JPH07296825A - Internal manifold type solid electrolyte fuel cell - Google Patents

Abstract

PURPOSE:To provide a high-performance composite separator of high accuracy at low cost by fitting a conductive oxide plate in a grooved portion having a flat bottom passing from one end surface to the opposite end surface of the air-electrode side portion of a heat resistant metallic main body portion. CONSTITUTION:A separator 1 is a combination of a heat resistant metallic main body portion 1A and a conductive oxide plate 1B, with plural lines of gas circulating channels and projections formed on the bottom surface of the main body portion 1A to make contact with the fuel electrode surface of a cell. A grooved portion 1d consisting of a flat surface passing from on end surface 1g to the opposite end surface 1g is formed in the center of the top surface of the main body portion 1A other than both end portions 1d, and the plate 1B is fitted into the grooved portion 1e. Since the grooved portion 1e is not a recess, it is cut by a shaping machine and has its surface finish polished by a polishing machine. Similarly, the bottom surface of the plate 1B is ground and polished. Therefore, the manufacturing process is simple and the contact resistance of the fuel cell is decreased by the close contact between both sides. Also, plural lines of air circulating channels 5c and projections 5b are formed on the top surface of the plate 1B to make contact with the air electrode of the cell.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal manifold type solid oxide fuel cell having a composite separator composed of a refractory metal and a conductive oxide.

[0002]

2. Description of the Related Art Recently, a fuel cell that directly converts chemical energy originally possessed by fuel into electric energy by using oxygen and hydrogen as an oxidant and a fuel, respectively, is a resource saving,
It is drawing attention from the perspective of environmental protection. A solid oxide fuel cell that uses zirconia doped with yttria, etc. as the electrolyte layer of a single cell and uses a heat-resistant metal or a conductive oxide as a separator has a high operating temperature, high power generation efficiency, and high temperature waste heat. Since the total efficiency is high due to use,
Research and development is progressing.

In the solid oxide fuel cell, a flat plate-shaped single cell in which a fuel electrode and an air electrode are arranged so as to sandwich a solid electrolyte layer and an adjacent single cell are electrically connected in series and each single cell is connected. It is configured as a multi-layer stack by alternately stacking separators that distribute fuel gas and air. The internal manifold type solid oxide fuel cell has an integrated structure in which a cell material such as a separator has a function of supplying and discharging oxygen and fuel gas, a function of distributing, and an electrical connection function. Therefore, a gas supply / exhaust hole is formed in the peripheral portion of the separator, each gas is supplied / exhausted from the hole to the electrode surface of the unit cell, and further, in order to evenly distribute the gas to all the corners of the electrode surface, In addition, a plurality of gas flow grooves are formed on the electrode surface for connecting adjacent batteries in series. Gas supply / exhaust holes provided in the peripheral portion are connected in the process of stacking the unit cells to form a gas passage inside the stack.

FIG. 3 is a perspective view of a composite separator used in a conventional internal manifold type solid oxide fuel cell.

Conventionally, a separator used in an internal manifold type solid oxide fuel cell is constructed as a composite separator composed of a main body 11 made of a refractory metal and a plate 12 made of a conductive oxide. The surface of the composite separator on the fuel electrode side (the surface on the back side of the main body 11 in FIG. 3) is a heat-resistant metal surface. However, most of the opposite surface on the air electrode side (the surface on the front side of the main body 11 in FIG. 3) is a heat resistant metal surface, and the remaining part of the surface is recessed to form the pocket portion 13. The conductive oxide plate 12 as a current collector is fitted in the portion 13. The conductive oxide plate 12 is obtained, for example, by pressure-molding strontium dope lanthanum chromite and firing it in air. When fitted as described above, the flat bottom surface of the pocket portion 13 of the heat-resistant metal main body portion 11 and the flat bottom surface of the conductive oxide plate 12 are overlapped with each other, and a surface having both oxygen and fuel gas flow grooves. Will be exposed top and bottom to each other. In addition,
The conductive oxide plate 12 has a gas flow groove 12a on the upper surface,
The lower surface is flat. A fuel gas flow groove (not shown) is formed on the fuel electrode side surface of the main body 1 corresponding to the gas flow groove 12a.
Are formed.

This composite separator has high mechanical strength and few cracks, and unlike the case where an oxide film is coated on a metal, there is also a problem of peeling due to a difference in thermal expansion and a problem of increasing interfacial resistance due to peeling. Therefore, the solid oxide fuel cell using the composite separator has advantages such as resistance to heat cycle, high durability, easy manufacture and repair, and low cost.

