Deep eutectic solvents (DESs) have been emerging as newer environmentally benign electrolytes for energy storage devices with the high-temperature operational capability. For the first-time, we propose ethylene glycol and tetrapropylammonium bromide based non-fluoro DESs as electrolytes for the supercapacitor. Different compositions of DESs were also evaluated. Also, the high-temperature operational capability of the proposed electrolytes was evaluated with the free-standing microporous commercial activated carbon (AC) and mesoporous rice husk-derived bio-activated carbon (Bio-AC). The maximum cell voltages of 1.3 V and 1.0 V are identified for AC and Bio-AC based supercapacitors, respectively at 25 degrees C. The specific capacitances of both AC and Bio-AC electrodes are similar to 100 F g(-1) at 0.1 A g(-1) . The proposed DES electrolyte can be operated at the maximum temperature of 115 degrees C, which is higher than the previously reported DESs (80 degrees C). The specific capacitance increases with increasing temperature, and the maximum specific capacitance of an electrode is 172 F g(-1) at 115 degrees C for Bio-AC supercapacitor. Excellent long-term stability is noted after 10,000 cycles at 25 degrees C and 115 degrees C for both AC and Bio-AC supercapacitors. The supercapacitors here may be practically used in high-temperature applications. (C) 2018 Elsevier Ltd. All rights reserved.