TWI686990B - Bipolar plate for fuel cell and method of the same - Google Patents

Abstract

Provided is a bipolar plate for a fuel cell, including a substrate and an anti-corrosion layer. The substrate has a plurality of flow channels. The anti-corrosion layer covers the substrate. The surface roughness of the substrate is less than or equal to 1.2 mm.

Description

Fuel cell bipolar plate and manufacturing method thereof

The invention relates to a fuel cell and a manufacturing method thereof, and in particular to a fuel cell bipolar plate and a manufacturing method thereof.

Fuel cells have high energy conversion efficiency, clean, low pollution, high energy density, fast start-up, and long continuous power supply time. Therefore, they are considered to be an ideal power generation device and energy independent strategic option that can meet both energy and environmental requirements in the future. . The fuel cell can be made of ultra-thin metal sheet to make the bipolar plate to increase the flow channel density of the bipolar plate, thereby increasing the energy density of the battery. However, in the process of stamping the ultra-thin sheet metal flow path, the ultra-thin metal bipolar plate is prone to high deformation at the contact with the mold, making its surface rough, and it is easy to produce local corrosion and fracture.

The embodiments of the present invention provide a bipolar plate for a fuel cell and a manufacturing method thereof, which can improve the corrosion resistance and life span of the bipolar plate for a fuel cell.

An embodiment of the present invention provides a bipolar plate for a fuel cell, which includes a base material and a resist layer. The substrate has multiple flow channels. The resist layer covers the substrate. The surface roughness of the substrate is less than or equal to 1.2 μm.

An embodiment of the present invention further provides a method for manufacturing a bipolar plate of a fuel cell, which includes providing a plate and performing a rolling process on the plate. A heat treatment process is performed on the board. The stamping process is performed on the plate by a stamping die to form a substrate, and the substrate has a plurality of flow channels. Carry out the demoulding process.

Based on the above, the fuel cell bipolar plate of the embodiment of the present invention and the manufacturing method thereof can improve the corrosion resistance and service life of the fuel cell bipolar plate.

In order to make the above-mentioned features and advantages of the present invention more obvious and understandable, the embodiments are specifically described below in conjunction with the accompanying drawings for detailed description as follows.

The ultra-thin metal bipolar plate can be used to increase the flow channel density of the fuel cell bipolar plate and increase the energy density of the battery, but the increase in the ultra-thin metal plate flow channel density causes severe challenges to the uniformity of the coating, especially the ultra-thin The original grains of the metal sheet are thick after calendering. When the high-density runner is stamped and formed, obvious grains can be seen, which makes the surface of the runner rough. At this time, the uniformity of the coating becomes poor, and the corrosion resistance of the bipolar plate is reduced, which affects the use. life. The invention provides an ultra-thin metal bipolar plate, which has good coating uniformity, and can improve corrosion resistance and service life.

1A to 1F are flow cross-sectional views of a method for manufacturing a bipolar plate of a fuel cell according to an embodiment of the invention.

Referring to FIG. 1A, a plate 10 is provided. The plate 10 is, for example, a flat conductive material. Conductive materials include metals, metal derivatives, intermetallics, or combinations thereof. The metal is, for example, stainless steel, titanium alloy, nickel alloy, aluminum alloy, or a combination thereof. Stainless steel can be 430 stainless steel, 304 stainless steel, 316 stainless steel or a combination thereof; titanium alloys include: pure titanium, titanium aluminum vanadium alloy (Ti ₆ Al ₄ V), titanium palladium alloy or related alloys; nickel alloys include: pure nickel, nickel chromium Alloy, nickel molybdenum alloy or related alloy; aluminum alloy includes: pure aluminum, aluminum magnesium silicon alloy, aluminum copper magnesium alloy or related alloy. Derivatives may include carbides, nitrides, oxynitrides or cyanides. In the embodiment where the sheet material 10 is a derivative of a conductive material, the sheet material 10 is, for example, titanium, aluminum carbide, nitride, oxynitride, or cyanide. In the embodiment where the plate material 10 is an intermetallic material of a conductive material, the plate material 10 is, for example, a titanium nickel metal or a titanium aluminum metal. The thickness of the board 10 ranges from 100 micrometers (mm) to 1000 micrometers, for example. The grain size of the crystal grains of the plate 10 is, for example, 0.5 mm to 200 mm. The average grain size of the crystal grains of the plate 10 is, for example, 1 mm to 100 mm. The thickness of the plate 10 is, for example, 50 mm to 500 mm.

Referring to FIG. 1B, a rolling process 13 is performed on the board 10, so that the board 10 is thinned by rolling, and the board 10 is dynamically recrystallized to refine the crystal grains to form the board 10a. The calendering process 13 can be processed by a calender. The calender can be a two-roll calender, a 3-roll roll forming machine or a roll forming machine. In some embodiments, the pressure range for performing the calendering process is 100 MPa to 3000 MPa. In some embodiments, the pressure range for performing the calendering process is 100 MPa to 1500 MPa. In other embodiments, the pressure range of the rolling process is 200 MPa to 1000 MPa. In still other embodiments, the pressure during the rolling process is maintained at a certain value, such as 300 MPa, 600 MPa, or 800 MPa. The temperature range in which the rolling process is performed is, for example, 20 degrees Celsius to 900 degrees Celsius.

