JP2005019058A

JP2005019058A - Manufacturing method for solid electrolyte fuel cell and current collector

Info

Publication number: JP2005019058A
Application number: JP2003179202A
Authority: JP
Inventors: Yasushi Nakajima; 靖志中島
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 2003-06-24
Filing date: 2003-06-24
Publication date: 2005-01-20
Anticipated expiration: 2023-06-24
Also published as: JP4314514B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid electrolyte fuel cell wherein excellent electric connection and air permeability can be obtained under a high-temperature oxidation environment. <P>SOLUTION: This solid electrolytic fuel cell is provided with a power generation element 2 wherein an electrolyte 4 is sandwiched by an electrode 3 and a current collector 10 laminated on the electrode 3 of the power generation element 2. The current collector 10 is composed of an elastic linear conductor 11 in which at least a part of it is felt-like or brush-like. The linear conductor 11 of the current collector 10 is brought into contact with a metal plate 12 and surfaces of the linear conductor 11 and the metal plate 12 are covered with high purity iron films 13. At least a part of the high purity iron film 13 is covered with a film 14 composed of an iron oxide. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、２つの電極、すなわち、燃料極（アノード）と空気極（カソード）とで固体酸化物電解質を挟持する構成を発電要素として有していると共に、この電池要素の電極に積層される集電体を備え、燃料極側に水素やメタンなどの炭化水素系燃料ガスを流すと共に、空気極側に酸素や空気などの酸化性ガスを流して発電する固体電解質型燃料電池に関するものである。
【０００２】
【従来の技術】
従来、上記した固体電解質型燃料電池としては、厚いセラミックス材料を積層した構造を成すものが数多く発表されているが、可搬型システムへの電力供給を行ったり燃料電池自体の小型化を図ったりするうえで、重量又は体積当たりの出力密度の向上が求められており、その対応策の一つである燃料電池セルを薄くするフレキシブルディスク型スタックが考案されている（例えば、特許文献１参照。）。
【０００３】
このフレキシブルディスク型のように柔軟性を持たせたセルやセパレータを用いる場合、電力を取り出すための集電体（電気的接続体）は、電解質を電極で挟み込んでなる発電要素に対して、発生応力を吸収しつつそして接触抵抗及び接続抵抗を小さく抑えつつソフトコンタクトするが、この際、薄型化に伴ってガス流路の高さも低くなることから、十分な通気性を確保する必要がある（例えば、特許文献２〜６参照。）。
【０００４】
【特許文献１】
米国特許第６３４４２９０Ｂ１
【特許文献２】
特開平７−１４２０７４号公報
【特許文献３】
特開平９−３０６５１８号公報
【特許文献４】
特開平１０−３３４９２９号公報
【特許文献５】
特開平６−３６７８３号公報
【特許文献６】
特開平７−４５２９７号公報
【０００５】
【発明が解決しようとする課題】
しかしながら、上記の固体電解質型燃料電池では、集電体として耐熱金属メッシュやフェルトを用いるものの場合において、特にニッケルを含むものにおいて、燃料極側では酸化還元共存環境に弱いこと、７００℃を超えるあたりから弾性が低下すること、クロムを含むものに関しては電解質に対してクロムが被毒材料となってしまうことといった問題があるほか、これらの鉄を含む合金では、表面酸化物が結晶粒界組織に進入してもろくなるなどといった問題があり、一方、電解質材料や電解質を付着させたフェルトを用いるものの場合において、接触抵抗が高いこと及び製作し難いことといった問題があり、これらの問題を解決することが従来の課題となっていた。
【０００６】
【発明の目的】
本発明は、上記した従来の課題に着目してなされたもので、高温酸化環境下において良好な電気的接続性及び通気性が得られる固体電解質型燃料電池を提供することを目的としている。
【０００７】
【課題を解決するための手段】
本発明は、電解質を電極で挟み込んでなる発電要素と、この発電要素の電極に積層される集電体を備えた固体電解質型燃料電池において、上記集電体は弾性を有する線状導電体から成り、この線状導電体の少なくとも表面を高純度鉄膜で被覆すると共に、この高純度鉄膜上の少なくとも一部分を鉄酸化物から成る膜で被覆して成る構成としたことを特徴としており、この固体電解質型燃料電池の構成を前述した従来の課題を解決するための手段としている。
