JP2008021449A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress heat radiation from the end part cell without making the stack large in size in a fuel cell. <P>SOLUTION: The fuel cell has a stack 10 in which a plurality of unit cells 12 are laminated and a current collector 16 which is installed at both ends of the stack 10. The end part cells 14 placed at both ends of the stack 10 have a separator 26 of concavo-convex shape and have a coolant passage 30 formed by the recessed part of the separator 26 and the current collector 16 between the separator 26 and the current collector 16. A heat insulating material 32 is installed in the coolant passage 30. The heat insulating material 30 is formed of ceramic material and is formed on the current collector 16 side or separator 26 side of the coolant passage 30. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell, and more particularly to a fuel cell including a stack in which a plurality of single cells are stacked, and current collecting plates provided at both ends of the stack.

  In recent years, fuel cells have attracted attention as batteries having high efficiency and excellent environmental characteristics. In general, a fuel cell generates electric energy by chemically reacting oxygen in air with hydrogen, which is a fuel gas. As a result of the chemical 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.

  A polymer electrolyte fuel cell includes a stack in which a plurality of single cells are stacked. The single cell forming the stack includes an electrolyte membrane, a catalyst layer, a gas diffusion layer, and a separator. Of these, an electrolyte membrane, a catalyst layer, and a gas diffusion layer integrated together are generally called a membrane electrode assembly.

  The end cells, which are single cells placed at both ends of the stack, are provided with current collector plates (terminal plates) for taking out a direct current. A cooling medium flow path is formed between the end cell and the current collector plate. The end cell is cooled by the cooling medium flowing through the cooling medium flow path, and further cooled by contacting the current collector plate, so that the end cell cools more than the single cell placed at the center of the stack. Easy to be.

  Therefore, in the end cell, the generated water may remain in the cell when power generation is stopped (cooling). When the stack is exposed to a sub-freezing environment, the condensed water in the end cells freezes, which may cause cell deterioration, activation delay, and the like. In addition, flooding may occur during operation of the fuel cell.

  In Patent Document 1, a conductive heat insulating plate is interposed between both ends in the stacking direction of a stacked body in which a plurality of unit cells are stacked and a power extraction terminal plate, and heat insulation is performed between the heat insulating plate and the stacked body. A fuel cell stack that can effectively prevent heat generated in a unit cell from being transferred to a terminal plate by forming a working air layer is shown.

JP 2004-152502 A

  Here, as described above, in the case where a heat insulating air layer is formed between the stack and the current collector plate to suppress the heat radiation generated in the end cell, the end cell and the current collector are newly added. Since a heat insulating plate is provided between the plates to form a heat insulating air layer, the stack may be enlarged.

  Therefore, an object of the present invention is to provide a fuel cell that can suppress heat dissipation from the end cells without further increasing the size of the stack.

  A fuel cell according to the present invention includes a stack in which a plurality of single cells are stacked, and current collectors provided at both ends of the stack, and the end cells placed at both ends of the stack have uneven separators. A fuel cell having a cooling medium flow path formed between the separator and the current collecting plate between the separator and the current collecting plate, wherein a heat insulating material is provided in the cooling medium flow path. And

  In the fuel cell according to the present invention, the current collector plate is provided with a groove for forming a cooling medium flow path.

  In the fuel cell according to the present invention, the heat insulating material is formed of a ceramic material.

  In the fuel cell according to the present invention, the heat insulating material is disposed on the current collector plate side.

  In the fuel cell according to the present invention, the heat insulating material is arranged on the separator side.

  In the fuel cell according to the present invention, the heat insulating material is coated on the surface of the cooling medium flow path.

  As described above, according to the fuel cell of the present invention, by suppressing the flow of heat from the end cells to the cooling medium, it is possible to suppress heat dissipation from the end cells without further increasing the size of the stack. it can.

  Embodiments according to the present invention will be described below in detail with reference to the drawings. The fuel cell includes a stack in which a plurality of single cells are stacked, and current collector plates provided at both ends of the stack. FIG. 1 is a diagram illustrating a configuration of a stack 10 provided in a fuel cell. The fuel cell stack 10 is formed by stacking a plurality of, for example, several tens of single cells 12. A current collector plate 16 for taking out current is provided in the end cell 14 which is an end cell placed at both ends of the stack 10.

  FIG. 2 is a view showing a cross section of the end cell 14 provided with the current collector plate 16. First, in the end cell 14, a catalyst layer 20 is laminated on each side of the electrolyte membrane 18, and a gas diffusion layer 22 is laminated on each catalyst layer 20 to form a membrane electrode assembly 24. The separator 24 is laminated on the body 24.