The thickness of the sheet 10a after rolling may be 1/20 to 1/2 of the thickness of the sheet 10 before rolling. The thickness of the rolled sheet 10a may be 200 mm or less. In some embodiments, the thickness of the board 10a is 20 mm to 300 mm. The grain size of the crystal grains of the plate 10a is, for example, 5 mm to 100 mm, 1 mm to 50 mm, or 1 mm to 20 mm. The average grain size of the crystal grains of the plate 10a is, for example, 5 mm to 50 mm, 1 mm to 20 mm, or 0.5 mm to 10 mm.

In some embodiments, a small amount of precipitate is added to the board 10. The precipitates are added to the grain boundary to avoid recrystallization during the rolling process, resulting in the phenomenon of excessive growth of grains in the area, thereby limiting the size of the grains. The precipitates are, for example, metal carbides, alloys or metal borides. The metal carbide is, for example, M (Fe, Cr, Mo..) ₂₃ C ₆ , Fe ₃ C, Cr ₃ C, or Mo ₃ C. The alloy is, for example, Ti ₂ Pd or Ti ₃ Al. The metal boride is, for example, Ti ₃ B, Zr ₃ B, or the like.

Referring to FIG. 1C, after the rolling process is performed, a heat treatment (heat treatment process) 14 is performed on the plate 10a after the rolling process to change the microstructure of the plate 10a. The heat treatment 14 may be tempering treatment or annealing heat treatment. More specifically, the heat treatment 14 can regenerate and reform the grains of the plate 10a, and convert the strain energy after rolling into the kinetic energy of the regenerated grains to refine the grains, thereby making the grains of the heat-treated plate 10b The particle size is controlled within a certain range. The heat treatment 14 is performed in a vacuum environment, for example. The vacuum degree of the heat treatment 14 is, for example, less than 1´10 ^-2 torr. In some implementations, the vacuum degree of the heat treatment 14 is, for example, 1´10 ^-5 torr to 1´10 ^-2 torr. The temperature of the heat treatment 14 is, for example, a low temperature tempering less than 600 degrees Celsius. In some implementations, the temperature range of the heat treatment 14 is, for example, 300 degrees Celsius to 550 degrees Celsius. In still other implementations, the temperature range of the heat treatment is, for example, 300 degrees Celsius to 400 degrees Celsius. The time range of the heat treatment 14 is, for example, 1 hour to 6 hours. The method of the heat treatment 14 may be a continuous furnace or a heat treatment furnace.

In some embodiments, the grain size of the plate 10b after heat treatment is about 1/50 to 1/2 of the grain size of the grain of the plate 10 before rolling. In addition, the particle size of the crystal grains of the plate 10b after heat treatment is about 1/30 to 1/2 of the particle size of the crystal grains of the plate 10a before the treatment (after rolling). The grain size of the crystal grains of the heat-treated plate 10b is, for example, 1 mm to 7 mm, 1 mm to 5 mm, or 0.1 mm to 3 mm. The average grain size of the crystal grains of the sheet 10b is, for example, 1 mm to 6 mm, 2 mm to 4 mm, or 0.1 mm to 1 mm.

Referring to FIGS. 1D and 2, after the heat treatment, a stamping process is performed on the plate 10b. The stamping process can be implemented by using a stamping die. The stamping die includes an upper die (not shown) and a lower die 12. The shape of the upper mold corresponds to that of the lower mold. The lower mold 12 includes a main body portion 12B and a plurality of convex portions 12P. The convex portion 12P protrudes from the main body portion 12B. Since the convex portion 12P is provided on the main body portion 12B at intervals, the surface 12T having irregularities with the main body portion 12B is formed. The side wall 12S of the convex portion 12P is connected to the surface of the main body portion 12B.

Please refer to FIGS. 1D and 2, the top surface 12Pt of the convex portion 12P may be a single plane or a plurality of planes, curved surfaces, or a combination thereof. The vertex a'of the convex portion 12P may be a chamfer, and the chamfer is an obtuse angle or a rounded obtuse angle. In an embodiment where the vertex angle a'of the convex portion 12P is a rounded obtuse angle, the vertex surface 12Pt of the convex portion 12P includes a plane Ft' located between the two vertex angles a'. The width of the plane Ft' is, for example, 0.2 mm to 3 mm. The apex angle a'is a rounded obtuse angle, and its radius of curvature may range from 0.01 mm to 0.5 mm, for example, 0.1 mm, 0.2 mm, or 0.25 mm.

In the cross-sectional view, the side wall 12S of the convex portion 12P is an inclined straight line, an arc, or a parabola. In other words, the side wall 12S of the convex portion 12P may be an inclined surface, a curved surface, or a parabolic surface. The height H′ of the convex portion 12P, that is, the distance between the top surface 12Pt of the convex portion 12P and the surface 12Bb of the body 12B may range from 0.2 mm to 3 mm, 0.2 mm to 2 mm, or 0.2 mm to 0.8 mm, for example, 0.35 mm, 0.45mm or 0.55mm. In some embodiments, the height H'of the convex portion 12P is also referred to as the height of the side wall 12S of the convex portion 12P.

