Three-dimensional heat conduction structure, method for preparing three-dimensional heat conduction structure, phase change heat storage material and method for preparing phase change heat storage material

Abstract

The invention discloses a three-dimensional heat conduction structure which comprises a one-dimensional heat conduction nanometer material and a two-dimensional heat conduction nanometer material, the mass ratio of the one-dimensional heat conduction nanometer material to the two-dimensional heat conduction nanometer material is 2: 1-4: 1, and the one-dimensional heat conduction nanometer material and the two-dimensional heat conduction nanometer material are mutually wound and communicated to form a heat conduction channel. And the heat conduction channel can keep a three-dimensional heat conduction structure in a water phase. In addition, the invention further provides a method for preparing the three-dimensional heat conduction structure, a phase change heat storage material and a method for preparing the phase change heat storage material.

Description

Technical Field

[0001] This application relates to the field of thermal storage, and in particular to a three-dimensional thermally conductive structure and a method for preparing the same, and a phase change thermal storage material and a method for preparing the same. Background Technology

[0002] Thermal energy storage is a key technology for improving energy efficiency and achieving carbon neutrality. Among various thermal storage materials, hydrated salt phase change materials have been widely studied due to their advantages such as high thermal density and low cost. However, the inherently low thermal conductivity of these materials severely limits their practical application, resulting in slow system charge and discharge rates and low power density.

[0003] To address this issue, existing technologies typically employ methods such as adding high thermal conductivity fillers (e.g., carbon materials, metal particles) or constructing a three-dimensional thermally conductive framework. However, these methods all face a common core technical challenge: to achieve effective thermal conductivity enhancement, a high proportion of fillers must be introduced, which significantly reduces the heat storage density of the composite material and increases its viscosity and cost, severely compromising the economic viability and application feasibility of hydrated salt phase change materials. Summary of the Invention

[0004] The main objective of this application is to provide a three-dimensional thermally conductive structure to improve the thermal conductivity of hydrated salts with extremely low filler content, while maintaining their high heat storage density and good fluidity.

[0005] Additionally, this application also provides a method for preparing a three-dimensional thermally conductive structure, a phase change thermal storage material, and a method for preparing the same. A three-dimensional thermally conductive structure includes a one-dimensional thermally conductive nanomaterial and a two-dimensional thermally conductive nanomaterial, wherein the mass ratio of the one-dimensional thermally conductive nanomaterial to the two-dimensional thermally conductive nanomaterial is 2:1-4:1, and the one-dimensional thermally conductive nanomaterial and the two-dimensional thermally conductive nanomaterial are intertwined and interconnected to form a thermally conductive channel, wherein the thermally conductive channel can maintain the three-dimensional thermally conductive structure in an aqueous phase.

[0006] In some possible implementations, the one-dimensional thermally conductive nanomaterial includes at least one of carbon nanotubes, silver nanowires, copper nanowires, aluminum nanowires, boron nitride nanotubes, and silicon carbide nanowires.

[0007] In some possible implementations, the two-dimensional thermally conductive nanomaterial includes at least one of graphene, graphene oxide, boron nitride nanosheets, MXene, molybdenum disulfide, and black phosphorus.

[0008] In some possible implementations, the mass ratio of the one-dimensional thermally conductive nanomaterial to the two-dimensional thermally conductive nanomaterial is 2:1 to 3:1.

[0009] In some possible embodiments, the surface of the one-dimensional thermally conductive nanomaterial has oxygen-containing functional groups, which are obtained by one or more of the following methods: oxidizing the carbon nanotubes to introduce hydroxyl and carboxyl groups; oxidizing the silver nanowires to form silver-oxygen bonds and hydroxyl groups; oxidizing or alkali treating the copper nanowires to form a copper oxide layer on the surface; treating the aluminum nanowires with an alkaline solution to form a hydroxylated alumina layer; oxidizing the boron nitride nanotubes with oxygen plasma or wet chemical oxidation to introduce boron-oxygen bonds and hydroxyl groups; and oxidizing the silicon carbide nanowires with wet chemical oxidation to introduce a surface hydroxyl layer.

[0010] In some possible embodiments, the surface of the two-dimensional thermally conductive nanomaterial has polar functional groups, which are obtained by one or more of the following methods: by oxidizing and partially reducing the graphene; by amine grafting modification of the graphene oxide; by oxygen plasma treatment of the boron nitride nanosheets; by acid or fluoride-assisted exfoliation or alkali treatment of the MXene; by ethylenediamine functionalization of the molybdenum disulfide; or by polyethylene glycol composite of the black phosphorus.

[0011] In some possible implementations, the three-dimensional thermally conductive structure is obtained by achieving mutual entanglement and self-assembly in an alcohol solvent.

[0012] A method for preparing a three-dimensional thermally conductive structure includes: performing surface oxygen-containing functionalization treatment on a one-dimensional thermally conductive nanomaterial; performing polar functionalization treatment on a two-dimensional thermally conductive nanomaterial; mixing the one-dimensional thermally conductive nanomaterial and the two-dimensional thermally conductive nanomaterial at a mass ratio of 2:1-4:1 to form a solid mixture; mixing the solid mixture with a solvent and a dispersant; and dispersing the mixture by stirring and ultrasonication to form a uniform dispersion system; and removing the solvent to allow the one-dimensional thermally conductive nanomaterial and the two-dimensional thermally conductive nanomaterial to intertwine and form a through-hole three-dimensional thermally conductive structure.

[0013] In some possible implementations, the mass fraction of the dispersion system is 1, and the mass fraction of the dispersant is 0.1-0.5%, wherein the dispersant includes at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, polyethylene glycol, Tween 80, sodium cholate, and polyvinylpyrrolidone.

[0014] In some possible implementations, the solvent includes an alcohol solvent, the ultrasonic dispersion power is 200-500W, the time is 20-45min, and the solvent removal temperature is 80-100℃ for 2-6h.

[0015] In some possible embodiments, the surface of the one-dimensional thermally conductive nanomaterial has oxygen-containing functional groups, which are obtained by one or more of the following methods: the one-dimensional thermally conductive nanomaterial is carbon nanotubes refluxed with concentrated nitric acid at about 110°C for 4-8 hours to introduce oxygen-containing functional groups; the one-dimensional thermally conductive nanomaterial is copper nanowires and surface-treated with a mixed solution of NaOH and hydrogen peroxide at room temperature to 50°C for 1-3 hours; the one-dimensional thermally conductive nanomaterial is silver nanowires and surface-treated with a 0.1-0.5 vol% hydrogen peroxide solution at room temperature for 1-2 hours; the one-dimensional thermally conductive nanomaterial is aluminum nanowires and obtained by reacting with NaOH mixture at 25-40°C for 30-60 minutes.

