Adhesive composition, adhesive layer comprising the same and new energy automobile power battery assembly

Abstract

The present application provides an adhesive composition, an adhesive layer comprising the adhesive composition and a new energy automobile power battery assembly. The adhesive composition comprises: 30-40 wt% of a thermoplastic polymer; 5-15 wt% of a thermally conductive filler; 3-8 wt% of a plasticizer; 1-4 wt% of a coupling agent; 0.5-3 wt% of a stabilizer; and an organic solvent, wherein: the thermoplastic polymer is a blend of a thermoplastic copolyester and a thermoplastic polyacrylate at a weight ratio of 2:1-1:2. The technical solution according to the present application makes the adhesive have high adhesion strength at room temperature and easy disassembly at high temperature, and the adhesive layer formed has high thermal conductivity and high insulation properties, and when applied to the power battery assembly, it can improve the battery volume rate, shorten the disassembly time, reduce the maintenance damage rate, and meet the full-temperature use requirements.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of new energy automobile power battery packaging, in particular to an adhesive composition, an adhesive layer comprising the adhesive composition and a new energy automobile power battery assembly. BACKGROUND

[0002] With the acceleration of global energy transformation and the rapid expansion of the new energy automobile industry, as the core power source of new energy automobiles, the advancement of power battery packaging technology directly determines the vehicle's endurance, safety performance and life cycle maintenance cost, and has become a key link restricting the high-quality development of the industry. At present, the mainstream in the field of new energy automobile power battery packaging adopts heat-conducting structural adhesive to replace traditional metal mechanical fasteners to integrate the battery module and the cooling plate. Compared with mechanical fastening, this scheme can significantly reduce the weight of the battery pack and improve the volume efficiency of the battery pack, and is therefore widely used in various new energy automobile power battery assemblies. However, the existing technical solutions gradually expose multiple insurmountable technical defects in actual application, and cannot meet the requirements of new energy automobiles for "high reliability, easy maintenance and long life" of power batteries.

[0003] Firstly, the existing heat-conducting structural adhesive generally faces the binary contradiction between "adhesion strength and disassembly convenience", which has become the core bottleneck restricting the efficiency of battery maintenance and recycling. In order to ensure the structural stability of the battery pack under complex working conditions, including continuous vibration during high-speed driving of the vehicle, instantaneous impact during emergency braking or collision, and long-term service environment under normal working conditions, the dynamic shear strength of the existing heat-conducting structural adhesive is generally high. However, this high adhesion strength makes it difficult to separate the battery module and the cooling plate when the battery needs to be repaired or recycled. The operator needs to use a "high-temperature heating + mechanical prying" composite process to achieve separation, which leads to complex and time-consuming disassembly of single modules, and seriously reduces the maintenance efficiency. More importantly, high-temperature disassembly above 120℃ can cause thermal decomposition of the positive electrode material of the battery, damage the structure of the active material of the battery, and further reduce the recycling value.

[0004] Secondly, the "insufficient functional integration" of the existing packaging solution leads to complex structure and redundant weight, which is contrary to the development goal of "lightweight and high energy density" of new energy vehicles. The power battery packaging needs to meet multiple functional requirements such as heat conduction, insulation, weather resistance, and cushioning. However, the adhesive in the existing technology only has a single adhesive function, and other performances need to be achieved by stacking 3-4 independent functional films. For example, to meet the thermal conductivity requirement, a separate thermal filler layer is needed; to meet the insulation standard of volume resistivity, an additional epoxy resin insulation film is needed; to resist high temperature and humidity, salt spray and other harsh environmental erosion, a weather-resistant protective layer is needed. This "multi-layer stacking" design mode increases the total thickness of the packaging structure and the overall weight of the battery pack, directly leading to a decrease in battery volume rate and indirectly affecting the vehicle's range. At the same time, the interface matching between the multi-layer structure is poor, and the difference between the thermal expansion coefficients of each layer is large.

[0005] Finally, the "low efficiency and high pollution" of the existing disassembly process does not meet the requirements of green development. During the current battery pack disassembly process, organic solvents (such as toluene and ethyl acetate) are needed to soften the structural glue, and solvent residues will cause the cycle life of the repaired battery to be shortened. At the same time, the volatilization of organic solvents not only harms the health of the operators, but also pollutes the environment. In addition, the existing packaging solution lacks consideration of the whole life cycle of the battery. After the disassembly of the retired battery, the adhesive and the battery material are difficult to completely separate, leading to an increase in the difficulty of recycling valuable resources such as positive materials and copper foil.

[0006] In summary, the existing adhesive and related assembly technology for packaging new energy vehicle power batteries have significant defects in key dimensions such as "strength-disassembly balance", "functional integration", "cost-performance matching", and "green recycling". Developing an adhesive composition that can balance normal temperature reliability, high temperature disassembly, multi-functional integration, and low cost mass production has become a core technical problem that needs to be solved in the field. SUMMARY

[0007] From the above technical problems, one of the purposes of the present application is to solve the defects of the existing adhesive and assembly technology for packaging new energy vehicle power batteries, to ensure the normal temperature service reliability of new energy vehicle power batteries, to meet the requirements of 25°C high shear strength, 55°C high retention rate, and full temperature range use; to improve the convenience of high temperature disassembly, to reduce the shear strength and separation force at 80°C, and to shorten the disassembly time; to realize efficient functional integration, to balance high thermal conductivity, high insulation, and weather resistance, to reduce the number of functional films, and to build a simple structure, light weight, and high battery volume rate of the power battery assembly.

[0008] Specifically, according to one aspect of the present application, an adhesive composition is provided, which comprises, based on its total solid content:

[0009] 30-40 wt% of a thermoplastic polymer;

[0010] 5-15 wt% of a thermally conductive filler;

[0011] 3-8 wt% of a plasticizer;

[0012] 1-4 wt% of a coupling agent;

[0013] 0.5-3 wt% of a stabilizer; and

[0014] an organic solvent, wherein:

[0015] the thermoplastic polymer is a blend of a thermoplastic copolyester and a thermoplastic polyacrylate in a weight ratio of 2: 1-1:2; the thermoplastic copolyester is a butylene terephthalate-adipate block copolymer having a glass transition temperature of 53-58 °C and a number average molecular weight of 15000-21000 g / mol; and the thermoplastic polyacrylate is a methyl methacrylate-ethyl acrylate-butyl acrylate terpolymer having a glass transition temperature of 60-65 °C and a number average molecular weight of 20000-23000 g / mol.

[0016] According to certain preferred embodiments of the present application, the thermally conductive filler is selected from one or more of alumina, silica, magnesia, beryllia, titania, aluminum nitride, silicon nitride, boron nitride, graphene, silicon carbide, and carbon fiber.

