Ion-electron coupling type thermoelectric material and preparation method thereof

Abstract

The invention discloses an ion-electron coupling type thermoelectric material and a preparation method thereof, and belongs to the technical field of novel thermoelectric materials. The thermoelectric material is prepared from an ion-electron conductor material and an ionic liquid phase material in a coupling mode, carriers of the thermoelectric material are ions and electrons, output voltage mainly comes from voltage generated by ionic thermal diffusion, and output current mainly comes from drift current, caused by ionic thermal diffusion, in an electron conductor. The output power of the thermoelectric material provided by the invention is several orders of magnitude higher than that of an existing ionic thermoelectric material, the problem that the output power of the existing ionic thermoelectric material is relatively low and cannot be applied is solved, and power can be supplied to daily electronic elements without increasing voltage, so that the thermoelectric material reaches the application level; the material shows huge potential in low-grade heat energy recovery close to room temperature, the preparation raw materials are wide in source, low in price and easy to obtain, the preparation method is simple, convenient and easy to operate, and the material has extremely high commercial value.

Description

[0001] This application is a divisional application of a Chinese patent application with the application number 202210085064.0, the application date of January 25, 2022, and the invention title "An Ion-Electron Coupled Thermoelectric Material and Its Preparation Method". Technical Field

[0002] The present invention relates to an ion-electron coupled thermoelectric material and its preparation method, belonging to the technical field of novel thermoelectric materials. Background Art

[0003] Thermoelectric materials are functional materials that utilize the migration of carriers (electrons, holes, ions, etc.) inside a solid to directly convert thermal energy and electrical energy into each other. The basic parameters for evaluating the performance of thermoelectric materials are the Seebeck coefficient (V / K), electrical conductivity (S / m), and thermal conductivity (W / (m·K)). According to the types of carriers, thermoelectric materials can be classified. Thermoelectric materials using electrons and holes as carriers are called electronic thermoelectric materials, and materials using anions and cations as carriers are called ionic thermoelectric materials. According to the results of literature research, the Seebeck coefficients of existing electronic thermoelectric materials are basically in the range of dozens to hundreds of μV / K, while the Seebeck coefficients of existing ionic thermoelectric materials are basically in the range of mV / K.

[0004] In daily life, the voltages for normal operation of electronic components are all above 1.5V. However, the thermoelectric potential of traditional electronic thermoelectric materials is basically below 200 μV / K. In order to achieve power supply with thermoelectric materials, hundreds or thousands of thermoelectric materials need to be connected in series to increase the voltage, which undoubtedly increases the complexity and integration of the device; or an external boost chip needs to be connected to increase the voltage, but this will increase power consumption and cost. Although the thermoelectric potential of ionic thermoelectric materials with ions as carriers can reach the level of mV / K, since the voltage formed by ions under a temperature difference can only be utilized by means of an induction capacitor, the generated energy density is very low, making it impossible for ionic thermoelectric materials with a theoretically high thermoelectric figure of merit to exhibit a high thermoelectric conversion efficiency that matches it, and still unable to directly supply power to electronic components, and still difficult to meet daily applications. This makes existing thermoelectric conversion devices have problems such as complex structure, high cost, and low power.

[0005] Thermoelectric materials can achieve the direct conversion of thermal energy and electrical energy, and have important application prospects in the fields of self-powered power supplies for the Internet of Things, 5G communication, electronic skin, deep space exploration, etc. Low-grade thermal energy (temperature below 200 °C) exists widely on the earth, and its content accounts for more than 60% of the world's primary energy. Based on the thermoelectric conversion technology of thermoelectric materials, the temperature difference at both ends of an object is used to promote the directional movement of internal carriers, forming a continuous and stable output voltage and current, realizing the direct conversion between thermal energy and electrical energy. It is an effective and economical way to utilize thermal energy, and can achieve the transformation from difficult-to-use low-grade thermal energy to clean and efficient electrical energy. While promoting the application of thermoelectric conversion technology, countries around the world are also constantly researching and exploring new high-performance thermoelectric materials.

[0006] In summary, it is of great significance to develop a thermoelectric material with low cost, excellent thermoelectric performance and simple preparation method. Summary of the Invention

[0007] In view of this, aiming at the deficiencies of the existing technology, the present invention provides an ion-electron coupled thermoelectric material, which improves the output power of the existing thermoelectric material, and also provides a simple, convenient and low-cost preparation method for this thermoelectric material.

[0008] To solve the above technical problems, the technical solution of the present invention provides an ion-electron coupled thermoelectric material. The carriers of the ion-electron coupled thermoelectric material are ions and electrons. The ion-electron coupled thermoelectric material is prepared by a coupling method from an ion-electron conductor material and an ionic liquid phase material. Its output voltage mainly comes from the voltage generated by ion thermal diffusion, and the output current mainly comes from the drift current in the electron conductor caused by ion thermal diffusion.

[0009] Furthermore, the ion-electron conductor material includes an ion-electron integrated conductor material and an ion-electron hybrid conductor material; the coupling method between the ion-electron integrated conductor material and the ionic liquid phase material is that the ionic liquid phase material is filled inside the ion-electron integrated conductor material; or, the coupling method between the ion-electron hybrid conductor material and the ionic liquid phase material is that the ionic liquid phase material is mixed with the ion-electron hybrid conductor material.

[0010] Furthermore, the ion-electron integrated conductor material includes a carbonized biomass material.

