Graphene conductive polymer composite conductive slurry and preparation method of coating current collector of graphene conductive polymer composite conductive slurry

Abstract

The invention belongs to the technical field of lithium batteries, and particularly relates to a preparation method of graphene conductive polymer composite conductive slurry and a preparation method of a coating current collector of the graphene conductive polymer composite conductive slurry. In the preparation method of the composite conductive paste, a traditional binder is replaced by a conductive polymer monomer, and a functionalized ionic liquid and a dynamic cross-linking agent are integrated to construct an integrated conductive network and a self-repairing system. The preparation method of the coating current collector comprises the following steps: sequentially coating the composite conductive slurry on the base material to form a coating surface on the base material; irradiating the coating surface of the substrate with ultraviolet light; rolling the irradiated base material; performing heat treatment on the rolled base material; and etching a pattern on the surface of the coating of the base material subjected to heat treatment to obtain the optimized coating current collector. The coating prepared by the preparation method of the coating current collector provided by the invention has good conductivity, cycle life, self-repairing efficiency, flexibility and salt fog resistance, and breaks through the problems of low conductivity, interface failure and pollution of the traditional carbon-coated current collector.

Description

Technical Field

[0001] This application belongs to the field of battery technology, specifically relating to a method for preparing a graphene conductive polymer composite conductive paste and its coating current collector. Background Technology

[0002] Graphene-coated current collectors, as a new generation of current collector technology, have significant advantages over traditional carbon-coated current collectors (such as acetylene black / conductive carbon black coatings).

[0003] In related technologies, there is room for improvement in the conductivity, interfacial bonding strength, and cycle life of graphene coatings in collective flow. Summary of the Invention

[0004] Based on the above-mentioned technical problems, this application provides a method for preparing graphene conductive polymer composite conductive paste and its coating current collector, which aims to improve the conductivity, interfacial bonding force and cycle life of graphene coating current collector to a certain extent.

[0005] In a first aspect, this application provides a method for preparing a graphene-conductive polymer composite conductive paste, the method comprising: The raw materials include expanded graphite, conductive polymer monomers, functionalized ionic liquids, and dispersants. The process involves stripping the provided raw materials to extract graphene that has been polymerized in situ with conductive polymers. Carbon nanotubes and a dynamic crosslinking agent were added to the obtained graphene to obtain a composite conductive paste.

[0006] In some embodiments, the conductive polymer monomer includes at least one of polyaniline, polypyrrole, polythiophene, sulfonated polyaniline, carboxylated polypyrrole, aniline-thiophene block copolymer, and poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid; the conductive polymer monomer accounts for 5-12 wt% of the composite conductive paste to be prepared.

[0007] In some embodiments, the functionalized ionic liquid comprises at least one of 1-epoxypropyl-3-methylimidazolium hexafluorophosphate, 1-sulfonyl-3-methylimidazolium hydrogen sulfate, 1-carboxyethyl-3-butylimidazolium acetate, 1-mercaptopropyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, and 1-aminopropyl-3-ethylimidazolium tetrafluoroborate; the functionalized ionic liquid accounts for 2-5 wt% of the composite conductive paste to be prepared.

[0008] In some embodiments, the dynamic crosslinking agent is compounded with furan-maleimide and disulfide-crosslinked polyacrylic acid at a mass ratio of 1:1; the proportion of the dynamic crosslinking agent in the composite conductive paste to be prepared is 3-5 wt%.

[0009] In some implementations, the processing of the provided raw material specifically includes: performing a shearing pre-intercalation process on the provided raw material, wherein the parameters of the shearing pre-intercalation include: a rotational speed of 800-1200 r / min and a temperature gradient of 50℃→70℃→80℃.

[0010] In some implementations, carbon nanotubes and a dynamic crosslinking agent are added to the obtained graphene to obtain a composite conductive slurry. Specifically, the graphene and the dynamic crosslinking agent are mixed in a microfluidic reactor at a flow rate of 5-15 mL / min to obtain a composite conductive slurry with a particle size distribution D50 of 1.5 ± 0.1 μm.

