Packaging material for power storage device

Abstract

To provide an exterior material for a power storage device capable of achieving both seal strength under high temperature and initial seal strength at a sufficiently high level.SOLUTION: A power storage device packaging material comprising a substrate layer, a barrier layer, and a sealant layer in this order, wherein the sealant layer includes a polypropylene layer P formed from a resin composition containing polypropylene and a β - crystal nucleating agent.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an exterior material for an electricity storage device and an electricity storage device. [Background technology]

[0002] Known examples of power storage devices include secondary batteries such as lithium-ion batteries, nickel-metal hydride batteries, and lead-acid batteries, as well as electrochemical capacitors such as electric double-layer capacitors. Due to the miniaturization of portable devices and limitations on installation space, there is a demand for further miniaturization of power storage devices, and lithium-ion batteries with high energy density have attracted attention. While metal cans have traditionally been used as the exterior materials for lithium-ion batteries, multilayer films have begun to be used, which are lightweight, have excellent heat dissipation properties, and can be produced at low cost.

[0003] Lithium-ion batteries that use the above multilayer film as an exterior material are called laminated lithium-ion batteries. The exterior material covers the battery contents (positive electrode, separator, negative electrode, electrolyte, etc.) and prevents moisture from penetrating into the battery. Laminated lithium-ion batteries are manufactured, for example, by forming a recess in part of the exterior material by cold forming, accommodating the battery contents in the recess, folding back the remaining part of the exterior material, and heat-sealing the edges (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-101765 Summary of the Invention [Problem to be solved by the invention]

[0005] Meanwhile, research and development is being conducted on power storage devices known as all-solid-state batteries as the next generation of lithium-ion batteries. All-solid-state batteries are characterized by using a solid electrolyte instead of an organic electrolyte solution as the electrolyte material. While lithium-ion batteries cannot be used at temperatures higher than the boiling point of the electrolyte solution (approximately 80°C), all-solid-state batteries can be used at temperatures exceeding 100°C, and the conductivity of lithium ions can be increased by operating them under high temperature conditions (for example, 100 to 150°C).

[0006] However, when a laminate-type all-solid-state battery is manufactured using a conventional laminate as an exterior material, there is a risk that the heat resistance of the exterior material will be insufficient, resulting in insufficient sealing of the package of the all-solid-state battery.

[0007] An object of the present disclosure is to provide an exterior packaging material for an electricity storage device that can achieve sufficiently high levels of both sealing strength at high temperatures and initial sealing strength, and to provide an electricity storage device using the exterior packaging material for an electricity storage device. [Means for solving the problem]

[0008] An exterior packaging material for a power storage device according to one aspect of the present disclosure comprises a base layer, a barrier layer, and a sealant layer in this order, and the sealant layer includes a polypropylene layer P formed from a resin composition containing polypropylene and a β-crystal nucleating agent.

[0009] Polypropylene is known to have four types of crystalline structures: α, β, γ, and smectic. While most of the structures formed under typical conditions are α-type, the inventors deliberately used an additive (a nucleating agent) to induce the formation of β-type structures during heat sealing, thereby successfully achieving both high-temperature durability and initial seal strength. The inventors speculate as follows about the reason for this excellent effect. Initial seal strength: The seal strength measured at room temperature (25°C). · Stress relaxation ability is important (if it is hard and brittle, it is difficult to develop strength). In the β type, stress relaxation ability is improved and strength is exhibited. High temperature seal strength: Seal strength measured at high temperature (150°C). It is important that the resin is difficult to heat and difficult to melt even when heat is applied. The β type melts (endotherm) at around 150°C, making it difficult to apply heat to the resin. Also, once the β type melts, it immediately transitions to the α type, making it difficult for the resin to melt even when exposed to high temperatures.

[0010] In one embodiment of the packaging material for a power storage device, the content of the β-crystal nucleating agent may be 0.001 to 15% by mass based on the total amount of the resin composition.

[0011] In one embodiment of the packaging material for a power storage device, the β-crystal nucleating agent may be an amide-based compound.

[0012] In one embodiment of the packaging material for a power storage device, the sealant layer may include two or more polypropylene layers, at least one of which may be the polypropylene layer P.

[0013] In one embodiment of the packaging material for a power storage device, the sealant layer may include two or more polypropylene layers, and at least one of the polypropylene layers may be the polypropylene layer P on the barrier layer side.

[0014] In one embodiment of the packaging material for a power storage device, the polypropylene layer P may contain acid-modified polypropylene.

[0015] In one embodiment of the packaging material for a power storage device, the sealant layer may include two or more polypropylene layers, at least one of which may include long-chain branched polypropylene.

[0016] An energy storage device according to one aspect of the present disclosure includes an energy storage device main body, terminals electrically connected to the energy storage device main body, and the above-described energy storage device exterior material that sandwiches the terminals and houses the energy storage device main body, and the ends of the energy storage device exterior material are heat-sealed.

[0017] In one embodiment of the electricity storage device, the polypropylene layer P in the heat-sealed portion of the packaging material for an electricity storage device may have a crystallinity of β crystals of 3 to 90%.

[0018] In one embodiment of the electricity storage device, the polypropylene layer P may have a crystallinity ratio (β / α) of 0.01 to 50 in the heat-sealed portion of the packaging material for the electricity storage device.

[0019] In one embodiment of the energy storage device, when the energy storage device is left standing at 150°C for one week and then cooled to 25°C, the crystallinity of the α crystal of the polypropylene layer P in the heat-sealed portion of the exterior material for the energy storage device may be 25% or more, and the crystallinity ratio (β / α) may be 0 to 1. [Effects of the Invention]

[0020] According to the present disclosure, there is provided an exterior material for an electricity storage device that can achieve both sufficiently high levels of sealing strength at high temperatures and initial sealing strength. Furthermore, according to the present disclosure, there is provided an electricity storage device using the exterior material for an electricity storage device. Although not particularly limited, the exterior material for an electricity storage device according to the present disclosure can be suitably used in an all-solid-state battery that may be exposed to a high-temperature environment. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a perspective view showing an example of a power storage device. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1, and is a cross-sectional view schematically illustrating the configuration of a heat-sealed portion of an exterior packaging material for an electricity storage device. [Figure 3] FIG. 3 is a cross-sectional view that schematically shows an example of an exterior packaging material for a power storage device. [Figure 4] FIG. 4 is a plan view schematically showing the evaluation samples prepared in the examples and comparative examples. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and duplicate explanations will be omitted. Furthermore, the dimensional ratios of the drawings are not limited to those shown in the drawings.

