A novel electrolyte of ternary deep eutectic solvent for wide temperature region supercapacitor with superior performance

In present work, we successfully synthesize a novel ternary deep eutectic solvent electrolyte for wide-temperature region supercapacitor (-40–115 °C) through adjusting the molar ratio between choline chloride, ethylene glycol and urea. Notably, when the molar ratio is 1: 2: 1 (choline chloride:ethylene glycol:urea), the electrolyte under 115 °C not only exhibits prominent transport properties (viscosity: 3.39 cP; conductivity: 13.41 mS cm–1), but also delivers the excellent electrochemical performances with specific capacitance up to 317 F g–1 (specific energy: 74.37 Wh kg−1), and the stability after 10,000 cycles close to 100%. Besides, the theoretical calculation by density functional theory reveals that the total energy of electrolyte with a molar ratio of 1: 2: 1 is the largest (24.66 eV), confirming its outstanding performances. More importantly, hydrogen bonding indeed occurs in such electrolytes which helps the electrolyte to achieve normal operation over a wide-temperature range. This electrolyte possesses the capacity for lighting bulb and maintaining brightness for 50 s. The present ternary deep eutectic solvent offers a bran-new research idea for wide-temperature region electrolyte employed to supercapacitors.