The main body portion 12B between two adjacent convex portions 12P may be referred to as a concave portion 12B. The bottom surface (surface) 12Bb of the recess 12B may be a single plane or a plurality of planes, curved surfaces, or a combination thereof. The bottom corner b'of the recess 12B may be a chamfer, and the chamfer is an obtuse angle or a rounded obtuse angle. The angle range of the bottom angle b'of the recess 12B is, for example, 90 degrees to 150 degrees. In an embodiment where the bottom angle b'of the recess 12B is a rounded obtuse angle, the bottom surface 12Bb of the recess 12B includes a plane Fb' located between the two bottom corners b'. The width of the plane Fb' may range from 0.2 mm to 3 mm, for example, 0.5 mm, 1 mm or 2 mm. The bottom angle b'is a rounded obtuse angle, and its radius of curvature may range from 0.01 mm to 0.5 mm, for example, 0.1 mm, 0.2 mm, or 0.25 mm. The radius of curvature of the bottom angle b'and the top angle a'may be the same or different.

The bottom angle g'of the convex portion 12P of the lower mold 12, that is, the angle between the side wall 12S of the convex portion 12P and the extension line of the surface of the main body portion 12B, may be referred to as the draft angle g', or the draft angle (Draft angle) g'. In some embodiments of the present invention, the range of the draft angle g'is, for example, greater than or equal to 30 degrees, or greater than or equal to 40 degrees. In some examples, the draft angle g'is, for example, between 40 degrees and 90 degrees. In still other examples, the draft angle g'may be between 40 degrees and 80 degrees. The draft angle g'is, for example, 70 degrees, 60 degrees, and 45 degrees.

In addition, the pitch P'of two adjacent convex portions 12P may be less than or equal to 3 mm. In some embodiments, the pitch P'between two adjacent protrusions 12P is, for example, 1 mm to 2.4 mm. In other embodiments, the pitch P'between two adjacent protrusions 12P is, for example, 1.2 mm to 2 mm.

In some implementations, the stamping die is installed on the stamping machine. When punching, the punching machine applies pressure to the plate 10 to cause plastic deformation of the plate 10. The press can be a mechanical press or a hydraulic press. The pressure applied to the plate 10 is, for example, 100 MPa to 1000 MPa. The stamping process can be performed at room temperature or higher. More specifically, the temperature at which the stamping process is performed is, for example, 20 degrees Celsius to 300 degrees Celsius.

Since the grains of the sheet 10b are refined and uniform in size, the high curvature of the sheet 10b, such as the draft, is also not easy to break during the stamping process, so plastic deformation can occur, resulting in the formation of a flow channel pattern and thickness Uniform substrate 11.

The thickness of the substrate 11 may be, for example, 200 mm or less. In some embodiments, the thickness of the substrate 11 ranges from 40 mm to 200 mm. In other embodiments, the thickness of the substrate 11 ranges from 150 mm to 200 mm. In still other embodiments, the thickness of the substrate 11 ranges from 50 mm to 100 mm. The grain size range of the base material 11 is, for example, 0.3 mm to 15 mm, 1 mm to 6 mm, or 0.1 mm to 8 mm. The average grain size of the crystal grains of the substrate 11 is, for example, 0.3 mm to 5 mm. The surface roughness Ra of the base material 11 is, for example, 1.2 mm or less. In some embodiments, the surface roughness Ra of the substrate 11 ranges from 0.156 mm to 1.171 mm, 0.242 mm to 0.739 mm, or 0.1 mm to 1.2 mm, for example.

Next, referring to FIG. 1E, after performing the stamping process, in some embodiments, a resist layer 20 is also formed on the surface of the substrate 11. The conductivity of the resist layer 20 is, for example, 1´10 ³ S/cm to 1´10 ⁵ S/cm. The material of the resist layer 20 is, for example, carbon, metal carbon compound, metal nitride, or metal carbon-nitrogen mixture. The resist layer 20 can be formed by dry plating or wet plating. For example, the dry-type coating may be a physical vapor deposition method, such as evaporation or sputtering, or use a chemical vapor deposition method, such as a plasma enhanced chemical vapor deposition method. The wet coating method may be an electrochemical method, such as chemical plating method, electroless plating method, molten salt method, and the like.

In some embodiments, the thickness of the resist layer 20 ranges from 0.1 mm to 5 mm, for example. Since the crystal grains and surface roughness of the base material 11 are very small, the step coverage of the resist layer 20 is high, and the surface of the base material 11 can be effectively covered. Therefore, the resist layer 20 does not need to be too thick to cover the substrate 11. In some embodiments, the thickness of the resist layer 20 is, for example, less than or equal to 3 mm. The thickness of the resist layer 20 ranges from 3 mm to 0.2 mm, for example. In some embodiments, the thickness of the resist layer 20 is less than 0.5 mm.

In the mold release process, the base material 11 covered with the resist layer 20 is taken out of the stamping die to form the bipolar plate 30 with flow channels.

In the embodiment of the present invention, a stamping die with a larger draft angle q is used for stamping, so that after the die is removed, the flow channels 16 of the formed bipolar plate 30 can have a smaller distance between them.

Please refer to FIG. 3. More specifically, the base material 11 of the bipolar plate 30 has a convex portion 11P and a concave portion 11R. The concave portion 11R shares the side wall 11S with the convex portion 11P. That is, the side wall 11S connects the bottom surface 11Rb of the concave portion 11R and the top surface 11Pt of the convex portion 11P.

The top surface 11Pt of the convex portion 11P may be a single or multiple flat surfaces, curved surfaces, or a combination thereof. The vertex a of the convex portion 11P may be a chamfer, and the chamfer is an obtuse angle or a rounded obtuse angle. In the embodiment where the vertex angle a of the convex portion 11P is a rounded obtuse angle, the top surface 11Pt of the convex portion 11P includes a plane Ft between the two vertex a angles. The width of the plane Ft is, for example, 0.2 mm to 3 mm. The apex angle a is a rounded obtuse angle, and its radius of curvature may range from 0.01 mm to 0.5 mm, for example, 0.1 mm, 0.2 mm, or 0.25 mm.

