Preparation method of sulfur-doped graphene composite copper conductive paste

Abstract

The invention discloses a preparation method of sulfur-doped graphene composite copper conductive paste, and belongs to the field of conductive material preparation. Sulfur-doped graphene (S-G) is used as a coating layer of copper powder, sulfur atoms and the surface of copper form chemical bonds (Cu-S), the interface bonding force is remarkably enhanced, meanwhile, the intrinsic conductivity of the graphene is improved through the p-type doping effect of sulfur, copper oxidation can be inhibited, agglomeration can be reduced, copper particles can be in bridge connection through a high-conductivity network of the graphene, and the conductivity of the copper particles is improved. A metal-carbon dual-path conductive system is formed, and continuity of a conductive path is guaranteed. Sulfur doping and coating integration is realized by adopting a hydrothermal-ball milling method, a high-energy-consumption CVD (Chemical Vapor Deposition) process is avoided, and the preparation method is simpler in process, low in cost, environment-friendly, suitable for large-scale production, higher in application value, excellent in overall dispersity and suitable for large-scale production. The uniform and stable conductive paste can be formed and can be better applied to preparation of a composite conductive paste flexible conductive film or an electromagnetic shielding material.

Description

Technical Field

[0001] The present invention relates to the field of conductive material preparation, and in particular to a method for preparing a sulfur-doped graphene composite copper conductive slurry. Background Art

[0002] Conductive pastes, as key functional materials for electronic devices, are widely used in lithium-ion battery electrodes, flexible circuit printing, electromagnetic shielding coatings and other fields. Traditional conductive pastes mostly rely on silver powder or copper powder as the conductive phase, but silver powder is expensive, and copper powder is easily oxidized to form insulating copper oxide, resulting in paste conductivity attenuation and interface contact failure. In recent years, carbon-based materials (such as graphene and carbon nanotubes) have been introduced into conductive paste systems due to their high conductivity and chemical stability, but their interface compatibility with metal particles is poor, making it difficult to form a stable and efficient conductive network, limiting the improvement of overall performance. For example, the Chinese patent application number CN202411847983.2 discloses a graphene conductive paste, its preparation method and application. The graphene conductive paste prepared in this patent comprises the following raw materials: graphene; aminopyrimidine; epoxy resin; metal oxide; solvent. By introducing amino groups and nitrogen-containing heterocycles into graphene through aminopyrimidine, the surface of graphene has more polar functional groups, thereby enhancing the dispersibility of graphene in polar solvents and reducing the agglomeration between graphene sheets, thereby forming a more uniform and stable conductive paste.

[0003] Conventional copper pastes exhibit a resistivity increase of >35% after 48 hours of exposure to air (ASTM B193 testing), and high-temperature curing (>200°C) can cause deformation of heat-sensitive substrates (such as PET). Existing technologies inhibit copper powder oxidation through polymer coating (such as polyvinyl pyrrolidone) or surface passivation (such as nickel plating). However, the passivation layer significantly increases interfacial resistance (for example, the resistivity of the nickel plating layer is >10-6 Ω·m), and the process is complex and costly.

[0004] Graphene coating faces technical bottlenecks. Physical mixing methods have low coating rates, chemical vapor deposition (CVD) requires temperatures exceeding 800°C, which destroys the copper crystal structure (lattice distortion >15%). Graphene and copper powder bond only through physical adsorption, resulting in high interfacial contact resistance and easy graphene aggregation, leading to discontinuous conductive paths. Furthermore, undoped graphene has a low carrier concentration (<1013 cm-2), making it difficult to meet the high conductivity requirements. Therefore, the existing technology still faces these urgent technical challenges. Summary of the Invention

[0005] Based on this, in order to solve one of the above problems, the present invention provides a method for preparing a sulfur-doped graphene composite copper conductive paste, and the specific technical solution is as follows:

[0006] A method for preparing a sulfur-doped graphene composite copper conductive paste, the preparation method comprising the following steps:

[0007] Sulfur-doped graphene was prepared through a hydrothermal reaction and high-temperature annealing process;

[0008] The modified copper powder was mixed with sulfur-doped graphene and then a composite coating process was performed to obtain the SG@Cu composite material.

