Patent Application
20070122674
The present invention relates to a solid oxide fuel cell and more particularly to a solid oxide fuel cell which can be produced by a method which includes forming one fuel cell unit in the form of a plurality of partial laminate divisions during the firing of a laminate of an electrolyte substrate, a cathode electrode layer an anode electrode layer and electrically connecting the partial laminate divisions to each other with an electrically-conductive material layer to provide a simple structure requiring no enclosure, thereby attaining both cost reduction and enhancement of impact resistance.
The volume density of the electrolyte becomes equal to or less than 70% by firing and becomes equal to or more than 90% by sintering.
A solid oxide fuel cell of the type including a solid electrolyte is heretofore developed. An example of the fuel cell including a solid electrolyte is one including as an oxygen-ionically conductive solid electrolyte substrate a fired material made of stabilized zirconia having yttria (Y2O3) incorporated therein. A cathode electrode layer is formed on one side of the solid electrolyte substrate while an anode electrode layer is formed on the other side of the solid electrolyte substrate. Oxygen or an oxygen-containing gas is supplied into the fuel cell on the cathode electrode layer side thereof while a fuel gas such as methane is supplied into the fuel cell on the anode electrode layer side thereof.
In this fuel cell, oxygen (O2) which is supplied into the cathode electrode layer is ionized to oxygen ion (O2−) at the interface of the cathode electrode layer with the solid electrolyte substrate. The oxygen ion is conducted through the solid electrolyte substrate to the anode electrode layer where it then reacts with the gas such as methane (CH4) which is supplied thereinto to produce water (H2O), carbon dioxide (CO2), hydrogen (H2) and carbon monoxide (CO). In this reaction, oxygen ion releases electron to make some difference in potential between the cathode electrode layer and the anode electrode layer. Accordingly, a lead wire can be attached to the cathode electrode layer and the anode electrode layer so that electron in the anode electrode layer flows through the lead wire toward the cathode electrode layer to generate electricity as a fuel cell. The driving temperature of the fuel cell is about 1,000° C.
However, this type of a fuel cell requires that separate chambers be provided, that is, an oxygen or oxygen-containing gas supplying chamber be provided at the cathode electrode layer side thereof and a fuel gas supplying chamber be provided at the anode electrode layer side thereof. Further, since this type of a fuel cell is exposed to an oxidizing atmosphere and a reducing atmosphere at high temperatures, it is difficult to enhance the durability as fuel cell unit.
On the other hand, a fuel cell is developed which includes a cathode electrode layer and an anode electrode layer provided on the opposing sides of two sheets of solid electrolyte substrate, respectively, to form a fuel cell unit that is adapted to be disposed in a fuel gas such as mixture of methane gas and oxygen gas to cause the generation of electromotive force between the cathode electrode layer and the anode electrode layer. The principle of this type of a fuel cell in the generation of electromotive force between the cathode electrode layer and the anode electrode layer is the same as that of the aforementioned separate chamber type fuel cell. However, since the aforementioned proposal is advantageous in that the fuel cell unit can be entirely disposed in substantially the same atmosphere, it can be in the form of a single chamber which can be supplied with a mixed fuel gas, making it possible to enhance the durability of the fuel cell unit.
However, this single chamber type fuel cell, too, must be driven at a temperature as high as about 1,000° C. and thus is subject to the risk of explosion of mixed fuel gas. When the oxygen concentration is lowered under the flammability limit to avoid this risk, the carbonation of the fuel such as methane proceeds, raising a problem of deterioration of cell performance. In order to solve this problem, a single chamber type fuel cell is proposed which can employ a mixed fuel gas in an oxygen concentration allowing prevention of explosion of mixed fuel gas as well as prevention of progress of carbonation of fuel.
The above proposed single chamber type fuel cell includes fuel cell units containing a solid electrolyte substrate laminated on each other parallel to the flow of the mixed fuel gas. The fuel cell unit has a solid electrolyte substrate having a dense structure and a porous cathode electrode layer and a porous anode electrode layer formed on the respective side of the solid electrolyte substrate. A plurality of fuel cell units having the same configuration are laminated in a vessel made of ceramic. These fuel cell units are hermetically sealed in the vessel by an end plate with a filler provided interposed therebetween.
