Amino acids assisted to improve the voltage window of deep eutectic electrolyte formed by ethylene glycol and tetra methyl ammonium chloride

Herein, a novel deep eutectic solvent (DES) as suitable electrolyte is prepared by means of ethylene glycol (EG) and tetra methyl ammonium chloride (TMAC), and seven amino acids with different acidities are used as ad-ditives to explore the effect of amino acid on the voltage window of the electrolyte. The prepared serial DES are systematic studied and used as the electrolytes in supercapacitor. The results show that the addition of basic amino acids significantly increase the voltage window of the prepared DES electrolyte, neutral amino acids slightly increase the voltage window, and the acidic amino acids reduce the voltage window of the electrolyte. The proposed mechanism is that basic amino acids preferentially adsorb on the electrode surface increases the distance between chloride ions and the interface, thus hindering the oxidation of chloride ions. The high con-ductivity (3.51 mS cm(-1)) and low viscosity (30.4 cP) of DES electrolyte formed by EG, TMAC and arginine (Arg) is well suited in supercapacitors. Comparing with the electrolyte of non amino acids additive, using the opti-mized TMAC-EG-Arg-1.2 as electrolyte, the voltage window of the assembled activated carbon based super-capacitor is increased from 0.9 V to 2.0 V, and the energy density is as high as 20.55 Wh kg(-1). Furthermore, the electrolyte has a wide operating temperature range (-20 similar to 100 degrees C). This study uncovers a new possibility for enlarging the voltage window of DES electrolyte by addition of amino acids, which used as electrolyte with high performance in supercapacitor.

Automated summary

A novel deep eutectic solvent (DES) electrolyte is prepared using ethylene glycol (EG) and tetra methyl ammonium chloride (TMAC), and the effect of amino acids on the electrolyte voltage window is explored. It is found that basic amino acids increase the voltage window, neutral amino acids slightly increase the voltage window, and acidic amino acids reduce the voltage window of the electrolyte. The proposed mechanism suggests that basic amino acids adsorb on the electrode surface, increasing the distance between chloride ions and the interface, hindering the oxidation of chloride ions. The optimized electrolyte demonstrates high performance in supercapacitors, with increased voltage window and energy density.