N-type ion thermoelectric thin film and preparation method and application thereof

Abstract

The invention relates to the technical field of thermoelectric materials, in particular to an N-type ion thermoelectric thin film and a preparation method and application thereof. The preparation method of the N-type ion thermoelectric thin film comprises the following steps: preparing an anionic polyelectrolyte solution; mixing the anionic polyelectrolyte solution with a two-dimensional nano material to obtain a mixed precursor solution; coating the surface of a substrate with the mixed precursor liquid to obtain a film; and heating and drying the thin film, and controlling the moisture and humidity to form the N-type ion thermoelectric thin film. According to the method, the N-type ion thermoelectric film with high Seebeck coefficient, high conductivity, high thermoelectric figure of merit and high power factor can be prepared; the preparation method is simple and has the advantages of good environmental friendliness and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of thermoelectric materials, and particularly to an N-type ionic thermoelectric thin film, a preparation method thereof, and an application thereof. Background Art

[0002] With the increasingly severe global energy crisis and environmental pollution problems, the development of efficient and clean energy conversion technologies has become an urgent task. Thermoelectric materials are materials that can directly convert thermal energy into electrical energy and have broad application prospects in fields such as waste heat recovery and solid-state refrigeration. The thermoelectric performance of thermoelectric materials can be measured by the thermoelectric figure of merit ZT (ZT = σS 2 T / κ, where σ is the electrical conductivity, S is the Seebeck coefficient, T is the temperature, and κ is the thermal conductivity). The larger the thermoelectric figure of merit (ZT), the better the thermoelectric performance of the thermoelectric material. According to the carrier type of thermoelectric materials, thermoelectric materials are divided into two types: N-type and P-type. Among them, the N-type ionic thermoelectric material driven by the Soret effect shows great application potential in low-grade heat energy collection, temperature monitoring, and sensing due to its huge thermoelectric potential.

[0003] Currently, traditional methods mainly prepare N-type ionic thermoelectric materials by enhancing the interaction between cations and polymers to limit the thermal diffusion of cations under a temperature gradient, and then making anions the main ions for thermal diffusion. However, this method has some problems: (1) This method depends on the interaction between specific polymers and cations, restricting the material selection range; (2) The N-type ionic thermoelectric materials prepared by this method often have the problem of a low Seebeck coefficient, resulting in an unsatisfactory overall thermoelectric performance of the materials. Summary of the Invention

[0004] The present invention provides a preparation method of an N-type ionic thermoelectric thin film, which can prepare an N-type ionic thermoelectric thin film with a high Seebeck coefficient, high electrical conductivity, high thermoelectric figure of merit, and high power factor; this preparation method is simple and has advantages such as good environmental friendliness.

[0005] The present invention also provides an N-type ionic thermoelectric thin film, which is prepared by the above preparation method. Therefore, this N-type ionic thermoelectric thin film has the characteristics of a high Seebeck coefficient, high electrical conductivity, high thermoelectric figure of merit, and high power factor.

[0006] The present invention also provides a device, including the above N-type ionic thermoelectric thin film. Therefore, this device also has the characteristics of a high Seebeck coefficient, high electrical conductivity, high thermoelectric figure of merit, and high power factor.

[0007] The present invention provides a preparation method of an N-type ionic thermoelectric thin film in a first aspect, including the following steps:

[0008] Preparation of anionic polyelectrolyte solution;

[0009] Mix the anionic polyelectrolyte solution with two-dimensional nanomaterials to obtain a mixed precursor solution;

[0010] Coat the mixed precursor solution on the surface of the substrate to obtain a thin film;

[0011] Perform heat drying treatment on the thin film and control the moisture humidity to form the N-type ionic thermoelectric thin film.

[0012] The method for preparing the N-type ionic thermoelectric thin film as described above, wherein the anionic polyelectrolyte in the anionic polyelectrolyte solution is at least one of polystyrene sulfonic acid, poly(4-styrenesulfonate), poly(2-acrylamido-2-methylpropanesulfonic acid), poly(vinylsulfonic acid), polyacrylic acid, polymethacrylic acid, polysulfonated polyether ether ketone, and polysulfonated polybenzimidazole.

[0013] The method for preparing the N-type ionic thermoelectric thin film as described above, wherein the two-dimensional nanomaterials are at least one of MXene, graphene, graphene oxide, and reduced graphene oxide, and the MXene is Ti3C2T x 、Ti2CT x 、Nb2CT x 、V2CT x 、Mo2CT x or Ta4C3T x 。

[0014] The method for preparing the N-type ionic thermoelectric thin film as described above, in the N-type ionic thermoelectric thin film, the solid content of the anionic polyelectrolyte is 80% wt to 95% wt, and the solid content of the two-dimensional nanomaterials is 5% wt to 20% wt.

[0015] The method for preparing the N-type ionic thermoelectric thin film as described above, the temperature of the heat drying treatment is 30°C to 100°C, and the time is 20 min to 100 min.

[0016] The method for preparing the N-type ionic thermoelectric thin film as described above, the controlled moisture humidity is 20% RH to 80% RH.

[0017] The method for preparing the N-type ionic thermoelectric thin film as described above, the solid content of the anionic polyelectrolyte in the anionic polyelectrolyte solution is 35% wt to 45% wt.

