Support film for semi-solid battery current collector

Abstract

This support film for a semi-solid battery current collector comprises: a base; and an adhesion layer disposed on one surface of the base. The adhesion layer contains a resin A. The melting point of the resin A is not higher than 130°C. The acid value of the resin A is not less than 6 mgKOH / g. A semi-solid battery of the present invention comprises: an outer packaging bag obtained by using said support film; and a plurality of power storage elements that are housed in the outer packaging bag and that are provided adjacent to each other. Each of the power storage elements has a semi-solid electrolyte and a pair of electrodes having a current collector. The adhesion layer of the support film is bonded to the current collector of the pair of electrodes.

Description

Support film for current collectors in semi-solid batteries

[0001] The present disclosure relates to a support film for a current collector for a semi-solid battery.

[0002] In recent years, semi-solid batteries have attracted attention because they are safer and can achieve higher energy densities than liquid batteries, which use liquid electrolytes. Semi-solid batteries have a gel, clay, or other electrolyte and electrodes (positive and negative electrodes), and the electrodes are composed of a positive electrode current collector, a positive electrode active material, a separator, a negative electrode active material, and a negative electrode current collector, in this order.

[0003] The electrodes are sealed with a support film to form a single pouch (unit cell), and in secondary batteries, multiple unit cells are stacked to form a battery assembly (stack cell) to improve battery capacity. The support film isolates the active material, current collector, etc. from the outside, protects them from moisture and other foreign matter, and prevents short-circuiting between adjacent electrodes. Such unit cells are fabricated, for example, by the method described in Patent Document 1.

[0004] Special Publication No. 2023-545410

[0005] The support film is required to be in close contact with the current collector (e.g., copper foil, aluminum foil) to protect the current collector from moisture and other foreign substances, etc. Therefore, an object of the present disclosure is to provide a support film for a current collector for a semi-solid battery that has excellent adhesion to the current collector.

[0006] One aspect of the present disclosure includes, for example, the following inventions. [1] A support film for a current collector for a semi-solid battery, comprising: a substrate; and an adhesive layer disposed on one surface of the substrate, wherein the adhesive layer contains resin A, and the melting point of the resin A is 130°C or less, and the acid value of the resin A is 6 mgKOH / g or more. [2] The support film according to [1], wherein the melting point of the resin A is 50 to 110°C. [3] The support film according to [1] or [2], wherein the melting point of the resin A is 90 to 100°C. [4] The support film according to any one of [1] to [3], wherein the acid value of the resin A is 15 to 60 mgKOH / g. [5] The support film according to any one of [1] to [4], wherein the acid value of the resin A is 30 to 50 mgKOH / g. [6] The support film according to any one of [1] to [5], wherein the substrate contains a polyester resin, and the resin A is a thermoplastic resin. [7] The support film according to any one of [1] to [6], wherein the resin A is an ethylene-vinyl acetate copolymer. [8] The support film according to any one of [1] to [7], wherein the thickness of the substrate is 4 to 100 μm. [9] The support film according to any one of [1] to [8], wherein the thickness of the adhesive layer is 2 to 30 μm.

[10] The support film according to any one of [1] to [9], wherein the thickness of the adhesive layer is 2 to 5 μm.

[11] The support film according to any one of [1] to

[10] , wherein the thickness is 5 to 80 μm.

[12] The support film according to any one of [1] to

[11] , wherein the adhesive layer has an adhesion strength A1 to copper foil of 5 N / 15 mm or more, as measured by the following peel test. <Peel test> The adhesive layer of the support film and the shiny side of an electrolytic copper foil (thickness 18 μm, surface roughness 0.33 μm) are overlapped, a PET film is placed on the surface of the support film opposite the substrate, and the support film is sandwiched between them, and heat is applied only from the adhesive layer side of the support film using a heat seal tester to perform thermocompression bonding under the conditions of 150°C, 0.2 MPa, and 1 second.

[13] The support film according to any one of [1] to

[12] , wherein the adhesive strength A1 of the adhesive layer to the copper foil measured by the following peel test is 2 N / 15 mm or more, and the adhesive strength A1 is greater than the adhesive strength A2 of the adhesive layer to the substrate measured by the following peel test. <Peel test> The adhesive layer of the support film was superimposed on the shiny side of an electrolytic copper foil (thickness 18 μm, surface roughness 0.33 μm) or a test substrate identical to the substrate, and a PET film was placed on the surface of the support film opposite the substrate to sandwich the support film, and heat was applied only from the adhesive layer side of the support film using a heat seal tester to perform thermocompression bonding under the conditions of 150°C, 0.2 MPa, and 1 second. According to JIS K 6854-2, the thermocompression-bonded support film is adjusted to a width of 15 mm, the end of the thermocompression-bonded support film is fixed to the grip of an autograph tester, and the adhesive layer and the electrolytic copper foil are peeled at a 180° angle at a rate of 300 mm / min at the interface between the adhesive layer and the electrolytic copper foil. The peel strength is measured every 0.01 s from the maximum peak at the start of peeling for 4.00 seconds, and the average of the measured values ​​is defined as adhesion strength A1. The adhesive layer is peeled at a 180° angle at a rate of 300 mm / min at the interface between the adhesive layer and the test substrate. The peel strength is measured every 0.01 s from the maximum peak at the start of peeling for 4.00 seconds, and the average of the measured values ​​is defined as adhesion strength A2.

[14] The support film according to any one of [1] to

[13] , wherein the adhesive layer is a layer formed by a wet coating method.

[15] The support film according to any one of [1] to

[14] , wherein the support film is wound into a roll.