The side wall 11S may be a smooth surface. More specifically, the side wall 11S may be a single or multiple inclined surfaces, curved surfaces, or a combination thereof. The height H of the side wall 11S, that is, the vertical distance between the bottom surface 11Rb of the concave portion 11R and the top surface 11Pt of the convex portion 11P, may be 0.2 mm to 3 mm, for example, 0.35 mm, 0.45 mm, or 0.55 mm.

The recess 11R can also be referred to herein as the flow path of the bipolar plate. The bottom surface 11Rb of the recess 11R may be a single or multiple flat surfaces, curved surfaces, or a combination thereof. The bottom angle b of the recess 11R may be a chamfer, and the chamfer is an obtuse angle or a rounded obtuse angle. The angle range of the bottom angle b of the recess 11R is, for example, 90 degrees to 150 degrees. In the embodiment where the bottom angle b of the recess 11R is a rounded obtuse angle, the bottom surface 11Rb of the recess 11R includes the plane Fb between the two bottom corners b. The width of the plane Fb may range from 0.2 mm to 3 mm, for example, 0.5 mm, 1 mm, or 2 mm. The bottom angle b is a rounded obtuse angle, and its radius of curvature may range from 0.01 mm to 0.5 mm, for example, 0.1 mm, 0.2 mm, or 0.25 mm. The radius of curvature of the bottom angle b and the top angle a may be the same or different.

In addition, the angle between the horizontal extension line of the bottom surface 11Rb of the concave portion (flow channel) 11R and the side wall 11S is also referred to as the draft angle g. In some embodiments, the draft angle g range is, for example, greater than or equal to 30 degrees, or greater than or equal to 40 degrees. In some examples, the draft angle g is, for example, between 40 degrees and 90 degrees. In still other examples, the draft angle g is, for example, between 40 degrees and 80 degrees. The draft angle g is, for example, 70 degrees, 60 degrees, and 45 degrees.

In addition, the pitch P of two adjacent convex portions 11P may be less than or equal to 3 mm. In some embodiments, the pitch P of two adjacent convex portions 11P is, for example, 1 mm to 2.4 mm. In other embodiments, the pitch P of two adjacent protrusions 11P is, for example, 1.2 mm to 2 mm. When the bipolar plate 30 is applied to a fuel cell, the narrower spacing between the flow channels 16 helps increase the current density of the cell.

4A is a schematic cross-sectional view of a fuel cell unit according to an embodiment of the present invention. Referring to FIG. 4A, the fuel cell 100 includes a membrane electrode assembly (MEA) 102 and a pair of bipolar plate assemblies 130a and 130b. The membrane electrode group 102 includes a proton exchange membrane (PEM) 104 and gas diffusion layers 106a and 106b. The proton exchange membrane 104 may be a perfluorosulfonic acid ion membrane (Nafion). The gas diffusion layers 106a and 106b are provided on both sides of the proton exchange membrane 104, respectively. The gas diffusion layers 106a and 106b may be graphite fibers, titanium metal fibers, or noble metal (for example, Ag, Au, Pt) fibers. The bipolar plate groups 130a and 130b are disposed outside the gas diffusion layers 106a and 106b, respectively.

The bipolar plate group 130a includes bipolar plates 131a and 132a. The bipolar plates 131a and 132a can use the bipolar plate 30 of the above embodiment. The bipolar plate 131a is located between the gas diffusion layer 106a and the bipolar plate 132a. The bipolar plates 131a and 132a have first cooling channels 116a and first gas channels 118a. The first cooling flow channels 116a and the first gas flow channels 118a are alternately arranged. Specifically, the convex portion 131P _{1 of the} bipolar plate 131a corresponds to the concave portion 132R _{1 of the} bipolar plate 132a, and the first gas flow path is formed between the convex portion 131P _{1 of the} bipolar plate 131a and the gas diffusion layer 106a 118a. Recessed portion 131a of the bipolar plate of the bipolar plate 131R ₁ of the convex portion 132a provided corresponding 132P _1, and the accommodating space formed therefrom as a first cooling flow passage 116a.

Similarly, the bipolar plate group 130b includes bipolar plates 131b and 132b. The bipolar plate 131b is located between the gas diffusion layer 106b and the bipolar plate 132b. The bipolar plates 131b and 132b have second cooling channels 116b and second gas channels 118b. The second cooling flow channels 116b and the second gas flow channels 118b are arranged alternately with each other, for example. Specifically, the convex portion 131b of the bipolar plate 131R ₂ recessed portion 132b of the bipolar plate to be disposed opposite 132P _2, as the second gas flow passage between the recesses 118b and 131b of the bipolar plate 131R ₂ the gas diffusion layer 106b . The convex portion 131P _{2 of the} bipolar plate 131b is provided corresponding to the concave portion 132R _{2 of the} bipolar plate 132b, and the accommodating space formed by it serves as the second cooling flow channel 116b.