[0009] The adhesive is dissolved in solvent B and stirred magnetically, and then the SG@Cu composite material, conductive carbon black and dispersant are added, and a sulfur-doped graphene composite copper conductive slurry is prepared through a dispersion process.

[0010] Furthermore, the process conditions of the hydrothermal reaction are: mixing graphene oxide, thiourea and solvent A, with a mass ratio of graphene oxide to thiourea of 2:1, a reaction temperature of 160°C-200°C, and a reaction time of 10h-14h.

[0011] Furthermore, the process conditions of the high temperature annealing are: under the protection of inert gas, heating to 700° C.-900° C. at 3° C. / min-8° C. / min, and keeping the temperature for 1 hour-3 hours.

[0012] Furthermore, the copper powder is nano-scale copper particles with a particle size range of 50nm-200nm;

[0013] The surface modification comprises the following steps: adding copper powder into a dispersion of polyvinyl pyrrolidone, performing ultrasonic dispersion, centrifugal treatment and drying treatment to obtain modified copper powder.

[0014] Furthermore, the composite coating process is: sulfur-doped graphene and modified copper powder are evenly mixed in a mass ratio of 1:(1-3), and coated by ball milling, with a ball milling speed of 200-400 rpm, a ball-to-material ratio of (5-15):1, and a ball milling time of 4h-8h.

[0015] Furthermore, the sulfur-doped graphene composite copper conductive paste includes the following components in percentage by mass: 60-80 wt% of SG@Cu composite material; 5-15 wt% of conductive carbon black; 8-12 wt% of binder; 3-7 wt% of dispersant; and solvent B adjusted to a solid content of 25-35%.

[0016] Furthermore, the binder is polyvinylidene fluoride; and the solvent B is N-methylpyrrolidone.

[0017] Furthermore, the dispersion process is: first pre-disperse at a low speed of 400-600 rpm for 10 min-20 min; then disperse at a high speed of 1500-2500 rpm for 20 min-40 min; and then ultrasonically treat for 0.5 h-1.5 h, with an ultrasonic power of 180 W-220 W.

[0018] Furthermore, when the sulfur-doped graphene-coated copper composite conductive paste forms a coating with a thickness of 10 μm, the electrical conductivity is ≥1000 S / cm and the sheet resistance of the coating is ≤50 Ω / sq.

[0019] In addition, the present invention also provides an application of a sulfur-doped graphene-coated copper composite conductive paste, wherein the application is the application of the sulfur-doped graphene-coated copper composite conductive paste in the preparation of electromagnetic shielding materials, flexible OLED display materials, antistatic composite materials, smart packaging RFID tag antennas, and sodium ion battery positive electrode conductive additives. Compared with the prior art, the present invention also has the following advantages:

[0020] Beneficial effects:

[0021] 1. The present invention uses sulfur-doped graphene (SG) as a coating layer for copper powder. The sulfur atoms form a chemical bond (Cu-S) with the copper surface, significantly enhancing the interfacial bonding strength. At the same time, the p-type doping effect of sulfur improves the intrinsic conductivity of graphene.

[0022] 2. The present invention utilizes sulfur-doped graphene (SG) as a wrapping layer, which not only inhibits copper oxidation and reduces agglomeration, but also bridges copper particles through the highly conductive network of graphene to form a "metal-carbon" dual-pathway conductive system, ensuring the continuity of the conductive path.

[0023] 3. The hydrothermal-ball milling method is used to achieve the integration of sulfur doping and coating, avoiding the high-energy consumption CVD process. The process is simpler, low-cost and environmentally friendly, suitable for large-scale production, and has higher application value.

