JP2009123441A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell from which sufficiently high output characteristics can be obtained in order to operate a portable equipment. <P>SOLUTION: The fuel cell includes: an electromotive part equipped with a membrane electrode assembly having a cathode, an anode, and an electrolyte membrane pinched between the cathode and the anode; a cathode current collector electrically contacted with the opposite side to the electrolyte membrane side of the cathode; and an anode current collector electrically contacted with the opposite side to the electrolyte membrane side of the anode. The anode current collector is arranged on an insulation film on the face opposite to the face contacted with the anode, and is equipped with an anode sealing frame to seal between the electrolyte membrane and the insulation film surrounding the anode current collector. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell effective for the operation of a portable electronic device.

  In recent years, various electronic devices such as personal computers and mobile phones have been miniaturized with the development of semiconductor technology, and attempts have been made to use fuel cells as power sources for these small devices. Fuel cells have the advantage that they can generate electricity simply by supplying fuel and oxidant, and can continuously generate electricity if only the fuel is replenished / replaced. For this reason, if the size can be reduced, it can be said that the system is extremely advantageous for the operation of the portable electronic device. Direct methanol fuel cells (DMFCs), in particular, use methanol with high energy density as the fuel, and can extract current directly from methanol on the electrocatalyst, enabling miniaturization and handling of fuel. Since it is easy compared to hydrogen gas fuel, it is promising as a power supply for small devices, so it is expected to be put into practical use as an optimal power source for cordless portable devices such as notebook computers, mobile phones, portable audio devices, and portable game machines. Yes.

  The DMFC fuel supply method includes gas supply type DMFC that vaporizes liquid fuel and then feeds it into the fuel cell with a blower, etc., liquid supply type DMFC that feeds liquid fuel directly into the fuel cell with a pump and the like, and liquid fuel An internal vaporization type DMFC that vaporizes in a cell is known. Among these, the internal vaporization type DMFC is described in Patent Document 1, for example. In the internal vaporization type DMFC, the vaporized component of the liquid fuel held in the fuel permeation layer is diffused in the fuel vaporization layer (anode gas diffusion layer), and the diffused vaporized fuel is supplied to the anode catalyst layer, and the cathode catalyst layer Power generation reaction occurs in the electrolyte membrane with the oxidant from the side.

  Further, as a small fuel cell mainly used in a mobile device, a passive fuel cell that does not use an active transfer means such as a fuel pump to supply liquid fuel to the anode electrode is described in Patent Document 2, for example. ing. In such a fuel cell for a mobile device, it is required to use pure methanol as a fuel in order to realize miniaturization.

  In a passive type fuel cell, a membrane electrode assembly (MEA) is formed by joining an anode electrode to one surface of an electrolyte membrane and a cathode electrode to the other surface, and on the anode side of the MEA. A fuel supply mechanism is disposed, and an air supply mechanism is disposed on the cathode side. The anode electrode includes an anode catalyst layer and an anode gas diffusion layer. An anode current collector is laminated on the surface of the anode gas diffusion layer opposite to the anode catalyst layer, and electrically connects the anode electrode to an external circuit. Similarly, the cathode electrode includes a cathode catalyst layer and a cathode gas diffusion layer. A cathode current collector is laminated on the opposite surface of the cathode gas diffusion layer to the cathode catalyst layer, and the cathode electrode is connected to an external circuit.

In particular, in a fuel cell that uses a liquid fuel such as methanol as the fuel, the liquid fuel leaks through the interface between the anode current collector and the anode electrode to the outer peripheral side of the anode electrode, and does not pass through the electrolyte membrane to the cathode side. There is a possibility of wrapping around. When the wraparound phenomenon of the fuel from the anode to the cathode occurs, the power generation efficiency of the fuel cell decreases. In particular, in a fuel cell for portable electronic devices, downsizing is an important design point, and therefore, development of a seal structure that can reliably seal the interface without increasing the size is required. .
Japanese Patent No. 3413111 International Publication Number WO2006 / 057283

  However, in conventional fuel cells, it is difficult to obtain sufficiently high output characteristics for operating a portable electronic device. In a conventional fuel cell, for example, a methanol aqueous solution in which methanol and water are mixed at a molar ratio of 1: 1 is used as a liquid fuel, and both methanol and water are supplied to the anode. Since the vapor pressure is low and the vaporization rate of water is slower than the vaporization rate of methanol, when both methanol and water are supplied to the anode by vaporization, the relative supply amount of water relative to the methanol supply amount is insufficient. This is because the reaction resistance of the reaction for internally reforming methanol is increased.

  In addition, since DMFC has a low operating voltage per unit cell of about 0.3 to 0.5 V, it is necessary to connect a plurality of unit cells in series and incorporate them in a device. When incorporating into small portable electronic devices such as portable game machines, it is necessary to arrange a plurality of unit cells on the same plane.

  In addition, in DMFC, if the internal seal is incomplete, the ratio of fuel contributing to the reaction is reduced and fuel utilization efficiency is lowered, so that the fuel cell performance is lowered.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a fuel cell that can obtain sufficiently high output characteristics for operating a portable device.

  A fuel cell according to the present invention includes an electromotive unit including a membrane electrode assembly having a cathode, an anode, and an electrolyte membrane sandwiched between the cathode and the anode, and the cathode opposite to the electrolyte membrane side. A cathode current collector in electrical contact with the anode side; and an anode current collector in electrical contact with a side of the anode opposite to the electrolyte membrane side, the anode current collector comprising: An anode seal frame is disposed on the insulating film on a surface opposite to the contact surface, and surrounds the anode current collector and seals between the electrolyte membrane and the insulating film.

  According to the present invention, the anode current collector is disposed on the insulating film on the surface opposite to the surface in contact with the anode, and the anode current collector is surrounded to seal between the electrolyte membrane and the insulating film. As a result, the fuel does not flow from the anode side to the cathode side in the membrane electrode assembly, the wiring of the fuel cell in which a plurality of unit cells are arranged in a plane can be simplified, and this can greatly contribute to the miniaturization of the fuel cell. For this reason, it becomes possible to improve the volume energy density in the power generation unit of the fuel cell, and obtain sufficiently high output characteristics for operating cordless portable devices such as mobile phones, portable audio devices, portable game machines, and notebook personal computers. be able to.

