A silver selenide-based composite room-temperature thermoelectric material and its preparation method

Abstract

The present invention discloses a silver selenide-based composite room-temperature thermoelectric material. The preparation method is as follows: first, polycrystalline Ag2Se and nanoscale amorphous Sb2S3 are synthesized by solvent thermal reaction and room-temperature ultrasound-assisted method, respectively. Subsequently, amorphous nano-Sb2S3 is successfully uniformly modified on the surface of Ag2Se powder by liquid phase composite at room temperature. Then, a bulk Ag2Se / Sb2(S,Se)3 composite thermoelectric material is prepared by combining spark plasma sintering technology with a sintering pressure of 45MPa and a sintering temperature of 300-380°C. In the thermoelectric material, ternary amorphous Sb2(S,Se)3 as a second phase enhances phonon scattering, significantly reduces thermal conductivity, has a high power factor, and exhibits excellent thermoelectric performance. In the temperature range of 300K to 390K, the average ZT value of the Ag2Se / Sb2(S,Se)3 composite material is higher than 1, which is significantly better than that of pure phase Ag2Se material.

Description

Technical Field

[0001] The present invention relates to the technical field of thermoelectric materials, in particular to a silver selenide-based composite room-temperature thermoelectric material and a preparation method thereof. Background Art

[0002] The development of the Internet of Things and mobile electronic devices has led to a large demand for self-powered power supplies, miniaturized cooling components, and fast-response temperature sensors. Room-temperature thermoelectric materials have attracted widespread attention due to their potential as key electronic components. In addition, thermoelectric materials have also shown attractive prospects in the recovery of low-grade waste heat, which has further stimulated research on high-performance room-temperature thermoelectric materials. Thermoelectric performance depends on the thermoelectric figure of merit, which is defined as ZT = S 2 σT / κ, where S is the Seebeck coefficient, σ is the electrical conductivity, κ is the thermal conductivity, T is the absolute temperature of the material, S 2 σ is also called power factor (PF). High-performance thermoelectric materials need to have both high power factor and low thermal conductivity.

[0003] Silver selenide (Ag2Se) is an n-type narrow-bandgap semiconductor with high electron mobility, excellent electrical properties, and ultra-low intrinsic lattice thermal conductivity, showing great promise for room-temperature thermoelectric applications. The thermoelectric figure of merit (ZT) of Ag2Se can be effectively improved through methods such as doping / solid solutionization, altering the stoichiometric ratio, defect manipulation, and the incorporation of second phases. The incorporation of appropriate second phases not only optimizes the material's thermoelectric properties but also effectively enhances its mechanical properties. Currently, a variety of materials have been introduced as second phases into Ag2Se, such as carbon nanotubes, Te, CuAgSe, AgSbSe2, and AgAl. However, these second phases are all stable crystalline materials. Compared to crystals, amorphous materials exhibit metastable properties, leading to uncontrollable issues during the preparation of composite amorphous materials. For example, temperature and pH during the preparation process can cause the amorphous material to undergo a crystallization transition, thus negating the significance of the composite amorphous second phase. Therefore, the incorporation of amorphous second phases into thermoelectric materials has not been widely explored. However, the absence of the typical long-range order of crystals in amorphous materials leads to some unconventional structural features in amorphous nanomaterials, such as abundant surface dangling bonds and highly unsaturated coordination. These structural characteristics can modulate electronic properties, and amorphous nanomaterials show potential for practical applications in thermoelectrics. Therefore, the introduction of amorphous nanophases into thermoelectric materials warrants in-depth understanding and research. Summary of the Invention

[0004] In view of the current technical difficulties in introducing amorphous nano second phase values ​​into thermoelectric materials, the present invention provides a silver selenide-based composite room-temperature thermoelectric material and a preparation method thereof. Specifically, the thermoelectric material is an Ag2Se-based material of composite amorphous nano Sb2(S,Se)3.

[0005] Firstly, polycrystalline Ag2Se and nanoscale amorphous Sb2S3 were synthesized by solvothermal reaction and room temperature ultrasound-assisted method, respectively. Then, amorphous nano-Sb2S3 was successfully introduced uniformly into the Ag2Se matrix by liquid phase composite method at room temperature. Bulk Ag2Se / Sb2(S,Se)3 composite thermoelectric material was prepared by combining spark plasma sintering technology.

