JP2001102034A - Battery lead wire, thin battery using the lead wire, and method of using battery lead wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lead line for a battery which can be sealed perfectly for easy fusion with thermal plastic resin but without causing any interval on the fusion part adjacent to the lateral part of the lead line. SOLUTION: To use a lead line for battery wherein the surface of obverse and reverse is a lead line of plain band type and the flange of both side has become thin, it is preferable for the cross section vertical to the longitudinal direction of the above lead line to be a chamfered rectangular type or a rectangular type incorporating half ellipse, wherein the proportion of major axis against minor axis is more than 1.5 on the end.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead wire (leading electrode) mainly used for a thin battery, for example, a polymer battery having a light weight and a high energy density.

[0002]

2. Description of the Related Art With the demand for miniaturization and thinning of portable equipment and cordless equipment, thin batteries such as polymer batteries using a solid polymer electrolyte have been receiving attention.
In these batteries, a polymer solid electrolyte such as a polymer gel is used, and there is no fear that the electrolyte solution leaks. For this reason, a lightweight exterior material such as a resin film laminated with aluminum can be used, and a lightweight thin battery can be manufactured.

FIG. 1 is a cross-sectional view of an example of a thin battery, and FIG. 2 is a front view showing a part of the internal structure of the thin battery by a broken line.
As shown in FIG. 1, an aluminum foil 1
(A current collector), a positive electrode 2, a polymer solid electrolyte 5, a negative electrode 4, and a copper foil 3 (a current collector) are arranged in layers. The aluminum foil 1 and the copper foil 3 which are current collectors have ears 10 respectively.
Are provided, and a negative electrode lead wire 8 is provided at the ear portion on the negative electrode side.
However, a positive electrode lead wire 9 is connected to the ear on the positive electrode side. The whole is covered with a container of a lightweight exterior film 6, and the inside is impregnated with an electrolytic solution. Each of the lead wires is partially exposed to the outside through the heat-sealed portion 7, but the inside is in a sealed state by providing the heat-sealed portion. The heat-sealed portion is provided by sandwiching a lead wire with an exterior film and melting a thermoplastic resin layer on the surface of the exterior film by heating.

As the exterior film 6, a film made of a thermoplastic resin sandwiching a metal foil such as an aluminum foil is used. Conventionally, the positive electrode lead wire has a band shape, and a cut surface perpendicular to the length direction has a thickness of about 80 μm.
A flat rectangular aluminum wire or the like is used, and as the negative electrode lead wire, a copper wire or the like having a similar shape is used.

[0005]

