Battery module cover and battery pack

Abstract

Provided is a module cover (41) for use in a battery pack (100) obtained by accommodating a battery module (21) having a plurality of battery cells (11) in a housing (30), the module cover making it possible to prevent thermal diffusion from occurring when any of the battery cells (11) undergo thermal runaway. The module cover (41) is disposed between the battery module (21), obtained by assembling the plurality of battery cells (11), and the housing (30) accommodating the battery module (21). Each of the battery cells (11) has a cell body (12) and a relief part (16) including a relief valve that opens when the internal pressure of the cell body (12) exceeds a set pressure. The module cover (41) comprises a cover body (42) that covers the plurality of battery cells (11). The cover body (42) has gas-permeable parts (44) each provided above a corresponding one of the relief parts (16) so as to cover at least a portion of the corresponding relief part (16) and heat-shielding covering parts (45) that are impermeable to gas.

Description

Battery module cover and battery pack

[0001] This invention relates to a battery module cover and a battery pack.

[0002] In recent years, with the advancement of research and development in electric and hybrid vehicles, efforts have been made to increase the energy density and reduce the weight of batteries. In batteries, for example, an internal short circuit in a battery cell can cause gas to be generated due to the decomposition and vaporization of the electrolyte, leading to an abnormal increase in internal pressure. In such cases, the discharge valve provided in the battery cell may open, causing the vaporized electrolyte and high-temperature components inside the battery to be ejected forcefully in a short period of time accompanied by flames, resulting in what is known as thermal runaway.

[0003] Patent Document 1 proposes a battery pack in which a battery module, which is an assembly of multiple battery cells, is housed in a casing made of a specific material that has excellent flame resistance and strength, in order to delay the spread of fire to automotive interior materials when a flame occurs due to thermal runaway of battery cells.

[0004] Japanese Patent Publication No. 2024-60540

[0005] In a battery pack containing modules with multiple battery cells housed in a casing, if one battery cell experiences thermal runaway, other battery cells may be heated by the high-temperature ejected material, potentially causing a chain reaction of thermal runaway. Suppressing such heat diffusion within the casing is desirable. This invention provides a module cover that can suppress heat diffusion when thermal runaway occurs in a battery cell.

[0006] The present invention has the following embodiments: <1> A module cover disposed between a battery module, which is an assembly of a plurality of battery cells, and a housing that houses the battery module, wherein the battery cell has a cell body and a discharge portion equipped with a discharge valve that opens when the internal pressure of the cell body exceeds a set pressure, and the module cover has a cover body that covers the plurality of battery cells, and the cover body has a gas permeable portion provided above the discharge portion so as to cover at least a part of the discharge portion and a heat-shielding covering portion that does not allow gas to pass through, a module cover. <2> The module cover according to <1>, wherein the gas permeable portion is a through hole. <3> The module cover according to <1>, wherein the gas permeable portion is made of a nonwoven fabric. <4> The module cover according to any one of <1> to <3>, wherein the heat-shielding covering portion is made of a laminate having a resin layer containing a flame retardant and a fiber layer. <5> The module cover according to <4>, wherein the fiber layer is continuous with the heat-shielding covering portion and the gas permeable portion. <6> A battery pack comprising a battery module in which multiple battery cells are assembled, housed in a housing, wherein a module cover according to any one of <1> to <5> is disposed between the housing and the battery module. <7> The battery pack according to <6>, wherein the housing has exhaust holes.

[0007] By placing the module cover of the present invention between the housing and the battery module, heat diffusion can be suppressed in the event of thermal runaway of the battery cells.

[0008] This is a schematic cross-sectional view showing a first embodiment of the battery pack according to the present invention. This is a plan view of the module cover of the first embodiment as seen from above. This is a schematic cross-sectional view showing a main part of a second embodiment of the battery pack according to the present invention. This is a plan view of the module cover of the second embodiment as seen from above. This is a schematic cross-sectional view showing a modified example of the first embodiment. This is a diagram for explaining the method of evaluating flame resistance. This is a perspective view of the battery pack of Example 1 used in the evaluation of the temperature rise suppression effect. This is a perspective view of the battery pack of Example 2 used in the evaluation of the temperature rise suppression effect. This is a perspective view of the battery pack of the Comparative Example used in the evaluation of the temperature rise suppression effect. This is a perspective view of the battery pack of the Reference Example used in the evaluation of the temperature rise suppression effect. This is a temperature distribution contour diagram, which is the simulation result in the evaluation of the temperature rise suppression effect of the battery pack of Example 1. This is a temperature distribution contour diagram, which is the simulation result in the evaluation of the temperature rise suppression effect of the battery pack of Example 2. This is a temperature distribution contour diagram, which is the simulation result in the evaluation of the temperature rise suppression effect of the battery pack of the Comparative Example. This is a temperature distribution contour diagram, which is the simulation result in the evaluation of the temperature rise suppression effect of the battery pack of the Reference Example.

[0009] The following description of a battery pack according to an embodiment of the present invention will be given with reference to the drawings. Note that the following diagrams are schematic diagrams intended to clearly illustrate the configuration, and the dimensional ratios of each component may differ from those of the actual components.

[0010] The battery used in the battery pack of this embodiment is not particularly limited. Examples include secondary batteries such as lithium-ion batteries, nickel-metal hydride batteries, lithium-sulfur batteries, nickel-cadmium batteries, nickel-iron batteries, nickel-zinc batteries, sodium-sulfur batteries, lead-acid batteries, and air batteries. Among these, lithium-ion batteries are preferred.

[0011] <First Embodiment> Figures 1 and 2 show a battery pack of the first embodiment, with Figure 1 being a cross-sectional view and Figure 2 being a plan view of the module cover seen from above. The battery pack 100 of this embodiment comprises a battery module 21 which is a collection of multiple battery cells (individual batteries) 11, a housing 30 which houses the battery module 21, and a module cover 41 which is positioned between the battery module 21 and the housing 30.

[0012] The housing 30 has a bottomed, hollow housing formed by a bottom plate 33 and four side plates 32, and a lid 31 that closes the opening of the housing. The battery module 21 is housed on the bottom plate 33 of the housing 30 via a cushioning material 35. The battery cell 11 constituting the battery module 21 has a cell body 12 and a discharge section 16. The discharge section 16 includes a discharge valve (not shown) that opens when the internal pressure of the cell body exceeds a set pressure, and a discharge hole 16a that connects the inside and outside of the cell body when the discharge valve is open. The cell body 12 is a rectangular parallelepiped having a height direction (H), a width direction (W), and a thickness direction (D), and the discharge section 16 is provided on one end face 14 perpendicular to the height direction. In this embodiment, the side of the cell body 12 in the height direction (H) where the discharge section 16 is located is the upper side, and the end face 14 is the upper surface 14. In the battery module 21, multiple battery cells 11 are arranged such that the upper surfaces 14 of the cell bodies 12 are at the same position in the height direction (H). Spacers 34 are placed between adjacent battery cells 11.

[0013] The module cover 41 has a cover body 42 that covers a plurality of battery cells 11. The cover body 42 is sheet-like with the height direction (H) of the battery cell 11 as its thickness direction. The cover body 42 is positioned between the upper surface 14 of the cell body 12 and the lid 31 of the housing 30, and covers the upper surface 14 of the plurality of cell bodies 12. A space S exists between the upper surface of the cover body 42 and the lid 31 of the housing 30. Although not shown, the housing 30 may be provided with exhaust holes that connect the space S to the outside of the housing 30.

