JP2005085521A - Solid oxide fuel cell - Google Patents

Solid oxide fuel cell Download PDF

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JP2005085521A
JP2005085521A JP2003313718A JP2003313718A JP2005085521A JP 2005085521 A JP2005085521 A JP 2005085521A JP 2003313718 A JP2003313718 A JP 2003313718A JP 2003313718 A JP2003313718 A JP 2003313718A JP 2005085521 A JP2005085521 A JP 2005085521A
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current collector
fuel
gas
fuel electrode
electrode current
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JP4529393B2 (en
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Akbay Taner
アクベイ タナー
Norihisa Chitose
範壽 千歳
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Kansai Electric Power Co Inc
Mitsubishi Materials Corp
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Mitsubishi Materials Corp
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    • 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
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Abstract

<P>PROBLEM TO BE SOLVED: To enhance power generating efficiency by preventing useless exhaust of gas from the peripheral part of a fuel electrode current collector and an opposite diffusion phenomenon of gas to a fuel electrode side. <P>SOLUTION: A solid oxide fuel cell has seal-less structure in which a fuel electrode layer 3 and an oxidizing agent electrode layer 4 are arranged on both sides of a solid electrolyte layer 2, a fuel electrode current collector 6 and an oxidizing agent electrode current collector 7 each made of a porous metallic material are arranged on the outside of the fuel electrode layer 3 and the oxidizing agent electrode layer 4 respectively, a separator 8 is arranged on the outside of the fuel electrode current collector 6 and the oxidizing agent electrode current collector 7, and fuel gas and oxidizing agent gas are supplied to the fuel electrode layer 3 and the oxidizing agent electrode layer 4 through the fuel electrode current collector 6 and the oxidizing agent electrode current collector 7 from the separator 8. An insulating cover 20 having a gas exhausting hole 22 is installed so as to cover the peripheral part of the fuel electrode layer 3 and the fuel electrode current collector 6, and exhausting portions of excess gas exhausted from the peripheral part are regulated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

本発明は、固体酸化物形燃料電池に関し、詳しくは、燃料極集電体におけるガスの逆拡散現象を防止して発電効率の向上を図ったガスシールレス構造の固体酸化物形燃料電池に関する。   The present invention relates to a solid oxide fuel cell, and more particularly to a solid oxide fuel cell having a gas sealless structure in which a gas back diffusion phenomenon in a fuel electrode current collector is prevented to improve power generation efficiency.

酸化物イオン伝導体からなる固体電解質層を空気極層（酸化剤極層）と燃料極層との間に挟んだ積層構造を持つ固体酸化物形燃料電池は、第三世代の発電用燃料電池として開発が進んでいる。固体酸化物形燃料電池では、空気極側に酸素（空気）が、燃料極側には燃料ガス（Ｈ2 、ＣＯ等）が供給される。空気極と燃料極は、ガスが固体電解質との界面に到達することができるように、いずれも多孔質とされている。 A solid oxide fuel cell having a laminated structure in which a solid electrolyte layer made of an oxide ion conductor is sandwiched between an air electrode layer (oxidant electrode layer) and a fuel electrode layer is a third generation fuel cell for power generation. Development is progressing. In a solid oxide fuel cell, oxygen (air) is supplied to the air electrode side, and fuel gas (H 2 , CO, etc.) is supplied to the fuel electrode side. The air electrode and the fuel electrode are both porous so that the gas can reach the interface with the solid electrolyte.

空気極側に供給された酸素は、空気極層内の気孔を通って固体電解質層との界面近傍に到達し、この部分で、空気極から電子を受け取って酸化物イオン（Ｏ2-）にイオン化される。この酸化物イオンは、燃料極の方向に向かって固体電解質層内を拡散移動する。燃料極との界面近傍に到達した酸化物イオンは、この部分で、燃料ガスと反応して反応生成物（Ｈ2 Ｏ、ＣＯ2 等）を生じ、燃料極に電子を放出する。 Oxygen supplied to the air electrode side passes through the pores in the air electrode layer and reaches the vicinity of the interface with the solid electrolyte layer. At this part, it receives electrons from the air electrode and converts them into oxide ions (O 2− ). Ionized. The oxide ions diffuse and move in the solid electrolyte layer toward the fuel electrode. Oxide ions that have reached the vicinity of the interface with the fuel electrode react with the fuel gas at this portion to generate reaction products (H 2 O, CO 2, etc.), and emit electrons to the fuel electrode.

