JP6575354B2 - Fuel cell - Google Patents

Description

  The present invention relates to a fuel cell.

  A polymer electrolyte fuel cell includes a membrane electrode assembly in which catalyst electrode layers are disposed on both sides of an electrolyte membrane having proton conductivity. In the membrane electrode assembly, an electrochemical reaction proceeds and water is generated, so water exists in the fuel cell. When the fuel cell is operated for a long time, the cation impurities contained in the inhaled air are mixed into the water in the fuel cell, or the cation impurities contained in the material constituting the electrolyte membrane and the catalyst electrode layer are mixed with the water in the fuel cell. Or elute. As a result, the power generation performance is degraded. Thus, it is known that by operating the fuel cell at a high load, the cation impurities are reduced to restore the power generation performance (for example, Patent Documents 1 and 2).

JP 2006-85959 A JP 2001-85037 A

  According to the method of recovering the power generation performance by operating the fuel cell at a high load, a large amount of generated water is generated by operating the fuel cell at a high load, and thus the cation impurities are discharged to the outside together with the generated water. Thus, cation impurities can be reduced. However, a water repellent layer may be provided on the side surface of the membrane electrode assembly in order to keep the amount of water in the membrane electrode assembly properly. In this case, water generated in the membrane electrode assembly is blocked by the water repellent layer. Therefore, it is difficult to be discharged outside in the state of liquid water. In addition, even if a part of the generated water is drained to the outside due to the generation of a large amount of generated water, the diffusion rate of the cationic impurities is slow, so the cationic impurities are difficult to move to the newly generated generated water. As a result, the amount of cationic impurities discharged with the produced water is small.

  The present invention has been made in view of the above problems, and an object thereof is to provide a fuel cell and a fuel cell system capable of discharging a large amount of cationic impurities to the outside.

  The present invention is a fuel cell, comprising a membrane electrode assembly in which electrode catalyst layers are provided on both surfaces of an electrolyte membrane, and first and second surfaces provided on one side and the other side of the membrane electrode assembly, respectively. A second water repellent layer, a pair of separators sandwiching the membrane electrode assembly through the first and second water repellent layers, and an outer periphery of the membrane electrode assembly, and the pair of separators A plurality of single cells each including an insulating member sandwiched between, a pair of end plates sandwiching the plurality of single cells, one of the pair of end plates and the pair of separators of the plurality of single cells, and A gas discharge manifold that is provided through the insulating member and discharges the gas discharged from the membrane electrode assembly to the outside of the fuel cell. Mounted A storage part in which liquid water accumulates below the membrane electrode assembly, and the electrolyte membranes of the plurality of single cells extend into the storage part and are inserted into either of the pair of end plates. On the other hand, the fuel cell is characterized by having a drainage channel capable of discharging the liquid water accumulated in the water reservoir to the outside of the fuel cell.

  According to the present invention, a large amount of cationic impurities can be discharged to the outside.

FIG. 1 is a diagram illustrating a configuration of a single cell constituting the fuel cell according to the first embodiment. 2A is a perspective view of the anode-side separator, FIG. 2B is a perspective view of the insulating member, and FIG. 2C is a perspective view of the cathode-side separator. 3 is a cross-sectional view taken along a line AA in FIG. FIG. 4 is a diagram illustrating the configuration of the fuel cell according to the first embodiment. FIG. 5 is a diagram for explaining the mechanism that the cationic impurities contained in the liquid water in the fuel cell are not easily discharged outside the fuel cell in the fuel cell according to the comparative example. 6 (a) and 6 (b) are diagrams illustrating a mechanism by which cationic impurities are discharged to the outside of the fuel cell by operating the fuel cell at a high load in the fuel cell according to the comparative example. . FIG. 7A to FIG. 7C are diagrams for explaining the effect of the fuel cell of the first embodiment. FIG. 8 is a diagram showing the amount of cationic impurities that finally reach an equilibrium state in the membrane electrode assembly and the water storage unit with respect to the water storage amount of the water storage unit. FIG. 9A is a diagram illustrating the configuration of the fuel cell according to the second embodiment, and FIG. 9B is a cross-sectional view taken along the line AA in FIG. 9A. FIG. 10 is a diagram illustrating the configuration of the fuel cell according to the third embodiment.

  Embodiments of the present invention will be described below with reference to the drawings.

