JP5286174B2 - 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 surface of the separator. 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, it has been studied to use a porous body in which internal pores communicate with each other as a separator instead of a channel flow path, and use the pores of the porous body as a flow path (for example, Patent Document 1). When the porous body is used in this manner, the current-carrying portion and the power generation portion can be mixed and made uniform, so that it is expected that the power generation portion will be greatly increased even if it is not doubled. That is, it can be expected to increase the output density. However, in order to realize a high output density, it is necessary to increase the current density. Reaction water produced in the membrane electrode assembly (hereinafter referred to as MEA) increases in proportion to the current density. If this generated water is not excluded, the reaction gas passage is blocked to inhibit the electrochemical reaction and cause performance deterioration. Therefore, it is necessary to provide a highly drainable flow path in the porous body.

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 and the water vapor concentration increases and exceeds the saturation concentration, it can no longer exist as steam, so condensed water is generated, causing gas shortage or flooding due to condensed water, reducing cell voltage In addition, there is a problem in that the life is shortened. At the same time, latent heat is released due to the generation of condensed water, and the temperature distribution tends to be biased, which tends to increase the maximum temperature of the cell. Therefore, from the viewpoint of protecting the MEA, it has been necessary to lower the fuel utilization rate to lower the output.

  However, in order to increase the output density to the limit and increase the 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 achieve gas diffusion, reaction product water removal, and pressure loss reduction, it is necessary to use a high-porosity porous body having a small skeleton volume. However, since the height of the gas flow path is 1 mm or less, it is necessary to exclude the generated reaction product water downstream in order to increase the output density. It also needs to be performed without hindering the reaction product water drainage generated from the downstream MEA and the downstream reaction gas MEA supply. Even if it is designed to secure water and air flow paths in the porous material by changing the hydrophilic / hydrophobic treatment and the pore diameter, there is a limit to the improvement of drainage. This is because the flow path is formed in the porous body, and therefore there are infinite number of bends, the diameter is changed, and there is a flow path that becomes a dead end. Therefore, in order to further increase the current density, the pore diameter should be increased from the viewpoint of drainage. However, since the height of the gas flow path is 1 mm or less, there is a problem that it cannot be increased further.

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

  In order to solve the above problems, the present invention has been solved by applying the uniform current density and the uniform reaction gas concentration, which are the characteristics of the porous structure. That is, a porous body having a pore diameter having a peak between 10 and 100 μm is used, and a linear through hole is provided in the porous body to promote distribution of reaction gas and reaction product water to increase the current density. Improve performance. If the part of the porous network-like communication hole network is a branch pipe, it is similar to providing a main pipe that directly sends the reaction gas and reaction product water to it, and only the communication hole whose inherent bend diameter has changed in the porous body Then, the reaction product water and reaction gas that cannot be discharged or distributed are distributed and eliminated. Thereby, the micro piping network which can be equally distributed and discharged uniformly can be formed. Thereby, the solution of the problem was sought by forming a water and gas flow path separation structure using both capillary force and fluid force.

  The present invention provides a fuel cell separator including at least a metal porous body and a conductive plate supporting the metal porous body, wherein a hole of the metal porous body serves as a gas flow path. A fuel cell separator having a through hole.

  The fuel cell separator is characterized in that the linear through hole is provided with an inclination of 30 degrees or more with respect to a vertical line of a surface facing the membrane electrode assembly.

  Further, the fuel cell separator is characterized in that the linear through hole is provided in parallel with a surface facing the membrane electrode assembly.

  Further, the linear through hole inclined at 30 degrees or more with respect to the vertical line of the surface facing the membrane electrode assembly, and the linear through hole provided in parallel to the surface facing the membrane electrode assembly, Is a separator for a fuel cell.

  Further, the fuel cell separator is characterized in that the diameter of the linear through hole is 100 to 600 μm.

  The linear through hole is a fuel cell separator having a through hole having a diameter of 10 to 50 μm and a through hole having a diameter of 100 to 600 μm.

