Giant thermoelectric potential ionic thermoelectric film and preparation method thereof

Abstract

The present invention discloses a giant thermoelectric potential ionic thermoelectric film and a preparation method thereof. Polyethylene oxide is mixed with a solvent to obtain a polymer solution; an ionic liquid is added to the polymer solution, and the obtained mixture is cast in a mold and dried. The film and device of the present invention have good flexibility and elongation at break, the synthesis method is simple, and are suitable for large-scale preparation. Most importantly, the thermoelectric film exhibits ultra-high ionic thermoelectric potential at a comfortable humidity for the human body, filling the gap in high-performance ionic thermoelectric materials at current conventional humidity, has excellent thermoelectric response, achieves simultaneous optimization of Seebeck coefficient and electrical conductivity, does not have the problem of parameter coupling in traditional thermoelectric materials, and at the same time has excellent air stability and is easy to be processed into flexible thermoelectric devices, providing a new way for thermal energy collection, conversion and storage, which is of great significance to the development of high-performance flexible thermoelectric devices with giant thermoelectric potential.

Description

Technical Field

[0001] The invention relates to an ionic thermoelectric film with giant thermoelectric potential under comfortable humidity for human body and a preparation method thereof, belonging to the technical field of ionic thermoelectric films and preparation thereof. Background Art

[0002] The current energy crisis and waste heat consumption have drawn attention to low-energy energy harvesting and conversion technologies. Thermoelectric technology can achieve the conversion of thermal energy into electrical energy, and the development of wearable electronic devices has also promoted the research of flexible thermoelectric materials and devices. Traditional thermoelectric materials have a relatively low Seebeck coefficient, typically less than 1mV / K, and the coupling relationship between the Seebeck coefficient and electrical conductivity has restricted their further application. Unlike traditional thermoelectric materials that use electrons and holes as charge carriers, ionic thermoelectric materials driven by ion diffusion have recently attracted increasing attention. For example, due to the huge thermovoltage and ionic Seebeck voltage that are 2-3 orders of magnitude higher than those of electronic materials, they have great potential for the development of integrated energy conversion and storage devices.

[0003] Compared to aqueous ion gels, which must overcome performance instability caused by water evaporation, ionic liquids are non-volatile, effectively improving the stability of ion gels. However, currently reported ionic thermoelectric materials typically exhibit high Seebeck coefficients at high humidities around 90%, and the Seebeck coefficients of materials at low humidities need to be improved. For wearable thermoelectric material systems, the human body's comfortable humidity range is between 30% and 60%, so developing ionic thermoelectric materials with high Seebeck coefficients at low humidities is of great application significance.

[0004] Crispin et al. (Zhao D., Wang H., Khan ZU, Chen J., Gabrielsson R., Jonsson M.P., Berggren M., Crispin XJE, Science E., Ionic thermoelectric supercapacitors. 2016, 9(4): 1450-1457.) prepared an ionic thermoelectric material composed of liquid PEO and NaOH, whose ionic Seebeck coefficient was 11.1 mV / K and the electrical conductivity of this material was only 8.13×10 -2mS / cm and cannot be stretched. Klas Tybrandt et al. (Kim N., Lienemann S., Petsagkourakis I., Mengistie DA, Kee S., Ederth T., Gueskine V., Leclere P., Lazzaroni R., Crispin X., Tybrandt K., Elastic conducting polymer composites in thermoelectric modules. Nature Communications 2020, 11(1).) prepared a composite film of waterborne polyurethane, PEDOT:PSS and ionic liquid. The elongation at break of the material was greater than 600%, but the Seebeck coefficient was only 22 μV / K. Sung-Yeon Jang et al. (Akbar Z.A., Jeon J.-W., Jang S.-Y., Intrinsically self-healable, stretchable thermoelectric materials with a large ionic Seebeck effect. Energy & Environmental Science 2020, 13(9): 2915-2923.) prepared a composite gel of polyaniline, polyelectrolyte and phytic acid with an elongation at break of up to 750%. The thermoelectric performance of this material is highly dependent on humidity, and the Seebeck coefficient reaches 8.1 mV / K at a high humidity of 90%. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: the problem that existing thermoelectric films are seriously dependent on high humidity and how to achieve the decoupling of the ionic Seebeck coefficient and electrical conductivity while giving the thermoelectric film ultra-high elongation at break and stable thermoelectric performance.

