JP5286070B2 - Fuel cell separator - Google Patents

Description

  The present invention relates to a polymer electrolyte fuel cell.

  Fuel cells are required to have high output density for in-vehicle use and social infrastructure use. For this purpose, it is necessary to generate power uniformly over the entire separator surface. In the conventional channel system, the rib portion is responsible for only energization, and the channel portion is responsible for only the power generation reaction. Therefore, subdivision is necessary for equalization. However, there is a limit to channel segmentation from the viewpoint of processing technology.

  As a countermeasure, a method using a porous flow path in which internal holes communicate with each other instead of the channel flow path can be considered. That is, when a porous body is used, it becomes possible to mix and make the energization part and the power generation part uniform. Even if it does not go twice, it can be expected to greatly increase the power generation part. That is, it can be expected to increase the output density.

  An example of using a metal porous for the separator is, for example, Patent Document 1 and the like, and a porous body composed of two or more layers having different pore distributions in the fuel gas and oxidant gas flow paths of the separator. Application is disclosed.

JP 2008-84703 A

  In the fuel cell, hydrogen, which is an anode gas (hereinafter referred to as An gas), and oxygen in the air, which is a cathode gas (hereinafter referred to as Ca gas), are consumed by the following reaction to generate water, heat and electric power.

2H ₂ + O ₂ → 2H ₂ O + (heat) + (electric power)
Since this reaction occurs while flowing from upstream to downstream along the conventional flow path, the reaction gas flow rate decreases according to the flow, and the reaction-generated water vapor flows in on the Ca gas side, and concentration diffusion and on the An gas side. If water based on electroosmosis flows in, the water vapor concentration increases and exceeds the saturation concentration, condensed water is generated, causing gas shortage or flooding due to condensed water, leading to a decrease in cell voltage and a decrease in service life. is there. At the same time, latent heat is released due to the generation of condensed water, causing temperature non-uniformity and uneven temperature distribution, increasing the maximum temperature and lowering the fuel utilization rate and reducing the output from the viewpoint of protecting the membrane electrode assembly (hereinafter referred to as MEA). I had to.

  However, in order to increase the output density to the limit to achieve high efficiency (high output density), that is, to reduce the cost, the fuel utilization rate must be increased to nearly 100%. At the same time, it is necessary to reduce the area of the frame portion including the separator manifold and increase the power density by reducing the volume.

  As part of accomplishing this, it is possible to employ a communication porous body in the reaction gas flow path. When the communicating porous body is used, the space where the reaction gas contacts the MEA, that is, the power generation section expands, and at the same time, the metal part constituting the frame of the porous body becomes the conductive section, and the conductive section becomes uniform Since it is dispersed, it is possible to make the power generation section and the conductive section in the flow path height direction uniform. However, in particular, in order to reduce gas diffusion and pressure loss, it is necessary to use a high-porosity porous body with a small skeleton volume, but since the gas flow path height is 1 mm or less, A commercially available metal porous material must be compressed in the stacking direction. Therefore, when the compression direction is the x direction and the direction perpendicular to the compression direction is the r direction, the transmittance k and the pore diameter d after compression are as follows. The porosity ε is as follows before and after compression.

k _r <k _x
d _r <d _x
Before ε _compression > _After ε _compression
In the structure after compression, in the x direction, the diffusion of the reaction gas and the discharge of the generated water are improved, but the diffusion of the reaction gas in the r direction related to the direction toward the outlet manifold and the discharge of the generated water are Be inhibited. In the case of a hydrophobic material, the condensed liquid water passes through a portion of a relatively large pore size and the condensed water of the product water has a relatively small pore size. It is known that when gas passes through a portion, the performance is exhibited without blocking each other's passages up to a certain saturation level in the porous body.

  However, if the x direction is compressed, the flow path height in the r direction decreases, so that the pressure loss increases, and the auxiliary power increases accordingly.

  In addition, since the physical properties are different between the x direction and the r direction, there is a problem that it takes time to analyze the design.

  Thus, in order to use a porous body with a low pressure loss, a high porosity is essential, and in order to apply it to an ultrathin separator flow path, a pore having a uniform pore diameter and porosity is manufactured. There arises a problem that the quality is compressed in one direction to cause directionality and deviate from the design concept.

  In view of the above-described problems, an object of the present invention is to provide a fuel cell separator that can easily control the flow of a reaction gas and water while taking advantage of a porous body.

