Exterior material for power storage device, exterior case for power storage device, power storage device, and composition for heat-fusible resin layer formation of the exterior material for power storage device

Abstract

To provide an exterior material for a power storage device which prevents the thickness of a heat-fusible resin layer from becoming too thin in pressurization of heat fusion, while maintaining adhesion to a barrier layer of the heat-fusible resin layer.SOLUTION: An exterior material for a power storage device includes a base material layer, a barrier layer, and a heat-fusible resin layer in this order, wherein the heat-fusible resin layer contains a first heat-fusible resin layer and a second heat-fusible resin layer in this order from the side of the barrier layer, the second heat-fusible resin layer contains non-molten particles, and the average particle diameter of the non-molten particles is 30% to 60% of the thickness of the second heat-fusible resin layer.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to an exterior material for a power storage device, an exterior case for a power storage device, a power storage device, and a composition for forming a heat-sealable resin layer of an exterior material for a power storage device.

Background Art

[0002] Power storage devices are used as energy suppliers for mobile devices such as electric vehicles and hybrid vehicles, and for portable devices such as power tools and mobile terminals. Conventionally, metal cans have been mainly used as the casings of power storage devices. However, in order to facilitate movement and carrying, weight reduction and miniaturization of power storage devices are required. Therefore, as the casing of a power storage device, an exterior material (also referred to as a laminate material) having a base material layer, a barrier layer, and a heat-sealable resin layer (also referred to as a sealant layer) in this order is often used. The above-mentioned exterior material is arranged so that the heat-sealable resin layers face each other, sandwiches the main body of the power storage device, and heat-seals the heat-sealable resin layers at the outer edge of the exterior material, thereby accommodating and enclosing the main body of the power storage device in the exterior member (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When heat-sealing the heat-sealable resin layers, it has been found that the thickness of the melted heat-sealable resin layer may become thinner than necessary in order to press the exterior material in the thickness direction from the viewpoint of ensuring airtightness. If the thickness of the heat-sealable resin layer becomes too thin, the insulating function of the heat-sealable resin layer may be impaired.

[0005] An object of the present disclosure is to provide an exterior material for a power storage device that maintains the adhesiveness of a heat-sealable resin layer to a barrier layer and does not cause the thickness of the heat-sealable resin layer to become too thin during the pressure application of heat-sealing. Another object of the present disclosure is to provide an exterior case for a power storage device and a power storage device using this exterior material for a power storage device. Further, an object of the present disclosure is to provide a composition for forming the heat-sealable resin layer of this exterior material for a power storage device.

Means for Solving the Problems

[0006] The present disclosure includes the following embodiments. <1> It includes a base material layer, a barrier layer, and a heat-sealable resin layer in this order. The heat-sealable resin layer includes a first heat-sealable resin layer and a second heat-sealable resin layer in order from the barrier layer side. The second heat-sealable resin layer contains non-molten particles, and the average particle diameter of the non-molten particles is 30% to 60% of the thickness of the second heat-sealable resin layer. An exterior material for a power storage device. <2> The exterior material for a power storage device according to <1>, wherein the non-molten particles contain inorganic particles. <3> The exterior material for a power storage device according to <1> or <2>, wherein the average particle diameter of the non-molten particles is 10 μm to 30 μm. <4> The exterior material for a power storage device according to any one of <1> to <3>, wherein the proportion of the non-molten particles in the second heat-sealable resin layer is 1,000 mass ppm to 30,000 mass ppm. <5> The exterior material for a power storage device according to any one of <1> to <4>, wherein the thickness of the second heat-sealable resin layer is 40% to 90% of the total thickness of the heat-sealable resin layer. <6> The exterior material for a power storage device according to any one of <1> to <5>, wherein the heat-sealable resin layer is composed of three or more layers. <7> An exterior case for a power storage device, which is a molded body of the exterior material for a power storage device according to any one of <1> to <6>. <8> A power storage device main body portion, An exterior member including the exterior material for a power storage device according to any one of <1> to <6>. A power storage device, wherein the power storage device main body is externally covered with the exterior member. <9> A composition for forming a heat-sealable resin layer of an exterior material for a power storage device, containing a heat-sealable resin and non-fused particles having an average particle diameter of 10 μm to 30 μm.

Advantages of the Invention

[0007] According to the present disclosure, there is provided an exterior material for a power storage device that maintains the adhesiveness of the heat-sealable resin layer to the barrier layer and does not excessively reduce the thickness of the heat-sealable resin layer during heat-sealing pressurization. Further, the present disclosure provides an exterior case for a power storage device and a power storage device using this exterior material for a power storage device. Further, the present disclosure provides a composition for forming a heat-sealable resin layer of this exterior material for a power storage device.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present disclosure will be described in detail. However, the embodiments of the present disclosure are not limited to the following embodiments. In the following embodiments, the components (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values and their ranges, which do not limit the embodiments of the present disclosure. In the present disclosure, in the numerical range indicated by "~", the numerical values described before and after "~" are included as the minimum value and the maximum value, respectively. In the numerical ranges described stepwise in the present disclosure, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another numerically described stepwise range. Also, in the numerical ranges described in the present disclosure, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples. In the present disclosure, each component may contain a plurality of corresponding substances. When there are a plurality of substances corresponding to each component in the composition, the content rate or content of each component means the total content rate or content of the plurality of substances present in the composition, unless otherwise specified. In the present disclosure, the particles corresponding to each component may contain a plurality of types. When there are a plurality of types of particles corresponding to each component in the composition, the particle diameter of each component means a value for the mixture of the plurality of types of particles present in the composition, unless otherwise specified. In the present disclosure, the term "layer" includes not only the case where it is formed over the entire region where the layer exists when observing the region where the layer exists, but also the case where it is formed only in a part of the region.

