JP2005339931A - Battery, battery pack, and connection joint between different kind metals - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery preventing corrosion of terminals even when terminals made of different kind metals are joined, and to provide a battery pack and connection joint between different kind metals. <P>SOLUTION: A secondary battery 1 has an electrode body 11, a negative terminal 13 whose inner end is connected to the electrode body 11, a positive terminal 12 whose inner end is connected to the electrode body 11, having self-potential lower than that of metal constituting the negative terminal 13, an insulating film 15 partially covering a position between the inner end and the outer end of the both terminals 12, 13, and a laminate film 14 covering and sealing the whole part of the electrode body 11 and a part of the insulating film 15, an aluminum cover 18 formed with metal constituting the positive terminal 12 is installed on the whole surface of a part exposed to the outside from the insulating film 15 out of the negative terminal 13, an edge of the aluminum cover 18 is positioned outside than innermost side in a region where the negative terminal 13 and the insulating film 15 come in contact each other. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a battery such as a secondary battery, a battery pack in which a plurality of batteries are connected, and a joint between different metals such as a joint portion between terminals of the battery. More specifically, the present invention relates to a battery having both terminals made of dissimilar metals, an assembled battery in which the dissimilar metal terminals of the battery are joined together, and a connection joint between dissimilar metals.

  Conventionally, a laminated lithium ion battery has been widely used as a small and light secondary battery. This laminated lithium ion battery generally has a copper terminal and an aluminum terminal as bipolar terminals. Here, when this laminated lithium-ion battery is used in a device that requires a large amount of power, such as an automobile, since the voltage obtained by the battery alone is low, a plurality of batteries are often connected in series. . In this case, it is necessary to join terminals made of dissimilar metals that are bipolar terminals.

  However, it is known that when dissimilar metals are joined as they are, corrosion proceeds even with a slight amount of moisture in the air due to the local battery phenomenon. For example, in the case of a joint between copper and aluminum, the aluminum is corroded and the conductivity is gradually deteriorated. Various methods have been tried to cope with this problem. For example, there is one in which a member such as a SUS material is sandwiched therebetween and connected by bolt fastening so that a copper terminal and an aluminum terminal are not in direct contact. This method has a problem that the number of parts is large and the connection resistance increases.

On the other hand, there has been proposed a bonding method in which a bonding portion between a copper terminal and an aluminum terminal is coated with a metal having a natural potential between the natural potential of aluminum and the natural potential of copper (for example, Patent Documents). 1). Alternatively, a battery is proposed in which a portion exposed to the outside of an aluminum current collector or a copper current collector is covered with a metal covering material such as nickel or nickel-plated copper, iron, or stainless steel. (For example, refer to Patent Document 2). Alternatively, a structure of a connecting portion in which an exposed surface of aluminum connected to copper is covered with a sacrificial anode made of a metal having a lower natural potential than aluminum has been proposed (see, for example, Patent Document 3).
JP-A-3-154310 JP 2000-215879 A Japanese Patent Laid-Open No. 8-227741

  However, the conventional connection structures described above have the following problems. For example, the method of Patent Document 1 can reduce the progress of corrosion by reducing the difference in natural potential between adjacent metals, but does not prevent corrosion. Moreover, the method of patent document 2 has to coat | cover both terminals, and a process is complicated and becomes expensive. In addition, the method of Patent Document 3 is expensive because there are not many kinds of metals having a lower natural potential than aluminum, and the sacrificial anode is severely corroded, so that it is difficult to obtain a long-life terminal structure.

  The present invention has been made to solve the problems of the conventional techniques described above. That is, an object of the present invention is to provide a battery, an assembled battery and a joint between different metals that can prevent corrosion of the terminals even when both terminals made of different metals are joined.

  The battery of the present invention made for the purpose of solving this problem includes a power generation element, a first terminal having an inner end connected to the power generation element, and a metal constituting the first terminal while having an inner end connected to the power generation element. A battery having a second terminal made of a metal having a natural potential lower than that of the natural potential, and a packaging material covering and sealing all of the power generating element, a part of the first terminal, and a part of the second terminal. In addition, a coating formed of a metal constituting the second terminal is provided on the entire surface of the portion of the first terminal that is exposed outside the packaging material, and the edge of the coating is formed between the first terminal and the packaging. It is located outside the innermost part of the range where the material contacts.