[0018] The present invention provides, in a second aspect, an N-type ionic thermoelectric thin film prepared by the method for preparing the N-type ionic thermoelectric thin film as described above.

[0019] The N-type ionic thermoelectric thin film as described above, the Seebeck coefficient of the N-type ionic thermoelectric thin film is -1 mV / K to -50 mV / K, the ionic conductivity > 10 S / m, the thermoelectric figure of merit > 0.04, and the power factor > 200 mW / m·K 2 .

[0020] The present invention provides a device in a third aspect, including the N-type ionic thermoelectric thin film described above.

[0021] Compared with the prior art, the solution of the present invention has at least the following effects:

[0022] The present invention provides a preparation method of an N-type ionic thermoelectric thin film. First, an anionic polyelectrolyte solution is mixed with a two-dimensional nanomaterial to obtain a mixed precursor solution. Then, the mixed precursor solution is coated on the surface of a substrate to obtain a thin film. Finally, the thin film is heated and dried to form an N-type ionic thermoelectric thin film. The N-type ionic thermoelectric thin film has the advantages of high Seebeck coefficient, high conductivity, high thermoelectric figure of merit, and high power factor. The present invention combines a two-dimensional nanomaterial with a positive surface charge (such as MXene) with a negatively charged anionic polyelectrolyte to adjust the ratio of intermediate water to bound water inside the polymer network, so that a moisture content gradient is generated inside the N-type ionic thermoelectric thin film. Then, the moisture content gradient is used to change the ion transport direction of cations under the condition of a temperature gradient. The N-type ionic thermoelectric thin film prepared based on this strategy has excellent Seebeck coefficient, power factor, and thermoelectric figure of merit. The preparation method is simple and has the advantages of good environmental protection.

[0023] The N-type ionic thermoelectric thin film provided by the present invention has the advantages of high Seebeck coefficient, high conductivity, high thermoelectric figure of merit, and high power factor, and has broad application prospects in the fields of thermoelectricity, optoelectronic thermoelectricity, flexible electronics, etc. Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0025] Figure 1 It is a physical diagram of the mixed precursor solution in Embodiment 1 of the present invention;

[0026] Figure 2 It is a test result diagram of the rheological behavior of the mixed precursor solution in Embodiment 1 of the present invention, wherein Figure 2 (a) is a test result diagram of the viscosity changing with the shear rate, Figure 2Figure (b) shows the test result graph of the viscosity change with time at shear rates of 0.1 1 / s and 1001 / s, Figure 2 Figure (c) shows the test result graph of the loss modulus and storage modulus changing with the angular frequency, Figure 2 Figure (d) shows the test result graph of the loss modulus and storage modulus changing with the vibration strain;

[0027] Figure 3 are the optical photos of the mixed precursor solution printed on different substrate surfaces. Among them, Figure 3 Figure (a) shows the optical photo of the mixed precursor solution printed on the ceramic substrate surface in Example 3 of the present invention, Figure 3 Figure (b) shows the optical photo of the mixed precursor solution printed on the glass substrate surface in Example 1 of the present invention, Figure 3 Figure (c) shows the optical photo of the mixed precursor solution printed on the polyimide substrate surface in Example 4 of the present invention, Figure 3 Figure (d) shows the optical photo of the mixed precursor solution printed on the polyurethane substrate surface in Example 5 of the present invention;

[0028] Figure 4 is the SEM image of the film cross-section in Example 1 of the present invention;

[0029] Figure 5 is the Seebeck coefficient curve graph of the N-type ionic thermoelectric film in Example 1 of the present invention;

[0030] Figure 6 is the Seebeck coefficient curve graph of the N-type ionic thermoelectric film in Example 2 of the present invention;

[0031] Figure 7 is the Seebeck coefficient curve graph of the N-type ionic thermoelectric film in Comparative Example 1 of the present invention;

[0032] Figure 8 is the Seebeck coefficient curve graph of the thermoelectric film in Comparative Example 2 of the present invention;

[0033] Figure 9 is the Seebeck coefficient curve graph of the thermoelectric film in Comparative Example 3 of the present invention;

[0034] Figure 10 are the conductivities of the N-type ionic thermoelectric films in Examples 1 - 2 of the present invention, the N-type ionic thermoelectric film in Comparative Example 1, and the thermoelectric film in Comparative Example 2;

[0035] Figure 11 are the thermal conductivities of the N-type ionic thermoelectric films in Examples 1 - 2 of the present invention, the N-type ionic thermoelectric film in Comparative Example 1, and the thermoelectric film in Comparative Example 2;

[0036] Figure 12 is the alternating current impedance spectrum curve of the N-type ionic thermoelectric film in Example 1 of the present invention;

[0037] Figure 13 This is the AC impedance spectrum curve of the N-type ionic thermoelectric thin film in Example 2 of the present invention;

[0038] Figure 14 This is the AC impedance spectrum curve of the N-type ionic thermoelectric thin film in Comparative Example 1 of the present invention;

[0039] Figure 15 This is the AC impedance spectrum curve of the thermoelectric thin film in Comparative Example 2 of the present invention;

[0040] Figure 16 This is the test result graph of the cycling performance of the N-type ionic thermoelectric thin film in Example 1 of the present invention;

[0041] Figure 17 This is the optothermoelectric curve of the N-type ionic thermoelectric thin film in Example 1 of the present invention;

[0042] Figure 18 This is the spot graph of the infrared excitation light source with a wavelength of 808 nm in the present invention;

[0043] Figure 19 This is the optothermoelectric curve of the unit integrated device in the application example of the present invention. Detailed implementation manners

[0044] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0045] In the embodiments of the present invention, where specific technologies or conditions are not specified, they shall be carried out according to the technologies or conditions described in the literature in the field or according to the product specifications. For reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through commercial purchase.

