JP4844040B2 - Solid oxide fuel cell - Google Patents

Description

  The present invention relates to a fuel cell, and more particularly to a solid oxide fuel cell that generates power stably in a mixed gas of a fuel gas and an oxidant gas.

  Conventionally, a flat plate type, a cylindrical type, and the like have been proposed as cell designs for solid oxide fuel cells.

  In such a cell, a fuel electrode and an air electrode are respectively disposed on the front surface and the back surface of the electrolyte, and power generation is performed by separately supplying fuel gas and oxidant gas using the electrolyte as a partition wall. . In order to improve the performance of such a partition-type cell, it is necessary to reduce the thickness of the electrolyte, and it is necessary to reduce the internal resistance of the electrolyte material. However, if the electrolyte is too thin, it becomes brittle, There was a problem that durability deteriorated.

  For this reason, as a fuel cell that replaces the partition type cell described above, the fuel electrode and the air electrode are arranged on the same surface of the substrate made of a solid electrolyte, and power is generated by supplying a mixed gas of fuel gas and oxidant gas. A possible non-membrane type solid oxide fuel cell has been proposed (for example, Patent Document 1). According to this fuel cell, since it is not necessary to separate the fuel gas and the oxidant gas, the separator and the gas seal are not required, and the structure and the manufacturing process can be greatly simplified.

Further, in this non-membrane type solid oxide fuel cell, the conduction of oxygen ions occurs near the surface layer of the solid electrolyte, and the fuel electrode and the air electrode are formed close to each other on the same surface of the solid electrolyte. The thickness of the electrolyte does not directly affect the performance of the battery as in the case of the cylinder type. Therefore, the thickness of the electrolyte can be increased while maintaining the performance of the battery, thereby improving the vulnerability.
JP-A-8-264195 (page 2-3, FIG. 1)

  As described above, in the fuel cell described in Patent Document 3, an electrolyte is used as a substrate, and a plurality of fuel electrodes and air electrodes are arranged on one surface thereof. However, what is required for the battery reaction in the electrolyte is a portion in the vicinity of the electrode, and in a configuration in which the fuel electrode and the air electrode are simply arranged on a flat electrolyte, there are many electrolytes that do not contribute to the battery reaction. Therefore, there was a limit to high output. Further, in order to improve battery performance, it was necessary to shorten the distance between different poles as much as possible to achieve high integration. However, an electrode on an electrolyte as represented by a screen printing method or the like was required. In the method of forming an electrode by applying this paste, there is a problem that there is a limit to shortening the interval in order to prevent short-circuiting between different poles due to sagging or bleeding after application or sintering.

  The present invention was made in order to solve the above-mentioned problem, and since the interval can be shortened without bringing the different poles into contact with each other, it is possible to highly integrate the electrodes, It is an object of the present invention to provide a solid oxide fuel cell capable of increasing the output by minimizing the electrolyte that does not contribute to the cell reaction.

In order to solve the above-described problems, a solid oxide fuel cell according to the present invention includes an electrolyte and an electrode pair including a pair of a fuel electrode and an air electrode, and one electrolyte is provided on at least one surface. The electrode pair is formed so that either the fuel electrode or the air electrode of the electrode pair is accommodated in the recess, and the other of the fuel electrode or the air electrode of the electrode pair is connected to the recess. It is formed on the surface of the electrolyte so as to be adjacent to each other.

  The shape of the cross section of the recess is not particularly limited, but is preferably rectangular or triangular, and it is also preferable that at least a part of the inner surface of the recess has an uneven shape. Moreover, it is preferable that the said recessed part is 10-100 micrometers in maximum depth, and is 10 micrometers-10 mm in width.

  A substrate for supporting the electrolyte may be further provided, and the substrate is preferably made of a metal or metal oxide type material.

