JPH0810600B2 - Laminated fuel cell separator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel cell, particularly a laminated fuel cell constituted by laminating a large number of flat electrolyte plates, electrodes and separators, in which reaction gas is mixed, The present invention relates to a separator structure suitable for realizing a fuel cell having excellent stirring and distribution performance and a high gas utilization rate.

[Conventional technology]

Laminated fuel cells have a large number of flat plate-shaped electrolyte plates, positive electrode plates, negative electrode plates, and separators stacked, and a fuel gas and an oxidant gas are used as a medium of an electrochemical reaction by using an electrolyte solution impregnated in the electrolyte plates. By causing an electrochemical reaction,
It converts fuel gas into electrical energy.

The electric power for the unit cell generated in the electrolyte plate can be taken out as a voltage and a current between the negative electrode plate on the fuel gas side and the positive electrode plate on the oxidant gas side. The voltage per unit cell obtained by the electrochemical reaction is low, and is 0.6 to 0.8 V for a molten carbonate fuel cell, for example. Therefore, in order to obtain a practicable voltage, in a fuel cell, power of a practicable voltage is taken out by stacking several hundred unit battery cells.

On the other hand, the generated current density is greater per unit area of the power obtained by the electrochemical reaction, for example in the molten carbonate fuel cell, a ^{0.1A / cm 2 ~0.2A / cm 2} . In the molten carbonate type battery, a voltage of 0.6 to 0.8 V and a current density of 0.1 to 0.2 A / cm ² are used as the power generation conditions of the unit battery cell from the viewpoints of fuel cell performance, manufacturing cost, power generation cost and the like. For this reason, in a laminated fuel cell, it is necessary to connect a large number of separators and electrical connecting portions of electrolytic plates in series and to pass a large current through these connecting portions. Therefore, the internal loss due to the contact electric resistance cannot be ignored in the fuel cell, and the size of the contact electric resistance influences the performance of the fuel cell.

Here, as an example of the output characteristics of the fuel cell, FIG. 5 shows the output characteristics of the molten carbonate fuel cell. Then, the relationship between the output characteristics of the fuel cell and the cell performance will be described based on FIG. In the figure, the horizontal axis represents the current density i (A / cm ² ) and the vertical axis represents the voltage E (V) and the power P (W). Since the fuel cell mainly exhibits a right-down output characteristic due to polarization resistance, the i-E characteristic as shown by the curve a is obtained. Then, the current density range of the range A is usually used from the power generation efficiency of the fuel cell, the energization current, the energy conversion efficiency, and the like.

On the other hand, when the power generation performance of the fuel cell is poor or when the internal electric resistance is large, the i-E characteristic shown by the curve b is obtained.
Further, the battery having the characteristic of the curve a can obtain the i-P characteristic of the curve c, and the battery of the characteristic of the curve b can obtain the i-P characteristic of the curve d. As can be seen from the figure, in the battery having the bad output characteristics as shown by the curve b, the obtained power is significantly reduced.

By the way, in the conventional laminated fuel cell, the separator surface is used as a gas flow path, and a number of perforated pipes are joined in parallel on a flat plate so as to have good gas flow mixing, stirring and distribution performance. A separator having a flow path has been proposed (Japanese Utility Model Laid-Open No. 58-113968). In this separator, the contact portion with the electrode plate of the separator is a curved surface of the pipe and the contact surface is a line, and the contact area is small. Further, a separator has been proposed in which a large number of protrusions are formed on both sides of a flat plate, and the space formed by these protrusions and the electrode plate serves as a gas flow path (Japanese Patent Laid-Open No. 59-98472). In this separator, the contact portion of the separator with the electrode plate is a point at the tip of the protrusion or a small circle, and the contact area is small. Further, there has been proposed a separator in which a plurality of parallel grooves for gas passages are formed on both surfaces of one thick plate and a plurality of connecting grooves are formed so as to intersect the parallel grooves (Japanese Patent Laid-Open No. 59-27467). There is also proposed a separator in which a plurality of parallel grooves for the gas flow path are formed on both sides of one thick plate and a certain undulation pattern is formed on the surfaces of the parallel grooves (Shokai Sho 60). -57065).

