Hydrated salt composite phase change material, preparation method and application thereof

Abstract

The application relates to the technical field of battery thermal safety, in particular to a hydrated salt composite phase change material and a preparation method and application thereof. The application provides a hydrated salt composite phase change material, and preparation raw materials include a hydrated salt phase change matrix, a thickening agent, a coordination polymer skeleton and expanded graphite; the coordination polymer skeleton is prepared by carrying out a coordination reaction on a soluble magnesium salt and polyethylene glycol. The hydrated salt composite phase change material can effectively solve the problems of inherent supercooling, phase separation, leakage and low thermal conductivity of inorganic hydrated salt materials.

Description

Technical Field

[0001] This invention relates to the field of battery thermal safety technology, and in particular to a hydrated salt composite phase change material, its preparation method, and its application. Background Technology

[0002] As the energy density requirements of lithium-ion batteries for electric vehicles and energy storage systems continue to increase, the problem of thermal runaway under high-temperature and high-rate conditions is becoming increasingly prominent, posing a severe challenge to system safety. Inorganic hydrated salt materials, with their high latent heat and wide-temperature-range heat absorption, are considered potential materials for battery thermal management. However, these materials still face significant bottlenecks in practical applications: on the one hand, they suffer from severe overcooling, phase separation, and loss of crystal water, leading to rapid degradation of thermal performance during cycling; on the other hand, their inherent low thermal conductivity and easy leakage in liquid form also limit thermal response speed and service life. Although current research has attempted to improve these materials through porous framework encapsulation or the addition of nucleating agents, single-scale control strategies often struggle to synergistically optimize multiple objectives such as overcooling suppression, leakage prevention, and enhanced thermal conductivity, and the encapsulation structure may become unstable at high temperatures. Therefore, developing a hydrated salt composite phase change material that can simultaneously address overcooling and leakage issues while also possessing long-term cycling stability has become an urgent research direction for improving the effectiveness of battery thermal safety management. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a hydrated salt composite phase change material, its preparation method and application, wherein the hydrated salt composite phase change material can effectively solve the inherent problems of supercooling, phase separation, leakage and low thermal conductivity of inorganic hydrated salt materials.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a hydrated salt composite phase change material, the raw materials for which include a hydrated salt phase change matrix, a thickener, a coordination polymer framework, and expanded graphite; The coordination polymer backbone is prepared by coordination reaction of soluble magnesium salt and polyethylene glycol.

[0005] Preferably, the hydrated salt phase change matrix comprises sodium thiosulfate pentahydrate and calcium sulfate dihydrate; The mass ratio of sodium thiosulfate pentahydrate to calcium sulfate dihydrate is (9.3~9.5):(0.5~0.7).

[0006] Preferably, the thickener includes one or more of sodium polyacrylate, sodium carboxymethyl cellulose, and borax; The mass ratio of the hydrated salt phase change matrix to the thickener is (75~90):(1~3).

[0007] Preferably, the mass ratio of the soluble magnesium salt to polyethylene glycol is (0.3125~7.5):(2.5~10); The total mass ratio of the hydrated salt phase change matrix and the thickener to the mass ratio of the coordination polymer backbone is (75~90):(5~20).

[0008] Preferably, the total mass ratio of the hydrated salt phase change matrix and the thickener to the mass ratio of the expanded graphite is (75~90):(4~6).

[0009] This invention also provides a method for preparing the hydrated salt composite phase change material described in the above technical solution, comprising the following steps: The hydrated salt phase change matrix is ​​mixed with a thickener to obtain a thickened and dispersed hydrated salt phase change material. The coordination polymer backbone is mixed with the thickening and dispersing hydrated salt phase change material, and then encapsulated to obtain a hydrated salt composite phase change material. The hydrated salt composite phase change material is mixed with expanded graphite and then solidified to obtain the hydrated salt composite phase change material.

[0010] Preferably, the temperature of the first mixing is 60~80℃ and the time is 0.3~0.6h.

