JP3795172B2

JP3795172B2 - Method for forming a fuel electrode in a solid oxide fuel cell

Info

Publication number: JP3795172B2
Application number: JP04444597A
Authority: JP
Inventors: 伸二竹内; 淳一藤田; 波子兼田; 幹幸小野; 正孝望月; 雅克永田; 力岩澤
Original assignee: Fujikura Ltd; Kansai Electric Power Co Inc
Current assignee: Fujikura Ltd; Kansai Electric Power Co Inc
Priority date: 1997-02-27
Filing date: 1997-02-27
Publication date: 2006-07-12
Anticipated expiration: 2017-02-27
Also published as: JPH10241710A

Description

【０００１】
【発明の属する技術分野】
本発明は、固体電解質型燃料電池の燃料極成膜方法に関する。
【０００２】
【従来の技術】
近年、固体電解質型燃料電池の研究、開発が鋭意に行われている。この固体電解質型燃料電池には平板方式と円筒方式とがあり、さらに円筒方式には縦縞方式と横縞方式とがある。そして特に、円筒縦縞方式の固体電解質型燃料電池は図５に示す構造のものがある。この従来の単電池１０６は、内側から順に多孔質ランタンマンガネート系酸化物（ＬａＭｎＯｎ）の空気極支持管１０１、イットリア安定化ジルコニア（ＹＳＺ）製の固体電解質１０２、ニッケル又はニッケル合金とＹＳＺとのサーメット製の燃料極１０３の積層構造にして、外周面の一部にインタコネクタ１０４を燃料極１０３から絶縁し、かつ内部の空気極支持管１０１に接続する形で配置している。
【０００３】
しかしながら、このような従来の縦縞円筒方式の固体電解質型燃料電池では、各要素の材料がすべてセラミックス製で、かつ約８５０〜１０５０℃の高温で作動するため、特に熱膨張率の違う異種材料が重なり合うインタコネクタ１０４の付近や電池底部に応力が集中してクラックが発生しやすい問題点があった。
【０００４】
そこで、この従来の問題点を解決するものとして、特開平７−２６３００１号公報では、図６に示す構造の固体電解質型燃料電池１１０が提案されている。この提案されている従来の固体電解質型燃料電池１１０は、中心部に燃料供給用導電性チューブ１１１を挿入する構造を特徴としている。すなわち、内側から順に燃料極１１２、固体電解質１１３、空気極１１４を形成し、中心部に燃料噴出のために多孔質にした燃料供給用導電性チューブ１１１を挿入し、この導電性チューブ１１１と燃料極１１２との間に燃料改質機能を持つ導電性フェルト１１５を充填し、そして導電性チューブ１１１に燃料ガス１１６を供給し、外周に空気１１７を流通させるようにした構造である。
【０００５】
この固体電解質型燃料電池１１０の発電作用について説明すると、電池１１０の導電性チューブ１１１内に天然ガス、メタン、石炭ガス化ガスなどの燃料ガス１１６を供給し、導電性チューブ１１１の多孔質の管壁を通じて導電性フェルト１１５の部分に噴出させ、この導電性フェルト１１５と燃料極１１２と固体電解質１１３の部分で高温度条件下、通常、６５０℃〜１０５０℃の条件下で、次式の改質反応を起こす。
【０００６】
【化１】

この改質反応で発生する水素に対して、固体電解質１１３を介して対極する燃料極１１２と空気極１１４との部分で次の化２式の発電反応を起こし、遊離した電子を集電することによって発電力を得る。
【０００７】
【化２】

