JP6204106B2 - Fuel cell and fuel cell stack - Google Patents

Description

  The present invention relates to a fuel battery cell configured as a flat plate member having a fuel electrode, an air electrode, and an electrolyte layer, and a fuel battery cell stack including the fuel battery cell.

  Conventionally, a solid oxide fuel cell (SOFC) including a solid electrolyte layer (solid oxide layer) is known as a fuel cell which is a kind of power generation device. This solid oxide fuel cell has a very high energy conversion efficiency of 50% or more and can be miniaturized, and therefore has been developed as a power source for household cogeneration systems and automobiles.

  Specifically, the solid oxide fuel cell includes a flat fuel cell in which a fuel electrode in contact with the fuel gas and an air electrode in contact with the oxidant gas are disposed on both sides of the solid electrolyte layer (for example, Patent Documents 1 to 3). The fuel gas is for generating hydrogen, and the oxidant gas is for generating oxygen. Then, when hydrogen and oxygen react via a solid electrolyte layer (power generation reaction), DC power is generated with the air electrode as the positive electrode and the fuel electrode as the negative electrode.

  In the solid oxide fuel cell disclosed in Patent Document 1, conductive strips are continuously provided on the surfaces of the fuel electrode and the air electrode. In this fuel cell, electrons flow parallel to the electrodes through the conductive strips. That is, the conductive strip functions as a current collector and the resistance in the planar direction is reduced. For this reason, the electric current generated at each electrode flows in a direction parallel to the electrode without voltage loss.

  In the solid oxide fuel cell disclosed in Patent Document 2, a conductive electrode that joins the air electrode and the air electrode side current collector between the air electrode and the air electrode side current collector in the fuel cell. The adhesion layer is formed in a lattice shape. By providing this adhesion layer, the air electrode and the air electrode side current collector are reliably in contact with each other, and their contact resistance can be kept low.

  By the way, in the fuel cell described above, when the shape of the fuel cell is a flat plate and the reaction gas flow is carried out from the end surface of the fuel cell, the flow of the reaction gas (fuel gas and oxidant gas) (gas flow) ) May be crossflow (cross flow), counterflow (counterflow), coflow (parallel flow), or the like. When power generation is performed using these gas flows, since the reaction gas is used by the power generation reaction, the gas concentration is not uniform in the cell plane (in the plane of each electrode of the fuel cell). That is, on the outflow side (downstream portion) compared to the inflow side (upstream portion) of the reaction gas, the oxygen concentration decreases at the air electrode, and the fuel concentration (concentration of hydrogen or the like) decreases at the fuel electrode. Due to the oxygen concentration difference and the hydrogen concentration difference between the upstream and downstream of the reaction gas, a large difference occurs in the current density (oxygen ion conductivity) in the cell plane. As a result, the temperature distribution is caused by the difference in the amount of power generation in the cell surface, and stress is generated in the fuel cell, which makes it easy for the fuel cell to break or the performance of the fuel cell deteriorates quickly. Occur.

  Patent Document 3 discloses a solid oxide fuel cell configured to suppress the occurrence of temperature distribution in the cell plane by changing the arrangement interval of the current collector according to the flow of the reaction gas. Yes. In this fuel cell, a plurality of fuel cells (power generation unit) and interconnectors are stacked to constitute a fuel cell stack. On the surface of the interconnector, a plurality of ribs (projections) functioning as current collectors are disposed along the direction of the gas flow path. And the arrangement | positioning space | interval of these ribs is set so that it may become large gradually toward the outflow side from a gas inflow side. In this case, since the gas permeation area is small on the gas inflow side, the amount of power generation on the gas inflow side is kept low, and the heat generation amount decreases. On the other hand, since the gas permeation area increases on the gas outflow side, the amount of power generation on the gas outflow side increases and the heat generation amount also increases. As a result, the difference in the amount of current (ion conduction amount) in the surface is suppressed, and the generation of the temperature distribution in the cell surface is suppressed.

JP-A-4-298963 JP 2009-99308 A JP-A-11-297341

  However, in the fuel cell of Patent Document 3, since the number of ribs is large on the gas inflow side, when power is actually generated, the amount of power generation increases on the gas inflow side. On the other hand, since the number of ribs is small on the gas outflow side, the power generation amount decreases. As a result, power generation is concentrated on the gas inflow side, and heat generation accompanying power generation is large on the gas inflow side and small on the gas outflow side. The problem that becomes. That is, in the fuel cell of Patent Document 3, although the power generation area (reacting power generation reaction) through which the reaction gas flows is adjusted, the adjustment is performed by the current collector (conductor). Many electrons try to flow on the gas inflow side where the number of ribs is increased when connected. Therefore, a substantial effective power generation area (considering power generation reaction and current) increases, and a partial increase in current density occurs in the cell plane. As a result, the effective power generation distribution (temperature distribution) in the single cell plane (including the current collector and the like) becomes large. Moreover, since it is necessary to change the shape of the current collector, the processing cost increases.

