Core-shell structure low-temperature phase change energy storage material and preparation method thereof

Abstract

The application discloses a core-shell structure low-temperature phase change energy storage material and a preparation method thereof. The phase change energy storage material is a sandwich structure material, the inner core of which is a graphene quantum dot / gallium-indium-silver alloy composite, the intermediate layer of which is a nitrogen-rich carbon material obtained by high-temperature carbonization of polyaniline under an inert atmosphere, and the outer layer of which is a zirconium-titanium composite oxide with an average thickness of 10-30 nm. The graphene quantum dot / gallium-indium-silver composite@polyaniline@zirconium-titanium composite oxide is placed in a tube furnace, argon is introduced, the temperature is raised to 800-1200 DEG C, and the reaction is carried out for 1-6 hours to obtain the core-shell structure low-temperature phase change energy storage material. The core-shell structure low-temperature phase change energy storage material has high latent heat of phase change, good thermal conductivity and excellent stability. The low-temperature phase change energy storage material has excellent application prospects in fields such as buildings and transportation.

Description

Technical Field

[0001] This invention relates to the field of phase change energy storage technology, and in particular to a core-shell structured low-temperature phase change energy storage material and its preparation method. Background Technology

[0002] Phase change energy storage materials can store energy that overflows during energy utilization through phase changes and release the stored energy when needed. Phase change energy storage materials make significant contributions to energy conservation and emission reduction, and alleviate the imbalance in energy utilization, and have broad application prospects in fields such as construction and transportation.

[0003] Metal-based phase change energy storage materials (PCEs) have attracted widespread attention due to their advantages such as high thermal conductivity, high energy density, and good chemical stability. However, during the phase change process, PCEs are prone to leakage due to changes in volume and fluidity, leading to a decrease in their energy storage efficiency. Furthermore, leakage of the metal also poses significant environmental pollution and safety hazards. Therefore, research on how to suppress leakage of metal-based PCE particles has gradually become a hot topic in PCE research. One of the most effective methods is to encapsulate the metal-based PCE particles with a non-metallic material, forming a microcapsule-type catalytic material with the metal-based PCE particle as the core and the non-metallic material as the shell. This structure can effectively prevent leakage of metal-based PCE particles during the phase change process.

[0004] Chinese patent application No. 202111040362.X discloses a phase change microcapsule coated with MQ resin. This phase change composite material utilizes a three-dimensional cross-linked network structure of MQ resin as the shell material and a phase change material as the core to form microcapsules. The outer MQ resin coating can significantly improve the problems of easy flow and leakage of phase change materials. Chinese patent application No. 202110745777.0 discloses a phase change energy storage composite material. This composite material uses porous carbon foam to coat the phase change material, which to some extent solves the problem of melt leakage of phase change materials. However, these core-shell structure phase change composite materials lack necessary metal particle size control schemes, resulting in phase change materials with large macroscopic particles, which is not conducive to maximizing the energy storage performance of phase change materials. On the other hand, in order to effectively suppress the loss of phase change material particles, a large outer shell thickness is often required, which significantly reduces the thermal conductivity of the phase change energy storage material. Summary of the Invention

[0005] The purpose of this invention is to provide a core-shell structured low-temperature phase change energy storage material that solves the technical problems of large particle size, low thermal conductivity, and easy loss in existing phase change energy storage materials. Simultaneously, a method for preparing the aforementioned core-shell structured low-temperature phase change energy storage material is also provided.

[0006] To achieve the above objectives, the phase change energy storage material technology adopted in this invention is: a core-shell structure low-temperature phase change energy storage material, wherein the phase change energy storage material is a sandwich structure material, the core is a graphene quantum dot / gallium indium silver alloy composite, the middle layer is a nitrogen-rich carbon material obtained by high-temperature carbonization of polyaniline under an inert atmosphere, and the outer layer is a zirconium titanium composite oxide with an average thickness of 10~30 nm.

[0007] The preparation method adopted in this invention is as follows: a method for preparing a core-shell structured low-temperature phase change energy storage material, comprising the following steps:

[0008] Step 1: Disperse graphene quantum dots in deionized water, add ionic liquid, stir for 1-6 hours, heat to 35-70℃, add liquid gallium indium silver alloy dropwise, stir for 4-12 hours, cool to room temperature, and obtain graphene quantum dot / gallium indium silver composite dispersion.

