JP4638070B2

JP4638070B2 - Cylindrical fuel cell, method for producing the same, and fuel cell

Info

Publication number: JP4638070B2
Application number: JP2001052408A
Authority: JP
Inventors: 祥二山下
Original assignee: Kyocera Corp
Current assignee: Kyocera Corp
Priority date: 2001-02-27
Filing date: 2001-02-27
Publication date: 2011-02-23
Anticipated expiration: 2021-02-27
Also published as: JP2002260683A

Description

【０００１】
【発明の属する技術分野】
本発明は、円筒型燃料電池セルおよび燃料電池に関するもので、特に円筒状の固体電解質の片面に燃料極、他面に空気極が形成された燃料電池セルの本体の外面に、集電体が形成された円筒型燃料電池セル及びその製法並びに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１０００〜１０５０℃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。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、発電の単位体積当り出力密度が高いという特長を有するが、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長がある。両形状の固体電解質型燃料電池セルとも、それぞれの特長を生かして積極的に研究開発が進められている。
【０００３】
近年の円筒型燃料電池セルでは、空気極、固体電解質、集電体を共焼結して形成することが行われている。この共焼結法は、例えば、空気極材料から円筒状の支持管を作製し、仮焼を施し、この空気極仮焼体の表面に固体電解質材料を用いて形成されたシート状成形体を巻き付けて、空気極仮焼体の表面に固体電解質成形体を形成し、再度仮焼を行い、前記固体電解質仮焼体の両端部間を研磨し、空気極仮焼体が露出した連続同一面を形成し、この連続同一面に集電体材料からなるシート状成形体を固体電解質仮焼体に一部重畳するように積層し、焼成する方法である。燃料極については、空気極、固体電解質、集電体と同時に共焼結したり、空気極、固体電解質、集電体を共焼結した後、焼き付けて形成されている。
【０００４】
このような方法によれば、セル作製上のプロセスが簡単で、且つ、少ない工程数で量産性に優れ製造コストが低いという大きな利点がある。
【０００５】
【発明が解決しようとする課題】
従来、外径が１５ｍｍ以上の円筒型燃料電池セルを作製しており、このような大型のセルでは、固体電解質仮焼体１の両端部３間をセル外形に沿った滑らかな連続同一面を形成し、集電体の接合強度を向上して、空気極内部のガス漏出を防止するため、図４に示すように、固体電解質仮焼体１の両端部３間をセルの周方向に研磨し、空気極仮焼体５が露出した連続同一面７を形成し、この連続同一面７に集電体を形成するシート状成形体を積層していた。このため、研磨痕９が、連続同一面７および固体電解質仮焼体１の両端部３に周方向に形成されていた。
【０００６】
しかしながら、近年においては、外径が１０ｍｍ以下の円筒型燃料電池セルが要望されており、このような小型のセルでは、従来と同様に周方向に研磨すると、研磨痕がセル外周に周方向に形成されているため、多孔質の空気極内部のガスが研磨痕を介してセルの外部に漏出し、燃料効率が低下するという問題があった。一方、このようなセルを不良品とすると、セルの歩留まりが悪くなるという問題があった。
【０００７】
即ち、集電体は、多孔質な空気極からのガス漏出を防止する役割をなすが、セルを小径化した場合でも、固体電解質の両端部上に重畳する集電体の面積を大径のセルと同様とすると、多孔質な空気極からのガス漏出を防止することは可能となるものの、セル表面における集電体の占める割合が増加し、燃料極形成面積が低減し、セルの出力低下をもたらす。
【０００８】
このため、外径が１０ｍｍ以下の円筒型燃料電池セルを作製する場合には、固体電解質の両端部上に重畳する集電体の面積は必然的に小さくなり、多孔質な空気極からのガス漏出が生じやすくなる傾向がある。これに加えて、従来と同様に周方向に研磨すると、研磨痕がセル外周に周方向に形成されるため、多孔質の空気極内部のガスが研磨痕を介して、セルの外部に漏出し易いという問題があった。
【０００９】
本発明は、セル本体内部のガス漏出を防止できるとともに、高い出力密度を得ることができる円筒型燃料電池セル及びその製法並びに燃料電池を提供することを目的とする。
【００１０】
【課題を解決するための手段】
本発明の円筒型燃料電池セルは、円筒状の固体電解質の片面に燃料極、他面に空気極が形成された燃料電池セル本体の外面に、前記固体電解質の内面に形成された前記燃料極または前記空気極と電気的に接続する集電体を設けてなるとともに、前記固体電解質の一部に設けられた開口部に、前記固体電解質の内面に形成されている前記燃料極または前記空気極の一部を露出させ、前記燃料極または前記空気極の露出面と該露出面近傍の固体電解質端部とを連続した同一面となし、該連続同一面に前記集電体を設けてなる円筒型燃料電池セルであって、前記連続同一面に、研磨痕が前記燃料電池セル本体の長手方向に形成されていることを特徴とする。
【００１１】
このような円筒型燃料電池セルでは、連続同一面に、研磨痕が燃料電池セル本体の長手方向に形成されているため、燃料極または空気極の露出面から周方向に延びる研磨痕は形成されておらず、研磨によって形成された細かい溝がセルの長手方向に形成されており、集電体と固体電解質との重畳面積が小さい場合でも、集電体の被覆により周方向に完全に封止され、研磨痕を介してのガスリーク発生を防止でき、これによる歩留まり低下を抑制できる。