  Incidentally, in the fuel cell of Patent Document 1, conductive strips are uniformly formed on the surface of the air electrode. For this reason, it cannot be avoided that the power generation amount varies in the cell plane due to the flow of the reaction gas and the power generation amount becomes non-uniform (that is, power generation amount variation). Further, in the fuel cell of Patent Document 2, conductive adhesion layers are regularly provided in a lattice shape within the surface of the air electrode, and these adhesion layers are formed using the same conductive material. For this reason, the variation in the amount of power generation in the cell plane due to the flow of the reaction gas cannot be avoided.

  The present invention has been made in view of the above problems, and an object of the present invention is to eliminate a variation in power generation amount (due to a power generation reaction and current collection) in a plane of an electrode, and to efficiently perform power generation. To provide a cell. Another object is to provide a fuel cell stack that can efficiently generate power using the fuel cell.

And as a means (means 1) for solving the above-mentioned problem, a flat plate member arranged adjacent to a current collector having a plurality of projections for current collection and having a fuel electrode, an air electrode and an electrolyte layer A fuel cell comprising a current collector contact portion configured to be in the form of scattered dots on the surface of at least one of the fuel electrode and the air electrode. And a conductive layer provided on the surface of the electrode, wherein the conductive layer is provided in an inner region of each of the plurality of current collector contact portions, and a contact with which a projection of the current collector contacts A plurality of abutting pad portions having a conductive material composition having a higher conductivity on the outflow side of the reaction gas than on the inflow side of the reaction gas supplied along the planar direction of the electrode. A fuel cell formed using a material There is Le.

  Therefore, according to the invention described in the means 1, the conductive layer is provided on the surface of the electrode, and the conductive layer is a contact pad portion with which the protrusions of the current collector contact in the inner region of the plurality of current collector contact portions. have. These contact pad portions are formed by varying the composition (conductivity) of the conductive material according to the flow of the reaction gas supplied along the planar direction of the electrode. In a fuel cell, power generation occurs when electrons are transferred from the current collector to the electrode. Therefore, by installing a contact pad portion having such a different conductivity at the current collector contact portion, A difference in current collection resistance occurs. The current collecting resistance in the present invention is not an electric resistance of only the current collector, but a three-phase interface (interface between the reaction gas, the electrode, and the solid electrolyte layer) through the current collector and the electrode (fuel electrode and air electrode). ) Refers to the electrical resistance. Then, by reversing the increase or decrease of the current collecting resistance with respect to the increase or decrease of the gas concentration in the cell plane, the variation in the amount of power generation in the plane of the fuel cell is eliminated, and the difference in temperature distribution during power generation is reduced. As a result, cell cracks and early deterioration of cell characteristics can be avoided. In the present invention, the power generation amount includes both the power generation reaction and the power generation resistance obtained by the power generation reaction. Further, in the fuel cell of the present invention, the protrusions of the current collector are arranged in the form of dots with a predetermined interval, and the current collector arrangement interval according to the flow of the reaction gas as in the prior art There is no need to change the shape. For this reason, in the fuel cell, a sufficient flow rate of the reaction gas supplied to each electrode can be ensured, and power generation can be performed efficiently. Furthermore, since the processing cost accompanying the shape change of a collector is unnecessary, the manufacturing cost of a fuel cell can be held down.

  Specifically, the plurality of contact pad portions are formed using a conductive material having a material composition with higher conductivity on the reaction gas outflow side than on the reaction gas inflow side. That is, the plurality of contact pad portions are formed using a conductive material having a smaller resistance value on the reaction gas outflow side than in the reaction gas inflow side. In this case, on the inflow side where the concentration of the reaction gas is high and the power generation amount tends to increase, the power generation amount is suppressed by suppressing the flow of electrons by the contact pad portion having a low conductivity (high resistance). On the other hand, on the outflow side where the concentration of the reaction gas is low and the power generation amount tends to decrease, the power generation amount is increased by facilitating the flow of electrons by the contact pads with high conductivity (low resistance). Therefore, in the fuel cell, the increase / decrease in the gas concentration in the cell surface and the increase / decrease in the current collecting resistance are reversed, so that it is difficult for a difference in power generation between the inflow side and the outflow side of the reaction gas. As a result, it is possible to eliminate variations in the amount of power generation in the plane of the fuel cell, and avoid cell cracks and early deterioration of cell characteristics.

  Each of the contact pad portions formed on the surface of the plurality of current collector contact portions has the same shape and the same area, and may be regularly arranged in a grid pattern vertically and horizontally on the surface of the electrode. Good. If it does in this way, each contact area of each processus | protrusion of an electrical power collector and each contact pad part will become equal. For this reason, the contact resistance between each protrusion and the electrode can be accurately adjusted by the conductivity of the contact pad portion, and by changing the contact resistance according to the flow of the reaction gas, the planar direction in the fuel cell It is possible to surely eliminate the power generation variation.

  The contact pad portion is formed using a conductive material having a resistance value lower than that of the electrode forming material. Specifically, the contact pad portion includes platinum (Pt), silver (Ag), palladium (Pd), lanthanum (La), strontium (Sr), manganese (Mn), cobalt (Co), iron (Fe). , Copper (Cu), nickel (Ni), gold (Au), iridium (Ir), ruthenium (Ru), and rhodium (Rh). For example, when the plurality of contact pad portions include two materials of silver and palladium, the contact ratio of each contact pad portion is changed so that the proportion of silver is larger on the outflow side than on the reaction gas inflow side. It is formed.