The thickness of the thermoplastic resin layer on the surface of the exterior film is usually about 25 μm. When a conventional lead wire having a rectangular cut end is sandwiched by an exterior film and heat-sealed, the lead wire is considerably thicker than the resin layer. Will occur. In order to prevent this, it is necessary to take measures such as attaching a hot melt resin in advance to the portions of each lead wire to be thermally fused. However, in this method, it is necessary to previously attach a hot melt resin to a predetermined position of the lead wire and perform positioning at the time of heat fusion, which significantly increases the cost. In addition, since the hot melt resin has high moisture permeability, there is a problem that the cycle life of the battery is shortened due to moisture absorption. An object of the present invention is to provide a lead wire capable of completely sealing a heat-sealed portion without using a hot melt resin.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a lead wire for a battery, which is a strip-shaped lead wire having flat front and back surfaces and having thinner side edges. Preferably, the cut surface perpendicular to the length direction of the lead wire is a chamfered rectangle. Further, it is preferable that a chamfer angle with respect to a long side of the rectangle is 45 ° or less. In addition, it is preferable that the cut surface perpendicular to the length direction of the lead wire has a shape in which a semi-ellipse having a ratio of a major axis to a minor axis of 1.5 or more is combined with a rectangular end. . Further, the present invention is a thin battery in which the power generation element is sealed with an exterior film having a thermoplastic resin layer on the surface, wherein the lead wire is connected to each electrode of the power generation element, and The present invention relates to a thin battery that is led out from a heat-sealed portion.
Further, the present invention provides a method for using a lead wire comprising a step of sandwiching the lead wire with an exterior film having a thermoplastic resin layer on the surface, melting the resin layer by applying heat and pressure, and bringing the resin layer into close contact with the lead wire. In addition, the present invention relates to a use method in which the thickness of the outermost portion of the lead wire is t or less, where t is the thickness of the resin layer.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A lead wire according to the present invention has a substantially flat band shape on the front and back surfaces, and the thickness of both side edges is smaller than that of other portions. As the lead wire, for example, a cut surface perpendicular to the length direction has a tapered shape, a chamfered rectangular shape, and a half at a rectangular end (corresponding to a shorter side). One having a shape in which a circle or a semi-ellipse is united is exemplified. When the cut surface perpendicular to the length direction is a chamfered rectangle, the chamfer angle with respect to the long side (longer side) of the rectangle is 45 ° or less, and more preferably 20 to 45 °. It is preferable from the viewpoint of the sealing property of the fusion joint. The chamfer angle is 45
When the angle exceeds °, the effect of chamfering cannot be sufficiently obtained. There is no particular problem even if the chamfer angle is less than 20 °, but it is necessary to make the thickness of the outermost portion (tips on both side edges) thin enough to obtain the effect of chamfering. That is, the ratio of the thickness of the outermost portion on the chamfered side portion to the thickness of the non-chamfered portion of the lead wire (hereinafter referred to as the “most side / central portion ratio”).
That. ) Is preferably 0.5 or less from the viewpoint of the sealing property of the heat-sealed portion. If the ratio of the outermost portion / center portion is too large, the effect of chamfering cannot be sufficiently obtained.

When the cut surface perpendicular to the length direction has a shape in which a semicircle or a semiellipse is united with the end of the rectangle, the semiellipse has a ratio of the major axis to the minor axis of 1. A semi-ellipse of 5 or more, more preferably 1.5 to 2.5 is preferable from the viewpoint of the sealing property of the heat-sealed portion. If the ratio of the major axis to the minor axis is less than 1.5, the effect of thinning the end cannot be sufficiently obtained.

In the lead wire of the present invention, a cut surface perpendicular to the length direction of the lead wire is a chamfered rectangular lead wire, which is preferable as a lead wire used in a portable thin battery. Here are the things: (Embodiment 1) Lead wire thickness 30 to 80 µm Lead wire width 2 to 6 mm Outermost / center ratio 0 to 0.5 Chamfer angle to long side 20 to 45 °

In the lead wire of the present invention, the cut surface perpendicular to the length direction of the lead wire is a rectangular lead wire having a semicircle or a semi-ellipse united at the end, and is a portable thin battery. Preferred examples of the lead wire used in the above are as follows. (Embodiment 2) Lead wire thickness 30 to 80 μm Lead wire width 2 to 6 mm Ratio of major axis to minor axis 1.5 or more

According to the lead wire of the present invention, the power generating element can be completely sealed in a state where the power generation element is sealed in a container of an exterior film and a part of the lead wire is led out from the heat-sealed portion.
It is particularly suitable for a thin battery using an exterior film having a thermoplastic resin layer on the surface. As the exterior film,
What laminated | stacked the aluminum foil and the thermoplastic resin layer, especially the polyolefin-type thermoplastic resin layer is preferable. A lead wire having a rectangular shape whose cut surface perpendicular to the length direction is chamfered is sandwiched between laminated films having a thermoplastic resin layer on the surface, and the resin layer is melted by heating and pressing,
In the case where the resin layer and the lead wire are brought into close contact with each other, assuming that the thickness of the resin layer is t, the thickness of the outermost portion of the lead wire is preferably t or less from the viewpoint of the sealing property of the heat-sealed portion. . If the thickness of the outermost portion of the lead wire exceeds t, a gap is likely to be formed near the heat-sealed portion.