【００１２】
本発明の円筒状燃料電池セルは、燃料電池セル本体の外径が１０ｍｍ以下であることが望ましい。このような小径のセルの場合には、固体電解質の両端部に重畳する集電体の面積は必然的に小さくなるため、本発明を用いる意義は大きい。特に、固体電解質端部と集電体との周方向への重畳幅が１．５ｍｍ以下である場合に好適である。
【００１３】
本発明では、集電体近傍の固体電解質表面に、研磨痕が燃料電池セル本体の長手方向に形成されていることが望ましい。連続同一面だけでなく、集電体近傍の固体電解質表面も研磨されているため、集電体の積層面積が広がり、集電体を余裕をもって積層することができる。
【００１４】
本発明の円筒型燃料電池セルの製法は、円筒状の固体電解質成形体（仮焼体も含む概念である）の内面に空気極成形体（仮焼体も含む概念である）が形成され、固体電解質成形体の一部に設けられた開口部に、前記固体電解質成形体の内面に形成されている空気極成形体の一部が露出した円筒状成形体（仮焼体も含む概念である）を作製する工程と、前記空気極成形体の露出面と該露出面近傍における固体電解質成形体端部の表面とを、前記円筒状成形体の長手方向に研磨して連続同一面とする工程と、該連続同一面に集電体成形体を積層する工程と、焼成する工程とを具備する製法である。
【００１５】
本発明の燃料電池は、反応容器内に、上記円筒型燃料電池セルを複数収容してなるものである。
【００１６】
【発明の実施の形態】
本発明の円筒型燃料電池セルを図面を用いて詳細に説明する。本発明の円筒型燃料電池セルは、図１および図２に示すように、円筒状の固体電解質３１の内面に空気極３２、外面に燃料極３３を形成して燃料電池セル本体３４が構成されており、この燃料電池セル本体３４の外面に、多孔質の空気極３２と電気的に接続する集電体３５を設けてなるものである。本発明の燃料電池セル本体３４の外径は１０ｍｍ以下、特には５ｍｍ以下が望ましい。
【００１７】
本発明に用いられる空気極３２は、自己支持管としての機能を有する円筒状の空気極成形体により作製される。この空気極３２は、ペロブスカイト型結晶相を主相とするＬａＭｎＯ₃系の材料で、その平均結晶粒径は３〜２０μｍ、特に５〜１５μｍであることが望ましい。なお、空気極３２の開気孔率は２０〜４５％、特に３０〜４０％が適当である。また、平均細孔径は１．０〜５．０μｍの範囲がガス透過性に優れる。
【００１８】
空気極３２の表面に形成される緻密な固体電解質３１は、平均粒径が０．５〜３μｍのＹ₂Ｏ₃等の周知の安定化剤により安定化されたＺｒＯ₂からなる粉体を用いてスラリーを調製し、その後ドクターブレード法等により作製されたグリ−ンシートを空気極成形体の外周面に巻き付けて形成されたものである。
【００１９】
空気極３２と電気的に接続する緻密な集電体３５は、燃料電池セル本体３４の外面に形成され段差のない連続同一面３９を覆うように形成されており、後述する多孔質の燃料極３３とは電気的に接続されていない。固体電解質３１両端部３６と集電体３５との周方向における重畳幅Ｂは１．５ｍｍ以下であることが、燃料極３３形成面積を大きくするという点から望ましい。特に０．５〜１．０ｍｍが望ましい。
【００２０】
連続同一面３９は、固体電解質３１の一部に開口部を設けて該固体電解質３１の内面に形成されている空気極３２の一部を露出させるとともに、開口部近傍の固体電解質３１の両端部３６と空気極３２の露出面３７とを連続した同一面（固体電解質３１の両端部３６と空気極３２の露出面３７とが段差のない平面、或いは段差のない曲面）となして構成されている。
【００２１】
この連続同一面３９は固体電解質仮焼体の両端部と空気極仮焼体の露出面とが連続した同一面となるまで仮焼体外周面を、長手方向に研磨することにより形成されている。この研磨によって、図２に示すように、開口部近傍の固体電解質仮焼体３１ａの両端部３６ａと空気極仮焼体３２ａの露出面４１には、燃料電池セル本体３４の長手方向に研磨痕４２が形成されている。
【００２２】
この連続同一面３９に形成される集電体３５は空気極３２と電気的に接続されている。集電体３５はＬａＣｒＯ₃系のスラリーを調製し、その後ドクターブレード法等により作製された帯状のグリーンシートを連続同一面３９に積層して形成されたものである。
【００２３】
そして、本発明の円筒型燃料電池セルの製法は、空気極成形体の外周面に固体電解質成形体を積層したものを、酸化性雰囲気で１０００〜１３００℃の温度で１〜３時間程度仮焼し、集電体の積層箇所となる固体電解質仮焼体の表面を固体電解質仮焼体の端部と空気極仮焼体の露出面とが連続した同一面（平面）となるまで、長手方向に研磨し、この連続同一面に集電体成形体を積層する。
【００２４】
このようにして作製した空気極／固体電解質／集電体積層体は、大気等の酸化性雰囲気中、１３００〜１６００℃の温度で３〜１５時間程度同時焼成することにより焼結させる。
【００２５】
そして、燃料極として、Ｎｉを３０〜８０重量％含有し残部が安定化ＺｒＯ₂（Ｙ₂Ｏ₃等の安定化剤を含む）からなる多孔質のサーメット材料を使用し、上記積層焼結体の所定箇所に燃料極成形体を積層して焼結させることにより、円筒型燃料電池セルが製造される。空気極／固体電解質／集電体積層成形体を形成した後、さらに燃料極成形体を積層し、これらを同時に焼成することもできる。
【００２６】
具体的には、まず、セル本体を作製するために、自己支持管としての機能を有する円筒状の空気極成形体を押出し成形により作製し、その後１２００〜１３００℃の温度で５〜２０時間程度脱バインダー・仮焼を行い、空気極仮焼体を作製する。
【００２７】
次に空気極仮焼体の表面に固体電解質を構成する材料の成形体層を形成する。この固体電解質成形体層は平均粒子径が０．５〜３μｍのＹ₂Ｏ₃等の周知の安定化剤により安定化されたＺｒＯ₂からなる粉体を用いてスラリーを調製し、その後ドクターブレード法などにより作製されたグリーンシートを巻きつけて形成される。グリーンシートは、その両端部間に隙間を形成するように巻き付けられる。