[0006] The specific preparation method steps of the Ag2Se / Sb2(S,Se)3 composite thermoelectric material are as follows:

[0007] S1. Prepare pure Ag2Se powder as follows:

[0008] S11. Dissolve AgNO3 in ethylene glycol, add Se powder, and stir until the Se powder is evenly dispersed in the solution to obtain a dispersion; the molar ratio of AgNO3 to Se powder is 2:1.

[0009] S12. Add NaOH solution to the dispersion, stir evenly, heat to 200-250°C, and react for 24 hours.

[0010] S13. After the reaction is completed, the solid product is collected by centrifugation, and the solid product is washed and vacuum-dried to obtain pure Ag2Se powder.

[0011] S2. Preparation of amorphous nano-Sb2S3 powder, specifically as follows:

[0012] S21. Dissolve SbCl3 in HCl solution to obtain solution A; dissolve Na2S·9H2O in NaOH solution to obtain solution B; the molar ratio of SbCl3 and Na2S·9H2O is 2:3.

[0013] S22. During continuous ultrasonic oscillation, solution B was slowly added dropwise to solution A, and ultrasonication was continued for 2 h. The solid product was then collected by centrifugation, and further washed and dried to obtain amorphous nano-Sb2S3 powder.

[0014] S3. Preparation of Ag2Se / Sb2(S,Se)3 composite thermoelectric material, specifically as follows:

[0015] S31. Ultrasonic dispersion of pure Ag2Se powder in acidic water to form an Ag2Se dispersion; ultrasonic dispersion of Sb2S3 powder in another portion of acidic water to form an Sb2S3 dispersion.

[0016] S32. Under continuous ultrasonication, the Ag2Se dispersion is dropped into the Sb2S3 dispersion, followed by mechanical stirring for 2-3 hours. The mixture is then allowed to settle. The precipitated powder is collected and vacuum-dried at 50-70°C for 20-24 hours to obtain an Ag2Se / Sb2S3 composite powder. In this step, amorphous Sb2S3 nanoparticles are uniformly modified on the surface of the Ag2Se powder through electrostatic adsorption.

[0017] S33. The Ag2Se / Sb2S3 composite powder is sintered into a block by spark plasma sintering at a sintering pressure of 45 MPa, a sintering temperature of 300-380°C, and a holding time of 5-7 min to finally obtain an Ag2Se / Sb2(S,Se)3 composite thermoelectric material.

[0018] Preferably, in step S31, the amount of Sb2S3 powder used accounts for 0.1-0.6% of the mass of the pure phase Ag2Se powder.

[0019] Preferably, in step S31, the acidic water used is an aqueous solution adjusted to pH=3.

[0020] Compared with the prior art, the present invention is beneficial in that:

[0021] (1) In the present invention, amorphous Sb2S3 is used as the second phase. Due to its metastable characteristics, S in amorphous Sb2S3 is easily volatilized during spark plasma sintering, resulting in a lack of anions in the second phase. The lack of anions prompts the second phase to react with the anions in the matrix to compensate for the charge, that is, the second phase easily reacts with Se in the Ag2Se matrix; a small amount of Se in the Ag2Se matrix enters the amorphous material to form a ternary amorphous Sb2(S,Se)3 second phase.

[0022] (2) The thermoelectric material of the present invention optimizes the thermoelectric performance by introducing a ternary amorphous Sb2(S,Se)3 second phase; Sb2(S,Se)3 can adjust the composition of the silver selenide matrix, thereby adjusting the carrier concentration and band structure of the material; suppressing the thermal excitation of electrons, and Sb2(S,Se)3 can strongly scatter phonons, significantly reducing the thermal conductivity of the material, so that the material obtains a high thermoelectric figure of merit and a high average thermoelectric figure of merit; in the temperature range of 300K to 390K, the average ZT value of the Ag2Se / Sb2(S,Se)3 composite material is higher than 1, which is significantly better than the pure phase Ag2Se material.

