JP2007273100A - Cell and stack of fuel battery as well as fuel battery system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve efficiency of cell voltage and stack voltage. <P>SOLUTION: A cell of the fuel battery is provided with a membrane electrode assembly 5 and separators 4. The membrane electrode assembly 5 consists of an electrolyte membrane 5a, a cathode electrode 5b jointed to one face of the electrolyte membrane 5a and supplied with air, and an anode electrode 5c jointed to the other face of the electrode membrane 5a and supplied with fuel. The separators 4 are in a pair pinching the membrane electrode assembly 5 so as to form an air chamber at a side of the cathode electrode 5b, and a fuel chamber at a side of the anode electrode 5c. The air chamber formed between wire rods of a first mesh material 2 is so formed that an upstream region is to have a smaller communication area than a downstream region. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell and stack and a fuel cell system.

  The general fuel cell stack disclosed in Patent Document 1 is formed by stacking a plurality of cells 10 as shown in FIG. Each cell 10 includes a separator 12 made of a conductive material, a membrane electrode assembly (MEA) 11 and a separator 12. In the stack, adjacent cells 10 share a separator 12.

  Each membrane electrode assembly 11 includes an electrolyte membrane 11a made of a solid polymer membrane such as Nafion (registered trademark, Nafion (manufactured by Dupon)), and a cathode electrode joined to one surface of the electrolyte membrane 11a and supplied with air. 11b and an anode 11c joined to the other surface of the electrolyte membrane 11a and supplied with fuel.

  As shown in FIG. 9, the cathode electrode 11b is located on the electrolyte membrane 11a side, and has a catalyst layer 13a having a catalyst-supported carbon in which a catalyst is supported on carbon particles and an electrolyte, and air adjacent to the catalyst layer 13a. It comprises a diffusion layer 13b that diffuses. The anode 11c is located on the electrolyte membrane 11a side, and includes a catalyst layer 14a having catalyst-supporting carbon and an electrolyte, and a diffusion layer 14b that diffuses fuel adjacent to the catalyst layer 14a.

  As shown in FIG. 8, the separators 12 are stacked with the membrane electrode assemblies 11 interposed therebetween. The air chamber 12b is formed in a plurality of grooves on one surface of each separator 12 on the cathode electrode 11b side, and the fuel chamber 12c is formed in a plurality of grooves on the other surface on the anode electrode 11c side. Has been. Since each air chamber 12b and each fuel chamber 12c are both formed in a groove shape, the communication areas are equally formed from the upstream region to the downstream region. Further, each air chamber 12b and each fuel chamber 12c extend in the opposite direction or in the direction orthogonal to each other. The air supplied to the stack flows through all the air chambers 12 b of each cell 10, and the fuel supplied to the stack flows through all the fuel chambers 12 c of each cell 10.

This stack is a fuel cell system together with an air supply device such as an air blower for supplying air to each air chamber 12b and a fuel supply device such as a hydrogen tank for supplying hydrogen as fuel to each fuel chamber 12c. In this fuel cell system, an electrochemical reaction occurs between the air supplied to the air chamber 12b and the fuel supplied to the fuel chamber 12c in the stack. Specifically, hydrogen ions obtained at the anode 11c move to the cathode 11b side through the electrolyte membrane 11a containing moisture in the form of protons (H ³ O ⁺ ), and oxygen in the air at the cathode 11b. Reacts with water to form water. On the other hand, the electrons obtained at the anode 11c move to the cathode 11b side through the load. Thus, an electromotive force is generated in this stack.

  At this time, in many stacks, in order to maintain a good power generation state, the inside of the air chamber 12b is humidified, and the electrolyte membrane 11a of each cell 10 is appropriately moistened. This is because if the electrolyte membrane 11a is dried, protons are inhibited from moving from the fuel chamber 12c to the air chamber 12b via the electrolyte membrane 11a, and as a result, the power generation capacity of the cell 10 is reduced. It is. And if that state continues, it is possible that a performance degradation or failure that is difficult to recover can occur in the stack.

