JP2008277178A - Fuel cell - Google Patents

Abstract

An object of the present invention is to further improve the discharge of produced water or the like in a fuel cell.
SOLUTION: An electrolyte membrane 12, a catalyst layer 14 laminated on both surfaces of the electrolyte membrane 12, a gas diffusion layer 18 laminated on the catalyst layer 14, and a gas diffusion layer 18 are laminated to form a gas flow path. The expanded molded body 20 and a separator 22 laminated on the expanded molded body 20 and separating the gas between adjacent cells, and the separator 22 includes a separator substrate 26 molded of a metal material. 10 is provided between the separator substrate 26 and the metal foil 28, and is expanded by absorbing water by being attached between the separator substrate 26 and the metal foil 28. It has a water absorbent resin 34 that pushes up the other end 32 of the foil 28 and makes contact with the water droplets 40 formed on the surface of the separator substrate 26.
[Selection] Figure 5

Description

  The present invention relates to a fuel cell, and in particular, an electrolyte membrane, a catalyst layer laminated on both surfaces of the electrolyte membrane, a gas diffusion layer laminated on the catalyst layer, and a gas diffusion layer laminated on the gas diffusion layer. And a separator that is stacked on the gas flow path structure and separates the gas between adjacent cells.

  In recent years, fuel cells have attracted attention as batteries having high efficiency and excellent environmental characteristics. 2. Description of the Related Art In general, a fuel cell generates electric energy by electrochemically reacting hydrogen, which is a fuel gas, with oxygen in the air, which is an oxidant gas. As a result of the electrochemical reaction between hydrogen and oxygen, water is generated.

  Types of fuel cells include phosphoric acid type, molten carbonate type, solid electrolyte type, alkali type, and solid polymer type. Among these, solid polymer fuel cells that have advantages such as startup at normal temperature and quick startup time have been attracting attention. Such a polymer electrolyte fuel cell is used as a power source for a moving body, for example, a vehicle.

  A polymer electrolyte fuel cell is assembled by laminating a plurality of single cells, current collector plates, end plates, and the like. The fuel cell includes an electrolyte membrane, a catalyst layer, a gas diffusion layer, and a separator.

  Patent Document 1 includes an electrolyte / electrode structure in which a pair of electrodes are provided on both sides of an electrolyte, and a laminate in which a separator is horizontally stacked, and the electrolyte / electrode structure and one separator In the meantime, a reaction gas flow path for supplying a reaction gas along the surface direction of the electrode is formed, and a reaction gas communication hole communicating with an end of the reaction gas flow path is provided in the stacking direction of the stacked body. A fuel cell stack formed through is described. The fuel cell stack includes a manifold member disposed at at least one end of the laminate, and the manifold member has an opening shape that communicates with the reaction gas communication hole and is different from the reaction gas communication hole. A manifold communication hole is provided, and the manifold member is formed with a plurality of protrusions such as a concave shape portion, a convex shape portion, or a concavo-convex shape portion at a connection portion between the reaction gas communication hole and the manifold communication hole. It is described that water such as water is prevented from forming water droplets by surface tension.

JP 2006-236841 A

  By the way, as described above, water droplets may be formed on the gas flow path side of the separator surface due to water droplets such as generated water and dew condensation water being formed by surface tension. And when the water droplet formed in the separator surface grows, discharge | emission of generated water etc. will be inhibited by a water droplet, and discharge | emission property may fall. Moreover, when the discharge | emission property of produced water etc. falls, supply of fuel gas and oxidant gas is suppressed, and there exists a possibility that the electric power generation performance of a fuel cell may fall.

  Then, the objective of this invention is providing the cell for fuel cells which improves discharge | emission characteristics, such as produced water, more.

