Composite film, preparation method thereof and battery pack

Abstract

The invention discloses a composite film, a preparation method thereof and a battery pack, relates to the technical field of batteries, and aims to solve the problem of warping of an adhesive film. The composite film comprises a substrate layer and a functional layer which are stacked and connected. The functional layer is at least used for providing a heat-insulating function. Wherein the moisture absorption rate of the material of the substrate layer under the preset condition is smaller than a first set threshold value, and the first set threshold value is used for controlling the deformation condition of the substrate layer under the moisture absorption condition. The moisture absorption rate of the material of the functional layer under the preset condition is smaller than a second set threshold value; the second set threshold value is used for controlling the deformation condition of the functional layer under the moisture absorption condition. The second set threshold value is smaller than the first set threshold value.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a composite film and a preparation method thereof, and a battery pack. Background Art

[0002] With the rapid development of new energy vehicles and the continuous improvement of vehicle integration, the safety requirements of power battery systems are increasing; therefore, the high temperature electrolyte insulation performance of various components in the battery pack needs to be improved. At present, insulating films such as polyimide films and related adhesive films are commonly used to improve the high temperature electrolyte insulation performance of various components in the battery pack, but there is a problem that the insulating film is prone to warping. Summary of the invention

[0003] The purpose of the present application is to provide a composite film and a preparation method thereof, and a battery pack, aiming to solve the problem of easy warping of the insulating film.

[0004] In order to achieve the above objectives, this application adopts the following technical solutions:

[0005] In a first aspect, the present application provides a composite film, which comprises: a base layer and a functional layer which are stacked and connected, wherein the functional layer is used to provide at least a heat insulation function.

[0006] Wherein, the moisture absorption rate of the material of the base layer under preset conditions is less than a first set threshold value, and the first set threshold value is used to control the deformation of the base layer under moisture absorption conditions.

[0007] The moisture absorption rate of the material of the functional layer under preset conditions is less than a second set threshold value; the second set threshold value is used to control the deformation of the functional layer under moisture absorption conditions. The second set threshold value is less than the first set threshold value.

[0008] In the composite film provided in the embodiment of the present application, the base layer can provide support for the functional layer, and the heat insulation function of the functional layer can make the composite film have better heat insulation performance, preventing the performance of the object to be isolated from changing due to high temperature. The material of the base layer has a low moisture absorption rate, so that the base layer can better resist the influence of changes in environmental humidity on its shape and size, thereby maintaining a high dimensional stability. The material of the functional layer has a low moisture absorption rate, so that the functional layer can better resist the influence of changes in environmental humidity on its shape and size, thereby maintaining a high dimensional stability. Moreover, the functional layer has a lower moisture absorption rate than the base layer, which can make the part of the composite film that performs the heat insulation function better maintain the stability of size and shape when the environmental humidity changes, and is not prone to expansion or contraction, which helps to improve the overall dimensional stability of the composite film, reduce deformation caused by humidity changes, and prevent the composite film from warping.

[0009] In some embodiments, the first set threshold is 0.35%.

[0010] In some embodiments, the second set threshold is 0.25%.

[0011] In some embodiments, the heat deformation temperature of the functional layer is greater than or equal to 260°C.

[0012] In some embodiments, the size of the base layer along the first direction ranges from 100 μm to 300 μm; the first direction is the direction in which the base layer and the functional layer are layered.

[0013] In some embodiments, a size of the functional layer along a first direction ranges from 25 μm to 150 μm; the first direction is a direction in which the base layer and the functional layer are layered.

[0014] In some embodiments, the material of the base layer includes polyethylene terephthalate.

[0015] In some embodiments, the material of the functional layer includes: polyphenylene sulfide.

[0016] In some embodiments, the composite film further includes: a first adhesive layer disposed between the base layer and the functional layer.

[0017] In some embodiments, the shear strength of the first adhesive layer is greater than 8 MPa.

[0018] In some embodiments, the pull-out strength of the first adhesive layer is greater than 8 MPa.

[0019] In some embodiments, the size of the first adhesive layer along the first direction is smaller than the size of the base layer along the first direction. The first direction is the direction in which the base layer and the functional layer are layered.

[0020] In some embodiments, a dimension of the first adhesive layer along the first direction ranges from 20 μm to 40 μm.

[0021] In some embodiments, the material of the first adhesive layer includes: any one of epoxy resin glue and polyester glue.

[0022] In some embodiments, the materials for forming the epoxy resin glue include: 80 to 120 parts by weight of a first resin, 40 to 80 parts by weight of a first curing agent, and 1 to 10 parts by weight of a first auxiliary agent.

[0023] In some embodiments, the first resin includes at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, and epoxy alcohol.

[0024] In some embodiments, the first curing agent includes at least one of hydrazide, imidazole compound, boron trifluoride monoethylamine complex, aromatic amine, acid anhydride and polyphenol.

[0025] In some embodiments, the first auxiliary agent includes at least one of a first toughening agent, a first plasticizer, a first filler, a first leveling agent, a first defoaming agent, a first wetting agent, a first dispersant, a first thermal stabilizer, a first anti-settling agent, and a first anti-skinning agent.

[0026] In some embodiments, the materials for forming the polyester glue include: 80 to 120 parts by weight of unsaturated polyester resin, 1 to 10 parts by weight of a second curing agent, and 1 to 20 parts by weight of a second auxiliary agent.

[0027] In some embodiments, the second curing agent includes at least one of benzoyl peroxide and styrene.

[0028] In some embodiments, the second auxiliary agent includes at least one of a second toughening agent, a second plasticizer, a second leveling agent, a second defoaming agent, a second wetting agent, a second dispersant, a second thermal stabilizer, a second anti-settling agent, and a second anti-skinning agent.

[0029] In some embodiments, the composite film further comprises: a second adhesive layer and a release film which are stacked. The second adhesive layer and the release film are located on a side of the functional layer away from the base layer. The second adhesive layer is closer to the functional layer than the release film.

[0030] In some embodiments, the shear strength of the second adhesive layer is greater than 1.5 MPa.

[0031] In some embodiments, the second adhesive layer has an adhesive peeling force to the aluminum plate greater than 0.6 N / mm.

[0032] In some embodiments, the material of the second adhesive layer includes: a first acrylate pressure-sensitive adhesive. The material forming the first acrylate pressure-sensitive adhesive includes: 50 to 120 parts by weight of acrylate resin monomer, 5 to 20 parts by weight of a first tackifier, 1 to 10 parts by weight of a first cross-linking agent, 0.05 to 0.1 parts by weight of a first initiator, 80 to 160 parts by weight of a first solvent, and 1 to 10 parts by weight of a third auxiliary agent.

[0033] In some embodiments, the acrylic resin monomer includes a first monomer, a second monomer and a functional monomer. The mass ratio of the first monomer, the second monomer and the functional monomer is in the range of (60-70): (20-40): (5-20). The first monomer includes at least one of isooctyl acrylate, butyl acrylate and ethyl acrylate.

[0034] In some embodiments, the second monomer includes at least one of methyl methacrylate, vinyl acetate, acrylonitrile, acrylamide, and styrene.

[0035] In some embodiments, the functional monomer includes at least one of acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate.

[0036] In some embodiments, the first initiator includes at least one of dibenzoyl peroxide and azobisisobutyronitrile.

[0037] In some embodiments, the third auxiliary agent includes at least one of a second filler, a third leveling agent, a third defoaming agent, a third wetting agent, a third dispersant, a third thermal stabilizer, a third anti-settling agent, and a third anti-skinning agent.

[0038] In some embodiments, the first tackifier includes at least one of anatase resin, a natural resin, and a synthetic resin.

[0039] In some embodiments, the first cross-linking agent includes at least one of tris(methacrylamide)triazine, epoxy acrylate, benzoyl peroxide, polyisocyanate, and amino resin.

[0040] In some embodiments, the material of the second adhesive layer includes: a second acrylic pressure-sensitive adhesive. The material forming the second acrylic pressure-sensitive adhesive includes: a prepolymer, a first acrylic monomer, a first photosensitizer, and a fourth auxiliary agent. The mass ratio of the prepolymer, the first acrylic monomer, the first photosensitizer, and the fourth auxiliary agent is in the range of: (50-60): (90:110): (0.2-2.2): (5-20).

[0041] In some embodiments, the prepolymer is formed of materials including: a second acrylic monomer, an inorganic filler, and a second initiator. The first acrylic monomer and / or the second acrylic monomer includes: at least one of ethylhexyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, butanediol diacrylate, butanediol diacrylate, hexanediol diacrylate, and trimethylolpropane triacrylate.

[0042] In some embodiments, the inorganic filler includes at least one of powdered silica gel and hollow glass fiber clusters.

[0043] In some embodiments, the second initiator is at least one of azobisisobutyronitrile and dibenzoyl peroxide.

[0044] In some embodiments, the fourth auxiliary agent includes at least one of a second cross-linking agent, a third curing agent, a third filler, a fourth leveling agent, a second tackifier, a fourth defoaming agent, an anti-aging agent, and an inhibitor.

