Composite phase change heat storage material and preparation method

Abstract

An embodiment of the present invention provides a composite phase-change heat storage material and a preparation method. The composite phase-change heat storage material is a microcapsule with a core-shell structure, wherein the core is a metallic iron microsphere, which is used to store heat through phase change during the heat storage and release process of the energy storage system; the shell is a metal oxide with high-temperature stability and high thermal conductivity, which is used to encapsulate the metallic iron microspheres and serve as a heat-conducting medium during the heat storage and release process of the energy storage system. According to the embodiment of the present invention, the composite phase-change heat storage material has an extremely high phase change temperature and a large energy storage density. The packaging technology can ensure that the phase-change material is not prone to leakage after the phase change. The use of this composite phase-change heat storage material can extend the service life of the energy storage system.

Description

Technical Field

[0001] The present invention relates to the field of energy storage technology, and in particular to a composite phase-change heat storage material and a preparation method thereof. Background Art

[0002] Renewable energy, as an alternative to fossil fuels, is crucial for addressing the urgent need for environmental protection and the growing challenge of energy supply. However, the intermittent and fluctuating nature of renewable resources such as wind and solar power limits their application, resulting in significant waste of resources. Furthermore, the power system faces challenges of supply and demand imbalance and significant peak-to-valley load differences, which urgently need to be addressed. Therefore, the development of long-term and efficient energy storage technologies has become key to enabling renewable energy to effectively compete with traditional fossil fuels.

[0003] Thermal energy storage technology uses heat storage materials as a medium. It can convert thermal energy from solar thermal, geothermal, industrial waste heat, etc., as well as clean electricity generated by renewable resources such as wind energy and solar energy, or electricity during low-voltage periods of the power grid into thermal energy for long-term storage, and release it for use when needed. It effectively solves the problem of large-scale consumption of renewable resources and the mismatch between energy supply and demand due to differences in time, space or intensity, and greatly improves the utilization efficiency of the entire energy system.

[0004] Among various thermal energy storage technologies, chemical reaction heat storage offers the highest energy storage density. Storing heat through chemical reactions reduces equipment insulation requirements and facilitates long-term storage. However, most chemical reaction processes are not only complex but also pose potential safety risks, so chemical reaction heat storage is still in the research and development stage. Sensible heat storage relies on the temperature fluctuation range of solids or liquids to store energy. Its energy storage density is limited by the material's specific heat capacity and usable temperature range. Key materials include concrete, mineral rocks, molten salts, and thermal oil. While these are low-cost, their operating temperatures and energy storage densities are relatively low. Unlike sensible heat storage, phase change heat storage utilizes the latent heat generated during phase changes. Therefore, it typically has a higher energy storage density and effectively reduces the required equipment volume. Furthermore, the phase change heat storage process occurs at a nearly constant temperature and is accompanied by minimal volume changes, making it simpler to control and more reliable and safer. In terms of unit energy storage cost, phase change heat storage lies between sensible and chemical reaction heat storage and is lower than most electrical energy storage technologies.

[0005] Currently, phase-change thermal storage materials used in thermal energy storage systems suffer from low thermal conductivity, hindering their large-scale application. For example, a Mg-Zn-Ni low-corrosion, high-temperature phase-change thermal storage material and its preparation method were developed. A high-temperature phase-change thermal storage material was prepared by alloying magnesium, a magnesium-nickel master alloy, and zinc. The material exhibits a phase transition temperature of 470-485°C and a latent heat of 150.9-170.3 kJ / kg. This high-temperature phase-change thermal storage material exhibits minimal temperature fluctuations during charging and discharging, low corrosion resistance, and a long service life, making it suitable for use in solar thermal power generation systems. However, these metal-based phase-change materials still suffer from issues such as low phase-change temperature and low energy storage density, limiting their application. Furthermore, metal materials are highly corrosive and can easily corrode the walls of equipment, directly impacting the life of the energy storage system. Summary of the Invention

[0006] In view of the above problems, a composite phase change heat storage material and a preparation method are proposed to overcome the above problems or at least partially solve the above problems, including:

[0007] A composite phase-change heat storage material is a microcapsule with a core-shell structure, wherein the core is a metallic iron microsphere, which is used to store heat through phase change during the heat storage and release process of an energy storage system; and the shell is a metal oxide with high-temperature stability and high thermal conductivity, which is used to encapsulate the metallic iron microsphere and serve as a heat-conducting medium during the heat storage and release process of the energy storage system.

