Energy storage device having improved heat-dissipation characteristic

1. An energy storage device, comprising:

a cell assembly formed by connecting at least two cylindrical energy storage cells in series;

a case having an accommodation portion shaped corresponding to an outer surface of the energy storage cells to accommodate the cell assembly; and

a heat-dissipating pad installed between the outer surface of the energy storage cells of the cell assembly and an inner surface of the accommodation portion,

wherein the case includes at least two case blocks,

wherein the accommodation portion is formed by coupling the case blocks,

wherein the heat-dissipating pad has elasticity, and

wherein an interval between the accommodation portion and the energy storage cells is smaller than a thickness of the heat-dissipating pad before being compressed and greater than a diameter tolerance of the energy storage cells.

2. The energy storage device according to claim 1 , wherein the energy storage cells contact the heat-dissipating pad with a central angle of 30 to 60 degrees.

3. The energy storage device according to claim 2 , wherein the accommodation portion forms an arc with a length greater than a length of the heat-dissipating pad.

4. The energy storage device according to claim 1 , wherein the heat-dissipating pad is attached to the energy storage cells.

5. The energy storage device according to claim 1 , wherein the heat-dissipating pad is a thermal conductive filler.

6. The energy storage device according to claim 1 , wherein an adhesive layer is provided at one side of the heat-dissipating pad.

7. The energy storage device according to claim 1 , wherein the energy storage cells are ultra-capacitors.

8. The energy storage device according to claim 1 , wherein at least one of the case blocks includes:

a plurality of convex portions having the same arc shape as an outer shape of the energy storage cells;

a convex portion connector configured to connect the plurality of convex portions; and

a concave portion formed between the convex portions and the convex portion connector.

9. The energy storage device according to claim 8 , wherein at least one heat-dissipating plate is formed at the concave portion to protrude perpendicularly.

10. The energy storage device according to claim 8 , wherein the at least one of the case blocks has an ‘L’ shape or a ‘⊂’ shape.

11. The energy storage device according to claim 10 , wherein when the at least one of the case blocks has the ‘L’ shape, one of a plurality of outermost convex portions of the plurality of convex portions is connected so that the arc shapes of the convex portions are connected.

12. The energy storage device according to claim 11 , wherein the at least one of the case blocks further includes a case block connector extending from one of the outermost convex portions and bent in a longitudinal direction of the at least one of the case blocks.

13. The energy storage device according to claim 10 , wherein when the at least one of the case blocks has the ‘⊂’ shape, a plurality of outermost convex portions of the plurality of convex portions are connected so that the arc shapes of the convex portions are connected.

14. The energy storage device according to claim 13 , wherein the at least one of the case blocks further includes a case block connector extending from each of the outermost convex portions and bent in a longitudinal direction of the at least one of the case blocks.

15. The energy storage device according to claim 8 , wherein a tab is formed at the convex portion connector to cover a cover.

16. The energy storage device according to claim 1 , wherein a distance between the energy storage cells and the case is gradually increasing from an end point of the heat-dissipating pad so that the energy storage cells and the case are insulated from each other.

17. The energy storage device according to claim 1 , wherein an insulation film is further formed at the outer surface of the energy storage cells.