JP2007073277A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent deterioration of power generation performance of a fuel cell even while excellently keeping discharge of generated water. <P>SOLUTION: A groove (a recessed part) 27 linearly extended in the same direction corresponding to an oxidation gas flow path 42 is provided in a range of a surface fc of a cathode side gas diffusion layer 25 corresponding to the oxidation gas flow path 42 formed to a cathode side separator 40. A flow path cross-section formed by the groove 27 is rectangular. A width W1 of the groove 27 is narrower than a width W2 of the oxidation gas flow path 42. The depth d1 of the groove 27 is smaller than a film thickness d2 of the cathode side gas diffusion layer 25. The groove 27 does not reach the cathode side catalyst layer 23 since the depth d1 is smaller than the film thickness d2 of the cathode side gas diffusion layer 25. The groove 27 thereby does not become the through-hole of the cathode side gas diffusion layer 25. Respective contact areas between the gas diffusion layers 24, 25 and the catalyst layers 22, 23 are not reduced since the groove 27 does not become the through-hole of the cathode side gas diffusion layer 25. Consequently, power collection performance is not deteriorated. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell.

  A fuel cell is a battery that directly takes out electric energy by electrochemically reacting hydrogen and oxygen, and generates power in units of single cells. In this single cell, both sides of a membrane electrode assembly are sandwiched by a separator having a fuel gas channel and an oxidizing gas channel. The membrane electrode assembly is composed of an electrolyte membrane, a catalyst layer formed on both sides of the electrolyte membrane, and a gas diffusion layer formed outside the catalyst layer. Here, the electrolyte membrane functions as an ionic conductor of the fuel cell, and a solid polymer is generally used for convenience of handling.

  By the way, in the fuel cell, water is generated in the process of power generation. If this generated water is not discharged well, the water content of the electrolyte membrane cannot be maintained properly, and the performance of the fuel cell is lowered. For this reason, it is important to ensure drainage in the fuel cell.

  Conventionally, as one technique for ensuring drainage performance in a fuel cell, there is a configuration in which a through hole penetrating in the film diffusion direction of the gas diffusion layer is provided in the gas diffusion layer (see, for example, Patent Document 1). Water generated in the process of power generation is discharged to the fuel gas channel and the oxidizing gas channel side through the through hole.

JP 2003-151585 A

  However, in the prior art, since the gas diffusion layer is penetrated by the through hole, the contact area between the gas diffusion layer and the catalyst layer is reduced. For this reason, there is a possibility that the current collection performance is lowered and the power generation performance of the entire fuel cell is lowered.

  This invention is made | formed in view of said point, and makes it a subject to prevent the fall of the electric power generation performance of a fuel cell, keeping the discharge | emission of produced water favorable.

In order to solve the above problems, the fuel cell of the present invention comprises:
A joined body in which a catalyst layer is formed on both sides of the electrolyte membrane, and a gas diffusion layer is formed outside the catalyst layer;
A fuel cell comprising: a separator that includes a groove and that forms a reaction gas flow path by facing the surface of the joined body;
In the range of the surface portion of the gas diffusion layer corresponding to the groove portion of the separator, a recess having a width narrower than the groove portion of the separator and not reaching the catalyst layer is provided.

  According to the fuel cell having the above-described configuration, since the concave portion is provided in the range of the surface portion of the gas diffusion layer corresponding to the groove portion of the separator, the surface of the gas diffusion layer in contact with the reaction gas is increased. Accumulated water or water staying in the vicinity of the catalyst layer is easily taken away by the flow of the reaction gas. For this reason, moisture, such as produced water, present in the joined body can be efficiently discharged. Moreover, since the said recessed part is the depth which does not reach a catalyst layer, even if it provides in a gas diffusion layer, the contact area between a gas diffusion layer and a catalyst layer does not reduce. For this reason, since the current collection performance is not lowered, it is possible to prevent the power generation performance of the entire fuel cell from being lowered.

  Furthermore, since the recess is provided within the range of the surface portion of the gas diffusion layer corresponding to the groove portion of the separator, the distance between the portion where the reaction gas flows and the catalyst layer is shortened, so that the reaction gas is supplied to the catalyst layer. It becomes easy to do. As a result, the power generation performance of the fuel cell can be improved. In addition, a recess is provided in the range of the surface portion of the gas diffusion layer corresponding to the groove portion of the separator, and the width of the recess is narrower than the width of the groove portion of the separator. Even if there is a dimensional deviation in assembly with the joined body (deviation in the surface direction of the joined body), it is possible to ensure a contact area between the gas diffusion layer and a portion (mountain portion) that is not a groove of the separator. For this reason, since it can prevent that the current passage at the time of performing electrode reaction and the heat flow passage which discharges the heat in a fuel cell can be prevented, the fall of power generation performance can be prevented further.

