JP6003170B2 - Secondary battery - Google Patents

Description

  The present invention relates to a secondary battery.

  As secondary batteries, lithium-ion batteries that can be reduced in weight with high energy density are often used in connection with downsizing of portable devices such as mobile phones and notebook computers. As a secondary battery exterior material (hereinafter, sometimes simply referred to as “exterior material”), in particular, for secondary battery applications for large-sized devices, unlike cans conventionally used, A laminate-type packaging material that is superior in terms of thinning, lightening, and heat dissipation (for example, a packaging material having a laminated structure such as a base material layer / adhesive layer / metal foil layer / heat-bonding layer) is noted. Has been.

Examples of the secondary battery using a laminate type exterior material include the following.
One exterior material is folded in two so that the heat-sealing layer faces each other, two of the three edge parts other than the folded part are heat-sealed, and the battery contents (positive electrode, negative electrode, separator, electrolytic) inside A three-side seal type in which the edge portion remaining after containing the liquid etc. is heat-sealed and sealed,
A four-side seal type in which two exterior materials are stacked so that the heat-sealing layers face each other, three edge portions are heat-sealed, and the edge portions remaining after housing the battery contents are heat-sealed and sealed.
The side edges of the exterior material are combined to form a cylinder, the side edges are heat-sealed, the lower part of the cylindrical body is further heat-sealed, the battery contents are accommodated inside, and the upper part is heat-sealed and sealed. Stopped pillow pouch type,
A concave portion is formed by deep drawing by cold forming in one region when the outer packaging material is folded in two, and the battery contents are accommodated in the concave portion, and then the outer packaging material is folded and the edge portion is heat-sealed and sealed. Stopped emboss type, etc.

By the way, in lithium ion batteries, lithium salts such as LiPF ₆ and LiBF ₄ are used as electrolytes. However, when water enters the secondary battery, the lithium salts are hydrolyzed to generate hydrofluoric acid. Hydrofluoric acid causes corrosion of the metal surface of the battery member and a decrease in laminate strength between the layers of the exterior material.
A multi-layer film having a metal foil layer is used for the laminate type exterior material, and moisture entering the battery from the exterior material surface is blocked by the metal foil layer. However, in a secondary battery having an edge portion in which the heat-sealing layers of the exterior material are heat-sealed, moisture penetrates gradually from the side end surfaces of the edge portion through the heat-sealing layer. Also, the electrolyte inside the battery permeates through the thermal fusion layer at the edge and gradually evaporates from the side end face (dry up).

As an attempt to reduce the amount of moisture entering from the edge portion of the exterior material and the amount of dry-up, it has been proposed to reduce the thickness of the heat-sealing layer of the heat seal portion at the edge portion (for example, Patent Document 1, 2).
However, in a secondary battery using a laminate-type exterior material, a tab for taking out electricity from the inside of the battery is inserted into at least one edge portion. It is necessary to ensure a certain thickness of the thermal fusion layer at the edge where the tab is inserted in order to ensure the insulation between the metal foil layer of the exterior material and the tab. In addition, the edge portion to be heat-sealed last after injecting the electrolytic solution tends to have a weak heat-sealing strength because the heat-sealing layer is swollen with the electrolytic solution when heat-sealing. Therefore, it is necessary to ensure a certain thickness for the heat-sealing layer at the edge portion to be heat-sealed last. For these reasons, the method of reducing the thickness of the heat-sealing layer in the heat-sealed portion may be insufficient in the effect of suppressing moisture intrusion and dry-up.

In addition, by making the edge part to be heat-sealed as wide as possible and lengthening the permeation path of moisture and electrolyte, it is also possible to suppress the intrusion and dry-up of moisture from the side end face of the edge part. In this case, in order to make the accommodation space of the secondary battery as small as possible, the secondary battery is accommodated in a portable device or the like with the edge portion folded back.
However, especially when the storage space of the secondary battery is small, the width of the edge portion is often narrowed (about 3 mm), and in that case, moisture intrusion and dry-up at the edge portion may not be sufficiently suppressed. . In addition, since the edge portion where the tab is inserted cannot be folded back, in consideration of the reduction in the storage space of the secondary battery, the effect of suppressing moisture intrusion and dry-up by increasing the width of the edge portion is achieved. There are limits.

JP 2001-176466 A JP 2001-199413 A

  An object of this invention is to provide the secondary battery which can reduce the water | moisture content and dry-up amount which penetrate | invade from the side end surface of the edge part which heat-sealed the heat sealing layers of the exterior | packing material.

The secondary battery of the present invention has a container body formed of a secondary battery exterior material in which at least a metal foil layer and a heat-sealing layer are sequentially laminated on one surface side of a base material layer, and a part of a tab. A battery member accommodated in the container body so as to be exposed to the outside,
The container body is sealed by sealing the secondary battery exterior material into a container shape with the heat-sealing layer inside, and heat-sealing a belt-like edge portion where the heat-sealing layers are in contact with each other Has been
The ratio of the thickness of the heat-sealing layer of the heat seal portion of the edge portion without the tab to the thickness of the heat-sealing layer of the heat seal portion of the edge portion where the tab is sandwiched is 20 to 95%,
Among the strip-shaped edge portions, the length direction of the strip-shaped edge portion having the largest value P defined by the following formula (I) is parallel to the MD direction of the thermal fusion layer. To do.

(However, in the formula (I), Q is the thickness (mm) of the heat-sealing layer of the heat-sealed portion in the belt-shaped edge portion, and R is the length (mm) of the heat-sealed portion in the belt-shaped edge portion. ), And S is the width (mm) of the heat seal portion in the band-shaped edge portion.)
In the secondary battery of the present invention, it is preferable that the belt-like edge portion without the tab is folded.
Moreover, it is preferable that the said heat sealing | fusion layer is a layer by which the adhesive resin layer and the sealant layer are laminated | stacked from the said metal foil layer side.

  The secondary battery of the present invention can reduce the amount of moisture and the amount of dry-up entering from the side end surfaces of the edge portions where the heat-sealing layers of the exterior material are heat-sealed.

