Lid body, power storage device, peripheral edge member

Abstract

To provide a lid body, a power storage device, and a peripheral edge member that contribute to suitably holding an electrode body by means of an exterior film.SOLUTION: A lid body is used for an exterior body of a power storage device, and includes a heat-sealable resin layer composed mainly of an olefin-based copolymer.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a lid body, a power storage device, and a peripheral member.

Background Art

[0002] Patent Document 1 discloses an example of a power storage device. This power storage device includes an electrode body and an exterior body that seals the electrode body. The exterior body includes an exterior film that wraps the electrode body and a lid body that is joined to the exterior film.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above power storage device, when the exterior film and the lid body are not sufficiently joined, there is a possibility that a gap is formed between the outer layer film and the lid body. Therefore, there is room for improvement in suitably sealing the electrode body with the exterior body.

[0005] An object of the present invention is to provide a power storage device that can suitably seal an electrode body with an exterior body, a lid body used for this power storage device, and a peripheral member that constitutes this lid body.

Means for Solving the Problems

[0006] The lid body according to the first aspect of the present invention is a lid body used for an exterior body of a power storage device, and the lid body includes a heat-sealable resin layer whose main material is an olefin copolymer.

[0007] The lid according to the second aspect of the present invention is a lid used for the exterior body of a power storage device, the lid including a lid body and a peripheral member joined to at least a part of the peripheral edge of the lid body, the peripheral member including a heat-sealable resin layer whose main material is an olefin copolymer.

[0008] The lid according to the third aspect of the present invention is the lid according to the second aspect, wherein the peripheral member is an adhesive film joined to the lid body.

[0009] The lid according to the fourth aspect of the present invention is the lid according to the second aspect, wherein the peripheral member is a frame joined to the lid body.

[0010] The lid according to the fifth aspect of the present invention is the lid according to any one of the first to third aspects, wherein the olefin copolymer is an olefin random copolymer.

[0011] The lid according to the sixth aspect of the present invention is the lid according to any one of the first to fifth aspects, the lid including a lid seal portion sealed with an exterior film constituting the exterior body and a protruding portion protruding from the lid seal portion.

[0012] The lid according to the seventh aspect of the present invention is the lid according to any one of the first to sixth aspects, wherein the heat-sealable resin layer contains a fatty acid amide lubricant.

[0013] The lid according to the eighth aspect of the present invention is the lid according to the seventh aspect, wherein a plurality of types of fatty acid amide lubricants are present, and at least one of the fatty acid amide lubricants is a saturated fatty acid amide.

[0014] The lid according to the ninth aspect of the present invention is the lid according to the eighth aspect, wherein the plurality of types of fatty acid amide lubricants further contain an unsaturated fatty acid amide.

[0015] The lid according to the tenth aspect of the present invention is the lid according to the eighth or ninth aspect, wherein the saturated fatty acid amide has 18 or more carbon atoms.

[0016] The lid according to the 11th aspect of the present invention is the lid according to any one of the 8th to 10th aspects, and the saturated fatty acid amide is behenic acid amide.

[0017] The lid according to the 12th aspect of the present invention is the lid according to the 9th aspect, and the unsaturated fatty acid amide is erucic acid amide.

[0018] The lid according to the 13th aspect of the present invention is the lid according to any one of the 1st to 4th aspects, and the heat-sealable resin layer is composed of any one of an acid-modified polyolefin resin, an unsaturated carboxylic acid graft polyolefin resin, a polypropylene resin, a metal ion crosslinked polyethylene, a copolymer resin of ethylene and an acrylic acid derivative, and a copolymer resin of ethylene and a methacrylic acid derivative.

[0019] The lid according to the 14th aspect of the present invention is the lid according to any one of the 1st to 4th aspects, and the heat-sealable resin layer contains a propylene-based elastomer resin having a melting point higher than 150°C.

[0020] The power storage device according to the 15th aspect of the present invention includes an electrode body and an exterior body that seals the electrode body. The exterior body includes an exterior film that wraps the electrode body and a lid that is joined to the exterior film. The lid includes a heat-sealable resin layer whose main material is an olefin copolymer.

[0021] The power storage device according to the 16th aspect of the present invention includes an electrode body and an exterior body that seals the electrode body. The exterior body includes an exterior film that wraps the electrode body and a lid that is joined to the exterior film. The lid includes a lid body and a peripheral member that is joined to at least a part of the peripheral edge of the lid body. The peripheral member includes a heat-sealable resin layer whose main material is an olefin copolymer.

[0022] The peripheral member according to the 17th aspect of the present invention is a peripheral member that constitutes a lid used for the exterior body of a power storage device, the lid including a lid body and the peripheral member joined to at least a part of the peripheral edge of the lid body, and the peripheral member includes a heat-sealable resin layer whose main material is an olefin copolymer.

[0023] The peripheral member according to the 18th aspect of the present invention is the peripheral member according to the 17th aspect, and is an adhesive film joined to the lid body.

[0024] The peripheral member according to the 19th aspect of the present invention is the peripheral member according to the 17th aspect, and is a frame joined to the lid body.

[0025] The lid according to the 20th aspect of the present invention is a lid used for the exterior body of a power storage device, including a heat-sealable resin layer. The heat-sealable resin layer measures temperature difference T1 and temperature difference T2 by the following method, and the value obtained by dividing temperature difference T2 by temperature difference T1 is 0.60 or more. By differential scanning calorimetry, measure temperature difference T1 between the extrapolated onset temperature and the extrapolated end temperature of the melting peak temperature of the heat-sealable resin layer. In an environment at a temperature of 85°C, after allowing the heat-sealable resin layer to stand in an electrolytic solution, which is a solution with a concentration of 1 mol / l of lithium hexafluorophosphate and a volume ratio of ethylene carbonate, diethyl carbonate, and dimethyl carbonate of 1:1:1, for 72 hours, then dry it. By differential scanning calorimetry, measure temperature difference T2 between the extrapolated onset temperature and the extrapolated end temperature of the melting peak temperature of the dried heat-sealable resin layer.

[0026] The lid according to the 21st aspect of the present invention is a lid used for the exterior body of a power storage device, including a heat-sealable resin layer. The lid has a lid seal portion sealed with an exterior film that constitutes the exterior body. Regarding the cross-section in the thickness direction of the lid seal portion, a sea-island structure is observed in the cross-sectional image obtained using a field emission scanning electron microscope, and in the cross-sectional image, the ratio of the area of the island portion of the sea-island structure is 0.1% or more and 50% or less.

[0027] The peripheral member according to the 22nd aspect of the present invention is a peripheral member that constitutes a lid body used for the exterior body of a power storage device. The lid body includes a lid main body and the peripheral member joined to at least a part of the peripheral edge of the lid main body. The peripheral member includes a heat-sealable resin layer. The heat-sealable resin layer measures the temperature difference T1 and the temperature difference T2 by the following method, and the value obtained by dividing the temperature difference T2 by the temperature difference T1 is 0.60 or more. By differential scanning calorimetry, the temperature difference T1 between the extrapolated melting start temperature and the extrapolated melting end temperature of the melting peak temperature of the heat-sealable resin layer is measured. In an environment at a temperature of 85 °C, the heat-sealable resin layer is allowed to stand in an electrolytic solution that is a solution with a concentration of 1 mol / l of lithium hexafluorophosphate and a volume ratio of ethylene carbonate, diethyl carbonate, and dimethyl carbonate of 1:1:1 for 72 hours, and then dried. By differential scanning calorimetry, the temperature difference T2 between the extrapolated melting start temperature and the extrapolated melting end temperature of the melting peak temperature of the dried heat-sealable resin layer is measured.

[0028] The peripheral member according to the 23rd aspect of the present invention is a peripheral member that constitutes a lid body used for the exterior body of a power storage device. The lid body includes a lid main body and the peripheral member joined to at least a part of the peripheral edge of the lid main body. The peripheral member includes a peripheral member seal portion that is sealed with an exterior film constituting the exterior body. For the cross-section in the thickness direction of the peripheral member seal portion, a sea-island structure is observed in the cross-sectional image obtained using a field emission scanning electron microscope. In the cross-sectional image, the area ratio of the island portion of the sea-island structure is 0.1% or more and 50% or less.

Advantages of the Invention

[0029] According to the power storage device, lid body, and peripheral member of the present invention, it is possible to contribute to suitably sealing the electrode body with the exterior body.

Brief Description of the Drawings

[0030]

Figure 1A

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Best Mode for Carrying Out the Invention

[0031] Hereinafter, a power storage device according to an embodiment of the present invention will be described with reference to the drawings. In this specification, the numerical range indicated by "~" means "or more" and "or less". For example, the notation 2~15 mm means 2 mm or more and 15 mm or less.

[0032] [Embodiment] <1-1. Configuration of the power storage device> FIG. 1A is a plan view schematically showing a power storage device 10 of the first embodiment. FIG. 1B is a diagram regarding a method for measuring the seal strength of the second sealing portion 80 of the power storage device 10 of FIG. 1A. FIG. 2 is a cross-sectional view showing the layer structure of the exterior film 50 provided in the power storage device 10 of FIG. 1A. FIG. 3 is a view of the exterior film 50 provided in the power storage device 10 of FIG. 1A in an unfolded state. FIG. 4 is a cross-sectional view taken along line D4-D4 of FIG. 1A. FIG. 5 is a side view of the lid 60 provided in the power storage device 10 of FIG. 1A. FIG. 6 is a plan view of the lid 60 of FIG. 5. In FIGS. 1A, 4 to 6, 8, and 9, the direction of arrow UD indicates the thickness direction of the power storage device 10, the direction of arrow LR indicates the width direction of the power storage device 10, and the direction of arrow FB indicates the depth direction of the power storage device 10. The directions indicated by each of the arrows UDLRFB are common in the following figures.

[0033] The power storage device 10 includes an electrode body 20, electrode terminals 30, and an exterior body 40. The electrode body 20 includes, for example, electrodes (a positive electrode and a negative electrode) that constitute a power storage member such as a lithium-ion battery, a capacitor, an all-solid-state battery, a semi-solid-state battery, a quasi-solid-state battery, a polymer battery, an all-resin battery, a lead-acid battery, a nickel-hydrogen storage battery, a nickel-cadmium storage battery, a nickel-iron storage battery, a nickel-zinc storage battery, a silver oxide-zinc storage battery, a metal-air battery, a polyvalent cation battery, or a capacitor, as well as a separator and the like. In the present embodiment, the shape of the electrode body 20 is a substantially rectangular parallelepiped. Note that the "substantially rectangular parallelepiped" includes, in addition to a perfect rectangular parallelepiped, a solid that can be regarded as a rectangular parallelepiped by, for example, modifying the shape of a part of the outer surface. The shape of the electrode body 20 may be, for example, a cylinder or a polygonal prism.

[0034] In the present embodiment, the power storage device 10 includes two electrode terminals 30. The electrode terminals 30 are metal terminals used for inputting and outputting power in the electrode body 20. One end of the electrode terminal 30 is electrically connected to an electrode (positive electrode or negative electrode) included in the electrode body 20. The other end of the electrode terminal 30 protrudes outward from, for example, the edge of the exterior body 40. Note that the electrode terminal 30 only needs to be able to input and output power of the electrode body 20, and for example, it does not have to protrude from the exterior body 40. When the lid body 60 described later is made of, for example, metal, the lid body 60 may also serve as the function of the electrode terminal 30. In this case, the lid body 60 having the function as an electrode terminal may or may not protrude from the exterior body 40.

[0035] The metal material constituting the electrode terminal 30 is, for example, aluminum, nickel, copper, or the like. For example, when the electrode body 20 is a lithium-ion battery, the electrode terminal 30 connected to the positive electrode is usually made of aluminum or the like, and the electrode terminal 30 connected to the negative electrode is usually made of copper, nickel, or the like. Note that the outermost layer of the electrode body 20 does not necessarily have to be an electrode, and may be, for example, a protective tape or a separator.

[0036] The exterior body 40 seals the electrode body 20. The exterior body 40 includes an exterior film 50 and a lid body 60. The exterior film 50 wraps the electrode body 20 so as to have an opening 40A. In the present embodiment, the exterior film 50 is wound around the electrode body 20 so as to have the opening 40A. The lid body 60 is disposed laterally of the electrode body 20 so as to close the opening 40A. Note that the electrode body 20 may be accommodated inside the cylindrically configured exterior film 50 such that the opening 40A is formed, and the opening 40A may be closed by the lid body 60.

