JP4687707B2 - Manufacturing method of fuel cell separator - Google Patents

Description

  The present invention relates to a method of manufacturing a separator that is disposed between each unit cell constituting a fuel cell stack and that has a current collecting function and forms a fuel gas channel and an oxidizing gas channel. .

  For example, in a solid electrolyte fuel cell, electrodes are provided on both sides of a thin-film electrolyte to form a single cell (single cell), and a fuel cell stack is formed by stacking a large number of single cells. It is configured to extract electric power by voltage and current. In that case, in order to supply the reaction gas such as fuel gas (for example, hydrogen gas) and oxidizing gas (for example, air) to the surface of the electrolyte through each electrode and to take out electric power through each electrode, A separator is arranged on the surface side, that is, between each single cell.

  Therefore, the separator is made of a conductive material for taking out electric power, and has a structure that forms a flow path for allowing a reaction gas to flow between the electrode and the surface of the electrode while being in contact with the electrode. Need to be. In order to satisfy such a demand, a separator having a gas flow path formed by forming a large number of concave and convex portions on a conductive plate material such as metal, contacting the convex portions with the electrodes, and communicating the concave portions with each other is used. Has been tried.

  By the way, since a fuel cell obtains an electromotive force by an electrochemical reaction between a fuel gas and an oxidizing gas via an electrolyte, an oxidation reaction occurs on the anode side and a reduction reaction occurs on the cathode side. Since the separator is installed in such a reducing atmosphere and an oxidizing atmosphere, high corrosion resistance is required, and at the same time, high electrical conductivity is required as much as possible. Furthermore, since the electric power obtained from the single cell is small, it is necessary to form a stack by integrating several tens to several hundreds of single cells for practical use. A structure that can be manufactured as inexpensively as possible is required.

  Under such a technical background, Patent Document 1 has proposed a separator in which a number of protrusions are formed on a surface of a metal substrate with a synthetic resin and a metal thin film is formed on the surface. Specifically, in the separator described in Patent Document 1, protrusions are injection-molded on a surface of a metal base such as aluminum using a polymer having excellent fluidity, and a metal thin film is applied to the entire surface. A separator formed by coating.

Japanese Patent Laid-Open No. 10-12246

  If it is a separator mentioned above, since the projection part which contacts an electrode can be formed by injection-molding synthetic resin on the surface of a metal substrate, it is not necessary to perform metal processing, such as press processing of a metal substrate, There is a possibility that the manufacturability becomes good and an inexpensive separator can be obtained. However, since the protrusions are in contact with the electrodes to form an electric circuit, and at the same time, a gas flow path is formed between the protrusions, it is preferable that the protrusions are as small as several millimeters and have a high density. It is desirable to form. Furthermore, when this protrusion is formed of synthetic resin, the metal thin film is formed as described above to ensure conductivity, so that the metal thin film contacts the metal substrate between the protrusions, It is desirable to ensure conductivity with respect to the metal substrate for each protrusion. Therefore, a large number of the above-mentioned protrusions are formed with a slight gap between each other. Thousands to several tens of thousands of such minute synthetic resin protrusions are securely attached to the surface of the metal substrate. It is technically difficult to form, and a stable separator that can be used practically has not been produced.

  Moreover, in the separator described in Patent Document 1, conduction between the protrusion and the metal substrate is performed by a metal thin film. However, in consideration of manufacturability and cost, the metal thin film is acceptable. It is desirable to be as thin as possible, so that the electrical conductivity of the metal thin film is lowered, the electrical resistance of the separator as a whole is increased, and the power generation efficiency of the fuel cell may be lowered. In addition, the metal thin film and the metal substrate come into contact with each other between the protrusions, but the space allowed for the contact is extremely limited. There was a possibility that the electrical characteristics would deteriorate.

  The present invention has been made paying attention to the above technical problem, and an object of the present invention is to provide a method capable of easily manufacturing a fuel cell separator having excellent electrical characteristics.