[0046] In the present invention, the term "at least one" means one or more, and "a plurality" means two or more.

[0047] In the first aspect, the present invention provides a preparation method for an N-type ionic thermoelectric thin film, comprising the following steps:

[0048] Prepare an anionic polyelectrolyte solution;

[0049] Mix the anionic polyelectrolyte solution with a two-dimensional nanomaterial to obtain a mixed precursor solution;

[0050] Coat the mixed precursor solution on the surface of a substrate to obtain a thin film;

[0051] The thin film is heated and dried, and the moisture humidity is controlled to form an N-type ionic thermoelectric thin film.

[0052] Specifically, the present invention first prepares an anionic polyelectrolyte solution, and then mixes the anionic polyelectrolyte solution with a two-dimensional nanomaterial to obtain a mixed precursor solution. The purpose of mixing is to uniformly disperse the anionic polyelectrolyte and the two-dimensional nanomaterial to form a stable mixed precursor solution, providing a basis for the subsequent preparation of the thin film. Then, the mixed precursor solution is coated on the surface of the substrate to form a thin film. The purpose of coating is to form a thin film on the surface of the substrate. Finally, the thin film is heated and dried, and the moisture humidity is controlled to obtain an N-type ionic thermoelectric thin film with a high Seebeck coefficient, high conductivity, high thermoelectric figure of merit, and high power factor. The purpose of the heating and drying treatment is to make the thin film lose moisture and maintain a good morphology. The purpose of controlling the moisture humidity is to facilitate the volatilization of moisture and reduce the interference of humidity changes on ion transport. The inventor analyzed this: By using the two-dimensional nanomaterial to adjust the increase in the proportion of intermediate water inside the anionic polyelectrolyte, the thin film is easily dehydrated under the heating and drying treatment, creating a moisture content gradient inside the thin film. Using the moisture content gradient to change the ion transport direction of cations under the temperature gradient condition, an N-type ionic thermoelectric thin film is prepared. At the same time, the increase in the proportion of intermediate water comes from the transformation of bound water in the anionic polyelectrolyte network, and the release of bound water promotes the dissociation of the functional groups of the anionic polyelectrolyte, increasing the number of freely mobile ions in the thin film and further improving the thermoelectric performance of the N-type ionic thermoelectric thin film (the Seebeck coefficient, conductivity, thermoelectric figure of merit, and power factor are improved).

[0053] The specific preparation process of the anionic polyelectrolyte solution of the present invention is not particularly limited, and it can be prepared according to the preparation methods well-known in the art. For example, the above anionic polyelectrolyte solution can be prepared through the following process:

[0054] The anionic polyelectrolyte aqueous solution is concentrated at a temperature of 70 °C and a rotation speed of 200 rpm to obtain the anionic polyelectrolyte solution.

[0055] The specific method of the above coating of the present invention is not particularly limited, and methods well-known to those skilled in the art can be used. In some embodiments, methods such as screen printing, doctor blading, spin coating, and vacuum filtration can be used for coating. Further, the mixed precursor solution can be printed on the surface of the substrate at a screen printing pressure of 0.2 Mpa and a doctor blade tilt angle of 45° to obtain a thin film.

[0056] The present invention does not particularly limit the specific material of the above-mentioned substrate, and it can be selected according to actual needs. In some embodiments, the above-mentioned substrate can be any one of a glass substrate, a rubber substrate, a ceramic substrate, a polyimide substrate, and a polyethylene terephthalate substrate.

[0057] The present invention does not particularly limit the specific operation of the above-mentioned heat drying treatment, and it can be selected according to actual needs. In some embodiments, the film can be placed on a hot stage for heat drying treatment.

[0058] The present invention does not particularly limit the specific operation of controlling the moisture humidity, and it can be selected according to actual needs. In some embodiments, the film can be placed in a humidity chamber to control the moisture humidity. For example, the film can be placed in a humidity chamber with a humidity of 20%RH - 80%RH.

[0059] In a specific embodiment, the anionic polyelectrolyte in the above-mentioned anionic polyelectrolyte solution is at least one of polystyrene sulfonic acid, poly(4-styrenesulfonate), poly(2-acrylamide-2-methylpropanesulfonic acid), poly(vinylsulfonic acid), polyacrylic acid, polymethacrylic acid, polysulfonated polyether ether ketone, and polysulfonated polybenzimidazole. Further, polystyrene sulfonic acid can be preferably selected.

[0060] When the anionic polyelectrolyte in the anionic polyelectrolyte solution is the above-mentioned substance, a large number of ions dissociated from the sulfonic acid functional groups exist in the anionic polyelectrolyte solution system rich in sulfonic acid functional groups, providing the free moving ions required for the N-type ionic thermoelectric film.