[0010] When describing the embodiments in the present disclosure with reference to the drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. Also, the sizes of the members in each drawing are conceptual, and the relative size relationships between the members are not limited thereto.

[0011] In the present disclosure, the thickness of each layer can be measured by a scanning electron microscope (SEM). The thickness in the present disclosure is taken as the average value when measuring at five locations. In the present disclosure, the "non-melting particles" refer to particles that do not melt at the general heating temperature of thermal fusion, which is 200°C.

[0012] <Outer packaging material for power storage device> The outer packaging material for a power storage device of the present disclosure (hereinafter, may be abbreviated as "outer packaging material") includes a base material layer, a barrier layer, and a heat-sealable resin layer in this order. The heat-sealable resin layer includes a first heat-sealable resin layer and a second heat-sealable resin layer in order from the barrier layer side. The second heat-sealable resin layer contains non-melting particles, and the average particle diameter of the non-melting particles is 30% to 60% with respect to the thickness of the second heat-sealable resin layer.

[0013] The outer packaging material having the above configuration maintains the adhesiveness (laminability) of the heat-sealable resin layer to the barrier layer, and the thickness of the heat-sealable resin layer does not become too thin under the pressure of thermal fusion. In the heat-sealable resin layer, the first heat-sealable resin layer disposed on the barrier layer side is provided as a layer that functions for laminability. Non-melting particles are contained in the second heat-sealable resin layer disposed on the side farther from the barrier layer than the first heat-sealable resin layer. These non-melting particles do not melt during thermal fusion and maintain their size even when heated by thermal fusion. Since the average particle diameter of the non-melting particles is 30% or more with respect to the thickness of the second heat-sealable resin layer, the non-melting particles function as spacers, and it is suppressed that the thickness of the heat-sealable resin layer becomes too thin under the pressure of thermal fusion. Also, since the average particle diameter of the non-melting particles is 60% or less with respect to the thickness of the second heat-sealable resin layer, the laminability is maintained.

[0014] The evaluation of the degree to which the thickness of the heat-sealable resin layer becomes thin under the pressure of thermal fusion can be carried out by a heat seal tester device under the conditions of a heating temperature of 150 to 220°C and a pressure of 0.1 to 0.5 MPa. It is preferable that the thickness of the heat-sealable resin layer after the pressure of thermal fusion is maintained at 40% or more, more preferably 50% or more, and even more preferably 60% or more, with respect to the thickness of the heat-sealable resin layer before the pressure of thermal fusion.

[0015] FIG. 1 is a schematic cross-sectional view showing an example of an exterior material for a power storage device. With reference to FIG. 1, an example of the layer structure of the exterior material for a power storage device will be described. The exterior material 1 for a power storage device includes a base material layer 2, a barrier layer 4, and a heat-sealable resin layer 3 in this order.

[0016] The heat-sealable resin layer 3 includes a first heat-sealable resin layer 7 and a second heat-sealable resin layer 8 in order from the barrier layer 4 side. The heat-sealable resin layer 3 may be composed of three or more layers. For example, as shown in FIG. 1, a third heat-sealable resin layer 9 may be further disposed on the surface of the second heat-sealable resin layer 8 opposite to the barrier layer 4.

[0017] In FIG. 1, the base material layer 2 is provided on one surface of the barrier layer 4 via a first adhesive layer 5. Also, in FIG. 1, the heat-sealable resin layer 3 is provided on the other surface of the barrier layer 4 via a second adhesive layer 6.

[0018] FIG. 2 is a schematic cross-sectional view showing a first embodiment of the heat-sealable resin layer 3. The heat-sealable resin layer 31 shown in FIG. 2 has a two-layer structure and includes a first heat-sealable resin layer 71 and a second heat-sealable resin layer 81. The second heat-sealable resin layer 81 contains non-molten particles 10.

[0019] From the viewpoint of ensuring insulation, the total thickness of the heat-sealable resin layer 31 is preferably 20 μm or more, and preferably 25 μm or more. Also, from the viewpoints of weight reduction and thinning, the thickness of the heat-sealable resin layer 31 is preferably 100 μm or less, and more preferably 80 μm or less.

[0020] From the viewpoint of suppressing the thickness of the heat-sealable resin layer 31 from becoming too thin during heat-sealing pressure, the thickness of the second heat-sealable resin layer 81 containing the non-molten particles 10 is preferably 40% or more, more preferably 50% or more, and even more preferably 55% or more with respect to the total thickness of the heat-sealable resin layer 31. Further, from the viewpoint of ensuring the sealing property of the heat-sealable resin layer, the thickness of the second heat-sealable resin layer 81 is preferably 90% or less, more preferably 80% or less, and even more preferably 70% or less with respect to the total thickness of the heat-sealable resin layer 31.

