Intrinsic flame-retardant solid-solid phase change material, preparation method thereof and battery module adopting intrinsic flame-retardant solid-solid phase change material

Abstract

The invention discloses an intrinsic flame-retardant solid-solid phase change material and a preparation method thereof and a battery module adopting the phase change material. The preparation method comprises the following steps: fully reacting a molten phase change substance with hydroxyl with boric acid and phosphorus pentoxide to generate a phase change substance 1 with a boric acid phosphate structure; the preparation method comprises the following steps: adding expanded graphite and phosphoric acid flame retardant powder into a phase-change substance 1, uniformly stirring, adding melamine into a molten mixture, quickly stirring, uniformly mixing the phase-change substance 1 and melamine, reacting to generate a phase-change substance 2 grafted with melamine, and performing post-treatment to obtain the solid-solid phase-change material. The solid-solid phase change material prepared by the preparation method disclosed by the invention has non-flammability and can resist leakage.

Description

Technical Field

[0001] The present application relates to the technical field of phase change materials, and in particular to an intrinsic flame retardant solid-solid phase change material and a preparation method thereof, and a battery module using the phase change material. Background Art

[0002] In recent years, due to the large amount of fossil energy burned by traditional cars, the pollution of the environment and the greenhouse effect have been aggravated, and human beings are facing severe environmental protection problems. Since electric vehicles (EVs) have the characteristics of no pollution and high energy density, using electric vehicles instead of traditional cars is one of the ways to solve the problem of environmental pollution. However, as a mainstream power source for electric vehicles, lithium-ion batteries (LIBs) are extremely sensitive to temperature: when the temperature is too high and heat accumulation occurs, it is easy to cause electrochemical side reactions in LIBs, and the temperature inside the battery rises sharply, resulting in thermal runaway. In view of this, thermal management of batteries is a necessary means to prevent thermal runaway of batteries. At present, there are three mainstream thermal management methods: air cooling, liquid cooling and phase change material cooling: air cooling and liquid cooling require additional auxiliary equipment, which is inconsistent with the high energy density and high integration characteristics of electric vehicles. Compared with the other two cooling methods, phase change material cooling not only has the advantages of high integration, high energy storage density and low cost, but also is a passive thermal management technology, which is more suitable for application in actual use.

[0003] The principle of phase change material cooling is to absorb heat through the phase change process of the material, so that the temperature of the battery module is maintained at a certain level, and the temperature of the batteries in the battery module is basically the same. Paraffin, polyethylene glycol, etc. have received widespread attention due to their high latent heat characteristics. However, due to the defects of paraffin / polyethylene glycol such as flammability and easy leakage, their application is greatly limited. To address this problem, traditional methods usually add flame retardants / support materials to avoid the shortcomings of flammability / easy leakage of materials by physical mixing. However, this method does not essentially change the solid-liquid phase change characteristics of the phase change material. The support material only delays leakage. After long-term multi-cycle use, it will inevitably lead to latent heat loss problems, and even corrosion of the battery module. Flame retardants will also have the problem of reduced flame retardant effect or even failure due to long-term wear during use. Therefore, it is urgent to develop a phase change material that is durable, non-flammable and non-leaking to achieve thermal management of batteries. Summary of the invention

[0004] In view of the defects in the prior art, the present invention proposes an intrinsic flame retardant solid-solid phase change material and a preparation method thereof and a battery module using the phase change material, so as to solve the technical problem that the phase change material in the power source material is easy to leak and burn.

[0005] In a first aspect, the present application provides a method for preparing an intrinsic flame retardant solid-solid phase change material, wherein the raw materials include a phase change material with a hydroxyl group, boric acid, phosphorus pentoxide, expanded graphite, a phosphoric acid flame retardant and melamine, and the preparation method comprises the following steps:

[0006] Step 1: heating and melting the phase change material with hydroxyl group, adding boric acid after it is completely melted and setting the temperature to 140-170° C., stirring continuously for 5-8 hours, adding phosphorus pentoxide under continuous stirring after the reaction is complete, and continuing the reaction for 2-3 hours, finally obtaining a phase change material 1 with a boric acid phosphate structure;

[0007] Step 2: Heat and melt the above synthesized material, then add expanded graphite and phosphoric acid flame retardant and continue stirring for 1-2 hours, add melamine after the mixture is stirred evenly, and continue stirring until the reaction is complete to generate phase change material 2 grafted with melamine;

[0008] Step 3: Pour the above-mentioned phase change material 2 grafted with melamine into a mold, and solidify and shape it at room temperature to obtain an intrinsic flame retardant solid-solid phase change material.