The vessel is provided with a feed pipe for mixed fuel gas containing a fuel such as methane and oxygen and a discharge pipe for exhaust gas. The vessel is filled with a filler in the space excluding the fuel cell unit and allowing the flow of the mixed fuel gas and the discharge gas in such an arrangement that a proper gap is formed. In this arrangement, when this system is driven as a fuel cell, ignition cannot occur even when a mixed fuel gas within the flammability range exists.
A fuel cell having another configuration is developed. The basic configuration of this fuel cell is the same as that of the aforementioned single chamber type fuel cell. However, this fuel cell includes fuel cell units containing a solid electrolyte substrate laminated along the axis of the vessel perpendicular to the flow of the mixed fuel gas. In this case, the fuel cell unit includes a porous solid electrolyte substrate and a porous cathode electrode layer and an anode electrode layer formed on the respective side of the solid electrolyte substrate. A plurality of fuel cell units having the same configuration are laminated in a vessel.
The aforementioned fuel cell includes fuel cell units received in a chamber. On the other hand, a solid oxide fuel cell device is proposed which is adapted to be disposed in or in the vicinity of flame so that the heat of flame causes the solid oxide fuel cell to be kept at its operating temperature to generate electricity. An embodiment of this solid oxide fuel cell is a solid oxide fuel cell including an anode electrode layer formed on the outer surface of a tubular solid electrolyte substrate. This type of a solid oxide fuel cell is mainly disadvantageous in that radical components from flame cannot be supplied into the upper half of the anode electrode layer, disabling the effective use of the entire surface of the anode electrode layer formed on the outer surface of the tubular solid electrolyte substrate. Thus, this type of a solid oxide fuel cell exhibits a low electricity generation efficiency. Further, since this type of a solid oxide fuel cell is unevenly heated directly by flame, it is disadvantageous in that sudden temperature change can easily cause cracking.
In order to solve these problems, an electricity generating device including a solid oxide fuel cell is proposed as a simple electricity supplying unit which employs a solid oxide fuel cell of the type allows direct utilization of flame produced by the combustion of a fuel in such a manner that the entire surface of an anode electrode layer formed on a flat solid oxide substrate is exposed to flame, thereby enhancing the durability and electricity generation efficiency and reducing the size and cost (for example, refer to Patent Reference 1).
An electricity generation device including the above proposed solid oxide fuel cell is shown in
The solid oxide fuel cell C thus configured is used as an electricity generation device which is adapted to be exposed to flame f produced by the combustion of a fuel gas while being supported over a gas burner 4 into which a fuel gas is supplied with the anode electrode layer 3 of the fuel cell C facing downward. A fuel which is combusted to produce flame causing oxidation is supplied into the gas burner 4. As the fuel there may be used phosphorus, sulfur, fluorine, chlorine or a compound thereof. An organic material which requires no discharge gas treatment is preferred. Examples of the organic fuel employable herein include gases such as methane, ethane, propane and butane, gasoline-based liquids such as hexane, heptane and octane, alcohols such as methanol, ethanol and propanol, ketones such as acetone, other organic solvents, food oils, kerosine, paper, and wood. Particularly preferred among these organic materials are gases.
Flame may be diffusion flame or premixed flame. However, since diffusion flame is unstable and generates soot that can easily deteriorate the performance of the anode electrode layer, premixed flame is preferred. Premixed flame is stable and can be easily adjusted in its size. Further, premixed flame can be properly adjusted in fuel concentration to prevent the generation of soot.
Since the solid oxide fuel cell C is in a flat form, flame f from the burner 4 can be uniformly applied to the anode electrode layer 3 of the solid oxide fuel cell C, making it possible to apply flame f to the anode electrode layer without unevenness as compare with the tubular fuel cell. Further, by disposing the anode electrode layer 3 facing flame f, hydrocarbons, hydrogen, radicals (OH, CH, C2, O2H, CH3) existing in the flame can be easily used as fuel for electricity generation based on oxidation-reduction reaction. Moreover, since the cathode electrode layer 2 is exposed to a gas containing oxygen such as air, oxygen can be easily used on the cathode electrode layer 2. Further, by blowing a gas containing oxygen onto the cathode electrode layer 2, the solid oxide fuel cell can be more efficiently rendered more oxygen-rich on the cathode electrode layer side thereof.
