Patent Grant
11764383
The present disclosure relates to a single fuel cell, a fuel cell module, a power generation system, a high-temperature steam electrolysis cell, and methods for manufacturing the same, and particularly to a cell of a solid oxide fuel cell and a method for manufacturing the same.
A solid oxide fuel cell (SOFC) includes single elements (cells) each configured by an anode, an electrolyte, and a cathode, and interconnectors for electrically connecting adjacent cells to each other. Although a power generation voltage per cell is small, it is possible to increase the voltage and obtain a practical output by connecting a plurality of cells in series to form a cell stack.
In an SOFC, a flow path of fuel gas and a flow path of oxidizing agent are isolated from each other. Unnecessary mixing of fuel gas and oxidizing agent is not preferable. Therefore, a seal layer for preventing gas permeation may be provided at an appropriate place.
For example, if a gas permeation preventing function of the seal layer is insufficient, oxygen in the oxidizing agent may permeate through the seal layer and enter the fuel gas to oxidize the fuel gas, thereby reducing power generation efficiency. In PTL 1, a dense film is provided on a main surface and side end surfaces of a support substrate to prevent mixing of the fuel gas and the oxidizing agent.
A fuel cell described in PTL 2 includes an intermediate layer that is electrically connected to a power generation section. Here, the intermediate layer is formed of NiO+YSZ, NiO+Y2O3 or the like. However, there is a risk that Ni contained in the intermediate layer may be oxidized by oxygen gas, which deteriorates the electronic conductivity function of the intermediate layer. In PTL 2, an outer surface of the support substrate is covered with a dense seal layer to prevent mixing of the fuel gas on the support substrate side and air on an outer periphery of the dense seal layer.
[PTL 1] Japanese Unexamined Patent Application, Publication No. 2016-122645
[PTL 2] Japanese Unexamined Patent Application, Publication NO. 2017-201601
In PTL 1, an electrolyte is densified by using YSZ (yttria stabilized zirconia) to form a dense film. The dense film in PTL 1 has “high density to the extent that gas does not permeate therethrough”, but has a limited effect of preventing penetration of oxygen ions because the dense film is formed of YSZ having oxygen ion permeability.
In PTL 2, a dense seal layer is formed of an electronic insulating material such as glass, brazing material, or ceramics. Examples of ceramics include CSZ (calcia stabilized zirconia), NiO (nickel oxide)+YSZ, NiO+Y2O3 (yttria), and MgO (magnesium oxide)+MgAl2O4 (magnesia alumina spinel), and all of CSZ, YSZ and Y2O3 have oxygen ion permeability. When a material having oxygen ion permeability is used, the effect of preventing penetration of oxygen ions is limited.
The present disclosure has been made in view of such circumstances, and has an object to provide a single fuel cell capable of preventing gas permeation, particularly penetration of oxygen ions, a fuel cell module and a power generation system including the single fuel cell, and a high-temperature steam electrolysis cell, and methods for manufacturing the same.
In order to solve the above problem, a single fuel cell, a fuel cell module, a power generation system, a high-temperature steam electrolysis cell and methods for manufacturing the same adopt the following solutions.
A first aspect of the present disclosure provides a single fuel cell comprising a power generation section in which an anode, an electrolyte, and a cathode are stacked, a power non-generation section that does not include the power generation section, and an oxygen-ion-insulating gas seal film arranged so as to cover at least a part of a surface of the power non-generation section, wherein the gas seal film comprises a structure formed by firing a material containing MTiO3 (M: alkaline earth metal element) and metal oxide.
When a material obtained by adding metal oxide to MTiO3 is fired, a structure including a first structure and a second structure is formed. The first structure contains M and Ti derived from MTiO3 as main components. The second structure contains a metal contained in the metal oxide in a larger amount than the first structure, and contains M and Ti derived from MTiO3. A second structure component has a lower melting point than a first structure component. Therefore, a liquid phase occurs during a firing step and infiltrates into the first structure. As a result, rearrangement, dissolution, reprecipitation, and the like of the first structure occur, and densification of the gas seal film is promoted.
In addition, since the melting point decreases as the second structure increases, a dense film can be obtained even by firing at a low temperature. In general, the gas seal film is integrally fired together with a base material serving as a base. If a dense film can be obtained at a low temperature, it will lead to protection of the base material.
The gas seal film formed by firing the material in which metal oxide is added to MTiO3 may have low electronic conductivity and may be insulating. When the gas seal film is used to prevent gas leakage only, electronic conductivity may not be necessary. Such a gas seal film is suitably arranged at a place where electronic conductivity is unnecessary. By making the gas seal film electronically insulating, a short-circuit between power generation sections can be prevented.
The gas seal film formed by firing the material in which metal oxide is added to MTiO3 is an oxygen-ion-insulating film. Therefore, penetration of oxygen ions can be more reliably prevented than a gas seal film formed of a material having high oxygen-ion permeability such as YSZ. Here, the term “oxygen-ion-insulating” means that oxygen ion permeability is zero, or oxygen ions are less permeable than at least stabilized zirconia.