  The fuel cell according to Example 1 is a polymer electrolyte fuel cell that generates electric power by receiving supply of a fuel gas (for example, hydrogen) and an oxidant gas (for example, air) as a reaction gas. For example, a fuel cell vehicle or an electric vehicle Etc. FIG. 1 is a diagram illustrating a configuration of a single cell 100 that constitutes the fuel cell according to the first embodiment. In FIG. 1, the direction of gravity in the state where the fuel cell is mounted on the vehicle is illustrated as the lower side of the drawing (the same applies to FIGS. 3, 4, 9, and 10). As shown in FIG. 1, the single cell 100 includes a membrane electrode assembly (MEA) 10 in which an anode catalyst layer 14 a and a cathode catalyst layer 14 c that are catalyst electrode layers are formed on both surfaces of an electrolyte membrane 12. . The anode catalyst layer 14a and the cathode catalyst layer 14c have different lengths, and the lower end of the anode catalyst layer 14a is located below the lower end of the cathode catalyst layer 14c. In addition, the lower end of the cathode catalyst layer 14c may be located below the lower end of the anode catalyst layer 14a, or the respective lower ends may be aligned.

  The electrolyte membrane 12 is a solid polymer membrane formed of a fluorine resin material or a carbon resin material, and has good proton conductivity in a wet state. The anode catalyst layer 14a and the cathode catalyst layer 14c include carbon particles (for example, carbon black) carrying a catalyst (for example, platinum or a platinum-cobalt alloy) that progresses an electrochemical reaction, and an ionomer having proton conductivity. .

  On both sides of the MEA 10, a pair of water-repellent layers (anode-side water-repellent layer 16a and cathode-side water-repellent layer 16c) for maintaining an appropriate amount of moisture contained in the MEA 10 and a pair of gas diffusion layers (anode gas diffusion) A layer 18a and a cathode gas diffusion layer 18c) are arranged. The MEA 10, the pair of water repellent layers, and the pair of gas diffusion layers are collectively referred to as a membrane electrode gas diffusion layer assembly (MEGA) 30. The anode-side water-repellent layer 16a and the anode gas diffusion layer 18a are provided at positions where the lower ends thereof are substantially aligned with the lower end of the anode catalyst layer 14a. The cathode-side water repellent layer 16c and the cathode gas diffusion layer 18c are provided at positions where the lower ends thereof are substantially aligned with the lower end of the cathode catalyst layer 14c. The lower end of the catalyst layer, the water repellent layer, and the gas diffusion layer may not be aligned.

  The anode-side water-repellent layer 16a, the cathode-side water-repellent layer 16c, the anode gas diffusion layer 18a, and the cathode gas diffusion layer 18c are formed of members having gas permeability and electron conductivity. For example, carbon cloth or carbon paper is used. It is formed of a porous carbon member such as. The anode-side water-repellent layer 16a and the cathode-side water-repellent layer 16c have smaller pores of the porous carbon member than the anode gas diffusion layer 18a and the cathode gas diffusion layer 18c. For example, the pore size of the anode side water repellent layer 16a and the cathode side water repellent layer 16c is about 0.1 μm to 1 μm in diameter, and the pore size of the anode gas diffusion layer 18a and the cathode gas diffusion layer 18c is The diameter is about 10 μm to 100 μm. As described above, since the pores of the anode-side water-repellent layer 16a and the cathode-side water-repellent layer 16c are small, it is possible to prevent liquid water from flowing out from the anode catalyst layer 14a and the cathode catalyst layer 14c. The moisture contained in the inside can be kept at an appropriate amount.

  A pair of separators (an anode side separator 20a and a cathode side separator 20c) that sandwich the MEGA 30 are disposed on both sides of the MEGA 30. The anode-side separator 20a and the cathode-side separator 20c are formed of members having gas barrier properties and electronic conductivity. For example, a carbon member such as dense carbon which is made impermeable to gas by compressing carbon, or press-molded stainless steel It is formed of a metal member such as steel. The anode-side separator 20a and the cathode-side separator 20c have irregularities for forming a flow path through which gas flows on the surface. Between the anode side separator 20a and the anode gas diffusion layer 18a, an anode gas passage 22a through which hydrogen can flow is formed. The cathode separator 20c forms a cathode gas flow path 22c through which air can flow between the cathode gas diffusion layer 18c. The anode side separator 20a and the cathode side separator 20c form refrigerant flow paths 24a and 24c through which refrigerant can flow. A gasket 26 is provided on the lower side surface of the anode-side separator 20a. In Example 1, the anode and the cathode are provided with the diffusion layers, but the present invention is not limited to this. A configuration in which one or both of the diffusion layers are not provided may be employed. In this case, gas is directly supplied to the catalyst layer from the anode gas channel or the cathode gas channel via the water repellent layer. In a configuration without a diffusion layer, a sheet member having functions of water repellency, gas permeation, and conductivity is used for the water repellent layer.