[0011] In a second aspect of this application, a method for preparing a coated current collector is also provided. The method includes: pretreating a substrate to form surface nanoscale trenches on the substrate; sequentially coating the pretreated substrate with a composite conductive paste prepared by the method described in the first aspect to form a coating surface on the substrate; irradiating the coating surface of the substrate with ultraviolet light; rolling the irradiated substrate; heat-treating the rolled substrate; and etching a pattern on the coating surface of the heat-treated substrate to obtain the coated current collector.

[0012] In some embodiments, during the process of coating the composite conductive paste onto the pretreated substrate, a vertical magnetic field is applied to the substrate, causing the carbon nanotubes to align along the direction of the magnetic field to form an anisotropic conductive network.

[0013] In some embodiments, the pretreatment of the substrate to form surface nanoscale trenches on the substrate specifically includes: performing plasma activation treatment on the substrate in an argon atmosphere to form surface nanoscale trenches on the substrate, wherein: the power of the plasma activation treatment is 200-500W, the time is 5-10min, and the depth of the surface nanoscale trenches is 50-200nm.

[0014] In some implementations, the composite conductive paste is coated three times on the pretreated substrate, with the thickness of each coating increasing sequentially, the coating speed being 30-50 m / min, and the gap accuracy being ±2 μm.

[0015] In some embodiments, the curing time for irradiating the coating surface of the substrate with ultraviolet light is less than or equal to 10 seconds; The processing temperature of the substrate after roller pressing and irradiation is 80-120℃ and the pressure is 5-10MPa, so as to reduce the porosity of the substrate to below 5%. The temperature of the substrate after heat treatment and rolling is 60°C for 30 minutes to activate Diels-Alder bond recombination and improve the interfacial bonding energy to -3.5 eV. The etching pattern on the coating surface of the heat-treated substrate specifically includes: using a femtosecond laser to etch a micrometer-level grid on the coating surface, wherein the line width of the micrometer-level grid is 20 μm and the spacing is 100 μm, so as to reduce the sheet resistance of the substrate to 0.2 Ω / □.

[0016] The coated current collector prepared by the method provided in this application has a conductivity ≥1200 S / cm and a sheet resistance ≤0.2 Ω / □; durability: capacity retention rate >92% (1C, LiFePO4) after 5000 cycles, salt spray resistance time ≥2500 hours, and meets the IEC62133 requirement of no metal ion precipitation as tested by SGS. This solves the technical problems of low conductivity, weak interfacial bonding force and easy failure and short cycle life in related technologies, and has self-healing ability and can improve environmental pollution. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying 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.

[0018] Figure 1 A schematic flowchart of a method for preparing a graphene conductive polymer composite conductive paste according to one or more embodiments of this application is shown. Figure 2 A schematic flowchart of a method for preparing a coated current collector according to one or more embodiments of this application is shown; Figure 3 Transmission electron microscope (TEM) images of the graphene composite slurry prepared in Example 4 are shown. Detailed Implementation

[0019] To enable those skilled in the art to more clearly understand this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0020] Carbon-coated current collectors are a core component in lithium-ion battery manufacturing and are a type of coated current collector. However, existing carbon-coated current collector technologies suffer from at least the following drawbacks: 1. Insufficient conductivity: relying on insulating binders requires the addition of additional conductive agents, leading to a lower proportion of active material and higher internal resistance; 2. Poor interface stability: weak coating adhesion, easily detaching during cycling or bending, causing capacity decay; 3. Environmental and safety risks: the use of organic solvents such as NMP results in VOC emissions, and metal impurities (Fe...)... 3+ Cu 2+ This may induce dendrite growth and thermal runaway.

[0021] Graphene-coated current collectors, as a new generation of current collector technology, have the following significant advantages compared to traditional carbon-coated current collectors (such as acetylene black / conductive carbon black coatings): the intrinsic conductivity of graphene (≈10) 6 S / m) far exceeds that of traditional carbon materials (carbon black ≈ 10 2 The areal density (S / m) of graphene can significantly reduce the internal resistance of the battery. Lightweight breakthrough: Graphene's areal density (0.3-0.5 mg / cm³) can significantly reduce battery internal resistance. 2 It is only equivalent to a traditional carbon coating layer (1.2-1.5 mg / cm²). 2 The weight of the current collector is reduced by more than 25% while maintaining the same conductivity, resulting in a significant increase in battery energy density. Enhanced corrosion resistance: The chemical inertness of graphene ensures that its corrosion current density in electrolytes (such as LiPF6 / EC-DMC) is ≤1μA / cm². 2 (Traditional carbon coating ≥5μA / cm) 2 Cycle life is increased by more than 30%. Flexibility advantage: Graphene coating bending fatigue strength > 10. 4 (Traditional carbon coating <5×10) 3 This method is suitable for the development of flexible batteries.

