KR20130122371A - Hybrid bipolar plate for fuel cell - Google Patents

Abstract

The present invention relates to a complex separation plate for a fuel cell which has excellent mechanical strength and conductivity, low contact resistance and gas permeability, and low density for reducing the weight of a product. The complex separation plate for the fuel cell contains metal powder paste filling the inside of a metal supporter for improving the conductivity.

Description

Hybrid bipolar plate for fuel cell

The present invention relates to a composite separator for fuel cells, and more particularly to a composite separator for fuel cells with improved mechanical strength, electrical conductivity, density, gas permeability, contact resistance, and the like.

The polymer electrolyte fuel cell has a lower operating temperature, higher current density and higher power density, shorter start-up time, and faster response to hatching changes than other types of fuel cells. In particular, the use of a polymer membrane as the electrolyte, there is no electrolyte loss, it is possible to apply the existing reforming technology of methanol reformer, it is less sensitive to changes in the pressure of the reactor. In addition, the design is simple, easy to manufacture, and has the advantage of producing a wide range of output, so that it can be applied to a variety of fields, the current intensive R & D as a power source for fuel cell cars, household power generation and portable devices Several prototypes have been announced, some of which are under test. The commercialization of such a polymer electrolyte fuel cell depends on how much the price of the stack, which is currently thousands of dollars per KW, can be lowered. When analyzing the fuel cell price by parts with current technology, the separator accounted for the highest share of 50% of the total stack price, 18% of the electrolyte, 15% of the catalyst, and 6% of the carbon material used as the gas diffusion layer. do. Therefore, in order to lower the price of the polymer electrolyte fuel cell stack, it is necessary to lower the price of the separator, which accounts for 50% of the stack cost. The most widely used separator plate is graphite, which has excellent electrical conductivity, corrosion resistance, and low density, making it possible to manufacture lightweight stacks. However, since graphite has a lot of pores and high gas permeability, a certain thickness is required along with the resin impregnation to prevent mixing of the reaction gas, and as a result, the volume of the stack becomes large. In addition, it is easy to break, and must be subjected to machining during molding, the manufacturing price is expensive and there is a disadvantage in that mass production is difficult. However, there is a problem that there is a current lack of low-cost separator material to replace such graphite.

The present invention has been made to solve the above problems, the object of the present invention is

As a composite separator for fuel cells at a lower cost than graphite separators, a composite separator for fuel cells having excellent processability, mechanical strength, electrical conductivity, contact resistance, etc., and having low density and gas permeability is provided.

A composite separator for a fuel cell according to an aspect of the present invention for solving the above problems includes a metal support paste filled inside the metal support to improve the metal support and electrical conductivity. In addition, the metal support is characterized in that it comprises a through-hole filled with the metal powder paste. In addition, the metal powder paste filled in the through hole is characterized in that the thickness of 0.45 ~ 0.55mm. In addition, the through hole is characterized in that a plurality. In addition, the metal powder is characterized in that any one or more selected from the group consisting of silver, platinum, nickel or copper. In addition, the metal support is characterized in that any one or more selected from the group consisting of aluminum, magnesium or stainless steel. In addition, a graphite layer in which a polymer resin is mixed is formed on at least one surface of the filled metal powder paste. In addition, the polymer resin is characterized in that any one or more selected from the group consisting of polypropylene, polycarbonate or polymethyl methacrylate. In addition, the graphite layer in which the polymer resin is mixed is characterized in that 55 to 65% graphite and 35 to 45% by volume of the polymer resin is mixed. In addition, the graphite layer mixed with the polymer resin is characterized in that the thickness of 0.25 ~ 0.35mm. In addition, at least one surface is formed as a carbon sheet or a carbon foil on at least one surface of the graphite layer mixed with the polymer resin.

The composite separator according to the present invention has excellent processability, mechanical strength, electrical conductivity, contact resistance, etc. in addition to low cost of production, which is a condition required to be used as a separator material, and has low density and gas permeability. It is possible to provide a high quality composite separator for fuel cells.