[0011] Preferably, both the second mixing and encapsulation are carried out under stirring conditions; The temperature of the second mixing is 60~80℃, and the temperature of the encapsulation is 60~80℃; The second mixing and encapsulation processes are carried out at independent speeds of 400-600 rpm for 0.3-0.6 h.

[0012] Preferably, the third mixing is carried out under stirring conditions; The stirring speed is 400~600 rpm, and the time is 0.3~0.6 h.

[0013] The present invention also provides the application of the hydrated salt composite phase change material described in the above technical solution or the hydrated salt composite phase change material prepared by the preparation method described in the above technical solution in a battery thermal safety system.

[0014] This invention provides a hydrated salt composite phase change material, comprising a hydrated salt phase change matrix, a thickener, a coordination polymer framework, and expanded graphite. The coordination polymer framework is prepared by a coordination reaction between a soluble magnesium salt and polyethylene glycol. In the hydrated salt composite phase change material of this invention, the coordination polymer framework is a stable framework formed by strong coordination bonds between ether oxygen atoms on the soluble magnesium salt and polyethylene glycol segments. This framework, through physical entanglement, firmly binds the hydrated salt components within its grid structure at the molecular level, effectively preventing macroscopic flow and structural support of the molten salt during the phase change process. This significantly alleviates the material's structural degradation and performance decline caused by phase separation, component migration, or loss of crystal water during long-term cycling, and is key to ensuring the long-term cycling stability of the composite material. Expanded graphite, with its loose, porous, layered, open worm-like structure, physically fixes the molten hydrated salt through strong capillary adsorption, preventing localized leakage. Meanwhile, its inherent high thermal conductivity graphite sheets overlap each other inside the composite material, forming an efficient continuous three-dimensional thermal conduction path, which greatly improves the overall thermal conductivity and thermal response speed of the material. Attached Figure Description

[0015] Figure 1 The results of the anti-leakage test of the hydrated salt composite phase change material described in Comparative Example 2 are shown. Figure 2 The results of the leak resistance test of the hydrated salt composite phase change material described in Example 1; Figure 3 The undercooling test curves of the hydrated salt composite phase change materials described in Example 1 and Comparative Example 1 are shown. Figure 4 Images showing the cyclic stability test results of the hydrated salt composite phase change materials described in Example 1 and Comparative Example 1; Figure 5 The image shows a vertical combustion test image of the hydrated salt composite phase change material described in Comparative Example 2. Figure 6 The image shows a vertical combustion test image of the hydrated salt composite phase change material described in Example 1. Figure 7 The images show actual battery modules and thermal management effects of the phase change materials described in Example 1 and Comparative Examples 1 and 3. Detailed Implementation

[0016] This invention provides a hydrated salt composite phase change material, the raw materials for which include a hydrated salt phase change matrix, a thickener, a coordination polymer framework, and expanded graphite; The coordination polymer backbone is prepared by coordination reaction of soluble magnesium salt and polyethylene glycol.

[0017] In this invention, unless otherwise specified, all raw materials used in the preparation are commercially available products well known to those skilled in the art.

[0018] In this invention, the hydrated salt phase change matrix preferably comprises sodium thiosulfate pentahydrate and calcium sulfate dihydrate, and the mass ratio of sodium thiosulfate pentahydrate to calcium sulfate dihydrate is preferably (9.3~9.5):(0.5~0.7), more preferably 9.3:0.5, 9.3:0.6, 9.3:0.7, 9.4:0.5, 9.4:0.6, 9.4:0.7, 9.5:0.5, 9.5:0.6, or 9.5:0.7. In an embodiment of this invention, the mass ratio of sodium thiosulfate pentahydrate to calcium sulfate dihydrate is 9.4:0.6.

[0019] In this invention, the method for preparing the hydrated salt phase change matrix preferably includes the following steps: Sodium thiosulfate pentahydrate and calcium sulfate dihydrate are melt-mixed to obtain the hydrated salt phase change matrix.