[0016] In some possible embodiments, the surface of the two-dimensional thermally conductive nanomaterial has polar functional groups, which are obtained through one or more of the following methods: the two-dimensional thermally conductive nanomaterial is graphene and hydroxyl, carboxyl, or epoxy groups are introduced through oxidation and partial reduction; the two-position thermally conductive nanomaterial is graphene oxide and amino groups are introduced through amine grafting modification; the two-dimensional thermally conductive nanomaterial is boron nitride nanosheets and treated with 100-200W oxygen plasma for 5-15 min to introduce boron-oxygen bonds and hydroxyl groups on the surface; the two-dimensional thermally conductive nanomaterial is MXene and after HF etching, it is treated with HCl and LiF for assisted exfoliation or with 0.1mol / L NaOH solution at room temperature for about 2 h to form hydroxyl groups on the surface; the two-dimensional thermally conductive nanomaterial is molybdenum disulfide and is stirred with ethylenediamine at about 80°C for about 12 h to introduce amino groups on the surface; the two-dimensional thermally conductive nanomaterial is black phosphorus and mixed with polyethylene glycol at a mass ratio of 1:10-20 to form hydroxyl and ether bond-like polar functional groups on the surface.

[0017] A phase change thermal storage material comprises: one-dimensional thermally conductive nanomaterials and two-dimensional thermally conductive nanomaterials, a dispersant, a thickener, an inorganic salt, water, and a nucleating agent. The mass ratio of the one-dimensional thermally conductive nanomaterials to the two-dimensional thermally conductive nanomaterials is 2:1-4:1. The total mass of water and inorganic salts is 100%. The total amount of the one-dimensional and two-dimensional thermally conductive nanomaterials added is 1-5%. The amount of the dispersant added is 0.1-0.5%. The amount of the thickener added is 0.5-5%. The amount of the nucleating agent added is 1-3%. The amount of inorganic salts is 27-57%.

[0018] In some possible implementations, the one-dimensional thermally conductive nanomaterial includes at least one of carbon nanotubes, silver nanowires, copper nanowires, aluminum nanowires, boron nitride nanotubes, and silicon carbide nanowires; the two-dimensional thermally conductive nanomaterial includes at least one of graphene, graphene oxide, boron nitride nanosheets, MXene, molybdenum disulfide, and black phosphorus.

[0019] In some possible implementations, the dispersant includes at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, polyethylene glycol, Tween 80, sodium cholate, and polyvinylpyrrolidone.

[0020] In some possible embodiments, the thickener includes at least one selected from sodium carboxymethyl cellulose, guar gum, xanthan gum, sodium alginate, gum arabic, corn starch, cyclodextrin, hydroxypropyl methylcellulose, hydroxyethyl cellulose, sodium polyacrylate, polyacrylate, polyvinyl alcohol, bentonite, kaolin, and aluminum silicate.

[0021] In some possible implementations, the inorganic salt includes at least one of magnesium sulfate, sodium acetate, trisodium phosphate, and calcium nitrate, and the water includes at least one of ultrapure water, deionized water, and tap water.

[0022] In some possible embodiments, the nucleating agent includes at least one of barium sulfate, barium carbonate, barium chloride, strontium sulfate, disodium hydrogen phosphate dodecahydrate, sodium hydrogen phosphate decahydrate, sodium chloride, potassium chloride, sorbitol, aluminum oxide, silicon dioxide, and titanium oxide.

[0023] In some possible implementations, the actual amount of water added is based on the theoretical crystallization water content of the target hydrated salt and adjusted within the range of 105%-110% to compensate for evaporation losses.

[0024] A method for preparing phase change thermal storage materials includes: performing surface oxygen-containing functionalization treatment on one-dimensional thermally conductive nanomaterials and polar functionalization treatment on two-dimensional thermally conductive nanomaterials; mixing the one-dimensional and two-dimensional thermally conductive nanomaterials at a mass ratio of 2:1-4:1 to obtain a solid mixture; mixing the solid mixture with a solvent and a dispersant, and then dispersing it by stirring and ultrasonication to form a uniform dispersion system; removing the solvent under heating conditions to allow the one-dimensional and two-dimensional thermally conductive nanomaterials to synergistically self-assemble into a solid mixture. A three-dimensional thermally conductive structure is formed; the three-dimensional thermally conductive structure is added to the water and ultrasonically treated until it becomes a gel; a thickener is added to the resulting gel system in two steps, wherein, in the first step, 1 / 10 of the thickener is added; an inorganic salt is added and reacted with the water under stirring and heating conditions to generate an inorganic hydrated salt; in the second step, the remaining 9 / 10 of the thickener is added, and a nucleating agent is added and stirred and dispersed to obtain the phase change thermal storage material, wherein the mass of the three-dimensional thermally conductive structure is 1%-5% of the mass of the inorganic hydrated salt.

[0025] In some possible implementations, the ultrasonic treatment time is 5-30 min and the stirring speed is 300-600 rpm.

[0026] In some possible embodiments, the dispersant has a mass fraction of 0.1-0.5%, and the dispersant includes at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, polyethylene glycol, Tween 80, sodium cholate, and polyvinylpyrrolidone.

[0027] In some possible implementations, the solvent is an alcohol solvent, the ultrasonic dispersion power is 200-500W, the time is 20-45min, and the solvent is removed at a temperature of 80-100℃ for 2-6h.

[0028] In some possible implementations, the actual amount of water added is based on the theoretical amount of crystallization water of the inorganic hydrated salt and adjusted in the range of 105%-110% to compensate for evaporation losses.

[0029] In some possible implementations, the inorganic salt is anhydrous sodium acetate and reacts with the water at 50°C to 65°C to produce sodium acetate trihydrate.

[0030] In some possible embodiments, the nucleating agent is added in an amount of 1-3% of the inorganic hydrated salt, and the nucleating agent includes at least one of barium sulfate, barium carbonate, barium chloride, strontium sulfate, disodium hydrogen phosphate dodecahydrate, sodium hydrogen phosphate decahydrate, sodium chloride, potassium chloride, sorbitol, aluminum oxide, silicon dioxide, or titanium oxide.

[0031] In some possible embodiments, the surface of the one-dimensional thermally conductive nanomaterial undergoes oxygen-containing functionalization treatment, which includes one or more of the following methods: when the one-dimensional thermally conductive nanomaterial is a carbon nanotube, it is refluxed with concentrated nitric acid at approximately 110°C for 4-8 hours to achieve oxygen-containing functionalization of the surface; when the one-dimensional thermally conductive nanomaterial is a copper nanowire, it is surface oxidized by reacting a mixed solution of NaOH and hydrogen peroxide at room temperature to 50°C for 1-3 hours; when the one-dimensional thermally conductive nanomaterial is a silver nanowire, it is reacted with a hydrogen peroxide solution with a volume fraction of 0.1-0.5% at room temperature for 1-2 hours to form silver-oxygen bonds and hydroxyl sites; when the one-dimensional thermally conductive nanomaterial is an aluminum nanowire, it is reacted with NaOH solution at 25-40°C for 30-60 minutes to obtain a surface hydroxylated aluminum oxide layer.

