JP3952093B2 - battery - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a battery in which positive and negative electrodes are wound or laminated via a separator and these positive and negative electrodes are connected to positive and negative terminals via leads.
[0002]
[Prior art]
As shown in FIG. 3, the wound type lithium ion secondary battery is formed by winding a belt-like positive electrode 1, a negative electrode 2, and two separators 3, 3. The positive electrode 1 is obtained by applying a positive electrode active material 1b to the front and back surfaces of a strip-like aluminum foil 1a, and the negative electrode 2 is obtained by applying a negative electrode active material 2b to the front and back surfaces of a belt-like copper foil 2a. A plurality of positive electrode leads 4 are connected and fixed at appropriate positions on the upper side of the positive electrode 1, and a plurality of negative electrode leads 5 are connected and fixed at appropriate positions on the negative electrode 2. The positive electrode lead 4 is made of a vertically elongated aluminum foil, and the negative electrode lead 5 is made of a vertically elongated copper foil. For the separators 3 and 3, strip-like thin insulating nonwoven fabric or the like that is slightly wider than the positive and negative electrodes 1 and 2 is used.
[0003]
The positive and negative electrodes 1 and 2 and the two separators 3 and 3 are alternately overlapped and wound to constitute a battery element 6 as shown in FIG. At this time, the plurality of positive and negative leads 4, 5 protrude at random from the upper end of the battery element 6. Therefore, as shown in FIG. 5, the positive electrode lead 4 is connected and fixed to the positive electrode terminal 7 attached to a battery case (not shown) by collecting these upper end portions together. Further, the plurality of negative electrode leads 5 are also connected and fixed to the negative electrode terminal 8 by gathering the upper ends thereof together. However, since the positive electrode lead 4 and the negative electrode lead 5 protrude from random positions, they may come into contact with each other when connecting to the positive and negative terminals 7 and 8. For this reason, these positive and negative electrode leads 4 and 5 are preliminarily pasted with insulating tape such as polypropylene on both surfaces to prevent short circuit due to contact.
[0004]
[Problems to be solved by the invention]
In the lithium ion secondary battery, when the positive and negative terminals 7 and 8 are short-circuited outside, a large external short-circuit current flows through the positive and negative electrodes 4 and 5 inside the battery. However, conventionally, the positive and negative electrode leads 4 and 5 have not been designed to withstand this external short-circuit current. Therefore, when an external short circuit occurs and an external short circuit current flows through the positive and negative electrode leads 4 and 5, the aluminum or copper foil is melted and cut by heat generation, and the insulating tape is melted and scattered at this time. The cut part is exposed. In addition, only one of the positive and negative electrode leads 4 and 5 is not always blown, and both may be blown together. Therefore, the exposed cut portions of the positive electrode lead 4 and the negative electrode lead 5 are in contact with each other to cause an internal short circuit. There is a risk of causing.
[0005]
For this reason, in the conventional lithium ion secondary battery, when an external short circuit occurs, the positive and negative electrode leads 4 and 5 inside the battery may be fused together, which may cause an internal short circuit. there were.
[0006]
This problem is not limited to the above-described wound type lithium ion secondary battery, and is common to batteries having a structure in which the positive and negative electrode leads 4 and 5 randomly protrude from one end of the battery element 6. The same applies to an elliptical battery in which 6 is wound in an elliptical shape.
[0007]
However, when the positive and negative electrodes 1 and 2 and the separators 3 and 3 are wound, the positive electrode lead 4 and the negative electrode lead 5 are distributed to the left and right of the upper end of the battery element 6 respectively, or the positive electrode lead 4 and the negative electrode lead When 5 is divided into the upper and lower ends of the battery element 6 and protrudes, even if the positive and negative electrode leads 4 and 5 are fused together as described above, they are not in direct contact with each other. Also, in the case of a stacked battery in which the positive and negative electrodes 1 and 2 are stacked via the separators 3 and 3, the protruding positions of the positive electrode lead 4 and the negative electrode lead 5 can be easily separated, so that they are in direct contact with each other. It can be easily prevented. However, even in such a battery, when the positive and negative electrode leads 4 and 5 are fused together, there is a possibility that these exposed cut portions may come into contact with a conductive battery case or the like at different locations. There is a problem that an internal short circuit may occur through the case or the like.
