JP2001167751A - Battery lead wire connection method and device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] Prior to the connection between an electrode plate made of metallic lithium and a lead wire, the surface of the lead wire does not require any pre-processing such as embossing or grid blasting. Provided is an ultrasonic bonding method and apparatus capable of performing stable ultrasonic bonding. SOLUTION: In a battery using a metal foil made of metallic lithium or a lithium alloy as a negative electrode plate, the negative electrode plate is
At the time of ultrasonic bonding with superposed wire, a thin or heat-resistant polyolefin film or fluorine resin film is mechanically or bonded to the surface of the metal anvil that supports the negative electrode plate in contact with the negative electrode plate surface By fixing with a chemical and moving the film or anvil according to the degree of damage to the film by ultrasonic bonding, ultrasonically bonding the metal lithium on the surface of the metal lithium adhesion prevention layer with a film that is not damaged at all times I do.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method and an apparatus for connecting a lead wire to a negative electrode plate of a lithium primary battery using a metal lithium foil for a negative electrode plate.

[0002]

2. Description of the Related Art Generally, a lithium metal foil or a lithium alloy is used as a negative electrode plate of a cylindrical lithium primary battery, and nickel-plated mild steel tape or nickel-mild steel-nickel is used as a lead wire. A clad material or the like having three layers is used, and the connection between the electrode plate and the lead wire is a combination of different metals. For this reason, it is difficult to adopt a connection method by electrical spot welding, and embossing, blasting, etc. are performed on the surface of the lead wire, and the unevenness is provided on the surface, and the lead wire is overlaid with the lithium metal foil serving as the negative electrode plate. Most commonly, a connection method by a cold pressure welding method, in which pressure is applied together, is employed.

As an example for reference, as shown in FIG. 7, the surface of a portion of the lead wire 1 which is to be connected to the metal lithium electrode plate 2 is intensively pressed to reduce the height of the protrusion. A large number of projections (grated beams) 5 of 0.16 mm are provided in advance, and this portion is superimposed on the metal lithium electrode plate 2 serving as the negative electrode plate, and 10 parts of a 5 mm × 18 mm bonding area are formed.
Both were joined by a cold pressure welding method applying a force of 0N.
(See FIG. 6) At this time, if the metal lithium electrode plate is directly supported with metal on the load receiving portion of the cold welding, metal lithium easily adheres to the metal surface of the load receiving portion. ), Or a method of supporting with polyurethane rubber or the like.

Japanese Patent Application Laid-Open No. 6-155051 discloses a method for connecting a lead wire of a lithium secondary battery, in which a metal foil as a current collector of an electrode plate is a copper foil or an aluminum foil having a thickness of 5 μm to 30 μm. Is a joining method when a nickel plate or an aluminum plate is used as the lead wire, but the work support surface of the anvil is sandblasted,
A method is disclosed in which the processed surface of an ultrasonic horn is an irregular surface processed into a pyramid at a constant pitch, and a lead wire and a metal foil are overlapped to perform ultrasonic bonding. When two metal parts are joined by ultrasonic bonding, they are not necessarily limited to the same type of metal, and are not affected by the oxide film on the connection part surface. Is one of the widely used methods.

[0005]

Prior to the connection between the lead plate and the electrode plate made of metallic lithium, the surface to be joined to the lead wire is subjected to embossing or grid blasting to intentionally provide irregularities. Performing cold pressure welding increases the bonding strength and makes it possible to stabilize the contact resistance at the joints at a low level.However, preliminary processing is required in advance, the lead time required for production is long, and the production cost increases. Become. Further, in order to further stabilize the bonding strength and the contact resistance, stabilization of the shape of the embossed projection, the height of the projection, and the like have been important issues.

However, in order to reduce the manufacturing cost, preliminary preliminary processing on the lead wire is omitted, and the lithium metal foil and the nickel-plated mild steel strip-shaped lead wire are overlapped and cooled. If only pressure contact is performed, the bonding strength tends to be insufficient, the contact resistance is unstable, and the variation in battery characteristics tends to increase. In addition, if the pressing force of the cold welding process is increased and the joining strength is increased, the joint portion of the metal lithium electrode plate may be deformed or damaged, so a simple cold welding method, It cannot be used as a lead wire connection method for mass production.

Also, a lead wire made of nickel or nickel plated on a negative electrode plate made of metallic lithium foil by utilizing the ultrasonic bonding method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 6-155051. It is expected that lithium metal can be easily connected to a lithium electrode plate without performing preliminary processing on the lead wire because metal lithium is very easily welded to various metals.

