Exterior materials for all-solid-state batteries and all-solid-state batteries

Abstract

To provide a sheath material for an all-solid battery that has an excellent moldability and that can suppress generation of floating of a base material layer during heat sealing.SOLUTION: Provided is a sheath material for an all-solid battery that comprises at least a base material layer, a barrier layer, and a sealant layer in this order. The base material layer includes at least two biaxially extended resin films. A water content rate of the resin films other than the outermost resin film among the resin films is equal to or less than 4,000 mass ppm.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to an outer casing material for all-solid-state batteries and all-solid-state batteries. [Background technology]

[0002] In recent years, the development of all-solid-state batteries, which can achieve high capacity, has been progressing rapidly. Unlike current lithium-ion batteries, all-solid-state batteries use a solid electrolyte, which allows them to be used at high temperatures that were previously impossible. This eliminates the need for cooling equipment, and is expected to lead to improved space efficiency, cost reduction, and lower power consumption.

[0003] Such an all-solid-state battery comprises a battery body containing a solid electrolyte and electrodes, and an outer bag that houses the battery body, the outer bag being obtained by heat-sealing an outer material.

[0004] Incidentally, for lithium-ion battery applications, studies have been conducted on exterior materials comprising a base layer, a barrier layer (metal foil layer), and a sealant layer. In this context, it has been proposed to use a laminated film, which is made by laminating multiple films, as the base layer in order to further improve the deep-draw moldability of the exterior material and increase the battery capacity (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2016 / 159278 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, when a laminated film like the one described in Patent Document 1 is used as the base layer for the exterior material of an all-solid-state battery, air bubbles generated from the base layer during heat sealing may remain within the base layer and be observed as so-called "lifting." The occurrence of lifting can trigger the delamination of the base layer, leading to a decrease in reliability in terms of chemical resistance, scratch resistance, etc.

[0007] This disclosure has been made in view of the above-mentioned problems, and aims to provide an exterior material for all-solid-state batteries and an all-solid-state battery using the same, which has excellent moldability and can suppress the occurrence of lifting in the base material layer during heat sealing. [Means for solving the problem]

[0008] The inventors investigated the cause of the phenomenon in which lifting occurs in the base material layer as described above. As a result, they concluded that this phenomenon is caused by heat-sealing the exterior material at high temperatures. This is because, anticipating use in high-temperature environments, development of exterior materials for all-solid-state batteries is progressing in the direction of raising the melting point of the sealant layer. Furthermore, when the base material layer is composed of multiple resin films to improve moldability or impart different properties, the heat from heat sealing becomes less easily transferred to the sealant layer. Due to these circumstances, the heat-sealing temperature tends to be high for exterior materials for all-solid-state batteries. The inventors hypothesized that when the exterior material is heat-sealed at high temperatures, the moisture in the resin films constituting the base material layer rapidly vaporizes and remains between the resin films even after cooling. The inventors also hypothesized that the above phenomenon is highly dependent on the moisture content in the resin films. Therefore, the inventors conducted further intensive research and found that the above problem can be solved by the following disclosure.

[0009] In other words, the present disclosure relates to an exterior material for an all-solid-state battery comprising at least a base layer, a barrier layer, and a sealant layer in that order, wherein the base layer includes at least two layers of biaxially stretched resin film, and the water content of the resin film, excluding the outermost layer, is 4000 ppm by mass or less.

[0010] According to the exterior packaging material of this disclosure, since the base layer is a multilayer film, the base layer itself has excellent strength. Furthermore, since the generation of air bubbles from the base layer can be suppressed during heat sealing, lifting of the base layer is less likely to occur, and the decrease in adhesion between the resin films constituting the base layer is suppressed. Therefore, excellent moldability is obtained, and even when the battery body containing the solid electrolyte expands due to the use of all-solid-state batteries in high-temperature environments and a force acts on the outer bag that tries to open it, the reliability of the exterior packaging material can be maintained. In addition, pressure is sometimes applied to the battery cell to improve the ionic conductivity of the solid electrolyte. In this case, if foreign matter enters between the pressurizing device and the battery cell, it is easy for holes to form in the battery cell, but by making the base layer a multilayer film, it is easier to deal with such problems.

[0011] In the above-mentioned exterior material for all-solid-state batteries, the thickness of the base layer is preferably 24 to 100 μm. This allows for effective protection of the barrier layer by the base layer and makes it easier to suppress the transfer of heat to the sealant layer during heat sealing.

[0012] In the above-mentioned exterior material for all-solid-state batteries, it is preferable that the resin films are bonded together via an adhesive layer with a thickness of 1 to 10 μm. This makes it easier to obtain an improvement in moldability and to suppress the decrease in the volumetric energy density of the battery. In addition, although CO2 may be generated when the adhesive layer is formed, the amount of CO2 generated can be easily suppressed by keeping the adhesive layer from being too thick (this also suppresses the generation of bubbles).

[0013] In the above-mentioned exterior material for all-solid-state batteries, it is preferable that the resin film is a polyester film containing a polyester resin. Polyester films, which have excellent heat resistance, are suitable for heat sealing at high temperatures and for use of batteries in high-temperature environments.

[0014] In the above-mentioned exterior material for all-solid-state batteries, it is preferable that the adhesive layer contains a polyester urethane resin which is a reaction product of a polyester polyol and an isocyanate. The polyester urethane resin, which has excellent heat resistance, is suitable for heat sealing at high temperatures and for use of the battery in a high-temperature environment.

[0015] In the above-mentioned exterior material for all-solid-state batteries, it is preferable that the CO2 permeability measured in accordance with JIS K 7126 of the resin film is 60 ml·mm / m 2 ·d·MPa or more. Although CO2 may be generated when the adhesive layer is formed, the amount of CO2 generated increases when the base material layer is made into multiple layers. The CO2 thus generated stays as bubbles in the adhesive layer, so there is a risk that the adhesive layer is likely to break and the moldability of the exterior material decreases. To address this, it is preferable that the resin film constituting the base material layer has the above-mentioned CO2 permeability.

[0016] In the above-mentioned exterior material for all-solid-state batteries, it is preferable that the melting point of the above-mentioned sealant layer is 150°C or higher. In this case, even when the exterior material is used in a high-temperature environment, it is possible to suppress a decrease in the seal strength of the exterior material.

[0017] In the above-mentioned exterior material for all-solid-state batteries, it is preferable to further provide a modified layer containing a silicone resin on the base material layer. When using a film with high wettability (for example, a polyester film) as the base material layer, bleeding is likely to occur when printing a bar code for lot traceability with an inkjet printer after battery production. This causes a problem that it becomes difficult to read the bar code. By providing a modified layer on the base material layer, such a problem can be addressed.

[0018] Moreover, the present disclosure is an all-solid-state battery including a battery body having a solid electrolyte and an exterior bag housing the battery body, wherein the exterior bag is an exterior bag obtained by heat-sealing the above-mentioned exterior material for all-solid-state batteries.

[0019] According to the all-solid-state battery of the present disclosure, an outer packaging bag is obtained by heat-sealing the above-described outer packaging material for an all-solid-state battery. Here, according to the above-described outer packaging material, since the base material layer is a multilayer film, the base material layer itself has excellent strength. In addition, at the time of heat-sealing, generation of bubbles from the base material layer can be suppressed, so that floating hardly occurs in the base material layer, and a decrease in adhesion between the resin films constituting the base material layer is suppressed. Therefore, excellent moldability can be obtained, and even when the battery body expands due to use of the all-solid-state battery in a high-temperature environment and a force to open the outer packaging bag acts, the all-solid-state battery can maintain the sealed state of the outer packaging bag by the outer packaging material.

Effect of the Invention

[0020] According to the present disclosure, there are provided an outer packaging material for an all-solid-state battery, which is excellent in moldability and can suppress the generation of floating in the base material layer during heat-sealing, and an all-solid-state battery using the same.

