COMPUTATIONAL STUDY OF SALT ASSOCIATION IN LI-ION BATTERY ELECTROLYTE

摘要

Salt association of LiPF_6 has been investigated through molecular dynamics (MD) simulations in a variety of solvents: ethylene carbonate, propylene carbonate (PC),γ-butyro lactone, dimethyl carbonate, ethyl methyl carbonate (EMC), diethyl carbonate, and others. A new computational method has been presented to determine the degree of salt association based on MD simulation. The predicted values for the degree of association of LiPF_6 showed a comparable trend to the experimental association constants. The method 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 Li~+ trapping agents. The results demonstrated that the crown ethers are effective in separating the Li~+ ion from the PF_6~- anion and the ability depends on the size of the crown ether with 15-crown-5 having the largest effect in destabilizing the ion association.