JP5023647B2 - Fuel cell separator - Google Patents

Description

  The present invention relates to a fuel cell, and more particularly to a separator having a gas flow path formed of a porous material.

  The polymer electrolyte fuel cell is an electrolyte membrane / electrode catalyst composite in which a solid polymer electrolyte membrane and both sides thereof are coated with a fuel electrode (hereinafter referred to as an anode) catalyst layer and an oxidant electrode (hereinafter referred to as a cathode) catalyst layer. Are sandwiched between gas diffusion layers made of a porous carbon material. Further, a plurality of unit cells each having a separator for supplying fuel gas and oxidant gas are arranged on both sides to form a laminated body, and both ends of the laminated body are clamped by a clamping plate to form a fuel cell. Configure the cell stack. This fuel cell stack is stacked and installed such that the in-plane direction of the electrolyte membrane / electrode catalyst composite is perpendicular to the horizontal direction.

  A conventional separator has a corrugated shape having a flow path groove for fuel gas or oxidant gas on one side and a cooling water flow path groove on the other side. In the fuel cell using this separator, the convex surface of the fuel gas channel is in contact with the gas diffusion layer on the anode side, and the convex surface of the oxidant gas channel is in contact with the cathode side. At this contact portion, the electrons generated by the reaction are transferred, and the heat generated by the electrochemical reaction is transferred to the cooling water. Further, the fuel gas or oxidant gas flows through the recess and is supplied to the catalyst electrode via the gas diffusion layer. The cooling water is formed by concave portions facing each other when the convex surfaces on the cooling water flow path side of two adjacent separators are in contact with each other.

  In the polymer electrolyte fuel cell, hydrogen in the fuel gas flowing through the separator channel diffuses in the gas diffusion layer, and when it reaches the anode, it emits electrons by a catalytic reaction to become protons. Proton moves from the anode side to the cathode side through the solid polymer electrolyte membrane, but electrons cannot move from the anode side to the cathode side, so it passes through an external circuit via a conductive gas diffusion layer and a separator. Move to the cathode side.

  On the other hand, on the cathode side, protons moved through the solid polymer electrolyte membrane, electrons sent from an external circuit, and the oxidant gas (air) flowing through the separator channel and diffusing in the gas diffusion layer. Reacts with oxygen to produce water. Most of the generated water evaporates in the unreacted gas and is directly discharged out of the cell stack, but remains as liquid phase water in a supersaturated state. When liquid phase water generated by the electrochemical reaction oozes out from the gas diffusion layer, it is conceivable that the liquid phase water stays in the reaction gas flow path and hinders diffusion of the reaction gas. In Japanese Patent Application Laid-Open No. 2005-142015, a separator is constituted by a porous body, and water that has oozed out of the gas diffusion layer is effectively moved to prevent the reaction gas passage from being blocked.

  Japanese Patent Laid-Open No. 2005-123122 discloses that a gas flow path portion is formed by alternately forming a porous silicon layer and a non-porous layer in the horizontal direction by anodizing, and further forming a gas diffusion layer by using a discharge device. At this time, according to the arrangement of the porous silicon, by changing the particle size of the carbon-based fine particles and shaping, a certain amount of gas can be uniformly supplied at any location in the reaction layer.

JP-A-2005-142015 JP-A-2005-123122

  As seen in the background art, porous is used for water management, especially for efficient removal and humidification of generated water, and the porosity is changed in the flow direction. There are many examples in which the flow path is configured by partitioning the flow path with partition walls.

  In this way, the flow path structure using the porous material makes use of the porous characteristics to prevent drying and flooding of the membrane by controlling the suction of generated water by power generation, and there is a performance advantage by uniformly supplying the reaction gas. However, due to the flat porous structure, no consideration has been given to the distribution of water and reaction gas in the thickness direction, especially flooding in the channel on the downstream side of the cathode and reaction gas concentration in the vicinity of the reaction layer. Issues such as a decrease or an increase in pressure loss remained.