[0022] Despite the aforementioned advantages, graphene coating technology still faces several bottlenecks hindering its industrial application. The preparation process is complex and relies on high-temperature reduction (>800℃) or ultracentrifugation (>10000rpm) to disperse graphene, resulting in energy consumption as high as 8-10kWh / kg. Furthermore, multi-step centrifugation and fractionation increase equipment investment by 40%, with a yield <80%. Performance synergy challenges: The homogeneous structure design leads to a contradiction between conductivity and interfacial bonding; increasing sheet size can reduce sheet resistance but weakens the bond with electrode materials. Solvent pollution and cost: The use of toxic solvents such as NMP (boiling point >200℃) requires a corresponding recovery device, increasing the cost of processing each ton of slurry by 1500; the high price of ionic liquid intercalating agents (>500 / kg) results in a graphene cost >200 / kg. Lack of self-healing function: Existing graphene coatings develop microcracks due to stress accumulation during charge-discharge cycles, resulting in a capacity decay of >15% after 500 cycles.

[0023] This application aims to address the problems of low conductivity of coatings, easy interface failure, lack of self-healing ability, and environmental pollution in related technologies, and provides a method for preparing a composite conductive slurry with excellent conductivity, strong interfacial adhesion, dynamic self-healing ability, and green processing characteristics, as well as a method for preparing a coated current collector.

[0024] In a first aspect of this application, a method for preparing a graphene conductive polymer composite conductive paste is provided. Figure 1 A schematic flow chart illustrating a method for preparing a graphene-conductive polymer composite conductive paste according to one or more embodiments of this application is shown. (Combined with...) Figure 1 The preparation method of this composite conductive paste includes: S1: Provide raw materials, including expanded graphite, conductive polymer monomers, functionalized ionic liquids and dispersants; S2: The process involves peeling off the provided raw materials to extract graphene that has been polymerized in situ with conductive polymers. S3: Add carbon nanotubes and dynamic crosslinking agent to the obtained graphene to obtain a composite conductive paste.

[0025] In some embodiments, the conductive polymer monomer includes at least one selected from polyaniline, polypyrrole, polythiophene, sulfonated polyaniline (SPAN), carboxylated polypyrrole, aniline-thiophene block copolymer, and poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS). The conductive polymer monomer accounts for 5-12 wt% of the composite conductive paste to be prepared.

[0026] In some embodiments, the functionalized ionic liquid includes any one or more of 1-epoxypropyl-3-methylimidazolium hexafluorophosphate ([EPOXY-MIM][PF6]), 1-sulfonyl-3-methylimidazolium hydrogen sulfate ([HSO3-BMIM][HSO4]), 1-carboxyethyl-3-butylimidazolium acetate ([COOH-BBIM][Ac]), 1-mercaptopropyl-3-methylimidazolium bis(trifluoromethanesulfonylimide) ([SH-PMIM][TFSI]), and 1-aminopropyl-3-ethylimidazolium tetrafluoroborate ([NH2-PEIM][BF4]); and the functionalized ionic liquid accounts for 2-5 wt% of the composite conductive paste to be prepared. During dynamic crosslinking, the functionalized ionic liquid undergoes π-π stacking and chemical bonding with graphene and carbon nanotubes to enhance the interface, or improves the interfacial adhesion with copper or aluminum foil through S-Cu bonds, ether bonds, Al-OP bonds, and hydrogen bonds, thereby optimizing the coating durability.

[0027] In some embodiments, the dynamic crosslinking agent is compounded with furan-maleimide (Diels-Alder bond) and disulfide-crosslinked polyacrylic acid at a mass ratio of 1:1; the proportion of the dynamic crosslinking agent in the composite conductive paste to be prepared is 3-5 wt%. The Diels-Alder bond triggers thermal repair at 60-80℃, and the disulfide bond achieves redox response repair at room temperature, so that the composite conductive paste has dynamic self-healing capability.