Further, in the present invention, an anode current collector is disposed on an insulating film on a surface opposite to a surface in contact with the anode, and a current collector that surrounds the anode current collector and seals between the electrolyte membrane and the insulating film. Since it arrange | positions and fixes on an insulating film, position alignment with an electrical power collector and an electromotive part becomes easy, and it becomes possible to provide a fuel cell with high assembly precision.

  The fuel cell of the present invention has a cathode current collector in electrical contact with the opposite side of the cathode to the electrolyte membrane side and an anode current collector in electrical contact with the side opposite to the anode electrolyte membrane side. The anode current collector is disposed on the insulating film on the surface opposite to the surface in contact with the anode, and surrounds the anode current collector and seals between the electrolyte membrane and the insulating film. Since the frame is provided, the anode seal frame effectively prevents the fuel from flowing from the anode side to the cathode side in the membrane electrode assembly. For this reason, fuel can be used effectively, the volume energy density of the electromotive part is improved, and the output efficiency is increased.

  In the present invention, the cathode current collector is further disposed on the insulating film on the surface opposite to the surface in contact with the cathode, and surrounds the cathode current collector and seals between the cathode and the insulating film. It is preferable to have a cathode frame. By attaching a cathode seal frame in addition to the anode seal frame, not only the anode side but also the cathode side is sealed, so that a double seal structure is formed, so that the fuel that goes around the outer periphery of the membrane electrode assembly can be more effectively Can be prevented.

  In this case, it is preferable that the anode current collector and the cathode current collector are disposed on the common insulating film. By using such a common insulating film, the common insulating film can be folded in half, and an electromotive portion can be sandwiched between the folded insulating films to produce a unitized current collector assembly. Such a two-fold structure is described in Patent Document 2 described above, and can reduce the number of parts and processes, and can easily align the current collector pattern of both electrodes and the electromotive part including the membrane electrode assembly. There is a merit.

  When producing a current collector assembly having a two-fold structure, it may further include an inter-electrode conductive member provided between the anode current collector and the cathode current collector and connecting the anode electrode in series with the cathode electrode. it can. In this case, when the distance from the cathode electrode to the anode electrode in the plane before the interelectrode conductive member is folded in half is W5, the cathode gas diffusion layer including the membrane electrode assembly is changed to the anode gas diffusion layer. It is desirable to satisfy the relationship of 1.5t ≦ W5 ≦ 4t with respect to the thickness t. When metal plates are used for the anode electrode and the cathode electrode, if the separation distance W5 is less than 1.5 times the thickness t, it is difficult to bend 180 ° with a sufficient radius of curvature. This is because even if it can be bent, the bent portion is deformed sharply and plastically hardened, and the bent portion becomes brittle and easily breaks. On the other hand, if the separation distance W5 exceeds four times the thickness t, the mutual distance from the opposing anode electrode to the cathode electrode becomes too large, and the fuel cell becomes large. In this case, it is desirable that the thickness t from the cathode diffusion layer including the membrane electrode assembly to the anode diffusion layer is 600 to 900 μm, and the separation distance W5 is 0.75 to 3.6 mm. When the anode electrode and the cathode electrode are made of metal plates, the electrode thickness t1 is preferably 50 μm to 200 μm. This is because if the electrode thickness is 50 μm or less, the desired strength is insufficient and the electrode is easily damaged. On the other hand, when the electrode thickness t1 exceeds 200 μm, the rigidity increases and the force required for bending becomes excessive and bending becomes difficult. On the other hand, when the separation distance W5 is less than 0.75 mm, the force required for bending becomes excessively difficult to bend, and the bent portion becomes acute and easily broken. On the other hand, if the separation distance W5 exceeds 3.6 mm, the distance between the opposing anode current collector and the cathode current collector becomes too large, and the fuel cell becomes larger.

  For the cathode current collector and the anode current collector, for example, a porous layer (for example, mesh) or a foil body made of a metal material such as gold or nickel, or a conductive metal material such as stainless steel (SUS) is used. A composite material coated with a highly conductive metal such as gold can be used.

  Moreover, it is desirable that the mutual spacing W2 between the cathode electrodes and the mutual spacing W4 between the anode electrodes be 0.3 mm or more and 1.5 mm or less, respectively. This is because if the inter-electrode spacing W2, W4 is less than 0.3 mm, a short circuit may occur depending on the insulating performance of the interelectrode insulating seal portion. On the other hand, if the mutual intervals W2 and W4 of the electrode portions exceed 1.5 mm, the fuel cell becomes large and becomes incompatible as a power source for portable electronic devices.

  The inter-electrode conductive member is a conductive part for taking out electrons generated by each electrode to an external circuit, and the resistance is reduced as the cross-sectional area is increased, but if the thickness of the conductive part is increased and the cross-sectional area is increased. Since it becomes difficult to bend and the width of the conductive part is increased, the possibility of contact with other terminals increases. Therefore, the thickness of the conductive part is preferably 50 μm to 200 μm, and the width W6 of the interelectrode conductive member is other than The distance to the terminal may be 0.4 mm or more and may be bent.

  Moreover, it is preferable that the width W1 of the cathode electrode and the width of the anode electrode W3 are each 1 mm or more. The width of each electrode portion is the width in the arrangement direction when the electrodes are arranged in a plane, and the width in the short direction when the electrodes are substantially rectangular. When the electrode is substantially rectangular, the ratio of the longitudinal direction to the lateral direction (aspect ratio) is preferably 10 to 1 or less.

  Hereinafter, various embodiments for carrying out the present invention will be described with reference to the accompanying drawings.

  First, an overview of the entire fuel cell will be described with reference to FIGS. The entire fuel cell 1 is covered with an exterior cover (cover plate) 21 and a fuel distribution mechanism 11 and has a plurality of unit cells therein. The plurality of unit cells are arranged side by side on substantially the same plane, and are not shown through cathode current collector 7a, anode current collector 7b, and terminals 77 and 78 connected to each current collector. They are connected in series by lead wiring. The cathode current collector 7 a is disposed on the insulating film 70 on the surface opposite to the surface in contact with the cathode gas diffusion layer 4, and the anode current collector 7 b is on the surface opposite to the surface in contact with the anode gas diffusion layer 5. It is disposed on the insulating film 70.

