Characteristics of electric double layer capacitors prepared with electrolytes based on deep eutectic solvents

Abstract

The storage capacity of electric double layer capacitors or electrochemical supercapacitors with electrolytes based on deep eutectic solvents (DES) composed of L-lactic acid with several hydrogen bond acceptors (nicotinamide, L-alanine, ammonium acetate, sodium acetate, choline chloride, amino acetic acid) with a molar ratio of 7:1 have been investigated. A DES based on urea and choline chloride with at a molar ration of 2:1 has also been included for comparison. The electrochemical supercapacitors were prepared using commercial activated carbon electrodes after removing the volatile organic electrolyte with a vacuum pump. The characteristics of the electrochemical supercapacitors were determined by cyclic voltammetry at temperature room temperature and also after heating at 353 K using scan rates that varied from 2 to 25 mVs-1. Lowest scan rate led to higher specific capacitance of 150±8 Fg-1 with a maximum applied potential of 1.7 V for the urea and choline chloride DES with a molar ration of 2:1. The lactic acid with all the hydrogen bond acceptors with a molar ratio 7:1 it has been necessary to increase the temperature above room temperature to improve the specific capacitance.