因みに、燃料に水素を用いた場合の電極反応は次のようになる。
空気極： １／２ Ｏ2 ＋ ２ｅ- → Ｏ2-
燃料極： Ｈ2 ＋ Ｏ2- → Ｈ2 Ｏ＋２ｅ-
全体 ： Ｈ2 ＋ １／２ Ｏ2 → Ｈ2 Ｏ Incidentally, the electrode reaction when hydrogen is used as the fuel is as follows.
Air electrode: 1/2 O 2 + 2e − → O 2−
Fuel electrode: H 2 + O 2− → H 2 O + 2e −
Overall: H 2 +1/2 O 2 → H 2 O

固体電解質層は、酸化物イオンの移動媒体であると同時に、燃料ガスと空気を直接接触させないための隔壁としても機能するため、ガス不透過性の緻密な構造となっている。この固体電解質層は、酸化物イオン伝導性が高く、空気極側の酸化性雰囲気から燃料極側の還元性雰囲気までの条件下で化学的に安定で、熱衝撃に強い材料から構成する必要があり、かかる要件を満たす材料として、イットリアを添加した安定化ジルコニア（ＹＳＺ）が一般的に使用されている。   The solid electrolyte layer is a moving medium for oxide ions and also functions as a partition wall for preventing direct contact between the fuel gas and air, and thus has a dense structure that is impermeable to gas. This solid electrolyte layer should have a high oxide ion conductivity, be chemically stable under conditions from the oxidizing atmosphere on the air electrode side to the reducing atmosphere on the fuel electrode side, and be made of a material that is resistant to thermal shock. There is generally used stabilized zirconia (YSZ) to which yttria is added as a material satisfying such requirements.

一方、電極である空気極（カソード）層と燃料極（アノード）層はいずれも電子伝導性の高い材料から構成する必要がある。空気極材料は、７００℃前後の高温の酸化性雰囲気中で化学的に安定でなければならないため、金属は不適当であり、電子伝導性を持つペロブスカイト型酸化物材料、具体的にはＬａＭｎＯ3 もしくはＬａＣｏＯ3 、または、これらのＬａの一部をＳｒ、Ｃａ等に置換した固溶体が一般に使用されている。また、燃料極材料は、Ｎｉ、Ｃｏなどの金属、或いはＮｉ−ＹＳＺ、Ｃｏ−ＹＳＺなどのサーメットが一般的である。 On the other hand, both the air electrode (cathode) layer and the fuel electrode (anode) layer, which are electrodes, must be made of a material having high electron conductivity. Since the air electrode material must be chemically stable in a high-temperature oxidizing atmosphere around 700 ° C., the metal is inappropriate, and a perovskite-type oxide material having electron conductivity, specifically LaMnO 3 Alternatively, LaCoO 3 or a solid solution in which a part of these La is substituted with Sr, Ca or the like is generally used. The fuel electrode material is generally a metal such as Ni or Co, or a cermet such as Ni—YSZ or Co—YSZ.

固体酸化物形燃料電池には、１０００℃前後の高温で作動させる高温作動型のものと、７００℃前後の低温で作動させる低温作動型のものとがある。低温作動型の固体酸化物形燃料電池は、例えば電解質であるイットリアを添加した安定化ジルコニア（ＹＳＺ）の厚さを１０μｍ程度まで薄膜化して電解質の抵抗を低くし、低温でも燃料電池として発電するように改良された発電セルを使用する。   Solid oxide fuel cells include a high-temperature operation type that operates at a high temperature of about 1000 ° C. and a low-temperature operation type that operates at a low temperature of about 700 ° C. A low temperature operation type solid oxide fuel cell, for example, stabilizes the thickness of stabilized zirconia (YSZ) added with yttria as an electrolyte to a thickness of about 10 μm to reduce the resistance of the electrolyte, and generates electricity as a fuel cell even at low temperatures. So that the improved power generation cell is used.

高温の固体酸化物形燃料電池では、セパレータには、例えばランタンクロマイト（ＬａＣｒＯ3 ）等の電子伝導性を有するセラミックスが用いられるが、低温作動型の固体酸化物形燃料電池では、ステンレス等の金属材料を使用することができる。 In a high-temperature solid oxide fuel cell, ceramics having electronic conductivity such as lanthanum chromite (LaCrO 3 ) is used as a separator. In a low-temperature operation type solid oxide fuel cell, a metal such as stainless steel is used. Material can be used.

また、固体酸化物形燃料電池の構造には、円筒型、モノリス型、及び平板積層型の３種類が提案されている。それらの構造のうち、低温作動型の固体酸化物形燃料電池には、金属のセパレータを使用できることから、金属のセパレータに形状付与しやすい平板積層型の構造が適している。   Three types of solid oxide fuel cell structures have been proposed: a cylindrical type, a monolith type, and a flat plate type. Among these structures, since a metal separator can be used for a low temperature operation type solid oxide fuel cell, a flat plate type structure that is easy to give a shape to the metal separator is suitable.

