JP4845296B2

JP4845296B2 - Solid oxide fuel cell and fuel cell

Info

Publication number: JP4845296B2
Application number: JP2001229695A
Authority: JP
Inventors: 祥二山下; 雅人西原
Original assignee: Kyocera Corp
Current assignee: Kyocera Corp
Priority date: 2001-07-30
Filing date: 2001-07-30
Publication date: 2011-12-28
Anticipated expiration: 2021-07-30
Also published as: JP2003045446A

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セル及び燃料電池に関し、特に、空気極の表面に、固体電解質、燃料極を順次積層してなり、空気極、固体電解質、第１燃料極が同時に焼結された固体電解質型燃料電池セル及び燃料電池に関するものである。
【０００２】
【従来技術】
従来より、固体電解質型燃料電池はその作動温度が９００〜１０５０℃と高温であるため発電効率が高く、第３世代の発電システムとして期待されている。
【０００３】
一般に固体電解質型燃料電池セルには、円筒型と平板型が知られている。平板型燃料電池セルは、発電の単位体積当たり出力密度は高いという特徴を有するが、実用化に関してはガスシール不完全性やセル内の温度分布の不均一性などの問題がある。それに対して、円筒型燃料電池セルでは、出力密度は低いものの、セルの機械的強度が高く、またセル内の温度の均一性が保てるという特徴がある。両形状の固体電解質型燃料電池セルとも、それぞれの特徴を生かして積極的に研究開発が進められている。
【０００４】
円筒型燃料電池セルは、図５に示すように開気孔率３０〜４０％程度のＬａＭｎＯ₃系材料からなる多孔性の空気極支持管２を形成し、その表面にＹ₂Ｏ₃安定化ＺｒＯ₂からなる固体電解質３を形成し、さらにこの表面に多孔性のＮｉ−ジルコニアの燃料極４を形成して構成されている。
【０００５】
燃料電池のモジュールにおいては、各単セルはＬａＣｒＯ₃系の集電体（インターコネクタ）５を介して接続される。発電は、空気極支持管２内部に空気（酸素）６を、外部に燃料（水素）７を流し、１０００〜１０５０℃の温度で行われる。
【０００６】
上記のような燃料電池セルを製造する方法としては、近年ではセルの製造工程を簡略化し且つ製造コストを低減するために、各構成材料のうち少なくとも２つを同時焼成する、いわゆる共焼結法が提案されている。この共焼結法は、例えば、円筒状の空気極成形体に固体電解質成形体及び集電体成形体をロール状に巻き付けて同時焼成を行い、その後固体電解質表面に燃料極を形成する方法である。またプロセス簡略化のために、固体電解質成形体の表面にさらに燃料極成形体を積層して、同時焼成する共焼結法も提案されている。
【０００７】
この共焼結法は非常に簡単なプロセスで製造工程数も少なく、セルの製造時の歩留まり向上、コスト低減に有利である。
【０００８】
【発明が解決しようとする課題】
燃料極は金属粒子を主成分とし、他のセラミックスからなる空気極、固体電解質、集電体とは熱膨張係数が大きく異なるため、空気極成形体に、固体電解質成形体、集電体成形体および燃料極成形体を積層して、同時焼成する場合には、燃料極成形体の厚みを薄くしなければ剥離やクラックが発生するため、その厚みは２０μｍ以下とされていたが、このような２０μｍ以下の厚さの燃料極では電気抵抗が高く、発生した電流を効率良く集電することができず、結果として発電効率が低下するという問題があった。
【０００９】
このような問題を解決するため、本出願人は、先に、空気極の表面に、固体電解質、第１燃料極、第２燃料極を順次積層してなり、空気極、固体電解質、第１燃料極を同時焼成し、第２燃料極を第１燃料極の表面に焼き付けて形成した固体電解質型燃料電池セルを提案した。
【００１０】
ここでは、第１燃料極は、金属粉末（あるいは金属酸化物粉末）とセラミック粉末を含むシート状の第１燃料極成形体を固体電解質成形体に積層し、空気極、固体電解質、集電体との同時焼成によって形成し、この第１燃料極の表面に、金属粉末（あるいは金属酸化物粉末）とセラミック粉末、さらにセラミックを構成する元素を含む有機金属塩からなるペーストを塗布し、焼き付けることによって第２燃料極を形成していた。
【００１１】
このような固体電解質型燃料電池セルでは、固体電解質を構成するＺｒＯ₂膜と高温焼結により強固に結合されている第１燃料極内部のＺｒＯ₂粒子の表面に、より微粒でサブミクロンレベルのＺｒＯ₂微粒子を付着堆積させ焼結（焼き付け）され、第２燃料極の下層部に存在するＺｒＯ₂微粒子が第１燃料極のＺｒＯ₂粒子と結合一体化し、強固な界面を形成できる。
【００１２】
しかしながら、同時焼成して形成された第１燃料極と、固体電解質との接合強度が未だ低いという問題があった。これにより、長期間連続して発電すると、固体電解質から第１燃料極の剥離が発生し易いという問題があった。特に、近年、直径が１０ｍｍ以下の小径の円筒状セルが用いられるようになっているが、このような小径のセルでは曲率が大きいために、第１、第２燃料極に過大な応力が発生し易く、長期間の発電により第１、第２燃料極が剥離し易くなるという問題があった。
【００１３】
本発明は、第１燃料極と第２燃料極間の接合界面を強固にできるとともに、第１燃料極の固体電解質からの剥離を有効に防止でき、高い発電能力を長期間維持できる固体電解質型燃料電池セル及び燃料電池を提供することを目的とする。
【００１４】
本発明の固体電解質型燃料電池セルは、固体電解質の片面に燃料極、他方の面に空気極を形成してなる固体電解質型燃料電池セルであって、前記燃料極が前記固体電解質表面に形成された第１燃料極と、該第１燃料極の表面に形成された第２燃料極とを具備するとともに、前記第１燃料極及び前記第２燃料極に前記固体電解質を構成する材料からなるセラミック粒子と鉄族金属粒子又は鉄族金属酸化物粒子とが存在し、かつ、前記鉄族金属粒子又は鉄族金属酸化物粒子の表面に、前記固体電解質を構成する材料からなり、前記セラミック粒子より粒径が小さい膜状及び／又は微粒子状の微粒セラミック粒子が存在しており、前記第１燃料極の微粒セラミック粒子は、主として前記固体電解質側に存在し、前記第２燃料極の微粒セラミック粒子は、主として前記第１燃料極側に存在することを特徴とする。
【００１５】
このような固体電解質型燃料電池では、第１燃料極の微粒セラミック粒子は、主として固体電解質側に存在し、第２燃料極の微粒セラミック粒子は、主として第１燃料極側に存在するが、例えば、第２燃料極を構成する鉄族金属粒子又は鉄族金属酸化物粒子の表面に存在する、膜状及び／又は微粒子状のＺｒＯ₂粒子（微粒セラミック粒子）が、第１燃料極内部のＺｒＯ₂粒子（セラミック粒子）の表面に結合一体化し、強固な界面を形成でき、第２燃料極の第１燃料極への接合強度を向上できるとともに、例えば、第１燃料極を構成する鉄族金属粒子又は鉄族金属酸化物粒子の表面に存在する、膜状及び／又は微粒子状のＺｒＯ₂粒子（微粒セラミック粒子）が、固体電解質内部のＺｒＯ₂粒子の表面に結合一体化し、強固な界面を形成でき、第１燃料極の固体電解質への接合強度を向上でき、高い発電能力を長期間維持できる。
【００１６】
