Stretchable composite conductor material with high conductivity and wide electrochemical window and preparation method thereof

Abstract

The invention discloses a high-conductivity and wide-electrochemical-window stretchable composite conductor material and a preparation method thereof.The preparation method comprises the steps that metal particles such as silver nanowires and carbon-based particles such as carbon nanotubes or graphene oxide are adopted to construct a composite electrode, a conductive layer is constructed on a flexible substrate through a spraying technology, and wet etching and heat treatment processes are combined to prepare the high-conductivity and wide-electrochemical-window stretchable composite conductor material. A conductive network with interpenetrating silver nanowires and a carbon-based material is formed in the electrode, and meanwhile, an all-carbon protection layer is formed on the surface of the electrode. The prepared composite conductor shows excellent comprehensive performance, compared with the prior art, through unique structural design and process optimization, the technical problem that a stretchable conductor material is difficult to consider high conductivity and wide electrochemical window at the same time is successfully solved, and the composite conductor is simple in preparation process, low in cost and suitable for industrial production. The method is suitable for large-scale manufacturing of flexible electronic devices.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible electronic devices, and in particular relates to a highly conductive and wide electrochemical window stretchable composite conductor material and a preparation method thereof. Background Art

[0002] In recent years, wearable electronic technology has made significant progress in the fields of human-computer interaction, health monitoring, and virtual reality, and has gradually achieved commercial applications, showing huge market potential. As a key material supporting the new generation of flexible electronic devices, stretchable conductors play a vital role in improving the flexibility of the equipment. Such materials not only need to have excellent mechanical flexibility to achieve a perfect fit with the curves of the human body, but more importantly, they must be able to maintain stable high conductivity under dynamic deformation conditions (such as stretching, bending, torsion, etc.), thereby ensuring the reliability and durability of electronic devices in various complex usage scenarios. Therefore, the development of stretchable conductor materials with both high conductivity and excellent mechanical properties has become a key breakthrough in promoting the development of flexible electronic technology.

[0003] Currently, the realization of stretchable conductors relies primarily on two technical approaches: structural design and composite materials. The structural design approach uses micro-nanofabrication techniques to fabricate traditional conductive materials, such as metal films, into specialized structures such as serpentine lines and island bridges (CN118356196A, CN101681695A). While this engineering-based approach offers the advantage of a wide range of materials, it suffers from two significant limitations: first, specialized structural designs significantly increase the space occupied by the conductor, reducing device integration; second, the complex micro-nanofabrication processes lead to high production costs. In contrast, the composite material approach achieves stretchability through material microstructural design. This approach uniformly disperses micro- and nanoscale conductive fillers, such as carbon-based materials, metal particles, and nanowires, in an elastic polymer matrix, utilizing the interconnected interconnections between the conductive particles to form a stable three-dimensional conductive network. This design imparts intrinsic stretchability and high conductivity to the material. Furthermore, composite materials can be directly patterned using solution processing techniques such as printing and spray coating, providing a simple and efficient fabrication route for the construction of functional electrodes and devices.

[0004] Electrochemical stability is one of the key performance indicators of stretchable composite conductor materials. This property is mainly characterized by the electrochemical window, that is, the potential range in which the material does not undergo redox reactions in an electrolyte environment. A wider electrochemical window means that the material can remain stable under more harsh electrochemical environments, which is particularly critical for two important application areas: first, in implantable devices in the body, the material needs to withstand the complex electrochemical environment of biological fluids for a long time; second, in electrochemical energy storage devices such as supercapacitors and flexible batteries, the material must maintain structural integrity and functional stability during the charge and discharge process. Therefore, the development of stretchable conductor materials with a wide electrochemical window has become an important research direction in this field.

