A double-scale encapsulated hydrated salt composite phase change material, a preparation method thereof, a battery module and application thereof

Abstract

This invention relates to the field of battery thermal safety technology, and particularly to a dual-scale encapsulated hydrated salt composite phase change material, its preparation method, battery module, and its application. The invention provides a dual-scale encapsulated hydrated salt composite phase change material, comprising a composite phase change material core and a dense protective layer encapsulated on the outer surface of the composite phase change material core. The raw materials for preparing the composite phase change material core include a eutectic hydrated salt phase change matrix, a thickener, hydrophilic fumed silica, and expanded graphite. The eutectic hydrated salt phase change matrix includes sodium thiosulfate pentahydrate and sodium acetate trihydrate. The dense protective layer is a UV-curable resin layer. The dual-scale encapsulated hydrated salt composite phase change material achieves synergistic optimization of the hydrated salt composite material in terms of low undercooling, high thermal conductivity, leakage resistance, and long-term cycle stability by constructing a dual-scale encapsulation structure of "microscopic adsorption-macroscopic coating."

Description

Technical Field

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

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

[0003] In view of this, the purpose of the present invention is to provide a dual-scale encapsulated hydrated salt composite phase change material and its preparation method, battery module and its application. The dual-scale encapsulated hydrated salt composite phase change material achieves synergistic optimization of hydrated salt composite materials in terms of low undercooling, high thermal conductivity, leakage resistance and long-term cycle stability by constructing a dual-scale encapsulation structure of "microscopic adsorption-macroscopic coating".

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a dual-scale encapsulated hydrated salt composite phase change material, comprising a composite phase change material core and a dense protective layer encapsulated on the outer surface of the composite phase change material core; The raw materials for preparing the composite phase change material core include a eutectic hydrated salt phase change matrix, a thickener, hydrophilic fumed silica, and expanded graphite. The eutectic hydrated salt phase change matrix includes sodium thiosulfate pentahydrate and sodium acetate trihydrate; The dense protective layer is a UV-curable resin layer.

[0005] Preferably, the mass ratio of sodium thiosulfate pentahydrate to sodium acetate trihydrate is (6.5~7.5):(2.5~3.5).

[0006] Preferably, the thickener includes one or more of sodium polyacrylate, carboxymethyl cellulose, and bentonite.

[0007] Preferably, the mass ratio of the eutectic hydrated salt phase change matrix to the thickener is (85~100):(1~3).

[0008] Preferably, the mass ratio of the eutectic hydrated salt phase change matrix to hydrophilic fumed silica is (85~100):(4~8).

[0009] Preferably, the mass ratio of the eutectic hydrated salt phase change matrix to expanded graphite is (85~100):(2~6).

[0010] This invention also provides a method for preparing the dual-scale encapsulated hydrated salt composite phase change material described in the above technical solution, comprising the following steps: Sodium thiosulfate pentahydrate and sodium acetate trihydrate were melt-mixed to obtain a eutectic hydrated salt phase change matrix; The eutectic hydrated salt phase change matrix is ​​mixed with a thickener to obtain a thickened and dispersed eutectic hydrated salt phase change material. The thickened and dispersed eutectic hydrated salt phase change material was melted and then mixed sequentially with hydrophilic fumed silica and expanded graphite to obtain a composite phase change material slurry. The composite phase change material slurry is molded to obtain a hydrated salt composite phase change material core material; The surface of the hydrated salt composite phase change material core is coated with a UV-curable resin and then UV-cured to obtain the dual-scale encapsulated hydrated salt composite phase change material.

[0011] Preferably, the melting and mixing temperature is 60~80℃, and the time is 0.3~0.6h; The temperature of the first mixing is 60~80℃, and the time is 0.3~0.6h; The mixing with hydrophilic fumed silica is carried out under stirring conditions, wherein the stirring speed is 400~600 rpm and the time is 0.3~0.6 h; The mixing with expanded graphite is carried out under stirring conditions, wherein the stirring speed is 800~1200 rpm and the time is 0.3~0.6 h; The UV curing light wavelength is 365 nm, and the intensity is 25~35 mW·cm. -2 The curing time is 30~90s.

