JP2023077398A - Outer material for power storage device - Google Patents

Abstract

To provide an outer material for a power storage device, enabling efficient discharge of gas at a high temperature.SOLUTION: An outer material for a power storage device includes: a metal foil layer 4; a resin base material layer 2 provided on an outer surface side of the metal foil layer 4; and a thermal fusion resin thermal fusion layer 3 provided on an inner surface side of the metal foil layer 4 and for performing a heat sealing, the thermal fusion layer 3 includes : a seal layer 30 arranged in its innermost surface; and a metal foil side layer 33 arranged on the outer surface side of the seal layer 30. The outer material for the power storage device, is constructed in such a manner that when a residual ratio of a thickness of the thermal fusion layer 3 by the heat sealing under a condition that a temperature is 180°C, a pressure 0.3 MPa, and a time is 4s is adjusted to 40% to 80%, a sealing strength under a normal temperature atmosphere in a heat sealing portion of both of seal layers in a state where both of the seal layers are sealed is "Pn", the sealing strength under an atmosphere of 130°C is "Pb", the following relation is established: Pn≥50 N/15 mm and Pb≤10 N/15 mm.SELECTED DRAWING: Figure 1

Description

The present invention relates to exterior materials for power storage devices such as mobile devices such as laptop computers, smartphones, and tablet terminals, vehicle-mounted secondary batteries, and stationary secondary batteries, especially lithium-ion secondary batteries for mobile devices, and related technologies. Regarding.

In recent years, as mobile devices such as smartphones and tablet terminals have become thinner and lighter, the lithium-ion secondary batteries installed in these devices have replaced the conventional metal cans and cases with exterior materials such as aluminum laminate sheets. By using an exterior case (outer envelope) formed by overlapping and sealing the peripheral edge by heat sealing, it can be processed into a variety of shapes according to the usage situation, improving versatility and making it thinner It is also becoming lighter and lighter.

In addition, the performance of mobile devices themselves has advanced dramatically, and in order to maintain their functions, batteries such as secondary batteries for mobile devices have been required to have a high capacity, that is, to have a high energy density as much as possible. .

As the capacity of the battery increases, there is a concern that the battery may generate heat, catch fire, or the like.

For example, in a lithium-ion battery or the like, the temperature of the battery rises and the electrolyte thermally decomposes to generate combustible gas, which may lead to ignition.

Conventionally, power storage devices (batteries) disclosed in Patent Documents 1 and 2 below have been proposed as a preventive measure against ignition of batteries. In the power storage device disclosed in Patent Document 1, a pressure release valve is separately attached to the exterior case, and when the pressure inside the battery rises due to a temperature rise, the pressure release valve opens to release gas, thereby reducing the pressure and temperature. to prevent ignition.

Further, in the electric storage device disclosed in Patent Document 2, the heat-sealed portion (heat-sealed portion) of the exterior material as the exterior case is peeled off and opened at high temperatures, thereby releasing gas and preventing ignition. I'm trying

Patent No. 6540871 JP 2019-29300

However, the conventional electricity storage device disclosed in Patent Literature 1 has a problem that the number of parts may increase and productivity may decrease because a separate pressure release valve needs to be attached.

In addition, in the electricity storage device disclosed in Patent Document 2, there is a risk that the outer case may be opened in a low temperature range before reaching a high temperature at which decomposition gas is generated, and gas cannot be efficiently vented. rice field.

The present invention has been made in view of the above problems, and is capable of efficiently releasing gas at high temperatures, sufficiently ensuring safety against ignition, etc., while reducing the number of parts and improving productivity. An object of the present invention is to provide an exterior material for an electric storage device that can be used and related technology.

In order to solve the above problems, the present invention has the following means.

[1] A metal foil layer, a resin base layer provided on the outer surface side of the metal foil layer, and a heat-sealing resin base layer provided on the inner surface side of the metal foil layer and for heat sealing a heat-sealing layer, wherein the heat-sealing layer includes a seal layer arranged on the innermost surface thereof, and a metal foil side layer arranged on the outer surface side of the seal layer. hand,
The residual rate of the thickness of the thermal adhesive layer after heat sealing under the conditions of temperature 180° C., pressure 0.3 MPa, and time 4 s is adjusted to 40% to 80%,
In the state where the seal layers are heat-sealed, the seal strength at the heat-sealed portion between the seal layers under a normal temperature atmosphere is "Pn", and the seal strength under an atmosphere of 130 ° C. is "Pb",
Pn≧50N/15mm
Pb≤10N/15mm
An exterior material for an electricity storage device, characterized in that it is configured so that the relationship of

[2] Assuming that the seal strength at the heat-sealed portion between the seal layers under an atmosphere of 100°C is "Pa",
Pa≧20N/15mm
Pa-Pb = 20N/15mm to 60N/15mm
1. The exterior material for an electricity storage device according to the preceding item 1, which is configured so that the relationship of

[3] The exterior material for an electricity storage device according to the preceding item 1 or 2, wherein the metal foil side layer has a melting point of 140°C or higher.

[4] The sealing layer according to any one of the preceding items 1 to 3, which includes a first sealing layer and a second sealing layer laminated on the outer surface side thereof and having a melting point different from that of the first sealing layer. Exterior material for power storage devices.

[5] Equipped with the exterior material according to any one of the preceding items 1 to 4,
An exterior case for an electricity storage device, wherein the sealing layers are heat-sealed to each other.

[6] The exterior case for an electric storage device according to [5] above, wherein the heat-sealed portion between the sealing layers is cohesively peeled off as the internal pressure increases.

[7] an electricity storage device main body;
and the exterior case according to the preceding item 5 or 6,
An electricity storage device, wherein the electricity storage device main body is enclosed in the exterior case.

[8] an electricity storage device main body;
The exterior material according to any one of the preceding items 1 to 4,
An electricity storage device, wherein the electricity storage device body is covered with the exterior material.

