JP5352943B2 - Solid oxide fuel cell and stack structure thereof - Google Patents

Description

  The present invention relates to a solid oxide fuel cell that generates power using a fuel gas and an oxidant gas, and a stack structure thereof.

Conventionally, a flat plate type, a cylindrical type, and the like have been proposed as cell designs for solid oxide fuel cells. However, there are problems with the current cell design. In order to improve the performance of both flat and cylindrical cells, it is necessary to reduce the internal resistance by thinning the electrolyte. However, if the electrolyte is too thin, it becomes vulnerable to vibration and thermal cycles. This is a problem that vibration resistance and durability are lowered. In view of this, a battery has also been proposed in which a single cell is arranged on a substrate to improve mechanical characteristics. For example, in the battery described in Patent Document 1, an air electrode, an electrolyte, and a fuel electrode are stacked in this order on a substrate composed of a porous region and a non-porous region disposed on the periphery thereof. The substrate is supported by a ferritic stainless steel bipolar plate.
JP 2004-512651 A

  By the way, in the fuel cell, the fuel electrode is sandwiched between the substrate and the electrolyte so that the oxidant gas supplied to the air electrode is not mixed with the fuel gas. The electrolyte is joined to the non-porous region of the substrate so that fuel gas does not leak, and this non-porous region is hermetically connected to the bipolar plate. Accordingly, there is a problem in that the battery is composed of two members, a substrate including cells and a bipolar plate, and a seal portion is necessary.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a solid oxide fuel cell having a high structure and a simple structure.

The present invention has been made to solve the above problems, and is a porous substrate, a fuel electrode disposed on the substrate, an electrolyte disposed on the fuel electrode, and disposed on the electrolyte. An air electrode and a non-porous separator that supports the substrate, the periphery of the electrolyte extends downward so as to cover the periphery of the fuel electrode, and is joined to the substrate and the separator. The fuel electrode accommodated between the electrolyte and the separator is hermetically isolated from the air electrode, and the separator is configured to communicate the substrate with the outside, and the substrate has a hydrogen separation function. ing. The present invention has been made in order to solve the above-described problem, and includes a porous substrate, and an electrode of either a fuel electrode (anode) or an air electrode (cathode) disposed on the substrate. An electrolyte disposed on the one electrode, the other electrode disposed on the electrolyte, and a non-porous separator that supports the substrate, the periphery of the electrolyte being the one electrode The one electrode accommodated between the electrolyte and the separator is hermetically isolated from the other electrode by extending downward to cover the periphery of the substrate and being joined to the substrate and the separator. is composed of the substrate so as to communicate with the outside, the substrate is fixed in a recess of the separator by a glass seal which is applied on both sides in the width direction, the peripheral edge of the electrolyte Serial extends downwardly to cover the periphery of one electrode, the substrate is bonded to the glass seal and the separator.

  According to this structure, since the electrolyte is joined to the separator by the peripheral edge of the electrolyte, the two electrodes are isolated by the electrolyte, so that two chambers can be achieved with a simple structure. Moreover, since the single cell which consists of an electrode and an electrolyte is supported by the board | substrate and the separator, it can improve a mechanical characteristic. It should be noted that both ends of the electrolyte and the separator can be directly joined or indirectly joined via an insulating member such as a glass seal, and in short, the other electrode is isolated between the two. It is only necessary to form an open space.

  Here, when the periphery of the electrolyte and the substrate are joined and one electrode is accommodated between the electrolyte and the substrate, the one electrode and the other electrode can be more reliably isolated.

  Since the substrate has porosity, if a gas is supplied thereto, the gas can be supplied to one electrode. However, at least the substrate and the separator on the surface where the substrate and the separator contact each other. On the other hand, when the groove through which the gas flows is formed, the flow rate of the gas contacting the electrode can be increased, and the output can be improved.

  In the case where the one electrode is a fuel electrode, if the substrate has a hydrogen separation function, hydrogen can be separated from the supplied hydrocarbon-based gas. Thereby, since hydrogen required for a fuel electrode can be supplied directly, the supply efficiency of gas can be improved. In addition, the power generation performance is improved, carbon deposition on the fuel electrode can be reduced, and the durability of the cell can be improved.

