A Flexible Supercapacitor Based on Deep Eutectic Solvent/[EMIM][TFSI] Ionogel with High Energy Density and Wide Temperature Range
Guangpeng Ma, Feng Pan, Xinpu Zhou, Zhipeng Yong, Xiaodong Wang, Chenglong Li, Wenyu Bai, Shuang Wang
Abstract
Hydrogel electrolytes have attracted wide attention because of their high ionic conductivity and anti-leakage characteristics. However, these advantages are hindered under extreme conditions. In this paper, an ionogel electrolyte for supercapacitors with a wide temperature range is constructed. It consists of a double cross-linked structure of polyacrylamide and 1-vinyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([VMIM][TFSI]), with the addition of ethylene glycol and choline chloride to form a deep eutectic solvent with a large hydrogen bonding network. On this basis, a partial ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM] [TFSI]) is innovatively added to choline chloride. The ionogel electrolyte exhibits a conductivity of up to 13.26 mS/cm at 90 °C. A flexible supercapacitor is assembled with activated carbon electrodes and has a wide voltage window of 2.4 V. The specific capacitance and energy density are 43.81 F/g and 35.1 Wh/kg, respectively, when the current density is 0.25 A/g. Remarkably, the device retains high coulombic efficiency (97.1%) and capacitance retention (94.3%) after 10 000 cycles. These excellent properties show that the ionogel electrolyte prepared in this work has broad application prospects.