A high thermal conductivity and high stability phase change material, its preparation method and application, and a battery module and its potting method.

Abstract

This invention provides a high thermal conductivity and high stability phase change material, its preparation method and application, a battery module and its potting method, belonging to the field of power battery technology. This invention uses dopamine hydrochloride to modify graphite nanosheets, forming a layer of polydopamine on the surface of the graphite nanosheets, effectively enhancing the adhesion of silver nanoparticles to the graphite nanosheet surface; then, silver nanoparticles are attached to the surface of the graphite nanosheets, forming a large-area silver nanoparticle-graphite nanosheet thermally conductive network, significantly improving the thermal conductivity of the phase change material; simultaneously, epoxy resin is used to ensure that the phase change material maintains a high quality retention rate even after long-term use at high temperatures, thereby achieving temperature control and compactness of the battery module, solving the problem of thermal runaway in phase change material battery modules due to poor heat transfer performance, and effectively adapting to battery thermal management.

Description

Technical Field

[0001] This invention relates to the field of power battery technology, and in particular to a high thermal conductivity and high stability phase change material, its preparation method and application, and a battery module and its potting method. Background Technology

[0002] In recent years, due to the energy crisis and environmental pollution caused by the large-scale use of fossil fuels, electric vehicles using clean energy have been widely promoted as they can effectively reduce fossil fuel consumption and greenhouse gas emissions. Among these vehicles, the power battery system, as the energy storage component, directly affects the safety of the electric vehicle. In practical applications, power battery systems tend to accumulate heat under different operating conditions, such as high temperatures and high-rate discharge. If this heat cannot be transferred in time, it can lead to battery performance degradation or even thermal runaway. Therefore, power battery systems require a reasonable and effective battery thermal management system to control the operating temperature of the battery module within a safe range.

[0003] Currently, mainstream battery thermal management systems are divided into passive and active thermal management. Active thermal management includes liquid cooling, forced air cooling, and heat pipe cooling. These systems require additional energy to control battery temperature, resulting in increased weight and cost, and they cannot control the temperature uniformity of the battery module. Passive thermal management includes natural air cooling and phase change material (PCM) thermal management. Natural air cooling suffers from low volumetric energy density and is not well-suited for battery thermal management. PCMs, due to their isothermal absorption or release of large amounts of heat during phase change, are widely used in solar energy and building insulation, and are also suitable for use as heat dissipation modules in battery thermal management to control the temperature uniformity of individual cells. Currently, PCMs in practical applications include solid-solid PCMs and solid-liquid PCMs. Solid-solid PCMs have disadvantages such as low latent heat of phase change and low thermal conductivity, limiting their applications compared to solid-liquid PCMs. Solid-liquid PCMs, on the other hand, suffer from low thermal conductivity and are prone to leakage. Summary of the Invention

[0004] The purpose of this invention is to provide a high thermal conductivity and high stability phase change material, its preparation method and application, a battery module and its potting method, which can solve the problems of low thermal conductivity and easy leakage of phase change materials.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing a phase change material, comprising the following steps:

[0007] Graphite nanosheets, dopamine hydrochloride, alkaline reagent and water are mixed and self-polymerized to obtain graphite nanosheets with attached polydopamine.

[0008] The graphite nanosheets with attached polydopamine, a reducing agent, a silver salt solution, an acid reagent, and water were mixed and reduced to obtain graphite nanosheets with attached silver nanoparticles.

[0009] The graphite nanosheets with attached silver nanoparticles, the phase change substrate, and the epoxy resin are mixed, and the resulting phase change substrate mixture is cured to obtain a phase change material.

[0010] Preferably, the mass ratio of dopamine hydrochloride to graphite nanosheets is (0.5-1):10; the self-polymerization pH is 9-10, and the time is 2-4 hours.

[0011] Preferably, the ratio of the graphite nanosheets with attached polydopamine, the silver salt solution, and the reducing agent is 1g:(6-12)mL:(0.5-1)g; the concentration of the silver salt solution is 0.1mol / L; the pH value of the reduction is 3-4, and the time is 2-4h.