  The fuel cell 1 is configured as one unit in which a plurality of unit cells are integrated by, for example, caulking the end 21a of the outer cover 21 to the outer surface of the fuel distribution mechanism 11. Furthermore, it is desirable to integrate the outer cover 21 and the fuel distribution mechanism 11 by fastening them with, for example, bolts and nuts (not shown).

The outer periphery of the unit cell in the fuel cell 1 is liquid-tightly sealed by the cathode seal frame 8a and the anode seal frame 8b. The anode seal frame 8b and the cathode seal frame 8a are made of a rubber material having a permeation amount of 9 × 10 ⁷ g / m ³ · 24 hr · atm or less and a volume resistivity of 10 ¹¹ to 10 ¹⁵ Ω · cm. It is desirable to become. This is because if the amount of permeation is large, the amount of fuel that contributes to power generation decreases and the performance of the fuel cell is lowered. As the rubber material, EPDM (ethylene propylene rubber), fluorine rubber, silicon rubber or the like can be used.

  A plurality of fuel supply holes 18 are opened in the anode current collector 7 b, and fuel components are supplied from the fuel distribution mechanism 11 to the anode gas diffusion layer 5 and the anode catalyst layer 3 through the holes 18.

  For example, a gas-liquid separation membrane 9 is provided between the anode current collector 7 b and the fuel distribution mechanism 11. The peripheral portion of the gas-liquid separation membrane 9 is sandwiched between the flange insulating film 70 of the fuel distribution mechanism 11. The gas-liquid separation membrane 9 is made of a polytetrafluoroethylene (PTFE) sheet having a large number of pores, and has a property of blocking the liquid component of the liquid fuel and allowing the gas component to permeate.

  The liquid reservoir 40 is composed of a gap of a predetermined capacity whose periphery is defined by the fuel distribution mechanism 11, and a fuel injection port (not shown) is opened at an appropriate place (for example, a side surface of the fuel distribution mechanism 11).

  A liquid fuel impregnation layer (not shown) is provided inside the liquid reservoir 40. The liquid fuel impregnated layer is uniformly supplied to the gas-liquid separation membrane 9 even when the liquid fuel in the liquid reservoir 40 is reduced or when the fuel cell body is inclined and placed in a biased fuel supply. As a result, it is possible to supply the vaporized liquid fuel to the anode catalyst layer 3 uniformly. As the liquid fuel-impregnated layer, for example, multi-rigid fibers such as porous polyester fiber and porous olefin resin, and open-cell porous resin are preferable. In addition to the polyester fiber, it may be composed of various water-absorbing polymers such as acrylic resin, and is composed of a material that can hold the liquid by utilizing the permeability of the liquid, such as a sponge or an aggregate of fibers. . Such a liquid fuel-impregnated portion is effective for supplying an appropriate amount of fuel regardless of the posture of the main body.

  A plurality of gas flow holes 18 are opened in the cathode current collector 7a, and air introduced from the air holes 22 passes through the moisture retaining plate 19 and then passes through the holes 18 to be supplied to the gas diffusion layer 4 and the cathode catalyst layer 2. It has come to be. The central axis of the gas flow hole 18 is preferably disposed so as to substantially coincide with the central axis of the vent hole 22 formed in the exterior cover 21.

  The exterior cover 21 also serves to pressurize the stack including the cell structure 20 and enhance its adhesion, and is formed of a metal plate such as SUS304, for example. The moisturizing plate 19 plays a role of preventing the transpiration of water generated in the cathode catalyst layer 2 and promotes uniform diffusion of the oxidant into the cathode catalyst layer 2 by uniformly introducing the oxidant into the cathode diffusion layer 4. It also serves as an auxiliary diffusion layer. For the moisture retaining plate 19, a porous film having a porosity of, for example, 20 to 60% is preferably used.

  The unit cell of the fuel cell includes an anode catalyst layer 3, an anode gas diffusion layer 5, a cathode catalyst layer 2, a cathode gas diffusion layer 4, and proton conduction sandwiched between the anode catalyst layer 3 and the cathode catalyst layer 2. The membrane electrode assembly in which the electrolyte membrane 6 having a property is integrated is configured. The anode catalyst layer 3 oxidizes the fuel supplied via the anode gas diffusion layer 5 and extracts electrons and protons from the fuel. The anode catalyst layer 3 is made of, for example, carbon powder containing a catalyst. Examples of the catalyst include fine particles of platinum (Pt), transition metals such as iron (Fe), nickel (Ni), cobalt (Co), ruthenium (Ru) and molybdenum (Mo), oxides thereof, and alloys thereof. Are used. Since it is possible to prevent inactivation of the catalyst due to adsorption of carbon monoxide (CO), it is preferable to use Pt-Ru which is highly resistant to methanol and carbon monoxide as the anode catalyst and platinum as the cathode catalyst. desirable. However, the catalyst is not limited to this. Further, a supported catalyst using a conductive support such as a carbon material may be used, or an unsupported catalyst may be used.

  The anode catalyst layer 3 more preferably contains fine particles of resin used for the electrolyte membrane 6. This is to facilitate the movement of the generated protons. The anode gas diffusion layer 5 is made of, for example, a thin film made of a porous carbon material, and specifically made of carbon paper or carbon fiber.

  The cathode has a cathode catalyst layer 2 and a cathode gas diffusion layer 4. The cathode catalyst layer 2 reduces oxygen and reacts electrons with protons generated in the anode catalyst layer 3 to generate water. For example, the cathode catalyst layer 2 is configured similarly to the anode catalyst layer 3 described above. That is, the cathode has a laminated structure in which a cathode catalyst layer 2 made of carbon powder containing a catalyst and a cathode gas diffusion layer 4 (gas permeable layer) made of a porous carbon material are stacked in this order from the electrolyte membrane 6 side. ing. The catalyst used for the cathode catalyst layer 2 is the same as that of the anode catalyst layer 3, and the anode catalyst layer 2 may contain fine particles of resin used for the electrolyte membrane 6 in the same manner as the anode catalyst layer 2.