Please refer to FIGS. 5A and 5B. In some embodiments, the extending direction of the flow channel Ca of the bipolar plate group (only the bipolar plate 131a is shown in the figure) may be the same as that of the bipolar plate group (only the bipolar plate is shown in the figure). The extending direction of the flow path Cb of the plate 131b) is the same, as shown in FIG. 5A. In this embodiment, the extending direction of the flow channels Ca/Cb refers to the extending direction of the first cooling flow channels 116a/second cooling flow channels 116b and/or the first gas flow channels 118a/second gas flow channels 118b. In FIG. 5A, the flow path Ca of the bipolar plate 131a and the flow path Cb of the bipolar plate 131b both extend along the first direction D1. In addition, the first cooling flow channel 116a and the second cooling flow channel 116b are arranged to be aligned up and down; the first gas flow channel 118a and the second gas flow channel 118b are also arranged to correspond to the up and down and aligned manner, however, this The embodiments of the invention are not limited thereto.

In other embodiments, the flow path of the bipolar plate 131a and the flow path of the bipolar plate 131b may both extend along the first direction D1. However, the first cooling flow channel 116a and the second cooling flow channel 116b are arranged parallel to each other, but are phase-shifted; the first gas flow channel 118a and the second gas flow channel 118b are also arranged parallel to each other, but phase-shifted.

In other embodiments, the extending direction of the flow channel Ca' of the bipolar plate group (only the bipolar plate 131a is shown in the figure) can be the same as the flow path of the bipolar plate group (only the bipolar plate 131b is drawn in the figure). The extension direction of Cb' is different, as shown in FIG. 5B. In FIG. 5B, the flow path Ca' of the bipolar plate 131a extends along the first direction D1; and the flow path Cb' of the bipolar plate 131b extends along the second direction D2. The first direction D1 is different from the second direction D2. In some embodiments, the first direction D1 is perpendicular to the second direction D2, however, the embodiments of the present invention are not limited thereto.

In addition, referring to FIG. 4B, the pitch P _c1 of the first cooling flow channels 116 a of the bipolar plate group 130 a may be the same as or different from the pitch P _c2 of the second cooling flow channels 116 b of the bipolar plate group 130 b. The pitch P _g1 of the first gas flow channels 118a of the bipolar plate group 130a may be the same as or different from the pitch P _g2 of the second gas flow channels 118b of the bipolar plate group 130b.

In addition, FIG. 6 is a schematic cross-sectional view of a fuel cell stack according to some embodiments of the present invention. In FIG. 6, the fuel cell stack includes a plurality of stacked fuel cells 200. In addition, a structure such as a unipolar plate, a collector plate, an end plate, etc. may be provided outside the fuel cell stack of the third embodiment, but the present invention is not limited to this.

Several examples are listed below to confirm the efficacy of the present invention, but the scope of the present invention is not limited to the following.

<Example 1>

Provide 316L stainless steel plate with a size of 25cm´60cm and a thickness of 200 microns. The original grain size of the stainless steel plate is 25 microns to 60 microns, and the average grain size of the original grain is 30 microns to 50 microns. In an environment of 900 degrees Celsius, the stainless steel sheet was rolled to a thickness of 100 microns with a force of 1350 MPa, and then the furnace was cooled to room temperature, and the sheet was taken out. The average grain size of the rolled sheet is measured to be 20 microns to 45 microns. Take the above partially rolled sheet and anneal it for 3 hours in an environment of 550 degrees Celsius and a vacuum of 1´10 ^-2 torr. And using a hydraulic press under the conditions of 20 degrees Celsius and a pressure of 225MPa, the stainless steel sheet after the rolling and annealing treatment is punched into a runner to form a stainless steel substrate with a runner. The die used for stamping is shown in Figure 2. Please refer to FIG. 2. In this example, the lower mold of the adopted mold is similar to the convex portion 12P of the lower mold 12, and its height (that is, the depth of the flow channel) H′ is 0.5 mm. The vertex angle a'of the convex portion (flow channel) 12P is a rounded obtuse angle, and its radius of curvature is 0.25 mm. In addition, the width of the flat surface (or referred to as a flat surface) Fb' of the main body portion 12B between two adjacent convex portions 12P is 1 mm. In addition, the mold used has multiple sets of patterns with different pitches P'and draft angle g'. The draft angle g'/spacing P'of Example 1 was 70 degrees/2.36mm, respectively. Thereafter, the particle diameter of the crystal grains was measured, and the surface roughness analysis was performed using a contact probe measuring instrument (α-stepper, manufactured by Kosaka Laboratory Ltd., model ET-4000A).

<Example 2>

Provide 316L stainless steel plate with a size of 25cm´60cm and a thickness of 200 microns. The original grain size of the stainless steel plate is 25 microns to 60 microns, and the average grain size of the original grain is 30 microns to 50 microns. In an environment of 900 degrees Celsius, the stainless steel sheet was rolled to a thickness of 100 microns with a force of 1350 MPa, and then the furnace was cooled to room temperature, and the sheet was taken out. The average grain size of the rolled sheet is measured to be 20 microns to 45 microns. Take the above partially rolled sheet and anneal it for 3 hours in an environment of 550 degrees Celsius and a vacuum of 1´10 ^-2 torr. And using a hydraulic press under the conditions of 20 degrees Celsius and a pressure of 225MPa, the stainless steel sheet after the rolling and annealing treatment is punched into a runner to form a stainless steel substrate with a runner. The die used for stamping is shown in Figure 2. Please refer to FIG. 2. In this example, the mold used is similar to the convex portion 12P of the mold 12, and its height (that is, the depth of the flow channel) H′ is 0.5 mm. The vertex angle a'of the convex portion (flow channel) 12P is a rounded obtuse angle, and its radius of curvature is 0.25 mm. In addition, the width of the flat surface (or referred to as a flat surface) Fb' of the main body portion 12B between two adjacent convex portions 12P is 1 mm. In addition, the mold used has multiple sets of patterns with different pitches P'and draft angle g'. The draft angle g'/spacing P'of Example 2 was 45 degrees/3mm, respectively. Thereafter, the particle diameter of the crystal grains was measured, and the surface roughness analysis was performed using a contact probe measuring instrument (α-stepper, manufactured by Kosaka Laboratory Ltd., model ET-4000A).