[0012]

Next, the lead wire of the present invention will be described with reference to a case where the lead wire is used in a thin Li-ion polymer battery as shown in FIG. Example 1 DBP (dibutyl phthalate) was added as a plasticizer to 100 parts by weight of a PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene) copolymer.
0 parts by weight and 200 parts by weight of acetone were added and mixed to form a paste. Next, a positive electrode active material (LiCoO ₂ )
The paste and the acetylene black were added at a weight ratio of 20: 10: 1, respectively, and mixed well to obtain a positive electrode mixture. Further, each of the negative electrode active material (highly crystalline carbon), the paste, and acetylene black was
The mixture was added at a weight ratio of 0: 10: 1 and mixed well to obtain a negative electrode mixture. The positive electrode mixture was applied to an aluminum foil, and the negative electrode mixture was applied to a copper foil, to obtain a positive electrode and a negative electrode.

Next, 40 parts by weight of DBP and 30 parts by weight of silicon oxide were added to 100 parts by weight of the PVDF-HFP copolymer, mixed and heated, and extruded from a T-die onto a polyethylene terephthalate film. Apply,
An electrolyte film was obtained. The electrolyte film was thermally transferred onto the positive electrode, the negative electrode was placed thereon, and the positive electrode, the electrolyte, and the negative electrode were integrated by passing through a hot roll. Next, DBP was extracted with diethyl ether.

Thereafter, a copper wire having a cut surface perpendicular to the length direction shown in FIG. 3A is used as a negative electrode lead wire, and an aluminum wire having the same shape is used as a positive electrode lead wire, and ultrasonic waves are applied to ears of the negative electrode and the positive electrode, respectively. Joined by welding. An external film container in which a positive electrode, an electrolyte, and a negative electrode are integrated and a lead wire is joined to a lug, and a 25 μm-thick thermoplastic resin layer (here, a layer of a modified polyolefin is used) is provided on the surface. Inserted in. Next, a required amount of electrolyte is added, and PVDF-HF is added.
The pores of P were impregnated in vacuum and heated at 45 ° C. for 1 hour to gel. Thereafter, charging and discharging were performed once, and the container was sealed by heat fusion without subjecting the lead wire to hot melt resin treatment, thereby completing the battery.

A cycle life test was performed on the obtained battery. The charge conditions were 20 ° C., 0.5 C rate current, 4.2 V constant current, constant voltage charge (cut for 2.5 hours), and the discharge condition was 1
C rate discharge (3.0 V cut). Table 1 shows the cycle until the discharge capacity reaches 60% of the initial discharge capacity.

Example 2 A copper wire having a cut surface perpendicular to the longitudinal direction shown in FIG. 3B was used as a negative electrode lead wire, and an aluminum wire of the same shape was used as a positive electrode lead wire.
A battery similar to that of Example 1 was assembled, and a similar test was performed. Table 1 shows the results.

Example 3 A copper wire having a cross section perpendicular to the length direction shown in FIG. 3C was used as a negative electrode lead and an aluminum wire of the same shape was used as a positive electrode lead.
A battery similar to that of Example 1 was assembled, and a similar test was performed. Table 1 shows the results.

Comparative Example 1 A conventional copper wire having a cut surface perpendicular to the longitudinal direction shown in FIG. 3 (f) was used as a negative electrode lead and a conventional aluminum wire of the same shape was used as a positive electrode lead. Assembled the same battery as in Example 1 and performed the same test. Table 1 shows the results.

Comparative Example 2 A battery similar to that of Comparative Example 1 was assembled and subjected to the same test, except that a hot-melt resin was previously attached to a portion of the lead wire to be heat-sealed to provide a heat-sealed portion. Was done. Table 1 shows the results.

Example 4 A copper wire having a cut surface perpendicular to the length direction shown in FIG. 3D was used as a negative electrode lead and an aluminum wire of the same shape was used as a positive electrode lead.
A battery similar to that of Example 1 was assembled, and a similar test was performed. Table 1 shows the results.

