Method for manufacturing secondary battery

A method for manufacturing a secondary battery comprising

• an electrode body that comprises a positive electrode, a negative electrode, and a separator that separates the positive electrode and the negative electrode, and comprises at least a pair of rectangular surfaces, and
• a battery case that accommodates the electrode body,
• the method comprising the steps of:
• accommodating the electrode body in the battery case to produce a battery assembly;
• arranging a gripping tool on the outside of the battery case of the battery assembly and gripping the battery assembly with the gripping tool, wherein the battery case comprises two facing surfaces facing the pair of rectangular surfaces of the electrode body accommodated inside the case, and the two facing surfaces of the battery case are sandwiched with the gripping tool;
• drying the inside of the battery assembly, wherein the battery assembly is gripped and heated at 60° C. or higher and 150° C. or lower,
• after the drying, injecting an electrolytic solution to the battery case through an injection hole on the battery case;
• after the injecting, sealing the injection hole;
• and
• after the sealing, performing an initial charging and an aging treatment,
• wherein in the gripping, a larger restraining pressure is applied to a central region including a center line in a long side direction of the rectangular surface of the electrode body than to other regions of the rectangular surface excluding the central region,
• the ratio (L2/L1) of the length L2 in the long side direction of the central region to the length L1 in the long side direction of the rectangular surface of the electrode body is ⅛ or more and ½ or less,
• the gripping tool has gripping plates arranged in a direction, and a plate heater on which the gripping plates are arranged outside,
• in the gripping,
• a plurality of the battery assembly are prepared,
• each of the plurality of the battery assembly is arranged between two adjacent gripping plates in the direction where the gripping plates are arranged to form grip bodies, wherein each of the grip bodies is composed of the two adjacent gripping plates and the battery assembly arranged therebetween,
• the grip bodies are arranged on the plate heater,
• an elastic body is arranged in a space between two adjacent grip bodies to apply a restraining pressure to each of the plurality of the battery assembly.