Ion-electron coupling type thermoelectric material and preparation method thereof

Abstract

The present invention discloses an ion-electron coupling thermoelectric material and a preparation method thereof, belonging to the technical field of new thermoelectric materials. The thermoelectric material is prepared by coupling an ion-electron conductor material and an ionic liquid phase material, and its carriers are ions and electrons. The output voltage mainly comes from the voltage generated by ion thermal diffusion, and the output current mainly comes from the drift current in the electronic conductor caused by ion thermal diffusion. The output power of the thermoelectric material provided by the present invention is several orders of magnitude higher than that of the existing ionic thermoelectric material, which solves the problem that the current ionic thermoelectric material has low output power and cannot be applied. It can power daily electronic components without supercharging, so that the thermoelectric material reaches the application level; it shows great potential in low-grade heat energy recovery close to room temperature, its preparation raw materials are widely available, cheap and easy to obtain, the preparation method is simple and easy to operate, and it has strong commercial value.

Description

Technical Field

[0001] The invention relates to an ion-electron coupling type thermoelectric material and a preparation method thereof, belonging to the technical field of new thermoelectric materials. Background Art

[0002] Thermoelectric materials are functional materials that use the migration of solid internal carriers (electrons, holes, ions, etc.) to achieve direct conversion between thermal energy and electrical energy. The basic parameters for evaluating the performance indicators of thermoelectric materials are Seebeck coefficient (V / K), electrical conductivity (S / m) and thermal conductivity (W / (m·K)). Thermoelectric materials can be classified according to the type of carriers. Thermoelectric materials that use electrons and holes as carriers are called electronic thermoelectric materials, and materials that use 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 at the level of tens to hundreds of μV / K, while the Seebeck coefficients of existing ionic thermoelectric materials are basically at the level of mV / K.

[0003] In daily life, the voltage required for the normal operation of electronic components is above 1.5V. However, the thermoelectric potential of traditional electronic thermoelectric materials is basically below 200μV / K. In order to realize the power supply of 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 is required to increase the voltage, but it will increase power consumption and cost. Although the thermoelectric potential of ionic thermoelectric materials with ions as carriers can reach the mV / K level, the voltage formed by ions under temperature difference can only be utilized by induction capacitance, and the energy density generated is very low, so that ionic thermoelectric materials with higher thermoelectric merit in theory cannot play a high thermoelectric conversion efficiency that matches it, and still cannot directly power electronic components, and it is still difficult to meet daily applications. This makes the existing thermoelectric conversion devices have problems such as complex structure, high cost, and low power.

[0004] Thermoelectric materials can realize the direct conversion of thermal energy and electrical energy, and have important application prospects in the fields of IoT self-powered power supply, 5G communication, electronic skin, deep space exploration, etc. Low-grade thermal energy (temperature below 200°C) is widely present on the earth, and its content accounts for more than 60% of the world's primary energy. Thermoelectric conversion technology based on thermoelectric materials uses the temperature difference at both ends of the object to promote the directional movement of internal carriers, forming a continuous and stable output voltage and current, and realizing the direct conversion between thermal energy and electrical energy. It is an effective and economical way to utilize thermal energy, which can realize 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 conducting research and exploration of new high-performance thermoelectric materials.

[0005] 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

[0006] In view of this, and in view of the deficiencies in the prior art, 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 the thermoelectric material.

[0007] In order to solve the above technical problems, the technical solution of the present invention provides an ion-electron coupled thermoelectric material, wherein the carriers of the ion-electron coupled thermoelectric material are ions and electrons, and the ion-electron coupled thermoelectric material is prepared by coupling an ion-electron conductor material and an ionic liquid phase material, and 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 electronic conductor caused by ion thermal diffusion.

[0008] Furthermore, the ion-electron conductor material includes an ion-electron integrated conductor material and an ion-electron mixed conductor material; the coupling mode of 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 mode of the ion-electron mixed conductor material and the ionic liquid phase material is that the ionic liquid phase material is mixed with the ion-electron mixed conductor material.

[0009] Furthermore, the ion-electron integrated conductor material includes carbonized biomass material.

[0010] More preferably, the carbonized biomass material includes one or more of carbonized grapefruit peel, carbonized wood, and carbonized bamboo. Carbonized grapefruit peel is an electronic conductor that can conduct electricity, and its electronic conductivity is about 30S / m. At the same time, it has functional groups such as hydroxyl, carboxyl, and carbonyl on the surface, which play a very good role in ion selectivity. In theory, carbonized wood or carbonized bamboo can realize the transport of electrons / holes, and the oxygen-containing functional groups on the surface can also transport ions. Therefore, carbonized wood or carbonized bamboo, like carbonized grapefruit peel, can both conduct electricity and select ions. According to actual conditions, the carbonized biomass materials can also be used in combination.

