P-N flipped ionic thermoelectric gel and preparation method and application thereof
By developing P-N flipped ionic thermoelectric gels, the problems of poor flexibility and high cost facing inorganic thermoelectric materials in commercial applications are solved, and efficient thermoelectric conversion and flexible application adaptability are achieved.
Patent Information
- Application Number
- CN202510009496.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-03
- Publication Date
- 2025-06-03
AI Technical Summary
In the wide commercial application of existing inorganic thermoelectric materials, the problems of scarce raw materials, complex processing, high cost, toxicity and poor flexibility, and it is difficult to meet the needs of flexible electronic devices.
A P-N flipped ionic thermoelectric gel is developed to control the thermoelectric properties and conductivity of the material by accurately adjusting the ionic liquid components, thereby achieving flipping between P-type and N-type conductivity.
It improves the thermoelectric performance of the gel, has good flexibility and adjustability, and is suitable for the fields of thermoelectric power generation, heat dissipation adjustment and self-energy supply, reduces production costs and improves the thermoelectric conversion efficiency.
Smart Images
Figure CN120091750A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of thermoelectric materials, and particularly to a P-N inverted ionic thermoelectric gel and its preparation method and application. Background Art
[0002] The energy crisis is one of the most critical problems faced by modern society. Most of the electricity globally relies on heat engines for production, but their efficiency is only 30% to 40%, which means that at least 60% of fossil fuels are dissipated in the form of waste heat. The temperature of this waste heat is called low-grade heat because its temperature is below 100°C, and heat engines cannot convert low-grade heat into electrical energy. To further improve energy utilization efficiency, thermoelectric conversion materials are often used to convert low-grade heat energy into usable electrical energy. By means of the temperature gradient at both ends of the material, it induces the directional migration of carriers or ions inside the material to form a Seebeck voltage, thereby realizing the conversion of heat energy into electrical energy. The development of new thermoelectric materials helps to promote energy utilization efficiency and provides new impetus for the sustainable development and low-carbon economy of our country.
[0003] According to the type of carriers, thermoelectric materials can be divided into electronic thermoelectric materials and ionic thermoelectric materials. Currently, inorganic thermoelectric materials in electronic thermoelectric materials have successfully achieved commercial applications due to their outstanding thermoelectric performance. These inorganic thermoelectric materials exhibit relatively high thermoelectric conversion efficiency in practical applications and can effectively convert heat energy into electrical energy. However, these inorganic thermoelectric materials are not perfect, and they have many problems that limit their further extensive commercialization. First of all, these inorganic materials face challenges such as scarce raw materials, complex processing, high cost, and toxicity. Secondly, these materials have poor flexibility, and in application scenarios that require bending or stretching, their performance will be greatly reduced, unable to meet the requirements of modern technology for flexible electronic devices and other aspects.
[0004] In contrast, organic thermoelectric materials, as a type of electronic thermoelectric materials, have unique advantages. One of their most prominent features is excellent flexibility, which gives it great application potential in the field of flexible electronics. In addition, organic thermoelectric materials also have relatively high thermal conductivity, which can ensure the effective transfer of heat to a certain extent. However, its overall Seebeck coefficient is relatively low. Usually, the Seebeck coefficient of organic thermoelectric materials is only a few hundred μV K -1 , and such a coefficient level greatly limits the power generation efficiency in practical applications, resulting in the realization of high-performance flexible thermoelectricity becoming a difficult problem that needs to be overcome urgently. Summary of the Invention
[0005] The object of the present invention is to overcome the deficiencies in the prior art and provide a P-N flipped ionic thermoelectric gel, its preparation method and application. The manufacturing process of this gel involves precisely adjusting the composition of ionic liquids. By changing different ionic species and their ratios, the thermoelectric properties and conductivity of the material can be effectively regulated. Specifically, this adjustment method enables the ionic thermoelectric gel to achieve flipping between P-type and N-type conductivity. This P-N flipping ability not only improves the thermoelectric properties of the gel but also enables it to flexibly adapt to different application scenarios, such as in the fields of thermoelectric power generation, heat dissipation regulation, and self-power supply. Therefore, the ionic thermoelectric gel of the present invention not only fills some technical gaps in basic research but also shows broad prospects and value in practical applications.