According to the power storage device exterior material of the invention [1], the residual rate of the heat-sealing layer after heat-sealing is set within a specific range. The accumulation enhances the sealing performance at room temperature, and the sealing strength under the room temperature atmosphere can be reliably adjusted to a desired value. In addition, since the seal strength at room temperature and 130°C is set within a specific range, when the internal pressure rises and reaches a high temperature range at the heat seal portion, the seal strength decreases, and gas can be removed efficiently at high temperatures. As a result, it is possible to reliably prevent problems such as ignition due to a decrease in pressure and temperature.

According to the exterior material for an electricity storage device of the invention [2], since the seal strength at a high temperature of 130°C and the seal strength at a slightly high temperature of 100°C are specified, heat sealing is performed up to a high temperature of 130°C. Since the portion gradually softens and is gradually opened, the gas can be smoothly released, thereby reliably preventing accidental rapid gas release.

According to the exterior material for an electricity storage device of the invention [3], since the metal foil side layer having a high melting point exists outside the sealing layer in the heat sealing layer, the sealing layer inside the metal foil side layer at high temperatures. , that is, the desired heat-sealing position, and the degree of gas release can be accurately controlled. From this point of view, it is possible to reliably prevent accidental release of gas.

According to the exterior material for an electricity storage device of the invention [4], since the seal layer is composed of the first and second seal layers having different melting points, resin pooling is more likely to occur in the heat-sealed portion at room temperature, Due to the occurrence of this resin pool, the sealing performance at room temperature can be further improved.

According to the electric storage device exterior cases of inventions [5] and [6], the same effects as those of the exterior materials can be obtained.

According to the electric storage devices of the inventions [7] and [8], the same effect as that of the exterior material can be obtained.

FIG. 1 is a cross-sectional view showing an exterior material for an electric storage device, which is an embodiment of the present invention. FIG. 2 is a cross-sectional view showing an electricity storage device manufactured using the exterior material of the embodiment. FIG. 3 is a perspective view showing an exploded electricity storage device of the embodiment. FIG. 4 is a graph showing the relationship between the seal strength and the ambient temperature for each resin for the seal layer.

FIG. 1 is a cross-sectional view showing an exterior material 1 for an electric storage device, which is an embodiment of the present invention. As shown in the figure, the electrical storage device exterior material 1 consists of a substrate layer 2/outer adhesive layer 52/metal foil layer (barrier layer) 4/inner adhesive layer 51/heat-sealed in order from the top (outside). It is composed of a laminate (laminate sheet) in which layers (sealant layers) 3 are laminated.

That is, the power storage device exterior material 1 includes a metal foil layer 4 made of metal foil, an outer adhesive layer 52 provided on the outer surface side of the metal foil layer 4, and an outer adhesive layer 52 provided on the outer surface side. A base layer 2 made of a heat-resistant resin as an outer layer, an inner adhesive layer 51 provided on the inner surface side of the metal foil layer 4, and an inner layer provided on the inner surface side of the inner adhesive layer 51 A heat-sealing layer (sealant layer) 3 made of a heat-sealing resin is provided.

Here, in the present embodiment, in the state of the exterior case 65 of the electric storage device 6, the exterior material 1 has the base material layer 2 on the outside and the heat sealing layer 3 on the inside. In the present embodiment, when the position of each layer constituting the exterior material 1 is described in terms of direction, the direction of the base layer 2 side is the outside and the heat sealing layer 3 side is the direction in accordance with the inside and outside directions of the exterior case 65. The direction is called inner.

The substrate layer 2 is made of a heat-resistant resin such as a biaxially oriented polyamide film, a biaxially oriented polybutylene terephthalate (PBT) film, a biaxially oriented polyethylene terephthalate (PET) film, or a biaxially oriented polyethylene naphthalate (PEN) film. is preferred. Among these, the polyamide film is not particularly limited, but for example, 6 nylon film, 6,6 nylon film, MXD nylon film, etc. can be preferably used.

Further, the thickness of the base material layer 2 is preferably set to 9 μm to 50 μm. That is, when the base material layer 2 is adjusted to this thickness, it is possible to secure sufficient strength as the exterior material 1 and to reduce the stress during forming such as stretch forming and draw forming, thereby further improving formability. can. A more preferable thickness of the substrate layer 2 is 9 μm to 30 μm. When the base material layer 2 is a multilayer, let total thickness be said thickness. Moreover, when the base material layer 2 is a multilayer, the thickness of the adhesive agent which bonds several layers together is also included in said thickness.

The substrate layer 2 may be formed of a single layer, or may be formed of multiple layers as described above. When forming with multiple layers, for example, multiple layers made of polyester film/polyamide film (multiple layers made of PET film/nylon film, etc.) can be mentioned.

The base material layer 2 is a layer that constitutes the outer layer. In addition to the base material layer 2, the layer that constitutes the outer layer includes a protective layer that is attached to the outside of the base material layer 2 and a layer that constitutes the outer layer. An adhesive layer or the like for bonding can be used.

As the base material layer 2, a heat-resistant resin film that does not melt at the heat-sealing temperature when the exterior material 1 is heat-sealed is used. Specifically, it is preferable to use a resin having a melting point higher by 10° C. or more than all the resins (resin layers 31 to 33) constituting the heat-sealing layer 3, more preferably a resin higher by 20° C. or more.

The metal foil layer 4 is made of aluminum (Al) foil, copper (Cu) foil, stainless steel (SUS) foil, titanium (Ti) foil, or nickel (Ni) foil. A clad material or the like in which metal foil is laminated can be suitably used. Among them, as the metal foil layer 4, an aluminum foil can be preferably used. In particular, an Al—Fe alloy foil containing 0.7% by mass to 1.7% by mass of Fe has excellent strength and ductility, and therefore can obtain good formability.