  Further, the contact pad portion on the inflow side and the contact pad portion on the outflow side of the reactive gas may be formed using a conductive material containing another metal material having a different resistance value. For example, the contact pad portion on the reaction gas inflow side is formed using a conductive material containing palladium as a main material, and the contact pad portion on the outflow side is formed using a conductive material containing silver as a main material. The In the fuel cell, even if the contact pad portion is formed in this way, it is difficult for a difference in power generation between the inflow side and the outflow side of the reaction gas, and cell cracks and early deterioration of cell characteristics can be avoided. it can.

  The fuel cell is used in a solid oxide fuel cell, and the electrode on which the contact pad portion is formed may be a fuel electrode or an air electrode. In this case, since the transfer of electrons between each electrode and the current collector is efficiently performed via the contact pad portion, the power generation efficiency can be sufficiently increased.

In the case where the electrolyte layer constituting the fuel cell is a solid oxide layer, examples of the forming material include ZrO ₂ ceramic and LaGaO ₃ ceramic.

The air electrode is in contact with an oxidant gas (reactive gas) serving as an oxidant, and functions as a positive electrode in the fuel cell. Here, examples of the material for forming the air electrode include a metal material, a metal oxide, and a metal composite oxide. Preferable examples of the metal material include Pt, Au, Ag, Pd, Ir, Ru, Rh, etc., and alloys thereof. Preferable examples of metal oxides include La, Sr, Ce, Co, Mn, Fe oxides (La ₂ O ₃ , SrO, CeO ₂ , Co ₂ O ₃ , MnO ₂ , FeO). . Preferable examples of metal composite oxides include, for example, composite oxides containing La, Pr, Sm, Sr, Ba, Co, Fe, and Mn (La _1-x Sr _x CoO ₃ -based composite oxide, La _{1 -x} Sr _x FeO _3-based composite _{oxide, La 1-x Sr x Co} 1-y Fe y O 3 composite _{oxide, La 1-x Sr x MnO} 3 composite _oxide, Pr _1-x Ba _x CoO ₃ type composite oxide, Sm _1-x Sr _x CoO ₃ type composite oxide) and the like.

  Examples of the oxidant gas include a mixed gas of oxygen and another gas. This mixed gas may contain an inert gas such as nitrogen or argon. The mixed gas is preferably safe and inexpensive air.

The fuel electrode is in contact with a fuel gas (reactive gas) serving as a reducing agent and functions as a negative electrode in the fuel cell. Here, examples of the material for forming the fuel electrode include ZrO ₂ ceramics stabilized by rare earth elements (Sc, Y, etc.), and CeO ₂ ceramics doped with rare earth elements (Sm, Gd, etc.). Among them, a metal ceramic material in which at least one ceramic material is mixed with at least one of metal materials such as Pt, Au, Ag, Pd, Ir, Ru, Rh, Ni, Fe and alloys of these metal materials. Mixtures (cermets) can be used.

  Examples of the fuel gas include hydrogen gas, hydrocarbon gas, and a mixed gas of hydrogen gas and hydrocarbon gas. When the hydrocarbon gas is selected as the fuel gas, the type of the hydrocarbon gas is not particularly limited, but is preferably natural gas, naphtha, coal gasification gas, or the like. It is obtained by mixing water vapor with fuel gas obtained by passing gas (hydrogen gas, hydrocarbon gas, mixed gas) in water and humidifying it, or gas (hydrogen gas, hydrocarbon gas, mixed gas). The fuel gas to be used may be selected. Further, only one type of fuel gas may be used, or a plurality of types of fuel gas may be used in combination. Further, the fuel gas may contain an inert gas such as nitrogen or argon. Moreover, what vaporized the liquid raw material can be used as fuel gas, or hydrogen gas produced by reforming a gas other than hydrogen gas can be used as fuel gas.

  Further, as another means (means 2) for solving the above-mentioned problem, the fuel cell according to means 1 and a plurality of projections for collecting current are provided, and the front end surfaces of the plurality of projections are A current collector disposed on the surface of the electrode so as to contact the current collector contact portion, and a plurality of the fuel cells and the current collector are stacked. There is a fuel cell stack.

  According to the invention described in Means 2, the fuel cell stack is configured by laminating a plurality of fuel cells and current collectors of Means 1. In this fuel cell stack, in each fuel cell, it becomes difficult for a difference in power generation between the inflow side and the outflow side of the reaction gas, and cell cracks and early deterioration of cell characteristics can be avoided. Therefore, it is possible to efficiently generate power in the fuel cell stack.

  In the fuel cell stack, the tip end surface of the protrusion may be bonded to the surface of the electrode via the contact pad portion.

  Moreover, a solid oxide fuel cell (SOFC) is mentioned as a fuel cell comprised using said fuel cell stack. The fuel cell of the present invention includes a solid oxide electrochemical cell such as a solid oxide electrolytic cell (SOEC).

The schematic block diagram which shows the fuel cell of this Embodiment. The schematic sectional drawing which shows a fuel cell stack. The top view which shows arrangement | positioning of the processus | protrusion of a collector. The top view which shows a collector contact part and a conductive layer. The top view which shows the conductive layer of another embodiment in case a gas flow is a coflow. The top view which shows the conductive layer of another embodiment in case a gas flow is a cross flow.