[0006] The present invention is achieved through the following technical solutions: On the one hand, a P-N flipped ionic thermoelectric gel is provided. This ionic thermoelectric gel is obtained by mixing a polymer matrix and an ionic liquid in an organic solvent and then performing thermal annealing; wherein, the mass ratio of the polymer matrix: ionic liquid: organic solvent is 1:(0.4 - 1):(10 - 50).
[0007] Through the above technical solution, the ionic thermoelectric material uses an ionic conductive material as the carrier of the charge carriers, and its conduction mechanism is realized by relying on the ions that can move freely in the material. This type of thermoelectric material has a series of remarkable advantages. First of all, the ionic thermoelectric material has good flexibility and can well adapt to various shapes and curved application scenarios, which provides a basis for its application in the field of flexible electronics. Secondly, its raw materials are abundant and are not restricted by the scarcity of raw materials like inorganic thermoelectric materials, which makes large-scale production possible and can effectively reduce production costs. Moreover, the structure of the ionic thermoelectric material is adjustable. By designing and adjusting the material structure, its thermoelectric properties can be optimized to meet the requirements of different application scenarios. In addition, the cost of the ionic thermoelectric material is relatively low, which is very beneficial for its promotion in commercial applications. Finally, the Seebeck coefficient of the ionic thermoelectric material is relatively high and can exceed 1 mV K -1 , this advantage gives it great potential in terms of thermoelectric conversion efficiency and makes it a strong competitor among electronic thermoelectric materials.
[0008] A method for preparing the P-N flipped ionic thermoelectric gel according to claim 1 is also provided, including the following steps:
[0009] Step S1: Dissolve the polymer matrix in an organic solvent, heat and stir until completely dissolved to obtain a polymer solution;
[0010] Step S2: Add an ionic solution to the polymer solution obtained in step S1 and stir until the solution is uniform to obtain a sol;
[0011] Step S3: Heat the sol obtained in Step S2 to 50 - 90°C for shaping, and then it is obtained.
[0012] Through the above technical method, the PVDF - HFP solution and LiTFSI are mixed evenly in DMF and stirred until the solution is homogeneous to obtain a sol. In the sol, the polymer chains and ionic liquids are in a relatively dispersed state, presenting a uniform appearance. In the sol state, the components in the system have not formed a fixed three - dimensional network structure yet, but already have the potential to form a gel;
[0013] Pour the sol into a mold and conduct heat treatment. As the temperature rises, the solvent begins to volatilize. During this process, the movement ability of the polymer chains gradually decreases, and they start to entangle and aggregate with each other. At the same time, the ionic liquid is further restricted in the polymer network, forming a stable gel structure. In the initial stage of heating, the fluidity of the sol gradually decreases and it becomes more viscous; as the heating continues, the sol gradually loses its fluidity and forms a gel with a certain shape and mechanical strength.
[0014] Further, in Step S1, the polymer matrix is selected from one or more of poly(vinylidene fluoride - co - hexafluoropropylene), poly(vinylidene fluoride - co - trifluoroethylene), poly(vinylidene fluoride - co - tetrafluoroethylene), poly(vinylidene fluoride - co - chlorotrifluoroethylene); wherein, the mass percentage of the polymer matrix is 10% - 30%.
[0015] Further, in Step S1, the organic solvent is selected from any one of N,N - dimethylformamide, dimethyl sulfoxide, and acetone.
[0016] Further, in Step S2, the ionic liquid is selected from one or more of 1 - ethyl - 3 - methylimidazolium bis(trifluoromethylsulfonyl)imide, sodium bis(trifluoromethylsulfonyl)imide, 1 - ethyl - 3 - methylimidazolium dicyanamide, 1 - ethyl - 3 - methylimidazolium chloride, and lithium bis(trifluoromethylsulfonyl)imide; the mass percentage of the ionic liquid is 2% - 10%.
[0017] Further, in Step S2, the stirring time is 1 - 2 h, the stirring temperature is 60 - 80°C, and the stirring speed is 600 rpm;
[0018] Or, in Step S2, the obtained sol is in a flowing transparent state;
[0019] Through the above technical solution, from the apparent state, the sol presents a transparent state without signs of turbidity, precipitation, etc., indicating that the components inside the sol are mixed evenly; at the same time, it has excellent fluidity.