[0008]
In the conventional battery, when an external short circuit occurs, both the positive and negative electrode leads 4 and 5 may not melt, and in this case, the external short circuit current continues to flow. When only an external short-circuit occurs, the external short-circuit current flows divided into a plurality of positive and negative leads 4 and 5, respectively. However, when an internal short-circuit occurs, the internal short-circuit current actually contacts each one Therefore, the amount of heat generation increases and the risk of safety valve operation and battery rupture increases. Therefore, in order to prevent the occurrence of such an internal short circuit, it has been strongly desired to eliminate the above problem. However, even when only an external short-circuit occurs, a large external short-circuit current flows inside the battery.Therefore, it is not possible to completely avoid the risk of safety valve operation or battery rupture due to heat generation. In the past, there has been a demand for reliable blocking. In order to cut off such an external short-circuit current, a current circuit cut-off device called CID may be provided. However, if a current circuit cut-off device called CID is separately installed inside the battery, the battery space is reduced. There is a problem that the manufacturing cost increases as the pressure is reduced.
[0009]
The present invention has been made in view of such circumstances. When an external short circuit occurs, only one of the positive and negative leads is actively melted to prevent the occurrence of an internal short circuit due to the melting of both leads. It aims to provide a battery that can be used.
[0010]
[Means for Solving the Problems]
The invention according to claim 1 is a battery in which positive and negative electrodes are arranged close to each other via a separator, and each of these positive and negative electrodes is connected to positive and negative terminals via one or more leads, respectively. Set the lead connected to one electrode so that the fusing limit current based on the material and the total cross-sectional area is less than the external short-circuit current, and connect the lead connected to the other electrode to the material and the total cut By setting the fusing limit current based on the area to a value that exceeds the external short-circuit current, when the external short-circuit current flows through the positive and negative leads, only the lead connected to one electrode is fused, while the other The leads connected to the electrodes are not fused .
[0011]
According to the invention of claim 1, when the positive and negative terminals are short-circuited outside the battery and an external short-circuit current flows through the leads connected to the positive and negative electrodes, the lead connected to one of the electrodes is Since a current exceeding the fusing limit current flows, all the fusing is performed and the gap between the electrode and the terminal is interrupted. However, since the lead connected to the other electrode does not exceed the fusing limit current of this lead even if an external short-circuit current flows, none of the leads is blown. Therefore, when an external short circuit occurs, the lead connected to one of the electrodes is surely melted and the external short circuit current is interrupted, so that these leads can function as a fuse. Moreover, even if an external short circuit occurs, the leads connected to the other electrode will not melt, so the leads connected to the positive and negative electrodes will melt together and short-circuit each other directly or via a battery case, etc. This eliminates the possibility of an internal short circuit.
[0012]
The fusing limit current is a limit current value at which one or more leads connected to one or the other electrode reach fusing, and is a value determined based on the material and total cross-sectional area of these leads. is there. The external short-circuit current is a value determined by the terminal voltage and internal resistance of the battery.
[0013]
[0014]
[0015]
[0016]
[0017]
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0019]
1 and 2 show an embodiment of the present invention. FIG. 1 is a perspective view of a battery element in a wound lithium ion secondary battery, and FIG. 2 is a positive and negative electrode with positive and negative electrode leads connected and fixed. FIG. In addition, the same number is attached | subjected to the structural member which has a function similar to the prior art example shown in FIGS.
[0020]
In the present embodiment, a wound type lithium ion secondary battery will be described. As shown in FIG. 2, the lithium ion secondary battery of this embodiment also uses a positive electrode 1, a negative electrode 2, and two separators 3 and 3 having the same configuration as that of the conventional example shown in FIG. In addition, a plurality of positive electrode leads 4 and negative electrode leads 5 similar to those in the conventional example are connected and fixed to the upper sides of the positive electrode 1 and the negative electrode 2, respectively.
[0021]
However, the negative electrode lead 5 is formed so that the foil width is less than half that of the positive electrode lead 4. The negative electrode lead 5 is made of a copper foil having a thickness of about 70 μm, and the positive electrode lead 4 is made of an aluminum foil having a conductivity of about 70% of copper, but the width of the foil is the same. If so, these allowable currents are almost the same. Therefore, the actual allowable current of the negative electrode lead 5 is less than half of the allowable current of the positive electrode lead 4. Further, since the fusing limit current at which the positive and negative leads 4 and 5 reach fusing is larger than this depending on the allowable current, the fusing limit current of the negative lead 5 is the fusing limit of the positive lead 4. It is sufficiently smaller than the current. The fusing limit current of the negative electrode lead 5 is smaller than the external short circuit current that flows when the lithium ion secondary battery of this embodiment generates an external short circuit, and the fusing limit current of the positive electrode lead 4 is the external short circuit. It is set to be larger than the current. The fusing limit currents and allowable currents of the positive and negative electrode leads 4 and 5 are the sum of the fusing limit currents and allowable currents of the plurality of positive and negative electrode leads 4 and 5, respectively.