[0009] Among them, the temperature for heating and melting in step one can be optionally 60-80°C, such as 60, 70, 80°C, and the stirring speed can be optionally 400-800r / min, such as 400, 500, 600, 700, 800r / min; the temperature for heating and melting in step two can be optionally 60-80°C, such as 60, 70, 80°C, and the stirring speed can be optionally 700-900r / min, such as 700, 800, 900r / min.

[0010] The phase-change material 1 with boric acid phosphate is generated by fully reacting the molten phase-change material with hydroxyl groups with boric acid and phosphorus pentoxide, so that the phase-change material 1 can stably graft melamine. The sequential addition of boric acid and phosphorus pentoxide can ensure that the subsequent melamine can be connected to the phase-change material 1. In addition, a certain flame retardant ability is provided, and the intrinsic flame retardant effect of the material is achieved by combining with melamine and phosphoric acid flame retardant. Expanded graphite and phosphoric acid flame retardant powder are added to the phase-change material 1 and stirred evenly, and melamine is added to the molten mixture and stirred quickly, so that the phase-change material 1 and melamine are mixed evenly and react to generate grafted melamine. The phase change material 2 of amine, the phase change material chain segment with hydroxyl in the formed material provides latent heat characteristics, the access of boric acid, phosphoric acid group and melamine gives the phase change material flame retardant characteristics, the traditional method of adding flame retardants through physical mixing will cause the material to have problems such as flame retardant sedimentation and aggregation or uneven distribution of flame retardant performance due to multiple phase changes, the present application realizes the intrinsic flame retardant performance of the phase change material through physical mixing of phosphoric acid flame retardant and access of melamine, so that the flame retardant effect of the material will not decrease due to wear and tear, etc.; melamine can also effectively improve the thermal conductivity of the phase change material to achieve rapid heat dissipation.

[0011] Phase change materials with hydroxyl groups alone do not react with melamine, so it is necessary to first add boric acid and phosphorus pentoxide to react to form a phase change material with a boric acid phosphate structure (a precursor of an intrinsic flame-retardant solid-solid phase change material) to provide the possibility of grafting it with melamine, and then add expanded graphite and phosphoric acid flame retardant by physical mixing, and finally add melamine to react to produce an intrinsic flame-retardant solid-solid phase change material. Among them, melamine must be added last. If it is added in advance, the expanded graphite and phosphoric acid flame retardant cannot be evenly embedded in it.

[0012] By reacting the amino groups in melamine with the hydroxyl groups in the phase change material 1, the phase change components are grafted into high molecular polymers, so that the phase change morphology of the phase change components is changed from solid-liquid phase change to solid-solid phase change, thereby changing the phase change characteristics of the phase change material 1, achieving intrinsic anti-leakage, and solving the problem that the phase change material used in the battery thermal management module is prone to leakage during the phase change process, thereby causing degradation of the thermal management performance.

[0013] Furthermore, the phase change material with hydroxyl groups is any one of polyethylene glycol, hexadecanol, tetradecanol and octadecyl alcohol.

[0014] Furthermore, the polyethylene glycol is one or more of polyethylene glycol 1500, polyethylene glycol 2000, and polyethylene glycol 4000, so that the prepared phase change material can maintain the melting point below the safe operating temperature of the battery while obtaining a high enthalpy value.

[0015] Furthermore, the phosphoric acid flame retardant is any one of ammonium polyphosphate, aluminum hypophosphite, monoalkyl phosphinate or aluminum diethylphosphinate.

[0016] Furthermore, the mass ratio of melamine to phase change material 1 is (0.2-0.45):1, such as 0.2:1, 0.25:1, 0.3:1, 0.35:1, 0.4:1, and 0.45:1. If the mass ratio of melamine to phase change material 1 is too low, it will affect the grafting amount, and thus the physical form of the material cannot meet the requirements, for example, the material is too soft after the phase change and the flame retardant performance is insufficient. If the mass ratio is too high, the material will be too hard. Within this mass ratio range, the material can be reshaped by external force and will not collapse (the phase change enthalpy is too low). Preferably, the mass ratio of melamine to phase change material 1 is (0.25-0.4):1, and more preferably 0.28:1.

