Melamine / ammonium polyphosphate synergistic flame-retardant flexible composite phase change material, and preparation method and application thereof

Abstract

The application provides a melamine / ammonium polyphosphate synergistic flame-retardant flexible composite phase change material and a preparation method and application thereof, and the preparation method comprises the following steps: heating and melting paraffin wax, adding olefin block copolymer, then adding expanded graphite, melamine and ammonium polyphosphate to form a synergistic flame-retardant system, and preparing the composite phase change material through a melt blending process.The prepared composite phase change material simultaneously realizes the comprehensive performance of anti-leakage, heat-induced flexibility, high thermal conductivity and high efficiency of flame retardation, and the thermal conductivity is up to 1.12 W·m ‑1 ·K ‑1 , and the phase change enthalpy is up to 114.5 J / g; the preparation process of the application is simple and the conditions are controllable, the prepared material considers the energy storage density, thermal conductivity efficiency, flexibility adaptability and flame-retardant safety, is suitable for efficient thermal management under high rate working conditions of lithium batteries, can effectively inhibit the temperature rise of the battery and reduce the risk of thermal runaway, and has a good engineering application prospect.

Description

Technical Field

[0001] This invention belongs to the field of phase change energy storage materials technology, specifically relating to a shaped, flexible, high thermal conductivity, and flame-retardant composite phase change material and its preparation method, as well as the application of this material in the thermal management system of lithium-ion batteries. Background Technology

[0002] Phase change materials (PCMs) have become a research hotspot in the field of lithium battery thermal management due to their excellent temperature uniformity, strong heat storage capacity, and compact system structure. Among them, paraffin-based PCMs have been widely studied and applied due to their high latent heat value, good chemical stability, and low cost.

[0003] However, existing paraffin-based phase change materials face three major technical bottlenecks in practical applications: First, paraffin has extremely low intrinsic thermal conductivity (typically about 0.2 W·m). -1 ·K -1 Firstly, the heat generated by the high-rate discharge of the battery is difficult to be quickly absorbed and diffused; secondly, paraffin is an organic flammable material, posing a significant fire safety hazard, and can easily exacerbate the spread of fire when the battery is thermally runaway; thirdly, paraffin has high rigidity at room temperature and is prone to leakage after melting, making it difficult to adhere tightly to the battery surface, which can easily create contact thermal resistance, and the leaked material may also contaminate the battery module and cause a short circuit.

[0004] To address the aforementioned issues, existing technologies often employ high thermal conductivity fillers such as expanded graphite and carbon nanotubes to enhance thermal conductivity, use polymers such as olefin block copolymers to improve material flexibility and shape retention, and add flame retardants to improve material safety. However, existing technologies can only address these shortcomings individually or partially, making it difficult to simultaneously achieve high thermal conductivity, efficient flame retardancy, thermally induced flexibility, and good shape retention stability within the same system. Furthermore, the flame retardant efficiency of a single flame retardant is limited, and excessive addition can significantly reduce the material's phase change enthalpy, impairing energy storage performance. Therefore, developing composite phase change materials (CPCMs) that combine efficient thermal management, excellent flame retardancy and safety, and good application adaptability is a pressing technical challenge in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention aims to solve the technical problems of poor thermal conductivity, flammability, lack of flexibility, and easy leakage of existing PCMs, and to provide a PCM that combines flame retardancy and thermally induced flexibility, as well as its preparation method and application.

[0006] To achieve the above objectives, the solution of the present invention is: A melamine / ammonium polyphosphate synergistic flame-retardant flexible composite phase change material (CPCM) is composed of the following components: 55-65 wt% paraffin (PA), 18-24 wt% olefin block copolymer (OBC), 3-5 wt% expanded graphite (EG), and 12-18 wt% synergistic flame retardant.

[0007] The synergistic flame retardant is composed of melamine (MA) and ammonium polyphosphate (APP), with a mass ratio of MA to APP of 1.2-1.6:1.

[0008] In a preferred embodiment, the CPCM consists of the following components in parts by weight: 60 wt% PA, 21 wt% OBC, 4 wt% EG, and the synergistic flame retardant consists of 9 wt% MA and 6 wt% APP.

[0009] OBC forms a three-dimensional cross-linked structure inside the material, thereby confining the paraffin within the structure and providing leakage prevention; at the same time, OBC is a polymer composed of soft segments and hard segments. The soft segments become flexible after the temperature rises to a certain level, i.e., thermally induced flexibility, while the hard segments provide mechanical support and shape stability.

