The cyclic voltammetry was used to study the behavior of a symmetric supercapacitor with activated carbon cloth electrodes and a solution of an ionic liquid (C8H15N2PF6) in freon-22 as an electrolyte in the temperature range from − 140 to + 130°C. The measurements were carried out in a special autoclave. At temperatures above 90°C, the supercapacitor exhibits purely capacitive behavior, whereas at the temperature lowering, the influence of resistance strongly increases.