[0023] <Electricity storage device> The energy storage device includes an energy storage device main body, terminals electrically connected to the energy storage device main body, and an exterior material for an energy storage device that sandwiches the terminals and houses the energy storage device main body. The terminals extend from the energy storage device main body. Between the terminals and the exterior material in the energy storage device, a portion of the outer circumferential surface of the terminals is covered with a resin film for terminals. Ends of the exterior material for an energy storage device are heat-sealed, and the energy storage device main body is hermetically sealed by the exterior material for an energy storage device.

[0024] Fig. 1 is a perspective view showing a schematic configuration of a power storage device according to this embodiment. In Fig. 1, an all-solid-state battery is illustrated as an example of a power storage device 100, and the following description will be given. The power storage device having the configuration shown in Fig. 1 may be called a battery pack or a battery cell.

[0025] The energy storage device 100 is an all-solid-state battery, and includes an energy storage device main body 50, an exterior packaging material 10 for an energy storage device, a pair of metal terminals 30, and a terminal resin film 40 (tab sealant). The energy storage device main body 50 is a battery main body that performs charging and discharging. The exterior packaging material 10 for an energy storage device covers the surface of the energy storage device main body 50 and is disposed so as to be in contact with a portion of the terminal resin film 40.

[0026] Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1, and is a cross-sectional view schematically showing the configuration of the heat-sealed portion of the packaging material for an energy storage device. As shown in the drawing, the end of the packaging material for an energy storage device 10 is heat-sealed, and the symbol H indicates the heat-sealed portion.

[0027] [Exterior materials for energy storage devices] The packaging material for an electricity storage device comprises a base material layer, a barrier layer, and a sealant layer, in this order. Hereinafter, the packaging material for an electricity storage device may be simply referred to as the packaging material. Fig. 3 is a cross-sectional view showing an example of a cut surface of the packaging material 10. The packaging material 10 has a multilayer structure comprising, from the outside to the inside (the electricity storage device main body 50 side), a base material layer 11, a first adhesive layer 12, a barrier layer 13, a corrosion prevention treatment layer 14, a second adhesive layer 17, and a sealant layer 16, in this order.

[0028] (sealant layer) The sealant layer 16 is a layer that imparts heat-sealing properties to the packaging material 10, and is placed on the inside and heat-sealed (thermally fused) when assembling the electricity storage device. From the viewpoint of achieving both initial seal strength and high-temperature seal strength, the heat sealing is preferably carried out at 250 to 300°C, more preferably 270 to 290°C, and after heat sealing, the material is cooled preferably at a temperature decrease rate of 1 to 100°C / min.

[0029] The sealant layer 16 includes a polypropylene layer P formed from a resin composition containing polypropylene and a β-crystal nucleating agent. The polypropylene layer P is obtained by adding a β-crystal nucleating agent to a polypropylene base resin and kneading (dry blending) the mixture to prepare a sealant layer-forming material, which is then molded by a T-die method, inflation method, or the like. A masterbatch may be prepared by kneading a high concentration of the crystal nucleating agent into the base resin, and this may be diluted and used as a raw material for layer formation.

[0030] The polypropylene may be a homopolymer of propylene (homopolypropylene), a copolymer of propylene with ethylene, butene, octene, or the like (random polypropylene), or a polypropylene in which polyethylene (preferably polyethylene covered with ethylene propylene rubber (EPR)) is dispersed in homopolypropylene (block polypropylene). From the viewpoint of achieving both initial and high-temperature seal strength, the melting point of the polypropylene base resin may be 150 to 175°C, or may be 160 to 170°C. From this viewpoint, a homopolymer of propylene is preferably used as the polypropylene.

[0031] The polypropylene may be acid-modified polypropylene. Acid-modified polypropylene is polypropylene into which acidic groups have been introduced. Specific examples include those obtained by copolymerizing or graft-polymerizing maleic anhydride, carboxylic acid, sulfonic acid, or derivatives thereof with polypropylene. From the viewpoint of adhesion to the barrier layer or the resin film for terminals, the acid-modified polypropylene may be maleic anhydride-modified polypropylene, and from the viewpoint of adhesion and melting point, the polymerization method may be graft polymerization. During polypropylene crystallization, crystal nuclei are generated from a crystal nucleating agent, and crystals grow while forming a chemical three-dimensional network. It is presumed that the acid-modified component in the polypropylene assists network formation, thereby easily promoting the formation of β crystals.

[0032] The polypropylene may contain long-chain branched polypropylene, which strengthens the entanglement of the resin and further improves the seal strength (heat resistance). From the viewpoint of flexibility and heat resistance, the content of long-chain branched polypropylene in the polypropylene can be 2 to 30% by mass, or may be 5 to 20% by mass.

[0033] The content of the β-crystal nucleating agent can be 0.001 to 15% by mass, or alternatively 0.005 to 5% by mass, 0.005 to 1% by mass, or 0.02 to 0.5% by mass, based on the total amount of the resin composition. When the content of the β-crystal nucleating agent is at least the above lower limit, it is easy to prevent a decrease in initial and high-temperature seal strength due to insufficient formation of β crystals, and when the content is at most the above upper limit, it is easy to prevent a decrease in initial and high-temperature seal strength due to a decrease in cohesive force.

[0034] Examples of β-crystal nucleating agents include amide compounds, tetraoxaspiro compounds, and quinacridone compounds, from the viewpoint of β-crystal formability. The amide compound may be an amide compound having a naphthalene skeleton, a compound having a naphthalene skeleton and two amide bonds, or an amide compound having a cyclohexyl group and a naphthalene skeleton. The amide compound may be N,N'-dicyclohexyl-2,6-naphthalene dicarboxamide or a derivative thereof, or N,N'-dicyclohexyl-2,6-naphthalene dicarboxamide. The above β-crystal nucleating agents may be used alone or in a blend of two or more.

