JP2008243403A - Fuel cell and fuel cell stack - Google Patents

Abstract

To provide a fuel cell and a fuel cell stack that are optimized so that the generated water can be easily discharged and the power generation performance is enhanced, and the power generation performance is maximized.
According to a fuel battery cell of the present invention, a conductive mesh material which is one of the constituent elements is formed into a three-dimensional network structure from conductive fibers and has a large number of pores inside. In addition, the porosity of the pores is 50% to 95%, and the fiber equivalent diameter of the conductive fibers constituting the conductive network material is 60 μm to 150 μm. By using such a conductive mesh material, a fuel cell and a fuel cell stack exhibiting excellent power generation performance can be provided.
[Selection] Figure 6

Description

  The present invention relates to a polymer electrolyte fuel cell and a fuel cell stack, and more particularly to a fuel cell and a fuel cell stack that can exhibit excellent power generation performance.

  A unit cell of a polymer electrolyte fuel cell has a configuration in which a solid polymer electrolyte membrane is sandwiched between an anode electrode (fuel electrode) and a cathode electrode (oxidant electrode), and fuel gas supplied to the anode electrode Power generation is performed by electrochemically reacting (for example, hydrogen) and an oxidant gas (for example, air) supplied to the cathode electrode.

  Specifically, as a result of the following electrode reactions that occur at the anode electrode and the cathode electrode, the unit cell of the polymer electrolyte fuel cell, as a whole, undergoes water generation reaction with hydrogen and oxygen to generate electromotive force. appear.

Anode electrode: H ₂ → 2H ⁺ + 2e ⁻
Cathode electrode: (1/2) O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O

  Conventionally, as a general polymer electrolyte fuel cell, for example, a polymer electrolyte membrane fuel cell described in Patent Document 1 can be cited. Here, with reference to FIG. 13 and FIG. 14, the structure of the fuel cell 100 which is a unit cell of the conventional general polymer electrolyte fuel cell will be described.

  FIG. 13 is an exploded perspective view of the fuel cell 100, and FIG. 14 is an enlarged partial cross-sectional view schematically showing a membrane electrode assembly 110 used in the fuel cell 100. As shown in FIG.

  As shown in FIG. 13, the fuel cell 100 includes a pair of separators 120 formed of a conductive material and a membrane electrode assembly 110 sandwiched between the pair of separators 120.

  On the surface of the separator 120 on the side facing the cathode electrode 110b of the membrane electrode assembly 110, ribs extending in one direction (vertical direction in FIG. 13) are provided in parallel to form a plurality of groove-like oxidant gas flow paths. 120a is formed.

  On the other hand, on the surface of the separator 120 on the side facing the anode electrode 110c of the membrane electrode assembly 110, the direction orthogonal to the oxidant gas flow path 120a (the direction from the near side to the far side of the separator 120 shown in FIG. 13). ) Are provided in parallel to form a plurality of groove-like fuel gas passages 120b extending in a direction orthogonal to the oxidant gas passage 120a.

  The oxidant gas is supplied to the cathode electrode 110b of the membrane electrode assembly 110 by flowing through the oxidant gas flow channel 120a, and the fuel gas is supplied to the membrane electrode assembly 110 by flowing through the fuel gas flow channel 120b. To the anode electrode 110c.

  As shown in FIG. 14, the membrane electrode assembly 110 includes a solid polymer electrolyte membrane 110a such as Nafion (registered trademark: manufactured by DuPont) or Aciplex (registered trademark: manufactured by Asahi Kasei Co., Ltd.), and the solid polymer electrolyte. The cathode 110b is in contact with one surface of the membrane 110a, and the anode 110c is in contact with the surface opposite to the surface with which the cathode 110b is in contact with the solid polymer electrolyte membrane 110a.

  The cathode electrode 110b has a catalyst layer 130a in contact with the solid polymer electrolyte membrane 110a and a gas in contact with the surface of the catalyst layer 130a opposite to the surface in contact with the solid polymer electrolyte membrane 110a. And a diffusion layer 130b.

  The anode electrode 110c has a catalyst layer 140a in contact with the solid polymer electrolyte membrane 110a and a gas in contact with the surface of the catalyst layer 140a opposite to the surface in contact with the solid polymer electrolyte membrane 110a. And a diffusion layer 140b.

  The catalyst layers 130a and 140a are layers that promote an electrochemical reaction between the oxidant gas and the fuel gas, and are layers that include catalyst-supported carbon and an electrolyte. The gas diffusion layer 130b is a layer for diffusing the oxidant gas supplied to the cathode electrode 110b, and the gas diffusion layer 140b is a layer for diffusing the fuel gas supplied to the anode electrode 110c. These gas diffusion layers 130b and 140b are made of, for example, a carbon-based material such as carbon paper or carbon cloth, a metal mesh, a metal porous body, or the like.

As described above, the oxidant gas is supplied to the cathode electrode 110b by flowing through the oxidant gas flow path 120a, while the fuel gas is supplied to the anode electrode 110c by flowing through the fuel gas flow path 120b. When supplied, an electromotive force is generated as a result of the electrochemical reaction that occurs between the cathode electrode 110b and the anode electrode 110c.
JP-A-3-295176

  However, in the case of a unit cell in which the oxidant gas flow path 120a and the fuel gas flow path 120b are formed in a groove shape like the fuel cell 100 described above, the water generated by the electrochemical reaction that is the principle of power generation is As a result, gas in the gas channels 120a and 120b and the electrodes 110b and 110c adjacent to the gas channels 120a and 120b (oxidant gas or There is a problem that the flow path of the fuel gas) may be blocked.

  When the gas flow paths 120a, 120b and the gas flow paths in the electrodes 110b, 110c are blocked with liquid water, a portion where no reaction occurs due to the mixture of the gas flow and the water flow is generated, so that the power generation performance is reduced. Invite.