  The present invention provides a high-performance fuel cell with high performance due to uniform dispersion of reaction gas at the reaction interface and preventing flooding and membrane drying, and low pressure loss.

  In the fuel cell of the present invention, the reaction gas is supplied to the upper and lower porous layers separated in the thickness direction of the gas flow path constituted by the porous body so that the gas is switched in the vertical direction in the middle of the flow. A structural device is provided for the porous flow path. That is, a first dense layer is provided on the entire surface in the flow direction in order to separate the upper and lower porous flow paths, and flows in each of the upper and lower porous layers separated in order to reverse the vertical direction of the gas. The second and third dense layers are provided over the entire width of the separator, and the obstructed gas passes from the top to the bottom through the openings provided in the first dense layer in the vicinity of the second and third dense layers. Alternatively, it can move from the bottom to the top, and the above function is provided by forming a dense or coarse layer with many voids inside the porous channel.

  Furthermore, the pressure loss of the whole flow path is reduced by making the porosity and flow path height of the two upper and lower porous flow paths different.

  According to the present invention, the fresh reaction gas flows near the electrode reaction layer, and the product gas and product water after the reaction flow away from the electrode side, so that the reaction gas can be uniformly distributed and supplied at a high concentration. This makes it possible to easily adjust the amount of water in the vicinity of the reaction section, preventing flooding and drying of the film, and improving the performance. Furthermore, low pressure loss can be achieved. Further, since the dense layer serves as a support, there is an advantage that the strength is maintained even at a high porosity and deformation can be prevented.

  An electrolyte membrane / electrocatalyst composite, a gas flow path section composed of a porous body for a fuel electrode sandwiched between the composite fuel electrode and the outer side of the composite oxidant electrode In a fuel cell comprising separators each formed with a gas flow path portion composed of a porous body for an oxidant electrode provided in the electrode, preferably flows in the first dense layer in the porous gas flow path portions of both electrodes. It is preferable to separate the porous gas flow path in two layers in the thickness direction by providing it in parallel with the direction. And in one of the separated porous gas channels, the second dense layer is provided across the entire width from the end of one side to the end of the other side so as to block the second dense layer in the flow direction. In the other porous gas flow path, one side of the second dense layer is damped in the flow direction alternately at the upstream and downstream positions with the second dense layer sandwiched in the vicinity of the second dense layer position. It is preferable to provide a third dense layer over the entire width in the same manner as the second dense layer from one end to the other end.

A part or all of the closed region portion on the plane formed in the first dense layer surrounded by the second dense layer and the third dense layer is formed of an open or coarse porous body. It is preferable that the gas flowing in one porous flow path through the opening or the coarse porous section is moved to the other porous flow path here, and the upside down is reversed. Most preferably, the second dense layer is formed a plurality of times along the flow direction and is performed a plurality of times. For this reason, the third dense layer has a second dense layer on the most upstream side and a second dense layer on the most upstream side sandwiched between the second dense layer on the most upstream side and the second dense layer on the downstream side. From the end of one side to the end of the other side, forming a shape that alternates between the upstream side of the dense layer and the downstream side of the optional second dense layer for each second dense layer While providing a third dense layer connected by one over the entire width,
At each second dense layer position, a part of the closed region on the plane formed in the first dense layer surrounded by the second dense layer and the third dense layer is opened or rough porous It is preferable to be comprised with a body.

  Hereinafter, detailed embodiments of the present invention will be described with reference to the drawings.

  The first embodiment will be described with reference to FIGS. 1A, 1B, 2 and 3. FIG. FIG. 1 is a cross-sectional view of a first embodiment of the present invention, FIG. 2 is a plan view, and FIG. 3 is a bird's-eye view of an invention portion.

FIGS. 1A and 1B are cross-sectional views on one pole side of the fuel cell of the present invention. Between the electrolyte membrane / electrode catalyst complex 1 and the partition plate 2 that separates the gas flowing through both electrodes, the electrolyte membrane / electrode catalyst complex 1 on one electrode side is in contact with the electrolyte membrane / electrode catalyst complex 1, and the reaction gas is dispersed by gas diffusion. Gas flow paths 3a and 3b that serve to supply the body 1 are provided, and a separation layer 4 that separates both flow paths is provided between the gas flow paths 3a and 3b. The gas flow paths 3a and 3b are made of a porous material. The separation layer 4 is also made of a porous material that is very dense and has almost no voids.