平板積層型の固体酸化物形燃料電池のスタックは、発電セル、集電体、セパレータを交互に積層した構造を持つ。一対のセパレータが発電セルを両面から挟んで、一方は空気極集電体を介して空気極と、他方は燃料極集電体を介して燃料極と接している。燃料極集電体には、Ｎｉ基合金等のスポンジ状の多孔質体を使用することができ、空気極集電体には、Ａｇ基合金等の同じくスポンジ状の多孔質体を使用することができる。スポンジ状の多孔質体は、集電機能、ガス透過機能、均一ガス拡散機能、クッション機能、熱膨脹差吸収機能等を兼ね備えるので、多機能の集電体材料として適している。   A stack of flat plate type solid oxide fuel cells has a structure in which power generation cells, current collectors, and separators are alternately stacked. A pair of separators sandwich the power generation cell from both sides, one being in contact with the air electrode via the air electrode current collector and the other being in contact with the fuel electrode via the fuel electrode current collector. A sponge-like porous body such as a Ni-based alloy can be used for the fuel electrode current collector, and a sponge-like porous body such as an Ag-based alloy can be used for the air electrode current collector. Can do. A sponge-like porous body has a current collecting function, a gas permeation function, a uniform gas diffusion function, a cushion function, a thermal expansion difference absorption function, and the like, and is therefore suitable as a multifunctional current collector material.

セパレータは、発電セル間を電気接続すると共に、発電セルに対してガスを供給する機能を有するもので、燃料ガスをセパレータ外周面から導入してセパレータの燃料極層に対向する面から吐出させる燃料ガス通路と、酸化剤ガスをセパレータ外周面から導入してセパレータの酸化剤極層に対向する面から吐出させる酸化剤ガス通路を備えている。   The separator has a function of electrically connecting the power generation cells and supplying gas to the power generation cells. The fuel is introduced from the outer peripheral surface of the separator and discharged from the surface facing the separator fuel electrode layer. A gas passage and an oxidant gas passage for introducing an oxidant gas from the outer peripheral surface of the separator and discharging the gas from a surface facing the oxidant electrode layer of the separator are provided.

ところで、この種の固体酸化物形燃料電池では、発電セルの外周部のガスシール機構を備えていないシールレス構造の固体酸化物形燃料電池がある。
従来は、発電セルの外周部にガスシール機構を施した構造が一般的であり、そのガスシール機構として、特許文献１が開示されているが、シールレス構造の固体酸化物形燃料電池は、発電セルの外周部のシール機構を無くすことで構造を単純化し、生産性の向上が図れると共に、構成部材間の熱膨脹差に基づくトラブルを無くすことができるというメリットを有する。
特開平９−１１５５３０号公報 By the way, in this type of solid oxide fuel cell, there is a solid oxide fuel cell having a sealless structure that does not include a gas seal mechanism at the outer peripheral portion of the power generation cell.
Conventionally, a structure in which a gas seal mechanism is provided on the outer peripheral portion of the power generation cell is generally used, and as the gas seal mechanism, Patent Document 1 is disclosed, but a solid oxide fuel cell having a sealless structure is By eliminating the sealing mechanism at the outer peripheral portion of the power generation cell, the structure can be simplified, productivity can be improved, and troubles based on the difference in thermal expansion between the constituent members can be eliminated.
JP-A-9-115530

しかしながら、シールレス構造の固体酸化物形燃料電池は、上記したようなメリットの他、シールレス構造が故の問題点も有していた。   However, the solid oxide fuel cell having the sealless structure has problems due to the sealless structure in addition to the above-described advantages.

即ち、シールレス構造では、運転時に発電セル内に燃料ガスと酸化剤ガスを供給して発電反応を生じさせると共に、発電反応に使用されなかった残余のガス（排ガス）を発電セルの外周部からセル外部に放出するようになっている。
従って、発電セル周部における流通ガスと外周部を流れる空気の線速度の相違から、発電セル外の空気を逆に燃料極側に巻き込む、所謂、逆拡散現象が生じ易い構造であり、運転時に、この逆拡散空気と発電セル内の燃料ガスが燃焼反応して電極反応に使用可能な燃料ガスを消費し、発電性能が低下するという問題や、この燃焼反応による局部的な温度上昇で発電セル内の熱応力分布が不均一となり、燃料電池スタックの寿命を極度に短縮させるという問題等を有していた。 That is, in the sealless structure, fuel gas and oxidant gas are supplied into the power generation cell during operation to cause a power generation reaction, and residual gas (exhaust gas) that has not been used for the power generation reaction is discharged from the outer periphery of the power generation cell. It discharges outside the cell.
Therefore, because of the difference in the linear velocity between the gas flowing in the peripheral part of the power generation cell and the air flowing in the outer peripheral part, the so-called reverse diffusion phenomenon, in which the air outside the power generation cell is entrapped in the reverse direction, is likely to occur. The problem is that this back-diffused air and the fuel gas in the power generation cell undergo a combustion reaction and consumes a fuel gas that can be used for the electrode reaction, resulting in a decrease in power generation performance and a local temperature rise due to this combustion reaction. There is a problem that the thermal stress distribution in the inside becomes uneven and the life of the fuel cell stack is extremely shortened.