[0007]

However, such a conventional composite separator has the following drawbacks. (1) Pocket part 13 provided in the main body 11 of heat-resistant metal
Since is a dent with a raised periphery, this must be manufactured by milling (milling). That is, it must be cut with an end mill. Further, the grinding process after the milling process is difficult or impossible. As a result, the pocket portion 13
Can not improve the accuracy of the bottom surface of. If this surface accuracy is poor, the lower surface of the conductive oxide plate 12 (see FIG. 4) does not adhere to the bottom surface of the pocket portion 13, and the contact between the two becomes poor.
The contact resistance of the fuel cell, that is, the internal resistance increases, and the performance thereof deteriorates. Further, it takes a lot of time for the milling process and the subsequent polishing and finishing, and the manufacturing cost increases. (2) When an internal manifold type solid oxide fuel cell is assembled by alternately stacking cells and separators and applying pressure to assemble them into a stack of multiple layers, the peripheral portions of the front surface and the back surface of the main body 1 are solid cells of the single cells. It seals with the electrolyte layer in an airtight manner and serves as a sealing surface for preventing gas leakage. On the other hand, the top surface of the protrusion of the air flow groove 12a of the conductive oxide plate 12 comes into contact with the air electrode surface of the unit cell when the fuel cell is assembled (see FIG. 3). At this time, the pressing force mainly acts on the sealing surface of the peripheral edge portion 11a of the main body portion 11, but does not act on the top surface of the projection of the air circulation groove 12a of the conductive oxide plate 12 so much that the pressing force becomes small. This is because the above-mentioned poor processing accuracy of the pocket portion 13 (its depth) and the airtightness of the peripheral portion of the main body portion 11 are emphasized. Therefore, the contact resistance of the fuel cell, that is, the internal resistance of the fuel cell is increased and the performance thereof is deteriorated.

The present invention has been made in view of the above points, and provides an internal manifold type solid oxide fuel cell having a composite separator, which is easy to manufacture, low in cost, high in accuracy, and good in performance. The purpose is to do.

[0009]

In order to solve the above-mentioned problems, the present invention relates to a plate-shaped unit cell in which a fuel electrode and an air electrode are arranged so as to sandwich a solid electrolyte layer, and an adjacent unit cell is electrically connected in series. In a solid oxide fuel cell in which separators that connect and distribute fuel gas and air to each unit cell are alternately laminated, the separator is provided with through holes for supplying and exhausting fuel gas and air in the peripheral portion, and A structure for distributing air to the electrode side is provided on the front surface, and a structure for distributing fuel gas to the fuel electrode is provided on the back surface, and a structure for distributing air to the air electrode side is provided from one end surface of the separator to the opposite end surface. A heat-resistant metal main body having a groove portion having a flat bottom penetrating therethrough on the air electrode side, a front surface facing the air electrode, and a back surface closely fitted to the flat bottom portion of the groove portion of the main body portion and fitted into the groove portion. Conductive oxide Characterized by including and.

[0010]

The separator is a composite type composed of a heat-resistant metal main body and a conductive oxide plate fitted in a groove provided on a part of one side of the main body, and the shape of the groove is one of the separators. Since it has a structure that has a flat bottom that penetrates from the end face to the opposite end face, this groove is cut by a die-cutting machine and polished by a grinder, as a result, the finishing accuracy of the flat surface is improved, and the battery It has the effect of reducing contact resistance.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view of a composite separator used for the internal manifold type solid oxide fuel cell of the present invention before assembly, and FIG. 2 is a composite separator used for the internal manifold type solid oxide fuel cell of the present invention. FIG. 4 is a plan view after assembly of FIG.

The solid oxide fuel cell of the internal manifold type of the present invention is constructed by stacking flat plate cells and separators 1 alternately to form a stack. The unit cell uses Ni / Y as the fuel electrode so that the solid electrolyte layer is sandwiched between them.
SZ cermet as an air electrode (La, Sr) MnO
It is an arrangement of ₃ coated by screen printing. The solid electrolyte layer is made of a zirconia sintered body (YSZ) doped with yttria or the like. Gas supply / exhaust holes are formed at four corners of the solid electrolyte layer.
The gas supply / exhaust holes have the same size and arrangement as the through holes 1a as the supply / exhaust holes at the four corners of the separator 1.

The separator 1 has a function of separating the fuel gas and the oxidant gas used for the fuel electrode and the air electrode of the unit cell to prevent cross leak and a function of electrically connecting the unit cells in series. To do. Separator 1 is N
a main body 1A made of a heat-resistant metal such as i or Ni-based alloy,
It is configured as a composite with a conductive oxide plate 1B adapted to be fitted on the upper surface of the main body portion (see FIG. 1), and the upper surface of the composite separator 1 constitutes a structure for distributing air to the air electrode side, Further, the lower surface thereof constitutes a structure for distributing the fuel to the fuel electrode side. 1 shows a state before the conductive oxide plate 1B is fitted into the main body 1A, and FIG. 2 shows a fitted state.