[16] A semi-solid battery comprising: an outer bag obtained using a support film; and a plurality of electric storage elements housed in the outer bag and arranged adjacent to each other, wherein the electric storage elements have a pair of electrodes each having a current collector, and a semi-solid electrolyte, the support film being the support film according to any one of [1] to

[15] , and the adhesive layer of the support film and the current collectors of the pair of electrodes are bonded together.

[17] A method for producing a support film for a current collector for a semi-solid battery, comprising a step of forming an adhesive layer on one surface of a substrate, the adhesive layer containing resin A, the melting point of the resin A being 130°C or less, and the acid value of the resin A being 6 mgKOH / g or more.

[0007] According to the present disclosure, it is possible to provide a support film for a current collector for a semi-solid battery, which has excellent adhesion to the current collector.

[0008] FIG. 1 is a schematic cross-sectional view of a support film for a current collector for a semi-solid battery according to one embodiment.

[0009] Hereinafter, embodiments of the present disclosure will be described in detail, but the present disclosure is not limited to the following embodiments.

[0010] In the numerical ranges described herein, the upper or lower limit of the numerical range may be replaced with a value shown in the examples. Furthermore, the lower and upper limits of a numerical range can be arbitrarily combined with the lower or upper limit of another numerical range. When a numerical range is described as "A to B," the values ​​A and B at both ends are included as the lower and upper limits of the numerical range, respectively. In this specification, for example, "10 or more" means 10 and a value greater than 10, and this also applies when the numerical values ​​differ. Furthermore, for example, "10 or less" means 10 and a value less than 10, and this also applies when the numerical values ​​differ. Furthermore, unless otherwise specified, each component and material exemplified herein may be used alone or in combination of two or more types. In this specification, when multiple substances corresponding to each component are present in the composition, the content of each component in the composition refers to the total amount of the multiple substances present in the composition, unless otherwise specified.

[0011] 1 is a schematic cross-sectional view of a support film for a current collector for a semi-solid battery according to one embodiment. The support film 10 includes a substrate 1 and an adhesive layer 2 disposed on one surface of the substrate 1.

[0012] (Substrate) The substrate may be a resin substrate (resin film). Examples of resins constituting the substrate include polyolefin resins (LLDPE, PP, COP, CPP, etc.), polyester resins (PET, etc.), fluororesins (PTFE, ETFE, EFEP, PFA, FEP, PCTFE, etc.), PVC, PVA, acrylic resins, epoxy resins, polyamide resins, polyimide resins, etc. The substrate may contain a polyester resin. The substrate is transparent, making it easier to check the contents (e.g., current collector) and to detect any abnormalities. The substrate may be a laminate of multiple substrates.

[0013] The thickness of the substrate may be 4 μm or more, 5 μm or more, or 6 μm or more from the viewpoint of easily preventing a short circuit when an overvoltage is applied, and may be 100 μm or less, 50 μm or less, or 25 μm or less from the viewpoint of improving loading efficiency and enabling a high capacity by making the support film thinner. From these viewpoints, the thickness of the substrate may be 4 to 100 μm, 4 to 50 μm, 5 to 50 μm, or 6 to 25 μm.

[0014] (Adhesive Layer) The adhesive layer contains a resin (hereinafter also referred to as resin A) having a melting point of 130°C or less and an acid value of 6 mgKOH / g or more. By containing a resin having a melting point of 130°C or less and an acid value of 6 mgKOH / g or more, the adhesive layer has excellent adhesion to the current collector. In particular, in the past, when the adhesive layer was thin (for example, 5 μm or less), adhesion to the current collector was sometimes insufficient. However, by containing a resin having a melting point of 130°C or less and an acid value of 6 mgKOH / g or more, the adhesive layer has excellent adhesion to the current collector. The melting point and acid value can be measured by the method described in the Examples below.

[0015] The inventors speculate that the reason why the adhesive layer containing Resin A exhibits excellent adhesion to the current collector is as follows. Specifically, the resin constituting the adhesive layer has a relatively low melting point, which makes it easier for the resin to melt during thermocompression bonding. This increases the fluidity of the resin, making it easier to form a uniform adhesive layer on the current collector, and the resin penetrates into the fine irregularities of the current collector, resulting in excellent adhesion to the current collector. Furthermore, the resin constituting the adhesive layer has a relatively high acid value, which improves chemical reactivity with the current collector and forms a strong bond between the current collector and the adhesive layer, resulting in excellent adhesion to the current collector. However, the mechanism of the present disclosure is not limited to the above reasons.

[0016] The melting point of resin A may be 40°C or higher, 50°C or higher, 60°C or higher, 70°C or higher, 80°C or higher, 90°C or higher, or 95°C or higher from the viewpoint of superior adhesion to the current collector, and from the same viewpoint, it may be 120°C or lower, 110°C or lower, 105°C or lower, or 100°C or lower. From these viewpoints, the melting point of resin A may be 40 to 130°C, 40 to 120°C, 50 to 110°C, 60 to 110°C, 70 to 105°C, 80 to 105°C, or 90 to 100°C. The melting point of resin A can be adjusted by changing the structure (e.g., type of monomer) and molecular weight of the resin used; for example, it can be adjusted by increasing the molecular weight to increase the melting point.

[0017] From the viewpoint of superior adhesion to the current collector, the acid value of resin A may be 80 mgKOH / g or less, 70 mgKOH / g or less, 60 mgKOH / g or less, 55 mgKOH / g or less, 50 gKOH / g or less, 45 gKOH / g or less, 40 gKOH / g or less, or 35 gKOH / g or less, and from the same viewpoint, it may be 10 mgKOH / g or more, 15 mgKOH / g or more, 20 mgKOH / g or more, 25 mgKOH / g or more, or 30 mgKOH / g or more. From these viewpoints, the acid value of resin A may be 5 to 80 mgKOH / g, 10 to 60 mgKOH / g, 15 to 60 mgKOH / g, 15 to 55 mgKOH / g, 20 to 55 mgKOH / g, 25 to 50 mgKOH / g, or 30 to 50 mgKOH / g. The acid value of resin A can be adjusted by changing the structure (e.g., type of monomer) and molecular weight of the resin used, for example, by adding a large amount of monomers having acid sites or by acid modification.

