JP5610562B2 - Fuel cell and manufacturing method thereof - Google Patents

Description

  The present invention relates to a fuel cell and a method for manufacturing the same, and more particularly to a fuel cell that can be miniaturized, such as a polymer electrolyte type, and a method for manufacturing the same.

  In recent years, countermeasures against environmental problems and resource problems have become important, and fuel cells have attracted attention as one of the countermeasures. In particular, there is an increasing demand for fuel cells for smaller portable devices. For example, polymer electrolyte fuel cells use hydrogen gas as a fuel and are excellent in low cost and compactness. It is promising as a small-sized consumer power supply for computers. The polymer electrolyte fuel cell generally has a cell structure in which a solid electrolyte layer (proton transport layer) 130 is sandwiched between two electrodes, that is, a fuel electrode portion 120 and an air electrode portion 140, and hydrogen as a fuel is provided in the fuel electrode portion 120. To supply electricity. Referring to FIG. 1, in an actual polymer electrolyte fuel cell, a fuel cell is formed by sandwiching the above cell structure with a conductive separator 110 that supplies a gas such as hydrogen or air to an electrode and extracts generated electricity. Composed. Here, a groove serving as a gas flow path 111 for supplying gas is formed in the separator 110, and a gas such as fuel or air is introduced into the surface of the electrode through the gas flow path 111 as shown in FIG. Then, a reaction is caused in the catalyst layer of the electrode to generate ions and electricity. The generated electricity is taken out from the convex portion 112 because the convex portion 112 between the grooves of the gas flow path 111 is in contact with the electrode.

  Here, the structure of the electrode part 120 will be described with reference to FIG. 2. The conventional electrode part 120 is a current collector that is electrically conductive, porous, and allows gas to pass therethrough, which is a catalyst layer based on a catalyst noble metal. The electrode 201 has a structure in contact with the separator through the current collector plate 202. With such a structure, gas is sufficiently supplied to the electrode 201, and the generated electricity can be taken out efficiently. That is, the gas flowing through the gas flow path 111 is introduced to the entire surface of the electrode 201 through the current collector plate 202, and electricity generated on the surface of the electrode 201 is taken out and supplied to the convex portion 112, so that electricity can be taken out efficiently. . Various techniques for miniaturizing the fuel cell including such a separator have been proposed (see, for example, Patent Document 1).

JP 2003-346825 A

  However, the conventional small technology improves the various members, structures, manufacturing methods, etc., but basically, on the premise of the configuration of the conventional fuel cell, separators, current collector plates, electrodes, etc. There is a problem that it is intended to reduce the thickness and that there is a limit to the size reduction.

  The present invention has been made in view of such problems, and by adopting a fine structure for the separator, a current collecting plate can be eliminated, and the basic configuration of the fuel cell is reviewed and drastically changed. The object is to propose a new cell structure of a fuel cell that is thin.

In order to achieve such an object, a fuel cell according to the present invention includes an electrolyte layer, a catalyst layer disposed in contact with the electrolyte layer, and a gas flow path that is disposed in direct contact with the catalyst layer and introduces gas. On the surface in contact with the catalyst layer, wherein both the channel width and the channel interval of the gas channel have a microstructure. both the channel width and the channel spacing is obtained by a 0.2mm or less, the electrolyte layer is sandwiched by two electrodes Rutotomoni, each of the two electrodes consists only catalyst layer, each of the two electrodes Is disposed so that the separator is in direct contact with the surface opposite to the surface in contact with the electrolyte layer, and the flow path width and flow path of the microstructure of the separator that is in contact with one of the two electrodes are Fine contact separator Unlike the channel width and the channel spacing of the structure, the two electrodes are a hydrogen electrode and an air electrode, and the channel width and channel spacing of the microstructure of the separator in contact with the hydrogen electrode are the same as those of the separator in contact with the air electrode. It is smaller than the channel width and channel interval of the microstructure.