The thickness of the metal foil layer 4 is preferably set to 20 μm to 100 μm. That is, when the thickness is 20 μm or more, it is possible to prevent the occurrence of pinholes during rolling when manufacturing the metal foil, and when it is 100 μm or less, the stress during forming such as stretch forming and draw forming can be reduced. can improve sexuality.

A base layer is preferably formed on at least one of the inner and outer surfaces of the metal foil layer 4 .

The underlayer can be formed by coating with a silane coupling agent or chemical conversion treatment such as chromate treatment.

The thickness of the underlayer is preferably set to 0.01 μm to 1 μm.

By forming the base layer in this manner, the adhesive strength between the adhesive layers 51 and 52 provided on both the inner and outer surfaces of the metal foil layer 4 can be improved, and peeling of the adhesive layers 51 and 52 can be effectively prevented. can do. Further, the chemical conversion treatment can sufficiently prevent the corrosion of the metal foil surface due to the contents (electrolyte of the battery, etc.).

When the base layer is formed by a chemical conversion coating (chemical conversion coating), the chemical conversion coating may be selected depending on the combination with the adhesive layers 51 and 52. For example, chromic acid coating, chromate phosphate A film by treatment, a film by zinc phosphate treatment, a film by non-chromate treatment using zirconium or titanium as a metal component in place of Cr, and an oxide film by boehmite treatment can be preferably used.

The base material layer 2 is adhered to the outer surface of the metal foil layer 4 with an outer adhesive layer 52 interposed therebetween to be integrally laminated.

The adhesive constituting the outer adhesive layer 52 for bonding the base material layer 2 and the metal foil layer 4 is selected from the group consisting of polyurethane polyols, polyester polyols, polyether polyols, and polyester urethane polyols, for example. A two-liquid curable adhesive or the like composed of a first liquid consisting of one or two or more polyols and a second liquid (curing agent) consisting of isocyanate can be used.

The thickness of this outer adhesive layer is preferably set to 2 μm to 5 μm.

Examples of the adhesive that constitutes the inner adhesive layer 51 provided on the inner surface of the metal foil layer 4 include polyurethane-based resins, acrylic-based resins, epoxy-based resins, polyolefin-based resins, elastomer-based resins, fluorine-based resins, and acid-modified polypropylene resins. Among them, it is particularly preferable to use an adhesive composed of a polyurethane composite resin based on an acid-modified polyolefin.

The thickness of the inner adhesive layer 51 is preferably set to 2 μm to 5 μm.

Also when the outer layer is composed of multiple layers (including the case where the substrate layer is multiple layers), it is preferable to use the same kind of adhesive.

In this embodiment, the heat-sealing layer 3 includes a seal layer 30 provided on the innermost surface (lowest end in FIG. 1) and a metal foil side layer provided on the outermost surface (uppermost end in FIG. 1) outside the seal layer 30. 33 and at least a two-layer structure. The sealing layer 30 itself may be composed of a single layer, or may be composed of a multi-layer structure of two or more layers.

The heat-sealing layer 3 can be composed of, for example, a laminated (multilayer) film obtained by laminating films constituting each layer such as the sealing layer 30 and the metal foil side layer 33 by co-extrusion or the like.

In this embodiment, the heat-sealable layer 3 is composed of a three-layer laminated film. That is, the seal layer 30 in the heat-sealing layer 3 is composed of a first seal layer 31 disposed on the inner surface side and a second seal layer 32 laminated on the outer surface side of the first seal layer 31. By laminating the metal foil side layer 33 on the outer surface side of the sealing layer 30, the heat sealing layer 3 having a three-layer structure as a whole is formed.

In this embodiment, the thickness of the heat-sealable layer 3 is preferably set to 20 μm to 100 μm. That is, if the thickness is less than 20 μm, sufficient insulation cannot be obtained, and if the thickness exceeds 100 μm, the sealing time becomes long and uneconomical.

Furthermore, when the heat-sealing layer 3 has a three-layer structure of the first sealing layer 31, the second sealing layer 32 and the metal foil side layer 33 as in the present embodiment, the thickness of the first sealing layer 31 is set to "T1 , the thickness of the second seal layer 32 as "T2", and the thickness of the metal foil side layer 33 as "T3", it is preferable to establish the following relationship.

T1:T2:T3=(1-3):(4-8):(1-3)
A propylene-ethylene random copolymer (rPP) can be used as the resin forming the sealing layer 30 . Propylene-ethylene random copolymer (rPP) is a propylene-ethylene copolymer (random PP), propylene-butene copolymer (random PP). As random PP, metallocene-based polypropylene (m-PP) polymerized using a metallocene catalyst and Ziegranatta-based polypropylene (zn-PP) polymerized using a Ziegranatta catalyst can be suitably used.

5% to 50% polyolefin elastomer containing linear low-density polyethylene (LLDPE), metallocene-catalyzed LLDPE (m-LLDPE), or ethylene-propylene rubber as a modifier for m-PP and Zn-PP. is preferably added. A more preferable addition amount is 10% to 40%.

The modifier has a lower melting point than the main resin that constitutes the seal layer 30 , and by including this modifier in the seal layer 30 , the softening property of the seal layer 30 can be enhanced. As the modifier, the softening property can be sufficiently improved by using a modifier of a polyolefin compound having a temperature lower than that of rPP by 15°C or more.

When the seal layer 30 is composed of multiple layers, it is preferable that at least one layer contains the modifier, and more preferably the first seal layer 31 contains the modifier.

The base rPP has a melting point of 120° C. to 140° C. calculated by differential scanning calorimetry.

