Ionic thermoelectric gel material and preparation method and application thereof

Abstract

The invention discloses an ionic thermoelectric gel material and a preparation method and application thereof. The ionic thermoelectric gel material comprises the following components: a hydrophilic polymer, a bio-based polymer, an electronic thermoelectric material, a water-soluble electrolyte and water, and the preparation method of the ionic thermoelectric gel material comprises the following steps: dissolving the bio-based polymer in water; adding a hydrophilic monomer containing a carbon-carbon double bond, an electronic thermoelectric material, a water-soluble electrolyte, an initiator and a cross-linking agent, uniformly mixing, and carrying out a free radical polymerization reaction through an ultraviolet light initiation or thermal initiation method. The ionic thermoelectric gel material has the advantages of excellent thermoelectric conversion performance, excellent flame retardant property, good flexibility and the like, can directly and continuously supply power to external circuit electronic elements, and is suitable for being used in the fields of intelligent fire fighting, energy storage devices, low-order waste heat collection and conversion and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of thermoelectric conversion, and particularly relates to an ionic thermoelectric gel material, a preparation method thereof, and an application thereof. Background Art

[0002] Thermoelectric conversion materials can achieve the conversion of thermal energy into electrical energy through the migration of carriers (such as electrons, holes, ions, etc.) inside the materials, and have very broad application prospects in the fields of intelligent fire protection, energy storage devices, energy enrichment and conversion, etc. Thermoelectric conversion materials can be divided into electronic thermoelectric materials (using electrons / holes as carriers) and ionic thermoelectric materials (using cations and anions as carriers) according to the types of migrating carriers. Although the existing electronic thermoelectric materials have excellent electrical conductivity, their Seebeck coefficients are generally only dozens to hundreds of μV·K -1 (the thermoelectric potential generated by a single individual is generally lower than 200 μV·K -1 ), so usually hundreds or thousands of thermoelectric material components need to be assembled to achieve normal power supply, which greatly increases the complexity and integration of the fire alarm response path. Although the existing ionic thermoelectric materials can generate thermoelectric potentials up to the mV·K -1 level, but because the thermoelectric potential formed by ions under the temperature gradient can only be applied through the intermittent induction capacitance method, the high thermoelectric conversion efficiency cannot be exerted at all, so it cannot directly supply power to electronic components. In summary, it can be seen that the existing electronic thermoelectric materials and ionic thermoelectric materials are both difficult to fully meet the actual application requirements, and their applications are greatly limited.

[0003] Therefore, it is of great significance to develop a thermoelectric conversion material with sustainable power supply, high thermoelectric efficiency, and excellent flame retardant performance. Summary of the Invention

[0004] The purpose of the present invention is to provide an ionic thermoelectric gel material, a preparation method thereof, and an application thereof.

[0005] The technical solution adopted by the present invention is as follows:

[0006] An ionic thermoelectric gel material, which comprises the following components in mass percentage:

[0007] Hydrophilic polymer: 6.6% - 16.1%;

[0008] Bio-based polymer: 1.2% - 6.7%;

[0009] Electronic thermoelectric material: 0.05% - 0.18%;

[0010] Water-soluble electrolyte: 3.0% - 3.3%;

[0011] Water: 74.6% - 87.5%.

[0012] Preferably, the hydrophilic polymer is polymerized from hydrophilic monomers containing carbon-carbon double bonds.

[0013] Preferably, the hydrophilic monomer containing carbon-carbon double bonds is at least one of acrylamide, acrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid.

[0014] Preferably, the biopolymer is at least one of sodium alginate, carboxymethyl chitosan, and sodium carboxymethyl cellulose.

[0015] Preferably, the electronic thermoelectric material is at least one of poly(3,4-ethylenedioxythiophene)-polystyrenesulfonic acid, polypyrrole, and polyaniline.

[0016] Preferably, the water-soluble electrolyte is at least one of sodium chloride, potassium chloride, sodium sulfate, and potassium sulfate.

[0017] A preparation method of the ionic thermoelectric gel material as described above includes the following steps: dissolving the biopolymer in water, adding the hydrophilic monomer containing carbon-carbon double bonds, the electronic thermoelectric material, the water-soluble electrolyte, the initiator, and the crosslinking agent, mixing evenly, and then carrying out a free radical polymerization reaction by means of ultraviolet light initiation or thermal initiation to obtain the ionic thermoelectric gel material.

