Composite heat dissipation film, preparation method and application thereof

Abstract

The application provides a composite heat dissipation film, which is constructed by two-dimensional nanomaterials and one-dimensional nanomaterials to form a three-dimensional self-assembled heat-conducting and flame-retardant network structure, and ionic halides are adsorbed on the three-dimensional framework formed by the two-dimensional nanomaterials and the one-dimensional nanomaterials. In the production, an ultrasonic cell disrupter is used to ultrasonically disperse the two-dimensional nanomaterials in deionized water; a plasma cleaning machine is used to perform hydrophilic treatment on the one-dimensional nanomaterials; the hydrophilic treated one-dimensional nanomaterials and anhydrous ionic halides are added into the dispersed two-dimensional nanomaterial solution to be ultrasonically dispersed, and then dried to obtain the composite heat dissipation film. The three-dimensional porous structure design is beneficial to increasing the contact area of the ionic halides and air, and ensures that the ionic halides are fully water-absorbed.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, and in particular relates to a composite heat dissipation film, its preparation method and its application. Background Technology

[0002] Faced with the pressing challenges of environmental pollution and the energy crisis, carbon neutrality is an urgent task that countries around the world need to accomplish. New energy electric vehicles offer a way to break free from the constraints of fossil fuels, reduce environmental pollution, and lower transportation energy consumption. Lithium-ion batteries, with their high stability, high energy density, and long cycle life, have become one of the best candidates for power sources in new energy vehicles. The complex electrochemical reactions during battery charging and discharging generate heat, and the high current output of the power battery causes significant Joule heat to be generated due to the battery's internal resistance. However, the performance of lithium-ion batteries is affected by operating temperature. At high temperatures (above 45°C), the battery will successively experience side reactions such as SEI (Solid Electrolyte Interface) membrane decomposition, separator melting, electrolyte decomposition, negative electrode reaction with electrolyte, and positive electrode decomposition, leading to capacity and lifespan degradation. When the temperature exceeds the critical temperature (150°C), the battery will experience thermal runaway, triggering dangerous accidents such as combustion and explosion. With the increasing demand for high-rate charge-discharge lithium-ion batteries, developing materials that combine heat dissipation and flame retardancy to achieve efficient thermal management of batteries and improve their flame retardancy during thermal runaway is of significant research and application value.

[0003] In recent years, battery thermal management has primarily employed two methods: active cooling and passive cooling. For active cooling, forced air cooling systems have limited cooling capacity due to the low thermal conductivity (0.023 W / (mK)) and specific heat capacity (1.003 kJ / (kgK)) of air, the heat transfer medium. Furthermore, they require fans to increase airflow, resulting in secondary energy consumption and high costs, thus failing to meet the cooling requirements of batteries operating at high power. Liquid cooling systems improve heat dissipation by selecting suitable cooling media, increasing coolant flow rate, and increasing the number of flow channels, but still suffer from large space requirements, easy coolant leakage, and secondary energy consumption. Passive cooling systems increase the effective contact area with air by using finned heat sinks or creating microstructures, enhancing natural convection heat transfer, but still cannot meet the heat dissipation requirements of high-rate charging and discharging of batteries.

[0004] In recent years, the heat absorption properties of solid-liquid phase change materials such as paraffin and fatty acids during melting have been utilized for heat dissipation in batteries, offering the advantage of low energy consumption. However, the low thermal conductivity, small latent heat of phase change (180–230 kJ / kg), flammability, and leakage after melting of these materials hinder their practical application in heat dissipation. Water, with its high latent heat of liquid-gas phase change (2260 kJ / kg), is also used for thermal management of electronic devices. The evaporation of water molecules in hydrogels when heated can remove heat, achieving a significant heat dissipation effect. However, hydrogels suffer from drawbacks such as large deformation after water loss, low thermal conductivity, the need for immersion in water for secondary applications, poor high-temperature resistance, and flammability. Summary of the Invention

[0005] In view of this, the present invention provides a composite heat dissipation film, a preparation method thereof, and its application, in order to solve the problems existing in the above-mentioned background art.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0007] A composite heat dissipation film is constructed from two-dimensional nanomaterials and one-dimensional nanomaterials to form a three-dimensional self-assembled thermally conductive and flame-retardant network structure, with ionic halides adsorbed on the three-dimensional framework formed by the two-dimensional and one-dimensional nanomaterials.

