Technologies are described herein for implementing a space-efficient internal energy storage apparatus in a data storage device or other electronic device have a metallic or otherwise electrically-conductive housing or case structure. A first carbon layer is applied to an inner surface of the metallic housing, and a dielectric spacer is applied upon the first carbon layer. Next, a conductive layer having a second carbon layer is applied over the dielectric spacer, and the metallic housing and the conductive layer is electrically connected to a circuitry of the electronic device.