Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
  • H01M4/88—Processes of manufacture
  • H01M4/8878—Treatment steps after deposition of the catalytic active composition or after shaping of the electrode being free-standing body
  • H01M4/8882—Heat treatment, e.g. drying, baking
  • H01M4/8885—Sintering or firing
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
  • C04B35/26—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on ferrites
  • C04B35/2608—Compositions containing one or more ferrites of the group comprising manganese, zinc, nickel, copper or cobalt and one or more ferrites of the group comprising rare earth metals, alkali metals, alkaline earth metals or lead
  • C04B35/2633—Compositions containing one or more ferrites of the group comprising manganese, zinc, nickel, copper or cobalt and one or more ferrites of the group comprising rare earth metals, alkali metals, alkaline earth metals or lead containing barium, strontium or calcium
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
  • C04B35/26—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on ferrites
  • C04B35/2641—Compositions containing one or more ferrites of the group comprising rare earth metals and one or more ferrites of the group comprising alkali metals, alkaline earth metals or lead
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/50—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on rare-earth compounds
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B38/00—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
  • H01M4/90—Selection of catalytic material
  • H01M4/9016—Oxides, hydroxides or oxygenated metallic salts
  • H01M4/9025—Oxides specially used in fuel cell operating at high temperature, e.g. SOFC
  • H01M4/9033—Complex oxides, optionally doped, of the type M1MeO3, M1 being an alkaline earth metal or a rare earth, Me being a metal, e.g. perovskites
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/02—Details
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/10—Fuel cells with solid electrolytes
  • H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
  • C04B2111/00241—Physical properties of the materials not provided for elsewhere in C04B2111/00
  • C04B2111/00413—Materials having an inhomogeneous concentration of ingredients or irregular properties in different layers
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
  • C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
  • C04B2111/00853—Uses not provided for elsewhere in C04B2111/00 in electrochemical cells or batteries, e.g. fuel cells
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
  • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
  • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
  • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
  • C04B2235/3205—Alkaline earth oxides or oxide forming salts thereof, e.g. beryllium oxide
  • C04B2235/3208—Calcium oxide or oxide-forming salts thereof, e.g. lime
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
  • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
  • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
  • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
  • C04B2235/3205—Alkaline earth oxides or oxide forming salts thereof, e.g. beryllium oxide
  • C04B2235/3213—Strontium oxides or oxide-forming salts thereof
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
  • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
  • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
  • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
  • C04B2235/3224—Rare earth oxide or oxide forming salts thereof, e.g. scandium oxide
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
  • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
  • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
  • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
  • C04B2235/3224—Rare earth oxide or oxide forming salts thereof, e.g. scandium oxide
  • C04B2235/3229—Cerium oxides or oxide-forming salts thereof
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
  • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
  • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
  • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
  • C04B2235/327—Iron group oxides, their mixed metal oxides, or oxide-forming salts thereof
  • C04B2235/3272—Iron oxides or oxide forming salts thereof, e.g. hematite, magnetite
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
  • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
  • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
  • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
  • C04B2235/327—Iron group oxides, their mixed metal oxides, or oxide-forming salts thereof
  • C04B2235/3275—Cobalt oxides, cobaltates or cobaltites or oxide forming salts thereof, e.g. bismuth cobaltate, zinc cobaltite
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
  • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
  • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
  • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
  • C04B2235/3281—Copper oxides, cuprates or oxide-forming salts thereof, e.g. CuO or Cu2O
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
  • C04B2235/70—Aspects relating to sintered or melt-casted ceramic products
  • C04B2235/74—Physical characteristics
  • C04B2235/77—Density
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
  • C04B2235/70—Aspects relating to sintered or melt-casted ceramic products
  • C04B2235/74—Physical characteristics
  • C04B2235/79—Non-stoichiometric products, e.g. perovskites (ABO3) with an A/B-ratio other than 1
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
  • H01M2004/8678—Inert electrodes with catalytic activity, e.g. for fuel cells characterised by the polarity
  • H01M2004/8689—Positive electrodes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/10—Fuel cells with solid electrolytes
  • H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
  • H01M2008/1293—Fuel cells with solid oxide electrolytes
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/50—Fuel cells

