JP2011228271A - Air electrode material and solid oxide fuel cell - Google Patents
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Abstract
Description
本発明は、固体酸化物形燃料電池に用いられるペロブスカイト型酸化物系の空気極材料に関する。 The present invention relates to a perovskite oxide-based air electrode material used in a solid oxide fuel cell.
近年、固体酸化物形燃料電池の作動温度を６００〜８００℃の温度域まで低温化させることを目的とした、低温作動型の固体酸化物形燃料電池の研究が精力的に行われている。この低温作動型の固体酸化物形燃料電池に用いる空気極としては、６００〜８００℃の温度域で酸素と電子から酸化物イオンを生成させるための触媒性能を有することが求められる。
従来、６００〜８００℃の温度域で酸化ガスとの十分な反応性を有する空気極材料としてランタン（Ｌａ）を含むペロブスカイト型酸化物、例えば、Ｌａとストロンチウム（Ｓｒ）とコバルト（Ｃｏ）と鉄（Ｆｅ）とを含むペロブスカイト型酸化物（以下、ＬＳＣＦ）が知られている（例えば、特許文献１参照。）。
In recent years, vigorous research has been conducted on a low-temperature operation type solid oxide fuel cell for the purpose of lowering the operation temperature of the solid oxide fuel cell to a temperature range of 600 to 800 ° C. The air electrode used in the low-temperature operation type solid oxide fuel cell is required to have catalytic performance for generating oxide ions from oxygen and electrons in a temperature range of 600 to 800 ° C.
Conventionally, a perovskite oxide containing lanthanum (La) as an air electrode material having sufficient reactivity with an oxidizing gas in a temperature range of 600 to 800 ° C., such as La, strontium (Sr), cobalt (Co), and iron A perovskite oxide (hereinafter referred to as LSCF) containing (Fe) is known (for example, see Patent Document 1).
しかしながら、上記従来の空気極材料においては、６００〜８００℃の温度域で十分な触媒性能は得られるものの、長時間に渡って燃料電池の運転を続けることにより空気極の状態が変化し、これが燃料電池の出力性能を経時的に低下させる原因となっている。本発明は、従来の空気極材料を比較して、燃料電池の出力性能を長時間に渡って安定して維持することが可能な空気極材料を提供しようとするものである。 However, in the above conventional air electrode material, although sufficient catalyst performance is obtained in the temperature range of 600 to 800 ° C., the state of the air electrode changes by continuing the operation of the fuel cell for a long time. This is the cause of the deterioration of the output performance of the fuel cell over time. An object of the present invention is to provide an air electrode material capable of stably maintaining the output performance of a fuel cell over a long period of time as compared with conventional air electrode materials.
本発明者らは、今般、Ｌａを含むペロブスカイト型酸化物において、ペロブスカイト構造のＡサイトに含まれる金属のモル数の合計と、Ｂサイトに含まれる金属のモル数の合計との比をＡ／Ｂ比としたときに、粒子間で異なるＡ／Ｂ比を有するペロブスカイト型酸化物において、６００〜８００℃の温度域で十分な触媒性能を有し、さらに、６００〜８００℃の温度域に長時間曝されても安定して存在し、よって、固体酸化物形燃料電池の空気極として用いたときに、固体酸化物形燃料電池において十分な初期性能と、長時間に渡って出力性能を安定して維持できる耐久性能とを実現できる空気極材料であることを見出した。
本発明はこれらの知見に基づくものである。
In the perovskite-type oxide containing La, the present inventors have determined the ratio of the total number of moles of metal contained in the A site of the perovskite structure to the total number of moles of metal contained in the B site as A / When the B ratio is used, the perovskite type oxide having different A / B ratios between particles has sufficient catalytic performance in the temperature range of 600 to 800 ° C., and further in the temperature range of 600 to 800 ° C. Even if it is exposed to time, it exists stably. Therefore, when used as the air electrode of a solid oxide fuel cell, the initial performance of the solid oxide fuel cell is stable and the output performance is stable for a long time. It has been found that this is an air electrode material capable of realizing durability performance that can be maintained as a result.
The present invention is based on these findings.