[0008] Optionally, the metal oxide includes any one of aluminum oxide, magnesium oxide, and beryllium oxide.

[0009] Optionally, the particle size of the metallic iron microspheres ranges from 25 to 2000 μm.

[0010] A method for preparing a composite phase-change heat storage material, the method being used to prepare the composite phase-change heat storage material, the method comprising:

[0011] A supersaturated metal hydroxide solution is generated based on deionized water, a water-soluble metal salt, and ammonia water; wherein the water-soluble metal salt is a water-soluble metal salt corresponding to a metal oxide having high temperature stability and high thermal conductivity;

[0012] Adding iron microsphere powder to the supersaturated metal hydroxide solution and continuously stirring to allow the metal hydroxide corresponding to the supersaturated metal hydroxide solution to coat the surface of the iron microspheres to form a metal hydroxide precursor;

[0013] The metal hydroxide precursor is washed, filtered, dried, and then heat-treated to obtain a composite phase-change heat storage material.

[0014] Optionally, the heat treatment conditions are in air or nitrogen atmosphere, a temperature of 800 to 1800° C., a heating rate of 0.1° C. to 20° C. / min, and a time of 0.5 to 2 hours.

[0015] Optionally, the water-soluble metal salt includes any one of a hydrate of a water-soluble metal chloride, a hydrate of a water-soluble metal sulfate, and a hydrate of a water-soluble metal nitrate.

[0016] Optionally, the amount of deionized water added is 50-500 ml, the amount of metal salt added is 3-100 g, and the total amount of ammonia water added is 5-50 ml.

[0017] Optionally, the iron microsphere powder is added in an amount of 0.1 to 2 g, and the stirring time is 2 to 24 hours.

[0018] A fluidized bed or a fixed bed, wherein the fluidized bed or the fixed bed is filled with the composite phase change heat storage material as described above.

[0019] An energy storage system comprises the fluidized bed or fixed bed as described above.

[0020] The embodiments of the present invention have the following advantages:

[0021] The composite phase change heat storage material in the embodiment of the present invention is a microcapsule with a core-shell structure, wherein the core is a metal iron microsphere, which is used to store heat through phase change during the heat storage and release process of the energy storage system. The shell is a metal oxide with high temperature stability and high thermal conductivity, which is used to encapsulate the metal iron microsphere and serve as a heat conducting medium during the heat storage and release process of the energy storage system. Therefore, the composite phase change heat storage material has an extremely high phase change temperature and a large energy storage density. The packaging technology can ensure that the phase change material is not easy to leak after the phase change. The use of this composite phase change heat storage material can extend the service life of the energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the description of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 1 is a schematic structural diagram of a composite phase change heat storage material provided by one embodiment of the present invention;

[0024] Figure 2a This is a flow chart of the steps of a method for preparing a composite phase change heat storage material provided by one embodiment of the present invention;

[0025] Figure 2b This is a flow chart of the steps of another method for preparing a composite phase change heat storage material provided by one embodiment of the present invention;

[0026] Figure 2c This is a flow chart of the steps of another method for preparing a composite phase change heat storage material provided by one embodiment of the present invention;

[0027] Figure 2d This is a flow chart of the steps of another method for preparing a composite phase change heat storage material provided by one embodiment of the present invention;

[0028] Figure 3 This is a schematic diagram of a fluidized bed or fixed bed structure provided by one embodiment of the present invention;

[0029] Figure 4 It is a structural diagram of an energy storage system provided by one embodiment of the present invention. DETAILED DESCRIPTION

[0030] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments described are only a portion of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

[0031] Reference Figure 1 , showing a structural diagram of a composite phase change heat storage material provided by one embodiment of the present invention: the composite phase change heat storage material includes metal iron microspheres 101 and metal oxide 102 wrapping the metal iron microspheres 101.

[0032] In the embodiment of the present invention, the composite phase change heat storage material is a microcapsule with a core-shell structure, wherein the core is a metal iron microsphere, which is used to store heat through phase change during the heat storage and release process of the energy storage system; the shell is a metal oxide with high temperature stability and high thermal conductivity, which is used to encapsulate the metal iron microsphere and serve as a heat conduction medium during the heat storage and release process of the energy storage system.

[0033] In one example, the metal oxide may include any one of aluminum oxide, magnesium oxide, and beryllium oxide.