[0061] In a specific embodiment, the two-dimensional nanomaterial is at least one of MXene, graphene, graphene oxide, and reduced graphene oxide. MXene is Ti3C2T x 、Ti2CT x 、Nb2CT x 、V2CT x 、Mo2CT x or Ta4C3T x Ti3C2T x . Further, the two-dimensional nanomaterial can be preferably Ti3C2T x .

[0062] When the two-dimensional nanomaterial is the above-mentioned substance, various functional groups rich on the surface of the two-dimensional nanomaterial can form hydrogen bonds or electrostatic interactions with the functional groups in the anionic polyelectrolyte to promote the dissociation of free moving ions and enhance the thermoelectric performance; at the same time, the two-dimensional nanomaterial provides more channels for the anionic polyelectrolyte, which is beneficial to improving the conductivity of the anionic polyelectrolyte.

[0063] In a specific embodiment, in the above N-type ionic thermoelectric thin film, the solid content of the anionic polyelectrolyte is 80% wt to 95% wt, and the solid content of the two-dimensional nanomaterial is 5% wt to 20% wt.

[0064] When the solid contents of the anionic polyelectrolyte and the two-dimensional nanomaterial in the N-type ionic thermoelectric thin film are within the above ranges respectively, the anionic polyelectrolyte and the two-dimensional nanomaterial can act synergistically, so as to prepare an N-type ionic thermoelectric thin film with a high Seebeck coefficient, high electrical conductivity, high thermoelectric figure of merit and high power factor.

[0065] Further, by mass percentage, in the above N-type ionic thermoelectric thin film, the solid content of the anionic polyelectrolyte is 95% wt, and the solid content of the two-dimensional nanomaterial is 5% wt.

[0066] When the solid content of the anionic polyelectrolyte in the N-type ionic thermoelectric thin film is 95% wt and the solid content of the two-dimensional nanomaterial is 5% wt, the anionic polyelectrolyte and the two-dimensional nanomaterial can act better synergistically, so as to prepare an N-type ionic thermoelectric thin film with a higher Seebeck coefficient, higher electrical conductivity, higher thermoelectric figure of merit and higher power factor.

[0067] In a specific embodiment, the temperature of the above heat drying treatment is 30°C to 100°C, and the time is 20 min to 100 min.

[0068] When the parameters of the temperature and time of the heat drying treatment are within the above ranges, the morphology of the N-type ionic thermoelectric thin film after the heat drying treatment is good and the thermoelectric performance is stable. The inventor found during the experiment that: (1) When the temperature of the heat drying treatment is too high (exceeding 100°C) or the time of the heat drying treatment is too long (exceeding 100 min), the thin film will crack; when the temperature of the heat drying treatment is too low (lower than 30°C) or the time of the heat drying treatment is shorter (shorter than 20 min), there will be some residual water vapor inside the thin film, interfering with the performance of the thermoelectric property.

[0069] In a specific embodiment, the above controlled moisture humidity is 20% RH to 80% RH, and preferably 30% RH to 50% RH.

[0070] When the humidity of the N-type ionic thermoelectric thin film is controlled within the above range, it is beneficial to the volatilization of water, reduces the interference of humidity change on ion transport, and promotes the formation of an N-type ionic thermoelectric thin film with a high Seebeck coefficient, high electrical conductivity, high thermoelectric figure of merit and high power factor under the heat drying treatment.

[0071] In a specific embodiment, the solid content of the anionic polyelectrolyte in the above anionic polyelectrolyte solution is 35% wt to 45% wt.

[0072] When the parameter of the solid content of the anionic polyelectrolyte in the anionic polyelectrolyte solution is within the above range, after mixing with the two-dimensional nanomaterial, a mixed precursor solution with excellent viscosity and rheological properties is obtained, which is beneficial to the subsequent coating operation.

[0073] In a second aspect, the present invention provides an N-type ionic thermoelectric thin film, which is prepared by the preparation method of the N-type ionic thermoelectric thin film described above. Therefore, the N-type ionic thermoelectric thin film has the advantages of high Seebeck coefficient, high electrical conductivity, high thermoelectric figure of merit, and high power factor.

[0074] In a specific embodiment, the Seebeck coefficient of the above N-type ionic thermoelectric thin film is -1 mV / K to -50 mV / K, the ionic conductivity > 10 S / m, the thermoelectric figure of merit > 0.04, and the power factor > 200 mW / m·K 2 。

[0075] The thermoelectric figure of merit (ZT value) is an important parameter for measuring the thermoelectric performance of thermoelectric materials, and its calculation formula is:

[0076] ZT = σS 2 T / κ, where σ is the electrical conductivity, S is the Seebeck coefficient, T is the temperature, and κ is the thermal conductivity.

[0077] The power factor (PF) is an important parameter for measuring the output power ability of thermoelectric materials, and its calculation formula is:

[0078] PF = σS 2 , where σ is the electrical conductivity and S is the Seebeck coefficient.

