A design method of organic-inorganic composite thermoelectric material based on anisotropy degree of filler thermal conductivity

Abstract

The present application relates to a kind of based on filler thermal conductivity anisotropy degree of organic-inorganic composite thermoelectric material design method;The composite thermoelectric material designed by the method is composed of inorganic filler and organic polymer material matrix, by controlling the difference degree between the axial thermal conductivity and radial thermal conductivity of filler, and combining the parameters such as material, length-diameter ratio, volume fraction of filler, the electric transport network and heat conduction network in composite system are constructed.Electrons mainly transport along percolation conductive network, so as to improve the conductivity of system;Heat flow is propagated through filler skeleton, matrix and extended network, and the anisotropy of thermal conductivity of filler makes the heat flow be subjected to axial / radial collaborative bottleneck restriction in the process of turning, bridging and bridging, so as to inhibit the thermal conductivity of composite system.Using this method, the electrical conductivity of the composite system is improved while the thermal conductivity is inhibited, thereby the thermoelectric figure of merit of the composite system as a whole is improved, and the composite thermoelectric material designed by the method has good ductility.

Description

Technical Field

[0001] This invention relates to a design method for organic-inorganic composite thermoelectric materials, specifically a design method for organic-inorganic composite thermoelectric materials based on the degree of anisotropy of the thermal conductivity of fillers. Background Technology

[0002] With the transformation and upgrading of the energy structure and the rapid development of miniaturized and intelligent electronic devices, high-efficiency energy conversion and thermal management technologies have become an important research direction in the fields of materials science and device engineering. Thermoelectric materials can achieve direct conversion between thermal energy and electrical energy driven by temperature difference, combining power generation and cooling functions. They have advantages such as no moving mechanical parts, no noise, and high reliability, showing promising application prospects in wearable electronics, self-powered sensors, waste heat recovery, and flexible energy devices. In contrast, traditional bulk thermoelectric materials are mostly inorganic semiconductors or alloy systems, which generally suffer from high rigidity, difficult processing, high cost, and difficulty in achieving large-area flexible integration, thus limiting their widespread application in flexible electronic systems.

[0003] To address the aforementioned issues, composite thermoelectric materials have gradually become a research hotspot. These materials typically employ a "conductive phase / insulating matrix" or "organic / inorganic" composite structure. By introducing functional fillers such as metal nanowires, carbon-based materials, and semiconductor nanoparticles into a polymer matrix, the electrical transport capacity of the system is improved while maintaining the material's flexibility, processability, and lightweight characteristics. Existing research shows that in an insulating organic matrix, when the volume fraction of conductive filler exceeds the percolation threshold, a continuous conductive network can form within the system. Electrons are primarily transported along this network, and the electrical conductivity increases significantly with increasing filler volume fraction. High-performance thermoelectric materials typically need to balance high electrical conductivity with low thermal conductivity. However, in practical systems, these parameters are often coupled. For composite systems containing metals or highly conductive fillers, enhancing the connectivity of the conductive network usually improves electrical conductivity, but it may also lead to an increase in thermal transport capacity, thus limiting further improvements in the thermoelectric figure of merit. Therefore, how to improve electrical transport capacity while suppressing the simultaneous increase in thermal conductivity has become a key issue in the design of composite thermoelectric materials.

[0004] From a microscopic transport mechanism perspective, electrical and thermal transport in composite systems do not entirely follow the same pathways. Electrical transport is primarily dominated by the conductive network formed by the packing material, while heat flow, in addition to being transferred along the packing skeleton, can also pass through the organic matrix simultaneously, and is affected by the interfacial thermal resistance between packing materials and between the packing material and the matrix. Existing theoretical analyses show that the effective thermal conductivity of a composite system is closely related to parameters such as the packing volume fraction, aspect ratio, and interfacial thermal resistance. Although thermal conductivity increases with increasing volume fraction, its change is usually smaller than that of electrical conductivity, thus providing a possibility for increasing the ratio of electrical conductivity to thermal conductivity.

