Capsule-type phase change material and preparation method and application thereof

Abstract

The present invention relates to a capsule-type phase change material and a preparation method and application thereof. The capsule-type phase change material is a core-shell structure; the core material includes any one of tetradecane, eicosane, docosane, paraffin wax, dodecanoic acid, neopentyl glycol, disodium hydrogen phosphate dodecahydrate, zinc nitrate hexahydrate, sodium thiosulfate pentahydrate or magnesium sulfate heptahydrate or a combination of at least two thereof; the shell material includes any one of polystyrene, poly(styrene-co-methacrylate), poly(styrene-co-butyl acrylate) or poly(2-cyanoethyl acrylate) or a combination of at least two thereof; the melting point of the capsule-type phase change material is 35-50°C. The capsule-type phase change material of the present invention has a melting point between 35-50°C, has a strong heat storage capacity, and has stable thermodynamic properties, and is suitable for heat dissipation of lithium-ion battery cells.

Description

Technical Field

[0001] The present invention relates to the technical field of phase change materials, and in particular to a capsule-type phase change material and a preparation method and application thereof, and in particular to a mono-element nano-capsule-type phase change material and a preparation method and application thereof. Background Art

[0002] In daily life, accidents involving lithium-ion battery combustion occur frequently, so how to ensure the safe operation of lithium-ion batteries is a common concern. Temperature has a great impact on the life of lithium-ion batteries. The higher the temperature, the lower the life of lithium-ion batteries. Experiments have shown that at around 70°C, a spontaneous exothermic reaction will occur inside the battery, causing the temperature to rise sharply. At around 130°C, lithium-ion batteries will produce gas, causing excessive internal pressure, pushing open the battery and causing combustion and explosion. The safe operating temperature of lithium-ion batteries is between -20-60°C. In order to ensure the safe operating temperature of lithium-ion batteries, phase change materials in specific temperature ranges need to be synthesized.

[0003] Nanocapsule phase change material (NEPCM) is a leader in phase change materials. It has outstanding advantages such as stable thermophysical properties, strong mechanical properties and wide application fields (suitable for high-end fields such as microelectronics). It has broad application prospects and has been used in the fields of construction, food and solar cells. However, the application of nanocapsule phase change material in thermal management system of lithium-ion battery is rarely reported.

[0004] Ho and Yan et al. (International Journal of Heat and Mass Transfer, 2021, 165, 120717) studied the convective heat transfer process between nanocapsule-type phase change materials and water in staggered microchannels. The use of nanocapsule-type phase change materials has obvious advantages under low Reynolds number and low thermal power conditions. Compared with pure water, the heat transfer efficiency of the suspension with nanocapsule-type phase change materials added is increased by 82%.

[0005] Sirohi et al. (RSC Advances, 2015, 5: 34377-34382) successfully synthesized nanocapsules for electrospinning polyvinyl alcohol composite fibers encapsulating octadecane; phenylethyl disulfide and azobisisobutyl nitrile were added to the reaction system as RAFT agent and initiator, respectively; ammonia solution was added to the mixed system of octadecane, amphiphilic RAFT agent, styrene and deionized water; when styrene: maleic anhydride: phenylethyl disulfide: azobisisobutyl nitrile ≈ 225:25:5:1, the synthesized NEPCMs had good particle morphology and thermal properties; DSC graphs showed that the phase transition temperature and latent heat of the material were 27°C and 44 J / g, respectively, when melting, and 23°C and 43 J / g, respectively, when crystallizing; the composite fiber obtained by electrospinning absorbed 4.3 J / g of heat at a comfortable temperature of 25.3°C, and released 4.8 J / g of heat at 9.2°C, which was obviously cold; thermal performance tests showed that NEPCMs had good heat storage performance.

