electrolytes with low ion concentrations, Li+ transport occurs through the vehicular codiffusion of lithium ions and the polyanions. In contrast, for higher anion compositions, the primary mechanism of Li+ transport is through Li+ ion hopping among the percolated ionic aggregates. Finally, we demonstrate that the behavior of ion hopping is influenced in a nonintuitive manner by the ion cluster morphology based on SICPE anion identity.