US Patent 7618748 Three-dimensional microbattery

An electrical energy storage device includes a substrate having an outer surface and having a plurality of cavities communicating with the outer surface. The cavities have interior cavity surfaces. A first electrode layer is deposited at least over the interior cavity surfaces. An electrolyte separator layer is formed over the first electrode layer so as to fill the cavities and to extend over the outer surface of the planar substrate. A second electrode layer is formed over the electrolyte separator layer on the outer surface of the planar substrate.