  According to a first aspect of the present invention, there is provided a method for manufacturing a fuel cell separator having a large number of protrusions which are brought into electrical contact with each other by contacting the surface of an electrode. In this state, by applying a coating treatment with a conductive material, the protrusion that is joined to the substrate through the through hole and protrudes to the surface side of the masking member and rises from the surface of the masking member. In this method, the masking member is exposed at a portion between the protrusions.

  The invention of claim 2 is the method according to claim 1, wherein the masking member is made of a corrosion-resistant material.

  Therefore, according to the first aspect, it is possible to manufacture a separator having a structure in which a large number of conductive protrusions protrude from a so-called base portion having a flat plate shape, and it is possible to employ a plating method as the coating method. Can be manufactured.

  Therefore, in the invention of claim 2, in addition to obtaining the same effect as that of the invention of claim 1, a separator having a structure in which a large number of conductive protrusions protrude from a so-called base portion of a flat plate can be manufactured. A portion between the protrusions can be corrosion-resistant coated, and a separator having excellent conductivity and durability can be manufactured.

  Next, a basic configuration example of a separator that can be manufactured in the present invention will be specifically described with reference to the drawings. FIG. 1 shows a cross-sectional view of a separator 1 according to the present invention. The separator 1 shown here has a structure in which a plurality of conductive protrusions 3 are provided on at least one surface of a conductive substrate 2. It is. The separator 1 is disposed between single cells (not shown) in the fuel cell stack, and is electrically connected to the electrode 4 by bringing each protrusion 3 into contact with the electrode 4 to serve as a current collector. In addition to functioning, the space formed between the protrusions 3 serves as a flow path 5 through which a fuel gas such as hydrogen, an oxidizing gas such as air, or a liquid such as water flows.

  The conductive substrate 2 has strength to maintain airtightness and watertightness and maintain a flat plate shape, and has a function of guiding current from between each unit cell to the outside. Or a metal plate such as aluminum, a conductive ceramic plate, a thin plate obtained by applying a conductive coating to the ceramic plate, a carbon molded body, a conductive sheet material, a conductive resin, or the like. The separator 1 may be disposed on the cathode side of the fuel cell and may be disposed on the anode side, but the one disposed on any electrode side may have the same configuration. Since the cathode side has a strong oxidizing atmosphere, it is preferable to employ a material excellent in oxidation resistance as the material of the substrate 2.

  Further, the protrusion 3 is a minute one having an outer dimension and a height of about 1 mm or about several mm, and is provided at intervals of about 1 mm or about several mm. The shape and arrangement pattern are shown in FIG. The example shown in FIG. 2A is an example in which the protrusions 3 are formed in a columnar shape and arranged in a matrix. The example shown in (B) is an example in which the protrusions 3 are formed in a prismatic shape and arranged in a matrix. Furthermore, the example shown in (C) is an example in which the protrusions 3 are formed in an elliptical cross section, arranged in a staggered manner, and the direction of the oval is reversed in each row.

  The material forming the projections 3 is only required to have conductivity, and the same kind of material as that of the substrate 2 or a different kind of conductive material can be used. If the same kind of material is used, the bonding strength between the protrusion 3 and the substrate 2 is increased, and even if the kind is different, if the protrusion 3 is formed of the same material as the substrate 2, the protrusion 3 and the substrate 2 The bonding strength of the is increased. In addition, since this projection part 3 forms the electric circuit between the electrode 4 and the board | substrate 2, it is preferable to have high electroconductivity and in addition to this, since it contacts the electrode 4 directly, oxidation resistance Therefore, it is preferable to form the protrusions 3 with a metal that is relatively difficult to oxidize, such as nickel (Ni) or tin (Sn).

