JP4340417B2 - Polymer electrolyte fuel cell - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel cell using a solid polymer electrolyte used for a portable power source, an electric vehicle power source, a home cogeneration system, and the like.
[0002]
[Prior art]
A fuel cell using a solid polymer electrolyte generates electric power and heat simultaneously by electrochemically reacting a fuel gas containing hydrogen and an oxidant gas containing oxygen such as air. is there. This fuel cell basically comprises a polymer electrolyte membrane that selectively transports hydrogen ions, and a pair of electrodes disposed on both sides of the electrolyte membrane. The electrode includes a catalyst layer mainly composed of carbon powder supporting a platinum group metal catalyst, and a gas diffusion layer formed on the outer surface of the catalyst layer and having both air permeability and electronic conductivity.
Gas seals and gaskets are placed around the electrodes with a polymer electrolyte membrane around them so that the supplied fuel gas and oxidant gas do not leak to the outside or the two types of reaction gases mix with each other. The The sealing material and gasket are assembled in advance by being integrated with the electrode and the polymer electrolyte membrane. This is called MEA (electrolyte membrane-electrode assembly). On the outside of the MEA, a conductive separator plate for mechanically fixing the MEA and electrically connecting adjacent MEAs to each other in series is disposed. In the portion of the separator plate that comes into contact with the MEA, a gas flow path for supplying the reaction gas to the electrode surface and carrying away the generated water and surplus gas is formed. Although the gas flow path can be provided separately from the separator plate, it is common to provide a gas flow path by providing a groove on the surface of the separator plate.
[0003]
In order to supply fuel gas or oxidant gas to the gas flow path of the separator plate, the pipe for supplying fuel gas or oxidant gas is branched into the number of separator plates to be used, and the branch destination is directly connected to the separator plate. A piping jig connected to the groove is required. This jig is called a manifold, and the type in which the fuel gas or oxidant gas supply pipe is directly connected to the groove is called an external manifold. There is a type of this manifold called an internal manifold with a simplified structure. The internal manifold is a separator plate in which a gas flow path is formed, and a through hole is provided, and an inlet / outlet of the gas flow path is connected to the hole, and a reaction gas is directly supplied from the hole.
These MEAs and separator plates are alternately stacked to laminate 10 to 200 cells, the laminate is sandwiched between end plates via current collector plates and insulating plates, and both end plates are clamped with fastening rods. The structure of the battery.
[0004]
A typical structure of a fuel cell in which a conductive separator plate and MEA are laminated is shown in FIG. MEA 5 composed of the polymer electrolyte membrane 2 and the anode 3 and the cathode 4 sandwiching the polymer electrolyte membrane 2 are alternately laminated with the separator plate 1. The anode and the cathode are composed of a catalyst layer in contact with the electrolyte membrane and a gas diffusion layer in contact with the separator plate. The separator plate 1 has a gas flow path 6 for supplying and discharging fuel gas to the anode 3, and a gas flow path 7 for supplying and discharging oxidant gas to the cathode 4. FIG. 15 shows a front view of the separator plate 1 viewed from the cathode surface side. A region surrounded by an alternate long and short dash line represented by X in the drawing is in contact with the electrode. The separator plate 1 is provided with an inlet side manifold hole 8a and an outlet side manifold hole 8b for oxidizing gas, and an inlet side manifold hole 9a and an outlet side manifold hole 9b for fuel gas. The oxidizing gas channel 7 is formed by four parallel grooves that connect the manifold holes 8a and 8b.
[0005]
In the fuel cell having such a configuration, all the reactive gas during power generation does not flow through the gas flow path formed on the separator plate surface, but also in the porous gas diffusion layer located at the outermost part of the MEA. Gas circulates. This flow is called downflow. In order to stably maintain high battery performance, it is important to make the balance between gas flow and subsidence in the gas flow path uniform over the entire electrode area. The flow of subsidence is determined by the porosity and thickness of the gas diffusion layer and the gas pressure flowing therethrough. Therefore, due to these variations, there are portions that are rich in gas supply and portions that are insufficient in the electrode surface. For this reason, there is a problem in that portions with different amounts of power generation occur within the electrode surface, and the battery voltage decreases because the current density increases at the portion where power generation concentrates. Further, when the reaction gas is supplied to the battery in a highly humidified state, there is a problem in that condensed water and generated water are accumulated in the gas flow path where the gas supply is not large, resulting in more power generation amount distribution.