[0017] According to certain preferred embodiments of the present application, the thermally conductive filler is a compounding of nano-alumina and hexagonal boron nitride in a weight ratio of 1: 1-2: 1, wherein the nano-alumina has a particle size of 50-100 nm and the hexagonal boron nitride has a particle size of 1-5 μιη.

[0018] According to certain preferred embodiments of the present application, the plasticizer is selected from one or more of phthalate plasticizers, aliphatic dibasic acid ester plasticizers, polyester plasticizers, phosphate plasticizers, epoxy plasticizers, and citrate plasticizers.

[0019] According to certain preferred embodiments of the present application, the plasticizer is a compounding of dioctyl phthalate and polyethylene adipate glycol in a weight ratio of 1: 1-2: 1.

[0020] According to certain preferred embodiments of the present application, the polyethylene adipate glycol has a number average molecular weight of 500-2000 g / mol.

[0021] According to certain preferred embodiments of the present application, the coupling agent is selected from one or more of silane coupling agents, titanate coupling agents, and aluminate coupling agents.

[0022] According to certain preferred embodiments of the present application, the coupling agent is a complex of γ-aminopropyltriethoxysilane and isopropyl tri(dioctylpyrophosphato) titanate in a weight ratio of 2:1 to 3:1.

[0023] According to certain preferred embodiments of the present application, the stabilizer is selected from one or more of an antioxidant, a light stabilizer, an anti-hydrolysis stabilizer, an anti-metal ion stabilizer, and an ultraviolet absorber.

[0024] According to certain preferred embodiments of the present application, the stabilizer is a complex of tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid] pentaerythritol ester and 2-(2H-benzotriazol-2-yl)-4,6-di-tert-amylphenol in a weight ratio of 2:1 to 3:1.

[0025] According to certain preferred embodiments of the present application, the adhesive composition comprises 10 to 20% by weight of the organic solvent, based on the total weight thereof.

[0026] According to certain preferred embodiments of the present application, the organic solvent is selected from one or more of methyl ethylene ketone, acetone, butanone, cyclohexanone, ethyl acetate, butyl acetate, isobutyl acetate, propylene glycol methyl ether acetate, toluene, and xylene.

[0027] According to another aspect of the present application, there is provided an adhesive layer comprising the adhesive composition described above.

[0028] According to certain preferred embodiments of the present application, the adhesive layer has a thickness of 15 to 80 μm.

[0029] According to yet another aspect of the present application, there is provided a new energy automobile power battery assembly comprising:

[0030] a battery module;

[0031] a thermally conductive structural adhesive layer in contact with the battery module;

[0032] an adhesive layer in contact with the thermally conductive structural adhesive layer, the adhesive layer being cured from the adhesive composition described above;

[0033] an insulating buffer layer in contact with the adhesive layer; and

[0034] a cooling plate in contact with the insulating buffer layer.

[0035] According to certain preferred embodiments of the present application, the thermally conductive structural adhesive layer has a thickness of 0.5 to 2 mm.

[0036] According to some preferred embodiments of the present application, the thickness of the adhesive layer is 15-80 μm.

[0037] According to some preferred embodiments of the present application, the insulating buffer layer is formed of an epoxy resin-based material and has a thickness of 25-50 μm.

[0038] According to some preferred embodiments of the present application, the cooling plate is a metal plate with a circulating pipe inside.

[0039] According to some preferred embodiments of the present application, the cooling plate is an aluminum alloy plate and the diameter of the circulating pipe is 3-5 mm. BRIEF DESCRIPTION OF DRAWINGS

[0040] The accompanying drawings are provided in the present specification to more clearly explain the technical solutions of the present application, however the present application is not limited thereto.

[0041] Figure 1 A partial surface structure schematic diagram of a new energy automobile power battery assembly according to one specific embodiment of the present application is shown. DETAILED DESCRIPTION

[0042] The present application will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It will be understood that other embodiments are contemplated, and can be practiced without departing from the scope or spirit of the present application. Therefore, the following detailed description is non-limiting.

[0043] Unless otherwise indicated, all numbers expressing features, quantities and physical characteristics in the specification are to be understood as approximations based on the terms "about" and "at or about." Therefore, unless otherwise indicated, the numerical parameters set forth in the specification and attached claims are approximations that can vary depending on the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein. At the very least, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0044] As described herein, the term "formulation" has a similar or identical meaning as the terms "blend", "mixture", "composition" and "combination", unless otherwise specified, and denotes a combination of two or more components.

[0045] As described above, the existing heat-conductive structural adhesive for new energy automobile power battery packaging has a contradiction between adhesive strength and disassembly convenience. Although high strength at room temperature ensures stable working conditions, the strength is still high at high temperature, which leads to difficult disassembly and high module damage rate. In addition, the traditional adhesive has single function, and multiple functional films need to be stacked, which increases the packaging thickness and weight, reduces the battery volume rate, and the interface matching between layers is poor, which is prone to peeling after thermal cycling, and there is a risk of thermal runaway. The present application aims to solve the above technical problems.

[0046] In particular, according to one aspect of the present application, there is provided an adhesive composition comprising, based on the total solid content thereof:

[0047] 30-40 wt% of a thermoplastic polymer;

[0048] 5-15 wt% of a thermally conductive filler;

[0049] 3-8 wt% of a plasticizer;

[0050] 1-4 wt% of a coupling agent;

[0051] 0.5-3 wt% of a stabilizer; and

[0052] an organic solvent, wherein:

[0053] the thermoplastic polymer is a blend of a thermoplastic copolyester and a thermoplastic polyacrylate at a weight ratio of 2:1-1:2; the thermoplastic copolyester is a butylene terephthalate-butylene adipate block copolymer having a glass transition temperature of 53-58℃ and a number average molecular weight of 15000-21000 g / mol; and the thermoplastic polyacrylate is a methyl methacrylate-ethyl acrylate-butyl acrylate terpolymer having a glass transition temperature of 60-65℃ and a number average molecular weight of 20000-23000 g / mol.

[0054] The thermoplastic polymer as the matrix skeleton of the adhesive composition determines the mechanical strength, temperature response characteristics and interfacial bonding capacity of the adhesive layer. Specifically, the thermoplastic copolyester selected by the present application is a butylene terephthalate-butylene adipate block copolymer (PBAT), which contains both rigid butylene terephthalate (PBT) segments and flexible butylene adipate (PBA) segments in the molecular chain. By adjusting the block ratio of the two segments, the glass transition temperature (Tg), crystallinity and mechanical properties of the polymer can be adjusted.