The structure includes a first structure and a second structure that are different in composition, the first structure contains components derived from the MTiO3 in larger amounts than the second structure, the second structure contains a metal element contained in the metal oxide in a larger amount than the first structure, and an area ratio of the second structure in the structure is not less than 1% and not more than 50%.
The gas seal film in which the second structure has an area ratio of 1% or more has a low open porosity and is sufficiently dense. Therefore, gas leakage can be prevented by providing the aforementioned gas seal film in the power non-generation section. However, when the area ratio of the second structure is too high, a crack occurs in the gas seal film due to a difference in thermal expansion between the support substrate and the underlayer film, and gas permeation occurs. Therefore, it is preferable that the area ratio of the second structure is not less than 1% and not more than 50%.
A second aspect of the present disclosure provides a single fuel cell comprising a power generation section in which an anode, an electrolyte, and a cathode are stacked, a power non-generation section that does not include the power generation section, and an oxygen-ion-insulating gas seal film arranged so as to cover at least a part of a surface of the power non-generation section, wherein the gas seal film comprises a structure formed by firing a material containing M(1+x)TiO3 (M: alkaline earth metal element, 0<x) or MTi(1+y)O3 (M: alkaline earth metal element, 0<y), and metal oxide.
The gas seal film defined in the second aspect has low oxygen-ion permeability. As a result, penetration of oxygen ions can be prevented. Furthermore, the gas seal film using M(1+x)TiO3 or MTi(1+y)O3 has low electronic conductivity. Such a gas seal film is suitably applied to a place where electronic conductivity is unnecessary.
The second structure is formed by firing a material in which metal oxide is added to M(1+x)TiO3 or MTi(1+y)O3 under a state where M or Ti is excessive. This influence enhances sinterability between first structures, and forms a dense structure having a reduced open porosity. Gas leakage can be prevented by covering the power non-generation section with the gas seal film having such a structure.
Furthermore, the inventors of the present application have conducted intensive studies, and as a result, have obtained knowledge that the second structure contains M or Ti derived from M(1+x)TiO3 or MTi(1+y)O3, and the content ratio of the second structure is different from that of the first structure. This knowledge suggests that the first structure may become a structure deficient in M or Ti. Such a structure loses stability and becomes less reliable. In the above disclosure, by adding M or Ti in excess, a state where M or Ti is insufficient in the first structure is mitigated, and a film with improved reliability can be obtained.
In the aforementioned second aspect, it is preferable that the structure includes a first structure and a second structure that are different in composition, the first structure contains components derived from M(1+x)TiO3 or components derived from MTi(1+y)O3 in larger amounts than the second structure, the second structure contains a metal element contained in the metal oxide in a larger amount than the first structure, and an area ratio of the second structure in the structure is not less than 1% and not more than 50%.
The gas seal film in which the second structure has the area ratio of 1% or more has a low open porosity and is dense. Therefore, gas leakage can be prevented by providing the gas seal film as described above in the power non-generation section. However, when the area ratio of the second structure exceeds 50%, a crack occurs in the gas seal film due to a difference in thermal expansion between the support substrate and the underlayer film, and gas permeation occurs.
In the first and second aspects, by arranging the gas seal film on the surface of the power non-generation section which does not include the power generation section, permeation of oxygen ions at an undesired location can be prevented without inhibiting permeation of gas which is required for power generation.
In the first and second aspects, the power non-generation section includes a lead film that may be electrically connected to the power generation section at an end portion, the gas seal film may be arranged so as to cover at least a part of a surface of the lead film.
In the first and second aspects, the power non-generation section may include an interconnector that electrically connects the power generation sections to each other, and the gas seal film may be arranged so as to cover at least a part of a surface of the interconnector.
In the first and second aspects, the power non-generation section may include a lead film electrically connected to the power generation section at an end portion, an interconnector for electrically connecting the power generation sections to each other, and a portion other than the lead film and the interconnector, and the gas seal film may be arranged so as to cover at least a part of a surface of the portion other than the lead film and the interconnector.
In the first and second aspects, the alkaline earth metal element is any one of Mg, Ca, Sr, and Ba.
In the first and second aspects, the metal oxide is preferably any one of B2O3, Al2O3, Ga2O3, In2O3, Tl2O3, Fe2O3, Fe3O4, MgO, NiO, and SiO2.
The present disclosure provides a fuel cell module comprising a plurality of single fuel cells each of which includes an anode, an electrolyte, and a cathode and is described in the first aspect or the second aspect, a fuel gas supply pipe for supplying fuel gas to the anodes, and an oxidant gas supply pipe for supplying an oxidant gas to the cathodes of the plurality of single fuel cells.
