JP5685463B2 - Fuel cell - Google Patents

Description

  The present invention relates to a fuel cell.

  Fuel cells are expected to be put to practical use as new power sources for portable electronic devices that support the information society. Fuel cells are classified into a phosphoric acid type, a molten carbonate type, a solid electrolyte type, a solid polymer type, a direct alcohol type, and the like according to the classification of the electrolyte material and fuel used. In particular, solid polymer fuel cells and direct alcohol fuel cells that use an ion exchange membrane, which is a solid polymer, as the electrolyte material can achieve high power generation efficiency at room temperature. Practical application as a small fuel cell is under study.

  The direct alcohol fuel cell that uses alcohol or an aqueous alcohol solution as the fuel has a simplified structure of the fuel cell because the fuel storage chamber can be designed relatively easily compared to the case where the fuel is a gas. Space-saving is possible, and the expectation as a small fuel cell for the purpose of application to portable electronic devices is particularly high.

In a direct alcohol fuel cell that uses a cation exchange membrane as an electrolyte membrane, when fuel (alcohol or an alcohol aqueous solution) is supplied to the fuel electrode, the fuel is oxidized and a gas such as carbon dioxide (hereinafter referred to as byproduct gas). ) And protons. For example, when methanol is used as the alcohol,
CH ₃ OH + H ₂ O → CO ₂ ↑ + 6H ⁺ + 6e ⁻
By the oxidation reaction, carbon dioxide is generated on the fuel electrode side as a by-product gas.

Protons generated on the fuel electrode side are transmitted to the air electrode side through the electrolyte membrane. And the proton and oxygen in the air supplied to the air electrode are
3 / 2O ₂ + 6H ⁺ + 6e ⁻ → 3H ₂ O
This causes a reduction reaction of water to produce water. At this time, electrons pass through an external electronic device (load), move from the fuel electrode to the air electrode, and electric power is taken out.

  In a fuel cell using liquid fuel (hereinafter referred to as liquid fuel) such as a direct alcohol fuel cell, a liquid supply system for supplying the liquid fuel to the fuel electrode as it is and a vaporized component of the liquid fuel as the fuel. There is a vaporization supply system that supplies to the pole. For example, Patent Document 1 discloses a fuel cell of a vaporization supply system in which a gas-liquid separation film that allows vaporized fuel (hereinafter referred to as vaporized fuel) to pass between a liquid fuel storage chamber and a fuel electrode is disposed. ing.

International Publication No. 2008/023633

  In a fuel cell in which a gas-liquid separation membrane capable of transmitting gas is disposed between a liquid fuel storage chamber and a fuel electrode in order to obtain a vaporization supply system as described in Patent Document 1, the fuel electrode The produced by-product gas enters the liquid fuel storage chamber through the gas-liquid separation membrane. The intrusion of by-product gas into the liquid fuel storage chamber reduces the amount of liquid fuel in contact with the gas-liquid separation membrane, resulting in a decrease in the amount of vaporized fuel supplied to the fuel electrode and a stable supply of vaporized fuel. And the output stability of the fuel cell is lowered.

  The present invention has been made to solve the above problems, and an object thereof is to provide a fuel cell having good output stability.

  The present invention is a fuel cell comprising a unit cell having a fuel electrode, an electrolyte membrane, and an air electrode in this order, and a fuel supply unit that is disposed on the fuel electrode side of the unit cell and supplies fuel to the fuel electrode. The fuel supply unit is a space that is open on the fuel electrode side, and has a fuel supply chamber for circulating or containing liquid fuel (liquid fuel), and a fuel supply chamber so as to cover the opening of the fuel supply chamber A first region having a bubble point of 30 kPa or more when the measurement medium is methanol. And a second region provided on the unit cell side in the thickness direction and capable of transmitting vaporized fuel (vaporized fuel).

  The intervening layer is preferably disposed on the fuel supply chamber so as to cover the opening of the fuel supply chamber, the first layer having a bubble point of 30 kPa or more when the measurement medium is methanol, and the unit cell in the first layer It is laminated on the side surface and has a two-layer structure composed of a second layer that can permeate vaporized fuel.

  The fuel cell of the present invention can further include a third layer having a through hole penetrating in the thickness direction between the first layer and the second layer. A preferable example of the third layer is a thermoplastic resin sheet having a plurality of through holes penetrating in the thickness direction. Other preferable examples of the third layer include a porous layer formed from an adhesive resin or resin composition, and a metal plate having a plurality of through holes penetrating in the thickness direction. it can.

  The unit cell preferably further includes an anode current collecting layer laminated on the fuel electrode and a cathode current collecting layer laminated on the air electrode. As the fuel, pure methanol or an aqueous methanol solution can be preferably used.

  According to the present invention, it is possible to prevent the by-product gas generated at the fuel electrode from entering the fuel supply chamber. As a result, a sufficient amount of vaporized fuel can be stably supplied to the fuel electrode, so that good output stability can be maintained. The fuel cell of the present invention is suitable as a small fuel cell intended for application to a portable electronic device, particularly as a small fuel cell mounted on a portable electronic device.

It is a schematic sectional drawing which shows an example of the fuel cell of this invention. FIG. 2 is a schematic top view of the fuel cell shown in FIG. 1. It is a schematic sectional drawing in the III-III line | wire shown by FIG. It is a schematic sectional drawing in the IV-IV line shown by FIG. It is a schematic sectional drawing in the VV line shown by FIG. It is a schematic sectional drawing which shows another example of a fuel supply part. It is a schematic sectional drawing which shows another example of a fuel supply part. It is a schematic sectional drawing which shows another example of the fuel cell of this invention. It is a schematic sectional drawing which shows another example of the fuel cell of this invention. FIG. 10 is a schematic top view showing a third layer provided in the fuel cell shown in FIG. 9. 3 is a schematic top view showing a first layer of an intervening layer used in Example 1. FIG. 3 is a schematic top view showing a second layer of the intervening layer used in Example 1. FIG. 3 is a schematic top view showing a box housing used in Example 1. FIG. 6 is a schematic top view showing a third layer of the intervening layer used in Example 3. FIG.

Hereinafter, the fuel cell of the present invention will be described in detail with reference to embodiments.
<First Embodiment>
FIG. 1 is a schematic cross-sectional view showing a fuel cell of the present embodiment, and FIG. 2 is a schematic top view of the fuel cell. 3 to 5 are sectional views taken along lines III-III, IV-IV and VV shown in FIG. 1, respectively. The fuel cell 100 of the present embodiment shown in these drawings is laminated on the fuel electrode 11 and the membrane electrode assembly 20 including the fuel electrode 11, the electrolyte membrane 10 and the air electrode 12 in this order, and electrically A unit cell 30 comprising: an anode current collecting layer 21 connected to the cathode; and a cathode current collecting layer 22 laminated on the air electrode 12 and electrically connected thereto; A fuel supply chamber 60 composed of a space opened on the 11 side; a first layer 1 disposed on the fuel supply chamber 60 so as to cover an opening of the fuel supply chamber 60 (an open surface to the fuel electrode side), and a first layer 1 is basically composed of an intervening layer comprising a second layer 2 laminated on the surface of the unit cell 30; and a fuel storage chamber 70 for containing fuel (not shown).

  A fuel supply section of the fuel cell 100 is formed by a fuel storage chamber 70 that stores liquid fuel, a fuel supply chamber 60 that circulates the fuel, and an intermediate layer that is disposed so as to cover the opening of the fuel supply chamber 60. Yes. The fuel storage chamber 70 and the fuel supply chamber 60 are connected by a flow path.

  The box housing 40 has a recess (groove) that forms the fuel supply chamber 60, and the fuel supply chamber 60 (internal space) is formed by laminating the first layer 1 so as to cover the recess. . Further, the box housing 40 has a portion constituting the fuel supply chamber 60 of the fuel cell 100 and a portion constituting the bottom wall and side wall of the fuel storage chamber 70 as an integral unit.

  The fuel cell 100 according to this embodiment includes a by-product gas discharge unit 90 for discharging the by-product gas generated at the fuel electrode 11 to the outside of the fuel cell. In the present embodiment, the by-product gas discharge unit 90 includes a first through hole 91 that penetrates the side wall of the box housing 40 in the thickness direction and a second through hole 92 that penetrates the first layer 1 in the thickness direction (FIG. 4 and FIG. 5). The second through hole 92 is disposed immediately above the first through hole 91, and these through holes communicate with each other.

