JP2005317315A - Positive electrode terminal for lithium secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make easy to connect a positive electrode terminal for a lithium secondary battery, formed together with an outer made of an aluminum laminate film for housing a thin battery pack, to outer devices and to prevent the terminal from corroding as well as to enhance the strength of the positive electrode terminal section and to avoid damage when the lithium secondary battery is used. <P>SOLUTION: The positive electrode terminal 2 for a lithium secondary battery includes a first connector made of aluminum foil or aluminum alloy foil. At least one end of the first connector 8 is joined to another connector 9 made of a metal material other than aluminum and a joint part between the first connector and the other connector is covered with a sealing means 4 made of resin. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a positive electrode terminal for a lithium secondary battery having improved connectivity to an external lead wire in a lithium secondary battery or the like, and in particular, an exterior body made of an aluminum laminate film for housing a thin pack battery, The present invention relates to an integrally molded positive electrode terminal for a lithium secondary battery.

In general, a thin pack battery typified by a lithium secondary battery is used particularly for portable devices. As shown in FIG. 1, a general thin battery pack 1 is provided with a positive electrode terminal 2 and a negative electrode terminal 3.

FIG. 2 shows an enlarged cross-sectional view of the vicinity of the positive electrode terminal 2 when the thin battery pack 1 using the positive electrode terminal 2 of the prior art shown in FIG. The positive electrode terminal 2 is made of a strip-like aluminum foil, and a sealing means 4 made of a modified polypropylene resin film is bonded in advance to the portion of the front and back surfaces where the positive electrode terminal 2 and the outer package 5 made of an aluminum laminate film overlap. .

The positive electrode terminal 2 is joined by ultrasonic welding to the positive electrode constituting the battery element 7 of the lithium secondary battery whose surface is coated with the positive electrode active material. Then, after the positive electrode, the negative electrode, and the separator to which the positive electrode terminal 2 is joined are wound or laminated to form the battery element 7 of the lithium secondary battery, the battery element 7 is stored in the outer package 5 as shown in FIG. Is done.

At this time, when the portion of the sealing means 4 of the positive electrode terminal 2 is thermocompression-molded together with the exterior body 5, the resin film layer 6 exists on the inner surface of the exterior body 5, so that it is heat-sealed with the sealing means 4 of the positive electrode terminal 2. The portion where the positive electrode terminal 2 overlaps the exterior body 5 is sealed.

As described above, the general positive electrode terminal 2 used for the lithium secondary battery is formed from a single material of aluminum or aluminum alloy, but a thin oxide layer is formed on the surface of aluminum or aluminum alloy during heat treatment such as welding. For this reason, it has been impossible to connect a lead wire electrically connected to another device by a simple and inexpensive welding method such as soldering.

Further, in order to connect to the lead wire outside the exterior body 5 using the conventional positive electrode terminal 2 made of aluminum or the like, it is necessary to use a connection method using a special device such as an ultrasonic welding device. As a result, there has been a problem that the manufacturing cost of the device using the lithium secondary battery becomes expensive. Further, the welding using such a special device cannot provide a strong connection, and the lead wire of another device is detached from the positive electrode terminal 2 when the lithium secondary battery is moved, and the lithium secondary battery There was also a problem that was completely unusable.
JP-A-9-63549 Japanese Patent Laid-Open No. 10-233233 JP-A-11-250934 JP 2003-282044 A

The present invention relates to a positive electrode terminal for a lithium secondary battery formed integrally with an exterior body made of an aluminum laminate film for housing a thin battery pack, and facilitates electrical connection to an external device. At the same time, it was developed for the purpose of preventing the corrosion of the positive electrode terminal and enhancing the strength and preventing damage of the positive electrode terminal connection part when handling the lithium secondary battery.

That is, the present invention is a positive electrode terminal for a lithium secondary battery using one connection terminal made of an aluminum foil or an aluminum alloy foil, wherein at least one end of the one connection terminal is other than aluminum. For the lithium secondary battery in which the other connection terminal made of the metal material is joined, and the joint portion between the one connection terminal and the other connection terminal is covered with the sealing means made of resin A positive electrode terminal is provided.