[0045] In some embodiments, the first photosensitizer includes at least one of benzoin ether and acetophenone.

[0046] In some embodiments, the third curing agent includes at least one of chlorinated paraffin and chlorinated aromatic ether.

[0047] In some embodiments, the second cross-linking agent includes at least one of ethylene glycol diacrylate, trimethylolpropane triacrylate, and a triazine compound.

[0048] In a second aspect, the present application provides a method for preparing a composite film. The method for preparing the composite film comprises:

[0049] A base layer and a functional layer are formed which are stacked and connected, and the functional layer is used to provide at least a heat insulation function.

[0050] Wherein, the moisture absorption rate of the material of the base layer under preset conditions is less than a first set threshold value, and the first set threshold value is used to control the deformation of the base layer under moisture absorption conditions.

[0051] The moisture absorption rate of the material of the functional layer under preset conditions is less than a second set threshold value; the second set threshold value is used to control the deformation of the functional layer under moisture absorption conditions. The second set threshold value is less than or equal to the first set threshold value.

[0052] It can be understood that the beneficial effects that can be achieved by the composite membrane prepared by the composite membrane preparation method provided in the above embodiments of the present application can refer to the beneficial effects of the composite membrane mentioned above, which will not be repeated here.

[0053] In some embodiments, forming the stacked and connected base layer and functional layer includes: using a cast co-extrusion process to co-extrude the material of the base layer and the material of the functional layer.

[0054] In some embodiments, forming a stacked and connected base layer and functional layer includes: using a lamination process to fix and fit the base layer and the functional layer.

[0055] In some embodiments, forming a stacked and connected base layer and functional layer includes:

[0056] Forming the base layer.

[0057] A first adhesive layer is formed on the base layer. And,

[0058] The functional layer is attached to the side of the first adhesive layer that is away from the substrate layer.

[0059] In some embodiments, the method for preparing the composite membrane further comprises:

[0060] The second adhesive layer is connected to the side of the functional layer facing away from the substrate layer.

[0061] The side of the second adhesive layer away from the functional layer is covered with a release film.

[0062] In a third aspect, the present application further provides a battery pack. The battery pack comprises: a battery pack component and a composite film as described in any one of the above embodiments. The functional layer is closer to the battery pack component than the base layer.

[0063] It can be understood that the beneficial effects that can be achieved by the battery pack provided in the above embodiments of the present application can refer to the beneficial effects of the composite film mentioned above, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0065] Figure 1 Schematic diagram of the application of composite membranes in some embodiments;

[0066] Figure 2 Schematic diagram of the application of composite membranes in some other embodiments;

[0067] Figure 3 Schematic diagram of a composite membrane in some embodiments;

[0068] Figure 4 Schematic diagrams of composite membranes in some other embodiments;

[0069] Figure 5 The present invention is a flow chart of the preparation method of the composite membrane provided in some embodiments.

[0070] Reference numerals: 10 - composite film, 11 - base layer, 12 - functional layer, 13 - first adhesive layer, 14 - second adhesive layer, 15 - release film. DETAILED DESCRIPTION

[0071] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0072] In the description of this application, it should be understood that the terms "upper", "lower", "left", "right", "front", "back", "inside", "outside", etc. indicate directions or positional relationships based on the directions or relative positional relationships shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on this application. Unless otherwise specified, the above-mentioned directional description can be flexibly set in the process of actual application under the condition that the relative positional relationship shown in the accompanying drawings is met.

[0073] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0074] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection. It can be directly connected, or indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0075] In the present application, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, article or device. In the absence of further restrictions, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the process, article or device including the element.

[0076] In the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0077] In the description of this specification, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0078] The present application provides a battery pack. The battery pack includes: battery pack parts and a composite film 10. When in use, structural adhesive or thermal conductive structural adhesive can be applied on one or both sides of the composite film 10 according to needs, and then pasted on the battery pack parts that need to be resistant to high temperature and electrolyte insulation protection.

[0079] Exemplarily, battery pack parts may be cold plates, trays, upper covers, expansion beams, and the like.

[0080] like Figure 1 and Figure 2 As shown, a composite film 10 is disposed at a relatively flat position on the battery pack parts. The composite film 10 can serve as an additional barrier to protect the battery pack parts, which is beneficial to the quality control of finished products and promotes production yield and speed.

[0081] Therefore, the performance of the composite film 10 is very important. At present, the commonly used high temperature and electrolyte resistant insulating materials in battery packs are polyimide films and related adhesive films, but polyimide film products are expensive. After being placed at room temperature, the polyimide film will warp, affecting its performance. It is urgent to find an insulating film material that is both resistant to high temperature and electrolyte.

[0082] The inventors of the present application have found through research that polyimide film is easy to absorb moisture and is more likely to warp after absorbing moisture, so moisture absorption of the material is one of the causes of warping.

[0083] Based on this, Figure 3 As shown, the present application provides a composite film 10. The composite film 10 comprises: a stacked and connected substrate layer 11 and a functional layer 12. The functional layer 12 is at least used to provide a heat insulation function.

[0084] The base layer 11 provides support for the composite film 10 , and the heat insulation function of the functional layer 12 can make the composite film 10 have better heat insulation performance, thereby preventing the performance of the object to be isolated from being affected by high temperature and changing.

[0085] The moisture absorption rate of the material of the base layer 11 under preset conditions is less than the first set threshold value, and the first set threshold value is used to control the deformation of the base layer under moisture absorption conditions. In other words, the moisture absorption rate of the material of the base layer 11 is low, so that the base layer 11 can better resist the influence of environmental humidity changes on its shape and size, thereby maintaining a high dimensional stability.

[0086] The moisture absorption rate of the material of the functional layer 12 under preset conditions is less than the second set threshold value; the second set threshold value is used to control the deformation of the functional layer under moisture absorption conditions. In other words, the moisture absorption rate of the material of the functional layer 12 is low, so that the functional layer 12 can better resist the influence of environmental humidity changes on its shape and size, thereby maintaining a high dimensional stability.

[0087] For example, the preset condition may be a condition where the temperature is 85° C. and the humidity is 85%.

[0088] Moreover, the second set threshold is less than the first set threshold, indicating that the functional layer 12 has a lower moisture absorption rate than the base layer 11, which can make the part of the composite film 10 that performs the heat insulation function better maintain the stability of size and shape when the ambient humidity changes, and is not prone to expansion or contraction, which helps to improve the overall dimensional stability of the composite film 10, reduce deformation caused by humidity changes, and prevent the composite film 10 from warping.

[0089] In some embodiments, the first set threshold is 0.35%.

[0090] It can be understood that the moisture absorption rate of the material of the base layer 11 is less than 0.35%, which means that the moisture absorption rate of the base layer 11 under preset conditions is controlled at a low level, so that the expansion or contraction stress of the base layer 11 due to moisture absorption is small, thereby reducing the risk of deformation of the base layer 11, helping to maintain the overall flatness and shape accuracy of the composite film 10 and preventing it from warping.

[0091] In some embodiments, the second set threshold is 0.25%.

[0092] It can be understood that the moisture absorption rate of the material of the functional layer 12 is less than 0.25%, which means that the moisture absorption rate of the functional layer 12 under preset conditions is controlled at a low level, so that the expansion or contraction stress of the functional layer 12 due to moisture absorption is small, thereby reducing the risk of deformation of the functional layer 12. The moisture absorption rate of the functional layer 12 helps to maintain the overall flatness and shape accuracy of the composite film 10 and prevent it from warping; moreover, the lower moisture absorption rate of the functional layer 12 greatly reduces the impact on the thermal conductivity of the functional layer 12, ensuring the long-term stability of its thermal insulation performance.

[0093] In some embodiments, the heat deformation temperature of the functional layer 12 is greater than or equal to 260°C.

[0094] For example, the thermal deformation temperature of the functional layer 12 may be 260° C., 280° C., 300° C., 320° C., or 340° C., etc., which is not limited herein.

[0095] It can be understood that, as a part of the composite film 10 , the setting of the heat deformation temperature of the functional layer 12 being greater than or equal to 260° C. helps to improve the high temperature resistance and overall stability of the entire composite film 10 .

[0096] In some embodiments, Figure 3 As shown, the dimension D1 of the base layer 11 along the first direction Y ranges from 100 μm to 300 μm. The first direction Y is the direction in which the base layer 11 and the functional layer 12 are disposed.

[0097] Exemplarily, a dimension D1 of the base layer 11 along the first direction Y may be 100 μm, 150 μm, 175 μm, 200 μm, 250 μm or 300 μm, etc., which is not limited here.

[0098] It can be understood that setting the dimension D1 of the base layer 11 along the first direction Y within a range of 100 μm to 300 μm can improve the supporting performance of the base layer 11 .

[0099] In some embodiments, Figure 3 As shown, the dimension D2 of the functional layer 12 along the first direction Y ranges from 25 μm to 150 μm. The first direction Y is the direction in which the base layer 11 and the functional layer 12 are layered.

[0100] For example, the dimension D2 of the functional layer 12 along the first direction Y may be 25 μm, 45 μm, 65 μm, 115 μm or 150 μm, etc., which is not limited here.

