Organic-inorganic hydrated salt composite phase change material, and preparation method and application thereof

Abstract

The application relates to the technical field of power batteries, and provides an organic-inorganic hydrated salt composite phase change material and a preparation method and application thereof. The application utilizes coordination of organic ligands and metal ion ligands to form a metal organic coordination polymer, the metal organic coordination polymer has a compact porous network structure, can fix the hydrated salt phase change material in the skeleton pores, prevents leakage of the hydrated salt phase change material, improves shape stability of the material, improves problems of the inorganic hydrated salt phase change material, such as easy deliquescence, large supercooling degree and phase separation, improves cycle stability of the composite phase change material, and meanwhile, the advantages of non-combustibility and large heat storage capacity are retained. The composite phase change material provided by the application can accurately match the best working temperature range of a battery, reduces temperature fluctuation in the charging and discharging process of the battery, and realizes accurate temperature control. Moreover, excellent flame retardant performance and large heat storage density of the composite phase change material can inhibit heat diffusion when the battery is in thermal runaway, greatly reduces the risk of thermal runaway of a module, and significantly improves the safety of the battery module.

Description

Technical Field

[0001] This invention relates to the field of power battery technology, and in particular to an organic-inorganic hydrated salt composite phase change material, its preparation method, and its application. Background Technology

[0002] With the development of new energy technologies such as electric vehicles and energy storage power stations, the thermal safety of battery systems has become increasingly prominent, becoming a key research topic restricting the industry's development. Lithium-ion batteries generate a large amount of heat at high discharge rates, easily triggering complex electrochemical reactions and side reactions within battery components. If this heat accumulates and cannot be dissipated in time, it can trigger thermal runaway, even leading to battery system fires and explosions, seriously threatening social and public safety. In this context, battery thermal safety protection systems not only need excellent thermal management capabilities but also must prevent the occurrence and propagation of thermal runaway, eliminating safety accidents caused by battery overheating at their source and ensuring the safety of personnel and equipment.

[0003] Phase change material (PCM) cooling technology, as an emerging battery thermal management method, utilizes the principle that PCM absorbs / releases a large amount of latent heat during melting / solidification to control battery temperature and ensure safe operation. Inorganic hydrated salt PCMs have advantages such as high energy density per unit volume, low cost, and non-flammability. Their heating process involves three endothermic stages: phase change, water evaporation, and solid decomposition. This multi-stage endothermic mechanism gives them superior heat storage capacity compared to organic PCMs. However, inorganic hydrated salts also have some drawbacks in application, such as poor shape stability, hygroscopicity, high supercooling, easy leakage, poor thermal conductivity, and poor cycle stability. These problems limit their effectiveness in thermal management systems.

[0004] In summary, current phase change materials are insufficient to meet the requirements of battery thermal management systems, and there is an urgent need to provide a new type of phase change material to solve the thermal safety problem of battery systems. Summary of the Invention

[0005] In view of this, the present invention provides an organic-inorganic hydrated salt composite phase change material, its preparation method, and its application. The present invention combines a metal-organic coordination polymer with a hydrated salt phase change material, and the resulting composite phase change material can meet the requirements of a battery thermal management system, thereby effectively solving the thermal safety problem of the battery system.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] An organic-inorganic hydrated salt composite phase change material comprises the following components in parts by weight: 40-80 parts of hydrated salt phase change material, 10-50 parts of metal-organic coordination polymer, 2-10 parts of phase change temperature regulator, and 1-5 parts of thermal conductivity enhancer; wherein the metal-organic coordination polymer is formed by coordination of organic ligands and metal ion ligands; wherein the organic ligand is polyethylene glycol, and the metal ion ligand is a soluble calcium salt.

[0008] Preferably, the hydrated salt phase change material includes one or more of sodium acetate trihydrate, sodium thiosulfate pentahydrate, sodium metasilicate nonahydrate, sodium pyrophosphate decahydrate, and disodium hydrogen phosphate dodecahydrate.

[0009] Preferably, the metal ion ligand is calcium chloride.

[0010] Preferably, the mass ratio of the organic ligand to the metal ion ligand is 5~45:1~5.

[0011] Preferably, the phase change temperature regulator includes one or more of potassium chloride, ammonium chloride, potassium nitrate, glycerol, urea, and glycine; the thermal conductivity enhancer includes one or more of boron nitride, silicon carbide, expanded graphite, and carbon nanotubes.

[0012] This invention also provides a method for preparing the organic-inorganic hydrated salt composite phase change material described above, comprising the following steps:

[0013] The organic-inorganic hydrated salt composite phase change material is obtained by mixing hydrated salt phase change material, temperature regulator, organic ligand, metal ion ligand, solvent and thermal conductivity enhancer; the mixing is carried out in the molten state of hydrated salt phase change material.

[0014] Preferably, the mixing temperature is 60~90℃; the mixing includes: first mixing the hydrated salt phase change material and the phase change temperature regulator to obtain a first mixture; dissolving the metal ion ligand in a solvent to obtain a metal ion ligand solution; second mixing the metal ion ligand solution and molten organic ligand to obtain a second mixture; third mixing the first mixture and the second mixture to obtain a third mixture; and fourth mixing the third mixture and a thermal conductivity enhancer to obtain the organic-inorganic hydrated salt composite phase change material.

[0015] The present invention also provides the application of the organic-inorganic hydrated salt composite phase change material described in the above-described scheme or the organic-inorganic hydrated salt composite phase change material prepared by the preparation method described in the above-described scheme in power batteries.

[0016] Preferably, the organic-inorganic hydrated salt composite phase change material is used in the thermal management system of a power battery.

[0017] The present invention also provides a battery module prepared from the organic-inorganic hydrated salt composite phase change material described in the above scheme or the organic-inorganic hydrated salt composite phase change material prepared by the preparation method described in the above scheme.

[0018] This invention provides an organic-inorganic hydrated salt composite phase change material, comprising the following components in parts by weight: 40-80 parts of hydrated salt phase change material, 10-50 parts of metal-organic coordination polymer, 2-10 parts of phase change temperature regulator, and 1-5 parts of thermal conductivity enhancer; wherein the metal-organic coordination polymer is formed by coordination of organic ligands and metal ion ligands; wherein the organic ligand is polyethylene glycol, and the metal ion ligand is a soluble calcium salt. This invention utilizes the coordination of organic ligands and metal ions to form a metal-organic coordination polymer (MOC). This MOC exhibits excellent thermal stability and a dense, porous network structure, enabling it to fix hydrated salt phase change materials within the framework pores via capillary forces, preventing leakage, improving the material's shape stability, and mitigating the problems of hygroscopicity and phase separation in hydrated salt phase change materials. Furthermore, the MOC provides suitable nucleation sites for hydrated salts, effectively lowering the nucleation energy barrier and allowing the material to form stable crystal nuclei at relatively low supercooling, thereby effectively reducing supercooling. In addition, the interaction between the MOC and the hydrated salt phase change material enables the composite phase change material to maintain excellent performance during multiple thermal cycles, exhibiting superior cycling stability.

[0019] Furthermore, the organic ligands in metal-organic coordination polymers are themselves organic phase change thermal storage materials, which can produce a synergistic effect with hydrated salt phase change materials, significantly improving the latent heat storage capacity of composite phase change materials and enhancing thermal storage performance. At the same time, by adjusting the ratio of organic ligands and metal ion ligands, the phase change temperature and thermal storage performance of composite phase change materials can be precisely adjusted to better meet the needs of different application scenarios.

[0020] Furthermore, the present invention also incorporates a thermal conductivity enhancer, wherein the thermal conductivity enhancer can be expanded graphite, which has a unique porous worm-like structure that can adsorb phase change materials to form highly thermally conductive channels, thereby improving the thermal conductivity of the composite.

[0021] In summary, the composite phase change material provided by this invention solves the problem that organic phase change materials struggle to simultaneously possess high heat storage density, high thermal conductivity, and high flame retardancy. It improves upon the issues of poor shape stability, hygroscopicity, high supercooling, easy leakage, poor thermal conductivity, and poor cycle stability inherent in hydrated salts, while retaining the advantages of hydrated salts' non-flammability and large heat storage capacity. The composite phase change material provided by this invention integrates thermal management and thermal runaway protection functions. During normal battery operation, its combined high heat storage density and good thermal conductivity can quickly absorb the heat generated during battery operation, regulating the battery temperature within the optimal operating range, effectively avoiding performance degradation caused by localized overheating, ensuring long-term stable battery service, and playing a reliable thermal management role. When the battery is on the verge of thermal runaway due to extreme operating conditions, its excellent flame retardant properties and high heat storage density can suppress thermal diffusion during battery thermal runaway, significantly reducing the risk of module thermal runaway and significantly improving the safety of the battery module. Attached Figure Description

[0022] Figure 1 The formation mechanism and characterization results of the metal-organic coordination polymer are shown in (a) schematic diagram of the formation mechanism, (b) FTIR spectrum, (c) XRD test results, (d) SEM image of polyethylene glycol, and (e) test results of coordination polymer 4.

[0023] Figure 2 The results of shape stability and thermal stability analysis of the metal-organic coordination polymer are shown in (a) shape stability test results, (b) DSC test results, (c) melting enthalpy and crystallization enthalpy test results, (d) TGA curve, and (e) DTG curve.

[0024] Figure 3 The results of phase separation and supercooling tests of the composite phase change materials obtained in Example 2 and Comparative Examples 1-3 are shown, where (a) is the phase separation test result, (b) is the supercooling test result, (b1) is a partial enlarged view of (b), and (b2) is a partial enlarged view of (b1).

[0025] Figure 4 The results of the tests on the deliquescence and molding performance of the composite phase change materials obtained in Examples 1-3 and Comparative Examples 1-3 are shown, where (a) is the test result of deliquescence, (b) and (c) are the test results of deliquescence weight gain, and (d) is the test graph of molding ability.

[0026] Figure 5 The results of the anti-leakage performance test of the composite phase change materials obtained in Examples 1-3 and Comparative Examples 1-3 are shown, where (a) is the morphological change of the sample at different times, and (b) is the mass retention test result.