[0014] As shown in FIG. 2, the cover body 42 has a gas permeation part 44 provided above the discharge part 16 and a heat insulation covering part 45 that does not allow gas to permeate, so as to cover at least a part of the discharge part 16. In the present embodiment, the gas permeation part 44 is made of a material that allows gas to permeate (hereinafter, also referred to as "gas permeable material"). The gas permeation part 44 may be composed only of through holes as in the second embodiment described later. The heat insulation covering part 45 is made of a material that has heat shielding properties and does not allow gas to permeate. In this specification, the gas permeable material means that in the ventilation test by the fragile form method defined in JIS L 1913 (2010), the ventilation rate is more than 0 cm ２ , ,

[0015] / cm ２ ·s. The ventilation rate may be 5 cm ３ / cm ２ ·s or more, 10 cm ３ / cm ２ ·s or more, 20 cm ３ / cm ２ ·s or more. On the other hand, the upper limit of the ventilation rate may be 1,000 cm ３ / cm ２ ·s or less, or 500 cm​​​​​​As shown in Figure 2, when the module cover 41 is viewed from above in plan view, the gas permeable portion 44 is located within the region where the discharge portion 16 exists, and the discharge hole 16a is located inside the gas permeable portion 44. The planar shape of the gas permeable portion 44 is formed to be smaller than the planar shape of the upper surface of the discharge portion 16. It is preferable that there is a contact portion 47 that covers at least a part of the discharge portion 16, that is, around the discharge hole 16a, where the upper surface of the discharge portion 16 and the lower surface of the cover body 42 are in close contact. It is preferable that the gas permeable portion 44 is provided so as to cover the discharge hole 16a. It is preferable that the contact portion 47 is in contact with the heat-shielding coating portion 45. It is preferable that the gas permeable portion 44 covers the discharge hole 16a, and that at least a part of the discharge portion 16 around the discharge hole 16a (the contact portion 47) is in contact with the heat-shielding coating portion 45. Note that the upper surface of the discharge portion 16 and the heat-shielding coating portion 45 do not have to be in contact. In other words, the contact portion 47 does not have to exist. In this embodiment, the planar shape of the gas permeable section 44 and the planar shape of the upper surface of the discharge section 16 are rectangular, but are not limited to this and can be changed as appropriate.

[0016] Other components (not shown) may be interposed between the cover body 42 of the module cover 41 and the discharge section 16. Examples of other components include O-rings. The module cover 41 may further have a structure that enhances the airtightness between the discharge section 16 and the cover body 42 at the contact section 47.

[0017] The gas permeable section 44 plays the role of releasing heat and gas discharged from the discharge hole 16a into the space S when the discharge valve is opened. Since the area around the gas permeable section 44 is covered with a heat-shielding covering section 45, it is possible to prevent high-temperature gas generated from one battery cell 11 from coming into contact with other battery cells 11. Therefore, heat diffusion can be suppressed in the event of thermal runaway of a battery cell. Examples of gas permeable materials constituting the gas permeable section 44 include fibrous materials such as nonwoven fabrics, woven fabrics, and knitted fabrics. Nonwoven fabrics are preferred. However, the gas permeable material is not limited to these, and examples of porous materials that can be used include porous films, microporous membranes, stretched polytetrafluoroethylene (ePTFE) membranes, resin foams with open structures, sintered porous bodies of metal or resin, paper / pulp sheets, glass fiber sheets, ceramic sheets, resin meshes, metal meshes, or films with micropores. Furthermore, these materials may be used individually or in layers of two or more.

[0018] The material constituting the heat-shielding coating portion 45 is preferably a laminate having a resin layer containing a flame retardant and a fiber layer. Flame resistance is obtained by including a flame retardant in the resin layer. The fiber layer contributes to improving the strength, rigidity, and impact resistance of the resin layer. Furthermore, the presence of a fiber layer further enhances flame resistance. The resin constituting the resin layer is preferably a thermoplastic resin due to its excellent processability. The thermoplastic resin, flame retardant, and fibers of the resin layer will be described later.

[0019] When the heat-shielding coating portion 45 consists of the laminate, as illustrated in Figure 1, the fiber layer 45b may be located closer to the battery module 21 than the resin layer 45a, or the resin layer 45a may be located closer to the battery module 21 than the fiber layer 45b. Also, as illustrated in Figure 5, the laminate may have the fiber layer 45b located between the resin layers 45a, or the resin layer 45a located between the fiber layers 45b. Among these, the configuration in which the fiber layer 45b is located closer to the battery module 21 than the resin layer 45a, as illustrated in Figure 1, and the configuration in which the fiber layer 45b is located between the resin layers 45a, as illustrated in Figure 5, are preferred. Any other layer may exist between the resin layer 45a and the fiber layer 45b.

[0020] If the gas permeable portion 44 is made of a fibrous material, the fibrous layer 45b of the laminate may be continuous with the heat-shielding coating portion 45 and the gas permeable portion 44, as illustrated in Figures 1 and 5. Alternatively, the fibrous layer 45b of the laminate may not be present in the gas permeable portion 44, and the gas permeable portion 44 may be constructed from a different fibrous material than the fibrous layer 45b.

[0021] In the laminate constituting the heat-shielding coating portion 45, the thickness of the fiber layer is preferably uniform. The thickness of the fiber layer is preferably 0.01 mm or more. If it is 0.01 mm or more, the bonding between the fiber layer and the resin layer will be good, and the fiber layer will be able to support the resin layer even if the resin layer melts due to heat. The thickness of the fiber layer is more preferably 0.05 mm or more, and even more preferably 0.1 mm or more. On the other hand, as an upper limit for the thickness of the fiber layer, from the viewpoint of suppressing the weight of the module cover 41 and cost, it is preferably 5 mm or less, more preferably 2 mm or less, even more preferably 1 mm or less, and particularly preferably 0.5 mm or less.

[0022] In the laminate, the thickness of the resin layer is preferably twice or more the thickness of the fiber layer. When the thickness of the resin layer is twice or more the thickness of the fiber layer, the flame-retardant properties of the laminate are further enhanced. The thickness of the resin layer is more preferably 2.5 times or more the thickness of the fiber layer, even more preferably 5 times or more, particularly preferably 8 times or more, and most preferably 10 times or more. On the other hand, the upper limit of the thickness of the resin layer may be, for example, 50 times or less, 45 times or less, 30 times or less, 20 times or less, or 15 times or less the thickness of the fiber layer.

[0023] In the laminate, from the viewpoint of providing the laminate with even better flame-retardant properties, it is also preferable that the thickness of the resin layer is 70% or more of the total thickness of the resin layer and the fiber layer. From the same viewpoint, it is more preferable that the thickness of the resin layer is 75% or more of the total thickness of the resin layer and the fiber layer, even more preferable that it is 80% or more, and particularly preferable that it is 85% or more. There is no particular upper limit, and for example it may be 98% or less, or 95% or less.

[0024] The laminate does not exclude embodiments having an adhesive layer between the resin layer and the fiber layer. From the viewpoint of improving flame resistance, it is preferable that the resin layer and the fiber layer are directly bonded without the need for other layers. From a similar viewpoint, it is more preferable that the laminate is directly bonded in such a way that at least a portion of the resin composition contained in the resin layer melts and bonds with the fiber layer. It is particularly preferable that the laminate is directly bonded in such a way that at least a portion of the resin composition contained in the resin layer melts and impregnates the fiber layer, thereby bonding with it.

[0025] <Second Embodiment> Figures 3 and 4 show the battery pack of the second embodiment, with Figure 3 being a cross-sectional view and Figure 4 being a plan view of the module cover seen from above. Components identical to those in Figures 1 and 2 are denoted by the same reference numerals, and their descriptions may be omitted. In the first embodiment, a gas permeable portion 44 made of a gas-permeable material was provided, but this embodiment differs in that a through-hole 54 is used as the gas permeable portion. In this embodiment, the through-hole (gas permeable portion) 54 plays the role of releasing heat and gas discharged from the discharge hole 16a when the discharge valve is opened into the space S. Since the area around the through-hole (gas permeable portion) 54 is covered with a heat-shielding coating portion 45, it is possible to prevent high-temperature gas generated from one battery cell 11 from coming into contact with other battery cells 11. Therefore, heat diffusion can be suppressed in the event of thermal runaway of a battery cell.

[0026] <Modification> In the above embodiment, the side where the battery cell 11 discharge portion 16 is located was set to the upper side in the height direction (H), but this is not limited to this. For example, with the battery pack 100 installed in a predetermined position, the height direction (H) of the battery cell 11 may be vertical, horizontal, or any other method.

[0027] In the above embodiment, the shape of the battery cell body is a rectangular parallelepiped having a height direction (H), a width direction (W), and a thickness direction (D), but it is not limited to this. For example, it may be cylindrical with H being the height direction and D being the diameter direction. The shape of the discharge valve and discharge hole 16a in the discharge section 16 is not particularly limited, and any shape can be adopted.

[0028] <Method for Manufacturing Module Covers> Module covers can be manufactured by a molding method using a mold (for example, injection molding). When the module cover consists of a laminate having a resin layer and a fiber layer, the cover body can be molded by a method comprising the steps of inserting a fiber sheet (for example, a glass fiber nonwoven fabric sheet described later) which will become the fiber layer into the mold, filling the mold with resin, and curing the resin in the mold. When the gas permeable portion consists of through holes, the through holes may be drilled after manufacturing the laminate using the method described above, or a fiber sheet with through holes corresponding to the gas permeable portion may be inserted into the mold, and the portion other than the gas permeable portion may be filled with resin and cured. When the gas permeable portion consists of a fiber layer, a continuous fiber sheet may be inserted into the mold, and the portion other than the gas permeable portion may be filled with resin and cured.

