Abstract: In one embodiment, an energy storage device comprises a container containing a first electrode generating a positive charge, a second electrode generating a negative charge, and an electrolyte in ionic contact with the electrodes. The container comprises a base and one or more walls defining an opening in the container, the base having a first terminal in electrical connection with the first electrode. A cap is shaped to close the opening and is electrically isolated from the container, while having a second terminal in electrical connection with the second electrode. A collector plate is interposed between the first electrode and the base and is electrically conductive, providing the electrical connection between the first electrode and the first electrical terminal and exhibiting an extension with a concave side oriented in the direction of the base, which is connected to the base by interference fitting against a mating protrusion on the base.