It is the perspective view which showed the secondary battery of this invention. It is the top view which showed the secondary battery of this invention. FIG. 2 is a cross-sectional view of a tip edge portion of the secondary battery of FIG. 1 cut along a straight line I-I ′. It is the perspective view which showed the secondary battery of this invention. It is sectional drawing of the exterior material in the secondary battery of this invention.

Hereinafter, an example of the secondary battery of the present invention will be described with reference to FIGS.
As shown in FIG. 1, the secondary battery 100 of this embodiment includes a container body 110 formed of a secondary battery exterior material 1 (hereinafter simply referred to as “exterior material 1”), and a container body 110. And a battery member 112 accommodated so that a part of the tab 114 is exposed to the outside.

[Exterior material 1]
As shown in FIG. 5, the exterior material 1 has an adhesive layer 12, a metal foil layer 13, a corrosion prevention treatment layer 14, and a heat sealing layer 15 sequentially laminated on one surface side of the base material layer 11. This is a laminate in which a base material protective layer 16 is laminated on the other surface side of the material layer 11. That is, the exterior material 1 is a laminate in which a base material protective layer 16, a base material layer 11, an adhesive layer 12, a metal foil layer 13, a corrosion prevention treatment layer 14, and a heat fusion layer 15 are sequentially laminated from the outside. is there.

The base material protective layer 16 is a layer that protects the base material layer 11. The base material protective layer 16 suppresses deterioration of the base material layer 11 due to adhesion of the electrolytic solution during production of the secondary battery, deterioration of cold formability due to moisture absorption of the base material layer 11 in a highly humid environment, and the like. Moreover, the base material protective layer 16 improves the pinhole resistance of the exterior material 1 during processing and distribution, the insulation between the metal foil layer 13 and other metal such as a tab, and the heat resistance during heat sealing.
Examples of the base material protective layer 16 include a layer formed of a polyester film, or a layer formed of an acrylic polyol and an aliphatic isocyanate curing agent (for example, methylene diisocyanate, isopropylene diisocyanate, lysine diisocyanate, etc.). Can be mentioned. Especially, the layer formed with the polyester film is preferable from the point which is excellent in pinhole resistance.
From the point which is excellent in workability, 1-30 micrometers is preferable and, as for the thickness of the base material protective layer 16, 1-12 micrometers is more preferable.

The base material layer 11 is a layer that suppresses pinholes that may occur during processing and distribution, and prevents breakage of the metal foil layer 13 during cold forming.
As a material which forms the base material layer 11, the extending | stretching of a polyamide film or an unstretched film is mentioned, for example. Especially, the stretched film of a polyamide film is preferable from the point which is excellent in a moldability.
The thickness of the base material layer 11 is preferably 6 to 40 μm and more preferably 10 to 25 μm from the viewpoint of excellent pinhole resistance and workability.

The adhesive layer 12 is a layer that bonds the base material layer 11 and the metal foil layer 13 together. In addition to excellent adhesiveness, the adhesive layer 12 is also required to have follow-up properties for suppressing breakage of the metal foil layer 13 during cold forming.
As an adhesive constituting the adhesive layer 12, a two-component curable polyurethane in which a bifunctional or higher functional aromatic or aliphatic isocyanate is allowed to act as a curing agent on a main component such as polyester polyol, polyether polyol, and acrylic polyol. System adhesives are preferred.
The thickness of the adhesive layer 12 is preferably 1 to 10 μm and more preferably 3 to 7 μm from the viewpoint of excellent adhesive strength, followability, workability, and the like.

As the metal foil layer 13, various metal foils such as aluminum and stainless steel can be used. Of these, aluminum foil is preferable from the viewpoints of workability such as moisture resistance and spreadability, and cost. As the aluminum foil, a general soft aluminum foil can be used, and a degreased aluminum foil is preferable. Moreover, the aluminum foil containing iron is more preferable from the point which is excellent in pinhole resistance and the extensibility at the time of shaping | molding.
The thickness of the metal foil layer 13 is preferably 9 to 200 μm and more preferably 15 to 100 μm from the viewpoint of excellent barrier properties, pinhole resistance, and workability.

The corrosion prevention treatment layer 14 functions as an anchor, improves the adhesion between the metal foil layer 13 and the heat-sealing layer 15, and the metal foil layer 13 made of electrolytic solution or hydrofluoric acid generated by the reaction between the electrolytic solution and moisture. Plays a role in inhibiting corrosion.
As the corrosion prevention treatment layer 14, a coating film formed by a coating type or immersion type acid-resistant corrosion prevention treatment agent is preferable from the viewpoint that the metal foil layer 13 has an excellent corrosion prevention effect against acid. As the coating film, for example, a coating film formed by ceriazol treatment with a corrosion prevention treatment agent comprising cerium oxide, phosphate and various thermosetting resins, chromate, phosphate, fluoride and various thermosetting Examples thereof include a coating film formed by chromate treatment with a corrosion-inhibiting treatment agent made of a functional resin. Moreover, the corrosion prevention process layer 14 will not be limited to the coating film formed by the said process, if the corrosion resistance of the metal foil layer 13 is fully obtained.
The thickness of the corrosion prevention treatment layer 14 is preferably 10 nm to 5 μm, more preferably 20 nm to 500 nm, from the viewpoint of excellent corrosion prevention function and anchor function.

The heat sealing layer 15 is a layer in which the adhesive resin layer 17 and the sealant layer 18 are laminated from the metal foil layer 13 side.
The adhesive resin layer 17 is a layer that bonds the sealant layer 18 and the metal foil layer 13 on which the corrosion prevention treatment layer 14 is formed.
The resin constituting the adhesive resin layer 17 is preferably an acid-modified thermoplastic resin. Examples thereof include resins obtained by graft-modifying acids such as maleic anhydride to polyolefin resins and elastomer resins.
Examples of the polyolefin resin include low density, medium density, and high density polyethylene, ethylene-α olefin copolymer, homo, block or random polypropylene, and propylene-α olefin copolymer. These polyolefin resin may be used individually by 1 type, and may use 2 or more types together.
Examples of the elastomer resin include styrene-based or olefin-based thermoplastic elastomers.