[0005] Existing research on optimizing the transport properties of organic / inorganic composite materials mostly focuses on enhancing interfacial coupling, optimizing filler morphology and aspect ratio, controlling orientation, and constructing percolation networks. However, the impact of filler thermal conductivity anisotropy on the overall thermal transport behavior of the composite system remains poorly studied. Recent research indicates that anisotropic nanowire fillers significantly suppress the effective thermal conductivity of the composite material, and this suppression effect is robust to the definition of anisotropy ratios, interfacial thermal boundary conduction, and filler orientation distribution. This is because heat flow in the composite system not only propagates along the percolation framework but also undergoes random transport through the matrix-mediated extended network. Anisotropic fillers form axial / radial synergistic bottlenecks during heat flow redirection, bridging, and bonding, thereby reducing overall thermal transport efficiency.

[0006] Therefore, current technologies still lack a method for synergistically designing the electrical and thermal transport behaviors of composite systems by using the anisotropy of filler thermal conductivity as the core control parameter and combining it with factors such as filler material, volume fraction, and aspect ratio. In particular, how to utilize the directional differences in filler thermal conductivity to suppress the growth of effective thermal conductivity and increase the ratio of electrical to thermal conductivity, thereby creating conditions for improving thermoelectric figure of merit, while ensuring the continuity of the conductive network and the flexibility and processing performance of the materials, remains a pressing technical problem in this field. Conducting systematic theoretical analysis and experimental verification around this problem has significant theoretical and practical value for developing a new generation of high-performance, scalable composite thermoelectric materials. Summary of the Invention

[0007] To address the aforementioned problems, the main objective of this invention is to provide an organic-inorganic composite thermoelectric material composed of inorganic fillers and an organic polymer matrix. This method involves controlling one or more of the following: the material, aspect ratio, degree of thermal conductivity anisotropy, and volume fraction of the inorganic filler. This allows for the systematic construction of highly efficient electrical conduction but inhibited thermal transport pathways, resulting in a current path within the composite system while hindering the formation of a smooth thermal flow path.

[0008] The specific technical solution of this invention is as follows: Electrical transport in the composite system is mainly dominated by the conductive network formed by the filler, while thermal transport, in addition to being transmitted along the filler skeleton, is also affected by the thermal conductivity of the organic polymer matrix, the interfacial thermal conductivity between fillers, and the interfacial thermal conductivity between the filler and the matrix. Therefore, this invention employs different numerical solution paths for the electrical and thermal transport of the composite system. Specifically, the electrical conductivity of the composite system is preferably solved using a resistance network algorithm based on the filler conductive network combined with Kirchhoff's current law; the thermal conductivity of the composite system is preferably solved using the finite element method. In the thermal transport solution process, firstly, a computational domain for the composite system is established based on randomly dispersed inorganic fillers and the organic polymer matrix. Then, based on the anisotropy of the axial and radial thermal conductivity of the inorganic fillers, and combined with the matrix thermal conductivity, filler-filler interfacial thermal conductivity, and filler-matrix interfacial thermal conductivity, a steady-state thermal conduction finite element model is established. By applying temperature difference boundary conditions at both ends of the thermal conduction direction, the temperature field and heat flow field of the composite system are solved, thereby obtaining the effective thermal conductivity of the composite system along the predetermined direction. This invention uses the anisotropy of the thermal conductivity of the filler as the core control variable, and combines it with parameters such as filler material, aspect ratio, and volume fraction to achieve synergistic control of the electrical and thermal conductivity of the composite system. This provides an feasible numerical design method for the design of high electrical conductivity and low thermal conductivity composite thermoelectric materials.