  The concave portion may be provided inside the gas diffusion layer at a predetermined distance from both edges of the groove portion of the separator in the surface direction of the gas diffusion layer. According to this configuration, it is possible to reliably prevent the above-described dimensional deviation in the assembly of the separator and the joined body, and it is possible to sufficiently ensure the contact area between the peak portion of the separator and the gas diffusion layer.

  The groove portion of the separator may be configured to be linear, and the concave portion may be configured to extend linearly corresponding to the groove portion of the separator. According to this structure, the said recessed part functions also as a flow path of the water discharged | emitted from the conjugate | zygote, and can improve drainage further.

  The electrolyte membrane can be a solid polymer membrane. According to this configuration, the handling of the fuel cell is convenient.

Next, embodiments of the present invention will be described in the following order based on examples.
A. Example:
A-1: Configuration of fuel cell:
A-2: Effect:
B. Other embodiments:

A. Example:
A-1: Configuration of fuel cell:

  FIG. 1 is a perspective view showing a configuration of a single cell 10 inside a fuel cell in one embodiment of the present invention. FIG. 2 is an explanatory diagram schematically showing a cross section of the single cell 10. The fuel cell of the present embodiment is a polymer electrolyte fuel cell, and has a stack structure in which a plurality of single cells 10 shown in FIG. 1 are stacked and connected in series. As shown in FIGS. 1 and 2, the single cell 10 is configured by sandwiching a membrane-electrode assembly (MEA) 20 from both sides by separators 30 and 40.

  As shown in FIG. 2, the MEA 20 is a bonded structure in which the catalyst layers 22 and 23 are formed on both surfaces (both sides) of the solid polymer electrolyte membrane 21 and the gas diffusion layers 24 and 25 are formed outside the catalyst layers 22 and 23. Is the body. In a narrow sense, the structure in which the catalyst layers are formed on both sides of the solid polymer electrolyte membrane is often referred to as MEA, but here, the structure in which the catalyst layers 22 and 23 are formed on both sides of the solid polymer electrolyte membrane 21 is gas. A configuration including the diffusion layers 24 and 25 is referred to as MEA. The MEA 20 corresponds to the “joint” in the claims.

  The solid polymer electrolyte membrane 21 is a proton conductive ion exchange membrane formed of, for example, a fluorine-based resin, and exhibits good electrical conductivity in a wet state. The catalyst layers 22 and 23 are layers having platinum as a catalyst or an alloy made of platinum and another metal, and serve as an anode (hydrogen electrode) and a cathode (oxygen electrode). The gas diffusion layers 24 and 25 are formed of a gas diffusible conductive member, for example, a carbon cloth (carbon fiber woven fabric) woven with yarns made of carbon fibers. The configuration of the gas diffusion layers 24 and 25 corresponds to the main part of the present invention and will be described in detail later.

  The anode side separator 30 and the cathode side separator 40 are formed of dense carbon plates. Both separators 30 and 40 have a plurality of linear grooves. By this groove portion, a flow path for a reactive gas used for an electrochemical reaction is formed between the MEA 20 and the MEA 20. That is, a fuel gas flow path 32 through which a fuel gas containing hydrogen passes is formed between the anode side separator 30 and the MEA 20. Further, an oxidizing gas passage 42 through which an oxidizing gas containing oxygen such as air passes is formed between the cathode side separator 40 and the MEA 20.

  FIG. 3 is an explanatory diagram showing an enlarged cross section of the cathode-side gas diffusion layer 25 and its periphery. As shown in the drawing, within the range of the surface portion fc of the cathode side gas diffusion layer 25 corresponding to the oxidizing gas channel 42 formed in the cathode side separator 40, the same direction (in the drawing) corresponding to the oxidizing gas channel 42 is shown. Grooves (concave portions) 27 extending linearly in the front and back direction are provided. The cross section of the flow path formed by the groove 27 (the cross section in the direction perpendicular to the flow direction) is rectangular. The width W1 of the groove 27 is narrower than the width W2 of the oxidizing gas flow path 42, and the depth d1 of the groove 27 is smaller than the film thickness d2 of the cathode-side gas diffusion layer 25. Since the depth d1 is smaller than the film thickness d2 of the cathode-side gas diffusion layer 25, the groove 27 does not reach the cathode-side catalyst layer 23 and cannot be a through hole of the cathode-side gas diffusion layer 25.

