A preparation method and composite heat-conducting film and application thereof

Abstract

The application discloses a preparation method and application of a composite heat-conducting film, and belongs to the technical field of heat-conducting materials.The composite film takes polyvinyl alcohol as a base body, introduces two-dimensional heat-conducting materials and zero-dimensional fillers as synergistic heat-conducting fillers, and optimizes the proportion of the two-dimensional heat-conducting materials and the zero-dimensional fillers.Through planetary centrifugal mixing, vacuum defoaming, rolling film forming and subsequent hot-pressing curing treatment, a three-dimensional heat-conducting network structure is constructed.Compared with the prior art, the prepared composite film has excellent filler orientation and compact structure, improves the thermal conductivity, and simultaneously shows excellent flame-retardant performance, electric insulation performance and flexibility caused by high breaking elongation, and can improve the battery capacity retention rate by about 10% at 60 DEG C compared with traditional aluminum plastic films, significantly reduces the interface thermal resistance and improves the battery thermal management and safety performance, has the advantages of simple process steps, easily available raw materials, is suitable for large-area and batch preparation, and is suitable for soft-packaged battery packaging and other electronic device heat dissipation fields.

Description

Technical Field

[0001] This invention belongs to the field of thermally conductive materials, and more specifically, relates to a preparation method, a composite thermally conductive film, and its application. Background Technology

[0002] The most commonly used flexible packaging material is aluminum-plastic film, which typically consists of a three-layer composite structure (nylon / aluminum foil / polypropylene) to balance barrier properties, mechanical strength, and chemical stability. However, the interfacial thermal resistance caused by its multilayer structure (e.g., at the interface between the positive electrode / electrolyte / aluminum-plastic film) severely limits heat transfer efficiency, resulting in approximately 60% of the heat failing to dissipate in time at the interface. Traditionally, aluminum nitride is directly treated with a polymer matrix to enhance thermal conductivity for thermal interface materials. Boron nitride, aluminum oxide, magnesium oxide, zinc oxide, and silicon carbide, due to their extremely high thermal conductivity and high resistivity, have become common thermal interface materials and are now widely used to solve heat dissipation problems in electronic devices.

[0003] While existing research reports have shown that they can improve the orientation or interfacial heat transfer of thermally conductive materials to varying degrees, they generally suffer from network structures that are limited to two dimensions and make it difficult to construct continuous heat dissipation channels to the outside.

[0004] In view of this, the applicant proposes a new technical solution for fabricating thermally conductive composite film materials, in which layered two-dimensional thermally conductive materials and zero-dimensional filler particles synergistically construct a three-dimensional thermally conductive network, achieving efficient heat dissipation through anisotropic thermal conductive channels. The functional groups on the filler can effectively interact with the polymer matrix, enabling effective dispersion of the mixed filler in the composite material. Thus, the addition of a two-component thermally conductive filler constructs a superior thermally conductive structure within the polymer matrix, significantly reducing interfacial thermal resistance. Summary of the Invention

[0005] The main objective of this invention is to provide a preparation method and a composite thermal conductive film and its application. The aim is to use new processes and formulations to enable layered two-dimensional thermal conductive materials and zero-dimensional filler particles to synergistically construct a three-dimensional thermal conductive network, thereby forming anisotropic thermal conductive channels to achieve efficient heat dissipation.

[0006] To achieve the above objectives, according to a first aspect of the present invention; This invention discloses a method for preparing a composite thermally conductive film, the preparation process of which is as follows: Using polyvinyl alcohol as the matrix material, two-dimensional thermally conductive materials and particulate zero-dimensional fillers are added and dispersed into the matrix material to obtain a matrix slurry; Under vacuum conditions, glutaraldehyde crosslinking agent is added to the matrix slurry and stirred. During the stirring process, ultrasonic waves are applied to the matrix slurry to expel air bubbles and allow the two-dimensional thermally conductive material and particulate filler to fully disperse in the matrix slurry, thereby obtaining a composite slurry. The composite slurry is uniformly coated onto the release film or steel strip through a precision coating head to form a wet film. The wet film is then treated with a hot press roller to cause the sheet-like two-dimensional thermally conductive material in the wet film to be oriented and aligned, finally obtaining a pre-oriented film. The zero-dimensional fillers in the wet film are oriented using filler orientation technology, and the pre-oriented film is then cured in an oven or processed by hot pressing to obtain a composite thermally conductive film. The particulate zero-dimensional filler is dispersed around the two-dimensional thermally conductive material and solidifies and fills the interfaces between the two-dimensional thermally conductive material layers and the matrix material, forming a stable three-dimensional network structure.