[0009] This invention solves the above-mentioned technical problems through the following technical solution: a design method for organic-inorganic composite thermoelectric materials based on the anisotropy of filler thermal conductivity, wherein the organic-inorganic composite thermoelectric material comprises an organic polymer matrix and an inorganic filler filled in the matrix, and the inorganic filler has an axial thermal conductivity κ. l and radial thermal conductivity is κ d , and κ l and κ d They vary; the degree of anisotropy of the thermal conductivity of the inorganic filler is determined by C=κ. l / κ d Or C=κ d / κ l Definition; the design method includes the following steps:

[0010] Step 1: Add inorganic fillers to an organic polymer substrate and use numerical simulation to randomly disperse the fillers in the substrate to obtain a mixed system of inorganic fillers and organic polymer materials.

[0011] Step 2: Using numerical simulation, the anisotropy of the thermal conductivity of the inorganic filler inside the mixture designed in Step 1 is controlled.

[0012] Step 3: Based on the hybrid system obtained in Step 2, model the electrical and thermal transport of the hybrid system separately. The electrical transport is solved using a resistance network algorithm based on the packing conductive network. The thermal transport is solved using a steady-state heat conduction model established by the finite element method. The temperature field and heat flow field are solved by combining the thermal conductivity of the matrix, the axial thermal conductivity of the packing, the radial thermal conductivity of the packing, the thermal conductivity of the packing-packing interface, and the thermal conductivity of the packing-matrix interface. The effective thermal conductivity of the composite system is then calculated accordingly.

[0013] Based on the calculated electrical and thermal conductivity, one or more design parameters are adjusted, including the material, aspect ratio, anisotropy, and volume fraction of the filler in the organic polymer matrix, of the internal inorganic filler. When the thermal conductivity of the mixed system, calculated by numerical simulation, is controlled within the range of 2.5–3 W / m², the desired effect is achieved. -1 K -1 The conductivity was controlled at 1.53 × 10⁻⁶. 5 ~1.98×10 6 When S / m, the design of organic-inorganic composite thermoelectric material is completed.

[0014] In a specific embodiment of the present invention, in step one, the inorganic filler is one or a combination of several of the following: metallic materials or porous crystalline materials. The metallic materials are selected from one or more of the following: nickel (Ni), cobalt (Co), iron (Fe), gadolinium (Gd), dysprosium (Dy), and manganese (Mn). The porous crystalline materials are selected from one or a mixture of several of the following: AFI type aluminum phosphate molecular sieve AlPO4-5, AEL type aluminum phosphate molecular sieve AlPO4-11, LTL type zeolite molecular sieve, MFI type zeolite molecular sieve, and VFI type aluminum phosphate molecular sieve VPI-5.

[0015] In a specific embodiment of the present invention, in step one, the inorganic filler is in the shape of one of rods, wires, fibers or nanowires.

[0016] In a specific embodiment of the present invention, in step one, the length of the inorganic filler is designed to be in the range of 0.05 to 1000 micrometers, and the diameter is designed to be in the range of 0.001 to 200 micrometers.

[0017] In a specific embodiment of the present invention, in step one, the inorganic filler accounts for 5% to 70% of the volume percentage in the composite thermoelectric material, preferably 10% to 30%.

[0018] In a specific embodiment of the present invention, in step one, the organic polymer material matrix is ​​one or more of epoxy resin, polylactide, polyvinylidene fluoride, vinyl silicone oil, polyurethane, polydimethylsiloxane, polybenzoxazine, polyimide, silicone resin, polycarbonate or polyacrylate.

[0019] In a specific implementation of the present invention, in step two, the inorganic filler in the mixture is designed with a specific degree of thermal conductivity anisotropy through numerical simulation.

[0020] In a specific embodiment of the present invention, in step three, the thermal conductivity tensor of the inorganic filler in the local coordinate system is composed of axial thermal conductivity and radial thermal conductivity, and is mapped to the global coordinate system after coordinate rotation transformation according to the filler orientation angle.