[0018] From the viewpoint of achieving better adhesion to the current collector and of more easily suppressing the occurrence of short circuits due to better dielectric breakdown strength, the content of resin A in the adhesive layer may be more than 50% by mass, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 100% by mass, based on the total mass of the adhesive layer. If the content of resin A in the adhesive layer is more than 50% by mass, it can be said that resin A is the main component of the adhesive layer.

[0019] The adhesive layer is a layer formed from a resin composition containing a binder resin, resin A, and a liquid medium for dissolving and dispersing the binder resin. The binder resin may consist of resin A, or may be a mixture of resin A and a resin other than resin A (for example, a thermoplastic resin or a thermosetting resin).

[0020] Examples of thermoplastic resins include polyolefin resins such as polypropylene resin, polyethylene resin, polybutene resin, and polypentene resin; modified polyolefin resin, polyester resin, polystyrene resin, acrylonitrile-butadiene-styrene copolymer, methyl methacrylate-butadiene-styrene copolymer, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, polycarbonate resin, polyphenylene ether resin, acrylic copolymer, polyamide resin, polyvinyl chloride resin, polyvinyl alcohol resin (PVA), polyvinyl acetal resin, and ionomer. The adhesive layer may be formed from a resin composition containing at least one selected from the group consisting of modified polyolefin resin, polyester resin, ethylene-vinyl acetate copolymer, ethylene-methacrylic acid copolymer, and ionomer, from the viewpoints of achieving better adhesion to the current collector, allowing the adhesive layer of the support film to remain on the current collector, and further suppressing the occurrence of short circuits.

[0021] Examples of the thermosetting resin include epoxy resin, phenol resin, polyurethane resin, polyisocyanate resin, polyisocyanurate resin, and polyvinyl ether resin.

[0022] The liquid medium may be an organic solvent, such as a water-soluble solvent, including alcohols such as methanol, ethanol, isopropyl alcohol, and n-propyl alcohol; ketones such as acetone and methyl ethyl ketone; glycols such as ethylene glycol and diethylene glycol; and glycol ethers such as N-methylpyrrolidone (NMP), tetrahydrofuran, and butyl cellosolve.

[0023] The resin composition may further contain other components in addition to the binder resin and the liquid medium, such as a curing agent, a filler, a lubricant, a UV absorber, a matting agent, a flexibility imparting agent, a surfactant, etc.

[0024] The resin composition may further contain a filler, which may be an organic filler or an inorganic filler, in order to more easily prevent blocking when the support film is wound into a roll.

[0025] Examples of organic fillers include fillers made of thermoplastic resins. A filler made of a thermoplastic resin means a filler in which the proportion of the thermoplastic resin in the filler is 90 mass % or more. When the filler is made of a thermoplastic resin, the filler made of the thermoplastic resin melts when the support film and the current collector are bonded by heating and / or pressure, which makes it easier to achieve excellent adhesion to the current collector while suppressing the occurrence of blocking.

[0026] When the organic filler is a filler made of a thermoplastic resin, the thermoplastic resin may be a polyolefin resin or an acid-modified polyolefin resin from the viewpoint of achieving better adhesion to the current collector.

[0027] The particle size of the filler is not particularly limited as long as it is within a range that provides a blocking suppression effect in the adhesive layer, and can be appropriately adjusted depending on the type of thermoplastic resin used in the adhesive layer and the film thickness of the adhesive layer. The average particle size of the filler may be 1 μm or more, 3 μm or more, or 5 μm or more from the viewpoint of providing a sufficient blocking suppression effect in the adhesive layer, and may be 100 μm or less, 30 μm or less, or 20 μm or less from the viewpoint of providing better adhesion to the current collector. In this specification, "average particle size" means the median diameter (D50) and can be measured using a laser diffraction particle size distribution analyzer.

[0028] The filler content may be 1 mass% or more, 2 mass% or more, or 3 mass% or more relative to the total mass of the thermoplastic resin, from the viewpoint of providing the adhesive layer with a sufficient blocking suppression effect, and may be less than 30 mass%, 20 mass% or less, or 10 mass% or less, from the viewpoint of excellent formability of the adhesive layer.

[0029] The adhesive layer may be a single layer or may be composed of multiple layers. When the adhesive layer is composed of multiple layers, each adhesive layer may be formed based on the description regarding the resin composition described above.

[0030] The thickness of the adhesive layer may be 1 μm or more, 1.5 μm or more, 2 μm or more, 2.5 μm or more, 3 μm or more, or 4 μm or more from the viewpoint of achieving better adhesion to the current collector and allowing the adhesive layer of the support film to remain on the current collector even when the support film is peeled off, thereby further suppressing the occurrence of short circuits. Furthermore, the thickness of the adhesive layer may be 50 μm or less, 30 μm or less, 10 μm or less, 8 μm or less, 6 μm or less, or 5 μm or less from the viewpoint of improving loading efficiency, enabling higher capacity, and suppressing deterioration of handling due to curling of the support film. Conventionally, a thin adhesive layer (e.g., 5 μm or less) may result in insufficient adhesion to the current collector, but by including a resin having a melting point of 130° C. or less and an acid value of 6 mg KOH / g or more in the adhesive layer, excellent adhesion to the current collector is achieved. From these perspectives, the thickness of the adhesive layer may be 1 to 50 μm, 1 to 30 μm, 1.5 to 30 μm, 2 to 30 μm, 2 to 10 μm, 2 to 8 μm, 2 to 6 μm, or 2 to 5 μm.

