Fuel cell and fuel cell

Abstract

To realize appropriate drainage capability by a microporous layer.SOLUTION: A fuel battery cell comprises an electrolyte membrane, a catalyst layer that is formed on a surface of the electrolyte membrane, a gas diffusion layer that is disposed to the catalyst layer on a side opposite the electrolyte membrane, and a microporous layer a bore diameter of which is smaller than the gas diffusion layer. The microporous layer includes a first surface part which is formed between the catalyst layer and the gas diffusion layer and which extends over an entire surface of the gas diffusion layer, and a plurality of second surface parts which is formed on an underside of a rib of a separator that demarcates a passage for the reaction gas supplied to the catalyst layer, between the gas diffusion layer and the separator, and which extends in a width direction of the rib and are intermittently formed in the width direction of the rib or in a length direction of the rib that is perpendicular thereto. A portion of the surface of the gas diffusion layer that faces the direction of the separator is exposed from the microporous layer between the adjacent second surface parts.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a fuel cell.

Background Art

[0002] Patent Document 1 describes a laminated structure of a fuel cell including a gas diffusion layer and a microporous layer (MPL). The microporous layer is a porous structure having a smaller inner diameter of pores (hereinafter sometimes referred to as "pore diameter") than the gas diffusion layer. In this fuel cell, the microporous layer extends over the entire surface of the gas diffusion layer between the catalyst layer formed on the surface of the electrolyte membrane and the gas diffusion layer, and is arranged so as to fill the pores of the gas diffusion layer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The microporous layer has a property that water is less likely to accumulate inside compared to the gas diffusion layer. Here, in a structure where the microporous layer covers the entire surface of the gas diffusion layer and fills the pores of the gas diffusion layer, that is, the space part excluding the bridges, there is a concern that the drainage property obtained by the microporous layer may be excessive, the humidification of the electrolyte membrane may be insufficient, and the power generation performance of the fuel cell may rather decrease.

[0005] Therefore, an object of the present invention is to provide a fuel cell and a fuel cell in which appropriate drainage property is obtained by a microporous layer.

Means for Solving the Problems

[0006] To solve the aforementioned problems, the fuel cell cell according to the present invention comprises an electrolyte membrane, a catalyst layer formed on the surface of the electrolyte membrane, a gas diffusion layer disposed on the opposite side of the catalyst layer from the electrolyte membrane, and a microporous layer having a smaller pore diameter than the gas diffusion layer, wherein the microporous layer has a first surface portion formed between the catalyst layer and the gas diffusion layer and extending over the entire surface of the gas diffusion layer, and a plurality of second surface portions formed between the gas diffusion layer and the separator, facing the lower surface of the separator rib that defines the flow path of the reaction gas supplied to the catalyst layer, extending in the width direction of the rib and intermittently formed in the width direction of the rib or in the length direction of the rib perpendicular thereto. The second surface portion extends over its entire width relative to the rib, The gas diffusion layer teeth A portion of the surface facing the separator is exposed from the microporous layer between adjacent second surface portions.

[0007] The fuel cell according to the present invention comprises a plurality of fuel cell cells arranged in a stacked manner, a separator disposed between adjacent fuel cell cells among the plurality of fuel cell cells, and a pair of output terminals, a positive electrode and a negative electrode, configured to be able to apply the series output of the plurality of fuel cell cells. [Effects of the Invention]

[0008] According to the present invention, it is possible to achieve appropriate drainage in a fuel cell cell and fuel cell by using a microporous layer, thereby improving battery performance. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram showing the overall configuration of a fuel cell system equipped with a fuel cell according to an embodiment of the present invention. [Figure 2] This is a schematic cross-sectional view showing the internal structure of a fuel cell according to an embodiment of the present invention. [Figure 3] This is a schematic cross-sectional view showing the configuration of a fuel cell cell according to an embodiment of the present invention. [Figure 4] This is a cross-sectional view showing the configuration of the cathode electrode and its surrounding region according to the first embodiment of the fuel cell cell described above. [Figure 5] This is a cross-sectional view showing the configuration of the cathode electrode and its surrounding region according to a second embodiment of the same fuel cell cell. [Figure 6] This is a cross-sectional view showing the configuration of the cathode electrode and its surrounding region according to a third embodiment of the fuel cell cell described above. [Figure 7] This is a plan view showing an example of the arrangement of the microporous layer (second surface portion) in a fuel cell cell according to an embodiment of the present invention. [Figure 8] This is a plan view showing another example of the arrangement of the microporous layer (second surface) in the same fuel cell cell. [Figure 9] This is a plan view showing yet another example of the arrangement of the microporous layer (second surface) in the same fuel cell cell. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described below with reference to the drawings.

