JP2015072821A - Secondary battery exterior material and secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheath material for a secondary material which is manufactured without providing an end part coating process separately and inhibits exposure of a metal foil of an end part.SOLUTION: A sheath material 1 for a secondary material of the invention includes: a metal foil layer 30; a base material layer 10 laminated on a first surface of the metal foil layer; and a sealant layer 20 containing a heat sealable resin and laminated on a second surface of the metal foil layer that is located at the opposite side of the first surface. A size of the metal foil layer is smaller than those of the base material layer and the sealant layer in a first direction. The metal foil layer is disposed so as to be positioned at an intermediate part in the first direction relative to the base material layer and the sealant layer.

Description

  The present invention relates to a packaging material for a secondary battery, more specifically, a packaging material for a secondary battery excellent in insulation, and a secondary battery using the packaging material.

  As exterior materials for secondary batteries such as lithium-ion batteries, exterior materials made of multilayer films that are lighter, have higher heat dissipation than conventional metal cans, and can be used at low cost are widely used. ing. As such an exterior material, for example, a laminate in which a base material layer, a metal foil layer made of aluminum or the like, and a sealant layer are laminated is widely known.

  In the case of forming a secondary battery using the outer packaging material, for example, a concave portion is formed by cold molding in one portion when the outer packaging material is folded in half, and a positive electrode, a separator, a negative electrode, an electrolytic solution are formed in the concave portion. And the like, and the remaining part is folded and the edge part is heat-sealed and sealed. The secondary battery formed in this way is also called a battery pack or a battery cell.

  By the way, in the said exterior material, the metal foil layer is exposed to the side surface extended in thickness direction. When the battery cell is manufactured, the metal foil layer remains exposed because heat sealing is performed with the sealant layers of the exterior material facing each other. If this is left unattended, there is a possibility of short-circuiting with leads and other cells. In order to prevent this, Patent Document 1 proposes covering the end portion where the metal foil layer is exposed by heat sealing. In Patent Document 2, it is proposed to cover the end portion with an injection molding resin.

Japanese Patent No. 4523080 JP 2006-310039 A

  However, if the end portion is to be covered by the method described in Patent Document 1 or Patent Document 2, it is necessary to provide a coating process separately from the manufacturing process of the exterior material, and it is difficult to avoid an increase in manufacturing cost. There's a problem.

In view of the above circumstances, an object of the present invention is to provide a secondary battery exterior material that can be manufactured without providing an end covering step, and that the exposure of the end of the metal foil layer is suppressed.
Another object of the present invention is to provide a secondary battery that can be manufactured at a low cost and that has an insulating property suitably secured.

  A first aspect of the present invention includes a metal foil layer, a base material layer laminated on the first surface of the metal foil layer, and a heat-bondable resin. The metal foil layer has a dimension in a first direction smaller than that of the base material layer and the sealant layer, and the base material layer and the sealant layer. On the other hand, the secondary battery exterior material is disposed so as to be positioned at the intermediate portion in the first direction.

In the packaging material for a secondary battery of the present invention, the base material layer and the sealant layer are bonded to each other on both sides in the first direction via a heat-adhesive resin layer, and the metal foil layer You may seal so that the edge part of the one direction both sides may not be exposed.
Alternatively, the base material layer and the sealant layer may be bonded via an adhesive layer on both sides in the first direction.

  The distance between the end portion in the first direction of the metal foil layer and the end portion in the first direction of the base material layer and the sealant layer is at least twice the thickness of the metal foil layer, Also good.

  A second aspect of the present invention is a secondary battery including the outer packaging material for a secondary battery according to the present invention, wherein the metal foil layer is coated on both sides in the first direction.

According to the secondary battery exterior material of the present invention, the secondary battery exterior material can be manufactured without a separate end covering step, and the secondary battery exterior material in which exposure of the metal foil layer at the end is suppressed can be obtained.
Moreover, according to the secondary battery of this invention, it can manufacture at low cost and can also ensure insulation suitably.