  In order to solve the above problems, the present invention has been solved by applying a porous similar structure. That is, the solution was achieved by forming a water and gas flow path separation structure using capillary force by forming a plurality of conductive pillars having dimensions of 1 mm or less.

  The present invention provides a fuel cell separator composed of a metal plate or a metal porous plate, and has a plurality of conductors having different diameters or outer dimensions formed on the metal plate or the metal porous plate, and between the conductors. Is configured as a reaction gas flow path, and is separated into a flow path for selectively circulating gas and a flow path for selectively flowing water, wherein the conductors are arranged at predetermined intervals. It is a battery separator.

  Further, the formation density distribution of the conductor formed on the metal plate or the metal porous plate is changed.

  Further, a conductor having a different diameter or outer dimension is further formed on the conductor formed on the metal plate or the metal porous plate, and a plurality of flow paths between the conductors are formed. And

  In addition, a hole penetrating the metal plate or the metal porous plate is provided, and cooling and humidification are performed by injecting a cooling medium into the reaction gas.

  Further, the present invention is characterized in that a through hole and a slit communicating with the through hole are provided at a central portion in the conductor provided on the hole penetrating the metal plate or the metal porous plate.

  Further, the predetermined interval between the conductors is two types of intervals of 10 to 50 μm and 100 to 600 μm.

  The conductor has a first diameter and a second diameter, a first flow path formed between conductors having the first diameter, a conductor having the first diameter, A second flow path configured with a conductor having a second diameter, wherein the first flow path and the second flow path are provided at different intervals, and the first flow path And the second channel and the channel for selectively circulating gas and the channel for selectively circulating water are separated.

  In the fuel cell separator of the present invention, two or more kinds of conductors having different dimensions are formed on a metal plate or a metal porous plate, thereby partially forming a porous simulated structure and adjusting the channel width. The gas flow path and the water flow path that do not interfere with each other are formed, and an effect equivalent to that of the porous body material can be exhibited, and there is an advantage that high power density operation can be performed. Further, unlike the porous body, since the flow path can be configured two-dimensionally, there is an advantage that it is easy to design and the flow of the reaction gas and water is easy to control.

  The separator of the present invention and a fuel cell formed by using the separator will be described with reference to examples.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention. FIG. 1 is a plan view of the cathode side of the separator 1 according to the first embodiment. On the cathode side plane, an MEA is laminated via a gas diffusion layer (hereinafter referred to as GDL) (not shown). However, GDL may be omitted. In the following description, the oxidizing gas is assumed to be air, and the fuel gas is assumed to be hydrogen. Of course, the oxidizing gas is best to be oxygen, and the fuel gas is applicable to hydrogen-rich gas.

  First, the configuration of the separator 1 will be described. When the separator 1 flows through the channel network 16, the cathode (hereinafter referred to as “Ca”) gas inlet manifold 2, the channel network 16 for flowing the oxidant gas from the Ca gas inlet manifold 2, and the channel network 16. Oxygen is consumed at the Ca electrode of the MEA (not shown, but on the flow path surface) to generate water, and the Ca gas outlet manifold 3 for discharging the Ca exhaust gas and water is hydrogen at the An electrode of the MEA. An gas inlet manifold 4, an An gas outlet manifold 5 for discharging consumed An exhaust gas (exhaust hydrogen) from the separator 5, a metal plate 9 for forming these flow paths, and An gas ( Hydrogen gas) and Ca gas (air) are mainly composed of a seal 8 for preventing mixing. An enlarged view is shown at the bottom of the figure. The upper figure of the enlarged view shows a plan view, and the lower figure shows a cross-sectional view. When the flow channel network 16 is enlarged, it is composed of the following. In close contact with the metal plate 9, conductive small cylinders 6 and conductive large cylinders 7 are arranged in a grid pattern. The large cylinders 7 are arranged at intervals of L1 in the flow direction and at intervals of L2 in a direction orthogonal to the flow direction. In the meantime, the small cylinders 6 are arranged in every other row.