[0101] It can be understood that setting the dimension D2 of the functional layer 12 along the first direction Y within a range of 25 μm to 150 μm can improve the heat insulation performance of the functional layer 12 .

[0102] In some embodiments, the material of the base layer 11 includes polyethylene terephthalate.

[0103] It is understandable that polyethylene terephthalate (PET) has excellent mechanical properties, including high rigidity, high hardness, good impact resistance and folding resistance, so that when PET is used as the base layer 11, it can provide stable support and ensure the overall structural strength of the composite film 10. In addition, PET is resistant to oil, fat, olefinic acid, dilute alkali and most solvents, can remain stable in a variety of complex environments, and is not easily corroded by chemical substances. PET has a low gas and water vapor permeability, so that PET can effectively prevent the penetration of gas and water. Therefore, the base layer 11 uses polyethylene terephthalate as a material, which can improve the overall performance of the composite film 10.

[0104] In some embodiments, the material of the functional layer 12 includes polyphenylene sulfide.

[0105] It can be understood that polyphenylene sulfide (PPS film) has high heat resistance, and its melting point is as high as 281°C; PPS film can resist erosion by sulfuric acid, hydrochloric acid, phosphoric acid, hydrofluoric acid, sodium hydroxide, potassium hydroxide, hydrogen peroxide, etc., and has good corrosion resistance; moreover, PPS film has good moisture resistance, and the moisture absorption rate of PPS film is only 0.05% under the condition of 75% humidity, so that PPS film can still maintain its dimensional stability in a humid environment. Moreover, PPS film will not deteriorate in high-temperature steam, and will not hydrolyze, which further proves its excellent moisture resistance. Therefore, the functional layer 12 uses polyphenylene sulfide as the material, which can significantly improve the moisture resistance of the composite film 10, prevent the composite film 10 from warping, and also have high temperature resistance and electrolyte corrosion resistance.

[0106] In some embodiments, Figure 3 As shown, the composite film 10 further includes: a first adhesive layer 13 disposed between the base layer 11 and the functional layer 12 .

[0107] It can be understood that the first adhesive layer 13 has adhesive properties, which can firmly combine the base layer 11 and the functional layer 12 together, thereby improving the overall structural stability of the composite film 10 and reducing the warping of the composite film 10; it also enables the layers of the composite film 10 to work together and jointly bear stress when the composite film 10 is subjected to external forces, thereby improving the durability and reliability of the composite film.

[0108] In some embodiments, the shear strength of the first adhesive layer 13 is greater than 8 MPa.

[0109] Illustratively, the shear strength of the first adhesive layer 13 may be 8 MPa, 8.2 MPa, 8.4 MPa, 8.6 MPa, 8.8 MPa or 9 MPa, etc., which is not limited here.

[0110] It can be understood that the shear strength of the first adhesive layer 13 is greater than 8 MPa, so that the composite film 10 has higher bonding strength and resistance to shear failure, which can protect the stability of the overall structure of the composite film 10 to a certain extent and further prevent the composite film 10 from warping.

[0111] In some embodiments, the pull-out strength of the first adhesive layer 13 is greater than 8 MPa.

[0112] For example, the pull-out strength of the first adhesive layer 13 may be 8 MPa, 8.2 MPa, 8.4 MPa, 8.6 MPa, 8.8 MPa or 9 MPa, etc., which is not limited here.

[0113] It can be understood that the tensile strength of the first adhesive layer 13 is greater than 8 MPa, so that the composite film 10 has higher bonding strength and tensile resistance, which can protect the stability of the overall structure of the composite film 10 to a certain extent and further prevent the composite film 10 from warping.

[0114] In some embodiments, a dimension D3 of the first adhesive layer 13 along the first direction Y is smaller than a dimension D1 of the base layer 11 along the first direction Y; that is, D3<D1. The first direction Y is the direction in which the base layer 11 and the functional layer 12 are disposed.

[0115] It can be understood that the first adhesive layer 13 is smaller than the base layer 11 and the functional layer 12, so that the first adhesive layer 13 forms a "narrow band" connection between the base layer 11 and the functional layer 12, which helps to disperse the stress more evenly to the entire base layer 11 and the functional layer 12 when subjected to external force, rather than concentrating on the first adhesive layer 13, thereby improving the overall structural stability of the composite film 10. In addition, using less adhesive material can reduce production costs.

[0116] In some embodiments, a dimension D3 of the first adhesive layer 13 along the first direction Y ranges from 20 μm to 40 μm.

[0117] Exemplarily, a dimension D3 of the first adhesive layer 13 along the first direction Y may be 20 μm, 25 μm, 30 μm, 35 μm or 40 μm, etc., which is not limited here.

[0118] It can be understood that setting the dimension D3 of the first adhesive layer 13 along the first direction Y within a range of 20 μm to 40 μm can improve the bonding performance between the base layer 11 and the functional layer 12 and further prevent the composite film 10 from warping.

[0119] In some embodiments, the material of the first adhesive layer 13 includes: any one of epoxy resin glue and polyester glue.

[0120] Epoxy resin glue has high adhesion and can form a strong bond with a variety of materials; moreover, the preparation cost of epoxy resin glue is relatively low, and the preparation process is simple and easy, which helps to reduce the manufacturing cost of the composite film.

[0121] Polyester glue has good flexibility and impact resistance and can maintain good bonding effect when subjected to external impact.

[0122] Any one of the above epoxy resin glue and polyester glue can be used as the material of the first adhesive layer 13 to ensure good adhesion of the composite film 10 and reduce costs.

[0123] In some embodiments, the materials for forming the epoxy resin glue include: 80 to 120 parts by weight of a first resin, 40 to 80 parts by weight of a first curing agent, and 1 to 10 parts by weight of a first auxiliary agent.

[0124] For example, the weight of the first resin may be 80 parts, 90 parts, 100 parts, 110 parts or 120 parts, etc., which is not limited here.

[0125] For example, the weight proportion of the first curing agent may be 40 parts, 50 parts, 60 parts, 70 parts or 80 parts, etc., which is not limited here.

[0126] For example, the weight proportion of the first auxiliary agent may be 1 part, 2 parts, 4 parts, 6 parts, 8 parts or 10 parts, etc., which is not limited here.

[0127] It can be understood that among the materials forming the above-mentioned epoxy resin glue, 80 to 120 parts by weight of the first resin is the main part of the epoxy resin glue, providing basic physical and chemical properties. 40 to 80 parts by weight of the first curing agent transforms the epoxy resin from liquid to solid, and the first curing agent reacts chemically with the first resin to form a cross-linked network structure, thereby making the epoxy resin glue have better performance; at the same time, the amount of 80 to 120 parts by weight of the first resin and 40 to 80 parts by weight of the first curing agent is matched, so that the epoxy resin glue can be cured better. In addition, 1 to 10 parts by weight of the first auxiliary agent can achieve fine-tuning of the performance of the epoxy resin glue, thereby improving the processing performance and storage stability of the epoxy resin glue.

[0128] In some embodiments, the first resin includes at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, and epoxy alcohol.

[0129] Bisphenol A epoxy resin has good physical and mechanical properties, chemical resistance, electrical insulation and weather resistance due to its high transparency, excellent adhesion and high strength after curing. Bisphenol F epoxy resin has good heat resistance and corrosion resistance. Epoxy alcohol refers to a compound containing epoxy and alcohol hydroxyl groups, which can improve the performance of the material when added to the material.

[0130] At least one of bisphenol A epoxy resin, bisphenol F epoxy resin and epoxy alcohol in the first resin is used to form the main part of the epoxy resin glue, which can improve the performance of the epoxy resin glue.

[0131] In some embodiments, the first curing agent includes at least one of hydrazide, imidazole compound, boron trifluoride monoethylamine complex, aromatic amine, acid anhydride and polyphenol.

[0132] Hydrazide compounds are a class of compounds containing hydrazine and acyl groups and have high reactivity.

[0133] Imidazole compounds are a class of organic compounds containing imidazole rings, which have excellent catalytic activity and thermal stability and are used as medium-temperature or high-temperature curing agents.

[0134] Boron trifluoride and ethylamine form a complex in the boron trifluoride monoethylamine complex, which is relatively stable at room temperature, but can quickly initiate a curing reaction under certain conditions (such as heating).

[0135] Aromatic amines are a class of amine compounds containing aromatic rings. Due to the stability of the aromatic ring and the activity of the amine group, aromatic amines are used as high-temperature curing agents.

[0136] Acid anhydride is the anhydride of acid (carboxylic acid), that is, a cyclic compound formed by the dehydration reaction of two carboxyl groups. It has high reactivity and can react with a variety of functional groups (such as hydroxyl, amino, etc.).

[0137] Polyphenols (such as bisphenol A) can react with epoxy groups to form a cross-linked network structure, thereby improving the performance of epoxy resin adhesives.

[0138] At least one of hydrazide, imidazole compound, boron trifluoride monoethylamine complex, aromatic amine, acid anhydride and polyphenol in the first curing agent is used to form the curing of epoxy resin glue, which can improve the curing effect of epoxy resin glue.