[0011] Figure 1 is a schematic diagram illustrating the configuration of a fuel cell system S equipped with a fuel cell 1 according to one embodiment of the present invention.

[0012] In this embodiment, the fuel cell system S includes a fuel cell 1 as a power source or power generation device, and other peripheral or auxiliary devices including a fuel gas tank 11, a fuel gas circulation pump 12, a flow control valve 13, a compressor 14, an internal cooler 15, a bypass control valve 16, a pressure control valve 17, an inverter 21, and an electric motor 22.

[0013] The fuel gas tank 11 is connected to the inlet of the fuel gas supply pipe P11 and stores the fuel gas supplied to the fuel cell 1 in a compressed state. In this embodiment, the fuel gas is hydrogen. It is also possible to install a fuel tank and reformer instead of the fuel gas tank 11, and generate hydrogen by reforming liquid raw fuel, which can then be used as fuel gas.

[0014] The fuel gas circulation pump 12 is installed in the fuel residual gas circulation path P3, supplied to the fuel cell 1, and circulates the remaining fuel gas other than the fuel gas actually used for power generation in the fuel cell 1 (hereinafter referred to as "fuel residual gas") from the fuel residual gas discharge pipe P12 to the fuel gas supply pipe P11. The fuel gas supply pipe P11 and the fuel residual gas discharge pipe P12 are connected to each other by the fuel residual gas circulation path P3. The fuel gas circulation pump 12 sucks out the fuel residual gas from the fuel residual gas discharge pipe P12 and discharges it toward the fuel gas supply pipe P11.

[0015] The flow rate regulating valve 13 is installed at the introduction part of the oxidant gas supply pipe P21 and regulates the flow rate of the oxidant gas sucked into the oxidant gas supply pipe P21. In the present embodiment, the oxidant gas is air, specifically, oxygen in the air.

[0016] The compressor 14 is installed on the downstream side of the flow rate regulating valve 13 in the oxidant gas supply pipe P21, compresses the oxidant gas sucked into the oxidant gas supply pipe P21, and sends it toward the fuel cell 1.

[0017] The internal cooler 15 is installed on the downstream side of the compressor 14 in the oxidant gas supply pipe P21, cools the oxidant gas compressed by the compressor 14, reduces the temperature of the oxidant gas supplied to the fuel cell 1, and increases the density.

[0018] The bypass control valve 16 is installed in the bypass pipe P4 and adjusts the flow rate of the oxidizer gas introduced into the internal cooler 15. The bypass pipe P4 is connected to the oxidizer gas supply pipe P21 before and after the internal cooler 15. The oxidizer gas is branched from the oxidizer gas supply pipe P21 upstream of the internal cooler 15, bypasses the internal cooler 15, and rejoins the oxidizer gas supply pipe P21 downstream of the internal cooler 15. For example, if the power generated by the fuel cell 1 is high and the load on the compressor 14 is high, the bypass control valve 16 is closed to relatively increase the flow rate of the oxidizer gas supplied to the fuel cell 1 via the internal cooler 15. On the other hand, if the load on the compressor 1 is low, the bypass control valve 16 is opened to relatively increase the flow rate of the oxidizer gas supplied to the fuel cell 1 via the bypass pipe P4.

[0019] The pressure regulating valve 17 is installed in the oxidizer gas discharge pipe P22 and adjusts the pressure at the oxidizer gas outlet of the fuel cell 1 to control the pressure and flow rate of the oxidizer gas inside the fuel cell 1.