本発明は、このようなシールレス構造特有の問題点に鑑み、燃料極集電体の外周部におけるガスの逆拡散現象を防止して、発電効率の向上を図った固体酸化物形燃料電池を提供することを目的としている。   In view of such problems inherent to the sealless structure, the present invention provides a solid oxide fuel cell that prevents the gas back-diffusion phenomenon in the outer peripheral portion of the anode current collector and improves the power generation efficiency. It is intended to provide.

すなわち、請求項１に記載の本発明は、固体電解質層の両面に燃料極層と酸化剤極層を配置し、当該燃料極層と酸化剤極層の外側にそれぞれ多孔質金属体で成る燃料極集電体と酸化剤極集電体を配置し、当該燃料極集電体と酸化剤極集電体の外側にセパレータを配置し、当該セパレータから前記燃料極集電体および酸化剤極集電体を通して前記燃料極層および酸化剤極層に燃料ガスおよび酸化剤ガスを供給するシールレス構造の固体酸化物形燃料電池において、前記燃料極層および前記燃料極集電体の外周部を覆うように、ガス排出孔を有する絶縁性カバーを配設し、外周部から排出される余剰ガスの排出箇所を制限する構成とした。     That is, according to the present invention, the fuel electrode layer and the oxidant electrode layer are disposed on both sides of the solid electrolyte layer, and the fuel is composed of a porous metal body on the outside of the fuel electrode layer and the oxidant electrode layer. An electrode current collector and an oxidant electrode current collector are disposed, a separator is disposed outside the fuel electrode current collector and the oxidant electrode current collector, and the fuel electrode current collector and the oxidant electrode current collector are disposed from the separator. In a solid oxide fuel cell having a sealless structure for supplying a fuel gas and an oxidant gas to the fuel electrode layer and the oxidant electrode layer through an electric body, covering the outer periphery of the fuel electrode layer and the fuel electrode current collector As described above, an insulating cover having a gas discharge hole is provided to restrict the discharge locations of excess gas discharged from the outer peripheral portion.

本構成では、燃料極集電体の外周部からの燃料ガスの無駄な排出や、燃料極側へのガスの逆拡散現象を防止することができ、発電効率を向上し、燃料電池の高出力密度化が図れる。   In this configuration, it is possible to prevent wasteful discharge of fuel gas from the outer periphery of the anode current collector and back diffusion phenomenon of gas to the anode side, improving power generation efficiency, and high output of the fuel cell Densification can be achieved.

また、請求項２に記載の本発明は、請求項１に記載の固体酸化物形燃料電池において、前記カバーは、内側に前記燃料極層および前記燃料極集電体が収まる輪状の扁平体で成り、前記セパレータと前記固体電解質層の間に介在されると共に、当該扁平体の端面に凹溝が形成されている。
本構成では、溝加工により、カバーとセパレータおよび／または固体電解質層との当接部分にガス排出孔を形成することができる。このように、扁平体への孔加工を無くして溝加工とすることで、カバーの加工性、生産性を向上することができる。 The present invention according to claim 2 is the solid oxide fuel cell according to claim 1, wherein the cover is a ring-shaped flat body in which the fuel electrode layer and the fuel electrode current collector are accommodated. In addition, it is interposed between the separator and the solid electrolyte layer, and a concave groove is formed on the end surface of the flat body.
In this configuration, the gas discharge hole can be formed in the contact portion between the cover and the separator and / or the solid electrolyte layer by groove processing. Thus, the processability and productivity of the cover can be improved by eliminating the hole processing on the flat body and performing the groove processing.

また、請求項３に記載の本発明は、請求項１または請求項２の何れかに記載の固体酸化物形燃料電池において、前記カバーを複数の分割構造とした。
本構成では、分割したカバーの各々を突き合わせて組み立てる構造にすることにより、積層時におけるカバーの配設が容易となり、燃料電池スタックの組み立て性が向上する。 According to a third aspect of the present invention, in the solid oxide fuel cell according to the first or second aspect, the cover has a plurality of divided structures.
In this configuration, by providing a structure in which each of the divided covers is abutted and assembled, the cover can be easily arranged at the time of stacking, and the assemblability of the fuel cell stack is improved.

また、請求項４に記載の本発明は、請求項１から請求項３までの何れかに記載の固体酸化物形燃料電池において、前記カバーは、アルミナ、ジルコニア等のセラミックスで構成されている。
カバーとして、このような耐熱性に優れる絶縁性材料を用いることにより、発電セル間の短絡を防止し、信頼性を確保できる。 According to a fourth aspect of the present invention, in the solid oxide fuel cell according to any one of the first to third aspects, the cover is made of ceramics such as alumina and zirconia.
By using such an insulating material having excellent heat resistance as a cover, short-circuiting between power generation cells can be prevented and reliability can be ensured.