  As described above, the space portion formed between the protrusions 3 serves as the flow path 5 for flowing gas or water, so that this portion is directly exposed to an oxidizing atmosphere or a reducing atmosphere. Therefore, a corrosion-resistant layer 6 such as a corrosion-resistant film is formed between the protrusions 3. The corrosion-resistant layer 6 is formed of a synthetic resin such as acrylic, epoxy, polypropylene, vinyl chloride, or polyethylene, ceramic such as silicon oxide, zirconia, or alumina, or metal such as gold, platinum, silver, tungsten, titanium, or chromium. Can do. Of these, a material having electrical insulation is particularly preferable. When such a corrosion-resistant layer 6 is provided, it is possible to make the substrate 2 have a structure in which electrical characteristics are more important than corrosion resistance, and the protrusion 3 can have a structure in which electrical characteristics and corrosion resistance are emphasized. Thus, the degree of freedom in material selection and design is improved.

  As described above, since the protrusion 3 is brought into direct contact with the electrode 4 and directly exposed to an oxidizing atmosphere or a reducing atmosphere, corrosion resistance is required in addition to conductivity. Therefore, in the above example, an example of using an oxidation-resistant metal such as nickel or tin is shown, but instead of or in addition to this, a corrosion-resistant coating may be provided. An example thereof is schematically shown in FIG. 3, and a corrosion-resistant coating 7 is formed on the entire outer surface exposed to the outside of the protrusion 3 and the entire surface of the corrosion-resistant layer 6. The corrosion-resistant coating 7 needs to have higher corrosion resistance than the material forming the protrusions 3 and also needs to be electrically conductive, and thus is made of a noble metal such as gold (Au) or silver (Ag). In addition, when providing this kind of corrosion-resistant coating 7, the said corrosion-resistant layer 6 can also be omitted.

  Next, a method for manufacturing the separator 1 will be described. As described above, the basic structure of the separator 1 according to the present invention is a structure in which a large number of conductive protrusions 3 are bonded to at least one surface of the conductive substrate 2. As the material, a plate material 10 that is not subjected to special processing such as drilling or bending is prepared ((A) in FIG. 4). That is, the above-described metal plate, ceramic plate, carbon molded body, or conductive sheet. On at least one surface of the material plate 10, a conductive material such as nickel or tin is joined in a number of dot shapes to form the protrusions 3 ((B) of FIG. 4).

  As a method for forming the projection 3, for example, as shown in FIG. 5, the material plate 10 is sandwiched between molds 11 to form a cavity 12 corresponding to the shape of the projection 3, and the cavity 12 is electrically conductive. By pressurizing and injecting the conductive material 13, it is possible to adopt a method in which the conductive material 13 is formed into a protrusion and simultaneously joined to the material plate 10.

  Another method of forming the protrusion 3 is a plating method. That is, as shown in FIG. 6, a masking sheet 15 provided with a large number of through holes 14 in the shape and position corresponding to the protrusion 3 is joined to the surface of the material plate 10 for the substrate 2 ((A in FIG. 6). )). As the masking sheet 15, an insulating material is used in order to prevent the conductive material from adhering during the plating described below.

  With the material plate 10 and the masking sheet 15 set in this manner, the material plate 10 and the masking sheet 15 are placed in a plating apparatus and plated with a conductive material such as nickel or tin. Since only the portion corresponding to the through hole 14 is exposed to the plating solution in the material plate 10, the conductive material is gradually deposited on the portion, and finally the surface side of the masking sheet 15 is exposed. The protrusion 3 is formed in a nugget shape (FIG. 6B).

  When the corrosion-resistant film 7 shown in FIG. 3 is formed on the surface of the separator 1 manufactured by the method described with reference to FIGS. 4 to 6, the ion plating, sputtering, CVD method (chemical The corrosion-resistant material may be formed into a thin film by a method such as a vapor deposition method or a PVD method (physical vapor deposition method).

  The separator 1 manufactured by the above-described method of the present invention is arranged between the single cells and stacked together with the single cells to form a fuel cell stack, as in the prior art. The example is typically shown about the cell in FIG. That is, a hydrogen electrode 21 serving as a cathode and an oxygen electrode 22 serving as an anode are formed on both sides of the electrolyte membrane 20, and the separators 1 are respectively disposed on the surface sides thereof, and the protrusions 3 are formed on the electrodes 21 and 22. Is in contact. In this state, the space between the protrusions 3 forms a flow path for gas and water.

