WO2012043871A1 - Current collecting material for fuel cell - Google Patents

Current collecting material for fuel cell Download PDF

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Publication number
WO2012043871A1
WO2012043871A1 PCT/JP2011/072912 JP2011072912W WO2012043871A1 WO 2012043871 A1 WO2012043871 A1 WO 2012043871A1 JP 2011072912 W JP2011072912 W JP 2011072912W WO 2012043871 A1 WO2012043871 A1 WO 2012043871A1
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WIPO (PCT)
Prior art keywords
current collector
fuel cell
fuel
cell
metal
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Application number
PCT/JP2011/072912
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French (fr)
Japanese (ja)
Inventor
明宜 樫本
純歌 阪本
宏孝 茂木
正樹 安倍
明久 樋口
陽司 濱田
後藤　雅史
達哉 高水
Original Assignee
マグネクス株式会社
地方独立行政法人 東京都立産業技術研究センター
株式会社島精機製作所
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Application filed by マグネクス株式会社, 地方独立行政法人 東京都立産業技術研究センター, 株式会社島精機製作所 filed Critical マグネクス株式会社
Priority to KR1020137006447A priority Critical patent/KR101502996B1/en
Priority to DE112011103324T priority patent/DE112011103324T5/en
Publication of WO2012043871A1 publication Critical patent/WO2012043871A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/02—Details
    • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
    • H01M8/023—Porous and characterised by the material
    • H01M8/0232—Metals or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/02—Details
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
    • H01M2008/1293—Fuel cells with solid oxide electrolytes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • the present invention relates to a current collector for a fuel cell, and in particular, a current collector provided between a MEA cell of a flat plate type solid oxide fuel cell and a separator, and a MEA cell of a cylindrical solid oxide fuel cell.
  • the present invention relates to a current collector provided on an inner peripheral surface or an outer peripheral surface of an air electrode and a fuel electrode.
  • a solid oxide fuel cell which is a kind of fuel cell, is a fuel cell that operates at a high temperature of 600 ° C. to 900 ° C.
  • the fuel cell system is characterized in that all components are completely solid, and high power generation efficiency can be obtained.
  • solid electrolytes having ion conductivity are often used for the electrolyte, the degree of freedom of the shape is high, and there are flat plate type and cylindrical type as single cell shapes.
  • FIG. 6 shows the power generation principle of a solid oxide fuel cell (SOFC).
  • 6A shows the power generation principle in the case of hydrogen fuel
  • FIG. 6B shows the power generation principle in the case of carbon monoxide fuel.
  • the solid oxide fuel cell (SOFC) 10 uses hydrogen, carbon monoxide, or the like as a fuel, and the following electrode reactions proceed in the air electrode (cathode) 4 and the fuel electrode (anode) 5.
  • Fluel electrode 5 in the case of carbon monoxide fuel CO + O 2 ⁇ ⁇ CO 2 + 2e (Air electrode 4) 1 / 2O 2 + 2e ⁇ O 2 ⁇
  • oxygen ions (O 2 ⁇ ) generated at the air electrode 4 pass through the electrolyte 3 and move to the fuel electrode 5.
  • FIG. 7 is a perspective view showing the appearance and configuration of the flat plate fuel cell 10a.
  • FIG. 7A shows the appearance of the entire flat plate fuel cell 10 a
  • FIG. 7B shows the configuration of the single cell stack 11.
  • the single cell stack 11 of the flat plate type fuel cell 10a includes an electrolyte 3 and an air electrode (cathode) 4 and a fuel electrode (anode) 5 as a pair of electrodes.
  • a cell stack 14 stacked on the substrate is formed.
  • the cell stack 14 is integrated by stacking the component parts of the single cell stack 11 by the number of components and tightening the whole.
  • the air (cathode) 4 is supplied with air as an oxidizing gas
  • the fuel electrode (anode) 5 is supplied with hydrogen (or carbon monoxide) as a fuel gas.
  • the separators 6 and 7 of the fuel cell partition the individual cell stacks 11 in the cell stack 14.
  • the role of the separators 6 and 7 is to separate the fuel gas and the oxidizing gas, but the role of collecting the electricity generated in the MEA cell 2 and the role of supplying and discharging the fuel gas and the oxidizing gas are also I'm in charge. Therefore, the flow path of the fuel gas and the oxidizing gas is provided on the surface by groove processing.
  • a current collector is provided between the cathode separator 6 and the MEA cell 2 and between the anode separator 7 and the MEA cell 2 in order to increase power generation efficiency.
  • FIG. 8 shows a general configuration of a cylindrical fuel cell in cross section.
  • a cylindrical electrolyte 3 and a pair of electrodes, an air electrode (cathode) 4 and a fuel electrode (anode) 5, are formed. Then, fuel gas is supplied from the inside of the cylindrical tube as the fuel gas supply passage 13, and oxidizing gas is supplied from the outside of the cylindrical tube as the oxidizing gas supply passage 12.
  • Each of the air electrode (cathode) 4 and the fuel electrode (anode) 5 is provided with a cathode terminal 18 or an anode terminal 17, and power generation is performed by connecting a current line 16 to the cathode terminal 18 and the anode terminal 17, respectively.
  • oxygen ions (O 2 ⁇ ) generated at the air electrode 4 move to the fuel electrode 5 through the electrolyte 3, and hydrogen or carbon monoxide as a fuel is converted into oxygen ions (O 2 ⁇ at the fuel electrode 5).
  • oxygen ions (O 2 ⁇ ) generated at the air electrode 4 move to the fuel electrode 5 through the electrolyte 3, and hydrogen or carbon monoxide as a fuel is converted into oxygen ions (O 2 ⁇ at the fuel electrode 5).
  • the positions of the air electrode (cathode) 4 and the fuel electrode (anode) 5 are reversed, and the oxidizing gas is supplied using the inside of the cylindrical tube as the oxidizing gas supply passage 12, and the fuel gas supply passage 13 is provided outside the cylindrical tube.
  • the fuel gas may be supplied as a configuration. Conventionally, materials such as metal mesh, expanded metal, and porous metal have been used as current collectors for solid oxide fuel cells.
  • FIG. 9 shows changes in voltage (V) and output (W) corresponding to the current (A) value due to a thermal cycle when a conventional current collector is used. It can be seen that the voltage (V) and output (W) decrease in the second cycle relative to the first cycle.
  • FIG. 10 shows changes in stack voltage (V) and deterioration rate (%) depending on the number of thermal cycles when a conventional current collector is used. It can be seen that as the number of thermal cycles increases, the voltage (V) decreases and the deterioration rate (%) calculated from the current value and the voltage value increases.
  • Patent Document 1 discloses a fuel electrode current collector for a flat plate type solid electrolyte fuel cell that has little sintering / shrinkage and good adhesion between a separator (interconnector) and a cell plate.
  • a fuel electrode current collector capable of improving durability and output by improving the adhesion between the current collector and the fuel electrode, and a solid oxide fuel cell using the same. ing.
  • a current collector containing a partially oxidized active material and an electronic conductive material contained in the fuel electrode is described.
  • the air electrode and the fuel electrode of the MEA cell are directly sandwiched between the separators, flatness such as roughness of the opposing surfaces of the separator and the MEA cell, warpage or twisting of the surface cannot be secured. As a result, an electrical resistance is generated on the contact surface between the separator and the MEA cell, and as a result, there is a problem that the power generation performance of the fuel cell is lowered.
  • the MEA cell may cause a defect such as a crack due to a difference in thermal expansion coefficient between the metal separator and the MEA cell.