[0020] Alternatively, in step S3, the obtained ion thermoelectric gel with P-N inversion has a porous structure.
[0021] Through the above technical solution, from the apparent state, the gel exhibits good flexibility, and no cracks, fractures, etc. occur during simple manual twisting tests; from the internal microstructure, through scanning electron microscopy observation, it is found that the densely stacked PVDF-HFP chains transform into a porous structure. After the n-type to p-type thermoelectric gel transformation, the size of its quasi-spherical particles decreases, indicating that the interaction between polymer chains and ions also changes accordingly.
[0022] There is also provided an N-type ion thermoelectric gel prepared by the above method, wherein the polymer matrix is poly(vinylidene fluoride-co-hexafluoropropylene) PVDF-HFP; the ionic liquid is lithium bis(trifluoromethanesulfonyl)imide LiTFSI.
[0023] Through the above technical solution, LiTFSI exhibits high ionic conductivity and can efficiently conduct ions in the gel system, which is crucial for the ion thermoelectric gel to achieve good thermoelectric performance. At the same time, it can maintain stable physical and chemical properties within a wide temperature range, adapt to different working environment temperatures, and ensure the reliability of the thermoelectric gel performance during long-term use. Particularly importantly, LiTFSI shows good compatibility with gel matrices such as PVDF-HFP, and the two can be uniformly mixed to form a stable and uniform system. In addition, the fluorine atoms in PVDF-HFP have strong electronegativity, and LiTFSI will dissociate into Li + and TFSI - , Li + and the fluorine atoms on the PVDF-HFP molecular chain will produce ion-dipole interactions. This interaction enables LiTFSI to stably exist in the PVDF-HFP system rather than freely diffuse or precipitate. At the same time, the ion-dipole interaction also provides a certain guiding effect for the transport of ions in the system, which is beneficial to the directional migration of ions under a temperature gradient.
[0024] There is also provided a P-type ion thermoelectric gel prepared by the above method, wherein the polymer matrix is poly(vinylidene fluoride-co-hexafluoropropylene) PVDF-HFP; the ionic liquid is prepared by mixing lithium bis(trifluoromethanesulfonyl)imide LiTFSI and 1-ethyl-3-methylimidazolium chloride [EMIm][Cl]; wherein, the mass ratio of LiTFSI: [EMIm][Cl] is (0.4 - 1):(0.2 - 1).
[0025] Through the above technical solution, 1-ethyl-3-methylimidazolium chloride [EMIm][Cl] is based on the Cl- ions therein and Li in LiTFSI+ The metal-halogen interaction between ions affects the migration rate of ions in the gel, thereby affecting its thermoelectric performance.
[0026] Finally, a thermoelectric device is provided, which is characterized in that the thermoelectric device includes a substrate, an ionic gel material inkjet-printed on the substrate, and metal electrodes disposed at both ends of the ionic gel material; the ionic gel material is the above-mentioned P-N inverted ionic thermoelectric gel.
[0027] Through the above technical solutions, the substrate is made of glass or polyethylene terephthalate (PET); the inkjet printing gel technology has made remarkable progress in recent years and shown great potential in multiple fields. With the continuous progress of technology, the inkjet printing technology has become increasingly mature, and the preparation of gels by inkjet printing has also attracted wide attention, which has important development significance and great potential in multiple fields such as flexible electronics and biomedicine. However, parameters such as the size and shape of the nozzle and the viscosity, surface tension, and stability characteristics of the ink all have an important impact on the inkjet printing quality. Preparing thermoelectric gels by inkjet printing technology can achieve batch preparation of flexible thermoelectric gels, and also has a wide range of application prospects in the fields of wearable devices and personal thermoelectric management, etc., and is expected to promote the development of related industries. However, there is no relevant literature reporting inkjet-printed thermoelectric ionic gels.
[0028] The present invention precisely controls the rheological properties of the ionic gel by adjusting the ratio of the materials used in the preparation process to meet the working requirements of the inkjet printer. Using inkjet printing technology to manufacture ionic thermoelectric gels can not only achieve one-time printing of materials, but also greatly improve production efficiency and reduce costs, thus making batch preparation of thermoelectric modules possible. This technological innovation not only helps to promote the commercial application of thermoelectric materials, but also may open up a variety of emerging markets, laying a solid foundation for the development of future energy conversion and energy conservation and emission reduction technologies.