[Problems to be solved by the invention]

In the internal electric resistance of the laminated fuel cell, the ratio of the contact electric resistances of the separator, the electrode plate and the electrolyte plate is considerably higher than other factors.
In each of the conventional techniques disclosed in Japanese Patent No. 113968 and Japanese Patent Laid-Open No. 59-98472, the contact area between the separator and the electrode plate is small, and there are various problems as described below.

(1) The contact electric resistance between the separator and the electrode plate is increased, and the internal electric resistance is increased accordingly. As described in FIG. 5, the electric power obtained by the fuel cell is significantly reduced.

(2) The energization current density of the contact portion between the separator and the electrode plate increases, and resistance heat generation and local electric corrosion increase.

(3) The local creep deformation of the porous electrode plate and the electrolyte plate becomes large.

Further, the above-mentioned Japanese Patent Laid-Open No. 59-27467 and Japanese Utility Model Laid-Open No. 60-5.
In the prior art of the 7065 publication, since the gas flow passage cross-sectional area increases and decreases in the middle of the flow passage, a pressure loss occurs in the gas flow when passing through a portion where the cross-sectional area decreases, that is, a cross groove or an undulating portion. There was a problem.

The object of the present invention is to reduce the electrical connection resistance between the laminated separator and the electrode plate, and improve the stirring and distribution performance of the reaction gas without increasing or decreasing the gas flow passage cross-sectional area in the middle of the flow passage. It is an object of the present invention to provide a method and a structure for manufacturing a separator for a laminated fuel cell as described above.

[Means for solving problems]

In order to achieve such an object, the laminated fuel cell separator of the present invention comprises one metallic partition plate and one metallic corrugated plate joined to the partition plate. , The groove section of each of the convex portion and the concave portion of the corrugated plate is trapezoidal, and the convex portion of the corrugated plate is composed of a series of small convex portions having an inlet and an outlet arranged at a certain interval along the longitudinal direction thereof, and At the outlet of each small protrusion, a plate piece that is inclined inward or outward of the groove from one of the two sides that form the cross section of the trapezoidal groove is provided, and the top surface of the small protrusion is the partition plate surface. It is characterized by being joined.

[Action]

When the laminated fuel cell separator configured as described above is laminated and assembled as a fuel cell, a plate-shaped electrode is bonded to the opposite surface of the corrugated plate from the surface to which the partition plate is bonded. It Thus, together with the gas flow path formed by the groove in the concave portion of the corrugated plate formed between the corrugated plate and the partition plate, the gas flow path is formed by the groove in the convex portion of the corrugated plate formed between the corrugated plate and the electrode. Then, the reaction gas flowing in the former flow channel does not contribute to the electrochemical reaction, while the reaction gas flowing in the latter flow channel contributes to the electrochemical reaction.

In the laminated fuel cell separator of the present invention, a plate piece is provided at the outlet of each groove of the small convex portion, and since the plate piece is inclined inward or outward of the groove of the small convex portion, for example, the plate piece is a groove. If it is tilted inward, the small convex groove, that is,
The reaction gas, which has passed through the flow channel where the electrochemical reaction occurs, is bent by the plate piece at the outlet, and is partially formed from the flow channel where the electrochemical reaction does not occur in the next stage, that is, the recess and the partition plate. Flow into the flow path of the small convex portion where the electrochemical reaction occurs, and when the plate piece is tilted to the outside of the groove of the small convex portion, it is separated from the concave portion. In the flow path formed between the plate and the plate, the reaction gas that did not cause the electrochemical reaction is bent by the plate piece at the output, and a part of it flows into the flow path where the electrochemical reaction occurs in the next stage. , The rest will flow into the flow channel in which no electrochemical reaction occurs, thus mixing and stirring is performed from upstream to downstream, and the entire amount of the reaction gas is passed through the gas flow channel in which the electrochemical reaction takes place. Increase the amount of reaction gas that contributes to It is possible.

