Rechargeable battery

1. A rechargeable battery comprising:

an electrode assembly including a first electrode, a separator, and a second electrode;

a case that accommodates the electrode assembly, and of which one side through which the electrode assembly is inserted comprises an opening;

a cap assembly provided in the opening of the case by being fixed thereto;

a vent hole that is a through-hole formed in a bottom plate of the case, and of which side walls are multi-stepped; and

a vent member provided in the vent hole,

wherein a depth of the vent hole is greater than a thickness of a first region of the bottom plate that is adjacent to the vent hole and outside a perimeter of the vent hole,

wherein a first inner surface defining an edge of a through portion of the vent hole is connected to the first region of the bottom plate through a corner portion,

wherein the vent hole comprises a first hole, a second hole, and a third hole sequentially arranged toward an inside of the case, the first hole being adjacent to the second hole and penetrating an outer surface of the bottom plate, and the third hole being a through-hole through the first inner surface, and

wherein the vent member is located in the second hole and configured to protrude in a direction from the third hole toward the first hole due to an internal pressure of the case, and a height of a side wall of the first hole is less than the thickness of the first region of the bottom plate and is equal to or greater than a maximum height of protrusion of the vent member prior to rupture of the vent member due to the internal pressure of the case.

2. The rechargeable battery of claim 1 , wherein the first inner surface protrudes more into the case than an inner surface of the first region of the bottom plate.

3. The rechargeable battery of claim 2 , wherein the corner portion is chamfered.

4. The rechargeable battery of claim 3 , wherein the corner portion is formed inside the case.

5. The rechargeable battery of claim 1 , wherein the first hole has a first width, the second hole has a second width that is smaller than the first width, and the third hole has a third width that is smaller than the second width, and

a width of the vent hole is decreased toward the inside of the case.

6. The rechargeable battery of claim 5 , wherein a side wall height of the first hole is higher than a side wall height of the second hole, and the side wall height of the second hole is higher than a side wall height of the third hole.

7. The rechargeable battery of claim 1 , wherein the first hole exposes a first stepped portion that is disposed between the side wall of the first hole and a side wall of the second hole, the second hole, and the third hole, and

the second hole exposes a second stepped portion disposed between the side wall of the second hole and a side wall of the third hole, and the third hole.

8. The rechargeable battery of claim 7 , wherein the vent member is disposed on the second stepped portion and fixed to the side wall of the second hole by welding.

9. The rechargeable battery of claim 8 , wherein a height of the side wall of the second hole is equal to or greater than a thickness of an edge of the vent member.

10. The rechargeable battery of claim 1 , wherein the vent member comprises a notch that is ruptured when the internal pressure of the case exceeds a predetermined pressure.

11. The rechargeable battery of claim 1 , wherein the electrode assembly has a shape of a jelly roll.

12. The rechargeable battery of claim 1 , wherein the first inner surface defining the edge of the through portion of the vent hole is directly connected to the first region of the bottom plate through the corner portion.