JPH0421988B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a matrix fuel cell, and particularly to a seal structure thereof.

Fuel cells are well known as energy conversion devices that utilize electrochemical reactions to directly convert the chemical energy of fuel into electrical energy, aiming at highly efficient power generation. The single cell that forms the basis of the above-mentioned matrix fuel cell consists of a matrix impregnated with an electrolyte, for example, phosphoric acid, and a pair of porous electrodes placed on both sides of the matrix.
Through these electrodes, fuel gas (generally hydrogen gas is used) is supplied from one side, oxidizing gas (generally air is used) from the other side, and electrical energy is extracted directly from both electrodes. . In this case, the output obtained from the above cell is
1V or less, and in order to obtain the required output as a practical power source, the required number of single cells are combined in series or parallel to form a cell stack as the fuel cell main body.

On the other hand, in order for the above battery body to operate normally, it is necessary to supply reactive gas uniformly to each cell, and the specific structure for this purpose is the ribbed electrode type shown below. , a ribbed separator type has been developed. Figures 1 and 2 show the structure of one cell of each of these types, in which 1 is a matrix impregnated with electrolyte, 2 is a fuel electrode, and 3 is an air electrode.
In the ribbed electrode type shown in FIG. 1, the fuel electrode 2 and
A unit cell 6 is constructed by layering an air electrode 3 and overlapping electrode base materials 4 and 5 with a matrix 1 in between. Then, fuel gas and air are allowed to flow from the outside into the groove passages between the ribs of the electrode base materials 4 and 5 as shown by the arrows, thereby supplying the reaction gas to the electrodes 2 and 3. In addition, in such a ribbed electrode type, a gas-impermeable conductive material is used to prevent fuel gas and air from mixing between the stacked cells and to electrically connect the cells. A separate plate 7 made of is inserted between adjacent unit cells. On the other hand, the ribbed separator type shown in Fig. 2 is called a bipolar plate, and has a ribbed separator 8 made of a gas-impermeable carbon plate having reaction gas passage grooves orthogonal to each other on both sides. An assembly of a single cell 6 consisting of a matrix, a fuel electrode and an air electrode in which the electrodes are layered on a gas-permeable electrode base material such as carbon paper is sandwiched from both sides in a sandwich pattern to form one cell. There is. In such fuel cells, a seal is applied to the periphery of each unit cell in order to prevent mixture of fuel and air and leakage of electrolyte.

[Prior art and its problems]

Next, FIG. 3 shows a conventional sealing structure of a cell stack in which the above-described ribbed electrode cell is combined with a separate plate and laminated. The cell stack consists of alternating layers of single cells 6 and separate plates 7.
Further, end plates 9 are disposed at both upper and lower ends, and the entire assembly is assembled by tightening them together. In order to supply reactant gases such as fuel and air to the cell stack, a manifold 10 is arranged on the circumferential side of the cell stack via a packing. The illustrated manifold 10 is a fuel manifold, and an air manifold (not illustrated) is provided on the front and rear end surfaces in the direction perpendicular to the plane of the paper. The fuel gas sent from the outside through the manifold 10 flows through the fuel passage 11 defined between the ribs of the fuel electrode base material 4 as shown by the arrow, and diffuses inside the porous electrode base material to form the fuel electrode. 4 is supplied to the catalyst layer. Note that the reference numeral 12 indicates an air passage on the air electrode side. In this case, between adjacent unit cells, the separate plate 7 has a fuel passage 11 and an air passage 1.
The matrix 1 is impregnated with electrolyte and prevents the fuel and air from coming into contact with each other in the overlapping area inside the unit cell. On the other hand, as mentioned above, each of the electrode base materials 4 and 5 is made of a gas-permeable porous material so as to have a gas diffusion and supply function for the reaction gas, and as shown in the figure, the electrode base materials 4 and 5 are Since the passages 12 are orthogonal to each other, gas leakage occurs through the left and right end surfaces of the electrode base materials 4 and 5 parallel to the reaction gas passages, and mixture of fuel and air occurs. Electrolyte also leaks from the periphery of the matrix 1. As a means to prevent this, conventionally, as shown in the figure, seals are applied to the peripheral edges of the air electrode, including the fuel electrode and the matrix, to prevent the above-mentioned gas leaks and electrolyte leaks. Conventionally, for this seal structure, the peripheral edge of the electrode is coated with, for example, a fluororesin-based coating material to form the seal film 13, but in this method, since the surface of the electrode base material is porous, Formation of a sealing film is accompanied by difficulties, such as the coating material penetrating into the matrix of the electrode base material. Moreover, during long-term use, the sealing film formed in this way is exposed to the solvent of the coating material that has penetrated into the electrode base material, the reaction gas of the battery, etc., resulting in deterioration and deterioration, and eventually blowholes form in the sealing film. There is a good chance that the sealing function will be lost.
In addition, in the conventional sealing structure described above, it is technically difficult to make the thickness of the sealing film uniform, and if the sealing film is too thick, the adhesion between the electrode and the matrix will be insufficient, which will affect the output characteristics of the battery. If the sealing film is too thin, the strength of the sealing film decreases and the resistance to differential pressure decreases, resulting in problems in that sufficient reliability in sealing performance cannot be obtained. Furthermore, if the thickness of the sealing film on the end face of the electrode base material is uneven, the circumferential surface of the cell stack assembly will become uneven, making it impossible for the manifold 10 described in FIG. This will lead to complete failure.