[0037] For example, there is a method of forming a housing portion (depression) for housing the electrode body 20 in the exterior film 50 through cold forming. However, it is not always easy to form a deep housing portion by such a method. If an attempt is made to deeply form the housing portion (depression) (for example, a forming depth of 15 mm) by cold forming, pinholes or cracks are likely to occur in the exterior film 50, increasing the possibility of deterioration of battery performance. On the other hand, since the exterior body 40 seals the electrode body 20 by winding the exterior film 50 around the electrode body 20, the electrode body 20 can be easily sealed regardless of the thickness of the electrode body 20. In order to reduce the dead space between the electrode body 20 and the exterior film 50 to improve the volumetric energy density of the power storage device 10, a state in which the exterior film 50 is wound so as to contact the outer surface of the electrode body 20 is preferable. Also, in a all-solid-state battery, from the viewpoint that it is necessary to uniformly apply a high pressure from the outside of the battery to exhibit battery performance, it is necessary to eliminate the space between the electrode body 20 and the exterior film 50, and thus a state in which the exterior film 50 is wound so as to contact the outer surface of the electrode body 20 is preferable.

[0038] As shown in FIG. 2, the exterior film 50 is a laminate (laminated film) having, for example, a base material layer 51, a barrier layer 52, and a heat-sealable resin layer 53 in this order. Note that not all of these layers need to be included in the exterior film 50. For example, the barrier layer 52 may not be included. That is, the exterior film 50 may be made of a material having flexibility and being easy to bend, and may be made of, for example, a resin film. Note that the exterior film 50 is preferably heat-sealable. The outermost layer and the innermost layer of the exterior film 50 may be the heat-sealable resin layer 53. In this case, the exterior film 50 may wrap the electrode body 20 and the lid body 60 by joining the outermost layer and the innermost layer.

[0039] The base material layer 51 included in the exterior film 50 is a layer that imparts heat resistance to the exterior film 50 and suppresses the occurrence of pinholes that may occur during processing or distribution. The base material layer 51 is composed of, for example, at least one layer of a stretched polyester resin layer and a stretched polyamide resin layer. For example, by including at least one layer of a stretched polyester resin layer and a stretched polyamide resin layer in the base material layer 51, the barrier layer 52 can be protected during processing of the exterior film 50, and breakage of the exterior film 50 can be suppressed. Also, from the viewpoint of increasing the tensile elongation of the exterior film 50, the stretched polyester resin layer is preferably a biaxially stretched polyester resin layer, and the stretched polyamide resin layer is preferably a biaxially stretched polyamide resin layer. Further, from the viewpoint of excellent puncture strength or impact strength, the stretched polyester resin layer is more preferably a biaxially stretched polyethylene terephthalate (PET) film, and the stretched polyamide resin layer is more preferably a biaxially stretched nylon (ONy) film. Note that the base material layer 51 may be composed of both a stretched polyester resin layer and a stretched polyamide resin layer. The thickness of the base material layer 51 is preferably, for example, 5 to 300 μm, and more preferably 5 to 150 μm, from the viewpoint of film strength.

[0040] The barrier layer 52 is a layer that at least suppresses the ingress of moisture. The barrier layer 52 is joined to the base material layer 51 via, for example, an adhesive layer 54. Examples of the barrier layer 52 include a metal foil having barrier properties, a vapor deposition film, and a resin layer. Examples of the vapor deposition film include a metal vapor deposition film, an inorganic oxide vapor deposition film, and a carbon-containing inorganic oxide vapor deposition film. Examples of the resin layer include fluorine-containing resins such as polyvinylidene chloride, polymers mainly composed of chlorotrifluoroethylene (CTFE), polymers mainly composed of tetrafluoroethylene (TFE), polymers having a fluoroalkyl group, and polymers mainly composed of fluoroalkyl units, and ethylene vinyl alcohol copolymers. Further, examples of the barrier layer 52 include a resin film provided with at least one of these vapor deposition films and resin layers. A plurality of barrier layers 52 may be provided. The barrier layer 52 preferably includes a layer made of a metal material. Specific examples of the metal material constituting the barrier layer 52 include aluminum alloys, stainless steel, titanium steel, and steel plates. When used as a metal foil, it preferably includes at least one of an aluminum alloy foil and a stainless steel foil.

[0041] In the barrier layer 52, the layer made of the above-described metal material may contain a recycled material of the metal material. Examples of the recycled material of the metal material include recycled materials of aluminum alloys, stainless steel, titanium steel, or steel plates. These recycled materials can be obtained by known methods respectively. The recycled material of the aluminum alloy can be obtained, for example, by the production method described in International Publication No. 2022 / 092231. The barrier layer 52 may be composed only of the recycled material, or may be composed of a mixed material of the recycled material and a virgin material. Note that the recycled material of the metal material refers to a metal material that has been recovered, isolated, refined, etc. from various products used in the market, waste from the manufacturing process, etc. to be in a reusable state. Also, the virgin material of the metal material refers to a new metal material refined from a natural resource (raw material) of the metal and not a recycled material.

[0042] The aluminum alloy foil is preferably a soft aluminum alloy foil composed of, for example, an annealed aluminum alloy or the like from the viewpoint of improving the formability or followability of the exterior film 50, and is preferably an aluminum alloy foil containing iron from the viewpoint of further improving the formability or followability. In the aluminum alloy foil containing iron (100% by mass), the content of iron is preferably 0.1 to 9.0% by mass, and more preferably 0.5 to 2.0% by mass. When the content of iron is 0.1% by mass or more, an exterior film 50 having better formability can be obtained. When the content of iron is 9.0% by mass or less, an exterior film 50 having better flexibility can be obtained. Also, silicon, magnesium, copper, manganese, etc. may be added as necessary. The softening can be performed by annealing or the like. From the viewpoint of improving the mechanical strength of the exterior film 50, the aluminum alloy foil is more preferably a hard aluminum alloy foil composed of, for example, a work-hardened aluminum alloy or the like.

[0043] Examples of the stainless steel foil include austenitic, ferritic, austenitic-ferritic, martensitic, and precipitation-hardening stainless steel foils. Further, from the viewpoint of providing an exterior film 50 having excellent formability, the stainless steel foil is preferably composed of an austenitic stainless steel.

[0044] Specific examples of the austenitic stainless steel constituting the stainless steel foil include SUS304, SUS301, SUS316L, etc. Among these, SUS304 is particularly preferred.

[0045] In the case of a metal foil, the thickness of the barrier layer 52 only needs to exhibit a function as a barrier layer that at least suppresses the intrusion of moisture. For example, it can be about 5 to 200 μm. The thickness of the barrier layer 52 is preferably about 85 μm or less, more preferably about 50 μm or less, still more preferably about 40 μm or less, and particularly preferably about 35 μm or less. Also, the thickness of the barrier layer 52 is preferably about 9.0 μm or more, still more preferably about 20 μm or more, and more preferably about 25 μm or more. Further, the preferable range of the thickness of the barrier layer 52 includes about 9.0 to 85 μm, about 9.0 to 50 μm, about 9.0 to 40 μm, about 9.0 to 35 μm, about 20 to 85 μm, about 20 to 50 μm, about 20 to 40 μm, about 20 to 35 μm, about 25 to 85 μm, about 25 to 50 μm, about 25 to 40 μm, and about 25 to 35 μm. When the barrier layer 52 is composed of an aluminum alloy foil, the above-mentioned range is particularly preferable. Also, from the viewpoint of imparting high formability and high rigidity to the exterior film 50, the thickness of the barrier layer 52 is preferably about 35 μm or more, more preferably about 45 μm or more, still more preferably about 50 μm or more, and even more preferably about 55 μm or more. Also, it is preferably about 200 μm or less, more preferably about 85 μm or less, still more preferably about 75 μm or less, and even more preferably about 70 μm or less. The preferable range includes about 35 to 200 μm, about 35 to 85 μm, about 35 to 75 μm, about 35 to 70 μm, about 45 to 200 μm, about 45 to 85 μm, about 45 to 75 μm, about 45 to 70 μm, about 50 to 200 μm, about 50 to 85 μm, about 50 to 75 μm, about 50 to 70 μm, about 55 to 200 μm, about 55 to 85 μm, about 55 to 75 μm, and about 55 to 70 μm. When the exterior film 50 has high formability, deep drawing forming becomes easy, which can contribute to increasing the capacity of the power storage device. Also, when the capacity of the power storage device is increased, the weight of the power storage device increases, but by increasing the rigidity of the exterior film 50, it can contribute to the high sealing performance of the power storage device.Further, particularly when the barrier layer 52 is made of a stainless steel foil, the thickness of the stainless steel foil is preferably about 60 μm or less, more preferably about 50 μm or less, still more preferably about 40 μm or less, still more preferably about 30 μm or less, and particularly preferably about 25 μm or less. Also, the thickness of the stainless steel foil is preferably about 10 μm or more, more preferably about 15 μm or more. Further, preferable ranges of the thickness of the stainless steel foil include about 10 to 60 μm, about 10 to 50 μm, about 10 to 40 μm, about 10 to 30 μm, about 10 to 25 μm, about 15 to 60 μm, about 15 to 50 μm, about 15 to 40 μm, about 15 to 30 μm, and about 15 to 25 μm.

[0046] In addition, when the barrier layer 52 is an aluminum foil, it is preferable to provide a corrosion-resistant film on at least the surface opposite to the base material layer 51 in order to prevent dissolution and corrosion. The barrier layer 52 may be provided with corrosion-resistant films on both sides. Here, the corrosion-resistant film refers to, for example, a thin film that is formed by performing a hot water conversion treatment such as a boehmite treatment, a chemical conversion treatment, an anodizing treatment, a plating treatment such as nickel or chromium, or a corrosion prevention treatment of applying a coating agent on the surface of the barrier layer 52 to provide the barrier layer 52 with corrosion resistance (such as acid resistance and alkali resistance). Specifically, the corrosion-resistant film means a film that improves the acid resistance of the barrier layer 52 (acid-resistant film), a film that improves the alkali resistance of the barrier layer 52 (alkali-resistant film), and the like. As the treatment for forming the corrosion-resistant film, one type may be performed, or two or more types may be combined. Further, not only a single layer but also a multilayer structure can be formed. Furthermore, among these treatments, the hot water conversion treatment and the anodizing treatment are treatments that dissolve the surface of the metal foil with a treatment agent to form a metal compound having excellent corrosion resistance. Note that these treatments may be included in the definition of the chemical conversion treatment. Also, when the barrier layer 52 is provided with a corrosion-resistant film, the barrier layer 52 including the corrosion-resistant film is used.

[0047] The corrosion-resistant film prevents delamination between the barrier layer 52 (e.g., aluminum alloy foil) and the base material layer 51 during the molding of the outer packaging film 50, and prevents dissolution and corrosion of the surface of the barrier layer 52 by hydrogen fluoride generated by the reaction of the electrolyte and moisture, especially the dissolution and corrosion of aluminum oxide present on the surface of the barrier layer 52 when the barrier layer 52 is an aluminum alloy foil. In addition, it improves the adhesiveness (wettability) of the surface of the barrier layer 52, and shows the effect of preventing delamination between the base material layer 51 and the barrier layer 52 during heat sealing and preventing delamination between the base material layer 51 and the barrier layer 52 during molding.

[0048] The heat-sealable resin layer 53 is joined to the barrier layer 52, for example, via the adhesive layer 55. The heat-sealable resin layer 53 contained in the outer packaging film 50 is a layer that imparts sealing properties by heat sealing to the outer packaging film 50. Examples of the heat-sealable resin layer 53 include polyester resins such as polyethylene terephthalate-based resins and polybutylene terephthalate-based resins, polyolefin resins such as polyethylene-based resins and polypropylene-based resins, or resin films made of acid-modified polyolefin resins obtained by graft-modifying these polyolefin resins with an acid such as maleic anhydride. From the viewpoints of sealing properties and strength, the thickness of the heat-sealable resin layer 53 is preferably, for example, 20 to 300 μm, and more preferably 40 to 150 μm.

[0049] The outer packaging film 50 preferably has one or more layers having a buffering function (hereinafter referred to as "buffer layer") outside the heat-sealable resin layer 53, more preferably outside the barrier layer 52. The buffer layer may be laminated outside the base material layer 51, or the base material layer 51 may also serve as the buffer layer. When the outer packaging film 50 has a plurality of buffer layers, the plurality of buffer layers may be adjacent to each other, or may be laminated via the base material layer 51 or the barrier layer 52 or the like.

[0050] The material constituting the buffer layer can be arbitrarily selected from materials having cushioning properties. Materials having cushioning properties are, for example, rubber, non-woven fabric, or foamed sheet. The rubber is, for example, natural rubber, fluororubber, or silicone rubber. The rubber hardness is preferably about 20 to 90. The material constituting the non-woven fabric is preferably a material having excellent heat resistance. When the buffer layer is constituted by a non-woven fabric, the lower limit value of the thickness of the buffer layer is preferably 100 μm, more preferably 200 μm, still more preferably 1000 μm. When the buffer layer is constituted by a non-woven fabric, the upper limit value of the thickness of the buffer layer is preferably 5000 μm, more preferably 3000 μm. The preferable range of the thickness of the buffer layer is 100 μm to 5000 μm, 100 μm to 3000 μm, 200 μm to 5000 μm, 200 μm to 3000 μm, 1000 μm to 5000 μm, or 1000 μm to 3000 μm. Among these, the range of the thickness of the buffer layer is most preferably 1000 μm to 3000 μm.

