Pouch-typed battery cell comprising electrode lead having current breaking function

Abstract

A battery cell includes an electrode assembly and a battery case. The electrode assembly includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode. The battery case includes an upper case and a lower case, at least one of the upper case and the lower case being provided with a receiving part, in which the electrode assembly is mounted. One end of each of electrode tabs extending from electrode plates of the electrode assembly is coupled to a corresponding end of an electrode lead, which protrudes outward from the battery case. The electrode lead is provided with at least one notch part configured to rupture in response to expansion deformation of the battery case when the pressure in the battery cell increases to achieve the electrical cutoff of the battery.

Claims

1. A battery cell, comprising: an electrode assembly comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; and a battery case comprising an upper case and a lower case, at least one of the upper case and the lower case being provided with a receiving part, in which the electrode assembly is mounted, wherein: one end of each of electrode tabs extending from the electrode assembly is coupled to a corresponding end of an electrode lead, and the electrode lead extends from the electrode tabs to protrude outward from the battery case, the electrode lead is provided with at least one notch part configured to rupture in response to expansion deformation of the battery case when a pressure in the battery cell increases in order to achieve an electrical cutoff of the battery, the electrode lead is attached to one of the upper case and the lower case by a first insulative film that is interposed between a portion of one surface of the electrode lead and an inner surface of the one of the upper case and the lower case, the first insulative film is closer to the electrode assembly than the notch part, the electrode lead is attached to the upper case and the lower case by second insulative films that are interposed respectively between portions of opposite surfaces of the electrode lead and the inner surfaces of the upper case and the lower case such that the second insulative films are farther from the electrode assembly than the notch part and such that the second insulative films seal the battery case, one of the second insulative films is longer than the other of the second insulative films, the one of the second insulative films that is longer than the other of the second insulative film is on a surface of the electrode lead that is opposite to the surface of the electrode lead on which the first insulative film is attached, and the notch part is formed on the surface of the electrode lead that is opposite to the surface of the electrode lead on which the first insulative film is attached.

2. The battery cell according to claim 1, wherein the notch part is formed at a location on the electrode lead that is 10% to 50% of a total length of the electrode lead from a coupling region between the electrode tabs and the electrode lead.

3. The battery cell according to claim 1, wherein the notch part is formed so as to have a depth of 20 to 80% a total thickness of the electrode lead.

4. The battery cell according to claim 1, wherein the one of the second insulative films that is longer has a length of 0.8 to 1 times a distance from the notch part to an end of the battery case, the other of the second insulative films has a length of 0.7 to 0.3 times the distance from the notch part to an end of the battery case, and ends of the second insulative films away from the notch part are located at a same position in a longitudinal direction of the electrode lead.

5. The battery cell according to claim 1, wherein each of the insulative films is a polypropylene film or a polyimide film.

6. The battery cell according to claim 1, wherein the electrode tabs are coupled to the electrode lead by welding.

7. The battery cell according to claim 1, wherein positive electrode tabs and negative electrode tabs are formed in a same direction.

8. The battery cell according to claim 1, wherein positive electrode tabs and negative electrode tabs are formed in opposite directions.

9. The battery cell according to claim 1, wherein the battery case is made of a laminate sheet comprising an outer resin layer, a metal blocking layer, and a thermally fusible resin sealant layer.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) 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:

(2) FIG. 1 is a perspective view of a conventional pouch-shaped battery cell;

(3) FIG. 2 is a side see-through view of a battery cell according to an embodiment of the present invention;

(4) FIG. 3 is a side see-through view of the battery cell of FIG. 2, showing the shape in which an electrode lead is broken when the pressure in the battery cell increases; and

(5) FIG. 4 is a side see-through view of a battery cell according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(6) Now, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted, however, that the illustrated embodiments are given for easier understanding of the present invention and thus the scope of the present invention is not limited by the illustrated embodiments.