[0021] The non-molten particles 10 may be any non-molten particles, and may be inorganic particles, organic particles, metal particles, composite particles thereof, etc. From the viewpoint of suppressing deformation due to heat during heat melting, the non-molten particles 10 are preferably inorganic particles, metal particles, or composite particles thereof. From the viewpoints of further ensuring the insulating function of the heat-sealable resin layer 3 and weight reduction, the non-molten particles 10 are preferably inorganic particles, organic particles, or composite particles thereof. From these comprehensive viewpoints, the non-molten particles 10 more preferably contain inorganic particles. The non-molten particles 10 may be used alone or in combination of two or more.

[0022] Examples of the inorganic particles include inorganic oxide particles (such as silica particles, alumina particles, titanium oxide particles, etc.), inorganic carbonate particles (such as calcium carbonate particles, barium carbonate particles, etc.), inorganic silicate particles (such as aluminum silicate particles, talc particles, kaolin particles, etc.).

[0023] Examples of the organic particles include acrylic resin particles, polyolefin resin particles (such as polyethylene resin particles, polypropylene resin particles, etc.), polystyrene resin particles, etc.

[0024] Examples of the metal particles include aluminum particles, etc.

[0025] The average particle diameter of the non-molten particles 10 is 30% to 60% with respect to the thickness of the second heat-fusible resin layer 81, preferably 40% to 60%, and more preferably 50% to 60%. Specifically, the average particle diameter of the non-molten particles 10 is preferably 5 μm to 30 μm, more preferably 10 μm to 30 μm, and even more preferably 10 μm to 25 μm.

[0026] The average particle diameter of the non-molten particles 10 can also be measured by observing and actually measuring the cross-section of the heat-fusible resin layer 3 with a scanning electron microscope. Specifically, the heat-fusible resin layer 3 is embedded in a transparent epoxy resin, polished with a polisher, slurry, etc., and the cross-section of the heat-fusible resin layer is observed to measure the particle diameter. The average particle diameter is the arithmetic mean value of the particle diameters of 50 non-molten particles 10.

[0027] From the viewpoint of suppressing the thickness of the second heat-fusible resin layer 81 from becoming too thin during the pressurization of heat fusion, the proportion of the non-molten particles 10 in the second heat-fusible resin layer 81 may be 1,000 mass ppm or more, may be 3,000 mass ppm or more, or may be 7,000 mass ppm or more. Also, the proportion of the non-molten particles 10 in the second heat-fusible resin layer 81 may be 30,000 mass ppm or less, may be 20,000 mass ppm or less, or may be 15,000 mass ppm or less.

[0028] From the viewpoint of maintaining the laminating property and suppressing peeling between the barrier layer 4 and the heat-fusible resin layer 71, the proportion of the non-molten particles 10 in the first heat-fusible resin layer 71 is preferably 4 mass% or less, more preferably 2 mass% or less, even more preferably 0.5 mass% or less, and the non-molten particles 10 may not be included.

[0029] The first heat-fusible resin layer 71 may contain non-molten particles 11 (also referred to as small-particle-diameter non-molten particles) that are smaller than the non-molten particles 10 (not shown in FIG. 2). The material of the small non-molten particles 11 is the same as that of the non-molten particles 10. As the anti-blocking agent, those known as such may be applied to the small non-molten particles 11. The small non-molten particles 11 may be used alone or in combination of two or more kinds.

[0030] From the viewpoint of ensuring the sealing property, the average particle diameter of the small non-molten particles 11 is preferably 4 μm or less, more preferably 3 μm or less, and even more preferably 2 μm or less. The lower limit value of the average particle diameter of the small non-molten particles 11 is not particularly limited and may be 0.5 μm or more, or may be 0.7 μm or more. The average particle diameter of the small non-molten particles 11 can be measured in the same manner as the average particle diameter of the non-molten particles 10.

[0031] The proportion of the small non-molten particles 11 in the first heat-fusible resin layer 71 may be 1,000 mass ppm or more, may be 3,000 mass ppm or more, or may be 7,000 mass ppm or more. Also, the proportion of the small non-molten particles 11 in the first heat-fusible resin layer 71 may be 30,000 mass ppm or less, may be 20,000 mass ppm or less, or may be 15,000 mass ppm or less.

[0032] FIG. 3 is a schematic cross-sectional view showing a second embodiment of the heat-fusible resin layer 3. The heat-fusible resin layer 32 shown in FIG. 3 has a three-layer structure and includes a first heat-fusible resin layer 72, a second heat-fusible resin layer 82, and a third heat-fusible resin layer 92. The non-molten particles 10 are contained in the second heat-fusible resin layer 82.

[0033] The total thickness of the heat-fusible resin layer 32 in the second embodiment is the same as that of the heat-fusible resin layer 31 in the first embodiment. The non-molten particles 10 used in the heat-fusible resin layer 32 in the second embodiment are also the same as the non-molten particles 10 used in the heat-fusible resin layer 31 in the first embodiment.

[0034] The thickness of the second heat-sealable resin layer 82 containing the non-fused particles 10 is preferably 40% or more, more preferably 50% or more, and even more preferably 55% or more with respect to the total thickness of the heat-sealable resin layer 32. Also, from the viewpoint of ensuring the sealing property of the heat-sealable resin layer, the thickness of the second heat-sealable resin layer 82 is preferably 90% or less, more preferably 80% or less, and even more preferably 70% or less with respect to the total thickness of the heat-sealable resin layer 32.