[0051] When the buffer layer is constituted by rubber, the lower limit value of the thickness of the buffer layer is preferably 0.5 mm. When the buffer layer is constituted by rubber, the upper limit value of the thickness of the buffer layer is preferably 10 mm, more preferably 5 mm, still more preferably 2 mm. When the buffer layer is constituted by rubber, the preferable range of the thickness of the buffer layer is 0.5 mm to 10 mm, 0.5 mm to 5 mm, or 0.5 mm to 2 mm.

[0052] When the exterior film 50 has a buffer layer, since the buffer layer functions as a cushion, it is possible to suppress the exterior film 50 from being damaged by the impact when the power storage device 10 falls or by the handling during the manufacture of the power storage device 10.

[0053] The lid body 60 is, for example, in the shape of a rectangular parallelepiped and is made of, for example, a resin material. Note that the lid body 60 may be formed by, for example, cold-forming the exterior film 50, or may be a metal formed product. When the lid body 60 is a metal formed product, it is preferable that the lid body 60 has the corrosion-resistant film described for the barrier layer 52. The lid body 60 has a lid main body 60A. The lid main body 60A has a first surface 61, a second surface 62, and a lid seal portion 63. The first surface 61 faces the electrode body 20. The second surface 62 is the surface on the side opposite to the first surface 61. The lid seal portion 63 is connected to the first surface 61 and the second surface 62 and is heat-sealed to the heat-fusible resin layer 53 of the exterior film 50. The lid seal portion 63 includes a first seal surface 63A, a second seal surface 63B, a third seal surface 63C, and a fourth seal surface 63D. The first seal surface 63A constitutes the upper surface of the lid body 60. The first seal surface 63A extends in a first direction (in this embodiment, the LR direction) in a front view of the lid body 60. The second seal surface 63B and the third seal surface 63C are connected to the first seal surface 63A and constitute the side surface of the lid body 60. The second seal surface 63B and the third seal surface 63C extend in a second direction (in this embodiment, the UD direction) that intersects the first direction in a front view of the lid body 60. In this embodiment, in a front view of the lid body 60, the first direction and the second direction are orthogonal. The first direction and the second direction do not have to be orthogonal in a front view of the lid body 60. The fourth seal surface 63D constitutes the lower surface of the lid body 60. The fourth seal surface 63D extends in a first direction (in this embodiment, the LR direction) in a front view of the lid body 60.

[0054] When the lid body 60 is plate-shaped, even when the power storage devices 10 are stacked, it is preferable that the lid body 60 has a certain thickness so that the exterior body 40 is suppressed from deforming. From another perspective, when the lid body 60 is plate-shaped, in order to preferably heat-seal the lid seal portion 63 of the lid body 60 and the exterior film 50 when forming the second sealing portion 80 described later, it is preferable that the lid seal portion 63 of the lid body 60 has a certain thickness. The minimum value of the thickness of the lid seal portion 63 of the lid body 60 is, for example, 1.0 mm, more preferably 3.0 mm, and even more preferably 4.0 mm. The maximum value of the thickness of the lid seal portion 63 of the lid body 60 is, for example, 20 mm, more preferably 15 mm, and even more preferably 10 mm. The maximum value of the thickness of the lid seal portion 63 of the lid body 60 may be 20 mm or more. The preferable ranges of the thickness of the lid seal portion 63 of the lid body 60 are 1.0 mm to 20 mm, 1.0 mm to 15 mm, 1.0 mm to 10 mm, 3.0 mm to 20 mm, 3.0 mm to 15 mm, 3.0 mm to 10 mm, 4.0 mm to 20 mm, 4.0 mm to 15 mm, and 4.0 mm to 10 mm. In the present embodiment, when the lid body 60 is described as plate-shaped, an aspect in which the lid body 60 is composed only of a film defined by the [Packaging Terms] standard of JIS (Japanese Industrial Standards) is not included. Note that the thickness of the lid seal portion 63 of the lid body 60 may vary depending on the part of the lid body 60. When the thickness of the lid seal portion 63 of the lid body 60 varies depending on the part, the thickness of the lid seal portion 63 of the lid body 60 is the thickness of the thickest part.

[0055] The lid seal portion 63 further includes boundaries 64, 65, 66, and 67. The boundary 64 is the boundary between the first seal surface 63A and the second seal surface 63B. The boundary 65 is the boundary between the first seal surface 63A and the third seal surface 63C. The boundary 66 is the boundary between the fourth seal surface 63D and the second seal surface 63B. The boundary 67 is the boundary between the fourth seal surface 63D and the third seal surface 63C. The shapes of the boundaries 64 to 67 may be corners, or may be rounded by performing R processing. In the present embodiment, the boundaries 64 to 67 are corners.

[0056] From the viewpoint of suitably heat-sealing the lid body 60 and the exterior film 50, it is preferable that the material constituting the lid body 60 and the material constituting the heat-sealable resin layer 53 of the exterior film 50 have the same main material. In the present embodiment, the material constituting the lid body 60 and the material constituting the heat-sealable resin layer 53 are mainly made of polypropylene. Here, the main material refers to, for example, a material that occupies 50% or more of the materials included in the component.

[0057] In the present embodiment, the lid body 60 includes a heat-sealable resin layer 60Z whose main material is an olefin copolymer. In the present embodiment, the entire lid body 60 is constituted by the heat-sealable resin layer 60Z. It is sufficient that at least the portion including the lid seal portion 63 of the lid body 60 is constituted by the heat-sealable resin layer 60Z. The main material constituting the heat-sealable resin layer 60Z is preferably an olefin random copolymer.

[0058] The heat-sealable resin layer 60Z includes a polyolefin skeleton such as polyolefin and acid-modified polyolefin. Whether the resin constituting the heat-sealable resin layer 60Z contains a polyolefin skeleton can be analyzed by, for example, infrared spectroscopy, gas chromatography-mass spectrometry, etc. Further, when the resin constituting the heat-sealable resin layer 60Z is analyzed by infrared spectroscopy, it is preferable that a peak derived from maleic anhydride is detected. For example, when measuring maleic anhydride-modified polyolefin by infrared spectroscopy, peaks derived from maleic anhydride are detected in the vicinity of a wave number of 1760 cm -1 and in the vicinity of a wave number of 1780 cm -1 When the heat-sealable resin layer 60Z is a layer made of maleic anhydride-modified polyolefin, a peak derived from maleic anhydride is detected when measured by infrared spectroscopy. However, if the degree of acid modification is low, the peak may become small and not be detected. In that case, it can be analyzed by nuclear magnetic resonance spectroscopy.

[0059] The heat-sealable resin layer 60Z preferably contains a resin containing a polyolefin backbone as a main component, more preferably contains a polyolefin as a main component, and even more preferably contains polypropylene as a main component. Here, the main component means that among the resin components contained in the heat-sealable resin layer 60Z, the content rate is, for example, 35% by mass or more, preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably 99% by mass or more of the resin component. For example, when the heat-sealable resin layer 60Z contains polypropylene as a main component, it means that among the resin components contained in the heat-sealable resin layer 60Z, the content rate of polypropylene is, for example, 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably 99% by mass or more.

[0060] Specific examples of the polyolefin include polyethylene such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; ethylene-α-olefin copolymers; polypropylene such as homopolypropylene, block copolymers of polypropylene (for example, block copolymers of propylene and ethylene), and random copolymers of polypropylene (for example, random copolymers of propylene and ethylene); propylene-α-olefin copolymers; and terpolymers of ethylene-butene-propylene. Among these, polypropylene is preferred. The polyolefin resin in the case of a copolymer may be a block copolymer or a random copolymer. These polyolefin-based resins may be used alone or in combination of two or more.

[0061] Further, the polyolefin may be a cyclic polyolefin. The cyclic polyolefin is a copolymer of an olefin and a cyclic monomer. Examples of the olefin that is a constituent monomer of the cyclic polyolefin include ethylene, propylene, 4-methyl-1-pentene, styrene, butadiene, isoprene, and the like. Examples of the cyclic monomer that is a constituent monomer of the cyclic polyolefin include cyclic alkenes such as norbornene; cyclic dienes such as cyclopentadiene, dicyclopentadiene, cyclohexadiene, and norbornadiene. Among these, cyclic alkenes are preferred, and norbornene is more preferred.

[0062] Further, the polyolefin may be an acid-modified polyolefin. The acid-modified polyolefin is a polymer obtained by block polymerization or graft polymerization of a polyolefin with an acid component. As the polyolefin to be acid-modified, the above-mentioned polyolefin, a copolymer obtained by copolymerizing a polar molecule such as acrylic acid or methacrylic acid with the above-mentioned polyolefin, or a polymer such as a crosslinked polyolefin can also be used. Examples of the acid component used for acid modification include carboxylic acids such as maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride, or their anhydrides.

[0063] The acid-modified polyolefin may be an acid-modified cyclic polyolefin. The acid-modified cyclic polyolefin is a polymer obtained by copolymerizing a part of the monomers constituting the cyclic polyolefin by replacing it with an acid component, or by block polymerization or graft polymerization of an acid component with respect to the cyclic polyolefin. The cyclic polyolefin to be acid-modified is the same as described above. Also, the acid component used for acid modification is the same as the acid component used for the modification of the above-mentioned polyolefin.

[0064] Preferred acid-modified polyolefins include polyolefins modified with carboxylic acids or their anhydrides, polypropylenes modified with carboxylic acids or their anhydrides, maleic anhydride-modified polyolefins, and maleic anhydride-modified polypropylenes.

[0065] It is preferable that a plurality of types of amide-based lubricants are present in the heat-sealable resin layer 60Z. In the manufacture of the power storage device 10, when the lid body 60 is subjected to molding, an amide-based lubricant is present on the surface of the heat-sealable resin layer 60Z. As a result, the slipperiness of the surface of the heat-sealable resin layer 60Z is improved, and the moldability of the lid body 60 is enhanced.

[0066] As a method of making an amide-based lubricant present in the heat-sealable resin layer 60Z, there are methods such as coating the surface of the heat-sealable resin layer 60Z of the lid body 60 with an amide-based lubricant, or blending an amide-based lubricant into a polyolefin resin or the like that forms the heat-sealable resin layer 60Z. In addition, even when an amide-based lubricant is blended into a polyolefin resin or the like that forms the heat-sealable resin layer 60Z, an amide-based lubricant can be made to be present on the surface of the heat-sealable resin layer 60Z by bleeding out the amide-based lubricant on the surface of the heat-sealable resin layer 60Z. On the other hand, even when the surface of the heat-sealable resin layer 60Z of the lid body 60 is coated with an amide-based lubricant, an amide-based lubricant can be made to be present inside the heat-sealable resin layer 60Z by a part of the amide-based lubricant migrating from the surface to the inside. As a method of bleeding out an amide-based lubricant on the surface of the heat-sealable resin layer 60Z, it is common to age the lid body 60 at a slightly high temperature of about 30 to 50 °C for several hours to about 3 days to promote bleeding. However, as it approaches the melting point of the amide-based lubricant, the saturated lubricant amount in the heat-sealable resin layer 60Z increases, so attention is required for the addition amount and the aging temperature.

[0067] In the present embodiment, it is preferable that a plurality of types of fatty acid amide-based lubricants are present in the heat-sealable resin layer 60Z, and at least one of the fatty acid amide-based lubricants is a saturated fatty acid amide. One type of fatty acid amide-based lubricant may be present in the heat-sealable resin layer 60Z.

[0068] As the saturated fatty acid amide, it may be used alone or in combination of two or more. The saturated fatty acid amide is not particularly limited, but from the viewpoint of further improving the moldability and the continuous productivity of the power storage device 10, it is preferably a saturated fatty acid amide having 18 or more carbon atoms, more preferably stearic acid amide, behenic acid amide, arachidic acid amide, etc., and particularly preferably behenic acid amide.