[0031] The ratio of the thickness of the adhesive layer to the thickness of the resin substrate (thickness of adhesive layer / thickness of resin substrate) may be 0.1 or more, 0.3 or more, 0.5 or more, 0.7 or more, 0.9 or more, 1.1 or more, 1.3 or more, or 1.5 or more from the viewpoint of better adhesion to the current collector, and may be 2 or less, 1.5 or less, 1.2 or less, 1 or less, 0.8 or less, 0.6 or less, or 0.4 or less from the viewpoint of making the support film less prone to curling.

[0032] The total thickness of the resin substrate and the adhesive layer may be 5 μm or more, 10 μm or more, 12 μm or more, 14 μm or more, 16 μm or more, 18 μm or more, or 20 μm or more from the viewpoint that the dielectric breakdown strength is better and the occurrence of short circuits is more easily suppressed, and from the viewpoint that the loading efficiency is improved by thinning the support film and high capacity is possible, it may be 150 μm or less, 100 μm or less, 80 μm or less, 60 μm or less, 40 μm or less, 30 μm or less, or 25 μm or less. From these viewpoints, the total thickness of the resin substrate and the adhesive layer may be 5 to 150 μm, 5 to 80 μm, 5 to 60 μm, 5 to 25 μm, 10 to 150 μm, 10 to 80 μm, 10 to 60 μm, or 10 to 25 μm.

[0033] The adhesive strength A1 of the adhesive layer to the copper foil may be 1 N / 15 mm or more, 2 N / 15 mm or more, 3 N / 15 mm or more, 4 N / 15 mm or more, 5 N / 15 mm or more, 6 N / 15 mm or more, 7 N / 15 mm or more, or 8 N / 15 mm or more, from the viewpoint of achieving better adhesion to the current collector, allowing the adhesive layer of the support film to remain on the current collector, and further suppressing the occurrence of short circuits. The adhesive strength A1 may be 15 N / 15 mm or less, 10 N / 15 mm or less, 8 N / 15 mm or less, 6 N / 15 mm or less, or 4 N / 15 mm. The adhesive strength A1 can be adjusted by the type of binder resin and the type of filler contained in the resin composition forming the adhesive layer. The adhesive strength A1 can be measured by the following peel test. <Peel Test> The adhesive layer of a support film was superimposed on the glossy side of an electrolytic copper foil (thickness 18 μm, surface roughness 0.33 μm). A PET film was placed on the surface of the support film opposite the substrate, and the support film was sandwiched. Using a heat seal tester, heat was applied only from the adhesive layer side of the support film to perform thermocompression bonding. The bonding conditions were 150°C, 0.2 MPa, and 1 second. In accordance with JIS K 6854-2, the thermocompression-bonded support film was adjusted to a width of 15 mm, and the end of the thermocompression-bonded support film was fixed to the grip of an autograph tester. The interface between the adhesive layer and the electrolytic copper foil was peeled at a speed of 300 mm / min at a 180° angle. The peel strength was measured every 0.01 second for 4.00 seconds from the maximum peak at the start of peeling, and the average of the measured values ​​was measured as adhesion strength A1.

[0034] The adhesion strength A2 of the adhesive layer to the substrate may be 8 N / 15 mm or less, 7 N / 15 mm or less, 6 N / 15 mm or less, or 5 N / 15 mm or less, from the viewpoint that even when the support film is peeled off, the adhesive layer of the support film remains on the current collector and the occurrence of a short circuit is easily suppressed. The adhesion strength A2 may be 0.5 N / 15 mm or more, 1 N / 15 mm or more, 2 N / 15 mm or more, 3 N / 15 mm or more, or 4 N / 15 mm or more, from the viewpoint of excellent adhesion to the substrate. The adhesion strength A2 can be adjusted by the type of binder resin contained in the resin composition forming the adhesive layer, the type of filler, etc. The adhesion strength A2 can be measured by the following peel test. <Peel Test> The adhesive layer of the support film and a test substrate identical to the substrate are overlapped, a PET film is placed on the surface of the support film opposite the substrate, and the support film is sandwiched between them, and heat is applied only from the adhesive layer side of the support film using a heat seal tester to perform thermocompression bonding. The pressure bonding conditions are 150°C, 0.2 MPa, and 1 second. In accordance with JIS K 6854-2, the thermocompression-bonded support film is adjusted to a width of 15 mm, and the end of the thermocompression-bonded support film is fixed to the grip of an autograph tester. The interface between the adhesive layer and the test substrate is peeled at a rate of 300 mm / min at an angle of 180°. The peel strength is measured every 0.01 s for 4.00 seconds from the maximum peak at the start of peeling, and the average of the measured values ​​is recorded as adhesion strength A2.

[0035] The difference between the adhesion force A1 and the adhesion force A2 (adhesion force A1 - adhesion force A2) may be 0.2 N / 15 mm or more, 0.3 N / 15 mm or more, or 0.4 N / 15 mm or more, from the viewpoint that even when the support film is peeled off, the adhesive layer of the support film remains on the current collector and the occurrence of a short circuit is easily suppressed. The difference between the adhesion force A1 and the adhesion force A2 (adhesion force A1 - adhesion force A2) may be 5 N / 15 mm or less, 4 N / 15 mm or less, 3 N / 15 mm or less, 2 N / 15 mm or less, or 1 N / 15 mm or less.