[0024] 4. The sulfur-doped graphene composite copper conductive paste prepared by the present invention has excellent overall dispersibility, can form a uniform and stable conductive paste, and can be better applied in the preparation of composite conductive paste flexible conductive films or electromagnetic shielding materials. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with its embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not limit the scope of protection of the present invention.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0027] A method for preparing a sulfur-doped graphene composite copper conductive paste in one embodiment of the present invention comprises the following steps:

[0028] Sulfur-doped graphene was prepared through a hydrothermal reaction and high-temperature annealing process;

[0029] The modified copper powder was mixed with sulfur-doped graphene and then a composite coating process was performed to obtain the SG@Cu composite material.

[0030] The adhesive is dissolved in solvent B and stirred magnetically, and then the SG@Cu composite material, conductive carbon black and dispersant are added, and a sulfur-doped graphene composite copper conductive slurry is prepared through a dispersion process.

[0031] In one embodiment, the process conditions of the hydrothermal reaction are: mixing graphene oxide, thiourea and solvent A, with a mass ratio of graphene oxide to thiourea of 2:1, a reaction temperature of 160°C-200°C, and a reaction time of 10h-14h.

[0032] In one embodiment, the solvent A is deionized water.

[0033] In one embodiment, the process conditions of the high temperature annealing are: under the protection of inert gas, heating to 700°C-900°C at 3°C / min-8°C / min, and keeping the temperature for 1h-3h.

[0034] In one embodiment, the inert gas is one of argon and nitrogen.

[0035] In one embodiment, the copper powder is nano-scale copper particles with a particle size range of 50nm-200nm;

[0036] The surface modification comprises the following steps: adding copper powder into a dispersion of polyvinyl pyrrolidone, performing ultrasonic dispersion, centrifugal treatment and drying treatment to obtain modified copper powder.

[0037] In one embodiment, the mass ratio of polyvinyl pyrrolidone to copper powder is 1:20-1:10.

[0038] In one embodiment, the centrifugal treatment is performed at a speed of 6000-10000 rpm for 10-15 min.

[0039] In one embodiment, the drying process is vacuum drying at a temperature of 50°C-70°C and a vacuum degree of -0.08 to -0.1 MPa.

[0040] In one embodiment, the composite coating process is: sulfur-doped graphene and modified copper powder are evenly mixed in a mass ratio of 1:(1-3), and coated by ball milling, with a ball milling speed of 200-400 rpm, a ball-to-material ratio of (5-15):1, and a ball milling time of 4h-8h.

[0041] In one embodiment, the composite coating process requires centrifugation and drying after ball milling. The centrifugation speed is 6,000 to 10,000 rpm for 10 to 15 minutes. The drying temperature is 50°C to 70°C, and the vacuum is controlled at -0.08 to -0.1 MPa. The ball milling time is controlled here; too long or too short a time can lead to uneven coating.

[0042] In one embodiment, the sulfur-doped graphene-copper conductive paste comprises the following components in percentage by weight: 60-80 wt% SG@Cu composite material; 5-15 wt% conductive carbon black; 8-12 wt% binder; 3-7 wt% dispersant; and solvent B adjusted to a solid content of 25-35%. The present invention requires precise control of the sulfur doping level; excessive sulfur doping may increase graphene defects and reduce conductivity. N-methylpyrrolidone is toxic and must be handled in a fume hood. Avoid residual oxygen during high-temperature annealing.

[0043] In one embodiment, the binder is polyvinylidene fluoride; and the solvent B is N-methylpyrrolidone.

[0044] In one embodiment, the mass ratio of the polyvinylidene fluoride to the solvent B which is N-methylpyrrolidone is 1:8-1:10.

[0045] In one embodiment, the dispersion process is: first pre-dispersion at a low speed of 400-600 rpm for 10 min-20 min; then high-speed shear dispersion at 1500-2500 rpm for 20 min-40 min; and then ultrasonic treatment for 0.5 h-1.5 h, with an ultrasonic power of 180 W-220 W.

[0046] In one embodiment, when the sulfur-doped graphene-coated copper composite conductive paste forms a coating with a thickness of 10 μm, the conductivity is ≥1000 S / cm and the coating square resistance is ≤50 Ω / sq.