JP-A-3-295176

  However, according to the inventor's knowledge, the conventional cell 10 is more likely to dry up in the upstream region of the air chamber 12b than the other portions. In the portion other than the upstream region of the air chamber 12b, the amount of generated water generated at the cathode electrode 11b is large, but in the upstream region of the air chamber 12b, air is sequentially supplied from the atmosphere, and the flow velocity in the upstream region is the other portion. This is because it is considered that the water content in the electrolyte 11a is reduced.

  However, if humidified water is more actively supplied to the upstream region of the air chamber 12b, it becomes difficult to supply air to the cathode electrode 11b at that position, or to the anode electrode 11c at that position. It becomes difficult to supply fuel.

  For this reason, in the conventional cell, a portion where the overvoltage increases is likely to occur in the anode 11c and the cathode 11b, and in this case, the cell voltage decreases. For this reason, it is difficult to generate a sufficient stack voltage in a stack in which a plurality of cells 10 are stacked.

  The present invention has been made in view of the above-described conventional situation, and an object to be solved is to improve the efficiency of the cell voltage and the stack voltage.

  The cell of the fuel cell of the present invention comprises an electrolyte membrane, a cathode electrode joined to one surface of the electrolyte membrane and supplied with air, and an anode electrode joined to the other surface of the electrolyte membrane and supplied with fuel. A membrane electrode assembly,

  A fuel cell comprising: an air chamber formed on the cathode electrode side; and a pair of conductive material separators sandwiching the membrane electrode assembly so as to form a fuel chamber on the anode electrode side. In

  The air chamber is characterized in that the upstream area has a smaller communication area than the downstream area.

  In an air chamber formed such that the upstream area has a smaller communication area than the downstream area, for example, a diffuser-shaped air chamber, the membrane electrode assembly side and the separator wall surface side that are perpendicular to the air flow direction , The static pressure is low in the upstream region and high in the downstream region. For this reason, in the cell of the present invention, on the membrane electrode assembly side of the air chamber and the wall surface side of the separator, water such as generated water flows from the downstream region toward the upstream region, thereby mitigating dry-up in the upstream region of the air chamber. . In addition, since an air chamber can distribute | circulate air toward a downstream, the electrochemical reaction in an upstream area is not inhibited.

  For this reason, in this cell, it is not necessary to supply the humidified water more actively to the upstream region of the air chamber, so that air is suitably supplied to the entire cathode electrode. For this reason, the whole cathode electrode suitably causes an electrochemical reaction, and the efficiency of the cell voltage is improved. In a stack in which a plurality of cells are stacked, a sufficient stack voltage is generated.

  Therefore, according to the cell of the present invention, the efficiency of the cell voltage and the stack voltage is improved.

  The separator is provided on one surface of a plate made of a conductive material, and is formed in a porous shape having conductivity and hydrophilicity and having many pores, and configures an air chamber in each pore. And netting.

  In this case, water such as generated water diffuses in the thickness direction due to the surface tension of the mesh material, and the water is not easily clogged. For this reason, in this cell, it is hard to produce the pressure loss of air and can exhibit the outstanding supply property. For this reason, in this cell, the outstanding current collection property can also be exhibited.

  The mesh material is formed in a three-dimensional mesh shape with a conductive wire material and a hydrophilic wire material, and an air chamber may be formed between the wire materials. As the conductive wire material, conductive fibers such as ordinary nickel, titanium, SUS, tantalum, and carbon can be employed. In addition, as the hydrophilic wire, a metal oxide whisker, plant fiber, or the like can be used. As the conductive and hydrophilic wires, conductive fibers such as nickel, titanium, SUS, tantalum, and carbon that have been subjected to hydrophilic treatment can be employed. As the hydrophilic treatment, alkali treatment, surface oxidation treatment, or the like can be employed.

  The net member preferably has a water-absorbing water storage layer formed on the plate side. In this case, the water diffused in the thickness direction of the mesh material is collected in the reservoir and easily flows upstream due to static pressure.

  The membrane electrode assembly may be composed of a catalyst layer located on the electrolyte membrane side, and the catalyst layer and the network material may be joined. This is because the separator netting material can serve as a conventional diffusion layer. In this case, the structure of the membrane electrode assembly is simplified, and the manufacturing cost can be reduced.

  The fuel cell stack of the present invention is characterized in that a large number of the cells of the present invention are stacked. According to this stack, it is possible to improve the efficiency of the stack voltage.