  The electrolyte membrane 6 is for transporting protons generated in the anode catalyst layer 3 to the cathode catalyst layer 2 and is made of a material that does not have electron conductivity and can transport protons. For example, it is composed of a polyperfluorosulfonic acid resin film, specifically, a Nafion film manufactured by DuPont, a Flemion film manufactured by Asahi Glass, or an Aciplex film manufactured by Asahi Kasei Kogyo. In addition to polyperfluorosulfonic acid-based resin films, copolymer films of trifluorostyrene derivatives, polybenzimidazole films impregnated with phosphoric acid, aromatic polyether ketone sulfonic acid films, or aliphatic hydrocarbon-based films You may make it comprise the electrolyte membrane 6 which can transport protons, such as a resin container. However, the proton conductive electrolyte membrane 6 is not limited to these. The cathode gas diffusion layer 4 is laminated on the upper surface side of the cathode catalyst layer 2, and the anode gas diffusion layer 5 is laminated on the lower surface side of the anode catalyst layer 3. The cathode gas diffusion layer 4 plays a role of uniformly supplying the oxidant to the cathode catalyst layer 2, but also serves as a current collector for the cathode catalyst layer 2. On the other hand, the anode gas diffusion layer 5 serves to uniformly supply fuel to the anode catalyst layer 3 and also serves as a current collector for the anode catalyst layer 3. The cathode current collector 7a and the anode current collector 7b are in electrical contact with the cathode gas diffusion layer 4 and the anode gas diffusion layer 5, respectively.

  A fuel distribution mechanism 11 is provided below the cell structure 20. The main body of the fuel distribution mechanism 11 is a rectangular box having a plurality of fuel supply ports 14 on one side. In the liquid reservoir 40, liquid fuel such as liquid methanol or methanol aqueous solution is accommodated. Here, the vaporized component of the liquid fuel means vaporized methanol when liquid methanol is used as the liquid fuel, and from the vaporized component of methanol and the vaporized component of water when an aqueous methanol solution is used as the liquid fuel. Is a mixed gas.

  Next, the cell structure of the fuel cell will be described with reference to FIGS.

  In the present embodiment, the current collector assembly 7A has a two-fold structure. The cathode current collector 7a and the anode current collector 7b constituting the current collector assembly 7A are formed of a composite material obtained by gold-plating stainless steel, and are disposed on a common insulating film 70. As an arrangement method, a method using an adhesive, a method of vulcanizing and crosslinking a liquid rubber, a method of crosslinking a liquid rubber by radiation irradiation, and the like can be used. The membrane electrode assembly 10 is accommodated while the common insulating film 70 is folded in two, that is, the current collector assembly 7A is folded in two. That is, the cathode current collector 7a is in electrical contact with the cathode gas diffusion layer 4 stacked on the cathode catalyst layer 2, and the anode gas diffusion layer 5 stacked on the anode catalyst layer 3 is electrically connected to the anode current collector 7b. The membrane electrode assembly 10 is sandwiched on both sides by the folded current collector assembly 7A so as to be in contact with each other. An anode seal frame 8b that surrounds the anode current collector 7b and seals between the electrolyte 6 and the insulating film 70 is disposed on the anode side of the insulating film 70. Further, a cathode seal frame 8 a is disposed on the cathode side of the insulating film 70 so as to surround the cathode current collector 7 a and seal between the electrolyte 6 and the insulating film 70.

  The cathode current collector 7 a and the anode current collector 7 b have a plurality of air circulation holes 18 for supplying air to the cathode catalyst layer 2 and a plurality of fuel supply holes 18 for supplying fuel to the anode catalyst layer 3. Each is drilled. Further, a similar flow hole 18 is formed in the common insulating film 70.

  Such a cell structure 20 is manufactured as follows.

  First, the cathode current collector 7a and the anode current collector 7b are formed in a desired pattern using a method such as a wet etching method, a dry etching method, or a punching method (punching method). As shown in FIG. 4, the produced current collectors 7a and 7b include a plurality of cathode-side electrodes 71 arranged in parallel, a plurality of anode-side electrodes 73 arranged in parallel, a plurality of inter-electrode conductive members 75, and A pair of terminals 77 and 78 are provided. The cathode side electrode 71 and the anode side electrode 73 are elongated strips. Both terminals 77 and 78 are arranged at the positions of the cathode side electrode 71 and the anode side electrode 73 that are farthest from each other (one end and the other end of the multipolar arrangement). The cathode electrode 71 and the anode electrode 73 having no terminal are connected by an interelectrode conductive member 75. In other words, the non-terminal cathode electrode 71 and the anode electrode 73 are connected in series by connecting the electrodes arranged at a position shifted by one row one-to-one by the interelectrode conductive member 75. In order to prevent a short circuit, the shortest distance L1 (FIG. 4) between the interelectrode conductive member 75 and the electrode portions 71 and 73 needs to be 0.4 mm or more. However, in the arrangement in which the shortest distance L1 is excessively large, the fuel cell becomes large, so it is desirable to set the shortest distance L1 to 3.0 mm or less.

  Such a cathode current collector 7 a and an anode current collector 7 b are arranged on a common insulating film 70. In this arrangement, use of a method of vulcanizing and crosslinking liquid rubber or a method of crosslinking liquid rubber by radiation irradiation has an advantage that the cathode seal frame 8a or the anode seal frame 8b can be formed simultaneously.

  In this way, the cathode seal frame 8a and the anode seal frame 8b are respectively installed, and in the case of five series, the five conductive layers are folded with respect to a plurality of electrodes as shown in FIG. 5 (illustration of the seal frame), It is installed at a predetermined position as shown in FIG.

  As shown in FIG. 2, the cathode seal frame 8a is bonded in advance to the outer periphery of the cathode current collector 7a (cathode electrode 71), and the anode seal frame 8b is bonded in advance to the outer periphery of the anode current collector 7b (anode electrode portion 73). Or forming. This is because the periphery of the electromotive unit 20 is defined by the cathode seal frame 8a and the anode seal frame 8b, so that the electromotive unit 20 can be easily positioned with respect to the cathode current collector 7a and the anode current collector 7b.

  An example of the size of each part of the current collector assembly 7A in the embodiment is shown below.

