JP5572534B2 - Solid polymer electrolyte fuel cell - Google Patents

Description

  The present invention relates to a solid polymer electrolyte fuel cell using a solid polymer having hydrogen ion conductivity as an electrolyte.

  In recent years, fuel cells have attracted attention as highly efficient energy conversion devices. Such fuel cells are classified into several types according to the difference in electrolyte. Among these, a solid polymer electrolyte fuel cell using a solid polymer having hydrogen ion conductivity as an electrolyte can obtain a high output density with a compact structure and can be operated by a simple system. Therefore, it has attracted a great deal of attention as a power source for space use, vehicle use, home use and portable use.

  A solid polymer electrolyte fuel cell is generally configured as a laminated structure in which a plurality of unit cells are stacked. The unit cell includes a joined body in which a solid polymer electrolyte membrane is sandwiched between a fuel electrode and an oxidant electrode, and a set of separators arranged outside the joined body. Each of the fuel electrode and the oxidant electrode has a gas diffusion layer made of a conductive porous material. Furthermore, the gas diffusion layer has a structure in which a catalyst layer containing a catalyst and a solid polymer electrolyte is disposed on the surface facing the joined body. Further, the battery stack is configured by alternately laminating the joined bodies and the separators and laminating a plurality of unit cells.

  By the way, the solid polymer electrolyte membrane has hydrogen ion conductivity that carries hydrogen ions generated at the fuel electrode to the oxidant electrode, together with a reaction gas separation function for separating the fuel gas and the oxidant gas. In order to maintain this hydrogen ion conductivity satisfactorily, it is necessary to replenish water in order to maintain the wetness of the solid polymer electrolyte membrane. To the conventional battery stack, moisture is supplied by supplying the reaction gas used for the battery reaction from the outside of the battery stack in a humidified state in advance.

  On the other hand, when the battery stack generates power over a long period of time, the generated water generated by the battery reaction stays downstream in the unit cell surface, particularly inside the oxidant electrode, and the supply of the reaction gas is hindered. May cause a flooding phenomenon. In order to prevent this flooding phenomenon, the moisture in the unit cell surface may be adjusted by previously bringing the reaction gas supplied from the upstream portion into the battery stack into a low moisture state. In this case, for example, in the vicinity of the inlet of the fuel gas supply groove or the oxidant gas supply groove of the separator, or the fuel electrode surface or the oxidant electrode of the joined body facing the inlet, corresponding to the cell surface inlet of the reaction gas. At the outer peripheral portion of the surface, water generated by the battery reaction is carried away by a gas having a low water content, so that it is exposed to a lower humidified state than the central portion in the cell surface.

  If such a low humidification state continues, the solid polymer electrolyte membrane dries at the outer periphery of the fuel electrode surface or oxidant electrode surface of the assembly, and at the catalyst layer interface due to the generation of hydrogen peroxide as a side reaction product. Chemical degradation such as depletion of the solid polymer electrolyte membrane proceeds. In addition, at the outer periphery of the solid polymer electrolyte membrane, at the boundary between the catalyst layer and the surface of the solid polymer electrolyte membrane, a deterioration occurs due to the influence of mechanical stress such as shear stress due to local contraction caused by bending or stepping. This causes pinholes and cracks. Due to such deterioration factors, there is a concern that the solid polymer electrolyte membrane may be broken and easily cross-leak.

  As these measures, it is considered to reinforce the solid polymer electrolyte membrane by forming a frame-shaped protective film so as to cover the outer peripheral portion of the solid polymer electrolyte membrane (see, for example, Patent Document 1). ). In addition, to protect the solid polymer electrolyte membrane, the outer periphery of the solid polymer electrolyte membrane is covered with a fluorocarbon resin as a gas seal material for the insulating spacer to prevent direct exposure of the reaction gas. It has also been studied to suppress the deterioration of the solid polymer electrolyte membrane (for example, see Patent Document 2).

JP-A-5-2442897 JP-A-10-308228

  As described above, in the conventional solid polymer electrolyte fuel cell, when the reaction gas is continuously supplied with low humidity, the outer boundary of the catalyst layer in the cell plane corresponding to the inlet of the fuel gas or oxidant gas In the vicinity of the part, the generated water generated by the battery reaction is accelerated to evaporate and becomes dry. For this reason, it becomes difficult to keep the electrolyte membrane moist, and there is a possibility of causing pinholes and cracks due to deterioration of the electrolyte membrane. Even in a configuration in which a gas seal layer is installed so as to cover the outer peripheral portion of the solid polymer electrolyte membrane, although the solid polymer electrolyte membrane can be reinforced to some extent, deterioration due to drying cannot be sufficiently prevented. .