[0028] In some embodiments, the processing of the provided raw materials specifically includes: performing a shear pre-intercalation treatment on the provided raw materials in a high-pressure homogenizer. The parameters for the shear pre-intercalation include: a rotation speed of 800-1200 r / min and a temperature gradient of 50℃→70℃→80℃. In specific implementations, dynamic parameters of the high-pressure homogenizer are required to complete the in-situ copolymerization of graphene exfoliation and conductive polymer.

[0029] In some embodiments, carbon nanotubes and a dynamic crosslinking agent are added to the obtained graphene to obtain a composite conductive slurry. Specifically, the graphene and the dynamic crosslinking agent are mixed in a microfluidic reactor at a flow rate of 5-15 mL / min to obtain a composite conductive slurry with a particle size distribution D50 of 1.5 ± 0.1 μm.

[0030] The method for preparing a graphene-conductive polymer composite conductive slurry disclosed in this application involves replacing traditional binders with conductive polymer monomers, combining functionalized ionic liquids and dynamic crosslinking agents to construct an integrated conductive network and self-healing system, and simultaneously exfoliating graphene and in-situ copolymerizing conductive polymers through a high-pressure homogenization process to control the uniformity of the slurry.

[0031] Based on the composite conductive paste prepared by the above-mentioned method, this application also provides a method for preparing a coated current collector. Figure 2 A schematic flowchart illustrating the preparation method of the coated current collector according to one or more embodiments of this application is shown. (In conjunction with...) Figure 2 The preparation method of the coated current collector includes: S4: Pre-treat the substrate to form surface nanoscale trenches on the substrate; S5: The composite conductive paste prepared in the first aspect is sequentially coated on the pretreated substrate to form a coating surface on the substrate; S6: Using ultraviolet light to irradiate the coating surface of the substrate; S7: Substrate after roll pressing and irradiation; S8: Substrate after heat treatment and roll pressing; S9: Etch a pattern on the coated surface of the heat-treated substrate to obtain a coated current collector.

[0032] In step S4 of this application, the substrate can be copper foil or aluminum foil. The pretreatment of the substrate includes: plasma activation treatment of the substrate under an argon atmosphere to form surface nanoscale trenches on the substrate, wherein: the power of the plasma activation treatment is 200-500W, the time is 5-10min, and the depth of the surface nanoscale trenches is 50-200nm. Alternatively, the substrate pretreatment may also include chemical etching, for example, using a mixture of nitric acid and phosphoric acid in a volume ratio of 1:3 for 30s, resulting in a surface roughness Ra of 0.5-1.0μm after etching.

[0033] In step S5 of this application, a slit coater can be used to coat the composite conductive paste on the pretreated substrate in three stages. The solid content of the composite conductive paste can be 25-35%, and the thickness of each coating layer increases sequentially, for example, 10μm→20μm→30μm. The coating speed is 30-50m / min, and the gap accuracy is ±2μm. Furthermore, the viscosity of the composite conductive paste varies with each coating layer, for example, it can decrease sequentially: the first layer has a viscosity of 1000cP, the second layer 800cP, and the third layer 600cP. The viscosity is dynamically controlled by the shear rate. Additionally, during the coating process on the pretreated substrate, a perpendicular magnetic field is applied to the substrate. The magnetic field intensity can be 0.5-1.0T, causing the carbon nanotubes to align along the magnetic field direction, forming an anisotropic conductive network.

[0034] In S6 of this application, the wavelength of the ultraviolet light can be 365nm and the intensity can be 50mW / cm. The ultraviolet light irradiates the coating surface, triggering the polymerization of acrylated EDOT monomers, and the curing time can be less than or equal to 10 seconds.

[0035] S7, S8, and S9 of this application can be defined as post-treatment of slurry coating, specifically: S7 can be defined as hot-press densification. Specifically, the processing temperature of the substrate after irradiation is 80-120℃ and the pressure is 5-10MP when the substrate is rolled by a hot roller press to reduce the porosity of the substrate to below 5%. S8 can be defined as dynamic crosslinking reinforcement. Specifically, the temperature of the substrate after heat treatment and rolling is 60°C and the time is 30 min to activate Diels-Alder bond recombination and improve the interfacial bonding energy to -3.5 eV. S9 can be defined as laser etching patterning, specifically, etching patterns on the coating surface of a heat-treated substrate, including: using a femtosecond laser to etch a micron-level grid on the coating surface, with a linewidth of 20 μm and a spacing of 100 μm, to reduce the sheet resistance of the substrate to 0.2 Ω / □.

