High-extension flexible electrode and preparation method thereof

Abstract

The invention discloses a high-extension flexible electrode and a preparation method thereof, and relates to the field of electric heating conductive materials. The preparation method comprises the following steps: firstly, uniformly pre-stretching a metal base material at room temperature, then placing the metal base material in a vacuum or low-oxygen inert gas protective atmosphere for heating and heat preservation, and then cooling; punching the treated base material to form an initial hole array, and performing two-way stretching at the speed of 1-5mm / s to form a periodic grid; and finally, flattening under the pressure of 5-15MPa, so that the surface flatness tolerance of the electrode is less than or equal to + / -10 microns. The electrode prepared by the method adopts a rhombic or hexagonal periodic grid structure, has high elongation, excellent conductivity, stable interface bonding capacity and low cycle resistance change rate, can adapt to high-elongation production processes such as mould pressing and hot pressing, and effectively solves the problem of performance weakness of a traditional electrode in a complex deformation scene.

Description

Technical Field

[0001] This invention belongs to the field of electric heating conductive materials technology, specifically relating to a highly elongated flexible electrode suitable for molding processes and its preparation method. Background Technology

[0002] With the rapid development of flexible electronics technology, products such as electric heating elements, wearable devices, and flexible sensors are gradually becoming industrialized. These products often need to undergo large deformation production processes such as molding and hot pressing, and must maintain stable conductivity and mechanical reliability during long-term use, which places stringent requirements on electrode materials.

[0003] Currently available electrode materials mainly include paste-type electrodes such as copper paste and silver paste, metal foil electrodes such as copper foil, and conductive polymer electrodes. However, all of these materials have significant drawbacks. While paste-type electrodes possess a certain degree of flexibility, their conductivity is poor, with a volume resistivity typically greater than 10 Ω·cm. -5 The maximum elongation is generally less than 10%, and silver paste also has the problem of high cost; metal foil electrodes have excellent conductivity, but extremely low elongation, usually less than 5%, which cannot adapt to complex deformation scenarios; conductive polymer electrodes face the dual dilemma of high cost and insufficient conductivity.

[0004] Besides the limitations of the materials themselves, the structural design of traditional electrodes also has flaws. Planar electrodes are prone to stress concentration during molding, leading to fracture and causing localized failure or poor contact in the heating element. Simultaneously, the interfacial bonding strength between the electrode and the substrate is low, and delamination easily occurs after repeated deformation. In terms of process adaptability, existing electrodes struggle to meet the requirements of high-elongation production processes such as molding and hot pressing. During three-dimensional molding, their conductive network is easily damaged, failing to maintain structural integrity. Furthermore, repeated stretching or bending can cause the interface between the electrode and the heating material to fail, leading not only to a sharp increase in resistance but also severely impacting the long-term stability of the product, and even causing uneven heating and localized failure. This makes it difficult to meet the high cycle life and low resistance change rate requirements of products such as smart knee braces and automotive seat heating pads.

[0005] Therefore, developing an electrode that can be adapted to high elongation production processes and has excellent conductivity, high elongation, stable interfacial bonding ability and low cyclic resistance change rate has become an urgent technical problem to be solved in the field of flexible electronics. Summary of the Invention

[0006] To address the shortcomings of the prior art, a highly elongated flexible electrode suitable for molding processes and its fabrication method are provided.

[0007] To achieve the above objectives, the following technical solution is adopted: This invention provides a method for preparing a highly elongated flexible electrode, comprising the following steps: S101. Perform uniform pre-stretching of the metal substrate at room temperature; S102. The pre-stretched metal substrate is heated and kept at a constant temperature in a vacuum or protective atmosphere, and then cooled before being removed from the furnace; S103. Punch holes in the metal substrate after step S102 to form a regular initial hole array; then stretch the metal substrate with the initial hole array in both the warp and weft directions at a rate of 1-5 mm / s, with the warp stretching ratio controlled at 1.5-3.0 and the weft stretching ratio controlled at 1.1-1.5, to form an electrode with a periodic grid. S104. Flatten the electrode with a periodic grid.