  Hereinafter, an embodiment in which the present invention is embodied in a fuel cell will be described in detail with reference to the drawings.

  The fuel cell 200 of the present embodiment is a solid oxide fuel cell (SOFC). As shown in FIG. 1, the fuel cell 200 includes a fuel cell stack 212 formed by stacking a plurality of fuel cells 211 as a minimum unit of power generation.

  The fuel cell stack 212 has, for example, a substantially rectangular parallelepiped shape with a length of 180 mm × width of 180 mm × height of 80 mm. In the present embodiment, the number of stacked fuel cells 211 constituting the fuel cell stack 212 is about 20. Further, in the fuel cell stack 212, end plates 14 and 15 are arranged at both ends (upper end and lower end in FIG. 1) in the stacking direction of the fuel cells 211. Furthermore, a plurality of through-holes that penetrate the stack 212 in the thickness direction are formed in the peripheral portion of the cell stack 212. Then, the fastening bolts 18 are inserted into the respective through holes, and nuts 19 are screwed onto the lower end portions of the bolts 18 protruding from the lower surface of the cell stack 212. In this way, the plurality of fuel cells 211 are fixed by tightening the end plates 14 and 15 in the stacking direction of the fuel cells 211 using the fastening bolts 18 and the nuts 19. Further, the end plates 14 and 15 arranged at both ends of the cell stack 212 serve as output terminals for current output from the cell stack 212.

  As shown in FIG. 2, the fuel cell 211 constituting the cell stack 212 is configured as a flat plate member having the air electrode 21, the fuel electrode 22, and the solid electrolyte layer 23, and generates electric power by a power generation reaction. In addition to the fuel cell 211, the cell stack 212 is provided with a connector plate 24, a separator 25, an air electrode current collector 27, a fuel electrode current collector 28, and the like, and a plurality of these are stacked. ing.

  More specifically, the connector plates 24 are made of a conductive material such as stainless steel, and a pair of connector plates 24 are arranged on both sides of the fuel cell 211 in the thickness direction. Each connector plate 24 ensures conduction between the fuel cells 211 in the thickness direction. The connector plate 24 disposed between the adjacent fuel cells 211 serves as an interconnector, and separates the adjacent fuel cells 211.

  The separator 25 is made of a conductive material such as stainless steel and has a substantially rectangular frame shape having a rectangular opening 29 at the center. The separator 25 functions as a partition plate between the fuel cells 211.

  The solid electrolyte layer 23 is formed in a rectangular plate shape by a ceramic material (oxide) such as yttria stabilized zirconia (YSZ). The solid electrolyte layer 23 is fixed to the lower surface of the separator 25 and is disposed so as to close the opening 29 of the separator 25. The solid electrolyte layer 23 functions as an oxygen ion conductive solid electrolyte body.

  An air electrode 21 in contact with the oxidant gas supplied to the cell stack 212 is attached to the upper surface of the solid electrolyte layer 23, and the fuel gas supplied to the cell stack 212 is also attached to the lower surface of the solid electrolyte layer 23. A fuel electrode 22 in contact therewith is affixed. That is, the air electrode 21 and the fuel electrode 22 are disposed on both sides of the solid electrolyte layer 23. The air electrode 21 is disposed in the opening 29 of the separator 25 so as not to contact the separator 25. In the fuel cell 211 of the present embodiment, a fuel chamber 31 is formed below the separator 25 and an air chamber 32 is formed above the separator 25.

In the fuel cell 211 of the present embodiment, the air electrode 21 is formed in a rectangular plate shape by LSCF (La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ ) which is a metal complex oxide. Has been. The fuel electrode 22 is formed in a rectangular plate shape by a mixture of nickel and yttria-stabilized zirconia (Ni-YSZ). In the fuel cell 211, the air electrode 21 functions as a cathode layer, and the fuel electrode 22 functions as an anode layer.

  The air electrode 21 is electrically connected to the connector plate 24 by the air electrode side current collector 27, and the fuel electrode 22 is electrically connected to the connector plate 24 by the fuel electrode side current collector 28. The air electrode side current collector 27 is made of a dense metal plate such as a SUS430 ferrite alloy to which a small amount of La, Mn, Ti, Si, C, Ni, Al, Zr or the like is added. On the other hand, the fuel electrode side current collector 28 is made of, for example, a nickel porous body so that the fuel gas can pass therethrough.

  As shown in FIGS. 2 to 4, the air electrode side current collector 27 has a plurality of protrusions 35 for collecting current, and the tip surfaces of the protrusions 35 are on the surface of the air electrode 21. It arrange | positions adjacent to the fuel cell 211 so that the collector contact part 37 set in the shape of a scattered dot may be contacted. In the present embodiment, the plurality of current collector contact portions 37 are, for example, rectangular regions, have the same shape and the same area, and are regularly set in a grid pattern vertically and horizontally on the surface of the air electrode 21. ing. The plurality of protrusions 35 in the air electrode side current collector 27 are quadrangular protrusions having the same shape and the same size, and are regularly arranged in a lattice shape vertically and horizontally.