The above rPP has a low sealing strength at 110° C. to 130° C. and the seal is easily removed, and the sealing strength is maintained at a temperature lower than that. When the temperature of the battery manufactured with the exterior material 1 of the present embodiment rises, gas is generated due to volatilization of the electrolyte and the like, and at around 130° C., the internal pressure of the battery rises and the case begins to expand. The above-described temperature range in which the seal strength is lowered corresponds to a temperature higher than the assumed operating temperature range of the battery and lower than the temperature at which expansion begins. Therefore, when the temperature of the battery suddenly rises and the internal pressure starts to rise due to the generation of gas, the seal is broken and the case is opened. When the case is opened, the gas is released gently, preventing the case from bursting or igniting.

The above-mentioned rPP derived from the metacelon catalyst has a highly uniform molecular weight and is highly effective in reducing the seal strength at the intended temperature.

In this embodiment, the melting point of the sealing layer 30 can be adjusted by the mixing ratio of rPP and LLDPE.

In the present embodiment, the second seal layer 32 of the seal layers 30 preferably uses a resin having a higher melting point than the first seal layer 31 . Furthermore, the melting point difference between the first sealing layer 31 and the second sealing layer 32 is preferably set to 5°C to 10°C, more preferably 6°C to 8°C.

Specifically, as the first seal layer 31, the main resin is rPP with a melting point of 110°C to 140°C, preferably 120°C to 130°C. - LLDPE (metallocene-catalyzed linear low-density polyethylene) may be added as a modifier. The amount to be added is preferably adjusted to 5 wt % to 60 wt %, more preferably 10 wt % to 40 wt %. By adding the modifier to the first sealing layer 31 in this way, the softening property of the first sealing layer 31 can be improved.

As the second sealing layer 32, rPP with a melting point of 120°C to 150°C, preferably 125°C to 135°C is used as the main resin, and m-LLDPE with a melting point of 90°C to 110°C is modified to this resin. It is better to add it as a material. The amount to be added is preferably adjusted to 5 wt % to 60 wt %, more preferably 10 wt % to 40 wt %. If the modifier is added to the first seal layer 31, it is not necessarily added to the second seal layer 32, and may not be added.

When the exterior material 1 has a plurality of seal layers, when the battery exterior case is manufactured, the heat-sealed portion between the first seal layers 31 of the two heat-sealed exterior materials 1 is heat-fused so that the case can be unsealed. The adhesive layer 3 is preferably designed so that delamination of the heat-sealable layer 3 does not occur before the seal between the first sealing layers 31 is broken. If delamination occurs in the heat-sealable layer 3, it may be difficult for the gas generated inside the battery to escape in a high-temperature environment.

As the sealing layer 30 (the first sealing layer 31 and the second sealing layer 32), those having a melt flow rate (MFR) of 0.5 to 20, preferably 1 to 10, more preferably 2 to 8 should be used. That is, when the sealing layer 30 having the MFR in the above range is used, the sealing layer is easily crushed during heat sealing and is not crushed excessively. can. The sealing layer 30 having the MFR in the above range mixes with the mating sealing layer after sealing, molecules diffuse between each other, and a strong adhesive force is maintained at room temperature, and cohesive peeling occurs when unsealing.

The modifier contained in the seal layer 30 has a value equal to or close to the MFR of the resin constituting the seal layer 30, specifically a modifier with an MFR of 2 to 8. preferably. By including this modifying material in the seal layer 30, the dispersibility of the modifying material in the resin is improved, and the modifying material can be uniformly dispersed.

Since the first sealing layer 31 has a low melting point, the amount of heat required for melting is reduced. Therefore, even if the heat is taken away by the electrolytic solution contaminating the sealing part, the electrolytic solution is pushed out and the sealing performance is improved. can be made

The elastomer or plastomer as a modifier contained in the second seal layer 32 swells with the electrolytic solution, and can suppress the penetration of the electrolytic solution into the metal foil side layer 33 . In particular, when the thickness of the second seal layer 32 is large, the effect of suppressing permeation of the electrolytic solution can be sufficiently obtained.

As will be described in detail later, the heat-sealing layer 3 has properties peculiar to the present invention when the sealing layers 30 are heat-sealed.

Polypropylene random copolymer (rPP), polypropylene block copolymer (bPP), homopropylene (hPP), and the like can be suitably used as the resin constituting the metal foil side layer 33 . By forming the metal foil side layer 33 from an ethylene-propylene random copolymer, a strong bonding force to the metal foil layer 4 can be obtained.

As the metal foil side layer 33, a resin having a melting point of 140° C. or higher is preferably used, more preferably a resin having a melting point of 160° C. or lower, still more preferably a resin having a melting point of 150° C. or lower, and even more preferably a resin having a melting point of 145° C. or lower. is good.

Specifically, as the metal foil side layer 33, the main resin is rPP with a melting point of 130° C. to 150° C., preferably 135° C. to 145° C., and a PO elastomer with a melting point of 130° C. or higher is added to this resin. It is good to add it as a modifier. The addition amount is preferably adjusted to 10 wt % to 30 wt %, more preferably 15 wt % to 25 wt %. By adding an elastomer to the metal foil side layer 33, flexibility is obtained and the adhesive strength with the inner adhesive layer 51 is improved. If the amount of the modifier added is too large, the resistance to the electrolyte will be poor, and if it is too small, sufficient flexibility will not be obtained.

Further, in this embodiment, an intermediate layer may be formed between the seal layer 30 and the metal foil side layer 33 . The intermediate layer may be a propylene homopolymer, a copolymer containing propylene or a copolymer component other than propylene as a copolymer component, or a mixture of a plurality of types of polymers. In particular, the intermediate layer is preferably composed of block polypropylene (bPP film). Also, if the intermediate layer contains the same propylene-based resin as the seal layer 30, the adhesion between the seal layer 30 and the intermediate layer is improved. Also, the intermediate layer may be either a single layer or multiple layers. Furthermore, by forming an intermediate layer, electrical insulation and impact resistance can be improved.