[0055] Specifically, the Tg of the PBAT block copolymer of the present application is controlled at 53-58℃, which is of great significance. On the one hand, the Tg of 53-58℃ is higher than the normal working temperature of the power battery (25-55℃), which ensures that the polymer matrix remains rigid under normal working conditions such as vehicle driving and fast charging, providing stable shear strength and structural support for the adhesive layer and avoiding module displacement or interfacial peeling due to matrix softening; on the other hand, the Tg is lower than the high-temperature disassembly temperature (80℃), when the disassembly temperature reaches 80℃, the PBAT segment changes from glassy state to high-elastic state, the molecular chain movement ability is enhanced, and the matrix rigidity is reduced, thereby reducing the adhesive strength.

[0056] The number average molecular weight of the PBAT of the present application is 15000-21000 g / mol. The selection of this molecular weight range is based on the following considerations: if the molecular weight is lower than 15000 g / mol (such as 12000 g / mol), the polymer molecular chain is short, the degree of interchain entanglement is insufficient, the tensile strength of the adhesive layer and the interfacial bonding force are significantly reduced, the dynamic shear strength at 25℃ is low, and the working condition requirements of vibration resistance and impact resistance of the power battery cannot be met; if the molecular weight is higher than 21000 g / mol (such as 25000 g / mol), the molecular chain entanglement is too tight, the molecular chain movement is hindered at high temperature (80℃), even in the high elastic state, the adhesive layer still maintains a high cohesive strength, the shear strength at 80℃ is too high, resulting in too large separation force during disassembly, and the module damage rate increases.

[0057] In addition, according to the technical scheme of the present application, the thermoplastic polyacrylate selected by the present application is methyl methacrylate-ethyl acrylate-butyl acrylate terpolymer (MMA-EA-BA), which solves the deficiencies of single acrylate polymer in rigidity, adhesion or weather resistance through synergistic copolymerization of three monomers, and forms a performance complementary blending system with PBAT.

[0058] The present application controls the Tg of the terpolymer to be 60-65℃ by adjusting the weight ratio of MMA, EA and BA. This Tg design forms a reasonable gradient with the Tg of PBAT (53-58℃): the Tg of 60-65℃ further ensures the structural stability of the adhesive layer at high temperature working conditions of 55℃, avoiding the strength attenuation caused by matrix softening; at the same time, there is still a temperature difference of 15-20℃ between 60-65℃ and the disassembly temperature of 80℃, which ensures that the terpolymer can also change from glassy state to high elastic state at high temperature, and cooperates with PBAT to reduce the adhesion strength.

[0059] According to the technical scheme of the present application, the number average molecular weight of the methyl methacrylate-ethyl acrylate-butyl acrylate terpolymer is 20000-23000 g / mol, which is selected based on the compatibility of the blending system with PBAT and the matching of mechanical properties. If the molecular weight is lower than 20000 g / mol (such as 18000 g / mol), the blending system of the terpolymer and PBAT is prone to phase separation, resulting in uneven internal structure of the adhesive layer and large fluctuation of mechanical properties; if the molecular weight is higher than 23000 g / mol (such as 25000 g / mol), the melt viscosity of the blending system is significantly increased, which is not conducive to the implementation of the subsequent coating process, and the molecular chain movement is difficult at high temperature, affecting the disassembly performance.

[0060] The present application realizes synergistic enhancement effect by blending PBAT with terpolymer at a weight ratio of 2:1-1:2, utilizing the structural complementarity of the two polymers. Specifically, without being bound by theory, the rigid segment (PBT) of PBAT and the MMA unit of the terpolymer synergistically enhance the room temperature rigidity and shear strength of the adhesive layer, and the flexible segment (PBA) of PBAT and the EA, BA units of the terpolymer synergistically improve the toughness and low-temperature anti-brittle performance of the adhesive layer. In addition, the Tg of PBAT (53-58℃) and the Tg of the terpolymer (60-65℃) form a temperature response gradient, and within the working temperature range of 25-55℃, both polymers are in a glassy state, and the adhesive layer maintains high rigidity and high adhesive strength; when the temperature rises to 60-70℃, PBAT first changes to an elastomeric state, and the adhesive strength begins to decrease; when the temperature reaches 80℃, the terpolymer also changes to an elastomeric state, and the adhesive strength rapidly decreases, achieving efficient disassembly.

[0061] The source of the thermoplastic copolyester and the thermoplastic polyacrylate that can be used in the present application is not particularly limited, and it can be commercially available or can be prepared according to known organic synthesis methods in the art.

[0062] According to certain preferred embodiments of the present application, the thermally conductive filler is selected from one or more of alumina, silica, magnesium oxide, beryllium oxide, titanium dioxide, aluminum nitride, silicon nitride, boron nitride, graphene, silicon carbide, and carbon fiber.

[0063] Preferably, the thermally conductive filler is a compound of nano-alumina and hexagonal boron nitride at a weight ratio of 1:1-2:1, wherein the particle size of the nano-alumina is 50-100 nm, and the particle size of the hexagonal boron nitride is 1-5 μm. According to the above technical solution, nano-alumina (particle size 50-100 nm) and hexagonal boron nitride (particle size 1-5 μm) are compounded at a weight ratio of 1:1-2:1 to construct a "point-surface combined" dual thermal conduction network, significantly improving the thermal conductivity of the adhesive layer. Without being bound by theory, nano-alumina (50-100 nm) is spherical or spherical-like particles with a large specific surface area, which can be uniformly dispersed in the adhesive matrix, forming a primary thermal conduction path through "point contact" between particles. On the other hand, hexagonal boron nitride (h-BN) has a flaky layered structure with excellent in-plane thermal conductivity, and its flaky structure will be oriented and arranged along the coating direction during the coating process, forming a secondary thermal conduction network through "face-to-face stacking". The present application found in the research that the layered structure of flaky h-BN can span the gap between nano-alumina particles, further reducing thermal resistance and improving thermal conductivity efficiency.

