Foamed metal / Bismuth telluride thermoelectric composite

Abstract

The present invention discloses a foam metal / bismuth telluride thermoelectric composite material. The foam metal has three-dimensional through holes, the surface of the framework of the foam metal is covered with bismuth telluride, and the three-dimensional through holes of the foam metal are filled with bismuth telluride. Wherein the mass ratio of bismuth telluride in the thermoelectric composite material is 45% to 70%. The foam metal / bismuth telluride thermoelectric composite material of the present invention exhibits excellent thermoelectric performance and excellent flexibility. The equipment required for preparation is simple, the operation is convenient, the process parameters are controllable, and it is suitable for large-scale industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of materials, and particularly relates to a foam metal / bismuth telluride thermoelectric composite material. Background Art

[0002] Thermoelectric materials are functional materials that convert thermal energy and electrical energy into each other based on the Seebeck effect and the Peltier effect. Power generation and refrigeration devices assembled based on thermoelectric materials can directly convert electrical energy and thermal energy into each other, without moving components, and have the advantages of good stability, long life, no noise pollution, safety, small size, etc. In the future, they can be widely used in chip heat dissipation, self-power supply of wearable electronic devices, and recovery of industrial waste heat and engine waste heat. The thermoelectric performance of bulk thermoelectric materials can be compared by the dimensionless thermoelectric figure of merit ZT (ZT = S2σT / k, where S is the Seebeck coefficient, σ is the electrical conductivity, k is the thermal conductivity, and T is the absolute temperature). However, for thin film thermoelectric materials, due to their thin thickness, it is impossible to accurately measure the thermal conductivity, and the thermoelectric performance is mostly compared by the power factor PF (PF = S2σ).

[0003] So far, bismuth telluride is still the material with the most excellent thermoelectric performance near room temperature and has become one of the main materials selected for commercial thermoelectric devices. However, due to the rigid lattice structure of bismuth telluride and its lack of intrinsic flexibility, most thermoelectric devices made of bismuth telluride-based alloys are rigid bulk devices. Since rigid devices cannot be bent, they cannot closely adhere to the heat source to collect heat in the actual application environment, which greatly limits the conversion efficiency of the devices. Therefore, improving the flexibility of bismuth telluride materials has great application value and commercial potential. Literature (Adv Electron Mater, 2019, 5: 1800786-1800795; JMater Sci-Mater El, 2016, 27: 1769-1776; Energ Environ Sci, 2012, 5: 8351-8358) etc. all focus on compounding with organic substances to improve its flexibility and have achieved good results. However, the electrical conductivity of organic substances themselves is relatively low, which makes the thermoelectric performance of the composite materials not high, and the types of n-type conductive polymers are few and difficult to store. The problem above can be well solved by using the method of compounding with inorganic substances.

[0004] For example, metals such as nickel, bismuth, and copper-nickel have a not-low Seebeck coefficient and excellent electrical conductivity, and after foaming, their flexibility, mechanical strength, and compression performance are all very excellent. However, no one has been involved in using it as the second phase to compound with bismuth telluride. Summary of the Invention

[0005] In view of the technical problem of poor flexibility of bismuth telluride materials in the prior art, the present invention aims to provide a new foam metal / bismuth telluride thermoelectric composite material. The foam metal / bismuth telluride thermoelectric composite material of the present invention uses a solvothermal method with a foam metal as a framework, and fills bismuth telluride into the framework to prepare the foam metal / bismuth telluride thermoelectric composite material. On the premise of maintaining good thermoelectric performance, the flexibility of bismuth telluride is greatly improved. The preparation method has low cost and simple operation, and has good application prospects.

[0006] In the foam metal / bismuth telluride thermoelectric composite material of the present invention, the foam metal has three-dimensional through holes, wherein the surface of the skeleton of the foam metal is covered with bismuth telluride, and the three-dimensional through holes of the foam metal are filled with bismuth telluride.

[0007] Preferably, the mass ratio of bismuth telluride in the thermoelectric composite material is 30% to 70%, and preferably 40% to 70%.