  Specifically, the width W2 of the oxidizing gas flow path 42 is 0.8 [mm], whereas the width W1 of the groove 27 is 0.4 [mm]. The thickness d2 of the cathode-side gas diffusion layer 25 is 0.2 [mm], whereas the depth d1 of the groove 27 is 0.1 [mm].

  As described above, the groove 27 formed in the cathode side gas diffusion layer 25 is provided within the range of the surface portion fc of the cathode side gas diffusion layer 25 corresponding to the oxidizing gas flow path 42, but here it is referred to here. “Within the range of the surface portion fc” means between the both edges 42 a and 42 b of the oxidizing gas channel 42 on the surface of the cathode-side gas diffusion layer 25.

  In the case of the present embodiment, as illustrated, the groove portion 27 formed in the cathode side gas diffusion layer 25 is the middle between the edges 42a and 42b of the oxidizing gas flow path 42 on the surface of the cathode side gas diffusion layer 25. Is provided. That is, in the surface direction of the cathode-side gas diffusion layer 25, the distance S1 between the edge 42a on the left side (left side in the figure, the same applies hereinafter) of the oxidizing gas channel 42 and the left edge 27a of the groove 27, and the oxidizing gas The arrangement position of the groove 27 is determined so that the distance S2 between the right edge 42b of the flow path 42 (the right side in the figure, the same applies hereinafter) and the right edge 27b of the groove 27 have the same size. Yes. In this embodiment, the distances S1 and S2 are 0.2 [mm]. It should be noted that this arrangement position can be implemented as a modified example of this embodiment in a mode in which it is changed to another position as long as it is within the range of the surface portion fc described above.

  FIG. 4 is an explanatory view showing an embodiment in which the groove portion 27 is disposed on the leftmost side within the range of the surface portion fc. As shown in the drawing, the groove 27 is arranged so that the left edge 27 a of the groove 27 and the left edge 42 a of the oxidizing gas flow channel 42 coincide with each other in the surface direction of the cathode side gas diffusion layer 25. Even in this case, the groove 27 is provided within the range of the surface portion fc of the cathode-side gas diffusion layer 25 corresponding to the oxidizing gas flow path 42, and constitutes the present invention.

  FIG. 5 is an explanatory diagram showing an example in which the groove portion 27 is arranged on the rightmost side within the range of the surface portion fc. As shown in the drawing, the groove 27 is arranged so that the right edge 27 b of the groove 27 and the right edge 42 b of the oxidizing gas flow channel 42 coincide with each other in the surface direction of the cathode-side gas diffusion layer 25. Even in this case, the groove 27 is provided within the range of the surface portion fc of the cathode-side gas diffusion layer 25 corresponding to the oxidizing gas flow path 42, and constitutes the present invention.

  That is, the configuration shown in FIG. 4 is a case where the groove portion 27 is arranged on the leftmost side in the range of the surface portion fc, and the configuration shown in FIG. 5 is the groove portion 27 on the rightmost side in the range of the surface portion fc. 4 is arranged between the configuration of FIG. 4 and the configuration of FIG. 5, that is, from the configuration of FIG. 4, the arrangement position of the groove portion 27 is moved to the right side until the configuration of FIG. 5 is obtained. It can be set as the aspect which changed the arrangement position of the groove part 27 to each position. In other words, in the surface direction of the cathode-side gas diffusion layer 25, the distance S1 between the left edge 42a of the oxidizing gas passage 42 and the left edge 27a of the groove 27 is set to a size from 0 to W2-W1. The distance S2 between the right edge 42b of the oxidizing gas flow path 42 and the right edge 27b of the groove 27 at that time is a size from W2−W1 to zero.

