JPH10255753A - Manufacture of electrode for sealed type square battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent any welding damage on a separator so as to weld lugs to each other and the lugs to a strap by previously disposing, in a welded section, a metal body having a spectral reflectance lower than that of metal constituting a conductive metal foil, and irradiating a laser beam so as to fuse the metal body. SOLUTION: A negative electrode 1 comprises a base material of a copper foil having a thickness of 10-20μm, an electrode part having an active substance mixture layer made of meso-carbon micro beads formed thereat, and a lug 11. A positive electrode 2 has the same structure as that of the negative electrode 1 except that an active substance mixture layer is made of LiCoO2 . The negative and positive electrodes 1, 2 are alternately laminated inside a separator 3 of a non-woven fabric bag made of polypropylene. The lug 11 of the negative electrode 1 projecting from the separator 3 and the lug of the positive electrode 2 are aligned along the ends, laminated via Ni foils 4 of 15μm, and then, caulked by a strap 5. Even if a laser beam of a low output is irradiated on a welded part of the lugs 11, a metallic body having a spectral reflectance lower than that of a conductive metal foil is fused preferentially, thereby achieving speedy welding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electrode of a sealed rectangular battery such as a negative electrode of a lithium ion battery and a negative electrode of a nickel-metal hydride battery.

[0002]

2. Description of the Related Art Among the characteristics of batteries, smaller and lighter batteries and higher capacity have recently been particularly required. Therefore, in lithium-ion batteries and the like, batteries that have been made smaller by increasing the surface area of electrodes by laminating a plurality of metal foils each having an active material layer and increasing the electrode surface area have come to be used. I have.

In order to manufacture such an electrode composed of a plurality of metal foils, a plurality of conductive metal foils each having an active material layer formed thereon and having ears are laminated with a separator interposed therebetween. After the reinforcing plates are laminated, the ears are welded to each other by a resistance welding method or the like. The welded ears are used as electrode leads. Further, since it is desirable to minimize the internal resistance, highly conductive copper is used as the material of the metal foil, and an extremely thin copper foil having a thickness of about 10 to 20 μm is used.

However, when the lugs are welded to each other by the resistance welding method, the copper foil melted during the resistance welding adheres to the welding electrode to increase maintenance, and the range of welding setting conditions is narrow, making setting difficult. However, there is a problem that productivity and reliability are low. Therefore, Japanese Patent Application Laid-Open No.
Japanese Patent Publication No. 08-083811 discloses a method in which a protruding piece having a substantially U-shaped cross section is provided at a position corresponding to an electrode lead on a reinforcing plate, and the protruding piece grips a laminated ear portion and welds through the protruding piece. A method for manufacturing an electrode of a sealed prismatic battery is disclosed.

[0005] According to this manufacturing method, since the welding electrode and the like do not directly contact the ear portion, a problem that a molten copper foil adheres is avoided. Further, the range of welding setting conditions is widened, and workability is also improved. When the number of laminated copper foils is large, the copper foil is divided into a plurality of sets, and as shown in FIG. 6, the ears of each set are sandwiched by straps and welded. In this case, the strap has the same function as the above-mentioned protruding piece, and the same effect can be obtained.

[0006]

By the way, copper is a metal having high conductivity as well as having a higher thermal conductivity than iron or nickel as shown in Table 1 at the same time. On the other hand, a polyolefin-based thermoplastic resin is generally used as the separator. Therefore, when an electrode is manufactured by the method disclosed in the above publication, heat during welding is easily transmitted from the copper foil to the separator, and as shown in FIG. There was a defect that was.

[0007]

[Table 1] This problem can be solved by using a metal foil having a low thermal conductivity instead of copper or by increasing the heat capacity of the separator. However, when a metal foil having a low thermal conductivity is used instead of copper, the conductivity is lower than that of copper, so that the capacity is often lowered or the cost is soared in many cases. In order to increase the heat capacity of the separator, it is general to increase the thickness of the separator. However, this method is not preferable because it is against the demand for downsizing.

The present invention has been made in view of such circumstances, and it is an object of the present invention to use a conductive metal foil and a separator similar to those of the related art, and to prevent the separator from being damaged.