[0011] Furthermore, the ion-electron hybrid conductor material includes ion conductor material and electron conductor material. The ion conductor material plays a selective role in ion conduction, increasing the difference in ion distribution and thus increasing the voltage; the electron conductor material plays a role in transmitting 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 that it can be utilized.

[0012] Furthermore, for the ion conductor material, it is preferred to have an ion selective functional group or a polar polymer, which restricts the migration of anions or cations, making the distribution difference of anions and cations further larger, and finally increasing the thermovoltage. The ion selective functional group includes one or more of hydroxyl, carboxyl, carbonyl, amino and sulfonate groups; the polar polymer includes one or more of polyethylene glycol, polyvinyl alcohol and polystyrene sulfonic acid.

[0013] 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.

[0014] Furthermore, the electronic conductor material includes one or more of carbon nanotubes, poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate, polyaniline, polystyrene, graphite, and graphene.

[0015] Further, the ionic liquid phase material includes an inorganic salt solution and an ionic liquid. The inorganic salt solution includes one or more of a sodium iodide solution, a potassium iodide solution, a sodium chloride solution, a potassium chloride solution and a sodium hydroxide solution. 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.

[0016] 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 means of inductive capacitance. The energy density generated by this utilization method is very low and has not been able to reach daily applications so far. The guiding ideology of the technical solution of the thermoelectric material of the present invention is to insert a layer of electronic conductor into the ionic thermoelectric material, which can conduct ions while also conducting electrons, and directly form a loop with the external circuit. The principle can be understood as follows: after the ions undergo directional migration under the temperature difference, the migration of the ions drives the movement of the electrons, and then forms an electric current that 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, thereby achieving the purpose of increasing the output power, so that the thermoelectric material can reach the application level (for example, lighting up light-emitting diodes, driving fans, etc.).

[0017] First, the origin of the voltage of the thermoelectric material of the present invention is mainly contributed by ions. It can be understood that the anions and cations in the solution (mainly in the ionic liquid phase material) migrate from the hot end to the cold end due to the Soret effect under the temperature difference, but the different migration rates of each ion cause the anions and cations to have certain differences in spatial distribution, and the ions are charged, and this distribution difference will generate an electric field, thereby forming a voltage. The purpose of the ion conductor is mainly to increase this ion distribution difference, thereby increasing the voltage. The purpose of the electronic conductor is to export the diffusion current generated by ion migration to the external circuit in the form of drift current, so that it can be utilized. For example, the carbonized biomass material (carbonized grapefruit peel) and ionic liquid (1-butyl-3-methylimidazolium chloride) used in the following Example 1, the carbonized grapefruit peel is both conductive and selective for ions, the anions in 1-butyl-3-methylimidazolium chloride are chloride ions, and the carbonized grapefruit 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 of anions and cations, thereby generating voltage. Therefore, the hydroxyl, carboxyl, carbonyl and other functional groups on the surface of the carbonized grapefruit peel select the migration of ions, increase the distribution differential pressure of ions, and then increase the voltage, and the conductive ability of the carbonized grapefruit peel exports the diffusion current generated by ion migration to the external circuit in the form of drift current, thereby being utilized.

[0018] When a temperature difference occurs, the ions diffuse in a directional manner, generating a diffusion current J Diff In order to balance this current, a drift current J will be generated in the electronic conductor. Drift According to the Born-Einstein ion thermal diffusion relationship and the Nernst-Planck-Poisson equation and Maxwell equation, the diffusion current J Diff and drift current J Drift The size of can be expressed by the following two formulas:

[0019]

[0020]

[0021] According to the open circuit condition, the total current is 0, that is, J Diff =J Drift Finally, we can deduce the result:

[0022]

[0023] Where V is the obtained thermovoltage; x is the diffusion length; q is the elementary charge; σ e-TE Indicates the conductivity of electronic conductor materials; D+ represents the diffusion coefficient of cations, D - represents the diffusion coefficient of anions; z + represents the valence state of the cation, z - Indicates the valence state of anions; C + represents the concentration of cations, C - Indicates the concentration of anions; It indicates the ion selectivity of ion conductor materials. As can be seen from the above formula, in order to obtain a considerable voltage and output current, the conductivity of the electronic conductor should not be too high and the ion selectivity of the ion conductor should be very strong.