The electric power generated in the solid oxide fuel cell C is drawn out through lead wires L1, L2 extending from the cathode electrode layer 2 and the anode electrode layer 3, respectively. As each of the lead wires L1, L2 there is used one made of heat-resistant platinum or platinum alloy.
The solid oxide fuel cell C shown in
In some detail, a plurality of sheet-like solid electrolyte substrate 1 are used. A cathode electrode layer 2 and an anode electrode layer 3 are formed on the respective side of each of these sheet-like solid electrolyte substrate 1 to form a plurality of solid oxide fuel cell C11 to C33. The cathode electrode layer of these fuel cells are electrically connected to each other with a wiring E1 and the anode electrode layer of these fuel cells are electrically connected to each other with a wiring E2. These anode electrode layers each are entirely exposed to flame produced by combustion of a fuel while air is supplied into these cathode electrode layers. By properly devising the electrical connection of the plurality of solid oxide fuel cell, the area of electricity generation can be increased to provide a solid oxide fuel cell having a raised output. The plurality of solid oxide fuel cell cannot be only disposed in plane but also in three-dimension such as cylinder and sphere.
[Patent Reference 1] JP-A-2004-139936
[Patent Reference 2] JP-A-2005-63692
The solid oxide fuel cells mentioned above each include a cathode electrode layer and an anode electrode layer formed on a sheet of flat solid electrolyte substrate. A step of producing such a solid oxide fuel cell is shown in
Subsequently, a cathode electrode paste layer is formed on one side of the electrolyte substrate 1 by printing while an anode electrode paste layer is formed on the other side of the electrolyte substrate 1 by printing (Step S4). Thereafter, a metallic mesh is added to one or both of the cathode electrode paste layer and the anode electrode paste layer thus formed (Step S5). Further, a laminate of the electrolyte substrate 1, the cathode electrode paste layer, the anode electrode paste layer and the metallic mesh is formed. The laminate is then entirely fired (Step S6). Thus, a sheet of solid oxide fuel cell having a predetermined size including a cathode electrode layer 2 and an anode electrode layer 3 formed thereon is completed (Step S7).
The metallic mesh added to the cathode electrode paste layer and the anode electrode paste layer has an effect of retaining small pieces of fuel cell which would be produced even if the substrate is cracked by thermal shock applied to the solid oxide fuel cell during electricity generation. The fuel cell thus cracked remains capable of generating electricity. The metallic mesh acts to electrically connect small pieces of fuel cell. In this arrangement, electric power can be drawn out through lead wires L1 and L2. The metallic mesh also prevents the separation of fuel cell pieces produced by cracking to maintain the form of a sheet of solid oxide fuel cell.
In accordance with the procedure of producing a solid oxide fuel cell shown in
It is therefore an aim of the invention to provide a solid oxide fuel cell which can be produced by a method which includes forming a plurality of small fuel cell divisions resistant to thermal shock to enhance thermal shock resistance during electricity generation and reduce the manufacturing cost of fuel cell and a method for manufacturing thereof.
In order to solve the aforementioned problems, there is provided a solid oxide fuel cell including: a laminate including a solid electrolyte substrate, a cathode electrode layer formed on a first side of the substrate and an anode electrode layer formed on a second side of the substrate, and an electrically-conductive material layer made of a plurality of conductors formed all over the solid electrolyte substrate on one or both of the cathode electrode layer side and the anode electrode layer side thereof, wherein the laminate includes a plurality of partial laminate divisions which are electrically connected to each other with the conductors.
Further, the electrically-conductive material layer is formed by a metallic mesh, and the partial laminate division has an irregular shape developed during the sintering thereof.
The electrically-conductive material layer extends from the laminate in at least one direction, or the electrically-conductive material layer on the cathode electrode layer side extends in directions different from directions on the anode electrode side of the laminate. Further, an insulating fixing material layer is formed on the peripheral edge the laminate.
Further, there is provided a method for manufacturing a solid oxide fuel cell including: a step of forming an electrolyte sheet having a predetermined shape by an electrolyte green sheet; a step of forming a cathode electrode paste layer on a first side of the electrolyte sheet and forming an anode electrode paste layer on a second side of the electrolyte sheet; a step of adding an electrically-conductive material layer made of a plurality of conductors to one or both of the cathode electrode paste layer and the anode electrode paste layer; and a step of sintering a laminate including the electrolyte sheet, the cathode electrode paste layer, the anode electrode paste layer and the electrically-conductive material layer.