[0036] The adhesion strength A3 of the adhesive layer to the aluminum foil may be 1 N / 15 mm or more, 2 N / 15 mm or more, 3 N / 15 mm or more, 4 N / 15 mm or more, 5 N / 15 mm or more, or 6 N / 15 mm or more, from the viewpoint of better adhesion to the current collector. The adhesion strength A3 may be 10 N / 15 mm or less, 8 N / 15 mm or less, 6 N / 15 mm or less, or 4 N / 15 mm. The adhesion strength A3 can be adjusted by the type of binder resin contained in the resin composition forming the adhesive layer, the type of filler, etc. The adhesion strength A3 can be measured by the following peel test. <Peel Test> The adhesive layer of the support film and the glossy side of aluminum foil (alloy 8079, thickness: 7 μm, surface roughness: 0.98 μm) are overlapped, a PET film is placed on the surface of the support film opposite the substrate, and the support film is sandwiched between them. Using a heat seal tester, heat is applied only from the adhesive layer side of the support film to perform thermocompression bonding. The pressure bonding conditions are 150°C, 0.2 MPa, and 1 second. In accordance with JIS K 6854-2, the thermocompression-bonded support film is adjusted to a width of 15 mm, the end of the thermocompression-bonded support film is fixed to the grip of an autograph tester, and the interface between the adhesive layer and the aluminum foil is peeled at a speed of 300 mm / min at an angle of 180°. The peel strength is measured every 0.01 s for 4.00 seconds from the maximum peak at the start of peeling, and the average of the measured values ​​is measured as adhesion strength A3.

[0037] The support film may be one that peels off at the interface between the substrate and the adhesive layer when the substrate is peeled off after the support film is adhered to the copper foil (copper foil used in measuring the adhesion force A1). That is, the support film may be one that does not peel off at the interface between the adhesive layer and the copper foil (copper foil used in measuring the adhesion force A1) when the substrate is peeled off after the support film is adhered to the copper foil (copper foil used in measuring the adhesion force A1). If the support film is one that peels off at the interface between the substrate and the adhesive layer when the substrate is peeled off after the support film is adhered to the copper foil (copper foil used in measuring the adhesion force A1), even when the support film is peeled off from the current collector, the adhesive layer of the support film remains on the current collector, and the occurrence of a short circuit can be suppressed.

[0038] The adhesive layer can be formed by known methods. For example, the adhesive layer can be formed by applying a resin composition to a substrate, forming a coating film, and then drying the coating. The resin composition can be applied by a wet coating method, which facilitates uniform thickness of the adhesive layer, thereby preventing localized peeling of the adhesive layer of the support film from the current collector and further suppressing the occurrence of short circuits. That is, the above-mentioned support film can be obtained by a manufacturing method including a step of forming an adhesive layer on one side of the substrate. If the adhesive layer is formed by extrusion lamination, it is difficult to control the thickness of the adhesive layer, and differences in the in-plane thickness may result in localized reduced adhesion. Examples of wet coating methods include gravure coating, comma coating, dip coating, curtain coating, spin coating, sponge roll coating, and die coating. The coating film can be dried, for example, at 60 to 100°C for 0.5 to 2 minutes.

[0039] The support film may further include layers other than the substrate and the adhesive layer. For example, the support film may include a release layer on the surface of the adhesive layer opposite the substrate.

[0040] The thickness of the support film may be 5 μm or more, 10 μm or more, 12 μm or more, 14 μm or more, 16 μm or more, 18 μm or more, or 20 μm or more from the viewpoint that the dielectric breakdown strength is better and the occurrence of short circuits is more easily suppressed, and from the viewpoint that a thinner support film improves loading efficiency and enables higher capacity, the thickness of the support film may be 150 μm or less, 100 μm or less, 80 μm or less, 60 μm or less, 40 μm or less, 30 μm or less, or 25 μm or less. From these viewpoints, the thickness of the support film may be 5 to 150 μm, 5 to 80 μm, 5 to 60 μm, 5 to 25 μm, 10 to 150 μm, 10 to 80 μm, 10 to 60 μm, or 10 to 25 μm.

[0041] When the support film described above is superimposed on another support film so that the adhesive layers face each other to produce a first test piece, the haze of the first test piece is H1, and the haze of a second test piece obtained by thermocompression bonding the first test piece is H2, the haze change rate (unit: %) calculated by ((H1-H2) / H1) x 100 may be 25% or more.

[0042] The above-mentioned support film may have an arithmetic mean roughness Ra of 0.2 μm or more on the surface of the adhesive layer opposite the substrate, and the adhesion strength A1 of the adhesive layer to the copper foil measured in the above-mentioned peel test may be 1 N / 15 mm or more.

[0043] The support film described above may have an adhesive layer with a thickness of T1 and a copper foil with a strength of X1, as measured in the peel test described below, and an adhesive layer with a thickness of T2 (where T2 > T1) and a copper foil with a strength of X2, such that (X2 - X1) / (T2 - T1) is 0.7 [(N / 15 mm) / μm] or less, and X1 is 2 N / 15 mm or more. <Peel Test> The adhesive layer (thickness T1 or T2) of the support film is superimposed on the shiny side of an electrolytic copper foil (thickness 18 μm, surface roughness 0.33 μm), a PET film is placed on the surface of the support film opposite the substrate, and the support film is sandwiched between them. Using a heat seal tester, heat is applied only from the adhesive layer side of the support film to perform thermocompression bonding. The bonding conditions are 150°C, 0.2 MPa, and 1 second. In accordance with JIS K 6854-2, the thermocompression-bonded support film is adjusted to a width of 15 mm, the end of the thermocompression-bonded support film is fixed to the gripping portion of an autograph testing machine, and the interface between the adhesive layer and the electrolytic copper foil is peeled at an angle of 180° at a speed of 300 mm / min. The peel strength is measured every 0.01 s for 4.00 seconds from the maximum peak at the start of peeling, and the average values ​​of the measured values ​​are taken as adhesion strengths X1 and X2.