[0018] Preferably, the dissolving method is magnetic stirring at room temperature, the stirring rate is 500 rpm to 800 rpm, and the stirring time is 14 h to 24 h.

[0019] Preferably, the initiator is at least one of ammonium persulfate and 2-hydroxy-2-methylpropiophenone.

[0020] Preferably, the dosage of the initiator is 2.0% to 5.0% of the weight of the hydrophilic monomer containing carbon-carbon double bonds.

[0021] Preferably, the crosslinking agent is at least one of N,N'-methylenebisacrylamide and ethylene glycol dimethacrylate.

[0022] Preferably, the dosage of the crosslinking agent is 0.4% to 1.0% of the weight of the hydrophilic monomer containing carbon-carbon double bonds.

[0023] Preferably, the mixing method is magnetic stirring at room temperature, the stirring rate is 500 rpm to 800 rpm, and the stirring time is 10 min to 30 min.

[0024] Preferably, the ultraviolet light initiation is carried out under an ultraviolet light intensity of 100 mW·cm -2 ~150 mW·cm -2It is carried out under the condition that , and the polymerization reaction time is 10 min to 15 min.

[0025] Preferably, the thermal initiation is carried out under the condition that the temperature is 55 °C to 65 °C, and the polymerization reaction time is 1 h to 3 h.

[0026] A fire warning device, which comprises the above-mentioned ionic thermoelectric gel material.

[0027] Principle of the present invention: The ionic thermoelectric gel material of the present invention contains a skeleton formed by a hydrophilic polymer and a gel network formed by a bio-based polymer. Its thermoelectric conversion performance and fire warning function are mainly realized by the electron Seebeck effect and the ionic thermal diffusion effect inside the gel material under a temperature difference. When there is a certain temperature gradient inside the gel material, holes / electrons in the electron-type thermoelectric material dispersed inside the gel material migrate directionally and accumulate at the cold end. At the same time, free electrolyte cations and anions can migrate from the hot end to the cold end under the action of the temperature gradient and accumulate at the cold end. Since the gel network contains groups with strong electrostatic interactions such as sulfonate groups and carboxylate groups, the gel system shows strong cation selectivity. Moreover, there is also a strong electrostatic interaction between the gel network and the electron-type thermoelectric material, which further increases the migration difference of free cations and anions. The migration speed of electrolyte cations is faster, while the migration of anions is blocked, and more positive charges accumulate at the cold end, resulting in an inconsistent electric potential inside the gel material, thus causing a thermoelectric potential difference, and finally endowing the gel material system with high thermoelectric efficiency. In addition, electrons / holes can further drift under the induced electric field generated by the thermal diffusion of cations and anions, further increasing the ionic thermal current of the gel material. Through the synergistic action of two thermoelectric conversion mechanisms of electrons and ions inside the gel material under a temperature difference, it has high thermoelectric conversion performance and can generate an electron flow directly supplied to the external circuit, making up for the defects of the external power supply methods of traditional electron-type or ionic thermoelectric materials, and greatly expanding the application scenarios of thermoelectric conversion materials.

[0028] The beneficial effects of the present invention are as follows: The ionic thermoelectric gel material of the present invention has excellent thermoelectric conversion performance, excellent flame retardant performance, good flexibility, etc., and can directly and continuously supply power to external circuit electronic components, and is suitable for use in fields such as intelligent fire protection, energy storage devices, low-grade waste heat collection and conversion.