[0005] In terms of specific material selection, carbon-based materials, such as graphene, carbon nanotubes, and carbon black, are widely used to prepare composite stretchable conductor materials (CN109354009A, CN110203916A, CN114854202A, CN104282444A, CN106883610A, etc.). They are widely used in the field of bioelectronics due to their excellent electrochemical stability and biocompatibility. However, their intrinsic conductivity is low, resulting in the conductive properties of composite materials usually being limited to the range of 1-10S / cm, which is difficult to meet high performance requirements. Silver nanowires have become an ideal choice for high-conductivity composite conductors due to their excellent conductivity and high aspect ratio (CN110277198A, CN113502087A, CN117766227A). However, they are prone to oxidative corrosion in electrolyte environments, resulting in a narrow electrochemical window (Energy Storage Mater. 2022, 47, 386-393), which seriously restricts the application range of the device. In response to the stability problem of silver nanowire composite materials, the existing technology adopts two solutions: surface modification and multilayer structure composite. Surface modification strategies include precious metal coating, such as gold coating (Nat. Nanotechnol. 2018, 13, 1048-1056; CN118186756A) and chemical modification, such as thiol compound modification (CN114566328A). Although they can effectively broaden the electrochemical window, they have problems such as complex process and high cost. There are several ways to implement the multilayer structure composite strategy: one is to deposit a protective layer of nitride oxide (ACS Appl. Mater. Interfaces 2022, 14, 4423-4433) or indium tin oxide (CN114121346A) on the surface of silver nanowires by magnetron sputtering, but this method not only increases the process cost but also limits the stretchability of the material; the second is to construct a double-layer composite structure of silver nanowires and carbon-based materials such as graphene and carbon nanotubes (CN112071472A; ACS Materials Lett. 2022, 4, 2401-2408). Although this method can improve the electrochemical stability, the complex multilayer alignment process significantly increases the difficulty and cost of graphical preparation, thereby restricting the practical application of such materials.

[0006] It can be seen that there is currently a lack of simple and efficient preparation methods for stretchable composite conductor materials with both high conductivity and wide electrochemical window, which makes it difficult to fully meet the research and development needs of corresponding electronic devices and equipment. Summary of the Invention

[0007] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.

[0008] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0009] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing a stretchable composite conductor material with high conductivity and a wide electrochemical window.

[0010] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0011] The elastomer is dissolved in an organic solvent to obtain an elastomer solution, and the elastomer solution is evenly poured on a silane-modified glass. After natural leveling, the elastomer solution is thermally cured to obtain a flexible substrate.

[0012] The silver nanowires are mixed with chloroform and then centrifuged for washing, the washed silver nanowires are mixed with chloroform to form a silver nanowire solution, and an elastomer is added to the silver nanowire solution to obtain a silver nanowire composite conductive ink;

[0013] The carbon-based material is added to an organic solvent and dispersed uniformly to obtain a carbon-based material solution, an elastomer is added, and ultrasonic treatment is performed to form a uniform carbon-based material composite conductive ink;

[0014] Spraying silver nanowire composite conductive ink and carbon-based material composite conductive ink on a flexible substrate to obtain a silver nanowire / carbon-based material composite electrode;

[0015] soaking the composite electrode in an etching solution and then performing heat treatment to obtain a composite conductor material;

[0016] Wherein, the carbon-based material includes one of multi-walled carbon nanotubes and graphene oxide; the elastomer includes one of thermoplastic polyurethane elastomer, silicone rubber and styrene thermoplastic elastomer.

[0017] As a preferred embodiment of the method for preparing the highly conductive and wide electrochemical window stretchable composite conductor material described in the present invention, the method further comprises: dissolving the elastomer in an organic solvent, wherein the organic solvent comprises one of toluene, cyclohexane, and xylene; adding the carbon-based material to the organic solvent, wherein the organic solvent comprises one of cyclohexane and ethanol; and the etching solution comprises aqueous ammonia and hydrogen peroxide.

[0018] As a preferred solution of the method for preparing the highly conductive and wide electrochemical window stretchable composite conductor material of the present invention, the temperature of the thermal curing is 40-60° C. and the time is 2-3 hours.

[0019] As a preferred embodiment of the method for preparing a highly conductive and wide electrochemical window stretchable composite conductor material according to the present invention, the volume ratio of the silver nanowires to chloroform is 1:2 to 4; the rotation speed of the centrifugal washing is 2000 to 3000 rpm / min, and the time is 10 to 20 minutes; the concentration of the silver nanowire solution is 2 to 3 mg / mL.

[0020] As a preferred solution of the method for preparing the highly conductive and wide electrochemical window stretchable composite conductor material described in the present invention, the volume ratio of the silver nanowires to the elastomer in the silver nanowire composite conductive ink is 3:15-20.

[0021] As a preferred solution of the method for preparing the highly conductive and wide electrochemical window stretchable composite conductor material of the present invention, the concentration of the carbon-based material solution is 0.2-0.4 mg / mL.

[0022] As a preferred solution of the method for preparing the highly conductive and wide electrochemical window stretchable composite conductor material described in the present invention, the mass ratio of the carbon-based material to the elastomer in the carbon-based material composite conductive ink is 1:4 to 4.2; the power of the ultrasonic dispersion is 50 to 80%, and the time is 1.5 to 3 hours.