[0006] It is known from the prior art that the melting phase change temperature of nanocapsule-type phase change materials is in the two major regions of 0-35°C and 60-90°C, while the safe operating temperature of lithium-ion batteries is -20-60°C. In order to improve the safety performance of the normal operation of lithium-ion batteries, it is urgently necessary to synthesize nanocapsule-type phase change materials with a melting phase change temperature between 35-50°C. Summary of the invention

[0007] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a capsule-type phase change material and a preparation method and application thereof. The capsule-type phase change material has a melting point between 35-50°C, strong heat storage performance, stable thermodynamic properties, and is suitable for heat dissipation of lithium-ion battery cells.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a capsule-type phase change material, wherein the capsule-type phase change material is a core-shell structure;

[0010] The core material includes any one of tetradecane, eicosane, docosane, paraffin wax, dodecanoic acid, neopentyl glycol, disodium hydrogen phosphate dodecahydrate, zinc nitrate hexahydrate, sodium thiosulfate pentahydrate, or magnesium sulfate heptahydrate, or a combination of at least two thereof, wherein typical but non-limiting combinations include: a combination of tetradecane, eicosane, and docosane, a combination of docosane, paraffin wax, dodecanoic acid, neopentyl glycol, disodium hydrogen phosphate dodecahydrate, and zinc nitrate hexahydrate, a combination of paraffin wax, dodecanoic acid, neopentyl glycol, disodium hydrogen phosphate dodecahydrate, zinc nitrate hexahydrate, sodium thiosulfate pentahydrate, and magnesium sulfate heptahydrate, etc.;

[0011] The shell material includes any one of polystyrene, poly(styrene-co-methacrylate), poly(styrene-co-butyl acrylate) or poly(2-ethyl cyanoacrylate), or a combination of at least two thereof, wherein typical but non-limiting combinations include: a combination of polystyrene and poly(styrene-co-methacrylate), a combination of poly(styrene-co-methacrylate), poly(styrene-co-butyl acrylate) and poly(2-ethyl cyanoacrylate), a combination of polystyrene, poly(styrene-co-methacrylate), poly(styrene-co-butyl acrylate) and poly(2-ethyl cyanoacrylate), and the like;

[0012] The melting point of the capsule-type phase change material is 35-50°C, for example, 36°C, 38°C, 40°C, 42°C, 44°C, 46°C, 48°C, etc.

[0013] In the present invention, the capsule-type phase change material has excellent thermal performance and has significant advantages in potential application in the field of thermal management systems of lithium-ion batteries.

[0014] Preferably, the core material comprises any one of tetradecane, docosane, paraffin wax or dodecanoic acid or a combination of at least two thereof, wherein typical but non-limiting combinations include: a combination of tetradecane and docosane, a combination of docosane, paraffin wax and dodecanoic acid, a combination of tetradecane, docosane, paraffin wax and dodecanoic acid, etc.;

[0015] The core material includes poly(styrene-co-methacrylate), and more preferably poly(styrene-co-methyl methacrylate).

[0016] In the present invention, the capsule-type phase change material is preferably the above-mentioned material because the raw materials are cheap and readily available, and have excellent heat storage performance and thermal stability.

[0017] In the present invention, the solid paraffin includes solid paraffin RT46-48.

[0018] Preferably, based on the total mass of the capsule-type phase change material as 100%, the mass percentage of the core material is 35.0%-85.0%, for example, 35%, 45%, 55%, 65%, 75%, 85%, etc.

[0019] Preferably, in the capsule-type phase change material, the particle size of the core structure is 100-1000 nm, for example, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, etc.

[0020] Preferably, in the capsule-type phase change material, the thickness of the shell structure is 0-100 nm, and is not equal to 0 nm, for example, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, etc.

[0021] Preferably, the melting point of the capsule-type phase change material is 44.8-45.2°C, such as 44.9°C, 45.0°C, 45.1°C, etc.

[0022] In a second aspect, the present invention provides a method for preparing the capsule-type phase change material according to the first aspect, the preparation method comprising the following steps:

[0023] (1) mixing an emulsifier with water to form an aqueous phase;

[0024] (2) mixing the polymerized monomer of the shell material, the core material and the co-emulsifier to form an oil phase;

[0025] (3) The water phase and the oil phase are mixed, finely emulsified, and polymerized to obtain the capsule-type phase change material.

[0026] In the present invention, the polymerized monomers of the shell material and the core material are obtained by mini-emulsion free radical polymerization under the barrier of an emulsifier.

[0027] In the present invention, the preparation method has the characteristics of short material preparation route and simple operation. High-performance monolithic nanocapsule-type phase change material can be prepared only by mini-emulsion free radical polymerization. The monolithic nanocapsule-type phase change material is superior to microcapsule-type phase change material and macro-encapsulation phase change material in thermal and mechanical properties, and has significant advantages in potential application in the field of thermal management systems of lithium-ion batteries.

