CN113621235A - Conductive composite material, preparation method thereof and bipolar plate for fuel cell stack - Google Patents
Conductive composite material, preparation method thereof and bipolar plate for fuel cell stack Download PDFInfo
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K9/00—Use of pretreated ingredients
- C08K9/10—Encapsulated ingredients
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/02—Elements
- C08K3/04—Carbon
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/02—Elements
- C08K3/04—Carbon
- C08K3/041—Carbon nanotubes
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/02—Elements
- C08K3/08—Metals
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/02—Details
- H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
- H01M8/0204—Non-porous and characterised by the material
- H01M8/0223—Composites
- H01M8/0226—Composites in the form of mixtures
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/02—Elements
- C08K3/08—Metals
- C08K2003/0806—Silver
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/02—Elements
- C08K3/08—Metals
- C08K2003/085—Copper
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K2201/00—Specific properties of additives
- C08K2201/001—Conductive additives
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
Abstract
The invention belongs to the technical field of materials, and particularly relates to a conductive composite material and a preparation method thereof, in particular to a bipolar plate for a fuel cell stack. The conductive composite material comprises the following raw material components in percentage by mass based on 100% of the total mass of the conductive composite material: 31-50% of graphite, 25-35% of resin, 15-25% of metal powder, 0.5-1% of coupling agent and 3-8% of carbon nano tube. The conductive composite material provided by the invention has excellent conductive performance, processability and mechanical property simultaneously through the synergistic effect of raw material components such as graphite, metal powder, carbon nano tubes, resin, coupling agent and the like and the proportion thereof, and is particularly suitable for fuel cell stack bipolar plates.
Description
Technical Field
The invention belongs to the technical field of materials, and particularly relates to a conductive composite material and a preparation method thereof, in particular to a bipolar plate for a fuel cell stack.
Background
At present, carbon dioxide emissions from fossil energy fuels are the most dominant greenhouse gas emissions source. In the face of global severe energy conservation and emission reduction and energy shortage, fuel cell vehicles are used as future strategic directions of the automobile industry at home and abroad, and the technical change of commercial vehicles with high energy consumption and high emission is more urgent. Under the background of increasingly prominent energy environmental problems such as energy safety, carbon emission limit and the like, special management organizations are arranged in many countries and regions, a large amount of resources are invested, relevant regulations and policies are released, and the rapid development of the hydrogen energy and fuel cell industry is promoted. The fuel cell device is beneficial to realizing mobility, light weight and large-scale popularization of hydrogen energy, and can be widely applied to scenes such as transportation, industry, buildings and the like.
Due to the characteristics of low working temperature, quick start, high specific power and the like, a Proton Exchange Membrane Fuel Cell (PEMFC) is very suitable for being applied to the fields of transportation and fixed power stations and gradually becomes a mainstream application technology at home and abroad at the present stage. The main components of a PEMFC stack include a Membrane Electrode (MEA) and a bipolar plate (also called a collector plate), wherein the MEA is composed of a proton exchange membrane, a catalyst layer, and a gas diffusion layer. The bipolar plate is a core multifunctional part of the PEMFC, the weight of the bipolar plate accounts for 60-80% of that of the galvanic pile, the cost accounts for 20-30%, and the cost and the weight of the PEMFC can be effectively reduced by carrying out lightweight treatment on the bipolar plate. At present, graphite, metal and composite materials are widely used for preparing PEMFC bipolar plates, wherein a more mature technology is applied to the graphite bipolar plates.
However, graphite bipolar plates lack durability and engineering validation for small scale use; poor mechanical processing performance, slow processing process, longer period, high requirement on mechanical precision and higher cost of the graphite plate. And air holes are easy to generate in the manufacturing structure, especially for the bipolar plate with a complex and smooth surface, the processing cost is too high, and the bipolar plate is not suitable for large-scale production. Although the injection molding process can greatly reduce the cost of the bipolar plate, the raw materials are required to have good fluidity, and the performance requirements of the bipolar plate, especially the conductivity, are simultaneously met, and the addition amount of the conductive filler is required to be more than 70%, which seriously reduces the processing performance and the physical and mechanical properties of the material.
Disclosure of Invention
Problems to be solved by the invention
The invention aims to provide a conductive composite material, and aims to solve the technical problems that the conductive composite material of the bipolar plate for the fuel cell stack in the prior art cannot simultaneously meet the conductive performance, the processing performance, the physical and mechanical properties and the like.
Another object of the present invention is to provide a method for preparing a conductive composite material.