[0009] Step 2: Add aniline to the graphene quantum dot / gallium indium silver composite dispersion prepared in Step 1, stir for 0.5~2h, slowly add hydrochloric acid solution containing ammonium persulfate, stir for 0.5~2h, let stand for 12~24h, centrifuge, wash with water to obtain graphene quantum dot / gallium indium silver composite@polyaniline composite.

[0010] Step 3: Disperse the graphene quantum dot / gallium indium silver composite@polyaniline composite obtained in Step 2 in an ethanol-ammonia water mixed solution, stir, add a mixture of zirconium source and titanium source in ethanol, react for 8~20h, filter, wash, and obtain graphene quantum dot / gallium indium silver composite@polyaniline@zirconium titanium composite oxide;

[0011] Step 4: Place the graphene quantum dot / gallium indium silver composite@polyaniline@zirconium titanium composite oxide obtained in Step 3 into a tube furnace, introduce argon gas, heat to 800~1200℃, and react for 1~6 hours to obtain a core-shell structured low-temperature phase change energy storage material.

[0012] The following is a further improvement to the above preparation method:

[0013] 1. In the above scheme, the elemental mass ratio of gallium, indium and silver in the gallium-indium-silver alloy in step one is 1:0.01~0.08:0.008~0.02, and the mass ratio of the gallium-indium-silver alloy to graphene quantum dots is 1:0.02~0.1.

[0014] 2. In the above scheme, the ratio of graphene quantum dots to deionized water in step one is 0.001~0.01:1, the ionic liquid is 1-octyl-3-methylimidazolium chloride bromide or 1-butyl-3-vinylimidazolium bromide, and the mass ratio of ionic liquid to graphene quantum dots is 1:0.05~0.5.

[0015] 3. In the above scheme, the mass ratio of aniline to graphene quantum dot / gallium indium silver composite in step two is 1:0.2~1, the mass ratio of hydrochloric acid solution containing ammonium persulfate to aniline is 1:0.05~0.1, the mass fraction of ammonium persulfate in hydrochloric acid solution is 10~40wt%, and the mass fraction of hydrochloric acid is 5~15wt%.

[0016] 4. In the above scheme, the mass fraction of ammonia in the ethanol-ammonia water mixed solution in step three is 5 wt%~20 wt%, the zirconium salt is zirconium butoxide or zirconium isopropoxide, the titanium source is tetrabutyl titanate or titanium tetrachloride, the mass ratio of titanium source to zirconium source in the ethanol mixture of zirconium source and titanium source is 1:0.2~5, and the mass ratio of zirconium source to ethanol is 1:5~20.

[0017] 5. In the above scheme, the mass ratio of the graphene quantum dot / gallium indium silver composite@polyaniline composite to the ethanol-ammonia water mixture in step three is 1:5~10, and the mass ratio of the graphene quantum dot / gallium indium silver composite@polyaniline composite to the zirconium source is 1:0.2~1.

[0018] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0019] 1. The core-shell structured low-temperature phase change energy storage material of the present invention utilizes graphene quantum dots to fill the phase change alloy and combines it with the high thermal conductivity of nitrogen-rich carbon layer material, which can significantly improve the thermal conductivity of the phase change alloy and enhance the thermal response rate of the phase change alloy. At the same time, the thickness of the outer zirconium-titanium composite oxide is controlled to be less than 20 nm, reducing the influence of the outer zirconium-titanium composite oxide on the thermal conductivity of the phase change material, resulting in a phase change alloy material with high thermal conductivity.

[0020] 2. The core-shell structure low-temperature phase change energy storage material of the present invention utilizes graphene quantum dots to fill the phase change alloy, which can play the role of graphene quantum dots dispersing metal alloy, forming micro-nano-scale phase change alloy dispersed particles, thereby improving the latent heat capacity of the material's phase change.