[0027] Figure 6The results are the thermal performance test results of the composite phase change materials prepared in Examples 1-3 and Comparative Examples 1-4; where (a) is the phase change heat storage-heat release performance test result of different samples, (b) is the two-stage heat storage test result of different samples and (c) is the thermal conductivity test result of different samples.

[0028] Figure 7 The results are the vertical combustion test results of the composite phase change materials obtained in Examples 1-3 and Comparative Examples 2-4;

[0029] Figure 8 The results of cone calorimetry tests on the composite phase change materials obtained in Examples 1-3 and Comparative Examples 2 and 4 are shown, where (a) is the average heat release rate (ARHE), (b) is the heat release rate (HRR), (c) is the total heat release (THR), (d) is the smoke production rate (SPR), (e) is the total smoke production (TSP), and (f) is the mass loss rate (MLR).

[0030] Figure 9 These are schematic diagrams and physical images of the power battery modules prepared and assembled from the composite phase change materials of Example 2, Comparative Example 2, and Comparative Example 4.

[0031] Figure 10 The charge-discharge cycle curves of the battery module in Comparative Example 4 are shown under 1C, 1.5C and 2C conditions, where (a) is 1C, (b) is 1.5C and (c) is 2C.

[0032] Figure 11 The charge-discharge cycle curves of the battery module in Comparative Example 2 are shown under 1C, 1.5C and 2C conditions, where (a) is 1C, (b) is 1.5C and (c) is 2C.

[0033] Figure 12 The charge-discharge cycle curves of the battery module in Example 2 under 1C, 1.5C and 2C conditions are shown, where (a) 1C, (b) 1.5C and (c) 2C.

[0034] Figure 13 Infrared thermal imaging cloud images of the battery modules of Comparative Example 4, Comparative Example 2 and Example 2 during constant current discharge under 1C, 1.5C and 2C conditions, where (a) 1C, (b) 1.5C, and (c) 2C.

[0035] Figure 14 The results show the thermal runaway and propagation behavior of the battery module (a) in Comparative Example 4 and the battery module (b) in Example 2 after the battery is heated by a heating plate.

[0036] Figure 15The battery damage of Comparative Example 4 and Example 2 after thermal runaway propagation is shown in (a) for the battery module of Comparative Example 4, and (a1) and (a2) for the cell weight of the battery module of Comparative Example 4 after testing; (b) for the battery module of Example 2, and (b1) and (b2) for the cell weight of the battery module of Comparative Example 2 after testing.

[0037] Figure 16 To compare the leakage resistance test results of skeletons 1-5 during heating at 70℃ for 2 hours;

[0038] Figure 17 To compare the leakage resistance test results of skeletons 1-5 during heating at 100℃ for 2 hours;

[0039] Figure 18 To compare the leakage resistance test results of skeletons 1-5 during heating at 150℃ for 2 hours;

[0040] Figure 19 To compare the leakage resistance test results of skeletons 1-5 during heating at 200℃ for 2 hours;

[0041] Figure 20 The results of the anti-leakage performance test of the composite phase change materials obtained in Comparative Examples 10-13 are shown, where (a) is the sample morphology change recorded every 2 hours during the 8-hour heating process, and (b) is the mass retention test result.

[0042] Figure 21 The test results of the two-stage thermal storage performance of the composite phase change materials obtained in Comparative Examples 10-13 are as follows: (a): Comparative Example 10, (b): Comparative Example 11, (c): Comparative Example 12, (d): Comparative Example 13. Detailed Implementation

[0043] This invention provides an organic-inorganic hydrated salt composite phase change material, comprising the following components in parts by weight: 40-80 parts of hydrated salt phase change material, 10-50 parts of metal-organic coordination polymer, 2-10 parts of phase change temperature regulator, and 1-5 parts of thermal conductivity enhancer; wherein the metal-organic coordination polymer is formed by coordination of organic ligands and metal ion ligands; wherein the organic ligand is polyethylene glycol, and the metal ion ligand is a soluble calcium salt.

[0044] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0045] Based on mass parts, the organic-inorganic hydrated salt composite phase change material provided by the present invention comprises 40-80 parts of hydrated salt phase change material, specifically 40.5, 58.5, or 76.5 parts; the hydrated salt phase change material preferably comprises one or more of sodium acetate trihydrate, sodium thiosulfate pentahydrate, sodium metasilicate nonahydrate, sodium pyrophosphate decahydrate, and disodium hydrogen phosphate dodecahydrate; when the hydrated salt phase change material is one or more of the above selections, the present invention does not have a special limitation on the specific proportion of the substances, and they can be mixed in any proportion. In a specific embodiment of the present invention, sodium acetate trihydrate and sodium metasilicate nonahydrate can be used, and the mass ratio of sodium acetate trihydrate to sodium metasilicate nonahydrate can be (36~68):(4.5~8.5), specifically 36:4.5, 52:6.5 or 68:8.5; the sodium acetate trihydrate is from Shanghai Maclean Biochemical Technology Co., Ltd., with a melting point of 58℃ and a latent heat value of 260.4 J / g; the sodium metasilicate nonahydrate is from Shanghai Aladdin Biochemical Technology Co., Ltd., with a melting point of 48.7℃ and a latent heat value of 254 J / g.

[0046] Based on the mass fraction of the hydrated salt phase change material, the organic-inorganic hydrated salt composite phase change material provided by the present invention comprises 10-50 parts of a metal-organic coordination polymer, specifically 10 parts, 30 parts, or 50 parts; the metal-organic coordination polymer is formed by coordination of an organic ligand and a metal ion ligand, the coordination is carried out in a solvent, preferably an alcohol solvent, specifically anhydrous ethanol; the preferred ratio of the metal ion ligand to the solvent is 1g:5-25mL, specifically 1g:5mL, 1g:10mL, or 1g:15mL; the organic ligand is polyethylene glycol, preferably with a weight-average molecular weight of 1500-3000; the metal ion ligand is a soluble calcium salt, preferably calcium chloride; The preferred mass ratio of organic ligands to metal ion ligands is 5~45:1~5, more preferably 6~9:1~4, and specifically 9:1, 8:2, 7:3, 2:1 or 6:4. In specific embodiments of the present invention, the mass fraction of the metal-organic coordination polymer is based on the total mass fraction of the organic ligands and metal ion ligands. Specifically, based on the mass fraction of the hydrated salt phase change material, the mass fraction of the organic ligands is 9~45 parts, specifically 9 parts, 27 parts or 45 parts, and the mass fraction of the metal ion ligands is 1~5 parts, specifically 1 part, 3 parts or 5 parts. In specific embodiments of the present invention, the ligand polymer backbone is preferably formed by a coordination reaction of polyethylene glycol and calcium chloride in anhydrous ethanol solvent.

[0047] In this invention, the metal-organic coordination polymer is a polymer skeleton with excellent thermal stability formed by the interaction of organic ligands and metal ion ligands through metal coordination bonds. It has a dense porous network structure and phase change characteristics, which can adsorb hydrated salt phase change materials, improve the compatibility and adhesion between hydrated salt phase change materials and pure organic phase change materials, promote the dispersion of hydrated salts, and improve the thermal stability of composite phase change materials.

[0048] Traditional MOF materials are typically formed by the self-assembly of metal ions and rigid organic small molecules, with their main structural features and functions derived from their periodically arranged pore system. In contrast, this invention directly utilizes inexpensive polyethylene glycol (PEG) long chains as organic ligands, serving as both the framework and the heat storage component. Through a mild reaction, these chains bind with metal ions to form a three-dimensional network. The core function of this network is not to provide high specific surface area adsorption sites, but rather to directly fix phase change materials (such as PEG segments) within its structure via chemical bonds, thereby achieving macroscopic shape stability and leak resistance at high temperatures. Simultaneously, the inherent heat storage function of the coordination polymer enhances the phase change heat storage performance of the composite phase change material to some extent. Furthermore, the porous adsorption characteristics, hydrophilicity, and high thermal stability of the coordination polymer enhance the adsorption of hydrated salt phase change materials, improving the water-locking capacity and cycle stability of the composite phase change material. In summary, the combination and coordination mode of organic ligands and metal ion ligands endow metal-organic coordination polymers with unique thermodynamic and physicochemical properties, making them superior to existing metal-organic frameworks in terms of thermal stability, adsorption performance, and compatibility with hydrated salt phase change materials. This provides key technical support for the efficient application of composite phase change materials in the fields of thermal management and thermal runaway protection.

[0049] Taking polyethylene glycol and calcium chloride as an example, the specific coordination principle is as follows: Calcium ions can undergo a coordination reaction with the organic ligand polyethylene glycol, thereby generating a metal-organic coordination polymer. This coordination polymer possesses a potential porous structure. The core of this process is the formation of coordination bonds between polyethylene glycol and anhydrous calcium chloride in an ethanol solution system. Utilizing the porous structure of this material, phase change components can be adsorbed, thus effectively ensuring the shape stability of the phase change components. Figure 1 As shown, anhydrous ethanol dissolves calcium chloride, thereby providing free Ca. 2+ Ca 2+ It coordinates with ethanol molecules, forming a highly reactive intermediate, [Ca(CH3CH2OH)4]Cl2, in situ. When polyethylene glycol is added to the solution, the intermediate is removed during the evaporation of ethanol by heating. 2+ Coordinated ethanol ligands, thereby in Ca 2+Highly active coordination vacancies are left around it. Subsequently, as ethanol is continuously removed and polyethylene glycol continues to coordinate, a coordination polymer network formed by polyethylene glycol and calcium chloride gradually forms in situ.

[0050] In a specific embodiment of the present invention, when studying the structure and properties of the organometallic coordination polymer alone, the organometallic coordination polymer can be prepared by the following steps: heating and melting the organic ligand; dissolving the metal ion ligand in anhydrous ethanol (using 5 mL of anhydrous ethanol per 1 g of metal ion ligand) to obtain a metal ion ligand solution; mixing the metal ion ligand solution and the melted organic ligand and then drying to obtain the organometallic coordination polymer; the drying is preferably vacuum drying, the temperature of which can be 90~100℃ and the time can be 2~8h; the temperature at which the organic ligand is heated and melted can be 70℃.