It is yet another object of the present invention to provide a bipolar plate for a fuel cell stack.
Means for solving the problems
In order to achieve the purpose of the invention, the technical scheme adopted by the invention is as follows:
the conductive composite material comprises the following raw material components in percentage by mass based on 100% of the total mass of the conductive composite material:
further, the resin includes: at least one of polyphenylene sulfide powder, polystyrene, polypropylene, acrylonitrile-butadiene-styrene copolymer and polyvinylidene fluoride.
Further, the coupling agent comprises: at least one of silane coupling agent and titanate coupling agent.
Further, the metal powder includes: at least one of copper powder, silver-coated copper powder and silver powder.
Further, the mesh number of the metal powder is not higher than 400 meshes.
Further, the diameter of the carbon nanotube is 1 to 50nm, and the length of the carbon nanotube is 1 to 200 μm.
Further, the conductive composite material comprises the following raw material components in percentage by mass based on 100% of the total mass of the conductive composite material:
in order to achieve the above object, the present invention adopts another technical solution as follows:
a preparation method of a conductive composite material comprises the following steps:
mixing and granulating 31-50 parts of graphite, 25-35 parts of resin, 15-25 parts of metal powder, 0.5-1 part of coupling agent and 3-8 parts of carbon nano tubes to obtain the conductive composite material.
Further, the mixing and granulating step comprises:
carrying out drying pretreatment on a graphite raw material to obtain graphite;
carrying out first mixing treatment on the graphite and the resin to obtain a first mixture;
carrying out second mixing treatment on the metal powder and the first mixture, and then carrying out first melting granulation to obtain mixed particles;
and carrying out third mixing treatment on the coupling agent, the carbon nano tube and the mixed particles, and then carrying out second melting granulation to obtain the conductive composite material.
Further, the step of dry pre-treatment comprises: and treating the graphite raw material for 10-15 min under the conditions that the temperature is 90-100 ℃ and the rotating speed is 200-500 r/min.
Further, the conditions of the first mixing process include: and (3) after the graphite is subjected to heat treatment for 10-15 min, adding the resin, and mixing for 15-25 min under the condition that the rotating speed is 1000-1500 r/min.
Further, the conditions of the second mixing process include: mixing and processing for 20-30 min under the condition that the rotating speed is 1000-1500 r/min.
Further, the step of subjecting the coupling agent, the carbon nanotubes and the mixed particles to a third mixing process includes: and mixing the coupling agent and the mixed particles for 20-30 min under the condition that the rotating speed is 1000-1500 r/min, and then adding the carbon nano tubes for mixing for 20-30 min under the condition that the rotating speed is 1000-1500 r/min.
Further, the first melt granulation and the second melt granulation are respectively and independently melt-extruded and granulated by a twin-screw extruder.
Further, the particle size of the conductive composite material is 2-6 microns.
Further, the resin includes: at least one of polyphenylene sulfide powder, polystyrene, polypropylene, acrylonitrile-butadiene-styrene copolymer and polyvinylidene fluoride.
Further, the coupling agent comprises: at least one of silane coupling agent and titanate coupling agent.
Further, the metal powder includes: at least one of copper powder, silver-coated copper powder and silver powder.
Further, the mesh number of the metal powder is not higher than 400 meshes.
Further, the diameter of the carbon nanotube is 1 to 50nm, and the length of the carbon nanotube is 1 to 200 μm.
In order to achieve the above object, the present invention adopts another technical solution as follows:
the bipolar plate for the fuel cell stack is made of the conductive composite material or the conductive composite material prepared by the method.
Effects of the invention
The conductive composite material provided by the invention comprises the raw material components of 31-50% of graphite, 25-35% of resin, 15-25% of metal powder, 0.5-1% of coupling agent and 3-8% of carbon nano tubes, wherein the graphite is used as a conductive agent of the conductive composite material, the processing performance of the conductive composite material is influenced if the content is too high, and the conductivity of the composite material is not good if the content is too low. The resin plays a role in binding and is connected with components such as graphite, metal powder, carbon nanotubes and the like to form the conductive composite material, if the content is too high, the conductivity of the composite material is reduced, and if the content is too low, the binding stability of the conductive composite material is influenced. The metal powder has excellent conductivity, and can further provide the conductivity of the composite material in cooperation with components such as graphite, carbon nanotubes and the like; but also can improve the fluidity among the raw material components, prevent the raw material components from agglomerating and improve the processing performance and the mechanical property of the conductive composite material. The coupling agent can improve the compatibility of the conductive agent, the metal powder, the graphite and the carbon nano tube with the resin matrix, thereby improving the processing performance of the conductive composite material, and if the content is too high, the conductive performance of the composite material can be reduced. The carbon nano tube can play a role of a conductive bridge in the conductive composite material to form a three-dimensional conductive network, so that the conductivity of the conductive composite material is improved, and the mechanical property of the material is improved. If the content of the carbon nanotubes is too high, the processability of the conductive composite material may be reduced. The conductive composite material has excellent conductive performance, processing performance and mechanical performance through the synergistic effect of the raw material components such as graphite, metal powder, carbon nano tubes, resin, coupling agent and the like and the proportion thereof, and is particularly suitable for fuel cell stack bipolar plates.