[0010] Furthermore, the preparation process of EG is as follows: anhydrous ethanol is added and the expandable graphite powder is immersed, stirred and washed, the upper suspension is removed, washed and dried to obtain graphite powder, and then heated at 750°C to obtain EG.

[0011] EG itself has high thermal conductivity, and its expanded porous worm-like structure forms a thermally conductive network inside the material. At the same time, flame retardants help to improve thermal conductivity to some extent.

[0012] Furthermore, the CPCM exhibits the highest phase transition enthalpy of 114.5 J / g and the highest thermal conductivity of 1.12 W·m. -1 ·K -1 .

[0013] A method for preparing the above-mentioned melamine / ammonium polyphosphate synergistic flame-retardant flexible composite phase change material includes the following steps: (1) Heat PA to a molten state, add OBC, and stir at a first temperature and a first stirring speed for a first time to obtain a first mixture; (2) Add EG, MA and APP to the first mixture, and stir at a second temperature and a second stirring speed for a second time to obtain a second mixture; (3) The second mixture is cast into a mold, cooled and demolded to obtain the CPCM.

[0014] In the above preparation process, the step-by-step addition is mainly to ensure uniform mixing. For example, the OBC used is a polymer, which is relatively difficult to melt and mix. If the mixture is not uniform, the leak-proof performance of the material will be greatly reduced.

[0015] Furthermore, in step (1), the melting temperature of the PA is 60-80°C.

[0016] Further, in step (1), the first temperature is 160-180℃, the first stirring speed is 100-200rpm, and the first time is 1-2h.

[0017] Further, in step (2), the preparation process of EG is as follows: add anhydrous ethanol and immerse the expandable graphite powder, stir and wash, remove the upper suspension, repeat the washing, dry to obtain graphite powder, and then heat at 750°C to obtain EG.

[0018] Further, in step (2), the second temperature is 160-180℃, the second stirring speed is 700-900rpm, and the second time is 0.5-1.5h.

[0019] Application of the above-mentioned melamine / ammonium polyphosphate synergistic flame-retardant flexible composite phase change material in battery thermal management.

[0020] Due to the adoption of the above solution, the beneficial effects of the present invention are: This invention uses PA as the phase change matrix, OBC as the shaped flexible skeleton, EG as the thermal conductivity enhancer, and MA and APP in a specific ratio to form a synergistic flame retardant system, which is prepared through a melt blending process. The resulting composite phase change material simultaneously achieves comprehensive performance including leak resistance, thermally induced flexibility, high thermal conductivity, and high flame retardancy, with a maximum thermal conductivity of up to 1.12 W·m. -1 ·K -1 The phase transition enthalpy is as high as 114.5 J / g; the total duration of vertical combustion is only 3.6 s; and when used for thermal management of 46950 lithium batteries at a 2.5C rate, the highest battery temperature can be controlled at 42.1℃. Therefore, the preparation process of this invention is simple and the conditions are controllable. The material produced balances energy density, thermal conductivity, flexibility, and flame retardancy, making it suitable for efficient thermal management of lithium batteries under high-rate conditions. It can effectively suppress battery temperature rise and reduce the risk of thermal runaway, showing good prospects for engineering applications. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the preparation process of the MA / APP synergistic flame-retardant flexible CPCM in Embodiment 1 of the present invention.

[0022] Figure 2 This is a leakage test diagram of Embodiment 1 of the present invention.

[0023] Figure 3 This is a diagram of thermally induced flexible bending in Embodiment 1 of the present invention.

[0024] Figure 4 The images show vertical combustion test diagrams of Embodiment 1, Comparative Example 1, Comparative Example 5, Comparative Example 7, and Comparative Example 8 of the present invention.

[0025] Figure 5The diagram shows the cone calorimetry test curves of Embodiment 1, Comparative Example 7, and Comparative Example 8 of the present invention.

[0026] Figure 6 This is a DSC curve before and after the cycle in Embodiment 1 of the present invention.

[0027] Figure 7 This is a comparison of the temperature rise curves of CPCM cooling and natural convection cooling used for 46950 batteries under 2.5C discharge conditions in Embodiment 1 (POEMA2) of the present invention. Detailed Implementation

[0028] This invention provides a melamine / ammonium polyphosphate synergistic flame-retardant flexible composite phase change material, its preparation method, and its application.