[0007] Furthermore, the two-dimensional thermally conductive material is a sheet-like structure composed of one or a combination of hexagonal boron nitride, graphene, aluminum nitride, and molybdenum sulfide. The zero-dimensional filler includes granular powder composed of one or a combination of alumina, aluminum nitride, silicon nitride, and magnesium oxide.

[0008] Furthermore, the thickness of the two-dimensional thermally conductive material is 10-50 μm, and the particle size of the zero-dimensional filler is 0.5 μm-2 μm; The mass ratio of two-dimensional thermally conductive material to zero-dimensional filler is between 0.5:9.5 and 2:8, the concentration of polyvinyl alcohol solution is between 3% and 15 wt%, and the amount of glutaraldehyde added is between 2% and 20% of the mass of the polyvinyl alcohol.

[0009] Furthermore, the matrix slurry is subjected to ultrasonic waves, and the ultrasonic treatment power is between 200W and 500W, with a time between 0.5h and 4h.

[0010] Furthermore, the hot press roller treatment method includes: The temperature inside the rollers is maintained at 100°C, and the release film or steel belt feeds the wet film into the rollers. A double-roller roller is installed in the roller compartment. The double-roller roller is connected to the release film or steel belt. The double-roller roller rolls the wet film at a linear speed of 0.1-5 m / min. The wet film is rolled into a thin sheet and peeled off from the roller, and enters the next cooling roller. After the temperature of the wet film drops rapidly, the wet film is fed into the twin-roller press through a release film or steel belt for rolling, and the rolling times are 1-10 times.

[0011] Furthermore, the pre-oriented film is placed in an oven for curing at a temperature of 75°C. The hot pressing process is performed at a pressure of 5-50 MPa, a temperature of 60°C-90°C, and a time of 1-4 hours.

[0012] Furthermore, the filler orientation technology includes: The core is made of magnetic Fe or Fe3O4 nanoparticles, and the outer layer is the zero-dimensional filler. The pre-oriented film containing the zero-dimensional filler is subjected to an external magnetic field during the curing process or hot pressing process, and the direction and intensity of the external magnetic field change regularly with time. Under the influence of an external magnetic field, the zero-dimensional filler moves in a direction perpendicular or parallel to the magnetic field, forming a dense network structure with the two-dimensional thermally conductive material.

[0013] Furthermore, the composite thermally conductive film has a uniform thickness of 1 mm, and the surface of the composite thermally conductive film is textured to reduce contact thermal resistance.

[0014] According to a second aspect of the invention: This invention provides a composite thermally conductive film prepared by the method described above.

[0015] According to a third aspect of the invention; This invention provides an application of a composite thermal conductive film, wherein the composite thermal conductive film described above is installed in a soft-pack battery, including power batteries, energy storage batteries, consumer electronics batteries, and wearable device batteries.

[0016] The beneficial effects of applying this invention; The synergistic thermal conductivity network significantly improves in-plane thermal conductivity: The thermal conductivity material and zero-dimensional particles are used as synergistic fillers. The thermal conductivity material is highly oriented in the film plane through rolling induction, while the zero-dimensional particles fill the gaps between the layers to form a dense and stable three-dimensional thermal conductivity network, achieving high in-plane thermal conductivity and excellent heat dissipation efficiency.

[0017] Excellent flexibility and battery compatibility: Using polyvinyl alcohol as the matrix, combined with glutaraldehyde crosslinking and a specific curing process, the material retains good flexibility while obtaining sufficient mechanical strength. It can closely fit the surface of the soft-pack battery and deform with it, solving the compatibility problem of rigid heat dissipation materials.

[0018] High electrical insulation and flexible application methods, safe and reliable: The material itself has electrical insulation properties, can directly contact the battery cell, and eliminate the risk of short circuit. At the same time, due to its excellent flexibility and high in-plane thermal conductivity, it can be attached to the surface of the soft pack battery or the middle of the module as a flexible heat dissipation patch, or it can be integrated into the battery packaging structure to realize the rapid lateral diffusion of battery hotspots and adapt to the deformation requirements during battery operation, thereby ensuring the long-term safe and reliable operation of the battery system in a variety of application scenarios. Attached Figure Description

[0019] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a flowchart of the process for preparing a composite thermally conductive film disclosed in this invention; Figure 2 This is a flowchart of the hot press roller processing disclosed in this invention; Figure 3 This is a scanning electron microscope image of the composite thermally conductive film disclosed in this invention; Figure 4 The X-ray diffraction pattern of the composite thermally conductive film disclosed in this invention; Figure 5 This is a mechanical tensile curve of the composite thermally conductive film disclosed in this invention; Figure 6 These are experimental record charts of the composite thermally conductive film disclosed in this invention. Detailed Implementation

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0021] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0022] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0023] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented, for example, in sequences other than those illustrated or described herein.