[0079] When the thermoelectric figure of merit of the N-type ionic thermoelectric thin film > 0.04, it indicates that the N-type ionic thermoelectric thin film has excellent thermoelectric conversion efficiency and can efficiently convert thermal energy into electrical energy.

[0080] In a specific embodiment, the power factor of the above N-type ionic thermoelectric thin film > 200 mW / m·K 2 。

[0081] When the power factor of the N-type ionic thermoelectric thin film > 200 mW / m·K 2 it indicates that the N-type ionic thermoelectric thin film can output a relatively high electrical power and is suitable for thermoelectric power generation devices that require high power output.

[0082] The embodiments and comparative examples of the present invention are used to illustrate the embodiments of the present invention in detail.

[0083] Example 1

[0084] The preparation method of the N-type ionic thermoelectric thin film provided in this example includes the following steps:

[0085] Place 10 g of an aqueous solution of polystyrene sulfonic acid with a solid content of 30% wt in a glass bottle, and then perform concentration treatment at a temperature of 70 °C and a rotation speed of 200 rpm to obtain a concentrated polystyrene sulfonic acid solution with a solid content of 40% wt;

[0086] Mix 668.75 mg of the concentrated polystyrene sulfonic acid solution with a solid content of 40% wt with 15.79 mg of Ti3C2T x Mix evenly to obtain a mixed precursor liquid;

[0087] Print the mixed precursor liquid on the surface of a glass substrate at a screen printing pressure of 0.2 MPa and a 45° blade tilt angle to obtain a thin film;

[0088] Place the thin film on a 50 °C heating table in a constant humidity box with a humidity of 50% and perform heating and drying treatment for 60 min to form an N-type ionic thermoelectric thin film (in the N-type ionic thermoelectric thin film, the solid content of polystyrene sulfonic acid is 95% wt, and the solid content of Ti3C2T x is 5% wt).

[0089] Example 2

[0090] The preparation method of the N-type ionic thermoelectric thin film provided in this example includes the following steps:

[0091] Place 10 g of an aqueous solution of polystyrene sulfonic acid with a solid content of 30% wt in a glass bottle, and then perform concentration treatment at a temperature of 70 °C and a rotation speed of 200 rpm to obtain a concentrated polystyrene sulfonic acid solution with a solid content of 40% wt;

[0092] Mix 668.75 mg of the concentrated polystyrene sulfonic acid solution with a solid content of 40% wt with 22.58 mg of Ti3C2T x Mix evenly to obtain a mixed precursor liquid;

[0093] Print the mixed precursor liquid on the surface of a glass substrate at a screen printing pressure of 0.2 Mpa and a 45° blade tilt angle to obtain a thin film;

[0094] Place the thin film on a 50 °C heating table in a constant humidity box with a humidity of 50% and perform heating and drying treatment for 60 min to form an N-type ionic thermoelectric thin film (in the N-type ionic thermoelectric thin film, the solid content of polystyrene sulfonic acid is 93% wt, and the solid content of Ti3C2T x is 7% wt).

[0095] Example 3

[0096] The preparation method of the N-type ionic thermoelectric thin film provided in this example is basically the same as that in Example 1, except that:

[0097] Replace the glass substrate with a ceramic substrate.

[0098] Example 4

[0099] The method for preparing the N-type ionic thermoelectric thin film provided in this example is basically the same as that in Example 1, except that:

[0100] Replace the glass substrate with a polyimide substrate.

[0101] Example 5

[0102] The method for preparing the N-type ionic thermoelectric thin film provided in this example is basically the same as that in Example 1, except that:

[0103] Replace the glass substrate with a polyurethane substrate.

[0104] Comparative Example 1

[0105] The method for preparing the N-type ionic thermoelectric thin film provided in this comparative example includes the following steps:

[0106] Place 10 g of an aqueous solution of polystyrene sulfonic acid with a solid content of 30% wt in a glass bottle, and then perform concentration treatment at a temperature of 70 °C and a rotation speed of 200 rpm to obtain a concentrated solution of polystyrene sulfonic acid with a solid content of 40% wt;

[0107] Mix 668.75 mg of the concentrated polystyrene sulfonic acid solution with a solid content of 40% wt and 9.28 mg of Ti3C2T x uniformly to obtain a mixed precursor solution;

[0108] Print the mixed precursor solution on the surface of the glass substrate with a screen printing pressure of 0.2 Mpa and a 45° blade tilt angle to obtain a thin film;

[0109] Place the thin film on a 50 °C heating table in a constant humidity box with a humidity of 50% and perform heat drying treatment for 60 min to form an N-type ionic thermoelectric thin film (in the N-type ionic thermoelectric thin film, the solid content of polystyrene sulfonic acid is 97% wt, and the solid content of Ti3C2T x is 3% wt).

[0110] Comparative Example 2 (without adding Ti3C2T x )

[0111] The method for preparing the thermoelectric thin film provided in this comparative example includes the following steps:

[0112] Place 10 g of an aqueous solution of polystyrene sulfonic acid with a solid content of 30% wt in a glass bottle, and then perform concentration treatment at a temperature of 70 °C and a rotation speed of 200 rpm to obtain a concentrated solution of polystyrene sulfonic acid with a solid content of 40% wt;

[0113] Print a polystyrene sulfonic acid concentrate with a solid content of 40% wt and a mass of 668.75 mg on the surface of a glass substrate at a screen printing pressure of 0.2 Mpa and a blade tilt angle of 45° to obtain a film.