  As shown in FIG. 2, the anode side gas diffusion layer 24 is also provided with a groove (concave portion) 26 similar to the cathode side gas diffusion layer 25. That is, within the range of the surface portion of the anode-side gas diffusion layer 24 corresponding to the fuel gas passage 32 formed in the anode-side separator 30, it is linear in the same direction as the fuel gas passage 32 (the front and back direction in the drawing). An extending groove (concave portion) 26 is provided. The width W3 of the groove 26 is narrower than the width W4 of the fuel gas flow path 32, and the depth d3 of the groove 26 is smaller than the film thickness d4 of the anode-side gas diffusion layer 24. Since the depth d3 is smaller than the film thickness d4 of the anode side gas diffusion layer 24, the groove 26 does not reach the anode side catalyst layer 22 and cannot be a through hole of the anode side gas diffusion layer 24. As used herein, “within the range of the surface portion of the anode gas diffusion layer 24 corresponding to the fuel gas flow channel 32” refers to the two edges 32 a and 32 b of the fuel gas flow channel 32 on the surface of the anode gas diffusion layer 24. Say between.

A-2: Effect:
FIG. 6 is an explanatory view showing the function and effect of the fuel cell of this embodiment. As shown in the figure, by providing grooves 26 and 27 in the range of the surface portions of the gas diffusion layers 24 and 25 corresponding to the gas flow paths 32 and 42 of the separators 30 and 40, the gas diffusion layer in contact with the reaction gas. Since the surfaces 24 and 25 are increased, the water WA accumulated in the gas diffusion layers 24 and 25 or stagnating in the vicinity of the catalyst layers 22 and 23 is easily taken away by the flow of the reaction gas, and water clogging can be prevented. As a result, in this embodiment, moisture such as generated water existing in the MEA can be efficiently discharged. The water discharged from the MEA flows through the grooves 26 and 27 and is discharged outside the fuel cell.

  Further, since the groove portions 26 and 27 do not reach the catalyst layers 22 and 23, even if the gas diffusion layers 24 and 25 are provided with the groove portions 26 and 27, the gas diffusion layers 24 and 25 and the catalyst layer 22, The area of contact with 23 does not decrease. For this reason, since the current collection performance is not lowered, it is possible to prevent the power generation performance of the entire fuel cell from being lowered. Further, by providing the groove portions 26 and 27 in the range of the surface portions of the gas diffusion layers 24 and 25 corresponding to the gas flow paths 32 and 42 of the separators 30 and 40, the portion through which the reaction gas flows and the catalyst layer 22 are provided. , 23 becomes short, and it becomes easy to supply the reaction gas to the catalyst layers 22, 23. As a result, the power generation performance of the fuel cell can be improved.

  Further, the groove portions 26 and 27 are provided in the range of the surface portions of the gas diffusion layers 24 and 25 corresponding to the gas flow paths 32 and 42 of the separators 30 and 40, and the widths of the groove portions 26 and 27 are set to When the fuel cell is manufactured, even if there is a dimensional deviation in assembly between the separators 30 and 40 and the MEA (a deviation in the surface direction of the joined body), the separator 30 or 40 A contact area between the mountain portion and the gas diffusion layers 24 and 25 can be secured. For this reason, since it can prevent that the electric current channel | path at the time of performing electrode reaction and the heat flow channel | path which discharge | releases the heat | fever in a fuel cell can be prevented, the fall of power generation performance can be prevented further. In particular, in this embodiment, the grooves 26 and 27 in the gas diffusion layers 24 and 25 have a predetermined distance S1 (> 0) from the left edge 42a of the gas flow paths 32 and 42 in the surface direction of the gas diffusion layers 24 and 25. The above-described dimensions of the assembly of the separators 30 and 40 and the MEA are provided on the inner side separated by a predetermined distance S2 (> 0) from the right edge 42b of the gas flow paths 32 and 42. The contact area between the crests of the separators 30 and 40 and the gas diffusion layers 24 and 25 can be reliably ensured regardless of whether the deviation is in the left or right direction in the figure.

  Further, in this embodiment, the groove portions 26 and 27 formed in the gas diffusion layers 24 and 25 are configured to extend linearly corresponding to the gas flow paths 32 and 42 of the separators 30 and 40. The groove portions 26 and 27 formed in the gas diffusion layers 24 and 25 also function as a flow path of the water discharged from the MEA 20 and can further improve drainage.

B. Other embodiments:
Note that the present invention is not limited to the above-described embodiments and modifications, and can be implemented in various modes without departing from the gist thereof. For example, the following other embodiments are also possible. is there.