[0024] Furthermore, the terms “including” and “having” and any variations thereof are intended to cover non-exclusive inclusion, such as a process, method, system, product, or apparatus that includes a series of steps or units, which is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or apparatus.

[0025] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., may be used here to describe the spatial positional relationship of a device or feature to other devices or features as shown in the figure. It should be understood that spatial relative terms are intended to include different orientations in use or operation in addition to the orientation of the device as described in the figure.

[0026] For example, if a device in the accompanying drawings is inverted, a device described as "above" or "on top of" other devices or structures will subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below". The device may also be positioned differently, rotated 90 degrees, or in other orientations, and the spatial relative descriptions used herein will be interpreted accordingly.

[0027] Please refer to this as well. Figures 1-6 This invention discloses a method for preparing a composite thermally conductive film, used to manufacture a thin film that combines high thermal conductivity, electrical insulation, flexibility, and processability. It enables the formation of a three-dimensional thermally conductive network structure at the microscopic level, composed of layered two-dimensional thermally conductive materials and zero-dimensional filler particles. Simultaneously, the thermally conductive film achieves efficient heat dissipation through anisotropic thermal channels. The preparation process includes the following steps: First, a matrix material is prepared, and step S1 is performed. The matrix material is primarily polyvinyl alcohol (PVA), which is dissolved in a suitable solvent to form a homogeneous solution. Then, a two-dimensional thermally conductive material and particulate zero-dimensional filler are added and dispersed into the matrix material to obtain a matrix slurry. Next, step S2 is performed where, under vacuum conditions, glutaraldehyde crosslinking agent is added to the matrix slurry, and the mixture is stirred using a planetary centrifuge to ensure uniform dispersion of the filler in the PVA. During stirring, ultrasonic waves are applied to the matrix slurry to expel air bubbles and allow the two-dimensional thermally conductive material and particulate filler to fully disperse within the matrix slurry, resulting in a composite slurry. After obtaining the composite slurry... Steps S3 and S4 are performed to uniformly coat the composite slurry onto the release film or steel strip through a precision coating head, forming a wet film. The wet film is then treated with a hot press roller to orient the sheet-like two-dimensional thermally conductive material within it. The hot press roller process is a key physical method for improving the orientation of the sheet-like filler, i.e., the two-dimensional thermally conductive material, in the composite material. Its core principle is that the sheet-like filler, originally randomly oriented in a viscous polymer melt or slurry, experiences a strong, directional shear flow field when passing through the narrow gap (roll gap) between two closely rotating rollers. In this shear flow, a velocity difference exists between the fluid layers. Under the influence of fluid mechanics, the two-dimensional thermally conductive material tends to align its maximum plane (i.e., the surface of the two-dimensional thermally conductive material) parallel to the streamlines to reduce flow resistance, thus obtaining a pre-oriented film. In step S5, based on the pre-oriented film, filler orientation technology is used to orient the zero-dimensional filler within the wet film. Finally, in step S6, the pre-oriented film is sent into an oven for curing or subjected to hot pressing to obtain a composite thermally conductive film. This allows the particulate zero-dimensional filler to be dispersed around the two-dimensional thermally conductive material and to be cured and filled between the layers of the two-dimensional thermally conductive material and at the interface of the matrix material, forming a stable three-dimensional network structure.

[0028] In this embodiment, during step S2 under vacuum conditions, the filler is homogenized by applying ultrasonic waves to the matrix slurry. The power of the ultrasonic treatment is between 200W and 500W, and the time is between 0.5h and 4h.

[0029] In this embodiment, when performing step S1, the two-dimensional thermal conductive material is a sheet-like structure composed of one or a combination of hexagonal boron nitride, graphene, aluminum nitride, and molybdenum sulfide, while the zero-dimensional filler includes particulate powder composed of one or a combination of alumina, aluminum nitride, silicon nitride, and magnesium oxide. Furthermore, the thickness of the two-dimensional thermal conductive material is 10-50 μm, the particle size of the zero-dimensional filler is 0.5 μm-2 μm, the mass ratio of the two-dimensional thermal conductive material to the zero-dimensional filler is between 0.5:0.5 and 2:8, the concentration of the polyvinyl alcohol solution is between 3%wt and 15 wt%, and the amount of glutaraldehyde added is between 2% and 20% of the mass of polyvinyl alcohol.

[0030] The preparation method disclosed in this embodiment obtains the optimal structure by adjusting the specific values ​​of different variables through experiments. The specific experiments include the following procedures, detailed in [link to details]. Figure 6 .