[0047] In addition, the present invention also provides an application of a sulfur-doped graphene-coated copper composite conductive paste, which is the application of the sulfur-doped graphene-coated copper composite conductive paste in the preparation of electromagnetic shielding materials, flexible OLED display materials, antistatic composite materials, smart packaging RFID tag antennas, and sodium ion battery positive electrode conductive additives.

[0048] The key step in the composite conductive paste described in the above scheme is sulfur-doping graphene. Sulfur doping can introduce additional carriers, optimize the electronic structure of graphene, and enhance the overall conductivity of the composite material. Sulfur atoms can act as a "bridge" to strengthen the interfacial interaction between graphene and copper, reduce interfacial resistance, and improve mechanical stability. Therefore, it can effectively solve the problem of poor interfacial compatibility between conductive materials and system components in the prior art, making it difficult to form a stable and efficient conductive network. In addition, the preparation method of sulfur-doped graphene-coated copper composite conductive paste is simple and low-cost. The prepared sulfur-doped graphene-coated copper composite conductive paste has excellent overall dispersibility, uniform and stable, chemically bonded, high conductivity, and better application value.

[0049] The embodiments of the present invention will be described in detail below with reference to specific examples.

[0050] Example 1:

[0051] A method for preparing a sulfur-doped graphene composite copper conductive paste comprises the following steps:

[0052] 1.0 g of graphene oxide and 0.5 g of thiourea were dissolved in 50 mL of deionized water and ultrasonically dispersed for 30 min. After uniform dispersion, the mixture was transferred to a Teflon reactor and kept at 180°C for 12 h. The mixture was washed with 5-10 times water and freeze-dried to obtain a composite material. The composite material was then annealed at 800°C for 2 h under argon protection to obtain sulfur-doped graphene (SG);

[0053] 2.0 g of nano-copper powder (100 nm) and 0.1 g of polyvinyl pyrrolidone were ultrasonically dispersed in ethanol for 1 h. After drying, the modified copper powder was mixed with 1.0 g of sulfur-doped graphene (SG). 50 mL of ethanol was added and ultrasonically dispersed for 30 min. The mixture was then ball-milled for 6 h using a ball mill (300 rpm, ball-to-material ratio of 10:1) to uniformly coat the copper particles with SG. The mixture was then centrifuged and dried in a vacuum at 60 °C for 12 h to obtain the SG@Cu composite material.

[0054] Polyvinylidene fluoride was dissolved in N-methylpyrrolidone, and the mass ratio of polyvinylidene fluoride to N-methylpyrrolidone was adjusted to 1:9. The mixture was magnetically stirred for 2 hours, and then SG@Cu (70%), conductive carbon black (10%), and polyvinyl pyrrolidone (5%) were added in sequence. The mixture was first pre-dispersed by low-speed stirring (stirring at a speed of 500 rpm for 20 minutes, and then switched to high-speed shear dispersion (stirring at a speed of 2000 rpm for 40 minutes), followed by ultrasonic treatment (power 200 W, pulse mode) for 1.5 hours to eliminate bubbles and further disperse. After vacuum drying at 90°C, a sulfur-doped graphene-coated copper composite conductive slurry was obtained, which was recorded as S1.

[0055] The sulfur-doped graphene-coated copper composite conductive paste of Example 1 is used for preparing electromagnetic shielding materials.

[0056] A sulfur-doped graphene-coated copper composite conductive paste (72% solids content) was mixed with waterborne polyurethane in a 3:1 mass ratio, and 0.5% KH-550 coupling agent was added. After three-roll milling (10μm gap), the viscosity was controlled at 3500 cP (25°C). A 3μm coating was formed on a PET substrate by spin coating and cured at 80°C to produce an electromagnetic shielding material.

[0057] The surface resistance of the electromagnetic shielding material in Example 1 reaches 0.8Ω / sq. According to ASTM D4935 testing, the shielding effectiveness (SE) in the 8-12GHz band is >48dB, and the SE value retention rate after 500 bends (r=2mm) is >95%.

