WO2008050640A1

WO2008050640A1 - Fuel cell

Info

Publication number: WO2008050640A1
Application number: PCT/JP2007/070181
Authority: WO
Inventors: Takashi Shimoyamada; Hiroyuki Hasebe; Hideaki Yasui; Michiyuki Kitamoto; Kiyoshi Senoue; Yoshie Ozeki; Nobuyasu Negishi; Kenichi Takahashi; Koichi Kawamura
Original assignee: Kabushiki Kaisha Toshiba; Toshiba Electronic Engineering Corporation
Priority date: 2006-10-20
Filing date: 2007-10-16
Publication date: 2008-05-02
Also published as: JPWO2008050640A1; KR20090068262A; TW200828661A

Abstract

Disclosed is a fuel cell comprising a membrane electrode assembly, wherein an electrode containing a catalyst layer and a diffusion layer is arranged on both sides of an electrolyte membrane, and collectors which are respectively in surface contact with the diffusion layers of the electrodes for taking out the generated power. At least a part of the collectors comes into respective diffusion layers.

Description

Specification

Fuel cell

Technical field

TECHNICAL FIELD [0001] The present invention relates to a planar arrangement series-connected fuel cell effective for the operation of a portable device.

Background art

[0002] As a power source for mobile phones, notebook computers, and other mopile devices, a small fuel cell that does not require charging is drawing attention. In general, secondary batteries used as the power source for mopile equipment use battery capacity! / When they are fulfilled, they need to be recharged. On the other hand, fuel cells need only be refilled with fuel. It is said that it is easy to use. However, one of the drawbacks of small fuel cells is that the output of single cells is low. For this reason, in order to obtain an output for driving the device, a plurality of single cells must be connected in series as described in, for example, Japanese Patent Application Laid-Open No. 2004-014148 and International Publication No. 2005 / 112172A1. In this case, it is necessary to reduce the electrical resistance generated at the connection as much as possible in order to suppress the decrease in output.

[0003] The electrical resistance at the connection between single cells is a force S involving many parameters, and in particular, the material and structure of the current collector and diffusion layer have a strong influence on the electrical resistance at the connection. Therefore, if the electrical resistance of the connecting part can be reduced by devising the structure of the current collector and the diffusion layer, there are merits such as widening the range of material selection and increasing the degree of design freedom.

Disclosure of the invention

[0004] 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 reduce the electrical resistance of a connecting portion that connects the cells.

[0005] A fuel cell according to the present invention includes a membrane electrode assembly in which electrodes each including a catalyst layer and a diffusion layer are disposed on both surfaces of an electrolyte membrane, and a diffusion layer of the both electrodes in order to extract a power generation output. A fuel cell comprising current collectors in surface contact with each other, wherein at least a part of the current collector penetrates into the diffusion layer.

Brief Description of Drawings

[0006] FIG. 1 is an internal perspective sectional view showing a fuel cell according to an embodiment of the present invention. FIG. 2 is a plan view showing an example of a current collector.

FIG. 3 is a cross-sectional view of a current collector according to an embodiment.

FIG. 4 is a cross-sectional view of a current collector according to another embodiment.

FIG. 5 is a plan view of a current collector (6 series) according to another embodiment.

FIG. 6 is an internal perspective sectional view showing a fuel cell according to another embodiment of the present invention.

FIG. 7 is a perspective view showing a fuel distribution mechanism.

BEST MODE FOR CARRYING OUT THE INVENTION

[0007] In order for the current collector to bite into the diffusion layer, it is necessary that the diffusion layer be made of a material that is softer and easier to deform than the current collector. Carbon paper or carbon cross is used for the diffusion layer. It is preferable to use a porous layer (for example, a metal mesh) or a foil body that also has a metallic material force such as a precious metal such as platinum or gold, a corrosion-resistant metal such as nickel or stainless steel, etc. as a current collector. A material obtained by surface treatment of a conductive material such as carbon with a dissimilar metal, for example, a composite material obtained by coating copper or stainless steel with a good conductive metal such as gold can be used. Carbon paper has a role as a diffusion layer for the fuel supplied to the anode and the air supplied to the power sword, so the force to use the porous material is uniform and the pore distribution is uniform to diffuse the fuel and air uniformly. Is desirable. Carbon paper also plays a role as a conductor, so it is better to have a low volume resistivity. For example, TGP (Toray Graphite Paper: trade name) manufactured by Toray Industries, Inc. and Carbell (trade name) manufactured by Japan Gore-Tex. Can be used. The thickness of the current collector is preferably 30 m or more and 200 m or less, more preferably 50 to 100 m. If the thickness of the current collector is less than 30 m, depending on the type of material, the rigidity is insufficient and the deformation becomes squeezed, which cannot be absorbed into the diffusion layer. On the other hand, if the thickness force of the current collector exceeds ¾00 m, the thickness of the fuel cell itself becomes unnecessarily thick and the space efficiency deteriorates.

[0008] As a method of causing the current collector to enter the diffusion layer, a method of pressing with a pressure as typified by press working can be mentioned as a simple method. For example, the membrane electrode assembly is sandwiched between current collectors arranged on both sides of the membrane electrode assembly, and in this state, the membrane electrode assembly is pressed by a pressing machine to enter. At this time, the press working is performed at a temperature of 100 ° C or higher (for example, 10 ° C). Heating to 0 to 150 ° C) and heating may be performed at a temperature slightly higher than room temperature (for example, 40 to 60 ° C), or heating may be performed at room temperature. . In addition, the membrane electrode assembly sandwiched between the current collectors is finally built into the exterior material to become a fuel cell. However, the current collector may be pressed and penetrated in the process of being built in. . Specifically, the outer packaging material is fixed by caulking screws, etc., but at this time, the pressure is applied so that the current collector enters the diffusion layer of the membrane electrode assembly. Also good.