[0139] In some embodiments, the first auxiliary agent includes at least one of a first toughening agent, a first plasticizer, a first filler, a first leveling agent, a first defoaming agent, a first wetting agent, a first dispersant, a first thermal stabilizer, a first anti-settling agent, and a first anti-skinning agent.

[0140] Understandably, the first toughening agent can improve the toughness of epoxy resin glue. The first plasticizer is a substance that can increase the plasticity of epoxy resin glue but does not change its properties, can reduce the hardness and brittleness of epoxy resin glue, and improve the flexibility and processing performance of epoxy resin glue. The first filler can adjust the rheological properties, mechanical properties, thermal properties, etc. of epoxy resin glue. The first leveling agent can improve the fluidity and spreadability of epoxy resin glue, so that the epoxy resin glue can form a smooth and uniform coating during application. The first defoamer can eliminate and suppress the foam in the epoxy resin glue. The first wetting agent can promote the spreading and penetration of epoxy resin glue on the surface of the base layer 11. The first dispersant can prevent the aggregation and sedimentation of epoxy resin glue particles. The first thermal stabilizer can improve the stability of epoxy resin glue at high temperature. The first anti-settling agent can maintain the uniformity and stability of the epoxy resin glue system. The first anti-skinning agent can prevent the surface of the epoxy resin glue from forming a skin during storage and use, can maintain the fluidity and availability of the epoxy resin glue, and improve the storage stability of the product.

[0141] At least one of the first toughening agent, the first plasticizer, the first filler, the first leveling agent, the first defoaming agent, the first wetting agent, the first dispersant, the first thermal stabilizer, the first anti-settling agent and the first anti-skinning agent in the above-mentioned first auxiliary agent is used to form epoxy resin glue, which can improve the performance of epoxy resin glue.

[0142] In some embodiments, the materials for forming the polyester glue include: 80 to 120 parts by weight of unsaturated polyester resin, 1 to 10 parts by weight of a second curing agent, and 1 to 20 parts by weight of a second auxiliary agent.

[0143] For example, the weight percentage of the unsaturated polyester resin may be 80 parts, 90 parts, 100 parts, 110 parts or 120 parts, etc., which is not limited here.

[0144] For example, the weight proportion of the second curing agent may be 1 part, 3 parts, 5 parts, 7 parts or 10 parts, etc., which is not limited here.

[0145] For example, the weight proportion of the second auxiliary agent may be 1 part, 5 parts, 10 parts, 15 parts or 20 parts, etc., which is not limited here.

[0146] It can be understood that among the materials forming the polyester glue, 80 to 120 parts by weight of the unsaturated polyester resin contain unsaturated double bonds in the molecular chain, which can form a three-dimensional network structure through cross-linking and curing reaction, so that the polyester glue has excellent performance. 1 to 10 parts by weight of the second curing agent can chemically react with the unsaturated double bonds in the unsaturated polyester resin to promote the formation of a cross-linked network between the molecular chains of the unsaturated polyester resin, thereby transforming the unsaturated polyester resin from a linear structure to a three-dimensional structure. 1 to 20 parts by weight of the second auxiliary agent plays an auxiliary and modifying role in the formation of the polyester glue, which can improve the processing performance, physical and mechanical properties, chemical stability and use effect of the polyester glue.

[0147] In some embodiments, the second curing agent includes at least one of benzoyl peroxide and styrene.

[0148] Benzoyl peroxide can initiate free radical polymerization of unsaturated double bonds in unsaturated polyester resin to form a cross-linked network structure, thereby curing the polyester glue; the advantages of benzoyl peroxide are fast curing speed and high reaction activity.

[0149] The unsaturated double bonds of styrene and the double bonds in the unsaturated polyester resin form a cross-linking structure, thereby solidifying the polyester glue.

[0150] At least one of the above-mentioned benzoyl peroxide and styrene can be added as the second curing agent during the formation of the polyurethane adhesive to improve the performance of the polyester adhesive.

[0151] In some embodiments, the second auxiliary agent includes at least one of a second toughening agent, a second plasticizer, a second leveling agent, a second defoaming agent, a second wetting agent, a second dispersant, a second thermal stabilizer, a second anti-settling agent, and a second anti-skinning agent.

[0152] The role played by the second auxiliary agent in the formation process of the polyurethane adhesive is similar to the role played by the first auxiliary agent in the formation process of the epoxy resin adhesive, and will not be repeated here.

[0153] In some embodiments, Figure 4 As shown, the composite film 10 further includes: a stacked second adhesive layer 14 and a release film 15. The second adhesive layer 14 and the release film 15 are located on a side of the functional layer 12 away from the base layer 11. The second adhesive layer 14 is closer to the functional layer 12 than the release film 15.

[0154] The second adhesive layer 14 can provide adhesion between the release film 15 and the functional layer 12 , so that the functional layer 12 can be firmly attached to the battery pack components.

[0155] The release film 15 is a thin film with a smooth surface and is easy to peel off. In the composite film 10, the release film 15 can protect the second adhesive layer 14 from contamination or damage and maintain its adhesive properties. When the composite film 10 needs to be adhered to the target surface, the release film 15 can be easily peeled off from the second adhesive layer 14 to expose the adhesive surface. The existence of the release film 15 simplifies the use process of the composite film 10 and improves its processing efficiency.

[0156] When in use, the release film 15 of the composite film 10 is peeled off and pasted on the parts in the battery pack that need to be insulated and protected against high temperature and electrolyte.

[0157] Illustratively, the release film 15 may be any one of a polypropylene film, a polyethylene film, a polyvinyl chloride film, a polystyrene film and a polyester film.

[0158] Exemplarily, the size of the release film 15 along the first direction Y may be 10 μm, 15 μm, 20 μm, 25 μm, 30 μm or 35 μm, etc., which is not limited here.

[0159] In some embodiments, the shear strength of the second adhesive layer 14 is greater than 1.5 MPa.

[0160] For example, the shear strength of the second adhesive layer 14 may be 1.5 MPa, 3 MPa, 4.5 MPa, 6 MPa, 7.5 MPa or 9 MPa, etc., which is not limited here.

[0161] It can be understood that the shear strength of the second adhesive layer 14 is greater than 1.5 MPa, so that the composite film 10 has a higher bonding strength and resistance to shear damage, which can protect the stability of the overall structure of the composite film 10 to a certain extent, so that the functional layer 12 can be firmly attached to the battery pack parts.

[0162] In some embodiments, the second adhesive layer 14 has an adhesive peeling force to the aluminum plate greater than 0.6 N / mm.

[0163] For example, the pull-out strength of the second adhesive layer 14 may be 0.6 MPa, 1.2 MPa, 1.8 MPa, 2.4 MPa or 3 MPa, etc., which is not limited here.

[0164] It can be understood that the bonding peeling force of the second adhesive layer 14 to the aluminum plate is greater than 0.6N / mm, so that the composite film 10 has a higher bonding strength and tensile strength, which can protect the stability of the overall structure of the composite film 10 to a certain extent, and enable the functional layer 12 to be firmly attached to the battery pack parts.

[0165] In some embodiments, the material of the second adhesive layer 14 includes: a first acrylic pressure-sensitive adhesive.

[0166] It can be understood that the first acrylate pressure-sensitive adhesive has excellent adhesion properties and can firmly adhere to the functional layer 12, so that the second adhesive layer 14 can effectively combine the functional layer 12 of the composite film 10 with the battery pack parts; moreover, the first acrylate pressure-sensitive adhesive has good durability and can resist the influence of environmental factors (such as humidity, temperature, ultraviolet rays, etc.) on the adhesion performance, so that the composite film 10 can maintain a stable adhesion effect during long-term use. In addition, the first acrylate pressure-sensitive adhesive only needs to apply a slight contact pressure to achieve adhesion, which is convenient and quick, thereby improving the efficiency of the composite film 10.

[0167] The materials for forming the first acrylic ester pressure-sensitive adhesive include: 50 to 120 parts by weight of acrylic ester resin monomer, 5 to 20 parts by weight of a first tackifier, 1 to 10 parts by weight of a first cross-linking agent, 0.05 to 0.1 parts by weight of a first initiator, 80 to 160 parts by weight of a first solvent, and 1 to 10 parts by weight of a third auxiliary agent.

[0168] For example, the weight of the acrylic resin monomer may be 50 parts, 70 parts, 90 parts, 110 parts or 120 parts, etc., which is not limited here.

[0169] For example, the weight proportion of the first tackifier may be 5 parts, 10 parts, 15 parts or 20 parts, etc., which is not limited here.

[0170] For example, the weight proportion of the first cross-linking agent may be 1 part, 3 parts, 5 parts, 7 parts or 10 parts, etc., which is not limited here.

[0171] For example, the weight portion of the first initiator can be 0.05 parts, 0.06 parts, 0.06 parts, 0.25 parts, 0.09 parts or 0.1 parts, etc., which is not limited here.

[0172] For example, the weight proportion of the first solvent may be 80 parts, 100 parts, 120 parts, 140 parts or 160 parts, etc., which is not limited herein.