[0051] Based on the mass fraction of the hydrated salt phase change material, the organic-inorganic hydrated salt composite phase change material provided by the present invention includes 2 to 10 parts of a phase change temperature regulator, specifically 4.5, 6.5, or 8.5 parts; the phase change temperature regulator preferably includes one or more of potassium chloride, ammonium chloride, potassium nitrate, glycerol, urea, and glycine, and in the examples, it can be urea.

[0052] Based on the mass fraction of the hydrated salt phase change material, the organic-inorganic hydrated salt composite phase change material provided by the present invention includes 1 to 5 parts of thermal conductivity enhancer, specifically 1, 2, 3, 4 or 5 parts; the thermal conductivity enhancer preferably includes one or more of boron nitride, silicon carbide, expanded graphite and carbon nanotubes, and in the embodiments it can be expanded graphite.

[0053] In this invention, the thermal conductivity of the organic-inorganic hydrated salt composite phase change material is preferably greater than 1.50 W / m·K, more preferably 1.75~2.22 W / m·K; the latent heat of phase change of the organic-inorganic hydrated salt composite phase change material is preferably greater than 120 J / g, more preferably 150.9~172.1 J / g.

[0054] This invention also provides a method for preparing the organic-inorganic hydrated salt composite phase change material described above, comprising the following steps:

[0055] The organic-inorganic hydrated salt composite phase change material is obtained by mixing hydrated salt phase change material, temperature regulator, organic ligand, metal ion ligand, solvent and thermal conductivity enhancer.

[0056] In this invention, the mixing is carried out in the molten state of the hydrated salt phase change material. Specifically, the mixing temperature is preferably 60~90℃, and in the embodiments it can be 60℃, 70℃, 80℃ or 90℃. The mixing is preferably carried out under stirring conditions. This invention does not have special limitations on the stirring conditions and parameters, and can use processes well known to those skilled in the art.

[0057] In this invention, the mixing preferably includes: first mixing a hydrated salt phase change material and a phase change temperature regulator to obtain a first mixture; dissolving a metal ion ligand in a solvent to obtain a metal ion ligand solution; second mixing the metal ion ligand solution with molten organic ligands to obtain a second mixture; third mixing the first mixture and the second mixture to obtain a third mixture; and fourth mixing the third mixture with a thermal conductivity enhancer to obtain the organic-inorganic hydrated salt composite phase change material.

[0058] In this invention, the rotational speed of the first mixing is preferably 200-300 rad / min, and the mixing time is preferably 30-60 min.

[0059] In this invention, the type of solvent and the ratio of metal ion ligand to solvent are the same as in the above scheme, and will not be repeated here; the second mixing speed is preferably 300~400 r / min, and the mixing time is preferably 30~60 min, during which the organic ligand and metal ion ligand undergo partial coordination; the third mixing time is preferably 60~120 min, and the mixing speed is preferably 300~400 r / min; the fourth mixing speed is preferably 400~500 rad / min, and the mixing time is preferably 30~60 min; during the third and fourth mixing processes, anhydrous ethanol continues to evaporate, and the organic ligand and metal ion ligand continue to coordinate, forming a metal-organic coordination polymer, which is then combined with hydrated salt phase change materials, thermal conductivity enhancers, etc., to form the composite phase change material of this invention; the first, second, third, and fourth mixing processes are all preferably carried out in a constant temperature oil bath equipped with an electric stirrer, and the mixing temperature is preferably 60~90℃, specifically 70℃.

[0060] This invention directly adds a second mixture to molten hydrated salt. Polyethylene glycol and calcium ions undergo in-situ coordination to form a metal-organic polymer while simultaneously adsorbing the hydrated salt, achieving a tight bond between the metal-organic coordination polymer and the hydrated salt phase change material. The metal-organic coordination polymer can form a uniform three-dimensional network structure that penetrates the hydrated salt phase change material, enhancing shape stability, effectively reducing the supercooling of the hydrated salt, suppressing phase separation, and simultaneously eliminating interfacial voids and optimizing the heat transfer path, thus achieving a synergistic improvement in structural stability and thermal performance.

[0061] This invention also provides the application of the organic-inorganic hydrated salt composite phase change material described in the above-described scheme or the organic-inorganic hydrated salt composite phase change material prepared by the preparation method described in the above-described scheme in power batteries; the organic-inorganic hydrated salt composite phase change material is preferably applied in the thermal management system of the power battery. In a specific embodiment of this invention, the organic-inorganic hydrated salt composite phase change material is preferably used as a raw material for preparing the battery module of the power battery.

[0062] The present invention also provides a battery module prepared from the organic-inorganic hydrated salt composite phase change material described in the above scheme or the organic-inorganic hydrated salt composite phase change material prepared by the preparation method described in the above scheme.

[0063] In this invention, the method for preparing the battery module preferably includes the following steps:

[0064] A hydrated salt phase change material, a metal ion ligand, an organic ligand, a solvent, a phase change temperature regulator, and a thermal conductivity enhancer are mixed. The resulting mixture is poured into a mold, cooled to room temperature, and then demolded to obtain the battery module. The mixing method is the same as described above and will not be repeated here. The present invention does not impose any special limitations on the cooling and demolding process; any process well known to those skilled in the art can be used.

[0065] The organic-inorganic hydrated salt composite phase change material provided by this invention, when applied to the thermal management system of power batteries, not only has excellent heat dissipation and temperature uniformity, improving the temperature consistency of power batteries; but also, when thermal runaway occurs, the composite phase change material can effectively suppress the spread of fire, isolate heat and oxygen, and prevent further thermal disasters.

[0066] 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. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0067] In the following examples, 1 part by weight is 1g, and the polyethylene glycol used is PEG2000.

[0068] Example 1

[0069] The composition of the organic-inorganic hydrated salt composite phase change material by mass parts is as follows: 68 parts sodium acetate trihydrate and 8.5 parts sodium metasilicate nonahydrate as hydrated salt phase change material, 8.5 parts urea as phase change temperature regulator, 9 parts polyethylene glycol as organic ligand of metal-organic coordination polymer, 1 part anhydrous calcium chloride as metal ion ligand of metal-organic coordination polymer, 5 mL anhydrous ethanol as solvent for coordination reaction between metal ion ligand and organic ligand, and 5 parts expanded graphite as thermal conductivity enhancer.

[0070] The preparation method of organic-inorganic hydrated salt composite phase change material is as follows:

[0071] S1: Sodium acetate trihydrate, sodium metasilicate nonahydrate and urea are placed in a constant temperature oil bath equipped with an electric stirrer and heated until melted. The mixture is stirred at 300 r / min for 60 min to obtain the first mixture.

[0072] S2: Polyethylene glycol is melted at 70°C. Anhydrous calcium chloride and anhydrous ethanol are placed in a beaker and magnetically stirred until the calcium chloride particles dissolve to form a calcium chloride ethanol solution. Then, the calcium chloride ethanol solution is added to the molten polyethylene glycol and stirred at 400 r / min for 60 min to obtain a milky white second mixture.

[0073] S3: Add the second mixture to the first mixture obtained above, and stir at 70°C and 400 r / min for 120 min to obtain the third mixture;

[0074] S4: Add 5 parts of expanded graphite to the third mixture obtained above, and stir at 70°C and 500 r / min for 120 min to obtain the organic-inorganic hydrated salt composite phase change material (denoted as SSEC1).

[0075] Example 2

[0076] The composition of the organic-inorganic hydrated salt composite phase change material by mass parts is as follows:

[0077] 52 parts of sodium acetate trihydrate and 6.5 parts of sodium metasilicate nonahydrate were used as hydrated salt phase change materials, 6.5 parts of urea were used as phase change temperature regulators, 27 parts of polyethylene glycol were used as organic ligands of metal-organic coordination polymers, 3 parts of anhydrous calcium chloride were used as metal ion ligands of metal-organic coordination polymers, 15 mL of anhydrous ethanol was used as solvent for coordination reactions between metal ion ligands and organic ligands, and 5 parts of expanded graphite were used as thermal conductivity enhancers.

[0078] The preparation method of organic-inorganic hydrated salt composite phase change material is as follows:

[0079] S1: Sodium acetate trihydrate, sodium metasilicate nonahydrate and urea are placed in a constant temperature oil bath equipped with an electric stirrer and heated until melted. The mixture is stirred at 300 r / min for 60 min to obtain the first mixture.

[0080] S2: Polyethylene glycol is melted at 70°C. Anhydrous calcium chloride and anhydrous ethanol are placed in a beaker and magnetically stirred until the calcium chloride particles dissolve to form a calcium chloride ethanol solution. Then, the calcium chloride ethanol solution is added to the molten polyethylene glycol and stirred at 400 r / min for 60 min to obtain a milky white second mixture.

[0081] S3: Add the second mixture to the first mixture obtained above, and stir at 70°C and 400 r / min for 120 min to obtain the third mixture;

[0082] S4: Add expanded graphite to the third mixture obtained above, and stir at 70°C and 500 r / min for 120 min to obtain the organic-inorganic hydrated salt composite phase change material (denoted as SSEC3).

[0083] Example 3

[0084] The composition of the organic-inorganic hydrated salt composite phase change material by mass parts is as follows:

[0085] 36 parts of sodium acetate trihydrate and 4.5 parts of sodium metasilicate nonahydrate were used as hydrated salt phase change materials, 4.5 parts of urea were used as phase change temperature regulators, 45 parts of polyethylene glycol were used as organic ligands of metal-organic coordination polymers, 5 parts of anhydrous calcium chloride were used as metal ion ligands of metal-organic coordination polymers, 25 mL of anhydrous ethanol was used as solvent for coordination reactions between metal ion ligands and organic ligands, and 5 parts of expanded graphite were used as thermal conductivity enhancers.

[0086] The preparation method of organic-inorganic hydrated salt composite phase change material is as follows:

[0087] S1: Sodium acetate trihydrate, sodium metasilicate nonahydrate and urea are placed in a constant temperature oil bath equipped with an electric stirrer and heated until melted. The mixture is stirred at 300 r / min for 60 min to obtain the first mixture.