According to the preparation method of the conductive composite material, the conductive composite material can be obtained by mixing and granulating 31-50 parts of graphite, 25-35 parts of resin, 15-25 parts of metal powder, 0.5-1 part of coupling agent and 3-8 parts of carbon nano tubes, and the fluidity of the material is maintained and the processability of the raw material components is improved on the premise of meeting the requirement of the conductivity of the material through the synergistic effect of the raw material components and the proportion thereof, so that the preparation process is simplified, the preparation efficiency of the conductive composite material is improved, and the preparation cost is reduced. Meanwhile, the method is suitable for a more efficient injection molding process, improves the production efficiency of the bipolar plate for the fuel cell stack, and reduces the manufacturing cost of the bipolar plate.
The bipolar plate for the fuel cell stack is prepared by adopting the conductive composite material, and the conductive composite material has excellent conductivity, processability and mechanical property, so that the conductive performance of the bipolar plate is ensured, the bipolar plate can be processed conveniently, the manufacturing efficiency is improved, and the cost is reduced.
Drawings
Fig. 1 and 2 are scanning electron micrographs of the conductive composite provided in example 1 of the present invention.
Detailed Description
In order to make the purpose, technical solution and technical effect of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention is clearly and completely described, and it is obvious that the described embodiments are a part of the embodiments of the present invention, but not all embodiments. All other embodiments obtained by a person of ordinary skill in the art without any inventive step in connection with the embodiments of the present invention shall fall within the scope of protection of the present invention.
In the description of the present invention, it is to be understood that the terms "first", "second" and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
The weight of the related components mentioned in the description of the embodiments of the present invention may not only refer to the specific content of each component, but also represent the proportional relationship of the weight among the components, and therefore, the content of the related components is scaled up or down within the scope disclosed in the description of the embodiments of the present invention as long as it is in accordance with the description of the embodiments of the present invention. Specifically, the weight in the description of the embodiment of the present invention may be a unit of mass known in the chemical industry field such as μ g, mg, g, kg, etc.
The embodiment of the invention provides a conductive composite material, which comprises the following raw material components in percentage by mass based on 100% of the total mass of the conductive composite material:
the conductive composite material provided by the embodiment of the invention comprises 31-50% of graphite, 25-35% of resin, 15-25% of metal powder, 0.5-1% of coupling agent and 3-8% of carbon nano tubes, wherein the graphite is used as a conductive agent of the conductive composite material, and if the content is too high, the processability of the conductive composite material is influenced, and if the content is too low, the conductivity of the composite material is poor. The resin plays a role in binding and is connected with components such as graphite, metal powder, carbon nanotubes and the like to form the conductive composite material, if the content is too high, the conductivity of the composite material is reduced, and if the content is too low, the binding stability of the conductive composite material is influenced. The metal powder has excellent conductivity, and can further provide the conductivity of the composite material in cooperation with components such as graphite, carbon nanotubes and the like; but also can improve the fluidity among the raw material components, prevent the raw material components from agglomerating and improve the processing performance and the mechanical property of the conductive composite material. The coupling agent can improve the compatibility of the conductive agent, the metal powder, the graphite and the carbon nano tube with the resin matrix, thereby improving the processing performance of the conductive composite material, and if the content is too high, the conductive performance of the composite material can be reduced. The carbon nano tube can play a role of a conductive bridge in the conductive composite material to form a three-dimensional conductive network, so that the conductivity of the conductive composite material is improved, and the mechanical property of the material is improved. If the content of the carbon nanotubes is too high, the processability of the conductive composite material may be reduced. According to the conductive composite material disclosed by the embodiment of the invention, the raw material components such as graphite, metal powder, carbon nano tubes, resin, a coupling agent and the like and the proportioning synergistic effect are utilized, so that the conductive composite material has excellent conductivity, processability and mechanical properties at the same time, and is particularly suitable for fuel cell stack bipolar plates.