The present disclosure provides a power generation system comprising the aforementioned fuel cell module, and rotating equipment for generating rotational power by using an exhaust fuel gas and an exhaust oxidant gas that are exhausted from the fuel cell module, wherein the fuel cell module is supplied with the oxidant gas compressed by using the rotational power, and the fuel cell module generates electric power by using the fuel gas and the compressed oxidant gas.
The rotating equipment comprises a gas turbine or a turbocharger.
In the fuel cell module and the power generation system, deterioration in power generation performance caused by gas leakage is reduced as compared with conventional products in which YSZ or the like is used as a gas seal film.
A third aspect of the present disclosure provides a method of manufacturing a single fuel cell including a power generation section in which an anode, an electrolyte, and a cathode are stacked, and a power non-generation section that does not contain the power generation section, the method comprising: coating, on a surface of the power non-generation section, slurry of a material containing MTiO3 (M: alkaline earth metal element) and metal oxide that is added in an amount of 3 mol % or more to the MTiO3, and then firing the slurry to form an oxygen-ion-insulating gas seal film.
By adding 3 mol % or more of the metal oxide to MTiO3, the area ratio of the second structure in the structure after firing can be set to 1% or more. The gas seal film in which the second structure has the area ratio of 1% or more has a low open porosity and is dense. Therefore, gas leakage can be prevented by providing the gas seal film as described above in the power non-generation section.
A fourth aspect of the present invention provides a method of manufacturing a single fuel cell including a power generation section in which an anode, an electrolyte, and a cathode are stacked, and a power non-generation section that does not contain the power generation section, the method comprising:
coating slurry of a material containing M(1+x)TiO3 (M: alkaline earth metal element, 0<x) or MTi(1+y)O3 (M: alkaline earth metal element, 0<y) and metal oxide on a surface of the power non-generation section, and then firing the slurry to form an oxygen-ion-insulating gas seal film.
The gas seal film defined in the fourth aspect has low oxygen-ion permeability. As a result, leakage of oxygen ions can be prevented. Furthermore, the gas seal film using M(1+x)TiO3 or MTi(1+y)O3 has low electronic conductivity. Such a gas seal film is suitably applied to a place where electronic conductivity is unnecessary.
The second structure is formed by firing a material in which metal oxide is added to M(1+x)TiO3 or MTi(1+y)O3 in a state where M or Ti is excessive. This influence enhances sinterability between the first structures, and forms a dense structure in which the open porosity is reduced. Gas leakage can be prevented by covering the power non-generation section with the gas seal film having such a structure.
In the fourth aspect, the metal oxide may be added in an amount of 3 mol % or more to the M(1+x)TiO3 or the MTi(1+y)O3.
By adding 3 mol % or more of metal oxide to MTiO3, the area ratio of the second structure in the structure after firing can be set to 1% or more. The gas seal film in which the second structure has the area ratio of 1% or more has a low open porosity and is dense. Therefore, gas leakage can be prevented by providing the gas seal film as described above in the power non-generation section.
In the third and fourth aspects, by arranging the gas seal film on the surface of the power non-generation section which does not include the power generation section, permeation of oxygen gas and oxygen ions at an undesired location can be prevented without inhibiting permeation of a gas required for power generation.
In the third and fourth aspects, the power non-generation section may include a lead film electrically connected to the power generation section at an end portion, and the gas seal film may be arranged so as to cover at least a part of a surface of the lead film.
In the third and fourth aspects, the power non-generation section may include an interconnector that electrically connects the power generation sections to each other, and the gas seal film may be arranged so as to cover at least a part of a surface of the interconnector.
In the third and fourth aspects, the power non-generation section may include a lead film electrically connected to the power generation section at an end portion, an interconnector for electrically connecting the power generation sections to each other, and a portion other than the lead film and the interconnector, and the gas seal film may be arranged so as to cover at least a part of a surface of the portion other than the lead film and the interconnector.
In the third and fourth aspects, the alkaline earth metal element is preferably any one of Mg, Ca, Sr, and Ba.
A fifth aspect of the present disclosure provides a high-temperature steam electrolysis cell comprising: a hydrogen generation section in which an anode, an electrolyte, and a cathode are stacked; a hydrogen non-generation section that does not include the hydrogen generation section; and an oxygen-ion-insulating gas seal film arranged so as to cover at least a part of a surface of the hydrogen non-generation section, wherein the gas seal film comprises a structure formed by firing a material containing MTiO3 (M: alkaline earth metal element) and metal oxide.
A sixth aspect of the present invention provides a high-temperature steam electrolysis cell comprising: a hydrogen generation section in which an anode, an electrolyte, and a cathode are stacked; a hydrogen non-generation section that does not include the hydrogen generation section; and an oxygen-ion-insulating gas seal film arranged so as to cover at least a part of a surface of the hydrogen non-generation section, wherein the gas seal film comprises a structure formed by firing a material containing M(1+x)TiO3 (M: alkaline earth metal element, 0<x) or MTi(1+y)O3 (M: alkaline earth metal element, 0<y), and metal oxide.