  A frame-like insulating member 40 that covers the outer periphery of the MEGA 30 and is sandwiched between the anode-side separator 20a and the cathode-side separator 20c is disposed. The insulating member 40 is bonded by an adhesive 41. Here, the anode side separator 20a, the cathode side separator 20c, and the insulating member 40 will be described in more detail. 2A is a perspective view of the anode side separator 20a, FIG. 2B is a perspective view of the insulating member 40, and FIG. 2C is a perspective view of the cathode side separator 20c.

  As shown in FIGS. 2A to 2C, the anode side separator 20a and the cathode side separator 20c are provided with holes a1 to a3 and holes c1 to c3, respectively. Similarly, the insulating member 40 is provided with holes s1 to s3. The holes a1 to a3, the holes s1 to s3, and the holes c1 to c3 communicate with each other, the holes a1, s1, and c1 are the hydrogen supply manifold, the holes a2, s2, and c2 are the refrigerant supply manifold, and the hole a3, s3 and c3 define an air exhaust manifold.

  The anode side separator 20a and the cathode side separator 20c are provided with holes a4 to a6 and holes c4 to c6, respectively. Similarly, the insulating member 40 is provided with holes s4 to s6. The holes a4 to a6, s4 to s6, and c4 to c6 communicate with each other, the holes a4, s4, and c4 are the air supply manifold, the holes a5, s5, and c5 are the refrigerant discharge manifold, and the holes a6, s6, And c6 define a hydrogen discharge manifold.

  Since the holes a3, s3, and c3 have an L shape, the air discharge manifold has an L shape. Since the other holes have a rectangular shape, the other manifolds have a rectangular shape. Further, the MEGA 30 is disposed inside the insulating member 40. In other words, the insulating member 40 is disposed so as to cover the outer periphery of the MEGA 30.

  An anode gas flow path 22a through which hydrogen flows through the hydrogen supply manifold and the hydrogen discharge manifold is formed on the surface of the anode separator 20a facing the MEGA 30. A cathode gas flow path 22c through which air flows through the air supply manifold and the air discharge manifold is formed on the surface of the cathode separator 20c facing the MEGA 30. The coolant is supplied to the surface of the anode separator 20a opposite to the surface where the anode gas flow path 22a is formed and to the surface of the cathode separator 20c opposite to the surface where the cathode gas flow path 22c is formed. Refrigerant flow paths 24a and 24c are formed through which the manifold and the refrigerant discharge manifold communicate with each other.

  3 is a cross-sectional view taken along a line AA in FIG. In FIG. 3, the adhesive 41 is not shown. As shown in FIGS. 1 and 3, holes a3, s3, and c3 provided in the anode-side separator 20a, the insulating member 40, and the cathode-side separator 20c are formed below the MEGA 30 with water generated by an electrochemical reaction, A water storage section 32 is formed in which liquid water such as dew condensation water generated when the fuel cell is stopped is accumulated. That is, since the holes a3, s3, and c3 define an air discharge manifold, the air discharge manifold has a water storage portion 32 in which liquid water is accumulated below the MEGA 30. A part of the electrolyte membrane 12 extends and is inserted into the water storage section 32.

  Above the hole s3, both side surfaces of the electrolyte membrane 12 are held by the insulating member 40. The lower end portion of the electrolyte membrane 12 is also held by the insulating member 40. Thus, since the upper part and the lower part of the part extended from the anode catalyst layer 14a and the cathode catalyst layer 14c of the electrolyte membrane 12 are hold | maintained by the insulating member 40, the electrolyte membranes 12 of an adjacent cell may contact. It is suppressed.

  FIG. 4 is a diagram illustrating a configuration of the fuel cell 200 according to the first embodiment. In FIG. 4, a part of the structure of the single cell is simplified for the sake of clarity. As shown in FIG. 4, the fuel cell 200 of the first embodiment has a stack structure in which the plurality of single cells 100 described in FIGS. 1 to 3 are sandwiched between a pair of end plates 70 and 72. The end plates 70 and 72 are made of metal, for example, but may be made of other materials.