Example 5 A copper wire having a cut surface perpendicular to the longitudinal direction shown in FIG. 3E was used as a negative electrode lead and an aluminum wire of the same shape was used as a positive electrode lead.
A battery similar to that of Example 1 was assembled, and a similar test was performed. Table 1 shows the results.

[0022]

[Table 1]

According to Table 1, when a lead wire having thinner side edges is used, the bevel angle is 45 ° or less, and the thinner side portion has a better cycle life of the battery. You can see that there is. In Example 1, the cycle life is remarkably improved as compared with Comparative Example 2 in which a hot melt resin is previously attached to a conventional lead wire and a heat-sealed portion is provided. This is considered to be because in Comparative Example 2, the hot melt resin layer was formed thick in the heat-sealed portion, and water easily permeated therefrom. Further, when the conventional lead wire is used as it is, a gap is easily formed at the outermost portion of the lead wire, and it is found that a sufficient cycle life cannot be obtained. Furthermore, when the shape of the cut surface perpendicular to the length direction of the lead wire is a rectangle in which a semicircle or a semiellipse is united at the end, particularly, the ratio between the long axis and the short axis is 1.5 or more. It can be seen that even in the case of a rectangle having a semi-ellipse united at the end, a superior cycle life is exhibited as compared with a conventional lead wire.

[0024]

The lead wire of the present invention is excellent in the sealing property of the heat-sealed portion. For example, when applied to a thin polymer battery, the exterior film and the lead wire are easily adhered completely, preventing leakage of sealed liquid or gas, invasion of external moisture, etc., and shortening the cycle life of the battery. Be improved. Also,
By using the lead wire of the present invention, the manufacturing process of the thin battery can be simplified, and the cost can be significantly reduced. The lead wire of the present invention is suitable not only for a thin polymer battery but also for a product sealed with a hot melt resin, such as a capacitor.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an example of a thin battery.

FIG. 2 is a front view showing a part of the internal structure of an example of a thin battery by a broken line.

FIGS. 3A to 3E show main parts of a cross-sectional view obtained by cutting a lead wire perpendicularly to a length direction, wherein FIGS. 3A to 3E show a lead wire according to an embodiment of the present invention, and FIG. Shows the lead wire.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Aluminum foil 2 Positive electrode 3 Copper foil 4 Negative electrode 5 Polymer solid electrolyte 6 Outer film 7 Heat fusion part 8 Negative lead wire 9 Positive lead wire 10 Ear part

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kenichi Takeyama 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture F-term (reference) 5H011 AA09 AA17 EE04 FF04 GG09 HH02 JJ25 JJ27 KK02 KK03 5H022 AA09 BB01 BB06 BB05 CC05 CC08 CC09 KK08 5H029 AJ14 AJ15 AK03 AL06 AM00 AM16 BJ04 BJ12 CJ02 CJ03 DJ03 DJ05 HJ00 HJ04

Claims (6)

[Claims] 1. A lead wire for a battery, wherein the front and back surfaces are flat strip-shaped leads, and the thickness of both side edges is thin. 2. A cross section perpendicular to the length direction of the lead wire,
The lead according to claim 1, wherein the lead is a chamfered rectangle. 3. A chamfer angle with respect to a long side of the rectangle is 4
3. The lead wire according to claim 2, which is at most 5 °. 4. A cross section perpendicular to the length direction of the lead wire,
The lead wire according to claim 1, wherein the end wire has a shape in which a semi-ellipse having a ratio of a major axis to a minor axis of 1.5 or more is combined with an end of the rectangle. 5. A thin battery in which a power generation element is sealed with an exterior film having a thermoplastic resin layer on its surface,
A thin battery in which the lead wire according to any one of (1) to (4) is connected to each electrode of the power generation element, and is led out from a heat-sealed portion of the exterior film. 6. A method of using a lead wire comprising the steps of sandwiching a lead wire with an exterior film having a thermoplastic resin layer on its surface, melting the resin layer by applying heat and pressure, and bringing the resin layer into close contact with the lead wire. The method according to claim 1, wherein the thickness of the outermost portion of the lead wire is t or less, where t is the thickness of the resin layer.