[0023] As a preferred embodiment of the method for preparing a highly conductive and wide electrochemical window stretchable composite conductor material according to the present invention, the mass ratio of silver nanowires to carbon-based materials in the silver nanowire composite conductive ink and carbon-based material composite conductive ink is 40 to 80:1; and the spraying distance is 10 to 15 cm.

[0024] As a preferred embodiment of the method for preparing a stretchable composite conductor material with high conductivity and wide electrochemical window described in the present invention, the composite electrode is immersed in the etching solution for 10 to 20 minutes; the heat treatment temperature is 110 to 120°C and the time is 10 to 20 minutes.

[0025] Another object of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing a stretchable composite conductor material with high conductivity and a wide electrochemical window to obtain a stretchable composite conductor material with high conductivity and a wide electrochemical window.

[0026] As a preferred embodiment of the present invention, a highly conductive and wide electrochemical window stretchable composite conductor material has the following characteristics:

[0027] (i) The length of the stretchable composite conductor material was fixed at 2 cm and the width was 1 cm. The thickness was first measured using a laser confocal microscope, and then the resistance was measured using a four-probe tester. Finally, the resistivity was calculated according to the resistance law. The conductivity was calculated as the reciprocal of the resistivity, and the conductivity of the composite conductor material was calculated to be 5000-5120 S / cm.

[0028] (ii) Using an electrochemical workstation, the composite conductor material was used as the working electrode, the carbon rod was used as the counter electrode, and Ag / AgCl was used as the reference electrode. When a linear scan was performed in PBS solution, the electrochemical window of the composite conductor material was -1.3 to 1.3 V.

[0029] Beneficial effects of the present invention:

[0030] (1) The present invention addresses the technical bottleneck of existing flexible conductor materials in terms of electrical conductivity, electrochemical stability and mechanical properties, and provides a high-performance composite conductor material and a preparation method thereof;

[0031] (2) By innovatively using a multiphase composite system of metallic silver nanowires, carbon-based carbon nanotubes or graphene oxide and polymer elastomers, and optimizing their microstructure and post-processing process, they successfully solved the performance balance problem between conductivity, electrochemical stability and stretchability;

[0032] (3) The composite conductor prepared by this method not only achieves excellent electrical properties with a conductivity exceeding 5000S / cm and an electrochemical window greater than 2.5V, but also maintains a stretchable strain capacity of more than 100%. The preparation process is simple and the cost is low, providing an ideal conductive material solution for flexible electronic devices and wearable devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0034] Figure 1 The absorbance of the silver nanowire and carbon nanotube conductive composite ink prepared in Example 1 of the present invention increases with time;

[0035] Figure 2 This is a comparison of the physical images of the composite conductor material prepared in Example 1 of the present invention before and after etching;

[0036] Figure 3 XPS graph and conductivity comparison graph of the composite conductor material prepared in Example 1 of the present invention before and after etching and heat treatment;

[0037] Figure 4 The linear sweep voltammetry curve of the composite conductor material prepared in Example 1 of the present invention in a PBS solution before and after etching and heat treatment;

[0038] Figure 5 The resistance change curves of the composite conductor material prepared in Example 1 of the present invention at different stretching amplitudes and the linear sweep voltammetry curves in PBS solution at the initial state and the state of stretching 120% are shown;

[0039] Figure 6 The cyclic voltammogram of the composite conductor material prepared in Example 1 of the present invention in 3,4-ethylenedioxythiophene (EDOT) monomer and sodium styrene sulfonate (NaPSS) aqueous solution and the surface SEM image of the PEDOT:PSS modified composite conductor material are shown.

[0040] Figure 7 This is a resistance change curve of the composite conductor material prepared in Example 1 of the present invention after being continuously stretched 1000 times at a stretching amplitude of 50%, and a linear sweep voltammetry curve of the composite conductor material in the initial state and after being continuously stretched 1000 times at a stretching amplitude of 50% and returning to the initial position in PBS solution.

[0041] Figure 8 The conductivity curves of different composite conductor materials obtained by adjusting the mass ratio of silver nanowires to carbon nanotubes at different etching times and the resistance curves at different stretching amplitudes in Example 1 of the present invention are as follows;

[0042] Figure 9 The curves of the conductivity of the composite conductor material prepared with or without the introduction of an elastomer in Example 1 of the present invention versus time are shown;

[0043] Figure 10 The linear sweep voltammetry curves of the composite conductor material prepared in Example 1 of the present invention in PBS solutions treated at different temperatures are shown; DETAILED DESCRIPTION

[0044] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0045] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0046] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0047] The styrene thermoplastic elastomer (SEBS) used in the present invention is model H1221.