[0032] In some possible embodiments, the surface of the two-dimensional thermally conductive nanomaterial is subjected to polar functionalization treatment, which includes one or more of the following methods: oxidizing and partially reducing graphene to introduce hydroxyl, carboxyl, or epoxy groups onto the surface; modifying graphene oxide with amine grafting to introduce amino groups onto the surface; treating boron nitride nanosheets with oxygen plasma to introduce boron-oxygen bonds and hydroxyl groups onto the surface; treating MXene with acid or alkali to form hydroxyl groups on the surface; functionalizing molybdenum disulfide with ethylenediamine to introduce amino groups onto the surface; and compositing black phosphorus with polyethylene glycol to form hydroxyl and ether-like polar functional groups on the surface.

[0033] In this application, a three-dimensional thermally conductive network is formed by compositing one-dimensional and two-dimensional thermally conductive nanomaterials at a mass ratio of 2:1 to 4:1 and then filling them with inorganic hydrated salts at a low filling amount of 1-5%. This significantly improves the thermal conductivity of the phase change thermal storage material while maintaining high thermal density. A dispersant ensures uniform distribution of the nanofiller, a thickener improves the system's rheology and inhibits phase separation, inorganic salts and water constitute the main thermal storage matrix, and a nucleating agent promotes crystal formation and reduces supercooling. This achieves improved thermal conductivity of the hydrated salt system with extremely low filling amounts, while maintaining high thermal density, low supercooling, and good flowability. The material as a whole exhibits excellent thermal stability and cycle reliability. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0035] Figure 1 This is a flowchart illustrating a method for preparing a three-dimensional thermally conductive structure according to an embodiment of this application.

[0036] Figure 2 This is a flowchart illustrating a method for preparing phase change thermal storage materials according to an embodiment of this application.

[0037] Figure 3 This is a schematic diagram of the structure of a phase change thermal storage material provided in an embodiment of this application.

[0038] Figure 4 The images show the DSC spectra of the phase change thermal storage materials in Examples 1 to 3.

[0039] Figure 5 The diagram shows the supercooling performance of the phase change thermal storage materials in Examples 1 to 3.

[0040] Figure 6The thermal conductivity diagrams are for the phase change thermal storage materials in Examples 1 to 3 and sodium acetate trihydrate in Comparative Example 5.

[0041] Figure 7 The graph shows the thermal conductivity of the phase change thermal storage material in Example 1 and Comparative Examples 1 to 5.

[0042] Figure 8 The images shown are DSC spectra of Embodiment 1 and Comparative Examples 2 to 5 of this application.

[0043] Figure 9 The images are DSC spectra of Example 1 and Comparative Example 5 of this application before and after 200 cycles.

[0044] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0045] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0046] Please see Figure 1 One embodiment of this application provides a method for preparing a three-dimensional thermally conductive structure, comprising: S1: Surface oxygen-containing functionalization treatment is performed on one-dimensional thermally conductive nanomaterials to enhance hydrophilicity and dispersibility and reduce interfacial thermal resistance.

[0047] In this embodiment, the one-dimensional thermally conductive nanomaterial includes one of carbon nanotubes, silver nanowires, copper nanowires, aluminum nanowires, boron nitride nanotubes, and silicon carbide nanowires. Step S1 specifically includes at least one or more of the following steps: S11: Surface oxygen-containing functionalization treatment of carbon nanotubes. For example, carbon nanotubes are mixed with concentrated nitric acid at a mass ratio of 5-15:1 and refluxed at 110℃ for 4-8 hours; after the reaction, they are washed with deionized water until the pH is 6-7 and dried at 60-80℃ to obtain carbon nanotubes with -OH / -COOH introduced on the surface.

[0048] S12: Surface functionalization of silver nanowires with oxygen-containing groups. For example, treatment in 0.1-0.5 vol% hydrogen peroxide solution at room temperature for 1-2 h (silver nanowires: solution = 1:10-20), followed by washing and drying at 50-60℃ to obtain sparse Ag-O / -OH sites on the surface.

[0049] S13: Treat the surface of copper nanowires with oxygen-containing functional groups. For example, in a mixed solution of 0.1-0.5 mol / L NaOH and 0.1-0.5 vol% hydrogen peroxide, react at a mass ratio of copper nanowires to the mixed solution of 1:10-20 for 1-3 hours at room temperature to 50°C. Then wash with deionized water until neutral and dry to obtain copper nanowires with hydroxyl and copper oxide functional groups introduced on the surface.

[0050] S13: Surface functionalization of aluminum nanowires with oxygen-containing groups. For example, react with 0.01-0.1 mol / L NaOH solution at 25-40℃ for 30-60 min, wash until neutral, and dry at 50-60℃ to obtain a thin layer of hydroxylated aluminum oxide surface layer.

[0051] S14: Polar functionalization treatment of boron nitride nanotubes. For example, treatment with oxygen plasma at 80-150W for 5-10 min, or gentle oxidation with 0.05mol / L NaOH + 0.1vol% hydrogen peroxide for 1-2 h, to introduce BO / -OH sites.

[0052] S15: Surface functionalization of silicon carbide nanowires with oxygen-containing groups. For example, ammonia-hydrogen peroxide-water (1:1:5, volume ratio) is reacted at 70℃ for 15-30 min to introduce a -OH enrichment layer.

[0053] S2: Polar functionalization of two-dimensional thermally conductive nanomaterials is performed to improve the interfacial bonding strength with one-dimensional materials and the matrix, maintain heat transfer channels, and provide out-of-plane anchoring active sites.

[0054] In this embodiment, the two-dimensional thermally conductive nanomaterial includes one of graphene, graphene oxide, boron nitride nanosheets, MXene, molybdenum disulfide, and black phosphorus. Step S2 specifically includes at least one or more of the following steps: S21: Oxidation and partial reduction of graphene. For example, graphene oxide (GO) is prepared using a modified Hummers process. The Hummers process uses natural graphite as a raw material, which is mixed with concentrated sulfuric acid under ice bath conditions. Potassium permanganate is slowly added as the main oxidant, and the reaction temperature is controlled to not exceed 20°C to prevent violent exothermic reactions. After the reaction is complete, the temperature is raised to 35-40°C and stirring is continued for 1-2 hours. Then, hydrogen peroxide is slowly added dropwise to terminate the reaction, causing the system color to change from dark brown to golden yellow. After multiple washings to neutrality and drying, GO is obtained. Subsequently, it is reduced at 200-400°C for 2-4 hours to obtain partially reduced graphene (rGO), retaining appropriate amounts of -COOH, -OH, and epoxy groups to maintain dispersibility and interfacial activity.

[0055] S22: Amine grafting modification of graphene oxide. For example, GO is dispersed in water, ethylenediamine (GO:EDA=1:10-20, mass ratio) is added, and the mixture is stirred at 80℃ for 12h to introduce amino groups.

[0056] S23: Oxygen plasma treatment of boron nitride nanosheets. For example, treatment at 100-200W for 5-15 min introduces polar BO / -OH sites.

