JP2000223090A - Battery - Google Patents

Abstract

(57) [Problem] To prevent dissipation of an electrolytic solution from a seal portion of a laminate sheet in a battery having a laminate sheet as an outer case. SOLUTION: A laminate sheet having a metal foil layer and a heat-fusible resin layer is cut into a predetermined shape, folded in two on a center line thereof and overlapped, and a heat forming a laminate sheet is formed around the periphery thereof. A double seal portion composed of an inner seal in which the fusion resin films are welded to each other and an outer seal in which the metal foils are welded to each other is provided adjacent to each other. The outer metal seal has a welded structure with the primary purpose of preventing the escape of the electrolyte, and the inner heat-fusible resin seal has a mechanical and chemical protection and reinforcement of the outer seal. Heat welded structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery having a laminate sheet as an outer case, which is used for a lithium polymer secondary battery or the like.

[0002]

2. Description of the Related Art A battery using a laminated sheet obtained by laminating an insulating resin film and a metal foil as an integrated case as an outer case has been conventionally known as disclosed in, for example, JP-A-10-214606. ing.

FIG. 3 is a diagram generally known from the prior art.
FIG. 4 is a cross-sectional view showing a configuration of a battery using the laminate sheets 14 and 15 as the outer case 12, and FIG. 4 is a plan view thereof. In these figures, an electrode group 4 constituted by laminating a positive electrode plate 1 and a negative electrode plate 2 with a separator 3 interposed therebetween is provided.
And the outer periphery 12 of the laminated sheet is sealed by a method such as heat fusion to form the outer case 12 for accommodating the laminated electrode group 4. However, the electrode group is impregnated with an electrolytic solution, and the main purpose of the sealing portion is to prevent the electrolytic solution from escaping outside the battery case and to prevent foreign substances from entering the battery case.

[0004] The laminated electrode 4 sealed in the battery outer case 12 is sealed in a state where an electrolyte is injected into the outer case 12. In such a battery using the laminate sheets 14 and 15 as the outer case, the dissipation of the electrolyte sealed in the outer case 12 mainly occurs in the cross section of the seal portion around the outer case P. That is, the vapor of the electrolytic solution diffuses in the bonding resin of the seal portion and escapes from the outer case 12 from the cross section of the seal portion as time passes. Since the dissipation of the electrolytic solution is closely related to the deterioration of the battery performance, it is necessary to prevent the dissipation as much as possible. As means for preventing the dissipation of the electrolytic solution, a method of providing a wide seal portion, or reducing the thickness of the resin layer constituting the seal portion as much as possible to reduce the permeation cross-sectional area of the electrolytic solution, etc. Can be considered.

[0005] However, increasing the seal width wastefully increases the battery volume, and reducing the thickness of the resin layer in the seal portion is not suitable for use in a laminate sheet manufacturing process or when used as a battery outer case. There are also restrictions on strength. Also, there is a limit to reducing the permeation cross section of the electrolyte. Therefore, a method has been proposed in which the seal structure as shown in FIG. 5 is employed to substantially increase the seal width and limit the dissipation of the electrolyte.
There are problems such as not only increasing the amount of the laminated material used as the outer case, but also increasing the number of steps for processing the seal portion.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems. In a battery using a laminate sheet as an outer case, a laminate sheet, in which dissipation of an electrolytic solution is greatly suppressed by simple processing, is provided. It is an object to provide a battery as a case.

[0007]

According to the present invention, in order to achieve the above object, at least one layer has a metal foil, and another layer has a heat-fusible resin film layer, and has a center line interposed therebetween. A single laminated sheet with a symmetrical shape is folded in two on the center line so that the heat-fusible resin film layer is inside the metal foil layer, and the laminated sheets are laminated. Around P
By double sealing, that is, at the inner sealing portion, the heat-fusible resin film layers superimposed on each other are heat-welded to each other, and further, the heat-fusible resin film layer is removed on the outside thereof. To expose the surface of the metal foil, and provide a seal portion where the metal foils are overlapped and welded.

[0008] In this manner, a rectangular bag-shaped battery outer case is prepared from the laminated sheet, and a laminated electrode group in which a positive electrode and a negative electrode are laminated via a separator is housed therein. The sealing portion of the battery outer case, except for the lead wire lead-out portion, has a double structure to prevent the electrolyte solution from dissipating.

The inner seal portion mainly prevents the liquid electrolyte from directly contacting the outer metal seal portion to promote the corrosion of the metal seal portion, and has a mechanical strength. Accordingly, the main purpose is to reinforce the outer seal, and the outer seal portion is mainly intended to prevent the electrolyte from escaping out of the outer case.