[0036] In the preparation method of the composite conductive paste shown in this application, the substrate is activated by plasma and coated with gradient, and magnetically oriented carbon nanotubes form an anisotropic conductive network. In the post-processing, laser etching of micro-mesh and hot pressing densification further optimize the performance. The current collector has good conductivity, cycle life, self-healing efficiency, flexibility and salt spray resistance, breaking through the problems of low conductivity, interface failure and contamination of traditional carbon-coated current collectors.

[0037] In summary, the beneficial effects of this application are as follows: 1. By replacing PVDF with conductive polymer, it has intrinsic conductivity (≥1200S / cm), eliminating the need for conductive agent, increasing the active material content to 90%, and has good conductivity, with a conductivity ≥1200 S / cm and sheet resistance ≤0.3Ω / □, which is 3–4 times better than traditional carbon-coated current collectors. 2. Through chemical bonding of functionalized ionic liquid with graphene / substrate, the peel strength is >8N / cm, achieving ASTM 5B grade; 3. The dynamic cross-linking network (Diels-Alder bond + disulfide bond) can achieve self-healing at 60℃ (efficiency > 95%), realize wide temperature range and multi-mechanism crack repair, and has a cycle life > 5000 times; 4. The slurry is cured by ultraviolet light, which can achieve zero VOC emissions, simplify the process by 50%, reduce energy consumption by 40%, and eliminate the need for conductive agents and PVDF, reducing raw material costs by about 25% and increasing the production line yield to ≥95%; 5. The coated current collector prepared by the method provided in this application has the advantages of high flexibility (>20,000 bends), wide temperature adaptability (-40℃~120℃), and high shielding effectiveness (up to 68 dB), and is suitable for multiple high-end scenarios such as flexible electronics, military industry, and energy storage.

[0038] Through collaborative innovation in materials and processes, we have overcome bottlenecks in conductivity, durability, and environmental protection, providing new solutions for high-energy-density lithium batteries and flexible electronics. These solutions can be applied not only to the preparation of lithium-ion batteries but also to sodium-ion batteries, zinc-ion batteries, supercapacitors, and other applications, demonstrating great practicality.

[0039] Example 1: High conductivity silicon anode lithium battery current collector: The slurry formulation of the composite conductive paste is as follows: 30g expanded graphite (300 mesh), 8g sulfonated polyaniline (SPAN), 5wt% [EPOXY-MIM][PF6] ionic liquid, 5g carbon nanotubes (CNTs), and 4wt% dynamic crosslinking agent (furan-maleimide:DSPA=1:1). Preparation of composite conductive paste: The parameters of the high-pressure homogenizer are: 12000rpm, temperature gradient of 50℃→80℃, and control layer D50 of the microfluidic reactor is 1.5±0.1μm; Preparation process of coated current collector: aluminum foil is activated by plasma (300W, 8min) and etched by nitric acid / phosphoric acid (Ra=0.8μm), gradient coating (viscosity 1000→600cP, total thickness 60μm), magnetic field orientation (1.0T); post-treatment: ultraviolet light irradiation on the coating surface, rolling and heat treatment to densify it (10MPa, 100℃), laser etching of grid (line width 20μm).

[0040] The performance data of the high-conductivity silicon anode lithium battery current collector prepared by the above process are as follows: conductivity: 1350 S / cm, sheet resistance: 0.18 Ω / □; cycle performance: 5000 cycles at 1C, capacity retention: 94.2%; silicon anode compatibility: silicon loading: 15 mg / cm³. 2 Volume expansion rate <10% (traditional >30%). Advantages: Adapts to the high volume expansion requirements of silicon anodes, significantly improving energy density to 350Wh / kg.