[0012] The present invention also provides a battery module, including a battery module and a phase change material skeleton; The material of the phase change material skeleton is the dual-scale encapsulated hydrated salt composite phase change material described in the above technical solution or the dual-scale encapsulated hydrated salt composite phase change material prepared by the preparation method described in the above technical solution.

[0013] The present invention also provides the application of the battery module described in the above technical solution in energy storage devices and electric vehicles.

[0014] This invention provides a dual-scale encapsulated hydrated salt composite phase change material, comprising a composite phase change material core and a dense protective layer encapsulated on the outer surface of the composite phase change material core; the raw materials for preparing the composite phase change material core include a eutectic hydrated salt phase change matrix, a thickener, hydrophilic fumed silica, and expanded graphite; the eutectic hydrated salt phase change matrix includes sodium thiosulfate pentahydrate and sodium acetate trihydrate; the dense protective layer is a UV-curable resin layer. In this invention, hydrophilic fumed silica can form strong hydrogen bonds with the crystal water molecules of hydrated salts through its abundant surface silanol groups, constructing a three-dimensional nanoporous adsorption network to form a nanoconfining effect. This nanoconfining effect not only effectively inhibits the free migration of ions and phase separation of hydrated salts during phase transition, but also provides a large number of heterogeneous nucleation sites for hydrated salt crystallization on its rough surface, significantly reducing the crystallization energy barrier. Expanded graphite, with its open worm-like porous layered structure, strengthens the physical adsorption of molten hydrated salts through capillary forces, and constructs a continuous three-dimensional thermally conductive network by utilizing the high thermal conductivity of graphite sheets. The UV-curable resin undergoes rapid cross-linking polymerization under the action of a photoinitiator, forming a dense polymer protective layer on the surface of the composite material. This flexible polymer coating can not only adapt to volume changes during phase transition, but its excellent chemical inertness and mechanical strength can also effectively block water vapor escape and prevent high-temperature melt leakage, ultimately achieving a dual protection mechanism of micro-adsorption and macro-coating. Attached Figure Description

[0015] Figure 1 The results of the anti-leakage test of the hydrated salt composite phase change material described in Comparative Example 1 are shown. Figure 2 The leakage resistance test results are those of the dual-scale encapsulated hydrated salt composite phase change material described in Example 1. Figure 3 The image shows a vertical combustion test image of the hydrated salt composite phase change material described in Comparative Example 2. Figure 4 The image shows a vertical combustion test image of the dual-scale encapsulated hydrated salt composite phase change material described in Example 1. Figure 5 The image shows a vertical combustion test image of the hydrated salt composite phase change material described in Comparative Example 1. Figure 6The thermal management effects of the dual-scale encapsulated hydrated salt composite phase change material described in Example 1, the hydrated salt composite phase change material described in Comparative Example 1, and the hydrated salt composite phase change material described in Comparative Example 2 are shown. Figure 7 Supercooling test curves for uncomposite hydrated salt phase change matrix sodium thiosulfate pentahydrate (STP) and dual-scale encapsulated hydrated salt composite phase change materials described in Examples 1 and 3 (Example 3 corresponds to SPHE1+UV, and Example 1 corresponds to SPHE2+UV). Figure 8 The results are the cycle stability test results of the dual-scale encapsulated hydrated salt composite phase change material described in Example 1 and the hydrated salt composite phase change materials described in Comparative Examples 1 and 3. Detailed Implementation

[0016] This invention provides a dual-scale encapsulated hydrated salt composite phase change material, comprising a composite phase change material core and a dense protective layer encapsulated on the outer surface of the composite phase change material core; The raw materials for preparing the composite phase change material core include a eutectic hydrated salt phase change matrix, a thickener, hydrophilic fumed silica, and expanded graphite. The eutectic hydrated salt phase change matrix includes sodium thiosulfate pentahydrate and sodium acetate trihydrate; The dense protective layer is a UV-curable resin layer.

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

[0018] In this invention, the preferred mass ratio of sodium thiosulfate pentahydrate to sodium acetate trihydrate is (6.5~7.5):(2.5~3.5), more preferably 6.5:2.5, 6.5:3, 6.5:3.5, 7:2.5, 7:3, 7:3.5, 7.5:2.5, 7.5:3, or 7.5:3.5. In an embodiment of this invention, the mass ratio of sodium thiosulfate pentahydrate to sodium acetate trihydrate can be 7:3.