Further, there is provided a method for manufacturing a solid oxide fuel cell including: a step of forming an electrolyte sheet having a predetermined shape by an electrolyte green sheet; a step of adding an electrically-conductive material layer made of a plurality of conductors to one or both sides of the electrolyte sheet; a step of forming a cathode electrode paste layer on a first side of the electrolyte sheet and forming an anode electrode paste layer on a second side of the electrolyte sheet, with the electrically-conductive material layer interposed therebetween; and a step of sintering a laminate including the electrolyte sheet, the cathode electrode paste layer, the anode electrode paste layer and the electrically-conductive material layer.
Further, there is provided a method for manufacturing a solid oxide fuel cell including: a step of forming an electrolyte sheet having a predetermined shape by an electrolyte green sheet; a step of providing an electrically-conductive material layer on a first and a second sides of the electrolyte sheet to interpose thereof; a step of forming a cathode electrode paste layer on a first side of the electrolyte sheet and forming an anode electrode paste layer on a second side of the electrolyte sheet, with the electrically-conductive material layer interposed therebetween; and a step of sintering a laminate including the electrolyte sheet, the cathode electrode paste layer, the anode electrode paste layer and the electrically-conductive material layer.
Further, there is provided a method for manufacturing a solid oxide fuel cell including: a step of forming a cathode electrode paste layer on an electrically-conductive material layer made of a plurality of conductors; a step of forming an anode electrode paste layer on the electrically-conductive material layer made of a plurality of conductors; a step of forming a solid electrolyte paste layer interposed between the cathode electrode paste layer and the anode electrode paste layer; and a step of sintering a laminate including the cathode electrode paste layer and the anode electrode paste layer containing the electrically-conductive material layer, and the solid electrolyte paste layer.
As mentioned above, the solid oxide fuel cell of the invention includes an electrically-conductive material layer made of a plurality of conductors formed all over a solid oxide substrate on one or both of the cathode electrode layer side thereof and the anode electrode layer side thereof, a laminate of a cathode electrode layer and a solid electrolyte substrate and an anode electrode layer including a plurality of partial laminate divisions wherein the plurality of partial laminate divisions are connected to each other with a conductor to form a plurality of small fuel cell portions. In this arrangement, at the step of producing the solid oxide fuel cell, the laminate can be divided into a plurality of small portions having a size large enough to undergo no effects of thermal shock during electricity generation to inhibit further occurrence of cracking, making it possible to enhance the thermal shock resistance of the solid oxide fuel cell.
The method for manufacturing a solid oxide fuel cell of the invention includes forming a cathode electrode paste layer and an anode electrode paste layer on one and the other sides of an electrolyte sheet having a predetermined shape, respectively, adding an electrically-conductive material layer made of a plurality of conductors to one or both of the cathode electrode paste layer and the anode electrode paste layer to form a laminate of an electrolyte sheet, a cathode electrode paste layer, an anode electrode paste layer and an electrically-conductive material layer and then sintering the laminate. In this manner, the step of sintering only the solid electrolyte substrate particularly as in the related art technique can be eliminated. Accordingly, even when the laminate is cracked and divided into a plurality of small fuel cell portions, the presence of the electrically-conductive material layer prevents the laminate from being completely separated from each other and thus allows the solid oxide fuel cell thus obtained to remain capable of generating electricity as it is. Thus, no strict quality control for enhancing yield in manufacturing is required.
Moreover, the job of forming the laminate of an electrolyte sheet, a cathode electrode paste layer, an anode electrode paste layer and an electrically-conductive material layer can be simplified to reduce the manufacturing cost. When sintered, the laminate undergoes cracking that causes division into a plurality of small fuel cell portions. The formation of the solid oxide fuel cell of the invention, however, is arranged such that small fuel cell portions having a size large enough to undergo no effects of thermal shock are formed to enhance the thermal shock resistance of the fuel cell during heating. Therefore, the occurrence of cracking during the sintering of the laminate is advantageous and can be made the effective use of to form a plurality of small fuel cell portions.
