JP2006252941A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell which is prevented from spread of current density generated at each air electrode and each fuel electrode, controlled in a flow of current along the in-plane direction of a cell, and decreased in voltage loss to obtain high efficiency in power generation. <P>SOLUTION: The fuel cell comprises a cell 1A which generates electric power on the basis of fuel gas 7A and air gas 7B, and collector members 2A and 2F which collect electricity and the cell 1A includes electrolyte 5A. The cell 1A comprises: a fuel electrode 4A which transmits the fuel gas 7A along the surface of the electrolyte 5A; an air electrode 3A opposed to the fuel electrode 4A through the electrolyte 5A to transmit the air gas 7B in the same direction parallel to the fuel gas 7A; a fuel electrode 4E placed on the electrolyte 5A apart from the fuel electrode 4A to transmit the fuel gas 7A which has passed through the fuel electrode 4A; and an air electrode 3E opposed to the fuel electrode 4E through the electrolyte 5A apart from the air electrode 3A to transmit the air 7B which has passed through the air electrode 3A. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention includes a cell that generates electric power based on fuel gas and air gas, and a current collecting member that collects the electric power generated by the cell. The cell performs oxidation-reduction reaction between the fuel gas and air gas. The present invention relates to a fuel cell including an electrolyte for conducting ions to be conducted.

  The solid oxide fuel cell includes a solid electrolyte, an air electrode and a fuel electrode arranged with the solid electrolyte interposed therebetween. The solid electrolyte is made of yttria-stabilized zirconia (YSZ) or the like, the air electrode is made of, for example, a perovskite-type lanthanum complex oxide, and the fuel electrode has nickel or the like as a main component. The solid oxide fuel cell configured as described above obtains an electromotive force by an oxidation-reduction reaction between fuel gas and air via a solid electrolyte.

  In this type of fuel cell, the amount of power that can be obtained from a single cell is small, so a module is formed by connecting a plurality of cells in series and parallel, and a plurality of modules are arranged to obtain the required power. .

As a conventional typical series and parallel connection method, cells are connected in series using a conductive material such as nickel felt to form a stack structure connected in series. Then, the end portions of the stacks are connected in series or in parallel to form a final stack structure. Also disclosed is a configuration in which three or more cells are connected in parallel by a breathable conductive material.
Japanese Patent Laid-Open No. 11-339836

  However, when the stack structure connected in series and in parallel is formed by the above-described method, the density of current generated by the power generation near the fuel gas and air gas inlets and the power generation near the fuel gas and air gas outlets are generated. In order to make the current density uniform, current flows along the in-plane direction of the cell. For this reason, voltage loss arises and the problem that power generation efficiency falls arises.

  It is difficult to distribute air and fuel gas evenly and evenly to each cell, resulting in variations of several percent to 10 percent. For this reason, if the non-uniformity in the distribution of air and fuel gas is temporarily increased for some reason, the air and fuel gas may be insufficient in some cells, so that the cell voltage may drop and the cell may be destroyed. There is a problem that there is.

  An object of the present invention is to provide a fuel cell with high power generation efficiency.

  A fuel cell according to the present invention includes at least one cell that generates electric power based on fuel gas and air gas, and at least one current collecting member that collects the electric power generated by the cell. In the fuel cell, the cell includes an electrolyte for conducting an ion-reduction reaction between the fuel gas and the air gas. The cell transmits the fuel gas along a surface of the electrolyte. A fuel electrode, a first air electrode disposed at a position facing the first fuel electrode with the electrolyte interposed therebetween to allow the air gas to permeate in the same direction as the fuel gas, and the first fuel electrode. In order to permeate the fuel gas, the second fuel electrode disposed on the electrolyte separately from the first fuel electrode, and the air gas permeated through the first air electrode are permeated. electrolytic And a second air electrode disposed separately from the first air electrode at a position facing the second fuel electrode with the current collector interposed therebetween, wherein the current collecting member includes the first fuel electrode and the first air A first current collector connected to one of the electrodes, and a second current collector connected to one of the second fuel electrode and the second air electrode separately from the first current collector It is characterized by including.