[0020] The inverter 21 is connected to the fuel cell 1, specifically to the output terminal 104 of the fuel cell 1, and converts the DC voltage applied by the fuel cell 1 into an AC voltage. In this embodiment, the DC voltage of the fuel cell 1 is converted into a three-phase AC voltage.

[0021] The electric motor 22 constitutes a load for the fuel cell system S and operates using AC power converted by the inverter 21. The electric motor 22 is installed, for example, in a fuel cell vehicle and operates as a drive motor for vehicle propulsion. In this case, the electric motor 22 can operate in a power mode that forms the propulsion force when the fuel cell vehicle moves forward and backward, as well as in a regenerative mode. The power generated in the regenerative mode can be stored in a secondary battery (not shown).

[0022] In the fuel cell system S, fuel gas stored in the fuel gas tank 11 is supplied to the anode electrode of the fuel cell 1 via the fuel gas supply pipe P11. On the other hand, air taken in from the atmosphere by the compressor 14 is supplied to the cathode electrode of the fuel cell 1 via the oxidant gas supply pipe P21. The air contains oxygen, which is the oxidant gas. Inside the fuel cell 1, the chemical reactions shown in equations (1a) and (1b) proceed at the electrodes of the anode and cathode, respectively, generating electricity. H2 → 2H + +2e - …(1a) 4H + +O2+4e - → 2H2O …(1b)

[0023] A portion of the residual fuel gas discharged from fuel cell 1 is recirculated to the fuel gas supply pipe P11 via the residual fuel gas circulation path P3, where it merges with newly supplied fuel gas from the fuel gas tank 11 and is supplied to the anode of fuel cell 1. The remaining residual fuel gas is discharged into the atmosphere via the residual fuel gas discharge pipe P12. Unreacted oxidizer gas discharged from fuel cell 1 can be introduced into the residual fuel gas discharge pipe P12 and used to dilute the residual fuel gas before it is discharged into the atmosphere.

[0024] Figure 2 is a schematic cross-sectional view showing the internal structure of the fuel cell 1 according to this embodiment.

[0025] In this embodiment, the fuel cell 1 is a polymer electrolyte fuel cell. The fuel cell 1 comprises a fuel cell stack formed by stacking a plurality of fuel cell cells 101a, 101b, and 101c. Each of the fuel cell cells 101a, 101b, and 101c constituting the fuel cell stack has the same configuration. For convenience, Figure 2 shows only three fuel cell cells 101a, 101b, and 101c, but there is no limit to the number of fuel cell cells 101 that constitute the fuel cell stack, and it is possible to configure a fuel cell stack by stacking an appropriate number of fuel cell cells 101 according to the output required for the fuel cell 1.

[0026] The fuel cell 1 or fuel cell stack includes a plurality of fuel cell cells 101a, 101b, and 101c, as well as a separator 102 corresponding to the number of fuel cell cells 101, a pair of end plates 103, and a pair of output terminals 104 (positive electrode output terminal 104a, negative electrode output terminal 104b).

[0027] The separator 102 is sandwiched between adjacent fuel cell cells 101a, 101b, and 101c, forming a flow path for the fuel gas supplied to the anode electrode and the oxidizer gas supplied to the cathode electrode of the fuel cell 101 (the fuel gas and oxidizer gas are sometimes collectively referred to as "reaction gas").

[0028] In this embodiment, on the separator 102, a plurality of ribs 102a (Figure 4) are formed parallel to each other on the surface facing the electrodes of the fuel cell cell 101, and grooves surrounded or defined by adjacent ribs 102a function as flow paths C1 and C2 for the reaction gas supplied to the electrodes during power generation. Therefore, in a separator 102 where the fuel cell cell 101 is arranged on only one side, ribs 102a are formed only on the surface of that one side, and in a separator 102 where the fuel cell cell 101 is arranged on both sides, ribs 102a are formed on both surfaces. There are no restrictions on the shape of the ribs 102a or flow paths C1 and C2 formed on the separator 102, but in this embodiment, for the sake of simplicity, they are assumed to be a shape that extends linearly between two opposing sides of the four sides that form the outer contour of the separator 102.