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0030] Source of materials: All raw materials used in the embodiments of this invention can be obtained commercially. Among them, paraffin wax (PA, grade PCM-40) was purchased from Shengbang Plastics Technology Co., Ltd., China; olefin block copolymer (OBC, grade 9530) was purchased from Dow Chemical Company, USA; expanded graphite (EG) was prepared by high-temperature expansion of expandable graphite powder (particle size 80 mesh, purchased from Greenfa Carbon Materials Co., Ltd., China); anhydrous ethanol was purchased from Hunan Huihong Reagent Co., Ltd.; melamine (MA) and ammonium polyphosphate (APP) were both purchased from Maclean Biochemical Technology Co., Ltd., China.

[0031] Preparation of EG: Place expandable graphite powder in a beaker, add excess anhydrous ethanol to immerse the powder, and stir thoroughly to clean it. The powder should settle to the bottom of the beaker. Discard the upper suspension containing impurities to remove any fine debris carried within. Repeat this cleaning process three times. Dry the resulting graphite powder in an oven to remove residual ethanol solvent, obtaining cleaned expandable graphite powder. Then, transfer the cleaned powder to a muffle furnace and heat at 750°C for 1 minute to allow it to fully expand, obtaining worm-like expanded graphite (EG) for later use.

[0032] Example 1: (Preparation of the optimal CPCM ratio) like Figure 1 As shown, the method for MA / APP synergistic flame-retardant flexible CPCM in this embodiment includes the following steps: (1) Place 60wt%PA in a beaker and heat it in an oil bath at 70℃ until it is completely melted. Then add 21wt%OBC, raise the oil bath temperature to 170℃, and stir at 150rpm for 1.5h to obtain the first mixture. (2) Add 4wt%EG, 9wt%MA and 6wt%APP (the mass ratio of MA to APP is 1.5:1) to the first mixture in sequence, increase the stirring speed to 800rpm, keep the temperature at 170℃ and stir continuously for 1h to make the mixture fully mixed to obtain the second mixture; (3) Pour the second mixture into the mold, cool and demold to obtain the CPCM sample, which is labeled as POEMA2.

[0033] The preparation process of EG is as follows: add anhydrous ethanol and immerse expandable graphite powder, stir and wash, remove the upper suspension, repeat the washing 3 times, dry to obtain graphite powder, and then heat it in a muffle furnace at 750°C for about 1 minute.

[0034] Comparative Example 1: The method for CPCM (flame retardant only 15 wt% MA) in this comparative example includes the following steps: (1) Place 60wt%PA in a beaker and heat it in an oil bath at 70℃ until it is completely melted. Then add 21wt%OBC, raise the oil bath temperature to 170℃, and stir at 150rpm for 1.5h to obtain the first mixture. (2) Add 4wt%EG and 15wt%MA to the first mixture in sequence, increase the stirring speed to 800rpm, keep the temperature at 170℃ and stir continuously for 1h to make the mixture fully mixed and obtain the second mixture; (3) Pour the second mixture into the mold, cool and demold to obtain the sample POEM.

[0035] The preparation process of EG is as follows: add anhydrous ethanol and immerse expandable graphite powder, stir and wash, remove the upper suspension, repeat the washing 3 times, dry to obtain graphite powder, and then heat it in a muffle furnace at 750°C for about 1 minute.

[0036] Comparative Example 2: The method for CPCM (flame retardant of 12wt% MA and 3wt% APP) in this comparative example includes the following steps: (1) Place 60wt%PA in a beaker and heat it in an oil bath at 70℃ until it is completely melted. Then add 21wt%OBC, raise the oil bath temperature to 170℃, and stir at 150rpm for 1.5h to obtain the first mixture. (2) Add 4wt%EG, 12wt%MA and 3wt%APP to the first mixture in sequence, increase the stirring speed to 800rpm, keep the temperature at 170℃ and stir continuously for 1h to make the mixture fully mixed and obtain the second mixture; (3) Pour the second mixture into the mold, cool and demold to obtain sample POEMA1.

[0037] The preparation process of EG is as follows: add anhydrous ethanol and immerse expandable graphite powder, stir and wash, remove the upper suspension, repeat the washing 3 times, dry to obtain graphite powder, and then heat it in a muffle furnace at 750°C for about 1 minute.