[0021] In a specific embodiment of the present invention, in step three, the electrical conductivity of the composite system is solved using a resistance network algorithm combined with Kirchhoff's current law; the thermal conductivity of the composite system is solved using the finite element method. A steady-state heat conduction model is established within the computational domain containing the organic polymer matrix and the inorganic filler. An anisotropic thermal conductivity tensor is constructed based on the axial and radial thermal conductivity of the inorganic filler. The temperature field and heat flow field of the composite system are solved by combining the filler-filler interface thermal conductivity, the filler-matrix interface thermal conductivity, and the matrix thermal conductivity, thereby obtaining the effective thermal conductivity of the composite system.

[0022] In a specific embodiment of the present invention, in step three, through numerical simulation calculation, the thermal conductivity of the composite thermoelectric material is controlled within the range of 2.5–3 W / m². -1 K -1 The conductivity is controlled within the range of 1.53 × 10⁻⁶. 5 ~1.98×10 6 When S / m, the design of organic-inorganic composite thermoelectric materials based on the degree of anisotropy of the filler is completed.

[0023] The positive and progressive effects of this invention are as follows: The design method for organic-inorganic composite thermoelectric materials based on the anisotropy of filler thermal conductivity provided by this invention has the following advantages: This invention utilizes the fundamental principle of the difference between electropercolation and heat transport to propose a design method for organic-inorganic composite thermoelectric materials with the anisotropy of filler thermal conductivity as the core control. Under the premise of ensuring the formation of a continuous electronic conduction network, by adjusting the difference between the axial and radial thermal conductivity of the filler, the propagation of heat flow in the filler skeleton, matrix, and extended network is restricted by a synergistic axial / radial bottleneck, thereby inhibiting the synchronous growth of effective thermal conductivity, improving the ratio of electrical conductivity to thermal conductivity of the composite system, and providing conditions for improving the thermoelectric figure of merit. The composite thermoelectric material designed by this invention possesses the excellent flexibility, ductility, and processing adaptability endowed by the organic polymer matrix, and can be widely applied in fields such as flexible electronics, wearable devices, and waste heat utilization. Attached Figure Description

[0024] Figure 1 A schematic diagram of the thermal conductivity characteristics of a single packing material in this invention.

[0025] Figure 2A schematic diagram of the design of the organic-inorganic composite thermoelectric material with anisotropic filler thermal conductivity according to the present invention.

[0026] Figure 3 Schematic diagram of the effective thermal conductivity of the composite system under different filler volume fractions and degrees of thermal conductivity anisotropy.

[0027] Figure 4 Schematic diagram of the effective thermal conductivity of the composite system under different filler aspect ratios and degrees of thermal conductivity anisotropy. Detailed Implementation

[0028] The preferred embodiments of the present invention are given below with reference to the accompanying drawings to illustrate the technical solution of the present invention in detail.

[0029] To characterize the influence of the anisotropy of the thermal conductivity of the filler on the thermal transport behavior of the composite system, this invention employs a numerical modeling approach combining the Monte Carlo method and the finite element method. First, a two-dimensional square computational domain is established, with a side length denoted as L. The inorganic filler is simplified into rectangular elements of length l and width d, randomly distributed within the organic polymer matrix. Preferably, the filler satisfies l / L = 0.2 and an aspect ratio l / d = 20. Filler extending beyond the boundary of the computational domain is truncated. Filler extending beyond the domain along the direction perpendicular to heat conduction is periodically translated back into the square to ensure the continuity of the filler's spatial distribution. In the finite element model of thermal transport, the thermal conductivity of the organic polymer matrix is ​​denoted as κ. m axial thermal conductivity is κ l The radial thermal conductivity is κ. d The degree of anisotropy of the thermal conductivity of the packing can be characterized by either the ratio of axial thermal conductivity to radial thermal conductivity or the ratio of radial thermal conductivity to axial thermal conductivity. A degree of anisotropy of 1 indicates isotropy. To ensure the consistency of the intrinsic thermal conductivity of the packing under different anisotropic conditions, it is preferable to satisfy κ. f = In the local coordinate system of a single packing material, its thermal conductivity tensor is expressed as K. local = Then, based on the packing orientation angle θ, rotate to the global coordinate system to obtain the global thermal conductivity tensor K for the corresponding packing region. global And assign it to the filler region in the finite element model.