[0009] As described above, when the current collector is pushed into the diffusion layer, at least a part of the current collector penetrates into the diffusion layer. When the volume average porosity before being pushed into the diffusion layer is α%, and the crushing ratio of the portion where the diffusion layer is crushed when at least a part of the current collector is pushed into the diffusion layer is 3% In addition, it is preferable to satisfy the relationship β≤α / 3. Deviating from this range / 3> In the range of α / 3, the diffusion layer may be crushed too much to inhibit diffusion, and in extreme cases, the diffusion layer may be excessively deformed and break. is there. Here, the “volume average porosity” is the average porosity per unit volume, and is the porosity of the diffusion layer before the current collector is pushed into the diffusion layer. In the case of evaluating the material after being pushed in, the current collector can be pushed into the diffusion layer and replaced with the porosity of the part. The volume average porosity can be measured using, for example, a porosimeter. In addition, the “crush rate” is the ratio of the thickness of the diffusion layer where the current collector is pushed into the diffusion layer to the thickness of the diffusion layer where the current collector is not pushed in (the current collector) Is the thickness decrease of the diffusion layer in the portion where the current is pressed into the diffusion layer / the thickness of the diffusion layer in the portion where the current collector is not pressed). For example, when the diffusion layer is rectangular, the current collector is pushed in by averaging five points (near the center of the part and near the center of each side) of the area where the current collector is not pushed into the diffusion layer. The thickness of the unexposed portion of the diffusion layer is taken. In addition, when a large number of current collectors are arranged in series on the same diffusion layer, the average of the results measured in the area where the current collector near the center of each current collector exists is pushed into the diffusion layer. It is assumed that the thickness of the diffusion layer is reduced.

[0010] It is possible to use a perforated flat plate having a plurality of holes through which fuel or air flows as a current collector. It is preferable that the aperture ratio of this perforated flat plate be 35% or more. It is more preferable than S to be at least%. That is, the total area obtained by two-dimensionally projecting a plurality of holes is set to 35% or more of the total area obtained by projecting the entire current collector two-dimensionally. This is because if the aperture ratio is less than 35%, the portion of the diffusion layer that collapses due to the indentation of the current collector increases, which in turn reduces the output characteristics of the fuel cell. If the aperture ratio is 50% or more, the output characteristics are further improved, and stable output characteristics can be obtained.

[0011] In the fuel cell of the present invention, the current collector is superimposed on the diffusion layer, and the current collector is bitten into the diffusion layer by applying a surface pressure with a press or the like. As it improves, the mutual contact area between the two increases. This reduces the contact resistance at the connection between the current collector / diffusion layer and reduces the power generation output loss.

[0012] Further, since the intruding portion of the current collector is located closer to the catalyst layer than the conventional structure, the current path in the power generation unit is shortened, and the internal resistance is reduced. This also reduces the loss of power output.

[0013] Various modes for carrying out the present invention will be described below with reference to the accompanying drawings.

[0014] (First embodiment)

First, an overview of the entire fuel cell will be described with reference to FIG.

The fuel cell 1 has a plurality of unit cells whose outer sides are covered with an outer case 21 and are arranged in a plane and connected in series. The fuel cell 1 may be configured as a single unit in which a plurality of single cells are integrated by, for example, caulking the end portion of the outer case 21 to the outer surface of the fuel storage chamber structure 20. 21 and the fuel storage chamber structure 20 may be integrally formed by tightening them with a bolt and a nut.

The fuel cell 1 includes a membrane electrode assembly 10 as a power generation unit, a force sword current collector 7 and an anode current collector 9 as current collectors, a gas-liquid separation membrane 13 as a vaporized membrane, and a liquid fuel space 14 A fuel storage chamber structure 20 is formed. The membrane electrode assembly 10 includes a force sword catalyst layer 2 and an anode catalyst layer 3 integrally formed on both sides of a proton conductive solid electrolyte membrane 6 by a heat press method, and a force sword gas on the outside thereof. A diffusion layer 4 and an anode gas diffusion layer 5 are provided. Further, the positive electrode current collector 7 is electrically connected to the force sword gas diffusion layer 4 of the membrane electrode assembly 10, and the negative electrode current collector 9 is electrically connected to the anode gas diffusion layer 5. The power generated by the power generation unit through these positive and negative current collectors 7 and 9 is output to a load (not shown). It has become.

[0017] Various spaces and gaps are formed in the fuel cell 1 by rubber seals 8 and O-rings (not shown). Among these spaces and gaps, for example, the space on the force sword side is used as an air introduction part having a moisture retaining plate, and the space on the anode side communicates with the liquid fuel storage chamber 14 via the gas-liquid separation membrane 13. Used as a vaporizing chamber.

A vaporization chamber (not shown) is provided adjacent to the liquid fuel storage chamber 14, and the two chambers are partitioned by a gas-liquid separation film 13. The gas-liquid separation membrane 13 is supported in a state where its peripheral edge is sandwiched between a seal member (not shown) and the flange of the fuel storage chamber structure 20. The gas-liquid separation membrane 13 is made of a polytetrafluoroethylene (PTFE) sheet having a large number of pores, blocks liquid fuel (such as methanol liquid or its aqueous solution), and permeates vaporized fuel (such as methanol gas). It is something to be made.

A plurality of air holes 22 are opened at predetermined pitch intervals on the main surface of the outer case 21 and communicated with the internal moisture retaining plate 19. These air holes 22 form openings through which the outside air passes, but do not hinder the passage of the outside air, and prevent the entry or contact of minute or needle-like foreign substances to the force sword gas diffusion layer 4 from the outside. The shape that can be obtained is devised.