Embodiments of implementation of the solid oxide fuel cell of the invention will be described with reference to the configuration and manufacturing method of the solid oxide fuel cell in connection with FIGS. 1 to 13. The description of the configuration of the present embodiment of the solid oxide fuel cell will be preceded by the description of the electrolyte substrate material, the cathode electrode material and the anode electrode material which can be commonly used in solid oxide fuel cells.
As a solid electrolyte substrate 1 there may be used, e.g., any known material. Examples of such a material include the following materials.
a) YSZ (yttria-stabilized zirconia), ScSZ (scandia-stabilized zirconia), zirconia-based ceramics obtained by doping these materials with Ce, Al or the like
b) Ceria-based ceramics such as SDC (samaria-doped ceria) and GDC (gadolia-doped ceria)
c) LSGM (lanthanum gallate), bismuth oxide-based ceramics
As an anode electrode layer 3 there may be used, e.g., any known material. Examples of such a material include the following materials.
d) Cermets of nickel with yttria-stabilized zirconia-based, scandia-stabilized-based or ceria-based (e.g., SDC, GDC, YDC) ceramics
e) Sintered material mainly including an electrically-conductive oxide (50% to 99% by weight) (As the electrically-conductive oxide there may be used nickel oxide having lithium dissolved in solid state therein or the like)
f) Metal made of platinum element or oxide thereof incorporated in the materials d) and e) in an amount of from 1% to 10% by weight
Particularly preferred among these materials are materials d) and e).
Due to its excellent oxidation resistance, the sintered material mainly including the electrically-conductive oxide e) can prevent phenomena occurring due to the oxidation of the anode layer, e.g., drop of electricity generation efficiency or incapability of electricity generation due to the rise of the electrode resistivity of the anode layer and exfoliation of the anode layer from the solid electrolyte layer. As the electrically-conductive oxide there is preferably used nickel oxide having lithium dissolved therein in solid state. Further, the incorporation of a metal such as platinum group element or rhenium or oxide thereof in the materials d) and e) makes it possible to obtain a high electricity generation capability.
As the cathode electrode layer 2 there may be used any known material. Examples of such a material include manganate (e.g., lanthanum strontium manganite), gallate and cobaltate (e.g., lanthanum strontium cobaltate, samarium strontium cobaltate) of an element belonging to the group III such as lanthanum having strontium (Sr) incorporated therein.
The cathode electrode layer 2 and the anode electrode layer 3 each are formed by a porous material. The solid electrolyte substrate 1, too, can be in the form of porous material. As in the related art, the solid electrolyte substrate 1 may be in a dense form. However, a dense solid electrolyte substrate exhibits a low thermal shock resistance and thus can be easily cracked also by sudden temperature change. In general, the solid electrolyte substrate is formed thicker than the anode electrode layer and the cathode electrode layer. Accordingly, triggered by the cracking of the solid electrolyte substrate, the related art solid oxide fuel cell is entirely cracked. As a result, the solid oxide fuel cell is completely divided into pieces.
The porous solid electrolyte substrate thus formed cannot be cracked against sudden temperature change caused by flame ignition or extinction, even against heat cycle having a great temperature difference, during electricity generation, making it possible to enhance the thermal shock resistance of the solid oxide fuel cell. When the percent porosity of the solid electrolyte substrate, if porous, falls below 10%, the resulting solid oxide fuel cell is not observed to have remarkable enhancement of thermal shock resistance. When the percent porosity of the solid electrolyte substrate is 10% or more, the resulting solid oxide fuel cell is observed to have a good thermal shock resistance. When the percent porosity of the solid electrolyte substrate is 20% or more, the resulting solid oxide fuel cell is observed to have a better thermal shock resistance. This is presumably because when the solid electrolyte layer is porous, the thermal expansion caused by heating is relaxed by the void.
As shown in
However, even the porous solid electrolyte substrate thus produced cannot be completely prevented from being cracked by thermal shock. In order to prevent this trouble, it is practiced as in the manufacturing step shown in
Focusing on the fact that even when the solid oxide fuel cell is cracked and divided into small portions by thermal shock, the small portions themselves remain capable of generating electricity as fuel cell as previously mentioned, the manufacturing of the solid oxide fuel cell is arranged such that the laminate is previously divided into a plurality of small portions having a size large enough to undergo no effects of thermal shock during electricity generation at the step of producing the solid oxide fuel cell.