[0031] Program 1; Boron nitride (30 μm) and aluminum nitride (1 μm) powders were dispersed in 0.7 g of polyvinyl alcohol at a 9:1 mass ratio. The mixture was stirred for 5 minutes at 2000 rpm using a planetary centrifuge and then ultrasonically treated to ensure uniform dispersion of the filler in the polyvinyl alcohol. 1.1 g of glutaraldehyde crosslinking agent was added to obtain a composite slurry. The composite slurry was formed into a wet film and rolled in a rolling mill to obtain a pre-oriented film. The pre-oriented film was then subjected to a hot-pressing process at 75°C, 4 MPa, and 3 h to obtain a boron nitride / aluminum nitride / polyvinyl alcohol composite thermally conductive film. The volume resistivity reached 8.2 × 10⁹ Ω·m, and the flame retardancy test achieved a V-1 flame retardancy rating under the UL-94 standard. When applied to aqueous zinc-ion batteries, the battery capacity reached 140.7 mAh g⁻¹, representing a 10% increase in cycle capacity compared to batteries with aluminum-plastic film casings. In addition, a comparative example was added. The comparative example differed from Procedure 1 in that aluminum nitride powder was not added, while all other conditions (polyvinyl alcohol dosage, dispersion process, crosslinking agent, rolling and hot pressing parameters) were exactly the same as in Procedure 1. The obtained boron nitride / polyvinyl alcohol composite film had a thermal conductivity of 1.9 W·m⁻¹·K⁻¹ (average of three tests), a volume resistivity of 6.2 × 10⁹ Ω·m, achieved a flame retardancy rating of V-1 under the UL-94 standard, and a battery capacity of 140.7 mAh g⁻¹.

[0032] Program 2: This example differs from Procedure 1 in that the aluminum nitride powder has a particle size of 5 μm. The resulting boron nitride / aluminum nitride / polyvinyl alcohol composite thermally conductive film has a thermal conductivity of 2.9 W·m⁻¹·K⁻¹ (average of three tests). The volume resistivity reaches 8.1 × 10⁹ Ω·m, and the flame retardancy test achieves a V-1 flame retardancy rating under the UL-94 standard. When applied to aqueous zinc-ion batteries, the battery capacity reaches 140.4 mAh g⁻¹, representing a 9.8% increase in cycle capacity compared to aluminum-plastic film-cased batteries.

[0033] Program 3: This example differs from Procedure 1 in that the aluminum nitride powder has a particle size of 10 μm. The resulting composite thermally conductive film has a thermal conductivity of 2.8 W·m⁻¹·K⁻¹ (average of three tests). The volume resistivity reaches 7.9 × 10⁹ Ω·m, and the flame retardancy test achieves a V-1 flame retardancy rating under the UL-94 standard. When applied to aqueous zinc-ion batteries, the battery capacity reaches 140.2 mAh g⁻¹, representing a 9.6% increase in cycle capacity compared to aluminum-plastic film-cased batteries.

[0034] Program 4: This example differs from Procedure 1 in that the mass ratio of aluminum nitride to boron nitride is 0.5:9.5. The resulting composite thermally conductive film has a thermal conductivity of 2.7 W·m⁻¹·K⁻¹ (average of three tests). The volume resistivity reaches 8.1 × 10⁹ Ω·m, and the flame retardancy test achieves a V-1 flame retardancy rating under the UL-94 standard. When applied to aqueous zinc-ion batteries, the battery capacity reaches 140.1 mAh g⁻¹, representing a 9.5% increase in cycle capacity compared to aluminum-plastic film-cased batteries.

[0035] Program 5: This example differs from Procedure 1 in that the mass ratio of aluminum nitride to boron nitride is 1.5:8.5. The resulting composite thermally conductive film has a thermal conductivity of 2.8 W·m⁻¹·K⁻¹ (average of three tests). The volume resistivity reaches 7.5 × 10⁹ Ω·m, and the flame retardancy test achieves a V-1 flame retardancy rating under the UL-94 standard. When applied to aqueous zinc-ion batteries, the battery capacity reaches 140.3 mAh g⁻¹, representing a 9.7% increase in cycle capacity compared to aluminum-plastic film-cased batteries.

[0036] Program 6: This example differs from Procedure 1 in that the mass ratio of aluminum nitride to boron nitride is 2:8. The resulting composite thermally conductive film has a thermal conductivity of 2.8 W·m⁻¹·K⁻¹ (average of three tests). The volume resistivity reaches 8.3 × 10⁹ Ω·m, and the flame retardancy test achieves a V-1 flame retardancy rating under the UL-94 standard. When applied to aqueous zinc-ion batteries, the battery capacity reaches 140.3 mAh g⁻¹, representing a 9.7% increase in cycle capacity compared to aluminum-plastic film-cased batteries.