[0021] 3. The core-shell structured low-temperature phase change energy storage material of this invention uses graphene quantum dots, which have abundant functional groups. These functional groups can promote the bonding of the phase change alloy after dispersion with the ionic liquid, forming a phase change alloy uniformly coated with the ionic liquid. At the same time, the middle layer is a nitrogen-rich carbon material obtained by carbonizing polyaniline. During its preparation, the abundant functional groups of polyaniline can play a coordination role with the ionic liquid, realizing the effective coating and encapsulation of the phase change alloy by polyaniline. Combined with the encapsulation of zirconium-titanium composite oxide, the flow and aggregation of the phase change alloy during carbonization and phase change can be significantly suppressed, improving the cycle stability of the phase change alloy. The latent heat of phase change changes little during multiple cycles of energy storage and release. Detailed Implementation

[0022] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship shown in the technical solution, and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention; the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance; furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly, for example, they can be fixed connections, detachable connections, or integral connections; they can be mechanical connections or electrical connections; they can be direct connections or indirect connections through an intermediate medium; they can be internal connections between two elements. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0023] The present invention will be further described below with reference to embodiments:

[0024] Example 1: A core-shell structured low-temperature phase change energy storage material, wherein the phase change energy storage material is a sandwich structure material, the core is a graphene quantum dot / gallium indium silver alloy composite, the middle layer is a nitrogen-rich carbon material obtained by high-temperature carbonization of polyaniline under an inert atmosphere, and the outer layer is a zirconium titanium composite oxide with an average thickness of 10~30 nm.

[0025] A method for preparing the above-mentioned core-shell structured low-temperature phase change energy storage material includes the following steps:

[0026] At 25℃, 1g of graphene quantum dots were weighed and dispersed in 100mL of deionized water. 1g of 1-butyl-3-vinylimidazolium bromide was added and stirred for 3h. The temperature was raised to 70℃ and 6g of liquid gallium-indium-silver alloy with an elemental mass ratio of gallium, indium and silver of 1:0.02:0.010 was added dropwise. The mixture was stirred for 6h and cooled to 25℃ to obtain a graphene quantum dot / gallium-indium-silver composite dispersion.

[0027] At 25℃, 37g of ammonium persulfate and 51mL of concentrated hydrochloric acid were weighed to prepare 200mL of ammonium persulfate hydrochloric acid solution; 24.5g of aniline was added to the graphene quantum dot / gallium indium silver composite dispersion obtained above, stirred for 2h, the above ammonium persulfate hydrochloric acid solution was slowly added, stirred for 2h, allowed to stand for 20h, centrifuged, and washed with water to obtain graphene quantum dot / gallium indium silver composite@polyaniline composite;

[0028] At 25℃, 130 mL of a 15 wt% ethanol-ammonia mixed solution was weighed, 20 g of graphene quantum dot / gallium indium silver composite@polyaniline composite was added, and the mixture was stirred. Then, 50 mL of an ethanol solution containing 5 g zirconium isopropoxide and 1 g tetrabutyl titanate was added. The mixture was reacted for 14 h, filtered, and washed to obtain graphene quantum dot / gallium indium silver composite@polyaniline@zirconium titanium composite oxide.

[0029] The obtained graphene quantum dot / gallium indium silver composite@polyaniline@zirconium titanium composite oxide was placed in a tube furnace, argon gas was introduced, the temperature was raised to 1000℃, and the reaction was carried out for 6 hours to obtain a core-shell structured low-temperature phase change energy storage material.

[0030] The core-shell structured low-temperature phase change energy storage material has an average size of 78.1 nm for the core graphene quantum dot / gallium indium silver composite and an average thickness of 18.7 nm for the outer zirconium titanium composite oxide shell. The phase change material has a thermal conductivity of 85.8 W / m·K, a phase change temperature of 35.9℃, and a latent heat of phase change of 198.8 J / g. After 50 cycles of energy storage and release, the latent heat of phase change is 192.0 J / g, indicating good stability.

[0031] Example 2: A core-shell structured low-temperature phase change energy storage material, wherein the phase change energy storage material is a sandwich structure material, the core is a graphene quantum dot / gallium indium silver alloy composite, the middle layer is a nitrogen-rich carbon material obtained by high-temperature carbonization of polyaniline under an inert atmosphere, and the outer layer is a zirconium titanium composite oxide with an average thickness of 10~30 nm.