[0019] In this invention, the thickener preferably includes one or more of sodium polyacrylate, sodium carboxymethyl cellulose, and bentonite, more preferably sodium polyacrylate; when the thickener is two or more of the above-mentioned specific selections, this invention does not have any special limitation on the ratio of the above-mentioned specific substances, and they can be mixed in any ratio. In the embodiments of this invention, the thickener can be sodium polyacrylate.

[0020] In this invention, the thickener is preferably a thickener solution, and the mass concentration of the thickener solution is preferably 10-40%, more preferably 10%, 20%, 30%, 40% or 50%. In an embodiment of this invention, the mass concentration of the thickener solution can be 30%.

[0021] In this invention, the preferred mass ratio of the hydrated salt phase change matrix to the thickener is (85~100):(1~3), more preferably 85:1, 85:2, 85:3, 90:1, 90:2, 90:3, 95:1, 95:2, 95:3, 100:1, 100:2, or 100:3. In an embodiment of this invention, the mass ratio of the hydrated salt phase change matrix to the thickener can be 100:2. In this invention, the mass ratio of the hydrated salt phase change matrix to the thickener is understood as the mass ratio of the hydrated salt phase change matrix to the thickener solution.

[0022] In this invention, the preferred mass ratio of the eutectic hydrated salt phase change matrix to the hydrophilic fumed silica is (85~100):(4~8), more preferably 85:4, 85:5, 85:6, 85:7, 85:8, 90:4, 90:5, 90:6, 90:7, 90:8, 95:4, 95:5, 95:6, 95:7, 95:8, 100:4, 100:5, 100:6, 100:7, or 100:8. In embodiments of this invention, the mass ratio of the eutectic hydrated salt phase change matrix to the hydrophilic fumed silica can be 100:4, 100:6, or 100:8.

[0023] In this invention, the preferred mass ratio of the eutectic hydrated salt phase change matrix to expanded graphite is (85~100):(2~6), more preferably 85:2, 85:3, 85:4, 85:5, 85:6, 90:2, 90:3, 90:4, 90:5, 90:6, 95:2, 95:3, 95:4, 95:5, 95:6, 100:2, 100:3, 100:4, 100:5, or 100:6. In embodiments of this invention, the mass ratio of the eutectic hydrated salt phase change matrix to expanded graphite can be 100:4, 100:6, or 100:2.

[0024] This invention also provides a method for preparing the dual-scale encapsulated hydrated salt composite phase change material described in the above technical solution, comprising the following steps: Sodium thiosulfate pentahydrate and sodium acetate trihydrate were melt-mixed to obtain a eutectic hydrated salt phase change matrix; The eutectic hydrated salt phase change matrix is ​​mixed with a thickener to obtain a thickened and dispersed eutectic hydrated salt phase change material. The thickened and dispersed eutectic hydrated salt phase change material was melted and then mixed sequentially with hydrophilic fumed silica and expanded graphite to obtain a composite phase change material slurry. The composite phase change material slurry is molded to obtain a hydrated salt composite phase change material core material; The surface of the hydrated salt composite phase change material core is coated with a UV-curable resin and then UV-cured to obtain the dual-scale encapsulated hydrated salt composite phase change material.

[0025] This invention involves melting and mixing sodium thiosulfate pentahydrate and sodium acetate trihydrate to obtain a eutectic hydrated salt phase change matrix.

[0026] In this invention, the melting and mixing temperature is preferably 60~80℃, more preferably 60℃, 65℃, 70℃, 75℃ or 80℃; the time is preferably 0.3~0.6h, more preferably 0.3h, 0.4h, 0.5h or 0.6h. In an embodiment of this invention, the melting and mixing temperature can be 75℃ and the time can be 0.5h. In this invention, the melting and mixing is preferably carried out under stirring conditions. This invention does not impose any special limitations on the stirring process; any process well known to those skilled in the art can be used.

[0027] After obtaining the eutectic hydrated salt phase change matrix, the present invention mixes the eutectic hydrated salt phase change matrix with a thickener to obtain a thickened and dispersed eutectic hydrated salt phase change material.