[0034] In another example, the particle size of the metallic iron microspheres ranges from 25 μm to 2000 μm. For example, the particle size of the metallic iron microspheres may be 25 μm, 200 μm, or 2000 μm.

[0035] In practical applications, the melting point of iron is approximately 1538°C (2798°F). When the iron microspheres reach this temperature, they can transition from solid to liquid. Below the melting point, they remain solid. The metal oxide shell, however, is stable at high temperatures. For example, the melting point of aluminum oxide is approximately 2072°C; the melting point of magnesium oxide is approximately 2852°C; and the melting point of beryllium oxide is approximately 2570°C. These temperatures are all higher than the melting point of iron. When the iron microspheres change phase, the metal oxide shell remains solid, preventing leakage from corroding the walls of the equipment and affecting the service life of the energy storage system.

[0036] In addition, the shell also has a high thermal conductivity, which facilitates the transfer of heat between the metal iron microspheres and the outside, achieving heat storage or release.

[0037] The composite phase change heat storage material in the embodiment of the present invention can be used in the fields of industrial waste heat recovery and utilization, solar thermal power generation, green electricity consumption, regional and building heating, high-temperature and high-emission industrial energy supply, etc.

[0038] A composite phase-change heat storage material proposed in an embodiment of the present invention has an extremely high phase-change temperature and a large energy storage density. The packaging technology can ensure that the phase-change material is not easy to leak after the phase change. The use of this composite phase-change heat storage material can extend the service life of the energy storage system.

[0039] Reference Figure 2a , showing a step flow chart of a method for preparing a composite phase-change heat storage material provided by one embodiment of the present invention, wherein the composite phase-change heat storage material prepared by the method is a microcapsule having a core-shell structure, wherein the core is a metal iron microsphere, and the metal iron microsphere is used to store heat through phase change during the heat storage and release process of the energy storage system, and the shell is a metal oxide with high-temperature stability and high thermal conductivity, and the shell is used to encapsulate the metal iron microsphere and serve as a heat-conducting medium during the heat storage and release process of the energy storage system.

[0040] The preparation method of the composite phase change heat storage material may specifically include the following steps:

[0041] Step 201: generating a supersaturated metal hydroxide solution based on deionized water, a water-soluble metal salt, and ammonia water; wherein the water-soluble metal salt is a water-soluble metal salt corresponding to a metal oxide having high temperature stability and high thermal conductivity;

[0042] In practice, a pre-set ratio of deionized water and a water-soluble metal salt can be added to a round-bottom flask and stirred at a preset speed on a magnetic stirrer until the salt is completely dissolved. Ammonia is then added dropwise to make the solution slightly alkaline, thereby forming a supersaturated metal hydroxide solution.

[0043] Step 202, adding iron microsphere powder to the supersaturated metal hydroxide solution and continuously stirring, so that the metal hydroxide corresponding to the supersaturated metal hydroxide solution is coated on the surface of the iron microspheres to form a metal hydroxide precursor;

[0044] After the supersaturated metal hydroxide solution is generated, iron microsphere powder can be added to the solution and continuously stirred, so that the metal hydroxide can be coated on the surface of the iron microspheres in the solution to form a metal hydroxide precursor.

[0045] Step 203 : washing, filtering, drying, and then heat-treating the metal hydroxide precursor to obtain a composite phase change heat storage material.

[0046] After obtaining the metal hydroxide precursor, it can be washed, filtered, and dried to remove impurities, and then heat treated; during the heat treatment process, the metal hydroxide in the outer layer of the metal hydroxide precursor is gradually converted into metal oxide, that is, the final product is a microcapsule with a metal oxide as a shell and a metal iron microsphere as a core. The microcapsule is a composite phase change heat storage material that can be used to store heat in an energy storage system. Therefore, in an embodiment of the present invention, an iron-based microencapsulated composite phase change heat storage material with a core-shell structure can be prepared by precipitation coating + high-temperature heat treatment.

[0047] The heat treatment conditions may be in air or nitrogen atmosphere, at a temperature of 800 to 1800° C., at a heating rate of 0.1 to 20° C. / min, and for 0.5 to 2 hours, such as 0.5 h, 1 h, or 2 h.

[0048] In one example, the water-soluble metal salt includes any one of a water-soluble metal chloride hydrate, a water-soluble metal sulfate hydrate, and a water-soluble metal nitrate hydrate.