  • An object of the present application is to provide a current collector for a fuel cell that solves this problem, improves the electrical connection between the MEA cell and the separator, and improves the power generation efficiency and cycle characteristics of the fuel cell.
  • a current collector for a fuel cell includes a metal fiber braided on a surface where an air electrode and a fuel electrode of a MEA cell of a flat plate type solid oxide fuel cell respectively face a separator.
  • the formed flat metal fiber knit is disposed as a current collector, and is sandwiched between an electrode and a separator and pressed.
  • the current collector for the fuel cell has the elasticity of the current collector by the metal fiber knit formed by braiding metal, that is, the restoring force characteristic that the deformed metal fiber knit tries to return to the original shape.
  • a current collector for a fuel cell braids metal fibers along the air electrode and the inner or outer peripheral surface of the MEA cell of a cylindrical solid oxide fuel cell.
  • a cylindrical metal fiber knit formed in the above is arranged as a current collector, and a circuit is formed by connecting a current collector on the air electrode side and a current collector on the fuel electrode side through a current line.
  • the current collector for the fuel cell has the circuit itself in order to form a circuit by winding the air electrode side current collector and the fuel electrode side current collector around the cylindrical fuel cell and taking out the current line from each current collector. This shortens the power generation efficiency.
  • the current collector for the fuel cell is preferably formed by braiding a metal fiber knit with metal fibers made of a transition metal, a noble metal, or a heat-resistant alloy, and the transition metal includes nickel, cobalt, and copper.
  • the noble metal preferably includes platinum, gold, and silver.
  • the metal fiber preferably has a wire diameter of about 0.02 mm to about 0.2 mm.
  • the optimal cushioning property of a metal fiber knit can be set by selecting the wire diameter of a metal fiber.
  • the metal fiber knit is preferably knitted by weft knitting or warp knitting, and the weft knitting includes flat knitting, rubber knitting, pearl knitting, and smooth knitting.
  • the warp knitting preferably includes a single tricot, a single cord, and a single atlas.
  • the current collector for a fuel cell that improves the electrical connection between the MEA cell and the separator and improves the power generation efficiency and cycle characteristics of the fuel cell. Can be provided.
  • FIG. 1 is a cross-sectional view showing a schematic configuration of one embodiment of a current collector for a flat plate fuel cell according to the present invention by an internal configuration of a single cell.
  • FIG. 2 is a chart showing the amount of deformation (collapse) when a load is applied to a sample of the current collector for a fuel cell according to the present invention.
  • FIG. 3 is a chart showing the amount of deformation (collapse) when a load is applied to a sample of a current collector for a fuel cell.
  • FIG. 4 is a chart showing resistance values per unit area when pressure is applied to a sample of a current collector for a fuel cell according to the present invention.
  • FIG. 5 is a perspective view and a sectional view showing a schematic configuration of one embodiment of a current collector for a cylindrical fuel cell according to the present invention.
  • FIG. 6 is an explanatory diagram showing the power generation principle of a solid oxide fuel cell (SOFC).
  • FIG. 7 is a perspective view showing the appearance and configuration of a flat plate type solid oxide fuel cell (SOFC).
  • FIG. 8 is a cross-sectional view showing a general configuration of a cylindrical fuel cell.
  • FIG. 9 is a chart showing a decrease in power generation efficiency due to a thermal cycle when a conventional current collector is used.
  • FIG. 10 is a chart showing a decrease in power generation efficiency due to a thermal cycle when a conventional current collector is used.
  • FIG. 1 shows a schematic configuration of one embodiment of a current collector 1 used in a flat plate fuel cell 10a according to the present invention.
  • FIG. 1 is a sectional view showing the internal configuration of the single cell stack 11 for explanation.
  • a single cell stack 11 of the flat plate fuel cell 10a shown in FIG. 1 includes an MEA cell 2 composed of an electrolyte 3 and a pair of electrodes, an air electrode (cathode) 4 and a fuel electrode (anode) 5, and two cathodes.
  • a side separator 6, an anode side separator 7, and a pair of cathode side current collector 8 and anode side current collector 9 are configured.
  • the air (cathode) 4 is supplied with air as an oxidizing gas from an oxidizing gas supply path 12, and the fuel electrode (anode) 5 is supplied with hydrogen or carbon monoxide as a fuel gas from a fuel gas supplying path 13. Is supplied.
  • the MEA cell 2 includes an electrolyte 3 and a pair of electrodes, an air electrode (cathode) 4 and a fuel electrode (anode) 5. That is, the air electrode (cathode) 4 and the fuel electrode (anode) 5 are joined to both surfaces of the electrolyte 3, respectively.
  • the electrolyte 3 is generally made of yttria-stabilized zirconia that can be easily thinned.
  • the cathode side separator 6 is connected to the air electrode (cathode) 4, and the anode side separator 7 is connected to the fuel electrode (anode) 5.
  • the fuel gas and the oxidizing gas are separated by the cathode side separator 6 and the anode side separator 7.
  • a cathode-side current collector 8 is disposed and sandwiched between a cathode-side separator 6 and an air electrode (cathode) 4 and is pressurized with a pressure (P) by a single cell stack 11. .
  • an anode-side current collector 9 is disposed between and sandwiched between the anode-side separator 7 and the fuel electrode (anode) 5, and at a pressure (P) by the single cell stack 11 shown in FIG. Pressurized.
  • a metal fiber knit formed by weaving metal is disposed as current collectors 8 and 9 on the surfaces of the flat-type fuel cell 10a where the air electrode 4 and the fuel electrode 5 face the separator, respectively. And pressurize.
  • the metal fiber knit is disposed as the current collectors 8 and 9 and is sandwiched between the electrode and the separator and pressed to improve the contact property between the separator and the MEA cell 2 due to the elasticity of the metal fiber knit. As a result, the power generation performance of the fuel cell is improved.
  • the metal fiber knit used as the cathode-side current collector 8 and the anode-side current collector 9 is, for example, a braided metal M such as nickel, silver, or a heat-resistant alloy.
  • the method of knitting the metal M for example, knitting methods used for fabrics such as sweaters such as rubber knitting (milling knitting) and smooth knitting (double-side knitting) are known.
  • the knitting method of the metal M is not limited to these knitting methods, and any knitting method having elasticity that improves the electrical connection between the MEA cell 2 and the separator may be used.
  • Rubber knitting is a basic structure of weft knitting, and is characterized in that the stitches on the back are arranged next to the stitches on the front, and the stitches are arranged vertically. This rubber knitting is widely used as a structure of cuffs and hems because it has a large expansion and contraction and is particularly stretchable in the width direction.
  • smooth knitting is a combination of rubber knitting and the same stitches on both sides. This smooth knitting is a fabric that does not have the same elasticity as rubber knitting but has a good touch.
  • Samples 1 to 3 show the amount of deformation (crushing) when a load is applied to samples of various current collectors.
  • Table 1 shows samples of current collectors whose deformation (crushing) amount was measured.
  • Samples 1 to 3 are current collectors according to the present invention, which are metal fiber knits made of nickel material and smooth knitted (samples 1 and 2) and rubber knitted (sample 3).
  • Samples 4 to 7 are conventional current collectors, nickel expanded metal (sample 4), nickel porous metal (sample 5), heat resistant alloy M etching press (sample 6), and heat resistant alloy M mesh press. (Sample 7).
  • FIG. 2 is a measurement result in the case of the current collector according to the present invention, in which the horizontal axis is a load, and the vertical axis is a deformation (crushing) amount.