(1) In the above-described embodiment, the cross section of the flow path formed by the groove portions 26 and 27 provided in the gas diffusion layers 24 and 25 is rectangular, but instead, it may be triangular. FIG. 7 is an explanatory diagram showing an embodiment in which the cross section of the flow path formed by the groove 127 is a triangle. As shown in the drawing, within the range of the surface portion fc of the cathode side gas diffusion layer 25 corresponding to the oxidizing gas channel 42 formed in the cathode side separator 40, the same direction (in the drawing) corresponding to the oxidizing gas channel 42 is shown. A groove portion (recessed portion) 127 extending linearly in the front and back direction is provided. The cross section of the flow path formed by the groove 127 is a triangle. This embodiment has the same effect as the above-described example.

(2) Moreover, in the said Example, although the groove parts (recessed part) 26 and 27 with which the gas diffusion layers 24 and 25 were provided became the flow path extended linearly, it replaces with this and gas diffusion layers are changed. It is good also as a recessed part formed of the large hole which does not penetrate. FIG. 8 is an explanatory diagram showing an embodiment including a recess 227 formed by a large hole. In the figure, (a) shows a cross section of the gas diffusion layer 25 and its periphery, and (b) shows a cross section of the cross section of (a) when cut in the direction of the line AA in the figure. is there. As shown in the figure, the depth of the recess 227 formed by the large hole is smaller than the film thickness of the gas diffusion layer 25 and does not penetrate the gas diffusion layer 25. The large hole is elliptical when viewed from above, and is accommodated within the range of the surface portion fc of the gas diffusion layer 25 corresponding to the oxidizing gas flow path 42 formed in the separator 40.

  The concave portion 227 does not have a linearly extending groove shape as in the above embodiment, but the water discharged from the MEA is temporarily stored in the concave portion 227, and then flows down by its own weight. (Although it is in the horizontal orientation in (a) in the figure, the fuel cell is usually placed in the vertical orientation), it is discharged outside the fuel cell. Therefore, also in this embodiment, as in the above-described example, it is possible to prevent the power generation performance of the fuel cell from being deteriorated while maintaining good discharge of generated water. In addition, although the said recessed part 227 became an ellipse seeing from the upper part, it can replace with this and can also be a perfect circle.

(3) Although the fuel cell is a polymer electrolyte fuel cell in the above embodiment, it can be applied to different types of fuel cells such as a solid oxide fuel cell and a phosphoric acid fuel cell.

It is a perspective view which shows the structure of the single cell 10 inside the fuel cell in one Example of this invention. 3 is an explanatory diagram schematically showing a cross section of a single cell 10. FIG. It is explanatory drawing which expands and shows the cross section of the cathode side gas diffusion layer 25 and its periphery. It is explanatory drawing which shows the embodiment when the groove part 27 is arrange | positioned in the leftmost side within the range of the surface part fc. It is explanatory drawing which shows an example when the groove part 27 is arrange | positioned on the rightmost side within the range of the surface part fc. It is explanatory drawing which shows the effect of the fuel cell of a present Example. It is explanatory drawing which shows embodiment whose flow-path cross section formed of the groove part 127 is a triangle. It is explanatory drawing which shows embodiment provided with the recessed part 227 formed by the large hole.

Explanation of symbols

10 ... Single cell 20 ... Membrane electrode assembly (MEA)
21 ... Solid polymer electrolyte membrane 22, 23 ... Catalyst layer 24, 25 ... Gas diffusion layer 26, 27 ... Groove 30, 40 ... Separator 32 ... Fuel gas flow path 42. ..Oxidizing gas flow path 127 ... groove 227 ... concave

Claims (4)

A joined body in which a catalyst layer is formed on both sides of the electrolyte membrane, and a gas diffusion layer is formed outside the catalyst layer;
A fuel cell comprising: a separator that includes a groove and that forms a reaction gas flow path by facing the surface of the joined body;
A fuel cell comprising: a recess having a width narrower than a groove of the separator and a depth not reaching the catalyst layer within a range of a surface portion of the gas diffusion layer corresponding to the groove of the separator. The fuel cell according to claim 1,
The said recessed part is the structure provided in the inner side spaced apart only predetermined distance from the both edges of the groove part of the said separator in the surface direction of the said gas diffusion layer. Fuel cell. The fuel cell according to claim 1 or 2,
The groove portion of the separator is configured in a straight line,
The said recessed part is the structure extended linearly corresponding to the groove part of the said separator.   The fuel cell according to claim 1, wherein the electrolyte membrane is a solid polymer membrane.

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