[0035] The β-crystal nucleating agent can be analyzed by known analytical methods such as IR, NMR, various mass spectrometry, X-ray analysis, and Raman spectroscopy.

[0036] The sealant layer 16 may include two or more polypropylene layers from the viewpoint of easily adjusting the physical properties of the film. The number of polypropylene layers may be 2 to 10 from the viewpoint of processability, and may be 2 to 3, with the proviso that at least one of the layers is the polypropylene layer P. The polypropylene layers other than the polypropylene layer P are formed from a resin composition containing polypropylene. The polypropylenes serving as base resins constituting the respective layers may be the same or different.

[0037] When the sealant layer 16 includes two or more polypropylene layers, at least one of the layers on the barrier layer side may be the polypropylene layer P. In the sealant layer 16, the layer that is most susceptible to load (easily cracked) and that is in contact with the barrier layer has the greatest effect on the seal strength. Therefore, by arranging the polypropylene layer P so that it is in contact with at least the barrier layer, the seal strength at an initial stage and at high temperatures can be easily improved.

[0038] When the sealant layer 16 includes two or more polypropylene layers, from the viewpoints of adhesion to the barrier layer and cost, the polypropylene included in at least one of the layers on the barrier layer side may be acid-modified polypropylene, but the polypropylene included in all layers may be acid-modified polypropylene.

[0039] When the sealant layer 16 includes two or more polypropylene layers, from the viewpoints of flexibility and heat resistance, the polypropylene included in at least one of the layers on the barrier layer side may include long-chain branched polypropylene, or the polypropylene included in all layers may include long-chain branched polypropylene.

[0040] The resin composition forming the polypropylene layer may contain other components such as an antioxidant, a slip agent, a flame retardant, an antiblocking agent, a light stabilizer, a dehydrating agent, a hydrogen sulfide adsorbent, a tackifier, etc. The resin composition forming the polypropylene layer may contain, for example, zinc oxide or cupric oxide to impart hydrogen sulfide resistance, or zeolite to impart moisture barrier properties.

[0041] The thickness of the sealant layer 16 can be 5 μm or more from the viewpoint of sealing performance, and can be 300 μm or less from the viewpoint of cell volume. From this viewpoint, the thickness of the sealant layer 16 may be 25 to 200 μm, or 50 to 150 μm.

[0042] When the sealant layer includes two or more polypropylene layers, the thickness ratio of each layer can be, for example, 1:2, 1:1, 2:1, etc. for two layers, and 1:2:1, 2:4:4, 2:3:5, 4:4:2, 5:3:2, etc. for three layers.

[0043] When the sealant layer 16 includes two polypropylene layers, multiple resin compositions may be prepared and laminated by the T-die method or the inflation method, one layer may be formed and then another layer may be extruded onto it, or each layer may be produced by the T-die method or the inflation method and then laminated by bonding them together with an adhesive. As the adhesive to be used, an agent containing acid-modified polypropylene and a curing agent (e.g., isocyanate) may be used from the viewpoint of interfacial adhesion.

[0044] The lamination of the sealant layer 16 onto the barrier layer 13 can be carried out by preparing a sealant layer in advance as described above and then dry laminating using the second adhesive layer 17, but it may also be carried out by thermal lamination without using the second adhesive layer 17. The sealant layer may also be laminated directly onto the barrier layer 13 by applying heat to the sealant layer-forming material and thermal laminating using the T-die method.

[0045] The crystallinity of the β-crystals of the polypropylene layer P (polypropylene layer P after heat sealing) at room temperature (25°C) in the heat-sealed portion of the packaging material formed by heat sealing can be 3 to 90%, alternatively 15 to 80%, or alternatively 30 to 70%. When the crystallinity of the β-crystals is equal to or greater than the above lower limit, it becomes easier to ensure initial seal strength. When the crystallinity of the β-crystals is equal to or less than the above upper limit, it becomes easier to ensure seal strength at high temperatures (if a large amount of β-crystals remains, seal strength at high temperatures tends to decrease). The crystallinity and crystallinity ratio can be measured by wide-angle X-ray diffraction.

[0046] The crystallinity ratio (β / α: ratio of β crystals to α crystals) of the polypropylene layer P at room temperature (25°C) in the heat-sealed portion of the packaging material formed by heat sealing can be 0.01 to 50, or alternatively 0.5 to 30, or 1 to 25. When the crystallinity ratio is equal to or greater than the above lower limit, it becomes easier to ensure initial seal strength. When the crystallinity ratio is equal to or less than the above upper limit, it becomes easier to ensure seal strength at high temperatures (if a large amount of β crystals remains, seal strength at high temperatures tends to decrease).

[0047] When the electricity storage device is left standing at 150°C for one week and then cooled to 25°C, the crystallinity of the α-crystals of the polypropylene layer P at room temperature (25°C) in the heat-sealed portion of the packaging material formed by heat sealing can be 25% or more, and the crystallinity ratio (β / α) can be 0 to 1. The crystallinity and crystallinity ratio (β / α) may be 35% or more and 0 to 0.8, or 50% or more and 0 to 0.5, respectively. A sufficiently high proportion of α-crystals (a low proportion of β-crystals) after leaving the device standing at 150°C for one week means that sufficient transition from β-crystals to α-crystals has occurred, and indicates excellent seal strength at high temperatures.

[0048] Whether or not a polypropylene layer can be suitably used as the sealant layer 16 can be determined by the following method. The polypropylene layer is subjected to DSC measurement under the following conditions to confirm whether it has a main melting peak at 160 to 170°C in the first run and a main melting peak at 140 to 160°C in the second run. Such a layer (polypropylene layer P) can be determined to be suitable for use as the sealant layer 16. The first run is a profile intended to form α crystals by gradual heating and then transition to β crystals by gradual cooling. The second run is a profile intended to prevent transition to α crystals by rapid heating. <Measurement conditions> 1st run: Heat up from 25°C to 290°C (rate: 1.5°C / min, hold: 290°C - 10 min), cool down from 290°C to 25°C (1.5°C / min, 25°C - 10 min) 2nd run: Temperature increase from 25℃ to 290℃ (150℃ / min, 290℃-10min)

[0049] The melting peak temperature of the sealant layer 16 varies depending on the application, but in the case of an exterior material for an all-solid-state battery, it is preferably 160 to 280° C. because this improves heat resistance.

