JP2008123958A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell in which corrosion is prevented at a site where a separator and a current collecting plate contact. <P>SOLUTION: In the fuel cell in which a first surface layer 16a of the separator 16 and a second surface layer 17a of the current collecting plate 17 contact, the first surface layer 16a is electro-chemically nobler than the second surface layer 17a. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell.

  A fuel cell system is a system that directly converts chemical energy of a fuel into electrical energy, and supplies a fuel gas containing hydrogen to the anode of a pair of electrodes provided with an electrolyte in between, and the other An oxidant gas containing oxygen is supplied to the cathode electrode, and electric energy is extracted from the electrodes by using the following electrochemical reaction that occurs at the pair of electrodes. Each electrode performs (1) and (2) reactions.

Anode reaction: H ₂ → 2H ⁺ + 2e ⁻ (1)
Cathode reaction: 2H ⁺ + 2e ⁻ + (1/2) O ₂ → H ₂ O (2)
The fuel gas supplied to the anode electrode is supplied by a method of supplying directly from a hydrogen storage device or a method of supplying a hydrogen-containing gas obtained by reforming a fuel such as methanol, gasoline, alcohol and natural gas. Examples of the hydrogen storage device include a high-pressure gas tank, a liquefied hydrogen tank, and a hydrogen storage alloy tank. Air is generally used as the oxidant gas supplied to the cathode electrode.

Conventionally, carbon separators that are press-molded with a composite material composed mainly of graphite or resin and graphite powder have been used as bipolar separators, but especially for the purpose of loading fuel cells on moving objects. In order to reduce the size and increase the power density associated therewith, developments have been made to use metal separators that can be made thinner. In the case where the separator material is a nonmetal such as carbon, electrolytic corrosion between the separator and the current collector plate did not occur in principle. However, the use of a metal separator causes a problem of electrolytic corrosion between the metal separator and the current collector plate. However, regarding the use of a metal separator, treatments such as multilayering, surface modification and coating are performed mainly for the purpose of improving the corrosion resistance and improving the performance of the metal separator on the side facing the membrane electrode assembly (Patent Document 1). 2 and 3).
JP 2002-75395 A JP 2002-63914 A JP 2005-190964 A

  Since the fuel cell has an electromotive voltage per unit cell of about 1.2 [V] or less, when used as a power source for a mobile body, the unit cell is stacked and connected in series to increase the voltage. A current collector plate for collecting the generated electricity is provided at both electrodes of the fuel cell, and the fuel cell is sandwiched between the current collector plates. Therefore, the current collector plate and the metal separator are opposed to each other at both electrode portions of the fuel cell. The part of the fuel cell where the separator and the current collector plate face each other is different if a metal material is used for the separator and the current collector plate, and the combination of the material of the separator and current collector plate or the material of the surface layer is not specified. There will be a metal contact. In this case, the opposing surface of the current collector plate and the separator may cause galvanic corrosion depending on the combination of the materials used, and when the separator side is the metal elution side (anode reaction side), the separator plate is thin. Perforation can occur due to corrosion. In addition to this, a fuel cell that is exposed to a change in potential accompanying a change in the operating load of the fuel cell, a change in the operating temperature of the fuel cell, and an atmosphere through which three fluids of dried or humidified fuel gas, oxidant gas, and refrigerant flow. It becomes a peculiar environment, and it becomes the environment where corrosion phenomenon including electric corrosion is promoted. In the case where the current collector plate side is electrochemically noble with respect to the separator, the separator undergoes an oxidation reaction, and the metal is eluted, so that the separator is perforated. Further, when the separator is made thick in order to prevent perforation of the separator, the cost increases because the amount of metal used increases in addition to an obstacle to improvement in output density due to downsizing of the fuel cell system. There is no example that defines the combination of materials between the metal separator and the current collector plate, considering the corrosion resistance against electric corrosion on the surface facing the current collector plate as a problem.

  The present invention has been made to solve the above problems, and a fuel cell according to the present invention is a fuel cell in which a first surface layer of a separator and a second surface layer of a current collector plate are in contact with each other. The first surface layer is electrochemically more noble than the second surface layer.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel cell by which corrosion was prevented in the site | part which a separator and a current collector plate contact is provided.