  Further, in the configuration in which the outer peripheral portion of the gas diffusion layer of the fuel electrode and the oxidant electrode is sealed, part of the fuel gas and the oxidant gas is transferred from the gas supply groove to the solid polymer electrolyte membrane via the gas diffusion layer. May be exposed directly. In this case, reaction gas cross-leakage occurs due to pinhole formation as a result of deterioration of the solid polymer electrolyte membrane due to changes in the humidification conditions of the reaction gas during power generation and thermal expansion and contraction due to thermal history. There are concerns.

Further, in the catalyst layer of the fuel electrode and the oxidant electrode, hydrogen peroxide (H ₂ O ₂ ) is generated as a side reaction product of the cell reaction, and H ₂ O ₂ causes a decomposition reaction to generate a hydroxy radical (OH ⁻ ) And other radicals are generated. Some of the generated radicals move in the catalyst layer and act to cut the polymer structure of the solid polymer electrolyte constituting the catalyst layer and the solid polymer electrolyte membrane adjacent to the catalyst layer. As a result, chemical degradation due to decomposition and wear of the catalyst layer and the solid polymer electrolyte membrane proceeds, and further, the mechanical strength of the solid polymer electrolyte membrane is lowered to generate pinholes and cracks, thereby There is a concern that it may cause a cross leak with the oxidant electrode. In particular, in a state where the reaction gas is supplied with low humidification, there is a concern of promoting the generation of the radicals by evaporation of moisture.

  As described above, in the configuration of a conventional solid polymer electrolyte fuel cell, there is a concern that pinholes may be formed due to long-term deterioration of the solid polymer electrolyte membrane, resulting in cross leak and hindering the cell reaction. It was. As a result, there are problems that the cell voltage characteristics are lowered and the battery life is shortened.

  The present invention has been made to solve the above-mentioned problems, and retains moisture in the solid polymer electrolyte membrane at the outer peripheral portion of the fuel electrode or the oxidizer electrode of the joined body and at the reaction gas inlet portion, thereby achieving wettability. To provide a solid polymer electrolyte fuel cell that can prevent cross leak due to deterioration of the solid polymer electrolyte membrane, exhibit stable voltage characteristics over a long period of time, and improve life characteristics. It is aimed.

A solid polymer electrolyte fuel cell according to an embodiment of the present invention is disposed on one surface of a solid polymer electrolyte membrane using a solid polymer having hydrogen ion conductivity as an electrolyte, and the solid polymer electrolyte membrane. A fuel electrode having a gas diffusion layer including a battery reaction surface in the center of the surface, an oxidant electrode disposed on the other surface of the solid polymer electrolyte membrane, and the solid polymer electrolyte membrane of the fuel electrode; Are disposed on the opposite surface, the fuel electrode side separator formed with a gas flow path for distributing and supplying fuel gas on the surface of the fuel electrode, and the solid polymer electrolyte membrane of the oxidant electrode disposed on the opposite side, the outer peripheral end of the oxidant electrode side separator gas flow path is formed for dispensing the oxidizing agent gas on the surface of the oxidizer electrode, the gas diffusion layer of the fuel electrode Gas passage of the fuel electrode side separator A portion corresponding to at least the gas inlet portion, and said arranged from the portion corresponding to the gas inlet portion so as to cover the range over the battery reaction surface and a polymer resin having a conductive material and a hydrophilic functional group And a coating layer that is formed so as to transmit the fuel gas.

  According to the present invention, stable voltage characteristics can be exhibited over a long period of time, and life characteristics can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a basic structure of a solid polymer electrolyte fuel cell according to a first embodiment with a part cut away. 1 is a cross-sectional view showing an overall configuration of a solid polymer electrolyte fuel cell according to a first embodiment. The top view which shows the example of arrangement | positioning of the coating layer used for the solid polymer electrolyte fuel cell of 1st Embodiment. Sectional drawing which shows the modification of 1st Embodiment. The top view which shows the modification of 1st Embodiment. The top view which shows the principal part structure of the solid polymer electrolyte fuel cell concerning 2nd Embodiment. The top view which shows the principal part structure of the solid polymer electrolyte fuel cell concerning 2nd Embodiment. FIG. 8 is a cross-sectional view taken along the line YY in FIG. The top view which shows the modification of this invention.