[0023] (3) In the prior art, amorphous materials are difficult to compound using traditional melting, mechanical alloying, and one-step solvent thermal methods because they are prone to crystallization transformation at high temperatures. The present invention adopts a relatively mild room-temperature ultrasound-assisted liquid-phase compounding method, utilizing the opposite surface potentials of the two materials to achieve uniform mixing of amorphous Sb2S3 in Ag2Se powder. Subsequently, spark plasma rapid sintering is performed to achieve a chemical reaction between amorphous Sb2S3 and the matrix material Ag2Se, resulting in an Ag2Se / Sb2(S,Se)3 composite thermoelectric material.

[0024] Other advantages, objectives and features of the present invention will be reflected in part from the following description and will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 SEM images of pure phase Ag2Se powder and powder samples of Ag2Se / Sb2(S,Se)3 composite thermoelectric material, where (a) is pure phase Ag2Se powder and (b) is composite thermoelectric material AS-0.4.

[0026] Figure 2 TEM characterization results of Ag2Se / Sb2(S,Se)3 composite thermoelectric material (AS-0.4), where (a) and (b) are HAADF images and corresponding EDS results, respectively, and (c) and (d) are HRTEM images.

[0027] Figure 3 Performance test data of Ag2Se / Sb2(S,Se)3 composite thermoelectric materials with different Sb2S3 contents, where (a) is the variation of thermal conductivity with temperature in the temperature range of 300-390K; (b) is the Grüneisen parameter diagram; (c) is the variation of ZT value with temperature; (d) is the average ZT value in the temperature range of 300-390K.

[0028] Figure 4 The figure shows the change of ZT value of the composite materials of pure phase Ag2Se (AS-0), Ag2Se composite amorphous Sb2S3 (AS-0.4SS / A) and Ag2Se composite crystalline Sb2S3 (AS-0.4SS / C) with temperature.

[0029] Figure 5 The graph shows the change of thermal conductivity of the composite materials of pure phase Ag2Se (AS-0), Ag2Se composite amorphous Sb2S3 (AS-0.4SS / A) and Ag2Se composite crystalline Sb2S3 (AS-0.4SS / C) with temperature.

[0030] Figure 6The power factor (PF) of the composite materials of pure phase Ag2Se (AS-0), Ag2Se composite amorphous Sb2S3 (AS-0.4SS / A) and Ag2Se composite crystalline Sb2S3 (AS-0.4SS / C) changes with temperature. DETAILED DESCRIPTION

[0031] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0032] Example 1

[0033] A method for preparing an Ag2Se / Sb2(S,Se)3 composite thermoelectric material, comprising the following steps:

[0034] S1. Preparation of pure Ag2Se powder:

[0035] (1) 45 ml of ethylene glycol was added to a 100 ml polytetrafluoroethylene liner. 1.6987 g of AgNO3 powder was added to the liner and stirred on a magnetic stirring table until the AgNO3 was completely dissolved. 0.3948 g of Se powder was then added to the liner and stirred until the Se powder was evenly dispersed in the solution.

[0036] (2) Add 5 ml of 10 mol / L NaOH solution to the inner liner, continue stirring at room temperature for 15 min, and then transfer the polytetrafluoroethylene inner liner to a stainless steel reactor; move the reactor to a high-temperature oven, set the reaction temperature to 230 °C, and set the reaction time to 24 h; after the reaction is completed, turn off the oven power supply, cool the reactor with the oven, and open the reactor when the reactor temperature drops to room temperature and take out the inner liner.

[0037] (3) The reaction solution was centrifuged to collect the solid product, and the solid product was washed three times in a high-speed centrifuge using deionized water and anhydrous ethanol respectively; the powder was then placed in a vacuum drying oven and dried at 60°C for 24 hours to obtain pure phase Ag2Se powder.

[0038] S2. Preparation of amorphous nano-Sb2S3 powder:

[0039] (1) Weigh 0.9124 g of SbCl₃ and dissolve it in 48 ml of 4 mol / L HCl solution to obtain solution A. Weigh 1.441 g of Na₂S·9H₂O and dissolve it in 56 ml of 2 mol / L NaOH solution to obtain solution B.