<Comparative Example 1>

Similar to Example 1, but no annealing treatment is performed after rolling but before stamping. Using a hydraulic press under the conditions of 20 degrees Celsius and a pressure of 225 MPa, the stainless steel sheet after the rolling and annealing treatment of Example 1 was runner-pressed to form a stainless steel substrate with a runner. The die used for stamping is shown in Figure 2. Referring to FIG. 2, in this example, the mold used is similar to the convex portion 12P of the mold 12, and its height (i.e., the depth of the flow channel) H'is 0.5 mm. The vertex angle a'of the convex portion (flow channel) 12P is a rounded obtuse angle, and its radius of curvature is 0.25 mm. In addition, the width of the flat surface (or referred to as a flat surface) Fb' of the main body portion 12B between two adjacent convex portions 12P is 1 mm. In addition, the mold used has multiple sets of patterns with different pitches P'and draft angles g'. The draft angle g'/pitch P'of Example 1 was 70 degrees/2.36 mm, respectively. Thereafter, the particle diameter of the crystal grains was measured, and the surface roughness analysis was performed using a contact probe measuring instrument (α-stepper, manufactured by Kosaka Laboratory Ltd., model ET-4000A).

<Example 3>

On the stainless steel plate of Example 1 above, a 3 micron carbon film was formed in the carbonate at 350 degrees Celsius by the salt bath method as a resist film, and an electrochemical corrosion test was conducted to estimate the corrosion life. The electrochemical corrosion test is carried out in a potassium hydroxide solution with a concentration of 1M at 80 degrees Celsius. The surface roughness analysis was performed using a contact probe measuring instrument (α-stepper, manufactured by Kosaka Laboratory Ltd., model ET-4000A). The results are shown in Table 2.

<Comparative example 2>

Similar to Example 3, but replacing the stainless steel plate with heat treatment of Example 1 with the stainless steel plate with no heat treatment of Comparative Example 1. The results are shown in Table 2.

Table 1

Table 2

7A is an SEM image of the stainless steel grain of Example 1. FIG. 7B is an SEM image of stainless steel crystal grains of Comparative Example 1. FIG. The results of FIG. 7A and FIG. 7B show that the grain size of the stainless steel grain of Example 1 which is heat-treated after rolling is much smaller than that of the stainless steel grain of Comparative Example 1 which is not heat-treated after rolling.

8A is an analysis of the surface roughness of the stainless steel substrate of Example 1. FIG. 8B is a surface roughness analysis of the stainless steel substrate of Comparative Example 1. FIG. The results of FIGS. 8A and 8B show that the surface roughness of the stainless steel substrate of Example 1 which is heat-treated after rolling is much smaller than that of the stainless steel substrate of Comparative Example 1 which is not heat-treated after rolling.

9A is an image view of an optical microscope of a stainless steel substrate obtained in Example 2 after being stamped with a die having a draft angle of 45 degrees. 9B is an image view of an optical microscope of a stainless steel substrate obtained by punching with a mold having a draft angle of 70 degrees in Example 1. FIG. The results of FIGS. 9A and 9B show that the stainless steel substrate after punching is continuous and uniform in thickness.

In addition, the electrochemical corrosion results and life prediction results from Table 2 show that the electrochemical corrosion rate of Example 3 which is heat-treated after rolling is lower than that of Comparative Example 2 which is not heat-treated after rolling, and its life can be increased by about 33.1%. The reason for this increase is presumed to be that the stainless steel grains are refined after heat treatment, and the surface roughness is reduced, resulting in a decrease in the electrochemical corrosion rate.

<Example 4> A titanium plate with a thickness of 100 μm is taken. The original grain range is 6 μm to 20 μm, and the average grain size of the original grains is 9 μm to 15 μm. Taking the above-mentioned part of the titanium plate for annealing for 1 hour in an environment of 350 degrees Celsius and a vacuum of 1´10 ^-2 torr, the average grain size of the formed grains is 0.1 μm to 3 μm. The die used for stamping is shown in Figure 2. Please refer to FIG. 2. In this example, the mold used is similar to the convex portion 12P of the mold 12, and its height (that is, the depth of the flow channel) H′ is 0.5 mm. The vertex angle a'of the convex portion (flow channel) 12P is a rounded obtuse angle, and its radius of curvature is 0.25 mm. In addition, the width of the flat surface (or referred to as a flat surface) Fb' of the main body portion 12B between two adjacent convex portions 12P is 1 mm. In addition, the mold used has multiple sets of patterns with different pitches P'and draft angle g'. The draft angle g'/spacing P'of Example 1 was 70 degrees/2.36mm, respectively. The results are shown in Table 3.

