JPH103900A - Secondary battery and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the manufacture of secondary battery, which can obtain a junction part having stabilized strength and impedance, by forming the structure that a collector can be easily joined to a positive electrode lead in a wide range of condition. SOLUTION: A main body 5 of a positive electrode 2 is formed into a sheet, and a lead 4 and a collector 3 are joined to an upper edge of the positive electrode main body 5 by resistance welding. The upper edge of the positive electrode main body 5 is pressed so as to be formed at a thickness at about half of the thickness of the main body 5, and a narrow and long lead 4 is overlapped along the upper edge of the positive electrode main body 5. Furthermore, the collector 3, which is formed with a projecting part in a surface to be joined, is overlapped so that this projecting part abuts on the lead 4, and this overlapped part is pressurized, and welding current is applied to this pressurized part so as to partially melt an area of the projection, and the collector 3 is joined to the lead 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a secondary battery and a secondary battery.

[0002]

2. Description of the Related Art In recent years, various batteries such as an alkaline secondary battery and a lithium ion secondary battery have been developed and put into practical use in response to the demand for high-performance, high-capacity batteries. Alkaline secondary batteries are widely used because they are less expensive to manufacture than lithium ion secondary batteries, have higher safety, and can be discharged with a large current.

For example, in a nickel hydride secondary battery,
An electrode group produced by interposing a separator made of a synthetic resin fiber non-woven fabric between a positive electrode containing nickel oxide and a negative electrode containing a hydrogen storage alloy, and a strong alkaline electrolyte such as a potassium hydroxide solution. It is housed in a battery container.
A lead is attached to the edge of the positive electrode, and a tab as a current collector is joined to the lead.

In a conventional secondary battery, a positive electrode current collector (tab) is directly welded directly to a positive electrode lead using an ultrasonic welding method. Since the junction between the positive electrode lead and the current collector has a large effect on the impedance of the battery circuit, it is important to maintain and maintain the quality of the secondary battery at a predetermined level.

[0005]

However, in the conventional direct welding method, when the materials of the positive electrode lead and the current collector are different from each other or when the thicknesses thereof are different, the welding conditions or the like for obtaining a good joint portion can be obtained. Since the welding range is considerably narrowed and it is difficult to obtain a product of constant quality, the incidence of rejected products increases.

Further, in the conventional direct welding method, the tip shape changes due to splattering and the like while welding a large number of pieces repeatedly, and welding defects tend to occur, which is a major problem in quality control. .

[0007] By the way, the separator made of a nonwoven fabric made of a synthetic resin fiber such as a polypropylene resin is ultrasonically bonded at both edges in a shape to cover the positive electrode, but the fused portion is shrunk and the separator is flat. Due to the irregular shape, the separator is drawn from the fused portion as a starting point. In addition, spots of fusion due to shrinkage occur at the joints at both edges of the separator, and the strength in the tensile direction decreases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is possible to easily join a current collector to a positive electrode lead under a wide range of conditions, and to obtain a joint having stable strength and impedance. An object of the present invention is to provide a method of manufacturing a secondary battery that can be performed and a secondary battery manufactured by the method.

Another object of the present invention is to provide a method of manufacturing a secondary battery capable of satisfactorily joining the edges of a separator enclosing a positive electrode, and a secondary battery manufactured by the method.

[0010]

First, a method of manufacturing a secondary battery according to the present invention is directed to a method of manufacturing a secondary battery in which a current collector is bonded to a positive electrode lead. A projection is formed on the surface to be formed, the positive electrode current collector is overlapped on the lead such that the projection comes into contact with the lead at the edge of the positive electrode, a welding current is applied while applying pressure to the overlap region, and a welding current is applied. The region is partially melted, and the positive electrode current collector is joined to the lead.

In this case, the projection has a conical shape with a height of 0.5 to 0.8 mm and a diameter of 0.6 to 1.
Preferably, it is 0 mm. Furthermore, as welding conditions,
The current value is set in the range of 0.5 to 2 kA, and the pressure is set to 0.
It is desirable to set it in the range of 9 to 1.2 kg / cm ² .

Further, a secondary battery according to the present invention comprises a battery container having a cap, a positive electrode and a negative electrode housed in the battery container together with an electrolytic solution, and provided between the positive electrode and the negative electrode to separate both electrodes. A positive electrode current collector that is resistance-welded to the lead and pressed against the cap when the positive electrode is housed in a battery container. The electric body is joined to the lead via at least one protrusion.

[0013] The mechanical properties, particularly the tensile strength, of a joint formed by resistance welding strongly depend on three factors: current value (current density), pressing force, and energizing time. This will be described with reference to FIGS.