[0006] In order to solve the above technical problems, the present invention provides a method for preparing a giant thermoelectric potential ionic thermoelectric film, comprising the following steps:

[0007] Step 1): mixing polyethylene oxide with a solvent, heating and stirring under sealed conditions to obtain a polymer solution;

[0008] Step 2): adding the ionic liquid to the polymer solution, and continuing to heat and stir under sealed conditions;

[0009] Step 3): The mixture obtained in step 2) is poured into a mold, and after the solvent evaporates naturally, the mixture is placed in an oven and dried to obtain an ion gel film, which is a giant thermoelectric potential ion thermoelectric film.

[0010] Preferably, the molecular weight of the polyethylene oxide in step 1) is 1,000,000-6,000,000; a non-ionic liquid plasticizer is further added to the polymer solution, specifically a block copolymer polyethylene oxide-polypropylene oxide-polyethylene oxide, silicon oxide or strontium titanate fiber; and the solvent is acetonitrile or ethanol.

[0011] More preferably, the molecular weight of the block copolymer polyethylene oxide-polypropylene oxide-polyethylene oxide (P123) is 5800; the particle size of the silicon oxide is 15 nm; and the length of the strontium titanate fiber is 1-2 μm.

[0012] Preferably, in step 1), the mass percentage of the non-ionic liquid plasticizer is not higher than 60% based on the sum of the masses of polyethylene oxide and the non-ionic liquid plasticizer.

[0013] Preferably, the ionic liquid in step 2) accounts for 30-80% of the total mass of the ion gel membrane.

[0014] Preferably, the ionic liquid in step 2) is at least one of 1-ethyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium dicyanamide, 1-hexyl-3-methylimidazolium acetate and 1-decyl-3-methylimidazolium acetate.

[0015] The present invention also provides a giant thermopotential ionic thermoelectric film prepared by the above-mentioned method for preparing the giant thermopotential ionic thermoelectric film.

[0016] Preferably, the humidity of the environment in which the giant thermopotential ionic thermoelectric film is used is 50-60%.

[0017] The present invention also provides a giant thermoelectric potential ionic thermoelectric film device at a comfortable humidity for the human body, which includes the above-mentioned giant thermoelectric potential ionic thermoelectric film. The giant thermoelectric potential ionic thermoelectric film is connected to an external resistor through an electrode to form an ionic thermal capacitor, which realizes low-energy level heat collection, storage and conversion.

[0018] Preferably, the electrode is a silver ribbon prepared by inkjet printing; and the external resistor is 9 kΩ-1 MΩ.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) This invention prepares a quasi-solid-state ionic thermoelectric gel with a sensitive thermoelectric response. The thermovoltage reaches 12.7 mV at a temperature difference of 0.7 K and 280 mV at a temperature difference of 16 K. The ionic Seebeck coefficient is 17.8 mV / K at a humidity of 50%-60%, and the ionic conductivity is as high as 1.3 mS / cm.

[0021] (2) The quasi-solid-state ionic thermoelectric gel of the present invention has excellent mechanical properties, with a maximum elongation at break of 970%. After 100% stretching, the ionic Seebeck coefficient only decreases by 20%.

[0022] (3) The ionic thermoelectric gel prepared by the present invention has air stability. After being placed for 600 hours, the ionic Seebeck coefficient can be retained up to 80%.

[0023] (4) The ionic thermal capacitor assembled in the present invention can harvest energy up to 195 nJ for a temperature difference of 1.3 K under a load of 1 MΩ.

[0024] (5) The method of the present invention can simultaneously improve the ionic Seebeck and electrical conductivity of the ionic thermoelectric film. It is low-cost, non-toxic, and has a simple preparation method. It has excellent thermoelectric performance stability, greatly improves the processability and practicality of the thermoelectric film, and fills the gap in ionic thermoelectric materials with high thermoelectric performance under low humidity. It has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the Seebeck coefficient of the ionic thermoelectric films prepared in Examples 1-4 and different ionic liquid types and ionic liquid contents;

[0026] Figure 2 The change of the electrical conductivity of the imidazolium acetate ion thermoelectric films prepared in Examples 1, 3, and 4;

[0027] Figure 3 is the Seebeck coefficient of the ternary composite ion thermoelectric thin films prepared in Examples 5 and 6;

[0028] Figure 4 The change of the electrical conductivity of the ternary composite ion thermoelectric films prepared in Examples 5 and 6;

[0029] Figure 5 The elongation at break of the imidazolium acetate ion thermoelectric films prepared in Examples 3, 4, and 6;

[0030] Figure 6 The thermovoltage response of the ternary composite ion thermoelectric film prepared in Example 6 under different temperature differences;

[0031] Figure 7 The change of Seebeck coefficient of the ionic thermoelectric film prepared in Example 6 under different stretching degrees;

[0032] Figure 8 The change of Seebeck coefficient of the ionic thermoelectric film prepared in Example 6 after being placed for different time periods;

[0033] Figure 9This is a demonstration of the working process of the ionic thermoelectric capacitor assembled with the ionic thermoelectric film prepared in Example 6 in four stages under a temperature difference of 1.3K.