1) Width W1 of the cathode electrode part: 6 mm
2) Width W2 of the insulating seal part between the cathode electrodes; 1.2 mm
3) Anode electrode width W3; 6 mm
4) Width W4 of the insulating seal portion between the anode electrodes; 1.2 mm
5) Separation distance W5 between both electrode parts when flattened: 2.8 mm
6) Inter-electrode conductive member width W6; 1.2 mm
7) The shortest distance L1 from the interelectrode conductive member to the electrode part; 0.4 mm
8) Diameter of holes d1, d2; φ4mm
In the present embodiment, the cathode current collector 7a and the anode current collector 7b connected in series can be made compact, so that sufficiently high output characteristics can be obtained for operating the portable electronic device.

  Next, fuel cells of various fuel supply systems to which the present invention can be applied will be described with reference to FIGS. In addition, the same figure number is used about the same structure as FIGS.

  First, a fuel cell 1A of the type shown in FIG. 6 includes a cell structure 20, a fuel distribution mechanism 11 that supplies fuel to the cell structure 20, and a flow path 51 that connects the fuel distribution mechanism 11 and the fuel supply source 50. And a pump 31 for supplying liquid fuel to the fuel distribution mechanism 11 from the fuel supply source 50 connected to the flow path 51.

  The cell structure 20 has a plurality of unit cells, and the plurality of unit cells are arranged side by side on substantially the same plane and connected in series. Each unit cell includes an anode (fuel electrode) composed of an anode catalyst layer 3 and an anode gas diffusion layer 5, a cathode (air electrode / oxidant electrode) composed of a cathode catalyst layer 2 and a cathode gas diffusion layer 4, and an anode catalyst. A membrane electrode assembly 10 including a proton conductive electrolyte membrane 6 sandwiched between the layer 3 and the cathode catalyst layer 2, an anode conductive layer 7 b, and a cathode conductive layer 7 a are provided. The membrane electrode assembly 10 has a configuration in which rectangular cathodes are arranged in parallel on one surface of the electrolyte membrane 6, and a plurality of rectangular anodes are arranged in parallel at a location facing the cathode on the other surface of the electrolyte membrane 6. It has become.

  Examples of the catalyst contained in the anode catalyst layer 3 and the cathode catalyst layer 2 include a simple substance of a platinum group element such as Pt, Ru, Rh, Ir, Os, and Pd, an alloy containing the platinum group element, and the like. For the anode catalyst layer 3, it is preferable to use Pt—Ru, Pt—Mo, or the like having strong resistance to methanol, carbon monoxide, or the like. It is preferable to use Pt, Pt—Ni or the like for the cathode catalyst layer 2. However, the catalyst is not limited to these, and various substances having catalytic activity can be used. The catalyst may be either a supported catalyst using a conductive support such as a carbon material or an unsupported catalyst.

  The electrolyte membrane 6 is for transporting protons generated in the anode catalyst layer 3 to the cathode catalyst layer 2 and is made of a material that does not have electron conductivity and can transport protons. Examples thereof include a fluorine-based resin having a sulfonic acid group (for example, a perfluorosulfonic acid polymer), a hydrocarbon-based resin having a sulfone sun group, tungstic acid, phosphotungstic acid, and the like. Specifically, it is composed of Nafion (registered trademark) manufactured by DuPont, Flemion (registered trademark) manufactured by Asahi Kasei Kogyo Co., Ltd., etc. An electrolyte membrane 6 capable of transporting protons such as a polymer membrane, a polybenzimidazole membrane containing phosphoric acid, an aromatic polyether ketone sulfonic acid membrane, or an aliphatic hydrocarbon resin membrane may be formed. The proton conductive electrolyte membrane 6 is not limited to these.

  The cathode gas diffusion layer 4 is laminated on the upper surface side of the cathode catalyst layer 2, and the anode gas diffusion layer 5 is laminated on the lower surface side of the anode catalyst layer 3. The cathode gas diffusion layer 4 plays a role of uniformly supplying the oxidant to the cathode catalyst layer 2, but also serves as a current collector for the cathode catalyst layer 2. On the other hand, the anode gas diffusion layer 5 serves to uniformly supply fuel to the anode catalyst layer 3 and also serves as a current collector for the anode catalyst layer 3. The cathode current collector 7a and the anode current collector 7b are in electrical contact with the cathode gas diffusion layer 4 and the anode gas diffusion layer 5, respectively.

  In the present embodiment, the hypothetical structure 20 is configured by making the current collector assembly into a two-fold structure. The cathode current collector 7a and the anode current collector 7b constituting the current collector assembly are formed of a composite material in which stainless steel is gold-plated, and are disposed on a common insulating film 70. As an arrangement method, a method using an adhesive, a method of vulcanizing and crosslinking a liquid rubber, a method of crosslinking a liquid rubber by radiation irradiation, and the like can be used. The membrane electrode assembly 10 is accommodated while the common insulating film 70 is folded in two, that is, the current collector assembly is folded in two. That is, the cathode current collector 7a is in electrical contact with the cathode gas diffusion layer 4 stacked on the cathode catalyst layer 2, and the anode gas diffusion layer 5 stacked on the anode catalyst layer 3 is electrically connected to the anode current collector 7b. The membrane electrode assembly 10 is sandwiched on both sides by a folded current collector assembly so as to be in contact with each other. An anode seal frame 8b that surrounds the anode current collector 7b and seals between the electrolyte 6 and the insulating film 70 is disposed on the anode side of the insulating film 70. The cell structure 20 is configured by disposing a cathode seal frame 8 a that surrounds the cathode current collector 7 a and seals between the electrolyte 6 and the insulating film 70 on the cathode side of the insulating film 70.

  The cathode current collector 7 a and the anode current collector 7 b have a plurality of air circulation holes 18 for supplying air to the cathode catalyst layer 2 and a plurality of fuel supply holes 18 for supplying fuel to the anode catalyst layer 3. Each is drilled. Further, a similar flow hole 18 is formed in the common insulating film 70.

These seal frames 8a and 8b are made of a rubber material having a volume resistivity of 10 ¹¹ to 10 ¹⁵ Ω · cm, and these seal members prevent fuel leakage and oxidant leakage from the membrane electrode assembly 10. .