The resin constituting the adhesive resin layer 17 is preferably an acid-modified polyolefin-based resin because it is excellent in resistance to an electrolytic solution and hardly deteriorates in adhesion even when hydrofluoric acid is generated.
Moreover, it is also preferable to add an elastomer resin to at least one selected from the group consisting of acid-modified polyolefin resins. This improves stretch whitening resistance due to cracks during cold forming, improves adhesion by improving wettability, and improves properties such as film forming properties and heat seal strength by reducing anisotropy. .
1-50 micrometers is preferable and, as for the thickness of the adhesive resin layer 17, 5-40 micrometers is more preferable. If the thickness of the adhesive resin layer 17 is equal to or higher than the lower limit value, the adhesive strength is high, and if the thickness is equal to or lower than the upper limit value, the moisture amount and the dry-up amount that enter from the side end surface of the edge portion of the secondary battery can be further reduced.

The sealant layer 18 is the innermost layer of the exterior material 1 and is a layer that is heat-sealed during battery assembly.
As resin which comprises the sealant layer 18, a thermoplastic resin is preferable from the point which is excellent in impact resistance and heat-sealing property, and polyolefin-type resin, such as polyethylene and a polypropylene, is preferable.
The sealant layer 18 may be a single layer or a multilayer. For example, for the purpose of imparting moisture resistance, a multilayer film in which a layer formed of a resin such as an ethylene-cycloolefin copolymer or polymethylpentene is interposed may be used.
The thickness of the sealant layer 18 is preferably 20 to 100 μm. If the thickness of the sealant layer 18 is equal to or higher than the lower limit value, the heat sealability is excellent, and if the thickness is equal to or lower than the upper limit value, the moisture amount and the dry-up amount that enter from the side end face of the edge portion of the secondary battery can be further reduced.

  In the present invention, like the exterior material 1 of this example, the heat-sealing layer is preferably a layer in which an adhesive resin layer and a sealant layer are laminated from the metal foil layer side. Thereby, it is possible to reduce the amount of moisture and the amount of dry-up that enter from the side end face of the edge portion of the secondary battery while ensuring excellent adhesion between the heat-sealing layer and the metal foil layer.

As a manufacturing method of the exterior material 1, the method which has the following process (X1)-(X3) is mentioned, for example.
(X1) A step of forming the corrosion prevention treatment layer 14 on the metal foil layer 13.
(X2) The base material layer 11 is bonded to the side opposite to the side on which the corrosion prevention treatment layer 14 is formed in the metal foil layer 13 via the adhesive layer 12, and the base material protective layer 16 is further formed on the base material layer 11. Process.
(X3) A step of bonding the sealant layer 18 to the corrosion prevention treatment layer 14 side of the metal foil layer 13 through the adhesive resin layer 17 to form the heat fusion layer 15.

Step (X1):
For example, a corrosion prevention treatment agent is applied to one surface of the metal foil layer 13 and dried to form the corrosion prevention treatment layer 14. Examples of the anti-corrosion treatment agent include the above-described anti-corrosion treatment agent for ceriazole treatment, anti-corrosion treatment agent for chromate treatment, and the like. The coating method of the corrosion inhibitor is not particularly limited, and various methods such as gravure coating, reverse coating, roll coating, and bar coating can be employed.

Step (X2):
The base material layer 11 is bonded to the side of the metal foil layer 13 opposite to the side on which the corrosion prevention treatment layer 14 is formed using an adhesive that forms the adhesive layer 12 by a technique such as dry lamination. Then, the film which forms the base material protective layer 16 is bonded on the base material layer 11 by a technique such as dry lamination using the same adhesive as the adhesive that forms the adhesive layer 12. The base material protective layer 16 may be formed by applying a base material protective agent containing an acrylic polyol and an aliphatic isocyanate curing agent on the base material layer 11 and drying it.
Further, a resin for forming the base material layer 11 and the base material protective layer 16 is coextruded to produce a multilayer film, and the multilayer film is used for an adhesive such as dry lamination using an adhesive for forming the adhesive layer 12. You may affix with the metal foil layer 13 by the method.
In the step (X2), an aging treatment may be performed in the range of room temperature to 100 ° C. for the purpose of improving adhesion.

Step (X3):
An adhesive resin layer is formed on the side of the corrosion prevention treatment layer 14 of the laminate in which the substrate protection layer 16, the substrate layer 11, the adhesive layer 12, the metal foil layer 13, and the corrosion prevention treatment layer 14 are laminated in this order by an extrusion lamination method. 17 is formed, and the heat seal layer 15 is formed by bonding the sealant layer 18 through the adhesive resin layer 17. The adhesive resin layer 17 may be formed by dry lamination or the like. The lamination of the sealant layer 18 is preferably performed by sandwich lamination.
In addition, the heat fusion layer 15 is prepared by coextruding the resins forming the adhesive resin layer 17 and the sealant layer 18 to produce a multilayer film, and the multilayer film is heated on the corrosion prevention treatment layer 14 of the laminate. It may be formed by laminating.
In the step (X3), for the purpose of improving the adhesion, aging treatment or thermal lamination may be performed in the range of room temperature to 100 ° C.

The packaging material 1 is obtained by the steps (X1) to (X3) described above.
In addition, the manufacturing method of the exterior material 1 is not limited to the method of implementing the said process (X1)-(X3) sequentially. For example, the step (X1) may be performed after performing the step (X2).

[Container 110]
As shown in FIGS. 1 and 2, the container body 110 has a first container part 110a and a second container part 110b in which the rectangular outer packaging material 1 is folded in two with the heat sealing layer 15 as the inner side. In addition, the first container portion 110a has a container shape by being provided with a concave battery member housing portion 116 that protrudes from the heat fusion layer 15 side to the base material protective layer 16 side by deep drawing. .
The tip edge portion 118, which is a strip-shaped edge portion in contact with the heat sealing layers 15 located on the opposite sides of the folded portion 110c in the first container portion 110a and the second container portion 110b, is a part of the tab 114. It is heat-sealed with a pinch in between. Further, the first side edge portion 120 and the second side edge portion 122 which are band-like edge portions located on both sides of the battery member accommodating portion 116 are also heat-sealed.
As described above, the container body 110 has three strip-shaped edge portions of the tip edge portion 118, the first side edge portion 120, and the second side edge portion 122, and each of the three sides of the rectangular secondary battery 100. They are formed and sealed by heat sealing. In addition, the container body 110 is sealed in a state in which the electrolytic solution is accommodated together with the battery member 112 in the battery member accommodating portion 116.