  In that case, each protrusion 3 in the separator 1 comes into contact with the electrodes 21 and 22 of the unit cell and is electrically connected, so that electric power can be taken out to the external load 23. In the separator 1 according to the present invention, since the protrusion 3 is formed of a conductive material, the entire protrusion 3 constitutes an electric circuit, and therefore, the distance from the electrode to the substrate 2 or the terminal (not shown). As a result, the electrical conductivity is increased, the resistance value of the separator 1 as a whole is lowered, and the separator 1 is excellent in electrical characteristics. Further, each protrusion 3 can be formed by bonding a molten metal to the substrate 2 or by a method such as plating, so that the bonding strength between the protrusion 3 and the substrate 2 is high. It is possible to obtain a separator 1 having high mechanical strength and high durability in that respect. Further, when the corrosion-resistant layer 6 is provided in the portion between the protrusions 3 or when the corrosion-resistant film 7 is formed on the entire surface, corrosion in an oxidizing atmosphere is prevented or suppressed. Durability is improved.

  In the above-described method according to the present invention, minute and numerous projections 3 can be formed without subjecting the substrate 2 to mechanical processing such as drilling, bending, coining, etc. A battery separator can be easily and inexpensively manufactured.

  The separator manufactured according to the present invention only needs to have a structure in which a large number of conductive protrusions are formed on a conductive substrate. Therefore, as shown in FIG. The coating 3a of the same material may be applied, the protrusions 3 may be formed integrally with the coating 3a, and the corrosion-resistant layer 6 may be provided between the protrusions 3 and on the surface of the coating 3a.

  Moreover, when forming the protrusion part 3 by the plating method, you may use the masking sheet 15a of the structure shown in FIG. That is, the masking sheet 15a shown in FIG. 9 is formed by integrally forming a cylindrical portion 14a around the through hole 14, and plating is performed using the masking sheet 15a, so that the conductive material can be obtained. The protrusions 3 are formed by being gradually deposited inside the cylindrical portion 14a. As a result, the cylindrical portion 14a is wrapped around the formed protrusion 3, and the material forming the masking sheet 15a is insulative and has electrical corrosion resistance during power generation in the fuel cell. Therefore, the corrosion resistance of the side surface portion of the protrusion 3 is improved, and the durability of the separator 1 is improved.

  By the way, the factors that improve the power generation efficiency of the fuel cell include the matter of expanding the reaction area between the gas such as oxygen and hydrogen and the electrode or the diffusion region of the gas to the electrode as much as possible, and the electrons from the electrode to the separator. In order to enhance the current collection effect by promoting the movement of the electrode, there is a matter of expanding the contact area between the electrode and the protrusion as much as possible. However, in a state where the electrode and the protrusion are in contact, the reaction surface between the gas and the electrode and the contact surface between the electrode and the protrusion are disposed adjacent to each other, and the gas diffusion region is The electrode is formed inside the electrode corresponding to the contact surface between the protrusion and the protrusion. For this reason, conventionally, it has been difficult to achieve both of the above two items (in other words, contradictory characteristics).

  Therefore, it is possible to cope with such a problem by configuring the separator 1 manufactured according to the present invention as described below. A configuration example of the separator 1 for that purpose will be described with reference to FIGS. FIG. 10 is a cross-sectional view schematically showing the separator 1, and the entire protrusion 3 is composed of a sintered body obtained by baking a large number of conductive particles 24. A plurality of stages are arranged between the substrate 2 and the electrode 4 in a state where the conductive particles 24 are in contact with each other. Examples of the sintered body constituting the protrusion 3 include carbon, metal, conductive resin, and conductive ceramic. The particle diameter of each conductive particle 24 is set in the range of φ0.01 mm to φ2.0 mm. Further, in FIG. 10, the particle diameters of the conductive particles 24 are all set to be the same. In FIG. 10, the corrosion resistant layer 6 of FIG. 1 is omitted for convenience.

