JP2005026055A

JP2005026055A - Composite electrode for fuel cell, and solid electrolyte fuel cell

Info

Publication number: JP2005026055A
Application number: JP2003189982A
Authority: JP
Inventors: Hiromi Sugimoto; 博美杉本; Itaru Shibata; 格柴田; Mitsugi Yamanaka; 貢山中
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 2003-07-02
Filing date: 2003-07-02
Publication date: 2005-01-27

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite electrode for a fuel cell possible to be easily manufactured in the low-temperature condition, facilitated in structure control and having many three-phase interfaces, and to provide a manufacturing method thereof and a solid electrolyte fuel cell using the same. <P>SOLUTION: This composite electrode for a fuel cell is formed by coating a porous electrode substrate with a second component by a chemical solution method. The porous electrode substrate as a first component has an opening part, and narrow holes having a mean narrow hole diameter of 500 μm or less, and the second component is coated on the porous electrode substrate in thickness of 0.01-10 μm. The porous electrode substrate as the first component is coated with a solution containing the second component or a precursor of the second component to act on each other, and a metal layer or a metal oxide layer is formed to form the composite electrode for a fuel cell. The solid electrolyte fuel cell uses this composite electrode for a fuel cell. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、燃料電池用複合電極、その製造方法及び固体電解質型燃料電池に係り、更に詳細には、２つの主成分から成り、構造を容易に制御できる燃料電池用複合電極、その製造方法及び固体電解質型燃料電池に関する。
【０００２】
【従来の技術及び発明が解決しようとする課題】
従来から、化学エネルギーを電気化学的な反応により電気エネルギーに変換する装置として、固体酸化物形燃料電池（ＳＯＦＣ）が知られている。このＳＯＦＣは、燃料極、固体電解質及び空気極の各層を互いに積層した３層を燃料電池の発電部とし、外部から燃料極には水素、炭化水素等の燃料ガスを供給し、空気極には空気等の酸化剤ガスを供給して電気を発生させる。
【０００３】
また、ＳＯＦＣにおいて、電極性能を向上させる技術として、粒子内の構造をミクロに制御したサーメット粉体の製造方法が提案されている。この製造方法は、図８に示すように、２種類以上の微粒子で電極を構成し、このうち１種類を外周部に偏在させること、また、ミスト状の原料を乾燥させ熱分解により反応させること、を特徴とする（例えば、特許文献１参照。）。
【０００４】
【特許文献１】
特開平９−３０９７６８号公報
【０００５】
更に、図９に示すように、多孔質酸化物粉体（ＹＳＺ等）に金属塩水溶液を含浸、熱処理し、表面に金属が担持された粒子を成型・焼成して電極とすることが提案されている。（例えば、特許文献２参照。）。
【０００６】
【特許文献２】
特開平１０−１４４３３７号公報
【０００７】
しかし、作製された粉体を粉砕・スラリー化して焼成するので、２段階の焼成工程が必要となる、また、ミクロ構造制御したサーメット粉体を粉砕・混合する際に解砕してしまい、焼成後に所望の構造が得られないことがある、という問題点があった。
【０００８】
更にまた、発泡剤を用いて多孔化した酸化物多孔質電極基体に粉体スラリーを含浸させてコーティングする方法が提案されている。この方法では、図１０に示すように、骨格を発泡体で形成し、スラリー状の粉体を塗布して焼成することで、空間部の内壁まで粒子を被覆する（例えば、特許文献３参照。）。
【０００９】
【特許文献３】
特開２０００−２００６１４号公報
【００１０】
しかしながら、粉体スラリーを塗布するためには、ある程度以上の開口径を有するが多孔質電極基体を使用しなければならない、また、粉体塗布後に焼成工程が必要であるため、基体材料が限定される、という問題点があった。
【００１１】
本発明は、このような従来技術の有する課題に鑑みてなされたものであり、その目的とするところは、低温下で簡略に製造でき、構造制御が容易で、多くの三相界面を有する燃料電池用複合電極、その製造方法及び固体電解質型燃料電池を提供することにある。
【００１２】
【課題を解決するための手段】