(7) FIG. 2 is a side see-through view schematically showing a battery cell according to an embodiment of the present invention, and FIG. 3 is a side see-through view of the battery cell, schematically showing the shape in which an electrode lead is broken when the pressure in the battery cell increases.

(8) Referring to FIGS. 2 and 3, the battery cell, denoted by reference numeral 100, includes an electrode assembly 110 and a battery case 120.

(9) The electrode assembly 110 includes positive electrodes 111, negative electrodes 112, and separators interposed respectively between the positive electrodes 111 and the negative electrodes 112.

(10) The battery case 120 includes an upper case 122 and a lower case 123. A receiving part 121, in which the electrode assembly 110 is mounted, is formed in the upper case 122 and the lower case 123.

(11) Electrode tabs 130 extend from electrode plates of the positive electrodes 111 and the negative electrodes 112. In FIGS. 2 and 3, which are side see-through views, only electrode tabs 130 extending from the electrode plates of one of the positive and negative electrodes, e.g. from the electrode plates of the negative electrodes 112, are shown. Electrode tabs (not shown) extending from the electrode plates of the positive electrodes 111 may extend in the same direction as the direction in which the electrode tabs 130 of the negative electrodes 112 extend, or may extend in the direction that is opposite the direction in which the electrode tabs 130 of the negative electrodes 112 extend.

(12) One end of each of the electrode tabs 130 extending from the electrode plates of the negative electrodes 112 is coupled to a corresponding end of an electrode lead 140, which protrudes outward from the battery case 120, by ultrasonic welding to constitute a coupling region 150.

(13) The electrode lead 140 according to the present invention is provided with a notch part 141, which is configured to rupture in response to expansion deformation of the battery case 120 when the pressure in the battery cell 100 increases in order to achieve the electrical cutoff of the battery 100.

(14) In addition, the electrode lead 140 is connected to the lower case 123 by fusion in the state in which a first insulative film 160 is interposed between a portion of one surface of the electrode lead 140 that is adjacent to the electrode assembly 110 on the basis of the notch part 141 and the inner surface of the lower case 123, and the electrode lead 140 is connected to the upper case 122 and the lower case 123 by fusion in order to seal the battery case in the state in which second insulative films 124 and 125 are interposed respectively between portions of opposite surfaces of the electrode lead 140 that is distant from the electrode assembly 110 on the basis of the notch part 141 and the inner surfaces of the upper case 122 and the lower case 123.

(15) One of the second insulative films 124 and 125 that is opposite the first insulative film 160 on the basis of the electrode lead 140, i.e. the second insulative film 124, is longer than the second insulative film 125, which is located on the same side as the second insulative film 124, and is connected to the battery case 120 by fusion. In addition, ends of the second insulative films 124 and 125 that are distant from the notch part 141 are located at the same position in the longitudinal direction of the electrode lead 140. As a result, the second insulative film 124 is connected to the battery case 120 by fusion in the state of being located so as to be closer to the notch part 141 than the second insulative film 125.

(16) On the basis of the notch part 141, therefore, the electrode lead 140 can be securely connected to the lower case 123 by fusion via the first insulative film 160 on the surface of the electrode lead 140 that is opposite the surface of the electrode lead 140 in which the notch part 141 is formed, and the electrode lead 140 can be more securely connected to the upper case 122 by fusion via the second insulative film 124 on the same surface of the electrode lead 140 as the surface of the electrode lead 140 in which the notch part 141 is formed.

(17) Here, the notch part 141 is formed in the surface of the electrode lead 140 that is opposite the surface of the electrode lead 140 on which the insulative films 125 and 160 are located.

(18) When the battery case 120 is deformed by expansion thereof as the pressure in the battery cell 100 increases (as indicated by the arrows), as shown in FIG. 3, therefore, a portion of the electrode lead 140 that is adjacent to the electrode assembly 110 on the basis of the notch part 141 is pushed downward together with the lower case 123, and a portion of the electrode lead 140 that is distant from the electrode assembly 110 on the basis of the notch part 141 remains securely fixed to the upper case 122, whereby the rupture of the electrode lead 140 is effectively achieved.