[0069] In this embodiment, the amide lubricants other than saturated fatty acid amides are not particularly limited. For example, other saturated fatty acid amides other than the saturated fatty acid amides exemplified above, unsaturated fatty acid amides, substituted amides, methylol amides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, etc. can be mentioned. Specific examples of other saturated fatty acid amides include lauric acid amide, palmitic acid amide, stearic acid amide, hydroxystearic acid amide, etc. Specific examples of unsaturated fatty acid amides include oleic acid amide, erucic acid amide, etc. Specific 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, N-stearyl erucic acid amide, etc. Specific examples of methylol amides include methylol stearic acid amide, etc. Specific examples of saturated fatty acid bisamides include methylene bisstearic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, ethylene bisstearic acid amide, ethylene bishydroxystearic acid amide, ethylene bisbehenic acid amide, hexamethylene bisstearic acid amide, hexamethylene bisbehenic acid amide, hexamethylene hydroxystearic acid amide, N,N'-distearyl adipic acid amide, N,N'-distearyl sebacic acid amide, etc. Specific examples of unsaturated fatty acid bisamides include ethylene bisoleic acid amide, ethylene biserucic acid amide, hexamethylene bisoleic acid amide, N,N'-dioleyl adipic acid amide, N,N'-dioleyl sebacic acid amide, etc. Specific examples of fatty acid ester amides include stearoamide ethyl stearate, etc. Specific examples of aromatic bisamides include m-xylylene bisstearic acid amide, m-xylylene bishydroxystearic acid amide, N,N'-cis-stearyl isophthalic acid amide, etc. These amide lubricants may be used alone or in combination of two or more.

[0070] In the present embodiment, in addition to the saturated fatty acid amide, it is preferable that a plurality of types of amide-based lubricants further contain an unsaturated fatty acid amide. Thereby, when the lid body 60 is not exposed to high temperatures, the moldability and the continuous productivity of the power storage device 10 can be further improved. Although the details of this mechanism are not clear, it can be considered as follows, for example. That is, the unsaturated fatty acid amide has a double bond in its molecular structure, and when aggregates are formed between molecules, it has a structure in which olefin chains are folded. Therefore, the unsaturated fatty acid amide is relatively easy to move inside the heat-sealable resin layer 60Z, is easy to bleed to the surface of the heat-sealable resin layer 60Z, and is easy to exhibit lubricity. On the other hand, the saturated fatty acid amide does not have a double bond in its molecular structure, is linear, and has a bulky structure when aggregates are formed between molecules (especially when the number of carbon atoms is 18 or more). Therefore, it is difficult to bleed to the surface of the heat-sealable resin layer 60Z even during high-temperature storage, and it is difficult to exhibit lubricity. As one speculation, it is considered that an aggregate with appropriate bleeding properties and lubricity is formed by the association of the unsaturated fatty acid amide and the saturated fatty acid amide. As a second speculation, it is considered that the unsaturated fatty acid bleeds first to form a first layer on the surface of the heat-sealable resin layer 60Z, and then the bleeded saturated fatty acid is formed as a second layer between the first layer and the heat-sealable resin layer 60Z. Therefore, further bleeding of the unsaturated fatty acid, which causes the problem of white powder, is suppressed.

[0071] Regarding the number of carbon atoms of the saturated fatty acid amide, the weight loss due to overheating in the temperature range of about 230 to 280 °C for melt extrusion processing of the resin (such as polypropylene) forming the heat-sealable resin layer 60Z reaches about 50% or more when the number of carbon atoms is less than 18. From the viewpoint of content management, it is desirable that the number of carbon atoms is 18 or more. Furthermore, as described above, since the saturated fatty acid suppresses excessive bleeding of the lubricant (in any of the above speculations), it is desirable that the number of carbon atoms is about 22, such as behenic acid amide. From the viewpoint of further improving the moldability and the continuous productivity of the power storage device 10, erucic acid amide is particularly preferable as the unsaturated fatty acid amide. The unsaturated fatty acid amide may be used alone or in combination of two or more.

[0072] In another example, the heat-sealable resin layer 60Z may be composed of any one of an acid-modified polyolefin resin, an unsaturated carboxylic acid graft polyolefin resin, a polypropylene resin, a metal ion crosslinked polyethylene, a copolymer resin of ethylene and an acrylic acid derivative, and a copolymer resin of ethylene and a methacrylic acid derivative.

[0073] In yet another example, the heat-sealable resin layer 60Z may be composed of a polyolefin resin added with a propylene-based elastomer having a melting point higher than 150°C. Compared with a polyolefin resin not added with a propylene-based elastomer resin having a melting point higher than 150°C, the adhesion strength between the heat-sealable resin layer 60Z and the heat-sealable resin layer 53 of the outer film 50 is stable in an environment near 150°C. This is because the heat-sealable resin layer 60Z is formed in a state where a propylene-based elastomer resin having a melting point higher than 150°C is uniformly dispersed in the polyolefin resin, and even after heat sealing (for example, sealing temperature 190°C, surface pressure 1.0 MPa, sealing time 3.0 seconds), the high melting point propylene-based elastomer resin is kept uniformly dispersed in the polyolefin resin. Thereby, even in a high temperature environment near 150°C, the portion where the heat-sealable resin layer 60Z and the heat-sealable resin layer 53 are sealed, that is, the second sealing portion 80 described later, is prevented from melting and softening.

[0074] The heat-sealable resin layer 60Z is characterized by including at least one layer having an elastic modulus measured by a pushing load of 100 μN in the FB direction of 1300 MPa or more. Since the elastic modulus of the heat-sealable resin layer 60Z is 1300 MPa or more, even when there are minute foreign substances in the heat-sealed portion of the heat-sealable resin layer 60Z, it can exhibit high insulation. Since the heat-sealable resin layer 60Z includes at least one layer having a high elastic modulus of 1300 MPa or more, even when heat-sealed at a location where minute foreign substances are present, it is possible to effectively prevent the heat-sealable resin layer 60Z from becoming thin.

[0075] From the perspective of further enhancing insulation, the elastic modulus is preferably 1500 MPa or more, more preferably 1800 MPa or more, still more preferably 2000 MPa or more. Also, it is preferably 3000 MPa or less, more preferably 2800 MPa or less, still more preferably 2500 MPa or less. The preferable range is about 1300 - 3000 MPa, about 1300 - 2800 MPa, about 1300 - 2500 MPa, about 1500 - 3000 MPa, about 1500 - 2800 MPa, about 1500 - 2500 MPa, about 1800 - 3000 MPa, about 1800 - 2800 MPa, about 1800 - 2500 MPa, about 2000 - 3000 MPa, about 2000 - 2800 MPa, about 2000 - 2600 MPa. More specifically, when the heat-sealing resin layer 60Z is a layer with an elastic modulus of 1300 MPa or more, the above elastic modulus is preferable.

[0076] The elastic modulus of the heat-sealing resin layer 60Z is measured by the indentation method as follows. Use a nanoindenter (TriboIndenter TI950 manufactured by HYSITRON) to measure the elastic modulus. In the nanoindenter, use a indenter (TI-0039 manufactured by HYSITRON) with a tip in the shape of a regular triangular pyramid (Berkovich type) made of a diamond tip. At room temperature (25 °C), cut the heat-sealing resin layer 60Z to expose the cross-section of the heat-sealing resin layer 60Z. Next, using the nanoindenter, measure the elastic modulus when the indenter is pushed vertically into the cross-section of the layer to be measured in the heat-sealing resin layer 60Z. The measurement conditions are the load control method, and the indentation load is constant at 100 μN (load from 0 to 100 μN in 10 seconds, hold 100 μN for 5 seconds, and unload from 100 to 0 μN in 10 seconds).

[0077] The heat-sealing resin layer 60Z preferably has a logarithmic decrement ΔE at 120 °C in the rigid pendulum measurement of 0.50 or less. When the logarithmic decrement ΔE at 120 °C is 0.50 or less, the collapse when the heat-sealing resin layer 60Z is heat-sealed is effectively suppressed.

[0078] The logarithmic decrement at 120 °C in the rigid pendulum measurement is an index representing the hardness of the resin in a high-temperature environment of 120 °C, which means that the smaller the logarithmic decrement, the higher the hardness of the resin. The temperature for heat-sealing the heat-sealable resin layer 60Z is high, and in the heat-sealed portion formed by heat-sealing the heat-sealable resin layer 60Z, the heat-sealable resin layer 60Z may protrude significantly inside the heat-sealed portion (on the side of the space where the electrode body 20 is accommodated). When the heat-sealable resin layer 60Z protrudes significantly inside the heat-sealed portion, cracks may occur in the heat-sealable resin layer 60Z starting from this protruding portion (so-called polymer accumulation), and the insulation property is likely to deteriorate. Therefore, when the heat-sealable resin layer 60Z protrudes significantly inside the heat-sealed portion and a protruding portion is formed, the insulation property is likely to deteriorate due to cracks. For this reason, it is important to control the shape of the heat-sealed portion, and for this purpose, the hardness of the heat-sealable resin layer 60Z at high temperatures is important. Therefore, in the present embodiment, the logarithmic decrement at a high temperature of 120 °C is adopted. In the rigid pendulum measurement, the attenuation rate of the pendulum is measured when the temperature of the resin is raised from low to high. In the rigid pendulum measurement, generally, the edge portion is brought into contact with the surface of the measurement object, and the pendulum is moved in the left-right direction to impart vibration to the measurement object. In the present embodiment, since the heat-sealable resin layer 60Z having a logarithmic decrement of 0.50 or less in a high-temperature environment of 120 °C is used as the material constituting the lid 60, the collapse (thinning) of the heat-sealable resin layer 60Z during heat-sealing of the lid 60 is suppressed. By suppressing the collapse of the heat-sealable resin layer 60Z, in the heat-sealed portion formed by heat-sealing the heat-sealable resin layer 60Z, the heat-sealable resin layer 60Z is suppressed from protruding significantly inside the heat-sealed portion, and the deterioration of the insulation property of the lid 60 due to heat-sealing is effectively suppressed.

[0079] Note that the logarithmic decrement ΔE is calculated by the following formula. ΔE = [ln(A1 / A2) + ln(A2 / A3) + ··· ln(An / An+1)] / n A: Amplitude n: Number of waves

[0080] From the perspective of effectively suppressing the collapse of the heat-sealable resin layer 60Z when heat-sealing the heat-sealable resin layer 60Z, the logarithmic decrement ΔE at 120 °C is preferably about 0.10 or more, more preferably about 0.11 or more, still more preferably about 0.12 or more. Also, preferably it is about 0.50 or less, more preferably about 0.30 or less, still more preferably about 0.22 or less, and still more preferably 0.16 or less. The preferable range of the logarithmic decrement ΔE is, for example, about 0.10 to 0.50, about 0.10 to 0.30, about 0.10 to 0.22, about 0.10 to 0.16, about 0.11 to 0.50, about 0.11 to 0.30, about 0.11 to 0.22, about 0.11 to 0.16, about 0.12 to 0.50, about 0.12 to 0.30, about 0.12 to 0.22, about 0.12 to 0.16.

[0081] The logarithmic decrement ΔE of the heat-sealable resin layer 60Z can be adjusted, for example, by the melt mass flow rate (MFR), molecular weight, melting point, softening point, molecular weight distribution, crystallinity, etc. of the resin constituting the heat-sealable resin layer 60Z.

[0082] In the measurement of the logarithmic decrement ΔE, a commercially available rigid pendulum type physical property tester is used, and a cylindrical cylinder edge is used as the edge part pressed against the heat-sealable resin layer 60Z. A rigid pendulum physical property test is performed on the heat-sealable resin layer 60Z under the conditions of an initial amplitude of 0.3 degree and a heating rate of 3 °C / min in the temperature range from 30 °C to 200 °C.

[0083] The melt mass flow rate of the heat-sealable resin layer 60Z at 230 °C is preferably included in the range of 1 g / 10 min to 80 g / 10 min, and more preferably included in the range of 5 g / 10 min to 60 g / 10 min. The melt mass flow rate is measured based on JIS K7210-1:2014.

[0084] From the perspective of effectively suppressing the misalignment of the second sealing portion 80 described below, the melting point Tm1 of the heat-sealable resin layer 60Z is preferably 90°C or higher and 245°C or lower, more preferably 100°C or higher and 220°C or lower. Also, from the same perspective, the softening point Ts1 of the heat-sealable resin layer 60Z is preferably 70°C or higher and 180°C or lower, more preferably 80°C or higher and 150°C or lower.

[0085] Here, the melting point Tm1 of the heat-sealable resin layer 60Z is a value measured by the DSC method in accordance with JIS K6921-2 (ISO1873-2.2:95) for the melting point of the resin component constituting the heat-sealable resin layer 60Z. Also, when the heat-sealable resin layer 60Z is formed of a blend resin containing a plurality of resin components, the melting point Tm1 can be obtained by determining the melting points of the respective resins as described above and calculating their weighted average based on the mass ratio.

[0086] Also, the softening point Ts1 of the heat-sealable resin layer 60Z is a value measured by the thermo-mechanical analysis method (TMA: Thermo-Mechanical Analyzer). Also, when the heat-sealable resin layer 60Z is formed of a blend resin containing a plurality of resin components, the softening point Ts1 can be obtained by determining the softening points of the respective resins as described above and calculating their weighted average based on the mass ratio.