  The fuel cell 100 of the present embodiment includes a box housing 40 and a lid housing 50 that is stacked on the cathode current collecting layer 22 and has a plurality of openings 51, and the unit cell 30 includes the box housing 40 and the lid housing 50. It is pinched by. The lid housing 50 integrally has a portion constituting the upper wall (ceiling wall) of the fuel storage chamber 70 together with a portion laminated on the cathode current collecting layer 22, and the box housing 40, the lid housing 50, and A fuel storage chamber 70 is formed by side surfaces of the unit cell 30 and the like. A sealing layer 80 made of a cured product layer of an epoxy curable resin composition or the like is formed on the end surfaces of the unit cell 30 and the intervening layer so that the fuel stored in the fuel storage chamber 70 does not enter. Has been. In the fuel cell 100 of the present embodiment, the fuel storage chamber 70 is disposed on the side of the unit cell 30 and the fuel supply chamber 60 disposed below the unit cell 30.

  The fuel storage chamber 70 includes an opening 71 that communicates the internal space with the outside of the fuel cell 100. The opening 71 is a through hole provided in the lid housing 50.

The fuel cell 100 of the present embodiment generates power by the following operation. The liquid fuel that has flowed from the fuel storage chamber 70 into the fuel supply chamber 60 through the flow channel reaches the entire fuel supply chamber 60 and wets the first layer 1 of the intervening layer. The liquid fuel exuded from the first layer 1 is gas-liquid separated by the second layer 2, and only the vaporized fuel permeates to the unit cell 30 side. The vaporized fuel that has passed through the second layer 2 is supplied to the fuel electrode 11 through the opening of the anode current collecting layer 21. And as an example of an aqueous methanol solution as the liquid fuel, the gaseous methanol aqueous solution supplied to the fuel electrode 11 is:
CH ₃ OH + H ₂ O → CO ₂ ↑ + 6H ⁺ + 6e ⁻
This causes an oxidation reaction represented by the formula: The vaporized fuel will be consumed according to the amount of current generated by the fuel cell 100. To compensate for this, the liquid fuel continues to evaporate from the second layer 2 at any time. The vapor pressure of is kept substantially constant.

On the other hand, in the air electrode 12, oxygen in the air that has reached through the opening 51 of the lid housing 50 and the opening of the cathode current collecting layer 22 and the fuel electrode 11 are transmitted to the air electrode 12 through the electrolyte membrane 10. Proton
3 / 2O ₂ + 6H ⁺ + 6e ⁻ → 3H ₂ O
The reduction reaction represented by the formula Through the above oxidation-reduction reaction, electrons move in the route of the fuel electrode 11 → the anode current collecting layer 21 → the external electronic device (load) → the cathode current collecting layer 22 → the air electrode 12, and the electrons are transferred to the external electronic device. Power is supplied.

By-product gas (CO ₂ in the above formula) generated by the power generation by power generation does not enter the fuel supply chamber 60 due to the presence of the intervening layer, and the opening of the anode current collecting layer 21, the second layer 2 and It is discharged to the outside of the fuel cell through the byproduct gas discharge unit 90.

  The intervening layer composed of the first layer 1 and the second layer 2 disposed between the fuel supply chamber 60 and the unit cell 30 is in a state where the fuel supply to the fuel electrode 11 is uniformly controlled to an appropriate amount. Makes it possible to do with Thereby, fuel crossover can be effectively suppressed, temperature unevenness hardly occurs in the power generation unit, and a stable power generation state can be maintained.

Next, each member constituting the fuel cell 100 will be described in detail.
[Intervening layer]
(1) First layer The fuel supply chamber 60 and the unit cell 30 cover the opening of the fuel supply chamber 60 (the open surface to the fuel electrode side) (that is, cover the recess forming the fuel supply chamber 60). The intervening layer disposed between the first layer 1 and the first layer 1 stacked on the fuel supply chamber 60 so as to cover the opening of the fuel supply chamber 60 as in the example shown in FIG. The two-layer structure of the second layer 2 stacked on the unit battery 30 side surface may be employed. The first layer 1 is a layer having a bubble point of 30 kPa or more when the measurement medium is methanol. By arranging the first layer 1 so as to cover the opening of the fuel supply chamber 60, the first layer 1 Since liquid fuel is held in the pores of 1 by capillary force, it is possible to effectively prevent the by-product gas (such as CO ₂ gas) generated in the fuel electrode 11 from entering the fuel supply chamber 60. . Thereby, since it can prevent that the supply amount of the vaporized fuel to the fuel electrode 11 falls or the stable supply of vaporized fuel is inhibited, the output stability of a fuel cell can be maintained favorably. In addition, since the by-product gas permeates and the internal pressure of the fuel supply chamber 60 increases, peeling at the interface between the constituent members and destruction of the constituent members can be suppressed, so that the reliability of the fuel cell can be improved.

The installation of the first layer 1 is also advantageous in the following points.
(A) Since the liquid fuel can be transported from the fuel storage chamber 70 into the fuel supply chamber 60 by using the capillary force of the first layer 1, the liquid fuel can be passively supplied. Thereby, auxiliary machines, such as a pump for sending liquid fuel, can be omitted. In addition, since fuel supply by capillary force is possible, the dependency on the direction of fuel supply can be eliminated (that is, power generation can be performed regardless of the direction when the fuel cell is used).

  (B) When a low thermal conductivity material such as a polymer material is used for the first layer, the liquid fuel held in the first layer is less susceptible to the sudden temperature rise of the power generation unit, The temperature rise becomes slow. As a result, since the liquid fuel held in the first layer can be stably maintained at a relatively low temperature, the supply amount of vaporized fuel supplied to the fuel electrode can be stabilized. This contributes to improving the reliability of the fuel cell.

  (C) Since liquid fuel is uniformly spread and held in the first layer surface, vaporized fuel can be supplied uniformly to the fuel electrode surface, and a local excessive supply of fuel to the power generation unit, Since there is no fuel shortage, deterioration of materials such as catalysts can be suppressed. This contributes to improved output and improved fuel cell reliability.

  (D) Generated in the fuel electrode 11 by increasing the pressure in the fuel supply chamber 60 by a method such as pumping the liquid fuel stored in the fuel storage chamber 70 to the fuel supply chamber 60 using a pumping means such as a pump. Although it is possible to prevent the by-product gas from entering the fuel supply chamber 60 to some extent, the effect of preventing the infiltration by the first layer 1 exceeds this, so the internal pressure in the fuel supply chamber 60 is increased. There is no need. Thereby, the risk of liquid leakage due to an increase in internal pressure can be avoided, and the reliability of the fuel cell can be improved.

  (E) Since the by-product gas does not enter even when the internal pressure in the fuel electrode 11 increases, the diameter of the through-hole constituting the by-product gas discharge unit 90 can be further reduced. As a result, the discharge of unused vaporized fuel can be reduced, so that the fuel utilization efficiency can be improved (this effect will be described in detail later).

Here, the bubble point is the minimum pressure at which bubbles are observed on the surface of the layer (film) when air pressure is applied from the back side of the layer (film) wetted with the liquid medium. The higher the bubble point, the lower the gas permeability. The bubble point ΔP is expressed by the following formula (1):
ΔP [Pa] = 4γcos θ / d (1)
(Γ is the surface tension [N / m] of the measurement medium, θ is the contact angle between the material of the layer (film) and the measurement medium, and d is the maximum pore diameter of the layer (film)).
Defined by In the present invention, the bubble point is measured according to JIS K3832, using methanol as the measurement medium.

  From the viewpoint of effectively preventing the by-product gas from entering the fuel supply chamber 60, the bubble point of the first layer 1 is preferably 50 kPa or more, and more preferably 100 kPa or more. As understood from the above (1), the bubble point of the first layer 1 can be controlled by adjusting the pore diameter and the contact angle of the material used as the first layer 1.

  In order to achieve a bubble point of 30 kPa or more, the maximum pore diameter of the pores of the first layer 1 is preferably 1 μm or less, and more preferably 0.7 μm or less. The maximum pore diameter can be obtained by measuring the bubble point, but can be measured by mercury porosimetry as another method. However, since the mercury intrusion method can measure only a pore distribution of 0.005 μm to 500 μm, it is an effective measuring means when pores outside this range do not exist or can be ignored.

