Method for producing secondary battery

A method for producing a secondary battery,

• wherein the secondary battery includes:
• an electrode assembly including a first electrode plate, a second electrode plate having a polarity different from the polarity of the first electrode plate, and a separator disposed between the first electrode plate and the second electrode plate, and
• a first electrode current collector electrically connected to the first electrode plate,
• wherein the first electrode plate includes a first electrode core and a first electrode active material layer formed on the first electrode core, wherein the first electrode core includes a first electrode-core exposed portion on which the first electrode active material layer is not formed, the first electrode-core exposed portion being located at a first end portion of the first electrode core in a first direction, and
• the second electrode plate includes a second electrode core and a second electrode active material layer formed on the second electrode core, wherein the second electrode core includes a second electrode-core exposed portion on which the second electrode active material layer is not formed, the second electrode-core exposed portion being located at a second end portion of the second electrode core opposite to the first end portion of the first electrode core in the first direction,
• wherein the electrode assembly includes a first electrode core-stacked portion in which the first electrode-core exposed portion is stacked and a second electrode core-stacked portion in which the second electrode-core exposed portion is stacked,
• wherein the first electrode core-stacked portion is located in a first end of the electrode assembly, corresponding to the first end portion of the first electrode core, in the first direction, and
• wherein the second electrode core-stacked portion is located in a second end of the electrode assembly, which is opposed to the first end and corresponding to the second end portion of the second electrode core, in the first direction,
• the method comprising:
• an electrode assembly production step of producing the electrode assembly including the first electrode core-stacked portion and the second electrode core-stacked portion;
• and
• an ultrasonic bonding step of ultrasonically bonding the first electrode current collector to the first electrode core-stacked portion,
• wherein, in the ultrasonic bonding step, the first electrode current collector has a thin-walled portion having a smaller thickness than an annular thicker portion surrounding the thin-walled portion,
• the thin-walled portion is smaller than the first electrode core-stacked portion in the first direction,
• a part of the annular thicker portion is located between an end of the second electrode plate and the thin-walled portion in the first direction, said end of the second electrode plate being an end in the first direction adjacent to the first electrode core-stacked portion,
• the part of the annular thicker portion includes a rib formed on a surface of the part of the annular thicker portion opposed to a surface of the part of the annular thicker portion facing the first electrode core-stacked portion,
• in the part of the annular thicker portion, an area where the rib is formed is thicker than another area of the part of the annular thicker portion, and
• the thin-walled portion and the first electrode core-stacked portion are sandwiched between a horn and an anvil and then ultrasonically bonded together.