つまり、燃料極１１２においては化２（ａ）式に示すように、改質反応で生成された水素が、固体電解質１１３から供給される酸化物イオンと反応して水蒸気と電子を生成する。そして燃料極１１２で生成された電子が導電性フェルト１１５と導電性チューブ１１１を経て陰極１１８から外部回路に回り、陽極１１８を経て空気極１１４に到達すると、この空気極１１４において、化２（ｂ）式に示すように空気１１７中の酸素と反応して酸化物イオンを生成し、これが固体電解質１１３に放出され、燃料極１１２側に到達して化２（ａ）式の反応に供されるのである。
【０００８】
このような発電機構の燃料電池１１０において、空気極１１４、固体電解質１１３及び燃料極１１２の部分は次にようにして形成している。まず空気極１１４となるランタンマンガネート系の多孔質の基材に対して電気化学蒸着法、つまり、ＣＶＤ（Chemical Vapor Deposition ）−ＥＶＤ（Electrocheical Vapor Deposition ）法を用いて薄く、かつ緻密なＹＳＺ膜を固体電解質１１３として形成し、さらにこのＹＳＺ膜にニッケル、コバルト、ニッケル又はコバルトを主成分とする合金、あるいはニッケルジルコニアサーメットの粉末をスラリーコートし、同じように電気化学蒸着法を施して多孔質の燃料極１１２を成膜し、あるいは特開平４−３４９３４３号公報に掲載されているような溶射法を用いて成膜するのである。
【０００９】
【発明が解決しようとする課題】
ところが、このような従来の固体電解質型燃料電池の各膜の成膜方法において、特に燃料極の成膜方法については、スラリーコートによるか、溶射による方法を用いていたのであるが、スラリーコート法の場合には膜厚を均一にすることが困難であり、また溶射法による場合、管体の内周面に成膜しようすると最低でも６０ｍｍφの内径を要し、それよりも小さい内径の管の内周面には成膜することができない問題点があった。
【００１０】
本発明はこのような従来の問題点に鑑みてなされたもので、管内径が小さくてもその内周面に燃料極膜を成膜することができ、かつ均一な膜厚で燃料極膜を成膜することができる固体電解質型燃料電池の燃料極成膜方法を提供することを目的とする。
【００１１】
【課題を解決するための手段】
請求項１の発明の固体電解質型燃料電池の燃料極成膜方法は、ニッケル、コバルト、ニッケル又はコバルトを主成分とする合金、あるいはそれらのいずれかのサーメットの粉末とＹＳＺ粉末とをバインダに混合した燃料極材料混合液中に基体を浸漬する工程と、前記基体を水平に保持しつつ回転させて、前記基体に付着している前記燃料極材料を乾燥させて燃料極材料膜を前記基体の内周面に形成する工程と、前記燃料極材料膜を焼成して前記基体の内周面に燃料極膜を形成する工程とから成るものである。
【００１２】
この請求項１の発明の固体電解質型燃料電池の燃料極成膜方法では、浸漬工程でニッケル、コバルト、ニッケル又はコバルトを主成分とする合金、あるいはそれらのいずれかのサーメットの粉末とＹＳＺ粉末とをバインダに混合した燃料極材料混合液中に基体を浸漬することにより、基体の内径が小さくても容易にその内周面全体に燃料極材料混合液を付着させることができ、この後にこの基体を水平に保持しつつ回転させて、基体内周面に付着している燃料極材料を乾燥させることにより、均一にして基体の内周面と密着性の良い燃料極材料膜を形成することができ、このために、この後に燃料極材料膜を焼成して基体の内周面に燃料極膜を形成することによって、均一にして基体の内周面と密着性の良い燃料極膜を成膜することができる。
【００１３】
請求項２の発明は、請求項１の固体電解質型燃料電池の燃料極成膜方法において、前記燃料極材料混合液の浸漬工程と、前記燃料極材料の乾燥工程とを前記燃料極材料膜が所定の膜厚になるまで繰り返し、その後に前記焼成工程に移行して所定の膜厚の燃料極膜を形成するものであり、燃料極膜の膜厚制御が正確にできる。
【００１４】
請求項３の発明は、請求項１又は２の固体電解質型燃料電池の燃料極成膜方法において、前記焼成工程に代えて、ＹＳＺのＥＶＤ工程を行うものであり、基体の内周面との密着性が良好で、かつ材質にすぐれた燃料極膜を形成することができる。
【００１５】
請求項４の発明は、請求項１又は２の固体電解質型燃料電池の燃料極成膜方法において、前記焼成工程の後に、ＹＳＺのＥＶＤ工程を行うものであり、基体の内周面との密着性が良好で、かつ材質にすぐれた燃料極膜を形成することができる。
【００１６】
請求項５の発明は、請求項１〜４の固体電解質型燃料電池の燃料極成膜方法において、前記燃料極材料の乾燥工程において、温風を前記基体の中心孔に挿通させるものであり、これによって基体の内周面に付着した燃料極材料の乾燥を早め、成膜時間の短縮が図れる。
請求項６の発明は、請求項１〜５の固体電解質型燃料電池の燃料極成膜方法において、前記燃料極材料混合液中には、希釈剤を混入することを特徴とするものであり、必要に応じて燃料極材料混合液中に希釈剤を混入することで燃料極材料混合液の粘度を調整できる。
【００１７】
【発明の実施の形態】
以下、本発明の実施の形態を図に基づいて詳説する。基体１０は、従来例で説明したのと同様に、ストロンチウム添加ランタンマンガネート（ＬＳＭ）製、円筒体の多孔質空気極１の内周面に、イットリア安定化ジルコニア（ＹＳＺ）製の緻密な固体電解質２をＣＶＤ−ＥＶＤ法によって形成したものである。この基体１０の寸法は特に制限されるものではないが、固体電解質型燃料電池用として、以下では外形２０ｍｍφ、内径１７ｍｍφ、長さ０．５〜１ｍのものを用いた場合について説明する。
【００１８】
燃料極材料混合液は、ニッケル（Ｎｉ）粉末、コバルト粉末（Ｃｏ）粉末、酸化ニッケル（ＮｉＯ）粉末、酸化コバルト（ＣｏＯ）粉末、あるいはニッケルジルコニアサーメット粉末とＹＳＺ粉末との混合粉末を、後の焼成温度で分解するセルロース系樹脂を主成分とするバインダと１：１／５〜２の重量比で混合し、さらに必要に応じて濃度調整のためにエーテルのような希釈剤１／５〜２の重量比で添加して混合したものである。
【００１９】
そして図１に示すように、基体１０の外周面全体に有機セルロース系テープやフィルムのカバー１２を被着し、これを上記の燃料極材料混合液１３の入った容器１４内に差し入れて全体を液中に沈め、基体１０の中心孔から内部に燃料極材料混合液を侵入させ、その後、この基体１０を引き上げる。
【００２０】
次に、燃料極材料混合液が基体１０の内周面に付着した状態のまま（外周面にも付着するが、これは後の乾燥工程後にカバー１２を取り除くことによって除去することができる）、図２及び図３に示すように対向して同一方向に回転する回転板１５，１５に両端を支持させ、回転させながら燃料極材料を乾燥させ、燃料極材料膜を基体１０の内周面に生成させる。燃料極材料膜の厚さは１０〜１００μｍである。
【００２１】
各回転板１５はモータで駆動され、回転速度の制御が可能であり、また基体１０の長さに対応して相互の間隔を広狭移動調整することができるもので、さらに基体１０の端部開口に差し込んで基体１０の端部を支持すると共に、基体１０の内部に温風１７を吹き込む支持管１６を備えている。
【００２２】
