Computational Study of Salt Association in Li-Ion Battery Electrolyte

The salt association of has been investigated through molecular dynamics (MD) simulations in a variety of solvents: ethylene carbonate, propylene carbonate (PC), γ-butyrolactone, dimethyl carbonate, ethyl methyl carbonate (EMC), diethyl carbonate, a 1:1 mixture of PC and 1, 2-dimethoxyethane, a 1:1 mixture of PC and methyl propionate, and a 1:1 mixture of PC and EMC. The degree of salt association for each electrolyte system was estimated using the pair distribution function of and the anion calculated from MD simulation trajectories. The predicted values for the salt association factor of showed a comparable trend to the experimental association constants. The same approach was applied to examine the salt association in the presence of a series of crown ethers: 9-crown-3, 12-crown-4, 13-crown-4, and 15-crown-5 as the trapping agents. The results demonstrated that the crown ethers were effective in separating the ion from the anion, and the ability depended on the size of the crown ether; 15-crown-5 had the largest effect on destabilizing the ion association. The method presented here may be used to screen new solvents or new salts for Li rechargeable batteries. The strength of the current method is that it can be applied to any salt, any solvent, and any mix of solvents.