[0017] Furthermore, the molar ratio of the boric acid to the phase change material with hydroxyl groups is 1:(2.8-3.2), and the molar ratio of the phosphorus pentoxide to the phase change material with hydroxyl groups is 1:(1.8-2.2); maintaining the addition amount of boric acid and phosphorus pentoxide within an appropriate range can avoid the enthalpy value of the solid-solid phase change material being too low, and at the same time help the solid-solid phase change material after melamine grafting to meet the application state requirements.

[0018] Furthermore, in the step 2, melamine is added uniformly to avoid excessive local reaction. When the mixture of melamine and phase change material 1 is mixed, the addition speed of melamine is controlled to avoid excessive reaction between melamine and phase change material 1, which leads to uneven mixing and destruction of the continuity of the phase change material.

[0019] The present invention also provides a solid-solid phase change material prepared by the preparation method of the phase change material.

[0020] A second aspect of the present invention provides a battery module, which includes a battery module and a phase change material skeleton made based on the solid-solid phase change material.

[0021] Furthermore, the phase change material skeleton is the same size as the battery module in height.

[0022] The present invention also provides application of the battery module in energy storage equipment and electric vehicles.

[0023] In summary, compared with the prior art, the present invention achieves the following technical effects:

[0024] (1) The solid-solid phase change material provided by the present invention has high anti-leakage performance;

[0025] (2) The solid-solid phase change material provided by the present invention has high flame retardant properties;

[0026] (3) The solid-solid phase change material provided by the present invention is remodelable;

[0027] (4) The phase change material skeleton made of the solid-solid phase change material provided by the present invention can load batteries and form an integrated battery thermal management system, greatly improving structural stability, resistance to external impact, and improving thermal conductivity;

[0028] (5) The battery module provided by the present invention achieves temperature consistency of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 An image of leakage phenomenon of an intrinsic flame-retardant and reshapeable solid-solid phase change material provided in Example 1 of the present invention when continuously heated at 250° C.;

[0030] Figure 2 The test results of a vertical combustion test of an intrinsic flame retardant and remodelable solid-solid phase change material provided in Example 1 of the present invention;

[0031] Figure 3 It is a cone calorimetry test result diagram of the solid-solid phase change materials of Examples 1, 4-6;

[0032] Figure 4 This is a graph showing the thermal management test results of the solid-solid phase change material battery module of Example 1;

[0033] Figure 5 This is a graph showing the thermal management test results of the solid-solid phase change material battery module of Example 6;

[0034] Figure 6 A schematic diagram of the structure of a battery module provided in Example 7 of the present invention;

[0035] Figure 7 A partial exploded view of a battery module provided in Example 7 of the present invention;

[0036] Figure 8 A schematic diagram of the top view of the structure of the phase change material skeleton and the battery in a battery module provided in Example 7 of the present invention. DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only embodiments of a part of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0038] Example

[0039] The present invention is further described below in conjunction with specific examples and comparative examples. The following specific examples are all preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the following examples, and are particularly not limited to the types of the various component raw materials used in the following specific examples.

[0040] 1. Sources of Raw Materials in Examples and Comparative Examples

[0041] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present invention are commercially available.

[0042] 2. Various performance test methods

[0043] (1) Anti-leakage test: The obtained solid-solid phase change material samples were subjected to an anti-leakage test. The test method was as follows: the phase change material was placed on a constant temperature heating table at a temperature of 250°C, and the appearance and mass changes of the phase change material before and after continuous heating for 5 hours were observed and recorded. The mass retention rate was calculated using the following formula: 1-[(m 1 -m 2 ) / m 1 ], where m 1 represents the initial mass of the phase change material, m 2 It indicates the mass of the phase change material after continuous heating for 5 hours. The thermal stability of the phase change material is characterized by the mass change of the phase change material in the anti-leakage test.

[0044] (2) Flame retardant performance test: Tested according to UL-94-2016 standard:

[0045] A vertical combustion test was performed on the prepared solid-solid phase change material sample (h=0.3mm, d=10mm, l=100mm). The test method is: the phase change material sample was ignited twice. After the first ignition test, it was extinguished within 10s, and after the second ignition, it was extinguished within 30s, and there was no burning drop, which is the highest rating V-0.