[0058] Example 2:

[0059] A method for preparing a sulfur-doped graphene composite copper conductive paste comprises the following steps:

[0060] 1.0 g of graphene oxide and 0.5 g of thiourea were dissolved in 50 mL of deionized water and ultrasonically dispersed for 30 min. After uniform dispersion, the mixture was transferred to a Teflon reactor and kept at 180 ° C for 12 h. The mixture was washed with 5-10 times water and freeze-dried to obtain a composite material. The composite material was then annealed at 800 ° C for 2 h under argon protection to obtain sulfur-doped graphene (SG);

[0061] 2.0 g of nano-copper powder (100 nm) and 0.1 g of polyvinyl pyrrolidone were ultrasonically dispersed in ethanol for 1 h. After drying, the modified copper powder was mixed with 1.0 g of sulfur-doped graphene (SG). 50 mL of ethanol was added and ultrasonically dispersed for 30 min. The mixture was then ball-milled for 6 h using a ball mill (300 rpm, ball-to-material ratio of 10:1) to uniformly coat the copper particles with SG. The mixture was then centrifuged and dried in a vacuum at 60 °C for 12 h to obtain the SG@Cu composite material.

[0062] Polyvinylidene fluoride was dissolved in N-methylpyrrolidone, and the mass ratio of polyvinylidene fluoride to N-methylpyrrolidone was adjusted to 1:9. The mixture was magnetically stirred for 2 hours, and then SG@Cu (68%), conductive carbon black (12%), and polyvinyl pyrrolidone (5%) were added in sequence. The mixture was pre-dispersed by low-speed stirring (stirring at 500 rpm for 20 minutes), and then switched to high-speed shear dispersion (stirring at 2000 rpm for 40 minutes). Subsequently, the mixture was ultrasonically treated (power 200 W, pulse mode) for 1.5 hours to eliminate bubbles and further disperse. After vacuum drying at 90°C, a sulfur-doped graphene-coated copper composite conductive slurry was obtained, which was recorded as S2.

[0063] S-Cu@G composite particles were refined to 50nm and compounded with 20nm diameter silver nanowires in a mass ratio of 7:3. 0.5% sodium dodecylbenzenesulfonate (SDBS) was then added as a dispersant and dissolved in a 4:1 ethanol / water mixture. The solids content was adjusted to 12%. 0.3% hydroxypropyl methylcellulose (HPMC) was added to stabilize the slurry viscosity at 220 cP (25°C) and the surface tension at 28 mN / m.

[0064] The film was deposited on a PET substrate (thickness 125 μm) using an ultrasonic spray coating device (Sono-Tek ExactaCoat) with a nozzle diameter of 100 μm, a carrier gas pressure of 0.3 MPa, and a substrate temperature of 80°C to form a continuous film with a thickness of 80 nm. The film was annealed at 150°C for 30 min and then laser sintered in a N atmosphere (wavelength 1064 nm, power 15 W, scanning speed 5 mm / s).

[0065] The sulfur-doped graphene-coated copper composite conductive paste of Example 2 is used for preparing flexible OLED display materials.

[0066] Photoelectric performance tests show that: (1) the transmittance is 89% at a wavelength of 550nm (5% better than ITO film at the same square resistance); (2) the square resistance is 18Ω / sq measured by the four-probe method; (3) after bending 10,000 times at a curvature radius of 3mm, the resistance change rate is <3% (AFM shows crack density <0.1μm-1); (4) after aging at 85℃ / 85%RH for 500h, the square resistance increases by <8%.

[0067] Example 3:

[0068] A method for preparing a sulfur-doped graphene composite copper conductive paste comprises the following steps:

[0069] 1.0 g of graphene oxide and 0.5 g of thiourea were dissolved in 50 mL of deionized water and ultrasonically dispersed for 30 min. After uniform dispersion, the mixture was transferred to a Teflon reactor and kept at 180 ° C for 12 h. The mixture was washed with 5-10 times water and freeze-dried to obtain a composite material. The composite material was then annealed at 800 ° C for 2 h under argon protection to obtain sulfur-doped graphene (SG);

[0070] 2.0 g of nano-copper powder (100 nm) and 0.1 g of polyvinyl pyrrolidone were ultrasonically dispersed in ethanol for 1 h. After drying, the modified copper powder was mixed with 1.0 g of sulfur-doped graphene (SG). 50 mL of ethanol was added and ultrasonically dispersed for 30 min. The mixture was then ball-milled for 6 h using a ball mill (300 rpm, ball-to-material ratio of 10:1) to uniformly coat the copper particles with SG. The mixture was then centrifuged and dried in a vacuum at 60 °C for 12 h to obtain the SG@Cu composite material.