【０００８】
また、本発明は、電解質を電極で挟み込んでなる発電要素と、この発電要素の電極に積層される集電体を備えた固体電解質型燃料電池において、上記集電体は少なくとも一部分がフェルト状又はブラシ状を成す弾性を有する線状導電体から成り、この集電体の線状導電体を金属板上に密着させて線状導電体及び金属板の双方の表面を高純度鉄膜で被覆すると共に、この高純度鉄膜上の少なくとも一部分を鉄酸化物から成る膜で被覆して、上記集電体にインターコネクタの機能を保持させた構成としたことを特徴としており、この固体電解質型燃料電池の構成を前述した従来の課題を解決するための手段としている。
【０００９】
さらに、本発明は、電解質を電極で挟み込んでなる発電要素と、この発電要素の電極に積層される集電体を備えた固体電解質型燃料電池において、上記集電体は少なくとも一部分がフェルト状又はブラシ状を成す弾性を有する線状導電体から成り、この集電体の線状導電体を金属板上に密着させて線状導電体及び金属板の双方の表面を高純度鉄膜で被覆すると共に、この高純度鉄膜上の少なくとも一部分を鉄酸化物から成る膜で被覆して、上記集電体にガスセパレータの機能を保持させた構成としたことを特徴としており、この固体電解質型燃料電池の構成を前述した従来の課題を解決するための手段としている。
【００１０】
【発明の効果】
本発明の固体電解質型燃料電池によれば、集電体の線状導電体の少なくとも表面を被覆する高純度鉄膜が柔軟性に富んでおり、そして、この高純度鉄膜表面の少なくとも一部分を緻密な鉄酸化物から成る膜で被覆するようにしているので、高純度鉄膜及び鉄酸化膜はいずれも保護膜となって線状導電体を保護しつつ良好な酸化物導電性を示すこととなり、したがって、空気極集電体として好適な集電特性を保持することができ、加えて、高純度鉄膜及び鉄酸化膜の主たる導電材料が鉄の単一材料から成っているので、使用温度による変質が少なく安定している、すなわち、高温酸化環境下において上記線状導電体のバネ性を保持し且つ良好な電気的接続性及び通気性を確保することが可能であるという非常に優れた効果がもたらされる。
【００１１】
また、本発明の固体電解質型燃料電池によれば、集電体の少なくとも一部分がフェルト状又はブラシ状を成す線状導電体を金属板上に密着させて線状導電体及び金属板の双方の表面を高純度鉄膜で被覆していると共に、この高純度鉄膜上の少なくとも一部分を鉄酸化物から成る鉄酸化膜で被覆するようにしているので、空気極集電体として好適な集電特性を保持しつつインターコネクタ（あるいはガスセパレータ）としての電気的接続を改善することができ、金属板がステンレスであったとしても、表面には被毒剤となるクロムを含んでいないので、クロムの放散を防止することが可能であるという非常に優れた効果がもたらされる。
【００１２】
【発明の実施の形態】
本発明の固体電解質型燃料電池において、集電体の高純度鉄の鉄酸化膜は、緻密且つ安定な保護膜となって高純度鉄膜の内部を保護しつつ良好な酸化物導電性を示すこととなり、加えて、高純度鉄はその内部での酸化の進行が極端に遅いために、初期酸化のＦｅ_３Ｏ_４状態を維持し、且つ本組成は低抵抗の酸化物である。また、高温環境ではＦｅＯの組成が出現し、これも低抵抗であることから、集電体の鉄酸化膜の成分として、ＦｅＯ及びＦｅ_３Ｏ_４の少なくともいずれかを含んでいるものを採用することが望ましい。
【００１３】
また、本発明の固体電解質型燃料電池において、集電体の線状導電体を炭素繊維又はＳｉＣを成分として含む繊維とすると、この線状導電体は、１０００℃程度の高温において弾性を維持して高い強度を示すものの比較的抵抗が大きくなるが、この線状導電体に対して、その表面に高純度鉄膜を被覆すれば、柔軟性が高い高純度鉄膜は、高温において弾性を維持する上記繊維材料に追従して変形しながら接触状態を維持し、この際、上述のように、酸化を極表面に留めて内部の抵抗値の増加を防ぐことから、接続抵抗が安定に保たれることとなる。つまり、従来不可能であった高温で弾性を維持する低抵抗の集電体を実現し得ることから、集電体の線状導電体には、炭素繊維又はＳｉＣを成分として含む繊維を使用することが望ましい。
【００１４】
線状導電体に用いる繊維材料としては、耐熱性の有る導電性のものであれば使用可能であり、炭素繊維やＳｉＣを成分として含む繊維の他に、『チラノ』（宇部興産の登録商標）繊維と呼ばれるＳｉＣ＋Ｔｉ系の合金からなる材料等を用いることができる。なお、この『チラノ』繊維は酸化に対する耐性はあるものの、電気抵抗は大きい。
【００１５】
さらに、本発明の固体電解質型燃料電池において、線状導電体を織り込んで成る生地繊維部分と、この生地繊維部分から略直交する方向に突出する突起繊維部分を有している集電体とすることで、セルにおけるガス流路の設計に対応した集電体の配置を集電体製造の段階で構築することができ、その結果、組立工程管理が容易なものとなる。
【００１６】
さらにまた、本発明の固体電解質型燃料電池において、集電体の線状導電体と高純度鉄膜との間に、金，銀，銅のうちの少なくとも１種類の金属から成る層を介在させると、これらの金属層を高純度鉄膜が保護して内部構造を維持しつつ、これらの金属層を介在させることによる電気抵抗の低減効果を得ることができ、加えて、金属板にステンレスを用いる場合には、上記金属はステンレスの成分であるクロムとも合金を形成し難く、金属層へのクロムの拡散が阻止されて、クロムによる電解質の被毒も防止できることとなる。
【００１７】
一方、上記固体電解質型燃料電池の集電体を製造するに際して、電気メッキにより上記線状導電体及び金属板の双方の表面を高純度鉄膜で被覆する第１のメッキ工程、及び、上記線状導電体及び金属板に対して上記第１のメッキ工程で用いた電源供給部位とは異なる場所に電源を供給して上記線状導電体及び金属板にさらに高純度鉄膜を被覆する第２のメッキ工程とを設けると、原理的に緻密且つピンホールの無い鉄膜を形成し得ると共に、膜がない場所が生じるのを回避し得ることとなる。
【００１８】