  • the amount of deformation increases as the load increases, and the amount of deformation decreases as the load decreases. From this result, it can be seen that the smooth knitting of samples 1 and 2 has higher longitudinal elastic force than the rubber knitting of sample 3.
  • FIG. 3 shows a measurement result in the case of a conventional current collector, where the horizontal axis is a load and the vertical axis is a deformation (crushing) amount.
  • the deformation amount is extremely small except for the etching press of the heat resistant alloy M of the sample 6.
  • FIG. 4 shows the resistance value (ASR) per unit area when the pressure (bar) is changed in the fuel cell current collector sample.
  • Samples 1 to 3 shown in FIG. 4 are measurement results in the case of the current collector according to the present invention, and it can be seen that in any case, the resistance value is almost constant regardless of the change in pressure. From the above results, the current collector according to the present invention has a higher elastic force when pressure is applied than the conventional current collector, and the resistance value per unit area shows a constant value regardless of the pressure.
  • FIG. 5 shows a schematic configuration of one embodiment of the current collectors 8 and 9 used in the cylindrical fuel cell 10b according to the present invention.
  • FIG. 5A is a perspective view of the entire cylindrical fuel cell 10b
  • FIG. 5B is a cross section of the cylindrical fuel cell 10b.
  • a cylindrical fuel cell 10b includes a cylindrical electrolyte 3 and a pair of electrodes, an air electrode (cathode) 4 and a fuel electrode (anode) 5.
  • power generation is performed by connecting current lines 16 to the cathode-side current collector 8 and the anode-side current collector 9, respectively. That is, oxygen ions (O 2 ⁇ ) generated at the air electrode 4 move to the fuel electrode 5 through the electrolyte 3, and hydrogen or carbon monoxide as a fuel is converted into oxygen ions (O 2 ⁇ at the fuel electrode 5). ) To emit electrons (2e), and the electrons (2e) move to the air electrode 4 via the current line 16. In this manner, the cathode-side current collector 8 and the anode-side current collector 9 are wound around the cylindrical fuel cell 10b, and the current line 16 is taken out from each current collector to constitute a circuit. That is, the cathode-side current collector 8 and the anode-side current collector 9 can be directly connected to the air electrode (cathode) 4 and the fuel electrode (anode) 5, respectively, and the power generation efficiency can be easily increased.

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Abstract

Provided is a current collecting material for fuel cells that improves the electrical contact between an MEA cell and a separator and improves fuel cell power generating efficiency and cycle characteristics. In the collecting material for a flat plate type fuel cell, a metal fiber knit formed by interleaving metal fiber is disposed as current collecting material (8, 9) on surfaces where the air electrode (cathode) (4) and fuel electrode (anode) (5) of a flat plate type fuel cell (10a) face the cathode side separator (6) and anode side separator (7) respectively. The metal fiber knit is sandwiched and pressed between the electrodes (4, 5) and the separators (6, 7).

Description

燃料電池用集電材Current collector for fuel cell
　本発明は、燃料電池用集電材に係り、特に、平板型の固体酸化物型燃料電池のＭＥＡセルとセパレータの間に設けられる集電材、及び円筒型の固体酸化物型燃料電池のＭＥＡセルの空気極と燃料極の内周面又は外周面に設けられる集電材に関する。 The present invention relates to a current collector for a fuel cell, and in particular, a current collector provided between a MEA cell of a flat plate type solid oxide fuel cell and a separator, and a MEA cell of a cylindrical solid oxide fuel cell. The present invention relates to a current collector provided on an inner peripheral surface or an outer peripheral surface of an air electrode and a fuel electrode.
　燃料電池の一種である固体酸化物型燃料電池（ＳＯＦＣ；Ｓｏｌｉｄ　Ｏｘｉｄｅ　Ｆｕｅｌ　Ｃｅｌｌ）は、６００℃~９００℃という高温で動作する燃料電池である。また、構成部品が全て完全な固体であるという特徴を有し、高い発電効率が得られる燃料電池システムである。また、電解質にイオン伝導性を有する固体のセラミックを用いる場合が多いことから、その形状についての自由度が高く、単セルの形状として平板型及び円筒型がある。
　図６に、固体酸化物型燃料電池（ＳＯＦＣ）の発電原理を示す。図６（ａ）は、水素燃料の場合の発電原理を示し、図６（ｂ）は、一酸化炭素燃料の場合の発電原理を示す。固体酸化物型燃料電池（ＳＯＦＣ）１０は、燃料として水素、一酸化炭素などを使用し、空気極（カソード）４、及び燃料極（アノード）５において、下記に示す電極反応が進行する。
（水素燃料の場合の燃料極５）　　　　Ｈ２＋Ｏ２−→Ｈ２Ｏ＋２ｅ
（一酸化炭素燃料の場合の燃料極５）　ＣＯ＋Ｏ２−→ＣＯ２＋２ｅ
（空気極４）　　　　　　　　　　　　１／２Ｏ２＋２ｅ→Ｏ２−
この反応式に示されるように、空気極４で発生した酸素イオン（Ｏ２−）が電解質３を通過して燃料極５へと移動する。一方、燃料極５では、燃料である水素或いは一酸化炭素が酸素イオン（Ｏ２−）と反応して電子（２ｅ）を放出し、その電子（２ｅ）が外部回路を経由して空気極４へと移動する。
　図７に、平板型燃料電池１０ａの外観及び構成を斜視図で示す。図７（ａ）は、平板型燃料電池１０ａ全体の外観を示し、図７（ｂ）は、単セルスタック１１の構成を示す。図７（ｂ）に示すように、平板型燃料電池１０ａの単セルスタック１１は、電解質３と一対の電極である空気極（カソード）４及び燃料極（アノード）５とから構成されるＭＥＡセル２、及び、２枚の（カソード側）セパレータ６及び（アノード側）セパレータ７から構成される。そして、一個の単セルスタック１１自体は０．３Ｖ~１．０Ｖ程度なので、必要な電圧とするために単セルスタック１１を数十枚~数百枚重ねて、図７（ａ）に示すように積層されたセルスタック１４を形成する。このセルスタック１４では、単セルスタック１１の構成部品を構成枚数だけ重ねて全体を締め付けることで一体化する。そして、空気極（カソード）４には、酸化ガスである空気が供給され、燃料極（アノード）５には、燃料ガスである水素（又は一酸化炭素）が供給される。
　燃料電池のセパレータ６，７は、セルスタック１４中の個々の単セルスタック１１間を仕切っている。このセパレータ６，７の役割は、燃料ガスと酸化ガスを分離することであるが、ＭＥＡセル２において発電された電気を集電するという役割、及び燃料ガスと酸化ガスの供給や排出の役目も担っている。そのため、その表面には、溝加工により燃料ガス及び酸化ガスの流路が設けられている。このカソード側セパレータ６とＭＥＡセル２との間、及びアノード側セパレータ７とＭＥＡセル２との間には、発電効率を上げるために集電材が設けられるのが一般的である。
　図８に、円筒型燃料電池の一般的な構成を断面で示す。円筒型燃料電池１０ｂは、円筒である電解質３と一対の電極である空気極（カソード）４及び燃料極（アノード）５とが形成される。そして、円筒管の内部を燃料ガス供給路１３として燃料ガスを供給し、円筒管の外部を酸化ガス供給路１２として酸化ガスを供給する。空気極（カソード）４及び燃料極（アノード）５には、それぞれカソードターミナル１８又はアノードターミナル１７が設けられ、カソードターミナル１８及びアノードターミナル１７にそれぞれ電流線１６を接続させることで発電が行われる。すなわち、空気極４で発生した酸素イオン（Ｏ２−）が電解質３を経由して燃料極５へと移動し、燃料極５では、燃料である水素或いは一酸化炭素が酸素イオン（Ｏ２−）と反応して電子（２ｅ）を放出し、その電子（２ｅ）が、電流線１６を経由して空気極４へと移動する。なお、空気極（カソード）４と燃料極（アノード）５との位置を逆にして、円筒管の内部を酸化ガス供給路１２として酸化ガスを供給し、円筒管の外部を燃料ガス供給路１３として燃料ガスを供給する構成とすることもできる。
　従来、固体酸化物型燃料電池の集電材としては、例えば、金属メッシュ、エクスパンドメタル、ポーラスメタルなどの材料が使用されていた。しかし、これらの材料は、後述するように、弾力性に乏しく、繰り返し使用するとＭＥＡセルやセパレータの熱膨張による変化のため接触状況が変化し、発電効率が低下するという性質がある。
　図９に、従来の集電材を用いた場合の熱サイクルによる、電流（Ａ）値に対応する電圧（Ｖ）及び出力（Ｗ）の変化を示す。電圧（Ｖ）及び出力（Ｗ）は、第１サイクルに対して第２サイクルで低下することが分かる。また、図１０に、従来の集電材を用いた場合の熱サイクル数によるスタック電圧（Ｖ）と劣化率（％）の変化を示す。熱サイクル数が増加するに従って、電圧（Ｖ）が低下し、電流値と電圧値から算出される劣化率（％）が上昇することが分かる。