そこでこの回転板１５，１５の回転によって基体１０内に５０〜１００℃の温風１７を吹き込みながら回転させることによって、図４に示すように、浸漬工程で基体１０の内周面に付着した燃料極材料のバインダと溶剤が乾燥し、均一な燃料極材料膜１８を生成する。回転板１５，１５の回転速度は実験的に決定するべきものであるが、例示すれば１０〜３００ｒｐｍとする。そして燃料極材料膜１８の膜厚は目標として１０〜１００μｍであり、用いる燃料極材料混合液の濃度によって１回の浸漬と回転乾燥で形成される膜厚は異なってくる。たとえば、ニッケル１：バインダ２の割合の混合液であれば濃度が高いので１回の浸漬と回転乾燥工程によって３０μｍ程度の膜厚の燃料極材料膜１８を形成することができる。またニッケル１：バインダ１：溶剤２の割合の混合液の場合、濃度が比較的低いので１回の浸漬と回転乾燥工程によって形成される燃料極材料膜１８の膜厚は５〜１０μｍである。
【００２３】
ここで１回の浸漬と回転乾燥工程とで基体１０の内周面に形成される燃料極材料膜１８の膜厚は上述のように燃料極材料混合液の濃度によって異なってくるので、１回の工程で燃料極材料膜１８が目的とする膜厚に達しない場合には、この浸漬工程と回転乾燥工程を何度か繰り返して目的の膜厚を形成するようにする。
【００２４】
次に、この燃料極材料膜１８の形成された基体１０に対して、従来から行われている焼成を行うことによって燃料極材料膜１８をサーメット化して多孔質の燃料極膜を形成する。この焼成条件は特に限定されないが、例示すれば約１０００〜１２００℃、約３〜８時間で行う。
【００２５】
こうして基体１０の内周面に形成された燃料極材料膜１８は、回転乾燥の工程で基体１０の内周面に均一厚に密着するので、その結果、燃料極膜も膜厚が均一で基体１０の固体電解質２との密着性も良好なものとなる。
【００２６】
なお、１回の浸漬、回転乾燥工程で所望の膜厚の燃料極材料膜１８が形成できない場合に、この浸漬、回転乾燥工程を何度か繰り返して所望の膜厚の燃料極材料膜１８を形成する方法に代えて、浸漬−回転乾燥−焼成までのすべての工程を何度か繰り返して所望の膜厚の燃料極膜を成膜する方法を採用することができる。さらに、上述した回転乾燥工程では、基体１０の内部に温風１７を吹き込む方法を採ったが、これに代えて、あるいはこれと共に周囲雰囲気温度を高温に保ちつつ回転乾燥させる方法を採用してもよい。
【００２７】
またさらに、上述した実施の形態では最終工程に焼成工程を採用したが、焼成工程に代えて、あるいは焼成工程の後でさらにＹＳＺのＥＶＤ法を用いることが好ましい。
【００２８】
ＹＳＺのＥＶＤ法を実施する場合、電気化学蒸着設備において１０００〜１２００℃の温度条件下で、基体１０の外側にＨ₂とＨ₂Ｏとの混合酸化ガスを導入し、内側にイットリウム、ジルコニウムそれぞれの塩化物蒸気をキャリアガスに混入して供給し、２〜５時間電気化学蒸着を行い、燃料極膜のさらに内側にＹＳＺ膜を成膜することになり、この成膜したＹＳＺ膜も併せて最終的な燃料極膜となる。
【００２９】
【実施例】
（実施例１）
空気極となる外径２０ｍｍφのＬＳＭ管の内周面に固体電解質膜となるＹＳＺ膜を形成し、内径１７ｍｍφ、長さ５０ｃｍの基体の外周面をセロファンフィルムでカバーし、これをＮｉ粉末１：セルロース系樹脂を主成分とするバインダ２の割合で混合した燃料極材料混合液中に浸漬した後引き上げて、回転板に両端支持するように水平に取り付け、基体の内部に５０℃の温風を吹き込み、また外部雰囲気も５０℃にした乾燥条件で、１００ｒｐｍの回転速度で回転させながら乾燥させた。完全に乾燥した後に回転板から取り外して、内部に形成された燃料極材料膜を観察したが、膜厚は３０μｍであった。
【００３０】
続いて、この基体から外部のセロファンカバーを取り去り、焼成炉に入れて焼成した。焼成条件は１２００℃、５時間であった。
【００３１】
この結果、基体の内周面に成膜された燃料極膜は、３０μｍの均一な膜厚であった。
【００３２】
（実施例２）
実施例１と同じサイズ、材質の基体を、Ｎｉ粉末１：バインダ１：エーテル２の割合で混合した燃料極材料混合液中に浸漬した後、実施例１と同様の回転乾燥条件で回転乾燥させた。内部に形成された燃料極材料膜は、膜厚が１０μｍであった。そこで、この浸漬、回転乾燥工程を３回繰り返し、燃料極材料膜の膜厚を３０μｍにした。続いて、この基体を実施例１と同じ焼成条件で焼成した。
【００３３】
この結果、基体の内周面に成膜された燃料極膜は、３０μｍの均一な膜厚であった。
【００３４】
（実施例３）
実施例１，２それぞれで得られた固体電解質型燃料電池管に対して、さらにＹＳＺのＥＶＤを行った。ＥＶＤ法は、電気化学蒸着設備において１０００℃の温度下で、基体の外側にＨ₂とＨ₂Ｏとの混合酸化ガスを導入し、内側にイットリウム、ジルコニウムそれぞれの塩化物蒸気をキャリアガスに混入して供給して５時間を行い、燃料極膜のさらに内側に膜厚１０μｍのＹＳＺ膜を形成した。
【００３５】
（実施例４）
実施例１と同じサイズ、材質の基体を、Ｎｉ粉末１：バインダ１：エーテル２の割合で混合した燃料極材料混合液中に浸漬した後、実施例１と同様の回転乾燥条件で回転乾燥させた。内部に形成された燃料極材料膜は、膜厚が１０μｍであった。続いて、この基体を実施例１と同じ焼成条件で焼成して膜厚１０μｍの燃料極膜を形成した。
【００３６】
この後、上記の浸漬、回転乾燥、焼成工程をさらに２回繰り返して、最終的に膜厚３０μｍの燃料極膜を形成した。
【００３７】
（実施例５）
実施例１と同一の条件で浸漬、回転乾燥工程を行って、基体の内部に膜厚３０μｍの燃料極材料膜を形成した。続いて、この基体から外部のセロファンカバーを取り去り、実施例３と同一の条件でＹＳＺのＥＶＤを行った。
【００３８】
この結果、基体の内周面に成膜された燃料極膜は、Ｎｉ層が３０μｍの均一な膜厚であり、さらにＹＳＺ層が１０μｍの膜厚で共に均一であった。
【００３９】
（実施例６）
実施例２と同一の条件で浸漬、回転乾燥工程を３回繰り返し、燃料極材料膜の膜厚を３０μｍにした基体を得た。続いて、この基体に実施例５と同じ条件でＹＳＺのＥＶＤを行った。
【００４０】
この結果、基体の内周面に成膜された燃料極膜は、Ｎｉ層が３０μｍの均一な膜厚であり、さらにＹＳＺ層が１０μｍの膜厚で共に均一であった。
【００４１】
（実施例７）
実施例１と同じサイズ、材質の基体を、Ｎｉ粉末１：バインダ１：エーテル２の割合で混合した燃料極材料混合液中に浸漬した後、実施例１と同様の回転乾燥条件で回転乾燥させた。内部に形成された燃料極材料膜は、膜厚が１０μｍであった。続いて、この基体を実施例５と同じ条件でＥＶＤを行い、Ｎｉ層の膜厚１０μｍ、ＹＳＺ層の膜厚１０μｍの燃料極膜を形成した。この後、上記の浸漬、回転乾燥、ＥＶＤ工程を繰り返して、最終的にＮｉ層、ＹＳＺ層が２層ずつ交互に積層した合計４０μｍの燃料極膜を形成した。
【００４２】
これらの各実施例で基体の内周面に成膜された燃料極膜の状態は、いずれも膜厚が均一であり、また固体電解質膜との密着性も良好なものであった。
【００４３】
【発明の効果】
以上のように請求項１の発明によれば、浸漬工程でニッケル、コバルト、ニッケル又はコバルトを主成分とする合金、あるいはそれらのいずれかのサーメットの粉末とＹＳＺ粉末とをバインダに混合した燃料極材料混合液中に基体を浸漬することにより、基体の内径が小さくても容易にその内周面全体に燃料極材料混合液を付着させることができ、この後にこの基体を水平に保持しつつ回転させて、基体内周面に付着している燃料極材料を乾燥させることにより、均一にして基体の内周面と密着性の良い燃料極材料膜を形成することができ、このために、この後に燃料極材料膜を焼成して基体の内周面に燃料極膜を形成することによって、均一にして基体の内周面と密着性の良い燃料極膜を成膜することができる。
【００４４】