[0048] The electrochemical stability test method of the present invention is as follows: using an electrochemical workstation, the conductive composite material prepared by the present invention is used as a working electrode, a carbon rod is used as a counter electrode, and Ag / AgCl is used as a reference electrode, a linear scan is performed in a PBS solution to obtain a linear voltammetric characteristic curve.

[0049] The conductivity test method of the present invention is as follows: the sample size is fixed at 2 cm in length and 1 cm in width. The thickness of the sample is first measured using a laser confocal microscope, and then its resistance is measured using a four-probe probe. Finally, the resistivity is calculated according to the resistance law. Then, the resistivity and conductivity are converted into the reciprocal of each other to obtain the final conductivity.

[0050] Example 1

[0051] This embodiment provides a method for preparing a stretchable composite conductor material with high conductivity and a wide electrochemical window, specifically:

[0052] (1) Preparation of a flexible substrate: The substrate is made of styrene thermoplastic elastomer (SEBS) raw material. SEBS particles are pre-dissolved in toluene solvent to obtain a 20 wt% SEBS solution. The SEBS solution is evenly poured onto octadecyltrichlorosilane (OTS)-modified glass. After natural leveling, the solution is thermally cured at 40°C for 2 h to obtain a flexible substrate.

[0053] (2) Preparation of composite conductive ink:

[0054] Preparation of silver nanowire composite conductive ink: Silver nanowires synthesized by the polyol method were mixed with chloroform in a volume ratio of 1:2, and then centrifuged at 2000 rpm / min for 10 minutes. The supernatant was removed and the silver nanowire sediment was retained at the bottom. After repeated centrifugation and washing three times, the washed silver nanowires were mixed with chloroform to obtain a silver nanowire solution with a concentration of 2 mg / mL. Finally, SEBS particles were added to the silver nanowire / chloroform mixed solution and fully dissolved to obtain a silver nanowire conductive composite ink, wherein the volume ratio of silver nanowires to SEBS was 3:20;

[0055] Preparation of carbon nanotube composite conductive ink: 80 mg of multi-walled carbon nanotubes (MWCNTs) were added to 400 mL of cyclohexane and ultrasonically dispersed at 80% power for 1.5 h. Subsequently, 320 mg of SEBS particles were added and ultrasonicated for 1.5 h to form a uniform carbon nanotube composite conductive ink;

[0056] (3) Patterned deposition: The silver nanowire and carbon nanotube composite conductive ink prepared in step (2) are respectively loaded into a syringe, and the ink is pushed to the bottom of the syringe by a piston. The syringe is then mounted on a propeller, and the propulsion speeds of the silver nanowire and carbon nanotube composite conductive inks are set to 4 mm / min and 1 mm / min, respectively. The air pressure is set to 0.1 MPa. The vertical distance between the spraying needles of the silver nanowire and carbon nanotube composite conductive inks and the flexible substrate is set to 15 cm. The co-assembled silver nanowire / carbon nanotube composite electrode is sprayed on the flexible substrate, and the desired pattern is defined using a mask.

[0057] (4) Post-treatment process: The composite electrode prepared in step (3) is immersed in an etching solution for 15 minutes so that the surrounding silver nanowires are etched away and then taken out, and heat-treated at 120°C for 10 minutes. Due to the self-leveling process of the thermoplastic elastomer during heat treatment, the defective positions of the etched silver nanowires are filled, and the final composite conductor material is obtained, wherein the etching solution is a mixed solution of 30% ammonia water and 28% hydrogen peroxide with a mass ratio of 1:1.

[0058] The silver nanowire and carbon nanotube composite conductive ink prepared in step (2) of Example 1 was left to stand for 60 minutes for stability characterization. The results are as follows: Figure 1 shown.

[0059] like Figure 1 As shown in the figure, it was observed that the color of the silver nanowire and carbon nanotube composite conductive ink remained uniform after standing for 60 minutes, and no obvious sedimentation of the conductive material was observed. The overall system was still a stable dispersion, indicating that the prepared composite conductive ink laid a good foundation for subsequent high-quality spraying.

[0060] The morphology test of the composite electrode before etching in step (3) of Example 1 and the composite conductor material after etching in step (4) was carried out. The results are as follows: Figure 2 shown.