[0009]

The feature of the method for manufacturing an electrode of a sealed prismatic battery according to the present invention which solves the above-mentioned problems is that a plurality of conductive metal foils having ears are laminated via a separator. In a method for manufacturing an electrode of a sealed prismatic battery, the method comprises the steps of: laminating an ear portion with a strap; and welding the stacked ear portions together and welding the ear portion to the strap. A metal body having a lower spectral reflectance than the metal constituting the metal foil is disposed, and the welding step is performed by irradiating the metal body with a laser beam to melt the metal body.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the laminating step, a plurality of conductive metal foils are laminated via a separator. Copper foil is usually used as the conductive metal foil, but other conductive metals can also be used. However, in the case of metals other than copper, the conductivity may be lower than that of copper, so that the capacity may decrease or the cost may increase. The thickness of this conductive metal foil is 1 as in the prior art.
Those having a size of 0 to 20 μm are generally used. If the thickness of the conductive metal foil is less than 10 μm, handling becomes difficult,
If the thickness is larger than 0 μm, the battery becomes large to have the same capacity as the conventional one, and if the electrode has the same volume as the conventional one, the capacity becomes insufficient.

As the separator, polypropylene, polyethylene or the like can be used as in the prior art, and a separator having a thickness of generally 30 to 50 μm is used. As the state of the separator, a porous state such as a nonwoven fabric is used so that the electrolytic solution can enter and exit. Then, the stacked ears are gripped by the strap. The material of the strap is not particularly limited as long as it can be welded to the ear, and stainless steel or the like is used as in the conventional case.

In the welding step, which is a feature of the present invention, a metal body having a lower spectral reflectance than the metal constituting the conductive metal foil is previously arranged on the welded portion, and the welding step is performed by irradiating the metal body with a laser beam. Let the body melt. As a result, the ear portions and the ear portion and the strap are welded by the molten metal body. According to the laser beam welding method, a narrower range can be welded in a short time. However, in the case of metals such as copper, which have a high spectral reflectance, a long time is required for melting because the laser beam is reflected, and a high-power laser beam is required. However, when the irradiation time is lengthened or a high-output laser beam is used, heat conduction proceeds excessively, and the separator may be melted.

Therefore, in the present invention, a metal body having a lower spectral reflectance than the metal constituting the conductive metal foil is arranged in the welded portion in advance. By doing so, the laser beam is preferentially absorbed by the metal body and the metal body is melted, so that it is possible to quickly weld using a low-power laser beam and prevent the separator from being melted and damaged. be able to.

As the material of the metal body, for example, when copper foil is used as the conductive metal foil, as shown in Table 2, iron and nickel having a lower spectral reflectance than copper can be used. Further, as a method of disposing the metal body, a method in which a powdery or foil-like metal body is sandwiched between ear portions and between a strap and an ear portion, an ear laminated with metal body foil or metal body powder. For example, a method of covering the end face of the part is exemplified.

[0015]

[Table 2] It is desirable to use a laser beam having an oscillation wavelength of 0.3 to 1.0 μm, such as an N ₂ laser or a YAG laser.

[0016]

The present invention will be described below in detail with reference to examples. In this embodiment, the present invention is applied to manufacture of an electrode for a lithium ion battery. Example 1 First, as shown in FIG. 1, a negative electrode plate 1 having a copper foil having a thickness of 18 μm as a base material is prepared. This negative electrode plate 1
A 45 mm × 45 mm square electrode section 10 and a 20 mm × 10 mm rectangular ear section 11 protruding from one end of one side of the electrode section 10, and mesocarbon microbeads (MCMB ) Is formed.

On the other hand, the material of the active material mixture layer is LiCoO ₂
A positive electrode plate 2 having the same configuration as that of the negative electrode plate 1 is prepared except for the above. Next, each of the negative electrode plate 1 and the positive electrode plate 2 is placed in a bag-shaped separator 3 made of a nonwoven fabric having a thickness of 25 μm made of polypropylene, and ten negative electrode plates 1 and positive electrode plates 2 are alternately laminated. The ear 11 and the ear 21 project from the separator 3. Then, the ears 11 of the negative electrode plate 1 were aligned at one end, the ears 21 of the positive electrode plate 2 were aligned at the other end, and a 15 μm-thick Ni foil 4 was laminated between the ears. Finally, the ears 11 and 21 of the laminate are
The i-foil 4 was interposed therebetween, and was caulked with a SUS304 strap 5 and sandwiched. The state is shown in FIG. 2 and FIG.