[0088] S2: Polyethylene glycol is melted at 70°C. Anhydrous calcium chloride and anhydrous ethanol are placed in a beaker and magnetically stirred until the calcium chloride particles dissolve to form a calcium chloride ethanol solution. Then, the calcium chloride ethanol solution is added to the molten polyethylene glycol and stirred at 400 r / min for 60 min to obtain a milky white second mixture.

[0089] S3: Add the second mixture to the first mixture obtained above, and stir at 70°C and 400 r / min for 120 min to obtain the third mixture;

[0090] S4: Add expanded graphite to the third mixture obtained above, and stir at 70°C and 500 r / min for 120 min to obtain the organic-inorganic hydrated salt composite phase change material (denoted as SSEC5).

[0091] Comparative Example 1: Thermal conductivity enhancer and metal-organic coordination polymer omitted.

[0092] The composite phase change material is composed of the following components by mass: 80 parts sodium acetate trihydrate and 10 parts sodium metasilicate nonahydrate as hydrated salt phase change material, and 10 parts urea as phase change temperature regulator.

[0093] The preparation method of composite phase change materials is as follows:

[0094] S1: Sodium acetate trihydrate, sodium metasilicate nonahydrate and urea are placed in a constant temperature oil bath equipped with an electric stirrer and heated until melted. The mixture is stirred at 300 r / min for 60 min to obtain the composite phase change material (denoted as SS).

[0095] Comparative Example 2: Omitted metal-organic coordination polymers

[0096] The composite phase change material is composed of the following components by mass: 76 parts sodium acetate trihydrate and 9.5 parts sodium metasilicate nonahydrate as hydrated salt phase change material, 9.5 parts urea as phase change temperature regulator, and 5 parts expanded graphite as thermal conductivity enhancer.

[0097] The preparation method of composite phase change materials is as follows:

[0098] S1: Sodium acetate trihydrate, sodium metasilicate nonahydrate and urea are placed in a constant temperature oil bath equipped with an electric stirrer and heated until melted. The mixture is stirred at 300 r / min for 60 min to obtain the first mixture.

[0099] S2: Add expanded graphite to the mixture obtained above, and stir at 70°C and a stirring speed of 500 r / min for 120 min to obtain the composite phase change material (denoted as SSE).

[0100] Comparative Example 3: Thermal conductivity enhancer omitted

[0101] The composite phase change material is composed of the following components by mass: 56 parts sodium acetate trihydrate and 7 parts sodium metasilicate nonahydrate as hydrated salt phase change material, 7 parts urea as phase change temperature regulator, 27 parts polyethylene glycol as organic ligand of metal-organic coordination polymer, 3 parts anhydrous calcium chloride as metal ion ligand of metal-organic coordination polymer, and 15 mL anhydrous ethanol as solvent for coordination reaction between metal ion ligand and organic ligand.

[0102] The preparation method of composite phase change materials is as follows:

[0103] S1: Sodium acetate trihydrate, sodium metasilicate nonahydrate and urea are placed in a constant temperature oil bath equipped with an electric stirrer and heated until melted. The mixture is stirred at 300 r / min for 60 min to obtain the first mixture.

[0104] S2: Polyethylene glycol is melted at 70°C. Anhydrous calcium chloride and anhydrous ethanol are placed in a beaker and magnetically stirred until the calcium chloride particles dissolve to form a calcium chloride ethanol solution. Then, the calcium chloride ethanol solution is added to the molten polyethylene glycol and stirred at 400 r / min for 60 min to obtain a milky white second mixture.

[0105] S3: Add the second mixture to the first mixture obtained above, and stir at 70°C and a stirring speed of 500 r / min for 120 min to obtain the composite phase change material (denoted as SSC).

[0106] Comparative Example 4

[0107] The composite phase change material is composed of the following components by mass: 67 parts Joule paraffin as the phase change material, 5 parts epoxy resin A as component A of the supporting skeleton, 5 parts epoxy resin B as component B of the supporting skeleton and acting as a curing agent, 18 parts ammonium polyphosphate as a flame retardant, and 5 parts expanded graphite as a thermal conductivity enhancer.

[0108] The preparation method of composite phase change materials is as follows:

[0109] S1: Place Joule paraffin, epoxy resin A and epoxy resin B into a constant temperature oil bath equipped with an electric stirrer and heat until melted. Stir at 300 r / min for 60 min to obtain the first mixture.

[0110] S2: Add expanded graphite to the first mixture obtained above, and stir at 70°C and a stirring speed of 500 r / min for 120 min to obtain the second mixture;

[0111] S3: Add ammonium polyphosphate flame retardant to the second mixture obtained above, and stir at 70°C and a stirring speed of 500 r / min for 120 min to obtain the composite phase change material (denoted as PEEA).

[0112] The group allocation examples in Examples 1-3 and Comparative Examples 1-4 are shown in Table 1;

[0113] Table 1. Distribution ratios of each group in Examples 1-3 and Comparative Examples 1-4

[0114]

[0115] Example 4

[0116] To investigate the structure and properties of organometallic coordination polymers, polymer backbones with different ratios of polyethylene glycol and calcium chloride were prepared. The specific preparation methods are as follows:

[0117] Based on ion coordination reactions, different amounts of CaCl2 were first used as the metal ion source. CaCl2 was dissolved in anhydrous ethanol (calcium chloride to anhydrous ethanol ratio of 1 g:5 mL) to form a CaCl2-ethanol solution. The CaCl2 reacted with ethanol for 1 h to form a coordination compound. Then, molten polyethylene glycol (the total weight of polyethylene glycol and anhydrous calcium chloride was 100 g for preparing coordination polymers 1-5) was added as an organic ligand to the CaCl2-ethanol solution. The mixture was melt-stirred at 60 °C for 2 h, followed by vacuum drying at 100 °C for 8 h. The PEG molecular chain was linked to the CaCl2 ion compound through coordination bonds. As the ethanol ligand evaporated, the highly active vacancies in the coordination compound were filled by the CH2CH2O molecular chains of the PEG polymer. This process is called a ligand substitution reaction, ultimately generating the [Ca(PEG)2]Cl2 coordination polymer (reaction principle as follows). Figure 1 As shown in (a)). Based on the above coordination reaction principle, [Ca(PEG)2]Cl2 with different ratios was designed and prepared, denoted as PC1, PC2, PC3, PC4 and PC5, respectively. The ratio of polyethylene glycol and calcium chloride is shown in Table 2. The organometallic coordination polymers with different ratios are referred to as coordination polymers 1 to 5 in sequence.

[0118] Table 2. Ratios of different metal-organic coordination polymers

[0119]

[0120] Test Example 1

[0121] This test case provides a detailed study of the chemical structure and microstructure of the metal-organic coordination polymer prepared in Example 4.

[0122] Pure polyethylene glycol and a series of prepared organometallic coordination polymers 1-5 were characterized by FTIR spectroscopy, and the results are as follows: Figure 1 As shown in (b). In the infrared spectrum of pure polyethylene glycol, at 3492 cm⁻¹ -1 A broad absorption peak was detected at 3425 cm⁻¹, corresponding to the terminal hydroxyl group of polyethylene glycol. Similarly, a peak of 3425 cm⁻¹ was observed in all metal-organic coordination polymers. -1 The broad absorption peak at 883 cm⁻¹ indicates a slight peak shift in the generated organometallic coordination polymer. Meanwhile, the peak at 883 cm⁻¹... -1 The peak indicates the presence of a Ca-O group absorption peak, which confirms the existence of a coordination reaction between polyethylene glycol and anhydrous calcium chloride.

[0123] XRD tests were performed on pure polyethylene glycol, anhydrous calcium chloride, and a series of prepared organometallic coordination polymers 1-5. The results are as follows: Figure 1 As shown in (c), the XRD patterns show that polyethylene glycol exhibits clear crystalline peaks at 19.56° and 23.76°. Coordination polymer 1 shows obvious diffraction peaks at 19.58° and 23.74°, indicating that coordination formation did not affect the crystal structure of polyethylene glycol, but the diffraction peak intensity decreased. With the increase of anhydrous calcium chloride content in the complex, the coordination reaction intensity increased. Coordination polymer 2 showed only a weak crystalline peak at the corresponding position, while coordination polymers 3, 4, and the backbone 5 completely lost the original crystalline structure contained in polyethylene glycol.

[0124] In addition, SEM tests were performed on pure polyethylene glycol and coordination polymer 4, and the results are as follows: Figure 1 As shown in (d) and (e), compared to the uniform and smooth structure of pure polyethylene glycol, the SEM images of the coordination polymer 4 sample contain a porous network structure, which provides a larger support surface for the adsorption phase change matrix, further confirming the formation of coordination chemical bonds between polyethylene glycol and anhydrous calcium chloride.

[0125] Test Example 2

[0126] To further verify the functionality of the metal-organic coordination polymers, the thermal stability of coordination polymers 1–5 was tested, including shape stability and thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and differential thermal weight loss analysis (DTG). The test results are as follows: Figure 2 As shown, Figure 2 (a) shows the shape stability test results, (b) shows the DSC test results, (c) shows the melting enthalpy and crystallization enthalpy test results, (d) shows the TGA curve, and (e) shows the DTG curve.

[0127] like Figure 2As shown in Figure (a), five groups of organometallic coordination polymers 1–5 with different proportions were placed on a constant-temperature heating stage and heated at 70, 100, 150, and 200 °C for 2 h, respectively. It was observed that no leakage occurred at 70 °C. With increasing heating temperature, coordination polymers 1 and 2 showed more leakage after heating at 150 °C for 2 h. However, coordination polymers 3, 4, and 5 exhibited excellent thermal stability, showing no leakage even at 200 °C. This is mainly because the coordination reaction between polyethylene glycol and excess anhydrous calcium chloride in the coordination polymers formed a more compact three-dimensional network structure.

