Effect of Deep Eutectic Solvent (DES) on physicochemical and electrochemical properties of triethylmethylammonium tetrafluoroborate in propylene carbonate and aqueous propylene carbonate solvent systems for energy storage applications: A comparative analysis

Abstract

The use of non-toxic and biodegradable Deep Eutectic Solvents (DES) in energy storage has attracted a lot of attention as the toxic, costly and flammable organic electrolytes do not seem to be sustainable for the environment. So, to analyse the potential of DESs in this area their physicochemical properties and molecular interaction study can be quite helpful. The measurements were made of the density, sound speed, and electrical conductivity of Triethylmethylammonium Tetrafluoroborate (TEMABF4) at four different temperatures in two different solvent systems: propylene carbonate (PC) with ethaline DES (a mixture of ethylene glycol and chlorine in a 1:2 ratio) added as an additive, and binary aqueous PC with ethaline DES again, added as an additive. Density and speed of sound measurements were used to determine the physicochemical characteristics such as apparent molar volume and partial molar volume), apparent molar isentropic compressibility and partial molar isentropic compressibility and limiting molar expansibilities. The effects of DES on the intermolecular interactions in the PC and aqueous PC solvent environment were demonstrated using these parameters. The findings demonstrated that the solute–solvent interactions in both systems were enhanced by the addition of DES. Hepler’s constant additionally showed that TEMABF4 behaved as a structure maker in the DES in aq. PC system and a structure breaker in the DES in PC system. In order to investigate the electrochemical applications, the electrochemical stability and electrical conductivity of the systems being studied are also reported in this paper.