[0028] In this invention, the first mixing process is preferably carried out under magnetic stirring conditions, in which a thickener is added to the molten eutectic hydrated salt phase change matrix. This invention does not impose any special limitations on the process of adding the thickener, and any process known to those skilled in the art can be used.

[0029] In this invention, the temperature of the first mixing is preferably 60-80°C, more preferably 60°C, 65°C, 70°C, 75°C, or 80°C; the time is preferably 0.3-0.6 hours, more preferably 0.3 hours, 0.4 hours, 0.5 hours, or 0.6 hours. In an embodiment of this invention, the temperature of the first mixing can be 70°C, and the time can be 0.5 hours. In this invention, the first mixing is preferably carried out under stirring conditions. This invention does not impose any special limitations on the stirring process; any process well known to those skilled in the art can be used.

[0030] After obtaining the thickened and dispersed eutectic hydrated salt phase change material, the present invention melts the thickened and dispersed eutectic hydrated salt phase change material and mixes it sequentially with hydrophilic fumed silica and expanded graphite to obtain a composite phase change material slurry.

[0031] In this invention, the mixing process with hydrophilic fumed silica and expanded graphite is preferably carried out after the thickener-dispersed eutectic hydrated salt phase change material has melted, followed by the sequential addition of hydrophilic fumed silica and expanded graphite. This invention does not impose any special limitations on the process of mixing the hydrophilic fumed silica and expanded graphite; any process well-known to those skilled in the art can be used. In this invention, the mixing process with hydrophilic fumed silica and expanded graphite is a micro-impregnation and encapsulation process.

[0032] In this invention, the mixing with hydrophilic fumed silica is carried out under stirring conditions. The stirring speed is preferably 400-600 rpm, more preferably 400 rpm, 450 rpm, 500 rpm, 550 rpm, or 600 rpm; the stirring time is preferably 0.3-0.6 h, more preferably 0.3 h, 0.4 h, 0.5 h, or 0.6 h. In an embodiment of this invention, the stirring speed can be 500 rpm, and the stirring time can be 0.5 h.

[0033] In this invention, the mixing with expanded graphite is carried out under stirring conditions. The stirring speed is preferably 800-1200 rpm, more preferably 800 rpm, 900 rpm, 1000 rpm, 1100 rpm, or 1200 rpm; the stirring time is preferably 0.3-0.6 h, more preferably 0.3 h, 0.4 h, 0.5 h, or 0.6 h. In an embodiment of this invention, the stirring speed can be 1000 rpm, and the stirring time can be 0.5 h.

[0034] After obtaining the composite phase change material slurry, the present invention molds the composite phase change material slurry to obtain a hydrated salt composite phase change material core.

[0035] The present invention does not impose any special limitations on the molding process, and any process known to those skilled in the art can be used.

[0036] After the molding process is completed, the present invention preferably includes cooling. The present invention does not impose any special limitations on the cooling process, and any process known to those skilled in the art can be used.

[0037] After obtaining the hydrated salt composite phase change material core, the present invention coats the surface of the hydrated salt composite phase change material core with a UV-curable resin and performs UV curing to obtain the dual-scale encapsulated hydrated salt composite phase change material.

[0038] In this invention, the coating method is preferably dip coating. This invention does not impose any special limitations on the dip coating process, and any process well known to those skilled in the art can be used.

[0039] In this invention, the ultraviolet-curable resin is preferably a polyurethane acrylate ultraviolet-curable resin.

[0040] In this invention, the wavelength of the ultraviolet light curing is preferably 365 nm, and the intensity is preferably 25~35 mW·cm. -2 More preferably 25mW·cm -2 26mW·cm -2 27mW·cm -2 28mW·cm -2 29mW·cm -2 30mW·cm -2 31mW·cm -2 32mW·cm -2 33mW·cm -2 34mW·cm -2 Or 35mW·cm -2 The curing time is preferably 30-90 seconds, more preferably 30 seconds, 40 seconds, 50 seconds, 60 seconds, 70 seconds, 80 seconds, or 90 seconds. In embodiments of the present invention, the wavelength of the ultraviolet light used for curing can be 365 nm, and the intensity can be 30 mW·cm. -2 The time can be 60 seconds.