[0064] The plasticizer in the adhesive composition mainly plays a role in reducing the glass transition temperature of the polymer matrix, improving the flexibility and low-temperature anti-brittle performance of the adhesive layer, and optimizing the dispersibility of the filler and the interfacial bonding capacity of the adhesive layer. According to some preferred embodiments of the present application, the plasticizer is selected from one or more of phthalate plasticizers, aliphatic dibasic acid ester plasticizers, polyester plasticizers, phosphate plasticizers, epoxy plasticizers and citrate plasticizers. More preferably, the plasticizer is a compound of dioctyl phthalate and polyethylene adipate with a weight ratio of 1:1 to 2:1. The present application uses a compound of dioctyl phthalate (DOP) and polyethylene adipate (PEA) with a weight ratio of 1:1 to 2:1, which utilizes the complementary properties of the two plasticizers to achieve a synergistic optimization of the "room temperature flexibility-low temperature anti-brittle performance-migration resistance" of the adhesive layer. Without being bound by theory, DOP is a small molecule phthalate plasticizer, which contains flexible octyl chains and polar ester groups in its molecular structure, can quickly insert between the molecular chains of PBAT and the terpolymer, weaken the intermolecular force, and reduce the glass transition temperature (Tg) of the polymer matrix. In addition, PEA is a high molecular weight polyester plasticizer, which contains multiple ester groups and hydroxyl groups in its molecular chain. On the one hand, its flexible aliphatic segment can entangle with the polymer molecular chain to form a stable plasticizing structure, which has excellent migration resistance and can maintain the plasticizing effect for a long time; on the other hand, the hydroxyl groups at the end of the PEA molecular chain can form hydrogen bonds with the ester groups in the PBAT / terpolymer molecular chain, enhancing the intermolecular force and maintaining the flexibility of the molecular chain in a low temperature environment (-40°C), thereby avoiding the brittle fracture of the adhesive layer.

[0065] Preferably, the polyethylene adipate has a number average molecular weight of 500-2000 g / mol.

[0066] According to some preferred embodiments of the present application, the coupling agent is selected from one or more of silane coupling agents, titanate coupling agents and aluminate coupling agents. Examples of coupling agents that can be used include but are not limited to: γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, isopropyl tri(dioctyl pyrophosphoryloxy) titanate, isopropyl tri-stearyl titanate and di-stearyloxyisopropyl aluminate. Preferably, the coupling agent is a compound of γ-aminopropyltriethoxysilane and isopropyl tri(dioctyl pyrophosphoryloxy) titanate with a weight ratio of 2:1 to 3:1. By selecting a specific ratio of a compound of γ-aminopropyltriethoxysilane and isopropyl tri(dioctyl pyrophosphoryloxy) titanate, the adhesion strength of the adhesive layer under working conditions can be greatly improved.

[0067] In addition, the power battery will face complex environments such as high temperature, high humidity, and ultraviolet radiation during long-term service, which can easily lead to degradation of the polymer matrix in the adhesive composition and breaking of chemical bonds, thereby causing the mechanical properties, thermal conductivity, and insulation performance of the adhesive layer to deteriorate. The adhesive composition according to the present application comprises a stabilizer to improve the relevant performance. According to certain preferred embodiments of the present application, the stabilizer is selected from one or more of an antioxidant, a light stabilizer, an anti-hydrolysis stabilizer, an anti-metal ion stabilizer, and an ultraviolet absorber. Preferably, the stabilizer is a complex of tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]pentaerythritol ester (i.e., antioxidant 1010) and 2-(2H-benzotriazol-2-yl)-4,6-di-tert-amylphenol at a weight ratio of 2:1 to 3:1. By selecting the above specific stabilizer complex system, the salt spray corrosion resistance of the obtained adhesive layer can be greatly improved.

[0068] The organic solvent mainly plays a role in dissolving the polymer matrix and dispersing the fillers and additives in the adhesive composition. Preferably, the adhesive composition comprises 30-55% by weight of the organic solvent based on the total weight thereof. Preferably, the organic solvent is selected from one or more of methyl vinyl ketone, acetone, butanone, cyclohexanone, ethyl acetate, butyl acetate, isobutyl acetate, propylene glycol methyl ether acetate, toluene, and xylene.

[0069] According to another aspect of the present application, there is provided an adhesive layer comprising the adhesive composition described above. Preferably, the thickness of the adhesive layer is 15-80 μm.

[0070] According to still another aspect of the present application, there is provided a new energy automobile power battery assembly, which comprises:

[0071] a battery module;

[0072] a thermally conductive structural adhesive layer in contact with the battery module;

[0073] an adhesive layer in contact with the thermally conductive structural adhesive layer, the adhesive layer being cured from the adhesive composition described above;

[0074] an insulation buffer layer in contact with the adhesive layer; and

[0075] a cooling plate in contact with the insulation buffer layer.

[0076] The adhesive layer cured from the adhesive composition of the present application is finally applied to the new energy automobile power battery assembly, and through optimization of the layered structure of the assembly, the functions of "thermal conduction-insulation-buffering-adhesion" are integrated, thereby solving the problems of complex structure, large weight, and low volume ratio of the traditional assembly.

[0077] Figure 1 A partial surface structure schematic diagram of a new energy automobile power battery assembly 100 according to a specific embodiment of the present application is shown. As shown in Figure 1 The new energy automobile power battery assembly 100 includes: a battery module 1; a heat-conducting structural adhesive layer 2 in contact with the battery module 1; an adhesive layer 3 in contact with the heat-conducting structural adhesive layer 2; an insulating buffer layer 4 in contact with the adhesive layer 3; and a cooling plate 5 in contact with the insulating buffer layer 4. In Figure 1 The structure of the new energy automobile power battery assembly is shown in a layer-by-layer laminated form, however, it should be noted that the new energy automobile power battery assembly according to the present application is by no means limited to this, and the new energy automobile power battery assembly according to the present application can also have an encapsulation structure in which each layer completely covers the battery module.

[0078] Specifically, the thickness of the heat-conducting structural adhesive layer is 0.5-2 mm. The material of the heat-conducting structural adhesive layer is not particularly limited and can be selected from conventional conductive adhesives. Preferably, the thickness of the adhesive layer is 15-80 μm. According to certain preferred embodiments of the present application, the insulating buffer layer is formed of an epoxy resin-based material and has a thickness of 25-50 μm. According to certain preferred embodiments of the present application, the cooling plate is a metal plate with a circulating pipe inside.

[0079] Preferably, the cooling plate is an aluminum alloy plate and the diameter of the circulating pipe is 3-5 mm.

[0080] Compared with the prior art, the adhesive composition, the adhesive layer comprising the adhesive composition, and the new energy automobile power battery assembly according to the present application have the following advantages:

[0081] 1. The adhesive composition greatly increases the dynamic shear strength at 25°C and the strength retention rate at 55°C by precisely regulating the types and proportions of the components, thereby meeting the stable requirements under driving vibration, collision and other working conditions; the single-module disassembly time is greatly shortened, which is much better than the disassembly time of the prior art, and the secondary damage rate to the module is reduced.

[0082] 2. The adhesive composition has high thermal conductivity, high insulation, salt mist corrosion resistance and other properties, and does not need to be stacked with 3-4 layers of functional films, thereby solving the problem of thick and heavy encapsulation of the traditional scheme, which helps to reduce the weight of the battery pack.