  Hereinafter, a fuel cell according to an embodiment of the present invention will be described. In the embodiment of the present invention, an example applied to a polymer electrolyte fuel cell using a polymer electrolyte membrane is shown.

First Embodiment FIG. 1 is a perspective view showing an appearance of a fuel cell stack 10 including a fuel cell according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line II-II of the fuel cell stack 10 shown in FIG. 1, and shows both ends as a schematic diagram when implemented as a stack. 3 is a cross-sectional view taken along line III-III of the fuel cell stack 10 shown in FIG. 1, and is a cross-sectional view of the fuel cell stack 10 in a plane perpendicular to the flow direction of gas and refrigerant. 2 and 3 show an example in which the fuel cell stack 10 is configured by monotonically stacking the anode separator 15 and the cathode separator 16 to both ends of the fuel cell stack 10. For convenience, description will be made based on the configuration example shown in FIGS. FIG. 4 is a partially enlarged view of FIG. 3 and is a schematic view of a portion where the cathode separator 16 and the current collector plate 17 are in contact with each other. FIG. 5 is a graph showing a result of comparing the relationship of the corrosion of the separator material or the surface layer with respect to time when the fuel cell according to the first embodiment of the present invention is implemented with a conventional combination.

  As shown in FIG. 1, a fuel cell stack 10 includes an electrolyte membrane electrode assembly 14 (MEA) composed of an electrolyte membrane 11 and a catalyst electrode 12 and an anode separator 15 and a cathode that sandwich a gas diffusion layer 13. The separator 16 is configured by stacking a plurality of single cells serving as a basic unit for generating power by an electrochemical reaction. These elements stacked in the fuel cell stack 10 are fixed by fastening a pair of current collecting plates 17 provided at both ends in the stacking direction with fastening bolts (not shown). The fuel cell stack 10 may be fixed by a spring mechanism that applies a fastening force. The current collector plate 17 has a function of collecting the power generated by the fuel cell stack 10 at both ends, and is connected to a device driven by electricity and a device storing electricity through wiring. As shown in FIG. 1, the fuel cell stack 10 includes an anode gas supply line for supplying an anode gas containing hydrogen such as hydrogen gas to each cell, a cathode gas supply line for supplying cathode gas, and a cooling device. A manifold hole 28 that functions as a cooling water supply line for supplying water is provided. The stacking direction is not limited to the vertical direction and may be any direction. In the following example, the upper and lower sides are defined according to FIGS. That is, the stacking direction of the fuel cell stack 10 is defined as the vertical direction. In the first embodiment of the present invention, the fuel cell stack 10 is formed by stacking a plurality of single cells, but the same effect can be obtained even in the case of a single cell having a single stack.

  As the electrolyte membrane 11, a fluorine-based cation exchange membrane can be used, and other than that, for example, a hydrocarbon-based membrane may be used. The catalyst electrode 12 may be formed by hot-pressing platinum-supported carbon onto an electrolyte exchange membrane. For example, an alloy with other metal such as ruthenium may be used instead of platinum, and activated carbon as a support. Alternatively, graphite or the like may be used. Further, a catalyst may be supported on the gas diffusion layer 13 side. Although carbon paper can be used for the gas diffusion layer 13, a conductive porous body such as carbon cloth or metal can also be used. Different specifications may be used for both anode and cathode.

  The anode separator 15 and the cathode separator 16 were formed by press forming an austenitic stainless steel material and forming a channel shape through which a fluid passes. At this time, the separator material may be another metal such as aluminum or titanium, or may be a ferrite material as long as it is a stainless steel material. In addition, surface treatment such as plating or coating may be performed to improve corrosion resistance and electrical conductivity. As the forming method, machining, etching, or the like can be used. An anode gas flow path 18 for supplying an anode gas (hydrogen-containing gas) is formed in the anode separator 15, and a cathode gas flow path 19 for supplying a cathode gas (mainly air) is formed in the cathode separator 16. Has been. A refrigerant flow path 20 for flowing a refrigerant (mainly cooling water) is formed on each back surface. Although the compression seal 21 utilizing the reaction force of the compression force of the anode separator 15 and the cathode separator 16 is used for sealing the refrigerant, it can be sealed by welding.