[0041] In this invention, using sodium thiosulfate pentahydrate / sodium acetate trihydrate eutectic hydrate as the phase change matrix and hydrophilic fumed silica and expanded graphite as the composite framework materials, the preparation method of this invention involves thoroughly mixing the molten hydrated salt with a thickener solution, then sequentially compounding it with hydrophilic fumed silica and expanded graphite, and finally encapsulating it with UV-cured resin to successfully construct a composite phase change material with a dual-scale encapsulation structure. In this composite phase change material, the hydrated salt matrix provides significant latent heat of phase change and dehydration endothermic capacity; the hydrophilic fumed silica effectively suppresses supercooling and promotes heterogeneous nucleation through its nanoporous structure and abundant surface hydroxyl groups; the expanded graphite constructs a continuous three-dimensional thermally conductive network, significantly improving the material's thermal conductivity; and the UV-cured resin forms a tight encapsulation layer that ensures the material maintains excellent structural integrity and leak-proof performance under high-temperature conditions. Ultimately, this achieves a synergistic unity of efficient energy storage, rapid heat transfer, and long-term stability in thermal management applications of the phase change material.

[0042] The present invention also provides a battery module, including a battery module and a phase change material skeleton; The material of the phase change material skeleton is the dual-scale encapsulated hydrated salt composite phase change material described in the above technical solution or the dual-scale encapsulated hydrated salt composite phase change material prepared by the preparation method described in the above technical solution.

[0043] The present invention does not impose any special limitations on the battery module; any module well known to those skilled in the art can be used.

[0044] This invention also provides the application of the battery module described above in energy storage devices and electric vehicles. This invention does not impose any special limitations on the methods for these applications; methods well-known to those skilled in the art can be used.

[0045] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0046] Example 1 70g of sodium thiosulfate pentahydrate and 30g of sodium acetate trihydrate were placed in a beaker and heated to melt in an oil bath at 75°C. The mixture was stirred continuously for 0.5h under magnetic stirring to obtain a homogeneous eutectic hydrated salt phase change matrix. 2g of 30% sodium polyacrylate solution was slowly added dropwise to the eutectic hydrated salt phase change matrix, and the mixture was stirred at 70°C for 0.5h to obtain a thickened dispersion system. 6g of hydrophilic fumed silica was added to the thickening and dispersion system in three portions, and the mixture was stirred at 500 rpm for 0.5 h to complete the microporous adsorption encapsulation. 4g of expanded graphite was added, and the mixture was stirred at 1000 rpm for 0.5 h to obtain a uniform composite phase change material slurry. The composite phase change material slurry was injected into a cylindrical silicone mold and cooled to room temperature to cure, resulting in a composite phase change material core material with a diameter of 35 nm and a thickness of 10 mm. The composite phase change material core is impregnated with a polyurethane acrylate UV-curable resin and cured under UV light (wavelength 365nm, intensity 30mW / cm²). 2 (With a time of 60s), a dense protective layer with a thickness of 200μm was formed, resulting in a dual-scale encapsulated hydrated salt composite phase change material.

[0047] Example 2 70g of sodium thiosulfate pentahydrate and 30g of sodium acetate trihydrate were placed in a beaker and heated to melt in an oil bath at 75°C. The mixture was stirred continuously for 0.5h under magnetic stirring to obtain a homogeneous eutectic hydrated salt phase change matrix. 2g of 30% sodium polyacrylate solution was slowly added dropwise to the eutectic hydrated salt phase change matrix, and the mixture was stirred for 0.5h to obtain a thickened dispersion system. 4g of hydrophilic fumed silica was added to the thickening and dispersion system in three portions, and the mixture was stirred at 500 rpm for 0.5 h to complete the microporous adsorption and encapsulation. 6g of expanded graphite was added, and the mixture was stirred at 1000 rpm for 0.5 h to obtain a uniform composite phase change material slurry. The composite phase change material slurry was injected into a cylindrical silicone mold and cooled to room temperature to cure, resulting in a composite phase change material core material with a diameter of 35 nm and a thickness of 10 mm. The composite phase change material core is impregnated with a polyurethane acrylate UV-curable resin and cured under UV light (wavelength 365nm, intensity 30mW / cm²). 2 (With a time of 60s), a dense protective layer with a thickness of 200μm was formed, resulting in a dual-scale encapsulated hydrated salt composite phase change material.