[0029] ≪Resin Layer≫ The resin layer constituting the module cover consists of a resin composition comprising (A) a thermoplastic resin and (B) a flame retardant. The resin composition may further contain (C) fibers. Embodiments of the (A) thermoplastic resin, (B) flame retardant, and (C) fibers constituting the resin composition will be described in detail below.

[0030] <(A) Thermoplastic Resin> In this embodiment, there are no particular restrictions on the thermoplastic resin (A) included in the resin composition constituting the resin layer, and examples include polyolefin resin, polycarbonate resin, polyester resin, acrylonitrile styrene resin, ABS resin, polyamide resin, modified polyphenylene oxide, polyvinyl chloride, polystyrene, polyvinyl acetate, polyurethane, etc. One of these may be used, or two or more may be used in combination. For example, the thermoplastic resin (A) may be a composite resin of two or more of the above thermoplastic resins. Of these, polyolefin resin is preferred from the viewpoint of resin properties, versatility, cost, etc., and polypropylene resin is particularly preferred. Furthermore, from the viewpoint of protecting the wiring of the cell by its insulating properties, it is also preferable to use a polybutylene terephthalate resin among polyester resins.

[0031] There are no particular restrictions on the polyolefin resin, and examples thereof include the resins described later. There are no particular restrictions on the polyester resin, and examples thereof include polybutylene terephthalate. There are no particular restrictions on the polyamide resin, and examples thereof include nylon 66 and nylon 6. Among them, this embodiment is particularly useful especially when (A) the thermoplastic resin contains at least a polyolefin resin. In this specification, the "polyolefin resin" means a resin in which the proportion of olefin units or cycloolefin units is 90 mol% or more with respect to 100 mol% of all the constituent units constituting the resin. The proportion of olefin units or cycloolefin units with respect to 100 mol% of all the constituent units constituting the polyolefin resin is preferably 95 mol% or more, and particularly preferably 98 mol% or more.

[0032] Examples of the polyolefin resin include polyethylene, polypropylene, and α-olefin-propylene block or random copolymers having 4 or more carbon atoms. Examples of the polyethylene include low-density polyethylene, linear low-density polyethylene, and high-density polyethylene. Examples of the polypropylene include isotactic polypropylene, syndiotactic polypropylene, hemi-isotactic polypropylene, and stereoblock polypropylene. In the α-olefin-propylene block or random copolymer having 4 or more carbon atoms, examples of the α-olefin having 4 or more carbon atoms include butene, 3-methyl-1-butene, 3-methyl-1-pentene, and 4-methyl-1-pentene. Among these, it is particularly preferable that (A) the thermoplastic resin is a polypropylene-based resin. The polypropylene-based resin will be described in detail later. The above polyolefin resin may be used alone or in combination of two or more.

[0033] (Melt Flow Rate (MFR)) In the present embodiment, the melt flow rate (hereinafter also referred to as "MFR") of the (A) thermoplastic resin contained in the resin layer (at 230 ° C and a load of 2.16 kg) is preferably 5 to 500 g / 10 min. When the MFR is 5 g / 10 min or more, for example, good fluidity can be obtained when producing a module cover by injection molding, and the processability is good. On the other hand, when it is 500 g / 10 min or less, the strength of the module cover becomes sufficient. From the above viewpoints, the MFR is preferably in the range of 10 to 300 g / 10 min, more preferably 20 to 200 g / 10 min, and even more preferably 25 to 100 g / 10 min. Incidentally, the (A) thermoplastic resin can adjust the MFR, for example, by controlling the hydrogen concentration during polymerization. Also, the MFR is a value measured in accordance with JIS K7210-1.

[0034] ((Content of (A) Thermoplastic Resin)) In the present embodiment, the content of the (A) thermoplastic resin in the above resin composition is not particularly limited, but is preferably 15 to 80% by mass. When the content of the (A) thermoplastic resin is 15% by mass or more, the molding processability becomes particularly good, and the molding of the module cover becomes easy. On the other hand, when it is 80% by mass or less, a sufficient amount of (B) flame retardant, (C) fiber, etc. can be contained, and good flame shielding properties can be obtained. From the above viewpoints, the content of the (A) thermoplastic resin in the resin composition is preferably 35 to 70% by mass, and more preferably 40 to 60% by mass. Incidentally, even when the (A) thermoplastic resin is the above-described suitable polypropylene-based resin, the suitable content is the same.

[0035] <(A-1) Polypropylene-Based Resin>In the present embodiment, as the (A) thermoplastic resin constituting the above resin composition, as described above, it is preferable to include the (A-1) polypropylene-based resin. Examples of the (A-1) polypropylene-based resin include a propylene homopolymer or a propylene-α-olefin copolymer. Here, the propylene-α-olefin copolymer may be either a random copolymer or a block copolymer.

[0036] (α-olefins) Examples of α-olefins constituting the above copolymer include ethylene, 1-butene, 2-methyl-1-propene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, 2-ethyl-1-butene, 2,3-dimethyl-1-butene, 2-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 3,3-dimethyl-1-butene, 1-heptene, methyl-1-hexene, dimethyl-1-pentene, ethyl-1-pentene, trimethyl-1-butene, 1-octene, etc. These may be copolymerized with propylene using one type, or two or more types may be copolymerized with propylene. Among these, ethylene or 1-butene is preferred from the viewpoint of improving the impact strength of the module cover, and ethylene is the most preferred.

[0037] (Propylene-ethylene random copolymer) In the case of a random copolymer of propylene and ethylene, it is preferable that it contains 90 to 99.5% by mass of propylene units, more preferably 92 to 99% by mass, and 0.5 to 10% by mass of ethylene units, more preferably 1 to 8% by mass. If the amount of ethylene units is above the lower limit, sufficient impact resistance of the module cover can be obtained, and if it is below the upper limit, sufficient rigidity can be maintained. The content of propylene units and ethylene units in a random copolymer of propylene and ethylene can be adjusted by controlling the composition ratio of propylene and ethylene during polymerization of the random copolymer of propylene and ethylene. Furthermore, the propylene content of a random copolymer of propylene and ethylene is a value measured using a cross-separation device or FT-IR, and the measurement conditions can be, for example, the method described in Japanese Patent Application Publication No. 2008-189893.

[0038] <Modified Polyolefin Resin> In this embodiment, the resin composition may further include a modified polyolefin resin in addition to the (A-1) polypropylene resin. Specifically, examples of modified polyolefin resins include acid-modified polyolefin resins and hydroxy-modified polyolefin resins, which may be used individually or in combination. There are no particular restrictions on the type of acid-modified polyolefin resin and hydroxy-modified polyolefin resin used as the modified polyolefin resin, and conventionally known resins may be used.

[0039] (Acid-modified polyolefin resins) Examples of acid-modified polyolefin resins include those obtained by chemically modifying polyolefins such as polyethylene, polypropylene, ethylene-α-olefin copolymers, ethylene-α-olefin-non-conjugated diene compound copolymers (EPDM, etc.), and ethylene-aromatic monovinyl compound-conjugated diene compound copolymer elastomers by graft copolymerization with an unsaturated carboxylic acid such as maleic acid or maleic anhydride. This graft copolymerization is carried out, for example, by reacting the above polyolefin with an unsaturated carboxylic acid in a suitable solvent using a radical generating agent such as benzoyl peroxide. In addition, the unsaturated carboxylic acid or its derivative component can also be introduced into the polymer chain by random or block copolymerization with a monomer for polyolefins.

[0040] Examples of unsaturated carboxylic acids used for modification include compounds having polymerizable double bonds into which carboxyl groups and, if necessary, functional groups such as hydroxyl groups or amino groups have been introduced, such as maleic acid, fumaric acid, itaconic acid, acrylic acid, and methacrylic acid. Derivatives of unsaturated carboxylic acids include their acid anhydrides, esters, amides, imides, and metal salts. Specific examples include maleic anhydride, itaconic anhydride, methyl acrylate, ethyl acrylate, butyl acrylate, and methyl methacrylate. Of these, maleic anhydride is preferred.