[0029] Beneficial effects
[0030] 1) The ionic thermoelectric gel prepared by the present invention is an innovative material, and its unique properties and application potential have attracted much attention in the field of energy conversion. The manufacturing process of this gel involves precise adjustment of the composition of ionic liquids. By changing different ion species and their ratios, the thermoelectric performance and conductivity of the material can be effectively regulated. Specifically, this adjustment method enables the ionic thermoelectric gel to achieve the inversion between P-type and N-type conductivities. This P-N inversion ability not only improves the thermoelectric performance of the gel, but also enables it to flexibly adapt to different application scenarios, such as in the fields of thermoelectric power generation, heat dissipation regulation, and self-power supply. Therefore, the ionic thermoelectric gel of the present invention not only fills some technical gaps in basic research, but also shows broad prospects and value in practical applications.
[0031] 2) The present invention relates to a preparation method of a novel ionic thermoelectric gel. This ionic gel has key physical parameters such as adjustable viscosity and surface energy, which enables it to be highly compatible with inkjet printing technology. Specifically, by adjusting the ratio of materials used in the preparation process, the rheological properties of the ionic gel are precisely controlled to meet the working requirements of an inkjet printer. Using inkjet printing technology to manufacture ionic thermoelectric gels can not only achieve one-time printing of materials, but also greatly improve production efficiency and reduce costs, thus making it possible to mass-produce thermoelectric modules. This technological innovation not only helps to promote the commercial application of thermoelectric materials, but also may open up a variety of emerging markets, laying a solid foundation for the development of future energy conversion and energy conservation and emission reduction technologies. Brief Description of the Drawings
[0032] Figure 1 It is a schematic diagram of the structure of a thermoelectric device (in the figure, 1 - substrate, 2, 3 - metal electrodes, 4 - gel) and thermoelectric testing in an embodiment of the present invention.
[0033] Figure 2 It is a sol state diagram in Embodiment 1 and Embodiment 2 of the present invention.
[0034] Figure 3 It is a morphological diagram of the ionic thermoelectric gel in Embodiment 1 and Embodiment 2 of the present invention.
[0035] Figure 4 In (a) and (b), they are SEM diagrams of the ionic thermoelectric gel in Embodiment 1 of the present invention at different magnifications; in (c) and (d), they are SEM diagrams of the ionic thermoelectric gel in Embodiment 2 of the present invention at different magnifications.
[0036] Figure 5 It is a flexibility display diagram of the ionic thermoelectric gel in Embodiment 1 and Embodiment 2 of the present invention.
[0037] Figure 6 It is the Seebeck coefficient of gels with different ionic liquid contents in Embodiment 1 and Embodiment 2 of the present invention.
[0038] Figure 7 It is the thermoelectric performance diagram of the ionic thermoelectric gel in (a) Embodiment 1 and (b) Embodiment 2 of the present invention.
[0039] Figure 8 It is the Seebeck coefficient diagram of Embodiment 1 and Embodiment 2 of the present invention.
[0040] Figure 9 It is the thermoelectric performance of thermoelectric devices using different metal electrodes in Embodiment 1 and Embodiment 2.
[0041] Figure 10 It is the viscosity-shear rate diagram of Embodiments 1 - 6 of the present invention.
[0042] Figure 11 In (a) and (b) are the contact angles of Example 1 of the present invention with water and diiodomethane; (c) and (d) are the contact angles of Example 2 of the present invention with water and diiodomethane; (e) is the surface energy of Example 1 and Example 2 of the present invention.
[0043] Figure 12 It is a flow chart for preparing an inkjet printing gel. Detailed implementation manners
[0044] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.
[0045] Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention. The experimental methods without specific conditions noted in the following embodiments are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. Unless otherwise specified, all percentages, ratios, proportions or parts are by weight.
[0046] The reagents and raw materials used in the embodiments and comparative examples of the present invention can be obtained through commercial channels without special instructions.
