Composite molded titanium-carbon bipolar plate and method for manufacturing the same

Abstract

The application discloses a composite formed titanium-carbon bipolar plate and a preparation method thereof, which comprises the following structure: metal, carbon attached to the surface of the metal, composite plate strip hot rolling rubbing, and surface leveling. The composite formed titanium-carbon bipolar plate provided by the application has good mechanical strength and stability, good corrosion resistance, good hydrophobicity and good conductivity, can realize mass production of coiled materials, and is suitable for fuel cells.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell metal bipolar plate technology, specifically relating to a composite molded titanium-carbon bipolar plate and its preparation method. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) have faced limitations in widespread application due to cost and service life issues. During PEMFC operation, the bipolar plates function as supports for the membrane electrode assembly, current collection, heat conduction, gas distribution, and fuel and oxidant isolation. Therefore, they require high corrosion resistance, low interfacial resistivity, good mechanical strength, hydrophobicity, and good stability in the PEMFC operating environment. Currently, metal bipolar plates are typically produced by etching or stamping followed by PVD coating, which is costly and requires further improvement in service life. Therefore, there is an urgent need for a metal bipolar plate fabrication technology that can both reduce costs and improve service life. Summary of the Invention

[0003] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0004] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0005] Therefore, the purpose of this invention is to overcome the shortcomings of existing battery bipolar plate products and provide a composite molded titanium-carbon bipolar plate.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a composite molded titanium-carbon bipolar plate, which includes the following structure: metal, metal surface coated with carbon, composite plate strip hot rolled and leveled surface, wherein the metal, metal surface coated with carbon, composite plate strip hot rolled and leveled surface are distributed from the inside to the outside and are closely attached.

[0007] Another object of the present invention is to provide a method for preparing a composite molded titanium-carbon bipolar plate.

[0008] To address the aforementioned technical problems, this invention provides the following technical solution: a method for preparing a composite molded titanium-carbon bipolar plate, comprising the following steps: metal surface processing: forming a multidimensional porous layer by electro-etching and chemical etching of the metal surface;

[0009] Prepare a metal surface processing slurry: The slurry includes expanded graphite, solvent, binder, and dispersant; stir the above raw materials evenly.

[0010] Baking of carbon composite coating on metal surface: The slurry is coated on the metal surface and heated, and then baked to achieve carbonization of the slurry on the metal surface to form a coating.

[0011] Hot rolling: The metal and special layer are hot rolled to obtain a coated electrode plate with a thickness of 0.15 mm.

[0012] Preparation of bipolar plates: A coated metal plate is stamped into shape, and graphite and PVB are brushed onto the bent corners. The bipolar plates are then baked to obtain the bipolar plates.

[0013] In a preferred embodiment of the method for preparing the composite molded titanium-carbon bipolar plate of the present invention, the metal used in the metal surface processing is titanium.

[0014] As a preferred embodiment of the preparation method of the composite molded titanium-carbon bipolar plate of the present invention, the metal surface processing slurry includes, by weight, 50-60% expanded graphite, 12% binder, 0.2% dispersant, and the balance being solvent.

[0015] As a preferred embodiment of the preparation method of the composite molded titanium-carbon bipolar plate of the present invention, the metal surface processing slurry includes, by weight, 55% expanded graphite, 12% binder, 0.2% dispersant, and the balance being solvent.

[0016] In a preferred embodiment of the method for preparing the composite molded titanium-carbon bipolar plate of the present invention, the solvent is alcohol or N-methylpyrrolidone, the dispersant is tristearate, and the binder is polyvinyl butyral.

[0017] In a preferred embodiment of the method for preparing the composite molded titanium-carbon bipolar plate of the present invention, the thickness of the carbon composite layer coated on the metal surface during baking is approximately 1 mm.

