Battery pack containing PCM employed with safety member having a protection circuit with a fusing part

Abstract

A battery pack including a battery cell having an electrode assembly of a cathode/separator/anode structure mounted in a battery case together with an electrolyte in a sealed state, and a protection circuit module (PCM) electrically connected to the battery cell. The PCM includes a protection circuit board (PCB) electrically connected to the battery cell, the PCB being provided on a region where a circuit is connected with a conductive pattern including a fusing part, having relatively high resistance, configured to fuse itself for interrupting the flow of current when a large amount of current is conducted.

Claims

1. A battery pack comprising: a battery cell having an electrode assembly of a cathode/separator/anode structure mounted in a battery case together with an electrolyte in a sealed state; and a protection circuit module electrically connected to the battery cell, wherein the protection circuit module includes a protection circuit board electrically connected to the battery cell, the protection circuit board including: a protection circuit printed on the protection circuit board and electrically connected to the battery cell, the protection circuit including: a conductive pattern on a bottom surface of the protection circuit board as a part of the protection circuit and electrically connected to the battery cell, a connection member having a first end connected to an end of the conductive pattern, the connection member having a first width, a fusing part in the conductive pattern, the fusing part having a width of 10-90% of the first width of the connection member, wherein the fusing part is configured to fuse itself to interrupt the flow of current when a predetermined amount of current is conducted through the conductive pattern, and wherein the fusing part has electrical resistance due to current density.

2. The battery pack according to claim 1, wherein the conductive pattern is made of gold, printed on the protection circuit board.

3. The battery pack according to claim 1, wherein the fusing part is formed of a metal material exhibiting predetermined specific resistance.

4. The battery pack according to claim 1, wherein the conductive pattern is formed of a metal material exhibiting specific resistance greater than that of a protection circuit pattern printed on the protection circuit board.

5. The battery pack according to claim 3, wherein the metal material exhibiting specific resistance is tin or a tin alloy.

6. The battery pack according to claim 4, wherein the metal material exhibiting specific resistance is tin or a tin alloy.

7. The battery pack according to claim 1, wherein one or both side edges of the connection member extend toward a middle of the connection member to form the fusing part.

8. The battery pack according to claim 1, further comprising a positive temperature coefficient (PTC) element connected to a bottom surface of the conductive pattern, and wherein the connection member is connected to a bottom surface of the PTC element so that the PTC element is between the conductive pattern and connection member.

9. The battery pack according to claim 1, further comprising an operation circuit on the bottom surface of the protection circuit board, wherein the connection member has a second end connected to the operation circuit.

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 is a perspective view illustrating a protection circuit module (PCM) configured to be mounted to a battery cell according to an embodiment of the present invention;

(3) FIG. 2 is a plan view illustrating a PCM configured to be mounted to a battery cell according to another embodiment of the present invention;

(4) FIG. 3 is a plan view illustrating a PCM configured to be mounted to a battery cell according to another embodiment of the present invention;

(5) FIG. 4 is a plan view illustrating a PCM configured to be mounted to a battery cell according to a further embodiment of the present invention;

(6) FIG. 5 is an exploded perspective view illustrating a battery pack according to an embodiment of the present invention; and

(7) FIG. 6 is a vertical sectional view illustrating the upper part of the battery pack shown in FIG. 5.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(8) FIG. 1 is a perspective view typically illustrating a protection circuit module (PCM) configured to be mounted to a battery cell according to an embodiment of the present invention.

(9) Referring to FIG. 1, the PCM 150 includes a protection circuit board (PCB) 200, a protection circuit 212 printed on the bottom of the PCB 200, a positive temperature coefficient (PTC) element 300 of which the top is attached to an end 211 of the protection circuit 212, and a connection member 310 attached to the bottom of the PTC element 300.