[0049] For example, when a composite phase-change thermal storage material having an aluminum oxide shell is to be synthesized, the water-soluble metal salt includes any one of AlCl3 hydrate, Al2(SO4)3 hydrate, and Al(NO3)3 hydrate. Specifically, the AlCl3 hydrate may be AlCl3·6H2O, the Al2(SO4)3 hydrate may be Al2(SO4)3·6H2O, and the Al(NO3)3 hydrate may be Al(NO3)3·6H2O.

[0050] When synthesizing a composite phase-change thermal storage material having a beryllium oxide shell, the water-soluble metal salt includes any one of MgCl2 hydrate, MgSO4 hydrate, and Mg(NO3)2 hydrate. Specifically, the MgCl2 hydrate may be MgCl2·6H2O, the MgSO4 hydrate may be MgSO4·7H2O, and the Mg(NO3)2 hydrate may be Mg(NO3)2·6H2O.

[0051] When it is necessary to synthesize a composite phase-change heat storage material whose shell is beryllium oxide, the water-soluble metal salt includes any one of BeCl2 hydrate, BeSO4 hydrate, and Be(NO3)2 hydrate.

[0052] In one embodiment of the present invention, the raw materials for synthesizing the composite phase change heat storage material include deionized water, water-soluble metal salt and ammonia water. The three are mixed in an appropriate proportion according to the preparation method of the composite phase change heat storage material in the embodiment of the present invention to prepare a composite phase change heat storage material with metal iron microspheres as the core and metal oxide as the shell. For example, the amount of deionized water added is 50ml~500ml, the amount of water-soluble metal salt added is 3~100g, and the total amount of ammonia water added is 5~50ml to prepare the composite phase change heat storage material. The amount can be increased or decreased according to the proportion to prepare the composite phase change heat storage material on demand.

[0053] Reference Figure 2b , is a preparation flow chart of a composite phase change heat storage material with magnesium oxide as the shell in an embodiment of the present invention.

[0054] First, add 50-500ml of deionized water and 3-100g of water-soluble aluminum salt (such as AlCl3·6H2O) into a round-bottom flask and stir at a certain speed on a magnetic stirring device until it is completely dissolved. Then, add ammonia water drop by drop to make the solution weakly alkaline. In the solution, Al 3+ Reacting with OH- can generate Al(OH)3, thereby forming a supersaturated Al(OH)3 solution.

[0055] Add iron microsphere powder to the supersaturated Al(OH)3 solution and continue stirring to make Al(OH)3 evenly coated on the surface of the iron microspheres to form an Al(OH)3 precursor.

[0056] After washing, filtering, and drying the Al(OH)3 precursor, the sample was heat-treated in a tube furnace in air or nitrogen atmosphere at a temperature of 800-1800°C, a heating rate of 0.1°C-20°C / min, and a duration of 0.5-2 hours. The sample was then removed after cooling naturally to room temperature, yielding an iron-based microencapsulated composite phase-change thermal storage material, namely, Fe@Al2O3.

[0057] Reference Figure 2c, is a preparation flow chart of a composite phase change heat storage material with magnesium oxide as the shell in an embodiment of the present invention.

[0058] First, add 50-500ml of deionized water and 3-100g of water-soluble magnesium salt into a round-bottom flask and stir at a certain speed on a magnetic stirring device until it is completely dissolved. Then, add ammonia water drop by drop to make the solution weakly alkaline. In the solution, Mg 2+ With OH - The reaction can generate Mg(OH)2, thereby forming a supersaturated Mg(OH)2 solution.

[0059] Add iron microsphere powder to the supersaturated Mg(OH)2 solution and continue stirring to make Mg(OH)2 evenly coated on the surface of the iron microspheres to form a Mg(OH)2 precursor.

[0060] After washing, filtering, and drying the Mg(OH)2 precursor, the sample was heat-treated in a tube furnace in air or nitrogen atmosphere at a temperature of 800-1800°C, a heating rate of 0.1°C-20°C / min, and a duration of 0.5-2 hours. The sample was then naturally cooled to room temperature and removed to obtain an iron-based microencapsulated composite phase-change thermal storage material, namely, Fe@MgO.

[0061] Reference Figure 2d , is a preparation flow chart of a composite phase change heat storage material with beryllium oxide as the shell in an embodiment of the present invention.

