Energy storage device inner case and energy storage device

Abstract

The present invention provides an energy storage device inner case that is composed of a three-dimensional molded body of a resin sheet, and thus makes it possible to sufficiently narrow a gap between an energy storage element and a metal exterior body while achieving insulation between the energy storage element and the metal exterior body, thereby achieving miniaturization and improved heat dissipation of the energy storage device and contributing to a reduction in the number of assembly steps of the energy storage device. The present invention also provides an energy storage device comprising such an energy storage device inner case. The energy storage device inner case according to the present invention comprises a bottom part facing a housing space for housing an energy storage element, and a peripheral wall part rising from an edge portion of the bottom part and facing the housing space. The energy storage device inner case is composed of a three-dimensional molded body of an insulating resin sheet, and when in use is housed in a metal exterior body with the energy storage element housed in the housing space, and is embedded in a filler filling the inside of the metal exterior body.

Description

Inner case for energy storage device and energy storage device

[0001] This invention relates to an inner case for an energy storage device and an energy storage device.

[0002] Patent Document 1 discloses an electrical insulating paper containing aramid floc (short fibers made of aramid) for insulating energy storage elements such as capacitors. Aramid is useful as an electrical insulating paper because it possesses properties such as flame retardancy and heat resistance.

[0003] Furthermore, a metal casing may be used as the outer case that houses the energy storage element. Because metal casings have excellent heat dissipation and water vapor barrier properties, they contribute to the high reliability of energy storage devices.

[0004] Japanese Patent Publication No. 2016-125185

[0005] Electrical insulating paper prevents short circuits between the energy storage element and its outer casing by covering it. However, electrical insulating paper has poor workability, which presents a challenge as it increases the labor involved in covering the energy storage element. Furthermore, when considering the covering properties, it is unavoidable that the electrical insulating paper sheets overlap, making it difficult to achieve sufficient thinness.

[0006] The object of the present invention is to provide an inner case for an energy storage device, which is made of a three-dimensional molded resin sheet, and which can sufficiently narrow the gap between the energy storage element and the metal casing while providing insulation between them, thereby enabling miniaturization and improved heat dissipation of the energy storage device, as well as contributing to a reduction in the assembly man-hours of the energy storage device, and an energy storage device equipped with such an inner case for an energy storage device.

[0007] Such objectives are achieved by the present invention as described in (1) to (11) below. (1) An inner case for an energy storage device, characterized in that it is made of a three-dimensional molded body of an insulating resin sheet having a bottom facing a housing space for housing an energy storage element, and a peripheral wall portion rising from the end of the bottom and facing the housing space, and is used to be housed inside a metal casing with the energy storage element housed in the housing space, and to be embedded in a filler material that fills the metal casing.

[0008] (2) The inner case for the energy storage device according to (1) above, wherein the thickness of the resin sheet is 0.05 mm or more and 0.50 mm or less.

[0009] (3) An inner case for an energy storage device according to (1) or (2) above, wherein the resin sheet is mainly made of thermoplastic resin.

[0010] (4) The inner case for an energy storage device according to (3) above, wherein the thermoplastic resin is an aromatic polycarbonate resin.

[0011] (5) The inner case for an energy storage device according to (3) above, wherein the thermoplastic resin is a polymer alloy of an aromatic polycarbonate resin and a compatible resin.

[0012] (6) The inner case for an energy storage device according to (3) above, wherein the thermoplastic resin is a polymer alloy of a polyphenylene ether resin and a compatible resin.

[0013] (7) The inner case for an energy storage device according to (5) or (6) above, wherein the compatible resin is a polyolefin resin, a polystyrene resin, a polyamide resin, an aliphatic polycarbonate resin, or a heat-resistant polycarbonate resin.

[0014] (8) The inner case for an energy storage device according to (7) above, wherein the comparative tracking index CTI of the compatible resin is 50V or more higher than the comparative tracking index CTI of the aromatic polycarbonate resin.

[0015] (9) The inner case for an energy storage device according to (5) or (6) above, wherein the proportion of aromatic rings in the entire polymer alloy is 75% by mass or less.

[0016] (10) An inner case for an energy storage device according to any one of (1) to (9) above, wherein the resin sheet contains a flame retardant composed of a nitrogen-containing compound.

[0017] (11) An energy storage device comprising: an inner case for an energy storage device as described in any of (1) to (10) above; an energy storage element housed in the housing space; a metal casing housing the energy storage element and the inner case for the energy storage device; and a filler material filled inside the metal casing so as to embed the inner case for the energy storage device.

[0018] According to the present invention, since it is composed of a three-dimensional molded resin sheet, it is possible to sufficiently narrow the gap between the energy storage element and the metal casing while providing insulation between them, thereby enabling miniaturization and improved heat dissipation of the energy storage device, and contributing to a reduction in the assembly man-hours of the energy storage device.

[0019] Furthermore, according to the present invention, since the above-mentioned inner case for the energy storage device is provided, a compact energy storage device with excellent heat dissipation can be obtained.

[0020] Figure 1 is a cross-sectional view showing an energy storage device according to an embodiment. Figure 2 is an exploded perspective view showing the energy storage element and inner case of Figure 1. Figure 3 is a partial cross-sectional view showing an inner case according to a modified example. Figure 4 is a cross-sectional view illustrating a method for manufacturing the inner case shown in Figure 2. Figure 5 is a cross-sectional view illustrating a method for manufacturing the inner case shown in Figure 2. Figure 6 is a cross-sectional view illustrating a method for manufacturing the inner case shown in Figure 2. Figure 7 is a cross-sectional view illustrating a method for manufacturing the inner case shown in Figure 2.

[0021] The inner case for the energy storage device and the energy storage device according to the present invention will be described in detail below based on preferred embodiments shown in the accompanying drawings.

[0022] 1. Energy Storage Device First, the energy storage device according to the embodiment will be described.

[0023] Figure 1 is a cross-sectional view showing an energy storage device 1 according to an embodiment. In the figures of this application, the X-axis, Y-axis, and Z-axis are defined as three mutually orthogonal axes, and each axis is indicated by an arrow. The base end of the arrow is referred to as the negative side of each axis, and the tip end is referred to as the positive side of each axis. Furthermore, the positive side of the Z-axis is also referred to as "up," and the negative side of the Z-axis is also referred to as "down."

[0024] The energy storage device 1 shown in Figure 1 comprises an energy storage element 2, an inner case 3 (an inner case for the energy storage device according to this embodiment), a metal outer casing 4, an insulator 6, and a filler 7.

[0025] The energy storage element 2 is an element that has an energy storage function. The inner case 3 defines a housing space 30 located inside. The energy storage element 2 is housed in the housing space 30. The metal casing 4 defines a housing space 40 located inside. The housing space 40 houses the energy storage element 2 and the inner case 3 provided on the outside of it. The insulator 6 is interposed between the electrode bodies 21 and 22 of the energy storage element 2, insulating them from each other. The filler material 7 is filled into the housing space 40 of the metal casing 4. The filler material 7 fixes the energy storage element 2 and the inner case 3 housed in the housing space 40 to the metal casing 4 by embedding them. It also thermally connects the energy storage element 2 and the metal casing 4, transferring heat generated from the energy storage element 2 to the metal casing 4.

[0026] The inner case 3 is made of a three-dimensional molded body of an insulating resin sheet. The inner case 3 is embedded in the filler material 7 and is interposed between the energy storage element 2 and the metal outer casing 4.

[0027] Figure 2 is an exploded perspective view showing the energy storage element 2 and inner case 3 of Figure 1. The inner case 3 shown in Figure 2 has a bottom portion 31 and a peripheral wall portion 32. The bottom portion 31 is plate-shaped and extends along the XY plane. The peripheral wall portion 32 rises from the end of the bottom portion 31. The bottom portion 31 and the peripheral wall portion 32 each face the housing space 30.

[0028] According to the above configuration, by using the inner case 3 composed of a three-dimensional molded resin sheet, it is possible to realize a power storage device 1 in which the gap between the power storage element 2 and the metal exterior 4 is sufficiently narrowed while achieving insulation between them. As a result, the power storage device 1 can be downsized. In addition, since the thermal conductivity through the gap is improved, the power storage device 1 can be made highly heat dissipative. Furthermore, by using the inner case 3, it is possible to contribute to reducing the number of assembly steps of the power storage device 1 compared to the conventional configuration using electrical insulating paper or the like. Therefore, a power storage device 1 that is small and has excellent heat dissipation can be realized.