  In addition, in the case of a unit cell in which the oxidant gas flow path 120a and the fuel gas flow path 120b are configured in a groove shape like the fuel cell 100 described above, the pitch of the oxidant gas flow path 120a and the fuel gas flow path 120b. And optimization of groove depth (channel depth, channel height) contributes to the improvement of current collection.

  However, on the other hand, the pitches and groove depths of the gas flow paths 120a and 120b are liable to affect the current collecting property of the fuel cell 100. That is, the pitch and the groove depth of the gas flow paths 120a and 120b are liable to affect the reduction of the contact area between the gas and the electrodes 110b and 110c and the drying of the membrane electrode assembly 110. The pitch and the groove depth of the fuel cell 100 are liable to cause a power generation loss in the fuel cell 100.

  Practically, a form of a stack (not shown) in which a plurality of fuel cells 100 are connected in series is adopted. However, even in such a stack, the above-described causes caused by the fuel cells 100 as constituent elements are used. Problems arise.

  The present invention has been made to solve the above-described problems, and is a fuel optimized to maximize the power generation performance while facilitating the discharge of generated water and improving the power generation performance. It aims at providing a battery cell and a fuel cell stack.

  In order to achieve this object, an electrode for a fuel cell according to claim 1 includes a solid polymer electrolyte membrane, an anode catalyst layer that contacts one of the solid polymer electrolyte membranes and contains a catalyst, and the solid high electrolyte membrane. A cathode catalyst layer containing a catalyst in contact with the other of the molecular electrolyte membrane, and a surface having hydrophilicity on the surface and electrically opposite the surface of the cathode catalyst layer that is in contact with the solid polymer electrolyte membrane; A plate-like conductive net member made of conductive fibers arranged in a connected state and having a plurality of pores that serve as a flow path for an oxidant gas by a three-dimensional network structure, and the conductive net A conductive plate having gas barrier properties in contact with a surface of the material opposite to the surface facing the cathode catalyst layer, and the conductive mesh material has a fiber equivalent diameter of the conductive fiber of 60 μm or more. And 150 μm or less, and the voids due to the holes The porosity is 50% or more and 95% or less.

  The fuel cell according to claim 2 is the fuel cell according to claim 1, wherein the channel height of the channel of the oxidant gas is 0.3 mm or more.

  A fuel cell stack according to a third aspect includes a plurality of fuel battery cells according to the first or second aspect, and is configured by electrically connecting the plurality of cells in series.

  According to the fuel cell of claim 1, a cathode catalyst layer and an anode catalyst layer containing a catalyst are disposed on both sides of the solid polymer electrolyte membrane, respectively, and the solid polymer in the cathode catalyst layer On the surface opposite to the electrolyte membrane, a conductive mesh material is disposed in a state of being electrically connected to the cathode catalyst layer. Further, the surface of the conductive mesh material opposite to the surface facing the cathode catalyst layer is in contact with a conductive plate having gas barrier properties.

  In addition, in claim 1, the conductive net member is “disposed in an electrically connected state” means that the conductive net member is disposed in contact with the catalyst layer and / or the plate. In addition, it is intended to include that a state in which the conductive net member is electrically connected to the catalyst layer and / or the plate through the conductive member is formed.

  Here, the conductive mesh material is a plate-shaped mesh material formed in a three-dimensional network structure from conductive fibers and having a large number of pores communicating with each other, and has a gas barrier property with the catalyst layer. By being disposed between the plate and the plate, it is possible to make a large number of holes existing inside the conductive mesh member function as a flow path for the oxidant gas or the fuel gas.

  In addition, since the conductive mesh material has hydrophilicity on the surface, water generated by the reaction can be diffused in the thickness direction by the surface tension of the mesh material, effectively blocking the oxidant gas flow path with liquid water. Can be prevented. Therefore, since it is possible to prevent the oxidant gas flow path of the fuel cell from being blocked by liquid water, the pressure loss and flooding of the oxidant gas due to the blockage of the oxidant gas flow path can be suppressed, As a result, there is an effect that a decrease in power generation performance can be suppressed.

  According to the fuel cell of claim 1, since the porosity due to the pores in the conductive network material is 50% or more, the pressure loss of the oxidant gas flowing through the oxidant gas flow path is reduced. This has the effect of being able to be suppressed and exhibiting excellent power generation performance.

  In addition, since the porosity due to the pores in the conductive mesh material pores is 95% or less, the pressure loss of the oxidant gas flowing through the oxidant gas flow path can be suppressed, and the conductivity can be reduced. There is an effect that it is possible to suppress a significant increase in the production cost of the net material.

  Furthermore, according to the fuel cell of claim 1, since the fiber equivalent diameter of the conductive fiber constituting the conductive network material is set to 60 μm or more, the fiber is formed in a three-dimensional network structure by the fiber. Strength and elasticity that can sufficiently withstand a load (shared load) applied from the outside can be imparted to the conductive mesh material.

  Therefore, since the load loss of the conductive net material due to the deformation by the applied load at the time of the configuration of the fuel cell is suppressed, there is an effect that it is possible to suppress a decrease in power generation performance due to the load loss of the conductive net material.

  In addition, according to the fuel battery cell of claim 1, since the fiber equivalent diameter of the conductive fiber constituting the conductive mesh material is set to 150 μm or less, between the fibers constituting the conductive mesh material. There is an effect that the pitch can be set to an appropriate interval in terms of current collection efficiency, and excellent power generation performance can be exhibited.

  In addition, in Claim 1, the “fiber equivalent diameter” is a diameter corresponding to the circumference of the circumference of the fiber (the length of the outer circumference) as a circumference. That is, R = L / π where R is the fiber equivalent diameter and L is the circumference of the fiber.

  According to the fuel cell of claim 2, in addition to the effect of the fuel cell of claim 1, the following effect is obtained. Since the flow path height of the oxidant gas flow path is 0.3 mm or more, the pressure loss of the oxidant gas flowing through the oxidant gas flow path can be suppressed low, and excellent power generation performance can be exhibited. There is an effect.