In some embodiments, the resin comprises: at least one of polyphenylene sulfide powder, polystyrene, polypropylene, acrylonitrile-butadiene-styrene copolymer and polyvinylidene fluoride; the resin materials have good adhesive property, and can effectively improve the combination stability of each component in the conductive composite material. In some preferred embodiments, the resin is selected from polyphenylene sulfide powder, which has the advantages of high mechanical strength, high temperature resistance, chemical resistance, flame retardancy, good thermal stability, excellent electrical properties, and the like.
In some embodiments, the coupling agent comprises: at least one of silane coupling agent and titanate coupling agent, which can improve the compatibility of the conductive components such as graphite, carbon nano tube, metal powder and the like with resin. In some preferred embodiments, the coupling agent is a silane coupling agent, which has reactivity with inorganic substances such as metal powder, and the organic functional group has reactivity or compatibility with organic substances such as resin, so that a connecting bridge is formed between inorganic and organic interfaces, and the compatibility, the combination stability and the like of each raw material component in the conductive composite material are improved.
In some embodiments, the metal powder comprises: at least one of copper powder, silver-coated copper powder and silver powder, wherein the metal powder has better conductivity, and the conductivity of the composite material can be effectively improved by cooperating with the graphite and the carbon nano tube. In some preferred embodiments, the metal powder is selected from silver-coated copper powder. In some embodiments, the silver-coated copper powder can form silver coatings with different thicknesses on the surface of the superfine copper powder through a chemical plating technology and a specific forming and surface treatment process, so that the defects that the copper powder is easy to oxidize and the silver powder is expensive and easy to migrate are overcome, and the silver-coated copper powder has the characteristics of good conductivity, high chemical stability, difficult oxidation and the like.
In some embodiments, the mesh number of the metal powder is not higher than 400 meshes, and the metal powder with small particle size has a large specific surface area, so that the compatibility and the fluidity among raw material components such as carbon nanotubes and the like are improved, the raw material components are prevented from agglomerating, and the processing performance and the mechanical performance of the conductive composite material are improved.
In some embodiments, the carbon nanotubes have a diameter of 1 to 50nm and a length of 1 to 200 μm. The carbon nanotube material adopted by the embodiment of the invention has high length-diameter ratio, not only has better conductivity, but also is more beneficial to the carbon nanotube to form a three-dimensional conductive network structure in the conductive composite material.
In some preferred embodiments, the conductive composite material comprises the following raw material components in percentage by mass based on 100% of the total mass of the conductive composite material:
the conductive composite material provided by the embodiment of the invention can be prepared by the following method of the embodiment.
The embodiment of the invention also provides a preparation method of the conductive composite material, which comprises the following steps:
s10, mixing and granulating 31-50 parts of graphite, 25-35 parts of resin, 15-25 parts of metal powder, 0.5-1 part of coupling agent and 3-8 parts of carbon nano tubes to obtain the conductive composite material.
According to the preparation method of the conductive composite material provided by the embodiment of the invention, the conductive composite material can be obtained by mixing and granulating 31-50 parts of graphite, 25-35 parts of resin, 15-25 parts of metal powder, 0.5-1 part of coupling agent and 3-8 parts of carbon nano tubes, and the fluidity of the material is maintained and the processability of the raw material components is improved on the premise of meeting the requirement of the conductivity of the material through the synergistic effect of the raw material components and the mixture ratio thereof, so that the preparation process is simplified, the preparation efficiency of the conductive composite material is improved, and the preparation cost is reduced. Meanwhile, the method is suitable for a more efficient injection molding process, improves the production efficiency of the bipolar plate for the fuel cell stack, and reduces the manufacturing cost of the bipolar plate.
In some embodiments, in the step S10, the mixing and granulating step includes:
s11, carrying out drying pretreatment on a graphite raw material to obtain graphite;
s12, carrying out first mixing treatment on graphite and resin to obtain a first mixture;
s13, carrying out second mixing treatment on the metal powder and the first mixture, and carrying out first melting granulation to obtain mixed particles;
s14, carrying out third mixing treatment on the coupling agent, the carbon nano tube and the mixed particles, and then carrying out second melting granulation to obtain the conductive composite material.