[0020] The outer case 21 is preferably made of a metal material having excellent corrosion resistance, such as stainless steel or nickel alloy, but is not limited to a metal material, and a resin material can be used. A hard resin that does not easily swell with a liquid fuel, such as ether ketone (PEEK: trademark of Victorex PLC), polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE) may be used.

[0021] Various rubber-based materials ranging from hard to soft, resin-based materials, or metal materials can be used for the seal member. Of these, rubber-based materials (for example, EPDM (ethylene propylene rubber), FKM (fluoro rubber) ), NBR (nitrile butadiene rubber), SBR (styrene butadiene rubber)) are most suitable.

FIG. 2 shows the negative electrode current collector 9 of one unit cell inside the fuel cell 1. The negative electrode current collector 9 has a plurality of openings 16. These openings 16 communicate with the anode gas diffusion layer 3 side. When a part of the liquid fuel in the liquid fuel storage chamber 14 is vaporized, the vaporized fuel passes through the gas-liquid separation membrane 13 and enters the vaporization chamber, and further collects current from the vaporization chamber. It is introduced into the anode gas diffusion layer 5 and the anode catalyst layer 3 through the opening 16 of the body 9 and contributes to the power generation reaction.

Similarly, the positive electrode current collector 7 also has a plurality of openings 16. These openings 16 communicate with the vent hole 22 of the outer case 21 through a moisture retaining plate (not shown). When air is introduced from the vent hole 22, it is humidified through the moisture retaining plate in the air conditioning space, and is introduced into the force sword gas diffusion layer 4 and the force sword catalyst layer 2 through the opening 16 of the current collector 7 to generate power. Contributes to the reaction.

As shown in FIG. 2, the current collectors 7 and 9 have a substantially square shape, and leads 7a and 9a extend from the center of one side. Leads 7a and 9a are connected to the terminals of the load (not shown). The current collector opening 16 is a rectangle of substantially the same size, and a total of 20 columns in 5 rows x 4 rows is regularly arranged in a grid pattern!

[0025] In order to extract electrons from the anode side of the power generation unit 10 to the negative electrode current collector 9 and to make efficient use of the power generation energy, a part of the current collector 9 is used as shown in FIG. It penetrates into the diffusion layer 5. Similarly, on the force sword side, part of the positive electrode current collector 7 is bitten into the diffusion layer 4. In the present embodiment, the current collectors 7 and 9 are formed in the diffusion layers 4 and 5 to half the thickness (tl / 2) by warm pressing using a press machine at a temperature of about 100 ° C. Each bite. If the thickness tl of the current collectors 7 and 9 is, for example, 0 · lmm dOC ^ m), the biting depth dl of the current collectors 7 and 9 with respect to the diffusion layers 4 and 5 is 50 m.

[0026] Fig. 4 shows an example in which a part of the current collector 9A is bitten into the diffusion layer 5A. Similarly, on the force sword side, a part of the positive electrode current collector 7A is bitten into the diffusion layer 4A. In the present embodiment, the current collectors 7A and 9A are bitten into the diffusion layers 4 and 5 to the thickness tl by hot pressing at a temperature of about 150 ° C. using a press machine. When the thickness tl of the current collectors 7A and 9A is, for example, 0 · lmmdOC ^ m), the biting depth dl of the current collectors 7A and 9A with respect to the diffusion layers 4A and 5A is 100 m.

[0027] The current collectors 7 and 9 are made of a 0.1 mm thick stainless steel plate plated with gold to capture the fuel to be supplied to the anode and the air required for the power sword. Each hole has been drilled so as not to interfere. Some of these current collectors 7 and 9 are drawn out of the fuel cell and serve as external terminals. [0028] Platinum or a catalyst made of platinum and other metals is applied to both surfaces of the solid polymer film 6 to form catalyst layers 2 and 3, and carbon paper is used for the diffusion layers 4 and 5 disposed on both sides thereof. I used it. The thickness t2 of the carbon paper used is 0.4 mm on both the anode side and the force sword side. The catalyst part contributing to power generation and the size of the carbon paper are 40 mm square, solid polymer on each side of the power generation part. The size of the solid polymer film 6 was 50 mm × 50 mm square so that the film 6 protruded 5 mm.

A fuel introduction port 15 is opened in the liquid fuel storage chamber 14. For example, a key groove type coupler is attached to the fuel inlet 15, and a nozzle of a fuel cartridge (not shown) is inserted into the coupler so that liquid fuel is supplied to the liquid fuel storage chamber 14.

A liquid fuel impregnation layer (not shown) is accommodated in the liquid fuel storage chamber 14. For the liquid fuel-impregnated layer, it is preferable to use, for example, a multi-rigid fiber such as porous polyester fiber or porous olefin resin, or an open-cell porous material resin. The liquid fuel impregnated layer is uniformly supplied to the gas-liquid separation membrane even when the liquid fuel in the fuel tank is reduced or even when the fuel cell body is tilted and the fuel supply is biased. Thus, it is possible to supply the vaporized liquid fuel to the anode catalyst layer 3 uniformly. In addition to polyester fiber, it is composed of a material that can hold the liquid using the permeability of the liquid, such as sponges or fiber aggregates that can be composed of various water-absorbing polymers such as acrylic resins. To do. This liquid fuel impregnation part is effective for supplying an appropriate amount of fuel regardless of the posture of the main body.