[0029] 1.1. Power storage element The power storage element 2 is an element having a power storage function. Examples of the power storage element 2 include a capacitor, a capacitor, a lithium ion battery, a nickel hydrogen battery, a all-solid-state battery, and the like.

[0030] Among these, examples of the capacitor include a film capacitor, a ceramic capacitor, an aluminum electrolytic capacitor, a tantalum electrolytic capacitor, a conductive polymer capacitor, an electric double layer capacitor, and the like.

[0031] In addition, examples of the film capacitor include a wound film capacitor, a multilayer film capacitor, and the like. Such a film capacitor has characteristics such as a high internal insulation resistance, excellent high-frequency characteristics, and a long life compared to other capacitors, and is suitable for applications that require high reliability.

[0032] The power storage element 2 shown in FIG. 1 has a power storage unit 20 that stores power, and electrode bodies 21 and 22 that are responsible for input and output of power to and from the power storage unit 20.

[0033] When the power storage element 2 is a film capacitor, the power storage unit 20 is, for example, a wound body formed by winding a laminate of a resin film and a metal foil, a laminate of a resin film and a metal foil, a wound body of a metallized film, a laminate of a metallized film, and the like.

[0034] The electrode bodies 21 and 22 are conductors made of a conductive material. Examples of the conductive material include copper, a copper alloy, aluminum, an aluminum alloy, and the like.

[0035] The electrode body 21 is located between the energy storage unit 20 and the bottom 31 of the inner case 3, and is electrically connected to the energy storage unit 20 at its lower surface. The electrode body 21 has a portion that extends along the lower surface of the energy storage unit 20, a portion that extends along the peripheral wall 32, and a portion that extends outside the inner case 3. The electrode body 22 has a portion that extends along the upper surface of the energy storage unit 20 and a portion that extends outside the inner case 3.

[0036] The shape of the energy storage element 2 is not limited to the shape shown in the illustration, and may be any shape. For example, the energy storage element 2 may be plate-shaped, cylindrical, or prismatic. In that case, the shapes of the inner case 3 and the metal outer casing 4 will also be changed to match the shape of the energy storage element 2.

[0037] 1.2. Inner Case 1.2.1. Overview The inner case 3 (inner case for the energy storage device according to the embodiment) has a bottomed, elongated cylindrical shape. The inner case 3 defines an internal storage space 30. The storage space 30 houses the energy storage element 2.

[0038] As described above, the inner case 3 is made of a three-dimensional molded body of an insulating resin sheet and has a bottom portion 31 and a peripheral wall portion 32.

[0039] The inner case 3 provides insulation between the energy storage element 2 and the metal casing 4. Because the inner case 3 is made of a three-dimensional molded resin sheet, the outside of the energy storage element 2 can be covered seamlessly with the inner case 3. This ensures insulation between the energy storage element 2 and the metal casing 4. As a result, the gap between the energy storage element 2 and the metal casing 4 can be sufficiently narrowed, enabling miniaturization of the energy storage device 1. Furthermore, because the inner case 3 is made of a three-dimensional molded resin sheet, it does not require overlapping or folding during packaging, unlike conventional electrical insulating paper, for example. Therefore, it can be easily made thin with minimal thickness variations. Consequently, the thermal resistance between the energy storage element 2 and the metal casing 4 can be reduced, enabling high heat dissipation of the energy storage device 1.

[0040] Furthermore, since the inner case 3 is made of a three-dimensional molded resin sheet, it can maintain its three-dimensional shape independently even before assembly. In other words, it is easy to maintain the shape in which the peripheral wall portion 32 rises from the edge of the bottom portion 31 on its own. For this reason, the inner case 3 has good handling and assembly characteristics as a component, and can contribute to reducing assembly man-hours compared to, for example, conventional electrical insulating paper.

[0041] The shape of the bottom portion 31 is not particularly limited, as it is set appropriately according to the shape of the energy storage element 2. Examples include various circular shapes such as ellipses, oblongs, and perfect circles, various polygons such as squares and hexagons, and other irregular shapes.

[0042] The bottom portion 31 may be a flat plate or a plate with irregularities in the thickness direction (Z-axis direction).

[0043] The peripheral wall portion 32 rises from the end of the bottom portion 31 and is continuous in a closed annular shape. As a result, the bottom portion 31 and the peripheral wall portion 32 define the housing space 30 located inside them. It is preferable that the peripheral wall portion 32 is continuous in a closed annular shape, but it may be partially missing or have holes as long as it does not impair insulation.

[0044] The peripheral wall portion 32 may be provided with irregularities that are recessed or protruding in the thickness direction of the bottom portion 31, as needed.

[0045] The thickness of the resin sheet is not particularly limited, but is preferably 0.05 mm to 0.50 mm, more preferably 0.07 mm to 0.40 mm, and even more preferably 0.10 mm to 0.30 mm. This provides an inner case 3 with excellent insulation and heat dissipation properties. Furthermore, when the inner case 3 is formed by thermoforming, the shape of the inner case 3 can be formed with high precision and in a short time.

[0046] If the thickness of the resin sheet falls below the lower limit, the insulating properties of the inner case 3 may decrease. Also, the rigidity of the inner case 3 may decrease, and the self-supporting ability of the peripheral wall portion 32 may decrease. On the other hand, if the thickness of the resin sheet exceeds the upper limit, the heat dissipation performance of the inner case 3 may decrease. Also, the moldability of the inner case 3 may decrease. The thickness of the resin sheet is the average value of the thickness of the bottom portion 31 and the thickness of the peripheral wall portion 32.

[0047] The inner case 3 may have parts other than those described above. Examples of such parts include partitions that divide the storage space 30 into multiple sections, and lids that cover the openings of the storage space 30. In addition, the insulator 6, which will be described later, may be connected to the inner case 3 and form an integrated unit.

[0048] 1.2.2. Constituent Materials The inner case 3 is composed of a three-dimensional molded body of a resin sheet. The proportion of resin material in the resin sheet is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. This provides an inner case 3 that is excellent in insulating properties and moldability, and is easy to reduce in weight.

[0049] Examples of resin materials include various thermoplastic resins such as polyolefin resins, polystyrene resins, polyamide resins, polyester resins, aliphatic polycarbonate resins, aromatic polycarbonate resins, heat-resistant polycarbonate resins, polyarylate resins, polyethylene terephthalate resins, polybutylene terephthalate resins, polylactic acid, styrene copolymers, polyacetal resins, polyphenylene ether resins, polyphenylene sulfide resins, polymethyl methacrylate resins, and cellulose ester resins, as well as various thermosetting resins such as polyimide, polyurethane, epoxy resins, and phenolic resins. One or more of these resins may be used in combination as the resin material.

[0050] The resin sheet preferably uses thermoplastic resin as its main material. "Main material" means that the proportion of thermoplastic resin in the resin sheet is within the above-mentioned range. A resin sheet using thermoplastic resin as its main material is capable of plastic deformation by heat and exhibits excellent secondary processability. Therefore, an inner case 3 that can be manufactured by thermoforming and has excellent ease of manufacture can be obtained.

[0051] Examples of thermoplastic resins include polyolefin resins, polystyrene resins, polyamide resins, aliphatic polycarbonate resins, aromatic polycarbonate resins, heat-resistant polycarbonate resins, and polyphenylene ether resins. Of these, polymer alloys containing aliphatic polycarbonate resins, aromatic polycarbonate resins, aromatic polycarbonate resins, or polyphenylene ether resins are preferably used as thermoplastic resins. This results in an inner case 3 having excellent heat resistance and flame retardancy derived from its aromatic ring structure.

[0052] Furthermore, resin materials with high tracking resistance are preferably used. Tracking resistance refers to resistance to the phenomenon of conductive paths (tracking) being formed by discharge occurring on the surface of an insulator. Such tracking resistance can be quantified, for example, by the comparative tracking index CTI, which is an indicator of tracking resistance measured in accordance with ASTM D3638.

[0053] The comparative tracking index (CTI) of the resin material is preferably 400V or higher, and more preferably 600V or higher. This results in an inner case 3 with particularly good tracking resistance.

[0054] The glass transition temperature Tg of the resin material is preferably 125°C or higher, and more preferably 130°C or higher and less than 200°C. This makes it easier to suppress discoloration due to carbonization, even if surface discharge occurs in the inner case 3. As a result, it is possible to suppress the occurrence of appearance defects in the inner case 3 and the decrease in insulation performance due to carbonization. The glass transition temperature Tg of the resin material is measured by the DSC (Differential Scanning Calorimeter) method. The heating rate in the DSC method is set to 10°C / min.