[0028] Preferably, in step (1), the emulsifier comprises any one of sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate or sodium stearate, or a combination of at least two of them, wherein typical but non-limiting combinations include: a combination of sodium dodecyl sulfonate and sodium dodecylbenzene sulfonate, a combination of sodium dodecylbenzene sulfonate and sodium stearate, a combination of sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate and sodium stearate, etc.

[0029] Preferably, based on 100 parts by total weight of water, the weight portion of the emulsifier is 0.05-0.5 parts, for example, 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, 0.4 parts, 0.45 parts, etc.

[0030] Preferably, in step (2), the co-emulsifier comprises any one of octylphenol polyethylene glycol, sorbitan monooleate or sorbitan monooleate, or a combination of at least two thereof, wherein typical but non-limiting combinations include: a combination of octylphenol polyethylene glycol and sorbitan monooleate, a combination of sorbitan monooleate and sorbitan monooleate, a combination of octylphenol polyethylene glycol, sorbitan monooleate and sorbitan monooleate, and the like.

[0031] Preferably, based on 100 parts of the total weight of the core material, the weight proportion of the co-emulsifier is 1-5 parts, for example, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, etc.

[0032] Preferably, in step (3), the fine emulsification method includes high-speed stirring.

[0033] In the present invention, high-speed homogeneous stirring and demulsification are adopted to ensure that the droplets in the polymerization process are maintained at the nanometer scale, thereby synthesizing the nano-capsule type phase change material.

[0034] Preferably, the rotation speed of the high-speed stirring is 5000-10000 rpm, for example, 5500 rpm, 6000 rpm, 6500 rpm, 7000 rpm, 7500 rpm, 8000 rpm, 8500 rpm, 9000 rpm, 9500 rpm, etc.

[0035] Preferably, the high-speed stirring time is 10-20 min, for example, 12 min, 14 min, 16 min, 18 min, 20 min, etc.

[0036] Preferably, the process after the fine emulsification and before the polymerization further comprises a low-temperature water bath.

[0037] Preferably, the temperature of the low-temperature water bath is 0-10°C, such as 2°C, 4°C, 6°C, 8°C, etc.

[0038] Preferably, the low-temperature water bath time is 1-10 min, such as 2 min, 4 min, 6 min, 8 min, etc.

[0039] Preferably, the polymerization is carried out under a protective atmosphere and with stirring.

[0040] Preferably, the polymerization temperature is 50-100°C, for example, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, etc.

[0041] Preferably, the polymerization time is 1-24 h, for example 2 h, 5 h, 10 h, 12 h, 20 h, etc.

[0042] Preferably, the stirring speed is 100-1000 rpm, for example, 200 rpm, 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, etc.

[0043] Preferably, the polymerization is carried out under the action of a catalyst.

[0044] Preferably, the catalyst comprises any one of azobisisoheptylnitrile, azobisisobutylnitrile or dimethyl azobisisobutyrate, or a combination of at least two thereof, wherein typical but non-limiting combinations include: a combination of azobisisoheptylnitrile and azobisisobutylnitrile, a combination of azobisisobutylnitrile and dimethyl azobisisobutyrate, a combination of azobisisoheptylnitrile, azobisisobutylnitrile and dimethyl azobisisobutyrate, and the like.

[0045] Preferably, the polymerization further comprises filtering, washing and drying.

[0046] As a preferred technical solution, the preparation method comprises the following steps:

[0047] (1) mixing an emulsifier with water to form an aqueous phase;

[0048] (2) mixing the polymerized monomer of the shell material, the core material and the co-emulsifier to form an oil phase;

[0049] (3) mixing the aqueous phase and the oil phase, stirring at a speed of 5000-10000 rpm for 10-20 min to complete fine emulsification, placing in a low-temperature water bath at 0-10° C. for 1-10 min, polymerizing at 50-100° C. and 100-1000 rpm under a protective atmosphere for 1-24 h, and then filtering, washing and drying to obtain the capsule-type phase change material;

[0050] Optionally, a catalyst is added to the system during the mixing in step (1) or before the polymerization in step (3).