[0011] Preferably, the carbonized biomass material includes one or more of carbonized pomelo peel, carbonized wood, and carbonized bamboo. Carbonized pomelo peel is an electronic conductor that can conduct electricity, with an electronic conductivity of about 30 S / m. At the same time, it has functional groups such as hydroxyl, carboxyl, and carbonyl on its surface, which play a very good role in the selectivity of ions. In theory, carbonized wood or carbonized bamboo can achieve the transport of electrons / holes, and the oxygen-containing functional groups on the surface can also transport ions. Therefore, like carbonized pomelo peel, carbonized wood or carbonized bamboo can both conduct electricity and select ions. According to the actual situation, the carbonized biomass materials can also be used in combination.

[0012] Furthermore, the ion-electron hybrid conductor material includes an ion conductor material and an electronic conductor material. The ion conductor material plays a selective role in ion conduction, increasing the ion distribution difference, and thus increasing the voltage; the electronic conductor material plays a role in transporting electrons, and its purpose is to export the diffusion current generated by ion migration to the external circuit in the form of drift current, so as to be utilized.

[0013] Furthermore, for the ion conductor material, preferably, it has ion-selective functional groups or polar polymers, which play a restrictive role in the migration of anions or cations, making the distribution difference between anions and cations further increase, and ultimately increasing the thermoelectric voltage. The ion-selective functional groups include one or more of hydroxyl, carboxyl, carbonyl, amino, and sulfonate groups; the polar polymers include one or more of polyethylene glycol, polyvinyl alcohol, and polystyrene sulfonic acid.

[0014] Preferably, the ion conductor material includes one or more of cellulose, polyvinyl alcohol, polyethylene glycol, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride, gelatin, polyurethane, and polystyrene sulfonic acid.

[0015] Furthermore, the electronic conductor material includes one or more of carbon nanotubes, poly(3,4-ethylenedioxythiophene) / polystyrene sulfonate, polyaniline, polystyrene, graphite, and graphene.

[0016] Furthermore, the ionic liquid phase material includes inorganic salt solutions and ionic liquids. The inorganic salt solutions include one or more of sodium iodide solution, potassium iodide solution, sodium chloride solution, potassium chloride solution, and sodium hydroxide solution. The ionic liquids include one or more of 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium bromide, 1-hexyl-2,3-dimethylimidazolium tetrafluoroborate, 1-hexyl-2,3-dimethylimidazolium hexafluorophosphate, and 1-ethyl-3-methylimidazolium dicyanamide.

[0017] Since the ions of existing ionic thermoelectric materials cannot enter the external circuit, the voltage formed by the ions under the temperature difference can only be utilized by the way of inductive capacitance. The energy density generated by this utilization method is very low and cannot reach the level of daily application so far. The guiding ideology of the thermoelectric material technical solution of the present invention is to insert an electronic conductor into the ionic thermoelectric material, which can conduct both ions and electrons and directly form a loop with the external circuit. Its principle can be understood as follows: after the ions migrate directionally under the temperature difference, the migration of the ions drives the movement of electrons, and then a current is formed and directly enters the external circuit. In this way, although the ions cannot enter the external circuit, the electrons driven by the ion migration can be directly utilized, so as to achieve the purpose of increasing the output power and enabling the thermoelectric material to reach the application level (such as lighting a light-emitting diode, driving a fan, etc.).

[0018] First of all, the origin of the voltage of the thermoelectric material of the present invention is mainly contributed by ions. It can be understood that in the solution (mainly in the ionic liquid-phase material), anions and cations migrate from the hot end to the cold end under the temperature difference due to the Soret effect. However, the migration rates of each ion are different, resulting in a certain difference in the spatial distribution of anions and cations. Since ions carry charges, this distribution difference will generate an electric field, thus forming a voltage. The purpose of the ion conductor is mainly to increase this ion distribution difference, and then increase the voltage. The purpose of the electronic conductor is to export the diffusion current generated by the ion migration to the external circuit in the form of a drift current and thus be utilized. For example, the carbonized biomass material (carbonized pomelo peel) and ionic liquid (1-butyl-3-methylimidazolium chloride) used in Example 1 below. The carbonized pomelo peel can both conduct electricity and select ions. The anion in 1-butyl-3-methylimidazolium chloride is chloride ion. When the carbonized pomelo peel is immersed in 1-butyl-3-methylimidazolium chloride, the migration of chloride ions is hindered by the negatively charged functional groups on the surface, while the cations migrate along the surface functional groups, increasing the spatial distribution difference between anions and cations, thus generating a voltage. Therefore, the functional groups such as hydroxyl, carboxyl, and carbonyl groups on the surface of the carbonized pomelo peel select the migration of ions, increasing the ion distribution differential pressure, and then increasing the voltage. The electrical conductivity of the carbonized pomelo peel exports the diffusion current generated by the ion migration to the external circuit in the form of a drift current and thus is utilized.

[0019] When the temperature difference occurs, the directional diffusion of ions generates a diffusion current J Diff , in order to balance this current, a drift current J Drift will be generated in the electronic conductor to balance it. According to the ion thermodiffusion relationship of Born-Einstein and the Nernst-Planck-Poisson equation and Maxwell equation, the diffusion current J Diff and the drift current J DriftIts size can be expressed by the following two equations: According to the condition that the total current is 0 under the open - circuit condition, that is, J Diff = J Drift The relationship, and finally the result can be deduced: Among them, V represents the obtained thermal voltage; x represents the diffusion length; q represents the elementary charge; represents the electrical conductivity of the electronic conductor material; D + represents the diffusion coefficient of cations, D - represents the diffusion coefficient of anions; z + represents the valence state of cations, z - represents the valence state of anions; C + represents the concentration of cations, C - represents the concentration of anions; represents the ion - selective ability of the ion - conductor material. It can be seen from the above formula that in order to obtain an observable voltage and output current, it is required that the electrical conductivity of the electronic conductor is not too high and the ion - selective ability of the ion conductor is very strong.