  In order to prevent the anode gas and the cathode gas from leaking to the outside, a sealing material 22 is disposed on the electrolyte membrane 11 side between the joined body of the electrolyte membrane 11, the anode separator 15, and the cathode separator 16. The sealing material 22 is formed of, for example, silicon, and the sealing material 22 is crushed by pressure and maintains a sealing property by obtaining a reaction force. Although the sealing material 22 is formed and disposed on the seal support layer 23, the seal support layer 23 may not be provided. The sealing material 22 may be formed on the separator side.

In the fuel cell stack 10 including the fuel cell according to the first embodiment of the present invention, the first surface layers 15a and 16a of the separators 15 and 16 and the second surface layer 17a of the current collector plate 17 are in contact with each other. The first surface layers 15a and 16a are electrochemically more noble than the second surface layer 17a. As an example of the combination, gold plating can be used for the first surface layer, and silver plating can be used for the second surface layer. The first surface layers 15a and 16a may be made of the same material as the base material of the separators 15 and 16. Similarly, the second surface layer 17a may be made of the same material as the base material of the current collector plate 17. Even when the surface layer is made of the same material as the base material, the same effect can be obtained if the first surface layers 15a and 16a of the separator are electrochemically nobler than the second surface layer 17a of the current collector. . FIG. 4 is a schematic view of a portion where the cathode separator 16 and the current collector plate 17 are in contact with each other. The first surface layer 16 a of the cathode separator 16 includes contact portions 16 a ₂ , 16 a ₄ , 16 a ₆ , 16 a ₈ that are in contact with the second surface layer 17 a of the current collector plate 17, and the second surface of the current collector plate 17. Non-contact portions 16a ₁ , 16a ₃ , 16a ₅ , 16a ₇ , 16a ₉ that do not contact the layer 17a, and the second surface layer 17a of the current collector plate 17 is the first surface layer 16a of the cathode separator 16. Contact portions 17a ₂ , 17a ₄ , 17a ₆ , and 17a ₈ that are in contact with each other, and non-contact portions 17a ₁ , 17a ₃ , 17a ₅ , 17a ₇ , and 17a ₉ that are not in contact with the first surface layer 16a of the cathode separator 16. Have. Non-contact portions 16a ₁ , 16a ₃ , 16a ₅ , 16a ₇ , 16a ₉ of the first surface layer 16a and non-contact portions 17a ₁ , 17a ₃ , 17a ₅ , 17a ₇ , 17a ₉ of the second surface layer 17a are The flow path 24 is defined. As shown in FIG. 3, the anode separator 15 defines a flow path 25 by the anode separator 15 and the current collector plate 17. A fluid that prevents oxidation may flow through the channels 24 and 25. When gold plating is applied to the first surface layer shown as an example and silver plating is applied to the second surface layer, the first surface layers 15a and 16a are electrochemically noble compared to the second surface layer 17a. Become. Therefore, even when galvanic corrosion due to contact with different metals occurs, the silver of the second surface layer 17a is on the anode reaction (oxidation reaction) side, so that the separators 15 and 16 become thinner in the thickness direction due to elution, and the holes are perforated. Deters from reaching Further, when a fluid for preventing oxidation is supplied to the flow paths 24 and 25, corrosion at the contact portion between the cathode separator 16 and the current collector plate 17 can be suppressed from environmental factors to which the portion is exposed. For this reason, the fuel cell in which corrosion is prevented at the contact portions 16a ₂ , 16a ₄ , 16a ₆ and 16a ₈ where the separators 15 and 16 and the current collector plate 17 are in contact with each other is provided.

  Here, as an example, gold plating is applied to the first surface layers 15a and 16a, and silver plating is applied to the second surface layer 17a. However, the material or surface layer of the separators 15 and 16 is the surface of the current collector plate 17. If it is electrochemically noble or equivalent, the effect of preventing corrosion can be obtained. Moreover, as long as it is formed from a metal material, for example, the metal species may be different depending on a surface layer or a portion interspersed with a plurality of types of metal materials. For example, the first surface layer (the surface layer of the separators 15 and 16) includes any metal selected from gold, platinum, ruthenium, palladium, rhodium, iridium, osmium, silver, copper, and metal nitride, The second surface layer (the surface layer of the current collector plate 17) preferably contains any metal selected from silver, copper, and metal nitride. The surface layer of the separators 15 and 16 can be made electrochemically noble or equivalent to the surface layer of the current collector plate 17 by appropriately defining and selecting the electrochemical height from among them. In addition to preventing the holes 15 and 16 from being perforated and improving the durability of the separators 15 and 16, the thickness can be reduced. For example, a combination using silver on the surface on the separators 15 and 16 side and copper on the surface on the current collector plate 17 side, or a combination using metal nitrides on both the surfaces on the separators 15 and 16 side and the current collector plate 17 side can be given. . Moreover, the copper and metal nitride shown in the present embodiment are particularly inexpensive, and there is an effect of cost reduction by appropriately selecting the relationship with the material of the separators 15 and 16 surface.

