JP4341098B2 - battery - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a battery having a laminate sheet as an outer case used for a lithium polymer secondary battery or the like.
[0002]
[Prior art]
A battery using a laminate sheet obtained by laminating and integrating an insulating resin film and a metal foil as an exterior case has been conventionally known, for example, as disclosed in JP-A-10-214606.
[0003]
FIG. 3 is a cross-sectional view showing a configuration of a battery using laminate sheets 14 and 15 as an exterior case 12 that is generally known in the past, and FIG. 4 is a plan view thereof. In these figures, an electrode group 4 is formed by laminating a positive electrode plate 1 and a negative electrode plate 2 with a separator 3 interposed therebetween, and the upper and lower sides thereof are covered with laminate sheets 14 and 15, respectively. The battery structure is shown as an outer case 12 that accommodates the laminated electrode group 4 by sealing P by a method such as heat fusion. However, the electrode group is impregnated with an electrolytic solution, and the main purpose of the seal portion is to prevent the electrolytic solution from escaping out of the battery case and to prevent foreign matter from entering the battery case.
[0004]
The laminated electrode 4 sealed in the battery outer case 12 is sealed in a state in which an electrolytic solution is injected into the outer case 12. In such a battery having the laminate sheets 14 and 15 as the outer case, the dissipation of the electrolyte enclosed 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 dissipates out of the outer case 12 from the cross section of the seal portion as time elapses. Since the dissipation of the electrolyte is closely related to the deterioration of the battery performance, it is necessary to prevent the dissipation as much as possible. As a means to prevent the electrolyte from escaping, a method such as providing a wide seal part or reducing the thickness of the resin layer constituting the seal part as much as possible to reduce the electrolyte cross section. Can be considered.
[0005]
However, increasing the seal width unnecessarily increases the battery volume, and reducing the resin layer of the seal portion is also necessary for the laminate sheet manufacturing process and the strength when used as a battery outer case. There are also restrictions. There is also a limit to reducing the permeation cross-sectional area of the electrolytic solution. Therefore, by adopting a seal structure as shown in FIG. 5, a method of substantially expanding the seal width and limiting the dissipation of the electrolyte has been proposed, but the use of a laminate material used as an outer case is also proposed. In addition to increasing the amount, there are problems such as increasing the number of steps for processing the seal portion.
[0006]
[Problems to be solved by the invention]
The present invention solves the above-described problems, and provides a battery using an outer case as a laminate sheet in which the dissipation of the electrolyte is greatly suppressed by simple processing in a battery using the laminate sheet as an outer case. Objective.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, at least one layer has a metal foil, and another layer has a heat-fusible resin film layer, and has a symmetrical shape across the center line. The laminate sheet is folded in two on the center line so that the heat-fusible resin film layer is on the inner side of the metal foil layer, and the periphery P of the laminated sheet is double sealed. In other words, in the inner seal portion, the heat-sealable resin film layers that are overlaid are heat-welded to each other, and the heat-sealable resin film layer is removed on the outer side to expose the surface of the metal foil. And providing a seal portion in which the metal foils are overlapped and welded.
[0008]
In this way, a rectangular bag-shaped battery outer case is manufactured from a laminate sheet, and a battery having a stacked electrode group in which a positive electrode and a negative electrode are stacked with a separator interposed therebetween is contained in a lead wire. The sealing part of the battery outer case excluding the drawer part has a double structure to prevent the electrolyte from escaping.
[0009]
The inner seal part mainly prevents the liquid electrolyte from coming into direct contact with the outer metal seal part to cause the corrosion of the metal seal part to progress, and by providing mechanical strength. The main purpose is to reinforce the outer seal, and the outer seal part is mainly intended to prevent the electrolyte from escaping outside the outer case.
[0010]
The reason for selecting a laminate sheet having at least one each of a heat-fusible film layer and a metal foil layer is that when the heat-sealing of the periphery of the laminate sheet as a battery outer case using an ultrasonic welding machine is performed. A laminate sheet having a heat-sealing film layer has good efficiency and is capable of highly reliable heat welding, and is laminated using a PP film, a polyethylene film, a heat-fusible polyimide film, or the like. Is available. In addition, the seal portion where the metal foil layers are welded together is relatively easy to weld and has a function of completely preventing the electrolyte from escaping. As the metal foil, aluminum foil, stainless steel foil, nickel foil, etc. Can be used.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be briefly described according to embodiments with reference to the drawings.
[0012]
FIG. 1 is a view for explaining a manufacturing process and a sealing structure for manufacturing a battery outer case 12 having a rectangular bag shape from a laminate sheet 15 according to the present invention 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.