[0038] Comparative Example 3: The method for CPCM (flame retardants of 6 wt% MA and 9 wt% APP) in this comparative example includes the following steps: (1) Place 60wt%PA in a beaker and heat it in an oil bath at 70℃ until it is completely melted. Then add 21wt%OBC, raise the oil bath temperature to 170℃, and stir at 150rpm for 1.5h to obtain the first mixture. (2) Add 4wt%EG, 6wt%MA and 9wt%APP to the first mixture in sequence, increase the stirring speed to 800rpm, keep the temperature at 170℃ and stir continuously for 1h to make the mixture fully mixed and obtain the second mixture; (3) Pour the second mixture into the mold, cool and demold to obtain sample POEMA3.

[0039] The preparation process of EG is as follows: add anhydrous ethanol and immerse expandable graphite powder, stir and wash, remove the upper suspension, repeat the washing 3 times, dry to obtain graphite powder, and then heat it in a muffle furnace at 750°C for about 1 minute.

[0040] Comparative Example 4: The method for CPCM (flame retardant of 3wt% MA and 12wt% APP) in this comparative example includes the following steps: (1) Place 60wt%PA in a beaker and heat it in an oil bath at 70℃ until it is completely melted. Then add 21wt%OBC, raise the oil bath temperature to 170℃, and stir at 150rpm for 1.5h to obtain the first mixture. (2) Add 4wt%EG, 3wt%MA and 12wt%APP to the first mixture in sequence, increase the stirring speed to 800rpm, keep the temperature at 170℃ and stir continuously for 1h to make the mixture fully mixed and obtain the second mixture; (3) Pour the second mixture into the mold, cool and demold to obtain sample POEMA4.

[0041] The preparation process of EG is as follows: add anhydrous ethanol and immerse expandable graphite powder, stir and wash, remove the upper suspension, repeat the washing 3 times, dry to obtain graphite powder, and then heat it in a muffle furnace at 750°C for about 1 minute.

[0042] Comparative Example 5: The method for CPCM (flame retardant is only 15 wt% APP) in this comparative example includes the following steps: (1) Place 60wt%PA in a beaker and heat it in an oil bath at 70℃ until it is completely melted. Then add 21wt%OBC, raise the oil bath temperature to 170℃, and stir at 150rpm for 1.5h to obtain the first mixture. (2) Add 4wt%EG and 15wt%APP to the first mixture in sequence, increase the stirring speed to 800rpm, keep the temperature at 170℃ and stir continuously for 1h to make the mixture fully mixed and obtain the second mixture; (3) Pour the second mixture into the mold, cool and demold to obtain sample POEA.

[0043] The preparation process of EG is as follows: add anhydrous ethanol and immerse expandable graphite powder, stir and wash, remove the upper suspension, repeat the washing 3 times, dry to obtain graphite powder, and then heat it in a muffle furnace at 750°C for about 1 minute.

[0044] Comparative Example 6: PA was placed in a beaker and heated in an oil bath at 70°C until completely melted. Then it was poured into a mold, cooled, and demolded to obtain sample PA.

[0045] Comparative Example 7: The method for CPCM (without flame retardant) in this comparative example includes the following steps: (1) Place 60wt%PA in a beaker and heat it in an oil bath at 70℃ until it is completely melted. Then add 36wt%OBC, raise the oil bath temperature to 170℃, and stir at 150rpm for 1.5h to obtain the first mixture. (2) Add 4wt%EG to the first mixture in sequence, increase the stirring speed to 800rpm, keep the temperature at 170℃ and stir continuously for 1h to make the mixture fully mixed and obtain the second mixture; (3) Pour the second mixture into the mold, cool and demold to obtain the sample POE.

[0046] The preparation process of EG is as follows: add anhydrous ethanol and immerse expandable graphite powder, stir and wash, remove the upper suspension, repeat the washing 3 times, dry to obtain graphite powder, and then heat it in a muffle furnace at 750°C for about 1 minute.

[0047] Comparative Example 8: The method for CPCM (without adding thermal conductivity enhancer EG and flame retardant) in this comparative example includes the following steps: (1) Place 60wt%PA in a beaker and heat it in an oil bath at 70℃ until it is completely melted. Then add 40wt%OBC, raise the oil bath temperature to 170℃, and stir at 150rpm for 1.5h to obtain a mixture. (2) Pour the mixture into the mold, cool and demold to obtain sample PO.

[0048] Characterization and testing: The samples prepared in the above embodiments and comparative examples were characterized and tested using the following methods: Thermal conductivity test: The thermal conductivity of the sample was measured at room temperature using a HotDisk thermal constant analyzer.