[0041] Example 2: Current collector for flexible wearable devices: The composite conductive paste formulation is as follows: 25g expanded graphite (500 mesh), 10wt% PEDOT:PSS and aniline-thiophene block copolymer, 3wt% [SH-PMIM][TFSI] ionic liquid (to enhance copper foil adhesion), and 3wt% dynamic crosslinking agent (Diels-Alder:DSPA=1:2). The preparation of the composite conductive paste is the same as in Example 1, and will not be repeated here; The fabrication process of the coated current collector is as follows: chemical etching of copper foil (Ra=1.0μm), three coatings (total thickness 50μm), and UV curing time of 8 seconds; flexible design: femtosecond laser etching of serpentine mesh (line width 15μm, spacing 80μm).

[0042] Transmission electron microscope (TEM) image of the current collector for the flexible wearable device prepared by the above process is shown below. Figure 3 The performance data of the current collector for flexible wearable devices are shown below: Flexibility: 25,000 180° bends, resistance change 2.3%; Self-healing efficiency: 97% crack repair rate after 10 minutes of repair at 60°C; Energy density: 45Wh / kg (flexible full battery). Advantages: Combines high flexibility (bending > 20,000 times) with self-healing function, adapting to the stringent deformation requirements of wearable devices.

[0043] Example 3: Current collector for high-power supercapacitors: The slurry formulation of the composite conductive paste is as follows: 35g of expanded graphite (200 mesh), polypyrrole / carboxylated polypyrrole (total percentage 12wt%), 4wt% of [HSO3-BMIM][HSO4] ionic liquid (to enhance proton conduction), and dynamic crosslinking agent (mainly DSPA, accounting for 2wt%). The preparation of the composite conductive paste is the same as in Example 1, and will not be repeated here; Preparation process of coated current collector: Plasma activation of aluminum foil (500W, 5min), single-layer coating thickness of 30μm, magnetic field orientation (0.8T). Post-treatment: hot pressing densification (120℃, 8MPa), porosity 4.5%.

[0044] Performance data of the high-power supercapacitor current collector prepared by the above process: Power density: 85kW / kg (fully charged in 3 seconds, twice that of the traditional system); Cycle life: 98% capacitance retention after 1 million cycles; Temperature range stability: Capacitor decay <3% at -40℃ to 120℃. Advantages: Ultra-high power and wide temperature range adaptability, meeting the requirements of grid-scale energy storage.

[0045] Example 4: Corrosion-resistant electromagnetic shielding current collector The slurry formulation of the composite conductive paste is as follows: 28g of expanded graphite (400 mesh), 7wt% of polythiophene / polyaniline composite, 5wt% of [NH2-PEIM][BF4] ionic liquid (resistant to salt spray corrosion), and dynamic crosslinking agent (mainly Diels-Alder bond, accounting for 4wt%). The preparation of the composite conductive paste is the same as in Example 1, and will not be repeated here; Fabrication process of coated current collector: Substrate treatment: Aluminum foil double etching (plasma + chemical etching, Ra=1.2μm); Coating design: Gradient coating thickness of 70μm, laser-etched honeycomb grid (line width 25μm); Corrosion resistance treatment: Surface spin-coated hydrophobic layer (contact angle >150°).

[0046] Performance data of the corrosion-resistant electromagnetic shielding current collector prepared by the above process: Shielding effectiveness: 68dB (1-10GHz), 40% higher than traditional coatings; Salt spray resistance: no corrosion after 3000 hours (GB / T1771); Environmental stability: shielding attenuation <5% in humid and hot environments (85℃ / 85%RH). Advantages: Combines high shielding effectiveness with extreme environmental durability, suitable for marine military and industrial scenarios.

[0047] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0048] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", and "counterclockwise" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0049] In this application, unless otherwise expressly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0050] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0051] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for preparing a graphene-conductive polymer composite conductive paste, characterized in that, The preparation method of the composite conductive paste includes: The raw materials include expanded graphite, conductive polymer monomers, functionalized ionic liquids, and dispersants. The process involves stripping the provided raw materials to extract graphene that has been polymerized in situ with conductive polymers. Carbon nanotubes and a dynamic crosslinking agent were added to the obtained graphene to obtain a composite conductive paste.

2. The method for preparing the graphene conductive polymer composite conductive paste according to claim 1, characterized in that, The conductive polymer monomer includes at least one of polyaniline, polypyrrole, polythiophene, sulfonated polyaniline, carboxylated polypyrrole, aniline-thiophene block copolymer, and poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid; The conductive polymer monomer accounts for 5-12 wt% of the composite conductive slurry to be prepared.