[0047] A method for preparing an ion thermoelectric gel with P-N inversion includes the following steps:
[0048] Step S1: Dissolve the polymer matrix in an organic solvent, heat and stir until completely dissolved to obtain a polymer solution;
[0049] Step S2: Add an ionic solution to the polymer solution obtained in Step S1 and stir until the solution is uniform to obtain a sol;
[0050] Step S3: Heat the sol obtained in Step S2 to 50 - 90 °C for molding, and then it is obtained.
[0051] The preparation steps of the thermoelectric device are as follows:
[0052] 1) Cut a glass substrate with a length of 5 cm and a width of 1.5 cm. First, clean it with a surface cleaning agent, and then ultrasonically clean it successively with acetone, water, and isopropanol; clean it in acetone for 20 min, once; clean it in ultrapure water for 5 min, three times; clean it in isopropanol for 5 min, once; dry the cleaned glass sheet with nitrogen;
[0053] 2) Deposit 80 nm of metal on the glass substrate using a mask and physical vapor deposition to form a metal thin film, and prepare metal electrodes 2 and 3;
[0054] 3) Print the gel on the above-mentioned substrate with metal electrodes by inkjet printing and cure it at 60 °C for 1 h to obtain a thermoelectric device. The preparation process is as Figure 12 shown.
[0055] Thermoelectric performance test:
[0056] Use a Peltier to form a temperature difference at both ends of the thermoelectric device, record the generated thermal voltage through an electrochemical workstation, and record its temperature through a thermocouple.
[0057] Example 1
[0058] 1) Weigh 1 g of PVDF-HFP and 9 g of DMF, stir at 60 °C for 2 h to obtain a PVDF-HFP solution;
[0059] 2) Add 1 g of LiTFSI to the solution and mix and stir for 1 h to obtain a sol;
[0060] 3) Pour the sol into a mold and heat it to 60 °C. After 8 h, an ion gel is formed.
[0061] Based on the above technical solution, the obtained sol is as Figure 2 shown in Example 1, presenting a transparent and uniform state, having good fluidity. When it is inverted, there is no wall hanging phenomenon. Its morphology is as Figure 3 (a) shown, being a nearly transparent solid. In order to explore its microstructure, it is photographed with a Zeiss Sigma 300. Its scanning electron micrograph is as Figure 4 (a)(b) shown. It can be seen from the figure that there are many uniformly distributed particles on the surface of the ion gel, and the shape is close to spherical. Further apply an external force to the material to examine its mechanical response characteristics. As Figure 5 (a) shows the twisted deformation state. When the material of Example 1 is subjected to an external force for twisting operation, it can obediently undergo significant deformation, rather than being easily broken like some brittle materials. This characteristic means that in actual application scenarios, when the material encounters external forces, whether it is in daily slight touches, bends, or in some specific engineering applications with moderate pulling, squeezing and other complex stress situations, it has sufficient toughness and flexibility to maintain its own structural integrity, while flexibly adapting to external force changes and not being damaged due to stress, thus providing a solid guarantee for its extended applications in various fields such as wearable devices and flexible electronic devices.
[0062] Its scanning electron micrograph is as Figure 4 shown in (a)(b) in it. It can be seen that there are many uniformly distributed particles on the surface of the ion gel, and the shape is close to spherical. Its twisted deformation is as Figure 5(a) As can be seen, Example 1 has a certain flexibility derived from this twisted form. This means that when the material is subjected to external forces, it can deform without easily breaking.
[0063] Example 2:
[0064] 1) Weigh 1 g of PVDF-HFP and 9 g of DMF, and stir them at 60 °C for 2 h to obtain a PVDF-HFP solution;
[0065] 2) Add 1 g of LiTFSI and 1 g of [EMIm][Cl] to the above solution, mix and stir for 1 h to obtain a sol;
[0066] 3) Pour the sol into a mold and heat it to 60 °C. After 8 h, an ion gel is formed, and its morphology is as shown in Figure 3 (b), which is a semi-transparent solid. The change in optical properties is due to the change in the interaction between them after adding [EMIm][Cl]; its scanning electron micrograph is as shown in Figure 4 (c)(d) below. It can be seen from this that there are many uniformly distributed particles on the surface of the ion gel, and the shape is close to spherical. Compared with Example 1, the particle distribution is denser, and the quasi-spherical size decreases, which is caused by the change in the interaction between ions and between ions and polymers inside after adding [EMIm][Cl]. Its twisted deformation is as shown in Figure 5 (b). Similarly, it can be seen that Example 2 also exhibits a certain flexibility.