[0051] In a third aspect, the present invention provides an application of the capsule-type phase change material described in the first aspect in a lithium battery.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] (1) The capsule-type phase change material of the present invention has strong mechanical properties, is not easy to break, has stable thermodynamic properties, high thermal conductivity, and a narrow particle size distribution, and is suitable for heat dissipation of lithium-ion battery cells.

[0054] (2) The capsule-type phase change material of the present invention has a melting point of 35-50°C, a solidification point of 40.1-42.1°C, and a melting enthalpy of 81.9 J·g -1Above, the thermal decomposition temperature is above 123.3℃, ​​and the thermal conductivity is 0.18W·m -1 ·K -1 Above, the particle size distribution is between 0.43-0.87. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is the particle size distribution image of the nanocapsule phase change capsule in Example 3;

[0056] Figure 2 TG curve of the nanocapsule phase change capsule in Example 3;

[0057] Figure 3 is the SEM image of the nanocapsule phase change capsule in Example 3;

[0058] Figure 4 This is the particle size distribution image of the nanocapsule phase change capsule in Example 4;

[0059] Figure 5 TG curve of the nanocapsule phase change capsule in Example 4;

[0060] Figure 6 This is the SEM image of the nanocapsule phase change capsule in Example 4. DETAILED DESCRIPTION

[0061] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0062] In the present invention, the raw material information of each embodiment is as follows:

[0063] Docosane: purchased from Shanghai MacLean Biochemical Technology Co., Ltd., brand number D835750;

[0064] Tetradecane: purchased from Shanghai MacLean Biochemical Technology Co., Ltd., brand number T818478;

[0065] Dodecanoic acid: purchased from Sane Chemical Technology (Shanghai) Co., Ltd., brand number A011020;

[0066] Solid paraffin RT46-48: purchased from Shanghai MacLean Biochemical Technology Co., Ltd., brand number P887025;

[0067] Octylphenol polyethylene glycol: purchased from Shanghai MacLean Biochemical Technology Co., Ltd., brand number O821357.

[0068] Example 1

[0069] This embodiment provides a monolithic nanocapsule-type phase change material, wherein the monolithic nanocapsule-type phase change material has docosane as a core and poly(styrene-co-methyl methacrylate) as a shell.

[0070] Taking the total mass of the nanocapsule-type phase-change material as 100%, the mass percentage of the core material is 63.7%; the particle size of the core structure is 754 nm, and the thickness of the shell structure is 97 nm.

[0071] The monolithic nanocapsule-type phase change material is prepared by the following method, which comprises the following steps:

[0072] (1) 10 g of styrene (St), 1 g of methyl methacrylate (MMA), 0.08 g of azobisisoheptyl nitrile (AIVN), 10 g of docosane and 0.2 g of octylphenol polyethylene glycol (OP-10) were mixed to obtain an oil phase;

[0073] (2) adding 0.2 g of sodium dodecyl sulfate (SDS) emulsifier to 200 g of deionized water and stirring to form an aqueous phase;

[0074] (3) Add the oil phase and the water phase into a 1000 mL flask, set the speed to 8000 rpm, and use a high-speed homogenizer to shear the mixture for 10 min to complete fine emulsification;

[0075] (4) After standing in a 5°C low-temperature water bath for 5 minutes, the miniemulsion was transferred to a three-necked flask equipped with a stirrer and a condenser, nitrogen was passed for 15 minutes to remove oxygen in the system, and the reaction device was immersed in a 60°C constant temperature oil bath, the speed was set to 350 rpm, and stirred in an inert gas atmosphere for 9 hours and 20 minutes. Stirring was stopped and the mixed system was slowly cooled to room temperature to obtain a latex;

[0076] (5) 40 mL of anhydrous ethanol was added and refluxed for 30 min. The mixture was filtered, washed and dried to obtain 4.2 g of solid particles, which are NEPCM materials, i.e., the monolithic nanocapsule-type phase change material.

[0077] Example 2

[0078] This embodiment provides a monolithic nanocapsule-type phase change material. The monolithic nanocapsule-type phase change material has dodecanoic acid as a core and poly(styrene-co-methyl methacrylate) as a shell.

[0079] Taking the total mass of the nanocapsule-type phase-change material as 100%, the mass percentage of the core material is 78.5%; the particle size of the core structure is 537 nm, and the thickness of the shell structure is 68 nm.