[0022]
The positive and negative electrodes 1 and 2 to which the positive and negative electrode leads 4 and 5 are respectively connected and fixed are alternately overlapped and wound via two separators 3 and 3 to form a battery element 6 as shown in FIG. Then, the upper ends of the positive leads 4 protruding randomly from the upper ends of the battery elements 6 are collected and fixed to the positive terminal 7, and the upper ends of the negative leads 5 protruding randomly from the same upper ends are collected together. Connect and fix to terminal 8. At this time, since each of the positive and negative electrode leads 4 and 5 is preliminarily pasted with an insulating tape such as polypropylene on both sides as in the prior art, it does not short-circuit even if it contacts with each other. Then, only the upper ends of the positive and negative terminals 7 and 8 are protruded to the outside, the battery element 6 is housed in a battery case (not shown), filled with an electrolyte and sealed to complete a lithium ion secondary battery. To do.
[0023]
In the lithium ion secondary battery having the above-described configuration, when the positive and negative terminals 7 and 8 are short-circuited externally and an external short-circuit current flows, a current exceeding the fusing limit current flows through the negative electrode lead 5. All the leads 5 are melted and the gap between the negative electrode 2 and the negative electrode terminal 8 is cut off. Therefore, when an external short circuit occurs, the negative electrode lead 5 is surely melted and the external short circuit current is interrupted, so that these negative electrode leads 5 can function as current interrupting means. In addition, since the fusing limit current is larger than the external short circuit current, the positive electrode lead 4 is not blown even if an external short circuit occurs. Therefore, even if the negative electrode lead 5 is melted and the cut portion exposed by melting and scattering of the insulating tape comes into contact with the positive electrode lead 4, the positive electrode lead 4 is covered with the insulating tape. There is no risk of a short circuit.
[0024]
In this embodiment, the external short-circuit current is set to be between the fusing limit current of the negative electrode lead 5 and the fusing limit current of the positive electrode lead 4, but the allowable current of the negative electrode lead 5 is independent of the external short-circuit current. May be set to be equal to or less than half of the allowable current of the positive electrode lead 4. In this case, only when the external short circuit current that flows due to the occurrence of the external short circuit greatly exceeds the allowable current of the negative electrode lead 5, the negative electrode lead 5 is melted and the negative electrode 2 and the negative electrode terminal 8 are disconnected. However, since the allowable current of the positive electrode lead 4 is more than twice the allowable current of the negative electrode lead 5, even if the external short circuit current exceeds the allowable current of the positive electrode lead 4, the negative electrode lead 5 melts first. Thus, the external short circuit current is interrupted, so that fusing of the positive electrode lead 4 is avoided. Therefore, in this case, it is not always possible to cut off the external short-circuit current when an external short-circuit occurs, but the positive and negative leads 4 and 5 are not likely to melt together, so that the occurrence of an internal short-circuit is reliably prevented. can do.
[0025]
In the above embodiment, the fusing limit current and the allowable current on the negative electrode lead 5 side are reduced, but the same effect can be obtained even if the positive electrode lead 4 side is reduced. The fusing limit current and allowable current of the positive and negative electrode leads 4 and 5 can be adjusted not only by the width of the foil as in this embodiment, but also by the thickness of the foil, the material of the foil, or the number of positive and negative electrode leads 4 and 5. . Furthermore, in the above embodiment, each of the positive and negative electrode leads 4 and 5 is composed of a single piece of homogeneous aluminum or copper foil, but these materials are arbitrary, and the material and cross-sectional area are changed in the middle. It may be a thing. In this case, the fusing limit current and allowable current of the positive and negative electrode leads 4 and 5 are determined based on the portion where the individual fusing limit current and allowable current in the positive and negative electrode leads 4 and 5 are the smallest. Moreover, the positive electrode lead 4 and the negative electrode lead 5 are not limited to a plurality of each as in the present embodiment, but may be only one each.
