Ionic liquid-1,2-dimethoxyethane mixture as electrolyte for high power density supercapacitors

Abstract

In this work we have studied the effect of 1,2-dimethoxyethane (1,2-DME) addition (from 0 to 90 vol%) on the electrochemical behaviour of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulphonyl)imide (EMImTFSI) as an electrolyte for supercapacitors, using cyclic voltammetry, electrochemical impedance spectroscopy and constant power methods. Also, the ionic conductivity and viscosity of EMImTFSI and 1,2-DME have been measured and discussed. The conductivity of the EMImTFSI could be increased from 5.67mS/cm up to 24.21mS/cm by mixing EMImTFSI with 1,2-DME. The stored power values for supercapacitors increased from 13kW/kg to 20.5kW/kg (correspond to 2s application line), when the concentration of 1,2-DME increased up to 40 vol%. The supercapacitors based on the 40 vol% of 1,2-DME deliver the higher power density at the constant energy density, showing an excellent characteristics applicable in high rate supercapacitor devices. Nearly ideal capacitive behaviour has been established at potential scan rates v≤10mV/s and cell potential ΔE≤2.7V.