[0020] The ion - electron conductor material used in the present invention can have various material forms. For example, it can be a carbonized biomass material which is an integrated body of an ion conductor and an electronic conductor. It is both an electronic conductor with a not - too - high electrical conductivity and also has selective functional groups such as hydroxyl, carboxyl, and carbonyl groups on its surface, which play a very good role in the selectivity of ions. It can also be an ion - electron hybrid conductor material prepared by mixing an ion conductor material and an electronic conductor material.

[0021] Furthermore, in order to obtain the above - mentioned ion - electron hybrid thermoelectric material, the present invention also provides a preparation method for this thermoelectric material, which specifically includes the following steps: (1) Prepare the ion - electron conductor material: Take the biomass material and obtain the carbonized biomass material with an integrated ion - electron structure through a carbonization process as the ion - electron conductor material for standby; Or take the ion conductor material and the electronic conductor material and mix them with deionized water to obtain the ion - electron hybrid conductor material as the ion - electron conductor material for standby; The biomass material includes one or more of pomelo peel, wood, and bamboo; the carbonization process of the pomelo peel is as follows: the outer skin of the fresh pomelo peel is removed, frozen at 0°C for 5 to 48 hours, and then freeze-dried under vacuum at a temperature below 0°C for 12 to 72 hours. The obtained dried pomelo peel is then placed in a tube furnace, and heated at a rate of 5 to 20°C per minute under a nitrogen atmosphere to 500 to 1100°C and maintained for 1 to 3 hours, and then cooled to room temperature to obtain the carbonized pomelo peel.

[0022] The ion conductor material includes one or more of cellulose, polyvinyl alcohol, polyethylene glycol, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride, gelatin, polyurethane, and polystyrene sulfonic acid; The electronic conductor material includes one or more of carbon nanotubes, poly(3,4-ethylenedioxythiophene) / polystyrene sulfonate, polyaniline, polystyrene, graphite, and graphene.

[0023] (2) Preparation of the ionic liquid phase material: Take an ionic liquid as the ionic liquid phase material for standby; Or dissolve an inorganic salt in deionized water to prepare an inorganic salt solution as the ionic liquid phase material for standby; Or dissolve an ionic liquid in deionized water to prepare an ionic liquid solution as the ionic liquid phase material for standby; The ionic liquid includes one or more of 1-butyl-3-methylimidazolium chloride ionic liquid, 1-butyl-3-methylimidazolium bromide ionic liquid, 1-hexyl-2,3-dimethylimidazolium tetrafluoroborate ionic liquid, and 1-hexyl-2,3-dimethylimidazolium hexafluorophosphate ionic liquid.

[0024] The inorganic salt includes one or more of sodium iodide, potassium iodide, sodium chloride, potassium chloride, and sodium hydroxide.

[0025] (3) Preparation of the ion-electron coupled thermoelectric material: Soak the carbonized biomass material prepared in step (1) in the ionic liquid phase material prepared in step (2) for 2 to 48 hours and then take it out to obtain the ion-electron coupled thermoelectric material; Or mix the ion-electron hybrid conductor material prepared in step (1) with the ionic liquid phase material prepared in step (2) to obtain the ion-electron coupled thermoelectric material; Or directly mix the ion conductor material and the electronic conductor material in step (1) with the ionic liquid phase material in step (2) to obtain the ion-electron coupled thermoelectric material.

[0026] Compared with the prior art, the beneficial effects of the present invention are: (1) The ion - electron coupled thermoelectric material provided by the present invention has an electron conductor incorporated, enabling the output power of the thermoelectric material to be several orders of magnitude higher than that of existing ionic thermoelectric materials, thus solving the problem that the output power of current ionic thermoelectric materials is too low to reach the level of practical application. (2) The Seebeck coefficient of the ion - electron coupled thermoelectric material provided by the present invention can reach 31 mV / K, and the maximum current density obtained at a temperature difference of 20 °C can reach 3.97 A / m 2 without the need for pressurization to power daily electronic components (such as Figure 4 ), enabling the thermoelectric material to reach the application level. (3) The excellent thermoelectric performance of the thermoelectric material of the present invention can recover low - grade heat energy close to room temperature, showing great potential in the recovery of low - grade heat energy close to room temperature. Moreover, the raw materials for preparing the thermoelectric material of the present invention are widely sourced, inexpensive and easily available, and the preparation method is simple, convenient and easy to operate, having extremely strong commercial value.

[0027] In the present invention, "filling" means that ions in the ionic liquid phase material enter the pores formed by the carbon - based porous framework of the ion - electron integrated conductor material (such as carbonized pomelo peel of carbonized biomass material) through a fully soaking method.

[0028] In the present invention, "gel - like" refers to a state where the ion - electron conductor material presents a mixture of a solid phase (or semi - solid phase) and a liquid phase, in which the liquid phase material is dispersed in the network structure formed by the solid phase (or semi - solid phase) material and loses or weakens its fluidity, making the whole present as a semi - solid that stably maintains a certain shape. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0030] Figure 1 It is a physical picture of the thermoelectric material prepared in Example 1; Figure 2 It is a working curve diagram of the thermoelectric material prepared in Example 1 (the material area is 9×14 mm 2 ); Figure 3 It is a physical picture of the thermoelectric material prepared in Example 8; Figure 4 It is a practical application display diagram of the thermoelectric material series device prepared in Example 1 at a temperature difference of 20 °C; Figure 5 Schematic diagram of the principle of the ion - electron coupled thermoelectric material provided by the present invention. Specific embodiments

[0031] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0032] It should be noted that in this document, the term "comprising", "including" or any other variation thereof is intended to cover a non - exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the phrase "comprising a..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the element.