[0030] After establishing the aforementioned geometric model and material parameters, the steady-state heat conduction problem of the composite system is solved using the finite element method. A temperature difference boundary condition is applied along the heat conduction direction, preferably at X=0, where temperature T is applied. l =295 K, apply temperature T at X=L r=305 K, thus forming a stable temperature gradient within the computational domain. The finite element method (FEM) solution object is the temperature field and heat flow field inside the composite system; the model simultaneously considers the influence of matrix thermal conductivity, effective thermal conductivity of filler, filler-filler interface thermal conductivity, and filler-matrix interface thermal conductivity on overall heat transport. Based on the total heat flow obtained from the finite element solution, the effective thermal conductivity of the composite system along the heat conduction direction can be calculated. To reduce statistical fluctuations caused by the randomly distributed structure, finite element solutions are performed on multiple independently generated filler distribution configurations, and the average value of the results is taken; preferably, the average result of 100 independent configurations under each set of parameters is taken as the effective thermal conductivity of the composite system.

[0031] like Figure 1 , Figure 2 As shown, the specific steps of the present invention are as follows: A design method for organic-inorganic composite thermoelectric materials based on the anisotropy of filler thermal conductivity includes the following steps:

[0032] Step 1: Add inorganic fillers to an organic polymer substrate and use numerical simulation to randomly disperse the fillers in the substrate to obtain a mixed system of inorganic fillers and organic polymer materials.

[0033] Step 2: Using numerical simulation, the anisotropy of the thermal conductivity of the inorganic filler inside the mixture designed in Step 1 is controlled.

[0034] Step 3: Based on the hybrid system with a specific degree of thermal conductivity anisotropy obtained in Step 2, model the electrical and thermal transport of the composite thermoelectric material separately. Electrical transport is solved using a resistance network algorithm based on the packing conductive network; thermal transport is modeled using the finite element method to establish a steady-state heat conduction model. The temperature and heat flow fields are solved by combining the thermal conductivity of the matrix, the axial thermal conductivity of the packing, the radial thermal conductivity of the packing, the thermal conductivity at the packing-packing interface, and the thermal conductivity at the packing-matrix interface, and the effective thermal conductivity of the composite system is calculated accordingly.

[0035] Based on the calculated electrical and thermal conductivity, one or more design parameters are adjusted, including the material of the internal inorganic filler, aspect ratio, degree of anisotropy, and volume fraction of the filler into the organic polymer matrix. When the electrical and thermal conductivity calculated by numerical simulation meets certain requirements, the design of the organic-inorganic composite thermoelectric material is completed.

[0036] Furthermore, in step one, the inorganic filler is a metallic material selected from one or more of nickel (Ni), cobalt (Co), iron (Fe), gadolinium (Gd), dysprosium (Dy), and manganese (Mn); the inorganic filler is a porous crystalline material selected from one or more of AFI type aluminum phosphate molecular sieve AlPO4-5, AEL type aluminum phosphate molecular sieve AlPO4-11, LTL type zeolite molecular sieve, MFI type zeolite molecular sieve, and VFI type aluminum phosphate molecular sieve VPI-5.

[0037] Furthermore, in step one, the inorganic filler is in the shape of one of the following: rod-shaped, wire-shaped, fibrous, or nanowire-shaped.

[0038] Furthermore, in step one, the length of the inorganic filler is designed to range from 0.05 to 1000 micrometers, and the diameter is designed to range from 0.001 to 200 micrometers.

[0039] Furthermore, in step one, the inorganic filler accounts for 5% to 70% of the volume percentage in the composite thermoelectric material, preferably 10% to 30%.

[0040] Furthermore, in step one, the organic polymer matrix is ​​one or more of epoxy resin, polylactide, polyvinylidene fluoride, vinyl silicone oil, polyurethane, polydimethylsiloxane, polybenzoxazine, polyimide, silicone resin, polycarbonate, or polyacrylate.

