Development of many-body polarizable force fields for Li-battery applications: 2. LiTFSI-doped oligoether, polyether, and carbonate-based electrolytes

A quantum chemistry study of Li+ interactions with ethers, carbonates, alkanes, and a trifluoromethanesulfonylimide anion (TFSI-) was performed at the MP2, B3LYP, and HF levels using the aug-cc-pvDz basis set for solvents and TFSI- anion, and [8s4p3d/5s3p2d]-type basis set for Li. A classical many-polarizable force field was developed for the LiTFSI salt interacting with ethylene carbonate (EC), gamma-butyrolactone (GBL), dimethyl carbonate (DMC), acetone, oligoethers, n-alkanes, and perfluoroalkanes. Molecular dynamics (MD) simulations were performed for EC/LiTFSI, PC/LiTFSI, GBL/LiTFSI, DMC/LiTFSI, 1,2-dimethoxyethane/ LiTFSI, pentaglyme/LiTFSI, and poly(ethylene oxide) (MW = 2380)/LiTFSI electrolytes at temperatures from 298 to 423 K and salt concentrations from 0.3 to 5 M. The ion and solvent self-diffusion coefficients, electrolyte conductivity, electrolyte density, LiTFSI apparent molar volumes, and structure of the Li+ cation environment predicted by MD simulations were found in good agreement with experimental data.