[0033] As used in this specification, the term "about" typically means + / - 5% of the stated value, more typically + / - 4% of the stated value, more typically + / - 3% of the stated value, more typically + / - 2% of the stated value, even more typically + / - 1% of the stated value, and even more typically + / - 0.5% of the stated value.

[0034] In this specification, certain embodiments may be disclosed in a format that is within a certain range. It should be understood that this type of "within a certain range" description is merely for convenience and brevity and should not be construed as a rigid limitation on the disclosed range. Therefore, the description of the range should be considered to have specifically disclosed all possible sub - ranges and the individual numerical values within that range. For example, the description of the range 1 - 6 should be considered to have specifically disclosed sub - ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and the individual numbers within that range, such as 1, 2, 3, 4, 5, and 6. The above rules apply regardless of the breadth of the range.

[0035] Example 1: Take a fresh pomelo peel, remove the outer epidermal cutin layer, freeze it in a refrigerator at 0°C for 2 hours, and vacuum dry it at -10°C for 48 hours. Then put the dried pomelo peel into a tubular furnace, heat it at a rate of 10°C per minute under a nitrogen atmosphere to 900°C and maintain it for 2 hours, and then cool it to room temperature. Take out the carbonized pomelo peel, rinse it with alcohol, and cut it into regular shapes. Take 1.747 g of 1-butyl-3-methylimidazolium chloride, dissolve it in 10 mL of deionized water to prepare a 1 mol / L solution. Immerse the prepared carbonized pomelo peel in the 1 mol / L 1-butyl-3-methylimidazolium chloride solution and let it stand for 12 hours. Take out the immersed and prepared carbonized pomelo peel to obtain an ion-electron coupled thermoelectric material, as Figure 1 shown.

[0036] After testing, the Seebeck coefficient of this thermoelectric material is 31 mV / K, and the maximum current density at a temperature difference of 20°C is 3.97 A / m 2 .

[0037] See Figure 2 , Figure 2 which is the working result of the ion-electron coupled thermoelectric material prepared in this example at a temperature difference of 20 K. As Figure 2 shown, the abscissa represents time, and the two ordinates represent voltage and current respectively. Place the ion-electron coupled thermoelectric device at a temperature difference of 20 K. The migration of ions under the temperature difference causes the thermoelectric device to exhibit an open-circuit voltage, and this voltage keeps rising with time (as shown by the solid line), and finally can reach about 0.65 V. At this time, close the external circuit to test the short-circuit current, which shows a current that decays with time (as shown by the dashed line). It can be seen that the open-circuit voltage is at the level of V, and the short-circuit current is at the level of μA, indicating that this thermoelectric material can reach the application level.

[0038] Figure 4 This is the actual application display diagram of the thermoelectric material series device prepared in this example at a temperature difference of 20°C; where Figure 4 a is a schematic diagram of a 5-section thermoelectric material series device, Figure 4 b is the thermoelectric series device and an unconnected temperature-humidity meter, Figure 4 c is to connect the temperature-humidity meter in series to the thermoelectric device, Figure 4 d is that the series thermoelectric devices directly supply power to the humidity-thermometer.

[0039] Example 2: Take a fresh pomelo peel, remove the cutin layer of the outer epidermis, freeze it in a refrigerator at 0 °C for 12 hours, and vacuum dry it at -10 °C for 36 hours. Then put the obtained dried pomelo peel into a tube furnace, heat it at a rate of 10 °C per minute under a nitrogen atmosphere to 500 °C and maintain it for 2 hours, and then cool it to room temperature. Take out the carbonized pomelo peel, rinse it with alcohol, and cut it into regular shapes. Take 1.747 g of 1-butyl-3-methylimidazolium chloride, dissolve it in 10 mL of deionized water, and prepare a 1 mol / L solution. Immerse the prepared carbonized pomelo peel in the 1 mol / L 1-butyl-3-methylimidazolium chloride solution and let it stand for 6 hours. Take out the immersed and prepared carbonized pomelo peel to complete the preparation of the ion-electron coupled thermoelectric material.

[0040] Example 3: Take a fresh pomelo peel, remove the cutin layer of the outer epidermis, freeze it in a refrigerator at 0 °C for 2 hours, and vacuum dry it at -20 °C for 24 hours. Then put the obtained dried pomelo peel into a tube furnace, heat it at a rate of 8 °C per minute under a nitrogen atmosphere to 800 °C and maintain it for 2 hours, and then cool it to room temperature. Take out the carbonized pomelo peel, rinse it with alcohol, and cut it into regular shapes. Take 3.494 g of 1-butyl-3-methylimidazolium chloride, dissolve it in 10 mL of deionized water, and prepare a 2 mol / L solution. Immerse the prepared carbonized pomelo peel in the 2 mol / L 1-butyl-3-methylimidazolium chloride solution and let it stand for 12 hours. Take out the immersed and prepared carbonized pomelo peel to complete the preparation of the ion-electron coupled thermoelectric material.

[0041] Example 4: Take a fresh pomelo peel, remove the cutin layer of the outer epidermis, freeze it in a refrigerator at 0 °C for 2 hours, and vacuum dry it at -20 °C for 24 hours. Then put the obtained dried pomelo peel into a tube furnace, heat it at a rate of 10 °C per minute under a nitrogen atmosphere to 900 °C and maintain it for 1.5 hours, and then cool it to room temperature. Take out the carbonized pomelo peel, rinse it with alcohol, and cut it into regular shapes. Take 0.21 g of sodium iodide, dissolve it in 14 mL of deionized water, and prepare a 0.1 mol / L solution. Immerse the prepared carbonized pomelo peel in the 0.1 mol / L sodium iodide solution and let it stand for 12 hours. Take out the immersed and prepared carbonized pomelo peel to complete the preparation of the ion-electron coupled thermoelectric material.