[0035] The ratio of the thicknesses of the three layers of the first heat-sealable resin layer 72, the second heat-sealable resin layer 82, and the third heat-sealable resin layer 92 is preferably set in the range of the thickness of the first heat-sealable resin layer 7 / the thickness of the second heat-sealable resin layer 8 / the thickness of the third heat-sealable resin layer 9 = 5 to 30 / 90 to 40 / 5 to 30.

[0036] From the viewpoint of maintaining the laminating property and suppressing peeling between the barrier layer 4 and the heat-sealable resin layer 72, the proportion of the non-fused particles 10 in the first heat-sealable resin layer 72 is the same as in the case of the first heat-sealable resin layer 71.

[0037] As shown in FIG. 3, the first heat-sealable resin layer 72 may or may not contain the small-particle-size non-fused particles 11. The small-particle-size non-fused particles 11 used in the first heat-sealable resin layer 72 have the same meaning as the small-particle-size non-fused particles 11 described in the first embodiment, and the content rate is also the same.

[0038] From the viewpoint of heat-sealing the third heat-sealable resin layers to maintain the airtightness (sealing property), the proportion of the small-particle-size non-fused particles 10 in the third heat-sealable resin layer 92 is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less, and it may not contain the non-fused particles 10.

[0039] As shown in FIG. 3, the third heat-sealable resin layer 92 may or may not contain small non-molten particles 11. When the third heat-sealable resin layer 92 contains small non-molten particles 11, when the exterior material for the power storage device is stacked and stored in a roll form or in sheets, the third heat-sealable resin layer 92, which is the outermost layer, is suppressed from blocking the overlapping opposing layer. The small non-molten particles 11 used in the third heat-sealable resin layer 92 have the same meaning as the small non-molten particles 11 described in the first embodiment, and the content rate is also the same.

[0040] The first heat-sealable resin layer 72 and the third heat-sealable resin layer 92 may be formed from the same composition or may be formed from different compositions. When the first heat-sealable resin layer 72 and the third heat-sealable resin layer 92 are formed from different compositions, for example, the heat-sealable resin layer 33 having the layer configuration shown in FIG. 4 can be cited.

[0041] In FIG. 4, the first heat-sealable resin layer 73 does not contain small non-molten particles 11, and the third heat-sealable resin layer 93 contains small non-molten particles 11. In this case, the first heat-sealable resin layer 73 is likely to have improved laminating properties, and the third heat-sealable resin layer 93 is likely to have suppressed blocking. Note that the second heat-sealable resin layer 83 is the same as the second heat-sealable resin layer 82.

[0042] As shown in FIG. 3, when both the first heat-sealable resin layer 72 and the third heat-sealable resin layer 92 contain small non-molten particles 11, and the content rate of small non-molten particles 11 in the third heat-sealable resin layer 92 is higher than that in the first heat-sealable resin layer 72, an effect similar to that of the heat-sealable resin layer 33 in FIG. 4 is easily obtained.

[0043] For comparison, when the single-layer heat-sealable resin layer 3 contains non-molten particles 10, it is suppressed that the thickness of the heat-sealable resin layer becomes too thin during heat-sealing pressure, but the laminating property is impaired. In addition, when the heat-sealable resin layer 3 has a single-layer structure and contains no non-molten particles 10 but contains small-diameter non-molten particles 11, lamination properties are ensured, but it is not possible to suppress the excessive thinning of the thickness of the heat-sealable resin layer during heat-sealing pressurization. In addition, when the heat-sealable resin layer 3 has a two-layer structure and the first heat-sealable resin layer 7 contains non-molten particles 10, it is possible to suppress the excessive thinning of the thickness of the heat-sealable resin layer during heat-sealing pressurization, but the lamination properties are impaired. In addition, even when the heat-sealable resin layer 3 has a three-layer structure and the first heat-sealable resin layer 7 contains non-molten particles 10, it is possible to suppress the excessive thinning of the thickness of the heat-sealable resin layer during heat-sealing pressurization, but the lamination properties are impaired.

[0044] Hereinafter, the components of each layer and the like will be described.

[0045] (Heat-sealable resin layer) The heat-sealable resin layer 3 plays a role of imparting heat-sealability to the exterior material. The heat-sealable resin layer contains a heat-sealable resin. As the heat-sealable resin, one having a melting point equal to or lower than the heat-sealing temperature is selected so as to melt at the heat-sealing temperature. The heat-sealable resin is not particularly limited as long as it has the above melting point, and is preferably at least one selected from the group consisting of polyethylene, polypropylene, olefin copolymers, acid-modified products thereof, and ionomers. "Polyethylene, polypropylene, olefin copolymers, acid-modified products thereof, and ionomers" is also referred to as "specific polyolefin".

[0046] Among the resins contained in the heat-sealable resin layer 3, the proportion of the specific polyolefin is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, particularly preferably 80% by mass or more, extremely preferably 90% by mass or more, and may be 95% by mass or more, may be 98% by mass or more, or may be 99% by mass or more.