Brief Description of the Drawings

[0021] [Figure 1] It is a cross-sectional view schematically showing an outer packaging material for an all-solid-state battery according to an embodiment of the present disclosure. [Figure 2] It is a cross-sectional view schematically showing an outer packaging material for an all-solid-state battery according to another embodiment of the present disclosure. [Figure 3] It is a cross-sectional view schematically showing an outer packaging material for an all-solid-state battery according to still another embodiment of the present disclosure. [Figure 4] It is a perspective view showing an all-solid-state battery according to an embodiment of the present disclosure. [Figure 5] It is a plan view showing a structure for obtaining evaluation samples in Examples and Comparative Examples.

Mode for Carrying Out the Invention

[0022] Hereinafter, preferred embodiments of the present disclosure will be described in detail with appropriate reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant descriptions are omitted. In addition, the dimensional ratios in the drawings are not limited to the illustrated ratios.

[0023] [Exterior material for all-solid-state batteries] Figure 1 is a schematic cross-sectional view showing an exterior material for an all-solid-state battery according to one embodiment of the present disclosure. As shown in Figure 1, the exterior material for an all-solid-state battery (hereinafter also simply referred to as "exterior material") 10 of this embodiment comprises a base layer 11, a first adhesive layer 12a, a barrier layer 13, a second adhesive layer 12b, and a sealant layer 16 in this order. The base layer 11 includes an outermost resin film 11a and a resin film 11b laminated on the inner layer side (barrier layer side) of the resin film 11a via the base adhesive layer 11c. The outermost resin film 11a is the resin film furthest from the barrier layer 13 among the resin films constituting the base layer. The resin film laminated on the inner layer side of the resin film 11a can be called an inner layer resin film. In Figure 1, only one layer of resin film 11b is depicted as an inner layer resin film, but the base layer 11 may include multiple layers of inner layer resin films. Here, the moisture content of the resin film 11b is 4000 ppm by mass or less. Compared to the case where the moisture content of the resin film 11b exceeds 4000 ppm by mass, the generation of air bubbles in the base layer 11 of the outer packaging material 10 can be more suppressed when the outer packaging material 10 is heat-sealed.

[0024] The barrier layer 13 may have a first corrosion-preventive treatment layer 14a on the base layer 11 side. The barrier layer 13 may also have a second corrosion-preventive treatment layer 14b on the sealant layer 16 side. In the exterior material 10, the base layer 11 is the outermost layer, and the sealant layer 16 is the innermost layer. That is, the exterior material 10 is used with the base layer 11 facing the outside of the solid-state battery and the sealant layer 16 facing the inside of the solid-state battery.

[0025] The following describes in detail each layer that makes up the exterior material 10.

[0026] <Base material layer> The base layer 11 provides heat resistance during the sealing process when manufacturing solid-state batteries and plays a role in suppressing the occurrence of pinholes that may occur during molding and distribution. In particular, for casing materials of large solid-state batteries, it can also provide scratch resistance, chemical resistance, and insulation.

[0027] The base layer 11 is preferably a layer formed of an insulating resin film. Suitable resins include polyester resin, polyamide resin, polyimide resin, polyamide-imide resin, polyetherketone resin, polyphenylene sulfide resin, polyetherimide resin, polysulfone resin, fluororesin, phenol resin, melamine resin, urethane resin, allyl resin, silicone resin, epoxy resin, furan resin, acetylcellulose resin, and the like.

[0028] Among these resins, polyester resin is preferred as the base layer 11 because it has excellent moldability, low moisture absorption, and excellent heat resistance. Examples of polyester resins include polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate.

[0029] As the resin film, a biaxially oriented film is used from the viewpoint of obtaining excellent deep-draw moldability. Examples of stretching methods for biaxially oriented films include sequential biaxial stretching, tubular biaxial stretching, and simultaneous biaxial stretching. From the viewpoint of obtaining even better deep-draw moldability, it is preferable that the biaxially oriented film is stretched by the tubular biaxial stretching method.

[0030] The base layer 11 includes at least two layers of resin film. The resin film includes resin film 11a and resin film 11b which is laminated on the inner side of resin film 11a. These two or more layers of resin film included in the base layer 11 may each contain the same resin or different resins. The resin films can be laminated together via an adhesive layer. This adhesive layer is called the base adhesive layer 11c. From the viewpoint of processing lead time and material cost, it is preferable that the resin film consists of at most three layers.

[0031] Specifically, the materials constituting the base adhesive layer 11c include, for example, polyurethane resins obtained by reacting a main component such as polyester polyol, polyether polyol, acrylic polyol, or carbonate polyol with a bifunctional or higher isocyanate compound (polyfunctional isocyanate compound). The various polyols mentioned above can be used alone or in combination of two or more, depending on the functions and performance required for the exterior material 10. Since it is suitable for heat sealing at high temperatures and for the use of batteries in high-temperature environments, it is preferable that the base adhesive layer 11c contains polyester urethane resin, which is a reaction product of polyester polyol and isocyanate. Examples of isocyanate compounds include isophorone diisocyanate (IPDI), tolylene diisocyanate (TDI), hexamethylene diisocyanate (HDI), etc., and it is preferable to use a combination of these isocyanate compounds from the viewpoint of easily obtaining heat resistance and flexibility. Depending on the performance required for the adhesive, the base adhesive layer 11c may also contain various other additives such as stabilizers in addition to the adhesive components.

[0032] It is preferable that the resin films are bonded together via a substrate adhesive layer 11c with a thickness of 1 to 10 μm. A thickness of 1 μm or more makes it easier to obtain an improvement in moldability, and a thickness of 10 μm or less makes it easier to suppress the decrease in the volumetric energy density of the battery. In addition, although CO2 may be generated when the substrate adhesive layer 11c is formed, if the substrate adhesive layer 11c is not too thick, it is easier to suppress the amount of CO2 generated (this also suppresses the generation of bubbles). From this viewpoint, the thickness of the substrate adhesive layer 11c is more preferably 2 to 7 μm, and even more preferably 3 to 6 μm.

[0033] The moisture content of the inner layer resin film, including resin film 11b, is 4000 ppm by mass or less. This suppresses the generation of air bubbles in the base layer 11 during heat sealing, and prevents a decrease in adhesion between the resin films constituting the base layer 11 (for example, between resin films 11a and 11b) and between the base layer 11 and the barrier layer 13. From this viewpoint, the moisture content is preferably 3500 ppm by mass or less, and more preferably 3000 ppm by mass or less. The moisture content may be 0 ppm by mass. However, from the viewpoint of dimensional stability, the moisture content can be 500 ppm by mass. The moisture content can be adjusted by changing the storage temperature, humidity, and storage time of the resin film.

[0034] The moisture content is measured as follows: A resin film stored in a 23°C, 50% RH environment for two days is cut into 10 cm squares. These are heated in a vaporization heater (HIRANUMA Corporation, EV-2000) set to 300°C, and the amount of moisture generated is measured for 30 minutes using a Karl Fischer apparatus (HIRANUMA Corporation, AQ-2100). Dry N2 gas is used as the carrier gas. The moisture content is then calculated using the measured moisture content value based on the following formula. Moisture content (mass ppm) = Amount of water measured (g) / Mass of film (g)

[0035] The CO2 transmission rate of the resin film constituting the base layer 11, measured in accordance with JIS K 7126, is 60 ml·mm / m². 2 It is preferable that the CO2 permeability is d·MPa or higher. CO2 may be generated when the adhesive layer is formed, and the amount of CO2 generated increases with the multilayering of the base material. The CO2 generated in this way remains in the adhesive layer as bubbles, which may cause the adhesive layer to break easily and reduce the moldability of the exterior material. To address this, it is preferable that the resin film constituting the base material layer has the above-mentioned CO2 permeability. From this viewpoint, a CO2 permeability of 100 ml·mm / m 2 It is more preferable that the pressure be d·MPa or higher, and 500 ml·mm / m 2 It is even more preferable that the pressure be d·MPa or higher.