  Examples of the first layer 1 include a porous layer made of a polymer material, a metal material, an inorganic material, or the like, or a polymer film. Specific examples are as follows.

  1) A porous layer made of the following materials. Fluorine resins such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE); acrylic resins; ABS resins; polyolefin resins such as polyethylene and polypropylene; polyester resins such as polyethylene terephthalate; cellulose acetate and nitrocellulose Cellulose resins such as ion exchange cellulose; Nylon; Polycarbonate resins; Chlorine resins such as polyvinyl chloride; Polyetheretherketone; Polyethersulfone; Glass; Ceramics; Stainless steel, titanium, tungsten, nickel, aluminum, steel, etc. Metal material. The porous layer can be a foam, a sintered body, a nonwoven fabric or a fiber (such as glass fiber) made of these materials.

  2) A polymer film made of the following materials. Perfluorosulfonic acid polymer; styrene graft polymer, trifluorostyrene derivative copolymer, sulfonated polyarylene ether, sulfonated polyetheretherketone, sulfonated polyimide, sulfonated polybenzimidazole, phosphonated polybenzimidazole Those that can be used as electrolyte membrane materials such as hydrocarbon polymers such as sulfonated polyphosphazene. These polymer films have nano-order pores as gaps between polymers that are three-dimensionally entangled.

  When a polymer material is used as the material constituting the first layer 1, it is subjected to a hydrophilization treatment by a method such as introduction of a hydrophilic functional group, and water on the pore surface (thus, fuel such as methanol or methanol aqueous solution). The bubble point of the 1st layer 1 can also be raised by improving the wettability with respect to. In addition, by applying a hydrophilization treatment to the first layer 1, the liquid fuel can be circulated in the fuel supply chamber 60 with a lower pressure loss.

  Although the thickness in particular of the 1st layer 1 is not restrict | limited, From a viewpoint of thickness reduction of a fuel cell, Preferably it is 20-500 micrometers, More preferably, it is 50-200 micrometers.

  The first layer 1 is provided with a second through hole 92 that forms a part of the by-product gas discharge unit 90. The second through hole 92 is formed at a position where it communicates with the first through hole 91 when the first layer 1 is stacked on the box housing 40 (that is, directly above the first through hole 91).

(2) Second Layer The second layer 2 stacked on the surface of the first layer 1 on the unit cell 30 side is a porous layer having a hydrophobic property of vaporized fuel permeability and liquid fuel impermeability, and the fuel electrode 11. This is a layer (gas-liquid separation layer) that enables vaporization and supply of fuel to the tank. The second layer 2 has a function of controlling (limiting) the amount or concentration of vaporized fuel supplied to the fuel electrode 11 to an appropriate amount and making it uniform. By providing the second layer 2, it is possible to effectively suppress the crossover of the fuel, to prevent temperature unevenness from occurring in the power generation unit, and to maintain a stable power generation state.

  The second layer 2 is not particularly limited as long as it has gas-liquid separation ability with respect to the fuel to be used. For example, fluorine resin such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride, water repellent treatment is performed. In particular, a porous film or a porous sheet made of silicone resin or the like can be mentioned. Specifically, it is a porous film made of polytetrafluoroethylene made by Nitto Denko Co., Ltd. Temish [TEMISH (registered trademark)]. Examples thereof include “NTF2026A-N06” and “NTF2122A-S06”.

  Since the second layer 2 has vaporized fuel permeability, the second layer 2 has a bubble point smaller than that of the first layer 1. The bubble point according to the measurement method of the second layer 2 is preferably 10 kPa or less, and the larger the contact angle of methanol with respect to the second layer 2, the better, preferably 45 degrees or more, more preferably about 90 degrees or more. . Further, from the viewpoint of imparting vaporized fuel permeability and liquid fuel impermeability, the maximum pore diameter of the pores of the second layer 2 is preferably 0.1 to 10 μm, and preferably 0.5 to 5 μm. It is more preferable. The maximum pore diameter of the pores of the second layer 2 can be determined by measuring the bubble point using methanol or the like as in the first layer 1.

  Although the thickness in particular of the 2nd layer 2 is not restrict | limited, In order to fully express the said function, it is preferable that it is 20 micrometers or more, and it is more preferable that it is 50 micrometers or more. Further, from the viewpoint of reducing the thickness of the fuel cell, the thickness of the second layer 2 is preferably 500 μm or less, and more preferably 300 μm or less.

[Electrolyte membrane]
The electrolyte membrane 10 constituting the membrane electrode assembly 20 has a function of transmitting protons from the fuel electrode 11 to the air electrode 12, and a function of maintaining electrical insulation between the fuel electrode 11 and the air electrode 12 and preventing a short circuit. Have. The material of the electrolyte membrane is not particularly limited as long as it has proton conductivity and electrical insulation, and a polymer membrane, an inorganic membrane, or a composite membrane can be used. As the polymer membrane, for example, Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei), Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.), which is a perfluorosulfonic acid electrolyte membrane, etc. Can be mentioned. Also, styrene-based graft polymer, trifluorostyrene derivative copolymer, sulfonated polyarylene ether, sulfonated polyetheretherketone, sulfonated polyimide, sulfonated polybenzimidazole, phosphonated polybenzimidazole, sulfonated polyphosphazene. Hydrocarbon electrolyte membranes such as can also be used.

  Examples of the inorganic film include films made of phosphate glass, cesium hydrogen sulfate, polytungstophosphoric acid, ammonium polyphosphate, and the like. Examples of the composite film include a composite film of an inorganic material such as tungstic acid, cesium hydrogen sulfate, and polytungstophosphoric acid and an organic material such as polyimide, polyetheretherketone, and perfluorosulfonic acid.

  The thickness of the electrolyte membrane 10 is, for example, 1 to 200 μm. The EW value (dry weight per mole of proton functional groups) of the electrolyte membrane 10 is preferably about 800 to 1100. The smaller the EW value, the smaller the resistance of the electrolyte membrane accompanying proton transfer, and a higher output can be obtained.

[Fuel electrode and air electrode]
The fuel electrode 11 laminated on one surface of the electrolyte membrane 10 and the air electrode 12 laminated on the other surface are provided with a catalyst layer composed of a porous layer having at least a catalyst and an electrolyte. The catalyst for the fuel electrode 11 catalyzes a reaction that generates protons and electrons from a liquid fuel such as an aqueous methanol solution, and the electrolyte has a function of conducting the generated protons to the electrolyte membrane 10. The catalyst for the air electrode 12 catalyzes a reaction that generates water from protons that have been conducted through the electrolyte and oxygen in the air.

  The catalyst for the fuel electrode 11 and the air electrode 12 may be supported on the surface of a conductor such as carbon or titanium, among which carbon or titanium having a hydrophilic functional group such as a hydroxyl group or a carboxyl group. It is preferably carried on the surface of the conductor. Thereby, the water retention of the fuel electrode 11 and the air electrode 12 can be improved. The electrolyte of the fuel electrode 11 and the air electrode 12 is preferably made of a material having an EW value smaller than the EW value of the electrolyte membrane 10. Specifically, the electrolyte is the same material as the electrolyte membrane 10, but the EW value. An electrolyte material having a thickness of 400 to 800 is preferred. The water retention of the fuel electrode 11 and the air electrode 12 can also be improved by using such an electrolyte material. By improving the water retention of the fuel electrode 11 and the air electrode 12, it is possible to improve the resistance of the electrolyte membrane 10 accompanying proton transfer and the potential distribution in the fuel electrode 11 and the air electrode 12. In addition, since the electrolyte with a low EW value has a high liquid fuel permeability, vaporized fuel can be uniformly supplied to the catalyst layer of the fuel electrode 11 by using an electrolyte with a low EW value.