[0032] A method for preparing the above-mentioned core-shell structured low-temperature phase change energy storage material includes the following steps:

[0033] At 25℃, 0.8g of graphene quantum dots were weighed and dispersed in 100mL of deionized water. 1g of 1-octyl-3-methylimidazolium chloride bromide was added and stirred for 4h. The temperature was raised to 70℃ and 8g of liquid gallium-indium-silver alloy with an elemental mass ratio of gallium, indium and silver of 1:0.08:0.01 was added dropwise. The mixture was stirred for 12h and cooled to 25℃ to obtain a graphene quantum dot / gallium-indium-silver composite dispersion.

[0034] At 25℃, 33g of ammonium persulfate and 42.5mL of concentrated hydrochloric acid were weighed to prepare 200mL of ammonium persulfate hydrochloric acid solution; 21g of aniline was added to the graphene quantum dot / gallium indium silver composite dispersion obtained above, and the mixture was stirred for 1h. The ammonium persulfate hydrochloric acid solution was slowly added, and the mixture was stirred for 1h. The mixture was allowed to stand for 18h, centrifuged, and washed with water to obtain graphene quantum dot / gallium indium silver composite@polyaniline composite.

[0035] At 25℃, 120 mL of a 10 wt% ethanol-ammonia mixed solution was weighed, 19 g of graphene quantum dot / gallium indium silver composite@polyaniline composite was added, and the mixture was stirred. Then, 45 mL of an ethanol solution containing 5 g of zirconium butoxide and 10 g of tetrabutyl titanate was added. The mixture was reacted for 20 h, filtered, and washed to obtain graphene quantum dot / gallium indium silver composite@polyaniline@zirconium titanium composite oxide.

[0036] The obtained graphene quantum dot / gallium indium silver composite@polyaniline@zirconium titanium composite oxide was placed in a tube furnace, argon gas was introduced, the temperature was raised to 900℃, and the reaction was carried out for 5 hours to obtain a core-shell structured low-temperature phase change energy storage material.

[0037] The core-shell structured low-temperature phase change energy storage material has an average size of 86.7 nm for the core graphene quantum dot / gallium indium silver composite and an average thickness of 15.2 nm for the outer zirconium titanium composite oxide shell. The phase change material has a thermal conductivity of 77.5 W / m·K, a phase change temperature of 37.2 °C, and a latent heat of phase change of 172.4 J / g. After 50 cycles of energy storage and release, the latent heat of phase change is 168.2 J / g, indicating good stability.

[0038] Example 3: A core-shell structured low-temperature phase change energy storage material, wherein the phase change energy storage material is a sandwich structure material, the core is a graphene quantum dot / gallium indium silver alloy composite, the middle layer is a nitrogen-rich carbon material obtained by high-temperature carbonization of polyaniline under an inert atmosphere, and the outer layer is a zirconium titanium composite oxide with an average thickness of 10~30 nm.

[0039] A method for preparing the above-mentioned core-shell structured low-temperature phase change energy storage material includes the following steps:

[0040] At 25℃, 0.6g of graphene quantum dots were weighed and dispersed in 80mL of deionized water. 0.8g of 1-octyl-3-methylimidazolium chloride bromide was added and stirred for 5h. The temperature was raised to 65℃ and 6g of liquid gallium-indium-silver alloy with an elemental mass ratio of gallium, indium and silver of 1:0.04:0.02 was added dropwise. The mixture was stirred for 8h and cooled to 25℃ to obtain a graphene quantum dot / gallium-indium-silver composite dispersion.

[0041] At 25℃, 28g of ammonium persulfate and 34mL of concentrated hydrochloric acid were weighed to prepare 200mL of ammonium persulfate hydrochloric acid solution; 17.5g of aniline was added to the graphene quantum dot / gallium indium silver composite dispersion obtained above, and the mixture was stirred for 2h. The ammonium persulfate hydrochloric acid solution was slowly added, and the mixture was stirred for 1.5h. The mixture was allowed to stand for 16h, centrifuged, and washed with water to obtain graphene quantum dot / gallium indium silver composite@polyaniline composite.