[0050] (base material layer) The base layer 11 provides heat resistance in the sealing process when manufacturing the electricity storage device and plays a role in suppressing the occurrence of pinholes that may occur during molding and distribution. In particular, in the case of an exterior material for a large-scale electricity storage device, the base layer 11 can also provide scratch resistance, chemical resistance, insulation, etc.

[0051] The base layer 11 is preferably a layer made of a resin film formed from an insulating resin. Examples of the resin film include stretched or unstretched films such as polyester film, polyamide film, polypropylene film, and polyphenylene sulfide film. The base layer 11 may be a single-layer film made of any of these resin films, or a laminate film made of two or more of these resin films.

[0052] Among these, polyester film and polyamide film are preferred as the base layer 11 due to their excellent formability, and polyamide film is more preferred. These films are preferably biaxially stretched films. Examples of polyester resins constituting polyester films include polyethylene terephthalate. Examples of polyamide resins constituting polyamide films include nylon 6, nylon 6,6, copolymers of nylon 6 and nylon 6,6, nylon 6,10, polymetaxylylene adipamide (MXD6), nylon 11, and nylon 12. Among these, nylon 6 (ONy) is preferred due to its excellent heat resistance, puncture strength, and impact strength.

[0053] Examples of the stretching method for the biaxially stretched film include sequential biaxial stretching, tubular biaxial stretching, simultaneous biaxial stretching, etc. From the viewpoint of obtaining better deep drawability, the biaxially stretched film is preferably one stretched by the tubular biaxial stretching method.

[0054] The thickness of the substrate layer 11 is preferably 6 to 40 μm, and more preferably 10 to 30 μm. When the thickness of the substrate layer 11 is 6 μm or more, the pinhole resistance and insulating properties of the packaging material 10 tend to be improved. When the thickness of the substrate layer 11 exceeds 40 μm, the total thickness of the packaging material 10 tends to be large.

[0055] (First adhesive layer) The first adhesive layer 12 is a layer that bonds the base layer 11 and the barrier layer 13. Specific examples of materials that constitute the first adhesive layer 12 include polyurethane resins in which a bifunctional or higher isocyanate compound is reacted with a base material such as polyester polyol, polyether polyol, acrylic polyol, or carbonate polyol. The various polyols described above can be used alone or in combination of two or more types depending on the functions and performance required of the exterior material. In addition, various other additives and stabilizers may be blended with the polyurethane resins described above depending on the performance required of the adhesive.

[0056] The thickness of the first adhesive layer 12 is not particularly limited, but from the viewpoint of obtaining the desired adhesive strength, conformability, processability, etc., it is preferably, for example, 1 to 10 μm, more preferably 3 to 7 μm.

[0057] (barrier layer) The barrier layer 13 has water vapor barrier properties that prevent moisture from penetrating into the interior of the electricity storage device. The barrier layer 13 also has extensibility that allows for deep drawing. The barrier layer 13 can be made of various metal foils such as aluminum, stainless steel, and copper, as well as metal vapor deposition films, inorganic oxide vapor deposition films, carbon-containing inorganic oxide vapor deposition films, and films provided with these vapor deposition films. From the standpoints of mass (specific gravity), moisture resistance, processability, and cost, metal foils are preferred, and aluminum foil is more preferred.

[0058] As the aluminum foil, soft aluminum foil that has been annealed is particularly preferred because it can impart the desired ductility during molding. However, it is more preferable to use aluminum foil containing iron for the purpose of imparting further pinhole resistance and ductility during molding. The iron content in the aluminum foil is preferably 0.1 to 9.0 mass%, more preferably 0.5 to 2.0 mass%, based on 100 mass% of the aluminum foil. By having an iron content of 0.1 mass% or more, an exterior packaging material 10 having better pinhole resistance and ductility can be obtained. By having an iron content of 9.0 mass% or less, an exterior packaging material 10 having better flexibility can be obtained. Although untreated aluminum foil may be used, it is preferable to use aluminum foil that has been degreased. When degreasing aluminum foil, the degreasing treatment may be performed on only one side of the aluminum foil, or on both sides.

[0059] The thickness of the barrier layer 13 is not particularly limited, but is preferably 9 to 200 μm, more preferably 15 to 100 μm, in consideration of barrier properties, pinhole resistance, and processability.

[0060] (Corrosion prevention treatment layer) The corrosion prevention treatment layer 14 is a layer provided to prevent corrosion of the barrier layer 13. The corrosion prevention treatment layer 14 is formed by, for example, degreasing treatment, hydrothermal treatment, anodizing treatment, chemical conversion treatment, or a combination of these treatments.

[0061] Examples of degreasing treatments include acid degreasing and alkaline degreasing. Acid degreasing can be achieved by using inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, and hydrofluoric acid, either singly or in combination. Alkaline degreasing can be achieved by using sodium hydroxide or the like.

[0062] An example of the hydrothermal modification treatment is boehmite treatment, in which aluminum foil is immersed in boiling water containing triethanolamine. An example of the anodization treatment is alumite treatment.

[0063] The chemical conversion treatment may be an immersion type or a coating type. Examples of the immersion type chemical conversion treatment include chromate treatment, zirconium treatment, titanium treatment, vanadium treatment, molybdenum treatment, calcium phosphate treatment, strontium hydroxide treatment, cerium treatment, ruthenium treatment, and various chemical conversion treatments consisting of a mixture of these. On the other hand, an example of the coating type chemical conversion treatment is a method in which a coating agent having corrosion prevention properties is applied to the barrier layer 13.