1 is a view showing the upper surface of the metal support of the composite separator plate for fuel cells according to the present invention.
2 is a view showing a cross section of the composite separator plate for a fuel cell according to an embodiment of the present invention.
3 is a photograph of a composite separator for a fuel cell according to the present invention.
Figure 4 is a graph showing the bending strength of the composite separator for fuel cells according to Examples 1-1 to 1-3 and Comparative Examples.
5 is a graph showing the electrical conductivity of the composite separator plate for a fuel cell according to Examples 1-1 to 1-3 and Comparative Examples.
6 is a graph showing contact resistance of a composite separator for a fuel cell according to Examples 1-1 to 1-3 and Comparative Examples.
7 is a graph illustrating gas permeability of the composite separator for a fuel cell according to Examples 1-1 to 1-3 and Comparative Examples.
8 is a graph illustrating densities of composite separator plates for fuel cells according to Examples 1-1 to 1-3 and Comparative Examples.
9 is a photograph of the state of Example 2, Example 3 and Example 4 according to the amount of graphite and polymer resin.

Accordingly, the present inventors have completed the present invention by confirming that it is possible to provide a composite separator plate for a fuel cell according to the present invention as a result of earnest research efforts to solve the problems of the prior art.

In general, in the separator for fuel cell, the MEA (membrane-electrode assembly) is located on both sides of the separator (Anode, Cathode junction) so that the reaction gas moves through the flow path. The electrons move through the external conductors to generate electricity. In addition, the composite separator plate for the fuel cell is located on both sides of the electrode support to play a role to move the current generated in the battery should be good in the ability to conduct electricity.

1 shows a metal support 110 of the composite separator plate for a fuel cell according to the present invention. The metal support 110 may include a through hole 111. The through hole 111 is not particularly limited in number, but one or more may be included in the metal support 110.

2 is a view showing a cross section of the composite separator for a fuel cell according to the present invention. The composite separator plate for a fuel cell according to the present invention as shown in FIG. 2 includes the metal support 110. In addition, the metal support 110 may be at least one selected from the group consisting of aluminum, magnesium, stainless steel, and their respective alloys. When the at least one selected from the group consisting of the aluminum, magnesium, stainless steel and their respective alloys as the metal support 110, it is possible to provide a composite separator plate for fuel cells excellent in mechanical strength and electrical conductivity, and fuel Low gas permeability is achieved so that the gas used in the cell does not flow out of the separator plate. In addition, when the aluminum support or magnesium is more preferably selected as the metal support 110, it is possible to provide a low density fuel cell composite separator, which is advantageous as a fuel cell separator. Provision is possible.

The metal support 110 may include a metal powder paste 120 filled in the metal support. The metal powder may be selected without particular limitation as long as it is a material that improves electrical conductivity and thermal conductivity of the composite separator. Preferably, the metal powder may be any one or more selected from the group consisting of silver, platinum, nickel or copper. In addition, the size of the metal powder is not particularly limited, but may be preferably 10nm to 100㎛. In addition, the paste means that the paste is modified into a grass shape to facilitate handling of the metal powder. The reason why the metal powder is used as a paste is to discharge heat generated inside the fuel cell to the outside. In other words, when the paste is used, excellent thermal conductivity is achieved, whereas when the paste is not used, the thermal conductivity is remarkably decreased. In addition, the paste may be made of preferably 55 to 65% by weight of the metal powder and 35 to 45% by weight of the conductive filler. When the metal powder is mixed at less than 55% by weight, it is difficult to expect sufficient electrical conductivity, and when it exceeds 65% by weight, it is difficult to achieve an appropriate viscosity and excellent thermal conductivity. In addition, the conductive filler may be preferably made of 1-Methoxy-2Propanol. In addition, the viscosity of the metal powder is preferably 300 to 500 poise (poise). When the metal powder paste 120 is filled in the metal support 110, the electrical conductivity of the composite separator may be further improved.