[0055] 1.2.2.1. Polyolefin resins Examples of polyolefin resins include high-density polyethylene resin, polypropylene resin, polybutene resin, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylate methyl copolymer, ethylene-(meth)acrylate ethyl copolymer, ethylene-vinyl acetate copolymer, maleic anhydride modified polyethylene, carboxylic acid modified polyethylene, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, and the like.

[0056] Polyolefin resins exhibit excellent chemical resistance to various chemicals. Furthermore, polyolefin resins possess good tracking resistance based on their hydrocarbon chain structure. Therefore, polyolefin resins contribute to improving the chemical resistance and tracking resistance of the inner case 3.

[0057] Of these, polypropylene resin is preferably used. Polypropylene resin particularly improves the chemical resistance and tracking resistance of the inner case 3.

[0058] 1.2.2.2. Polyamide Resins Examples of polyamide resins include polycaproamide (polyamide 6), polytetramethylene adipamide (polyamide 46), polyhexamethylene adipamide (polyamide 66), polyhexamethylene sevacamide (polyamide 610), polyhexamethylene dodecamide (polyamide 612), polyundecamethylene adipamide (polyamide 116), polyundecanamide (polyamide 11), polydodecanamide (polyamide 12), polytrimethylhexamethylene terephthalamide (polyamide TMHT), polyhexamethylene terephthalamide (polyamide 6T), polyhexamethylene isophthalamide (polyamide 6I), and poly Examples include xamethylene terephthalamide / isophthalamide (polyamide 6T / 6I), polybis(4-aminocyclohexyl)methanedodecamamide (polyamide PACM12), polybis(3-methyl-4-aminocyclohexyl)methanedodecamamide (polyamide dimethyl PACM12), polymetaxylylene adipamide (polyamide MXD6), polynonameethylene terephthalamide (polyamide 9T), polydecamethylene terephthalamide (polyamide 10T), polyundecamethylene terephthalamide (polyamide 11T), and polyundecamethylene hexahydroterephthalamide (polyamide 11T(H)), and copolymers or mixtures thereof may also be used.

[0059] Polyamide resin can be obtained, for example, by polymerizing or copolymerizing a nylon salt composed of a diamine and a dicarboxylic acid using known methods such as melt polymerization, solution polymerization, or solid-phase polymerization. By using polyamide resin as the resin material, the tracking resistance of the inner case 3 can be further improved.

[0060] As the diamine, an aliphatic diamine may be used, but alicyclic diamines or aromatic diamines are preferred, and alicyclic diamines are more preferred. By using these, polyamide resins having cyclic structures such as aromatic ring structures or alicyclic structures can be prepared. Such polyamide resins contribute to improving the heat resistance of the inner case 3. In particular, alicyclic diamines contribute to improving the tracking resistance of the inner case 3.

[0061] Examples of alicyclic diamines include 1,3-cyclohexanediamine, 1,4-cyclohexanediamine, 1,3-cyclohexanedimethylamine, 1,4-cyclohexanedimethylamine, bis(4-aminocyclohexyl)methane, bis(4-aminocyclohexyl)propane, bis(3-methyl-4-aminocyclohexyl)methane, bis(3-methyl-4-aminocyclohexyl)propane, 5-amino-2,2,4-trimethyl-1-cyclopentanemethylamine, 5-amino-1,3,3-trimethylcyclohexanemethylamine (isophoronediamine), bis(aminopropyl)piperazine, bis(aminoethyl)piperazine, norbornanedimethylamine, tricyclodecanedimethylamine, etc., and one or more of these can be used.

[0062] Examples of aromatic diamines include m-xylylenediamine and p-xylylenediamine.

[0063] The dicarboxylic acid may be an alicyclic dicarboxylic acid or an aromatic dicarboxylic acid, but an aliphatic dicarboxylic acid is preferred. This makes it possible to prepare a polyamide resin having a hydrocarbon chain structure. Such a polyamide resin contributes to improving the tracking resistance of the inner case 3.

[0064] Examples of dicarboxylic acids include aliphatic dicarboxylic acids such as adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanediic acid, dodecanediic acid, tridecanediic acid, tetradecanediic acid, pentadecanediic acid, hexadecanedioic acid, octadecanediic acid, and eicosanedioic acid; alicyclic dicarboxylic acids such as 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, dicyclohexanemethane-4,4'-dicarboxylic acid, and norbornanedicarboxylic acid; and aromatic dicarboxylic acids such as isophthalic acid, terephthalic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 2,7-naphthalenedicarboxylic acid, with one or more of these being used.

[0065] Preferably, polyamide 6T, polyamide PACM12, polyamide dimethyl PACM12, polyamide MXD6, polyamide 9T, polyamide 10T, polyamide 11T, or polyamide 11T(H) are used as the polyamide resin, with polyamide PACM12 or polyamide dimethyl PACM12 being more preferably used. Since these have both cyclic structures such as aromatic ring structures and alicyclic structures, and structures derived from aliphatic monomers, they contribute to improving both the heat resistance and tracking resistance of the inner case 3.

[0066] Polyamide PACM12 contains structural units represented by the following formula (2).

[0067]

[0068] The above-mentioned polyamide PACM12 is synthesized using bis(4-aminocyclohexyl)methane (PACM) and dodecanediic acid as raw materials.

[0069] Polyamidedimethyl PACM12 contains a structural unit represented by the following formula (3).

[0070]

[0071] The above-mentioned polyamidedimethyl PACM12 is synthesized using bis(3-methyl-4-aminocyclohexyl)methane (MACM) and dodecanediic acid as raw materials.

[0072] 1.2.2.3. Aliphatic Polycarbonate Resins Examples of aliphatic polycarbonate resins include those containing aliphatic carbonate units with 2 to 12 carbon atoms. Specifically, examples include polyethylene carbonate, polypropylene carbonate, polytrimethylene carbonate, polytetramethylene carbonate, polypentamethylene carbonate, polyhexamethylene carbonate, polyheptamethylene carbonate, polyoctamethylene carbonate, polynonamethylene carbonate, polydecamethylene carbonate, polyoxydiethylene carbonate, poly-3,6-dioxyoctane carbonate, poly-3,6,9-trioxyundecane carbonate, polyoxydipropylene carbonate, polycyclopentene carbonate, and polycyclohexene carbonate.

[0073] Furthermore, the aliphatic polycarbonate resin may also be a resin containing aliphatic carbonate units that contain diol residues represented by the following formula (4).

[0074] (In formula (4), R ５ ~R ８ Each of these is independently a hydrogen atom, an alkyl group, a cycloalkyl group, or an aryl group.

[0075] The aliphatic polycarbonate resin preferably contains 30 mol% to 100 mol% of aliphatic carbonate units containing the diol residue represented by the above formula (4) in the total structural units, and more preferably contains 50 mol% to 90 mol%.

[0076] The diol residue represented by formula (4) above has a structure in which two tetrahydrofuran rings are fused. By including such a structure in the structural unit, the glass transition temperature Tg of the aliphatic polycarbonate resin can be increased. As a result, an inner case 3 with excellent heat resistance and tracking resistance can be obtained.

[0077] Examples of diols that make up the diol residue represented by formula (4) above include isosorbide, isomannide, and isoidide. These carbohydrate-derived diols are useful because they can also be obtained from natural biomass.

[0078] 1.2.2.4. Aromatic Polycarbonate Resins Aromatic polycarbonate resins can be obtained by methods such as the phosgene method, which involves reacting various dihydroxydiaryl compounds with phosgene; the transesterification method, which involves reacting dihydroxydiaryl compounds with carbonate esters such as diphenyl carbonate; the ring-opening polymerization method of cyclic carbonate compounds; and the interfacial polycondensation method. Such aromatic polycarbonate resins impart excellent heat resistance and flame retardancy to the inner case 3, derived from their aromatic ring structure.

[0079] Examples of the dihydroxydiaryl compound include, in addition to bisphenol A, bis(hydroxyaryl)alkanes such as bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)octane, bis(4-hydroxyphenyl)phenylmethane, 2,2-bis(4-hydroxyphenyl-3-methylphenyl)propane, 1,1-bis(4-hydroxy-3-tert-butylphenyl)propane; bis(hydroxyaryl)cycloalkanes such as 1,1-bis(4-hydroxyphenyl)cyclopentane, 1,1-bis(4-hydroxyphenyl)cyclohexane; dihydroxydiaryl ethers such as 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxy-3,3'-dimethyldiphenyl ether; dihydroxydiaryl sulfides such as 4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfide; dihydroxydiaryl sulfoxides such as 4,4'-dihydroxydiphenyl sulfoxide, 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfoxide; dihydroxydiaryl sulfones such as 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfone. These may be used alone or in combination of two or more.