[0036] In the base layer 11, from the viewpoint of further improving moldability, it is preferable that adjacent resin films are laminated so as to satisfy the following conditions. In biaxially oriented films, due to the Boeing effect, there are directions in which the strength is high but it is difficult to stretch, and directions in which the strength is low but it is easy to stretch (there are inconsistencies in breaking strength and elongation at breaking). This can occur even when using the same mother roll base material, depending on the position after slitting. By making the base layer 11 a laminated film, the strength will be superior to that of a single layer film of the same thickness, but by laminating biaxially oriented films with different stretching states as described below, the strength of the films is complemented, the elongation at breaking is improved, and moldability is further improved. (Condition) The resin films are laminated such that the direction in which the stress value at 10% stretch is greater in the Tensilon tensile test conducted at 45 degrees and 135 degrees relative to the stretching direction of one resin film is greater, and the direction in which the stress value at 10% stretch is smaller in the Tensilon tensile test conducted at 45 degrees and 135 degrees relative to the stretching direction of the other resin film are greater.

[0037] The thickness of the base layer 11 is preferably 24 to 100 μm. A thickness of 24 μm or more facilitates the protection of the barrier layer by the base layer, while a thickness of 100 μm or less helps to suppress the transfer of heat to the sealant layer during heat sealing. From this viewpoint, the thickness of the base layer 11 is more preferably 25 to 75 μm, and even more preferably 27 to 50 μm.

[0038] The thickness of the individual resin films constituting the base layer 11 is not particularly limited, but from the viewpoint of processability, it is more preferably 8 to 50 μm, and even more preferably 12 to 38 μm.

[0039] The melting point of the resin film constituting the base layer 11 is preferably higher than the melting point of the sealant layer 16, and more preferably 30°C or more higher than the melting point of the sealant layer 16, in order to suppress deformation of the base layer 11 during sealing.

[0040] <First adhesive layer> The first adhesive layer 12a is a layer that adheres the substrate layer 11 and the barrier layer 13. Specific examples of materials constituting the first adhesive layer 12a include those exemplified in the substrate adhesive layer 11c. The materials constituting the first adhesive layer 12a and the materials constituting the substrate adhesive layer 11c may be the same or different.

[0041] The thickness of the first adhesive layer 12a is not particularly limited, but from the viewpoint of obtaining desired adhesive strength, conformability, processability, and suppression of CO2 generation, for example, 1 to 10 μm is preferred, and 2 to 7 μm is more preferred.

[0042] <Barrier layer> The barrier layer 13 has water vapor barrier properties that prevent moisture from entering the interior of the all-solid-state battery. The barrier layer 13 may also have ductility for deep drawing. As the barrier layer 13, for example, various metal foils such as aluminum, stainless steel, and copper, or metal vapor-deposited films, inorganic oxide vapor-deposited films, carbon-containing inorganic oxide vapor-deposited films, or films with these vapor-deposited films can be used. As films with vapor-deposited films, for example, aluminum vapor-deposited films and inorganic oxide vapor-deposited films can be used. These can be used individually or in combination of two or more types. As the barrier layer 13, metal foil is preferred in terms of mass (specific gravity), moisture resistance, processability, and cost, and aluminum foil is more preferred.

[0043] As for the aluminum foil, soft aluminum foil that has undergone annealing treatment is particularly preferred because it can provide the desired ductility during molding. However, it is even more preferable to use aluminum foil containing iron in order to provide further pinhole resistance and ductility during molding. The iron content in the aluminum foil is preferably 0.1 to 9.0% by mass, and more preferably 0.5 to 2.0% by mass, of 100% by mass of aluminum foil. By having an iron content of 0.1% by mass or more, an exterior material 10 with better pinhole resistance and ductility can be obtained. By having an iron content of 9.0% by mass or less, an exterior material 10 with better flexibility can be obtained. As for the aluminum foil, untreated aluminum foil may be used, but it is preferable to use degreased aluminum foil in order to provide corrosion resistance. When degreasing the aluminum foil, the degreasing treatment may be applied to only one side of the aluminum foil, or to both sides.

[0044] The thickness of the barrier layer 13 is not particularly limited, but it is preferably 9 to 200 μm, and more preferably 15 to 100 μm, considering barrier properties, pinhole resistance, and processability.

[0045] <First and second corrosion-preventive treatment layers> The first and second corrosion-preventive treatment layers 14a and 14b are layers provided to prevent corrosion of the metal foil (metal foil layer) and other materials constituting the barrier layer 13. The first corrosion-preventive treatment layer 14a also plays a role in increasing the adhesion between the barrier layer 13 and the first adhesive layer 12a. The second corrosion-preventive treatment layer 14b also plays a role in increasing the adhesion between the barrier layer 13 and the second adhesive layer 12b. The first corrosion-preventive treatment layer 14a and the second corrosion-preventive treatment layer 14b may be layers with the same composition or layers with different compositions. The first and second corrosion-preventive treatment layers 14a and 14b (hereinafter also simply referred to as "corrosion-preventive treatment layers 14a and 14b") may be formed by, for example, degreasing, hot water modification, anodizing, chemical conversion, or a combination thereof.

[0046] Degreasing treatments include acid degreasing and alkaline degreasing. Acid degreasing methods include using inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, and hydrofluoric acid individually, or mixtures thereof. Furthermore, as an acid degreasing method, using an acid degreasing agent obtained by dissolving a fluorine-containing compound such as monosodium ammonium difluoride in the above inorganic acid not only provides a degreasing effect on aluminum, especially when aluminum foil is used for the barrier layer 13, but also allows the formation of a passive aluminum fluoride, which is effective in terms of corrosion resistance. Alkaline degreasing methods include using sodium hydroxide, etc.

[0047] Examples of hydrothermal alteration treatments include the boehmite treatment, which involves immersing aluminum foil in boiling water to which triethanolamine has been added. Examples of anodizing treatments include the anodizing treatment.

[0048] Chemical treatments can be immersion-type or coating-type. Immersion-type chemical treatments include, for example, chromate treatment, zirconium treatment, titanium treatment, vanadium treatment, molybdenum treatment, calcium phosphate treatment, strontium hydroxide treatment, cerium treatment, ruthenium treatment, or various chemical treatments consisting of mixed phases of these. On the other hand, a coating-type chemical treatment is a method of applying a coating agent having corrosion-preventive properties onto the barrier layer 13.

[0049] Of these corrosion prevention treatments, if at least a portion of the corrosion prevention treatment layer is formed by hot water modification, anodizing, or chemical conversion, it is preferable to perform the degreasing treatment described above beforehand. Furthermore, if a degreased metal foil, such as a metal foil that has undergone an annealing process, is used as the barrier layer 13, it is not necessary to perform degreasing treatment again when forming the corrosion prevention treatment layers 14a and 14b.

[0050] The coating agent used in the coating-type chemical conversion treatment preferably contains trivalent chromium. The coating agent may also contain at least one polymer selected from the group consisting of cationic polymers and anionic polymers, as described later.

[0051] Furthermore, in particular, the hydrothermal alteration treatment and anodic oxidation treatment among the above treatments dissolve the surface of the aluminum foil with a treatment agent, forming aluminum compounds (boehmite, anodized aluminum) with excellent corrosion resistance. As a result, a co-continuous structure is formed from the barrier layer 13 using aluminum foil to the corrosion-preventive treatment layers 14a and 14b, and therefore the above treatment is included in the definition of chemical conversion treatment. On the other hand, as will be described later, it is also possible to form the corrosion-preventive treatment layers 14a and 14b using only a pure coating method that is not included in the definition of chemical conversion treatment. One example of this method is to use a sol of a rare earth element oxide such as cerium oxide with an average particle size of 100 nm or less, which has an aluminum corrosion-preventive effect (inhibitor effect) and is also environmentally suitable. By using this method, it is possible to impart a corrosion-preventive effect to metal foils such as aluminum foil even with a general coating method.

[0052] Examples of sols for the above-mentioned rare earth element oxides include sols using various solvents such as aqueous, alcoholic, hydrocarbon, ketone, ester, and ether-based solvents. Among these, aqueous sols are preferred.

[0053] In the sols of the rare earth element oxides mentioned above, inorganic acids such as nitric acid, hydrochloric acid, and phosphoric acid, or their salts, or organic acids such as acetic acid, malic acid, ascorbic acid, and lactic acid are usually used as dispersion stabilizers to stabilize their dispersion. Of these dispersion stabilizers, phosphoric acid in particular is expected to provide the following benefits in the exterior material 10: (1) stabilization of sol dispersion, (2) improved adhesion with the barrier layer 13 by utilizing the aluminum chelating ability of phosphoric acid, (3) imparting corrosion resistance by capturing aluminum ions (passivation), and (4) improved cohesive force of the corrosion prevention treatment layers (oxide layers) 14a and 14b due to the ease with which dehydration condensation of phosphoric acid occurs even at low temperatures.

