Supercapacitors have emerged as energy storage devices exhibiting higher energy densities than traditional capacitors, as well as higher power densities than batteries or fuel cells. Current supercapacitor technology is limited by the operational temperature range of the electrolyte. This proposal will investigate deep eutectic solvents (DESs) as a novel class of electrolytes to enable high-performance supercapacitors with an operating temperature range between -45 C to 65 C. By contrast, aqueous electrolytes are limited to above-zero temperatures (freezing point of water) and have a low breakdown voltage (~ 1.2 V). Although organic electrolytes operate over a larger temperature range and exhibit higher breakdown voltages (~ 2.5 V), they also possess much lower conductivities, and correspondingly lower power densities for the supercapacitor, and can be highly flammable. DESs are expected to display wider operational temperature ranges and larger electrochemical stability windows (breakdown voltage in the range 3-7 V) as compared with conventional aqueous or organic electrolytes, resulting in supercapacitors exhibiting higher energy and power densities. The proposed approach utilizes a combination of experimental and supercomputing methods that will simultaneously maximize the probability of success and minimize the cost-per-eutectic investigated.