FIG. 5 shows the current value (current density (mA / c) on the horizontal axis.
FIG. 8 is a graph qualitatively showing a result of examining the dependence of impedance on current density when the pressure and energization time are kept constant by taking m ² )) and taking the impedance (Ω) on the vertical axis. As is clear from FIG. 5, the impedance increases at a current density in a certain intermediate region, but decreases in a low current density region and a high current density region outside the intermediate region. However, it is desirable to weld in a region with a high current density, because a portion welded in a region with a low current density may not have a predetermined level of strength.

FIG. 6 shows the pressing force (kgf / cm) on the horizontal axis.
FIG. 2B is a graph qualitatively showing the result of examining the dependence of the impedance on the pressing force when the current value and the conduction time are kept constant by taking ² ) and taking the impedance (Ω) on the vertical axis. As is clear from FIG. 6, the pressing force and the impedance are almost inversely proportional, and the higher the pressing force, the lower the impedance. But,
If the pressure is too high, the welding tip will deteriorate in a short period of time, so it is desirable that the pressure is moderate.

In order to obtain proper impedance and welding strength from the above-described current density dependency and the applied pressure dependency, the current collector is connected to the positive electrode lead in a high current density region and under a condition that a non-excessive applied pressure is applied. Welding is preferred.

Secondly, a method for manufacturing a secondary battery according to the present invention is a method for manufacturing a secondary battery, in which a separator enclosing the positive electrode is formed to separate the positive electrode from the negative electrode, the method being provided on the positive electrode body. The current collector is resistance welded to the lead, the positive electrode body is inserted into the separator so that at least a part of the current collector protrudes, and ultrasonic waves are applied while applying pressure to both edges of the separator to join. Ultrasonic welding is performed in a predetermined pattern in which portions and non-joined portions alternately exist.

Further, the secondary battery according to the present invention comprises a battery container, a positive electrode and a negative electrode housed in the battery container together with an electrolytic solution, and a separator provided between the positive electrode and the negative electrode to separate both electrodes. , A lead provided along the edge of the positive electrode, and a positive electrode current collector resistance-welded to the lead, and both edges of the separator are provided with a joining portion and a non-joining portion alternately. It is characterized by being ultrasonically welded in a predetermined pattern.

By adopting a predetermined pattern in which a joining portion and a non-joining portion are alternately present in the fused portion of the separator, the separator can be extended, and the strength of the joining portion in the tensile direction is improved.

[0020]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. As a nickel-hydrogen secondary battery not containing an electrolyte, a battery manufactured by the following method was used. That is, a mixed powder consisting of 90 parts by weight of nickel hydroxide powder and 10 parts by weight of cobalt monoxide powder was mixed with 0.3 part by weight of carboxymethyl cellulose and a suspension of polytetrafluoroethylene (specific gravity: 1 0.5, 60 parts by weight of solid content), and 0.5 parts by weight of solid content were added thereto, and 45 parts by weight of distilled water was added thereto and kneaded to prepare a paste.

Next, after filling the paste into a nickel-plated fiber substrate as a conductive substrate, the paste is further applied to both surfaces thereof, dried, and rolled by a roller press to obtain a thickness of 0.1 mm. A 65 mm paste-type positive electrode was produced. A positive electrode lead tab 4 is attached to the obtained positive electrode 2.
Was connected at one end.

On the other hand, LmNi _4.0 Co _0.4 Mn _0.3 Al
0.5 part by weight of sodium polyacrylate, 0.125 part by weight of carboxymethylcellulose (CMC), and dispersion of polytetrafluoroethylene (specific gravity: 1.25 parts by weight) per 100 parts by weight of a hydrogen storage alloy powder having a composition of _0.3 .
5, a solid content of 60 wt%) was mixed with 2.5 parts by weight of solid content and 1.0 part by weight of carbon powder as a conductive material together with 50 parts by weight of water to prepare a paste. This paste was applied to a punched metal as a conductive substrate, dried, and then molded under pressure to produce a paste-type negative electrode having a thickness of 0.40 mm.

A non-woven fabric made of a polyolefin-based synthetic resin fiber having a weight per unit area of 55 g / m ² and a thickness of 0.18 mm between the obtained positive electrode 2 and negative electrode was graft-copolymerized with an acrylic acid monomer. These were spirally wound with a separator 11 interposed therebetween as shown in FIG. 3 to produce an electrode group.

The electrode group was housed in a bottomed cylindrical container (4 / 5A size) 8 having a rising portion at the upper opening so that the lamination surface was parallel to the depth direction of the container 8. In addition,
A sealant (for example, made of asphalt) is applied to the inner surface of the upper opening in order to increase the adhesion between the insulating gasket and the inner surface of the upper opening of the container to improve airtightness.