[0020] In this invention, the melting and mixing temperature is preferably 60~80℃, more preferably 60℃, 65℃, 70℃, 75℃ or 80℃; the time is preferably 0.3~0.6h, more preferably 0.3h, 0.4h, 0.5h or 0.6h. In an embodiment of this invention, the melting and mixing temperature can be 70℃ and the time can be 0.5h. In this invention, the melting and mixing is preferably carried out under stirring conditions. This invention does not impose any special limitations on the stirring process; any process well known to those skilled in the art can be used.

[0021] In this invention, the thickener preferably includes one or more of sodium polyacrylate, sodium carboxymethyl cellulose, and borax, more preferably sodium polyacrylate; when the thickener is two or more of the above-mentioned specific selections, this invention does not have any special limitation on the ratio of the above-mentioned specific substances, and they can be mixed in any ratio. In the embodiments of this invention, the thickener can be sodium polyacrylate.

[0022] In this invention, the thickener is preferably a thickener solution, and the mass concentration of the thickener solution is preferably 20% to 40%, more preferably 20%, 30%, or 40%. In an embodiment of this invention, the mass concentration of the thickener solution can be 30%.

[0023] In this invention, the preferred mass ratio of the hydrated salt phase change matrix to the thickener is (75~90):(1~3), more preferably 75:1, 75:2, 75:3, 80:1, 80:2, 80:3, 85:1, 85:2, 85:3, 90:1, 90:2, or 90:3. In an embodiment of this invention, the mass ratio of the hydrated salt phase change matrix to the thickener can be 83:1.7. In this invention, the mass ratio of the hydrated salt phase change matrix to the thickener is understood as the mass ratio of the hydrated salt phase change matrix to the thickener solution.

[0024] In this invention, the coordination polymer backbone is prepared by a coordination reaction between a soluble magnesium salt and polyethylene glycol.

[0025] In this invention, the preferred mass ratio of the soluble magnesium salt to polyethylene glycol is (0.3125~7.5):(2.5~10), more preferably (2~6):(3~8), and most preferably (3~5):(4~6). In an embodiment of this invention, the mass ratio of the soluble magnesium salt to polyethylene glycol can be 1:1.

[0026] In this invention, the soluble magnesium salt preferably includes anhydrous magnesium chloride and / or magnesium chloride hexahydrate, more preferably anhydrous magnesium chloride; when the soluble magnesium salt is two or more of the above-mentioned specific selections, this invention does not impose any special limitation on the ratio of the above-mentioned specific substances, and they can be mixed in any ratio. In the embodiments of this invention, the soluble magnesium salt can be anhydrous magnesium chloride.

[0027] In this invention, the method for preparing the coordination polymer backbone preferably includes the following steps: A soluble magnesium salt suspension and polyethylene glycol were mixed and subjected to a coordination reaction to obtain the coordination polymer backbone.

[0028] In this invention, the soluble magnesium salt suspension preferably comprises soluble magnesium salt and anhydrous ethanol; the mass ratio of the soluble magnesium salt to anhydrous ethanol is preferably (0.5~1.5):(1.5~2.5), more preferably 0.5:1.5, 0.5:2, 0.5:2.5, 1:1.5, 1:2, 1:2.5, 1.5:1.5, 1.5:2, or 1.5:2.5. In an embodiment of this invention, the mass ratio of the soluble magnesium salt to anhydrous ethanol can be 1:2.

[0029] In this invention, the method for preparing the soluble magnesium salt suspension preferably includes the following steps: The soluble magnesium salt and anhydrous ethanol are mixed to obtain the soluble magnesium salt suspension.

[0030] In this invention, the mixing is preferably carried out under stirring conditions, and the stirring speed is preferably 400~600 rpm, more preferably 400 rpm, 450 rpm, 500 rpm, 550 rpm or 600 rpm; the stirring time is preferably 0.3~0.6 h, more preferably 0.3 h, 0.4 h, 0.5 h or 0.6 h. In an embodiment of this invention, the stirring speed can be 500 rpm and the stirring time can be 0.5 h.