[0083] 3. By synergistically designing the plasticizer and the polymer, the embrittlement temperature of the adhesive layer is reduced to below -40°C, and the adhesive layer can stably work in the full temperature range of -40°C-85°C, thereby avoiding the risk of high peeling rate and easy heat runaway after thermal cycling of the prior art.

[0084] 4. The battery assembly of the application has a battery volume rate greatly improved, and the interface matching of the cooling plate and the adhesive layer is optimized, so that the heat dissipation power of the unit weight cooling plate is improved.

[0085] The application will be described in more detail below with reference to the embodiments. It should be noted that these descriptions and embodiments are intended to facilitate the understanding of the application, and are not limiting to the application.

[0086] Embodiments

[0087] In the application, unless otherwise specified, the reagents used are commercially available products, which are used directly without further purification treatment. In addition, the "%" mentioned is "wt%" and the "parts" mentioned is "wt parts".

[0088] Performance test method

[0089] The adhesive compositions prepared in the following examples and comparative examples were respectively tested for normal temperature service reliability, high temperature disassembly convenience, thermal conductivity, and salt spray corrosion resistance by the following detailed description.

[0090] Normal temperature service reliability test

[0091] 25℃ dynamic shear strength test: according to GB / T 7124-2021 "Determination of Tensile Shear Strength of Adhesives (Rigid Material to Rigid Material)", the adhesive composition samples prepared in the following examples or comparative examples were coated between the aluminum alloy substrate (size 100mm×25mm×2mm) for power battery and the battery module simulation substrate (size 100mm×25mm×3mm), the thickness of the adhesive layer was controlled to be 30μm, and the adhesive layer was cured by 60℃ hot air drying for 1h and 100℃ vacuum drying for 30min. A universal testing machine was used to test the shear strength at a tensile rate of 5mm / min, each group was tested in parallel for 5 times, and the average value was taken.

[0092] 55℃ strength retention rate test: the cured shear sample was placed in a 55℃ constant temperature box, and statically placed for 1000h, then taken out and balanced at 25℃ environment for 2h, and the shear strength was tested at the same tensile rate, and the ratio of the strength after 55℃ aging to the initial 25℃ strength (i.e. strength retention rate) was calculated.

[0093] Full temperature range (-40℃-55℃) cycle stability test: the shear sample was placed in a high and low temperature cycle box, and 1 cycle was performed according to -40℃ (2h)→ heating to 55℃ (2h). A total of 500 cycles were performed. After the cycle was completed, the 25℃ dynamic shear strength was tested, and the ratio to the initial strength was calculated.

[0094] Evaluation criteria:

[0095] Excellent: dynamic shear strength ≥ 3.2 MPa at 25℃, strength retention rate ≥ 85% at 55℃ for 1000h, strength retention rate ≥ 80% after 500 cycles in full temperature range, excellent performance in power battery normal temperature work.

[0096] Good: dynamic shear strength 2.5-3.1 MPa at 25℃, strength retention rate 75%-84% at 55℃ for 1000h, strength retention rate 70%-79% after 500 cycles in full temperature range, can meet the requirements of power battery normal temperature service.

[0097] Poor: dynamic shear strength < 2.5 MPa at 25℃, strength retention rate < 75% at 55℃ for 1000h, strength retention rate < 70% after 500 cycles in full temperature range, prone to module displacement and interface peeling, unable to meet the requirements of power battery normal temperature service.

[0098] High temperature disassembly convenience test

[0099] Take the adhesive sample (aluminum alloy substrate-adhesive layer-battery module substrate, adhesive layer thickness 15-80 μm) prepared by curing the adhesive composition of the following examples or comparative examples, and place it in an 80℃ constant temperature environment box for 30min (simulating the actual disassembly preheating temperature). Using a universal testing machine, test the 80℃ dynamic shear strength of the sample at a rate of 10mm / min; at the same time, use a digital push-pull force meter to measure the minimum separation force for separating the battery module from the substrate, and take the average value of 5 parallel tests for each group.

[0100] Evaluation criteria:

[0101] Excellent: 80℃ dynamic shear strength ≤ 0.8 MPa, separation force ≤ 0.5 MPa, single module disassembly time ≤ 10min, no secondary damage to the module, meets the requirements of rapid repair and recycling;

[0102] Good: 80℃ dynamic shear strength 0.9-1.2 MPa, separation force 0.6-0.8 MPa, single module disassembly time 11-20min, slight damage rate ≤ 10%;

[0103] Poor: 80℃ dynamic shear strength > 1.2 MPa, separation force > 0.8 MPa, single module disassembly time > 20min, damage rate > 10%, unable to meet the requirements of efficient disassembly and recycling.

[0104] Thermal conductivity test

[0105] The adhesive composition prepared in the following examples or comparative examples was coated on a polyimide film substrate with a thickness of 50 μm, dried by hot air at 60°C for 1 h and vacuum dried at 100°C for 30 min to form an adhesive layer sample. According to GB / T 22588-2008 "Measurement of thermal diffusivity or thermal conductivity by flash method", the thermal conductivity of the adhesive layer was tested at two temperature points of 25°C and 55°C using a laser flash thermal conductivity instrument, and each group was tested in triplicate, and the average value was taken.

[0106] Evaluation criteria:

[0107] Excellent: thermal conductivity at 25°C ≥ 2.3 W / (m•K), thermal conductivity at 55°C ≥ 2.5 W / (m•K), which can well meet the fast charging heat dissipation requirements of power batteries;

[0108] Good: thermal conductivity at 25°C 1.8-2.2 W / (m•K), thermal conductivity at 55°C 2.0-2.4 W / (m•K), which can meet the fast charging heat dissipation requirements of power batteries;

[0109] Poor: thermal conductivity at 25°C < 1.8 W / (m•K), thermal conductivity at 55°C < 2.0 W / (m•K), which is prone to cause local overheating of the battery and cannot meet the packaging heat dissipation requirements.

[0110] Salt spray corrosion resistance test

[0111] The adhesive composition prepared in the following examples or comparative examples was coated on the surface of an aluminum alloy substrate (size 100 mm x 50 mm x 2 mm) for power batteries with a thickness of 50 μm, dried by hot air at 60°C for 1 h and vacuum dried at 100°C for 30 min to form an adhesive layer sample. According to GB / T 10125-2021 "Artificial atmosphere corrosion test - Salt spray test", a neutral salt spray test chamber was used to test the salt spray at 35°C with a 5% sodium chloride solution (pH 6.5-7.2), a spray rate of 1.5 mL / (h•cm²), and a test duration of 1000 h. After the test, the sample was taken out, washed with water and dried, and the appearance of the adhesive layer and the bonding state with the substrate were observed.