　特許文献１には、焼結・収縮が少なく、かつセパレータ（インタコネクタ）及びセルプレートの密着性が良好な平板型固体電解質燃料電池用燃料極集電材が開示されている。ここでは、ニッケルフェルト原材料にセラミックス繊維及び／又は加熱膨張性セラミックス微粒子を混合することが記載されている。
　また、特許文献２には、集電材と燃料極との密着性が向上し、耐久性および出力の向上が可能な燃料極用集電材、及びそれを用いた固体酸化物型燃料電池が開示されている。ここでは、部分酸化活性材と、燃料極に含有される電子導電性材を含有する集電材が記載されている。 A solid oxide fuel cell (SOFC), which is a kind of fuel cell, is a fuel cell that operates at a high temperature of 600 ° C. to 900 ° C. In addition, the fuel cell system is characterized in that all components are completely solid, and high power generation efficiency can be obtained. In addition, since solid electrolytes having ion conductivity are often used for the electrolyte, the degree of freedom of the shape is high, and there are flat plate type and cylindrical type as single cell shapes.
FIG. 6 shows the power generation principle of a solid oxide fuel cell (SOFC). 6A shows the power generation principle in the case of hydrogen fuel, and FIG. 6B shows the power generation principle in the case of carbon monoxide fuel. The solid oxide fuel cell (SOFC) 10 uses hydrogen, carbon monoxide, or the like as a fuel, and the following electrode reactions proceed in the air electrode (cathode) 4 and the fuel electrode (anode) 5.
(Fuel electrode 5 in the case of hydrogen fuel) H 2 + O 2− → H 2 O + 2e
(Fuel electrode 5 in the case of carbon monoxide fuel) CO + O 2− → CO 2 + 2e
(Air electrode 4) 1 / 2O 2 + 2e → O 2−
As shown in this reaction formula, oxygen ions (O 2− ) generated at the air electrode 4 pass through the electrolyte 3 and move to the fuel electrode 5. On the other hand, in the fuel electrode 5, hydrogen or carbon monoxide as a fuel reacts with oxygen ions (O 2− ) to release electrons (2 e), and the electrons (2 e) pass through an external circuit and the air electrode 4. Move to.
FIG. 7 is a perspective view showing the appearance and configuration of the flat plate fuel cell 10a. FIG. 7A shows the appearance of the entire flat plate fuel cell 10 a, and FIG. 7B shows the configuration of the single cell stack 11. As shown in FIG. 7 (b), the single cell stack 11 of the flat plate type fuel cell 10a includes an electrolyte 3 and an air electrode (cathode) 4 and a fuel electrode (anode) 5 as a pair of electrodes. 2 and two (cathode side) separators 6 and (anode side) separators 7. Since one single cell stack 11 itself is about 0.3 V to 1.0 V, several tens to several hundreds of single cell stacks 11 are stacked in order to obtain a necessary voltage as shown in FIG. A cell stack 14 stacked on the substrate is formed. The cell stack 14 is integrated by stacking the component parts of the single cell stack 11 by the number of components and tightening the whole. The air (cathode) 4 is supplied with air as an oxidizing gas, and the fuel electrode (anode) 5 is supplied with hydrogen (or carbon monoxide) as a fuel gas.
The separators 6 and 7 of the fuel cell partition the individual cell stacks 11 in the cell stack 14. The role of the separators 6 and 7 is to separate the fuel gas and the oxidizing gas, but the role of collecting the electricity generated in the MEA cell 2 and the role of supplying and discharging the fuel gas and the oxidizing gas are also I'm in charge. Therefore, the flow path of the fuel gas and the oxidizing gas is provided on the surface by groove processing. In general, a current collector is provided between the cathode separator 6 and the MEA cell 2 and between the anode separator 7 and the MEA cell 2 in order to increase power generation efficiency.
FIG. 8 shows a general configuration of a cylindrical fuel cell in cross section. In the cylindrical fuel cell 10b, a cylindrical electrolyte 3 and a pair of electrodes, an air electrode (cathode) 4 and a fuel electrode (anode) 5, are formed. Then, fuel gas is supplied from the inside of the cylindrical tube as the fuel gas supply passage 13, and oxidizing gas is supplied from the outside of the cylindrical tube as the oxidizing gas supply passage 12. Each of the air electrode (cathode) 4 and the fuel electrode (anode) 5 is provided with a cathode terminal 18 or an anode terminal 17, and power generation is performed by connecting a current line 16 to the cathode terminal 18 and the anode terminal 17, respectively. That is, oxygen ions (O 2− ) generated at the air electrode 4 move to the fuel electrode 5 through the electrolyte 3, and hydrogen or carbon monoxide as a fuel is converted into oxygen ions (O 2− at the fuel electrode 5). ) To emit electrons (2e), and the electrons (2e) move to the air electrode 4 via the current line 16. The positions of the air electrode (cathode) 4 and the fuel electrode (anode) 5 are reversed, and the oxidizing gas is supplied using the inside of the cylindrical tube as the oxidizing gas supply passage 12, and the fuel gas supply passage 13 is provided outside the cylindrical tube. The fuel gas may be supplied as a configuration.
Conventionally, materials such as metal mesh, expanded metal, and porous metal have been used as current collectors for solid oxide fuel cells. However, as will be described later, these materials have poor elasticity, and when repeatedly used, the contact state changes due to a change due to thermal expansion of the MEA cell or the separator, and the power generation efficiency is lowered.
FIG. 9 shows changes in voltage (V) and output (W) corresponding to the current (A) value due to a thermal cycle when a conventional current collector is used. It can be seen that the voltage (V) and output (W) decrease in the second cycle relative to the first cycle. FIG. 10 shows changes in stack voltage (V) and deterioration rate (%) depending on the number of thermal cycles when a conventional current collector is used. It can be seen that as the number of thermal cycles increases, the voltage (V) decreases and the deterioration rate (%) calculated from the current value and the voltage value increases.
Patent Document 1 discloses a fuel electrode current collector for a flat plate type solid electrolyte fuel cell that has little sintering / shrinkage and good adhesion between a separator (interconnector) and a cell plate. Here, it is described that ceramic fibers and / or heat-expandable ceramic fine particles are mixed with a nickel felt raw material.