[0054] The corrosion-preventive treatment layers 14a and 14b formed by the above-mentioned rare earth element oxide sols are aggregates of inorganic particles, and therefore, even after the drying and curing process, the cohesive force of the layers themselves may decrease. Therefore, in this case, it is preferable that the corrosion-preventive treatment layers 14a and 14b are compounded with an anionic polymer or a cationic polymer to compensate for the cohesive force.

[0055] The corrosion-preventive treatment layers 14a and 14b are not limited to the layers described above. For example, they may be formed using a treatment agent that combines a resin binder (such as aminophenol) with phosphoric acid and a chromium compound, as is known with coated chromate. Using this treatment agent, a layer can be formed that possesses both corrosion-preventive function and adhesion. Furthermore, although it is necessary to consider the stability of the coating liquid, a layer can be formed that possesses both corrosion-preventive function and adhesion by using a coating agent that pre-mixes a rare earth element oxide sol with a polycationic polymer or a polyanionic polymer into a single liquefaction.

[0056] The mass per unit area of ​​the corrosion-preventive treatment layers 14a and 14b is 0.005 to 0.200 g / m², regardless of whether it is a multilayer or single-layer structure. 2 Preferably, 0.010 to 0.100 g / m 2 A more preferable mass per unit area is 0.005 g / m². 2 If the above is true, it is easier to impart corrosion prevention functionality to the barrier layer 13. Also, the above mass per unit area is 0.200 g / m². 2 Even beyond this limit, the corrosion prevention function does not change significantly. On the other hand, when using rare earth element oxide sols, if the coating film is thick, the heat during drying may result in insufficient curing, potentially leading to a decrease in cohesive force. The thickness of the corrosion prevention treatment layers 14a and 14b can be calculated from their specific gravity.

[0057] The corrosion-preventive treatment layers 14a and 14b may, from the viewpoint of making it easier to maintain adhesion between the sealant layer 16 and the barrier layer 13, for example, contain cerium oxide, 1 to 100 parts by mass of phosphoric acid or phosphate per 100 parts by mass of cerium oxide, and a cationic polymer; or they may be formed by applying a chemical conversion treatment to the barrier layer 13; or they may be formed by applying a chemical conversion treatment to the barrier layer 13 and also contain a cationic polymer.

[0058] <Second adhesive layer> The second adhesive layer 12b is a layer that bonds the barrier layer 13 and the sealant layer 16. A general adhesive for bonding the barrier layer 13 and the sealant layer 16 can be used for the second adhesive layer 12b.

[0059] If a second corrosion-preventive treatment layer 14b is provided on the barrier layer 13, and the second corrosion-preventive treatment layer 14b has a layer containing at least one polymer selected from the group consisting of cationic polymers and anionic polymers described above, it is preferable that the second adhesive layer 12b is a layer containing a compound that is reactive with the polymer contained in the second corrosion-preventive treatment layer 14b (hereinafter also referred to as "reactive compound").

[0060] For example, if the second corrosion-preventive treatment layer 14b contains a cationic polymer, the second adhesive layer 12b contains a compound that is reactive with the cationic polymer. If the second corrosion-preventive treatment layer 14b contains an anionic polymer, the second adhesive layer 12b contains a compound that is reactive with the anionic polymer. Furthermore, if the second corrosion-preventive treatment layer 14b contains both a cationic polymer and an anionic polymer, the second adhesive layer 12b contains a compound that is reactive with the cationic polymer and a compound that is reactive with the anionic polymer. However, the second adhesive layer 12b does not necessarily have to contain the above two types of compounds, and may contain a compound that is 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 12b may further contain an acid-modified polyolefin resin.

[0061] Compounds that react with cationic polymers include at least one compound selected from the group consisting of polyfunctional isocyanate compounds, glycidyl compounds, compounds having a carboxyl group, and compounds having an oxazoline group.

[0062] Examples of these polyfunctional isocyanate compounds, glycidyl compounds, compounds having a carboxyl group, and compounds having an oxazoline group include the polyfunctional isocyanate compounds, glycidyl compounds, compounds having a carboxyl group, and compounds having an oxazoline group that were previously exemplified as crosslinking agents for creating a crosslinked structure of cationic polymers. Among these, polyfunctional isocyanate compounds are preferred because they have high reactivity with cationic polymers and readily form crosslinked structures.

[0063] Compounds that react with anionic polymers include at least one compound selected from the group consisting of glycidyl compounds and compounds having an oxazoline group. Examples of these glycidyl compounds and compounds having an oxazoline group include the glycidyl compounds and compounds having an oxazoline group that were previously exemplified as crosslinking agents for creating a crosslinked structure of cationic polymers. Among these, glycidyl compounds are preferred due to their high reactivity with anionic polymers.

[0064] When the second adhesive layer 12b contains an acid-modified polyolefin resin, it is preferable that the reactive compound is also reactive with the acidic groups in the acid-modified polyolefin resin (i.e., forms a covalent bond with the acidic groups). This further improves adhesion to the second corrosion-preventive treatment layer 14b. In addition, the acid-modified polyolefin resin becomes a cross-linked structure, further improving the solvent resistance of the exterior material 10.

[0065] The content of the reactive compound is preferably equal to or 10 times the amount of the acidic groups in the acid-modified polyolefin resin. If the content of the reactive compound is equal to or greater than the amount of the acidic groups in the acid-modified polyolefin resin, the reactive compound will react sufficiently with the acidic groups in the acid-modified polyolefin resin. On the other hand, if the content of the reactive compound exceeds 10 times the amount, the crosslinking reaction with the acid-modified polyolefin resin has reached saturation, and unreacted material will be present, raising concerns about a decrease in various performance characteristics. 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.

[0066] Acid-modified polyolefin resins are polyolefin resins into which acidic groups have been introduced. Examples of acidic groups include carboxyl groups, sulfonic acid groups, and acid anhydride groups, with maleic anhydride groups and (meth)acrylic acid groups being particularly preferred. As an acid-modified polyolefin resin, for example, the same type as the modified polyolefin resin used in the sealant layer 16 can be used.

[0067] The second adhesive layer 12b may contain various additives such as flame retardants, slip agents, antiblocking agents, antioxidants, light stabilizers, and tackifiers.

[0068] The second adhesive layer 12b may, from the viewpoint of suppressing a decrease in laminate strength when an electrolyte is involved and further suppressing a decrease in insulating properties, include, for example, an acid-modified polyolefin and at least one curing agent selected from the group consisting of a polyfunctional isocyanate compound, a glycidyl compound, a compound having a carboxyl group, a compound having an oxazoline group, and a carbodiimide compound. Examples of carbodiimide compounds include N,N'-di-o-toluylcarbodiimide, N,N'-diphenylcarbodiimide, N,N'-di-2,6-dimethylphenylcarbodiimide, N,N'-bis(2,6-diisopropylphenyl)carbodiimide, N,N'-dioctyldecylcarbodiimide, N-triyl-N'-cyclohexylcarbodiimide, N,N'-di-2,2-di-t-butylphenylcarbodiimide, N-triyl-N'-phenylcarbodiimide, N,N'-di-p-nitrophenylcarbodiimide, N,N'-di-p-aminophenylcarbodiimide, N,N'-di-p-hydroxyphenylcarbodiimide, N,N'-di-cyclohexylcarbodiimide, and N,N'-di-p-toluylcarbodiimide.

[0069] Furthermore, as the adhesive forming the second adhesive layer 12b, for example, a polyurethane-based adhesive containing a polyester polyol composed of hydrogenated dimer fatty acids and diols, and a polyisocyanate can be used. Examples of adhesives include polyurethane resins obtained by reacting a bifunctional or more isocyanate compound with a main component such as a polyester polyol, polyether polyol, acrylic polyol, or carbonate polyol, and epoxy resins obtained by reacting an amine compound with a main component having epoxy groups, which are preferred from the viewpoint of heat resistance.