In the fifth and sixth aspects, the structure may include a first structure and a second structure that are different in composition, the first structure may contain components derived from the MTiO3 in larger amounts than the second structure, and the second structure may include a metal element contained in the metal oxide in a larger amount than the first structure, and an area ratio of the second structure in the structure may be not less than 1% and not more than 50%.
A seventh aspect of the present invention provides a method of manufacturing a high-temperature steam electrolysis cell including a hydrogen generation section in which an anode, an electrolyte, and a cathode are stacked, and a hydrogen non-generation section that does not include the hydrogen generation section, the method comprising: coating, on a surface of the hydrogen non-generation section, slurry of a material containing MTiO3 (M: alkaline earth metal element) and metal oxide that is added in an amount of 3 mol % or more to the MTiO3, and then firing the slurry to form an oxygen-ion-insulating gas seal film.
An eighth aspect of the present invention provides a method of manufacturing a high-temperature steam electrolysis cell including a hydrogen generation section in which an anode, an electrolyte, and a cathode are stacked, and a hydrogen non-generation section that does not include the hydrogen generation section, the method comprising: coating, on a surface of the hydrogen non-generation section, slurry of a material containing M(1+x)TiO3 (M: alkaline earth metal element, 0<x) or MTi(1+y)O3 (M: alkaline earth metal element, 0<y) and metal oxide, and then firing the slurry to form an oxygen-ion-insulating gas seal film.
The single fuel cell and the high-temperature steam electrolysis cell which have the gas seal film according to the present disclosure are dense and can prevent gas leakage, and have low oxygen ion permeability, so that deterioration caused by penetration of oxygen ions can be prevented.
Hereinafter, embodiments of a single fuel cell, a fuel cell module, a power generation system, and methods of manufacturing the same according to the present disclosure will be described with reference to the drawings.
In the following description, for convenience of description, the positional relationship of respective components described with expressions “up” and “down” on paper surface indicates a vertically upper side and a vertically lower side, respectively. Also, in the present embodiment, in a case where the same effect can be obtained between an up-and-down direction and a horizontal direction, an up-and-down direction on paper surface is not necessarily limited to a vertically up-and-down direction, and the up-and-down direction on paper surface may correspond to, for example, a horizontal direction orthogonal to a vertical direction.
A cylindrical single fuel cell using a substrate tube will be described as an example according to the present embodiment with reference to
A single fuel cell 101 includes a cylindrical substrate tube 103, a plurality of power generation sections 105 formed on the outer peripheral surface of the substrate tube 103, and power non-generation sections 110 each formed between adjacent power generation sections 105. The power generation section 105 is configured by stacking an anode 109, an electrolyte 111, and a cathode 113. The single fuel cell 101 includes a lead film 115 which is electrically connected via an interconnector 107 to a cathode 113 of a power generation section 105 formed at one end of most distal ends in an axial direction of the substrate tube 103 out of the plurality of power generation sections 105 formed on the outer peripheral surface of the substrate tube 103, and a lead film 115 which is electrically connected to an anode 109 of a power generation section 105 formed at the other end of the most distal ends.
Further, in the present embodiment, gas seal films 117 are arranged so as to cover at least a part of the surfaces of the power non-generation sections 110. In the single fuel cell 101, the “power non-generation section” means a region which does not contain the power generation section 105 in which three phases of the anode 109, the electrolyte 111 and the cathode 113 are stacked. In
The arrangement of the gas seal films 117 is not limited to that of
A side of the substrate tube 103 on which the cathode 113 is provided is set in an oxidizing agent atmosphere during power generation. An inside of the substrate tube 103 is set in a fuel gas atmosphere during power generation, and at the time of an emergency stop, the inside of the substrate tube 103 is purged with nitrogen after the fuel gas is shut off, so that the inside of the substrate tube 103 is set in a reducing atmosphere. The oxidizing agent is a gas containing about 15% to 30% of oxygen. Typically, air is preferable, but a mixed gas of a combustion exhaust gas and air, a mixed gas of oxygen and air or the like may also be used instead of air. Hydrogen (H2) and not only hydrocarbon gas such as carbon monoxide (CO) or methane (CH4), city gas, or natural gas, but also a gas manufactured by gasifying carbonaceous raw materials such as petroleum, methanol, or coal with gasifying facilities.
The substrate tube 103 is formed by firing a porous material. The porous material includes, as a main component, CaO stabilized ZrO2 (CSZ), a mixture of CSZ and nickel oxide (NiO) (CSZ+NiO), Y2O3 stabilized ZrO2 (YSZ), MgAl2O4 or the like, for example. The substrate tube 103 supports the power generation sections 105, the interconnectors 107, and the lead films 115, and causes the fuel gas supplied to the inner peripheral surface of the substrate tube 103 to diffuse to the anodes 109 formed on the outer peripheral surface of the substrate tube 103 through pores of the substrate tube 103.
