Physicochemical and Electrochemical Properties of the Organic Solvent Electrolyte with Lithium Bis(fluorosulfonyl)Imide (LiFSI) As Lithium-Ion Conducting Salt for Lithium-Ion Batteries.

摘要

In this study, we investigated the physicochemical and electrochemical properties of LiFSI solution comparing with those of LiPF_6 in EC/DEC (3/7, v/v), and discuss the difference in ionic conductivity between these electrolyte solutions based on self-diffusion coefficients measured by PFG-NMR. Self-diffusion coefficients of solvent molecules and ions in 1M LiFSI solution are about 1.5 times larger than those of 1M LiPF_6 solution. On the other hand, the degree of dissociation of LiFSI estimated by the Nernst-Einstein Equation from measured ionic conductivity and self-diffusion coefficients of Li~+ and FSI~- is lower than that of LiPF_6. Therefore it is strongly suggested that almost the same ionic conductivity of 1M LiFSI solution as that of 1M LiPF_6 in EC/DEC (3/7, v/v) is the result of cancelation of these two factors in the opposite direction.