Patent Publication Number: US-2012034498-A1

Title: Fuel cell, plate having through-plane conductivity, and manufacturing method thereof

Description:
FIELD OF THE INVENTION 
     The present invention relates to a fuel cell, a plate having through-plane conductivity, and a manufacturing method of the plate; and more particularly to a plate having linear conductors arranged therein and extended in a direction perpendicular to a plane surface of the plate, a manufacturing method of the plate, and a fuel cell including bipolar plates made of such plates. 
     BACKGROUND OF THE INVENTION 
     With the gradually expanded fuel cell application market, a key component of the fuel cell, namely, the bipolar plate, has received gradually increased attention among the fuel cell field. The bipolar plate is also referred to as a flow field plate, a bipolar electrode, a current collector, a delivery plate or an internal connector, and is a basic structure for the fuel cell to operate. The bipolar plates in the fuel cell carry fuel and air into their corresponding electrode to ensure the air and the fuel are completely separated from each other. The bipolar plates provide a mechanical support and necessary strength to the membrane electrode assembly (MEA), enable required seal strength in delivering air and fuel, incorporate manifolds thereinto, and assist in adjustment of fuel cell stack temperature. The manifold functions like a windpipe in the human respiratory system to send gas into channels, which function like a man&#39;s bronchia, formed on the bipolar plate. Finally, the gas flows through gas diffusion layers to finely and uniformly distribute in catalytic layers. 
     The bipolar plates are the most important factor that determines the weight power density and the volumetric power density of the fuel cell. In a typically designed fuel cell, when the end plates are excluded, the bipolar plates account for more than 80% of an overall weight of the fuel cell stack, and account for almost the entire volume of the fuel cell stack. Natural graphite is one form of pure carbon having a melting point as high as 4500° C., which is the highest one among the currently available solid-state materials, and has the best stability compared to other solid materials. As to synthetic graphite, it is a carbon-carbon composite material, initially developed for aerospace industry, and has now been widely used in making rocket nozzles and airplane brake disks. Due to its high strength, good conductivity and chemical stability, the synthetic graphite is the earliest material that is used to make the bipolar plates for fuel cells. 
     However, in the conventional bipolar plates, the carbon fibers added thereinto are not oriented. That is, the carbon fibers are disorderly distributed in the bipolar plates, resulting in poor through-plane conductivity of the bipolar plates. Under this circumstance, the fuel cell efficiency is apparently lowered particularly when a high current density is applied thereto. 
     SUMMARY OF THE INVENTION 
     A primary object of the present invention is to provide a fuel cell, a plate having through-plane conductivity, and a manufacturing method of the plate, so as to overcome the problem of low efficiency of conventional fuel cells that do not include bipolar plates having oriented linear conductors. 
     To achieve the above and other objects, the plate having through-plane conductivity according to the present invention includes a substrate and a plurality of linear conductors arranged in the substrate. The linear conductors are oriented by a magnetic field to have an extending direction perpendicular to a plane surface of the substrate, and are respectively coasted with a metal material. 
     In the present invention, the linear conductors are carbon fibers. 
     In the present invention, the substrate is made of an epoxy resin material. 
     In the present invention, the metal material is a magnetic material, such as iron, cobalt, or nickel. 
     To achieve the above and other objects, the manufacturing method of the plate having through-plane conductivity includes the steps of coating each of a plurality of linear conductors with a metal material; mixing the linear conductors with a substrate material; injecting the mixture of the substrate material and the linear conductors into a mould for injection molding a plate; and applying a magnetic field to the mixture in the mould, so that the linear conductors in the substrate material are oriented to extend in a direction perpendicular to a plane surface of the molded plate. 
     In the manufacturing method of the present invention, the linear conductors are carbon fibers. 
     In the manufacturing method of the present invention, the substrate is made of an epoxy resin material. 
     In the manufacturing method of the present invention, the metal material is a magnetic material, such as iron, cobalt, or nickel. 
     To achieve the above and other objects, the fuel cell according to the present invention includes a first end plate; a first current collector arranged on the first end plate; a first conductive carbon paper arranged on the first current collector; a first bipolar plate arranged on the first conductive carbon paper; a membrane electrode arranged on the first bipolar plate; a second bipolar plate arranged on the membrane electrode; a second conductive carbon paper arranged on the second bipolar plate; a second current collector arranged on the second bipolar plate; and a second end plate arranged on the second current collector. The first bipolar plate includes a first substrate and a plurality of linear conductors arranged in the first substrate and oriented by a magnetic field to extend in a direction perpendicular to a plane surface of the first substrate; and the linear conductors are respectively coated with a metal material. 
     In the fuel cell of the present invention, the second bipolar plate includes a second substrate and a plurality of linear conductors arranged in the second substrate and oriented by a magnetic field to extend in a direction perpendicular to a plane surface of the second substrate; and the linear conductors are respectively coated with a metal material. 
     In the fuel cell of the present invention, the linear conductors are carbon fibers. 
     In the fuel cell of the present invention, the substrate is made of an epoxy resin material. 
     In the fuel cell of the present invention, the metal material is a magnetic material, such as iron, cobalt, or nickel. 
     In the fuel cell of the present invention, one of the first and the second substrate is provided on one surface facing toward the membrane electrode with a gas channel. 