  At this time, with this arrangement, the size of the narrowest part between the large cylinders 7 is 100 to 600 μm, and the flow path between the large cylinder 7 and the small cylinder 6 is 10 to 50 μm at the narrowest part. The height is preferably 0.2 mm to 1 mm or less. With this configuration, the operation is as follows. In addition, it demonstrates on the assumption that the material of these cylinders is hydrophobic. In the case of hydrophilicity, the gas flow path and the water flow path are reversed, but in the case of water, since the viscosity is large, it is considered advantageous in terms of pressure loss. Although not shown, oxygen in Ca gas (air) that has entered the flow channel network 16 from the Ca gas inlet manifold 2 reacts with hydrogen via the MEA that is above the flow channel network 16 (on the drawing in the drawing). It flows downstream while generating electricity, heat, and reaction product water. At that time, oxygen is consumed, and as a result, reaction product water (in the form of water vapor) and part of the heat are added to the Ca exhaust gas. Although this flow is a flow in a direction perpendicular to the separator 1, this vertical flow path and the flow paths of gas and condensed water are separated by this arrangement. Thus, the Ca exhaust gas flowing toward the downstream increases in water vapor concentration while adding a part of the reaction product water. Thereafter, although it varies depending on the operating temperature, when it is around about 70 ° C., when the Ca exhaust gas temperature exceeds the saturated water vapor concentration at 70 ° C., it condenses into liquid water and becomes a two-phase flow of Ca exhaust gas and condensed water. And discharged to the Ca gas outlet manifold 3. At this time, the condensed water flows through the flow path between the large cylinders 7 due to the action of capillary force, and the Ca exhaust gas is separated by flowing through the flow path between the small cylinders 6 and 7, so that the condensed water The flow of Ca exhaust gas is not hindered from flowing in the direction of the MEA and in the downstream direction, so that it is difficult for flooding to occur and the performance is improved. Similarly, an An gas (hydrogen gas) flows on the back surface (not shown) of the separator 1 and is subjected to the same action, thereby contributing to performance improvement.

  Further, by adopting a cylinder instead of the porous material, it can also function as a spacer that maintains a constant flow path height regardless of the surface pressure and the surface pressure distribution. In the figure, although it is a columnar shape, even if it is a column with a thin top and a trapezoidal cross section, if the gap size is the above-mentioned size, there is no problem in terms of function. In addition, even if the shape seen from above is a quadrangle, an ellipse or a triangle, the minimum function / action can be ensured if the above gap size is satisfied.

  With such a configuration, the following effects are specific to this embodiment. In other words, since the conductor is formed on the metal plate, the electrical and thermal contact resistance with the metal plate is reduced, the flow path height is kept constant, the repulsive force is constant against the surface pressure, and the high output density. It is possible to simplify the flow path design, improve the reliability and reduce the cost by using a two-dimensional flow path.

  FIG. 2 is a plan view of the cathode side of the separator 1 according to the second embodiment, which is a modification of the first embodiment. In FIG. 2, the interval L2 of the large cylinder 7 is changed to L2 ′, and the interval L1 is maintained as it is. As a result, the water flow path of the flow path network 16 is expanded and the amount of reaction product vapor is accumulated and condensed. Corresponding to the downstream where the amount of water generated increases, the Ca exhaust gas with increased viscosity containing steam up to the saturated concentration at the reaction gas temperature at that time, and water with increased pressure resistance due to increased condensed water It is designed to discharge smoothly. Thus, in the upstream where almost no condensed water is generated, it is possible to promote the humidification action and evaporation to keep the water and prevent the MEA from drying, and in the downstream where much condensed water is generated, water and the Ca exhaust gas. The flow of water can be promoted to prevent flooding, and operation at a high power density with a large amount of condensed water can be realized. By adopting such a configuration, humidification and latent heat cooling can be further promoted than in the first embodiment, so that there is an effect that high output density can be achieved and supply cooling water can be reduced.