  In the present invention, among the strip-shaped edge portions, the length direction of the strip-shaped edge portion having the largest value P defined by the following formula (I) is parallel to the MD direction of the heat-sealing layer of the exterior material. It is characterized by. That is, in the container body 110 of the secondary battery 100, the three belt-shaped edge portions of the tip edge portion 118, the first side edge portion 120, and the second side edge portion 122 are defined by the following formula (I). The length direction of the strip-shaped edge portion having the largest value P is parallel to the MD direction of the heat-sealing layer 15 of the exterior material 1. Thereby, the amount of moisture and the amount of dry-up entering from the side end face of the edge portion are reduced.

However, in formula (I), Q is the thickness (mm) of the heat-sealing layer of the heat-sealed portion at the belt-shaped edge portion, and R is the length (mm) of the heat-sealed portion at the belt-shaped edge portion, S is the width (mm) of the heat seal part in the belt-like edge part.
The length of the heat-sealed portion in the belt-shaped edge portion is the distance between the intersecting points when both end sides in the length direction of the heat-sealed portion of the edge portion intersect with the heat-sealed portion of the other edge portion. When one end side in the length direction of the heat seal portion of the edge portion intersects the heat seal portion of the other edge portion, the intersection point and the other end portion of the heat seal portion of the edge portion And the distance. Further, the width of the heat seal portion at the belt-shaped edge portion is an average value of distances between both ends in the direction perpendicular to the length direction of the heat seal portion of the belt-shaped edge portion. In addition, the thickness of the heat-sealing layer of the heat-sealed portion at the belt-shaped edge portion is an average value of the values obtained by summing the thicknesses of the heat-sealing layers of each other in the range of the length of the heat-sealed portion at the belt-shaped edge portion. is there. In addition, in the band-shaped edge part where the tab is sandwiched, the total thickness of the heat-sealing layers mutually welded on the upper and lower sides of the tab in the band-shaped edge part, and the length of the heat seal part in the band-shaped edge part The average value is calculated from the sum of the thicknesses of the heat-sealing layers in a portion where no tab exists in the range.

In this example, as shown in FIG. 2, the length _{R 1} of the heat-sealed portion 118a of the leading edge portion 118, the intersection 118c of the heat-sealed portion 120a of the first side edge portion 120 of the heat-sealed portions 118a , The distance of the intersection 118d of the second side edge portion 122 and the heat seal portion 122a. Length _{R 2} of the heat-sealed portion 120a of the first side edge portion 120, the intersection 120c of the heat-sealed portion 118a in the heat-sealed portion 120a, opposite end portion 120d and the point of intersection 120c of heat-sealed portions 120a And the distance. Length _{R 3} of the heat-sealed portion 122a of the second side edge portion 122, the intersection 122c of the heat-sealed portion 118a in the heat-sealed portion 122a, opposite end portion 122d and the point of intersection 122c of heat-sealed portions 122a And the distance.
The width _{S 1} of the heat sealed portion 118a of the leading edge portion 118, the tip edge portion 118 of the direction perpendicular direction along the side edge 118b ends 118e, an average value of the distance 118f. Width _{S 2} of the heat seal portion 120a of the first side edge portion 120, a first side edge portion 120 of the side end 120b perpendicular to the direction of the ends 120e along, the average value of the distance 120f. Width _{S 3} of heat-sealed portion 122a of the second side edge portion 122, a second side edge portion 122 of the side end 122b in along a direction perpendicular to the direction of the ends 122e, an average value of the distance 122f.
Further, as shown in FIG. 3, the thickness to _{Q 1} heat-sealed portion 118a of the leading edge portion 118 is the average of the values obtained by summing the thickness of each other heat sealable layer 15, 15 in the heat-sealed portion 118a. Similarly, the thickness _{Q 2} of heat-sealed portion 120a of the first side edge portion 120 is the average of the values obtained by summing the thickness of each other heat sealable layer 15, 15 in the heat-sealed portion 120a. Thickness _{Q 3} of heat-sealed portion 122a of the second side edge portion 122 is the average of the values obtained by summing the thickness of each other heat sealable layer 15, 15 in the heat-sealed portion 122a.

The value P ₁ (= Q ₁ × R ₁ / S ₁ ) in the heat seal portion 118a of the front end edge portion 118 and the value P in the heat seal portion 120a of the first side edge portion 120 calculated by the above formula (I), respectively. ₂ (= Q ₂ × R ₂ / S ₂ ), the value P ₃ (= Q ₃ × R ₃ / S ₃ ) in the heat seal portion 122a of the second side edge portion 122 is compared, and the largest belt-like edge portion And the MD direction of the heat-sealing layer 15 of the exterior material 1 are made parallel to each other.
Specifically, the value P ₁ of the heat seal portion 118a in the front end edge portion 118 is greater than the values P ₂ and P ₃ of the heat seal portions 120a and 122a in the first side edge portion 120 and the second side edge portion 122. Is increased, the MD direction of the heat-sealing layer 15 of the exterior material 1 and the length direction of the tip edge portion 118 (FIG. 2, x-axis direction) are made parallel. The value _{P 2} or a second 122a value _{P 3} of the side edge portion 122 of the heat-sealed portion 120a of the first side edge portion 120, when greater than the value _{P 1} of the heat-sealed portion 118a in the distal end portion 118 The MD direction of the heat sealing layer 15 of the exterior material 1 and the length direction of the first side edge portion 120 or the second side edge portion 122 (FIG. 2, y-axis direction) are made parallel.

The MD direction of the heat sealing layer 15 of the exterior material 1 is an extrusion direction in the melt extrusion method when forming the adhesive resin layer 17 and the sealant layer 18. In the present invention, the heat sealing layer is a layer formed by laminating an adhesive resin layer and a sealant layer. When the MD direction of the adhesive resin layer and the MD direction of the sealant layer are different, the MD direction of the adhesive resin layer is heated. The MD direction of the fusion layer is used.
When the heat-sealing layer is a layer in which an adhesive resin layer and a sealant layer are laminated, the production efficiency of the exterior material is high, and the effect of reducing the amount of moisture entering from the side end surface of the edge portion and the dry-up amount is excellent Therefore, the MD direction of the adhesive resin layer and the MD direction of the sealant layer are preferably the same direction.