[0024] The ion-electron conductor material used in the present invention can be in various material forms, for example, it can be a carbonized biomass material that is a unified body of ion conductor and electron conductor, which is not only an electron conductor with not too high conductivity, but also has selective functional groups such as hydroxyl, carboxyl, carbonyl, etc. on the surface, which plays a very good role in ion selectivity. It can also be an ion-electron mixed conductor material prepared by mixing ion conductor material and electron conductor material.

[0025] Furthermore, in order to obtain the above-mentioned ion-electron hybrid thermoelectric material, the present invention also provides a method for preparing the thermoelectric material, which specifically comprises the following steps:

[0026] (1) Preparation of ion-electron conductor material: taking biomass material and carbonizing it to obtain ion-electron integrated carbonized biomass material as ion-electron conductor material for standby use;

[0027] Alternatively, an ion conductor material and an electronic conductor material are mixed with deionized water to prepare an ion-electron mixed conductor material as an ion-electron conductor material for standby use;

[0028] The biomass material includes one or more of grapefruit peel, wood, and bamboo; the carbonization process of the grapefruit peel is as follows: the outer skin of the fresh grapefruit peel is removed, the peel is frozen at 0°C for 5 to 48 hours, and then the peel is freeze-dried in a vacuum below 0°C for 12 to 72 hours. The obtained dried grapefruit peel is then placed in a tubular furnace, heated to 500 to 1100°C at a rate of 5 to 20°C per minute in a nitrogen atmosphere, maintained for 1 to 3 hours, and then cooled to room temperature to obtain the carbonized grapefruit peel.

[0029] 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;

[0030] .The electronic conductor material includes one or more of carbon nanotubes, poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate, polyaniline, polystyrene, graphite, and graphene.

[0031] (2) Preparation of ionic liquid phase materials:

[0032] Taking the ionic liquid as the ionic liquid phase material for standby use;

[0033] Alternatively, an inorganic salt is dissolved in deionized water to prepare an inorganic salt solution as an ionic liquid phase material for later use;

[0034] Alternatively, the ionic liquid is dissolved in deionized water to prepare an ionic liquid solution as an ionic liquid phase material for later use;

[0035] 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.

[0036] The inorganic salt includes one or more of sodium iodide, potassium iodide, sodium chloride, potassium chloride and sodium hydroxide.

[0037] (3) Preparation of ion-electron coupled thermoelectric materials:

[0038] The carbonized biomass material prepared in step (1) is soaked in the ionic liquid phase material prepared in step (2) for 2-48 hours and then taken out to obtain an ion-electron coupling thermoelectric material;

[0039] Alternatively, the ion-electron hybrid conductor material prepared in step (1) is mixed with the ionic liquid phase material prepared in step (2) to obtain the ion-electron coupled thermoelectric material;

[0040] Alternatively, the ion conductor material and the electronic conductor material of step (1) can be directly mixed with the ionic liquid phase material of step (2) to obtain the ion-electron coupling thermoelectric material.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] (1) The ion-electron coupling thermoelectric material provided by the present invention has an electronic conductor loaded therein, which makes the output power of the thermoelectric material several orders of magnitude higher than that of the existing ionic thermoelectric materials, thus solving the problem that the output power of the existing ionic thermoelectric materials is too low to be applied.

[0043] (2) The Seebeck coefficient of the ion-electron coupling 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 , can power daily electronic components without boosting (such as Figure 4 ), making thermoelectric materials reach application level;

[0044] (3) The excellent thermoelectric performance of the thermoelectric material of the present invention can realize the recovery of low-grade thermal energy close to room temperature, showing great potential in the recovery of low-grade thermal energy close to room temperature. In addition, the raw materials for preparing the thermoelectric material of the present invention are widely available, cheap and easy to obtain, and the preparation method is simple, convenient and easy to operate, which has strong commercial value.

[0045] In the present invention, "filling" means that the ions in the ionic liquid phase material enter into the pores formed by the carbon-based porous skeleton of the ion-electron integrated conductor material (such as the carbonized grapefruit peel of the carbonized biomass material) by fully immersing.

[0046] In the present invention, "gel-like" refers to the state in which the ion-electron conductor material is a mixture of a solid phase (or a semi-solid phase) and a liquid phase, wherein the liquid phase material is dispersed in a network structure formed by the solid phase (or semi-solid phase) material and loses or weakens its fluidity, so that the whole material appears as a semi-solid that stably maintains a certain shape. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor.