  The cell structure 20 and the fuel supply mechanism 11 are integrated by an exterior cover (not shown), and a moisture retaining plate and a surface layer (not shown) are optionally provided between the exterior cover and the cathode. The fuel supply source 50 stores liquid fuel corresponding to the cell structure 20. Examples of the liquid fuel include methanol fuels such as aqueous methanol solutions of various concentrations and pure methanol. The liquid fuel is not necessarily limited to methanol fuel. The liquid fuel may be, for example, an ethanol fuel such as an ethanol aqueous solution or pure ethanol, a propanol fuel such as a propanol aqueous solution or pure propanol, a glycol fuel such as a glycol aqueous solution or pure glycol, dimethyl ether, formic acid, or other liquid fuel. In any case, liquid fuel corresponding to the fuel cell is accommodated.

  A fuel distribution mechanism 11 is arranged on the anode (fuel electrode) side of the cell structure 20. The fuel distribution mechanism 11 is connected to the fuel supply source 50 by a tubular channel 51. Liquid fuel is introduced into the fuel distribution mechanism 11 from the fuel supply source 50 through the flow path 51. The flow path 51 is not limited to piping independent of the fuel distribution mechanism 11 and the fuel supply source 50. For example, when the fuel distribution mechanism 11 and the fuel supply source 50 are stacked and integrated, a liquid fuel flow path connecting them may be used. The fuel distribution mechanism 11 only needs to be connected to the fuel supply source 50 via the flow path 51.

  A pump 31 is inserted between a flow path 51 connecting the fuel supply source 50 and the fuel distribution mechanism 11. That is, the pump 31 is not a circulation pump that circulates fuel, but is a fuel supply pump that sends liquid fuel from the fuel supply source 50 to the fuel distribution mechanism 41. By supplying liquid fuel when necessary with such a pump 41, the controllability of the fuel supply amount can be improved.

  In the fuel cell 1 </ b> A shown in FIG. 6, the fuel supplied from the fuel distribution mechanism 11 to the cell structure 20 is used for a power generation reaction, and is not circulated and returned to the fuel supply source 50 thereafter. Since the fuel cell 1A shown in FIG. 6 does not circulate the fuel, it is different from the conventional active method and does not impair the downsizing of the apparatus. Further, since the pump 31 is used for supplying the liquid fuel, which is different from the pure passive method such as the conventional internal vaporization type, the fuel cell 1A shown in FIG. 6 employs a method called a semi-passive type, for example. Is.

  The type of the pump 31 is not particularly limited, but a rotary pump (rotary vane pump) and an electroosmotic flow pump can be used from the viewpoint that a small amount of liquid fuel can be fed with good controllability and can be reduced in size and weight. It is preferable to use a diaphragm pump, a squeezing pump or the like. A rotary pump rotates a wing with a motor and feeds liquid. The electroosmotic flow pump uses a sintered porous material such as silica that causes an electroosmotic flow phenomenon. The diaphragm pump is a pump that feeds liquid by driving the diaphragm with an electromagnet or piezoelectric ceramics. The squeezing pump presses a part of the flexible fuel flow path and squeezes the fuel. Among these, it is more preferable to use an electroosmotic pump or a diaphragm pump having piezoelectric ceramics from the viewpoint of driving power, size, and the like.

  Since the main object of the fuel cell 1A is a small electronic device, it is preferable to set the liquid feeding amount of the pump 31 in the range of 10 μL / min to 1 mL / min. If the amount of liquid delivery exceeds 1 mL / min, the amount of liquid fuel delivered at one time becomes too large, and the stop time of the pump 31 occupying the entire operation period becomes long. For this reason, the fluctuation in the amount of fuel supplied to the cell structure 20 increases, and as a result, the fluctuation in output increases. A reservoir for preventing this may be provided between the pump 31 and the fuel distribution mechanism 11, but even if such a configuration is applied, fluctuations in the fuel supply amount cannot be sufficiently suppressed, and This will increase the size of the device.

  On the other hand, if the amount of liquid fed by the pump 31 is less than 10 μL / min, there may be a shortage of supply capacity when the amount of fuel consumption increases when the apparatus is started up. As a result, the start-up characteristics and the like of the fuel cell 31 are degraded. From such a point, it is preferable to use the pump 31 having a liquid feeding capacity in the range of 10 μL / min to 1 mL / min. It is more preferable that the liquid feeding amount of the pump 31 is in the range of 10 to 200 μL / min. In order to stably realize such a liquid feeding amount, it is preferable to apply an electroosmotic flow pump or a diaphragm pump to the pump 31.

  In the fuel cell 1 </ b> A shown in FIG. 6, the liquid fuel is supplied from the fuel supply source 50 to the fuel distribution mechanism 11 by operating the pump 31 when necessary. The liquid fuel introduced into the fuel distribution mechanism 11 is guided to the plurality of fuel supply ports 14 as in the above-described embodiment. Then, fuel is supplied from the plurality of fuel supply ports 14 to the entire surface of the cell structure 20 to cause a power generation reaction. Thus, even when the liquid fuel is fed from the fuel supply source 50 to the fuel distribution mechanism 11 by the pump 31, the fuel distribution mechanism 11 functions effectively, so that the fuel supply amount to the cell structure 20 is made uniform. It becomes possible.

  As shown in FIG. 7, the fuel distribution mechanism 11 includes at least one fuel inlet 12 through which liquid fuel flows in through a flow path 51, and a plurality of fuel supply ports 14 through which liquid fuel and its vaporized components are discharged. Are provided.

  A liquid reservoir 41 that functions as a liquid fuel passage is formed inside the fuel distribution mechanism 11. A fuel inlet 12 is provided at one end (starting end) of the liquid reservoir 41. The liquid reservoir 41 is branched into a plurality of parts on the way, and a fuel supply port 14 is provided at each terminal portion of the branched liquid reservoir 41. The liquid reservoir 41 is preferably a through hole having an inner diameter of 0.05 to 5 mm, for example.