The obtained nickel-hydrogen rechargeable battery 1 not containing an electrolytic solution was placed in an injection device with a distance of 0.5 mm between the upper end of the electrode group of the battery and the lower end of the outlet of the injection member. After incorporating, the pressure in the vessel was reduced to 110 Torr, and 2.5 cc of an alkaline electrolyte composed of 7N KOH and 1N LiOH was injected into the vessel while applying a centrifugal force at a rotation speed of 1000 rpm.

Further, the current collector 3 is joined to the cap 9,
The current collector 3 was bent, and the cap 9 was put on the container 8, and the two were joined, whereby the secondary battery 1 was obtained. Next, FIG.
The positive electrode 2 will be described in more detail with reference to FIG.

As shown in FIG. 1, the main body 5 of the positive electrode 2 has a sheet shape, and the lead 4 and the current collector 3 are joined to the upper edge 5b of the positive electrode body 5 by resistance welding. As shown in FIG. 2, most of the positive electrode body 5 is made of the uncoated layer 6.

As shown in FIG. 4, the upper edge portion 5b is pressed to have a thickness of about half the thickness of the positive electrode body 5, and the elongated leads 4 are overlapped along the upper edge portion 5b. Further, the current collector 3 is superimposed on an appropriate position of the lead 4. Two protrusions 3b are provided on the superposed joint surface of the current collector 3.
Are formed. The protrusion 3b has a conical shape or a hemispherical shape, each height is formed in a range of 0.5 to 0.8 mm, and each diameter is formed in a range of 0.6 to 1.0 mm.

When these three members are overlapped and resistance-welded, as welding conditions, the current value is set in the range of 0.5 to ² kA, and the pressure is set in the range of 0.9 to 1.2 kg / cm ² . Set.

Since the current collector 3 also has a role of a safety fuse, it is desirable that the impedance between the current collector 3 and the upper edge lead 4 has a certain value. For this reason, a hole 3a is formed in the current collector 3 to facilitate melting down of the current collector 3 when an abnormal current flows in the battery.

FIG. 7 shows the measured impedance (Ω) on the horizontal axis and the measured welding strength (kgf) on the ultrasonic joint on the vertical axis, using the product of the embodiment using the method of the present invention and the conventional method. It is the graph which compared the result of having investigated about the product of the comparative example which was. The impedance is measured by connecting a test lead (not shown) to the current collector 3 and connecting a tester terminal between the test lead and the upper edge lead 4. The welding strength was measured by pulling the sample at a constant speed using a push-pull gauge and measuring the breaking strength. In the figure, white squares show the results of the examples using the method of the present invention, and black squares show the results of the comparative examples using the conventional method.

As can be seen from the figure, the measured impedance of the product of the comparative example is in the range of 0.3 to 2.8 Ω, and the measured value of the product of the example is 1.6 to 1.6 while the dispersion of measured values is large. It is in the range of 2.8Ω, and the dispersion of the measured values is small. Thus, it was found that the product of the example was more stable in quality than the product of the comparative example. Further, the welding strength of the example product is 2.3 to 6.6 k.
Measurements in the gf range were obtained, with results equal to or greater than those of the comparative example product.

Thus, it has been found that a product provided with a positive electrode current collector joined by the method of the present invention has superior quality to a conventional product. Some of the comparative examples have extremely small impedance measurement values. This is because the current collector 3 easily melts down when an abnormal current flows between the current collector 3 and the upper edge lead 4. Otherwise, the safety of the battery is impaired, which is not preferable. Since the current collector 3 has a role of a safety fuse in the secondary battery, the current collector 3
This is because the impedance between the upper edge lead 4 and the upper edge lead does not have to be small, but it is desirable that the impedance has a certain magnitude.

Next, with reference to FIGS.
The welding assembly of the separator 11 enclosing the above will be described. As shown in FIGS. 8 and 9, the positive electrode 2 is inserted into a bag-shaped separator 11. At this time, the current collector 3 protrudes outside the separator 11.

As shown in FIG. 10, the separator 11 is placed on the support 21 of the ultrasonic welding machine, and the upper anvil 22 faces this. The positive electrode 2 with the tab 3 projecting from the separator 11 is inserted into the separator 11. Support base 21
Has a built-in ultrasonic generator (not shown). When electricity is supplied to the ultrasonic generator, ultrasonic waves of a predetermined frequency are applied to the separator 11 on the support 21.

The anvil 22 is supported by a lifting mechanism and a pressing mechanism (not shown). A predetermined concavo-convex pattern is formed on a pair of tips of the anvil 22. When the ultrasonic wave is applied while lowering the anvil 22 and pressing the left and right edges of the separator 11 with the anvil 22, the left and right edges of the separator 11 are joined.

In this embodiment, the upper and lower two separators 11 are overlapped and joined, but one separator 1
Alternatively, the left and right edges may be joined together after folding back 1. Further, in addition to the left and right edges of the separator 11, a bottom edge may be joined.