The metal support 110 may include a through hole 111 filled with the metal powder paste 120. The thickness of the metal powder paste filled in the through hole is not particularly limited, but is preferably 0.45 to 0.55 mm. When the thickness of the metal powder paste filled in the through-hole 111 exceeds 0.55mm, the surface of the graphite layer mixed with the polymer resin is not evenly distributed and the efficiency decreases. It is not preferable because there is a problem that a sufficient role as the metal powder paste 120 filled in the through hole 111 may not be expected for the purpose of providing excellent electrical conductivity.

The at least one surface of the filled metal powder paste 120 may be formed of a graphite layer 130 in which a polymer resin is mixed, and preferably formed on both surfaces of the metal powder paste 120. The graphite may further improve the thermal conductivity of the composite separator for fuel cells. In addition, due to the graphite, the corrosion resistance of the composite separator for fuel cells is further improved. In addition, the graphite layer 130 mixed with the polymer resin formed on at least one surface of the metal powder paste may be formed by being fused together with the metal support 110, as compared with the case where a single graphite plate is selected as a separator for a fuel cell. The volume is significantly reduced, and thus it is possible to provide a composite separator plate for fuel cells more advantageous than the graphite single plate.

In addition, the polymer resin is not particularly limited as long as it is a material for imparting electrical conductivity to the composite separator for fuel cell. Preferably, the polymer resin may be any one or more selected from the group consisting of polypropylene, polycarbonate, or polymethyl methacrylate.

In addition, the graphite layer 130 mixed with the polymer resin is preferably graphite

55 to 65% by volume and 35 to 45% by volume of the polymer resin may be mixed. If the graphite is mixed in excess of 65% by volume it is difficult to expect a perfect fusion with the metal support because the mixing is not made. In addition, when the graphite is mixed at less than 55% by volume, the mixing is well done, but it is not preferable due to the problem that it is difficult to expect perfect fusion because it does not become thin and thus does not form itself.

In addition, the thickness of the graphite layer 130 mixed with the polymer resin is not particularly limited, but the thickness is preferably 0.25 to 0.35 mm. When the thickness of the graphite layer 130 in which the polymer resin is mixed exceeds 0.35 mm, the carbon sheet layer 140 must be relatively thin, and thus, excellent corrosion resistance is difficult to be expected, and the thickness thereof is less than 0.25 mm. In this case, there is a problem that it is difficult to expect the role of the graphite layer 130 in which the polymer resin is mixed to achieve excellent thermal conductivity, which is not preferable.

In addition, in order to prevent corrosion on at least one surface of the graphite layer 130 in which the polymer resin is mixed and to maintain excellent electrical and thermal conductivity of the composite separator for fuel cells according to the present invention, a carbon sheet or carbon One or more layers 140 of carbon foil may be formed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

Example

Example  1-1; aluminum Metal support  making

The metal support to be used for the composite separator plate for fuel cell with aluminum was manufactured, and FIG. 1 illustrates the top surface of the metal support according to the embodiment 1-1.

Example  1-2; magnesium Metal support  making

The metal support to be used for the composite separator plate for fuel cell with magnesium was manufactured, and the metal support according to the present embodiment was manufactured in the same shape as the metal support of FIG. 1.

Example  1-3; Stainless steel Metal support  making

The metal support to be used in the composite separator plate for fuel cells with stainless steel was manufactured, and the metal support according to the present embodiment was manufactured in the same shape as the metal support of FIG. 1.

Example  2;

Silver having a specific gravity of 2.23 g / cc, a viscosity of 300 to 500 poise, and an average particle size of 10 μm in the metal support inner through-hole portion manufactured by Examples 1-1, 1-2, and 1-3. ) A silver paste prepared by mixing 60% by weight of powder and 40% by weight of 1-Methoxy-2Propanol as a conductive filler was added and dried at 100 ° C. for 5 hours. After drying, the graphite and the polypropylene resin powder were mixed at a ratio of about 60: 40% by volume, and firstly molded using a hot press in a mold manufactured to specifications at 180 ° C., 50 minutes, and 10 MPa. After 20 minutes, the carbon sheet cut to the standard was bonded to the primary molded surface, and the secondary molding was performed using a hot press at 180 ° C., 30 minutes, and 3 MPa, which was about 20 minutes. After separation at room temperature. The manufacturing process of the fuel cell composite separator according to the present embodiment is shown in Table 1 below, and the cross section of the fuel cell composite separator plate thus prepared is shown in FIG. 2. In addition, the final composite fuel cell composite separator thus produced is shown in FIG. 3.