[0080] The monolithic nanocapsule-type phase change material is prepared by the following method, which comprises the following steps:

[0081] (1) 10 g of styrene (St), 1 g of methyl methacrylate (MMA), 10 g of dodecanoic acid and 0.2 g of octylphenol polyethylene glycol (OP-10) were mixed to obtain an oil phase;

[0082] (2) adding 0.2 g of sodium dodecyl sulfate (SDS) emulsifier to 200 g of deionized water and stirring to form an aqueous phase;

[0083] (3) Add the oil phase and the water phase into a 1000 mL flask, set the speed to 8000 rpm, and use a high-speed homogenizer to shear the mixture for 16 min to complete fine emulsification;

[0084] (4) The miniemulsion was transferred to a three-necked flask equipped with a stirrer and a condenser, nitrogen was passed through for 15 min to remove oxygen in the system, the reaction apparatus was immersed in a constant temperature oil bath at 60° C., 0.08 g of azobisisoheptylnitrile (AIVN) was added, and the mixture was stirred at 500 rpm for 8 h. The stirring was stopped and the mixed system was slowly cooled to room temperature to obtain a latex;

[0085] (5) 100 mL of anhydrous ethanol was added and refluxed for 30 min, filtered, washed with anhydrous ethanol and water for 3 times respectively, and dried in a vacuum oven at 60° C. overnight to obtain 3.15 g of solid particles, which are NEPCM materials, i.e., the monolithic nanocapsule-type phase change material.

[0086] Example 3

[0087] The present embodiment provides a monolithic nanocapsule-type phase change material, wherein the monolithic nanocapsule-type phase change material has docosane as a core and poly(styrene-co-methyl methacrylate) (PS-PMMA) as a shell.

[0088] Taking the total mass of the nanocapsule-type phase-change material as 100%, the mass percentage of the core material is 66.4%; the particle size of the core structure is 655 nm, and the thickness of the shell structure is 87 nm.

[0089] The monolithic nanocapsule-type phase change material is prepared by the following method, which comprises the following steps:

[0090] (1) 10 g of styrene (St), 1 g of methyl methacrylate (MMA), 10 g of docosane and 0.2 g of octylphenol polyethylene glycol (OP-10) were mixed to obtain an oil phase;

[0091] (2) adding 0.2 g of sodium dodecyl sulfate (SDS) emulsifier to 200 g of deionized water and stirring to form an aqueous phase;

[0092] (3) Add the oil phase and the water phase into a 1000 mL flask, set the speed to 8000 rpm, and use a high-speed homogenizer to shear the mixture for 16 min to complete fine emulsification;

[0093] (4) The miniemulsion was transferred to a three-necked flask equipped with a stirrer and a condenser, nitrogen was passed through for 15 min to remove oxygen in the system, the reaction apparatus was immersed in a constant temperature oil bath at 60° C., 0.08 g of azobisisoheptylnitrile (AIVN) was added, and the mixture was stirred at 500 rpm for 8 h. The stirring was stopped and the mixed system was slowly cooled to room temperature to obtain a latex;

[0094] (5) 100 mL of anhydrous ethanol was added and refluxed for 30 min, filtered, washed with anhydrous ethanol and water for 3 times respectively, and dried in a vacuum oven at 60° C. overnight to obtain 6.39 g of solid particles, which are NEPCM materials, i.e., the monolithic nanocapsule-type phase change material.

[0095] Example 4

[0096] This embodiment provides a unitary nano-capsule type phase change material. The unitary nano-capsule type phase change material has solid paraffin RT46-48 as a core and poly(styrene-co-methyl methacrylate) as a shell.

[0097] Taking the total mass of the nanocapsule-type phase-change material as 100%, the mass percentage of the core material is 39.5%; the particle size of the core structure is 615 nm, and the thickness of the shell structure is 71 nm.