以上説明したように、本発明によれば、燃料極層および燃料極集電体の外周部を覆うように、ガス排出孔を設けたカバーを配設し、外周部から排出される余剰ガスの排出箇所を制限するように構成したので、燃料極集電体の外周部からの無駄なガスの放出や、外部から燃料極側へのガスの逆拡散現象が防止される。これにより、発電効率が向上し、燃料電池の高出力密度化が図れると共に、燃料電池の高寿命化が図れる。   As described above, according to the present invention, the cover provided with the gas discharge holes is disposed so as to cover the outer peripheral portions of the fuel electrode layer and the fuel electrode current collector, and the excess gas discharged from the outer peripheral portion is disposed. Since the discharge location is limited, it is possible to prevent unnecessary gas discharge from the outer peripheral portion of the fuel electrode current collector and back diffusion phenomenon of gas from the outside to the fuel electrode side. As a result, the power generation efficiency is improved, the fuel cell can have a high output density, and the life of the fuel cell can be extended.

以下、図１〜図３に基づいて本発明の一実施形態を説明する。
図１は本発明が適用された固体酸化物形燃料電池スタックの断面図、図２は固体酸化物形燃料電池スタックの要部を示す分解斜視図、図３は運転時のガスの流れを示す説明図である。 Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
1 is a cross-sectional view of a solid oxide fuel cell stack to which the present invention is applied, FIG. 2 is an exploded perspective view showing the main part of the solid oxide fuel cell stack, and FIG. 3 shows a gas flow during operation. It is explanatory drawing.

図１、図２に示すように、燃料電池スタック１は、固体電解質層２の両面に燃料極層３と空気極層（酸化剤極層）４を配した発電セル５と、燃料極層３の外側の燃料極集電体６と、空気極層４の外側の空気極集電体（酸化剤極集電体）７と、各集電体６、７の外側のセパレータ８を順番に積層した構造を有する。   As shown in FIGS. 1 and 2, the fuel cell stack 1 includes a power generation cell 5 in which a fuel electrode layer 3 and an air electrode layer (oxidant electrode layer) 4 are disposed on both surfaces of a solid electrolyte layer 2, and a fuel electrode layer 3. A fuel electrode current collector 6 on the outer side, an air current collector (oxidant electrode current collector) 7 on the outer side of the air electrode layer 4, and a separator 8 on the outer side of the current collectors 6 and 7 are laminated in order. Has the structure.

ここで、固体電解質層２は、イットリアを添加した安定化ジルコニア（ＹＳＺ）等で構成され、燃料極層３は、Ｎｉ、Ｃｏ等の金属あるいはＮｉ−ＹＳＺ、Ｃｏ−ＹＳＺ等のサーメットで構成され、空気極層４は、ＬａＭｎＯ3 、ＬａＣｏＯ3 等で構成され、燃料極集電体６は、Ｎｉ基合金等のスポンジ状の多孔質焼結金属板で構成され、空気極集電体７は、Ａｇ基合金等のスポンジ状の多孔質焼結金属板で構成され、セパレータ８は、ステンレス等で構成されている。 Here, the solid electrolyte layer 2 is made of stabilized zirconia (YSZ) or the like to which yttria is added, and the fuel electrode layer 3 is made of a metal such as Ni or Co or a cermet such as Ni—YSZ or Co—YSZ. The air electrode layer 4 is made of LaMnO 3 , LaCoO 3 or the like, the fuel electrode current collector 6 is made of a sponge-like porous sintered metal plate such as a Ni-based alloy, and the air electrode current collector 7 is made of The separator 8 is made of stainless steel or the like, and is made of a sponge-like porous sintered metal plate such as an Ag-based alloy.

セパレータ８は、発電セル５間を電気接続すると共に、発電セル５に対してガスを供給する機能を有するもので、内部に燃料ガスをセパレータ８の外周面から導入してセパレータ８の燃料極集電体６に対向する面のほぼ中央部から吐出させる燃料ガス通路１１と、酸化剤ガスをセパレータ８の外周面から導入してセパレータ８の空気極集電体７に対向する面から吐出させる酸化剤ガス通路１２を有している。但し、両端のセパレータ８（８Ａ、８Ｂ）は、ガス通路１１、１２の何れか一方のみを有する。   The separator 8 has a function of electrically connecting the power generation cells 5 and supplying gas to the power generation cells 5. The fuel gas is introduced into the separator 8 from the outer peripheral surface thereof to collect the fuel electrode of the separator 8. A fuel gas passage 11 that is discharged from the substantially central portion of the surface facing the electric body 6 and an oxidation gas that is introduced from the outer peripheral surface of the separator 8 and discharged from the surface of the separator 8 that faces the air electrode current collector 7. An agent gas passage 12 is provided. However, the separators 8 (8A, 8B) at both ends have only one of the gas passages 11, 12.

