JP3799959B2 - Film seal type battery and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a battery sealed with a film-shaped outer package, and more particularly, to a battery having a collar portion to which the film is fused and at least a part of the collar portion being bent.
[0002]
[Prior art]
As electronic devices have become thinner and smaller in recent years, there is a strong demand for further thinner and smaller batteries. A battery in which a power generation element is housed in a thin exterior material such as a laminate film is considered a battery having an advantageous configuration from such a viewpoint. The laminate film is a film in which a metal foil and a polymer resin layer as a sealing material are laminated, and has attracted attention as a new type of battery exterior material. In this type of battery, there is a need to reduce the volume of extra non-functional parts and increase the space efficiency to cope with the thinning and downsizing of the device, and the intrusion of outside air into the battery and the leakage of the electrolyte in the battery. There are both requirements to ensure the sealing reliability of the laminate film so that it does not occur.
[0003]
Sealing reliability is an important issue especially for batteries containing non-aqueous electrolytes. When there is a sealing failure, battery performance is significantly deteriorated due to moisture entering from the outside. Moreover, the electrolytic solution is a highly soluble organic electrolytic solution, and the range of resin materials that can withstand this is narrow. For these reasons, the sealing reliability of batteries containing non-aqueous electrolytes has long been a problem for developers.
[0004]
For this, for example, the following configuration is considered. Japanese Patent Laid-Open No. 2000-58013 has a structure in which an outer envelope material made of a resin film is sealed around a flat rectangular power generation element, and an extra outer envelope material sealed with two long sides is folded inward. A flat battery is disclosed. The purpose of this configuration is to increase the space efficiency while ensuring the reliability of the seal by widening the seal width by bending the extra sealed envelope material.
[0005]
Japanese Patent Application Laid-Open No. 11-86807 describes that a power generation element is enclosed in an encapsulating bag made of a plastic layer and heat-sealed to form a battery, followed by radiation treatment. The purpose of this method is to prevent electrolyte leakage.
[0006]
[Problems to be solved by the invention]
It can be easily conceived that by combining the above two methods, it is possible to expect a further improvement in seal reliability and a further improvement in space efficiency as compared with the case where each method is used alone. However, according to the study by the present inventors, it has been found that the problems described below occur when the above methods are simply combined.
[0007]
When the periphery of the flat power generation element is sealed with the laminate film, a “rib” -shaped seal portion thinner than the power generation element portion is formed. When the entire periphery of the power generation element is sealed and irradiated with an electron beam, the seal resin in the collar portion is cross-linked to improve the electrolyte resistance, and the seal reliability of the collar portion is improved.
[0008]
However, after that, as shown in Japanese Patent Application Laid-Open No. 2000-58013, it is difficult to bend because the sealing resin is cross-linked and hardened. If bent forcibly, cracks may occur. Since a non-crosslinked seal resin is generally flexible, there is no problem in bending. However, since a highly crosslinked seal resin is hardened by irradiating a large amount of electron beam or the like, cracking may occur when it is sharply bent. If the crack is formed so as to be connected from the inside of the battery to the outside, there is a risk that it may become an outside air intrusion or a leak path for liquid leakage.
[0009]
If the electron beam dose is moderately controlled and the cross-linking degree of the sealing resin is not so high, bending to some extent is possible, but for that purpose the electron beam dose (= cross-linking degree) must be limited. As a result, the resistance to the electrolyte solution is impaired, which is a trade-off relationship.
[0010]
It is also conceivable to irradiate the electron beam after bending the collar part in the reverse order. However, in that case, the bent surface of the collar portion is perpendicular to the electron beam irradiation direction, so that a sufficient electron beam irradiation effect cannot be obtained.
[0011]
The present invention is intended to solve the above problem, and in a film-sealed battery in which a power generation element is enclosed using a film having a polymer resin layer as a sealing material as an exterior material, sealing reliability is improved. In addition to ensuring, when the collar portion to which the film is fused is folded, the object is to facilitate folding and prevent cracking.
[0012]
[Means for Solving the Problems]
The present inventors have found that the above problem can be solved by using a specific configuration or using a specific method.