[0040] (2) During continuous ultrasonic oscillation, solution B was slowly added dropwise to solution A; ultrasonication was continued for 2 h, and then the solid product was collected by centrifugation. The solid product was washed with deionized water and anhydrous ethanol for 3 times, respectively, and centrifuged; the product was placed in a vacuum drying oven, set to 80°C, and dried for 12 h to obtain amorphous nano-Sb2S3 powder.

[0041] S3. Prepare Ag2Se / Sb2(S,Se)3 composite thermoelectric materials, and control the amount of Sb2S3 to 0.1%, 0.2%, 0.4%, and 0.6% of the mass of Ag2Se, respectively, to prepare composite thermoelectric materials with different Sb2S3 contents; the specific method is as follows:

[0042] (1) Weigh 3.6 g of pure Ag2Se powder and disperse it in 90 ml of a pH = 3 aqueous solution, and ultrasonically disperse it for 30 min. Weigh Sb2S3 according to the amount ratio of Sb2S3 and Ag2Se, and disperse it in 100 ml of a pH = 3 aqueous solution, and ultrasonically disperse it for 30 min. The pH = 3 aqueous solution is obtained by adding hydrochloric acid to deionized water to adjust the pH.

[0043] (2) The Ag2Se dispersion was slowly dripped into the Sb2S3 dispersion during continuous ultrasound; then the mixture was placed on a magnetic stirring table and vigorously stirred for 2 h; after the stirring was completed, the powder was allowed to settle, the precipitated powder was collected, and the powder was centrifuged and washed three times with deionized water and anhydrous ethanol respectively; the powder was placed in a vacuum drying oven, the drying temperature was set at 333 K, and dried for 24 h to obtain Ag2Se-x wt.% Sb2S3 (x = 0.1, 0.2, 0.4, 0.6) composite powders.

[0044] (3) The composite powders with different contents obtained in step (2) are sintered into blocks by spark plasma sintering. The sintering temperature is set to 350°C, the sintering pressure is set to 45 MPa, the heating rate is set to 50°C / min, and the holding time is set to 5 min. During the sintering process, Sb2S3 reacts with Se in the matrix to form a Sb2(S,Se)3 ternary amorphous composite phase, thereby obtaining an Ag2Se / Sb2(S,Se)3 composite thermoelectric material.

[0045] Ag2Se-x wt.%Sb2S3 (x=0.1, 0.2, 0.4, 0.6) composite powders were plasma sintered to prepare Ag2Se / Sb2(S,Se)3 composite thermoelectric materials with different contents, which are referred to as AS-0.1, AS-0.2, AS-0.4, and AS-0.6 respectively.

[0046] The pure phase Ag2Se powder prepared in step S1 and the Ag2Se / Sb2(S,Se)3 composite thermoelectric material obtained in step S3 were observed by scanning electron microscopy. Figure 1(a) is an SEM image of pure Ag2Se powder (abbreviated as AS-0), and (b) is an SEM image of AS-0.4. It can be seen that the pure Ag2Se powder is in the form of micron-sized particles. After the recombination treatment in step S3, a distinct second phase is present on the surface of the Ag2Se particles, and the distribution is relatively uniform. This demonstrates that the method of the present invention successfully achieves uniform recombination of Ag2Se with the amorphous second phase.

[0047] Figure 2 TEM characterization results of Ag2Se / Sb2(S,Se)3 composite thermoelectric material (AS-0.4) obtained from Ag2Se-0.4%Sb2S3 composite powder. Figure 2 (a) and (b) are the HAADF images and the corresponding EDS results, respectively. It can be seen from the figures that the particle size of the second phase is between 300 and 400 nm, and the three elements Sb, S, and Se are evenly distributed in the second phase. Figure 2 (c) and (d) are HRTEM images, corresponding to Figure 2 The red and blue regions in (a) show that the Ag2Se matrix is ​​crystalline, while the second phase is amorphous. These results indicate that during the spark plasma sintering process of the Ag2Se and Sb2S3 composite powder, the second phase reacts with the matrix under the influence of temperature and pressure to form a new ternary amorphous second phase, Sb2(S,Se)3.

