JP2004319290A - Solid electrolyte fuel cell - Google Patents

Abstract

Provided is a solid oxide fuel cell in which a contact resistance between a current collector and an inter-cell separator on an air electrode side is reduced and a stable output is maintained.
The fuel cell has a structure in which a plurality of single cells are stacked via metal inter-cell separators 211 and 212 (such as a heat-resistant alloy such as SUS430). The layer 11 (such as stabilized zirconia such as ScSZ), the fuel electrode 12 (Ni and ScSZ) provided on one surface of the solid electrolyte layer, and the air electrode 13 (La _1-x Sr _x MnO ₃ ) provided on the other surface And the like, and a current collector 5 (a dense body made of Inconel or the like) interposed between the air electrode and the inter-cell separator, and at least a part of the current collector 5 is provided. In addition to the dense portion, at least a part of the dense portion and the intercell separator are in contact with each other via a bonding material (such as a brazing silver material).
[Selection] Figure 3

Description

【００２４】
表１の結果によれば、集電体▲１▼〜▲５▼の緻密質部がろう付けされている実験例１〜７の総抵抗は、多孔体である角板がろう付けされている比較実験例１の総抵抗より非常に低いことが分かる。従って、実験例１〜７では、集電体として電気抵抗を小さく抑えると共に、ガス流路を容易に形成することができる有効な手法であることがわかった。また、集電体▲１▼〜▲５▼へのろう材の滲入は見られず、集電体▲１▼〜▲５▼の緻密質部が良好に接合されていた。
【００２５】
実施例１（積層された３個の単セルを有し、燃料極を基板とする内部マニホールド型の平板型ＳＯＦＣスタック）
（１）構造
▲１▼発電層及び各種セパレータ
３個の発電層等が積層された平板型ＳＯＦＣスタック１００の外観を図１に斜視図により示す。また、図２は、図１におけるＡ−Ａ断面の模式図であり、図３は、図１におけるＢ−Ｂ断面の模式図である。
この平板型ＳＯＦＣスタック１００では、３個の単セルがセル間セパレータ２１１、２１２を介して積層されている。各々の単セルが備える発電層は、それぞれＮｉとＳｃＳＺとからなり、平面形状が正方形であり、厚さが１０００μｍの燃料極１２を基板としている。この燃料極１２の表面にはそれぞれＳｃＳＺからなり、平面方向の形状、寸法が燃料極１２と同じであり、厚さが３０μｍの固体電解質層１１が形成されている。更に、この固体電解質層１１の表面にはそれぞれＬａ_１−ｘＳｒ_ｘＭｎＯ_３からなり、平面方向の形状が固体電解質層１１と同じであり、寸法が固体電解質層１１より小さく、厚さが３０μｍの空気極１３が形成されている。
【００２６】
上部単セルは、セル間セパレータ２１１の上面に配設されたニッケルフェルトからなる集電体４、基板となる燃料極１２、固体電解質層１１、空気極１３、インコネルからなる緻密質集電体５及び蓋部材２２をこの順に備える。この緻密質集電体５は、上下方向に貫通するガス流路５ａが形成されている（図６及び７参照。）。この緻密質集電体５と蓋部材２２とは、これらが接触する面の全面において、９５質量％のＡｇと５質量％のＰｄとからなるろう材によりろう付けされ、ろう付け部６が形成されている。また、上部単セルでは、固体電解質層１１の上面が上部単セル用隔離セパレータ２３と接合され、この上部単セル用隔離セパレータ２３の上面が絶縁性セラミックであるＭｇＯ−ＭｇＡｌ_２Ｏ_４焼結体からなる枠体７及び金属製枠体８１を介して蓋部材２２と接合されている。
【００２７】
中間部単セルは、セル間セパレータ２１２の上面に配設されたニッケルフェルトからなる集電体４、基板となる燃料極１２、固体電解質層１１、空気極１３、及びインコネルからなる緻密質集電体５をこの順に備える。この緻密質集電体５は、上部単セルの場合と同様にして、ガス流路５ａが形成されていると共に、セル間セパレータ２１１の下面とろう付けされ、ろう付け部６が形成されている。また、中間部単セルでは、固体電解質層１１の上面が中間単セル用隔離セパレータ２４と接合され、この中間単セル用隔離セパレータ２４の上面が絶縁性セラミックであるＭｇＯ−ＭｇＡｌ_２Ｏ_４焼結体からなる枠体７及び金属製枠体８３を介してセル間セパレータ２１１と接合されている。
【００２８】
下部単セルは、底部材２６の上面に配設されたニッケルフェルトからなる集電体４、基板となる燃料極１２、固体電解質層１１、空気極１３、及びインコネルからなる緻密質集電体５をこの順に備える。この緻密質集電体５は、上部単セルの場合と同様にして、ガス流路５ａが形成されていると共に、セル間セパレータ２１２の下面とろう付けされ、ろう付け部６が形成されている。また、下部単セルでは、固体電解質層１１の上面が下部単セル用隔離セパレータ２５と接合され、下部単セル用隔離セパレータ２５の上面が枠体７及び金属製枠体８５を介してセル間セパレータ２１２と接合されている。
【００２９】
セル間セパレータ２１１、２１２、蓋部材２２、上部単セル用隔離セパレータ２３、中間単セル用隔離セパレータ２４、下部単セル用隔離セパレータ２５、底部材２６、金属製枠体８１、８２、８３、８４、８５、８６は、いずれもＳＵＳ４３０により形成されている。更に、蓋部材２２と金属製枠体８１、金属製枠体８１と枠体７、枠体７と上部単セル用隔離セパレータ２３、上部単セル用隔離セパレータ２３と金属製枠体８２、金属製枠体８２とセル間セパレータ２１１、セル間セパレータ２１１と金属製枠体８３、金属製枠体８３と枠体７、枠体７と中間単セル用隔離セパレータ２４、中間単セル用隔離セパレータ２４と金属製枠体８４、金属製枠体８４とセル間セパレータ２１２、セル間セパレータ２１２と金属製枠体８５、金属製枠体８５と枠体７、枠体７と下部単セル用隔離セパレータ２５、下部単セル用隔離セパレータ２５と金属製枠体８６、及び金属製枠体８６と底部材２６、はそれぞれＡｇ、Ｐｄ及び少量のＴｉを含有する接合材により接合され、接合層１０が形成されている。
【００３０】
▲２▼燃料ガス導入管又は排出管、及び支燃性ガス導入管又は排出管
上部単セルにおいて、上部単セル用隔離セパレータ２３とセル間セパレータ２１１との間に形成された空間には、上部単セルの燃料極１２に燃料ガスを導入するための燃料ガス導入管９１が開口している（図２参照）。また、この空間の燃料ガス導入管９１の開口部と対向する側には、上部単セルの燃料極１２から燃料ガスを排出するための燃料ガス排出管９２が開口している（図２参照）。更に、蓋部材２２と上部単セル用隔離セパレータ２３との間に形成された空間には、上部単セルの空気極１３に支燃性ガスを導入するための支燃性ガス導入管９３が開口している（図３参照）。また、この空間の支燃性ガス導入管９３の開口部と対向する側には、上部単セルの空気極１３から支燃性ガスを排出するための支燃性ガス排出管９４が開口している（図３参照）。さらに、それら支燃性ガス導入管９３及び支燃性ガス排出管９４が開口する空間は、所定の連絡路（図示せず）を介して緻密質集電体５のガス流路５ａと連絡されている。
【００３１】
また、中間部単セルにおいて、中間部単セル用隔離セパレータ２４とセル間セパレータ２１２との間に形成された空間には、中間部単セルの燃料極１２に燃料ガスを導入するための燃料ガス導入管９１が開口している（図２参照）。更に、この空間の燃料ガス導入管９１の開口部と対向する側には、中間部単セルの燃料極１２から燃料ガスを排出するための燃料ガス排出管９２が開口している（図２参照）。また、セル間セパレータ２１１と中間部単セル用隔離セパレータ２４との間に形成された空間には、中間部単セルの空気極１３に支燃性ガスを導入するための支燃性ガス導入管９３が開口している（図３参照）。更に、この空間の支燃性ガス導入管９３の開口部と対向する側には、中間部単セルの空気極１３から支燃性ガスを排出するための支燃性ガス排出管９４が開口している（図３参照）。さらに、それら支燃性ガス導入管９３及び支燃性ガス排出管９４が開口する空間は、所定の連絡路（図示せず）を介して緻密質集電体５のガス流路５ａと連絡されている。
【００３２】