[0049] Phase transition enthalpy and melting point test: Differential scanning calorimetry (DSC) was used to test under N2 atmosphere, with a heating rate of 5℃ / min.

[0050] Leakage test: Place a sample with a diameter of 40 mm and a height of 4 mm on a 60℃ heating plate and heat for 6 hours. Weigh the sample before and after heating and calculate the leakage rate.

[0051] Flexibility test: After the sample is heated and softened on a 40°C heating platform, its bending deformation capacity under external force is observed.

[0052] Flame retardant performance testing: The material was prepared into 125mm×13mm×3mm specimens, and a combustion test was conducted by vertically clamping the specimens. The total duration of combustion after two ignitions was recorded. To further verify the flame retardant performance of the material, 100mm×100mm×4mm specimens were prepared, and the heat release rate (HRR), total heat release (THR), smoke generation rate (SPR), and total smoke production (TSP) curves of the specimens were recorded using a cone calorimeter under 35kW irradiation.

[0053] Cyclic stability test: The sample was cyclically heated and cooled on an electric heating plate with a temperature range of 20-70℃. After 100 cycles, the melting point and phase transition enthalpy of the sample were measured and compared with the results before the cycle.

[0054] Battery thermal management effect test: The sample was cast into a cylindrical ring (about 17mm thick) that matched the 46950 battery (purchased from China BAK Power Battery Co., Ltd.), which was then wrapped around the side of the battery. The sample was subjected to a 2.5C constant current discharge in a 25℃ temperature chamber. T-type thermocouples were used to record the battery temperature rise curve, and the result was compared with the natural convection cooling condition.

[0055] Test results: 1. Thermophysical properties The group assignments for Examples 1 and Comparative Examples 1-8 are shown in Table 1, and the test data for thermal conductivity, melting point, and phase transition enthalpy are shown in Table 2. The results show that Example 1 (POEMA2) has the highest thermal conductivity, reaching 1.12 W·m. -1 ·K -1 Compared to Comparative Example 6 (pure PA), the performance was improved by 433.3%, and it also showed a significant improvement over Comparative Example 7 (POE), and was slightly higher than Comparative Examples 1 and 2. Meanwhile, the phase transition enthalpy of Example 1 was 114.5 J / g, the highest among all comparative examples (excluding Comparative Example 6), and the melting point was 38.5℃. These data indicate that when the mass ratio of MA to APP in the synergistic flame retardant is 1.5:1, POEMA2 has the highest thermal conductivity (1.12 W·m). -1 ·K -1 The resulting composite material, while introducing expanded graphite (EG) to enhance thermal conductivity, can maintain optimal thermal conductivity and phase change enthalpy, thereby significantly improving the thermal conductivity of the material while maintaining a high phase change energy storage capacity.

[0056] Table 1. Proportions of each component in CPCM

[0057] Table 2 Thermal conductivity, melting point, and enthalpy of different samples

[0058] 2. Leakage rate and thermally induced flexibility The leakage test diagram of Example 1 (POEMA2) is shown below. Figure 2 As shown. After heating at 60°C for 6 hours, the leakage rate of Example 1 was only 1.2%. The OBC provides both shape stability and thermally induced flexibility, so no obvious structural collapse was observed in the overall appearance, indicating that it has excellent shape stability. Figure 3 The image shows a bending photograph of Example 1 after being heated to 40°C. After heating the sample of Example 1 to 40°C, it can be easily bent without breaking, indicating that it has excellent thermally induced flexibility.

[0059] 3. Flame retardant properties Vertical combustion photographs of Example 1 (POEMA2), Comparative Example 1 (POEM), Comparative Example 5 (POEA), Comparative Example 7 (POE), and Comparative Example 8 (PO) are shown below. Figure 4 As shown in the figure. The total combustion time of Example 1 was only 3.6 s, significantly lower than that of Comparative Examples 1 and 5 (containing only a single flame retardant) and Comparative Example 7 (without added flame retardant), and much lower than that of Comparative Example 8 (without added paraffin and flame retardant). The cone calorimetry test results of Example 1, Comparative Example 7, and Comparative Example 8 are shown in the figure. Figure 5As shown, the peak heat release rate (PHRR), total heat release (THR), peak smoke generation rate (SPR), and total smoke generation (TSP) of Example 1 were reduced by 45.8%, 34.2%, 67.7%, and 52.4%, respectively, compared to Comparative Example 8. The above two-phase flame retardant tests fully demonstrate the excellent flame retardant effect of Example 1. Therefore, POEMA2, using a synergistic flame retardant, has the shortest burning time, which is shorter than that of POEM and POEA, which use single flame retardants.