  The end plate 72 includes a flow path 74. The flow path 74 is provided with a throttle portion 80. The hole a3 provided in the anode side separator 20a of each of the plurality of single cells 100, the hole s3 provided in the insulating member 40, and the hole c3 provided in the cathode side separator 20c communicate with the flow path 74 of the end plate 72. Thus, an air discharge manifold 34 for discharging the cathode off gas discharged from the MEA 10 to the outside of the fuel cell 200 is formed. Although not shown, the end plate 72 also includes a flow path that defines a hydrogen supply manifold, a refrigerant supply manifold, an air supply manifold, a refrigerant discharge manifold, and a hydrogen discharge manifold.

  The cross-sectional area of the flow path 74 of the end plate 72 is such that the hole a3 provided in the anode separator 20a of the single cell 100, the hole s3 provided in the insulating member 40, and the hole c3 provided in the cathode separator 20c are cut off. Smaller than the area. As a result, a water storage section 32 in which liquid water 36 such as generated water or condensed water is accumulated is formed in the air discharge manifold 34 below the MEGA 30. Since the water reservoir 32 is formed across the plurality of single cells 100, a large amount of liquid water 36 can be stored in the water reservoir 32. The electrolyte membranes 12 of the plurality of single cells 100 extend to the water storage section 32 and are inserted into the liquid water 36 accumulated in the water storage section 32.

  The end plate 72 and the throttle unit 80 are provided with a channel 76 that communicates the water storage unit 32 and the channel 74. The liquid water 36 accumulated in the water storage section 32 enters the flow path 76. Since the throttle portion 80 having a narrow cross-sectional area is provided at a portion communicating with the flow path 76 of the flow path 74 in the end plate 72, the flow rate of the cathode off discharged to the outside through the flow path 74 increases, and the water storage section When the amount of liquid water 36 accumulated in 32 increases, the liquid water 36 is sucked out from the water storage section 32 through the flow path 76 by the negative pressure generated by the flow rate of the cathode off gas and drained to the outside. Therefore, even during the power generation of the fuel cell, if the liquid water 36 accumulates in the water storage section 32 and the flow rate of the cathode off gas increases, the liquid water 36 can be drained to the outside at any time. The channel 76 functions as a drain channel that can drain the liquid water 36 accumulated in the water storage unit 32 to the outside of the fuel cell 200. For example, while the fuel cell is stopped, the liquid water 36 is stored in the water storage section 32, and a large amount of liquid water 36 can be stored in the water storage section 32 for a long time. Further, the communication part of the flow path 76 to the flow path 74 and the throttle part 80 are not limited to being provided only in the end plate 72, and may be provided outside the end plate 72.

  Here, in describing the effect of the fuel cell of Example 1, the fuel cell of the comparative example will be described. In the fuel cell of the comparative example, the air discharge manifold has a rectangular shape like the other manifolds, and the electrolyte membrane is provided at a position where the lower end thereof is substantially aligned with the lower end of the anode catalyst layer. Different from the fuel cell. That is, in the fuel cell of the comparative example, the water storage part is not formed in the air discharge manifold, and accordingly, the electrolyte membrane does not extend to the water storage part. Other configurations are the same as those in the first embodiment.

FIG. 5 is a diagram for explaining the mechanism that the cationic impurities contained in the liquid water in the fuel cell are not easily discharged outside the fuel cell in the fuel cell according to the comparative example. Although FIG. 5 illustrates the cathode side as an example, the same thing occurs on the anode side. As shown in FIG. 5, generated water (liquid water 36) is generated by an electrochemical reaction in the cathode catalyst layer 14c, and the liquid water 36 exists in the electrolyte membrane 12 and the cathode catalyst layer 14c. When the fuel cell is operated for a long time, the inhaled air and the cation impurities 42 contained in the materials constituting the electrolyte membrane and the electrode catalyst layer are contained in the liquid water 36 together with the protons 44. If the cation impurity 42 is present in the electrolyte membrane 12, the power generation performance is degraded. Examples of the cation impurity 42 include Ca ²⁺ , Mg ²⁺ , and Co ²⁺ .

During the operation of the fuel cell, the cation impurity 42 in the liquid water 36 diffuses in the liquid water 36 due to a potential difference in a direction intersecting (orthogonal) with the plane of the electrolyte membrane 12, and in the plane direction of the electrolyte membrane 12. It diffuses in the liquid water 36 due to the concentration difference. While the fuel cell is stopped, the cation impurity 42 in the liquid water 36 diffuses in the liquid water 36 due to the concentration difference both in the direction intersecting (orthogonal) with the planar direction of the electrolyte membrane 12 and in the planar direction. . The amount of diffusion can be expressed by Equation 1, and the final ratio of the cationic impurities 42 is equal between the electrolyte membrane 12 and the cathode catalyst layer 14c.