  The separator for a fuel cell according to the present invention is provided with a direct conduit for distributing reaction gas and discharging reaction product water by creating a through-hole network in the porous structure. Since discharge can be promoted, there is an advantage that high power density operation is possible. In addition, by connecting through the holes penetrating the upstream and downstream, it can be distributed to the downstream before the reaction gas is consumed, that is, the MEA can be effectively utilized because it can be distributed over the entire surface of the MEA in a state where the concentration hardly decreases. Therefore, there is an advantage that high power density operation is possible. Similarly, the reaction product water in the upstream can be drained without accumulating downstream in the middle, so it is easy to prevent flooding, and the MEA can be used uniformly over the entire surface, so that the operation with high power density can be performed. There is.

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 separator of Example 6. FIG.

  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 shows a plan view and a sectional view of a cathode 1 of a separator 1 of Example 1. The configuration will be described below. The cathode side has a center plate 2 made of a conductor that supports a porous body 3 composed of two types of porous bodies 4 and 5, and a Ca inlet manifold 6 covered with the coarse porous body 4. , The Ca outlet manifold 7, the An inlet manifold 8, the An outlet manifold 9, the seal 10 that separates these two kinds of gases, and the honeycomb porous body 5, which are covered with the coarse porous body 4, are a plan view and a sectional view. As shown in FIG. 2, two types of pipe through holes, that is, a Ca gas through hole 11 and a water through hole 12 are provided. As shown in the sectional view, an MEA (membrane electrode assembly) 13 is laminated on the porous body. Although a gas diffusion layer may be placed between the MEA 13 and the porous body 3, it is omitted in this embodiment.

In the present embodiment, the water discharge through-hole 12 is inclined 45 degrees so that it can be easily drained downstream with respect to the MEA 13. Similarly, the Ca gas through hole 11 is similarly inclined by 45 degrees to facilitate the supply of Ca gas to the MEA 13. When the gas flows at a flow velocity u (m / s) and the inclination when the downstream direction of the center plate 2 is 0 degrees is Θ degrees, the pressure applied to the joining portion is simply the porous pore diameter and porosity. If is ignored, it can be expressed as Here, the pressure ΔP (Pa) applied to the substance in the through hole is set, and the density of the reaction gas is set to ρ (kg / m ³ ).

ΔP = 1 / 2ρu ² cosΘ
In order to draw water, ΔP needs to be negative, and Θ> 90 degrees at this time, but Θ> 120 degrees is desirable because the value is smaller than this due to the porosity of the porous body. The angle based on the vertical line with respect to the MEA 13 plane is 30 degrees or more. Similarly, when distributing the reaction gas to the MEA, ΔP needs to be positive, and it is necessary to secure about half or more of the kinetic energy, so Θ <60 degrees is desirable. This is 30 degrees or more although the direction is reversed on the basis of the vertical line with respect to the MEA 13 plane.

  At this time, it is desirable that the water through hole 12 has a pore diameter of 100 to 600 μm, the Ca gas through hole 11 has a pore diameter of 10 to 50 μm, the honeycomb body 5 has a porosity of 85% or more, and a pore diameter of 10 to 50 μm. The coarse porous body 4 preferably has a pore diameter of 100 to 600 μm. This porous body is more desirably hydrophobic.