  A fuel cell according to the present invention includes an electrolyte membrane, a catalyst layer laminated on both surfaces of the electrolyte membrane, a gas diffusion layer laminated on the catalyst layer, and a gas diffusion layer to form a gas flow path. A fuel cell comprising: a gas flow path structure; and a separator stacked on the gas flow path structure and separating a gas between adjacent cells, the separator including a separator substrate formed of a metal material The separator substrate is provided between the separator foil and the metal foil, one end of which is fixed to the gas flow path side of the separator substrate, absorbs water and expands, and pushes up the other end of the metal foil to separate the separator substrate. And a water-absorbing resin brought into contact with water droplets formed on the surface.

  In the fuel cell according to the present invention, the gas flow path structure includes a gas flow path member that contacts the separator substrate, and against water droplets formed at an acute contact portion between the separator substrate and the gas flow path member. The other end is opposite and the metal foil is fixed.

In the fuel cell according to the present invention, the length L of the metal foil is represented by the following formula (1) as the distance L from the contact portion to the fixed end of the metal foil and the angle A between the separator substrate and the gas flow path member. It is characterized by satisfying.
X <LsinA ... Formula (1)

  In the fuel cell according to the present invention, the water absorbent resin is a polyacrylate.

  In the fuel cell according to the present invention, the metal foil is a titanium foil or a stainless steel foil.

  According to the fuel battery cell having the above-described configuration, it is possible to further improve the discharge of generated water and the like by suppressing the growth of water droplets.

  Embodiments according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a view showing a cross section of a fuel cell 10. The fuel cell 10 includes a membrane electrode assembly 16 (Mebrane Electrode Assembly: MEA) that forms an electrode of a fuel cell by integrating an electrolyte membrane 12 and a catalyst layer 14, a gas diffusion layer 18, a gas flow An expanded molded body 20 that is a gas flow path structure that forms a path, and a separator 22 that separates fuel gas or oxidant gas between adjacent cells (not shown) are configured.

  The electrolyte membrane 12 has a function of moving hydrogen ions generated on the anode electrode side to the cathode electrode side. As the material of the electrolyte membrane 12, a chemically stable fluorine-based resin, for example, an ion exchange membrane of perfluorocarbon sulfonic acid is used.

  The catalyst layer 14 is laminated on both surfaces of the electrolyte membrane 12 and has a function of promoting a hydrogen oxidation reaction on the anode electrode side and an oxygen reduction reaction on the cathode electrode side. The catalyst layer 14 includes a catalyst and a catalyst carrier. In order to increase the electrode area to be reacted, the catalyst is generally used in the form of particles and attached to the catalyst support. As the catalyst, platinum, which is a platinum group element having a smaller activation overvoltage, is used for the oxidation reaction of hydrogen and the reduction reaction of oxygen. A carbon material such as carbon black is used for the catalyst carrier.

  The gas diffusion layer 18 is laminated on the catalyst layer 14 and functions to diffuse the fuel gas, for example, hydrogen gas or the like and the oxidant gas, for example, air or the like, to the catalyst layer 14 or move electrons. It has functions. The gas diffusion layer 18 is made of carbon fiber woven fabric, carbon paper or the like, which is a conductive material.

  The expanded molded body 20 is stacked on the gas diffusion layer 18 and has a function as a gas flow path structure that forms a gas flow path. The expanded molded body 20 is laminated in contact with the gas diffusion layer 18 and the separator 22, and is electrically connected to the gas diffusion layer 18 and the separator 22. The expanded molded body 20 includes a gas flow path member 24 that forms a gas flow path.

  For the expanded molded body 20, for example, an expanded metal shown in JIS G 3351, a metal lath shown in JIS A 5505, or the like can be used. The expanded metal is formed by subjecting a titanium sheet, a stainless steel sheet or the like to a drawing process. For example, the expanded metal is cut into a zigzag pattern in a titanium sheet or a stainless sheet, and at the same time, the expanded metal is stretched and stretched to form a mesh, and is integrally formed.