Both the gas flow path of the separator in contact with the hydrogen electrode and the gas flow path of the separator in contact with the air electrode are rectangular cross-sectional grooves formed on the surface of the separator, and the flow path of the gas flow path of the separator in contact with the hydrogen electrode The width and the channel interval may be equal to each other, and the channel width and the channel interval of the gas channel of the separator in contact with the air electrode may be equal to each other .

  As described above, according to the present invention, an electrode disposed in contact with an electrolyte layer and a conductive separator that is disposed in direct contact with the electrode and has a gas flow path for introducing gas on the surface in contact with the electrode. In addition, by providing a separator having a microstructure in which both the channel width and the channel interval of the gas channel are small values, a current collector plate can be eliminated, and a basic fuel cell configuration It is possible to provide a new cell structure of a fuel cell that has been drastically reduced in thickness.

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

(First embodiment)
FIG. 3 is a cross-sectional view showing the structure of a fuel cell according to an embodiment of the present invention.

  Here, when explaining the fine structure of the separator that does not require the current collector plate of the present invention, first, returning to FIG. 2, the necessity of the current collector plate will be confirmed again. Referring to FIG. 2, fuel gas such as hydrogen or air is supplied to the electrode from the gas flow path 111 of the separator. At this time, since the gas is supplied only from the portion facing the gas flow path 111, the gas is supplied. In order to make the gas contact evenly on the surface of the electrode that hardly penetrates, a current collector plate having a certain thickness that allows the gas to pass therethrough is required. That is, in order to supply gas evenly to the electrode side surface portion facing the convex portion 112 between the flow channels, the gas molecules are transmitted (in this case, the function of conducting electricity is irrelevant). If a current collector plate is required and the current collector plate does not have a certain thickness according to the width of the projection 112, the gas does not diffuse sufficiently in the current collector plate, and the gas is evenly distributed on the electrode surface. Can not supply.

  Next, the current collecting function of the current collecting plate 202 will be described. Since the electricity appearing on the surface of the electrode is taken out from the convex portion 112 of the conductive separator 110, the gas in which the conductive member of the separator does not directly contact the electrode. Only a part of the electricity generated on the surface of the electrode facing the flow path 111 can be taken out, or even if it is taken out, it becomes a large resistance. Here, if the current collector plate 202 is provided between the electrode and the separator, even the electricity generated on the electrode surface facing the gas flow path 111 where direct electricity cannot be taken out is easily collected on the current collector plate that is in direct contact. Thus, it reaches between the convex portions 112 of the separator and can be taken out with normal efficiency. Thus, referring to FIG. 2, the current collector plate 202 has both a function of conveying gas that cannot be introduced by the convex portion 112 of the separator 110 to the electrode surface and a function of collecting electricity that cannot be taken out by the gas flow path 111. It can be said that it is essential in the conventional fuel cell structure.

  As described above, it has become clear that the current collector plate is necessary for the conventional fuel cell, but the present invention makes the current collector plate unnecessary by forming the gas flow path as a fine structure. This point will be specifically described with reference to FIG. 3. The cross-sectional view shown in FIG. 3 is a structure on the separator 301 side of the two separators 301 and 401 of the fuel cell structure 300 according to the present invention shown in FIG. It is sectional drawing for demonstrating. Referring to FIG. 4, the separator 301 is a fuel electrode side separator, and the separator 401 is an air electrode side separator. However, since the structure of this embodiment is the same in both cases, the separator 301 side will be described.

  In FIG. 3 and the drawings showing the separator attached to the present application, the gas flow paths are all straight and have a uniform groove structure, so that the convex part in contact with the electrode or the current collector plate is a concave part of the groove. It has a symmetrical shape. This is because, according to the knowledge in this technical field including the conventional separator, it is the most common and appropriate shape and is suitable for the description of the present invention. Any shape can be used without being limited to the shape. Even when a flow path having a shape different from the flow path described in the present embodiment is used, in order to achieve the function as a conductive separator, a portion (convex portion) between the gas flow path and the flow path for taking out electricity is used. As a whole, if the gas flow path is not uniform and the microstructure is narrow as a whole and the gap between the flow paths is narrow, the effects of the present invention can be obtained. Can play.