Definitions

• Cathode material for a high-temperature fuel cell (SOFC) and a cathode that can be produced from it SOFC and a cathode that can be produced from it
• the invention relates to a cathode material for a fuel cell, in particular for a high-temperature fuel cell, and to a suitable method for producing a cathode comprising this cathode material.
• SOFC High-temperature fuel cells
• cathode material used in high-temperature fuel cells should have the following properties in particular: It should have a coefficient of thermal expansion that is adapted to the surrounding materials in order to avoid thermal, stress-related stresses and the associated destruction.
• the cathode material should also be chemically compatible with the adjacent materials and have a high electrochemical activity. This means that the cathode material shows good oxygen reduction behavior.
• high electrical conductivity and high ionic conductivity desirability.
• an electrode material which consists of (AI, Co, Mg, Ni) y C0 3 exists, whereby 0.05 ⁇ y ⁇ 0.2 applies.
• This material shows high-temperature fuel cells for suitable thermal expansion behavior.
• EP 510 820 A2 electrodes which consist of substoichiometric perovskites. According to EP 568 281 A1, the ratio (lanthanum + calcium) / manganese in lanthanum / calcium manganites should be less than 1 in order to ensure that no lanthanum hydroxides are formed.
• EP 510 820 A2 states that there is a calcium, lanthanum or strontium deficiency in the pervskit materials used for electrodes. Lan- tan manganate or lanthanum cobaltate are mentioned as materials, whereby part of the calcium can be replaced by strontium.
• German patent DE 197 02 619 Cl shows that the electrochemical properties can be improved, for example, by using cobalt-containing cathode materials.
• the sub-stoichiometry of the material is said to advantageously result in increased electrochemical activity due to an improved oxygen reduction behavior.
• La, Sr (Co, Fe) oxides are known as very good materials for a cathode material for high-temperature fuel cells, in particular Lao, 6Sr 0 , 4 C ⁇ o, 2 Feo, 8 ⁇ 3- ⁇ is mentioned.
• the object of the invention is to provide an improved cathode material for high-temperature fuel cells, which has a significant increase in performance compared to the cathode materials known to date from the prior art. Furthermore, it is the object of the invention to provide a production method for a cathode from the aforementioned cathode material.
• the objects of the invention are achieved by a cathode material with all the features according to the main claim. Furthermore, the object of the invention is achieved by a production method for a cathode and by a cathode with all the features according to the subclaims. Advantageous embodiments of the cathode material, the cathode and the manufacturing process can be found in the claims that refer back to them.
• the sophisticated cathode material consists of one
• This crystal structure has proven to be suitable for the high-temperature fuel cell in terms of material properties.
• the combination of lanthanum and strontium has proven to be particularly advantageous.
• the material according to the invention is the
• the sub-stoichiometry ranges between 0.02 and 0.05, so that the proportion of lanthanum and strontium, for example, is less than 1 but is regularly greater than 0.95.
• the positive properties of the cathode material are not regularly affected by the replacement of calcium instead of strontium or other lanthanides instead of lanthanum.
• the cathode according to the invention has one of the aforementioned cathode materials according to the invention. Furthermore, this material lies in the cathode with an average grain size in the range from 0.4 to 1.0 ⁇ m, in particular in the range from 0.6 to 0.8 ⁇ m. A grain size distribution around 0.8 ⁇ m has proven to be particularly suitable.
• Preferred cathodes have the compositions La 0 / 58Sro, 4Feo, 8C ⁇ o, 2 ⁇ 3- ⁇ , or La 0 , 55Sr 0 4Feo, 8C ⁇ o, 2 ⁇ 3 - ⁇ or also La 0 , 78 Sro, 2Fe 0 , 8C ⁇ o, 2 ⁇ 3- ⁇ as cathode materials without being intended to limit the other compositions disclosed.
• Another advantageous compound that falls under the invention and has a somewhat higher proportion of cobalt is, for example
• the aforementioned advantageous grain size distribution within the cathode is possible in particular through a special manufacturing process.
• the d 50 value is to be understood as the median of the grain size distribution, ie 50% of the particles (by number) are less than or equal to the d 50 value.
• the average grain size distribution can be determined, for example, by means of image analysis an electron micrograph can be determined. An estimate based on an electron microscope image is also possible