[0064] When forming at least a part of the corrosion prevention treatment layer by any of these corrosion prevention treatments, i.e., hydrothermal conversion treatment, anodizing treatment, or chemical conversion treatment, it is preferable to perform the degreasing treatment described above beforehand. Note that when a degreased metal foil, such as a metal foil that has been subjected to an annealing process, is used as the barrier layer 13, there is no need to perform a degreasing treatment again when forming the corrosion prevention treatment layer 14.

[0065] The coating agent used in the spray-type chemical conversion coating preferably contains trivalent chromium and may also contain at least one polymer selected from the group consisting of cationic polymers and anionic polymers, which will be described later.

[0066] Among the above treatments, hydrothermal conversion treatment and anodizing treatment, in particular, dissolve the aluminum foil surface with a treatment agent to form aluminum compounds (boehmite, anodized aluminum) with excellent corrosion resistance. Therefore, a bicontinuous structure is formed from the aluminum foil barrier layer 13 to the corrosion prevention treatment layer 14, and these treatments are included in the definition of chemical conversion treatment. On the other hand, as described below, it is also possible to form the corrosion prevention treatment layer 14 using a pure coating method, which is not included in the definition of chemical conversion treatment. One example of such a method is to use a sol of a rare earth oxide, such as cerium oxide, with an average particle size of 100 nm or less, which has an aluminum corrosion prevention effect (inhibitor effect) and is environmentally friendly. Using this method, it is possible to impart corrosion prevention effects to metal foils such as aluminum foil using a conventional coating method.

[0067] Examples of the rare earth element oxide sol include sols using various solvents such as water, alcohol, hydrocarbon, ketone, ester, and ether. Among these, water-based sols are preferred. To stabilize the dispersion of the rare earth element oxide sol, inorganic acids such as nitric acid, hydrochloric acid, and phosphoric acid or their salts, and organic acids such as acetic acid, malic acid, ascorbic acid, and lactic acid are typically used as dispersion stabilizers. Among these dispersion stabilizers, phosphoric acid is particularly expected to contribute to the exterior packaging material 10 by (1) stabilizing the dispersion of the sol, (2) improving adhesion to the barrier layer 13 by utilizing the aluminum chelating ability of phosphoric acid, and (3) improving the cohesion of the corrosion prevention treatment layer 14 (oxide layer) due to the tendency of phosphoric acid to undergo dehydration condensation even at low temperatures.

[0068] The corrosion prevention treatment layer 14 formed from the rare earth element oxide sol is an aggregate of inorganic particles, and therefore the cohesive strength of the layer itself may be reduced even after the dry-cure process. Therefore, in this case, the corrosion prevention treatment layer is preferably compounded with the following anionic polymer or cationic polymer to compensate for the cohesive strength.

[0069] The corrosion prevention treatment layer is not limited to the layers described above. For example, it may be formed using a treatment agent in which phosphoric acid and a chromium compound are blended with a resin binder (such as aminophenol), as in the case of a known paint-type chromate. Use of this treatment agent makes it possible to obtain a layer that combines both corrosion prevention functionality and adhesion. Furthermore, although the stability of the coating liquid must be taken into consideration, a coating agent in which a rare earth element oxide sol and a cationic or anionic polymer are preliminarily mixed into a one-component solution can be used to obtain a layer that combines corrosion prevention functionality and adhesion.

[0070] The mass per unit area of ​​the corrosion prevention treatment layer is 0.005 to 0.200 g / m, whether it is a multi-layer structure or a single-layer structure. 2 is preferable, and 0.010 to 0.100 g / m 2 It is more preferable that the mass per unit area is 0.005 g / m 2If the mass per unit area is 0.200 g / m or more, it is easy to impart a corrosion prevention function to the barrier layer 13. 2 Even if the thickness exceeds 1000 nm, the corrosion prevention function does not change significantly. On the other hand, when a rare earth element oxide sol is used, if the coating is thick, the heat curing during drying may be insufficient, which may result in a decrease in cohesive force. The thickness of the corrosion prevention treatment layer 14 can be calculated from its specific gravity.

[0071] From the viewpoint of adhesion between the sealant layer and the barrier layer, the corrosion prevention treatment layer may be, for example, an embodiment containing cerium oxide, 1 to 100 parts by mass of phosphoric acid or a phosphate salt per 100 parts by mass of the cerium oxide, and a cationic polymer, or may be an embodiment formed by subjecting the barrier layer 13 to a chemical conversion treatment, or may be an embodiment formed by subjecting the barrier layer to a chemical conversion treatment and containing a cationic polymer.

[0072] (Second adhesive layer) The second adhesive layer 17 is a layer that bonds the barrier layer 13, on which the corrosion prevention treatment layer 14 has been formed, to the sealant layer 16. For the second adhesive layer 17, a general adhesive for bonding the barrier layer 13 to the sealant layer 16 can be used.

[0073] When the corrosion prevention treatment layer 14 has a layer containing at least one polymer selected from the group consisting of the above-mentioned cationic polymers and anionic polymers, the second adhesive layer 17 is preferably a layer containing a compound (hereinafter also referred to as a "reactive compound") that is reactive with the above-mentioned polymer contained in the corrosion prevention treatment layer 14.

[0074] For example, if the corrosion prevention treatment layer 14 contains a cationic polymer, the second adhesive layer 17 contains a compound reactive with the cationic polymer. If the corrosion prevention treatment layer 14 contains an anionic polymer, the second adhesive layer 17 contains a compound reactive with the anionic polymer. If the corrosion prevention treatment layer 14 contains both a cationic polymer and an anionic polymer, the second adhesive layer 17 contains a compound reactive with the cationic polymer and a compound reactive with the anionic polymer. However, the second adhesive layer 17 does not necessarily have to contain both of these compounds; it may contain a compound reactive with both the cationic polymer and the anionic polymer. Here, "reactive" means forming a covalent bond with the cationic polymer or the anionic polymer. The second adhesive layer 17 may also contain an acid-modified polyolefin resin.

[0075] The compound reactive with the cationic polymer may be at least one compound selected from the group consisting of a polyfunctional isocyanate compound, a glycidyl compound, a compound having a carboxy group, and a compound having an oxazoline group.