Further, Patent Document 2 discloses a fuel electrode current collector capable of improving durability and output by improving the adhesion between the current collector and the fuel electrode, and a solid oxide fuel cell using the same. ing. Here, a current collector containing a partially oxidized active material and an electronic conductive material contained in the fuel electrode is described.
特開平６−３６７８３号公報JP-A-6-36783 特開２００８−２５７８９０号公報JP 2008-257890 A
　ＭＥＡセルの空気極と燃料極とをそれぞれセパレータで直接挟んだ場合には、セパレータやＭＥＡセルの対向する表面の粗さ、或いは表面の反りや捩れなど、平面性が確保できない。このことにより、セパレータとＭＥＡセルとの接触面に電気抵抗が発生し、その結果、燃料電池の発電性能が低下するという問題がある。
　また、金属製のセパレータとセラミック製のＭＥＡセルとが熱サイクルを受けると、金属セパレータとＭＥＡセルとの熱膨張率の差により、ＭＥＡセルが割れなどの欠陥を引き起こす場合がある。このとき、セパレータとＭＥＡセルとの接触面に電気抵抗が発生し、その結果、燃料電池の発電性能が低下するという問題がある。
　さらに、固体酸化物型燃料電池の集電材として、例えば、金属メッシュ、エクスパンドメタル、ポーラスメタルなどの材料が使用されているが、これらの材料は、弾力性に乏しく、繰り返し使用するとＭＥＡセルやセパレータの熱膨張による変化のため接触状況が変化し、発電効率が低下するという問題がある。
　本願の目的は、かかる課題を解決し、ＭＥＡセルとセパレータの間の電気的な接続を改善し、燃料電池の発電効率及びサイクル特性を向上させる燃料電池用集電材を提供することである。 When the air electrode and the fuel electrode of the MEA cell are directly sandwiched between the separators, flatness such as roughness of the opposing surfaces of the separator and the MEA cell, warpage or twisting of the surface cannot be secured. As a result, an electrical resistance is generated on the contact surface between the separator and the MEA cell, and as a result, there is a problem that the power generation performance of the fuel cell is lowered.
Moreover, when a metal separator and a ceramic MEA cell are subjected to a thermal cycle, the MEA cell may cause a defect such as a crack due to a difference in thermal expansion coefficient between the metal separator and the MEA cell. At this time, there is a problem that electric resistance is generated on the contact surface between the separator and the MEA cell, and as a result, the power generation performance of the fuel cell is lowered.
Furthermore, materials such as metal mesh, expanded metal, and porous metal are used as current collectors for solid oxide fuel cells. However, these materials have poor elasticity, and when used repeatedly, MEA cells and separators are used. There is a problem that the contact state changes due to the change due to the thermal expansion of the battery and the power generation efficiency decreases.
An object of the present application is to provide a current collector for a fuel cell that solves this problem, improves the electrical connection between the MEA cell and the separator, and improves the power generation efficiency and cycle characteristics of the fuel cell.
　上記目的を達成するため、本発明に係る燃料電池用集電材は、平板型固体酸化物型燃料電池のＭＥＡセルの空気極と燃料極とがそれぞれセパレータと対向する面において、金属繊維を編み込んで形成された平板状の金属繊維ニットを集電材として配設し、電極とセパレータとの間に挟み込んで加圧することを特徴とする。この構成により、燃料電池用集電材は、金属を編み込んで形成された金属繊維ニットによる集電材の有する弾力性、すなわち変形した金属繊維ニットが元の形状に戻ろうとする復元力特性により、集電材が、ＭＥＡセルを形成する空気極及び燃料極と、それぞれの電極に対向するセパレータとに密着し、ＭＥＡセルとセパレータの間の電気的な接続を向上させることができる。
　上記目的を達成するため、本発明に係る燃料電池用集電材は、円筒型固体酸化物型燃料電池のＭＥＡセルの空気極と燃料極の内周面又は外周面に沿って、金属繊維を編み込んで形成された円筒状の金属繊維ニットを集電材として配設し、空気極側の集電材と燃料極側の集電材とを電流線を介して接続させ回路を形成することを特徴とする。この構成により、燃料電池用集電材は、円筒型燃料電池に、空気極側集電材及び燃料極側集電材を巻き付け、それぞれの集電材から電流線を取り出して回路を構成するために回路自体が短くなり、それにより容易に発電効率を上げることができる。
　また、燃料電池用集電材は、金属繊維ニットが、遷移金属、貴金属、又は耐熱合金からなる金属繊維を編み込んで形成されることが好ましく、前記遷移金属には、ニッケル、コバルト、及び銅が含まれ、前記貴金属には、白金、金及び銀が含まれることが好ましい。これにより、燃料電池の空気極側及び燃料極側で最適な素材による金属繊維ニットを形成することができる。
　また、燃料電池用集電材は、前記金属繊維が、線径が略０．０２ｍｍから略０．２ｍｍであることが好ましい。これにより、金属繊維の線径を選択することで、金属繊維ニットの最適なクッション性を設定することができる。
　また、燃料電池用集電材は、前記金属繊維ニットが、金属繊維をよこ編又はたて編により編み込むことが好ましく、前記よこ編には、平編み、ゴム編み、パール編み、及びスムース編みが含まれ、前記たて編には、シングルトリコット、シングルコード、及びシングルアトラスが含まれることが好ましい。これにより、金属繊維ニットの有するクッション性によりＭＥＡセルとセパレータの接触面での電気抵抗が低減され、発電効率やサイクル特性を向上させることができる。 In order to achieve the above object, a current collector for a fuel cell according to the present invention includes a metal fiber braided on a surface where an air electrode and a fuel electrode of a MEA cell of a flat plate type solid oxide fuel cell respectively face a separator. The formed flat metal fiber knit is disposed as a current collector, and is sandwiched between an electrode and a separator and pressed. With this configuration, the current collector for the fuel cell has the elasticity of the current collector by the metal fiber knit formed by braiding metal, that is, the restoring force characteristic that the deformed metal fiber knit tries to return to the original shape. However, it can adhere to the air electrode and fuel electrode which form a MEA cell, and the separator which opposes each electrode, and can improve the electrical connection between a MEA cell and a separator.
In order to achieve the above object, a current collector for a fuel cell according to the present invention braids metal fibers along the air electrode and the inner or outer peripheral surface of the MEA cell of a cylindrical solid oxide fuel cell. A cylindrical metal fiber knit formed in the above is arranged as a current collector, and a circuit is formed by connecting a current collector on the air electrode side and a current collector on the fuel electrode side through a current line. With this configuration, the current collector for the fuel cell has the circuit itself in order to form a circuit by winding the air electrode side current collector and the fuel electrode side current collector around the cylindrical fuel cell and taking out the current line from each current collector. This shortens the power generation efficiency.
The current collector for the fuel cell is preferably formed by braiding a metal fiber knit with metal fibers made of a transition metal, a noble metal, or a heat-resistant alloy, and the transition metal includes nickel, cobalt, and copper. The noble metal preferably includes platinum, gold, and silver. Thereby, the metal fiber knit by the optimal material can be formed on the air electrode side and the fuel electrode side of the fuel cell.
In the current collector for a fuel cell, the metal fiber preferably has a wire diameter of about 0.02 mm to about 0.2 mm. Thereby, the optimal cushioning property of a metal fiber knit can be set by selecting the wire diameter of a metal fiber.