  Next, the operation will be described. Ca gas that has entered from the Ca inlet manifold 1 passes through the coarse porous 4 and enters the honey porous 5 and diffuses through the porous communication holes. The Ca reaction gas which is guided by the pressure of the Ca gas flowing through the MEA 13 and goes straight to the MEA 13 and reacts with the An gas coming from the opposite side of the MEA 13 by the MEA 13 to generate electric power, water and heat is the coarse porous body 4 Is discharged from the Ca outlet manifold 7 to the outside. The generated heat is transferred to the Ca gas and water through the metal frame structure (not shown) of the porous body 5 to cool the MEA 13. In addition, electrons generated in the MEA 13 are transmitted to the center plate 2 by this metal frame structure, and are collected uniformly over the center plate 2 and the entire surface of the MEA 13. At this time, An gas (not shown) on the opposite side of the MEA 13 enters the upper side of the MEA 13 from the An inlet manifold 8, and hydrogen in the An gas reacts with oxygen in the Ca gas at the MEA 13 and is consumed. The remaining An gas is discharged from the An outlet manifold 9. This reaction product water is collected in the water through hole 12 by the pressure of the Ca gas and is removed from the vicinity of the MEA 13 toward the center plate 2 side. By the way, the coarse porous body 4 is arranged so as to cover the Ca inlet manifold 6 and the Ca outlet manifold 7 to prevent uneven flow in the manifold when stacking about 100 separators. This is for the purpose of uniform distribution.

  As a result, a Ca gas supply path to the MEA 13 is secured. If this material is hydrophobic or hydrophobic, liquid water can easily go from thin to thick by capillary force. Since it becomes easy to move to the water through-hole 12 having a large hole diameter, and moreover, it becomes difficult for the gas to run out, so that there is an effect that high output density can be achieved. Further, the water removed by the water through holes 12 is collected in the center plate 2, and the center plate 2 is latently cooled to become water vapor, which can be discharged from the downstream as the gas through the honey porous body 5, thereby reducing the cooling water. There is also. In addition, since this structure can be applied also to the An side, there exists an effect that it can also contribute to the high current density on the An side.

  With such a configuration, the following effects are specific to this embodiment. In other words, since the straight through-holes are inclined, drainage can be improved by taking advantage of the uniformity of the current density and gas concentration, which is a merit of the porous material, so that high output density, improved reliability, and cost reduction can be achieved. There is an effect that it can be planned. Further, since the flow rate distribution in the manifold can be made uniform by covering the inlet / outlet manifold with the coarse porous body, there is an effect that the manifold area can be reduced and the electrode area can be increased accordingly to increase the output density.

  In FIG. 2, the cathode side top view and sectional drawing of the separator 1 of Example 2 which is a modification of Example 1 are shown. In Example 2, the rectification of the coarse porous body 4 of Example 1 is performed in a stack in which the seal receiving porous body 3 is placed instead of the coarse porous body 4 of Example 1 and the number of stacked layers is less than 100. Since the effect is small, the basic operation is the same with only the seal receiving effect. By adopting such a configuration, pressure loss at the inlet / outlet of the manifold can be reduced, so that the power of the Ca gas supply pump can be reduced more than in the first embodiment, and the output density can be increased.

  FIG. 3 shows a cathode side sectional view of a separator 1 of Example 3 which is a modification of Example 1, a porous partial view seen from the MEA side, and a porous partial view seen from the center plate 2. A Ca gas longitudinal through hole 15 that connects the Ca gas through hole 11 of Example 1 from upstream to downstream, and a water longitudinal through hole 14 that connects the water through hole 12 of Example 1 from upstream to downstream are provided. Different from the first embodiment. Each diameter is set to be equal to or smaller than the through hole to be connected, and is set so that the water through hole 12 is filled and then pushed out to the water vertical through hole 14. Is preventing.

  The operation is as follows. When the Ca gas flows through the porous body, at the initial stage of power generation, the Ca gas is distributed to the MEA 13 while flowing through the porous communication hole, the Ca gas longitudinal through hole 15 and the water longitudinal through hole 14 and is electrochemically reacted in the Ca gas. Oxygen is consumed and water is generated. When the generated water passes through a communication hole (not shown) of the dense porous body 5 and collects water in the water through hole 12 having a large diameter by the capillary force and the pressure of Ca gas, the water through hole 12 is filled. The pressure is used to feed the water through-hole 14 having a diameter that is substantially equal or smaller, and is discharged toward the Ca outlet manifold 7 by the pressure of Ca gas. At this time, since Ca gas is linear, it flows through the Ca gas longitudinal pipe through hole 15 having a small pressure resistance, and a part thereof is distributed to the MEA 13 through the Ca gas through hole 11. At this time, since water has a sufficiently small diameter, water cannot enter due to large capillary force and pressure resistance. For these reasons, water (liquid) and Ca gas (including vapor) are drained to cope with a high current density in which the passage is physically separated and the amount of generated water increases without causing flooding. And Ca gas distribution are improved.