[0042] Example 5: Take a fresh pomelo peel, remove the outer cutin layer, freeze it in a refrigerator at 0°C for 2 hours, and then vacuum dry it at -20°C for 24 hours. The obtained dried pomelo peel is then placed in a tubular furnace. Under a nitrogen atmosphere, it is heated to 800°C at a rate of 10°C per minute and maintained at this temperature for 1.5 hours, and then cooled to room temperature. Take out the carbonized pomelo peel, rinse it with alcohol, and cut it into regular shapes. Weigh 0.21 g of sodium iodide and dissolve it in 14 mL of deionized water to prepare a 0.1 mol / L solution. Immerse the prepared carbonized pomelo peel in the 0.1 mol / L sodium iodide solution and let it stand for 12 hours. Take out the immersed and prepared carbonized pomelo peel to complete the preparation of the ion-electron coupled thermoelectric material.

[0043] Example 6: Weigh 1 g of polyvinyl alcohol and 7 g of deionized water and place them in a sealed bottle. After heating and stirring at 90°C for 30 minutes, weigh 1 g of poly(3,4-ethylenedioxythiophene) / polystyrene sulfonate and add it thereto. Continue stirring for 15 minutes to prepare an ion-electron hybrid conductor material. Dissolve sodium iodide in deionized water to prepare a 0.1 mol / L solution. Take 1 mL of the sodium iodide solution and dissolve it in 9 g of the prepared ion-electron hybrid conductor material to complete the preparation of the ion-electron coupled thermoelectric material.

[0044] Example 7: Weigh 1 g of polyvinyl alcohol and 7 g of deionized water and place them in a sealed bottle. After heating and stirring at 120°C for 30 minutes, weigh 0.5 g of poly(3,4-ethylenedioxythiophene) / polystyrene sulfonate and add it thereto. Continue stirring for 30 minutes to prepare an ion-electron hybrid conductor material. Dissolve sodium iodide in deionized water to prepare a 0.1 mol / L solution. Take 1 mL of the sodium iodide solution and dissolve it in 8.5 g of the prepared ion-electron hybrid conductor material to complete the preparation of the ion-electron coupled thermoelectric material.

[0045] Example 8: Dissolve 8 g of cellulose and 92 g of 1-butyl-3-methylimidazolium chloride at 85°C, add 5 g of carbon nanotubes and mix evenly, and then vacuum stand for 24 hours to obtain the ion-electron coupled thermoelectric material, as Figure 3 shown.

[0046] Example 9: Dissolve 1 g of polyvinylidene fluoride-hexafluoropropylene in 10 g of acetone solution, stir evenly, add 2 g of 1-ethyl-3-methylimidazolium dicyanamide, mix evenly and then add 0.5 g of graphite, and bake at 70°C for 20 minutes to complete the preparation of the ion-electron coupled thermoelectric material. Among them, the purpose of baking is to completely volatilize acetone. In addition to baking, other methods (such as air drying) can also be selected to volatilize acetone.

[0047] Example 10: Dissolve 0.1 g of potassium chloride in 1 g of water, disperse the resulting solution in 5 g of gelatin, and mix it with 1 g of graphene to complete the preparation of the ion - electron coupled thermoelectric material.

[0048] Example 11: Dissolve 1 g of polyvinylidene fluoride in 10 g of acetone solution, stir evenly, add 2 g of 1 - butyl - 3 - methylimidazolium bromide, and after mixing evenly, add 0.5 g of carbon nanotubes, and bake at 70 °C for 20 minutes to complete the preparation of the ion - electron coupled thermoelectric material. Among them, the purpose of baking is to completely volatilize acetone. In addition to baking, other methods (such as air drying) can also be selected to volatilize acetone.

[0049] Example 12: Add 5 g of polyurethane aqueous solution to 1 g of polystyrene sulfonic acid, stir evenly, mix in 2 g of polyaniline, and bake at 70 °C for 24 hours to remove moisture to complete the preparation of the ion - electron coupled thermoelectric material.

[0050] Example 13: Mix 0.1 g of sodium hydroxide, 0.5 g of deionized water, 1 g of poly(3,4 - ethylenedioxythiophene) / polystyrene sulfonate, and 4 g of polyethylene glycol, and stir evenly to complete the preparation of the ion - electron coupled thermoelectric material.

[0051] Example 14: Mix 0.1 g of potassium iodide, 0.5 g of deionized water, 1 g of poly(3,4 - ethylenedioxythiophene) / polystyrene sulfonate, and 4 g of polyethylene glycol, and stir evenly to complete the preparation of the ion - electron coupled thermoelectric material.

[0052] Example 15: Mix 0.1 g of sodium chloride, 0.5 g of deionized water, 1 g of poly(3,4 - ethylenedioxythiophene) / polystyrene sulfonate, and 4 g of polyethylene glycol, and stir evenly to complete the preparation of the ion - electron coupled thermoelectric material.

[0053] Example 16: Take a fresh pomelo peel, remove the outer epidermal cutin layer, freeze it in a 0°C refrigerator for 2 hours, and vacuum dry it at -20°C for 24 hours. Then put the dried pomelo peel into a tubular furnace, heat it at a rate of 10°C per minute under a nitrogen atmosphere to 900°C and maintain it for 1.5 hours, and then cool it to room temperature. Take out the carbonized pomelo peel, rinse it with alcohol, and cut it into regular shapes. Take 2.1 g of 1-hexyl-2,3-dimethylimidazolium hexafluorophosphate and dissolve it in 14 mL of deionized water to prepare an aqueous solution. Immerse the prepared carbonized pomelo peel in the 1-hexyl-2,3-dimethylimidazolium hexafluorophosphate solution and let it stand for 12 hours. Take out the immersed and prepared carbonized pomelo peel to complete the preparation of the ion-electron coupled thermoelectric material.