• the relatively small grain size of the starting material in connection with the selected cathode material advantageously enables a low sintering temperature, which is regularly below 1100 ° C.
• the sub-stoichiometry is particularly crucial for the high sintering activity.
• the low sintering temperature in turn causes the necessary porosity on the one hand through the microstructure produced thereby and on the other hand advantageously provides the required stability.
• the cathode material according to the invention for a high-temperature fuel cell makes it possible, owing to its advantageous composition in connection with an optimal production process adapted to it, to create a cathode which, when operated at 750 ° C. and a cell voltage of 0.7 V, reproducibly has a power of more than 1 W / cm 2 can achieve.
• a suitable production method for a cathode according to the invention is, for example, the one described below.
• An anode-electrolyte composite is first produced.
• An intermediate layer with a low porosity is first applied to this.
• Such a layer is, for example, a (Ce, Gd) 0 2 ⁇ layer (CGO layer) with 0 ⁇ 0,2 0.25.
• This intermediate layer is in the form of a powder with an average grain size d 50 smaller than 2 ⁇ m, in particular especially applied with a grain size d 50 smaller than 0.8 ⁇ m. Sintering takes place at temperatures in the range of 1250 and 1350 ° C. In this way, an intermediate layer with a porosity of regularly less than 35%, in particular less than 30%, is obtained.
• the powder of the intermediate layer can be applied by conventional methods such as screen printing.
• Electrolyte interlayer composite applied the cathode in the form of a powder with an average grain size d 50 smaller than 2 ⁇ m, in particular with a grain size d 50 between 0.6 and 0.8 ⁇ m.
• All of the above-mentioned iron and cobalt or copper-containing cathode materials with A-place understoichiometry are suitable as powder materials. These are then sintered at temperatures in the range from 950 to 1150 ° C., with the lowest possible sintering temperature depending on the cathode material. In this way, a cathode with a porosity of regularly 20 to 40%, in particular 25 to 35%, is obtained.
• the average grain size is between 0.4 and 1.0 ⁇ m, in particular between 0.6 and 0.8 ⁇ m. An average grain size of 0.8 ⁇ m has proven particularly advantageous.
• the powder for the cathode layer can also be applied by customary methods, such as screen printing.
• the cathode material of the cathode according to the invention consists of Ln ⁇ . x - y M y Fe ⁇ - zz 0 3 - ⁇ with 0.02 ⁇ x ⁇ 0.05, 0.1 ⁇ y ⁇ 0.6 and 0.1 ⁇ z ⁇ 0.3.
• Ln lanthanide
• M strontium or calcium
• C cobalt or copper.
• the cathode material with the composition La 0 ⁇ 5 8Sr 0 , Feo, 8C ⁇ o, 2 ⁇ 3- ⁇ will be discussed below.
• the strontium diffusion is additionally prevented by the higher stability of the substoichiometric material compared to the Sr expansion.
• the cobalt-containing and especially the stoichiometric perovskites are generally not completely stable chemically.
• the YSZ - the material easily becomes poor in strontium. This effect is also called Sr expansion or strontium depletion.
• ⁇ Ceo, 8GD 0, 2 ⁇ 2- ⁇ powder CGO
• ⁇ Cathode material containing iron and cobalt or copper e.g. La 0 , 58Sro, 4Feo, 8Co 0 / 2 ⁇ 3- ⁇
• La 0 , 58Sro, 4Feo, 8Co 0 / 2 ⁇ 3- ⁇ e.g. La 0 , 58Sro, 4Feo, 8Co 0 / 2 ⁇ 3- ⁇
• the materials are applied to the anode-electrolyte composite using screen printing or similar processes.
• the two layers, the intermediate layer and the cathode must then be sintered at temperatures which are low enough on the one hand to avoid a reaction with the YSZ electrolyte, but on the other hand high enough to be sufficient Effect sintering of the materials.
• this temperature is between 1250 and 1350 ° C., in particular at approximately 1300 ° C., when the cathode is sintered between 950 and 1150 ° C., in particular at approximately 1080 ° C.
• the result is an intermediate layer and a cathode with a microstructure, as is shown, for example, in FIG. 2b.
• the porosity of the CGO layer is as low as possible, in any case below 30%.
• the porosity of the sintered cathode should be between 20 and 40% and have an average grain size between 0.4 and 1.0 ⁇ m, in particular 0.8 ⁇ m.
• FIGS. 1 and 2 The influence of the sintering temperature on the microstructure of a cathode material can be seen in FIGS. 1 and 2.
• FIG. 1 a commercial (La, Sr) Mn0 3 cathode material was used and sintered at different temperatures. The cathode was then used in a high-temperature fuel cell and tested under standard conditions (cathode size 40 ⁇ 40 mm 2 , 750 ° C., 0.7 V cell voltage, gas flow parallel to the electrode surfaces).