[0008] Furthermore, the three-dimensional self-assembled thermally conductive and flame-retardant network is composed of two-dimensional nanomaterials (expandable to h-BN, aluminum nitride, molybdenum disulfide, graphene) and one-dimensional nanomaterials (expandable to carbon nanotubes, expanded graphite, copper foam, carbon foam, graphite felt). Its main function is to form a thermally conductive network to improve thermal conductivity. The porous structure in the three-dimensional support can increase the contact area between the hygroscopic salt and the air to ensure that the hygroscopic salt fully absorbs water. At the same time, the capillary force in the porous structure can adsorb the salt solution formed after the hygroscopic salt absorbs moisture without leakage, ensuring the stability of the material.

[0009] Ionic halides: Composed of calcium chloride (which can be expanded to lithium chloride, lithium bromide, and MIL-101(Cr)). Their main function is to reduce the vapor pressure of the composite material, allowing the hygroscopic salt to absorb moisture from the air. During operation, the electronic device relies on water evaporation to absorb heat and dissipate it, while simultaneously undergoing spontaneous water absorption and regeneration during standby.

[0010] This invention also provides a method for preparing a composite heat dissipation film, including...

[0011] Two-dimensional nanomaterials were ultrasonically dispersed with deionized water using an ultrasonic cell disruptor.

[0012] Hydrophilic treatment of one-dimensional nanomaterials was performed using a plasma cleaner.

[0013] One-dimensional nanomaterials treated with hydrophilicity and anhydrous ionic halides are added to a well-dispersed two-dimensional nanomaterial solution, ultrasonically dispersed, and then dried to obtain a composite heat dissipation film.

[0014] Furthermore, by using an ultrasonic cell disruptor to ultrasonically disperse two-dimensional nanomaterials with deionized water at a ratio of 1:2000, the water can effectively peel off the layered structure of the two-dimensional nanomaterials with the help of the ultrasonic cell disruptor. The two-dimensional nanomaterials will generate hydrophilic groups -OH, which can effectively disperse the two-dimensional nanomaterials in the water.

[0015] Since one-dimensional nanomaterials are hydrophobic and poorly dispersed, a plasma cleaner is used to hydrophilize them, generating hydrophilic groups such as -OH and -COOH on their surface. This makes the one-dimensional nanomaterials hydrophilic and improves their dispersibility in water.

[0016] Compared to untreated one-dimensional nanomaterials, hydrophilically treated one-dimensional nanomaterials can adsorb more hygroscopic salts, thus exhibiting higher cooling efficiency. Hydrophilically treated one-dimensional nanomaterials and anhydrous ionic halides are added to a well-dispersed two-dimensional nanomaterial solution, ultrasonically dispersed, and then dried (the mass ratio of two-dimensional nanomaterials, one-dimensional nanomaterials, and ionic halides ranges from 23–32 wt%, 23–32 wt%, and 35–54 wt%). Relying on van der Waals forces, the anhydrous ionic halides can adsorb onto the three-dimensional framework formed by the two-dimensional and one-dimensional nanomaterials. This process spontaneously forms a self-supporting three-dimensional structure without the need for any binder.

[0017] The present invention also provides an application of a composite heat dissipation film, which is used in batteries and electronic devices.

[0018] Furthermore, the dispersed two-dimensional nanomaterials, one-dimensional nanomaterials, and ionic halides were placed in a drying oven and dried at 100°C for 12 hours to obtain a flexible, self-supporting three-dimensional network. Depending on the battery shape (cylindrical, cubic, or pouch), the dried samples were placed in 3D-printed molds (molds were made according to the battery shape, size, and film thickness: cylindrical batteries were placed in cylindrical molds, and cubic and pouch batteries were placed in slotted molds) and dried at 60°C for 2 hours to form a film with heat dissipation and flame retardant capabilities. The film adheres to the battery surface using the strong van der Waals forces of the one-dimensional nanomaterials, eliminating the need for any adhesive tape. This allows for better contact between the film and the battery, effectively reducing interfacial thermal resistance and improving thermal conductivity.