[0054] Perform thermoelectric performance testing on the thermoelectric material prepared in the above embodiment according to the following testing method, and the test results are shown in the following table: (1)Testing of open-circuit voltage and Seebeck coefficient: Use copper electrodes to clamp both ends of the sample, one end is in contact with the heating sheet to increase the temperature, and the other end is in contact with the cooling sheet to create a temperature difference. Use Keithley 2400 to detect the voltage between the copper electrodes and record the voltage trend over time with a computer. Use a Unit-325 dual-channel temperature acquisition instrument to collect the temperature between the two electrodes and continuously record the temperature difference with a computer. The recorded voltage is the open-circuit voltage, and dividing the recorded voltage by the temperature difference gives the Seebeck coefficient.

[0055] (2)Testing of short-circuit current: Use copper electrodes to clamp both ends of the sample, one end is in contact with the heating sheet to increase the temperature, and the other end is in contact with the cooling sheet to create a temperature difference. Use Keithley 2400 to detect the current between the two electrodes and record the current trend over time with a computer, which is the short-circuit current. Divide the recorded current by the electrode area to obtain the current density.

[0056] As can be seen from the above table, the open-circuit voltages of the thermoelectric materials provided by the present invention are all at the level of V, and the short-circuit currents are all at the level of μA. Compared with the existing ionic thermoelectric materials, the thermoelectric output performance has been significantly improved and can reach the application level.

[0057] The ion-electron coupled thermoelectric material (including ion-electron integrated conductor material and ion-electron hybrid conductor material) prepared in the embodiment of the present invention is in a gel-like form. Figure 5 This is a schematic diagram of the principle of the ion-electron coupled thermoelectric material prepared in the embodiment of the present invention, where Figure 5 A represents the structural distribution of the ion-electron coupled thermoelectric material without a temperature difference (the gray part represents the electron and ion conductors, and the white part represents the ionic liquid phase material); Figure 5B represents the diffusion current J generated by the thermal diffusion of ions in the ion-electron coupled thermoelectric material under a temperature difference, Diff the current J generated by the electron conductor inside the material due to the Seebeck effect, e-TE and the drift current J generated by the electron conductor inside the material caused by the thermal diffusion of ions. Drift Inside the material, the directions of the drift current and the diffusion current are opposite.

[0058] Comparative Example 1: Preparation method: Spin-coat poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) on a cleaned glass substrate and anneal it on a hot plate at 120 °C for 20 minutes. Post-treat the PEDOT:PSS film with 1 M sulfuric acid at 160 °C for 5 minutes. After repeating the post-treatment three times, wash the film with deionized water and then dry it. Dilute the ionic liquid 1-ethyl-3-methylimidazolium dicyanamide in methanol and spin-coat it on the PEDOT:PSS film at a speed of 3000 revolutions per minute to complete the preparation.

[0059] Thermoelectric performance test method: Heating and cooling plates are used to create a temperature difference. Place the sample between the heating and cooling plates. Metal electrodes with a width of 1 mm and a length of 13 mm are arranged in parallel on the sample, and the length direction of the electrodes is perpendicular to the temperature difference direction. Use Keithley 2000 to record the voltage between the two electrodes, and use a two-channel thermocouple to record the temperature difference between the two electrodes. The Seebeck coefficient is calculated by dividing the temperature difference by the voltage.

[0060] The detected Seebeck coefficient is 0.065 mV / K, the maximum open-circuit voltage is 0.000065 V, and no short-circuit current is detected.

[0061] The structure of the thermoelectric material prepared in Comparative Example 1 is a laminated structure, that is, a layer of ionic liquid is covered on a layer of electron thermoelectric material. Its essence is still an electron-type thermoelectric material. The covered layer of ionic liquid plays an energy filtering role and enhances the Seebeck coefficient of the bottom electron thermoelectric material; since the main body of thermal diffusion is electron-based, the generated voltage is only dozens of microvolts. In contrast, in the present invention, ions are directly embedded inside the electron thermoelectric material, and diffusion current and voltage are generated through the thermal diffusion of ions (the main origin of the thermoelectric performance of the thermoelectric material provided by the present invention), and the generated voltage is as high as several hundred millivolts.

[0062] Comparative Example 2: Preparation method: Dissolve ionic liquid 1-ethyl-3-methylimidazolium dicyanamide and polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) in acetone. The weight ratio of PVDF-HFP to acetone is 1:9, and the weight ratio of 1-ethyl-3-methylimidazolium dicyanamide to PVDF-HFP is 1:9. Then spin-coat the solution on a glass substrate at a speed of 1800 revolutions per minute. The glass substrate is pre-cleaned with UV-ozone for 60 seconds. After heating in an oven at 70 °C for 3 hours, an ion gel film is obtained.

[0063] Thermoelectric performance test method: Heating and cooling plates are used to create a temperature difference. Place the sample between the heating and cooling plates. Metal electrodes with a size of 1 mm wide and 13 mm long are arranged in parallel on the sample. The length direction of the electrodes is perpendicular to the direction of the temperature difference. Use Keithley 2000 to record the voltage between the two electrodes, and use a two-channel thermocouple to record the temperature difference between the two electrodes. The Seebeck coefficient is calculated by dividing the temperature difference by the voltage.