本発明者らは、上記課題を解決すべく鋭意検討を重ねた結果、化学溶液を用いて第１成分の有する細孔内に第２成分を浸入させること、第１成分として所定の細孔径を有するものを使用することにより、上記課題が解決できることを見出し、本発明を完成するに至った。
【００１３】
【発明の実施の形態】
以下、本発明の燃料電池用複合電極について詳細に説明する。なお、本明細書において、「％」は特記しない限り質量百分率を示す。
また、説明の便宜上、基体や電極などの一方の面を「表面」、他の面を「裏面」などと記載するが、これらは等価な要素であり、相互に置換した構成も本発明の範囲に含まれるのは言うまでもない。
【００１４】
上述の如く、本発明の燃料電池用複合電極は、第１成分として用いる多孔質電極基体に第２成分を被覆して成る。
具体的には、多孔質電極基体の表面、裏面のいずれか一方又は双方と、この表面、裏面のいずれか一方又は双方に開口部を有する細孔に、第２成分を化学溶液法（ＣＳＤ法）により被覆して得られる。
ここで、「化学溶液法」とは、出発原料として被覆成分を含む溶液状の薬剤を基体に被覆し、加熱その他の手段で反応を進行させることにより、所望の成分より成る被覆層を形成する方法を示す。例えば、熱スプレー分解法（ＳＰＤ法）により第２成分又はその前駆物質を被覆すると同時に反応させることで、多孔質電極基体の細孔内まで第２成分から成る薄膜を形成でき、更にこの表面にも連続して電極層又は電解質層を形成できるので、工程が簡略化できるとともに、分子レベルで連続的に機能や構造を傾斜させて燃料電池を作製できる。
【００１５】
このように、本発明では第２成分又はその前駆物質を溶液状にして被覆するので、多孔質電極基体の細孔内まで第２成分が侵入し、第２成分の被覆面積が増大する。言い換えれば、多孔質電極基体に流通させるガスが接触する部分の多くに所望の第２成分を被覆できる。また、ミクロな構造制御が可能となるので、電極性能に重要な三相界面が増大する等、燃料電池の性能が向上する。更に、通常は２種成分を粉体で混合する場合は、それぞれの粉体を製造した後に混合するが、ＣＳＤ法を使用することによりかかる工程が簡略化される。
【００１６】
また、本発明の燃料電池用複合電極は、表面、裏面のいずれか一方又は双方に開口部を有し平均細孔径が５００μｍ以下の細孔を有する多孔質電極基体を用いる。また、この多孔質電極基体の表面、裏面のいずれか一方又は双方と細孔内に第２成分を０．０１〜１０μｍの厚さで被覆して成る。これより、多孔質電極基体に流通するガスと第２成分との接触頻度が高められるため３相界面が増大し、優れた電極性能を発揮させ得る。平均細孔径が５００μｍを超えると、三相界面が減少し電極としての性能を発揮できない。また、第２成分の被覆厚が上記範囲から外れると、ガス透過能が低下したり、剥離が起こったりして電池性能が低下する。また、上記平均細孔径は１００μｍ以下であることがより好適である。
なお、上記「細孔」とは、ガス透過体である多孔質電極基体においてガスと接触可能な基体内部空間を示す。例えば、多孔質電極基体が粉末焼結体の場合は、粒子間の空隙、造孔剤等で作った空間部などを含み、多孔質電極基体が金属繊維の場合は、繊維間の空間部をいう。また、「平均細孔径」とは、多孔質電極基体を光学顕微鏡又はＳＥＭ等で、同一視野の中に１０個以上の空間部が点在する倍率で観察し、空間部の隔壁間サイズ平均を算出するものとする。
【００１７】
また、上記多孔質電極基体としては、所定の細孔を有する種々の材料を選択でき、例えば、粉体状、薄膜状及び板状などの形状で使用できる。
代表的には、厚さが１μｍ〜２ｍｍである電極材料焼結体、具体的には、Ｎｉ、Ｐｔ、ＮｉＯ、Ｓｍ添加セリア（ＳＤＣ）、Ｙ添加安定化ジルコニア（ＹＳＺ）、Ｓｃ添加安定化ジルコニア（ＳＳＺ）、Ｓｒ添加ランタンコバルト酸化物（ＬＳＣ）、Ｓｒ添加ランタンマンガン酸化物（ＬＳＭ）、Ｓｒ添加Ｓｍコバルト酸化物（ＳＳＣ）等の酸化物や金属粉体を塗布させたもの、又は成型後に焼結させたものを使用できる。なお、厚さが１μｍ未満であると、第２成分が電極基体（第１成分）層を完全に覆ってしまい、三相界面が得られないことがある。また、２ｍｍを超えると燃料電池全体の重量・体積が増加し、小型軽量化が困難となり易い。より好ましくは５μｍ〜１ｍｍとするのが良い。
【００１８】
また、厚さが０．０５ｍｍ〜２ｍｍである多孔質金属、即ちそれ自体がガス透過性を有する金属基板を使用できる。具体的には、金属を繊維状にして接着した不織布、メッシュ状金属、発泡状金属及びスルーホール金属板等が挙げられる。厚さが０．０５ｍｍ未満であると、支持体としての強度を保持することが困難であり、２ｍｍを超えると燃料電池全体の重量・体積が増加し、小型軽量化が困難となり易い。
【００１９】
更に、Ｎｉ、Ｃｕ、ＳＵＳ及びインコネル等の金属から成り、エッチング加工やＥＢパンチング加工等により穿孔して得られるスルーホール金属板の貫通孔（孔径０．１〜１ｍｍ程度）に電極材料粉体（電解質材料、燃料極材料又は空気極材料）を充填して得られるガス透過性電極基体も使用できる。このときはより三相界面を増大させ得る。なお、上記孔径を有するメッシュ金属や発泡金属などに電極材料粉体を充填することもできる。
【００２０】
一方、上記第２成分としては、イオン導電性、混合導電性のいずれか一方又は双方を有する酸化物などが挙げられる。これより、電極層及び電解質層を連続的に形成して三相界面を増大させ得るので、燃料電池の性能を向上できる。また、第１成分（被覆される基板など）として、単一材の金属基板が使用できるので安価に製造できる。更に、金属成分を骨格とするときは、集電体の機能を付与できるので、小型化・薄膜化を実現できる。
【００２１】
具体的には、上記酸化物としては、化学溶液法で得られる酸素イオン伝導性材料、例えば、安定化ジルコニア、セリア固溶体、酸化ビスマス固溶体又はぺロブスカイト、及びこれらの任意の組合せに係るものを使用できる。上記安定化ジルコニア、セリア（ＣｅＯ_２）系固溶体、酸化ビスマス固溶体は、酸化サマリウム（Ｓｍ_２Ｏ_３）、酸化ガドリニウム（Ｇｄ_２Ｏ_３）、酸化ネオウジム（Ｎｄ_２Ｏ_３）、イットリア（Ｙ_２Ｏ_３）又は酸化スカンジウム（Ｓｃ_２Ｏ_３）、及びこれらの任意の組合せに係るものを固溶して成り、上記ペロブスカイトは、ランタンガリウム（ＬａＧａ）にＳｒ、Ｍｎ等を固溶して成る。