[0018] As a preferred embodiment of the preparation method of the composite molded titanium-carbon bipolar plate of the present invention, in the baking process of coating the carbon composite layer on the metal surface, the heating is carried out after the coating slurry is finished. The coating is first baked at 200°C for 10 minutes in a heating furnace, and then the temperature is increased to 350°C for curing for 120 minutes. Then the temperature is increased to 500°C for micro-carbonization for 30 minutes to ensure the conductivity of the coating.

[0019] In a preferred embodiment of the method for preparing the composite molded titanium-carbon bipolar plate of the present invention, the hot rolling temperature is 500°C and the deformation amount per cycle is 10%.

[0020] As a preferred embodiment of the preparation method of the composite molded titanium-carbon bipolar plate of the present invention, in the preparation of the bipolar plate, the stamping pressure is 100 N / cm2 and the pressure is held for 30 s, the corner part is coated with a slurry of graphite (60%) and PVB (40%), the coating thickness is 10 micrometers, and finally it is baked at 300°C for 30 min.

[0021] Beneficial effects of this invention:

[0022] This invention provides a fuel cell bipolar plate and its preparation method, which has good mechanical strength and coating adhesion, good corrosion resistance, and good hydrophobicity and conductivity. It can realize mass production of rolled materials and is suitable for fuel cells. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0024] Figure 1 The figure shown in this invention is a microscopic image of the surface micropores after electrochemical and chemical etching.

[0025] Figure 2 This is a physical image of the bipolar plate substrate after rolling in Embodiment 1 of the present invention. Detailed Implementation

[0026] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0027] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0028] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments. Example

[0029] To roughen the surface of the titanium metal and improve the adhesion of the slurry: the metal surface is cleaned with hydrochloric acid (0.5 mol / L) for 60 seconds, followed by rinsing with water. NaOH (5 mol / L) is used as the electrolyte at a current density of 0.6 A / cm². 2 The surface is made with some flocculent voids and parts directly etched off by alkaline solution. Photochemical etching is used to create strip channels. First, ammonium bifluoride is used as the etching solution with a concentration of 10 mol / L. After applying a coating, it is exposed and developed. The strip channel spacing is 0.3 mm, the etching depth is 0.05 mm, and the etching time is 50 s, so that micro-nano and densely distributed straight channels are formed on the surface of the metal substrate.

[0030] The slurry includes expanded graphite calcined at high temperature, alcohol or N-methylpyrrolidone as a solvent, and polyvinyl butyral as a binder. The slurry includes expanded graphite calcined at temperatures above 2200℃, and uses alcohol or N-methylpyrrolidone as a solvent. The presence of the solvent ensures that the mixture is in a slurry state, which is convenient for surface coating and also facilitates the dispersion of the effective components. Finally, the solvent will evaporate during the curing process. Polyvinyl butyral is added as a binder, and additional dispersant is added. By weight fraction, expanded graphite accounts for 55%, binder accounts for 12%, dispersant accounts for 0.2%, and the dispersant component is tristearate glyceryl ester. The remainder is filled with solvent.

[0031] The slurry is applied to the titanium electrode plate using a spraying device. The carbon composite layer is dried and cured, and micro-carbonization is carried out to improve conductivity. The surface of the obtained surface-treated titanium metal plate is coated with the slurry from step 5. The thickness of the slurry coating is about 1 mm. The plate is first baked at 200°C for 10 minutes in a heating furnace, then the temperature is increased to 350°C for curing for 120 minutes. Finally, the temperature is increased to 500°C for micro-carbonization for 30 minutes to ensure the conductivity of the coating.

[0032] The coated titanium electrode plate is further rolled to densify and homogenize the carbon coating, ensuring a thickness of 0.15 mm. It is then leveled. This process enables the production of bipolar plate material in coils: the obtained sample is hot-rolled at 500°C with a deformation of 10% each time, and the pressure is set to allow for tufting. During this process, both the titanium electrode plate and the coating thin simultaneously. This process can be repeated multiple times depending on the thickness of the titanium electrode plate, ultimately obtaining a coated electrode plate with a thickness of 0.15 mm.