  Note that the expression electrochemically noble may be understood as being almost synonymous with the expression that the standard electrode potential is high. In this embodiment, when the level of the electrochemical potential of the material used for the material of the separators 15 and 16 and the current collector plate 17 or the surface layer is unknown, the material is immersed in an acid solution typified by sulfuric acid, for example. Then, a reference electrode typified by a silver-silver chloride electrode is inserted, and the immersion potential when the material is immersed in the acid solution is measured. The higher measured potential can be judged electrochemically noble.

  In this way, when elution on the separator side can be prevented as in this embodiment, there is no risk of fluid leakage due to perforation of the separator, so the thickness of the separator is reduced with the aim of higher output density by downsizing Is also possible.

  FIG. 5 is a graph showing a result of comparing the relationship of the corrosion of the separator material or the surface layer with respect to time when the fuel cell according to the first embodiment of the present invention is implemented with a conventional combination. In the conventional combination, the separator surface becomes a base with respect to the current collector plate. The conventional combination A indicated by A in the figure is a combination in which the difference in the immersion potential between the current collector and the separator is larger than the conventional combination B indicated by B in the figure. The curve indicated by C in the figure shows the result of the fuel cell according to the first embodiment of the present invention, and shows the case where the separator is electrochemically noble than the current collector plate. In the figure, the vertical axis indicates the metal elution amount from the separator, and the larger the metal elution amount, the faster the perforation of the separator occurs. The metal elution amount was determined by quantifying the metal ions contained in the liquid water discharged from the fuel cell by ICP-MS (inductively coupled plasma mass spectrometer). In the case of a combination in which the difference in the immersion potential between the current collector and the separator was larger, the amount of metal eluted from the separator increased as the operating time became longer. In addition, when the separator was electrochemically more noble than the current collector plate, the metal elution amount was suppressed, and the metal elution amount remained low even when the operation time was long. Thus, it was shown that when the separator is electrochemically more noble than the current collector plate, the durability of the separator is improved.

  The same effect can be obtained when the surface layer of the separators 15 and 16 and the surface layer of the current collector plate 17 are electrochemically equivalent, and the surface layer of the separators 15 and 16 is thicker than the surface layer of the current collector plate 17. can get. In this case, since the materials or surface layers of the separators 15 and 16 and the current collector plate 17 are electrochemically equivalent, the electrolytic corrosion of the separators 15 and 16 and the current collector plate 17 is suppressed by the combination of the materials. However, there is a possibility that the surface layers of the separators 15 and 16 are exposed to a corrosive environment peculiar to the fuel cell due to large changes in temperature, potential, and atmospheric gas accompanying the operation of the fuel cell, and change over time, and deteriorate or deteriorate. is there. Therefore, even when the surface layers of the separators 15 and 16 are changed, the surface on the side of the separators 15 and 16 with respect to the surface layer of the current collector plate 17 in order to suppress the elution of the material of the separators 15 and 16. By increasing the thickness of the layer, the durability of the surface layers of the separators 15 and 16 is improved. For example, when the surface layers of the separators 15 and 16 and the current collector plate 17 are both processed by silver plating, the thickness of the silver plating layer on the separators 15 and 16 side is increased, and the corrosion resistance on the separators 15 and 16 side is increased. Achieve by improving. Thus, by increasing the thickness of the material or the surface layer on the separators 15 and 16 side, the possibility of deterioration due to a defect in the material or surface layer on the separators 15 and 16 side or a change with time decreases. As described above, the corrosion resistance of the separators 15 and 16 is improved, so that perforation due to metal elution from the separators 15 and 16 is prevented, and the durability of the separators 15 and 16 is improved. Thinning can be achieved.