[0031] In this invention, the polyethylene glycol is preferably molten polyethylene glycol.

[0032] In this invention, the preferred mass ratio of the soluble magnesium salt suspension to polyethylene glycol is (2.5~10):(2.5~10), more preferably 2.5:2.5, 2.5:5, 2.5:7.5, 2.5:10, 5:2.5, 5:7.5, 7.5:2.5, 7.5:5, 7.5:10, 10:2.5, or 10:7.5. In an embodiment of this invention, the mass ratio of the soluble magnesium salt suspension to polyethylene glycol can be 5:5.

[0033] In this invention, the coordination reaction is preferably carried out under stirring conditions, wherein the stirring speed is preferably 900~1100 rpm, more preferably 900 rpm, 950 rpm, 1000 rpm, 1050 rpm, or 1100 rpm; and the stirring time is preferably 0.5~1.5 h, more preferably 0.5 h, 1 h, or 1.5 h. In an embodiment of this invention, the temperature of the coordination reaction can be 1000 rpm, and the time can be 1 h.

[0034] In this invention, the mass ratio of the total mass of the hydrated salt phase change matrix and the thickener to the mass of the coordination polymer backbone is preferably (75~90):(5~20), more preferably 75:5, 75:10, 75:15, 75:20, 80:5, 80:10, 80:15, 80:20, 85:5, 85:10, 85:15, 85:20, 90:5, 90:10, 90:15, or 90:20. In an embodiment of this invention, the mass ratio of the total mass of the hydrated salt phase change matrix and the thickener to the mass of the coordination polymer backbone can be 85:10.

[0035] In this invention, the preferred mass ratio of the hydrated salt phase change matrix and thickener to the expanded graphite is (75~90):(4~6), more preferably 75:4, 75:5, 75:6, 80:4, 80:5, 80:6, 85:4, 85:5, 85:6, 90:4, 90:5, or 90:6. In an embodiment of this invention, the mass ratio of the hydrated salt phase change matrix and thickener to the expanded graphite can be 85:5.

[0036] This invention also provides a method for preparing the hydrated salt composite phase change material described in the above technical solution, comprising the following steps: The hydrated salt phase change matrix is ​​mixed with a thickener to obtain a thickened and dispersed hydrated salt phase change material. The coordination polymer backbone is mixed with the thickening and dispersing hydrated salt phase change material, and then encapsulated to obtain a hydrated salt composite phase change material. The hydrated salt composite phase change material is mixed with expanded graphite and then solidified to obtain the hydrated salt composite phase change material.

[0037] The present invention mixes a hydrated salt phase change matrix with a thickener to obtain a thickened and dispersed hydrated salt phase change substance.

[0038] In this invention, the temperature of the first mixing is preferably 60~80℃, more preferably 60℃, 65℃, 70℃, 75℃ or 80℃; the time is preferably 0.3~0.6h, more preferably 0.3h, 0.4h, 0.5h or 0.6h. In an embodiment of this invention, the temperature of the first mixing can be 70℃ and the time can be 0.5h.

[0039] In this invention, the first mixing process is preferably carried out by adding a thickener to a molten hydrated salt phase change matrix under magnetic stirring. This invention does not impose any special limitations on the process of adding the thickener; any process well-known to those skilled in the art can be used.

[0040] After obtaining the thickened and dispersed hydrated salt phase change material, the present invention mixes the coordination polymer skeleton with the thickened and dispersed hydrated salt phase change material in the second stage, and encapsulates it to obtain the hydrated salt composite phase change material.

[0041] In this invention, both the second mixing and encapsulation are preferably carried out under stirring conditions; the temperature of the second mixing is preferably 60~80℃, more preferably 60℃, 65℃, 70℃, 75℃ or 80℃; the temperature of the encapsulation is preferably 60~80℃, more preferably 60℃, 65℃, 70℃, 75℃ or 80℃; the rotation speeds of the second mixing and encapsulation are preferably 400~600 rpm, more preferably 400 rpm, 500 rpm or 600 rpm; the time is preferably 0.3~0.6h, more preferably 0.3h, 0.4h, 0.5h or 0.6h.