[0080] Examples of the aromatic polycarbonate resin include those having a structural unit represented by the following formula (1).

[0081] (In formula (1), R １ and R ２ each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, an aryl group having 6 to 12 carbon atoms, or a halogen atom. m and n each independently represent an integer of 0 to 4. X represents a direct bond, O, S, SO, SO ２ , CR ３ R ４ (R ３ and R ４Each of these independently represents a hydrogen atom, a C1-C6 alkyl group, or a C6-C12 aryl group, which may be the same or different from each other. ), a C2-C10 alkylene group, a polydimethylsiloxane group, or C(CF ３ ) ２ (This represents...)

[0082] The aromatic polycarbonate resin having the structural unit represented by the above formula (1) provides the inner case 3 with particularly excellent heat resistance and flame retardancy.

[0083] Of the total structural units constituting the aromatic polycarbonate resin, the proportion of structural units represented by the above formula (1) is preferably 55 mol% or more, more preferably 70 mol% or more, and even more preferably 80 mol% or more.

[0084] Furthermore, from the perspective of ease of acquisition, cost, etc., R １ and R ２ However, it is preferable that each is a hydrogen atom, and X is CR ３ R ４ And, R ３ and R ４ Preferably, each of these is either a methyl group or a hydrogen atom.

[0085] The aromatic polycarbonate resin is preferably a polycarbonate resin having structural units derived from bisphenol A (2,2-bis(4-hydroxyphenyl)propane). This further enhances the flame retardancy and heat resistance of the inner case 3.

[0086] The viscosity-average molecular weight (M) of the aromatic polycarbonate resin is not particularly limited, but is preferably 5,000 to 100,000, more preferably 12,000 to 35,000, even more preferably 15,000 to 30,000, and particularly preferably 18,000 to 28,000.

[0087] The viscosity-average molecular weight (M) is calculated using the viscosity (η) of the methylene chloride solution of the resin, where η = kM. αIt is calculated using the following formula. k and α are constants specific to the polymer. A Ubbelohde viscometer is used to measure viscosity, and the measurement is performed at 20°C.

[0088] Furthermore, the aromatic polycarbonate resin may be a blend of a resin with a high viscosity-average molecular weight (high viscosity resin) and a resin with a low viscosity-average molecular weight (low viscosity resin). This makes it possible to obtain an inner case 3 with excellent moldability without compromising the heat resistance and flame retardancy of the aromatic polycarbonate resin.

[0089] The difference between the viscosity-average molecular weight of the high-viscosity resin and the viscosity-average molecular weight of the low-viscosity resin is not particularly limited, but is preferably 3,000 to 20,000, and more preferably 5,000 to 10,000. This results in an inner case 3 with particularly good moldability.

[0090] When the amount of high-viscosity resin is M1 and the amount of low-viscosity resin is M2, the blending ratio M1 / M2 is preferably 0.5 to 8.0 by mass, more preferably 0.8 to 6.0, and even more preferably 0.9 to 5.0. This results in an inner case 3 with particularly good moldability.

[0091] The glass transition temperature Tg of the aromatic polycarbonate resin is preferably between 130°C and less than 160°C, and more preferably between 140°C and 155°C. If the glass transition temperature Tg of the aromatic polycarbonate resin is within the above range, the heat resistance and flame retardancy of the inner case 3 can be sufficiently enhanced. The glass transition temperature Tg of the aromatic polycarbonate resin is measured by the DSC (Differential Scanning Calorimeter) method. The heating rate in the DSC method is set to 10°C / min.

[0092] The content of aromatic polycarbonate resin in the inner case 3 is not particularly limited, but is preferably 20% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more.

[0093] 1.2.2.5. Heat-resistant polycarbonate resins Examples of heat-resistant polycarbonate resins include resins containing carbonate units (bisphenol isophorone carbonate units) represented by the following formula (5). Such polycarbonate resins have higher heat resistance than aromatic polycarbonate resins. In this specification, polycarbonate resins containing bisphenol isophorone carbonate units are referred to as "heat-resistant polycarbonate resins".

[0094] (In formula (5), R ａ and R ｂ Each of these is an alkyl group having 1 to 12 carbon atoms, and R ｇ (where is an alkyl group having 1 to 12 carbon atoms, p and q are independently 0 to 4, and t is 0 to 10.)

[0095] Note that each R ａ and R ｂ It is preferable that at least one of these is positioned at the meta position relative to the cyclohexylidene crosslinking group.

[0096] Also, R ａ and R ｂ Each of these is an alkyl group having 1 to 4 carbon atoms, and R ｇ is an alkyl group having 1 to 4 carbon atoms, p and q are each 0 or 1, and t may be 0 to 5.

[0097] Furthermore, R ａ , R ｂ , and R ｇ Each of the three is a methyl group, p and q are each 0 or 1, and t is 0 or 3, preferably 0.

[0098] Specific examples of such heat-resistant polycarbonate resins include resins containing carbonate units derived from bisphenol A (2,2-bis(4-hydroxyphenyl)propane) (bisphenol A carbonate units) and carbonate units represented by formula (5) (bisphenol isophorone carbonate units). In this case, p and q in the bisphenol isophorone carbonate units are each 0, and each R ｇThe group is preferably a methyl group, and t is preferably 3. As a result, the bisphenol isophorone carbonate unit is a carbonate unit that includes a structure derived in particular from bisphenol TMC (1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane).

[0099] Such bisphenol isophorone carbonate units contain both aromatic ring and alicyclic structures. Therefore, bisphenol isophorone carbonate units contribute particularly to improving the heat resistance, flame retardancy, and tracking resistance of the inner case 3.

[0100] The proportion of bisphenol isophorone carbonate units among all structural units constituting the heat-resistant polycarbonate resin is preferably 30 mol% or more, more preferably 50 mol% or more, and even more preferably 55 mol% or more. This contributes to improving both the heat resistance, flame retardancy, and tracking resistance of the inner case 3.

[0101] The glass transition temperature Tg of the heat-resistant polycarbonate resin is preferably 160°C to 230°C, and more preferably 165°C to 220°C. If the glass transition temperature Tg of the heat-resistant polycarbonate resin is within the above range, the heat resistance of the inner case 3 can be particularly enhanced. As a result, even if surface discharge occurs in the inner case 3, for example, discoloration due to carbonization can be particularly suppressed, thereby particularly suppressing the occurrence of appearance defects and the decrease in insulation performance due to carbonization.

[0102] Furthermore, if the glass transition temperature Tg falls below the lower limit, surface discharge may increase the likelihood of appearance defects and carbonization. On the other hand, if the glass transition temperature Tg exceeds the upper limit, the molding temperature of the heat-resistant polycarbonate resin may become too high, increasing the likelihood of molding defects.

[0103] 1.2.2.6. Polyphenylene ether resin The polyphenylene ether resin provides the inner case 3 with particularly excellent heat resistance and flame retardancy.

[0104] The glass transition temperature Tg of the polyphenylene ether resin is preferably 180°C or higher and less than 250°C, and more preferably 200°C or higher and 240°C or lower. If the glass transition temperature Tg of the polyphenylene ether resin is within the above range, the heat resistance and flame retardancy of the inner case 3 can be sufficiently enhanced. The glass transition temperature Tg of the polyphenylene ether resin is measured by the DSC (Differential Scanning Calorimeter) method. The heating rate in the DSC method is 10°C / min.

[0105] The content of polyphenylene ether resin in the inner case 3 is not particularly limited, but is preferably 30% by mass or more, and more preferably 40% by mass or more. This results in an inner case 3 with particularly good heat resistance and flame retardancy.

[0106] 1.2.2.7. The polymer alloy thermoplastic resin may be a polymer alloy (polymer alloy containing aromatic polycarbonate) obtained by alloying an aromatic polycarbonate resin with a compatible resin, or a polymer alloy (polymer alloy containing polyphenylene ether resin) obtained by alloying a polyphenylene ether resin with a compatible resin. A polymer alloy refers to a single-phase material or a stable multi-phase material obtained by mixing multiple types of polymers, preferably a single-phase material. In this specification, "alloying" refers to the preparation of such a single-phase or multi-phase material by kneading or the like to raw materials containing multiple types of polymers. In particular, by alloying an aromatic polycarbonate resin with a compatible resin or a polyphenylene ether resin with a compatible resin, an inner case 3 can be obtained that combines the heat resistance derived from the aromatic polycarbonate resin or polyphenylene ether resin with other properties derived from the compatible resin.