[0048] Figure 1 This is a physical picture of the thermoelectric material prepared in Example 1;

[0049] Figure 2 The working curve of the thermoelectric material prepared in Example 1 (the material area is 9×14 mm 2 );

[0050] Figure 3 This is a physical picture of the thermoelectric material prepared in Example 8;

[0051] Figure 4 This is a diagram showing the actual application of the thermoelectric material series device prepared in Example 1 at a temperature difference of 20°C;

[0052] Figure 5 This is a schematic diagram of the principle of the ion-electron coupling thermoelectric material provided by the present invention. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0054] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0055] 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.

[0056] In this specification, some embodiments may be disclosed in a format of being in a certain range. It should be understood that such description of "being in a certain range" is only for convenience and brevity, and should not be interpreted 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 independent numerical values ​​within this range. For example, the range 1 The description of 6 should be considered to have specifically disclosed subranges 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., as well as individual numbers within this range, such as 1, 2, 3, 4, 5, and 6. The above rules apply regardless of the breadth of the range.

[0057] Embodiment 1:

[0058] Take a piece of fresh grapefruit peel, remove the cuticle of the outer skin, freeze it in a refrigerator at 0°C for 2 hours, and vacuum dry it at -10°C for 48 hours. Put the dried grapefruit peel into a tube furnace and heat it to 900°C at a rate of 10°C per minute under a nitrogen atmosphere for 2 hours, then cool it to room temperature. Take out the carbonized grapefruit peel, rinse it with alcohol, and cut it into regular shapes. Take 1.747g of 1-butyl-3-methylimidazolium chloride, dissolve it in 10mL of deionized water, and prepare a 1mol / L solution. Soak the prepared carbonized grapefruit peel in a 1mol / L 1-butyl-3-methylimidazolium chloride solution and let it stand for 12 hours. Take out the soaked carbonized grapefruit peel to obtain an ion-electron coupling thermoelectric material, such as Figure 1 shown.

[0059] The thermoelectric material has a Seebeck coefficient of 31mV / K and a maximum current density of 3.97A / m at a temperature difference of 20°C. 2 .

[0060] See also Figure 2 , Figure 2 The working results of the ion-electron coupling thermoelectric material prepared in this embodiment under a temperature difference of 20K. Figure 2 As shown, the horizontal axis represents time, and the two vertical axes represent voltage and current respectively. When the ion-electron coupled thermoelectric device is placed under a temperature difference of 20K, the migration of ions under the temperature difference causes the thermoelectric device to show an open circuit voltage, which continues to rise with time (as shown by the solid line) and finally reaches about 0.65V. At this time, the external circuit is closed and the short-circuit current is tested, showing a current that decays with time (as shown by the dotted line). It can be seen that the open circuit voltage is at the V level and the short-circuit current is at the μA level, indicating that the thermoelectric material can reach the application level.

[0061] Figure 4 This is a diagram showing the actual application of the thermoelectric material series device prepared in this example at a temperature difference of 20°C; Figure 4 a is a schematic diagram of a 5-section thermoelectric material series device. Figure 4 b is a thermoelectric series device and a temperature-humidity meter that is not connected. Figure 4 c is to connect the thermometer-hygrometer in series to the thermoelectric device, Figure 4 d is the series-connected thermoelectric device that directly powers the humidity-thermometer.

[0062] Embodiment 2:

[0063] Take a piece of fresh grapefruit peel, remove the outer epidermal stratum corneum, freeze in a refrigerator at 0°C for 12 hours, vacuum dry at -10°C for 36 hours, and then put the dried grapefruit peel into a tube furnace, heat to 500°C for 2 hours at a rate of 10°C per minute under a nitrogen atmosphere, and then cool to room temperature. Take out the carbonized grapefruit peel, rinse with alcohol, and cut into regular shapes. Take 1.747g of 1-butyl-3-methylimidazolium chloride, dissolve it in 10mL of deionized water, and prepare a 1mol / L solution. Soak the prepared carbonized grapefruit peel in a 1mol / L 1-butyl-3-methylimidazolium chloride solution and let it stand for 6 hours. Take out the soaked carbonized grapefruit peel to complete the preparation of ion-electron coupling thermoelectric materials.