Further, in the current collector for a fuel cell, the metal fiber knit is preferably knitted by weft knitting or warp knitting, and the weft knitting includes flat knitting, rubber knitting, pearl knitting, and smooth knitting. The warp knitting preferably includes a single tricot, a single cord, and a single atlas. Thereby, the electrical resistance in the contact surface of a MEA cell and a separator is reduced by the cushioning property which a metal fiber knit has, and electric power generation efficiency and cycling characteristics can be improved.
　以上のように、本発明に係る燃料電池用集電材によれば、ＭＥＡセルとセパレータの間の電気的な接続を改善し、燃料電池の発電効率及びサイクル特性を向上させる燃料電池用集電材を提供することができる。 As described above, according to the current collector for a fuel cell according to the present invention, the current collector for a fuel cell that improves the electrical connection between the MEA cell and the separator and improves the power generation efficiency and cycle characteristics of the fuel cell. Can be provided.
　図１は、本発明に係る平板型燃料電池用集電材の１つの実施形態の概略構成を、単セルの内部構成により示す断面図である。
　図２は、本発明に係る燃料電池用集電材のサンプルに荷重を加えた際の変形（つぶれ）量を示す図表である。
　図３は、従来の燃料電池用集電材のサンプルに荷重を加えた際の変形（つぶれ）量を示す図表である。
　図４は、本発明に係る燃料電池用集電材のサンプルに圧力変化させた場合の単位面積当たりの抵抗値を示す図表である。
　図５は、本発明に係る円筒型燃料電池用集電材の１つの実施形態の概略構成を示す斜視図及び断面図である。
　図６は、固体酸化物型燃料電池（ＳＯＦＣ）の発電原理を示す説明図である。
　図７は、平板型固体酸化物型燃料電池（ＳＯＦＣ）の外観及び構成を示す斜視図である。
　図８は、円筒型燃料電池の一般的な構成を示す断面図である。
　図９は、従来の集電材を用いた場合の熱サイクルによる発電効率の低下を示す図表である。
　図１０は、従来の集電材を用いた場合の熱サイクルによる発電効率の低下を示す図表である。 FIG. 1 is a cross-sectional view showing a schematic configuration of one embodiment of a current collector for a flat plate fuel cell according to the present invention by an internal configuration of a single cell.
FIG. 2 is a chart showing the amount of deformation (collapse) when a load is applied to a sample of the current collector for a fuel cell according to the present invention.
FIG. 3 is a chart showing the amount of deformation (collapse) when a load is applied to a sample of a current collector for a fuel cell.
FIG. 4 is a chart showing resistance values per unit area when pressure is applied to a sample of a current collector for a fuel cell according to the present invention.
FIG. 5 is a perspective view and a sectional view showing a schematic configuration of one embodiment of a current collector for a cylindrical fuel cell according to the present invention.
FIG. 6 is an explanatory diagram showing the power generation principle of a solid oxide fuel cell (SOFC).
FIG. 7 is a perspective view showing the appearance and configuration of a flat plate type solid oxide fuel cell (SOFC).
FIG. 8 is a cross-sectional view showing a general configuration of a cylindrical fuel cell.
FIG. 9 is a chart showing a decrease in power generation efficiency due to a thermal cycle when a conventional current collector is used.
FIG. 10 is a chart showing a decrease in power generation efficiency due to a thermal cycle when a conventional current collector is used.
（平板型燃料電池用集電材）
　以下に、図面を用いて本発明に係る燃料電池用集電材の実施形態につき、詳細に説明する。図１に、本発明に係る、平板型燃料電池１０ａに用いられる集電材１の１つの実施形態の概略構成を示す。この図１は、単セルスタック１１の内部構成を説明用に断面図で示したものである。
　図１に示す平板型燃料電池１０ａの単セルスタック１１は、電解質３と一対の電極である空気極（カソード）４及び燃料極（アノード）５とから構成されるＭＥＡセル２、２枚のカソード側セパレータ６及びアノード側セパレータ７、及び一対のカソード側集電材８及びアノード側集電材９から構成される。そして、空気極（カソード）４には、酸化ガス供給路１２から酸化ガスである空気が供給され、燃料極（アノード）５には、燃料ガス供給路１３から燃料ガスである水素又は一酸化炭素が供給される。
　ＭＥＡセル２は、電解質３と一対の電極である空気極（カソード）４及び燃料極（アノード）５とから構成される。すなわち、電解質３の両面には、空気極（カソード）４及び燃料極（アノード）５がそれぞれ接合される。この電解質３は、一般的には、薄膜化が容易なイットリア安定化ジルコニアが用いられる。
　カソード側セパレータ６は空気極（カソード）４に接続し、アノード側セパレータ７は燃料極（アノード）５に接続する。このように、カソード側セパレータ６及びアノード側セパレータ７により燃料ガスと酸化ガスとが分離される。
　図１に示すように、カソード側集電材８が、カソード側セパレータ６と空気極（カソード）４との間に配設されて挟み込まれ、単セルスタック１１により圧力（Ｐ）で加圧される。同様に、アノード側）集電材９が、アノード側セパレータ７と燃料極（アノード）５との間に配設されて挟み込まれ、図７（ａ）に示す単セルスタック１１により圧力（Ｐ）で加圧される。
　平板型燃料電池１０ａの空気極４と燃料極５とがそれぞれセパレータと対向する面において、金属を編み込んで形成された金属繊維ニットを集電材８，９として配設し、電極とセパレータとの間に挟み込んで加圧する。ＭＥＡセル２の空気極４と燃料極５とをそれぞれセパレータで直接挟んだ場合には、セパレータやＭＥＡセル２の対向する表面の粗さ、或いは表面の反りや捩れなど、平面性が確保できないが、金属繊維ニットを集電材８，９として配設し、電極とセパレータとの間に挟み込んで加圧することで、金属繊維ニットの弾力性によりセパレータとＭＥＡセル２との接触性が改善され、その結果、燃料電池の発電性能が向上する。
　カソード側集電材８及びアノード側集電材９として用いられる金属繊維ニットは、例えば、ニッケル、銀、耐熱合金などの金属Ｍを編み込んだものである。この金属Ｍの編み方には、例えば、ゴム編み（フライス編み）、スムース編み（両面編み）などセーター等の生地に用いられる編み方が知られている。但し、この金属Ｍの編み方は、これらの編み方に限らず、ＭＥＡセル２とセパレータの間の電気的な接続を改善するような弾力性を有する編み方であれば良い。
　ゴム編みは、よこ編みの基本組織であり、表の編み目の次に裏の編み目が並ぶ編み方で、縦に編み目が並ぶのが特徴である。このゴム編みは伸び縮みが大きく、特に幅方向の伸縮性に富むため袖口や裾の組織として多用されている。一方、スムース編みは、ゴム編みを重ね編みしたもので、表裏同じような編み目になるのが特徴である。このスムース編みは、ゴム編みほどの伸縮性はないが肌触りがよい生地となる。
　図２及び図３に、各種の集電材のサンプルに荷重を加えた際の変形（つぶれ）量を示す。また、表１に変形（つぶれ）量を測定した集電材のサンプルを示す。サンプル１~サンプル３は、本発明に係る集電材であり、ニッケル材を用いてスムース編み（サンプル１，２）、ゴム編み（サンプル３）とした金属繊維ニットである。サンプル４~サンプル７は、従来の集電材であり、ニッケルエキスパンド・メタル（サンプル４）、ニッケルポーラス・メタル（サンプル５）、耐熱合金Ｍのエッチングプレス（サンプル６）、及び耐熱合金Ｍのメッシュプレス（サンプル７）である。
　図２は、本発明に係る集電材の場合の測定結果であり、横軸は荷重であり、縦軸は変形（つぶれ）量である。いずれのサンプルの場合も荷重の増加につれて変形量が増加し、荷重を減少させると変形量も減少する弾性的な特性を示している。この結果から、サンプル１，２のスムース編みのほうが、サンプル３のゴム編みに比べて縦方向の弾性力が高いことが分かる。一方、図３は、従来の集電材の場合の測定結果であり、横軸は荷重であり、縦軸は変形（つぶれ）量である。サンプル６の耐熱合金Ｍのエッチングプレス以外は変形量が極端に小さい。また、耐熱合金Ｍのエッチングプレスについても荷重を減少させても変形量が戻らず、弾力性があるとは言えない。
　図４に、燃料電池用集電材のサンプルに圧力（ｂａｒ）を変化させた場合の単位面積当たりの抵抗値（ＡＳＲ）を示す。図４に示すサンプル１~３は、本発明に係る集電材の場合の測定結果であり、いずれの場合も圧力の変化に拘わらずほぼ一定の抵抗値を示すことが分かる。
　以上の結果から、本発明に係る集電材は、従来の集電材に比べて圧力を加えた際の弾性力が高く、単位面積当たりの抵抗値が圧力にかかわらず一定の値を示す。これらの特性を有する編み込まれた金属繊維ニットによりＭＥＡセル２とセパレータの接触面での電気抵抗が低減され、発電効率やサイクル特性を向上させることができる。
（円筒型燃料電池用集電材）