[0087] The number average molecular weight (Mn) of the resin constituting the heat-sealable resin layer 60Z is preferably 70,000 or higher and 80,000 or lower, the weight average molecular weight (Mw) is 320,000 or higher and 370,000 or lower, and the dispersity (Mw / Mn) is 4.5 or higher and 5.5 or lower.

[0088] Also, although the details of the mechanism by which the number average molecular weight (Mn) and weight average molecular weight (Mw) of the resin constituting the heat-sealing resin layer 60Z can impart high insulation and heat-sealing properties to the lid body 60 are not necessarily clear, for example, it can be considered as follows. That is, when the number average molecular weight (Mn) is less than 70,000, since there are many low molecular weight components, the amount crushed by the pressure during heat sealing increases, and the insulation property decreases. Also, when the number average molecular weight (Mn) is greater than 80,000, there are few low molecular weight components, there is concern about a decrease in MFR, and there is a risk that the film-forming property will be impaired. Furthermore, when the weight average molecular weight (Mw) is less than 320,000, since there are few high molecular weight bodies as a whole, the amount crushed by the pressure during heat sealing increases, and the insulation property decreases. Also, when the weight average molecular weight (Mw) is greater than 370,000, since there are many high molecular weight bodies as a whole, there is concern about a decrease in MFR, and there is a risk that the film-forming property will be impaired. Furthermore, although the details of the mechanism by which the dispersity (Mw / Mn) of the resin constituting the heat-sealing resin layer 60Z can impart high insulation and heat-sealing properties to the lid body 60 are not necessarily clear, for example, it can be considered as follows. That is, when the dispersity (Mw / Mn) is less than 4.5, the molecular weight distribution is narrow, and there is a risk of causing a decrease in film-forming property such as neck-in during extrusion. Also, when the dispersity (Mw / Mn) is greater than 5.5, the molecular weight distribution becomes wide and the low molecular weight components also increase, so the amount crushed by the pressure during heat sealing increases, and the insulation property decreases.

[0089] In this embodiment, a through-hole 60X into which the electrode terminal 30 is inserted is formed in the lid body 60. The through-hole 60X penetrates the first surface 61 and the second surface 62. With the electrode body 20 housed, the electrode terminal 30 protrudes outside the exterior body 40 through the through-hole 60X formed in the lid body 60. A slight gap between the through-hole 60X of the lid body 60 and the electrode terminal 30 is filled with, for example, resin. In the power storage device 10, the position where the electrode terminal 30 protrudes outside can be arbitrarily selected. For example, the electrode terminal 30 may protrude outside through a hole formed in any one of the six surfaces of the exterior body 40. In this case, a slight gap between the exterior body 40 and the electrode terminal 30 is filled with, for example, resin. In the power storage device 10, the lid body 60 and the electrode terminal 30 are provided as separate bodies, but the lid body 60 and the electrode terminal 30 may be integrally formed. Note that when the electrode terminal 30 does not protrude from the edge of the exterior body 40, the through-hole 60X may not be formed in the lid body 60.

[0090] In this embodiment, with the exterior film 50 wound around the periphery of the electrode body 20 so as to have the opening 40A, the surfaces (heat-sealable resin layers 53) of the exterior film 50 facing each other are heat-sealed to form the first sealing portion 70.

[0091] The first sealing portion 70 is formed by heat-sealing a portion including the first edge 50A of the exterior film 50 and a portion including the second edge 50B shown in FIG. 3. The first sealing portion 70 extends in the longitudinal direction of the exterior body 40. In the exterior body 40, the position where the first sealing portion 70 is formed can be arbitrarily selected. In this embodiment, it is preferable that the base 70X of the first sealing portion 70 is located on the side 43 at the boundary between the first surface 41 and the second surface 42 of the exterior body 40. The first surface 41 has a larger area than the second surface 42. The base 70X of the first sealing portion 70 may be located on any surface of the exterior body 40. In this embodiment, the first sealing portion 70 protrudes outward from the electrode body 20 in a plan view. The first sealing portion 70 may be folded, for example, toward the second surface 42 of the exterior body 40 or toward the first surface 41.

[0092] In this embodiment, the second sealing portion 80 is formed by heat-sealing the heat-sealable resin layer 53 of the exterior film 50 and the lid seal portion 63 of the lid body 60. Hereinafter, the sealing strength between the heat-sealable resin layer 53 of the exterior film 50 and the lid seal portion 63 of the lid body 60 may be referred to as the sealing strength of the second sealing portion 80. The sealing strength of the second sealing portion 80 is the sealing strength between the heat-sealable resin layer 53 and the lid body 60 in the long-side portion of the lid seal portion 63, that is, the lid seal portion 63 extending in the LR (width) direction in FIG. 1A.

[0093] The sealing strength of the second sealing portion 80 is measured as follows. First, a cut is formed in the portion of the exterior film 50 that constitutes the first surface 41 of the exterior body 40 to form three strip members 41X, 41Y, and 41Z arranged in the LR direction (see the two-dot chain line in FIG. 1B). The width of the three strip members 41X, 41Y, and 41Z in the LR direction is 15 mm. The ends of the strip members 41X, 41Y, and 41Z are joined to the lid body 60 at the second sealing portion 80. The length of the lid body 60 in the LR direction is 45 mm or more. Next, the sealing strengths of the strip members 41X, 41Y, and 41Z are measured respectively by pulling the ends of the strip members 41X, 41Y, and 41Z opposite to the ends joined to the lid body 60 upward in the UD direction (the direction opposite to the first surface 41B). In this embodiment, the sealing strength of the second sealing portion 80 is the average value of the sealing strengths of the strip members 41X, 41Y, and 41Z. When the length of the lid body 60 in the LR direction is less than 45 mm, three strip members with an arbitrary width X mm less than 15 mm are formed, and the sealing strengths of the three strip members are measured in the same manner as when the length of the lid body 60 in the LR direction is 45 mm or more. By dividing the obtained sealing strengths by the arbitrary width X mm and multiplying by 15 respectively, the sealing strengths of the three strip members at a width of 15 mm are converted respectively. The sealing strength of the second sealing portion 80 is the average value of the sealing strengths of the three strip members converted to a width of 15 mm. In addition, when the lid body 60 is divided into a plurality of parts including a long side and a short side, the sealing strength of the second sealing portion 80 is the sealing strength in the long-side portion of the lid seal portions 63 of the plurality of parts.

[0094] From the viewpoint of suitably maintaining the state in which the electrode body 20 is sealed by the exterior body 40, the sealing strength of the second sealing portion 80 is preferably 40 N / 15 mm or more, more preferably 50 N / 15 mm or more, still more preferably 60 N / 15 mm or more, still more preferably 70 N / 15 mm or more, still more preferably 85 N / 15 mm or more. When the sealing strength of the second sealing portion 80 is 40 N / 15 mm or more, even if the power storage device 10 is used for, for example, several years (less than 10 years), the state in which the electrode body 20 is sealed by the exterior body 40 is suitably maintained. When the sealing strength of the second sealing portion 80 is 85 N / 15 mm or more, even if the power storage device 10 is used for, for example, 10 years or more, the state in which the electrode body 20 is sealed by the exterior body 40 is suitably maintained. The sealing strength of the second sealing portion 80 is preferably 300 N / 15 mm or less. The preferable range of the sealing strength of the second sealing portion 80 is 40 N / 15 mm to 300 N / 15 mm, 50 N / 15 mm to 300 N / 15 mm, 60 N / 15 mm to 300 N / 15 mm, 70 N / 15 mm to 300 N / 15 mm, or 85 N / 15 mm to 300 N / 15 mm.

[0095] In this embodiment, it is preferable that the lid body 60 has a protruding portion 68 that protrudes from the lid seal portion 63 so that a gap is less likely to be formed between the exterior film 50 and the lid body 60. The protruding portion 68 may be integrally formed with the lid main body 60A, or may be formed separately from the lid main body 60A and joined to the lid main body 60A. In this embodiment, the protruding portion 68 is integrally formed with the lid main body 60A. In the lid seal portion 63, the position where the protruding portion 68 is formed can be arbitrarily selected. The gap between the exterior film 50 and the lid body 60 is likely to be formed, for example, between the base 70X of the first sealing portion 70 and the lid body 60. In particular, when the base 70X of the first sealing portion 70 is located at the boundaries 64 to 67 of the lid body 60, the resin filling property between the base 70X of the first sealing portion 70 and the lid body 60 is likely to decrease. For this reason, it is preferable that the protruding portion 68 is formed at the position where the base 70X of the first sealing portion 70 is located in the lid seal portion 63. In this embodiment, the base 70X of the first sealing portion 70 is located at the boundary 64 of the lid body 60. For this reason, it is preferable that the protruding portion 68 is formed at the boundary 64 in the lid seal portion 63. In this embodiment, the first sealing portion 70 is sealed with the protruding portion 68 sandwiched therebetween. Note that the protruding portion 68 may be formed on at least one of the first seal surface 63A, the second seal surface 63B, the third seal surface 63C, the fourth seal surface 63D, the boundary 65, the boundary 66, and the boundary 67.

[0096] The shape of the protruding portion 68 can be arbitrarily selected. In this embodiment, the shape of the protruding portion 68 is plate-like. The thickness of the protruding portion 68 can be arbitrarily selected. In this embodiment, the thickness of the protruding portion 68 becomes thinner as it moves away from the boundary 64. In other words, the protruding portion 68 has a tapered shape as it moves away from the boundary 64. The thickness of the protruding portion 68 may be constant, or may become thicker as it moves away from the boundary 64.

[0097] The direction in which the protruding portion 68 extends can be arbitrarily selected. In this embodiment, the protruding portion 68 extends along the first direction (in this embodiment, the LR direction). The protruding portion 68 may extend along the second direction (in this embodiment, the UD direction).

[0098] The length of the protruding portion 68 can be arbitrarily selected within the range that is equal to or less than the length of the first sealing portion 70. For example, the length of the protruding portion 68 may be substantially equal to the length of the first sealing portion 70, or may be 30% to 50% of the length of the first sealing portion 70.

[0099] <1-2. Method for manufacturing a power storage device> FIG. 7 is a flowchart showing an example of a method for manufacturing the power storage device 10. The method for manufacturing the power storage device 10 includes, for example, a first step, a second step, a third step, and a fourth step. The first to fourth steps are performed, for example, by a manufacturing apparatus for the power storage device 10.

[0100] In the first step of step S11, the manufacturing apparatus arranges the lid body 60 in a state where the electrode terminals 30 are attached to both ends of the electrode body 20. By completing the first step, the electrode terminals 30 and the electrodes of the electrode body 20 are electrically connected. In the first step, the lid body 60 may be connected to the electrode terminals 30 that are electrically connected to the electrode body 20.

[0101] The second step of step S12 is performed after the first step. In the second step, the manufacturing apparatus winds the exterior film 50 around the electrode body 20 and the lid body 60 while the tension acts on the exterior film 50 while restricting the movement of the electrode body 20 and the lid body 60 by a restricting means. The restricting means is, for example, a groove into which the electrode body 20 and the lid body 60 are fitted. The restricting means may be a device that applies an external force to the electrode body 20 and the lid body 60 so that the electrode body 20 and the lid body 60 do not move. The restricting means may be a device that applies a force in a direction opposite to the direction in which the exterior film 50 is pulled to the electrode body 20 and the lid body 60. Note that the restricting means may include a roller that travels on the exterior film 50 in a state where the exterior film 50 is being pulled in order to remove wrinkles in the exterior film 50.

[0102] The third step of step S13 is carried out after the second step. In the third step, the manufacturing apparatus heat-seals the heat-fusible resin layer 53 of the portion including the first edge 50A of the exterior film 50 and the heat-fusible resin layer 53 of the portion including the second edge 50B while restricting the movement of the electrode body 20 and the lid body 60 and while tension is applied to the exterior film 50 so that the protruding portion 68 of the lid body 60 is sandwiched by the exterior film 50, thereby forming the first sealing portion 70. Note that the third step corresponds to the step of forming the first sealing portion 70.

[0103] The fourth step of step S14 is carried out after the third step. The manufacturing apparatus forms the second sealing portion 80 by heat-sealing the exterior film 50 and the lid body 60.

[0104] <1-3. Action and Effect of Power Storage Device> According to the power storage device 10, since the lid body 60 is constituted by the heat-fusible resin layer 60Z, it is favorably heat-sealed with the heat-fusible resin layer 53 of the exterior film 50. For this reason, the electrode body 20 can be favorably sealed by the exterior body 40.