  Hereinafter, embodiments will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a perspective view showing a basic structure of a solid polymer electrolyte fuel cell according to a first embodiment of the present invention, with a part cut away. 2 is a cross-sectional view showing the overall configuration of the solid polymer electrolyte fuel cell according to the embodiment, and FIGS. 3A and 3B are plan views showing the main configuration. FIG. 2 corresponds to a cross section taken along the line XX ′ in FIG.

  As shown in FIG. 1, a solid polymer electrolyte membrane-electrode assembly 2 (hereinafter simply referred to as a “joint”) in a unit cell 1 includes a solid polymer electrolyte membrane 3 and the solid polymer electrolyte membrane 3. The fuel electrode 4 and the oxidant electrode 5 are disposed so as to be sandwiched between each other.

  The solid polymer electrolyte membrane 3 is a perfluorocarbon sulfonic acid membrane (for example, Nafion: manufactured by DuPont) having a thickness of about 10 to 100 μm. The fuel electrode 4 and the oxidant electrode 5 have gas diffusion layers 6 and 7 made of a conductive porous material such as carbon paper or carbon cloth. Further, the gas diffusion layers 6 and 7 of the fuel electrode 4 and the oxidant electrode 5 are arranged on the surfaces of the fuel electrode 4 and the oxidant electrode 5 facing the solid polymer electrolyte membrane 3, respectively. It has become. The joined body 2 is configured such that the gas diffusion layers 6 and 7 of the fuel electrode 4 and the oxidant electrode 5 face the solid polymer electrolyte membrane 3 so that the catalyst layers 8 and 9 are sandwiched therebetween, and further the adhesive layers 10 and 11, etc. And are joined by thermocompression bonding with a hot press or the like.

  The cell reaction surfaces 19 and 20 are formed in the ranges in contact with the catalyst layers at the center of the gas diffusion layers 6 and 7 of the fuel electrode 4 or the oxidant electrode 5, respectively. Airtight gas seal layers 16 and 17 are formed on the part. That is, gas seal layers 16 and 17 are formed on the outer peripheral portions of the fuel electrode 4 surface and the oxidizer electrode 5 surface of the assembly 2 so as to face the peripheral portions of the opposing separators 12 and 13, respectively. The gas seal layers 16 and 17 surround the outer periphery of the solid polymer electrolyte membrane 3 of the joined body 2 to prevent leakage of fuel gas and oxidant gas, and the fuel electrode 4 surface and the oxidant electrode 5 of the joined body 2. The insulation between the surfaces is secured.

  A pair of separators 12 and 13 are arranged outside the joined body 2 so as to sandwich the fuel electrode 4 and the oxidant electrode 5. A fuel gas supply groove 14 and a fuel electrode side gas seal surface 21 are formed on the surface of the separator 12 in contact with the fuel electrode 4 as a plurality of gas flow paths for distributing and supplying the fuel gas. An oxidant gas supply groove 15 and an oxidant electrode side gas seal surface 22 are formed on the surface of the oxidant electrode side separator 13 in contact with the oxidant electrode 5 as a plurality of gas flow paths for distributing and supplying the oxidant gas. Has been. The gas seal layers 16 and 17 at the outer peripheral ends of the fuel electrode 4 and the oxidant electrode 5 are in contact with the fuel electrode side gas seal surface 21 and the oxidant electrode side gas seal surface 22 of the separators 12 and 13, respectively. Is forming.

  Further, the battery stack is configured by alternately laminating the joined bodies 2 and the separators 12 and 13 and laminating a plurality of unit cells 1.

  In FIG. 1, the fuel gas supply groove 14 is formed from the lower left to the upper right of the drawing, and the oxidant gas supply groove 15 is formed from the left to the right of the drawing. In FIG. 2, the fuel gas supply groove 14 is formed along the left-right direction of the paper surface, and the oxidant gas supply groove 15 is formed along the front-back direction of the paper surface. That is, the fuel gas supply groove 14 and the oxidant gas supply groove 15 are orthogonal to each other. However, the grooves 14 and 15 do not necessarily cross each other and may be arranged in parallel to each other.