[0006]
These problems are particularly remarkable when the gas flow path 7 has a meandering shape as shown in FIG. Then, the downflow increased in the hatched area represented by Y in FIG. 15, and power generation was concentrated in this area. Therefore, in the region far from both the manifold holes 8a and 8b other than that region, the reaction gas becomes insufficient. Therefore, water is accumulated in this region particularly when a highly humidified reaction gas is used. If the gas flow path has a meandering shape consisting of a straight part and a turn part, paying attention to the forward and return paths of the straight part in one flow path, the gas pressure difference between the inlet side and the outlet side is larger than that in the turn part. Therefore, the flow rates flowing through the gas diffusion layer are different in the forward path and the return path of the one flow path.
[0007]
When the gas flow path is composed of a plurality of grooves, it is difficult to uniformly control gas distribution from the gas inlet side to the gas flow path. Since the gas supply amount is relatively large on the upstream side relative to the downstream side, there is no difference in power generation performance. However, on the downstream side, gas is consumed on the upstream / middle stream side, and the absolute amount of gas decreases, so that it is greatly affected by the initial distribution amount. That is, on the downstream side where gas distribution is poor, battery performance is degraded due to insufficient gas supply. Further, when the fuel is depleted, there is a problem in that deterioration of battery performance is promoted by elution of carbon in the electrode.
[0008]
[Problems to be solved by the invention]
The present invention solves the above problems, and provides a separator plate that can achieve a stable gas supply by making the ratio of the flow in the gas flow path in the electrode surface uniform to the down flow.
An object of this invention is to provide the polymer electrolyte fuel cell provided with such a separator plate.
[0009]
[Means for Solving the Problems]
  In order to solve the above-described problems, the present invention provides a hydrogen ion conductive polymer electrolyte membrane, a rectangular cathode and anode sandwiching the hydrogen ion conductive polymer electrolyte membrane, and supplies / discharges an oxidant gas to the cathode. A cathode side conductive separator plate having a gas flow path, and an anode side conductive separator plate having a gas flow path for supplying and discharging fuel gas to and from the anode, wherein the cathode is the hydrogen ion conductive polymer electrolyte A catalyst layer disposed on the membrane side and a gas diffusion layer disposed on the cathode side conductive separator plate side, and the anode comprises a catalyst layer disposed on the hydrogen ion conductive polymer electrolyte membrane side And a gas diffusion layer disposed on the anode side conductive separator plate side, the cathode side conductive separator plate and the anode side conductive separator. At least one of the plates has a sub-manifold having an increased cross-sectional area perpendicular to the electrode on the inlet side and the outlet side of the gas flow path, and the gas flow path is located on one side of the cathode and the anode. The sub-manifold is substantially parallel to the straight part of the gas flow path and has the same length as one side of the cathode and the anode. The gas flow pathIs covered by the cathode or anode,The sub-manifold isThe cathode or anode orThe gas diffusion layer of the cathodeOrThe present invention relates to a polymer electrolyte fuel cell, which is covered with the gas diffusion layer of the anode. This sub-manifold eliminates the non-uniformity of gas supply within the electrode surface, eliminates power generation distribution, and ensures stable battery performance.
[0010]
According to the present invention, the deterioration in performance during long-term operation of the fuel cell is gradually accumulated in the gas diffusion layer of the electrode, and is limited to a region where the gas flow in the gas diffusion layer is narrow due to unevenly condensed water and product water. In view of the fact that the other part is due to a decrease in power generation capacity, attention was paid to the gas flow in the gas diffusion layer in order to make the battery structure in which condensed water and generated water are unlikely to accumulate and unevenly distribute.
The present invention is particularly effective when the gas flow path of the separator plate is formed in a meandering shape, and a sub-manifold having an increased volume per unit length in the gas flow path direction is formed in a part of the gas flow path. By doing so, it is based on the finding that the reaction gas is uniformly supplied to the electrode and the fuel cell can be stably operated.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a cathode-side conductive separator plate having a hydrogen ion conductive polymer electrolyte membrane, a cathode and an anode sandwiching the hydrogen ion conductive polymer electrolyte membrane, and a gas flow path for supplying and discharging an oxidant gas to the cathode And an anode side conductive separator plate having a gas flow path for supplying and discharging fuel gas to and from the anode, wherein at least one of the cathode side conductive separator plate and the anode side conductive separator plate is the gas flow path. The present invention relates to a polymer electrolyte fuel cell having sub-manifolds having increased cross-sectional areas perpendicular to the electrodes on the inlet side and the outlet side of the fuel cell.