  Alternatively, the battery of the present invention includes a power generation element, a first terminal having an inner end connected to the power generation element, and a natural potential lower than a natural potential of a metal having an inner end connected to the power generation element and constituting the first terminal. A second terminal made of metal having first and second terminals, first and second insulating members partially covering a position between the inner end and the outer end of the first and second terminals, all of the power generation elements and the first A battery having a packaging material that covers and seals a part of one insulating member and a part of a second insulating member, wherein the entire surface of a portion of the first terminal exposed outside the first insulating member , A coating formed of a metal constituting the second terminal is provided, and the edge of the coating is positioned outside the innermost side of the range where the first terminal and the packaging material or the first insulating member are in contact with each other. There may be.

  According to such a battery of the present invention, of the first and second terminals made of dissimilar metals, the surface of the first terminal composed of a metal having a high natural potential has a low natural potential constituting the second terminal. A film made of metal is provided. That is, in the portion exposed outside the packaging material, the surfaces of both terminals are formed of the same metal. Therefore, there is no difference in natural potential between them, and no foreign metal corrosion occurs outside the packaging material. Furthermore, since the edge of the film is located outside the innermost area in the range where the first terminal and the packaging material or the first insulating member are in contact with each other, no film is present in the portion in contact with the power generation element. Therefore, no foreign metal corrosion occurs inside the packaging material. From these facts, even when both terminals made of different metals are joined, the battery can prevent the corrosion of the terminals.

  Furthermore, the present invention extends to an assembled battery formed by connecting a plurality of the batteries of the present invention having the above characteristics in series.

The dissimilar metal connecting joint of the present invention includes a first terminal having one end covered with a packaging material, a metal having one end covered with the packaging material and a natural potential lower than the natural potential of the metal constituting the first terminal. A dissimilar metal connecting joint in which the other ends of the first and second terminals are connected to each other, and a portion of the first terminal that protrudes from the packaging material A film made of a metal constituting the second terminal is provided on the entire surface of the substrate.
According to this dissimilar metal-to-metal connection joint, the portion protruding from the packaging material is formed of the metal constituting the second terminal on the entire surface of both the first and second terminals. Therefore, there is no difference in natural potential on the surface of this dissimilar metal joint, so that the terminal is not corroded.

  According to the battery, the assembled battery, and the dissimilar metal connection joint of the present invention, even when both dissimilar metal terminals are joined, the corrosion of the terminals can be prevented.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best mode for embodying the present invention will be described in detail with reference to the accompanying drawings. In the present embodiment, the present invention is applied to a laminated secondary battery and a battery pack formed by connecting a plurality of the secondary batteries in series.

  The secondary battery 1 of this embodiment is a laminate type lithium ion battery. As shown in FIG. 1, the secondary battery 1 includes a substantially rectangular and flat electrode body 11, and flat plate-like positive electrode terminals 12 and negative electrode terminals 13 respectively connected to the electrode bodies 11. . The electrode body 11 is formed by winding a positive electrode plate and a negative electrode plate with a separator sheet interposed therebetween, and a positive electrode terminal 12 is connected to the positive electrode plate, and a negative electrode terminal 13 is connected to the negative electrode plate. Furthermore, the electrode body 11 is entirely covered with a laminate film 14, and the tip portions of the positive electrode terminal 12 and the negative electrode terminal 13 protrude from the same position in the vertical direction of the laminate film 14 to the left and right, respectively.

  Each of the positive electrode terminal 12 and the negative electrode terminal 13 is provided with an insulating film 15 at a contact point with the laminate film 14, and a connecting through hole 16 is provided at the tip. The positive terminal 12 is a flat terminal made of aluminum as a whole. On the other hand, the negative electrode terminal 13 is made of copper and has a flat plate-like terminal member 17 provided with an aluminum coating 18. In the drawing, the thickness of the aluminum coating 18 is drawn exaggeratedly, but it is actually very thin.