ここで、高純度鉄膜の形成は、一例としてフソー株式会社（兵庫県尼崎市）の電気メッキ法によれば、非常に高価な高純度の鉄を原料として用いなくても、純度９９．９８％以上の高純度鉄膜の形成が可能であり、比較的安価に形成することができる。
【００１９】
また、酸素及び不活性ガスから成るガス中にて２００℃以上９０６℃未満の酸化処理を施す工程を設けると、高純度鉄膜の酸化される部分の極表面にのみ安定してＦｅＯ及びＦｅ_３Ｏ_４の少なくともいずれかを含む酸化膜を形成することができ、さらに、金属板上において線状導電体の一部と金属板とを電気的に接続するべく密着させる工程を設けると、金属板に繊維を予め固定せずに圧縮して機械的及び電気的に接続を行うことができ、繊維を溶接したり埋め込んだり挟んだりし難い薄い金属板であっても、一体の被覆加工が可能となる。
【００２０】
この際、酸化は２００℃程度でも行われるが、高温側ではガンマ鉄相が出ることから、９０６℃未満が好ましい。文献（一例として、最新酸化物便覧、（有）日・ソ通信社発行、ｐ．４０９、図５５）からも解るように、温度条件との組み合わせで、鉄表面はＦｅ_３Ｏ_４とＦｅＯとＦｅ_２Ｏ_３とＦｅの間で組成が変化して、実用上では本発明を供する固体電解質型燃料電池のように高温で作動させる場合はＦｅＯ組成が出現する状態となるが、これは低抵抗を示す組成であり、好都合である。
【００２１】
鉄は、純度が高くなると、従来知られている特性とは大きく異なり、表面に緻密で且つ安定した非常に薄い酸化膜が形成され、また、この酸化膜は内部に侵入しないことが、新聞や雑誌や書籍や論文等で広く紹介されている。さらに、高純度の鉄は非常に柔らかい性質を持ち、低温でも延性に富むことなども知られている。
【００２２】
【実施例】
以下、本発明を図面に基づいて説明する。
【００２３】
［実施例１］
図１〜図４は本発明の固体電解質型燃料電池の一実施例を示している。
【００２４】
図１に部分的に示すように、この固体電解質型燃料電池１は、電解質支持型のものであって、電解質４を電極３，３で挟み込んでなる発電要素２と、この発電要素２の電極３に積層される集電体１０を備えており、この集電体１０は、少なくとも一部分がフェルト状（又はブラシ状）を成す弾性を有する線状導電体１１から成り、この集電体１０の線状導電体１１を金属板１２上に密着させて線状導電体１１及び金属板１２の双方の表面を高純度鉄膜１３で被覆すると共に、この高純度鉄膜１３上の表面を鉄酸化物から成る膜１４で被覆してある。
【００２５】
この場合の金属板１２に集電体１０が一体接合された外観断面構造を図２に示すが、集電体１０の線状導電体１１として、太さφ５０μｍの炭素繊維を荒いフェルト状に織ったものを準備し、一方、集電体１０が一体化して接合される金属板１２として、厚さ１００μｍのＳＵＳ４３０耐熱ステンレス薄板を準備した。
【００２６】
上記した固体電解質型燃料電池１の集電体１０を製造するに際しては、まず、図３（Ａ）に示すように、格子状に組んだＡＢＳ樹脂性の第１の絶縁体２１の上に金属板１２を載せるのに続いて、この金属板１２上に線状導電体１１を載せる。
【００２７】
次いで、図３（Ｂ）に示すように、上記第１の絶縁体２１とほぼ同一の構造を有する第２の絶縁体２２を用意し、これらの絶縁体２１，２２間に上記線状導電体１１を載せた金属板１２を挟み込んで圧力を印加して、線状導電体１１を潰しながら金属板１２に密着させて電気的に接続させる。
【００２８】
この際、柔軟性をもたせるための繊維状に編んだ線状導電体１１を金属板１２に溶接したり埋め込んだりする必要が無いため、薄い金属板１２を用いることが可能となる。このような薄い金属板１２を用いると、積層型燃料電池スタックにおいて、出力密度向上に大きく寄与することとなる。
【００２９】
次に、図３（Ｃ）に示すように、線状導電体１１及び金属板１２を上記絶縁体２１，２２で挟んだまま高純度鉄メッキ液２３に浸漬して第１の電気メッキを行う。このとき、電気めっき用の第１の電源線２４を線状導電体１１の方に接続すれば、抵抗が小さい金属板１２の方が優先的にメッキされてしまうといったばらつきを抑制することができる。
【００３０】
このように、第１のメッキによって線状導電体１１及び金属板１２の表面に１０μｍ厚程の鉄層が連続して形成されたところで、これをメッキ浴から引き上げ、上記絶縁体２１，２２を取り外すと、図４（Ａ）に示すように、鉄皮膜が形成された線状導電体１１’と同じく鉄皮膜が形成された金属板１２’とがメッキ膜により接合された構造体１０’が得られる。
【００３１】
この後、図４（Ｂ）に示すように、表面に鉄メッキされた上記構造体１０’を再びメッキ液２３に浸漬して、全体にメッキ膜を５μｍ程積み増しする。このとき、第２の電源線２５として、第１の電源線２４と異なる部分にめっき用の電源線を接続すると、絶縁体２１，２２によりマスクされていた部分や、電源線２４の接続によりマスクされていた部分にも鉄メッキを施すことができ、メッキされない領域が生じるのを回避することができる。
【００３２】
このメッキにより得られる構造体１０’’において、第２の絶縁体２２に潰されていた部分がそのままメッキされているので、潰した形状がメッキ時に影響して窪み１９が形成される。
【００３３】
そして、図４（Ｃ）に示すように、上記メッキ工程で得られた構造体１０’’に対して酸素と窒素の混合ガスからなる４００℃の酸化炉２６で酸化処理を施すと、極表面のみに緻密なＦｅ_３Ｏ_４を含む鉄酸化膜１４が形成される。
【００３４】
以上の工程により、図２に示すように、インターコネクタの機能を有する集電体１０を金属板１２の片面に形成したガスセパレータを製造することができる。
【００３５】
ここで、室温で１Ωｍ以下の低抵抗性を示す金属酸化物は、貴金属・ＩＴＯ系及び従来の課題で指摘したＣｒＯ_２を除くと、Ｖ_２Ｏ_３，Ｖ_２Ｏ_５，ＦｅＯ，Ｆｅ_３Ｏ_４，ＣｕＯ，Ｎｂ_２Ｏ_５等しか明らかでないが、このうちのＶは現状においてメッキ法により形成することができないことから全面被覆が困難であり、Ｎｂは高価な希少金属であり、Ｃｕは酸素拡散が表面にとどまらない性質を持つなど、それぞれがいずれも大きな欠点を有する。
【００３６】
