Energy storage element

An energy storage element comprising:

• a container;
• an electrode assembly housed in the container;
• an electrode terminal;
• a current collector which electrically connects the electrode terminal and the electrode assembly;
• and
• an internal insulation sealing member which insulates the container and the current collector,
• wherein the container includes a wall having an outer surface and an inner surface,
• the outer surface has a protrusion part formed to protrude outward from the outer surface,
• the inner surface has a recess part formed at a position corresponding to a position of the protrusion part,
• the recess part has a bottom surface which is outermost and an inner side surface formed continuously between the bottom surface and the inner surface of the wall of the container,
• at least part of the inner side surface of the recess part is formed to be tilted with respect to a direction in which the protrusion part protrudes, and
• the internal insulation member is positioned between the current collector and the recess part of the container, and has a first wall part which is parallel to the at least part of the inner side surface of the recess part.