Complex Ion Dynamics in Carbonate Lithium-Ion Battery Electrolytes
MT Ong and H Bhatia and AG Gyulassy and EW Draeger and V Pascucci and PT Bremer and V Lordi and JE Pask, JOURNAL OF PHYSICAL CHEMISTRY C, 121, 6589-6595 (2017).
Li-ion battery performance is strongly influenced by ionic conductivity, which depends on the mobility of the Li ions in solution, and is related to their solvation structure. In this work, we have performed first- principles molecular dynamics (FPMD) simulations of a LiPF6 salt solvated in different Li-ion battery organic electrolytes. We employ an analytical method using relative angles from successive time intervals to characterize complex ionic motion in multiple dimensions from our FPMD simulations. We find different characteristics of ionic motion on different time scales. We find that the Li ion exhibits a strong caging effect due to its strong solvation structure, while the counterion, PF6 undergoes more Brownian-like motion. Our results show that ionic motion can be far from purely diffusive and provide a quantitative characterization of the microscopic motion of ions over different time scales.
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