[0013]
That is, the present invention uses a film having a polymer resin layer as a sealing material as an exterior material, and in a film-sealed battery in which a power generation element is enclosed, has a flange portion to which the film is fused, At least a part of the collar part is bent, the polymer resin layer of the crease part of the collar part is not crosslinked, and at least a part of the polymer resin layer of the collar part excluding the crease part is crosslinked. The present invention relates to a film seal type battery.
[0014]
In addition, in a method for manufacturing a film-sealed battery in which a power generation element is enclosed by using a film having a polymer resin layer as an exterior material and enclosing the power generation element, the film is fused with the film to form a collar portion. And a method of manufacturing a film-sealed battery comprising: irradiating at least a part of the collar part with an electron beam in a state where at least the part to be folded of the collar part is shielded, and then bending the part to be folded About.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
FIG. 1 is a schematic view of a film seal type battery as an embodiment of the present invention when viewed from the front. FIG. 2 schematically shows a cross section taken along the line AA ′ of the battery of FIG. The periphery of the flat wound power generation element 4 is heat sealed with a laminate film exterior material made of 11 to 17, and the power generation element 4 is hermetically sealed. In this example, a concave portion for accommodating the power generation element is formed in a part of one laminated film by molding, and a material cut into an appropriate shape is used as an exterior material, and the power generation element is stored in the concave portion. After that, the film is folded and the surroundings are heat sealed. Reference numerals 12 and 13 denote brim-shaped seal portions of the laminate film. Reference numerals 2 and 3 are a positive electrode lead terminal and a negative electrode lead terminal, respectively, and are drawn out from the power generation element inside the battery in a state of being heat sealed and hermetically sealed so as to be sandwiched between laminate film exterior materials at the position 14. .
[0016]
The laminate film exterior material is obtained by laminating at least a metal foil and a polymer resin layer (hereinafter referred to as a seal resin layer) as a seal material. Examples of materials that can be used for the sealing resin layer include acid-modified polyethylene such as polyethylene, polypropylene, ionomer, maleic acid-modified polyethylene, and acid-modified polypropylene such as maleic acid-modified polypropylene. The thickness of the sealing resin layer is preferably about 1 to 200 μm. Examples of materials that can be used as the metal foil include aluminum, copper, stainless steel, nickel, gold, silver, and the like, and aluminum is particularly preferable. The film thickness of the metal foil is preferably about 1 to 200 μm. A heat resistant resin layer made of polyethylene terephthalate or nylon may be formed on the surface of the metal foil opposite to the seal resin layer.
[0017]
In the present invention, from the viewpoint of easy electron beam crosslinking, the material used for the sealing resin layer is preferably acid-modified polyethylene such as polyethylene, ionomer, maleic acid-modified polyethylene, and among others, ionomer is particularly preferable because it is easily electron beam crosslinked.
[0018]
In the example of FIGS. 1 and 2, the collar-shaped seal portion 12 of the laminate film exterior material is bent along 13 fold lines according to the present invention. Since the laminate film exterior material of the seal portion is heat-sealed, the seal resin layers 16 and 17 are integrated as shown in FIG. Here, according to the present invention, the seal resin layer 17 in the fold portion is not crosslinked, and the seal resin layer 16 in the collar portion that is not the fold portion is crosslinked. Here, the width of the uncrosslinked portion 13, that is, the width of the portion 17 is preferably about 0.5 mm to 2 mm.
[0019]
1 and 2 can be manufactured, for example, as follows. First, the periphery of the power generation element is heat-sealed with a laminate film exterior material, and the collar portion is stretched horizontally without being bent. Next, the electron beam is irradiated in a state where a mask for shielding the electron beam having the shape shown in FIG. 3 is placed on the battery. Then, the seal resin layer 17 of the belt-shaped portion (13 portion in FIG. 1) where the electron beam is shielded by the 51 portion (shaded portion) of the mask is uncrosslinked, and the seal resin layer of the other flange portion 16 is crosslinked by an electron beam. Next, the collar portion is bent along the line of the uncrosslinked portion 13 to obtain a form as shown in FIG.
[0020]
By doing so, the peripheral portion of the fold is hardened while maintaining the flexibility of the fold, so that it becomes easy to bend sharply. This effect is the same as the effect of facilitating bending along the line when one or more marking lines are attached to the part to be bent with a needle on the cardboard, and the part to be bent is soft in a linear or belt shape. This effect is obtained because the surrounding area is harder than that.