[0064] Embodiment 3:

[0065] Take a piece of fresh grapefruit peel, remove the outer skin cuticle, freeze it in a refrigerator at 0℃ for 2 hours, and vacuum dry it at -20℃ for 24 hours. The dried grapefruit peel is then placed in a tube furnace and heated to 800℃ for 2 hours at a rate of 8℃ per minute under a nitrogen atmosphere, and then cooled to room temperature. Take out the carbonized grapefruit peel, rinse it with alcohol, and cut it into regular shapes. Take 3.494g of 1-butyl-3-methylimidazolium chloride, dissolve it in 10mL of deionized water, and configure it into a 2mol / L solution. Soak the prepared carbonized grapefruit peel in a 2mol / L 1-butyl-3-methylimidazolium chloride solution and let it stand for 12 hours. Take out the soaked carbonized grapefruit peel to complete the preparation of ion-electron coupling thermoelectric materials.

[0066] Embodiment 4:

[0067] Take a piece of fresh grapefruit peel, remove the cuticle of the outer skin, freeze it in a refrigerator at 0℃ for 2 hours, and vacuum dry it at -20℃ for 24 hours. Put the dried grapefruit peel into a tubular furnace and heat it to 900℃ at a rate of 10℃ per minute in a nitrogen atmosphere for 1.5 hours, then cool it to room temperature. Take out the carbonized grapefruit peel, rinse it with alcohol, and cut it into regular shapes. Take 0.21g of sodium iodide, dissolve it in 14mL of deionized water, and prepare a 0.1mol / L solution. Soak the prepared carbonized grapefruit peel in a 0.1mol / L sodium iodide solution and let it stand for 12 hours. Take out the soaked carbonized grapefruit peel to complete the preparation of the ion-electron coupling thermoelectric material.

[0068] Embodiment 5:

[0069] Take a piece of fresh grapefruit peel, remove the cuticle of the outer skin, freeze it in a refrigerator at 0℃ for 2 hours, and vacuum dry it at -20℃ for 24 hours. Put the dried grapefruit peel into a tube furnace and heat it to 800℃ at a rate of 10℃ per minute in a nitrogen atmosphere for 1.5 hours, then cool it to room temperature. Take out the carbonized grapefruit peel, rinse it with alcohol, and cut it into regular shapes. Take 0.21g of sodium iodide, dissolve it in 14mL of deionized water, and prepare a 0.1mol / L solution. Soak the prepared carbonized grapefruit peel in a 0.1mol / L sodium iodide solution and let it stand for 12 hours. Take out the soaked carbonized grapefruit peel to complete the preparation of the ion-electron coupling thermoelectric material.

[0070] Embodiment 6:

[0071] Weigh 1g of polyvinyl alcohol and 7g of deionized water into a sealed bottle, heat and stir at 90°C for 30 minutes, then weigh 1g of poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate and add it, and continue stirring for 15 minutes to prepare an ion-electron hybrid conductor material. Sodium iodide is dissolved in deionized water to prepare a 0.1mol / L solution. Take 1mL of sodium iodide solution and dissolve it in 9g of the prepared ion-electron hybrid conductor material to complete the preparation of the ion-electron coupled thermoelectric material.

[0072] Embodiment 7:

[0073] Weigh 1g of polyvinyl alcohol and 7g of deionized water into a sealed bottle, heat and stir at 120°C for 30 minutes, weigh 0.5g of poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate and add it, continue stirring for 30 minutes to make an ion-electron hybrid conductor material. Dissolve sodium iodide in deionized water to make a 0.1mol / L solution. Dissolve 1mL of sodium iodide solution in 8.5g of the prepared ion-electron hybrid conductor material to complete the preparation of the ion-electron coupled thermoelectric material.

[0074] Embodiment 8:

[0075] 8 g of cellulose and 92 g of 1-butyl-3-methylimidazolium chloride were dissolved at 85° C., 5 g of carbon nanotubes were added and mixed evenly, and the mixture was allowed to stand in vacuum for 24 hours to obtain an ion-electron coupling thermoelectric material, such as Figure 3 shown.

[0076] Embodiment 9:

[0077] Dissolve 1g of polyvinylidene fluoride-hexafluoropropylene in 10g of acetone solution, stir evenly, add 2g of 1-ethyl-3-methylimidazolium dicyanamide, mix evenly, add 0.5g of graphite, bake at 70°C for 20 minutes, and complete the preparation of ion-electron coupling thermoelectric material. The purpose of baking is to completely volatilize the acetone. In addition to baking, other methods (such as drying) can also be selected to volatilize the acetone.

[0078] Embodiment 10:

[0079] 0.1 g of potassium chloride was dissolved in 1 g of water, the resulting solution was dispersed in 5 g of gelatin, and mixed with 1 g of graphene to complete the preparation of the ion-electron coupling thermoelectric material.