The main body 1A has a rectangular shape occupying most of the separator 1, and gas supply / exhaust holes 1a are formed at four corners, and the fuel gas is evenly distributed to the corners of the fuel electrode surface of the unit cell. In order to do so, and in order to connect in series with adjacent cells, a plurality of rows of fuel gas flow grooves and protrusions are provided on the electrode surface. When the fuel cell is assembled, the top surface of this protrusion is
It is designed to come into contact with the fuel electrode surface of the unit cell. However, these grooves and protrusions are formed only on the lower surface of the main body portion 1A, while the upper surface of the main body portion 1A has a groove portion 1e formed over the entire width of the central portion, leaving both side end portions 1d.
The conductive oxide plate 1B is fitted in the groove 1e.

As shown in FIG. 1, the groove portion 1e formed on the upper surface of the conductive oxide plate 1B is a flat surface penetrating from one end surface 1g of the separator 1 to the opposite end surface 1g, and is not a recess. Absent. This is very important, as the blade reciprocates on the work surface of the work piece, and has a space in front of and behind the work surface. This makes it possible to cut the groove portion 1e from one end to the other with a shaping machine and further to finish the surface polishing with a grinding machine, so that the accuracy of the plane can be secured. Of course, the lower surface of the conductive oxide plate 1B can also be cut by a shaper, and the surface accuracy can be ensured by planar polishing. The separator 1 has a function of electrically connecting cells and cells in series electrically. Therefore, the contact resistance, that is, the internal resistance of the fuel cell can be reduced by bringing the two surfaces that have been finely finished into close contact with each other.

Grooves on the lower surface of the main body 1A communicate with two diagonal air supply / exhaust holes 1a. The two right and left diagonal air supply / exhaust holes 1a communicate with the air flow groove 5c of the conductive oxide plate 1B as described later. Both ends 1d of the front surface and the back surface of the separator 1 are surfaces for overlapping with the solid electrolyte layer of the unit cell.

The conductive oxide plate 1B is, for example, a flat plate-shaped sintered body obtained by pressure-molding strontium dope lanthanum chromite and firing in air. The plate 1B is provided with a plurality of air circulation grooves 5c and projections 5b for flowing air on the air electrode surface of the unit cell on the upper surface thereof. The top surface of the protrusion 5b comes into contact with the air electrode surface of the unit cell when the fuel cell is assembled. The groove 5c of the plate 1B communicates with the air supply / exhaust holes 1a of two right and left diagonal through holes through the recesses 1f of the main body 1A of the separator 1 (see FIG. 1). In this way, the upper surface of the separator 1 constitutes a structure for distributing air to the air electrode side.

[0019]

As described above, according to the present invention, the separator is composed of a heat-resistant metal main body and a conductive oxide plate which fits in a groove provided in a part of one surface of the main body. As a composite separator, a structure in which a flat bottom surface that penetrates from one end surface of the separator to the end surface on the opposite side is formed in the groove portion, and a flat bottom surface of the main body portion is superposed and closely adhered to one flat surface of the conductive oxide plate Since the solid oxide fuel cell of the internal manifold type is assembled using this composite separator, the following excellent effects can be obtained. (1) Since it is easy to process the fitting portion between the groove formed in the main body of the composite separator and the conductive oxide plate, mass production is possible and cost is reduced. (2) The finishing accuracy of the bottom surface of the groove formed in the main body can be improved. (3) It is possible to increase the compression load that acts on the fitting portion between the main body of the composite separator and the conductive oxide plate when the fuel cell is assembled into the stack. (4) Since the main body of the composite separator and the conductive oxide plate are in good surface contact with each other and the pressing force is increased, the contact resistance, that is, the internal resistance of the fuel cell is reduced, and the performance of the fuel cell is improved. .

[Brief description of drawings]

FIG. 1 is a perspective view before assembly of a composite separator used in an internal manifold type solid oxide fuel cell of the present invention.

FIG. 2 is a plan view after assembly of a composite separator used in an internal manifold type solid oxide fuel cell of the present invention.

FIG. 3 is a perspective view of a composite separator used in a conventional solid oxide fuel cell of the internal manifold type.

[Explanation of symbols]

 1 Separator 1A Heat Resistant Metal Main Body 1B Conductive Oxide Plate 1a Through Hole 1d End 1e Groove 1f Indentation 1g End Face 5b Protrusion 5c Groove

Claims (1)

[Claims] 1. A flat plate cell in which a fuel electrode and an air electrode are arranged so as to sandwich a solid electrolyte layer, and adjacent cell cells are electrically connected in series, and fuel gas and air are distributed to each cell. In a solid oxide fuel cell in which separators are alternately laminated, the separator is provided with a through hole for supplying and exhausting fuel gas and air in a peripheral portion, and a surface is provided with a structure for distributing air to the air electrode side, and A structure for distributing fuel gas to the fuel electrode is provided on the back surface, and a structure for distributing air to the air electrode side is provided with a groove portion having a flat bottom portion penetrating from one end face of the separator to the opposite end face on the air electrode side. A heat-resistant metal main body, and a conductive oxide plate fitted into the groove so that the front surface faces the air electrode and the back surface is in close contact with the flat bottom of the groove of the main body. Internal manifold Type solid oxide fuel cell.