In the mixing and granulating step in the preparation of the conductive composite material, firstly, the graphite raw material is subjected to drying pretreatment, water in graphite is removed, the purity of the graphite is improved, the interference of the water on a subsequent mixing process is avoided, and then, the graphite and resin are subjected to mixing treatment, so that the graphite and the resin are fully and uniformly mixed; then mixing the metal powder with the mixed particles to obtain an even dispersion of the metal powder, graphite and resin, and then carrying out primary granulation to obtain mixed particles; and then mixing the mixture with a coupling agent and carbon nano tubes to form a uniform mixture, and then carrying out secondary granulation to obtain the conductive composite material. By mixing the raw material components in sequence and in stages and combining secondary granulation, the uniform mixing of the raw material components can be fully ensured, and the uniform and stable conductive composite material is formed.
In some embodiments, in the step S11, the step of drying the pre-treatment includes: under the conditions that the temperature is 90-100 ℃ and the rotating speed is 200-500 r/min, the graphite raw material is treated for 10-15 min, water is removed, the purity of graphite is improved, the subsequent mixing process is prevented from being interfered by water and the like, and the stability of the conductive composite material is improved.
In some embodiments, in the above step S12, the conditions of the first mixing process include: and (3) mixing for 15-25 min under the condition that the rotating speed is 1000-1500 r/min, so that the graphite and the resin are fully and uniformly mixed to form stably dispersed mixed slurry.
In some embodiments, in the above step S13, the conditions of the second mixing process include: and mixing the metal powder and the first mixture for 20-30 min under the condition that the rotating speed is 1000-1500 r/min, so that the metal powder is fully dispersed into the mixture of the graphite and the resin.
In some embodiments, in step S13, after the metal powder and the first mixture are mixed for 20 to 30 minutes at a rotation speed of 1000 to 1500r/min, a twin-screw extruder is used to melt and extrude the mixture for granulation, so as to obtain the mixed particles.
In some embodiments, in the step S14, the step of performing a third mixing process on the coupling agent, the carbon nanotubes and the mixed particles includes: mixing the coupling agent and the mixed particles for 20-30 min at the rotating speed of 1000-1500 r/min, and then adding the carbon nano tubes for mixing for 20-30 min at the rotating speed of 1000-1500 r/min; the step-by-step mixing and the synergistic effect of the coupling agent are more favorable for enabling the carbon nano tube to be uniformly and stably mixed in the material.
In some embodiments, in step S14, after the coupling agent and the mixed particles are mixed for 20 to 30min at a rotation speed of 1000 to 1500r/min, the carbon nanotubes are added and mixed for 20 to 30min at a rotation speed of 1000 to 1500 r/min; and then, carrying out melt extrusion granulation by adopting a double-screw extruder to obtain the conductive composite material.
In some embodiments, the particle size of the conductive composite material is about 4 μm, such as 2-6 μm, and the conductive composite material with the particle size has small particle size and high uniformity, and is beneficial to application in preparation of fuel cell stack bipolar plates.
In some embodiments, the resin comprises: at least one of polyphenylene sulfide powder, polystyrene, polypropylene, acrylonitrile-butadiene-styrene copolymer and polyvinylidene fluoride.
In some embodiments, the coupling agent comprises: at least one of silane coupling agent and titanate coupling agent.
In some embodiments, the metal powder comprises: at least one of copper powder, silver-coated copper powder and silver powder.
In some embodiments, the mesh size of the metal powder is not higher than 400 mesh.
In some embodiments, the carbon nanotubes have a diameter of 1 to 50nm and a length of 1 to 200 μm.
The technical effects of the above embodiments of the present invention are discussed in detail in the foregoing, and are not described herein again.
The embodiment of the invention also provides a bipolar plate for a fuel cell stack, which is made of the conductive composite material or the conductive composite material prepared by the method.
The bipolar plate for the fuel cell stack provided by the embodiment of the invention is prepared by adopting the conductive composite material, and the conductive composite material has excellent conductivity, processability and mechanical property, so that the conductive performance of the bipolar plate is ensured, the bipolar plate can be processed conveniently, the manufacturing efficiency is improved, and the cost is reduced.
According to the conductive composite material provided by the embodiment of the invention, the conductive composite material keeps the fluidity of the material and improves the processing performance of raw material components on the premise of meeting the conductive performance requirement of the material through the synergistic effect of the high-conductivity silver-coated copper powder, the graphite, the carbon nano tube and other carbon-based conductive agents, so that the preparation process is simplified, the preparation efficiency of the conductive composite material is improved, and the preparation cost is reduced. Meanwhile, the method is suitable for a more efficient injection molding process, improves the production efficiency of the bipolar plate for the fuel cell stack, and reduces the manufacturing cost of the bipolar plate.