[0080] Embodiment 11:

[0081] 1g of polyvinylidene fluoride was dissolved in 10g of acetone solution, stirred evenly, 2g of 1-butyl-3-methylimidazolium bromide was added, 0.5g of carbon nanotubes was added after mixing evenly, and baked at 70°C for 20 minutes to complete the preparation of ion-electron coupling thermoelectric material. The purpose of baking is to completely volatilize the acetone. In addition to baking, other methods (such as drying) can be selected to volatilize the acetone.

[0082] Embodiment 12:

[0083] 5 g of polyurethane aqueous solution was dissolved in 1 g of polystyrene sulfonic acid, stirred evenly, mixed with 2 g of polyaniline, and baked at 70° C. for 24 hours to remove moisture, thereby completing the preparation of the ion-electron coupling thermoelectric material.

[0084] Embodiment 13:

[0085] 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 were mixed and stirred evenly to complete the preparation of the ion-electron coupling thermoelectric material.

[0086] Embodiment 14:

[0087] .Mix 0.1g potassium iodide, 0.5g deionized water, 1g poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate) and 4g polyethylene glycol, stir evenly to complete the preparation of the ion-electron coupling thermoelectric material.

[0088] Embodiment 15:

[0089] 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 were mixed and stirred evenly to complete the preparation of the ion-electron coupling thermoelectric material.

[0090] Embodiment 16:

[0091] Take a piece of fresh grapefruit peel, remove the cuticle of the outer skin, freeze it in a refrigerator at 0℃ for 2 hours, and vacuum dry it at -20℃ for 24 hours. The dried grapefruit peel is then placed in a tube furnace and heated to 900℃ for 1.5 hours at a rate of 10℃ per minute under a nitrogen atmosphere, and then cooled to room temperature. Take out the carbonized grapefruit peel, rinse it with alcohol, and cut it into regular shapes. Take 2.1g of 1-hexyl-2,3-dimethylimidazolium hexafluorophosphate, dissolve it in 14mL of deionized water, and prepare it into an aqueous solution. Soak the prepared carbonized grapefruit peel in a 1-hexyl-2,3-dimethylimidazolium hexafluorophosphate solution and let it stand for 12 hours. Take out the soaked carbonized grapefruit peel to complete the preparation of the ion-electron coupling thermoelectric material.

[0092] The thermoelectric performance of the thermoelectric material prepared in the above example was tested according to the following testing method. The test results are shown in the following table:

[0093] (1) Open circuit voltage and Seebeck coefficient test:

[0094] .Use copper electrodes to clamp the two ends of the sample, one end contacts the heating plate to increase the temperature, and the other end contacts the cooling plate to create a temperature difference. Use Keithley2400 to detect the voltage between the copper electrodes and use a computer to record the voltage trend over time. Use Unit-325 dual-channel temperature acquisition instrument to collect the temperature between the two electrodes and use a computer to continuously record the temperature difference. The recorded voltage is the open circuit voltage, and the Seebeck coefficient is obtained by dividing the recorded voltage by the temperature difference.

[0095] (2) Short-circuit current test:

[0096] .Use copper electrodes to clamp the two ends of the sample, one end contacts the heating plate to increase the temperature, and the other end contacts the cooling plate to create a temperature difference. Use Keithley2400 to detect the current between the two electrodes and use a computer to record the trend of the current over time, which is the short-circuit current. The recorded current divided by the electrode area is the current density.

[0097]

[0098] It can be seen from the above table that the open circuit voltage of the thermoelectric materials provided by the present invention is at the V level, and the short circuit current is at the μA level. Compared with the existing ionic thermoelectric materials, the thermoelectric output performance is significantly improved and can reach the application level.

[0099] The ion-electron coupling thermoelectric material (including ion-electron integrated conductor material and ion-electron mixed conductor material) prepared in the embodiment of the present invention is in the form of gel. Figure 5 The schematic diagram of the principle of the ion-electron coupling thermoelectric material prepared in the embodiment of the present invention is shown in FIG. Figure 5 A represents the structural distribution of ion-electron coupled thermoelectric materials without temperature difference (the gray part represents the electron and ion conductors, and the white part represents the ionic liquid phase material); FIG5B represents the diffusion current J generated by the thermal diffusion of ions in the ion-electron coupled thermoelectric material when there is a temperature difference. Diff , the current J generated by the electronic conductor inside the material due to the Seebeck effect e-TE And the drift current J generated by the electronic conductor inside the material due to the thermal diffusion of ions Drift , the directions of drift current and diffusion current inside the material are opposite.