更に、下部単セルにおいて、下部単セル用隔離セパレータ２５と底部材２６との間に形成された空間には、下部単セルの燃料極１２に燃料ガスを導入するための燃料ガス導入管９１が開口している（図２参照）。また、この空間の燃料ガス導入管９１の開口部と対向する側には、下部単セルの燃料極１２から燃料ガスを排出するための燃料ガス排出管９２が開口している（図２参照）。更に、セル間セパレータ２１２と下部単セル用隔離セパレータ２５との間に形成された空間には、下部単セルの空気極１３に支燃性ガスを導入するための支燃性ガス導入管９３が開口している（図３参照）。また、この空間の支燃性ガス導入管９３の開口部と対向する側には、下部単セルの空気極１３から支燃性ガスを排出するための支燃性ガス排出管９４が開口している（図３参照）。さらに、それら支燃性ガス導入管９３及び支燃性ガス排出管９４が開口する空間は、所定の連絡路（図示せず）を介して緻密質集電体５のガス流路５ａと連絡されている。
【００３３】
また、上部単セル、中間部単セル及び下部単セルの各々に燃料ガス又は支燃性ガスを導入し、又は排出するためのそれぞれの管は、本管に側管が取り付けられた構造であり、上部単セル、中間部単セル及び下部単セルの各々の発電層に燃料ガス及び支燃性ガスが同時に導入され、且つ排出される。更に、燃料ガス導入管と燃料ガス排出管、及び支燃性ガス導入管と支燃性ガス排出管は、この実施例１の場合は、燃料ガス及び支燃性ガスがそれぞれ対向方向に流通するような位置に取り付けられている。これにより、上部単セル、中間部単セル及び下部単セルのそれぞれの発電層の各々の燃料極と燃料ガス、及び空気極と支燃性ガスをそれぞれ効率よく接触させることができる。
【００３４】
（２）燃料電池からの電力の取り出し
この平板型ＳＯＦＣスタック１００では、上部単セルの燃料極１２は、ニッケルフェルトからなる集電体４を介してセル間セパレータ２１１と電気的に接続されている。また、セル間セパレータ２１１は、インコネルからなる緻密質集電体５を介して中間部単セルの空気極１３と電気的に接続されている。更に、中間部単セルの燃料極１２は、集電体４を介してセル間セパレータ２１２と電気的に接続されている。また、セル間セパレータ２１２は、緻密質集電体５を介して下部単セルの空気極１３と電気的に接続されている。このように上部単セル、中間部単セル及び下部単セルは各々直列に接続されている。また、スタックを所定の動作温度に昇温させ、燃料ガス導入管９１に水素等の燃料ガスを導入して燃料極１２と接触させ、支燃性ガス導入管９３に空気等の支燃性ガスを導入して空気極１３と接触させることにより、燃料極１２と空気極１３との間に起電力が生じ、この電力を外部に取り出すことにより発電装置として機能させることができる。
【００３５】
電力は、燃料極側においては下部単セルの発電層の下面に配設された集電体４を介して底部材２６に取り出され、空気極側においては上部単セルの発電層の上面に配設された緻密質集電体５を介して蓋部材２２に取り出され、蓋部材２２と底部材２６との間でスタック全体の電力を取り出すことができる。この平板型ＳＯＦＣスタック１００では、３個の発電層がそれぞれ燃料極支持型であり、この構造の場合、６００℃程度の動作温度でも電流を取り出すことができ、蓋部材、各種セパレータ、金属製枠体及び底部材を、セラミックではなくＳＵＳ４３０等のステンレス鋼により形成することができるものである。
【００３６】
（３）燃料ガス及び支燃性ガス
実施例１の固体電解質型燃料電池を用いて発電させる場合、燃料極側には燃料ガスを導入し、空気極側には支燃性ガスを導入する。燃料ガスとしては、水素、水素源となる炭化水素、水素と炭化水素との混合ガス、及びこれらのガスを所定温度の水中を通過させ加湿した燃料ガス、これらのガスに水蒸気を混合させた燃料ガス等が挙げられる。炭化水素は特に限定されず、例えば、天然ガス、ナフサ、石炭ガス化ガス等が挙げられる。更に、メタン、エタン、プロパン、ブタン及びペンタン等の炭素数が１〜１０、好ましくは１〜７、より好ましくは１〜４の飽和炭化水素、並びにエチレン及びプロピレン等の不飽和炭化水素を主成分とするものが好ましく、飽和炭化水素を主成分とするものが更に好ましい。これらの燃料ガスは１種のみを用いてもよいし、２種以上を併用することもできる。また、５０体積％以下の窒素及びアルゴン等の不活性ガスを含有していてもよい。
【００３７】
支燃性ガスとしては、酸素と他の気体との混合ガス等が挙げられる。また、この混合ガスには８０体積％以下の窒素及びアルゴン等の不活性ガスが含有されていてもよい。これらの支燃性ガスのうちでは安全であって、且つ安価であるため空気（約８０体積％の窒素が含まれている。）が好ましい。
【００３８】
実施例２（積層された３個の単セルを有し、燃料極を基板とする内部マニホールド型の平板型ＳＯＦＣスタック）
尚、本実施例２においては、集電体の構成以外は実施例１と同じ構成であり、その同じ構成部位には同符号を付けて詳細な説明を省略する。
図４及び５に示すように、平板型ＳＯＦＣスタック２００を構成する上部単セルは、セル間セパレータ２１１の上面に配設されたニッケルフェルトからなる集電体４、基板となる燃料極１２、固体電解質層１１、空気極１３、Ｌａ_０．８Ｓｒ_０．２ＭｎＯ_３からなる集電体５０及び蓋部材２２をこの順に備える。この集電体５０は、緻密質部５０ａ（気孔率３％）と、この緻密質部５０ａの下面側に積層される多孔質部５０ｂ（気孔率４０％）とを有している。この集電体５０の緻密質部５０ａと蓋部材２２とは、これらが接触する面の全面において、９５質量％のＡｇと５質量％のＰｄとからなるろう材によりろう付けされ、ろう付け部６が形成されている。
【００３９】
中間部単セルは、セル間セパレータ２１２の上面に配設されたニッケルフェルトからなる集電体４、基板となる燃料極１２、固体電解質層１１、空気極１３、及びＬａ_０．８Ｓｒ_０．２ＭｎＯ_３からなる集電体５０をこの順に備える。この集電体５０は、上部単セルの場合と同様にして、緻密質部５０ａ及び多孔質部５０ｂを積層してなると共に、その緻密質部５０ａがセル間セパレータ２１１の下面とろう付けされ、ろう付け部６が形成されている。
【００４０】
下部単セルは、底部材２６の上面に配設されたニッケルフェルトからなる集電体４、基板となる燃料極１２、固体電解質層１１、空気極１３、及びＬａ_０．８Ｓｒ_０．２ＭｎＯ_３からなる集電体５０をこの順に備える。この集電体５０は、上部単セルの場合と同様にして、緻密質部５０ａ及び多孔質部５０ｂを積層してなると共に、その緻密質部５０ａがセル間セパレータ２１２の下面とろう付けされ、ろう付け部６が形成されている。
【００４１】
また、上部単セル、中間部単セル及び下部単セルの各々は、実施例１と同様にして、電気的に直列に接続されている。そして、スタックを所定の動作温度に昇温させた状態で、燃料ガス導入管９１に水素等の燃料ガスを導入すると共に、支燃性ガス導入管９３に空気等の支燃性ガスを導入する。すると、燃料ガスが集電体４を透過して燃料極１２と接触し、支燃性ガスが集電体５０の多孔質部５０ｂを透過して空気極１３と接触することにより、燃料極１２と空気極１３との間に起電力が生じ、この電力を外部に取り出すことにより発電装置として機能させることができる。
【００４２】
尚、本発明では上記の実施例に限られず、目的、用途等によって本発明の範囲内において種々変更した実施例とすることができる。例えば、蓋部材、各種セパレータ、底部材を形成するステンレス鋼としては、フェライト系ステンレス鋼、マルテンサイト系ステンレス鋼、オーステナイト系ステンレス鋼が挙げられる。フェライト系ステンレス鋼としては、ＳＵＳ４３０以外に、ＳＵＳ４３４、ＳＵＳ４０５等が挙げられる。マルテンサイト系ステンレス鋼としては、ＳＵＳ４０３、ＳＵＳ４１０、ＳＵＳ４３１等が挙げられる。オーステナイト系ステンレス鋼としては、ＳＵＳ２０１、ＳＵＳ３０１、ＳＵＳ３０５等が挙げられる。更に、ニッケル基合金としては、インコネル６００、インコネル７１８、インコロイ８０２等が挙げられる。クロム基合金としては、Ｄｕｃｒｌｌｏｙ ＣＲＦ（９４Ｃｒ５Ｆｅ１Ｙ_２Ｏ_３）等が挙げられる。これらの各種の耐熱合金は、それぞれ積層体の用途等によって選択することができる。
【００４３】
発電層等の平面形状は、長方形、円形及び楕円形等とすることができ、同様の平面形状を有する固体電解質型燃料電池とすることができる。また、平板型ＳＯＦＣスタックでは、各種セパレータ等の金属成形体の間は溶接などの方法によっても接合することができる。しかし、実施例の内部マニホールド型のスタックにおけるセパレータの周縁の貫通孔の内部は溶接では接合することができない。この場合、Ａｇを含有する特定の接合材を使用すれば、展延性に優れるＡｇによって貫通孔の周縁を十分に気密に密着させることができる。
【００４４】
更に、固体電解質層の形成に用いる材料はＳｃＳＺに限定されず、平板型ＳＯＦＣスタックの使用条件等により適宜選択することができる。この材料としては、例えば、ＺｒＯ_２系セラミック、ＬａＧａＯ_３系セラミック、ＢａＣｅＯ_３系セラミック、ＳｒＣｅＯ_３系セラミック、ＳｒＺｒＯ_３系セラミック及びＣａＺｒＯ_３系セラミック等が挙げられる。これらのセラミック系材料のうちでは、ＺｒＯ_２系セラミックが好ましく、Ｙ及び希土類元素のうちの少なくとも１種により安定化されたＺｒＯ_２系セラミックが好ましい。こられの安定化ジルコニアもＳｃＳＺと同様に優れたイオン伝導性及び機械的強度を有する。
尚、この固体電解質層の厚さは電気抵抗と強度とを勘案し、５〜１００μｍ、特に５〜５０μｍ、更には５〜３０μｍとすることができる。
【００４５】
また、燃料極の形成に用いる材料もＮｉ及びＳｃＳＺに限定されず、平板型ＳＯＦＣスタックの使用条件等により適宜選択することができる。この材料としては、例えば、Ｐｔ、Ａｕ、Ａｇ、Ｃｕ、Ｐｄ、Ｉｒ、Ｒｕ、Ｒｈ、Ｎｉ及びＦｅ等の金属が挙げられる。これらの金属は１種のみでもよいし、２種以上の金属の合金でもよい。また、これらの金属及び／又は合金と、Ｙ及び希土類元素のうちの少なくとも１種により安定化されたジルコニア等のジルコニア系セラミック、セリア系セラミック及び酸化マンガン等のセラミックとの混合物（サーメットを含む。）が挙げられる。更に、Ｎｉ及びＦｅ等の金属の酸化物と、上記セラミックのうちの少なくとも１種との混合物などが挙げられる。