[0033] Finally, based on the flow channel design, the final bipolar plate is obtained by stamping: the titanium bipolar plate is stamped in a stamping die with a pressure set to 100 N / cm. 2Simultaneously, the pressure is maintained for 30 seconds, and the coating condition of the obtained bipolar plate is checked. A slurry of graphite (60%) and PVB (40%) is brushed onto the corner part, with a coating thickness of 10 micrometers. The method is spraying and trimming, and then it is baked in the furnace at 300℃ for 30 minutes to obtain the final bipolar plate. Example

[0034] To roughen the surface of the titanium metal and improve the adhesion of the slurry: the metal surface is cleaned with hydrochloric acid (0.5 mol / L), followed by rinsing with water. Medical-grade NaOH (5 mol / L) is used as the electrolyte, with a current density of 0.6 A / cm². 2 The surface is made with some flocculent voids and parts directly etched off by alkaline solution. Photochemical etching is used to create strip channels. First, ammonium bifluoride is used as the etching solution with a concentration of 10 mol / L. After applying a coating, it is exposed and developed. The strip channel spacing is 0.3 mm, the etching depth is 0.05 mm, and the etching time is 50 s, so that micro-nano and densely distributed straight channels are formed on the surface of the metal substrate.

[0035] The slurry includes high-temperature calcined expanded graphite, alcohol or N-methylpyrrolidone as a solvent, and polyvinyl butyral as a binder. The slurry comprises expanded graphite calcined at temperatures above 2200℃, using alcohol or N-methylpyrrolidone as a solvent, polyvinyl butyral as a binder, and additional dispersant. By weight, expanded graphite accounts for 50%, binder for 12%, dispersant for 0.2%, and the remainder is filled with solvent. The slurry is coated onto a titanium electrode plate using a spraying device. The carbon composite layer is dried and cured, and micro-carbonization is continued to improve conductivity. The surface of the obtained surface-treated titanium metal plate is coated with the slurry from step 5, with a slurry coating thickness of approximately 1 mm. It is first baked at 200℃ for 10 minutes in a heating furnace, then the temperature is increased to 350℃ for curing for 120 minutes, and then the temperature is increased to 500℃ for micro-carbonization for 30 minutes to ensure the conductivity of the coating.

[0036] The coated titanium electrode plate is further rolled to densify and homogenize the carbon coating, ensuring that the thickness of the titanium electrode plate reaches 0.15 mm and then leveled. This process enables the production of bipolar plate material coils: the sample obtained in step 6 is hot-rolled at 500℃, and the titanium electrode plate and coating are thinned simultaneously. This process can be repeated multiple times depending on the thickness of the titanium electrode plate, ultimately obtaining a coated electrode plate with a thickness of 0.15 mm.

[0037] Finally, according to the flow channel design, the final bipolar plate is obtained by stamping: the titanium metal bipolar plate is stamped in the stamping die and held under pressure for 30 seconds. The obtained bipolar plate is inspected for coating. A slurry of graphite (60%) and PVB (40%) is brushed onto the corner part and baked in the furnace at 300℃ for 30 minutes to obtain the final bipolar plate. Example

[0038] To roughen the surface of the titanium metal and improve the adhesion of the slurry: the metal surface is cleaned with hydrochloric acid (0.5 mol / L), followed by rinsing with water. Medical-grade NaOH (5 mol / L) is used as the electrolyte, with a current density of 0.6 A / cm². 2 The surface is made with some flocculent voids and parts directly etched off by alkaline solution. Photochemical etching is used to create strip channels. First, ammonium bifluoride is used as the etching solution with a concentration of 10 mol / L. After applying a coating, it is exposed and developed. The strip channel spacing is 0.3 mm, the etching depth is 0.05 mm, and the etching time is 50 s, so that micro-nano and densely distributed straight channels are formed on the surface of the metal substrate.