     In the present invention, by providing oriented linear conductors in the bipolar plate manufactured with the method of the present invention, the bipolar plate and the fuel cell using such bipolar plate can have upgraded through-plane conductivity to thereby effectively overcome the problem of poor efficiency in the conventional fuel cells. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The structure and the technical means adopted by the present invention to achieve the above and other objects can be best understood by referring to the following detailed description of the preferred embodiments and the accompanying drawings, wherein 
         FIG. 1  is a flowchart showing the steps of manufacturing a plate having through-plane conductivity according to the present invention; 
         FIG. 2  is a schematic view of a plate having through-plane conductivity according to the present invention; 
         FIG. 3  is an image of an embodiment of the plate having through-plane conductivity according to the present invention; and 
         FIG. 4  is an exploded perspective view of a fuel cell according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Please refer to  FIG. 1  that is a flowchart showing the steps included in a method of manufacturing a plate having through-plane conductivity. As shown, the manufacturing method includes the following steps: coating each of a plurality of linear conductors with a metal material (S 10 ); mixing the linear conductors with a substrate material (S 20 ); injecting the mixture of the substrate material and the linear conductors into a mould for injection molding a plate (S 30 ); and applying a magnetic field to the mixture in the mould, so that the linear conductors in the substrate material are oriented to extend in a direction perpendicular to a plane surface of the molded plate (S 40 ). 
     In some preferred embodiments of the present invention, the linear conductors preferably have a length about 1 mm, and a diameter about 10 μm. The metal material for coating the linear conductors can be nickel. The substrate material is preferably a two-component epoxy resin material including a component A and a component B, which have a viscosity of 850 cps and 60 cps, respectively, and are mixed at a ratio of 3:1. The linear conductors and the epoxy resin material for the substrate are mixed and stirred for 30 minutes, and the mixture is then injected into a desired mould. The field fringing effect is ignored and a maximum magnetic field density of 0.069 Tesla is applied to the mixture in the mould for 30 minutes. The mould is opened after 12 hours and the finished product is removed from the mould.  FIG. 3  is an image showing oriented linear conductors are distributed in the injection molded plate manufactured using the method of the present invention. 
     Please refer to  FIG. 2  that schematically shows a plate having through-plane conductivity according to the present invention, which is generally denoted by reference numeral  1  and is also briefly referred to as the plate herein. As shown, the plate  1  includes a substrate  10  and a plurality of linear conductors  11 . The linear conductors  11  are oriented by a magnetic field to arrange in the substrate  10  with an extending direction perpendicular to a plane surface of the substrate  10 . Further, each of the linear conductors  11  is coated with a metal material  110 . In some preferred embodiments, the metal material  110  can be a magnetic material, such as iron, cobalt or nickel; and the substrate  10  can be made of an epoxy resin material. 
     Please refer to  FIG. 3  that is an image of an embodiment of the plate having through-plane conductivity according to the present invention. As shown, the linear conductors  11  extend through the substrate  10  in a thickness direction thereof and are in the form of straight lines perpendicular to the plane surface of the substrate  10 . With these linear conductors  11  arranged in the substrate  10  and extended in a direction perpendicular to the plane surface of the substrate  10 , the plate  1  can have largely increased electric conductivity in the extending direction of the linear conductors  11 . 
       FIG. 4  is an exploded perspective view of a fuel cell  2  according to the present invention. As shown, the fuel cell  2  includes a first end plate  20 , a first current collector  21 , a first conductive carbon paper  22 , a first bipolar plate  23 , a membrane electrode  24 , a second bipolar plate  25 , a second conductive carbon paper  26 , a second current collector  27 , and a second end plate  28 . The first current collector  21  is arranged on the first end plate  20 , the first conductive carbon paper  22  is arranged on the first current collector  21 , the first bipolar plate  23  is arranged on the first conductive carbon paper  22 , the membrane electrode  24  is arranged on the first bipolar plate  23 , the second bipolar plate  25  is arranged on the membrane electrode  24 , the second conductive carbon paper  26  is arranged on the second bipolar plate  25 , the second current collector  27  is arranged on the second conductive carbon paper  26 , and the second end plate  28  is arranged on the second current collector  27 . The first bipolar plate  23  includes a first substrate  230  and a plurality of linear conductors  231 . The linear conductors  231  are oriented by a magnetic field to arrange in the first substrate  230  in an extending direction perpendicular to a plane surface of the first substrate  230 . And, each of the linear conductors  231  is coated with a metal material  110 . 
     Similarly, the second bipolar plate  25  includes a second substrate  250  and a plurality of linear conductors  251 . The linear conductors  251  are oriented by a magnetic field to arrange in the second substrate  250  in an extending direction perpendicular to a plane surface of the second substrate  250 . And, each of the linear conductors  251  is coated with a metal material  110 . In the present invention, the first substrate  230  and the second substrate  250  can be made of an epoxy resin material, and the metal material  110  can be a magnetic material, such as iron, cobalt, or nickel. Further, the first substrate  230  or the second substrate  250  is provided on one surface facing toward the membrane electrode  24  with a gas channel  232  or  252  to assist in the flowing of gases and the occurrence of reaction between the gases in the fuel cell  2 . 
     In the present invention, due to the oriented linear conductors, such as carbon fibers, in the bipolar plate manufactured with the method of the present invention, the bipolar plate and the fuel cell using such bipolar plate can have upgraded through-plane conductivity to thereby effectively overcome the problem of poor efficiency in the conventional fuel cells. 
     The present invention has been described with some preferred embodiments thereof and it is understood that many changes and modifications in the described embodiments can be carried out without departing from the scope and the spirit of the invention that is intended to be limited only by the appended claims.