  According to the present invention, since either one or both of the electrode pair is accommodated in the recess formed on the electrolyte surface, it is possible to suppress the sag and blur that occurs when forming the electrode. Since contact between each other can be prevented, the interval between the different polarities can be further shortened. In addition, since the contact area between the electrode and the electrolyte can be increased by forming the electrode in the recess, high output can be achieved.

  In addition, since at least a part of the inner surface of the recess has an uneven shape, the contact area between the electrode and the electrolyte can be increased, and higher output can be achieved.

  Furthermore, since the electrolyte is supported by the substrate, high durability against vibration and thermal cycle can be maintained even when a thin film electrolyte is formed. In particular, in a non-membrane type solid oxide fuel cell, many of the parts that contribute to the cell reaction are near the surface layer of the electrolyte, so even if the electrolyte on the substrate is thinned, the battery performance is not greatly affected. Cost can be reduced by thinning. As a method for reducing the thickness of the electrolyte, for example, there is a method in which an electrolyte is formed by printing, and a method in which a sheet-like electrolyte is attached to a substrate.

  Hereinafter, embodiments of a solid oxide fuel cell according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view (a) and a plan view (b) of a solid oxide fuel cell according to the present embodiment.

  As shown in FIG. 1, the fuel cell includes an electrolyte 1 and an electrode pair E including a pair of fuel electrodes 3 and an air electrode 5 and is configured as follows. First, two rows of concave portions 7 are formed on one surface of the electrolyte 1, and the fuel electrode 3 and the air electrode 5 are formed so as to be accommodated in the concave portion 7. At this time, the height of the fuel electrode 3 and the air electrode 5 is preferably smaller than the depth of the recess 7. Here, when the depth of the recess 7 is 10 μm or more, there is an advantage that the reaction field (three-phase interface) is increased and the battery characteristics are improved. Since there exists an advantage that it can do, it is preferable that the depth of the recessed part 7 is 10-100 micrometers. Moreover, it is more preferable that it is 10-50 micrometers. In addition, if the width of the recess 7 is 10 μm or more, there is an advantage that manufacture becomes easy. If the width is 10 mm or less, the portion not contributing to the battery reaction is reduced, and the electrode can be highly integrated. Since there exists an advantage that the output per unit area of a board can be made high, it is more preferable that it is 10 micrometers-10 mm. Moreover, it is more preferable that it is 100 micrometers-1 mm. Furthermore, it is preferable that the space | interval d of the recessed part 7 on the electrolyte 1 is 10-500 micrometers. Various shapes can be adopted as the shape of the concave portion 7, for example, it can be an elongated groove shape, a cylindrical shape, etc. In this embodiment, the cross section is a rectangular shape, but a triangular shape is used. The inner surface of the concave portion 7 may be formed into an uneven shape.

  Next, the material of the fuel cell configured as described above will be described. First, the material of the electrolyte 1 may be any material having hydrogen ion conductivity, and a known material can be used as the electrolyte of the solid oxide fuel cell, such as samarium or gadolinium. An oxygen ion conductive ceramic material such as a ceria-based oxide doped with strontium or magnesium, or a zirconia-based oxide containing scandium or yttrium can be used.

  As the fuel electrode 3, for example, a mixture of a metal catalyst and a ceramic powder material made of an oxide ion conductor can be used. As the metal catalyst used at this time, a material that is stable in a reducing atmosphere, such as nickel, iron, cobalt, or a noble metal (platinum, ruthenium, palladium, etc.) and has hydrogen oxidation activity can be used. In addition, as the oxide ion conductor, one having a fluorite structure or a perovskite structure can be preferably used. Examples of those having a fluorite structure include ceria-based oxides doped with samarium, gadolinium, and the like, and zirconia-based oxides containing scandium and yttrium. In addition, examples of those having a perovskite structure include lanthanum galide oxides doped with strontium and magnesium. Among the above materials, it is preferable to form the fuel electrode 3 with a mixture of an oxide ion conductor and nickel. The mixed form of the ceramic material made of the oxide ion conductor and nickel may be a physical mixed form or a form of powder modification to nickel. Moreover, the ceramic material mentioned above can be used individually by 1 type or in mixture of 2 or more types. Moreover, the fuel electrode 3 can also be comprised using a metal catalyst alone.

