Flexible thermoelectric device with efficient thermal management function and preparation method thereof

Abstract

The invention provides a flexible thermoelectric device with an efficient thermal management function and a preparation method thereof, the flexible thermoelectric device comprises a low heat conduction material, P / N type thermoelectric units are arranged on the low heat conduction material in a rectangular array, each P / N type thermoelectric unit comprises a plurality of groups of P / N type thermoelectric pairs connected in series, the series structure is a P / N / P series structure, the P / N type thermoelectric units are provided with gaps, and the gaps are communicated with the gaps. The gaps are filled with low-heat-conduction materials, the top and the bottom of the P / N type thermoelectric unit are connected with electrode materials, flexible heat conductors are arranged on the upper surface and the lower surface of the P / N type thermoelectric unit filled with PMDS colloid and connected with the electrode materials, PDMS colloid or polyurethane is adopted as the low-heat-conduction materials, and high-heat-conduction silica gel materials or high-heat-conduction elastomer materials are adopted as the flexible heat conductors. The thermal conductivity of the flexible thermoelectric device can be improved. The flexible thermoelectric device provided by the invention has relatively good flexibility and thermal management capability, can be used as a wearable self-powered power supply, and realizes long-term stable self-power supply in a wearable application scene.

Description

Technical Field

[0001] This invention belongs to the field of thermoelectric device fabrication, specifically relating to a flexible thermoelectric device with efficient thermal management function and its fabrication method. Background Technology

[0002] With the rapid development of the Internet of Things (IoT), wearable electronic devices, and distributed sensor networks, the demand for miniaturized and sustainable power supply systems is increasing. Traditional battery technology suffers from problems such as rigid structure, limited cycle life, and waste pollution, making it difficult to meet the power supply requirements of flexible electronic devices for lightweight, highly adaptable, and long-term maintenance-free operation. Against this backdrop, thermoelectric conversion technology has become a research hotspot in power supply technology due to its advantages such as no moving parts, no emissions, and the ability to utilize environmental waste heat. Thermoelectric conversion technology is based on the Seebeck effect, which generates an electromotive force when there is a temperature difference between the two ends of two different conductors or semiconductors, thereby directly converting heat energy into electrical energy. This technology is particularly suitable for the recovery and utilization of low-grade heat energy (such as human body heat and industrial waste heat) and has important application value in wearable devices, medical monitoring, and wireless sensor networks.

[0003] However, existing thermoelectric technologies face three key challenges in their practical application: 1. Encapsulation thermal resistance contradiction: Traditional flexible packaging materials have low thermal conductivity, resulting in heat accumulation at the hot end and insufficient heat dissipation at the cold end, which significantly reduces the effective temperature difference.

[0004] 2. Poor environmental stability: The encapsulation material is prone to aging in humid and hot environments, and the performance degradation of thermoelectric materials is accelerated.

[0005] 3. Insufficient long-term power output stability: The millivolt-level voltage generated by the human body temperature difference (ΔT<10K) is insufficient to power the device after it reaches thermal steady state, and cannot drive low-power devices to achieve long-term self-powering.

[0006] The aforementioned problems severely restrict the practical application and large-scale application of thermoelectric conversion technology in fields such as flexible electronics and wearable devices, hindering the breakthrough of thermoelectric technology from laboratory research to practical application. Summary of the Invention

[0007] To overcome the problems of existing flexible thermoelectric device technology, this invention provides a flexible thermoelectric device with efficient thermal management function and its preparation method. By optimizing the encapsulation material, the thermal conductivity is improved, and the heat collection and dissipation capacity of low thermal conductivity materials is enhanced, thereby establishing a larger temperature difference and improving power generation efficiency.

[0008] On one hand, the present invention provides a flexible thermoelectric device with efficient thermal management function, comprising a low thermal conductivity material, wherein the low thermal conductivity material is a flexible organic compound, and P / N type thermoelectric units are arranged in a rectangular array on the low thermal conductivity material. The P / N type thermoelectric units include multiple sets of P / N type thermoelectric pairs connected in series, wherein the series structure is a P / N / P series structure. The P / N type thermoelectric units have gaps, which are filled by the low thermal conductivity material. An electrode material is connected to the outer surface of the P / N type thermoelectric units, and a flexible thermal conductor is disposed on the outer surface of the P / N type thermoelectric units that fill the low thermal conductivity material and connect the electrode material.