したがって、高温の酸化雰囲気においても良好な導電性を確保することが安価に実現できる手段として、高温で弾性を有する炭素繊維等の表面に満遍なく高純度鉄膜１３を形成すると共にその表面を鉄酸化膜１４で覆うことで、内部を保護するようにした本発明が非常に有用であることが判る。
【００３７】
［実施例２］
図５は本発明の固体電解質型燃料電池の他の実施例を示している。
【００３８】
図５に示すように、この固体電解質型燃料電池の集電体５０が先の実施例の固体電解質型燃料電池１の集電体１０と相違するところは、金属板１２の両面に線状導電体１１を密着させて、線状導電体１１及び金属板１２の双方の表面を高純度鉄膜１３で被覆すると共に、この高純度鉄膜１３上の表面を鉄酸化物から成る鉄酸化膜１４で被覆した点にある。
【００３９】
この集電体５０は、上記した先の実施例の製造方法を金属板１２の両面に対して施すことで製造できる。固体電解質型燃料電池において、この集電体５０をガスセパレータとして用いると、セルをフレキシブルディスク型スタックのように積み重ねていく場合には、隣接するセルの電極との電気的接続及びその反対側で隣接するセルの電極との接続を同時に且つ良好に実施することができる。
【００４０】
［実施例３］
図６及び図７は本発明の固体電解質型燃料電池のさらに他の実施例を示している。
【００４１】
図６に示すように、この固体電解質型燃料電池の集電体６０は、線状導電体としてのポリアクリロニトリル等の炭素繊維原料糸をいわゆる段通やビロードやタオル等の様に平織又は綾織に織り込んで成る生地繊維部分６１と、この生地繊維部分６１から略直交する方向に突出する突起繊維部分６２を有しており、これを高温で蒸し焼きにすることで形成した導電性を有する炭素繊維織物の表面に、図７に示すように、上記した先の実施例による電気メッキを施して、高純度鉄膜６３を形成したものであって、この高純度鉄膜６３の表面には、緻密で且つ安定した非常に薄い鉄酸化膜６４が形成されている。
【００４２】
この場合、生地繊維部分６１の織目がメッキ膜によりふさがれる厚さまでメッキを行うと気密性が確保され、一方、メッキ厚をそれ程厚くしない場合には逆に通気性が得られることとなり、生地繊維部分６１の織密度により必要なメッキ厚は変化する。
【００４３】
本実施例では、生地繊維部分６１上の突起繊維部分６２の配置によりガスの通気抵抗が変化するので、集電体６０の接触部位等の配置を予め設計に従って盛り込んでおくことができ、性能の向上及び組立時の工程管理の簡略化を実現することができる。また、メッキ厚を厚くした場合には、集電体６０自体がセパレータとして機能し得る上記実施例の金属板１２を形成してしまうことから、部品の製造工程の簡略化をも実現可能である。
【００４４】
［実施例４］
図８は本発明の固体電解質型燃料電池のさらに他の実施例における集電体部分を示している。
【００４５】
図８に示すように、この固体電解質型燃料電池の集電体８０は、線状導電体１１と高純度鉄膜１３との間に、銅層８５を介在させた構成を成しており、他の構成は、先の実施例１における固体電解質型燃料電池の集電体１０と同じである。
【００４６】
上記銅層８５は鉄との合金を形成し難いことから、高純度鉄膜１３の純度が維持され、したがって、集電体８０としての層構造及び上述した高温酸化雰囲気における良好な導電性を保持したまま電気抵抗の低減が可能である。
【００４７】
この実施例では、最も安価な銅層８５を線状導電体１１と高純度鉄膜１３との間に介在させた構成としたが、金や銀も電解メッキが可能であることから、条件次第では炭素繊維等の表面への形成が可能である。また、金属板１２にステンレスを用いる場合には、上記金属はステンレスの成分であるクロムとも合金を形成し難いことから、表層へのクロムの拡散が阻止されて、クロムによる電解質の被毒も防止できることとなる。
【図面の簡単な説明】
【図１】本発明の固体電解質型燃料電池の一実施例を示す集電体部分の拡大断面説明図である。
【図２】図１に示した集電体の側面説明図である。
【図３】図１に示した集電体の製造方法の前半を説明する工程図（Ａ）〜（Ｃ）。
【図４】図１に示した集電体の製造方法の後半を説明する工程図（Ａ）〜（Ｃ）。
【図５】本発明の固体電解質型燃料電池の他の実施例を示す集電体の側面説明図である。
【図６】本発明の固体電解質型燃料電池のさらに他の実施例を示す集電体の基材となる織物の断面説明図である。
【図７】図６に示した基材となる織物に高純度鉄膜を形成し成る集電体の断面説明図である。
【図８】本発明の固体電解質型燃料電池のさらに他の実施例を示す集電体部分の拡大断面説明図である。
【符号の説明】
１固体電解質型燃料電池
２発電要素
３電極
４電解質
１０，５０，６０，８０集電体
１１線状導電体
１２金属板
１３，６３高純度鉄膜
１４，６４鉄酸化膜
６１生地繊維部分
６２突起繊維部分
８５銅層[0001]
BACKGROUND OF THE INVENTION
The present invention has a configuration in which a solid oxide electrolyte is sandwiched between two electrodes, that is, a fuel electrode (anode) and an air electrode (cathode), and is laminated on the electrode of this battery element. The present invention relates to a solid oxide fuel cell that has a current collector and generates electricity by flowing a hydrocarbon fuel gas such as hydrogen or methane to the fuel electrode side and flowing an oxidizing gas such as oxygen or air to the air electrode side. .