[0008] Preferably, the foam metal is foam nickel, foam bismuth or foam constantan. The pore diameter range of the three-dimensional through holes of the foam metal is 50 to 1500 μm, preferably 100 to 1000 μm, and the skeleton width of the foam metal is 15 to 750 μm, preferably 25 to 500 μm.

[0009] Another object of the present invention is to provide a method for preparing the foam metal / bismuth telluride thermoelectric composite material of the present invention, which successively includes the following steps:

[0010] Step S1, using a solvothermal method, carrying out a synthesis reaction on the raw material solution of the bismuth telluride filling phase under sealing at a temperature of 150 to 250 °C, preferably 170 to 200 °C, to generate bismuth telluride on the surface of the skeleton and in the three-dimensional through holes of the clean and dry foam metal;

[0011] Step S2, vacuum-drying the foam metal obtained in Step S1 and pressing it into shape at 3 to 45 Mpa, preferably 5 to 30 MPa, to obtain a dense process foam metal / bismuth telluride thermoelectric composite material;

[0012] Step S3, annealing the process foam metal / bismuth telluride thermoelectric composite material obtained in Step S2 in a tellurium gas atmosphere under vacuum sealing to obtain the final foam metal / bismuth telluride thermoelectric composite material.

[0013] Preferably, before Step S1, the following pretreatment steps are further included:

[0014] Pretreatment step Sa, sequentially putting the foam metal into hydrochloric acid solution, deionized water, and absolute ethanol for ultrasonic cleaning and vacuum drying to obtain a clean and dry foam metal;

[0015] Pretreatment step Sb: Weigh sodium tellurite, bismuth nitrate pentahydrate, sodium hydroxide, and polyvinylpyrrolidone in reaction amounts for the solvothermal synthesis as raw materials for the bismuth telluride filling phase. Dissolve them in ethylene glycol solvent under heating and stirring to obtain the raw material solution of the bismuth telluride filling phase.

[0016] In step S1, heat at a constant heating rate of 5 - 40 °C per minute to 150 - 220 °C, preferably 160 - 200 °C, and then keep it at 150 - 220 °C, preferably 160 - 200 °C for 6 - 36 h, preferably 10 - 24 h. Carry out the synthesis reaction on the raw material solution of the bismuth telluride filling phase under sealing to deposit bismuth telluride on the surface of the clean and dry foam metal skeleton and in the three-dimensional through holes, and then slowly cool to room temperature.

[0017] In step S2, vacuum dry the foam metal obtained in step S1 at 30 - 90 °C for 0.1 - 24 h, preferably 3 - 24 h, and press it into shape at 3 - 45 Mpa, preferably 5 - 30 MPa for 1 - 30 min, preferably 5 - 15 min to obtain a dense process foam metal / bismuth telluride thermoelectric composite material.

[0018] In step S3, under vacuum sealing, heat the process foam metal / bismuth telluride thermoelectric composite material obtained in step S2 in a tellurium gas atmosphere at a heating rate of 1 - 50 °C / min, preferably 5 - 40 °C / min to 200 - 400 °C, preferably 200 - 350 °C, keep it for 0.5 - 3 h, preferably 0.5 - 2 h, and then slowly cool to room temperature for annealing to obtain the final foam metal / bismuth telluride thermoelectric composite material.

[0019] In pretreatment step Sa, put the foam metal into hydrochloric acid solutions with concentrations of 0.01 - 9 mol / L, preferably 0.5 - 3 mol / L, deionized water, and anhydrous ethanol in sequence for ultrasonic cleaning and drying to obtain a clean and dry foam metal. Among them, the ultrasonic frequency is 20 - 30 kHz, the ultrasonic time is 1 - 60 min, preferably 3 - 15 min, the drying temperature is 20 - 90 °C, preferably 50 - 70 °C, and the drying time is 1 - 72 h, preferably 3 - 12 h.