【００２８】
そして、空気極／固体電解質成形体を１０００〜１３００℃の温度で１〜５時間程度仮焼し、その後集電体の積層箇所となる固体電解質仮焼体の両端部間を研磨し、空気極仮焼体を露出させ、固体電解質仮焼体の両端部および空気極仮焼体の露出面に集電体成形体を積層する。
【００２９】
固体電解質仮焼体の両端部間の研磨は、図２に示すように燃料電池セル本体の長手方向に対して、平行に行うことが必要である。これは、他の方向、例えば周方向に研磨を行うと、研磨された固体電解質仮焼体の表面部分に、焼成後空気極仮焼体から周方向に向けて小さな溝が形成されることになり、固体電解質と集電体との接合が不完全となり、その結果、固体電解質と集電体の接合界面からガスリークを発生させることになる。
【００３０】
１本のセル出力を大きくするためには、発電面積を広くする必要があり、そのためには固体電解質と集電体の重なり幅はできるだけ少なくしたほうが良く、そのためには、長手方向の研磨が特に望ましい。
【００３１】
集電体成形体はＬａＣｒＯ₃系の材料を使用し、固体電解質成形体と同様にグリーンシートを積層して形成される。また、燃料極成形体はＮｉ金属とＹ₂Ｏ₃等の周知の安定化剤で安定化されたＺｒＯ₂との混合粉末を使用し、スクリーン印刷で薄層の固体電解質シートの表面に印刷したシートを前記の固体電解質仮焼体表面に積層して形成される。
【００３２】
このようにして作製した積層体は、大気などの酸化雰囲気中、１３００〜１６００℃の温度で３〜１５時間程度同時に焼成することにより共焼結させ、円筒状のセルを作製する。
【００３３】
本発明の燃料電池は、例えば、図３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。
【００３４】
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。
【００３５】
一方の固体電解質型燃料電池セル５９の集電体と他方の固体電解質型燃料電池セル５９の燃料極の一部分を金属フェルトで接続したり、一方の固体電解質型燃料電池セル５９の燃料極と他方の固体電解質型燃料電池セル５９の燃料極を金属フェルトで一部分接続して、複数の固体電解質型燃料電池セル５９が電気的に接続されている。
【００３６】
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。
【００３７】
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。
【００３８】
このような燃料電池は、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にて燃焼させ、燃焼したガスが排気口６９から外部に排出される。
【００３９】
尚、本発明の燃料電池は、上記した図３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。
【００４０】
【実施例】
空気極を形成する粉末として市販の純度９９．９％以上のＬａ₂Ｏ₃、ＣａＣＯ₃、Ｍｎ₂Ｏ₃を出発原料として、これをＬａ_0.8Ｃａ_0.2ＭｎＯ₃の組成になるように秤量混合した後、１３００℃で３時間仮焼し粉砕して平均粒子径５μｍの固溶体粉末を得た。また、この固溶体粉末にバインダーを添加し、押し出し成形法で円筒状の空気極成形体を作製した。この空気極成形体を、乾燥後１２５０℃で１０時間脱バインダー・仮焼することにより円筒状の空気極仮焼体を作製した。
【００４１】
次に、共沈法により得られたＹ₂Ｏ₃を８ｍｏｌ％の割合で含有する平均粒子径が１μｍのＺｒＯ₂粉末に、トルエンとバインダーを添加してスラリーを調製し、ドクターブレード法により厚み１００μｍの固体電解質シートを作製した。
【００４２】
次に、市販の純度９９．９％以上のＬａ₂Ｏ₃、Ｃｒ₂Ｏ₃、ＣａＣＯ₃を出発原料として、これをＬａ_0.8Ｃａ_0.22ＣｒＯ₃の組成になるように秤量混合した後、１５００℃で３時間仮焼し粉砕して、平均粒子径が２μｍの固溶体粉末を得た。次に、この固溶体粉末にトルエンとバインダーを添加してスラリーを調製し、ドクターブレード法により厚み１００μｍの集電体シートを作製した。
【００４３】
燃料極を形成する粉末として、平均粒子径１μｍのＮｉ粉末と平均粒子径が０．５μｍのＺｒＯ₂（８モル％Ｙ₂Ｏ₃含有）とを７：３で混合して混合粉末を作製した。この混合粉末にバインダーを添加しスラリーを作製した。厚さ２０μｍの薄層の電解質シートを作製し、その上部にスクリーン印刷によって燃料極スラリーを厚さ３０μｍで塗布した。
【００４４】
前記円筒状空気極仮焼体に前記固体電解質シートを、その両端部が所定間隔で離間されるようにロール状に巻き付け、１１００℃で３時間の仮焼を行った。仮焼後、集電体シートの積層箇所となる固体電解質仮焼体の両端部間を、長手方向に、研磨加工機により空気極仮焼体が露出するまで平面研磨し、平面状連続同一面を形成し、帯状の集電体シートを連続同一面に積層した。また、電解質シートに形成された燃料極シートを、固体電解質仮焼体の所定箇所に巻きつけた。その後、大気中１５００℃で６時間の条件で共焼結を試みた。
【００４５】
そして、得られた円筒状の燃料電池セルの片端を冶具に挿入して塞ぎ、他端の開口端から、外気圧に対してセル本体内部の内気圧を外気圧よりも＋１ｋｇｆ／ｃｍ²高くなるように空気で加圧し、これを水没させ、気泡の発生の有無により、リークの有無を観察した。
【００４６】
固体電解質端部間の研磨方向、セル本体の外径、および固体電解質と集電体の重畳幅Ｂを表１に示すように変化させ、セルを作製し、得られたセルの固体電解質と集電体の界面から発生するガスリークの有無によって、セルの歩留まりを求め、結果を良品率として表１に記載した。尚、セル本体の最大直径を外径とした。
【００４７】
【表１】

【００４８】