The reason for selecting a laminate sheet having at least one heat-fusible film layer and at least one metal foil layer is that the periphery of the laminate sheet is heat-welded as an outer battery case using an ultrasonic welding machine or the like. In this case, a laminated sheet having a heat-sealing film layer has high efficiency and is capable of performing highly reliable heat welding, and is laminated using a PP film, a polyethylene film, a heat-fusible polyimide film, or the like. What you do is available. In addition, the seal portion where the metal foil layers are welded to each other is relatively easy to weld and has a function of completely preventing the dissipation of the electrolytic solution. As the metal foil, aluminum foil, stainless steel foil, nickel foil, etc. Can be used.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 1 is a view for explaining a manufacturing process for manufacturing a rectangular bag-shaped battery outer case 12 from a laminate sheet 15 based on the present invention and a sealing structure thereof in order of processes. FIG. 2 shows a plan view and a cross-sectional view of a battery manufactured using the battery outer case of the present invention.

The rectangular laminated sheet 1 of the present invention
5, when manufacturing an outer case of a bag-shaped battery, fold it into two on the center line 8 of the laminate sheet,
It is necessary to seal at least two surrounding sides of the four sides formed by overlapping. However, in FIG. 1, there is no difference in the structure and the processing method between the two sides to be sealed.
The case where only the side is sealed is illustrated.

It is not necessary to re-seal one side formed by folding the laminate sheet.
In addition, as shown in FIG. 2, on the side from which the lead wires connected to the electrode plate group are taken out, in order to insulate the lead wires 16 and 17 from the battery case 12, the surface of the lead wire passes through the battery outer case. Wire insulation member 1 which is a heat-fusible resin such as a modified polyolefin resin having good adhesion to metal
8 and heat-welding, it is necessary to use a sealing method and structure different from the present invention.

Hereinafter, a process of sealing a battery according to an embodiment of the present invention will be described with reference to FIG. FIG. 1A is a perspective view of a laminate sheet 15 cut into a rectangle in order to manufacture an outer case 12 of a battery, and includes a heat-fusible resin film layer 5, a metal foil layer 6, and a resin film layer 7.
And a laminate sheet 15 composed of an adhesive layer interposed very thinly between these three layers (not shown).

In the embodiment, both the heat-fusible resin film layer 5 and the resin film layer 7 are made of a polypropylene (hereinafter abbreviated as PP) film having a thickness of 20 μm, and the metal foil layer 6 is formed of a 40 μm-thick film. It is made of aluminum foil. As the adhesive, a laminated sheet adhered using an adhesive that does not deteriorate or dissolve or cause a chemical reaction due to an electrolytic solution or heat during welding processing is used.

FIG. 1B shows a portion of the heat-fusible resin film layer 5 laminated on the surface of the metal foil 6 to be welded in a later step as an outer seal portion 11 of the battery outer case 12 by excimer laser beam irradiation. FIG. 4 is a perspective view of the laminate sheet 15 removed in advance by irradiation or a mechanical method, and the width W of a portion 9 from which the heat-fusible resin film layer 5 is removed is set to 2 mm. Efficiently moving the film peeling part of the laminate sheet in the direction perpendicular to the amplitude direction of the laser beam while oscillating the irradiation part of the laser beam at a high speed with an amplitude of 1 mm,
In addition, the heat-fusible resin film layer 5 could be easily removed with a width of 2 mm.

FIG. 1C shows that, after a part of the heat-fusible resin film layer 5 of the laminate sheet 15 is removed as shown in FIG. A half section of a state in which the peripheral portions P of the laminated sheets are overlapped so that the misalignment does not occur, with the conductive resin film layer 5 inside, is shown. The laminate sheet is attached to a welding jig (not shown) in such a posture. Hold.

FIG. 1D shows the inner sealing portion 1 around the periphery P of the laminated sheet held by positioning on the welding jig.
0 is welded using an ultrasonic welding method or a thermal welding method. That is, the laminated sheet 1
By welding the heat-fusible film layer 5 to a width of 2 mm on all sides except for the side to be the lead wire lead-out portion of the battery outer case and the side formed by folding the laminate sheet. 5 shows a half section in a state where the processing of the inner seal portion 10 is completed.

FIG. 1E shows the processing of the outer seal portion 11 having a width of 1 mm by positioning the inner seal portion 10 at a distance of 0.5 mm and irradiating the outer portion with an ultrasonic welding machine or irradiating a carbon dioxide laser beam. 2 shows a half section in a state where the above has been completed. When a carbon dioxide laser beam is used for welding aluminum foil, a laminate jig (not shown) is used to weld the aluminum foil 6 so that the aluminum foils 6 are in close contact with each other at the welded portion and are integrated when heated and melted. It is necessary to hold down the periphery lightly, but it is easy to adjust the welding width, the carbon dioxide laser beam has a large energy capacity, and it is easily absorbed as heat energy on the aluminum foil surface, Since the welding speed can be set faster, it is highly effective in improving productivity.

The PP film 7 covering the surface of the welded portion
Can be efficiently welded without removing the PP film in advance because the film is thin and relatively transparent to the carbon dioxide laser beam.