[0048] Example 3 70g of sodium thiosulfate pentahydrate and 30g of sodium acetate trihydrate were placed in a beaker and heated to melt in an oil bath at 75°C. The mixture was stirred continuously for 0.5h under magnetic stirring to obtain a homogeneous eutectic hydrated salt phase change matrix. 2g of 30% sodium polyacrylate solution was slowly added dropwise to the eutectic hydrated salt phase change matrix, and the mixture was stirred for 0.5h to obtain a thickened dispersion system. 8g of hydrophilic fumed silica was added to the thickening and dispersion system in three portions, and the mixture was stirred at 500 rpm for 0.5 h to complete the microporous adsorption encapsulation. 2g of expanded graphite was added, and the mixture was stirred at 1000 rpm for 0.5 h to obtain a uniform composite phase change material slurry. The composite phase change material slurry was injected into a cylindrical silicone mold and cooled to room temperature to cure, resulting in a composite phase change material core material with a diameter of 35 nm and a thickness of 10 mm. The composite phase change material core is impregnated with a polyurethane acrylate UV-curable resin and cured under UV light (wavelength 365nm, intensity 30mW / cm²). 2 (With a time of 60s), a dense protective layer with a thickness of 200μm was formed, resulting in a dual-scale encapsulated hydrated salt composite phase change material.

[0049] Comparative Example 1 70g of sodium thiosulfate pentahydrate and 30g of sodium acetate trihydrate were placed in a beaker and heated to melt in an oil bath at 75°C. The mixture was stirred continuously for 0.5h under magnetic stirring to obtain a homogeneous eutectic hydrated salt phase change matrix. 2g of 30% sodium polyacrylate solution was slowly added dropwise to the eutectic hydrated salt phase change matrix, and the mixture was stirred for 0.5h to obtain a thickened dispersion system. 10g of expanded graphite was added to the thickening and dispersing system in three portions and stirred at 1000rpm for 0.5h to obtain a uniform composite phase change material slurry. The composite phase change material slurry was injected into a cylindrical silicone mold and cooled to room temperature to cure, resulting in a hydrated salt composite phase change material with a diameter of 35 nm and a thickness of 10 mm.

[0050] Comparative Example 2 55g of paraffin wax was used as the phase change matrix and melted in an oil bath at 75℃. Then, 11g of styrene-ethylene-butene-styrene block copolymer was added as a thickener and stirred at 600rpm for 1h to ensure full cross-linking. Subsequently, 4g of expanded graphite was added as a thermally conductive filler and stirred at 800rpm for 0.5h. Finally, 30g of melamine was added as a flame retardant and stirred at 800rpm for 0.5h until the mixture was homogeneous, thus obtaining the composite slurry. The composite slurry was injected into a cylindrical silicone mold and cooled to room temperature to cure, resulting in an organic composite phase change material with a diameter of 35 nm and a thickness of 10 mm.

[0051] Comparative Example 3 70g of sodium thiosulfate pentahydrate and 30g of sodium acetate trihydrate were placed in a beaker and heated to melt in an oil bath at 75°C. The mixture was stirred continuously for 0.5h under magnetic stirring to obtain a homogeneous eutectic hydrated salt phase change matrix. 2g of 30% sodium polyacrylate solution was slowly added dropwise to the eutectic hydrated salt phase change matrix, and the mixture was stirred for 0.5h to obtain a thickened dispersion system. 4g of hydrophilic fumed silica was added to the thickening and dispersion system in three portions, and the mixture was stirred at 500 rpm for 0.5 h to complete the microporous adsorption and encapsulation. 6g of expanded graphite was added, and the mixture was stirred at 1000 rpm for 0.5 h to obtain a uniform composite phase change material slurry. The composite phase change material slurry was injected into a cylindrical silicone mold and cooled to room temperature to cure, resulting in a hydrated salt composite phase change material with a diameter of 35 nm and a thickness of 10 mm.