[0070] The thickness of the second adhesive layer 12b is not particularly limited, but from the viewpoint of obtaining the desired adhesive strength and processability, it is preferably 1 to 10 μm, and more preferably 2 to 7 μm.

[0071] <Sealant layer 16> The sealant layer 16 is a layer that provides heat sealing properties to the exterior material 10, and is placed on the inside and heat-sealed (heat-fused) during the assembly of the all-solid-state battery.

[0072] As the sealant layer 16, for example, a film containing a thermoplastic resin such as polyolefin resin, polyester resin, polycarbonate resin, polyphenylene ether resin, polyacetal resin, polystyrene resin, polyvinyl chloride resin, or polyvinyl acetate resin can be used. By blending the various resins listed above to form a polymer alloy, the sealing properties and heat resistance can be controlled. In particular, it is preferable to use a film containing polyolefin resin (hereinafter also referred to as "polyolefin film") or a film containing polyester resin (hereinafter also referred to as "polyester film"). In this case, the sealing properties to the exterior material 10 will be better. Furthermore, since polyolefin film and polyester film have heat resistance, the heat resistance of the exterior material 10 can be further improved.

[0073] Examples of polyolefin resins include low-density, medium-density, or high-density polyethylene; ethylene-α-olefin copolymers; polypropylene; block or random copolymers containing propylene as a copolymer component; and polyolefin resins such as propylene-α-olefin copolymers. The polyolefin resin may also be an acid-modified polyolefin resin obtained by modifying a polyolefin resin with an acid or glycidyl. When the polyolefin film is directly laminated to the barrier layer 13 without the corrosion-preventive treatment layer 14b and the second adhesive layer 12b, it is preferable that the polyolefin film contains an acid-modified polyolefin resin layer containing an acid-modified polyolefin resin, and that this acid-modified polyolefin resin layer is directly laminated to the barrier layer 13.

[0074] Examples of polyester resins include polyethylene terephthalate (PET) resin, polybutylene terephthalate (PBT) resin, polyethylene naphthalate (PEN) resin, polybutylene naphthalate (PBN) resin, and copolymers thereof. These polyester resins may be used individually or in combination of two or more. Alternatively, a copolymer of any acid and glycol may be used.

[0075] Furthermore, the sealant layer 16 may further contain additives such as antioxidants, slip agents, flame retardants, antiblocking agents, light stabilizers, dehydrating agents, tackifiers, crystal nucleating agents, and plasticizers in order to provide sealing properties, heat resistance, and other functionalities.

[0076] The melting point of the sealant layer 16 is not particularly limited, but is preferably 150°C or higher, more preferably 155°C or higher, and even more preferably 160°C or higher. Having a melting point of 150°C or higher for the sealant layer 16 helps to suppress a decrease in the sealing strength of the exterior material 10 even when it is used in a high-temperature environment.

[0077] The melting point of the sealant layer 16 is preferably 250°C or lower, more preferably 230°C or lower, and even more preferably 210°C or lower. In this case, the melting point of the sealant layer 16 being 250°C or lower allows the heat sealing temperature to be reduced. Therefore, the generation of air bubbles in the base layer 11 during heat sealing can be further suppressed. Consequently, the deterioration of the moldability of the exterior material is further suppressed. In addition, the exterior material 10 can also suppress the intrusion of moisture through the exterior material 10.

[0078] In this disclosure, "melting point" refers to the "melting peak temperature" determined in accordance with the method described in JIS K7121-1987, and if two or more melting peaks appear independently, the lowest melting peak temperature is adopted.

[0079] The sealant layer 16 may be a single-layer film or a multi-layer film, and the choice should be made according to the required function. If the sealant layer 16 is a multi-layer film, the layers may be laminated by co-extrusion or by dry lamination. However, if the sealant layer 16 is a multi-layer film, it is preferable to use the same type of resin from the viewpoint of interlayer adhesion. For example, a layer containing a modified polyolefin resin may be placed in contact with the barrier layer 13, and a single layer of unmodified polyolefin resin may be extruded onto that layer, or multiple layers of polyolefin resin may be co-extruded and laminated.

[0080] The thickness of the sealant layer 16 is not particularly limited, but is preferably 10 to 100 μm, and more preferably 20 to 60 μm. A thickness of 10 μm or more of the sealant layer 16 provides sufficient sealing strength. A thickness of 100 μm or less of the sealant layer 16 reduces the amount of water vapor that penetrates from the periphery of the exterior material 10.

[0081] Although preferred embodiments of the casing material for all-solid-state batteries of this embodiment have been described in detail above, this disclosure is not limited to such specific embodiments.

[0082] For example, Figure 1 shows a case where corrosion-preventive treatment layers 14a and 14b are provided on both sides of the barrier layer 13, but it is also possible that only one of the corrosion-preventive treatment layers 14a and 14b is provided, or that no corrosion-preventive treatment layer is provided at all.

[0083] Figure 1 shows a case where the barrier layer 13 and the sealant layer 16 are laminated using a second adhesive layer 12b, but the barrier layer 13 and the sealant layer 16 may also be laminated using an adhesive resin layer 15, as shown in the all-solid-state battery exterior material 20 in Figure 2. In the all-solid-state battery exterior material 20 shown in Figure 2, the second adhesive layer 12b may be provided between the barrier layer 13 and the adhesive resin layer 15.

[0084] <Adhesive resin layer 15> The adhesive resin layer 15 is generally composed of an adhesive resin composition as the main component and additive components as needed. The adhesive resin composition is not particularly limited, but it is preferable that it contains a modified polyolefin resin.

[0085] The modified polyolefin resin is preferably a polyolefin resin that has been graft-modified with an unsaturated carboxylic acid, or an unsaturated carboxylic acid derivative derived from either its acid anhydride or ester.

[0086] Examples of polyolefin resins include low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-α-olefin copolymer, homopolypropylene, block polypropylene, random polypropylene, and propylene-α-olefin copolymer.

[0087] The modified polyolefin resin is preferably a polyolefin resin modified with maleic anhydride. Suitable modified polyolefin resins include, for example, "Admer" manufactured by Mitsui Chemicals, Inc. and "Modic" manufactured by Mitsubishi Chemical Corporation. Such modified polyolefin resins exhibit excellent reactivity with various metals and polymers having various functional groups, and this reactivity can be used to impart adhesion to the adhesive resin layer 15. The adhesive resin layer 15 may also contain various additives as needed, such as various compatible and incompatible elastomers, flame retardants, slip agents, antiblocking agents, antioxidants, light stabilizers, and tackifiers.

[0088] The thickness of the adhesive resin layer 15 is not particularly limited, but from the viewpoint of stress relaxation and moisture permeability, it is preferable that it be the same as or less than that of the sealant layer 16.

[0089] Furthermore, in the exterior material 20 for all-solid-state batteries, the total thickness of the adhesive resin layer 15 and the sealant layer 16 is preferably in the range of 5 to 100 μm, and more preferably in the range of 20 to 80 μm, from the viewpoint of achieving both thinning and improved heat seal strength in high-temperature environments.

[0090] Furthermore, the exterior material of this disclosure may further include a modified layer 17 disposed on the surface of the base layer 11 opposite to the barrier layer 13 side, as shown in Figure 3, for the exterior material 30 for all-solid-state batteries. In Figure 3, the adhesive resin layer 15 may be a second adhesive layer 12b.

[0091] <Modified layer 17> When a highly wettable film (e.g., polyester film) is used as the base layer, bleeding is likely to occur when printing barcodes for lot tracing with an inkjet printer after battery manufacturing. This creates a problem where barcode reading becomes difficult. This problem can be addressed by providing a modified layer 17 on the base layer 11. The modified layer 17 contains a silicone resin and can be formed by coating the base layer 11 with a coating solution obtained by diluting silicone oil with a solvent. The coating solution may also contain an amide-based lubricant such as erucic acid amide to improve moldability. The modified layer 17 may also be formed as a protective layer using the same material as the first adhesive layer 12a.

[0092] [Manufacturing method for exterior materials] Next, an example of a manufacturing method for the exterior material 10 shown in Figure 1 will be described. Note that the manufacturing method for the exterior material 10 is not limited to the method described below.