更に、ランタンコバルト系酸化物（Ｌａ_１−ｘＳｒ_ｘＣｏＯ_３など）やランタンマンガン系酸化物（Ｌａ_１−ｘＳｒ_ｘＭｎＯ_３など）又はランタン鉄系酸化物、及びこれらを任意に組合わせたものを空気極材料として使用できる。
【００２２】
また、上記第２成分としては、金属、金属酸化物のいずれか一方又は双方を使用することもできる。これより、ＳＯＦＣ等の高温作動させるデバイスに使用するときは、電解質材料と同一材料で骨格を形成後に、金属等の第２成分を添加して、熱膨張係数を合わせることができ、熱サイクルによる熱衝撃等を有効に軽減できる。
具体的には、ニッケル（Ｎｉ）、白金（Ｐｔ）、パラジウム（Ｐｄ）、ルテニウム（Ｒｕ）、コバルト（Ｃｏ）、モリブデン（Ｍｏ）、タングステン（Ｗ）、鉄（Ｆｅ）、銅（Ｃｕ）、銀（Ａｇ）又はクロム（Ｃｒ）、及びこれらの任意の組合せに係るものを含むことが好適である。
更に、上記金属や金属酸化物は、その前駆体である、金属アルコキシド、金属アセチルアセトナート、金属酢酸塩、シュウ酸塩等のカルボン酸塩、ナフテン酸塩、オクチル酸塩、金属硝酸塩、塩化物、オキシ塩化物又は酸化物微粒子、及びこれらの任意の組合せに係るものを含む溶液を、加熱などにより反応させて得ることができる。
【００２３】
次に、本発明の燃料電池用複合電極の製造方法について詳細に説明する。
まず、第１成分として、上述した電極材料などで構成される多孔質電極基体を用意する。次いで、この多孔質電極基体の表面、裏面のいずれか一方又は双方と、この表面、裏面のいずれか一方又は双方に開口部を有する細孔に、第２成分、この前駆体のいずれか一方又は双方を含む溶液を被覆する。その後、被覆した溶液を反応させて金属層又は金属酸化物層を形成して、燃料電池用複合電極とする。
【００２４】
このとき、上記金属層又は金属酸化物層は、金属アルコキシド、金属アセチルアセトナート、金属酢酸塩、シュウ酸塩等のカルボン酸塩、ナフテン酸塩、オクチル酸塩、金属硝酸塩、塩化物、オキシ塩化物又は酸化物微粒子、及びこれらの任意の組合せに係るものを含む溶液を用いて形成することが好適である。
また、上記被覆工程においては、スピンコート法、ディッピング法、スプレー法、熱スプレー分解法、ポッティング法又は刷毛塗り法、及びこれらを任意に組合せることが、工程簡略化、量産化の観点から好適である。
このように、本発明では、低温下で簡略に燃料電池用複合電極を製造できる。また、図１１に示すように第１成分や第２成分を適宜選択することで、容易に構造を制御でき、多くの三相界面を有する燃料電池用複合電極が得られる。
【００２５】
次に、本発明の固体酸化物形燃料電池について詳細に説明する。
かかる燃料電池は、上述の燃料電池用複合電極を用い、従来の製法より低温で燃料電池を作製できるので、選択できる材料種が大幅に増大し、安価な材料を適宜使用することで低コスト化が可能となる。また、全体を薄膜化できるので、電池の内部抵抗が低減し、高出力、また低温作動型のＳＯＦＣ設計が可能となる。更に、三相界面が多数点在することより電極反応が大幅に向上する。例えば、図１２に示すような燃料電池スタックが挙げられる。
【００２６】
【実施例】
以下、本発明を実施例及び比較例により更に詳細に説明するが、本発明はこれら実施例に限定されるものではない。
【００２７】
（実施例１）
多孔質金属基体として、厚さ０．１ｍｍ、開孔径０．１ｍｍ（開孔率７０％）のＳＵＳ３０４をケミカルエッチングにて作製した。次いで、この多孔質金属基体の穿孔部にＮｉ−Ｂ（ボロン）粉末を充填し６００℃で焼結させた。このときの多孔質金属基体の気孔率は３０％であった。
また、Ｎｉ充填後の多孔質金属基体に、Ｙ添加安定化ジルコニア（以下「ＹＳＺ」とする）原料として、アセチルアセトンジルコニア＋塩化イットリウムブチルカルビトール溶液（８ｍｏｌ％Ｙ_２Ｏ_３に調製）を基板加熱３００℃で熱スプレー分解法にて被覆し、厚さ５０ｎｍのＣＳＤ層を形成し、燃料電池用複合電極を得た。
得られた燃料電池用複合電極に、電解質層及び電極層を被覆し、燃料電池用単セルを得た。この詳細を表１に、概略図を図１に示す。
【００２８】
（実施例２）
Ｎｉの周囲に、多孔質電極基体として、ＹＳＺ粉末を１２００℃で焼結させて、厚さ５μｍ、気孔率３０％のＹＳＺ層を作製した。次いで、この周囲にＮｉ原料として硝酸ニッケル水溶液をスプレー法にて被覆し７００℃に加熱して反応させ、厚さ５０ｎｍのＣＳＤ層を形成し、燃料電池用複合電極を得た。このときのＳＥＭ写真を図２及び図３に示す。
得られた燃料電池用複合電極に、電解質層及び電極層を積層し、燃料電池用単セルを得た。この詳細を表１に、概略図を図４に示す。
【００２９】
（実施例３）
多孔質電極基体として、ＹＳＺグリーンシートを１２００℃で焼結させて、厚さ１ｍｍ、気孔率３０％のＹＳＺ層を作製した。次いで、この上にＳｒ添加コバルト酸化物（以下「ＬＳＣ」とする）原料として、Ｌａ_２Ｏ_３、ＣｏＯ_３、ＳｒＣＯ_３の硝酸水溶液（（Ｌａ_０．８Ｓｒ_０．２）_０．９ＣｏＯ_３に調製）をスピンコート法にて被覆し８００℃に加熱して反応させ、厚さ１００ｎｍのＣＳＤ層を形成し、燃料電池用複合電極を得た。
得られた燃料電池用複合電極に、電解質層及び電極層を被覆し、燃料電池用単セルを得た。この詳細を表１に、概略図を図５に示す。
【００３０】
（実施例４）
多孔質電極基体として、厚さ２５０μｍ、気孔率７０％のＳＵＳ３０４不織布を用意した。次いで、この上にＳｍ添加セリア（以下「ＳＤＣ」とする）原料として、ＣｅＯ_２、Ｓｍ_２Ｏ_３の硝酸水溶液（Ｃｅ_０．８Ｓｍ_０．２Ｏ_１．９に調製）を５００℃でディッピング法にて被覆し、厚さ１００ｎｍのＣＳＤ層を形成し、燃料電池用複合電極を得た。
得られた燃料電池用複合電極に、電解質層及び電極層を積層し、燃料電池用単セルを得た。この詳細を表１に、概略図を図６に示す。
【００３１】
（比較例１）
多孔質電極基体として、ＮｉＯ粉末を１２００℃で焼結させて、厚さ２０μｍ、気孔率３０％のＮｉＯ層を得た。次いで、この上に電解質層及び電極層を積層し、燃料電池用単セルを得た。この詳細を表１に、概略図を図７に示す。
【００３２】
【表１】