A first embodiment of the solid oxide fuel cell according to the invention is shown in
Though depending on the gap between the conductors constituting the metallic mesh, when the four small fuel cell portions each have an area of 10 mm2 or less for example, these small fuel cell portions can be difficultly cracked even against thermal shock occurring during the electricity generation by the solid oxide fuel cell. This is presumably because these small fuel cell portions allow uniform and rapid conduction of heat. The method for manufacturing the solid oxide fuel cell according to the first embodiment will be described later.
A second embodiment of the solid oxide fuel cell according to the invention is shown in
A specific example 1 of the solid oxide fuel cell C2 including the plurality of irregularly shaped small fuel cell portions 2n shown in
While the metallic mesh M is shown embedded in both the cathode electrode layer 2 and the anode electrode layer 3 in
The solid oxide fuel cell C2 shown in
While an example of the formation of a plurality of irregularly shaped small fuel cell portions is shown in
The solid oxide fuel cell C2 shown in
The solid oxide fuel cell C2 according to the specific example 2 of
As mentioned above, the solid oxide fuel cells according to the first and second embodiments shown in FIGS. 1 to 4 themselves each include a plurality of rectangular or irregularly shaped small fuel cell portions formed during manufacturing the fuel cell and thus can relax the occurrence of thermal shock due to heating during the electricity generation by the fuel cell and hence inhibit further occurrence of cracking.
As the metallic mesh to be used in the first and second embodiments there is used a lattice-like or networked high melting metal conductor layer which allows good conduction of heat by the heating of the solid oxide fuel cell and can act as current collecting electrode. In the case where a method metal is provided on the both sides of the electrolyte substrate, the electrically-conductive material layer is not necessarily lattice-like or networked but may be formed by rod-shaped conductors disposed juxtaposed. In this case, juxtaposed conductors disposed on the respective side of the electrolyte substrate can be arranged such that they extend in directions perpendicular to each other to fairly retain the plurality of small fuel cell portions.
The method for manufacturing the solid oxide fuel cell according to the present embodiment will be described in connection with flow charts shown in FIGS. 5 to 8.
Firstly, a circular or rectangular sheet having a predetermined size allowing shrinkage which would be caused by sintering is formed by a green sheet obtained by kneading a solid electrolyte material with a binder (Step S11). The green sheet is then dried to a predetermined size (Step S12). The binder is then combusted (Step S13). Thus, an electrolyte sheet constituting the electrolyte substrate 1 of the solid oxide fuel cell is prepared (Step S14).
Subsequently, a cathode electrode paste layer and an anode electrode paste layer are formed on one and the other sides of the electrolyte sheet produced at Step S14 by printing, respectively (Step S15). Thereafter, a metallic mesh is bonded to one or both of the cathode electrode paste layer and the anode electrode paste layer with an electrode paste (Step S16).
Thus, a laminate of an electrolyte sheet, a cathode electrode paste layer, an anode electrode paste layer and a metallic mesh is formed. The laminate is then entirely sintered (Step S17). During the sintering of the laminate, the electrolyte sheet of the laminate shrinks while the metallic mesh doesn't. Accordingly, when the laminate is converted to a sintered ceramic material, the difference in shrinkage factor between the electrolyte sheet and the metallic mesh causes the laminate to be cracked and divided into a plurality of irregularly shaped small fuel cell portions. Thus, a solid oxide fuel cell having a predetermined size including a plurality of irregularly shaped small fuel cell divisions is completed (Step S18). In this manner, a solid oxide fuel cell according to the specific example 1 shown in
While the present example of the step of producing a solid oxide fuel cell is described with reference to the case where irregularly shaped small fuel cell portions are formed, the manufacture of the solid oxide fuel cell according to the first embodiment shown in
Subsequently, a cathode electrode paste layer and an anode electrode paste layer are formed on the metallic mesh formed at Step S22 on one and the other sides of the electrolyte sheet by printing, respectively (Step S23).