  According to the present invention, a fuel cell with high power generation efficiency can be provided.

  In the fuel cell according to the present embodiment, the cell includes a first fuel electrode that allows fuel gas to permeate along the surface of the electrolyte, and an electrolyte that allows air gas to permeate in the same direction parallel to the fuel gas. A first air electrode disposed at a position opposite to the first fuel electrode across the first fuel electrode and a first air electrode separated from the first fuel electrode and disposed on the electrolyte in order to allow the fuel gas that has passed through the first fuel electrode to pass therethrough. Two fuel electrodes and a second air electrode disposed separately from the first air electrode at a position facing the second fuel electrode across the electrolyte in order to transmit the air gas that has passed through the first air electrode. And a current collecting member includes a first current collector connected to one of the first fuel electrode and the first air electrode, and a first current collector on one of the second fuel electrode and the second air electrode. And a second current collector connected separately. For this reason, the air electrode is divided into first and second air electrodes, and the fuel electrode is divided into first and second fuel electrodes. Therefore, since it is possible to prevent the density of current generated at each air electrode and each fuel electrode from spreading, current flow along the in-plane direction of the cell is suppressed, and voltage loss is reduced. As a result, the power generation efficiency of the fuel cell can be improved.

  In this embodiment, it is preferable that the length of the first fuel electrode along the permeation direction of the fuel gas is longer than the length of the second fuel electrode along the permeation direction of the fuel gas.

  The length of the first fuel electrode is preferably 70% or more and 75% or less of a total of the length of the first fuel electrode and the length of the second fuel electrode.

  The at least one cell is preferably a plurality of cells arranged in parallel with each other along a direction intersecting the fuel gas permeation direction.

  The at least one current collecting member is preferably a plurality of current collecting members respectively disposed between the plurality of adjacent cells.

  The first fuel electrode and the first air electrode provided in each of the plurality of cells are connected in series by the first current collector, and the second fuel electrode provided in each of the plurality of cells. The second air electrode is preferably connected in series by the second current collector.

  A surface of the first current collector facing the first fuel electrode is formed with a groove along a direction in which the fuel gas permeates, and the surface of the second current collector facing the second fuel electrode. Preferably, a groove is formed along the direction in which the fuel gas permeates.

  A surface facing the first air electrode of the first current collector is formed with a groove along a direction through which the air gas permeates, and the surface facing the second air electrode of the second current collector Preferably, a groove is formed along the direction in which the air gas permeates.

  It is preferable that a conductive porous body is provided between the first current collector and the first fuel electrode and between the second current collector and the second fuel electrode, respectively.

  It is preferable that a conductive porous body is provided between the first current collector and the first air electrode and between the second current collector and the second air electrode, respectively.

  The first and second air electrodes preferably include a reduction catalyst.

  It is preferable that at least one of the first and second air electrodes includes a perovskite complex oxide including a rare earth element.

  The porosity of the first and second air electrodes is preferably 20% or more and 60% or less.

  It is preferable that the first and second fuel electrodes include an oxidation catalyst.

  Preferably, at least one of the first and second fuel electrodes includes at least one selected from nickel, platinum, nickel-zirconia, nickel-ceria, platinum-zirconia, and platinum-ceria.

  It is preferable that the porosity of the first and second fuel electrodes is 20% or more and 60% or less.

  The electrolyte preferably includes an ion conductive material.

  The electrolyte preferably includes at least one of yttria-stabilized zirconia and lanthanum garade-based perovskite oxide.

  The cell is preferably a long flat plate cell.

  The cell is preferably either a circular cell or a cylindrical cell.

  The fuel cell is preferably a solid oxide fuel cell.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a fuel cell 100 according to the present embodiment. The fuel cell 100 includes a rectangular parallelepiped cell 1A. The cell 1A generates electric power based on the fuel gas 7A and the air gas 7B. The fuel cell 100 is provided with current collectors 2A and 2F. Current collectors 2A and 2F collect the electric power generated by cell 1A.

