Enhancement of Lithium Ion Mobility in Ionic Liquid Electrolytes in Presence of Additives

Ionic liquids are widely considered as potential electrolytes for lithium batteries due to their tunable electrochemical properties. In the present study, the mobility and transport characteristics of lithium ions in N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide (mppy(+)TFSI(-)) ionic liquids were characterized using the molecular dynamics method. Results from the simulations indicate that inclusion of organic additives such as ethylene carbonate, vinylene carbonate, and tetrahydrofuran decreases the extent of coordination of the lithium ion with the anion of the ionic liquid and hence increases its mobility and overall ionic conductivity. The mobility of lithium ions in the ionic liquid based electrolyte increases with increasing concentration of the additive. Of the additives investigated, ethylene carbonate was identified as the most effective in increasing the mobility of lithium ions, while vinylene carbonate increases the overall ionic conductivity to the greatest extent.