[0064] The detected Seebeck coefficient is 0.043 mV / K, the maximum open-circuit voltage is 0.00008 V, and no short-circuit current is detected.

[0065] The structure of the thermoelectric material prepared in Comparative Example 2 is a laminated structure, that is, an ion gel is covered on a layer of electronic thermoelectric material. Its essence is still an electronic thermoelectric material. The covered ion gel will generate a relatively high voltage for the fluctuating temperature difference during heat diffusion; however, since the main heat diffusion is dominated by electrons, the generated voltage is only dozens of microvolts.

[0066] Comparative Example 3: Preparation method: Disperse 30 mg of single-walled carbon nanotubes in 6 mL of deionized water (containing 150 mg of sodium dodecyl sulfate), and use a 140 W ultrasonic probe to ultrasonically act for 15 min at an amplitude of 40% to obtain a single-walled carbon nanotube dispersion. Add gelatin and 1-ethyl-3-methylimidazolium dicyanamide to the dispersion, stir at 60 °C for 30 minutes, place the mixture at room temperature, and let it stand and dry for 12 hours to complete the preparation.

[0067] Thermoelectric performance test method: Heating and cooling plates are used to create a temperature difference. Place the sample between the heating and cooling plates. Metal electrodes with a size of 1 mm wide and 13 mm long are arranged in parallel on the sample. The length direction of the electrodes is perpendicular to the direction of the temperature difference. Use Keithley 2000 to record the voltage between the two electrodes, and use a two-channel thermocouple to record the temperature difference between the two electrodes. The Seebeck coefficient is calculated by dividing the temperature difference by the voltage.

[0068] The detected Seebeck coefficient is 8 mV / K, the maximum open-circuit voltage is 0.004 V, and no short-circuit current is detected.

[0069] Although the thermoelectric material prepared in this comparative example is an ion-electron hybrid thermoelectric material, the thermal diffusion of the ionic liquid phase material is intermittent and only enhances the voltage generated by thermoelectricity under fluctuating temperature differences. The current utilized is the current generated by the Seebeck effect under temperature differences. In the present invention, however, the thermal diffusion of ions in the ionic liquid phase material is the main source of voltage. It should be emphasized that the thermoelectric material provided by the present invention operates under temperature differences, rather than only under fluctuating temperature differences, and the output current utilized is the drift current generated by the electronic conductor, and the direction of the drift current is opposite to that of the current generated by the Seebeck effect.

[0070] Comparative Example 4: Preparation method: Tetrachloroperylene bisimide bulk (100 mg) and 10 ml of hydrazine hydrate were sealed in an autoclave and heated at 140 °C for 24 hours. The autoclave containing the anion solution was opened in a nitrogen glove box. The obtained aqueous solution was dropped onto a cleaned quartz, and then heat-treated by annealing at 50 °C for 30 minutes and annealing at 80 °C for 30 minutes in sequence to remove the solvent, completing the preparation.

[0071] Thermoelectric performance test method: The sample was cut into dimensions of 20.0 and 3.0 mm in length and width, and suspended using thermal paste between two Peltier devices (usually 20 mm apart) to generate a temperature difference. The temperature gradient along the long side of the specimen was measured using two T-type thermocouples, and the voltage generated along the long side was measured using a Keithley 2700.

[0072] The detected Seebeck coefficient was 3.021 mV / K, the maximum open-circuit voltage was 0.063 V, and no short-circuit current was detected.

[0073] The thermoelectric material prepared in this comparative example is an ion-electron integrated thermoelectric material. This material can conduct electrons and ionize ions by itself, with electron carriers being dominant. The generation of its voltage comes from electron thermal diffusion and ion dissociation, and the current it utilizes is also the thermal diffusion current generated by the Seebeck effect of the electronic material. In the present invention, however, the voltage mainly comes from ion thermal diffusion, and the output current mainly comes from the drift current in the electronic conductor caused by the thermal diffusion of ions. The directions of the drift current and the thermal diffusion current are opposite inside the material.

[0074] Comparative Example 5: Preparation method: The PEDOT:PSS aqueous solution was drop-coated on a glass substrate and air-dried for 12 hours, and then annealed at 130 °C for 5 minutes. The dimethyl sulfoxide (DMSO) solution was dropped on the sample, annealed at 130 °C for 30 minutes, washed with deionized water after drying, and then dried to remove moisture, completing the preparation.

[0075] Thermoelectric performance test method: The heating sheet and the cooling sheet are used to create a temperature difference. The sample is placed between the heating sheet and the cooling sheet. Metal electrodes with a width of 1 mm and a length of 13 mm are arranged in parallel on the sample. The length direction of the electrodes is perpendicular to the temperature difference direction. The Keithley 2000 is used to record the voltage between the two electrodes, and a two-channel thermocouple is used to record the temperature difference between the two electrodes. The Seebeck coefficient is calculated by dividing the temperature difference by the voltage.

[0076] The detected Seebeck coefficient is 24 mV / K, the maximum open-circuit voltage is 0.360 V, and no short-circuit current is detected.

[0077] The working principle of the thermoelectric material prepared in this comparative example is to inhibit hydrogen ions in PEDOT:PSS by chemical methods, thereby reducing ions and increasing the conductivity of PEDOT:PSS to obtain a stable thermal voltage; in the present invention, ions are introduced to increase the voltage. Therefore, there are essential differences between the two.

[0078] The embodiments of the present invention have been described above in conjunction with the accompanying drawings. However, the present invention is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many forms without departing from the spirit and scope protected by the claims of the present invention. All of these fall within the protection scope of the present invention.