[0002]
[Prior art]
Conventionally, many solid electrolyte fuel cells described above have a structure in which thick ceramic materials are laminated, but power is supplied to a portable system or the fuel cell itself is downsized. In addition, an improvement in power density per weight or volume has been demanded, and a flexible disk type stack for thinning the fuel cell, which is one of the countermeasures, has been devised (for example, see Patent Document 1). .
[0003]
When a flexible cell or separator such as this flexible disk type is used, a current collector (electrical connection body) for taking out electric power is generated against a power generation element in which an electrolyte is sandwiched between electrodes. Soft contact while absorbing stress and suppressing contact resistance and connection resistance is small. At this time, the height of the gas flow path is reduced as the thickness is reduced, so it is necessary to ensure sufficient air permeability ( For example, see Patent Documents 2 to 6.)
[0004]
[Patent Document 1]
US Pat. No. 6,344,290 B1
[Patent Document 2]
Japanese Patent Laid-Open No. 7-142074 [Patent Document 3]
Japanese Patent Laid-Open No. 9-306518 [Patent Document 4]
JP-A-10-334929 [Patent Document 5]
JP-A-6-36783 [Patent Document 6]
Japanese Patent Application Laid-Open No. 7-45297
[Problems to be solved by the invention]
However, in the above solid oxide fuel cell, in the case of using a refractory metal mesh or felt as a current collector, particularly in the case of containing nickel, the fuel electrode side is weak in the redox coexistence environment, and the temperature exceeds 700 ° C. In addition to the problems that the elasticity decreases from the above, and those containing chromium, chromium becomes a poisoning material for the electrolyte, and in these alloys containing iron, the surface oxides become grain boundary structures. On the other hand, there are problems such as brittleness when entering, and on the other hand, there are problems such as high contact resistance and difficulty in manufacturing in the case of using an electrolyte material or felt with attached electrolyte. Has become a conventional problem.
[0006]
OBJECT OF THE INVENTION
The present invention has been made paying attention to the above-described conventional problems, and an object of the present invention is to provide a solid oxide fuel cell capable of obtaining good electrical connectivity and air permeability in a high temperature oxidation environment.
[0007]
[Means for Solving the Problems]
The present invention relates to a solid oxide fuel cell including a power generation element in which an electrolyte is sandwiched between electrodes and a current collector laminated on the electrode of the power generation element. The current collector is made of a linear conductor having elasticity. Comprising at least the surface of the linear conductor with a high-purity iron film, and at least a part of the high-purity iron film with a film made of iron oxide. The configuration of the solid oxide fuel cell is used as a means for solving the above-described conventional problems.
[0008]
Further, the present invention provides a solid oxide fuel cell comprising a power generation element in which an electrolyte is sandwiched between electrodes and a current collector laminated on the electrode of the power generation element, wherein the current collector is at least partially felt-shaped or It consists of a linear conductor with elasticity in the shape of a brush, and the surface of both the linear conductor and the metal plate is covered with a high-purity iron film by adhering the linear conductor of the current collector onto the metal plate. And at least a portion of the high-purity iron film is covered with a film made of iron oxide, and the current collector is configured to retain the function of an interconnector. The configuration of the battery is used as a means for solving the above-described conventional problems.
[0009]
Furthermore, the present invention provides a solid oxide fuel cell comprising a power generation element in which an electrolyte is sandwiched between electrodes and a current collector laminated on the electrode of the power generation element, wherein the current collector is at least partially felt-shaped or It consists of a linear conductor with elasticity in the shape of a brush, and the surface of both the linear conductor and the metal plate is covered with a high-purity iron film by adhering the linear conductor of the current collector onto the metal plate. The solid electrolyte fuel is characterized in that at least a part of the high purity iron film is covered with a film made of iron oxide so that the current collector functions as a gas separator. The configuration of the battery is used as a means for solving the above-described conventional problems.
[0010]
【The invention's effect】
According to the solid oxide fuel cell of the present invention, the high purity iron film covering at least the surface of the linear conductor of the current collector is rich in flexibility, and at least a part of the surface of the high purity iron film is formed. Since it is covered with a film made of dense iron oxide, both the high-purity iron film and the iron oxide film serve as protective films and show good oxide conductivity while protecting the linear conductor. Therefore, current collecting characteristics suitable as an air electrode current collector can be maintained, and in addition, the main conductive material of the high-purity iron film and iron oxide film is made of a single material of iron, so that it can be used. It is very stable that there is little deterioration due to temperature, that is, it is possible to maintain the spring property of the linear conductor and ensure good electrical connectivity and air permeability in a high temperature oxidation environment. Effect.
[0011]
Further, according to the solid oxide fuel cell of the present invention, the linear conductor in which at least a part of the current collector forms a felt shape or a brush shape is brought into close contact with the metal plate, so that both the linear conductor and the metal plate are provided. Since the surface is coated with a high-purity iron film and at least a part of the high-purity iron film is coated with an iron oxide film made of iron oxide, the current collector is suitable as an air electrode current collector. The electrical connection as an interconnector (or gas separator) can be improved while maintaining the characteristics, and even if the metal plate is stainless steel, the surface does not contain chromium as a poisoning agent. It is possible to provide a very excellent effect that it is possible to prevent the emission of the above.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
In the solid oxide fuel cell of the present invention, the high-purity iron iron oxide film of the current collector becomes a dense and stable protective film and exhibits good oxide conductivity while protecting the inside of the high-purity iron film. In addition, high-purity iron maintains an initially oxidized Fe ₃ O ₄ state because the progress of oxidation inside thereof is extremely slow, and this composition is a low-resistance oxide. In addition, since a composition of FeO appears in a high temperature environment and this also has a low resistance, a component containing at least one of FeO and Fe ₃ O ₄ is adopted as a component of the iron oxide film of the current collector. It is desirable.