In some embodiments, the conductive composite material is melt-pressed into a plate-shaped material and then etched with flow fields on both surfaces thereof to obtain the bipolar plate for the battery stack.
In order to clearly understand the details and operation of the above-mentioned embodiments of the present invention for those skilled in the art, and to obviously show the advanced performance of the conductive composite material, the preparation method thereof and the bipolar plate for fuel cell stack in the embodiments of the present invention, the above-mentioned technical solutions are exemplified by a plurality of examples.
Example 1
An electrically conductive composite, prepared by the steps of:
weighing 450g of conductive graphite, putting the conductive graphite into a mixer, and preheating for 15min at the temperature of 100 ℃ and at the speed of 400 r/min; 290g of polyphenylene sulfide (PPS) powder is weighed and poured into a mixer, and is stirred with conductive graphite for 25min at 1500r/min to be uniformly mixed; obtaining a first mixture;
secondly, weighing 200g of silver-coated copper powder, pouring the silver-coated copper powder into a mixer, and treating the silver-coated copper powder for 25min at 1500r/min to achieve uniform dispersion again; performing melt extrusion granulation by adopting a double-screw extruder to obtain mixed granules;
thirdly, weighing 10g of silane coupling agent and the conductive filler pre-dispersing agent according to the proportion, pouring the silane coupling agent and the conductive filler pre-dispersing agent into a mixer, treating the mixture for 25min at 1500r/min, adding 50g of Carbon Nanotubes (CNTs) after uniformly mixing and dispersing, continuously and uniformly mixing the mixture under the same condition, and carrying out melt blending granulation through a double-screw extruder to obtain the PPS/CNT conductive composite material.
Example 2
An electrically conductive composite, prepared by the steps of:
weighing 450g of conductive graphite, putting the conductive graphite into a mixer, and preheating for 15min at the temperature of 100 ℃ and at the speed of 400 r/min; 290g of polyphenylene sulfide (PPS) powder is weighed and poured into a mixer, and is stirred with conductive graphite for 25min at 1500r/min to be uniformly mixed; obtaining a first mixture;
secondly, weighing 200g of copper powder, pouring the copper powder into a mixer, and treating the copper powder for 25min at 1500r/min to achieve uniform dispersion again; performing melt extrusion granulation by adopting a double-screw extruder to obtain mixed granules;
thirdly, weighing 10g of silane coupling agent and the conductive filler pre-dispersing agent according to the proportion, pouring the silane coupling agent and the conductive filler pre-dispersing agent into a mixer, treating the mixture for 25min at 1500r/min, adding 50g of Carbon Nanotubes (CNTs) after uniformly mixing and dispersing, continuously and uniformly mixing the mixture under the same condition, and carrying out melt blending granulation through a double-screw extruder to obtain the PPS/CNT conductive composite material.
Example 3
An electrically conductive composite, prepared by the steps of:
weighing 450g of conductive graphite, putting the conductive graphite into a mixer, and preheating for 15min at the temperature of 100 ℃ and at the speed of 400 r/min; weighing 310g of polyphenylene sulfide (PPS) powder, pouring the powder into a mixer, and stirring the powder and conductive graphite at 1500r/min for 25min to uniformly mix the powder and the conductive graphite; obtaining a first mixture;
secondly, weighing 200g of silver-coated copper powder, pouring the silver-coated copper powder into a mixer, and treating the silver-coated copper powder for 25min at 1500r/min to achieve uniform dispersion again; performing melt extrusion granulation by adopting a double-screw extruder to obtain mixed granules;
thirdly, weighing 10g of silane coupling agent and the conductive filler pre-dispersing agent according to the proportion, pouring the silane coupling agent and the conductive filler pre-dispersing agent into a mixer, treating the mixture for 25min at 1500r/min, adding 30g of Carbon Nanotubes (CNTs) after uniformly mixing and dispersing, continuously and uniformly mixing the mixture under the same condition, and carrying out melt blending granulation through a double-screw extruder to obtain the PPS/CNT conductive composite material.