Claims

1. An ion - electron coupled thermoelectric material, characterized in that: the carriers of the ion - electron coupled thermoelectric material are ions and electrons. The ion - electron coupled thermoelectric material is prepared by coupling an ion - electron conductor material and an ionic liquid phase material. Its output voltage comes from the voltage generated by ionic thermal diffusion, and the output current comes from the drift current in the electron conductor caused by ionic thermal diffusion; the ion - electron conductor material includes an ion - electron hybrid conductor material; the coupling method of the ion - electron hybrid conductor material and the ionic liquid phase material is that the ionic liquid phase material is mixed with the ion - electron hybrid conductor material; the ion - electron hybrid conductor material is prepared by mixing an ion conductor material and an electron conductor material.

2. The ion - electron coupled thermoelectric material according to claim 1, characterized in that: the ionic liquid phase material includes an inorganic salt solution or an ionic liquid.

3. The ion - electron coupled thermoelectric material according to claim 1, characterized in that: the ion conductor material has ion - selective functional groups, and the ion - selective functional groups include one or more of hydroxyl, carboxyl, carbonyl, amino, and sulfonate groups; or, the ion conductor material is a polar polymer, and the polar polymer includes one or more of polyethylene glycol, polyvinyl alcohol, and polystyrene sulfonic acid.

4. The ion - electron coupled thermoelectric material according to claim 1, characterized in that: the electron conductor material includes one or more of carbon nanotubes, poly(3,4 - ethylenedioxythiophene) / polystyrene sulfonate, polyaniline, polystyrene, graphite, and graphene.

5. The ion - electron coupled thermoelectric material according to claim 2, characterized in that: the inorganic salt solution includes one or more of sodium iodide solution, potassium iodide solution, sodium chloride solution, potassium chloride solution, and sodium hydroxide solution.

6. The ion - electron coupled thermoelectric material according to claim 2, characterized in that: the ionic liquid includes one or more of 1 - butyl - 3 - methylimidazolium chloride, 1 - butyl - 3 - methylimidazolium bromide, 1 - hexyl - 2,3 - dimethylimidazolium tetrafluoroborate, 1 - hexyl - 2,3 - dimethylimidazolium hexafluorophosphate, and 1 - ethyl - 3 - methylimidazolium dicyanamide.

7. The ion - electron coupled thermoelectric material according to claim 1, characterized in that: the ion - electron coupled thermoelectric material outputs voltage according to the following formula: ； Among them, V represents the obtained Seebeck voltage; x represents the diffusion length; q represents the elementary charge; represents the electrical conductivity of the electronic conductor material; D + represents the diffusion coefficient of the cation, D - represents the diffusion coefficient of the anion; z + represents the valence state of the cation, z - represents the valence state of the anion; C + represents the concentration of the cation, C - represents the concentration of the anion; represents the ion selectivity of the ionic conductor material.

8. A preparation method of an ion - electron coupled thermoelectric material, characterized in that: it includes the following steps: (1) Prepare the ion - electron conductor material: Take an ion conductor material and an electron conductor material and mix them with deionized water to obtain an ion - electron hybrid conductor material as the ion - electron conductor material for standby; (2) Prepare the ionic liquid phase material: Take an ionic liquid as the ionic liquid phase material for standby; Or take an inorganic salt and dissolve it in deionized water to obtain an inorganic salt solution as the ionic liquid phase material for standby; Alternatively, an ionic liquid solution is prepared by dissolving an ionic liquid in deionized water and used as an ionic liquid phase material for standby; (3) Prepare an ion-electron coupled thermoelectric material: Mixing the ion-electron hybrid conductor material prepared in step (1) with the ionic liquid phase material prepared in step (2) can obtain an ion-electron coupled thermoelectric material; Alternatively, directly mixing the ionic conductor material and the electronic conductor material in step (1) with the ionic liquid phase material in step (2) can obtain an ion-electron coupled thermoelectric material.

9. A method for preparing an ion-electron coupled thermoelectric material according to claim 8, characterized in that: The ionic conductor material includes one or more of cellulose, polyvinyl alcohol, polyethylene glycol, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride, gelatin, polyurethane, and polystyrene sulfonic acid; or The electronic conductor material includes one or more of carbon nanotubes, poly(3,4-ethylenedioxythiophene) / polystyrene sulfonate, polyaniline, polystyrene, graphite, and graphene; or The inorganic salt includes one or more of sodium iodide, potassium iodide, sodium chloride, potassium chloride, and sodium hydroxide; or The ionic liquid includes one or more of 1-butyl-3-methylimidazolium chloride ionic liquid, 1-butyl-3-methylimidazolium bromide ionic liquid, 1-hexyl-2,3-dimethylimidazolium tetrafluoroborate ionic liquid, and 1-hexyl-2,3-dimethylimidazolium hexafluorophosphate ionic liquid.

10. An application of an ion-electron conductor material in the preparation of an ion-electron coupled thermoelectric material, characterized in that: The carriers of the ion-electron coupled thermoelectric material are ions and electrons, its output voltage comes from the voltage generated by ion thermal diffusion, and the output current comes from the drift current in the electronic conductor caused by ion thermal diffusion. Inside the ion-electron coupled thermoelectric material, the directions of the drift current and the thermal diffusion current are opposite; the ion-electron coupled thermoelectric material is prepared by coupling the ion-electron conductor material and the ionic liquid phase material; the coupling method of the ion-electron hybrid conductor material and the ionic liquid phase material is mixing the ionic liquid phase material with the ion-electron hybrid conductor material; the ion-electron conductor material includes the ion-electron hybrid conductor material; the ion-electron hybrid conductor material is prepared by mixing an ionic conductor material and an electronic conductor material.

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