The anodes 109 are formed by using, as a material, an oxide of a composite material of Ni and a zirconia-based electrolyte material and firing the material. For example, Ni/YSZ is used as the material of the anodes 109. The thickness of the anodes 109 is 50 to 250 μm, and the anodes 109 may be formed by screen-printing slurry of the material. In this case, Ni as a component of the anodes 109 has a catalytic action on the fuel gas. This catalytic action serves to react the fuel gas supplied through the substrate tube 103, for example, a mixed gas of methane (CH4) and steam and reform the mixed gas into hydrogen (H2) and carbon monoxide (CO). The anodes 109 serve to electrochemically react hydrogen (H2) and carbon monoxide (CO) obtained by the reforming with oxygen ions (O2−) supplied through the electrolyte 111 in the vicinity of the interface with the electrolyte 111 to generate water (H2O) and carbon dioxide (CO2). Note that at this time, the power generation sections 105 generate power by electrons emitted from oxygen ions.
The electrolyte 111 is formed by firing a material having airtightness which makes a gas difficult to permeate and having high oxygen ion conductivity at high temperature. YSZ is mainly used for the material. The electrolyte 111 serves to transfer oxygen ions (O2−) generated at the cathode 113 to the anode 109. The film thickness of the electrolytes 111 located on the surfaces of the anodes 109 is 10 to 100 μm. The electrolytes 111 may be formed by screen-printing slurry of the material.
The cathodes 113 are formed by firing a material composed of, for example, LaSrMnO3-based oxide or LaCoO3-based oxide. The cathodes 113 may be formed by screen-printing slurry of the material or coating the slurry with a dispenser. The cathode 113 serves to dissociate oxygen in oxidant gas such as supplied air in the vicinity of the interface with the electrolyte 111 to generate oxygen ions (O2−).
The cathode 113 may be formed to have a two-layer configuration. In this case, a cathode layer (cathode intermediate layer) on the electrolyte 111 side is formed of a material having high ionic conductivity and excellent catalytic activity. The cathode layer (cathode conductive layer) on the cathode intermediate layer may be made of a perovskite type oxide represented by Sr and Ca-doped LaMnO3, which makes it possible to further enhance the power generation performance.
The interconnectors 107 are formed by firing a material composed of a conductive perovskite type oxide represented by M(1−z)LzTiO3 (M represents an alkaline earth metal element and L represents a lanthanoid element) such as SrTiO3. The interconnectors 107 may be formed by scree-printing slurry of the material. The interconnector 107 forms a dense film so that the fuel gas and the oxidant gas do not mix. The interconnectors 107 have stable durability and electronic conductivity under both an oxidizing atmosphere and a reducing atmosphere. The interconnector 107 electrically connects the cathode 113 of one power generation section 105 of adjacent power generation sections 105 and the anode 109 of the other power generation section 105 of the adjacent power generation sections 105, thereby connecting the adjacent power generation sections 105 to each other in series.
It is necessary that the lead film 115 has electronic conductivity and has a coefficient of thermal expansion which is close to those of other materials constituting the single fuel cell 101. Therefore, the lead film 115 is formed of firing a composite material of Ni and a zirconia-based electrolyte material such as Ni/YSZ or a material composed of M(1−z)LzTiO3 (M represents an alkaline earth metal element and L represents a lanthanoid element) such as SrTiO3. The lead film 115 serves to lead DC power generated by the plurality of power generation sections 105 connected in series through the interconnectors 107 to the vicinities of the end portions of the single fuel cell 101.
The gas seal film 117 forms a dense film so that the fuel gas and the oxidizing agent do not mix. The gas seal film 117 is formed by firing a material containing titanate MTiO3 (M represents an alkaline earth metal element) doped with alkaline earth metal and metal oxide.
The thickness of the gas seal films 117 is 1 μm to 100 μm. The gas seal films 117 may be formed by screen-printing slurry of the above material. The gas seal film 117 is a film having insulating performance to oxygen ions.
The alkaline earth metal element is any one of Mg, Ca, Sr, and Ba. The alkaline earth metal element is preferably Sr or Ba. The metal oxide is B2O3, Al2O3, Ga2O3, In2O3, Tl2O3, Fe2O3, Fe3O4, MgO, NiO, SiO2 or the like. The metal oxide is added in an amount of 3 mol % or more to MTiO3. The metal oxide is added up to 100 mol % to MTiO3.
The structure of the gas seal film 117 includes a first structure 11 and a second structure 12 which are different in composition. The first structure 11 includes M and Ti derived from MTiO3 contained in the material as main components. The second structure 12 contains a metal element derived from the metal oxide contained in the material in a larger amount than the first structure 11. The area ratio of the second structure 12 to the structure of the gas seal film 117 is not less than 1% and not more than 50%. The gas seal film 117 of the present embodiment serves to prevent gas permeation in the power non-generation sections 110, and thus is not required to have electrical characteristics.