[0012]
In a preferred embodiment of the present invention, the gas flow path has a meandering shape consisting of a straight part and a turn part extending substantially in parallel, and the sub-manifold extends substantially parallel to the straight part of the gas flow path. Yes. In this case, it is preferable that the sub-manifold has a length extending substantially along its entire side along one side of the square electrode.
The sub-manifold is preferably on the inlet side of the gas flow path and / or on the outlet side of the gas flow path.
The separator plate includes an inlet-side manifold hole and an outlet-side manifold hole for supplying and discharging gas to the gas flow path, and is connected to the inlet-side manifold hole of the inlet-side submanifold or the outlet-side submanifold. It is preferable that the groove depth of the sub-manifold is deepest in the connecting portion with the outlet side manifold hole.
[0013]
In another preferred embodiment of the present invention, the separator plate includes an inlet side manifold hole and an outlet side manifold hole for supplying and discharging gas to the gas flow path, and the inlet side manifold hole or the outlet side manifold hole is provided. Has the function of the sub-manifold.
Furthermore, it is preferable to have a sub-manifold in the middle part of the gas flow path.
It is preferable that a larger number of the sub-manifolds are arranged on the gas outlet side than on the gas inlet side.
The cross-sectional area of the sub-manifold is preferably 1.2 to 3.0 times the cross-sectional area of the gas flow path.
[0014]
The separator plate includes an inlet-side manifold hole and an outlet-side manifold hole for supplying and discharging gas to the gas flow path, and a cross-sectional area S of the manifold hole.₁And cross-sectional area S of the sub-manifold₂The relationship is S₁/ 100 <S₂<S₁/ 25 is preferably satisfied.
[0015]
In still another preferred embodiment of the present invention, the apparatus includes an inlet side sub-manifold and an outlet side sub-manifold extending in parallel to each other on the gas inlet side and the outlet side, and a plurality of gas flow paths connecting both the sub-manifolds, Each gas flow path has a meandering shape, and the region surrounded by each gas flow path is independent.
Each of the gas flow paths preferably has a meandering shape including a straight portion inclined with respect to the sub-manifold and a turn portion connecting the straight portions.
Embodiments of the present invention will be described below with reference to the drawings.
[0016]
Embodiment 1
The separator plate of the present embodiment is shown in FIG. The separator plate 11 is formed by machining, for example, an isotropic graphite plate, and includes an inlet side manifold hole 12a and an outlet side manifold hole 12b for the oxidant gas, an inlet side manifold hole 13a and an outlet side manifold hole 13b for the fuel gas. And a gas flow path 17 that connects the manifold holes 12a and 12b. The gas flow path 17 is composed of four parallel grooves. And the part connected with the manifold holes 12a and 12b of the gas flow path 17 forms the submanifolds 18a and 18b. The sub-manifolds 18 a and 18 b have a larger cross-sectional area perpendicular to the electrode surface than the grooves forming the gas flow path 17. In the illustrated example, the widths of the submanifolds 18 a and 18 b are larger than the width of the groove of the gas flow path 17. Instead of increasing the width of the groove, the depth of the groove may be increased, or both the width and depth of the groove may be increased.
[0017]
A portion surrounded by a one-dot chain line 15 in FIG. The electrodes shown here are rectangular, and the sub-manifolds 18a and 18b extend along the longitudinal direction of the electrodes at positions corresponding to the short sides of the electrodes. The gas flow path 17 shown here is composed of a straight portion extending along the longitudinal direction of the electrode and a turn portion substantially perpendicular thereto. The separator plate 11 has an oxidant gas flow channel 17 on one surface and a fuel gas flow channel similar to the flow channel 17 on the other surface, serving both as a cathode side separator plate and an anode side separator plate. Yes. 1 also has a sub-manifold as in the front side.
[0018]
As described above, the separator plate 11 of the present embodiment has the meandering gas flow path 17 composed of a straight forward path and a return path extending along the longitudinal direction of the electrode, and the inlet side and the outlet side thereof , Having sub-manifolds 18a and 18b having a large cross-sectional area and having a length substantially along the entire length of the electrode. In these submanifolds, the gas pressure is equal, so that the ratio between the flow in the gas flow path 17 in the electrode surface and the subsurface flow through the gas diffusion layer of the electrode is made uniform, and stable gas supply can be realized.