[0008] In some embodiments, the metal substrate in step S101 is a metal plate of oxygen-free copper, red copper, or high-strength copper alloy with a thickness of 0.1-0.3 mm; the shape of the periodic grid of the electrode in step S103 is a rhombic or hexagonal grid.

[0009] In some embodiments, in step S101, pre-stretching is to uniformly stretch the metal substrate in both the warp and weft directions at room temperature, wherein the stretching length is 5%-8% of the length of the metal substrate in both the warp and weft directions.

[0010] In some embodiments, in step S102, the protective atmosphere is an inert gas with an oxygen content of <10ppm; the inert gas is helium or nitrogen.

[0011] In some embodiments, the heating and heat preservation process in step S102 is as follows: the pre-stretched metal substrate is heated to 200–250°C at a heating rate of 3–5°C / min and then kept at that temperature for 45–70 minutes.

[0012] In some embodiments, in step S104, an electrode with a periodic grid is flattened using a pressure of 5-15 MPa, so that the surface flatness tolerance of the electrode is ≤ ±10 μm.

[0013] In some embodiments, in step S102, the metal substrate is kept at a temperature of 0.1 mm for 45 minutes; the metal substrate is kept at a temperature of 0.2 mm for 55 minutes; and the metal substrate is kept at a temperature of 0.3 mm for 60-70 minutes.

[0014] The present invention also provides a highly elongated flexible electrode, which is prepared according to the method described above; the electrode is an electrode with a periodic grid, the grid size being in the range of 0.5 mm × 1 mm to 10 mm × 20 mm, and the cross-sectional area of ​​each strip in the grid being 0.01–0.1 mm². 2.

[0015] The present invention also provides an electric heating element, which is made by integrating a highly elongated flexible electrode as described above into a heating substrate.

[0016] In some embodiments, the electrodes are integrated into the heating substrate by means of sewing or hot-pressing embedding.

[0017] The present invention has the following beneficial technical effects: The high-elongation flexible electrode and its preparation method disclosed in this invention optimize the microstructure of the metal substrate and release internal stress through a pretreatment process of room temperature pre-stretching followed by heating and heat preservation. Then, through a continuous process of punching, precise bidirectional stretching (rate 1-5 mm / s, warp stretching ratio 1.5-3.0, weft stretching ratio 1.1-1.5), and flattening, it can not only form a uniform and complete periodic grid, fully retaining the high conductivity of the metal substrate, but also significantly improve the electrode elongation by means of deformation absorption mechanism of grid node rotation and grid bending. It is suitable for high elongation production processes such as molding and hot pressing and complex deformation scenarios. At the same time, the flattening step eliminates the surface warping defects of the electrode, enhances the adhesion and interface bonding stability with the heating substrate, avoids delamination problems after repeated deformation, and the electrode formed by the overall process has good mechanical durability. The conductive network is not easy to fail during long-term stretching and release cycles, and the resistance change rate remains at a low level. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a flowchart of the method for preparing the highly elongated flexible electrode of the present invention; Figure 2 This is a schematic diagram of the periodic grid of electrodes according to an embodiment of the present invention; Figure 3 The electrode configuration is shown in the embodiment of the present invention; Figure 4 The electrode configuration is shown in the embodiment of the present invention; Figure 5 This is an embodiment of the electrode embedding method of the present invention; Figure 6 Material deformation and electrode stretching after molding, as described in an embodiment of the present invention; Figure 7 The lateral deformation of the electrode after molding is shown in an embodiment of the present invention.

[0020] List of reference numerals in the attached diagram: 1-Electrode; 2-Heating substrate; 3-Mold cavity. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0022] It should be understood that the embodiments of the invention shown in the exemplary embodiments are merely illustrative. Although only a few embodiments have been described in detail in this invention, those skilled in the art will readily recognize that various modifications are possible without substantially departing from the teachings of the invention. Accordingly, all such modifications should be included within the scope of the invention. Other substitutions, modifications, variations, and deletions can be made to the design, operating conditions, and parameters of the following exemplary embodiments without departing from the spirit of the invention.

