Patent ID: 7924548

Claim:
An electric double layer capacitor comprising: a positive electrode including: a first current collector made of a metal foil; and a first polarizable electrode layer on the first current collector, the first polarizable electrode layer containing a phosphorus compound, wherein the first polarizable layer comprises a first phosphorus-containing region and a second phosphorus-containing region that is located a greater distance from the first current collector than the first phosphorus-containing region, and a content of the phosphorus compound in the first phosphorus-containing region is higher than a content of the phosphorus compound in the second phosphorus-containing region; a negative electrode facing the positive electrode and being electrically insulated therefrom, the negative electrode including: a second current collector made of a metal foil; and a second polarizable electrode layer on the second current collector; and an electrolyte solution having fluorine-containing anions as an electrolyte solute, the first polarizable electrode layer and the second polarizable electrode layer being impregnated with the electrolyte solution.