[0100] Comparative Example 1:

[0101] Preparation method: Spin-coat poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) on a clean glass substrate and anneal on a 120°C hot plate for 20 minutes. Post-treat the PEDOT:PSS film with 1M sulfuric acid at 160°C for 5 minutes. Repeat the post-treatment three times, then rinse with deionized water and dry. Dilute the ionic liquid 1-ethyl-3-methylimidazole dicyandiamide in methanol and spin-coat it on the PEDOT:PSS film at 3000 rpm to complete the preparation.

[0102] Thermoelectric performance test method: The heating plate and the cooling plate are used to create a temperature difference. The sample is placed between the heating plate and the cooling plate. 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 electrode is perpendicular to the temperature difference direction. Keithley2000 is used to record the voltage between the two electrodes. A dual-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.

[0103] The detected Seebeck coefficient was 0.065mV / K, the maximum open-circuit voltage was 0.000065V, and no short-circuit current was detected.

[0104] 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 electronic thermoelectric material, and its essence is still an electronic thermoelectric material. The covering layer of ionic liquid plays the role of energy filtering, enhancing the Seebeck coefficient of the bottom electronic thermoelectric material; since the main thermal diffusion is mainly electrons, the voltage generated is only tens of microvolts. The present invention directly embeds ions into the electronic thermoelectric material, generates diffusion current and voltage (the main origin of the thermoelectric performance of the thermoelectric material provided by the present invention) through the thermal diffusion of ions, and the generated voltage is as high as hundreds of millivolts.

[0105] Comparative Example 2:

[0106] Preparation method: The ionic liquid 1-ethyl-3-methylimidazole dicyandiamide and polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) were dissolved in acetone. The weight ratio of PVDF-HFP to acetone was 1:9, and the weight ratio of 1-ethyl-3-methylimidazole dicyandiamide to PVDF-HFP was 1:9. The solution was then spin-coated on a glass substrate at a speed of 1800 rpm, and the glass substrate was pre-cleaned with UV-ozone for 60 seconds. The ion gel film was obtained after heating in an oven at 70°C for 3 hours.

[0107] Thermoelectric performance test method: The heating plate and the cooling plate are used to create a temperature difference. The sample is placed between the heating plate and the cooling plate. 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 electrode is perpendicular to the temperature difference direction. Keithley2000 is used to record the voltage between the two electrodes. A dual-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.

[0108] The detected Seebeck coefficient was 0.043mV / K, the maximum open circuit voltage was 0.00008V, and no short-circuit current was detected.

[0109] The structure of the thermoelectric material prepared in Comparative Example 2 is a laminated structure, that is, a layer of ion gel is covered on a layer of electronic thermoelectric material, and its essence is still an electronic thermoelectric material. The covered ion gel will generate a higher voltage for the fluctuating temperature difference during thermal diffusion; however, since the main thermal diffusion is mainly electrons, the voltage generated is only tens of microvolts.

[0110] Comparative Example 3:

[0111] Preparation method: 30 mg of single-walled carbon nanotubes were dispersed in 6 mL of deionized water (containing 150 mg of sodium dodecyl sulfate), and ultrasonicated for 15 min with a 140 W ultrasonic probe at an amplitude of 40% to obtain a single-walled carbon nanotube dispersion. Gelatin and 1-ethyl-3-methylimidazole dicyandiamide were added to the dispersion, stirred at 60° C. for 30 minutes, and the mixture was placed at room temperature and dried for 12 hours to complete the preparation.

[0112] Thermoelectric performance test method: The heating plate and the cooling plate are used to create a temperature difference. The sample is placed between the heating plate and the cooling plate. 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 electrode is perpendicular to the temperature difference direction. Keithley2000 is used to record the voltage between the two electrodes. A dual-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.

[0113] The detected Seebeck coefficient was 8mV / K, the maximum open circuit voltage was 0.004V, and no short circuit current was detected.

[0114] 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 has a gain on the voltage generated by thermoelectricity under a fluctuating temperature difference, and the current used is the current generated by the Seebeck effect under the temperature difference. In the present invention, 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 works under a temperature difference, rather than only working under a fluctuating temperature difference, and the output current used is the drift current generated by the electronic conductor, and the direction of the drift current is opposite to the current generated by the Seebeck effect.

[0115] Comparative Example 4:

[0116] Preparation method: Bulk tetrachloroperylene bisimide (100 mg) and 10 ml 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 dripped onto the cleaned quartz, and then heat-treated at 50°C for 30 minutes and 80°C for 30 minutes in sequence to remove the solvent and complete the preparation.