[0020] In the pre-treatment step Sb, weigh sodium tellurite, bismuth nitrate pentahydrate, sodium hydroxide, and polyvinylpyrrolidone in reaction amounts for the solvothermal synthesis as raw materials for the bismuth telluride filling phase. Heat and stir at 30 °C to 80 °C, preferably 40 °C to 60 °C, and 50 to 800 rpm, preferably 150 to 450 rpm, and dissolve them in ethylene glycol solvent to obtain a raw material solution of the bismuth telluride filling phase. The molar ratio of sodium tellurite to bismuth nitrate pentahydrate is 1:1 to 2:1, preferably 4:3 to 2:1. The molar ratio of sodium hydroxide to ethylene glycol is 1:35 to 1:100, preferably 1:60 to 1:90. The mass ratio of polyvinylpyrrolidone to sodium hydroxide is 1:4 to 1:1. The mass ratio of bismuth telluride in the thermoelectric composite material is 30% to 70%, preferably 40% to 70%.

[0021] In step S1, the foam metal is foam nickel, foam bismuth, or foam constantan; in step S2, roll press, tablet press, and manual tablet pressing are used for molding; in step S3, the raw materials are vacuum-sealed in a quartz tube using a hydrogen-oxygen flame, acetylene flame, or argon plasma flame. The vacuum involved in steps S2, S3, and Sa refers to an air pressure of 0.1 to 25 Pa.

[0022] The positive and progressive effects of the present invention are as follows:

[0023] 1) The foam metal / bismuth telluride thermoelectric composite material prepared by the present invention exhibits good thermoelectric performance and flexibility.

[0024] 2) The thermoelectric performance and stability of the foam metal / bismuth telluride thermoelectric composite material prepared by the present invention can be improved simultaneously by annealing.

[0025] 3) The equipment required for the preparation of the present invention is simple, the operation is easy, the process parameters are controllable, and it is suitable for large-scale industrial production. Description of the Drawings

[0026] Figure 1 It is the X-ray diffraction pattern of foam nickel, the process foam nickel / bismuth telluride thermoelectric composite material, and the foam nickel / bismuth telluride thermoelectric composite material in Example 1.

[0027] Figure 2 It is the conductivity and Seebeck coefficient of foam nickel, the process foam nickel / bismuth telluride thermoelectric composite material, and the foam nickel / bismuth telluride thermoelectric composite material in Example 1.

[0028] Figure 3 It is the power factor of foam nickel, the process foam nickel / bismuth telluride thermoelectric composite material, and the foam nickel / bismuth telluride thermoelectric composite material in Example 1.

[0029] Figure 4 It is the relationship diagram of the conductivity of the foam nickel / bismuth telluride thermoelectric composite material changing with the bending radius in Example 1.

[0030] Figure 5 It is a graph showing the relationship between the conductivity of the nickel foam / bismuth telluride thermoelectric composite material in Example 1 and the number of bending cycles when the bending radius is 5 mm. Specific implementation mode

[0031] In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further elaborated below with reference to specific illustrations.

[0032] Foam metal / bismuth telluride thermoelectric composite materials of Examples 1 to 4

[0033] Taking the foam metal as the framework phase and bismuth telluride as the filling phase, the mass ratio of bismuth telluride in the composite material is shown in the table.

[0034] Pretreatment step Sa: The cut foam metal is sequentially ultrasonically treated in 3 mol / L hydrochloric acid aqueous solution, deionized water and absolute ethanol, and then the foam metal is placed in vacuum for heating and drying for standby;

[0035] Pretreatment step Sb: According to the optimal ratio of the raw materials used for synthesizing bismuth telluride by the solvothermal method and the mass ratio of bismuth telluride in the thermoelectric composite material, sodium tellurite, bismuth nitrate pentahydrate, sodium hydroxide and vinyl pyrrolidone are weighed as the raw materials for the bismuth telluride filling phase; Measure ethylene glycol solution into the reaction kettle, put in the raw materials for the bismuth telluride filling phase, and continuously stir and dissolve the filling phase raw materials under heating until the solution is clear.

[0036] Step S1: The pretreated foam metal is horizontally placed at the bottom of the reaction kettle, and then the clear solution is transferred to the reaction kettle. After the reaction kettle is sealed, it is placed in a heating device and heated at a heating rate of V S1 to T S1 °C for insulation for t S1 hours, and then slowly cooled to room temperature.