In the fuel cell according to the first embodiment of the present invention, the flow paths 24 and 25 are provided, and the antioxidant can flow there. In this case, the corrosivity between the separators 15 and 16 and the current collector plate 17 is changed by the antioxidant. For this reason, the flow paths 24 and 25 are filled with an antioxidant for preventing metal oxidation to suppress corrosion. One example is ammonia. In addition to ammonia, fluids that prevent metal oxidation include sodium hydroxide, potassium hydroxide, dicyclohexylammonium nitrite, cyclohexylamine carbonate, ethanolamine carbonate, and hydrogen. Thus, by flowing the antioxidant, the contact portions 16a ₂ , 16a ₄ , 16a ₆ , 16a ₈ and the contact portions 17a ₂ , 17a ₄ , 17a ₆ , 17a ₈ between the separators 15, 16 and the current collector plate 17 are used. , Metal elution due to the oxidation reaction of the separators 15 and 16 can be suppressed. For this reason, in addition to preventing the separators 15 and 16 from being perforated and improving the durability of the separators 15 and 16, the cost can be reduced and the thickness can be reduced.

  The antioxidant may be present in the space defined by the non-contact portion on the anode side of the fuel cell, or it may be on the cathode side. Further, when the separator 15 and the separator 16 are monotonously repeated and stacked, different fluids can be easily passed through the flow paths 24 and 25 defined by the separators 15 and 16 and the current collector plate 17. As the fluid for preventing metal oxidation, for example, ammonia, sodium hydroxide, potassium hydroxide, dicyclohexylammonium nitrite, cyclohexylamine carbonate, ethanolamine carbonate, and hydrogen can be used.

  Among them, the antioxidant is preferably a hydrogen-containing gas. In this case, metal elution due to the oxidation reaction of the separators 15 and 16 is suppressed between the separators 15 and 16 and the current collector plate 17. For this reason, the separators 15 and 16 can be prevented from being perforated, the durability of the separators 15 and 16 can be improved, and the cost can be reduced and the thickness can be reduced.

  Furthermore, the hydrogen-containing gas is preferably a gas used for the fuel gas of the fuel cell. In this case, no special mechanism is required to prevent oxidation, and it can be shared with fuel gas, leading to simplification of the entire system and cost reduction. The hydrogen-containing gas suppresses metal elution due to the oxidation reaction of the separators 15 and 16 between the separators 15 and 16 and the current collector plate 17. For this reason, perforation of the separators 15 and 16 can be prevented, and the durability of the separators 15 and 16 is improved.

  As described above, in the fuel cell according to the first embodiment of the present invention, in the fuel cell in which the first surface layer of the separator and the second surface layer of the current collector plate are in contact, the first surface layer Is electrochemically more noble than the second surface layer, so that a fuel cell in which corrosion is prevented at a portion where the separator and the current collector plate contact is provided.

Second Embodiment Next, a fuel cell according to a second embodiment of the present invention will be described. FIG. 6 is a partially enlarged view of the fuel cell according to the second embodiment of the present invention, and is a schematic view of a portion where the separator 26 and the current collector plate 17 are in contact with each other. In FIG. 5, the first embodiment differs from the first embodiment only in that the first surface layer 26 a of the separator 26 is provided only on the rib formed on the surface of the separator 26. Since the other configurations are substantially the same, the same reference numerals are given to the same components and the description thereof is omitted.

As shown in FIG. 6, in the second embodiment, the first surface layer 26 a is provided only at the portion where the separator 26 and the current collector plate 17 are in contact, and the second surface of the first surface layer 26 a and the current collector plate 17 is provided. The surface layer 17a was in contact, and the first surface layer 26a was an electrochemically noble combination over the second surface layer 17a. As an example of the combination, the effect can be obtained by using gold plating for the first surface layer and silver plating for the second surface layer. The first surface layer 26 a of the separator 26 has contact portions 26 a ₁ , 26 a ₂ , 26 a ₃ , and 26 a ₄ that are in contact with the second surface layer 17 a of the current collector plate 17. The surface layer 17 a includes contact portions 17 a ₂ , 17 a ₄ , 17 a ₆ , and 17 a ₈ that are in contact with the first surface layer 26 a of the separator 26, and a non-contact portion 17 a ₁ that is not in contact with the first surface layer 26 a of the separator 26. 17a ₃ , 17a ₅ , 17a ₇ , and 17a ₉ . The non-contact portions 26 ₁ , 26 ₂ , 26 ₃ , 26 ₄ , 26 ₅ and the non-contact portions 17 a ₁ , 17 a ₃ , 17 a ₅ , 17 a ₇ , 17 a _{9 that} are not in contact with the current collector plate 17 of the separator 26 are flow paths 27. Is defined.