また、燃料極の平面形状は特に限定されないが、固体電解質層及び空気極と同じ形状であることが好ましい。更に、燃料極と固体電解質層とは各々の全面で積層されていることが好ましい。
【００４６】
固体電解質型燃料電池において、各々の単セルが有する発電層は、強度の観点から過度に薄くすることは好ましくないが、発電性能の観点では前記のように固体電解質層を厚くすることは好ましくない。そのため、実施例１のように燃料極支持型とすることができ、この燃料極支持型では、燃料極は固体電解質層の２０倍以上の厚さであることが好ましい。２０倍未満であると発電層の機械的強度が不十分となる傾向にある。この燃料極の厚さは２００〜３０００μｍ、特に５００〜２０００μｍであることが好ましい。２００μｍ未満であると基板として有効に機能せず、３０００μｍを越えると、体積当たりの発電効率が低下する傾向にある。一方、空気極支持型とすることもでき、この場合は、燃料極の厚さは、１０〜５０μｍ、特に２０〜４０μｍであることが好ましい。この厚さが１０〜５０μｍであれば、電極として十分に機能し、５０μｍを越えて厚くする必要はない。
【００４７】
また、空気極の形成に用いる材料はＬａ_１−ｘＳｒ_ｘＭｎＯ_３系複合酸化物に限定されず、平板型ＳＯＦＣスタックの使用条件等により適宜選択することができる。この材料としては、例えば、Ｐｔ、Ａｕ、Ａｇ、Ｐｄ、Ｉｒ、Ｒｕ及びＲｈ等の金属が挙げられる。これらの金属は１種のみでもよいし、２種以上の金属の合金でもよい。更に、Ｌａ、Ｓｒ、Ｃｅ、Ｃｏ及びＭｎ等の酸化物（例えば、Ｌａ_２Ｏ_３、ＳｒＯ、Ｃｅ_２Ｏ_３、Ｃｏ_２Ｏ_３、ＭｎＯ_２及びＦｅＯ等）が挙げられる。また、Ｌａ、Ｓｒ、Ｃｅ、Ｃｏ及びＭｎ等のうちの少なくとも１種を含有する各種の複合酸化物（例えば、Ｌａ_１−ｘＳｒ_ｘＣｏＯ_３系複合酸化物、Ｌａ_１−ｘＳｒ_ｘＦｅＯ_３系複合酸化物、Ｌａ_１−ｘＳｒ_ｘＣｏ_１−ｙＦｅ_ｙＯ_３系複合酸化物、Ｐｒ_１−ｘＢａ_ｘＣｏＯ_３系複合酸化物及びＳｍ_１−ｘＳｒ_ｘＣｏＯ_３系複合酸化物等）が挙げられる。
【００４８】
また、この空気極の平面形状は特に限定されないが、固体電解質層及び燃料極と同じ形状であることが好ましい。更に、その平面方向の寸法は、特に、隔離セパレータが固体電解質層の一表面の周縁に接合されない場合等、燃料電池の構造によっては、固体電解質層及び燃料極と同じにすることもできる。これら空気極と固体電解質層とは各々の全面で積層されていることが好ましい。
【００４９】
空気極は、発電層の強度を支持する基板として形成することもできる。空気極支持型である場合は、空気極の厚さは固体電解質層の２０倍以上の厚さであることが好ましい。２０倍未満であると発電層の機械的強度が不十分となる傾向にある。この空気極の厚さは２００〜３０００μｍ、特に５００〜２０００μｍであることが好ましい。２００μｍ未満であると基板として有効に機能せず、３０００μｍを越えると、体積当たりの発電効率が低下する傾向にある。一方、燃料極支持型である場合は、空気極の厚さは１０〜１００μｍ、特に２０〜５０μｍであることが好ましい。１０μｍ未満であると電極として十分に機能しないことがあり、１００μｍを越えると固体電解質層から剥離することがある。
【００５０】
ろう材には、Ｃｕが含有されていてもよい。Ｃｕが含有されている場合のＡｇ、Ｐｄ及びＣｕの各々の含有量は特に限定されないが、Ａｇ、Ｐｄ及びＣｕの合計を１００質量％とした場合に、Ａｇの含有量は４５〜６５質量％、特に５０〜６０質量％、Ｐｄの含有量は１５〜３５質量％、特に２０〜３０質量％、Ｃｕの含有量は１０〜３０質量％、特に１５〜２５質量％であることが好ましい。Ｃｕが含有されている場合、含有されていないろう材に比べてより多量のＰｄを含有していても、十分な流動性を有し、優れた密着性が維持される。一方、ＡｇとＣｕの合計が６５質量％未満、即ち、Ｐｄの含有量が３５質量％を越えると、流動性が低下し、密着性が不十分になる傾向にある。
【００５１】
ろう材にＴｉが含有されていることにより、接合温度が比較的低い場合でも、特に大きな接合強度が得られる。このＴｉの含有量は、Ａｇ、Ｐｄ及びＴｉの合計を１００質量％とした場合に、又はＣｕが含有されているときは、Ａｇ、Ｐｄ、Ｃｕ及びＴｉの合計を１００質量％とした場合に、０．０５〜１０質量％であることが好ましく、特に０．０５〜８質量％、更には０．０５〜６質量％であることがより好ましい。Ｔｉの含有量が０．０５〜１０質量％であれば、ろう付けの雰囲気が真空ではなく、アルゴン等の不活性雰囲気であっても、実用上、十分な強度を有するろう付け部を形成することができる。また、ろう付けの雰囲気が真空である場合は、Ｔｉの含有量は、０．０５〜２０質量％、特に０．０５〜１５質量％とすることもでき、更に、Ｔｉの含有量が０．０８〜１０質量％であれば、接合強度が大きく向上する。
【００５２】
ろう材には、接合強度及び密着性等が低下しない範囲で更に他の成分が含有されていてもよい。この他の成分としてはＳｎ、Ｉｎ、Ｎｉ、Ｎｂ等が挙げられる。これらの他の成分は、ＡｇとＰｄとの合計、更にＣｕを含有する場合はＡｇ、Ｐｄ及びＣｕの合計、更にＴｉを含有する場合はＡｇ、Ｐｄ及びＴｉの合計、又はＡｇ、Ｐｄ、Ｃｕ及びＴｉの合計を１００質量部とした場合に、１０質量部以下、特に０．１〜１０質量部、更には０．５〜５質量部含有させることができる。
【００５３】
また、上記実施例では、空気極側においてセル間セパレータと集電体とをろう付けにより接合するようにしたが、これに限定されず、例えば、導電性材料を含有する導電性ペーストをセル間セパレータ及び集電体のうちの少なくとも一方に塗布し、その塗布面を介して両者を接触させた状態で熱処理することによって、空気極側のセル間セパレータと集電体とを接合するようにしてもよい。
【００５４】
また、上記実施例２では、緻密質部と多孔質部とを積層して集電体を構成したが、これに限定されず、例えば、図８に示すように、緻密質部と、気孔率の異なる複数層の多孔質部とを積層して集電体を構成してもよい。この場合、集電体を構成する緻密質部とセル間セパレータとがろう付けされることとなる。また、図９に示すように、同一平面内に緻密質部と多孔質部とを交互に配設して集電体を構成してもよい。この場合、集電体を構成する緻密質部及び多孔質部の一方の面とセル間セパレータとがろう付けされると共に、緻密質部及び多孔質部の他方の面と空気極とが接触することとなる。ここで、セル間セパレータと集電体の多孔質部との界面に接合材が導入されていても、燃料電池としての性能に悪影響を与えない。また、多孔質部の上下面側に緻密質部を積層して集電体を構成してもよい。この場合、空気極側の緻密質部にはガス流路が形成される。さらに、上記実施例１では、緻密質集電体５のガス流路を上下に開口するようにしたが、これに限定されず、例えば、図１１に示すように、ガス流路は、少なくとも空気極側に開口していればよい。
【００５５】
また、セル間セパレータと燃料極との間に介装される集電体としては、ニッケルフェルトに限られず前記の空気極の場合と同様の形状のものを用いることができる。この燃料極側の集電体はセル間セパレータとの接触面において空気極側と同様にしてろう付けされていてもよいが、燃料極側ではセル間セパレータは酸化され難いため、ろう付けされていなくてもよい。
【図面の簡単な説明】
【図１】実施例１の燃料電池の外観を示す斜視図である。
【図２】図１の燃料電池のＡ−Ａ断面を示す模式図である。
【図３】図１の燃料電池のＢ−Ｂ断面を示す模式図である。
【図４】実施例２の燃料電池の縦断面を示し、図１のＡ−Ａ断面に相当する模式図である。
【図５】実施例２の燃料電池の縦断面を示し、図１のＢ−Ｂ断面に相当する模式図である。
【図６】実験例で使用した集電体▲１▼を模式的に示す説明図である。
【図７】図６のＶＩＩ−ＶＩＩ線断面図である。
【図８】実験例で使用した集電体▲２▼を模式的に示す説明図である。
【図９】実験例で使用した集電体▲３▼を模式的に示す説明図である。
【図１０】実験例で使用した集電体▲４▼を模式的に示す説明図である。
【図１１】実験例で使用した集電体▲５▼を模式的に示す説明図である。
【図１２】総抵抗の評価に用いた試験体を模式的に示す説明図である。
【符号の説明】
１００，２００；平板型ＳＯＦＣスタック、１１；固体電解質層、１２；燃料極、１３；空気極、２１１、２１２；セル間セパレータ、２２；蓋部材、２３；上部単セル用隔離セパレータ、２３１、２３２；貫通孔、２４；中間単セル用隔離セパレータ、２５；下部単セル用隔離セパレータ、２６；底部材、２５１、２５２；貫通孔、３１；燃料ガスの流路、３２；支燃性ガスの流路、４；ニッケルフェルトからなる集電体、５；緻密質集電体、５ａ；ガス流路、５０；集電体、５０ａ；緻密質部、５０ｂ；多孔質部、６；ろう付け部、７；枠体、８１、８２、８３、８４、８５、８６；金属製枠体、９１；燃料ガス導入管、９２；燃料ガス排気管、９３；支燃性ガス導入管、９４；支燃性ガス排気管、１０；接合層。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a solid oxide fuel cell. More specifically, in a fuel cell in which a plurality of single cells are stacked, the contact resistance between a current collector interposed between an air electrode and an inter-cell separator in each single cell and the inter-cell separator The present invention relates to a solid oxide fuel cell capable of maintaining a stable output for a long time by reducing the fuel cell.