〔Example〕

Hereinafter, the present invention will be described based on the embodiments shown in the drawings.

FIG. 1 is a perspective view showing a schematic structure of a separator according to an embodiment of the present invention, FIG. 2 is a longitudinal sectional view of a laminated fuel cell equipped with the separator according to the present invention, and FIG. It is a top view which shows the structure of the corrugated plate of the separator concerning an example, and FIG. 4 is a IV-IV sectional drawing of FIG.

The laminated fuel cell 1 has a flat electrolyte plate 2, a positive electrode plate 3,
A large number of negative electrode plates 5 and separators 6 are laminated. As shown in detail in FIG. 1, the separator 6 is composed of a partition plate 8 and first and second corrugated plates 9 and 10. The partition plate 8 is made of metal and formed in a flat plate shape. .

The first corrugated plate 9 is made of a metal flat plate, and its surface is formed into a corrugated concave-convex portion 11 by plastic working so that the groove portion 12 which is a concave portion and the rib portion 13 which is a convex portion are parallel to each other. The bottom surface of the groove portion 12 and the top surface of the rib portion 13 are flat portions 12a and 13a. The hollow portion 13b of the groove portion 12 and the rib portion 13 serves as the fuel gas passage 15.

The second corrugated sheet 10, like the first corrugated sheet 9, is made of a metal flat plate, and the surface thereof is formed into a corrugated uneven portion 16 by plastic working. Groove portion 18 which is a concave portion and rib portion which is a convex portion
19 and the groove 18 are formed so as to be parallel to each other.
The bottom surface and the top surface of the rib portion 19 are flat portions 18a and 19a. The second corrugated sheet 10 is metallically joined to the lower surface of the partition plate 8 so that the concave and convex portions 16 are orthogonal to the concave and convex portions 11 of the first corrugated sheet 9, and the groove portion 18 and the rib portion 19 are formed. Hollow part
19b is the oxidant gas flow path 20. And the first,
When joining the second corrugated plates 9 and 10 to the partition plate 8, between the first and second corrugated plates 9 and 10 and the partition plate 8 is 50 to 100 μm.
After sandwiching the brazing material rolled into the foil shape, and temporarily or temporarily applying these by resistance welding, they are collectively brazed in an atmosphere furnace or a vacuum furnace.

The separator 6 of the present invention uses the first and second corrugated plates 9 and 10 as gas flow paths, and is partitioned by the partition plate 8 from the positive electrode plate 3 and the negative electrode plate 5 attached to both sides of the separator 6. Most of the open space can be used as a gas flow path, and the space is hardly wasted. Therefore, the height in the stacking direction of the separator 6 of the fuel cell 1 can be made thinner than that of the conventional one, and the fuel cell 1 becomes compact.

Further, as described above, the separator 6 of the present invention has a wide gas flow passage cross-sectional area and is excellent in gas mixing and stirring performance. (1) The gas flow velocity in the fuel cell 1 can be reduced. The gas can contribute to the power generation reaction for a long time.

(2) The non-uniform portion of the gas concentration distribution is reduced, and the whole is uniform, and the gas is sufficiently used for the power generation reaction.

The height of the separator 6 in the stacking direction is determined by the first and second corrugated plates.
It is the sum of the height of the uneven portions 11 and 16 of 9, 10 and the thickness of the partition plate 8 and the thickness of the bonding layers of the first and second corrugated plates 9 and 10 and the partition plate 8. The plate thickness and the bonding layer thickness of the partition plate 8 can be reproduced with extremely high dimensional accuracy, and the dimensional variation is small. On the other hand, the heights of the concave-convex portions 11 and 16 of the first and second corrugated sheets 9 and 10 are formed by plastic working, so that the dimensional accuracy is good and there is little variation. Therefore, the accuracy of the height of the separator 6 in the stacking direction, in other words, the flatness of the contact surface becomes extremely good.