すなわち、本発明の一つの態様によれば、空気極材料が提供され、その空気極材料は、固体酸化物形燃料電池に用いる空気極材料であって、少なくともランタンを含むペロブスカイト酸化物からなり、前記固体酸化物形燃料電池の空気極材料は複数の粒子から構成され、前記粒子のそれぞれにおいて、ペロブスカイト酸化物のＡサイトに含まれる金属のモル数と、ペロブスカイト酸化物のＢサイトに含まれる金属のモル数と、の比率をＡ／Ｂ比として表したときに、前記固体酸化物形燃料電池の空気極材料に異なるＡ／Ｂ比を有する粒子が含まれてなることを特徴とするものである。 That is, according to one aspect of the present invention, an air electrode material is provided, and the air electrode material is an air electrode material used for a solid oxide fuel cell, and comprises a perovskite oxide containing at least lanthanum, The air electrode material of the solid oxide fuel cell is composed of a plurality of particles, and in each of the particles, the number of moles of metal contained in the A site of the perovskite oxide and the metal contained in the B site of the perovskite oxide. When the ratio of the number of moles is expressed as an A / B ratio, the air electrode material of the solid oxide fuel cell contains particles having different A / B ratios. is there.
本発明による空気極材料は、６００〜８００℃の温度域に長時間曝されても安定して存在することから、固体酸化物形燃料電池の運転環境においても長時間に渡って安定である。したがって、耐久性能の高い固体酸化物形燃料電池への適用が可能となる。 Since the air electrode material according to the present invention is stably present even when exposed to a temperature range of 600 to 800 ° C. for a long time, it is stable for a long time even in the operating environment of the solid oxide fuel cell. Therefore, application to a solid oxide fuel cell with high durability performance is possible.
本発明の空気極材料は、固体酸化物形燃料電池に用いる空気極材料であって、少なくともランタンを含むペロブスカイト酸化物からなり、前記固体酸化物形燃料電池の空気極材料は複数の粒子から構成され、前記粒子のそれぞれにおいて、ペロブスカイト酸化物のＡサイトに含まれる金属のモル数と、ペロブスカイト酸化物のＢサイトに含まれる金属のモル数と、の比率をＡ／Ｂ比として表したときに、前記固体酸化物形燃料電池の空気極材料に異なるＡ／Ｂ比を有する粒子が含まれてなるものである。 The air electrode material of the present invention is an air electrode material used for a solid oxide fuel cell, and is composed of a perovskite oxide containing at least lanthanum, and the air electrode material of the solid oxide fuel cell is composed of a plurality of particles. When the ratio of the number of moles of metal contained in the A site of the perovskite oxide to the number of moles of metal contained in the B site of the perovskite oxide is expressed as an A / B ratio in each of the particles. The air electrode material of the solid oxide fuel cell includes particles having different A / B ratios.
本発明による空気極材料は、６００〜８００℃の温度域に長時間曝されても安定して存在することから、固体酸化物形燃料電池の運転環境においても長時間に渡って安定であり、高い耐久性能を有する高性能な空気極材料となる。 The air electrode material according to the present invention stably exists even when exposed to a temperature range of 600 to 800 ° C. for a long time. Therefore, the air electrode material is stable for a long time even in the operating environment of the solid oxide fuel cell. It becomes a high-performance cathode material with high durability performance.
本発明による空気極材料がこのような高い耐久性能を有する理由は定かではないが、次のように予想される。ただし、以下の理論はあくまで予想であって、本発明はこの理論に限定されるものではない。 The reason why the air electrode material according to the present invention has such a high durability performance is not clear, but is expected as follows. However, the following theory is only an expectation, and the present invention is not limited to this theory.