[0114] Place the film on a 50 °C heating table in a constant humidity box with a humidity of 50% and perform heat drying treatment for 60 min to form a thermoelectric film.

[0115] Comparative Example 3 (without adding polystyrene sulfonic acid)

[0116] The preparation method of the thermoelectric film provided in this comparative example includes the following steps:

[0117] Mix 15.79 mg of Ti3C2T x with water to obtain a Ti3C2T x solution with a solid content of 40% wt;

[0118] Print the Ti3C2T x solution on the surface of a glass substrate at a screen printing pressure of 0.2 Mpa and a blade tilt angle of 45° to obtain a film;

[0119] Place the film on a 50 °C heating table in a constant humidity box with a humidity of 50% and perform heat drying treatment for 60 min to form an N-type ionic thermoelectric film.

[0120] Application Example

[0121] The present application example provides a preparation method for a unit integrated device, including the following steps:

[0122] Use the N-type ionic thermoelectric film in Example 1 of the present invention as a unit, and print 30 pairs of units on the surface of a polyimide substrate by screen printing and assemble them to obtain a unit integrated device.

[0123] Result Explanation

[0124] 1. Figure 1 This is a physical picture of the mixed precursor solution in Example 1 of the present invention.

[0125] As Figure 1 can be seen, the mixed precursor solution has good stability. The inventor analyzed this and believes the reason is that: the polystyrene sulfonic acid concentrate and Ti3C2T x form a stable composite system through uniform dispersion and interfacial interaction.

[0126] 2. Figure 2 This is a test result graph of the rheological behavior of the mixed precursor solution in Example 1 of the present invention, where Figure 2(a) is a test result graph of the viscosity varying with the shear rate, Figure 2 (b) is a test result graph of the viscosity varying with time at shear rates of 0.1 1 / s and 100 1 / s, Figure 2 (c) is a test result graph of the loss modulus and storage modulus varying with the angular frequency, Figure 2 (d) is a test result graph of the loss modulus and storage modulus varying with the vibration strain.

[0127] From Figure 2 (a), it can be seen that the mixed precursor liquid in Example 1 of the present invention exhibits obvious shear thinning characteristics, and these characteristics enable the mixed precursor liquid to meet operations such as printing. From Figure 2 (b), it can be seen that the rheological characteristics at different shear rates prove that the mixed precursor liquid has excellent thixotropic behavior, indicating that its internal network can be quickly restored and reconstructed after being extended under an external force. From Figure 2 (c)-(d), it can be seen that the mixed precursor liquid in Example 1 of the present invention has the characteristics of high storage modulus and loss modulus, indicating that it can be printed and adhered to the surface of the substrate. In summary, the mixed precursor liquid provided by the present invention has excellent viscosity and rheological properties.

[0128] 3. Figure 3 are optical photos of the mixed precursor liquid printed on different substrate surfaces. Among them, Figure 3 (a) is an optical photo of the mixed precursor liquid printed on the ceramic substrate surface in Example 3 of the present invention, Figure 3 (b) is an optical photo of the mixed precursor liquid printed on the glass substrate surface in Example 1 of the present invention, Figure 3 (c) is an optical photo of the mixed precursor liquid printed on the polyimide substrate surface in Example 4 of the present invention, Figure 3 (d) is an optical photo of the mixed precursor liquid printed on the polyurethane substrate surface in Example 5 of the present invention.

[0129] From Figure 3 (a)-(d), it can be seen that the mixed precursor liquid provided by the present invention can be printed on the surface of hard substrates or flexible substrates by screen printing, indicating that it has a very wide range of application scenarios.

[0130] 4. The film in Example 1 of the present invention is quenched by liquid nitrogen fracture, and then the film cross-section is tested by a scanning electron microscope (SEM). The results are as Figure 4 shown.

[0131] From Figure 4 , it can be seen that the inside of the film is evenly dispersed, indicating that Ti3C2T x has good affinity with polystyrenesulfonic acid.

[0132] 5. Thermoelectric performance test

[0133] ① Seebeck coefficient

[0134] Figure 5 is the Seebeck coefficient curve of the N-type ionic thermoelectric thin film in Example 1 of the present invention; Figure 6 is the Seebeck coefficient curve of the N-type ionic thermoelectric thin film in Example 2 of the present invention; Figure 7 is the Seebeck coefficient curve of the N-type ionic thermoelectric thin film in Comparative Example 1 of the present invention; Figure 8 is the Seebeck coefficient curve of the thermoelectric thin film in Comparative Example 2 of the present invention; Figure 9 is the Seebeck coefficient curve of the thermoelectric thin film in Comparative Example 3 of the present invention.

[0135] It can be seen from Figures 5 - 9 that the N-type ionic thermoelectric thin film in Examples 1-2 of the present invention has the advantage of high Seebeck coefficient. As the content of Ti3C2T x increases, the Seebeck coefficient of the N-type ionic thermoelectric thin film first gradually increases and then decreases, indicating that an appropriate amount of Ti3C2T x helps to improve the dissociation of free moving ions of polystyrene sulfonic acid and increase the proportion of intermediate water, which is beneficial to improving the Seebeck coefficient of the N-type ionic thermoelectric thin film.