この表１より、固体電解質表面の研磨において、研磨方向をセルの長手方法と平行とすることによって、同じ研磨幅の場合でも、共焼結した後のセルでは固体電解質と集電体の重なった部分からのガスリークが減少し、その結果、セル作製の歩留まりが向上することが分かる。
【００４９】
【発明の効果】
本発明の円筒型燃料電池セルでは、連続同一面に、研磨痕が燃料電池セル本体の長手方向に形成されているため、固体電解質表面の研磨部分に細かい溝がセルの長手方向に形成され、集電体との接合焼成後も、この部分から周方向へのガスリークの発生を抑制することができ、その結果、共焼結後のセルの歩留まりを向上させることができる。
【図面の簡単な説明】
【図１】本発明の円筒型燃料電池セルを示す断面図である。
【図２】本発明の円筒型燃料電池セルの研磨方向を説明するための斜視図である。
【図３】本発明の燃料電池を示す説明図である。
【図４】従来の円筒型燃料電池セルの研磨方向を説明するための斜視図である。
【符号の説明】
３１・・・固体電解質
３２・・・空気極
３３・・・燃料極
３４・・・燃料電池セル本体
３５・・・集電体
３６・・・固体電解質の端部
３７・・・露出面
３９・・・連続同一面
４２・・・研磨痕
５１・・・反応容器
５９・・・円筒型燃料電池セル[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cylindrical fuel cell and a fuel cell. In particular, a current collector is provided on the outer surface of a main body of a fuel cell in which a fuel electrode is formed on one side of a cylindrical solid electrolyte and an air electrode is formed on the other side. The present invention relates to a formed cylindrical fuel cell, a manufacturing method thereof, and a fuel cell.
[0002]
[Prior art]
Conventionally, a solid oxide fuel cell has a high power generation efficiency because its operating temperature is as high as 1000 to 1050 ° C., and is expected as a third generation power generation system. In general, 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 the mechanical strength of the cell is high and the temperature in the cell can be kept uniform although the output density is low. Both types of solid oxide fuel cells are actively researched and exploited, taking advantage of their respective characteristics.
[0003]
In recent cylindrical fuel cells, an air electrode, a solid electrolyte, and a current collector are co-sintered and formed. In this co-sintering method, for example, a cylindrical support tube is produced from an air electrode material, calcined, and a sheet-like molded body formed using a solid electrolyte material on the surface of the air electrode calcined body is obtained. Winding, forming a solid electrolyte molded body on the surface of the air electrode calcined body, performing calcining again, polishing between both ends of the solid electrolyte calcined body, the continuous same surface where the air electrode calcined body is exposed Is formed, and a sheet-like molded body made of a current collector material is laminated on the same continuous surface so as to partially overlap the solid electrolyte calcined body and fired. The fuel electrode is formed by co-sintering the air electrode, the solid electrolyte, and the current collector, or by co-sintering the air electrode, the solid electrolyte, and the current collector, and then baking.