Of the leading edge portion 118, the first side edge portion 120, and the second side edge portion 122, the length direction of the belt-like edge portion having the largest value P defined by the formula (I), and the exterior material 1 The following factors can be considered as the factors that reduce the amount of moisture and the amount of dry-up that penetrates from the side end face of the edge portion because the MD direction of the heat-sealing layer 15 is parallel.
When forming a heat-sealing layer (adhesive resin layer, sealant layer) by a melt extrusion method such as a T-die method or an inflation method, the heat-sealing layer is stretched not a little in the MD direction, which is the winding direction. Therefore, the heat-sealable layer is likely to be anisotropic due to the molecular orientation of the resin material forming the heat-sealable layer in the MD direction. This anisotropy can be alleviated to some extent if a heat laminating step is performed when forming the heat-fusible layer. However, at the time of heat sealing when assembling the battery, when the heat-fusible layer is gradually cooled and recrystallized, the molecules reorient in the MD direction and anisotropy occurs again. In the heat-fusible layer in which the crystal phase having such anisotropy is formed, it is difficult for moisture and electrolyte to permeate in the TD direction (direction perpendicular to the MD direction) as compared with the MD direction.
The value P increases as the thickness of the heat-sealing layer in the heat-sealed portion of the belt-shaped edge portion increases, the length of the heat-sealed portion increases, and the width decreases. On the other hand, the thicker the heat-sealing layer in the heat-sealed portion of the belt-like edge portion, the longer the heat-sealing portion, the larger the heat-sealing layer through which moisture and electrolyte solution permeate. The amount of transmission increases. In addition, the narrower the width of the heat seal portion, the shorter the path through which moisture and electrolyte solution permeate, so that the amount of moisture and electrolyte solution permeated increases. In other words, the strip-shaped edge portion having the largest value P is an edge portion that is in a condition where moisture and electrolyte are most easily transmitted among the strip-shaped edge portions to be heat-sealed. In the present invention, by making the length direction of the belt-like edge portion heat-sealed under such disadvantageous conditions that water and electrolyte are most easily transmitted in parallel with the MD direction of the heat-sealing layer of the exterior material, The permeation direction of moisture and electrolyte at the belt-like edge portion is the TD direction in which moisture and electrolyte are difficult to permeate. Therefore, the permeation of moisture and electrolyte in the strip-shaped edge portion is effectively suppressed, and as a result, the amount of moisture and the amount of dry-up entering from the side end surface of the edge portion are reduced as a whole secondary battery. It is done.

In addition, when the adhesive resin layer of the heat-sealing layer is a layer in which an elastomer resin is added to at least one selected from the group consisting of the acid-modified polyolefin resins, a non-crystalline island portion and a crystalline property are used. A sea-island structure consisting of the sea part of the sea may be formed. In general, a non-crystalline portion is more permeable to moisture and electrolyte than a crystalline portion. Therefore, in this case, the longer the length along the width direction of the band-like edge portion in the non-crystalline island portion in the band-like edge portion, the more moisture and electrolyte solution permeate the band-like edge portion. An easy path is formed long in the width direction.
On the other hand, the amorphous island portion is easily deformed into an elliptical shape that is long in the MD direction and short in the TD direction in the melt extrusion method. In the present invention, since the length direction of the strip-shaped edge portion having the largest value P and the MD direction of the heat-sealing layer of the exterior material are made parallel, even when the sea-island structure is formed, the strip-shaped edge In the portion, the non-crystalline island portion is longer in the length direction of the strip-shaped edge portion and shorter in the width direction. In this way, in the band-shaped edge portion, the transmission path formed by the non-crystalline island portion is short in the width direction, so that moisture and electrolyte are difficult to permeate. It is considered that the amount of moisture and the amount of dry-up entering from the side end surface of the portion are reduced.

In the secondary battery 100, it is preferable that the band-shaped edge portion having the largest value P is the leading edge portion 118 that is heat-sealed in a state where the tab 114 is sandwiched.
The portion of the front edge portion 118 where the tab 114 is sandwiched needs to have a certain thickness in order to ensure insulation between the tab lead and the metal foil layer of the exterior material. In addition, there is a limit to the thinning of the heat-fusible layer 15 compared to the portion where the tab 114 is not sandwiched.
Therefore, the thicknesses Q ₂ and Q ₃ in the first side edge portion 120 and the second side edge portion 122 where the tab 114 is not sandwiched are more than the thickness Q ₁ in the tip end edge portion 118 where the tab 114 is sandwiched. Is easy to thin. From this, the first side edge portion 120 and the second side edge portion 122 where the tab 114 is not sandwiched particularly have the thicknesses Q ₂ and Q ₃ of the heat-sealing layers 15 and 15 of the heat seal portions 120a and 122a. By reducing the thickness, the penetration of moisture and electrolyte is suppressed, and the tip edge portion 118 between which the tab 114 is sandwiched has the MD direction of the thermal fusion layer 15 parallel to the length direction of the tip edge portion 118 and the moisture and electrolyte solution. By suppressing the permeation of water, it is possible to efficiently reduce the amount of moisture and the amount of dry-up that penetrates as a whole.

In the present invention, the ratio of the thickness of the heat-sealing layer of the heat seal portion of the edge portion without the tab to the thickness of the heat-sealing layer of the heat seal portion of the edge portion where the tab is sandwiched is 20 to 95%. It is preferably 40 to 90%. If the said ratio is more than a lower limit, the heat seal intensity | strength in the heat seal part of the edge part which does not have a tab will be excellent. If the said ratio is below an upper limit, the reduction effect of the moisture content which permeates from the side end surface of the edge part which does not have a tab and the dry-up amount is high.
The thickness of the heat-sealed layer of the heat-sealed portion of the edge portion between which the tab is sandwiched is the total thickness of the heat-sealed layers welded to the top and bottom of the tab in the heat-sealed portion of the belt-like edge portion. It is. In addition, the thickness of the heat-sealing layer of the heat-sealed portion of the edge portion without the tab is the total thickness of the heat-sealing layers of the heat-shielding portion of the belt-like edge portion where the tab does not exist. It is.