3. The method for preparing the graphene conductive polymer composite conductive paste according to claim 1, characterized in that, The functionalized ionic liquid includes at least one of the following: 1-epoxypropyl-3-methylimidazolium hexafluorophosphate, 1-sulfonyl-3-methylimidazolium hydrogen sulfate, 1-carboxyethyl-3-butylimidazolium acetate, 1-mercaptopropyl-3-methylimidazolium bis(trifluoromethanesulfonylimide) salt, and 1-aminopropyl-3-ethylimidazolium tetrafluoroborate. The functionalized ionic liquid accounts for 2-5 wt% of the composite conductive paste to be prepared.

4. The method for preparing the graphene conductive polymer composite conductive paste according to claim 1, characterized in that, The dynamic crosslinking agent is a compound of furan-maleimide and disulfide bond crosslinked polyacrylic acid at a mass ratio of 1:

1. The dynamic crosslinking agent accounts for 3-5 wt% of the composite conductive paste to be prepared.

5. The method for preparing the graphene conductive polymer composite conductive paste according to claim 1, characterized in that, The processing of the provided raw materials specifically includes: The provided raw materials are added to a high-speed homogenizer and pre-shearing intercalation is performed first. The shearing rate is 800-1200 r / min and the time is 10-30 min. Then the speed is increased to 10000-25000 r / min, and the temperature gradient is 50℃→70℃→80℃. The processing time is 30-120 min.

6. The method for preparing the graphene conductive polymer composite conductive paste according to claim 1, characterized in that, Carbon nanotubes and a dynamic crosslinking agent are added to the obtained graphene to obtain a composite conductive paste, specifically including: Graphene and a dynamic crosslinking agent were mixed in a microfluidic reactor at a flow rate of 5-15 mL / min to obtain a composite conductive slurry with a particle size distribution D50 of 1.5 ± 0.1 μm.

7. A method for preparing a coated current collector, characterized in that, The method for preparing the coated current collector includes: Pre-treating the substrate to form surface nanoscale trenches on the substrate; The composite conductive paste prepared by any one of claims 1-6 is sequentially coated onto a pretreated substrate to form a coating surface on the substrate. The coating surface of the substrate is irradiated with ultraviolet light; The substrate after roll pressing and irradiation; The substrate after heat treatment and rolling; Patterns are etched onto the coated surface of the heat-treated substrate to obtain a coated current collector.

8. The method for preparing the coated current collector according to claim 7, characterized in that, During the process of coating the pretreated substrate with the composite conductive paste, a vertical magnetic field is applied to the substrate, causing the carbon nanotubes to align along the direction of the magnetic field and form an anisotropic conductive network.

9. The method for preparing the coated current collector according to claim 7, characterized in that, The pretreated substrate, to form surface nanoscale trenches on the substrate, specifically includes: The substrate is subjected to plasma activation treatment in an argon atmosphere to form surface nanoscale trenches on the substrate, wherein: the power of the plasma activation treatment is 200-500W, the time is 5-10min, and the depth of the surface nanoscale trenches is 50-200nm.

10. The method for preparing the coated current collector according to claim 7, characterized in that, The composite conductive paste is coated three times on the pretreated substrate, with the thickness of each coating increasing sequentially. The coating speed is 30-50 m / min, and the gap accuracy is ±2 μm.

11. The method for preparing the coated current collector according to claim 9, characterized in that, The curing time of the coating surface of the substrate irradiated with ultraviolet light is less than or equal to 10 seconds; The processing temperature of the substrate after roller pressing and irradiation is 80-120℃ and the pressure is 5-10MPa, so as to reduce the porosity of the substrate to below 5%. The temperature of the substrate after heat treatment and rolling is 60°C for 30 minutes to activate Diels-Alder bond recombination and improve the interfacial bonding energy to -3.5 eV. The etching pattern on the coating surface of the heat-treated substrate specifically includes: using a femtosecond laser to etch a micrometer-level grid on the coating surface, wherein the line width of the micrometer-level grid is 20 μm and the spacing is 100 μm, so as to reduce the sheet resistance of the substrate to 0.2 Ω / □.

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