(19) Meanwhile, FIG. 4 is a side see-through view schematically showing a battery cell 200 according to another embodiment of the present invention.

(20) Referring to FIG. 4, the battery cell 200 is configured to have a structure in which an electrode assembly 210, including positive electrodes 211, negative electrodes 212, and separators interposed respectively between the positive electrodes 211 and the negative electrodes 212, is mounted in a receiving part 221 defined between an upper case 222 and a lower case 223 constituting a battery case 220, in the same manner as in FIGS. 2 and 3. Electrode tabs 230 extend from electrode plates of the negative electrodes 212. (Electrode tabs extending from electrode plates of the positive electrodes 211 are not shown.) One end of each of the electrode tabs 230 extending from the electrode plates of the negative electrodes 112 is coupled to a corresponding end of an electrode lead 240, which protrudes outward from the battery case 220, by ultrasonic welding to constitute a coupling region 250. In addition, the electrode lead 240 is provided with a notch part 241, which is configured to rupture in response to expansion deformation of the battery case 220 when the pressure in the battery cell 200 increases in order to achieve the electrical cutoff of the battery 200.

(21) Meanwhile, compared with the battery cell 100 of FIG. 2, the battery cell 200 is identical to the battery cell 100 of FIG. 2 in that the electrode lead 240 is connected to the lower case 223 by fusion in the state in which a first insulative film 260 is interposed between a portion of one surface of the electrode lead 240 that is adjacent to the electrode assembly 210 on the basis of the notch part 241 and the inner surface of the lower case 223, and the electrode lead 240 is connected to the upper case 222 and the lower case 223 by fusion in order to seal the battery case in the state in which second insulative films 224 and 225 are interposed respectively between portions of opposite surfaces of the electrode lead 240 that is distant from the electrode assembly 210 on the basis of the notch part 241 and the inner surfaces of the upper case 222 and the lower case 223. However, the battery cell 200 is different from the battery cell 100 of FIG. 2 in that the second insulative films 224 and 225 have the same length and in that an auxiliary insulative film 270 is further disposed on and fused to the surface of the electrode lead 240 in which the notch part 241 is formed, i.e. the surface of the electrode lead 240 that is opposite the surface of the electrode lead 240 on which the first insulative film 260 is located, so as to be located between the notch part 241 and the second insulative film 224, which is distant from the electrode assembly 210 on the basis of the notch part 241.

(22) Even in the case in which the second insulative film 224, which is interposed between the upper case 222 and the electrode lead 240, and the second insulative film 225, which is interposed between the lower case 223 and the electrode lead 240, are configured to have the same length, therefore, the electrode lead 240 can be securely fused to the battery case 220 on the surface of the electrode lead 240 in which the notch part 241 is formed by the provision of the auxiliary insulative film 270.

(23) When the battery case 220 is deformed by expansion thereof as the pressure in the battery cell 200 increases, therefore, a portion of the electrode lead 240 that is adjacent to the electrode assembly 210 on the basis of the notch part 241 is pushed downward together with the lower case 223, and a portion of the electrode lead 240 that is distant from the electrode assembly 210 on the basis of the notch part 241 remains securely fixed to the upper case 222, whereby the rupture of the electrode lead 240 is effectively achieved, in the same manner as what is described with reference to FIG. 3.

(24) Hereinafter, the present invention will be described in more detail with reference to the following examples. These examples are provided only for illustration of the present invention and should not be construed as limiting the scope of the present invention.

Manufacture Example

(25) Manufacture of Positive Electrode

(26) 96.25 weight % of LiNi.sub.0.6Co.sub.0.2Mn.sub.0.2O.sub.2 as a positive electrode active material, 1.5 weight % of Fx35 as a conductive agent, and 2.25 weight % of PVdF as a binder were mixed with N-methyl-2-pyrrolidone (NMP) as a solvent to manufacture a positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry was coated, dried, and pressed over aluminum foil to manufacture a positive electrode.