[0173] For example, the weight proportion of the third auxiliary agent may be 1 part, 3 parts, 5 parts, 7 parts or 10 parts, etc., which is not limited here.

[0174] In the materials forming the first acrylic pressure-sensitive adhesive, 50 to 120 parts by weight of acrylic resin monomers form a polymer network through free radical polymerization, so that the first acrylic pressure-sensitive adhesive has good viscosity. 5 to 20 parts by weight of the first tackifier can improve the viscosity and holding force of the first acrylic pressure-sensitive adhesive. 1 to 10 parts by weight of the cross-linking agent can promote the cross-linking reaction between the acrylic resin monomers, forming a denser and more stable polymer network, which can improve the cohesive strength and heat resistance of the first acrylic pressure-sensitive adhesive. 0.05 to 0.1 parts by weight of the first initiator can initiate the polymerization reaction of the acrylic resin monomer, ensuring that the polymerization reaction can proceed smoothly and obtain the required polymer molecular weight. 80 to 160 parts by weight of the solvent allows the first acrylic pressure-sensitive adhesive to be formed in a relatively suitable state. 1 to 10 parts by weight of the third auxiliary agent plays an auxiliary and modifying role in the formation of the first acrylic pressure-sensitive adhesive, which can improve the processing performance, physical and mechanical properties, chemical stability and use effect of the first acrylic pressure-sensitive adhesive.

[0175] In some embodiments, the acrylic resin monomer includes a first monomer, a second monomer, and a functional monomer. The mass ratio of the first monomer, the second monomer, and the functional monomer is in the range of (60-70): (20-40): (5-20).

[0176] For example, the mass ratio of the first monomer, the second monomer and the functional monomer may be 60:20:5, 65:30:12.5 or 70:40:20, etc., which is not limited here.

[0177] It can be understood that the first monomer is an acrylate monomer, which is the main component of the first acrylate pressure-sensitive adhesive and has an important influence on the adhesion, cohesive strength and performance of the first acrylate pressure-sensitive adhesive. The second monomer includes other acrylate monomers or other monomers that can copolymerize with the first monomer. The addition of the second monomer can further improve the adhesion of the first acrylate pressure-sensitive adhesive, improve the processing performance or adjust the curing speed, etc. The functional monomer contains special functional groups, such as hydroxyl, carboxyl, epoxy, etc., which can form a cross-linked structure and improve the heat resistance, water resistance, solvent resistance, etc. of the first acrylate pressure-sensitive adhesive.

[0178] By adjusting the mass ratio of the first monomer, the second monomer and the functional monomer to the range of (60-70):(20-40):(5-20), the adhesion and performance of the first acrylic pressure-sensitive adhesive can be further improved.

[0179] In some embodiments, the first monomer includes at least one of isooctyl acrylate, butyl acrylate, and ethyl acrylate.

[0180] It can be understood that isooctyl acrylate has a longer alkyl chain, which can provide good softness and elasticity, so that the first acrylate pressure-sensitive adhesive can better adapt to the surface shape of the adherend during pasting, thereby improving the tightness and durability of pasting. Isooctyl acrylate also helps to improve the low-temperature resistance of the first acrylate pressure-sensitive adhesive, so that the first acrylate pressure-sensitive adhesive can still maintain a good pasting effect in a low-temperature environment. Butyl acrylate can increase the intermolecular force between the first acrylate pressure-sensitive adhesive and the adherend, and can improve the adhesion and cohesion of the first acrylate pressure-sensitive adhesive, thereby improving the adhesion effect.

[0181] At least one of the above-mentioned isooctyl acrylate, butyl acrylate and ethyl acrylate as the first monomer for forming the first acrylic pressure-sensitive adhesive can improve the adhesion of the first acrylic pressure-sensitive adhesive.

[0182] In some embodiments, the second monomer includes at least one of methyl methacrylate, vinyl acetate, acrylonitrile, acrylamide, and styrene.

[0183] Methyl methacrylate can play a role in viscosity adjustment and adhesion enhancement. Vinyl acetate can participate in the cross-linking reaction, form a stable network structure with the first monomer and the functional monomer, and enhance the flexibility and weather resistance of the first acrylic pressure-sensitive adhesive. The addition of acrylonitrile can improve the strength and hardness of the first acrylic pressure-sensitive adhesive. Acrylamide can improve the water resistance of the first acrylic pressure-sensitive adhesive. Styrene can copolymerize with other acrylic monomers to form a cross-linking structure, thereby improving the strength and adhesion of the glue.

[0184] At least one of the above-mentioned methyl methacrylate, vinyl acetate, acrylonitrile, acrylamide and styrene as the second monomer for forming the first acrylic pressure-sensitive adhesive can improve the adhesion of the first acrylic pressure-sensitive adhesive.

[0185] In some embodiments, the functional monomer includes at least one of acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate.

[0186] The hydroxyl groups in hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate and hydroxypropyl methacrylate can form hydrogen bonds to enhance the adhesion of the first acrylate pressure-sensitive adhesive. Acrylic acid and methacrylic acid monomers have good weather resistance and chemical stability, and can enhance the adhesion and stability of the first acrylate pressure-sensitive adhesive.

[0187] At least one of the above-mentioned isooctyl acrylate, butyl acrylate and ethyl acrylate as a functional monomer for forming the first acrylic pressure-sensitive adhesive can improve the adhesion and stability of the first acrylic pressure-sensitive adhesive.

[0188] In some embodiments, the first initiator includes at least one of dibenzoyl peroxide and azobisisobutyronitrile.

[0189] Benzoyl peroxide and azobisisobutyronitrile can decompose and generate free radicals under appropriate conditions, thereby initiating free radical polymerization of monomers such as acrylate to form a stable first acrylate pressure-sensitive adhesive.

[0190] In some embodiments, the third auxiliary agent includes at least one of a second filler, a third leveling agent, a third defoaming agent, a third wetting agent, a third dispersant, a third thermal stabilizer, a third anti-settling agent, and a third anti-skinning agent.

[0191] The role played by the third auxiliary agent in the formation process of the polyurethane adhesive is similar to the role played by the first auxiliary agent in the formation process of the epoxy resin adhesive, and will not be repeated here.

[0192] In some embodiments, the first tackifier includes at least one of anatase resin, a natural resin, and a synthetic resin.

[0193] Anatase resin can improve the interaction between the first acrylate pressure-sensitive adhesive and the adherend to improve the bonding force. Natural resin can increase the viscosity of the adhesive, improve its wettability and fluidity, and thus improve the adhesion effect. Synthetic resin can improve the adhesion performance and stability of the first acrylate pressure-sensitive adhesive by changing the molecular structure, polarity or cross-linking density of the adhesive.

[0194] At least one of the anatase resin, natural resin and synthetic resin can be used as the first tackifier for forming the first acrylic pressure-sensitive adhesive to increase the adhesion of the first acrylic pressure-sensitive adhesive.

[0195] In some embodiments, the first cross-linking agent includes at least one of tris(methacrylamide)triazine, epoxy acrylate, benzoyl peroxide, polyisocyanate, and amino resin.

[0196] Tris(methacrylamide)triazine contains multiple reactive groups, such as methacrylamide, which can react with acrylate monomers to form a cross-linked network structure, which helps to improve the performance of the first acrylate pressure-sensitive adhesive.

[0197] Epoxy acrylate combines the excellent properties of epoxy resin and the activity of acrylate, and can react with groups such as hydroxyl or carboxyl in acrylate polymer to form a stable cross-linking structure, thereby improving the performance of the first acrylate pressure-sensitive adhesive.

[0198] Benzoyl peroxide promotes the cross-linking reaction between the monomer molecules of acrylate resin.

[0199] The polyisocyanate can react with the groups in the acrylate polymer to form a strong chemical bond, thereby improving the cohesion and performance of the first acrylate pressure-sensitive adhesive.

[0200] Amino resins such as melamine formaldehyde resins can react with groups in acrylate polymer monomers to form a stable cross-linked structure. When the amino resin is used as a cross-linking agent, the performance of the first acrylate pressure-sensitive adhesive can be improved.

[0201] At least one of the above tris(methacrylamide)triazine, epoxy acrylate, benzoyl peroxide, polyisocyanate and amino resin can be used as the first crosslinking agent to form the first acrylate pressure-sensitive adhesive, which can improve the performance of the first acrylate pressure-sensitive adhesive.

[0202] In some embodiments, the material of the second adhesive layer 14 includes: a second acrylic pressure-sensitive adhesive. The forming material of the second acrylic pressure-sensitive adhesive includes: a prepolymer, a first acrylic monomer, a first photosensitizer, and a fourth auxiliary agent. The mass ratio of the prepolymer, the first acrylic monomer, the first photosensitizer, and the fourth auxiliary agent is in the range of: (50-60): (90:110): (0.2-2.2): (5-20).