[0012] Preferably, the phase change substrate includes paraffin, polyethylene glycol, or hexadecylamine; the mass ratio of the phase change substrate, graphite nanosheets with attached silver nanoparticles, and epoxy resin is (6-6.5):(0.5-1):3.

[0013] Preferably, the phase change substrate is a molten phase change substrate, and the melting temperature is 60-70°C; the temperature at which the graphite nanosheets with attached silver nanoparticles, the phase change substrate, and the epoxy resin are mixed is 60-70°C.

[0014] Preferably, the content of silver nanoparticles in the phase change material is 1 to 2 wt% of the total mass of the phase change material.

[0015] The present invention provides a phase change material prepared by the preparation method described above, comprising an epoxy resin skeleton and a phase change component encapsulated in the epoxy resin skeleton; the phase change component comprises a graphite nanosheet-phase change substrate composite with attached silver nanoparticles.

[0016] This invention provides the application of the phase change material described in the above technical solution in a power battery system.

[0017] The present invention provides a battery module, including a housing and a loading hole disposed in the housing; the housing is made of the phase change material described in the above technical solution.

[0018] This invention provides a method for potting the battery module described in the above technical solution, comprising the following steps:

[0019] The phase change substrate mixture is poured into a mold containing a battery. After curing, the mold is removed to obtain the battery module.

[0020] This invention provides a method for preparing a phase change material. The invention uses dopamine hydrochloride to modify graphite nanosheets, forming a layer of polydopamine on the surface of the graphite nanosheets. The polydopamine has a high content of primary and secondary amines as well as catechol (3,4-diol). The coexistence of these two functional groups helps to improve the adhesion ability of polydopamine, thereby effectively enhancing the adhesion ability of the graphite nanosheet surface to silver nanoparticles, thus making full use of the thermal conductivity of silver nanoparticles and improving the thermal conductivity of the material.

[0021] This invention reduces silver salts under the action of a reducing agent, attaching silver nanoparticles to the surface of graphite nanosheets. The graphite nanosheets with polydopamine attached to their surface also have adsorption properties for organic materials. During the mixing process with the phase change substrate, the graphite nanosheets with attached silver nanoparticles adsorb small-molecule phase change materials (i.e., graphite nanosheets with attached silver nanoparticles-phase change substrate composites) onto the graphite nanosheets. At the same time, the graphite nanosheets with attached silver nanoparticles connect and overlap with each other, thereby forming a large-area silver nanoparticle-graphite nanosheet thermally conductive network, which significantly improves the thermal conductivity of the phase change material.

[0022] This invention utilizes the three-dimensional network structure of epoxy resin to encapsulate small-molecule phase change materials (PCMs), effectively adsorbing and encapsulating them, and forming a robust supporting framework. This allows the PCMs to maintain high quality retention even after prolonged use at high temperatures, thereby achieving temperature control in the battery module. Batteries generate significant heat during charging and discharging. PCMs possess high latent heat, enabling them to absorb or release substantial amounts of heat isothermally during phase change. Because this invention improves the thermal conductivity of the PCMs, it accelerates the heat transfer process from the PCMs to the surrounding environment, thus achieving temperature control in the battery module. This solves the problem of thermal runaway in PCM battery modules due to poor heat transfer performance, effectively adapting to battery thermal management.

[0023] The phase change material prepared by this invention has a phase change temperature range of 48–52 °C and a thermal conductivity as high as 3.1 W / (m·K).

[0024] In addition, because the three-dimensional network structure of epoxy resin can encapsulate small molecule phase change materials within it, and because epoxy resin is a thermosetting material that does not soften when heated after curing, leakage can be effectively prevented.

[0025] This invention provides a battery module potting method using a one-step potting process. This method tightly adheres the battery and phase change material together, preventing battery detachment during operation and effectively reducing the contact thermal resistance between the battery and the phase change material. This enhances heat transfer performance while achieving a compact battery module. Furthermore, the one-step potting process directly pots the phase change material into a mold with the battery already fixed in place, eliminating the need to use a battery mold to replace the battery.