[0009] Preferably, the P / N / P series structure is as follows: the electrode materials at the bottom of the N-type thermoelectric particles and the P-type thermoelectric particles in the P / N thermoelectric pair are non-conductive, and the N-type thermoelectric particles and the P-type thermoelectric particles in two adjacent sets of P / N thermoelectric pairs are connected in series through the electrode materials at the top.

[0010] On the other hand, the present invention proposes a method for fabricating the above-mentioned flexible thermoelectric device with efficient thermal management function, comprising the following steps: S1: Assemble P / N type thermocouples, select multiple sets of P / N type thermocouples, arrange them alternately in a rectangular mold to form a P / N / P alternating arrangement structure, and then take them out from the rectangular mold.

[0011] S2: Connecting electrode materials. The electrode material pattern is designed using design software, and the electrode material is prepared according to the pattern. Then, solder paste is printed onto the top and bottom of the P / N type thermoelectric pair. The electrode material is then bridged between the P / N type thermoelectric pairs according to the P / N / P series structure to achieve the end-to-end series connection between the P / N type thermoelectric pairs. At the same time, the electrode material is also individually bridged on the starting P-type thermoelectric particles and the ending N-type thermoelectric particles of the P / N type thermoelectric pair arranged in step S1, which are used as subsequent power sources. Finally, the electrode material is placed on a heating table for soldering to obtain the P / N type thermoelectric unit.

[0012] S3: Encapsulate the low thermal conductivity material. First, cover the electrodes at both ends of the P / N type thermoelectric unit with polyimide tape. Then, fill the gap between the P / N type thermoelectric pairs with the low thermal conductivity material. After filling, cure the material. Finally, remove the polyimide tape to obtain a flexible thermoelectric device with exposed electrode material. The low thermal conductivity material is PDMS colloid or polyurethane.

[0013] S4: Encapsulate the flexible thermal conductor by uniformly filling the upper and lower surfaces of the flexible thermoelectric device obtained in step S3, and then curing it at room temperature to finally prepare the flexible thermoelectric device; the flexible thermal conductor is made of high thermal conductivity silicone material or high thermal conductivity elastomer material, which can improve the thermal conductivity of the flexible thermoelectric device.

[0014] Preferably, the P / N type thermoelectric pair in step S1 uses Bi2Te3-based thermoelectric particles, which are a combination of P-type Sb2Te3-based thermoelectric particles and N-type Bi2Te3-based thermoelectric particles.

[0015] Preferably, the length, width, and height of the P / N type thermocouple in step S1 are 0.8-4 mm, 0.8-4 mm, and 0.8-4 mm, and the gap between the P / N type thermoelectric units is not less than 0.3 mm.

[0016] Preferably, the electrode material in step S2 is prepared using laser cutting technology, the thickness of the electrode material is 0.1 mm, and the size of the electrode material needs to cover the adjacent two sets of P / N type thermocouples; the electrode material is one of copper electrode, silver electrode and liquid metal.

[0017] Preferably, the PDMS colloid is prepared by mixing PDMS and a curing agent at a mass ratio of 10:1, and the curing temperature is 60°C for 2 hours. The PDMS colloid has the characteristics of insulation, flexibility, and oxidation resistance, and also has mechanical properties of bending resistance, which can increase the service life of flexible thermoelectric devices.

[0018] Preferably, the polyurethane is prepared by mixing polyurethane A part and polyurethane B part in a mass ratio of 1:1; the curing temperature is 60°C and the curing time is 0.5 hours.

[0019] Preferably, the high thermal conductivity elastomer material is prepared by mixing and stirring the polyurethane, liquid metal and nano-graphene sheets in a mass ratio of 1:1:0.1.

[0020] Preferably, the high thermal conductivity silicone material is prepared by mixing and stirring the curable silicone matrix and the graphite powder at a mass ratio of 2:1. The addition of graphite can effectively improve the thermal conductivity.

[0021] The present invention has the following beneficial effects: The flexible thermoelectric device of the present invention is encapsulated with a highly thermally conductive flexible material to enhance thermal conductivity and heat dissipation capabilities. When collecting ambient waste heat, it can establish a larger temperature difference, increase the output voltage, and effectively improve the heat exchange performance of cold end heat dissipation, increase the steady-state temperature difference, and achieve long-term stable self-power supply in wearable application scenarios, breaking through the limitations of traditional technology.