However, when a bonding experiment was conducted, it was found that the metal lithium electrode plate and the lead wire exhibited a firm and stable bonding state. The metal lithium electrode plate was also joined to the surface of the metal anvil supporting the load, and the metal lithium electrode plate was in a good condition and could not be easily removed from the anvil. Therefore, it is necessary to cover the work surface of the anvil with a surface treatment as a measure for preventing joining with the metallic lithium, or to cover the surface of the anvil with a material which does not easily adhere to the metallic lithium.

In general, the metal surface has a strong bonding force with metal lithium, but the load supporting surface of the ultrasonic bonding anvil uses a metal material which is easy to process and is inexpensive, and which has a metal lithium electrode plate. It is desirable that the metal lithium can be prevented from being bonded to the surface of the anvil for ultrasonic bonding.

According to a simple test, when the surface of the anvil is extremely smoothed by lapping or burnishing, it is possible to weaken the bonding force of the metal lithium electrode plate to the surface of the anvil somewhat. It is possible to perform ultrasonic bonding several times, but as the ultrasonic bonding process is repeated, the joining force between the work and the anvil suddenly increases, making it difficult to remove the workpiece. It turns out that it is impossible to use it over and over again.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and does not require any preliminary processing on the surface of the lead wire. An object of the present invention is to provide a processing method and an apparatus capable of joining an inexpensive and firmly stable lead wire to a foil.

[0012]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is to connect a lead wire to a metal lithium electrode plate by using an ultrasonic bonding method, wherein the load supporting surface of the anvil is made of polypropylene. By covering with a film (hereinafter referred to as PP), a Teflon film or the like and supporting the metal lithium foil, the adhesion of the metal lithium to the anvil is effectively reduced.

Further, a PP tape or a Teflon tape (film layer thickness: 20 μm, pressure-sensitive adhesive layer thickness: 20 μm) with a rubber-based adhesive is adhered to the work supporting surface of the anvil, thereby leading to ultrasonic bonding. Ensuring wire joint strength. In addition, it is possible to prevent the metal lithium electrode plate from being removed from the anvil due to the anvil. Thin P
In the case of a P tape or a Teflon tape, when two or three sheets are stacked and used, the interval before the tape needs to be replaced with a new one tends to be longer than when only one sheet is stuck on the anvil. , 2000 to 30
Withstands the use of 00 ultrasonic bonding. However, as the number of tapes is increased (the film thickness is increased), the bonding strength tends to decrease.

However, the life of the PP film attached to the portion of the anvil that comes into contact with the lithium metal foil is short, and if ultrasonic bonding is repeated about 2,000 to 3,000 times, the PP film will be damaged and its life will be exhausted. As an example of a structure that can be easily exchanged, a PP tape in which an adhesive is applied to one surface of the tape is used, and the cross-sectional shape of each of the work supporting surfaces of the anvil having a polygonal shape matches the tape width. By processing the shallow groove and using the groove for positioning, the positioning when the PP tape is stuck on the surface of the anvil is facilitated, and the bonding is performed a predetermined number of times by a signal of a counter that counts the number of ultrasonic bonding. Each time, by rotating the polygonal anvil by a predetermined angle, the surface is replaced with a new PP tape surface, and the metal A structure to support the Umm plate.

Further, the PP tape to which no adhesive is applied, or the anvil to which the adhesive-applied PP tape is adhered, is displaced little by little each time the ultrasonic bonding is repeated, so that the PP tape has almost no damage. It is also possible to adopt a structure in which the work is always supported in the aspect described above. As an example, using a PP tape that is not coated with an adhesive,
Each time the ultrasonic bonding is repeated, the number of times is counted by a counter, and when the predetermined number of bondings is reached, the PP tape feed roller is rotated by a predetermined angle using a pulse motor, and the tape is moved little by little. It is also possible to cover the work supporting surface of the anvil with PP tape having little damage.

Incidentally, in the case of a commercially available PP tape or Teflon tape having an adhesive applied to one surface, the surface on which the adhesive is not applied has a thickness of about 1 μm. It is common to have the following extremely thin release agent layer, but in such a thin case, regardless of the presence or absence of the release agent layer, it is effectively used for the ultrasonic bonding of the present invention. It is possible. Further, it is also possible to use a tape obtained by applying an undercoat of a rubber-based adhesive to the surface of a PP tape very thinly and then applying a rubber-based adhesive or the like.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a view schematically showing a main part of an apparatus for carrying out the ultrasonic bonding method of the present invention. An ultrasonic horn that superimposes a metal lithium electrode plate 2 serving as a negative electrode and a lead wire 1 on a work supporting surface of an anvil 7 in a state where they are aligned with each other, and minutely vibrates in a direction parallel to the work supporting surface of the anvil 7. 9 is lowered toward the anvil 7 by the air cylinder 10, and the surfaces of both workpieces are pressed to each other by the anvil 7 and the ultrasonic horn 9, thereby applying ultrasonic vibration energy to the workpieces. Connect lead wire 1 to metallic lithium electrode plate 2
To be joined.