[0105] [2. Modification Example] The above-described embodiment is an exemplification of the forms that the lid body, the power storage device, and the peripheral member related to the present invention can take, and is not intended to limit the form. The lid body, the power storage device, and the peripheral member related to the present invention can take forms different from the forms exemplified in the embodiment. One example is a form in which a part of the configuration of the embodiment is replaced, changed, or omitted, or a form in which a new configuration is added to the embodiment. Some examples of modification examples of the embodiment are shown below. Note that the following modification examples can be combined with each other as long as there is no technical contradiction.

[0106] <2-1. First Modification Example> In the power storage device 10 of the above-described embodiment, the lid body 60 may not have the protruding portion 68. Note that the first modification example can be similarly applied to the following second to fourteenth modification examples.

[0107] <2-2. Second Modification Example> In the power storage device 10 of the above-described embodiment, the direction in which the protruding portion 68 extends can be arbitrarily changed. For example, as shown in FIG. 8, the protruding portion 68 may extend in a third direction that intersects a first direction (LR direction in the embodiment) and a second direction (UD direction in the embodiment) in a front view of the lid body 60.

[0108] <2-3. Third Modification Example> In the power storage device 10 of the above-described embodiment, the configuration of the lid body 60 can be arbitrarily changed. As shown in FIG. 9, the lid body 60 may include a peripheral member 60B that is joined to at least a part of the peripheral edge of the lid main body 60A. In the third modification example, the peripheral member 60B is a frame that covers the entire peripheral edge of the lid main body 60A. In this modification example, for example, any material such as metal or resin can be used for the material constituting the lid main body 60A. The material constituting the peripheral member 60B is a heat-sealable resin layer 60BZ. The specifications of the heat-sealable resin layer 60BZ can be applied to the specifications of the heat-sealable resin layer 60Z. In the third modification example, the lid seal portion 63 and the protruding portion 68 of the lid body 60 are formed on the peripheral member 60B. In the third modification example, the lid main body 60A and the peripheral member 60B may be configured as separate bodies and joined to each other. In the third modification example, the lid main body 60A and the peripheral member 60B may be integrally formed by two-color molding or insert molding.

[0109] In the third modification example, the power storage device 10 may include at least one of an adhesive film and an adhesive layer that preferably joins the lid main body 60A and the peripheral member 60B to each other. The adhesive film or the adhesive layer may be a single layer or a multi-layer, and preferably contains a resin material having at least a polar group. The adhesive layer can be formed by dip coating, dispenser, inkjet, spraying, or screen printing, etc. From the viewpoint of preferably joining the lid main body 60A and the peripheral member 60B to each other, it is preferable that at least the surface of the lid seal portion 63 of the lid main body 60A is subjected to a roughening treatment.

[0110] In the third modification example, even when the power storage devices 10 are stacked, it is preferable that the lid seal portion 63 of the peripheral member 60B has a certain thickness so that the exterior body 40 is suppressed from deforming. From another perspective, when forming the second sealing portion 80, it is preferable that the lid seal portion 63 of the peripheral member 60B has a certain thickness so that the lid seal portion 63 of the peripheral member 60B and the exterior film 50 can be suitably heat-sealed. The minimum value of the thickness of the lid seal portion 63 of the peripheral member 60B is, for example, 1.0 mm, more preferably 3.0 mm, and even more preferably 4.0 mm. The maximum value of the thickness of the lid seal portion 63 of the peripheral member 60B is, for example, 20 mm, more preferably 15 mm, and even more preferably 10 mm. The maximum value of the thickness of the lid seal portion 63 of the peripheral member 60B may be 20 mm or more. The preferable range of the thickness of the lid seal portion 63 of the peripheral member 60B is 1.0 mm to 20 mm, 1.0 mm to 15 mm, 1.0 mm to 10 mm, 3.0 mm to 20 mm, 3.0 mm to 15 mm, 3.0 mm to 10 mm, 4.0 mm to 20 mm, 4.0 mm to 15 mm, 4.0 mm to 10 mm.

[0111] <2-4. Fourth Modification Example> In the power storage device 10 of the above embodiment, the specific method of forming the protruding portion 68 of the lid body 60 can be arbitrarily changed. For example, the protruding portion 68 may be formed by an adhesive film or the like joined to the lid seal portion 63 of the lid main body 60A. In this modification example, for example, a plurality of adhesive films may be joined to the lid seal portion 63 so as to overlap to form the protruding portion 68, or the adhesive film may be joined to the lid seal portion 63 in a flap shape to form the protruding portion 68.

[0112] <2-5. Fifth Modification Example> In order to preferably adhere the exterior film 50 and the lid body 60, the power storage device 10 of the above-described embodiment may have a peripheral member 60C disposed between the exterior film 50 and the lid main body 60A as shown in FIG. 10. In the fifth modification, the peripheral member 60C is an adhesive film joined to the peripheral portion (lid seal portion 63) of the lid main body 60A. In the fifth modification, for example, any material such as metal or resin can be used as the material constituting the lid main body 60A. In the fifth modification, the peripheral member 60C is adhered to substantially the entire lid seal portion 63 of the lid main body 60A. Note that the peripheral member 60C may be adhered to at least a part of the first surface 61 and at least a part of the second surface 62 of the lid body 60.

[0113] In the fifth modification, for example, after the lid body 60 with the peripheral member 60C adhered thereto is attached to the openings 40A at both ends of the exterior body 40, the second sealing portion 80 is formed. The peripheral member 60C may be wound around the lid body 60 so as to cover the entire surface of the lid seal portion 63 of the lid body 60, for example. The peripheral member 60C is preferably configured to be wider than the lid seal portion 63 of the lid body 60 as a whole. In this case, the peripheral member 60C can be easily adhered to the lid body 60. Furthermore, since the boundaries 64 to 67 of the lid seal portion 63 are covered by the peripheral member 60C, the adhesiveness between the lid body 60 and the peripheral member 60C is enhanced.

[0114] FIG. 11 is a cross-sectional view showing an example of the layer structure of the peripheral member 60C. The peripheral member 60C is a film capable of adhering the exterior film 50 and the lid body 60. The peripheral member 60C preferably has a heat-sealable resin layer 60CA at least at a portion joined to the heat-sealable resin layer 53 of the exterior film 50. In the example shown in FIG. 11, the peripheral member 60C is a laminate (laminated film) having at least a heat-sealable resin layer 60CA, a barrier layer 60CB, and a heat-sealable resin layer 60CC in this order. The peripheral member 60C may have a single-layer structure of the heat-sealable resin layer 60CA. Specifications regarding the heat-sealable resin layers 60CA and 60CC of the peripheral member 60C can be applied to the specifications regarding the heat-sealable resin layer 60Z. Specifications regarding the barrier layer 60CB can be applied to the specifications regarding the barrier layer 52 of the exterior film 50. Instead of the heat-sealable resin layer 60CC on the side of the peripheral member 60C that is adhered to the lid body 60, the peripheral member 60C may have a heat-sealable resin layer. The material constituting the heat-sealable resin layer is preferably an acid-modified polyolefin resin graft-modified with an acid such as maleic anhydride. The material constituting the heat-sealable resin layer 60CC of the peripheral member 60C can be arbitrarily selected as long as it can be joined to the lid main body 60A.

[0115] The peripheral member 60C may have a heat-resistant base material layer instead of or in addition to the barrier layer 60CB. The heat-resistant base material layer may be a film made of a heat-resistant resin. For example, unstretched or stretched films such as polyethylene terephthalate, polyethylene naphthalate, polyphenylene sulfide, polymethylpentene (registered trademark), polyacetal cyclic polyolefin, polyethylene, and polypropylene can be used. Among them, polyethylene terephthalate is inexpensive and has high strength, and is particularly preferable.

[0116] The peripheral member 60C preferably has adhesiveness. When the peripheral member 60C has adhesiveness, when the second sealing portion 80 is formed with the peripheral member 60C disposed between the exterior film 50 and the lid body 60, the position of the peripheral member 60C with respect to the lid body 60 and the exterior film 50 is less likely to shift. By including an adhesion-imparting resin in the heat-sealable resin layers 60CA and 60CC of the peripheral member 60C, adhesiveness can be imparted to the peripheral member 60C. Examples of the adhesion-imparting resin include amorphous polyolefin. Examples of the amorphous polyolefin include amorphous polypropylene, or a copolymer of amorphous propylene and other α-olefins. The content of the adhesion-imparting resin with respect to the base material constituting the heat-sealable resin is preferably 10 to 20% by weight or less.

[0117] <2-6. Sixth Modification Example> In the above embodiment, the position where the electrode terminal 30 is disposed can be arbitrarily selected. For example, the electrode terminal 30 may protrude from the first sealing portion 70.

[0118] <2-7. Seventh Modification Example> In the above embodiment, the exterior film 50 of the power storage device 10 may protrude outside at least one of the two lid bodies 60 in the FB direction. By closing the portion of the exterior film 50 that protrudes outside the lid body 60, the electrode body 20 is sealed. The portion of the exterior film 50 that protrudes outside the lid body 60 may be folded like a gable-top type pouch or a brick type pouch.

[0119] <2-8. Eighth Modification Example> In the above-described embodiment, the exterior body 40 may not have one of the two lid bodies 60. In this modification, in the FB direction, at the portion of the exterior body 40 where the lid body 60 is omitted, the portion of the exterior film 50 that protrudes outward from the electrode body 20 is closed, whereby the electrode body 20 is sealed. In this modification, the portion of the exterior film 50 that protrudes outward from the electrode body 20 may be folded like a gable-top pouch or a brick-type pouch.

[0120] <2-9. Ninth Modification Example> In the above-described embodiment, the outer shape of the exterior body 40 can be arbitrarily changed. The outer shape of the exterior body 40 may be a cylinder, a prism, or a cube.

[0121] <2-10. Tenth Modification Example> In the above-described embodiment, instead of the heat-sealable resin layer 60Z shown in FIG. 4, the lid body 60 may be configured to include a heat-sealable resin layer 160Z as shown in FIG. 12. In the third modification example, instead of the heat-sealable resin layer 60BZ shown in FIG. 9, the peripheral member 60B may be configured to include a heat-sealable resin layer 160ZB as shown in FIG. 13. In the fifth modification example, instead of the heat-sealable resin layer 60CA shown in FIG. 11, the peripheral member 60C may be configured to include a heat-sealable resin layer 160CA as shown in FIG. 14. Hereinafter, when the heat-sealable resin layer 160Z, the heat-sealable resin layer 160ZB, and the heat-sealable resin layer 160CA are not particularly distinguished, they may be simply referred to as the heat-sealable resin layer.

[0122] In the tenth modification example, the heat-sealable resin layer is characterized in that when the temperature difference T1 and the temperature difference T2 are measured by the following method, the value (ratio T2 / T1) obtained by dividing the temperature difference T2 by the temperature difference T1 is 0.60 or more.

[0123] (Measurement of Temperature Difference T1) In accordance with the provisions of JIS K7121:2012, a DSC curve is obtained for the heat-sealable resin layer by differential scanning calorimetry (DSC). From the obtained DSC curve, the temperature difference T1 between the extrapolated onset temperature and the extrapolated end temperature of the melting peak temperature of the heat-sealable resin layer is measured. Note that the measurement of the temperature difference T1 is different from the measurement of the following temperature difference T2, and is for a heat-sealable resin layer that has not been subjected to treatments such as immersion in an electrolytic solution.

[0124] (Measurement of temperature difference T2) In an environment at a temperature of 85°C, the heat-sealable resin layer is allowed to stand in an electrolytic solution having a concentration of lithium hexafluorophosphate of 1 mol / l and a volume ratio of ethylene carbonate, diethyl carbonate, and dimethyl carbonate of 1:1:1 for 72 hours, and then dried. Next, in accordance with the provisions of JIS K7121:2012, a DSC curve is obtained for the dried heat-sealable resin layer by differential scanning calorimetry (DSC). From the obtained DSC curve, the temperature difference T2 between the extrapolated onset temperature of the melting peak temperature and the extrapolated end temperature of the heat-sealable resin layer is measured.

[0125] The resin component used for the heat-sealable resin layer is not particularly limited as long as it is heat-sealable, and examples thereof include polyolefin, cyclic polyolefin, acid-modified polyolefin, and acid-modified cyclic polyolefin. That is, the heat-sealable resin layer may contain a polyolefin backbone, and preferably contains a polyolefin backbone. Whether the heat-sealable resin layer contains a polyolefin backbone can be analyzed by, for example, infrared spectroscopy, gas chromatography-mass spectrometry, etc., and the analysis method is not particularly limited. For example, when measuring maleic anhydride-modified polyolefin by infrared spectroscopy, peaks derived from maleic anhydride are detected in the vicinity of a wave number of 1760 cm -1 and in the vicinity of a wave number of 1780 cm -1 . However, if the degree of acid modification is low, the peak may become small and may not be detected. In that case, it can be analyzed by nuclear magnetic resonance spectroscopy.