[0031] The liquid fuel includes methanol fuel such as methanol aqueous solution, pure methanol, ethanol aqueous solution such as ethanol aqueous solution, pure ethanol, propanol fuel such as propanol aqueous solution and pure propanol, and Daricol fuel such as glycol aqueous solution and pure glycol. Organic aqueous solutions containing hydrogen such as aqueous formic acid, aqueous sodium formate, aqueous acetic acid, aqueous sodium borohydride, aqueous potassium borohydride, aqueous lithium hydride, aqueous ethylene glycol, and dimethyl ether are used. Among these, an aqueous methanol solution is preferable because it has carbon number of 1 and carbon dioxide gas is generated during the reaction, and can generate electricity at a low temperature and can be produced relatively easily from industrial waste. . In addition, fuels with various concentrations in the range from 100% to several percent can be used. [0032] The solid electrolyte membrane 6 is for transporting protons generated in the anode catalyst layer 3 to the force sword catalyst layer 2, and is composed of a material that does not have electron conductivity and can transport protons. Has been. For example, it is composed of a polyperfluorosulfonic acid resin membrane, specifically, a naphthoion membrane manufactured by DuPont, a Flemion membrane manufactured by Asahi Glass, or an aciplex membrane 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 An electrolyte membrane 6 capable of transporting protons such as an aliphatic hydrocarbon resin membrane may be formed.

[0033] The anode catalyst layer 3 oxidizes vaporized fuel supplied via the gas diffusion layer 5 to extract 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 platinum (Pt) fine particles, iron (Fe), nickel (Ni), cobalt (Co), ruthenium (Ru), molybdenum (Mo), and other transition metals or oxides thereof or their oxides. Fine particles such as alloys are used. However, it is preferable that the catalyst is made of an alloy of ruthenium and platinum, since inactivation of the catalyst due to adsorption of carbon monoxide (CO) can be prevented.

[0034] Further, it is more desirable that the anode catalyst layer 3 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, specifically made of carbon paper or carbon fiber.

[0035] The force sword catalyst layer 2 reduces oxygen and reacts electrons with the proton generated in the anode catalyst layer 3 to generate water. For example, the above-mentioned anode catalyst layer 3 and The configuration is the same as that of the node gas diffusion layer 5. That is, the force sword has a laminated structure in which a force sword catalyst layer 3 made of carbon powder containing a catalyst and a force sword gas diffusion layer 5 made of a porous carbon material are stacked in order from the solid electrolyte membrane 11 1 side. ing. The catalyst used for the force sword catalyst layer 2 is the same as that of the anode catalyst layer 3, and the anode catalyst layer 3 may contain fine particles of resin used for the solid electrolyte membrane 6. It is the same. Incidentally, the thickness of the electrolyte membrane 6 is 10 to 250 111, the thickness of the force sword catalyst layer 2 and the anode catalyst layer 3 is 50 to; 100 m, the thickness of the force sword diffusion layer 4 and the anode diffusion layer 5 is 250. The optimum values for the thicknesses of ~ 500 Hm, positive electrode current collector 7 and negative electrode current collector 9 can be selected from the range of 30 to 200 μm.

[0036] The outer case 21 and the fuel storage chamber structure 20 can be made of a metal material having excellent corrosion resistance, such as stainless steel or nickel metal. In this case, it is desirable to apply a resin coating to prevent elution of metal ions. Polyetheretherketone (PEEK: trademark of Victorex PLC), polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), etc.

[0037] (Second Embodiment)

Next, a second embodiment of the present invention will be described with reference to FIG. Note that description of portions in which the present embodiment overlaps with the first embodiment is omitted.

[0038] The fuel cell 1A has therein a plurality of single cells arranged on substantially the same plane. The plurality of single cells arranged horizontally on the same plane are connected in series via positive and negative current collectors 7A and 9A. Since the thickness size of mobile devices is severely limited, the same requirements apply to the fuel cells built into them, and it is difficult to adopt a stack structure in which a plurality of single cells are stacked. Adopt a flat arrangement structure. A battery pack is formed by connecting a plurality of cells arranged flat in this way in series.

[0039] In the fuel cell 1A of the present embodiment, the current collectors 7A, 9A are, as shown in Fig. 5, six rows of substantially rectangular current collectors 7A, 9A arranged, from the center of one side thereof. Leads 7a and 9a are extended. The leads 7a and 9a are respectively connected to the bipolar terminals of a load (not shown).

[0040] The current collectors 7A and 9A are made by using a 0.1 mm thick stainless steel plate plated with gold to capture the fuel to be supplied to the anode and the air required for the power sword. Each hole has been drilled so as not to interfere. A part of these current collectors 7A, 9A is drawn out of the fuel cell and serves as an external terminal.

[0041] The openings 16 of the current collectors 7A and 9A are substantially the same size rectangle, and are vertically arranged with 8 pieces. It is arranged.

[0042] In order to take out electrons from the anode side of the power generation unit 10 to the negative electrode current collector 9A and to make efficient use of the power generation energy, FIG. 3 or FIG. 4 shows the same as in the first embodiment. As shown, eat a part of the current collector in the diffusion layer!

[0043] [Examples !! ~ 5]

In a general fuel cell, the power to secure the output voltage with an assembled battery in which a plurality of single cells are connected in series. Examples described below;! To 5 are used for the purpose of confirming the effect of the present invention. The fuel cell is composed of single cells.

[0044] The solid polymer film 6 is coated with a catalyst made of platinum or platinum and other metals on both sides to form catalyst layers 2 and 3, and carbon paper is used for the diffusion layers 4 and 5 disposed on both sides thereof. I used it. The thickness t2 of the carbon paper used is 0.4 mm on both the anode side and the force sword side. The catalyst part contributing to power generation and the size of the carbon paper are 40 mm square, solid polymer on each side of the power generation part. The size of the solid polymer film 6 was 50 mm × 50 mm square so that the film 6 protruded 5 mm.