  FIG. 2 is a diagram showing a configuration of an expanded molded body 20 using an expanded metal, FIG. 2 (A) is a schematic diagram of the expanded molded body 20, and FIG. 2 (B) is a view in the AA direction. It is sectional drawing. The expanded molded body 20 has a mesh structure including a large number of openings. The mesh formed on the expanded molded body 20 has a function as a gas flow path for fuel gas and oxidant gas. Thus, since the expanded molded body 20 has a large number of openings, more fuel gas or the like comes into contact with the gas diffusion layer 18 and undergoes an electrochemical reaction. Therefore, the power generation efficiency of the fuel cell 10 can be further increased. The plate thickness (t) of the gas flow path member 24, the mesh center distance (SW) in the mesh direction, the mesh center distance (LW) in the mesh direction, the step width (W), the thickness (X) of the expanded molded body 20 ) Are each set to a predetermined size.

  Returning to FIG. 1 again, the separator 22 is stacked on the expanded molded body 20 and has a function of separating the fuel gas and the oxidant gas in the adjacent cell (not shown). The separator 22 has a function of electrically connecting adjacent cells (not shown). The separator 22 includes a separator substrate 26.

Separator substrate 26 is preferably formed of titanium, a titanium alloy, stainless steel, or the like. This is because these metal materials have high mechanical strength and form a passive film made of a stable oxide (TiO ₂ , Cr ₂ O _3, etc.) on the surface and have excellent corrosion resistance. As the stainless steel, austenitic stainless steel, ferritic stainless steel, or the like can be used. Of course, depending on other conditions, the metal material for forming the separator substrate 26 is not limited to titanium, stainless steel, or the like, and other metal materials can be used. For the separator substrate 26, for example, a titanium sheet, a stainless steel sheet, or the like is used.

  The metal foil 28 is provided on the gas flow path side of the separator substrate 26 and has a function of contacting water droplets formed by water droplets such as generated water and draining the water droplets. FIG. 3 is an enlarged view showing the gas flow path side of the separator substrate 26. One end of the metal foil 28 is fixed to the separator substrate 26 to form a fixed end 30. Here, it is preferable that the metal foil 28 is fixed with the other end 32 facing the water droplet formed at the acute contact portion 33 between the separator substrate 26 and the gas flow path member 24. This is because water droplets are likely to be formed at the acute contact portion 33 between the separator substrate 26 and the gas flow path member 24, so that formation of more water droplets and growth of water droplets can be suppressed. Of course, depending on other conditions, the arrangement of the metal foil 28 is not limited to the above arrangement.

  As the metal material of the metal foil 28, acid-resistant metal such as stainless steel (SUS316 series), titanium, gold, platinum, or the like can be used. The metal foil is manufactured by a general metal foil manufacturing method. Moreover, it is preferable that the surface of the metal foil 28 has hydrophilicity with a contact angle of 60 degrees or less. This is because water droplets can be easily drained by further increasing the wettability of the surface of the metal foil 28. The metal foil 28 and the separator substrate 26 are fixed by, for example, welding or adhesion. Depending on other conditions, instead of the metal foil 28, a carbon sheet formed of a hydrophilic carbon material or the like may be used.

  The water absorbent resin 34 is provided between the separator substrate 26 and the metal foil 28, absorbs water and expands, pushes up the other end 32 of the metal foil 28, and comes into contact with water droplets formed on the surface of the separator substrate 26. It has a function to make it. By pushing up the other end 32 of the metal foil 28 and bringing the water droplet formed on the surface of the separator substrate 26 into contact with the other end 32 of the metal foil 28, the water of the water droplet is drained through the metal foil 28. Formation and growth can be suppressed. The water absorbent resin 34 can be provided, for example, at a predetermined distance from the fixed end 30 of the metal foil 28. The water absorbent resin 34 is bonded to the separator substrate 26 and the metal foil 28 with, for example, an adhesive. Further, the water-absorbent resin 34 that has expanded by absorbing water can be shrunk by heating or drying with gas or the like.