本発明による空気極材料は、少なくともランタンを含むペロブスカイト酸化物からなり、前記固体酸化物形燃料電池の空気極材料は複数の粒子から構成され、前記粒子のそれぞれにおいて、ペロブスカイト酸化物のＡサイトに含まれる金属のモル数と、ペロブスカイト酸化物のＢサイトに含まれる金属のモル数と、の比率をＡ／Ｂ比として表したときに、前記固体酸化物形燃料電池の空気極材料に異なるＡ／Ｂ比を有する粒子が含まれてなる。
ランタン系ペロブスカイト型酸化物は酸素ガス分圧が低い環境に置かれると、燃料電池の運転温度程度の温度下においてはペロブスカイト型酸化物の分解が進行して、ペロブスカイト型酸化物とは異なるＬａを含む酸化物（例えば、Ｌａ２Ｏ３等）が生成し、これが空気極としての性能を低下させる原因となっていた。具体的には、例えば、Ｌａを含むペロブスカイト型酸化物がＬａＣｏＯ３の場合であれば、一部がＬａ２ＣｏＯ４とＣｏＯに分解し、さらにはＬａ２Ｏ３とＣｏに分解してしまう可能性がある。ペロブスカイト型酸化物の分解に対する安定性はＡ／Ｂ比によって異なると考えられ、異なるＡ／Ｂ比を有する粒子が隣接することで、一方の粒子でＬａを含むペロブスカイト型酸化物の結晶安定性が維持できない程度に酸素ガス分圧が低下した場合において、他方の粒子に含まれる酸素の移動がおきて、Ｌａを含むペロブスカイト型酸化物の分解を効果的に抑制していると考えられる。
The air electrode material according to the present invention comprises a perovskite oxide containing at least lanthanum, and the air electrode material of the solid oxide fuel cell is composed of a plurality of particles, and each of the particles has an A site of the perovskite oxide. When the ratio between the number of moles of metal contained and the number of moles of metal contained in the B site of the perovskite oxide is expressed as an A / B ratio, A different from the air electrode material of the solid oxide fuel cell. Particles having a / B ratio are included.
When the lanthanum perovskite oxide is placed in an environment where the oxygen gas partial pressure is low, decomposition of the perovskite oxide proceeds at a temperature of about the operating temperature of the fuel cell, and La different from that of the perovskite oxide. The oxide (for example, La2O3 etc.) which contains was produced, and this became the cause of reducing the performance as an air electrode. Specifically, for example, if the perovskite oxide containing La is LaCoO 3, there is a possibility that a part thereof decomposes into La 2 CoO 4 and CoO, and further decomposes into La 2 O 3 and Co. The stability of the perovskite oxide is considered to be different depending on the A / B ratio. When particles having different A / B ratios are adjacent to each other, the crystal stability of the perovskite oxide containing La in one particle is improved. When the oxygen gas partial pressure is lowered to such an extent that it cannot be maintained, the oxygen contained in the other particle moves, and it is considered that the decomposition of the perovskite oxide containing La is effectively suppressed.
固体酸化物形燃料電池においては、高い電流密度になると空気極近傍で酸素不足を生じ易くなるが、本発明の空気極材料を用いることで、高い電流密度で運転した場合であっても高い耐久性能を実現することができる。 In a solid oxide fuel cell, oxygen deficiency is likely to occur near the air electrode at a high current density. However, by using the air electrode material of the present invention, high durability even when operated at a high current density. Performance can be realized.
以下に、本発明における固体酸化物形燃料電池の一実施形態について説明する。図１は本発明の固体酸化物形燃料電池における単電池の断面の一態様であり、燃料極側を支持体とした円筒タイプの単電池である。
単電池は、図１に示すように燃料極支持体１と燃料極反応触媒層４と燃料極側反応防止層５と固体電解質層２と空気極３とが順に積層された構造である。
Hereinafter, an embodiment of a solid oxide fuel cell according to the present invention will be described. FIG. 1 shows one embodiment of a cross section of a unit cell in a solid oxide fuel cell of the present invention, which is a cylindrical unit cell having a fuel electrode side as a support.
The unit cell has a structure in which a fuel electrode support 1, a fuel electrode reaction catalyst layer 4, a fuel electrode side reaction prevention layer 5, a solid electrolyte layer 2, and an air electrode 3 are laminated in order as shown in FIG.
空気極３は、少なくともランタンを含むペロブスカイト酸化物からなり、前記固体酸化物形燃料電池の空気極材料は複数の粒子から構成され、前記粒子のそれぞれにおいて、ペロブスカイト酸化物のＡサイトに含まれる金属のモル数と、ペロブスカイト酸化物のＢサイトに含まれる金属のモル数と、の比率をＡ／Ｂ比として表したときに、前記固体酸化物形燃料電池の空気極材料に異なるＡ／Ｂ比を有する粒子が含まれてなるものである。
ランタンが少なくとも含まれたペロブスカイト酸化物としては、ランタンコバルト系ペロブスカイト酸化物（例えば、ＬａＣｏＯ３）、ランタンフェライト系ペロブスカイト酸化物（例えば、ＬａＦｅＯ３）、あるいはＬＳＣＦ（（Ｌａ，Ｓｒ）（Ｃｏ，Ｆｅ）Ｏ３）のような複合ペロブスカイト型酸化物など、固体酸化物形燃料電池の空気極として機能する種々のペロブスカイト型酸化物を用いることができる。
The air electrode 3 is made of a perovskite oxide containing at least lanthanum, and the air electrode material of the solid oxide fuel cell is composed of a plurality of particles, and each of the particles contains a metal contained in the A site of the perovskite oxide. When the ratio of the number of moles of the metal and the number of moles of the metal contained in the B site of the perovskite oxide is expressed as an A / B ratio, the A / B ratio differs depending on the air electrode material of the solid oxide fuel cell. The particles having the following are included.