[0046] (3) Thermal management performance test: 25 26650 cylindrical batteries are connected in series and in parallel to form a 5×5 battery module (a thermocouple is fixed in the middle of the surface of each battery). The assembled battery module is placed in a constant temperature box and the temperature is set to 25°C. The real-time temperature data of the charging and discharging process at different magnifications is transmitted to the temperature collector through the thermocouple through the battery testing system.

[0047] (4) Cone calorimetry test: According to ISO 5660:2015, the combustion behavior of CPCM was studied using an FTT CONE calorimeter. The dimensions of the CPCM were 100 mm × 100 mm × 3.2 mm, and the thermal radiation power density was 35 KW / m 2 .

[0048] Example 1

[0049] Step 1: Pour 100 g of polyethylene glycol 2000 into a magnetic stirring oil bath at a temperature of 70° C. and heat to melt. When the polyethylene glycol is completely melted, add boric acid (in a molar ratio of 1:3 to polyethylene glycol) and set the temperature of the magnetic stirring oil bath to 160° C., and continue stirring for 6 hours. After the reaction is complete, add phosphorus pentoxide (in a molar ratio of 1:2 to polyethylene glycol) under stirring at 600 r / min, and continue stirring for 2 hours to finally obtain polyethylene glycol boric acid phosphate;

[0050] Step 2: Add 70g of the polyethylene glycol boric acid phosphate obtained in step 1 into an oil bath at 70°C, then add 2g of expanded graphite and 8g of ammonium polyphosphate and stir at 800r / min for 1h to mix evenly, add 20g of melamine to the polyethylene glycol boric acid phosphate mixture at the same stirring speed and mix evenly;

[0051] Step 3: Pour the mixture obtained in step 2 into a mold and solidify it at room temperature to obtain an intrinsic flame retardant and reshapeable solid-solid phase change material.

[0052] The obtained solid-solid phase change material was subjected to an anti-leakage test to verify whether melamine was successfully grafted onto the polyethylene glycol phosphate, that is, whether the phase change morphology was successfully transformed from solid-liquid phase change to solid-solid phase change. Figure 1 , it can be seen that the phase change material sample has almost no leakage at high temperature, and the quality retention rate is still above 97% after continuous heating for 5 hours, which indicates that the anti-leakage performance of the phase change material has been greatly improved;

[0053] Test the flame retardancy of the material, such as Figure 2 It can be seen that in the vertical combustion test, the phase change material sample goes out after 1s after the first ignition and goes out after 3s after the second ignition, meeting the UL-94 test V-0 standard, which shows that the flame retardant performance of the phase change material has been greatly improved;

[0054] Cone calorimetry tests are performed on materials such as Figure 3 The HRR and THR of the phase change material in Example 1 are 252.76 kW / m 2 and 109.79MJ / m 2 The lower values ​​indicate that the material has good flame retardant properties and high thermal safety. The SPR and TSP are 0.021m 2 / s and 7.98m 2 This indicates that phase change materials produce less smoke when burned and have strong smoke suppression capabilities.

[0055] Example 2

[0056] Step 1: Pour 100 g of polyethylene glycol 4000 into a magnetic stirring oil bath at a temperature of 80° C. and heat to melt. When the polyethylene glycol is completely melted, add boric acid (in a molar ratio of 1:3 to polyethylene glycol) and set the temperature of the magnetic stirring oil bath to 140° C., and continue stirring for 8 hours. After the reaction is complete, add phosphorus pentoxide (in a molar ratio of 1:2 to polyethylene glycol) under stirring at 400 r / min, and continue stirring for 3 hours to finally obtain polyethylene glycol boric acid phosphate;

[0057] Step 2: Add 70g of the polyethylene glycol boric acid phosphate obtained in step 1 into a 60°C oil bath, then add 2g of expanded graphite and 8g of aluminum hypophosphite and stir at 700r / min for 2h to mix evenly, add 20g of melamine to the polyethylene glycol boric acid phosphate mixture at the same stirring speed and mix evenly;

[0058] Step 3: Pour the mixture obtained in step 2 into a mold and solidify it at room temperature to obtain an intrinsic flame retardant and reshapeable solid-solid phase change material.