  As shown in FIG. 4, a conductive layer 238 made of a conductive material is provided on the surface of the air electrode 21. The conductive layer 238 is provided in an inner region of each current collector contact portion 37, and has rectangular island-shaped contact pad portions 238a, 238b, and 238c with which the protrusions of the current collector contact. In the fuel cell 211 of the present embodiment, the air electrode 21 and the air electrode side current collector 27 (the tip surface of each projection 35) are joined via the contact pad portions 238a to 238c (see FIG. 2). ). The contact pad portions 238a to 238c are made of a silver-palladium alloy and have a thickness of, for example, about several tens of micrometers. Each of the plurality of contact pad portions 238a to 238c has the same shape and the same area. The contact pad portions 238 a to 238 c are regularly arranged in a grid pattern vertically and horizontally so as to overlap the current collector contact portions 37 on the surface of the air electrode 21.

  In the fuel cell stack 212 of the present embodiment, a fuel supply path (not shown) for supplying fuel gas to the fuel chamber 31 of each fuel battery cell 211, and a fuel discharge path for discharging fuel gas from the fuel chamber 31 ( (Not shown). The cell stack 212 is provided with an air supply path (not shown) for supplying air to the air chamber 32 of each fuel battery cell 211 and an air discharge path (not shown) for discharging air from the air chamber 32. ing. Each supply path and each discharge path are connected to an external pipe (not shown) via a joint portion (not shown) provided on the side surface of the fuel cell stack 212.

  In the present embodiment, the reaction gas (fuel gas and oxidant gas) is supplied from the end surface portion of the fuel cell 211 through an external pipe or each supply path. Specifically, as shown in FIG. 4, a cross flow (orthogonal flow) system is adopted as the flow of the reaction gas (fuel gas F1 and oxidant gas A1). In the fuel cell 211, the oxidant gas A <b> 1 is supplied from the right side to the left side in FIG. 4 along the surface direction of the air electrode 21. On the other hand, the fuel gas F <b> 1 is supplied from the upper side to the lower side in FIG. 4 along the surface direction of the fuel electrode 22 on the back side of the air electrode 21. That is, in the present embodiment, the flow of the oxidant gas A1 and the flow of the fuel gas F1 are orthogonal.

  The contact pad portions 238a to 238c on the surface of the air electrode 21 are formed by changing the composition of the conductive material according to the flow of the reaction gases F1 and A1 supplied along the planar direction of the electrodes. . More specifically, each of the contact pad portions 238a to 238c is made of a conductive material having a material composition in which the contact pad portion 238c on the outflow side has a higher conductivity than the contact pad portion 238a on the inflow side of the reaction gases F1 and A1. It is formed using. In the present embodiment, the mixing ratio is changed so that the contact pad portion 238c on the outflow side has a higher silver ratio than the contact pad portion 238a on the inflow side of the reaction gases F1 and A1. Since silver has a higher conductivity than palladium, the conductivity of the contact pad portion 238c on the outflow side is increased by increasing the proportion of silver in this way. On the other hand, the conductivity of the contact pad portion 238a on the inflow side becomes lower than the conductivity of the contact pad portion 238c on the outflow side by reducing the ratio of silver. That is, the resistance value of the contact pad portion 238c on the outflow side is lower than the resistance value of the contact pad portion 238a on the inflow side.

  Note that when the reaction gases F1 and A1 are supplied in a cross flow (cross flow) manner as in the present embodiment, the conductivity of the contact pad portion 238a provided at the upper right in the air electrode 21 of FIG. 4 is the highest. On the other hand, the conductivity of the contact pad portion 238c provided at the lower left is the highest. Further, the contact pad portion 238b located at the center of the air electrode 21 has an intermediate conductivity (resistance value) between the contact pad portion 238a on the inflow side and the contact pad portion 238c on the outflow side. .

  During power generation of the fuel cell 200, electrons associated with a power generation reaction are performed between the air electrode 21 and the air electrode side current collector 27 via the contact pad portions 238a to 238c formed as described above. It is like that.

  Next, a method for manufacturing the fuel cell stack 212 in the present embodiment will be described.

  First, for example, a plate material made of SUS430 is punched to manufacture the connector plate 24 and the separator 25. Further, the material of the solid electrolyte layer 23 is printed on the green sheet of the fuel electrode 22, and the material of the air electrode 21 is printed thereon, followed by firing. By this firing, a flat fuel cell 211 having the air electrode 21, the fuel electrode 22, and the solid electrolyte layer 23 is manufactured.

  Thereafter, the fuel cell 211 and the separator 25 are fixed by brazing. Further, the air electrode side current collector 27 and the fuel electrode side current collector 28 are fixed to the adjacent upper connector plate 24 and lower connector plate 24 by brazing, respectively.