[0037] Program 7: This example differs from Procedure 1 in that the hot-pressing temperature is 60°C. The resulting composite thermally conductive film has a thermal conductivity of 2.9 W·m⁻¹·K⁻¹ (average of three tests). The volume resistivity reaches 8.1 × 10⁹ Ω·m, and the flame retardancy test achieves a V-1 flame retardancy rating under the UL-94 standard. When applied to aqueous zinc-ion batteries, the battery capacity reaches 140.4 mAh g⁻¹, representing a 9.8% increase in cycle capacity compared to aluminum-plastic film-cased batteries.

[0038] Program 8: This example differs from Procedure 1 in that the hot-pressing temperature is 65°C. The resulting composite thermally conductive film has a thermal conductivity of 3.0 W·m⁻¹·K⁻¹ (average of three tests). The volume resistivity reaches 8.1 × 10⁹ Ω·m, and the flame retardancy test achieves a V-1 flame retardancy rating under the UL-94 standard. When applied to aqueous zinc-ion batteries, the battery capacity reaches 140.5 mAh g⁻¹, representing a 9.9% increase in cycle capacity compared to aluminum-plastic film-cased batteries.

[0039] Program 9: This example differs from Procedure 1 in that the hot-pressing temperature is 70°C. The resulting composite thermally conductive film has a thermal conductivity of 3.0 W·m⁻¹·K⁻¹ (average of three tests). The volume resistivity reaches 8.5 × 10⁹ Ω·m, and the flame retardancy test achieves a V-1 flame retardancy rating under the UL-94 standard. When applied to aqueous zinc-ion batteries, the battery capacity reaches 140.5 mAh g⁻¹, representing a 9.9% increase in cycle capacity compared to aluminum-plastic film-cased batteries.

[0040] Program 10: This example differs from Procedure 1 in that the hot-pressing temperature is 80°C. The resulting composite thermally conductive film has a thermal conductivity of 3.0 W·m⁻¹·K⁻¹ (average of three tests). The volume resistivity reaches 8.4 × 10⁹ Ω·m, and the flame retardancy test achieves a V-1 flame retardancy rating under the UL-94 standard. When applied to aqueous zinc-ion batteries, the battery capacity reaches 140.5 mAh g⁻¹, representing a 9.9% increase in cycle capacity compared to aluminum-plastic film-cased batteries.

[0041] Program 11: This example differs from Procedure 1 in that the hot-pressing time is 1 hour. The thermal conductivity of the resulting composite thermally conductive film is 2.9 W·m⁻¹·K⁻¹ (average of three tests). The volume resistivity reaches 7.3 × 10⁹ Ω·m, and the flame retardancy test achieves a V-1 flame retardancy rating under the UL-94 standard. When applied to aqueous zinc-ion batteries, the battery capacity reaches 140.4 mAh g⁻¹, representing a 9.8% increase in cycle capacity compared to aluminum-plastic film-cased batteries.

[0042] Program 12: This example differs from Procedure 1 in that the hot-pressing time is 1.5 h. The resulting composite thermally conductive film has a thermal conductivity of 3.0 W·m⁻¹ K⁻¹ (average of three tests). The volume resistivity reaches 7.5 × 10⁹ Ω·m, and the flame retardancy test achieves a V-1 flame retardancy rating under the UL-94 standard. When applied to aqueous zinc-ion batteries, the battery capacity reaches 140.2 mAh g⁻¹, representing a 9.6% increase in cycle capacity compared to aluminum-plastic film-cased batteries.

[0043] Program 13: This example differs from Procedure 1 in that the hot-pressing time is 2 hours. The thermal conductivity of the resulting composite thermally conductive film is 3.1 W·m⁻¹·K⁻¹ (average of three tests). The volume resistivity reaches 7.6 × 10⁹ Ω·m, and the flame retardancy test achieves a V-1 flame retardancy rating under the UL-94 standard. When applied to aqueous zinc-ion batteries, the battery capacity reaches 140.2 mAh g⁻¹, representing a 9.6% increase in cycle capacity compared to aluminum-plastic film-cased batteries.

[0044] Program 14: This example differs from Procedure 1 in that the hot-pressing time is 2.5 h. The thermal conductivity of the resulting composite thermally conductive film is 3.1 W·m⁻¹·K⁻¹ (average of three tests). The volume resistivity reaches 8.1 × 10⁹ Ω·m, and the flame retardancy test achieves a V-1 flame retardancy rating under the UL-94 standard. When applied to aqueous zinc-ion batteries, the battery capacity reaches 140.2 mAh g⁻¹, representing a 9.6% increase in cycle capacity compared to aluminum-plastic film-cased batteries.