請求項２の発明によれば、燃料極材料混合液の浸漬工程と、燃料極材料の乾燥工程とを燃料極材料膜が所定の膜厚になるまで繰り返し、その後に焼成工程に移行して所定の膜厚の燃料極膜を形成するものであり、燃料極膜の膜厚制御が正確にできる。
【００４５】
請求項３の発明によれば、焼成工程に代えてＹＳＺのＥＶＤ工程を行うことにより、基体の内周面との密着性が良好で、かつ材質にすぐれた燃料極膜を形成することができる。
【００４６】
請求項４の発明によれば、焼成工程の後にＹＳＺのＥＶＤ工程を行うことにより、基体の内周面との密着性が良好で、かつ材質にすぐれた燃料極膜を形成することができる。
【００４７】
請求項５の発明によれば、燃料極材料の乾燥工程において温風を基体の中心孔に挿通させるものであり、これによって基体の内周面に付着した燃料極材料の乾燥を早め、成膜時間の短縮が図れる。
請求項６の発明によれば、燃料極材料混合液中に希釈剤を混入することで燃料極材料混合液の粘度を調整できる。
【図面の簡単な説明】
【図１】本発明における基体の浸漬工程を示す説明図。
【図２】本発明における回転乾燥工程を示す説明図。
【図３】上記の回転乾燥工程に用いてる回転板の説明図。
【図４】本発明において回転乾燥工程を終えた時の気体の内部構造を示す断面図。
【図５】従来例の斜視図。
【図６】他の従来例の斜視図。
【符号の説明】
１空気極
２固体電解質
１０基体
１２カバー
１３燃料極材料混合液
１４容器
１５回転板
１６支持管
１７温風
１８燃料極材料膜[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel electrode film forming method for a solid oxide fuel cell.
[0002]
[Prior art]
In recent years, research and development of solid oxide fuel cells have been intensively conducted. This solid oxide fuel cell has a flat plate method and a cylindrical method, and the cylindrical method has a vertical stripe method and a horizontal stripe method. In particular, a cylindrical vertical stripe type solid oxide fuel cell has a structure shown in FIG. The conventional unit cell 106 includes a porous lanthanum manganate-based oxide (LaMnOn) air electrode support tube 101, yttria-stabilized zirconia (YSZ) solid electrolyte 102, nickel or nickel alloy, and YSZ in order from the inside. A cermet fuel electrode 103 is laminated, and the interconnector 104 is insulated from the fuel electrode 103 and connected to the internal air electrode support tube 101 at a part of the outer peripheral surface.
[0003]
However, in such a conventional vertical-stripe cylindrical solid oxide fuel cell, the materials of each element are all made of ceramics and operate at a high temperature of about 850 to 1050 ° C. There is a problem in that stress is concentrated near the overlapping interconnector 104 and the bottom of the battery and cracks are likely to occur.
[0004]
In order to solve this conventional problem, Japanese Patent Application Laid-Open No. 7-263001 proposes a solid oxide fuel cell 110 having a structure shown in FIG. This proposed conventional solid oxide fuel cell 110 is characterized by a structure in which a conductive tube 111 for fuel supply is inserted in the center. That is, a fuel electrode 112, a solid electrolyte 113, and an air electrode 114 are formed in this order from the inside, and a fuel supply conductive tube 111 that is made porous for fuel injection is inserted into the central portion. In this structure, a conductive felt 115 having a fuel reforming function is filled between the electrode 112 and the fuel gas 116 is supplied to the conductive tube 111 so that air 117 is circulated on the outer periphery.
[0005]
The power generation operation of the solid oxide fuel cell 110 will be described. A fuel gas 116 such as natural gas, methane, or coal gasification gas is supplied into the conductive tube 111 of the battery 110, and the porous tube of the conductive tube 111 is supplied. The conductive felt 115 is jetted through the wall, and the conductive felt 115, the fuel electrode 112, and the solid electrolyte 113 are subjected to the reforming of the following formula under high temperature conditions, usually 650 ° C. to 1050 ° C. Cause a reaction.
[0006]
[Chemical 1]