(10) The PCB 200 is constructed in a structure in which the protection circuit 212, which controls overcharge, overdischarge, and overcurrent of the battery cell and achieves the electrical connection between the battery cell and an external input and output terminal, is printed on a rectangular parallelepiped structure made of epoxy composite. The top of the PTC element 300 is directly attached to the one end 211 of the protection circuit 212 electrically connected to the external input and output terminal, among the circuits printed on the PCB 200, by soldering.

(11) No additional connection member is used to achieve the electrical connection between the PTC element 300 and the PCM 150. Consequently, it is possible to reduce the internal space of the battery cell, to increase the size of the battery cell as compared with other battery cells having the same standard, and to omit a welding process, thereby improving process efficiency.

(12) Meanwhile, the connection member 310 is attached to the bottom of the PTC element 300 by soldering. The connection member 310 is coupled to a corresponding electrode terminal of the battery cell (not shown) by welding or soldering to achieve the electrical connection between the battery cell and the PTC element 300.

(13) In this structure, electric current flows from the battery cell to the protection circuit 212 on the PCB 200 via the PTC element 300 by the connection member 310. Consequently, when the battery cell overheats, with the result that the temperature of the battery cell abruptly increases, for example, the PTC element 300 interrupts the introduction of the electric current to the protection circuit 212 to secure the safety of the battery cell.

(14) FIG. 2 is a plan view illustrating a PCM configured to be mounted to a battery cell according to another embodiment of the present invention.

(15) Referring to FIG. 2, the PTC element 300 is directly coupled to one end 211 of the protection circuit 212, which is electrically connected to the external input and output terminal, in the same manner as in FIG. 1. The connection member 310 is attached to the bottom of the PTC element 300. Also, the connection member 310 is coupled to one end 221 of another circuit on the PCB 200, i.e., an operation circuit 222 necessary to operate a battery pack.

(16) In this structure, for example, electric current flows from the battery cell to the operation circuit 222 on the PCB 200 and then flows to the protection circuit 212 connected to the external input and output terminal via the PTC element 300 by the connection member 310. Consequently, when the internal temperature of the battery cell increases, the PTC element 300 interrupts the introduction of the electric current to the protection circuit 212 to secure the safety of the battery cell.

(17) FIG. 3 is a plan view illustrating a PCM configured to be mounted to a battery cell according to another embodiment of the present invention. The PCM of FIG. 3 is identical to that of FIG. 2 except the shape of a connection member attached to the PTC element. Therefore, a detailed description of other components excluding the connection member will not be given.

(18) Referring to FIG. 3, the connection member 311, attached to the top of the PTC element 300, has an overcurrent interruption part 320, which is partially provided at opposite sides thereof with depressions 321. Due to the depressions 321, the overcurrent interruption part 320 has a width less than that of the other region of the connection member 311. In consideration of a fact that a resistance value R is in inverse proportion to the sectional area, as previously described, the overcurrent interruption part 320 has a resistance value higher than that of the other region of the connection member 311 on the assumption that the connection member 311 has the same thickness. Consequently, when overcurrent is generated, and therefore, the battery cell is in an abnormal operation state, the amount of heat generated from the overcurrent interruption part 320 increases, with the result that the overcurrent interruption part 320 is easily cut off. In particular, there is a great possibility that a narrow width region W will be cut off when overcurrent is generated.

(19) The connection member 311 with the above-stated construction is not only electrically connected to the battery cell or the circuit formed on the PCM but also performs to interrupt the flow of electric current therethrough by cutting itself off when overcurrent is generated. Consequently, there is no necessity to mount an additional protection element for overcurrent interruption, and therefore, it is possible to reduce the number of parts of the battery pack and to easily achieve the assembling process, thereby improving productivity.

(20) Meanwhile, although the depressions 321 of the overcurrent interruption part 320 are formed at the opposite sides of the connection member 311 as shown in the drawing, a depression 321 may be formed at only one side of the connection member 311. Also, the depressions 321 may be formed in a notch shape or in a square shape although the depressions 321 are formed in a round shape.