  The electrolyte membrane 18 has a function of moving hydrogen ions generated on the anode electrode side to the cathode electrode side. The material of the electrolyte membrane 18 is a chemically stable fluororesin, for example, an ion exchange membrane of perfluorocarbon sulfonic acid. As an ion exchange membrane of perfluorocarbon sulfonic acid, a Nafion membrane (registered trademark of DuPont) or the like can be used.

  The catalyst layer 20 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 20 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 small activation overvoltage, is used for the oxidation reaction of hydrogen and the reduction reaction of oxygen. As the catalyst carrier, a carbon material such as carbon black is used. As carbon black which is a carrier of the catalyst, Ketjen black (manufactured by Lion), Denka black (manufactured by Denki Kagaku Kogyo) or the like can be used.

  The gas diffusion layer 22 has a function of diffusing hydrogen as a fuel and oxygen as an oxidant into the catalyst layer 20, a function of moving electrons, and the like. For the gas diffusion layer 22, carbon fiber woven fabric, carbon paper, or the like, which is a conductive material, can be used. And the membrane electrode assembly 24 can be manufactured by laminating | stacking the electrolyte membrane 18, the catalyst layer 20, and the gas diffusion layer 22, and heat-pressing.

  The separator 26 is stacked on the gas diffusion layer 22 of the membrane electrode assembly 24 and has a function of separating hydrogen, which is a fuel gas, and air, which is an oxidant, in the adjacent unit cell 12. The separator 26 has a function of electrically connecting one unit cell 12 and the other unit cell 12.

  As the separator 26, it is preferable to use a separator 26 having an uneven shape. The separator 26 is formed with a gas flow path 28 through which fuel gas, air, and the like flow, a cooling medium flow path 30 through which a cooling medium such as LLC (Long Life Coolant) that cools the single cell 12 and cooling water, and the like. It is. For example, a gas flow path 28 such as fuel gas or air can be formed by the convex portion of the separator 26 and the gas diffusion layer 22. Of course, depending on other conditions, the shape of the separator 26 is not limited to an uneven shape.

  For the separator 26, a metal material such as stainless steel, titanium, copper, or a carbon material, which is a conductive material, can be used. Of course, depending on other conditions, the material of the separator 26 is not limited to the above material. Then, the sheet material of metal material can be formed into a concavo-convex shape by, for example, pressing, and a concavo-convex separator can be manufactured. Of course, depending on other conditions, the separator can be manufactured by machining a metal material or the like, and is not limited to press working.

  The current collecting plates 16 are provided at both ends of the stack 10 and have a function of taking out a direct current generated in the cells 12 and 14. Then, the current collector plate 16 is provided in contact with the convex portions of the separator 26 formed in a concave-convex shape in the end cell 14 placed at both ends of the stack 10.

  For the current collector plate 16, a metal material such as stainless steel or copper, a carbon material, or the like, which is a conductive material, can be used. Further, the current collector plate 16 may be used by applying gold plating to a metal sheet material such as stainless steel or copper. Of course, depending on other conditions, the material of the current collector plate 16 is not limited to the above materials.

  Between the separator 26 and the current collector plate 16, as described above, the cooling medium flow path 30 through which the cooling medium for cooling the cells flows is formed by the concave portion of the separator 26 and the current collector plate 16. This is because when the fuel cell is operated with high current density power generation, more heat is generated also in the end cells 14 and thus cooling is necessary.

  Here, the current collecting plate 16 is preferably provided with a groove 31 in order to increase the cross-sectional area of the cooling medium flow path 30. As will be described later, even when a heat insulating material 32 or the like is provided in the cooling medium flow path 30 formed by the concave portion of the separator 26 and the current collector plate 16, the end portion is provided by providing the current collector plate 16 with the groove 31. This is because the pressure loss of the cooling medium in the cell 14 can be made substantially the same as the other single cells 12 other than the end cell 14. Of course, depending on other conditions, the cooling medium flow path 30 can be formed without providing the grooves 31 in the current collector plate 16.

  A heat insulating material 32 is provided in the cooling medium flow path 30 formed by the recess of the separator 26 and the current collector plate 16. By providing a heat insulating material 32 in the cooling medium flow path 30 formed by the recess of the separator 26 and the current collector plate 16, heat generated in the end cell 14 is transferred from the gas diffusion layer 22 of the end cell 14 to the separator 26. This is because the heat insulating material 32 can suppress the flow into the cooling medium through the recess. This is because by providing the heat insulating material 32 in the cooling medium flow path 30, it is possible to reduce the heat radiation path of the heat generated in the end cell 14. As a result, the temperature drop of the combustion gas, air, etc. flowing through the gas flow path 28 in the end cell 14 can be suppressed, and the ability to discharge generated water generated by power generation can be further enhanced.