【００３３】
＜評価試験方法＞
実施例１〜４及び比較例１で得られた燃料電池用単セルを還元雰囲気にて１０００℃に保温した炉内に、１０時間保持することにより耐久試験を行った。
【００３４】
実施例１〜４で得られた燃料電池用単セルは、本発明の好適形態である材料を使用して成るため、長時間高温で使用した場合でもシンタリングが発生しにくいことがわかった。
一方、比較例１で得られた燃料電池用単セルは、ＣＳＤ層を設けていないため、長期間加熱されるとＮｉＯの焼結が進行し、性能が劣化することがわかった。
【００３５】
【発明の効果】
以上説明してきたように、本発明によれば、化学溶液を用いて第１成分の有する細孔内に第２成分を浸入させること、第１成分として所定の細孔径を有するものを使用することとしたため、低温下で簡略に製造でき、構造制御が容易で、多くの三相界面を有する燃料電池用複合電極、その製造方法及び固体電解質型燃料電池を提供することができる。
【図面の簡単な説明】
【図１】実施例１で得られた燃料電池用単セルを示す概略図である。
【図２】実施例２で用いた燃料電池用複合電極の正面断面を示すＳＥＭ写真である。
【図３】実施例２で用いた燃料電池用複合電極の側面端部を示すＳＥＭ写真である。
【図４】実施例２で得られた燃料電池用単セルを示す概略図である。
【図５】実施例３で得られた燃料電池用単セルを示す概略図である。
【図６】実施例４で得られた燃料電池用単セルを示す概略図である。
【図７】比較例１で得られた燃料電池用単セルを示す概略図である。
【図８】従来の電極材料の一例を示す概略図である。
【図９】従来の電極材料の他の例を示す概略図である。
【図１０】従来の電極材料の更に他の例を示す概略図である。
【図１１】第１成分及び第２成分の一例を示す概略図である。
【図１２】燃料電池スタックの一例を示す概略図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a composite electrode for a fuel cell, a method for producing the same, and a solid oxide fuel cell, and more specifically, a composite electrode for a fuel cell comprising two main components and capable of easily controlling the structure, a method for producing the same, and The present invention relates to a solid oxide fuel cell.
[0002]
[Prior art and problems to be solved by the invention]
Conventionally, a solid oxide fuel cell (SOFC) is known as a device that converts chemical energy into electrical energy by an electrochemical reaction. This SOFC uses a fuel cell, a solid electrolyte, and an air electrode layered together as a power generation part of a fuel cell. Fuel gas such as hydrogen and hydrocarbon is supplied to the fuel electrode from the outside, and the air electrode is supplied to the air electrode. Electricity is generated by supplying an oxidant gas such as air.
[0003]
Also, in SOFC, as a technique for improving electrode performance, a method for producing a cermet powder in which the structure inside the particles is controlled to be microscopically has been proposed. In this manufacturing method, as shown in FIG. 8, an electrode is composed of two or more kinds of fine particles, one of which is unevenly distributed in the outer periphery, and a mist-like raw material is dried and reacted by thermal decomposition. (For example, refer to Patent Document 1).
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 9-309768
Furthermore, as shown in FIG. 9, it has been proposed to impregnate a porous oxide powder (YSZ or the like) with an aqueous metal salt solution, heat-treat, and mold and sinter particles carrying the metal on the surface to form an electrode. ing. (For example, refer to Patent Document 2).
[0006]
[Patent Document 2]
Japanese Patent Laid-Open No. 10-144337
However, since the produced powder is pulverized / slurried and fired, a two-step firing process is required, and when the microstructured cermet powder is pulverized / mixed, it is crushed and fired. There was a problem that a desired structure could not be obtained later.
[0008]
Furthermore, a method has been proposed in which a porous oxide electrode substrate porous with a foaming agent is impregnated with a powder slurry and coated. In this method, as shown in FIG. 10, the skeleton is formed of a foam, and the particles are covered to the inner wall of the space portion by applying and baking slurry-like powder (see, for example, Patent Document 3). ).
[0009]
[Patent Document 3]
[Patent Document 1] Japanese Patent Laid-Open No. 2000-200614
However, in order to apply the powder slurry, a porous electrode substrate must be used although it has an opening diameter of a certain degree or more, and since a baking process is necessary after the powder application, the substrate material is limited. There was a problem that.
[0011]
The present invention has been made in view of such problems of the prior art. The object of the present invention is to provide a fuel that can be simply manufactured at low temperature, has an easy structure control, and has many three-phase interfaces. The object is to provide a composite electrode for a battery, a method for producing the same, and a solid oxide fuel cell.
[0012]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have made a second pore penetrate into the pores of the first component using a chemical solution, and have a predetermined pore diameter as the first component. By using what has, it discovered that the said subject could be solved and came to complete this invention.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the composite electrode for a fuel cell of the present invention will be described in detail. In the present specification, “%” indicates a mass percentage unless otherwise specified.
Further, for convenience of explanation, one surface of the substrate or the electrode is described as “front surface”, and the other surface is described as “rear surface”. However, these are equivalent elements, and the configurations substituted for each other are also within the scope of the present invention. It goes without saying that it is included in
[0014]
As described above, the composite electrode for a fuel cell according to the present invention is formed by coating the second component on the porous electrode substrate used as the first component.
Specifically, the second component is added to a chemical solution method (CSD method) in pores having openings on either or both of the front and back surfaces of the porous electrode substrate and on either or both of the front and back surfaces. ) To obtain.
Here, the “chemical solution method” is to form a coating layer composed of a desired component by coating a substrate with a solution-like drug containing a coating component as a starting material and causing the reaction to proceed by heating or other means. The method is shown. For example, a thin film comprising the second component can be formed into the pores of the porous electrode substrate by coating and reacting with the second component or its precursor by the thermal spray decomposition method (SPD method). In addition, since the electrode layer or the electrolyte layer can be continuously formed, the process can be simplified, and the fuel cell can be manufactured by continuously inclining the function and structure at the molecular level.
[0015]