[0047] The heat-sealing resin layer 3 may be composed of a single type of heat-sealing resin or may be composed of two or more types of heat-sealing resins. The first heat-sealing resin layer 7 and the second heat-sealing resin layer 8 (when further heat-sealing resin layers such as the third heat-sealing resin layer 9 are provided, including such heat-sealing resin layers) may each be composed of the same type of heat-sealing resin or may be composed of different heat-sealing resins.

[0048] As the heat-sealing resin layer 3, a resin film previously formed on a resin film may be used. The resin film applied as the heat-sealing resin layer 3 may be a non-stretched heat-sealing resin film layer. Alternatively, the heat-sealing resin forming the heat-sealing resin layer 3 may be applied onto the surface of the barrier layer 4 or the second adhesive layer 6 by extrusion molding, coating, etc. to form the heat-sealing resin layer 3.

[0049] When previously forming a resin film, examples of the heat-sealing resin constituting the first heat-sealing resin layer 7 include random copolymers containing "propylene" and "other copolymer components excluding propylene" as copolymer components, and examples of the heat-sealing resin constituting the second heat-sealing resin layer 8 include block copolymers containing "propylene" and "other copolymer components excluding propylene" as copolymer components. Examples of the heat-sealing resin constituting the third heat-sealing resin layer 9 include random copolymers containing "propylene" and "other copolymer components excluding propylene" as copolymer components. "Other copolymer components excluding propylene" are not particularly limited and include, in addition to olefin components such as ethylene, 1-butene, 1-hexene, 1-pentene, 4-methyl-1-pentene, etc., butadiene, etc.

[0050] When a heat - fusible resin layer 3 is formed by applying a heat - fusible resin onto the surface of the barrier layer 4 or the second adhesive layer 6, examples of the heat - fusible resin constituting the first heat - fusible resin layer 7 include acid - modified polypropylene, and it may further contain polyethylene and an elastomer. Examples of the heat - fusible resin constituting the second heat - fusible resin layer 8 include a random copolymer containing "propylene" and "other copolymer components excluding propylene" as copolymer components, and it may further contain polyethylene and an elastomer. The polyethylene that may be included in the first heat - fusible resin layer 7 and the second heat - fusible resin layer 8 may be low - density polyethylene (LDPE).

[0051] The heat - fusible resin layer 3 may further contain a lubricant. The lubricant is not particularly limited, and examples include fatty acid amides. The fatty acid amides are not particularly limited, and examples include saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylol amides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, fatty acid ester amides, aromatic bisamides, etc.

[0052] The lubricant may be contained in any of the first heat - fusible resin layer 7, the second heat - fusible resin layer 8, and the third heat - fusible resin layer 9, or may not be contained.

[0053] The content of the lubricant in the heat - fusible resin layer serving as the outermost layer of the exterior material (for example, the second heat - fusible resin layer 81 in the case of FIG. 2 and the third heat - fusible resin layer 92 in the case of FIG. 3) is preferably set to 100 ppm to 2000 ppm, and more preferably set to 100 ppm to 1000 ppm.

[0054] When the second heat - fusible resin layer 8 is an intermediate layer, the content of the lubricant in the second heat - fusible resin layer 8 is preferably set to 500 ppm to 5000 ppm.

[0055] From the viewpoint of maintaining laminability, the content of the lubricant in the first heat - fusible resin layer 7 is preferably set to exceed 0 ppm and be 250 ppm or less.

[0056] (Base material layer) The base material layer 2 is preferably formed of a heat-resistant resin. The heat-resistant resin refers to a resin that does not melt at the heat-sealing temperature when heat-sealing the exterior material 1. As the heat-resistant resin, those having a melting point 10°C or higher than the melting point of the heat-fusible resin layer 3 (the melting point of the layer having the highest melting point among the plurality of heat-fusible resin layers) are preferable, and those having a melting point 20°C or higher than the melting point of the heat-fusible resin layer 3 (the melting point of the layer having the highest melting point among the plurality of heat-fusible resin layers) are more preferable.

[0057] Examples of the heat-resistant resin layer include polyamide films such as nylon films, and polyester films, and these stretched films are preferably used. Among them, as the heat-resistant resin layer, biaxially stretched polyamide films such as biaxially stretched nylon films, biaxially stretched polybutylene terephthalate (PBT) films, biaxially stretched polyethylene terephthalate (PET) films, or biaxially stretched polyethylene naphthalate (PEN) films are more preferable. Examples of the nylon film include 6-nylon films, 6,6-nylon films, MXD-nylon films, etc. The base material layer may be formed as a single layer or may be composed of two or more layers. Examples of the base material layer composed of two or more layers include polyester film / polyamide film, and specifically, PET film / nylon film.

[0058] The thickness of the base material layer 2 is preferably 2 μm to 50 μm. When using a polyester film as the base material layer, the thickness is preferably 2 μm to 50 μm, and when using a nylon film, the thickness is preferably 7 μm to 50 μm. When set above the above lower limit value, sufficient strength as an exterior material tends to be maintained. When set below the above upper limit value, the stress during forming such as overhanging forming and drawing forming can be reduced, and the formability tends to be improved.