• the parameters for the tests are:
• a cathode material according to the invention (La 0 , s8Sr 0 , 4Feo, 8C ⁇ o, 2 ⁇ 3- ⁇ ) was used accordingly and also sintered at different temperatures and then tested in a high-temperature fuel cell under standard conditions.
• the parameters for the tests are:
• Figure 2a Sintering at 1120 ° C, power: 0.53 W / cm 2
• Figure 2b Sintering at 1080 ° C, power: 1.01 W / cm 2
• the figures show that the power density can be almost doubled by lowering the sintering temperature by only 40 ° C to 1080 ° C. This
• FIG. 3a shows the comparison between a commercial manganese-containing (La 0 / 65Sro, 3Mn0 3 _ ⁇ ) and an inventive (La 0 , 58Sr 0 , 4Feo, 8C ⁇ o, 2 ⁇ 3- ⁇ ) cathode material.
• the fuel cell with the manganese-containing cathode reaches almost 0.7 A / cm 2 , while the cathode according to the invention achieves almost double.
• 1.43 A / cm 2 corresponds to a power density of approx. 1 W / cm 2 . This power density is also significantly higher than that of manganese-based cells from other manufacturers [3].
• FIGS. 3b and 3c compare fuel cells with cathodes made from substoichiometric (La, Sr) (Fe, Co) 0 3 and cathodes made from stoichiometric cathode material under standard conditions.
• a cathode made of stoichiometric ao, 6Sro, 4Feo, 8Co 0 , 2 ⁇ 3-8 is compared as a cathode material with two cathodes, which is a 2% (La 0 58 Sr 0 , 4Feo, 8C ⁇ o, 2 ⁇ 3- ⁇ ) and one 5% (Lao, 55 Sro, 4Feo, 8C ⁇ o, 2 ⁇ 3 - ⁇ ) understoichiometry in the A place.
• the 5% sub-stoichiometry brings about a significant increase in performance of more than about 35%, while the 2% sub-stoichiometry even shows an improvement of more than 70%.
• FIG. 3c shows a comparison between a stoichiometric (La 0/8 Sro, 2Feo, sC ⁇ o, 2 ⁇ 3- ⁇ ) and another substoichiometric cathode according to the invention (La 0 / 78Sro, 2Fe 0 , 8C ⁇ o, 2 ⁇ 3- ⁇ ).
• the strontium content is chosen to be only half as large as in the examples from FIG. 3b.
• a 2% sub-stoichiometry on the A-space already leads to an improvement in performance of more than 30%.
• the increased electrochemical activity of the cathode according to the invention due to an improved oxygen reduction behavior compared to the aforementioned prior art makes it possible to operate SOFC fuel cells at relatively low temperatures of 750 ° C. or less and still achieve high performance ten, especially above 1 W / cm 2 at 0.7 V to achieve.
• these should be tested under identical conditions, in particular under conditions that correspond to those used in fuel cell stacks. These include, for example, the minimum size of a cell, which should not be less than 40 x 40 mm 2 . A gas flow should also be provided parallel to the electrode surfaces. It is also important to provide the power measurement at a certain cell voltage. A cell voltage of 0.7 volts is particularly suitable for this. Deviating measurement conditions can sometimes lead to higher power densities [4], [5]. However, these measurement conditions are generally not relevant to the application. Mechanical stresses are less likely to cause failure with a smaller electrode area, while a vertical flow that is not feasible in the fuel cell stack regularly leads to a higher gas exchange and thus to higher power densities. In addition, the cells described there can disadvantageously not be operated continuously at a cell voltage of less than 0.7 V, because otherwise there is a risk that the nickel of the anode will be oxidized.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Materials Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Organic Chemistry (AREA)
• Structural Engineering (AREA)
• Electrochemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Sustainable Development (AREA)
• Sustainable Energy (AREA)
• Inert Electrodes (AREA)

Priority Applications (5)

Applications Claiming Priority (2)

Publications (2)

Family

ID=34559436

Family Applications (1)

Country Status (9)

Families Citing this family (17)

Family Cites Families (9)

• 2003
  • 2003-11-07 DE DE10351955A patent/DE10351955A1/de not_active Withdrawn
• 2004
  • 2004-11-04 CA CA002544728A patent/CA2544728A1/en not_active Abandoned
  • 2004-11-04 US US10/578,297 patent/US20070148529A1/en not_active Abandoned
  • 2004-11-04 AU AU2004307760A patent/AU2004307760A1/en not_active Abandoned
  • 2004-11-04 EP EP04802674A patent/EP1680832A2/de not_active Withdrawn
  • 2004-11-04 WO PCT/DE2004/002443 patent/WO2005045979A2/de not_active Ceased
  • 2004-11-04 CN CNA2004800398846A patent/CN1902778A/zh active Pending
  • 2004-11-04 JP JP2006537058A patent/JP2007538354A/ja active Pending
  • 2004-11-04 KR KR1020067010218A patent/KR20060120675A/ko not_active Withdrawn

Also Published As

Similar Documents

Legal Events