[0117] Thermoelectric performance test method: The sample was cut into a size of 20.0 and 3.0 mm in length and width, and suspended between two cooling devices (usually 20 mm apart) using thermal paste to generate a temperature difference. The temperature gradient of the long side of the sample was measured using two T-type thermocouples, and the voltage generated by the long side was tested using Keithley2700.

[0118] The detected Seebeck coefficient was 3.021mV / K, the maximum open circuit voltage was 0.063V, and no short-circuit current was detected.

[0119] The thermoelectric material prepared in this comparative example is an ion-electron integrated thermoelectric material, which can conduct electrons and ionize ions, in which electron carriers are dominant, and the voltage is generated from electron thermal diffusion and ion dissociation, and the current used is also the thermal diffusion current generated by the Seebeck effect of the electronic material. The voltage in the present invention 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.

[0120] Comparative Example 5:

[0121] Preparation method: PEDOT:PSS aqueous solution was dropped on the glass substrate, air-dried for 12 hours, and then annealed at 130°C for 5 minutes. 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 to complete the preparation.

[0122] Thermoelectric performance test method: The heating plate and the cooling plate are used to create a temperature difference. The sample is placed between the heating plate and the cooling plate. 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 electrode is perpendicular to the temperature difference direction. Keithley2000 is used to record the voltage between the two electrodes. A dual-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.

[0123] The detected Seebeck coefficient was 24mV / K, the maximum open circuit voltage was 0.360V, and no short circuit current was detected.

[0124] The working principle of the thermoelectric material prepared in this comparative example is to suppress the hydrogen ions in PEDOT:PSS by chemical methods, thereby reducing the ions and increasing the conductivity of PEDOT:PSS to obtain a stable thermovoltage; the present invention introduces ions to increase the voltage, so there is an essential difference between the two.

[0125] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can make many forms without departing from the scope of protection of the purpose of the present invention and the claims, which are all protected by the present invention.

Claims

1. An ion-electron coupling 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 ion thermal diffusion, and its output current comes from the drift current in the electronic conductor caused by ion thermal diffusion. The ion-electron conductor material includes an ion-electron integrated conductor material, and the ionic liquid phase material includes an inorganic salt solution or an ionic liquid. The ion-electron integrated conductor material includes a carbonized biomass material.

2. The ion-electron coupling thermoelectric material according to claim 1, characterized in that: The coupling mode of the ion-electron integrated conductor material and the ion liquid phase material is that the ion liquid phase material is filled inside the ion-electron integrated conductor material.

3. The ion-electron coupling thermoelectric material according to claim 1, characterized in that: The carbonized biomass material includes one or more of carbonized grapefruit peel, carbonized wood, and carbonized bamboo.

4. The ion-electron coupling thermoelectric material according to claim 1, characterized in that: The inorganic salt solution includes one or more of a sodium iodide solution, a potassium iodide solution, a sodium chloride solution, a potassium chloride solution and a sodium hydroxide solution.

5. The ion-electron coupling thermoelectric material according to claim 1, 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.

6. The ion-electron coupling thermoelectric material according to claim 1, characterized in that: The ion-electron coupling type thermoelectric material outputs voltage according to the following formula: ； in, V represents the obtained thermal voltage; x represents the diffusion length; q represents elementary charge; It indicates the conductivity of electronic conductor materials; D + represents the diffusion coefficient of the cation, D - represents the diffusion coefficient of anions; z + represents the valence state of the cation, z - Indicates the valence state of the anion; C + represents the concentration of cations, C - Indicates the concentration of anions; Indicates the ion selectivity of ion conductor materials.

7. A method for preparing an ion-electron coupling thermoelectric material, characterized in that: The following steps are involved: (1) Preparation of ion-electron conductor material: taking biomass material and carbonizing it to obtain ion-electron integrated carbonized biomass material as ion-electron conductor material for standby use; (2) Preparation of ionic liquid phase materials: Taking the ionic liquid as the ionic liquid phase material for standby use; Alternatively, an inorganic salt is dissolved in deionized water to prepare an inorganic salt solution as an ionic liquid phase material for later use; Alternatively, the ionic liquid is dissolved in deionized water to prepare an ionic liquid solution as an ionic liquid phase material for later use; (3) Preparation of ion-electron coupled thermoelectric materials: The carbonized biomass material prepared in step (1) is immersed in the ionic liquid phase material prepared in step (2) for 2-48 hours and then taken out to obtain the ion-electron coupling thermoelectric material.

8. The method for preparing an ion-electron coupling thermoelectric material according to claim 7, characterized in that: The biomass material includes one or more of grapefruit peel, wood, and bamboo; 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.

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