[0023] Based on the above objectives, a first aspect of the embodiments of the present invention proposes a method for preparing a highly elongated flexible electrode suitable for molding processes.

[0024] like Figure 1 As shown, the preparation method may include the following steps: S101. Perform uniform pre-stretching of the metal substrate at room temperature; S102. The pre-stretched metal substrate is heated and kept at a constant temperature in a vacuum or protective atmosphere, and then cooled before being removed from the furnace; S103. Punch holes in the metal substrate after step S102 to form a regular initial hole array; then stretch the metal substrate with the initial hole array in both the warp and weft directions at a rate of 1-5 mm / s, with the warp stretching ratio controlled at 1.5-3.0 and the weft stretching ratio controlled at 1.1-1.5, to form an electrode with a periodic grid. S104. Flatten the electrode with a periodic grid.

[0025] In a preferred embodiment of the present invention, the metal substrate in step S101 is oxygen-free copper (TU1), pure copper (T2), or a high-strength copper alloy, with a thickness of 0.1-0.3 mm. The high-strength copper alloy can be beryllium copper alloy (beryllium content range: 1.6%~2.7%; grade such as national standard TU1 type high beryllium copper) or phosphorus copper alloy (usually containing 0.03wt%-0.35wt% phosphorus). The oxygen-free copper (TU1), pure copper (T2), or high-strength copper alloy is a high-purity, high-ductility conductive metal with a conductivity ≥58MS / m (corresponding to a resistivity ≤1.72×10⁻⁶). -8(Ω·m), single filament elongation >30%. Metal substrates with such properties lay the foundation for electrodes to achieve low initial resistance and high mechanical properties.

[0026] In a preferred embodiment of the present invention, the periodic grid of the electrode in step S103 is a rhombic or hexagonal grid. The rhombic grid of electrode 1 is as follows: Figure 3 As shown, the hexagonal grid of electrode 1 has the following shape: Figure 4 As shown.

[0027] In a preferred embodiment of the present invention, in step S101, the pre-stretching is to uniformly stretch the metal substrate in both the warp and weft directions at room temperature, wherein the stretching length is 5%-8% of the length of the metal substrate in both the warp and weft directions.

[0028] The sequence of "light pre-stretching followed by annealing" yields better overall performance. The dislocations introduced by pre-deformation become recrystallization nucleation sites during subsequent annealing, promoting the formation of fine, uniform equiaxed grains.

[0029] The copper sheet obtained by annealing followed by 5% pre-stretching has an elongation of approximately 32% and a resistivity of 1.68 × 10⁻⁶. -8 Ω·m. Copper sheets pre-stretched by 5% followed by annealing can achieve an elongation of 38-40% and a resistivity of 1.65 × 10⁻⁶ Ω·m. -8 Ω·m, and the strength is slightly improved.

[0030] In a preferred embodiment of the present invention, in step S102, the protective atmosphere is an inert gas with an oxygen content of <10 ppm; the inert gas is helium or nitrogen. The heating and holding process in step S102 is as follows: the pre-stretched metal substrate is heated to 200–250°C at a heating rate of 3-5°C / min and held at that temperature for 45-70 minutes. This step aims to optimize the microstructure of the copper material through atomic-level lattice control. The heating rate is controlled at 3-5°C / min to avoid thermal stress.

[0031] In a preferred embodiment of the present invention, the heat preservation time is adjusted according to the thickness: in step S102, the heat preservation time is 45 minutes when the thickness of the metal substrate is 0.1 mm; 55 minutes when the thickness of the metal substrate is 0.2 mm; and 60-70 minutes when the thickness of the metal substrate is 0.3 mm.

[0032] In a preferred embodiment of the present invention, in step S102, after the heat preservation is completed, the furnace is cooled to below 50°C and then removed from the furnace.