[0004]
According to such a method, there is a great advantage that the process for manufacturing the cell is simple, the number of steps is small, the mass productivity is excellent, and the manufacturing cost is low.
[0005]
[Problems to be solved by the invention]
Conventionally, a cylindrical fuel cell having an outer diameter of 15 mm or more has been manufactured. In such a large-sized cell, a smooth continuous same surface along the outer shape of the cell is formed between both end portions 3 of the solid electrolyte calcined body 1. In order to improve the bonding strength of the current collector and prevent gas leakage inside the air electrode, as shown in FIG. 4, the gap between both ends 3 of the solid electrolyte calcined body 1 is polished in the circumferential direction of the cell. Then, the continuous identical surface 7 where the air electrode calcined body 5 is exposed was formed, and a sheet-like molded body forming a current collector was laminated on the continuous identical surface 7. For this reason, the polishing marks 9 were formed in the circumferential direction on the continuous same surface 7 and both ends 3 of the solid electrolyte calcined body 1.
[0006]
However, in recent years, a cylindrical fuel cell having an outer diameter of 10 mm or less has been demanded. In such a small cell, when polishing is performed in the circumferential direction as in the conventional case, the polishing marks are circumferentially formed on the outer periphery of the cell. As a result, the gas inside the porous air electrode leaks to the outside of the cell through the polishing marks, resulting in a problem that the fuel efficiency is lowered. On the other hand, when such a cell is a defective product, there is a problem that the yield of the cell is deteriorated.
[0007]
In other words, the current collector plays a role of preventing gas leakage from the porous air electrode. However, even when the cell size is reduced, the area of the current collector superimposed on both ends of the solid electrolyte is increased. If it is the same as the cell, it is possible to prevent gas leakage from the porous air electrode, but the proportion of the current collector on the cell surface increases, the fuel electrode formation area decreases, and the cell output decreases. Bring.
[0008]
For this reason, when a cylindrical fuel cell having an outer diameter of 10 mm or less is manufactured, the area of the current collector superimposed on both ends of the solid electrolyte is inevitably small, and the gas from the porous air electrode Leakage tends to occur. In addition to this, when polishing in the circumferential direction as before, polishing marks are formed in the circumferential direction on the outer periphery of the cell, so the gas inside the porous air electrode leaks out of the cell through the polishing marks. There was a problem that it was easy.
[0009]
An object of the present invention is to provide a cylindrical fuel cell, a method of manufacturing the same, and a fuel cell that can prevent gas leakage inside the cell body and obtain a high power density.
[0010]
[Means for Solving the Problems]
The cylindrical fuel cell according to the present invention includes the fuel electrode formed on the inner surface of the solid electrolyte on the outer surface of the fuel cell body in which the fuel electrode is formed on one surface of the cylindrical solid electrolyte and the air electrode is formed on the other surface. Alternatively, a current collector that is electrically connected to the air electrode is provided, and the fuel electrode or the air electrode that is formed on the inner surface of the solid electrolyte in an opening provided in a part of the solid electrolyte A cylinder in which the exposed surface of the fuel electrode or the air electrode and the solid electrolyte end portion in the vicinity of the exposed surface are formed on the same surface, and the current collector is provided on the continuous surface. It is a type | mold fuel cell, Comprising: The grinding | polishing trace is formed in the longitudinal direction of the said fuel cell main body on the said continuous continuous surface.
[0011]
In such a cylindrical fuel cell, since polishing marks are formed in the longitudinal direction of the fuel cell body on the same continuous surface, polishing marks extending in the circumferential direction from the exposed surface of the fuel electrode or air electrode are formed. The fine grooves formed by polishing are formed in the longitudinal direction of the cell, and even when the overlapping area between the current collector and the solid electrolyte is small, the current is completely sealed by covering the current collector In addition, the occurrence of gas leak through the polishing marks can be prevented, and the yield reduction due to this can be suppressed.
[0012]
In the cylindrical fuel cell of the present invention, the outer diameter of the fuel cell body is preferably 10 mm or less. In the case of such a small-diameter cell, the area of the current collector superimposed on both ends of the solid electrolyte is inevitably small, so that the significance of using the present invention is great. In particular, it is suitable when the overlapping width in the circumferential direction between the solid electrolyte end and the current collector is 1.5 mm or less.
[0013]
In the present invention, it is desirable that polishing marks are formed in the longitudinal direction of the fuel cell body on the surface of the solid electrolyte near the current collector. Since the surface of the solid electrolyte in the vicinity of the current collector as well as the continuous same surface is polished, the lamination area of the current collector is widened, and the current collector can be laminated with a margin.