It is a top view which shows the exterior material for secondary batteries which concerns on 1st embodiment of this invention. It is sectional drawing in the II line | wire of FIG. It is sectional drawing which shows the exterior material for secondary batteries which concerns on 2nd embodiment of this invention.

A first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a plan view showing a secondary battery exterior material (hereinafter simply referred to as “exterior material”) 1 of the present embodiment, and FIG. 2 is a cross-sectional view taken along the line II of FIG.
As shown in FIGS. 1 and 2, the exterior material 1 includes a base material layer 10, a heat-sealable sealant layer 20, and a metal foil layer 30 disposed between the base material layer 10 and the sealant layer 20. And. That is, the base material layer 10 is laminated on one surface (first surface) of the metal foil layer 30, and the sealant layer 20 is laminated on the opposite surface (second surface).

  As the base material layer 10, a film made of a polyester resin, a polyamide resin or the like can be used. Although the thickness of a base material layer can be set suitably, for example, 6-40 micrometers (micrometer) is preferable and 10-30 micrometers is more preferable. If the thickness of the base material layer 10 is equal to or greater than the lower limit value, the pinhole resistance, the insulating properties, and the moldability become better. If the thickness of the base material layer 10 is less than or equal to the upper limit value, the expansion and contraction of the portion stretched by the molding process is suppressed, and the shape after the molding process can be maintained.

As the metal foil layer 30, various metal foils such as aluminum and stainless steel can be used, and aluminum foil is preferable from the viewpoint of workability such as moisture resistance and spreadability and cost. A general soft aluminum foil can be used as the aluminum foil. Among these, an aluminum foil containing iron is preferable from the viewpoint of excellent pinhole resistance and extensibility during molding.
0.1-9.0 mass% is preferable and, as for content of iron in the aluminum foil (100 mass%) containing iron, 0.5-2.0 mass% is more preferable. When the iron content is 0.1% by mass or more, the exterior material 1 is excellent in pinhole resistance and spreadability. If the iron content is 9.0% by mass or less, the exterior material 1 is excellent in flexibility.
The thickness of the metal foil layer 30 is preferably 9 to 200 μm, more preferably 15 to 100 μm, from the viewpoint of barrier properties, pinhole resistance, and workability. Moreover, it is preferable that a corrosion prevention treatment layer formed by ceria sol treatment or the like is provided on at least one surface of the metal foil layer 30.

The sealant layer 20 is a layer that is bonded by heat sealing when the battery cell is formed using the exterior material 1. That is, the sealant layer 20 constitutes the innermost layer when forming the battery cell.
The material of the sealant layer 20 is preferably a thermoplastic resin because of excellent impact resistance and heat sealing properties, and is preferably an olefin resin such as polyethylene or polypropylene. For example, polypropylene includes homo, block, or random polypropylene. The sealant layer 20 may be a layer made of a single layer film or a layer made of a multilayer film. The thickness of the sealant is preferably 20 to 100 μm. If the thickness of the sealant layer is 20 μm or more, excellent heat sealability is easily obtained. Moreover, if it is 100 micrometers or less, it will be easy to reduce the water | moisture content permeate | transmitted into a battery inside from a seal end surface.

As shown in FIG. 2, the base material layer 10 and the metal foil layer 30 are joined by an adhesive layer 40. As a component of the adhesive layer 40, a two-component curable urethane-based adhesive in which a bifunctional or higher aromatic or aliphatic isocyanate compound is allowed to act as a curing agent on a main component such as polyester polyol, polyether polyol, and acrylic polyol. Agents are preferred.
For example, the urethane-based adhesive is aged at 40 ° C. for 4 days or more after coating, whereby the reaction of the hydroxyl group of the main agent and the isocyanate group of the curing agent proceeds to enable strong adhesion. The thickness of the adhesive layer 40 is preferably 1 to 10 μm and more preferably 3 to 7 μm from the viewpoints of adhesive strength, followability, and processability.