In the second embodiment, the contact portions 26a ₁ , 26a ₂ , 26a ₃ , 26a ₄ and the contact portions 17a ₂ , 17a ₄ , 17a ₆ , 17a ₈ where the separator 26 and the current collector plate 17 are in contact with each other On the other hand, since the separator 26 side is electrochemically noble, the second surface layer 17a of the current collector plate 17 becomes the anode reaction (oxidation reaction) side even when electrolytic corrosion due to contact of different metals occurs, and the separator 26 material Elution and deterring from being perforated. In this way, perforation of the separator 26 due to electrolytic corrosion between the separator 26 and the current collector plate 17 is prevented with a minimum material specification. For this reason, in addition to improving the durability of the separator 26, when the material or surface layer of the separator 26 is expensive, such as a noble metal, the first surface layer is formed only at the portion where the separator 26 and the current collector plate 17 are in contact with each other. It is also possible to reduce the cost by forming. In addition, the fuel cell can be made thinner. In the present embodiment, the separator 26 can be applied to either an anode separator or a sword separator.

Third Embodiment Next, a fuel cell according to a third embodiment of the present invention will be described. FIG. 7 is a partially enlarged view of the fuel cell according to the third embodiment of the present invention, and is a partial schematic view of the separator 36. In FIG. 7, compared with the first embodiment, manifold holes 37, 38, 39 forming the first surface layer 40 of the separator 36 and the manifold of the surface 36 b in contact with the current collector plate 17 of the separator 36, Only the point provided between the seal 29 and the seal 29 is different. Since the other configurations are substantially the same, the same reference numerals are given to the same components and the description thereof is omitted.

  In FIG. 7, the lower surface of the separator 36 is a surface 36 a that does not contact the current collector plate 17, and the upper surface is a surface 36 b that contacts the current collector plate 17. The separator 36 is provided with a seal 29 that prevents fluid leakage around the manifold holes 37, 38, and 39, and the separator 36 is provided with a seal 41 that prevents fluid leakage. The seal 28 may not be arranged like the non-seal portion 40a around the manifold hole 39 depending on the type of fluid to flow in the surface direction. In FIG. 7, the fluid flows in the direction indicated by the arrow D, and the fluid flows in the separator surface direction only in the portion where the seal is not disposed. A first surface layer 40 was formed between the manifold holes 37, 38, 39 and the seal 29, and a second surface layer 17 a was formed on the surface of the current collector plate 17.

  Even in this configuration, a combination is provided in which the separator 36 side is electrochemically noble. As a result, even when electrolytic corrosion due to contact of different metals occurs, the surface of the current collector plate 17 becomes the anode reaction (oxidation reaction) side, and the separator 36 material is eluted and the separator 36 is prevented from being perforated. In particular, when the vicinity of the manifold hole is perforated and mixed with other fluids, fluid is supplied to all cells downstream of the manifold hole with other fluids mixed in, reducing performance and durability. In this embodiment, this phenomenon is prevented. In the present embodiment, the separator 36 can be applied to either an anode separator or a cathode separator.

Fourth Embodiment Next, a fuel cell according to a fourth embodiment of the present invention will be described. FIG. 8 is a partial enlarged view of the fuel cell according to the fourth embodiment of the present invention, and is a schematic view of a portion where the separator 46 and the current collector plate 17 are in contact with each other. FIG. 9 is a partially enlarged view of FIG. In FIG. 8, compared with the thing of 1st embodiment, only the point which has the welding parts 48 and 49 in the separator 46 surface (1st surface layer) is different. Welding is used for the purpose of joining separators and sealing fluids. Since the other configurations are substantially the same, the same reference numerals are given to the same components and the description thereof is omitted.