[0026] Furthermore, the phase change substrate used in this invention has a low phase change melting temperature (60-70°C), allowing it to be stirred and mixed with epoxy resin at a lower temperature. This enables low-temperature mixing of the phase change substrate, preventing damage to the battery casing and internal structure during the potting process. It allows for one-step potting without the need for a battery mold. In contrast, existing phase change materials require high temperatures (140-160°C) to melt into a liquid state, necessitating the use of a battery mold to prevent damage to the battery casing and internal structure during potting of the phase change material stirred and mixed at high temperatures. The mold is then removed after the phase change material cools and solidifies, and the battery is inserted into the module. Attached Figure Description

[0027] Figure 1 SEM images of the different products obtained in Example 1 and Comparative Example 1;

[0028] Figure 2 The thermal conductivity results are shown in the graphs for the different products prepared in Example 1 and Comparative Examples 1-2.

[0029] Figure 3 The graph shows the average mass retention of the product GPPEG-10 obtained in Example 1 after continuous heating at different temperatures.

[0030] Figure 4 This is a schematic diagram of the battery module structure in an application example; where 1 is the housing; 2 is the loading hole; and 3 is the battery.

[0031] Figure 5 The figures show the 3C discharge performance test results of battery modules encapsulated with different products prepared in Example 1 and Comparative Examples 1-2. Detailed Implementation

[0032] This invention provides a method for preparing a phase change material, comprising the following steps:

[0033] Graphite nanosheets, dopamine hydrochloride, alkaline reagent and water are mixed and self-polymerized to obtain graphite nanosheets with attached polydopamine.

[0034] The graphite nanosheets with attached polydopamine, a reducing agent, a silver salt solution, an acid reagent, and water were mixed and reduced to obtain graphite nanosheets with attached silver nanoparticles.

[0035] The graphite nanosheets with attached silver nanoparticles, the phase change substrate, and the epoxy resin are mixed, and the resulting phase change substrate mixture is cured to obtain a phase change material.

[0036] In this invention, unless otherwise specified, the required materials or reagents are all commercially available products well known to those skilled in the art.

[0037] This invention involves mixing graphite nanosheets, dopamine hydrochloride, an alkaline reagent, and water, and then performing self-polymerization to obtain graphite nanosheets with attached polydopamine.

[0038] In this invention, the preferred method for preparing the graphite nanosheets includes:

[0039] Expanded graphite, anhydrous ethanol, and N-methylpyrrolidone are mixed and then ball-milled to obtain graphite nanosheets. In this invention, the ball milling is preferably performed in a planetary ball mill. The mass ratio of the milling beads to the expanded graphite is preferably (10-30):1, more preferably 20:1. The preferred ratio of the amount of expanded graphite, anhydrous ethanol, and N-methylpyrrolidone is 1 g:50 mL:10 mL. The preferred milling speed is 800 rad / min, and the preferred milling time is 3 h. In this invention, the density of anhydrous ethanol is lower than that of expanded graphite, allowing the expanded graphite to be uniformly dispersed in the anhydrous ethanol. N-methylpyrrolidone prevents the graphite nanosheets from re-agglomerating under high-speed rotation during the ball milling process.

[0040] After completing the ball milling, the present invention preferably filters the obtained product with deionized water and dries it to obtain graphite nanosheets; the present invention does not have any special limitations on the specific process of the filtration and drying, and can be carried out according to the process known in the art.

[0041] In this invention, the preferred mass ratio of dopamine hydrochloride to graphite nanosheets is (0.5-1):10.

[0042] In this invention, the alkaline reagent is preferably anhydrous sodium carbonate; the amount of the alkaline reagent is preferably sufficient to achieve the pH required for self-polymerization.

[0043] In this invention, the preferred method for mixing the graphite nanosheets, dopamine hydrochloride, alkaline reagent, and water is to add the graphite nanosheets to the water, add the alkaline reagent to the resulting solution, adjust the pH value to the desired value, and then add the dopamine hydrochloride to the pH-adjusted solution.

[0044] In this invention, the pH value of the self-polymerization is preferably 9-10, and the time is preferably 2-4 hours; the self-polymerization is preferably carried out under stirring conditions, and the stirring rate is preferably 400-600 rad / min.

