Solid electric heating material and preparation method and application thereof
By preparing the organic-inorganic hybrid ferroelectric material [(CH3)3NCH2Cl]CdCl3, the problem of insufficient isothermal entropy change under low driving electric field was solved, and efficient and safe electrothermal cooling effect was achieved.
Patent Information
- Application Number
- CN202411216582.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-02
- Publication Date
- 2026-03-10
AI Technical Summary
Existing electrothermal materials have insufficient isothermal entropy change under low driving electric fields, and high driving electric fields may cause safety hazards, making it difficult to achieve efficient and safe electrothermal cooling.
Organic-inorganic hybrid ferroelectric material [(CH3)3NCH2Cl]CdCl3 was prepared by chemical synthesis. By combining inorganic CdCl3 and organic (CH3)3NCH2Cl ions, a one-dimensional long molecular chain structure was formed, which achieved a large electrothermal effect under a small electric field.
Under a small electric field of 7.3 MV m⁻¹, the material exhibits an entropy change of up to 50 J kg⁻¹ K⁻¹ and a thermal hysteresis of less than 3.2 K, which significantly improves the efficiency and safety of the electrothermal effect.
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Figure CN121627728A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to a kind of solid-state electrocaloric materials and its preparation method and application, specifically related to a kind of organic-inorganic hybrid solid-state electrocaloric materials with low electric field driving large electrocaloric effect and its preparation method and related refrigeration applications. BACKGROUND
[0002] Refrigeration industry energy consumption accounts for more than 15% of total energy consumption. The Carnot cycle efficiency of the commonly used gas compression refrigeration technology is only about 25%, and the gas refrigerant used in gas compression refrigeration will exacerbate the greenhouse effect. Exploring pollution-free, green and environmentally friendly refrigeration materials and developing new low-energy and high-efficiency refrigeration technology is an urgent problem that the world needs to solve today.
[0003] Solid-state thermoelectric refrigeration technology has the advantages of green and environmentally friendly, stable and reliable, and has attracted widespread attention worldwide in recent years. Solid-state thermoelectric materials have also been fully explored, and many high-performance materials that are expected to be applied to refrigeration technology have emerged.
[0004] Solid-state thermoelectric effect is mainly divided into three categories: magnetic heat effect, electrocaloric effect and mechanical heat effect. Among them, the magnetic heat effect depends on the driving of the magnetic field, and the mechanical heat effect needs the action of mechanical force. However, among the three effects, the electrocaloric effect has more significant practicality due to its economic and easy-to-obtain electric field driving characteristics.
[0005] As the power source of electrocaloric effect, electric field not only has relatively low cost, but also is easy to obtain, which makes electrocaloric refrigeration technology have significant advantages in practical application. Under the background of the current society's pursuit of environmentally friendly refrigeration and high-efficiency refrigeration, the research and development of electrocaloric refrigeration technology is particularly important. It not only can meet the demand of high efficiency and low energy consumption in the field of refrigeration, but also can promote the development of refrigeration technology to a more green and environmentally friendly direction, which has far-reaching practical significance for the refrigeration revolution.
[0006] Electrocaloric effect refers to the reversible thermal response caused by electric field. Electrocaloric materials can be roughly divided into two categories from the source of electrocaloric effect: one is a relaxor ferroelectric body with dispersed second-order phase change, and electric field can cause thermal effect by inducing polarization disorder-order change near the dispersed second-order phase change; the other is a conventional ferroelectric body with a first-order phase change from ferroelectric to paraelectric, and electric field can cause thermal effect by inducing crystal structure change near the phase change temperature. It is generally believed that the isothermal entropy change (and adiabatic temperature change) under electric field can be used to evaluate the electrocaloric performance of electrocaloric materials.
[0007] According to existing reports, organic relaxor ferroelectric PVDF system materials exhibit excellent isothermal entropy change performance, with a value of more than 100 J kg -1 K -1 However, this excellent performance is at the cost of a high electric field of 100 MV m-1 In contrast, inorganic relaxor ferroelectrics and conventional ferroelectric ceramics, such as BaTiO3 system, (Na, Bi)TiO3 system, Pb(Sc, Ta)O3 system and Pb(Zr, Ti)O3 system, etc., although their driving electric fields are generally lower, usually in the range of 10 MV m-1to 20 MV m-1, their isothermal entropy changes are also relatively limited, generally less than 10 J kg-1K-1. -1 In contrast, inorganic relaxor ferroelectrics and conventional ferroelectric ceramics, such as BaTiO3 system, (Na, Bi)TiO3 system, Pb(Sc, Ta)O3 system and Pb(Zr, Ti)O3 system, etc., although their driving electric fields are generally lower, usually in the range of 10 MV m-1to 20 MV m-1, their isothermal entropy changes are also relatively limited, generally less than 10 J kg-1K-1. -1 K -1 .