[0203] The prepolymer has a specific molecular weight and functional group, and can react with other components to provide a basic polymer skeleton for the second acrylic pressure-sensitive adhesive. The first acrylic monomer can copolymerize with the prepolymer to further adjust the properties of the adhesive, such as adhesion, cohesion, flexibility, etc. The first photosensitizer can promote the photocuring reaction, so that when the second acrylic pressure-sensitive adhesive is exposed to light of a specific wavelength, it absorbs light energy and triggers a chemical reaction, and cures rapidly. The fourth auxiliary agent plays an auxiliary and modifying role in the formation of the second acrylic pressure-sensitive adhesive, and can improve the processing performance, physical and mechanical properties, chemical stability and use effect of the second acrylic pressure-sensitive adhesive.

[0204] Meanwhile, by setting the mass ratio of the prepolymer, the first acrylic monomer, the first photosensitizer and the fourth auxiliary agent to the range of (50-60): (90:110): (0.2-2.2): (5-20), a second acrylic pressure-sensitive adhesive with better bonding effect can be obtained.

[0205] The prepolymer, the first acrylic monomer, the first photosensitizer and the fourth auxiliary agent are used as materials for forming the second acrylic pressure-sensitive adhesive, and can form the second acrylic pressure-sensitive adhesive with good adhesion.

[0206] In some embodiments, the fourth auxiliary agent includes at least one of a second cross-linking agent, a third curing agent, a third filler, a fourth leveling agent, a second tackifier, a fourth defoaming agent, an anti-aging agent, and an inhibitor.

[0207] The second cross-linking agent promotes the cross-linking effect between the molecules of the second acrylic pressure-sensitive adhesive through a cross-linking reaction, thereby improving the cohesion and temperature resistance of the adhesive. The third curing agent reacts with the prepolymer, the monomer or the cross-linking agent to form a stable cross-linked network structure, and promotes the curing reaction to initiate the curing process. The first tackifying resin can increase the adhesion of the second acrylic pressure-sensitive adhesive. The filler can increase the volume of the second acrylic pressure-sensitive adhesive, reduce costs, and improve processing performance. The fourth leveling agent can improve the leveling performance of the second acrylic pressure-sensitive adhesive, making the surface of the second acrylic pressure-sensitive adhesive smoother and more uniform. The second tackifier can improve the adhesion of the second acrylic pressure-sensitive adhesive. The fourth defoaming agent can eliminate bubbles in the second acrylic pressure-sensitive adhesive liquid to prevent bubbles from adversely affecting product quality. The anti-aging agent can delay the aging process of the second acrylic pressure-sensitive adhesive caused by oxidation, ultraviolet radiation and other factors, thereby extending the service life of the material. The inhibitor can inhibit unnecessary polymerization reactions during the formation of the second acrylic pressure-sensitive adhesive.

[0208] The second acrylic pressure-sensitive adhesive formed by using at least one of the second crosslinking agent, the third curing agent, the third filler, the fourth leveling agent, the second tackifier, the fourth defoaming agent, the anti-aging agent, and the polymerization inhibitor as the fourth auxiliary agent has good adhesion.

[0209] In some embodiments, the prepolymer forming materials include: a second acrylic monomer, an inorganic filler, and a second initiator.

[0210] Similar to the first initiator, the second initiator can increase the adhesion of the second acrylic pressure-sensitive adhesive. The first photosensitizer promotes the photocuring reaction.

[0211] The inorganic filler can improve the physical properties of the prepolymer, thereby improving the performance of the second acrylate pressure-sensitive adhesive. The second acrylate monomer forms the prepolymer through polymerization and is the main component of the prepolymer.

[0212] The second acrylic monomer, inorganic filler and second initiator are used as materials for forming a prepolymer, and can form a prepolymer with good performance.

[0213] In some embodiments, the second initiator is at least one of azobisisobutyronitrile and dibenzoyl peroxide.

[0214] In some embodiments, the first acrylic monomer and / or the second acrylic monomer includes at least one of ethylhexyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, butanediol diacrylate, butanediol diacrylate, hexanediol diacrylate, and trimethylolpropane triacrylate.

[0215] The second acrylic ester pressure-sensitive adhesive formed by using ethylhexyl acrylate as the first acrylic monomer and / or the second acrylic monomer maintains good adhesion performance at low temperatures.

[0216] Hydroxyethyl acrylate and hydroxypropyl acrylate contain hydroxyl functional groups in their molecules. When used as the first acrylic monomer and / or the second acrylic monomer to form the second acrylic pressure-sensitive adhesive, the wettability to the surface of the adherend can be improved, thereby enhancing the adhesion effect.

[0217] The second acrylic ester pressure-sensitive adhesive formed by butanediol diacrylate and hexanediol diacrylate as the first acrylic monomer and / or the second acrylic monomer maintains good adhesion properties under high temperature or high stress conditions.

[0218] Trimethylolpropane triacrylate has excellent reactivity and cross-linking properties, and can be used as the second acrylic acid ester pressure-sensitive adhesive formed by the first acrylic acid monomer and / or the second acrylic acid monomer to improve the adhesion of the second acrylic acid ester pressure-sensitive adhesive.

[0219] The second acrylic ester pressure-sensitive adhesive formed by using at least one of the above-mentioned ethylhexyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, butanediol diacrylate, butanediol diacrylate, hexanediol diacrylate and trimethylolpropane triacrylate as the first acrylic monomer and / or the second acrylic monomer has good adhesion.

[0220] In some embodiments, the inorganic filler includes at least one of powdered silica gel and hollow glass fiber clusters.

[0221] Powdered silicone has good weather resistance and can resist the influence of extreme environmental conditions such as ultraviolet rays, high temperature and low temperature. Adding it to the second acrylic pressure-sensitive adhesive can improve the overall weather resistance of the pressure-sensitive adhesive and extend its service life.

[0222] The hollow glass fiber cluster has the characteristics of high strength and light weight, which can enhance the structural strength of the second acrylic pressure-sensitive adhesive and help improve the stability and durability of the pressure-sensitive adhesive when subjected to external forces.

[0223] At least one inorganic filler in the powdered silica gel and hollow glass fiber cluster as the forming material of the second acrylic pressure-sensitive adhesive can improve the performance of the second acrylic pressure-sensitive adhesive.

[0224] In some embodiments, the first photosensitizer includes at least one of benzoin ether and acetophenone.

[0225] Benzoin ether can quickly absorb light energy and convert it into chemical energy under the irradiation of ultraviolet rays or light of a specific wavelength, thereby initiating chemical reactions such as curing and cross-linking, so that the second acrylate pressure-sensitive adhesive can be quickly cured.

[0226] Acetophenone can react stably under light irradiation, and the obtained second acrylic ester pressure-sensitive adhesive has high stability.

[0227] At least one of the above-mentioned photosensitizers, benzoin ether and acetophenone, can be used as a material for forming the second acrylate pressure-sensitive adhesive to improve the performance of the second acrylate pressure-sensitive adhesive.

[0228] In some embodiments, the third curing agent includes at least one of chlorinated paraffin and chlorinated aromatic ether.

[0229] Chlorinated paraffin has waterproof and moisture-proof effects, and can improve the water resistance of the second acrylate pressure-sensitive adhesive, so that it can still maintain a stable curing effect in a humid or water-immersed environment.

[0230] Chlorinated aromatic ether has efficient curing performance and can quickly initiate polymerization under light conditions to promote the curing process of the second acrylate pressure-sensitive.

[0231] At least one third curing agent selected from the above-mentioned chlorinated paraffin and chlorinated aromatic ether as a forming material of the second acrylate pressure-sensitive adhesive can improve the curing effect of the second acrylate pressure-sensitive adhesive.

[0232] In some embodiments, the second cross-linking agent includes at least one of ethylene glycol diacrylate, trimethylolpropane triacrylate, and a triazine compound.

[0233] Ethylene glycol diacrylate (EGDA) can form chemical crosslinking points in the second acrylate pressure-sensitive adhesive, thereby improving the cohesion and adhesion of the pressure-sensitive adhesive.

[0234] Trimethylolpropane triacrylate (TMPTA) can rapidly undergo crosslinking reaction under light or heat initiation to form a dense crosslinking network.

[0235] The triazine compound can promote other materials in the second acrylate pressure-sensitive adhesive to form a stronger interaction force, thereby enhancing the adhesion of the second acrylate pressure-sensitive adhesive.

[0236] At least one second crosslinking agent selected from the group consisting of ethylene glycol diacrylate, trimethylolpropane triacrylate and triazine compounds can be used as a material for forming the second acrylic pressure-sensitive adhesive to improve the adhesion effect of the second acrylic pressure-sensitive adhesive.

[0237] Second, as Figure 5 As shown, the present application provides a method for preparing a composite film 10. The method for preparing the composite film 10 comprises: S1.

[0238] S1: forming a stacked and connected base layer 11 and functional layer 12, wherein the functional layer 12 is used to provide at least a heat insulation function. The moisture absorption rate of the material of the base layer 11 under preset conditions is less than a first set threshold value, and the first set threshold value is used to control the deformation of the base layer 11 under the moisture absorption condition. The moisture absorption rate of the material of the functional layer 12 under preset conditions is less than a second set threshold value; the second set threshold value is used to control the deformation of the functional layer 12 under the moisture absorption condition. The second set threshold value is less than or equal to the first set threshold value.