[0033] In a preferred embodiment of the invention, in step S103, the punched substrate is fixed to a biaxial tensile testing machine. Simultaneous or stepwise biaxial stretching is performed at a low rate (1-5 mm / s). The stretch ratio (final size / initial size) is a key parameter: the warp stretch ratio is controlled between 1.5 and 3.0, and the weft stretch ratio is controlled between 1.1 and 1.5. This parameter range ensures that the mesh uniformly deforms into a rhombus / hexagon and forms flexible "micro-hinges" at the nodes, while avoiding mesh tearing. For example, to obtain a 1 mm × 2 mm mesh, the initial mesh array may be stretched with a warp stretch ratio of 2.5 and a weft stretch ratio of 1.2.

[0034] In some embodiments, in step S104, an electrode with a periodic grid is flattened using a pressure of 5-15 MPa, so that the surface flatness tolerance of the electrode is ≤ ±10 μm.

[0035] Specifically, slight warping may occur at the nodes of the stretched mesh electrode. A precision roller with adjustable pressure is used to flatten it, with the pressure range set between 5-15 MPa. After flattening, the surface flatness tolerance of the electrode should be controlled within ±10 μm to ensure perfect adhesion to the heating material.

[0036] A second aspect of the present invention provides a highly elongated flexible electrode suitable for molding processes, prepared according to the method described above; the electrode is an electrode with a periodic grid, the grid size ranging from 0.5 mm × 1 mm to 10 mm × 20 mm, and the cross-sectional area of ​​each strip in the grid is 0.01-0.1 mm². 2 .

[0037] The basic mesh configuration is a periodic rhombic or hexagonal mesh. When stretched, the mesh nodes can rotate and the mesh wires bend instead of being simply stretched, thus converting macroscopic strain into local bending strain and significantly reducing the effective modulus.

[0038] To accommodate deformation requirements in different directions during practical applications, asymmetrical designs are implemented for the warp (main stretching direction) and weft directions. Different theoretical elongation rates are achieved by designing different mesh sizes. The theoretical elongation rate (ε) is geometrically related to the initial mesh length (L0) and the wire side length (a) as follows: ε ≈ (L-L0) / L0, where the stretched length L is related to the change in mesh geometry. For a rhomboid mesh, when the stretching direction coincides with the mesh diagonal, the theoretical elongation rate can be approximated as: ε_theoretical≈√((a×sinθ)). 2 +(2a×cosθ+Δ) 2 ) / (2a×cosθ)-1 (where θ is the included angle of the mesh strips and Δ is the nodal displacement). The initial mesh length (L0) is the length in the stretching direction.

[0039] A metal substrate with an initial array of holes is bidirectionally stretched in both the warp and weft directions at a rate of 1-5 mm / s, with the warp stretch ratio controlled at 1.5-3.0 and the weft stretch ratio controlled at 1.1-1.5, forming an electrode with a periodic grid. The main stretching direction (warp direction, i.e.,...) Figure 2 The mesh size (e.g., in the meridional spacing direction of electrode 1) of the electrode shown. Figure 2 The longitudinal spacing of electrode 1 shown is much smaller than that in the latitudinal direction (i.e., the latitudinal direction). Figure 2 Mesh size (as shown in the latitudinal spacing direction) Figure 2 (The weft spacing is shown). For example, if the designed mesh size is 1mm (warp spacing) × 2mm (weft spacing), the theoretical elongation in the warp direction is ≥120%, and the theoretical elongation in the weft direction is ≥10%. The mesh size can be adjusted within the range of 0.5mm × 1mm to 10mm × 20mm.

[0040] The maximum safe deformation that an electrode can withstand (without plastic yielding or fracture) is directly related to the mesh size and the diameter of the copper wire.

[0041] Define the aspect ratio of the mesh (R=L) 经向 / L 纬向 The mesh size (d) and the wire diameter (d) are given. For a given wire diameter, there exists an optimal range of mesh sizes to maximize stretchability.