[0014]
In the manufacturing method of the cylindrical fuel cell of the present invention, an air electrode molded body (concept including a calcined body) is formed on the inner surface of a cylindrical solid electrolyte molded body (concept including a calcined body), A cylindrical molded body (including a calcined body) in which a part of an air electrode molded body formed on the inner surface of the solid electrolyte molded body is exposed in an opening provided in a part of the solid electrolyte molded body. And a step of polishing the exposed surface of the air electrode molded body and the surface of the end portion of the solid electrolyte molded body in the vicinity of the exposed surface in the longitudinal direction of the cylindrical molded body so as to be continuously on the same plane. And a step of laminating the current collector molded body on the continuous same surface and a step of firing.
[0015]
The fuel cell of the present invention is formed by accommodating a plurality of the cylindrical fuel cells in a reaction vessel.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The cylindrical fuel cell of the present invention will be described in detail with reference to the drawings. As shown in FIGS. 1 and 2, the cylindrical fuel cell of the present invention has a fuel cell body 34 formed by forming an air electrode 32 on the inner surface of a cylindrical solid electrolyte 31 and a fuel electrode 33 on the outer surface. A current collector 35 that is electrically connected to the porous air electrode 32 is provided on the outer surface of the fuel cell main body 34. The outer diameter of the fuel cell body 34 of the present invention is preferably 10 mm or less, particularly 5 mm or less.
[0017]
The air electrode 32 used in the present invention is made of a cylindrical air electrode molded body having a function as a self-supporting tube. The air electrode 32 is a LaMnO ₃ -based material having a perovskite crystal phase as a main phase, and the average crystal grain size is desirably 3 to 20 μm, particularly 5 to 15 μm. The open porosity of the air electrode 32 is 20 to 45%, particularly 30 to 40%. Moreover, the average pore diameter is excellent in gas permeability in the range of 1.0 to 5.0 μm.
[0018]
The dense solid electrolyte 31 formed on the surface of the air electrode 32 uses a powder made of ZrO ₂ stabilized with a known stabilizer such as Y ₂ O ₃ having an average particle diameter of 0.5 to 3 μm. Then, a slurry is prepared, and then a green sheet produced by a doctor blade method or the like is wound around the outer peripheral surface of the air electrode molded body.
[0019]
A dense current collector 35 electrically connected to the air electrode 32 is formed on the outer surface of the fuel cell body 34 so as to cover a continuous identical surface 39 without a step, and a porous fuel electrode to be described later. 33 is not electrically connected. The overlapping width B in the circumferential direction between the both ends 36 of the solid electrolyte 31 and the current collector 35 is preferably 1.5 mm or less from the viewpoint of increasing the area where the fuel electrode 33 is formed. 0.5 to 1.0 mm is particularly desirable.
[0020]
The continuous coplanar surface 39 is provided with an opening in a part of the solid electrolyte 31 to expose a part of the air electrode 32 formed on the inner surface of the solid electrolyte 31, and both ends of the solid electrolyte 31 in the vicinity of the opening. 36 and the exposed surface 37 of the air electrode 32 are configured to be the same continuous surface (both ends 36 of the solid electrolyte 31 and the exposed surface 37 of the air electrode 32 are flat surfaces having no steps or curved surfaces having no steps). Yes.
[0021]
The continuous identical surface 39 is formed by polishing the outer peripheral surface of the calcined body in the longitudinal direction until both end portions of the solid electrolyte calcined body and the exposed surface of the air electrode calcined body are continuous and the same surface. . By this polishing, as shown in FIG. 2, both ends 36a of the solid electrolyte calcined body 31a in the vicinity of the opening and the exposed surface 41 of the air electrode calcined body 32a are polished in the longitudinal direction of the fuel cell body 34. 42 is formed.
[0022]
The current collector 35 formed on the continuous same surface 39 is electrically connected to the air electrode 32. The current collector 35 is formed by preparing a LaCrO ₃ -based slurry and then laminating a belt-like green sheet produced by a doctor blade method or the like on the continuous same surface 39.
[0023]
And the manufacturing method of the cylindrical fuel cell of the present invention is a method in which a solid electrolyte molded body is laminated on the outer peripheral surface of an air electrode molded body and calcined at a temperature of 1000 to 1300 ° C. for about 1 to 3 hours in an oxidizing atmosphere. In the longitudinal direction, the surface of the solid electrolyte calcined body, which is the stacking location of the current collector, is the same plane (plane) where the end of the solid electrolyte calcined body and the exposed surface of the air electrode calcined body are continuous. The current collector molded body is laminated on the continuous same surface.
[0024]
The air electrode / solid electrolyte / current collector laminate thus produced is sintered by co-firing for about 3 to 15 hours at a temperature of 1300 to 1600 ° C. in an oxidizing atmosphere such as air.
[0025]
And as a fuel electrode, a porous cermet material containing 30 to 80% by weight of Ni and the balance made of stabilized ZrO ₂ (including a stabilizer such as Y ₂ O ₃ ) is used, and the above-mentioned laminated sintered body A cylindrical fuel cell is manufactured by laminating and sintering a fuel electrode molded body at a predetermined location. After forming the air electrode / solid electrolyte / current collector laminated molded body, a fuel electrode molded body can be further laminated, and these can be fired simultaneously.