また 各セパレータ８の燃料ガス通路１１には、外部から供給される燃料ガスを導入するための接続管１３が、また、酸化剤ガス通路１２には、酸化剤ガス（空気）を導入するための接続管１４が接続されている。   A connecting pipe 13 for introducing a fuel gas supplied from the outside is provided in the fuel gas passage 11 of each separator 8, and an oxidant gas (air) is introduced in the oxidant gas passage 12. A connecting pipe 14 is connected.

ところで、この固体酸化物形燃料電池は、発電セル５の外周部にガス漏れ防止シールを設けないシールレス構造とされており、運転時には、図３に示すように、燃料ガス通路１１および酸化剤ガス通路１２を通してセパレータ８の略中心部から発電セル５に向けて供給される燃料ガスおよび酸化剤ガス（空気）を発電セル５の外周方向に拡散させながら燃料極層３および空気極層４の全面に行き渡らせて発電反応を生じさせると共に、発電反応で消費されなかった残余の高温ガスを、発電セル５の外周部から外に自由に排出するようになっている。また、各集電体６、７内を拡散するガスの一部は発電セル側に供給されないまま、集電体６、７の空孔を通して外周部の全面より排出されている。   By the way, this solid oxide fuel cell has a sealless structure in which a gas leakage prevention seal is not provided on the outer peripheral portion of the power generation cell 5, and during operation, as shown in FIG. The fuel electrode layer 3 and the air electrode layer 4 are diffused while the fuel gas and the oxidant gas (air) supplied from the substantially central portion of the separator 8 to the power generation cell 5 through the gas passage 12 are diffused in the outer peripheral direction of the power generation cell 5. The power generation reaction is caused to spread over the entire surface, and the remaining high-temperature gas that has not been consumed in the power generation reaction is freely discharged from the outer peripheral portion of the power generation cell 5 to the outside. Further, a part of the gas diffusing in the current collectors 6 and 7 is discharged from the entire surface of the outer peripheral portion through the holes of the current collectors 6 and 7 without being supplied to the power generation cell side.

そして、このようなシールレス構造において、本実施形態では、特に、図１、図２に示すように、燃料極層３および燃料極集電体６の外周部を覆うように、セパレータ８と固体電解質層２の間に輪状の扁平体で成るカバー２０が配設される構成としている。カバー２０は、扁平体の内側に燃料極層３および燃料極集電体６を収納した状態で介在されており、これらの外周面に密着するように配設されるのが好ましい。   In such a sealless structure, in the present embodiment, as shown in FIGS. 1 and 2, in particular, the separator 8 and the solid so as to cover the outer periphery of the fuel electrode layer 3 and the fuel electrode current collector 6 are covered. A cover 20 made of an annular flat body is disposed between the electrolyte layers 2. The cover 20 is interposed in a state where the fuel electrode layer 3 and the fuel electrode current collector 6 are housed inside the flat body, and is preferably disposed so as to be in close contact with the outer peripheral surface thereof.

また、このカバー２０は、例えば、アルミナ、ジルコニア等の耐熱性、絶縁性に優れるセラミックスで構成されており、図２に示すように、固体電解質層２に当接するカバー２０の端面には、全周に多数の凹溝２１が所定の間隔でほぼ均一に形成されており、係るカバー２０を介在してセパレータ８、燃料極集電体６、発電セル５を順に積層すると、燃料極層３および燃料極集電体６の外周部にガス排出孔２２が形成される。カバー２０に絶縁性材料を用いることにより、発電セル５間の短絡を防止し、信頼性を確保できる。   Further, the cover 20 is made of ceramics having excellent heat resistance and insulation properties such as alumina and zirconia, for example. As shown in FIG. 2, the end surface of the cover 20 that contacts the solid electrolyte layer 2 is entirely covered. A large number of concave grooves 21 are formed substantially uniformly at a predetermined interval around the circumference, and when the separator 8, the fuel electrode current collector 6, and the power generation cell 5 are sequentially stacked through the cover 20, the fuel electrode layer 3 and A gas discharge hole 22 is formed in the outer periphery of the fuel electrode current collector 6. By using an insulating material for the cover 20, a short circuit between the power generation cells 5 can be prevented and reliability can be ensured.