[0022] This invention combines high-performance Bi2Te3-based thermoelectric particle materials with flexible polyurethane or PDMS elastomers, enabling the fabricated flexible thermoelectric devices to adapt to complex curved surfaces such as human skin and spheres, reducing contact thermal resistance and improving heat recovery efficiency.

[0023] The high-performance flexible thermoelectric device of the present invention can directly collect waste heat from the human body to generate electricity, and can power a health sensor without the need for an external power source. Attached Figure Description

[0024] Figure 1 This is a top view of an 8*10 array formed by arranging P / N type thermocouples of the present invention with P / N / P intervals; Figure 2 This is a diagram of a series thermocouple formed after the copper electrode of the present invention is bridged with a P / N type thermocouple; Figure 3 This is a three-dimensional view of the array formed by the P / N / P series structure of the present invention; Figure 4 This is a schematic diagram of the unfolded flexible thermoelectric device of the present invention; Figure 5 This is a comparison chart of the thermal conductivity results between the high thermal conductivity silicone material and the graphite-free silicone material of this invention.

[0025] In the diagram: 1-P-type thermoelectric particles; 2-N-type thermoelectric particles; 3-Electrode material; 4-P / N-type thermoelectric couple; 5-Low thermal conductivity material; 6-Flexible thermal conductor. Detailed Implementation

[0026] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with specific embodiments. Example 1

[0027] like Figure 1-4 As shown, this invention provides a flexible thermoelectric device with efficient thermal management, comprising a low thermal conductivity material 5, on which P / N type thermoelectric units are arranged in a rectangular array. Each P / N type thermoelectric unit includes multiple sets of P / N type thermoelectric pairs 4 connected in series, with the series structure being a P / N / P series structure, as shown. Figure 3 As shown, the P / N type thermoelectric unit has a gap filled with a low thermal conductivity material 5. Electrode materials 3 are connected to the top and bottom of the P / N type thermoelectric unit. Flexible thermal conductors 6 are provided on the upper and lower surfaces of the P / N type thermoelectric unit filled with PMDS colloid and connected with electrode materials 3.

[0028] Specifically, the P / N / P series structure is as follows: the bottom electrode materials 3 of the N-type thermoelectric particles 2 and P-type thermoelectric particles 1 in the P / N type thermoelectric pair 4 are non-conductive, and the N-type thermoelectric particles 2 and P-type thermoelectric particles 1 of two adjacent sets of P / N type thermoelectric pairs 4 are connected in series through the top electrode material 3.

[0029] The present invention also provides a method for preparing the above-mentioned flexible thermoelectric device, comprising the following steps: S1: Assemble P / N type thermoelectric pairs 4. Select 80 sets of P / N type thermoelectric pairs 4. The P / N type thermoelectric pairs 4 use Bi2Te3-based thermoelectric particles, including 80 P-type Sb2Te3-based thermoelectric particles and 80 N-type Bi2Te3-based thermoelectric particles. The dimensions of the P-type Sb2Te3-based thermoelectric particles and the N-type Bi2Te3-based thermoelectric particles are: length 2mm, width 2mm, height 1.8mm. The gap between the P / N type thermoelectric units is 0.3mm. Place these P-type Sb2Te3-based thermoelectric particles and N-type Bi2Te3-based thermoelectric particles into a rectangular mold at intervals to form a shape as shown. Figure 1 After arranging the P / N / P intervals as shown, remove it from the rectangular mold.

[0030] S2: Connecting electrode material 3. Using AutoCAD software, pre-design the electrode material 3 with a length and width of 6mm and 2mm respectively. Based on the design, prepare the electrode material 3 on a 0.1mm thick copper foil using laser cutting technology. Then, use a screen printing plate to print low-temperature solder paste with a melting point of 138℃ onto the top of the P / N type thermoelectric pair 4. According to the P / N / P series structure, bridge the qualified electrode material 3 between each group of P / N type thermoelectric pairs 4. At the same time, bridge the electrode material 3 on the starting point P-type thermoelectric particle 1 and the ending point N-type thermoelectric particle 2 of the arranged P / N type thermoelectric pair 4 respectively, as the load for subsequent connection. The end of the P-type thermoelectric particle 1 is the positive electrode, and the end of the N-type thermoelectric particle 2 is the negative electrode. Finally, place it on a heating table at 180℃ and weld for 3 minutes to obtain the P / N type thermoelectric unit. The electrode material 3 can be one of copper electrode, silver electrode, and liquid metal.