At this time, when the work supporting surface of the anvil 7 is made of metal, the metal lithium electrode plate 2 easily adheres to the anvil, and not only the lead wire 1 is joined to the metal lithium electrode plate, but also Since the metal lithium electrode plate 2 adheres to the surface of the anvil 7 and cannot be easily removed from the anvil 7, as a preventive measure, the work supporting surface of the anvil 7 is covered with the PP tape 8 and ultrasonic bonding is repeatedly performed.

Although the life of the PP tape 8 is relatively long,
When ultrasonic bonding is repeated, the tape is gradually worn and damaged. In order to continuously supply undamaged PP tape to the work supporting surface of the anvil, a counter (not shown) counts the number of times of ultrasonic bonding. Each time the number of repetitions of the ultrasonic bonding reaches the set value, the tape feed roller 19 is driven by the pulse motor 20 for driving the tape feed roller.
By rotating the PP tape by a predetermined length, the PP tape is fed by a predetermined length.

By doing so, it is possible to cover the work supporting surface of the anvil with the PP tape 8 which is not damaged at all times, and it is possible to prevent the metal lithium electrode plate 2 from adhering to the anvil and being unable to be removed from the anvil. .

FIG. 1 shows a case where only one PP tape is used. However, the present invention is not limited to one PP tape, and two or three PP tapes are used to form a double or triple PP tape. It is also possible to cover.

FIG. 2 is a perspective view showing a main part of another apparatus for carrying out the ultrasonic bonding method of the present invention. A plurality of anvils 7 are arranged at equal intervals on the cylindrical surface 14 of the rotating disk and easily replaceable, and the work supporting surface of the anvil 7 is provided with one or more PP tapes 8 coated with an adhesive on one surface.
About three sheets are stacked and pasted. Regarding the number of the anvils 7, apart from the ones in use, several pieces are prepared in a state where a PP tape is attached as a spare, and each time the PP tape 8 is damaged, each time it is replaced with an anvil attached with a new PP tape. To use.

In this apparatus, the lead wire 1 is temporarily fixed in advance to a predetermined position on the metal lithium electrode plate 2 with an insulating adhesive tape 6 (see FIG. 3). Vacuum suction hole 16 provided on surface 14
And is held so as to be wound around the cylindrical surface, and the joint of the lead wire is held so as to coincide with the work supporting surface of the anvil 7. The rotating disk 25 rotates intermittently in the direction of the arrow, stops at the position where the anvil 7 faces the ultrasonic horn 9, and the ultrasonic horn 9
When the anvil 7 advances to the anvil 7, the anvil 7 and the ultrasonic horn 9 sandwich the joint between the metal lithium electrode plate and the lead wire, apply ultrasonic pressure, apply ultrasonic vibration energy, and join.

FIG. 3 is a plan view of a metal lithium negative electrode plate for a lithium primary battery, which has been ultrasonically bonded by the method of the present invention. In this case, the area of the joint by ultrasonic bonding is 2 mm × 10 mm, which is slightly smaller than before, but the mechanical strength of the joint is smaller than that of the conventional joining method using embossing and cold pressing. This level is sufficient because it is strong and the electric resistance of the junction is low.

FIG. 4 shows a P with an adhesive used in the present invention.
FIG. 1 is a perspective view showing the configuration of an example of a P tape 8. FIG. 5 shows the direction in which the lead wire 1 was joined to the metal lithium electrode plate 2 by the ultrasonic joining method of the present invention and the mechanical joining strength was checked by applying a force in which direction. Is shown.

The conditions for ultrasonic bonding according to the lead wire connection method of the present invention are as follows: a bonding area is a rectangle of 10 mm × 2 mm, an output of 300 W, a frequency of 40 kHz, and an amplitude of 20 μm.
Then, the ultrasonic horn vibrating in a direction substantially parallel to the work support surface of the anvil was positioned on the work support surface of the anvil made of structural steel (S45C) by an air cylinder with a pressing force of 200 N and superposed. Pressing from the lead wire side of the material to be joined, processing time was 200 msec, and the lead wire 1 was broken by pulling the lead wire 1 in the direction perpendicular to the electrode plate 2 as shown in FIG. As a result of the test, the tensile strength was higher than that of the conventional product, and all the metal lithium electrode plates were broken in a state where they were torn off by the lead wire, and the result that the bonding state was good was obtained.