[0093] The manufacturing method for the exterior material 10 of this embodiment generally includes the steps of: providing corrosion prevention treatment layers 14a and 14b on the barrier layer 13; bonding the base material layer 11 and the barrier layer 13 using a first adhesive layer 12a; further laminating a sealant layer 16 via a second adhesive layer 12b to produce a laminate; and, if necessary, aging the obtained laminate.

[0094] (Lamination process of corrosion-preventive treatment layer onto barrier layer) This process is to form the corrosion prevention treatment layers 14a and 14b on the barrier layer 13. As methods, as described above, methods such as degreasing treatment, hot water conversion treatment, anodic oxidation treatment, chemical conversion treatment on the barrier layer 13, or applying a coating agent having corrosion prevention performance can be mentioned.

[0095] Also, when the corrosion prevention treatment layers 14a and 14b are multi-layered, for example, apply the coating solution (coating agent) constituting the lower-layer side (barrier layer 13 side) of the corrosion prevention treatment layer to the barrier layer 13, bake it to form the first layer, and then apply the coating solution (coating agent) constituting the upper-layer side of the corrosion prevention treatment layer to the first layer and bake it to form the second layer.

[0096] The degreasing treatment can be performed by the spray method or the immersion method. The hot water conversion treatment and the anodic oxidation treatment can be performed by the immersion method. For the chemical conversion treatment, according to the type of chemical conversion treatment, the immersion method, the spray method, the coating method, etc. can be appropriately selected and performed.

[0097] Regarding the coating method of the coating agent having corrosion prevention performance, various methods such as gravure coating, reverse coating, roll coating, bar coating, etc. can be used.

[0098] As described above, various treatments can be performed on either both sides or one side of the metal foil. However, in the case of one-sided treatment, it is preferable to perform the treatment on the side where the sealant layer 16 is laminated. In addition, according to requirements, the above treatment may also be performed on the surface of the base material layer 11.

[0099] Also, the coating amount of the coating agent for forming the first layer and the second layer is preferably 0.005 - 0.200 g / m 2 and more preferably 0.010 - 0.100 g / m 2 is more preferable.

[0100] Also, when drying and curing are required, according to the drying conditions of the corrosion prevention treatment layers 14a and 14b used, it can be performed in the range of 60 - 300 °C as the base material temperature.

[0101] (Lamination process between the substrate layer and the barrier layer) This process involves bonding a barrier layer 13, which is provided with corrosion-preventive treatment layers 14a and 14b, to a substrate layer 11 via a first adhesive layer 12a. The bonding method can be dry lamination, non-solvent lamination, or wet lamination, using the materials that constitute the first adhesive layer 12a described above. The first adhesive layer 12a is applied in a dry coating amount of 1 to 10 g / m². 2 In the range of 2 to 7 g / m², more preferably 2 to 7 g / m² 2 It is provided within the specified range. Furthermore, as the base layer 11, a laminated film is prepared in advance by bonding resin films together using a base adhesive layer 11c in the same bonding method as described above.

[0102] Furthermore, it is preferable to perform a resin film selection process prior to the above lamination process. Specifically, the selection process involves measuring the moisture content of resin films stored in a 23°C 50%RH environment for two days, and selecting films with a moisture content of 4000 ppm by mass or less as the inner layer resin film to be laminated on the inner layer side of the resin film 11a. This makes it possible to understand the degree of moisture absorption of the resin film, and makes it easier to suppress the generation of air bubbles in the base layer 11 during heat sealing at high temperatures.

[0103] (Lamination process of the second adhesive layer and sealant layer) This process involves bonding the sealant layer 16 to the second corrosion-preventive treatment layer 14b side of the barrier layer 13 via the second adhesive layer 12b. Methods of bonding include wet processes and dry lamination.

[0104] In the wet process, a solution or dispersion of the adhesive constituting the second adhesive layer 12b is applied onto the second corrosion-preventive treatment layer 14b, and the solvent is evaporated at a predetermined temperature to form a dry film, or a baking treatment is performed as needed after drying. Subsequently, a sealant layer 16 is laminated to manufacture the exterior material 10. Various coating methods as exemplified above can be used as coating methods. The preferred dry application amount of the second adhesive layer 12b is the same as that of the first adhesive layer 12a.

[0105] In this case, the sealant layer 16 can be manufactured by a melt extrusion molding machine using, for example, a resin composition for forming a sealant layer containing the components of the sealant layer 16 described above. From the viewpoint of productivity, the processing speed of the melt extrusion molding machine can be set to 80 m / min or more.

[0106] (Aging process) This process involves aging (curing) the laminate. Aging the laminate promotes adhesion between the barrier layer 13, the second corrosion-preventive treatment layer 14b, the second adhesive layer 12b, and the sealant layer 16. The aging process can be carried out in a temperature range of room temperature to 100°C. The aging time is, for example, 1 to 10 days.

[0107] In this way, the exterior material 10 of this embodiment, as shown in Figure 1, can be manufactured.

[0108] Next, an example of a manufacturing method for the exterior material 20 shown in Figure 2 will be described. Note that the manufacturing method for the exterior material 20 is not limited to the method described below.

[0109] The manufacturing method for the exterior material 20 of this embodiment generally includes the steps of: providing corrosion-preventive treatment layers 14a and 14b on the barrier layer 13; bonding the base layer 11 and the barrier layer 13 using the first adhesive layer 12a; further laminating the adhesive resin layer 15 and the sealant layer 16 to produce a laminate; and, if necessary, heat-treating the obtained laminate. Note that the steps up to bonding the base layer 11 and the barrier layer 13 can be carried out in the same manner as the manufacturing method for the exterior material 10 described above.

[0110] (Lamination process of adhesive resin layer and sealant layer) This step involves forming an adhesive resin layer 15 and a sealant layer 16 on the second corrosion-preventive treatment layer 14b formed in the previous step. One method for this is sand lamination of the adhesive resin layer 15 together with the sealant layer 16 using an extrusion laminating machine. Furthermore, lamination is also possible by tandem lamination or co-extrusion, in which the adhesive resin layer 15 and the sealant layer 16 are extruded. In forming the adhesive resin layer 15 and the sealant layer 16, for example, each component is blended to satisfy the above-described configuration of the adhesive resin layer 15 and the sealant layer 16. The above-described sealant layer forming resin composition is used to form the sealant layer 16.

[0111] This process yields a laminate in which each layer is laminated in the following order, as shown in Figure 2: base material layer 11 / first adhesive layer 12a / first corrosion prevention treatment layer 14a / barrier layer 13 / second corrosion prevention treatment layer 14b / adhesive resin layer 15 / sealant layer 16.

[0112] The adhesive resin layer 15 may be laminated by directly extruding the dry-blended material using an extrusion laminating machine to achieve the material composition described above. Alternatively, the adhesive resin layer 15 may be laminated by extruding the granulated material, which has been melt-blended using a melt-kneading device such as a single-screw extruder, twin-screw extruder, or Brabender mixer, using an extrusion laminating machine.

[0113] The sealant layer 16 may be laminated by directly extruding a dry-blended material, which has been prepared to have the above-described material composition as a component of the resin composition for forming the sealant layer, using an extrusion laminating machine. Alternatively, the adhesive resin layer 15 and the sealant layer 16 may be laminated by a tandem lamination method or co-extrusion method, in which the adhesive resin layer 15 and the sealant layer 16 are extruded using an extrusion laminating machine after melt blending the granulated material using a melt-kneading device such as a single-screw extruder, twin-screw extruder, or Bravender mixer. Furthermore, a single sealant film may be prepared in advance as a cast film using the resin composition for forming the sealant layer, and this film may be laminated together with the adhesive resin by sand lamination. From the viewpoint of productivity, the formation speed (processing speed) of the adhesive resin layer 15 and the sealant layer 16 can be, for example, 80 m / min or more.

[0114] (Heat treatment process) This process involves heat-treating the laminate. Heat-treating the laminate improves the adhesion between the barrier layer 13, the second corrosion-preventive treatment layer 14b, the adhesive resin layer 15, and the sealant layer 16. Preferably, the heat treatment is performed at a temperature at least equal to or above the melting point of the adhesive resin layer 15.