[0057] S24: Perform acid / fluoride-assisted stripping or alkaline treatment on MXene. For example, HF etching followed by HCl / LiF-assisted stripping, or 0.1 mol / L NaOH at room temperature for about 2 hours to increase the -OH end group density. MXene is a class of two-dimensional transition metal carbides, nitrides, or carbonitrides obtained by selective etching of MAX phase precursors, with the general formula M... n+1 X n T x In this system, M represents a transition metal element (such as titanium, niobium, vanadium, etc.), X represents carbon and / or nitrogen, and T represents a surface end group (such as hydroxyl, oxide, or fluorine group, etc.).

[0058] S25: Functionalization of molybdenum disulfide (MoS2) with ethylenediamine (EDA). For example, MoS2:EDA = 1:20-50 (mass ratio), stirred at 80°C for 12 h.

[0059] S26: Polyethylene glycol (PEG) composites are formed on black phosphorus. For example, black phosphorus and PEG (molecular weight 2k-10k) are mixed at a ratio of 1:10-20 and incubated at room temperature for 6-12 hours to obtain a PEG-BP composite structure.

[0060] S3: Mix one-dimensional thermally conductive nanomaterials and two-dimensional thermally conductive nanomaterials at a mass ratio of 2:1 to 4:1 to form a solid mixture.

[0061] S4: Mix the solid mixture with solvent and dispersant, and then disperse it by stirring and ultrasonication to form a uniform dispersion system.

[0062] In this embodiment, step S4 includes: S41: The solvent is an alcohol-based solvent. Add 2-8g of one-dimensional material and 0.5-4g of two-dimensional material to 1000mL of methanol. Simultaneously, add a dispersant at a mass fraction of 0.1-0.5% of the dispersion system. The dispersant is selected from one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, polyethylene glycol, Tween 80, sodium cholate, or polyvinylpyrrolidone, with an addition amount of 0.79-3.96g. Pre-disperse the dispersion system by magnetic stirring at room temperature for 1-3 hours, then ultrasonically disperse it at 200-500W power for 20-45 minutes, intermittently cooling during this period to prevent material structure damage and solvent overheating.

[0063] S5: Remove the solvent to enable one-dimensional thermally conductive nanomaterials and two-dimensional thermally conductive nanomaterials to synergistically self-assemble and form a continuous three-dimensional thermally conductive structure.

[0064] In this embodiment, step S5 specifically includes: S51: Raise the temperature of the dispersion system to 80-100℃ and maintain it for 2-6 hours to allow methanol to evaporate completely, promote the co-entanglement and self-assembly of one-dimensional and two-dimensional materials, and form a uniform, stable, and interconnected three-dimensional thermally conductive structure.

[0065] One embodiment of this application provides a three-dimensional thermally conductive structure, including a one-dimensional thermally conductive nanomaterial and a two-dimensional thermally conductive nanomaterial. The mass ratio of the one-dimensional thermally conductive nanomaterial to the two-dimensional thermally conductive nanomaterial is 2:1-4:1. The one-dimensional thermally conductive nanomaterial and the two-dimensional thermally conductive nanomaterial are intertwined and interconnected to form a thermally conductive channel. The thermally conductive channel can maintain the three-dimensional thermally conductive structure in an aqueous phase.

[0066] In this embodiment, the mass ratio of one-dimensional thermally conductive nanomaterials to two-dimensional thermally conductive nanomaterials is 2:1 to 3:1. The one-dimensional thermally conductive nanomaterials include one of carbon nanotubes, silver nanowires, copper nanowires, aluminum nanowires, boron nitride nanotubes, and silicon carbide nanowires. The two-dimensional thermally conductive nanomaterials include one of graphene, graphene oxide, boron nitride nanosheets, MXene, molybdenum disulfide, and black phosphorus.

[0067] In this embodiment, the surface of the one-dimensional thermally conductive nanomaterial has oxygen-containing functional groups to enhance hydrophilicity and dispersibility. These oxygen-containing functional groups are obtained through one or more of the following methods: oxidation of carbon nanotubes to introduce hydroxyl and carboxyl groups; mild oxidation of silver nanowires to form silver-oxygen bonds and hydroxyl groups; oxidation or alkaline treatment of copper nanowires to form a copper oxide layer on the surface; alkaline solution treatment of aluminum nanowires to form a hydroxylated alumina layer; oxygen plasma or wet chemical oxidation of boron nitride nanotubes to introduce boron-oxygen bonds and hydroxyl groups; and wet chemical oxidation of silicon carbide nanowires to introduce a surface hydroxyl layer.

[0068] Two-dimensional thermally conductive nanomaterials possess polar functional groups on their surfaces to enhance interfacial bonding. These polar functional groups are obtained through one or more of the following methods: oxidation and partial reduction of graphene; amine grafting modification of graphene oxide; oxygen plasma treatment of boron nitride nanosheets; acid or fluoride-assisted exfoliation or alkali treatment of MXene; ethylenediamine functionalization of molybdenum disulfide; and polyethylene glycol composite of black phosphorus.

[0069] In some embodiments, the three-dimensional thermally conductive structure is obtained by achieving co-entanglement self-assembly in an alcohol solvent. Specifically, treated one-dimensional thermally conductive nanomaterials and two-dimensional thermally conductive nanomaterials are mixed at a predetermined mass ratio, and appropriate amounts of alcohol solvent and dispersant are added. The mixture is stirred and ultrasonically dispersed to form a uniform dispersion system, with the concentration of the three-dimensional thermally conductive structure in the dispersion system being 2-10 mg / mL. Subsequently, the alcohol solvent is removed under heating conditions, allowing the one-dimensional and two-dimensional thermally conductive nanomaterials to co-assemble and construct a continuous three-dimensional thermally conductive structure.

[0070] Please see Figure 2 An embodiment of this application also provides a method for preparing phase change thermal storage materials, comprising: S6: Provide the three-dimensional thermally conductive structure from step S5.

[0071] S7: Add the three-dimensional thermally conductive structure to water and sonicate it until it becomes a gel. The actual amount of water added is based on the theoretical crystal water content of the inorganic hydrated salt and adjusted within the range of 105%-110% to compensate for evaporation loss. The sonication time is 5-30 min, preferably 20 min, and the stirring speed is 300-600 rpm.

[0072] S8: Add the thickener to the resulting gel system in two steps. In the first step, add 1 / 10 of the thickener.

[0073] In this embodiment, the thickener includes at least one of sodium carboxymethyl cellulose, guar gum, xanthan gum, sodium alginate, gum arabic, corn starch, cyclodextrin, hydroxypropyl methylcellulose, hydroxyethyl cellulose, sodium polyacrylate, polyacrylate, polyvinyl alcohol, bentonite, kaolin, and aluminum silicate.

[0074] S9: Add inorganic salt and react it with water under stirring and heating conditions to generate inorganic hydrated salt. The three-dimensional thermally conductive structure is added at 1% to 5% of the inorganic hydrated salt. The total amount of thickener added is 0.5-5% of the mass of the inorganic hydrated salt. The inorganic salt includes at least one of magnesium sulfate, sodium acetate, trisodium phosphate, and calcium nitrate, and the water includes at least one of ultrapure water, deionized water, and tap water. Preferably, the inorganic salt is anhydrous sodium acetate, which reacts with water at 50℃-65℃ to generate sodium acetate trihydrate.