[0062] First, add 50-500ml of deionized water and 3-100g of water-soluble magnesium salt into a round-bottom flask and stir at a certain speed on a magnetic stirring device until it is completely dissolved. Then, add ammonia water drop by drop to make the solution weakly alkaline. In the solution, Be 2+ With OH - The reaction can generate Be(OH)2, thereby forming a supersaturated Be(OH)2 solution.

[0063] Add iron microsphere powder to the supersaturated Be(OH)2 solution and continue stirring to ensure that Be(OH)2 is evenly coated on the surface of the iron microspheres to form a Be(OH)2 precursor.

[0064] After washing, filtering, and drying the Be(OH)2 precursor, the sample was heat-treated in a tube furnace in air or nitrogen atmosphere at a temperature of 800-1800°C, a heating rate of 0.1°C-20°C / min, and a duration of 0.5-2 hours. The sample was then naturally cooled to room temperature and removed to obtain an iron-based microencapsulated composite phase-change thermal storage material, namely, Fe@BeO.

[0065] In an embodiment of the present invention, a supersaturated metal hydroxide solution is generated based on deionized water, a water-soluble metal salt, and ammonia water; wherein the water-soluble metal salt is a water-soluble metal salt corresponding to a metal oxide having high temperature stability and high thermal conductivity; iron microsphere powder is added to the supersaturated metal hydroxide solution, and continuously stirred so that the metal hydroxide corresponding to the supersaturated metal hydroxide solution is coated on the surface of the iron microspheres to form a metal hydroxide precursor; the metal hydroxide precursor is washed, filtered, dried, and then heat-treated to obtain a composite phase change heat storage material. Thus, the composite phase change heat storage material can have an extremely high phase change temperature and a large energy storage density. The packaging technology can ensure that the phase change material is not easy to leak after the phase change. The use of the composite phase change heat storage material can extend the service life of the energy storage system.

[0066] Reference Figure 3 , shows a schematic diagram of a fluidized bed 301 or a fixed bed 301 in an embodiment of the present invention, wherein the cavity of the fluidized bed 301 or the fixed bed 301 is filled with a composite phase change heat storage material 302. The composite phase change material 302 has a microcapsule with a core-shell structure, wherein the core is a metal iron microsphere, and the metal iron microsphere is used to store heat through phase change during the heat storage and release process of the energy storage system; the shell is a metal oxide with high temperature stability and high thermal conductivity, and the shell is used to encapsulate the metal iron microsphere and serve as a heat conducting medium during the heat storage and release process of the energy storage system. Wherein, the metal oxide includes any one of aluminum oxide, magnesium oxide, and beryllium oxide;

[0067] The composite phase change material is prepared by the following method:

[0068] A supersaturated metal hydroxide solution is generated based on deionized water, a water-soluble metal salt and ammonia water; wherein the water-soluble metal salt is a water-soluble metal salt corresponding to a metal oxide with high-temperature stability and high thermal conductivity; iron microsphere powder is added to the supersaturated metal hydroxide solution and continuously stirred so that the metal hydroxide corresponding to the supersaturated metal hydroxide solution is coated on the surface of the iron microspheres to form a metal hydroxide precursor; the metal hydroxide precursor is washed, filtered, dried, and then heat-treated to obtain a composite phase change heat storage material.

[0069] In practical applications, heat storage and release can be achieved by filling a fluidized or fixed bed with a phase change material. This phase change material can be a composite phase change heat storage material with iron microspheres as the core and a metal oxide shell, as in the embodiments of the present invention. The metal oxide shell contains the iron microspheres, and at high temperatures, the iron microspheres undergo a phase change. The metal oxide shell prevents the iron microspheres from overflowing after the phase change.

[0070] When the composite phase change heat storage material in the embodiment of the present invention is filled in a fluidized bed or a fixed bed, after the fluid working medium flows into the cavity of the fluidized bed or the fixed bed, it can exchange heat with the composite phase change heat storage material, thereby achieving heat transfer.

[0071] Specifically, when a high-temperature fluid working medium flows into a fluidized bed or a fixed bed, the high-temperature fluid working medium can transfer heat to the composite phase change heat storage material filled in the fluidized bed or the fixed bed, thereby realizing heat storage energy of the fluidized bed or the fixed bed; when a low-temperature fluid working medium flows into the fluidized bed or the fixed bed, the composite phase change heat storage material that has previously stored heat can transfer a large amount of phase change latent heat generated by the phase change to the low-temperature fluid working medium based on the temperature difference with the fluid working medium, thereby heating the low-temperature fluid working medium, and then the fluid working medium is heated to become a high-temperature fluid working medium, flowing out of the fluidized bed or the fixed bed, thereby realizing energy release of the fluidized bed or the fixed bed.