For the hydrogen generated by this reforming reaction, a power generation reaction of the following chemical formula 2 is caused at the portion of the fuel electrode 112 and the air electrode 114 opposite to each other through the solid electrolyte 113, and the released electrons are collected. To get the generated power.
[0007]
[Chemical 2]

That is, at the fuel electrode 112, as shown in the chemical formula 2 (a), hydrogen generated by the reforming reaction reacts with oxide ions supplied from the solid electrolyte 113 to generate water vapor and electrons. Then, when the electrons generated in the fuel electrode 112 pass through the conductive felt 115 and the conductive tube 111 to the external circuit from the cathode 118 and reach the air electrode 114 through the anode 118, in the air electrode 114, the chemical formula 2 (b As shown in the formula, it reacts with oxygen in the air 117 to generate oxide ions, which are released to the solid electrolyte 113, reach the fuel electrode 112 side, and are subjected to the reaction of formula 2 (a). It is.
[0008]
In the fuel cell 110 of such a power generation mechanism, the air electrode 114, the solid electrolyte 113, and the fuel electrode 112 are formed as follows. First, a thin and dense YSZ film is formed on the lanthanum manganate-based porous base material to be the air electrode 114 by using an electrochemical deposition method, that is, a CVD (Chemical Vapor Deposition) -EVD (Electrochemical Vapor Deposition) method. Is formed as a solid electrolyte 113, and the YSZ film is further coated with nickel, cobalt, nickel or an alloy containing nickel as a main component, or nickel zirconia cermet powder, and similarly subjected to electrochemical vapor deposition to be porous. The fuel electrode 112 is formed into a film, or the film is formed by using a spraying method as disclosed in Japanese Patent Laid-Open No. 4-349343.
[0009]
[Problems to be solved by the invention]
However, in such a conventional method for forming each film of the solid oxide fuel cell, the method for forming the fuel electrode, in particular, is based on slurry coating or thermal spraying. In this case, it is difficult to make the film thickness uniform, and in the case of the spraying method, it is necessary to have a minimum inner diameter of 60 mmφ when trying to form a film on the inner peripheral surface of the pipe body. There was a problem that the film could not be formed on the inner peripheral surface.
[0010]
The present invention has been made in view of such conventional problems. Even when the inner diameter of the tube is small, the fuel electrode film can be formed on the inner peripheral surface thereof, and the fuel electrode film can be formed with a uniform film thickness. An object of the present invention is to provide a method for forming a fuel electrode for a solid oxide fuel cell capable of forming a film.
[0011]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a method for forming a fuel electrode in a solid oxide fuel cell, wherein nickel, cobalt, nickel or an alloy containing cobalt as a main component, or a cermet powder of any of them and a YSZ powder are mixed in a binder. immersing the substrate to the fuel electrode material mixture liquid was, said is rotated while held horizontally substrate, dried fuel electrode material layer using the fuel electrode material attached to the base of said substrate It comprises a step of forming on the inner peripheral surface and a step of firing the fuel electrode material film to form a fuel electrode film on the inner peripheral surface of the substrate.
[0012]
In the fuel electrode film forming method for a solid oxide fuel cell according to the first aspect of the present invention, nickel, cobalt, nickel or an alloy containing nickel as a main component in the immersing step, or a cermet powder of any of them, and a YSZ powder By immersing the substrate in the fuel electrode material mixture mixed with the binder, the fuel electrode material mixture can easily adhere to the entire inner peripheral surface of the substrate even if the inner diameter of the substrate is small. The fuel electrode material adhering to the inner peripheral surface of the substrate is dried by rotating while holding the electrode horizontally to form a fuel electrode material film having good adhesion to the inner peripheral surface of the substrate. For this purpose, the fuel electrode material film is subsequently fired to form the fuel electrode film on the inner peripheral surface of the substrate, thereby forming a uniform fuel electrode film having good adhesion to the inner peripheral surface of the substrate. can do
[0013]
According to a second aspect of the present invention, in the fuel electrode film forming method for a solid oxide fuel cell according to the first aspect, the fuel electrode material film comprises a dipping step of the fuel electrode material mixed solution and a drying step of the fuel electrode material. The process is repeated until a predetermined film thickness is obtained, and then the process proceeds to the firing step to form a fuel electrode film having a predetermined film thickness, whereby the film thickness of the fuel electrode film can be accurately controlled.
[0014]
According to a third aspect of the present invention, in the fuel electrode film forming method of the solid oxide fuel cell according to the first or second aspect, instead of the firing step, an EVD step of YSZ is performed, A fuel electrode film having good adhesion and excellent material can be formed.
[0015]
According to a fourth aspect of the present invention, in the method for forming a fuel electrode of a solid oxide fuel cell according to the first or second aspect, the EVD step of YSZ is performed after the firing step, and is in close contact with the inner peripheral surface of the substrate. It is possible to form a fuel electrode film having good properties and excellent material.
[0016]
The invention of claim 5 is the fuel electrode film forming method of the solid oxide fuel cell according to claims 1 to 4, wherein hot air is inserted into the center hole of the substrate in the drying process of the fuel electrode material. Thereby, drying of the fuel electrode material adhering to the inner peripheral surface of the substrate can be accelerated, and the film formation time can be shortened.
Invention of Claim 6 is a fuel electrode film-forming method of the solid oxide fuel cell of Claims 1-5, In the said fuel electrode material liquid mixture, a diluent is mixed, It is characterized by the above-mentioned. If necessary, the viscosity of the fuel electrode material mixture can be adjusted by mixing a diluent into the fuel electrode material mixture.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The substrate 10 is made of strontium-added lanthanum manganate (LSM) as described in the prior art, and a dense solid made of yttria-stabilized zirconia (YSZ) on the inner peripheral surface of the cylindrical porous air electrode 1. The electrolyte 2 is formed by the CVD-EVD method. Although the size of the substrate 10 is not particularly limited, a case where an outer diameter of 20 mmφ, an inner diameter of 17 mmφ, and a length of 0.5 to 1 m is used for a solid oxide fuel cell will be described below.
[0018]
The fuel electrode material mixed liquid is nickel (Ni) powder, cobalt powder (Co) powder, nickel oxide (NiO) powder, cobalt oxide (CoO) powder, or mixed powder of nickel zirconia cermet powder and YSZ powder, A binder based on a cellulose resin that decomposes at the firing temperature is mixed in a weight ratio of 1: 1/5 to 2, and a diluent such as ether is used to adjust the concentration if necessary. And mixed at a weight ratio of
[0019]
Then, as shown in FIG. 1, an organic cellulose tape or film cover 12 is attached to the entire outer peripheral surface of the substrate 10, and this is inserted into a container 14 containing the above-mentioned fuel electrode material mixture 13 and the whole is Submerged in the liquid, the fuel electrode material mixed solution enters from the center hole of the base 10 into the inside, and then the base 10 is pulled up.
[0020]
Next, the fuel electrode material mixed solution remains attached to the inner peripheral surface of the substrate 10 (it also adheres to the outer peripheral surface, which can be removed by removing the cover 12 after the subsequent drying step). As shown in FIGS. 2 and 3, both ends are supported by rotating