[0239] In some embodiments, the base layer 11 and the functional layer 12 forming a stacked arrangement and connected include: SA.

[0240] SA: The material of the base layer 11 and the material of the functional layer 12 are co-extruded by using a cast co-extrusion process.

[0241] In some embodiments, the stacked and connected substrate layer 11 and functional layer 12 are formed, including: SB.

[0242] SB: The base layer 11 and the functional layer 12 are fixedly attached by a lamination process.

[0243] In some embodiments, forming a stacked and connected base layer 11 and functional layer 12 includes: S1.1 to S1.3.

[0244] S1.1: forming a base layer 11.

[0245] S1.2: Forming a first adhesive layer 13 on the base layer 11 .

[0246] S1.3: Connect the functional layer 12 to the side of the first adhesive layer 13 away from the base layer 11 .

[0247] For example, during production, the roll of the base layer 11 is unwound first, the coating of the first adhesive layer 13 is coated on the base layer 11, and then it is passed through a 130-150°C oven and compounded with the functional layer 12, and then it is aged at 40-50°C for 3-4 days before being rolled up.

[0248] In some embodiments, the method for preparing the composite film 10 further includes: S2 to S3.

[0249] S2: The second adhesive layer 14 is connected to the side of the functional layer 12 away from the base layer 11 .

[0250] S3: Covering the release film 15 on the side of the second adhesive layer 15 away from the functional layer 12 .

[0251] In some embodiments, the composite film of any one of the above embodiments; or the composite film 10 prepared by the composite film preparation method of any one of the above embodiments, is applied to a battery pack part, wherein the functional layer 12 is closer to the battery pack part than the base layer 11.

[0252] Based on the above-described composite film 10, the following examples are provided.

[0253] Example 1

[0254] The composite membrane 10 of Example 1 includes the following preparation steps: R1 to R3.

[0255] R1: Prepare the functional layer 12, using a PPS film with a thickness of 65 μm.

[0256] R2: Prepare a base layer 11, using a PET film with a thickness of 200 μm.

[0257] R3: forming a first bonding layer 13, wherein the material of the first bonding layer 13 is a thermosetting adhesive, and epoxy resin adhesive is selected, wherein the epoxy resin adhesive is composed of 95 parts by weight of a first resin, 63 parts by weight of a first curing agent, and 8 parts by weight of a first auxiliary agent.

[0258] The performance of the composite film 10 is tested. (1) After the composite film 10 is cured, the surface of the composite film 10 obtained must be free of defects such as oil stains, wrinkles, bubbles, scratches, ripples, foreign matter, damage, excessively deep indentations, notches and tears, and burrs; and there must be no defects such as bubbles and large warping between the layers of the composite film 10.

[0259] (2) The shear strength of the first adhesive layer 13 of the composite film 10 was 8 MPa, and the tensile strength of the first adhesive layer 13 was 8.2 MPa.

[0260] (3) The composite film 10 was attached to an aluminum sheet with a high temperature tape, and a pressurized aluminum sheet and a heating stage were placed above and below the film-attached aluminum sheet. A DC voltage of 700 V was applied, and 2 ml of electrolyte was dripped onto the PPS film (test area 13000 mm 2 ), raise the temperature of the heating table to 260℃ and keep it for 1h. There is no breakdown and sparkover of the tested samples.

[0261] Example 2

[0262] The composite membrane 10 of Example 2 includes the following preparation steps: P1 to P3.

[0263] P1: Prepare the functional layer 12, using a PPS film with a thickness of 65 μm.

[0264] P2: Prepare the base layer 11, using a PET film with a thickness of 200 μm.

[0265] P3: forming a first adhesive layer 13, the material of the first adhesive layer 13 is a thermosetting adhesive, and polyester adhesive is selected, wherein the polyester adhesive is composed of 90 parts by weight of unsaturated polyester resin, 5 parts by weight of a second curing agent, and 10 parts by weight of a second auxiliary agent.

[0266] The performance of the composite film 10 is tested. (1) After the composite film 10 is cured, the surface of the composite film 10 obtained must be free of defects such as oil stains, wrinkles, bubbles, scratches, ripples, foreign matter, damage, excessively deep indentations, notches and tears, and burrs; and there must be no defects such as bubbles and large warping between the layers of the composite film 10.

[0267] (2) The shear strength of the first adhesive layer 13 of the composite film 10 was 7.8 MPa, and the tensile strength of the first adhesive layer 13 was 8 MPa.

[0268] (3) The composite film 10 was attached to an aluminum sheet with a high temperature tape, and a pressurized aluminum sheet and a heating stage were placed above and below the film-attached aluminum sheet. A DC voltage of 700 V was applied, and 2 ml of electrolyte was dripped onto the PPS film (test area 13000 mm 2 ), raise the temperature of the heating table to 260℃ and keep it for 1h. There is no breakdown and sparkover of the tested samples.

[0269] Example 3

[0270] The composite membrane 10 of Example 3 includes the following preparation steps: T1 to T5.

[0271] T1: Prepare the functional layer 12, using a PPS film with a thickness of 65 μm.

[0272] T2: Prepare the base layer 11, using a PET film with a thickness of 200 μm.

[0273] T3: forming a first bonding layer 13, wherein the material of the first bonding layer 13 is a thermosetting adhesive, and epoxy resin adhesive is selected, wherein the epoxy resin adhesive is composed of 95 parts by weight of a first resin, 63 parts by weight of a first curing agent, and 8 parts by weight of a first auxiliary agent.

[0274] T4: forming a second adhesive layer 14, wherein the material of the second adhesive layer 14 is a first acrylic pressure-sensitive adhesive, wherein the first acrylic pressure-sensitive adhesive is composed of 80 parts by weight of acrylic resin, 10 parts by weight of a first tackifier, 5 parts by weight of a first cross-linking agent, 0.09 parts by weight of a first initiator, and 120 parts by weight of a first solvent.

[0275] T5: Prepare a release film 15, using a PET film with a thickness of 25 μm.

[0276] The performance of the composite film 10 is tested. (1) After the composite film 10 is cured, the surface of the composite film 10 obtained must be free of defects such as oil stains, wrinkles, bubbles, scratches, ripples, foreign matter, damage, excessively deep indentations, notches and tears, and burrs; and there must be no defects such as bubbles and large warping between the layers of the composite film 10.

[0277] (2) The shear strength of the second adhesive layer 15 of the composite film 10 was 1.6 MPa, and the pull-out strength of the second adhesive layer 15 was 0.6 MPa.

[0278] (3) The composite film 10 was attached to an aluminum sheet with a high temperature tape, and a pressurized aluminum sheet and a heating stage were placed above and below the film-attached aluminum sheet. A DC voltage of 700 V was applied, and 2 ml of electrolyte was dripped onto the PPS film (test area 13000 mm 2 ), raise the temperature of the heating table to 260℃ and keep it for 1h. There is no breakdown and sparkover of the tested samples.

[0279] Example 4

[0280] The composite membrane 10 of Example 4 includes the following preparation steps: Q1 to Q5.

[0281] Q1: Prepare the functional layer 12, using a PPS film with a thickness of 65 μm.

[0282] Q2: Prepare the base layer 11, and select PET film with a thickness of 200 μm.

[0283] Q3: Forming the first adhesive layer 13, the material of the first adhesive layer 13 is a thermosetting adhesive, and polyester adhesive is selected. The polyester adhesive is composed of 90 parts by weight of unsaturated polyester resin, 5 parts by weight of a second curing agent, and 10 parts by weight of a second auxiliary agent.

[0284] Q4: forming a second adhesive layer 14, the material of the second adhesive layer 14 is a first acrylic pressure-sensitive adhesive, wherein the first acrylic pressure-sensitive adhesive is composed of 80 parts by weight of acrylic resin, 10 parts by weight of a first tackifier, 5 parts by weight of a first cross-linking agent, 0.09 parts by weight of a first initiator, and 120 parts by weight of a first solvent.

[0285] Q5: Prepare a release film 15, using PET film with a thickness of 25 μm.

[0286] The performance of the composite film 10 is tested. (1) After the composite film 10 is cured, the surface of the composite film 10 obtained must be free of defects such as oil stains, wrinkles, bubbles, scratches, ripples, foreign matter, damage, excessively deep indentations, notches and tears, and burrs; and there must be no defects such as bubbles and large warping between the layers of the composite film 10.

[0287] (2) The shear strength of the second adhesive layer 15 of the composite film 10 was 1.5 MPa, and the pull-out strength of the second adhesive layer 15 was 0.6 MPa.

[0288] (3) The composite film 10 was attached to an aluminum sheet with a high temperature tape, and a pressurized aluminum sheet and a heating stage were placed above and below the film-attached aluminum sheet. A DC voltage of 700 V was applied, and 2 ml of electrolyte was dripped onto the PPS film (test area 13000 mm 2 ), raise the temperature of the heating table to 260℃ and keep it for 1h. There is no breakdown and sparkover of the tested samples.