The liquid fuel introduced into the fuel distribution mechanism 11 from the fuel injection port 12 is guided to the plurality of fuel supply ports 14 through the liquid reservoirs 41 branched into a plurality. By using the fuel distribution mechanism 11 having such a structure, the liquid fuel injected into the fuel distribution mechanism 11 from the fuel injection port 12 is evenly distributed to the plurality of fuel supply ports 14 regardless of the direction or position. be able to. Therefore, it is possible to further improve the uniformity of the power generation reaction in the plane of the cell structure 20. A plurality of fuel supply ports 14 are provided on the surface of the flow path plate 13 in contact with the anode so that fuel can be supplied to the entire cell structure 20. The number of the fuel supply ports 14 may be two or more. However, in order to equalize the fuel supply amount in the plane of the cell structure 20, there are 0.1 to 10 / cm ² fuel supply ports 14. It is preferable to form so as to.

  Furthermore, by connecting the fuel injection port 12 and the plurality of fuel supply ports 14 with the liquid reservoir 41, a design can be made such that more fuel is supplied to a specific location of the fuel cell 1. For example, in the case where the heat radiation of the half part of the fuel cell 1A is improved due to the convenience in mounting the apparatus, the temperature distribution is conventionally generated, and the average output is inevitably lowered. On the other hand, by adjusting the formation pattern of the liquid reservoir 41 and arranging the fuel supply ports 14 densely in a portion where heat dissipation is good in advance, it is possible to increase the heat generated by the power generation in that portion. Thereby, the in-plane power generation degree can be made uniform, and it is possible to suppress a decrease in output.

  In the embodiment described above, the mechanism for feeding the liquid fuel from the fuel supply source 50 to the fuel distribution mechanism 11 is not particularly limited. For example, when the installation location at the time of use is fixed, the liquid fuel can be dropped from the fuel supply source 50 to the fuel distribution mechanism 11 and fed using gravity. Further, by using the flow path 51 filled with a porous body or the like, liquid can be fed from the fuel supply source 50 to the fuel distribution mechanism 11 by capillary action.

  The fuel released from the fuel distribution mechanism 11 is supplied to the anode (fuel electrode) of the cell structure 20 as described above. In the cell structure 20, the fuel is diffused in the anode gas diffusion layer 5 and supplied to the anode catalyst layer 3. When methanol fuel is used as the liquid fuel, an internal reforming reaction of methanol represented by the following formula (1) occurs in the anode catalyst layer 3. When pure methanol is used as the methanol fuel, the water generated in the cathode catalyst layer 2 or the water in the electrolyte membrane 6 is reacted with methanol to cause the internal reforming reaction of the following formula (1). Alternatively, the internal reforming reaction is caused by another reaction mechanism that does not require water.

CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻ (1)
Electrons (e ⁻ ) generated by this reaction are guided to the outside via a current collector, and are operated to a cathode (air electrode) after operating a portable electronic device or the like as so-called electricity. In addition, protons (H ⁺ ) generated by the internal reforming reaction of the formula (1) are guided to the cathode through the electrolyte membrane 6. Air is supplied to the cathode as an oxidant. Electrons (e ⁻ ) and protons (H ⁺ ) that have reached the cathode react with oxygen in the air in the cathode catalyst layer 2 according to the following formula (2), and water is generated with this reaction.

6e ⁻ + 6H ⁺ + (3/2) O ₂ → 3H ₂ O (2)
In the power generation reaction of the fuel cell described above, in order to increase the power to be generated, it is important that the catalytic reaction be performed smoothly and that the entire electrode of the cell structure 20 contribute more effectively to power generation. In contrast to this, when there is one fuel supply port 14 for supplying fuel to the cell structure 20, the fuel concentration in the vicinity of the fuel discharge port is sufficient for power generation. The fuel concentration rapidly decreases as the distance from the mouth 14 increases. For this reason, the average output when viewed as a whole of the fuel cell remains at a low value due to the influence of the portion where the supply of fuel is small.

  Control of the fuel supply (liquid feeding) pump 31 is preferably performed with reference to the output of the fuel cell 1A. The output of the fuel cell 1A is detected by a control circuit (not shown), and a control signal is sent to the pump 31 based on the detection result. The pump 31 is controlled to be turned on / off based on a control signal sent from the control circuit. The operation of the pump 31 is controlled based on temperature information, operation state information of an electronic device that is a power supply destination, and the like in addition to the output of the fuel cell 1A, so that more stable operation can be achieved.

  Further, a fuel cutoff valve (not shown) may be arranged in series with the pump 31 in order to enhance the stability and reliability of the fuel cell.

  In this way, by inserting the fuel cutoff valve between the fuel supply source 50 and the fuel distribution mechanism 11, the consumption of a minute amount of fuel inevitably generated even when the fuel cell 1A is not used and the above-described pump re-operation. It is possible to avoid poor suction at times. These greatly contribute to the improvement of practical convenience of the fuel cell 1.

  Furthermore, a balance valve (not shown) that balances the pressure in the fuel supply source 50 with the outside air may be attached to the fuel supply source 50 or the flow path 51.

  When the liquid fuel is supplied from the fuel supply source 50 to the fuel distribution mechanism 11 and the internal pressure of the fuel supply source 50 is reduced, the balance valve is opened. Based on the open state of the balance valve, outside air is introduced so as to reduce the pressure difference between inside and outside. When the pressure difference between the inside and outside is eliminated, the valve is sealed again.

  By installing the balance valve that operates in this manner in the fuel supply source 50 or the like, it is possible to suppress fluctuations in the amount of liquid sent due to a decrease in the internal pressure of the fuel supply source 50 that occurs with the supply of liquid fuel.

  The liquid fuel 49 of each embodiment described above is effective when various liquid fuels are used, and the type and concentration of the liquid fuel are not limited. However, the characteristic of the fuel distribution mechanism 11 having the plurality of fuel supply ports 14 becomes more apparent when the fuel concentration is high. For this reason, the fuel cell 49 of each embodiment can exhibit its performance and effects particularly when methanol having a concentration of 80% or more is used as the liquid fuel. Therefore, each embodiment has a concentration of 80%. It is preferable to apply to the fuel cell using the above methanol as a liquid fuel.

  Although various embodiments have been described above, the present invention is not limited only to the above-described embodiments, and the constituent elements can be modified and embodied without departing from the spirit of the invention in the implementation stage. . In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined. The liquid fuel vapor supplied to the MEA may be all supplied as a liquid fuel vapor, but the present invention can be applied even when a part of the liquid fuel vapor is supplied in a liquid state. In addition, in this semi-passive type fuel cell, a fuel cutoff valve may be arranged in place of the pump as long as fuel is supplied from the fuel storage portion to the membrane electrode assembly. In this case, the fuel cutoff valve is provided to control the supply of liquid fuel through the flow path.