  The cell 1A includes an electrolyte 5A for causing a redox reaction between the fuel gas 7A and the air gas 7B. The cell 1A is provided with a fuel electrode 4A. The fuel electrode 4A is bonded to the surface of the electrolyte 5A on the inlet side into which the fuel gas 7A flows in order to allow the fuel gas 7A to permeate along the surface of the electrolyte 5A.

  The cell 1A has an air electrode 3A. The air electrode 3A is bonded to a position facing the fuel electrode 4A across the electrolyte 5A in order to allow the air gas 7B to pass through in the same direction in parallel with the fuel gas 7A.

  The cell 1A is provided with a fuel electrode 4E. The fuel electrode 4E is separated from the fuel electrode 4A and bonded on the outlet side of the electrolyte 5A in order to allow the fuel gas 7A that has passed through the fuel electrode 4A to pass therethrough. The cell 1A has an air electrode 3E. The air electrode 3E is separated and bonded to the air electrode 3A at a position facing the fuel electrode 4E across the electrolyte 5A so as to transmit the air gas 7B that has passed through the air electrode 3A.

  The current collector 2A collects the electric power generated by the air electrode 3A. The current collector 2F collects the electric power generated by the air electrode 3E.

  The fuel cell 100 includes cells 1B, 1C, and 1D having a rectangular parallelepiped shape. The fuel cell 100 is provided with current collectors 2B, 2C, 2D and 2E and current collectors 2G, 2H, 2I and 2J.

  Cells 1B, 1C, and 1D include electrolytes 5B, 5C, and 5D for causing a redox reaction between fuel gas 7A and air gas 7B, respectively. The cells 1B, 1C and 1D are provided with fuel electrodes 4B, 4C and 4D, respectively. The fuel electrodes 4B, 4C, and 4D are respectively bonded to the surfaces of the electrolytes 5B, 5C, and 5D on the inlet side into which the fuel gas 7A flows in order to permeate the fuel gas 7A along the surfaces of the electrolytes 5B, 5C, and 5D. ing.

  The cells 1B, 1C, and 1D have air electrodes 3B, 3C, and 3D. The air electrodes 3B, 3C, and 3D are parallel to the fuel gas 7A and are opposed to the fuel electrodes 4B, 4C, and 4D with the electrolytes 5B, 5C, and 5D interposed therebetween in order to transmit the air gas 7B in the same direction. It is glued to.

  The cell 1A is provided with fuel electrodes 4F, 4G, and 4H. The fuel electrodes 4F, 4G, and 4H are separated from the fuel electrodes 4B, 4C, and 4D, respectively, in order to permeate the fuel gas 7A that has passed through the fuel electrodes 4B, 4C, and 4D. Each is glued on top. The cell 1A has air electrodes 3F, 3G, and 3H. The air electrodes 3F, 3G, and 3H are opposed to the fuel electrodes 4F, 4G, and 4H across the electrolytes 5B, 5C, and 5D, respectively, in order to allow the air gas 7B that has passed through the air electrodes 3B, 3C, and 3D to pass therethrough. Are bonded separately from the air electrodes 3B, 3C and 3D.

  The air electrodes 3A, 3B, 3C and 3D arranged on the inlet side into which the fuel gas 7A and the air gas 7B flow, and the fuel electrodes 4A, 4B, 4C and 4D, and the current collectors 2A, 2B, 2C, 2D and 2E Are connected in series and constitute the stack 6A. The air electrodes 3E, 3F, 3G and 3H arranged on the outlet side of the fuel gas 7A and the air gas 7B, and the fuel electrodes 4E, 4F, 4G and 4H, and the current collectors 2F, 2G, 2H, 2I and 2J, They are connected in series and constitute the stack 6B. As described above, the stack 6A and the stack 6B are separately connected in series, and currents can be controlled independently of each other.

  The lengths of the fuel electrodes 4A, 4B, 4C and 4D along the permeation direction of the fuel gas 7A are longer than the lengths of the fuel electrodes 4E, 4F, 4G and 4H along the permeation direction of the fuel gas 7A. The lengths of the fuel electrodes 4A, 4B, 4C, and 4D are preferably 70% or more and 75% or less of the total length of the fuel electrode 4A and the length of the fuel electrode 4E.