Since the gas seal film 117 whose second structure 12 has an area ratio of 1% or more has a low open porosity and thus is sufficiently dense, gas leakage can be prevented by providing the gas seal films 117 as described above in the power non-generation sections 110. However, when the area ratio of the second structure 12 is too high, a crack occurs in the gas seal film 117 due to a difference in thermal expansion between the support substrate 302 and the lower film, and gas permeation occurs. Therefore, it is desirable that the area ratio of the second structure 12 in the structure of the gas seal film 117 is set to not less than 1% and not more than 50%.
The single fuel cell 101 of
First, a material such as calcia stabilized zirconia (CSZ) is molded in the form of the substrate tube 103 by an extrusion molding method.
A material constituting the anodes 109 is mixed with an organic vehicle (an organic solvent added with a dispersant or a binder) or the like to prepare slurry for the anodes. The slurry for the anodes is coated onto the substrate tube 103 by using the screen-printing method. The slurry for the anodes is coated in the circumferential direction on the outer peripheral surface of the substrate tube 103 while divided into a plurality of sections corresponding to the number of elements of the power generation sections 105. The thickness of the slurry to be formed by coating is appropriately set so that the anodes 109 have a predetermined thickness after sintering described later.
A material constituting the lead films 115 is mixed with an organic vehicle or the like to prepare slurry for the lead films.
After the slurry for the anodes is coated, the slurry for the lead films is coated so as to cover the substrate tube 103 by using the screen-printing method. The thickness of the slurry to be formed by coating is appropriately set so that the lead films 115 have a predetermined thickness after sintering described later.
A material constituting the electrolytes 111 and a material constituting the interconnectors 107 are mixed with an organic vehicle or the like respectively to prepare slurry for the electrolytes and slurry for the interconnectors.
After the slurry for the lead films is coated, the slurry for the electrolytes and the slurry for the interconnectors are coated in this order at predetermined positions on the substrate tube 103. The slurry for the electrolytes is coated on the outer surfaces of the anodes 109 and on the substrate tube 103 between the adjacent anodes 109. The slurry for the interconnectors is coated in the circumferential direction on the outer peripheral surface of the substrate tube 103 at positions corresponding to gaps between the adjacent power generation sections 105. The thickness of the slurry to be formed by coating is appropriately set so that the electrolytes 111 and the interconnectors 107 have predetermined thicknesses after sintering described later.
A material constituting the gas seal films 117 is mixed with an organic vehicle or the like to prepare slurry for the gas seal films. For example, mixed powder obtained by mixing raw materials (MTiO3 and metal oxide in
The substrate tube 103 coated with the aforementioned slurry is co-sintered in atmospheric air (in an oxidizing atmosphere). A sintering condition is specifically set to 1350° C. to 1450° C. and 3 to 5 hours.
By the co-sintering under the above condition, a gas seal film 117 including a first structure having a high content of MTiO3 and a second structure having a high content of metal oxide is formed, and a film in which the area ratio of the second structure is not less than 1% and not more than 50% becomes a dense film. A sintering mechanism is as follows. Since Al2O3 undergoes liquid phase sintering, Al2O3 melts and spreads at a firing temperature, fills gaps of the MTiO3, and partially becomes spinel-like MAl2O4 to form a second structure. A liquid-phase sintered portion has a larger content of Al2O3 (metal oxide) as compared with the first structure having a large content of MTiO3, so that the composition of the metal oxide in the second structure is large.
Next, a material constituting the cathodes 113 is mixed with an organic vehicle or the like to prepare slurry for the cathodes. The slurry for the cathodes is coated onto the co-sintered substrate tube 103. The slurry for the cathodes is coated on the outer surfaces of the electrolytes 111 and at predetermined positions on the interconnectors 107. The thickness of the slurry to be formed by coating is appropriately set so that the cathodes 113 have a predetermined thickness after firing.
After the slurry for the cathodes is coated, the slurry is fired at 1100° C. to 1250° C. for 1 to 4 hours in atmospheric air (in an oxidizing atmosphere). The firing temperature of the slurry for the cathodes is set to be lower than the co-sintering temperature when the components from the substrate tube 103 to the gas seal films 117 are formed.
In the present embodiment, the surfaces of the lead films 115 on the side of the oxidant gas atmosphere are covered with the gas seal films 117 to prevent oxidation of Ni contained in the lead films 115, thereby causing an electrolyte type fuel battery to suffer less damage and have high reliability.
The gas seal films 117 formed by using MTiO3 have low electronic conductivity. Such gas seal films 117 are suitable for preventing gas leakage in the power non-generation sections 110 which are portions where mixing of the fuel gas and the oxidizing agent is required to be prevented and insulating performance is required. The gas seal films 117 formed by using MTiO3 can reduce short-circuit current to a negligible level.
Furthermore, since MTiO3 has low oxygen ion conductivity, penetration of oxygen ions can be reduced to a negligible level.