[0013]
When manufacturing a bag-shaped battery outer case from the rectangular laminate sheet 15 of the present invention, it is folded in two on the center line 8 of the laminate sheet, and at least two sides around the four sides that can be overlapped. Need to be sealed. However, in FIG. 1, since there is no difference in structure and processing method between the two sides to be sealed, the case where only one side is sealed is illustrated.
[0014]
One side formed by folding the laminate sheet does not need to be sealed again, and as shown in FIG. 2, for the side where the lead wire connected to the electrode plate group is taken out, lead wires 16 and 17 and the battery In order to insulate from the case 12, the surface of the lead wire is covered with a lead wire insulating member 18 that is a heat-fusible resin such as a modified polyolefin resin having good adhesion to the metal in a portion that passes through the battery outer case, Some are thermally welded, and it is necessary to use a sealing method and structure different from the present invention.
[0015]
Hereinafter, a process of sealing a battery according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 a shows a perspective view of a laminate sheet 15 cut into a rectangle for producing a battery outer case 12, and shows a heat-fusible resin film layer 5, a metal foil layer 6, and a resin film layer 7. A laminate sheet 15 composed of three layers and an adhesive layer interposed between these layers (not shown) extremely thinly is used.
[0016]
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 microns, and the metal foil layer 6 is made of an aluminum foil having a thickness of 40 microns. Become. As the adhesive, a laminate sheet bonded using an adhesive that does not deteriorate or dissolve or cause a chemical reaction due to the electrolytic solution or heat during the welding process is used.
[0017]
FIG. 1 b shows the outer seal portion 11 of the battery outer case 12, a part of the heat-fusible resin film layer 5 laminated on the surface of the metal foil 6 to be welded in a later step, The perspective view of the laminate sheet 15 removed in advance by a mechanical method or the like is shown, and the width W of the portion 9 from which the heat-fusible resin film layer 5 is removed is 2 mm. By moving the laser beam irradiation part at a high speed with an amplitude of 1 mm and moving the film peel-off part of the laminate sheet in the direction perpendicular to the laser beam amplitude direction, it is efficient and easy to heat-seal. The resin film layer 5 could be removed with a width of 2 mm.
[0018]
As shown in FIG. 1 b, FIG. 1 c shows that after removing a part of the heat-fusible resin film layer 5 of the laminate sheet 15, the laminate sheet 15 is bent on the center line 8, Although the layer 5 is shown as an inner side and the peripheral portion P of the laminate sheet is overlapped so as not to be displaced, the laminate sheet is attached to a welding jig (not shown) and held in such a posture. .
[0019]
In FIG. 1d, welding is performed on the inner seal portion 10 around the periphery P of the laminate sheet positioned and held on the welding jig by using an ultrasonic welding method or a thermal welding method. That is, the heat-fusible film layer 5 is formed on all sides of the laminated sheet 15 except for the side to be a lead wire lead-out portion of the battery outer case and the side generated by folding the laminated sheet. The half cross section of the state which completed the process of the inner side seal part 10 by welding by 2 mm width is shown.
[0020]
In FIG. 1e, the inner seal portion 10 is positioned at a distance of 0.5 mm, and processing of the outer seal portion 11 having a width of 1 mm is completed by irradiating the outer seal portion with an ultrasonic welding machine or a carbon dioxide laser beam. The half section of a state is shown. When the carbon dioxide laser beam is used for welding aluminum foil, the aluminum foil 6 is in close contact with each other in the welded portion, and is integrated with the welding jig (not shown) so as to be integrated when heated and melted. Although it is necessary to lightly press the periphery, the adjustment of the welding width is easy, and the carbon dioxide laser beam has a large energy capacity, and moreover, it is easily absorbed as thermal energy on the aluminum foil surface. Since the welding speed can be set fast, it is very effective in improving productivity.
[0021]
Since the PP film 7 covering the surface of the welded portion is thin and relatively transparent with respect to the carbon dioxide laser beam, the PP film 7 can be efficiently welded without removing the PP film in advance. I can do it.
[0022]
In addition, the seal width between the inner seal portion 10 and the outer seal portion 11 and the distance between the inner and outer seal portions are preferably as small as possible in order to reduce the size of the battery as much 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. Moreover, it is also possible to adjoin without gap by positioning with sufficient precision.