[0008] It can be seen from the above that in the existing electrocaloric materials, a lower driving electric field is often accompanied by a smaller isothermal entropy change, and a large isothermal entropy change requires an extremely high electric field driving. This causes a dilemma in practical applications: if an inorganic ceramic with a small driving electric field is used in an electrocaloric refrigeration device, it will face the problem of insufficient isothermal entropy change and refrigeration power; and if an organic PVDF system material is used, although a higher isothermal entropy change can be obtained, the extremely high driving electric field may cause safety hazards.
[0009] Therefore, in order to promote the commercialization of electrocaloric refrigeration technology, it is a key and urgent need to develop a new type of electrocaloric material that can produce large electrocaloric effect under small electric field driving.
[0010] In summary, the ideal electrocaloric material should combine the low driving electric field requirement of inorganic ceramic ferroelectric and the high isothermal entropy change advantage of organic PVDF system ferroelectric, that is, to achieve significant electrocaloric effect under low electric field driving. Since organic-inorganic hybrid materials can usually combine the characteristics of inorganic and organic materials, it is reasonable to believe that through the careful design of organic-inorganic hybrid ferroelectric, it is expected to achieve such a large electrocaloric effect under small electric field driving, thereby leading the electrocaloric refrigeration technology to a new height. SUMMARY
[0011] Therefore, the purpose of the present application is to provide an organic-inorganic hybrid electrocaloric refrigeration working medium with small electric field driving and large electrocaloric effect, as well as a preparation method and application thereof.
[0012] The inventors of the present application have successfully prepared a new type of organic-inorganic hybrid ferroelectric material [(CH3)3NCH2Cl]CdCl3 by chemical synthesis, which is a typical first-order phase transition material. In the phase transition process, not only significant latent heat and entropy change are accompanied, but also the entropy change value is as high as 50 J kg-1K-1, which is significantly higher than that of similar materials. Moreover, the material exhibits a small thermal hysteresis in thermal response, with a minimum thermal hysteresis of only 3.2 K. What is particularly noteworthy is that the organic-inorganic hybrid ferroelectric material is extremely sensitive to electric field, and a large electrocaloric effect can be achieved under a small electric field (7.3 MV m-1). -1 K -1 , which is significantly higher than that of similar materials, and the material exhibits a small thermal hysteresis in thermal response, with a minimum thermal hysteresis of only 3.2 K. What is particularly noteworthy is that the organic-inorganic hybrid ferroelectric material is extremely sensitive to electric field, and a large electrocaloric effect can be achieved under a small electric field (7.3 MV m-1 ) driving, a maximum of 33.1 J kg -1 K -1 isothermal entropy change, indicating that it has excellent electrocaloric effect under small electric field. These performance advantages not only exceed all previously reported electrocaloric materials, but also bring new possibilities and breakthroughs to the field of electrocaloric refrigeration technology.
[0013] The first aspect of the present application provides a solid-state electrocaloric material, which has a chemical formula of: [(CH3)3NCH2Cl]CdCl3.
[0014] According to the solid-state electrocaloric material provided by the present application, the phase transition temperature of the material is 400K.
[0015] According to the solid-state electrocaloric material provided by the present application, the entropy change of the material during phase transition is higher than 50J kg -1 K -1 .
[0016] According to the solid-state electrocaloric material provided by the present application, the maximum isothermal entropy change of the material induced by an electric field with a strength of 7.3MV m -1 is higher than 30J kg -1 K -1 .
[0017] The second aspect of the present application provides a preparation method of the above-mentioned solid-state electrocaloric material, which comprises the following steps:
[0018] (1) adding trimethylamine and dichloromethane into oxolane and mixing uniformly, after the reaction is completed, removing the solvent to obtain chloromethyl trimethyl ammonium chloride (chemical formula: [(CH3)3NCH2Cl]Cl);
[0019] (2) adding the chloromethyl trimethyl ammonium chloride prepared in step (1) and cadmium chloride (CdCl2) into deionized water, fully reacting, filtering, and evaporating and crystallizing the filtrate to obtain the solid-state electrocaloric material with a chemical formula of [(CH3)3NCH2Cl]CdCl3.