[0059] Example 3

[0060] Step 1: Pour 100 g of polyethylene glycol 1500 into a magnetic stirring oil bath at a temperature of 70° C. and heat to melt. When the polyethylene glycol is completely melted, add boric acid (in a molar ratio of 1:3 to polyethylene glycol) and set the temperature of the magnetic stirring oil bath to 170° C., and continue stirring for 5 hours. After the reaction is complete, add phosphorus pentoxide (in a molar ratio of 1:2 to polyethylene glycol) under stirring at 800 r / min, and continue stirring for 2 hours to finally obtain polyethylene glycol boric acid phosphate;

[0061] Step 2: Add 70g of the polyethylene glycol boric acid phosphate obtained in step 1 into an oil bath at 80°C, then add 2g of expanded graphite and 8g of ammonium polyphosphate and stir at 900r / min for 1h to mix evenly, add 20g of melamine to the polyethylene glycol boric acid phosphate mixture at the same stirring speed and mix evenly;

[0062] Step 3: Pour the mixture obtained in step 2 into a mold and solidify it at room temperature to obtain an intrinsic flame retardant and reshapeable solid-solid phase change material.

[0063] Example 4

[0064] Step 1: Pour 100 g of polyethylene glycol 2000 into a magnetic stirring oil bath at a temperature of 70° C. and heat to melt. When the polyethylene glycol is completely melted, add boric acid (in a molar ratio of 1:3 to polyethylene glycol) and set the temperature of the magnetic stirring oil bath to 160° C., and continue stirring for 6 hours. After the reaction is complete, add phosphorus pentoxide (in a molar ratio of 1:2 to polyethylene glycol) under stirring at 600 r / min, and continue stirring for 2 hours to finally obtain polyethylene glycol boric acid phosphate;

[0065] Step 2: Add 73g of the polyethylene glycol boric acid phosphate obtained in step 1 into an oil bath at 70°C, then add 2g of expanded graphite and 8g of ammonium polyphosphate and stir at 800r / min for 1h to mix evenly, add 17g of melamine to the polyethylene glycol boric acid phosphate mixture at the same stirring speed and mix evenly;

[0066] Step 3: Pour the mixture obtained in step 2 into a mold and solidify it at room temperature to obtain an intrinsic flame retardant and reshapeable solid-solid phase change material.

[0067] Example 5

[0068] Step 1: Pour 100 g of polyethylene glycol 2000 into a magnetic stirring oil bath at a temperature of 70° C. and heat to melt. When the polyethylene glycol is completely melted, add boric acid (in a molar ratio of 1:3 to polyethylene glycol) and set the temperature of the magnetic stirring oil bath to 160° C., and continue stirring for 6 hours. After the reaction is complete, add phosphorus pentoxide (in a molar ratio of 1:2 to polyethylene glycol) under stirring at 600 r / min, and continue stirring for 2 hours to finally obtain polyethylene glycol boric acid phosphate;

[0069] Step 2: Add 65g of the polyethylene glycol boric acid phosphate obtained in step 1 into a 70°C oil bath, then add 2g of expanded graphite and 8g of ammonium polyphosphate and stir at 800r / min for 1h to mix evenly, add 25g of melamine to the polyethylene glycol boric acid phosphate mixture at the same stirring speed and mix evenly;

[0070] Step 3: Pour the mixture obtained in step 2 into a mold and solidify it at room temperature to obtain an intrinsic flame retardant and reshapeable solid-solid phase change material.

[0071] Example 6

[0072] Step 1: Pour 100 g of polyethylene glycol 2000 into a magnetic stirring oil bath at a temperature of 70° C. and heat to melt. When the polyethylene glycol is completely melted, add boric acid (in a molar ratio of 1:3 to polyethylene glycol) and set the temperature of the magnetic stirring oil bath to 160° C., and continue stirring for 6 hours. After the reaction is complete, add phosphorus pentoxide (in a molar ratio of 1:2 to polyethylene glycol) under stirring at 600 r / min, and continue stirring for 2 hours to finally obtain polyethylene glycol boric acid phosphate;

[0073] Step 2: Add 70g of the polyethylene glycol boric acid phosphate obtained in step 1 into an oil bath at 70°C, then add 2g of expanded graphite and stir at 800r / min for 1h to mix evenly, and add 28g of melamine to the polyethylene glycol boric acid phosphate mixture at the same stirring speed and mix evenly;

[0074] Step 3: Pour the mixture obtained in step 2 into a mold and solidify it at room temperature to obtain an intrinsic flame retardant and reshapeable solid-solid phase change material.