[0075] S10: In the second step, add the remaining 9 / 10 of the thickener, along with the nucleating agent, and stir to disperse to obtain the phase change thermal storage material. Figure 3In this phase change thermal storage material, the three-dimensional thermally conductive structure is synergistically constructed from one-dimensional and two-dimensional high thermal conductivity nanomaterials within the phase change material matrix. One-dimensional thermally conductive nanomaterials (such as carbon nanotubes and metal nanowires) form a continuous linear network in space, providing an efficient longitudinal thermal conduction path. Two-dimensional thermally conductive nanomaterials (such as graphene and boron nitride nanosheets) are distributed in planar structures within the network gaps, forming multi-point contacts and interfacial overlaps through surface-line interweaving with the one-dimensional materials, thereby achieving the connection of multi-dimensional thermal conduction pathways. The two types of nanomaterials are interconnected through physical entanglement, van der Waals forces, and polar functional group interactions, forming a stable three-dimensional thermally conductive network. This thermally conductive network is uniformly dispersed within the phase change thermal storage material, maintaining a spatial support framework even in the liquid phase, thus significantly improving the overall thermal conductivity of the material and suppressing phase separation. This thermally conductive network enables rapid heat conduction and dispersion within the system, ensuring uniform heat flow and energy conversion efficiency during the phase change process. This provides a foundation for achieving composite phase change thermal storage materials with high thermal conductivity, high thermal storage density, and low subcooling.

[0076] In this embodiment, step S10 includes: S101: After adding the remaining 9 / 10 of the thickener in the second step, the following steps are also included: stirring at 300-600 rpm for 10-30 minutes to ensure thorough dispersion and prevent phase separation of the materials. S102: Adding nucleating agent and stirring to disperse includes stirring at 300-600 rpm for 10-30 minutes to ensure uniform dispersion of the phase change thermal storage material.

[0077] In this embodiment, the amount of nucleating agent added is 1-3% of the mass of the inorganic hydrated salt. The nucleating agent includes at least one of barium sulfate, barium carbonate, barium chloride, strontium sulfate, disodium hydrogen phosphate dodecahydrate, sodium hydrogen phosphate decahydrate, sodium chloride, potassium chloride, sorbitol, aluminum oxide, silicon dioxide, or titanium oxide.

[0078] The following specific embodiments further illustrate the embodiments of this application and their beneficial effects, with the aim of providing a clearer explanation of this application and not constituting a limitation on the scope of this application.

[0079] Example 1 First, 0.4 g of hydroxylated carbon nanotubes (CNTs, obtained by reflux oxidation at 110°C for 6 hours using concentrated nitric acid at a mass ratio of 10:1) were weighed and mixed with 0.2 g of graphene oxide (GNP, prepared using a modified Hummers method, with a monolayer content >85% after ultrasonic exfoliation), at a mass ratio of approximately 2:1. The one-dimensional and two-dimensional materials were then added to 1000 mL of methanol to prepare a total concentration of 6.5 mg / mL. 2 g of polyethylene glycol (approximately 0.2% by mass) was added as a dispersant. The mixture was pre-dispersed by magnetic stirring at room temperature for 2 hours, followed by ultrasonication at 400 W for 30 minutes, with a 1-minute cooling interval every 5 minutes during ultrasonication to prevent structural damage. After completion, the system temperature was raised to 90°C and maintained for 4 hours to allow the methanol to evaporate, forming a three-dimensional thermally conductive network structure of co-entangled carbon nanotubes and graphene oxide.

[0080] The obtained three-dimensional structure was added to deionized water, with the water volume being 41% of the mass of the subsequent sodium acetate trihydrate (SAT or S). For example, if 20g of sodium acetate trihydrate is needed, 8.2g of water should be added. The system was sonicated at 400W for 20 minutes to form a gel-like structure. The mass of the three-dimensional structure was 3% of the mass of the sodium acetate trihydrate.

[0081] Subsequently, 0.06 g of carboxymethyl cellulose (CMC), representing 1 / 10 of the total planned addition, was added and stirred at 400 rpm for 15 minutes. Next, 11.8 g of anhydrous sodium acetate was added, and the mixture was stirred while being heated to 60°C, resulting in the exothermic formation of sodium acetate trihydrate, forming a homogeneous hydrated salt composite system. Then, the remaining 0.54 g of CMC was added, and the mixture was stirred at 500 rpm for 20 minutes to improve the stability of the system. Finally, 0.4 g of disodium hydrogen phosphate dodecahydrate (DSP) was added as a nucleating agent (approximately 2% of the mass of sodium acetate trihydrate), and the mixture was stirred at 500 rpm for 15 minutes to achieve uniform dispersion, resulting in a phase change thermal storage material with stable structure, excellent thermal conductivity, and no supercooling or phase separation.

[0082] Example 2 Surface treatment of copper nanowires was performed by mixing 0.2 mol / L NaOH with 0.2 vol% hydrogen peroxide at a mass ratio of 1:15 (copper nanowires to solution). The mixture was reacted at room temperature for 2 hours, followed by washing and drying to obtain hydroxylated copper nanowires. 0.3 g of the treated copper nanowires were weighed and mixed with 0.1 g of boron nitride nanosheets treated with oxygen plasma (150 W, 10 min). 100 mL of methanol was added, bringing the total system concentration to 4 mg / mL. 0.3 g of polyvinylpyrrolidone (PVP) was added as a dispersant, and the mixture was stirred at room temperature for 2 hours, sonicated at 400 W for 25 minutes, and intermittently cooled. The system was then heated to 85 °C and maintained for 3 hours to form a three-dimensional thermally conductive structure.

[0083] The three-dimensional thermally conductive structure was added to tap water, with the water volume being 42% of the mass of the subsequent anhydrous sodium acetate. The system was subjected to high-power sonication for 15 minutes until it reached a gel state. Then, 0.04 g of hydroxypropyl methylcellulose (HPMC) (1 / 10 of the planned thickener) was added, and the mixture was stirred for 10 minutes. Next, 8.4 g of anhydrous sodium acetate was added, and the mixture was stirred and heated to 40°C to dissolve and release heat, forming sodium acetate trihydrate. The remaining 0.36 g of HPMC was then added, and the mixture was stirred at 500 rpm for 20 minutes. Finally, 0.4 g of silica (approximately 2% of the system mass) was added as a nucleating agent, and the mixture was stirred at 500 rpm for 15 minutes to obtain the phase change thermal storage material. The mass of the three-dimensional thermally conductive structure was 2% of the mass of sodium acetate trihydrate.