また、本発明では、第２燃料極を構成する鉄族金属粒子又は鉄族金属酸化物粒子の平均粒径は、第１燃料極を構成する鉄族金属粒子又は鉄族金属酸化物粒子の平均粒径よりも大きいことが望ましい。このような構成によれば、第１燃料極を構成する鉄族金属粒子又は鉄族金属酸化物粒子は微粒子なため３重点を形成する反応場を十分確保でき、一方、第２燃料極を構成する鉄族金属粒子又は鉄族金属酸化物粒子は粗粒子なため、多孔質構造を確保でき、集電作用に加え、電極反応に必要な還元及び生成する水蒸気ガスの通気性をも十分確保することができる。
【００１７】
さらに、本発明の固体電解質型燃料電池セルは、外径が１０ｍｍ以下の円筒状であることが望ましい。このような小径のセルでは、曲率が大きいために、第１燃料極、第２燃料極に過大な応力が発生し易く、製造時における製造歩留まりが低下したり、長期間の発電により第１燃料極、第２燃料極が剥離し易くなる傾向があるため、本発明の固体電解質型燃料電池セルを用いる意義が大きい。
【００２０】
本発明の燃料電池は、反応容器内に、上記した固体電解質型燃料電池セルを複数収容してなるものである。
【００２１】
【発明の実施の形態】
本発明の固体電解質型燃料電池セルは、図１に示すように固体電解質３１の内面に円筒状の空気極３２、外面に燃料極３３を形成してセル本体３４が形成されており、空気極３２には集電体（インターコネクタ）３５が電気的に接続されている。
【００２２】
即ち、固体電解質３１の一部に切欠部３６が形成され、固体電解質３１の内面に形成されている空気極３２の一部が露出しており、この露出面３７及び切欠部３６近傍の固体電解質３１の表面が集電体３５により被覆され、集電体３５が、固体電解質３１の両端部表面及び固体電解質３１の切欠部３６から露出した空気極３２の表面に接合されている。
【００２３】
空気極３２と電気的に接続する集電体３５は、セル本体３４の外面に形成され、連続する円弧面状に形成された固体電解質３１の両端部表面と露出面３７を覆うように形成されており、燃料極３３とは電気的に接続されていない。
【００２４】
そして、本発明の固体電解質型燃料電池セルでは、図２に示すように、燃料極３３が、固体電解質３１、空気極３２、集電体３５と同時焼成により形成された第１燃料極３３ａと、この第１燃料極３３ａの表面に焼き付けて形成された第２燃料極３３ｂとから構成されている。これらの第１燃料極３３ａと第２燃料極３３ｂ中には、図３に示すように、セラミック粒子４１、４３と、鉄族金属粒子４５、４６表面に膜状及び／又は微粒子状の微粒セラミック粒子４７、４８が析出している。
【００２５】
この膜状及び／又は微粒子状の微粒セラミック粒子４７、４８としては、固体電解質３１を形成するＺｒＯ₂系材料との接合から考えて、Ｙ₂Ｏ₃を含有するＺｒＯ₂（ＹＳＺ）が望ましい。また、固体電解質３１との接合強度向上等の点から添加されるセラミック粒子４１、４３は、Ｙ₂Ｏ₃を含有するＺｒＯ₂（ＹＳＺ）が望ましい。鉄族金属粒子４５、４６としては、Ｆｅ、Ｃｏ、Ｎｉ等があるが、このうちＮｉが望ましい。
【００２６】
尚、鉄族金属粒子４５、４６の代わりに鉄族金属酸化物粒子を用いても良い。この場合には、第２燃料極３３ｂの焼き付け後における還元処理、或いは発電する際に還元雰囲気に晒されることにより、金属粒子となる。
【００２７】
第２燃料極３３ｂの鉄族金属粒子４６の平均粒径は第１燃料極３３ａの鉄族金属粒子４５の平均粒径よりも大きくされている。これにより、第１燃料極３３ａでは金属粒子４５の反応サイト数という観点から金属粒子４５の反応サイト数を十分に形成することができる。一方、第２燃料極３３ｂの金属粒子４６の平均粒径が第１燃料極３３ａよりも大きいため、集電能を良好にできるとともに、反応に預かるガスのみだけでなく、反応によって生成したガスの透過性を良好に保つことができる。
【００２８】
第１燃料極３３ａの微粒セラミック粒子４７は、主として固体電解質３１表面側に存在し、第２燃料極３３ｂの微粒セラミック粒子４８は、主として第１燃料極３３ａ表面側に存在している。
【００２９】
第１燃料極３３ａの鉄族金属粒子４５の表面に存在する微粒セラミック粒子４７は、固体電解質３１を構成するＹＳＺ粒子４９表面に接合し、第２燃料極３３ｂの鉄族金属粒子４６の表面に存在する微粒セラミック粒子４８は、第１燃料極３３ａ中のセラミック粒子４１に接合している。本発明では、セラミック粒子４１、４３は粒径が１μｍ以上として、微粒セラミック粒子４７、４８は粒径が０．５μｍとして存在する。
【００３０】
本発明の固体電解質型燃料電池セルは、外径が１０ｍｍ以下の円筒状とされている。このような小径のセルでは曲率が大きいため、成形時や焼成時に内部応力が発生し易く、第１燃料極３３ａ、第２燃料極３３ｂが剥離し易い傾向があるため、本発明を用いる意義が大きい。外径が５ｍｍ以下の場合が最も効果的である。尚、本発明でいうセルの外径とは、セルの最大外径である。
【００３１】
固体電解質３１は、例えば３〜１５モル％のＹ₂Ｏ₃含有した部分安定化あるいは安定化ＺｒＯ₂が用いられる。また、空気極３２としては、例えば、ＬａをＣａ又はＳｒで１０〜３０原子％、Ｙで５〜２０原子％置換したＬａＭｎＯ₃が用いられ、集電体３５としては、例えば、ＣｒをＭｇで１０〜３０原子％置換したＬａＣｒＯ₃が用いられる。
【００３２】
第１燃料極３３ａ及び第２燃料極３３ｂとしては、５０〜８０重量％Ｎｉを含むＺｒＯ₂（Ｙ₂Ｏ₃含有）サーメットが好適に用いられる。
【００３３】
固体電解質３１、空気極３２、集電体３５、第１燃料極３３ａ及び第２燃料極３３ｂとしては、上記例に限定されるものではなく、公知材料を用いても良い。
【００３４】
以上のように構成された固体電解質型燃料電池セルの製法は、まず、円筒状の空気極成形体を形成する。この円筒状の空気極成形体は、例えば所定の調合組成に従いＬａ₂Ｏ₃、Ｙ₂Ｏ₃、ＣａＣＯ₃及びＭｎ₂Ｏ₃の素原料を秤量、混合する。
【００３５】
この後、例えば、１５００℃程度の温度で２〜１０時間仮焼し、その後４〜８μｍの粒度に粉砕調製する。調製した粉体に、バインダーを混合、混練し押出成形法により円筒状の空気極成形体を作製し、さらに脱バインダー処理し、１２００〜１２５０℃で仮焼を行うことで円筒状の空気極仮焼体を作製する。
【００３６】
次に、固体電解質成形体を貼り付けるためのペーストの作製について説明する。Ｍｎ拡散防止層としての機能を有するペーストは、Ｙ₂Ｏ₃、ＣａＯの少なくとも一種を含有するＺｒＯ₂粉末と、ＹＤＣ粉末（Ｙ₂Ｏ₃を３０重量％ドープしたＣｅＯ₂）とを混合仮焼し、その後粒度調製した上記混合粉末に溶媒としてトルエンを添加し作製する。このペーストを円筒状の空気極仮焼体の表面に塗布してＭｎ拡散防止層の塗布膜を形成した。
【００３７】
シート状の第１固体電解質成形体として、Ｙ₂Ｏ₃を含有するＺｒＯ₂粉末にトルエン、バインダー、市販の分散剤を加えてスラリー化したものをドクターブレード等の方法により、例えば、１００〜１２０μｍの厚さに成形したものを用い、円筒状の空気極仮焼体の表面に形成されたＭｎ拡散防止層の塗布膜の表面に、第１固体電解質成形体を貼り付けて仮焼し、空気極仮焼体の表面に第１固体電解質仮焼体を形成する。尚、第１固体電解質成形体を仮焼したが、仮焼しなくても良い。
【００３８】
次に、シート状の第１燃料極成形体を作製する。まず、例えば、所定比率に調製したＮｉ粉体、Ｙ₂Ｏ₃を含有するＺｒＯ₂（ＹＳＺ）粉末に、トルエン、Ｚｒ、Ｙを含む有機金属塩溶液を加えてスラリー化したものを準備する。
【００３９】
前記第１固体電解質成形体の作製と同様、成形し、例えば、厚さ１５μｍのシート状の第２固体電解質成形体を成形、乾燥する。この第２固体電解質成形体上に上記スラリーを印刷、乾燥した後、第１固体電解質仮焼体上に、第１燃料極成形体が形成された第２固体電解質成形体を、第１固体電解質仮焼体に第２固体電解質成形体が当接するように巻き付け、積層する。第１燃料極のスラリー塗布により、有機金属塩が第２固体電解質成形体側に沈降する。
【００４０】
次に、固体電解質成形体の調製同様、１００〜１２０μｍの厚さに成形した集電体成形体を所定箇所に貼り付ける。