[0059] (Barrier layer) The barrier layer 4 serves to impart gas barrier properties to the exterior material 1 to prevent the intrusion of oxygen and moisture. The barrier layer 4 is not particularly limited, and examples include metal foils, vapor deposition films, resin layers, etc. Examples of the vapor deposition film include metal vapor deposition films, inorganic oxide vapor deposition films, carbon-containing inorganic oxide vapor deposition films, etc. Examples of the resin used for the resin layer include fluorine-containing resins, ethylene vinyl alcohol copolymers, etc. Examples of the fluorine-containing resin include polyvinylidene chloride, polymers mainly composed of chlorotrifluoroethylene (CTFE), polymers mainly composed of tetrafluoroethylene (TFE), polymers having a fluoroalkyl group, polymers mainly composed of fluoroalkyl units, etc.

[0060] The barrier layer 4 may be a single layer or a multilayer of two or more layers. In the case of a multilayer, it may be a laminate of the same type of layers or a laminate of different types of layers. Examples of the laminate of different types of layers include a combination of a vapor deposition film and a resin layer.

[0061] Among the above, the barrier layer 4 preferably includes a layer made of a metal material. Examples of the metal material constituting the barrier layer 4 include aluminum alloys, stainless steels, copper, nickel, titanium steel, steel plates, etc. When used as a metal foil, it preferably includes at least one of an aluminum alloy foil and a stainless steel foil.

[0062] The thickness of the barrier layer 4 can be appropriately set, preferably 5 μm to 120 μm, and more preferably 10 μm to 80 μm. When the thickness of the barrier layer 4 is 5 μm or more, pinhole generation during rolling is likely to be prevented when the barrier layer 4 is a metal foil. When the thickness of the barrier layer 4 is 120 μm or less, the stress during forming such as bulging forming and drawing forming can be reduced, and the formability tends to be improved.

[0063] When using a metal foil, from the viewpoint of preventing surface corrosion, the metal foil may be subjected to a chemical conversion treatment, and it is preferably subjected to a chemical conversion treatment on at least the surface on the side of the heat-sealable resin layer. Examples of the chemical treatment method include the following methods. For example, on the surface of a degreased metal foil, 1) an aqueous solution containing phosphoric acid, chromic acid, and at least one compound selected from the group consisting of metal salts of fluorides and non-metal salts of fluorides 2) an aqueous solution containing phosphoric acid, at least one resin selected from the group consisting of acrylic resins, chitosan derivative resins, and phenolic resins, and at least one compound selected from the group consisting of chromic acid and chromium(III) salts 3) an aqueous solution containing phosphoric acid, at least one resin selected from the group consisting of acrylic resins, chitosan derivative resins, and phenolic resins, at least one compound selected from the group consisting of chromic acid and chromium(III) salts, and at least one compound selected from the group consisting of metal salts of fluorides and non-metal salts of fluorides After applying any of the aqueous solutions of 1) to 3) above and then drying, a chemical conversion treatment is performed.

[0064] The chemical conversion film formed by the chemical conversion treatment has a chromium adhesion amount (per side) of 0.1 mg / m 2 ~50 mg / m 2 is preferable, and particularly 2 mg / m 2 ~20 mg / m 2 is preferable.

[0065] (First Adhesive Layer) The adhesive used for the first adhesive layer 5 may be any of chemical reaction type, solvent evaporation type, hot melt type, hot press type, etc. Also, it may be a two-component curing adhesive (two-component adhesive), a one-component curing adhesive (one-component adhesive), or a resin without a curing reaction. Also, the first adhesive layer 5 may be a single layer or a multi-layer of two or more layers.

[0066] Examples of the adhesive component contained in the adhesive include polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, and copolyester; polyethers; polyurethanes; epoxy resins; phenolic resins; polyamides such as nylon 6, nylon 66, nylon 12, and copolyamide; polyolefin resins such as polyolefin, cyclic polyolefin, acid-modified polyolefin, and acid-modified cyclic polyolefin; polyvinyl acetate; cellulose; (meth)acrylic resins; polyimides; polycarbonates; amino resins such as urea resin and melamine resin; rubbers such as chloroprene rubber, nitrile rubber, and styrene-butadiene rubber; silicone resins; and the like. Examples of the adhesive component in the thermosetting adhesive include polyolefin resins, epoxy resins, (meth)acrylic resins, and the like. The adhesive component may be contained alone or in combination of two or more.

[0067] The first adhesive layer 5 may contain other components. Examples of the other components include colorants, thermoplastic elastomers, tackifiers, fillers, and the like. When a colorant is contained in the first adhesive layer 5, an exterior material for a colored power storage device can be obtained. As the colorant, known ones such as pigments and dyes can be used. Also, the colorant may be contained alone or in combination of two or more.

[0068] The thickness of the first adhesive layer 5 is preferably set to 1 μm to 5 μm, and more preferably set to 1 μm to 3 μm from the viewpoint of thinning and weight reduction of the exterior material 1.

[0069] (Second Adhesive Layer) The adhesive used for the second adhesive layer 6 is not particularly limited, and examples thereof include the adhesives described for the first adhesive layer 5. The thickness of the second adhesive layer 6 is preferably set to 1 μm to 5 μm, and more preferably set to 1 μm to 3 μm from the viewpoint of thinning and weight reduction of the exterior material 1. As described in the method for manufacturing the exterior material for a power storage device described below, depending on the method for forming the heat-sealable resin layer, the second adhesive layer 6 may be omitted.