plates

15, 15 that face and rotate in the same direction, the fuel electrode material is dried while rotating, and the fuel electrode material film is applied to the inner peripheral surface of the substrate 10. Generate. The thickness of the fuel electrode material film is 10 to 100 μm.
[0021]
Each rotary plate 15 is driven by a motor, and the rotational speed can be controlled. The distance between the rotary plates 15 can be adjusted according to the length of the base 10. And a support tube 16 for blowing warm air 17 into the inside of the base 10.
[0022]
Therefore, by rotating the

rotary plates

15 and 15 while blowing hot air 17 of 50 to 100 ° C. into the base 10, the fuel adhering to the inner peripheral surface of the base 10 in the dipping process as shown in FIG. The electrode material binder and solvent are dried to produce a uniform fuel electrode material film 18. The rotational speed of the

rotary plates

15 and 15 should be determined experimentally, but is 10 to 300 rpm for example. The film thickness of the fuel electrode material film 18 is 10 to 100 μm as a target, and the film thickness formed by one dipping and rotary drying differs depending on the concentration of the fuel electrode material mixture used. For example, since the concentration of the mixed solution of nickel 1 and binder 2 is high, the fuel electrode material film 18 having a thickness of about 30 μm can be formed by one immersion and rotary drying process. In the case of a mixed solution of nickel 1: binder 1: solvent 2, since the concentration is relatively low, the film thickness of the fuel electrode material film 18 formed by one dipping and rotary drying process is 5 to 10 μm.
[0023]
Here, the film thickness of the fuel electrode material film 18 formed on the inner peripheral surface of the substrate 10 in one immersion and rotary drying process varies depending on the concentration of the fuel electrode material mixture as described above. If the fuel electrode material film 18 does not reach the target film thickness in this step, the target film thickness is formed by repeating this dipping process and rotary drying process several times.
[0024]
Next, the base 10 on which the fuel electrode material film 18 is formed is baked in the conventional manner to cermet the fuel electrode material film 18 to form a porous fuel electrode film. Although the firing conditions are not particularly limited, for example, the firing is performed at about 1000 to 1200 ° C. for about 3 to 8 hours.
[0025]
The fuel electrode material film 18 formed on the inner peripheral surface of the substrate 10 in this way adheres uniformly to the inner peripheral surface of the substrate 10 in the rotary drying process. As a result, the fuel electrode film also has a uniform film thickness. Adhesiveness with 10 solid electrolytes 2 is also good.
[0026]
In addition, when the fuel electrode material film 18 having a desired film thickness cannot be formed by one immersion and rotation drying process, the fuel electrode material film 18 having a desired film thickness is obtained by repeating this immersion and rotation drying process several times. Instead of the forming method, a method of forming a fuel electrode film having a desired film thickness by repeating all the steps from immersion to spin drying to firing several times can be employed. Furthermore, in the above-described rotary drying process, the method of blowing the warm air 17 into the inside of the base body 10 is adopted, but instead of this, a method of rotating and drying while keeping the ambient atmosphere temperature at a high temperature may be adopted. Good.
[0027]
Furthermore, in the above-described embodiment, the firing process is adopted as the final process, but it is preferable to use the YSZ EVD method instead of the firing process or after the firing process.
[0028]
When the EVS method of YSZ is carried out, a mixed oxidizing gas of H ₂ and H ₂ O is introduced to the outside of the substrate 10 under a temperature condition of 1000 to 1200 ° C. in an electrochemical deposition facility, and yttrium and zirconium are respectively inside. The chloride vapor is mixed and supplied to the carrier gas, electrochemical deposition is performed for 2 to 5 hours, and a YSZ film is formed further inside the fuel electrode film. The formed YSZ film is also combined. The final fuel electrode membrane.
[0029]
【Example】
Example 1
A YSZ film as a solid electrolyte film is formed on the inner peripheral surface of an LSM tube having an outer diameter of 20 mmφ serving as an air electrode, and the outer peripheral surface of a substrate having an inner diameter of 17 mmφ and a length of 50 cm is covered with a cellophane film. Immerse it in the fuel electrode material mixture mixed at the ratio of the binder 2 containing cellulose resin as a main component and then pull it up and attach it horizontally to support both ends of the rotating plate. It was dried while being rotated at a rotational speed of 100 rpm under the drying conditions of blowing and the external atmosphere at 50 ° C. After completely drying, it was removed from the rotating plate and the fuel electrode material film formed inside was observed. The film thickness was 30 μm.
[0030]
Subsequently, the external cellophane cover was removed from the substrate and placed in a firing furnace for firing. Firing conditions were 1200 ° C. and 5 hours.
[0031]
As a result, the fuel electrode film formed on the inner peripheral surface of the substrate had a uniform film thickness of 30 μm.
[0032]
(Example 2)
A substrate having the same size and material as in Example 1 was immersed in a fuel electrode material mixture mixed at a ratio of Ni powder 1: binder 1: ether 2 and then rotated and dried under the same rotational drying conditions as in Example 1. It was. The fuel electrode material film formed inside had a thickness of 10 μm. Therefore, the dipping and rotary drying processes were repeated three times, and the film thickness of the fuel electrode material film was set to 30 μm. Subsequently, this substrate was fired under the same firing conditions as in Example 1.
[0033]
As a result, the fuel electrode film formed on the inner peripheral surface of the substrate had a uniform film thickness of 30 μm.
[0034]
Example 3