[0045] Program 15: This example differs from Procedure 1 in that the hot-pressing time is 3.5 h. The thermal conductivity of the resulting composite thermally conductive film is 2.9 W·m⁻¹·K⁻¹ (average of three tests). The volume resistivity reaches 8.2 × 10⁹ Ω·m, and the flame retardancy test achieves a V-1 flame retardancy rating under the UL-94 standard. When applied to aqueous zinc-ion batteries, the battery capacity reaches 140.2 mAh g⁻¹, representing a 9.6% increase in cycle capacity compared to aluminum-plastic film-cased batteries.

[0046] Program 16: This example differs from Procedure 1 in that the hot-pressing pressure is 2 MPa. The thermal conductivity of the resulting composite thermally conductive film is 2.9 W·m⁻¹·K⁻¹ (average of three tests). The volume resistivity reaches 8.3 × 10⁹ Ω·m, and the flame retardancy test achieves a V-1 flame retardancy rating under the UL-94 standard. When applied to aqueous zinc-ion batteries, the battery capacity reaches 140.3 mAh g⁻¹, representing a 9.7% increase in cycle capacity compared to aluminum-plastic film-cased batteries.

[0047] Program 17: This example differs from Procedure 1 in that the hot-pressing pressure is 3 MPa. The resulting composite thermally conductive film has a thermal conductivity of 2.9 W·m⁻¹·K⁻¹ (average of three tests). The volume resistivity reaches 8.4 × 10⁹ Ω·m, and the flame retardancy test achieves a V-1 flame retardancy rating under the UL-94 standard. When applied to aqueous zinc-ion batteries, the battery capacity reaches 140.3 mAh g⁻¹, representing a 9.7% increase in cycle capacity compared to aluminum-plastic film-cased batteries.

[0048] Program 18: This example differs from Procedure 1 in that the hot-pressing pressure is 5 MPa. The resulting composite thermally conductive film has a thermal conductivity of 3.0 W·m⁻¹·K⁻¹ (average of three tests). The volume resistivity reaches 8.2 × 10⁹ Ω·m, and the flame retardancy test achieves a V-1 flame retardancy rating under the UL-94 standard. When applied to aqueous zinc-ion batteries, the battery capacity reaches 140.3 mAh g⁻¹, representing a 9.7% increase in cycle capacity compared to aluminum-plastic film-cased batteries.

[0049] Program 19: This example differs from Procedure 1 in that, after obtaining the pre-oriented film, it is placed in an oven to stand. The resulting composite thermally conductive film has a thermal conductivity of 2.9 W·m⁻¹·K⁻¹ (average of three tests). Its volume resistivity reaches 8.1 × 10⁹ Ω·m, and its flame retardancy test achieves a V-1 flame retardancy rating under the UL-94 standard. When applied to aqueous zinc-ion batteries, the battery capacity reaches 140.2 mAh g⁻¹, representing a 9.6% increase in cycle capacity compared to aluminum-plastic film-cased batteries.

[0050] Program 20: This example differs from Procedure 1 in that the 1μm aluminum nitride filler is replaced with 5μm magnesium oxide. After obtaining the pre-oriented film, it is placed in an oven to stand. The thermal conductivity of the resulting composite thermally conductive film is 2.4 W·m⁻¹·K⁻¹ (average of three tests). The volume resistivity reaches 8.1 × 10⁹ Ω·m, and the flame retardancy test achieves a V-2 flame retardancy rating under the UL-94 standard. When applied to aqueous zinc-ion batteries, the battery capacity reaches 137.5 mAh g⁻¹, representing a 7.5% increase in cycle capacity compared to aluminum-plastic film-cased batteries.

[0051] Program 21: This example differs from Procedure 1 in that the 1 μm aluminum nitride filler is replaced with 5 μm aluminum oxide. After obtaining the pre-oriented film, it is placed in an oven to stand. The thermal conductivity of the resulting composite thermally conductive film is 2.3 W·m⁻¹·K⁻¹ (average of three tests). The volume resistivity reaches 8.2 × 10⁹ Ω·m, and the flame retardancy test achieves a V-2 flame retardancy rating under the UL-94 standard. When applied to aqueous zinc-ion batteries, the battery capacity reaches 136.8 mAh g⁻¹, representing a 7.0% increase in cycle capacity compared to aluminum-plastic film-cased batteries.