  In the present invention, as can be understood by referring to FIG. 3, the gas flow passage width of 1 mm or more is reduced to 0.2 mm or less so that the current collector plate is not provided. Smooth gas supply and electricity extraction are now possible. That is, in the present invention, by reducing both the gas flow path width and the flow path interval (the width of the convex portion of the separator), the gas supply is changed from the gas flow channel to the convex portion if the convex portion is sufficiently narrow. Since gas flows around the surface of the facing electrode and is sufficiently supplied, smooth gas supply is possible even without a current collector plate. Also, regarding electricity extraction, if the width of the gas flow path is sufficiently narrow, electricity generated on the electrode surface of the gas flow path portion can also be efficiently extracted from the adjacent convex portion. As can be understood from the above results, the effect of the present invention can be achieved by providing the separator with a fine structure in which both the gas flow path and the flow path interval are smaller than conventional ones.

  As described above, the present invention proposes a cell structure capable of obtaining a fuel cell having the same performance as the conventional one without a current collector plate by adopting a fine structure of a certain value or less. This point will be described with reference to experimental results. FIG. 9 is a diagram comparing the characteristics of the fuel battery cell according to the present embodiment with the characteristics of a fuel battery cell having a conventional current collector plate. The conditions for measuring this characteristic are as shown in FIG. 8, Sample A and B are cells having a conventional gas flow path width of 1 mm, Sample C uses the separator having the fine structure of this embodiment, and current collector plate The cell does not have (carbon sheet). Sample C-200 has a gas flow path width of 0.2 mm, and Sample C-400 has a diameter of 0.4 mm. Although Sample B was expected to deteriorate in characteristics, it was obtained without using a current collector plate for comparison. Therefore, it is Sample A that uses a conventional fuel cell having a normal structure.

  As can be understood from the experimental results with reference to FIG. 9, the characteristics of the fuel cell using the separator having the microstructure of the present embodiment are not inferior to those of the conventional one. This is a case where the channel width is 0.2 mm or less, and the effect of the fine structure is insufficient at 0.4 mm. Therefore, in order to achieve the effect of the fine structure of the present embodiment, it has been found that the gas flow path width of approximately 0.2 mm or less is necessary at least under the conditions of this experiment. Of course, the effect may not be exhibited unless the value is smaller than 0.2 mm due to the difference in the member used, the design, and the usage conditions, and the opposite case may exist, but at least a certain amount smaller than the conventional one. It was confirmed that by applying a fine structure to the separator to the separator, it was possible to obtain the same characteristics as in the past while eliminating the need for a current collector plate.

  As described above, since the fuel cell of the present embodiment is thinned by the current collector plate, the fuel cell can be made much thinner than the conventional thin technology based on the current collector plate. In this regard, referring to FIG. 5, in an example of a conventional cell, the thicknesses of the solid electrolyte layer (electrolyte membrane), the electrode (catalyst layer), the current collector (carbon paper), and the separator are 50 μm, 10 μm, and 0.2 mm, respectively. And 0.5 to 1 mm, and in the cell of this embodiment, they can be 50 μm, 10 μm, 0 mm, and 0.3 mm, respectively. As a result, the conventional cell as a whole can be reduced from half of 1.5 to 2.5 mm to half that of 1.5 to 2.5 mm.

  Here, since the thickness of the separator is related to the size of the gas flow path, the gas is taken in from the surface of the electrode while flowing through the gas flow path. Since it is only taken in, it is not directly related to the height of the gas flow path. However, if it is too low, there is a possibility that the gas flow rate itself is insufficient. In the experiments at the present time, the height is set to about 0.2 mm, which is almost the same as the channel width, but it is considered that a lower value can be used by further searching for the limit. Here, since the thickness of the separator is determined to some extent by the height of the gas flow path, if the height of the gas flow path can be reduced, the thickness of the separator may be further reduced. Since it is as above, the thickness of the separator of this embodiment itself can be made thinner than the separator of the conventional fuel cell.

