Button-type secondary battery

A button-type secondary battery, comprising:

• an electrode assembly in which a negative electrode, a separator, and a positive electrode are layered wound in a state of being layered;
• a lower can in which the electrode assembly is mounted, and a space portion is defined as a surplus space in addition to a space in which the electrode assembly is mounted;
• an upper can coupled to the lower can to close the lower can in a state in which the electrode assembly is mounted in the lower can, and an electrolyte is injected;
• and
• a swelling member mounted in the lower can in a state of being coupled to an outer surface of the electrode assembly,
• wherein when the electrolyte is injected, the swelling member absorbs the electrolyte to be expanded in volume within the space portion,
• wherein the lower can comprises:
• a first sidewall formed upward along a circumference of a flat bottom surface;
• a first inclined portion formed in a shape of which a diameter gradually increases from an end of the first sidewall;
• and
• a first distal end extending in a direction parallel to the first sidewall from an end of the first inclined portion,
• wherein the first inclined portion is formed to have a diameter that is tapered in from an end of the first distal end, and
• wherein the upper can comprises:
• a second sidewall formed downward along a circumference of a flat top surface and parallel to the first distal end;
• a second inclined portion formed to have a diameter that is tapered in from an end of the second sidewall and being parallel to the first inclined portion;
• and
• a second distal end extending from an end of the second inclined portion and parallel to the first sidewall.