  According to the fuel cell stack according to claim 3, the fuel cells according to claim 1 or 2 are configured to be electrically connected in series, so that the fuel cells according to claim 1 or 2. Has the same effect as

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing a fuel cell system 1 including a fuel cell stack 50 according to an embodiment of the present invention.

  The fuel cell system 1 is connected to a predetermined location (for example, the lower portion) of the fuel cell stack 50 via a fuel cell stack 50, a hydrogen tank 33, an air fan 34, and a circulation pump 36, which will be described later with reference to FIG. The radiator 37 is mainly composed.

  In this fuel cell system 1, the hydrogen tank 33 is a tank that stores fuel gas (hydrogen in this embodiment), and a fuel gas supply port 50 c in the fuel cell stack 50 (see FIG. 2) via the valve 32. It is connected to the. By opening the valve 32, the hydrogen stored in the hydrogen tank 33 can be supplied into the fuel cell stack 50.

  The air fan 34 takes in the oxidant gas (air in the present embodiment) from the outside and blows it to the oxidant supply port 50a (see FIG. 2), thereby supplying the oxidant gas into the fuel cell stack 50. Is.

  As will be described in detail later, the air fan 34 is operated to supply the oxidant gas to the oxidant supply port 50a. On the other hand, when the valve 32 is opened, the fuel gas is supplied from the hydrogen tank 33 to the fuel gas supply port 50c. Then, each fuel cell 10 (see FIG. 2) constituting the fuel cell stack 50 generates power.

  The fuel cell stack 50 collects electricity generated by each fuel cell 10 and can extract a direct current from current collecting terminals 50e and 50f (both see FIG. 2) as current extraction units. The direct current extracted from the fuel cell stack 50 is supplied to a load 35 (for example, a motor of an automobile) electrically connected to the fuel cell stack 50, and as a result, the load 35 can be driven.

  FIG. 2 is a perspective view schematically showing the fuel cell stack 50 of the present embodiment. As shown in FIG. 2, the fuel cell stack 50 is a stacked body in which a plurality of later-described fuel cells 10 are stacked in the direction of arrows XX. In the fuel cell stack 50, adjacent fuel cells 10 are electrically connected in series by a separator 20 having conductivity.

  In this fuel cell stack 50, an oxidant gas flow path for supplying an oxidant gas to the cathode electrode 13 (see FIG. 6B) of each fuel cell 10 communicates between the separators 20. And holes in the first net member 21a (see FIG. 6B) in the cathode electrode 13 communicating with the flow paths 23d and 23e.

  In the fuel cell stack 50 of the present embodiment, an oxidant gas supply port 50a communicating with the flow path 23d is opened on the exposed surface of the separator 20 located on the most front side in FIG. The oxidant gas taken in is supplied to the fuel cell stack 50 from the oxidant gas supply port 50a.

  On the other hand, on the exposed surface of the separator 20 located on the innermost side in FIG. 2, an oxidant gas discharge port 50b communicating with the flow path 23e (not shown in FIG. 2 because it is the back side of the fuel cell stack 50). Is open. The oxidant gas supplied to the inside of the fuel cell stack 50 from the oxidant gas supply port 50a passes through the oxidant gas flow path in the fuel cell stack 50 and is then discharged from the oxidant gas discharge port 50b.

  Further, in the fuel cell stack 50, a fuel gas channel for supplying fuel gas to the anode electrode 14 (see FIG. 6B) of each fuel cell 10 communicates between the separators 20 (not shown). ) And holes in the second mesh member 22a (see FIG. 6B) in the anode electrode 14 communicating with the flow path (not shown).

  In the fuel cell stack 50 of the present embodiment, a fuel supply port 50c communicating with the fuel gas flow path is provided on the exposed surface of the separator 20 located on the foremost side in FIG. On the other hand, on the exposed surface of the separator 20 located on the innermost side in FIG. 2, a fuel discharge port 50d (not shown in FIG. 2 because it is the back side of the fuel cell stack 50) communicating with the fuel gas flow path is provided. It has been.

  Fuel gas can be supplied from the hydrogen tank 33 to the inside of the fuel cell stack 50 through the fuel gas supply port 50c. The fuel gas supplied to the inside of the fuel cell stack 50 passes through the fuel gas passage in the fuel cell stack 50 and is then discharged from the fuel gas discharge port 50d.

  Therefore, when the oxidant gas and the fuel gas are respectively supplied from the oxidant gas supply port 50a and the fuel gas supply port 50c to the inside of the fuel cell stack 50, the oxidant gas and the fuel gas are respectively contained in the fuel cell stack 50. As a result, each fuel cell 10 can generate electric power.

  Next, with reference to FIGS. 3 to 6, the fuel cell 10 according to an embodiment of the present invention will be described. FIG. 3 is a cross-sectional view schematically showing a first porous body 21 constituting a part of the cathode electrode 13 (see FIG. 6B) of the fuel cell 10 according to the embodiment of the present invention.

  As shown in FIG. 3, the first porous body 21 includes a first net member 21 a and a pore layer 21 b formed on one surface (left surface in FIG. 3) of the first net member 21. It is a plate-shaped member.

  The first net member 21a is formed in a three-dimensional network structure from conductive fibers (conductive fibers), and has a plate shape having pores communicating with each other (for example, pores having a minimum inner diameter of about 50 μm to 500 μm). It is a member. In the present embodiment, titanium fibers are employed as the conductive fibers constituting the first mesh material 21a, and the first mesh material 21a is configured as a titanium fiber sintered plate. In addition, as a conductive fiber which comprises the 1st net | network material 21a, metal fibers which have corrosiveness and electroconductivity, such as SUS, tantalum, or hastelloy other than titanium fiber, and electroconductivity, such as nickel or carbon Fiber can be employed.

  The porosity of the pores in the first net member 21a is preferably about 50% to 95%, and more preferably about 70 to 85%. The holes of the first net member 21 a function as a part of the oxidant gas flow path in the fuel cell 10. Therefore, by setting the porosity of the pores in the first net member 21a to about 50% or more, the pressure loss of the oxidant gas flowing through the oxidant gas flow path can be suppressed to a low level. The power generation performance excellent in 10 can be exhibited.