  In addition to the basic configuration so far, in this embodiment, as shown in the sectional view of FIG. 2 and the plan views of FIGS. 3A and 3B, the fuel electrode 4 to which fuel gas or oxidant gas is supplied into the cell. In addition, in the gas inlet portions 23 and 24 of the oxidant electrode 5, the gas seal layers 16 and 17 installed at the outer peripheral ends of the gas diffusion layers 6 and 7 of the fuel electrode 4 and the oxidant electrode 5 and the gas diffusion layers 6 and 7. The coating layers 25 and 26 are formed on all or a part of the boundary with the battery reaction surfaces 19 and 20.

  Specifically, as shown in FIG. 3A, gas is supplied from the left side to the right side of the drawing on the fuel electrode 4 side, and the gas flow of the fuel electrode side separator at the outer peripheral end of the fuel electrode 4. A coating layer 25 is formed so as to cover a portion corresponding to the gas inlet 23 of the passage. That is, the coating layer 25 is formed on the left end portion of the gas diffusion layer 6. As shown in FIG. 3B, the gas is supplied from the bottom to the top of the paper on the oxidant electrode 5 side, and the gas in the gas flow path of the oxidant side separator is provided at the outer peripheral end of the oxidant electrode 5. A coating layer 26 is formed so as to cover a portion corresponding to the inlet portion 24. That is, the coating layer 26 is formed at the lower end of the gas diffusion layer 7.

  The coating layers 25 and 26 are required to be conductive, hydrophilic, and gas permeable. For this reason, as the coating layers 25 and 26, for example, a conductive powder mainly composed of carbon black and a resin having a hydrophilic functional group, for example, a polymer resin having an ion exchange group containing fluorine-based sulfonic acid are used. Use. Further, platinum or the like may be supported on the conductive powder.

  The covering layers 25 and 26 are manufactured as follows, for example. First, after carbon black is dispersed in water, a solution containing perfluorocarbon sulfonic acid polymer resin is added, and the composition of the ink paste is adjusted so that the mixing weight ratio of carbon black and polymer resin solids is 50:50 did. Next, the boundary portion between the gas seal layers 16 and 17 installed at the outer peripheral ends of the gas diffusion layers 6 and 7 of the fuel electrode 4 and the oxidant electrode 5 and the cell reaction surfaces 19 and 20 of the gas diffusion layers 6 and 7 is applied. Masking was performed outside the range. Further, the ink paste is applied to the application range by an existing method using, for example, spraying, screen printing, pad printing, gravure coater, die coater, roll coater or the like. Then, after coating or impregnating the coating layers 25 and 26 on the surface or inside of the gas diffusion layers 6 and 7, the coating layers 25 and 26 were dried at a temperature of 80 ° C. to form the coating layers 25 and 26 having a thickness of 20 μm. .

  Next, on the side of the gas diffusion layer 6, 7 facing the solid polymer electrolyte membrane 3, catalyst layers 8, 9, which are mixed layers of carbon carrying a metal catalyst containing platinum and a solid polymer electrolyte, are provided. Form. The catalyst layers 8 and 9 may be formed by directly applying the catalyst layer material on the gas diffusion layers 6 or 7 or on the solid polymer electrolyte membrane 3. The surfaces of the fuel electrode 4 and the oxidant electrode 5 manufactured as described above opposite to the surfaces on which the gas diffusion layers 6 and 7 of the gas diffusion layers 6 and 7 are formed form the solid polymer electrolyte membrane 3 via the catalyst layers 8 and 9, respectively. It arrange | positions so that it may pinch | interpose, and it shape | molds as the conjugate | zygote 2 by thermocompression-bonding simultaneously and integrating.

  In such a configuration, hydrogen as the fuel gas diffuses in the fuel electrode side catalyst layer 8 via the fuel electrode side gas diffusion layer 6 and reacts when it reaches a catalyst such as platinum on the carbon carrier to react with hydrogen. Separated into ions and electrons. The electrons move from the fuel electrode 4 side through the external circuit to the oxidant electrode 5 side. The hydrogen ions move into the solid polymer electrolyte membrane 3 using the solid polymer electrolyte close to the catalyst in the fuel electrode side catalyst layer 8 as a transmission path, reach the oxidant electrode 5 and reach the oxidant electrode side catalyst layer 9. The solid polymer electrolyte in the inside diffuses as a transmission path and reacts with oxygen on the catalyst to form product water. The produced water moves or evaporates in the catalyst layers 8 and 9 and the gas diffusion layers 6 and 7, reaches the fuel gas supply groove 14 or the oxidant gas supply groove 15, and is removed to the outside along with the gas flow.