[Purpose of the invention]

This invention has been made in consideration of the above points, and aims to provide a fuel cell seal structure that eliminates the drawbacks of conventional structures, provides highly reliable seal performance, and is easy to manufacture and assemble. shall be.

[Key points of the invention]

In order to achieve the above object, according to the first invention, unit cells each having a fuel electrode, an air electrode, and a matrix impregnated with and retaining an electrolyte as elements are laminated with a gas-impermeable separate plate interposed therebetween. ,
In a fuel cell in which reactive gas is supplied to each electrode through reactant gas passages for fuel gas and air that are orthogonal to each other and are formed in an electrode base material or a separate plate, the separate plate has plate surfaces on the side edges of the upper and lower surfaces thereof. thick rib-like partitions that stand upright and are perpendicular to each other, and the partitions have air passages and fuel gas passages that cover both sides of the air electrode and fuel electrode of the unit cell, respectively. A frame-shaped electrically insulating sheet seal is formed on the outside along both left and right side surfaces parallel to the partition wall, and the sheet seal has an outer circumferential dimension that is approximately the same as the outer circumferential dimension of the partition wall portion and an inner circumferential surface of the sheet seal. Even if the size is large, it is formed smaller than the outer circumferential dimension of the matrix, and the inner circumferential area of the frame-shaped seal sheet is inserted between one electrode of the unit cell and the matrix, and the outer circumferential area is the laminated surface of the partition wall part. According to the second invention, a fuel electrode, an air electrode, and a matrix impregnated with and holding an electrolyte are used as element bodies. The unit cells are stacked with gas-impermeable separate plates in between, and the reactant gas is supplied to each electrode through reactant gas passages for fuel gas and air that are orthogonal to each other formed in the electrode base material or the separate plate. The fuel has a manifold hole formed at the peripheral end of the separate plate that communicates with the reaction gas passage inside the cell and passes through it in the vertical direction, and the reaction gas is supplied to the unit cell through this manifold hole. In the battery, the separate plate includes thick rib-shaped partitions that stand up from the side edges of the upper and lower surfaces and are perpendicular to each other, and the partitions are connected to the air electrode and the cell of the cell. A frame-shaped electrically insulating sheet seal is formed outside the fuel electrode along both left and right sides parallel to the air passage and the fuel gas passage, respectively, so as to cover both sides of the fuel electrode. The outer circumferential dimension is approximately the same as the outer circumferential dimension of the partition wall part, and the inner circumferential dimension is smaller than the outer circumferential dimension of the matrix even if the inner circumferential dimension is large, and the inner circumferential area of the frame-shaped seal sheet is formed with one electrode of the unit cell. The outer periphery is inserted between the matrix and the laminated surface of the partition wall to provide a gas seal between the fuel gas side and the air side, and the partition wall and the frame-shaped seal sheet are each A hole corresponding to the manifold hole is provided.

[Embodiments of the invention]