[0128] Furthermore, it was observed that coordination polymers 1 through 5 exhibited differences in thermal storage performance. (DSC test) Figure 2 The results in (b) indicate that as the coordination reaction between polyethylene glycol and anhydrous calcium chloride becomes more complete, polyethylene glycol is continuously consumed, leading to a gradual loss of its original heat storage capacity. Figure 2 As can be seen in (c), the melting enthalpy and crystallization enthalpy of coordination polymer 3 are at 20 J·g -1 The following results show almost complete loss. When the mass ratio of polyethylene glycol (PEG) to anhydrous calcium chloride is 2:1 (coordination polymer 4), all of the PEG is used for coordination with anhydrous calcium chloride, resulting in complete loss of phase transition enthalpy. Furthermore, the TGA curves show that a series of coordination polymers 1-5 and pure PEG exhibit similar thermal degradation patterns. As shown in the DTG curves, several samples experienced rapid mass loss at 400°C, due to the thermal decomposition of PEG at this high temperature. The difference lies in the fact that the thermal stability of coordination polymers 1-5 significantly increases with increasing anhydrous calcium chloride content; the residual mass after heating to 800°C is consistent with the content of anhydrous calcium chloride in the organometallic coordination polymer material.

[0129] Test Example 3

[0130] Phase separation and supercooling of the composite phase change materials obtained in Example 2 and Comparative Examples 1-3 were tested using the following method: Different composite phase change materials were placed in centrifuge tubes and heated until melted. The phase separation phenomenon of each sample group was then observed. Furthermore, the centrifuge tubes containing different samples were placed in a constant temperature and humidity chamber at 70°C. After maintaining temperature stability, the chamber was lowered to 0°C and maintained at that temperature. Temperature data was recorded using an Agilent data acquisition device and a T-type thermocouple during this process to analyze the supercooling.

[0131] Test results are as follows Figure 3 As shown, Figure 3 In the diagram, (a) shows the phase separation test results, (b) shows the supercooling test results, (b1) is a magnified view of (b), and (b2) is a magnified view of (b1).

[0132] from Figure 3 As shown in (a), both pure sodium acetate trihydrate and the sodium acetate trihydrate / urea mixture (sodium acetate trihydrate / urea mass ratio of 90:10) exhibit significant phase separation. Sodium metasilicate nonahydrate, acting as a nucleating agent, provides initial crystallization sites, making the crystallization process more uniform and thus reducing phase separation in Comparative Example 1. The addition of expanded graphite and the organometallic coordination polymer increases the viscosity of the entire system. It can be observed that the test tubes containing the samples from Comparative Example 3 and Example 2 exhibit consistent melting even when inverted, indicating that the organometallic coordination polymer forms a certain network structure in the composite phase change material. This structure can restrict the free movement of water molecules, resulting in a more uniform distribution of water molecules.

[0133] in addition, Figure 3 As shown in (b), the supercooling of sodium acetate trihydrate reached 15.8℃, meaning that the actual solidification temperature of sodium acetate trihydrate was 15.8℃ lower than the theoretical solidification temperature. This phenomenon is mainly caused by hydrogen bonding between water molecules and salt ions in the hydrated salt. Due to the relatively strong hydrogen bonds, molecules require sufficient energy to break these bonds and rearrange into a crystal structure, increasing the difficulty of crystallization and thus leading to supercooling. The introduction of heterogeneous nucleation sites can effectively lower the nucleation energy barrier, allowing the substance to form stable crystal nuclei at a lower supercooling, thereby promoting the crystallization process. Figure 3 As shown in (b1) and (b2), the supercooling of Comparative Example 2 and Comparative Example 3 was reduced to 4.2 °C and 2.9 °C, respectively. This is mainly because the expanded graphite in Comparative Example 2 and the metal-organic coordination polymer in Comparative Example 3 both provided suitable nucleation sites, promoting the nucleation rate and thus achieving a more efficient crystallization process. Furthermore, Example 2, which combined the effects of both, achieved an earlier spontaneous phase transition at a lower supercooling.

[0134] Test Example 4

[0135] The deliquescence and molding properties of the composite phase change materials obtained in Examples 1-3 and Comparative Examples 1-3 were tested. The test methods are as follows: Under the same humidity conditions, different annular samples were placed on filter paper, and the water absorption of the sample surface was recorded at different times, and the weight gain rate was calculated. Additionally, a 1kg weight was placed on the surface of the composite phase change material sample plates of different hydrated salts, and it was observed whether they would collapse or deform under the weight, thereby evaluating their molding ability. The test results are as follows: Figure 4 As shown, Figure 4 (a) shows the test results for deliquescence, (b) and (c) show the test results for deliquescence weight gain, and (d) shows the test results for molding capacity.

[0136] from Figure 4As can be seen in (a), Comparative Examples 1 and 2 absorbed moisture from the air, causing the filter paper surface to become wet and resulting in significant deliquescence. In contrast, the addition of the organometallic coordination polymer effectively improved the deliquescence problem. With the increase of the organometallic coordination polymer content, the surfaces and filter paper of Examples 2 and 3 did not become wet, and the water absorption phenomenon was reduced. Figure 4 Figures (b) and (c) also reflect that the metal-organic coordination polymer effectively reduced the deliquescence weight gain rate of the hydrated salt composite phase change material. Figure 4 The middle (d) reflects the nucleation ability of different hydrated salt composite phase change materials at the macroscopic level.

[0137] Test Example 5

[0138] The anti-leakage properties of the composite phase change materials obtained in Examples 1-3 and Comparative Examples 1-3 were tested. The testing procedure was as follows: different samples were prepared into Φ12×8mm... 3 The sample was placed on a heating platform and tested at 70°C for 8 hours. Digital photographs of the sample were recorded using a digital camera. The morphological changes and leakage of the sample at various temperatures were compared, and the mass retention rate was calculated. The test results are as follows: Figure 5 As shown, Figure 5 (a) shows the morphological changes of the sample at different times, and (b) shows the results of the quality retention test.

[0139] from Figure 5 As can be seen, except for Comparative Examples 1 and 2, the other composite phase change materials all incorporated metal-organic coordination polymers or epoxy resins as supporting framework materials, thus preventing significant collapse during heating. With increasing heating time, Comparative Example 1 completely leaked, with salt crystals seeping out and adhering to the filter paper; Comparative Example 2, with the addition of expanded graphite, maintained macroscopic shape stability, but the sample surface exhibited a whitening phenomenon. This is due to a dehydration reaction occurring during heating, releasing water molecules. As the water evaporates, the anhydrous form of the salt gradually becomes exposed on the surface.

[0140] No leakage was found in the composite phase change materials in Examples 1-3, and the mass retention rate was much higher than that in Comparative Examples 1-3, showing excellent thermal stability and anti-leakage performance. This is attributed to the adsorption of hydrated salt phase change materials by the metal-organic coordination polymer material with a three-dimensional network structure under the action of capillary adsorption force and surface tension.

[0141] Test Example 6

[0142] The melting point, thermal conductivity, and latent heat of the composite phase change materials prepared in Examples 1-3 and Comparative Examples 1-3, as well as sodium acetate trihydrate and Joule paraffin, were tested. The test results are shown in Table 3. The hydrated salt composite phase change materials complete energy storage and release through dehydration / hydration reactions, which corresponds to the melting and crystallization process of solid-liquid phase change materials. The phase change behavior of the hydrated salt composite phase change materials was determined by differential scanning calorimetry. The specific test results are as follows: Figure 6 As shown in Figure (a), the phase transition peak temperatures of Comparative Example 1 and Comparative Example 2 are 54.6 and 52.5 °C, respectively, with corresponding latent heat values ​​of 210.7 and 198.9 J·g. -1 With the addition of the metal-organic coordination polymer, the phase change temperature of the embodiments was stabilized at around 50°C. Moreover, the addition of an appropriate amount of metal-organic coordination polymer did not affect the latent heat value of the hydrated salt composite phase change material. Furthermore, due to the organic phase change characteristics and porous framework structure of the metal-organic coordination polymer itself, the dehydration and hydration processes of the hydrated salt composite phase change material were promoted, thereby enabling Embodiments 1, 2, and 3 to complete heat storage and release in a timely manner during the phase change process.

[0143] Table 3. Test results of the thermophysical properties of the composite phase change materials, sodium acetate trihydrate, and joule paraffin in Examples 1-3 and Comparative Examples 1-4.

[0144]

[0145] Hydrated salts exhibit dual-stage heat storage characteristics during gradual water loss, corresponding to 40–60°C and 110–130°C, respectively. Strictly speaking, non-phase change materials in non-vacuum environments only possess sensible heat storage capacity. In contrast, the heat storage capacity of hydrated salt composite phase change materials varies with ambient temperature, encompassing sensible heat storage, latent heat storage, and heat of vaporization storage. DSC curves of different hydrated salt composite phase change materials, including dehydration phase change and water evaporation processes, are shown below. Figure 6 As shown in (b), the dehydration process is represented by multiple endothermic peaks on the DSC curve, each corresponding to the removal of water of crystallization. The thermochemical heat storage density is listed in Table 3. With the increase of the metal-organic coordination polymer, the organic phase change framework improves the thermal properties of the hydrated salt composite phase change material while reducing the hydrated salt content, thus reducing the thermochemical heat storage density of the hydrated salt composite phase change material. However, it is worth noting that Example 2 still has a heat storage density of 628.9 J·g. -1 Its total heat storage density is far greater than that of various shape-stable composite phase change materials used in battery thermal management.

[0146] Figure 6(c) The thermal conductivity of different hydrated salt composite phase change materials at 40°C, 50°C, and 60°C was compared. Comparative Example 1 was a mixture formed by a ternary eutectic of sodium acetate trihydrate, sodium metasilicate nonahydrate, and urea. Due to lattice defects in the hydrated salt, phonon propagation was hindered, resulting in low thermal conductivity, even at 60°C, only 0.594 W / m·K. Hydrated salt composite phase change materials loaded on expanded graphite or metal-organic coordination polymers both showed enhanced thermal conductivity, with Comparative Examples 2 and 3 exhibiting thermal conductivity of 1.26 and 0.68 W / m·K at 40°C, respectively. Furthermore, the thermal conductivity increased with increasing temperature, which can be attributed to enhanced atomic vibrations within the stable-shaped hydrated salt composite phase change materials, thus enhancing the thermal conductivity of the solid phase. Further, with increasing metal-organic coordination polymer content, the thermal conductivity of Examples 1, 2, and 3 showed a linear increase, reaching a maximum of 2.784 W / m·K at 60°C. The main reason is that coordination bonds promote the orderliness of the metal-organic coordination polymer structure, reduce the heat dissipation of phonons in the disordered structure, and increase the mean free path of phonons.