(Method for producing fuel cell)
The structure of the fuel cell according to this embodiment has been described above. Next, the manufacturing method thereof will be described below. However, it goes without saying that any method known in this technical field can be used for the fuel cell of the present embodiment, in addition to such a manufacturing method, as long as a fine structure can be formed. For example, FIG. 6 shows an example of a method for producing a separator by electroforming. For example, an etching technique can be used, or a metal separator mold can be prepared and a carbon separator member can be pressed. .

  The fuel cell manufacturing method will be described with reference to FIGS. 6 and 7. FIG. 6 mainly shows the steps of the separator manufacturing method. First, in step S601, a conductive layer is formed on a substrate such as a silicon substrate, and a photosensitive film is applied (S602). Next, a pattern is formed on the thick film, the pattern is exposed and developed (S603), and then electroformed to form a nickel layer (S604 to S605), and the nickel separator substrate is taken out. (S606). The extracted substrate is gold-plated to improve corrosion resistance (S607). In this embodiment, the separator is prepared by electroforming with nickel, but other metals can also be used.

  As shown in FIG. 7, the separator substrate thus created is cut (S701), and after the separator is completed, fuel cells are produced as shown in FIG. First, in step S702, a catalyst layer to be an electrode is formed on a Teflon (registered trademark) sheet, and a solid polymer film is sandwiched between the two catalyst layers formed in this manner to form a membrane electrode composite without a current collector plate. A body (MEA) is created (S703). The MEA thus created and the gold-plated separator are joined (S704), and the fuel cell of this embodiment can be manufactured. FIG. 10 is a perspective view showing an example of the actual structure of the fuel cell manufactured in this way. Referring to FIG. 10, it can be understood that the separator 301 on the hydrogen electrode side and the separator 401 on the air electrode side are joined so as to sandwich the MEA 403 without a current collector plate. Further, an air supply hole 1001 for supplying air to the air electrode and an air discharge hole 1002 for discharging the air that has passed through the air electrode 401 are provided on the hydrogen electrode side, and a similar hole is provided in the air electrode 402. Hydrogen, which is a fuel, can be supplied.

  As mentioned above, although the example of the manufacturing method of the fuel cell of this embodiment was demonstrated centering on preparation of a separator, it is possible to create a separator having a fine structure other than the method described here, including the method of manufacturing an MEA. Any method known in this technical field can be used in combination as long as it is a method capable of producing a fuel cell without a current collector plate. Also, any technology or method known or changeable in the present embodiment, such as the shape of the air supply and discharge holes, the structure for supplying gas such as air and fuel, the shape of the flow path, the shape of the separator, etc. Can also be applied to this embodiment.

(Second Embodiment)
In the present embodiment, the separator on the hydrogen electrode side is basically the same as that of the first embodiment described above, but a separator wider than the gas flow path width of the separator of the first embodiment is used on the air electrode side. Is. FIG. 11 is a view showing a fuel cell structure 1100 of the present embodiment. As can be understood with reference to FIG. 11, the separator 301 having the fine structure of the first embodiment is used on the hydrogen electrode side, but the separator 1101 having a wider channel width is used on the air electrode side. This is because when the separator 301 on the hydrogen electrode side is made thinner, the flow rate of the inflowing gas is limited, so that a sufficient amount of hydrogen gas as fuel can be supplied, but in the case of air, the oxygen concentration This is because there is a possibility that supply is insufficient. In such a case, this problem can be solved by using a thicker separator with a wider channel width only on the air electrode side, and a thinner separator is used on the hydrogen electrode side than in the prior art. The effects of the present invention can still be achieved.