[0042] At 25℃, 90 mL of a 12 wt% ethanol-ammonia solution was weighed, 16 g of graphene quantum dot / gallium indium silver composite@polyaniline composite was added, and the mixture was stirred. Then, 40 mL of an ethanol solution containing 4 g of zirconium butoxide and 6 g of titanium tetrachloride was added. The mixture was reacted for 16 h, filtered, and washed to obtain graphene quantum dot / gallium indium silver composite@polyaniline@zirconium titanium composite oxide.

[0043] The obtained graphene quantum dot / gallium indium silver composite@polyaniline@zirconium titanium composite oxide was placed in a tube furnace, argon gas was introduced, the temperature was raised to 1200℃, and the reaction was carried out for 6 hours to obtain a core-shell structured low-temperature phase change energy storage material.

[0044] The core-shell structured low-temperature phase change energy storage material has an average size of 120.8 nm for the core graphene quantum dot / gallium indium silver composite and an average thickness of 9.4 nm for the outer zirconium titanium composite oxide shell. The phase change material has a thermal conductivity of 91.9 W / m·K, a phase change temperature of 35.3℃, and a latent heat of phase change of 192.1 J / g. After 50 cycles of energy storage and release, the latent heat of phase change is 185.7 J / g, indicating good stability.

[0045] Example 4: A core-shell structured low-temperature phase change energy storage material, wherein the phase change energy storage material is a sandwich structure material, the core is a graphene quantum dot / gallium indium silver alloy composite, the middle layer is a nitrogen-rich carbon material obtained by high-temperature carbonization of polyaniline under an inert atmosphere, and the outer layer is a zirconium titanium composite oxide with an average thickness of 10~30 nm.

[0046] A method for preparing the above-mentioned core-shell structured low-temperature phase change energy storage material includes the following steps:

[0047] At 25℃, 0.4g of graphene quantum dots were weighed and dispersed in 50mL of deionized water. 1g of 1-butyl-3-vinylimidazolium bromide was added and stirred for 1h. The temperature was raised to 60℃ and 8g of liquid gallium-indium-silver alloy with an elemental mass ratio of gallium, indium and silver of 1:0.02:0.008 was added dropwise. The mixture was stirred for 9h and cooled to 25℃ to obtain a graphene quantum dot / gallium-indium-silver composite dispersion.

[0048] At 25℃, 25g of ammonium persulfate and 25.5mL of concentrated hydrochloric acid were weighed to prepare 200mL of ammonium persulfate hydrochloric acid solution; 14g of aniline was added to the graphene quantum dot / gallium indium silver composite dispersion obtained above, and the mixture was stirred for 1.5h. The above ammonium persulfate hydrochloric acid solution was slowly added, and the mixture was stirred for 2h. The mixture was allowed to stand for 18h, centrifuged, and washed with water to obtain graphene quantum dot / gallium indium silver composite@polyaniline composite.

[0049] At 25℃, 70 mL of a 15 wt% ethanol-ammonia solution was weighed, 13 g of graphene quantum dot / gallium indium silver composite@polyaniline composite was added, and the mixture was stirred. Then, 35 mL of an ethanol solution containing 3.5 g zirconium isopropoxide and 7 g titanium tetrachloride was added. The mixture was reacted for 15 h, filtered, and washed to obtain graphene quantum dot / gallium indium silver composite@polyaniline@zirconium titanium composite oxide.

[0050] The obtained graphene quantum dot / gallium indium silver composite@polyaniline@zirconium titanium composite oxide was placed in a tube furnace, argon gas was introduced, the temperature was raised to 950℃, and the reaction was carried out for 5 hours to obtain a core-shell structured low-temperature phase change energy storage material.

[0051] The core-shell structured low-temperature phase change energy storage material has an average size of 112.9 nm for the core graphene quantum dot / gallium indium silver composite and an average thickness of 12.0 nm for the outer zirconium titanium composite oxide shell. The phase change material has a thermal conductivity of 82.5 W / m·K, a phase change temperature of 35.9 °C, and a latent heat of phase change of 197.4 J / g. After 50 cycles of energy storage and release, the latent heat of phase change is 191.4 J / g, indicating good stability.

[0052] Example 5: A core-shell structured low-temperature phase change energy storage material, wherein the phase change energy storage material is a sandwich structure material, the core is a graphene quantum dot / gallium indium silver alloy composite, the middle layer is a nitrogen-rich carbon material obtained by high-temperature carbonization of polyaniline under an inert atmosphere, and the outer layer is a zirconium titanium composite oxide with an average thickness of 10~30 nm.