[0061] according to Figure 2 It can be seen that before etching, the entire electrode appears silver-gray due to the interweaving of silver nanowires and carbon nanotubes. When placed in the etching solution, the exposed silver nanowires react violently with the etching solution, resulting in many bubbles on the electrode surface. After etching and heat treatment, only carbon nanotubes are left around the electrode, so the entire composite conductor material finally appears black.

[0062] The composite conductor material obtained before and after etching and after heat treatment in Example 1 was characterized by X-ray photoelectron spectroscopy (XPS) and conductivity. The results are as follows: Figure 3 As shown, Figure 3 a is the XPS comparison of the electrode before and after etching and heat treatment. Figure 3 b is the comparison of the conductivity of the electrode before and after etching and heat treatment.

[0063] from Figure 3 In figure a, it can be found that before etching, silver peaks appeared on the surface of the composite conductor material, proving that a large number of silver nanowires were exposed on the electrode surface. After etching and heat treatment, the silver peaks on the surfaces of both electrodes basically disappeared, verifying that the silver nanowires on the electrode surface were basically etched away.

[0064] Depend on Figure 3 b It can be seen that etching and heat treatment lead to a slight decrease in the conductivity of the electrode, but the conductivity of the entire composite conductor material is still as high as 5120S / cm, verifying that the staggered overlap of silver nanowires and carbon-based materials inside the material gives the entire material high conductivity.

[0065] The electrochemical stability test of the composite conductor material obtained before and after etching and heat treatment in Example 1 was carried out. The results are as follows: Figure 4 shown.

[0066] from Figure 4 As can be seen from the figure, before etching, due to the presence of a large number of silver nanowires on the electrode surface, the current density of the composite electrode at 0.20 V increased significantly, reaching a current density of 2.75 mA / cm 2 , corresponding to the oxidation of elemental Ag to Ag + After etching, the current density of the composite electrode at 0.20V was reduced to 0.75mA / cm 2 After heat treatment, due to the self-leveling process of the thermoplastic elastomer during heat treatment, the etched silver nanowire defect positions are filled, and the internal silver nanowires are well coated, making it difficult for them to precipitate and leak. The carbon nanotubes around the composite conductor material finally obtained have good chemical stability, which makes the composite conductor material show a wider electrochemical temperature window (-1.3~1.3V).

[0067] The electrical and electrochemical properties of the composite conductor material prepared in Example 1 (the mass ratio of silver nanowires to carbon nanotubes is 40:1) were tested under tension. The results are as follows: Figure 5 As shown, Figure 5 a is the resistance change curve of the composite conductor material under different stretching amplitudes. Figure 5b is a comparison diagram of the linear sweep voltammetry (LSV) curves of the composite conductor material in PBS solution at the initial state and at a tensile deformation of 120%.

[0068] from Figure 5 As can be seen in a, the initial square resistance of the composite conductor material is 0.10Ω / sq. As the stretching amplitude increases, the square resistance gradually increases. This is due to the slippage between the silver nanowires and carbon nanotubes. At 120% stretching, the square resistance increases to 4.22Ω / sq, but the composite conductor material still has excellent conductivity. Figure 5 b It can be seen that both have a wide electrochemical window (-1.3 ~ 1.3V), indicating that in the stretched state, the silver nanowires inside the composite conductor material are still effectively coated without leakage.

[0069] The surface modifiability of the composite conductor material prepared in Example 1 was tested, and the results were as follows: Figure 6 As shown, Figure 6 a is a cyclic voltammetry (CV) curve obtained by performing 30 cycles at a scan rate of 50 mV / s from -0.5 V to 1.2 V. Figure 6 b is the SEM image of the PEDOT:PSS modified electrode surface.

[0070] The present invention uses an electrochemical workstation to perform electrodeposition in a three-electrode structure, using the composite conductor material prepared in Example 1 as a working electrode, a conductive graphite rod as a counter electrode, and Ag / AgCl as a reference electrode. In a prepared aqueous solution of 0.01M 3,4-ethylenedioxythiophene (EDOT) monomer and 0.1M sodium styrene sulfonate (NaPSS), cyclic voltammetry (CV) is performed at a scan rate of 50mV / s for 30 cycles. The cyclic electrodeposition process is as follows: Figure 6 As shown in a. The voltage range of the electrodeposition cycle is between -0.5V and 1.2V. It can be seen that the electrochemical polymerization potential of the EDOT monomer in the initial cycle is around 0.9V. As the number of electrodeposition cycles increases, the closed area of ​​the CV curve gradually increases, proving that an effective conductive polymer layer is deposited on the electrode surface. Figure 6 b is the morphology of the composite conductor material after surface functional modification.