Here, how low the oxygen ion conductivity of MTiO3 is will be described by using SrTiO3 as an example.
(Diffusivity of Oxygen Ion)
According to
Therefore, it is considered that only at least about 1/1000 of oxygen ions of YSZ diffuse into the gas seal films 117 formed by firing a material containing Al2O3 and SrTiO3.
This embodiment is different from the first embodiment in the material constituting the gas seal films. Configurations which are not particularly described are the same as those in the first embodiment.
In place of titanate MTiO3(M represents an alkaline earth metal element) doped with an alkaline earth metal, the gas seal films of the present embodiment include any one of titanate (M(1+x)TiO3: M represents an alkaline earth metal element, 0<x) which is excessively doped with an alkaline earth metal, and excessive titanate (MTi(1+y)O3: M represents an alkaline earth metal element, 0<y) which is doped with an alkaline earth metal. Furthermore, the gas seal films contain metal oxide.
The alkaline earth metal element is any one of Mg, Ca, Sr, and Ba. The alkaline earth metal element is preferably Sr or Ba. The upper limits of x and y may be set to about ¼ of the amount of metal oxide (mol %). The metal oxide is B2O3, Al2O3, Ga2O3, In2O3, Tl2O3, Fe2O3, Fe3O4, MgO, NiO, SiO2 or the like. The metal oxide is added in an amount of 3 mol % or more to MTiO3. The metal oxide may be added up to 100 mol % to MTiO3.
The structure of the gas seal film includes a first structure and a second structure which are different in composition. The first structure includes, as main components, M and Ti derived from M(1+x)TiO3 or MTi(1+y)O3 contained in the material. The second structure contains a metal element derived from the metal oxide contained in the material in a larger amount than the first structure. The area ratio of the second structure in the structure of the gas seal film is not less than 1% and not more than 50%. The gas seal film of the present embodiment serves to prevent gas permeation in the power non-generation section 110.
Since the gas seal film including the second structure having the area ratio of 1% or more has a low open porosity and is sufficiently dense, gas leakage can be prevented by providing the gas seal film as described above in the power non-generation section 110. However, when the area ratio of the second structure is too high, a crack occurs in the gas seal film due to a difference in thermal expansion between a support substrate and an underlayer film, and gas permeation occurs. Therefore, it is desirable that the area ration of the second structure in the structure of the gas seal film is not less than 1% and not more than 50%.
Hereinafter, the structure of the gas seal film will be further described with reference to the drawings.
(Composition of Second Structure)
According to
From the foregoing results, by adding and firing metal oxide in a state where alkaline earth metal or TiO2 is excessive, particles (second structure) which contain, as a main component, metal derived from the metal oxide are formed in the structure. The sintering character between the particles is enhanced by the influence of the particles, and the gas seal films which are dense and reduced in open porosity are formed. Such gas seal films can more reliably prevent gas leakage.
(Addition Amount of Metal Oxide)
A test piece of a gas seal film was prepared by using Sr0.9La0.1TiO3(D10: 0.135 μm, D50: 0.472 μm, D90: 0.893 μm) and Al2O3(D10: 0.179 μm, D50: 0.289 μm, D90: 0.550 μm).
In
In the first embodiment and the second embodiment, a cylindrical horizontal stripe type is described as an example of the single fuel cell. However, the “gas seal film” using the material disclosed herein can be used for single fuel cells having various structures, for example, a single fuel cell such as a flat tubular in which the peripheral side surface of the cylinder is crushed vertically, and the shape and size are not particularly limited. Furthermore, with respect to the single fuel cell of the cylindrical horizontal stripe type described in the above embodiments, the single fuel cell is formed on the support substrate. However, the electrode (anode or cathode) may be formed to be thicker and also used as a substrate instead of the support substrate.
Further, the present invention can also be applied to a high-temperature steam electrolysis (SOSE) cell that produces hydrogen by applying power with the same configuration as the single fuel cell 101. In this case, the power generation section 105 in the first and second embodiments may be replaced with a hydrogen generation section for generating hydrogen without generating power, and the power non-generation section 110 may be replaced with a hydrogen non-generation section that does not generate hydrogen.
The single fuel cell 301 in
The single fuel cell 401 in
An anode 403 is provided on one surface of a flat portion of the conductive support substrate 402, and an electrolyte 404 is further stacked so as to cover the anode 403. A cathode 405 is stacked on the electrolyte 404 to form a power generation section 411. An interconnector 406 is provided on a surface of the conductive support substrate 402 which faces the anode 403. The voltage is increased by electrically connecting the cathode 405 and the interconnector 406 of adjacent single fuel cells 401 in series. By forming a gas seal film 407 on the upper surface of the power non-generation section where neither the electrolyte 404 nor the interconnector 406 is stacked and on the side surface of the conductive support substrate 402, it is possible to prevent the fuel gas from leaking to portions other than the power generation section.
