MULTI-LAYERED TYPE ELECTROCHEMISTRY CELL OF IMPROVED SAFETY

Abstract

Disclosed herein is an electrochemical cell constructed in a structure in which a plurality of full cells or bicells, as unit cells, are folded by a separation film formed in the shape of a long sheet, and separators of the unit cells are secured to the separation film by thermal welding. The electrochemical cell according to the present invention has the effect of preventing the electrodes of the stacked electrodes from being separated from the separation film or from being twisted due to external impacts and vibrations, thereby restraining the electrochemical cell from generating heat or catching fire. Furthermore, the structural stability of the electrochemical cell is maintained even when the temperature of the electrochemical cell is increased, or the volume of the electrochemical cell is increased due to the generation of gas.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIGS. 1 to 5 are typical views respectively illustrating an exemplary full cell and bicells that can be used as a unit cell of an electrochemical cell according to the present invention;

FIGS. 6 and 7 are typical views respectively illustrating electrochemical cells manufactured by folding the bicells shown in FIGS. 2 and 3, as unit cells, according to a preferred embodiment of the present invention and securing a separation film to opposite sides of the unit cells by thermal welding; and

FIG. 8 is a typical view illustrating an electrochemical cell manufactured by securing a separation film to lower ends of unit cells folded according to another preferred embodiment of the present invention.

Claims

1. A multi-layered type electrochemical cell constructed in a structure in which a plurality of full cells or bicells, as unit cells, are folded by a separation film formed in the shape of a long sheet, and separators of the unit cells are secured to the separation film by thermal welding.

2. The electrochemical cell according to claim 1, wherein the electrochemical cell is constructed in a structure in which the separation film has a unit length sufficient to wrap the unit cells, and the separation film is bent inward every unit length, whereby the separation film continuously wraps the unit cells from the central unit cell to the outermost unit cells.

3. The electrochemical cell according to claim 1, wherein the electrochemical cell is constructed in a structure in which the separation film has a unit length sufficient to wrap the unit cells, and the separation film is bent outward every unit length, whereby the separation film continuously wraps the unit cells from the lowermost unit cell to the upper most unit cell in a zigzag fashion, and the remainder of the separation film wraps the outer circumference of the stacked cells.

4. The electrochemical cell according to claim 1, wherein the thermal welding is performed at one side or opposite sides of each cell.

5. The electrochemical cell according to claim 1, wherein the thermal welding is performed at a lower end and/or an upper end of each cell.

6. The electrochemical cell according to claim 5, wherein a separator having a size sufficient to completely cover the lower end and/or the upper end of each cell is attached to the lower end and/or the upper end of each cell, and the thermal welding is performed at the lower end and/or the upper end of each cell.

7. The electrochemical cell according to claim 1, wherein the thermal welding is performed at a temperature of 70 to 140° C.

8. A lithium secondary battery comprising the electrochemical cell according to claim 1.