[0026]
Specifically, first, in order to produce a cell body, a cylindrical air electrode molded body having a function as a self-supporting tube is produced by extrusion molding, and then at a temperature of 1200 to 1300 ° C. for about 5 to 20 hours. The binder is calcined and calcined to produce an air electrode calcined body.
[0027]
Next, a formed body layer of a material constituting the solid electrolyte is formed on the surface of the air electrode calcined body. This solid electrolyte molded body layer is prepared by using a powder composed of ZrO ₂ stabilized with a known stabilizer such as Y ₂ O ₃ having an average particle size of 0.5 to 3 μm, and then a doctor blade. It is formed by winding a green sheet produced by a method or the like. The green sheet is wound so as to form a gap between its both ends.
[0028]
Then, the air electrode / solid electrolyte molded body is calcined at a temperature of 1000 to 1300 ° C. for about 1 to 5 hours, and thereafter, the gap between both ends of the solid electrolyte calcined body that becomes the stacking position of the current collector is polished. The calcined body is exposed, and the current collector molded body is laminated on both ends of the solid electrolyte calcined body and the exposed surface of the air electrode calcined body.
[0029]
Polishing between both end portions of the solid electrolyte calcined body needs to be performed in parallel to the longitudinal direction of the fuel cell body as shown in FIG. This is because, when polishing in another direction, for example, in the circumferential direction, small grooves are formed in the surface portion of the polished solid electrolyte calcined body from the calcined air electrode calcined body in the circumferential direction. Thus, the joining between the solid electrolyte and the current collector becomes incomplete, and as a result, a gas leak is generated from the joining interface between the solid electrolyte and the current collector.
[0030]
In order to increase the output of one cell, it is necessary to widen the power generation area. For this purpose, it is better to reduce the overlapping width of the solid electrolyte and the current collector as much as possible. desirable.
[0031]
The current collector formed body is formed by laminating green sheets using a LaCrO ₃ based material in the same manner as the solid electrolyte formed body. The fuel electrode molded body was a mixed powder of Ni metal and ZrO ₂ stabilized with a known stabilizer such as Y ₂ O _3, and printed on the surface of a thin solid electrolyte sheet by screen printing. It is formed by laminating a sheet on the surface of the solid electrolyte calcined body.
[0032]
The laminated body thus produced is co-sintered by simultaneously firing at a temperature of 1300 to 1600 ° C. for about 3 to 15 hours in an oxidizing atmosphere such as air to produce a cylindrical cell.
[0033]
For example, as shown in FIG. 3, 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.
[0034]
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.
[0035]
The current collector of one solid oxide fuel cell 59 and a part of the fuel electrode of the other solid electrolyte fuel cell 59 are connected by a metal felt, or the fuel electrode of one solid oxide fuel cell 59 and the other A plurality of solid oxide fuel cells 59 are electrically connected by partially connecting the fuel electrodes of the solid oxide fuel cells 59 with metal felt.
[0036]
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.
[0037]
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.
[0038]
Such a fuel cell supplies an oxygen-containing gas, for example air, from the oxygen-containing gas chamber A into the solid oxide fuel cell 59 via the oxygen-containing gas introduction pipe 63, and the fuel gas chamber D. Is supplied between the plurality of solid oxide fuel cells 59, reacted in the reaction chamber C to generate electric power, and excess air and unreacted fuel gas are combusted in the combustion chamber B. It is discharged to the outside through the exhaust port 69.
[0039]
The fuel cell of the present invention is not limited to the fuel cell of FIG. 3 described above, and it is sufficient that a plurality of the above-described fuel cells are accommodated in the reaction vessel.
[0040]
【Example】
As a powder forming the air electrode, commercially available La ₂ O ₃ , CaCO ₃ , and Mn ₂ O ₃ having a purity of 99.9% or more were used as starting materials, and these were weighed and mixed so as to have a composition of La _0.8 Ca _0.2 MnO ₃ . Thereafter, it was calcined at 1300 ° C. for 3 hours and pulverized to obtain a solid solution powder having an average particle size of 5 μm. Further, a binder was added to the solid solution powder, and a cylindrical air electrode molded body was produced by an extrusion molding method. The air electrode compact was dried and then debindered and calcined at 1250 ° C. for 10 hours to prepare a cylindrical air electrode calcined material.
[0041]
Next, a slurry is prepared by adding toluene and a binder to a ZrO ₂ powder having an average particle diameter of 1 μm containing Y ₂ O ₃ at a ratio of 8 mol% obtained by the coprecipitation method. A 100 μm solid electrolyte sheet was prepared.
[0042]
Next, commercially available La ₂ O ₃ , Cr ₂ O ₃ and CaCO ₃ having a purity of 99.9% or more are used as starting materials, and this is weighed and mixed so as to have a composition of La _0.8 Ca _0.22 CrO ₃ , and 1500 ° C. And calcinated for 3 hours to obtain a solid solution powder having an average particle size of 2 μm. Next, a slurry was prepared by adding toluene and a binder to the solid solution powder, and a current collector sheet having a thickness of 100 μm was prepared by a doctor blade method.