[0112] Evaluation criteria:

[0113] Excellent: after 1000 h of salt spray, the adhesive layer has no blistering, peeling, discoloration, and the grid test (grid spacing 1 mm) has an adhesion of 0 grade, which meets the outdoor and high humidity environment use requirements of power batteries;

[0114] Good: after 1000 h of salt spray, the adhesive layer has slight discoloration at the edge, no blistering and peeling, and the grid adhesion is grade 1;

[0115] Poor: after 1000 h of salt spray, the adhesive layer has blistering, peeling or obvious discoloration, and the grid adhesion is ≥ grade 2, which cannot meet the salt spray corrosion resistance requirements of power batteries.

[0116] Preparation Example 1 (Preparation of thermoplastic copolyester 1)

[0117] Into a 500 mL four-necked flask equipped with a stirrer, thermometer, condenser and nitrogen inlet, 100 parts by weight of terephthalic acid, 65 parts by weight of adipic acid and 92 parts by weight of 1,4-butanediol were sequentially added, followed by the addition of 0.05 parts by weight of tetrabutyl titanate (catalyst) and 0.02 parts by weight of triphenyl phosphate (stabilizer). The flask was purged with nitrogen three times to ensure that the system was free of oxygen. The temperature was raised to 160°C, and the system was stirred for 2 hours to perform the ester exchange reaction. During the reaction, the generated methanol was collected. Subsequently, the temperature was raised to 220°C, and the system was gradually vacuumed to an absolute pressure of 50 Pa. The system was kept at this temperature for 4 hours to perform the polycondensation reaction. The viscosity change of the system was monitored in real time. After the reaction was completed, the heating was stopped, and the vacuum was released by purging with nitrogen. The product was extruded through a spinneret and cut into particles to obtain thermoplastic copolyester 1. The glass transition temperature of the product was 55°C, as determined by differential scanning calorimetry (DSC). The number average molecular weight of the product was 18000 g / mol, as determined by gel permeation chromatography (GPC).

[0118] Preparation Example 2 (Preparation of thermoplastic copolyester 2)

[0119] Into a 1000 mL reactor with mechanical stirring, rectifying column and nitrogen inlet, 120 parts by weight of terephthalic acid, 70 parts by weight of adipic acid and 105 parts by weight of 1,4-butanediol were added, followed by the addition of 0.06 parts by weight of antimony trioxide (catalyst) and 0.03 parts by weight of triphenyl phosphite (antioxidant). High-purity nitrogen (purity ≥ 99.99%) was introduced to remove the air in the reactor and maintain a slight positive pressure of nitrogen. The temperature was raised to 180°C, and the system was kept at this temperature for 3 hours to perform the esterification reaction. The generated water (about 32 mL) was collected. Subsequently, the temperature was raised to 240°C, and the system was slowly vacuumed to an absolute pressure of 30 Pa. The polycondensation reaction was continued for 5 hours. During the reaction, the melt viscosity was monitored by an Ubbelohde viscometer. After the reaction was completed, the reactor was filled with nitrogen to normal pressure. The molten product was extruded through a spinneret, water-cooled and cut into particles to obtain thermoplastic copolyester 2. The glass transition temperature of the product was 57°C, as determined by differential scanning calorimetry (DSC). The number average molecular weight of the product was 20000 g / mol, as determined by gel permeation chromatography (GPC).

[0120] Preparation Example 3 (Preparation of thermoplastic polyacrylate 1)

[0121] A 500 mL four-necked flask equipped with mechanical stirring, reflux condenser, nitrogen inlet and constant pressure dropping device was charged with 180 parts by weight of butanone (solvent), and the system was purged with high-purity nitrogen (purity ≥ 99.99%) three times. The temperature was raised to 80°C and kept constant. A mixture of 55 parts by weight of methyl methacrylate, 30 parts by weight of ethyl acrylate and 15 parts by weight of butyl acrylate (total mass of monomers 100 parts) and 1.5 parts by weight of dibenzoyl peroxide (initiator) was prepared into a uniform prepolymer solution. The prepolymer solution was added into the flask at a rate of 1.5 drops per second through the constant pressure dropping device. After the addition was completed, the reaction was continued for 5 hours. After the reaction was completed, the reaction solution was slowly added into 1200 parts by weight of ethanol for precipitation. The light yellow solid was collected by filtration and dried in a vacuum drying oven (vacuum degree ≤ -0.09 MPa) at 85°C for 10 hours to obtain a methyl methacrylate-ethyl acrylate-butyl acrylate terpolymer 2. The glass transition temperature of the terpolymer was 64°C as determined by differential scanning calorimetry (DSC), and the number average molecular weight was 22500 g / mol as determined by gel permeation chromatography (GPC).

[0122] Preparation Example 4 (Preparation of thermoplastic polyacrylate 2)

[0123] A 500 mL four-necked flask equipped with mechanical stirring, reflux condenser, nitrogen inlet and constant pressure dropping device was charged with 180 parts by weight of butanone (solvent), and the system was purged with high-purity nitrogen (purity ≥ 99.99%) three times. The temperature was raised to 80°C and kept constant. A mixture of 55 parts by weight of methyl methacrylate, 30 parts by weight of ethyl acrylate and 15 parts by weight of butyl acrylate (total mass of monomers 100 parts) and 1.5 parts by weight of dibenzoyl peroxide (initiator) was prepared into a uniform prepolymer solution. The prepolymer solution was added into the flask at a rate of 1.5 drops per second through the constant pressure dropping device. After the addition was completed, the reaction was continued for 5 hours. After the reaction was completed, the reaction solution was slowly added into 1200 parts by weight of ethanol for precipitation. The light yellow solid was collected by filtration and dried in a vacuum drying oven (vacuum degree ≤ -0.09 MPa) at 85°C for 10 hours to obtain a methyl methacrylate-ethyl acrylate-butyl acrylate terpolymer 2. The glass transition temperature of the terpolymer was 64°C as determined by differential scanning calorimetry (DSC), and the number average molecular weight was 22500 g / mol as determined by gel permeation chromatography (GPC).