As the metal foil side layer 33, one having an MFR of 3 to 15, preferably 5 to 8, is used. That is, the metal foil side layer 33 has a higher melting point than the sealing layer 30 and a higher MFR than the sealing layer 30, so that it flows more easily than the sealing layer 30, and the sealing time can be shortened.

The modifier contained in the metal foil side layer 33 has a value equivalent to or close to the MFR of the resin constituting the seal layer 30, specifically a modifier with an MFR of 2 to 8. , more preferably 5 to 8 modifiers are used. By including this modifier in the metal foil side layer 33, the dispersibility of the modifier in the resin is improved, and the modifier can be uniformly dispersed.

Further, in the present embodiment, it is preferable that the seal layer 30 of the thermal fusion layer 3, particularly the first seal layer 31, contains a lubricant.

Examples of the lubricant include saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylolamides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, fatty acid ester amides, and aromatic bisamides.

Examples of saturated fatty acid amides include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide.

Examples of unsaturated fatty acid amides include oleic acid amide and erucic acid amide.

Examples of substituted amides include N-oleyl palmitic acid amide, N-stearyl stearic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide and N-stearyl erucic acid amide.

Furthermore, methylolamide can be exemplified by methylol stearamide.

Furthermore, saturated fatty acid bisamides include methylenebisstearic acid amide, ethylenebiscapric acid amide, ethylenebislauric acid amide, ethylenebisstearic acid amide, ethylenebishydroxystearic acid amide, ethylenebisbehenic acid amide, hexamethylenebisstearic acid amide. , hexamethylenebisbehenamide, hexamethylenehydroxystearic acid amide, N,N'-distearyladipic acid amide, N,N'-distearylsebacic acid amide.

Examples of unsaturated fatty acid bisamides include ethylenebisoleic acid amide, ethylenebiserucic acid amide, hexamethylenebisoleic acid amide, N,N'-dioleyladipic acid amide, and N,N'-dioleylsebacic acid amide. can do.

Further examples of fatty acid ester amides include stearamide ethyl stearate.

Furthermore, examples of aromatic bisamides include m-xylylenebisstearic acid amide, m-xylylenebishydroxystearic acid amide, and N,N'-stearylisophthalic acid amide.

Further, in this embodiment, it is preferable to add an anti-blocking agent (AB agent) to the sealing layer 30 .

As the anti-blocking agent, acrylic resin beads, aluminum silicate, calcium carbonate, barium carbonate, titanium oxide, talc, kaolin and the like can be preferably used.

Furthermore, as the antiblocking agent, one having an average particle size of 0.1 μm to 10 μm is preferably used, and one having an average particle size of 1 μm to 5 μm is more preferably used.

Furthermore, it is preferable to set the amount of the antiblocking agent added to 100 ppm to 5000 ppm by mass.

By incorporating an anti-blocking agent (particles) into the first sealing layer 31 of the heat-sealing layer 3, minute projections are formed on the surface of the first sealing layer 31, and the contact area between the films is reduced, thereby reducing the contact area between the sealing films. Blocking can be suppressed. In addition, by incorporating an anti-blocking agent (particles) together with the above lubricant, slipperiness during molding can be further improved.

The power storage device exterior material 1 of the present embodiment configured as described above is formed into a predetermined shape by cold forming such as deep drawing or stretch forming as it is in a sheet form, or as required. It is used as an exterior case for an electricity storage device.

For example, FIGS. 2 and 3 are a sectional view and an exploded perspective view showing an electricity storage device 6 manufactured using the exterior material 1 of this embodiment. As shown in both figures, this electric storage device 6 is a lithium ion secondary battery. In this embodiment, an exterior case 65 is composed of a tray member 64 obtained by molding the exterior material 1 and a lid member 60 made of the planar (sheet-like) exterior material 1 . Thus, a substantially rectangular parallelepiped electricity storage device main body (electrochemical element or the like) 61 is accommodated in the accommodation recess of the tray member 64 obtained by molding the exterior material 1 of the present invention. On top of this, the lid member 60 (armor material 1) of the present invention is arranged with the heat sealing layer 3 side facing inward (lower side), and the heat sealing layer 3 at the outer peripheral edge of the lid member 60 The sealing layer 30 (first sealing layer 31) and the sealing layer 30 (first sealing layer 31) of the heat-sealing layer 3 in the flange portion (sealing peripheral edge portion) 641 of the tray member 64 are heat-sealed and joined together. Then, the sealing layers 30 (the first sealing layers 31) are heat-sealed and joined together to form the electricity storage device 6. As shown in FIG. The inner surface of the accommodation recess of the tray member 64 is the heat-sealing layer 3 , and the outer surface of the accommodation recess is on the substrate layer 2 side.

In FIG. 2, reference numeral "69" denotes a heat-sealed portion where the outer peripheral edge of the lid member 60 and the flange (sealing peripheral edge) 641 of the tray member 64 are joined (welded). In addition, in the electricity storage device 6, the tip of the tab lead connected to the electricity storage device main body 61 is led out to the outside of the outer case 65, but the illustration is omitted.

The power storage device main body 61 is not particularly limited, but examples thereof include a battery main body, a capacitor main body, and a capacitor main body.

Here, in the present embodiment, when the heat-sealing layers 3 of the exterior material 1 are heat-sealed under the heat-sealing conditions of a temperature of 180° C., a pressure of 0.3 MPa, and a time of 4 seconds, the heat-sealing layer before heat-sealing The ratio of the thickness (remaining thickness) of the heat-sealing layer 3 after heat sealing to the thickness (original thickness) of the heat-sealing layer 3 is adjusted to be 40% to 80%.

In other words, when the heat-sealing layers 3 of the two exterior materials 1 are heat-sealed, the thickness of the heat-sealing layer 3 of the exterior material 3 on one side (one sheet) before heat-sealing is defined as "d0", Assuming that the total thickness (total thickness) of the heat-sealing layer 3 in which the exterior materials 3 on both sides (two sheets) are fused after heat sealing is "d1", the following relational expression is established. .