In this embodiment, the portion of the heat-seal portion 118a of the tip edge portion 118 where the tab 114 is not provided with respect to the thickness of the heat-sealing layers 15 and 15 of the portion where the tab 114 of the heat-seal portion 118a of the tip edge portion 118 is sandwiched. It is preferable that the ratio of the thickness of the heat sealing layers 15 and 15 is in the above range.
Further, to the thickness of the heat sealable layer 15, 15 of the portion tab 114 in heat-sealed portion 118a of the leading edge portion 118 is sandwiched, the tab 114 is not sandwiched in the thickness _{Q 2} in the first side edge portion 120 The ratio is preferably in the above range.
Further, to the thickness of the heat sealable layer 15, 15 of the portion tab 114 in heat-sealed portion 118a of the leading edge portion 118 is sandwiched, the tab 114 is not sandwiched in the thickness _{Q 3} of the second side edge portion 122 The ratio is preferably in the above range.

Further, for the same reason as above, with respect to the thickness _{Q 1} in the tip edge portion 118, the ratio of the thickness _{Q 2} in the first side edge portion 120, preferably 20 to 95%, more preferably from 40% to 90% . Further, with respect to the thickness _{Q 1} in the tip edge portion 118, the ratio of the thickness _{Q 3} of the second side edge portion 122 is preferably 20 to 95%, more preferably 40 to 90%.

Moreover, it is preferable that the 1st side edge part 120 and the 2nd side edge part 122 which are strip | belt-shaped edge parts which do not have the tab 114 are return | folded as shown in FIG. The widths S ₂ and S ₃ of the heat seal portions 120a and 122a of the first side edge portion 120 and the second side edge portion 122 are obtained by folding back the first side edge portion 120 and the second side edge portion 122. Thus, the occupied volume of the secondary battery 100 can be reduced while suppressing the permeation of moisture and electrolyte.
The first side edge portion 120 and the second side edge portion 122 without the tab 114 may be folded back two or more times.

[Battery member 112]
As shown in FIG. 1, the battery member 112 includes a battery member main body 124 having a positive electrode, a separator, and a negative electrode, and tabs 114, 114 connected to the positive electrode and the negative electrode of the battery member main body 124, respectively.
The battery member main body 124 is not particularly limited as long as it is normally used for a secondary battery, and examples thereof include a laminate in which a positive electrode, a separator, a negative electrode, and a separator are laminated in this order. As the positive electrode, the negative electrode, and the separator, those usually used for secondary batteries can be used without particular limitation.

As shown in FIGS. 1 and 3, the tabs 114 and 114 are wound around the leads 126 and 126 joined to the positive electrode and the negative electrode, and the leads 126 and 126, respectively. Tab sealant 128, 128. The tabs 114 and 114 are installed such that the base end side of the lead 126 is joined to the positive electrode and the negative electrode, respectively, and the tip end side is exposed to the outside of the container body 110.
Examples of the material of the lead 126 include aluminum, nickel, nickel-plated copper, and the like.
The material of the tab sealant 128 may be any material that can be welded to the heat-sealing layer 15 of the exterior material 1, and examples thereof include the same material as the material of the sealant layer 18 of the exterior material 1.

The tab sealant 128 is preferably wound around the lead 126 so that its MD direction is parallel to the width direction of the lead 126, that is, its MD direction is parallel to the length direction of the tip edge portion 118.
Since the tab sealant 128 plays a role of preventing a short circuit between the lead 126 of the tab 114 and the metal foil layer 13 constituting the exterior material 1, it is necessary to ensure a certain film thickness. However, by making the MD direction of the tab sealant 128 parallel to the length direction of the tip edge portion 118, the permeation of moisture and electrolyte is also suppressed in the tab sealant 128.

  The secondary battery 100 can be used for, for example, a portable terminal device such as a personal computer or a mobile phone, a video camera, a satellite, an electric vehicle, an electric motorcycle, an electric bicycle, or the like. The secondary battery 100 is particularly preferably a lithium ion battery used for these applications.

[Method for producing secondary battery]
Hereinafter, a method for manufacturing the secondary battery 100 will be described. In addition, the manufacturing method of the secondary battery 100 is not limited to the following method. Examples of the method for manufacturing the secondary battery 100 include a method having the following steps (Y1) to (Y4).
(Y1) The process of forming the battery member accommodating part 116 in the part used as the 1st container part 110a in the rectangular-shaped exterior material 1. FIG.
(Y2) The battery member 112 is disposed in the battery member housing portion 116 of the first container portion 110a, the portion that becomes the second container portion 110b of the exterior material 1 is folded back, and the tip edge portion 118 on the opposite side to the folded portion 110c is formed. Heat sealing so that a part of the tab 114 is exposed to the outside.
(Y3) A step of heat-sealing the first side edge portion 120.
(Y4) A step of heat-sealing and sealing the second side edge portion 122 after injecting the electrolyte into the battery member accommodating portion 116 from the opening on the second side edge portion 122 side.

Step (Y1):
From the heat sealing layer 15 side of the rectangular exterior material 1 toward the base material layer 11 side, deep drawing is performed with a mold so as to obtain a desired molding depth in consideration of the rebound amount, and the first container part A battery member accommodating portion 116 is formed in a portion to become 110a.
As the mold, those usually used for deep drawing can be used. At the time of deep drawing, for example, by using a lubricant or the like to reduce the friction coefficient of the surface of the exterior material 1, the friction between the mold and the exterior material 1 is reduced, and the mold is pressed from the film presser to the molded part. The exterior material 1 becomes easy to flow. Thereby, the deeper battery member accommodating part 116 can be formed, without producing a crack and a pinhole.

Step (Y2):
The battery member 112 is housed in the battery member housing portion 116 formed in the step (Y1), the portion that becomes the second container portion 110b of the exterior material 1 is folded back, and the tab 114 is formed on the tip edge portion 118 on the opposite side of the folded portion 110c. The tip edge portion 118 is heat-sealed so that a part thereof is exposed to the outside. At this time, the tab sealant 128 of the tab 114 is welded to both the heat fusion layer 15 on the first container portion 110a side and the heat fusion layer 15 on the second container portion 110b side in the exterior material 1.
The heat seal can be controlled by adjusting three conditions of the temperature of the heat seal bar, the surface pressure at the time of sealing, and the sealing time. These conditions are expressed by the above formula (I) in the heat seal portion 118a of the tip edge portion 118. the value P ₁ defined may be appropriately set to a predetermined value.