[0019] Compared to existing technologies, the composite heat dissipation film, its preparation method, and its application described in this invention have the following advantages:

[0020] 1. The three-dimensional porous structure design of this invention helps to increase the contact area between ionic halides and air, ensuring that ionic halides fully absorb water;

[0021] 2. The hydroxyl effect of h-BN\SACNT in this invention enables the capillary force of the porous structure to adsorb the salt solution formed after the ionic halide absorbs moisture without leakage, thereby improving the stability of the material.

[0022] 3. In terms of improving heat conduction, this invention selects highly thermally conductive two-dimensional nanomaterials and one-dimensional nanomaterials, and utilizes the synergistic effect of one-dimensional and two-dimensional materials to construct a highly thermally conductive network. When the battery generates heat, the heat is quickly transferred through the thermally conductive network. At the same time, this process is accompanied by the evaporation of water molecules, which enables rapid and efficient heat dissipation for the battery and electronic devices.

[0023] 4. In terms of improving flame retardancy, this invention uses a combination of chemically stable substances such as inorganic salts, h-BN, and carbon materials to make the composite material exhibit flame retardancy, so that it will not cause secondary fire accidents when a source of ignition is present. Attached Figure Description

[0024] The accompanying drawings, which form part of this invention, 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:

[0025] Figure 1 This is a schematic diagram of the preparation process of the composite heat dissipation film of the present invention;

[0026] Figure 2 This is a schematic diagram illustrating the working principle of the composite heat dissipation film of the present invention.

[0027] Figure 3 This is a schematic diagram of the structure of the composite heat dissipation film of the present invention and its actual application on a battery.

[0028] Figure 4 This is a schematic diagram of the microstructure of the composite heat dissipation film of the present invention;

[0029] Figure 5 This is a schematic diagram showing the morphological changes of the composite heat dissipation film of the present invention after moisture absorption and drying at 60°C for 5 hours.

[0030] Figure 6 The graph shows the cooling performance of the composite heat dissipation film of the present invention under different charge and discharge rates of the battery.

[0031] Figure 7 This is a comparison chart showing the application of the cyclic performance test of the present invention;

[0032] Figure 8 This is a schematic diagram illustrating the flame-retardant properties of the present invention. Detailed Implementation

[0033] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0034] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0035] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0036] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0037] This invention provides a composite heat dissipation film, which is constructed from two-dimensional nanomaterials and one-dimensional nanomaterials to form a three-dimensional self-assembled thermally conductive and flame-retardant network structure, with ionic halides adsorbed on the three-dimensional framework formed by the two-dimensional nanomaterials and one-dimensional nanomaterials.

[0038] like Figure 1 As shown, a method for preparing a composite heat dissipation film according to the present invention includes...

[0039] Two-dimensional nanomaterials were ultrasonically dispersed with deionized water using an ultrasonic cell disruptor.

[0040] Hydrophilic treatment of one-dimensional nanomaterials was performed using a plasma cleaner.

[0041] One-dimensional nanomaterials treated with hydrophilicity and anhydrous ionic halides are added to a well-dispersed two-dimensional nanomaterial solution, ultrasonically dispersed, and then dried to obtain a composite heat dissipation film.

[0042] The present invention will be further described below with reference to embodiments.

[0043] Example 1

[0044] (1) Take 100 mgh-BN and deionized water in a beaker at a mass ratio of 0.5 wt% deionized water to 95.5 wt% h-BN. Place the mixed solution in an ultrasonic cell disruptor and ultrasonically disperse it for 8 hours at 800 W to obtain a uniformly dispersed suspension. Pour the suspension into a centrifuge bottle, and then place the centrifuge bottle in a high-speed centrifuge and rotate it at 8000 rpm for 10 minutes. The supernatant is the well dispersed h-BN. The mass determination method is as follows: take 10 mL of the supernatant, dry it, weigh it, and calculate the mass of the uniformly dispersed h-BN in the beaker according to the volume ratio.

[0045] (2) Take 100 mg of SACNT detached from the silicon substrate and place it in a plasma cleaner. Turn on the vacuum pump and evacuate the chamber to 1 Pa. Then introduce air. Control the air intake by adjusting the fine-tuning valve to stabilize the vacuum at around 100 Pa. Select high power output to clean the sample surface for 1 minute to obtain hydrophilic SACNT.