The reaction gas 100a flowing through the upper stage 3a is in contact with the electrolyte membrane / electrode catalyst complex 1 and flows downstream while reacting, but the flow is blocked by the blocking material 5a. The arrangement of the blocking material 5a is shown in the plan view of FIG. 2, and is provided over the entire width of the reaction surface 51 from one end 50a of the reaction surface 51 to the other end 50b.

On the other hand, the reaction gas 101a flowing through the lower stage 3b does not directly contact the electrode by the separation layer 4, and thus flows downstream without causing an electrochemical reaction, but is blocked by the blocking material 5b in the middle. The arrangement of the blocking material 5b is shown in the plan view of FIG. 2 and the bird's-eye view of FIG. 3, and is provided across the entire width of the reaction surface 51 from one end 50a of the reaction surface 51 to the other end 50b. However, the closing materials 5b-1 and 5b-2 are always arranged alternately on the upstream side and the downstream side with respect to the previous closing material 5a, and 5b-1 and 5b-2 are connected by the closing material 5b-3. The reaction gas 101 a is capped over the entire width of the reaction surface 51.

  The plugging materials 5a and 5b are made of a dense porous material like the separation layer 4, and are preferably made of the same material as the separation layer 4.

Next, the blocked reaction gases 100a and 101a will be described. The reaction gas 100a in FIG. 2 passes through the opening 6a opened in the separation layer 4 at the position of the closed region surrounded by the blocking material 5a and the blocking material 5b on the upstream side of the blocking material 5a. The inside of 3b flows as a gas 100b without reacting to the outlet.

  Similarly, the reaction gas 100b passes through the opening 6b opened in the separation layer 4 at the position of the closed region surrounded by the blocking material 5a on the downstream side of the blocking material 5a and the blocking material 5b, and the gas flow path 3a in FIG. The gas flows inside the gas 101b while causing an electrochemical reaction to the outlet.

  If the reaction surface 51 is divided into an upstream reaction zone 52a and a downstream reaction zone 52b with the plugging material 5a as a boundary, the reaction gas is divided into upper and lower stages with this as a boundary. It is replaced with. The reactant gas 100a whose reactant concentration is significantly reduced by water or other gas that has been consumed in the electrochemical reaction due to consumption of the reactant and moved through the membrane is isolated from the electrode in the downstream reaction zone 52b, and conversely The fresh reaction gas 101a having a high substance concentration is exchanged to come into contact with the electrode.

  In the performance of the fuel cell, the supply rate of the reaction active material to the reaction interface is an important factor. When the supply rate is low, that is, when the diffusion rate is low, the voltage drop particularly under high current density operation deteriorates remarkably.

  In the conventional gas flow, the reactant concentration decreases as it goes downstream. As schematically shown in FIG. 4, particularly in the vicinity of the cathode electrode, the decrease in oxygen concentration is large due to the influence of water which is a generated gas. Moreover, the case where water comes out into the gas flow path occurs not only in the cathode but also in the anode. The occurrence of water in the flow path becomes a factor that hinders the flow in the flow path due to condensation or hinders the mass transfer of gas. In this embodiment, the influence of water is isolated from the electrode in the middle, and fresh reaction gas can be supplied, so the influence of water and the adverse effect of concentration distribution are not dragged to the outlet, improving the battery performance. Operation at high current density is improved. Furthermore, the operation with a high utilization rate of the reaction gas is possible by improving the concentration distribution in the channel height direction.

  In addition, when viewed from the viewpoint of water management of the electrolyte membrane, drying of the membrane on the inlet side is likely to occur due to the introduction of a new gas. In this example, the electrolyte membrane / electrode catalyst composite and Since the amount of gas in contact decreases, the amount of water evaporated from the membrane is also suppressed, and there is an advantage that membrane drying is less likely to occur.