[0029] Specifically:

[0030] 1) The ionic thermoelectric gel material of the present invention has both high-efficient flame retardant performance and sensitive fire warning function, can continuously and repeatedly trigger warnings under abnormal high temperatures, timely remind people of abnormal high temperatures and fire risks, so as to nip the fire in the bud. At the same time, the ionic thermoelectric gel material can also resist flame burning in a high-oxygen environment for a long time, showing high fire safety;

[0031] 2) The ionic thermoelectric gel material of the present invention achieves excellent thermoelectric conversion performance through an electron-ion coupled thermoelectric conversion mechanism, and can directly and sustainably supply power to external circuit electronic components through thermoelectric conversion, making it suitable for use in fields such as intelligent fire protection, energy storage devices, low-grade waste heat collection and conversion, etc.;

[0032] 3) Due to the unique cation selectivity of the system, the ionic thermoelectric gel material of the present invention has an increased migration difference between free anions and cations inside the gel, further enhancing its ionic thermoelectric conversion performance and thermoelectric efficiency;

[0033] 4) The preparation method of the ionic thermoelectric gel material of the present invention is simple, the raw materials are cheap and easily available, and it is easy to apply, making it suitable for large-scale industrial production and application. Description of the Drawings

[0034] Figure 1 It is a graph showing the test results of the flexibility of the ionic thermoelectric gel material in Example 1.

[0035] Figure 2 It is a bar graph of the Seebeck coefficients of the gel materials in Examples 1-9 and Comparative Examples 1-2.

[0036] Figure 3 It is a screenshot of the fire warning test video of the gel materials in Example 1 and Comparative Example 1.

[0037] Figure 4 It is a real-time voltage curve of the external power supply test of the gel materials in Example 1 and Comparative Example 2. Detailed Embodiments

[0038] The present invention will be further explained and illustrated below in conjunction with specific embodiments.

[0039] The electronic thermoelectric materials poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (product model: P191136), polyaniline (product model: P169039), and polypyrrole (product model: P476184) in Examples 1-9 and Comparative Example 1 were all purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., and the above electronic thermoelectric materials were respectively dispersed in deionized water to prepare a 1.5% mass fraction aqueous dispersion for standby.

[0040] Example 1:

[0041] An ionic thermoelectric gel material, and its preparation method is as follows:

[0042] Dissolve 0.2 g of sodium alginate in 11.8 g of water to prepare a sodium alginate solution (transparent and uniform). The stirring rate is 500 rpm and the stirring time is 14 h. Then add 2 g of acrylamide, 2 g of a 1.5% poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid aqueous dispersion, 0.5 g of sodium chloride, 50 mg of ammonium persulfate, and 10 mg of N,N'-methylenebisacrylamide and stir evenly to prepare a precursor solution. The stirring rate is 600 rpm and the stirring time is 30 min. Then place it in a forced-air oven and react at 65 °C for 1 h to obtain an ionic thermoelectric gel material.

[0043] The flexibility test results of the ionic thermoelectric gel material in this example are as Figure 1 shown.

[0044] As Figure 1 can be seen: The ionic thermoelectric gel material exhibits excellent flexibility and can withstand external force deformations such as bending 180°, twisting, and knotting, meeting the flexibility requirements for use as a solid-state flexible electrolyte.

[0045] Example 2:

[0046] An ionic thermoelectric gel material, and its preparation method is as follows:

[0047] Dissolve 0.5 g of sodium carboxymethylcellulose in 11.5 g of water to prepare a sodium carboxymethylcellulose solution (transparent and uniform). The stirring rate is 700 rpm and the stirring time is 20 h. Then add 1 g of acrylic acid, 1.5 g of acrylamide, 0.5 g of a 1.5% polyaniline aqueous dispersion, 0.5 g of potassium chloride, 50 mg of 2-hydroxy-2-methylpropiophenone, and 10 mg of ethylene glycol dimethacrylate and stir evenly to prepare a precursor solution. The stirring rate is 500 rpm and the stirring time is 10 min. Then place it in an ultraviolet curing box and irradiate it for 10 min under the condition of an ultraviolet light intensity of 100 mW·cm -2 to obtain an ionic thermoelectric gel material.

[0048] Example 3:

[0049] An ionic thermoelectric gel material, and its preparation method is as follows:

[0050] Dissolve 1 g of sodium carboxymethylcellulose by stirring in 11 g of water to prepare a sodium carboxymethylcellulose solution (transparent and uniform). The stirring rate is 800 rpm and the stirring time is 24 h. Then add 1.5 g of 2-acrylamido-2-methylpropanesulfonic acid, 1 g of a polypyrrole aqueous dispersion with a mass fraction of 1.5%, 0.5 g of sodium sulfate, 50 mg of ammonium persulfate, and 10 mg of N,N'-methylenebisacrylamide, and stir evenly to prepare a precursor solution. The stirring rate is 800 rpm and the stirring time is 30 min. Then place it in a forced-air oven and react at 55 °C for 3 h to obtain an ionic thermoelectric gel material.