Thus, in the present invention, since the second component or its precursor is coated in the form of a solution, the second component penetrates into the pores of the porous electrode substrate, and the coating area of the second component increases. In other words, a desired second component can be coated on many of the portions that are in contact with the gas flowing through the porous electrode substrate. In addition, since the micro structure can be controlled, the performance of the fuel cell is improved such that the three-phase interface important for the electrode performance is increased. In addition, when two kinds of components are usually mixed with powder, they are mixed after the respective powders are manufactured. However, the use of the CSD method simplifies such a process.
[0016]
The composite electrode for a fuel cell of the present invention uses a porous electrode substrate having openings on one or both of the front surface and the back surface and having pores with an average pore diameter of 500 μm or less. The porous electrode substrate is formed by coating the second component with a thickness of 0.01 to 10 [mu] m on one or both of the front and back surfaces and the pores. As a result, the contact frequency between the gas flowing through the porous electrode substrate and the second component is increased, so that the three-phase interface is increased and excellent electrode performance can be exhibited. When the average pore diameter exceeds 500 μm, the three-phase interface decreases and the performance as an electrode cannot be exhibited. On the other hand, if the coating thickness of the second component is out of the above range, the gas permeation ability is reduced or peeling occurs, resulting in a decrease in battery performance. The average pore diameter is more preferably 100 μm or less.
The “pore” refers to the internal space of the substrate that can contact the gas in the porous electrode substrate that is a gas permeable material. For example, when the porous electrode substrate is a powder sintered body, it includes voids between particles, spaces formed by a pore-forming agent, etc., and when the porous electrode substrate is metal fibers, the spaces between the fibers are included. Say. The “average pore diameter” means that the porous electrode substrate is observed with an optical microscope or SEM at a magnification at which 10 or more space portions are scattered in the same field of view, and the average size between the partition walls in the space portion is calculated. It shall be calculated.
[0017]
Further, as the porous electrode substrate, various materials having predetermined pores can be selected. For example, the porous electrode substrate can be used in the form of powder, thin film or plate.
Typically, an electrode material sintered body having a thickness of 1 μm to 2 mm, specifically, Ni, Pt, NiO, Sm-added ceria (SDC), Y-added stabilized zirconia (YSZ), and Sc-added stabilized Zirconia (SSZ), Sr-added lanthanum cobalt oxide (LSC), Sr-added lanthanum manganese oxide (LSM), Sr-added Sm cobalt oxide (SSC), etc. What was sintered later can be used. If the thickness is less than 1 μm, the second component may completely cover the electrode substrate (first component) layer, and a three-phase interface may not be obtained. On the other hand, if it exceeds 2 mm, the weight and volume of the entire fuel cell increase, and it is difficult to reduce the size and weight. More preferably, the thickness is 5 μm to 1 mm.
[0018]
Also, a porous metal having a thickness of 0.05 mm to 2 mm, that is, a metal substrate that itself has gas permeability can be used. Specifically, a nonwoven fabric, a mesh-like metal, a foam-like metal, a through-hole metal plate, and the like obtained by bonding a metal in a fibrous form can be used. If the thickness is less than 0.05 mm, it is difficult to maintain the strength as a support, and if it exceeds 2 mm, the weight and volume of the entire fuel cell increase, and it is difficult to reduce the size and weight.
[0019]
Furthermore, the electrode material powder (through the hole diameter of about 0.1 to 1 mm) made of a metal such as Ni, Cu, SUS, and Inconel, is obtained by drilling by etching or EB punching. A gas-permeable electrode substrate obtained by filling an electrolyte material, a fuel electrode material, or an air electrode material can also be used. At this time, the three-phase interface can be further increased. It is also possible to fill the electrode material powder with a mesh metal or foam metal having the above pore diameter.
[0020]
On the other hand, examples of the second component include oxides having one or both of ionic conductivity and mixed conductivity. Thus, the electrode layer and the electrolyte layer can be continuously formed to increase the three-phase interface, so that the performance of the fuel cell can be improved. Further, since a single metal substrate can be used as the first component (substrate to be coated, etc.), it can be manufactured at low cost. Furthermore, when the metal component is used as a skeleton, the function of the current collector can be imparted, so that downsizing and thinning can be realized.
[0021]
Specifically, as the oxide, an oxygen ion conductive material obtained by a chemical solution method, for example, a stabilized zirconia, a ceria solid solution, a bismuth oxide solid solution or a perovskite, and any combination thereof is used. it can. The stabilized zirconia, ceria (CeO ₂ ) -based solid solution, and bismuth oxide solid solution are samarium oxide (Sm ₂ O ₃ ), gadolinium oxide (Gd ₂ O ₃ ), neodymium oxide (Nd ₂ O ₃ ), yttria (Y ₂ O ₃ ) or scandium oxide (Sc ₂ O ₃ ) and any combination thereof. The perovskite is formed by dissolving Sr, Mn, etc. in lanthanum gallium (LaGa).
Furthermore, lanthanum cobalt-based oxides (La _1-x Sr _x CoO ₃ etc.), lanthanum manganese-based oxides (La _1-x Sr _x MnO ₃ etc.) or lanthanum iron-based oxides, and any combination thereof Can be used as the cathode material.
[0022]
In addition, as the second component, either one or both of a metal and a metal oxide can be used. As a result, when used in devices that operate at high temperatures, such as SOFC, the second component such as metal can be added after the skeleton is formed of the same material as the electrolyte material, and the thermal expansion coefficient can be adjusted. Thermal shock can be effectively reduced.