A positive electrode terminal for a lithium secondary battery according to the present invention is made of a metal material other than aluminum at an end portion on the opposite side of a portion where one connection terminal made of an aluminum foil or an aluminum alloy foil and the positive electrode are joined. The other connecting terminals are joined by ultrasonic welding or the like, and the joined portion is bonded so that the entire periphery is covered with a film-like sealing means made of a modified polypropylene resin or a modified polyethylene resin. The joint portion between the one connection terminal provided with the sealing means and the other connection terminal is made of the resin which is integrally heat-pressed together with the exterior body made of an aluminum laminate film and the like and is thermoset around it. A strong seal layer is formed to ensure the sealing performance and insulation of the joint portion, and the strength of the joint portion is reinforced so that the joint portion cannot be bent or detached. As a result, even when the lithium secondary battery is handled, the positive electrode terminal is not damaged due to detachment of other connection terminals.

Moreover, it is preferable that the other connection terminal which comprises the positive electrode terminal by this invention is other metal materials other than the aluminum which gave nickel or nickel plating.

When other metal materials other than aluminum are used for the other connection terminals, generally, an electric resistance generated between the other connection terminals and the lead wire electrically connecting the external device is increased. However, the battery capacity of the lithium secondary battery will be substantially reduced, but if other metal materials are pre-plated with nickel, the electrical resistance generated between the other connection terminals and the lead wires will be reduced. The battery capacity of the lithium secondary battery can be reduced without being reduced. In addition, the selection of the material used for such other connection terminals enables the selection of one connection terminal made of an aluminum foil or an aluminum alloy in the lithium secondary battery in contact with the electrolyte, and as a result, the entire positive electrode terminal It also contributes to improving the corrosion resistance.

In addition, as a method of forming the nickel layer on the surface of the other connection terminal as described above, a plating method is generally used, but other known surface treatment methods such as a vapor deposition method are used. Also good.

Moreover, it is preferable that it is what was chosen from either iron or copper as metal materials other than the aluminum by which nickel plating used for the other connection terminal was given.

If iron or copper is selected as the other metal material constituting the other connection terminal, it becomes easier to connect the other connection terminal and the lead wire than a simple and inexpensive welding method such as soldering. Because the strength of the connection part between the other connected connection terminal and the lead wire is increased, the lead wire is detached from the positive electrode terminal when the lithium secondary battery is moved, and the lithium secondary battery cannot be used at all. Such a problem can be solved.

The sealing means is preferably selected from either a modified polypropylene resin or a modified polyethylene resin.

If a film made of modified polypropylene resin or modified polyethylene resin is selected as the sealing means for covering the joint portion of one connection terminal and the other connection terminal, a strong seal layer made of resin is formed around the joint portion after thermo-press molding And the strength of the joint portion is reinforced so that the joint portion cannot be bent or detached, and functions to enhance the sealing and insulating properties of the joint portion.

Moreover, it is preferable that the sealing means is integrally formed with an exterior body made of an aluminum laminate film of a lithium secondary battery.

When the joint portion between one connection terminal and other connection terminal provided with sealing means is integrally heat-pressed together with an exterior body made of an aluminum laminate film or the like, the sealing means and the inner surface of the aluminum laminate film are present. Together with the resin film layer to be bonded, it is tightly fused and bonded around the joint portion to form a stronger sealing layer and insulating layer. As a result, even when the lithium secondary battery is handled, it is possible to prevent the positive terminal from being damaged due to other connection terminals being detached from the one connection terminal.

Furthermore, this sealing means is preferably arranged so as to be exposed to the inside and outside of the exterior body of the lithium secondary battery.

The sealing means for covering the joint portion between one connection terminal and the other connection terminal is wide with respect to the width of the exterior body joint surface of the lithium secondary battery to be thermo-pressurized and extends toward the exterior of the exterior body. When arranged, it becomes easy to join through the resin seal layer between the resin film layer and the positive electrode terminal present on the inner surface of the aluminum laminate film of the lithium secondary battery by heat and pressure molding. Since the seal layer exposed to the inside and outside of the exterior body is also cured by thermo-pressure molding, the strength of the joint between one connection terminal, the other connection terminal, the positive electrode terminal, and the exterior body of the lithium secondary battery is increased. Reinforce and prevent the positive electrode terminal from being bent when handling the lithium secondary battery. It also functions to further enhance the sealing and insulating properties between the positive electrode terminal and the outer package of the lithium secondary battery.