[0046] (3) Take 0.2g of anhydrous calcium chloride and add it to 200mL of the h-BN solution obtained in step (1). Stir the mixed solution with a magnetic stirrer at 700rpm until the anhydrous calcium chloride is completely dissolved to obtain a calcium chloride solution.

[0047] (4) Add the hydrophilic SACNT (mass ratio of 25wt% h-BN, 25wt% SACNT, and 50wt% CaCl2) obtained in step (2) to the solution in step (3), and stir the mixed solution magnetically at room temperature at 700 rpm for 10 minutes until the SACNT is submerged in the solution.

[0048] (5) The mixed solution obtained in step (4) is ultrasonically dispersed at a power of 720W for 30 minutes to obtain a uniformly dispersed suspension.

[0049] (6) The suspension obtained in step (5) is dried at 100°C for 12 hours to obtain a composite heat dissipation film.

[0050] Example 2

[0051] (1) Take 300 mgh-BN and deionized water in a beaker at a mass ratio of 0.5 wt% deionized water to 95.5 wt% h-BN. Place the mixed solution in an ultrasonic cell disruptor and ultrasonically disperse it for 8 hours at 800 W to obtain a uniformly dispersed suspension. Pour the suspension into a centrifuge bottle, and then place the centrifuge bottle in a high-speed centrifuge and rotate it at 8000 rpm for 10 minutes. The supernatant is the well dispersed h-BN. The mass determination method is as follows: take 10 mL of the supernatant, dry it, weigh it, and calculate the mass of the uniformly dispersed BN in the beaker according to the volume ratio.

[0052] (2) Take 300 mg of SACNT detached from the silicon substrate and place it in a plasma cleaner. Turn on the vacuum pump and evacuate the chamber to 1 Pa. Then introduce air. Control the air intake by adjusting the fine-tuning valve to stabilize the vacuum at around 100 Pa. Select high power output to clean the sample surface for 1 minute to obtain hydrophilic SACNT.

[0053] (3) Add 200 mL of anhydrous calcium chloride to the h-BN solution obtained in step (1), and stir the mixture using a magnetic stirrer at a speed of 700 rpm until the anhydrous calcium chloride is completely dissolved to obtain a calcium chloride solution.

[0054] (4) Add the hydrophilic SACNT (mass ratio of 18wt% h-BN, 18wt% SACNT, 64wt% CaCl2) obtained in step (2) to the solution in step (3), and stir the mixed solution magnetically at room temperature at 700 rpm for 10 minutes until the SACNT is submerged in the solution.

[0055] (5) The mixed solution obtained in step (4) is ultrasonically dispersed at a power of 720W for 1 hour to obtain a uniformly dispersed suspension.

[0056] (6) The suspension obtained in step (5) is dried at 100°C for 12 hours to obtain a composite heat dissipation film.

[0057] Example 3

[0058] (1) Take 500 mgh-BN and deionized water in a beaker at a mass ratio of 0.5 wt% deionized water to 95.5 wt% h-BN. Place the mixed solution in an ultrasonic cell disruptor and ultrasonically disperse it for 8 hours at 800 W to obtain a uniformly dispersed suspension. Pour the suspension into a centrifuge bottle, and then place the centrifuge bottle in a high-speed centrifuge and rotate it at 8000 rpm for 10 minutes. The supernatant is the well dispersed h-BN. The mass determination method is as follows: take 10 mL of the supernatant, dry it, weigh it, and calculate the mass of the uniformly dispersed BN in the beaker according to the volume ratio.

[0059] (2) Take 500 mg of SACNT detached from the silicon substrate and place it in a plasma cleaner. Turn on the vacuum pump and evacuate the chamber to 1 Pa. Then introduce air. Control the air intake by adjusting the fine-tuning valve to stabilize the vacuum at around 100 Pa. Select high power output to clean the sample surface for 1 minute to obtain hydrophilic SACNT.

[0060] (3) Take 2.5g of anhydrous calcium chloride and add it to 200mL of the h-BN solution obtained in step (1). Stir the mixed solution with a magnetic stirrer at 700rpm until the anhydrous calcium chloride is completely dissolved to obtain a calcium chloride solution.