[0051] Example 4:

[0052] An ionic thermoelectric gel material, and its preparation method is as follows:

[0053] Dissolve 0.3 g of sodium carboxymethylcellulose by stirring in 11.7 g of water to prepare a sodium carboxymethylcellulose solution (transparent and uniform). The stirring rate is 800 rpm and the stirring time is 14 h. Then add 1 g of acrylic acid, 1.5 g of a poly(3,4-ethylenedioxythiophene)-polystyrenesulfonic acid aqueous dispersion with a mass fraction of 1.5%, 0.5 g of potassium sulfate, 25 mg of ammonium persulfate, 25 mg of 2-hydroxy-2-methylpropiophenone, and 10 mg of N,N'-methylenebisacrylamide, and stir evenly to prepare a precursor solution. The stirring rate is 500 rpm and the stirring time is 20 min. Then place it in an ultraviolet curing box and irradiate it under the condition of an ultraviolet light intensity of 150 mW·cm -2 for 15 min to obtain an ionic thermoelectric gel material.

[0054] Example 5:

[0055] An ionic thermoelectric gel material, and its preparation method is as follows:

[0056] Dissolve 1 g of sodium alginate by stirring in 11 g of water to prepare a sodium alginate solution (transparent and uniform). The stirring rate is 500 rpm and the stirring time is 14 h. Then add 2 g of acrylamide, 1.5 g of a polypyrrole aqueous dispersion with a mass fraction of 1.5%, 0.5 g of sodium chloride, 50 mg of ammonium persulfate, and 10 mg of N,N'-methylenebisacrylamide, and stir evenly to prepare a precursor solution. The stirring rate is 800 rpm and the stirring time is 20 min. Then place it in a forced-air oven and react at 60 °C for 2 h to obtain an ionic thermoelectric gel material.

[0057] Example 6:

[0058] An ionic thermoelectric gel material, and its preparation method is as follows:

[0059] Dissolve 0.5 g of sodium carboxymethylcellulose by stirring in 11.5 g of water to prepare a sodium carboxymethylcellulose solution (transparent and homogeneous). The stirring rate is 600 rpm and the stirring time is 20 h. Then add 1.5 g of acrylic acid, 0.5 g of 2-acrylamido-2-methylpropanesulfonic acid, 1 g of a 1.5% mass fraction of polystyrene dispersion of polyaniline, 0.5 g of potassium chloride, 50 mg of 2-hydroxy-2-methylpropiophenone, and 10 mg of ethylene dimethacrylate, and stir evenly to prepare a precursor solution. The stirring rate is 500 rpm and the stirring time is 10 min. Then place it in an ultraviolet curing oven and irradiate it for 10 min under the condition of an ultraviolet light intensity of 100 mW·cm -2 to obtain an ionic thermoelectric gel material.

[0060] Example 7:

[0061] An ionic thermoelectric gel material, and its preparation method is as follows:

[0062] Dissolve 1 g of sodium alginate by stirring in 11 g of water to prepare a sodium alginate solution (transparent and homogeneous). The stirring rate is 800 rpm and the stirring time is 24 h. Then add 1.5 g of acrylamide, 0.5 g of acrylic acid, 2 g of a 1.5% mass fraction of polystyrene dispersion of polyaniline, 0.5 g of sodium sulfate, 50 mg of ammonium persulfate, and 10 mg of N,N'-methylenebisacrylamide, and stir evenly to prepare a precursor solution. The stirring rate is 700 rpm and the stirring time is 20 min. Then place it in a blast drying oven and react at 55 °C for 3 h to obtain an ionic thermoelectric gel material.