  Moreover, an Ag-Pd conductive paste is produced by mixing three rolls of Ag-Pd powder, ethyl cellulose, and an organic solvent. In the present embodiment, three types of conductive pastes having different conductivities are produced by changing the mixing ratio of Ag and Pd. Next, the conductive paste is screen-printed in three times on the surface of the air electrode 21 and dried. Here, island-like patterns (patterns to be contact pad portions 238a to 238c) are formed in the inner region of each current collector contact portion 37 using three types of conductive paste. Specifically, in the case of the air electrode 21 shown in FIG. 4, four island-like patterns located on the upper right are formed on the surface using a conductive paste having a low conductivity, and four islands located on the lower left are formed. The pattern is formed using a conductive paste having high conductivity. The remaining island patterns are formed using a conductive paste having an intermediate conductivity.

  Then, the above-described connector plate 24, the fuel battery cell 211 to which the separator 25 is brazed, the air electrode side current collector 27, the fuel electrode side current collector 28 and the like are assembled together, and those members including the fuel battery cell 211 are assembled. The fuel cell stack 212 is configured by stacking a plurality of layers. At this time, in the fuel cell stack 212, the fastening bolt 18 is fitted into the through hole, and the nut 19 is screwed to the tip. As a result, the fuel battery cell stack 212 is assembled by integrating the fuel battery cells 211 while being pressed in the stacking direction.

  The conductive paste described above becomes contact pad portions 238a to 238c (silver palladium alloy) by removing ethyl cellulose and the like at the operating temperature of the fuel cell 200 (for example, 700 ° C.). Further, at the operating temperature of the fuel cell 200, the silver-palladium alloy of the contact pad portions 238a to 238c is softened so that the air electrode 21 and the air electrode side current collector 27 are in close contact with each other. When the operation is stopped, the contact pad portions 238 a to 238 c of the current collector contact portion 37 are integrated by joining the air electrode 21 and the air electrode side current collector 27.

  Next, the operation of the fuel cell 211 in the fuel cell 200 of the present embodiment will be described.

  In the fuel cell 200, for example, while the fuel cell 200 is heated to the operating temperature, the fuel gas F1 is supplied from the fuel supply path to the fuel chamber 31, and the oxidant gas A1 is supplied from the air supply path to the air chamber 32. To do. In the present embodiment, in each fuel cell 211 of the cell stack 212, the oxidant along the plane direction of the air electrode 21 so that the flow of the fuel gas F1 and the oxidant gas A1 is a cross flow (cross flow). The gas A1 is supplied and the fuel gas F1 is supplied along the planar direction of the fuel electrode 22. At this time, hydrogen in the fuel gas F1 and oxygen in the oxidant gas A1 react (power generation reaction) through the solid electrolyte layer 23, and direct current power using the air electrode 21 as a positive electrode and the fuel electrode 22 as a negative electrode is generated. Occur. In the present embodiment, the plurality of contact pad portions 238a to 238c formed at each current collector contact portion 37 on the surface of the air electrode 21 are supplied with the reaction gas F1, which is supplied along the planar direction of the electrode. The conductivity is higher on the outflow side than on the inflow side of A1. In this case, on the inflow side where the concentration of the reaction gases F1 and A1 is high and the power generation reaction amount tends to increase, the power generation amount is suppressed by suppressing the flow of electrons by the contact pad portion 238a having a low conductivity (high resistance). . On the other hand, on the outflow side where the concentrations of the reaction gases F1 and A1 are low and the power generation reaction amount tends to decrease, the amount of power generation increases by facilitating the flow of electrons by the contact pads 238c with high conductivity (low resistance). As a result, in the electrode planes of the air electrode 21 and the fuel electrode 22, the power generation variation is eliminated between the inflow side and the outflow side of the reaction gases F1 and A1, and electric power is generated efficiently.

  In the cell stack 212 of the present embodiment, a plurality of fuel cells 211 are stacked and connected in series. For this reason, in the fuel cell 200, DC power is generated from the upper end plate 14 (positive electrode) electrically connected to the air electrode 21 and the lower end plate 15 (negative electrode) electrically connected to the fuel electrode 22. Is output.

  Therefore, according to the present embodiment, the following effects can be obtained.

  (1) In the fuel cell 211 of the present embodiment, the contact pads 238a to 238c provided in the inner region of the current collector contact portion 37 on the surface of the air electrode 21 are supplied along the planar direction. The conductivity is higher on the outflow side than on the inflow side of the reaction gas F1, A1. In the fuel cell 200, power generation occurs when electrons are transferred from the air electrode side current collector 27 to the air electrode 21. For this reason, by forming the contact pads 238a to 238c having different conductivities as in the present embodiment, the amount of electron exchange (collection resistance) in the fuel cell 211 according to the flow of the reaction gas F1, A1. By adjusting, the power generation amount in the plane becomes uniform. Therefore, the variation in power generation amount in the plane of the fuel cell 211 is eliminated, and the difference in temperature distribution during power generation is reduced. As a result, cell cracks and early deterioration of cell characteristics as in the prior art can be avoided, and power generation can be performed efficiently.

  (2) In the fuel cell 211 of the present embodiment, the protrusions 35 of the air electrode side current collector 27 are arranged in the form of scattered dots with a predetermined interval, and the reaction gases F1, A1 as in the prior art. It is not necessary to change the shape of the current collector 27 according to the flow of the current. For this reason, in the fuel cell 211, the flow rate of the oxidant gas A1 supplied to the air electrode 21 can be sufficiently secured, and power generation can be performed efficiently. Furthermore, in the fuel battery cell 211 of the present embodiment, the processing cost associated with the shape change of the air electrode side current collector 27 is not necessary, and therefore the manufacturing cost of the fuel battery cell 211 can be suppressed.