[0019]
  FIG. 2 shows a modification of FIG. The separator plate 21 has submanifolds 28 a and 28 b on the inlet side and outlet side of the gas flow path 27. These submanifolds are provided outside the electrode catalyst layer indicated by the alternate long and short dash line 25. However, the gas diffusion layer portion of the electrode has a size covering the sub-manifolds 28a and 28b. Portions 29a and 29b that connect the sub-manifolds 28a and 28b and the manifold holes 12a and 12b are constituted by four grooves. In this way, the sub-manifold is an electrodeCatalyst layerThe effect does not change even if it is arranged outside.
[0020]
Embodiment 2
The separator plate of the present embodiment is shown in FIG. In the first embodiment, the sub-manifold is provided only on the inlet side and the outlet side of the gas flow path 17, but the separator plate 31 shown here further has a sub-manifold 18 c in the middle of the gas flow path 17. The sub-manifold 18c has a start end connected to the upstream side of the gas flow path 17 and a terminal end connected to the downstream side of the gas flow path.
If a sub-manifold is formed in the middle part of the gas flow path 17, the underflow in the gas diffusion layer of the electrode can be made uniform. In addition, when the gas utilization rate increases, the gas flow rate decreases and the gas distribution tends to be affected downstream. When the sub-manifold is provided in the intermediate portion of the gas flow path, the gas distributed from the inlet side sub-manifold is once collected in the intermediate sub-manifold before reaching the outlet side sub-manifold, and the gas is redistributed. Therefore, the risk of gas shortage on the downstream side can be avoided.
The separator plate 41 of FIG. 4 is an example in which two submanifolds 18c and 18d are provided in the middle part of the gas flow path. When installing a plurality of submanifolds in the middle of the gas flow path, it is preferable to increase the installation ratio downstream.
[0021]
Embodiment 3
The separator plate of this embodiment is shown in FIG. This separator plate 51 is an example in which the widths of the inlet-side and outlet-side submanifolds 58a and 58b are made larger than those of the previous embodiment. When the width of the groove constituting the sub-manifold is increased, the weight of the separator plate cannot be applied to the electrode. Therefore, a plurality of ribs 59 are provided in the sub manifold.
[0022]
Embodiment 4
The separator plate of this embodiment is shown in FIG. The separator plate 61 connects an inlet side sub-manifold 68 a and an outlet side sub-manifold 68 b provided on the short side of the electrode through three gas passages 67. In the previous embodiment, each gas flow path is composed of an outward path and a return path extending along the longitudinal direction of the electrode, and is parallel to each of the forward path and the return path. In the separator plate 61, the area | region which each gas flow path 67 covers has taken the substantially independent form. In FIG. 6, the gas flow path 67 has a zigzag shape inclined with respect to the sub-manifold.
FIG. 7 shows a modification. The separator plate 71 connects the submanifolds 78 a and 78 b with three gas passages 77. In each gas flow path 77, the forward path and the return path are parallel to the sub-manifold.
[0023]
In order to make the subsurface flow in the gas diffusion layer of the electrode more uniform, it is easy to make each gas flow path straight when multiple gas flow paths are formed and designed to be independent flow areas. is there. However, in that case, it is difficult to obtain a pressure loss in the gas flow path unless the ratio of the longitudinal direction to the short direction of the electrode is ensured to some extent. Therefore, by making each gas flow path meander, it is possible to ensure a predetermined pressure loss even if the electrodes are nearly square.
In this way, by forming a plurality of meandering gas flow paths and making the regions surrounded by the gas flow paths independent, the length of the forward path and the return path of the meandering portion is shortened, and the subsidence flow between both flow paths is reduced. The difference can be reduced as much as possible. At that time, as shown in FIG. 6, if the gas flow path has a meandering shape composed of a turn part connecting the straight part and the straight part inclined with respect to the sub-manifold, the gas diffusion layer sandwiched between the forward path and the return path is formed. It is possible to make the flow rate uniform.
[0024]
referenceForm of1
  The separator plate of the present embodiment is shown in FIG. This separator plate 81 is provided with oxidant gas inlet side manifold holes 82a and 82b corresponding to the two opposing sides of the electrode, and the left end of the manifold hole 82b extends in parallel from the right end of the manifold hole 82a in the figure. The four gas flow paths 87 communicate with each other. 83a represents an inlet side manifold hole for fuel gas, and 83b represents an outlet side manifold hole. This separator plate has an inlet side manifold hole 84a and an outlet side manifold hole 84b.
