Uncovering Local Correlations in Polymer Electrolytes by X-ray Scattering and Molecular Dynamics Simulations

• DOI: 10.1021/acs.macromol.1c00995
• Publication Date: 2021-07-08T11:57:01Z
• Authors: Whitney S. Loo; Chao Fang; Nitash P. Balsara; Rui Wang
• Keywords: Small-angle X-ray scattering; Structure factor

Understanding the distribution of ionic species in electrolytes is important for predicting ion-transport properties. Here, a quantitative analysis wide-angle X-ray scattering (WAXS) profiles was conducted first time on series mixtures poly(ethylene oxide) (PEO) and lithium bis(trifluoromethanesulfonyl)imide salt (LiTFSI), PEO/LiTFSI, as function concentration melt state. Abnormal signatures were observed: while WAXS data showed single peak (Peak 1) absence salt, second 0) appeared at lower angles with added salt. Molecular dynamics simulations standard TraPPE-UA force field used to uncover molecular origins peaks. Qualitative agreement found between experimental simulated profiles. Simulations indicated that Peak 1 arises from correlations EO segments well TFSI– ions segments, 0 neighboring ions. There were, however, disagreements experiment simulations, which resolved by introduction charge rescaling factor, Rf, account polarization polymers. predicted formation anion-rich clusters occurs higher than emergence 0. While did not directly reflect presence clusters, they provided basis more refined calculation short-range ions, affect clustering properties such conductivities transference numbers.