[0042] After obtaining the hydrated salt composite phase change material, the present invention mixes the hydrated salt composite phase change material with expanded graphite and then solidifies it to obtain the hydrated salt composite phase change material. In this invention, the third mixing is preferably carried out under stirring conditions, the stirring speed is preferably 400~600 rpm, more preferably 400 rpm, 500 rpm or 600 rpm; the time is preferably 0.3~0.6 h, more preferably 0.3 h, 0.4 h, 0.5 h or 0.6 h.

[0043] In this invention, anhydrous sodium thiosulfate / calcium sulfate dihydrate composite system is used as the phase change matrix, and thickener, expanded graphite, and coordination polymer framework are the key functional components. The preparation method involves uniformly mixing molten hydrated salt with sodium polyacrylate solution, then sequentially compounding and mechanically stirring it with a pre-synthesized coordination polymer framework and expanded graphite, followed by casting to successfully construct a composite phase change material with a multi-level synergistic encapsulation structure. In this material, the hydrated salt matrix provides high latent heat of phase change and controllable dehydration endothermic capacity; calcium sulfate dihydrate acts as a nucleating agent to reduce supercooling; sodium polyacrylate enhances moisture locking and system homogeneity, effectively suppressing phase separation; the coordination polymer framework anchors the hydrated salt components through its three-dimensional network, improving leakage resistance; and expanded graphite constructs a continuous three-dimensional thermal conduction pathway, significantly improving the material's thermal response speed. Ultimately, this material achieves a synergistic unity of efficient utilization of latent heat of phase change, significant suppression of supercooling, excellent leakage resistance, and rapid heat conduction, providing a highly reliable heat storage and control solution for battery thermal safety systems.

[0044] The present invention also provides the application of the hydrated salt composite phase change material described in the above technical solution or the hydrated salt composite phase change material prepared by the preparation method described in the above technical solution in a battery thermal safety system.

[0045] In this invention, the hydrated salt composite phase change material is used as a battery thermal safety protection material in battery modules.

[0046] In this invention, the battery module preferably includes a battery module and a composite material skeleton, and the composite material skeleton is preferably the hydrated salt composite phase change material described in the above technical solution or the hydrated salt composite phase change material prepared by the preparation method described in the above technical solution.

[0047] The present invention does not impose any special limitations on the battery module; any module well known to those skilled in the art can be used.

[0048] In this invention, the battery module is preferably used in energy storage devices and electric vehicles.

[0049] 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.

[0050] Example 1 5.0 g of anhydrous magnesium chloride was placed in a beaker, and 10 mL of anhydrous ethanol was added. The mixture was mechanically stirred at 500 rpm at room temperature until a uniform white suspension was formed. Then, 5 g of pre-molten polyethylene glycol was added, and the mixture was transferred to a 70°C oil bath and mechanically stirred at 1000 rpm for 1 h. After the reaction was completed, a white viscous coordination polymer backbone was obtained.

[0051] 78 g of sodium thiosulfate pentahydrate and 5 g of calcium sulfate dihydrate were placed in another container, heated in an oil bath at 70°C and magnetically stirred until completely melted. Then, 1.7 g of sodium polyacrylate aqueous solution (mass concentration of 30%) was slowly added dropwise to the melt and stirred for 0.5 h to obtain a thickened dispersion system. The prepared coordination polymer skeleton was added to the above system and mechanically stirred at 500 rpm for 0.5 h at 70 °C. Then, 5 g of expanded graphite was added to the system and stirred at 500 rpm for 0.5 h until it was evenly dispersed. Finally, it was cooled and shaped to obtain the hydrated salt composite phase change material.