[0044] The support film described above may or may not be wound into a roll, but is preferably wound into a roll. In this case, the support film can be processed to any size as needed. Furthermore, continuous adhesion to the current collector becomes possible, improving efficiency in terms of storage. In particular, when the width of the adhesive layer (the length perpendicular to the thickness) is 600 mm or more, the support film is preferably wound into a roll.

[0045] The support film described above can be used as a support film for a current collector for a semi-solid battery. The support film can be adhered to the current collector for a semi-solid battery by applying heat and / or pressure to the current collector for a semi-solid battery.

[0046] The current collector for a semi-solid battery is, for example, a substrate, sheet, or foil containing a conductive material. The current collector for a semi-solid battery may contain aluminum, copper, lithium, nickel, stainless steel, tantalum, titanium, tungsten, vanadium, or an alloy of these metals. The current collector for a semi-solid battery may contain a non-metallic material such as carbon, carbon nanotubes, or a metal oxide. The current collector for a semi-solid battery may also be a mixture of these. From the viewpoint of enabling high capacity, the current collector for a semi-solid battery is preferably thin, and may be, for example, 20 μm or less.

[0047] An outer bag for a semi-solid battery can be obtained using the support film described above. That is, another embodiment of the present disclosure is a semi-solid battery including an outer bag obtained using the support film described above and a plurality of energy storage elements housed in the outer bag and arranged adjacent to each other, the energy storage elements including a pair of electrodes each having a current collector and a semi-solid electrolyte, and the adhesive layer of the support film and the current collectors of the pair of electrodes are bonded to each other.

[0048] The present disclosure will be specifically described below with reference to examples, but the present disclosure is not limited to the following examples.

[0049] Example 1 Arrowbase SE-1030N (acid-modified olefin, manufactured by Unitika Ltd.) was applied to a PET substrate (manufactured by Toray Industries, Inc., product name: P60, thickness: 12 μm) using a bar coater. After coating, the coating was dried at 100° C. for 1 minute to produce a support film having a 6 μm-thick adhesive layer on the substrate.

[0050] Example 2 A PET substrate (manufactured by Toray Industries, Inc., product name: P60, thickness: 12 μm) was coated with Aquatex EC1700 (ethylene-vinyl acetate copolymer, manufactured by Japan Coating Resins Co., Ltd.) using a bar coater. After coating, the substrate was dried at 100°C for 1 minute to produce a support film having a 4 μm thick adhesive layer on the substrate.

[0051] Example 3 A support film was produced in the same manner as in Example 2, except that the thickness of the adhesive layer was changed to 5 μm.

[0052] Example 4 A support film was produced in the same manner as in Example 2, except that the thickness of the adhesive layer was changed to 5.7 μm.

[0053] Example 5 A PET substrate (manufactured by Toray Industries, Inc., product name: P60, thickness: 12 μm) was coated with Aquatex AC3100 (ethylene methacrylic acid copolymer, manufactured by Japan Coating Resins Co., Ltd.) using a bar coater. After coating, the coating was dried at 100° C. for 1 minute to produce a support film having a 4 μm thick adhesive layer on the substrate.

[0054] Example 6 A support film was produced in the same manner as in Example 5, except that the thickness of the adhesive layer was changed to 5.4 μm.

[0055] Example 7 A support film was produced in the same manner as in Example 5, except that the thickness of the adhesive layer was changed to 6.7 μm.

[0056] Example 8 Superchron 930 (acid-modified chlorinated olefin, manufactured by Nippon Paper Industries Co., Ltd., solid content 20 parts by mass) was applied to a PET substrate (manufactured by Toray Industries, Inc., product name: P60, thickness: 12 μm) using a bar coater. After coating, the coating was dried at 100° C. for 1 minute to produce a support film having a 2 μm-thick adhesive layer on the substrate.

[0057] Example 9 A support film was produced in the same manner as in Example 5, except that the thickness of the adhesive layer was changed to 5 μm.

[0058] Comparative Example 1 Arrowbase DC-5100 (polypropylene resin, manufactured by Unitika Ltd.) was applied to a PET substrate (manufactured by Toray Industries, Inc., product name: P60, thickness: 12 μm) using a bar coater. After coating, the substrate was dried at 100° C. for 1 minute to produce a support film having a 6.5 μm thick adhesive layer on the substrate.

[0059] Comparative Example 2 Elitel UE-9800 (polyester resin, manufactured by Unitika Ltd.) was applied to a PET substrate (manufactured by Toray Industries, Inc., product name: P60, thickness: 12 μm) using a bar coater. After coating, the substrate was dried at 100° C. for 1 minute to produce a support film having a 2.5 μm thick adhesive layer on the substrate.

[0060] (Comparative Example 3) Elitel UE-3285 (polyester resin, manufactured by Unitika Ltd.) was coated on a PET substrate (manufactured by Toray Industries, Inc., product name: P60, thickness: 12 μm) using a bar coater. After coating, the coating was dried at 100° C. for 1 minute to produce a support film having an adhesive layer of 2.5 μm thickness on the substrate.

[0061] Comparative Example 4 Arrowbase YA-6010 (polypropylene resin, manufactured by Unitika Ltd.) was coated on a PET substrate (manufactured by Toray Industries, Inc., product name: P60, thickness: 12 μm) using a bar coater. After coating, the coating was dried at 100° C. for 1 minute to produce a support film having a 9 μm thick adhesive layer on the substrate.