[0021]
In the conventionally known configuration, the sealing resin layer of the collar part has a single hardness in both the bent part and the other part, so it is difficult to obtain a sharp crease, it becomes a rounded way of bending, and space efficiency Led to loss. In particular, it is difficult to bend after irradiating with an electron beam to crosslink and harden the seal resin, and there is a risk that the seal resin will break if it is forced to bend sharply. In the present invention, such inconveniences can be prevented.
[0022]
Further, in this embodiment, since the seal resin of the brim portion is cross-linked by the electron beam, the seal resin does not dissolve or swell in the electrolyte even when the electrolyte is an organic electrolyte, and at a high temperature. However, the seal resin is difficult to melt, and the seal reliability and heat resistance are high.
[0023]
In the above embodiment, since it is assumed that the power generation element includes an electrolyte solution in which a fluoride electrolyte salt such as LiPF6 is dissolved, the electrolyte solution is prevented from being irradiated with an electron beam to generate hydrofluoric acid. Therefore, a mask (FIG. 3) having a part that shields the power generation element part (11 in FIG. 1) and a linear protrusion part to shield the planned bending part (13 in FIG. 1) was used. However, in the present invention, it is also possible to use a mask that does not have a portion that shields the power generation element portion. In that case, the shape of the mask is, for example, a linear shape indicated by 51 in FIG.
[0024]
In the above embodiment, the collar portion is bent once, but may be bent one more time. That is, in FIG. 2, it is bent once upward at the base of the collar (in the valley folding direction when viewed from above), but downward once again near the center of the collar (when viewed from above, the mountain It may be folded (in the folding direction). In this case, since the second fold is 180 °, the effect of the present invention that it is easy to bend sharply works more effectively. Further, it may be folded 180 ° on the back side of the battery at the base of the collar portion on the opposite side to the configuration of FIG. In this case, the battery thickness increases, but the battery width can be reduced.
[0025]
In the present invention, heat may be applied when the collar portion is bent. By heating, the difference in deformability between the crosslinked part and the uncrosslinked part is further increased, so that it becomes easier to bend sharply.
[0026]
The present invention can be used in film seal type devices other than batteries and other various articles, and the same effect can be obtained in film seal type devices such as electric double layer capacitors, electrolytic capacitors, and various sensors. be able to.
[0027]
【Example】
Hereinafter, although the detail of this invention is concretely demonstrated using an Example, this invention is not limited to these Examples.
[0028]
<Example 1>
A lithium manganate powder having a spinel structure, a carbonaceous conductivity imparting material, and polyvinylidene fluoride were mixed and dispersed in NMP at a weight ratio of 90: 5: 5 and stirred to form a slurry. The amount of NMP was adjusted so that the slurry had an appropriate viscosity. This slurry was uniformly applied to one side of a 20 μm thick aluminum foil serving as a positive electrode current collector using a doctor blade, and vacuum dried at 100 ° C. for 2 hours. Similarly, the slurry was applied to the other surface and vacuum-dried. This sheet was roll-pressed to form a positive electrode active material layer. The theoretical capacity was set to 600 mAh.
[0029]
Next, amorphous carbon powder and polyvinylidene fluoride were mixed in NMP at a weight ratio of 91: 9, dispersed and stirred to obtain a slurry. The amount of NMP was adjusted so that the slurry had an appropriate viscosity. This slurry was uniformly applied to one side of a 10 μm thick copper foil serving as a negative electrode current collector using a doctor blade, and dried in a vacuum at 100 ° C. for 2 hours. At this time, the theoretical capacity per unit area of the negative electrode layer and the theoretical capacity per unit area of the positive electrode layer were adjusted to be 1: 1. Similarly, the slurry was applied to the other surface and dried in vacuum. This sheet was roll-pressed to form a negative electrode active material layer adhered to both surfaces of the negative electrode current collector.
[0030]
Winding up using an elliptical core through a microporous separator (Hoechst Celanese Co., Cellguard 2300) having a three-layer structure of polypropylene / polyethylene / polypropylene between the positive electrode and the negative electrode, followed by hot pressing A thin elliptical electrode winding was obtained.