[0052] Comparative Example 1 87.5 g of sodium thiosulfate pentahydrate and 5.5 g of calcium sulfate dihydrate were placed in another container, heated in an oil bath at 70°C and magnetically stirred until completely melted. Then, 1.9 g of sodium polyacrylate aqueous solution was slowly added dropwise to the melt and stirred for 0.5 h to obtain a thickened dispersion system. Add 5g of expanded graphite to the above system, stir at 500 rpm for 0.5 h at 70℃ until uniformly dispersed, and finally cool and solidify to obtain hydrated salt composite phase change material.

[0053] Comparative Example 2 70g of sodium thiosulfate pentahydrate and 30g of sodium acetate trihydrate were placed in a beaker and heated to melt in an oil bath at 75°C. The mixture was continuously stirred for 0.5h under magnetic stirring to form a homogeneous eutectic hydrated salt phase change matrix. A sodium polyacrylate solution with a total proportion of 5mL was slowly added dropwise to the eutectic hydrated salt phase change matrix, and stirring was continued for 0.5h to obtain a thickened dispersion system. Finally, the mixture was cooled and solidified to obtain a hydrated salt composite phase change material.

[0054] Comparative Example 3 51g of paraffin wax was weighed as the phase change matrix and melted in an oil bath at 75°C. Then, 15g of styrene-ethylene-butene-styrene block copolymer was added as a thickener, and the mixture was stirred at 600 rpm for 1 hour to ensure complete cross-linking. Subsequently, 4g of expanded graphite was added as a thermally conductive filler, and the mixture was stirred at 800 rpm for 0.5 hours. Finally, 30g of melamine was added as a flame retardant, and the mixture was stirred at 800 rpm for 0.5 hours until homogeneous. The resulting composite slurry was injected into a mold of the same specifications as in the example, cooled, and solidified to obtain the organic composite phase change material.

[0055] Test case Leakage resistance test: The specific test procedure is as follows: The hydrated salt composite phase change material described in Example 1 and Comparative Example 2 is placed on a constant temperature heating platform at 70°C. The appearance morphology and mass change before and after the leakage resistance test are observed and recorded at regular intervals. The thermal stability of the hydrated salt composite phase change material described in Example 1 and Comparative Example 2 is characterized by the mass change curve during the leakage resistance test. The mass change of the phase change material is shown in the curve. Figure 1 The results of the leak resistance test of the hydrated salt composite phase change material described in Comparative Example 2 are as follows. Figure 2 The leakage resistance test results of the hydrated salt composite phase change material described in Example 1 are obtained from... Figures 1-2 It can be seen that the hydrated salt composite phase change material described in Example 1 showed almost no leakage at high temperatures in the anti-leakage test, that is, the polymer skeleton effectively solved the leakage problem of hydrated salt in the phase change process; Supercooling resistance test: The specific test procedure was as follows: The uncomposite hydrated salt phase change matrix sodium thiosulfate pentahydrate (STP), the hydrated salt composite phase change material described in Example 1 (SCPE2), and Comparative Example 1 (SCE) were placed in a constant temperature and humidity chamber, and a program was set to first heat to 70°C and then cool down to 25°C. The temperature change curve of the material was monitored using thermocouples. The test results are as follows: Figure 3 As shown, by Figure 3 It can be seen that no obvious nucleation phenomenon was detected in sodium thiosulfate pentahydrate, i.e., no obvious phase transition plateau was observed, while Example 1 and Comparative Example 1 showed obvious phase transition plateaus. The supercooling degree of Example 1 was only 0.17℃, while that of Comparative Example 1 was 1.98℃. This indicates that the supercooling phenomenon of the hydrated salt composite phase change material was suppressed to a large extent.

[0056] Cyclic stability test: The specific test procedure was as follows: The hydrated salt composite phase change materials described in Example 1 (SCPE2) and Comparative Example 1 (SCE) were placed in a constant temperature and humidity chamber, and a program was set to first cool down to 25°C, then heat up to 70°C, and then cool down to 25°C, with 80 cycles. The latent heat of the sample was measured every 50 cycles. The test results are as follows: Figure 4 As shown, by Figure 4It can be seen that the latent heat of Comparative Example 1 decreased to 62.79% of its original value, while the latent heat of Example 1 remained at 95.28%. This indicates that the cycling stability of the hydrated salt composite phase change material after polymer framework encapsulation is significantly improved.