YSZ EVD was further performed on the solid oxide fuel cell tubes obtained in Examples 1 and 2, respectively. In the EVD method, a mixed oxidizing gas of H ₂ and H ₂ O is introduced to the outside of the substrate at a temperature of 1000 ° C. in an electrochemical vapor deposition facility, and chloride vapors of yttrium and zirconium are mixed into the carrier gas inside. The YSZ film having a film thickness of 10 μm was formed further inside the fuel electrode film for 5 hours.
[0035]
(Example 4)
A substrate having the same size and material as in Example 1 was immersed in a fuel electrode material mixture mixed at a ratio of Ni powder 1: binder 1: ether 2 and then rotated and dried under the same rotational drying conditions as in Example 1. It was. The fuel electrode material film formed inside had a thickness of 10 μm. Subsequently, this base was fired under the same firing conditions as in Example 1 to form a fuel electrode film having a thickness of 10 μm.
[0036]
Thereafter, the above immersion, rotary drying, and firing steps were repeated twice to finally form a fuel electrode film having a thickness of 30 μm.
[0037]
(Example 5)
A dipping and rotary drying process was performed under the same conditions as in Example 1 to form a fuel electrode material film having a thickness of 30 μm inside the substrate. Subsequently, the external cellophane cover was removed from the substrate, and EVD of YSZ was performed under the same conditions as in Example 3.
[0038]
As a result, in the fuel electrode film formed on the inner peripheral surface of the substrate, the Ni layer had a uniform film thickness of 30 μm, and the YSZ layer had a uniform film thickness of 10 μm.
[0039]
(Example 6)
Under the same conditions as in Example 2, the dipping and rotary drying steps were repeated three times to obtain a substrate having a fuel electrode material film thickness of 30 μm. Subsequently, this substrate was subjected to YSZ EVD under the same conditions as in Example 5.
[0040]
As a result, in the fuel electrode film formed on the inner peripheral surface of the substrate, the Ni layer had a uniform film thickness of 30 μm, and the YSZ layer had a uniform film thickness of 10 μm.
[0041]
(Example 7)
A substrate having the same size and material as in Example 1 was immersed in a fuel electrode material mixture mixed at a ratio of Ni powder 1: binder 1: ether 2 and then rotated and dried under the same rotational drying conditions as in Example 1. It was. The fuel electrode material film formed inside had a thickness of 10 μm. Subsequently, this substrate was subjected to EVD under the same conditions as in Example 5 to form a fuel electrode film having a Ni layer thickness of 10 μm and a YSZ layer thickness of 10 μm. Thereafter, the above immersion, rotary drying, and EVD processes were repeated to finally form a fuel electrode film having a total of 40 μm in which two Ni layers and two YSZ layers were alternately laminated.
[0042]
In each of these examples, the state of the fuel electrode film formed on the inner peripheral surface of the substrate was uniform, and the adhesion to the solid electrolyte film was good.
[0043]
【The invention's effect】
As described above, according to the first aspect of the present invention, a fuel electrode in which nickel, cobalt, nickel or an alloy containing cobalt as a main component, or any one of those cermet powders and YSZ powder is mixed in a binder in the dipping process. By immersing the substrate in the material mixture, the fuel electrode material mixture can be easily attached to the entire inner peripheral surface of the substrate even if the inner diameter of the substrate is small, and then the substrate is rotated while being held horizontally. Then, by drying the fuel electrode material adhering to the inner peripheral surface of the substrate, a fuel electrode material film having good adhesion to the inner peripheral surface of the substrate can be formed uniformly. By subsequently firing the fuel electrode material film to form the fuel electrode film on the inner peripheral surface of the substrate, it is possible to uniformly form the fuel electrode film having good adhesion to the inner peripheral surface of the substrate.
[0044]
According to the invention of claim 2, the step of immersing the fuel electrode material mixture and the step of drying the fuel electrode material are repeated until the fuel electrode material film reaches a predetermined film thickness, and then the process proceeds to the firing step. The thickness of the fuel electrode film can be accurately controlled.
[0045]
According to the invention of claim 3, by performing the EVD process of YSZ instead of the firing process, it is possible to form a fuel electrode film having good adhesion to the inner peripheral surface of the substrate and excellent in material. .
[0046]
According to the fourth aspect of the present invention, by performing the YSZ EVD step after the firing step, it is possible to form a fuel electrode film having good adhesion to the inner peripheral surface of the substrate and excellent in material.
[0047]
According to the fifth aspect of the present invention, in the drying process of the fuel electrode material, the hot air is inserted into the center hole of the substrate, thereby speeding up the drying of the fuel electrode material adhering to the inner peripheral surface of the substrate and forming the film. Time can be shortened.
According to the invention of claim 6, the viscosity of the fuel electrode material mixture can be adjusted by mixing the diluent into the fuel electrode material mixture.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a substrate immersing step in the present invention.
FIG. 2 is an explanatory view showing a rotary drying process in the present invention.
FIG. 3 is an explanatory diagram of a rotary plate used in the rotary drying process.
FIG. 4 is a cross-sectional view showing the internal structure of a gas when the rotary drying process is finished in the present invention.
FIG. 5 is a perspective view of a conventional example.
FIG. 6 is a perspective view of another conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Air electrode 2 Solid electrolyte 10 Base | substrate 12 Cover 13 Fuel electrode material mixed liquid 14 Container 15 Rotating plate 16 Support pipe 17 Hot air 18 Fuel electrode material film