[0098] The monolithic nanocapsule-type phase change material is prepared by the following method, which comprises the following steps:

[0099] (1) 10 g of styrene (St), 1 g of methyl methacrylate (MMA), 10 g of solid paraffin RT46-48 and 0.2 g of octylphenol polyethylene glycol (OP-10) were mixed to obtain an oil phase;

[0100] (2) adding 0.2 g of sodium dodecyl sulfate (SDS) emulsifier to 200 g of deionized water and stirring to form an aqueous phase;

[0101] (3) Add the oil phase and the water phase into a 1000 mL flask, set the speed to 8000 rpm, and use a high-speed homogenizer to shear the mixture for 16 min to complete fine emulsification;

[0102] (4) The miniemulsion was transferred to a three-necked flask equipped with a stirrer and a condenser, nitrogen was passed through for 15 min to remove oxygen in the system, the reaction apparatus was immersed in a 70°C constant temperature oil bath, 0.08 g of azobisisoheptylnitrile (AIVN) was added, and the mixture was stirred at 750 rpm for 8 h. Stirring was stopped and the mixed system was slowly cooled to room temperature to obtain a latex;

[0103] (5) 100 mL of anhydrous ethanol was added and refluxed for 30 min, filtered, washed with anhydrous ethanol and water for 3 times respectively, and dried in a vacuum oven at 60° C. overnight to obtain 11.14 g of solid particles, which are NEPCM materials, i.e., the monolithic nanocapsule-type phase change material.

[0104] Comparative Example 1

[0105] This comparative example provides a microcapsule phase change material, which was purchased from Guangzhou Zhongjia New Material Technology Co., Ltd. and has a product brand of ZJ-PCM-M-28.

[0106] Comparative Example 2

[0107] This comparative example provides a macro-package phase change material, which was purchased from Guangzhou Zhongjia New Material Technology Co., Ltd. and has a product brand of PCM-BM-42.

[0108] Performance Testing

[0109] The capsule-type phase change materials described in Examples 1-4 and Comparative Examples 1-2 were tested as follows:

[0110] (1) Melting point: measured on a TA DSC25 differential scanning calorimeter with a scanning rate of 10 °C / min and a scanning range of 0–80 °C;

[0111] Freezing point: carried out on a TA DSC25 differential scanning calorimeter with a scanning rate of -10°C / min and a scanning range of 80-0°C;

[0112] Melting enthalpy: It was measured on a TA DSC25 differential scanning calorimeter with a scanning rate of 10°C / min and a scanning range of 0-80°C.

[0113] (2) Thermal stability: The analysis was performed on a Netzsch STA 449F3 thermogravimetric analyzer with a scanning rate of 10 °C / min and a scanning range of room temperature to 600 °C.

[0114] (3) Thermal conductivity: The test was performed on a HotDisk TPS2500S thermal conductivity meter and on tablets at room temperature.

[0115] (4) Particle size distribution: The particle size distribution was measured on a Malvern Zetasizer Nano ZS90 nanoparticle size and zeta potential analyzer. The samples were dispersed in ethanol.

[0116] The test results are summarized in Table 1 and Figure 1-6 middle.

[0117] Table 1

[0118]

[0119] According to the data in Table 1, the melting point of the capsule-type phase change material of the present invention is between 44.8-45.2°C, the solidification point is between 40.1-42.1°C, and the melting enthalpy is 81.9 J·g -1 Above, the thermal decomposition temperature is above 123.3℃, ​​and the thermal conductivity is 0.18W·m -1 ·K -1 The particle size distribution is between 0.43 and 0.87. The capsule-type phase change has stable thermodynamic properties, high thermal conductivity, and narrow particle size distribution, and is suitable for heat dissipation of lithium-ion battery cells.

[0120] Taking Example 3 as an example, Figure 1 is the particle size distribution image of the capsule-type phase change material, Figure 2 Its TG curve is: Figure 3 The SEM image is shown, and the result proves that the capsule-type phase change material of the present invention is successfully prepared and has excellent thermal degradation performance. Figure 4 , Figure 5 and Figure 6 They are respectively the capsule-type phase change materials described in Example 4, and the results are similar.

[0121] Analysis of comparative examples 1-2 and example 1 shows that the performance of comparative examples 1-2 is not as good as that of example 1, which proves that the capsule-type phase change material of the present invention is superior to the microcapsule-type phase change material and the macro-encapsulation phase change material in thermal performance.