[0037] Step S2: Take out the foam metal from the reaction kettle cooled to room temperature, dry it in vacuum under heating, and then press it into shape to obtain the process foam metal / bismuth telluride thermoelectric composite material;

[0038] Step S3: Place the process foam metal / bismuth telluride thermoelectric composite material and tellurium powder together at the bottom of the quartz tube, and then vacuum seal the quartz tube; The sealed quartz tube is horizontally placed in the heating furnace and heated at a heating rate of V S3 to T S3 °C, keep warm for t S3 hours and then slowly cool to room temperature to finally obtain the foam metal / bismuth telluride thermoelectric composite material.

[0039] Table 1 Process parameters of Examples 1 to 9

[0040]

[0041] Table 1 (continued) Process parameters of Examples 1-9

[0042]

[0043] Table 1 (continued) Process parameters of Examples 1-9

[0044]

[0045] As Figures 1 to 5 shown is the comparison chart of each performance parameter of the nickel foam / bismuth telluride thermoelectric composite material obtained in Example 1.

[0046] Figure 1 are the X-ray diffraction patterns of nickel foam, the process nickel foam / bismuth telluride thermoelectric composite material, and the nickel foam / bismuth telluride thermoelectric composite material. The diffraction peaks in the nickel foam pattern are completely consistent with those of nickel (PDF#04-0850), and there are no other impurity phases, indicating that the possible contaminants and nickel oxide on the surface of the nickel framework have been successfully removed during the pretreatment process. The diffraction peaks in the XRD pattern of the process nickel foam / bismuth telluride composite film prepared by the solvothermal method can be found in both nickel (PDF#04-0850) and bismuth telluride (PDF#15-0863), which indicates that the process nickel foam / bismuth telluride thermoelectric composite material can be successfully synthesized by the solvothermal method. In the XRD spectrum of the nickel foam / bismuth telluride thermoelectric composite material prepared after annealing, in addition to the diffraction peaks corresponding to nickel and bismuth telluride, a diffraction peak of nickel ditelluride (PDF#08-0004) was also found at 31.48°. This is because nickel is relatively active and easy to diffuse. During the annealing process, at the two-phase interface, nickel atoms in the nickel foam will diffuse into the bismuth telluride phase and react with tellurium atoms therein to form a nickel ditelluride phase at the interface between nickel and bismuth telluride.

[0047] Figure 2 respectively show the conductivity and Seebeck coefficient of nickel foam, the process nickel foam / bismuth telluride thermoelectric composite material, and the nickel foam / bismuth telluride thermoelectric composite material. The conductivity of nickel foam is 10066.1 Scm -1 . The conductivity of the process nickel foam / bismuth telluride thermoelectric composite material synthesized by the solvothermal method is 10009.2 Scm -1 , which is slightly lower than the conductivity of nickel foam. The conductivity of the nickel foam / bismuth telluride thermoelectric composite material prepared after annealing is 11075.7 Scm -1 , which is higher than the conductivity of nickel foam and the process nickel foam / bismuth telluride thermoelectric composite material. The Seebeck coefficient of nickel foam is -17.7 μVK -1 . The Seebeck coefficient of the process nickel foam / bismuth telluride thermoelectric composite material synthesized by the solvothermal method is -22.5 μVK -1, it is slightly higher than the absolute value of the Seebeck coefficient of nickel foam. The Seebeck coefficient of the nickel foam / bismuth telluride thermoelectric composite prepared after annealing is -27.7 μV / K. -1 , which is much higher than the absolute value of the Seebeck coefficient of nickel foam and the nickel foam / bismuth telluride thermoelectric composite during the process.

[0048] Figure 3 Respectively show the power factors of nickel foam, the nickel foam / bismuth telluride thermoelectric composite during the process, and the nickel foam / bismuth telluride thermoelectric composite. The power factor of the nickel foam / bismuth telluride thermoelectric composite prepared after annealing is 8.50 μW / K²·cm. -2 cm -1 , the power factor is increased by 1.7 times compared with the nickel foam / bismuth telluride thermoelectric composite during the process, and is increased by 2.5 times compared with nickel foam. Thus, it can be seen that the thermoelectric performance of the composite material is greatly improved compared with that before compounding.