[0076] Examples of these polyfunctional isocyanate compounds, glycidyl compounds, compounds having a carboxy group, and compounds having an oxazoline group include the polyfunctional isocyanate compounds, glycidyl compounds, compounds having a carboxy group, and compounds having an oxazoline group exemplified above as crosslinking agents for forming a crosslinked structure from a cationic polymer. Among these, polyfunctional isocyanate compounds are preferred because they have high reactivity with cationic polymers and are easy to form a crosslinked structure.

[0077] The compound reactive with anionic polymers includes at least one compound selected from the group consisting of glycidyl compounds and compounds having an oxazoline group. These glycidyl compounds and compounds having an oxazoline group include the glycidyl compounds and compounds having an oxazoline group exemplified above as crosslinking agents for forming a crosslinked structure in cationic polymers. Among these, glycidyl compounds are preferred because of their high reactivity with anionic polymers.

[0078] When the second adhesive layer 17 contains an acid-modified polyolefin resin, the reactive compound preferably also has reactivity with the acidic groups in the acid-modified polyolefin resin (i.e., forms a covalent bond with the acidic groups). This further enhances adhesion to the corrosion prevention treatment layer 14. In addition, the acid-modified polyolefin resin forms a crosslinked structure, further improving the solvent resistance of the exterior packaging material 10.

[0079] The content of the reactive compound is preferably from 1 to 10 times the amount of the acidic groups in the acid-modified polyolefin resin. If the amount is equal to or greater than 10 times, the reactive compound will react sufficiently with the acidic groups in the acid-modified polyolefin resin. On the other hand, if the amount exceeds 10 times, the crosslinking reaction with the acid-modified polyolefin resin will be fully saturated, resulting in the presence of unreacted material, which may lead to a decrease in various performances. Therefore, for example, the content of the reactive compound is preferably 5 to 20 parts by mass (solid content ratio) per 100 parts by mass of the acid-modified polyolefin resin.

[0080] The acid-modified polyolefin resin is a polyolefin resin into which an acidic group has been introduced. Examples of the acidic group include a carboxyl group, a sulfonic acid group, and an acid anhydride group, with a maleic anhydride group and a (meth)acrylic acid group being particularly preferred. For example, the acid-modified polyolefin resin may be the same as the modified polyolefin resin used in the sealant layer 16.

[0081] The second adhesive layer 17 may contain various additives such as a flame retardant, a slip agent, an antiblocking agent, an antioxidant, a light stabilizer, and a tackifier.

[0082] Examples of adhesives that form the second adhesive layer 17 include polyurethane resins in which a bifunctional or higher isocyanate compound is reacted with a base material such as polyester polyol, polyether polyol, acrylic polyol, or carbonate polyol, and epoxy resins in which an amine compound or the like is reacted with a base material having an epoxy group, which are preferred from the standpoint of heat resistance.

[0083] The thickness of the second adhesive layer 17 is not particularly limited, but from the viewpoint of obtaining the desired adhesive strength, processability, etc., it is preferably 1 to 10 μm, more preferably 2 to 7 μm.

[0084] [Metal terminal (terminal)] Of the pair of metal terminals 30, 30, one metal terminal 30 is electrically connected to the positive electrode of the electricity storage device main body 50, and the other metal terminal 30 is electrically connected to the negative electrode of the electricity storage device main body 50. The pair of metal terminals 30, 30 extend from the electricity storage device main body 50 to the outside of the exterior material 10. The shape of the pair of metal terminals 30, 30 may be, for example, a flat plate shape.

[0085] Metals can be used as the material for the metal terminals 30. The metal to be used as the material for the metal terminals 30 can be determined taking into consideration the structure of the energy storage device main body 50, the materials of its components, and the like. For example, if the energy storage device 100 is an all-solid-state battery, aluminum can be used as the material for the metal terminal 30 connected to the positive electrode of the energy storage device main body 50. Copper with a nickel plating layer formed on the surface, or nickel, can be used as the material for the metal terminal 30 connected to the negative electrode of the energy storage device main body 50.

[0086] The thickness of the metal terminal 30 depends on the size and capacity of the battery. In the case of a small battery, the thickness of the metal terminal 30 can be, for example, 50 μm or more. In the case of a large battery for power storage or vehicle use, the thickness of the metal terminal 30 can be appropriately set within the range of, for example, 100 to 500 μm.

[0087] [Resin film for terminals] The terminal resin film is a film for covering part of the outer circumferential surface of a terminal in an electricity storage device that includes an electricity storage device main body and a terminal electrically connected to the electricity storage device main body.

[0088] The terminal resin film 40 is arranged so as to cover part of the outer peripheral surface of the metal terminal 30. Specifically, part of the outer peripheral surface of the metal terminal 30 is covered with the terminal resin film 40 by heat sealing between the metal terminal 30 and the exterior packaging material 10. By arranging the terminal resin film 40 between the metal terminal 30 and the exterior packaging material 10, it is possible to achieve even higher levels of sealing and insulation properties for the energy storage device 100. The terminal resin film 40 has heat resistance equivalent to or exceeding that of the sealant layer 16 and base material layer 11 described above.

[0089] The terminal resin film 40 can be made of a thermoplastic resin such as polyolefin, polyamide, polyester, polycarbonate, polyphenylene ether, polyacetal, polystyrene, polyvinyl chloride, or polyvinyl acetate, and polyolefin, polyamide, or polyester can be used from the viewpoint of heat resistance and sealing suitability.

[0090] Examples of polyolefin resins include low-density, medium-density, and high-density polyethylene, ethylene-α-olefin copolymers, polypropylene, and propylene-α-olefin copolymers. When the polyolefin resin is a copolymer, it may be a block copolymer or a random copolymer.

[0091] Examples of polyester resins include polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). These polyester resins may be used alone or in combination. Copolymers of any acid and glycol may also be used.

[0092] Examples of polyamide resins include nylon 6 and nylon 6,6.

[0093] In order to impart sealing properties, heat resistance, and other functionalities, for example, antioxidants, slip agents, flame retardants, antiblocking agents, light stabilizers, dehydrating agents, tackifiers, nucleating agents, plasticizers, etc. may be added to the resin film for terminals 40. For example, zinc oxide or cupric oxide may be added to the resin film for terminals to impart hydrogen sulfide resistance, and zeolite may be added to the resin film for terminals to impart moisture barrier properties.