Perovskite oxides containing at least lanthanum include lanthanum cobalt-based perovskite oxides (for example, LaCoO3), lanthanum ferrite-based perovskite oxides (for example, LaFeO3), or LSCF ((La, Sr) (Co, Fe) O3). Various perovskite oxides that function as the air electrode of a solid oxide fuel cell, such as composite perovskite oxides such as
空気極３の原料となる空気極材料の作製方法は特に限定されるものではないが、例えば、ペロブスカイト型酸化物の原料となる金属酸化物の粉末を混合・焼成して作製する方法（固相法）において混合条件や焼成条件を最適化することで、焼成時においてＡ／Ｂ比の異なる複数のペロブスカイト型酸化物を形成する方法で作製することもできるし、予めＡ／Ｂ比の異なる複数のペロブスカイト型酸化物を準備しておいて、それを所定の割合
で混合する方法で作製するのでも良い。
The method for producing the air electrode material as the raw material of the air electrode 3 is not particularly limited. For example, a method of producing by mixing and baking metal oxide powder as the raw material of the perovskite oxide (solid phase) In the method), it is possible to produce a plurality of perovskite oxides having different A / B ratios at the time of firing by optimizing the mixing conditions and firing conditions. Alternatively, the perovskite oxide may be prepared and mixed at a predetermined ratio.
燃料極支持体１および燃料極反応触媒層４として用いる材料には、燃料極としての特性を有するものであれば特に制限はなく、ＮｉＯおよび／またはＮｉとＤｏｐｅｄジルコニアとの混合物、ＮｉＯおよび／またはＮｉとＤｏｐｅｄセリアとの混合物、あるいは、ＮｉＯおよび／またはＮｉとランタンガレート酸化物との混合物等を用いることができる。 The material used as the fuel electrode support 1 and the fuel electrode reaction catalyst layer 4 is not particularly limited as long as it has characteristics as a fuel electrode. NiO and / or a mixture of Ni and Doped zirconia, NiO and / or A mixture of Ni and Doped ceria, a mixture of NiO and / or Ni and lanthanum gallate oxide, or the like can be used.
固体電解質２として用いる材料としては固体酸化物形燃料電池の運転温度で導電性を有するものであれば特に制限はなく、ＤｏｐｅｄジルコニアやＤｏｐｅｄセリア、あるいは、ランタンガレート酸化物等を用いることができる。
中でも、ランタンガレート酸化物からなる固体電解質は低温でも高い導電率を有するものであることから、固体酸化物形燃料電池の低温作動において有利な材料である。
The material used as the solid electrolyte 2 is not particularly limited as long as it has conductivity at the operating temperature of the solid oxide fuel cell, and Doped zirconia, Doped ceria, lanthanum gallate oxide, or the like can be used.
Among them, a solid electrolyte made of lanthanum gallate oxide has a high conductivity even at a low temperature, and is therefore an advantageous material for low-temperature operation of a solid oxide fuel cell.
燃料極側反応防止層５は燃料極と固体電解質との反応を防止するための層であり、反応防止の機能を有する種々の材料を用いることができる。例えば、Ｄｏｐｅｄセリアを好適に用いることができる。 The fuel electrode side reaction preventing layer 5 is a layer for preventing the reaction between the fuel electrode and the solid electrolyte, and various materials having a reaction preventing function can be used. For example, Doped ceria can be preferably used.