[0045] After the self-polymerization is completed, the present invention preferably filters the obtained product with deionized water to obtain graphite nanosheets with attached polydopamine. The present invention does not have any particular limitation on the filtration process; it can be carried out according to procedures well known in the art.

[0046] After obtaining graphite nanosheets with attached polydopamine, the present invention mixes the graphite nanosheets with attached polydopamine, a reducing agent, a silver salt solution, an acid reagent, and water, and performs reduction to obtain graphite nanosheets with attached silver nanoparticles.

[0047] In this invention, the reducing agent is preferably ascorbic acid; the silver salt in the silver salt solution is preferably silver nitrate; the silver salt solution is preferably an aqueous solution of silver salt; the concentration of the silver salt solution is preferably 0.1 mol / L; the acid reagent is preferably dilute hydrochloric acid, and the concentration of the dilute hydrochloric acid is preferably 1 mol / L.

[0048] In this invention, the preferred ratio of the graphite nanosheets with attached polydopamine, the silver salt solution, and the reducing agent is 1g:(6-12)mL:(0.5-1)g, more preferably 1g:12mL:0.5g; the amount of the acid reagent is preferably sufficient to reach the pH required for reduction.

[0049] In this invention, the preferred method for mixing the polydopamine-attached graphite nanosheets, reducing agent, silver salt solution, acid reagent, and water is to add the polydopamine-attached graphite nanosheets to water, add the acid reagent to the resulting solution, adjust to the desired pH value, and then add the silver salt solution and reducing agent to the resulting solution in sequence.

[0050] In this invention, the pH value of the reduction is preferably 3 to 4, and the time is preferably 2 to 4 hours; the reduction is preferably carried out under light-proof stirring conditions, and the stirring speed is preferably 400 to 600 rad / min.

[0051] After the reduction is completed, the present invention preferably filters the obtained product with deionized water to obtain graphite nanosheets with attached silver nanoparticles. The present invention does not have any particular limitation on the filtration process; it can be carried out according to procedures well known in the art.

[0052] After obtaining graphite nanosheets with attached silver nanoparticles, the present invention mixes the graphite nanosheets with attached silver nanoparticles, a phase change substrate, and an epoxy resin, and then cures the resulting phase change substrate mixture to obtain a phase change material.

[0053] In this invention, the phase change substrate preferably includes paraffin wax, polyethylene glycol, or hexadecylamine; the molecular weight of Mn of the polyethylene glycol is preferably 1000, 1500, or 2000; when the phase change substrate is preferably two or more of the above, this invention does not have a special limitation on the ratio of different types of phase change substrates, and any ratio is acceptable.

[0054] In this invention, the preferred mass ratio of the phase change substrate, the graphite nanosheets with attached silver nanoparticles, and the epoxy resin is (6-6.5):(0.5-1):3; the epoxy resin preferably includes epoxy resin A and epoxy resin B, and the preferred mass ratio of A and B is 1:1. This invention does not impose any specific limitation on the epoxy resin; commercially available products well-known in the art are acceptable. In the embodiments of this invention, epoxy resin A and B are specifically epoxy resin E44(6101).650.

[0055] In this invention, the phase change substrate is preferably a molten phase change substrate, and the melting temperature is preferably 60-70°C; the mixing temperature of the graphite nanosheets with attached silver nanoparticles, the phase change substrate, and the epoxy resin is preferably 60-70°C, which is within the safe temperature range of battery specifications.

[0056] In this invention, the preferred method for mixing the graphite nanosheets with attached silver nanoparticles, the phase change substrate, and the epoxy resin is to add the graphite nanosheets with attached silver nanoparticles to the molten phase change substrate, and then add epoxy resin A and B in sequence while stirring; the preferred stirring speed is 800-1000 rad / min.

[0057] In this invention, the curing is preferably carried out in a mold. The mold is not specifically limited in this invention; any mold well-known in the art is acceptable. In this invention, the curing is preferably carried out at room temperature, and the curing time is preferably 12 hours.

[0058] In this invention, the content of silver nanoparticles in the phase change material is preferably 1 to 2 wt% of the total mass of the phase change material.