division Manufacture process Stage 1 Fabrication of Metal Support Layers (Aluminum, Magnesium, Stainless Steel) Step 2 Metal powder paste filling (100 ℃, 5 hours) Step 3 Formation of graphite mixed polymer resin layer (Graphite: Polymer resin = about 60: 40% by volume, 180 ° C, 50 minutes, 10MPa) Step 4 Carbon sheet layer formation (180 ℃, 30 minutes, 3MPa) Step 5 Completed composite separator for fuel cell

Example  3;

A composite separator for a fuel cell was manufactured in the same manner as in Example 2, except that the graphite and the polymer resin were mixed at about 70: 30% by volume.

Example  4;

A composite separator for a fuel cell was manufactured in the same manner as in Example 2, except that the graphite and the polymer resin were mixed at about 50: 50% by volume.

Comparative Example

As a condition of the composite separator for excellent fuel cell quality, the US Department of Energy (DOE) presented the minimum conditions, the specific characteristics and conditions of which are shown in Table 2 below. In addition, the composite separator for a fuel cell having a minimum condition and characteristics according to Table 2 was prepared as the comparative example.

Property Unit Value Flexural strength MPa > 59 Electrical conductivity S / cm > 100 Contact resistance mΩ㎠ <20 Hydrogen permeability Cm 3 / cm 2 <2 × 10 ^-6 Density g / cm3 <5

As can be seen in Table 2, in the US Department of Energy DOE, in the fuel cell composite separator, the bending strength is advantageously greater than 59 MPa, and the electrical conductivity is advantageously greater than 100 S / cm, and the contact resistance is 20 Less than mΩcm 2 is advantageous, and more preferably hydrogen permeability, ie, gas permeability, less than 2 × 10 −6, and less than 5 g / cm 3 in density. Conditions and properties are presented. Thus, the composite separator for fuel cell according to the comparative example has a bending strength of 59 MPa, electrical conductivity of 100 S / cm, contact resistance of 20 mΩcm 2, gas permeability of 2 × 10-6, and density of 5 g / It is a composite separator for fuel cells having a physical property of cm 3.

Experimental Example

< Experimental Example  One; Bending strength  Measurement>

A fuel cell composite separator according to Comparative Example and a fuel cell composite separator according to Example 2 having respective metal supports according to Examples 1-1, 1-2 and 1-3, Specimens having lengths, widths, and thicknesses of 40 mm, 40 mm, and 1.5 mm, respectively. Each of the specimens was measured at a constant strain rate (1 mm / min) using a universal testing machine (Instron-4468). The results are shown in FIG.

As shown in FIG. 4, in the case of the composite separator for fuel cells manufactured with the metal supports of Examples 1-1, 1-2, and 1-3, the composite separator for fuel cells according to the comparative example It was confirmed that the bending strength is improved by four times or more than the case. In addition, in the case of the composite separator for fuel cells fabricated with the metal support of Example 1-3, it was confirmed that the bending strength was improved by at least six times than the composite separator for the fuel cell according to the comparative example. The excellent bending strength means that the mechanical strength is superior to that of the conventional composite separator for fuel cells, which is responsible for the mechanical strength in the metal support part, thereby making it easy to break the fragile disadvantage of the conventional separator using fuel graphite. I would say it solved.

< Experimental Example  2; Electrical conductivity measurement>

A fuel cell composite separator according to Example 1 and a fuel cell composite separator according to Example 2 having respective metal supports according to Example 1-1, Example 1-2, and Example 1-3 Electrical conductivity was measured. At this time, it was measured using a surface resistance meter (Milli-ohmmeter) by a 4-point-probe technique. The results are shown in FIG. 5 below.