[0084] Example 3 Silver nanowires were treated with 0.3 vol% hydrogen peroxide at a silver nanowire:solution mass ratio of 1:15 and reacted at room temperature for 1 hour, followed by washing and drying. 0.2 g of the treated silver nanowires were mixed with 0.1 g of MXene (etched with HF followed by 0.2 mol / L HCl and LiF-assisted exfoliation), and 50 mL of methanol was added, resulting in a total concentration of 6 mg / mL. 0.15 g of Tween 80 was added as a dispersant, and the mixture was stirred for 1 hour, sonicated at 300 W for 20 minutes, and then heated to 90 °C and maintained for 3 hours. After the methanol evaporated, a three-dimensional structure was formed.

[0085] The three-dimensional structure was added to deionized water, with the water volume being 40% of the mass of the subsequent anhydrous sodium acetate. The system was sonicated for 20 minutes until it reached a gel state. 0.01 g of guar gum (1 / 10 of the total thickener) was added, and the mixture was stirred for 10 minutes. Then, 5 g of anhydrous sodium acetate was added, and the mixture was stirred and heated to 50℃~65℃, preferably 50℃. Next, 0.09 g of guar gum was added, and the mixture was stirred at 500 rpm for 15 minutes. Finally, 0.1 g of barium carbonate (2% of the system mass) was added as a nucleating agent, and the mixture was stirred at 500 rpm for 15 minutes to obtain a phase change thermal storage material with a stable structure and good thermal conductivity. The mass of the three-dimensional structure was 1% of the mass of sodium acetate trihydrate.

[0086] The thermodynamic properties, subcooling properties, and thermal conductivity properties of the phase change thermal storage materials in Examples 1-3 are described below.

[0087] like Figure 4 As shown, the phase change thermal storage materials of Examples 1-3 all exhibited obvious exothermic peaks in the range of 55-65℃, with Example 1 showing the highest latent heat of phase change at 267 J / g; Examples 2 and 3 showed 255 J / g and 248 J / g, respectively. The exothermic peaks of the three samples were all relatively sharp, corresponding to a concentrated exothermic crystallization process, indicating that the prepared phase change thermal storage materials have good phase change consistency and thermal stability.

[0088] like Figure 5As shown, the temperature-time curves of the phase change thermal storage materials in Examples 1-3 all exhibit smooth transitions under the same cooling conditions, with clear heat release plateaus and almost no supercooling. Example 1 begins to release heat at approximately 52°C, with no significant delay in the temperature recovery phase; the initial heat release temperatures of Examples 2 and 3 are slightly lower.

[0089] like Figure 6 As shown, the thermal conductivity of the phase change thermal storage materials in Examples 1-3 is significantly higher than that of pure sodium acetate trihydrate. Example 1 reaches approximately 1.4 W / (m·K), more than twice that of the control sample; Examples 2 and 3 are approximately 1.1 W / (m·K) and 1.3 W / (m·K), respectively. These results indicate that the three-dimensional interconnected thermally conductive network formed by the synergistic use of one-dimensional and two-dimensional thermally conductive nanomaterials significantly improves the overall thermal conductivity of the composite phase change thermal storage material.

[0090] It can be observed that the composite phase change thermal storage materials described in Examples 1-3, while ensuring high latent heat, exhibit almost no supercooling, and a significantly improved thermal conductivity, demonstrating excellent thermal management performance and cycle stability. This verifies the effectiveness of the "three-dimensional thermally conductive structure construction + two-step thickening nucleation regulation" technical approach proposed in this invention in improving the thermal conductivity and stability of phase change materials.

[0091] The following systematic comparison between Comparative Examples 1 to 5 and Example 1 analyzes the role of each key component in the three-dimensional heat conduction network, and verifies the rationality and performance advantages of the formulation and structure described in Example 1.

[0092] Comparative Example 1 No carbon nanotubes (CNTs) were added; the amount of graphene nanosheets (GNPs) used was 0.6 g (0.2 g in Example 1). The remaining formulation and process conditions were consistent with those in Example 1.

[0093] Comparative Example 2 No graphene nanosheets (GNPs) were added; the amount of carbon nanotubes (CNTs) was 0.6 g (0.4 g in Example 1). The remaining formulation and process conditions were consistent with those in Example 1.

[0094] Comparative Example 3 No graphene nanosheets (GNPs) were added; the amount of carbon nanotubes (CNTs) used was 0.4 g (0.4 g in Example 1). The remaining formulation and process conditions were consistent with those in Example 1.

[0095] Comparative Example 4 No graphene nanosheets (GNPs) were added; the amount of carbon nanotubes (CNTs) was 0.2 g. The remaining formulation and process conditions were consistent with those in Example 1.

[0096] Comparative Example 5 Carboxymethyl cellulose (CMC), disodium hydrogen phosphate dodecahydrate (DSP), carbon nanotubes (CNTs) and graphene nanosheets (GNPs) were not added. Sodium acetate trihydrate (SAT) 20g was used as the matrix as a baseline control.

[0097] The following is a comparison table of key formulation parameters between Example 1 and Comparative Examples 1 to 5: The performance of Example 1 and Comparative Examples 1 to 5 is evaluated by comparing thermal conductivity, heat flux, and cycle stability.

[0098] Figure 7 The graph shows the thermal conductivity performance of the phase change thermal storage material in Example 1 and Comparative Examples 1 to 5. It can be seen that, based on pure sodium acetate trihydrate (SAT, denoted as Comparative Example 5), the increase in thermal conductivity of each composite sample is as follows: S-CMC3-DSP2-CNT1, 33.87%; S-CMC3-DSP2-CNT2, 38.71%; S-CMC3-DSP2-CNT3, 41.94%; S-CMC3-DSP2-GNP3, 48.39%. Example 1 (S-CMC3-DSP2-CNT2-GNP1) shows the highest increase at 125.81%. Therefore, a single filler (CNT only or GNP only) can moderately improve thermal conductivity, while the synergistic three-dimensional thermal conductive network of CNT+GNP can significantly reduce thermal resistance, resulting in a multiplier increase in thermal conductivity.

[0099] Figure 8 The following are the DSC spectra of Examples 1 and Comparative Examples 2 to 5 of this application. The latent heat of fusion (J / g) obtained from the DSC curves is: approximately 303.7 J / g for pure SAT; approximately 267.4 J / g for Example 1; the latent heat of other samples containing only CNTs decreases slightly with increasing CNT content (e.g., CNT1≈275.9 J / g, CNT2≈265.1 J / g, CNT3≈255.8 J / g). Therefore, the latent heat of the composite system, due to the inert mass fraction of CMC, DSP, and carbon materials, is slightly lower than that of pure SAT (approximately 11.9% decrease in Example 1). However, the phase transition peak remains concentrated and the plateau is stable, indicating that the crystallization / melting process of the composite system is repeatable and shows no significant degradation. For the CNT-only sequence, the higher the CNT content, the more significant the slight decrease in latent heat, reflecting the common trade-off between "increased thermal conductivity and diluted latent heat." Example 1 achieves the highest thermal conductivity while maintaining a high latent heat, resulting in superior overall performance.