  In the joined body 2, the fuel electrode 4 to which hydrogen, which is the main component of the fuel gas, is supplied and the oxidant electrode 5 to which oxygen in the air is supplied as the oxidant gas include the following (1) and The battery reaction (2) occurs.

Fuel electrode: H ₂ → 2H ⁺ + 2e ⁻ (1)
Oxidant electrode: 1/2 O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O (2)
Further, in the catalyst layer of the fuel electrode 4 and the oxidant electrode 5, hydrogen peroxide (H ₂ O ₂ ) is generated as a side reaction product, causing a decomposition reaction as shown in the following formula (3) to generate a hydroxy radical. Generate radicals such as (OH ⁻ ).

H ₂ O ₂ + H ⁺ + e ⁻ → OH ⁻ + H ₂ O (3)
Some of the generated radicals move in the catalyst layer and act to cut the polymer structure of the solid polymer electrolyte constituting the catalyst layer and the solid polymer electrolyte membrane 3 adjacent to the catalyst layer. . As a result, the catalyst layers 8 and 9 and the solid polymer electrolyte membrane 3 are degraded by chemical degradation, and further, the mechanical strength of the solid polymer electrolyte membrane 3 is lowered to generate pinholes and cracks. Thus, there is a concern that it may cause a cross leak between the fuel electrode 4 and the oxidant electrode 5.

  In particular, in the operating conditions in which the fuel gas and the oxidant gas are respectively supplied in a low humidified state at the gas inlet portions 23 and 24 of the joined body 2, the generated water generated by the cell reaction is the gas inlet portions 23 and 24. Since evaporation is promoted in this region, hydrogen peroxide generated in this portion tends to be locally high in concentration. As a result, the decomposition of the solid polymer electrolyte around the gas inlet portions 23 and 24 proceeds and pinholes are easily formed in the solid polymer electrolyte membrane 3.

  As these measures, in this embodiment, the gas inlet portions 23 and 24 of the joined body 2 to which fuel gas and oxidant gas are supplied in a low humidified state are respectively hydrophilic on the surface or inside of the gas diffusion layer of the joined body 2. Covering layers 25 and 26 are formed. The covering layers 25 and 26 are formed of a mixed layer made of a conductive carbon powder as a gas permeable conductive powder material and a polymer resin having a hydrophilic functional group. For this reason, when fuel gas or oxidant gas is supplied in a low humidified state, the coating layers 25 and 26 are on the surface of the gas diffusion layer where the coating layers 25 and 26 are formed. By suppressing the permeation of the agent gas to the inside of the joined body, the generated water generated inside the joined body is prevented from evaporating to the outside in the low humidified state through the surface of the gas diffusion layer. At this time, since the coating layers 25 and 26 include a polymer resin having a hydrophilic functional group, the water retention effect of the polymer resin having a hydrophilic functional group causes the coating layers 25 and 26 to be exposed from the surface of the coating layers 25 and 26. Moisture evaporation can be suppressed. For this reason, as a result of the generated water generated in the catalyst layer on the oxidant side permeating and moving through the catalyst layer and the adjacent solid polymer electrolyte membrane 3, it is held by the coating layers 25 and 26, and is in a wet state. It will be possible to keep water.

  On the other hand, since a fine pore structure is formed between the powder particles by the conductive powder material, gas permeation can be controlled to prevent deficiency of fuel gas and oxidant gas supplied to the catalyst layer in the vicinity of the coating layer. It becomes like this. As a result, the generated water can be retained without inhibiting the battery reaction, and the wettability at the gas inlet portions 23 and 24 of the joined body 2 can be ensured.

Here, as the conductive powder material contained in the coating layers 25 and 26, for example, conductive carbon powder containing carbon black such as Vulcan XC72 (registered trademark) , acetylene black, and ketjen black (registered trademark) is used. Yes. Further, the conductive carbon powder carries a metal catalyst containing at least one element of platinum, palladium, gold, iridium and rhodium.