(27) Manufacture of Negative Electrode

(28) 95.6 weight % of a mixture of artificial graphite and natural graphite as a negative electrode active material, 1.0 weight % of Super-C as a conductive agent, 0.3 weight % of SBR as a binder, and 1.1 weight % of CMC as a thickening agent were mixed with water as a solvent to manufacture a negative electrode mixture slurry. Subsequently, the negative electrode mixture slurry was coated, dried, and pressed over copper foil to manufacture a negative electrode.

(29) Manufacture of Secondary Battery

(30) An electrode assembly configured to have a structure in which a PE separator was interposed between the positive electrode and the negative electrode was placed in a pouch-shaped battery case, and an electrolytic solution having an additive, including VC, and 0.7 M of LiPF.sub.6+0.3 M of LiFSI as salt dissolved in a solvent of EC:EMC=3:7 was injected into the battery case to manufacture a secondary battery.

Example 1

(31) In the manufacturing example, each of a positive electrode lead and a negative electrode lead configured to be connected respectively to positive electrode tabs and negative electrode tabs was manufactured such that the depth of a notch part was 30% the depth of the electrode lead in order to manufacture a secondary battery as shown in FIG. 2. At this time, the adhesive force between insulative films and the battery case were set to be 6 kgf/15 mm or higher.

Example 2

(32) A secondary battery was manufactured in the same manner as in Example 1 except that each of the positive electrode lead and the negative electrode lead was manufactured such that the depth of the notch part was 50% the depth of the electrode lead.

Example 3

(33) A secondary battery was manufactured in the same manner as in Example 1 except that each of the positive electrode lead and the negative electrode lead was manufactured such that the depth of the notch part was 70% the depth of the electrode lead.

Comparative Example 1

(34) A secondary battery was manufactured in the same manner as in Example 1 except that no notch part was formed in each of the positive electrode lead and the negative electrode lead.

Experimental Example 1

(35) The pressures in the secondary batteries manufactured according to Examples 1 to 3 and Comparative Example 1 were increased. At this time, whether vents were formed in the battery cases of the secondary batteries and the pressures in the secondary batteries that caused electrical short circuits of the secondary batteries were measured. The results are shown in Table 1 below.

(36) TABLE-US-00001 TABLE 1 Formation of vent Pressure in battery when (Pressure in battery when electrical short circuit vent is formed) occurs Example 1 x 2 atm Example 2 x 1.5 atm Example 3 x 1.0 atm Comparative O (3 atm) example 1

(37) As can be seen from Table 1, in the battery cell according to the present invention, an electrical short circuit occurs in the battery cell before a vent is formed in the battery cell. Consequently, gas in the battery cell, which is harmful to the human body, is prevented from being discharged from the battery cell. In addition, it is possible to prevent the ignition and explosion of the battery cell, which may be caused by an increase in the temperature of the battery cell due to abnormal operation of the battery cell. In the conventional battery cell, on the other hand, no electrical short circuit occurs in the battery cell until the pressure in the battery cell reaches 3 atm, and a vent is formed in the battery cell when the pressure in the battery cell is 3 atm. As a result, gas in the battery cell, which is harmful to the human body, is discharged from the battery cell. Furthermore, even after the vent is formed in the battery cell, the battery cell is continuously operated, which may result in the ignition and explosion of the battery cell.

(38) In addition, referring to Examples 1 to 3, it can be seen that the pressure in the battery cell varies depending on the depth of the notch part when an electrical short circuit occurs in the battery cell. Consequently, it is possible to adjust the pressure in the battery cell at which the electrical short circuit occurs in the battery cell by adjusting the depth of the notch part, whereby it is possible to easily deal with various demands of customers.

(39) Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.