INDUSTRIAL APPLICABILITY The present invention can be widely used in solid oxide fuel cells having various structures.
[0002]
[Prior art]
A flat solid electrolyte fuel cell (hereinafter, also referred to as a “flat SOFC stack”) is formed by stacking a plurality of single cells with a separator interposed therebetween. This flat type SOFC stack is often operated at a high temperature exceeding 1000 ° C., but in recent years, the internal resistance has been reduced by making the solid electrolyte layer such as zirconia stabilized by Y or the like as thin as possible. In particular, research for operating in a relatively low temperature range of 800 ° C. or less has been activated. In this case, an inexpensive metal separator can be used in place of the conventionally used heat-resistant ceramic separator. In particular, if a cheaper stainless steel can be used, the cost can be significantly reduced. be able to.
[0003]
In such a flat-plate SOFC stack in which a metal separator is used and the fuel electrode and the air electrode of each single cell are electrically connected to the separator by a current collector, the distance between each electrode and the separator is increased. If the contact resistance is high, the output will decrease, causing a serious problem. In particular, on the air electrode side, oxygen gas is always present, the separator is easily oxidized, and the generated insulating oxide film tends to increase the contact resistance. In order to cope with such a problem, a current collector using Ag having excellent conductivity has been proposed (for example, see Patent Document 1). Further, a separator having excellent conductivity in which a silver plating layer is formed on a surface of a base material made of a heat-resistant alloy via a chromium oxide layer is also known (for example, see Patent Document 2).
[0004]
[Patent Document 1]
JP 2002-280026 A
[Patent Document 2]
JP 2002-289215 A
[0005]
[Problems to be solved by the invention]
It is described that if the current collector described in Patent Literature 1 and the separator described in Patent Literature 2 are used, a solid oxide fuel cell having a high output density can be obtained even when operated at a low temperature. However, these current collectors and separators are very expensive, are inexpensive, and require a contact means capable of sufficiently reducing the contact resistance.
The present invention has been made in view of the above circumstances, and a solid electrolyte fuel in which a stable output is maintained by reducing the contact resistance between the current collector and the inter-cell separator on the air electrode side. It is intended to provide a battery.
[0006]
[Means for Solving the Problems]
The present invention is as follows.
1. In a solid oxide fuel cell having a structure in which a plurality of single cells are stacked via a metal inter-cell separator, each single cell is a solid electrolyte layer, a fuel electrode provided on one surface of the solid electrolyte layer, And a power generation layer having an air electrode provided on the other surface, and a current collector interposed between the inter-cell separator and the air electrode, at least a part of the current collector has a dense portion. And a solid oxide fuel cell, wherein at least a part of the dense portion and the inter-cell separator are in contact with each other via a bonding material.
2. The above-mentioned 1., wherein the entire current collector is the dense portion. The solid oxide fuel cell according to the above.
3. A part of the current collector is the dense part, and another part of the current collector is a porous part capable of passing a supporting gas. The solid oxide fuel cell according to the above.
4. The joining material is a brazing material, and a surface where the dense portion and the inter-cell separator are in contact with each other is brazed. To 3. The solid oxide fuel cell according to any one of the above.
5. 3. The brazing material as described above, wherein the brazing material is mainly composed of Ag. The solid oxide fuel cell according to the above.
6). The above-described 1., wherein the current collector is configured to allow the supporting gas to pass toward the air electrode. To 5. The solid oxide fuel cell according to any one of the above.
[0007]
【The invention's effect】
In the solid oxide fuel cell of the present invention, the current collector and the inter-cell separator are joined to each other to reduce the contact resistance between them, and to maintain a stable output for a long time.
In addition, when the entire current collector is a dense portion, the contact resistance between the dense portion of the current collector and the separator between cells can be further reduced.
In addition, when a part of the current collector is a dense part and another part of the current collector is a porous part capable of passing the supporting gas, the shape of the supporting gas passage is free. In addition to increasing the degree, the current collector strength can be improved depending on the shape.
When the joining material is a brazing material and the surface where the dense portion and the intercell separator contact each other is brazed, the heat cycle resistance and the like are improved, and a more stable output is maintained.
When the brazing material is mainly composed of Ag, the contact resistance between the current collector and the intercell separator can be more stably reduced.
Further, when the current collector is configured to allow the supporting gas to pass toward the air electrode, it is possible to preferably bring the supporting gas into contact with the air electrode during the operation of the fuel cell. it can.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The solid oxide fuel cell according to the present embodiment is formed by stacking a plurality of single cells via a metal intercell separator. In this fuel cell, each single cell has a power generation layer, and each power generation layer has a solid electrolyte layer, a fuel electrode provided on one surface of the solid electrolyte layer, and an air electrode provided on the other surface. . Further, the fuel electrode and the air electrode of each power generation layer and the inter-cell separator are electrically connected to each other by a current collector. In addition, each unit cell has an isolation separator for isolating the fuel gas flow path and the supporting gas flow path, depending on the structure of the fuel cell, and this isolation separator is also formed of metal. Can be. Further, in order to electrically insulate each single cell, a frame made of insulating ceramic may be provided at a predetermined portion in the stacking direction.
[0009]
The “inter-cell separator” is made of a metal, and is particularly formed of a heat-resistant alloy such as stainless steel, a nickel-based alloy, and a chromium-based alloy. In addition, when another single cell is not laminated on the upper surface of the inter-cell separator, it functions as a lid member, and when another single cell is not laminated on the lower surface of the inter-cell separator, it functions as a bottom member.
Furthermore, depending on the structure of the flat-plate type SOFC stack, an inter-cell separator having a flow path for a fuel gas or a supporting gas may be used.
[0010]
Further, the “solid electrolyte layer” can be formed of zirconia stabilized by Sc (ScSZ) or the like. The solid electrolyte layer has an ion conductivity capable of moving at least a part of one of a fuel gas introduced into the fuel electrode and a supporting gas introduced into the air electrode during operation of the battery as ions. The type of ions that can be conducted is not particularly limited, and examples of the ions include oxygen ions and hydrogen ions.
The “fuel electrode” can be formed of Ni, ScSZ, or the like. The fuel electrode contacts a fuel gas serving as a hydrogen source and functions as a negative electrode in the flat-plate SOFC stack.
The "fuel gas" is not particularly limited as long as it can serve as a hydrogen source, but may be, for example, hydrocarbon gas such as methane or ethane in addition to hydrogen. Further, the fuel gas composition may be either pure gas or mixed gas.
The above “air electrode” is La _1-x Sr _x MnO ₃ It can be formed of a composite oxide or the like. The air electrode comes in contact with a supporting gas serving as an oxygen source, and functions as a positive electrode in the flat-plate SOFC stack.
The component of the “combustible gas” is not particularly limited as long as it can serve as an oxygen source, and examples thereof include a mixed gas of oxygen and another gas.
[0011]
The shape, material, and the like of the “current collector” are not particularly limited as long as at least a part of the current collector is a dense portion. The current collector is generally configured to allow the combustion supporting gas to pass (including permeation) toward the air electrode. Further, the current collector may be, for example, a dense portion entirely. In this case, as shown in FIGS. 6 and 11, the dense portion has a gas flow path through which the combustible gas can pass toward the air electrode. In addition, one surface of the dense portion contacts the inter-cell separator, and the other surface contacts the air electrode. In addition, the current collector may be, for example, a porous part capable of passing a combustible gas while part of the current collector is a dense part. In this case, as shown in FIGS. 8 to 10, the dense portion and the porous portion can be stacked on each other or disposed on the same plane. Examples of the porous portion include a ceramic porous body, a metal foam, a felt, a mesh, and the like. Further, this porous portion may be made of only one kind of material, or may be made of two or more kinds of materials.
In addition, when this current collector is used, the resistance of the separator between the cells on the air electrode side, the resistance of the current collector, and the total resistance including the contact resistance thereof are reduced by a porous current collector having no dense portion. Can be less than 50% (preferably, less than 30%) of the total resistance when using.
[0012]
The current collector preferably has oxidation resistance equal to or higher than that of the inter-cell separator. This oxidation is difficult because a test piece made of a material forming a current collector is heat-treated at the operating temperature of the fuel cell for about 500 hours, and then the cross section of the test piece is mirror-polished, and this cross section is observed with an electron microscope. The thickness can be evaluated by checking the thickness of the oxide film, and whether or not the oxide film has peeled off, or if the oxide film has peeled off, the degree of peeling. It is particularly preferable that the current collector is less likely to be oxidized than the inter-cell separator. In this case, when the current collector generates heat due to current concentration, the current collector is more difficult to be oxidized, and the electrical characteristics are less likely to deteriorate.