  By using the carbon powder as described above as the conductive powder material, the coating layers 25 and 26 are maintained in the corrosion resistance even under the condition of being exposed to the electrochemical corrosion environment accompanying the battery reaction, and the coating is performed. The fine pore structure formed between the powder particles of the layers 25 and 26 can be maintained and the gas permeability of the coating layers 25 and 26 can be maintained. Furthermore, when a metal catalyst containing platinum element is supported on the conductive carbon powder, the action of the metal catalyst that supports the hydrogen peroxide carried on the coating layers 25 and 26 by the movement of moisture on the conductive carbon powder. It becomes possible to provide a function of suppressing generation of radicals from hydrogen peroxide by being decomposed into water and oxygen.

  As a result, local deterioration of the solid polymer electrolyte membrane 3 can be suppressed, and the occurrence of pinholes can be prevented.

  As shown in FIG. 4, the gas diffusion layers 6 and 7 of the fuel electrode 4 and the oxidant electrode 5 forming the coating layers 25 and 26 are opposed to the catalyst layers 8 and 9 of the fuel electrode 4 and the oxidant electrode 5. In addition, in addition to the base material of the gas diffusion layers 6 and 7, conductive gas permeable layers 27 and 28 including carbon powder and a binder may be formed. Here, the covering layer 25 is not necessarily formed as far as the end of the sealing layer 17 as shown in FIG. 4A, but covers a part of the sealing layer 17 as shown in FIG. 4B. It may be formed.

  Further, the range of the coating layer 25 that covers a part of the gas diffusion layer 6 of the fuel electrode 4 is not limited to the inside of the gas seal layer 16, but as shown in FIG. 5A, the gas diffusion layer 6 of the fuel electrode 4. You may form in the range over the boundary part of the cell reaction surface 19 of the gas-seal layer 16 and the gas diffusion layer 6 installed in the outer peripheral edge part. Furthermore, as shown in FIG. 5B, the coating layer 25 may be formed so as to straddle the boundary between the gas seal layer 16 and the gas diffusion layer 6 and reach the outer end of the gas seal layer 16. The same can be applied to the coating layer 26 on the oxidizer electrode 5 side.

  In this case, the fuel gas and the oxidant gas are formed in the gap 18 sandwiched between the outer periphery of the gas diffusion layer and the outer periphery of the fuel electrode 4 and the oxidant electrode 5 and between the solid polymer electrolyte membrane 3. Can be prevented from being directly exposed to the solid polymer electrolyte membrane 3 from each gas supply groove via the gas diffusion layer.

  As described above, according to the present embodiment, regarding the configuration of the solid polymer electrolyte fuel cell, the solid polymer electrolyte membrane 3 is provided at the reaction gas inlet portions 23 and 24 in the cell surface to which fuel gas or oxidant gas is supplied. It is possible to keep the moisture in the inside and maintain high wettability, and to suppress the cross leak accompanying the generation of pinholes due to the deterioration of the solid polymer electrolyte membrane between the fuel electrode 4 and the oxidant electrode 5 . As a result, it is possible to provide a solid polymer electrolyte fuel cell with stable battery characteristics and improved lifetime.

  In addition, since the fuel and oxidant gas flow paths are orthogonal to each other, it is possible to prevent the gas supply ports from overlapping on the fuel electrode side and the oxidant electrode side, increasing the degree of freedom in designing the battery stack. Is possible. Furthermore, there is an advantage that it is possible to prevent inconveniences such as drying gas being supplied from the same part and promoting drying.

(Second Embodiment)
FIGS. 6 to 8 are views for explaining a solid polymer electrolyte fuel cell according to the second embodiment of the present invention. FIGS. 6 and 7 are plan views showing the main components, and FIG. FIG. 7 is a sectional view taken along line YY ′ of FIG.

  The basic configuration is the same as that of the first embodiment described above, and this embodiment is different from the first embodiment in the arrangement of the coating layer. In FIG. 6, the coating layer 25 is formed not only in the gas inlet portion 23 but also in a frame-like range sandwiching the boundary portion between the outer peripheral end portion of the gas diffusion layer 6 and the battery reaction surface 19. 7 and 8, the coating layer 25 is formed so as to reach the outer peripheral end of the gas diffusion layer 6 across the boundary. Although the coating layer 26 is not illustrated, the coating layer 26 is also formed in a frame shape like the coating layer 25.

  In such a configuration, since the coating layers 25 and 26 are provided in a frame shape, drying is performed not only on the gas inlet portions 23 and 24 but also on the entire outer peripheral end portion of the solid polymer electrolyte membrane 3. Can be suppressed. Therefore, the same effects as those of the first embodiment can be obtained, and it is possible to contribute to further stabilization of battery characteristics and longer life of the solid polymer electrolyte fuel cell.