  In the second embodiment of the present invention, as shown in FIG. 5, there is shown a case where there are two blocking members 5a, 5a-1, 5a-2, in the flow direction. As a result, the reaction surface 51 is divided into three, and the upper and lower stages are exchanged twice at the position of the blocking material 5a.

The arrangement of the blocking material 5b in this case will be described. The arrangement of the blocking material 5b in the blocking material 5a-1 is the same as that in the first embodiment. The concept is the same for the blocking material 5a-2. The blocking materials 5b-3 and 5b-4 are alternately arranged on the upstream side of 5a-1 and the downstream side of 5a-2 with the blocking materials 5a-1 and 5a-2 interposed therebetween. Are arranged, and 5b-3 and 5b-4 are connected by the blocking material 5b-5, and the reaction gas 102a is stopped over the entire width of the reaction surface 51.

  The reaction gas 101a flows through the reaction portion 52b from the opening 5b, and flows through the lower flow path from the opening 5c provided on the upstream side of the blocking portion 5a-2. The reaction gas 102a flows through the lower flow path formed by the blocking material 5b-5, and reaches the flow outlet while reacting the reaction part 52c through the opening 5d.

  By increasing the number of occlusions in the flow direction in this way, the number of replacement of the upper and lower stages increases, so that the in-plane dispersion of the fresh air reaction gas is further promoted, and the performance improvement effect is also increased.

  Similarly, FIG. 6 shows a case where the number of occlusions is further increased to five. Thus, when the number of divisions of the reaction part increases, flow distribution to each reaction part must be considered. In this embodiment, the reaction part is divided into six parts, the reaction gas 100a is supplied to the reaction part 52a, the reaction gas 101a is supplied to the same 52b, the 102a is supplied to the same 52c, and the following 105a is supplied to 52f. 6a to 6j form openings provided in the separation layer, and serve to supply reaction gas to the reaction parts 52a to 52f or to guide the reacted gas to the lower flow path.

  In order to evenly distribute the reaction gases 100a to 105a, the flow resistance from the inlet to the outlet of each reaction gas must be made as equal as possible. However, the ratio of the channel length flowing through the lower channel and the upper channel differs depending on each reaction gas. Since the gas flowing through the lower flow path does not react, the volume flow rate is constant, but when flowing through the upper flow path, a volume change accompanying the reaction occurs. Therefore, the volume change of each reaction gas must be taken into consideration.

  Specifically, the flow width of the lower flow paths 61a to 61e through which each reaction gas formed by the plugging material 5b flows is adjusted so that the reaction gas supplied to the reaction portion farther from the inlet is wider to adjust the flow resistance. To do. Furthermore, when the adjustment of the channel width is subject to size restrictions, it is possible to take measures to adjust the flow resistance by changing the porosity of the porous body of each lower channel from 61a to 61e. It is.

  5 and 6, the dense layers 5a and 5b run vertically and horizontally in the cell plane. Since the dense layer is less deformed by compression than other porous regions, it plays the role of a strut, so that deformation due to compression of the porous flow path can be suppressed when the cells are stacked and surface pressure is applied. There are also advantages.

  FIG. 7 is a plan view of a separator 8 showing a third embodiment of the present invention. In the present embodiment, the present invention is applied to a separator in which the reaction gas supply manifold 10a and the outlet manifold 10b are narrow and it is difficult to uniformly disperse the reaction gas in a plane with a low pressure loss.

  The separator 8 is provided with anode gas 10a, 10b, cell cooling water 9a, 9b, and cathode gas 11a, 11b as internal manifolds. This figure shows the anode surface side, and the anode gas flowing in from the manifold 10a is discharged from the manifold 10b while reacting. When the width of the reaction zone 12 is wider than the width of such a manifold, It tends to cause uneven flow distribution. On the other hand, in order to flow uniformly, the flow path structure becomes complicated due to rectification, and the pressure loss becomes large.