  The fuel gas 7A flows along one side of the current collectors 2B, 2C, 2D, 2G, 2H and 2I, and the air gas 7B flows along the other side. Therefore, each current collector should not have air permeability along the cross-sectional direction, but preferably has air permeability in the direction along the surface of the current collector through which the fuel gas 7A and the air gas 7B flow. . For this reason, it is preferable to form grooves on both surfaces of the current collector along the direction in which the fuel gas 7A and the air gas 7B flow. A conductive porous body may be inserted between the current collector and the fuel electrode and between the current collector and the air electrode. The conductive porous body is made of a stable material having high electrical conductivity in an air atmosphere on the air electrode side and in a fuel gas atmosphere on the fuel electrode side. The conductive porous body is preferably composed of metal fibers such as noble metals.

  The current collectors 2A to 2J are made of a material having high electrical conductivity and stability in an air atmosphere and a fuel gas atmosphere. The current collectors 2A to 2J are preferably made of a metal material such as a noble metal or stainless steel.

  The air electrodes 3A to 3H are constituted by a reduction catalyst. The air electrodes 3A to 3H are preferably composed of a perovskite complex oxide containing a rare earth element such as lanthanum, and particularly preferably composed of lanthanum cobaltite and samarium cobaltite.

  The manufacturing method of air electrode 3A-3H will not be specifically limited if it is the manufacturing method which closely_contact | adheres to electrolyte and produces a redox reaction. The air electrodes 3A to 3H are preferably formed to a thickness of 10 μm or more and 100 μm or less by mixing a powder such as lanthanum cobaltite with a binder and a solvent, and applying and baking on the electrolyte.

  The porosity of the air electrodes 3A to 3H is not less than 20% and not more than 60% from the viewpoint of sufficient air gas permeation to reach the surface of the electrode, electrode activity, and strength as a structure. It is preferable.

  The material of the fuel electrodes 4A to 4H is not particularly limited as long as it is an oxidation catalyst. From the viewpoint of hydrogen oxidation performance, the fuel electrodes 4A to 4H are preferably composed of a metal such as nickel or platinum, or a cermet such as nickel-zirconia, nickel-ceria, platinum-zirconia, or platinum-ceria.

  The manufacturing method of the fuel electrodes 4A to 4H is not particularly limited as long as it is a manufacturing method in which the fuel electrodes 4A to 4H are brought into close contact with an electrolyte to cause a redox reaction. The fuel electrodes 4A to 4H are preferably produced to a thickness of 10 μm or more and 100 μm or less by mixing a powder such as nickel with a binder and a solvent, and applying and baking the mixture on an electrolyte.

  The porosity of the fuel electrodes 4A to 4H is 20% or more and 60% or less from the viewpoint of sufficient permeation of the fuel gas to reach the surface of the electrode, electrode activity, and strength as a structure. It is preferable.

  The material of the electrolytes 5A to 5D is not particularly limited as long as it is an ion conductive material. The electrolytes 5A to 5D are preferably composed of yttria-stabilized zirconia and a lanthanum gallate perovskite oxide because the oxide ion conductivity is high and the oxide ion transport number is close to 1.

  The method for producing the electrolytes 5A to 5D is not particularly limited as long as it is a method using a dense body, but it is preferably formed to a thickness of 50 μm or more and 500 μm or less by a doctor blade method or the like.

  In the fuel cell 100 configured as described above, when the fuel gas 7A flows into the fuel electrodes 4A to 4D and the air gas 7B flows into the air electrodes 3A to 3D, oxide ions are converted from the air electrodes 3A to 3D into the electrolyte. An oxidation-reduction reaction that moves to the fuel electrodes 4A to 4D through 5A to 5D occurs, and an electromotive force is generated. The generated electromotive force is collected by the current collectors 2A to 2E.