FIGS. 4 and 5 show an embodiment of the present invention. First, two thick ribs are provided on the upper and lower side edges of the separate plate 7 with their directions changed by 90 degrees. The partition wall portions 14 and 15 are formed to stand up from the plate surface. Among these, the partition wall portion 14 on the upper surface side is formed on the outside along both left and right side surfaces parallel to the air passage 12 so as to cover both sides of the air electrode base material 5, and its bulging height dimension is the same as that of the electrode base material 5. The thickness is set to be the same as or slightly lower than the thickness of the laminate of the air electrode and matrix containing the material. The other partition wall portion 15 on the lower surface side is the partition wall portion 1 described above.
4 and 90 degrees, and are formed along the sides of the fuel electrode base material 4 so as to cover both sides thereof. The height of the bulge is determined according to the thickness of the fuel electrode including the electrode base material. Furthermore, a frame-shaped sheet seal indicated by reference numeral 16 is inserted and clamped between the matrix 1 and the fuel electrode 2 facing the matrix 1 within the unit cell. This sheet seal has an electrical insulation function as well as a sealing function to prevent fuel gas from coming into contact with air, as described below. Alternatively, a sheet made of a composite material of a fluororubber sheet and a polytetrafluoroethylene sheet, or a sheet made by coating the surface of a thin metal sheet with the above material may be used. As clearly shown in FIG. 4, this frame-shaped sheet seal 16 has an inner circumferential area in contact with the upper circumferential edge of the matrix 1, and an outer circumferential area in contact with the upper surface of the partition wall part 14 of the separate plate 7. The fuel electrode base member 4 is placed in close contact with the upper surface of the fuel electrode base material 4 or the partition wall portion 15 on the lower surface side of the separate plate one step above.

Now, according to the structure in which the sheet seal 16 is inserted and clamped across the peripheral edge between the opposing electrodes and the partition walls 14 and 15 of the gas-impermeable separate plate 7 as described above, As shown in Fig. 5, the left and right sides of the air electrode parallel to the air passage are separated by a separate plate 7.
The fuel gas space in the manifold 10 and the fuel electrode base material 4 are completely isolated by the partition wall 14 and the sheet seal 16. Similarly, both left and right side surfaces of the fuel electrode base material 4 parallel to the fuel poison path are completely isolated from the atmosphere on the air side by the separation plate 15 and the sheet seal 16, thereby preventing the fuel gas from flowing. Mixing contact with air is reliably prevented, and at the same time, the partition wall portions 14 and 15 of the separate plates are electrically insulated. Furthermore, the sheet seal 16 made as described above is free from the risk of blowholes and has a high resistance to differential pressure, compared to the conventional one in which a film is formed by directly coating the surface of the electrode base material. , the thickness is also uniform. Furthermore, this sheet seal 16 has the effect of blocking gas flowing from the side surface of one electrode base material to the other electrode through a small gap between the electrode base material and the partition wall. Therefore, a highly reliable sealing function can be obtained, and since the electrodes are in even contact with each other within the single cell, the output characteristics of the battery will not be impaired. Furthermore, the seal is not exposed on the circumferential side of the cell stack, and the outer circumferential surface of the separate plate can be machined, which eliminates the conventional problem of uneven circumferential surfaces and improves the sealing performance between the cell stack and the manifold. It can be increased sufficiently. Furthermore, such a sheet seal 16 can be manufactured and obtained at low cost, and can be easily incorporated into a cell without requiring a large number of man-hours.

FIG. 6 shows an applied example of the embodiment shown above, and shows an example corresponding to the invention of claim 4. In this embodiment, a fuel manifold for equally distributing fuel gas to each unit cell is configured as a hole penetrating vertically inside the cell stack in consideration of gas sealing properties and the like. That is, as shown in the figure, a fuel manifold part 17 is formed at the front and rear ends of the fuel electrode base material 4 by extending the separate plate 7 described in the previous embodiment, and the fuel passage of the fuel electrode base material 4 is formed in this part. A manifold hole 18 communicating with the manifold hole 11 and penetrating in the vertical direction is provided. Furthermore, cutout windows 19 are opened at both ends of the sheet seal 16 corresponding to the manifold holes 18, and the laminated surfaces of the manifold portions 17 of the vertically overlapping separate plates 7 are sealed through the sheet seals 16. and electrical insulation.

Each of the above-mentioned embodiments is an example for the ribbed electrode type shown in Fig. 1, but the same applies to the ribbed separate type fuel cell shown in Fig. 2. can. FIGS. 7 and 8 show an embodiment of a ribbed separator type fuel cell corresponding to FIG. 6, in which ribbed separate plates are provided with fuel passages 11 and air passages 12 orthogonal to each other on both sides. Similar to the previous embodiment, partition wall portions 14 and 15 are formed on the side edges of 8 to protrude.
Between the left and right partitions 14 is a laminate of an air electrode 3 containing a gas-permeable electrode base material and a matrix 1, and between the partitions 15 is a fuel electrode 2 containing a gas-permeable electrode base material. A frame-shaped sheet seal 16 is inserted between the separate plate 8 and the cell 6 for each cell. This embodiment can also achieve the same sealing effect as each of the previously described embodiments.