[0071] Polyvinylidene fluoride was dissolved in N-methylpyrrolidone, and the mass ratio of polyvinylidene fluoride to N-methylpyrrolidone was adjusted to 1:9. The mixture was magnetically stirred for 2 hours, and then SG@Cu (66%), conductive carbon black (14%), and polyvinyl pyrrolidone (5%) were added in sequence. The mixture was pre-dispersed by low-speed stirring (stirring at 500 rpm for 20 minutes), and then switched to high-speed shear dispersion (stirring at 2000 rpm for 40 minutes). Subsequently, the mixture was ultrasonically treated (power 200 W, pulse mode) for 1.5 hours to eliminate bubbles and further disperse. After vacuum drying at 90°C, a sulfur-doped graphene-coated copper composite conductive slurry was obtained, which was recorded as S3.

[0072] The sulfur-doped graphene-coated copper composite conductive paste in Example 3 is used to prepare an antistatic composite material.

[0073] A sulfur-doped graphene-coated copper composite conductive paste was blended with polyetheretherketone (PEEK) particles (2 mm in diameter) using a twin-screw extruder (380°C) at a 15 wt% sulfur-doped graphene-coated copper composite conductive paste. 30% carbon fibers (200 μm in length) were added, and standard test specimens were prepared using an injection molding process.

[0074] The performance test of the standard test specimen shows: conductivity: volume resistivity 3×10 2 Ω·cm; Mechanical properties: tensile strength 128MPa, impact toughness 9kJ / m 2 ; Under the conditions of 10-3Pa vacuum and -150℃, the resistance fluctuation is <5%; the surface potential after friction with aluminum alloy is <50V.

[0075] Example 4:

[0076] A method for preparing a sulfur-doped graphene composite copper conductive paste comprises the following steps:

[0077] 1.0 g of graphene oxide and 0.5 g of thiourea were dissolved in 50 mL of deionized water and ultrasonically dispersed for 30 min. After uniform dispersion, the mixture was transferred to a Teflon reactor and kept at 180 ° C for 12 h. The mixture was washed with 5-10 times water and freeze-dried to obtain a composite material. The composite material was then annealed at 800 ° C for 2 h under argon protection to obtain sulfur-doped graphene (SG);

[0078] 2.0 g of nano-copper powder (100 nm) and 0.1 g of polyvinyl pyrrolidone were ultrasonically dispersed in ethanol for 1 h. After drying, the modified copper powder was mixed with 1.0 g of sulfur-doped graphene (SG). 50 mL of ethanol was added and ultrasonically dispersed for 30 min. The mixture was then ball-milled for 6 h using a ball mill (300 rpm, ball-to-material ratio of 10:1) to uniformly coat the copper particles with SG. The mixture was then centrifuged and dried in a vacuum at 60 °C for 12 h to obtain the SG@Cu composite material.

[0079] Polyvinylidene fluoride was dissolved in N-methylpyrrolidone, and the mass ratio of polyvinylidene fluoride to N-methylpyrrolidone was adjusted to 1:9. The mixture was magnetically stirred for 2 hours, and then SG@Cu (64%), conductive carbon black (16%), and polyvinyl pyrrolidone (5%) were added in sequence. The mixture was pre-dispersed by low-speed stirring (500 rpm) for 20 minutes, and then switched to high-speed shear dispersion (2000 rpm, 40 minutes); then ultrasonic treatment (power 200 W, pulse mode) was performed for 1.5 hours to eliminate bubbles and further disperse the mixture. After vacuum drying at 90°C, a sulfur-doped graphene-coated copper composite conductive slurry was obtained, which was recorded as S4.