The metal foil layer 30 and the sealant layer 20 are joined by an adhesive resin layer 50. As a material of the adhesive resin layer 50, a thermoplastic resin is preferable. For example, an acid-modified elastomer resin obtained by graft-modifying an acid such as maleic anhydride to a polyolefin resin can be used. Examples of the polyolefin resin include low density, medium density, and high density polyethylene; ethylene-α olefin copolymer, homo, block, random polypropylene, and propylene-α olefin copolymer. These polyolefin resins may be used individually by 1 type, and may use 2 or more types together. The acid-modified polyolefin-based resin is excellent in resistance to electrolytic solution, and it is easy to suppress a decrease in adhesion due to deterioration of the adhesive resin even when hydrofluoric acid is generated. 1-50 micrometers is preferable and, as for the thickness of the adhesive resin layer 50, 5-40 micrometers is more preferable. If the thickness of the adhesive resin layer 50 is 1 μm or more, sufficient adhesive strength can be easily obtained, and if it is 50 μm or less, the amount of water vapor transmitted from the heat seal surface to the inside of the battery can be easily reduced.
The adhesive resin layer can also be formed by a technique such as dry lamination. When forming by dry lamination, the same adhesive as the adhesive layer 40 can also be used.

  As shown in FIG. 1, the exterior material 1 is a rectangle (a substantially rectangular shape is included) in planar view. The metal foil layer 30 is disposed over the longitudinal direction (second direction) of the packaging material 1. A dimension W2 in the width direction (first direction) orthogonal to the longitudinal direction of the metal foil layer 30 is smaller than a dimension W1 in the width direction of the exterior material 1, and the end of the metal foil layer in the width direction is the exterior material 1. It is arrange | positioned in the width direction intermediate part so that it may not be exposed to the end surface of both width direction.

As shown in FIG. 2, both sides in the width direction of the metal foil layer 30 are covered with a deformed adhesive resin layer 50, and the deformed adhesive resin layer 50 is adhered to the base material layer 10. Thereby, the edge part of the width direction of the metal foil layer 30 is sealed so that it may not be exposed, and the insulating property is provided.
The width dimension (hereinafter referred to as “sealing width”) W3 of the region formed only by the resin on both sides in the width direction of the metal foil layer 30 is the width direction end of the metal foil layer 30 and the base material. It is prescribed | regulated by the distance with the width direction edge part of the layer 10 and the sealant layer 20. FIG. The value of the sealing width W3 may be appropriately set within a range in which insulation can be ensured. When the base material layer 10 and the sealant layer 20 are bonded by thermal lamination, the thickness of the metal foil layer 30 is twice or more. 20 times or less is preferable. When the sealing width W3 is less than twice the thickness of the metal foil layer, the coating of the metal foil layer may be insufficient depending on the type of the adhesive resin layer. On the other hand, when the sealing width W3 exceeds 20 times the thickness of the metal foil layer, there is no problem in sealing the metal foil layer, but the sealant layer at the end in the width direction of the exterior material is shrunk and the appearance is poor. May be.
Moreover, when the base material layer 10 and the sealant layer 20 are joined by dry lamination, the thickness is preferably twice or more the thickness of the metal foil layer 30. When the sealing width W3 is less than twice the thickness of the metal foil layer, the metal foil layer may be insufficiently covered depending on the type of adhesive used as the adhesive resin layer. If the thickness of the metal foil layer is twice or more, there will be no problem in either sealing or appearance of the metal foil layer.

The manufacturing procedure of the exterior material 1 of the present embodiment configured as described above will be described.
First, the adhesive layer 40 is formed on one surface of the film to be the base material layer 10, and the metal foil layer 30 is disposed and laminated at the intermediate portion in the width direction of the film to be the base material layer 10. At this time, the adhesive layer 40 may be formed on the entire surface of the base material layer, or may be formed only in a region where the metal foil layer is disposed.
When the exterior material 1 is continuously manufactured by roll-to-roll, a metal foil layer 30 having a width dimension of W2 is laminated on a width direction intermediate portion of a base material layer having a width dimension of W1.