  In the present embodiment, the inlet side manifold hole 82a and the outlet side manifold hole 82b also serve as sub-manifolds. Since the inlet-side manifold hole 82a and the outlet-side manifold hole 82b are continuous with each cell, the gas diffusion layer of the electrode exposes the wall surface of the manifold hole, and the underflow enters and exits there. When the shape of the inlet side manifold hole and the outlet side manifold hole is not limited, the effect of the sub-manifold can be used more simply by using the present embodiment.
[0025]
Embodiment5
  The separator plate of this embodiment is shown in FIG. The separator plate 91 includes an inlet side manifold hole 92a and an outlet side manifold hole 92b for the oxidant gas, an inlet side manifold hole 93a and an outlet side manifold hole 93b for the fuel gas, and an inlet side manifold hole 94a and an outlet side manifold for the cooling water. It has a hole 94b. The manifold hole 92a and the manifold hole 92b are connected to each other by sub-manifolds 98a and 98b and four parallel meandering gas flow paths 97 that connect the sub-manifolds.
[0026]
Embodiment6
  The separator plate of this embodiment is shown in FIG. The separator plate 101 includes an inlet side manifold hole 102a and an outlet side manifold hole 102b for oxidant gas, an inlet side manifold hole 103a and an outlet side manifold hole 103b for fuel gas, and an inlet side manifold hole 104a and an outlet side manifold for cooling water. It has a hole 104b. The manifold hole 102a and the manifold hole 102b are connected to each other by sub-manifolds 108a and 108b and four parallel meandering gas flow paths 107 that connect the sub-manifolds. In this example, a sub-manifold 108 c is provided at an intermediate portion of the gas flow path 107.
[0027]
  Embodiment 14 and Reference form 1In the above description, a separator plate having an oxidant gas flow path on one side and a fuel gas flow path on the other side, that is, a separator plate serving as both a cathode side separator plate and an anode side separator plate has been described. The gas flow path and the sub manifold are shown on the oxidant gas side. However, it is obvious that the same applies to the fuel gas side. Needless to say, the present invention can also be applied to a separator plate having a manifold hole for cooling water.
  In the above description, the internal manifold type in which the manifold holes are provided in the separator plate has been described. However, the present invention can be similarly applied to the external manifold type.
[0028]
【Example】
Example 1
25% by weight of platinum particles having an average particle size of about 30% were supported on acetylene black carbon powder to prepare an electrode catalyst. This catalyst powder was dispersed in isopropyl alcohol. Further, perfluorocarbon sulfonic acid powder was dispersed in ethyl alcohol. These two types of dispersions were mixed to obtain an electrode paste. On the other hand, a carbon paper having a thickness of 300 μm was immersed in an aqueous dispersion of polytetrafluoroethylene (PTFE) and subjected to a drying treatment to obtain a water-repellent gas diffusion layer. A catalyst layer was formed by applying and drying the electrode paste on one side of the gas diffusion layer.
An electrolyte membrane-electrode assembly (MEA) is produced by hot pressing at a temperature of 110 ° C. for 30 seconds with the catalyst layer inside with the pair of electrodes produced as described above and sandwiching the polymer electrolyte membrane. did. Here, a perfluorocarbon sulfonic acid thinned to a thickness of 50 μm (Nafion manufactured by DuPont) was used as the polymer electrolyte membrane.
As the gas diffusion layer, in addition to the above-mentioned carbon paper, carbon cloth woven carbon fiber as a flexible material, carbon felt mixed with carbon fiber and carbon powder, and formed with organic binder added, etc. It can also be used.
[0029]
As the conductive separator plate, a gas flow path as shown in FIG. 1 was formed by machining an isotropic graphite plate having a thickness of 3 mm. The gas flow path 17 was composed of four parallel grooves having a width of 0.7 mm and a depth of 0.3 mm. The sub-manifolds 18a and 18b are provided at portions directly connected to the inlet-side manifold 12a and the outlet-side manifold 12b. The sub manifold has a groove width of 1.2 mm and a depth of 1.2 mm. Therefore, the cross-sectional area ratio of the sub-manifold to the gas flow path 17 is about 1.7 times, which satisfies the condition of 1.2 times or more and 3.0 times or less. The cross-sectional area S of the manifold hole 12a₁Is 100mm²Therefore, the cross-sectional area of the sub-manifold is S₂Then, S₁/ 100 <S₂<S₁/ 25 is satisfied.