[0045] The current collectors 7 and 9 are 0.1 mm thick stainless steel plates plated with gold to capture the fuel to be supplied to the anode and the air required for the power sword. Each hole has been drilled so as not to interfere. Some of these current collectors 7 and 9 are drawn out of the fuel cell and serve as external terminals.

[0046] These laminates are sandwiched by plastic parts as exterior materials via rubber seals 8 and sealed by screwing to form a fuel cell S, rubber seals 8 from carbon papers 4 and 5 The solid polymer membrane 6 was placed so as to contact the protruding portion of the polymer film 6 and sealed at that portion.

[0047] The material of the anode side exterior member 20 to be sandwiched was PPS. The inside of the exterior material 20 is adjacent to the anode electrode to form a liquid fuel storage chamber 14 and an external fuel supply port 15 is installed. Also, PPS is used for the force sword pole side exterior material 21 and a plurality of air holes 22 are opened so that air can be taken in from the outside.

[0048] Further, in this embodiment, the nonwoven fabric 13 capable of absorbing and holding the fuel is disposed between the fuel holding portion and the anode current collector for the purpose of assisting the uniform fuel supply to the anode electrode. [0049] However, the fuel supply to the anode electrode and the air supply to the force sword electrode may be supplied by using an auxiliary machine such as a pump, and in that case, a part in which a flow path is formed The fuel and air may be supplied using

[0050] [Example 1]

As Example 1, 50 fuel cells were prepared as follows.

[0051] As described above, carbon paper having a thickness of 0.4 mm is used for the diffusion layers 4 and 5 of the membrane electrode structure on both the anode side and the force sword side. % Selected. The thickness of the current collector disposed on the outer side is 0.1 mm. However, in the fuel cell of Example 1, the electrode membrane structure was pressed between the current collectors, and the entire current collector was carbonized. The thickness of the carbon paper and current collector combined in the paper was 0.4 mm.

[0052] In this case, the collapse rate / 3 is the thickness of the diffusion layer in the portion where the current collector is not pushed in, 0.4 mm, and the thickness of the diffusion layer in the portion where the current collector is pushed into the diffusion layer. The decrease is 0.1% (0.1 / 0.4) and 25%. Therefore, since the porosity α force is S75%, the relationship is 0≤a / 3. Note that the thickness reduction of the diffusion layer where the current collector is pushed into the diffusion layer is (the combined thickness of the carbon paper before the press and the current collector). Thickness).

[0053] Regarding the shape of the current collector, a terminal portion serving as an external terminal is extended to a 40 mm square portion that is the same as the size of carbon paper, but fuel is supplied to the anode electrode and air is supplied to the force sword electrode. As shown in Fig. 2, 20 holes of 5 x 8mm size were drilled. In this case, the hole spacing is Dx = l. 6 mm, Dy = 2.5 mm, and the aperture ratio of the current collector is 50%.

[0054] [Example 2]

As Example 2, when the current collector was embedded in carbon paper by pressing, the thickness of the current collector to be cut into the carbon paper was set to 0.05 mm, and the carbon paper and current collector on the anode side and the power sword side, respectively. 50 fuel cells different from Example 1 were produced only in that the combined thickness was 0 · 45 mm.

[0055] The combined thickness of the electrode film structure and the current collector is greater than that of Example 1. The torque of the screw for tightening the exterior material was the same, and the tightening was the same as in the example. Examples of different thicknesses described below Nitsu! /, But take the same action! /

[0056] In this case, the crush rate / 3 is the thickness of the diffusion layer in the portion where the current collector is not pushed in, 0.4 mm, and the thickness of the diffusion layer in the portion where the current collector is pushed into the diffusion layer. The ratio of decrease to 0.05 mm (0.05 / 0.4) is 12.5%. Therefore, since the porosity α is 75%,

/ 3≤ «/ 3.

[0057] [Example 3]

As Example 3, the current collector hole size is 5 X 6 mm, the hole spacing is Dx = 3.2 mm,

Fifty fuel cells were manufactured in the same manner as in Example 1 except that Dy = 2.5 mm and the aperture ratio of the current collector was changed to 37.5%.

[Example 4]

As Example 4, the current collector hole size is 5 X 5 mm, the hole spacing is Dx = 4. Omm,

Fifty fuel cells were manufactured in the same manner as in Example 1 except that Dy = 2.5 mm and the aperture ratio of the current collector was changed to 31.2%.

[0059] [Example 5]

In Example 5, the thickness of the current collector was changed to 0.15 mm, and the thickness of the current collector was embedded in carbon paper by pressing as in Example 1, and the thickness of the carbon paper and current collector combined. Fifty fuel cells were made with a thickness of 0.4 mm.

[0060] The crushing ratio β in this case is 0.4 mm in the thickness of the diffusion layer where the current collector is not pushed, and the thickness reduction of the diffusion layer where the current collector is pushed into the diffusion layer. Damage 0.15mm and IJ combined (0.15 / 0.4), 37.5%. / 3≥ α / 3.

[0061] [Comparative Example 1]

As Comparative Example 1, the components that make up the fuel cell are the same as in Example 1, but only the electrode membrane structure is pressed so that the thickness of the carbon paper is 0.3 mm, and current collectors are placed on both sides. Thus, 50 fuel cells different from Example 1 were produced only in that the combined thickness of the carbon paper and the current collector was 0.4 mm.

[0062] [Comparative Example 2]

As Comparative Example 2, the components that make up the fuel cell are the same as in Example 1, but the thickness of the carbon paper and the current collector combined without causing the current collector to bite into the carbon paper. 50 fuel cells different from Example 1 were produced only in that the value became 0.5 mm.

[0063] 50 fuel cells of each of the examples and comparative examples were prepared and the output was confirmed. The conditions for confirming the output were 5% by weight methanol aqueous solution, and a constant voltage output of 0.2V was confirmed.