【００４１】
この後、円筒状空気極仮焼体、Ｍｎ拡散防止層の塗布膜、第１固体電解質仮焼体、第２固体電解質成形体、第１燃料極成形体及び集電体成形体の積層体は、例えば、大気中１４００〜１５５０℃の温度で、４層同時に共焼成される。
【００４２】
次に、第２燃料極ペーストを作製する。所定比率に調製したＮｉ粉体、Ｙ₂Ｏ₃を含有するＺｒＯ₂（ＹＳＺ）粉体、Ｚｒ及びＹの有機金属塩に、トルエンを加えてスラリー化したものを準備する。
【００４３】
第２燃料極は、空気極、固体電解質、第１燃料極及び集電体を共焼結させた後に、第１燃料極の表面に第２燃料極のスラリーを塗布印刷し、乾燥して第２燃料極成形体を作製し、大気雰囲気下において１４００℃以下で熱処理（焼き付け）することにより行う。第２燃料極のスラリー塗布印刷により、有機金属塩が第１燃料極側に沈降する。
【００４４】
このように作製した第２燃料極は、膜の表面状態が優れ、また下地の第１燃料極との界面の接合状態も良好である。集電機能と併せ、部材間との構造的な安定性を図れるように第２燃料極を構成するＹＳＺの混在、混在比率の制御を行っているので、界面剥離、膜内部のクラック生成に伴う分極、実抵抗の増大を阻止でき、単セルで得た初期の高い出力密度を良好に集電でき、長時間にわたって維持できる。
【００４５】
尚、上記例では円筒状の固体電解質型燃料電池セルにおいて説明したが、平板型燃料電池セルであっても良い。
【００４６】
さらに、上記例では、空気極仮焼体、第１固体電解質仮焼体を形成した例について説明したが、これらが、空気極成形体、第１固体電解質成形体であっても良い。
【００４７】
本発明の燃料電池は、例えば、図４に示すように、反応容器５１内に、酸素含有ガス室仕切板５３、燃焼室仕切板５５、燃料ガス室仕切板５７を用いて酸素含有ガス室Ａ、燃焼室Ｂ、反応室Ｃ、燃料ガス室Ｄが形成されている。反応容器５１内には、上記した複数の有底筒状の固体電解質型燃料電池セル５９が収容されており、これらの固体電解質型燃料電池セル５９は、燃焼室仕切板５５に形成されたセル挿入孔６０に挿入固定されており、その開口部６１は燃焼室仕切板５５から燃焼室Ｂ内に突出しており、その内部には酸素含有ガス室仕切板５３に固定された酸素含有ガス導入管６３の一端が挿入されている。燃焼室仕切板５５には、余剰の未反応燃料ガスを反応室Ｃから燃焼室Ｂに排出するために、複数の排気孔６４が形成されており、燃料ガス室仕切板５７には、燃料ガス室Ｄから反応室Ｃ内に供給するための供給孔が形成されている。
【００４８】
また、反応容器５１には、例えば水素からなる燃料ガスを導入する燃料ガス導入口６５、例えば、空気を導入する酸素含有ガス導入口６７、燃焼室Ｂ内で燃焼したガスを排出するための排気口６９が形成されている。
【００４９】
このような固体電解質型燃料電池は、酸素含有ガス室Ａからの酸素含有ガス、例えば空気を、酸素含有ガス導入管６３を介して固体電解質型燃料電池セル５９内にそれぞれ供給し、かつ、燃料ガス室Ｄからの燃料ガスを複数の固体電解質型燃料電池セル５９間に供給し、反応室Ｃにて反応させ発電し、余剰の空気と未反応燃料ガスを燃焼室Ｂにて燃させ、燃焼したガスが排気口６９から外部に排出される。
【００５０】
尚、本発明の燃料電池は、上記した図４の燃料電池に限定されるものではなく、反応容器内に、上記した燃料電池セルを複数収容していれば良い。
【００５１】
【実施例】
円筒状の固体電解質型燃料電池セルを共焼結法により作製するため、まず円筒状の空気極仮焼体を以下の手順で作製した。市販の純度９９．９％以上のＬａ₂Ｏ₃、Ｙ₂Ｏ₃、ＣａＣＯ₃、Ｍｎ₂Ｏ₃を出発原料として、１５００℃で仮焼し、（Ｌａ_0.56Ｙ_0.14Ｃａ_0.3）_0.97ＭｎＯ₃を作製し、その後、４μｍの粒度に粉砕調整し、これを用いて、外径の異なる円筒形状の支持管を押出成形後、１２５０℃の条件で脱バイ、仮焼し、空気極仮焼体を作製した。
【００５２】
次に、Ｙ₂Ｏ₃を８モル％の割合で含有する平均粒径が１〜２μｍのＺｒＯ₂粉末を用いてスラリーを調製し、ドクターブレード法により厚さ１００μｍと厚さ１５μｍの第１及び２固体電解質成形体としてのシートを作製した。
【００５３】
次に、第１燃料極成形体の作製について説明する。平均粒径が０．５〜１．５μｍのＮｉ粉末に対し、Ｙ₂Ｏ₃を８モル％の割合で含有する平均粒径が０．６μｍのＺｒＯ₂（ＹＳＺ）粉末と、Ｚｒ、Ｙのそれぞれの有機金属塩を準備し、Ｎｉ／ＹＳＺ比率（重量分率）が６５／３５になるようにＹＳＺの粉末とＺｒ、Ｙのそれぞれの有機金属塩を調合し、スラリーを作製した。
【００５４】
その後、調製したスラリーを第２固体電解質成形体上に、３０μｍの厚さになるように全面に印刷し、その後乾燥し、第１燃料極成形体を第２固体電解質成形体上に形成した。
【００５５】
一方、第２燃料極成形体用のスラリーは、平均粒径が５〜１０μｍのＮｉ粉末に対し、Ｙ₂Ｏ₃を８モル％の割合で含有する平均粒径が０．６μｍのＺｒＯ₂（ＹＳＺ）粉末、及びＺｒ、Ｙのそれぞれの有機金属塩を準備し、Ｎｉ／ＹＳＺ比率（重量分率）が７２／２８になるように調合・混合し、スラリーを作製した。
【００５６】
次に、市販の純度９９．９％以上のＬａ₂Ｏ₃、Ｃｒ₂Ｏ₃、ＭｇＯを出発原料として、これをＬａ（Ｍｇ_0.3Ｃｒ_0.7）_0.97Ｏ₃の組成になるように秤量混合した後１５００℃で３時間仮焼粉砕し、この固溶体粉末を用いてスラリーを調製し、ドクターブレード法により厚さ１００μｍの集電体成形体を作製した。
【００５７】
Ｍｎ拡散防止層のペーストは、Ｙ₂Ｏ₃を８ｍｏｌ％含有するＺｒＯ₂粉末（８ＹＳＺ）と組成式（ＣｅＯ₂）０．７（Ｙ₂Ｏ₃）０．３で表わされるＹＤＣ粉末とを８ＹＳＺ：ＹＤＣ＝１：９（重量分率）になるように混合し、この混合粉末に溶媒としてトルエンを添加し作製した。
【００５８】
まず、前記空気極仮焼体に、Ｍｎ拡散防止層のペーストを塗布し、この塗布膜に、前記第１固体電解質成形体を、その両端部が開口するようにロール状に巻き付け１１５０℃で５時間の条件で仮焼した。仮焼後、第１固体電解質仮焼体の両端部間を空気極仮焼体を露出させるように円弧面状に研磨した。
【００５９】
次に、第１固体電解質仮焼体表面に、第２燃料極成形体が形成された第２固体電解質成形体を、第１固体電解質仮焼体と第２固体電解質成形体が当接するように積層し、乾燥した後、上記研磨面に集電体成形体を貼り付け、この後、大気中１５５０℃で３時間の条件で焼成を行い、共焼結体を５０本作製した。
【００６０】
この共焼結体の第１燃料極の表面に、第２燃料極をメッシュ製版を用いて印刷し、その後大気雰囲気下１４００℃、１時間の条件で熱処理して焼付けを行い、最大外径が４〜１５ｍｍのセルを作製した。
【００６１】
作製されたセルの第１、第２燃料極中のＮｉＯ粒子の平均粒径を求めた。作製した第２燃料極の評価は、走査型電子顕微鏡（ＳＥＭ）を用いて、端部の剥離有無の状況からセル５０本中の良品本数を算出し、製造歩留まりとして表１に記載した。
【００６２】
また、良好に作製されたセル１０本を用いて１０００℃でセルの内側に空気を、外側に水素を流し、出力値が安定した際の初期値と、１００時間保持後でそれぞれの性能を測定評価し、１００時間経過後に初期値の２／３以下に低下したセル本数を算出し、良品数を記載した。尚、表中の出力密度はセル１０本の平均値である。
これらの測定結果を表１に示す。尚、有機金属塩を用いて作製された第１、第２燃料極を走査型電子顕微鏡（ＳＥＭ）で観察したところ、ＮｉＯ粒子の表面に微粒子状の微粒セラミック粒子が存在していた。これらの微粒セラミック粒子は、第１、第２燃料極の下層に主に存在していた。一方、有機金属塩を用いないで作製された第１、第２燃料極中には、ＮｉＯ粒子の表面には微粒セラミック粒子は存在していなかった。
【００６３】
【表１】