[0059] The present invention provides a phase change material prepared by the preparation method described above, comprising an epoxy resin skeleton and a phase change component encapsulated in the epoxy resin skeleton; the phase change component comprises a graphite nanosheet-phase change substrate composite with attached silver nanoparticles.

[0060] This invention provides the application of the phase change material described in the above technical solution in a power battery system.

[0061] This invention provides a battery module, including a housing and a loading hole disposed within the housing; the housing is made of the phase change material described in the above-mentioned technical solution. This invention does not impose any special limitations on the manufacturing process of the housing; the housing can be manufactured according to methods well known in the art.

[0062] This invention does not impose any special limitations on the arrangement of batteries and loading holes in the battery module; any battery mold structure well known in the art is acceptable. In this invention, the height of the housing is preferably the same as the height of the batteries; the number of loading holes is preferably the same as the number of batteries; the interval between any two adjacent loading holes is 4 mm, and the interval between the loading hole and the edge of the housing is 4 mm; the preferred arrangement of the loading holes is 5 rows and 5 columns, corresponding to a 5-parallel and 5-series battery arrangement.

[0063] This invention provides a method for potting the battery module described in the above technical solution, comprising the following steps:

[0064] The phase change substrate mixture is poured into a mold containing a battery. After curing, the mold is removed to obtain the battery module.

[0065] In this invention, the mold equipped with the battery is preferably an acrylic mold, and the upper and lower plates of the acrylic mold (preferably two acrylic plates with a thickness of 3mm and 5 rows and 5 columns of round holes) are provided with holes for fixing the battery.

[0066] In this invention, phase change material is poured into an acrylic mold in which a battery is fixed. After the phase change material has solidified, the acrylic mold is removed, and the battery is then installed into the loading hole.

[0067] Existing phase change material (PCM) battery modules require a battery mold to replace the battery during potting. This is to prevent damage to the battery casing and internal structure during the high-temperature mixing of the PCM. After the PCM cools and solidifies, the mold is removed, and the battery is inserted into the module. In this invention, the mixing temperature of the PCM substrate is 60–70°C, which is within the safe range that the battery can withstand (-40–70°C). Therefore, there is no need to use a battery mold to replace the battery, nor is it necessary to use a cylindrical battery mold to create the loading hole first. The PCM can be directly potted into the acrylic mold with the battery already fixed in place. After the PCM solidifies, the loading hole is already assembled with the battery, which can reduce the contact thermal resistance between the battery and the PCM.

[0068] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0069] Example 1

[0070] (1) Add 2g of expanded graphite to a mixed solution of 100mL anhydrous ethanol and 20mL N-methylpyrrolidone, and place it in a planetary ball mill at 800rad / min for 3h. The mass ratio of the ball milling beads to the expanded graphite is 20:1. Filter the resulting mixture with deionized water and dry it to obtain graphite nanosheets GNS.

[0071] (2) Add 1g of graphite nanosheets to 100mL of deionized water, add 0.5g of anhydrous sodium carbonate to the resulting solution, adjust the pH of the solution to 10, add 0.1g of dopamine hydrochloride to the resulting solution, stir magnetically at 600rad / min for 2h, filter with deionized water to obtain graphite nanosheets with attached polydopamine.

[0072] (3) Add 1g of graphite nanosheets with attached polydopamine to 10mL of deionized water, add 2mL of 1mol / L dilute hydrochloric acid to the resulting solution to adjust the pH of the solution to 3, add 12mL of 0.1mol / L silver nitrate solution and 0.5g of ascorbic acid to the resulting solution in sequence, stir magnetically at 600rad / min in the dark for 2h, filter with deionized water, and dry to obtain graphite nanosheets GNP with attached silver nanoparticles;

[0073] (4) Add graphite nanosheets GNP with attached silver nanoparticles to polyethylene glycol-1500 melted at 60°C, and then add epoxy resin A and B glue in sequence (the mass ratio of A glue to B glue is 1:1, and the epoxy resin glue is E44 (6101).650). Stir the mixture. The mass ratio of graphite nanosheets GNP with attached silver nanoparticles, polyethylene glycol-1500 and epoxy resin is 0.5:6.5:3 and 1:6:3, respectively. Pour the mixture into a mold and cure the resulting phase change substrate mixture. The amount of graphite nanosheets with attached silver nanoparticles added is 5wt% and 10wt%, respectively. The resulting products are denoted as GPPEG-5 and GPPEG-10, respectively.

