An integrated energy storage device is provided that includes a supercapacitor and a battery surrounding the supercapacitor. The battery forms a shell around an exterior surface of the supercapacitor. The battery includes a first anode, a first cathode, and an electrolyte disposed between the first anode and the first cathode. The supercapacitor includes a second anode, a second cathode, and a separator disposed between the second anode and the second cathode.