  Since the cathode-side water-repellent layer 16c is provided on the side surface of the cathode catalyst layer 14c, the liquid water 36 is hardly drained from the cathode catalyst layer 14c to the outside. However, part of the liquid water 36 is discharged to the outside by being dissolved in the cathode off-gas and passing through the cathode-side water-repellent layer 16c. On the other hand, since the cation impurity 42 cannot be dissolved in the cathode offgas, it is difficult to dissolve in the cathode offgas like the liquid water 36 and to be discharged to the outside. For this reason, it is difficult for the cation impurities 42 in the liquid water 36 to be discharged outside the fuel cell.

  For example, according to Japanese Patent Laid-Open No. 2001-85037, the cation impurities are discharged to the outside by operating the fuel cell at a high load. This will be described with reference to FIGS. 6 (a) and 6 (b). 6 (a) and 6 (b) are diagrams illustrating a mechanism by which cationic impurities are discharged to the outside of the fuel cell by operating the fuel cell at a high load in the fuel cell according to the comparative example. .

  Since a large amount of generated water (liquid water 36) is generated by operating the fuel cell with a high load as shown in FIG. 6 (a), the liquid water 36 that is dissolved in the cathode off gas and exceeds the amount that can be discharged, The pressure of the liquid water 36 in the cathode catalyst layer 14c increases. As a result, the liquid water 36 is pushed out of the cathode catalyst layer 14c, passes through the cathode-side water-repellent layer 16c, and is drained to the cathode gas flow path 22c. Along with the drainage of the liquid water 36, the cation impurities 42 in the liquid water 36 are discharged.

  However, the amount of liquid water 36 that passes through the cathode-side water-repellent layer 16c and is drained to the cathode gas flow path 22c is not very large. In addition, since the cation impurity 42 diffuses in the liquid water 36 by concentration diffusion, the moving speed is slow, and it takes a long time to reach the state of the above formula 1. That is, the cation impurities 42 cannot move in a short time to the liquid water 36 generated by operating the fuel cell at a high load. For this reason, the cation impurity 42 discharged together with the liquid water 36 when the fuel cell is operated at a high load exists in the vicinity of the cathode-side water-repellent layer 16 c in the cathode catalyst layer 14 c before the operation at the high load. Only the cation impurities 42 diffused in the liquid water 36, and as shown in FIG. 6B, the cation impurities 42 contained in the liquid water 36 of the electrolyte membrane 12 are difficult to be discharged. Therefore, it is difficult to discharge a large amount of cationic impurities 42 to the outside.

  FIG. 7A to FIG. 7C are diagrams for explaining the effect of the fuel cell of the first embodiment. In the first embodiment, as described with reference to FIG. 4, a large amount of liquid water 36 is accumulated in the water storage section 32 for a long time, and a part of the electrolyte membrane 12 extends into the water storage section 32 so that it is inserted into the liquid water 36. The For this reason, as shown in FIG. 7A to FIG. 7C, a large amount of cationic impurities 42 contained in the liquid water 36 of the electrolyte membrane 12 diffuses into the liquid water 36 accumulated in the water storage section 32, The concentration of the cation impurity 42 in the liquid water 36 of the water reservoir 32 is increased. Accordingly, the liquid water 36 drained to the outside from the water storage section 32 through the air discharge manifold 34 contains a large amount of cationic impurities 42, and a large amount of cationic impurities 42 can be discharged to the outside. . Note that the diffusion of the cation impurity 42 in FIGS. 7A to 7C is dominated by concentration diffusion, and diffusion due to a potential difference need not be considered.