[0075] Example 7

[0076] Embodiment 9 provides a battery module, the battery module comprising a phase change material skeleton and a battery module, referring to Figure 3-5 .

[0077] The battery module of this embodiment uses the intrinsic flame retardant and remodelable solid-solid phase change material prepared in the above-mentioned embodiment 1, which includes a phase change material skeleton 1, a battery module 2 and a welding sheet 3, wherein the phase change material skeleton 1 is made of an intrinsic flame retardant and remodelable solid-solid phase change material, the phase change material skeleton 1 is the same in size as the battery module 2 in height, and the thickness is 3mm, and the welding sheet 3 is a nickel sheet. When loading the battery module 2, the phase change material skeleton 1 is first tightly fitted with the battery module 2, and then the two are fixed, and finally the battery module 2 is welded by the welding sheet 3 in a series-parallel manner;

[0078] Conduct thermal management tests on battery modules, such as Figure 4 , the maximum temperature at 2C discharge rate is significantly lower, the maximum temperature is controlled at 60℃, and through the temperature difference curve ( Figure 4 (Ⅱ) Figure 5 (II) It was found that the temperature difference of the solid-solid phase change material battery module of Example 1 was smaller than the temperature difference of the solid-solid phase change material battery module of Example 6, indicating that the solid-solid phase change material of Example 1 has better temperature uniformity.

[0079] Comparative Example 1

[0080] Step 1: Pour 100 g of polyethylene glycol 2000 into a magnetic stirring oil bath at a temperature of 70° C. and heat to melt. When the polyethylene glycol is completely melted, add boric acid (in a molar ratio of 1:3 to polyethylene glycol) and set the temperature of the magnetic stirring oil bath to 160° C., and continue stirring for 6 hours. After the reaction is complete, add phosphorus pentoxide (in a molar ratio of 1:2 to polyethylene glycol) under stirring at 600 r / min, and continue stirring for 2 hours to finally obtain polyethylene glycol boric acid phosphate;

[0081] Step 2: Add 70 g of the polyethylene glycol boric acid phosphate obtained in step 1 into an oil bath at 70° C., then add 2 g of expanded graphite and 8 g of ammonium polyphosphate and stir at a speed of 800 r / min for 1 h to obtain a mixture;

[0082] Step 3: Pour the mixture obtained in step 2 into a mold and solidify it at room temperature to obtain a phase change material.

[0083] Comparative Example 2

[0084] Step 1: Pour 100 g of polyethylene glycol 2000 into a magnetic stirring oil bath at a temperature of 70° C. and heat to melt. When the polyethylene glycol is completely melted, add phosphorus pentoxide (in a molar ratio of 1:2 to polyethylene glycol) under stirring at 600 r / min, and continue stirring for 2 hours. After the reaction is complete, add boric acid (in a molar ratio of 1:3 to polyethylene glycol) and set the temperature of the magnetic stirring oil bath to 160° C., and continue stirring for 6 hours to obtain a mixture 1;

[0085] Step 2: Add 70 g of the mixture 1 obtained in step 1 into a 70° C. oil bath, then add expanded graphite and ammonium polyphosphate and stir at a speed of 800 r / min for 1 h to mix evenly, and add melamine to the mixture 1 at the same stirring speed to mix evenly;

[0086] Step 3: Pour the mixture obtained in step 2 into a mold and solidify it at room temperature to obtain an intrinsic flame retardant and reshapeable solid-solid phase change material.

[0087] Comparative Example 3

[0088] Step 1: Pour 100 g of polyethylene glycol 2000 into a magnetic stirring oil bath at a temperature of 70° C. and heat to melt. When the polyethylene glycol is completely melted, add boric acid (in a molar ratio of 1:3 to polyethylene glycol) and set the temperature of the magnetic stirring oil bath to 160° C., and continue stirring for 6 hours. After the reaction is complete, add phosphorus pentoxide (in a molar ratio of 1:2 to polyethylene glycol) under stirring at 600 r / min, and continue stirring for 2 hours to finally obtain polyethylene glycol boric acid phosphate;

[0089] Step 2: Add 70g of the polyethylene glycol boric acid phosphate obtained in step 1 into a 70°C oil bath, then add 2g of expanded graphite and stir at 800r / min for 1h to mix evenly, add 20g of melamine to the polyethylene glycol boric acid phosphate mixture at the same stirring speed and mix evenly;

[0090] Step 3: Pour the mixture obtained in step 2 into a mold and solidify it at room temperature to obtain an intrinsic flame retardant and reshapeable solid-solid phase change material.