  On the other hand, by setting the porosity of the pores in the first mesh material 21a to about 95% or less, it is possible to suppress a significant increase in the production cost of the first mesh material 21a, and thus the production cost of the fuel cell 10 is increased. Can be suppressed.

  Moreover, it is preferable that the fiber equivalent diameter of the electroconductive fiber which comprises the 1st net | network material 21a is about 60 micrometers-150 micrometers. The “fiber equivalent diameter” is a diameter corresponding to the circumference of the circumference of the conductive fiber (the length of the outer circumference) as a circumference. That is, R = L / π where R is the fiber equivalent diameter and L is the circumference of the fiber.

  By setting the fiber equivalent diameter of the conductive fibers constituting the first mesh material 21a to about 60 μm or more, the first mesh material 21a formed in a three-dimensional network structure by the conductive fibers is imparted with high strength and high elasticity. can do. Therefore, since it is possible to prevent the first net member 21a from being lost due to the shared load applied to the first net member 21a when the fuel cell 10 is configured, the fuel cell unit 10 exhibits excellent power generation performance. be able to.

  On the other hand, by setting the equivalent fiber diameter of the conductive fibers constituting the first mesh member 21a to about 150 μm or less, the pitch between the fibers constituting the first mesh member 21a is not excessively widened, and the current collection efficiency is improved. Therefore, the fuel cell 10 can exhibit excellent power generation performance.

  Further, by setting the fiber equivalent diameter of the conductive fibers constituting the first mesh material 21a to about 150 μm or less, the pitch between the fibers constituting the first mesh material 21a is not excessively widened and contact with the catalyst layer 26 is achieved. Since a sufficient area can be secured, it is possible to prevent poor bonding with the catalyst layer 26.

  The pore layer (MPL: Micro Porous Layer) 21b is a layer having many pores communicating with each other and having a thickness of, for example, about 200 μm or less. The pores in the pore layer 21b are pores smaller than the pores of the first net member 21a described above (for example, pores having a minimum inner diameter of about 0.01 μm to several μm and a peak of less than about 2 μm). It is.

  Since the pore layer 21b has pores that allow the catalyst layer 26 and the first net member 21a to communicate with each other, electrons are transferred from the catalyst layer 26 (see FIG. 5) of the membrane electrode assembly 24 to the first net member 21a. In addition, the water in the catalyst layer 26 is moved to the pore layer 21b, and the excess water is discharged out of the system while keeping the catalyst layer 26 moderately. Responsible for suppressing reaction inhibition.

  The pore layer 21b preferably has water repellency such that the contact angle of water is about 120 ° or more. For example, the water repellency includes carbon particles and PTFE (Polytetrafluoroethylene). The pore layer can be employed. At this time, the mixing amount of PTFE is preferably about 20 to 60% by mass.

  Moreover, it is preferable that the pore layer 21b is disposed while biting into the first net member 21a. For example, it is preferable that the pore layer 21b is disposed while biting into the first net member 21a by about 30 μm or more. On the other hand, the surface of the pore layer 21b opposite to the first net member 21a preferably has smoothness.

  In addition, the 2nd porous body 22 which comprises a part of anode electrode 14 (refer FIG.6 (b)) in the fuel cell 10 of this embodiment is also comprised similarly to the 1st porous body 21 shown in FIG. . The numbers described in parentheses in FIG. 3 are numbering applied to the second net member 22. In addition, when applying description of the 1st net material 21 mentioned above to the 2nd net material 22, (1) "1st porous body 21" is read as "2nd porous body 22", (2) " “First mesh material 21a” is read as “second mesh material 22a”, (3) “pore layer 21b” is read as “pore layer 22b”, and (4) “catalyst layer 26 (see FIG. 5). “Catalyst layer 27 (see FIG. 5)” and (5) “oxidant gas” may be replaced with “fuel gas”.

  FIG. 4 is a cross-sectional view schematically showing the separator 20 in the fuel battery cell 10 of the present embodiment. As shown in FIG. 4, the separator 20 includes the first porous body 21 and the second porous body 22 described above, and a conductive plate 23 that houses the porous bodies 21 and 22.

  The conductive plate 23 constituting the separator 20 is a plate-like member made of a conductive material, and on one surface side (left side in FIG. 4), a first recess 23 a that houses the first porous body 21. Is recessed. Further, on the other surface side of the plate 23 (the right side in FIG. 4), a second recess 23b for storing the second porous body 22 and a third recess 23c for storing a membrane electrode assembly 24 (see FIG. 5) described later. Are recessed.

  Further, the plate 23 is provided with a pair of oxidant gas flow paths 23d and 23e communicating with both ends of the first recess 23a. The plate 23 is also provided with a pair of fuel gas passages (not shown) communicating with both ends of the second recess 23b. The flow paths 23d, 23e for the oxidant gas and the flow path for the fuel gas are provided so as to be shifted from each other by 90 degrees, and the first porous body 21 (the first net member 21a) is positioned according to the positional relationship. The supply direction of the oxidant gas supplied to and the supply direction of the fuel gas supplied to the second porous body 22 (second net member 22a) are orthogonal to each other.

  The first porous body 21 is accommodated in the first recess 23a of the plate 23 having such a configuration. At that time, the first porous body 21 is accommodated in the first recess 23a so that the surface on which the pore layer 21b is not disposed is in contact with the bottom surface of the first recess 23a and the pore layer 21b faces outward. Is done.

  Further, the second porous body 22 is accommodated in the second recess 23 b of the plate 23. At that time, the second porous body 22 is accommodated in the second recess 23b so that the surface on which the pore layer 22b is not disposed is in contact with the bottom surface of the second recess 23b and the pore layer 22b faces outward. Is done.