Next, the sealant layer 20 is laminated by heat lamination by extrusion sand lamination using the material of the adhesive resin layer 50. In the case of continuous production by roll-to-roll, the film that becomes the sealant layer 20 is also used with a widthwise dimension of W1. The extruded material of the adhesive resin layer is deformed so as to cover both sides in the width direction of the metal foil layer, and the base material layer 10 and the sealant layer 20 are joined.
When this is cut into a predetermined length along the width direction, the exterior material 1 is completed. The end in the width direction may be cut off by a certain amount for the purpose of adjusting the appearance, but in that case, the cut-off amount is set in consideration of the sealing width after cutting off. Usually, it is preferable that the cut-off amount of the end portion is about 0.5 mm to 1.0 mm in consideration of accuracy.

  Two finished exterior materials 1 are opposed to each other, or one exterior material 1 is folded back along the width direction so that the sealant layer 20 is opposed, and a tab member or the like serving as a power generation element or a terminal is disposed inside. When the peripheral edges are joined by heat sealing, a secondary battery cell using the exterior material 1 is completed. In the completed secondary battery cell, the end in the width direction is sealed by the adhesive resin layer 50 and formed so that the metal foil layer 30 is not exposed, thereby ensuring insulation. Note that the metal foil layer 30 is exposed on the side surface in the longitudinal direction of the exterior material, but for this, insulation is secured separately by a tab sealant or the like covering the periphery of the tab member.

According to the packaging material 1 of the present embodiment, the metal foil layer 30 having a width dimension smaller than that of the base material layer and the sealant layer is disposed in the width direction intermediate portion, and both sides in the width direction of the metal foil layer 30 are thermally adhesive. Covered with a resin layer 40. That is, it can manufacture without providing an edge part coating process separately, and it can be set as the secondary battery exterior material by which the metal foil layer exposure of the edge part was suppressed.
It is possible to provide an exterior material in which insulation at the width direction end portion is ensured without requiring a step of covering the end portion with another material.

In the present embodiment, the example using the metal foil layer in which only the dimension in the width direction is smaller than that of the base material layer and the sealant layer has been described. Instead, the dimension in the longitudinal direction is also smaller than that of the base material layer and the sealant layer. A metal foil layer may be used. In this case, by arranging and laminating the metal foil layer in the intermediate portion in the width direction and the intermediate portion in the longitudinal direction, it is possible to obtain an exterior material that is coated so that the metal foil is not exposed on all side surfaces.
On the other hand, as described above, even when the metal foil layer is sealed only at the end in the width direction, the manufacturing efficiency and insulation can be improved by arranging the tab member at the end in the longitudinal direction when forming the secondary battery. Etc. can be kept sufficiently high. Moreover, since the metal foil layer is arranged so as to be continuous in the longitudinal direction, there is an advantage that continuous production by roll-to-roll or the like becomes possible.

  A second embodiment of the present invention will be described with reference to FIG. The difference between the exterior material 61 of the present embodiment and the above-described exterior material 1 is the layer configuration and the manufacturing method. In the following description, components that are the same as those already described are assigned the same reference numerals and redundant description is omitted.

  FIG. 3 is a cross-sectional view of the exterior material 61, and shows a cross-section corresponding to FIG. The exterior material 61 has a layer structure suitable for manufacturing by dry lamination, and includes a second adhesive layer (adhesive layer) 62 instead of the heat-adhesive resin layer 50. The metal foil layer 30 and the sealant layer 20 are joined by the second adhesive layer 62, and both sides in the width direction of the metal foil layer 30 are covered by the second adhesive layer 62 so as not to be exposed.

  The material of the second adhesive layer 62 is not particularly limited as long as it can be adhered to the sealant layer 20 and the metal foil layer 30 and can be used for dry lamination, and may be the same as the material of the adhesive layer 40. Good.