Post-sealing residual rate (%) = d1/(2 x d0) x 100
In the electricity storage device of the present embodiment, since the post-sealing residual ratio of the heat-sealing layer 3 is set within the specific range described above, resin pooling is likely to occur in the heat-sealed portion. The sealing performance of is improved. Therefore, it is possible to reliably adjust the seal strength under normal temperature atmosphere to a desired value, which will be described later.

Further, in the present embodiment, when the seal layers 30 of the exterior material 1 are heat-sealed together, the seal strength at the heat-sealed portions of both seal layers 30 under a normal temperature (25° C.) atmosphere is defined as “Pn”, and the 130° C. atmosphere It is necessary to establish the following relational expressions (1) and (2) assuming that the lower seal strength is "Pb".

Pn≧50N/15mm (1)
Pb≤10N/15mm (2)
Furthermore, in the present embodiment, it is preferable to adjust the seal strength Pn under normal temperature to 60 N/15 mm or more, preferably 80 N/15 mm or more, and more preferably 100 N/15 mm or less.

In the electricity storage device of the present embodiment, since the seal strength at normal temperature and 130° C. is set within the above specific range, the heat sealing portion sufficiently maintains the sealing (sealing) property at normal temperature and low temperature, When the internal pressure rises and reaches a high temperature range, the sealing strength decreases, so that gas is efficiently vented at high temperatures, and the pressure and temperature decrease to reliably prevent problems such as ignition.

Further, in the present embodiment, it is preferable to establish the following relational expressions (3) and (4) with the seal strength under the atmosphere of 100° C. being “Pa”.

Pa≧20N/15mm (3)
Pa−Pb=20N/15mm to 60N/15mm (4)
Furthermore, in the present embodiment, the seal strength Pa under an atmosphere of 100° C. is preferably adjusted to 35 N/15 mm or more, still more preferably 40 N/15 mm or more, and still more preferably 50 N/15 mm or less.

In the present embodiment, the seal strength difference (Pa-Pb) at 100°C and 130°C is more preferably adjusted to 30 N/15 mm or more, even more preferably 40 N/15 mm or more, and still more preferably 55 N/15 mm or less. is good.

In the electricity storage device of the present embodiment, the seal strength at a high temperature of 130° C. and the seal strength at a slightly high temperature of 100° C. are specified in association with each other. Since the heat-sealed portion gradually softens and is gradually unsealed, the gas can be smoothly released, thereby reliably preventing unexpected rapid gas release and bumping of the electrolytic solution due to adverse effects thereof.

For example, in the graph showing the relationship between the seal strength and the ambient temperature in FIG. ) to (4) and is a seal layer resin unique to the present invention, and the seal layer resin of curves C3 to C6 indicated by broken lines is any of the above relations (1) to (4) and deviates from the gist of the present invention.

In addition, in this embodiment, since the metal foil side layer 33 having a high melting point exists on the outside of the sealing layer 30 in the heat sealing layer 3, the sealing layer 30 inside the metal foil side layer 33 at a high temperature. It becomes unsealed in position, ie in the desired heat-sealed position. For this reason, the degree of gas release can be controlled accurately, and from this point as well, it is possible to reliably prevent an unexpected outbreak of gas.

In the electricity storage device of the present embodiment, the seal layer 30 is composed of the first seal layer 31 and the second seal layer 32 having different melting points. When the first seal layer 31 and the second seal layer 32 are formed, the thickness is set to 24 μm or more and the seal layer 30 is thickened, so that a large resin pool can be formed. Formation of this resin reservoir can further improve the sealing performance (sealing performance) at room temperature.

In addition, in the electricity storage device of the present embodiment, since the seal layers 30 of the heat-sealed portion are diffused and firmly attached to each other, the resin is gradually softened by the modifier when the temperature inside the battery reaches around 100°C. It becomes easy to cohesive failure by. Since the heat-sealed portion undergoes cohesive failure (cohesive peeling) at high temperatures, the position at which gas is released can be reliably controlled at the heat-sealed portion, and rapid gas release can be more reliably avoided.

In addition, in the exterior material 1 of the present embodiment, when a lubricant is added to the inner surface side of the heat-sealable layer 3, the slipperiness with respect to a molding jig such as a molding die can be further improved, and stable Good moldability can be obtained more reliably.

In addition, in the electricity storage device of the present embodiment, there is no need to separately attach other parts such as a pressure relief valve for gas release at high temperatures, so the number of parts can be reduced and productivity can be improved accordingly.

In the above-described embodiment, the exterior case 65 is composed of the tray member 64 obtained by molding the exterior material 1 and the planar lid member 60. However, in the present invention, such a combination is particularly applicable. For example, the exterior case 65 may be composed of a pair of planar (sheet-shaped) exterior materials 1, or a pair of tray members 64 may be superimposed in a facing state. It may be configured as follows.

1. Preparation of film for heat sealing layer <Example 1>
As shown in Tables 1 to 3, co-extrusion using a T-die so that two layers of the film for the seal layer (first seal layer) and the film for the metal foil side layer disposed on the outer surface side are laminated. As a result, a 30 μm-thick film for a heat-sealable layer (sealant layer) in which the metal foil side layer was laminated on the sealing layer was obtained.

In this laminated film, the first sealing layer is composed of a propylene-ethylene random copolymer (rPP: melting point = 125°C, melt flow rate (MFR) = 7) and linear low-density polyethylene (m -LLDPE: Melting point 108°C, MFR = 2.5) is added to 30 wt% of the total amount, and 1000 ppm of erucamide (lubricant) and 2000 ppm of silica particles (anti-blocking agent: AB agent) are added. A seal layer film having a thickness of 24 μm was used. The MFR of the sealing layer (base) rPP was measured under the conditions of polypropyne (PP), and the MFR of the additive was measured under the conditions of polyethylene (PE) (the same applies to the following examples and comparative examples). .