  Each of the fuel electrode 11 and the air electrode 12 may include an anode conductive porous layer and a cathode conductive porous layer laminated on the catalyst layer. These conductive porous layers have a function of diffusing gas (vaporized fuel or air) supplied to the fuel electrode 11 and the air electrode 12 in the plane, and a function of transferring electrons to and from the catalyst layer. As the anode conductive porous layer and the cathode conductive porous layer, since the specific resistance is small and the decrease in voltage is suppressed, carbon materials; conductive polymers; noble metals such as Au, Pt, Pd; Ti, Porous materials comprising transition metals such as Ta, W, Nb, Ni, Al, Cu, Ag, Zn; nitrides or carbides of these metals; and alloys containing these metals typified by stainless steel Is preferably used. In the case of using a metal having poor corrosion resistance in an acidic atmosphere, such as Cu, Ag, Zn, etc., noble metals having resistance to corrosion such as Au, Pt, Pd, conductive polymers, conductive nitrides, conductive Surface treatment (film formation) may be performed with carbide, conductive oxide, or the like. More specifically, as the anode conductive porous layer and the cathode conductive porous layer, for example, foam metal, metal fabric and metal sintered body made of the above-mentioned noble metal, transition metal or alloy; and carbon paper, carbon cloth, An epoxy resin film containing carbon particles can be suitably used.

[Anode current collecting layer and cathode current collecting layer]
The anode current collecting layer 21 and the cathode current collecting layer 22 are laminated on the fuel electrode 11 and the air electrode 12, respectively, and constitute a unit cell 30 together with the membrane electrode assembly 20. Each of the anode current collecting layer 21 and the cathode current collecting layer 22 has a function of collecting electrons in the fuel electrode 11 and the air electrode 12 and a function of performing electrical wiring. The material of the current collecting layer is preferably a metal because it has a small specific resistance and suppresses a decrease in voltage even when a current is taken in the plane direction. In particular, it has electron conductivity and has an acidic atmosphere. More preferably, the metal has corrosion resistance. Such metals include noble metals such as Au, Pt, Pd; transition metals such as Ti, Ta, W, Nb, Ni, Al, Cu, Ag, Zn; and nitrides or carbides of these metals; and And alloys containing these metals typified by stainless steel. In the case of using a metal having poor corrosion resistance in an acidic atmosphere, such as Cu, Ag, Zn, etc., noble metals having resistance to corrosion such as Au, Pt, Pd, conductive polymers, conductive nitrides, conductive Surface treatment (film formation) may be performed with carbide, conductive oxide, or the like. When the anode conductive porous layer and the cathode conductive porous layer are made of, for example, metal and the conductivity is relatively high, the anode current collecting layer and the cathode current collecting layer may be omitted.

More specifically, the anode current collecting layer 21 is provided with a plurality of through holes (openings) penetrating in the thickness direction for guiding the vaporized fuel to the fuel electrode 11, and has a mesh shape or a punching metal shape made of the above metal material or the like. It can be a flat plate. This through-hole also functions as a path for guiding by-product gas (such as CO ₂ gas) generated in the catalyst layer of the fuel electrode 11 to the by-product gas discharge unit 90. Similarly, the cathode current collecting layer 22 has a mesh shape made of the above metal material or the like having a plurality of through holes (openings) penetrating in the thickness direction for supplying air outside the fuel cell to the catalyst layer of the air electrode 12 or It can be a flat plate having a punching metal shape.

[Fuel supply chamber]
The fuel supply chamber 60, together with a fuel storage chamber 70 to be described later, is a part that constitutes a fuel supply part that plays a role of fuel storage and fuel supply, and is preferably disposed immediately below the fuel electrode 11. In the fuel cell 100 of the present embodiment shown in FIG. 1, the fuel supply chamber 60 has a length equal to or longer than the length from the end of the fuel electrode 11 on the fuel storage chamber 70 side to the opposite end thereof. And a space having a width equal to or greater than the width of the fuel electrode 11. The height (depth) of the fuel supply chamber 60 is not particularly limited.

  In the fuel cell 100 of the present embodiment, the fuel supply chamber 60 includes a box housing 40 having a concave portion that constitutes an internal space of the fuel supply chamber 60, disposed in contact with the intervening layer below the unit cell 30, and an intervening layer And is formed by. The box housing 40 shown in FIG. 1 integrally has a portion constituting the fuel supply chamber 60 and a portion constituting the bottom wall and side wall of the fuel storage chamber 70, but is not limited thereto. Instead, the member constituting the fuel supply chamber 60 and the member constituting the fuel storage chamber 70 may be different members.

  The box housing 40 can be manufactured by using a plastic material or a metal material and molding it into an appropriate shape so as to have at least a recess that constitutes the internal space of the fuel supply chamber 60. Examples of the plastic material include polyphenylene sulfide (PPS), polymethyl methacrylate (PMMA), acrylonitrile butadiene styrene (ABS), polyvinyl chloride, polyethylene (PE), polyethylene terephthalate (PET), polyether ether ketone (PEEK). ), Polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and the like. As the metal material, for example, alloy materials such as stainless steel and magnesium alloy can be used in addition to titanium and aluminum. Among these, polyphenylene sulfide (PPS) and polyethylene (PE) are preferably used because they have high strength and can be processed inexpensively due to an increase in molecular weight due to three-dimensional crosslinking, and are lightweight.

[By-product gas discharge section]
The fuel cell 100 according to this embodiment includes a by-product gas discharge unit 90 for discharging the by-product gas generated at the fuel electrode 11 to the outside of the fuel cell. In the present embodiment, the by-product gas discharge unit 90 includes a first through hole 91 that penetrates the side wall of the box housing 40 in the thickness direction and a second through hole 92 that penetrates the first layer 1 in the thickness direction (FIG. 4 and FIG. 5). The second through hole 92 is disposed immediately above the first through hole 91, and these through holes communicate with each other. By providing the by-product gas discharge part 90, an excessive increase in internal pressure in the fuel electrode 11 can be prevented.

  As described above, in the fuel cell according to the present invention, the inclusion of the intervening layer effectively prevents the by-product gas from entering the fuel supply chamber 60, so that the internal pressure in the fuel electrode 11 is temporarily increased. However, there is no possibility that the by-product gas enters the fuel supply chamber 60. Therefore, there is an advantage that the diameter of the through hole constituting the by-product gas discharge unit 90 can be made smaller to allow the internal pressure in the fuel electrode 11 to rise to some extent. The by-product gas discharge unit 90 can provide a route through which unused vaporized fuel (vaporized fuel before reaching the fuel electrode 11) is discharged to the outside of the fuel cell. The reduction in the diameter of the hole is extremely advantageous for reducing the amount of unused vaporized fuel discharged, thereby improving the fuel utilization efficiency. Since the conventional fuel cell does not have means for preventing the by-product gas from entering the fuel supply chamber, when providing a path for discharging the by-product gas, the internal pressure in the fuel electrode 11 is prevented from rising. The diameter of the fuel must be increased, and the fuel utilization efficiency has been reduced.

  The means for discharging the by-product gas to the outside of the fuel cell includes a first through hole 91 and a second through hole 92 as shown in FIGS. 4 and 5 which the fuel cell 100 of the present embodiment has. It is not limited to the by-product gas discharge part 90, and any path extending from the vicinity of the fuel electrode 11 to the outside of the fuel cell may be used. For example, an intervening layer is not disposed on the first through hole 91 of the box housing 40 (the size of the intervening layer is reduced), and the first through hole 91 is extended to the anode current collecting layer 21 accordingly. There may be. In this case, the by-product gas discharge unit is composed only of the first through hole 91 and does not have the second through hole 92. Moreover, a through-hole penetrating in the thickness direction may be provided in the electrolyte membrane, and the by-product gas may be discharged to the air electrode side. The by-product gas discharged from the through hole is oxidized at the air electrode, so that the air electrode is not formed at a position directly above the through hole so that the output characteristics of the fuel cell are not deteriorated or the air is not excessively consumed. The structure which provides an area | region may be sufficient. In this case, the by-product gas discharge part is composed of a continuous space in a region where the through hole of the electrolyte membrane and the air electrode are not formed, and the by-product gas is discharged to the air electrode side.

[Fuel storage room]
The fuel storage chamber 70 is a chamber for storing liquid fuel, which is preferably disposed on the side of the unit cell 30 and the fuel supply chamber 60. In the fuel cell 100 of this embodiment, the fuel storage chamber 70 is formed by a lid housing 50, a box housing 40, a unit cell 30 and an intervening layer that are stacked on the cathode current collecting layer 22 and have a plurality of openings 51. The end surfaces of the unit cell 30 and the intervening layer on the fuel storage chamber side are sealed with a sealing layer 80 made of a cured product of an epoxy curable resin composition or the like so that the fuel stored in the fuel storage chamber 70 does not enter. ing.