[0067] Effect Example 1: Thermoelectric performance test
[0068] The test was carried out using the Donghua electrochemical workstation DH7000C. The temperature gradient was achieved by constructing a Peltier patch, and the temperature was recorded using a thermocouple.
[0069] 1) Test the thermoelectric performance of the gels with different ionic liquid contents in Example 1. The results are as shown in Figure 6 (a). When the LiTFSI content is 20 wt%, the gel has no thermoelectric performance; when the content increases to 40 wt%, the Seebeck coefficient increases to -1.48 mV.K -1 ; when the LiTFSI content is further increased to 100 wt%, the Seebeck coefficient reaches the maximum, which is -3.26 mV.K -1 .
[0070] 2) Figure 6 (a) shows the thermoelectric performance curve when the LiTFSI content in Example 1 is 100 wt%. It is found that as the temperature increases, the voltage shows a downward trend; when the temperature decreases, the voltage shows an upward trend, showing N-type thermoelectric behavior. Five consecutive heating and cooling cycles were tested.
[0071] 3) The thermoelectric properties of the gels with different ionic liquid contents in Example 2 were tested, and the results are as Figure 6 (b) shown. Since the Seebeck coefficient was the highest when the LiTFSI content was 100 wt% in Example 1, the LiTFSI content was fixed at 100 wt%, and the thermoelectric properties of the thermoelectric gel were regulated by changing the content of [EMIm][Cl]. When the content of [EMIm][Cl] was 20 wt%, the thermoelectric behavior of the thermoelectric gel had changed from N-type to P-type, and the Seebeck coefficient was 2.53 mV.K -1 ; when the content of [EMIm][Cl] increased to 40 wt%, the Seebeck coefficient increased to 3.55 mV.K -1 ; when the content of [EMIm][Cl] was further increased to 100 wt%, the Seebeck coefficient reached the maximum, which was 9.43 mV.K -1 .
[0072] 4) Figure 7 (b) shows the thermoelectric performance curve when the content of [EMIm][Cl] was 100 wt% in Example 2. It was found that as the temperature increased, the voltage showed an increasing trend; when the temperature decreased, the voltage showed a decreasing trend, showing P-type thermoelectric behavior. Five heating and cooling cycles were continuously tested.
[0073] Effect Example 2: Seebeck coefficient
[0074] Using the device as Figure 1 shown to measure the ionic Seebeck coefficient, the open-circuit voltage was recorded at different temperature gradients. The Seebeck coefficient (S) was calculated by formula (1):
[0075]
[0076] Therefore, according to importing ΔV and ΔT in Figure 7 into Origin, a scatter plot was drawn, and through linear fitting, the slope obtained was the Seebeck coefficient of Example 1 and Example 2. Therefore, the Seebeck coefficient of Example 1 was -3.26 mV.K -1 , and the Seebeck coefficient of Example 2 was 9.55 mV.K -1 , as Figure 8 shown.
[0077] Effect Example 3: Thermoelectric devices with different metal electrodes
[0078] The above thermoelectric properties and Seebeck coefficient calculations were all based on tests and calculations with silver electrodes. Considering that the material of the metal electrode may affect the thermoelectric properties of the gel, the thermoelectric properties of Example 1 and Example 2 were tested using gold, silver, and copper electrodes respectively, and their Seebeck coefficients were calculated, as Figure 9 shown.
[0079] Figure 9 (a) is the Seebeck coefficient of the thermoelectric device using different metal electrodes in Example 1. For the thermoelectric device using a gold electrode as the metal electrode, the Seebeck coefficient of Example 1 is -0.60 mV·K -1 ; for the thermoelectric device using a copper electrode as the metal electrode, the Seebeck coefficient of Example 1 is -2.94 mV·K -1 ; for the thermoelectric device using a silver electrode as the metal electrode, the Seebeck coefficient of Example 1 is -3.26 mV·K -1 .