Specifically, nickel (Ni), platinum (Pt), palladium (Pd), ruthenium (Ru), cobalt (Co), molybdenum (Mo), tungsten (W), iron (Fe), copper (Cu), It is preferred to include silver (Ag) or chromium (Cr) and any combination thereof.
Furthermore, the above metals and metal oxides are precursors thereof, such as metal alkoxides, metal acetylacetonates, metal acetates, carboxylates such as oxalates, naphthenates, octylates, metal nitrates, chlorides. , Oxychloride or oxide fine particles, and a solution containing any combination thereof can be obtained by reaction by heating or the like.
[0023]
Next, the manufacturing method of the composite electrode for fuel cells of this invention is demonstrated in detail.
First, as a first component, a porous electrode substrate composed of the electrode material described above is prepared. Next, either one or both of the front and back surfaces of the porous electrode substrate, and the pores having openings on either or both of the front and back surfaces, the second component, either one of the precursors or A solution containing both is coated. Thereafter, the coated solution is reacted to form a metal layer or a metal oxide layer to obtain a fuel cell composite electrode.
[0024]
At this time, the metal layer or metal oxide layer is composed of metal alkoxide, metal acetylacetonate, metal acetate, oxalate, or other carboxylate, naphthenate, octylate, metal nitrate, chloride, oxychloride. It is preferable to form using a solution containing a product or oxide fine particles and any combination thereof.
In the coating step, a spin coating method, a dipping method, a spray method, a thermal spray decomposition method, a potting method or a brush coating method, and any combination thereof are preferable from the viewpoint of process simplification and mass production. It is.
As described above, in the present invention, a composite electrode for a fuel cell can be simply manufactured at a low temperature. In addition, as shown in FIG. 11, by appropriately selecting the first component and the second component, the structure can be easily controlled, and a composite electrode for a fuel cell having many three-phase interfaces can be obtained.
[0025]
Next, the solid oxide fuel cell of the present invention will be described in detail.
Such a fuel cell uses the above-described composite electrode for a fuel cell and can produce a fuel cell at a lower temperature than the conventional manufacturing method. Therefore, the number of material types that can be selected is greatly increased, and the cost can be reduced by appropriately using inexpensive materials. Is possible. In addition, since the whole can be made thin, the internal resistance of the battery is reduced, and a high output and low temperature operation type SOFC design becomes possible. Furthermore, the electrode reaction is greatly improved by the presence of a large number of three-phase interfaces. For example, a fuel cell stack as shown in FIG.
[0026]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to these Examples.
[0027]
(Example 1)
As a porous metal substrate, SUS304 having a thickness of 0.1 mm and an opening diameter of 0.1 mm (opening ratio 70%) was produced by chemical etching. Next, Ni-B (boron) powder was filled in the perforated portion of the porous metal substrate and sintered at 600 ° C. At this time, the porosity of the porous metal substrate was 30%.
In addition, as a raw material for Y-added stabilized zirconia (hereinafter referred to as “YSZ”), acetylacetone zirconia + yttrium butyl carbitol solution (prepared to 8 mol% Y ₂ O ₃ ) is heated on the substrate on the porous metal substrate after Ni filling. A CSD layer having a thickness of 50 nm was formed by coating at 300 ° C. by a thermal spray decomposition method, and a composite electrode for a fuel cell was obtained.
The obtained fuel cell composite electrode was coated with an electrolyte layer and an electrode layer to obtain a fuel cell single cell. Details are shown in Table 1, and a schematic diagram is shown in FIG.
[0028]
(Example 2)
A YSZ layer having a thickness of 5 μm and a porosity of 30% was produced around Ni by sintering YSZ powder at 1200 ° C. as a porous electrode substrate. Next, a nickel nitrate aqueous solution was coated around this as a Ni raw material by a spray method and heated to 700 ° C. for reaction to form a CSD layer having a thickness of 50 nm to obtain a composite electrode for a fuel cell. The SEM photograph at this time is shown in FIGS.
An electrolyte layer and an electrode layer were laminated on the obtained composite electrode for fuel cells to obtain a single cell for fuel cells. Details are shown in Table 1, and a schematic diagram is shown in FIG.
[0029]
(Example 3)
As a porous electrode substrate, a YSZ green sheet was sintered at 1200 ° C. to prepare a YSZ layer having a thickness of 1 mm and a porosity of 30%. Next, as a raw material for Sr-added cobalt oxide (hereinafter referred to as “LSC”), an aqueous nitric acid solution of La ₂ O ₃ , CoO ₃ , SrCO ₃ ((La _0.8 Sr _0.2 ) _0.9 CoO _{3 is used.} Were prepared by spin coating and reacted by heating to 800 ° C. to form a CSD layer having a thickness of 100 nm to obtain a composite electrode for fuel cells.
The obtained fuel cell composite electrode was coated with an electrolyte layer and an electrode layer to obtain a fuel cell single cell. Details are shown in Table 1, and a schematic diagram is shown in FIG.
[0030]
(Example 4)
As the porous electrode substrate, a SUS304 nonwoven fabric having a thickness of 250 μm and a porosity of 70% was prepared. Next, a nitric acid aqueous solution of CeO ₂ and Sm ₂ O ₃ (prepared to Ce _0.8 Sm _0.2 O _1.9 ) was dipped at 500 ° C. as a Sm-added ceria (hereinafter referred to as “SDC”) material. Then, a CSD layer having a thickness of 100 nm was formed to obtain a composite electrode for a fuel cell.
An electrolyte layer and an electrode layer were laminated on the obtained composite electrode for fuel cells to obtain a single cell for fuel cells. Details are shown in Table 1, and a schematic diagram is shown in FIG.
[0031]
(Comparative Example 1)
As a porous electrode substrate, NiO powder was sintered at 1200 ° C. to obtain a NiO layer having a thickness of 20 μm and a porosity of 30%. Next, an electrolyte layer and an electrode layer were laminated thereon to obtain a fuel cell single cell. Details are shown in Table 1, and a schematic diagram is shown in FIG.
[0032]
[Table 1]