  The fuel storage chamber 70 does not necessarily need to be configured using the lid housing 50 and the box housing 40. For example, the fuel storage chamber 70 has a portion that forms an upper wall (ceiling wall), a side wall, and a bottom wall. It can also be comprised from one member included as one.

  In the fuel cell 100 of the present embodiment, the lid housing 50 functions as a protective plate that forms the upper wall (ceiling wall) of the fuel storage chamber 70 and prevents the unit cell 30 from being directly exposed. A plurality of openings 51 for allowing air to circulate (however, the number of openings may be one or more) is formed in a portion of the lid housing 50 immediately above the air electrode 12.

  The lid housing 50 can be manufactured by using a plastic material or a metal material and molding it into an appropriate shape. Examples of the plastic material include polyphenylene sulfide (PPS), polymethyl methacrylate (PMMA), acrylonitrile butadiene styrene (ABS), polyvinyl chloride, polyethylene (PE), polyethylene terephthalate (PET), polyether ether ketone (PEEK). ), Polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and the like. As the metal material, for example, alloy materials such as stainless steel and magnesium alloy can be used in addition to titanium and aluminum. Among these, polyphenylene sulfide (PPS) and polyethylene (PE) are preferably used because they have high strength and can be processed inexpensively due to an increase in molecular weight due to three-dimensional crosslinking, and are lightweight.

  The fuel storage chamber 70 preferably includes an opening 71 that communicates the internal space with the outside of the fuel cell. Thereby, even when the liquid fuel is transported to the fuel supply chamber 60, since the inside of the fuel storage chamber 70 is maintained at the atmospheric pressure, the liquid fuel can be transported smoothly. In the fuel cell 100 shown in FIG. 1, the opening 71 is a through-hole penetrating the lid housing 50 in the thickness direction, but is not limited thereto.

  In order to prevent leakage of the liquid fuel from the opening 71, the opening 71 preferably has a sufficiently small opening diameter (for example, a diameter of about 100 to 500 μm, preferably 100 to 300 μm), or to the outside of the fuel cell. A gas-liquid separation membrane (for example, a porous membrane made of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, or the like) for preventing leakage of liquid fuel may be provided in the opening 71.

(Modification)
The fuel cell according to the present embodiment is not limited to the above-described modifications, and includes, for example, the following modifications. The modifications described in this embodiment can be applied to other embodiments described later.

  (1) In the above embodiment, the intervening layer has a two-layer structure of the first layer 1 disposed so as to cover the opening of the fuel supply chamber and the second layer 2 stacked on the first layer 1. However, a single-layer structure having a region having the same functional characteristics as the first layer 1 and a region having the same functional characteristics as the second layer 2 can be used as the intervening layer. The “single-layer structure” referred to here is composed of one member and means that it is not a combination of two members. Such an intervening layer having a one-layer structure is advantageous in that poor adhesion (formation of a gap) between the first layer and the second layer, which can occur in a two-layer structure, cannot occur. If a gap is formed at a part of the interface, the by-product gas stays in the gap, resulting in variations in the amount of vaporized fuel that is excessively supplied or fuel is insufficient in the second layer surface, There is a possibility that the gap is widened by the pressure and the fuel supply chamber is blocked and fuel supply is hindered.

  More specifically, the intervening layer having a single-layer structure has the same functional characteristics as those of the first layer 1, which is a region on the fuel supply chamber 60 side in the thickness direction (bubbles when the measurement medium is methanol). A first region (having a point of 30 kPa or more) and a second region having the same functional characteristics as the second layer 2 (permeating vaporized fuel), which is a region on the unit cell 30 side in the thickness direction thereof The provided layer can be used. The bubble point of the 1st area | region which the intervening layer of 1 layer structure has is synonymous with the bubble point of the intervening layer of 1 layer structure. Similar to the relationship between the first layer 1 and the second layer 2, the bubble point of the second region is smaller than that of the first region, and the bubble point of the entire intervening layer matches that of the region where the bubble point is larger. It is.

  The intervening layer having a single-layer structure can be produced, for example, by a method of hydrophilizing only one region in the thickness direction of the porous layer that can be used as the second layer and increasing the bubble point of the region. it can.

  Such an intervening layer having a one-layer structure is advantageous in that poor adhesion (formation of a gap) between the first layer and the second layer, which can occur in a two-layer structure, cannot occur. If a gap is formed in a part of the interface, there is a possibility that the amount of vaporized fuel permeated in the second layer surface varies, and the fuel cannot be supplied uniformly to the fuel electrode, resulting in a decrease in output. Such a problem cannot occur if the intervening layer has a single layer structure. On the other hand, when using an intervening layer having a two-layer structure, in order to cope with the above problem, the fuel cell is fastened from above and below using a fastening member such as a bolt, nut or screw, It is preferable to ensure adhesion with the second layer.

  (2) The space shape of the fuel supply chamber 60 is not limited to that shown in FIG. The fuel supply chamber 60 may be formed of a plurality of branched flow paths as shown in FIG. 6, for example. Alternatively, it can be formed from a plurality of line-shaped channels, serpentine-shaped channels, and the like. FIG. 6 is a schematic sectional view similar to FIG. 4 showing another example of the fuel supply chamber.

  (3) FIG. 7 is a schematic sectional view similar to FIG. 4 showing another example of the fuel supply unit. As shown in FIG. 7, the fuel supply unit may include a fuel transport member 61 in addition to the intervening layer, the fuel supply chamber 60 and the fuel storage chamber 70. The fuel transport member 61 is a member that is disposed at least partially in the fuel supply chamber 60 and transports liquid fuel from the fuel storage chamber 70 to the fuel supply chamber 60 by utilizing capillary action. It plays the role which assists the liquid fuel transport using the capillary force of 1.

  The fuel transport member 61 is made of a material that exhibits a capillary action with respect to the liquid fuel. Examples of the material exhibiting such capillary action include acrylic resins, ABS resins, polyolefin resins such as polyethylene, polyester resins such as polyethylene terephthalate, nylon, polyvinyl chloride, polyether ether ketone, polyvinylidene fluoride, poly Fluorine resin such as tetrafluoroethylene; porous body having irregular pores made of polymer material (plastic material) such as cellulose; non-made of metal material such as stainless steel, titanium, tungsten, nickel, aluminum, steel Examples thereof include a porous body having regular pores. As a porous body, the nonwoven fabric which consists of the said metal material, a foam, a sintered compact, the nonwoven fabric which consists of the said polymeric material, etc. can be mentioned. Further, a plate-like body made of the above polymer material or metal material and having a regular or irregular slit pattern (groove pattern) on the surface as a capillary tube can be used as the fuel transport member 61.

  The pore diameter of the pores of the fuel transport member 61 is such that a sufficient capillary action with respect to gravity occurs, and a good suction height (the liquid fuel due to the capillary action when one end of the fuel transport member is immersed in the liquid fuel) In order to obtain a reachable position in the member) and a sucking speed (meaning a volume of liquid fuel sucked up per unit time when one end of the fuel transport member is immersed in the liquid fuel) It is preferable to set it as 500 micrometers, and it is more preferable to set it as 1-300 micrometers. The pore diameter of the pores of the fuel transport member 61 is a diameter measured by a mercury intrusion method.

  As a material showing the capillary action constituting the fuel transport member 61, it is preferable to use a material having a pumping distance after 30 minutes of 10 cm or more, and a material having a capacity of 15 cm or more from the viewpoint of the suction height and the suction speed. It is more preferable. As such, there are “Pigeon sheet” manufactured by Oji Kinocross Co., Ltd., “Water guide sheet” manufactured by Toray Industries, Inc., and the like. The pumping distance means the arrival height of the water after leaving the felt test piece 2 cm under water at a temperature of 25 ° C. and leaving it for a certain time (30 minutes).

  The shape of the fuel transport member 61 is not limited to a strip shape (more specifically, a rectangular parallelepiped shape) as shown in FIG. 7, but may be a shape of the entire fuel cell, a shape of a membrane electrode assembly, a shape of a fuel supply chamber, or the like. It can be set as the appropriate shape according to. As other examples other than a rectangular parallelepiped shape, for example, a cubic shape, a strip shape such as a shape whose width decreases or increases continuously or stepwise from one end to the other end (a shape whose surface is a trapezoid or a triangle, etc.) Can be mentioned.

