A high-temperature high-pressure supercapacitor based on ionic liquids for harsh environment applications

The study of energy storage devices able to work in harsh environments is becoming of paramount importance. Numerous applications require devices able to sustain extreme temperatures but often the pressure is discarded. Herein we present the evaluation of the energy storage performance of a prototype electrochemical supercapacitor from room temperature and ambient pressure up to 170 °C and 640 bar. The supercapacitor is fabricated by exploiting activated carbon-based electrodes and an ionic liquid as electrolyte. [PYR14][TFSI] has been selected for this scope since it possesses suitable features for the investigated case of study. The whole device was sealed in a vacuum pouch and tested into a customized high-temperature high-pressure (HTHP) test bench. The device shows typical EDLC behavior in the whole HTHP region with capacitive response ranging from the low value of 46.4 mF cm−2 at {RT, 600 bar} up to 84.6 mF cm−2 at {175 °C, 640 bar}, with a reference value of 58.8 mF cm−2. At these points, the rated energy values are 92.8 mWh cm−2 and 169.1 mWh cm−2. We observed that pressure mainly acts on dissipative parasite components of the device while temperature strongly impinges transport properties and capacitance as expected from literature results.