ELECTROCHEMICAL CAPACITOR

PROBLEM TO BE SOLVED: To enhance fire resistance and improve safety by making at least either of positive and negative electrodes to be a polarizing negative electrode, made mainly of carbonic substance and allowing a nonaqueous electrolyte solution to contain a specified phosphoric ester as a solvent represented by a specific formula. SOLUTION: This electrochemical capacitor uses a nonaqueous electrolyte solution, using a solvent containing a phosphoric ester of one or more which is selected from among a group consisting of a trialkyl phosphate, a methylethylene phosphate, and a methyl trimethylene phosphate represented by formula 1 (R1, R2, R3 which are independent alkyl group of carbon number 1 to 4), a compound represented by formula 2, a compound represented by formula 3, and a trimethylolethane phosphate. In addition, both positive and negative electrodes of the electro-chemical capacitor are comprised of polarizing electrode made mainly of a carbonic substance. The proportion of phosphoric ester in the solvent of the nonaqueous electrolyte solution is set at preferably 15 wt.% or more.