The substrate in the fuel cell is preferably composed of a conductive metal or a material having a metal oxide .

  When stacking the above-described batteries, the battery can be configured as follows. That is, the cell stack structure according to the present invention includes a plurality of the fuel cells described above, and in the two adjacent fuel cells, the separator of one fuel cell and the other electrode of the other fuel cell face each other. The electrodes of the other fuel cell, the electrolyte, and the substrate are hermetically accommodated between the two fuel cells, and the separator of the one fuel cell is connected to the other electrode of the other fuel cell. It is configured to communicate with the outside.

  According to the solid oxide fuel cell and the stack structure using the same according to the present invention, the structure can be simplified while having high mechanical characteristics.

  Hereinafter, an embodiment 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 of a solid oxide fuel cell according to the present embodiment, and FIG. 2 is a cross-sectional view taken along line AA of FIG. In the following description, the vertical direction in FIG. 2 is referred to as “front-rear direction” and the left-right direction is referred to as “width direction”, and other drawings will be described based on this.

  As shown in FIG. 1, the solid oxide fuel cell according to this embodiment includes a non-porous separator 1 having a recess 11 formed on the upper surface, and a porous substrate 2 is disposed in the recess 11. Has been. As shown in FIG. 2, the concave portion 11 is configured by a rectangular-shaped accommodation portion 111 in which the substrate 2 is disposed, and parallelogram-shaped extension portions 112 a and 112 b extending forward and backward from the accommodation portion 111. Yes. The extension portions 112a and 112b have substantially the same width as the front end and the rear end of the substrate 2, and a supply port 12 for supplying gas into the recess 11 is formed at the left end portion of the rear extension portion 112a. On the other hand, a discharge port 13 through which the gas in the recess 11 is discharged is formed at the right end of the front extension 112b. In addition, a plurality of grooves 14 extending in the front-rear direction at substantially the same depth as the extension portions 112a and 112b are formed on the bottom surface of the accommodating portion 11, and the gas flowing in from the supply port 12 is passed through the grooves 14 later. It flows from the side extension 111a to the front extension 111b and is discharged from the discharge port 13. In this process, the gas passing through the groove 14 contacts the substrate 2.

  The substrate 2 is fixed in the recess 11 by glass seals 3 applied on both sides in the width direction. A single cell 4 is disposed on the substrate 2. The single cell 4 is configured by laminating a thin-film fuel electrode 41, an electrolyte 42, and an air electrode 43 disposed on the substrate 2 in this order. The peripheral edge of the unit cell 4 extends downward so as to cover the peripheral edge of the fuel electrode 41, and is joined to the substrate 2 and the separator 1. Thereby, the substrate 2 and the fuel electrode 41 are accommodated between the electrolyte 42 and the separator 1, and the fuel electrode 41 is accommodated between the electrolyte 42 and the substrate 2. Thereby, the fuel electrode 41 and the air electrode 43 are isolated.

  Next, materials constituting the fuel cell will be described. As the material of the electrolyte 42, those known as electrolytes for solid oxide fuel cells can be used. Oxygen ion conductive ceramic materials such as oxides, zirconia-based oxides containing scandium and yttrium can be used.

  The fuel electrode 41 and the air electrode 43 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.

  As the fuel electrode 41, 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. Of the above materials, the fuel electrode 12 is preferably formed of 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 may be a powder modification to nickel or a nickel modification to ceramic material. Good. Moreover, the ceramic material mentioned above can be used individually by 1 type or in mixture of 2 or more types. Further, the fuel electrode 41 can be configured by using a metal catalyst alone.

As the ceramic powder material forming the air electrode 43, 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) (Fe, Co) O ₃ is preferable. The ceramic material mentioned above can be used individually by 1 type or in mixture of 2 or more types.

  The electrolyte 42, the fuel electrode 41, and the air electrode 43 are formed by adding the appropriate amount of binder resin, organic solvent, etc., with the above-described materials as the main components. 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.

