Electrolyte transport in lithium-ion battery systems with nanoporous polyethylene separators: Insights from molecular dynamics simulations

T Zheng and Y Zhang and NB Huang and HC Zhang, COMPUTATIONAL MATERIALS SCIENCE, 242, 113099 (2024).

DOI: 10.1016/j.commatsci.2024.113099

The performance of lithium-ion batteries relies heavily on the solvate structures of electrolytes and how electrolytes interact with porous polymeric separators. In the present work, the thermodynamics and electrodynamics of Li+-TFSI- +-TFSI- electrolytes in 1,2-dimethoxyethane (DME) and 1,3-dioxolane (DOL) solutions with without porous polyethylene films are investigated by molecular dynamics simulations. DME/DOL molecules exhibit competitive binding affinities in the first solvation shells of Li+ + ions and an increase in the Li+-TFSI- + concentration leads to more structured solvent configurations, thus reducing the diffusivities of the constituents in the ionic solutions. In addition, nano-porous polyethylene films, obtained through uniaxial stretching cesses, are able to regulate the transport properties of Li+ + ions with or without external electric fields. Reducing the pore sizes of polyethylene films or increasing Li+ + concentrations in the lithium-ion battery systems impedes the migration of ions and solvents across the porous films. Finally, due to the weak interaction between ethylene films and ionic solutions, the presence of polyethylene films does not cause biased distributions of solutions during the diffusion process. The present work provides molecular insights into the working principle the Li+-TFSI- +-TFSI- electrolytes with nano-porous polymer separators and their interfaces.

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