The inner seal portion 10 and the outer seal portion 1
It is preferable that the seal width and the distance between the inner and outer seal portions be as small as possible in order to make the size of the battery as small as possible. The distance between the inner and outer seal portions can be reduced to 1 mm or less if laser welding is used for the outer seal. In addition, it is also possible to make them adjacent to each other without gaps by accurately positioning them.

By providing a double-layered sealing portion around the laminated sheets thus superposed, particularly by providing a sealing portion formed by welding metal foils as the outer seal 11, dissipation of the electrolyte can be reduced. Battery outer case 12 significantly reduced compared to the conventional sealing structure
Can be manufactured. The width of the seal portion is preferably as narrow as possible in order to reduce the size of the battery. However, it is also possible to make the dimension L including the width of the inner and outer seal portions and the gap between these seals about 4 mm. is there.

Further, FIG. 2 shows an example in which the sealing structure of the battery outer case of the present invention as described above is applied, and the battery is manufactured using a laminate sheet having a two-layer structure in which a heat-fusible film layer and a metal foil layer are laminated. A plan view and a cross-sectional view of an example of a battery having a battery outer case are shown.

In this battery, a positive electrode active material and a positive electrode collector are contained in a bag-shaped battery outer case 12 having a double-layered sealing portion of a heat-fusible resin film welding portion 10 and a metal foil welding portion 11. Lead 1 at a position deviated to one side
The positive electrode plate 1 was formed by welding two sets of positive electrode plates 1 and negative electrode active material layers on both surfaces of a negative electrode current collector, and the lead 17 was welded to a position deviated in the opposite direction to the positive electrode plate. A separator 3 made of a polymer electrolyte is arranged between the negative electrode plate 2 and the electrode group 4 integrated by a heat welding method or a casting method is inserted, an electrolytic solution is injected, and the electrode is not sealed at the lead wire lead-out part. In order to insulate the portion from the battery outer case 12, the portion is covered with a lead wire insulating member 18 which is a heat-fusible resin such as a modified polyolefin resin having good adhesion to a metal, and is heat-sealed and sealed.

[0026]

As described above, in the present invention,
The seal part provided in the peripheral part of the battery outer case made by using a laminated sheet cut into a rectangular shape has a double structure, the seal part by welding of the heat-fusible films to the inside, the outside, By providing a seal portion by welding metal foils at a slight interval, mainly in the inner seal portion, sealing of the liquid electrolyte and mechanical strength are provided to reinforce the outer seal. It is an object of the present invention to provide an outer seal that seals a liquid electrolyte or a gaseous electrolyte so that the electrolyte is not completely scattered from the battery outer case.

As described above, the complete sealing effect of the electrolytic solution and
The mechanical strength and the chemical strength of the seal portion are greatly increased, and the reliability of the battery can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a sealing structure of a battery outer case of the present invention and a process of processing a sealing portion.

2a is a plan view of the battery according to the present invention; b is a cross-sectional view of the battery according to the present invention (a diagram showing a cross section taken along the line AA in FIG.

FIG. 3 is a cross-sectional view of a conventional battery (a cross-sectional view taken along line AA in FIG. 4).

FIG. 4 is a plan view of a conventional battery outer case.

FIG. 5 is an enlarged sectional view showing a conventional battery sealing structure.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Positive electrode plate 2 Negative electrode plate 3 Separator 4 Electrode group 5 Heat-fusible resin film layer 6 Aluminum foil 7 Resin film layer 8 Center line of laminate sheet cut into rectangles 9 Heat-fusible resin film layer removal part 10 Heat melting Adhesive resin film welded part 11 Metal foil welded part 12 Battery exterior case 14 Laminate sheet 15 Laminate sheet 16 Lead wire 17 Lead wire 18 Lead wire insulating member W Width of heat-fusible resin film layer removed part P Surrounding laminate sheet S Connection between lead wire and electrode

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H011 AA17 CC02 CC06 CC10 DD06 DD07 DD13 5H029 AJ15 AL12 BJ04 CJ03 CJ05 DJ02 EJ01 EJ12

Claims (3)

[Claims] 1. A positive electrode plate and a negative electrode plate with a separator interposed therebetween.
As an outer case of a battery containing a laminated electrode and an electrolytic solution formed by lamination, a single laminated sheet obtained by laminating a metal foil on at least one layer and a heat-fusible resin film on another layer and integrating them is prescribed. In a battery configured by cutting the laminated sheet into two pieces on a straight line passing through the center line of the cut laminated sheet and completely overlapping them, and sealing the periphery thereof, the sealing portion has heat. A battery having a portion having a double seal structure, a seal portion formed by welding fusion resin film layers and a seal portion formed by welding metal foils. 2. An inner seal portion of the double seal structure comprises a welded portion of a heat-fusible resin film layer and a heat-fusible resin film layer, and an outer seal portion is formed by welding a metal foil to a metal foil. The battery according to claim 1, comprising a seal portion formed by: 3. The battery according to claim 1, wherein the inner and outer double seal portions are in contact with each other without a gap or are adjacent to each other at an interval of 1 mm or less.