[0013]
Further, it is preferable that at least a part of the current collector contains the same element as the element constituting the air electrode. By containing the same element, the reaction between the air electrode and the current collector is suppressed, these are not deteriorated, the increase in contact resistance is suppressed, and a stable output is maintained. More preferably, at least a part of the current collector has the same composition as the air electrode. Even when the same element is contained, if the composition is different, the element or the like may migrate from the higher concentration side to the lower concentration side, and the deterioration and the increase in the contact resistance may not be sufficiently suppressed. On the other hand, if the composition is the same, the reaction between the air electrode and the current collector and the migration of elements and the like are sufficiently suppressed, and the output can be further stabilized.
[0014]
The material, shape, and the like of the “dense portion” are not particularly limited as long as at least a part thereof is in contact with the inter-cell separator via a bonding material described below. As the dense portion, for example, a block-shaped body, a plate-shaped body, a deformed body made of ceramic or metal, and the like can be given. Further, the dense portion may be made of only one kind of material, or may be made of two or more kinds of materials.
Here, the dense portion refers to a porosity of 8% or less, preferably 5% or less, particularly preferably 3% or less, and 1 mm when the surface of the current collector in contact with the intercell separator is mirror-polished. ² It means a part having the above area. As the measurement of the porosity, for example, an image of a mirror-polished surface is obtained by an electron microscope or the like, and an image analysis processing device is used for an arbitrary range, and the area occupied by the pores with respect to the entire area is calculated. The rate can be listed.
[0015]
The “joining material” is not particularly limited as long as the current collector and the inter-cell separator can be stuck and stably contacted. Examples of the joining material include a brazing material, a conductive material, and the like. As the brazing material, a material containing Ag as a main component is preferable from the viewpoint of heat resistance, oxidation resistance, corrosion resistance, and the like, particularly when the operating temperature of the flat SOFC stack is assumed to be 650 to 900 ° C. Further, those containing Ag as a main component and containing Pd, Ti and the like are more preferable. Ag as a main component means that Ag is 50% by mass or more when the brazing material is 100% by mass, and this Ag is 70 to 98% by mass, particularly 90 to 98% by mass, and more preferably 90 to 98% by mass. It is particularly preferred that the content is 93 to 97% by mass. If the brazing material contains 70 to 98% by mass, particularly 90 to 98% by mass of Ag, the brazing material sufficiently flows at the time of brazing, and the contact resistance can be reduced. Further, a brazed portion which is not easily oxidized and has sufficient durability can be formed.
[0016]
The temperature at which the current collector and the inter-cell separator are brazed using the brazing material is not particularly limited, but the temperature should be equal to or higher than the solidus point temperature of the brazing material and equal to or lower than the liquidus point temperature exceeding 50 ° C. Is preferred. Although the melting point of Ag is about 962 ° C., if brazing is performed at a temperature equal to or higher than the solidus point temperature of the brazing material, the Ag-containing brazing material is melted, and the Ag, which is highly extensible, is formed between the current collector and the cell. It flows sufficiently between the separator and the separator, and these can be adhered to each other. In particular, when brazing is performed at a temperature exceeding the liquidus temperature of the brazing material, more stable and sufficient adhesion and bonding strength are maintained, and there is no easy peeling. On the other hand, the brazing temperature does not need to be higher than the liquidus point temperature by more than 50 ° C., and it is sufficient if brazing is performed at a temperature higher than the solidus point temperature and lower than the liquidus point temperature higher than 50 ° C. Adhesion and bonding strength can be obtained.
[0017]
The atmosphere at the time of brazing is not particularly limited as long as it is an inert atmosphere. Vacuum and an inert gas atmosphere such as argon and nitrogen can be used. The atmosphere at the time of brazing is particularly preferably a vacuum, and if it is a vacuum atmosphere, the bonding strength can be greatly improved. The degree of this vacuum is 10 Pa or less, especially 1 × 10 ^-2 It is preferably set to 1 Pa.
In the flat type SOFC stack, in addition to the current collector and the separator between the cells, there are also many parts that need to be hermetically sealed with a bonding material containing Ag and the like. can do. Therefore, even if the current collector and the inter-cell separator are brazed, the number of operations and steps for manufacturing a flat SOFC stack is small.
[0018]
In addition, as the conductive material, for example, a material containing at least one of platinum, gold, silver, and palladium as a main component is preferable from the viewpoint of being chemically stable under the operating environment of a fuel cell. . Particularly, those containing silver as a main component are preferable from the viewpoint of cost, chemical stability and the like. Here, the term “main component” means that, when the conductive material is 100% by mass, the total of the metal as the main component is 50% by mass or more, and the main component is 70 to 98% by mass. In particular, it is particularly preferred that the content is 90 to 98% by mass, more preferably 93 to 97% by mass.
Further, a conductive paste containing a conductive material is applied to at least one of the dense portion of the current collector and the inter-cell separator, and the dense portion of the current collector and the inter-cell separator are applied through the applied surface. If the heat treatment is performed in a state where the conductive material is in contact with the conductive material, a conductive material can be interposed between the dense portion of the current collector and the inter-cell separator. Note that the conditions of the heat treatment are not particularly limited, and vary depending on the material, so that a suitable heat treatment temperature, time, atmosphere, and the like can be used.
[0019]
【Example】
Hereinafter, the present invention will be described specifically by way of examples.
Experimental Examples 1 to 7 and Comparative Experimental Example 1
Using the test piece of (1) below, the SUS square plate and the current collectors (1) to (5) or the square plate were brazed as in (2) below, and the test piece as shown in FIG. Was prepared, and the total resistance was measured as described in (3) below.
(1) Specimen
As a test piece of an experimental example, in a flat-plate SOFC stack, a 35 mm square, 0.3 mm thick SUS square plate (s1) made of SUS430 used as an inter-cell separator or the like, and a material shown in Table 1 below And current collectors (1) to (5) (s2) (in all cases, the outer shape is 30 mm square and 2 mm thick). Specifically, La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ (A porosity of 3% or less; described in Table 1 below as "LSCF6428".) A current collector (1) to (5) composed of Inconel 610 and a current collector (1) and (5) composed of Inconel 610 are prepared. did.
As the test piece of the comparative example, a SUS square plate (s1) having the same structure as the test example and a LSCF6428 porous body (porosity of 50%) having a shape of 30 mm square and 2 mm thick were used. (S2) was used.
[0020]
The current collector {circle around (1)} (s2) is a dense body in which a plurality of long holes (gas flow paths) (g) penetrating vertically are formed as shown in FIGS. As shown in FIG. 8, the current collector {circle around (2)} (s2) has a dense portion (thickness: 0.2 mm) (m) and a porous layer laminated on the lower surface side of the dense portion (m). Porous portion (porosity 20%, thickness 0.2 mm) (n1) and a porous portion (porosity 40%, thickness 1.6 mm) laminated on the lower surface side of the porous portion (n1) (n2) ). As shown in FIG. 9, the current collector {circle around (3)} (s2) has a dense portion (m) and a porous portion (n) alternately arranged, and a gas flow path (g) penetrating vertically. Is formed by the porous portion (n). As shown in FIG. 10, the current collector {circle around (4)} (s2) has a dense portion (thickness: 0.2 mm) (m) and a porous layer laminated on the lower surface side of the dense portion (m). (Porosity: 40%, thickness: 1.8 mm) (n). Further, as shown in FIG. 11, the current collector (5) (s2) is a dense body having a plurality of long grooves (gas flow paths) (g) opened on the lower surface side. In FIG. 6 to FIG. 11, in order to clarify the positional relationship when the SUS square plate (s1) and the current collectors (1) to (5) (s2) are used as fuel cells, the cell part i is assumed to be virtual. Shown by lines.
When the current collectors (1) to (5) are made of a ceramic material, for example, the current collectors (1), (2), (4), and (5) have different properties (porosity, etc.) or It can be manufactured by laminating and firing ceramic sheets in which a portion to be a gas passage is punched in advance. In addition, the current collectors (1) and (5) can be produced by firing a molded article formed at a time by press molding. In addition, the current collector (3) can be manufactured by extruding a molded product by alternately arranging materials having different properties (porosity and the like) by using an extrusion molding method. Further, in the case where the current collectors (1) to (5) are made of a metal material, for example, the current collectors are made by a powder metallurgy method (the same manufacturing method as that of the ceramic material is made by using a metal powder), or the like. A metal block can be produced by cutting.
[0021]
(2) Brazing (Experimental Examples 1 to 7 and Comparative Experimental Example 1)
The SUS square plate (s1) and the current collectors (1) to (5) or the square plate (s2) may be made of a brazing material composed of 95% by mass of Ag and 5% by mass of Pd. Connected. Specifically, the SUS square plate (s1) and the current collectors (1) to (5) or the square plate (s2) were composed of 95% by mass of Ag and 5% by mass of Pd, Lamination was performed with a brazing material sheet having a corner and a thickness of 50 μm. At this time, the layers were laminated such that their centers were the same. After that, it is introduced into a vacuum heat treatment furnace, brazed by holding at 1050 ° C. for 30 minutes, and the SUS square plate and the dense portion or square plate (s2) of the current collectors (1) to (5) are joined. A laminated body joined through the portion (c) was formed. The rate of temperature rise and fall was 500 ° C./hour in each case.