[0020] According to the preparation method provided by the present application, preferably, the preparation method can further comprise: (3) recrystallizing the crystal obtained in step (2) with deionized water and drying and storing.
[0021] According to the preparation method provided by the present application, the trimethylamine in step (1) is preferably provided in the form of a solution, preferably a trimethylamine ethanol solution with a concentration of 2-40wt%, more preferably a trimethylamine ethanol solution with a concentration of 20-40wt%.
[0022] In the preferred embodiment of the present application, the molar ratio of trimethylamine to dichloromethane in step (1) is 1:0.5-2, more preferably 1:0.8-1.2. Preferably, the amount of oxolane used is 0.1-1 ml relative to 1 mmol of trimethylamine.
[0023] Preferably, the reaction temperature of step (1) can be 0-35℃, more preferably 20-30℃; the reaction time can be 4-48 hours, more preferably 18-30 hours.
[0024] In the preferred embodiment of the present application, the molar ratio of trimethylamine to dichloromethane in step (1) is 1:0.5-2, more preferably 1:0.8-1.2. Preferably, the amount of oxolane used is 0.1-1 ml relative to 1 mmol of trimethylamine.
[0025] Preferably, the reaction temperature of step (2) can be 0-50℃, more preferably 20-35℃; the reaction time can be 4-48 hours, more preferably 18-30 hours.
[0026] In the preferred embodiment of the present application, the evaporation crystallization process in step (2) is carried out at room temperature of about 20-35℃.
[0027] According to the preparation method provided by the present application, the purity of dichloromethane and cadmium chloride is not less than 99wt.%.
[0028] The third aspect of the present application provides the application of the solid-state electrocaloric material or the solid-state electrocaloric material prepared according to the preparation method of the present application as a refrigeration working medium.
[0029] Compared with the prior art, the solid-state electrocaloric material of the present application has obvious advantages. The [(CH3)3NCH2Cl]CdCl3 material provided by the present application is a typical first-order phase change material. The phase change causes huge latent heat of phase change and entropy change. The entropy change of the phase change process can reach 50 J kg -1 K -1 At the same time, the hysteresis of the material is small, and the minimum thermal hysteresis can be as low as 3.2K. The phase change of the material is sensitive to electric field. The isothermal entropy change under a small electric field of 7.3 MV m -1 is more than 30 J Kg -1 K -1 , which is much higher than all the reported materials. The [(CH3)3NCH2Cl]CdCl3 material can realize large electrocaloric effect under a small electric field, and therefore has great potential application value in electrocaloric refrigeration technology. BRIEF DESCRIPTION OF DRAWINGS
[0030] Hereinafter, the embodiments of the present application will be described in detail with reference to the accompanying drawings, in which:
[0031] Figure 1 The room temperature single crystal diffraction test results of the [(CH3)3NCH2Cl]CdCl3 material provided by this invention;
[0032] Figure 2 The heat flow curve and entropy change of the [(CH3)3NCH2Cl]CdCl3 material in the absence of an electric field are provided by this invention.
[0033] Figure 3 The hysteresis loops of the [(CH3)3NCH2Cl]CdCl3 material provided by this invention at different temperatures;
[0034] Figure 4 The isothermal entropy change curves of the [(CH3)3NCH2Cl]CdCl3 material provided by this invention under different electric fields were calculated based on the hysteresis loop.
[0035] Figure 5 The heat flow curves and entropy changes of the [(CH3)3NCH2Cl]CdCl3 material under different electric fields provided by this invention;
[0036] Figure 6 The isothermal entropy change curves of the [(CH3)3NCH2Cl]CdCl3 material provided by this invention are obtained from the heat flow curves under different voltages and under different electric fields.
[0037] Figure 7 The heat flow curve of the isothermal entropy change of the [(CH3)3NCH2Cl]CdCl3 material provided by this invention is a direct measurement of heat flow.
[0038] Figure 8 Isothermal entropy change curves of the [(CH3)3NCH2Cl]CdCl3 material provided by this invention were obtained by different measurement methods. Detailed Implementation
[0039] The present invention will be further described in detail below with reference to specific embodiments. The embodiments given are only for illustrating the present invention and are not intended to limit the scope of the present invention.