【００６４】
表１より、本発明の試料では、外径が１０ｍｍよりも小さくなり、曲率が大きくなった場合においても、第１及び第２燃料極それぞれに有機金属塩を添加することによって、第１燃料極と第２燃料極の界面が強固に接合するとともに、第１燃料極と固体電解質との接合強度を向上でき、セルの製造時における歩留まりを向上できるとともに、出力密度の初期値が高く、しかも１００時間経過後においても殆ど出力密度は低下せず、出力密度が初期値の２／３以下に低下したセルはなく、高い出力密度を長期間維持できることが判る。
【００６５】
これに対して、第１燃料極のスラリー中に有機金属塩を添加しなかった試料Ｎｏ．１、５、９では、製造歩留まりは良好であるものの、初期における出力密度が低く、１００時間経過後において、出力密度が２／３以下に低下したセル本数が多かった。特にセル外径が小さくなる程、不良が多くなることが判る。この出力密度が減少したセルをＳＥＭで観察したところ、第１燃料極が固体電解質から一部剥離している箇所が見られた。
【００６６】
また、第２燃料極のスラリー中に有機金属塩を添加しなかった試料Ｎｏ．１０では、製造歩留まりが悪く、１００時間経過後の出力密度の低下率も大きかった。
【００６７】
【発明の効果】
以上詳述したように、本発明の固体電解質型燃料電池セルでは、第２燃料極を形成している鉄族金属粒子又は鉄族金属酸化物粒子の表面に存在する、膜状及び／又は微粒子状の微粒セラミック粒子が、第１燃料極内部のセラミック粒子の表面に結合一体化し、強固な界面を形成でき、第２燃料極の第１燃料極への接合強度を向上できるとともに、第１燃料極を形成している鉄族金属粒子又は鉄族金属酸化物粒子の表面に存在する、膜状及び／又は微粒子状の微粒セラミック粒子が、固体電解質内部のＺｒＯ₂粒子の表面に結合一体化し、強固な界面を形成でき、第１燃料極の固体電解質への接合強度を向上でき、長期間高い発電能力を有する固体電解質型燃料電池セルを得ることができる。
【図面の簡単な説明】
【図１】本発明の円筒状の固体電解質型燃料電池セルを示す断面図である。
【図２】図１の燃料極及びその近傍を拡大して示す断面図である。
【図３】図１の燃料極の一部を拡大して示す説明図である。
【図４】本発明の燃料電池を示す説明図である。
【図５】従来の円筒状の固体電解質型燃料電池セルを示す斜視図である。
【符号の説明】
３１・・・固体電解質
３２・・・空気極
３３・・・燃料極
３３ａ．．．第１燃料極
３３ｂ．．．第２燃料極
３５・・・集電体
４１・・・第１燃料極のセラミック粒子
４３．．．第２燃料極のセラミック粒子
４５・・・第１燃料極の鉄族金属粒子
４６・・・第２燃料極の鉄族金属粒子
４７・・・第１燃料極の微粒セラミック粒子
４８．．．第２燃料極の微粒セラミック粒子[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a solid oxide fuel cell及beauty fuel cells, in particular, on the surface of the air electrode, solid electrolyte, sequentially formed by laminating a fuel electrode, baked cathode, a solid electrolyte, a first anode at the same time it relates sintered solid oxide fuel cell及beauty fuel cells.
[0002]
[Prior art]
Conventionally, a solid oxide fuel cell has a high power generation efficiency because its operating temperature is as high as 900 to 1050 ° C., and is expected as a third generation power generation system.
[0003]
Generally, cylindrical and flat plate types are known as solid oxide fuel cells. The flat fuel cell has a feature that the power density per unit volume of power generation is high, but there are problems such as imperfect gas seal and non-uniform temperature distribution in the cell for practical use. On the other hand, the cylindrical fuel cell has the characteristics that although the power density is low, the cell has high mechanical strength and the temperature in the cell can be kept uniform. Both types of solid oxide fuel cells have been actively researched and developed taking advantage of their characteristics.
[0004]
As shown in FIG. 5, the cylindrical fuel battery cell is formed with a porous air electrode support tube 2 made of a LaMnO ₃ based material having an open porosity of about 30 to 40%, and Y ₂ O ₃ stabilized ZrO is formed on the surface thereof. _A solid electrolyte 3 made of 2 is formed, and a porous Ni-zirconia fuel electrode 4 is formed on this surface.
[0005]
In the fuel cell module, each single cell is connected via a LaCrO _{3 current} collector (interconnector) 5. Power generation is performed at a temperature of 1000 to 1050 ° C. by flowing air (oxygen) 6 inside the air electrode support tube 2 and flowing fuel (hydrogen) 7 outside.
[0006]
As a method of manufacturing the fuel cell as described above, in recent years, in order to simplify the cell manufacturing process and reduce the manufacturing cost, a so-called co-sintering method in which at least two of the constituent materials are simultaneously fired. Has been proposed. This co-sintering method is, for example, a method in which a solid electrolyte molded body and a current collector molded body are wound around a cylindrical air electrode molded body in a roll shape and fired simultaneously, and then a fuel electrode is formed on the surface of the solid electrolyte. is there. In order to simplify the process, a co-sintering method in which a fuel electrode molded body is further laminated on the surface of the solid electrolyte molded body and co-fired has been proposed.
[0007]
This co-sintering method is a very simple process and has a small number of manufacturing steps, and is advantageous in improving the yield during manufacturing of cells and reducing costs.
[0008]
[Problems to be solved by the invention]
The fuel electrode is composed mainly of metal particles, and has a coefficient of thermal expansion that is significantly different from that of air electrodes, solid electrolytes, and current collectors made of other ceramics. When the fuel electrode molded body is laminated and fired at the same time, peeling or cracking occurs unless the thickness of the fuel electrode molded body is reduced. Therefore, the thickness was set to 20 μm or less. A fuel electrode having a thickness of 20 μm or less has a high electric resistance, and cannot efficiently collect the generated current, resulting in a problem that power generation efficiency is lowered.
[0009]
In order to solve such a problem, the applicant of the present invention first laminated a solid electrolyte, a first fuel electrode, and a second fuel electrode on the surface of the air electrode in order. A solid oxide fuel cell was proposed in which the fuel electrode was co-fired and the second fuel electrode was baked onto the surface of the first fuel electrode.
[0010]
Here, the first fuel electrode is formed by laminating a sheet-shaped first fuel electrode molded body containing a metal powder (or metal oxide powder) and a ceramic powder on a solid electrolyte molded body, and an air electrode, a solid electrolyte, and a current collector. A paste made of metal powder (or metal oxide powder) and ceramic powder, and an organic metal salt containing an element constituting the ceramic is applied and baked on the surface of the first fuel electrode. Thus, the second fuel electrode was formed.
[0011]
In such a solid oxide fuel cell, the surface of the ZrO ₂ particles in the first fuel electrode, which is firmly bonded to the ZrO ₂ film constituting the solid electrolyte by high-temperature sintering, has a finer and submicron level. is sintered is deposited deposited ZrO ₂ fine particles (baking), ZrO ₂ fine particles present in the lower portion of the second fuel electrode is integrally bound with the ZrO ₂ grains of the first fuel electrode, it can form a strong interface.
[0012]
However, there is a problem that the bonding strength between the first fuel electrode formed by simultaneous firing and the solid electrolyte is still low. As a result, there is a problem that when the power is generated continuously for a long period of time, the first fuel electrode is easily separated from the solid electrolyte. In particular, in recent years, small-diameter cylindrical cells having a diameter of 10 mm or less have been used. Since such a small-diameter cell has a large curvature, excessive stress is generated in the first and second fuel electrodes. There is a problem that the first and second fuel electrodes are easily peeled off by long-term power generation.
[0013]
The present invention can solidify the junction interface between the first fuel electrode and the second fuel electrode, can effectively prevent the first fuel electrode from peeling off from the solid electrolyte, and can maintain high power generation capacity for a long period of time. and an object thereof is to provide a fuel cell及beauty fuel cells.
[0014]
The solid oxide fuel cell according to the present invention is a solid oxide fuel cell in which a fuel electrode is formed on one surface of the solid electrolyte and an air electrode is formed on the other surface, and the fuel electrode is formed on the surface of the solid electrolyte. the material constituting the first anode was made, as well as and a second fuel electrode made form the surface of the first anode, the solid electrolyte to the first anode and the second anode the ceramic particles and the iron group metal particles or iron group metal oxide particles are present consisting, and, on the surface before Kitetsu group metal particles or iron group metal oxide particles made of a material constituting the solid electrolyte, wherein and the particle size is small membranous and / or particulate fine ceramic particles are present from ceramic particles, wherein the fine ceramic particles of the first fuel electrode is present primarily the solid electrolyte side, said second anode Fine ceramic particles Characterized by predominantly present in the first fuel electrode side.
[0015]
In such a solid oxide fuel cell, the fine ceramic particles of the first fuel electrode are mainly present on the solid electrolyte side, and the fine ceramic particles of the second fuel electrode are mainly present on the first fuel electrode side. The film-like and / or fine-grain ZrO ₂ particles (fine ceramic particles) present on the surface of the iron group metal particles or iron group metal oxide particles constituting the second fuel electrode are the ZrO inside the first fuel electrode. Bonded and integrated with the surface of _two particles (ceramic particles) to form a strong interface, improving the bonding strength of the second fuel electrode to the first fuel electrode and, for example, the iron group metal constituting the first fuel electrode Film-like and / or fine-grained ZrO ₂ particles (fine ceramic particles) existing on the surface of the particles or iron group metal oxide particles are bonded and integrated with the surface of the ZrO ₂ particles inside the solid electrolyte, thereby providing a strong interface. Can be formed Can improve the bonding strength of the solid electrolyte of the first fuel electrode, it can maintain a high power generation capacity long time.
[0016]
In the present invention, the average particle diameter of the iron group metal particles or iron group metal oxide particles constituting the second fuel electrode is the average of the iron group metal particles or iron group metal oxide particles constituting the first fuel electrode. Desirably larger than the particle size. According to such a configuration, since the iron group metal particles or iron group metal oxide particles constituting the first fuel electrode are fine particles, a sufficient reaction field for forming a triple point can be secured, while the second fuel electrode is constituted. Since the iron group metal particles or iron group metal oxide particles are coarse particles, a porous structure can be secured, and in addition to the current collecting action, sufficient reduction for the electrode reaction and sufficient breathability of the generated water vapor gas are ensured. be able to.
[0017]
Furthermore, the solid oxide fuel cell of the present invention is preferably cylindrical with an outer diameter of 10 mm or less. In such a small-diameter cell, since the curvature is large, excessive stress is likely to be generated in the first fuel electrode and the second fuel electrode, the manufacturing yield at the time of manufacturing is reduced, and the first fuel is generated by long-term power generation. Since the electrode and the second fuel electrode tend to peel off, the use of the solid oxide fuel cell of the present invention is significant.
[0020]
The fuel cell of the present invention is one in which a plurality of the solid oxide fuel cells described above are accommodated in a reaction vessel.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
As shown in FIG. 1, the solid electrolyte fuel cell of the present invention has a cell body 34 formed by forming a cylindrical air electrode 32 on the inner surface of a solid electrolyte 31 and a fuel electrode 33 on the outer surface. A current collector (interconnector) 35 is electrically connected to 32.
[0022]
That is, a notch 36 is formed in a part of the solid electrolyte 31, and a part of the air electrode 32 formed on the inner surface of the solid electrolyte 31 is exposed, and the solid electrolyte near the exposed surface 37 and the notch 36. The surface of 31 is covered with a current collector 35, and the current collector 35 is joined to the surface of both ends of the solid electrolyte 31 and the surface of the air electrode 32 exposed from the notch 36 of the solid electrolyte 31.
[0023]
A current collector 35 that is electrically connected to the air electrode 32 is formed on the outer surface of the cell body 34 so as to cover both end surfaces of the solid electrolyte 31 formed in a continuous arc surface shape and the exposed surface 37. The fuel electrode 33 is not electrically connected.
[0024]
In the solid oxide fuel cell of the present invention, as shown in FIG. 2, the fuel electrode 33 includes a first fuel electrode 33a formed by simultaneous firing with the solid electrolyte 31, the air electrode 32, and the current collector 35; The second fuel electrode 33b is formed by baking on the surface of the first fuel electrode 33a. In these first fuel electrode 33a and second fuel electrode 33b, as shown in FIG. 3,

