An energy storage device of excellent input/output characteristics and having high density of stored energy, the device having a cathode comprising a material conducting faradic reaction and a material conducting non-faradic reaction, and an anode comprising a material conducting faradic reaction, in which the faradic reaction is desorption/intercalation reaction of lithium ions, higher input/output characteristics being obtainable by providing a mix layer comprising a material conducting faradic reaction on a cathode collector and providing a material layer conducting non-faradic reaction further to the surface layer thereof.