[0072] Reference Figure 4 , shows an energy storage system 400 in an embodiment of the present invention, the energy storage system 400 includes a fluidized bed 401 or a fixed bed 401 with a composite phase change heat storage material 402 filled in the cavity. The composite phase change material has a microcapsule with a core-shell structure, the core is a metal iron microsphere, and the metal iron microsphere is used to store heat through phase change during the heat storage and release process of the energy storage system; the shell is a metal oxide with high temperature stability and high thermal conductivity, and the shell is used to encapsulate the metal iron microsphere and serve as a heat conducting medium during the heat storage and release process of the energy storage system. Wherein, the metal oxide includes any one of aluminum oxide, magnesium oxide, and beryllium oxide.

[0073] The composite phase change material is prepared by the following method:

[0074] A supersaturated metal hydroxide solution is generated based on deionized water, a water-soluble metal salt and ammonia water; wherein the water-soluble metal salt is a water-soluble metal salt corresponding to a metal oxide with high-temperature stability and high thermal conductivity; iron microsphere powder is added to the supersaturated metal hydroxide solution and continuously stirred so that the metal hydroxide corresponding to the supersaturated metal hydroxide solution is coated on the surface of the iron microspheres to form a metal hydroxide precursor; the metal hydroxide precursor is washed, filtered, dried, and then heat-treated to obtain a composite phase change heat storage material.

[0075] The above is a detailed introduction to a composite phase change heat storage material and a preparation method provided. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for preparing a composite phase change heat storage material, characterized in that: The composite phase-change heat storage material is a microcapsule with a core-shell structure, wherein the core is a metal iron microsphere, which is used to store heat through phase change during the heat storage and release process of the energy storage system; the shell is a metal oxide with high temperature stability and high thermal conductivity, which is used to encapsulate the metal iron microsphere and serve as a heat-conducting medium during the heat storage and release process of the energy storage system; the metal oxide includes any one of aluminum oxide, magnesium oxide, and beryllium oxide; The preparation method of the composite phase change heat storage material comprises the following steps: A supersaturated metal hydroxide solution is generated based on deionized water, a water-soluble metal salt, and ammonia water; wherein the water-soluble metal salt is a water-soluble metal salt corresponding to a metal oxide having high temperature stability and high thermal conductivity; the amount of deionized water added is 50 to 500 ml, the amount of the water-soluble metal salt added is 3 to 100 g, and the total amount of ammonia water added is 5 to 50 ml; Adding iron microsphere powder to the supersaturated metal hydroxide solution and continuously stirring to allow the metal hydroxide corresponding to the supersaturated metal hydroxide solution to coat the surface of the iron microspheres to form a metal hydroxide precursor; The metal hydroxide precursor is washed, filtered, dried, and then heat-treated to obtain a composite phase change heat storage material; When it is necessary to synthesize a composite phase-change heat storage material with a shell of aluminum oxide, the water-soluble metal salt includes any one of AlCl3 hydrate, Al2(SO4)3 hydrate, and Al(NO3)3 hydrate; when it is necessary to synthesize a composite phase-change heat storage material with a shell of magnesium oxide, the water-soluble metal salt includes any one of MgCl2 hydrate, MgSO4 hydrate, and Mg(NO3)2 hydrate; when it is necessary to synthesize a composite phase-change heat storage material with a shell of beryllium oxide, the water-soluble metal salt includes any one of BeCl2 hydrate, BeSO4 hydrate, and Be(NO3)2 hydrate.

2. The preparation method according to claim 1, wherein: The particle size of the metallic iron microspheres ranges from 25 to 2000 μm.

3. The preparation method according to claim 1, wherein: The heat treatment conditions are as follows: in air or nitrogen atmosphere, the temperature is 800-1800° C., the heating rate is 0.1° C.-20° C. / min, and the time is 0.5-2 hours.

4. The preparation method according to claim 1, wherein: The amount of the iron microsphere powder added is 0.1 to 2 g, and the stirring time is 2 to 24 hours.

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