[0030]
A cell laminate in which 50 cells were connected in series by alternately stacking the above conductive separator plates and MEAs was assembled. This cell laminate is sandwiched between stainless steel end plates via a current collector plate and an insulating plate, and both end plates are fastened to 10 kgf / cm with fastening rods.²Fastened with pressure.
The batteries of the comparative example were all the same as the conditions of this example except that the entire region from the manifolds 8a to 8b was configured similarly to the gas flow path 17 of this example as shown in FIG.
The batteries of this example and the comparative example were kept at 85 ° C., and the humidified / heated fuel gas was humidified / heated to a dew point of 83 ° C. on the anode side, and the dew point was 78 ° C. on the cathode side. Each was supplied with warm air. The current-voltage characteristics were examined at an oxygen utilization rate of 30% and a fuel utilization rate of 70%. The result is shown in FIG. Also, current density is 0.3 A / cm²A continuous power generation test was conducted. The result is shown in FIG.
[0031]
In FIG. 11, the battery of the present example shows only a small advantage in the low current density region, but the effect of having a sub-manifold appears at a high current density and shows better battery performance. . This is considered as follows.
In the high current density region, the diffusivity of the reaction gas dominates the battery performance, and a uniform gas supply is required over the entire electrode surface. The underground flow in which the gas flows in the gas diffusion layer of the electrode is governed by the gas pressure. In the battery of this example, the sub-manifold ensures a wide range of regions where the gas pressure is equal on the gas inlet side and outlet side of the electrode surface. For this reason, the subsidence occurs more uniformly on the entire electrode surface, and a uniform gas supply is possible. The reason why the difference did not appear so much in the low current density region is that the rate limiting in the region on the gas inlet side and the outlet side is due to reaction rate limiting rather than diffusion rate limiting. In the battery of the comparative example, the gas pressure is different in the gas flow path corresponding to the sub-manifold of this embodiment. That is, the pressure is highest at a portion near the inlet side manifold hole, and the pressure is lowest at a portion near the outlet side manifold. For this reason, as shown in FIG. 15, the gas flow is concentrated in the vicinity of the line connecting the manifolds 8a and 8b, and the electrode portion located far from the line falls into a gas shortage and generates power generation. In particular, the battery performance is inferior at a high current density that is gas diffusion limited.
[0032]
At the initial stage of the continuous power generation test of FIG. 12, there is almost no difference. However, irreversible deterioration such as elution of carbon powder used in the electrode and coating resin in the vicinity of the catalyst occurs in the electrode portion where the gas of the comparative example battery has become insufficient with time. As a result, the power generation is concentrated more in the portion where gas supply is relatively rich from the beginning, and the current density is increased, so that the battery performance deteriorates with the passage of time. On the other hand, in the battery of this example, the stable gas supply to the entire electrode surface prevents deterioration due to gas shortage as in the comparative example, so that the battery voltage is equivalent to the initial value even after 2000 hours. The value is maintained.
As described above, it was confirmed that by providing the sub-manifold in the gas flow path of the separator plate, the gas can be uniformly supplied to the entire electrode surface and the battery performance can be improved.
[0033]
Example 2
In this embodiment, as shown in FIG. 3, in addition to the submanifolds 18 a and 18 b of the first embodiment, a submanifold 18 c is further formed in the middle portion of the gas flow path 17. Otherwise, a battery was fabricated under the same conditions as in Example 1.
The battery of this example and the battery of Example 1 were maintained at 85 ° C., and the fuel gas humidified and heated to a dew point of 83 ° C. on the anode side was humidified to a dew point of 78 ° C. on the cathode side. Each heated air was supplied. And current density 0.3A / cm²The test was conducted with a fuel utilization rate of 70% and various oxygen utilization rates. The result is shown in FIG.
From the results of FIG. 13, it can be seen that in the region where the oxygen utilization rate is high, the battery of this example maintains stable battery performance without causing a voltage drop. This is because the sub-manifold 18c is further provided in the battery of Example 1, thereby making it possible to make the subsidence in the gas diffusion layer uniform. When the oxygen utilization rate is high, the gas flow rate is decreased and the gas distribution tends to be influenced downstream. By forming the sub-manifold in the intermediate portion, the gas distributed from the manifold hole 12a is aggregated once before reaching the manifold hole 12b, and the gas is redistributed. This avoided the danger of gas shortage on the downstream side.
