Lithium secondary battery having enhanced safety

Abstract

Disclosed is a secondary battery, wherein an electrode assembly including at least one positive electrode respectively having positive electrode tabs not coated with a positive electrode active material; at least one negative electrode respectively having negative electrode tabs not coated with a negative electrode active material; and at least one separator disposed between the positive electrode and the negative electrode is sealed with an electrolyte solution in a battery case, the positive electrode tabs and the negative electrode tabs are respectively connected to positive electrode lead and negative electrode lead protruded to the outside of a battery case, and at least one an electrode terminal selected from the group consisting of the positive electrode tabs, the negative electrode tabs, the positive electrode lead and the negative electrode lead includes Wood's metal.

Claims

1. A secondary battery, wherein an electrode assembly includes at least one positive electrode respectively having positive electrode tabs not coated with a positive electrode active material; at least one negative electrode respectively having negative electrode tabs not coated with a negative electrode active material; and at least one separator disposed between the positive electrode and the negative electrode and sealed with an electrolyte solution in a battery case, the positive electrode tabs and the negative electrode tabs are respectively connected to positive electrode lead and negative electrode lead protruded to the outside of a battery case, and at least one electrode terminal selected from the group consisting of the positive electrode tabs, and the negative electrode tabs comprises Wood's metal, and wherein the Wood's metal is an alloy of Bi and Pb, or an alloy of Bi and Sn.

2. The secondary battery according to claim 1, wherein a melting point of the Wood's metal is 80° C. to 400° C.

3. The secondary battery according to claim 1, wherein the electrode terminal comprising Wood's metal is plated with aluminum (Al), copper (Cu) or nickel (Ni).

4. The secondary battery according to claim 1, wherein the electrode terminal comprising Wood's metal is positive electrode tabs.

5. The secondary battery according to claim 4, wherein the Wood's metal is an alloy of Bi and Pb, or an alloy of Bi and Sn.

6. The secondary battery according to claim 5, wherein the Bi and Pb are present in a molar ratio of 40:60 to 60:40.

7. The secondary battery according to claim 5, wherein the Bi and Sn are present in a molar ratio of 50:50 to 30:70.

8. The secondary battery according to claim 4, wherein the positive electrode tabs are plated with aluminum (Al).

9. The secondary battery according to claim 1, wherein the electrode terminal comprising Wood's metal is negative electrode tabs.

10. The secondary battery according to claim 9, wherein the Wood's metal is an alloy of Bi and Pb.

11. The secondary battery according to claim 10, wherein the Bi and Pb are present in a molar ratio of 40:60 to 60:40.

12. The secondary battery according to claim 9, wherein the negative electrode tabs are plated with copper (Cu) or nickel (Ni).

13. The secondary battery according to claim 1, wherein the positive electrode active material comprises a lithium transition metal oxide represented by Formula 1 or 2 below:
Li.sub.xM.sub.yMn.sub.2−yO.sub.4−zA.sub.z  (1), wherein M is at least one element selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, Ti and Bi; A is at least one monovalent or divalent anion; and
0.9≦x≦1.2, 0<y<2, and 0≦z<0.2,
(1-x)LiM′O.sub.2−yA.sub.y-xLi.sub.2MnO.sub.3−y′A.sub.y′  (2), wherein M′ is Mn.sub.aM.sub.b; M is at least one selected from the group consisting of Ni, Ti, Co, Al, Cu, Fe, Mg, B, Cr, Zr, Zn and Period II transition metals; A is at least one selected from the group consisting of anions such as PO.sub.4, BO.sub.3, CO.sub.3, F and NO.sub.3; and
0<x<1, 0<y≦0.02, 0<y′≦0.02, 0.5≦a≦1.0, 0≦b≦0.5, and a+b=1.

14. The secondary battery according to claim 1, wherein the negative electrode active material comprises a carbon-based material and/or Si.

15. The secondary battery according to claim 1, wherein the battery case is composed of a laminate sheet comprising a resin layer and a metal layer.

16. The secondary battery according to claim 1, wherein the secondary battery is a lithium ion battery, a lithium ion polymer battery or a lithium polymer battery.

17. The secondary battery according to claim 1, wherein at least one electrode terminal selected from the group consisting of the positive electrode lead and the negative electrode lead further comprises Wood's metal.

18. The secondary battery according to claim 17, wherein the positive electrode tabs and/or the positive electrode lead are plated with aluminum (Al).

19. The secondary battery according to claim 17, wherein the negative electrode tabs and/or the negative electrode lead are plated with copper (Cu) or nickel (Ni).

20. A battery module comprising the secondary battery according to claim 1 as a unit cell.

21. The battery pack comprising the battery module according to claim 20.

22. A device comprising the battery pack according to claim 21 as a power source.

23. The device according to claim 22, wherein the device is an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or a system for storing power.

Description

BRIEF DESCRIPTION OF THE 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 illustrates a schematic view of a secondary battery according to the present invention.

MODE FOR INVENTION

(3) Now, the present invention will be described in more detail with reference to the accompanying drawings. These examples are provided for illustrative purposes only and should not be construed as limiting the scope and spirit of the present invention.

Example 1

(4) An electrode assembly including a positive electrode tab and a negative electrode tab composed of an alloy including Bi and Pb in a molar ratio of 40:60 was embedded in a pouch type secondary battery, thereby manufacturing a secondary battery.