[0136] ② Electrical conductivity

[0137] Under the conditions of 40% relative humidity and 25 °C, the electrical conductivities of the N-type ionic thermoelectric thin films in Examples 1-2 of the present invention, the N-type ionic thermoelectric thin film in Comparative Example 1, and the thermoelectric thin film in Comparative Example 2 were respectively tested by electrochemical impedance spectroscopy (EIS), and the test results are as Figure 10 shown.

[0138] It can be seen from Figure 10 that the N-type ionic thermoelectric thin film in Example 1 of the present invention has the advantage of high electrical conductivity. Compared with the N-type ionic thermoelectric thin film in Comparative Example 1 and the thermoelectric thin film in Comparative Example 2, the electrical conductivity of the N-type ionic thermoelectric thin film provided in Example 1 of the present invention is significantly improved. The inventor analyzed this and believes that the reason is that due to the high electrical conductivity of Ti3C2T x itself, the addition of Ti3C2T x greatly improves the ionic conductivity of the N-type ionic thermoelectric thin film.

[0139] ③ Thermal conductivity

[0140] Under the conditions of 40% relative humidity and 25 °C, the thermal conductivities of the N-type ionic thermoelectric thin films in Examples 1-2 of the present invention, the N-type ionic thermoelectric thin film in Comparative Example 1, and the thermoelectric thin film in Comparative Example 2 were respectively tested by using a HotDisk TPS2500S thermal constant analyzer, as Figure 11 shown.

[0141] It can be seen from Figure 11 that when an appropriate amount of Ti3C2T x is added to the polystyrene sulfonic acid concentrate, the thermal conductivity of the N-type ionic thermoelectric thin film will decrease. This may be because Ti3C2T x is isolated and distributed inside the polystyrene sulfonic acid network, thus not forming a continuous heat conduction network inside the polystyrene sulfonic acid network; while when the content of Ti3C2T x is too much, the internal heat conduction network is gradually improved and the thermal conductivity increases.

[0142] ④Thermoelectric figure of merit (ZT)

[0143] The thermoelectric figure of merit (ZT) is an important parameter to measure the thermoelectric performance of thermoelectric materials, and its calculation formula is:

[0144] ZT = σS 2 T / κ, where σ is the electrical conductivity, S is the Seebeck coefficient, T is the temperature, and κ is the thermal conductivity.

[0145] According to the Seebeck coefficients, electrical conductivities, and thermal conductivities of the N-type ionic thermoelectric thin films in Examples 1 - 2, the N-type ionic thermoelectric thin film in Comparative Example 1, and the thermoelectric thin film in Comparative Example 2 obtained above, calculate the thermoelectric figures of merit of the N-type ionic thermoelectric thin films in Examples 1 - 2, the N-type ionic thermoelectric thin film in Comparative Example 1, and the thermoelectric thin film in Comparative Example 2 of the present invention at a temperature of 298K. The calculation results are shown in Table 1.

[0146] Table 1 Calculation results

[0147] Item Thermoelectric figure of merit Example 1 2.60 Example 2 1.2 Comparative Example 1 0.005 Comparative Example 2 0.04

[0148] It can be seen from Table 1 that compared with the N-type ionic thermoelectric thin film in Comparative Example 1 and the thermoelectric thin film in Comparative Example 2, the N-type ionic thermoelectric thin film provided by the examples of the present invention has excellent thermoelectric performance (the thermoelectric figure of merit can reach 2.60).

[0149] ⑤Power factor (PF)

[0150] The power factor (PF) is an important parameter to measure the output power ability of thermoelectric materials, and its calculation formula is:

[0151] PF = σS 2 , where σ is the electrical conductivity and S is the Seebeck coefficient.

[0152] According to the Seebeck coefficients and conductivities of the N-type ionic thermoelectric thin films in Examples 1 - 2, the N-type ionic thermoelectric thin film in Comparative Example 1, and the thermoelectric thin film in Comparative Example 2 obtained above, the power factors (PF) of the N-type ionic thermoelectric thin films in Examples 1 - 2 of the present invention, the N-type ionic thermoelectric thin film in Comparative Example 1, and the thermoelectric thin film in Comparative Example 2 were calculated respectively, and the calculation results are shown in Table 2.

[0153] Table 2 Calculation Results

[0154] Item <![CDATA[Power factor (mW / m·K 2 )]]> Example 1 9437 Example 2 2838 Comparative Example 1 18.29 Comparative Example 2 236.15

[0155] As can be seen from Table 2, compared with the N-type ionic thermoelectric thin film in Comparative Example 1 and the thermoelectric thin film in Comparative Example 2, the N-type ionic thermoelectric thin film provided in the examples of the present invention has excellent thermoelectric performance (the power factor can reach 9437 mW / m·K 2 )

[0156] 6. AC impedance spectroscopy test

[0157] The N-type ionic thermoelectric thin films in Examples 1 - 2 of the present invention, the N-type ionic thermoelectric thin film in Comparative Example 1, and the thermoelectric thin film in Comparative Example 2 were respectively subjected to AC impedance spectroscopy test; Figure 12 This is the AC impedance spectroscopy curve of the N-type ionic thermoelectric thin film in Example 1 of the present invention; Figure 13 This is the AC impedance spectroscopy curve of the N-type ionic thermoelectric thin film in Example 2 of the present invention; Figure 14 This is the AC impedance spectroscopy curve of the N-type ionic thermoelectric thin film in Comparative Example 1 of the present invention; Figure 15 This is the AC impedance spectroscopy curve of the thermoelectric thin film in Comparative Example 2 of the present invention.