[0064] The average output values of the fuel cells according to Examples 1 to 5 and Comparative Examples 1 and 2 when the average output value of Comparative Example 1 is 100 are shown in Table 1.

[table 1]

table 1

As is apparent from the results in Table 1, in Examples 1 to 5, outputs better than those in Comparative Examples 1 and 2 were confirmed. Among them, in Example 4 in which the aperture ratio of the current collector is as small as 31.2%, the output average value 105.0% in which the diffusion layer is largely crushed is a little small result, and the present invention The aperture ratio of the current collector used in the fuel cell is 35% or more, more preferably 50% or more.

[0066] Although carbon paper with a porosity of 75% is used, the average output value of the fuel cell of Example 5 in which the proportion of the carbon paper where the current collector falls is 37.5% However, the effect was slightly small at 106.5%, and it was confirmed that the effect diminished by crushing the carbon paper too much.

[0067] [Examples 6 to 10]

Examples 6 to 10 described below are examples of assembled batteries in which a plurality of single cells are connected in series. Except for the assembled battery, the basic fuel cell configuration is the same as in Examples 1 to 5.

As Example 6, 50 fuel cells having a power generation unit as shown in FIG. 5 were prepared. [0069] The current collectors 7 and 9 are in the form of strips and elongated rectangles as a whole, and leads 7a and 9a extend from the center of one side. The leads 7a and 9a are connected to the pole terminals of the load (not shown). The openings 16 of the current collector are substantially the same size rectangles, and a total of 48 columns of 8 vertical rows and 6 horizontal rows are regularly arranged in a grid pattern.

[0070] The membrane electrode assembly to be used is a common force solid electrolyte membrane composed of six power generation units arranged on the same plane. The size of the solid electrolyte membrane is 106mm x ll lmm, and there are six electrodes with length Gy = 100mm and width Gx = 15mm. The distance between the electrodes Mx and the solid electrolyte membrane from the electrode Hami out My was all 3mm.

A current collector having a length Ey = 100 mm and a width Ex = l lm m is disposed on each of the anode side and the force sword side of each electrode. The anode of the adjacent electrode and the force sword are electrically connected through the arranged current collector and terminal portions (leads) 7a and 9a drawn out of the electrode, and the six electrodes are connected in series. In this example, the current collector width Ex was narrower than the electrode width, but the current collector was arranged so that the center in the width direction of the current collector coincided with the center in the width direction of the electrode. Each current collector has holes 16 for taking in fuel and air. In this example, eight holes with a length Hy = 8 mm and a width Hx = 5 mm were formed in one row in the length direction. The distance in the length direction of the holes was Dy = 4mm, the width direction was set so that the holes were located in the center of the current collector, and the width of the frame part was Dx = 3mm.

[0072] The area of the current collector in the area of each electrode is 52%, and the aperture ratio is 48%.

[0073] Carbon paper having a thickness of 0.4 mm and a porosity of 75% was used for the diffusion layers on the anode side and the force sword side, respectively. The current collector was made of a gold-plated material on the stainless steel surface, and the material thickness after plating was 0.1 mm. These electrode membrane structures were pressed with the current collector sandwiched between them, and the entire thickness of the current collector was embedded in carbon paper, and the carbon paper and current collector on each of the anode side and the force sword side were combined. The thickness was set to 0.4 mm.

[0074] In this case, the crush rate / 3 is the thickness of the diffusion layer 0.4 mm where the current collector is not pushed in, and the thickness of the diffusion layer where the current collector is pushed into the diffusion layer The decrease is 0.1% (0.1 / 0.4) and 25%. Therefore, since the porosity α force is S75%, the relationship is 0≤a / 3. Note that the thickness of the diffusion layer where the current collector is pushed into the diffusion layer is reduced. A small amount is (the thickness of the carbon paper and the current collector before pressing) one (the thickness after the pressing of the paper and the current collector).

[0075] [Example 7]

As Example 7, when the current collector was embedded in carbon paper by pressing, the thickness of the current collector to be cut into the carbon paper was set to 0.05 mm, and the carbon paper and current collector on the anode side and the power sword side, respectively. 50 fuel cells different from Example 6 were produced only in that the combined thickness was 0 · 45 mm.

[0076] The combined thickness of the electrode film structure and the current collector is thicker than in Example 6. The torque of the screw for tightening the exterior material was the same, and the tightening was the same as in the example. For the examples with different thicknesses described later! /, Do the same!

[0077] [Example 8]

As Example 8, 50 fuel cells were manufactured in the same manner as in Example 6 except that the size of the current collector disposed on the anode side and the force sword side of each electrode was changed as follows.

The current collector used had a length Ey = 100 mm, a width Ex = 13 mm, and the hole size was a length Hy = 4 mm and a width Hx = 5 mm. As in Example 6, the number of holes arranged in one row in the length direction is 12. The distance in the length direction of the holes is Dy = 4 mm, and the width direction is set so that the holes are located in the center of the current collector. The width of the frame portion was Dx = 3 mm.

[0079] The area of the current collector in each electrode is about 64.3%, and the aperture ratio is 35.7%.

[0080] [Example 9]

Fifty fuel cells were manufactured in the same manner as in Example 6 except that the size of the current collector disposed on the anode side and the force sword side of each electrode was changed as follows.

The current collector used had a length Ey = 100 mm, a width Ex = 13 mm, and the hole size was a length Hy = 2 mm and a width Hx = 5 mm. The number of holes arranged in one row in the length direction is the same as in Example 1. The number of holes is 16 and the distance in the length direction of the holes is Dy = 4mm. In the width direction, the holes are positioned at the center of the current collector. The width of the frame portion was Dx = 3 mm.