[0057] Vertical burning test: The test procedure is in accordance with UL94 standard; Figure 5 The image shows a vertical combustion test image of the hydrated salt composite phase change material described in Comparative Example 2. Figure 6 The image shows a vertical combustion test image of the hydrated salt composite phase change material described in Example 1; [Image showing the image from the test]. Figure 5 It is known that the hydrated salt composite phase change material without a skeleton can extinguish rapidly after continuous combustion, but continuous dripping occurs during combustion; and according to Figure 6 It is known that hydrated salt composite phase change materials exhibit the best flame retardant properties, can quickly self-extinguish after the fire source is removed, and do not melt and drip during the entire combustion process.

[0058] Thermal management effect: Figure 7 To demonstrate the thermal management effect of the phase change materials described in Example 1 and Comparative Examples 1 and 3, by Figure 7 It can be seen that, compared with Comparative Examples 1 and 3, Example 1 maintains the battery operating temperature below the safe operating temperature of 50°C, and its battery module peak temperature is reduced by 2~3°C compared with Comparative Examples 1 and 3.

[0059] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles 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 hydrated salt composite phase change material, characterized in that, The raw materials for preparation include hydrated salt phase change matrix, thickener, coordination polymer framework and expanded graphite; The coordination polymer backbone is prepared by coordination reaction of soluble magnesium salt and polyethylene glycol.

2. The hydrated salt composite phase change material as described in claim 1, characterized in that, The hydrated salt phase change matrix includes sodium thiosulfate pentahydrate and calcium sulfate dihydrate; The mass ratio of sodium thiosulfate pentahydrate to calcium sulfate dihydrate is (9.3~9.5):(0.5~0.7).

3. The hydrated salt composite phase change material as described in claim 2, characterized in that, The thickener includes one or more of sodium polyacrylate, sodium carboxymethyl cellulose, and borax; The mass ratio of the hydrated salt phase change matrix to the thickener is (75~90):(1~3).

4. The hydrated salt composite phase change material as described in claim 1, characterized in that, The mass ratio of the soluble magnesium salt to polyethylene glycol is (0.3125~7.5):(2.5~10). The total mass ratio of the hydrated salt phase change matrix and the thickener to the mass ratio of the coordination polymer backbone is (75~90):(5~20).

5. The hydrated salt composite phase change material as described in claim 1, characterized in that, The total mass ratio of the hydrated salt phase change matrix and the thickener to the mass ratio of the expanded graphite is (75~90):(4~6).

6. A method for preparing the hydrated salt composite phase change material according to any one of claims 1 to 5, characterized in that, Includes the following steps: The hydrated salt phase change matrix is ​​mixed with a thickener to obtain a thickened and dispersed hydrated salt phase change material. The coordination polymer backbone is mixed with the thickening and dispersing hydrated salt phase change material, and then encapsulated to obtain a hydrated salt composite phase change material. The hydrated salt composite phase change material is mixed with expanded graphite and then solidified to obtain the hydrated salt composite phase change material.

7. The preparation method according to claim 6, characterized in that, The temperature of the first mixing is 60~80℃, and the time is 0.3~0.6h.

8. The preparation method according to claim 6, characterized in that, The second mixing and encapsulation are both carried out under stirring conditions; The temperature of the second mixing is 60~80℃, and the temperature of the encapsulation is 60~80℃; The second mixing and encapsulation processes are carried out at independent speeds of 400-600 rpm for 0.3-0.6 h.

9. The method as described in claim 6, characterized in that, The third mixing is carried out under stirring conditions; The stirring speed is 400~600 rpm, and the time is 0.3~0.6 h.

10. The application of the hydrated salt composite phase change material according to any one of claims 1 to 5 or the hydrated salt composite phase change material prepared by the preparation method according to any one of claims 6 to 9 in a battery thermal safety system.

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