(Modification)
The present invention is not limited to the above-described embodiments.

  The arrangement of the coating layer does not need to be formed in a frame shape like the gas inlet or the second embodiment as in the first embodiment, and can be appropriately changed according to the specification. For example, as shown to Fig.9 (a), you may make it provide in a gas inlet part and a gas outlet part. Furthermore, as shown in FIG. 9 (b), it may be provided on the side corresponding to the gas inlet and one side adjacent thereto. Further, as shown in FIG. 9C, when a gas supply direction is different in one separator, a coating layer may be provided at each gas inlet portion. In short, a coating layer may be provided at least in a portion corresponding to the gas inlet.

In the embodiment, carbon powder containing carbon black is used as the conductive powder material of the coating layer. However, the present invention is not limited to this, and as conductive metal group oxide particles serving as a substitute material for fibrous carbon and carbon material, titanium dioxide ( TiO ₂ ), SiO ₂ , ZrO, SnO ₂ , Al ₂ O ₃ , or CeO ₂ may be used. Even when these are used, the corrosion resistance of the coating layer is maintained even under the conditions of being exposed to the electrochemical corrosive environment accompanying the battery reaction, and the fine pore structure of the coating layer is maintained to maintain the coating layer. It is possible to maintain gas permeability. Furthermore, the metal catalyst supported on the conductive carbon powder is not limited to platinum, and a metal catalyst containing at least one element of platinum, palladium, gold, iridium, and rhodium can be used. Even when these are used, hydrogen peroxide carried to the coating layer by the movement of moisture is decomposed into water and oxygen by the action of the metal catalyst supported on the conductive carbon powder, and radicals are generated from hydrogen peroxide. It becomes possible to give the function which suppresses.

  Further, as the binder for the coating layer, for example, a fluorine-based sulfonic acid polymer resin having a sulfone group including a hydrogen ion exchange group having a polarity in the molecular structure was used as a polymer resin having a hydrophilic group. Not limited to this, an ion conductive resin containing at least one ion conductive group of a carboxyl group and a phosphate group may be used. Further, a fluororesin powder may be added as an additive to the binder and dispersed and mixed for binding.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Unit cell 2 ... Assembly 3 ... Solid polymer electrolyte membrane 4 ... Fuel electrode 5 ... Oxidant electrode 6 ... Fuel electrode gas diffusion layer 7 ... Oxidant electrode gas diffusion layer 8 ... Fuel electrode side catalyst layer 9 ... Oxidant Electrode side catalyst layer 10 ... Adhesive layer of fuel electrode 11 ... Adhesive layer of oxidant electrode 12, 13 ... Separator 14 ... Fuel gas supply groove 15 ... Oxidant gas supply groove 16 ... Fuel electrode side gas seal layer 17 ... Oxidant electrode Side gas seal layer 18 ... Gap portion 19 ... Fuel electrode side cell reaction surface 20 ... Oxidant electrode side cell reaction surface 21 ... Fuel electrode side gas seal surface 22 ... Oxidant electrode side gas seal surface 23 ... Gas inlet portion of fuel electrode 24 ... Gas inlet part of oxidant electrode 25 ... Fuel electrode side coating layer 26 ... Oxidant electrode side coating layer 27 ... Fuel electrode side gas permeable layer 28 ... Oxidant electrode side gas permeable layer

Claims (8)