[0031]
On the other hand, a laminate film having a structure in which an ionomer resin layer (a polymer resin layer as a sealing material, thickness of 100 μm), aluminum (50 μm), and polyethylene terephthalate (20 μm, not shown in FIG. 2) are laminated in order. It cut out to the magnitude | size and the recessed part suitable for the magnitude | size of said electrode winding body was formed in the part. This was folded to wrap the above-mentioned electrode winding body, and the periphery was heat-sealed (heat sealed) to produce a film-covered battery having a shape as schematically shown in FIGS. Unlike FIG. 1 and FIG. 2, the collar portion is in a state of extending horizontally). A positive electrode lead 2 and a negative electrode lead 3 (collectively referred to as electrode leads) are connected to the electrode winding body in advance, and the electrode lead is drawn out when the periphery of the electrode winding body is heat sealed with a laminate film. This part was heat-sealed so as to be sandwiched between shapes. The lead lead-out part was the side facing the laminated film folded part. As can be seen from FIG. 1, the collar portion of the battery includes one side that is an electrode lead extraction side and two sides that are not. An aluminum flat conductor having a thickness of 0.1 mm and a width of 4 mm was used as the positive electrode lead, and a nickel flat conductor having a thickness of 0.1 mm and a width of 4 mm was used as the negative electrode lead. The electrode winding body was impregnated with the electrolyte before heat sealing the last one side. The last one side is other than the electrode lead heat fusion part. The electrode winding body impregnated with the electrolytic solution corresponds to the power generation element 4 in FIG. The electrolyte was 1M LiPF6 as a supporting salt and a mixed solvent of propylene carbonate and ethylene carbonate (weight ratio 50:50) as a solvent.
[0032]
The width of the collar portion (seal width) was 4.5 mm for the side of the lead extraction portion, and 4 mm for the other side (long side in FIG. 1). The thickness of the battery was 3.6 mm.
[0033]
Next, a stainless steel electron beam shielding mask having both a portion that shields the power generation element storage portion and a portion that shields the planned bending portion of the collar portion was prepared. This mask has the shape shown in FIG. 3, and a linear protrusion for shielding a linearly-folded portion formed on the flange portion when the flange portion of the two sides that are not the electrode lead extraction portion is bent. Is provided. In FIG. 3, the portion that shields the power generation element storage portion is a portion without hatching, and the portion that shields the portion to be bent of the collar portion is the hatched portion. The thickness of the mask was 5 mm, and the width of the protrusion (the width of the hatched portion indicated by 51) was 1 mm. An electron beam was irradiated with this mask placed on the battery. The irradiation amount was 40 Mrad. In this way, all the collar parts other than the part to be bent are irradiated with the electron beam, the sealing resin layers 12 and 14 in FIG. 1 are cross-linked, and the band-like 13 part seal having a width of 1 mm is sealed. A battery was obtained in which the resin was uncrosslinked. Next, the brim portion was bent with the portion 13 as a crease, and the film seal type battery of the present invention was completed as shown in FIG.
[0034]
<Comparative Example 1>
A battery was fabricated in the same manner as in Example 1 except that the electron beam was not irradiated. The fold of the collar part of the manufactured battery was rounder than that of Example 1, and the width of the battery including the folded collar part was slightly larger than that of Example 1.
[0035]
<Comparative example 2>
A battery was fabricated in the same manner as in Example 1 except that a mask in which the portion 51 in FIG. 3 was omitted was used. Compared to the case of Example 1, it was difficult to bend. When it was folded with the same sharpness as in Example 1 with a stronger force than in Example 1, it was able to be folded, but when the crease seal resin was observed with a microscope, fine cracks were generated. Observed.
[0036]
<Comparative Example 3>
A battery was produced in the same manner as in Comparative Example 2 except that the electron beam irradiation dose was 5 Mrad. It was easier to bend than in the case of Comparative Example 2. When the crease seal resin was observed with a microscope, no cracks were observed.
[0037]
<Heat resistance test>
The batteries of Example 1, Comparative Example 1, and Comparative Example 3 were charged into an oven in a charged state, and the oven resistance was gradually increased to comparatively evaluate the leakage resistance at high temperatures. As a result, leakage was observed in the order of Comparative Example 1 and Comparative Example 3. In Example 1, even when both of the Comparative Examples leaked, the liquid was not leaked and the sealing property was maintained.