As the ceramic powder material forming the air electrode 5, for example, a metal oxide made of Co, Fe, Ni, Cr, Mn or the like having a perovskite structure or the like can be used. Specifically, (Sm, Sr) CoO ₃ , (La, Sr) MnO ₃ , (La, Sr) CoO ₃ , (La, Sr) (Fe, Co) O ₃ , (La, Sr) (Fe, Co , Ni) O _{3 and the} like, and (La, Sr) MnO ₃ is preferable. The ceramic material mentioned above can be used individually by 1 type or in mixture of 2 or more types.

  The fuel electrode 3 and the air electrode 5 can be formed of a ceramic powder material. The average particle size of the powder used at this time is preferably 10 nm to 100 μm, more preferably 50 nm to 50 μm, and particularly preferably 100 nm to 10 μm. In addition, an average particle diameter can be measured according to JISZ8901, for example.

  The fuel electrode 3 and the air electrode 5 are formed by adding appropriate amounts of a binder resin, an organic solvent, and the like with the above-described material as a main component. More specifically, it is preferable to add a binder resin or the like so that the main component is 50 to 95% by weight in the mixing of the main component and the binder resin. The film thicknesses of the fuel electrode 3 and the air electrode 5 are formed to be 1 to 500 μm after sintering, and preferably 10 to 100 μm.

  The fuel cell configured as described above generates power as follows. First, on one surface of the electrolyte 1 provided with the fuel electrode 3 and the air electrode 5, a mixed gas of a fuel gas composed of a hydrocarbon gas such as methane and ethane and an oxidant gas composed of air or the like is in a high temperature state ( For example, it supplies at 400-1000 degreeC). Thereby, ion conduction occurs mainly in the vicinity of the surface layer of the electrolyte 1 between the fuel electrode 3 and the air electrode 5 to generate electric power.

  Next, an example of the fuel cell manufacturing method described above will be described with reference to FIG. First, the electrolyte 1 produced by press-molding and sintering the above-described material is prepared (FIG. 2A). Subsequently, with the powder materials for the fuel electrode 3 and the air electrode 5 described above as main components, an appropriate amount of a binder resin, an organic solvent, and the like are added and kneaded to prepare a fuel electrode paste and an air electrode paste, respectively. The viscosity of each paste is appropriately set according to the coating method, but is preferably about 10 to 1000 mPa · s when a dispenser coating method as shown below is adopted.

  Next, two rows of recesses 7 are formed on the electrolyte 1 at positions where the pair of electrodes are arranged by cutting (FIG. 2B). Next, the fuel electrode paste is filled in one of the recesses 7a by a dispenser so as to be within the depth of the recesses 7a, and dried and sintered at a predetermined time and temperature to form the fuel electrode 3. Subsequently, similarly to the fuel electrode 3, the air electrode 5 is formed by the dispenser in the other recess 7 b formed to face the one recess 7 in which the fuel electrode 3 of the electrolyte 1 is formed. Through the above steps, the fuel cell shown in FIG. 1 is formed.

  As described above, in the fuel cell according to the present embodiment, the electrolyte 1 has the recess 7 on one surface, and the fuel electrode 3 and the air electrode 5 are accommodated, respectively. There is an effect like this. That is, in the fuel cell, by increasing the accuracy of processing the recess 7, the distance d between the different polarities can be shortened as much as possible, so that the internal resistance can be reduced and the output density is increased accordingly. In addition, since the distance d between the different poles can be shortened, the electrodes can be highly integrated, and the fuel cell can be miniaturized. Moreover, since the contact area of an electrode and the electrolyte 1 becomes large by forming an electrode in the recessed part 7, high output can be achieved.