[0041] Preferred acid-modified polyolefin resins include those obtained by graft polymerization of maleic anhydride onto an olefin polymer whose main polymer constituent units are ethylene and / or propylene, and those obtained by copolymerizing an olefin mainly composed of ethylene and / or propylene with maleic anhydride. Specifically, examples include combinations of polyethylene / maleic anhydride-grafted ethylene-butene-1 copolymer, or polypropylene / maleic anhydride-grafted polypropylene.

[0042] (Hydroxy-modified polyolefin resins) Hydroxy-modified polyolefin resins are modified polyolefin resins that contain hydroxyl groups. Hydroxy-modified polyolefin resins may have hydroxyl groups at appropriate locations, for example, at the ends of the main chain or in side chains. Examples of olefin resins constituting hydroxy-modified polyolefin resins include α-olefins alone or copolymers such as ethylene, propylene, butene, 4-methylpentene-1, hexene, octene, nonene, decene, and dodecene, as well as copolymers of the α-olefins with copolymerizable monomers. Examples of preferred hydroxy-modified polyolefin resins include hydroxy-modified polyethylene resins such as low-density, medium-density, or high-density polyethylene, linear low-density polyethylene, ultra-high molecular weight polyethylene, ethylene-(meth)acrylic acid ester copolymers, and ethylene-vinyl acetate copolymers; hydroxy-modified polypropylene resins such as polypropylene homopolymers like isotactic polypropylene, random copolymers of propylene and α-olefins (e.g., ethylene, butene, hexane, etc.), and propylene-α-olefin block copolymers, as well as hydroxy-modified poly(4-methylpentene-1).

[0043] <(B) Flame retardant> In this embodiment, the resin composition constituting the resin layer contains (B) a flame retardant. The (B) flame retardant is not particularly limited and examples include phosphorus-based flame retardants, bromine-based flame retardants, antimony-based flame retardants, etc. Among these, phosphorus-based flame retardants are preferred from the viewpoint of improving flame resistance. Furthermore, in a classification focusing on the mechanism of action of the flame retardant, it is preferable that the (B) flame retardant is an intomessecent flame retardant from the viewpoint of improving flame resistance.

[0044] (Phosphorus-based flame retardants) Phosphorus-based flame retardants are phosphorus compounds, that is, compounds containing a phosphorus atom in their molecule. Phosphorus-based flame retardants exert their flame-retardant effect by forming a char (carbonized film) when the resin composition is burned. Phosphorus-based flame retardants may be known substances, such as (poly)phosphates and (poly)phosphate esters. Here, "(poly)phosphate" refers to a phosphate or polyphosphate, and "(poly)phosphate ester" refers to a phosphate ester or polyphosphate ester. It is preferable that the phosphorus-based flame retardant is solid at 80°C.

[0045] As a phosphorus-based flame retardant, (poly)phosphates are preferred in terms of flame retardancy. Examples of (poly)phosphates include ammonium polyphosphate, melamine polyphosphate, piperazine polyphosphate, piperazine orthophosphate, melamine pyrophosphate, piperazine pyrophosphate, melamine orthophosphate, calcium phosphate, magnesium phosphate, etc. Compounds in which melamine or piperazine is replaced with other nitrogen compounds in the above examples can also be used in the same way. Examples of other nitrogen compounds include N,N,N',N'-tetramethyldiaminomethane, ethylenediamine, N,N'-dimethylethylenediamine, N,N'-diethylethylenediamine, N,N-dimethylethylenediamine, N,N-diethylethylenediamine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetraethylethylenediamine, 1,2-propanediamine, 1,3-propanediamine, and Tramethylenediamine, pentamethylenediamine, hexamethylenediamine, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, trans-2,5-dimethylpiperazine, 1,4-bis(2-aminoethyl)piperazine, 1,4-bis(3-aminopropyl)piperazine, acetoguanamine, benzoguanamine, acrylicguanamine, 2,4-diamino-6-nonyl-1,3 ,5-triazine, 2,4-diamino-6-hydroxy-1,3,5-triazine, 2-amino-4,6-dihydroxy-1,3,5-triazine, 2,4-diamino-6-methoxy-1,3,5-triazine, 2,4-diamino-6-ethoxy-1,3,5-triazine, 2,4-diamino-6-propoxy-1,3,5-triazine, 2,4-diamino-6-isopropoxy-1,3,5-triazine, 2,4-diamino-6- Examples include mercapto-1,3,5-triazine, 2-amino-4,6-dimercapto-1,3,5-triazine, ammeline, benzguanamine, acetoguanamine, phthalodiguanamine, melamine cyanurate, butylenediguanamine, norbornenediguanamine, methylenediguanamine, ethylenedimelamine, trimethylenedimelamine, tetramethylenedimelamine, hexamethylenedimelamine, and 1,3-hexylenedimelamine.These (poly)phosphates may be used individually or in combination of two or more.

[0046] Among the phosphorus-based flame retardants mentioned above, a salt of (poly)phosphoric acid and a nitrogen compound (hereinafter also referred to as "compound (B1)") is preferred. Compound (B1) is an intomessent flame retardant. Intomessent flame retardants are flame retardants that suppress the combustion of materials by forming an intumessent, which prevents radiant heat from the combustion source and the diffusion of combustion gases and smoke from the burning material to the outside. The formation of the intumessent suppresses the diffusion of decomposition products and heat transfer, resulting in excellent flame retardancy. Examples of nitrogen compounds in compound (B1) include ammonia, melamine, piperazine, and the other nitrogen compounds mentioned above. Specifically, examples include ammonium salts and amine salts of (poly)phosphoric acid such as ammonium polyphosphate, melamine polyphosphate, piperazine polyphosphate, ammonium pyrophosphate, melamine pyrophosphate, and piperazine pyrophosphate. Zinc oxide can also be included as a flame retardant aid. This is preferable because it further improves flame retardancy. Examples of commercially available phosphorus-based flame retardants include ADEKA stub FP-2100J, FP-2200, and FP-2500S (manufactured by ADEKA Corporation).

[0047] (Bromine-based flame retardants) Examples of bromine-based flame retardants include decabromodiphenyl ether, tetrabromobisphenol A, tetrabromobisphenol S, 1,2-bis(2',3',4',5',6'-pentabromophenyl)ethane, 1,2-bis(2,4,6-tribromophenoxy)ethane, 2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine, 2,6-dibromophenol, 2,4-dibromophenol, Examples include brominated polystyrene, ethylene bistetrabromophthalimide, hexabromocyclododecane, hexabromobenzene, pentabromobenzyl acrylate, 2,2-bis[4'(2'',3''-dibromopropoxy)-3',5'-dibromophenyl]-propane, bis[3,5-dibromo-4-(2,3-dibromopropoxy)phenyl]sulfone, and tris(2,3-dibromopropyl) isocyanurate.

[0048] (Antimony-based flame retardants) Examples of antimony-based flame retardants include antimony trioxide, antimony tetroxide, antimony pentoxide, sodium pyroantimonate, antimony trichloride, antimony trisulfide, antimony oxychloride, antimony perchloropentane dichloride, and potassium antimonate, with antimony trioxide and antimony pentoxide being particularly preferred.

[0049] Of the above (B) flame retardants, phosphorus-based flame retardants are preferred because they have no biological residue and excellent flame retardancy, and non-halogen-based flame retardants are preferred from an environmental standpoint. Furthermore, intomessent flame retardants are preferred from the viewpoint of improving the flame-retardant properties of the resulting module cover. Note that the above (B) flame retardants can be used individually or in combination of two or more types.

[0050] (Content of (B) Flame retardant) In this embodiment, the content of (B) flame retardant in the resin composition is not particularly limited, but is preferably in the range of 1 to 40% by mass. If it is 1% by mass or more, good flame retardancy can be imparted to the module cover and good flame shielding properties can be obtained. On the other hand, if the content of (B) flame retardant is 40% by mass or less, (A) thermoplastic resin can be included in a sufficient content ratio, so the moldability is better. From the above viewpoint, the content of (B) flame retardant in the resin composition in this embodiment is more preferably in the range of 1 to 35% by mass, even more preferably in the range of 3 to 30% by mass, and particularly preferably in the range of 5 to 25% by mass.