[0115] In this way, the exterior material 20 of this embodiment, as shown in Figure 2, can be manufactured.

[0116] [All-solid battery] Figure 4 is a perspective view showing one embodiment of an all-solid-state battery made using the exterior material 10 described above. As shown in Figure 4, the all-solid-state battery 50 is composed of a battery body 52 having a solid electrolyte, two metal terminals (current extraction terminals) 53 for extracting current from the battery body 52 to the outside, and an outer bag 54 that encloses the battery body 52 in an airtight state. The outer bag 54 is obtained by heat-sealing the exterior material 10 according to this embodiment described above, and is used as a container for housing the battery body 52. ​​In the exterior material 10, the base material layer 11 is the outermost layer, and the sealant layer 16 is the innermost layer. That is, the exterior material 10 is configured to enclose the battery body 52 inside by folding one laminate film in half and heat-sealing the periphery, or by overlapping two laminate films and heat-sealing the periphery, so that the base material layer 11 is on the outside side of the all-solid-state battery 50 and the sealant layer 16 is on the inside side of the all-solid-state battery 50. The metal terminal 53 is held between outer bags 54 with a sealant layer 16 on the inside. The metal terminal 53 may also be held between outer bags 54 via a tab sealant.

[0117] Before heat-sealing the outer packaging material 10, a step may be taken to confirm that the moisture content of the resin film 11b, which is laminated on the inner side of the resin film 11a, is 4000 ppm by mass or less, and if the moisture content is not 4000 ppm by mass or less, a step may be taken to adjust the moisture content of the resin film 11b to 4000 ppm by mass or less. The moisture content can be adjusted by changing the storage temperature, humidity, and storage time of the outer packaging material 10. This makes it easier to suppress the generation of air bubbles in the base layer 11 during heat sealing at high temperatures.

[0118] The battery body 52 has at least one power generation element consisting of a positive electrode, a solid electrolyte, and a negative electrode. The metal terminal 53 is a part of the current collector that is exposed to the outside of the outer casing material 10, and is made of metal foil such as copper foil or aluminum foil. Examples of solid electrolytes include oxide-based solid electrolytes and sulfide-based solid electrolytes.

[0119] The heat sealing conditions when heat sealing the outer packaging material 10 can be adjusted depending on the material constituting the sealant layer. For example, if the melting point of the sealant layer is 150°C or higher, the heat sealing conditions can be set to 180-230°C for 2-20 seconds. With the outer packaging material 10, the generation of air bubbles in the base material layer 11 can be suppressed during heat sealing. Therefore, with the all-solid-state battery 50, a decrease in the adhesion between the resin films constituting the base material layer is suppressed. Furthermore, since the base material layer is a multilayer film, the strength of the base material layer itself is improved. Consequently, even if the battery body 52 expands due to the use of the all-solid-state battery 50 in a high-temperature environment and a force acts to open the outer bag 54, the all-solid-state battery 50 can maintain its reliability as an outer packaging material 10. [Examples]

[0120] The present disclosure will be described in more detail below based on examples, but the present disclosure is not limited to the following examples.

[0121] <Materials used> The materials used in the examples and comparative examples are shown below.

[0122] (base material layer) The following resin film (biaxially oriented film) was used as the base layer. Polyethylene terephthalate film (PET, 25 μm thickness, Film A): Manufactured by Unitika Ltd., easy-to-form PET film, moisture content 2913 ppm by mass, CO2 transmission rate 74 ml·mm / m² 2 ·d·MPa Polybutylene terephthalate film (PBT, 25 μm thickness, Film B): Manufactured by Kojin Film & Chemicals Co., Ltd., Boblet (product name), moisture content 1648 ppm by mass, CO2 transmission rate 70 ml·mm / m² 2 ·d·MPa Polyamide film (PA(Ny6), 25μm thick, Film C): Manufactured by Toyobo Co., Ltd., Harden N1102 (product name), moisture content 23728 ppm by mass, CO2 transmission rate 50 ml·mm / m² 2 ·d·MPa The moisture content was measured as follows: A resin film stored in a 23°C, 50% RH environment for two days was cut into 10 cm squares. These were heated in a vaporization heater (HIRANUMA Corporation, EV-2000) set to 300°C, and the amount of moisture generated was measured for 30 minutes using a Karl Fischer apparatus (HIRANUMA Corporation, AQ-2100). Dry N2 gas was used as the carrier gas. The moisture content was then calculated using the measured moisture content values ​​based on the following formula. Moisture content (mass ppm) = Amount of water measured (g) / Mass of film (g) Furthermore, CO2 transmission rates were measured in accordance with JIS K 7126.

[0123] (Base adhesive layer and first adhesive layer) For the base adhesive layer and the first adhesive layer, a polyester urethane adhesive (manufactured by Toyo Morton Co., Ltd.) was used, which was formulated with a polyester polyol-based main component and a curing agent consisting of tolylene diisocyanate (TDI, CAT-10L), hexamethylene diisocyanate (HDI, SP curing agent), or tolylene diisocyanate (TDI) and isophorone diisocyanate (IPDI, CAT-RT1).

[0124] (First corrosion-preventive treatment layer and second corrosion-preventive treatment layer) The first corrosion-preventive treatment layer (on the substrate layer side) and the second corrosion-preventive treatment layer (on the sealant layer side) were formed using (CL-1) and (CL-2) as described below. (CL-1): A sodium polyphosphate-stabilized cerium oxide sol prepared using distilled water as the solvent, with a solid content concentration of 10% by mass. In this sodium polyphosphate-stabilized cerium oxide sol, 10 parts by mass of sodium phosphoric acid salt were added to 100 parts by mass of cerium oxide. (CL-2): A composition prepared using distilled water as the solvent, with a solid content concentration of 5% by mass. In this composition, the ratio of "polyallylamine (manufactured by Nitto Boseki Co., Ltd.)" to "polyglycerol polyglycidyl ether (manufactured by Nagase ChemteX Corporation)" was 90:10 (by mass).

[0125] (Barrier layer) As the barrier layer, annealed and degreased soft aluminum foil (manufactured by Toyo Aluminum Co., Ltd., product name: 8079 material, thickness 40 μm) was used.

[0126] (adhesive resin layer) As the adhesive resin layer, a polypropylene resin modified with maleic anhydride (thickness 27 μm, melting point 164°C) was used.

[0127] (Sealant layer) A polypropylene film (53 μm thick, melting point 164°C) was used as the sealant layer.

[0128] (modified layer) Polyether-modified silicone oil (Shin-Etsu Silicone Co., Ltd., KF-351A) was used to form the modified layer.

[0129] (Example 1) First, a first corrosion-preventive treatment layer and a second corrosion-preventive treatment layer were applied to the barrier layer in the following procedure. Specifically, (CL-1) was first applied to both surfaces of the barrier layer at a dry application rate of 70 mg / m². 2 The material was coated using microgravure coating and then baked in a drying unit at 200°C. Next, (CL-2) was applied to the resulting layer at a dry coating rate of 20 mg / m². 2 The material was coated using microgravure coating. In this way, composite layers consisting of (CL-1) and (CL-2) were formed on both surfaces of the barrier layer as the first and second corrosion-preventive treatment layers, respectively, to obtain a laminate. These composite layers exhibit corrosion-preventive performance by combining the two types, (CL-1) and (CL-2).

[0130] Next, two PET films (film A), which serve as the base layer, were bonded together using a polyurethane adhesive (base adhesive layer) containing a polyester polyol-based main component and TDI and IPDI as curing agents to obtain the base layer. Specifically, the polyurethane adhesive was applied to one side of one PET film to a thickness of 4 μm after curing, dried at 80°C for 1 minute, laminated with the other PET film, and aged at 80°C for 120 hours to obtain the base layer.

[0131] A laminate of the barrier layer and the substrate layer was obtained by dry lamination, using a polyurethane adhesive (first adhesive layer) on the side with the first corrosion-preventive treatment layer of the barrier layer, which was provided with a first corrosion-preventive treatment layer and a second corrosion-preventive treatment layer. Specifically, a polyurethane adhesive was applied to the surface of the barrier layer on the side with the first corrosion-preventive treatment layer so that the thickness after curing would be 5 μm, dried at 80°C for 1 minute, laminated with the substrate layer, and aged at 60°C for 120 hours to obtain the laminate.