次に、図１に示す固体酸化物形燃料電池を例として作動原理を以下に示す。空気極側に空気を流し、燃料極側に燃料を流すと空気中の酸素が、空気極と固体電解質層との界面近傍で酸素イオンに変わり、この酸素イオンが固体電解質層を通って燃料極に達する。そして燃料ガスと酸素イオンが反応して水および二酸化炭素になる。これらの反応は（１）、（２）および（３）式で表される。空気極と燃料極を外部回路で接続することによって外部に電気を取り出すことが出来る。
Ｈ２＋Ｏ２−→Ｈ２Ｏ＋２ｅ− （１）
ＣＯ＋Ｏ２−→ＣＯ２＋２ｅ− （２）
１／２Ｏ２＋２ｅ−→Ｏ２− （３）
Next, the operation principle will be described below by taking the solid oxide fuel cell shown in FIG. 1 as an example. When air is flowed to the air electrode side and fuel is flowed to the fuel electrode side, oxygen in the air changes to oxygen ions in the vicinity of the interface between the air electrode and the solid electrolyte layer, and these oxygen ions pass through the solid electrolyte layer to the fuel electrode. To reach. The fuel gas and oxygen ions react to form water and carbon dioxide. These reactions are represented by the formulas (1), (2) and (3). Electricity can be taken out by connecting the air electrode and the fuel electrode with an external circuit.
H2 + O2- → H2O + 2e- (1)
CO + O2- → CO2 + 2e- (2)
1 / 2O2 + 2e- → O2- (3)
なお燃料ガスに含まれるＣＨ４等も（１）式、（２）式と類似した電子を生成する反応があるとの報告もあるが固体酸化物形燃料電池の発電における反応のほとんどが（１）、（２）式で説明できるので、ここでは（１）、（２）式で説明することとした。 It has been reported that CH4 contained in the fuel gas has a reaction that generates electrons similar to the equations (1) and (2), but most of the reactions in the power generation of the solid oxide fuel cell are (1). Since it can be explained by the equation (2), it will be explained by the equations (1) and (2) here.
空気極材料の作製
空気極材料の作製は、固相法により行った。
（Ｌａ０．６Ｓｒ０．４）ｘ（Ｃｏ０．２Ｆｅ０．８）Ｏ３の組成式となるように、原料となる金属酸化物の粉末を秤量し、溶液中で混合した後に溶媒を除去して得られた粉末を、１２００℃で焼成し、粉砕することにより、空気極材料を作製した。なお、組成式中のｘで表されるＡ／Ｂ比については、０．９７、１．０、１．３の３種類の空気極材料をそれぞれ作製した。得られた３種類の空気極材料を、表１に示す体積比となるように、ジルコニアボールを使って溶液中で混合した後に、溶媒を除去して、所望の空気極材料を得た。
Production of the air electrode material The air electrode material was produced by a solid phase method.
The metal oxide powder as a raw material is weighed so as to have the composition formula of (La 0.6 Sr 0.4 ) x (Co 0.2 Fe 0.8 ) O 3 , mixed in the solution, and then the solvent. The air electrode material was produced by baking and pulverizing the powder obtained by removing the powder at 1200 ° C. For the A / B ratio represented by x in the composition formula, three types of air electrode materials of 0.97, 1.0, and 1.3 were produced. The obtained three types of air electrode materials were mixed in a solution using zirconia balls so as to have a volume ratio shown in Table 1, and then the solvent was removed to obtain a desired air electrode material.
固体酸化物形燃料電池の作製
上記のようにして得られた空気極材料を用いて、以下の方法で固体酸化物形燃料電池を作製した。
ＮｉＯと１０ＹＳＺ（１０ｍｏｌ％Ｙ２Ｏ３−９０ｍｏｌ％ＺｒＯ２）とを重量比６５：３５で混合して円筒状に成形し９００℃で仮焼した燃焼極支持体を作製した。この燃料極支持体上に、ＮｉＯとＧＤＣ１０（１０ｍｏｌ％Ｇｄ２Ｏ３−９０ｍｏｌ％ＣｅＯ２）とを重量比５０：５０で混合したものをスラリーコート法により製膜し、燃料極反応触媒層を形成した。さらに、燃料極反応触媒層上にＬＤＣ４０（４０ｍｏｌ％Ｌａ２Ｏ３−６０ｍｏｌ％ＣｅＯ２）、Ｌａ０．８Ｓｒ０．２Ｇａ０．８Ｍｇ０．２Ｏ３の組成のＬＳＧＭをスラリーコート法により順次積層し、電解質層を形成した。得られた成形体を１３００℃にて焼成した後に、上記の作製方法にて得られた空気極材料をスラリーコート法にて製膜し、１０５０℃で焼成することで固体酸化物形燃料電池を作製した。
作製した固体酸化物形燃料電池は、燃料極支持体が外径１０ｍｍ、肉厚１ｍｍであり、燃料極反応触媒層の厚さが２０μｍであり、ＬＤＣ層の厚みが１０μｍであり、ＬＳＧＭ層の厚みが３０μｍであり、空気極の厚みが２０μｍであり、かつ、空気極の面積が３５ｃｍ２である。
Production of Solid Oxide Fuel Cell A solid oxide fuel cell was produced by the following method using the air electrode material obtained as described above.
