Abstract: A capacitive electrical energy storage structure is fabricated as a thin-film device comprising electrodes on opposite sides of a dielectric layer. In one approach, a high surface area metallic sponge can be incorporated into the structure. The energy storage structure can comprise either single or multiple layers of capacitors connected in series, parallel, or a combination of such arrangements. The multi-layer capacitor structure can be either applied directly to supporting structures of portable or transportable devices or can be fabricated as a film which is applied as a laminate to such structures. Further, a conformal energy storage structure can be produced which is shaped to fit in voids within devices, which voids would otherwise be little used or unused.