  As described above, according to the first embodiment, as shown in FIG. 4, the air discharge manifold 34 has the water storage portion 32 in which the liquid water 36 is accumulated below the MEA 10. The electrolyte membranes 12 of the plurality of single cells 100 extend and are inserted into the water storage section 32. For this reason, as described with reference to FIGS. 7A to 7C, a large amount of cation impurities 42 contained in the liquid water 36 of the electrolyte membrane 12 may diffuse into the liquid water 36 of the water storage section 32. The concentration of the cation impurity 42 in the liquid water 36 of the water storage section 32 is increased. The fuel cell 200 according to the first embodiment includes the flow path 76 that can drain the liquid water 36 accumulated in the water storage portion 32 to the outside in the end plate 72, so that the cation impurities 42 in the water storage portion 32 are concentrated at a high concentration. The contained liquid water 36 can be drained to the outside. Thereby, a large amount of cationic impurities 42 can be discharged to the outside, and as a result, the power generation performance can be recovered satisfactorily. Moreover, since the water storage part 32 is outside the power generation part, it is possible to recover a power generation performance by discharging a large amount of the cation impurities 42 to the outside while suppressing a decrease in the power generation performance.

  Moreover, in Example 1, it is preferable that the volume of the water storage part 32 is 20% or more of the maximum water content of MEA10. This will be described with reference to FIG. FIG. 8 is a diagram showing the amount of the cation impurity 42 that finally reaches an equilibrium state with the MEA 10 and the water storage unit 32 with respect to the water storage amount of the water storage unit 32. FIG. 8 shows a case where the amount of the cation impurity 42 mixed per certain traveling distance (for example, 1000 km) is 1. The horizontal axis of FIG. 8 represents the ratio of the water storage amount of the water storage unit 32 to the maximum water content of the MEA 10 (water storage amount / maximum water content of the membrane electrode assembly). The vertical axis represents the amount of the cation impurity 42 that finally reaches an equilibrium state in the MEA 10 and the water storage unit 32 by repeatedly draining the liquid water 36 accumulated in the water storage unit 32.

  As shown in FIG. 8, when (the amount of stored water / the maximum water content of the membrane electrode assembly) is 1, the amount of positive impurities accumulated in the MEA 10 is about the amount of the cation impurities 42 mixed per certain travel distance. The amount of ionic impurities 42 is suppressed. Even if (the amount of stored water / the maximum water content of the membrane electrode assembly) is greater than 1, the amount of cationic impurities 42 accumulated in the MEA 10 is not so small. On the other hand, when (the amount of stored water / the maximum water content of the membrane electrode assembly) is smaller than 0.2, the amount of the cation impurities 42 accumulated in the MEA 10 increases rapidly.

  From the above, it is preferable that the volume of the water storage unit 32 is 20% or more of the maximum water content of the MEA 10 in order to reduce the amount of the cationic impurities 42 accumulated in the MEA 10. The volume of the water storage part 32 is more preferably 50% or more of the maximum water content of the MEA 10, and further preferably 80% or more. On the other hand, even if the volume of the water storage unit 32 is larger than 100% of the maximum water content of the MEA 10, the amount of the cation impurities 42 accumulated in the MEA 10 is hardly changed. Since the fuel cell may become larger as the volume of the water storage unit 32 increases, the volume of the water storage unit 32 is preferably 200% or less of the maximum water content of the MEA 10, and is 160% or less. Is more preferable, and the case of 140% or less is more preferable.

λは、電解質膜に含まれるＳＯ_３ ⁻の含水係数である。Ｖ_ｍｅｍ、ρ_ｍｅｍ、ＥＷ_ｍｅｍは、電解質膜１２の体積、密度、ＥＷ（Equivalent Weight）値である。Ｖ_{ｉｏｎ、ＡＮ}、ρ_{ｉｏｎ、ＡＮ}、ＥＷ_{ｉｏｎ、ＡＮ}は、アノード触媒層１４ａに含まれるアイオノマーの体積、密度、ＥＷ値である。Ｖ_{ｉｏｎ、ＣＡ}、ρ_{ｉｏｎ、ＣＡ}、ＥＷ_{ｉｏｎ、ＣＡ}は、カソード触媒層１４ｃに含まれるアイオノマーの体積、密度、ＥＷ値である。Ｖ_Ｗは、含水の体積である。ρ_Ｗ、Ｍ_Ｗは、水の密度、モル重量である。 The water content in the MEA 10 is substantially determined by the water content of the electrolyte membrane contained in the MEA 10 and the water content in the gap of the cathode catalyst layer 14c. The maximum water content of the electrolyte membrane is a value determined by one according to the structure of the electrolyte membrane, and can be obtained by the following equation (2).