[0071] The electrical and electrochemical properties of the composite conductor material prepared in Example 1 were characterized by tensile cycling. Figure 7 As shown, Figure 7 a is the change trend of the sheet resistance of the composite conductor material after 1000 cycles of stretching with a stretching amplitude of 50%; Figure 7 b is the electrochemical stability test results of the composite conductor material.

[0072] like Figure 7As shown in Figure a, during 1000 cyclic stretching tests at a 50% stretching amplitude, the composite conductor material exhibited relatively stable resistance, with no significant increase in resistance observed. After 1000 stretching cycles, the square resistance of the electrode increased only to 1.78Ω / sq, maintaining excellent conductivity. This indicates that continuous stretching deformation has limited damage to the electron conduction path.

[0073] like Figure 7 As shown in b, compared with the conductor material in the initial unstretched cycle test, the composite conductor material after the stretching cycle test still has a wide electrochemical window (-1.3~1.3V), indicating that even after repeated stretching deformation, the silver nanowires inside the composite conductor material are still effectively protected and do not precipitate.

[0074] Example 2

[0075] This embodiment provides a method for preparing a stretchable composite conductor material with high conductivity and a wide electrochemical window, specifically:

[0076] (1) Preparation of a flexible substrate: The substrate is made of styrene thermoplastic elastomer (SEBS) raw material. SEBS particles are pre-dissolved in toluene solvent to obtain a 20 wt% SEBS solution. The SEBS solution is evenly poured onto octadecyltrichlorosilane (OTS)-modified glass. After natural leveling, the solution is thermally cured at 40°C for 2 h to obtain a flexible substrate.

[0077] (2) Preparation of composite conductive ink:

[0078] Preparation of silver nanowire composite conductive ink: Silver nanowires synthesized by the polyol method were mixed with chloroform in a volume ratio of 1:2, and then centrifuged at 2000 rpm / min for 10 minutes. The supernatant was removed and the silver nanowire sediment was retained at the bottom. After repeated centrifugation and washing three times, the washed silver nanowires were mixed with chloroform to obtain a silver nanowire / chloroform mixed solution with a concentration of 2 mg / mL. Finally, SEBS particles were added to the silver nanowire / chloroform mixed solution and fully dissolved to obtain a silver nanowire conductive composite ink, wherein the volume ratio of silver nanowires to SEBS was 3:20;

[0079] Preparation of graphene oxide composite conductive ink: 80 mg of graphene oxide was added to 400 mL of cyclohexane and ultrasonically dispersed at 80% power for 1.5 h. Subsequently, 320 mg of SEBS particles were added and ultrasonicated for 1.5 h to form a uniform graphene oxide composite conductive ink;

[0080] (3) Patterned deposition: The silver nanowires and graphene oxide composite conductive ink prepared in step (2) are respectively loaded into a syringe, and the ink is pushed to the bottom of the syringe by a piston. The syringe is then mounted on a propeller, and the propulsion speeds of the silver nanowires and graphene oxide composite conductive ink are set to 4 mm / min and 1 mm / min, respectively. The air pressure is set to 0.1 MPa, and the vertical distance between the spray needle and the flexible substrate is set to 15 cm. The co-assembled silver nanowire / graphene oxide composite electrode is sprayed on the flexible substrate, and the desired pattern is defined using a mask.

[0081] (4) Post-treatment process: The composite electrode prepared in step (3) is immersed in an etching solution for 15 minutes so that the surrounding silver nanowires are etched away and then taken out, and heat-treated at 120°C for 10 minutes. Due to the self-leveling process of the thermoplastic elastomer during heat treatment, the defective positions of the etched silver nanowires are filled, and the final composite conductor material is obtained, wherein the etching solution is a mixed solution of 28% ammonia water and 28% hydrogen peroxide with a mass ratio of 1:1.

[0082] Comparative Example 1

[0083] This comparative example provides a method for preparing a highly conductive and wide electrochemical window stretchable composite conductor material. The difference from Example 1 is that the mass ratio of silver nanowires and carbon nanotubes is regulated to 10:1, 20:1, 40:1 and 80:1 respectively by adjusting the propulsion speed of the silver nanowire and carbon nanotube composite conductive ink in step (3) of Example 1. The remaining preparation processes are the same as those in Example 1 to prepare the composite conductor material of this comparative example.

[0084] Comparative Example 2

[0085] This comparative example provides a method for preparing a highly conductive and wide electrochemical window stretchable composite conductor material. The difference from comparative example 1 is that the etching time under the preparation conditions of the mass ratio of each silver nanowire and carbon nanotube is adjusted to 0, 5, 10, 15, and 20 minutes, respectively. The rest of the preparation process is the same as that of comparative example 1 to prepare the composite conductor material of this comparative example.