[0051] <(C) Fibers> In this embodiment, the resin composition constituting the resin layer may contain (C) fibers. The (C) fibers may be organic or inorganic fibers, but inorganic fibers are preferred from the viewpoint of heat resistance. Examples include glass fibers, rock wool, basalt fibers, alumina fibers, silica alumina fibers, potassium titanate fibers, calcium silicate (wollastonite) fibers, alkali earth silicate fibers (biosoluble), silica fibers, and other ceramic fibers or metal oxide fibers, carbon fibers, stainless steel fibers, tungsten fibers, and other metal fibers. These inorganic fibers may be used individually or in combination of two or more. Among these inorganic fibers, at least one selected from the group consisting of glass fibers, ceramic fibers such as alumina fibers, metal oxide fibers, and carbon fibers is preferred from the viewpoint of improving heat resistance and flame resistance.

[0052] The (C) fiber described above preferably has an average fiber diameter of 3 to 25 μm. Furthermore, the average fiber length is preferably in the range of 0.05 to 100 mm, more preferably in the range of 0.5 to 50 mm, even more preferably in the range of 1 to 25 mm, and particularly preferably in the range of 2 to 15 mm. When the average fiber length is within the above range, the module cover having a resin layer containing the resin composition exhibits superior mechanical strength (such as bending strength) and superior heat resistance. While not bound by any particular theory, it is believed that when the average fiber length is within the above range, the (C) fiber tends to orient in the resin layer, thus providing the above advantages. Within the above range, the longer the average fiber length, the greater the mechanical strength and heat resistance tend to be. If there are multiple types of fibers, it is sufficient that the average fiber diameter and average fiber length of at least one type of fiber are within the above range.

[0053] The average fiber length of (C) fibers in a resin composition may vary depending on the manufacturing method of the resin layer. For example, when using injection molding, as described later, the resin composition containing (C) fibers is heated and melted, causing the (C) fibers to break and tending to shorten the average fiber length. The above average fiber length refers to the average fiber length in the resin composition and is the fiber length before heat treatment. Therefore, the average fiber length of (C) fibers in a resin layer manufactured by methods such as injection molding is preferably in the range of 0.05 to 50 mm, more preferably in the range of 0.25 to 25 mm, even more preferably in the range of 0.5 to 15 mm, and particularly preferably in the range of 1 to 10 mm. On the other hand, when a laminate having a resin layer is manufactured by lamination, the average fiber length of (C) fibers in the resin composition and the average fiber length of (C) fibers in the resin layer do not change. The fiber diameter can be measured using an optical microscope or the like, and the average fiber diameter can be obtained, for example, by measuring the fiber diameter of 10 randomly selected fibers and calculating the average value. Furthermore, fiber length can be measured using a ruler, calipers, etc., from magnified images obtained with a microscope, etc., as needed. The average fiber length can be obtained, for example, by measuring the fiber length of 10 randomly selected fibers and calculating the average value.

[0054] (Content of (C) fibers) In this embodiment, the content of (C) fibers in the resin composition is not particularly limited, but is preferably in the range of 3 to 60% by mass. When the content of (C) fibers is 3% by mass or more, the strength, rigidity, and impact resistance of the module cover can be ensured. On the other hand, when it is 60% by mass or less, the manufacturing and processing of the module cover can be easily carried out. In addition, when the content of (C) fibers is 60% by mass or less, the specific gravity becomes low, which has the advantage of a greater weight reduction effect as a metal substitute. From the above viewpoint, the content of (C) fibers in the resin composition in this embodiment is more preferably 10 to 50% by mass, even more preferably 20 to 45% by mass, and still more preferably 25 to 40% by mass.

[0055] (Glass Fibers) Glass fibers are one of the inorganic fibers suitable as (C) fibers in the resin composition. The glass fibers may be long fibers with an average fiber length of 30 mm or more, or short fibers (chopped strands) with an average fiber length. More specifically, the average fiber length is preferably in the range of 0.05 to 100 mm. When the average fiber length is within the above range, the strength and impact resistance of the module cover are good. From the above viewpoint, it is more preferable that the range is 0.5 to 50 mm, even more preferable that it is in the range of 1 to 25 mm, and particularly preferable that it is in the range of 2 to 15 mm. In the case of glass fibers as (C) fibers in a resin layer manufactured by methods such as injection molding, the average fiber length is preferably in the range of 0.05 to 50 mm, more preferably in the range of 0.25 to 25 mm, even more preferable that it is in the range of 0.5 to 15 mm, and particularly preferable that it is in the range of 1 to 10 mm. There is no particular upper limit on the average fiber length of the glass fibers. For example, when using pellets manufactured by the plutonization method using glass fibers, the length of the pellet becomes the fiber length of the glass fiber, which is approximately 20 mm at most. In the case of swirl mat systems using long glass fibers, the length of the glass fibers in the roving used for manufacturing becomes the maximum fiber length, which can be as long as 17,000 m (17 km). However, if the fibers are cut to match the size of the laminate, the cut length becomes the maximum fiber length. The average fiber diameter of the glass fibers is preferably in the range of 9 to 25 μm. If the average fiber diameter is 9 μm or more, the rigidity and impact resistance of the module cover will be sufficient, while if the average fiber diameter is 25 μm or less, the strength of the module cover will be good. From this viewpoint, it is even more preferable that the average fiber diameter of the glass fibers be in the range of 10 to 15 μm. The average fiber diameter and average fiber length of the glass fibers can be measured by the method described above. There are no special restrictions on the material of the glass fiber used in this embodiment; it can be alkali-free glass, low-alkali glass, or alkali-containing glass, and various compositions that have been conventionally used as glass fibers can be used.

[0056] <Optional Additives> In this embodiment, in addition to the above components, the resin composition may contain optional additives for purposes such as further improving the effects of the invention or providing other effects, as long as they do not significantly impair the effects of the present invention. Specifically, examples include colorants, light stabilizers, ultraviolet absorbers, nucleating agents such as sorbitol, antioxidants, antistatic agents, neutralizing agents such as inorganic compounds, antibacterial and antifungal agents such as thiazole, flame retardants and flame retardant aids such as halogen compounds and lignophenol, plasticizers, dispersants such as organometallic salts, dispersants that help (B) the flame retardant to disperse well in (A) the thermoplastic resin, lubricants such as fatty acid amides, metal deactivators such as nitrogen compounds, polyolefin resins other than the polypropylene resin, thermoplastic resins such as polyamide resins and polyester resins, elastomers (rubber components) such as olefin elastomers and styrene elastomers. Two or more of these optional additives may be used in combination.

[0057] As colorants, inorganic and organic pigments, for example, are effective in imparting and improving the colored appearance, aesthetics, texture, commercial value, weather resistance, and durability of the resin composition and the module cover having a resin layer composed of the resin composition. Specific examples of inorganic pigments include carbon black such as furnace carbon and Ketjencarbon; titanium dioxide; iron oxide (such as red iron oxide); chromic acid (such as yellow lead); molybdic acid; selenides; ferrocyanides; and organic pigments include azo pigments such as sparingly soluble azo lakes, soluble azo lakes, insoluble azo chelates; condensable azo chelates; and other azo chelates; phthalocyanine pigments such as phthalocyanine blue and phthalocyanine green; slene pigments such as anthraquinone, perinone, perylene, and thioindigo; dye lakes; quinacridone-based pigments; dioxazine-based pigments; and isoindolinone-based pigments. Furthermore, to achieve a metallic or pearlescent finish, aluminum flakes or pearl pigments can be incorporated. Dyes can also be included.

[0058] For example, hindered amine compounds, benzotriazole compounds, benzophenone compounds, and salicylate compounds are effective in providing and improving the weather resistance and durability of the above-mentioned resin composition and the module cover having a resin layer composed of the resin composition, and are effective in further improving weather resistance and discoloration. Specific examples of hindered amine compounds include the condensate of dimethyl succinate and 1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine; poly[[6-(1,1,3,3-tetramethylbutyl)imino-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-piperidyl)imino]hexamethylene[(2,2,6,6-tetramethyl-4-piperidyl)imino]]; tetrakis(2,2,6,6-tetramethyl-4-piperidyl)1,2,3,4-butanetetracarboxylate; tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)1,2,3,4-butanetetracarboxylate; bis(1,2,2,6,6-pentamethyl Examples of light stabilizers include tyl-4-piperidyl sebacate and bis-2,2,6,6-tetramethyl-4-piperidyl sebacate. Benzotriazole-based light stabilizers include 2-(2'-hydroxy-3',5'-di-t-butylphenyl)-5-chlorobenzotriazole and 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole. Benzophenone-based light stabilizers include 2-hydroxy-4-methoxybenzophenone and 2-hydroxy-4-n-octoxybenzophenone. Salicylate-based light stabilizers include 4-t-butylphenyl salicylate and 2,4-di-t-butylphenyl 3',5'-di-t-butyl-4'-hydroxybenzoate. The method of using the above-mentioned light stabilizer and ultraviolet absorber in combination is preferable because it greatly improves weather resistance, durability, and weather-induced discoloration resistance.