[0031] S3: Encapsulate the low thermal conductivity material 5. The low thermal conductivity material 5 is PDMS colloid. First, the electrode materials 3 at both ends of the P / N type thermoelectric unit are pasted with polyimide tape to prevent the electrode materials 3 at both ends from being encapsulated by PDMS colloid. Then, PDMS and curing agent are mixed in a beaker at a mass ratio of 10:1 and stirred evenly to prepare PDMS colloid. Then, the PDMS colloid is filled into the gap between each P / N type thermoelectric pair 4 and cured at 60°C for 2 hours. After curing, the polyimide tape is removed to obtain a flexible thermoelectric device with exposed electrode material 3.

[0032] S4: Encapsulate the flexible thermal conductor 6 using a high thermal conductivity silicone material. First, mix the curable silicone and graphite powder in a 2:1 mass ratio to obtain the high thermal conductivity silicone material. Then, uniformly coat the high thermal conductivity silicone material onto the upper and lower surfaces of the flexible thermoelectric device obtained in step S3 and cure it at room temperature. After curing, the final flexible thermoelectric device is obtained. Example 2

[0033] In the preparation method provided in Example 1, the dimensions of the P-type Sb2Te3-based thermoelectric particles and the N-type Bi2Te3-based thermoelectric particles in step S1 are changed to: the length and width are both 0.8 mm, the height is 0.8 mm, the gap between the P / N type thermoelectric units is changed to 0.4 mm, and the rest remain unchanged. Example 3

[0034] In the preparation method provided in Example 1, the dimensions of the P-type Sb2Te3-based thermoelectric particles and the N-type Bi2Te3-based thermoelectric particles in step S1 are modified as follows: the length and width are both 4 mm, the height is 4 mm, the gap between the P / N type thermoelectric units is changed to 0.4 mm, and the rest remain unchanged. Example 4

[0035] In the preparation method provided in Example 1, the low thermal conductivity material 5 in step S3 is polyurethane. The polyurethane is prepared by mixing and stirring polyurethane A part and polyurethane B part in a mass ratio of 1:1 and curing at 60°C for 0.5 hours.

[0036] The flexible thermal conductor 6 is made of a highly elastic thermoelastic material prepared from polyurethane. Part A of the polyurethane (Ecoflex 00-20) and liquid metal are mixed at a mass ratio of 1:2 and magnetically stirred at 750 rad / min for at least 6 hours until a black emulsion, mixture A, is formed. Part B of the polyurethane and nano-graphene sheets are then mixed at a mass ratio of 5:1 and magnetically stirred at 750 rad / min for 1 hour until a black emulsion, mixture B, is formed. After uniformly mixing the polyurethane mixtures A and B, the mixture is encapsulated at both ends of the thermoelectric device and cured in a 60°C oven for 3 hours. The mass ratio of part A to part B is 1:1.

[0037] The thermal conductivity of the high thermal conductivity silicone material provided by this invention was compared with that of a graphite-free silicone material. The thermal conductivity of both materials in the horizontal and vertical directions (i.e., in-plane and out-of-plane thermal conductivity) was measured at room temperature. The results are as follows: Figure 5 As shown, Figure 5 (A) is a comparison diagram of in-plane thermal conductivity. Figure 5 (B) is a comparison of out-of-plane thermal conductivity, where c represents ordinary silicone material and d represents the high thermal conductivity silicone material with added graphite powder in this invention. Data shows that the average thermal conductivity of the high thermal conductivity silicone material reaches 2.78 W / m² in both the in-plane and out-of-plane directions.−1 K − ¹ and 2.11Wm −1 K − ¹, while the average thermal conductivity of graphite-free silicone material is only 0.42 W / m² in both the in-plane and out-of-plane directions. −1 K − ¹As can be seen, the flexible thermoelectric device of the present invention uses a high thermal conductivity silicone material with added graphite powder, which exhibits excellent thermal conductivity at room temperature and has high thermal conductivity both in-plane and out-of-plane, thus improving the thermal conductivity performance of the flexible thermoelectric device.

[0038] The high thermal conductivity elastomer material prepared by this invention, composed of a mixture of polyurethane, liquid metal, and nano-graphene sheets, has a thermal conductivity of 1.45 W / m in both the in-plane and out-of-plane directions. −1 K −1 and 1.16Wm −1 K −1 The Young's modulus and fracture strain are 0.82 MPa and 763.4%, respectively, ensuring the excellent thermal conductivity and conformal fit of the flexible thermoelectric device.