It is very important to select the material and thickness of the non-metal layer that covers the work supporting surface of the anvil. When covered, both workpieces move integrally on the anvil, and the generation of frictional heat at the contact surface between the workpieces decreases, so that even if adhesion to the anvil can be prevented, ultrasonic bonding is sufficient May not be possible.
Also, when the thickness of the non-metal layer such as resin or rubber covering the work supporting surface of the anvil is increased, the non-metal layer mainly vibrates, and the objects move integrally on the anvil. Since the generation of frictional heat at the contact surface of the joint is hindered, good joining may not be achieved.

[0028]

As described above, according to the present invention, nickel-plated metal lithium foil serving as a negative electrode plate is provided.
Or, by using ultrasonic bonding as a method of joining lead wires made of nickel clad material, etc., both can be connected more firmly than before, and the contact resistance at the joint part can be kept small and stable. Becomes possible,
The quality of the battery can be improved and stabilized. Further, preliminary processing such as blasting or embossing, which is conventionally performed on the surface of the lead wire to stabilize the bonding strength, can be omitted, and the effect of cost reduction is great.

[Brief description of the drawings]

FIG. 1 is a diagram showing a main part of an apparatus for connecting a lead wire to a lithium metal foil serving as a negative electrode according to the lead wire connection method of the present invention.

FIG. 2 is a perspective view showing a main part of another device for connecting a lead wire to the metal lithium electrode plate of the present invention.

FIG. 3 is a plan view showing a state in which a lead wire is connected to a metal lithium electrode plate using the present invention.

FIG. 4 is a perspective view showing the configuration of an example of a PP tape used in the lead wire connection method of the present invention.

FIG. 5 is a diagram showing a destructive test method for confirming the bonding strength of a lead wire.

FIG. 6 is a plan view showing a conventional lithium electrode plate.

FIG. 7 is a diagram showing a state of embossing which has been pre-processed on the surface of a lead wire in order to join the lead wire to a lithium electrode plate by a conventional lead wire connection method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lead wire 2 Metal lithium electrode plate 3 Ultrasonic bonding part 4 Cold press contact part 5 Emboss processing 6 Insulating film with adhesive 7 Anvil for ultrasonic bonding 8 PP tape 9 Ultrasonic bonding horn 10 Air cylinder for pressurization 11 Ultrasonic bonding Horn holder 12 Anvil fixing part 13 Ultrasonic vibration source 14 Cylindrical surface of rotating disk 15 Rotating disk shaft 16 Vacuum suction hole 17 PP tape supply unit 18 PP tape winding unit 19 PP tape feed roller 20 Tape feed roller drive pulse motor DESCRIPTION OF SYMBOLS 21 Ultrasonic welding apparatus frame 22 Tension roller 23 Metal lithium electrode plate support plate 24 Electrode plate positioning member 25 Rotating disk

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Satoshi Ogawa 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Masami Nonaka 1006 Okadoma Kadoma Kadoma City, Osaka Matsushita Electric Industrial F Terms (reference) 4E067 AA01 AA02 AA22 BF00 DA12 EA04 EB00 EC03 5H022 AA09 BB17 BB19 BB21 CC12 CC19 CC22 EE06 KK03

Claims (5)

[Claims] 1. In a lithium battery using a metal foil made of metallic lithium or a lithium alloy as a negative electrode plate, a lead wire is superposed on the negative electrode plate and ultrasonic bonding is performed.
A lead wire connection characterized in that a thin heat-resistant polyolefin-based or fluorine-based resin layer is provided on the surface of a metallic anvil that applies a pressing force to the negative electrode plate while being in contact with the negative electrode plate surface when connecting the two. Method. 2. An anvil, which is mechanically held or fixed using an adhesive, covers the surface of a portion of the anvil that comes into contact with metallic lithium by an olefin resin film or a fluorine resin film. Item 6. The lead wire connecting method according to Item 1. 3. An anvil in which one to three sheets of a polypropylene tape or a Teflon tape having a rubber-based adhesive applied to one surface thereof are superimposed and adhered to a work supporting surface of the anvil as a thin heat-resistant resin layer. The lead wire connection method according to claim 1, wherein: 4. An anvil coated with a polypropylene tape or a Teflon tape as a resin layer for preventing metal lithium from adhering to the surface of the anvil, or having an anti-adhesion coating applied thereto, damages the tape or the coating. Depending on the degree or every time the ultrasonic bonding is repeated a predetermined number of times, replace the anvil or move the position of the anvil to always support the metal lithium electrode plate on the surface of the lithium adhesion prevention layer with little damage A lead wire connection device for a lithium battery. 5. The work supporting surface of the anvil is covered with a polypropylene tape or a Teflon tape to which tension is appropriately applied, and each time ultrasonic bonding is repeated a predetermined number of times,
By operating the tape feed drive device to move the tape by a very small distance, the metal lithium electrode plate is supported on a surface of an anvil covered with a polypropylene tape or a Teflon tape with little damage at all times. Lithium battery lead wire connecting device.