[0094] The thickness of the terminal resin film 40 can be 25 μm or more from the viewpoint of sealing performance, and can be 500 μm or less from the viewpoint of productivity. From this viewpoint, the thickness of the terminal resin film 40 may be 50 to 300 μm, or may be 80 to 200 μm.

[0095] Although the embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the above embodiments, and various modifications and variations are possible within the scope of the gist of the present disclosure as set forth in the claims. In the above embodiment, an example is given in which the corrosion prevention treatment layer 14 is provided only on one surface (the second adhesive layer 17 side) of the barrier layer 13, but the corrosion prevention treatment layer 14 may also be provided on the other surface (the first adhesive layer 12 side) of the barrier layer 13. If the sealant layer 16 is attached to the barrier layer 13 by thermal lamination instead of dry lamination, the second adhesive layer 17 may not be provided. When the base layer 11 is provided by coating, the first adhesive layer 12 does not need to be provided. In the above embodiment, an all-solid-state battery is exemplified as an electricity storage device to which the exterior material 10 is applied, but the exterior material 10 may also be applied to other electricity storage devices (for example, lithium ion batteries). [Example]

[0096] Hereinafter, the present disclosure will be described more specifically based on examples, but the present disclosure is not limited to the following examples.

[0097] [Materials used] · Base layer (thickness 25 μm): Polyethylene terephthalate film with one side subjected to corona treatment was used. First adhesive layer (thickness 4 μm): A polyurethane adhesive (manufactured by Toyo Ink Co., Ltd.) was used, which is a polyester polyol-based base resin mixed with a tolylene diisocyanate adduct curing agent. Corrosion prevention treatment layer: The following solution was used. (CL-1): "Sodium polyphosphate-stabilized cerium oxide sol" was used, adjusted to a solids concentration of 10% by mass using distilled water as the solvent. The sodium polyphosphate-stabilized cerium oxide sol was obtained by blending 100 parts by mass of cerium oxide with 10 parts by mass of sodium phosphate. (CL-2): A composition consisting of 90% by mass of "polyallylamine (manufactured by Nitto Boseki Co., Ltd.)" adjusted to a solid content concentration of 5% by mass using distilled water as a solvent and 10% by mass of "polyglycerol polyglycidyl ether (manufactured by Nagase ChemteX Corporation)" was used. Barrier layer (thickness 40 μm): Annealed and degreased soft aluminum foil (manufactured by Toyo Aluminum Co., Ltd., "8079 material") was used. Second adhesive layer (thickness 3 μm): An epoxy adhesive was used, which was a mixture of 100 parts by mass of epoxy resin (manufactured by ADEKA Corporation, product name: EP4100) and 25 parts by mass of polyamidoamine curing agent (manufactured by ADEKA Corporation, product name: EH4602) diluted with ethyl acetate to a solid content of 30% by mass. Sealant layer (layer (1) thickness 53.3 μm, layer (2) thickness 26.7 μm, total thickness 80 μm): The base resin and nucleating agent shown in Table 1 were prepared. The nucleating agent was added to the base resin according to Tables 2 and 3, and the mixture was dry-blended (the blending ratios in the tables are "mass %"). A sealant layer was formed using this kneaded mixture (sealant layer-forming material). The layer (2) side was the barrier layer side.

[0098] [Table 1]

[0099] [Fabrication of exterior materials] Example 1 (CL-1) was applied to both sides of the barrier layer at a dry coating weight of 70 mg / m 2 The resulting layer was coated by microgravure coating so that the coating amount was 20 mg / m, and then baked in a drying unit at 200°C. 2 A composite layer consisting of (CL-1) and (CL-2) was formed as a corrosion prevention treatment layer by applying it by microgravure coating so that the corrosion prevention performance was realized by combining the two types of materials (CL-1) and (CL-2). The barrier layer with the corrosion prevention treatment layer was attached to the base layer by dry lamination using a polyurethane adhesive (first adhesive layer). The barrier layer and base layer were laminated by applying a polyurethane adhesive to one side of the barrier layer so that the thickness after curing would be 4 μm, drying it at 80°C for 1 minute, laminating it with the base layer, and aging it at 60°C for 5 days. While applying a temperature of 270°C to the sealant layer-forming material, the sealant layer was laminated on the side of the barrier layer opposite the substrate layer by thermal lamination using a T-die method. In this manner, an exterior material (a laminate of substrate layer / first adhesive layer / corrosion prevention treatment layer / barrier layer / corrosion prevention treatment layer / sealant layer) was produced.

[0100] Examples 2 to 9 Except for changing the layer structure of the sealant layer as shown in Table 2, exterior packaging materials were produced in the same manner as in Example 1.

[0101] Example 10 An exterior material was produced in the same manner as in Example 1, except that the lamination method for the sealant layer was dry lamination instead of thermal lamination. Specifically, the side of the barrier layer opposite the substrate layer was attached to the sealant layer using an epoxy adhesive (second adhesive layer) by dry lamination. The sealant layer was prepared in advance using the T-die method according to Table 2. The barrier layer and sealant layer were laminated by applying an epoxy adhesive to the surface of the barrier layer opposite the substrate layer so that the thickness after curing would be 3 μm, drying at 80°C for 1 minute, laminating with the sealant layer, and aging at 120°C for 3 hours. In this manner, an exterior material (a laminate of substrate layer / first adhesive layer / corrosion prevention treatment layer / barrier layer / corrosion prevention treatment layer / second adhesive layer / sealant layer) was produced.

[0102] (Examples 11 to 12) Except for changing the layer structure of the sealant layer as shown in Table 2, exterior packaging materials were produced in the same manner as in Example 10.

[0103] (Comparative Examples 1 to 4) Except for changing the layer structure of the sealant layer as shown in Table 3, exterior packaging materials were produced in the same manner as in Example 1.

[0104] (Comparative Example 5) Except for changing the layer structure of the sealant layer as shown in Table 3, exterior packaging materials were produced in the same manner as in Example 10.