[0049] Figure 4 is the image of the conductivity and the change of the film curvature radius of the nickel foam / bismuth telluride thermoelectric composite under bending stress. When the curvature radius of the film bending decreases from 10 mm to 5 mm, compared with before bending, the resistivity change is less than 10%. Figure 5 is the conductivity stability of the nickel foam / bismuth telluride thermoelectric composite when the film is repeatedly bent 100 times on a bent pipe with a radius of 5 mm. The experiment found that after being repeatedly bent 100 times, the conductivity decreased by less than 10%. Although cracks appeared on the film surface during the bending process, the internal nickel skeleton remained intact, and bismuth telluride did not peel off from the nickel foam skeleton or the through holes, resulting in little change in the film conductivity. This shows the excellent flexibility of the composite film.

[0050] The nickel foam / bismuth telluride thermoelectric composite obtained in Example 2 has a significant increase in both the Seebeck coefficient and the conductivity compared with the nickel foam in the skeleton phase, so the thermoelectric performance is greatly improved, and the power factor is 6.50 μW / K²·cm at room temperature. -2 cm -1 . Nickel foam provides excellent flexibility for the composite material, and the conductivity decreases by less than 10% when the bending radius is not less than 10 mm.

[0051] The nickel foam / copper-nickel alloy thermoelectric composite obtained in Example 3 has a significant increase in both the Seebeck coefficient and the conductivity compared with the nickel foam in the skeleton phase, so the thermoelectric performance is greatly improved, and the power factor is 7.91 μW / K²·cm at room temperature. -2 cm -1 . Nickel foam provides excellent flexibility for the composite material, and the conductivity decreases by less than 10% when the bending radius is not less than 7 mm.

[0052] The nickel foam / bismuth telluride thermoelectric composite obtained in Example 4 has significantly improved Seebeck coefficient and conductivity compared with the nickel foam of the skeleton phase. Therefore, the thermoelectric performance is greatly improved, and the power factor is 4.21 μW K at room temperature -2 cm -1 . The constantan foam provides excellent flexibility to the composite material. When the bending radius is not less than 5 mm, the conductivity decreases by less than 10%.

[0053] The bismuth foam / bismuth telluride thermoelectric composite obtained in Example 5 has significantly improved Seebeck coefficient and conductivity compared with the bismuth foam of the skeleton phase. Therefore, the thermoelectric performance is greatly improved, and the power factor is 6.15 μW K at room temperature -2 cm -1 . The bismuth foam provides excellent flexibility to the composite material. When the bending radius is not less than 8 mm, the conductivity decreases by less than 10%.

[0054] The constantan foam / bismuth telluride thermoelectric composite obtained in Example 6 has significantly improved Seebeck coefficient and conductivity compared with the constantan foam of the skeleton phase. Therefore, the thermoelectric performance is greatly improved, and the power factor is 7.23 μW K at room temperature -2 cm -1 . The constantan foam provides excellent flexibility to the composite material. When the bending radius is not less than 6 mm, the conductivity decreases by less than 10%.

[0055] The nickel foam / bismuth telluride thermoelectric composite obtained in Example 7 has significantly improved Seebeck coefficient and conductivity compared with the nickel foam of the skeleton phase. Therefore, the thermoelectric performance is greatly improved, and the power factor is 6.17 μW K at room temperature -2 cm -1 . The constantan foam provides excellent flexibility to the composite material. When the bending radius is not less than 9 mm, the conductivity decreases by less than 10%.

[0056] The bismuth foam / bismuth telluride thermoelectric composite obtained in Example 8 has significantly improved Seebeck coefficient and conductivity compared with the bismuth foam of the skeleton phase. Therefore, the thermoelectric performance is greatly improved, and the power factor is 6.24 μW K at room temperature -2 cm -1 . The bismuth foam provides excellent flexibility to the composite material. When the bending radius is not less than 12 mm, the conductivity decreases by less than 10%.

[0057] The constantan foam / bismuth telluride thermoelectric composite obtained in Example 9 has significantly improved Seebeck coefficient and conductivity compared with the constantan foam of the skeleton phase. Therefore, the thermoelectric performance is greatly improved, and the power factor is 7.12 μW K at room temperature -2 cm -1 . The constantan foam provides excellent flexibility to the composite material. When the bending radius is not less than 9 mm, the conductivity decreases by less than 10%.