[0033]
<Evaluation test method>
A durability test was conducted by holding the single cells for fuel cells obtained in Examples 1 to 4 and Comparative Example 1 in a furnace kept at 1000 ° C. in a reducing atmosphere for 10 hours.
[0034]
Since the single cells for fuel cells obtained in Examples 1 to 4 are formed using the material which is a preferred embodiment of the present invention, it has been found that sintering does not easily occur even when used at a high temperature for a long time.
On the other hand, since the single cell for fuel cells obtained in Comparative Example 1 was not provided with a CSD layer, it was found that when heated for a long period of time, NiO sintering progressed and the performance deteriorated.
[0035]
【The invention's effect】
As described above, according to the present invention, the second component is infiltrated into the pores of the first component using a chemical solution, and the first component having a predetermined pore diameter is used. Therefore, it is possible to provide a composite electrode for a fuel cell that can be simply manufactured at a low temperature, can be easily controlled, and has many three-phase interfaces, a manufacturing method thereof, and a solid oxide fuel cell.
[Brief description of the drawings]
1 is a schematic diagram showing a single cell for a fuel cell obtained in Example 1. FIG.
2 is a SEM photograph showing a front cross section of a composite electrode for a fuel cell used in Example 2. FIG.
3 is a SEM photograph showing a side end of a composite electrode for a fuel cell used in Example 2. FIG.
4 is a schematic view showing a single cell for a fuel cell obtained in Example 2. FIG.
5 is a schematic view showing a single cell for a fuel cell obtained in Example 3. FIG.
6 is a schematic view showing a single cell for a fuel cell obtained in Example 4. FIG.
7 is a schematic view showing a single cell for a fuel cell obtained in Comparative Example 1. FIG.
FIG. 8 is a schematic view showing an example of a conventional electrode material.
FIG. 9 is a schematic view showing another example of a conventional electrode material.
FIG. 10 is a schematic view showing still another example of a conventional electrode material.
FIG. 11 is a schematic diagram illustrating an example of a first component and a second component.
FIG. 12 is a schematic view showing an example of a fuel cell stack.

