Magnetic skyrmions are considered as a promising candidate for the next-generation information processing technology. Being topologically robust, magnetic skyrmions are swirling spin textures that can be used in a broad range of applications from memory devices, logic circuits, to neuromorphic computing. In a magnetic medium lacking inversion symmetry, magnetic skyrmion arises as a result of the interplay between magnetic exchange interactions, Dzyaloshinskii-Moriya interaction, and magnetic anisotropy. Instrumental to the integrated skyrmion-based applications are the creation and manipulation of magnetic skyrmions at a designated location, absent any need of a magnetic field. In this paper, we propose a generic design strategy to achieve that and a model system to demonstrate its feasibility. By implementing in a disk-shaped thin film heterostructure an inhomogeneous perpendicular magnetic anisotropy, stable sub-100-nm size skyrmions can be generated without magnetic field. This structure can be etched out via, for example, focused ion beam microscope. Using micromagnetic simulation, we show that such heterostructure not only stabilizes the edge spins of the skyrmion, but also protects its rotation symmetry. Furthermore, we may switch the spin texture between skyrmionic and vortex-like ones by tuning the slope of perpendicular anisotropy using a bias voltage. When embedded into a magnetic conductor and under a spin polarized current, such heterostructure emits skyrmions continuously and may function as a skyrmion source. This unique phenomenon is dubbed as skyrmion battery effect. Our proposal may open a novel venue for the realization of all-electric skyrmion-based device.