[0107] The compatible resins preferably include the polyolefin resins, polystyrene resins, polyamide resins, aliphatic polycarbonate resins, and heat-resistant polycarbonate resins mentioned above. In this case, the aromatic polycarbonate resin alloyed with these compatible resins preferably has a structural unit represented by formula (1) above. With such a combination, the tracking resistance (comparative tracking index CTI) of the compatible resin is higher than that of the aromatic polycarbonate resin having a structural unit represented by formula (1) above, so an inner case 3 with both heat resistance and tracking resistance can be obtained.

[0108] The ratio of compatible resin in the polymer alloy is not particularly limited, but is preferably 5% by mass or more and 80% by mass or less, more preferably 10% by mass or more and 75% by mass or less, even more preferably 20% by mass or more and 70% by mass or less, and particularly preferably 40% by mass or more and 65% by mass or less. With such a configuration, it is possible to realize a polymer alloy that has a good balance between the properties such as heat resistance and flame retardancy of aromatic polycarbonate resins and polyphenylene ether resins having structural units represented by the above formula (1), and the properties of the compatible resin.

[0109] The comparative tracking index CTI of the compatible resin is preferably 400V or higher, and more preferably 600V or higher. This results in an inner case 3 with particularly good tracking resistance.

[0110] Furthermore, the comparative tracking index CTI of the compatible resin is preferably 50V or more higher than that of the aromatic polycarbonate resin or polyphenylene ether resin, and more preferably 100V or more higher. This results in an inner case 3 that achieves a better balance between flame retardancy and tracking resistance.

[0111] The glass transition temperature Tg of the compatible resin is preferably 90°C or higher, more preferably 125°C or higher, and even more preferably 130°C to 230°C. This imparts heat resistance to the compatible resin, making it easier to suppress discoloration due to carbonization, for example, even if surface discharge occurs in the inner case 3. As a result, it is possible to suppress the occurrence of appearance defects in the inner case 3 and the decrease in insulation performance due to carbonization.

[0112] Here, we provide examples of tracking resistance and glass transition temperature (Tg) for resins (compounds) that can be used for the inner case 3. Table 1 below lists the CTI value representing tracking resistance and the glass transition temperature (Tg) for various resins. In addition, the viscosity-average molecular weight is also listed for aromatic polycarbonate resins.

[0113]

[0114] As shown in Table 1, aromatic polycarbonate resins and polyphenylene ether resins tend to have slightly lower tracking resistance compared to other resins. Therefore, alloying aromatic polycarbonate resins or polyphenylene ether resins with other resins is useful in terms of achieving a balance between the properties of both resins.

[0115] Furthermore, the compatible resin preferably has an aromatic ring ratio of 90% by mass or less, more preferably 70% by mass or less, even more preferably 50% by mass or less, and particularly preferably 30% by mass or less. Such a compatible resin has a relatively high proportion of aliphatic structures. Therefore, good tracking resistance can be imparted to the inner case 3. As a result, an inner case 3 with excellent flame retardancy and tracking resistance can be obtained.

[0116] Furthermore, the proportion of aromatic rings in the entire polymer alloy is preferably 75% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less. Such a polymer alloy has a relatively high proportion of aliphatic structures. Therefore, good tracking resistance can be imparted to the inner case 3. As a result, an inner case 3 with excellent flame retardancy and tracking resistance can be obtained. In addition, even if surface discharge occurs in the inner case 3, discoloration due to carbonization is easily suppressed. As a result, the occurrence of appearance defects in the inner case 3 and the decrease in insulation performance due to carbonization can be suppressed.

[0117] On the other hand, when considering the balance with heat resistance and flame retardancy, the proportion of aromatic rings in the entire polymer alloy is preferably 20% by mass or more, and more preferably 30% by mass or more.

[0118] The ratio of aromatic rings can be determined as follows. Here, as an example, the ratio of aromatic rings in a carbonate unit represented by the following formula is calculated.

[0119]

[0120] In the carbonate unit described above, there are 16 carbon atoms, 3 oxygen atoms, and 14 hydrogen atoms. Therefore, the molecular weight of the carbonate unit is 254.

[0121] Furthermore, one aromatic ring has 6 carbon atoms and 4 hydrogen atoms. Therefore, the molecular weight of one aromatic ring is 12 × 6 + 1 × 4 = 76.

[0122] In the above carbonate unit, there are two aromatic rings. Therefore, the ratio of aromatic rings [mass%] in the above carbonate unit is 76 × 2 / 254 × 100 = 59.8.

[0123] Furthermore, the polymer alloy may contain resins other than those listed above. In other words, the polymer alloy may be formed by alloying three or more types of resins.

[0124] An example of a polymer alloy preparation method is described below. First, the raw materials are pre-mixed and then melted and kneaded using a batch-type kneader or a twin-screw extruder. This mechanically agitates the raw materials, yielding a mixture containing the polymer alloy. The kneading and melting conditions are set appropriately according to the type and ratio of the raw materials, but as an example, a temperature of 200 to 250°C, a screw rotation speed of 300 to 1000 rpm, and a kneading time of approximately 3 to 20 minutes are used. Next, the mixture is pelletized as needed.

[0125] Furthermore, compatibilizers may be added to the raw materials as needed. Adding compatibilizers can further improve the compatibility of the resins being alloyed.

[0126] The amount of compatibilizer added is preferably 2 parts by mass or more and 30 parts by mass or less, and more preferably 5 parts by mass or more and 20 parts by mass or less, per 100 parts by mass of resin.

[0127] 1.2.2.8. The additive resin sheet may contain any additives. Examples of additives include flame retardants, colorants, stabilizers, lubricants, processing aids, antistatic agents, antioxidants, neutralizing agents, ultraviolet absorbers, dispersants, thickeners, mold release agents, fillers, flow improvers, plasticizers, and antibacterial agents. Note that the sheet may contain only one additive, or two or more additives in any combination.

[0128] Of these, the flame retardant enhances the flame retardancy of the inner case 3. Examples of flame retardants include halogenated flame retardants, inorganic phosphorus-based flame retardants such as red phosphorus and polyphosphate-based flame retardants such as ammonium polyphosphate, organophosphorus-based flame retardants such as triaryl phosphate compounds, metal hydroxide compounds, antimony oxide compounds, nitrogen-containing compounds, etc. In addition, two or more of these may be used in combination as the flame retardant.

[0129] Of these, phosphorus-based flame retardants or nitrogen-containing compounds are preferably used as flame retardants, and nitrogen-containing compounds are more preferably used. By using a nitrogen-containing compound as the flame retardant, the flame retardancy of the inner case 3 can be further enhanced. Furthermore, since nitrogen-containing compounds do not contain halogen atoms, it is possible to realize a so-called halogen-free and fluorine-free inner case 3.

[0130] Examples of nitrogen-containing compounds include compounds having a triazine skeleton. Examples of compounds having a triazine skeleton include melamine; melamine derivatives such as butylmelamine, trimethylolmelamine, hexamethylolmelamine, hexamethoxymethylmelamine, and melamine phosphate; cyanuric acid; cyanuric acid derivatives such as methyl cyanurate, diethyl cyanurate, trimethyl cyanurate, and triethyl cyanurate; isocyanuric acid; isocyanuric acid derivatives such as methyl isocyanurate, N,N'-diethyl isocyanurate, trismethyl isocyanurate, trisethyl isocyanurate, bis(2-carboxyethyl) isocyanurate, 1,3,5-tris(2-carboxyethyl) isocyanurate, and tris(2,3-epoxypropyl) isocyanurate; melamine cyanurate; and melamine isocyanurate. These compounds can be used individually or in combination of two or more.

[0131] Of these, the compound having a triazine skeleton is preferably one or more melamine-based compounds selected from the group consisting of melamine, melamine cyanurate, melamine isocyanurate, and derivatives thereof, with melamine cyanurate being more preferably used. This makes it possible to particularly enhance the flame retardancy of the inner case 3.

[0132] The amount of flame retardant added is preferably 0.1 parts by mass to 30 parts by mass, more preferably 1 part by mass to 20 parts by mass, and even more preferably 3 parts by mass to 10 parts by mass, per 100 parts by mass of resin. By keeping the amount of flame retardant added within the above range, the effect of enhancing flame retardancy is sufficiently exhibited, and side effects such as a decrease in mechanical properties due to excess flame retardant can be suppressed.