[0062] (Comparative Example 5) Arrowbase YA-6005N (polypropylene resin, manufactured by Unitika Ltd.) was coated on a PET substrate (manufactured by Toray Industries, Inc., product name: P60, thickness: 12 μm) using a bar coater. After coating, the coating was dried at 100° C. for 1 minute to produce a support film having a 6 μm thick adhesive layer on the substrate.

[0063] <Measurement of Melting Point> The resin materials used in each Example and Comparative Example were heated from 20°C to 150°C at a heating rate of 10°C / min in an air atmosphere using a differential scanning calorimeter (product name: DSC 7000X) manufactured by Hitachi High-Tech Science Corporation, and a DSC curve was obtained with a sampling period of 0.5 seconds. The peak-top temperature of the endothermic peak in the obtained DSC curve was measured as the melting point. When multiple endothermic peaks occurred, the peak-top temperature of the endothermic peak with the largest endothermic amount was measured as the melting point. The measurement results are shown in Tables 1 and 2.

[0064] <Measurement of Acid Value> The acid value of the resin material used in each example and comparative example was measured in accordance with JIS K2501:2003. Specifically, five drops of phenolphthalein indicator were added to a sample solution in which the resin material was completely dissolved in a solvent, and indicator titration was performed with a 0.02 mol / L sodium hydroxide benzyl alcohol solution. The end point was the time when the sample solution turned red for 30 seconds. A blank test was performed in the same manner without dissolving the resin material in the solvent. The acid value of the resin material was then calculated using the following formula. The measurement results are shown in Tables 1 and 2. The acid value of the resin material can be converted into units using 1 mmol / g = 56 mg KOH / g. Acid value of resin material [mmol / g] = ((V ０ -V １ ) × 0.02 × f) / S S: Mass of resin material: [g] V ０ V: Amount of 0.02 mol / L sodium hydroxide benzyl alcohol solution required to reach the endpoint in a blank test (solvent only) [ml] １ : Amount [ml] of 0.02 mol / L sodium hydroxide benzyl alcohol solution required to reach the endpoint in this test (sample solution containing resin material)

[0065] <Thermocompression bonding> (Thermocompression bonding with copper foil) The adhesive layer of the prepared support film was superimposed on the shiny side of an electrolytic copper foil (thickness 18 μm, surface roughness 0.33 μm, product name: 4-1592-02, manufactured by AS ONE), and the support film was sandwiched between PET films (thickness 25 μm, product name: Lumirror S10, manufactured by Toray) in the following order: PET film / electrolytic copper foil / support film / PET film. Thermocompression bonding was performed by applying heat only from the electrolytic copper foil side using a heat seal tester (product name: TP-701-B, manufactured by Tester Sangyo Co., Ltd.). The bonding conditions were 150°C, 0.2 MPa, and 1 second.

[0066] (Thermocompression bonding with aluminum foil) The adhesive layer of the prepared support film and the glossy side of an aluminum foil (alloy 8079, thickness: 7 μm, surface roughness 0.98 μm, manufactured by Toyo Aluminum) laminated with a PET film on one side were superimposed, and the support film was sandwiched using a PET film (thickness 25 μm, trade name: Lumirror S10, manufactured by Toray) in the order of PET film / aluminum foil / support film / PET film. Using a heat seal tester (trade name: TP-701-B, manufactured by Tester Sangyo Co., Ltd.), heat was applied only from the aluminum foil side to perform thermocompression bonding. The bonding conditions were 150 ° C., 0.2 MPa, and 1 second.

[0067] <Peel test> In accordance with JIS K 6854-2, a thermocompression-bonded support film was adjusted to a width of 15 mm, and the edge of the support film was fixed to the grip of an autograph testing machine (product name: AGS-X, manufactured by Shimadzu Corporation). The adhesive layer was peeled at a speed of 300 mm / min at a 180° angle at the interface between the adhesive layer and the electrolytic copper foil or aluminum foil. The peel strength was measured every 0.01 s for 4.00 seconds from the maximum peak at the start of peeling, and the average value of each measurement value was taken as the adhesion strength. The adhesion strength with the copper foil was designated A1, and the adhesion strength with the aluminum foil was designated A3. The measurement results are shown in Tables 1 and 2.

[0068]

[0069]

[0070] The support films produced in Examples 1 to 9 had sufficient adhesion to the current collector, with both adhesion strength A1 and adhesion strength A3 of 1 N / 15 mm or more. On the other hand, in Comparative Examples 1, 4, and 5, the melting point of the resin contained in the adhesive layer was 130°C or less, and both adhesion strength A1 and adhesion strength A3 were less than 1 N / 15 mm, resulting in insufficient adhesion to the current collector. In Comparative Examples 2 and 3, the acid value of the resin contained in the adhesive layer was 6 mg KOH / g or less, and both adhesion strength A1 and adhesion strength A3 were less than 1 N / 15 mm, resulting in insufficient adhesion to the current collector.

[0071] (Thermocompression bonding with substrate) The adhesive layer of the support film produced in Examples 2 and 8 and Comparative Example 2 was superimposed on a test PET substrate (manufactured by Toray Industries, Inc., product name: P60, thickness: 12 μm), and the support film was sandwiched using a PET film (thickness 25 μm, product name: Lumirror S10, manufactured by Toray) in the following order: PET film / test PET substrate / support film / PET film. Using a heat seal tester (product name: TP-701-B, manufactured by Tester Sangyo Co., Ltd.), heat was applied only from the test PET substrate side to perform thermocompression bonding. The compression bonding conditions were 150°C, 0.2 MPa, and 1 second.