As described above, according to the present invention, it is possible to facilitate electrical connection to an external device, prevent corrosion of the positive electrode terminal, and increase the strength of the positive electrode terminal portion and prevent damage when handling the lithium secondary battery. A positive electrode terminal for a lithium secondary battery is provided.

Examples of the positive electrode terminal for a lithium secondary battery according to the present invention will be specifically described below with reference to FIGS.

[Production of positive terminal]

FIG. 3 shows a sectional view of the positive electrode terminal 2 according to the present invention which is the first embodiment. The positive electrode terminal 2 according to the present invention has a connecting terminal 8 made of a strip-shaped aluminum foil having a thickness of 0.1 mm and another connecting terminal 9 made of a strip-shaped nickel foil having a thickness of 0.1 mm in one terminal region of the connecting terminal 8 made of a strip-shaped aluminum foil having a thickness of 0.1 mm. Joined by ultrasonic welding, and further, the sealing means 4 made of a belt-shaped modified polypropylene resin film is disposed by hot pressing so as to cover the entire circumference of the joined portion 10.

FIG. 4 shows a sectional view of a positive electrode terminal 2 according to the present invention which is a second embodiment. The positive electrode terminal 2 according to the present invention is connected to one end region on one side of one connection terminal 8 made of a strip-shaped aluminum foil having a thickness of 0.1 mm, and another connection made of a strip-shaped nickel foil having a thickness of 0.1 mm. Ultrasonic waves are formed at two locations in the longitudinal direction so that the front end and side end of the terminal 9 coincide with the front end and side end of the one connection terminal 8 and one connection terminal 8 and the other connection terminal 9 overlap each other. It joins by welding, and also is the rear end of the other connection terminal 9 where the one connection terminal 8 and the other connection terminal 9 overlap, and the exterior body of the lithium secondary battery is joined. The sealing means 4 made of a belt-shaped modified polypropylene resin film is disposed by hot pressing so as to cover the entire circumference of the portion.

FIG. 5 shows a sectional view of a positive electrode terminal 2 according to the present invention which is a third embodiment. In the positive electrode terminal 2 according to the present invention, another connection terminal 9 made of a strip-shaped nickel foil having a thickness of 0.1 mm is provided on one terminal region of the connection terminal 8 made of a strip-shaped aluminum foil having a thickness of 0.1 mm. One connection terminal 8 is bent and attached in a U shape so that the front and back surfaces of the one end region are completely sandwiched, and one side of the portion where one connection terminal 8 and another connection terminal 9 overlap is attached. Joined by ultrasonic welding at two locations in the longitudinal direction, and further at the rear end of the other connection terminal 9 where the one connection terminal 2 and the other connection terminal 9 overlap each other, and the lithium secondary The sealing means 4 made of a belt-shaped modified polypropylene resin film is disposed by hot pressing so as to cover the entire circumference of the portion to which the battery outer package is joined.

Comparative example

As a comparative example, a conventional lithium secondary battery using the positive electrode terminal 2 shown in FIG. 3 without the sealing means 4 was produced.

[Production of exterior body]

FIG. 6 shows a perspective view of the exterior body 5 that has been subjected to the concave processing made of an aluminum laminate film before the battery element 7 of the lithium secondary battery is incorporated. As a material constituting the outer package 5, an aluminum laminate film in which an aluminum foil having a thickness of 0.1 mm is laminated on a polypropylene resin film 6 is used, and a part of the aluminum laminate film is used for housing the battery element 7. What processed so that the recessed part was formed so that the film layer 6 might be used as an accommodation surface was used as the lithium secondary battery exterior body 5 (refer FIG. 6).