[0059] As antioxidants, for example, phenolic, phosphorus-based, and sulfur-based antioxidants are effective in imparting and improving the heat resistance, processing stability, and heat aging resistance of polypropylene resin compositions and their molded articles. Furthermore, as antistatic agents, for example, nonionic and cationic antistatic agents are effective in imparting and improving the antistatic properties of the above-mentioned resin compositions and the resin layers composed of said resin compositions.

[0060] Examples of olefin-based elastomers include ethylene-α-olefin copolymer elastomers such as ethylene-propylene copolymer elastomer (EPR), ethylene-butene copolymer elastomer (EBR), ethylene-hexene copolymer elastomer (EHR), and ethylene-octene copolymer elastomer (EOR); ethylene-α-olefin-diene terpolymer elastomers such as ethylene-propylene-ethylidene norbornene copolymer, ethylene-propylene-butadiene copolymer, and ethylene-propylene-isoprene copolymer; and styrene-butadiene-styrene triblock copolymer elastomer (SBS). Examples of styrene-based elastomers include styrene-isoprene-styrene triblock copolymer elastomer (SIS), styrene-ethylene-butylene copolymer elastomer (SEB), styrene-ethylene-propylene copolymer elastomer (SEP), styrene-ethylene-butylene-styrene copolymer elastomer (SEBS), styrene-ethylene-butylene-ethylene copolymer elastomer (SEBC), hydrogenated styrene-butadiene elastomer (HSBR), styrene-ethylene-propylene-styrene copolymer elastomer (SEPS), styrene-ethylene-ethylene-propylene-styrene copolymer elastomer (SEEPS), styrene-butadiene-butylene-styrene copolymer elastomer (SBBS), partially hydrogenated styrene-isoprene-styrene copolymer elastomer, partially hydrogenated styrene-isoprene-butadiene-styrene copolymer elastomer, and hydrogenated polymer elastomers such as ethylene-ethylene-butylene-ethylene copolymer elastomer (CEBC). In particular, the use of ethylene-octene copolymer elastomer (EOR) and / or ethylene-butene copolymer elastomer (EBR) is preferred because it is easy to impart appropriate flexibility to the module cover according to this embodiment, and it tends to have excellent impact resistance.

[0061] <Method for Manufacturing the Resin Composition> In this embodiment, a conventionally known method can be used to manufacture the above resin composition, and it can be manufactured by blending, mixing, and melt-kneading the above components. Mixing is performed using a mixer such as a tumbler, V-blender, or ribbon blender, and melt-kneading is performed using equipment such as a single-screw extruder, twin-screw extruder, Banbury mixer, roll mixer, Brabender plastograph, or kneader, and the mixture is melt-kneaded and granulated.

[0062] <<Fiber Layer>> The module cover according to this embodiment preferably has a heat-shielding coating made of a laminate having a resin layer and a fiber layer. The fiber layer, together with the resin layer, gives the laminate flame retardancy and fire-shielding properties. From the viewpoint of achieving these effects, it is preferable that the fiber layer is made of fibers (X), and among these, it is preferable that it is a nonwoven fabric layer made of nonwoven fabric, a woven fabric layer made of woven fabric, or a knitted fabric layer made of knitted fabric. Nonwoven fabric is particularly preferable compared to woven fabric or knitted fabric because a part of the resin layer penetrates more easily into the surface of the fiber layer, resulting in higher bonding properties. Nonwoven fabric is also preferable because, since the orientation direction of the fibers is not fixed, there is no directional dependence of mechanical strength.

[0063] The size of the fibers (X) constituting the fiber layer is not limited within the range that achieves the effects of the present invention, but the average diameter of the fibers is preferably in the range of 3 to 25 μm, and the average fiber length is preferably in the range of 5 to 100 mm. If the average fiber diameter is 3 μm or more, handling during the manufacturing process of the fiber layer is easy, and if it is 25 μm or less, breakage is less likely to occur. Furthermore, if the average fiber length is 5 mm or more, the effect of imparting flame resistance to the laminate is excellent, and sufficient strength can be provided. On the other hand, if the average fiber length is 100 mm or less, breakage is less likely to occur. The fiber length can be measured using a ruler, caliper, etc., from an image magnified with a microscope, etc., as needed, and the average fiber length can be obtained, for example, by measuring the fiber length of 10 random fibers and calculating the average value.

[0064] The fibers (X) constituting the fiber layer are not particularly limited as long as they achieve the effects of the present invention, and include inorganic fibers such as glass fibers, carbon fibers, boron fibers, ceramic fibers, metal fibers, and metal oxide fibers, and organic fibers such as aramid fibers and aromatic polyester fibers. Of these, inorganic fibers are preferred in that they provide excellent flame resistance, and among them, glass fibers, ceramic fibers, metal fibers, and metal oxide fibers are preferred, with glass fibers being particularly preferred. As described above, among the fibers (X), at least one selected from the group consisting of glass fibers and aramid fibers is preferred. It is desirable that the laminate used in the module cover has excellent flame resistance. In particular, glass fibers are more preferred as the fibers (X) constituting the fiber layer in that they can withstand flame contact from the fiber layer side constituting the laminate.

[0065] <Nonwoven Fabric Layer> The nonwoven fabric layer is composed of nonwoven fabric. The fibers constituting the nonwoven fabric are not particularly limited as long as they achieve the effects of the present invention, and include inorganic fibers such as glass fibers, carbon fibers, boron fibers, ceramic fibers, metal fibers, and metal oxide fibers, and organic fibers such as aramid fibers and aromatic polyester fibers. Of these, inorganic fibers are preferred because they provide excellent flame resistance, and among them, glass fibers, ceramic fibers, metal fibers, and metal oxide fibers are preferred, with glass fibers being particularly preferred.

[0066] (Glass Fiber Nonwoven Fabric) Examples of glass fiber nonwoven fabrics include felt and blankets processed from short-fiber glass cotton, chopped strand mats processed from continuous glass fibers, swirl mats of continuous glass fibers, and unidirectional aligned mats. Among these, using a glass fiber mat made by needle-punching a swirl mat of continuous glass fibers is preferable because it provides excellent strength and impact resistance to the laminate. The glass fibers are the same as those described above in (C) Fiber.

[0067] The ceramic fiber is preferably composed mainly of silica and alumina, for example, in the range of silica:alumina = 40:60 to 0:100. Specifically, silica-alumina fibers, mullite fibers, and alumina fibers can be used.

[0068] Preferred materials for the metal fibers include those primarily composed of iron, copper, aluminum, nickel, tungsten, titanium, molybdenum, beryllium, platinum, etc. Furthermore, one or more alloying elements other than the above metals, such as carbon, nitrogen, chromium, cobalt, gold, and silver, may also be included. Due to their excellent strength and corrosion resistance, fibers primarily composed of stainless steel, nickel, or titanium are particularly preferred.

[0069] Suitable materials for metal oxide fibers include, for example, alkaline earth metal oxides such as magnesium oxide and calcium oxide; Group 4 metal oxides such as titanium oxide and zirconium oxide; Group 13 element oxides such as alumina and indium oxide; Group 14 element oxides such as silica, tin oxide, and lead oxide; and Group 15 element oxides such as antimony oxide. Among these, Group 13 to Group 15 element oxide fibers are preferred in that they effectively provide a high level of heat resistance, more preferably Group 13 element oxide fibers, and particularly preferably alumina fibers.

[0070] While there are no restrictions on the size of the fibers constituting the nonwoven fabric as long as the effects of the present invention are achieved, the average fiber diameter is preferably in the range of 3 to 25 μm, and the average fiber length is preferably in the range of 5 to 100 mm. If the average fiber diameter is 3 μm or more, handling during the manufacturing process of the nonwoven fabric is easy, and if it is 25 μm or less, breakage is less likely to occur. Furthermore, if the average fiber length is 5 mm or more, flame resistance can be imparted to the laminate, and sufficient strength can be provided. On the other hand, if the average fiber length is 100 mm or less, breakage is less likely to occur. From the above viewpoint, the average fiber length is more preferably in the range of 10 to 50 mm, and even more preferably in the range of 15 to 30 mm. The average fiber length can be measured by the method described above.