[0091] Table 1 Technical solutions and effects of the embodiments

[0092]

[0093]

[0094] In Examples 1-6, phase change materials with hydroxyl groups, boric acid, phosphorus pentoxide, expanded graphite, phosphoric acid flame retardant and melamine are introduced, and all solid-solid phase change materials prepared in Examples 1-6 can achieve high anti-leakage performance and flame retardant performance, realizing the stable application of phase change materials in battery thermal management systems; Comparative Examples 1-3 are compared with Example 1. In Comparative Example 1, melamine is not added, and the shape stability of the solid-solid phase change material is significantly deteriorated. During the flame retardant test, the material will continue to drip and cannot be rated; in Comparative Example 2, the order of adding boric acid and phosphorus pentoxide is interchanged, and the anti-leakage performance and flame retardant performance of the obtained phase change material are significantly reduced. In Comparative Example 3, no phosphoric acid flame retardant is added, so that the flame retardant performance after grafting is only V-1. The above comparative examples cannot take into account both the flame retardant and anti-leakage performance of the materials.

[0095] Based on the data of 250°C / 5h mass retention rate, vertical combustion, cone calorimetry test and thermal management test in Table 1, the solid-solid phase change materials prepared by Examples 1-6 have obvious advantages over the comparative examples and can effectively meet the high standards of customers and the market.

[0096] 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 principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing an intrinsic flame retardant solid-solid phase change material, It is characterized in that The raw materials include a phase change material with hydroxyl groups, boric acid, phosphorus pentoxide, expanded graphite, a phosphoric acid flame retardant and melamine. The preparation method includes the following steps: Step 1: heating and melting the phase change material with hydroxyl group, adding boric acid after it is completely melted and setting the temperature to 140-170° C., stirring continuously for 5-8 hours, adding phosphorus pentoxide under continuous stirring after the reaction is complete, and continuing the reaction for 2-3 hours, finally obtaining a phase change material 1 with a boric acid phosphate structure; Step 2: Heat and melt the above synthesized material, then add expanded graphite and phosphoric acid flame retardant and continue stirring for 1-2 hours, add melamine after the mixture is stirred evenly, and continue stirring until the reaction is complete to generate phase change material 2 grafted with melamine; Step 3: Pour the above-mentioned phase change material 2 grafted with melamine into a mold, and solidify and shape it at room temperature to obtain an intrinsic flame retardant solid-solid phase change material.

2. The method for preparing the phase change material according to claim 1, It is characterized in that The phase change material with hydroxyl group is any one of polyethylene glycol, hexadecanol, tetradecanol and octadecyl alcohol.

3. The method for preparing the phase change material according to claim 1, It is characterized in that The mass ratio of the melamine to the phase change material 1 is (0.2-0.45):

1.

4. The method for preparing the phase change material according to claim 2, It is characterized in that The polyethylene glycol is one or more of polyethylene glycol 1500, polyethylene glycol 2000 and polyethylene glycol 4000.

5. The method for preparing the phase change material according to claim 1, It is characterized in that The phosphoric acid flame retardant is any one of ammonium polyphosphate, aluminum hypophosphite, monoalkyl phosphinate or aluminum diethylphosphinate.

6. The method for preparing the phase change material according to claim 1, It is characterized in that In the step 2, melamine is added uniformly.

7. A solid-solid phase change material obtained by the method for preparing the phase change material according to any one of claims 1 to 6.

8. A battery module, It is characterized in that The battery module comprises a battery module and a phase change material skeleton made of the solid-solid phase change material according to claim 7.

9. The battery module according to claim 8, It is characterized in that The phase change material skeleton is the same size as the battery module in height.

10. Application of the battery module according to any one of claims 8 to 9 in energy storage equipment and electric vehicles.

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