Step (Y3):
The first side edge portion 120, heat sealed so that the value P ₂ defined by the formula in heat-sealed portion 120a of the first side edge portion 120 (I) has a predetermined value.

Step (Y4):
For example, after injecting the electrolyte into the battery member housing portion 116 from the opening on the second side edge portion 122 side, the gas in the battery member housing portion 116 is extracted in a vacuum state. Then, the second side edge portion 122 to remain under vacuum, heat to the formula a value P ₃ defined by (I) in heat-sealed portion 122a of the second side edge portion 122 becomes a predetermined value the seal Then, the secondary battery 100 is obtained by sealing.

The secondary battery 100 is obtained by the steps (Y1) to (Y4) described above.
In addition, the manufacturing method of the secondary battery 100 is not limited to the said method. For example, the second side edge portion 122 may be heat sealed first, and the electrolyte may be injected from the first side edge portion 120 side, and then the first side edge portion 120 may be heat sealed and sealed. .

<Other embodiments>
The secondary battery of the present invention is not limited to the secondary battery 100 described above.
For example, the secondary battery of the present invention may be a four-side seal type in which two exterior members 1 are used to heat-seal each of the four belt-like edge portions. Moreover, the secondary battery in which both the 1st container part 110a and the 2nd container part 110b were deep-drawn and the battery member accommodating part was formed may be sufficient. Further, a three-side seal type, a four-side seal type, or a pillow pouch type that does not have a battery housing portion formed by deep drawing may be used. In the case of the three-way seal type, the length direction of the strip-shaped edge portion having the largest value P among the three-band strip-shaped edge portions, and in the case of the four-way seal type, the strip shape having the largest value P in the four-way strip-shaped edge portions. The length direction of the edge portion and the MD direction of the heat-sealing layer of the exterior material are parallel to each other. In the case of the pillow pouch type, the length direction of the belt-like edge portion having the largest value P among the belt-like edge portion on the back surface, the upper belt-like edge portion, and the lower belt-like edge portion, and the exterior material The MD direction of the heat sealing layer is parallel.
Further, in the case of a three-side seal type like the secondary battery 100, the secondary battery of the present invention may be one in which a tab is sandwiched between the side edge portions instead of the tip edge portion on the opposite side of the folded portion. .

Moreover, the exterior material used for the secondary battery of the present invention is not limited to the exterior material 1 described above. For example, an exterior material in which the base material protective layer 16 is not provided outside the base material layer 11 may be used. In this case, the base material layer 11 is preferably made of a material excellent in insulation between the metal foil layer 13 and other metal members of the secondary battery and heat resistance during heat sealing.
Moreover, the corrosion prevention process layer may be provided on both surfaces of the metal foil layer. By providing the corrosion prevention treatment layers on both sides, corrosion of the metal foil layer 13 not only from the inner layer side but also from the outer layer side can be prevented. The corrosion prevention treatment layer is preferably provided at least on the heat fusion layer side.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by the following description.
[Materials used]
The materials used in this example are shown below.
(Base material protective layer)
Base material protective film A-1: Polyester film (thickness: 12 μm).
(Base material layer)
Base film B-1: Nylon 6 film (thickness 25 μm).
(Adhesive layer)
Adhesive C-1: polyurethane adhesive.
(Metal foil layer)
Metal foil D-1: Soft aluminum foil 8079 material (thickness 40 μm).
(Corrosion prevention treatment layer)
Treatment agent E-1: Treatment agent for coating type ceriazole treatment mainly composed of cerium oxide, phosphoric acid and acrylic resin.
(Adhesive resin layer)
Adhesive resin F-1: Maleic anhydride-modified polypropylene resin.
(Sealant layer)
Sealant film G-1: unstretched polypropylene film (thickness 60 μm).

[Production Example 1: Production of exterior material]
The treatment agent E-1 was applied to both surfaces of the metal foil D-1 and dried to form a corrosion prevention treatment layer on both surfaces of the metal foil layer. Next, the base film B-1 was bonded to one of the corrosion prevention treatment layers by a dry laminating method using the adhesive C-1, and the base layer was laminated via the adhesive layer (thickness 3 μm). Then, the base material protective film A-1 was bonded together on the base material layer side by the dry laminating method using adhesive C-1, and the base material protective layer was laminated | stacked. Thereafter, aging was performed at 60 ° C. for 6 days. Next, the adhesive resin F-1 is extruded on the other corrosion prevention treatment layer side by an extrusion device, the sealant film G-1 is bonded, and sandwich lamination is performed, whereby the sealant is passed through the adhesive resin layer (thickness 20 μm). The layers were laminated to form a heat fusion layer. The MD direction of the adhesive resin layer and the MD direction of the sealant layer were the same direction. Thereafter, the adhesive resin layer and the sealant layer of the obtained laminate were melted at 160 ° C., 4 kg / cm ² , 2 m / min, and thermocompression bonded to the metal foil layer.