このように、燃料極集電体６の外周面をカバー２０で覆う構造にすることにより、燃料極集電体６の外周部より排出されるガスの排出箇所をガス排出孔２２部分のみに制限することができ、その結果、燃料極集電体６内を拡散する燃料ガスが、その外周部全体より排出されることが回避されて、発電反応に寄与しない燃料ガスの外周部からの排出量を抑えると共に、その分、燃料ガスを効率的に発電セル５側に供給することができるようになる。   As described above, by covering the outer peripheral surface of the fuel electrode current collector 6 with the cover 20, the discharge location of the gas discharged from the outer peripheral portion of the fuel electrode current collector 6 is limited to the gas discharge hole 22 only. As a result, it is avoided that the fuel gas diffusing in the anode current collector 6 is discharged from the entire outer peripheral portion, and the discharge amount of the fuel gas that does not contribute to the power generation reaction from the outer peripheral portion In addition, the fuel gas can be efficiently supplied to the power generation cell 5 side.

加えて、カバー２０により、燃料極側への空気の逆拡散現象が防止され、発電セル内部において発生した燃焼反応により電極反応に使用可能な燃料ガスが消費され発電性能を低下させるという問題や、燃焼による局部的な温度上昇で発電セル内の熱応力分布が不均一となり、燃料電池スタック１の寿命を短縮させるというシールレス構造特有の問題を極力無くすことができる。これにより、発電効率を向上し、燃料電池の高出力密度化が図れると共に、燃料電池スタック１の高寿命化が図れるようになる。   In addition, the cover 20 prevents the back diffusion phenomenon of air to the fuel electrode side, the fuel gas that can be used for the electrode reaction is consumed by the combustion reaction generated inside the power generation cell, and the power generation performance is reduced, The local temperature rise due to combustion makes the thermal stress distribution in the power generation cell non-uniform, and the problem peculiar to the sealless structure that shortens the life of the fuel cell stack 1 can be eliminated as much as possible. As a result, the power generation efficiency can be improved, the output density of the fuel cell can be increased, and the life of the fuel cell stack 1 can be increased.

また、発電セル５、集電体６、７、セパレータ８の積層過程において、このカバー２０が積層方向の加重に対するガイド板の役目を果たすことから、積層時の圧力により多孔質金属体で成る燃料極集電体６が過度に押し潰されることはなく、積層後も燃料極集電体６の内部には略球状の空孔が確保されることになり、当集電体６内において均一で良好なガスの流れを確保することができる。   Further, in the stacking process of the power generation cell 5, the current collectors 6 and 7, and the separator 8, the cover 20 serves as a guide plate for the load in the stacking direction. The electrode current collector 6 is not crushed excessively, and a substantially spherical hole is secured inside the fuel electrode current collector 6 even after stacking, and is uniform in the current collector 6. A good gas flow can be ensured.

因みに、通常、集電体としては、厚み約２ｍｍ程度の多孔質金属体が使用されており、カバー２０を有しない空気極集電体７の場合は、積層時の圧力で多孔質金属体が厚さ０．７ｍｍ程度に押し潰されてしまうが、当空気極集電体７には、元来、必要反応量の約２倍程の多量の空気が供給されるため、集電体内でのガス拡散性や発電セル側へのガス供給量等に問題は生じない。   Incidentally, a porous metal body having a thickness of about 2 mm is usually used as the current collector, and in the case of the air electrode current collector 7 having no cover 20, the porous metal body is formed by the pressure during lamination. Although it is crushed to a thickness of about 0.7 mm, the air electrode current collector 7 is originally supplied with a large amount of air that is about twice the required reaction amount. There is no problem in gas diffusibility, gas supply amount to the power generation cell side, and the like.

このように、燃料極集電体６の外周面をカバー２０で覆うことにより、積層後の燃料極集電体６の厚みをより厚く維持することができ、多孔質金属体の厚みが増せば内部を拡散する燃料ガスの流量を多くすることができる。集電体内に供給された多量の燃料ガスは、このカバー２０の配設により、外周部からの無駄な排出が制限されており、よって、集電体内に拡散したガスは効率良く発電セル５側に供給されるようになる。   Thus, by covering the outer peripheral surface of the fuel electrode current collector 6 with the cover 20, the thickness of the fuel electrode current collector 6 after lamination can be maintained thicker, and if the thickness of the porous metal body increases. The flow rate of the fuel gas diffusing inside can be increased. A large amount of the fuel gas supplied into the current collector is restricted from being discharged from the outer peripheral portion by the arrangement of the cover 20, so that the gas diffused in the current collector is efficiently disposed on the power generation cell 5 side. Will be supplied to.

以上、本実施形態では、カバー２０にガス排出孔２２を形成するため、カバー２０の端部に凹溝２１を形成したが、このような溝加工ではなく、カバー２０の外周に孔加工により直接ガス排出孔２２を設けても勿論構わない。但し、セラミックスの場合、加工性は孔加工より溝加工の方が優れているため、生産性の面より溝加工の方が好ましい。
尚、凹溝２１は、カバー２０の片端面だけでなく両端面に形成しても良いが、全周に亘って均一に設けることが好ましい。 As described above, in this embodiment, the concave groove 21 is formed in the end portion of the cover 20 in order to form the gas discharge hole 22 in the cover 20. However, instead of such groove processing, the outer periphery of the cover 20 is directly formed by hole processing. Of course, the gas discharge hole 22 may be provided. However, in the case of ceramics, grooving is more preferable than drilling because grooving is better than drilling.
The concave grooves 21 may be formed not only on one end face of the cover 20 but also on both end faces. However, it is preferable to provide the concave grooves uniformly over the entire circumference.