[0052] Test case Leakage resistance test: The specific test procedure is as follows: The composite phase change material core material described in Example 1 and the organic composite phase change material described in Comparative Example 2 are placed on a constant temperature heating table at 70°C. The appearance morphology and mass change before and after the leakage resistance test are observed and recorded at regular intervals. The thermal stability and mass change of the organic composite phase change material in Example 1 are characterized by the mass change curve during the leakage resistance test. Figure 1The leakage resistance test results of the hydrated salt composite phase change material described in Comparative Example 1 are shown (from left to right, the test sample morphology records at 0h, 1h, 2h, 3h, 4h and 5h). Figure 2 The leakage resistance test results of the dual-scale encapsulated hydrated salt composite phase change material described in Example 1 (from left to right, the morphology records of the test samples at 0h, 1h, 2h, 3h, 4h, and 5h) are provided by [the relevant authority / organization]. Figures 1-2 It can be seen that the composite phase change material core material described in Example 1 has almost no leakage at high temperature in the anti-leakage test, that is, the dual-scale encapsulation strategy effectively solves the leakage problem of hydrated salt in the phase change process; Vertical burning test: The test procedure is in accordance with UL94 standard; Figure 3 The images show vertical combustion test results of the hydrated salt composite phase change material described in Comparative Example 2 (from left to right, the vertical combustion sample morphology records at 1s, 5s, 10s, 15s, 20s, and 25s). Figure 4 The images shown are vertical combustion test images of the dual-scale encapsulated hydrated salt composite phase change material described in Example 1 (from left to right, the vertical combustion sample morphology records at 1s, 5s, 10s, 15s, 20s and 25s). Figure 5 The images shown are vertical combustion test images of the hydrated salt composite phase change material described in Comparative Example 1 (from left to right, these are records of the vertical combustion sample morphology at 1s, 5s, 10s, 15s, 20s, and 25s). Figure 3 It is known that although melamine can effectively suppress the spread of flames, there is still a risk of material dripping at high temperatures, and the molten dripping material can cause the cotton fibers below to ignite; therefore, Figures 4-5 It can be seen that the composite phase change material described in Example 1 and the composite phase change material described in Comparative Example 1 exhibit the best flame retardant performance. They can quickly self-extinguish after the fire source is removed, and there is no melting and dripping phenomenon during the entire combustion process, and the cotton wadding below remains intact. Thermal management effect: Figure 6 The thermal management effects of the dual-scale encapsulated hydrated salt composite phase change material described in Example 1, Comparative Example 1, and Comparative Example 2 (the upper figure shows the temperature of the battery module under operating conditions, and the lower figure shows the temperature difference of the battery module under operating conditions) are shown in the figure below. Figure 6 It can be seen that the composite phase change material core material described in Example 3 maintains the battery operating temperature below the safe operating temperature of 50°C compared with the composite phase change material core material described in Comparative Example 1 and the organic composite phase change material described in Comparative Example 2, and the maximum temperature difference of its battery module is reduced by 2~3°C compared with the composite phase change material core material described in Comparative Example 1 and the organic composite phase change material described in Comparative Example 2. Supercooling resistance test: The specific test procedure was as follows: The uncomposite hydrated salt phase change matrix sodium thiosulfate pentahydrate (STP) and the dual-scale encapsulated hydrated salt composite phase change materials described in Examples 1 and 3 (Example 3 corresponds to SPHE1+UV, and Example 1 corresponds to SPHE2+UV) were placed in a constant temperature and humidity chamber, and a program was set to first heat to 70°C and then cool down to 25°C. Thermocouples were used to monitor the temperature change curves of the materials. The test results are as follows: Figure 7 As shown, by Figure 7 It can be seen that no obvious nucleation phenomenon was detected in sodium thiosulfate pentahydrate, that is, no obvious phase transition plateau was observed. In contrast, the dual-scale encapsulated hydrated salt composite phase change materials described in Examples 1 and 3 exhibited obvious phase transition plateaus. The supercooling of the dual-scale encapsulated hydrated salt composite phase change material described in Example 1 was only 0.2℃, while the supercooling of the dual-scale encapsulated hydrated salt composite phase change material described in Example 3 was 3.6℃. This indicates that the supercooling phenomenon of the encapsulated hydrated composite phase change material was suppressed to a large extent. Cyclic stability test: The specific test procedure was as follows: The dual-scale encapsulated hydrated salt composite phase change material (SPHE2+UV) described in Example 1, along with the hydrated salt composite phase change materials described in Comparative Example 1 (SPE) and Comparative Example 3 (SPHE2), were placed in a constant temperature and humidity chamber. A program was set to first cool down to 25°C, then heat up to 70°C, and then cool down to 25°C, with 80 cycles. The latent heat of the sample was removed and tested every 40 cycles. The test results are as follows: Figure 8 As shown, by Figure 8 It can be seen that the latent heat of the hydrated salt composite phase change material described in Comparative Example 1 and the hydrated salt composite phase change material described in Comparative Example 3 decreased to 87.2% and 84.8% of their original values, respectively; while the latent heat of the dual-scale encapsulated hydrated salt composite phase change material described in Example 1 still maintained a latent heat of 96.6%, indicating that the cycling stability of the hydrated salt composite material after dual-scale encapsulation was greatly improved.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A dual-scale encapsulated hydrated salt composite phase change material, characterized in that, It includes a composite phase change material core and a dense protective layer encapsulated on the outer surface of the composite phase change material core; The raw materials for preparing the composite phase change material core include a eutectic hydrated salt phase change matrix, a thickener, hydrophilic fumed silica, and expanded graphite. The eutectic hydrated salt phase change matrix includes sodium thiosulfate pentahydrate and sodium acetate trihydrate; The dense protective layer is a UV-curable resin layer.