As can be seen in FIG. 5, a fuel cell composite separator prepared according to Example 2 having the metal supports of Examples 1-1, 1-2, and 1-3 was manufactured according to Comparative Example. It was confirmed that the electrical conductivity of the battery composite separator plate is improved by 3.5 times or more.

< Experimental Example  3; Contact Resistance Measurement>

A fuel cell composite separator according to Example 1 and a fuel cell composite separator according to Example 2 having respective metal supports according to Example 1-1, Example 1-2, and Example 1-3 Contact resistance was measured. At this time, it was measured using a surface resistance meter (Milli-ohmmeter) by a 4-point-probe technique. Also measured at the same pressure for accurate evaluation. The surface resistance measuring device is a device that can bite the specimen by using both jig, and each jig is a device that can measure the resistance of the specimen by passing a current and measuring the voltage generated at this time to calculate the resistance. The results of this experiment are shown in Figure 6 below.

As can be seen in FIG. 6, the composite separator for a fuel cell manufactured according to Example 2 with the metal support of Example 1-3 was found to have lower contact resistance than that of Comparative Example, which is Example 1-. The case of 3 means that the composite separator for a fuel cell has better contact resistance than that of the comparative example. In addition, it was confirmed that the composite separator for a fuel cell manufactured according to Example 2 with the metal support of Example 1-1 had the same contact resistance as that of the comparative example. In addition, the composite separator for a fuel cell manufactured according to Example 2 with the metal support of Example 1-2 has a slightly higher contact resistance than the comparative example, but the difference is not so great that the contact resistance comparable to the comparative example to some extent. It was confirmed to have. This means that it is possible to provide a composite separator for a fuel cell having a similar contact resistance at a lower production cost than a graphite single sheet.

< Experimental Example  4; Gas Permeability Measurement>

A fuel cell composite separator according to Example 1 and a fuel cell composite separator according to Example 2 having respective metal supports according to Example 1-1, Example 1-2, and Example 1-3 Gas permeability was measured with a universal testing machine (Instron-4468). The temperature was carried out at room temperature, the pressure of the feed portion was maintained at around 2 bar, the permeate portion was maintained in a vacuum of less than 0.2 torr. The measurement results of the gas permeability experiment are shown in FIG. 7.

As can be seen in FIG. 7, the composite separator for each fuel cell manufactured according to Example 2 with the respective metal supports according to Examples 1-1, 1-2, and 1-3 is a comparative example. It was confirmed that the gas permeability is significantly lower than the composite separator for fuel cells according to. This prevents the separation of gas through the separator plate to provide a fuel cell with improved performance. The composite separator plate for fuel cells according to Examples 1-1, 1-2 and 1-3 is used for the fuel cell of Comparative Example. It will be referred to as a composite separator for fuel cells superior to the composite separator.

< Experimental Example  5; Density Measurement>

As a composite separator for fuel cells and a composite separator for fuel cells according to Comparative Example, each of the composite separators prepared according to Example 2 with the respective metal supports according to Examples 1-1, 1-2 and 1-3. The specimens were 40 mm, 40 mm, and 1.5 mm in length, width, and thickness, respectively, and their volumes were measured. In addition, the weight was measured using an electronic balance. Thus, the density of the fuel cell composite separator according to Example 1-1, Example 1-2, and Example 1-3 and the fuel cell composite separator according to Comparative Example were measured. The measured result is shown in following FIG.

As shown in FIG. 8, the composite separator for fuel cells according to Examples 1-3 has a slightly higher density than the composite separator for fuel cells according to the comparative example, but the difference is not large and is boiling. This means that it is possible to provide a composite separator for fuel cells with similar density at low production cost. In addition, the fuel cell composite separator according to Examples 1-1 and 1-2 was found to be a fuel cell composite separator having a density reduced by more than half as compared with the comparative example. This low density means that it is possible to provide a lighter weight composite separator for fuel cells.