[0122] The applicant declares that the present invention illustrates the detailed method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed method, that is, it does not mean that the present invention must rely on the above-mentioned detailed method to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A capsule-type phase change material, characterized in that: The capsule-type phase change material is a core-shell structure; The core material includes any one of docosane, paraffin wax or dodecanoic acid or a combination of at least two thereof; Shell materials include poly(styrene- co -methacrylate), poly(styrene- co -butyl acrylate) or poly(ethyl 2-cyanoacrylate) or a combination of at least two thereof; The melting point of the capsule-type phase change material is 44.8-45.2°C; the particle size distribution of the capsule-type phase change material is between 0.43-0.87; The capsule-type phase change material is prepared by the following method, which comprises the following steps: (1) Mixing an emulsifier with water to form an aqueous phase; (2) mixing the polymer monomer of the shell material, the core material and the co-emulsifier to form an oil phase; (3) The water phase and the oil phase are mixed, and finely emulsified and polymerized under high-speed stirring at 5000-10000 rpm to obtain the capsule-type phase change material.

2. The capsule-type phase change material according to claim 1, characterized in that: Taking the total mass of the capsule-type phase change material as 100%, the mass percentage of the core material is 35.0%-85.0%.

3. The capsule-type phase change material according to claim 1, characterized in that: In the capsule-type phase change material, the particle size of the core structure is 100-1000 nm.

4. The capsule-type phase change material according to claim 1, characterized in that: In the capsule-type phase change material, the thickness of the shell structure is 0-100 nm, and is not equal to 0 nm.

5. A method for preparing the capsule-type phase change material according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: (1) Mixing an emulsifier with water to form an aqueous phase; (2) mixing the polymer monomer of the shell material, the core material and the co-emulsifier to form an oil phase; (3) The water phase and the oil phase are mixed, and finely emulsified and polymerized under high-speed stirring at 5000-10000 rpm to obtain the capsule-type phase change material.

6. The preparation method according to claim 5, characterized in that: In step (1), the emulsifier includes any one of sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate or sodium stearate, or a combination of at least two of them.

7. The preparation method according to claim 5, characterized in that: Based on 100 parts by weight of water, the weight portion of the emulsifier is 0.05-0.5 parts.

8. The preparation method according to claim 5, characterized in that: In step (2), the co-emulsifier includes any one of octylphenol polyethylene glycol, sorbitan monooleate or sorbitan monooleate, or a combination of at least two thereof.

9. The preparation method according to claim 5, characterized in that: Based on 100 parts of the total weight of the core material, the weight portion of the auxiliary emulsifier is 1-5 parts.

10. The preparation method according to claim 5, characterized in that: The high-speed stirring time is 10-20 minutes.

11. The preparation method according to claim 5, characterized in that: The process after the fine emulsification and before the polymerization also includes a low-temperature water bath.

12. The preparation method according to claim 11, characterized in that: The temperature of the low temperature water bath is 0 - 10 °C.

13. The preparation method according to claim 11, characterized in that: The time of the low temperature water bath is 1 - 10 min.

14. The preparation method according to claim 5, characterized in that: The polymerization was carried out under a protective atmosphere and with stirring.

15. The preparation method according to claim 5, characterized in that: The polymerization temperature is 50 - 100 °C.

16. The preparation method according to claim 5, characterized in that: The polymerization time is 1 - 24 h.

17. The preparation method according to claim 14, characterized in that: The stirring speed is 100 - 1000 rpm.

18. The preparation method according to claim 5, characterized in that: The polymerization is carried out under the action of a catalyst.

19. The preparation method according to claim 18, characterized in that: The catalyst includes any one of azobisisoheptylnitrile, azobisisobutylnitrile or dimethyl azobisisobutyrate or a combination of at least two thereof.

20. The preparation method according to claim 5, characterized in that: The polymerization process further includes filtering, washing and drying.

21. The preparation method according to claim 5, characterized in that: The preparation method comprises the following steps: (1) Mixing an emulsifier with water to form an aqueous phase; (2) mixing the polymer monomer of the shell material, the core material and the co-emulsifier to form an oil phase; (3) The aqueous phase and the oil phase are mixed, stirred at a speed of 5000-10000 rpm for 10-20 min to complete fine emulsification, placed in a low-temperature water bath at 0-10°C for 1-10 min, polymerized at 50-100°C and 100-1000 rpm under a protective atmosphere for 1-24 h, and then filtered, washed and dried to obtain the capsule-type phase change material.

22. The preparation method according to claim 21, characterized in that: During the mixing in step (1) or before the polymerization in step (3), a catalyst is added to the system.

23. Use of the capsule-type phase change material according to any one of claims 1 to 4 in a lithium battery.

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