[0147] Test Example 7

[0148] The composite phase change materials obtained in Examples 1-3 and Comparative Examples 2-4 were subjected to vertical combustion tests and cone calorimeter tests.

[0149] The vertical combustion test used a strip-shaped sample with a length of 130 mm, a width of 6.5 mm, and a thickness of 3.5 mm. The combustion test results are as follows: Figure 7 As shown; from such Figure 7 It can be seen that Comparative Example 4, with 18wt% flame retardant added, self-extinguishes after 10 seconds of initial ignition. However, upon immediate second ignition, the sample of Comparative Example 4 ignites and the flame continues to spread. This indicates that a certain amount of flame retardant can only enhance the flame retardant performance of Comparative Example 4, but cannot reach the highest flame retardant standard. In contrast, hydrated salts, as inorganic materials, have the advantage of being non-flammable. Comparative Examples 2 and 3 cannot be ignited after two 10-second ignition tests. The highest flame retardant rating can still be maintained after adding appropriate amounts of expanded graphite and metal-organic coordination polymers. It can be found that Examples 1 and 2 both self-extinguish within 1 second after two ignitions, achieving a flame retardant rating of V0. With further increases in the metal-organic coordination polymer, the flame retardant performance of Example 3 decreases slightly.

[0150] To evaluate the fire resistance performance of different composite phase change materials under real fire scenarios, cone calorimetry was conducted. The cone calorimetry test method was based on ISO 5660, with a heat flux density of 35 kW / m³. 2 Each result is the average of two parallel trials; Figure 8Tables (a) to (f) present the test results for the average heat release rate (ARHE), heat release rate (HRR), total heat release (THR), smoke production rate (SPR), total smoke production (TSP), and mass loss rate (MLR), respectively, and Table 4 summarizes the specific values ​​of each indicator. ARHE is defined as the ratio of cumulative radiant heat to time, and its peak value (PAHRE) can be used as an indicator to assess the trend of fire occurrence.

[0151] Table 4 shows the flame self-extinguishing time and cone calorimetry test results of the composite phase change materials obtained in Examples 1-3 and Comparative Examples 2 and 4.

[0152]

[0153] It can be observed that the PARHE in Comparative Example 4 reaches 431.43 KW / m 2 In Examples 1-3, the PARHE levels increased with the addition of the metal-organic coordination polymer, but remained significantly lower than in Comparative Example 4, greatly reducing the risk of fire. The peak HRR (PHRR) of Comparative Example 4 was close to 800 kW / m². 2 This poses a significant risk of exacerbating flame spread when used in battery modules. In contrast, both HRR and THR increase with increasing metal-organic coordination polymer content. Specifically, the HRR and THR of Example 2 are 232.82 kW / m³. 2 and 93.70 MJ / m 2 Compared with Comparative Example 4, the PSP and TSP were reduced by 70.7% and 45.4% respectively, clearly demonstrating the effect of limiting heat release. Furthermore, the smoke generated during combustion can pose a combustion hazard in the event of thermal runaway in the battery. It can be observed that the PSPR and TSP of several composite phase change materials are at low levels, with the TSP of Example 2 being only 1.27m. 2 This further verifies the environmental friendliness of this organic-inorganic hydrated salt composite phase change material. Additionally, from... Figure 8 The change in mass loss rate in (f) shows that the metal-organic coordination polymer delayed the peak MLR of Examples 1-3 and significantly enhanced the thermal stability of the composite phase change material.

[0154] As can be seen from the comprehensive test examples 1 to 7, the composite phase change material provided by the present invention has a high latent heat value and thermal conductivity, as well as good anti-leakage performance, thermal stability and flame retardant performance, and is suitable for thermal protection of power batteries.

[0155] Test Example 8

[0156] A battery module was prepared using the composite phase change material obtained in Example 2 as raw material; then, a power battery module (SSEC3-Module) was assembled using the battery module, and the temperature control performance was tested at high discharge rates of 1 C, 1.5 C and 2 C, respectively. The control groups were the power battery module (SSE-Module) prepared and assembled using the composite phase change material in Comparative Example 2 and the power battery module (PEEA-Module) prepared and assembled using the composite phase change material in Comparative Example 4.

[0157] The PEEA-Module, SSE-Module, and SSEC3-Module are all constructed by connecting five square lithium iron phosphate batteries in a 5S (five-series) configuration (see structural diagram and physical examples). Figure 9 As shown in the figure, each square lithium iron phosphate battery has an average capacity of 23000mAh. The battery module was placed in a thermostat (BTH 80C, Dongguan Bell Test Equipment Co., Ltd.) and charged and discharged under a simulated ambient temperature of 25℃ using a battery testing system (CT-3008-NA, Shenzhen Xinwei Electronic Equipment Co., Ltd.). The surface temperature of the battery was collected by a T-type thermocouple (TT-T-30, Shanghai Laiying Technology Co., Ltd.) and transmitted to an Agilent (34970A, Keysight Technologies Co., Ltd.) acquisition device for monitoring. Finally, the experimental data was collected by the matching computer system to obtain the surface temperature change curve of the battery module during the charging and discharging process.

[0158] The temperature change curves obtained from the charge-discharge tests of the battery membrane arrays in Comparative Example 4, Comparative Example 2, and Example 2 are shown below. Figures 10-12 As shown, the infrared thermal imaging cloud image of the battery module during the constant current discharge process is as follows: Figure 13 As shown.

[0159] Depend on Figures 10-12 It can be seen that the highest temperature and the maximum temperature difference of the three battery modules at a 1 C discharge rate are both within 40℃ and 5℃, respectively. Heat dissipation is mainly carried out through heat conduction, and the phase change heat storage of the composite phase change material has not yet played a role. Figure 13 A uniform temperature distribution was observed. As the discharge rate increased to 1.5 C and 2 C, the temperature difference of the PEEA-Module rose to 5.5 ℃ and 9.1 ℃, respectively. This indicates that the PEEA's heat dissipation capacity was insufficient, failing to control the temperature difference within a safe range. The SSE-Module, under the same operating conditions, reduced the temperature difference by 1 ℃ and 3.2 ℃, respectively, attributed to the SSE's superior thermal conductivity. However, both modules exceeded their optimal operating range in terms of center temperature and temperature difference at a 2 C discharge rate, exhibiting significant heat accumulation. Figure 13(c)). In contrast, the SSEC3 maintained the center temperature and temperature difference of the battery module at 50.7℃ and 4.1℃, respectively, even at a 2C discharge rate. This temperature reduction is attributed to the SSEC3's excellent thermal stability, high thermal conductivity, and large latent heat capacity, which absorbs a significant amount of heat, thereby enhancing temperature control. Meanwhile, Figure 13 As shown in (b) and (c), the SSEC3-Module exhibits no severe heat accumulation and displays a uniform and mild heat distribution. These results demonstrate that the appropriate ratio of metal-organic coordination polymers, hydrated salt phase change materials, phase change temperature regulators, and thermal conductivity enhancers has a synergistic effect in battery thermal management. The SSEC3-based battery thermal management system exhibits excellent thermal management performance and is an effective thermal management method.

[0160] Test Example 9

[0161] The organic flame-retardant composite phase change material (PEEA) obtained in Comparative Example 4 and the organic-inorganic hydrated salt composite phase change material (SSEC3) obtained in Example 2 were respectively assembled with ternary 60Ah batteries to construct two five-cell battery modules, which were then fixed using fixtures and named PEEA-Module and SSEC3-Module, respectively. All batteries were fully charged to 100% SOC according to the normal charging procedure. A heating plate was used to heat the outermost battery surface to trigger thermal runaway. The thermal runaway process was recorded using a camera, and the temperature and voltage changes of each battery module were recorded to evaluate the effectiveness of PEEA and SSEC3 in preventing the propagation of thermal runaway in the battery pack.

[0162] Figure 14 (a) and (b) show the test results of thermal runaway and propagation behavior of the PEEA-Module and SSEC3-Module after the batteries were heated by the heating plate, respectively. It can be seen that the PEEA-Module showed no significant changes before 815s, but rapidly emitted flames at 816s, followed by intense burning and explosions over the next 52s, accompanied by large areas of smoke, making it impossible to see clearly with the camera. These behaviors were caused by the heating plate triggering thermal runaway in battery I. Subsequently, batteries II, III, IV, and V exploded and emitted flames at 1524s, 1899s, 2307s, and 2883s, respectively. They experienced intense burning, stable burning, and eventual extinguishing, accompanied by dense smoke. It is worth noting that the times required to trigger thermal runaway in batteries II, III, IV, and V were 686s, 377s, 402s, and 577s, respectively. Therefore, the PEEA module has a poor ability to delay the propagation of thermal runaway and cannot prevent its spread, posing a significant fire and thermal hazard.

[0163] In contrast, the thermal runaway triggered by the heating plate in battery I did not propagate within the battery module enclosed in SSEC3. Figure 14 As shown in (b), battery I rapidly emitted flames after 863 seconds, with the flames erupting multiple times over the next 46 seconds before gradually weakening and extinguishing completely. This is similar to the thermal runaway behavior of battery I in the PEEA-Module. However, the other batteries in the SSEC3-Module did not trigger thermal runaway. The physical samples of the two battery modules after testing show that the PEEA-Module was completely burned down to residual carbon, while the four materials and batteries in the SSEC3-Module remained intact. Figure 15 (a) and (b)). This can also be further verified by the weighing results of the battery module cells after the test. Figure 15 As shown in (a1) and (a2), the quality retention rate of the five cells in the PEEA-Module is around 60%, while the quality retention rate of batteries II to V in the SSEC3-Module is close to 100%. Figure 15 (b1) and (b2)). These results are attributed to the fact that SSEC3 dehydrates and evaporates at high temperatures, absorbing a large amount of heat while maintaining the stability of its own structure. On the other hand, after absorbing heat to saturation, SSEC3 can also act as a heat insulation layer, effectively preventing the propagation of thermal runaway.