[0048] Figure 3 Performance test data of Ag2Se / Sb2(S,Se)3 composite thermoelectric materials prepared from Ag2Se–x wt.%Sb2S3 (x=0.1, 0.2, 0.4, 0.6) composite powders with different Sb2S3 contents. Figure 3 (a) shows the change of thermal conductivity of composite materials such as AS-0, AS-0.1, AS-0.2, AS-0.4, and AS-0.6 with temperature in the temperature range of 300-390K. It can be seen that compared with pure Ag2Se powder, the thermal conductivity of Ag2Se / Sb2(S,Se)3 composite thermoelectric materials is significantly reduced. As the Sb2S3 content increases from 0.1% to 0.4%, the thermal conductivity continues to decrease. When it increases to 0.6%, the thermal conductivity increases. This is because the second phase agglomerates and the distribution is no longer uniform. Figure 3 (b) is the Grüneisen parameter of composite materials such as AS-0, AS-0.1, AS-0.2, AS-0.4, and AS-0.6. It can be seen that as the Sb2S3 content increases from 0 to 0.6%, γ first increases and then decreases. The size of the Grüneisen parameter (γ) represents the strength of the anharmonicity in the crystal. The larger γ is, the stronger the anharmonicity of the lattice vibration, the stronger the scattering of phonons, and the lower the lattice thermal conductivity. Figure 3The results of (a) and (b) show that the introduction of uniformly distributed Sb2(S,Se)3 into Ag2Se can effectively reduce the thermal conductivity. Figure 3 (c) shows the ZT values ​​of composite materials such as AS-0, AS-0.1, AS-0.2, AS-0.4, and AS-0.6 as a function of temperature. It can be seen that compared with pure Ag2Se powder, the ZT value of Ag2Se / Sb2(S,Se)3 composite thermoelectric materials is significantly improved. At 390K, the ZT value of the sample with 0.4% Sb2S3 content is as high as 1.17, which shows obvious performance optimization compared with the uncomposite sample. Figure 3 (d) is the average ZT value of composite materials such as AS-0, AS-0.1, AS-0.2, AS-0.4, and AS-0.6 in the temperature range of 300 to 390 K. It can be seen that the average ZT of the sample with a Sb2S3 content of 0.4% is higher than 1, achieving optimization of thermoelectric performance.

[0049] Figure 4 The ZT values ​​of the composite materials of pure phase Ag2Se (AS-0), Ag2Se composite amorphous Sb2S3 (AS-0.4SS / A), and Ag2Se composite crystalline Sb2S3 (AS-0.4SS / C) as a function of temperature. The dosage ratio of amorphous Sb2S3 and crystalline Sb2S3 is the same, and their combined dosage accounts for 0.4% of the mass of Ag2Se. Crystalline Sb2S3 is a finished product purchased on the market, and the preparation method of Ag2Se composite crystalline Sb2S3 is the same as step S3 of Example 1. As can be seen from the figure, when the composite ratio of amorphous Sb2S3 and crystalline Sb2S3 is the same, the ZT value of the composite thermoelectric material of Ag2Se composite amorphous Sb2S3 is significantly higher than that of the thermoelectric material of Ag2Se composite crystalline Sb2S3 and pure phase Ag2Se. However, the ZT value of the thermoelectric material of Ag2Se composite crystalline Sb2S3 is lower than that of pure phase Ag2Se. It can be concluded that compared with crystalline Sb2S3, the composite material formed by amorphous Sb2S3 as the second phase and Ag2Se has excellent and outstanding thermoelectric properties.

[0050] Figure 5 The following chart shows the temperature-dependent thermal conductivity of composite materials of pure Ag2Se (AS-0), Ag2Se combined with amorphous Sb2S3 (AS-0.4SS / A), and Ag2Se combined with crystalline Sb2S3 (AS-0.4SS / C) within the temperature range of 300 to 390 K. It can be seen that the thermal conductivity of the composite thermoelectric material composed of Ag2Se combined with amorphous Sb2S3 is the lowest, significantly lower than that of the thermoelectric material composed of Ag2Se combined with crystalline Sb2S3 and pure Ag2Se. This further demonstrates that the composite material formed by combining amorphous Sb2S3 with Ag2Se has superior thermoelectric properties compared to crystalline Sb2S3.