[0071] The basis weight (amount of fiber per unit area) of nonwoven fabrics is typically between 10 and 500 g / m². ２ It is preferable that the weight is within this range. ２ With the above conditions, sufficient flame resistance and strength of the laminate can be obtained. On the other hand, 500 g / m ２ The following conditions result in good adhesion with the resin layer, sufficient flame resistance of the laminate, and prevent the weight from becoming excessively large. From this perspective, the basis weight is 20 to 300 g / m². ２ A range of 30 to 150 g / m² is more preferable. ２ A range of 35 to 100 g / m² is more preferable. ２ The range of 35 to 100 g / m² is particularly preferred. ２ Within this range, the basis weight is preferably 35 to 75 g / m². ２ More preferably 35 to 70 g / m ２ More preferably 35 to 45 g / m² ２ While not bound by any particular theory, it is believed that the lower the basis weight, the easier it is for the flame retardant-containing resin composition to penetrate from the resin layer, leading to better overall flame resistance.

[0072] Conventional methods known as the manufacturing method for nonwoven fabrics can be used, such as the dry method, wet method, spunbond method, meltplane method, and airlaid method. Furthermore, known methods such as chemical bonding, thermal bonding, needle punching, and water entanglement can be used to bond the fibers of the nonwoven fabric obtained by these manufacturing methods.

[0073] <Woven Fabric Layer> The woven fabric layer is composed of woven fabric. The fibers constituting the woven fabric are not particularly limited as long as they achieve the effects of the present invention, and the same fibers as those exemplified in the nonwoven fabric layer above can be used. As with the nonwoven fabric layer, inorganic fibers are preferred, and glass fibers are particularly preferred. The size of the fibers constituting the woven fabric (average fiber diameter, average fiber length) and the basis weight are the same as those described for the nonwoven fabric layer. The weave structure of the woven fabric made of the above fibers is not particularly limited and may be plain weave, twill weave, satin weave, etc.

[0074] <Knitted Layer> The knitted layer is composed of knitted fabric. The fibers constituting the knitted fabric are not particularly limited as long as they achieve the effects of the present invention, and the same fibers as those exemplified in the nonwoven fabric layer above can be used. As with the nonwoven fabric layer, inorganic fibers are preferred, and glass fibers are particularly preferred. The size (average fiber diameter, average fiber length) and basis weight of the fibers constituting the knitted fabric are the same as those described for the nonwoven fabric layer. The structure of the knitted fabric made of the above fibers is not particularly limited and may be rib knit, garter stitch, stockinette stitch, etc.

[0075] <Method for Manufacturing the Laminate> The method for manufacturing the laminate according to this embodiment is not particularly limited and various known methods can be used. Specifically, examples include a method in which a resin layer and a fiber layer are formed in advance and then bonded together, or a method in which a fiber layer is set in a mold and a resin composition for forming the resin layer is injected and then injection molded.

[0076] One method of bonding involves preparing a resin sheet to form the resin layer and a glass fiber nonwoven fabric sheet to form the fiber layer, laminating them, and then heating and pressurizing them. More specifically, this method involves press-molding the resin sheet and the glass fiber nonwoven fabric sheet in a mold equipped with a heating device. The heating temperature is preferably 170 to 300°C. If the heating temperature is 170°C or higher, sufficient bonding between the resin layer and the fiber layer is achieved, improving the flame resistance of the laminate. On the other hand, if the heating temperature is 300°C or lower, the resin composition constituting the resin layer does not deteriorate. The pressurizing pressure is preferably 0.1 to 1 MPa. If the pressurizing pressure is 0.1 MPa or higher, sufficient bonding between the resin layer and the fiber layer is achieved, improving the flame resistance of the laminate. On the other hand, if the pressure is 1 MPa or lower, burrs do not form on the resin layer. When bonding the resin layer and the fiber layer, an adhesive layer can also be placed between the resin layer and the fiber layer. However, in this embodiment, since the bonding between the resin layer and the fiber layer is important, it is preferable that the resin layer and the fiber layer are directly bonded without any other layers in between. The cooling temperature is not particularly limited as long as it is below the freezing point of the thermoplastic resin, but if the cooling temperature is 80°C or lower, the resulting molded body (module cover) will not deform when removed. From this viewpoint, the cooling temperature is preferably room temperature to 80°C. A laminated sheet may be manufactured by lamination, in which a resin sheet and a glass fiber nonwoven fabric sheet are heated and pressurized by passing them between two pairs of rollers equipped with a heating device, and this laminated sheet may be used as part of the module cover. Lamination is preferable because it allows for continuous production and has good productivity.

[0077] As a method for manufacturing a laminate by injection molding, for example, a method may be used in which a glass nonwoven fabric, which will become the fiber layer, is set in a movable mold, the movable mold is fitted into a fixed mold to form a cavity, and a resin composition is injected into the cavity to integrally mold the resin composition and the glass nonwoven fabric (fiber layer). By this method, a laminate can be obtained in which the fiber layer is laminated on one side of the resin layer. When this injection molding method is used, the long fibers in the glass nonwoven fabric are less likely to break, so the flame-retardant properties of the laminate can be further improved.

[0078] The effects of the present invention will be explained below with reference to examples, but the present invention is not limited to the configurations of the examples.

[0079] Example 1: A module cover as shown in Figure 1 was fabricated. It is composed of a laminate having a resin layer and a fiber layer.

[0080] (Resin layer) The resin composition forming the resin layer was obtained with the following composition. • Polypropylene resin ((A) Thermoplastic resin) Manufactured by Nippon Polypropylene Co., Ltd., "Novatec® BC03B" (Melt flow rate: 30g / 10min) • Flame retardant ((B) Flame retardant) Phosphorus-based flame retardant (Manufactured by ADEKA Corporation, Adeka Stab FP-2500S, non-halogen intomescent flame retardant) • Dispersant α-olefin / maleic anhydride copolymer (Manufactured by Mitsubishi Chemical Corporation, Diacarna 30M, weight-average molecular weight 7,800) • Glass fiber reinforced thermoplastic resin (Polypropylene resin ((A) Thermoplastic resin) / Glass fiber ((C) Fiber)) = 50 / 50, Pellet length 10mm, Manufactured by Nippon Polypropylene Co., Ltd., "Funkstar®") • Antioxidant / Phenol-based antioxidant (Manufactured by ADEKA Corporation, Adeka Stab AO-60) - Phosphate-based antioxidant (ADEKA Corporation, ADEKA Stab 2112) The above components were mixed in the ratios shown in Table 1 below to prepare the resin composition.

[0081] The ratio of the antioxidants, specifically the phenolic antioxidant and the phosphite antioxidant, was 0.007 parts by mass per 100 parts by mass of the resin composition.

[0082] (Fiber layer) Glass nonwoven fabric (manufactured by Olivest Co., Ltd., FAP-110, basis weight 110 g / m²) ２ A material with a thickness of 0.77 mm was used.

[0083] (Manufacturing of Laminate) A resin composition having the above composition was laminated onto the fiber layer using a FANUC ROBOSHOT α-S300iA injection molding machine manufactured by FANUC Corporation to produce a laminate. (Manufacturing of Module Cover) A SUS spacer measuring 20 mm (D) × 20 mm (W) × 1.4 mm (H) was placed in a mold, a glass nonwoven fabric with a thickness of 0.77 mm was placed on top of it, and then a resin composition with the formulation shown in Table 1 was injection molded on top of that to obtain a module cover measuring 200 mm in length × 200 mm in width × 2.0 mm in thickness. In the module cover of this embodiment, a gas permeable portion 44 is located above the battery cell discharge hole 16a.

[0084] Example 2 A module cover measuring 200 mm in length, 200 mm in width, and 2.0 mm in thickness was fabricated by placing a glass nonwoven fabric with a thickness of 0.77 mm inside a mold and then injection molding a resin composition with the formulation shown in Table 1 onto it. A 20 mm (D) x 20 mm (W) hole was then punched out on top of the cover to obtain a perforated module cover. In the module cover of this example, as shown in Figure 2, a through hole 54 is present above the battery cell discharge hole 16a.