[0126] Specific examples of the polyolefin include polyethylene such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; polypropylene such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymers of propylene and ethylene), random copolymers of polypropylene (e.g., random copolymers of propylene and ethylene); and terpolymers of ethylene-butene-propylene. Among these polyolefins, polyethylene and polypropylene are preferably used.

[0127] The cyclic polyolefin is a copolymer of an olefin and a cyclic monomer. Examples of the olefin that is a constituent monomer of the cyclic polyolefin include ethylene, propylene, 4-methyl-1-pentene, butadiene, isoprene, and the like. Examples of the cyclic monomer that is a constituent monomer of the cyclic polyolefin include cyclic alkenes such as norbornene; specifically, cyclic dienes such as cyclopentadiene, dicyclopentadiene, cyclohexadiene, and norbornadiene. Among these polyolefins, cyclic alkenes are preferably used, and norbornene is more preferably used.

[0128] The acid-modified polyolefin is a polymer obtained by modifying the polyolefin by block polymerization or graft polymerization with an acid component such as a carboxylic acid. Examples of the acid component used for modification include carboxylic acids or their anhydrides such as maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride.

[0129] The acid-modified cyclic polyolefin is a polymer obtained by copolymerizing a part of the monomers constituting the cyclic polyolefin by replacing it with an α,β-unsaturated carboxylic acid or its anhydride, or by block-polymerizing or graft-polymerizing an α,β-unsaturated carboxylic acid or its anhydride onto the cyclic polyolefin. The same applies to the cyclic polyolefin modified with a carboxylic acid. Further, the carboxylic acid used for the modification is the same as the acid component used for the modification of the polyolefin.

[0130] Among these resin components, polyolefins such as polypropylene and carboxylic acid-modified polyolefins are preferable; more preferably, polypropylene and acid-modified polypropylene are mentioned.

[0131] The heat-sealable resin layer may be formed of a single resin component alone, or may be formed of a blend polymer combining two or more resin components. Further, the heat-sealable resin layer may be formed of only one layer, but may also be formed of two or more layers with the same or different resin components.

[0132] The heat-sealable resin layer may contain a lubricant. Further, the lubricant present on the surface of the heat-sealable resin layer may be one that exudes the lubricant contained in the resin constituting the heat-sealable resin layer, or may be one with a lubricant applied to the surface of the heat-sealable resin layer.

[0133] More specifically, as can be understood from the measurement details of the following temperature differences T1 and T2, the closer the ratio T2 / T1 is to the upper limit value of 1.0, the smaller the change in the width between the start point (extrapolated melting start temperature) and the end point (extrapolated melting end temperature) of the melting peak before and after the heat-sealable resin layer comes into contact with the electrolyte. That is, the value of the temperature difference T2 is usually equal to or less than the value of the temperature difference T1. As a factor causing a large change in the width between the extrapolated melting start temperature and the extrapolated melting end temperature of the melting peak, the low-molecular-weight resin contained in the resin constituting the heat-sealable resin layer elutes into the electrolyte when it comes into contact with the electrolyte, and the width between the extrapolated melting start temperature and the extrapolated melting end temperature of the melting peak of the heat-sealable resin layer after contact with the electrolyte becomes smaller than before contact with the electrolyte. As one method for reducing the change in the width between the extrapolated melting start temperature and the extrapolated melting end temperature of the melting peak, there is a method of adjusting the proportion of the low-molecular-weight resin contained in the resin constituting the heat-sealable resin layer.

[0134] When measuring the extrapolated melting start temperature and the extrapolated melting end temperature of the melting peak temperature, a commercially available product can be used as the differential scanning calorimeter. Also, as the DSC curve, after holding the test sample at -50°C for 10 minutes, the temperature is raised to 200°C at a heating rate of 10°C / min (first time), held at 200°C for 10 minutes, then cooled to -50°C at a cooling rate of -10°C / min, held at -50°C for 10 minutes, and then the temperature is raised to 200°C at a heating rate of 10°C / min (second time), held at 200°C for 10 minutes, and the DSC curve when raising the temperature to 200°C for the second time is used. Also, when measuring the temperature difference T1 and the temperature difference T2, in each DSC curve, among the melting peaks appearing in the range of 120 to 160°C, analysis is performed on the melting peak with the largest difference in heat energy input. Even when there are two or more overlapping peaks, analysis is performed only on the melting peak with the largest difference in heat energy input.

[0135] In addition, the extrapolated melting start temperature means the starting point of the melting peak temperature, and is defined as the temperature of the intersection of a straight line obtained by extending the baseline on the low temperature side (65 - 75 °C) to the high temperature side and a tangent line drawn at the point where the gradient is maximized on the low temperature side curve of the melting peak where the difference in heat energy input is the largest. The extrapolated melting end temperature means the ending point of the melting peak temperature, and is defined as the temperature of the intersection of a straight line obtained by extending the baseline on the high temperature side (170 °C) to the low temperature side and a tangent line drawn at the point where the gradient is maximized on the high temperature side curve of the melting peak where the difference in heat energy input is the largest.

[0136] Even when the electrolytic solution comes into contact with the heat-sealing resin layer in a high-temperature environment and the heat-sealing resin layers are heat-sealed in a state where the electrolytic solution adheres to the heat-sealing resin layer, from the viewpoint of exhibiting an even higher seal strength due to heat-sealing, the value obtained by dividing the temperature difference T2 by the temperature difference T1 (ratio T2 / T1) is preferably 0.70 or more, more preferably 0.75 or more, and the preferable range is about 0.70 to 1.0, about 0.75 to 1.0. The upper limit is, for example, 1.0. In addition, in order to set such a ratio T2 / T1, for example, the type, composition, molecular weight, etc. of the resin constituting the heat-sealing resin layer are adjusted.

[0137] <2-11. The 11th modified example> In the fifth modification, the peripheral member 60C may be configured to include a heat-sealable resin layer 260CA as shown in FIG. 15, instead of the heat-sealable resin layer 60CA shown in FIG. 11. That is, in the eleventh modification, the peripheral member 60C is composed of a laminate including at least a barrier layer 60CB and a heat-sealable resin layer 260CA in this order from the inner side (the lid body 60 side) to the outer side (the exterior film 50 side). Note that the peripheral member 60C only needs to include at least the heat-sealable resin layer 260CA. The peripheral member 60C includes a peripheral member seal portion that is sealed to the exterior film 50 constituting the exterior body 40. In the eleventh modification, for the cross-section in the thickness direction of the peripheral member seal portion, an island structure is observed in the cross-sectional image obtained using a field emission scanning electron microscope. In the cross-sectional image, the ratio of the area of the island portion of the island structure is 0.1% or more and 50% or less. Note that the heat-sealable resin layer 260CA corresponds to the peripheral member seal portion. In the cross-sectional image, the ratio RA of the area of the island portion of the island structure is preferably 5% or more and 50% or less, more preferably 10% or more and 50% or less, and even more preferably 25% or more and 35% or less.

[0138] The main material constituting the heat-sealable resin layer 260CA can be arbitrarily selected as long as the ratio RA is included at 5% or more and 50% or less. The main material constituting the heat-sealable resin layer 260CA is preferably an olefin copolymer, and more preferably a random olefin copolymer. Note that in the eleventh modification, in the heat-sealable resin layer 260CA disposed on the first seal surface 63A or the fourth seal surface 63D, when observed using a scanning electron microscope for the cross-section cut by a plane perpendicular to the FB direction and the cross-section cut by a plane perpendicular to the LR direction, the cross-section with the average aspect ratio of the island shape closer to 1 in the TD direction is defined as the TD-direction cross-section. In the heat-sealable resin layer 260CA disposed on the second seal surface 63B or the third seal surface 63C, when observed using a scanning electron microscope for the cross-section cut by a plane perpendicular to the FB direction and the cross-section cut by a plane perpendicular to the UD direction, the cross-section with the average aspect ratio of the island shape closer to 1 in the TD direction is defined as the TD-direction cross-section.

[0139] To say that a sea-island structure is observed in a cross-sectional image means that a sea portion (sea part) and an island portion (island part) are observed in the cross-sectional image. When a small amount of polyethylene is added to polypropylene and a heat-sealable resin layer is formed by melt extrusion molding, a sea-island structure in which island portions of polyethylene are dispersed in the sea portion of polypropylene is formed. In addition, to observe the sea-island structure, as described later, the cross-section of the heat-sealable resin layer is stained with ruthenium tetroxide or the like, and a cross-sectional image is obtained and observed using a scanning electron microscope. Note that the specifications regarding the eleventh modification example can be similarly applied to the peripheral member 60B (frame body) shown in FIG. 9. The portion including the lid seal portion 63 among the peripheral members 60B corresponds to the peripheral member seal portion.

[0140] <2-12. The Twelfth Modification Example> In the above embodiment, the lid 60 may be configured to include a heat-sealable resin layer 260Z as shown in FIG. 16 instead of the heat-sealable resin layer 60Z shown in FIG. 4. Regarding the cross-section in the thickness direction of the lid seal portion 63 of the lid 60, a sea-island structure is observed in the cross-sectional image obtained using a field emission scanning electron microscope. In the cross-sectional image, the ratio RB of the area of the island portion of the sea-island structure is 0.1% or more and 50% or less, preferably 5% or more and 50% or less, more preferably 10% or more and 50% or less, and even more preferably 25% or more and 35% or less. In the twelfth modification example, it is sufficient that at least the portion including the lid seal portion 63 of the lid 60 is formed of the heat-sealable resin layer 260Z. The main material constituting the heat-sealable resin layer 260Z can be arbitrarily selected as long as the ratio RB is included in the range of 0.1% or more and 50% or less. The main material constituting the heat-sealable resin layer 260Z is preferably an olefin copolymer, and more preferably a random olefin copolymer.

[0141] When a sea-island structure is observed in a cross-sectional image, it means that a sea portion (sea part) and an island portion (island part) are observed in the cross-sectional image. When a small amount of polyethylene is added to polypropylene and a heat-sealable resin layer is formed by melt extrusion molding, a sea-island structure in which island portions of polyethylene are dispersed in the sea portion of polypropylene is formed. In order to observe the sea-island structure, the cross-section of the heat-sealable resin layer 260Z is stained with ruthenium tetroxide or the like, and a cross-sectional image is acquired and observed using a scanning electron microscope.

[0142] <2-13. The 13th modification example> In the 5th modification example, the peripheral member 60C as the adhesive film may be composed of cast polypropylene having necessary physical properties such as heat resistance and moisture resistance.

[0143] <2-14. The 14th modification example> FIG. 17 is a cross-sectional view of the power storage device 10 of the 14th modification example. FIG. 18 is a cross-sectional view of the lid body 60 in FIG. 17 and its periphery. As shown in FIGS. 17 and 18, from the viewpoint of suppressing the intrusion of at least one of moisture and gas into the exterior body 40, a barrier film 90 may be joined to the lid body 60. In the present embodiment, the barrier film 90 suppresses the intrusion of moisture and gas into the exterior body 40. The barrier film 90 may be joined at a position where it can be joined to the exterior film 50 of the lid body 60. In the example shown in FIGS. 17 and 18, the barrier film 90 covers the entire lid seal portion 63, the second surface 62, and the inside of the through hole 60X of the lid body 60. The barrier film 90 may cover the boundaries 64 to 67. Since the barrier film 90 covers the lid seal portion 63 and the boundaries 64 to 67, as well as the second surface 62 and the inside of the through hole 60X, the intrusion of moisture from between the electrode terminal 30 and the through hole 60X into the exterior body 40 is suppressed. The barrier film 90 may be composed of a single film. For example, the portion covering the lid seal portion 63 and the portion covering the second surface 62 may be configured separately. In other words, the barrier film 90 may be a plurality of divided films.

[0144] The positions of the ends 90A of the portion of the barrier film 90 covering the lid seal portion 63 and the positions of the ends 90B of the portion covering the inside of the through hole 60X of the lid body 60 can be arbitrarily selected. When the power storage device 10 is a battery containing an electrolytic solution such as a lithium ion battery, there is a risk that the gas such as hydrogen fluoride generated from the electrolytic solution comes into contact with the ends 90A and 90B of the barrier film 90, and the barrier layer 91 provided in the barrier film 90 described later may be corroded.

[0145] Therefore, from the viewpoint of suppressing the corrosion of the barrier layer 91, the end 90A is preferably located at a position closer to the second surface 62 than the boundary between the lid seal portion 63 and the first surface 61. From the same viewpoint, the end 90B is preferably located at a position closer to the opening on the second surface 62 side than the opening on the first surface 61 side of the through hole 60X. Note that the end 90A may be located at the boundary between the lid seal portion 63 and the first surface 61, or may extend to a position closer to the electrode body 20 than the lid body 60. The end 90B may be located in the vicinity of the opening on the first surface 61 side of the through hole 60X, or may extend to a position closer to the electrode body 20 than the lid body 60.