  As a method of forming the fuel electrode 41 and the air electrode 43, for example, a printing method can be used. Specifically, a printing method such as a screen printing method, a knife coating method, a doctor blade method, or a spray coating method can be used. it can. In addition to this, it is also possible to form electrodes by applying them on a sheet (so-called green body) and transferring them. The electrolyte 42 can be formed by various methods. In order to form the fuel electrode 41 and the air electrode 42 as a porous body, it is preferable to sinter at a lower temperature than these, for example, vacuum method, thermal spraying It can be formed by a low-temperature firing method such as a method.

The substrate 2 has electronic conductivity, but it is preferable that the ion conductivity is small enough to be ignored. Moreover, it is preferable to be comprised with the thermodynamically stable material. The electrical conductivity is preferably 10 ⁻² S · cm ⁻¹ or more at the operating temperature of the fuel cell. Thereby, the substrate 2 serves as a current collecting layer. In order to satisfy such requirements, the substrate can be configured as follows.

The porosity of the substrate 2 is preferably in the range of 10 to 80% in consideration of gas permeability and its strength. Further, as will be described later, a certain amount of thickness is required because it is necessary to allow gas to flow from the front and rear end faces of the substrate 2. In order to satisfy such a requirement, the material constituting the substrate 2 is made of a conductive metal such as Pt, Au, Ag, Ni, Ti, Cu, Fe, Cr, or La (Cr, Mg) O ₃ , (La, It can be formed of a lanthanum chromite-based conductive ceramic material such as Ca) CrO ₃ , (La, Sr) CrO _3, and one of these may be used alone, or two or more May be used in combination.

  The separator 1 is made of a conductive material. For example, a stainless metal material or a lanthanum chromite metal ceramic material can be used.

  The fuel cell configured as described above generates power as follows. First, a fuel gas made of hydrogen or a hydrocarbon such as methane or ethane is supplied to the battery from the supply port 12 of the separator 1. This fuel gas flows from the supply port 12 into the extension 112 a of the recess 11, enters the extension 112 b through the groove 14, and then is discharged from the discharge port 13 to the outside of the separator 1. The fuel gas passing through the groove 14 is supplied to the fuel electrode 41 through the porous substrate 2. On the other hand, an oxidant gas such as air is supplied to the air electrode 43 from the upper surface side of the electrolyte 42. These gases are supplied in a high temperature state (for example, 400 to 1000 ° C.). Thus, since the fuel electrode 41 and the air electrode 43 come into contact with the hydrogen gas and the oxidant gas, respectively, oxygen ion conduction through the electrolyte 41 occurs between the fuel electrode 41 and the air electrode 43 in each single cell 4, Power generation is performed.

  As described above, according to the present embodiment, since the periphery of the electrolyte 42 is joined to the separator 1, the fuel electrode 41 and the air electrode 43 accommodated therebetween are separated from each other. With a simple structure, two chambers can be achieved. Moreover, since the single cell 4 which consists of the electrodes 41 and 43 and the electrolyte 42 is supported by the board | substrate 2 and the separator 1, it can improve a mechanical characteristic.

  Here, when the substrate 2 is made of a metal such as Ro, Pd, Pt, or Ru, a hydrogen separation function can be imparted. Thereby, for example, when a hydrocarbon gas contacts or passes through the substrate 2, only hydrogen is separated. Therefore, hydrogen can be directly supplied to the fuel electrode 41, and the gas supply efficiency can be improved. Further, the power generation performance is improved, the carbon deposition at the fuel electrode 41 can be reduced, and the durability of the cell is improved.

  As mentioned above, although one Embodiment of this invention was described, this invention is not limited to this, A various change is possible unless it deviates from the meaning. For example, both sides of the electrolyte 42 and the separator 1 can be directly joined as shown in FIG. 1 or indirectly joined via an insulating member 7 such as a glass seal as shown in FIG. You can also

Moreover, in the said embodiment, although the groove | channel 14 is formed in the recessed part 11 of the separator 1 and gas is supplied to this, the groove | channel 21 may be formed in the board | substrate 2 side, as shown in FIG. it can. However, since the substrate 2 has porosity, if the gas is supplied to the substrate 2, the gas can be supplied to the fuel electrode 41, so that the gas can be supplied from the extension 112 to the substrate 2. For example, the groove is not always necessary. However, by forming the groove 21, the flow rate of the gas in contact with the fuel electrode 41 can be increased, and the output can be improved.
Further, as in the above embodiment, in addition to forming the recess 11 including the accommodating portion 111 and the extension portion 112 in the separator 1 and supplying gas from the supply port 12 to the separator 1, the separator 1 applies gas to the substrate 2. If it is the structure which can supply, it will not specifically limit.