Claims

A porous electrode substrate having openings on the front surface and / or back surface is used as the first component, and the second component is coated by a chemical solution method on the front surface and / or back surface and pores of the porous electrode substrate. A composite electrode for a fuel cell.

A fuel cell composite electrode comprising a porous electrode substrate used as a first component and a second component coated thereon,
The porous electrode substrate has pores having openings on the front surface and / or back surface and an average pore diameter of 500 μm or less, and the second component is formed on the front surface and / or back surface of the porous electrode substrate. A composite electrode for a fuel cell, wherein the pore is coated with a thickness of 0.01 to 10 μm.

The composite electrode for a fuel cell according to claim 1 or 2, wherein an average pore diameter of pores of the porous electrode substrate is 100 µm or less.

The said porous electrode base | substrate is an electrode material sintered compact, The thickness is 1 micrometer-2 mm, The composite electrode for fuel cells of any one of Claims 1-3 characterized by the above-mentioned.

The composite electrode for a fuel cell according to any one of claims 1 to 3, wherein the porous electrode substrate is a porous metal and has a thickness of 0.05 mm to 2 mm.

The composite electrode for a fuel cell according to any one of claims 1 to 3, wherein the porous electrode substrate is formed by filling a through hole of a through-hole metal substrate with a sintered body of an electrode material.

The composite electrode for a fuel cell according to any one of claims 1 to 6, wherein the second component is an oxide having ionic conductivity and / or mixed conductivity.

The oxide is obtained by a chemical solution method and is selected from the group consisting of stabilized zirconia, ceria solid solution, bismuth oxide solid solution, perovskite oxide, lanthanum cobalt oxide, lanthanum manganese oxide, and lanthanum iron oxide. 8. The fuel cell composite electrode according to claim 7, wherein the composite electrode is at least one kind.

The composite electrode for a fuel cell according to any one of claims 1 to 8, wherein the second component is a metal and / or a metal oxide.

The metal and / or metal oxide comprises at least one selected from the group consisting of nickel, platinum, palladium, ruthenium, cobalt, molybdenum, tungsten, iron, copper, silver and chromium. The composite electrode for a fuel cell according to claim 9.

The metal and / or metal oxide is composed of metal alkoxide, metal acetylacetonate, metal acetate, oxalate, naphthenate, octylate, metal nitrate, chloride, oxychloride and oxide fine particles. The composite electrode for a fuel cell according to claim 9 or 10, obtained by heating or reacting a solution containing at least one selected from the above.

In producing the composite electrode for a fuel cell according to any one of claims 1 to 11,
A solution containing the second component and / or a precursor of the second component in the surface and / or back surface of the porous electrode substrate used as the first component and pores having openings on the surface and / or back surface. A method for producing a composite electrode for a fuel cell, wherein a metal layer or a metal oxide layer is formed by coating and reacting.

The metal layer or metal oxide layer is made of metal alkoxide, metal acetylacetonate, metal acetate, oxalate, naphthenate, octylate, metal nitrate, chloride, oxychloride and oxide fine particles. 13. The method for producing a composite electrode for a fuel cell according to claim 12, wherein a solution containing at least one selected from the above is coated on the porous electrode substrate and reacted.

The coating step is performed by at least one method selected from the group consisting of a spin coating method, a dipping method, a spray method, a thermal spray decomposition method, a potting method, and a brush coating method. The manufacturing method of the composite electrode for fuel cells of description.

A solid oxide fuel cell comprising the composite electrode for a fuel cell according to any one of claims 1 to 11.