[0040] The raw materials and equipment used in the examples are described below:
[0041] (1) The purity of dichloromethane and cadmium chloride is not less than 99 wt.%, and both are purchased from Sinopharm Chemical Reagent Co., Ltd.
[0042] (2) The single crystal diffractometer was manufactured by Rigaku Corporation of Japan, model number Rigaku XtaLABPRO 007HF.
[0043] (3) The hysteresis loop was measured by an aixACCT TF Analyzer 2000 ferroelectric analyzer manufactured by aixACCT GmbH, Germany.
[0044] (4) The heat flow curve was measured using a fully automated differential scanning calorimeter NETZSCHDSC 214SET MFC LN2 manufactured by NETZSCH GmbH, Germany. The voltage was provided by a DC voltage source, model DW-P303-1ACH2, manufactured by Dongwen High Voltage Engineering Co., Ltd., China.
[0045] Example 1
[0046] Preparation of the [(CH3)3NCH2Cl]CdCl3 material of the present invention
[0047] 1) Trimethylamine (33% wt ethanol solution) and dichloromethane were mixed in oxepane at a molar ratio of 1:1 and reacted at room temperature for 24 hours. For 1 mmol of trimethylamine, the amount of oxepane used was 0.1 mL. The solution after reaction was transferred to a vacuum oven to remove the solvent, and chloromethyltrimethylammonium chloride [(CH3)3NCH2Cl]Cl was obtained.
[0048] 2) The prepared chloromethyltrimethylammonium chloride [(CH3)3NCH2Cl]Cl and cadmium chloride CdCl2 were added to deionized water in a 1:1 molar ratio. For 1 mmol of trimethylammonium chloride, the amount of oxacyclopentane was 1 mL. After the reaction was complete, the mixture was filtered through filter paper with a pore size of 0.22 μm to obtain the filtrate.
[0049] 3) Place the filtrate obtained in step 2) in a room temperature and normal pressure environment, allow it to evaporate naturally, and precipitate crystals to obtain the [(CH3)3NCH2Cl]CdCl3 material of the present invention.
[0050] Example 2
[0051] Preparation of the [(CH3)3NCH2Cl]CdCl3 material of the present invention
[0052] 1) Trimethylamine (22% wt ethanol solution) and dichloromethane were mixed in oxepane at a molar ratio of 1:1.2 and reacted at room temperature for 30 hours. For 1 mmol of trimethylamine, the amount of oxepane used was 0.5 mL. The solution after reaction was transferred to a vacuum oven to remove the solvent, and chloromethyltrimethylammonium chloride [(CH3)3NCH2Cl]Cl was obtained.
[0053] 2) The prepared chloromethyltrimethylammonium chloride [(CH3)3NCH2Cl]Cl and cadmium chloride CdCl2 were added to deionized water at a molar ratio of 1:0.8. For 1 mmol of trimethylammonium chloride, the amount of oxacyclopentane used was 3 mL. After the reaction was complete, the mixture was filtered through filter paper with a pore size of 0.22 μm to obtain the filtrate.
[0054] 3) Place the filtrate obtained in step 2) in a room temperature and normal pressure environment, allow it to evaporate naturally, and precipitate crystals to obtain the [(CH3)3NCH2Cl]CdCl3 material of the present invention.
[0055] Example 3
[0056] Preparation of the [(CH3)3NCH2Cl]CdCl3 material of the present invention
[0057] 1) Trimethylamine (40% wt ethanol solution) and dichloromethane were mixed in oxepane at a molar ratio of 1:0.8 and reacted at room temperature for 18 hours. For 1 mmol of trimethylamine, 1 mL of oxepane was used. The reaction solution was transferred to a vacuum oven to remove the solvent, yielding chloromethyltrimethylammonium chloride [(CH3)3NCH2Cl]Cl.
[0058] 2) The prepared chloromethyltrimethylammonium chloride [(CH3)3NCH2Cl]Cl and cadmium chloride CdCl2 were added to deionized water at a molar ratio of 1:1.2. For 1 mmol of trimethylammonium chloride, the amount of oxacyclopentane used was 5 mL. After the reaction was complete, the mixture was filtered through filter paper with a pore size of 0.22 μm to obtain the filtrate.
[0059] 3) Place the filtrate obtained in step 2) in a room temperature and normal pressure environment, allow it to evaporate naturally, and precipitate crystals to obtain the [(CH3)3NCH2Cl]CdCl3 material of the present invention.