[0053] A method for preparing the above-mentioned core-shell structured low-temperature phase change energy storage material includes the following steps:

[0054] At 25℃, 0.2g of graphene quantum dots were weighed and dispersed in 50mL of deionized water. 2g of 1-octyl-3-methylimidazolium chloride bromide was added and stirred for 1h. The temperature was raised to 45℃ and 10g of liquid gallium-indium-silver alloy with an elemental mass ratio of gallium, indium and silver of 1:0.01:0.008 was added dropwise. The mixture was stirred for 4h and cooled to 25℃ to obtain a graphene quantum dot / gallium-indium-silver composite dispersion.

[0055] At 25℃, 21g of ammonium persulfate and 17mL of concentrated hydrochloric acid were weighed to prepare 200mL of ammonium persulfate hydrochloric acid solution; 10.5g of aniline was added to the graphene quantum dot / gallium indium silver composite dispersion obtained above, and the mixture was stirred for 0.5h. The above ammonium persulfate hydrochloric acid solution was slowly added, and the mixture was stirred for 0.5h. The mixture was allowed to stand for 12h, centrifuged, and washed with water to obtain graphene quantum dot / gallium indium silver composite@polyaniline composite.

[0056] At 25℃, 50 mL of a 10 wt% ethanol-ammonia solution was weighed, 10 g of graphene quantum dot / gallium indium silver composite@polyaniline composite was added, and the mixture was stirred. Then, 30 mL of an ethanol solution containing 5 g of zirconium butoxide and 2 g of tetrabutyl titanate was added. The mixture was reacted for 10 h, filtered, and washed to obtain graphene quantum dot / gallium indium silver composite@polyaniline@zirconium titanium composite oxide.

[0057] The obtained graphene quantum dot / gallium indium silver composite@polyaniline@zirconium titanium composite oxide was placed in a tube furnace, argon gas was introduced, the temperature was raised to 800℃, and the reaction was carried out for 6 hours to obtain a core-shell structured low-temperature phase change energy storage material.

[0058] The core-shell structured low-temperature phase change energy storage material has an average size of 150.6 nm for the core graphene quantum dot / gallium indium silver composite and an average thickness of 17.6 nm for the outer zirconium titanium composite oxide shell. The phase change material has a thermal conductivity of 87.8 W / m·K, a phase change temperature of 38.2 °C, and a latent heat of phase change of 182.3 J / g. After 50 cycles of energy storage and release, the latent heat of phase change is 180.7 J / g, indicating good stability.

[0059] Comparative example:

[0060] A low-temperature phase change energy storage material, characterized in that: the phase change energy storage material is a core-shell structure material, the core of which is a gallium indium silver alloy composite, the outer layer is TiO2 oxide, and the average thickness is 220 nm.

[0061] A method for preparing a phase change energy storage material includes the following steps:

[0062] At 25℃, 2g of 1-octyl-3-methylimidazolium chloride bromide was weighed and dispersed in 50mL of deionized water. The mixture was stirred for 1h, heated to 45℃, and 10g of liquid gallium-indium-silver alloy with an elemental mass ratio of gallium, indium, and silver of 1:0.01:0.008 was added dropwise. The mixture was stirred for 4h, cooled to 25℃, centrifuged, and washed with 100mL of deionized water to obtain the modified gallium-indium-silver alloy.

[0063] At 25℃, 50 mL of a 10 wt% ethanol-ammonia mixed solution was weighed, 10 g of modified gallium indium silver alloy was added, and the mixture was stirred. Then, 30 mL of an ethanol solution containing 2 g tetrabutyl titanate was added, and the mixture was reacted for 10 h. After filtration and washing, gallium indium silver composite @TiO2 was obtained.

[0064] The obtained gallium indium silver composite@TiO2 was placed in a tube furnace, argon gas was introduced, the temperature was raised to 600℃, and the reaction was carried out for 6 hours to obtain a low-temperature phase change energy storage material.