[0041] Furthermore, in step two, the inorganic filler in the mixture is designed with a specific degree of thermal conductivity anisotropy through numerical simulation.

[0042] Furthermore, in step three, the thermal conductivity tensor of the inorganic filler in the local coordinate system is composed of axial thermal conductivity and radial thermal conductivity, and is mapped to the global coordinate system after coordinate rotation transformation according to the filler orientation angle.

[0043] Furthermore, in step three, the electrical conductivity of the composite system is solved using a resistance network algorithm combined with Kirchhoff's current law; the thermal conductivity of the composite system is solved using the finite element method. A steady-state heat conduction model is established within the computational domain containing the organic polymer matrix and the inorganic filler. An anisotropic thermal conductivity tensor is constructed based on the axial and radial thermal conductivity of the inorganic filler. The temperature field and heat flow field of the composite system are solved by combining the thermal conductivity at the filler-filler interface, the thermal conductivity at the filler-matrix interface, and the thermal conductivity of the matrix, thereby obtaining the effective thermal conductivity of the composite system.

[0044] Example 1

[0045] like Figure 3 As shown, nickel (Ni) nanowires were selected as the inorganic filler and polyvinylidene fluoride (PVDF) as the organic polymer material to design an organic-inorganic composite thermoelectric material based on the anisotropy of the filler. The inorganic filler was added to the organic polymer matrix, and numerical simulation was used to randomly disperse the filler in the matrix, ultimately obtaining a hybrid system of inorganic filler and organic polymer material. An aspect ratio of l was selected. Ni This study investigates the relationship between the anisotropy of Ni nanowire fillers with a density of 20 g / d and the effective thermal conductivity of the system. The heat conduction direction is chosen as the X-direction. Under constant conditions, the relationship between the filler volume fraction and the thermal conductivity is studied. As the filler thermal conductivity increased from 0.10 to 0.30, the effective thermal conductivity of the composite system generally showed an upward trend. However, at the same volume fraction, the effective thermal conductivity of the composite system decreased significantly as the anisotropy of the filler thermal conductivity increased. Furthermore, even though increasing the aspect ratio of the filler increased the effective thermal conductivity of the composite system, at the same aspect ratio, the anisotropy also showed a significant inhibitory effect on the effective thermal conductivity of the composite system, indicating that the anisotropy of the filler thermal conductivity can effectively weaken the system's heat transport capacity.

[0046] This invention designs an organic-inorganic composite thermoelectric material based on the degree of anisotropy of filler thermal conductivity, selecting l Ni =20 micrometers, aspect ratio l Ni / d=20, thermal conductivity 200Wm -1 K -1 Rectangular Ni nanowires were used as inorganic fillers with a thermal conductivity of 1 W / m². - 1 K -1 Using PVDF as the organic polymer substrate, the interfacial thermal conductivity between Ni nanowires and between Ni nanowires and the matrix was chosen to be 5 × 10⁻⁶. 7 Wm −2 K −1 Using numerical simulation and the Monte Carlo method, the organic polymer substrate was dimensionlessly transformed into a 1×1 square. Inorganic fillers were randomly filled into the organic polymer substrate. The anisotropy of the inorganic fillers was set through numerical simulation, and boundary conditions were applied. Fillers exceeding the region along the direction of heat conduction were truncated, and fillers exceeding the region perpendicular to the direction of heat conduction were truncated and periodically translated into the square. The percolation threshold of the inorganic fillers when electropercolation occurs within the system can be obtained through numerical model calculation. For electrical transport, the conductivity of the inorganic fillers, the interfacial resistance between fillers, the filler-matrix interfacial resistance, and the conductivity of the organic polymer matrix were assigned. A resistance network based on the filler conduction network was constructed, and Kirchhoff's current law was used to solve for the network node potential and branch current, thereby calculating the conductivity of the composite system. For thermal transport, the thermal conductivity of the organic polymer matrix and the axial thermal conductivity κ of the inorganic fillers were assigned. l Radial thermal conductivity κ d The thermal conductivity at the filler-filler interface and the filler-matrix interface was investigated. A steady-state thermal conduction model was established using the finite element method. Temperature difference boundary conditions were applied at both ends of the heat conduction direction to solve the temperature field and heat flow field of the composite system, and then the effective thermal conductivity of the composite system was calculated. Figure 3As shown, the direction of heat conduction is defined as transmission along the X-axis. When the volume fraction of the inorganic filler Ni nanowire is 20% and the anisotropy is 100 or higher, organic-inorganic composite thermoelectric materials based on the anisotropy of the filler's thermal conductivity can be successfully designed. In this case, the thermal conductivity range of the composite thermoelectric material is 2.5–3 W / m². -1 K -1 . Figure 4 The volume fraction of the filler The relationship between aspect ratio and anisotropy at an aspect ratio of 0.2 is intuitively shown: as the aspect ratio increases, the thermal conductivity of the composite system increases; however, at the same aspect ratio, as the degree of anisotropy increases, the thermal conductivity of the composite system decreases. For example, with an aspect ratio of l... Ni When / d=20, and the anisotropy is 100 or higher, the thermal conductivity of the composite system can successfully reach the range of 2.5–3 W / m². -1 K -1 .