[0060] 4. Cyclic stability Example 1: DSC curves before and after 100 cycles are shown below. Figure 6 As shown, after cycling, the melting point of Example 1 decreased by 0.6°C; the phase transition enthalpy decreased by 0.2 J / g, which is only 0.2% of the initial value, proving that Example 1 has good potential for long-term recycling.

[0061] 5. Battery thermal management effect The battery temperature rise curves at a discharge rate of 2.5C for natural convection cooling and CPCM (POEMA2 in Example 1) cooling are shown below. Figure 7 As shown, when natural convection cooling was used, the battery prematurely ended the discharge experiment due to excessively rapid temperature rise. However, when cooling was achieved using a CPCM (Concentrated Convection Cooling Membrane) coating, the temperature rose gradually throughout the discharge process, with the highest temperature effectively controlled at 42.1°C, a reduction of 15.1°C compared to natural convection cooling. This demonstrates that the CPCM of this invention has an extremely significant thermal management effect.

[0062] In summary, this invention has successfully prepared a composite phase change material that combines EG-enhanced thermal conductivity, OBC flexible support for leak prevention, and MA / APP synergistic flame retardant properties, demonstrating great application potential in the field of battery thermal management.

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, or improvements 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 melamine / ammonium polyphosphate synergistic flame-retardant flexible composite phase change material, characterized in that, It is composed of the following components: 55-65 wt% paraffin wax, 18-24 wt% olefin block copolymer, 3-5 wt% expanded graphite and 12-18 wt% synergistic flame retardant; The synergistic flame retardant is composed of melamine and ammonium polyphosphate, and the mass ratio of melamine to ammonium polyphosphate is 1.2-1.6:

1.

2. The melamine / ammonium polyphosphate synergistic flame-retardant flexible composite phase change material according to claim 1, characterized in that, It is composed of the following components in parts by weight: 60wt% paraffin wax, 21wt% olefin block copolymer, 4wt% expanded graphite, and the synergistic flame retardant consists of 9wt% melamine and 6wt% ammonium polyphosphate.

3. The melamine / ammonium polyphosphate synergistic flame-retardant flexible composite phase change material according to claim 1, characterized in that, The preparation process of the expanded graphite is as follows: add anhydrous ethanol and immerse the expandable graphite powder, stir and wash, remove the upper suspension, repeat washing, dry to obtain graphite powder, and then heat at 750°C to obtain expanded graphite.

4. The melamine / ammonium polyphosphate synergistic flame-retardant flexible composite phase change material according to claim 1, characterized in that, The composite phase change material has a maximum phase change enthalpy of 114.5 J / g and a maximum thermal conductivity of 1.12 W·m. -1 ·K -1 .

5. A method for preparing the melamine / ammonium polyphosphate synergistic flame-retardant flexible composite phase change material as described in any one of claims 1-4, characterized in that, It includes the following steps: (1) Heat paraffin to a molten state, add olefin block copolymer, and stir at a first temperature and a first stirring speed for a first time to obtain a first mixture; (2) Add expanded graphite, melamine and ammonium polyphosphate to the first mixture, and stir at a second temperature and a second stirring speed for a second time to obtain a second mixture; (3) The second mixture is cast into a mold, cooled and demolded to obtain the composite phase change material.

6. The method according to claim 5, characterized in that, In step (1), the temperature at which the paraffin wax melts is 60-80℃.

7. The method according to claim 5, characterized in that, In step (1), the first temperature is 160-180℃, the first stirring speed is 100-200rpm, and the first time is 1-2h.

8. The method according to claim 5, characterized in that, In step (2), the preparation process of the expanded graphite is as follows: add anhydrous ethanol and immerse the expandable graphite powder, stir and wash, remove the upper suspension, repeat the washing, dry to obtain graphite powder, and then heat at 750°C to obtain expanded graphite.

9. The method according to claim 5, characterized in that, In step (2), the second temperature is 160-180℃, the second stirring speed is 700-900rpm, and the second time is 0.5-1.5h.

10. The application of the melamine / ammonium polyphosphate synergistic flame-retardant flexible composite phase change material as described in any one of claims 1-4 in battery thermal management.

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