  In the example of FIG. 10, the protrusion 3 is formed of a sintered body obtained by sintering a large number of conductive particles 24, and a gap is formed between the conductive particles 24. 3, fine irregularities are formed by the respective conductive particles 24. For this reason, when a gas such as oxygen or hydrogen existing in the flow path 5 enters the gap, the reaction area between the gas and the electrode 4 is expanded as much as possible, and the diffusion region of the gas with respect to the electrode 4 is increased. Is enlarged. As described above, even if the reaction area between the gas and the electrode 4 is increased as much as possible, and the diffusion region of the gas with respect to the electrode 4 is expanded, the contact area between the electrode 4 and the protrusion 3 is reduced. In other words, the contact area between the electrode 4 and the protrusion 3 can be increased as much as possible, and the electrical resistance at the contact surface between the electrode 4 and the protrusion 3 is reduced. That is, the above-mentioned two matters can be made compatible, and the power generation efficiency of the fuel cell is improved.

  Furthermore, since the projection part 3 is comprised with the sintered compact, even if the shape of the projection part 3 is complicated, the shaping | molding can be performed easily. That is, according to the example of FIG. 10, it is not necessary to finely process the surface of the protrusion 3 that contacts the electrode 4 by machining or the like, so that the material constituting the protrusion 3 is wasted or processed. Longer time is suppressed, and an increase in manufacturing cost of the separator 1 can be suppressed. Furthermore, since the projection part 3 is comprised with the sintered compact, the various electroconductive materials mentioned above can be used as a sintered compact which comprises the projection part 3, and the freedom degree of selection of the material increases. In particular, ceramics that are difficult to process can be used as the protrusions 3.

  FIG. 11 is a cross-sectional view schematically showing the separator 1 manufactured according to the present invention. The protrusion 3 is composed of a sintered body obtained by sintering a large number of conductive particles 24 and 25. That is, the protrusion 3 includes a large number of conductive particles 24 disposed in contact with the substrate 2 and a large number of conductive particles 25 disposed in contact with the large number of conductive particles 24 and the electrode 4. ing. And the particle diameter of the many electroconductive particle 24 arrange | positioned in contact with the board | substrate 2 is set larger than the particle diameter of the many electroconductive particle 25 arrange | positioned at the side which contacts the electrode 4. FIG. . Also in the example of FIG. 11, the same operational effects as those of the example of FIG. 10 can be obtained.

  FIG. 12 is a cross-sectional view schematically showing the separator 1 manufactured according to the present invention. The protrusion 3 is composed of a sintered body obtained by sintering a large number of conductive particles 26. Here, the particle diameters of many conductive particles 26 are set to two or more types, and the conductive particles 26 having different particle diameters are irregularly arranged. Further, a flat surface 27 is formed by polishing the surface of the protrusion 3 opposite to the substrate 2. The flat surface 27 and the electrode 4 are in contact with each other. Also in the example of FIG. 12, the same effect as that of the example of FIG. 10 can be obtained.

  Next, an example of the arrangement pattern of the protrusions 3 shown in FIGS. 10 to 12 will be described with reference to FIG. FIG. 13 is a plan view of the substrate 2, that is, a view of the substrate 2 viewed from the electrode 4 side. The example shown in FIG. 13A is an example in which each protrusion 3 is configured in a prismatic shape and the protrusions 3 are arranged in a matrix. The example shown in FIG. 13B is an example in which each protrusion 3 is configured in a strip shape along the planar direction of the substrate 2 and a plurality of rows are arranged along each width of the protrusion 3. The example shown in FIG. 13C is an example in which the protrusions 3 are bent and arranged in a crank shape. The example shown in (D) of FIG. 13 is an example in which each protrusion 3 is configured in an approximately elliptical shape, and a plurality of protrusions 3 are arranged in the major axis direction and the minor axis direction.