[0047] The present invention, by controlling parameters such as the material, aspect ratio, anisotropy, and volume fraction of the inorganic filler within the organic polymer matrix, aims to suppress the thermal conductivity of the composite system, thus achieving the design of a composite thermoelectric material with enhanced electrical transport but suppressed thermal transport. Compared to existing thermoelectric materials, this invention, while ensuring the formation of a continuous electronic conduction network, adjusts the difference between the axial and radial thermal conductivity of the filler. This restricts the propagation of heat flow in the filler skeleton, matrix, and extended network through a synergistic axial / radial bottleneck, thereby suppressing the simultaneous increase in effective thermal conductivity, improving the electrical-to-thermal conductivity ratio of the composite system, and providing conditions for enhancing the thermoelectric figure of merit. The designed composite thermoelectric material is composed of anisotropic inorganic filler and an organic polymer matrix, possessing excellent flexibility and ductility, adaptable to more complex working environments. Its lightweight and bendable properties make it a promising candidate for wearable electronic devices.

[0048] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as defined by the appended claims and their equivalents.

Claims

1. A design method for organic-inorganic composite thermoelectric materials based on the degree of anisotropy of filler thermal conductivity, characterized in that: The organic-inorganic composite thermoelectric material comprises an organic polymer matrix and an inorganic filler filled in the matrix, wherein the inorganic filler has an axial thermal conductivity κ. l and radial thermal conductivity is κ d , and κ l and κ d They vary; the degree of anisotropy of the thermal conductivity of the inorganic filler is determined by C=κ. l / κ d Or C=κ d / κ l Definition; the design method includes the following steps: Step 1: Add inorganic fillers to an organic polymer substrate and use numerical simulation to randomly disperse the fillers in the substrate to obtain a mixed system of inorganic fillers and organic polymer materials. Step 2: Using numerical simulation, the anisotropy of the thermal conductivity of the inorganic filler inside the mixture designed in Step 1 is controlled. Step 3: Based on the hybrid system obtained in Step 2, model the electrical and thermal transport of the hybrid system separately. Electrical transport is solved using a resistance network algorithm based on the packing conductive network. Thermal transport is modeled using the finite element method to establish a steady-state heat conduction model. The temperature and heat flow fields are solved by combining the thermal conductivity of the matrix, the axial thermal conductivity of the packing, the radial thermal conductivity of the packing, the thermal conductivity at the packing-packing interface, and the thermal conductivity at the packing-matrix interface. Based on this, the effective thermal conductivity of the composite system is calculated. Based on the calculated electrical and thermal conductivity, one or more design parameters are adjusted, including the material, aspect ratio, anisotropy, and volume fraction of the filler in the organic polymer matrix, of the internal inorganic filler. When the thermal conductivity of the mixed system, calculated by numerical simulation, is controlled within the range of 2.5–3 W / m², the desired effect is achieved. -1 K -1 The conductivity was controlled at 1.53 × 10⁻⁶. 5 ~1.98×10 6 When S / m, the design of organic-inorganic composite thermoelectric material is completed.