  FIG. 5 is a cross-sectional view schematically showing the membrane electrode assembly 24. As shown in FIG. 5, the solid polymer electrolyte membrane 25, the catalyst layer 26 in contact with one surface (the right surface in FIG. 5) of the solid polymer electrolyte membrane 25, and the other of the solid polymer electrolyte membrane 25 This is a laminate composed of the catalyst layer 27 in contact with the surface (the left surface in FIG. 5).

  As described above, the membrane electrode assembly 24 employed in the fuel cell 10 of the present embodiment is different from the conventional membrane electrode assembly 110 (see FIG. 14) in that carbon paper or carbon adjacent to the catalyst layers 26 and 27 is used. The gas diffusion layers 130b and 140b (see FIG. 14) such as cloth are not included.

  Examples of the solid polymer electrolyte membrane 25 include solid polymer electrolyte membranes applicable to solid polymer fuel cells such as Nafion (registered trademark: manufactured by DuPont) and Aciplex (registered trademark: manufactured by Asahi Kasei Corporation). Can be used.

  As the catalyst layers 26 and 27, for example, a catalyst layer including a catalyst-supporting carbon in which a catalyst such as platinum is supported on carbon particles and an electrolyte can be employed. The catalyst layers 26 and 27 are layers constituting part of the cathode electrode 13 and the anode electrode 14 (see FIG. 6B), respectively, and electrochemical reaction between oxygen and hydrogen generated in the fuel cell 10. Responsible for promoting the function.

  6A is a cross-sectional view schematically showing the fuel battery cell 10, and FIG. 6B is an enlarged cross-sectional view of an E portion in FIG. 6A.

  As shown in FIG. 6A, the fuel cell 10 includes two adjacent separators 20 and a membrane electrode assembly 24 disposed between the separators 20. More specifically, the fuel cell 10 includes a first porous body 21 exposed on one surface of one separator 20 (the right separator 20 in FIG. 6A) and the other separator 20 (FIG. 6A). The membrane electrode assembly 24 accommodated in the third recess 23c of the left separator 20) in FIG.

  In the fuel cell stack 50, the adjacent fuel cells 10 share the separator 20 in common. That is, for example, the fuel cell 10 adjacent to the right side of the fuel cell 10 shown in FIG. 6A shares the right separator 20 in FIG. 6A.

  Here, when the membrane electrode assembly 24 is housed in the third recess 23c of the plate 23, the catalyst layer 27 contacts the pore layer 22b (a part of the second porous body 22), and the catalyst layer 26 is outside. It is stored so that it faces. Therefore, when the fuel cell 10 is composed of the two adjacent separators 20 and the membrane electrode assembly 24, the catalyst layer 26 comes into contact with the pore layer 21b (a part of the first porous body 21) ( (Refer FIG.6 (b)).

  As described above, the oxidant gas flowing through the flow path 23d in the separator 20 in the direction of the arrow is supplied to the first porous body 21 (first net member 21a), and the holes in the first net member 21a are indicated by arrows. And is discharged to the flow path 23e, and flows through the flow path 23e in the direction of the arrow. On the other hand, the fuel gas supplied from the fuel gas flow path (not shown) to the second porous body 22 (second net member 22a) flows through the pores in the second net member 22a.

  As a result, in the fuel cell 10 of the present embodiment, the first porous body 21 and the catalyst layer 26 function as the cathode electrode 13, the second porous body 22 and the catalyst layer 27 function as the anode electrode 14, An electromotive force is generated as a result of an electrochemical reaction between the oxidant gas supplied to the first porous body 21 (first network member 21a) and the fuel gas supplied to the second porous body (second network member 22a). (To generate electricity).

  According to the fuel cell 10 of the present embodiment shown in FIG. 6A, the first net member 21 a of the first porous body 21 and the second net member 22 a of the second porous body 22 communicate with each other. Due to the presence of the pores, the pores can function as a flow path for the oxidant gas and the fuel gas, and the water generated by the reaction is caused in the thickness direction of the conductive mesh material by the surface tension of the mesh material. Can be diffused. As a result, blockage of the gas flow path by water (liquid water) generated as a result of the electrochemical reaction between the oxidant gas and the fuel gas can be prevented. Therefore, since the pressure loss of the gas (oxidant gas or fuel gas) in the gas channel (oxidant gas channel or fuel gas channel) can be suppressed, it is possible to suppress a decrease in power generation performance.

  In addition, in the cathode electrode 13 of the fuel cell 10, the flow path height (thickness of the first net member 21a) h1 of the flow path of the oxidant gas supplied to the catalyst layer 26 is about 0.3 mm or more. It is preferable. By configuring the flow path height h1 of the flow path of the oxidant gas to be about 0.3 mm or more, the pressure loss of the oxidant gas can be suppressed to a suitable low level.

  Similarly, in the anode electrode 14 of the fuel battery cell 10, the flow path height (thickness of the second mesh member 22a) h2 of the flow path of the fuel gas supplied to the catalyst layer 27 is also about 0.3 mm or more. Preferably there is. By configuring the flow path height h2 of the fuel gas flow path to be about 0.3 mm or more, the pressure loss of the fuel gas can be suppressed to a suitable low level.

  In addition, the lower the flow path heights h1 and h2, the more advantageous the output density. In particular, the channel heights h1 and h2 are preferably about 1.5 mm or less. By configuring the flow path heights h1 and h2 to be about 1.5 mm or less, the power generation performance such as an improvement in output density is preferably improved.

  Furthermore, according to the fuel battery cell 10 of the present embodiment shown in FIGS. 6A and 6B, the first net member 21 that is a part of the cathode electrode 13 and a part of the anode electrode 14. A certain second net member 22 functions as a gas flow path. Therefore, in the fuel cell 10 of the present embodiment, as in the cell 100 (see FIG. 13), which is a conventional solid polymer fuel cell, a rib is provided in parallel with the separator 120 to provide an oxidant gas flow path. There is no need to form 120a or the fuel gas flow path 120b. Accordingly, since the separator 20 can be made thinner, the fuel cell 10 can be made thinner, and as a result, the output density can be improved.