[0013]
In the solid oxide fuel cell of the present invention, if the linear conductor of the current collector is a fiber containing carbon fiber or SiC as a component, the linear conductor maintains elasticity at a high temperature of about 1000 ° C. Although it exhibits high strength, its resistance is relatively large. However, if the surface of this linear conductor is covered with a high-purity iron film, the high-purity iron film with high flexibility maintains elasticity at high temperatures. In this case, the contact state is maintained while deforming following the fiber material. At this time, as described above, the oxidation is kept at the extreme surface to prevent an increase in the internal resistance value, so that the connection resistance is kept stable. Will be. That is, since a low-resistance current collector that maintains elasticity at a high temperature, which has been impossible in the past, can be realized, a carbon fiber or a fiber containing SiC as a component is used for the linear conductor of the current collector. It is desirable.
[0014]
As the fiber material used for the linear conductor, any heat-resistant conductive material can be used. In addition to carbon fiber and fiber containing SiC as a component, “Tyranno” (registered trademark of Ube Industries) A material made of an SiC + Ti alloy called fiber can be used. Although this “Tyranno” fiber is resistant to oxidation, it has a high electrical resistance.
[0015]
Furthermore, in the solid oxide fuel cell of the present invention, a current collector having a fabric fiber portion woven with a linear conductor and a protruding fiber portion protruding in a direction substantially perpendicular to the fabric fiber portion is provided. Thus, the current collector arrangement corresponding to the design of the gas flow path in the cell can be constructed at the stage of current collector production, and as a result, the assembly process can be easily managed.
[0016]
Furthermore, in the solid oxide fuel cell of the present invention, a layer made of at least one of gold, silver and copper is interposed between the linear conductor of the current collector and the high-purity iron film. In addition, these metal layers are protected by a high-purity iron film to maintain the internal structure, and the effect of reducing the electrical resistance by interposing these metal layers can be obtained. When used, the metal is difficult to form an alloy with chromium, which is a component of stainless steel, and diffusion of chromium into the metal layer is prevented, and poisoning of the electrolyte by chromium can be prevented.
[0017]
On the other hand, when manufacturing the current collector of the solid oxide fuel cell, a first plating step of coating the surfaces of both the linear conductor and the metal plate with a high-purity iron film by electroplating, and the wire A second power source is supplied to a place different from the power supply site used in the first plating step with respect to the linear conductor and the metal plate to further coat the linear conductor and the metal plate with a high-purity iron film. In this way, it is possible to form an iron film that is dense and free of pinholes in principle, and to avoid the occurrence of a place where there is no film.
[0018]
Here, for example, according to the electroplating method of Fuso Co., Ltd. (Amagasaki City, Hyogo), the high-purity iron film is formed with a purity of 99.98 without using very expensive high-purity iron as a raw material. % Or more of a high-purity iron film can be formed and can be formed at a relatively low cost.
[0019]
In addition, when a process of performing oxidation treatment at 200 ° C. or more and less than 906 ° C. in a gas composed of oxygen and an inert gas is provided, only FeO and Fe ₃ are stably provided only on the extreme surface of the oxidized portion of the high purity iron film. An oxide film containing at least one of O ₄ can be formed, and further provided with a step of closely contacting a part of the linear conductor and the metal plate on the metal plate to electrically connect the metal plate The fiber can be compressed and mechanically and electrically connected without fixing it in advance, and even if it is a thin metal plate that is difficult to weld, embed or pinch the fiber, it can be integrally coated Become.
[0020]
At this time, the oxidation is performed even at about 200 ° C., but since the gamma iron phase is produced on the high temperature side, the temperature is preferably less than 906 ° C. As can be seen from the literature (as an example, the latest oxide handbook, published by Japan-Soviet News Agency, p.409, FIG. 55), in combination with temperature conditions, the iron surface is composed of Fe ₃ O ₄ and FeO. The composition changes between Fe ₂ O ₃ and Fe, and in practice, when operating at a high temperature as in the solid oxide fuel cell provided with the present invention, the FeO composition appears, but this is a low resistance. This is a convenient composition.
[0021]
When the purity of iron increases, it is greatly different from the conventionally known characteristics. A dense and stable very thin oxide film is formed on the surface, and this oxide film does not penetrate into the inside. Widely introduced in magazines, books and papers. Furthermore, high-purity iron is known to have very soft properties and to be highly ductile even at low temperatures.
[0022]
【Example】
Hereinafter, the present invention will be described with reference to the drawings.
[0023]
[Example 1]
1 to 4 show an embodiment of the solid oxide fuel cell of the present invention.
[0024]
As shown partially in FIG. 1, the solid oxide fuel cell 1 is of an electrolyte support type, and includes a power generation element 2 in which an electrolyte 4 is sandwiched between electrodes 3 and 3, and an electrode of the power generation element 2. The current collector 10 is composed of a linear conductor 11 having elasticity that is at least partially felt-shaped (or brush-shaped). The linear conductor 11 is brought into close contact with the metal plate 12 so that the surfaces of both the linear conductor 11 and the metal plate 12 are covered with the high purity iron film 13 and the surface on the high purity iron film 13 is iron-oxidized. It is covered with a film 14 made of a material.
[0025]
FIG. 2 shows an external cross-sectional structure in which the current collector 10 is integrally joined to the metal plate 12 in this case. As a linear conductor 11 of the current collector 10, carbon fiber having a thickness of 50 μm is woven in a rough felt shape. On the other hand, a SUS430 heat-resistant stainless steel thin plate having a thickness of 100 μm was prepared as the metal plate 12 to which the current collector 10 was integrally joined.