[0082] The area of the current collector in each electrode is about 71.8%, and the aperture ratio is 28.2%.

[0083] [Example 10]

Example 10 is the same as Example 6 except that the thickness of the current collector is 0.15 mm. The entire thickness of the current collector was embedded in carbon paper by machining, and 50 fuel cells were prepared so that the combined thickness of carbon paper and current collector on the anode side and cathode side was 0.4 mm. .

[0084] [Comparative Example 3]

As Comparative Example 3, the components constituting the fuel cell are the same as in Example 6, but only the electrode membrane structure is pressed so that the thickness of the carbon paper is 0.3 mm, and current collectors are arranged on both sides thereof. Thus, 50 fuel cells different from Example 1 were produced only in that the combined thickness of the carbon paper and the current collector was 0.4 mm.

[0085] [Comparative Example 4]

As Comparative Example 4, the components that make up the fuel cell are the same as in Example 6, but the current collector is not digged into the carbon paper, and the combined thickness of the carbon paper and the current collector is 0.5 mm. Only 50 fuel cells different from Example 6 were produced.

[0086] Table 2 summarizes the size of each part of current collectors 7 and 9 of Examples 6 to 10 and Comparative Examples 3 and 4 described above.

[Table 2]

Table 2 Dimensions table for each example

[0087] 50 fuel cells of each Example and Comparative Example were prepared and the output was confirmed. Output The conditions for confirmation were 5% by weight methanol aqueous solution, and a constant voltage output of 0.2V was confirmed.

Table 3 shows the average output values of the fuel cells according to Examples 6 to 10 and Comparative Example 4 when the average output value of Comparative Example 3 which is one of the conventional examples is 100.

[Table 3] Table 3

As is clear from the results in Table 3, in Examples 6 to 10, a better output than Comparative Examples 3 and 4 was confirmed. Among them, in Example 9 where the aperture ratio of the current collector is as small as 28.3%, the output average value 101% in which the diffused layer is crushed in many parts is a little smaller result, and according to the present invention. The aperture ratio of the current collector used in the fuel cell is 35% or more, more preferably 50% or more.

[0090] Although the carbon paper with a porosity of 75% is used, the fuel cell of Example 10 in which the proportion of the carbon paper where the current collector falls is 37.5% is also the output average. The value was 106.5%, indicating that the effect was slightly small, and it was confirmed that the effect diminished due to excessive crushing of the carbon paper.

[0091] From the above Examples 1 to 10 and Comparative Examples 1 to 4, the power generation unit has a membrane electrode assembly in which electrodes composed of a catalyst layer and a porous diffusion layer are arranged on both sides of the electrolyte membrane, In the fuel cell in which electric energy is taken out through current collectors arranged on both sides of the membrane electrode assembly, the ratio of crushing the carbon paper by allowing the current collector to penetrate into the diffusion layer is the porosity of the current collector It was confirmed that the fuel cell of the present invention that maintains a good supply of fuel and air by controlling the above shows good characteristics.

In the above embodiment, the lower part of the membrane electrode assembly (MEA) 10 is used as the structure of the fuel cell. Although the present invention has been described with respect to a passive type fuel cell having a liquid fuel storage chamber 14, the present invention can also be applied to fuel cells of other structures. For example, the present invention may be used in a semi-passive fuel cell 301 as shown in FIG.

[0093] (Third embodiment)

The power generation unit 301a of the fuel cell according to the present embodiment includes a membrane electrode assembly 10, a force sword current collector 7 and an anode current collector 9 as current collectors. The membrane electrode assembly 10 is formed by integrally forming a force sword catalyst layer 2 and an anode catalyst layer 3 on both sides of a proton conductive electrolyte membrane 6 by a hot press method, and further forming a force sword gas diffusion layer on the outside thereof. 4 and an anode gas diffusion layer 5. Further, the positive electrode current collector 7 is electrically connected to the force sword gas diffusion layer 4 of the membrane electrode assembly 10, and the negative electrode current collector 9 is electrically connected to the anode gas diffusion layer 5. A part of the positive electrode current collector 7 penetrates into the force sword gas diffusion layer 4 as shown in FIG. Similarly, a part of the negative electrode current collector 9 penetrates into the anode gas diffusion layer 5 as shown in FIG. The power generated by the power generation unit through the pair of positive and negative current collectors 7 and 9 is output to the load (not shown).

[0094] A rubber O-ring 8 is inserted between the electrolyte membrane 6 and a fuel distribution mechanism 301e and a cover plate 21 to be described later, and the fuel cell power generation unit 301a is inserted by the pair of O-rings 8. To prevent fuel leaks and oxidizer leaks.

[0095] The cover plate 21 has a plurality of openings (not shown) for taking in the oxidant (air). Between the cover plate 21 and the power sword of the power generation unit 301a, a moisture retaining layer and a surface layer are disposed as necessary. The moisturizing layer (not shown) is impregnated with a part of the water generated in the force sword catalyst layer 2 to suppress the transpiration of water and promote the uniform diffusion of air to the force sword catalyst layer 2. Is. The surface layer (not shown) is for adjusting the amount of air taken in, and has a plurality of air inlets whose number and size are adjusted according to the amount of air taken in.

[0096] A fuel distribution mechanism 301e is disposed on the anode side of the power generation unit 301a. A fuel container 301b is connected to the fuel distribution mechanism 301e via a fuel flow path 301c such as a pipe. The fuel storage unit 301b stores liquid fuel of a type corresponding to the power generation unit 301a. [0097] Fuel is introduced into the fuel distribution mechanism 301e from the fuel storage portion 301b via the flow path 301c. The flow path 301c is not limited to piping independent of the fuel distribution mechanism 301e and the fuel storage portion 301b. For example, when the fuel distribution mechanism 301e and the fuel storage portion 301b are stacked and integrated, a liquid fuel flow path connecting them may be used. The fuel distribution mechanism 301e is connected to the fuel storage part 301b via the flow path 301c!