また、カバー２０を輪状の扁平体としたが、例えば、この輪状体を２分割、４分割等し、それらを組み合わせて輪状にするようにしても良い。カバー２０を分割構造とすることにより、積層時にカバーを配設し易くなり、燃料電池スタックの組み立て性を向上することかできる。   Further, although the cover 20 is a ring-shaped flat body, for example, the ring-shaped body may be divided into two parts, four parts, etc., and these may be combined to form a ring shape. By making the cover 20 into a divided structure, the cover can be easily disposed at the time of stacking, and the assemblability of the fuel cell stack can be improved.

本発明の実施形態による燃料電池スタックの断面図。1 is a cross-sectional view of a fuel cell stack according to an embodiment of the present invention. 同、燃料電池スタックの要部を示す分解斜視図。The exploded perspective view which shows the principal part of a fuel cell stack. 運転時のガスの流れを示す説明図。Explanatory drawing which shows the flow of the gas at the time of a driving | operation.

符号の説明Explanation of symbols

２ 固体電解質層
３ 燃料極層
４ 酸化剤極層（空気極層）
６ 燃料極集電体
７ 酸化剤極集電体（空気極集電体）
８ セパレータ
２０ カバー
２１ 凹溝
２２ ガス排出孔 2 Solid electrolyte layer 3 Fuel electrode layer 4 Oxidant electrode layer (air electrode layer)
6 Fuel electrode current collector 7 Oxidant electrode current collector (air electrode current collector)
8 Separator 20 Cover
21 Concave groove 22 Gas exhaust hole

Claims (4)

固体電解質層の両面に燃料極層と酸化剤極層を配置して発電セルを構成し、当該燃料極層と酸化剤極層の外側にそれぞれ多孔質金属体で成る燃料極集電体と酸化剤極集電体を配置し、当該燃料極集電体と酸化剤極集電体の外側にセパレータを配置し、当該セパレータから前記燃料極集電体および酸化剤極集電体を通して前記燃料極層および酸化剤極層に燃料ガスおよび酸化剤ガスを供給するシールレス構造の固体酸化物形燃料電池において、
前記燃料極層および前記燃料極集電体の外周部を覆うように、ガス排出孔を有する絶縁性カバーを配設し、外周部から排出される余剰ガスの排出箇所を制限したことを特徴とする固体酸化物形燃料電池。 A fuel cell and an oxidant electrode layer are arranged on both sides of the solid electrolyte layer to form a power generation cell, and a fuel electrode current collector and an oxide made of a porous metal body are formed outside the fuel electrode layer and the oxidant electrode layer, respectively. An anode current collector is disposed, a separator is disposed outside the fuel electrode current collector and the oxidant electrode current collector, and the fuel electrode is passed from the separator through the fuel electrode current collector and the oxidant electrode current collector. In a solid oxide fuel cell having a sealless structure for supplying fuel gas and oxidant gas to the layer and the oxidant electrode layer,
An insulating cover having a gas discharge hole is provided so as to cover the outer peripheral portion of the fuel electrode layer and the fuel electrode current collector, and the exhaust gas exhausting locations discharged from the outer peripheral portion are limited. Solid oxide fuel cell. 前記カバーは、内側に前記燃料極層および前記燃料極集電体が収まる輪状の扁平体で成り、前記セパレータと前記固体電解質層の間に介在されると共に、当該扁平体の端面に凹溝を形成して成ることを特徴とする請求項１に記載の固体酸化物形燃料電池。 The cover is formed of a ring-shaped flat body in which the fuel electrode layer and the fuel electrode current collector are accommodated inside, and is interposed between the separator and the solid electrolyte layer, and has a groove on the end surface of the flat body. The solid oxide fuel cell according to claim 1, wherein the solid oxide fuel cell is formed. 前記カバーが複数に分割されていることを特徴とする請求項１または請求項２の何れかに記載の固体酸化物形燃料電池。 The solid oxide fuel cell according to claim 1, wherein the cover is divided into a plurality of parts. 前記カバーは、アルミナ、ジルコニア等のセラミックスで構成されることを特徴とする請求項１から請求項３までの何れかに記載の固体酸化物形燃料電池。 The solid oxide fuel cell according to any one of claims 1 to 3, wherein the cover is made of ceramics such as alumina and zirconia.
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JP2007005133A (en) * 2005-06-23 2007-01-11 Mitsubishi Materials Corp Steam generator and fuel cell
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