Button cell

1. A button cell comprising:

an electrode assembly comprising a first electrode, a second electrode, a separator between the first electrode and the second electrode, a first electrode tab coupled to the first electrode, and a second electrode tab coupled to the second electrode;

a case accommodating the electrode assembly and coupled to the first electrode tab;

a cap assembly sealing an opening in the case, the cap assembly comprising:

a cap plate coupled to the case and covering the opening in the case; and

a terminal plate coupled to the cap plate; and

an insulating member having an outermost surface contacting an inner surface of the cap plate and an innermost surface facing the second electrode tab,

wherein the terminal plate comprises:

a flange portion coupled to and electrically insulated from the cap plate; and

a tab connecting portion protruding from the flange portion toward the electrode assembly and extending through a terminal opening in the cap plate, the tab connecting portion being coupled to the second electrode tab,

wherein outer surfaces of the flange portion and the tab connecting portion form a flat outer surface of the terminal plate, and

wherein the tab connecting portion has a flat inner surface that protrudes into the case.

2. The button cell of claim 1 , wherein the flange portion of the terminal plate is parallel to the cap plate.

3. The button cell of claim 1 , wherein a first end of the electrode assembly faces the case, and a second end of the electrode assembly faces the cap plate, and

wherein a height difference is formed between the inner surface of the tab connecting portion and the inner surface of the cap plate.

4. The button cell of claim 3 , wherein the inner surface of the tab connecting portion is nearer to the second end of the electrode assembly than the inner surface of the cap plate is.

5. The button cell of claim 3 , wherein, when the second end of the electrode assembly is a flat reference surface:

a first height is formed between the inner surface of the cap plate and the second end of the electrode assembly;

a second height is formed between the inner surface of the tab connecting portion and the second end of the electrode assembly; and

the second height is smaller than the first height.

6. The button cell of claim 3 , wherein a distal portion of the inner surface of the tab connecting portion that faces the second electrode tab is nearer to the second end of the electrode assembly than the inner surface of the cap plate is.

7. The button cell of claim 3 , wherein, when the second end of the electrode assembly is a flat reference surface:

a first height is formed between the inner surface of the cap plate and the second end of the electrode assembly;

a second height is formed between a distal portion of the inner surface of the tab connecting portion that faces the second electrode tab and the second end of the electrode assembly; and

the second height is smaller than the first height.

8. The button cell of claim 1 , wherein the insulating member has a plate shape with a through opening therein, and

wherein the through opening in the insulating member corresponds to the terminal opening in the cap plate.

9. The button cell of claim 8 , wherein the through opening in the insulating member has a smaller diameter than the terminal opening in the cap plate, and

wherein the through opening in the insulating member and the terminal opening in the cap plate are concentric.

10. The button cell of claim 1 , wherein, when the opening in the case is sealed and closed by the cap assembly, a height is a distance between the case and the outer surface of the terminal plate, a diameter is an outer diameter of the case, and a height-to-diameter ratio is 1 or less.

11. The button cell of claim 1 , wherein the electrode assembly is formed by winding the first electrode, the second electrode, and the separator interposed between the first electrode and the second electrode into a jelly roll shape.

12. The button cell of claim 1 , further comprising a heat-fusion member between the flange portion of the terminal plate and an outer surface of the cap plate.

13. The button cell of claim 12 , wherein the heat-fusion member and the insulating member are spaced apart from each other.

14. The button cell of claim 1 , wherein the terminal plate comprises forged aluminum.

15. A button cell comprising:

an electrode assembly comprising a first electrode, a second electrode, a separator between the first electrode and the second electrode, a first electrode tab coupled to the first electrode, and a second electrode tab coupled to the second electrode;

a case accommodating the electrode assembly and coupled to the first electrode tab; and

a cap assembly sealing an opening in the case, the cap assembly comprising:

a cap plate coupled to the case and covering the opening in the case; and

a terminal plate coupled to the cap plate,

wherein the terminal plate comprises:

a flange portion coupled to and electrically insulated from the cap plate; and

a tab connecting portion protruding from the flange portion toward the electrode assembly and extending through a terminal opening in the cap plate, the tab connecting portion being coupled to the second electrode tab,

wherein outer surfaces of the flange portion and the tab connecting portion form a flat outer surface of the terminal plate,

wherein the tab connecting portion has a flat inner surface that protrudes into the case, and

wherein the terminal plate comprises forged aluminum.