[0105] [Measurement of crystallinity after heat sealing] Two exterior materials were prepared, stacked with the sealant layers facing each other, and heat-sealed at 290°C, 0.5 MPa, for 15 seconds with a seal width of 5 mm. The material was then cooled to 25°C at a rate of 50°C / min. A cross section of the heat-sealed area was cut out, and the crystallinity of each layer in the sealant layer was measured using wide-angle X-ray diffraction. The conditions for wide-angle X-ray diffraction were as follows: Filter: Ni (Cu-Kα line) Output: 40kV, 40mA Analysis: Calculated from the diffraction peaks of the α crystal (040, 060, 110, 130) planes and the diffraction peak of the β crystal (300) plane. The conditions for measuring each crystallinity in the table were as follows: ·β crystallinity: Measured at 25°C after heat sealing. β / α: Measured at 25°C after heat sealing. · α Crystallinity, β / α: After heat sealing, the sample was left to stand in an environment of 150°C for one week, and then measured at 25°C.

[0106] [Table 2]

[0107] [Table 3]

[0108] [Measurement of room temperature heat seal strength] A 60mm x 120mm sample of packaging material was cut and folded in half, and one side was heat-sealed with a 10mm-wide sealing bar at 290°C, 0.5 MPa, and 15 seconds. The heat-sealed packaging material was aged at 150°C for 60 minutes and then cooled to room temperature. The heat-sealed area was cut into 15mm widths (see Figure 4), and the seal strength (T-peel strength) was measured using an Instron tester. The test was conducted in accordance with JIS K6854 at 25°C, 50% RH, and a peel rate of 50mm / min. The measured seal strength (burst strength) was evaluated according to the following criteria. A rating of C or higher was considered a pass. A: Seal strength is 90N / 15mm or more B: Seal strength is 80N / 15mm or more and less than 90N / 15mm C: Seal strength is 70N / 15mm or more and less than 80N / 15mm D: Seal strength is less than 70N / 15mm

[0109] [Measurement of high-temperature heat seal strength] A 60mm x 120mm sample of the packaging material was folded in half and one side was heat-sealed with a 10mm-wide seal bar at 290°C, 0.5 MPa, and 15 seconds. The heat-sealed area was then cut to a 15mm width (see Figure 4) and left to stand for 5 minutes in a 150°C environment. The seal strength (T-peel strength) was then measured at a peel rate of 50mm / min in a 150°C environment using a testing machine (manufactured by Instron). The measured seal strength (burst strength) was evaluated according to the following criteria. A rating of C or higher was deemed a pass. A: Seal strength is 35N / 15mm or more B: Seal strength is 30N / 15mm or more and less than 35N / 15mm C: Seal strength is 20N / 15mm or more and less than 30N / 15mm D: Seal strength is less than 20N / 15mm

[0110] [Table 4]

[0111] [Determining whether or not the polypropylene layer is suitable for use] DSC measurement was performed on some of the sealant layers under the conditions below to confirm whether the layers had a main melting peak at 160 to 170°C in the first run and a main melting peak at 140 to 160°C in the second run. The main melting peaks are shown in Table 5. In view of the results in Table 4, it can be seen that such polypropylene layers can be suitably used as sealant layers. <Measurement conditions> 1st run: Heat up from 25°C to 290°C (rate: 1.5°C / min, hold: 290°C - 10 min), cool down from 290°C to 25°C (1.5°C / min, 25°C - 10 min) 2nd run: Temperature increase from 25℃ to 290℃ (150℃ / min, 290℃-10min)

[0112] [Table 5] [Explanation of symbols]

[0113] 10...outer packaging material for electricity storage device, 11...base material layer, 12...first adhesive layer, 13...barrier layer, 14...corrosion prevention treatment layer, 16...sealant layer, 17...second adhesive layer, 30...metal terminal, 40...resin film for terminal, 50...electricity storage device main body, 100...electricity storage device, H...heat seal portion.

Claims

1. a substrate layer, a barrier layer, and a sealant layer, in that order; The sealing layer includes a polypropylene layer P formed from a resin composition containing polypropylene and a β-crystal nucleating agent.

2. 2. The exterior packaging material for a power storage device according to claim 1, wherein the content of the β-crystal nucleating agent is 0.001 to 15 mass % based on the total amount of the resin composition.

3. The packaging material for a power storage device according to claim 1 or 2, wherein the β-crystal nucleating agent is an amide-based compound.

4. The packaging material for a power storage device according to any one of claims 1 to 3, wherein the sealant layer comprises two or more polypropylene layers, at least one of which is the polypropylene layer P.

5. The packaging material for a storage battery device according to any one of claims 1 to 4, wherein the sealant layer includes two or more polypropylene layers, at least one of which on the barrier layer side is the polypropylene layer P.

6. The packaging material for a power storage device according to any one of claims 1 to 5, wherein the polypropylene layer P contains acid-modified polypropylene.

7. The packaging material for a power storage device according to any one of claims 1 to 6, wherein the sealant layer comprises two or more polypropylene layers, at least one of which contains long-chain branched polypropylene.

8. a power storage device main body; a terminal electrically connected to the power storage device body; The exterior packaging material for an electricity storage device according to any one of claims 1 to 7, which holds the terminals and houses the electricity storage device main body, an electricity storage device, wherein an end of the exterior packaging material for the electricity storage device is heat-sealed;

9. 9. The electricity storage device according to claim 8, wherein the polypropylene layer P has a crystallinity of β crystals in the heat-sealed portion of the packaging material for an electricity storage device of 3 to 90%.

10. 10. The electricity storage device according to claim 8, wherein the polypropylene layer P has a crystallinity ratio (β / α) of 0.01 to 50 in the heat-sealed portion of the packaging material for the electricity storage device.

11. The energy storage device according to any one of claims 8 to 10, wherein, when the energy storage device is left standing at 150°C for one week and then cooled to 25°C, the crystallinity of α crystals of the polypropylene layer P in the heat-sealed portion of the exterior material for the energy storage device is 25% or more, and a crystallinity ratio (β / α) is 0 to 1.

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