Preliminary Study of New Electrolytes Based on [MPPyr][TFSI] for Lithium Ion Batteries

Abstract

[Abstract] The application of ionic liquids in lithium ion batteries has increased in recent years in order to find new electrolytes that improve both performance and safety. The gathering of experimental data in order to understand the behaviour of these systems will help us design electrolytes that can be optimized for a specific objective. Data on electrolytes made up of a ternary mixture with an ionic liquid are missing in the literature. In this work, we provide new data on physical properties and refractive indexes for the ternary mixtures 1-methyl-1-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([MPPyr][TFSI]) + acetonitrile (AN) or γ butyrolactone (GBL) or dimethyl sulfoxide (DMSO) + lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) with different concentrations of salt, specifically, 10%, 15%, 20%, 30%, 35%. The measured properties were density (ρ), viscosity (η) and ionic conductivity (κ) in the temperature range of 278.15 to 358.15 K except for the mixtures with acetonitrile whose temperature range was 278.15 K to 328.15 K and the refractive indexes (nD) that were measured at a single temperature of 298.15 K. In general, the addition of salt in the binary mixtures provokes an increase of density and viscosity and therefore a decrease of ionic conductivity. It is worth mentioning that some of the studied systems showed values of ionic conductivity even better than those obtained for electrolyte systems based on carbonate.