[0146] FIGS. 19 and 20 are cross-sectional views showing an example of the layer structure of the barrier film 90. As shown in FIG. 19, the barrier film 90 may include a barrier layer 91 and a heat-sealable resin layer 92 laminated on the surface of the barrier layer 91 opposite to the surface joined to the lid body 60. The specifications regarding the barrier layer 91 can be applied to the specifications regarding the barrier layer 52.

[0147] The heat-sealable resin layer 92 is heat-sealed to the heat-sealable resin layer 53 of the exterior film 50. The specifications regarding the heat-sealable resin layer 92 can be applied to the specifications regarding the heat-sealable resin layers 60Z, 60BZ, 60CA, 60CC, 160Z, 160BZ, 160CA, 260CA, 260Z. The heat-sealable resin layer 92 may be thinner than the heat-sealable resin layer 53. The thickness of the heat-sealable resin layer 92 may be, for example, 5 to 20 μm.

[0148] As shown in FIG. 20, the barrier film 90 may include a heat-sealable resin layer 93 laminated on the surface of the barrier layer 91 that is joined to the lid body 60. The specifications of the heat-sealable resin layer 93 are the same as those of the heat-sealable resin layer 92. The heat-sealable resin layer 93 may be thinner than the heat-sealable resin layer 53. The thickness of the heat-sealable resin layer 93 may be, for example, 5 to 20 μm. When the barrier film 90 includes the heat-sealable resin layer 93, the barrier film 90 and the lid body 60 can be suitably joined by heat sealing. The barrier layer 91 and the heat-sealable resin layer 93 may be joined by an adhesive layer 55.

[0149] In the 14th modification, the barrier film 90 may be joined only to at least a part of the second surface 62 of the lid body 60. In this configuration, as in the 7th modification, the heat-sealable resin layer 53 of the portion of the outer packaging film 50 that protrudes outside the lid body 60 and the heat-sealable resin layer 92 of the barrier film 90 are heat-sealed, whereby the electrode body 20 may be sealed.

[0150] The 14th modification discloses the following technical idea. (A) A lid body used for an exterior body of a power storage device, The lid body, A lid main body, A barrier film joined to a position where the lid main body can be joined to an outer packaging film constituting the exterior body, and The barrier film includes a heat-sealable resin layer whose main material is an olefin copolymer Lid body.

[0151] (B) An electrode body, An exterior body for sealing the electrode body, and The exterior body, An outer packaging film that wraps the electrode body, A lid body joined to the outer packaging film, and The lid body, A lid main body, A barrier film that is joined to a position where it can be joined to an exterior film that constitutes the exterior body among the lid main body, The barrier film includes a heat-sealable resin layer whose main material is an olefin copolymer Power storage device.

[0152] (C) A barrier film that constitutes a lid used for the exterior body of a power storage device, The lid body, A lid main body, A barrier film that is joined to a position where it can be joined to an exterior film that constitutes the exterior body among the lid main body, The barrier film includes a heat-sealable resin layer whose main material is an olefin copolymer Barrier film.

[0153] (D) A barrier film that constitutes a lid used for the exterior body of a power storage device, The lid body, A lid main body, The barrier film that is joined to a position where it can be joined to the exterior film that constitutes the exterior body among the lid main body, The barrier film includes a heat-sealable resin layer, The heat-sealable resin layer measures a temperature difference T1 and a temperature difference T2 by the following method, and a value obtained by dividing the temperature difference T2 by the temperature difference T1 is 0.60 or more. Barrier film. (Measurement of temperature difference T1) By differential scanning calorimetry, measure the temperature difference T1 between the extrapolated melting start temperature and the extrapolated melting end temperature of the melting peak temperature of the heat-sealable resin layer. (Measurement of temperature difference T2) In an environment at a temperature of 85 °C, the heat-sealable resin layer is allowed to stand in an electrolytic solution having a concentration of lithium hexafluorophosphate of 1 mol / l and a volume ratio of ethylene carbonate, diethyl carbonate, and dimethyl carbonate of 1:1:1 for 72 hours, and then dried. By differential scanning calorimetry, the temperature difference T2 between the extrapolated melting start temperature and the extrapolated melting end temperature of the melting peak temperature of the dried heat-sealable resin layer is measured.

[0154] (E) A barrier film constituting a lid used for an exterior body of an electric storage device, The lid body, A lid main body, The barrier film joined to a position where it can be joined to the exterior film constituting the exterior body in the lid main body, The barrier film includes a heat-sealable resin layer sealed to the exterior film, Regarding the cross-section in the thickness direction of the heat-sealable resin layer, a sea-island structure is observed in the cross-sectional image obtained using a field emission scanning electron microscope, In the cross-sectional image, the ratio of the area of the island part of the sea-island structure is 0.1% or more and 50% or less, preferably 5% or more and 50% or less, more preferably 10% or more and 50% or less, and even more preferably 25% or more and 35% or less.

Explanation of reference numerals

[0155] 10: Electric storage device 20: Electrode body 40: Exterior body 50: Exterior film 60: Lid body 60B: Peripheral member (frame body) 60C: Peripheral member (adhesive film) 60Z, 60BZ, 60CA, 60CC, 160Z, 160BZ, 160CA, 260CA, 260Z: Heat-sealable resin layer 60CB: Barrier layer

Claims

1. A lid used for an exterior body of an electricity storage device, wherein the lid, includes a heat-sealable resin layer whose main material is an olefin copolymer, and is a resin molded product having a lid seal portion with a thickness sufficient to be joined to an exterior film constituting the exterior body. Lid.

2. A lid used for an exterior body of an electricity storage device, wherein the lid, includes a lid main body and, a peripheral member joined to at least a part of a peripheral edge of the lid main body, wherein the peripheral member, includes a heat-sealable resin layer whose main material is an olefin copolymer, is a resin molded product joined to the lid main body and having a lid seal portion with a thickness sufficient to be joined to an exterior film constituting the exterior body. Lid.

3. The lid according to claim 2, comprising at least one of an adhesive film and an adhesive layer disposed between the lid main body and the peripheral member and joining the lid main body and the peripheral member. Lid according to claim 2.

4. The lid according to claim 2 or 3, wherein the peripheral member is a frame joined to the lid main body. Lid according to claim 2 or 3.

5. The lid according to any one of claims 1 to 3, wherein the olefin copolymer is an olefin random copolymer. Lid according to any one of claims 1 to 3.

6. The lid according to any one of claims 1 to 3, wherein the heat-sealable resin layer contains a fatty acid amide-based lubricant. Lid according to any one of claims 1 to 3.

7. The lid according to claim 6, wherein a plurality of types of fatty acid amide-based lubricants are present, and at least one of the fatty acid amide-based lubricants is a saturated fatty acid amide. Lid according to claim 6.

8. The lid according to claim 7, wherein the plurality of types of fatty acid amide-based lubricants further contain an unsaturated fatty acid amide. Lid according to claim 7.

9. The lid according to claim 7, wherein the saturated fatty acid amide has 18 or more carbon atoms. Lid according to claim 7.

10. The lid according to claim 7, wherein the saturated fatty acid amide is behenic acid amide. Lid according to claim 7.

11. The lid according to claim 10, wherein the unsaturated fatty acid amide is erucic acid amide. Lid according to claim 10.

12. The lid according to any one of claims 1 to 3, wherein the heat-sealable resin layer is composed of any one of an acid-modified polyolefin resin, an unsaturated carboxylic acid graft polyolefin resin, a polypropylene resin, a metal ion crosslinked polyethylene, a copolymer resin of ethylene and an acrylic acid derivative, and a copolymer resin of ethylene and a methacrylic acid derivative. Lid according to any one of claims 1 to 3.

13. The lid according to any one of claims 1 to 3, wherein the heat-sealable resin layer contains a propylene-based elastomer resin having a melting point higher than 150°C. Lid according to any one of claims 1 to 3.

14. An electrode body, An exterior body that seals the electrode body, The exterior body is An exterior film that wraps the electrode body, Including a lid body joined to the exterior film, The lid body is Including a heat-sealable resin layer whose main material is an olefin copolymer, A resin molded product having a lid seal portion with a thickness sufficient to be joined to the exterior film constituting the exterior body A power storage device.

15. An electrode body, An exterior body that seals the electrode body, The exterior body is An exterior film that wraps the electrode body, Including a lid body joined to the exterior film, The lid body is A lid main body, Including a peripheral member joined to at least a part of the peripheral edge of the lid main body, The peripheral member is Including a heat-sealable resin layer whose main material is an olefin copolymer, A resin molded product that is joined to the lid main body and has a lid seal portion with a thickness sufficient to be joined to the exterior film constituting the exterior body A power storage device.

16. A peripheral member that constitutes a lid body used for the exterior body of a power storage device, The lid body is A lid main body, Including the peripheral member joined to at least a part of the peripheral edge of the lid main body, The peripheral member is Including a heat-sealable resin layer whose main material is an olefin copolymer, A resin molded product that is joined to the lid main body and has a lid seal portion with a thickness sufficient to be joined to the exterior film constituting the exterior body Peripheral member.

17. A frame body joined to the lid main body The peripheral member according to claim 16.

18. A lid body used for the exterior body of a power storage device, A resin molded product including a heat-sealable resin layer and having a lid seal portion with a thickness sufficient to be joined to the exterior film constituting the exterior body, The heat-sealable resin layer is a lid body obtained by measuring a temperature difference T1 and a temperature difference T2 by the following method and dividing the temperature difference T2 by the temperature difference T1 to obtain a value of 0.60 or more. (Measurement of temperature difference T1) By differential scanning calorimetry, measure the temperature difference T1 between the extrapolated onset temperature and the extrapolated end temperature of the melting peak temperature of the heat-sealable resin layer. (Measurement of temperature difference T2) In an environment at a temperature of 85°C, the heat-sealable resin layer is allowed to stand in an electrolytic solution having a concentration of lithium hexafluorophosphate of 1 mol / l and a volume ratio of ethylene carbonate, diethyl carbonate, and dimethyl carbonate of 1:1:1 for 72 hours, and then dried. By differential scanning calorimetry, the temperature difference T2 between the extrapolated melting start temperature and the extrapolated melting end temperature of the melting peak temperature of the dried heat-sealable resin layer is measured.

19. A lid used for the exterior body of an electric storage device, which is a resin molded product including a heat-sealable resin layer and having a lid seal portion with a thickness sufficient to be joined to the exterior film constituting the exterior body, wherein the lid includes a lid seal portion sealed to the exterior film constituting the exterior body, in the cross-section in the thickness direction of the lid seal portion, a sea-island structure is observed in the cross-sectional image obtained using a field emission scanning electron microscope, and in the cross-sectional image, the ratio of the area of the island portion of the sea-island structure is 0.1% or more and 50% or less lid.

20. A peripheral member constituting a lid used for the exterior body of an electric storage device, wherein the lid includes a lid body, and the peripheral member joined to at least a part of the peripheral edge of the lid body, and the peripheral member is a resin molded product including a heat-sealable resin layer, joined to the lid body, and having a lid seal portion with a thickness sufficient to be joined to the exterior film constituting the exterior body, wherein the heat-sealable resin layer measures temperature differences T1 and T2 by the following method, and the value obtained by dividing the temperature difference T2 by the temperature difference T1 is 0.60 or more. Peripheral member. (Measurement of temperature difference T1) By differential scanning calorimetry, the temperature difference T1 between the extrapolated melting start temperature and the extrapolated melting end temperature of the melting peak temperature of the heat-sealable resin layer is measured. (Measurement of temperature difference T2) In an environment at a temperature of 85°C, the heat-sealable resin layer is allowed to stand in an electrolytic solution having a concentration of lithium hexafluorophosphate of 1 mol / l and a volume ratio of ethylene carbonate, diethyl carbonate, and dimethyl carbonate of 1:1:1 for 72 hours, and then dried. By differential scanning calorimetry, the temperature difference T2 between the extrapolated melting start temperature and the extrapolated melting end temperature of the melting peak temperature of the dried heat-sealable resin layer is measured.

21. A peripheral member constituting a lid used for the exterior body of an electric storage device, wherein the lid includes a lid body, including the peripheral member joined to at least a part of the peripheral edge of the lid body; the peripheral member is a resin molded product having a lid seal portion with a thickness that can be joined to the lid body and the exterior film constituting the exterior body; it includes a peripheral member seal portion sealed with the exterior film constituting the exterior body; for the cross-section in the thickness direction of the peripheral member seal portion, an island structure is observed in the cross-sectional image obtained using a field emission scanning electron microscope, and in the cross-sectional image, the ratio of the area of the island portion of the island structure is 0.1% or more and 50% or less; Peripheral member.

Images