  Polyacrylate can be used for the water absorbent resin 34. This is because polyacrylate absorbs more water and swells. The water absorbent resin 34 may be a resin that swells by absorbing water used for the electrolyte membrane 12 of the fuel cell 10. Of course, depending on other conditions, the water absorbent resin 34 is not limited to the above resin.

The metal foil 28 is fixed with the other end 32 facing the water droplets formed on the acute contact portion 33 between the separator substrate 26 and the gas flow path member 24, and the metal foil 28 is fixed from the contact portion 33. As the distance L to the end 30 and the angle A between the separator substrate 26 and the gas flow path member 24, the length X of the metal foil 28 preferably satisfies the following formula (1).
X <LsinA ... Formula (1)

  When the other end 32 of the metal foil 28 is pushed up by the water-absorbing resin 34, the length X of the metal foil 28 is made shorter than the length of the perpendicular line extending from the fixed end 30 to the gas flow path member 24. This is because contact between the gas flow path member 24 and the gas flow path member 24 can be prevented. Of course, depending on other conditions, the length X of the metal foil 28 is not limited to a length that satisfies the above formula (1).

  The angle B between the metal foil 28 and the separator substrate 26 when the other end 32 of the metal foil 28 is pushed up by the water absorbent resin 34 is preferably approximately half of the angle A between the separator substrate 26 and the gas flow path member 24. When the angle A is, for example, 40 degrees or more and 60 degrees or less, the angle B is 20 degrees or more and 30 degrees or less. Of course, depending on other conditions, the angle B is not limited to the above angle.

  Next, the operation of the fuel cell 10 in the above configuration will be described.

  FIG. 4 is a diagram showing a state in which the amount of generated water or the like staying in the gas flow path is small. In a state where the amount of generated water or the like staying in the gas flow path is small, such as before the fuel cell is operated, the water absorbent resin 34 hardly expands, so that the other end 32 of the metal foil 28 is hardly pushed up by the water absorbent resin 34.

  FIG. 5 is a diagram illustrating a state in which a large amount of generated water stays in the gas flow path. During operation of the fuel cell, the fuel gas and the oxidant gas undergo an electrochemical reaction to generate generated water, and the water in the fuel gas is condensed to form dewed water, so that it stays in the gas flow path. The amount of water produced increases. When the water absorbent resin 34 absorbs water such as generated water or condensed water, the water absorbent resin 34 expands and pushes up the other end 32 of the metal foil 28 as shown in FIG. On the other hand, the water droplet 40 is formed at, for example, an acute contact portion 33 between the separator substrate 26 and the gas flow path member 24. When the water droplet 40 grows including generated water or the like, it contacts the other end 32 of the metal foil 28 pushed up by the expansion of the water absorbent resin 34. Thereby, the water which forms the water droplet 40 is drained through the metal foil 28, and the growth of the water droplet 40 is suppressed. The expanded water-absorbing resin 34 can be contracted by drying to return the fuel cell 10 to the state shown in FIG. 4 from the state shown in FIG.

  As described above, according to the above configuration, the metal foil having one end fixed to the gas flow path side of the separator substrate, and provided between the separator substrate and the metal foil, absorbs water and expands, and the other end of the metal foil is Since it has a water-absorbing resin that is pushed up and brought into contact with the water droplets formed on the surface of the separator substrate, the other end of the metal foil is pushed up and brought into contact with the water droplets formed on the surface of the separator substrate to form water droplets Or growth can be suppressed and drainage properties, such as generated water, can be improved more. Thereby, the gas diffusibility of the fuel gas or the oxidant gas can be increased, gas can be supplied more effectively, and the power generation performance of the fuel cell can be further improved.