[0023]
By providing a double-structured seal portion around the laminated sheets thus laminated, in particular, by providing a seal portion by welding metal foils as the outer seal 11, the dissipation of the electrolyte solution can be prevented by the conventional seal. The battery outer case 12 can be manufactured with much smaller number than the structure. The width of the seal portion is preferably as narrow as possible to reduce the size of the battery. However, the dimension L including the width of the seal portion inside and outside and the gap between these seals can be about 4 mm. is there.
[0024]
2 is applied to the battery outer case sealing structure of the present invention as described above, and the battery outer case 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. The top view and sectional drawing are shown about an example of the battery which has this.
[0025]
This battery includes a positive electrode active material, a positive electrode current collector, and a bag-shaped battery outer case 12 having a dual-structure seal portion of a heat-welding resin film welded portion 10 and a metal foil welded portion 11. Are stacked, and the negative electrode active material layer is laminated on both sides of the negative electrode current collector in a direction opposite to the positive electrode plate. A separator 3 made of a polymer electrolyte is disposed between the negative electrode plate 2 formed by welding leads 17 at the displaced positions, and an electrode group 4 integrated by a thermal welding method or a cast method is inserted, and an electrolyte solution The lead wire insulating member 18, which is a heat-fusible resin such as a modified polyolefin resin having good adhesiveness to the metal, is used to insulate the battery outer case 12 at a portion that is not sealed by the lead wire lead-out portion. Covered, heat welded and sealed.
[0026]
【The invention's effect】
As described above, in the present invention, the sealing portion provided in the peripheral portion of the battery outer case made using the laminate sheet cut into a rectangular shape has a double structure, and the inner side of the heat-fusible film is between The seal part by welding of the metal foil is provided on the outside of the seal part by welding metal foils at a slight interval, so that the liquid electrolyte is sealed and machined mainly in the inner seal part. The outer seal is intended to reinforce the outer seal with a certain level of strength, and the outer seal seals the electrolyte so that it does not dissipate completely from the battery outer case, whether it is liquid or gaseous. The purpose is that.
[0027]
As described above, a complete sealing effect of the electrolytic solution and a significant increase in strength both mechanically and chemically of the seal portion can be achieved, thereby improving the reliability of the battery.
[Brief description of the drawings]
FIG. 1 is a diagram showing a sealing structure of a battery outer case according to the present invention and a processing step of a sealing portion. FIG. 2a is a plan view of a battery according to the present invention. Figure showing
FIG. 3 is a cross-sectional view of a conventional battery (showing a cross section AA in FIG. 4).
FIG. 4 is a plan view of a conventional battery outer case. FIG. 5 is an enlarged cross-sectional view showing a conventional battery seal structure.
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 9 of laminated sheet cut into a rectangle 9 Heat-fusible resin film layer removal part 10 Adhesive resin film welded part 11 Metal foil welded part 12 Battery outer case 14 Laminate sheet 15 Laminate sheet 16 Lead wire 17 Lead wire 18 Lead wire insulation member W Width P of heat-sealable resin film layer removal part P Around laminate sheet S Connection between lead wire and electrode

Claims (3)

A laminated electrode formed by laminating a positive electrode plate and a negative electrode plate with a separator interposed therebetween, and a metal foil on at least one layer and a heat-sealable resin film on the other layer as a battery outer case containing an electrolytic solution It is configured by cutting a single laminated sheet into a predetermined shape, folding it into two on a straight line passing through the center line of the cut laminated sheet, and completely overlapping it, and sealing its periphery In the battery, the seal part has a part composed of a double seal structure , that is, a seal part by welding the heat-sealing resin film layers and a seal part by welding metal foils , and the double seal structure. The inner seal portion is composed of a welded portion of the heat-fusible resin film layer and the heat-fusible resin film layer, and the outer seal portion is not a seal portion formed by welding the metal foil to the metal foil. Battery, characterized in that. The battery according to claim 1 , wherein the inner and outer double seal portions are in contact with each other with no gap or are adjacent to each other with an interval of 1 mm or less. A laminated electrode made by laminating a positive electrode plate and a negative electrode plate with a separator interposed therebetween, and a metal foil on at least one layer and a heat-sealable resin film on the other layer as a battery outer case containing an electrolytic solution It is configured by cutting a single laminated sheet into a predetermined shape, folding it into two on a straight line passing through the center line of the cut laminated sheet, and completely overlapping it, and sealing its periphery In the battery, the seal portion has a portion having a double seal structure, that is, a seal portion by welding the heat-sealing resin film layers and a seal portion by welding metal foils, The seal portion by welding of the metal foils exposed by removing the fusible resin film layer is the seal portion by welding of the heat-fusible resin film layers. Battery, which is a neighboring position.

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