  (3) In the fuel cell 211 of the present embodiment, each of the contact pads 238a to 238c formed on the surface of the plurality of current collector contact portions 37 has the same shape and the same area, On the surface of the air electrode 21, they are regularly arranged in a grid pattern in the vertical and horizontal directions. When the contact pads 238a to 238c are formed in this way, the contact areas between the protrusions 35 of the air electrode side current collector 27 and the contact pads 238a to 238c become equal. For this reason, the contact resistance between each protrusion 35 and the air electrode 21 can be accurately adjusted by the conductivity of each contact pad 238a to 238c. And by changing these contact resistances according to the flow of the reaction gases F1 and A1, variations in the amount of power generation in the planar direction in the fuel cells 211 can be reliably eliminated.

  (4) In the fuel cell 211 of the present embodiment, the air electrode 21 and the air electrode side current collector 27 are joined via the contact pads 238a to 238c. If comprised in this way, the contact resistance between each processus | protrusion 35 of the air electrode side collector 27 and the air electrode 21 can be restrained low, and current collection efficiency can be improved.

  In addition, you may change embodiment of this invention as follows.

  In the above embodiment, the flow of the reaction gas (fuel gas F1 and oxidant gas A1) is embodied as a cross flow (cross flow), but coflow (parallel flow), counter flow (counter flow) May be embodied in FIG. 5 shows a specific example in which the fuel gas F1 and the oxidant gas A1 are supplied to each electrode by coflow. In FIG. 5, the oxidant gas A1 flows from the upper side to the lower side in the drawing along the plane direction of the air electrode 21, and along the plane direction of the fuel electrode 22 (not shown) on the back side of the air electrode 21. The fuel gas F1 flows from the upper side to the lower side in the figure. As shown in FIG. 5, on the surface of the air electrode 21, the contact pads 238 a to 238 c formed in the plurality of current collector contact portions 37 are on the inflow side of reaction gas F <b> 1, A <b> 1 (upper side in FIG. 5) The contact pad 238c on the outflow side (lower side in FIG. 5) is formed using a conductive material having higher conductivity than the contact pad 238a in FIG. Even when the contact pads 238a to 238c are formed as shown in FIG. 5, it is difficult for a difference in power generation between the inflow side and the outflow side of the reaction gases F1 and A1. As a result, cell cracks in the fuel cell 200 and early deterioration of cell characteristics can be avoided.

  In the above embodiment, as the conductive layer 238 provided on the surface of the air electrode 21, the island-shaped contact pads 238a to 238c are formed in the inner regions of the plurality of current collector contact portions 37, respectively. It is not limited to this. As in the conductive layer 239 shown in FIG. 6, in addition to the contact pads 238a to 238c of the plurality of current collector contact portions 37, connection portions 240a to 240c formed to connect the contact pads 238a to 238c. You may have. In FIG. 6, the current collector contact sites 37 adjacent to each other in the corner portion 41 among the plurality of current collector contact sites 37 arranged in the form of dots in the surface of the air electrode 21. Connection portions 240a to 240c are formed so as to connect the 37 contact pads 238a to 238c. The connection portions 240a to 240c are formed to have the same conductivity as the contact pad portions 238a to 238c connected thereto. In the fuel cell 211, the corner portion 41 of the air electrode 21 is likely to warp in the direction away from the air electrode side current collector 27 due to thermal deformation during power generation. When the connection portions 240 a to 240 c are formed as shown in FIG. 6, even when the current collector contact portion 37 of the corner portion 41 is separated from the protrusion 35 of the air electrode side current collector 27 due to thermal deformation of the fuel cell 211. The contact pad portions 238a to 238c of the electrical contact portion 37 and the contact pad portions 238a to 238c of the current collector contact portion 37 adjacent thereto are electrically connected by the connection portions 240a to 240c. For this reason, sufficient power collection capability can be secured in the fuel battery cell 211. Moreover, on the surface of the air electrode 21, by forming the connection portions 240a to 240c only at the portions where the warpage occurs, it is possible to reliably suppress a decrease in gas permeability.

  In the above embodiment, the contact pad portions 238a to 238c having different electrical conductivities are formed by changing the blending ratio of silver and palladium. However, the present invention is not limited to this. The contact pad portions 238a to 238c having different electrical conductivity may be formed by changing the blending ratio of the metal materials. Further, the contact pad portions 238a to 238c may be formed using a conductive material containing another metal material having a different resistance value. Here, when three metal materials having different resistance values are used, the inflow-side contact pad portion 238a is formed using, for example, a conductive material containing a first metal material having the highest resistance value. In addition, the conductive material including the second metal material having an intermediate resistance value is used to form the intermediate contact pad portion 238b, and the conductive material including the third metal material having the lowest resistance value. Is used to form the contact pad portion 238c on the outflow side. Even when the contact pad portions 238a to 238c are formed in this way, a difference in power generation amount hardly occurs between the inflow side and the outflow side of the reaction gases F1 and A1. As a result, cell cracks in the fuel cell and early deterioration of cell characteristics can be avoided.