  The length of the fuel transport member 61 (distance from one end on the fuel storage chamber 70 side to the other end facing the fuel transport member 61) is not particularly limited, and the shape of the entire fuel cell, the shape of the membrane electrode assembly, or the shape of the fuel supply chamber However, when one end of the fuel transport member 61 is disposed at a position where it can come into contact with the liquid fuel held in the fuel storage chamber 70, the other end is the fuel electrode 11 (or It is preferable that the first layer 1 has such a length that it is disposed at a position substantially immediately below the end (the end opposite to the fuel storage chamber 70 side) or longer.

  As shown in FIG. 7, the “position where the liquid fuel can be contacted” refers to the case where one end of the fuel transport member 61 is located inside the fuel storage chamber 70 as well as the one end of the fuel transport member 61 is supplied with fuel. This includes a case where the chamber 60 and the fuel storage chamber 70 are located inside a wall (which is a part of the box housing 40).

  (4) The fuel supply unit is not limited to one including a fuel supply chamber and a fuel storage chamber. For example, the fuel supply chamber 60 may serve as the fuel storage chamber 70 that stores liquid fuel, and the fuel storage chamber 70 (and the fuel transport member 61) may be omitted.

  (5) The layer configuration of the fuel cell is not limited to that shown in FIGS. 1 to 5, and the unit cell 30 is arranged on both sides of the fuel supply chamber 60 as shown in FIG. 8, for example. It may be. FIG. 8 is a schematic cross-sectional view similar to FIG. 5, showing an example of a fuel cell in which unit cells 30 are arranged on both surfaces of the fuel supply chamber 60. In such a configuration, the fuel supply chamber 60 needs to be open on both the upper and lower surfaces in order to supply fuel to the upper and lower fuel electrodes 11, so that the upper and lower surfaces are opened as the box housing 40. A member having a space is used. In such a fuel cell in which the unit cells 30 are arranged on both surfaces of the fuel supply chamber 60, one fuel supply unit is sufficient for two unit cells, so that the fuel cell can be thinned. The output per unit volume of the fuel cell can be improved. In the embodiment shown in FIG. 8, as shown in the figure, the first through hole 91 is connected to the first through hole 91 and has a discharge path extending laterally on the side wall of the box housing 40. The raw gas can be discharged from the side surface of the box housing 40 through this discharge path.

  (6) The fuel cell may include two or more unit cells 30 arranged on the same plane. In this case, the fuel supply chamber 60 may be provided for each unit cell 30 or may be provided in a number smaller than that of the unit cells 30.

  (7) The outer shape of the fuel cell is not limited to the shape of the above embodiment. For example, the shape (planar shape) when viewed from the thickness direction of the fuel cell may be a rectangle or the like.

  (8) The fuel cell can be provided with a pumping means such as a pump for pumping the liquid fuel accommodated in the fuel storage chamber to the fuel supply chamber. Since the fuel supply chamber can be filled in a short time, the startability of the fuel cell can be improved.

<Second Embodiment>
FIG. 9 is a schematic cross-sectional view showing the fuel cell of the present embodiment. The fuel cell 200 of the present embodiment is the same as that of the first embodiment, except that the intervening layer disposed between the fuel supply chamber 60 and the unit cell 30 further includes the third layer 3. FIG. 10 is a schematic top view showing the third layer 3 used in the fuel cell 200. Hereinafter, the third layer, which is a feature of the present embodiment, will be described in detail. Note that the various modifications described in the first embodiment can be similarly applied to this embodiment.

  The third layer is a layer that is disposed between the first layer and the second layer and has a through-hole penetrating in the thickness direction through which the liquid fuel can permeate. At least the first layer and the second layer are adhered to each other. It plays a role of good surface bonding, and preferably has a function of adjusting (limiting) the liquid fuel permeation amount to the second layer side. As the third layer, for example, a non-porous sheet (film) having a through-hole penetrating in the thickness direction as shown in FIGS. 9 and 10 can be used, and the material is preferably a thermoplastic resin. it can. By using this, the laminated body composed of the first layer / the third layer / the second layer is subjected to thermocompression bonding so that the respective layers can be surface-bonded with good adhesion. A fuel cell having a non-porous sheet that has a through-hole penetrating in the thickness direction as the third layer and capable of surface bonding is advantageous in the following points.

  (A) Since the first layer and the second layer can be bonded with good adhesion via the third layer, the by-product gas does not stay between the first layer and the second layer. Variations in the vaporized fuel permeation amount in the two-layer plane can be suppressed, whereby uniform fuel supply to the fuel electrode can be performed, and output can be improved. Further, when the third layer is made of a resin, there is an effect of making it difficult to transfer heat to the liquid fuel with respect to a rapid temperature rise of the power generation unit. As a result, the temperature rise of the liquid fuel becomes slow and the liquid fuel can be stably maintained at a relatively low temperature, so that the supply amount of vaporized fuel supplied to the fuel electrode can be stabilized. This contributes to improving the reliability of the fuel cell.

  (B) Adjust (limit) the liquid fuel permeation amount to the second layer side, and hence the vaporized fuel supply amount to the fuel electrode, to an appropriate amount according to the number of through holes formed in the third layer and the opening diameter. Can do. As a result, it is possible to prevent or suppress the crossover of the fuel and stabilize the fuel supply. The number of through holes is not particularly limited, but it is preferable that there are a plurality of through holes. From the viewpoint of uniformizing the amount of vaporized fuel permeated in the second layer surface, these are provided as fuel supply chambers (recesses in the box housing) in the third layer. It is preferable to distribute evenly in the region immediately above. The opening diameter (diameter) of the through hole can be set to about 0.1 to 5 mm, for example.

  (C) Since the third layer enables good surface joining between the first layer and the second layer, it is not necessary to tighten the fuel cell using a fastening member such as a bolt, a nut or a screw. The battery can be thinned.

  (D) Since the intervening layer can be easily produced by thermocompression bonding, the fuel cell production process can be simplified and the production efficiency can be improved.

  In addition to the thermoplastic resin sheet described above, the third layer may be formed, for example, from the following.

  1) A porous layer formed from an adhesive resin or resin composition, for example, a porous layer formed from an adhesive such as a hot-melt adhesive or a curable adhesive. When the adhesive is used, the third layer is an adhesive layer, that is, a porous layer made of the adhesive or a cured product thereof. Even when such a third layer is used, the same effects as in the above (a) to (c) can be obtained. The liquid fuel permeation amount to the second layer side is adjusted (restricted) by the pores of the porous layer.

  2) A through-hole penetrating in the thickness direction, preferably including a non-porous metal plate. In this case, an adhesive layer is formed on both surfaces of the metal plate in order to ensure good adhesion to the first layer and the second layer. Therefore, the third layer is formed of an adhesive layer / metal plate / The adhesive layer has a three-layer structure. The adhesive layer is a porous layer made of an adhesive or a cured product thereof. The adhesive may be a hot melt adhesive or a curable adhesive. Even when such a third layer is used, the same effects as in the above (a) to (c) can be obtained. The liquid fuel permeation amount to the second layer side can be adjusted (controlled) by the number of through-holes formed in the metal plate and the opening diameter as in the case of the thermoplastic resin sheet. The adhesive layer is preferably formed so as not to block the through hole. The number of through holes is not particularly limited, but it is preferable that there are a plurality of through holes. From the viewpoint of uniformizing the amount of vaporized fuel permeated in the second layer surface, these are formed in the fuel supply chamber (recess of the box housing) in the metal plate. It is preferable to uniformly distribute the region immediately above. The opening diameter (diameter) of the through hole can be set to about 0.1 to 5 mm, for example.

  When a non-porous sheet (film) having a through-hole penetrating in the thickness direction is used as the third layer, or when a non-porous metal plate having a through-hole penetrating in the thickness direction is used as the third layer Forms a through hole at a position directly above the second through hole in the first layer, and discharges by-product gas through the through hole, the first through hole in the box housing, and the second through hole in the first layer. Build a department. On the other hand, when the porous layer formed from an adhesive resin or resin composition is the third layer, the processing of the through holes is not particularly necessary.