NiO and 10YSZ (10 mol% Y 2 O 3 -90 mol% ZrO 2) were mixed at a weight ratio of 65:35, formed into a cylindrical shape and calcined at 900 ° C. to prepare a combustion electrode support. On this fuel electrode support, a mixture of NiO and GDC10 (10 mol% Gd2O3-90 mol% CeO2) at a weight ratio of 50:50 was formed by a slurry coating method to form a fuel electrode reaction catalyst layer. Further, LSGM having a composition of LDC40 (40 mol% La2O3-60 mol% CeO2) and La0.8Sr0.2Ga0.8Mg0.2O3 was sequentially laminated on the fuel electrode reaction catalyst layer by a slurry coating method to form an electrolyte layer. After the obtained molded body was fired at 1300 ° C., the air electrode material obtained by the above production method was formed into a film by a slurry coating method, and fired at 1050 ° C. to obtain a solid oxide fuel cell. Produced.
The produced solid oxide fuel cell has a fuel electrode support having an outer diameter of 10 mm and a wall thickness of 1 mm, a fuel electrode reaction catalyst layer thickness of 20 μm, an LDC layer thickness of 10 μm, and an LSGM layer The thickness is 30 μm, the thickness of the air electrode is 20 μm, and the area of the air electrode is 35 cm 2.
評価１：発電試験
得られた固体酸化物形燃料電池を用いて、発電試験を行った。
燃料極側の集電は、燃料極支持体の内側全面に銀ペーストを塗布した後、銀メッシュを焼付けて行った。空気極側の集電は、銀ペーストを塗布した後、銀メッシュを短冊状に切断し、螺旋状に巻きつけた後、焼付けて行った。
発電条件は以下である。
燃料ガス ：（Ｈ２＋３％Ｈ２Ｏ）とＮ２の混合ガス
燃料利用率：６０％
酸化ガス ：空気
運転温度 ：７００℃
電流密度 ：０．２Ａ／ｃｍ２
この条件で発電試験を行い、運転０時間後の初期電位（Ｖ０）と連続運転５０００時間後の電位（Ｖ５０００）とを測定した。耐久性能は、初期電位から５０００時間連続運転後の電位を差し引いた値を初期電位で割り１００を乗じた値（（Ｖ０−Ｖ５０００）＊１００／Ｖ０）とした。
Evaluation 1: Power Generation Test A power generation test was performed using the obtained solid oxide fuel cell.
The current collection on the fuel electrode side was performed by applying a silver paste to the entire inner surface of the fuel electrode support and then baking the silver mesh. Current collection on the air electrode side was performed by applying a silver paste, cutting the silver mesh into strips, winding them in a spiral, and then baking them.
The power generation conditions are as follows.
Fuel gas: (H2 + 3% H2O) and N2 mixed gas Fuel utilization: 60%
Oxidizing gas: Air Operating temperature: 700 ° C
Current density: 0.2 A / cm 2
A power generation test was performed under these conditions, and an initial potential (V0) after 0 hours of operation and a potential (V5000) after 5000 hours of continuous operation were measured. The durability performance was a value obtained by subtracting the potential after 5000 hours of continuous operation from the initial potential and dividing by the initial potential and multiplying by 100 ((V0−V5000) * 100 / V0).
評価２：テープ剥離試験
固体電解質層と空気極との密着性を評価するために、テープ剥離試験を行った。５０００時間連続運転したセルの銀メッシュを取り外し、粘着テープをセル表面に密着させた後、剥離した。銀メッシュを取り外す際、または粘着テープを剥離する際に、空気極が剥がれた場合、「剥離あり」として表１に記載した。
Evaluation 2: Tape peeling test A tape peeling test was conducted to evaluate the adhesion between the solid electrolyte layer and the air electrode. The silver mesh of the cell which was continuously operated for 5000 hours was removed, and the adhesive tape was adhered to the cell surface, and then peeled off. When the air electrode was peeled off when the silver mesh was removed or the adhesive tape was peeled off, it was listed in Table 1 as “with peeling”.