[0026]
Further, in the above embodiment, the lithium ion secondary battery has been described. However, other types of batteries can be used as long as the batteries connect the positive and negative electrodes 1 and 2 to the positive and negative terminals 7 and 8 through the positive and negative leads 4 and 5. The present invention can be similarly applied to a secondary battery and a primary battery. Further, the invention can be similarly applied to an elliptical battery as well as a wound type. However, in the case of a battery in which the positive and negative electrode leads 4, 5 are respectively projected to the left and right of the upper end of the battery element 6, or in the battery in which the positive and negative electrode leads 4, 5 are respectively projected to the upper and lower ends of the battery element 6. In the case of a laminated battery in which the positive and negative electrodes 1 and 2 are laminated via the separators 3 and 3 with the positive and negative electrode leads 4 and 5 protruding separately from each other, the positive and negative electrode leads 4 are originally provided. , 5 do not cause an internal short circuit due to direct contact with each other. However, even in such a battery, when the positive and negative electrode leads 4 and 5 are fused together, there is a possibility that these exposed cut portions may come into contact with a conductive battery case or the like at different locations. If the fusing of both the positive and negative electrode leads 4 and 5 is prevented according to the present invention, an indirect internal short circuit through the battery case or the like can be prevented.
[0027]
Further, in the above embodiment, the same insulating tape as the conventional one is attached to both surfaces of the positive and negative electrode leads 4, 5, but an insulating member is formed with a gap around one or both of the positive and negative electrode leads 4, 5. You may make it cover with. If an insulating member having an inner diameter equal to or larger than the foil width of the positive and negative electrode leads 4 and 5 is used, a gap can be formed at least on the front and back surfaces of the foil. When such an insulating member is used as an insulating material, even when the positive and negative electrode leads 4 and 5 are blown, the inner diameter portion where the edge of the foil contacts may be somewhat damaged by heat, so that it is insulated by the gap portion. Since the entire member is not melted, the insulation between the positive and negative electrode leads 4 and 5 is maintained. Therefore, in this case, even if both the positive and negative electrode leads 4 and 5 are melted by the external short-circuit current, at least one of the cut portions of the positive and negative electrode leads 4 and 5 is insulated and exposed by the insulating member. Therefore, the occurrence of an internal short circuit can be reliably prevented. In this case, an internal short circuit can be prevented even if both the positive and negative electrode leads 4 and 5 are fused, so that the fusing limit current or allowable current of either the positive or negative electrode leads 4 and 5 as in the above embodiment. There is no need to reduce the size.
[0028]
【The invention's effect】
As is clear from the above description, according to the battery of the present invention, when an external short circuit occurs, the external short circuit current can be reliably interrupted by the current interrupt function of either one of the leads. There is no need to provide a shut-off device.
[0029]
In addition, when an external short circuit occurs and the lead is blown, only one of the leads connected to the positive and negative electrodes is blown to eliminate the possibility of an internal short circuit due to the melting of both leads. , Safety valve operation and battery rupture can be reliably prevented.
[0030]
Furthermore, when an external short circuit occurs and the lead is melted, at least one of the leads connected to the positive and negative electrodes is covered with an insulating member with a gap between them. Is not exposed, and the possibility of an internal short circuit can be eliminated.
[Brief description of the drawings]
FIG. 1, showing an embodiment of the present invention, is a perspective view of a battery element in a wound lithium ion secondary battery.
FIG. 2 is a developed perspective view of a positive and negative electrode and a separator to which positive and negative electrode leads are connected and fixed, according to an embodiment of the present invention.
FIG. 3 is a developed perspective view of a positive and negative electrode and a separator to which positive and negative electrode leads are connected and fixed, showing a conventional example.
FIG. 4 is a perspective view of a battery element that shows a conventional example and is configured by winding positive and negative electrodes and a separator.
FIG. 5 is a perspective view of a battery element in a wound type lithium ion secondary battery, showing a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Positive electrode lead 5 Negative electrode lead 7 Positive electrode terminal 8 Negative electrode terminal

Claims (1)

In a battery in which positive and negative electrodes are arranged close to each other via a separator, and each of these positive and negative electrodes is connected to positive and negative terminals via one or more leads,
The lead connected to one of the positive and negative electrodes is set so that the fusing limit current based on the material and the total cross-sectional area is less than the external short circuit current, and the lead connected to the other electrode is made of the material When the external short-circuit current flows through the positive and negative leads, only the lead connected to one of the electrodes is blown The battery is characterized in that the lead connected to the other electrode is not melted .

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