  As mentioned above, although one embodiment of this embodiment was described, this invention is not limited to this, A various change is possible unless it deviates from the meaning. For example, in the above embodiment, both the fuel electrode 3 and the air electrode 5 are formed in the recess 7, but only the fuel electrode 3 is formed in the recess 7 as shown in FIG. Further, it can be formed on the electrolyte 1 so as to face the fuel electrode 3. Further, with the reverse configuration, the fuel electrode 3 can be formed on the electrolyte 1, and the air electrode 5 can be formed in the recess 7. At this time, when forming one electrode of the fuel electrode 3 or the air electrode 5 in the recess 7, a dispenser or an ink jet method is used. When forming the other electrode on the electrolyte 1, a doctor blade method is used. , Spray coating method, spin coating method, lithography method, electrophoresis method, roll coating method, gravure roll coating method, screen printing method, CVD, EVD, sputtering method, printing method such as transfer method, etc. An electrode can be formed on the electrolyte 1 by using a printing method. Moreover, as a post-process after printing, CIP (hydrostatic pressure press), HIP (hot isostatic press), uniaxial press, and other general press processes can also be used.

Moreover, in the said embodiment, although the fuel cell was comprised using a pair of electrode pair E, you may comprise using this. In this case, a plurality of electrode pairs E are connected by an interconnector 9 as shown in FIG. Details connects one of the electrode pairs E ₁ and the fuel electrode 3 of the air electrode 5 and the other electrode pairs E ₂ at the interconnector 9.

The interconnector 9 is made of a conductive metal such as Pt, Au, Ag, Ni, Cu, or SUS, or a metal-based material, or La (Cr, Mg) O ₃ , (La, Ca) CrO ₃ , (La, Sr). It can be formed of a lanthanum / chromite-based conductive ceramic material such as CrO _3, and one of these may be used alone, or two or more may be used in combination. Similarly to the fuel electrode 3 and the like, these materials are used as a main component, and a binder resin, an organic solvent, and the like are added in an appropriate amount. In the method of manufacturing the fuel cell shown in FIG. 4, the recess 7 is formed in the same manner as in the above embodiment, and the electrode pair E is formed in the recess 7. Then, the interconnector paste comprising the material is applied so as to connect the electrode pairs E ₁ and E ₂ by a printing method such as screen printing, drying and sintering to form the interconnector 9.

  Thus, a high power generation output can be obtained by using a plurality of electrode pairs E. The plurality of electrode pairs E may be connected in series or in parallel, or may be connected in a mixed state of series and parallel.

  Further, as shown in FIG. 5, a substrate 11 that supports the electrolyte 1 may be provided. At this time, the substrate 11 is preferably formed of a material having excellent adhesion to the electrolyte 1, and specifically, a ceramic material such as an alumina material, a silica material, or a titanium material is preferably used. Can do. In particular, it is preferable to use a ceramic material excellent in heat resistance of 1000 ° C. or higher, and the thickness of the substrate 11 is preferably 50 μm or more from the viewpoint of strength.

  Here, as a method of forming the electrolyte 1 on the substrate 11, an electrolyte paste is applied to the substrate 11 by printing and dried and sintered at a predetermined time and temperature, and a plate-like electrolyte 1 is prepared, A method of adhering the electrolyte 1 to the substrate 11 with an inorganic adhesive or the like can be mentioned.

  As described above, since the electrolyte 1 is supported by the substrate 11, high durability against vibration and thermal cycle can be maintained even if the electrolyte 1 is thinned. Further, since portions other than the vicinity of the surface layer of the electrolyte 1 hardly contribute to the battery reaction, even if the thin-film electrolyte 1 is formed on the substrate 11 by printing, the performance is not greatly affected. Therefore, the effect of cost reduction can be obtained by thinning the film.