[0051] Figure 6 The power factor (PF) of the composite materials of pure phase Ag2Se (AS-0), Ag2Se composite amorphous Sb2S3 (AS-0.4SS / A) and Ag2Se composite crystalline Sb2S3 (AS-0.4SS / C) varies with temperature in the temperature range of 300-390K. It can be seen that compared with pure phase Ag2Se, the power factor will be reduced to varying degrees after Ag2Se is composited with amorphous Sb2S3 and crystalline Sb2S3; but the effect of amorphous Sb2S3 on the power factor is relatively small, and the power factor is only slightly reduced, while crystalline Sb2S3 will cause the power factor to be greatly reduced. This is because the main function of amorphous Sb2S3 in the present invention is to reduce thermal conductivity, and the thermoelectric properties of the composite material are optimized by reducing thermal conductivity. Even if amorphous Sb2S3 has a weak negative effect on the power factor, this is within an acceptable range. Therefore, from the perspective of the comprehensive performance of the composite material, the introduction of amorphous Sb2S3 has a positive impact on the thermoelectric material and optimizes the thermoelectric performance.

[0052] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a silver selenide-based composite room-temperature thermoelectric material, characterized in that: The following steps are involved: S1, preparing pure phase Ag2Se powder; S2, preparing amorphous nano-Sb2S3 powder; S3, preparing Ag2Se / Sb2(S, Se)3 composite thermoelectric material, including the following sub-steps: S31. Ultrasonic dispersion of pure Ag2Se powder in acidic water to form an Ag2Se dispersion; ultrasonic dispersion of Sb2S3 powder in another portion of acidic water to form an Sb2S3 dispersion; the amount of Sb2S3 powder used is 0.1-0.6% of the mass of the pure Ag2Se powder; S32. Dropping the Ag2Se dispersion into the Sb2S3 dispersion under continuous ultrasonic conditions, followed by mechanical stirring for 2-3 hours, and then allowing the powder to settle. The precipitated powder was collected and vacuum-dried to obtain Ag2Se / Sb2S3 composite powder; S33. The Ag2Se / Sb2S3 composite powder is sintered into a block by spark plasma sintering at a sintering pressure of 45 MPa, a sintering temperature of 300-380°C, and a holding time of 5-7 min to finally obtain an Ag2Se / Sb2(S, Se)3 composite thermoelectric material.

2. The method for preparing the silver selenide-based composite room-temperature thermoelectric material according to claim 1, wherein: In step S31, the acidic water used is an aqueous solution adjusted to pH=3.

3. The method for preparing the silver selenide-based composite room-temperature thermoelectric material according to claim 1, wherein: In step S32, the vacuum drying temperature is 50-70°C, and the drying time is 20-24 hours.

4. The method for preparing the silver selenide-based composite room-temperature thermoelectric material according to claim 1, wherein: Step S1: The method for preparing pure phase Ag2Se powder is as follows: S11, dissolving AgNO3 in ethylene glycol, adding Se powder, and stirring until the Se powder is evenly dispersed in the solution to obtain a dispersion; S12, adding NaOH solution to the dispersion, stirring evenly, heating to 200-250°C, and reacting for 24 hours; S13. After the reaction is completed, the solid product is collected by centrifugation, and the solid product is washed and vacuum-dried to obtain pure Ag2Se powder.

5. The method for preparing the silver selenide-based composite room-temperature thermoelectric material according to claim 4, wherein: In step S11, the molar ratio of AgNO3 to Se powder is 2:

1.

6. The method for preparing the silver selenide-based composite room-temperature thermoelectric material according to claim 1, wherein: The method for preparing amorphous nano-Sb2S3 powder in step S2 is as follows: S21. Dissolve SbCl3 in HCl solution to obtain solution A; dissolve Na2S·9H2O in NaOH solution to obtain solution B; S22. During continuous ultrasonic oscillation, solution B was slowly added dropwise to solution A, and ultrasonication was continued for 2 h. The solid product was then collected by centrifugation, and further washed and dried to obtain amorphous nano-Sb2S3 powder.

7. The method for preparing the silver selenide-based composite room-temperature thermoelectric material according to claim 6, wherein: In step S21, the molar ratio of SbCl3 to Na2S·9H2O is 2:

3.

8. A silver selenide-based composite room-temperature thermoelectric material, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 7.

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