< Experimental Example  6; With graphite  Effect measurement by difference of volume% of polymer resin>

Using the composite separator for fuel cells prepared according to Example 2 and the composite separator for fuel cells according to Examples 3 and 4, an experiment was conducted to measure the effect of volume% difference between graphite and polymer resin. That is, the experiment was performed to compare the graphite layer mixed with the polymer resin according to each case. The results are shown in Figure 9 below.

 As shown in FIG. 9, when the volume% of the graphite and the polymer resin was about 60: 40% by volume as in Example 2, the graphite layer in which the polymer resin was mixed in the composite separator for fuel cells was not particularly problematic. Binding to the metal support

It could be confirmed in FIG. 9 (a). However, in Example 3 having the volume% of about 70: 30% by volume, it could be seen from FIG. 9B that the graphite layer in which the polymer resin was mixed with the metal support was not completely bound. This is because the content of graphite is too high to mix properly. In addition, even in the case of Example 4 in which the volume% of the graphite and the polymer resin was about 50: 50% by volume, it was confirmed in FIG. 9 (c) that the binder was not smoothly formed on the metal support. This was confirmed as a result of mixing well, unlike Example 3, but was too viscous to form the molding itself. Thus, as shown in Example 2, it was confirmed that the volume% of about 60: 40% by volume is a numerical range that more secures the binding with the metal support.

Through the above experiments, the composite separator for fuel cells according to the present invention has improved mechanical strength even at low production cost, excellent electrical conductivity, excellent contact resistance, low gas permeability, and low density, thus providing a lightweight fuel cell. It was confirmed that this is an excellent fuel cell composite separator.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. It is natural.

110: metal support, 120; Metal powder paste, 130: graphite layer mixed with polymer resin, 140: carbon sheet layer

Claims (14)

Metal support; A composite separator for a fuel cell comprising a metal powder paste filled in the metal support to improve electrical conductivity.
The method of claim 1,
The metal powder paste is a composite separator for a fuel cell, characterized in that it comprises a conductive filler as a solvent.
3. The method of claim 2,
The conductive filler is a composite separator for a fuel cell, characterized in that 1-Methoxy-2Propanol.
3. The method of claim 2,
55 to 65% by weight of the metal powder and 35 to 45% by weight of the conductive filler are mixed.
The method of claim 1,
The metal powder has a viscosity of 300 ~ 500 poise (poise) composite separator for a fuel cell, characterized in that.
The method of claim 1,
The metal support is a composite separator for a fuel cell, characterized in that it comprises at least one through hole filled with the metal powder paste.
The method according to claim 6,
The metal powder paste filled in the through hole has a thickness of 0.45 ~ 0.55mm composite separator plate for a fuel cell.
The method of claim 1,
The metal powder is a composite separator for a fuel cell, characterized in that at least one selected from the group consisting of silver, platinum, nickel or copper.
The method of claim 1,
The metal support is a composite separator for a fuel cell, characterized in that any one or more selected from the group consisting of aluminum, magnesium, stainless steel and their respective alloys.
The method of claim 1,
A composite separator for a fuel cell, characterized in that a graphite layer in which a polymer resin is mixed is formed on at least one surface of the filled metal powder paste.
The method of claim 10,
The polymer resin is a composite separator for a fuel cell, characterized in that at least one selected from the group consisting of polypropylene, polycarbonate or polymethyl methacrylate.
The method of claim 10,
The graphite layer mixed with the polymer resin is a composite separator for a fuel cell, characterized in that 55 to 65% graphite and 35 to 45% by volume polymer resin is mixed.
The method of claim 10,
The graphite layer of the polymer resin is mixed is a composite separator for a fuel cell, characterized in that the thickness of 0.25 ~ 0.35mm.
The method of claim 10,
And at least one layer formed on at least one surface of the graphite layer in which the polymer resin is mixed, as a carbon sheet or a carbon foil.

Images