  A plurality of electrolytes 1 may be separately formed on the same substrate 11 (see FIG. 6). Between the electrolytes 1, the adhesive 13 may be filled, or the interconnector 9 may be filled without filling the adhesive 13. Thus, by forming the electrolyte 1 separately, it is possible to block the oxide ion conduction path, and as a result, the original electromotive force by each electrode pair E and the electrolyte 1 is between adjacent electrode pairs. The so-called internal short-circuit phenomenon that is canceled and reduced by the electromotive force that is generated and has a reverse action can be reduced.

  Moreover, in the said embodiment, although the cutting process is mentioned as a formation method of the recessed part 7, it is not limited to this, A blast process, a laser processing, etc. may be sufficient, and the depth, width | variety, and space | interval of the recessed part 7 are set. Any formation method that can be controlled may be used.

  Hereinafter, the present invention will be described in more detail with reference to examples.

As Example 1, a solid oxide fuel cell shown in FIG. First, the electrolyte 1 produced by press-molding and sintering a powder made of GDC (Ce _0.9 Gd _0.1 O _1.9 ) was prepared. The electrolyte 1 has a size of 10 mm × 10 mm and a thickness of 1 mm.

The material of the fuel electrode 3 includes NiO powder (particle size 0.01 to 10 μm, average particle size 1 μm) and SDC (Ce _0.8 Sm _0.2 O _1.9 ) powder (particle size 0.01). 10 μm, average particle size 0.1 μm) is mixed so that the weight ratio is 7: 3, and then a cellulose binder resin is added to produce a fuel electrode paste in which the ratio of the mixture is 80% by weight. did. That is, the weight ratio of the mixture to the binder resin was set to 80:20. The viscosity of the fuel electrode paste was about 5 × 10 ² mPa · s suitable for the dispenser coating method by diluting with a solvent.

Subsequently, SSC (Sm _0.5 Sr _0.5 CoO ₃ ) powder (particle size 0.1 to 10 μm, average particle size 1 μm) is used as a material for the air electrode 5, and a cellulose binder resin is added. Then, an air electrode paste was prepared so that the ratio of the powder was 80%. That is, the weight ratio of the SSC powder to the binder resin was set to 80:20. As with the fuel electrode, the viscosity of the air electrode paste was diluted with a solvent to be about 5 × 10 ² mPa · s suitable for the dispenser coating method.

  First, two recesses 7 having a width of 500 μm, a length of 7 mm, and a depth of 100 μm were formed on the electrolyte 1 by sandblasting the abrasive grains together with compressed air at a high speed. The distance d between the recesses 7 was 50 μm.

  Next, the fuel electrode paste was applied into one of the recesses 7 using a dispenser. At this time, the fuel electrode paste is applied so that the width is 500 μm, the length is 7 mm, and the coating thickness is 50 μm. And after drying for 15 minutes at 130 degreeC, it sintered for 1 hour at 1450 degreeC, and the fuel electrode 3 was formed. Subsequently, as with the fuel electrode paste, the air electrode paste was applied to the other recess 7 using a dispenser. At this time, the air electrode paste is applied so that the width is 500 μm, the length is 7 mm, and the application thickness is 50 μm. And it dried at 130 degreeC for 15 minutes, Then, it sintered at 1200 degreeC for 1 hour, and produced one pair of electrode bodies E. FIG.

  Next, a solid oxide fuel cell shown in FIG. The materials for the electrolyte, fuel electrode, and air electrode, and paste formation are the same as in Example 1.

  First, one concave portion 7 having a width of 500 μm, a length of 7 mm, and a depth of 100 μm was formed on the electrolyte 1 by sandblasting and ejecting abrasive grains together with compressed air from the nozzle.

  Next, the fuel electrode paste was applied to the recess 7 using a dispenser. At this time, the fuel electrode paste is applied so that the width is 500 μm, the length is 7 mm, and the coating thickness is 50 μm. And after drying at 130 degreeC for 15 minutes, it sintered at 1450 degreeC for 1 hour.