[0058] All documents mentioned in the present invention are cited herein for reference as if each document was individually cited for reference. The above embodiments have described in detail the technical solutions of the present invention. Obviously, the present invention is not limited to the described embodiments. Based on the embodiments of the present invention, those skilled in the art can also make various changes accordingly, but any changes equivalent or similar to the present invention fall within the scope of protection of the present invention.

Claims

1. A method for preparing a foam metal / bismuth telluride thermoelectric composite material, characterized in that, It successively includes the following steps: Step S1: Using the solvothermal method, the raw material solution of the bismuth telluride filling phase is synthesized under sealing at a temperature of 150~250°C, and bismuth telluride is generated on the surface of the clean and dry foam metal skeleton and in the three-dimensional through holes; Step S2: The foam metal obtained in Step S1 is vacuum dried and pressed into shape at 3~45 Mpa to obtain a dense process foam metal / bismuth telluride thermoelectric composite material; Step S3: Under vacuum sealing, the process foam metal / bismuth telluride thermoelectric composite material obtained in Step S2 is annealed in a tellurium gas atmosphere to obtain the final foam metal / bismuth telluride thermoelectric composite material.

2. The method according to claim 1, characterized in that: Before Step S1, the following pretreatment steps are also included: Pretreatment step Sa: The foam metal is successively put into hydrochloric acid solution, deionized water, and absolute ethanol for ultrasonic cleaning and vacuum drying to obtain clean and dry foam metal; Pretreatment step Sb: Weigh sodium tellurite, bismuth nitrate pentahydrate, sodium hydroxide, and polyvinylpyrrolidone in an amount for the solvothermal synthesis reaction as the raw material of the bismuth telluride filling phase, and dissolve them in ethylene glycol solvent under heating and stirring to obtain the raw material solution of the bismuth telluride filling phase.

3. The method according to claim 1, characterized in that: In Step S1, it is heated at a constant heating rate of 5~40°C per minute to 150~220°C, and then kept at a temperature of 150~220°C for 6~36 h. The raw material solution of the bismuth telluride filling phase is synthesized under sealing, and bismuth telluride is generated on the surface of the clean and dry foam metal skeleton and in the three-dimensional through holes, and then slowly cooled to room temperature.

4. The method according to claim 3, wherein: In Step S1, the raw material solution of the bismuth telluride filling phase is synthesized under sealing at a temperature of 160~200°C. Specifically, it is heated at a constant heating rate of 5~40°C per minute to 160~200°C, and then kept at a temperature of 160~200°C for 10~24 h. The raw material solution of the bismuth telluride filling phase is synthesized under sealing.

5. The method according to claim 1, wherein: In Step S2, the foam metal obtained in Step S1 is vacuum dried at 30~90°C for 0.1~24 h and pressed into shape at 3~45 Mpa for 1~30 min to obtain a dense process foam metal / bismuth telluride thermoelectric composite material.

6. The method according to claim 5, wherein: In Step S2, the foam metal obtained in Step S1 is vacuum dried at 30~90°C for 3~24 h and pressed into shape at 5~30 Mpa for 5~15 min to obtain a dense process foam metal / bismuth telluride thermoelectric composite material.

7. The method according to claim 1, characterized in that: Step S3: Under vacuum sealing, the process foam metal / bismuth telluride thermoelectric composite material obtained in Step S2 is heated at a heating rate of 1~50°C / min in a tellurium gas atmosphere to 200~400°C, kept for 0.5~3 h, and then slowly cooled to room temperature for annealing to obtain the final foam metal / bismuth telluride thermoelectric composite material.

8. The method according to claim 7, characterized in that: Step S3: Under vacuum sealing, heat the as-prepared porous metal / tellurium bismuth thermoelectric composite material obtained in step S2 in a tellurium gas atmosphere at a heating rate of 5 - 40 °C / min to 200 - 350 °C, hold for 0.5 - 2 h, and then slowly cool to room temperature for annealing to obtain the final porous metal / tellurium bismuth thermoelectric composite material.

