Decoding polymer architecture effect on ion clustering, chain dynamics, and ionic conductivity in polymer electrolytes

Bakar, Recep and Darvishi, Saeid and Aydemir, Umut and Yahsi, Ugur and Tav, Cumali and Menceloğlu, Yusuf Z. and Senses, Erkan (2023) Decoding polymer architecture effect on ion clustering, chain dynamics, and ionic conductivity in polymer electrolytes. ACS Applied Energy Materials, 6 (7). pp. 4053-4064. ISSN 2574-0962

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Poly(ethylene oxide) (PEO)-based polymer electrolytes are a promising class of materials for use in lithium-ion batteries due to their high ionic conductivity and flexibility. In this study, the effects of polymer architecture including linear, star, and hyperbranched and salt (lithiumbis(trifluoromethanesulfonyl)imide (LiTFSI)) concentration on the glass transition (Tg), microstructure, phase diagram, free volume, and bulk viscosity, all of which play a significant role in determining the ionic conductivity of the electrolyte, have been systematically studied for PEO-based polymer electrolytes. The branching of PEO widens the liquid phase toward lower salt concentrations, suggesting decreased crystallization and improved ion coordination. At high salt loadings, ion clustering is common for all electrolytes, yet the cluster size and distribution appear to be strongly architecture-dependent. Also, the ionic conductivity is maximized at a salt concentration of [Li/EO ≈ 0.085] for all architectures, and the highly branched polymers displayed as much as three times higher ionic conductivity (with respect to the linear analogue) for the same total molar mass. The architecture-dependent ionic conductivity is attributed to the enhanced free volume measured by positron annihilation lifetime spectroscopy. Interestingly, despite the strong architecture dependence of ionic conductivity, the salt addition in the highly branched architectures results in accelerated yet similar monomeric friction coefficients for these polymers, offering significant potential toward decoupling of conductivity from segmental dynamics of polymer electrolytes, leading to outstanding battery performance.
Item Type: Article
Uncontrolled Keywords: free volume; homopolymer electrolytes; ion pairing and clustering; ionic conductivity; phase diagram; poly(ethylene oxide); polymer architecture; viscosity
Divisions: Faculty of Engineering and Natural Sciences
Depositing User: Yusuf Z. Menceloğlu
Date Deposited: 05 Aug 2023 12:54
Last Modified: 05 Aug 2023 12:54

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