Method for manufacturing energy storage device

A method for manufacturing an energy storage device comprising:

• housing, in a case, an electrode assembly in which a negative electrode and a positive electrode are stacked;
• housing an electrolyte solution in the case;
• housing a gas, soluble in the electrolyte solution, in the case after the electrolyte solution is housed in the case;
• and
• sealing the case in a state where the gas soluble in the electrolyte solution is housed in the case,
• wherein an elapsed time from completion of housing of the gas soluble in the electrolyte solution to sealing of the case is within 30 minutes,
• the case has a flat bottomed rectangular tube-shaped case body and a lid body, the flat bottomed rectangular tube-shaped case body including a bottom surface, an opening opposite to the bottom surface and closed with the lid body after the case is sealed, and a side surface extending between the bottom surface and the opening,
• after the case is sealed, a side surface of the electrode assembly is in direct contact with an inner surface of the side surface of the flat bottomed rectangular tube-shaped case body, or the side surface of the electrode assembly is indirect contact with the inner surface of the side surface of the flat bottomed rectangular tube-shaped case body via a spacer or a sheet having an insulating property interposed between the side surface of the electrode assembly and the inner surface of the side surface of the flat bottomed rectangular tube-shaped case body, and
• after the case is sealed, the gas is dissolved in the electrolyte solution, thereby an inside of the case is brought into a negative pressure state, and the side surface of the flat bottomed rectangular tube-shaped case body is recessed inward to pressurize the side surface of the electrode assembly in a thickness direction of the electrode assembly.