[0052] Comparative Example 1: This comparative example differs from Procedure 1 in that no aluminum nitride filler was added, and all fillers were replaced with an equal mass of boron nitride with a size of 30 μm (i.e., the total amount of boron nitride is the same as the sum of boron nitride and aluminum nitride in Procedure 1). All other conditions (polyvinyl alcohol dosage, dispersion process, crosslinking agent, rolling and hot pressing parameters) are exactly the same as in Procedure 1. The resulting boron nitride / polyvinyl alcohol composite film has a thermal conductivity of 1.9 W·m. -1 ·K -1 (The average value is taken from three tests). The volume resistivity reaches 8.2×109 Ω·m, and the flame retardancy test achieves a flame retardancy rating of V-2 under the UL-94 standard. When used in aqueous zinc-ion batteries, the battery capacity reaches 120.4 mAh g-1. Compared with aluminum-plastic film battery shells, the battery capacity during cycles is increased by 5.0%.

[0053] In some embodiments, when performing step S6 and curing the pre-oriented film in an oven, the curing temperature is 75°C, while the hot-pressing process involves a pressure between 1 MPa and 7 MPa, a temperature between 60 and 90°C, and a processing time of 1 to 4 hours. Compared to existing thermally conductive composite materials, the added bicomponent thermally conductive filler constructs a superior thermal conductivity path within the polymer matrix. Furthermore, the functional groups on the mixed filler effectively interact with the polymer matrix, enabling excellent dispersion of the mixed filler in the composite material, thereby significantly reducing interfacial thermal resistance. Results show that the composite material achieves a thermal conductivity of 3.2 W·m⁻¹·K⁻¹, and at a high temperature of 60°C, its battery capacity is increased by 10% compared to traditional aluminum-plastic films, validating its significant potential in battery thermal management applications.

[0054] In a specific embodiment of the present invention, the hot press roller processing method in step S4 includes the following steps: First, in step S41, the wet film is fed into the roller chamber through a release film or steel belt, and the temperature inside the roller chamber is maintained at 100°C. Then, in step S41, a double-roller roller is installed inside the roller chamber, and the double-roller roller is connected to the release film or steel belt. The double-roller roller rolls the wet film at a linear speed of 0.1-5 m / min. Finally, in step S43, the wet film is calendered into a thin sheet and peeled off from the rollers, and enters the next cooling roller. In this embodiment, an iterative optimization process concept is applied. After each rolling, the current structure is "frozen" by cooling. When it is fed back into the roller, it will be re-oriented and compacted based on the partially oriented structure. After the wet film temperature drops rapidly, the wet film is fed into a two-roller press through a release film or steel belt for rolling. The key to this process is to circulate the rolling 1-10 times, because each rolling further optimizes the orientation. The more times it is rolled, the higher the orientation degree. By balancing efficiency and performance, this process can gradually and maximize the in-plane orientation degree of the sheet filler in the wet film by repeatedly using shear force and thermoplasticity through multiple cycles of "hot pressing-cooling-re-hot pressing", thereby optimizing the in-plane thermal conductivity of the final product.

[0055] In this embodiment, the composite thermally conductive film has a uniform thickness of 1 mm, and the surface of the composite thermally conductive film is textured to reduce contact thermal resistance.

[0056] In a specific embodiment of the present invention, the filler orientation technique in step S5 uses a "magnetic core" to provide magnetic response for orientation, and a "shell" to provide high thermal conductivity and electrical insulation, specifically including the following steps: First, zero-dimensional fillers are formed using magnetic Fe or Fe3O4 nanoparticles as the core, and an extremely thin nickel or cobalt coating is deposited on the surface of the magnetic fillers. This thin metal coating provides magnetic response while avoiding the formation of conductive pathways due to its extremely thin thickness (or by controlling its content below the percolation threshold), and also improves the interfacial bonding with the polymer matrix. Then, during the curing or hot-pressing process, an external magnetic field is applied to the pre-oriented film containing the zero-dimensional fillers. The direction and intensity of the external magnetic field change regularly over time. Under the influence of the external magnetic field, the zero-dimensional fillers align and move perpendicular or parallel to the magnetic field direction, forming a dense network structure with the two-dimensional thermally conductive material.

[0057] In this embodiment, as Figure 3 In a vertical magnetic field arrangement, the magnetic filler can construct out-of-plane thermal conductivity pathways. After curing, the filler forms vertical columnar channels extending from the upper to the lower surface of the material, significantly improving the out-of-plane thermal conductivity. In a horizontal magnetic field arrangement, it can construct in-plane thermal conductivity pathways, forming a highly oriented network within the plane, greatly improving the in-plane thermal conductivity and achieving an effect similar to artificial graphite films. In summary, the composite film for soft-pack batteries obtained by this invention has advantages such as simple synthesis steps, mass production capability, readily available raw materials, and low synthesis cost. It is a composite material with excellent comprehensive performance (high thermal conductivity, high flame retardancy, high electrical insulation, and high elongation at break). The composite film prepared by this invention has strong heat dissipation capacity and high safety, making it highly suitable for industrial production and application in electronic products.