  The insulating film 15 has an insulating function between the laminate film 14 and both terminals 12 and 13 and a function that makes it difficult for water droplets to adhere to both terminals 12 and 13 even when condensation occurs on the outer surface of the laminate film 14. Further, the through hole 16 is formed in the same diameter at both terminals 12 and 13.

  Next, a method for manufacturing the negative electrode terminal 13 will be described. As shown in FIG. 2A, the negative electrode terminal 13 is first formed with a terminal member 17 using a copper plate. The size and shape of the terminal member 17 are the same as those of the positive terminal 12, and at this time, the through hole 16 is also formed. Next, as shown in FIG. 2B, an aluminum coating 18 is formed from the tip of the terminal member 17 to a predetermined position. The aluminum coating 18 may be formed by aluminum spraying or aluminum plating. Further, as shown in FIG. 2C, the insulating film 15 is stuck on both sides so as to cover the end of the base end side of the aluminum coating 18. Alternatively, a belt-shaped object may be wound. Thus, the negative electrode terminal 13 is completed.

  Therefore, in the negative electrode terminal 13 formed in this way, only the copper terminal member 17 is exposed from the insulating film 15 to the base end side (right side in FIG. 2C). Further, only the portion where the terminal member 17 is provided with the aluminum coating 18 is exposed from the insulating film 15 to the tip end side (left side in FIG. 2C).

  Next, when the electrode body 11 to which the negative electrode terminal 13 is connected is covered with the laminate film 14, the laminate film 14 is arranged so that the end of the laminate film 14 is on the insulating film 15 as shown in FIG. 1. Furthermore, it is preferable that the entire welding range for sealing the laminate film 14 is within the width of the insulating film 15. In this way, the portion of the negative electrode terminal 13 exposed to the inner side of the secondary battery 1 from the welding range of the laminate film 14 is only the portion without the aluminum coating 18. Therefore, no foreign metal corrosion occurs inside the laminate film 14. On the other hand, an aluminum coating 16 is applied to the entire exposed portion of the laminate film 14.

  Next, in the assembled battery 2 in which a plurality of secondary batteries 1 are connected in series, a plurality of secondary batteries 1 are arranged side by side as shown in FIG. 12 and the negative electrode terminal 13 are joined together by the joint 10. The positive electrode terminal 12 and the negative electrode terminal 13 are arranged by overlapping their through holes 16 and fastened by bolts 19. Since the aluminum coating 18 itself has conductivity, the through-hole 16 may be coated in the same manner as other portions. Note that the terminal 12 and 13 may be fixed by ultrasonic welding or the like instead of the bolt 19. In that case, the through hole 16 is unnecessary.

  In this assembled battery 2, as shown in FIG. 3, the exposed portions of both terminals 12, 13 are all covered with aluminum. Therefore, since there is no difference in potential, even if some moisture adheres to the surface, foreign metal corrosion does not occur. Corrosion of terminals is prevented even when used in an environment where condensation is likely to occur, such as in automobiles. Even if the aluminum coating 18 has some scratches or holes, the exposed copper surface area is much smaller than the exposed aluminum surface area. Therefore, the corrosion current due to the slightly exposed copper is dispersed on the vast surface of the aluminum, and the rate at which the aluminum is corroded is very small.

  This inventor formed the Example similar to the junction part 10 of the positive electrode terminal 12 and the negative electrode terminal 13 of this form, and performed the acceleration test compared with the comparative example. In both cases, a general salt spray test was performed by fixing a copper plate having the same thickness on an aluminum plate having a thickness of 300 μm. Specifically, 5% salt water was continuously sprayed in an environment of a temperature of 35 ° C. and a humidity of 98%. And the average board thickness of the part which is not corroded among aluminum boards was measured after progress for a predetermined time. The result is shown in the graph of FIG.