　図５に、本発明に係る円筒型燃料電池１０ｂに用いられる集電材８，９の１つの実施形態の概略構成を示す。図５（ａ）は、円筒型燃料電池１０ｂ全体の斜視図であり、図５（ｂ）は、円筒型燃料電池１０ｂの断面である。図５（ａ）に示すように、円筒型燃料電池１０ｂは、円筒である電解質３と一対の電極である空気極（カソード）４及び燃料極（アノード）５とが形成される。そして、円筒管の内部を燃料ガス供給路１３として燃料ガスを供給し、円筒管の外部を酸化ガス供給路１２として酸化ガスを供給することで発電が行われる。なお、空気極（カソード）４と燃料極（アノード）５との位置を逆にして、円筒管の内部を酸化ガス供給路１２として酸化ガスを供給し、円筒管の外部を燃料ガス供給路１３として燃料ガスを供給する構成とすることもできる。
　そして、図５（ｂ）に示すように、空気極（カソード）４の外周にカソード側集電材８を巻き付けて接続させる。同様に、燃料極（アノード）５の内側にアノード側集電材９を巻き付けて接続させる。さらに、カソード側集電材８及びアノード側集電材９にそれぞれ電流線１６を接続させることで発電が行われる。すなわち、空気極４で発生した酸素イオン（Ｏ２−）が電解質３を経由して燃料極５へと移動し、燃料極５では、燃料である水素或いは一酸化炭素が酸素イオン（Ｏ２−）と反応して電子（２ｅ）を放出し、その電子（２ｅ）が、電流線１６を経由して空気極４へと移動する。
　このように、円筒型燃料電池１０ｂに、カソード側集電材８及びアノード側集電材９を巻き付け、それぞれの集電材から電流線１６を取り出して回路を構成する。すなわち、カソード側集電材８及びアノード側集電材９をそれぞれ空気極（カソード）４及び燃料極（アノード）５に直接接続させることができ容易に発電効率を上げることができる。 (Current collector for flat plate fuel cell)
Hereinafter, embodiments of a current collector for a fuel cell according to the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic configuration of one embodiment of a current collector 1 used in a flat plate fuel cell 10a according to the present invention. FIG. 1 is a sectional view showing the internal configuration of the single cell stack 11 for explanation.
A single cell stack 11 of the flat plate fuel cell 10a shown in FIG. 1 includes an MEA cell 2 composed of an electrolyte 3 and a pair of electrodes, an air electrode (cathode) 4 and a fuel electrode (anode) 5, and two cathodes. A side separator 6, an anode side separator 7, and a pair of cathode side current collector 8 and anode side current collector 9 are configured. The air (cathode) 4 is supplied with air as an oxidizing gas from an oxidizing gas supply path 12, and the fuel electrode (anode) 5 is supplied with hydrogen or carbon monoxide as a fuel gas from a fuel gas supplying path 13. Is supplied.
The MEA cell 2 includes an electrolyte 3 and a pair of electrodes, an air electrode (cathode) 4 and a fuel electrode (anode) 5. That is, the air electrode (cathode) 4 and the fuel electrode (anode) 5 are joined to both surfaces of the electrolyte 3, respectively. The electrolyte 3 is generally made of yttria-stabilized zirconia that can be easily thinned.
The cathode side separator 6 is connected to the air electrode (cathode) 4, and the anode side separator 7 is connected to the fuel electrode (anode) 5. Thus, the fuel gas and the oxidizing gas are separated by the cathode side separator 6 and the anode side separator 7.
As shown in FIG. 1, a cathode-side current collector 8 is disposed and sandwiched between a cathode-side separator 6 and an air electrode (cathode) 4 and is pressurized with a pressure (P) by a single cell stack 11. . Similarly, an anode-side current collector 9 is disposed between and sandwiched between the anode-side separator 7 and the fuel electrode (anode) 5, and at a pressure (P) by the single cell stack 11 shown in FIG. Pressurized.
A metal fiber knit formed by weaving metal is disposed as current collectors 8 and 9 on the surfaces of the flat-type fuel cell 10a where the air electrode 4 and the fuel electrode 5 face the separator, respectively. And pressurize. When the air electrode 4 and the fuel electrode 5 of the MEA cell 2 are directly sandwiched between the separators, flatness such as roughness of the opposing surfaces of the separator and the MEA cell 2 or warping or twisting of the surface cannot be secured. The metal fiber knit is disposed as the current collectors 8 and 9 and is sandwiched between the electrode and the separator and pressed to improve the contact property between the separator and the MEA cell 2 due to the elasticity of the metal fiber knit. As a result, the power generation performance of the fuel cell is improved.
The metal fiber knit used as the cathode-side current collector 8 and the anode-side current collector 9 is, for example, a braided metal M such as nickel, silver, or a heat-resistant alloy. As the method of knitting the metal M, for example, knitting methods used for fabrics such as sweaters such as rubber knitting (milling knitting) and smooth knitting (double-side knitting) are known. However, the knitting method of the metal M is not limited to these knitting methods, and any knitting method having elasticity that improves the electrical connection between the MEA cell 2 and the separator may be used.
Rubber knitting is a basic structure of weft knitting, and is characterized in that the stitches on the back are arranged next to the stitches on the front, and the stitches are arranged vertically. This rubber knitting is widely used as a structure of cuffs and hems because it has a large expansion and contraction and is particularly stretchable in the width direction. On the other hand, smooth knitting is a combination of rubber knitting and the same stitches on both sides. This smooth knitting is a fabric that does not have the same elasticity as rubber knitting but has a good touch.
FIG. 2 and FIG. 3 show the amount of deformation (crushing) when a load is applied to samples of various current collectors. Table 1 shows samples of current collectors whose deformation (crushing) amount was measured. Samples 1 to 3 are current collectors according to the present invention, which are metal fiber knits made of nickel material and smooth knitted (samples 1 and 2) and rubber knitted (sample 3). Samples 4 to 7 are conventional current collectors, nickel expanded metal (sample 4), nickel porous metal (sample 5), heat resistant alloy M etching press (sample 6), and heat resistant alloy M mesh press. (Sample 7).