[0034]
Further, when the oxygen utilization rate increases, the ratio of generated water to the gas flow rate increases, and the possibility that the gas flow path is blocked by condensed water or generated water becomes higher. At the same time, when the gas passes through the gas flow path, the pressure loss is reduced, and when the water is blocked in the gas flow path, the restoring force to restore the water except the water is reduced. And it becomes impossible to supply gas to the gas flow path after the blocked point. If there is a sub-manifold in the middle of the gas flow path, it will be possible to supply gas downstream of the blockage point due to gas redistribution, minimizing the impact on battery performance due to the blockage of the gas flow path. An effect is obtained.
As described above, the oxygen utilization rate was made constant, and the hydrogen utilization rate was changed. As a result, the higher the utilization rate, the more stable the battery of this example. It was confirmed that In addition, assuming a gas obtained by reforming the city gas as the anode gas, the influence is remarkable when the mixed gas is 80% hydrogen and 20% carbon dioxide.
When there are a plurality of sub-manifolds installed in the middle part of the gas flow path, it has been confirmed that it is effective to increase the downstream installation ratio as shown in FIG.
[0035]
Example 3
In this example, the case where the groove width of the sub-manifold was increased as shown in FIG. 5 in the battery of Example 1 was verified. Batteries were fabricated with submanifolds 58a and 58b having a width of 2.8 mm and a groove depth of 0.8 mm. The cross-sectional area perpendicular to the electrode surface of this sub-manifold is about 2.7 times that of the gas flow path 17. Here, as the groove width becomes wider, it becomes impossible to apply a load to the electrode surface. Therefore, as shown in FIG. 5, ribs 59 are provided in the submanifold.
The current-voltage characteristics of this battery were examined under the same conditions as in Example 1. As a result, the same performance as in Example 1 was shown. Therefore, when forming a sub-manifold having a wide groove width, it has been confirmed that it is effective to install ribs inside the groove.
[0036]
Further, the effect of the sub-manifold was recognized when the cross-sectional areas of the sub-manifolds 58a and 58b were in the range of 1.2 times to 3.0 times that of the gas flow path 17. Similarly, the cross-sectional area S of the manifold hole 12a or 12b₁, The sectional area of the sub-manifold 58a or 58b is S₂When S₁/ 100 <S₂<S₁An effect was observed at / 25.
[0037]
Example 4
In this example, two types of batteries were manufactured. A battery in which the groove depth of the connecting portion of the sub-manifold 18a to the manifold hole 12a and the connecting portion of the sub-manifold 18b to the manifold hole 12b in the first embodiment is deepest in the sub-manifold; The battery is designed to be the shallowest in the manifold.
These batteries were tested by changing the dew point of the humidified air supplied to the cathode side. As a result, the battery performance of the battery having a shallow groove depth at the connecting portion with the manifold hole of the sub-manifold deteriorated at a lower dew point than the battery having a deep groove depth. Since the groove depth of the connecting part is shallow, it becomes difficult to discharge condensed water or generated water on the gas outlet side when the water content increases, and the condensed water or generated water stays in the sub manifold. This is because the function is lost. On the other hand, in a battery having a deep groove at the connecting portion, condensed water and generated water can be discharged smoothly, so that the battery performance does not deteriorate even in a humidified state where the supply gas is high. In this embodiment, the cathode side sub-manifold has been described, but the same tendency was observed in the anode side sub-manifold.
From the above, it is preferable that the groove depth of the connecting portion with the manifold hole of the sub manifold is the same as or deeper than other portions in the sub manifold.
[0038]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the gas pressure can be temporarily made uniform in a submanifold, and, thereby, the fuel cell which shows the highly efficient and stable performance can be provided.
[Brief description of the drawings]
FIG. 1 is a front view of a cathode side of a separator plate of a fuel cell according to an embodiment of the present invention.
FIG. 2 is a front view of a cathode side of a separator plate according to another embodiment of the present invention.
FIG. 3 is a front view of a cathode side of a separator plate according to still another embodiment of the present invention.
FIG. 4 is a front view of the separator plate according to the embodiment of the present invention on the cathode side.
FIG. 5 is a front view of the separator plate according to another embodiment of the present invention on the cathode side.