(21) FIG. 4 is a plan view illustrating a PCM configured to be mounted to a battery cell according to a further embodiment of the present invention.

(22) Referring to FIG. 4, the PCM 150 includes a PCB 200, a protection circuit 210 printed on the PCB 200, various elements 330 such as a field effect transistor (FET), a voltage detector, a resistor, and a condenser, and a conductive pattern 400 having a fusing part 410.

(23) At the PCB 200 is formed a terminal connection part 220 configured to be coupled to a corresponding electrode terminal of the battery cell (not shown). The terminal connection part 220 may be directly coupled to the electrode terminal. Alternatively, the terminal connection part 220 may be coupled to the electrode terminal via an additional conductive connection member (not shown), such as a nickel plate.

(24) The protection circuit 210, printed on the PCB 200, is electrically connected to an external input and output terminal (not shown) and the terminal connection part 220.

(25) The conductive pattern 400 is printed on the PCB 200 as a part of the protection circuit 210. Consequently, when overcurrent is generated, the flow of electric current in the protection circuit 210 is interrupted, thereby interrupting the electrical conduction between the external input and output terminal and the battery cell. In the drawing, the conductive pattern 400 is shown as a circuit of which one end is directly connected to the terminal connection part 220. Of course, however, the conductive pattern 400 may be formed at an arbitrary region of the circuit where the external input and output terminal and the terminal connection part 220 are connected to each other.

(26) The fusing part 410 is formed at a predetermined position of the conductive pattern 400. The fusing part 410 has a width less than the overall width of the conductive pattern 400. In this structure, the fusing part 410 has relatively low current density and relatively high resistance. When a large amount of electric current is conducted, therefore, the amount of heat generated from the fusing part 410 is large. Consequently, when a large amount of electric current is conducted, the fusing part 410 fuses itself by the generated heat to interrupt the flow of the electric current, thereby securing the safety of the battery cell. Meanwhile, the conductive pattern 400 may be made of gold (Au) exhibiting high conductivity. Alternatively, the conductive pattern 400 may be made of a metal material, such as tin, having a high specific resistance value. Also, the fusing part may be formed in the shape of a notch, a rectangle, or a circle. Furthermore, two or more fusing parts may be used according to circumstances.

(27) FIG. 5 is an exploded perspective view typically illustrating a battery pack 100 according to an embodiment of the present invention.

(28) Referring to FIG. 5, the secondary battery pack 100 according to this embodiment includes a battery cell 130 having an electrode assembly received in a battery case together with an electrolyte, a top cap 120 for sealing the top, which is open, of the battery case, a plate-shaped protection circuit module 150 having a protection circuit formed thereon, an insulative mounting member 140 mounted to the top cap 120 of the battery cell 130, an insulative cap 160 coupled to the upper end of the battery cell 130 for covering the insulative mounting member 140 in a state in which the protection circuit module 150 is loaded on the insulative mounting member 140, and a bottom cap 170 mounted to the lower end of the battery cell 130.

(29) A pair of protrusion-type electrode terminals 112 and 114, i.e., a first protrusion-type electrode terminal 112 and a second protrusion-type electrode terminal 114, protrude upward from opposite sides of the upper end of the top cap 120. The insulative mounting member 140 is provided with through-holes 142 and 144 having a shape and size corresponding to the lower ends of the protrusion-type electrode terminals 112 and 114. The protection circuit module 150 is provided with through-holes 152 and 154 having a shape and size corresponding to the upper ends of the protrusion-type electrode terminals 112 and 114.

(30) The first protrusion-type electrode terminal 112 is connected to a cathode (not shown) of the battery cell 130 while being electrically connected to the top cap 120. The second protrusion-type electrode terminal 114 is connected to an anode (not shown) of the battery cell 130 while being electrically isolated from the top cap 120.