[0158] From Figures 12 - 15 it can be seen that the N-type ionic thermoelectric thin film provided in the examples of the present invention has excellent ionic conductivity.

[0159] 7. Cycling performance test

[0160] The cycling performance test was carried out on the N-type ionic thermoelectric thin film in Example 1 of the present invention, and the results are as Figure 16 shown.

[0161] From Figure 16 it can be seen that within the test time range of 8000 s, the cycling performance of the N-type ionic thermoelectric thin film in Example 1 of the present invention has no attenuation and the output power is stable, indicating that it has excellent ionic thermoelectric cycling performance.

[0162] 8. Photo-thermoelectric performance test

[0163] The photo-thermoelectric performance test was carried out on the N-type ionic thermoelectric thin film in Example 1 of the present invention by using an infrared excitation light source with a wavelength of 808 nm; Figure 17Photothermal-electricity curve of the N-type ionic thermoelectric thin film in Embodiment 1 of the present invention; Figure 18 Spot diagram of the infrared excitation light source with a wavelength of 808 nm.

[0164] It can be seen from Figures 17 - 18 that the N-type ionic thermoelectric thin film in Embodiment 1 of the present invention can spontaneously generate a temperature gradient under local light illumination, thereby exhibiting excellent photothermal-electricity performance. This may be because the photothermal effect of Ti3C2T x significantly promotes the ion transport rate in the ion channels, making the N-type ionic thermoelectric thin film have a high Seebeck coefficient under photothermal conditions.

[0165] 9. Test of the unit integration device

[0166] Under the photothermal condition of 100 mW / cm 2 a simulated solar photothermal-electricity test was carried out on the unit integration device in the application example of the present invention, and the results are as Figure 19 shown.

[0167] It can be seen from Figure 19 that under the solar illumination intensity of 100 mW / cm 2 the unit integration device in the application example of the present invention achieved a stable voltage output of 1.64 V in an open environment, which fully proves the potential of the N-type ionic thermoelectric thin film provided in the embodiments of the present invention in practical applications.

[0168] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an N-type ionic thermoelectric thin film, characterized in that: The following steps are involved: preparing an anionic polyelectrolyte solution; mixing the anionic polyelectrolyte solution with the two-dimensional nanomaterial to obtain a mixed precursor solution; coating the mixed precursor liquid on the surface of a substrate to obtain a thin film; The film is subjected to a heating and drying process and the moisture content is controlled to form the N-type ion thermoelectric film.

2. The method for preparing an N-type ionic thermoelectric thin film according to claim 1, characterized in that: The anionic polyelectrolyte in the anionic polyelectrolyte solution is at least one of polystyrene sulfonic acid, poly(sodium 4-styrene sulfonate), poly(2-acrylamide-2-methylpropane sulfonic acid), poly(vinyl sulfonic acid), polyacrylic acid, polymethacrylic acid, polysulfonated polyetheretherketone, and polysulfonated polybenzimidazole.

3. The method for preparing an N-type ionic thermoelectric thin film according to claim 1, characterized in that: The two-dimensional nanomaterial is at least one of MXene, graphene, graphene oxide, and reduced graphene oxide, and the MXene is Ti3C2T x 、Ti2CT x 、Nb2CT x 、V2CT x 、Mo2CT x or Ta4C3T x .

4. The method for preparing an N-type ionic thermoelectric thin film according to claim 1, characterized in that: In the N-type ionic thermoelectric film, the solid content of the anionic polyelectrolyte is 80%wt-95%wt, and the solid content of the two-dimensional nanomaterial is 5%wt-20%wt.

5. The method for preparing an N-type ionic thermoelectric thin film according to claim 1, characterized in that: The temperature of the heating and drying treatment is 30° C. to 100° C., and the time is 20 min to 100 min.

6. The method for preparing an N-type ionic thermoelectric thin film according to claim 5, characterized in that: The controlled moisture humidity is 20% RH to 80% RH.

7. The method for preparing an N-type ionic thermoelectric thin film according to claim 1, characterized in that: The solid content of the anionic polyelectrolyte in the anionic polyelectrolyte solution is 35%wt-45%wt.

8. An N-type ionic thermoelectric film, characterized in that: The N-type ionic thermoelectric film is prepared by the preparation method of any one of claims 1 to 7.

9. The N-type ionic thermoelectric thin film according to claim 8, characterized in that: The Seebeck coefficient of the N-type ionic thermoelectric film is -1mV / K to -50mV / K, the ionic conductivity is >10S / m, the thermoelectric figure of merit is >0.04, and the power factor is >200mW / m·K 2 .

10. A device, characterized in that: It comprises the N-type ionic thermoelectric film as claimed in claim 8 or 9.

Images