  The fuel cell of the present invention can be a polymer electrolyte fuel cell or a direct alcohol fuel cell, and is particularly suitable as a direct alcohol fuel cell (in particular, a direct methanol fuel cell). Examples of the liquid fuel that can be used in the fuel cell of the present invention include alcohols such as methanol and ethanol; acetals such as dimethoxymethane; carboxylic acids such as formic acid; esters such as methyl formate; and aqueous solutions thereof. Can be mentioned. The liquid fuel is not limited to one type, and may be a mixture of two or more types. In view of low cost, high energy density per volume, high power generation efficiency, etc., an aqueous methanol solution or pure methanol is preferably used.

  The fuel cell of the present invention can be suitably used as a power source for electronic devices, in particular, small electronic devices such as mobile devices typified by mobile phones, electronic notebooks, and notebook computers.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

<Example 1>
A fuel cell having a configuration similar to that shown in FIG.

(1) Production of Membrane Electrode Composite Catalyst-supported carbon particles (TEC66E50, manufactured by Tanaka Kikinzoku Co., Ltd.) having a Pt loading amount of 32.5% by weight and a Ru loading amount of 16.9% by weight, and 20% by weight of Nafion as an electrolyte ( (Registered trademark) Alcohol solution (Aldrich), n-propanol, isopropanol, and zirconia balls are put into a fluororesin container at a predetermined ratio and mixed for 50 minutes at 500 rpm using a stirrer. As a result, a catalyst paste for the fuel electrode was prepared. Further, a catalyst paste for an air electrode was prepared in the same manner as the catalyst paste for a fuel electrode using catalyst-supported carbon particles (TEC10E50E, manufactured by Tanaka Kikinzoku Co., Ltd.) having a Pt loading of 46.8% by weight.

  Also, two pieces of carbon paper (GDL25BC, manufactured by SGL) cut into a length of 23 mm and a width of 28 mm were prepared and used as an anode conductive porous layer and a cathode conductive porous layer, respectively.

On the anode conductive porous layer, the fuel electrode catalyst paste is applied using a screen printing plate having a window of 22 mm in length and 27 mm in width so that the amount of catalyst supported is about 3 mg / cm ^2. By drying, a fuel electrode 11 having a thickness of about 100 μm in which an anode catalyst layer was formed at the center of the anode conductive porous layer was produced. Further, the air electrode catalyst paste is applied onto the cathode conductive porous layer using a screen printing plate having a window of 22 mm length and 27 mm width so that the amount of the catalyst supported is about 1 mg / cm ^2. Then, an air electrode 12 having a thickness of about 50 μm in which a cathode catalyst layer was formed in the center of the cathode conductive porous layer was produced.

  Next, a perfluorosulfonic acid ion exchange membrane having a thickness of about 175 μm (Nafion (registered trademark) 117, manufactured by DuPont) is cut into a length of 23 mm and a width of 28 mm to form an electrolyte membrane 10. The fuel electrode 11 and the electrolyte membrane 10 and the air electrode 12 are stacked in this order so that the respective catalyst layers face the electrolyte membrane 10, and then subjected to thermocompression bonding at 130 ° C. for 2 minutes, thereby connecting the fuel electrode 11 and the air electrode 12 to the electrolyte. Bonded to membrane 10. The superposition was performed so that the positions of the fuel electrode 11 and the air electrode 12 in the plane of the electrolyte membrane 10 coincided, and the centers of the fuel electrode 11, the electrolyte membrane 10 and the air electrode 12 coincided. Next, the end of the obtained laminate was cut to prepare a membrane electrode assembly 20 having a length of 22 mm and a width of 27 mm.

(2) Manufacture of unit cell A stainless steel plate (NSS445M2, manufactured by Nisshin Steel Co., Ltd.) having a thickness of 100 μm, length of 22 mm, and width of 27 mm is prepared. Two stainless steel plates having a plurality of through-holes penetrating in the thickness direction were produced by processing a hole pattern: zigzag 60 ° pitch 0.8 mm) from both sides by wet etching using a photoresist mask. Subsequently, in order to improve corrosion resistance and reduce electric resistance, the surfaces of these stainless steel plates were plated with gold to form an anode current collecting layer 21 and a cathode current collecting layer 22, respectively. The anode current collecting layer 21 and the cathode current collecting layer 22 are provided with electrical contacts for sweeping current during evaluation.

  Next, the anode current collecting layer 21 is laminated on the fuel electrode 11 via a conductive adhesive layer composed of carbon particles and an epoxy resin, and the cathode current collecting layer 22 is formed on the air electrode 12 with carbon particles. A unit battery 30 having a length of 22 mm and a width of 27 mm was produced by laminating the layers via a conductive adhesive layer made of epoxy resin and bonding them by thermocompression bonding. The anode current collecting layer 21 and the cathode current collecting layer 22 were laminated so that the regions where the through holes were formed were arranged immediately above the fuel electrode 11 and the air electrode 12, respectively.

(3) Production of Intervening Layer As the first layer 1 of the intervening layer, a porous film made of polyvinylidene fluoride having a length of 25 mm, a width of 27 mm, and a thickness of 0.1 mm as shown in FIG. 11 (Durapore membrane filter made by MILLIPORE) ) Was used. The maximum pore diameter of the pores of this porous film was 0.1 μm, and the bubble point based on JIS K3832 was 115 kPa when methanol was used as the measurement medium.

  As shown in FIG. 11, the first layer 1 includes through holes (inner diameter 1.0 mm) penetrating in the thickness direction as “hole group A” (five included in a region surrounded by a dotted frame). And a through hole (inner diameter 1.0 mm) penetrating in the thickness direction, denoted as “hole group B” (12 included in a region surrounded by another dotted frame). The hole group A is a hole for extracting air existing in the fuel supply chamber when the liquid fuel enters the fuel supply chamber disposed below the first layer (liquid fuel enters by extracting air). When the hole group A is provided, it is possible to evacuate the air in the fuel supply chamber even after the first layer is completely wetted with fuel. It will be filled with liquid fuel. Since the unit cell 30 is not disposed on the hole group A, the by-product gas does not enter the fuel supply chamber through the hole group A. On the other hand, the hole group B is the above-mentioned “second through hole 92” for discharging the by-product gas to the outside of the fuel cell, and constitutes a part of the by-product gas discharge unit.

  Further, as the second layer 2 of the intervening layer, a porous film made of polytetrafluoroethylene having a length of 25 mm, a width of 27 mm, and a thickness of 0.2 mm as shown in FIG. 12 (“TEMISH” manufactured by Nitto Denko Corporation) (Registered trademark)] NTF2122A-S06 "). The bubble point of this porous film based on JIS K3832 was 18 kPa when the measurement medium was methanol.

  The second layer 2 is laminated on the first layer 1 (laminated so that the AA ′ planes in FIGS. 11 and 12 coincide with each other), and the boundary layers on all side surfaces are joined with an adhesive to form an intervening layer Produced. The bubble point of the intervening layer coincides with the value of the layer having the largest bubble point among the constituent layers. Therefore, the bubble point of the intervening layer of this example is 115 kPa.

(4) Fabrication of fuel supply section As shown in FIG. 13, five concave portions (spaces serving as fuel supply chambers) having a length of 23.5 mm, a width of 1.0 mm, and a depth of 0.4 mm are formed on one surface. Further, a box housing 40 having a length of 30 mm, a width of 27 mm, and a thickness of 0.6 mm, in which a total of 12 first through holes 91 having an inner diameter of 1.0 mm were formed at the illustrated positions, was prepared. The box housing 40 has the same shape as that shown in FIG. 1, and includes a recess that constitutes the fuel storage chamber 70 on the side of the recess that becomes the fuel supply chamber 60. After the intervening layer is laminated on the concave portion of the box housing 40 via the polyolefin-based adhesive so that the first layer 1 side of the intervening layer becomes the box housing 40 side (the AA ′ plane in FIGS. 11 to 13 is The intervening layer and the box housing 40 were joined by performing thermocompression bonding. The second through hole 92 (hole group B) of the first layer 1 is disposed immediately above the first through hole 91 of the box housing 40.