  FIG. 3 is a plan view of the cathode side of the separator 1 according to the third embodiment which is a modification of the first embodiment. Although not shown in Example 1, the back surface of the metal plate 9 formed with a cylinder is used as a surface through which An gas (hydrogen gas) flows. Although the flow path configuration is not described, it is the same configuration as the surface of Example 1 in which the Ca gas flows. However, in the third embodiment, an An gas or a Ca gas is allowed to flow on the front surface, and a cooling medium, especially water, is allowed to flow on the back surface. For this reason, unlike the first embodiment, a cooling water inlet manifold 10 and a cooling water outlet manifold 11 are newly added. Since An gas and Ca gas are similar in configuration, the description will be made by using Ca gas as a representative. The left figure of FIG. 3 is the reaction gas side, and in this case, the Ca gas side is shown. The right side of FIG. 3 shows the cooling water side. The left and right figures show the reverse side of the separator when the metal plate 9 is sandwiched. The reaction gas side is provided with a large cylinder 7 and a small cylinder 6 as in the first embodiment, but differs from the first embodiment in that a liquid water hole 12 penetrating the metal plate 9 is provided and the reaction gas side is provided. It is set as the structure which cools and humidifies in the part with little condensed water by making it eject in the form of vapor | steam or water to the part which corresponds to the liquid water flow path. The size of the liquid water hole is 0.1 mm to 0.7 mm, which is the same level as the width of the liquid water channel, and the injection resistance is reduced. The cooling water side on the back side is configured with only the large cylinder 7. This is because, unlike the reaction gas side, there is no need to separate the gas and liquid flow paths using capillary forces.

  The operation on the reaction gas side is the same as in Example 1 except that water exudes from the cooling water side through the liquid water hole 12 and flows in the state of evaporation or water for cooling or humidification of the MEA. It is almost the same. The cooling water side on the back passes through the flow channel network 16 from the cooling water inlet manifold 10 and moves to the reaction gas side through the liquid water hole 12 while taking heat from the metal plate 9 (of course, the heat source is derived from the MEA although not shown). After the water is supplied, the fuel cell temperature is maintained at the optimum operating temperature by entering the cooling water outlet manifold 11 and finally flowing out of the stack while maintaining the heat in the form of specific heat. The water supplied to the reaction gas side is driven by the saturated concentration determined by the temperature of the reaction gas and the water vapor concentration at that time, and part of the water evaporates to take the heat of the metal plate 9 in the form of latent heat cooling. Is stored in the Ca exhaust gas and carried out from the Ca gas outlet manifold 3. Thereby, the cooling capacity can be improved with a small amount of water using latent heat cooling.

  By adopting such a configuration, unlike Example 1, Ca gas and An gas can be further subjected to latent heat cooling and humidification on the separator surface, so that there is an effect that the size can be further reduced and the output density can be increased.

  In FIG. 4, the cathode side top view of the separator 1 of Example 4 is shown. The present embodiment is a modification of the third embodiment, in which the liquid water hole 12 in the third embodiment is provided at the center of the large cylinder 7. For this reason, the large cylinder 7 is provided on both the reaction gas side and the cooling water side. It arrange | positions in the form which shares the liquid water hole 13 which penetrates the metal plate 9 in the same position of a back surface. However, since water cannot be introduced and supplied from the cooling water side of the separator to the reaction gas side only by the liquid water holes 13, slits 14 are provided in the large cylinder 7 on both the cooling water side and the reaction gas side. Thereby, unlike Example 3, the strength and deformation near the liquid water hole 12 can be suppressed, and Ca gas and An gas can be cooled and humidified on the separator surface. There is an effect that density can be increased.

  In FIG. 5, the cathode side top view of the separator 1 of Example 5 is shown. This embodiment is a modification of the third and fourth embodiments. Unlike Example 3, on the reaction gas side, the large cylinder 7 and the small cylinder 6 are not formed directly on the metal plate 9 but on the metal porous plate 15 adhered on the metal plate 9. 7 is formed, and the gas flow path that is the function of the small cylinder 6 is made to work on the metal porous, and the large cylinder 7 is responsible for securing the water flow path by utilizing the difference in capillary force. Is. This also simplifies the metal porous design. Another difference is that the large cylinder 7 on the cooling water side is a rounded quadrangular prism, thereby increasing the force to receive the surface pressure and reducing the hydraulic resistance of the cooling water. Thereby, unlike Example 4, the strength and deformation near the liquid water hole 12 are suppressed, and Ca gas and An gas can be latently cooled and humidified on the separator surface, so that the auxiliary power can be further reduced, and There is an effect that a highly reliable miniaturization and high power density can be achieved. In this embodiment, the large cylinder 7 is formed on the metal porous plate 15, but it is preferable to form it on the channel network 16 composed of two types of cylinder groups for simplification of the design.