ceramic particles

41, 43 and iron group metal particles 45, 46 are formed on the surface of a film and / or fine particles of fine ceramic.

Particles

47 and 48 are precipitated.
[0025]
The film-like and / or fine-grained fine

ceramic particles

47 and 48 are preferably ZrO ₂ (YSZ) containing Y ₂ O ₃ in view of bonding with the ZrO ₂ -based material forming the solid electrolyte 31. The

ceramic particles

41 and 43 added from the viewpoint of improving the bonding strength with the solid electrolyte 31 are preferably ZrO ₂ (YSZ) containing Y ₂ O ₃ . Examples of the iron group metal particles 45 and 46 include Fe, Co, and Ni. Of these, Ni is desirable.
[0026]
Instead of the iron group metal particles 45 and 46, iron group metal oxide particles may be used. In this case, it becomes metal particles by being subjected to a reduction treatment after baking of the second fuel electrode 33b, or being exposed to a reducing atmosphere during power generation.
[0027]
The average particle diameter of the iron group metal particles 46 of the second fuel electrode 33b is larger than the average particle diameter of the iron group metal particles 45 of the first fuel electrode 33a. Thereby, in the first fuel electrode 33a, the number of reaction sites of the metal particles 45 can be sufficiently formed from the viewpoint of the number of reaction sites of the metal particles 45. On the other hand, since the average particle diameter of the metal particles 46 of the second fuel electrode 33b is larger than that of the first fuel electrode 33a, the current collecting ability can be improved, and not only the gas left for the reaction but also the permeation of the gas generated by the reaction The property can be kept good.
[0028]
The fine ceramic particles 47 of the first fuel electrode 33a are mainly present on the surface side of the solid electrolyte 31, and the fine ceramic particles 48 of the second fuel electrode 33b are mainly present on the surface side of the first fuel electrode 33a.
[0029]
The fine ceramic particles 47 present on the surface of the iron group metal particles 45 of the first fuel electrode 33a are bonded to the surface of the YSZ particles 49 constituting the solid electrolyte 31, and are formed on the surface of the iron group metal particles 46 of the second fuel electrode 33b. The existing fine ceramic particles 48 are bonded to the ceramic particles 41 in the first fuel electrode 33a. In the present invention, the