[0034] Figure 10 Energy collection of the ionic thermoelectric capacitor assembled with the ionic thermoelectric film prepared in Example 6 under different loads. DETAILED DESCRIPTION

[0035] To make the present invention more clearly understood, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0036] Example 1

[0037] 1) Weigh 0.5 g of PEO (Annaigy, molecular weight 1,000,000) and mix with 15 mL of acetonitrile. Stir magnetically for 2 hours to obtain a uniform viscous solution.

[0038] 2) adding 0.5 g of 1-ethyl-3-methylimidazolium acetate to the viscous solution and continuing stirring for 2 hours to obtain a uniformly mixed viscous mixture solution;

[0039] 3) The mixture solution was cast into a glass mold, and after the solvent evaporated, an ion gel membrane was obtained, which had a Seebeck coefficient of 8 mV / K and an electrical conductivity of 0.27 mS / cm.

[0040] Example 2

[0041] 1) Weigh 0.5 g of PEO (Annaigy, molecular weight 1,000,000) and mix with 15 mL of acetonitrile. Stir magnetically for 2 hours to obtain a uniform viscous solution.

[0042] 2) adding 0.5 g of 1-ethyl-3-methylimidazolium dicyanamide to the viscous solution and continuing stirring for 2 hours to obtain a uniformly mixed viscous mixture solution;

[0043] 3) The mixture solution was cast into a glass mold, and after the solvent evaporated, an ion gel membrane was obtained, whose Seebeck coefficient was 6 mV / K.

[0044] Example 3

[0045] 1) Weigh 0.5 g of PEO (Annaigy, molecular weight 1,000,000) and mix with 15 mL of acetonitrile. Stir magnetically for 2 hours to obtain a uniform viscous solution.

[0046] 2) adding 0.75 g of 1-ethyl-3-methylimidazolium acetate to the viscous solution and continuing stirring for 2 hours to obtain a uniformly mixed viscous mixture solution;

[0047] 3) The mixture solution was cast into a glass mold, and after the solvent evaporated, an ion gel membrane was obtained, which had a Seebeck coefficient of 12 mV / K and an electrical conductivity of 0.6 mS / cm.

[0048] The quasi-solid-state ionic thermoelectric gel prepared in this example was cut into 1.5 cm×0.5 cm strips for tensile performance testing, and the elongation at break was 750%.

[0049] Example 4

[0050] 1) Weigh 0.5 g of PEO (Annaigy, molecular weight 1,000,000) and mix with 15 mL of acetonitrile. Stir magnetically for 2 hours to obtain a uniform viscous solution.

[0051] 2) adding 2 g of 1-ethyl-3-methylimidazolium acetate to the viscous solution and continuing stirring for 2 hours to obtain a uniformly mixed viscous mixture solution;

[0052] 3) The mixture solution was cast into a glass mold, and after the solvent evaporated, an ion gel membrane was obtained, which had a Seebeck coefficient of 14 mV / K and an electrical conductivity of 2.64 mS / cm.

[0053] The quasi-solid-state ionic thermoelectric gel prepared in this example was cut into 1.5 cm×0.5 cm strips for tensile performance testing, and the elongation at break was 970%.

[0054] Example 5

[0055] 1) Weigh 0.45 g of PEO (Annaigy, molecular weight 1,000,000) and 0.05 g of P123 and mix with 15 mL of acetonitrile and stir magnetically for 2 hours to obtain a uniform viscous solution;

[0056] 2) adding 0.75 g of 1-ethyl-3-methylimidazolium acetate to the viscous solution and continuing stirring for 2 hours to obtain a uniformly mixed viscous mixture solution;

[0057] 3) The mixture solution was cast into a glass mold, and after the solvent evaporated, an ion gel membrane was obtained, which had a Seebeck coefficient of 13.5 mV / K and an electrical conductivity of 0.98 mS / cm.