Example 4
An electrically conductive composite, prepared by the steps of:
weighing 450g of conductive graphite, putting the conductive graphite into a mixer, and preheating for 15min at the temperature of 100 ℃ and at the speed of 400 r/min; weighing 260g of polyphenylene sulfide (PPS) powder, pouring the powder into a mixer, and stirring the powder and conductive graphite at 1500r/min for 25min to uniformly mix the powder and the conductive graphite; obtaining a first mixture;
secondly, weighing 200g of silver-coated copper powder, pouring the silver-coated copper powder into a mixer, and treating the silver-coated copper powder for 25min at 1500r/min to achieve uniform dispersion again; performing melt extrusion granulation by adopting a double-screw extruder to obtain mixed granules;
thirdly, weighing 10g of silane coupling agent and the conductive filler pre-dispersing agent according to the proportion, pouring the silane coupling agent and the conductive filler pre-dispersing agent into a mixer, treating the mixture for 25min at 1500r/min, adding 80g of Carbon Nanotubes (CNTs) after uniformly mixing and dispersing, continuously and uniformly mixing the mixture under the same condition, and carrying out melt blending granulation through a double-screw extruder to obtain the PPS/CNT conductive composite material.
Comparative example 1
An electrically conductive composite, prepared by the steps of:
weighing 450g of conductive graphite, putting the conductive graphite into a mixer, and preheating for 15min at the temperature of 100 ℃ and at the speed of 400 r/min; weighing 340g of polyphenylene sulfide (PPS) powder and 10g of silane coupling agent, pouring into a mixer, and stirring with conductive graphite at 1500r/min for 25min to uniformly mix; weighing 200g of silver-coated copper powder, pouring into a mixer, and treating at 1500r/min for 25min to achieve uniform dispersion again; and (3) performing melt extrusion granulation by adopting a double-screw extruder to obtain the composite material.
The raw material composition ratios of the above examples and comparative examples are shown in table 1 below:
TABLE 1
| Item | Example 1 | Example 2 | Example 3 | Example 4 | Comparative example 1 |
| Polyphenylene sulfideEther PPS% | 29 | 29 | 31 | 27 | 34 |
| Carbon nanotube% | 5 | 5 | 3 | 7 | 0 |
| Conductive filler% | 45 | 45 | 45 | 45 | 45 |
| Copper powder% | 0 | 20 | 0 | 0 | 0 |
| Silver-coated copper powder% | 20 | 0 | 20 | 20 | 20 |
| Coupling agent% | 1 | 1 | 1 | 1 | 1 |
Further, in order to verify the advancement of the conductive composite material in the embodiment of the present invention, the conductive composite materials prepared in the embodiments 1 to 4 and the comparative example 1 were respectively tested for the density, the bending strength, the impact strength, the volume conductivity, and other properties, and the test results are shown in the following table 2:
and the morphology of the conductive composite material prepared in example 1 is observed, as shown in SEM scanning electron micrographs of fig. 1 and 2, it can be clearly observed from the drawings that the carbon nanotubes are uniformly distributed in the conductive composite material and form a network structure in contact with each other, which can effectively improve the conductivity and mechanical strength of the composite material.
TABLE 2
| Item | Example 1 | Example 2 | Comparative example 3 | Comparative example 4 | Comparative example 5 |
| Density g/cm3 | 1.72 | 1.72 | 1.72 | 1.72 | 1.72 |
| Bending strength MPa | 70 | 68 | 65 | 62 | 70 |
| Impact strength kJ/m2 | 5.2 | 4.5 | 6.2 | 3.8 | 6.5 |
| Volume conductivity S/cm | 150 | 90.62 | 130 | 190 | 18.92 |
From the above test results, under the condition that the addition amount of the conductive graphite is the same, the difference between the example 1 and the example 2 is that the silver-coated copper powder is adopted in the example 1, and the copper powder is adopted in the example 2, wherein the silver-coated copper powder is formed on the surface of the superfine copper powder by adopting a chemical plating technology through a specific forming and surface treatment process, so that the defect that the copper powder is easy to oxidize is overcome, and the conductive graphite has the characteristics of good conductivity, high chemical stability, difficult oxidation and the like. The mechanical property, the mechanical property and the electric conduction of the conductive material are greatly improved. The chemical plating technology of the silver-coated copper powder has good compatibility with the carbon nano tube, so that the agglomeration of the carbon nano tube is reduced, the carbon nano tube can better play a role of a conductive bridge agent, and a three-dimensional conductive network is formed in the PPS matrix. Meanwhile, the conductive graphite filler is uniformly dispersed in the matrix, so that the mechanical property of the conductive composite material is greatly improved.