ceramic particles

41 and 43 have a particle size of 1 μm or more, and the fine

ceramic particles

47 and 48 have a particle size of 0.5 μm.
[0030]
The solid oxide fuel cell of the present invention has a cylindrical shape with an outer diameter of 10 mm or less. Since such a small-diameter cell has a large curvature, internal stress is likely to occur during molding or firing, and the first fuel electrode 33a and the second fuel electrode 33b tend to peel off. large. The case where the outer diameter is 5 mm or less is most effective. The cell outer diameter referred to in the present invention is the maximum cell outer diameter.
[0031]
As the solid electrolyte 31, for example, partially stabilized or stabilized ZrO ₂ containing _{3 to} 15 mol% of Y ₂ O ₃ is used. As the air electrode 32, for example, LaMnO _{3 in} which La is replaced by 10 to 30 atomic% with Ca or Sr and 5 to 20 atomic% with Y is used. As the current collector 35, for example, Cr is replaced with Mg. LaCrO ₃ substituted by 10 to 30 atomic% is used.
[0032]
As the first fuel electrode 33a and the second fuel electrode 33b, ZrO ₂ (containing Y ₂ O ₃ ) cermet containing 50 to 80 wt% Ni is preferably used.
[0033]
The solid electrolyte 31, the air electrode 32, the current collector 35, the first fuel electrode 33a, and the second fuel electrode 33b are not limited to the above-described examples, and known materials may be used.
[0034]
In the manufacturing method of the solid oxide fuel cell configured as described above, first, a cylindrical air electrode molded body is formed. In this cylindrical air electrode molded body, for example, raw materials of La ₂ O ₃ , Y ₂ O ₃ , CaCO ₃ and Mn ₂ O ₃ are weighed and mixed according to a predetermined preparation composition.
[0035]
Then, for example, it is calcined at a temperature of about 1500 ° C. for 2 to 10 hours, and then pulverized to a particle size of 4 to 8 μm. The prepared powder is mixed and kneaded with a binder to produce a cylindrical air electrode molded body by extrusion molding. Further, the binder is debindered and calcined at 1200 to 1250 ° C. A fired body is produced.
[0036]
Next, preparation of a paste for attaching the solid electrolyte molded body will be described. A paste having a function as a Mn diffusion preventing layer is a mixture calcined with ZrO ₂ powder containing at least one of Y ₂ O ₃ and CaO and YDC powder (CeO ₂ doped with 30% by weight of Y ₂ O ₃ ). Thereafter, toluene is added as a solvent to the above mixed powder whose particle size has been prepared. This paste was applied to the surface of a cylindrical air electrode calcined body to form a coating film for the Mn diffusion prevention layer.
[0037]
As a sheet-like first solid electrolyte molded body, a slurry obtained by adding toluene, a binder, and a commercially available dispersant to ZrO ₂ powder containing Y ₂ O ₃ to form a slurry, for example, 100 to 120 μm. The first solid electrolyte molded body is attached to the surface of the coating film of the Mn diffusion prevention layer formed on the surface of the cylindrical air electrode calcined body, calcined, and air A first solid electrolyte calcined body is formed on the surface of the electrode calcined body. In addition, although the 1st solid electrolyte molded object was calcined, it is not necessary to calcine.
[0038]
Next, a sheet-shaped first fuel electrode molded body is produced. First, for example, a slurry prepared by adding an organometallic salt solution containing toluene, Zr, and Y to a ZrO ₂ (YSZ) powder containing Ni powder and Y ₂ O ₃ prepared at a predetermined ratio is prepared.
[0039]
In the same manner as the production of the first solid electrolyte molded body, the molded body is molded. For example, a sheet-shaped second solid electrolyte molded body having a thickness of 15 μm is molded and dried. After the slurry is printed and dried on the second solid electrolyte molded body, the second solid electrolyte molded body in which the first fuel electrode molded body is formed on the first solid electrolyte calcined body is used as the first solid electrolyte. The calcined body is wound and laminated so that the second solid electrolyte molded body comes into contact therewith. By applying the slurry on the first fuel electrode, the organometallic salt settles on the second solid electrolyte molded body side.
[0040]
Next, as in the preparation of the solid electrolyte molded body, the current collector molded body molded to a thickness of 100 to 120 μm is attached to a predetermined location.
[0041]
After this, the laminated body of the cylindrical air electrode calcined body, the coating film of the Mn diffusion preventing layer, the first solid electrolyte calcined body, the second solid electrolyte molded body, the first fuel electrode molded body and the current collector molded body is For example, four layers are co-fired at a temperature of 1400 to 1550 ° C. in the air at the same time.
[0042]
Next, a second fuel electrode paste is produced. A slurry prepared by adding toluene to an Ni powder prepared at a predetermined ratio, a ZrO ₂ (YSZ) powder containing Y ₂ O ₃ , and an organometallic salt of Zr and Y is prepared.
[0043]
After the air electrode, the solid electrolyte, the first fuel electrode, and the current collector are co-sintered, the second fuel electrode is coated with a slurry of the second fuel electrode on the surface of the first fuel electrode, dried, and dried. A two-electrode assembly is prepared and heat-treated (baked) at 1400 ° C. or lower in an air atmosphere. By the slurry application printing of the second fuel electrode, the organometallic salt settles on the first fuel electrode side.
[0044]
The thus produced second fuel electrode has an excellent film surface state and a good bonding state at the interface with the underlying first fuel electrode. In addition to the current collecting function, the YSZ that constitutes the second fuel electrode is controlled and the mixing ratio is controlled so that structural stability between the members can be achieved. The increase in polarization and actual resistance can be prevented, the initial high power density obtained with a single cell can be collected well, and can be maintained for a long time.
[0045]
In the above example, the cylindrical solid electrolyte fuel cell has been described. However, a flat plate fuel cell may be used.
[0046]
Furthermore, although the example which formed the air electrode calcined body and the 1st solid electrolyte calcined body was demonstrated in the said example, these may be an air electrode molded object and a 1st solid electrolyte molded object.
[0047]