[0039] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A flexible thermoelectric device with efficient thermal management function, characterized in that, The device includes a low thermal conductivity material (5), on which P / N type thermoelectric units are arranged in a rectangular array. Each P / N type thermoelectric unit includes multiple sets of P / N type thermoelectric pairs (4) connected in series. The series structure is a P / N / P series structure. There are gaps between the P / N type thermoelectric pairs (4), which are filled by the low thermal conductivity material (5). An electrode material (3) is connected to the outer surface of the P / N type thermoelectric unit. A flexible thermal conductor (6) is provided on the outer surface of the P / N type thermoelectric unit that fills the low thermal conductivity material (5) and connects the electrode material (3).

2. The flexible thermoelectric device with high-efficiency thermal management function as described in claim 1, characterized in that, The P / N / P series structure is as follows: the N-type thermoelectric particles (2) and the electrode material (3) at the bottom of the P-type thermoelectric particles (1) in the P / N type thermoelectric pair (4) are non-conductive, and the N-type thermoelectric particles (2) and the P-type thermoelectric particles (1) between two adjacent P / N type thermoelectric pairs (4) are connected in series through the electrode material (3) at the top.

3. A method for preparing the flexible thermoelectric device as described in any one of claims 1-2, characterized in that, Includes the following steps: S1: Assemble P / N type thermocouples (4). First, select multiple sets of P / N type thermocouples (4), arrange them alternately in a rectangular mold, form a P / N / P interval arrangement structure, and then take them out from the rectangular mold. S2: Connecting electrode material (3), first prepare the electrode material (3), then print solder paste onto the top and bottom of the P / N type thermoelectric pair (4), and then bridge the electrode material (3) to each group of P / N type thermoelectric pairs (4) according to the P / N / P series structure; at the same time, the electrode material (3) is individually bridged on the starting point P type thermoelectric particle (1) and the ending point N type thermoelectric particle (2) of the P / N type thermoelectric pair (4) arranged in S1, and finally placed on the heating table for welding to obtain the P / N type thermoelectric unit; S3: Encapsulate the low thermal conductivity material (5). First, cover the electrode materials (3) at both ends of the P / N type thermoelectric unit with tape. Then, fill the gap between the P / N type thermoelectric pairs (4) with the low thermal conductivity material (5). After filling, cure the material and remove the tape to obtain a flexible thermoelectric device with the electrode materials (3) exposed. The low thermal conductivity material (5) is PDMS colloid or polyurethane. S4: Encapsulate the flexible thermal conductor (6), uniformly fill the upper and lower surfaces of the flexible thermoelectric device obtained in step S3 with the flexible thermal conductor (6), and then cure it at room temperature to prepare the final flexible thermoelectric device; the flexible thermal conductor (6) is made of high thermal conductivity silicone material or high thermal conductivity elastomer material.

4. The preparation method according to claim 3, characterized in that, The P / N type thermoelectric pair (4) described in S1 uses Bi2Te3-based thermoelectric particles, which are composed of P-type Sb2Te3-based thermoelectric particles and N-type Bi2Te3-based thermoelectric particles.

5. The preparation method according to claim 3, characterized in that, The length of the P / N type thermocouple (4) in step S1 is 0.8-4mm, the width is 0.8-4mm, and the height is 0.8-4mm; the gap between the P / N type thermocouples is not less than 0.3mm.

6. The preparation method according to claim 3, characterized in that, The electrode material (3) in step S2 is prepared by laser cutting technology. The thickness of the electrode material (3) is 0.1 mm. The size of the electrode material (3) needs to cover the adjacent two sets of P / N type thermocouples (4). The electrode material (3) is one of copper electrode, silver electrode and liquid metal.

7. The preparation method according to claim 3, characterized in that, The PDMS colloid is prepared by mixing PDMS and the curing agent at a mass ratio of 10:1, and the curing temperature is 60°C for 2 hours.

8. The preparation method according to claim 3, characterized in that, The polyurethane is prepared by mixing polyurethane A and polyurethane B in a mass ratio of 1:1; the curing temperature is 60°C and the curing time is 0.5 hours.

9. The preparation method according to claim 8, characterized in that, The high thermal conductivity elastomer material is prepared by mixing and stirring the polyurethane, liquid metal and nano-graphene sheets in a mass ratio of 1:1:0.

1.

10. The preparation method according to claim 3, characterized in that, The high thermal conductivity silicone material is made by mixing and stirring a curable silicone matrix and graphite powder at a mass ratio of 2:1.

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