[0100] Figure 9The images show the DSC spectra of Example 1 and Comparative Example 5 before and after 200 cycles. It can be seen that: Pure SAT (Comparative Example 5): decreased from 303.7 J / g to 167.8 J / g, with a latent heat retention of approximately 55.3% and a decay of approximately 44.7%. Example 1: decreased from 267.4 J / g to 244.5 J / g, with a latent heat retention of approximately 91.4% and a decay of only approximately 8.6%. Therefore, the latent heat of pure SAT significantly decreases after repeated thermal cycling, indicating problems such as phase separation / leakage and crystal structure deterioration; while Example 1 exhibits high retention and low decay, demonstrating excellent structural stability and cycle reversibility. Comparing the data after 200 cycles, the latent heat of Example 1 (244.5 J / g) is approximately 45.6% higher than that of pure SAT (167.8 J / g).

[0101] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Any equivalent structural transformations made based on the content of the specification and drawings of this application under the concept of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A three-dimensional thermally conductive structure, characterized in that, It includes one-dimensional thermally conductive nanomaterials and two-dimensional thermally conductive nanomaterials, wherein the mass ratio of the one-dimensional thermally conductive nanomaterials to the two-dimensional thermally conductive nanomaterials is 2:1-4:1, and the one-dimensional thermally conductive nanomaterials and the two-dimensional thermally conductive nanomaterials are intertwined and interconnected to form a thermally conductive channel, which can maintain a three-dimensional thermally conductive structure in an aqueous phase.

2. The three-dimensional thermally conductive structure as described in claim 1, characterized in that, The one-dimensional thermally conductive nanomaterials include at least one of carbon nanotubes, silver nanowires, copper nanowires, aluminum nanowires, boron nitride nanotubes, and silicon carbide nanowires.

3. The three-dimensional thermally conductive structure as described in claim 1, characterized in that, The two-dimensional thermally conductive nanomaterials include at least one of graphene, graphene oxide, boron nitride nanosheets, MXene, molybdenum disulfide, and black phosphorus.

4. The three-dimensional thermally conductive structure as described in claim 1, characterized in that, The mass ratio of the one-dimensional thermally conductive nanomaterial to the two-dimensional thermally conductive nanomaterial is 2:1-3:

1.

5. The three-dimensional thermally conductive structure as described in claim 2, characterized in that, The surface of the one-dimensional thermally conductive nanomaterial has oxygen-containing functional groups, which are obtained through one or more of the following methods: The carbon nanotubes are oxidized to introduce hydroxyl and carboxyl groups; The silver nanowires are oxidized to form silver-oxygen bonds and hydroxyl groups; The copper nanowires are oxidized or treated with an alkali to form a copper oxide layer on the surface; The aluminum nanowires are treated with an alkaline solution to form a hydroxylated aluminum oxide layer; The boron nitride nanotubes are subjected to oxygen plasma or wet chemical oxidation treatment to introduce boron-oxygen bonds and hydroxyl groups; The silicon carbide nanowires are subjected to wet chemical oxidation treatment to introduce a surface hydroxyl layer.

6. The three-dimensional thermally conductive structure as described in claim 3, characterized in that, The surface of the two-dimensional thermally conductive nanomaterial has polar functional groups, which are obtained through one or more of the following methods: It is obtained by oxidizing and partially reducing the graphene. It was obtained by modifying the graphene oxide with amine grafting; The boron nitride nanosheets were obtained by oxygen plasma treatment. MXene is obtained by acid or fluoride-assisted stripping or alkaline treatment. The molybdenum disulfide was obtained by functionalizing it with ethylenediamine. It is obtained by compounding the black phosphorus with polyethylene glycol.

7. The three-dimensional thermally conductive structure as described in claim 1, characterized in that, The three-dimensional thermally conductive structure is obtained by self-assembly of intertwined components in an alcohol solvent.

8. A method for preparing a three-dimensional thermally conductive structure, characterized in that, include: Surface oxygen-containing functionalization treatment of one-dimensional thermally conductive nanomaterials; Polar functionalization of two-dimensional thermally conductive nanomaterials; The one-dimensional thermally conductive nanomaterial and the two-dimensional thermally conductive nanomaterial are mixed at a mass ratio of 2:1 to 4:1 to form a solid-liquid mixture. The solid mixture is mixed with a solvent and a dispersant, and then stirred and ultrasonically dispersed to form a uniform dispersion system. as well as The solvent is removed, causing the one-dimensional thermally conductive nanomaterial and the two-dimensional thermally conductive nanomaterial to intertwine and form a continuous three-dimensional thermally conductive structure.

9. The method as described in claim 8, characterized in that, With a mass fraction of 1 in the dispersion system, the mass fraction of the dispersant is 0.1-0.5%, and the dispersant includes at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, polyethylene glycol, Tween 80, sodium cholate, and polyvinylpyrrolidone.

10. The method as described in claim 8, characterized in that, The solvent includes alcohol solvents, the ultrasonic dispersion power is 200-500W, the time is 20-45min, and the solvent removal temperature is 80-100℃ for 2-6h.

11. The method as described in claim 8, characterized in that, The surface of the one-dimensional thermally conductive nanomaterial has oxygen-containing functional groups, which are obtained through one or more of the following methods: The one-dimensional thermally conductive nanomaterial is carbon nanotubes, which are refluxed with concentrated nitric acid at approximately 110°C for 4-8 hours to introduce oxygen-containing functional groups. The one-dimensional thermally conductive nanomaterial is copper nanowire, and its surface is treated by reacting a mixed solution of NaOH and hydrogen peroxide at room temperature to 50°C for 1-3 hours. The one-dimensional thermally conductive nanomaterial is silver nanowire, and its surface is treated with a 0.1-0.5 vol% hydrogen peroxide solution at room temperature for 1-2 hours. The one-dimensional thermally conductive nanomaterial is aluminum nanowire, which is obtained by reacting with NaOH at 25-40℃ for 30-60 minutes.

12. The method as described in claim 8, characterized in that, The surface of the two-dimensional thermally conductive nanomaterial has polar functional groups, which are obtained through one or more of the following methods: the two-dimensional thermally conductive nanomaterial is graphene and hydroxyl, carboxyl, or epoxy groups are introduced through oxidation and partial reduction. The two-position thermally conductive nanomaterial is graphene oxide, modified by amine grafting to introduce amino groups. The two-dimensional thermally conductive nanomaterial is boron nitride nanosheets, which are treated with 100-200W oxygen plasma for 5-15 minutes to introduce boron-oxygen bonds and hydroxyl groups on the surface. The two-dimensional thermally conductive nanomaterial is MXene, which is etched with HF and then exfoliated with HCl and LiF, or treated with 0.1 mol / L NaOH solution at room temperature for about 2 hours to form hydroxyl groups on the surface. The two-dimensional thermally conductive nanomaterial is molybdenum disulfide and is stirred with ethylenediamine at about 80°C for about 12 hours to introduce amino groups on the surface; The two-dimensional thermally conductive nanomaterial is black phosphorus mixed with polyethylene glycol at a mass ratio of 1:10-20 to form hydroxyl and ether-like polar functional groups on the surface.