[0080] Figure 9 (b) is the Seebeck coefficient of the thermoelectric device using different metal electrodes in Example 2. For the thermoelectric device using a gold electrode as the metal electrode, the Seebeck coefficient of Example 2 is 2.06 mV·K -1 ; for the thermoelectric device using a copper electrode as the metal electrode, the Seebeck coefficient of Example 2 is 3.20 mV·K -1 ; for the thermoelectric device using a silver electrode as the metal electrode, the Seebeck coefficient of Example 2 is 9.55 mV·K -1 .
[0081] In both Example 1 and Example 2, a consistent pattern is presented: for the thermoelectric device with a gold electrode as the metal electrode, its Seebeck coefficient is the lowest, followed by the copper electrode, and the Seebeck coefficient corresponding to the silver electrode is the highest. This phenomenon is most likely attributed to the difference in the intensity of the interaction between ions and different metal electrodes. In view of this, the thermoelectric device involved in the present invention selects a silver electrode as the metal electrode material. The silver electrode not only has the highest Seebeck coefficient and is more advantageous in terms of performance, but also, considering the cost, its price is lower than that of the gold electrode, which can effectively reduce the production cost and improve the market competitiveness of the product. At the same time, compared with the copper electrode, the silver electrode has more stable chemical properties and is not prone to redox reactions under complex environmental conditions, thereby ensuring the stability and reliability of the performance of the thermoelectric device during long-term use.
[0082] Effect Example 4: Rheological test
[0083] In order to obtain the viscosity of the ionic thermoelectric gel to meet the viscosity requirements for inkjet printing and prevent too high viscosity from causing nozzle blockage and affecting the printing effect. The rheological tests were respectively carried out on Examples 1, 2, 3, 4, 5, and 6 at room temperature and normal humidity using a Discovery HR rheometer of TA Instruments, USA, and the test results are as Figure 10 shown.
[0084] Examples 3, 4, 5, 6
[0085] Examples 3, 4, 5, and 6 are basically the same as Examples 1 and 2, except that: the mass of the solvent added in Examples 1 and 2 is different, and the mass of the added solvent is shown in Table 1.
[0086] Table 1 Solvent Dosage in Examples 1-6
[0087] Sample Name PVDF-HFP LiTFSI [EMIm][Cl] DMF Example 1 1g 1g 9g Example 2 1g 1g 1g 9g Example 3 1g 1g 20g Example 4 1g 1g 1g 20g Example 5 1g 1g 30g Example 6 1g 1g 1g 30g
[0088] Viscosity tests were respectively carried out on Examples 1, 3, and 5. As Figure 10 shown, it was found from Figure 10 (a), (c), and (e) that as the mass of the solvent increased, the viscosity also decreased to about 0.01 Pa·s; Figure 10 (b), (d), and (f) also showed that as the mass of the solution increased, the viscosity also decreased to about 0.01 Pa·s. It meets the viscosity requirements (1-20 mPa·s) for inkjet printing and has printing suitability. In addition, the viscosity can also be changed by further adjusting the mass of the solvent to meet the requirements of various printing processes.
[0089] Effect Example 5: Surface Energy Test
[0090] The surface energy of the ink affects its wettability and adhesion on paper or other substrates. Generally, the surface energy needs to match the surface energy of the substrate to obtain good printing effects. The surface tension of the ink required for inkjet printing is generally between 20-40 mN / m. A lower surface tension helps to improve the diffusibility and permeability of the ink, ensuring the formation of a uniform image on the substrate.
[0091] The surface energy of a solid can be divided into polar and non-polar parts. According to the Owens method, by using the contact angle data of two polar and non-polar liquids on a certain solid surface, the non-polar value and polar value of the surface tension of the solid can be obtained, and the sum of the two is approximately equal to the total surface tension of the solid.
[0092]
[0093] In the formula, there are only and two unknowns. As long as two known and probe liquids are found, measure the contact angles of these two liquids on the solid surface, and substitute the surface tension and contact angle data of the liquids into formula (2) respectively, two independent equations can be obtained. Solving this system of equations can obtain the and of the polymer and the surface tension γ S of the polymer. It is known that the of water is 51 mJ / m, is 21.8 mJ / m; for methylene iodide is 2.3 mJ / m, is 48.5 mJ / m. Therefore, in order to obtain the surface energy of the ionic thermoelectric gel, the contact angles of Examples 1 and 2 were tested using polar liquid water and non-polar methylene iodide, respectively. Figure 11 (a)(b) are the contact angles of Example 1 with water and methylene iodide, respectively. The contact angle with water is about 92.7°, and the contact angle with methylene iodide is about 73.3°; Figure 11 (c)(d) are the contact angles of Example 2 with water and methylene iodide, respectively. The contact angle with water is about 75.4°, and the contact angle with methylene iodide is about 65.0°. And the surface energy was calculated by formula (1), and the results are as Figure 11 (e) shows that the surface energy of Example 1 is about 24 mN / m, and the surface energy of Example 2 is about 32.76 mN / m, which meets the surface energy required for inkjet printing and has printability.