FIG. 2 is a measurement result in the case of the current collector according to the present invention, in which the horizontal axis is a load, and the vertical axis is a deformation (crushing) amount. In any case, the amount of deformation increases as the load increases, and the amount of deformation decreases as the load decreases. From this result, it can be seen that the smooth knitting of samples 1 and 2 has higher longitudinal elastic force than the rubber knitting of sample 3. On the other hand, FIG. 3 shows a measurement result in the case of a conventional current collector, where the horizontal axis is a load and the vertical axis is a deformation (crushing) amount. The deformation amount is extremely small except for the etching press of the heat resistant alloy M of the sample 6. Further, the etching press of the heat-resistant alloy M cannot be said to be elastic because the deformation amount does not return even if the load is reduced.
FIG. 4 shows the resistance value (ASR) per unit area when the pressure (bar) is changed in the fuel cell current collector sample. Samples 1 to 3 shown in FIG. 4 are measurement results in the case of the current collector according to the present invention, and it can be seen that in any case, the resistance value is almost constant regardless of the change in pressure.
From the above results, the current collector according to the present invention has a higher elastic force when pressure is applied than the conventional current collector, and the resistance value per unit area shows a constant value regardless of the pressure. The knitted metal fiber knit having these characteristics reduces the electrical resistance at the contact surface between the MEA cell 2 and the separator, thereby improving the power generation efficiency and cycle characteristics.
(Collector type fuel cell current collector)
FIG. 5 shows a schematic configuration of one embodiment of the current collectors 8 and 9 used in the cylindrical fuel cell 10b according to the present invention. FIG. 5A is a perspective view of the entire cylindrical fuel cell 10b, and FIG. 5B is a cross section of the cylindrical fuel cell 10b. As shown in FIG. 5A, a cylindrical fuel cell 10b includes a cylindrical electrolyte 3 and a pair of electrodes, an air electrode (cathode) 4 and a fuel electrode (anode) 5. Then, power is generated by supplying fuel gas inside the cylindrical tube as the fuel gas supply passage 13 and supplying oxidizing gas outside the cylindrical tube as the oxidizing gas supply passage 12. The positions of the air electrode (cathode) 4 and the fuel electrode (anode) 5 are reversed, and the oxidizing gas is supplied using the inside of the cylindrical tube as the oxidizing gas supply passage 12, and the fuel gas supply passage 13 is provided outside the cylindrical tube. The fuel gas may be supplied as a configuration.
And as shown in FIG.5 (b), the cathode side collector 8 is wound around the outer periphery of the air electrode (cathode) 4, and is connected. Similarly, the anode side current collector 9 is wound around and connected to the inside of the fuel electrode (anode) 5. Furthermore, power generation is performed by connecting current lines 16 to the cathode-side current collector 8 and the anode-side current collector 9, respectively. That is, oxygen ions (O 2− ) generated at the air electrode 4 move to the fuel electrode 5 through the electrolyte 3, and hydrogen or carbon monoxide as a fuel is converted into oxygen ions (O 2− at the fuel electrode 5). ) To emit electrons (2e), and the electrons (2e) move to the air electrode 4 via the current line 16.
In this manner, the cathode-side current collector 8 and the anode-side current collector 9 are wound around the cylindrical fuel cell 10b, and the current line 16 is taken out from each current collector to constitute a circuit. That is, the cathode-side current collector 8 and the anode-side current collector 9 can be directly connected to the air electrode (cathode) 4 and the fuel electrode (anode) 5, respectively, and the power generation efficiency can be easily increased.
１　　　集電材
２　　　ＭＥＡセル
３　　　電解質
４　　　空気極（カソード）
５　　　燃料極（アノード）
６　　　（カソード側）セパレータ
７　　　（アノード側）セパレータ
８　　　（カソード側）集電材
９　　　（アノード側）集電材
１０　　固体酸化物型燃料電池（ＳＯＦＣ）
１０ａ　平板型燃料電池
１０ｂ　円筒型燃料電池
１１　　単セルスタック
１２　　酸化ガス供給路
１３　　燃焼ガス供給路
１４　　セルスタック
１６　　電流線
１７　　アノードターミナル
１８　　カソードターミナル 1 Current collector 2 MEA cell 3 Electrolyte 4 Air electrode (cathode)
5 Fuel electrode (anode)
6 (Cathode side) Separator 7 (Anode side) Separator 8 (Cathode side) Current collector 9 (Anode side) Current collector 10 Solid oxide fuel cell (SOFC)
10a Flat fuel cell 10b Cylindrical fuel cell 11 Single cell stack 12 Oxidizing gas supply path 13 Combustion gas supply path 14 Cell stack 16 Current line 17 Anode terminal 18 Cathode terminal

Claims (6)

  1. 　平板型固体酸化物型燃料電池のＭＥＡセルの空気極と燃料極とがそれぞれセパレータと対向する面において、金属繊維を編み込んで形成された平板状の金属繊維ニットを集電材として配設し、電極とセパレータとの間に挟み込んで加圧することを特徴とする燃料電池用集電材。 A flat metal fiber knit formed by weaving metal fibers is disposed as a current collector on the surface where the air electrode and fuel electrode of the MEA cell of the flat plate type solid oxide fuel cell respectively face the separator. A current collector for a fuel cell, which is sandwiched between a separator and a pressurization.
  2. 　円筒型固体酸化物型燃料電池のＭＥＡセルの空気極と燃料極の内周面又は外周面に沿って、金属繊維を編み込んで形成された円筒状の金属繊維ニットを集電材として配設し、空気極側の集電材と燃料極側の集電材とを電流線を介して接続させ回路を形成することを特徴とする燃料電池用集電材。 A cylindrical metal fiber knit formed by braiding metal fibers along the inner or outer peripheral surface of the air electrode and fuel electrode of the MEA cell of the cylindrical solid oxide fuel cell is disposed as a current collector. A current collector for a fuel cell, wherein a current collector on the air electrode side and a current collector on the fuel electrode side are connected via a current line to form a circuit.
  3. 　請求項１又は２に記載の燃料電池用集電材であって、金属繊維ニットは、遷移金属、貴金属、又は耐熱合金からなる金属繊維を編み込んで形成されることを特徴とする燃料電池用集電材。 The current collector for a fuel cell according to claim 1 or 2, wherein the metal fiber knit is formed by braiding metal fibers made of a transition metal, a noble metal, or a heat-resistant alloy. .
  4. 　請求項３に記載の燃料電池用集電材であって、前記遷移金属には、ニッケル、コバルト、及び銅が含まれ、前記貴金属には、白金、金及び銀が含まれることを特徴とする燃料電池用集電材。 4. The fuel cell current collector according to claim 3, wherein the transition metal includes nickel, cobalt, and copper, and the noble metal includes platinum, gold, and silver. Current collector for batteries.
  5. 　請求項１乃至４のいずれか１項に記載の燃料電池用集電材であって、前記金属繊維は、線径が略０．０２ｍｍから略０．２ｍｍであることを特徴とする燃料電池用集電材。 5. The fuel cell current collector according to claim 1, wherein the metal fiber has a wire diameter of approximately 0.02 mm to approximately 0.2 mm. 6. Electrical material.
  6. 　請求項１乃至５のいずれか１項に記載の燃料電池用集電材であって、前記金属繊維ニットは、金属繊維をよこ編又はたて編により編み込むことを特徴とする燃料電池用集電材。 6. The fuel cell current collector according to any one of claims 1 to 5, wherein the metal fiber knit is made by weaving metal fibers by weft knitting or warp knitting.
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