[0070] The base material layer 2 and the heat-sealable resin layer 3 constituting the exterior material 1 for a power storage device may further contain an antioxidant, a plasticizer, an ultraviolet absorber, a fungicide, a coloring agent (such as a pigment or a dye), an antistatic agent, a rust preventive agent, a moisture absorbent, an oxygen absorber, etc. The plasticizer is not particularly limited, and examples thereof include glycerin fatty acid ester monoglyceride, glycerin fatty acid ester acetylated monoglyceride, glycerin fatty acid ester organic acid monoglyceride, glycerin fatty acid ester medium-chain fatty acid triglyceride, polyglycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid ester, special fatty acid ester, higher alcohol fatty acid ester, etc.

[0071] (Other layers) Since the surface on the opposite side of the barrier layer 4 of the base material layer 2 becomes the outermost surface of the exterior member when an exterior member for housing the power storage device main body is formed, a surface coating layer (not shown) may be provided as necessary. The surface coating layer may be formed by a known coating agent or the like.

[0072] (Applications) The exterior material for a power storage device of the present disclosure is also suitably used as an exterior material for a lithium-ion secondary battery. The exterior material for a power storage device of the present disclosure may be formed into an exterior case, and the power storage device main body may be housed inside this exterior case. Further, the exterior material for a power storage device of the present disclosure may be used to wrap the power storage device main body without being formed, and the periphery thereof may be heat-sealed.

[0073] <Composition for forming a heat-sealable resin layer of an exterior material for a power storage device> The composition for forming a heat-sealable resin layer of the exterior material of the power storage device of the present disclosure (hereinafter, also referred to as "the composition for forming a heat-sealable resin layer") contains a heat-sealable resin and non-molten particles having an average particle diameter of 10 μm to 30 μm. This composition for forming a heat-sealable resin layer can be used for forming the above-described second heat-sealable resin layer 8. The heat-sealable resin and the non-molten particles in the composition for forming a heat-sealable resin layer are synonymous with the heat-sealable resin and the non-molten particles 10 described in the exterior material for a power storage device, respectively.

[0074] The average particle diameter of the non-molten particles in the composition for forming a heat-sealable resin layer is defined as the particle diameter (D50) at which the weight cumulative particle size distribution is 50%. The weight cumulative particle size distribution is measured using the laser diffraction method. The measurement of the particle size distribution using the laser diffraction method can be performed using a laser diffraction scattering particle size distribution measuring device (for example, LS13 manufactured by Beckman Coulter).

[0075] The composition for forming a heat-sealable resin layer may further contain a lubricant, an antioxidant, a plasticizer, an ultraviolet absorber, a fungicide, a colorant (such as a pigment or a dye), an antistatic agent, a rust preventive agent, a moisture absorbent, an oxygen absorber, etc. described in the exterior material for a power storage device. Further, the composition for forming a heat-sealable resin layer may contain a solvent.

[0076] <Method for manufacturing an exterior material for a power storage device> The method for manufacturing an exterior material for a power storage device is not particularly limited as long as the above-described exterior material for a power storage device can be obtained. As an example of the method for manufacturing an exterior material for a power storage device, the following method can be mentioned.

[0077] Prepare a laminate A in which a base material layer 2, a first adhesive layer 5, and a barrier layer 4 are laminated in this order. The laminate A can be produced by a dry lamination method in which an adhesive component for forming the first adhesive layer 5 is applied to the base material layer 2 or the barrier layer 4 by a gravure coating method, a roll coating method, etc., dried, and then the barrier layer 4 or the base material layer 2 is laminated thereon. When the adhesive component is a curable resin, after laminating the barrier layer 4 or the base material layer 2 on the first adhesive layer 5, the first adhesive layer 5 is cured by heating or the like.

[0078] Next, a heat-sealable resin layer 3 is provided on the barrier layer 4 of the laminate A. The heat-sealable resin layer 3 may be a resin film that has been previously formed on a resin film and placed on the barrier layer 4 (first method), or a heat-sealable resin for forming the heat-sealable resin layer 3 may be applied onto the barrier layer 4 by extrusion molding, coating, etc. to form the heat-sealable resin layer 3 (second method). In the first method, a resin film that is a multilayer laminate such as a first heat-sealable resin layer 7 and a second heat-sealable resin layer 8 can be produced by a coextrusion method or the like.

[0079] In the case of the first method, the barrier layer 4 and the heat-sealable resin layer 3 are adhered by a second adhesive layer 6. In the case of the second method, the second adhesive layer 6 may be omitted or may be provided.

[0080] When the second adhesive layer 6 is provided between the barrier layer 4 and the heat-sealable resin layer 3, the second adhesive layer 6 and the heat-sealable resin layer 3 can be laminated by an extrusion lamination method, a thermal lamination method, a sandwich lamination method, a dry lamination method, etc. As the extrusion lamination method, there are methods such as laminating by extruding a second adhesive layer 6, a heat-sealable resin layer 3 (a first heat-sealable resin layer 7 and a second heat-sealable resin layer 8, and if necessary, a third heat-sealable resin layer 9) onto the barrier layer 4 of the laminate A (coextrusion lamination method, tandem lamination method), etc. As the thermal lamination method, there are methods such as forming a laminate B of the second adhesive layer 6 and the heat-sealable resin layer 3 separately and laminating them so that the second adhesive layer 6 of the laminate B faces the barrier layer 4 of the laminate A, forming a laminate C having the second adhesive layer 6 on the barrier layer 4 of the laminate A, and laminating the second adhesive layer 6 of the laminate C and the heat-sealable resin layer 3, etc. As the sandwich lamination method, there are methods such as pouring a molten second adhesive layer 6 between the barrier layer 4 of the laminate A and the heat-sealable resin layer 3 that has been previously formed in a film shape, etc. As the dry lamination method, there may be mentioned a method in which an adhesive component for forming the second adhesive layer 6 is solution-coated on the barrier layer 4 of the laminate A, dried or baked, and the heat-fusible resin layer 3 previously formed in a film shape is laminated on the second adhesive layer 6.