[0026]
When manufacturing the current collector 10 of the solid oxide fuel cell 1 described above, first, as shown in FIG. 3A, a metal is formed on the ABS resinous first insulator 21 assembled in a lattice shape. Following the placement of the plate 12, the linear conductor 11 is placed on the metal plate 12.
[0027]
Next, as shown in FIG. 3B, a second insulator 22 having substantially the same structure as the first insulator 21 is prepared, and the linear conductor is provided between these insulators 21 and 22. The metal plate 12 on which the metal plate 11 is placed is sandwiched between the metal plates 12 and applied with pressure so that the linear conductors 11 are crushed and electrically connected.
[0028]
At this time, since it is not necessary to weld or embed the linear conductor 11 knitted into a fiber shape to give flexibility, the thin metal plate 12 can be used. Use of such a thin metal plate 12 greatly contributes to an improvement in output density in the stacked fuel cell stack.
[0029]
Next, as shown in FIG. 3C, the linear conductor 11 and the metal plate 12 are immersed in the high-purity iron plating solution 23 while being sandwiched between the insulators 21 and 22, and the first electroplating is performed. . At this time, if the first power supply line 24 for electroplating is connected to the linear conductor 11, it is possible to suppress variations such that the metal plate 12 having a lower resistance is preferentially plated. .
[0030]
Thus, when an iron layer having a thickness of about 10 μm is continuously formed on the surfaces of the linear conductor 11 and the metal plate 12 by the first plating, the iron layer is pulled up from the plating bath, and the insulators 21 and 22 are connected. When removed, as shown in FIG. 4 (A), a structure 10 ′ in which a linear conductor 11 ′ with an iron coating and a metal plate 12 ′ with an iron coating formed thereon are joined together by a plating film is formed. can get.
[0031]
Thereafter, as shown in FIG. 4 (B), the structure 10 ′ whose surface is iron-plated is dipped again in the plating solution 23, and a plating film is accumulated by about 5 μm over the entire surface. At this time, if a power supply line for plating is connected to a portion different from the first power supply line 24 as the second power supply line 25, the portion masked by the insulators 21, 22 or the mask by the connection of the power supply line 24. The plated portion can also be iron-plated, and it is possible to avoid the occurrence of an unplated region.
[0032]
In the structure 10 ″ obtained by this plating, since the portion crushed by the second insulator 22 is plated as it is, the crushed shape affects the time of plating, and the recess 19 is formed.
[0033]
Then, as shown in FIG. 4 (C), when the structure 10 ″ obtained in the plating step is subjected to an oxidation treatment in an oxidation furnace 26 made of a mixed gas of oxygen and nitrogen, Only the dense iron oxide film 14 containing Fe ₃ O ₄ is formed.
[0034]
Through the above steps, a gas separator in which the current collector 10 having the function of an interconnector is formed on one surface of the metal plate 12 can be manufactured as shown in FIG.
[0035]
Here, the metal oxides exhibiting low resistance of 1 Ωm or less at room temperature are V ₂ O ₃ , V ₂ O ₅ , FeO, Fe ₃ O, excluding noble metals / ITO and CrO ₂ pointed out in the conventional problems. ₄ , CuO, Nb ₂ O _5, etc. are only clear, but V of these is difficult to form by plating at present, so that it is difficult to cover the entire surface, Nb is an expensive rare metal, and Cu is oxygen Each has major drawbacks, such as diffusion not only on the surface.
[0036]
Therefore, as a means that can ensure low-cost electric conductivity even in a high-temperature oxidizing atmosphere, the high-purity iron film 13 is uniformly formed on the surface of carbon fiber having elasticity at high temperature and the surface is oxidized with iron. It can be seen that the present invention in which the inside is protected by covering with the film 14 is very useful.
[0037]
[Example 2]
FIG. 5 shows another embodiment of the solid oxide fuel cell of the present invention.
[0038]
As shown in FIG. 5, the current collector 50 of the solid oxide fuel cell is different from the current collector 10 of the solid oxide fuel cell 1 of the previous embodiment. The body 11 is brought into close contact, and the surfaces of both the linear conductor 11 and the metal plate 12 are covered with a high-purity iron film 13, and the surface of the high-purity iron film 13 is covered with an iron oxide film 14 made of iron oxide. It is in the point coated with.
[0039]
The current collector 50 can be manufactured by applying the manufacturing method of the previous embodiment to both surfaces of the metal plate 12. In the solid oxide fuel cell, when the current collector 50 is used as a gas separator, when cells are stacked like a flexible disk type stack, electrical connection with an electrode of an adjacent cell and the opposite side thereof are performed. Connection with the electrodes of adjacent cells can be performed simultaneously and satisfactorily.
[0040]
[Example 3]
6 and 7 show still another embodiment of the solid oxide fuel cell of the present invention.
[0041]
As shown in FIG. 6, the current collector 60 of this solid oxide fuel cell has a plain weave or twill weave of carbon fiber raw material such as polyacrylonitrile as a linear conductor, such as a so-called step, velvet or towel. A carbon fiber fabric having conductivity, formed by weaving a fabric fiber portion 61 and a projecting fiber portion 62 projecting from the fabric fiber portion 61 in a direction substantially perpendicular to the fabric fiber portion 61 and steaming it at a high temperature. As shown in FIG. 7, the high-purity iron film 63 is formed on the surface of the high-purity iron film 63 by electroplating according to the above-described embodiment. A stable and very thin iron oxide film 64 is formed.
[0042]
In this case, if the texture of the fabric fiber portion 61 is plated to a thickness that is blocked by the plating film, airtightness is ensured. On the other hand, if the plating thickness is not so thick, air permeability will be obtained. The required plating thickness varies depending on the weave density of the fiber portion 61.