[0094] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
Claims
1. A PN-reversed ionic thermoelectric gel, which is prepared by mixing a polymer matrix and an ionic liquid in an organic solvent and then thermally annealing; wherein: The mass ratio of the polymer matrix: ionic liquid: organic solvent is 1: (0.4-1): (10-50).
2. A method for preparing the PN-reversed ion thermoelectric gel according to claim 1, characterized in that: The following steps are involved: Step S1, dissolving the polymer matrix in an organic solvent, heating and stirring until it is completely dissolved, to obtain a polymer solution; Step S2, adding the ion solution to the polymer solution obtained in step S1, stirring until the solution is uniform, to obtain a sol; Step S3, heating the sol obtained in step S2 to 50-90°C and forming the sol.
3. The method for preparing the PN-reversed ion thermoelectric gel according to claim 2, characterized in that: In step S1, the polymer matrix is selected from one or more of poly(vinylidene fluoride-co-hexafluoropropylene), poly(vinylidene fluoride-co-trifluoroethylene), poly(vinylidene fluoride-co-tetrafluoroethylene), and poly(vinylidene fluoride-co-chlorotrifluoroethylene); wherein the mass percentage of the polymer matrix is between 10% and 30%, and the mass ratios are all mass ratios to the solvent.
4. The PN-reversed ion thermoelectric gel according to claim 2, characterized in that: In step S1, the organic solvent is selected from any one of N,N-dimethylamide, dimethyl sulfoxide, and acetone.
5. The PN-reversed ion thermoelectric gel according to claim 2, characterized in that: In step S1, the stirring time is 1-2 hours, the stirring temperature is 60-80°C, and the stirring speed is 600 rpm.
6. The method for preparing the PN-reversed ion thermoelectric gel according to claim 2, characterized in that: In step S2, the ionic liquid is selected from one or more of 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonyl imide, sodium bistrifluoromethanesulfonyl imide, 1-ethyl-3-methylimidazolium dicyanamide, 1-ethyl-3-methylimidazolium chloride, and lithium bistrifluoromethanesulfonyl imide; the mass percentage of the ionic liquid is 2% to 10%.
7. The method for preparing the PN-reversed ion thermoelectric gel according to claim 2, characterized in that: In step S2, the stirring time is 1-2 hours, the stirring temperature is 60-80°C, and the stirring speed is 600 rpm; Alternatively, in step S2, the obtained sol is in a flowing transparent state; Alternatively, in step S3, the obtained PN-reversed ionic thermoelectric gel has a porous structure.
8. An N-type ionic thermoelectric gel prepared by the method according to any one of claims 2 to 7, characterized in that: The polymer matrix is poly(vinylidene fluoride-co-hexafluoropropylene) PVDF-HFP; and the ionic liquid is lithium bis(trifluoromethanesulfonyl imide) LiTFSI.
9. A P-type ionic thermoelectric gel prepared by the method according to any one of claims 2 to 7, characterized in that: The polymer matrix is poly(vinylidene fluoride-co-hexafluoropropylene) PVDF-HFP; the ionic liquid is prepared by compounding lithium bis(trifluoromethanesulfonyl)imide LiTFSI and 1-ethyl-3-methylimidazolium chloride [EMIm][Cl]; wherein the mass ratio of LiTFSI:[EMIm][Cl] is (0.4-1):(0.2-1).
10. A thermoelectric device, characterized in that: The thermoelectric device comprises a substrate, an ion gel material inkjet-printed on the substrate, and metal electrodes arranged at both ends of the ion gel material; the ion gel material is the PN-reversed ion thermoelectric gel described in claim 1.