A manufacturing procedure of the exterior material 61 of the present embodiment configured as described above will be described.
First, as in the first embodiment, the adhesive layer 40 is formed on one surface of the film to be the base material layer 10, and the metal foil layer 30 is disposed in the intermediate portion in the width direction of the film to be the base material layer 10. And stack.
Next, the second adhesive layer 62 is formed on the entire surface of one surface of the film to be the sealant layer 20, and the sealant layer 20 and the metal foil layer 30 are joined by dry lamination. At this time, sufficient pressure is applied to bond the base material layer 10 and the sealant layer 20 via the second adhesive layer 62 on both sides in the width direction of the metal foil layer. Thereby, the exterior material 61 with which the width direction edge part of the metal foil layer 30 was coat | covered is completed.

Similarly to the exterior material 1 of the first embodiment, the exterior material 61 of the present embodiment can be manufactured without a separate end covering step, and the exterior for the secondary battery in which the exposure of the metal foil layer at the end is suppressed. It can be a material.
Further, as described in the present embodiment, the exterior material of the present invention can be manufactured not only by heat lamination but also by dry lamination by changing the layer configuration. In particular, in the case of a dry laminate, since heat is not applied to the sealant layer, thermal shrinkage can be suppressed and appearance defects are unlikely to occur.

  In the present embodiment, the example in which the base material layer 10 and the metal foil layer 30 are first bonded and then the sealant layer 20 is bonded by dry lamination has been described, but instead, the sealant layer 20 and the metal foil layer are first bonded. After bonding 30, the base material layer 10 may be bonded by dry lamination. In this case, both sides in the width direction of the metal foil layer 30 are covered with the adhesive layer 40 that joins the base material layer 10 and the metal foil layer.

The packaging material and secondary battery of the present invention will be further described using examples and comparative examples. However, the present invention is not limited to the specific contents of the examples.
(Example 1)
Example 1 is an example using a thermal laminate for bonding. The material of each layer is as follows.
[Base material layer]
Base film A-1: Laminated film having a layer structure of polyester film (thickness 12 μm) / polyurethane adhesive (thickness 3 μm) nylon 6 film (thickness 25 μm)
[Adhesive layer]
Adhesive B-1: Polyurethane adhesive (thickness 3 μm)
[Metal foil layer]
Metal foil C-1: Soft aluminum foil 8079 material (thickness 40 μm)
[Corrosion prevention treatment layer]
Treatment agent D-1: Treatment agent for coating type ceria sol treatment mainly composed of cerium oxide, phosphoric acid and acrylic resin
[Adhesive resin layer]
Adhesive resin E-1: Maleic anhydride-modified polypropylene resin
[Sealant layer]
Sealant F-1: Polypropylene resin film

<Method of manufacturing secondary battery exterior material>
The treatment agent D-1 was applied to both sides of the metal foil C-1 and dried to form a corrosion prevention treatment layer on both sides of the metal foil. Next, the base film A-1 having a width 20 mm wider than that of the metal foil was bonded to one of the corrosion prevention treatment layers by a dry laminating method using the adhesive B-1, and laminated through the adhesive layer. A base material layer and a metal foil layer were formed. Thereafter, aging was performed at 60 ° C. for 6 days.
Next, after extruding the adhesive resin E-1 having a width 20 mm wider than that of the metal foil layer on the other corrosion prevention treatment layer side, the sealant F-1 having a width 20 mm wider than that of the metal foil layer is overlaid. And sand laminated. The obtained laminate was subjected to thermal lamination, and the base material layer and the adhesive resin layer were thermocompression bonded. Finally, both end portions in the width direction of the laminate are cut off so that the distance between the end portions in the width direction of the metal foil layer and the end portions in the width direction of the base material layer or the sealant layer is a predetermined condition. Got. The outer layer material of Example 1 was manufactured in five types, each having a sealing width 2 times, 5 times, 20 times, 100 times, and 400 times the thickness of the metal foil layer. A sealing width of 0.5 and 1 times the thickness of the metal foil layer was used as a comparative example.