[0063] Example 8:

[0064] An ionic thermoelectric gel material, and its preparation method is as follows:

[0065] Dissolve 0.5 g of sodium carboxymethylcellulose by stirring in 11.5 g of water to prepare a sodium carboxymethylcellulose solution (transparent and homogeneous). The stirring rate is 600 rpm and the stirring time is 20 h. Then add 1 g of acrylic acid, 1.5 g of 2-acrylamido-2-methylpropanesulfonic acid, 1 g of a 1.5% mass fraction of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate dispersion of polyaniline, 0.5 g of potassium sulfate, 25 mg of ammonium persulfate, 25 mg of 2-hydroxy-2-methylpropiophenone, and 10 mg of N,N'-methylenebisacrylamide, and stir evenly to prepare a precursor solution. The stirring rate is 500 rpm and the stirring time is 20 min. Then place it in an ultraviolet curing oven and irradiate it for 15 min under the condition of an ultraviolet light intensity of 150 mW·cm -2 to obtain an ionic thermoelectric gel material.

[0066] Example 9:

[0067] An ionic thermoelectric gel material, and its preparation method is as follows:

[0068] Dissolve 1 g of sodium alginate in 11 g of water to make a sodium alginate solution (transparent and uniform). The stirring rate is 800 rpm and the stirring time is 20 h. Then add 1 g of acrylamide, 1.5 g of 2-acrylamido-2-methylpropanesulfonic acid, 1 g of polypyrrole aqueous dispersion with a mass fraction of 1.5%, 0.5 g of sodium chloride, 25 mg of ammonium persulfate, 25 mg of 2-hydroxy-2-methylpropiophenone, and 10 mg of N,N'-methylenebisacrylamide, and stir evenly to make a precursor solution. The stirring rate is 500 rpm and the stirring time is 20 min. Then place it in a forced-air oven and react at 60 °C for 2 h to obtain the ionic thermoelectric gel material.

[0069] Comparative Example 1:

[0070] An electronic thermoelectric gel material, and its preparation method is as follows:

[0071] Dissolve 0.2 g of sodium alginate in 11.8 g of water to make a sodium alginate solution (transparent and uniform). The stirring rate is 500 rpm and the stirring time is 14 h. Then add 2 g of acrylamide, 2 g of poly(3,4-ethylenedioxythiophene)-polystyrenesulfonic acid aqueous dispersion with a mass fraction of 1.5%, 30 mg of ammonium persulfate, and 10 mg of N,N'-methylenebisacrylamide, and stir evenly to make a precursor solution. The stirring rate is 600 rpm and the stirring time is 30 min. Then place it in a forced-air oven and react at 65 °C for 1 h to obtain the electronic thermoelectric gel material.

[0072] Comparative Example 2:

[0073] An ionic thermoelectric gel material, and its preparation method is as follows:

[0074] Dissolve 0.2 g of sodium alginate in 11.8 g of water to make a sodium alginate solution (transparent and uniform). The stirring rate is 500 rpm and the stirring time is 14 h. Then add 2 g of acrylamide, 0.5 g of sodium chloride, 30 mg of ammonium persulfate, and 10 mg of N,N'-methylenebisacrylamide, and stir evenly to make a precursor solution. The stirring rate is 600 rpm and the stirring time is 30 min. Then place it in a forced-air oven and react at 65 °C for 1 h to obtain the ionic thermoelectric gel material.

[0075] Performance test:

[0076] Test method:

[0077] Tensile test: A mechanical tensile testing machine (Mark-10 Corporation, USA, model: ESM303) was used to conduct a room-temperature mechanical tensile test on the gel material test sample at a tensile rate of 40 mm·min -1 , and the corresponding mechanical tensile strength-elongation at break curve was recorded. The size of the gel material test sample was 50 mm×10 mm×1 mm.

[0078] Vertical burning test: Based on the ANSI / UL 94-2010 test standard, the gel material test sample was placed 20 mm above a propane Bunsen burner. The bottom of the gel material test sample was in contact with the Bunsen burner flame, with a flame length of 40 mm. After burning for 20 s in two times, the Bunsen burner was removed, and the combustion phenomena and data were recorded. The size of the gel material test sample was 80 mm×10 mm×1 mm.

[0079] Limiting oxygen index test: Based on the ASTM D2863-09 test standard, an oxygen index measuring instrument (Nanjing Jiangning Analytical Instrument Co., Ltd., model: JF-3) was used to test the gel material test sample. When the gel material test sample burned to 50 mm from the top fire source at 3 min, the oxygen index at this time was recorded as the limiting oxygen index. The size of the gel material test sample was 100 mm×10 mm×1 mm.