(31) The coupling of the insulative mounting member 140 and the protection circuit module 150 to the battery cell 130 is achieved by inserting the protrusion-type electrode terminals 112 and 114 through the through-holes 142 and 144, located at the opposite sides of the insulative mounting member 140, and the through-holes 152 and 154, located at the opposite sides of the protection circuit module 150, and pressing the ends of the protrusion-type electrode terminals 112 and 114. Also, the coupling of the insulative mounting member 140 to the top cap 120 may be achieved by an adhesive.

(32) The insulative cap 160 is coupled to the upper end of the battery cell 130 for covering the insulative mounting member 140 in a state in which the protection circuit module 150 is loaded on the insulative mounting member 140. The insulative cap 160 extends downward by a predetermined length to cover the outside of the upper part of the battery cell 130. The bottom cap 170 is mounted to the lower end of the battery cell 150.

(33) In the battery pack 100 with the above-stated construction, the top of a PTC element (not show) is attached to the bottom of the protection circuit module 150, and the bottom of the PTC element is directly coupled to the protrusion-type electrode terminals 112 and 114 via a connection member coupled to the bottom of the PTC element such that the PTC element is electrically connected to the protrusion-type electrode terminals 112 and 114, as in FIGS. 1 to 3.

(34) The upper part of the battery pack constructed in a structure in which the PTC element is directly coupled to the electrode terminals via the connection member is illustrated in FIG. 6 as a vertical sectional view.

(35) Referring to FIG. 6 together with FIG. 5, the insulative mounting member 140 and the protection circuit module 150 are sequentially mounted to the top cap 120, which is integrally formed with the first protrusion-type electrode terminal 112, at the top of the battery pack 100.

(36) A through-channel 1121, through which an electrolyte is injected, is formed at the central region of the first protrusion-type electrode terminal 112. Also, the first protrusion-type electrode terminal 112 is integrally formed with the top cap 120. On the other hand, the second protrusion-type electrode terminal 114 has a lower extension 1146 inserted through the through-hole 122 of the top cap 120 from above. At the interface between the second protrusion-type electrode terminal 114 and the top cap 120 is mounted an electrically insulative gasket 124 for achieving the insulation between the second protrusion-type electrode terminal 114 and the top cap 120. Also, depression grooves 1143 and 1145 are formed at ends of an upper extension 1144 and a lower extension 1146 of the second protrusion-type electrode terminal 114.

(37) The PTC element 300 is directly attached to the bottom of the protection circuit module 150. The connection member 310, attached to the bottom of the PTC element 300, is connected to the second protrusion-type electrode terminal 114. The coupling between the connection member 310 and the second protrusion-type electrode terminal 114 may be achieved by welding. However, it is possible to stably achieve the electrical connection between the connection member 310 and the second protrusion-type electrode terminal 114 even in a state in which the connection member 310 is simply inserted between the gasket 124 and the second protrusion-type electrode terminal 114 such that the connection member 310 is in tight contact with the gasket 124 and the second protrusion-type electrode terminal 114.

(38) In the battery pack 100 with the above-stated construction, on the other hand, the PCM 1560 may be directly electrically connected to the electrode terminal without using an additional connection member. Also, since a conductive pattern (not shown) for interrupting the flow of electric current when overcurrent is generated is printed at the bottom of PCM 150 as a part of the protection circuit, as shown in FIG. 4, it is not necessary to mount an safety element, having a predetermined volume, for overcurrent interruption. That is, the battery pack 100 according to the present invention does not require a space for electrical connection and mounting of the safety element. Consequently, it is possible to construct the battery pack in a very compact structure and to increase the volume density of the battery pack.

INDUSTRIAL APPLICABILITY

(39) As apparent from the above description, the battery pack according to the present invention is constructed in a structure in which the PCM is provided with the safety device of which the circuit is cut off when temperature is high or a large amount of electric current flows. Consequently, it is possible to increase the volume density of the battery pack and, at the same time, to efficiently improve the safety of the battery pack.

(40) Although the exemplary 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.