  As described above, according to the fuel battery cell 10 of the present embodiment, the porosity of the pores in the mesh members 21a and 22a that are part of the electrodes 13 and 14 is increased by about 50% or more. Since the pressure loss of the oxidant gas flowing through the agent gas flow path can be suppressed low, the fuel cell unit 10 can exhibit excellent power generation performance.

  Moreover, since the porosity of the pores in the mesh members 21a and 22a which are a part of the electrodes 13 and 14 is set to about 95% or less, a significant increase in the manufacturing cost of the first mesh material 21a can be suppressed. An increase in the manufacturing cost of the battery cell 10 can be suppressed.

  Furthermore, by setting the fiber equivalent diameter of the conductive fibers constituting the mesh materials 21a and 22a to about 60 μm or more, the mesh materials 21a and 22a formed in a three-dimensional network structure by such conductive fibers have high strength and high elasticity. Can be granted. Therefore, it is possible to prevent the load loss from being generated in the net members 21a and 22a due to the shared load applied to the net members 21a and 22a when the fuel cell 10 is configured, so that the fuel cell 10 exhibits excellent power generation performance. be able to.

  Further, by setting the equivalent fiber diameter of the conductive fibers constituting the net members 21a and 22a to about 150 μm or less, the pitch between the fibers constituting the net members 21a and 22a is not excessively widened, and the current collecting efficiency is improved. Since it can be set as an appropriate space | interval, the fuel cell 10 can exhibit the outstanding electric power generation performance.

  In addition, in the cathode electrode 13 of the fuel cell 10, the flow height of the flow path of the oxidant gas supplied to the catalyst layer 26 is configured to be about 0.3 mm or more, so that the gas pressure loss is favorable. It can be suppressed to low.

  As described above, the present invention has been described based on the embodiments, but the present invention is not limited to the above-described embodiments, and various improvements and modifications can be easily made without departing from the spirit of the present invention. It can be guessed.

  For example, in the above embodiment, the first porous body 21 is formed by forming the pore layer 21b on one side of the first net member 21a, but the pore layer 21b is not formed on one side of the first net member 21a. The first net member 21a itself may be the first porous body 21. Similarly, for the second porous body 22, the second net 22 a itself may be used as the second porous 22 without forming the pore layer 22 b on one side of the second net 22 a. Further, only one of the first porous body 21 and the second porous body 22 may have the pore layers 21b and 22b, and the other may not have the pore layers 21b and 22b.

  In the above embodiment, the pore layers 21b and 22b formed on one side of the first and second net members 21a and 22a are brought into contact with the catalyst layers 26 and 27. , 22a may be in direct contact with the catalyst layers 26, 27. Further, only one of the first porous body 21 and the second porous body 22 brings the pore layers 21b and 22b into contact with the catalyst layers 26 and 27, and the other is connected to the first and second net members 21a and 22a and the catalyst. You may comprise so that the layers 26 and 27 may be contact | abutted.

  In the above embodiment, the pore layers 21b and 22b are formed on the first and second mesh materials 21a and 22a. However, the pore layers 21b and 22b are formed on the outer surfaces of the catalyst layers 26 and 27, The pore layers 21b and 22b may be configured to exist alone.

  In the above embodiment, the catalyst layers 26, 27 are configured as a part of the membrane bonding electrode 24. However, the catalyst layers 26, 27 are disposed on the outermost layers of the first and second porous bodies 21, 22. You may comprise as follows. For example, when the catalyst layers 26 and 27 are disposed outside the pore layers 21b and 22b in the first and second porous bodies 21 and 22, or when the pore layers 21b and 22b are not provided, the first and second networks You may comprise so that the catalyst layers 26 and 27 may be arrange | positioned on the materials 21a and 22a.

  Moreover, in the said embodiment, although the 1st, 2nd porous bodies 21 and 22 comprised the 1st and 2nd net materials 21a and 22a and the pore layers 21b and 22b, the 1st and 2nd net materials 21a and 22a were comprised. A layer having hydrophilicity may be configured as a drainage layer on the surface opposite to the pore layers 21b and 22b. When the 1st, 2nd porous bodies 21 and 22 have a drainage layer, it arrange | positions so that a drainage layer may contact | abut on the bottom face of the 1st, 2nd recessed parts 23a and 23b.

  By providing a drainage layer on the surface of the first and second net members 21a and 22a opposite to the pore layers 21b and 22b, the drainage layer diffuses in the thickness direction of the first and second net members 21a and 22a. It collects the collected water (liquid water), creates a flow of water by its own weight and the pressure of oxidant gas, and discharges it out of the system. Such a drainage layer preferably has water absorption in addition to hydrophilicity.

  Moreover, it replaces with forming a drainage layer in the surface on the opposite side to the pore layers 21b and 22b in the 1st and 2nd net materials 21a and 22a, or the pores in the 1st and 2nd net materials 21a and 22a. While forming in the surface on the opposite side to the layers 21b and 22b, you may make it form by the hydrophilic treatment of the bottom face of the 1st, 2nd recessed parts 23a and 23b, or the coating of a hydrophilic polymer.

  The fuel cell and the fuel cell stack of the present invention exemplified as the above embodiments can be used as various power sources such as a moving power source for an electric vehicle, an outdoor stationary power source, a portable power source, and a portable electronic device power source. is there.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

[Example 1, Comparative Example 1]
As Example 1, the fuel cell stack 50 including the fuel cell 10 of the present invention was used, and as the Comparative Example 1, the fuel cell stack including the conventional fuel cell 100 shown in FIG. 13 was used under the same conditions. The IV characteristics were compared with each other.

The result is shown in FIG. FIG. 7 is a graph showing IV characteristics in Example 1 and Comparative Example 1. In the graph of FIG. 7, the horizontal axis indicates current I (unit: A / cm ² ) per unit area, and the vertical axis indicates voltage (unit: V).