[0038]
【The invention's effect】
As described above, according to the present invention, in a film seal type battery in which a film having a sealing resin layer is used as an exterior material and a power generation element is enclosed, sealing reliability is ensured and the film is fused. It is easy to bend when the collar portion is bent, and it can be bent sharper than before, so that space efficiency can be increased and cracking of the sealing resin due to the bending can be prevented.
[Brief description of the drawings]
FIG. 1 is a schematic view of a film seal type battery as an embodiment of the present invention when viewed from the front.
FIG. 2 schematically shows a cross section taken along the line AA ′ of the battery of FIG. 1;
FIG. 3 shows an electron beam shielding mask used in manufacturing a film seal type battery as one embodiment of the present invention.
[Explanation of symbols]
2 Positive Electrode Lead 3 Negative Electrode Lead 4 Power Generation Element 5 Electron Beam Shielding Mask 11 Laminate Film Exterior Material Power Generation Element Storage 12 Laminate Film Exterior Material Collar Seal Portion Laminate Film Exterior Material Laminate Film Exterior Material Collar Seal Sealing resin uncrosslinked portion 14 Electrode lead sealing portion 15 of laminated film exterior material 15 Metal foil 16 Crosslinked sealing resin 17 Uncrosslinked sealing resin 18 Sealing resin 51 of power generation element housing portion Exterior material collar portion sealing resin uncrosslinked Part for part formation

Claims (12)

A film seal type battery in which a film having a polymer resin layer having electron beam crosslinkability as a sealing material is used as an exterior material and encapsulating a power generation element, and has a flange portion to which the film is fused. And at least a part of the collar part is bent, the polymer resin layer of the crease part of the collar part is not crosslinked, and at least a part of the polymer resin layer of the collar part excluding the crease part is crosslinked. A film seal type battery characterized by comprising: A collar portion in which a polymer resin layer made of polyethylene, polypropylene, ionomer, acid-modified polyethylene, or acid-modified polypropylene is used as a sealing material , a power generation element is enclosed , and the film is fused. And at least a part of the collar part is bent, the polymer resin layer of the crease part of the collar part is not crosslinked, and at least a part of the polymer resin of the collar part excluding the crease part A film-seal type battery characterized in that the layers are cross-linked. The film seal according to claim 1 or 2 , wherein an uncrosslinked portion is linearly provided in the polymer resin layer along the fold of the collar portion, and the polymer resin layer of the surrounding collar portion is crosslinked. Type battery. The film seal type battery according to claim 3, wherein the polymer resin layers of all the brim portions other than the linear uncrosslinked portion are crosslinked. The collar portion comprises at least two sides of a first side fused with an electrode lead sandwiched therebetween and a second side without the electrode lead sandwiched, and the second side is bent. The film seal type battery according to any one of 1 to 4 . The film-sealed battery according to any one of claims 1 to 5 , wherein the exterior material is a laminated film in which a metal foil and a polymer resin layer are laminated. The film seal type battery according to any one of claims 1 to 6 , wherein the film seal type battery includes a non-aqueous electrolyte.   In a method for manufacturing a film-sealed battery in which a film having a polymer resin layer is used as an exterior material and a power generation element is enclosed, the step of fusing the film with the film to enclose the power generation element to form a brim And a method of manufacturing a film-sealed battery, comprising: irradiating at least a part of the collar part with an electron beam in a state where at least the part to be folded of the collar part is shielded, and then bending the part to be folded. The method for producing a film-seal type battery according to claim 8 , wherein the portion to be bent is shielded by a linear shield. The method for producing a film-sealed battery according to claim 9 , wherein an electron beam is irradiated to all the brim parts other than the part to be bent. The method for manufacturing a film-seal type battery according to any one of claims 8 to 10 , wherein the electron beam is irradiated in a state where the power generation element portion is shielded together with the bent portion of the collar portion. The method for producing a film-seal type battery according to claim 11 , wherein a shielding object having a portion that shields the power generation element portion and a portion that shields the planned bending portion is installed and irradiated with an electron beam.

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