[0029] The end plate 103 is positioned to sandwich the multiple fuel cell cells 101a, 101b, and 101c in their stacking direction, and holds the fuel cell stack from both sides in the stacking direction. For convenience, although not explicitly shown in the figures, the end plate 103 has a fuel gas inlet to which the fuel gas supply pipe P11 is connected, a fuel residual gas outlet to which the fuel residual gas discharge pipe P12 is connected, an oxidizer gas inlet to which the oxidizer gas supply pipe P21 is connected, and an oxidizer gas outlet to which the oxidizer gas discharge pipe P22 is connected.

[0030] The output terminal section 104 is configured to be able to apply the series output of multiple fuel cell cells 101a, 101b, and 101c, and is provided for both the positive and negative electrodes. In this embodiment, one of the pair of end plates 103, 103 is provided with the output terminal section 104a for the positive electrode, and the other with the output terminal section 104b for the negative electrode.

[0031] Figure 3 is a schematic cross-sectional view showing the configuration of the fuel cell cell 101 according to this embodiment.

[0032] The fuel cell cell 101 according to this embodiment comprises an electrolyte membrane 111, catalyst layers 112 and 113, and gas diffusion layers 114 and 115, with the gas diffusion layers 114 and 115 having attached microporous layers 116 and 117.

[0033] The electrolyte membrane 111 is composed of an ionic conductive polymer membrane and is conductive to hydrogen ions (also called "protons") generated at the negative electrode, i.e., the anode electrode. The hydrogen ions generated at the anode electrode move to the positive electrode, i.e., the cathode electrode, through the electrolyte membrane 111. Examples of polymer materials applicable to the electrolyte membrane 111 include fluorine-based polymer materials having sulfonic acid groups, such as Nafion®.

[0034] The catalyst layers 112 and 113 are formed on the front and back surfaces of the electrolyte membrane 111, respectively, and are integrated with the electrolyte membrane 111 to form a so-called membrane electrode assembly. In the example shown in Figure 3, the cathode electrode is formed by the catalyst layer 112, which is bonded to the upper surface of the electrolyte membrane 111 relative to the plane of the paper. The catalyst layer 112 receives oxidant gas through the oxidant gas supply pipe P21 and the flow path C1 of the separator 102 located on the cathode electrode side. In contrast, the anode electrode is formed by the catalyst layer 113, which is bonded to the lower surface. The catalyst layer 113 receives fuel gas through the fuel gas supply pipe P11 and the flow path C2 of the separator 102 located on the anode electrode side. In this embodiment, the flow of oxidant gas in flow path C1 and the flow of fuel gas in flow path C2 are in opposite directions.

[0035] The gas diffusion layers 114 and 115 are positioned on the opposite side from the electrolyte membrane 111 to the catalyst layers 112 and 113 on the cathode and anode sides, respectively. In other words, the gas diffusion layers 114 and 115 are positioned on both the front and back sides of the membrane electrode assembly, sandwiching the membrane electrode assembly between them. The reaction gas supplied to the fuel cell 1 is diffused through the gas diffusion layers 114 and 115 and supplied to the electrodes 112 and 113 on the surface of the electrolyte membrane 111. The gas diffusion layers 114 and 115 can be formed, for example, by applying a water-repellent treatment to a gas-diffusible substrate made of graphite fibers or the like.

[0036] The microporous layers 116 and 117 are porous structures with smaller pore diameters than the gas diffusion layers 114 and 115, and are attached to the gas diffusion layers 114 and 115, respectively, which are located on the cathode and anode sides. However, in this embodiment, the microporous layers 116 and 117 have different configurations on the cathode and anode sides. The microporous layers 116 and 117 can be formed, for example, by creating an MPL ink mainly composed of a water-repellent resin such as polytetrafluoroethylene (PTFE) and a conductive material such as carbon black particles, and applying or filling this ink into predetermined parts of the gas diffusion layers 116 and 117.