[0133] The flame retardant is, for example, in particulate form. In this case, the average particle size of the flame retardant is preferably 0.01 μm or more and 10 μm or less, more preferably 0.05 μm or more and 5 μm or less, and even more preferably 0.2 μm or more and 2 μm or less. By having the average particle size of the flame retardant within the above range, the dispersibility of the flame retardant becomes particularly good, and thus the flame retardancy of the inner case 3 can be particularly enhanced. The average particle size of the flame retardant is the particle size when the cumulative amount from the small diameter side in the volume-based particle size distribution is 50%, as measured using a laser diffraction particle size distribution analyzer.

[0134] The total amount of additives other than flame retardants is preferably 0.1 parts by mass or more and 10 parts by mass or less, more preferably 0.3 parts by mass or more and 5 parts by mass or less, and even more preferably 0.5 parts by mass or more and 3 parts by mass or less, per 100 parts by mass of resin.

[0135] 1.2.3. Multilayer Structure Next, we will describe the inner case 3 according to a modified example.

[0136] Figure 3 is a partial cross-sectional view showing an inner case 3 according to a modified example. The following description will explain the inner case 3 according to the modified example, but the following description will focus on the differences from the above embodiment, and similar matters will be omitted from the explanation.

[0137] The inner case 3 shown in Figure 3 is the same as the inner case 3 shown in Figure 2, except that it has a multi-layer structure.

[0138] The inner case 3 shown in Figure 3 is composed of a laminate in which a first layer 301, an intermediate layer 303, and a second layer 302 are laminated in this order. The intermediate layer 303 preferably contains an aromatic polycarbonate resin or a polyphenylene ether resin and a flame retardant. The first layer 301 is laminated on the lower surface of the intermediate layer 303 and contains a first resin. The second layer 302 is laminated on the upper surface of the intermediate layer 303 and contains a second resin. Preferably, the first resin and the second resin are materials with higher tracking resistance than the aromatic polycarbonate resin or polyphenylene ether resin contained in the intermediate layer 303.

[0139] With this configuration, the aromatic polycarbonate resin is a polycarbonate resin containing aromatic ring structures in its main chain, and because of the high proportion of aromatic ring structures, good heat resistance is imparted to the intermediate layer 303. Similarly, the polyphenylene ether resin also has a high proportion of aromatic ring structures, which imparts good heat resistance to the intermediate layer 303. Furthermore, because the intermediate layer 303 contains a flame retardant, the intermediate layer 303 has good flame retardancy.

[0140] Furthermore, the intermediate layer 303 is sandwiched between the first layer 301 and the second layer 302. Therefore, if surface discharge occurs in the inner case 3, the intermediate layer 303 is prevented from being directly exposed to corona discharge, etc. By using materials with higher tracking resistance than aromatic polycarbonate resin or polyphenylene ether resin as the resins contained in the first layer 301 and the second layer 302, the inner case 3 is given good tracking resistance. Thus, an inner case 3 with excellent flame retardancy and tracking resistance can be obtained.

[0141] Examples of manufacturing methods for the inner case 3 shown in Figure 3 include co-extrusion, dry lamination, extrusion lamination, and hot melt methods.

[0142] 1.2.4. Characteristics Next, we will explain the characteristics of the inner case 3.

[0143] 1.2.4.1. Tracking Resistance The tracking resistance of the tracking-resistant inner case 3 can be quantified by the comparative tracking index CTI, which is an indicator of tracking resistance measured in accordance with ASTM D3638.

[0144] The comparative tracking index CTI (CTI value) of the inner case 3 is preferably 600V or higher. If the CTI value is within the above range, the rank PLC, which represents tracking resistance, will be the highest rank of 0. Therefore, an inner case 3 with a CTI value within the above range can be said to have particularly good tracking resistance.

[0145] The measurement method specified in IEC 60112, third edition, measures the CTI value using a 0.1% by mass aqueous solution of ammonium chloride and a platinum electrode. More specifically, a specified number of drops (50 drops) of this ammonium chloride solution are added, and the voltage at which all of the test specimens (n=5) are not destroyed is determined and this is taken as the CTI value.

[0146] Furthermore, an inner case 3 with a thickness of 3 mm or more should be used as the test specimen. The test specimen may also consist of multiple inner cases 3 stacked on top of each other.

[0147] Furthermore, the method for measuring the comparative tracking index CTI of the aforementioned resin materials is the same as described above. In this case, the test specimen is a sheet with a thickness of 3 mm or more, obtained by extruding these resins.

[0148] 1.2.4.2. The flame retardancy of the flame-retardant inner case 3 can be quantified by the flame retardancy rank determined in accordance with the UL94 standard (rank determined by the UL94V test or UL94VTM test).

[0149] The flame retardancy of the inner case 3 preferably meets the following judgment ranks for each thickness of the test specimen.

[0150] - If the thickness of the test specimen is 0.25 mm or more, the judgment rank according to the UL94V test is V-0. - If the thickness of the test specimen is less than 0.25 mm, the judgment rank according to the UL94V test is V-0, or the judgment rank according to the UL94VTM test is VTM-0.

[0151] Inner case 3, which meets these evaluation ranks, has achieved the highest rank in each test, and therefore can be said to have particularly good flame retardancy.

[0152] In addition, the UL94V test involves a vertical combustion test using a test specimen with dimensions of 125 ± 5 mm × 13.0 ± 0.5 mm.

[0153] In addition, the UL94VTM test involves a vertical combustion test using a test specimen measuring 200 mm x 50 mm.

[0154] 1.2.4.3. Dielectric Breakdown Voltage The dielectric breakdown voltage of inner case 3 is the dielectric breakdown voltage measured in accordance with the method for measuring the strength of dielectric breakdown (AC test) specified in JIS C 2318:2020.

[0155] The dielectric breakdown voltage of the inner case 3 is preferably 5kV or higher, more preferably 7kV to 60kV, and even more preferably 10kV to 50kV. An inner case 3 that satisfies such a dielectric breakdown voltage contributes to ensuring sufficient insulation even with a short insulating space distance. The dielectric breakdown voltage may exceed the above upper limit, but it is preferable that it be below the above upper limit when considering the suppression of individual differences.

[0156] 1.3. Metal casing The metal casing 4 is a box-shaped structure with a bottom. The metal casing 4 defines an internal storage space 40. The storage space 40 houses the energy storage element 2 and the inner case 3.

[0157] Examples of materials that can be used to construct the metal casing 4 include aluminum, magnesium, copper, titanium, or other materials in their pure form or alloys, or stainless steel. Using such metal materials makes it possible to realize a metal casing 4 with low water vapor permeability, high heat dissipation, and high mechanical strength. This improves the moisture resistance, heat resistance, and reliability of the energy storage device 1.

[0158] The metal casing 4 may be a composite of a box made of the metal material described above and a resin layer covering at least one of the inner and outer surfaces of the box. This enhances the insulating properties of the surface of the metal casing 4.

[0159] 1.4. Insulator The insulator 6 is interposed between the electrode body 21 and electrode body 22 of the energy storage element 2, insulating them from each other. By using the insulator 6, the electrode body 21 and electrode body 22 can be placed in close proximity to each other. This makes it possible to reduce the parasitic inductance of the electrode bodies 21 and 22 and suppress surge voltage.

[0160] The constituent material of the insulator 6 is not particularly limited, but the aforementioned resin material is an example. By using a resin material, the insulating properties of the insulator 6 can be further enhanced, and the weight of the insulator 6 can be reduced.

[0161] 1.5. Filling material The filling material 7 is filled into the housing space 40 of the metal casing 4, and encapsulates the energy storage element 2 and inner case 3 housed in the housing space 40.

[0162] The constituent material of the filler 7 can be any resin suitable for the required function, such as epoxy resin, phenolic resin, oxetane resin, (meth)acrylate resin, unsaturated polyester resin, silicone resin, urethane resin, diallyl phthalate resin, maleimide resin, etc. While these resins alone may be used as the constituent material of the filler 7, inorganic powders may also be added. Examples of inorganic powders include silica powder composed of fused silica, crystalline silica, and amorphous silica, alumina powder, aluminum hydroxide powder, silicon nitride powder, and aluminum nitride powder. The addition of these inorganic powders enhances the mechanical properties, insulation, and thermal conductivity of the filler 7.