  As apparent from the graph of FIG. 7, both the fuel cell stack 50 of Example 1 and the fuel cell stack of Comparative Example 1 show substantially equivalent IV characteristics in the low current region, but in the high current region. There was a difference between the two. As shown in the graph of FIG. 7, the value of I at which V = 0.6 was 1.0 in the fuel cell stack of Comparative Example 1, whereas it was 1.4 in the fuel cell stack of Example 1. Met.

  That is, the fuel cell stack 50 of Example 1 had a smaller voltage drop in the high current region than the fuel cell stack of Comparative Example 1, and exhibited excellent IV characteristics. This is considered to be because the water discharging property of the fuel cell 10 constituting the fuel cell stack 50 of Example 1 is improved from the discharging property of the fuel cell 100 constituting the fuel cell stack of Comparative Example 1. . That is, since the water discharge performance of the fuel battery cell 10 is improved, the gas flow path of the fuel battery cell 10 is not blocked by water, and as a result, the gas supply performance to the catalyst layers 26 and 27 is improved. This is probably because the pressure loss of the oxidant gas was suppressed to a low level.

[Example 2, Comparative Example 2]
As Example 2, a load test was performed on the first and second net members 21a and 22a constituting the first and second porous bodies 21 and 22.

  In Example 2, a titanium sintered plate made of titanium fibers having a fiber equivalent diameter of 70 μm was used as the specimens as the first and second net members 21a and 22a. While increasing the amount of load applied to the specimen (surface pressure), the thickness of the specimen was measured when the load was applied and when the load was unloaded (unloading). Then, after reaching a predetermined load amount, the thickness of the specimen was measured again during load application and unloading while gradually decreasing the load amount to be applied.

The result is shown in FIG. FIG. 8 is a graph showing the relationship between the surface pressure and the thickness of the specimen in the load test of Example 2. Here, in the graph of FIG. 8, the horizontal axis indicates the surface pressure (unit: kgf / cm ² ), and the applied surface pressure increases from the left to the right in FIG. The vertical axis indicates the thickness (unit: mm) of the specimen. In the graph of FIG. 8, the symbol “■” is a measured value at the time of applying a load, and the symbol “●” is a measured value at the time of unloading.

  As is apparent from the graph of FIG. 8, the specimen prepared from titanium fiber having a fiber equivalent diameter of 70 μm is applied with an applied load (in the increasing process of the surface pressure applied to the specimen and in the subsequent decreasing process) It was shown that the thickness of the specimen was fully restored when the surface pressure was unloaded.

  On the other hand, as Comparative Example 2, a load test similar to that of Example 2 was performed using a titanium sintered plate made of titanium fiber having a fiber equivalent diameter of 40 μm as a specimen.

The result is shown in FIG. FIG. 9 is a graph showing the relationship between the surface pressure and the thickness of the specimen in the load test of Comparative Example 2. Here, in FIG. 9, the horizontal axis indicates the surface pressure (unit: kgf / cm ² ), and indicates that the applied surface pressure increases from left to right as in FIG. 8. The vertical axis indicates the thickness (unit: mm) of the specimen. In the graph of FIG. 9, the symbol “■” is a measured value at the time of applying a load, and the symbol “●” is a measured value at the time of unloading.

  As is apparent from the graph of FIG. 9, the specimen made from titanium fiber having a fiber equivalent diameter of 40 μm is almost restored to the thickness of the specimen at the time of unloading, particularly in the process of decreasing the surface pressure applied to the specimen. Showed that it will not.

  Therefore, based on the results of Example 2 and Comparative Example 2, by making the fiber equivalent diameter of the titanium fibers constituting the first and second mesh members 21a and 22a about 60 μm or more, the sharing applied during the construction of the fuel cells. It is considered that sufficient strength and elasticity can be imparted to the first and second net members 21a and 22a to suitably prevent the occurrence of load loss due to the load.

[Example 3]
As Example 3, the IV characteristics of the fuel cell stack 50 were confirmed under the same conditions except that the fiber equivalent diameters of the titanium fibers constituting the first and second net members 21a and 22a were different.

The result is shown in FIG. FIG. 10 is a graph showing the IV characteristics of the fuel cell stack 50. In the graph of FIG. 10, the horizontal axis indicates the current I (unit: A / cm ₂ ) per unit area, and the higher the current is from left to right in FIG. The vertical axis represents voltage (unit: V).

  In the graph of FIG. 10, the symbol “●” is a measured value when the first and second mesh materials 21 a and 22 a made from titanium fibers having an equivalent fiber diameter of R1 are used as test specimens, and the symbol “◯”. These are measured values when the first and second net members 21a and 22a made of titanium fibers having an equivalent fiber diameter of R2 are used as specimens. The fiber equivalent diameter R2 is larger than the fiber equivalent diameter R1 (that is, R2> R1).

  As apparent from the graph of FIG. 10, on the low current side (left side in the graph of FIG. 10), there was almost no difference in IV characteristics due to the difference in fiber equivalent diameter, but on the high current side (graph of FIG. 10). A difference due to the difference in fiber equivalent diameter occurred. That is, it was shown that the voltage drop on the high current side increases as the fiber equivalent diameter constituting the specimen increases.

  This result is considered to be due to the fact that the fiber-to-fiber pitch of the specimen increases and the current collection efficiency decreases as the equivalent fiber diameter constituting the specimen increases. Therefore, if the fiber equivalent diameter of the titanium fiber constituting the first and second net members 21a and 22a is too large, it is not preferable because the current collection efficiency is lowered, and it is presumed that it is preferably about 150 μm or less.

[Example 4]
As Example 4, the relationship between the porosity of the pores in the first and second net members 21a and 22a and the pressure loss of the gas in the fuel cell 10 was confirmed. Specifically, while the porosity of the pores in the second mesh member 22a is constant, a plurality of pores in the first mesh member 21a (about 40 mm × about 40 mm × about 1 mm) are changed. The fuel cell 10 was produced as a specimen, and the pressure loss of the dry gas (dried oxidant gas) at room temperature in each specimen was measured for three different amounts of current. The amount of gas flow was 3.3 liters / min.