In the corrugated plate of the separator according to the present invention, as shown in FIGS. 3 and 4, a plurality of notches 40 are pressed on the surface of the flat plate 39 with appropriate widths and intervals. Next, each segment 41 of the flat plate 39 formed by the two notches 40 is stretched and formed on one surface of the flat plate 39 to form a plurality of uneven portions 43. The concavo-convex portions 43 are arranged in parallel with each other. In each notch 40 of the corrugated plate 9 formed in this way, as shown in FIG. 3, a cut-and-raised portion 46, which is obtained by alternately cutting and raising a part of the section 41 in the opposite direction, faces. By the cut-and-raised portion 46, the flow of the reaction gas is sequentially bent from the front side (recess 45) of the corrugated plate 9 to the back side (hollow portion 43a of the protrusion 43) and from the back side to the front side. Then, in the portion where the flow direction of the reaction gas is bent, 50 to 80% of the flow rate is forced to change the flow path, and the rest flows to the flow path as it is. As a result, according to this example, a separator having excellent reaction gas mixing and stirring performance can be obtained. In addition, it is possible to maintain substantially the same flow path cross-sectional area over the entire surface of the flow path, and suppress an increase in pressure loss of the reaction gas flow.

The fuel potential separator 6 has an example in which the first and second corrugated plates 9 and 10 are attached to both surfaces of the partition plate 8 and the flow paths of the gas flowing on both surfaces are orthogonal to each other. The separator 6 of the invention is not limited to this shape. That is, when the gas flow paths flowing on both sides of the separator 6 are parallel to the same direction or parallel to the opposite directions, the gas flow paths flowing on one side or both sides of the separator 6 are within the plane of the separator 6. The present invention can be applied to the case of reversing and the case of reversing.

The present invention can also be applied to the case where the partition plate 8 is formed by projecting a convex portion only on one surface and forming the other surface on a flat surface portion by attaching a corrugated plate to form a separator structure. The present invention is also applied to a fuel cell having a structure in which a perforated metal thin plate (collector) is interposed between a separator and an electrode plate, which is a known technique, and the contact electric resistance between the separator and the electrode plate is reduced by the thin plate. Can be applied.

〔The invention's effect〕

As described above, according to the present invention, since the laminated fuel cell separator is provided with a plate piece inclined toward the inside or the outside of the groove on the outlet side of the groove of each small convex portion, , The small convex groove and the concave groove located on the downstream side, the reaction gas that contributed to the electrochemical reaction in the convex gas flow path on the upstream side and the electric current in the concave gas flow path Both gases that did not contribute to the chemical reaction flow in, are mixed and stirred,
This mixing and stirring is repeated from the upstream to the downstream to make the effective gas concentration distribution uniform, and the total amount of the reaction gas can pass through the gas passage of the recess to increase the amount of the reaction gas contributing to the electrochemical reaction. .

[Brief description of drawings]

FIG. 1 is a perspective view showing a schematic structure of a separator according to an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view of a laminated fuel cell,
FIG. 3 is a plan view showing the structure of a corrugated sheet according to one embodiment, FIG. 4 is a sectional view taken along line IV-IV of FIG. 3, and FIG. 5 is an output characteristic diagram of a fuel cell. 1 ... Stacked fuel cell, 3 ... Positive electrode plate, 5 ... Negative electrode plate,
6 ... separator, 8 ... partition plate, 9,10 ... corrugated plate, 1
1,16 …… Concave and convex part, 12a, 13a, 18a, 19a …… Flat part, 15 ……
Fuel gas passage, 20 ... Oxidant gas passage.

Claims (1)

[Claims] 1. A laminated fuel cell separator comprising one metal partition plate and one metal corrugated plate joined to the partition plate, wherein each of the convex and concave portions of the corrugated plate is The cross section of the groove is trapezoidal, and the convex part of the corrugated plate consists of a series of small convex parts arranged at a certain interval along the longitudinal direction and having an inlet and an outlet, and a trapezoidal groove cross section is formed at the outlet of each small convex part. A laminated fuel cell characterized in that a plate piece that is inclined inward or outward of the groove is provided from one of the two side edges, and the top surface of the small convex portion is joined to the partition plate surface. Separator.