A solid polymer electrolyte membrane using a solid polymer having hydrogen ion conductivity as an electrolyte; and
A fuel electrode having a gas diffusion layer disposed on one surface of the solid polymer electrolyte membrane and including a cell reaction surface in the center of the surface;
An oxidizer electrode disposed on the other surface of the solid polymer electrolyte membrane;
A fuel electrode side separator disposed on a surface of the fuel electrode opposite to the solid polymer electrolyte membrane, and having a gas flow path for distributing and supplying fuel gas on the surface of the fuel electrode;
An oxidant electrode-side separator disposed on the surface of the oxidant electrode opposite to the solid polymer electrolyte membrane and having a gas flow path for distributing and supplying oxidant gas on the surface of the oxidant electrode When,
The outer peripheral end of the gas diffusion layer of the fuel electrode, at least a portion corresponding to the gas inlet of the gas flow path of the fuel electrode-side separator, and a range extending from the portion corresponding to the gas inlet to the cell reaction surface A coating layer that is permeable to the fuel gas and is formed of a conductive material and a polymer resin having a hydrophilic functional group.
A solid polymer electrolyte fuel cell comprising: A solid polymer electrolyte membrane using a solid polymer having hydrogen ion conductivity as an electrolyte; and
A fuel electrode disposed on one surface of the solid polymer electrolyte membrane;
An oxidant electrode disposed on the other surface of the solid polymer electrolyte membrane and having a gas diffusion layer including a battery reaction surface in the center of the surface;
A fuel electrode side separator disposed on a surface of the fuel electrode opposite to the solid polymer electrolyte membrane, and having a gas flow path for distributing and supplying fuel gas on the surface of the fuel electrode;
An oxidant electrode-side separator disposed on the surface of the oxidant electrode opposite to the solid polymer electrolyte membrane and having a gas flow path for distributing and supplying oxidant gas on the surface of the oxidant electrode When,
From the outer peripheral end of the gas diffusion layer of the oxidant electrode and at least the part corresponding to the gas inlet part of the gas flow path of the oxidant electrode side separator and the part corresponding to the gas inlet part to the cell reaction surface A coating layer that is disposed so as to cover a wide range and is formed of a conductive material and a polymer resin having a hydrophilic functional group, and that transmits the oxidizing gas;
A solid polymer electrolyte fuel cell comprising: A solid polymer electrolyte membrane using a solid polymer having hydrogen ion conductivity as an electrolyte; and
A fuel electrode having a gas diffusion layer disposed on one surface of the solid polymer electrolyte membrane and including the first cell reaction surface in the center of the surface;
An oxidant electrode disposed on the other surface of the solid polymer electrolyte membrane and having a gas diffusion layer including the second battery reaction surface in the center of the surface;
A fuel electrode side separator disposed on a surface of the fuel electrode opposite to the solid polymer electrolyte membrane, and having a gas flow path for distributing and supplying fuel gas on the surface of the fuel electrode;
An oxidant electrode-side separator disposed on the surface of the oxidant electrode opposite to the solid polymer electrolyte membrane and having a gas flow path for distributing and supplying oxidant gas on the surface of the oxidant electrode When,
The first cell reaction surface from the outer peripheral end of the gas diffusion layer of the fuel electrode and at least a portion corresponding to the gas inlet of the gas flow path of the fuel electrode-side separator, and a portion corresponding to the gas inlet A fuel electrode side coating layer that is disposed so as to cover a range extending between and that includes a conductive material and a polymer resin having a hydrophilic functional group and that transmits the fuel gas;
From the outer peripheral end of the gas diffusion layer of the oxidant electrode and at least a part corresponding to the gas inlet part of the gas flow path of the oxidant electrode side separator, and a part corresponding to the gas inlet part, the second battery. An oxidant electrode side coating layer that is disposed so as to cover a range over the reaction surface and is formed by including a conductive material and a polymer resin having a hydrophilic functional group and that transmits the oxidant gas;
A solid polymer electrolyte fuel cell comprising:   The gas flow path of each separator is provided in a direction orthogonal to the facing direction of the fuel electrode or the oxidant electrode and the solid polymer electrolyte membrane, and the gas flow path of the fuel electrode side separator and the oxidant The solid polymer electrolyte fuel cell according to any one of claims 1 to 3, wherein the gas flow paths of the pole separator are orthogonal to each other.   5. The solid according to claim 1, wherein the conductive material constituting the coating layer includes at least one of conductive carbon powder, fibrous carbon, and conductive metal oxide particles. Polymer electrolyte fuel cell. The conductive carbon powder includes at least one of carbon black including Vulcan XC72 (registered trademark) , acetylene black, and ketjen black (registered trademark), and the conductive metal oxide particles are titanium dioxide (TiO ₂ ). The solid polymer electrolyte fuel cell according to claim 5, comprising at least one of SiO ₂ , ZrO, SnO ₂ , Al ₂ O ₃ , and CeO ₂ .   6. The solid polymer electrolyte fuel cell according to claim 5, wherein the conductive carbon powder carries a metal catalyst containing at least one element of platinum, palladium, gold, iridium and rhodium. .   The polymer resin having a hydrophilic functional group includes an ion conductive resin having at least one ion exchange group of a sulfone group, a carboxyl group, and a phosphate group. A solid polymer electrolyte fuel cell according to claim 1.

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