[Production of lithium secondary battery elements]

FIG. 7 shows a perspective view of the lithium secondary battery element 7 to which the positive electrode terminal 2 and the negative electrode terminal 3 according to the present invention are attached. The positive electrode terminal 2 (see FIG. 5) of Example 3 according to the present invention is attached to the positive electrode constituting the battery element 7 by ultrasonic welding before winding the electrode of the lithium secondary battery (see FIG. 7). Similarly, the negative electrode terminal 3 is attached to the negative electrode located on the opposite side of the battery element 7 to which the positive electrode terminal of the battery element 7 is attached by ultrasonic welding before the electrode is wound. After that, the negative electrode terminal 3 is bent in the vertical direction along the side surface of the battery element 7, and is further horizontally extended so that one side of the battery element 7 extends in the same plane as the positive electrode terminal 2. (See FIG. 7). At this time, the sealing means 4 adhered in advance to the positive electrode terminal 2 and the negative electrode terminal 3 is arranged so as to cover the positive electrode terminal 2 and the negative electrode terminal 3 in the vicinity of the battery element 7 (see FIG. 5).

Next, after assembling the battery element 7 to which the positive electrode terminal 2 and the negative electrode terminal 3 are attached in the recess of the outer package 5 shown in FIG. 6, the battery element 7 is bent so as to cover the remaining flat portion of the outer package 5. And accommodated in the exterior body 5. Then, the outer periphery 5 was overlapped with the positive electrode terminal 2 and the negative electrode terminal 3 together with the positive electrode terminal 2 and the negative electrode terminal 3, and the battery element 7 was sealed in the outer package body 5 to produce a lithium secondary battery. FIG. 8 shows an enlarged cross-sectional view of the vicinity of the positive electrode terminal 2 when the lithium secondary battery using the positive electrode terminal 2 according to the present invention shown in FIG. 7 is cut along the longitudinal center line of the positive electrode terminal 2. ing.

Comparison results such as the durability of the positive electrode terminal between the lithium secondary battery using the positive electrode terminal of Examples 1 to 3 according to the present invention and the lithium secondary battery using the conventional positive electrode terminal as a comparative example are as follows. Detailed description.

In the case of a lithium secondary battery using a conventional positive electrode terminal, the degree of damage to the bending load of the positive electrode terminal is such that the terminal portion made of nickel foil in which the lead wire is soldered in advance for connection to an external device is an aluminum foil. Since the terminal part made of is only joined by ultrasonic welding, the terminal part made of aluminum foil is torn or the positive terminal is twisted in use, resulting in a defect of about 6 out of 50 cells. did. On the other hand, in the lithium secondary battery using the positive electrode terminal according to the present invention, no problem occurs even if the lead wire is soldered directly to the surface of the other connection terminal. And the other connection terminals are integrated with the outer package of the lithium secondary battery, so that the terminal shape was hardly deformed even when the lead wires soldered to the other connection terminals were moved.

The lithium secondary battery was submerged for 24 hours and then left in the atmosphere for 3 days. In the sealing and corrosive observation test by disassembling investigation of the lithium secondary battery, a lithium secondary battery using a conventional positive electrode terminal was used. In the battery, occurrence of corrosion was observed at the seal portion between the outer package and the positive electrode terminal. On the other hand, in the lithium secondary battery using the positive electrode terminal according to the present invention, no corrosion was observed on the positive electrode terminal, and it was confirmed that the lithium secondary battery had high sealing properties and corrosion resistance.

This is because, when a metal material other than aluminum such as nickel is used as a positive electrode terminal in a portion in contact with the electrolyte, the positive electrode terminal may corrode due to a potential difference. However, in the positive electrode terminal according to the present invention, the battery is made of aluminum. Since one connection terminal is used and another connection terminal made of another metal material having high corrosion resistance is used outside the battery, it is considered that no problem with corrosion occurred.

Regarding the ease of manufacturing of the positive electrode terminal and the lithium secondary battery according to the present invention, in the case of manufacturing the lithium secondary battery using the positive electrode terminal according to the present invention, the mechanization / automation is performed even though the manufacturing process of the positive electrode terminal is increased. However, the productivity of the positive electrode terminal and the lithium secondary battery was not hindered. In the case of assembling a plurality of lithium secondary batteries, it is easy to connect the positive terminal and the lead wire connecting each battery or device, and as a result, the positive terminal and Productivity of lithium secondary batteries has been improved.