（比較例）
上記実施例で作製したＡ／Ｂ比が１．０の空気極材料を、他のＡ／Ｂ比の空気極材料と混合せずに使った以外は、上記実施例と同様の方法により空気極材料を用いて、固体酸化物形燃料電池の作製、および評価を行った。
(Comparative example)
The air electrode was produced in the same manner as in the above example except that the air electrode material having an A / B ratio of 1.0 produced in the above example was used without being mixed with the air electrode material having another A / B ratio. Using the materials, a solid oxide fuel cell was fabricated and evaluated.
サンプルＮｏ．１の空気極材料を用いて固体酸化物形燃料電池を作製して発電を行った結果、いずれも高い耐久性を示した。また、耐久試験後に行ったテープ剥離試験でも剥離は見られず、電解質層と空気極との高い密着性を確認することが出来た。一方、比較例であるサンプルＮｏ．２の空気極材料を用いた場合、Ｎｏ．１と比較して耐久性が悪かった。また、テープ剥離試験にて空気極の剥がれが確認され、密着性が長期に渡って安定的に確保できないことが分かった。以上の結果より、空気極材料に異なるＡ／Ｂ比を有する粒子を含む空気極を用いることで、電位の低下が少なくなる上に物理的な強度も向上し、これらが総合的に寄与して耐久性能の高い固体酸化物形燃料電池を実現することが確認できた。 Sample No. As a result of producing a solid oxide fuel cell using 1 air electrode material and generating electric power, all showed high durability. Moreover, peeling was not seen in the tape peeling test performed after the durability test, and high adhesion between the electrolyte layer and the air electrode could be confirmed. On the other hand, sample No. When the air electrode material of No. 2 is used, Compared with 1, the durability was poor. Moreover, peeling of the air electrode was confirmed in the tape peeling test, and it was found that the adhesion could not be secured stably over a long period of time. From the above results, by using an air electrode containing particles having different A / B ratios in the air electrode material, the decrease in potential is reduced and the physical strength is also improved, which contributes comprehensively. It was confirmed that a solid oxide fuel cell with high durability performance could be realized.
以上の実施例では、予めＡ／Ｂ比の異なる複数のペロブスカイト型酸化物を準備しておいて、それを所定の割合で混合する方法で作製する例を説明したが、本発明はこれに限るものではない。予めＡ／Ｂ比の異なる複数のペロブスカイト型酸化物を準備する方法に替えて、焼成時においてＡ／Ｂ比の異なる複数のペロブスカイト型酸化物を形成する方法を、以下説明する。 In the above embodiment, an example in which a plurality of perovskite oxides having different A / B ratios are prepared in advance and mixed at a predetermined ratio has been described, but the present invention is not limited to this. It is not a thing. A method for forming a plurality of perovskite oxides having different A / B ratios during firing will be described below in place of the method for preparing a plurality of perovskite oxides having different A / B ratios in advance.
空気極材料の作製−２
本実施例においても、空気極材料の作製は固相法により行った。
（Ｌａ０．６Ｓｒ０．４）（Ｃｏ０．２Ｆｅ０．８）Ｏ３の組成式となるように、
原料となる金属酸化物の粉末を秤量し、溶液中で混合した後に溶媒を除去して得られた粉末を、１２００℃で焼成し、粉砕することにより、空気極材料を作製した。なお、このとき１２００℃で焼成した後に異なるＡ／Ｂ比を持つ粒子が含まれるように、溶液中での混合条件の調整を実施した。例えば、溶液中で混合時の平均分散粒子径を１０μｍに調整することで異なるＡ／Ｂ比を持つ粒子の生成が促進される。なお平均分散粒子径は、金属酸化物粉末が分散した混合溶液をレーザー回折式粒度分布計にて測定した。
Production of air electrode material-2
Also in this example, the air electrode material was produced by a solid phase method.
In order to be a composition formula of (La 0.6 Sr 0.4 ) (Co 0.2 Fe 0.8 ) O 3 ,
The powder of the metal oxide used as a raw material was weighed and mixed in a solution, and then the solvent was removed. The powder obtained was fired at 1200 ° C. and pulverized to produce an air electrode material. At this time, the mixing conditions in the solution were adjusted so that particles having different A / B ratios were included after firing at 1200 ° C. For example, the production of particles having different A / B ratios can be promoted by adjusting the average dispersed particle size during mixing in a solution to 10 μm. The average dispersed particle size was measured with a laser diffraction particle size distribution meter for the mixed solution in which the metal oxide powder was dispersed.