  The fuel cell system of the present invention includes the stack of the present invention, an air supply device that supplies the air to each air chamber, and a fuel supply device that supplies the fuel to each fuel chamber,

  In the stack, each air chamber extends in a vertical direction, and the air supply device supplies the air to each air chamber from below.

  In the fuel cell system of the present invention, each air chamber of the stack extends in the vertical direction, and the air supply device supplies air from below to each air chamber. In this case, the generated water generated on the downstream side of each air chamber moistens the upstream region of the air chamber by gravity, thereby more effectively mitigating dry-up there. Also, excess water is effectively drained downward from the air chamber by gravity, preventing flooding there. When the water reservoir is formed on the plate side, these effects are particularly remarkable. In addition, the generated water generated in the upstream area of each air chamber becomes lighter than surrounding unreacted air, moves to the downstream area located above, and is discharged from the air chamber. Flooding is unlikely to occur.

  Embodiments 1 and 2 embodying the present invention will be described below with reference to the drawings.

  As shown in FIGS. 1 to 3, the stack of the fuel cell of Example 1 is sandwiched and stacked between a separator 4 composed of a plate 1, a first mesh member 2 and a third mesh member 3, and a pair of separators 4. The membrane electrode assembly 5 is employed.

  The plate 1 has both side surfaces 1a and 1b extending vertically when the air flow direction is up and down. Both side surfaces 1a and 1b have a trapezoidal shape with a short upper side and a long lower side. The surface 1c on the first mesh member 2 side of the plate 1 is an inclined surface that is inclined so as to move away upward in the air flow direction. As shown in FIG. 3, a concave portion 1 e is formed on the surface 1 d of the plate 1 opposite to the first net member 2.

  As shown in FIG. 2, the 1st net | network material 2 is formed in the three-dimensional mesh shape by the electroconductive and hydrophilic wire which consists of titanium fibers. The first net member 2 has a shape in which the upper and lower sides of the plate 1 are interchanged. That is, the 1st net | network material 2 has the both side surfaces 2a and 2b extended perpendicularly, when the direction where an air flows is made up and down. Both side surfaces 2a and 2b have a trapezoidal shape having a long upper side and a short lower side. The surface 2c of the first net member 2 on the plate 1 side is an inclined surface that is inclined so as to move away from the air flowing direction. A water-absorbing water storage layer 2d is formed on the surface 2c of the first net member 2 on the plate 1 side. The surface 1e on the opposite side of the plate 1 of the first net member 2 is vertical.

  As shown in FIG. 3, the 2nd net | network material 3 is also formed in the three-dimensional mesh shape with the electroconductive and hydrophilic wire which consists of titanium fibers. The second net member 3 has a flat plate shape. On the surface of the second net member 3 on the plate 1 side, a water-absorbing water storage layer 3a is formed.

  As shown in FIGS. 1 and 3, the first net member 2 is provided in a state where the water reservoir 2d is in contact with the inclined surface 1c of the plate 1, so that the upstream area between the wires is smaller than the downstream area. A diffuser-shaped air chamber is formed. On the other hand, the 2nd net | network material 3 is provided in the state which the water storage layer 3a contact | abuts to the bottom face of the recessed part 1e of the plate 1, as shown in FIG. 3, and the fuel chamber is formed between the wire materials by this.

  FIG. 4 shows a part of the cross section of the membrane / electrode assembly 5. The membrane / electrode assembly 5 is joined to an electrolyte membrane 5a made of a solid polymer membrane and one surface of the electrolyte membrane 5a and supplied with air. It has a cathode 5b and an anode 5c joined to the other surface of the electrolyte membrane 5a and supplied with fuel. The cathode electrode 5b and the anode electrode 5c are made of a catalyst layer located on the electrolyte membrane 5a side, and do not have a conventional diffusion layer adjacent to the catalyst layer.

  As shown in FIG. 5, a cell is constituted by the plate 1, the first net member 2, the membrane electrode assembly 5, and the second net member 3. A stack 6 is formed by stacking a plurality of cells in the housing 7. In the stack 6, each air chamber extends in the vertical direction, and each fuel chamber extends in the horizontal direction. Air passages 6a communicating with all the air chambers are provided horizontally at the upper side, and air passages 6b communicating with all the air chambers are provided horizontally at the lower side. Further, fuel passages communicating with all the fuel chambers are provided in the horizontal direction so as to be shifted from the air passages 6a and 6b by 90 °.