[0065] The average size of the gallium indium silver composite core in the low-temperature phase change energy storage material is 1250.6 nm. The thermal conductivity of the phase change material is 38.7 W / m·K, the phase change temperature is 38.0℃, and the latent heat of phase change is 92.3 J / g. After 50 cycles of energy storage and release, the latent heat of phase change is 50.3 J / g.

[0066] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A core-shell structured low-temperature phase change energy storage material, characterized in that: The phase change energy storage material is a core-shell structure material, with a core of graphene quantum dots / gallium indium silver alloy composite, a middle layer of nitrogen-rich carbon material obtained by high-temperature carbonization of polyaniline under an inert atmosphere, and an outer layer of zirconium titanium composite oxide with an average thickness of 10~30 nm.

2. A method for preparing the core-shell structured low-temperature phase change energy storage material according to claim 1, characterized in that: Includes the following steps: Step 1: Disperse graphene quantum dots in deionized water, add ionic liquid, stir for 1-6 hours, heat to 35-70℃, add liquid gallium indium silver alloy dropwise, stir for 4-12 hours, cool to room temperature, and obtain graphene quantum dot / gallium indium silver composite dispersion. Step 2: Add aniline to the graphene quantum dot / gallium indium silver composite dispersion prepared in Step 1, stir for 0.5~2h, slowly add hydrochloric acid solution containing ammonium persulfate, stir for 0.5~2h, let stand for 12~24h, centrifuge, wash with water to obtain graphene quantum dot / gallium indium silver composite@polyaniline composite. Step 3: Disperse the graphene quantum dot / gallium indium silver composite@polyaniline composite obtained in Step 2 in an ethanol-ammonia water mixed solution, stir, add a mixture of zirconium source and titanium source in ethanol, react for 8~20h, filter, wash, and obtain graphene quantum dot / gallium indium silver composite@polyaniline@zirconium titanium composite oxide; Step 4: Place the graphene quantum dot / gallium indium silver composite@polyaniline@zirconium titanium composite oxide obtained in Step 3 into a tube furnace, introduce argon gas, heat to 800~1200℃, and react for 1~6 hours to obtain a core-shell structured low-temperature phase change energy storage material.

3. The method for preparing core-shell structured low-temperature phase change energy storage material according to claim 2, characterized in that: In step one, the mass ratio of gallium, indium, and silver in the gallium-indium-silver alloy is 1:0.01~0.08:0.008~0.02, and the mass ratio of the gallium-indium-silver alloy to graphene quantum dots is 1:0.02~0.

1.

4. The method for preparing core-shell structured low-temperature phase change energy storage material according to claim 2, characterized in that: In step one, the ratio of graphene quantum dots to deionized water is 0.001 to 0.01:1, the ionic liquid is 1-octyl-3-methylimidazolium chloride bromide or 1-butyl-3-vinylimidazolium bromide, and the mass ratio of ionic liquid to graphene quantum dots is 1:0.05 to 0.

5.

5. The method for preparing core-shell structured low-temperature phase change energy storage material according to claim 2, characterized in that: In step two, the mass ratio of aniline to graphene quantum dot / gallium indium silver composite is 1:0.2~1, the mass ratio of hydrochloric acid solution containing ammonium persulfate to aniline is 1:0.05~0.1, the mass fraction of ammonium persulfate in hydrochloric acid solution is 10~40wt%, and the mass fraction of hydrochloric acid is 5~15wt%.

6. The method for preparing core-shell structured low-temperature phase change energy storage material according to claim 2, characterized in that: In step three, the mass fraction of ammonia in the ethanol-ammonia mixed solution is 5 wt% to 20 wt%. The zirconium source is zirconium butoxide or zirconium isopropoxide, and the titanium source is tetrabutyl titanate or titanium tetrachloride. The mass ratio of titanium source to zirconium source in the ethanol mixture of zirconium and titanium source is 1:0.2 to 5, and the mass ratio of zirconium source to ethanol is 1:5 to 20.

7. The method for preparing core-shell structured low-temperature phase change energy storage material according to claim 2, characterized in that: In step three, the mass ratio of the graphene quantum dot / gallium indium silver composite@polyaniline composite to the ethanol-ammonia mixture is 1:5~10, and the mass ratio of the graphene quantum dot / gallium indium silver composite@polyaniline composite to the zirconium source is 1:0.2~1.