Thereafter, a laminate of an electrolyte, a cathode electrode paste layer, an anode electrode paste layer and a metallic mesh is formed. The laminated is then entirely sintered (Step S24). During the sintering of the laminate, the electrolyte sheet of the laminate shrinks while the metallic mesh doesn't. Accordingly, when the laminate is converted to a sintered ceramic material, the difference in shrinkage factor between the electrolyte sheet and the metallic mesh causes the laminate to be cracked and divided into a plurality of irregularly shaped small fuel cell portions. Thus, a solid oxide fuel cell having a predetermined size including a plurality of irregularly shaped small fuel cell divisions is completed (Step S25). In this manner, a solid oxide fuel cell according to the specific example 2 shown in
While the example 2 of the step of producing a solid oxide fuel cell is described with reference to the case where irregularly shaped small fuel cell portions are formed, the manufacture of the solid oxide fuel cell according to the first embodiment shown in
Subsequently, a cathode electrode paste layer and an anode electrode paste layer are formed on the metallic mesh formed at Step S32 on one and the other sides of the electrolyte sheet by printing, respectively (Step S33).
Thus, a laminate of an electrolyte, a cathode electrode paste layer, an anode electrode paste layer and a metallic mesh is formed. The laminated is then entirely sintered (Step S34). During the sintering of the laminate, the electrolyte sheet of the laminate shrinks while the metallic mesh doesn't. Accordingly, when the laminate is converted to a sintered ceramic material, the difference in shrinkage factor between the electrolyte sheet and the metallic mesh causes the laminate to be cracked and divided into a plurality of irregularly shaped small fuel cell portions. Thus, a solid oxide fuel cell having a predetermined size including a plurality of irregularly shaped small fuel cell divisions is completed (Step S35). In this manner, a solid oxide fuel cell according to the specific example 2 shown in
While the example 3 of the step of producing a solid oxide fuel cell is described with reference to the case where irregularly shaped small fuel cell portions are formed, the manufacture of the solid oxide fuel cell according to the first embodiment shown in
Subsequently, a solid electrolyte paste is printed on any one of the cathode electrode paste layer and the anode electrode paste layer formed at Step S41 to a predetermined size to form a solid electrolyte paste layer (Step S42). Subsequently, the other of the cathode electrode paste layer and the anode electrode paste layer is laminated on the solid electrolyte paste layer to form a laminate of a solid electrolyte paste, a cathode electrode paste layer, an anode electrode paste layer and a metallic mesh which is then entirely sintered (Step S43).
During the sintering of the laminate, the electrolyte paste layer of the laminate shrinks while the metallic mesh doesn't. Accordingly, when the laminate is converted to a sintered ceramic material, the difference in shrinkage factor between the electrolyte paste layer and the metallic mesh causes the laminate to be cracked and divided into a plurality of irregularly shaped small fuel cell portions. Thus, a solid oxide fuel cell having a predetermined size including a plurality of irregularly shaped small fuel cell divisions is completed (Step S44). In this manner, a solid oxide fuel cell according to the specific example 1 of the second embodiment shown in
In accordance with the manufacturing methods according to the aforementioned manufacturing step examples, solid oxide fuel cells according to the first and second embodiments shown in
FIGS. 9 to 11 each depict a solid oxide fuel cell according to a third embodiment which provides reinforcement of the first and second embodiments and has a metallic mesh formed as a lead wire for drawing electric power.
The configuration shown in
Further, as shown in
Further, as shown in
The peripheral edge of the solid oxide fuel cell C2 is covered by an insulating inorganic material. For example, a fixing member layer 5 of an electrolyte material is formed all over the periphery of the solid electrolyte substrate 1 to a predetermined thickness. The fixing member layer 5 acts as a frame body for the fuel cell to which the entire periphery of the metallic meshes M1 and M2 are fixed. In this arrangement, the deflection of the solid oxide fuel cell C2 can be inhibited more than in the modification example 1 shown in
The procedure of manufacturing the solid oxide fuel cell C2 according to the modification example 2 of the third embodiment shown in
Subsequently, as shown in
The foregoing description is made with reference to the configuration of a sheet of solid oxide fuel cell and its manufacturing method. The use of a plurality of sheets of the solid oxide fuel cell in combination is shown in
In
Embodiments 1 and 2 of the solid oxide fuel cell having a plurality of irregularly shaped small fuel cell portions which is described will be described hereinafter.