[0124] Example 1 (E1)

[0125] In a 2000 mL stirred tank equipped with a high-speed disperser (2000 r / min) and a constant temperature water bath, 840 g of ethyl acetate was first added, the stirring was started and the water bath temperature was controlled at 30°C to ensure stable dispersion of the solvent. Then, 600 g of thermoplastic polymer was added. The thermoplastic polymer was a premix of thermoplastic copolyester 1 (product of Preparation Example 1, 400 g) and thermoplastic polyacrylate 1 (product of Preparation Example 3, 200 g) at a weight ratio of 2:1. The stirring speed was maintained for 60 minutes until the polymer was completely dissolved, forming a transparent and uniform resin solution. Next, 300 g of silica particles (particle size about 100 μm, pretreated and dried to a water content of ≤0.1%) and 160 g of plasticizer dioctyl phthalate were added in sequence, and the stirring speed was increased to 3000 r / min. The stirring was continued for 90 minutes to ensure uniform dispersion of the fillers without agglomeration. Then, 80 g of coupling agent γ-aminopropyl triethoxysilane and 20 g of stabilizer tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid] pentaerythritol ester were added, and the stirring was continued for 45 minutes. During this period, the dispersion of the fillers was monitored by a laser particle size analyzer to ensure that the particle size distribution D90 was ≤200 μm. After the stirring was completed, adhesive composition 1 was obtained.

[0126] Adhesive compositions 1-10 were tested according to the methods described above for reliability in normal temperature service, convenience in high temperature disassembly, thermal conductivity, and salt spray corrosion resistance, and the test results are shown in Table 1 below.

[0127] Examples 2-10 (E2-E10) and Comparative Examples 1-4 (CE1-CE4)

[0128] The operations were carried out in a similar manner as in Example 1 to prepare adhesive compositions 2-10 and comparative adhesive compositions 1-4, except that the types and proportions of the individual components were adjusted as shown in Table 1 below.

[0129] Adhesive compositions 2-10 and comparative adhesive compositions 1-4 were tested according to the methods described above for reliability in normal temperature service, convenience in high temperature disassembly, thermal conductivity, and salt spray corrosion resistance, and the test results are shown in Table 1 below.

[0130] Table 1 Formulation of adhesive compositions of Examples 1-10 (E1-E10) and Comparative Examples 1-4 (CE1-CE4) and performance test results

[0131] Thermoplastic polymer Thermally conductive filler Plasticizer Coupling agent Stabilizer Organic solvent Service reliability Disassembly convenience Thermal conductivity Salt spray corrosion resistance E1 30 wt%: thermoplastic copolyester 1 and thermoplastic polyacrylate 1 (2:1) 15 wt%: SiO2particles 8 wt%: dioctyl phthalate 4 wt%: γ-aminopropyl triethoxysilane 1 wt%: antioxidant 1010 Balance: ethyl acetate Excellent Excellent Good Good E2 30 wt%: thermoplastic copolyester 1 and thermoplastic polyacrylate 2 (2:1) 15 wt%: SiO2particles 8 wt%: dioctyl phthalate 4 wt%: γ-aminopropyl triethoxysilane 1 wt%: antioxidant 1010 Balance: ethyl acetate Excellent Excellent Good Good E3 30 wt%: thermoplastic copolyester 2 and thermoplastic polyacrylate 1 (2:1) 15 wt%: SiO2particles 8 wt%: dioctyl phthalate 4 wt%: γ-aminopropyl triethoxysilane 1 wt%: antioxidant 1010 Balance: ethyl acetate Excellent Excellent Good Good E4 40 wt%: thermoplastic copolyester 1 and thermoplastic polyacrylate 1 (2:1) 5 wt%: SiO2particles 3 wt%: dioctyl phthalate 4 wt%: γ-aminopropyl triethoxysilane 1 wt%: antioxidant 1010 Balance: ethyl acetate Excellent Excellent Good Good E5 30 wt%: thermoplastic copolyester 1 and thermoplastic polyacrylate 1 (2:1) 15 wt%: SiO2particles 8 wt%: dioctyl phthalate 1 wt%: γ-aminopropyl triethoxysilane 3 wt%: antioxidant 1010 Balance: ethyl acetate Excellent Excellent Good Good E6 30 wt%: thermoplastic copolyester 1 and thermoplastic polyacrylate 1 (1:2) 15 wt%: SiO2particles 8 wt%: dioctyl phthalate 4 wt%: γ-aminopropyl triethoxysilane 1 wt%: antioxidant 1010 Balance: ethyl acetate Excellent Excellent Good Good E7 30 wt%: thermoplastic copolyester 1 and thermoplastic polyacrylate 1 (2:1) 15 wt%: alumina (50 nm) + hexagonal boron nitride (2 μm) (2:1) 8 wt%: dioctyl phthalate 4 wt%: γ-aminopropyl triethoxysilane 1 wt%: antioxidant 1010 Balance: ethyl acetate Excellent Excellent Excellent Good E8 30 wt%: thermoplastic copolyester 1 and thermoplastic polyacrylate 1 (2:1) 15 wt%: alumina (50 nm) + hexagonal boron nitride (2 μm) (2:1) 8 wt%: dioctyl phthalate + polyethylene adipate (2:1) 4 wt%: γ-aminopropyl triethoxysilane 1 wt%: antioxidant 1010 Balance: ethyl acetate Excellent Excellent Excellent Good

[0132] E9 30 wt%: thermoplastic copolyester 1 and thermoplastic polyacrylate 1 (2:1) 15 wt%: alumina (50 nm) + hexagonal boron nitride (2 μm) (2:1) 8 wt%: dioctyl phthalate + polyethylene adipate (2:1) 4 wt%: γ-aminopropyl triethoxysilane + isopropyl tri(dioctyl pyrophosphato) titanate (3:1) 1 wt%: antioxidant 1010 Balance: ethyl acetate Excellent Excellent Excellent Good E10 30 wt%: thermoplastic copolyester 1 and thermoplastic polyacrylate 1 (2:1) 15 wt%: alumina (50 nm) + hexagonal boron nitride (2 μm) (2:1) 8 wt%: dioctyl phthalate + polyethylene adipate glycol (2:1) 4 wt%: gamma-aminopropyl triethoxysilane + isopropyl tri(dioctyl pyrophosphoryloxy) titanate (3:1) 1 wt%: antioxidant 1010 + 2-(2H-benzotriazol-2-yl)-4,6-di-tert-amylphenol (2:1) balance: ethyl acetate very good very good very good very good CE1 25 wt%: thermoplastic copolyester 1 and thermoplastic polyacrylate 1 (2:1) 15 wt%: SiO2particles 8 wt%: dioctyl phthalate 4 wt%: gamma-aminopropyl triethoxysilane 1 wt%: antioxidant 1010 balance: ethyl acetate poor good good good CE2 45 wt%: thermoplastic copolyester 1 and thermoplastic polyacrylate 1 (2:1) 15 wt%: SiO2particles 8 wt%: dioctyl phthalate 4 wt%: gamma-aminopropyl triethoxysilane 1 wt%: antioxidant 1010 balance: ethyl acetate good poor good good CE3 30 wt%: thermoplastic copolyester 1 and thermoplastic polyacrylate 1 (2:1) 3 wt%: SiO2particles 8 wt%: dioctyl phthalate 4 wt%: gamma-aminopropyl triethoxysilane 1 wt%: antioxidant 1010 balance: ethyl acetate good good poor good CE4 30 wt%: thermoplastic copolyester 1 and thermoplastic polyacrylate 1 (2:1) 20 wt%: SiO2particles 8 wt%: dioctyl phthalate 4 wt%: gamma-aminopropyl triethoxysilane 1 wt%: antioxidant 1010 balance: ethyl acetate poor poor good poor

[0133] From the results of Table 1 above, it can be seen that the adhesive compositions of Examples 1-10 within the scope of the present application all meet the requirements of new energy vehicle power batteries on the adhesion layer in terms of normal temperature service reliability, high temperature disassembly convenience, thermal conductivity, and salt mist corrosion resistance.