[0132] Next, the laminate of the barrier layer and the base material layer was set in the unwinding section of an extrusion laminating machine, and the adhesive resin layer was sand-laminated together with the sealant layer.

[0133] The structure obtained in this manner was subjected to heat treatment so that the maximum temperature reached by the structure was 200°C, thereby obtaining a laminate of a base layer, a barrier layer, and a sealant layer.

[0134] Next, a modified layer was created by coating the substrate layer of the laminate of the substrate layer, barrier layer, and sealant layer with a coating solution containing polyether-modified silicone oil. Specifically, the amount of silicone oil applied was 1.2 mg / m². 2 The material was applied to the base layer and dried at 40°C for 1 minute. This produced an exterior material (a laminate consisting of a modified layer, a base layer, a first adhesive layer, a first corrosion-preventive treatment layer, a barrier layer, a second corrosion-preventive treatment layer, an adhesive resin layer, and a sealant layer).

[0135] (Other examples and comparative examples) Except for the changes in the composition of the base layer, the composition and thickness of the base adhesive layer, and the presence or absence of the modified layer, as shown in Table 1, the exterior material was prepared in the same manner as in Example 1. In Table 1, the thickness of the base layer refers to the thickness of the resin film only, excluding the thickness of the base adhesive layer.

[0136] [Table 1]

[0137] <Evaluation of exterior materials> The exterior materials obtained in each example were evaluated as follows. The results are shown in Table 2.

[0138] (Moldability) Samples of the exterior material cut to a size of 120mm x 200mm (200mm in the MD direction) were subjected to 10 molding cycles at a molding depth of 6mm under the following conditions, and the presence or absence of pinholes and cracks was visually checked. The observation results were evaluated as follows. Grade A: No pinholes or / or cracks occurred in any of the molded samples. Grade B: Pinholes and / or cracks occurred in any of the molded samples. (conditions) Mold specifications (units in mm): Blank 120 x 200, molding area 80 x 70 (MD direction is 70), corner radius 1, punch radius 1, die radius 1. Molding conditions: Holding pressure 0.8 MPa. Molding position: A molding area measuring 80 mm x 70 mm (70 mm in the MD direction) was created at a position 30 mm from one of the shorter sides of the sample and 20 mm from each of the longer sides.

[0139] (Lifting of the substrate layer after heat sealing) The exterior material was cut to a size of 120 mm x 60 mm, folded in half with the sealant layer facing inward, and the longitudinal ends of the exterior material were overlapped. These ends were then heat-sealed at 200°C for 10 seconds while applying pressure of 0.5 MPa, forming a heat-sealed section (shaded area in Figure 5) with a width of 10 mm, and the structure was fabricated. The structure was then stored at room temperature for 24 hours. The heat-sealed section was visually inspected, and the observation results were evaluated as follows. Grade A: No delamination was observed in the substrate layer. Grade B: Delamination was observed in the substrate layer.

[0140] (Foaming of the adhesive layer after aging) The exterior material was placed in an oven and aged at 80°C for 120 hours. Afterwards, the appearance of the exterior material was examined with a 10x magnifying glass, and the observation results were evaluated as follows. Grade A: No foaming was observed. Grade B: Foaming was observed.

[0141] (Heat seal strength) The exterior material was cut to a size of 120 mm x 60 mm, folded in half with the sealant layer facing inward, and the longitudinal ends of the exterior material were overlapped. These ends were then heat-sealed at 200°C for 5 or 10 seconds while applying pressure of 0.5 MPa to form a heat-sealed section with a width of 10 mm (shaded area in Figure 5), thereby creating a structure. The structure was then stored at room temperature for 24 hours. Subsequently, a 15 mm x 30 mm section was cut from the longitudinal center of the heat-sealed section of the structure (see Figure 5) to create an evaluation sample. The heat-seal strength was measured using this evaluation sample. The measurement was performed as follows: the excess portion of the sample was chucked in a tensile testing apparatus, and the sample was pulled at a speed of 50 m / min. The maximum strength obtained at that time was defined as the heat-seal strength. The results obtained were evaluated as follows. Grade A: Heat seal strength was 50N / 15mm or higher in both 5-second and 10-second heat seal times. Grade B: When the heat sealing time was 5 seconds, the heat seal strength was less than 50 N / 15 mm, but when the heat sealing time was 10 seconds, the heat seal strength was 50 N / 15 mm or more.

[0142] (Discoloration of molded samples under high-temperature conditions) Except for setting the molding depth to 4.4 mm, molded samples were obtained in the same manner as the "moldability" evaluation described above. These were placed in an oven and stored at 110°C for 4 weeks. After that, the appearance of the molded samples was visually inspected, and the observation results were evaluated as follows. Grade A: No discoloration was observed before or after placing it in the oven. Grade B: Discoloration was observed before and after placing the product in the oven.

[0143] (Floating of the substrate layer of molded samples in high-temperature environments) Except for setting the molding depth to 4.4 mm, molded samples were obtained in the same manner as the "moldability" evaluation described above. These were placed in an oven and stored at 110°C or 150°C for 4 weeks. After that, the appearance of the molded samples was visually inspected, and the observation results were evaluated as follows. Grade A: No delamination was observed in the substrate layer even at a storage temperature of 150°C. Grade B: When the storage temperature was 150°C, delamination was observed in the base layer, but when the temperature was 110°C, delamination was not observed in the base layer.

[0144] (Barcode readability) A 2D barcode was printed on the surface layer of the substrate (or on the modified layer if one exists) using a Markemimage 9040 inkjet printer (M head). The readability of the barcode using a barcode reader was evaluated as follows. Grade A: Barcode was read in less than 1 second. Grade B: Barcodes could be read in 1-5 seconds.

[0145] [Table 2]

[0146] As shown in Table 1, the exterior material of the example using a base layer formed from at least two resin films with a water content of 4000 ppm by mass or less exhibited excellent moldability and suppressed the occurrence of lifting in the base layer during heat sealing. [Explanation of Symbols]

[0147] 10, 20, 30…Outer packaging material for all-solid-state batteries, 11…Base layer, 11a, 11b…Resin film, 11c…Base adhesive layer, 12a…First adhesive layer, 12b…Second adhesive layer, 13…Barrier layer, 14a…First corrosion prevention treatment layer, 14b…Second corrosion prevention treatment layer, 15…Adhesive resin layer, 16…Sealant layer, 17…Modification layer, 50…All-solid-state battery, 52…Battery body, 53…Metal terminals, 54…Outer bag.

Claims

1. An exterior material for an all-solid-state battery comprising at least a base layer, a barrier layer, and a sealant layer in this order, The substrate layer comprises at least two layers of biaxially stretched resin film, The aforementioned resin film is a polyester film containing a polyester resin, An outer casing material for all-solid-state batteries, wherein the resin film has a water content of 4000 ppm by mass or less.

2. The exterior material for all-solid-state batteries according to claim 1, wherein the thickness of the base material layer is 24 to 100 μm.

3. The exterior material for an all-solid-state battery according to claim 1 or 2, wherein the resin films are bonded together via an adhesive layer having a thickness of 1 to 10 μm.

4. The exterior material for an all-solid-state battery according to claim 3, wherein the adhesive layer comprises a polyester urethane resin which is a reaction product of a polyester polyol and an isocyanate.

5. The CO2 of the aforementioned resin film, measured in accordance with JIS K 7126 ２ The transmittance is 60 ml / mm / m ２ - An outer casing material for an all-solid-state battery according to claim 4, wherein the pressure is d·MPa or higher.

6. The outer casing material for an all-solid-state battery according to any one of claims 1 to 5, wherein the melting point of the sealant layer is 150°C or higher.

7. The exterior material for an all-solid-state battery according to any one of claims 1 to 6, further comprising a modified layer containing a silicone resin on the base material layer.

8. A battery body containing a solid electrolyte, The battery comprises an outer bag for housing the battery body, A solid-state battery in which the outer bag is an outer bag obtained by heat-sealing an outer bag for a solid-state battery described in any one of claims 1 to 7.

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