In the fourth embodiment of the present invention, the first surface layer 46a of the separator 46 and the second surface layer 17a of the current collector plate 17 are in contact with each other. The first surface layer 46a and the welded portion 49 are characterized by being electrochemically noble over the second surface layer 17a. FIG. 8 is a schematic view of a portion where the separator 46 and the current collector plate 17 are in contact with each other. The first surface layer 46 a of the separator 46 includes contact portions 46 a ₂ , 46 a ₄ , 46 a ₆ , 46 a ₈ that are in contact with the second surface layer 17 a of the current collector plate 17, and the second surface layer of the current collector plate 17. The second surface layer 17a of the current collector plate 17 is in contact with the first surface layer 46a of the separator 46. The non-contact portions 46a ₁ , 46a ₃ , 46a ₅ , 46a ₇ , 46a ₉ do not contact the 17a. Contact portions 17a ₂ , 17a ₄ , 17a ₆ , 17a ₈ and non-contact portions 17a ₁ , 17a ₃ , 17a ₅ , 17a ₇ , 17a ₉ that do not contact the first surface layer 46a of the separator 46. Non-contact portions 46a ₁ , 46a ₃ , 46a ₅ , 46a ₇ , 46a ₉ of the first surface layer 46a and non-contact portions 17a ₁ , 17a ₃ , 17a ₅ , 17a ₇ , 17a ₉ of the second surface layer 17a are The flow path 47 is defined. In the contact portions 46a ₂ , 46a ₄ , 46a ₆ , 46a ₈ , the separator 46 has welded portions 48, 49 on the surface, and the welded portion and the welded portion 48 not contacting the second surface layer of the current collector plate are collected. A description will be given separately for the welded portion 49 that is in contact with the second surface layer of the electric plate. When the welded portions 48 and 49 are welded after the first surface layer is formed, the metal composition may change due to the temperature effect exposed during welding, or the base material portion may be exposed.

After welding, the welded portion 49 comes into contact with the contact portions 17a ₂ , 17a ₄ , 17a ₆ , 17a _{8 of the current} collector plate 17. In the present embodiment, the welded portion 49 in contact with the current collector plate is electrochemically more noble than the contact portions 17a ₂ , 17a ₄ , 17a ₆ , and 17a _{8 of the current} collector plate 17. At this time, it is desirable to grasp the physical properties after welding, in which the welded portion 49 is changed by welding after the welding, by a preliminary test. As a result, even when the metal composition is changed by welding, the anode reaction (oxidation reaction) on the separator 46 side is suppressed even on the surfaces of the contact portions 46a ₂ , 46a ₄ , 46a ₆ , 46a ₈ that are in contact with the welded portion 49. And perforation is prevented. In the present embodiment, the separator 46 can be applied to either an anode separator or a cathode separator.

Fifth Embodiment Next, a fuel cell according to a fifth embodiment of the present invention will be described. FIG. 10 is a partial enlarged view of the fuel cell according to the fifth embodiment of the present invention, and is a partial schematic view of the separator 56. 10 is different from the third embodiment only in that a mechanism (notch) 61a through which anode gas flows is provided and a seal portion 61b is newly provided in a non-seal portion around the manifold hole 59. Since the other configurations are substantially the same, the same reference numerals are given to the same components and the description thereof is omitted.

  In FIG. 10, the lower surface of the separator 56 is a surface 56 a that does not contact the current collector plate 17, and the upper surface is a surface 56 b that contacts the current collector plate 17. The separator 56 is provided with a seal 61 that prevents fluid leakage around the manifold holes 57, 58, and 59. The separator 56 is provided with a seal 62 that prevents fluid leakage. The seal 61 is provided with a notch 61a in a part around the manifold hole 57 so that the anode gas flows in the direction indicated by the arrow E and communicates with the flow path defined by the separator 56 and the current collector plate 17. . A seal portion 61b is newly provided around the manifold hole 59. A first surface layer 60 was formed between the manifold holes 57, 58, 59 and the seal 61, and the surface layer of the current collector plate 17 was a second surface layer 17a. The first surface layer 60 may be applied to the entire surface of the separator 56b. In the present embodiment, the anode gas is supplied to a flow path (not shown) defined by the separator 56 and the current collector plate 17 to prevent corrosion between the separator 56 and the current collector plate 17. The anode gas was a hydrogen-containing gas. The seals 61 and 62 and the seal portion 61b can be formed of a material such as silicon, EPDM, or fluorine rubber.