[0080] Seebeck coefficient test: The test platform was constructed by two Peltier elements, a DC power supply, a thermocouple, copper foil electrodes, and a digital multimeter (Keithley Corporation, USA, model: DMM6500 6 1 / 2). The distance between the two Peltier elements was 30 mm. A DC power supply was used to supply power to one of the Peltier elements to generate a temperature difference across the sample. The temperatures of the two Peltier elements were recorded by the thermocouple. The gel material test sample was evenly placed on the two Peltier elements, and the copper foil electrodes were connected to the digital multimeter with wires. The size of the gel material test sample was 40 mm×10 mm×1 mm.

[0081] Fire warning test: The gel material test sample was connected to a digital multimeter (Keithley Corporation, USA, model: DMM6500 6 1 / 2) and a millivolt voltage alarm through wires. The alarm voltage was set at 50 mV. The gel material test sample was placed 20 mm above an alcohol lamp. The sample was in contact with the outer flame of the alcohol lamp, with a flame height of 40 mm. The fire warning time and voltage curve were recorded. The size of the gel material test sample was 40 mm×10 mm×1 mm.

[0082] External power supply test: The test circuit is constructed by a Peltier, a voltage amplifier, a protective resistor, a load bulb (rated voltage of 2.5V), a thermocouple, copper foil electrodes, a digital multimeter (manufactured by Keithley, USA, model: DMM6500 6 1 / 2), and a glass slide. Place the gel material test sample in the center of the Peltier, connect the copper foil electrodes, thermocouple, voltage amplifier, protective resistor, and load bulb with wires, record the voltage across the bulb using the digital multimeter, and the size of the gel material test sample is 10mm×10mm×1mm.

[0083] Specific tests:

[0084] 1) Cut the gel material test samples in Examples 1-9 and Comparative Examples 1-2 into appropriate sizes, and then conduct mechanical tensile tests, vertical burning tests, limiting oxygen index tests, Seebeck coefficient tests, and fire warning tests. The test results are as follows:

[0085] a) The bar charts of the Seebeck coefficients of the gel materials in Examples 1-9 and Comparative Examples 1-2 are as Figure 2 shown;

[0086] b) The screenshots of the fire warning test videos of the gel materials in Example 1 and Comparative Example 1 are as Figure 3 (a is the screenshot of the fire warning test video of the gel material in Comparative Example 1, and b is the screenshot of the fire warning test video of the gel material in Example 1) shown;

[0087] c) The tensile strength, elongation at break, Seebeck coefficient, and conductivity of the gel materials in Examples 1-9 and Comparative Examples 1-2 are shown in the following table:

[0088] Table 1 Test results of tensile strength, elongation at break, Seebeck coefficient, and conductivity of gel materials

[0089]

[0090] d) The limiting oxygen index, vertical burning self-extinguishing time, and repeated fire warning test results of the gel materials in Examples 1-9 and Comparative Examples 1-2 are shown in the following table:

[0091] Table 2 Test results of limiting oxygen index, vertical burning self-extinguishing time, and repeated fire warning of gel materials

[0092]

[0093]

[0094] As can be seen from Table 1: The gel materials in Examples 1-9 exhibit high mechanical strength and excellent mechanical tensile properties, meeting the mechanical strength requirements for use as solid-state flexible electrolytes.

[0095] As can be seen from Table 1 and Table 2, the gel materials in Examples 1-9 all have excellent ion thermoelectric conversion performance and flame retardancy, and at the same time exhibit good electrical conductivity and fire warning ability, showing very broad application prospects in energy storage devices, intelligent fire protection and other fields;