[0074] Comparative Example 1

[0075] (1) Add 2g of expanded graphite to a mixed solution of 100mL anhydrous ethanol and 20mL N-methylpyrrolidone, and place it in a planetary ball mill at 800rad / min for 3h. The mass ratio of the ball milling beads to the expanded graphite is 20:1. Filter the resulting mixture with deionized water and dry it to obtain graphite nanosheets GNS.

[0076] (2) Add 1g of graphite nanosheets to 10mL of deionized water, add 2mL of 1mol / L dilute hydrochloric acid to the resulting solution to adjust the pH of the solution to 3, add 12mL of 0.1mol / L silver nitrate solution and 0.5g of ascorbic acid to the resulting solution in sequence, stir magnetically at 600rad / min in the dark for 2h, filter with deionized water, and dry to obtain graphite nanosheets GNA with attached silver nanoparticles;

[0077] (3) Add graphite nanosheets GNA with attached silver nanoparticles to polyethylene glycol-1500 melted at 60°C, and then add epoxy resin A and B glue (Deyi epoxy resin glue E44 (6101).650) and stir. The mass ratio of graphite nanosheets GNA, polyethylene glycol-1500 and epoxy resin is 0.5:6.5:3 and 1:6:3, respectively. That is, the amount of graphite nanosheets with attached silver nanoparticles added is 5wt% and 10wt%, respectively. Pour into a mold and cure the resulting phase change substrate mixture. The resulting products are denoted as GAPEG-5 and GAPEG-10, respectively.

[0078] Comparative Example 2

[0079] (1) Add 2g of expanded graphite to a mixed solution of 100mL anhydrous ethanol and 20mL N-methylpyrrolidone, and place it in a planetary ball mill at 800rad / min for 3h. The mass ratio of the ball milling beads to the expanded graphite is 20:1. Filter the resulting mixture with deionized water and dry it to obtain graphite nanosheets GNS.

[0080] (2) Graphite nanosheets GNS were added to polyethylene glycol-1500 melted at 60°C, and epoxy resins A and B (Deyi epoxy resin E44 (6101).650) were added sequentially and stirred. The mass ratio of graphite nanosheets GNS, polyethylene glycol-1500 and epoxy resin was 0.5:6.5:3 and 1:6:3, respectively. That is, the amount of graphite nanosheets with attached silver nanoparticles added was 5wt% and 10wt%, respectively. The mixture of phase change substrates was poured into a mold and cured. The resulting products were named GSPEG-5 and GSPEG-10, respectively.

[0081] Characterization and performance testing

[0082] 1) Figure 1 SEM images of different products obtained in Example 1 and Comparative Example 1 are shown. In Comparative Example 1, a and b are SEM images of different regions (GNA-1 and GNA-2) on the graphite nanosheets GNA with attached silver nanoparticles prepared in Comparative Example 1, and c and d are SEM images of different regions (GNP-1 and GNP-2) on the graphite nanosheets GNP with attached silver nanoparticles prepared in Example 1. Figure 1It can be seen that the GNA product prepared in Comparative Example 1 showed virtually no silver nanoparticles on its surface in the scanning electron microscope (SEM) image. In contrast, the GNP product prepared in Example 1, with a polydopamine coating on its surface, clearly showed silver nanoparticles uniformly distributed on the graphite nanosheet surface in the SEM image. This indicates that the polydopamine-modified graphite nanosheets have a stronger adhesion to silver nanoparticles, thereby expanding the thermally conductive network on the graphite nanosheets.

[0083] 2) Two regions were randomly selected from the different products obtained in Examples 1 (GNP-1 and GNP-2) and Comparative Example 1 (GNA-1 and GNA-2) for EDS testing. The results are shown in Table 1.

[0084] Table 1 shows the energy dispersive spectroscopy (EDS) elemental analysis of the different products prepared in Example 1 and Comparative Example 1.