  In the fifth embodiment of the present invention, the flow path defined between the separator 56 and the current collector plate 17 is used as the anode gas (fuel gas) flowing through the anode gas flow path 18. In addition, it is possible to easily supply the antioxidant to the flow path, and it is possible to suppress an increase in size and cost due to a complicated system. Moreover, the oxidation reaction of the metal material can be suppressed by the antioxidant, and the separator can be prevented from being perforated. Furthermore, the separator 56 side becomes electrochemically noble. Therefore, even when electrolytic corrosion due to the contact of different metals occurs, silver on the surface of the current collector plate 17 becomes the anode reaction (oxidation reaction) side, and the material of the separator 56 is prevented from being eluted and perforated. The anode gas supplied to the flow path may be supplied by branching the anode gas as fuel and then discharged, or the anode gas system may be used as a circulation system and supplied to the flow path again. Absent. In the present embodiment, the separator 56 can be applied to either an anode separator or a cathode separator.

  Although the embodiment of the present invention has been described above, it should not be understood that the description and drawings that constitute part of the disclosure of the embodiment limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

1 is a perspective view showing an appearance of a fuel cell stack including a fuel cell according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view of the fuel cell stack taken along line II-II. FIG. 3 is a cross-sectional view of the fuel cell stack taken along line III-III. FIG. 4 is a partially enlarged view of FIG. 3. It is a graph which shows the result of having compared the relationship of the corrosion of a separator raw material or a surface layer with respect to time at the time of implementing the fuel cell which concerns on 1st embodiment of this invention with the conventional combination. It is the elements on larger scale of the fuel cell which concerns on 2nd embodiment of this invention. It is the elements on larger scale of the fuel cell which concerns on 3rd embodiment of this invention. It is the elements on larger scale of the fuel cell which concerns on 4th embodiment of this invention. It is the elements on larger scale of FIG. It is the elements on larger scale of the fuel cell which concerns on 5th embodiment of this invention.

Explanation of symbols

10 fuel cell stack 11 electrolyte membrane 12 catalytic electrode 13 the gas diffusion layer 14 membrane electrode assembly 15 anode separator 15a, 16a first surface layer 16 cathode separator _{16a 1, 16a 3, 16a 5} , 16a 7, 16a 9 noncontact part _{16a 2, 16a 4, 16a 6} , 16a 8 contact portion 17 current collector plate 17a second surface layer _{17a 1, 17a 3, 17a 5} , 17a 7, 17a 9 non-contact portion 17a _{2, 17a} 4, _17a 6, 17a ₈ contact portion 18 Anode gas flow path 19 Cathode gas flow path 20 Refrigerant flow path 21 Compression seal 22 Seal material 23 Seal support layers 24, 25 Flow path

Claims (11)

In the fuel cell in which the first surface layer of the separator and the second surface layer of the current collector plate are in contact with each other,
The fuel cell according to claim 1, wherein the first surface layer is electrochemically more noble than the second surface layer.   The fuel cell according to claim 1, wherein the separator includes a rib including the first surface layer.   3. The fuel cell according to claim 1, wherein the separator includes the first surface layer between a manifold hole and a seal.   The fuel cell according to any one of claims 1 to 3, wherein the separator has a welded portion on the first surface layer. The first surface layer includes any metal selected from gold, platinum, ruthenium, palladium, rhodium, iridium, osmium, silver, copper, and metal nitride,
5. The fuel cell according to claim 1, wherein the second surface layer includes any metal selected from silver, copper, and metal nitride.   6. The first surface layer and the second surface layer are electrochemically equivalent, and the first surface layer is thicker than the second surface layer. The fuel cell according to any one of the above.   The first surface layer has a contact portion that contacts the second surface layer and a non-contact portion that does not contact the second surface layer, and the non-contact portion defines a flow path for the antioxidant. The fuel cell according to any one of claims 1 to 6, wherein the fuel cell is formed.   The fuel cell according to any one of claims 1 to 7, wherein the antioxidant is present in a flow path defined by the non-contact portion on the anode side of the fuel cell.   The fuel cell according to any one of claims 1 to 8, wherein the antioxidant is present in a flow path defined by the non-contact portion on the cathode side of the fuel cell.   The fuel cell according to any one of claims 7 to 9, wherein the antioxidant is a hydrogen-containing gas.   The fuel cell according to claim 10, wherein the hydrogen-containing gas is a gas used for a fuel gas of the fuel cell.

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