(Third embodiment)
This embodiment is basically the same as the first embodiment with respect to the separator on the hydrogen electrode side, as in the second embodiment described above, and the air electrode side has a gas flow path width of the separator on the hydrogen electrode side. Although a wide separator is used, a current collector plate is further used on the air electrode side to make gas supply and electricity extraction more efficient. FIG. 12 is a view showing a fuel cell structure 1200 of the present embodiment. As can be understood with reference to FIG. 12, the separator 301 having the fine structure of the first embodiment is used on the hydrogen electrode side, but the separator 1201 and the current collector plate 1202 having a wider channel width are used on the air electrode side. ing. This is because, as in the case of the second embodiment described above, when the separator 301 on the hydrogen electrode side is made thinner, the flow rate of the gas that flows in is limited. Although it is possible, in the case of air, since the oxygen concentration is about 20%, there may be a case where supply is insufficient. In such a case, by using a thicker separator with a wider channel width only on the air electrode side, although supply shortage is resolved, gas supply and current collection are not performed efficiently, although depending on the channel width, the characteristics are It can get worse. In consideration of such a case, the current collector plate is provided in the fuel cell structure of this embodiment. As described above, in this embodiment, in order to solve the shortage of oxygen supply, a separator and a current collector plate having a flow path width and thickness similar to those of the conventional technology are used on the air electrode side. The thin separator is used and the current collecting plate is unnecessary, so that the effect of the present invention is still achieved.

It is a figure which shows an example of the structure of the conventional fuel cell. It is a figure for demonstrating the function of the current collecting plate in the conventional fuel cell. It is sectional drawing which shows the structure of the fuel battery cell concerning one Embodiment of this invention. It is a figure which shows an example of the structure of the fuel battery cell of this embodiment. It is a figure which shows the structure of the thickness direction of the fuel battery cell of this embodiment. It is a figure which shows an example of the separator preparation process of this embodiment. It is a figure which shows an example of the incorporating process of the separator of this embodiment. It is a figure which shows the conditions at the time of measuring the characteristic of the fuel cell concerning one Embodiment of this invention. It is a figure which shows the measurement result of the characteristic of the fuel cell concerning one Embodiment of this invention. It is a perspective view which shows an example of the incorporating process of the separator of this embodiment. It is sectional drawing which shows the structure of the fuel battery cell concerning one Embodiment of this invention. It is sectional drawing which shows the structure of the fuel battery cell concerning one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Conventional fuel cell 110 Conventional separator 111 Gas flow path 112 Convex part 120 Fuel electrode part 130 Solid electrolyte membrane 140 Air electrode part 201 Electrode 202 Current collecting plate 300 Fuel cell of this invention 301 Microstructure separator 401 Air electrode side Microstructure separator 402 Air electrode 403 MEA without current collector
1001 Air inflow hole 1002 Air discharge hole 1100 Fuel cell 1101 having a fine structure only on the hydrogen electrode side separator Oxygen electrode side separator 1200 having a large channel width Fuel cell 1201 having a current collecting plate only on the air electrode side Oxygen electrode side separator

Claims (2)

An electrolyte layer;
A catalyst layer disposed in contact with the electrolyte layer;
An electrically conductive separator that is arranged in direct contact with the catalyst layer and has a gas flow path for introducing gas on a surface in contact with the catalyst layer, wherein both the flow path width and the flow path interval of the gas flow path are fine. A separator having a structure,
The fine structure is one in which both the channel width and the channel interval of the gas channel are 0.2 mm or less ,
The electrolyte layer is sandwiched by two electrodes Rutotomoni, each of said two electrodes consists only catalyst layer,
The flow path width and the flow path interval of the microstructure of the separator in contact with one of the two electrodes are different from the flow path width and the flow path interval of the microstructure of the separator in contact with the other electrode,
The two electrodes are a hydrogen electrode and an air electrode, and the channel width and the channel interval of the microstructure of the separator in contact with the hydrogen electrode are the channel width and channel interval of the microstructure of the separator in contact with the air electrode. A fuel cell characterized by being smaller than the above. The separator gas flow path in contact with the hydrogen electrode and the separator gas flow path in contact with the air electrode are both rectangular cross-sectional grooves formed on the surface of the separator, and the separator gas flow path in contact with the hydrogen electrode. the flow channel width and the channel spacing equal to each other, the fuel cell according to claim 1, wherein the channel width and the channel spacing of the gas passage of the separator are equal to each other in contact with the air electrode.

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