Here, as shown in FIG. 7, the fuel distribution mechanism 301e includes at least one fuel inlet 25 through which fuel flows in through the flow path 301c, and a plurality of liquid fuel and its vaporized components. And a fuel distribution plate 23 having a fuel discharge port 26. A gap 24 is formed in the fuel distribution plate 23 as shown in FIG. The gap 24 combines the function of a flow path where the fuel introduced from the fuel injection port 25 flows and temporarily retains it, and the function of the header. The plurality of fuel discharge ports 26 communicate directly with the gap 24.

[0099] The fuel is introduced into the fuel distribution mechanism 301e from the fuel inlet 25, enters the gap 24, and is guided from the gap 24 to the plurality of fuel outlets 22, respectively. For example, a gas-liquid separator (not shown) that transmits only the vaporized component of the fuel and does not transmit the liquid component may be disposed in the plurality of fuel discharge ports 22. As a result, the vaporized component of the fuel is supplied to the anodes 3 and 5 of the power generation unit 301a. A gas-liquid separation membrane (not shown) may be inserted between the fuel distribution mechanism 301e and the anodes 3 and 5 of the power generation unit 30la. The vaporized component of the liquid fuel is discharged from a plurality of fuel discharge ports 26 toward a plurality of anodes 3 and 5 of the power generation unit 301a.

[0100] The fuel outlet 26 is provided with a plurality of fuel distribution plates 23 on the surface in contact with the anodes 3, 5 of the power generation unit 301a so that fuel can be supplied to the entire power generation unit 301a. The number of the fuel outlets 26 may be two or more. However, in order to equalize the fuel supply amount in the plane of the fuel cell power generation unit 301a, 0.;! ~ 10 / cm ² fuel outlets It is preferable to form so that 26 exists.

[0101] A pump 30 Id is inserted into the flow path 301c connecting the fuel distribution mechanism 301e and the fuel storage portion 301b. The pump 30 Id is a fuel supply pump that transfers fuel from the fuel storage portion 301b to the fuel distribution mechanism 301e even if it is not a circulating pump through which fuel is circulated. By supplying fuel with such a pump 301d when necessary, the amount of fuel supply This improves the controllability. In this case, as the pump 301d, a rotary vane pump, an electroosmotic pump, a diaphragm pump, a squeezing pump, or the like is used from the viewpoint that a small amount of fuel can be fed with good controllability and that further reduction in size and weight is possible. It is preferable. A rotary vane pump feeds liquid by rotating a wing with a motor. The electroosmotic pump uses a sintered porous material such as silica that causes an electroosmotic flow phenomenon. The diaphragm pump feeds liquid by driving the diaphragm with an electromagnet or piezoelectric ceramic. 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 viewpoints of driving power and size.

[0102] In such a configuration, the liquid fuel stored in the fuel storage portion 301b is transferred through the flow path 301c by the pump 301d and supplied to the fuel distribution mechanism 301e. The fuel released from the fuel distribution mechanism 301e is supplied to the anodes 3 and 5 of the power generation unit 301a. In the power generation unit 301a, the fuel diffuses through the anode gas diffusion layer 5 and is supplied to the anode catalyst layer 3. When methanol fuel is used as the liquid fuel, a predetermined internal reforming reaction of methanol occurs in the anode catalyst layer 3. When pure methanol is used as the methanol fuel, an internal reforming reaction occurs in which the water generated in the force sword catalyst layer 2 or the water in the electrolyte membrane 6 reacts with methanol. Alternatively, the internal reforming reaction is caused by another reaction mechanism that does not require water.

[0103] It should be noted that if the fuel supply mechanism 301e supplies fuel to the MEA, a fuel cutoff valve may be arranged instead of the pump 301d. In this case, the fuel cutoff valve is provided to control the supply of liquid fuel through the flow path.

[0104] According to the present invention, there is provided a fuel cell having a small electrical resistance at a connecting portion for connecting the cells. According to the present invention, good battery performance can be stably obtained, and output characteristics with little variation can be obtained as a power source of a mobile device such as a mobile phone, a notebook computer, a portable audio device, and a portable game machine. .

Note that the present invention is not limited to the above-described embodiments as they are, but can be embodied by modifying the constituent elements without departing from the spirit of the invention in the implementation stage. In addition, the above embodiment Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in. 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.

In addition, the liquid fuel vapor supplied to the MEA may be supplied entirely with liquid fuel vapor, or the present invention may be applied even when part of the liquid fuel is supplied in a liquid state. Can be applied.

Claims

The scope of the claims

[1] A membrane electrode assembly in which an electrode including a catalyst layer and a diffusion layer is disposed on both surfaces of an electrolyte membrane, and a current collector that is in surface contact with the diffusion layers of both electrodes in order to extract a power output. A fuel cell comprising:

A fuel cell, wherein at least a part of the current collector penetrates into the diffusion layer.

[2] The current collector is pushed into the diffusion layer, so that at least a part of the current collector penetrates into the diffusion layer, and the diffusion before the current collector is pushed into the diffusion layer. When the volume average porosity of the layer is α% and the collapse rate of the portion where the diffusion layer collapses when the current collector is pushed into the diffusion layer is 3%, the relationship of 13≤ «/ 3 The fuel cell according to claim 1, wherein:

[3] The perforated flat plate in which a plurality of holes for allowing fuel or air to flow is used as the current collector, and the aperture ratio of the perforated flat plate is 35% or more. 1. The fuel cell according to 1.