  Further, in the present invention, in the separator 1 shown in FIGS. 10 to 12, a conductive metal having higher corrosion resistance than the substrate 2 and the protrusion 3 on at least a part of at least one of the substrate 2 and the protrusion 3. Can also be coated. Here, the “surface” means a surface facing the electrode 4. For example, the protrusion 3 shown in FIG. 3 can be composed of the conductive particles shown in any of FIGS. When the separator 1 not provided with the corrosion resistant layer 6 is configured, the corrosion resistant coating 7 can be formed on the entire surface of the protrusion 3 and the surface of the substrate 2. Further, although not shown, a corrosion-resistant film can be formed only on the surface of the substrate 2 with respect to the separator 1 shown in FIGS.

  Further, in the separator 1 manufactured according to the present invention shown in FIGS. 10 to 12, the corrosion-resistant film can be formed only on the entire surface of the protrusion 3. Furthermore, in the separator 1 shown in FIGS. 10 to 12, the corrosion-resistant film can be formed only on the tip surface of the protrusion 3 that contacts the electrode 4. 10 to 12, when at least a part of the surface of the substrate 2 or the protrusion 3 is coated with the corrosion-resistant film 7 of FIG. 3, at least one of the substrate 2 or the protrusion 3. Even if the part is exposed to an oxidizing atmosphere or a reducing atmosphere, the corrosion is suppressed and the durability of the separator 1 is improved.

  10 to 13, the same effect as that of the specific example of FIG. 1 can be obtained. Further, in the examples of FIGS. 10 to 13, the same components as those in the specific examples of FIGS. 1 to 9 are denoted by the same reference numerals as those used in FIGS. 1 to 9, and the description thereof is omitted. . Here, the correspondence between the configuration of each specific example and the configuration of the separator 1 manufactured in the present invention will be described. The corrosion-resistant layer 6 corresponds to the corrosion-resistant film of the separator 1 manufactured in the present invention. The coating 7 corresponds to the conductive metal of the separator 1 manufactured in the present invention.

It is sectional drawing which shows typically an example of the separator manufactured in this invention. It is a figure which shows the shape and arrangement | sequence pattern of the protrusion part of the separator manufactured in this invention. It is sectional drawing which shows typically an example which gave corrosion resistance coating to the whole surface. It is a figure which shows typically the manufacturing process by the method of this invention. It is a schematic diagram for demonstrating the other example of the manufacturing method which concerns on this invention. It is a schematic diagram for demonstrating the further another example of the manufacturing method which concerns on this invention. It is a figure which shows typically the usage example of the structure of a fuel cell, ie, a separator. It is sectional drawing which shows typically the other example of the separator manufactured in this invention. It is a fragmentary sectional view which shows typically the other masking sheet which can be used by the plating method. It is sectional drawing which shows the other example of a separator typically. It is sectional drawing which shows the other example of a separator typically. It is sectional drawing which shows the other example of a separator typically. It is a figure which shows the planar shape of the projection part of FIGS. 10-12, and a planar arrangement pattern.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Separator, 2 ... Board | substrate, 3 ... Projection part, 4, 21, 22 ... Electrode, 6 ... Corrosion-resistant layer, 7 ... Corrosion-resistant film, 14 ... Through-hole, 15, 15a ... Masking sheet.

Claims (2)

In the method of manufacturing a fuel cell separator having a large number of protrusions that are brought into electrical contact with the surface of the electrode,
A masking member having a large number of through-holes is arranged on the surface of the conductive substrate, and in that state, the masking member is coated with a conductive material so that the masking member is bonded to the substrate through the through-holes and the surface side of the masking member. A method for producing a fuel cell separator, characterized in that the protrusions protruding from the surface of the masking member are formed, and the masking member is exposed at a portion between the protrusions.   The method for manufacturing a fuel cell separator according to claim 1, wherein the masking member is made of a corrosion-resistant material.

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