[0037] Figure 4 is an enlarged cross-sectional view showing the configuration of the cathode electrode and its surrounding region of the fuel cell cell 101 according to this embodiment. Figure 4(a) shows a cross-section of the rib 102a of the separator 102 along a plane parallel to the width direction W, and Figure 4(b) shows a cross-section of the rib 102a along a plane perpendicular to the width direction W and parallel to the length direction L, that is, a cross-section along line XX in Figure 4(a). The explanation of the microporous layer 116 will continue based on Figure 3, with appropriate reference to Figure 4.

[0038] The microporous layer 116 provided on the cathode side has a first surface portion 116a, a second surface portion 116b, and an intermediate portion 116c. In this embodiment, the first surface portion 116a, the second surface portion 116b, and the intermediate portion 116c have the same pore diameter, and all of them have a smaller pore diameter than the gas diffusion layer 114.

[0039] The first surface portion 116a is formed between the catalyst layer 112 and the gas diffusion layer 114, extending over the entire surface of the gas diffusion layer 114 facing the catalyst layer 112. In this embodiment, the first surface portion 116a can also be called a planar portion due to its shape. The thickness of the first surface portion 116a is sufficiently smaller than that of the gas diffusion layer 114. Water generated on the catalyst layer 112 during power generation (hereinafter sometimes referred to as "generated water") is removed from the surface of the catalyst layer 112 and its vicinity through the first surface portion 116a. The first surface portion 116a can be formed, for example, by applying MPL ink to the entire surface of the gas diffusion layer 114.

[0040] The second surface portion 116b is formed between the gas diffusion layer 114 and the rib 102a of the separator 102, facing the lower surface of the rib 102a, and in the width direction W of the rib 102a. In this embodiment, the second surface portion 116b is formed over the entire width direction W of the rib 102a, or in other words, the edge of the second surface portion 106b in the width direction W extends to a position where it protrudes in the width direction W relative to the lower surface of the rib 102a.

[0041] Figure 7 is a schematic plan view showing the arrangement of the microporous layer 116, particularly the second surface portion 116b, according to this embodiment, as viewed from a direction perpendicular to the surface of the gas diffusion layer 114.

[0042] As previously mentioned, the second surface portion 116b extends in the width direction W of the rib 102a. Figure 7 shows only the outer contour of the rib 102a by a dashed line. In this embodiment, the second surface portion 116b has a first discontinuity g1 between adjacent second surface portions 116b, 116b in the width direction W of the rib 102a, and a portion of the surface of the gas diffusion layer 114, that is, the end face of the gas diffusion layer 114 opposite to the surface facing the catalyst layer 112, that exists between adjacent ribs 102a, 102a is exposed to the flow channel C1 from the microporous layer 116 via the first discontinuity g1.

[0043] Furthermore, in addition to the first discontinuous portion g1, the second surface portion 116b has a second discontinuous portion g2 between adjacent second surface portions 116b in the longitudinal direction L of the rib 102a perpendicular to the width direction W, and a portion of the surface of the gas diffusion layer 114 facing the lower surface of the rib 102a is exposed from the microporous layer 116 via the second discontinuous portion g2.

[0044] In this embodiment, the second surface portions 116b are arranged in a grid pattern, aligned with each other in the width direction W and length direction L of the rib 102a, and can also be called flap-shaped portions due to their shape. The second surface portions 116b aligned in the width direction W of the rib 102a are arranged with equal pitch or center-to-center distance pw, and the second surface portions 116b aligned in the length direction L are also arranged with equal pitch or center-to-center distance pl. The arrangement of the second surface portions 116b is not limited to this, and they may be arranged alternately in a staggered pattern in the width direction W or length direction L of the rib 102a.

[0045] The second surface portion 116b can be formed, for example, by scraping a region of the surface of the gas diffusion layer 114 where the second surface portion 116b is to be placed, and applying the same MPL ink used to form the first surface portion 116a to this groove or recess. In this embodiment, the surface of the second surface portion 116b is substantially flush with the surface of the gas diffusion layer 114, and the surface of the gas diffusion layer 114 exposed through the second discontinuity g2 is in direct contact with the lower surface of the rib 102a.