１２００℃で焼成後（粉砕前）の空気極材料について、ＳＥＭ−ＥＤＸを用いて分析を行った。 空気極材料における粒子の分布状態を走査電子顕微鏡（ＳＥＭ）で４０００倍に拡大して観察した。また、エネルギー分散型Ｘ線分光器（ＥＤＸ）により、含まれる各種元素のマッピング分析を行った。それぞれの粒子のＡ／Ｂ比を、ＥＤＸのマッピング分析の結果から算出した。 The air electrode material after firing (before pulverization) at 1200 ° C. was analyzed using SEM-EDX. The distribution state of the particles in the air electrode material was observed with a scanning electron microscope (SEM) at a magnification of 4000 times. In addition, mapping analysis of various elements included was performed using an energy dispersive X-ray spectrometer (EDX). The A / B ratio of each particle was calculated from the results of EDX mapping analysis.
図２は、ＳＥＭ−ＥＤＸで分析した結果を示している。ＳＥＭ観察（図２（ａ））の結果より、空気極材料は複数の粒子を含んでいることが確認できた。この粒子のそれぞれについてＥＤＸ分析をした結果を図２（ｂ）（ｃ）（ｄ）に示す。ＥＤＸ分析の結果からそれぞれの粒子でのＡ／Ｂ比を算出した結果、０．９４６、１．３８０、１．２１４と異なるＡ／Ｂ比を有することが確認できた。
本実施例で作製した空気極材料を用いて固体酸化物形燃料電池を作製して発電試験を行った結果、初期の電位が０．８４３Ｖ、５０００時間経過後の電位が０．８４２Ｖとなり、５０００時間での電位低下率（耐久性能）が０．１２％であった。
FIG. 2 shows the result of analysis by SEM-EDX. From the results of SEM observation (FIG. 2A), it was confirmed that the air electrode material contained a plurality of particles. The results of EDX analysis of each of these particles are shown in FIGS. 2 (b), (c) and (d). As a result of calculating the A / B ratio of each particle from the result of EDX analysis, it was confirmed that the particles had A / B ratios different from 0.946, 1.380, and 1.214.
As a result of producing a solid oxide fuel cell using the air electrode material produced in this example and conducting a power generation test, the initial potential was 0.843 V, and the potential after 5000 hours was 0.842 V. The potential decrease rate (durability) over time was 0.12%.
１ 燃料極支持体
２ 固体電解質層
３ 空気極層
４ 燃料極反応触媒層
５ 燃料極側反応防止層
１０ 固体酸化物形燃料電池
DESCRIPTION OF SYMBOLS 1 Fuel electrode support body 2 Solid electrolyte layer 3 Air electrode layer 4 Fuel electrode reaction catalyst layer 5 Fuel electrode side reaction prevention layer 10 Solid oxide fuel cell
Claims (4)
少なくともランタンを含むペロブスカイト酸化物からなり、
前記固体酸化物形燃料電池の空気極材料は複数の粒子から構成され、
前記粒子のそれぞれにおいて、ペロブスカイト酸化物のＡサイトに含まれる金属のモル数と、ペロブスカイト酸化物のＢサイトに含まれる金属のモル数と、の比率をＡ／Ｂ比として表したときに、前記固体酸化物形燃料電池の空気極材料に異なるＡ／Ｂ比を有する粒子が含まれてなることを特徴とする空気極材料。 An air electrode material used for a solid oxide fuel cell,
Consisting of a perovskite oxide containing at least lanthanum,
The cathode material of the solid oxide fuel cell is composed of a plurality of particles,
In each of the particles, when the ratio between the number of moles of metal contained in the A site of the perovskite oxide and the number of moles of metal contained in the B site of the perovskite oxide is expressed as an A / B ratio, An air electrode material comprising particles having different A / B ratios in the air electrode material of a solid oxide fuel cell.
前記空気極が、請求項１に記載の空気極材料で形成されていることを特徴とする固体酸化物形燃料電池。 A solid oxide fuel cell comprising a solid electrolyte layer made of a metal oxide between an air electrode and a fuel electrode,
A solid oxide fuel cell, wherein the air electrode is formed of the air electrode material according to claim 1.
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