Various joining patterns of the separator enclosing the positive electrode will be described with reference to FIGS. As shown in FIG. 11, both left and right edges of the separator 11a are ultrasonically welded in a range of 1 to 2 mm in width. This ultrasonically welded area is not entirely joined but is partially joined. The pattern joining portion 12a of this embodiment adopts a cross pattern.

A diagonal pattern may be employed as in another pattern joint 12b shown in FIG.
An embossed pattern may be adopted as in a pattern joint 12c shown in FIG.

In the above embodiment, the case of a square secondary battery has been described. However, the present invention is not limited to this, and can be applied to other types of secondary batteries such as a round type and a box type.

[0041]

According to the present invention, there is provided a method of manufacturing a secondary battery, wherein a current collector can be easily bonded to a positive electrode lead under a wide range of conditions, and a bonded portion having stable strength and impedance can be obtained. A secondary battery can be provided.

[Brief description of the drawings]

FIG. 1 is a front view showing a pre-wound positive electrode current collector made by a method for manufacturing a secondary battery according to an embodiment of the present invention.

FIG. 2 is a plan view showing a positive electrode current collector before winding.

FIG. 3 is an exploded cross-sectional view showing an electrode inside a battery container.

FIG. 4 is a diagram showing a current collector, a lead, and an active material layer before welding.

FIG. 5 is a graph showing the relationship between the welding current value and the impedance when the pressing force and the conduction time are constant.

FIG. 6 is a graph showing a relationship between a pressing force and an impedance when a current value and a conduction time are constant.

FIG. 7 is a graph showing the effect of the present invention.

FIG. 8 is a diagram showing a positive electrode and a separator as viewed from the front.

FIG. 9 is a diagram showing a positive electrode and a separator viewed from the side.

FIG. 10 is a diagram showing a positive electrode and a separator set in the ultrasonic welding machine.

FIG. 11 is a diagram showing a positive electrode covered by a separator.

FIG. 12 is a diagram showing a positive electrode covered by a separator.

FIG. 13 is a diagram showing a positive electrode covered by a separator.

[Explanation of symbols]

2 ... Positive electrode, 3 ... Current collector (tab), 3a ... Hole, 3b ... Protrusion, 4 ... Upper edge lead, 5 ... Active material layer, 6 ... Uncoated layer, 11, 11a-11c ... Separator, 12a-12
c: pattern joint, 21: ultrasonic generator, 22: anvil.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahiko Lunar Legs 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo Toshiba Battery Corporation

Claims (6)

[Claims] 1. A method of manufacturing a secondary battery in which a current collector is joined to a lead of a positive electrode, wherein a projection is formed on a surface of the positive electrode current collector to be joined, and the projection abuts on a lead at an edge of the positive electrode. As described above, the positive electrode current collector is superimposed on the lead, and a welding current is applied while applying pressure to the superposed area to partially melt the area of the protrusion and join the positive electrode current collector to the lead. Manufacturing method for a secondary battery. 2. The secondary according to claim 1, wherein the projection has a conical shape, a height of 0.5 to 0.8 mm, and a diameter of 0.6 to 1.0 mm. Battery manufacturing method. 3. The welding conditions include a current value of 0.5 to 2 kA.
In the range of 0.9 to 1.2 kg / cm ²
The method for manufacturing a secondary battery according to claim 1, wherein the secondary battery is set in a range of: 4. A method for manufacturing a secondary battery, comprising forming a separator enclosing a positive electrode in order to separate a positive electrode and a negative electrode, wherein the current collector is resistance-welded to a lead provided on the positive electrode body. Insert the positive electrode body into the separator so that at least a part of it projects, apply ultrasonic waves while applying pressure to both edges of the separator,
A method for manufacturing a secondary battery, comprising: performing ultrasonic welding in a predetermined pattern such that a joined portion and a non-joined portion alternately exist. 5. A battery container having a cap, a positive electrode and a negative electrode housed in the battery container together with an electrolytic solution, a separator provided between the positive electrode and the negative electrode to separate both electrodes, and an edge of the positive electrode And a positive electrode current collector that is resistance welded to the lead and pressed against the cap when the positive electrode is housed in a battery container, wherein the positive electrode current collector has at least one protrusion. A secondary battery, wherein the secondary battery is joined to the lead via a wire. 6. A battery container, a positive electrode and a negative electrode accommodated in the battery container together with an electrolytic solution, a separator provided between the positive electrode and the negative electrode to separate the two electrodes, and along an edge of the positive electrode. A lead provided, and a positive electrode current collector resistance-welded to the lead, wherein both edges of the separator are ultrasonically welded in a predetermined pattern in which joined portions and non-joined portions alternately exist. A secondary battery.