[0096] From Table 1 and Figure 2 it can be seen that: the gel materials in Examples 1-9 have a relatively high Seebeck coefficient. Relying on the ion thermal diffusion effect of free anions and cations of the electrolytic salt and the coupled synergistic effect of the electron Seebeck effect of the electron-type thermoelectric material, when there is a certain temperature difference in the gel material, holes and electrons in the electron-type thermoelectric material move directionally. At the same time, the anions and cations inside it migrate directionally, generating a large thermal voltage, enabling it to have excellent thermoelectric conversion ability. In addition, electrons / holes can further drift under the induced electric field generated by ion thermal diffusion, thereby increasing the ion thermal current; the Seebeck coefficient of the gel material in Comparative Example 1 (only containing electron-type thermoelectric material) is only 0.18 mV·K -1 , and the Seebeck coefficient of the gel material in Comparative Example 2 (only containing water-soluble electrolytic salt) is only 6.45 mV·K -1 , while the Seebeck coefficient of the gel material in Example 1 is as high as 8.25 mV·K -1 , indicating that the ion thermal diffusion effect plays a dominant role in the thermoelectric conversion performance of this system, endowing it with excellent thermoelectric conversion performance. With the introduction of the electron-type thermoelectric material, an electron skeleton is constructed inside the gel, so that ion thermal diffusion and the electron Seebeck effect are simultaneously realized under the temperature difference. The two effects are coupled and synergistic, further increasing the thermoelectric efficiency of the gel and solving the problem of low thermal voltage generated by traditional electron-type thermoelectric conversion materials.

[0097] From Table 2 and Figure 3 it can be seen that: the gel materials in Examples 1-9 and Comparative Examples 1-2 can all exhibit high flame retardancy at the UL-94 V-0 level. After the gel materials are burned by the flame for 10 s twice, most of the gel structures can still be retained. This is because in a high-temperature environment or when encountering a flame, the water in the gel material evaporates rapidly, and non-combustible gases such as ammonia are generated, achieving oxygen isolation and heat insulation. In addition, the gel skeleton is carbonized at high temperature, forming a dense carbon layer, thus showing an efficient flame retardant effect. After encountering a flame, compared with the electron-type thermoelectric gel material in Comparative Example 1, the gel material in Example 1 rapidly generates a thermal voltage, and its voltage value can exceed 50 mV in about 2 s, successfully triggering the fire warning device. This is mainly because the free anions and cations inside the gel material migrate directionally and accumulate at the low-temperature end. Due to the different migration rates and migration numbers of anions and cations, mV·K is generated at both ends -1level of thermoelectric potential difference, and the electronic thermoelectric material framework in the gel material undergoes the electronic Seebeck effect under the temperature gradient to achieve electron-ion coupled thermoelectric conversion, thereby realizing fire warning. However, the electronic thermoelectric gel material in Comparative Example 1 can only undergo electron / hole migration, generating a thermoelectric potential difference of μV·K -1 level of thermoelectric potential difference, making it difficult to trigger a warning above 50 mV. In addition, the gel materials in Examples 2 to 9 and Comparative Example 2 can also trigger the fire warning device within a short time, mainly due to the thermoelectric potential difference of mV·K -1 level brought about by the thermal diffusion of cations and anions inside the gel, enabling it to successfully trigger a warning;

[0098] 2) The real-time voltage curves of the external power supply test of the gel materials in Example 1 and Comparative Example 2 are as follows Figure 4 (Based on the ion thermoelectric test platform in the present invention, supplemented with a voltage amplifier and a load bulb, an external power supply test circuit is constructed; a is a physical diagram of the test circuit, b is the real-time voltage curve of the gel material in Example 1 before and after the action of the voltage amplifier, and c is the real-time voltage curve of the gel material in Comparative Example 2 before and after the action of the voltage amplifier) as shown.

[0099] It can be seen from Figure 4 that

[0100] a) The gel material in Comparative Example 2 can generate a thermal voltage of about 129.0 mV through the migration of internal cations and anions under the temperature difference. After the voltage is amplified 19 times by the voltage amplifier, it reaches the rated voltage of the bulb (about 2.5 V). At this time, when the external circuit bulb is connected, due to the double-layer effect, the electrons on the hot-end electrode plate will migrate through the load to the cold-end electrode plate, making the electrode plates and the ionic gel electrolyte at both ends achieve electrostatic equilibrium, and the potential difference drops to around 0 mV, while outputting electrical energy to the external circuit. However, continuous power supply cannot be achieved only by ion thermal diffusion. It is necessary to disconnect the external circuit bulb and remove the temperature difference to gradually diffuse the ions inside the gel and restore them to the original disordered state, and repeat the above operations to supply power to the outside again;