  The result is shown in FIG. FIG. 11 is a graph showing the relationship between the porosity of the first net member 21a and the pressure loss of the gas. In the graph of FIG. 11, the horizontal axis indicates the porosity (unit:%). The vertical axis indicates the gas pressure loss (unit: Pa), and the pressure loss increases from the bottom to the top in FIG.

In the graph of FIG. 11, the curve J1 is a curve showing the relationship between the porosity of the first mesh member 21a and the pressure loss of the gas when the current amount is 1 A / cm ² , and the curve J2 is the current J It is a curve showing the relationship between the porosity of the first mesh member 21a and the gas pressure loss when the amount is 2 A / cm ² , and the curve J3 is the first mesh when the current amount is 3 A / cm ^2. It is a curve which shows the relationship between the porosity of the material 21a, and the pressure loss of gas.

  As is clear from the graph of FIG. 11, in all of the curves J1, J2, and J3, when the porosity of the first net member 21a is 50% or less, the pressure loss of the gas increased rapidly. Therefore, the oxidant flowing through the oxidant gas flow path (or the fuel gas flow path) by setting the porosity of the pores in the first mesh material 21a (or the second mesh material 22a) to about 50% or more. Since the pressure loss of the gas (or fuel gas) can be suppressed low, even the fuel cell 10, particularly the fuel cell 10 operating in a normal pressure system, can exhibit excellent power generation performance. it is conceivable that.

[Example 5]
As Example 5, the height of the gas flow path in the fuel battery cell 10 (the flow path height h2 of the oxidant gas flow path, the flow path height h2 of the fuel gas flow path), and the fuel battery cell 10 The relationship with the gas pressure loss was confirmed.

  Specifically, the flow path height h2 (thickness of the second net member 22a) on the anode electrode 14 side in the fuel cell 10 is constant (1.5 mm), while the flow path height on the cathode electrode 13 side is set. A plurality of fuel cells 10 having different thicknesses h1 (thickness of the first net member 21a) are produced as test specimens, and the pressure loss of the dry gas (dried oxidant gas) at normal temperature in each specimen is measured. did. The inflow of gas was 3.3 liters (normal) / min. The first and second net members 21a and 22a were about 40 mm × about 40 mm square.

  The result is shown in FIG. FIG. 12 is a graph showing the relationship between the flow path height h1 on the cathode electrode 13 side in the fuel cell 10 and the gas pressure loss. In the graph of FIG. 12, the horizontal axis indicates the flow path height h1 (unit: mm) on the cathode electrode 13 side, and the vertical axis indicates the gas pressure loss (unit: Pa).

  As is apparent from the graph of FIG. 12, when the flow path height h1 on the cathode electrode 14 side in the fuel cell 10 is 0.3 mm or less, the pressure loss of the gas increased rapidly. Therefore, by setting the flow path height of the gas flow path in the fuel cell 10 (the flow path height h1 of the oxidant gas flow path) to about 0.3 mm or more, the gas flow path (oxidant gas flow path) The pressure loss of the gas (oxidant gas) flowing through the fuel cell can be suppressed to a low level, so that even the fuel battery cell 10, particularly the fuel battery cell 10 operating in a normal pressure system, exhibits excellent power generation performance. It is thought that you can.

It is a mimetic diagram showing a fuel cell system constituted from a fuel cell stack in one embodiment of the present invention. It is a perspective view which shows a fuel cell stack typically. It is sectional drawing which shows a 1st porous body typically. It is sectional drawing which shows a separator typically. It is sectional drawing which shows a membrane electrode assembly typically. (A) is sectional drawing which shows a fuel battery cell typically, (b) is an expanded sectional view of the E section in (a). 6 is a graph showing IV characteristics in Example 1 and Comparative Example 1. 4 is a graph showing a relationship between a surface pressure and a thickness of a specimen in a load test of Example 2. 6 is a graph showing a relationship between a surface pressure and a thickness of a specimen in a load test of Comparative Example 2. It is a graph which shows the IV characteristic of a fuel cell stack. It is a graph which shows the relationship between the porosity of a 1st net material, and the pressure loss of gas. It is a graph which shows the relationship between the flow path height in the cathode electrode side in a fuel battery cell, and the pressure loss of gas. It is a disassembled perspective view of the conventional fuel cell. FIG. 14 is an enlarged partial cross-sectional view schematically showing a membrane electrode assembly used in the fuel battery cell of FIG. 13.

Explanation of symbols

10 Fuel cell 21a First mesh material (conductive mesh material)
22a Second mesh material (conductive mesh material)
23 Plate 25 Solid polymer electrolyte membrane 26 Catalyst layer (cathode catalyst layer)
27 Catalyst layer (Anode catalyst layer)
50 Fuel cell stack

Claims (3)

A solid polymer electrolyte membrane;
An anode catalyst layer in contact with one of the solid polymer electrolyte membranes and containing a catalyst;
A cathode catalyst layer in contact with the other of the solid polymer electrolyte membrane and containing a catalyst;
The surface has hydrophilicity and is disposed in a state of being electrically connected to the surface of the cathode catalyst layer opposite to the surface in contact with the solid polymer electrolyte membrane. A plate-like conductive net material made of conductive fibers in which a large number of pores serving as gas flow paths are formed;
A conductive plate having a gas barrier property in contact with a surface opposite to the surface facing the cathode catalyst layer in the conductive mesh material;
The conductive mesh material has a fiber equivalent diameter of the conductive fibers of 60 μm or more and 150 μm or less, and a porosity due to the pores is 50% or more and 95% or less. Fuel cell.   The fuel cell according to claim 1, wherein a flow path height of the oxidant gas flow path is 0.3 mm or more. A plurality of fuel cells according to claim 1 or 2,
A fuel cell stack configured by electrically connecting the plurality of cells in series.

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