[0042] For copper wire with d=0.05mm, the recommended relationships are shown in the table below:

[0043] In a preferred embodiment of the present invention, for non-uniform deformation devices, in addition to using a rhombic or hexagonal periodic grid as the basic grid configuration, the electrodes are also designed with different grid densities in different regions. For example, larger mesh sizes (low density) are used in regions where large deformation is expected (such as the right side of a curved surface), while smaller mesh sizes (high density) are used in regions where small deformation or low resistance is required (such as the left side). These different mesh densities can be designed during the punching of the metal substrate and then combined with subsequent biaxial stretching. Specifically, different mesh densities are punched at different densities during punching, and the stretching is performed to different degrees as required. The size and position of the punching determine the size, position, and shape of the hole after stretching. Different mesh densities can be achieved by using a "gradual transition zone" design to prevent stress concentration in areas of abrupt density changes: a transition zone with a length of 5-10 mesh openings is set between high and low density regions, where the mesh size gradually changes linearly or non-linearly, thereby smoothly dispersing stress and preventing fracture.

[0044] The cross-sectional area of ​​each strip (i.e., each copper wire) in the mesh is fixed (design range 0.01–0.1 mm).2 The total cross-sectional area and current carrying capacity of the electrodes can be flexibly adjusted by changing the number of copper wires per unit width (i.e., the mesh density) to meet different power requirements.

[0045] A third aspect of the present invention also provides an electric heating element made by integrating a highly elongated flexible electrode suitable for molding processes as described above into a heating substrate.

[0046] In a preferred embodiment of the present invention, the electrodes are integrated into the heating substrate by means of sewing or hot pressing embedding.

[0047] Figure 5 The manner and location of electrode 1 being embedded into heating substrate 2 are shown.

[0048] The heating substrate is an ultrathin, flexible substrate (such as a carbon nanotube membrane). The electrodes are integrated into the heating substrate via sewing: using a tension-controlled sewing machine, copper mesh strips are sewn along a designed path onto the substrate surface or its supporting fabric. The sewing tension is strictly controlled at 3-5N to avoid pre-stretching the electrodes. Subsequently, integration is achieved through low-temperature hot pressing or adhesive bonding.

[0049] The heating substrate is a heating material with a certain thickness and fluidity (such as graphene / polymer composites, carbon fiber felt). Electrodes are integrated into the heating substrate using hot-press embedding: Process parameters: Hot-pressing temperature is set according to the melting point of the substrate, typically between 120-180°C; pressure is 2-10 MPa; holding time is 30-90 seconds. For example, for silicone-based graphene heating elements, parameters of 150°C, 5 MPa, and 60 seconds can be used. Mold optimization: To prevent uneven electrode embedding depth, a mold with a gradient temperature field is used: the temperature in the center of the cavity is slightly higher than the edge area (temperature difference of approximately 5-10°C), allowing the substrate melt to solidify sequentially from the center to the edge, uniformly "wrapping" the electrode and expelling air. Simultaneously, the mold cavity depth is designed to be 50%-70% of the electrode wire diameter to control the embedding depth. Figure 6 The diagram illustrates the material deformation and electrode stretching after molding. It shows mold cavity 3, where the material with electrodes is molded through the cavity. The electrodes adapt to the material's deformation through their own deformation, maintaining conductivity. During molding, the mesh of the electrodes can adapt to the rotation and deformation of the substrate's three-dimensional curved surface, achieving conformal bonding. This technology ensures that even after pre-stretching, the electrode's resistance change rate is extremely small (target <5%) after the device is finally formed.

[0050] Figure 7 In the case of lateral deformation of the electrode after molding according to an embodiment of the present invention, the mold may exhibit a large difference in deformation between the left and right sides (such as an arc surface). If a conventional mesh design is used, one side may undergo excessive deformation, which may lead to breakage or thinning, affecting conductivity.

[0051] The present invention will be further illustrated by the following examples.

[0052] Example 1 Material: 0.1mm thick oxygen-free copper plate.