  Then, the fuel gas 7A flowing out from the fuel electrodes 4A to 4D flows into the fuel electrodes 4E to 4H, respectively, and the air gas 7B flowing out from the air electrodes 3A to 3D flows into the air electrodes 3E to 3H, respectively. Next, an oxidation-reduction reaction occurs between the fuel gas 7A flowing into the fuel electrodes 4E to 4H and the air gas 7B flowing into the air electrodes 3E to 3H via the electrolytes 5A to 5D, respectively, and an electromotive force is generated. The generated electromotive force is collected by the current collectors 2F to 2J.

  FIG. 2 is a graph showing the relationship between the voltage and current of a cell provided in the fuel cell according to the present embodiment. The horizontal axis indicates the cell current, and the vertical axis indicates the cell voltage. As shown by curve C1, as the current generated in the cell increases, the cell voltage decreases and the voltage loss L1 increases. According to the configuration according to the present embodiment, since each cell is divided into stack 6A and stack 6B, the density distribution of the current generated on each electrode does not spread, and the current along the in-plane direction of the cell As a result, voltage loss can be suppressed.

  As described above, according to the present embodiment, the cell 1A transmits the fuel gas 4A through the surface of the electrolyte 5A and the air electrode 7A through the air gas 7B in the same direction parallel to the fuel gas 7A. Therefore, the air electrode 3A disposed at a position facing the fuel electrode 4A across the electrolyte 5A and the fuel gas 7A that has permeated the fuel electrode 4A are separated and separated from the fuel electrode 4A on the electrolyte 5A. An air electrode 3E disposed separately from the air electrode 3A at a position facing the fuel electrode 4E across the electrolyte 5A in order to transmit the fuel electrode 4E disposed and the air gas 7B that has passed through the air electrode 3A. The current collecting member includes a current collector 2A connected to the air electrode 3A, and a current collector 2F connected to the air electrode 3E separately from the current collector 2A. For this reason, the air electrode is divided into air electrodes 3A and 3E, and the fuel electrode is divided into fuel electrodes 4A and 4E. Therefore, since it is possible to prevent the density of the current generated at each air electrode and each fuel electrode from spreading, the current flow along the in-plane direction of the cell 1A is suppressed, and the voltage loss is reduced. As a result, the power generation efficiency of the fuel cell can be improved by several percent.

  In addition, when the non-uniformity of gas distribution temporarily increases for some reason, a shortage of fuel gas or air gas has occurred in some cells in the conventional configuration. In the cell, even if a shortage of fuel gas or air gas occurs in the cell stack on the gas outlet side, a shortage of fuel gas and air gas hardly occurs in the cell stack on the gas inlet side. For this reason, the voltage loss as the whole stack becomes smaller, and the power generation efficiency can be improved.

  The power generation efficiency is expressed by the following (Formula 1).

(Power generation efficiency) = (Fuel utilization) × (Battery efficiency) (Equation 1)
It is preferable to generate electricity with the fuel utilization rate as high as possible. However, if the fuel utilization rate is too high, the fuel becomes diluted at the outlet side of the fuel cell, and the cell efficiency is extremely lowered. Therefore, it is preferable to appropriately adjust the balance between the fuel utilization rate and the cell efficiency.

  In the present embodiment, the fuel electrode is divided into the first fuel electrode and the second fuel electrode, and power is generated separately, so that power generation corresponding to each fuel utilization rate can be performed. Note that the power generation efficiency is improved by increasing the number of divisions of the fuel electrode, but there is a problem that the electric power obtained through each current collector becomes extremely small. Assuming a stack 6A that is as large as possible within a range that can accommodate variations in the distribution of fuel gas to each cell, the lengths of the fuel electrodes 4A, 4B, 4C, and 4D are the lengths of the fuel electrode 4A and the fuel electrode 4E. And 70% to 75% of the total.

  In the present embodiment, an example of a long flat cell has been described, but the present invention is not limited to this. The fuel gas and the air gas may be configured to flow in parallel and in the same direction. For example, the fuel gas and the air gas are introduced from the center part of the circular cell or the cylindrical cell and are discharged from the peripheral part. However, the present invention can be applied. Further, the number of cells constituting the stack is not limited to the number shown in FIG. 1, and can be configured to an arbitrary number.