  As shown in FIG. 6, the air blower 30 is provided so as to blow air into a suction port located below the stack 6, and the air supplied from the air blower 30 is guided to all the air chambers from below. It has become. Further, the stack 6 is adapted to exhaust the exhaust discharged from each air chamber from above.

  A hydrogen tank 31 is connected to the fuel passage of the stack 6 via a valve 32. The plates 1 at both ends of the stack 6 are electrically connected to a load 35 such as an automobile motor, and the side ends of the stack 6 are connected to a radiator 37 by a pump 36 so that cooling water circulates. Thus, the fuel cell system is configured.

  In the stack 6 configured as described above, an electromotive force is generated by an electrochemical reaction between air supplied to the air chamber and hydrogen supplied to the fuel chamber. Then, generated water is generated in the cathode 5b. Further, the air chamber is humidified.

  At this time, in the diffuser-shaped air chamber, the static pressure is low in the upstream region and high in the downstream region on the membrane electrode assembly 5 side and the inclined surface 1c side of the plate 1 which are perpendicular to the air flow direction. For this reason, in this fuel cell system, on the membrane electrode assembly 5 side of the air chamber and the inclined surface 1c side of the plate 1, water such as generated water flows from the downstream region to the upstream region, and the dry water in the upstream region of the air chamber flows. Relax up. In addition, since an air chamber can distribute | circulate air toward a downstream, the electrochemical reaction in an upstream area is not inhibited.

  For this reason, in this fuel cell system, it is not necessary to more actively supply humidified water to the upstream region of the air chamber, so that air is suitably supplied to the entire cathode electrode 5b. For this reason, the whole cathode electrode 5b suitably causes an electrochemical reaction, and the efficiency of the cell voltage is improved. In the stack 6 in which a plurality of cells are stacked, a sufficient stack voltage is generated.

  In this fuel cell system, each air chamber of the stack 6 extends in the vertical direction, and the air blower 30 supplies air from below to each air chamber. In this case, the generated water generated on the downstream side of each air chamber moistens the upstream region of the air chamber by gravity, thereby more effectively mitigating dry-up there. Also, excess water is effectively drained downward from the air chamber by gravity, preventing flooding there. In particular, in this fuel cell system, since the water reservoir 2d is provided on the plate 1 side of the first mesh member 2, water diffused in the thickness direction of the first mesh member 2 is collected in the reservoir layer 2d, and the static pressure It tends to flow upstream. In addition, the generated water generated in the upstream area of each air chamber becomes lighter than surrounding unreacted air, moves to the downstream area located above, and is discharged from the air chamber. Flooding is unlikely to occur.

  Therefore, in this fuel cell system, the cell voltage is unlikely to decrease, and a sufficient stack voltage is easily generated stably.

  Further, in this fuel cell system, the generated water and residual water are diffused in the thickness direction due to the surface tension of the first, second and second wire members 2 and 3, and the generated water and residual water are not easily clogged. For this reason, in this fuel cell system, it is hard to produce the pressure loss of air and hydrogen, and the outstanding supply property can be exhibited. Further, in the air chamber and the fuel chamber, the generated water and the residual water are diffused in the thickness direction due to the surface tension of the wire, and it is difficult to dry, and a stable contact area can be secured. For this reason, this fuel cell system can also exhibit excellent current collecting properties. In particular, in this fuel cell system, the reservoirs 2d and 3a are formed on the plates 1 side of the first and second mesh members 2 and 3, so that when the temporary water shortage occurs, the reservoirs 2d and 3a Reduce dryness.

  Further, in this stack 6, since the cathode electrode 5b and the anode electrode 5c of the membrane electrode assembly 5 are composed of only the catalyst layer, the structure of the membrane electrode assembly 5 is simple, and the manufacturing cost can be reduced. You can also. In this stack 1, it is also possible to employ the membrane electrode assembly 11 shown in FIG.

  As shown in FIG. 7, the stack of the second embodiment employs a plate 10, a first net member 20, a third net member (not shown), and a membrane electrode assembly 50.