13. A phase change thermal storage material, characterized in that, include: One-dimensional thermally conductive nanomaterials and two-dimensional thermally conductive nanomaterials, dispersant, thickener, inorganic salt, water and nucleating agent, wherein the mass ratio of the one-dimensional thermally conductive nanomaterials to the two-dimensional thermally conductive nanomaterials is 2:1-4:1; The total mass of water and inorganic salt is 100%, the total mass of the one-dimensional thermally conductive nanomaterial and the two-dimensional thermally conductive nanomaterial is 1-5%, the mass of the dispersant is 0.1-0.5%, the mass of the thickener is 0.5-5%, the mass of the nucleating agent is 1-3%, and the mass of the inorganic salt is 27-57%.

14. The material as claimed in claim 13, characterized in that, The one-dimensional thermally conductive nanomaterials include at least one of carbon nanotubes, silver nanowires, copper nanowires, aluminum nanowires, boron nitride nanotubes, and silicon carbide nanowires; the two-dimensional thermally conductive nanomaterials include at least one of graphene, graphene oxide, boron nitride nanosheets, MXene, molybdenum disulfide, and black phosphorus.

15. The material as claimed in claim 13, characterized in that, The dispersant includes at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, polyethylene glycol, Tween 80, sodium cholate, and polyvinylpyrrolidone.

16. The material as claimed in claim 13, characterized in that, The thickener includes at least one of sodium carboxymethyl cellulose, guar gum, xanthan gum, sodium alginate, gum arabic, corn starch, cyclodextrin, hydroxypropyl methylcellulose, hydroxyethyl cellulose, sodium polyacrylate, polyacrylate, polyvinyl alcohol, bentonite, kaolin, and aluminum silicate.

17. The material as claimed in claim 13, characterized in that, The inorganic salt includes at least one of magnesium sulfate, sodium acetate, trisodium phosphate, and calcium nitrate, and the water includes at least one of ultrapure water, deionized water, and tap water.

18. The material as claimed in claim 13, characterized in that, The nucleating agent includes at least one of barium sulfate, barium carbonate, barium chloride, strontium sulfate, disodium hydrogen phosphate dodecahydrate, sodium hydrogen phosphate decahydrate, sodium chloride, potassium chloride, sorbitol, aluminum oxide, silicon dioxide, and titanium oxide.

19. The material as claimed in claim 13, characterized in that, The actual amount of water added is based on the theoretical crystallization water content of inorganic hydrated salts and adjusted within the range of 105%-110% to compensate for evaporation losses.

20. A method for preparing phase change thermal storage materials, characterized in that, include: One-dimensional thermally conductive nanomaterials were surface-functionalized with oxygen-containing groups, and two-dimensional thermally conductive nanomaterials were polarized. The one-dimensional thermally conductive nanomaterial and the two-dimensional thermally conductive nanomaterial are mixed at a mass ratio of 2:1 to 4:1 to obtain a solid-liquid mixture. The solid mixture is mixed with a solvent and a dispersant, and then stirred and ultrasonically dispersed to form a uniform dispersion system. The solvent is removed under heating conditions, allowing the one-dimensional thermally conductive nanomaterial and the two-dimensional thermally conductive nanomaterial to synergistically self-assemble into a three-dimensional thermally conductive structure. The three-dimensional thermally conductive structure is added to the water and subjected to ultrasonic treatment until it becomes a gel. The thickener was added to the resulting gel system in two steps, wherein 1 / 10 of the thickener was added in the first step; Inorganic salts are added and reacted with water under stirring and heating conditions to generate inorganic hydrated salts; wherein the mass of the three-dimensional thermally conductive structure is 1%-5% of the mass of the inorganic hydrated salts; The second step involves adding the remaining 9 / 10 of the thickener, and Nucleating agents are added and the mixture is stirred and dispersed to obtain the phase change thermal storage material.

21. The method as described in claim 20, characterized in that, The ultrasonic treatment time is 5-30 minutes, and the stirring speed is 300-600 rpm.

22. The method as described in claim 20, characterized in that, The dispersant has a mass fraction of 0.1-0.5%, and the dispersant includes at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, polyethylene glycol, Tween 80, sodium cholate, and polyvinylpyrrolidone.

23. The method as described in claim 20, characterized in that, The solvent is an alcohol-based solvent, the ultrasonic dispersion power is 200-500W, the time is 20-45min, and the solvent is removed at a temperature of 80-100℃ for 2-6h.

24. The method as described in claim 20, characterized in that, The actual amount of water added is based on the theoretical crystallization water content of the target hydrated salt and adjusted within the range of 105%-110% to compensate for evaporation losses.

25. The method as described in claim 20, characterized in that, The inorganic salt is anhydrous sodium acetate, which reacts with water at 50°C to 65°C to produce sodium acetate trihydrate.

26. The method as described in claim 20, characterized in that, The nucleating agent is added at 1-3% of the total mass of the system, and the nucleating agent includes at least one of barium sulfate, barium carbonate, barium chloride, strontium sulfate, disodium hydrogen phosphate dodecahydrate, sodium hydrogen phosphate decahydrate, sodium chloride, potassium chloride, sorbitol, aluminum oxide, silicon dioxide, or titanium oxide.

27. The method as described in claim 20, characterized in that, The surface of the one-dimensional thermally conductive nanomaterial is subjected to oxygen-containing functionalization treatment, which includes one or more of the following methods: When the one-dimensional thermally conductive nanomaterial is carbon nanotube, it is refluxed with concentrated nitric acid at about 110°C for 4-8 hours to achieve oxygen-containing functionalization on the surface. When the one-dimensional thermally conductive nanomaterial is copper nanowire, a mixed solution of NaOH and hydrogen peroxide is used to react at room temperature to 50°C for 1-3 hours to perform surface oxidation treatment. When the one-dimensional thermally conductive nanomaterial is silver nanowire, a hydrogen peroxide solution with a volume fraction of 0.1-0.5% is used to react at room temperature for 1-2 hours to form silver-oxygen bonds and hydroxyl sites. When the one-dimensional thermally conductive nanomaterial is aluminum nanowire, a NaOH solution is used to react at 25-40℃ for 30-60 minutes to obtain a surface hydroxylated aluminum oxide layer.

28. The method as described in claim 20, characterized in that, The surface of the two-dimensional thermally conductive nanomaterial is subjected to polar functionalization treatment, which includes one or more of the following methods: Graphene is oxidized and partially reduced to introduce hydroxyl, carboxyl, or epoxy groups onto its surface; Amine grafting modification was performed on graphene oxide to introduce amino groups onto its surface; Boron nitride nanosheets were subjected to oxygen plasma treatment to introduce boron-oxygen bonds and hydroxyl groups on the surface; MXene is treated with acid or alkali to form hydroxyl groups on its surface; Molybdenum disulfide was functionalized with ethylenediamine to introduce amino groups onto its surface; Polyethylene glycol composites were applied to black phosphorus to form polar functional groups such as hydroxyl and ether bonds on the surface.

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