Claims

Immersing the substrate in a fuel electrode material mixture obtained by mixing nickel, cobalt, nickel or an alloy containing nickel as a main component, or a cermet powder of any of them and a YSZ powder in a binder;
Forming the fuel electrode material film on the inner peripheral surface of the substrate by rotating the substrate while holding it horizontally to dry the fuel electrode material adhering to the substrate;
A fuel electrode film forming method for a solid oxide fuel cell, comprising: baking the fuel electrode material film to form a fuel electrode film on an inner peripheral surface of the substrate.

The step of immersing the fuel electrode material mixed solution and the step of drying the fuel electrode material are repeated until the fuel electrode material film has a predetermined thickness, and then the process proceeds to the firing step to obtain a fuel having a predetermined film thickness. 2. The fuel electrode film forming method for a solid oxide fuel cell according to claim 1, wherein an electrode film is formed.

3. The method for forming a fuel electrode in a solid oxide fuel cell according to claim 1, wherein an EVD process of YSZ is performed instead of the firing process.

The method of forming a fuel electrode for a solid oxide fuel cell according to claim 1, wherein an EVD step of YSZ is performed after the firing step.

5. The fuel electrode film forming method for a solid oxide fuel cell according to claim 1, wherein in the drying step of the fuel electrode material, hot air is inserted into a central hole of the base body.

6. The fuel electrode film forming method for a solid oxide fuel cell according to claim 1, wherein a diluent is mixed in the fuel electrode material mixed solution.