  The plate 10 has a side surface 10a that extends vertically and a side surface 10b that approaches the side surface 10a toward the bottom when the air flow direction is up and down. The first net member 20 has a shape in which the upper and lower sides of the plate 10 are exchanged. That is, the first net member 20 has a side surface 20a that extends vertically and a side surface 20b that approaches the side surface 20a toward the lower side when the air flow direction is up and down. A water storage layer 20c having water absorption is formed on the surface of the first net member 20 on the plate 10 side. The membrane electrode assembly 50 has a trapezoidal plate shape.

  An intake manifold 8 is provided below the plate 10, the first mesh member 20, the third mesh member, and the membrane electrode assembly 50. Below the intake manifold 8, an opening 8 a for guiding the air supplied from the air blower 30 to the air chamber formed between the wire members of the first mesh member 20 is formed. Note that an exhaust manifold (not shown) is provided above the plate 10, the first mesh member 20, the third mesh member, and the membrane electrode assembly 50. Other configurations are the same as those of the first embodiment.

  In the air chamber of this fuel cell system, the upstream area has a smaller communication area than the downstream area. For this reason, in this fuel cell system, since the static pressure is lower in the upstream region and higher in the downstream region, the effects of the present invention are further produced. Other functions and effects are the same as those of the first embodiment.

  In the above, the present invention has been described with reference to the first and second embodiments. However, the present invention is not limited to the first and second embodiments, and can be appropriately modified and applied without departing from the spirit of the present invention. Needless to say.

  INDUSTRIAL APPLICABILITY The present invention can be used for a fuel cell system such as a moving power source for an electric vehicle, an outdoor stationary power source, and a portable power source.

2 is an exploded perspective view of a cell according to Embodiment 1. FIG. 2 is a cross-sectional view of a first net member according to Embodiment 1. FIG. 2 is a cross-sectional view of a cell of Example 1. FIG. 3 is a schematic enlarged partial cross-sectional view of a membrane electrode assembly according to a cell of Example 1. FIG. 3 is a cross-sectional view of a stack of Example 1. FIG. 1 is a configuration diagram of a fuel cell system of Example 1. FIG. 6 is an exploded perspective view of a cell of Example 2. FIG. It is a disassembled perspective view of the conventional cell. It is a model expanded partial sectional view of the conventional membrane electrode assembly.

Explanation of symbols

DESCRIPTION OF SYMBOLS 5 ... Membrane electrode assembly 5a ... Electrolyte membrane 5b ... Cathode electrode 5c ... Anode electrode 4 ... Separator 1, 10 ... Plate 2, 20 ... 1st net | network material 2d, 20c ... Water storage layer 6 ... Stack 30 ... Air blower (air supply) apparatus)
31 ... Hydrogen tank (hydrogen supply device)

Claims (7)

A membrane electrode assembly having an electrolyte membrane, a cathode electrode joined to one surface of the electrolyte membrane and supplied with air, and an anode electrode joined to the other surface of the electrolyte membrane and supplied with fuel;
A fuel cell comprising: an air chamber formed on the cathode electrode side; and a pair of conductive material separators sandwiching the membrane electrode assembly so as to form a fuel chamber on the anode electrode side. In
The fuel cell according to claim 1, wherein the air chamber is formed such that the upstream area has a smaller communication area than the downstream area.   The separator is provided on one surface of a plate made of a conductive material, and is formed in a porous shape having conductivity and hydrophilicity and having a large number of pores. The fuel cell according to claim 1, further comprising a net member constituting the chamber.   3. The fuel cell according to claim 2, wherein the mesh material is formed in a three-dimensional mesh shape by a conductive wire material and a hydrophilic wire material, and the air chamber is formed between the wire materials.   The fuel cell according to claim 2 or 3, wherein the mesh member has a water-absorbing water storage layer formed on the plate side.   5. The fuel cell according to claim 2, wherein the membrane electrode assembly includes a catalyst layer located on the electrolyte membrane side, and the catalyst layer and the mesh member are joined. 6.   6. A fuel cell stack comprising a large number of cells according to any one of claims 1 to 5. A stack according to claim 6, an air supply device that supplies the air to each of the air chambers, and a fuel supply device that supplies the fuel to each of the fuel chambers,
Each of the air chambers extends vertically in the stack, and the air supply device supplies the air to the air chambers from below.

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