  Examples of the present invention will be described below.

Example 1
<Production of anode>
A perfluorocarbon sulfonic acid solution, water and methoxypropanol were added to an anode catalyst (Pt: Ru = 1: 1) supported carbon black, and the catalyst supported carbon black was dispersed to prepare a paste. The obtained paste was applied to porous carbon paper as the anode gas diffusion layer 5 to produce an anode having an anode catalyst layer 3 with a thickness of 450 μm.

<Production of cathode>
A perfluorocarbon sulfonic acid solution, water and methoxypropanol were added to the cathode catalyst (Pt) -supported carbon black, and the catalyst-supported carbon black was dispersed to prepare a paste. The obtained paste was applied to porous carbon paper as the cathode gas diffusion layer 4 to produce a cathode electrode having a cathode catalyst layer 2 having a thickness of 400 μm.

  Between the anode catalyst layer 3 and the cathode catalyst layer 2, a perfluorocarbon sulfonic acid membrane 6 (a nafion membrane, manufactured by DuPont) having a thickness of 30 μm and a water content of 10 to 20% by weight is used as a proton conductive electrolyte membrane. The membrane electrode assembly (MEA) 10 was obtained by arranging and hot pressing them.

<Preparation of current collector assembly>
Each current collector assembly was fabricated as described in the above embodiment. By integrating the current collector pattern of both electrodes, the cathode insulating seal frame 8a, and the anode insulating seal frame 8b on the common insulating film 70, the respective positions are determined, and the manufacturing time of the cell structure is greatly reduced. I was able to. Further, a positioning pin is provided on the outer periphery of the insulating seal frame so that the position is determined when it is bent.

  By doing so, it was possible to significantly produce the cell structure, the resistance could be reduced by 50 mΩ, and the output characteristics could be improved.

  If there is no cathode insulating seal frame for positioning a plurality of cathode electrodes and an anode insulating seal frame for positioning a plurality of anode electrodes, the position of each electrode is not determined and it is not a predetermined electrode but another electrode. On the other hand, the conductive layer may come into contact. Further, the sealing material is also likely to be pressurized by the exterior cover and the fuel storage chamber structure on the portion where the conductive layer exists, and there is a possibility of fuel leakage from the portion where the conductive layer does not exist. However, the above-described problem can be solved by the structure in which the anode insulating seal frame 8b, the cathode insulating seal frame 8a, the anode current collector pattern 7b, and the cathode current collector pattern 7a according to the present invention are combined.

1 is an internal perspective sectional view showing a fuel cell according to an embodiment of the present invention. FIG. 2 is an exploded cross-sectional view for explaining a manufacturing method of a main part of the fuel cell of FIG. Sectional drawing which shows the principal part of the fuel cell of FIG. The top view which shows the electrical power collector assembly before folding in half. The perspective view which shows the collector assembly folded in half. The block sectional view showing the fuel cell system of other fuel supply methods. The perspective view which shows the outline | summary of a fuel distribution mechanism. The top view which shows the outline | summary of another fuel distribution mechanism.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1A ... Fuel cell, 2 ... Cathode catalyst layer, 3 ... Anode catalyst layer,
4 ... cathode gas diffusion layer, 5 ... anode gas diffusion layer, 6 ... electrolyte membrane (proton conductive membrane),
7A ... current collector assembly,
7a ... cathode current collector,
7b ... anode current collector,
70: Insulating film,
75 ... Electroconductive member between electrodes, 77, 78 ... Terminal,
8a ... cathode seal frame,
8b ... anode seal frame,
9: Gas-liquid separation membrane,
10 ... Membrane electrode assembly (MEA),
11, 11A ... Fuel distribution mechanism,
12 ... Fuel injection port, 13 ... Channel plate, 14 ... Fuel supply port,
18 ... Gas flow hole, 19 ... Moisturizing plate,
20 ... cell structure,
21 ... Cover plate (exterior cover), 22 ... Ventilation hole,
31 ... Pumps 40, 41 ... Liquid reservoir, 49 ... Liquid fuel, 50 ... Fuel supply source.

Claims (10)

An electromotive part comprising a membrane and electrode assembly having a cathode and an anode, and an electrolyte membrane sandwiched between the cathode and the anode;
A cathode current collector in electrical contact with the opposite side of the cathode to the electrolyte membrane side;
An anode current collector in electrical contact with the opposite side of the anode to the electrolyte membrane side;
The anode current collector is disposed on an insulating film on a surface opposite to the surface in contact with the anode, and an anode seal frame that surrounds the anode current collector and seals between the electrolyte membrane and the insulating film; ,
A fuel cell comprising: The cathode current collector is disposed on an insulating film on a surface opposite to a surface in contact with the cathode, and has a cathode frame surrounding the cathode current collector and sealing between the cathode and the insulating film. The fuel cell according to claim 1. The anode current collector and the cathode current collector are disposed on a common insulating film;
3. The fuel cell according to claim 1, wherein the electromotive portion is sandwiched between the insulating film folded in half. 4. 4. The inter-electrode conductive member provided between the anode current collector and the cathode current collector for connecting the anode electrode to the cathode electrode in series is further provided. The fuel cell according to claim 1. The fuel cell according to any one of claims 1 to 4, wherein the anode seal frame is bonded to the insulating film using an adhesive. The fuel cell according to claim 2, wherein the cathode seal frame is bonded to the insulating film using an adhesive. The fuel cell according to any one of claims 1 to 4, wherein the anode seal frame is bonded to the insulating film by vulcanizing and crosslinking liquid rubber. 5. The fuel cell according to claim 2, wherein the cathode seal frame is bonded by vulcanizing and crosslinking liquid rubber. 5. The fuel cell according to claim 1, wherein the anode seal frame is bonded to the film by cross-linking liquid rubber by radiation irradiation. 6. 5. The fuel cell according to claim 2, wherein the cathode seal frame is bonded to the film by cross-linking liquid rubber by radiation irradiation. 6.

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