Thermal influence on the electrochemical behavior of a supercapacitor containing an ionic liquid electrolyte

Emerging demands on heat-durable electronics have accelerated the need for high temperature supercapacitors as well as for understanding the influence of elevated temperatures on the capacitive behavior. In this work, we present a comprehensive study of the thermal influence on a supercapacitor containing 1-ethyl-3-methylimidazolium acetate (EMIM Ac) electrolyte and activated carbon (AC) electrodes. The performance variation as a function of temperature in a range from 21 degrees C to 150 degrees C reveals that a high specific capacitance of 142 F g(-1) can be achieved at 150 degrees C at a current density of 2 A g(-1) with a rate capability of 87% at 15 A g(-1) (relative to 2 A g(-1)). At 150 degrees C, equivalent series resistance (ESR) is only 0.37 Omega cm(2), which is a result of improved ionic conductivity of the electrolyte at elevated temperature. The ESR value of 2.5 Omega cm(2) at room temperature reflects a good compatibility between EMIM Ac and AC. In addition, a capacitance retention of more than 95% (in the end of 1000 cycles) is maintained up to 120 degrees C followed by 85% at 150 degrees C. These results confirm EMIM Ac as a suitable candidate for carbon-based high temperature supercapacitors, and the observations regarding the thermal influence on performance metrics e.g. usable operation voltage could be applicable to other energy storage devices. (C) 2018 Elsevier Ltd. All rights reserved.