[Example 1]
The exterior material produced in Production Example 1 was cut into a rectangular shape having a length of 140 mm and a width of 120 mm, and the exterior material was folded in two in the longitudinal direction. At this time, the vertical direction was the TD direction of the heat sealing layer, and the horizontal direction was the MD direction of the heat sealing layer.
Next, the tip edge part (length 120 mm) on the opposite side of the folded part of the exterior material folded in half with a seal bar having a width of 10 mm, temperature 190 ° C., surface pressure 0.5 MPa, sealing time 3 seconds Heat sealed under conditions. At this time, by inserting a gap (insertion piece) having a thickness of 0.25 mm between the heat seal bars and performing heat seal, the thickness of the heat-sealed layer of the heat seal portion at the tip edge portion is adjusted to 0.1 mm. did. One side edge portion (length 70 mm) was heat-sealed under the conditions of a temperature of 190 ° C., a surface pressure of 1 MPa, and a sealing time of 10 seconds. The heat sealing of the side edge portions without the gap, the value P ₂ in the side edge portion is set to be 0.5. Thereafter, 3 g of electrolyte (dimethyl carbonate: diethyl carbonate: ethylene carbonate (mass ratio) = 1: 1: 1 mixed solution) was added from the remaining side edge portion side, and the remaining side edge portion was subjected to a surface pressure of 190 ° C. Heat sealing was performed under conditions of 1 MPa and a sealing time of 10 seconds to obtain a sample container containing an electrolytic solution. Heat sealing the side edge portion of the該残Ri, the length of the heat-sealed portion in the leading edge portion 100 mm, the value P ₃ were adjusted to be 0.5. Thereafter, a part of the side edge side of the tip edge portion was cut out so that the heat seal width at the tip edge portion was 7 mm. The thickness and heat seal width of the heat-sealing layer in the heat seal portion at the front edge portion and both side edge portions were made uniform.
As described above, a sample container was obtained in which the length direction of the tip edge portion was parallel to the MD direction of the heat-sealing layer and the length direction of the side edge portion was parallel to the TD direction of the heat-sealing layer. The heat seal portion at the tip edge portion has a heat-sealing layer thickness Q ₁ of 0.1 mm, a heat seal length R ₁ of 100 mm, a heat seal width S ₁ of 7 mm, and P ₁ defined by the formula (I). 1.4, and P ₂ (= P ₃ ) defined by the formula (I) was 0.5.

[Examples 2 to 5]
Sample as in Example 1, except that the heat seal layer thickness Q ₁ , heat seal length R ₁ , and heat seal width S ₁ of the heat seal portion at the tip edge portion were changed as shown in Table 1. A container was obtained.

[Comparative Examples 1-5]
Using the exterior material cut into a rectangular shape of 140 mm in length and 120 mm in width so that the vertical direction is the MD direction of the thermal fusion layer and the horizontal direction is the TD direction of the thermal fusion layer, the length direction of the tip edge portion Is changed to be parallel to the TD direction of the heat-sealing layer and the length direction of the side edge portion is parallel to the MD direction of the heat-sealing layer, and the thickness of the heat-sealing layer of the heat seal portion at the tip edge portion is changed. A sample container was obtained in the same manner as in Example 1 except that Q ₁ , heat seal length R ₁ , and heat seal width S ₁ were changed as shown in Table 1.

[Method for measuring thickness of heat-sealing layer]
The thickness Q ₁ of the heat-sealing layer at the heat-sealed portion at the front end edge portion and the thickness Q ₂ (= Q ₃ ) of the heat-sealing layer at the heat-sealed portions at both side edge portions are the thicknesses of the respective heat-sealed portions. Was calculated by subtracting the film thickness (theoretical value, twice the thickness from the base material protective layer to the corrosion prevention treatment layer) other than the heat-fusible layer from the measured value.

[Evaluation method]
(Evaluation of water permeation)
After leaving the sample container obtained in each example in an environment of a temperature of 60 ° C. and a humidity of 95 RH% for 1500 hours, the water content in the electrolyte solution in the sample container was determined using a Karl Fischer AQ-2100ST manufactured by Hiranuma Sangyo Co., Ltd. It was measured.

(Evaluation of dry-up amount)
The sample container obtained in each example was allowed to stand for 1500 hours in an environment of a temperature of 60 ° C. and a humidity of 5 RH%, and then the change in mass from the time before being left was measured to obtain a dry-up amount.
Table 1 shows the moisture permeation amounts and dry-up evaluation results in Examples 1 to 5 and Comparative Examples 1 to 5.

  As shown in Table 1, in Examples 1 to 5 in which the length direction of the tip edge portion having a large value P defined by the formula (I) and the MD direction of the heat-sealing layer are parallel, the tip edge The moisture permeation amount and the dry-up amount were reduced as compared with Comparative Examples 1 to 5 under the same conditions except that the length direction of the portion and the TD direction of the heat fusion layer were parallel.

  DESCRIPTION OF SYMBOLS 1 ... Secondary battery exterior material, 11 ... Base material layer, 12 ... Adhesive layer, 13 ... Metal foil layer, 14 ... Corrosion prevention treatment layer, 15 ... Heat fusion Adhesion layer, 16 ... base material protective layer, 17 ... adhesive resin layer, 18 ... sealant layer, 100 ... secondary battery, 110 ... container body, 112 ... battery member, 114・ ・ ・ Tab, 116 ・ ・ ・ Battery member housing portion, 118 ・ ・ ・ Tip edge portion, 118 a ・ ・ ・ Heat seal portion, 120 ・ ・ ・ First side edge portion, 120 a ・ ・ ・ Heat seal portion, 122 ... Second side edge portion, 122a ... heat seal portion, 124 ... battery member main body, 126 ... lead, 128 ... tab sealant.

Claims (3)

A container body formed of a secondary battery exterior material in which at least a metal foil layer and a heat-sealing layer are sequentially laminated on one surface side of the base material layer, and the container so that a part of the tab is exposed to the outside. A battery member housed in the body,
The container body is sealed by sealing the secondary battery exterior material into a container shape with the heat-sealing layer inside, and heat-sealing a belt-like edge portion where the heat-sealing layers are in contact with each other Has been
The ratio of the thickness of the heat-sealing layer of the heat seal portion of the edge portion without the tab to the thickness of the heat-sealing layer of the heat seal portion of the edge portion where the tab is sandwiched is 20 to 95%,
Among the strip-shaped edge portions, the length direction of the strip-shaped edge portion having the largest value P defined by the following formula (I) is parallel to the MD direction of the thermal fusion layer. Secondary battery.

(However, in the formula (I), Q is the thickness (mm) of the heat-sealing layer of the heat-sealed portion in the belt-shaped edge portion, and R is the length (mm) of the heat-sealed portion in the belt-shaped edge portion. ), And S is the width (mm) of the heat seal portion in the band-shaped edge portion.) The secondary battery according to claim 1, wherein a strip-like edge portion without the tab is folded. The heat-fusible layer, a secondary battery according to claim 1 or 2 adhesive resin layer and the sealant layer is a layer formed by stacking of the metal foil layer side.

Images