[0061] (4) Add the hydrophilic SACNT (mass ratio of 14wt% h-BN, 14wt% SACNT, 72wt% CaCl2) obtained in step (2) to the solution in step (3), and stir the mixed solution magnetically at room temperature at 700 rpm for 10 minutes until the SACNT is submerged in the solution.

[0062] (5) The mixed solution obtained in step (4) is ultrasonically dispersed at a power of 720W for 2 hours to obtain a uniformly dispersed suspension.

[0063] (6) The suspension obtained in step (5) is dried at 100°C to obtain a composite heat dissipation film.

[0064] Comparative Example 1

[0065] (1) Take 100mg of SACNT detached from the silicon substrate and place it in a plasma cleaner. Turn on the vacuum pump and evacuate the chamber to 1Pa. Then introduce air. Control the air intake by adjusting the fine-tuning valve to stabilize the vacuum at around 100Pa. Select high power output to clean the sample surface for 1 minute to obtain hydrophilic SACNT.

[0066] (2) Take 0.2g of anhydrous calcium chloride and add it to 100ml of deionized water. Stir the mixture using a magnetic stirrer at 700rpm until the anhydrous calcium chloride is completely dissolved to obtain a calcium chloride solution.

[0067] (3) Add the hydrophilic SACNT obtained in step (1) to the solution in step (2), and stir the mixture magnetically at room temperature at 700 rpm for 10 minutes until the SACNT is submerged in the solution.

[0068] (4) The mixed solution obtained in step (3) is ultrasonically dispersed at a power of 720W for 30 minutes to obtain a uniformly dispersed suspension.

[0069] (5) The suspension obtained in step (4) is dried at 100°C to obtain a composite heat dissipation film. Compared with the example, Comparative Example 1 did not add h-BN, which reduced the two-dimensional thermal conductive network and lowered the thermal conductivity, which is not conducive to the heat transfer of the composite heat dissipation film during the heat dissipation process.

[0070] Comparative Example 2

[0071] (1) Take 100mg of SACNT that has been detached from the silicon substrate and place it in 100ml of deionized water. Add 0.1g of anhydrous calcium chloride and stir the mixture using a magnetic stirrer at 700rpm until the anhydrous calcium chloride is completely dissolved to obtain a calcium chloride solution.

[0072] (2) The mixed solution obtained in step (1) is ultrasonically dispersed at a power of 720W for 30 minutes to obtain a uniformly dispersed suspension;

[0073] (3) The suspension obtained in step (2) is dried at 100°C to obtain a composite heat dissipation film. In Comparative Example 2, no h-BN was added and no hydrophilic treatment was performed on the SACNT. Without the addition of h-BN, a two-dimensional thermally conductive network cannot be formed, which reduces the thermal conductivity. Since SACNT is hydrophobic, the lack of hydrophilic treatment will reduce the amount of CaCl2 salt solution adsorbed by the entire composite heat dissipation film, resulting in a decrease in water evaporation, which is not conducive to the heat dissipation of the overall composite heat dissipation film.

[0074] Comparative Example 3

[0075] (1) Take 100mg of SACNT detached from the silicon substrate and place it in a plasma cleaner. Turn on the vacuum pump and evacuate the chamber to 1Pa. Then introduce air. Control the air intake by adjusting the fine-tuning valve to stabilize the vacuum at around 100Pa. Select high power output to clean the sample surface for 20s to obtain hydrophilic SACNT.

[0076] (2) Take 0.2g of anhydrous calcium chloride and add it to 100ml of deionized water. Stir the mixture using a magnetic stirrer at 700rpm until the anhydrous calcium chloride is completely dissolved to obtain a calcium chloride solution.

[0077] (3) Add the hydrophilic SACNT obtained in step (1) to the solution in step (2), and stir the mixture magnetically at room temperature at 700 rpm for 10 min until the SACNT is submerged in the solution.

[0078] (4) The mixed solution obtained in step (3) is ultrasonically dispersed at a power of 720W for 30 minutes to obtain a uniformly dispersed suspension.