[0039] The slurry includes expanded graphite calcined at high temperature, alcohol or N-methylpyrrolidone as a solvent, and polyvinyl butyral as a binder; the slurry includes expanded graphite calcined at a high temperature above 2200℃, alcohol or N-methylpyrrolidone as a solvent, polyvinyl butyral as a binder, and additional dispersant. By weight fraction, expanded graphite accounts for 60%, binder accounts for 12%, dispersant accounts for 0.2%, and the remainder is filled with solvent;

[0040] The slurry is applied to the titanium electrode plate using a spraying device. The carbon composite layer is dried and cured, and micro-carbonization is carried out to improve conductivity. The surface of the obtained surface-treated titanium metal plate is coated with the slurry from step 5. The thickness of the slurry coating is about 1 mm. The plate is first baked at 200°C for 10 minutes in a heating furnace, then the temperature is increased to 350°C for curing for 120 minutes. Finally, the temperature is increased to 500°C for micro-carbonization for 30 minutes to ensure the conductivity of the coating.

[0041] The coated titanium electrode plate is further rolled to densify and homogenize the carbon coating, ensuring that the thickness of the titanium electrode plate reaches 0.15 mm and then leveled. This process enables the production of bipolar plate material coils: the sample obtained in step 6 is hot-rolled at 500℃, and the titanium electrode plate and coating are thinned simultaneously. This process can be repeated multiple times depending on the thickness of the titanium electrode plate, ultimately obtaining a coated electrode plate with a thickness of 0.15 mm.

[0042] Finally, according to the flow channel design, the final bipolar plate is obtained by stamping: the titanium metal bipolar plate is stamped in the stamping die and held under pressure for 30 seconds. The obtained bipolar plate is inspected for coating. A slurry of graphite (60%) and PVB (40%) is brushed onto the corner part and baked in the furnace at 300℃ for 30 minutes to obtain the final bipolar plate.

[0043] Comparative Example 1 is basically the same as Example 1, except that after forming a porous metal oxide film layer, a carbon resin composite layer is directly formed on the metal oxide film layer in Comparative Example 1. Example

[0044] The electrical and mechanical properties of the finished products obtained in Examples 1-3 and Comparative Example 1 were measured. The specific performance measurement methods are as follows:

[0045] Corrosion current density: Measured using the tangent method of potentiodynamic polarization curves on an electrochemical workstation, under a simulated fuel cell working environment of 0.5 M H2SO4 + 5 ppm HF at 80 °C.

[0046] Potential polarization curve: The current density corresponding to a constant potential of 0.6V for 5 hours was tested using an electrochemical workstation. The test simulated the working environment of a fuel cell: 0.6V, O2, 0.5M H2SO4 + 5ppm HF, and temperature 80℃.

[0047] Adhesion test for scratch resistance: verified by applying a nano-scratch test;

[0048] Interfacial contact resistance: ICR testing was used to verify the change in conductivity of the coating under different pressures, specifically at 140 N / cm. 2 Interfacial contact resistance under pressure.

[0049] Wetting angle: The size of the surface wetting angle is tested using the water droplet method to determine the hydrophobic properties of the material.

[0050] The data obtained above are recorded in Table 1.

[0051] Table 1. Mechanical and electrical properties of the finished products obtained in Examples 1-3 and Comparative Example 1

[0052] Example <![CDATA[Interface Contact Resistance / ICR, mΩ•cm 2 > <![CDATA[Self-corrosion current density / µA / cm 2 > Hydrophobic properties / wetting angle <![CDATA[0.6V current density µA / cm 2 > Scratch test adhesion / N Example 1 8.7 0.08 101° 0.4 28 Example 2 18.2 0.06 102.5° 0.32 28.3 Example 3 7.2 0.12 98° 0.58 19.5 Comparative Example 1 8.6 0.082 100.7° 0.42 21.6

[0053] In the molding process of our invention, expanded graphite in the raw materials mainly serves to provide conductivity, corrosion resistance, and hydrophobicity, while resin and solvent dispersants primarily enhance the composite strength and stability of the coating. Simultaneously, chemical etching further improves the bonding between the coating and the substrate, and the rolling process further increases the degree of bonding between the coating and the substrate, thereby improving the bonding strength and stability of the composite material. However, increasing the amount of resin will reduce the conductivity.