λ is the water content coefficient of SO ₃ ⁻ contained in the electrolyte membrane. V _mem , ρ _mem , and EW _mem are the volume, density, and EW (Equivalent Weight) value of the electrolyte membrane 12. V _{ion, AN} , ρ _{ion, AN} , EW _{ion, AN} are the volume, density, and EW value of the ionomer contained in the anode catalyst layer 14a. _{Vion, CA} , _{ρion, CA} , _{EWion, and CA} are the volume, density, and EW value of the ionomer included in the cathode catalyst layer 14c. _VW is the volume of water. ρ _W and M _W are the density and molar weight of water.

εは、空隙率であり、Ｓ_ＣＬは、カソード触媒層１４ｃの体積である。ｍ_Ｃ、ρ_Ｃは、カソード触媒層１４ｃに含まれるカーボン担体の質量、密度である。ｍ_ｉｏｎ、ρ_ｉｏｎは、カソード触媒層１４ｃに含まれるアイオノマーの質量、密度である。ｍ_ｐｔ、ρ_ｐｔは、カソード触媒層１４ｃに含まれる触媒の質量、密度である。 The gap of the cathode catalyst layer 14c is a value determined by one according to the structure of the cathode catalyst layer 14c, and can be obtained by the following equation (3). Since water is contained in the voids, the water content can be determined by determining the volume of the voids. The volume of the void can be calculated from the volume (area and thickness) of the cathode catalyst layer 14c and the porosity. The porosity is the ratio of the volume of the cathode catalyst layer 14c to the volume of the cathode catalyst layer 14c minus the volume of the material (carbon support, ionomer, catalyst) contained in the cathode catalyst layer 14c.

ε is the porosity, and _SCL is the volume of the cathode catalyst layer 14c. m _C and ρ _C are the mass and density of the carbon support contained in the cathode catalyst layer 14c. m _ion and ρ _ion are the mass and density of the ionomer contained in the cathode catalyst layer 14c. m _pt and ρ _pt are the mass and density of the catalyst contained in the cathode catalyst layer 14c.

For example, when the maximum water content per 1 cm ² is determined using the following representative physical properties, it is 1.08 mg / cm ² .
λ: 14
V _mem : 0.001 cm ³
ρ _mem : 2 g / m ³
EW _mem : 1000 g / mol
_{Vion, AN} : 7.5 × 10 ⁻⁵ cm ³
ρ _{ion, AN} : 2 g / cm ³
EW _{ion, AN} : 1000 g / mol
_{Vion, CA} : 1.5 × 10 ⁻⁴ cm ³
ρ _{ion, CA} : 2 g / cm ³
EW _{ion, CA} : 1000 g / mol
V _W : calculated value ρ _W : 1 g / cm ³
M _W: 18g / mol
ε: 0.45
S _CL : 0.001 cm ³
In a single cell having a power generation area of 200 cm ² , the maximum water content per sheet is 0.216 g. In this case, the volume of the water storage section 32 per single cell is preferably 0.043 cc or more, which is 20% or more of the maximum water content.

  FIG. 9A is a diagram illustrating a configuration of the fuel cell 300 according to the second embodiment, and FIG. 9B is a cross-sectional view taken along a line AA in FIG. 9A. As shown in FIGS. 9A and 9B, in the fuel cell 300 of Example 2, holes a3, s3, and c3 provided in the anode side separator 20a, the insulating member 40, and the cathode side separator 20c, respectively. Is provided under the MEGA 30 over the entire MEGA 30. That is, the air discharge manifold is provided below the MEGA 30 over the entire MEGA 30, and has a water storage portion 32 over the entire lower part of the MEGA 30. The electrolyte membrane 12 is extended and inserted in the water storage part 32 in several places. Since other configurations are the same as those of the first embodiment, the description thereof is omitted.

  According to the second embodiment, since the water storage unit 32 is provided in the entire lower part of the MEGA 30 of the single cell 100, the amount of liquid water 36 accumulated in the water storage unit 32 can be increased. Accordingly, a large amount of cationic impurities 42 can be contained in the liquid water 36 of the water storage section 32, and the amount of the cationic impurities 42 in the electrolyte membrane 12 can be reduced. Further, since a plurality of portions of the electrolyte membrane 12 are inserted into the water storage section 32 and inserted, the contact area between the electrolyte membrane 12 and the liquid water 36 of the water storage section 32 increases, and the liquid water 36 of the water storage section 32 extends from the electrolyte membrane 12. It is possible to promote the diffusion of the cationic impurities 42 into the surface. In addition, when a plurality of locations of the electrolyte membrane 12 are in contact with the liquid water 36 of the water storage section 32, the electrolyte membrane 12 is scattered and comes into contact with the liquid water 36 of the water storage section 32. The diffusion of the cation impurities 42 from the water to the liquid water 36 of the water storage section 32 can be promoted.