[0079] (5) The suspension obtained in step (4) is dried at 100°C to obtain a composite heat dissipation film. Compared with the example, Comparative Example 3 reduced the hydrophilic treatment time of SACNT, which reduced the number of hydrophilic functional groups such as -OH and -COOH on the surface of SACNT, resulting in a smaller amount of CaCl2 salt solution adsorbed by the composite heat dissipation film. The reduced mass of water evaporation is not conducive to the heat dissipation of the overall composite heat dissipation film.

[0080] like Figure 2 The diagram illustrates the heat dissipation principle of the composite heat dissipation film. First, when calcium chloride absorbs moisture, it forms hydrogen bonds with water molecules in the air to generate calcium chloride hexahydrate, which continues to absorb moisture to form a calcium chloride salt solution. When the battery is operating, heat is transferred through the three-dimensional thermally conductive network formed by carbon nanotubes via heat conduction. The calcium chloride hexahydrate absorbs energy, the hydrogen bonds break, and the desorbed water evaporates, releasing heat into the environment. Simultaneously, due to the film's high convection coefficient (h... c =10.8W / (m 2 With its high K) and radiative heat transfer coefficient (σ = 0.83), calcium chloride can also achieve efficient convective and radiative heat transfer. When the battery is in standby mode, calcium chloride spontaneously reabsorbs moisture to form calcium chloride hexahydrate, thus allowing for repeated use in a cycle.

[0081] like Figure 3 The image shows the structure of the composite heat dissipation film and a physical image of it wrapped around a battery. The composite heat dissipation film has the advantages of flexibility and large-area production.

[0082] like Figure 4 The image shows the microstructure of the composite heat dissipation film. In the figure, a represents the morphology of SACNT, b represents the morphology of SACNT / CaCl2, and c represents the morphology and elemental distribution of SACNT / CaCl2 / h-BN.

[0083] Figure 5 This is a schematic diagram showing the morphological changes after moisture absorption and drying at 60℃ for 5 hours. The three substances in the diagram are: on the left, PAM hydrogel immersed in CaCl2 solution; on the right, SACNT / CaCl2 composite material; and below, PAM hydrogel. It can be seen that the SACNT / CaCl2 composite material showed no change.

[0084] The composite heat dissipation film of this invention can be applied in battery management. During preparation, the prepared suspension is dried at 100°C for 12 hours. The composite material is then placed in different molds (e.g., cylindrical, cubic, pouch) according to the shape of the battery. Figure 1Different molds were prepared according to the size, shape and film thickness of the battery: cylindrical batteries were placed in cylindrical molds, and square and pouch-shaped batteries were placed in slot molds. The batteries were dried at 60°C for 2 hours to obtain a flexible, self-supporting three-dimensional SACNT structure. Then, the dried composite heat dissipation film was wrapped around the outer surface of an 18650 commercial lithium-ion battery (capacity 2Ah). The thickness of the composite heat dissipation film was 0.8mm. Different thicknesses of heat dissipation films could be obtained by adjusting the mass of h-BN, CaCl2 and SACNT.

[0085] The lithium-ion battery was placed in a constant temperature and humidity chamber (ambient temperature 25℃, relative humidity 65%). The lithium-ion battery was connected to a battery tester to perform constant current discharge-constant current and constant voltage charging performance tests. The tested charge and discharge rates were 10C and 15C. A thermistor attached to the outer surface of the lithium-ion battery was used to record the temperature in real time during the charging and discharging process.

[0086] To fully demonstrate the superior cooling performance of the composite heat dissipation film, bare batteries, batteries with SACNT / CaCl2, and batteries with SACNT / CaCl2 / h-BN heat dissipation films were subjected to constant current discharge temperature tests at 10C and 15C, respectively. Under an ambient temperature of 25℃ and relative humidity of 65%, the batteries with the SACNT / CaCl2 heat dissipation film showed a 11.2℃ and 17.4℃ reduction in maximum temperature during 10C and 15C constant current discharge compared to the bare batteries, respectively. The batteries with the SACNT / CaCl2 / h-BN heat dissipation film showed a 13.1℃ and 19.8℃ reduction in maximum temperature during 10C and 15C constant current discharge compared to the bare batteries, respectively. These results demonstrate that the cooling performance of the heat dissipation film is significantly better than that of the bare batteries. (Results are as follows...) Figure 6 As shown.