  According to the above configuration, the metal foil is fixed to the water droplets formed at the acute contact portion between the separator substrate and the gas flow path member so that the other end faces and is formed in the gas flow path. It is possible to suppress the formation or growth of easy water droplets, and to further improve the drainage of produced water and the like.

(Example)
A plurality of fuel cell units were manufactured, and the output characteristics of the cells were evaluated.

  A method for manufacturing a fuel cell in Example 1 will be described. First, a membrane electrode assembly was formed. As the electrolyte membrane, a polymer electrolyte membrane Nafion 112 (manufactured by DuPont) was used. In the cathode (air electrode) catalyst layer, 1 g of Ketjen Black EC (Ketjen Black International Co., Ltd.), which is carbon fine particles supporting 45% by mass of platinum, and SE20092 (manufactured by DuPont), which is a polymer electrolyte solution, are used. ) Was mixed with 2.2 g of porous hydrophilic fiber and 0.07 g of porous hydrophilic fiber was used. In the anode (fuel electrode) catalyst layer, 1 g of Vulcan XC-72R (manufactured by Nippon Cabot), which is carbon fine particles supporting 30% by mass of platinum, and 3 SE20092 (manufactured by DuPont), which is a polymer electrolyte solution, are used. A paste for anode catalyst prepared by mixing 5 g of. Then, the cathode catalyst paste was applied to one surface of the polymer electrolyte membrane, the anode catalyst paste was applied to the other surface, and heat-pressed to form a membrane electrode assembly.

  Carbon paper was used for the gas diffusion layer. And the expanded molded object which is a gas flow path structure used the expanded metal shape | molded with titanium. The expanded metal has a thickness of 0.1 mm, a width in the opening of 500 μm, and a length in the longitudinal direction of the opening of 1 mm.

  As the separator, a titanium separator formed of titanium was used. One end of the titanium foil was joined to the gas flow path side of the titanium substrate by resistance welding. Further, the titanium foil was disposed so that the other end thereof was opposed to an acute-angle contact portion between the titanium substrate and the expanded metal gas flow path member. The size of the titanium foil is 300 μm wide, 500 μm long, and 50 μm thick. A plurality of titanium foils were disposed on the gas flow path side of the titanium substrate. The spacing between the titanium foils was 200 μm in the width direction of the titanium substrate and 500 μm in the longitudinal direction. And the polyacrylate which is a water absorbing resin was arrange | positioned between the titanium substrate and titanium foil. The polyacrylate was provided at a location approximately 80 μm away from the fixed end of the titanium substrate and the titanium foil.

  After laminating carbon paper, which is a gas diffusion layer, on both sides of the membrane electrode assembly, laminating expanded metal on the carbon paper, and laminating a titanium separator so that the fixed titanium foil enters the opening of the expanded metal. Thus, the fuel cell for Example 1 was manufactured.

  A method for manufacturing a fuel cell in Comparative Example 1 will be described. In the fuel cell in Comparative Example 1, a titanium separator and a titanium separator were used without using a titanium foil or polyacrylate. About others, it manufactured with the manufacturing method same as the manufacturing method of the cell for fuel cells in Example 1. FIG.

  A method for manufacturing a fuel cell in Comparative Example 2 will be described. In the fuel cell in Comparative Example 2, a titanium separator having a titanium foil fixed to a titanium substrate was used. However, no polyacrylate was provided between the titanium substrate and the titanium foil. About others, it manufactured with the manufacturing method same as the manufacturing method of the cell for fuel cells in Example 1. FIG.

The output characteristics of the fuel cell are evaluated at a cell temperature of 50 ° C., which is a condition in which the produced water is more likely to stay, under full humidification conditions, and an average cell voltage for 10 minutes at 1.5 A / cm ² is measured. evaluated. In addition, hydrogen was used for fuel gas and air was used for oxidant gas. Table 1 is a table showing evaluation of output characteristics of fuel cell.