In the durability observation test of the positive electrode terminal with respect to the charge / discharge cycle of the lithium secondary battery, in the lithium secondary battery using the conventional positive electrode terminal, a special sealing means made of resin is used at the seal portion between the positive electrode terminal and the outer casing. Because it was not applied, an internal short circuit may occur in the exterior body due to contact between the positive electrode terminal due to volume expansion / contraction caused by the charge / discharge cycle of the battery element and the negative electrode protrusion constituting the battery element. Whereas, in the lithium secondary battery using the positive electrode terminal according to the present invention, the positive electrode terminal has a sufficient length up to a portion where there is a possibility of contact with the negative electrode protrusion. The internal short circuit did not cause such an internal short circuit.

Further, in the case of the lithium secondary battery using the positive electrode terminal according to the present invention, since the sealing means of the resin cured by thermo-pressure molding is exposed inside and outside the exterior body, the sealing means made of this cured resin Strengthens the strength against bending load at the joint between one connection terminal and the other connection terminal, and contacts the positive electrode terminal and other battery elements (such as negative electrode protrusions) caused by the movement of the positive electrode terminal inside the battery. It was possible to prevent it effectively.

In addition, this invention shows an example of the technical idea of this invention, and this invention is the dimension and position of the positive electrode terminal shown in the Example, as long as it followed the technical idea of this invention. The material and shape of the sealing means and the shape and capacity of the lithium secondary battery are not limited.

The perspective view of the conventional thin pack battery is shown. The expanded sectional view of the positive electrode terminal vicinity at the time of cut | disconnecting the thin pack battery shown by FIG. 1 by the AA line is shown. Sectional drawing of the front-end | tip part of the positive electrode terminal by this invention is shown. Example 1 Sectional drawing of the front-end | tip part of the positive electrode terminal by this invention is shown. (Example 2) Sectional drawing of the front-end | tip part of the positive electrode terminal by this invention is shown. Example 3 The perspective view of the exterior body of a thin pack battery is shown. 1 shows a perspective view of a lithium secondary battery element to which a positive electrode terminal according to the present invention is attached. FIG. The expanded sectional view of the positive electrode terminal vicinity at the time of using the positive electrode terminal by this invention is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Thin battery pack 2 Positive electrode terminal 3 Negative electrode terminal 4 Sealing means 5 Exterior body 6 Aluminum laminated film resin layer 7 Battery element 8 One connection terminal 9 Other connection terminal 10 Joining part 11 Bending part 12 Separator

Claims (7)

A positive electrode terminal for a lithium secondary battery using one connection terminal made of an aluminum foil or an aluminum alloy foil, wherein at least one end of the one connection terminal is made of a metal material other than aluminum The connecting terminal of the one connecting terminal and the other connecting terminal is covered with a sealing means made of resin, and a positive electrode terminal for a lithium secondary battery . 2. The positive electrode terminal for a lithium secondary battery according to claim 1, wherein the other connection terminal is made of a metal material other than nickel or nickel-plated aluminum. 3. The lithium secondary according to claim 1, wherein the metal material other than aluminum plated with nickel is one metal element selected from either iron or copper. 4. Positive terminal for batteries. The positive electrode terminal for a lithium secondary battery according to any one of claims 1 to 3, wherein the sealing means is selected from either a modified polypropylene resin or a modified polyethylene resin. The lithium secondary battery according to any one of claims 1 to 4, wherein the sealing means is formed integrally with an exterior laminate film of a lithium secondary battery to form a seal portion. Positive terminal for batteries. 6. The positive electrode terminal for a lithium secondary battery according to claim 1, wherein the sealing means is disposed so as to be exposed to the inside and outside of the outer package of the lithium secondary battery. . A lithium secondary battery, comprising the positive electrode terminal for a lithium secondary battery according to any one of claims 1 to 5.

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