[0022]
(3) Evaluation of total resistance
Two alumina tubes (a) having an outer diameter of 40 mm and a length of 500 mm were prepared by covering two ends with a Pt net (p), and one of them was set up vertically with the side covered with the Pt net upward. The above-described laminate was placed on the Pt net of No. 1 with the SUS square plate (s1) facing down. Thereafter, another alumina tube was erected on the laminate such that the Pt net was in contact with the current collectors (1) to (5) or the square plate (s2), thereby producing a test body (e). Then, at 700 ° C. under atmospheric pressure, a current is applied from the SUS square plate (s1) side to the current collectors (1) to (5) or the square plate (s2) side (current 2A). The resistance of the SUS square plate (s1), the resistance of the current collectors (1) to (5) or the square plate (s2), and the total resistance consisting of these contact resistances were measured. The results are shown in Table 1.
[0023]
[Table 1]

[0024]
According to the results shown in Table 1, the total resistance of Experimental Examples 1 to 7 in which the dense portions of the current collectors (1) to (5) were brazed was that the square plate that was a porous body was brazed. It can be seen that the total resistance is much lower than that of Comparative Example 1. Therefore, in Experimental Examples 1 to 7, it was found that the current collector was an effective technique capable of suppressing the electric resistance as a current collector and easily forming a gas flow path. No penetration of the brazing material into the current collectors (1) to (5) was observed, and the dense portions of the current collectors (1) to (5) were well joined.
[0025]
Example 1 (Internal manifold type flat plate SOFC stack having three unit cells stacked and using a fuel electrode as a substrate)
(1) Structure
(1) Power generation layer and various separators
FIG. 1 is a perspective view showing the appearance of a flat SOFC stack 100 in which three power generation layers and the like are stacked. FIG. 2 is a schematic diagram of a cross section taken along line AA in FIG. 1, and FIG. 3 is a schematic diagram of a cross section taken along line BB in FIG.
In this flat type SOFC stack 100, three single cells are stacked via inter-cell separators 211 and 212. The power generation layer of each unit cell is made of Ni and ScSZ, has a square planar shape, and has a fuel electrode 12 having a thickness of 1000 μm as a substrate. On the surface of the fuel electrode 12, a solid electrolyte layer 11 made of ScSZ and having the same shape and dimensions in the planar direction as the fuel electrode 12 and a thickness of 30 μm is formed. Further, the surface of the solid electrolyte layer 11 is _1-x Sr _x MnO ₃ The air electrode 13 has the same shape as the solid electrolyte layer 11 in the plane direction, a smaller dimension than the solid electrolyte layer 11, and a thickness of 30 μm.
[0026]
The upper single cell includes a current collector 4 made of nickel felt, which is disposed on the upper surface of the inter-cell separator 211, a fuel electrode 12 serving as a substrate, a solid electrolyte layer 11, an air electrode 13, and a dense current collector 5 made of Inconel. And a lid member 22 in this order. The dense current collector 5 is provided with a gas flow path 5a penetrating vertically (see FIGS. 6 and 7). The dense current collector 5 and the lid member 22 are brazed with a brazing material composed of 95% by mass of Ag and 5% by mass of Pd on the entire surface where they contact with each other to form a brazing portion 6. Have been. In the upper single cell, the upper surface of the solid electrolyte layer 11 is joined to the upper single-cell isolation separator 23, and the upper surface of the upper single-cell isolation separator 23 is made of an insulating ceramic such as MgO-MgAl. ₂ O ₄ It is joined to the lid member 22 via a frame 7 made of a sintered body and a metal frame 81.
[0027]
The intermediate unit cell includes a current collector 4 made of nickel felt disposed on the upper surface of the inter-cell separator 212, a fuel electrode 12 serving as a substrate, a solid electrolyte layer 11, an air electrode 13, and a dense current collector consisting of Inconel. The body 5 is provided in this order. As in the case of the upper single cell, the dense current collector 5 has a gas flow path 5a and is brazed to the lower surface of the inter-cell separator 211 to form a brazing portion 6. . In the intermediate unit single cell, the upper surface of the solid electrolyte layer 11 is joined to the intermediate single cell isolation separator 24, and the upper surface of the intermediate single cell isolation separator 24 is made of an insulating ceramic such as MgO-MgAl. ₂ O ₄ It is joined to the inter-cell separator 211 via a frame 7 made of a sintered body and a metal frame 83.
[0028]
The lower single cell includes a current collector 4 made of nickel felt, which is disposed on the upper surface of the bottom member 26, a fuel electrode 12 serving as a substrate, a solid electrolyte layer 11, an air electrode 13, and a dense current collector 5 made of Inconel. Are provided in this order. As in the case of the upper single cell, the dense current collector 5 has a gas flow path 5 a and is brazed to the lower surface of the inter-cell separator 212 to form a brazing portion 6. . In the lower unit cell, the upper surface of the solid electrolyte layer 11 is joined to the lower unit cell isolation separator 25, and the upper surface of the lower unit cell isolation separator 25 is connected to the inter-cell separator via the frame 7 and the metal frame 85. 212.
[0029]
Inter-cell separators 211 and 212, lid member 22, upper single-cell isolation separator 23, middle single-cell isolation separator 24, lower single-cell isolation separator 25, bottom member 26, metal frames 81, 82, 83, and 84. , 85 and 86 are all made of SUS430. Further, the lid member 22 and the metal frame 81, the metal frame 81 and the frame 7, the frame 7 and the upper single-cell isolation separator 23, the upper single-cell isolation separator 23 and the metal frame 82, The frame 82 and the inter-cell separator 211, the inter-cell separator 211 and the metal frame 83, the metal frame 83 and the frame 7, the frame 7 and the intermediate single-cell isolation separator 24, and the intermediate single-cell isolation separator 24. A metal frame 84, a metal frame 84 and an inter-cell separator 212, an inter-cell separator 212 and a metal frame 85, a metal frame 85 and a frame 7, a frame 7 and a lower single cell isolation separator 25, The lower single-cell isolation separator 25 and the metal frame 86, and the metal frame 86 and the bottom member 26 are respectively bonded by a bonding material containing Ag, Pd, and a small amount of Ti to form the bonding layer 10. I have.
[0030]
(2) Fuel gas introduction pipe or discharge pipe, and flammable gas introduction pipe or discharge pipe
In the upper unit cell, a fuel gas introduction pipe 91 for introducing a fuel gas into the fuel electrode 12 of the upper unit cell is opened in a space formed between the upper unit cell isolation separator 23 and the inter-cell separator 211. (See FIG. 2). Further, a fuel gas discharge pipe 92 for discharging fuel gas from the fuel electrode 12 of the upper single cell is opened on the side of this space facing the opening of the fuel gas introduction pipe 91 (see FIG. 2). . Further, in a space formed between the lid member 22 and the upper single-cell isolation separator 23, a combustible gas introduction pipe 93 for introducing a combustible gas into the air electrode 13 of the upper single cell is opened. (See FIG. 3). On the side of this space opposite to the opening of the supporting gas introduction pipe 93, a supporting gas discharge pipe 94 for discharging the supporting gas from the air electrode 13 of the upper single cell is opened. (See FIG. 3). Further, the space in which the oxidizing gas introducing pipe 93 and the oxidizing gas discharging pipe 94 are opened is connected to the gas flow path 5a of the dense current collector 5 through a predetermined communication path (not shown). ing.
[0031]
In the intermediate unit cell, a fuel gas for introducing fuel gas into the fuel electrode 12 of the intermediate unit cell is provided in a space formed between the intermediate unit single cell isolation separator 24 and the inter-cell separator 212. The introduction pipe 91 is open (see FIG. 2). Further, a fuel gas discharge pipe 92 for discharging fuel gas from the fuel electrode 12 of the intermediate unit single cell is opened on the side of this space facing the opening of the fuel gas introduction pipe 91 (see FIG. 2). ). Further, in a space formed between the inter-cell separator 211 and the intermediate unit single-cell isolation separator 24, a flammable gas introduction pipe for introducing flammable gas to the air electrode 13 of the intermediate unit single cell is provided. 93 is open (see FIG. 3). Further, on the side of this space facing the opening of the supporting gas introduction pipe 93, a supporting gas discharge pipe 94 for discharging the supporting gas from the air electrode 13 of the intermediate unit cell is opened. (See FIG. 3). Further, the space in which the oxidizing gas introducing pipe 93 and the oxidizing gas discharging pipe 94 are opened is connected to the gas flow path 5a of the dense current collector 5 through a predetermined communication path (not shown). ing.
[0032]
Further, in the lower unit cell, a fuel gas introduction pipe 91 for introducing fuel gas to the fuel electrode 12 of the lower unit cell is provided in a space formed between the lower unit cell isolation separator 25 and the bottom member 26. It is open (see FIG. 2). Further, a fuel gas discharge pipe 92 for discharging fuel gas from the fuel electrode 12 of the lower single cell is opened on the side of this space facing the opening of the fuel gas introduction pipe 91 (see FIG. 2). . Further, in a space formed between the inter-cell separator 212 and the lower single cell isolation separator 25, a flammable gas introduction pipe 93 for introducing a flammable gas into the air electrode 13 of the lower single cell is provided. It is open (see FIG. 3). On the side of this space facing the opening of the supporting gas introduction pipe 93, a supporting gas discharge pipe 94 for discharging the supporting gas from the air electrode 13 of the lower single cell is opened. (See FIG. 3). Further, the space in which the oxidizing gas introducing pipe 93 and the oxidizing gas discharging pipe 94 are opened is connected to the gas flow path 5a of the dense current collector 5 through a predetermined communication path (not shown). ing.