[0043]
As powder forming the fuel electrode, Ni powder having an average particle diameter of 1 μm and ZrO ₂ (containing 8 mol% Y ₂ O ₃ ) having an average particle diameter of 0.5 μm were mixed at 7: 3 to prepare a mixed powder. . A binder was added to the mixed powder to prepare a slurry. A thin electrolyte sheet having a thickness of 20 μm was prepared, and a fuel electrode slurry was applied to the top thereof by screen printing to a thickness of 30 μm.
[0044]
The solid electrolyte sheet was wound around the cylindrical air electrode calcined body in a roll shape so that both ends thereof were spaced apart at a predetermined interval, and calcined at 1100 ° C. for 3 hours. After calcining, planar polishing is performed between the both ends of the solid electrolyte calcined body, which is a stacking position of the current collector sheet, in the longitudinal direction until the air electrode calcined body is exposed by a polishing machine, And a belt-like current collector sheet was continuously laminated on the same surface. Further, the fuel electrode sheet formed on the electrolyte sheet was wound around a predetermined portion of the solid electrolyte calcined body. Thereafter, co-sintering was attempted in the atmosphere at 1500 ° C. for 6 hours.
[0045]
Then, closing one end of the resulting cylindrical fuel cell is inserted into the jig, from the open end of the other end, it becomes even + 1 kgf / cm ² higher than the outside atmospheric pressure the inner pressure within the cell body relative to ambient air pressure The air was pressurized as described above, submerged, and the presence or absence of leakage was observed depending on the presence or absence of bubbles.
[0046]
The polishing direction between the ends of the solid electrolyte, the outer diameter of the cell main body, and the overlapping width B of the solid electrolyte and the current collector were changed as shown in Table 1 to produce a cell. The yield of the cells was determined according to the presence or absence of a gas leak generated from the interface of the electric body. The maximum diameter of the cell body was taken as the outer diameter.
[0047]
[Table 1]

[0048]
From Table 1, in the polishing of the solid electrolyte surface, by making the polishing direction parallel to the cell longitudinal method, the solid electrolyte and the current collector overlapped in the cell after co-sintering even in the case of the same polishing width. It can be seen that the gas leak from the portion is reduced, and as a result, the yield of cell fabrication is improved.
[0049]
【The invention's effect】
In the cylindrical fuel cell of the present invention, because the polishing marks are formed in the longitudinal direction of the fuel cell body on the same continuous surface, a fine groove is formed in the longitudinal direction of the cell on the polished portion of the solid electrolyte surface, Even after bonding and firing with the current collector, the occurrence of gas leakage from this portion in the circumferential direction can be suppressed, and as a result, the yield of cells after co-sintering can be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a cylindrical fuel cell according to the present invention.
FIG. 2 is a perspective view for explaining a polishing direction of a cylindrical fuel cell according to the present invention.
FIG. 3 is an explanatory view showing a fuel cell of the present invention.
FIG. 4 is a perspective view for explaining a polishing direction of a conventional cylindrical fuel cell.
[Explanation of symbols]
31 ... Solid electrolyte 32 ... Air electrode 33 ... Fuel electrode 34 ... Fuel cell body 35 ... Current collector 36 ... End 37 of solid electrolyte ... Exposed surface 39 ..Continuous same surface 42 ... polishing mark 51 ... reaction vessel 59 ... cylindrical fuel cell

Claims

The fuel electrode or the air electrode formed on the inner surface of the solid electrolyte is electrically connected to the outer surface of the fuel cell body in which the fuel electrode is formed on one surface of the cylindrical solid electrolyte and the air electrode is formed on the other surface. A current collector is provided, and the fuel electrode or a part of the air electrode formed on the inner surface of the solid electrolyte is exposed to an opening provided in a part of the solid electrolyte, so that the fuel electrode is exposed. Alternatively, the cylindrical fuel cell in which the exposed surface of the air electrode and the end portion of the solid electrolyte in the vicinity of the exposed surface are formed on the same surface and the current collector is provided on the continuous surface. A cylindrical fuel cell, wherein polishing marks are formed on the same surface in the longitudinal direction of the fuel cell body.

The cylindrical fuel cell according to claim 1, wherein the outer diameter of the fuel cell body is 10 mm or less.

The cylindrical fuel cell according to claim 1 or 2, wherein the overlapping width between the solid electrolyte end and the current collector is 1.5 mm or less.

The cylindrical fuel cell according to any one of claims 1 to 3, wherein a polishing mark is formed in a longitudinal direction of the fuel cell body on the surface of the solid electrolyte near the current collector.

An air electrode molded body is formed on the inner surface of a cylindrical solid electrolyte molded body, and an air electrode molded body is formed on the inner surface of the solid electrolyte molded body in an opening provided in a part of the solid electrolyte molded body. Forming a cylindrical molded body with a part thereof exposed, and the exposed surface of the air electrode molded body and the surface of the end portion of the solid electrolyte molded body in the vicinity of the exposed surface in the longitudinal direction of the cylindrical molded body. A process for producing a cylindrical fuel cell, comprising: a step of polishing to form a continuous same surface; a step of laminating a current collector formed body on the continuous same surface; and a step of firing.

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