[0081] <Outer case for power storage device> The outer case for a power storage device of the present disclosure is a molded body of the outer packaging material for a power storage device of the present disclosure. The outer packaging material for a power storage device may be molded by deep drawing molding, overhang molding, or the like. Examples of the shape of the outer case for a power storage device include the outer cases 10 shown in FIGS. 5 and 6 described later.

[0082] <Power storage device> The power storage device of the present disclosure includes a power storage device main body portion and an outer member including the outer packaging material for a power storage device of the present disclosure, and the power storage device main body portion is externally packaged by the outer member. The outer member may be configured to include the outer case for a power storage device of the present disclosure.

[0083] An example of a power storage device 100 configured using the outer packaging material 1 for a power storage device of the present disclosure is shown in FIGS. 5 and 6. FIG. 5 is a schematic cross-sectional view showing an example of the power storage device. FIG. 6 is a schematic perspective view showing a state in which the components constituting the power storage device of FIG. 5 are separated. The power storage device 100 is a lithium-ion secondary battery.

[0084] In FIGS. 5 and 6, an outer member 15 is constituted by an outer case 10 which is a molded body of the outer packaging material 1 and the planar outer packaging material 1. A power storage device main body portion (electrochemical element or the like) 31 is housed in the housing recess of the outer case 10. Then, the planar outer packaging material 1 is arranged with the heat-fusible resin layer 3 side facing inward (downward in FIGS. 5 and 6), and the peripheral edge portion of the heat-fusible resin layer 3 of the planar outer packaging material 1 and the heat-fusible resin layer 3 of the flange portion (sealing peripheral edge portion) 37 of the outer case 10 are sealed and joined by heat fusion (heat seal).

[0085] In FIG. 5, reference numeral 39 denotes a heat seal portion where the peripheral edge of the exterior material 1 and the flange portion (sealing peripheral edge portion) 37 of the exterior case 10 are joined (welded). In the power storage device 100, the tip of the tab lead connected to the power storage device main body portion 110 is led out to the outside of the exterior member 15, but the illustration thereof is omitted.

[0086] The power storage device main body portion 110 is not particularly limited, and examples thereof include a battery main body portion, a capacitor main body portion, and a condenser main body portion.

[0087] From the viewpoint of ensuring sealing, the width of the heat seal portion 39 is preferably set to 0.5 mm or more, and more preferably set to 3 mm to 15 mm.

[0088] The form of the exterior member 15 is not limited to FIGS. 2 and 3, and the peripheral edges may be heat-sealed by a pair of planar exterior materials 1, or the peripheral edges may be heat-sealed by a pair of exterior cases 10.

Explanation of Reference Numerals

[0089] 1... Exterior material for power storage device 2... Base material layer 3, 31, 32... Heat-sealable resin layer 4... Barrier layer 7, 71, 72... First heat-sealable resin layer 8, 81, 82... Second heat-sealable resin layer 9, 92... Third heat-sealable resin layer 10... Non-melting particles 11... Small particle size non-melting particles 12... Exterior case 15... Exterior member 100... Power storage device 110... Power storage device main body portion

Claims

1. It comprises a base material layer, a barrier layer, and a heat-sealable resin layer in this order. The heat-sealable resin layer includes a first heat-sealable resin layer and a second heat-sealable resin layer in order from the barrier layer side. The second heat-sealable resin layer contains non-molten particles, and the average particle diameter of the non-molten particles is 30% to 60% with respect to the thickness of the second heat-sealable resin layer. An exterior material for a power storage device.

2. The exterior material for a power storage device according to Claim 1, wherein the non-molten particles contain inorganic particles.

3. The exterior material for a power storage device according to Claim 1, wherein the average particle diameter of the non-molten particles is 10 μm to 30 μm.

4. The exterior material for a power storage device according to Claim 1, wherein the proportion of the non-molten particles in the second heat-sealable resin layer is 1,000 mass ppm to 30,000 mass ppm.

5. The exterior material for a power storage device according to Claim 1, wherein the thickness of the second heat-sealable resin layer is 40% to 90% of the total thickness of the heat-sealable resin layer.

6. The exterior material for a power storage device according to Claim 1, wherein the heat-sealable resin layer is composed of three or more layers.

7. An exterior case for a power storage device, which is a molded body of the exterior material for a power storage device according to any one of Claims 1 to 6.

8. A power storage device main body part, and an exterior member including the exterior material for a power storage device according to any one of Claims 1 to 6, wherein the power storage device main body part is externally covered with the exterior member.

9. A composition for forming a heat-sealable resin layer of an exterior material for a power storage device, which contains a heat-sealable resin and non-molten particles having an average particle diameter of 10 μm to 30 μm.

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