  Table 1 shows the average cell voltage and voltage deviation of each fuel cell. Here, the voltage deviation is a standard deviation of the cell voltage measured for 10 minutes. The average cell voltage of the fuel cell in Example 1 is 0.52 V, and the voltage deviation is. It was 0.02V. The average cell voltage of the fuel cell in Comparative Example 1 was 0.34V, and the voltage deviation was 0.04V. The average cell voltage of the fuel cell in Comparative Example 2 was 0.31V, and the voltage deviation was 0.05V. Thus, the cell voltage larger than the average cell voltage of the cell for other fuel cells was obtained for the average cell voltage of the cell for fuel cells in Example 1. In addition, the voltage deviation of the fuel cell in Example 1 was smaller than the voltage deviation of the other fuel cell.

  As described above, in the fuel cell in Example 1, the polyacrylate that has absorbed the generated water and expanded the titanium foil pushes up the titanium foil, so that the titanium foil is in the titanium sheet and the expanded metal gas flow path member. The contact of water droplets formed at an acute contact portion or the like was suppressed, and the growth of the water droplets that were retained and drained through the titanium foil was suppressed. As a result, the drainage of produced water or the like is improved, and the gas diffusibility of the gas flowing through the gas flow path is improved. Therefore, the output characteristics of the fuel cell in Example 1 are higher than the output characteristics of other fuel cells. Also improved. On the other hand, in the fuel cell in Comparative Example 1 and Comparative Example 2, since the growth of water droplets is not suppressed, the drainage property and gas diffusibility of the generated water are reduced, and the output characteristics are higher than those in the fuel cell in Example 1. Decreased.

In embodiment of this invention, it is a figure which shows the cross section of the cell for fuel cells. In embodiment of this invention, it is a figure which shows the structure of the expanded molded object using an expanded metal. In embodiment of this invention, it is an enlarged view which shows the gas flow path side of a separator substrate. In embodiment of this invention, it is a figure which shows the state with few generated water etc. which remain in a gas flow path. In embodiment of this invention, it is a figure which shows the state with much produced water etc. which remain in a gas flow path.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Fuel cell cell, 12 Electrolyte membrane, 14 Catalyst layer, 16 Membrane electrode assembly, 18 Gas diffusion layer, 20 Expanded molding, 22 Separator, 24 Gas flow path member, 26 Separator substrate, 28 Metal foil, 30 Adhesive end 32, the other end, 33 contact portion, 34 water-absorbing resin, 40 water droplets.

Claims (5)

An electrolyte membrane;
A catalyst layer laminated on both sides of the electrolyte membrane;
A gas diffusion layer laminated on the catalyst layer;
A gas flow path structure that is stacked on the gas diffusion layer and forms a gas flow path;
A separator that is stacked on the gas flow path structure and separates the gas between adjacent cells;
With
The separator includes a separator substrate formed of a metal material,
A fuel cell,
A metal foil whose one end is fixed to the gas flow path side of the separator substrate;
A water-absorbing resin that is provided between the separator substrate and the metal foil, absorbs water and expands, and pushes up the other end of the metal foil to contact the water droplets formed on the separator substrate surface;
A cell for a fuel cell, comprising: The fuel cell according to claim 1,
The gas flow path structure includes a gas flow path member in contact with the separator substrate,
A fuel cell, wherein a metal foil is fixed to a water droplet formed at an acute-angle contact portion between a separator substrate and a gas flow path member with the other end facing the water droplet. The fuel cell according to claim 2,
A distance L from the contact portion to the fixed end of the metal foil;
As an angle A between the separator substrate and the gas flow path member,
A fuel cell, wherein the length X of the metal foil satisfies the following formula (1).
X <LsinA ... Formula (1) A fuel cell according to any one of claims 1 to 3,
A fuel cell, wherein the water absorbent resin is a polyacrylate. A fuel cell according to any one of claims 1 to 4, comprising:
The fuel cell, wherein the metal foil is titanium foil or stainless steel foil.

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