[0163] The average particle size of the inorganic powder is not particularly limited, but is preferably 1 μm to 50 μm, and more preferably 5 μm to 40 μm. This improves the packing efficiency of the filler 7 while further enhancing its mechanical properties, insulation properties, and thermal conductivity.

[0164] The inorganic powder content in the filler 7 is preferably 30% by mass or more and 90% by mass or less, more preferably 40% by mass or more and 80% by mass or less, and even more preferably 50% by mass or more and 75% by mass or less. This makes it possible to achieve both the filling properties of the filler 7 and the mechanical properties, insulating properties, and thermal conductivity of the filler 7.

[0165] 2. Method for Manufacturing an Energy Storage Device Next, an example of a method for manufacturing the energy storage device 1 will be described.

[0166] 2.1. Overview The energy storage device 1 is manufactured, for example, as follows:

[0167] First, the energy storage element 2 is housed in the housing space 30 of the inner case 3. The insulator 6 may be attached to the energy storage element 2 beforehand, or it may be attached after the assembly work described later is completed. Next, the inner case 3 containing the energy storage element 2 is housed in the housing space 40 of the metal casing 4. Next, the uncured filler material 7 is filled into the housing space 40. The uncured material fills not only the gap between the metal casing 4 and the inner case 3, but also the inside of the inner case 3. This encapsulates the energy storage element 2 and the inner case 3 with the uncured material. Next, the uncured material is cured. This yields the filler material 7. The energy storage device 1 is thus obtained.

[0168] 2.2. Method for Manufacturing the Inner Case Next, an example of a method for manufacturing the inner case 3 will be described.

[0169] Figures 4 to 7 are cross-sectional views illustrating the manufacturing method of the inner case 3 shown in Figure 2.

[0170] The inner case 3 is manufactured, for example, by molding a resin sheet 300 into a predetermined shape using a differential pressure molding method. Examples of differential pressure molding methods include vacuum molding, pressure molding, or vacuum pressure molding. These molding methods allow for the precise molding of the resin sheet 300 by utilizing a large pressure difference. Below, a representative method for manufacturing the inner case 3 using vacuum molding will be described.

[0171] Vacuum forming is a molding method that uses the pressure difference created by reducing the pressure inside a mold with vacuum holes to make the object to be molded adhere tightly to the mold.

[0172] Specifically, first, the resin sheet 300 is heated. Heating causes the resin sheet 300 to soften and become plastic. The heating temperature of the resin sheet 300 is set appropriately according to the constituent materials and thickness of the resin sheet 300.

[0173] The method for heating the resin sheet 300 is not particularly limited, but as an example, as shown in Figure 4, the resin sheet 300 is held horizontally and heated by the upper heater 91 and the lower heater 92, respectively.

[0174] Next, as shown in Figure 5, a mold 94 having a vacuum hole 93 and a pressure reducing box 95 hermetically connected to the mold 94 are prepared. The space V defined by the surface 944 of the mold 94 opposite to the molding surface 942 and the pressure reducing box 95 is depressurized by an exhaust pump 96.

[0175] Next, the heated resin sheet 300 is pressed against the molding surface 942 of the mold 94, as shown in Figure 6. Then, the space V is depressurized by the exhaust pump 96. This causes the air between the molding surface 942 and the resin sheet 300 to be discharged through the vacuum holes 93. As a result, the resin sheet 300 adheres tightly to the molding surface 942 of the mold 94 due to the pressure difference, and the resin sheet 300 is molded into a predetermined shape. Subsequently, the resin sheet 300 is cooled. This fixes the molded shape.

[0176] Next, the molded resin sheet 300 is removed from the mold 94. Then, trimming is performed as needed. This results in the inner case 3 shown in Figure 7.

[0177] 3. Effects of the Embodiment The inner case for the energy storage device (inner case 3) according to the embodiment has a bottom portion 31 and a peripheral wall portion 32. The bottom portion 31 faces the housing space 30 that houses the energy storage element 2. The peripheral wall portion 32 rises from the end of the bottom portion 31 and faces the housing space 30. The inner case 3 is made of a three-dimensional molded body of an insulating resin sheet. The inner case 3 is housed in the metal casing 4 with the energy storage element 2 housed in the housing space 30, and is used to be embedded in the filler material 7 that is filled inside the metal casing 4.

[0178] With this configuration, since it is made of a three-dimensional molded resin sheet, an inner case 3 can be obtained that provides sufficient insulation between the energy storage element 2 and the metal casing 4 while narrowing the gap between them. Furthermore, an inner case 3 can be obtained that contributes to miniaturization and improved heat dissipation of the energy storage device 1, as well as reducing the assembly man-hours for the energy storage device 1.

[0179] In the inner case (inner case 3) for the energy storage device according to the above embodiment, the thickness of the resin sheet is preferably 0.05 mm or more and 0.50 mm or less.

[0180] With this configuration, an inner case 3 with excellent insulation and heat dissipation properties can be obtained. Furthermore, when the inner case 3 is formed by thermoforming, the shape of the inner case 3 can be formed with high precision and in a short time.

[0181] In the inner case (inner case 3) for the energy storage device according to the above embodiment, it is preferable that the resin sheet is mainly made of thermoplastic resin.

[0182] A resin sheet primarily made of thermoplastic resin can be plastically deformed by heat and has excellent secondary processability. Therefore, it can be manufactured by thermoforming, resulting in an inner case 3 that is easy to manufacture.

[0183] In the inner case for the energy storage device (inner case 3) according to the above embodiment, the thermoplastic resin may be an aromatic polycarbonate resin.

[0184] With this configuration, an inner case 3 is obtained that has excellent heat resistance and flame retardancy derived from the aromatic ring structure.

[0185] In the inner case (inner case 3) for the energy storage device according to the above embodiment, the thermoplastic resin may be a polymer alloy of aromatic polycarbonate resin and a compatible resin.

[0186] With this configuration, an inner case 3 is obtained that has excellent heat resistance and flame retardancy derived from the aromatic ring structure. In addition, an inner case 3 is obtained that has other properties derived from a compatible resin alloyed with the aromatic polycarbonate resin.

[0187] In the inner case (inner case 3) for the energy storage device according to the above embodiment, the thermoplastic resin may be a polymer alloy of a polyphenylene ether resin and a compatible resin.

[0188] With this configuration, an inner case 3 is obtained that has excellent heat resistance and flame retardancy derived from the aromatic ring structure. In addition, an inner case 3 is obtained that has other properties derived from a compatible resin that is alloyed with the polyphenylene ether resin.

[0189] In the inner case (inner case 3) for the energy storage device according to the above embodiment, the compatible resin may be a polyolefin resin, a polystyrene resin, a polyamide resin, an aliphatic polycarbonate resin, or a heat-resistant polycarbonate resin.

[0190] With this configuration, an inner case 3 that possesses both heat resistance and tracking resistance can be obtained.

[0191] In the inner case for the energy storage device (inner case 3) according to the above embodiment, it is preferable that the comparative tracking index CTI of the compatible resin is 50V or higher than the comparative tracking index CTI of the aromatic polycarbonate resin.

[0192] With this configuration, an inner case 3 is obtained that achieves a better balance between flame retardancy and tracking resistance.

[0193] In the inner case for the energy storage device (inner case 3) according to the above embodiment, the ratio of aromatic rings in the entire polymer alloy may be 75% by mass or less.

[0194] This configuration provides the inner case 3 with excellent tracking resistance. As a result, an inner case 3 with superior flame retardancy and tracking resistance can be obtained. Furthermore, even if surface discharge occurs in the inner case 3, discoloration due to carbonization can be easily suppressed.

[0195] In the inner case for the energy storage device (inner case 3) according to the above embodiment, the resin sheet may contain a flame retardant composed of a nitrogen-containing compound.

[0196] This configuration allows for a further enhancement of the flame retardancy of the inner case 3. Furthermore, since the nitrogen-containing compound does not contain halogen atoms, it is possible to realize a so-called halogen-free and fluorine-free inner case 3.

[0197] The energy storage device 1 according to the above embodiment comprises an inner case for the energy storage device according to the above embodiment (inner case 3), an energy storage element 2, a metal outer casing 4, and a filler material 7. The energy storage element 2 is housed in a housing space 30. The metal outer casing 4 houses the energy storage element 2 and the inner case 3. The filler material 7 is filled into the metal outer casing 4 so as to embed the inner case 3. With this configuration, a compact energy storage device 1 with excellent heat dissipation can be realized.