<Evaluation method>
Ten samples of each exterior material produced by the above method were prepared. In order to confirm energization, a conductive solution is applied to the metal foil layer exposed at the longitudinal end of the exterior material and the widthwise end of the exterior material where the base material layer and the adhesive resin layer are joined. Water was dropped, a tester was connected to both, and a voltage of 25 V was applied for 5 seconds to measure the electrical resistance value. The case where the resistance value was 99.9 GΩ or more was regarded as acceptable, and the case where the resistance value was less than 99.9 GΩ was regarded as unacceptable.
Moreover, the external appearance of the exterior material was visually evaluated. Evaluation was made in the following two stages.
○: Appearance defects are not recognized in any sample.
Δ: There is a sample in which a slight appearance defect is observed, but there is no problem as a product.

  The evaluation results are shown in Table 1.

  As shown in Table 1, in the examples in which the sealing width is twice or more the thickness of the metal foil layer, none of the insulating failures was recognized, and the insulating properties at the end portions in the width direction were suitably secured. . However, in the example where the sealing width exceeded 20 times the thickness of the metal foil layer, the appearance was partially disturbed. In the comparative example in which the sealing width was less than twice the thickness of the metal foil layer, the insulation was rejected in some or all of the samples, and the insulation could not be secured.

(Example 2)
Example 2 is an example in which a dry laminate is used for bonding. The material of each layer is substantially the same as that of Example 1, but only the material of the adhesive resin layer was replaced with the above-described adhesive B-1 instead of the above-described E-1.
<Method of manufacturing secondary battery exterior material>
The same procedure as in Example 1 was performed until aging.
Next, a sealant F-1 having a width 20 mm wider than that of the metal foil layer was bonded to the corrosion prevention treatment layer not bonded to the base material by the dry laminating method using the adhesive E-2.
Finally, in the same manner as in Example 1, both end portions in the width direction of the laminate were cut off to obtain the exterior material of Example 2 and the exterior material of the comparative example.

<Evaluation method>
The same as in the first embodiment.

  The evaluation results are shown in Table 2.

  As shown in Table 2, in Examples in which the sealing width is twice or more the thickness of the metal foil layer, none of the insulating failures was recognized, and the insulating properties in the width direction end portions were suitably secured. . Moreover, even when the sealing width exceeded 20 times the thickness of the metal foil layer, the appearance was not disturbed, and the appearance was good in all examples. In the comparative example in which the sealing width was less than twice the thickness of the metal foil layer, the insulation was rejected in some or all of the samples, and the insulation could not be secured.

  The embodiments and examples of the present invention have been described above. However, the technical scope of the present invention is not limited to the above-described embodiments, and combinations of components may be changed without departing from the spirit of the present invention. Various changes can be added to or deleted from each component.

DESCRIPTION OF SYMBOLS 1,61 Outer packaging material 10 for secondary batteries Base material layer 20 Sealant layer 30 Metal foil layer 40 Adhesive layer 50 Thermal adhesive resin layer 62 Second adhesive layer (adhesive layer)

Claims (5)

A metal foil layer;
A base material layer laminated on the first surface of the metal foil layer;
A heat sealable resin, and in the metal foil layer, a sealant layer laminated on the second surface opposite to the first surface;
With
The metal foil layer has a dimension in a first direction smaller than that of the base material layer and the sealant layer, and is positioned at an intermediate portion in the first direction with respect to the base material layer and the sealant layer. A secondary battery exterior material is disposed.   On both sides of the first direction, the base material layer and the sealant layer are bonded via a heat-adhesive resin layer so that end portions on both sides of the metal foil layer in the first direction are not exposed. The packaging material for a secondary battery according to claim 1, wherein the packaging material is sealed.   On both sides in the first direction, the base material layer and the sealant layer are bonded via an adhesive layer, and sealing is performed so that the end portions on both sides in the first direction of the metal foil layer are not exposed. The packaging material for a secondary battery according to claim 1, wherein   The distance between the end of the metal foil layer in the first direction and the end of the base material layer and the sealant layer in the first direction is twice or more the thickness of the metal foil layer. The packaging material for a secondary battery according to any one of claims 1 to 3.   A secondary battery comprising the secondary battery exterior material according to claim 1, wherein the metal foil layer is coated on both sides in the first direction.

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