[0085]

[0086] As shown in Table 1, the silver nanoparticle content on the GNA product prepared in Comparative Example 1 was 0.559% and 0.180%, respectively. The silver nanoparticle content on the GNP product prepared in Example 1 after being coated with polydopamine was 4.864% and 4.727%, respectively, which was significantly higher than that of Comparative Example 1 of this application. This is because the polydopamine on the surface of the GNP product prepared in Example 1 has super strong adhesion, which can adsorb more silver nanoparticles, effectively expand the thermal conductivity network skeleton of the material, and enhance the heat transfer performance of the phase change material.

[0087] 3) The thermal conductivity of different products was tested using a hot disk thermal constant analyzer. Figure 2 The graph shows the thermal conductivity results of different products prepared in Example 1 and Comparative Examples 1-2. Figure 2 It can be seen that the thermal conductivity of GSPEG-5 and GSPEG-10, the products obtained from Comparative Example 2 with 5wt% and 10wt% GNS addition of graphite nanosheets, are 1.3 W / (m·K) and 1.6 W / (m·K), respectively. The thermal conductivity of GAPEG-5 and GAPEG-10, the products obtained from Comparative Example 1 with 5wt% and 10wt% GNA addition of graphite nanosheets without dopamine hydrochloride modification, are 1.53 W / (m·K) and 2.4 W / (m·K), respectively, showing a significant improvement in thermal conductivity. The graphite nanosheets modified with dopamine hydrochloride and coated with silver nanoparticles, with GNP additions of 5wt% and 10wt%, produced GPPEG-5 and GPPEG-10, respectively. Their thermal conductivity was 2.05 W / (m·K) and 3.1 W / (m·K), respectively, which greatly improved the thermal conductivity. Compared with the thermal conductivity of ordinary polyethylene glycol-1500 (PEG) of 0.26 W / (m·K), the thermal conductivity was improved by nearly 1100%, which can effectively improve the thermal management performance of the battery module.

[0088] 4) The product GPPEG-10 prepared in Example 1 was placed on a heating stage and heated at different temperatures. Samples were removed and weighed every 30 minutes, and the data was recorded. After the test, the mass change data of all samples at each temperature were averaged. The results are shown in [the table below]. Figure 3 ; Figure 3 The graph shows the average mass retention of the product GPPEG-10 obtained in Example 1 after continuous heating at different temperatures. Figure 3 The results show that after adding epoxy resins A and B to the product prepared in Example 1, the phase change materials all achieved good stability, with a mass retention rate of 99.8% after continuous heating at 50°C for 120 minutes. Furthermore, no significant leakage of the phase change components was observed after the temperature was raised to 80°C, and the mass retention rate remained above approximately 99% even after 120 minutes of heating.

[0089] 5) The phase transition temperature of the product GPPEG-10 prepared in Example 1 was tested using a low-temperature differential scanning calorimeter (DSC). The heating rate and temperature range of the DSC were 10℃ / min and 0-80℃. The DSC test data showed that the phase transition temperature was in the range of 48-52℃.

[0090] Application Example 1

[0091] according to Figure 4 The structure uses the different products prepared in Example 1 and Comparative Examples 1-2 in a battery module, including a housing 1, a loading hole 2 and a battery 3; the housing is made of the different products prepared in Example 1 and Comparative Examples 1-2.

[0092] The height of the housing 1 is the same as the height of the battery 3; the spacing between the loading holes 2 is 4mm, and the spacing between the loading holes 2 and the edge of the housing 1 is 4mm; the number of series and parallel connections on the battery 3 module is 5.

[0093] The battery module potting process: The phase change material prepared in Example 1 and Comparative Examples 1-2 is poured into the mold of the assembled battery in one step. After the phase change material is cured, the mold is removed to form the battery module.

