Approaches herein provide improved encapsulation of an energy storage device. In one approach, a thin film storage device stack is formed atop a first side of a substrate, and an encapsulant is formed over the thin film storage device stack. A recess formed in the substrate adjacent the thin film storage device stack provides an anchoring point for the encapsulant. In some approaches, the recess is provided partially through a depth of the substrate, and has a geometry to promote physical coupling between the encapsulant and the substrate.