[0134] In Comparative Example 1, the thermoplastic polymer accounted for 25% (lower than 30% of the present application), and the normal temperature service reliability was poor, and the remaining performance was good. The normal temperature strength was insufficient due to insufficient polymer.

[0135] In Comparative Example 2, the thermoplastic polymer accounted for 45% (higher than 40% of the present application), and the high temperature disassembly convenience was poor. The high temperature strength was difficult to reduce due to excessive polymer.

[0136] In Comparative Example 3, the thermal conductive filler accounted for 3% (lower than 5% of the present application), and the thermal conductivity was poor. The effective thermal conduction network could not be formed due to insufficient filler.

[0137] In Comparative Example 4, the thermal conductive filler accounted for 20% (higher than 15% of the present application), and the normal temperature service reliability, disassembly convenience, and salt mist resistance were poor. The structural stability was destroyed due to excessive filler.

[0138] Obviously, those skilled in the art can make various modifications and variations to the present disclosure without departing from the spirit and scope of the present disclosure. Thus, if these modifications and variations of the present disclosure fall within the scope of the claims of the present application and their equivalents, the present disclosure is also intended to include these modifications and variations.

Claims

1. An adhesive composition characterized in that, The adhesive composition comprises, based on the total weight thereof: 30-40 wt% of a thermoplastic polymer; 5-15 wt% of a thermally conductive filler; 3-8 wt% of a plasticizer; 1-4 wt% of a coupling agent; 0.5-3 wt% of a stabilizer; and an organic solvent, wherein: the thermoplastic polymer is a blend of a thermoplastic copolyester and a thermoplastic polyacrylate in a weight ratio of 2:1-1:2; the thermoplastic copolyester is a butylene terephthalate-adipate block copolymer having a glass transition temperature of 53-58°C and a number average molecular weight of 15000-21000 g / mol; and the thermoplastic polyacrylate is a methyl methacrylate-ethyl acrylate-butyl acrylate terpolymer having a glass transition temperature of 60-65°C, a number average molecular weight of 20000-23000 g / mol, and the thermally conductive filler is selected from one or more of alumina, silica, magnesia, beryllia, titania, aluminum nitride, silicon nitride, boron nitride, and silicon carbide.

2. The adhesive composition according to claim 1, characterized in that, the plasticizer is selected from one or more of phthalate plasticizers, aliphatic dibasic acid ester plasticizers, polyester plasticizers, phosphate plasticizers, epoxy plasticizers, and citrate plasticizers.

3. The adhesive composition of claim 1, wherein the coupling agent is selected from one or more of silane coupling agents, titanate coupling agents, and aluminate coupling agents.

4. The adhesive composition of claim 1, wherein the stabilizer is selected from one or more of antioxidants, light stabilizers, anti-hydrolysis stabilizers, anti-metal ion stabilizers, and ultraviolet absorbers.

5. The adhesive composition according to claim 1, wherein The adhesive composition comprises 30-55 wt% of an organic solvent, based on the total weight thereof.

6. An adhesive layer, characterized by The adhesive layer comprises the adhesive composition according to any one of claims 1-5.

7. A new energy vehicle power battery assembly, characterized in that, The new energy vehicle power battery assembly comprises: a battery module; a thermally conductive structural adhesive layer in contact with the battery module; an adhesive layer in contact with the thermally conductive structural adhesive layer, the adhesive layer being cured from the adhesive composition according to any one of claims 1-5; an insulating buffer layer in contact with the adhesive layer; and a cooling plate in contact with the insulating buffer layer.

8. The new energy vehicle power battery assembly according to claim 7, characterized in that, The adhesive layer has a thickness of 15-80 μm.

9. The new energy vehicle power battery assembly according to claim 7, characterized in that, The cooling plate is a metal plate having a circulating pipeline inside. The adhesive composition comprises, based on the total weight thereof: 30-40 wt% of a thermoplastic polymer; 5-15 wt% of a thermally conductive filler; 3-8 wt% of a plasticizer; 1-4 wt% of a coupling agent; 0.5-3 wt% of a stabilizer; and an organic solvent, wherein: the thermoplastic polymer is a blend of a thermoplastic copolyester and a thermoplastic polyacrylate in a weight ratio of 2:1-1:2; the thermoplastic copolyester is a butylene terephthalate-adipate block copolymer having a glass transition temperature of 53-58°C and a number average molecular weight of 15000-21000 g / mol; and the thermoplastic polyacrylate is a methyl methacrylate-ethyl acrylate-butyl acrylate terpolymer having a glass transition temperature of 60-65°C, a number average molecular weight of 20000-23000 g / mol, and the thermally conductive filler is selected from one or more of alumina, silica, magnesia, beryllia, titania, aluminum nitride, silicon nitride, boron nitride, and silicon carbide. the plasticizer is selected from one or more of phthalate plasticizers, aliphatic dibasic acid ester plasticizers, polyester plasticizers, phosphate plasticizers, epoxy plasticizers, and citrate plasticizers. the coupling agent is selected from one or more of silane coupling agents, titanate coupling agents, and aluminate coupling agents. the stabilizer is selected from one or more of antioxidants, light stabilizers, anti-hydrolysis stabilizers, anti-metal ion stabilizers, and ultraviolet absorbers. The adhesive composition comprises 30-55 wt% of an organic solvent, based on the total weight thereof. The adhesive layer comprises the adhesive composition according to any one of claims 1-5. The new energy vehicle power battery assembly comprises: a battery module; a thermally conductive structural adhesive layer in contact with the battery module; an adhesive layer in contact with the thermally conductive structural adhesive layer, the adhesive layer being cured from the adhesive composition according to any one of claims 1-5; an insulating buffer layer in contact with the adhesive layer; and a cooling plate in contact with the insulating buffer layer. The adhesive layer has a thickness of 15-80 μm. The cooling plate is a metal plate having a circulating pipeline inside.

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