[0060] Performance testing and characterisation
[0061] (1) Crystal structure measurement
[0062] The same results were obtained by determining the structure of the materials prepared in Examples 1-3 using a single-crystal diffractometer. Figure 1The crystal structures of [(CH3)3NCH2Cl]CdCl3 materials prepared in Examples 1-3 at room temperature are given. It can be seen that [(CH3)3NCH2Cl]CdCl3 is composed of long inorganic one-dimensional molecular chains of CdCl3 and organic ions of (CH3)3NCH2Cl. The long inorganic one-dimensional molecular chains are parallel to each other and uniformly arranged at specific intervals, while the organic ions fill the spaces between the inorganic one-dimensional molecular chains. Specifically, six Cl atoms are coordinated around each Cd atom, forming an octahedron. Adjacent CdCl6 octahedra are tightly connected by bridging Cl atoms, forming a stable inorganic Cd-Cl framework. Simultaneously, the organic ions are connected to the inorganic framework through Cl-Cl bonds, forming a stable crystal structure.
[0063] (2) Measurement of thermodynamic properties under zero electric field
[0064] The entropy change of the phase transition process of the sample in Example 1 was determined using differential scanning calorimetry. Figure 2 The heat flow curve of the [(CH3)3NCH2Cl]CdCl3 material in Example 1 is given. (1 K min) -1 At the heating and cooling rates, the measured heat flow curves show that [(CH3)3NCH2Cl]CdCl3 undergoes a phase transition near 400 K, and calculations show that the entropy change during the phase transition is 50 J / kg. -1 K -1 The thermal hysteresis is 3.2 K. This result indicates that the [(CH3)3NCH2Cl]CdCl3 material of the present invention exhibits a large phase transition entropy change and a small thermal hysteresis.
[0065] (3) Indirect measurement of hysteresis loop and electrothermal effect
[0066] The hysteresis loops of the sample in Example 1 before and after the phase transition were determined using a ferroelectric analyzer. Figure 3 The hysteresis loops of the [(CH3)3NCH2Cl]CdCl3 material of Example 1 at different temperatures are given. It can be seen that before the phase transition, i.e., at temperatures below 400 K, the material exhibits significant remanent polarization; while after the phase transition, i.e., at temperatures above 400 K, the material does not exhibit significant remanent polarization. Therefore, it is evident that the [(CH3)3NCH2Cl]CdCl3 material of this invention is in a ferroelectric phase before the phase transition and in a paraelectric phase after the phase transition. This material undergoes a phase transition from ferroelectric to paraelectric phase near 400 K.
[0067] Maxwell's relationship can be used to Figure 3 The electrothermal effect of the electrothermal material is calculated from the measured hysteresis loop; this method is called the indirect measurement method. Figure 4 The electrothermal effect of the material obtained using an indirect measurement method is demonstrated. It can be seen that 7.3 MV m -1The maximum isothermal entropy change that can be driven by a small electric field reaches 36.9 J kg. -1 K -1 Under the same driving field, this entropy change exceeds that of all previously reported electrothermal materials.
[0068] (4) Quasi-direct and direct measurement of thermodynamic properties and electrothermal effects under different electric fields
[0069] I. By using a differential scanning calorimeter (DSC) to measure the temperature-varying heat flux curves under different voltages, the entropy curves under different electric fields can be calculated, thereby calculating the electrothermal isothermal entropy change. This is the quasi-direct measurement method.
[0070] Figure 5 Heat flow curves of [(CH3)3NCH2Cl]CdCl3 from Example 1, measured using DSC, are presented under different electric fields. The curves show that the electric field can significantly increase the phase transition temperature, indicating that the electric field can effectively drive the material from a paraelectric phase to a ferroelectric phase transition, generating an electrothermal effect. Based on the heat flow curves measured under different electric fields, the entropy change with temperature under different electric fields is calculated (see...). Figure 5 The isothermal entropy change induced by the electric field is obtained by subtracting the entropy change curves using a quasi-direct measurement method (see...). Figure 6 For the material in question, 7.3 MV m -1 The maximum entropy change that can be driven by a small electric field reaches 34.4 J kg. -1 K -1 Similarly, under the same driving field, this entropy change exceeds that of all previously reported electrothermal materials.
[0071] II. The heat flow curves after applying and removing an electric field at a constant temperature are measured using a differential scanning calorimeter (DSC). The isothermal entropy change is then directly calculated from the heat flow curves. This is the direct measurement method.
