Method of manufacturing electrical energy storage device

A method of manufacturing an electrical energy storage device,

• the electrical energy storage device comprising:
• an electrode body including a positive electrode and a negative electrode, an electrolyte solution, and a case for housing the electrode body and the electrolyte solution, wherein
• the case comprises a case body having a first surface of a rectangular shape having a pair of long sides and a pair of short sides, a pair of second surfaces each extending from a corresponding long side of the pair of long sides and having a larger area than the first surface, a third surface opposite to the first surface, and one or more openings, and
• one or more sealing plates for sealing the one or more openings, wherein
• the first surface comprises a gas release valve, and
• the method comprising:
• a liquid-filling step of filling the electrolyte solution into the case through the filling port provided in the case,
• a charging step of performing charging,
• a case placement step of placing the case on a holding member, and
• a sealing step of sealing the filling port while the third surface is pressed in the first surface direction with a first pressing jig at a first load value, and the pair of second surfaces is pressed with second pressing jigs at a second load value to deform the second surfaces toward inner surfaces of the case body, wherein
• in the case placement step,
• the holding member comprises a base portion,
• the case is placed on the holding member so that the base portion is brought into contact with the first surface of the case body, and
• in the sealing step,
• a region of the first pressing jig where the first pressing jig faces the third surface of the case body is composed of a material having relatively lower hardness than the holding member, and
• the second load value is larger than the first load value.