The metal foil side layer is composed of ethylene-propylene random copolymer (rPP: melting point = 142°C, MFR = 7.5) and polyolefin elastomer (melting point = 142°C, MFR = 6) at 20 wt% of the total amount. A metal foil side layer film having a thickness of 6 μm and containing 1000 ppm of erucamide (lubricant) and 2000 ppm of silica particles (antiblocking agent) was used. The MFR of the rPP of the metal foil side layer (base) was measured under the condition of polypropyne (PP), and the MFR of the additive was measured under the condition of polyethylene (PE) (the same applies to the following examples and comparative examples). ).

Further, in the first embodiment, since the sealing layer is composed only of the first sealing layer that does not include the second sealing layer, it can be considered that the first sealing layer constitutes the entire sealing layer. The same applies to Examples 2 to 9 and Comparative Example 2).

<Examples 2 to 9>
Using the sealing layer (first sealing layer) film and the metal foil side layer film having the components shown in Tables 1 to 3, heat melting of Examples 2 to 9 with a two-layer structure was performed in the same manner as in Example 1 above. A layering film was produced.

Lubricants and anti-blocking agents are contained in the same manner as in Example 1 (the same applies to Comparative Example 2).

<Example 10>
As shown in Tables 1 to 3, the first sealing layer film, the second sealing layer film arranged on the outer surface side thereof, and the metal foil side layer arranged on the outer surface side of the second sealing layer film A film for the heat-sealable layer was obtained by co-extrusion in the same manner as in Example 1 so that three layers of the film for the heat-sealable layer were laminated.

In this laminated film, the film for the first seal layer is the same as in Example 1, except that the thickness is 6 μm. Further, as the film for the second sealing layer, rPP having a melting point of 125° C. and a thickness of 18 μm with an MFR of 7 and containing 1000 ppm of erucamide (lubricant) without adding any modifier was used. Furthermore, the film for the metal foil side layer is the same as in Example 1. The MFR of rPP of the second seal layer was measured under the conditions of PP (the same applies to the following examples and comparative examples).

The sealing layer in the heat sealing layer of Example 10 is composed of two layers, a first sealing layer and a second sealing layer, so that the entire heat sealing layer has a three-layer structure (see below for implementation). The same applies to Examples 11 to 24 and Comparative Example 1).

<Examples 11 to 24>
Using the first sealing layer film, the second sealing layer film and the metal foil side layer film having the components shown in Tables 1 to 3, Examples 11 to 24 with a three-layer structure were used in the same manner as in Example 10 above. was produced. The MFR as an additive for the second seal layer was measured under PE conditions (the same applies to the following examples and comparative examples).

Lubricants and antiblocking agents are contained in the same manner as in Example 10 (the same applies to Comparative Example 1).

<Comparative Examples 1 and 3>
Using the first sealing layer film, the second sealing layer film, and the metal foil side layer film having the components shown in Tables 1 to 3, the heat treatment of Comparative Example 1 having a three-layer structure was performed in the same manner as in Example 10 above. A film for the adhesive layer was produced.

<Comparative Example 2>
Using the sealing layer (first sealing layer) film and the metal foil side layer film having the components shown in Tables 1 to 3, the heat sealing layer of Comparative Example 2 having a two-layer structure was used in the same manner as in Example 1 above. A film for

2. Fabrication of Exterior Material for Electricity Storage Device Both sides of a 35 μm thick aluminum foil (A8079) as the metal foil layer 4 were coated with a chemical conversion treatment liquid containing polyacrylic acid, a trivalent chromium compound, water and alcohol, and then heated at 150°C. An aluminum foil having a chemical conversion film formed on both sides was prepared by drying. The amount of chromium adhered by this chemical conversion film was 5 mg/m ² on one side.

Next, a biaxially stretched 6 nylon (ONy ) The film was dry-laminated (bonded together).

Next, the outer surface of the metal foil side layer of the film for the heat sealing layer prepared in the above Examples and Comparative Examples is attached to the aluminum foil after the dry lamination (metal foil layer), and sandwiched between a rubber nip roll and a lamination roll heated to 100°C for dry lamination, followed by aging at 40°C for 10 days. By heating (heating), exterior materials for power storage devices of Examples 1 to 24 and Comparative Examples 1 to 3 were obtained.

3. Evaluation test for each exterior material <Residual rate after sealing>
At room temperature (25° C.), two specimens each having a width of 15 mm and a length of 150 mm were cut out from the exterior material of each example and each comparative example, and then these two specimens were brought into contact with each other at their inner sealant layers. Using a heat sealer (TP-701-A) manufactured by Tester Sangyo Co., Ltd., heat seal temperature: 180 ° C., seal pressure: 0.3 MPa (gauge display pressure), seal time : Heat-sealing was performed by heating one side under heat-sealing conditions for 4 seconds to prepare a sealed exterior material (test sample) in which the inner heat-sealable layers were heat-sealed to each other.

This sealed specimen was observed with a cross-sectional SEM, and the total thickness (residual thickness: d1) of the two heat-sealable layers was measured. Assuming that the thickness (original thickness) of one layer (one sheet) of the specimen before sealing is "d0", the post-sealing residual rate (%) was measured from the following relational expression.

Post-sealing residual rate (%) = d1/(2 x d0) x 100
Table 4 shows the results.

<Room temperature seal strength>
In the same manner as in the measurement of the seal residual rate, test specimens were cut out from the exterior materials of each example and each comparative example and heat-sealed to prepare sealed exterior materials (test specimens) for room temperature tests.

For this sealed exterior material (test piece) for the normal temperature test, the exterior material (test piece) is heat-sealed using a strograph (AGS-5kNX) manufactured by Shimadzu Access Co., Ltd. in accordance with JIS Z0238-1998. The peel strength when the inner heat-sealing layers (sealant layers) were T-separated at a tensile speed of 100 mm/min was measured, and this was defined as the normal temperature seal strength (N/15 mm width). Table 4 shows the results.