[0053] Preparation method: First, the oxygen-free copper plate is pre-stretched, with a stretching length of 5% of the length of the oxygen-free copper plate in both the warp and weft directions. Then, under nitrogen protection, the temperature is raised to 250℃ at 5℃ / min, held for 60 minutes, and then furnace cooled. Subsequently, holes are punched, and the plate is stretched at a rate of 2mm / s on a biaxial stretching machine (warp stretching ratio of 2.8 and weft stretching ratio of 1.15) to form a 1mm×2mm diamond mesh. Each unit width in the warp direction contains 6 copper wires (wire diameter of approximately 0.04mm), thus obtaining a flexible electrode.

[0054] Flexible electrode performance testing: Morphology: The mesh is uniform and the nodes are smooth hinge-like.

[0055] Mechanical properties: Samples were prepared according to ASTM E8 standard, with a tensile rate of 50 mm / min. Measured average elongation at break: 112% in the warp direction and 25% in the weft direction.

[0056] Electrical performance: Measurements were taken at 25°C constant temperature using a four-probe method, with one test point every 5 cm on the electrode (10 points in total). Average resistivity ≤ 1.67 × 10⁻⁶ -8 Ω·m.

[0057] Strain-resistance relationship: Resistance was measured simultaneously on a tensile testing machine. Results: When stretched by 30%, the resistance change rate was +1.8%; when stretched by 50%, +3.1%; when stretched by 80%, +4.5%; and when stretched by 100%, +5.8% (still lower than the traditional structure).

[0058] Cycle life: 10,000 tensile-release cycles (strain amplitude 30%) were performed. The rate of change of resistance was less than ±2% throughout the cycle. Cyclic voltammetry (CV) testing showed that after 10,000 mechanical cycles at a scan rate of 100 mV / s, the electrochemical active area of ​​the electrode decreased by less than 5%, indicating that its structure was stable and no obvious fatigue or fracture occurred.

[0059] Interfacial bonding strength: After the flexible electrode was hot-pressed into the graphene / silicone heating pad, a 90° peel test (ASTM D3330) was performed. The bonding strength reached 1.8 N / cm, and the failure mode was cohesive failure of the substrate rather than interfacial delamination.

[0060] Application: Used in intelligent knee pad heating pads, conforming to human joint movement, with dynamic resistance change <3%.

[0061] Example 2 Material: 0.15mm thick phosphor bronze alloy plate.

[0062] Preparation method: First, the phosphor bronze alloy plate is pre-stretched, with a stretching length of 7% of the total length of the phosphor bronze alloy plate in both the warp and weft directions. Then, under nitrogen protection, the temperature is increased to 230℃ at a rate of 3℃ / min, held for 50 minutes, and then furnace cooled. Next, holes are punched. During punching, the final electrode mesh density is designed, with a high conductivity area on the left side (0.8mm × 1.6mm mesh), a large deformation area on the right side (2.0mm × 4.0mm mesh), and a gradual transition zone with 8 mesh lengths in the middle. Subsequent processes are the same as in Example 1 to obtain a flexible electrode.

[0063] Application: Hot-pressed embedding of carbon fiber fabric heating pads for automotive seats. During the simulated seat surface forming process (complex three-dimensional stretching), the resistance uniformity (overall electrode resistance difference) is better than 5%, and there are no breaks in the transition zone.

[0064] The performance testing of the flexible electrode was the same as in Example 1.

[0065] The performance results of the electrodes in Examples 1-2 and the prior art are shown in Table 1.

[0066] Table 1. Performance of electrodes from Examples 1-2 and prior art

[0067] As shown in Table 1, the electrodes of Examples 1-2 exhibit significant performance advantages compared to prior art electrodes: Elongation capability: Maximum elongation rate >100%, far exceeding traditional copper foil electrodes (<5%), printed silver paste electrodes (<15%), and also significantly better than ordinary metal mesh (40-60%), which can fully adapt to high elongation production processes such as molding and hot pressing; Electrical conductivity: resistivity ≤ 1.7 × 10⁻⁶ -8 Ω m, comparable to traditional copper foil electrodes, far superior to printed silver paste electrodes (~5×10 m). -6 Ω (m), and is slightly better than ordinary metal mesh; Stability and durability: Extremely low resistance strain sensitivity, avoiding the problem of sudden resistance change after deformation of traditional electrodes; cycle life > 10,000 times, which is more than 5 times that of ordinary metal mesh and 100 times that of traditional copper foil electrodes, and can withstand repeated deformation for a long time. The electrodes of Examples 1-2 not only avoid the "extremely high" cost of printed silver paste electrodes, but also maintain economic applicability while having performance far exceeding that of traditional copper foil electrodes.