[0164] Comparative Example 5

[0165] The composition of the organometallic coordination polymer by mass is as follows: 90 parts polyethylene glycol as organic ligand, 10 parts anhydrous magnesium chloride as metal ion ligand, and 50 mL anhydrous ethanol as solvent for the coordination reaction between the metal ion ligand and the organic ligand.

[0166] The preparation method of metal-organic coordination polymers is as follows:

[0167] S1: Place anhydrous magnesium chloride and anhydrous ethanol in a beaker and stir magnetically at 300 r / min for 60 min until the anhydrous magnesium chloride particles are completely dissolved to obtain the first mixture;

[0168] S2: Melt polyethylene glycol at 70°C and add it to the first mixture obtained above. Stir at 70°C and 400 r / min for 60 min to obtain the second mixture.

[0169] S3: The second mixture was placed in a vacuum drying oven and dried under vacuum at 100°C for 8 hours to evaporate the ethanol solvent, thus obtaining the organometallic coordination polymer, denoted as Comparative Backbone 1.

[0170] Comparative Example 6

[0171] The components of the comparative organometallic coordination polymer, by mass parts, are as follows: 80 parts polyethylene glycol as organic ligand, 20 parts anhydrous magnesium chloride as metal ion ligand, and 100 mL anhydrous ethanol as solvent for the coordination reaction between the metal ion ligand and the organic ligand.

[0172] The preparation method of the metal-organic coordination polymer is the same as that of Comparative Example 5, and the resulting metal-organic coordination polymer is referred to as Comparative Backbone 2.

[0173] Comparative Example 7

[0174] The composition of the metal-organic coordination polymer by mass is as follows: 70 parts polyethylene glycol as organic ligand, 30 parts anhydrous magnesium chloride as metal ion ligand, and 150 mL anhydrous ethanol as solvent for the coordination reaction between the metal ion ligand and the organic ligand.

[0175] The preparation method of the metal-organic coordination polymer is the same as that of Comparative Example 5, and the resulting metal-organic coordination polymer is referred to as Comparative Backbone 3.

[0176] Comparative Example 8

[0177] The composition of the organometallic coordination polymer by mass is as follows: 90 parts lauric acid as organic ligand, 10 parts anhydrous calcium chloride as metal ion ligand, and 50 mL anhydrous ethanol as solvent for the coordination reaction between the metal ion ligand and the organic ligand.

[0178] The preparation method of the metal-organic coordination polymer is the same as that of Comparative Example 5, and the resulting metal-organic coordination polymer is referred to as Comparative Backbone 4.

[0179] Comparative Example 9

[0180] The composition of the organometallic coordination polymer by mass is as follows: 80 parts lauric acid as organic ligand, 20 parts anhydrous calcium chloride as metal ion ligand, and 100 mL anhydrous ethanol as solvent for the coordination reaction between the metal ion ligand and the organic ligand.

[0181] The preparation method of the metal-organic coordination polymer is the same as that of Comparative Example 5, and the resulting metal-organic coordination polymer is referred to as Comparative Backbone 5.

[0182] Test Case 10

[0183] The leakage resistance of the comparison skeletons 1-5 was tested. The test procedure was as follows: different samples were prepared into Φ12×8mm... 3 The sample was placed on a heating platform and tested at 70℃, 100℃, 150℃, and 200℃ for 2 hours each. Digital photographs of the sample were recorded using a digital camera, and the morphological changes and leakage of the sample at each temperature were compared. The test results are as follows: Figures 16 to 19 As shown.

[0184] Comparative frameworks 1-3 were formed by reacting polyethylene glycol with anhydrous magnesium chloride in ethanol solvent and then drying. Test results showed that even at 70°C, significant leakage occurred with prolonged heating time, and the degree of leakage slightly decreased with decreasing polyethylene glycol (i.e., increasing metal ion ligands), indicating that simply adjusting the ratio could not fundamentally improve its temperature resistance. When the temperature rose to 100°C or above, all comparative frameworks experienced severe melting and leakage within 2 hours, proving that the coordination network formed by this system completely collapsed at high temperatures. Comparative frameworks 4-5, with the organic ligands replaced by lauric acid and the metal ions replaced by anhydrous calcium chloride, maintained their macroscopic shape at 70°C, but large-area leakage appeared on the filter paper, indicating that while this combination had some shape retention capability, it could not effectively encapsulate the internal components and also failed rapidly at high temperatures. Figures 17 to 19 The results of leak resistance tests at 100℃, 150℃, and 200℃ are shown. With increasing test temperature, the control skeletons 1-5 failed to maintain macroscopic shape stability and almost melted and leaked within a 2-hour test period. In contrast, the leak resistance test results of the metal-organic coordination polymers 1-5 formed from polyethylene glycol and calcium chloride in this invention are as follows: Figure 2 As shown in (a), these coordination polymers did not exhibit any leakage at 70°C during the 2-hour test. As the heating temperature increased, coordination polymers 3–5 demonstrated excellent thermal stability, showing no leakage even at 200°C.

[0185] Comparative Example 10: First, a coordination polymer framework was prepared, and then adsorbed hydrated salts were impregnated.

[0186] The composition of the organic-inorganic hydrated salt composite phase change material is the same as that in Example 1, based on parts by mass.

[0187] The preparation method of organic-inorganic hydrated salt composite phase change material is as follows:

[0188] S1: Polyethylene glycol was melted at 70°C. Anhydrous calcium chloride and anhydrous ethanol were placed in a beaker and magnetically stirred until the calcium chloride particles dissolved to form a calcium chloride ethanol solution. Then, the calcium chloride ethanol solution was added to the molten polyethylene glycol and stirred at 400 r / min for 60 min until it turned milky white. It was then placed in a vacuum drying oven at 90°C for 8 hours to obtain the coordination polymer skeleton.

[0189] S2: Sodium acetate trihydrate, sodium metasilicate nonahydrate and urea are placed in a constant temperature oil bath equipped with an electric stirrer and heated until melted. The mixture is stirred at 300 r / min for 60 min to obtain the first mixture.

[0190] S3: Add the first mixture to the above coordination polymer skeleton, and vacuum impregnate the coordination polymer skeleton to adsorb the first mixture to obtain the second mixture;

[0191] S4: Add expanded graphite to the second mixture obtained above, and stir at 70°C and a stirring speed of 500 r / min for 120 min to obtain the organic-inorganic hydrated salt composite phase change material.

[0192] Comparative Example 11: First, a coordination polymer framework was prepared, and then it was impregnated with adsorbed hydrated salts.

[0193] The composition of the organic-inorganic hydrated salt composite phase change material is the same as that in Example 2, based on parts by mass.

[0194] The preparation method of the organic-inorganic hydrated salt composite phase change material is the same as that of Comparative Example 10.

[0195] Comparative Example 12: First, a coordination polymer framework was prepared, and then impregnated with adsorbed hydrated salts.

[0196] The composition of the organic-inorganic hydrated salt composite phase change material is the same as that in Example 3, based on parts by mass.

[0197] The preparation method of the organic-inorganic hydrated salt composite phase change material is the same as that of Comparative Example 10.

[0198] Comparative Example 13: Using polyacrylic acid as an organic ligand

[0199] The composition of the organic-inorganic hydrated salt composite phase change material by mass parts is as follows:

[0200] 68 parts of sodium acetate trihydrate and 8.5 parts of sodium metasilicate nonahydrate were used as hydrated salt phase change materials, 8.5 parts of urea were used as phase change temperature regulators, 3.02 parts of polyacrylic acid were used as polymers of hydrophilic coordination crosslinking network compounds, 0.334 parts of cellulose nanofibers were used as mechanical strength enhancers of hydrophilic coordination crosslinking network compounds, and 11.64 parts of calcium ion solution were used as metal ion ligands.

[0201] The preparation method of organic-inorganic hydrated salt composite phase change material is as follows:

[0202] S1: Polyacrylic acid and cellulose nanofibers were dissolved in water to prepare a homogeneous solution. A calcium ion solution with a concentration of 0.1 mol / L was added and stirred until a gel was formed. The resulting gel was allowed to stand and freeze for 15 hours. Then, it was freeze-dried for 30 hours to obtain a hydrophilic coordination crosslinking network compound.

[0203] S2: Sodium acetate trihydrate, sodium metasilicate nonahydrate and urea are placed in a constant temperature oil bath equipped with an electric stirrer and heated until melted. The mixture is stirred at 300 r / min for 60 min to obtain the first mixture.

[0204] S3: Add the first mixture to the above-mentioned hydrophilic coordination crosslinking network compound, and vacuum impregnate the first mixture with the hydrophilic coordination crosslinking network compound to obtain a hydrated salt composite phase change material.

[0205] Test Example 11

[0206] The anti-leakage performance of the composite phase change materials obtained in proportions 10-13 was tested. The testing procedure was as follows: different samples were prepared into Φ12×8mm... 3 The sample was placed on a heating platform and tested at 70°C for 8 hours. Digital photographs of the sample were recorded using a digital camera to compare its morphological changes and leakage at each temperature. Simultaneously, the mass change of the sample was recorded every 2 hours to analyze its mass retention rate. The test results are as follows: Figure 20 As shown, the macroscopic shape of the composite phase change materials in comparative examples 10-12 did not change with increasing heating time, and there was no leakage of liquid phase change material on the filter paper. However, leakage traces appeared on the heated surface at the bottom of the samples. The leakage improved with decreasing organic ligands and increasing metal ion ligands. Figure 20 The mass retention results in (b) also show an increasing trend in shape stability for Comparative Examples 10-12, with mass retention rates of 94.2%, 96.7%, and 97.1% respectively after 8 hours of leak resistance testing. This indicates that the composite phase change materials (Comparative Examples 10-13) obtained by the two-step method of first preparing a coordination polymer framework and then impregnating it with adsorbed hydrated salts also have good thermal stability. In contrast, the leak resistance test results of Examples 1-3 under the same conditions are as follows: Figure 5 As shown, the mass retention rates of Examples 1-3 after 8 hours of leak resistance testing were 94.6%, 97.5%, and 98.1%, respectively, indicating that the composite phase change materials (Examples 1-3) obtained by the preferred one-step method of the present invention have superior thermal stability.