2. The dual-scale encapsulated hydrated salt composite phase change material as described in claim 1, characterized in that, The mass ratio of sodium thiosulfate pentahydrate to sodium acetate trihydrate is (6.5~7.5):(2.5~3.5).

3. The dual-scale encapsulated hydrated salt composite phase change material as described in claim 1, characterized in that, The thickener includes one or more of sodium polyacrylate, carboxymethyl cellulose, and bentonite.

4. The dual-scale encapsulated hydrated salt composite phase change material as described in claim 1 or 3, characterized in that, The mass ratio of the eutectic hydrated salt phase change matrix to the thickener is (85~100):(1~3).

5. The dual-scale encapsulated hydrated salt composite phase change material as described in claim 1, characterized in that, The mass ratio of the eutectic hydrated salt phase change matrix to hydrophilic fumed silica is (85~100):(4~8).

6. The dual-scale encapsulated hydrated salt composite phase change material as described in claim 1, characterized in that, The mass ratio of the eutectic hydrated salt phase change matrix to expanded graphite is (85~100):(2~6).

7. The method for preparing the dual-scale encapsulated hydrated salt composite phase change material according to any one of claims 1 to 6, characterized in that, Includes the following steps: Sodium thiosulfate pentahydrate and sodium acetate trihydrate were melt-mixed to obtain a eutectic hydrated salt phase change matrix; The eutectic hydrated salt phase change matrix is ​​mixed with a thickener to obtain a thickened and dispersed eutectic hydrated salt phase change material. The thickened and dispersed eutectic hydrated salt phase change material was melted and then mixed sequentially with hydrophilic fumed silica and expanded graphite to obtain a composite phase change material slurry. The composite phase change material slurry is molded to obtain a hydrated salt composite phase change material core material; The surface of the hydrated salt composite phase change material core is coated with a UV-curable resin and then UV-cured to obtain the dual-scale encapsulated hydrated salt composite phase change material.

8. The preparation method according to claim 7, characterized in that, The melting and mixing temperature is 60~80℃, and the time is 0.3~0.6h; The temperature of the first mixing is 60~80℃, and the time is 0.3~0.6h; The mixing with hydrophilic fumed silica is carried out under stirring conditions, wherein the stirring speed is 400~600 rpm and the time is 0.3~0.6 h; The mixing with expanded graphite is carried out under stirring conditions, wherein the stirring speed is 800~1200 rpm and the time is 0.3~0.6 h; The UV curing light wavelength is 365 nm, and the intensity is 25~35 mW·cm. -2 The curing time is 30~90s.

9. A battery module, characterized in that, Including battery modules and phase change material framework; The material of the phase change material skeleton is the dual-scale encapsulated hydrated salt composite phase change material according to any one of claims 1 to 6 or the dual-scale encapsulated hydrated salt composite phase change material prepared by the preparation method according to claim 7 or 8.

10. The application of the battery module of claim 9 in energy storage devices and electric vehicles.

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