In this separator, as shown in the previous embodiment, the anode flow path is separated into two stages by the separation layer (not shown). The reaction zone 12 is divided into 70a and 70b by the blocking material 5a provided in the upper flow path. The reaction gas 100a flowing in from the manifold 10a flows into the reaction zone 70a toward the opening 6a, flows through the opening 6a through the lower channel 100b, and is discharged from the outlet manifold 10b. On the other hand, the reaction gas 101a that has entered the lower flow path from the manifold 10a is blocked by the closing material 5b provided at the lower stage, and flows into the upper stage side of the reaction zone 70b as the reaction gas 101b through the opening 6b. The inflowing reaction gas 101b flows while reacting along the guide 7 provided in the flow path, the flow direction is bent at the end, and is discharged from the outlet manifold 10b.

  In this embodiment, the supply position of the reaction gas 101a can be arbitrarily selected by the upper and lower two-stage structure, and the lower flow path portion can serve as a header, so that it can be uniformly distributed to the reaction zone 70b and is impossible. Supply with low pressure loss is possible without increasing pressure loss due to gas flow.

  In addition, the reaction zone 70a may be designed so that the reaction gas flows in a region in which a uniform flow rate distribution can be performed with respect to the width of the inlet manifold 10, and both the reaction zones 70a and 70b are provided. Uniform flow distribution is possible.

  This embodiment is an example, and the arrangement and shape of the blocking materials 5a and 5b and the optimum arrangement and number of the openings 6a and 6b are determined according to the separator shape and operating conditions.

(Production method)
The manufacturing method of the separator in this invention is demonstrated. The separator manufacturing method of the present invention includes a step of forming a first porous channel structure on a partition plate, a step of forming the separation layer on the first porous channel, and a second porous layer on the separation layer. The method includes a step of forming a flow channel structure and a step of forming an opening in the separation layer, both of which are performed using an inkjet discharge device.

  As a discharge device, there are a thermal method and a piezo method in which bubbles are generated by heating and a droplet is discharged.

The partition plate 2 shown in FIG. 8A is mounted on the table of the discharge device. A nozzle forming surface provided on the inkjet head and on which a number of nozzles for discharging conductive carbon-based fine particles, which are discharged materials, are arranged is set on the partition plate 2. A nozzle for applying carbon-based particles having a very small pore diameter to form a dense layer serving as the plugging material and a nozzle for applying carbon-based particles having a large pore diameter to form the porous flow path Are arranged corresponding to the planar pattern of the blocking material. As shown in FIG. 8B, a dense layer 5b serving as a blocking portion and a first porous flow path 3b are formed on the partition plate 2.

  Next, the separation layer 4 is formed on the first porous flow path layer 3b. A portion corresponding to the position of the opening of the separation layer is covered with a masking material 70. The masking material is preferably a resin that evaporates when the temperature is high. The nozzle forming surface of the ink jet head of the discharge device is set for forming a separation layer, and carbon-based fine particles for forming the separation layer are applied onto the first porous flow path layer 3b to form the separation layer 4 ( FIG. 8D).

Next, the second porous flow path layer 3 a is formed on the separation layer 4. Similarly to the formation of the first porous flow path 3b, the nozzle is formed with a nozzle and a porous flow path for applying fine carbon-based particles having a very small pore diameter to form the dense layer 5a serving as the plugging material. Nozzles for applying carbon-based particles having a large pore diameter are arranged corresponding to the planar pattern of the blocking material. The state after application is shown in FIG.

  Finally, the masking material remaining in the separation layer 4 is evaporated to raise the temperature, thereby forming the opening 6 to form the opening.

  The flow path formation on one side of the separator is completed by the above steps. In addition, when making both surfaces into the same porous flow path structure, the other side will be formed by the same method.

  In addition, as an additional step, it is possible to form a gas diffusion layer including a thin conductive carbon layer on the upper surface of the second porous flow channel in contact with the electrolyte / electrode catalyst composite side.

  In this manufacturing method, the nozzle forming surface provided in the inkjet head is changed for each process as a single ejection apparatus. However, the ejection apparatus is provided for each process, and a sample is transferred to each ejection apparatus by a transport device. Of course, it is possible to create a continuous line that can be mounted on a table.