[0068] The flexible electrode structure prepared in this embodiment of the invention employs a multi-level mesh topology and a gradient design approach, optimizing the density design along the warp and weft directions and the edge density variation to achieve a synergistic improvement in conductivity, elongation, and mechanical properties. In terms of manufacturing, a pre-annealing process is used in conjunction with a precision stamping-stretching synergistic process. It is also suitable for roll-to-roll continuous production processes, significantly improving processing efficiency. In terms of applications, it is adaptable to various integration schemes and can also utilize dynamic bonding technology to achieve diversified applications, while maintaining low material and process costs.

[0069] The above are exemplary embodiments disclosed in this invention. However, it should be noted that various changes and modifications can be made without departing from the scope of the embodiments of this invention as defined by the claims. Although the elements disclosed in the embodiments of this invention may be described or claimed individually, they may be understood as multiple unless explicitly limited to a singular number.

[0070] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of different aspects of the invention exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for preparing a highly elongated flexible electrode, characterized in that, Includes the following steps: S101. Perform uniform pre-stretching of the metal substrate at room temperature; S102. The pre-stretched metal substrate is heated and kept at a constant temperature in a vacuum or protective atmosphere, and then cooled before being removed from the furnace; S103. Punch holes in the metal substrate after step S102 to form an initial hole array; then stretch the metal substrate with the initial hole array in both the warp and weft directions at a rate of 1-5 mm / s, with the warp stretching ratio controlled at 1.5-3.0 and the weft stretching ratio controlled at 1.1-1.5, to form an electrode with a periodic grid. S104. Flatten the electrode with a periodic grid.

2. The preparation method according to claim 1, characterized in that, The metal substrate mentioned in step S101 is a metal plate of oxygen-free copper, red copper or high-strength copper alloy, with a thickness of 0.1-0.3 mm; the shape of the periodic grid of the electrode in step S103 is a rhombic or hexagonal grid.

3. The preparation method according to claim 1, characterized in that, In step S101, pre-stretching is the uniform stretching of the metal substrate in both the warp and weft directions at room temperature, wherein the stretching length is 5%-8% of the length of the metal substrate in both the warp and weft directions.

4. The preparation method according to claim 1, characterized in that, In step S102, the protective atmosphere is an inert gas with an oxygen content of <10ppm; the inert gas is helium or nitrogen.

5. The preparation method according to claim 2, characterized in that, The heating and heat preservation process in step S102 is as follows: the pre-stretched metal substrate is heated to 200–250°C at a heating rate of 3-5°C / min and then kept at that temperature for 45-70 minutes.

6. The preparation method according to claim 1, characterized in that, In step S104, the electrode with a periodic grid is flattened using a pressure of 5-15 MPa to make the surface flatness tolerance of the electrode ≤ ±10 μm.

7. The preparation method according to claim 5, characterized in that, In step S102, the metal substrate is kept at a temperature of 0.1 mm for 45 minutes; the metal substrate is kept at a temperature of 0.2 mm for 55 minutes; and the metal substrate is kept at a temperature of 0.3 mm for 60-70 minutes.

8. A highly elongated flexible electrode, characterized in that, The electrode is prepared using the method according to any one of claims 1-7; the electrode is an electrode with a periodic grid, the grid size being in the range of 0.5 mm × 1 mm to 10 mm × 20 mm, and the cross-sectional area of ​​each strip in the grid being 0.01-0.1 mm². 2 .

9. An electric heating element, characterized in that, It is made by integrating the highly elongated flexible electrode as described in claim 8 into a heating substrate.

10. The electric heating element according to claim 9, characterized in that, The electrodes are integrated into the heating substrate by either sewing or hot-pressing embedding.

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