In addition, under the condition that the addition amount of the conductive graphite filler is the same, example 2, comparative example 3 and comparative example 4 are different in the content of the carbon nanotube. It can be seen that the higher the content of the carbon nanotubes, the higher the conductivity of the composite material is, and when the carbon nanotubes are melted, blended and granulated in a twin-screw extruder, the higher the content of the carbon nanotubes is, the higher the melt viscosity is, the lower the processability is, the higher the conductivity is, but the mechanical properties are slightly reduced. Considering the processability, conductivity and cost of the process, when the carbon nano content is 5 wt%, the better conductivity and processability are simultaneously achieved.
Comparative example 1 has a mechanical strength slightly higher than that of the examples due to the absence of the carbon nanotubes added thereto, but has very low electrical conductivity in terms of electrical properties due to the absence of the carbon nanotubes forming a good three-dimensional conductive network in the matrix.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (10)
1. The conductive composite material is characterized by comprising the following raw material components in percentage by mass based on 100% of the total mass of the conductive composite material:
2. the conductive composite as claimed in claim 1, wherein the resin comprises: at least one of polyphenylene sulfide powder, polystyrene, polypropylene, acrylonitrile-butadiene-styrene copolymer and polyvinylidene fluoride;
and/or, the coupling agent comprises: at least one of a silane coupling agent and a titanate coupling agent;
and/or, the metal powder comprises: at least one of copper powder, silver-coated copper powder and silver powder.
3. The conductive composite as claimed in claim 1 or 2, wherein the mesh number of the metal powder is not higher than 400 mesh;
and/or the pipe diameter of the carbon nano tube is 1-50 nm, and the pipe length is 1-200 mu m.
4. The conductive composite material as claimed in claim 3, wherein the conductive composite material comprises the following raw material components by mass percent, based on 100% of the total mass of the conductive composite material:
5. the preparation method of the conductive composite material is characterized by comprising the following steps of:
mixing and granulating 31-50 parts of graphite, 25-35 parts of resin, 15-25 parts of metal powder, 0.5-1 part of coupling agent and 3-8 parts of carbon nano tubes to obtain the conductive composite material.
6. The method of preparing a conductive composite as claimed in claim 5, wherein the mixing and granulating step comprises:
carrying out drying pretreatment on a graphite raw material to obtain graphite;
carrying out first mixing treatment on the graphite and the resin to obtain a first mixture;
carrying out second mixing treatment on the metal powder and the first mixture, and then carrying out first melting granulation to obtain mixed particles;
and carrying out third mixing treatment on the coupling agent, the carbon nano tube and the mixed particles, and then carrying out second melting granulation to obtain the conductive composite material.
7. The method of preparing a conductive composite as claimed in claim 6, wherein the step of dry pre-treating comprises: treating the graphite raw material for 10-15 min under the conditions that the temperature is 90-100 ℃ and the rotating speed is 200-500 r/min;
and/or, the conditions of the first mixing process comprise: mixing for 15-25 min under the condition that the rotating speed is 1000-1500 r/min;
and/or, the conditions of the second mixing process comprise: mixing and processing for 20-30 min under the condition that the rotating speed is 1000-1500 r/min;
and/or the step of carrying out third mixing treatment on the coupling agent, the carbon nano tubes and the mixed particles comprises the following steps: and mixing the coupling agent and the mixed particles for 20-30 min under the condition that the rotating speed is 1000-1500 r/min, and then adding the carbon nano tubes for mixing for 20-30 min under the condition that the rotating speed is 1000-1500 r/min.
8. The method for preparing a conductive composite as claimed in claim 6 or 7, wherein the first melt-granulating and the second melt-granulating are melt-extruded and granulated separately using a twin-screw extruder.
9. The method for preparing the conductive composite material according to claim 8, wherein the particle size of the conductive composite material is 2 to 6 μm;
and/or, the resin comprises: at least one of polyphenylene sulfide powder, polystyrene, polypropylene, acrylonitrile-butadiene-styrene copolymer and polyvinylidene fluoride;
and/or, the coupling agent comprises: at least one of a silane coupling agent and a titanate coupling agent;
and/or, the metal powder comprises: at least one of copper powder, silver-coated copper powder and silver powder;
and/or the mesh number of the metal powder is not higher than 400 meshes;
and/or the pipe diameter of the carbon nano tube is 1-50 nm, and the pipe length is 1-200 mu m.
10. A bipolar plate for a fuel cell stack, wherein the bipolar plate for a fuel cell stack is made of the conductive composite material according to any one of claims 1 to 4 or the conductive composite material prepared by the method according to any one of claims 5 to 9.
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