[0289] It should be noted that in the above embodiments, the PPS film is a commercially available biaxially oriented polyphenylene sulfide insulating film, the PET film is a commercially available biaxially oriented polyethylene terephthalate insulating film, and the epoxy resin, curing agent, and other additives are also commercially available products.

[0290] The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A composite film, characterized in that include: A base layer and a functional layer are stacked and connected; the functional layer is at least used to provide a heat insulation function; Wherein, the moisture absorption rate of the material of the base layer under preset conditions is less than a first set threshold value, and the first set threshold value is used to control the deformation of the base layer under moisture absorption conditions; The moisture absorption rate of the material of the functional layer under the preset conditions is less than a second set threshold; the second set threshold is used to control the deformation of the functional layer under moisture absorption conditions; the second set threshold is less than the first set threshold.

2. The composite membrane according to claim 1, characterized in that The first set threshold is 0.35%; and / or the second set threshold is 0.25%.

3. The composite membrane according to claim 1, characterized in that The thermal deformation temperature of the functional layer is greater than or equal to 260°C.

4. The composite membrane according to claim 1, characterized in that The size of the base layer along the first direction ranges from 100 μm to 300 μm; the first direction is the direction in which the base layer and the functional layer are laid.

5. The composite membrane according to claim 1, characterized in that The size of the functional layer along the first direction ranges from 25 μm to 150 μm; the first direction is the direction in which the base layer and the functional layer are laid.

6. The composite membrane according to claim 1, characterized in that The material of the base layer includes: polyethylene terephthalate; and / or, The material of the functional layer includes: polyphenylene sulfide.

7. The composite film according to any one of claims 1 to 6, characterized in that Also includes: A first adhesive layer is provided between the base layer and the functional layer.

8. The composite membrane according to claim 7, characterized in that The shear strength of the first adhesive layer is greater than 8 MPa; and / or the tensile strength of the first adhesive layer is greater than 8 MPa.

9. The composite membrane according to claim 7, characterized in that The size of the first adhesive layer along a first direction is smaller than the size of the base layer along the first direction, and the first direction is the direction in which the base layer and the functional layer are layered.

10. The composite membrane according to claim 9, characterized in that The size of the first adhesive layer along the first direction ranges from 20 μm to 40 μm.

11. The composite membrane according to claim 7, characterized in that The material of the first adhesive layer includes: any one of epoxy resin glue and polyester glue.

12. The composite membrane according to claim 11, characterized in that The materials for forming the epoxy resin glue include: 80 to 120 parts by weight of a first resin, 40 to 80 parts by weight of a first curing agent, and 1 to 10 parts by weight of a first auxiliary agent.

13. The composite membrane according to claim 12, characterized in that The first resin comprises: at least one of bisphenol A epoxy resin, bisphenol F epoxy resin and epoxy alcohol; and / or, The first curing agent comprises at least one of hydrazide, imidazole compound, boron trifluoride monoethylamine complex, aromatic amine, acid anhydride and polyphenol; and / or, The first auxiliary agent includes at least one of a first toughening agent, a first plasticizer, a first filler, a first leveling agent, a first defoaming agent, a first wetting agent, a first dispersant, a first thermal stabilizer, a first anti-settling agent and a first anti-skinning agent.

14. The composite membrane according to claim 11, characterized in that The materials for forming the polyester glue include: 80 to 120 parts by weight of unsaturated polyester resin, 1 to 10 parts by weight of a second curing agent, and 1 to 20 parts by weight of a second auxiliary agent.

15. The composite membrane according to claim 14, characterized in that The second curing agent comprises: at least one of benzoyl peroxide and styrene; and / or, The second auxiliary agent includes at least one of a second toughening agent, a second plasticizer, a second leveling agent, a second defoaming agent, a second wetting agent, a second dispersant, a second thermal stabilizer, a second anti-settling agent and a second anti-skinning agent.

16. The composite film according to any one of claims 1 to 6, characterized in that Also includes: The second adhesive layer and the release film are stacked and located on a side of the functional layer away from the base layer, and the second adhesive layer is closer to the functional layer than the release film.

17. The composite membrane according to claim 16, characterized in that The shear strength of the second adhesive layer is greater than 1.5 MPa; and / or the adhesive peeling force of the second adhesive layer to the aluminum plate is greater than 0.6 N / mm.

18. The composite membrane according to claim 17, characterized in that The material of the second adhesive layer includes: a first acrylic pressure-sensitive adhesive; The materials for forming the first acrylic pressure-sensitive adhesive include: 50 to 120 parts by weight of acrylic resin monomer, 5 to 20 parts by weight of a first tackifier, 1 to 10 parts by weight of a first cross-linking agent, 0.05 to 0.1 parts by weight of a first initiator, 80 to 160 parts by weight of a first solvent, and 1 to 10 parts by weight of a third auxiliary agent.

19. The composite membrane according to claim 18, characterized in that The acrylic resin monomer includes a first monomer, a second monomer and a functional monomer; the mass ratio of the first monomer, the second monomer and the functional monomer is in the range of: (60-70): (20-40): (5-20); The first monomer comprises: at least one of isooctyl acrylate, butyl acrylate and ethyl acrylate; and / or, The second monomer comprises: at least one of methyl methacrylate, vinyl acetate, acrylonitrile, acrylamide and styrene; and / or, The functional monomer comprises at least one of acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate and hydroxypropyl methacrylate.

20. The composite membrane according to claim 18, characterized in that The first initiator comprises: at least one of dibenzoyl peroxide and azobisisobutyronitrile, and / or, The third auxiliary agent includes at least one of a second filler, a third leveling agent, a third defoamer, a third wetting agent, a third dispersant, a third thermal stabilizer, a third anti-settling agent and a third anti-skinning agent; and / or, The first tackifier comprises: at least one of anatase resin, a natural resin and a synthetic resin; and / or, The first cross-linking agent includes at least one of tris(methacrylamide)triazine, epoxy acrylate, benzoyl peroxide, polyisocyanate and amino resin.

21. The composite membrane according to claim 17, characterized in that The material of the second bonding layer includes: a second acrylate pressure-sensitive adhesive; The materials for forming the second acrylic ester pressure-sensitive adhesive include: a prepolymer, a first acrylic monomer, a first photosensitizer and a fourth auxiliary agent; the mass ratio of the prepolymer, the first acrylic monomer, the first photosensitizer and the fourth auxiliary agent is in the range of: (50-60): (90:110): (0.2-2.2): (5-20).

22. The composite membrane according to claim 21, characterized in that The forming materials of the prepolymer include: a second acrylic monomer, an inorganic filler and a second initiator; The first acrylic monomer and / or the second acrylic monomer include: at least one of ethylhexyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, butanediol diacrylate, butanediol diacrylate, hexanediol diacrylate and trimethylolpropane triacrylate; and / or, The inorganic filler comprises: at least one of powdered silica gel and hollow glass fiber clusters; and / or, The second initiator is at least one of azobisisobutyronitrile and dibenzoyl peroxide.

23. The composite membrane according to claim 21, characterized in that The fourth auxiliary agent includes at least one of a second cross-linking agent, a third curing agent, a third filler, a fourth leveling agent, a second tackifier, a fourth defoaming agent, an anti-aging agent, and an inhibitor; and / or, The first photosensitizer includes at least one of benzoin ether and acetophenone.

24. The composite membrane according to claim 23, characterized in that The third curing agent comprises: at least one of chlorinated paraffin and chlorinated aromatic ether; and / or, The second cross-linking agent includes at least one of ethylene glycol diacrylate, trimethylolpropane triacrylate and triazine compounds.

25. A method for preparing a composite film, characterized in that: include: Forming a base layer and a functional layer which are stacked and connected, wherein the functional layer is used to provide at least a heat insulation function; Wherein, the moisture absorption rate of the material of the base layer under preset conditions is less than a first set threshold value, and the first set threshold value is used to control the deformation of the base layer under moisture absorption conditions; The moisture absorption rate of the material of the functional layer under the preset conditions is less than a second set threshold; the second set threshold is used to control the deformation of the functional layer under moisture absorption conditions; the second set threshold is less than or equal to the first set threshold.

26. The method for preparing a composite membrane according to claim 25, characterized in that: The base layer and the functional layer formed into a stacked and connected state include: The material of the base layer and the material of the functional layer are co-extruded by using a cast co-extrusion process.

27. The method for preparing a composite membrane according to claim 25, characterized in that: The base layer and the functional layer formed into a stacked and connected state include: The base layer and the functional layer are fixedly attached to each other by adopting a lamination process.

28. The method for preparing a composite membrane according to claim 25, characterized in that: The base layer and the functional layer formed into a stacked and connected state include: forming the base layer; forming a first adhesive layer on the base layer; and, The functional layer is connected to a side of the first adhesive layer away from the base layer.

29. The method for preparing a composite membrane according to any one of claims 25 to 28, characterized in that: Also includes: Connecting a second adhesive layer to a side of the functional layer away from the base layer; A release film is covered on a side of the second adhesive layer away from the functional layer.

30. A battery pack, characterized in that: include: A battery pack component and a composite film as claimed in any one of claims 1 to 24; wherein the functional layer is closer to the battery pack component than the base layer.

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