2. The design method for organic-inorganic composite thermoelectric materials based on the degree of anisotropy of filler thermal conductivity according to claim 1, characterized in that: In step one, the inorganic filler is one or a combination of two of the following: metallic materials and porous crystalline materials. The metallic materials are selected from one or more of the following: nickel (Ni), cobalt (Co), iron (Fe), gadolinium (Gd), dysprosium (Dy), and manganese (Mn). The porous crystalline materials are selected from one or a mixture of one or more of the following: AFI type aluminum phosphate molecular sieve AlPO4-5, AEL type aluminum phosphate molecular sieve AlPO4-11, LTL type zeolite molecular sieve, MFI type zeolite molecular sieve, and VFI type aluminum phosphate molecular sieve VPI-5.

3. The design method for organic-inorganic composite thermoelectric materials based on the degree of anisotropy of filler thermal conductivity according to claim 1, characterized in that: In step one, the inorganic filler is in one of the following shapes: rod-shaped, wire-shaped, fibrous, or nanowire-shaped.

4. The design method for organic-inorganic composite thermoelectric materials based on the degree of anisotropy of filler thermal conductivity according to claim 1, characterized in that: In step one, the length of the inorganic packing is designed to be in the range of 0.05 to 1000 micrometers, and the diameter is designed to be in the range of 0.001 to 200 micrometers.

5. The design method for organic-inorganic composite thermoelectric materials based on the degree of anisotropy of filler thermal conductivity according to claim 1, characterized in that: In step one, the inorganic filler accounts for 5% to 70% of the volume percentage in the composite thermoelectric material.

6. The design method for organic-inorganic composite thermoelectric materials based on the degree of anisotropy of filler thermal conductivity according to claim 1, characterized in that: In step one, the organic polymer matrix is ​​one or more of epoxy resin, polylactide, polyvinylidene fluoride, vinyl silicone oil, polyurethane, polydimethylsiloxane, polybenzoxazine, polyimide, silicone resin, polycarbonate or polyacrylate.

7. The design method for organic-inorganic composite thermoelectric materials based on the degree of anisotropy of filler thermal conductivity according to claim 1, characterized in that: In step three, the thermal conductivity tensor of the inorganic filler in the local coordinate system is composed of axial thermal conductivity and radial thermal conductivity, and is mapped to the global coordinate system after coordinate rotation transformation according to the filler orientation angle.

8. The design method for organic-inorganic composite thermoelectric materials based on the degree of anisotropy of filler thermal conductivity according to claim 1, characterized in that: In step three, the electrical conductivity of the composite system is solved using a resistance network algorithm combined with Kirchhoff's current law; the thermal conductivity of the composite system is solved using the finite element method. A steady-state heat conduction model is established within the computational domain containing the organic polymer matrix and the inorganic filler. An anisotropic thermal conductivity tensor is constructed based on the axial and radial thermal conductivity of the inorganic filler. The temperature field and heat flow field of the composite system are solved by combining the thermal conductivity at the filler-filler interface, the thermal conductivity at the filler-matrix interface, and the thermal conductivity of the matrix, thereby obtaining the effective thermal conductivity of the composite system.

9. The design method for organic-inorganic composite thermoelectric materials based on the degree of anisotropy of filler thermal conductivity according to claim 1, characterized in that: In step three, numerical simulation calculations are performed to determine the thermal conductivity of the composite thermoelectric material within the range of 2.5–3 W / m². -1 K -1 The conductivity is controlled within the range of 1.53 × 10⁻⁶. 5 ~1.98×10 6 When S / m, the design of organic-inorganic composite thermoelectric materials based on the degree of anisotropy of the filler is completed.

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