A single fuel cell 501 of
An anode 503 is provided on the surface of the conductive substrate tube 502, and an electrolyte 504 is further stacked so as to cover the anode 503. A cathode 505 is stacked on the electrolyte 504 to form a power generation section 511. Gas seal films 507 are formed on both ends of the electrolyte 504 so as to partially overlap both the ends, and a current collecting member 508 is provided on the cathode 505 on one side and the conductive substrate tube 502 on the other side in a longitudinal direction.
The single fuel cells 301 and 401 (flat cylindrical cells (multi-element and single-element)) and the single fuel cell 501 (cylindrical single cell) described above are the support structure type single fuel cells 301, 401 and 501 using the porous substrate tube 502 or the support substrates 302 and 402. However, the support structure is not limited to the above type. The type of the support structure may be an electrolyte support type, an anode support type, a cathode support type, a metal support type, an insulating support type or the like. In the metal support type, the single fuel cells 301, 401, and 501 are supported by metal made of heat-resistant alloy such as stainless steel or Hastelloy. In the insulating support type, the single fuel cells 301, 401, and 501 are supported by a ceramic insulating material such as zirconia or alumina.
Next, power generation systems 600 and 700 including any one of the single fuel cells 101, 301, 401, and 501 described in the first embodiment, the second embodiment, or
The power generation system 600 of
The fuel cell module 601 includes a plurality of single fuel cells each including an anode (fuel-side electrode), an electrolyte, and a cathode (oxygen-side electrode). The fuel cell module 601 includes a fuel gas supply pipe 603 for supplying a fuel gas (F) to each anode, an oxidant gas supply pipe 604 for supplying an oxidant gas (A) to each cathode, a fuel gas exhaust pipe 605 through which the fuel gas supplied to each anode is exhausted, and an oxidant gas exhaust pipe 606 through which the oxidant gas supplied to each cathode is exhausted.
In
The compressor 602a is connected to the fuel cell module 601 via the oxidant gas supply pipe 604. The compressor 602a and the turbine 602b are integrally rotatably connected to each other by a rotation shaft 602e. The compressor 602a compresses oxidant gas (A) taken in from an oxidant gas intake line 602f by using rotation of the turbine 602b as power. The compressed oxidant gas (A) is supplied to each anode side of the fuel cell module 601 through the oxidant gas supply pipe 604.
The combustor 602d is connected to the fuel cell module 601 via the fuel gas exhaust pipe 605 and the oxidant gas exhaust pipe 606. The combustor 602d mixes and combusts the exhaust fuel gas (A′) and the exhaust oxidant gas (F′) which have been exhausted from the fuel cell module 601. Gas (combustion gas) generated by the combustion is supplied to the turbine 602b through a combustion gas supply line 602g.
Supply of the combustion gas to the turbine 602b causes the turbine 602b to rotate. The electric generator 602c is provided coaxially with the turbine 602b, and can generate power upon rotation of the turbine 602b.
The fuel cell module 601 can generate power by using the fuel gas (F) supplied through the fuel gas supply pipe 603 and the compressed oxidant gas (A) supplied through the oxidant gas supply pipe 604.
The power generation system 700 of
The fuel cell module 701 includes a plurality of single fuel cells each having an anode (fuel-side electrode), an electrolyte, and a cathode (oxygen-side electrode). The fuel cell module 701 includes a fuel gas supply pipe 703 for supplying a fuel gas (F) to each anode, an oxidant gas supply pipe 704 for supplying an oxidant gas (A) to each cathode, and an exhaust pipe 705 through which the supplied fuel gas and the oxidant gas supplied to each cathode are exhausted.
In
The compressor 702a is connected to the fuel cell module 701 via the oxidant gas supply pipe 704. The compressor 702a and the turbine 702b are integrally rotatably connected to each other by a rotating shaft 702e. The compressor 702a compresses oxidant gas (A) taken in from an oxidant gas intake line 702f by using rotation of the turbine 702b as power. The compressed oxidant gas (A) is supplied to each anode side of the fuel cell module 701 through the oxidant gas supply pipe 704.
The fuel cell module 701 can generate power by using the fuel gas (F) supplied through the fuel gas supply pipe 703 and the compressed oxidant gas (A) supplied through the oxidant gas supply pipe 704.
The fuel gas (F) and the oxidant gas (A) supplied to the fuel cell module 701 are discharged as exhaust fuel gas (F′) and exhaust oxidant gas (A′), and supplied to the turbine 702b through the exhaust pipe 705. The turbine 702b rotates upon supply of the exhaust fuel gas (F′) and the exhaust oxidant gas (A′) thereto.
| Number | Date | Country | Kind |
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| 2019-032909 | Feb 2019 | JP | national |
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| Number | Date | Country | |
|---|---|---|---|
| 20220246969 A1 | Aug 2022 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 16651174 | US | |
| Child | 17722797 | US |