[0198] Although the inner case for an energy storage device and the energy storage device according to the present invention have been described above, the present invention is not limited to the embodiments described above.

[0199] For example, the inner case for an energy storage device according to the present invention may have additional layers with arbitrary functions, such as an adhesive layer, bonding layer, protective layer, or release layer, compared to the layer configuration described in the above embodiment.

[0200] Furthermore, the energy storage device according to the present invention may have any additional configurations added to the above embodiment.

[0201] Next, specific embodiments of the present invention will be described. However, the present invention is not limited to these embodiments.

[0202] 4. Preparation of Test Specimens for Inner Cases In order to evaluate the performance of polymer alloys obtained by alloying the aforementioned aromatic polycarbonate resin (PC resin) or polyphenylene ether resin with a compatible resin as materials for inner cases, test specimens (test specimens for inner cases) were prepared as follows.

[0203] First, the materials shown in Table 2 were mixed in the proportions shown in Tables 3 to 6, and then melted and kneaded using a twin-screw extruder to prepare a pelletized resin composition. The prepared resin composition was extruded into a sheet using an asymmetric twin-screw extruder and a T-type die, etc., to produce test specimens with the layer structure and thickness shown in Tables 3 to 6.

[0204] Table 2 shows the attributes of each material, such as the compound name, viscosity-average molecular weight, tracking resistance (CTI value), glass transition temperature (Tg), and average particle size.

[0205] Furthermore, the compatible resin b1 shown in Table 2 is a heat-resistant polycarbonate resin derived from bisphenol A and bisphenol TMC. The content of structural units derived from bisphenol TMC in compatible resin b1 is 60 mol%.

[0206] Furthermore, the compatible resin b2 shown in Table 2 is an aliphatic polycarbonate resin containing aliphatic carbonate units including the diol residue represented by formula (4) in a proportion of 60 mol%.

[0207]

[0208] 5. Evaluation of Test Specimens for Inner Cases Next, the prepared test specimens were evaluated for the following items.

[0209] 5.1. Flame Retardancy The flame retardancy rank was determined for each test specimen No. shown in Tables 3 to 6 by testing in accordance with the UL94 standard described above. The test specimens prepared were used as subjects for flame retardancy evaluation. The thickness of the test specimen was the thickness of one layer as shown in Tables 3 to 6. The results were then evaluated against the following evaluation criteria. The evaluation results are shown in Tables 3 to 6.

[0210] A: Flame retardancy rating is V-0 or VTM-0 B: Flame retardancy rating is V-1 or V-2 or VTM-1 or VTM-2 C: Flame retardancy rating is less than V-2 or less than VTM-2

[0211] 5.2. Tracking Resistance The CTI values ​​were measured for each test specimen No. shown in Tables 3 to 6 using the tracking resistance evaluation test described above. For the tracking resistance evaluation, the test specimens used were those with a thickness of 3 mm or more, with one layer of each specimen as shown in Tables 3 to 6 stacked together. The measured CTI values ​​were then evaluated according to the following evaluation criteria. The evaluation results are shown in Tables 3 to 6.

[0212] A: CTI value is 600V or higher (rank is PLC0) B: CTI value is 400V or higher but less than 600V (rank is PLC1) C: CTI value is less than 400V (rank is PLC2 or lower)

[0213] 5.3. Carbenization due to tracking For each test specimen No. shown in Tables 3 to 6, the aforementioned tracking resistance evaluation test was performed, and the test area was visually observed. The observation results were then evaluated according to the following evaluation criteria. The evaluation results are shown in Tables 3 to 6.

[0214] A: Little discoloration due to carbonization (good appearance) B: Somewhat discoloration due to carbonization (somewhat poor appearance) C: Somewhat discoloration due to carbonization (poor appearance)

[0215] 5.4. Processability The processability of the test specimens was evaluated by bending each No. shown in Tables 3 to 6 as follows and evaluating the appearance of the processed specimens.

[0216] [1] Cut the test piece to cut out a sample for evaluating processability that is approximately square in shape, with a length of 15 mm ± 1 mm in the MD direction and a length of 15 mm ± 1 mm in the TD direction.

[0217] [2] Fold the subject in the middle, place a 3 kg weight on it, leave it for 1 minute, and then remove the weight.

[0218] [3] Open the specimen and visually observe and record the condition of the folded part. [4] With the specimen still open, place a 3 kg weight on it and leave it for 1 minute, then remove the weight. [5] Visually observe and record the condition of the folded part.

[0219] [6] Repeat the operations in [2] to [5] above, and count the number of repetitions until cracks or holes appear in the bent portion.

[0220] [7] The processability of the sample is evaluated based on the number of repetitions according to the following evaluation criteria. The evaluation results are shown in Tables 3 to 6.

[0221] A: No cracks or holes were observed even after more than 10 repetitions. B: Either cracks or holes occurred after 5 to 9 repetitions. C: Either cracks or holes occurred after 4 or fewer repetitions.

[0222]

[0223]

[0224]

[0225]

[0226] Based on the results shown in Tables 3 to 6, the following was observed regarding the constituent materials of the inner case.

[0227] Test specimens (No. 1-22) containing polymer alloys with aromatic polycarbonate resin or polyphenylene ether resin and a compatible resin exhibited good flame retardancy and tracking resistance.

[0228] It was found that using polycarbonate resin as a compatible resin makes it easier to improve flame retardancy.

[0229] It was found that when a resin with a low proportion of aromatic rings is used as the compatible resin (compatible resins b2, b3, b4, b6), or when a resin with a glass transition temperature of 90°C or higher is used (compatible resins b1, b2, b3, b5), carbonization associated with tracking is easily suppressed.

[0230] According to the present invention, since it is composed of a three-dimensional molded resin sheet, it is possible to sufficiently narrow the gap between the energy storage element and the metal casing while providing insulation between them, thereby enabling miniaturization and improved heat dissipation of the energy storage device, and providing an inner case for an energy storage device that contributes to reducing the assembly man-hours of the energy storage device. Therefore, the present invention has industrial applicability.

[0231] 1 Energy storage device 2 Energy storage element 3 Inner case 4 Metal casing 6 Insulator 7 Filler 20 Energy storage section 21 Electrode body 22 Electrode body 30 Housing space 31 Bottom 32 Peripheral wall 40 Housing space 91 Heater 92 Heater 93 Vacuum hole 94 Molding mold 95 Pressure reducing box 96 Exhaust pump 300 Resin sheet 301 First layer 302 Second layer 303 Intermediate layer 942 Molding surface 944 Opposite surface V Space

Claims

1. An inner case for an energy storage device, characterized in that it is made of a three-dimensional molded body of an insulating resin sheet, having a bottom portion facing a housing space for housing an energy storage element, and a peripheral wall portion rising from the end of the bottom portion and facing the housing space, and is used to house the energy storage element in the housing space within a metal casing and to be embedded in a filler material that fills the metal casing.

2. The inner case for an energy storage device according to claim 1, wherein the thickness of the resin sheet is 0.05 mm or more and 0.50 mm or less.

3. The inner case for an energy storage device according to claim 1 or 2, wherein the resin sheet is mainly made of thermoplastic resin.

4. The inner case for an energy storage device according to claim 3, wherein the thermoplastic resin is an aromatic polycarbonate resin.

5. The inner case for an energy storage device according to claim 3, wherein the thermoplastic resin is a polymer alloy of an aromatic polycarbonate resin and a compatible resin.

6. The inner case for an energy storage device according to claim 3, wherein the thermoplastic resin is a polymer alloy of a polyphenylene ether resin and a compatible resin.

7. The inner case for an energy storage device according to claim 5 or 6, wherein the compatible resin is a polyolefin resin, a polystyrene resin, a polyamide resin, an aliphatic polycarbonate resin, or a heat-resistant polycarbonate resin.

8. The inner case for an energy storage device according to claim 7, wherein the comparative tracking index CTI of the compatible resin is 50V or higher than the comparative tracking index CTI of the aromatic polycarbonate resin.

9. The inner case for an energy storage device according to claim 5 or 6, wherein the ratio of aromatic rings in the entire polymer alloy is 75% by mass or less.

10. The inner case for an energy storage device according to claim 1 or 2, wherein the resin sheet contains a flame retardant composed of a nitrogen-containing compound.

11. An energy storage device comprising: an inner case for an energy storage device according to claim 1 or 2; an energy storage element housed in the housing space; a metal casing housing the energy storage element and the inner case for the energy storage device; and a filler material filled inside the metal casing so as to embed the inner case for the energy storage device.

Images