[0101] b) In the case of a temperature difference, the gel material in Example 1 can also achieve the conversion of thermal energy into electrical energy and continuously output thermal voltage and current. Relying on the electron-ion coupled thermoelectric output circuit in the gel network, when the temperature difference between the two ends of the sustainable power supply high thermoelectric efficiency flame-retardant ionic gel reaches 20K, it can continuously generate a thermal voltage of 165.0 mV. At this time, connecting an external circuit light bulb can supply power externally. After the generated thermal voltage is amplified 15 times by a voltage amplifier, a light bulb with a rated voltage of 2.5V is successfully lit. Through the electron-ion coupled thermoelectric conversion mechanism, the gel can continuously output voltage and current for more than 10 minutes, showing good continuous power supply ability. This is essentially different from the intermittent capacitive power supply method of the gel material (traditional ionic thermoelectric conversion material) in Comparative Example 2, making up for the application defects of traditional ionic thermoelectric conversion materials;

[0102] In summary, the ionic thermoelectric gel material of the present invention has both excellent flame retardant performance and thermoelectric conversion performance. In addition, based on the electron-ion coupled thermoelectric conversion mechanism, the ionic thermoelectric gel material of the present invention has both a sensitive fire warning function and an efficient and continuous thermoelectric conversion ability, and can convert a certain temperature gradient into electrical energy to directly and continuously supply power to electronic components, providing a new way for the development of new ionic thermoelectric conversion materials.

[0103] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. An ionic thermoelectric gel material, characterized in that: The following components are included in mass percentage: Hydrophilic polymer: 6.6% to 16.1%; Bio-based polymers: 1.2% to 6.7%; Electronic thermoelectric materials: 0.05% to 0.18%; Water-soluble electrolytes: 3.0% to 3.3%; Water: 74.6%~87.5%.

2. The ionic thermoelectric gel material according to claim 1, characterized in that: The hydrophilic polymer is formed by polymerizing a hydrophilic monomer containing a carbon-carbon double bond; the hydrophilic monomer containing a carbon-carbon double bond is at least one of acrylamide, acrylic acid, and 2-acrylamide-2-methylpropanesulfonic acid.

3. The ionic thermoelectric gel material according to claim 1 or 2, characterized in that: The bio-based polymer is at least one of sodium alginate, carboxymethyl chitosan and sodium carboxymethyl cellulose.

4. The ionic thermoelectric gel material according to claim 1 or 2, characterized in that: The electronic thermoelectric material is at least one of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid, polypyrrole and polyaniline.

5. The ionic thermoelectric gel material according to claim 1 or 2, characterized in that: The water-soluble electrolyte is at least one of sodium chloride, potassium chloride, sodium sulfate and potassium sulfate.

6. A method for preparing an ionic thermoelectric gel material as claimed in any one of claims 1 to 5, characterized in that: The method comprises the following steps: dissolving a bio-based polymer in water, adding a hydrophilic monomer containing a carbon-carbon double bond, an electronic thermoelectric material, a water-soluble electrolyte, an initiator and a cross-linking agent, and mixing them evenly, and then performing a free radical polymerization reaction by ultraviolet light initiation or thermal initiation to obtain an ionic thermoelectric gel material.

7. The preparation method according to claim 6, characterized in that: The initiator is at least one of ammonium persulfate and 2-hydroxy-2-methylpropiophenone; the crosslinking agent is at least one of N,N'-methylenebisacrylamide and ethylene glycol dimethacrylate.

8. The preparation method according to claim 6 or 7, characterized in that: The dosage of the initiator is 2.0% to 5.0% of the weight of the hydrophilic monomer containing carbon-carbon double bonds; the dosage of the crosslinking agent is 0.4% to 1.0% of the weight of the hydrophilic monomer containing carbon-carbon double bonds.

9. The preparation method according to claim 6 or 7, characterized in that: The UV light initiation was performed at a UV light intensity of 100 mW·cm -2 ~150mW·cm -2 The polymerization reaction is carried out under the conditions of 10min to 15min; the thermal initiation is carried out under the conditions of a temperature of 55°C to 65°C, and the polymerization reaction time is 1h to 3h.

10. A fire warning device, characterized in that: The ionic thermoelectric gel material comprises the ionic thermoelectric gel material according to any one of claims 1 to 5.

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