(5) Sealing the end face of the unit cell and the fuel supply unit The unit cell 30 is placed so that the end surface on the long side of the unit cell 30 overlaps the AA ′ surface of the fuel supply unit (intervening layer and box housing 40). Laminated on the intervening layer. Next, the end surfaces of both the unit cell 30 and the fuel supply unit were coated with a sealing layer made of an epoxy resin by applying and curing a coating solution containing an epoxy resin using a mask. As a result, it is possible to prevent air from entering the fuel electrode from the outside of the fuel cell and fuel from leaking to the outside of the fuel cell.

(6) Fabrication of fuel cell An epoxy resin was applied to the end surfaces of the unit cell 30 and the intervening layer on the fuel storage chamber side and cured to form a sealing layer 80 (fuel intrusion prevention layer). Finally, a fuel cell was obtained by disposing a lid housing 50 having an opening 51 for supplying air to the air electrode 12 and an opening 71 (pressure adjusting hole) on the unit cell 30.

<Example 2>
The first layer 1 of the intervening layer has the same shape as the porous film used in Example 1 (the shape shown in FIG. 11 and has hole group A and hole group B), thickness, and material. However, a porous film (Durapore membrane filter, filter code: DVPP manufactured by MILLIPORE) having different maximum pore diameters was used. The maximum pore diameter of the pores of this porous film was 0.65 μm, and the bubble point based on JIS K3832 was 42 kPa when the measurement medium was methanol.

  The second layer 2 is the same as that of Example 1, and the second layer 2 is laminated on the first layer 1 (laminated so that the AA ′ planes in FIGS. An intervening layer was produced by joining the boundary portions of the layers with an adhesive. A fuel cell was obtained in the same manner as in Example 1 except that this intervening layer was applied to the fuel supply unit. The bubble point of the intervening layer of this example is 42 kPa.

<Example 3>
A fuel cell having a configuration similar to that shown in FIG. 9 was prepared by the following procedure.

  As the third layer 3 of the intervening layer, a thermoplastic film (“FB-ML4” manufactured by Nitto Shinko Co., Ltd.) having a length of 25 mm, a width of 27 mm, and a thickness of 0.07 mm as shown in FIG. 14 was used. The third layer 3 has through holes (inner diameter: 1.0 mm) penetrating in the thickness direction as “hole group C” (25 included in the region surrounded by a dotted frame), and the first layer 1 The same number of through-holes (inner diameter: 1.0 mm) are also provided at positions immediately above the hole groups A and B provided in (see FIG. 14). Although the film itself constituting the third layer 3 is impermeable to fuel, the fuel can pass through the hole group C from the first layer 1 side to the second layer 2 side.

  The first layer 1 and the second layer 2 are the same as those in the first embodiment, and the first layer 1, the third layer, and the second layer are stacked in this order (the AA ′ planes in FIGS. Then, thermocompression bonding was performed at 130 ° C. for 10 minutes to produce an intervening layer. A fuel cell was obtained in the same manner as in Example 1 except that this intervening layer was applied to the fuel supply unit. The bubble point of the intervening layer in this example is 115 kPa.

<Comparative Example 1>
Example except that a porous film made of ultra high molecular weight polyethylene having a length of 25 mm, a width of 27 mm, and a thickness of 0.1 mm (“Sunmap LC Series” manufactured by Nitto Denko Corporation) is used as the first layer of the intervening layer. An intervening layer was produced in the same manner as in Example 1, and a fuel cell was produced in the same manner as in Example 1 except that this intervening layer was used. The bubble point based on JIS K3832 of the 1st layer used by this comparative example was 8 kPa when the measurement medium was methanol. The bubble point of the intervening layer of this comparative example is 18 kPa (corresponding to the bubble point of the second layer).

(Evaluation of power generation characteristics of fuel cells)
Fuel supply is performed by passive supply using methanol aqueous solution as fuel, the obtained fuel cell is operated, and IV measurement is performed using a charge / discharge device ("SPEC20526" manufactured by Kikusui Electronics Co., Ltd.) The maximum instantaneous output was evaluated, and constant current measurement (current density 75 mA / cm ² ) was performed using the same apparatus. The output stability was evaluated based on the difference between the voltage after 2 hours of measurement and the reference voltage with reference to the voltage after 5 minutes when a constant current load was applied. The greater the voltage difference, the less output stability is due to the by-product gas entering the fuel supply chamber.

The concentration of the methanol aqueous solution supplied was 12 mol / dm ³ for the fuel cells of Examples 1 and 2 and Comparative Example 1. On the other hand, in the fuel cell of Example 3, methanol crossover is suppressed by the third layer of the intervening layer, and when the fuel having the same concentration as in Examples 1, 2 and Comparative Example 1 is used, the cell temperature is relatively high. Since it became low, the methanol aqueous solution of the density | concentration of 23 mol / dm < ³ > used as Example 1 and 2 and the battery temperature equivalent to the comparative example 1 was used as a fuel.

  The fuel cell of Example 1 had excellent output stability although the instantaneous maximum output was comparable to that of Comparative Example 1. This is probably because the bubble point of the intervening layer is large, so that by-product gas does not enter the fuel supply chamber and stable fuel supply is possible. The fuel cell of Example 2 had the same instantaneous maximum output and output stability as those of Example 1. Like the first embodiment, it is considered that the by-product gas can be stably supplied without entering the fuel supply chamber. The fuel cell of Example 3 was excellent in both instantaneous maximum output and output stability. The reason why the instantaneous maximum output is improved is considered to be that the fuel supply becomes better and the limit current density is improved because the fuel having a higher concentration can be used. In addition, the fuel cell of Example 3 has further improved output stability as compared with Example 1. This is because the first layer and the second layer are surface-bonded by the third layer. Therefore, it is considered that a gap is less likely to be generated between the first layer and the second layer, and a more stable fuel supply is achieved. In the fuel cell of Comparative Example 1, the output stability was too low to perform a constant current load of 2 hr, and the measurement was finished because the cell voltage was 0.1 V or less (the voltage difference compared with after 5 min was 0.3V or more).

  DESCRIPTION OF SYMBOLS 1 1st layer, 2nd layer, 3rd layer, 10 electrolyte membrane, 11 fuel electrode, 12 air electrode, 20 membrane electrode composite, 21 anode current collection layer, 22 cathode current collection layer, 30 unit cell, 40 Box housing, 50 lid housing, 51 opening, 60 fuel supply chamber, 61 fuel transport member, 70 fuel storage chamber, 71 opening, 80 sealing layer, 90 by-product gas discharge portion, 91 first through hole, 92 second Through hole, 100,200 Fuel cell.

Claims (8)

A fuel cell comprising: a unit cell having a fuel electrode, an electrolyte membrane, and an air electrode in this order; and a fuel supply unit that is disposed on the fuel electrode side of the unit cell and supplies fuel to the fuel electrode. ,
The fuel supply unit includes a space in which the fuel electrode side is opened, a fuel supply chamber for circulating or containing the liquid fuel, and the fuel supply chamber so as to cover an opening of the fuel supply chamber. An intervening layer disposed between the unit cells,
The intervening layer is provided on the fuel supply chamber side in the thickness direction, and is provided on the unit cell side in the thickness direction, the first region having a bubble point of 30 kPa or more when the measurement medium is methanol, A fuel cell having a second region through which the vaporized fuel can permeate.   The intervening layer is disposed on the fuel supply chamber so as to cover the opening of the fuel supply chamber, and a first layer having a bubble point of 30 kPa or more when methanol is used as a measurement medium; and a unit in the first layer 2. The fuel cell according to claim 1, wherein the fuel cell has a two-layer structure including a second layer that is laminated on the cell side surface and is capable of transmitting the vaporized fuel.   The fuel cell according to claim 2, further comprising a third layer having a through hole penetrating in a thickness direction between the first layer and the second layer.   The fuel cell according to claim 3, wherein the third layer is a thermoplastic resin sheet having a plurality of through holes penetrating in the thickness direction.   The fuel cell according to claim 3, wherein the third layer is a porous layer formed of an adhesive resin or resin composition.   The fuel cell according to claim 3, wherein the third layer includes a metal plate having a plurality of through holes penetrating in the thickness direction.   The fuel cell according to claim 1, wherein the unit cell further includes an anode current collecting layer laminated on the fuel electrode and a cathode current collecting layer laminated on the air electrode.   The fuel cell according to claim 1, wherein the fuel is pure methanol or an aqueous methanol solution.

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