<High temperature (100°C and 130°C) seal strength>
In the same manner as described above, test specimens were cut out from the exterior material of each example and each comparative example, heat-sealed, and a sealed exterior material (test body) for the 100°C test and a sealed exterior material for the 130°C test. An exterior material (test body) was produced.

Next, each test piece was left to stand in an environment of 100°C and 130°C for 24 hours, and in the same environment as above, the sealed exterior material (test piece) was heated to 100°C and 130°C in the same manner as above. The peel strength was measured and taken as the high temperature (100° C. and 130° C.) seal strength (N/15 mm width). Table 4 shows the results.

The “strength difference (Pa−Pb)” in Table 4 is the value obtained by subtracting the seal strength “Pb” at 130° C. atmosphere from the seal strength “Pa” at 100° C. atmosphere.

<Determination of peeling state>
The delamination state of the exterior material of each example and comparative example was determined based on visual observation and observation of the layer where delamination started by cross-sectional SEM. Table 4 shows the results.

<Melting point of resin (seal layer)>
The melting point of the seal layer of each test piece cut out from the exterior material of each example and comparative example was measured using differential scanning calorimetry (DSC) based on JIS K7121. Table 4 shows the results.

<Opening test>
A test piece with a width of 100 mm and a length of 200 mm was cut out from the exterior material of each example and comparative example, folded at the center in the length direction so that the heat sealing layers faced each other, and a heat sealing device manufactured by Tester Sangyo Co., Ltd. ( TP-701-A), heat sealing temperature: 180 ° C., sealing pressure: 0.3 MPa (gauge display pressure), sealing time: 4 seconds, sealing width: 5 mm. Two sides were heat-sealed to prepare a bag-like specimen (armoring material) with one side open facing the folded portion.

After 2.0 g of water was added to this bag-shaped specimen, the opening was sealed under the same sealing conditions as above to obtain a sealed sample.

Each sealed sample was placed in an oven, heated from 25° C. to 130° C. at a heating rate of 5° C./min, held for 30 minutes after reaching 130° C., and the state of the sealed sample was observed. Based on the observation, the openability was evaluated according to the following criteria. Table 4 shows the results.

A: The package was opened while the temperature was rising from 100°C to 130°C, and the gas slowly escaped.

B: The gas did not escape while the temperature was raised to 130°C, but the gas gradually escaped while the temperature was maintained at 130°C.

C: The package was opened while the temperature was rising from 100°C to 130°C, and gas suddenly escaped.

X: The package was not opened even during the holding at 130°C.

Y: Opened while the temperature was rising to 100°C.

<General comments>
As shown in Table 4, the exterior materials of Examples related to the present invention were evaluated excellently in the opening test, and sufficient sealing strength at room temperature could be ensured. On the other hand, the outer packaging material of the comparative example, which deviates from the gist of the present invention, was inferior in the evaluation of the opening test.

This application claims the priority of Japanese Patent Application No. 2021-189819 filed on November 24, 2021, and the disclosure content thereof constitutes a part of this application as it is. .

The exterior material for an electricity storage device of the present invention is used for batteries and capacitors used in mobile devices such as smartphones and tablets, hybrid vehicles, electric vehicles, wind power generation, solar power generation, and batteries and capacitors used for storing nighttime electricity. It can be suitably used when manufacturing an electric storage device such as.

1: Exterior material 2: Base material layer 3: Thermal adhesive layer 30: Seal layer 31: First seal layer 32: Second seal layer 33: Metal foil side layer 4: Metal foil layer 6: Electricity storage device 61: Device body Part 65: Exterior case 69: Heat seal part

Claims (8)

A metal foil layer, a base layer made of resin provided on the outer surface side of the metal foil layer, and a heat-sealing resin made of a heat-sealing resin provided on the inner surface side of the metal foil layer for heat sealing. a layer, wherein the heat sealing layer includes a sealing layer arranged on the innermost surface thereof, and a metal foil side layer arranged on the outer surface side of the sealing layer, wherein
The residual rate of the thickness of the thermal adhesive layer after heat sealing under the conditions of temperature 180° C., pressure 0.3 MPa, and time 4 s is adjusted to 40% to 80%,
In the state where the seal layers are heat-sealed, the seal strength at the heat-sealed portion between the seal layers under a normal temperature atmosphere is "Pn", and the seal strength under an atmosphere of 130 ° C. is "Pb",
Pn≧50N/15mm
Pb≤10N/15mm
An exterior material for an electricity storage device, characterized in that it is configured so that the relationship of Assuming that the seal strength at the heat-sealed portion between the seal layers under an atmosphere of 100°C is "Pa",
Pa≧20N/15mm
Pa-Pb = 20N/15mm to 60N/15mm
2. The exterior material for an electricity storage device according to claim 1, which is configured so that the relationship of is established. The exterior material for an electricity storage device according to claim 1 or 2, wherein the metal foil side layer has a melting point of 140°C or higher. 3. The power storage device exterior material according to claim 1, wherein the seal layer includes a first seal layer and a second seal layer laminated on the outer surface side thereof and having a melting point different from that of the first seal layer. Equipped with the exterior material according to claim 1 or 2,
An exterior case for an electricity storage device, wherein the sealing layers are heat-sealed to each other. 6. The electric storage device exterior case according to claim 5, wherein the heat-sealed portion between the seal layers is cohesive and peeled off as the internal pressure increases. an electricity storage device main body;
and the exterior case according to claim 5,
An electricity storage device, wherein the electricity storage device main body is enclosed in the exterior case. an electricity storage device main body;
and the exterior material according to claim 1 or 2,
An electricity storage device, wherein the electricity storage device body is covered with the exterior material.

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