[0058] Example 6

[0059] 1) Weigh 0.4 g of PEO (Annaigy, molecular weight 1,000,000) and 0.1 g of P123 and mix with 15 mL of acetonitrile and stir magnetically for 2 hours to obtain a uniform viscous solution;

[0060] 2) adding 0.75 g of 1-ethyl-3-methylimidazolium acetate to the viscous solution and continuing stirring for 2 hours to obtain a uniformly mixed viscous mixture solution;

[0061] 3) The mixture solution was cast into a glass mold, and after the solvent evaporated, an ion gel membrane was obtained, which had a Seebeck coefficient of 17.8 mV / K and an electrical conductivity of 1.3 mS / cm.

[0062] The quasi-solid-state ionic thermoelectric gel prepared in this example was cut into 1.5 cm x 0.5 cm strips for tensile testing, and its elongation at break was 789%. The Seebeck coefficient was measured at different stretch levels, and after 100% stretching, the Seebeck coefficient loss was only 20%.

[0063] The thermoelectric film produced in this example exhibits a sensitive response to temperature, with a thermoelectric voltage of 12.7 mV at a temperature difference of 0.7 K and 280 mV at a temperature difference of 16 K. After 600 hours of storage, the Seebeck coefficient decayed by less than 20%.

[0064] The thermoelectric gel film prepared in this example was connected to an external resistor via electrodes, which were silver strips prepared by inkjet printing, and an external resistor of 9 kΩ to 1 MΩ, to form an ionic thermal capacitor.

[0065] The ionic thermal capacitor assembled with the thermoelectric gel film prepared in this embodiment can collect energy up to 195nJ at a temperature difference of 1.3K.

Claims

1. A method for preparing a giant thermoelectric potential ionic thermoelectric film, characterized in that: The following steps are involved: Step 1): mixing polyethylene oxide with a solvent, heating and stirring under sealed conditions to obtain a polymer solution; a non-ionic liquid plasticizer is also added to the polymer solution; Step 2): adding an ion-containing liquid to the polymer solution and continuing heating and stirring under sealed conditions; the ion-containing liquid is at least one of 1-ethyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium dicyanamide, 1-hexyl-3-methylimidazolium acetate and 1-decyl-3-methylimidazolium acetate; Step 3): The mixture obtained in step 2) is poured into a mold. After the solvent evaporates naturally, the mixture is placed in an oven and dried to obtain an ion gel film, which is a giant thermoelectric potential ion thermoelectric film.

2. The method for preparing the giant thermoelectric potential ionic thermoelectric film according to claim 1, wherein: The molecular weight of the polyethylene oxide in step 1) is 1,000,000-6,000,000; the non-ionic liquid plasticizer is a block copolymer of polyethylene oxide-polypropylene oxide-polyethylene oxide, silicon oxide or strontium titanate fiber; and the solvent is acetonitrile or ethanol.

3. The method for preparing the giant thermoelectric potential ionic thermoelectric film according to claim 2, wherein: The molecular weight of the block copolymer polyethylene oxide-polypropylene oxide-polyethylene oxide is 5800; the particle size of the silicon oxide is 15 nm; and the length of the strontium titanate fiber is 1-2 μm.

4. The method for preparing the giant thermoelectric potential ionic thermoelectric film according to claim 1, wherein: In the step 1), the mass percentage of the non-ionic liquid plasticizer is not higher than 60% based on the sum of the mass of the polyethylene oxide and the non-ionic liquid plasticizer.

5. The method for preparing the giant thermopotential ionic thermoelectric film according to claim 1, wherein: In the step 2), the ionic liquid accounts for 30-80% of the total mass of the ion gel membrane. 6 . A giant thermopotential ionic thermoelectric film prepared by the method for preparing the giant thermopotential ionic thermoelectric film according to any one of claims 1 to 5 .

7. The giant thermopotential ionic thermoelectric film according to claim 6, characterized in that: The humidity of the operating environment is 50-60%.

8. A giant thermoelectric potential ionic thermoelectric thin film device at a comfortable humidity for human body, characterized in that: The invention comprises the giant thermoelectric film according to claim 6 or 7, wherein the giant thermoelectric film is connected to an external resistor via electrodes to form an ionic thermal capacitor.

9. The giant thermoelectric potential ionic thermoelectric thin film device under comfortable humidity for human body according to claim 8, characterized in that: The electrode is a silver ribbon prepared by inkjet printing; the external resistor is 9kΩ-1MΩ.

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