FIG. 6 is a front view on the cathode side of a separator plate according to another embodiment of the present invention.
FIG. 7 is a front view of a cathode side of a separator plate according to still another embodiment of the present invention.
FIG. 8 is a front view of a cathode side of a separator plate according to another embodiment of the present invention.
FIG. 9 is a front view of a cathode side of a separator plate according to still another embodiment of the present invention.
FIG. 10 is a front view of the separator plate according to the embodiment of the present invention on the cathode side.
FIG. 11 is a graph showing current-voltage characteristics of fuel cells of Examples and Comparative Examples of the present invention.
FIG. 12 is a graph showing changes in voltage in a continuous power generation test of a fuel cell according to an example of the present invention.
FIG. 13 is a graph showing the relationship between the oxygen utilization rate and the voltage of the fuel cells of Examples and Comparative Examples of the present invention.
FIG. 14 is a cross-sectional view of a main part of a typical fuel cell.
FIG. 15 is a front view of a cathode side of a separator plate of a conventional fuel cell.
[Explanation of symbols]
11 Conductive separator plate
12a Oxidant gas inlet manifold hole
12b Oxidant gas outlet manifold hole
13a Manifold hole on the fuel gas inlet side
13b Fuel gas outlet side manifold hole
17 Gas flow path
18a, 18b Sub manifold

Claims (8)

A hydrogen ion conductive polymer electrolyte membrane, a rectangular cathode and anode sandwiching the hydrogen ion conductive polymer electrolyte membrane, a cathode side conductive separator plate having a gas flow path for supplying and discharging oxidant gas to the cathode, and An anode side conductive separator plate having a gas flow path for supplying and discharging fuel gas to the anode;
The cathode comprises a catalyst layer disposed on the hydrogen ion conductive polymer electrolyte membrane side and a gas diffusion layer disposed on the cathode side conductive separator plate side,
The anode comprises a catalyst layer disposed on the hydrogen ion conductive polymer electrolyte membrane side, and a gas diffusion layer disposed on the anode side conductive separator plate side,
At least one of the cathode side conductive separator plate and the anode side conductive separator plate has a sub-manifold having an increased cross-sectional area perpendicular to the cathode and anode on the inlet side and outlet side of the gas flow path,
The gas flow path has a meandering shape consisting of a straight portion extending substantially parallel to one side of the cathode and the anode, and a turn portion;
The sub-manifold is substantially parallel to the straight portion of the gas flow path and extends substantially the same length as one side of the cathode and the anode;
The gas flow path is covered by the cathode or anode;
The sub-manifold is covered with the cathode or anode, the gas diffusion layer of the cathode, or the gas diffusion layer of the anode.   The separator plate includes an inlet-side manifold hole and an outlet-side manifold hole for supplying and discharging gas to and from the gas flow path, and is connected to the inlet-side manifold hole of the inlet-side submanifold or the outlet-side submanifold. 2. The polymer electrolyte fuel cell according to claim 1, wherein the groove depth of the sub-manifold is deepest in the connecting portion with the outlet side manifold hole.   The polymer electrolyte fuel cell according to claim 1, further comprising a sub-manifold at an intermediate portion of the gas flow path. 4. The polymer electrolyte fuel cell according to claim 3, wherein the sub-manifold is disposed more on the gas outlet side than on the gas inlet side.   The polymer electrolyte fuel cell according to claim 1, wherein a cross-sectional area of the sub-manifold is 1.2 times or more and 3.0 times or less of a cross-sectional area of the gas flow path. Said separator plate is provided with an inlet-side manifold aperture and an outlet-side manifold aperture for supplying and discharging the gas to the gas channel, the relationship of the cross-sectional area S ₂ of the sub-manifold and the cross-sectional area S ₁ of the manifold hole, S _1/100 <S ₂ <polymer electrolyte fuel cell according to claim 1, wherein satisfying the S _1/25.   An inlet side sub-manifold and an outlet side sub-manifold extending in parallel to each other on the gas inlet side and the outlet side, and a plurality of gas flow paths connecting the two sub-manifolds, each gas flow path having a meandering shape, and 2. The polymer electrolyte fuel cell according to claim 1, wherein regions surrounded by each gas flow path are independent from each other. 8. The polymer electrolyte fuel cell according to claim 7, wherein each of the gas flow paths has a meandering shape including a turn portion connecting the straight portion and the straight portion inclined with respect to the sub-manifold.

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