[0094] The battery module was subjected to 3C discharge performance testing in a constant temperature chamber at 25°C. The results are shown below. Figure 5 ; Figure 5 The graphs shown are 3C discharge performance test results (BTM represents the battery module) of battery modules encapsulated with different products prepared in Example 1 and Comparative Examples 1-2. In the graphs, a is the curve showing the highest temperature of the battery module over time, and b is the curve showing the maximum temperature difference of the battery module over time. Figure 3It can be seen that the battery module encapsulated with GSPEG-10 obtained in Comparative Example 2 reached a maximum temperature of 62.5℃ and a maximum temperature difference of 17.2℃ during 3C discharge, exceeding the safe operating temperature range of the battery (-20~60℃), and is prone to thermal runaway. The battery module encapsulated with GAPEG-10 obtained in Comparative Example 1 was able to control the maximum temperature during 3C discharge to 58.3℃, but its maximum temperature difference still reached 13.1℃. Excessive temperature difference within the battery module will cause a decrease in battery performance. For the battery module encapsulated with GPPEG-10 obtained in Example 1, the maximum temperature and maximum temperature difference during 3C discharge were only 51.3℃ and 3.0℃, respectively, which can effectively control the maximum temperature and maximum temperature difference of the battery module within a reasonable and safe temperature range, ensuring the efficient operation of the battery.

[0095] As can be seen from the above embodiments and comparative examples, the phase change material prepared by this invention has good thermal stability and maintains a high mass retention rate even after long-term use at high temperatures. This enables the compactness of battery modules and significantly improves the thermal conductivity of the phase change material, making it more suitable for battery heat dissipation management. It also effectively avoids leakage and thermal runaway problems caused by poor heat transfer performance in phase change material battery modules. The one-step potting process effectively reduces the contact thermal resistance between the battery and the phase change material, ensuring both battery loading stability and enhanced heat transfer performance of the battery module.

[0096] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for producing a phase change material, characterized by, The method comprises the following steps: mixing graphite nanosheets, dopamine hydrochloride, an alkaline reagent and water to perform self-polymerization, to obtain graphite nanosheets with polydopamine attached thereto; mixing the graphite nanosheets with polydopamine attached thereto, a reducing agent, a silver salt solution, an acid reagent and water to perform reduction, to obtain graphite nanosheets with silver nanoparticles attached thereto; mixing the graphite nanosheets with silver nanoparticles attached thereto, a phase change base and an epoxy resin, and curing the obtained phase change base mixture, to obtain a phase change material; The method for preparing the graphite nanosheets comprises the following steps: mixing expanded graphite, anhydrous ethanol and N-methyl pyrrolidone, and performing ball milling, to obtain graphite nanosheets; the expanded graphite, the anhydrous ethanol and the N-methyl pyrrolidone are used in a ratio of 1 g:50 mL:10 mL; the ball milling is performed at a speed of 800 rad / min for 3 h; the mass ratio of the dopamine hydrochloride to the graphite nanosheets is (0.5-1):10; the self-polymerization is performed at a pH value of 9-10 for 2-4 h; the graphite nanosheets with polydopamine attached thereto, the silver salt solution and the reducing agent are used in a ratio of 1 g:(6-12) mL:(0.5-1) g; the silver salt solution has a concentration of 0.1 mol / L; the reduction is performed at a pH value of 3-4 for 2-4 h; the phase change base comprises paraffin, polyethylene glycol or hexadecylamine; the phase change base, the graphite nanosheets with silver nanoparticles attached thereto and the epoxy resin are used in a mass ratio of (6-6.5):(0.5-1):3; the phase change base is a molten phase change base, and the melting temperature is 60-70℃; the graphite nanosheets with silver nanoparticles attached thereto, the phase change base and the epoxy resin are mixed at a temperature of 60-70℃; in the phase change material, the content of the silver nanoparticles is 1-2 wt% of the total mass of the phase change material.

2. The phase change material produced by the method of claim 1, characterized in that, The phase change material comprises an epoxy resin skeleton and a phase change component wrapped in the epoxy resin skeleton; the phase change component comprises graphite nanosheets with silver nanoparticles attached thereto-phase change base composites.

3. The phase change material of claim 2 is applied in a power battery system.

4. A battery module, characterized by The battery module comprises a box body and a loading hole arranged in the box body; the box body is made of the phase change material of claim 2.

5. The potting method of the battery module according to claim 4, wherein The method comprises the following steps: pouring the phase change base mixture into a mold with a battery assembled therein, curing, disassembling the mold, and obtaining a battery module.

Images