A ceramic material is preferably used for the heat insulating material 32. This is because ceramic materials that are inorganic materials generally have lower heat conductivity than other materials, and therefore have high heat insulation performance and excellent corrosion resistance. As the ceramic material, for example, alumina (Al ₂ O ₃ ), silica (SiO ₂ ), silicon carbide (SiC), silicon nitride (SiN), zirconia (ZrO ₂ ), or the like can be used. Examples of the ceramic material include _binary ceramic materials such as alumina (Al ₂ O ₃ ) -silica (SiO ₂ ) ceramics, and alumina (Al ₂ O ₃ ) -silica (SiO ₂ ) -zirconia (ZrO ₂ ). ) A ternary ceramic material such as a ceramic may be used. Of course, the ceramic material is not limited to the above materials.

  The heat insulating material 32 is preferably formed using a paint or paste material containing a ceramic material. This is because the heat insulating material 32 can be easily formed by applying, spraying, or filling the coating material or the paste material into the concave portion of the separator 26 that forms the cooling medium flow path 30. As the paint containing the ceramic material, for example, SUPER THERM manufactured by Superior Product, ceramic cover CC100 manufactured by Envirotrol, or the like can be used. Of course, the heat insulating material 32 may be a molded product formed of ceramic fiber, a porous ceramic material, or the like, and is not limited to the paint or paste material.

  As shown in FIG. 2, the heat insulating material 32 is preferably disposed on the separator 26 side of the cooling medium flow path 30. The heat generated in the end cell 14 flows into the cooling medium from the gas diffusion layer 22 of the membrane electrode assembly (MEA) 24 through the concave portion of the separator 26 formed into an uneven shape. This is because the heat flow into the cooling medium can be suppressed by disposing it on the side. As a result, more heat generated in the end cell 14 flows into the gas flow path 28 to increase the temperature of the fuel gas and air in the gas flow path 28, and the generated water is taken out of the system. The amount can be further improved. Moreover, since the convex part of the separator 26 formed into an uneven shape is in contact with the current collector plate 16, the heat generated in the end cell 14 flows from the convex part of the separator 26 to the current collector plate 16 to dissipate heat. Is done. For this reason, even when the fuel cell generates power at a high current density, the heat dissipation route of the end cell 14 is secured, and thus the overheating state of the end cell 14 is suppressed.

  When the heat insulating material 32 is formed in the concave portion of the separator 26 that forms the cooling medium flow path 30, the concave portion of the separator 26 can be filled with the above-described paint or paste material containing the ceramic material. As a filling method of the paint or paste material containing the ceramic material, a general filling method of the paint or paste material can be used. For example, the heat insulating material 32 can be embedded in the concave portion of the separator 26 by filling the concave portion of the separator 26 with the paint, paste material, or the like and then drying at a normal temperature or a predetermined temperature. Further, when a porous ceramic material or the like is used as the heat insulating material 32, the heat insulating material 32 can be formed by bonding to the concave portion of the separator 26 with a bonding material such as an adhesive. Of course, depending on other conditions, the method of forming the heat insulating material 32 in the recess of the separator 26 is not limited to the above method.

  Further, the surface of the cooling medium flow path 30 may be covered with the heat insulating material 32. FIG. 3 is a diagram illustrating a configuration in which the surface of the cooling medium flow path 30 is covered with the heat insulating material 32. The heat insulating material 32 can be covered by applying the above-described coating material containing the ceramic material to the concave portions of the separator 26 that is formed in the uneven shape forming the cooling medium flow path 30. As a coating method of a paint or paste material containing a ceramic material, a general coating method of a paint or paste material, for example, a spray method or a coating method can be used. And after spraying the said coating material, paste material, etc. to the recessed part of the separator 26, it is possible to coat | cover the heat insulating material 32 to the recessed part of the separator 26 by drying etc. at normal temperature or predetermined temperature. Of course, depending on other conditions, the coating method of the heat insulating material 32 is not limited to the above coating method.

  The heat insulating material 32 can be provided on the current collecting plate 16 side of the cooling medium flow path 30. FIG. 4 is a diagram illustrating a configuration in which the heat insulating material 32 is disposed on the current collecting plate 16 side of the cooling medium flow path 30. A groove 31 is formed in the current collector plate 16, and the heat insulating material 32 can be provided in the groove 31 of the current collector plate 16, for example. By providing the heat insulating material 32 on the side of the current collecting plate 16 of the cooling medium flow path 30, when the temperature of the cooling medium flowing through the cooling medium flow path 30 is higher than the temperature of the current collecting plate 16, It is because the heat which flows into can be suppressed. Further, when the heat insulating material 32 is provided on the current collecting plate 16 side of the cooling medium flow path 30, the heat insulating material 32 is collected using the above-described filling method or coating method of the paint or paste material containing the ceramic material. It can be provided on the plate 16 side. Of course, depending on other conditions, the method of forming the heat insulating material 32 on the current collector plate 16 side is not limited to the above method.