[0086] The conductivity of the electrodes before etching in Comparative Example 1 and Comparative Example 2 was tested, and the results were as follows: Figure 8 As shown, Figure 8 a is a conductivity curve of the conductor material prepared at different etching times under different mass ratios of silver nanowires and carbon nanotubes in Comparative Examples 1 and 2, Figure 8 b is the tensile electrical properties of the composite conductor materials prepared with different mass ratios of silver nanowires and carbon nanotubes in Comparative Example 1.

[0087] according to Figure 8a found that before etching, the conductivity increased with the increase of the mass ratio of silver nanowires to carbon nanotubes; after etching for 15 minutes, the conductivity of the electrode remained almost unchanged, and the average conductivity values ​​corresponding to the mass ratios of silver nanowires to carbon nanotubes of 10:1, 20:1, 40:1 and 80:1 were 1844S / cm, 3690S / cm, 5088S / cm and 5722S / cm respectively.

[0088] like Figure 8 As shown in Figure 2b, it can be found that with the increase of the stretching amplitude, the square resistance of the four ratio electrodes also increases. This is mainly due to the slip between the silver nanowires and carbon nanotubes, which leads to an increase in the electrode resistance. When the electrode is stretched to 120%, it is found that the square resistance of the silver nanowire and carbon nanotube with a mass ratio of 40:1 is the smallest (4.22Ω / sq), and it still has good conductivity. Therefore, the mass ratio of silver nanowires and carbon nanotubes is 40:1 as the optimal electrode preparation ratio.

[0089] Comparative Example 3

[0090] This comparative example provides a method for preparing a highly conductive and wide electrochemical window stretchable composite conductor material. The difference from Example 1 is that no elastomer is introduced during the preparation of the silver nanowire and carbon nanotube composite conductive ink. The remaining preparation processes are the same as those in Example 1 to prepare the composite conductor material of this comparative example.

[0091] The effects of different etching times on the conductivity of the electrodes in Example 1 and Comparative Example 3 were studied. The results are shown in FIG. Figure 9 As shown in the figure. It can be seen that although the initial conductivity of the electrode without the elastomer (8012 S / cm) is higher than the initial conductivity of the electrode with the elastomer (7022 S / cm), this is mainly attributed to the fact that the introduction of the elastomer increases the contact resistance between the conductive materials, thereby reducing the conductivity of the electrode. However, it was found that after 5 minutes of etching, the conductivity of the electrode without the elastomer dropped to 3.8 S / cm, which is basically the conductivity of the carbon nanotube material. This is mainly attributed to the fact that the lack of the elastomer makes the entire conductive network have larger pores, which allows the etching solution to easily penetrate into the conductive network and etch away all the silver nanowires.

[0092] Comparative Example 4

[0093] This comparative example provides a method for preparing a highly conductive and wide electrochemical window stretchable composite conductor material. The difference from Example 1 is that the heat treatment temperatures in step (4) of Example 1 are adjusted to 30°C, 70°C, and 120°C, respectively. The rest of the preparation process is the same as that of Example 1, and the composite conductor material of this comparative example is prepared.

[0094] The electrochemical stability test of the composite conductor material obtained after different heat treatment temperatures in Comparative Example 4 was carried out. The results are as follows: Figure 10 As shown in the figure, it can be seen that as the treatment temperature increases, the current density of the composite electrode at 0.20V gradually decreases. When treated at 120℃, the current density at this time is almost negligible, indicating that the composite conductor material treated at 120℃ exhibits a wide electrochemical temperature window. This also further shows that only when the temperature reaches the softening point of the thermoplastic elastomer can the surface etched silver nanowire defect positions be filled, and low-temperature treatment cannot achieve the self-leveling effect of the thermoplastic elastomer heat treatment.

[0095] In summary, the present invention provides a stretchable composite conductor material with both high conductivity and a wide electrochemical window, and a method for its preparation. This preparation method innovatively uses metal particles, such as silver nanowires, and carbon-based particles, such as carbon nanotubes or graphene oxide, to construct a composite electrode. A conductive layer is created on a flexible substrate using a spray coating technique. Combined with wet etching and heat treatment, this creates a conductive network of interpenetrating silver nanowires and carbon-based materials within the electrode, while also forming a full carbon protective layer on the electrode surface.