9. The method according to claim 2, wherein: In the pretreatment step Sa, the porous metal is successively placed in hydrochloric acid solutions with concentrations of 0.01 - 9 mol / L, deionized water, and absolute ethanol for ultrasonic cleaning and drying to obtain a clean and dry porous metal; wherein, the ultrasonic frequency is 20 - 30 kHz, the ultrasonic time is 1 - 60 min, the drying temperature is 20 - 90 °C, and the drying time is 1 - 72 h; In the pretreatment step Sb, weigh sodium tellurite, bismuth nitrate pentahydrate, sodium hydroxide, and polyvinylpyrrolidone in reaction amounts for solvothermal synthesis as raw materials for the tellurium bismuth filling phase. Under heating at 30 °C - 80 °C, stir and dissolve them in ethylene glycol solvent at a rotation speed of 50 - 800 rpm to obtain a raw material solution for the tellurium bismuth filling phase, wherein the molar ratio of sodium tellurite to bismuth nitrate pentahydrate is 1:1 - 2:1, the molar ratio of sodium hydroxide to ethylene glycol is 1:35 - 1:100, the mass ratio of polyvinylpyrrolidone to sodium hydroxide is 1:4 - 1:1, and the mass ratio of tellurium bismuth in the thermoelectric composite material is 30% - 70%.

10. The method according to claim 9, wherein: In the pretreatment step Sa, the porous metal is successively placed in hydrochloric acid solutions with concentrations of 0.5 - 3 mol / L, deionized water, and absolute ethanol for ultrasonic cleaning and drying to obtain a clean and dry porous metal; wherein, the ultrasonic frequency is 20 - 30 kHz, the ultrasonic time is 3 - 15 min, the drying temperature is 50 - 70 °C, and the drying time is 3 - 12 h; In the pretreatment step Sb, weigh sodium tellurite, bismuth nitrate pentahydrate, sodium hydroxide, and polyvinylpyrrolidone in reaction amounts for solvothermal synthesis as raw materials for the tellurium bismuth filling phase. Under heating at 40 °C - 60 °C, stir and dissolve them in ethylene glycol solvent at a rotation speed of 150 - 450 rpm to obtain a raw material solution for the tellurium bismuth filling phase, wherein the molar ratio of sodium tellurite to bismuth nitrate pentahydrate is 4:3 - 2:1, the molar ratio of sodium hydroxide to ethylene glycol is 1:60 - 1:90, the mass ratio of polyvinylpyrrolidone to sodium hydroxide is 1:4 - 1:1, and the mass ratio of tellurium bismuth in the thermoelectric composite material is 40 - 70%.

11. The method according to claim 2, wherein: In step S1, the porous metal is porous nickel, porous bismuth, or porous constantan; in step S2, roll presses, tablet presses, and manual tablet pressing are used for forming; in step S3, the raw materials are vacuum-sealed in a quartz tube using a hydrogen-oxygen flame, an acetylene flame, or an argon plasma flame. The vacuum involved in steps S2, S3, and Sa refers to an air pressure of 0.1 - 25 Pa.

12. A foam metal / bismuth telluride thermoelectric composite material prepared by the method according to any one of claims 1 to 11, wherein the foam metal has three-dimensional through holes, characterized in that, The surface of the framework of the porous metal is covered with tellurium bismuth, and the three-dimensional through-holes of the porous metal are filled with tellurium bismuth.

13. The foam metal / bismuth telluride thermoelectric composite material according to claim 12, characterized in that, The mass ratio of bismuth telluride in the thermoelectric composite material is 30% to 70%.

14. The foam metal / bismuth telluride thermoelectric composite material according to claim 13, wherein The mass ratio of bismuth telluride in the thermoelectric composite material is 40 to 70%.

15. The foam metal / bismuth telluride thermoelectric composite material according to claim 12, wherein The foam metal is foam nickel, foam bismuth or foam constantan. The pore diameter range of the three-dimensional through holes of the foam metal is 50 to 1500 μm, and the skeleton width of the foam metal is 15 to 750 μm.

16. The foam metal / bismuth telluride thermoelectric composite material according to claim 15, wherein The pore diameter range of the three-dimensional through holes of the foam metal is 100 to 1000 μm, and the skeleton width of the foam metal is 25 to 500 μm.

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