For example, as shown in FIG. 4, the fuel cell of the present invention includes an oxygen-containing gas chamber A using an oxygen-containing gas chamber partition plate 53, a combustion chamber partition plate 55, and a fuel gas chamber partition plate 57 in a reaction vessel 51. A combustion chamber B, a reaction chamber C, and a fuel gas chamber D are formed. A plurality of bottomed cylindrical solid oxide fuel cells 59 are accommodated in the reaction vessel 51, and these solid oxide fuel cells 59 are formed in the combustion chamber partition plate 55. The opening 61 is inserted and fixed in the insertion hole 60, and the opening 61 protrudes into the combustion chamber B from the combustion chamber partition plate 55, and an oxygen-containing gas introduction pipe fixed to the oxygen-containing gas chamber partition plate 53 is provided therein. One end of 63 is inserted. A plurality of exhaust holes 64 are formed in the combustion chamber partition plate 55 in order to discharge surplus unreacted fuel gas from the reaction chamber C to the combustion chamber B. The fuel gas chamber partition plate 57 includes a fuel gas. A supply hole for supplying the reaction chamber C from the chamber D into the reaction chamber C is formed.
[0048]
In addition, the reaction vessel 51 has, for example, a fuel gas inlet 65 for introducing a fuel gas made of hydrogen, for example, an oxygen-containing gas inlet 67 for introducing air, and an exhaust for discharging gas burned in the combustion chamber B. A mouth 69 is formed.
[0049]
Such a solid oxide fuel cell supplies an oxygen-containing gas from the oxygen-containing gas chamber A, for example, air, into the solid oxide fuel cell 59 via the oxygen-containing gas introduction pipe 63, and fuel. Fuel gas from the gas chamber D is supplied between the plurality of solid oxide fuel cells 59, reacted in the reaction chamber C to generate power, and surplus air and unreacted fuel gas are combusted in the combustion chamber B for combustion. The discharged gas is discharged from the exhaust port 69 to the outside.
[0050]
Note that the fuel cell of the present invention is not limited to the fuel cell of FIG. 4 described above, and it is sufficient that a plurality of the above-described fuel cells are accommodated in the reaction vessel.
[0051]
【Example】
In order to produce a cylindrical solid oxide fuel cell by a co-sintering method, a cylindrical air electrode calcined body was first produced by the following procedure. A commercially available La ₂ O ₃ , Y ₂ O ₃ , CaCO ₃ , Mn ₂ O ₃ with a purity of 99.9% or higher was calcined at 1500 ° C. and (La _0.56 Y _0.14 Ca _0.3 ) _0.97 MnO ₃ After that, after adjusting the pulverization to a particle size of 4 μm and using this, a cylindrical support tube having a different outer diameter is extruded and then deburied and calcined at 1250 ° C. Produced.
[0052]
Next, a slurry was prepared using a ZrO ₂ powder having an average particle diameter of 1 to ₂ μm containing Y ₂ O ₃ at a ratio of 8 mol%, and the first and the first 100 μm and 15 μm thick first and A sheet as a two-solid electrolyte molded body was produced.
[0053]
Next, production of the first fuel electrode molded body will be described. A ZrO ₂ (YSZ) powder having an average particle diameter of 0.6 μm containing Y ₂ O ₃ in a proportion of 8 mol% with respect to Ni powder having an average particle diameter of 0.5 to 1.5 μm; Each organometallic salt was prepared, and YSZ powder and each of the organometallic salts of Zr and Y were prepared so that the Ni / YSZ ratio (weight fraction) was 65/35 to prepare a slurry.
[0054]
Thereafter, the prepared slurry was printed on the entire surface of the second solid electrolyte molded body so as to have a thickness of 30 μm, and then dried to form a first fuel electrode molded body on the second solid electrolyte molded body.
[0055]
On the other hand, the slurry for the second fuel electrode molded body contains ZrO ₂ (average particle diameter of 0.6 μm) containing Y ₂ O ₃ at a ratio of 8 mol% with respect to Ni powder having an average particle diameter of 5 to 10 μm. YSZ) powder and organic metal salts of Zr and Y were prepared, and mixed and mixed so that the Ni / YSZ ratio (weight fraction) was 72/28 to prepare a slurry.
[0056]
Next, after commercially available La ₂ O ₃ , Cr ₂ O ₃ and MgO having a purity of 99.9% or more are used as starting materials, they are weighed and mixed so as to have a composition of La (Mg _0.3 Cr _0.7 ) _0.97 O _3. After calcining and pulverizing at 1500 ° C. for 3 hours, a slurry was prepared using this solid solution powder, and a current collector molded body having a thickness of 100 μm was prepared by a doctor blade method.
[0057]
Paste Mn diffusion preventing layer, 8YSZ and YDC powder represented by ZrO ₂ powder (8YSZ) and formula _{_{(CeO 2) 0.7 (Y 2}} O 3) 0.3 a Y ₂ O ₃ containing 8 mol% : YDC = 1: 9 (weight fraction) The mixture was prepared by adding toluene as a solvent to the mixed powder.
[0058]
First, a paste of an Mn diffusion preventing layer is applied to the air electrode calcined body, and the first solid electrolyte molded body is wound around the coating film in a roll shape so that both ends thereof are open. Calcination was performed under conditions of time. After the calcination, the first solid electrolyte calcined body was polished into an arcuate surface so that the air electrode calcined body was exposed between both ends.
[0059]
Next, the first solid electrolyte calcined body and the second solid electrolyte molded body are brought into contact with the second solid electrolyte molded body on which the second fuel electrode molded body is formed on the surface of the first solid electrolyte calcined body. After laminating and drying, the current collector molded body was attached to the polished surface, and then fired at 1550 ° C. in the atmosphere for 3 hours to prepare 50 co-sintered bodies.
[0060]
The second fuel electrode is printed on the surface of the first fuel electrode of the co-sintered body using a mesh plate making process, and then heat-treated and baked at 1400 ° C. for 1 hour in an air atmosphere. A 4-15 mm cell was produced.
[0061]
The average particle diameter of NiO particles in the first and second fuel electrodes of the produced cell was determined. Evaluation of the produced 2nd fuel electrode calculated | required the number of good products in 50 cells from the condition of the peeling presence or absence of the edge part using the scanning electron microscope (SEM), and described in Table 1 as a manufacturing yield.
[0062]
In addition, using 10 well-made cells, air was flown inside the cell at 1000 ° C., and hydrogen was flowed outside. The initial value when the output value was stabilized and the performance after holding for 100 hours were measured. Evaluation was made, the number of cells that had decreased to 2/3 or less of the initial value after 100 hours had elapsed was calculated, and the number of non-defective products was described. The power density in the table is an average value of 10 cells.
These measurement results are shown in Table 1. When the first and second fuel electrodes prepared using the organometallic salt were observed with a scanning electron microscope (SEM), finely divided fine ceramic particles were present on the surface of the NiO particles. These fine ceramic particles were mainly present in the lower layer of the first and second fuel electrodes. On the other hand, fine ceramic particles were not present on the surface of the NiO particles in the first and second fuel electrodes prepared without using the organic metal salt.
[0063]
[Table 1]