  The size of the heat insulating material 32, such as the thickness of the heat insulating material 32, can be determined by the heat insulating capacity of the heat insulating material 32, the cooling capacity of the cooling medium, or the like.

  When the heat conductivity of the heat insulating material 32 is smaller and the heat insulating capacity is higher, the thickness of the heat insulating material 32 is determined to be smaller. When the thickness of the heat insulating material 32 is increased, the ability to cool the end cell 14 is reduced. For example, when the fuel cell is operated with high current density power generation, the internal temperature of the end cell 14 may become excessively high. Because there is. In such a case, for example, as described above, the heat insulating material 32 can be coated on the surface of the cooling medium flow path 30.

  And when the heat conductivity of the heat insulating material 32 is larger and the heat insulating capacity is lower, the thickness of the heat insulating material 32 is determined to be larger. When the thickness of the heat insulating material 32 is reduced, a large amount of heat generated in the end cell 14 flows into the cooling medium, the internal temperature of the end cell 14 is lowered, and the generated water may remain in the gas flow path 28. It is. In such a case, for example, as described above, the cooling medium channel 30 can be filled with the heat insulating material 32.

  When the flow rate of the cooling medium is higher and the cooling capacity of the cooling medium is higher, the thickness of the heat insulating material 32 is determined to be smaller. When the thickness of the heat insulating material 32 is increased, as described above, the ability to cool the end cell 14 is reduced. For example, when the fuel cell is operated at high current density power generation, the internal temperature of the end cell 14 is excessive. It is because it may become high.

  When the flow rate of the cooling medium is smaller and the cooling capacity is lower, the thickness of the heat insulating material 32 is determined to be larger. When the thickness of the heat insulating material 32 is reduced, as described above, a large amount of heat generated in the end cell 14 flows into the cooling medium, and the internal temperature of the end cell 14 decreases.

  In the above configuration, the heat insulating material 32 is provided in the cooling medium flow path 30 provided between the end cell 14 and the current collector plate 16, but is further adjacent to the end cell 14 and the end cell 14. The above-described heat insulating material 32 may be provided in the cooling medium flow path provided between the single cells 12 stacked.

  According to the above configuration, by providing the heat insulating material in the cooling medium flow path formed by the concave portion of the separator and the current collector plate, heat generated in the end cells can be suppressed from flowing to the cooling medium, and the stack can be made larger. The heat radiation from the end cell can be suppressed without becoming. Thereby, it is possible to suppress cell deterioration, start-up delay, and the like due to flooding in the fuel cell and freezing of generated water. In particular, it is possible to suppress hydrogen depletion on the anode side, cell voltage drop, catalyst deterioration due to hydrogen depletion, and the like.

  According to the above configuration, by providing the current collector plate with the groove for forming the cooling medium flow path, the cooling flowing through the cooling medium flow path in which the heat insulating material is disposed even when the heat insulating material is provided in the cooling medium flow path. The pressure loss of the medium can be suppressed.

  According to the said structure, corrosion resistance can be improved more by forming a heat insulating material with a ceramic material.

In embodiment of this invention, it is a figure which shows the structure of the stack with which a fuel cell is equipped. In embodiment of this invention, it is a figure which shows the cross section of the edge part cell in which the current collecting plate was provided. In embodiment of this invention, it is a figure which shows the structure which coat | covered the surface of the cooling medium flow path with the heat insulating material. In embodiment of this invention, it is a figure which shows the structure which has arrange | positioned the heat insulating material to the current collecting plate side of a cooling medium flow path.

Explanation of symbols

  10 stacks, 12 single cells, 14 end cells, 16 current collector plate, 18 electrolyte membrane, 20 catalyst layer, 22 gas diffusion layer, 24 membrane electrode assembly, 26 separator, 28 gas flow channel, 30 cooling medium flow channel, 31 groove, 32 heat insulating material.

Claims (6)

A stack of multiple single cells,
Current collectors provided at both ends of the stack;
With
The end cells placed at both ends of the stack have uneven separators,
A fuel cell having a cooling medium flow path formed by a recess of the separator and a current collector plate between the separator and the current collector plate,
A fuel cell, characterized in that a heat insulating material is provided in the cooling medium flow path. The fuel cell according to claim 1,
A fuel cell, wherein a current collector plate is provided with a groove for forming a cooling medium flow path. The fuel cell according to claim 1 or 2,
The fuel cell, wherein the heat insulating material is formed of a ceramic material. The fuel cell according to any one of claims 1 to 3,
The fuel cell, wherein the heat insulating material is disposed on the current collecting plate side. The fuel cell according to any one of claims 1 to 3,
The fuel cell, wherein the heat insulating material is disposed on the separator side. A fuel cell according to any one of claims 1 to 5,
The fuel cell, wherein the heat insulating material is coated on a surface of the cooling medium flow path.

Images