<Example 5>

Taking a titanium plate with a thickness of 100 microns, the original grains range from 6 microns to 20 microns, and the average grain size of the original grains ranges from 9 microns to 15 microns. Taking the above-mentioned part of the titanium plate for annealing for 1 hour in an environment of 350 degrees Celsius and a vacuum of 1´10 ^-2 torr, the average grain size of the formed grains is 0.1 μm to 3 μm. The die used for stamping is shown in Figure 2. Please refer to FIG. 2. In this example, the mold used is similar to the convex portion 12P of the mold 12, and its height (that is, the depth of the flow channel) H′ is 0.5 mm. The vertex angle a'of the convex portion (flow channel) 12P is a rounded obtuse angle, and its radius of curvature is 0.25 mm. In addition, the width of the flat surface (or referred to as a flat surface) Fb' of the main body portion 12B between two adjacent convex portions 12P is 1 mm. In addition, the mold used has multiple sets of patterns with different pitches P'and draft angle g'. The draft angle g'/spacing P'of Example 2 was 45 degrees/3mm, respectively. Thereafter, the particle diameter of the crystal grains was measured, and the surface roughness analysis was performed using a contact probe measuring instrument (α-stepper, manufactured by Kosaka Laboratory Ltd., model ET-4000A).

<Comparative Example 3> It is similar to Example 4, but the titanium sheet is not annealed. The results are shown in Table 3. The die used for stamping is shown in Figure 2. Referring to FIG. 2, in this example, the mold used is similar to the convex portion 12P of the mold 12, and its height (i.e., the depth of the flow channel) H'is 0.5 mm. The vertex angle a'of the convex portion (flow channel) 12P is a rounded obtuse angle, and its radius of curvature is 0.25 mm. In addition, the width of the flat surface (or referred to as a flat surface) Fb' of the main body portion 12B between two adjacent convex portions 12P is 1 mm. In addition, the mold used has multiple sets of patterns with different pitches P'and draft angles g'. The draft angle g'/pitch P'of Example 1 was 70 degrees/2.36 mm, respectively. Thereafter, the particle diameter of the crystal grains was measured, and the surface roughness analysis was performed using a contact probe measuring instrument (α-stepper, manufactured by Kosaka Laboratory Ltd., model ET-4000A).

<Example 6>

Taking another part of the titanium plate of Example 4, the process of forming a resist film plating according to the above-mentioned Embodiment 3, and performing an electrochemical corrosion test to estimate the corrosion resistance life analysis. The results are shown in Table 4.

<Comparative Example 4>

Similar to Example 6, but replacing the plate of Example 4 with the unheated plate of Comparative Example 3. The results are shown in Table 4.

table 3

Table 4

10A is an SEM image of titanium grains of Example 4. FIG. FIG. 10B is an SEM image of titanium crystal grains of Comparative Example 3. FIG. The results of FIGS. 10A and 10B show that the particle size of titanium crystal grains of Example 4 subjected to heat treatment after rolling is much smaller than that of Comparative Example 3 without heat treatment.

11A is an analysis of the surface roughness of the titanium substrate of Example 4. FIG. 11B is an analysis of the surface roughness of the titanium substrate of Comparative Example 3. FIG. The results of FIGS. 11A and 11B show that the surface roughness of the titanium substrate of Example 4 subjected to heat treatment is much smaller than that of the titanium substrate of Comparative Example 3 without heat treatment.

FIG. 12A is an optical microscope image of a titanium substrate obtained after punching with a die having a 45-degree draft angle runner pattern in Example 5. FIG. 12B is an optical microscope image of a titanium substrate obtained after punching with a mold having a 70-degree draft angle runner pattern in Example 4. FIG. The results of FIGS. 12A and 12B show that the titanium substrate after stamping is continuous and uniform in thickness.

In addition, the electrochemical corrosion results and life prediction results in Table 4 show that the electrochemical corrosion rate of Example 6 with heat treatment is lower than that of Comparative Example 4 without heat treatment, and its life can be increased by about 47.6%. The reason for its increase is presumed to be that the titanium grains are refined after heat treatment, and the surface roughness is reduced, resulting in a decrease in the electrochemical corrosion rate.

In summary, the fuel cell of the embodiment of the present invention can improve the corrosion resistance and life of the bipolar plate. In some embodiments, the fuel cell of the present invention can be applied to ultra-thin metal bipolar plate assemblies under 200 microns, by refining the grain of the metal sheet (grain <15 microns), the surface of the runner after stamping is rough The degree of reduction (Ra <1.2um), and the coating layer material is selected when the draft angle of the flow channel is greater than ≧40 degrees, which promotes a higher coating coverage of the resist layer and more corrosion resistance.

Although the present invention has been disclosed as above with examples, it is not intended to limit the present invention. Any person with ordinary knowledge in the technical field can make some changes and modifications without departing from the spirit and scope of the present invention. The scope of protection of the present invention shall be subject to the scope defined in the appended patent application.