  In the above embodiment, three types of contact pad portions 238a to 238c having different conductivity (resistance values) are formed, but two types or four or more types of contact pad portions having different conductivity are formed. May be.

  In the above embodiment, the contact pad portions 238 a to 238 c are formed on the surface of the air electrode 21, but the contact pad portions may be formed on the surface of the fuel electrode 22. Even in this case, the fuel electrode-side current collector 28 has a plurality of protrusions, and the fuel electrode 22 has a current collector contact portion where the protrusions of the fuel electrode-side current collector 28 can come into contact with each other. The A contact pad portion is formed on the surface of the fuel electrode 22 by changing the composition of the conductive material in accordance with the flow of the reaction gases F1 and A1. Even if the fuel cell 211 is configured in this way, a difference in power generation amount hardly occurs between the inflow side and the outflow side of the reaction gases F1 and A1. As a result, cell cracks in the fuel cell and early deterioration of cell characteristics can be avoided.

  In the above embodiment, the contact pad portions 238a to 238c are formed on the surface of the square air electrode 21 (electrode). However, the electrode shape is not limited to the square shape, but a circular shape. Alternatively, the contact pad portion may be formed on the surface of a polygonal air electrode other than a square. In addition, the shape of the current collector contact portion 37 (each projection 35 of the air electrode side current collector 27) and the conductive layers 238 and 239 (contact pad portions 238a to 238c) are square shapes, but are rectangular and circular. Or a shape such as an ellipse.

  In the above embodiment, the contact pad portions 238a to 238c are formed by firing the conductive paste according to the operating temperature of the solid oxide fuel cell 200, but the contact pad portions 238a to 238c are formed. Alternatively, the fuel cell stack 212 may be manufactured by separately performing a firing process. Further, the contact pads 238a to 238c may be formed simultaneously with the firing step of the air electrode 21, the fuel electrode 22, and the solid electrolyte layer 23 in the fuel battery cell 211.

  Next, in addition to the technical ideas described in the claims, the technical ideas grasped by the embodiments described above are listed below.

  (1) In the means 1, the plurality of contact pad portions are formed using a conductive material having a smaller resistance value on the reaction gas outflow side than in the reaction gas inflow side. Fuel cell.

  (2) In the means 1, the contact pad portion includes platinum (Pt), silver (Ag), palladium (Pd), lanthanum (La), strontium (Sr), manganese (Mn), cobalt (Co), iron It is formed using a conductive material containing at least one of (Fe), copper (Cu), nickel (Ni), gold (Au), iridium (Ir), ruthenium (Ru), and rhodium (Rh). Fuel cell.

  (3) In the means 1, the plurality of contact pad portions include silver and palladium, and are formed by changing the blending ratio so that the ratio of silver is larger on the outflow side than on the inflow side of the reaction gas. The fuel cell characterized by the above-mentioned.

  (4) In the means 1, the contact pad portion on the inflow side of the reaction gas and the contact pad portion on the outflow side are formed using a conductive material containing another metal material having a different resistance value. A fuel battery cell characterized by comprising:

  (5) The fuel cell according to (1), wherein the electrode used in the solid oxide fuel cell and on which the contact pad portion is formed is the air electrode.

DESCRIPTION OF SYMBOLS 21 ... Air electrode 22 ... Fuel electrode 23 ... Solid electrolyte layer 27 ... Air electrode side current collector 35 ... Protrusion 37 ... Current collector contact part 200 ... Fuel cell 211 ... Fuel cell 212 ... Fuel cell Stacks 238, 239 ... conductive layers 238a to 238c ... contact pad parts 240a to 240c ... connection parts constituting the conductive layer A1 ... oxidant gas as reaction gas F1 ... fuel gas as reaction gas

Claims (4)

Adjacent to a current collector having a plurality of protrusions for current collection, and configured as a flat plate member having a fuel electrode, an air electrode and an electrolyte layer, and at least one of the fuel electrode and the air electrode On the surface of the electrode, a fuel battery cell in which a current collector contact portion capable of contacting a plurality of protrusions of the current collector is set in a scattered shape,
A conductive layer provided on a surface of the electrode, and the conductive layer is provided in an inner region of each of the plurality of current collector contact portions, and has a contact pad portion on which a projection of the current collector contacts. And
The plurality of contact pad portions are formed using a conductive material having a material composition having higher conductivity on the outflow side of the reaction gas than on the inflow side of the reaction gas supplied along the planar direction of the electrode. A fuel cell, characterized in that   Each of the contact pad portions formed on the surface of the plurality of current collector contact portions has the same shape and the same area, and is arranged in a grid pattern vertically and horizontally on the surface of the electrode. The fuel battery cell according to claim 1, wherein: The fuel battery cell according to claim 1 or 2,
A plurality of protrusions for current collection, and a current collector disposed such that tip surfaces of the plurality of protrusions are in contact with the current collector contact portion set on the surface of the electrode, A fuel cell stack, wherein a plurality of the fuel cells and the current collector are laminated.   4. The fuel cell stack according to claim 3, wherein a tip end surface of the protrusion is joined to a surface of the electrode via the contact pad portion. 5.

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