  By adopting such a configuration, there is an effect that higher output density can be achieved than in the first embodiment.

  FIG. 4 shows a cathode side cross-sectional view of a separator 1 of Example 4 which is a modification of Example 3, a porous partial view seen from the MEA side, and a porous partial view seen from the center plate 2. The present embodiment is a modification of the third embodiment, in which the Ca gas vertical through-hole 15 in the third embodiment is stopped from penetrating to the downstream side to form one kind of bag path state. Since a pressure loss occurs when passing through a part of the dense porous body 5, the pressure inside the Ca gas longitudinal through hole 15 is increased by this pressure difference, and the distribution of the Ca gas through the Ca gas through hole 11 is made more uniform. And since the residence time in the dense porous body 5 of Ca gas also increases a little, the density | concentration in Ca gas also increases. Thereby, compared with Example 3, it has the effect that uniform electric power generation can be performed and high output density can be achieved.

  FIG. 5 shows a cathode side sectional view of a separator 1 of Example 5 which is a modification of Example 4, a porous partial view seen from the MEA side, and a porous partial view seen from the center plate 2. The present embodiment is a modification of the fourth embodiment. The difference from the third embodiment is that the water through hole 12 and the water vertical through hole 14 are increased instead of the Ca gas through hole and the Ca gas vertical through hole 15 to enhance the drainage. Ca gas was distributed only through the communication holes of the dense porous body 5, and the current density was improved by enhancing the discharge performance of the reaction product water. This simplifies production. In this embodiment, the water drainage is further improved, so that the current density can be improved. Moreover, since the heat transfer area which water evaporates increases, cooling performance is also improved. From these facts, this embodiment has an effect of improving the cooling performance and increasing the power density.

  FIG. 6 shows a cathode side cross-sectional view of a separator 1 of Example 6, which is a modification of Example 5, a porous partial view seen from the MEA side, and a porous partial view seen from the center plate 2. In this embodiment, the water through hole 12 and the water vertical through hole 14 are further provided in the water through hole 12 and the water longitudinal through hole 16 in the fifth embodiment to enhance drainage. In this embodiment, the water drainage is further improved, so that the current density can be improved. Moreover, since the heat transfer area which water evaporates increases, cooling performance is also improved. From these facts, this embodiment has an effect of improving the cooling performance and increasing the 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.

DESCRIPTION OF SYMBOLS 1 Separator 2 Center plate 3 Porous body 4 Coarse porous body 5 Close porous body 6 Ca inlet manifold 7 Ca outlet manifold 8 An inlet manifold 9 An outlet manifold 10 Seal 11 Ca gas through-hole 12 Water through-hole 13 MEA
14 Water longitudinal through hole 15 Ca gas longitudinal through hole 16 Water transverse through hole

Claims (3)

In a fuel cell separator comprising at least a metal porous body and a conductive plate that supports the metal porous body, and using a hole in the metal porous body as a gas flow path,
A linear through hole is provided in the metal porous body ,
Connecting the linear through hole inclined at 30 degrees or more with respect to the vertical line of the surface facing the membrane electrode assembly and the linear through hole provided in parallel to the surface facing the membrane electrode assembly fuel cell separator which is characterized in that is. 2. The fuel cell separator according to claim 1, wherein the metal porous body is a porous body having a pore diameter peak between 10 and 100 μm, and the diameter of the linear through hole is 100 to 600 μm. A fuel cell separator. 2. The fuel cell separator according to claim 1, wherein the porous metal body is a porous body having a pore diameter peak between 10 and 100 μm, and the linear through hole is a through hole having a diameter of 10 to 50 μm. And a fuel cell separator having a through hole having a diameter of 100 to 600 μm.

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