[0072] Figure 7 The heat flow curves of [(CH3)3NCH2Cl]CdCl3, an example measured by DSC, with and without an electric field at different temperatures are presented. The curves show that when an electric field is applied to the material near the phase transition point of 400 K, a significant exothermic peak appears; when the electric field is removed, a significant endothermic peak appears, i.e., an electrothermal effect. Based on the heat flow curves, the isothermal entropy change is directly calculated using a direct measurement method. For this material, 7.3 MV m -1 The maximum entropy change that can be driven by a small electric field reaches 33.1 J kg. -1 K -1 (See Figure 8 Similarly, under the same driving field, this entropy change exceeds that of all previously reported electrothermal materials.
[0073] III. Compare the electrothermal effects of the material obtained by indirect measurement, quasi-direct measurement, and direct measurement (see...).Figure 8 As can be seen, the electrothermal effect curves obtained by the three methods are basically consistent.
[0074] The [(CH3)3NCH2Cl]CdCl3 material provided by this invention is at 7.3 MV m -1 The entropy change driven by the small electric field is higher than that of all previously reported electrothermal materials driven by the same magnitude of electric field.
[0075] The results of the above embodiments show that the [(CH3)3NCH2Cl]CdCl3 material provided by the present invention has a large intrinsic entropy change, a small thermal hysteresis, and a high sensitivity of phase transition to electric field. Near the phase transition temperature, a small electric field can drive the phase transition to occur, generating a large isothermal entropy change and electrothermal effect, and has potential application prospects as an electrothermal refrigerant.
Claims
1. A solid-state electrocaloric material, the chemical formula of the solid-state electrocaloric material being [(CH3)3NCH2Cl]CdCl3.
2. The solid-state electrocaloric material of claim 1, wherein, The phase transition temperature of the solid-state electrocaloric material is 400 K.
3. The solid-state electrocaloric material of claim 1 or 2, wherein, The solid-state electrocaloric material has an entropy change during phase transition higher than 50 J kg -1 K -1 .
4. The solid-state electrocaloric material of any one of claims 1 to 3, wherein, The solid-state electrocaloric material has a maximum isothermal entropy change induced by an electric field higher than 30 J kg -1 K -1 -7.3 MV m -1 -1.
5. A method for preparing the solid-state electrocaloric material according to any one of claims 1 to 4, the method comprising the following steps: (1) adding trimethylamine and dichloromethane into oxolane and mixing uniformly to react, after the reaction is completed, removing the solvent to obtain chloromethyltrimethylammonium chloride; (2) adding the obtained chloromethyltrimethylammonium chloride and cadmium chloride into deionized water, fully reacting, then filtering, and evaporating and crystallizing the filtrate to obtain the solid-state electrocaloric material with the chemical formula of [(CH3)3NCH2Cl]CdCl3.
6. The production method according to claim 5, wherein The method further comprises: (3) recrystallizing the crystal obtained in step (2) with deionized water and drying and storing.
7. The production method according to claim 5, wherein In step (1), the trimethylamine is provided in the form of a solution, preferably a trimethylamine ethanol solution with a concentration of 2 to 40 wt%, more preferably a trimethylamine ethanol solution with a concentration of 20 to 40 wt%.
8. The production method according to claim 5, wherein In step (1), the molar ratio of trimethylamine to dichloromethane is 1:0.5 to 2, preferably 1:0.8 to 1.2; Preferably, the amount of oxolane is 0.1 to 1 milliliter with respect to 1 millimole of trimethylamine; Preferably, the reaction temperature of step (1) is 0 to 35°C, more preferably 20 to 30°C; and the reaction time is 4 to 48 hours, more preferably 18 to 30 hours.
9. The production method according to claim 5, wherein In step (2), the molar ratio of chloromethyltrimethylammonium chloride to cadmium chloride is 1:0.5 to 2, preferably 1:0.8 to 1.2; Preferably, the amount of deionized water is 1 to 5 milliliters with respect to 1 millimole of chloromethyltrimethylammonium chloride; Preferably, the reaction temperature of step (2) is 0 to 50°C, more preferably 20 to 35°C; and the reaction time is 4 to 48 hours, more preferably 18 to 30 hours; Preferably, the evaporation and crystallization in step (2) is carried out at a temperature of 20 to 35°C.
10. Use of the solid-state electrocaloric material according to any one of claims 1 to 4 or prepared according to the method of any one of claims 5 to 9 as a refrigeration working medium.