〔Effect of the invention〕

As described above, according to the present invention, a partition part that covers the end face of the electrode base material from the side is formed upright on the side edge of the separate plate, and the fuel electrode in the unit cell is formed astride the partition part. By inserting and clamping a frame-shaped sheet seal between the air electrode, it reliably prevents the mixture of fuel and air at the periphery of the porous electrode base material, and is also durable and resistant to differential pressure. An excellent and highly reliable sealing structure can also be obtained.

[Brief explanation of drawings]

Figures 1 and 2 are exploded perspective views of a ribbed electrode type cell and a ribbed separator type unit cell, respectively; Figure 3 is a cross-sectional view showing the seal structure of a conventional fuel cell; Figures 4 and 5 are An exploded perspective view and a partially assembled sectional view showing the configuration of an embodiment of this invention, respectively, FIGS. 6 and 7 are exploded perspective views of the configuration of an applied embodiment of the invention, and FIG. 8 is a portion of FIG. 7. FIG. 1... Matrix, 4... Fuel electrode base material, 5
... Air electrode base material, 6 ... Cell, 7, 8 ... Separate plate, 11 ... Fuel passage, 12 ... Air passage, 14, 15 ... Partition wall, 16 ... Sheet seal, 17 ... Manifold part, 18...manifold hole.

Claims (1)

[Scope of Claims] 1. Single cells each consisting of a fuel electrode, an air electrode, and a matrix impregnated with and retaining an electrolyte are stacked together via gas-impermeable separate plates,
In a fuel cell in which reactive gas is supplied to each electrode through reactant gas passages for fuel gas and air that are orthogonal to each other and are formed in an electrode base material or a separate plate, the separate plate has plate surfaces on the side edges of the upper and lower surfaces thereof. thick rib-like partitions that stand upright and are perpendicular to each other, and the partitions have air passages and fuel gas passages that cover both sides of the air electrode and fuel electrode of the unit cell, respectively. A frame-shaped electrically insulating sheet seal is formed on the outside along both left and right side surfaces parallel to the partition wall, and the sheet seal has an outer circumferential dimension that is approximately the same as the outer circumferential dimension of the partition wall portion and an inner circumferential surface of the sheet seal. Even if the size is large, it is formed smaller than the outer circumferential dimension of the matrix, and the inner circumferential area of the frame-shaped seal sheet is inserted between one electrode of the unit cell and the matrix, and the outer circumferential area is the laminated surface of the partition wall part. 1. A fuel cell characterized in that the fuel cell is inserted into a fuel cell to provide a gas seal between a fuel gas side and an air side. 2. In the fuel cell according to claim 1, the sheet seal is a sheet made of a single material of fluororubber or polytetrafluoroethylene, or a composite material of fluororubber and polytetrafluoroethylene. A fuel cell characterized by: 3. In the fuel cell according to claim 1, the sheet seal is made of a single material of fluororubber or polytetrafluoroethylene on a metal sheet,
Alternatively, a fuel cell characterized by being a sheet coated with a composite material of fluororubber and polytetrafluoroethylene. 4 Single cells each consisting of a fuel electrode, an air electrode, and a matrix impregnated with and retaining an electrolyte are stacked together via gas-impermeable separate plates,
The reactant gas is supplied to each electrode through reactant gas passages for fuel gas and air that are orthogonal to each other formed in the electrode base material or the separate plate, and the reactant gas inside the battery is supplied to the peripheral edge of the separate plate. In a fuel cell in which a manifold hole is opened that communicates with a passage and penetrates in the vertical direction, and a reactive gas is supplied to the cell through this manifold hole, the separate plate has plate surfaces on the side edges of the upper and lower surfaces of the fuel cell. thick rib-like partitions that stand upright and are perpendicular to each other, and the partitions have air passages and fuel gas passages that cover both sides of the air electrode and fuel electrode of the unit cell, respectively. A frame-shaped electrically insulating sheet seal is formed on the outside along both left and right side surfaces parallel to the partition wall, and the sheet seal has an outer circumferential dimension that is approximately the same as the outer circumferential dimension of the partition wall portion and an inner circumferential surface of the sheet seal. Even if the size is large, it is formed smaller than the outer circumferential dimension of the matrix, and the inner circumferential area of the frame-shaped seal sheet is inserted between one electrode of the unit cell and the matrix, and the outer circumferential area is the laminated surface of the partition wall part. The fuel is inserted into the fuel tank to provide a gas seal between the fuel gas side and the air side, and the partition wall portion and the frame-shaped sealing sheet are each provided with a hole corresponding to the manifold hole. battery.