[0043]
In this embodiment, since the gas ventilation resistance changes depending on the arrangement of the protruding fiber portion 62 on the fabric fiber portion 61, the arrangement of the contact portion of the current collector 60 and the like can be incorporated according to the design in advance. Improvement and simplification of process management during assembly can be realized. In addition, when the plating thickness is increased, the current collector 60 itself forms the metal plate 12 of the above-described embodiment that can function as a separator, so that it is possible to simplify the manufacturing process of components. .
[0044]
[Example 4]
FIG. 8 shows a current collector portion in still another embodiment of the solid oxide fuel cell of the present invention.
[0045]
As shown in FIG. 8, the current collector 80 of the solid oxide fuel cell has a configuration in which a copper layer 85 is interposed between the linear conductor 11 and the high-purity iron film 13. Other configurations are the same as those of the current collector 10 of the solid oxide fuel cell in the first embodiment.
[0046]
Since the copper layer 85 is difficult to form an alloy with iron, the purity of the high-purity iron film 13 is maintained, and therefore, the layer structure as the current collector 80 and good conductivity in the high-temperature oxidizing atmosphere described above are maintained. The electrical resistance can be reduced as it is.
[0047]
In this embodiment, the cheapest copper layer 85 is interposed between the linear conductor 11 and the high-purity iron film 13, but gold and silver can also be electroplated. Then, formation on the surface of carbon fiber or the like is possible. In addition, when stainless steel is used for the metal plate 12, the metal is difficult to form an alloy with chromium, which is a component of stainless steel, so that diffusion of chromium to the surface layer is prevented, and electrolyte poisoning by chromium is also prevented. It will be possible.
[Brief description of the drawings]
FIG. 1 is an enlarged cross-sectional explanatory view of a current collector portion showing an embodiment of a solid oxide fuel cell of the present invention.
2 is an explanatory side view of the current collector shown in FIG. 1; FIG.
FIGS. 3A to 3C are process diagrams (A) to (C) for explaining the first half of the method for manufacturing the current collector shown in FIG. 1;
4A to 4C are process diagrams (A) to (C) for explaining the second half of the method for manufacturing the current collector shown in FIG. 1;
FIG. 5 is a side explanatory view of a current collector showing another embodiment of the solid oxide fuel cell of the present invention.
FIG. 6 is a cross-sectional explanatory view of a fabric that is a base material of a current collector showing still another embodiment of the solid oxide fuel cell of the present invention.
7 is a cross-sectional explanatory view of a current collector formed by forming a high-purity iron film on the fabric as a base material shown in FIG.
FIG. 8 is an enlarged cross-sectional explanatory view of a current collector portion showing still another embodiment of the solid oxide fuel cell of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Solid electrolyte type fuel cell 2 Electric power generation element 3 Electrode 4 Electrolyte 10, 50, 60, 80 Current collector 11 Linear conductor 12 Metal plate 13, 63 High-purity iron film 14, 64 Iron oxide film 61 Fabric fiber part 62 Protrusion Fiber part 85 Copper layer

Claims

In a solid oxide fuel cell comprising a power generation element in which an electrolyte is sandwiched between electrodes and a current collector laminated on the electrode of the power generation element, the current collector is made of a linear conductor having elasticity, and this wire A solid oxide fuel cell characterized in that at least a surface of the conductor is coated with a high-purity iron film and at least a part of the high-purity iron film is covered with a film made of iron oxide.

In a solid electrolyte fuel cell comprising a power generation element in which an electrolyte is sandwiched between electrodes and a current collector laminated on the electrode of the power generation element, the current collector has elasticity that is at least partially felt-shaped or brush-shaped. The current collector is in close contact with the metal plate to cover both surfaces of the wire conductor and the metal plate with a high-purity iron film. A solid oxide fuel cell, wherein at least a portion of the membrane is covered with a membrane made of iron oxide, and the current collector retains the function of an interconnector.

In a solid electrolyte fuel cell comprising a power generation element in which an electrolyte is sandwiched between electrodes and a current collector laminated on the electrode of the power generation element, the current collector has elasticity that is at least partially felt-shaped or brush-shaped. The current collector is in close contact with the metal plate to cover both surfaces of the wire conductor and the metal plate with a high-purity iron film. A solid oxide fuel cell characterized in that at least a part of the membrane is covered with a membrane made of iron oxide and the current collector retains the function of a gas separator.

The solid oxide fuel cell according to claim 1, wherein the iron oxide of the current collector film contains at least one of FeO and Fe ₃ O ₄ .

The solid electrolyte fuel cell according to any one of claims 1 to 4, wherein the linear conductor of the current collector is a fiber containing carbon fiber or SiC as a component.

6. The solid oxide fuel cell according to claim 5, wherein the current collector has a fabric fiber portion in which a linear conductor is woven, and a protruding fiber portion protruding in a direction substantially orthogonal to the fabric fiber portion. .

7. The method according to claim 1, wherein a layer made of at least one of gold, silver, and copper is interposed between the linear conductor of the current collector and the high-purity iron film. A solid oxide fuel cell according to 1.

When manufacturing the current collector of the solid oxide fuel cell according to any one of claims 2 to 5, a step of closely contacting a part of the linear conductor and the metal plate on the metal plate; Used in the first plating step for coating the surfaces of both the linear conductor and the metal plate with a high-purity iron film by electroplating, and the first plating step for the linear conductor and the metal plate. A second plating step in which power is supplied to a location different from the power supply site to coat the linear conductor and the metal plate with a high-purity iron film; and 200 ° C. in a gas composed of oxygen and an inert gas. The manufacturing method of the electrical power collector characterized by including the process of performing the oxidation process below 906 degreeC above.