[0085] The molding conditions in Example 1 and Example 2 are as follows: 1) Temperature conditions: Cylinder temperature (220°C), mold temperature (60°C) 2) Injection conditions: Injection pressure (200 MPa), holding pressure (82 MPa) 3) Metering conditions: Screw rotation speed (50 rpm), back pressure (15 MPa)

[0086] A module cover measuring 200 mm in length, 200 mm in width, and 2.0 mm in thickness was obtained by placing a glass nonwoven fabric with a thickness of 0.77 mm inside a comparative example mold and then injection molding a resin composition with the formulation shown in Table 1 onto it. The module cover of this comparative example does not have the gas permeable portion that is present in Example 1, nor the through-hole that is present in Example 2. The molding conditions in the comparative example are the same as those in the examples.

[0087] For the evaluation of flame resistance, the module covers obtained in Example 1, Example 2, and Comparative Example were subjected to a 1200°C burner flame, and the temperature between the module cover 41 and the SUS plate (lid 31) was measured for up to 200 seconds, as shown in Figure 6. From the results, the cumulative heat flux up to 100 seconds and the cumulative heat flux up to 200 seconds, calculated using Equation 1, are shown in Table 2 below.

[0088]

[0089] Here, U represents the heat transfer coefficient, and assuming natural heat convection, U = 10 W / m ２ Let K be the value. Tm represents the measured temperature between the module cover and the SUS plate. Ts represents the measured room temperature, and Ts = 20°C. The cumulative heat flux up to n seconds, expressed in Equation 1, relatively represents the amount of heat per unit area transferred from the high-temperature air heated by the burner to the SUS plate on the back side of the module cover.

[0090] The combined composition (in mass%) of the module cover, including the resin layer and the fiber layer, is shown in Table 2.

[0091]

[0092] Evaluation of Temperature Rise Suppression Effect The following simulations were performed to evaluate the temperature rise suppression effect of the module cover on the top surface of the cells, as obtained in Example 1, Example 2, and Comparative Example. As a reference example, the temperature change during thermal runaway of a battery pack without a module cover was also simulated.

[0093] <Battery Cell> The simulation targeted a fluid domain consisting of air composition and a solid domain consisting of components constituting the battery module (case / jelly roll / terminals / terminal cover / bus bar / tension plate / end plate / inter-cell spacer / module cover). Using a fluid-solid coupled scheme, the transient temperature changes of the fluid and solid domains during high-temperature gas ejection due to cell thermal runaway were calculated. The simulation was performed using computational fluid dynamics software (product name: STAR-CCM+ Ver. 2410, Siemens).

[0094] <Battery Cell and High-Temperature Gas Ejection Conditions> The cell dimensions were set to a height of 122 mm, a width of 26.9 mm, and a depth of 148.2 mm, including the case thickness of 1.0 mm. The jelly roll portion inside the cell was given an anisotropic thermal conductivity derived from the electrode stacking structure, and calculations were performed assuming a battery cell with a jelly roll portion in the half-cut model shown in Figures 7A to 7D. Figure 7A is a perspective view of the battery pack of Example 1 (with module cover, gas permeable portion 44 above the discharge hole 16a), Figure 7B is a perspective view of the battery pack of Example 2 (with module cover, through hole 54 above the discharge hole 16a), Figure 7C is a perspective view of the battery pack of the comparative example (with module cover, gas permeable portion 44 and through hole 54 are not present above the discharge hole 16a), and Figure 7D is a perspective view of the battery pack of the reference example (without module cover).

[0095] The calculation was performed assuming that during thermal runaway, a high-temperature gas at 727°C and a flow rate of 0.02 kg / s is ejected for 10 seconds from the left end vent of the battery pack shown in Figures 7A to 7D. The initial temperature of each component constituting the module and the gas inside the pack was assumed to be 23°C. An outlet pressure boundary was set at the right end of the battery pack shown in Figures 7A to 7D, so that the gas inside the pack is discharged from the system according to the pressure difference created by the ejection of the high-temperature gas. Note that these conditions are intended to analyze heat transfer via the high-temperature gas generated during cell thermal runaway, and internal heat generation of the thermal runaway cell is omitted. It was assumed that the air inside the pack is separated from the outside air by the pack, and the air inside the pack / pack interface has an outside air temperature of 20°C and a heat transfer coefficient of 10 W / m ２ - Natural convection boundary conditions were used for K. The half-cut surface was a symmetric boundary. In the gas permeable section (vented nonwoven fabric) in Figure 7A, a porous baffle with a porosity of 0.4 that provides fluid resistance was set.

[0096] The physical properties used for each component in the calculations are shown in Table 3. Note that x in the table represents temperature [K].

[0097]

[0098] Table 4 below shows the results of calculations assuming that the battery packs obtained in Example 1, Example 2, Comparative Example, and Reference Example, as shown in Figures 7A to 7D, experience thermal runaway. The "maximum temperature of cases other than the thermal runaway cell" for each condition was calculated.

[0099]

[0100] Furthermore, Figure 8 shows the temperature distribution contour plot obtained as a calculation result 10 seconds after high-temperature gas ejection. Figure 8A is the temperature distribution contour plot under the conditions used in Example 1, Figure 8B is the temperature distribution contour plot under the conditions used in Example 2, Figure 8C is the temperature distribution contour plot under the conditions used in the comparative example, and Figure 8D is the temperature distribution contour plot under the conditions used in the reference example.

[0101] In the battery pack using the module cover of Example 1, the temperature rise of the case can was suppressed. This is thought to be because high-temperature gas was released into the pack from the vent, and heat transfer from the high-temperature gas inside the pack was inhibited by the module cover and nonwoven fabric on the top surface of the case cans of cells other than the thermally runaway cells. In the battery pack using the module cover of Example 2, the temperature rise of the case can was suppressed, but the effect of suppressing the temperature rise was smaller than in Example 1. This is thought to be because high-temperature gas was released into the pack from the vent, and heat transfer from the high-temperature gas inside the pack was inhibited by the module cover on the top surface of the case cans of cells other than the thermally runaway cells, while heat exchange occurred between the high-temperature gas that passed through the perforations of the module cover and the case can. In the battery pack using the module cover of the Comparative Example, the case can became hotter. This is thought to be because the high-temperature gas filled the narrow space between the module cover and the top surface of the cells, and the high-temperature gas, at a higher temperature and flow rate, came into contact with the top surface of the cells and exchanged heat. In the Reference Example without a module cover, the case cans of cells other than the thermally runaway cells became hotter. This is thought to be because the top surface of the cell was heated by high-temperature gas.

[0102] In the temperature distribution contour diagram in Figure 8, black areas represent high temperatures and white areas represent low temperatures. In the comparative example (Figure 8C) and reference example (Figure 8D), the upper part of the cell is black and represents a high temperature, while in Example 1 (Figure 8A) and Example 2 (Figure 8B), the upper part of the cell is white to gray and represents a low temperature. From the evaluation of the temperature rise suppression effect, it is clear that the module cover of the present invention provides an effect of suppressing heat transfer from the top surface of the cell when high-temperature gas is ejected due to cell thermal runaway.

[0103] 11 Battery cell 12 Cell body 14 Top surface (end face) 16 Discharge section 16a Discharge hole 21 Battery module 30 Housing 31 Cover 32 Side plate 33 Bottom plate 34 Spacer 35 Cushioning material 41 Module cover 42 Cover body 44 Gas permeable section 45 Heat shielding coating section 45a Resin layer 45b Fiber layer 47 Adhesion section 54 Through hole (gas permeable section) 100 Battery pack

Claims

1. A module cover disposed between a battery module, which is an assembly of multiple battery cells, and a housing that houses the battery module, wherein each battery cell has a cell body and a discharge section equipped with a discharge valve that opens when the internal pressure of the cell body exceeds a set pressure, and the module cover has a cover body that covers the multiple battery cells, and the cover body has a gas permeable section provided above the discharge section and a heat-shielding covering section that does not allow gas to pass through, so as to cover at least a part of the discharge section.

2. The module cover according to claim 1, wherein the gas permeable portion is a through hole.

3. The module cover according to claim 1, wherein the gas permeable portion is made of a nonwoven fabric.

4. The module cover according to claim 1, wherein the heat-shielding covering portion is made of a laminate having a resin layer containing a flame retardant and a fiber layer.

5. The module cover according to claim 4, wherein the fiber layer is continuous with the heat-shielding coating portion and the gas permeable portion.

6. A battery pack comprising a battery module, which is a collection of multiple battery cells, housed in a housing, wherein a module cover according to any one of claims 1 to 5 is disposed between the housing and the battery module.

7. The battery pack according to claim 6, wherein the housing has exhaust holes.

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