[0207] Furthermore, the composite phase change material prepared by the two-step method using a polyacrylic acid-based hydrophilic coordination crosslinking network in Comparative Example 13 exhibited poor anti-leakage performance. After continuous heating at 70°C for 8 hours, its mass retention rate was only 86.4%, far lower than that of Comparative Examples 10-12 (94.2%-97.1%) and Examples 1-3 (94.6%-98.1%). This result indicates that the pre-prepared gel skeleton (polyacrylic acid / cellulose nanofiber network) struggles to achieve uniform filling and tight encapsulation of hydrated salts during impregnation and adsorption, leading to insufficient encapsulation integrity and making the phase change material more prone to leakage upon heating. In contrast, the one-step method, through in-situ reaction to form a metal-organic coordination polymer skeleton, achieves molecular-level uniform composite of the phase change material and the skeleton matrix, thereby constructing a denser and more stable three-dimensional network structure, effectively improving the material's long-term sealing performance and thermal stability.

[0208] Test Example 12

[0209] The phase transition temperature and latent heat storage performance of the composite phase change materials obtained in Comparative Examples 10-13 were tested. The testing procedure was as follows: in a nitrogen atmosphere, a differential scanning calorimeter was used at a speed of 50 mL / min. -1 The flow rate is set to 5℃·min. -1 The operating temperature range is 0℃ to 200℃. The phase transition temperature and latent heat of the composite phase change material are obtained from the tested heat flow-temperature curve. The phase transition temperature is determined by the intersection of the extrapolated line with the heat flow-temperature curve and the baseline at the point of maximum slope of the peak value. The latent heat of phase change is determined by the peak area integral. The test results are as follows: Figure 21 As shown, the peak melting points and phase transition temperatures of comparative examples 10-12 are all in the range of 40 to 60 °C, but their latent heat storage performance is poor, at 150.1 J·g⁻¹ respectively. -1 100.4 J·g -1 and 68.3 J·g -1Compared to composite phase change materials prepared using the one-step method (Examples 1-3), the latent heat storage performance of the two methods decreased by 12.8%, 38.6%, and 54.7%, respectively. This indicates that the difference in latent heat storage performance between the two methods becomes more pronounced as the hydrated salt content decreases. This is attributed to the fact that the method of preparing the framework first and then impregnating and adsorbing creates a confined pore structure and interfacial resistance within the porous framework, making it difficult to achieve a uniform and sufficient filling of hydrated salt, resulting in some phase change materials failing to effectively participate in the thermal storage process. Simultaneously, potential surface blockage or incomplete wetting of the framework during the two-step method further reduces the actual loading of hydrated salt and its effective utilization rate during the phase change process. In contrast, the one-step method, through in-situ composite, allows the phase change material to be fully mixed with the framework matrix, forming a denser and more uniform composite structure, thus preserving the energy storage capacity of the phase change material itself to a greater extent. Especially at low hydrated salt contents, the effective capacity loss caused by insufficient adsorption in the two-step method is more significant, leading to a more pronounced decrease in latent heat performance. Furthermore, the thermochemical thermal storage performance of Comparative Examples 10-12 in the range of 110-130℃ was also inferior to that of Examples 1-3, decreasing by 60.4%, 35.1%, and 21.6% respectively compared to Examples 1-3. This indicates that the homogeneous composite structure formed by the one-step method also demonstrates its advantages in the high-temperature thermochemical thermal storage stage. The uniformly dispersed phase change material forms a more stable reaction interface and efficient mass transfer channels with the framework, allowing the dehydration / decomposition reaction to proceed more thoroughly. In contrast, the two-step method suffers from uneven adsorption and poor interfacial contact, resulting in incomplete reaction or isolation of some active materials at high temperatures, leading to a significant reduction in thermochemical thermal storage capacity. It is worth noting that when the phase change material content is high, the structural defects of the two-step method, such as pore blockage, have the most prominent hindering effect on mass transfer, thus Comparative Example 10 shows the largest performance gap compared to Example 1. As the content decreases, the effect of structural inhomogeneity is mitigated, and the gap with the one-step method also narrows relatively.

[0210] Furthermore, the DSC test results of Comparative Example 13 further confirm the above conclusions. Its latent heat in the 40-60℃ phase transition range is only 62.4 J·g. -1 The concentration was significantly lower than that of the comparative sample 10-12 (150.1 J·g) in the same temperature range. -1 Up to 68.3 J·g -1 This indicates that even with a more hydrophilic polyacrylic acid network as the adsorption framework, the inherent structural inhomogeneity of the two-step method still leads to a significant decrease in the actual effective loading and utilization rate of the phase change material. Its latent heat storage performance is even inferior to that of comparative examples 10-13, which use the same two-step method but with different framework structures. Notably, its latent heat in the thermochemical storage region at 110-130℃ is 809.8 J·g. -1This is mainly attributed to the use of water as a solvent in its preparation process. The water molecules themselves participate in the high-temperature dehydration and decomposition reaction of the hydrated salt, thus contributing additional thermochemical heat storage capacity. However, considering its extremely low latent heat of phase change and the aforementioned serious leakage problem (8-hour mass retention rate of only 86.4%), it can be judged that the structural stability of this material has significant defects. Although the introduction of water temporarily improves the apparent heat storage value in the high-temperature range, it also exacerbates the migration and leakage of the phase change material within the encapsulation structure. Its energy storage process is accompanied by significant material loss, and its long-term cycle stability is poor. This further highlights that although the two-step method using different skeletons may adjust the heat storage performance in a certain temperature range, it is difficult to achieve high latent heat, high stability, and high encapsulation integrity simultaneously over a wide temperature range. In contrast, the one-step method adopted in this invention achieves molecular-level uniform composite and stable encapsulation of the phase change material and the supporting matrix by constructing a metal-organic coordination polymer skeleton in situ, thus exhibiting superior and more balanced comprehensive performance in both phase change heat storage and high-temperature thermochemical heat storage stages.

[0211] In summary, under the coupling effect of the metal-organic coordination polymer and the hydrated salt phase change material, Example 2 (SSEC3) exhibits optimal thermal conductivity and thermal stability, fully utilizing the enormous latent heat storage and thermochemical storage capabilities of the hydrated salt. These results demonstrate that the design of organic-inorganic hydrated salt composite phase change materials provides an efficient and reliable solution for battery thermal safety, with broad application prospects.

[0212] 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. An organic-inorganic hydrated salt composite phase change material, characterized in that, The composition comprises the following components in parts by weight: 40-80 parts of hydrated salt phase change material, 10-50 parts of metal-organic coordination polymer, 2-10 parts of phase change temperature regulator, and 1-5 parts of thermal conductivity enhancer; wherein the metal-organic coordination polymer is formed by coordination of organic ligands and metal ion ligands; wherein the organic ligand is polyethylene glycol, and the metal ion ligand is a soluble calcium salt; wherein the mass ratio of the organic ligand to the metal ion ligand is 5-45:1-5; The preparation method of the organic-inorganic hydrated salt composite phase change material includes the following steps: A hydrated salt phase change material, a phase change temperature regulator, an organic ligand, a metal ion ligand, a solvent, and a thermal conductivity enhancer are mixed to obtain the organic-inorganic hydrated salt composite phase change material. The mixing is carried out while the hydrated salt phase change material is molten. The mixing includes: first mixing the hydrated salt phase change material and the phase change temperature regulator to obtain a first mixture; dissolving the metal ion ligand in the solvent to obtain a metal ion ligand solution; second mixing the metal ion ligand solution with the molten organic ligand to obtain a second mixture; third mixing the first mixture and the second mixture to obtain a third mixture; and fourth mixing the third mixture with the thermal conductivity enhancer to obtain the organic-inorganic hydrated salt composite phase change material.

2. The organic-inorganic hydrated salt composite phase change material according to claim 1, characterized in that, The hydrated salt phase change material includes one or more of sodium acetate trihydrate, sodium thiosulfate pentahydrate, sodium metasilicate nonahydrate, sodium pyrophosphate decahydrate, and disodium hydrogen phosphate dodecahydrate.

3. The organic-inorganic hydrated salt composite phase change material according to claim 1, characterized in that, The metal ion ligand is calcium chloride.

4. The organic-inorganic hydrated salt composite phase change material according to claim 1, characterized in that, The phase change temperature regulator includes one or more of potassium chloride, ammonium chloride, potassium nitrate, glycerol, urea, and glycine; the thermal conductivity enhancer includes one or more of boron nitride, silicon carbide, expanded graphite, and carbon nanotubes.

5. The method for preparing the organic-inorganic hydrated salt composite phase change material according to any one of claims 1 to 4, characterized in that, Includes the following steps: A hydrated salt phase change material, a phase change temperature regulator, an organic ligand, a metal ion ligand, a solvent, and a thermal conductivity enhancer are mixed to obtain the organic-inorganic hydrated salt composite phase change material; the mixing is carried out in a molten state of the hydrated salt phase change material; the mixing includes: a first mixing of the hydrated salt phase change material and the phase change temperature regulator to obtain a first mixture; The metal ion ligand is dissolved in a solvent to obtain a metal ion ligand solution. The metal ion ligand solution and molten organic ligand are then mixed for a second time to obtain a second mixture. The first mixture and the second mixture are then mixed for a third time to obtain a third mixture. The third mixture and a thermal conductivity enhancer are then mixed for a fourth time to obtain the organic-inorganic hydrated salt composite phase change material.

6. The preparation method according to claim 5, characterized in that, The mixing temperature is 60~90℃.

7. The application of the organic-inorganic hydrated salt composite phase change material according to any one of claims 1 to 4 or the organic-inorganic hydrated salt composite phase change material prepared by the preparation method according to any one of claims 5 to 6 in power batteries.

8. The application according to claim 7, characterized in that, The organic-inorganic hydrated salt composite phase change material is used in the thermal management system of power batteries.

9. A battery module, characterized in that, The organic-inorganic hydrated salt composite phase change material is prepared by any one of the organic-inorganic hydrated salt composite phase change materials according to any one of claims 1 to 4 or by any one of the preparation methods according to claims 5 to 6.

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