  Subsequently, an air electrode paste was applied on the electrolyte 1 by screen printing. At this time, the width was 500 μm, the length was 7 mm, the coating thickness was 50 μm, and the distance from the fuel electrode 3 was 50 μm. And like the fuel electrode 3, after drying for 15 minutes at 130 degreeC, it sintered for 1 hour at 1200 degreeC, and produced one pair of electrode bodies E. FIG.

  Moreover, the comparative example contrasted with Example 1 and 2 as shown in FIG. 7 was manufactured as follows. In this comparative example, the fuel electrode 3 and the air electrode 5 are formed on the electrolyte 1 by screen printing. However, when the distance d between the fuel electrode 3 and the air electrode 5 is 50 μm, both electrodes are in contact with each other. The result was a short circuit condition.

The following evaluation experiments were performed on the examples and comparative examples thus manufactured. That is, by introducing a mixed gas of methane and oxygen at 800 ° C. and causing a reaction of CH ₄ + 1 / 2O ₂ → 2H ₂ + CO, nickel oxide as a fuel electrode is reduced, and current-voltage characteristics are Evaluation was performed. In addition, the distance d between the fuel electrode 3 and the air electrode 5 of the comparative example was evaluated at a safe distance of 200 μm in order to avoid a short circuit state.

表１より、実施例１及び２は、凹部７を形成しているために、電極対Ｅの間隔ｄを、比較例の電極対の間隔ｄの１／４とすることができるために、それに従い出力密度が約２８０％増加することが分かる。

From Table 1, since Examples 1 and 2 have the recesses 7 formed, the distance d between the electrode pair E can be ¼ of the distance d between the electrode pairs of the comparative example. It can be seen that the output density increases by about 280%.

It is sectional drawing (a) and top view (b) which show embodiment of the solid oxide fuel cell which concerns on this invention. It is a figure which shows an example of the manufacturing method of the solid oxide fuel cell shown in FIG. FIG. 3 is a cross-sectional view showing another example of the solid oxide fuel cell shown in FIG. 1. FIG. 3 is a cross-sectional view showing still another example of the solid oxide fuel cell shown in FIG. 1. FIG. 3 is a cross-sectional view showing still another example of the solid oxide fuel cell shown in FIG. 1. FIG. 3 is a cross-sectional view showing still another example of the solid oxide fuel cell shown in FIG. 1. It is sectional drawing of the solid oxide fuel cell which concerns on a comparative example.

Explanation of symbols

1 Electrolyte 3 Fuel electrode 5 Air electrode 7 Recess 11 Substrate E Distance between electrode pair d

Claims (7)

Electrolyte,
An electrode pair comprising a pair of fuel electrode and air electrode;
The electrolyte has one or more recesses on at least one surface, and is formed so that either the fuel electrode or the air electrode of the electrode pair is accommodated in the recess. A solid oxide fuel cell, wherein the other of the fuel electrode and the air electrode is formed on the surface of the electrolyte so as to be adjacent to the recess. 2. The solid oxide fuel cell according to claim 1, wherein a cross-sectional shape of the concave portion is a rectangular shape or a triangular shape. 3. The solid oxide fuel cell according to claim 1, wherein at least a part of the inner surface of the recess has an uneven shape. The recess, solid oxide fuel cell according to any one of claims 1 to 3, wherein a maximum depth of 10 to 100 [mu] m. The recess, solid oxide fuel cell according to claim 1, any one of 4, wherein the width is 10Myuemu～10mm. Solid oxide fuel cell according to any one of claims 1 to 5, characterized in that the substrate for supporting the electrolyte is further provided. The solid oxide fuel cell according to any one of claims 1 to 6 , wherein the substrate is made of a metal or a metal oxide-based material.

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