[0033]
In addition, each pipe for introducing or discharging the fuel gas or the supporting gas to each of the upper unit cell, the intermediate unit cell and the lower unit cell has a structure in which a side pipe is attached to the main pipe. The fuel gas and the supporting gas are simultaneously introduced into and discharged from the power generation layers of the upper unit cell, the middle unit cell and the lower unit cell. Further, in the case of the first embodiment, the fuel gas introduction pipe and the fuel gas exhaust pipe, and the fuel gas introduction pipe and the combustion supporting gas exhaust pipe, the fuel gas and the combustion supporting gas respectively flow in opposite directions. It is mounted in such a position. Thus, the fuel electrode and the fuel gas, and the air electrode and the supporting gas of each of the power generation layers of the upper unit cell, the intermediate unit cell, and the lower unit cell can be efficiently contacted.
[0034]
(2) Extraction of electric power from fuel cell
In the flat type SOFC stack 100, the fuel electrode 12 of the upper single cell is electrically connected to the inter-cell separator 211 via the current collector 4 made of nickel felt. The inter-cell separator 211 is electrically connected to the air electrode 13 of the intermediate unit cell via the dense current collector 5 made of Inconel. Further, the fuel electrode 12 of the intermediate unit cell is electrically connected to the intercell separator 212 via the current collector 4. The inter-cell separator 212 is electrically connected to the air electrode 13 of the lower single cell via the dense current collector 5. As described above, the upper unit cell, the middle unit cell, and the lower unit cell are connected in series. Further, the temperature of the stack is raised to a predetermined operating temperature, a fuel gas such as hydrogen is introduced into the fuel gas introduction pipe 91 and brought into contact with the fuel electrode 12, and a fuel gas such as air is supplied to the fuel gas introduction pipe 93. Is brought into contact with the air electrode 13 to generate an electromotive force between the fuel electrode 12 and the air electrode 13. By extracting this electric power to the outside, it is possible to function as a power generator.
[0035]
Electric power is extracted to the bottom member 26 via the current collector 4 disposed on the lower surface of the power generation layer of the lower single cell on the fuel electrode side, and is distributed on the upper surface of the power generation layer of the upper single cell on the air electrode side. The electric power is taken out to the lid member 22 via the dense dense current collector 5 provided, and the electric power of the entire stack can be taken out between the lid member 22 and the bottom member 26. In this flat type SOFC stack 100, the three power generation layers are of the fuel electrode support type, and in this structure, current can be taken out even at an operating temperature of about 600 ° C., and a lid member, various separators, and a metal frame The body and the bottom member can be formed of stainless steel such as SUS430 instead of ceramic.
[0036]
(3) Fuel gas and supporting gas
When power is generated using the solid oxide fuel cell of the first embodiment, a fuel gas is introduced into the fuel electrode side, and a supporting gas is introduced into the air electrode side. Examples of the fuel gas include hydrogen, a hydrocarbon serving as a hydrogen source, a mixed gas of hydrogen and a hydrocarbon, a fuel gas humidified by passing these gases through water at a predetermined temperature, and a fuel obtained by mixing steam with these gases. Gas and the like. The hydrocarbon is not particularly limited, and examples thereof include natural gas, naphtha, and coal gasification gas. Furthermore, methane, ethane, propane, butane, pentane and the like have 1 to 10, preferably 1 to 7, more preferably 1 to 4 saturated hydrocarbons, and unsaturated hydrocarbons such as ethylene and propylene as main components. Are preferable, and those containing a saturated hydrocarbon as a main component are more preferable. One of these fuel gases may be used alone, or two or more thereof may be used in combination. Further, it may contain 50% by volume or less of an inert gas such as nitrogen and argon.
[0037]
Examples of the supporting gas include a mixed gas of oxygen and another gas. The mixed gas may contain 80% by volume or less of an inert gas such as nitrogen and argon. Of these combustible gases, air (containing about 80% by volume of nitrogen) is preferred because it is safe and inexpensive.
[0038]
Example 2 (internal manifold type flat plate SOFC stack having three unit cells stacked and using a fuel electrode as a substrate)
Note that the second embodiment has the same configuration as the first embodiment except for the configuration of the current collector, and the same components are denoted by the same reference numerals and detailed description thereof will be omitted.
As shown in FIGS. 4 and 5, the upper single cell constituting the flat SOFC stack 200 includes a current collector 4 made of nickel felt disposed on the upper surface of an inter-cell separator 211, a fuel electrode 12 serving as a substrate, Electrolyte layer 11, air electrode 13, La _0.8 Sr _0.2 MnO ₃ A current collector 50 and a lid member 22 are provided in this order. The current collector 50 has a dense portion 50a (porosity 3%) and a porous portion 50b (porosity 40%) laminated on the lower surface side of the dense portion 50a. The dense portion 50a and the lid member 22 of the current collector 50 are brazed with a brazing material composed of 95% by mass of Ag and 5% by mass of Pd on the entire surface in contact with them. 6 are formed.
[0039]
The intermediate unit cell includes a current collector 4 made of nickel felt disposed on the upper surface of an inter-cell separator 212, a fuel electrode 12 serving as a substrate, a solid electrolyte layer 11, an air electrode 13, and La. _0.8 Sr _0.2 MnO ₃ Is provided in this order. This current collector 50 is formed by laminating a dense portion 50a and a porous portion 50b in the same manner as in the case of the upper single cell, and the dense portion 50a is brazed to the lower surface of the inter-cell separator 211, A brazing portion 6 is formed.
[0040]
The lower single cell includes a current collector 4 made of nickel felt disposed on the upper surface of the bottom member 26, a fuel electrode 12 serving as a substrate, a solid electrolyte layer 11, an air electrode 13, and La _0.8 Sr _0.2 MnO ₃ Is provided in this order. This current collector 50 is formed by laminating a dense portion 50a and a porous portion 50b in the same manner as in the case of the upper single cell, and the dense portion 50a is brazed to the lower surface of the inter-cell separator 212, A brazing portion 6 is formed.
[0041]
Each of the upper unit cell, the intermediate unit unit cell, and the lower unit cell is electrically connected in series similarly to the first embodiment. Then, while the stack is heated to a predetermined operating temperature, a fuel gas such as hydrogen is introduced into the fuel gas introduction pipe 91 and a flammable gas such as air is introduced into the flammable gas introduction pipe 93. . Then, the fuel gas permeates the current collector 4 and comes into contact with the fuel electrode 12, and the combustible gas passes through the porous portion 50 b of the current collector 50 and comes into contact with the air electrode 13. An electromotive force is generated between the battery and the air electrode 13, and the power can be taken out to function as a power generator.
[0042]
It should be noted that the present invention is not limited to the above embodiment, but may be variously modified within the scope of the present invention depending on the purpose, application, and the like. For example, examples of the stainless steel forming the lid member, various separators, and the bottom member include ferritic stainless steel, martensitic stainless steel, and austenitic stainless steel. Examples of the ferritic stainless steel include SUS434 and SUS405 in addition to SUS430. Examples of the martensitic stainless steel include SUS403, SUS410, and SUS431. Examples of the austenitic stainless steel include SUS201, SUS301, and SUS305. Further, examples of the nickel-based alloy include Inconel 600, Inconel 718, Incoloy 802, and the like. As a chromium-based alloy, Ducrroy CRF (94Cr5Fe1Y ₂ O ₃ ) And the like. These various heat-resistant alloys can be selected depending on the use of the laminate and the like.
[0043]
The planar shape of the power generation layer or the like can be rectangular, circular, elliptical, or the like, and a solid oxide fuel cell having a similar planar shape can be obtained. In the case of a flat-plate SOFC stack, metal moldings such as various separators can be joined by a method such as welding. However, the inside of the through hole at the peripheral edge of the separator in the internal manifold type stack of the embodiment cannot be joined by welding. In this case, if a specific bonding material containing Ag is used, the periphery of the through hole can be sufficiently airtightly adhered by Ag having excellent spreadability.
[0044]
Further, the material used for forming the solid electrolyte layer is not limited to ScSZ, and can be appropriately selected depending on the use conditions of the flat SOFC stack. As this material, for example, ZrO ₂ Ceramic, LaGaO ₃ Ceramic, BaCeO ₃ Ceramic, SrCeO ₃ Ceramic, SrZrO ₃ Ceramic and CaZrO ₃ Series ceramics and the like. Among these ceramic materials, ZrO ₂ ZrO stabilized with at least one of Y and rare earth elements ₂ Base ceramics are preferred. These stabilized zirconia also have excellent ionic conductivity and mechanical strength similarly to ScSZ.
The thickness of the solid electrolyte layer can be 5 to 100 μm, particularly 5 to 50 μm, and more preferably 5 to 30 μm in consideration of electric resistance and strength.
[0045]
Further, the material used for forming the fuel electrode is not limited to Ni and ScSZ, and can be appropriately selected depending on the conditions of use of the flat-plate type SOFC stack. Examples of the material include metals such as Pt, Au, Ag, Cu, Pd, Ir, Ru, Rh, Ni, and Fe. These metals may be only one kind or an alloy of two or more kinds of metals. Further, a mixture (including cermet) of these metals and / or alloys and zirconia-based ceramics such as zirconia stabilized with at least one of Y and rare earth elements, and ceramics such as ceria-based ceramics and manganese oxide. ). Further, a mixture of an oxide of a metal such as Ni and Fe with at least one of the above-mentioned ceramics may be used.
The planar shape of the fuel electrode is not particularly limited, but is preferably the same shape as the solid electrolyte layer and the air electrode. Further, it is preferable that the fuel electrode and the solid electrolyte layer are laminated on the entire surface of each.