Then, the YAG laser (pulse oscillation 10H) is applied in a non-oxidizing atmosphere of nitrogen and argon toward the respective protruding end faces of the ear portions 11 and the ear portions 21.
z) was irradiated for 10 milliseconds. As a result, Ni foil 4
Was melted, the ears 11 and the ears 21 were welded to each other, the strap 5 and the ears 11 and the strap 5 and the ears 21 were welded, and no erosion was observed in the separator 3.

(Comparative Example 1) A negative electrode plate 1 and a positive electrode plate 2 were prepared in the same manner as in Example 1, and were laminated and sandwiched by a strap 5 in the same manner as in Example 1 except that the Ni foil 4 was not used. . When laser welding was performed under the same conditions as in Example 1, welding was difficult because the copper foil reflected the laser beam. Therefore, the pulse oscillation is set to 10 Hz and the irradiation time is set to 20.
Welding was performed by irradiating with a YAG laser increased in milliseconds.
As a result, about 100 mm ² of erosion was observed near the ear 11 and the ear 21 of the separator 3.

Example 2 A negative electrode plate 1 and a positive electrode plate 2 were prepared as in Example 1, and laminated in the same manner as in Example 1 except that the Ni foil 4 was not used. Next, as shown in FIG.
The end faces 11 and 21 of the laminated body to be irradiated with the laser beam are covered with a Ni foil 6 having a thickness of 15 μm.
With the i-foil 6 sandwiched therebetween, the strap 11 sandwiched the ear 11 and the ear 21 of the laminate.

Then, when the YAG laser is irradiated under the same conditions as in the first embodiment, the Ni foil 6 is melted, and the molten nickel is separated between the ears 11 by the capillary phenomenon, and the ears 21 are irradiated.
The straps 5 and the ears 11 and the straps 5 and the ears 21 infiltrated and were welded to each other, and no erosion was observed in the separator 3. (Example 3) A negative electrode plate 1 and a positive electrode plate 2 were prepared in the same manner as in Example 1, and were laminated and sandwiched by a strap 5 in the same manner as in Example 1 except that the Ni foil 4 was not used.

Next, as shown in FIG.
The Ni powder 7 having an average particle size of 2 μm was uniformly placed on the end faces of the ears 21 and the laser beam irradiated with the laser beam, and irradiated with a YAG laser under the same conditions as in Example 1. Due to the capillary phenomenon, the molten nickel forms between the ears 11, between the ears 21, the strap 5 and the ears 11.
In addition, infiltration between the strap 5 and the ear portion 21 resulted in welding, and no erosion of the separator 3 was observed.

[0023]

According to the method of manufacturing an electrode of a sealed prismatic battery of the present invention, a metal foil having excellent conductivity such as a copper foil and a thin thermoplastic resin separator of about 25 μm are used to melt the separator. The ears and the ear and the strap can be welded together while preventing loss.

Therefore, according to the manufacturing method of the present invention, a small and high-capacity battery electrode can be easily and stably manufactured.

[Brief description of the drawings]

FIG. 1 is a perspective view of a negative electrode plate used in one embodiment of the present invention.

FIG. 2 is a perspective view of an electrode manufactured according to an embodiment of the present invention before a welding step.

FIG. 3 is an enlarged sectional view of a main part of FIG. 2;

FIG. 4 is an enlarged perspective view of a main part before a welding step of an electrode manufactured in a second embodiment of the present invention.

FIG. 5 is an enlarged perspective view of a main part before a welding step of an electrode manufactured in a third embodiment of the present invention.

FIG. 6 is a perspective view of a main part of an electrode manufactured in Comparative Example 1.

[Explanation of symbols]

1: negative electrode plate 2: positive electrode plate 3: separator 4: Ni foil 5: strap 11: ear

Claims (1)

[Claims] 1. A laminating step of laminating a plurality of conductive metal foils having ears via a separator, gripping the stacked ears with a strap, welding the stacked ears together, and forming the ears together. A method of manufacturing an electrode of a sealed prismatic battery comprising a welding step of welding a portion to a strap, wherein a metal body having a lower spectral reflectance than a metal constituting the conductive metal foil is disposed in a welding portion in advance, and the welding step is performed. A method for manufacturing an electrode for a sealed prismatic battery, comprising irradiating a laser beam to the metal body to melt the metal body.