[0080] The sulfur-doped graphene-coated copper composite conductive paste in Example 4 is used to prepare the smart packaging RFID tag antenna.

[0081] A sulfur-doped graphene-coated copper composite conductive paste was mixed with ethyl cellulose in a mass ratio of 88:12. A 2% terpene solvent was then added to reduce the viscosity to 1200 cP, suitable for inkjet printing. A 13.56 MHz RFID antenna (50 μm line width) was then printed on a PET substrate (50 μm thickness). After curing at 60°C, the resistivity reached 3.5 × 10-Ω·cm.

[0082] Material performance tests show a maximum read distance of 4.2m, attributed to lower antenna resistance; after aging for 500 hours at high temperature and humidity (85°C / 85% RH), the read distance attenuation is <5%; and after 5000 bends at a curvature radius of 2mm, the resonant frequency shift is <0.1MHz.

[0083] Example 5:

[0084] A method for preparing a sulfur-doped graphene composite copper conductive paste comprises the following steps:

[0085] 1.0 g of graphene oxide and 0.5 g of thiourea were dissolved in 50 mL of deionized water and ultrasonically dispersed for 30 min. After uniform dispersion, the mixture was transferred to a Teflon reactor and kept at 180 ° C for 12 h. The mixture was washed with 5-10 times water and freeze-dried to obtain a composite material. The composite material was then annealed at 800 ° C for 2 h under argon protection to obtain sulfur-doped graphene (SG);

[0086] 2.0 g of nano-copper powder (100 nm) and 0.1 g of polyvinyl pyrrolidone were ultrasonically dispersed in ethanol for 1 h. After drying, the modified copper powder was mixed with 1.0 g of sulfur-doped graphene (SG). 50 mL of ethanol was added and ultrasonically dispersed for 30 min. The mixture was then ball-milled for 6 h using a ball mill (300 rpm, ball-to-material ratio of 10:1) to uniformly coat the copper particles with SG. The mixture was then centrifuged and dried in a vacuum at 60 °C for 12 h to obtain the SG@Cu composite material.

[0087] Polyvinylidene fluoride was dissolved in N-methylpyrrolidone, and the mass ratio of polyvinylidene fluoride to N-methylpyrrolidone was adjusted to 1:9. The mixture was magnetically stirred for 2 hours, and then SG@Cu (62%), conductive carbon black (18%), and polyvinyl pyrrolidone (5%) were added in sequence. The mixture was pre-dispersed by low-speed stirring (stirring at 500 rpm for 20 minutes), and then switched to high-speed shear dispersion (stirring at 2000 rpm for 40 minutes). Subsequently, the mixture was ultrasonically treated (power 200 W, pulse mode) for 1.5 hours to eliminate bubbles and further disperse. After vacuum drying at 90°C, a sulfur-doped graphene-coated copper composite conductive slurry was obtained, which was recorded as S5.

[0088] The sulfur-doped graphene-coated copper composite conductive slurry in Example 5 is used as a positive electrode conductive additive for sodium ion batteries.

[0089] A core-shell structure was formed by ball milling a Na₃V₂(PO₄)₃(NVP) cathode material with a sulfur-doped graphene-coated copper composite conductive paste at a ratio of 90:10 (400 rpm for 6 hours). The composite powder and polyvinylidene fluoride binder were dissolved in N-methylpyrrolidone at a ratio of 95:5 to a solid content of 68%. A 150μm wet film was applied to aluminum foil, vacuum dried at 120°C, and then rolled to 80μm. The active material loading was 18mg / cm⁻¹. 2 .

[0090] Material performance tests show that the specific capacities at 0.5C, 5C, and 10C rates are 125mAh / g, 118mAh / g, and 105mAh / g, respectively; the capacity retention rate after 2000 cycles is 91%; and the capacity retention rate at 0.2C at -20°C is 85%, which is attributed to the increased ion diffusion rate caused by sulfur doping.