[0058] Based on the same inventive concept, the present invention provides a composite thermally conductive film prepared by the preparation method described above.

[0059] Based on the same inventive concept, the present invention also provides an application of a composite thermal conductive film, wherein the composite thermal conductive film is installed in a soft-pack battery, including a power battery, an energy storage battery, a consumer electronics battery, and a wearable device battery.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A preparation method, characterized in that, Its preparation process: Using polyvinyl alcohol as the matrix material, two-dimensional thermally conductive materials and particulate zero-dimensional fillers are added and dispersed into the matrix material to obtain a matrix slurry; Under vacuum conditions, glutaraldehyde crosslinking agent is added to the matrix slurry and stirred. During the stirring process, ultrasonic waves are applied to the matrix slurry to expel air bubbles and allow the two-dimensional thermally conductive material and particulate filler to fully disperse in the matrix slurry, thereby obtaining a composite slurry. The composite slurry is uniformly coated onto the release film or steel strip through a precision coating head to form a wet film. The wet film is then treated with a hot press roller to cause the sheet-like two-dimensional thermally conductive material in the wet film to be oriented and aligned, finally obtaining a pre-oriented film. The zero-dimensional fillers in the wet film are oriented using filler orientation technology, and the pre-oriented film is then cured in an oven or processed by hot pressing to obtain a composite thermally conductive film. The particulate zero-dimensional filler is dispersed around the two-dimensional thermally conductive material and solidifies and fills the interfaces between the two-dimensional thermally conductive material layers and the matrix material, forming a stable three-dimensional network structure.

2. The preparation method according to claim 1, characterized in that, The two-dimensional thermally conductive material is a sheet-like structure composed of one or a combination of hexagonal boron nitride, graphene, aluminum nitride, and molybdenum sulfide. The zero-dimensional filler includes granular powder composed of one or a combination of alumina, aluminum nitride, silicon nitride, and magnesium oxide.

3. The preparation method according to claim 1, characterized in that, The thickness of the two-dimensional thermally conductive material is 10μm-50μm, and the particle size of the zero-dimensional filler is 0.5μm-2μm; The mass ratio of two-dimensional thermally conductive material to zero-dimensional filler is between 0.5:9.5 and 2:8, the concentration of polyvinyl alcohol solution is between 3wt% and 15wt%, and the amount of glutaraldehyde added is between 2% and 20% of the mass of the polyvinyl alcohol.

4. The preparation method according to claim 1, characterized in that, The matrix slurry is subjected to ultrasonic waves, and the power of the ultrasonic treatment is between 200W and 500W, and the time is between 0.5h and 4h.

5. The preparation method according to claim 1, characterized in that, Hot press roller processing methods include: The temperature inside the rollers is maintained at 100°C, and the release film or steel belt feeds the wet film into the rollers. A double-roller roller is installed in the roller compartment. The double-roller roller is connected to the release film or steel belt. The double-roller roller rolls the wet film at a linear speed of 0.1-5 m / min. The wet film is rolled into a thin sheet and peeled off from the roller, and enters the next cooling roller. After the temperature of the wet film drops rapidly, the wet film is fed into the twin-roller press through a release film or steel belt for rolling, and the rolling times are 1-10 times.

6. The preparation method according to claim 1, characterized in that, The pre-oriented film is placed in an oven for curing at a temperature of 75°C. The hot pressing process is performed at a pressure of 5-50 MPa, a temperature of 60-90°C, and a time of 1-4 hours.

7. The preparation method according to claim 1, characterized in that, The packing orientation technology includes: The core is made of magnetic Fe or Fe3O4 nanoparticles, and the outer layer is the zero-dimensional filler. The pre-oriented film containing the zero-dimensional filler is subjected to an external magnetic field during the curing process or hot pressing process, and the direction and intensity of the external magnetic field change regularly with time. Under the influence of an external magnetic field, the zero-dimensional filler moves in a direction perpendicular or parallel to the magnetic field, forming a dense network structure with the two-dimensional thermally conductive material.

8. The preparation method according to claim 1, characterized in that, The composite thermally conductive film has a uniform thickness of 1 mm, and its surface is textured to reduce contact thermal resistance.

9. A composite thermally conductive film, characterized in that, It is prepared by the preparation method described in any one of claims 1-7.

10. An application of a composite thermally conductive film, using the composite thermally conductive film of claim 9, characterized in that, The composite thermal conductive film is installed in pouch batteries, including power batteries, energy storage batteries, consumer electronics batteries, and wearable device batteries.

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