The typical sectional view showing the porous channel structure of the separator applied to the first embodiment of the fuel cell concerning the present invention. 1 is a schematic plan view showing a porous flow channel structure of a separator applied to a first embodiment of a fuel cell according to the present invention. The typical bird's-eye view which shows the porous flow-path structure of the separator applied to 1st embodiment of the fuel cell concerning this invention. The schematic diagram which shows the density | concentration distribution of the reactive gas in the gas flow path concerning a present Example. The typical top view which shows the porous flow-path structure of the separator applied to 2nd embodiment of the fuel cell concerning this invention. The typical top view which shows the porous flow-path structure of the separator applied to 2nd embodiment of the fuel cell concerning this invention. The typical top view which shows the porous flow-path structure of the separator applied to 3rd embodiment of the fuel cell concerning this invention. Typical sectional drawing which shows the manufacturing process of the separator concerning a present Example.

Explanation of symbols

1 Electrolyte Membrane / Electrocatalyst Complex 2 Partition Plate 3 Porous Channel 4 Separation Layer 5 Occlusion Material 6 Opening 52 Reaction Region 61 Lower Porous Channel 100 Upper Reaction Gas 101 Lower Reaction Gas

Claims (5)

  An electrolyte membrane / electrocatalyst composite and the composite sandwiched between the fuel electrode gas diffusion layer and gas flow path provided outside the composite fuel electrode, and provided outside the composite oxidant electrode In the fuel cell comprising the gas diffusion layer for the oxidant electrode and the separator each formed with the gas flow path portion, the gas flow path on at least one electrode side is separated into two upper and lower stages parallel to the gas flow direction A partition portion is provided, and the gas is blocked by at least one plugging material in the middle of each separated flow path, and an opening is provided in the partitioning portion in the vicinity of each plugging material upstream side, A fuel cell using a flow system in which the gas flowing through each of the separated gas flow paths is switched between upper and lower stages through the opening. An electrolyte membrane / electrocatalyst composite, a gas flow path section composed of a porous body for a fuel electrode sandwiched between the composite fuel electrodes and provided outside the composite fuel electrode, and the composite oxidant electrode In a fuel cell comprising separators each formed with a gas flow path composed of a porous body for an oxidant electrode provided outside
The porous gas channel is separated in two stages in the height direction by providing the first dense layer in parallel to the flow direction in the porous gas channel for the fuel electrode and / or the oxidant electrode. In one of the separated porous gas channels, the second dense layer is provided across the entire width from the end of one side to the end of the other side so as to block the second dense layer in the flow direction. In the other porous gas channel, one side of the second dense layer is located in the vicinity of the position of the second dense layer, and is damped in the flow direction alternately at the upstream side and downstream side of the second dense layer. A third dense layer connected to one end over the entire width from the end of the other side,
A closed region on a plane formed in the first dense layer surrounded by the second dense layer and the third dense layer is formed by an opening or a porous body having a larger porosity than the dense layer A fuel cell. The second dense layer described in the second item is provided over the entire width from one side edge to the other side edge in a shape in which a plurality of second dense layers are stopped at an arbitrary position in the flow direction. The upstream side of the second dense layer on the most upstream side with the second dense layer on the most upstream side and the remaining second dense layer located on the downstream side of the second dense layer. Formed alternately at the downstream position of the second dense layer for each second dense layer position, and connected to one over the entire width from the end of one side to the end of the other side Providing a third dense layer,
At each second dense layer position, a part of a closed region portion on a plane formed in the first dense layer surrounded by the second dense layer and the third dense layer is opened, or the A fuel cell comprising a porous body having a larger porosity than the dense layer.   The fuel cell according to claim 2, wherein the two separated porous gas flow paths are formed of porous materials having different porosity and different flow path heights. 4. The fuel cell according to claim 3, wherein the two separated porous gas flow paths according to claim 2 that are partitioned by the plurality of second dense layers are different from each other. A fuel cell.

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