[0091] In addition, the present application also conducted performance tests on the sulfur-doped graphene-coated copper composite conductive paste samples of Examples 1 to 5 above, and the results are shown in Table 1 below.

[0092] Table 1: Performance test results

[0093]

[0094] From the data analysis of Table 1, it can be seen that the sulfur-doped graphene-coated copper composite conductive paste prepared in this application has excellent stability and conductivity.

[0095] In summary, the present invention provides a method for preparing a sulfur-doped graphene-coated copper composite conductive paste, and applies it to conductive materials. The composite conductive paste exhibits high electrical conductivity and low square resistance. Therefore, the sulfur-doped graphene-coated copper composite conductive paste has broad application prospects in the fields of electromagnetic shielding, antistatic materials, and smart materials.

[0096] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0097] The above-described embodiments merely represent several implementation methods of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing a sulfur-doped graphene composite copper conductive paste, characterized in that: The preparation method comprises the following steps: Sulfur-doped graphene was prepared through a hydrothermal reaction and high-temperature annealing process; The modified copper powder was mixed with sulfur-doped graphene and then a composite coating process was performed to obtain the SG@Cu composite material. The adhesive is dissolved in solvent B and stirred magnetically, and then the SG@Cu composite material, conductive carbon black and dispersant are added, and a sulfur-doped graphene composite copper conductive slurry is prepared through a dispersion process.

2. The preparation method according to claim 1, wherein The process conditions of the hydrothermal reaction are: mixing graphene oxide, thiourea and solvent A, with a mass ratio of graphene oxide to thiourea of 2:1, a reaction temperature of 160° C.-200° C., and a reaction time of 10 h-14 h.

3. The preparation method according to claim 1, wherein The process conditions of the high temperature annealing are: under the protection of inert gas, heating to 700° C.-900° C. at 3° C. / min-8° C. / min, and keeping the temperature for 1 hour-3 hours.

4. The preparation method according to claim 1, wherein The copper powder is nano-scale copper particles with a particle size range of 50nm-200nm; The surface modification comprises the following steps: adding copper powder into a dispersion of polyvinyl pyrrolidone, performing ultrasonic dispersion, centrifugal treatment and drying treatment to obtain modified copper powder.

5. The preparation method according to claim 1, wherein The composite coating process comprises: uniformly mixing sulfur-doped graphene and modified copper powder in a mass ratio of 1:(1-3), coating by ball milling, with a ball milling speed of 200-400 rpm, a ball-to-material ratio of (5-15):1, and a ball milling time of 4h-8h.

6. The preparation method according to claim 1, wherein The sulfur-doped graphene composite copper conductive paste comprises the following components in percentage by mass: 60-80 wt% of SG@Cu composite material; 5-15 wt% of conductive carbon black; 8-12 wt% of binder; 3-7 wt% of dispersant; and solvent B adjusted to a solid content of 25-35%.

7. The preparation method according to claim 6, wherein The binder is polyvinylidene fluoride; and the solvent B is N-methylpyrrolidone.

8. The preparation method according to claim 1, wherein The dispersion process is as follows: pre-dispersion at a low speed of 400-600 rpm for 10-20 minutes; then high-speed shear dispersion at 1500-2500 rpm for 20-40 minutes; and then ultrasonic treatment for 0.5-1.5 hours, with an ultrasonic power of 180W-220W.

9. The sulfur-doped graphene-coated copper composite conductive paste prepared by any one of claims 1 to 8, characterized in that: When the sulfur-doped graphene-coated copper composite conductive paste forms a coating with a thickness of 10 μm, the conductivity is ≥1000 S / cm and the coating square resistance is ≤50 Ω / sq.

10. An application of a sulfur-doped graphene-coated copper composite conductive paste, characterized in that: The application is the use of the sulfur-doped graphene-coated copper composite conductive paste prepared by any method of claims 1-8 in the preparation of electromagnetic shielding materials, flexible OLED display materials, antistatic composite materials, smart packaging RFID tag antennas and sodium ion battery positive electrode conductive additives.

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