  Furthermore, in the present embodiment, an example of a solid oxide fuel cell has been described, but the present invention is not limited to this. Any fuel cell that can have the same cell and stack configuration as the configuration shown in FIG. 1 may be used, and the present invention is also applied to phosphoric acid fuel cells, polymer electrolyte fuel cells, molten carbonate fuel cells, and the like. Can do.

  The present invention includes a cell that generates electric power based on fuel gas and air gas, and a current collecting member that collects the electric power generated by the cell. The cell performs oxidation-reduction reaction between the fuel gas and air gas. It can apply to the fuel cell containing the electrolyte for making it.

The block diagram which shows the structure of the fuel cell which concerns on this Embodiment. The graph which shows the relationship between the voltage and electric current of the cell provided in the fuel cell which concerns on this Embodiment

Explanation of symbols

1A Cell 2A, 2F Current collector 3A, 3E Air electrode 4A, 4E Fuel electrode 5A Electrolyte 7A Fuel gas 7B Air gas

Claims (14)

At least one cell that generates electrical power based on fuel gas and air gas;
And at least one current collecting member for collecting the electric power generated by the cell,
In the fuel cell, the cell includes an electrolyte for conducting ions that cause a redox reaction between the fuel gas and the air gas.
The cell includes a first fuel electrode that allows the fuel gas to permeate along a surface of the electrolyte;
A first air electrode disposed at a position facing the first fuel electrode with the electrolyte interposed therebetween to allow the air gas to permeate in the same direction as the fuel gas;
A second fuel electrode disposed on the electrolyte separately from the first fuel electrode in order to permeate the fuel gas that has passed through the first fuel electrode;
A second air electrode disposed separately from the first air electrode at a position facing the second fuel electrode across the electrolyte in order to transmit the air gas that has passed through the first air electrode; In addition,
The current collecting member includes a first current collector connected to one of the first fuel electrode and the first air electrode;
A fuel cell comprising: a second current collector connected to one of the second fuel electrode and the second air electrode separately from the first current collector.   2. The fuel cell according to claim 1, wherein a length of the first fuel electrode along the permeation direction of the fuel gas is longer than a length of the second fuel electrode along the permeation direction of the fuel gas.   3. The fuel cell according to claim 2, wherein the length of the first fuel electrode is 70% to 75% of a total of the length of the first fuel electrode and the length of the second fuel electrode.   2. The fuel cell according to claim 1, wherein the at least one cell is a plurality of cells arranged in parallel with each other along a direction crossing a permeation direction of the fuel gas.   The fuel cell according to claim 4, wherein the at least one current collecting member is a plurality of current collecting members respectively disposed between the plurality of cells adjacent to each other. The first fuel electrode and the first air electrode respectively provided in the plurality of cells are connected in series by the first current collector,
The fuel cell according to claim 5, wherein the second fuel electrode and the second air electrode respectively provided in the plurality of cells are connected in series by the second current collector.   The conductive porous body is provided between the first current collector and the first fuel electrode and between the second current collector and the second fuel electrode, respectively. The fuel cell as described.   2. The conductive porous body is provided between the first current collector and the first air electrode and between the second current collector and the second air electrode, respectively. The fuel cell as described.   2. The fuel cell according to claim 1, wherein the first and second air electrodes include a reduction catalyst, and the first and second fuel electrodes include an oxidation catalyst.   10. The fuel cell according to claim 9, wherein at least one of the first and second air electrodes includes a perovskite complex oxide containing a rare earth element.   The fuel of claim 9, wherein at least one of the first and second fuel electrodes comprises at least one selected from nickel, platinum, nickel-zirconia, nickel-ceria, platinum-zirconia and platinum-ceria. battery.   2. The fuel cell according to claim 1, wherein the porosity of the first and second air electrodes is 20% or more and 60% or less.   2. The fuel cell according to claim 1, wherein the porosity of the first and second fuel electrodes is 20% or more and 60% or less.   2. The fuel cell according to claim 1, wherein the electrolyte includes at least one of yttria-stabilized zirconia and lanthanum garade-based perovskite oxide.

Images