[0096] The prepared composite conductor exhibits excellent overall performance, with a conductivity of 5120 S / cm, an electrochemical window exceeding 2.5V, and a stretchable strain exceeding 100%. Compared to existing technologies, this invention, through unique structural design and process optimization, successfully overcomes the technical difficulties of stretchable conductor materials in achieving both high conductivity and a wide electrochemical window. Furthermore, the preparation process is simple and low-cost, making it suitable for large-scale manufacturing of flexible electronic devices.

[0097] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a stretchable composite conductor material with high conductivity and wide electrochemical window, characterized by: include, The elastomer is dissolved in an organic solvent to obtain an elastomer solution, and the elastomer solution is evenly poured on a silane-modified glass. After natural leveling, the elastomer solution is thermally cured to obtain a flexible substrate. The silver nanowires are mixed with chloroform and then centrifuged for washing, the washed silver nanowires are mixed with chloroform to form a silver nanowire solution, and an elastomer is added to the silver nanowire solution to obtain a silver nanowire composite conductive ink; The carbon-based material is added to an organic solvent and dispersed uniformly to obtain a carbon-based material solution, an elastomer is added, and ultrasonic treatment is performed to form a uniform carbon-based material composite conductive ink; Spraying silver nanowire composite conductive ink and carbon-based material composite conductive ink on a flexible substrate to obtain a silver nanowire / carbon-based material composite electrode; soaking the composite electrode in an etching solution and then performing heat treatment to obtain a composite conductor material; Wherein, the carbon-based material includes one of multi-walled carbon nanotubes and graphene oxide; the elastomer includes one of thermoplastic polyurethane elastomer, silicone rubber and styrene thermoplastic elastomer.

2. The method for preparing a stretchable composite conductor material with high conductivity and wide electrochemical window according to claim 1, wherein: The elastomer is dissolved in an organic solvent, which includes one of toluene, cyclohexane, and xylene; the carbon-based material is added to the organic solvent, which includes one of cyclohexane and ethanol; and the etching solution is composed of ammonia water and hydrogen peroxide.

3. The method for preparing a stretchable composite conductor material with high conductivity and wide electrochemical window according to claim 1, characterized in that: The temperature of the thermal curing is 40-60° C., and the time is 2-3 hours.

4. The method for preparing a stretchable composite conductor material with high conductivity and wide electrochemical window according to claim 1, wherein: The volume ratio of the silver nanowires to chloroform is 1:2-4; the concentration of the silver nanowire solution is 2-3 mg / mL.

5. The method for preparing a stretchable composite conductor material with high conductivity and wide electrochemical window according to claim 1, wherein: The volume ratio of the silver nanowires to the elastomer in the silver nanowire composite conductive ink is 3:15-20.

6. The method for preparing a stretchable composite conductor material with high conductivity and wide electrochemical window according to claim 1, wherein: The concentration of the carbon-based material solution is 0.2-0.4 mg / mL.

7. The method for preparing a stretchable composite conductor material with high conductivity and wide electrochemical window according to claim 1, wherein: The mass ratio of the carbon-based material to the elastomer in the carbon-based material composite conductive ink is 1:4-4.

2.

8. The method for preparing a stretchable composite conductor material with high conductivity and wide electrochemical window according to claim 1, wherein: The mass ratio of silver nanowires to carbon-based materials in the silver nanowire composite conductive ink and carbon-based material composite conductive ink is 40 to 80:1; and the spraying distance is 10 to 15 cm.

9. The method for preparing a stretchable composite conductor material with high conductivity and wide electrochemical window according to claim 1, wherein: The composite electrode is immersed in the etching solution for 10 to 20 minutes; the heat treatment temperature is 110 to 120° C. and the time is 10 to 20 minutes.

10. A stretchable composite conductor material with high conductivity and wide electrochemical window prepared by the preparation method according to any one of claims 1 to 9, characterized in that: It has the following characteristics, (i) The length of the stretchable composite conductor material was fixed at 2 cm and the width was 1 cm. The thickness was first measured using a laser confocal microscope, and then the resistance was measured using a four-probe tester. Finally, the resistivity was calculated according to the resistance law. The conductivity was calculated as the reciprocal of the resistivity, and the conductivity of the composite conductor material was calculated to be 5000-5120 S / cm. (ii) Using an electrochemical workstation, the composite conductor material was used as the working electrode, the carbon rod was used as the counter electrode, and Ag / AgCl was used as the reference electrode. When a linear scan was performed in PBS solution, the electrochemical window of the composite conductor material was -1.3 to 1.3 V.

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