  In FIG. 4, a graph L <b> 1 indicated by a circle is the present example, and the surface of the copper plate was covered with aluminum in the same manner as the structure of the joint portion 10. A graph L2 indicated by Δ is Comparative Example 1, in which a SUS material is sandwiched between an aluminum plate and a copper plate. A graph L3 indicated by □ is Comparative Example 2, and neither a coating nor a SUS material is used. As can be seen from this figure, in the present example, the original aluminum plate having a thickness of 300 μm remained with an aluminum plate having a thickness of 260 μm or more even after 200 hours or more had elapsed. Here, some corrosion occurs due to the self-corrosion of aluminum. On the other hand, the corrosion progressed until the remaining thickness was 240 μm in Comparative Example 1 and the remaining thickness was 50 μm in Comparative Example 2.

  As described in detail above, according to the secondary battery 1 of the present embodiment, the negative electrode terminal 13 is manufactured simply by applying the aluminum coating 18 to the terminal member 17 before connection, and therefore, the number of processes is small and the manufacture is easy. . Furthermore, since the surface of the part exposed to the outside from the laminate film 14 is aluminum, both terminals 12 and 13 do not cause corrosion between different metals even if they are directly joined. Even if the aluminum coating 18 is slightly scratched, the exposed copper is so small that the rate at which the aluminum is corroded is very small. Accordingly, even in the assembled battery 2 in which both the terminals 12 and 13 are joined, the corrosion of the terminals 12 and 13 can be prevented, and the assembled battery 2 can obtain a long life.

In addition, this form is only a mere illustration and does not limit this invention at all. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof.
For example, in the above embodiment, the present invention is applied to the negative electrode terminal 13 of the secondary battery 1, but the present invention is not limited to this as long as it is a joint between different metals.
For example, the material of the positive electrode terminal 12 and the negative electrode terminal 13 is not limited to aluminum and copper. The metal with the lower natural potential may be covered with the metal with the higher natural potential.
Further, for example, even if a material having conductivity is used in the laminate film 14, if the laminate film 14 and both terminals 12, 13 can be appropriately insulated, the insulating film 15 is not provided. Also good.

It is explanatory drawing which shows schematic shape of the secondary battery to which the terminal structure of this form was applied. It is explanatory drawing which shows the manufacturing method of a negative electrode terminal. It is explanatory drawing which shows schematic shape of the assembled battery which connected multiple secondary batteries. It is a graph which shows the result of the comparison experiment of the terminal structure of this form, and the conventional terminal structure.

Explanation of symbols

1 Secondary battery (battery)
2 Battery 10 Joint (dissimilar metal joint)
12 Positive terminal (second terminal)
13 Negative terminal (first terminal)
14 Laminate film (packaging material)
15 Insulating film (first insulating member, second insulating member)
18 Aluminum coating (film)

Claims (4)

A power generation element, a first terminal having an inner end connected to the power generation element, and a metal having an inner end connected to the power generation element and having a natural potential lower than a natural potential of a metal constituting the first terminal A battery having a second terminal formed and a packaging material covering and sealing all of the power generation element, a part of the first terminal, and a part of the second terminal;
A coating formed of a metal constituting the second terminal is provided on the entire surface of the portion exposed outside the packaging material of the first terminal,
The battery is characterized in that an edge of the film is located outside the innermost side of a range where the first terminal and the packaging material are in contact with each other. A power generation element, a first terminal having an inner end connected to the power generation element, and a metal having an inner end connected to the power generation element and having a natural potential lower than a natural potential of a metal constituting the first terminal A second terminal, a first and second insulating member partially covering a position between the inner end and the outer end of the first and second terminals, all of the power generation element and the first insulation In a battery having a packaging material that covers and seals a part of the member and a part of the second insulating member,
A coating formed of a metal constituting the second terminal is provided on the entire surface of the portion exposed outside the first insulating member of the first terminal,
The battery is characterized in that an edge of the film is positioned outside the innermost side in a range where the first terminal contacts the packaging material or the first insulating member. An assembled battery comprising a plurality of the batteries according to claim 1 connected in series. A first terminal whose one end is covered with a packaging material, and a second terminal whose one end is covered with a packaging material and which has a natural potential lower than the natural potential of the metal constituting the first terminal. , In a dissimilar metal joint where the other ends of the first and second terminals are connected to each other,
A dissimilar metal-to-metal connection joint, wherein a coating formed of a metal constituting the second terminal is provided on the entire surface of a portion of the first terminal that is outside the packaging material.

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