[0046]
In the solid oxide fuel cell, the power generation layer of each single cell is not preferably excessively thin from the viewpoint of strength, but it is not preferable to increase the thickness of the solid electrolyte layer as described above from the viewpoint of power generation performance. . Therefore, the anode support type can be used as in the first embodiment. In this anode support type, the anode is preferably 20 times or more the thickness of the solid electrolyte layer. If it is less than 20 times, the mechanical strength of the power generation layer tends to be insufficient. The thickness of this fuel electrode is preferably 200 to 3000 μm, particularly preferably 500 to 2000 μm. If it is less than 200 μm, it does not function effectively as a substrate, and if it exceeds 3000 μm, the power generation efficiency per volume tends to decrease. On the other hand, it is also possible to use an air electrode support type. In this case, the thickness of the fuel electrode is preferably 10 to 50 μm, particularly preferably 20 to 40 μm. If this thickness is 10 to 50 μm, it functions sufficiently as an electrode and does not need to be thicker than 50 μm.
[0047]
The material used for forming the air electrode is La _1-x Sr _x MnO ₃ The type of the composite oxide is not limited, and can be appropriately selected depending on the conditions of use of the flat SOFC stack. Examples of the material include metals such as Pt, Au, Ag, Pd, Ir, Ru, and Rh. These metals may be only one kind or an alloy of two or more kinds of metals. Further, oxides such as La, Sr, Ce, Co, and Mn (for example, La ₂ O ₃ , SrO, Ce ₂ O ₃ , Co ₂ O ₃ , MnO ₂ And FeO). In addition, various composite oxides containing at least one of La, Sr, Ce, Co, Mn, and the like (for example, La _1-x Sr _x CoO ₃ Composite oxide, La _1-x Sr _x FeO ₃ Composite oxide, La _1-x Sr _x Co _1-y Fe _y O ₃ Based composite oxide, Pr _1-x Ba _x CoO ₃ -Based composite oxide and Sm _1-x Sr _x CoO ₃ System composite oxide).
[0048]
The planar shape of the air electrode is not particularly limited, but is preferably the same shape as the solid electrolyte layer and the fuel electrode. Furthermore, the dimension in the planar direction can be the same as the solid electrolyte layer and the fuel electrode depending on the structure of the fuel cell, particularly when the separator is not joined to the periphery of one surface of the solid electrolyte layer. It is preferable that the air electrode and the solid electrolyte layer are laminated on the entire surface.
[0049]
The air electrode can also be formed as a substrate that supports the strength of the power generation layer. In the case of an air electrode support type, the thickness of the air electrode is preferably at least 20 times the thickness of the solid electrolyte layer. If it is less than 20 times, the mechanical strength of the power generation layer tends to be insufficient. The thickness of the air electrode is preferably 200 to 3000 μm, particularly preferably 500 to 2000 μm. If it is less than 200 μm, it does not function effectively as a substrate, and if it exceeds 3000 μm, the power generation efficiency per volume tends to decrease. On the other hand, in the case of the fuel electrode support type, the thickness of the air electrode is preferably 10 to 100 μm, particularly preferably 20 to 50 μm. If it is less than 10 μm, it may not function sufficiently as an electrode, and if it exceeds 100 μm, it may peel off from the solid electrolyte layer.
[0050]
The brazing material may contain Cu. The content of each of Ag, Pd and Cu when Cu is contained is not particularly limited, but when the total of Ag, Pd and Cu is 100% by mass, the content of Ag is 45 to 65% by mass. Preferably, the content of Pd is 15 to 35% by mass, particularly 20 to 30% by mass, and the content of Cu is 10 to 30% by mass, particularly 15 to 25% by mass. When Cu is contained, even if it contains a larger amount of Pd than a brazing material that does not contain Cu, it has sufficient fluidity and excellent adhesion is maintained. On the other hand, if the total of Ag and Cu is less than 65% by mass, that is, if the Pd content exceeds 35% by mass, the fluidity tends to decrease and the adhesion tends to be insufficient.
[0051]
By including Ti in the brazing material, particularly high joining strength can be obtained even when the joining temperature is relatively low. The content of Ti is determined when the total of Ag, Pd, and Ti is set to 100% by mass, or when Cu is included, when the total of Ag, Pd, Cu, and Ti is set to 100% by mass. , 0.05 to 10% by mass, more preferably 0.05 to 8% by mass, and even more preferably 0.05 to 6% by mass. If the Ti content is 0.05 to 10% by mass, a brazing portion having practically sufficient strength is formed even when the brazing atmosphere is not a vacuum but an inert atmosphere such as argon. be able to. When the brazing atmosphere is vacuum, the content of Ti can be 0.05 to 20% by mass, particularly 0.05 to 15% by mass. When the content is 08 to 10% by mass, the joining strength is greatly improved.
[0052]
The brazing material may further contain other components as long as the joining strength and the adhesion are not reduced. Other components include Sn, In, Ni, Nb and the like. These other components are the sum of Ag and Pd, the sum of Ag, Pd and Cu when further containing Cu, the sum of Ag, Pd and Ti when further containing Ti, or the sum of Ag, Pd and Cu. When the total of Ti and Ti is 100 parts by mass, the content can be 10 parts by mass or less, particularly 0.1 to 10 parts by mass, and further 0.5 to 5 parts by mass.
[0053]
Further, in the above embodiment, the inter-cell separator and the current collector are joined by brazing on the air electrode side. However, the present invention is not limited to this. For example, a conductive paste containing a conductive material may be used between the cells. By applying to at least one of the separator and the current collector, and performing heat treatment in a state where both are in contact via the coated surface, to join the separator between the air electrode side and the current collector Is also good.
[0054]
In the second embodiment, the current collector is formed by laminating the dense part and the porous part. However, the present invention is not limited to this. For example, as shown in FIG. A current collector may be formed by laminating a plurality of different porous portions. In this case, the dense portion constituting the current collector and the inter-cell separator are brazed. As shown in FIG. 9, a current collector may be formed by alternately arranging dense portions and porous portions in the same plane. In this case, one surface of the dense portion and the porous portion constituting the current collector are brazed to the inter-cell separator, and the other surface of the dense portion and the porous portion come into contact with the air electrode. It will be. Here, even if the bonding material is introduced at the interface between the inter-cell separator and the porous portion of the current collector, the performance of the fuel cell is not adversely affected. Further, a current collector may be formed by laminating dense portions on the upper and lower surfaces of the porous portion. In this case, a gas flow path is formed in the dense portion on the air electrode side. Further, in the first embodiment, the gas flow path of the dense current collector 5 is vertically opened. However, the present invention is not limited to this. For example, as shown in FIG. What is necessary is just to open to the pole side.
[0055]
Further, the current collector interposed between the inter-cell separator and the fuel electrode is not limited to nickel felt, and may have a shape similar to that of the above-described air electrode. The current collector on the fuel electrode side may be brazed at the contact surface with the inter-cell separator in the same manner as the air electrode side, but the inter-cell separator is hardly oxidized on the fuel electrode side, and thus is brazed. It is not necessary.
[Brief description of the drawings]
FIG. 1 is a perspective view illustrating an appearance of a fuel cell according to a first embodiment.
FIG. 2 is a schematic view showing an AA cross section of the fuel cell of FIG.
FIG. 3 is a schematic diagram showing a BB cross section of the fuel cell of FIG. 1;
FIG. 4 is a schematic view illustrating a vertical cross section of the fuel cell according to the second embodiment, which corresponds to a cross section AA in FIG. 1;
FIG. 5 is a schematic view illustrating a vertical cross section of the fuel cell according to the second embodiment, corresponding to a cross section taken along line BB of FIG. 1;
FIG. 6 is an explanatory view schematically showing a current collector (1) used in an experimental example.
7 is a cross-sectional view taken along line VII-VII in FIG.
FIG. 8 is an explanatory view schematically showing a current collector (2) used in an experimental example.
FIG. 9 is an explanatory view schematically showing a current collector (3) used in an experimental example.
FIG. 10 is an explanatory diagram schematically showing a current collector (4) used in an experimental example.
FIG. 11 is an explanatory diagram schematically showing a current collector (5) used in an experimental example.
FIG. 12 is an explanatory view schematically showing a test body used for evaluating the total resistance.
[Explanation of symbols]
100, 200; flat-plate SOFC stack, 11; solid electrolyte layer, 12; fuel electrode, 13; air electrode, 211, 212; inter-cell separator, 22; lid member, 23; Through-hole, 24; isolation separator for intermediate unit cell, 25; isolation separator for lower unit cell, 26; bottom member, 251, 252; through-hole, 31; fuel gas flow path, 32; Current collector made of nickel felt, 5; dense current collector, 5a; gas flow path, 50; current collector, 50a; dense portion, 50b; porous portion, 6; brazing portion, 7; frame, 81, 82, 83, 84, 85, 86; metal frame, 91; fuel gas introduction pipe, 92; fuel gas exhaust pipe, 93; flammable gas introduction pipe, 94; Gas exhaust pipe, 10; bonding layer.

Claims (6)

In a solid oxide fuel cell having a structure in which a plurality of single cells are stacked via a metal inter-cell separator, each single cell is a solid electrolyte layer, a fuel electrode provided on one surface of the solid electrolyte layer, And a power generation layer having an air electrode provided on the other surface, and a current collector interposed between the inter-cell separator and the air electrode, at least a part of the current collector has a dense portion. And a solid oxide fuel cell wherein at least a part of the dense portion and the inter-cell separator are in contact with each other via a bonding material. 2. The solid oxide fuel cell according to claim 1, wherein the entirety of the current collector is the dense portion. 2. The solid oxide fuel cell according to claim 1, wherein a part of the current collector is the dense part, and another part of the current collector is a porous part capable of passing a combustible gas. 3. The solid oxide fuel cell according to any one of claims 1 to 3, wherein the joining material is a brazing material, and a surface where the dense portion and the inter-cell separator are in contact is brazed. 5. The solid oxide fuel cell according to claim 4, wherein said brazing material contains Ag as a main component. The solid oxide fuel cell according to any one of claims 1 to 5, wherein the current collector is configured to allow the supporting gas to pass toward the air electrode.

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