This work investigates the effect of zwitterionic molecules on ionic association in ethylene oxide (EO)-based electrolytes using molecular dynamics simulations. Zwitterionic molecules can associate with cations and anions because they possess both positively and negatively charged groups. This unique feature can be leveraged to develop electrolytes with high ionic conductivity if we understand how zwitterionic molecules influence ionic associations. We investigate the ionic associations in the electrolytes composed of oligo(ethylene oxide) (EO) (EOx, x = 2, 3, 4, and 5), LiTFSI and zwitterionic molecules containing cationic imidazole group and anionic sulfonate group using molecular dynamics simulations. The analyzed properties include the radial distribution functions between Li+, [TFSI]-, EOx and zwitterionic molecules, the structures and dynamics of Li+-[TFSI]-, Li+- EOx and Li+-zwitterion associations, and the diffusion coefficients of Li+, [TFSI]-, EOx and zwitterionic molecules. The simulation results show two distinct effects of zwitterionic molecules on ionic associations in the electrolytes. First, they could release Li+ from the trapping effect of EOx chains and accelerate Li+ transport. Second, they can associate with Li+ themselves and slow down the Li+ transport. The competition between these two effects relates to the length of the EOx chains. Our simulations suggest that zwitterionic molecules could help manipulate the ionic conductivity of polyethylene oxide electrolytes.
|Journal||Fluid Phase Equilibria|
|State||Published - Jul 1 2020|
Bibliographical noteFunding Information:
The authors thank for the financial support provided by the Startup Funds of the University of Kentucky and the computational facilities provided by the High-Performance Computing Center of the University of Kentucky .
© 2020 Elsevier B.V.
Copyright 2020 Elsevier B.V., All rights reserved.
- Ethylene oxide
- Ionic association
- Lithium-ion battery
ASJC Scopus subject areas
- Chemical Engineering (all)
- Physics and Astronomy (all)
- Physical and Theoretical Chemistry