In Embodiment 1, a paste made of a mixture of 50 wt-% of samarium strontium cobaltite (SSC) and 50 wt-% of samarium-doped ceria (Ce0.8Sm0.2O1.9, SDC) is printed on a #80 (Japanese Industrial Standards) platinum mesh having a size of about 6 mm×15 mm in an area of about 6 mm×6 mm at one end thereof, and then dried. An SDC paste is printed on the paste layer in a slightly larger area, and then dried.
A paste made of a 15:45:40 (by weight) mixture of NiO—CoO—SDC is printed on another platinum mesh having the same shape as mentioned above, and then dried. The same paste is further spread over the SDC paste layer. The SDC paste layer of the platinum mesh on which the SSC paste layer is formed is laminated on the SDC paste layer, and then dried to form an integrated body. Subsequently, the integrated body is calcined at 1,200° C. in the atmosphere for 2 hours.
The solid oxide fuel cell thus obtained by calcining is observed having a number of fine irregular cracks running to form irregularly shaped and sized island-shaped small fuel cell divisions. However, these small fuel cell divisions are observed firmly connected to each other with the platinum mesh. In order to evaluate the solid oxide fuel cell for electricity generation capability as a fuel cell, the surface of the anode electrode layer of the solid oxide fuel cell is directly exposed to premixed flame of n-butane. As a result, the open circuit voltage is about 0.5 V and the short-circuit current is about 200 mA.
In Embodiment 2, a mixture of SDC powder, polyvinyl butyral and dibutyl phthalate is slurried by a ball mill method. A green sheet having a thickness of about 0.2 mm is then prepared from the slurry. A paste made of a mixture of 50 wt-% of SSC and 50 wt-% of SDC is printed on one side of the green sheet while a paste made of a 15:45:40 (by weight) mixture of NiO—CoO—SDC is printed on the other side of the green sheet. The coated green sheet is then dried. The green sheet thus dried is then stamped to a disc having a diameter of about 20 mm.
Subsequently, two sheets of #80 platinum mesh having a diameter of about 20 mm obtained by stamping are welded to a platinum wire. The two sheets of platinum mesh are then pressed between flat metallic plates with the disc of green sheet prepared above interposed therebetween to form an integrated body. The aforementioned SSC-SDC mixture paste is printed on the SSC-SDC printed side of the integrated disc, and then dried. The aforementioned NiO—CoO—SDC mixture paste is spread over the other side of the disc thus dried, and then dried. The disc is then calcined at 1,200° C. in the atmosphere for 2 hours.
The solid oxide fuel cell thus obtained by calcining is observed having a number of fine irregular cracks running to form irregularly shaped and sized island-shaped small fuel cell divisions. However, these small fuel cell divisions are observed firmly connected to each other with the platinum mesh. The surface of the anode electrode layer of the solid oxide fuel cell is directly exposed to premixed flame of n-butane. As a result, the open circuit voltage is about 0.5 V and the short-circuit current is about 200 mA.
[
S11: Prepare green sheet having a predetermined size
S12: Dry green sheet
S13: Combust binder
S14: Prepare electrolyte sheet
S15: Print electrode paste
S16: Add metallic mesh with electrode paste
S17: Sinter laminate
S18: Complete solid oxide fuel cell
[
S21: Prepare electrolyte sheet having a predetermined size from green sheet
S22: Add metallic mesh
S23: Print electrode paste
S24: Sinter laminate
S25: Complete solid oxide fuel cell
[
S31: Prepare green sheet having a predetermined size
S32: Press green sheet interposed between metallic meshes to prepare clamped body
S33: print electrode paste
S34: Sinter laminate
S35: Complete solid oxide fuel cell
[
S41: Print electrode paste on metallic mesh
S42: Print electrolyte paste on electrode layer
S43: Sinter laminate
S44: Complete solid oxide fuel cell
[
A1: Air
A2: Flame
A3: Gas
[
S1: Prepare green sheet having a predetermined size
S2: Sinter green sheet
S3: Prepare electrolyte substrate
S4: Print electrode paste
S5: Add metallic mesh
S6: Fire laminate
S7: Complete solid oxide fuel cell
| Number | Date | Country | Kind |
|---|---|---|---|
| P. 2005-344190 | Nov 2005 | JP | national |