  FIG. 10 is a diagram illustrating the configuration of the fuel cell 400 according to the third embodiment. As shown in FIG. 10, in the fuel cell 400 of the third embodiment, the throttle portion 80 is not provided in the flow path 74 of the end plate 72. The end plate 72 is provided with a flow path 78 that allows the water storage section 32 to communicate with the outside of the fuel cell 400. The flow path 78 can drain the liquid water 36 accumulated in the water storage section 32 to the outside of the fuel cell 400. Functions as a drainage channel. Outside the fuel cell 400, a valve 82 is installed in a flow path connected to the flow path 78, and switching between drainage and non-drainage of the liquid water 36 of the water storage section 32 by switching the valve 82 is performed. it can. The valve 82 may be an electronic control valve (for example, an electromagnetic valve) that automatically opens and closes based on an instruction from the control device, or may be a manual valve (for example, a manual cock) that opens and closes manually. Since other configurations are the same as those of the first embodiment, the description thereof is omitted.

  According to the third embodiment, for example, the valve 82 is opened by an instruction from the control device every predetermined travel distance, predetermined travel time, and predetermined power generation time, so that the liquid water 36 in the water storage section 32 is drained to the outside, and the cation Impurities 42 can be discharged to the outside. Further, for example, the liquid water 36 in the water storage section 32 may be drained to the outside by manually opening the valve 82 at the time of periodic inspection.

  In the third embodiment, the flow path 78 is provided in the end plate 72 where the air discharge manifold 34 is formed. However, the flow path 78 is provided in the end plate 70 where the air discharge manifold 34 is not formed. It may be the case.

  In the first to third embodiments, it is preferable that all the electrolyte membranes 12 of the plurality of single cells 100 extend and be inserted into the water storage section 32. However, the electrolyte membranes 12 of some of the single cells 100 may be The case where it does not extend to the water reservoir 32 may be used.

  In the first to third embodiments, the case where the water storage portion 32 is formed in the air discharge manifold 34 is shown as an example, but the case where the water storage portion is formed in the hydrogen discharge manifold may be used. However, since a large amount of generated water is generated on the cathode side, the water storage section 32 is preferably formed in the air discharge manifold 34.

  In the first to third embodiments, the case where generated water, condensed water, or the like accumulates in the water storage section 32 is shown as an example. However, for example, liquid water 36 is supplied to the water storage section 32 from the outside during periodic inspections, for example. It may be accumulated.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

DESCRIPTION OF SYMBOLS 10 Membrane electrode assembly 12 Electrolyte membrane 14a Anode catalyst layer 14c Cathode catalyst layer 16a Anode side water repellent layer 16c Cathode side water repellent layer 18a Anode gas diffusion layer 18c Cathode gas diffusion layer 20a Anode side separator 20c Cathode side separator 22a Anode gas flow Path 22c Cathode gas flow path 30 Membrane electrode gas diffusion layer assembly 32 Water storage section 34 Air discharge manifold 36 Liquid water 40 Insulation member 41 Adhesive 42 Cationic impurity 44 Proton 70, 72 End plates 74 to 78 Flow path 80 Restriction section a1 -A6, s1-s6, c1-c6 hole 100 single cell 200-400 fuel cell

Claims (1)

A fuel cell,
A membrane electrode assembly in which an electrode catalyst layer is provided on both surfaces of the electrolyte membrane; a first and second water repellent layer provided on each of one surface and the other surface of the membrane electrode assembly; And a pair of separators that sandwich the membrane electrode assembly via the second water repellent layer, and an insulating member that is disposed so as to cover the outer periphery of the membrane electrode assembly and is sandwiched between the pair of separators. Including a plurality of single cells,
A pair of end plates sandwiching the plurality of single cells;
A gas that is provided through one of the pair of end plates and the pair of separators and the insulating member of the plurality of single cells, and discharges the gas discharged from the membrane electrode assembly to the outside of the fuel cell. A discharge manifold,
The gas discharge manifold has a water storage part in which liquid water is stored below the membrane electrode assembly in a state where the fuel cell is mounted on a vehicle.
The electrolyte membranes of the plurality of single cells are extended and inserted into the water reservoir,
Either one of the pair of end plates has a drainage channel capable of discharging the liquid water accumulated in the water reservoir to the outside of the fuel cell.

Images