  Moreover, what is necessary is just to comprise as shown in FIG. 5, for example, when making the said fuel cell into a stack. FIG. 5 is a cross-sectional view of a stacked fuel cell. As shown in the figure, in this stack structure, a groove 17 extending in the front-rear direction is formed on the lower surface of the separator 1 of each fuel cell F. And in the adjacent fuel cell, the lower surface of the separator 1 of one battery F and the cell 4 of the other battery F are opposed to each other, and an insulating seal 8 is arranged around the cell 4, Adjacent fuel cell separators are connected. By providing the insulating seal 8 in this way, the cells 4 are kept airtight in the adjacent separators 1. The gas is supplied to the air electrode 43 of each cell 4 through the groove 17 formed on the lower surface of the separator 1. With the above configuration, a plurality of fuel cells can be easily stacked, and these are electrically connected in series. In addition, the structure which supplies gas to the groove | channel on the lower surface of a separator is not specifically limited, As shown in FIG. 2, the recessed part which consists of an extension part and an accommodating part can also be formed in the lower surface of a separator.

1 is a cross-sectional view of a solid oxide fuel cell according to an embodiment of the present invention. It is the sectional view on the AA line of FIG. It is sectional drawing which shows the other example of the fuel cell of FIG. FIG. 6 is a cross-sectional view showing still another example of the fuel cell in FIG. 1. It is sectional drawing which shows the state which made the fuel cell of FIG. 1 a stack.

Explanation of symbols

1 Separator 2 Substrate 4 Single cell 41 Fuel electrode 42 Electrolyte 43 Air electrode 8 Seal member (insulating member)

Claims (6)

A porous substrate;
A fuel electrode disposed on the substrate;
An electrolyte disposed on said anode,
An air electrode disposed on the electrolyte;
A non-porous separator that supports the substrate,
The periphery of the electrolyte extends downward so as to cover the periphery of the fuel electrode , and is joined to the substrate and the separator so that the fuel electrode accommodated between the electrolyte and the separator is airtight from the air electrode. Isolated
The separator is configured to communicate the substrate with the outside ;
A solid oxide fuel cell, wherein the substrate has a hydrogen separation function . A porous substrate;
Either one of a fuel electrode and an air electrode disposed on the substrate;
An electrolyte disposed on the one electrode;
The other electrode disposed on the electrolyte;
A non-porous separator that supports the substrate,
The peripheral edge of the electrolyte extends downward so as to cover the peripheral edge of the one electrode, and is joined to the substrate and the separator so that the one electrode accommodated between the electrolyte and the separator is the other electrode. Airtightly isolated from the electrodes,
The separator is configured to communicate the substrate with the outside ;
The substrate is fixed in the recess of the separator by glass seals applied on both sides in the width direction,
A solid oxide fuel cell , wherein a peripheral edge of the electrolyte extends downward so as to cover a peripheral edge of the one electrode, and is joined to the substrate, the glass seal, and the separator . The solid oxide fuel cell according to claim 2 , wherein the one electrode is a fuel electrode, and the substrate has a hydrogen separation function. The solid oxide fuel cell according to any one of claims 1 to 3 , wherein a groove through which a gas flows is formed in at least one of the substrate and the separator on a surface where the substrate and the separator are in contact with each other . Wherein the substrate is made of a material having a metal or metal oxide having conductivity, solid oxide fuel cell according to any one of claims 1 to 4. A plurality of the fuel cells according to any one of claims 1 to 5 ,
The two adjacent fuel cells are stacked so that the separator of one fuel cell and the other electrode of the other fuel cell face each other,
Between the two fuel cells, the electrode, electrolyte and substrate of the other fuel cell are hermetically accommodated,
The separator of the one fuel cell is a stack structure of a solid oxide fuel cell configured such that the other electrode of the other fuel cell communicates with the outside.