[0072] <Peel Test> In accordance with JIS K 6854-2, a thermocompression-bonded support film was adjusted to a width of 15 mm, and the edge of the support film was fixed to the grip of an autograph testing machine (product name: AGS-X, manufactured by Shimadzu Corporation). The adhesive layer was peeled at a speed of 300 mm / min at a 180° angle at the interface between the adhesive layer and the test PET substrate. The peel strength was measured every 0.01 s for 4.00 seconds from the maximum peak at the start of peeling, and the average value of the measured values ​​was taken as the adhesion strength. The adhesion strength with the test PET substrate was designated A2. The measurement results are shown in Table 3.

[0073]

[0074] The support films produced in Examples 2 and 8 had an adhesion strength A1 of 2 N / 15 mm or more and had a relationship of adhesion strength A1 > adhesion strength A2. On the other hand, the adhesion strength A1 of Comparative Example 2 was less than 2 N / 15 mm, making it difficult to use as a support film for a current collector for a semi-solid battery.

[0075] 1...substrate, 2...adhesive layer, 10...support film

Claims

1. A support film for a current collector for a semi-solid battery, comprising: a substrate; and an adhesive layer disposed on one surface of the substrate; wherein the adhesive layer contains a resin A, the melting point of the resin A is 130°C or less, and the acid value of the resin A is 6 mgKOH / g or more.

2. The support film according to claim 1, wherein the melting point of said resin A is 50 to 110°C.

3. The support film according to claim 1, wherein the melting point of said resin A is 90 to 100°C.

4. The support film according to claim 1 or 2, wherein the acid value of said resin A is 15 to 60 mgKOH / g.

5. The support film according to claim 1 or 2, wherein the acid value of said resin A is 30 to 50 mgKOH / g.

6. The support film according to claim 1 or 2, wherein the substrate comprises a polyester resin, and the resin A is a thermoplastic resin.

7. The support film according to claim 1 or 2, wherein said resin A is an ethylene-vinyl acetate copolymer.

8. The support film according to claim 1 or 2, wherein the thickness of the substrate is 4 to 100 μm.

9. The support film according to claim 1 or 2, wherein the adhesive layer has a thickness of 2 to 30 μm.

10. The support film according to claim 1 or 2, wherein the adhesive layer has a thickness of 2 to 5 μm.

11. The support film according to claim 1 or 2, having a thickness of 5 to 80 μm.

12. The support film according to claim 1 or 2, wherein the adhesive strength A1 of the adhesive layer to the copper foil measured by the following peel test is 5 N / 15 mm or more. <Peel Test> The adhesive layer of the support film is superimposed on the shiny side of an electrolytic copper foil (thickness 18 μm, surface roughness 0.33 μm), a PET film is placed on the surface of the support film opposite the substrate, and the support film is sandwiched between them. Using a heat seal tester, heat is applied only from the adhesive layer side of the support film to perform thermocompression bonding. The compression conditions are 150°C, 0.2 MPa, and 1 second. In accordance with JIS K 6854-2, the thermocompression-bonded support film is adjusted to a width of 15 mm, and the end of the thermocompression-bonded support film is fixed to the gripping portion of an autograph testing machine. The adhesive layer and the electrolytic copper foil are peeled at an angle of 180° at a speed of 300 mm / min at the interface between them, and the peel strength is measured every 0.01 s for 4.00 seconds from the maximum peak at the start of peeling, and the average value of the measured values ​​is determined as adhesion strength A1.

13. The support film according to claim 1 or 2, wherein the adhesive strength A1 of the adhesive layer to the copper foil measured in the following peel test is 2 N / 15 mm or more, and the adhesive strength A1 is greater than the adhesive strength A2 of the adhesive layer to the substrate measured in the following peel test. <Peel Test> The adhesive layer of the support film is superimposed on the shiny side of an electrolytic copper foil (thickness 18 μm, surface roughness 0.33 μm) or a test substrate identical to the substrate, a PET film is placed on the surface of the support film opposite the substrate, and the support film is sandwiched between them. Using a heat seal tester, heat is applied only from the adhesive layer side of the support film to perform thermocompression bonding. The compression conditions are 150°C, 0.2 MPa, and 1 second. In accordance with JIS K 6854-2, the thermocompression-bonded support film is adjusted to a width of 15 mm, and the end of the thermocompression-bonded support film is fixed to the gripping portion of an autograph testing machine. The adhesive layer and the electrolytic copper foil are peeled at an angle of 180° at a speed of 300 mm / min at the interface between them, and the peel strength is measured every 0.01 s for 4.00 seconds from the maximum peak at the start of peeling. The average of the measured values ​​is defined as adhesion strength A1. The adhesive layer and the test substrate are peeled at an angle of 180° at a speed of 300 mm / min at the interface between them, and the peel strength is measured every 0.01 s for 4.00 seconds from the maximum peak at the start of peeling. The average of the measured values ​​is defined as adhesion strength A2.

14. The support film according to claim 1 or 2, wherein the adhesive layer is a layer formed by a wet coating method.

15. The support film according to claim 1 or 2, which is wound into a roll.

16. A semi-solid battery comprising: an outer bag obtained by using a support film; and a plurality of storage elements housed in the outer bag and arranged adjacent to each other, wherein the storage elements have a pair of electrodes each having a current collector, and a semi-solid electrolyte, the support film being the support film defined in claim 1 or 2, and the adhesive layer of the support film being bonded to the current collectors of the pair of electrodes.

17. A method for manufacturing a support film for a current collector for a semi-solid battery, comprising a step of forming an adhesive layer on one surface of a substrate, wherein the adhesive layer contains resin A, the melting point of resin A is 130°C or less, and the acid value of resin A is 6 mgKOH / g or more.

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