[0087] like Figure 7 As shown, during 500 cycles, the capacity retention rates of the bare cell, the SACNT / CaCl2 cell, and the cell with added SACNT / CaCl2 / h-BN were 80%, 90%, and 92%, respectively, demonstrating the stable and excellent cooling effect of the composite heat dissipation film during cycling.

[0088] The composite material was subjected to thermogravimetric analysis (TGA) by heating it to 800°C in an oxygen environment at a heating rate of 10°C / min. Figure 8 The absence of an exothermic peak before 400℃ indicates that the composite material was not oxidized by air. Furthermore, when the composite material was wrapped around a copper column and burned with a high-temperature torch, no combustion was observed, indicating that the composite material has flame-retardant properties.

[0089] In summary, this invention first employs a passive heat dissipation method, overcoming the additional energy consumption problem inherent in active heat dissipation methods such as air cooling and liquid cooling. It utilizes ionic halides to spontaneously absorb water molecules from the external air during battery standby, and these water molecules evaporate and absorb heat during battery operation, allowing for repeated use in a cycle. Furthermore, it leverages the high latent heat of water (2260 kJ / kg) to dissipate heat from the battery, overcoming the problems of low thermal conductivity, easy leakage after melting, and low latent heat of phase change (180–230 kJ / kg) of traditional solid-liquid phase change materials. This results in excellent heat dissipation performance, meeting the requirements of high-power applications. A support network is constructed using high thermal conductivity SACNT and h-BN, utilizing the synergistic effect of one-dimensional and two-dimensional materials to improve thermal conductivity. The SACNT is then further processed... Plasma treatment generates hydrophilic -OH groups on the SACNT surface, allowing it to adsorb more salt solution than untreated SACNTs, thus improving heat dissipation performance. The van der Waals forces between SACNTs form a self-supporting three-dimensional structure, enabling it to adhere to the battery without any adhesive, reducing interfacial thermal resistance between the film and the battery and improving thermal conductivity. The manufacturing process is simple, flexible, and bendable, allowing for the fabrication of heat dissipation films of any shape and size according to application requirements. It is suitable for cylindrical, cubic, and pouch batteries and mobile phone heat dissipation. The use of a combination of chemically stable inorganic salts, h-BN, and carbon materials gives the entire composite material flame retardancy, preventing secondary fires when exposed to ignition sources and improving battery safety.

[0090] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A composite heat dissipation film, characterized in that: A three-dimensional self-assembled thermally conductive and flame-retardant network structure is constructed from two-dimensional and one-dimensional nanomaterials, and ionic halides are adsorbed into the three-dimensional framework formed by the one-dimensional and two-dimensional nanomaterials. The composite heat dissipation film absorbs moisture from the air to form a salt solution through ionic halides. It uses the heat generated when the battery is working to evaporate water molecules and absorb heat for heat dissipation. When the battery is in standby mode, it spontaneously absorbs water from the air again to achieve recycling. The ionic halides include one or more of calcium chloride, lithium chloride, lithium bromide, and MIL-101(Cr).

2. The composite heat dissipation film according to claim 1, characterized in that: The thickness of the composite heat dissipation film is 0.3-1.2 mm.

3. The composite heat dissipation film according to claim 1, characterized in that: The two-dimensional nanomaterials include one or more of h-BN, aluminum nitride, molybdenum disulfide, and graphene.

4. The composite heat dissipation film according to claim 1, characterized in that: The one-dimensional nanomaterials include one or more of SACNT, carbon nanotubes, expanded graphite, copper foam, carbon foam, and graphite felt.

5. A method for preparing a composite heat dissipation film as described in any one of claims 1-4, characterized in that: include Two-dimensional nanomaterials were ultrasonically dispersed with deionized water using an ultrasonic cell disruptor. One-dimensional nanomaterials are hydrophilically treated using a plasma cleaner to generate -OH and / or -COOH hydrophilic groups on the surface of the one-dimensional nanomaterials. One-dimensional nanomaterials treated with hydrophilicity and anhydrous ionic halides are added to a well-dispersed two-dimensional nanomaterial solution, ultrasonically dispersed, and then dried to obtain a composite heat dissipation film.

6. An application of the composite heat dissipation film as described in any one of claims 1-4, characterized in that: Applications of the composite heat dissipation film in batteries and electronic devices.

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