Example 2

(5) A secondary battery was manufactured in the same manner as in Example 1, except that a positive electrode tab and a negative electrode tab were composed of an alloy including Bi and Pb in a molar ratio of 60:40.

Example 3

(6) A secondary battery was manufactured in the same manner as in Example 1, except that a positive electrode tab was composed of an alloy including Bi and Sn in a molar ratio of 50:50.

Example 4

(7) A secondary battery was manufactured in the same manner as in Example 1, except that a positive electrode tab was composed of an alloy including Bi and Sn in a molar ratio of 30:70.

Comparative Example 1

(8) A secondary battery was manufactured in the same manner as in Example 1, except that a positive electrode tab and negative electrode tab were composed of alloy including Bi and Pb in a molar ratio of 70:30.

Comparative Example 2

(9) A secondary battery was manufactured in the same manner as in Example 1, except that a positive electrode tab and a negative electrode tab were composed of alloy including Bi and Pb in a molar ratio of 30:70.

Comparative Example 3

(10) A secondary battery was manufactured in the same manner as in Example 1, except that a positive electrode tab was composed of an alloy including Bi and Sn in a molar ratio of 20:80.

Comparative Example 4

(11) A secondary battery was manufactured in the same manner as in Example 1, except that a positive electrode tab was composed of an alloy including Bi and Sn in a molar ratio of 80:20.

Comparative Example 5

(12) A secondary battery was manufactured in the same manner as in Example 1, except that a positive electrode tab and a negative electrode tab were compose of only Bi.

Comparative Example 6

(13) A secondary battery was manufactured in the same manner as in Example 1, except that a positive electrode tab was composed of aluminum and a negative electrode tab was composed of copper.

Experimental Example 1

(14) In order to perform safety tests according to overcharge of secondary batteries according to Examples 1 to 4 and Comparative Examples 1 to 6, each of the secondary batteries was charged at 6.3V CC/CV under conditions of 0% SOC and 1 C, and a 6.3 V overcharge state was maintained for two hours. Results are summarized in Table 1 below.

(15) TABLE-US-00001 TABLE 1 Example 1 Disconnection of positive electrode tab at 121° C. Example 2 Disconnection of positive electrode tab at 81° C. Example 3 Disconnection of positive electrode tab at 138° C. Example 4 Disconnection of positive electrode tab at 142° C. Comparative Disconnection of positive electrode tab does not occur, cell Example 1 ignition Comparative Disconnection of positive electrode tab does not occur, cell Example 2 ignition Comparative Disconnection of positive electrode tab does not occur, cell Example 3 ignition Comparative Disconnection of positive electrode tab does not occur, cell Example 4 ignition Comparative Disconnection of positive electrode tab does not occur, cell Example 5 ignition Comparative Disconnection of positive electrode tab does not occur, cell Example 6 ignition

(16) Referring to Table 1, it can be confirmed that, in the cases of Examples 1 to 4, the positive electrode tabs composed of Wood's metal alloy were melted and disconnected at 200° C. or less having a high cell ignition risk according to overcharge, whereby charge of the secondary batteries was stopped and, as a result, cell ignition according to overcharge may be prevented. On the other hand, it can be confirmed that, in the secondary batteries according to Comparative Examples 1 to 4 which included Wood's metal alloys composed of compositions that were different from Examples 1 to 4, the secondary battery according to Comparative Example 5 which used only Bi as Wood's metal, and the secondary battery according to Comparative Example 6 which did not include Wood's metal, cell ignition of the positive electrode tabs proceeded without disconnection.

Experimental Example 2

(17) In order to perform a safety test according to short circuit of the secondary batteries manufactured according to Examples 1 to 4 and Comparative Examples 1 to 6, the secondary batteries were subjected to short circuit of 0.1 V or less under conditions of SOC 100%, and 1 ohm or less at room temperature. Results are summarized in Table 2 below.

(18) TABLE-US-00002 TABLE 2 Example 1 Disconnection of positive electrode tab at 118° C. Example 2 Disconnection of positive electrode tab at 88° C. Example 3 Disconnection of positive electrode tab at 130° C. Example 4 Disconnection of positive electrode tab at 139° C. Comparative Disconnection of positive electrode tab does not occur, Example 1 cell ignition Comparative Disconnection of positive electrode tab does not occur, Example 2 cell ignition Comparative Disconnection of positive electrode tab does not occur, Example 3 cell ignition Comparative Disconnection of positive electrode tab does not occur, Example 4 cell ignition Comparative Disconnection of positive electrode tab does not occur, Example 5 cell ignition Comparative Disconnection of positive electrode tab does not occur, Example 6 cell ignition

(19) Referring to Table 2, it can be confirmed that, when the secondary battery according to Examples 1 to 4 were subjected to external short circuit, positive electrode tabs composed of Wood's metal alloy were melted and disconnected at 200° C. or less having a high cell ignition risk, and thus, cell ignition may be prevented. On the other hand, it can be confirmed that, in the secondary batteries according to Comparative Examples 1 to 6, the positive electrode tabs or the negative electrode tabs were not melted, and thus, cell ignition may not be prevented.

(20) 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.

INDUSTRIAL APPLICABILITY

(21) As described above, since, in a secondary battery according to the present invention, electrode terminals are composed of Wood's metal having a low melting point, Wood's metal is melted and a current carrying function of the electrode terminals is lost, when temperature of the secondary battery is abnormal. Accordingly, safety of the secondary battery may be enhanced.