[0054] As shown in Table 1, our invention provides a method for preparing a good fuel bipolar plate and its coating. The finished product has good mechanical and electrical properties. Considering the electrical properties, mechanical properties, corrosion resistance, etc., the raw material ratio used in the preferred embodiment is the preferred raw material ratio.

[0055] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A composite molded titanium-carbon bipolar plate, characterized in that: It includes the following structure: metal, metal surface with carbon coating, hot-rolled composite strip, and leveled surface, wherein the metal, metal surface with carbon coating, hot-rolled composite strip, and leveled surface are distributed from the inside out and are closely bonded together; The method for preparing the composite molded titanium-carbon bipolar plate includes the following steps: Metal surface processing: forming a multi-dimensional porous layer by combining electrical etching and chemical etching on the metal surface; Prepare the metal surface processing slurry: The slurry raw materials include expanded graphite, solvent, binder, and dispersant. Stir the above raw materials evenly. Baking of carbon composite coating on metal surface: The slurry is coated on the metal surface and heated, and then baked to achieve carbonization of the slurry on the metal surface to form a coating. Hot rolling: The metal and special layer are hot rolled to obtain a coated electrode plate with a thickness of 0.15 mm. Preparation of bipolar plates: A coated metal plate is stamped into shape, and graphite and PVB are brushed onto the bent corners and baked to obtain bipolar plates. In the aforementioned metal surface processing, the metal is titanium. The electro-etching and chemical etching process includes first using 5 mol / L NaOH as the electrolyte, at a current of 0.6 A / cm². 2 Electrical etching was performed at a current density of 10 mmol / L; then film coating and exposure development were performed, followed by etching for 50 seconds with 10 mmol / L ammonium bifluoride to form strip-shaped channels with a spacing of 0.3 mm and a depth of 0.05 mm. The prepared metal surface processing slurry, by weight, includes 50-60% expanded graphite, 12% binder, 0.2% dispersant, and the balance being solvent; The solvent is alcohol or N-methylpyrrolidone, the dispersant is glyceryl tristearate, and the binder is polyvinyl butyral; In the hot rolling process, the hot rolling temperature is 500℃, and the deformation amount per cycle is 10%.

2. The composite molded titanium-carbon bipolar plate according to claim 1, characterized in that: The prepared metal surface processing slurry comprises, by weight, 55% expanded graphite, 12% binder, 0.2% dispersant, and the remainder is solvent.

3. The composite molded titanium-carbon bipolar plate according to claim 1, characterized in that: During the baking process of the carbon composite layer coated on the metal surface, the coating is a slurry with a thickness of 1 mm.

4. The composite molded titanium-carbon bipolar plate according to claim 1, characterized in that: During the baking process of the carbon composite layer coated on the metal surface, the heating is carried out after the coating slurry is finished. The coating is first baked at 200°C for 10 minutes in a heating furnace, then the temperature is increased to 350°C for curing for 120 minutes, and then the temperature is increased to 500°C for micro-carbonization for 30 minutes to ensure the conductivity of the coating.

5. The composite molded titanium-carbon bipolar plate according to claim 1, characterized in that: In the fabrication of the bipolar plate, the stamping pressure is 100 N / cm. 2 Simultaneously, maintain pressure for 30 seconds, coat the corners with a slurry of 60% graphite and 40% PVB, with a coating thickness of 10 micrometers, and finally bake at 300°C for 30 minutes.

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