[0064]
From Table 1, in the sample of the present invention, even when the outer diameter is smaller than 10 mm and the curvature is increased, the first fuel electrode is added by adding the organometallic salt to each of the first and second fuel electrodes. The interface between the first fuel electrode and the second fuel electrode is firmly bonded, the bonding strength between the first fuel electrode and the solid electrolyte can be improved, the yield in manufacturing the cell can be improved, the initial value of the power density is high, and 100 It can be seen that even after the elapse of time, the output density hardly decreases, and there is no cell in which the output density is reduced to 2/3 or less of the initial value, and a high output density can be maintained for a long time.
[0065]
In contrast, Sample No. in which no organometallic salt was added to the slurry of the first fuel electrode. In 1, 5 and 9, although the production yield was good, the output density in the initial stage was low, and after 100 hours, the number of cells in which the output density decreased to 2/3 or less was large. In particular, it can be seen that the smaller the cell outer diameter, the more defects. When the cell with the reduced power density was observed with an SEM, a portion where the first fuel electrode was partially detached from the solid electrolyte was observed.
[0066]
Sample No. in which no organometallic salt was added to the slurry of the second fuel electrode was used. No. 10, the production yield was poor, and the rate of decrease in output density after 100 hours was large.
[0067]
【The invention's effect】
As described above in detail, in the solid oxide fuel cell of the present invention, the film and / or fine particles present on the surface of the iron group metal particles or iron group metal oxide particles forming the second fuel electrode. Shaped fine ceramic particles are bonded and integrated with the surface of the ceramic particles inside the first fuel electrode, a strong interface can be formed, the bonding strength of the second fuel electrode to the first fuel electrode can be improved, and the first fuel The film-like and / or fine-grained fine ceramic particles present on the surface of the iron group metal particles or iron group metal oxide particles forming the pole are bonded and integrated with the surface of the ZrO ₂ particles inside the solid electrolyte, A solid interface can be formed, the bonding strength of the first fuel electrode to the solid electrolyte can be improved, and a solid oxide fuel cell having a high power generation capacity for a long time can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a cylindrical solid oxide fuel cell of the present invention.
2 is an enlarged cross-sectional view showing a fuel electrode and its vicinity in FIG.
FIG. 3 is an explanatory view showing an enlarged part of the fuel electrode in FIG. 1;
FIG. 4 is an explanatory view showing a fuel cell of the present invention.
FIG. 5 is a perspective view showing a conventional cylindrical solid oxide fuel cell.
[Explanation of symbols]
31 ... Solid electrolyte 32 ... Air electrode 33 ... Fuel electrode 33a. . . First fuel electrode 33b. . . Second fuel electrode 35 ... current collector 41 ... first fuel electrode ceramic particles 43. . . Ceramic particles 45 of the second fuel electrode ... Iron group metal particles 46 of the first fuel electrode ... Iron group metal particles 47 of the second fuel electrode ... Fine ceramic particles 48 of the first fuel electrode 48. . . Fine ceramic particles of the second fuel electrode

Claims

A fuel electrode on one side of the solid electrolyte, an other by forming a cathode on a surface solid oxide fuel cell, a first fuel electrode the fuel electrode is made form the solid electrolyte surface, said as well as and a second fuel electrode made form the surface of the first fuel electrode, the ceramic particles and the iron group metal particles or iron of a material constituting the solid electrolyte to the first anode and the second anode there is a group metal oxide particles, and, on the surface before Kitetsu group metal particles or iron group metal oxide particles, wherein the solid electrolyte made membrane of a material constituting the membrane and the particle diameter is smaller than the ceramic particles / Or fine ceramic particles are present , the fine ceramic particles of the first fuel electrode are mainly present on the solid electrolyte side, and the fine ceramic particles of the second fuel electrode are mainly used for the first fuel. Exists on the extreme side Solid oxide fuel cell, characterized in that.

The average particle diameter of the iron group metal particles or iron group metal oxide particles constituting the second fuel electrode, than the average particle size of the iron group metal particles that make up the first fuel electrode or iron group metal oxide particles The solid oxide fuel cell according to claim 1, wherein

Claims fine ceramic particles of the first fuel electrode is bonded to the solid electrolyte surface, fine ceramic particles of the second fuel electrode, characterized in that it is bonded to the ceramic particles in the first fuel electrode 3. The solid oxide fuel cell according to 1 or 2 .

The solid oxide fuel cell according to any one of claims 1 to 3 , wherein the solid electrolyte fuel cell has an outer diameter of 10 mm or less.

A fuel cell comprising a plurality of solid oxide fuel cells according to any one of claims 1 to 4 in a reaction vessel.