10, 10a, 10b: plate

11: substrate

11P: convex part

11R, 131R ₁ , 131R ₂ , 132R ₁ , 132R ₂ : recess

11Pt: top surface

11Rb: bottom surface

11S: Side wall

12: Lower mold

12B: Main body

12P, 131P ₁ , 131P ₂ , 132P ₁ , 132P ₂ : convex part

12Pt: top surface

12Rb: bottom surface

12S: Side wall

12Bb, 12T: surface

13: Rolling process

14: Heat treatment process

16: flow channel

20: Anti-corrosion layer

30, 131a, 131b, 132a, 132b: bipolar plate

102: Membrane electrode group

104: Proton exchange membrane

106a, 106b: gas diffusion layer

116a: the first cooling channel

116b: Second cooling channel

118a: the first gas flow path

118b: Second gas flow path

130a, 130b: Bipolar plate group

200: fuel cell

Ca’, Cb’: flow channel

D1: First direction

D2: Second direction

P, P’, Pc1, Pc2, Pg1, Pg2: pitch

a, a’: vertex angle

b, b’: bottom corner

g, g’: draft angle

Ft, Ft’, Fb, Fb’: plane

H, H’: height

1A to 1F are cross-sectional views of the flow of a method for manufacturing a bipolar plate of a fuel cell according to an embodiment of the invention. 2 is a cross-sectional view of a mold according to an embodiment of the invention. 3 is a cross-sectional view of a substrate with flow channels according to an embodiment of the invention. 4A is a schematic cross-sectional view of a fuel cell according to an embodiment of the invention. 4B is a schematic cross-sectional view of a fuel cell corresponding to the flow path of a bipolar plate according to an embodiment of the present invention. 5A is a schematic cross-sectional view of a fuel cell with parallel flow paths of bipolar plates according to an embodiment of the present invention. FIG. 5B is a schematic cross-sectional view of a fuel cell having a bipolar plate with a perpendicular flow channel according to an embodiment of the present invention. 6 is a schematic cross-sectional view of a fuel cell stack according to an embodiment of the present invention. 7A is an SEM image of the stainless steel grain of Example 1. FIG. 7B is an SEM image of stainless steel grains of Comparative Example 1. FIG. 8A is an analysis of the surface roughness of the stainless steel substrate of Example 1. FIG. 8B is a surface roughness analysis of the stainless steel substrate of Comparative Example 1. FIG. 9A is an optical microscope (OM) image of a stainless steel substrate obtained after punching with a die having a draft angle of 45 degrees in Example 2. FIG. 9B is an image view of an optical microscope of a stainless steel substrate obtained by punching with a mold having a draft angle of 70 degrees in Example 1. FIG. FIG. 10A is an SEM image of titanium grains of Example 4. FIG. FIG. 10B is an SEM image of titanium crystal grains of Comparative Example 3. FIG. 11A is an analysis of the surface roughness of the titanium substrate of Example 4. FIG. 11B is an analysis of the surface roughness of the titanium substrate of Comparative Example 3. FIG. 12A is an optical microscope image of a titanium substrate obtained by punching a mold with a 45-degree draft angle runner pattern in Example 5. FIG. 12B is an optical microscope image of a titanium substrate obtained after punching with a mold having a 70-degree draft angle runner pattern in Example 4. FIG.

11: substrate

11P: convex part

11R: recess

11S: Side wall

16: flow channel

20: resist film

30: Bipolar plate group

Claims (11)

A bipolar plate for a fuel cell, including: a base material having a plurality of flow channels, the base material including stainless steel, titanium, nickel, chromium, the foregoing derivatives, the foregoing intermediary metals or a combination of the foregoing, titanium or chromium Carbide, nitride, oxynitride, cyanide, titanium-nickel intermetallic or titanium-aluminum intermetallic; and a resist layer covering the substrate, the resist layer includes carbon, metal carbon compound, metal nitrogen The carbon-nitrogen mixture of compounds or metals, wherein the surface roughness of the substrate is less than or equal to 1.2 μm. The bipolar plate for a fuel cell as described in item 1 of the patent application range, wherein the average grain size of the crystal grains of the base material ranges from 0.3 μm to 15 μm. The bipolar plate of a fuel cell as described in item 1 of the patent application, wherein the distance between the flow channels is less than or equal to 3 mm. The bipolar plate of a fuel cell as described in item 1 of the patent application, wherein the draft angle of the flow path of the base material is greater than 40 degrees. The bipolar plate of a fuel cell as described in item 1 of the patent application range, wherein the conductivity of the resist layer is 1×10 ³ S/cm to 1×10 ⁵ S/cm. The bipolar plate for a fuel cell as described in item 1 of the patent application, wherein the thickness of the resist layer is less than or equal to 3 μm. A method for manufacturing a bipolar plate of a fuel cell, comprising: providing a plate, the substrate includes stainless steel, titanium, nickel, chromium, the foregoing Derivatives, the aforementioned intermediary metals or combinations of the foregoing, titanium or chromium carbides, nitrides, oxynitrides, cyanides, titanium-nickel intermetallic metals or titanium-aluminum intermetallic metals; Performing heat treatment process on the sheet material; and performing stamping process on the sheet material with a stamping die to form a substrate, the substrate having a plurality of flow channels, wherein the draft angle of the stamping die is greater than 40 degrees. The method for manufacturing a bipolar plate for a fuel cell as described in item 7 of the patent application range, wherein the pressure in the rolling process is 100 MPa to 1500 MPa. The method for manufacturing a bipolar plate for a fuel cell as described in item 7 of the patent application scope, wherein the temperature of the heat treatment process is 300 degrees Celsius to 600 degrees Celsius. The method of manufacturing a bipolar plate for a fuel cell as described in item 7 of the scope of the patent application further includes a mold release process. The method for manufacturing a bipolar plate for a fuel cell as described in item 10 of the scope of the patent application further includes forming a resist layer on the substrate before the mold release process, the resist layer including carbon, Metal carbon compounds, metal nitrides or metal carbon-nitrogen mixtures.

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