H2O assisted to improve the electrochemical performance of deep eutectic electrolyte formed by choline chloride and magnesium chloride hexahydrate

Introduction of H2O provides an effective strategy to tailor conductivity and viscosity in the electrolyte based on deep eutectic solvent (DES), as well as customize the energy storage performance. Herein, a novel DES as a suitable electrolyte is prepared by means of choline chloride (ChCl) and with crystalline magnesium chloride (MgCl2·6H2O), with different amounts of H2O added as additives to investigate its effect on the electrolyte's electrochemical properties. The prepared DESs are systematic theoretical and experimental studied, as well as utilized as electrolytes in supercapacitors. The results show that the addition of H2O significantly optimized the ion conductivity and the viscosity of the prepared DES electrolyte. The proposed mechanism is that introduction of H2O ‘dilutes’ the interaction betwaeen ions and hydrogen bonds, enhance the capacity of ion transport and diffusion in the electrolyte system. The supercapacitor assembled by the optimized DES electrolyte (DES-1-1.0) exhibits superior electrochemical properties within a voltage range of 0~2.6 V, delivering a remarkable energy density of 87.7 Wh kg−1 at a high-power density of 1.69 kW kg−1 and retains 90.25% of its initial capacitance after undergoing 30000 cycles at 10 A g-1.