  FIG. 6 shows a schematic diagram of a fuel cell stack of Example 6. FIG. 6 shows a stack 100 in which the separators of Examples 2 to 5 are stacked. The structure of this stack is as follows. A supply port 112 for supplying An gas, a supply port 111 for supplying Ca gas, a supply port 110 for supplying cooling water, insulating plates 109 at both ends, a current collecting plate 113 for taking out power to the outside, and the present invention A stack 100 in which two separators 101 are placed with the cooling water flow passage part 121 side back to each other, and a power generation part 105 sandwiched between an electrolyte membrane 102 and an electrode 103 and a gas diffusion layer 106 alternately. It comprises a discharge port 104 for discharging An gas, a discharge port 108 for discharging Ca gas, and a discharge port 107 for discharging cooling water. The power generation portion 105 is in contact with the An gas flow path portion 120 and the Ca gas flow path portion 122 to supply hydrogen and oxygen to the power generation portion 105. At the same time, heat generated in the power generation portion 105 is absorbed by the cooling water flow channel portion 121 formed on the back side of each gas flow channel portion 120, 122. Note that the stack in which the first embodiment is stacked is not shown here, but the cooling water portion is omitted, and cooling is performed by supplying a gas previously contained in the Ca gas or An gas outside the stack. .

  With the configuration of this embodiment, the temperature distribution of the reaction gas flow paths in the entire stack can be made uniform by the effect of the separator of the present invention. This has the effect of enabling a compact stack with high power density.

  In addition to fuel cells, it can also be used for power generation elements in which electric power and heat are generated by an electrochemical reaction that require higher output.

FIG. 3 is an explanatory diagram showing a configuration of a separator of Example 1. 6 is an explanatory diagram showing a configuration of a separator according to Example 2. FIG. 6 is an explanatory diagram showing a configuration of a separator of Example 3. FIG. FIG. 6 is an explanatory diagram showing a configuration of a separator of Example 4. FIG. 10 is an explanatory diagram showing a configuration of a separator of Example 5. It is explanatory drawing which showed the structure of the stack using the separator of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Separator 2 Ca gas inlet manifold 3 Ca gas outlet manifold 4 An gas inlet manifold 5 An gas outlet manifold 6 Small cylinder 7 Large cylinder 8 Seal 9 Metal plate 10 Cooling water inlet manifold 11 Cooling water outlet manifold 12, 13 Liquid water hole 14 Slit 15 Metal porous plate 16 Channel network 100 Stack 101 Separator 102 Electrolyte membrane 103 Electrode 104 An gas outlet 105 Power generation part 106 Gas diffusion layer 107 Cooling water outlet 108 Ca gas outlet 109 Insulating plate 110 Cooling water supply port 111 Ca gas supply port 112 An gas supply port 113 Current collector plate 120 An gas flow channel portion 121 Cooling water flow channel portion 122 Ca gas flow channel portion

Claims (5)

In a fuel cell separator comprising a metal plate or a metal porous plate,
A plurality of conductors having different diameters or outer dimensions formed on the metal plate or the metal porous plate, and the conductors are configured as a reaction gas flow path,
The conductor has a first diameter and a second diameter;
A first flow path configured between conductors having a first diameter; a second flow path configured between a conductor having a first diameter and a conductor having a second diameter; Have
The first flow path and the second flow path are provided at different intervals, a flow path for selectively flowing gas through the first flow path and the second flow path , and selective flow of water. A fuel cell separator, characterized in that a flow path to be separated is separated.   2. The fuel cell separator according to claim 1, wherein a formation density distribution of a conductor formed on the metal plate or the metal porous plate is changed. 2. The fuel cell separator according to claim 1, wherein the conductor is provided on both surfaces of the metal plate or the metal porous plate, and the flow path through which the reaction gas flows on one surface of the metal plate or the metal porous plate, The flow path through which the cooling water flows is formed by the conductor.
The metal plate or the metal porous plate is provided with liquid water holes penetrating the metal plate or the metal porous plate ,
A fuel cell separator, characterized in that the liquid water hole causes the cooling water flowing on the other surface to be ejected into a flow path for selectively circulating water formed on the one surface . In the fuel cell separator according to claim 3, the fuel cell separator and having a slit communicating with the through hole and the through hole in its central portion of the conductive body provided on the liquid water hole. In the fuel cell separator according to claim 1, intervals between the conductor is, 10 to 50 [mu] m, and a fuel cell separator, which is a two intervals 100～600Myuemu.

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