[0046] Returning to Figure 4, the intermediate portion 116c is formed perpendicular to the surface of the gas diffusion layer 114 from the first surface portion 116a and extends to the end face of the gas diffusion layer 114 opposite to the surface facing the catalyst layer 112. In other words, in this embodiment, one end of the intermediate portion 116c is connected to the first surface portion 116a, while the other end faces the flow path C1 at the end face of the gas diffusion layer 114. The intermediate portion 116c can also be called a columnar portion due to its shape.

[0047] The intermediate portion 116c, like the second surface portion 116b, has discontinuous portions in the longitudinal direction L of the rib 102a, and in a cross-section of a plane parallel to the surface of the gas diffusion layer 114, it may have a circular shape such as a perfect circle or an ellipse, or an angular shape such as a square or a rectangle. In this case, the intermediate portion 116c can be positioned aligned in the longitudinal direction L between adjacent second surface portions 116b, 116b in the width direction W of the rib 102a, or it can be positioned offset in the longitudinal direction L. Furthermore, the intermediate portion 116c can be formed continuously over the entire flow path C1 in the longitudinal direction L of the rib 102a between adjacent ribs 102a, 102a.

[0048] The intermediate portion 116c can be formed, for example, by hollowing out an internal region of the gas diffusion layer 114 where the intermediate portion 116c is planned to be located, and filling this hole or space with MPL ink that is the same as, or has a higher viscosity than, the ink used to form the first surface portion 116a.

[0049] In contrast, the microporous layer 117 provided on the anode side has only elements corresponding to the first surface portion 116a of the microporous layer 116 provided on the cathode side.

[0050] The configuration of the microporous layer 117 provided on the anode side is not limited to this, and may have the same configuration as the microporous layer 116 provided on the cathode side, or it may have elements corresponding to a second surface portion 116b or an intermediate portion 116c in addition to the first surface portion 116a. Since the formation of the microporous layer 117 is more expensive than that of the gas diffusion layer 115, it is possible to make it have an appropriate configuration by taking into account various factors such as productivity and economics in addition to the required drainage performance.

[0051] The configuration of the fuel cell 1 and fuel cell cell 101 according to this embodiment is as described above, and the effects obtained by this embodiment will be explained below.

[0052] Figure 4 shows the path by which water generated during power generation, i.e., the generated water, moves through the gas diffusion layer 114 and the microporous layer 116 towards the channel C1 of the separator 102, indicated by arrows f1, f2, and f3. Figure 4 will be referred to as appropriate in the following explanation.

[0053] Firstly, although both the gas diffusion layer 114 and the microporous layer 116 are porous, the microporous layer 116 has smaller pore sizes than the gas diffusion layer 114. Due to this difference in pore size, water is less likely to accumulate inside the microporous layer 116, while it tends to accumulate relatively easily in the gas diffusion layer 114.

[0054] In this embodiment, the microporous layer 116 is provided with a first surface portion 116a and a second surface portion 116b. The first surface portion 116a extends across the entire surface of the gas diffusion layer 114 near the catalyst layer 112, while the second surface portion 116b is interposed between the gas diffusion layer 114 and the rib 102a of the separator 102. This removes the generated water from the surface of the catalyst layer 112 and its vicinity, thereby suppressing the situation in which the supply of reaction gas to the catalyst layer 112, in this embodiment, oxygen which is the oxidizing gas, is hindered by this generated water. In Figure 4, arrow f1 indicates the path of movement of the generated water removed from the surface of the catalyst layer 112 and its vicinity.

[0055] Here, the second surface portion 116b promotes the discharge of generated water from directly below and near the rib 102a, where drainage tends to be particularly poor, thereby suppressing the situation in which the diffusion of reaction gases is inhibited by the accumulation of generated water below the rib 102a. In Figure 4, arrow f2 indicates the path of movement of generated water discharged directly below and near the rib 102a.

[0056] Furthermore, the presence of discontinuous portions g1 and g2 on the second surface portion 116b increases the opportunities for contact between the generated water discharged through the microporous layer 116 and the reaction gas flowing through the channel C1 of the separator 102, thereby improving drainage. At the same time, the inflow of reaction gas into the gas diffusion layer 114 is inhibited by the second surface portion 116b, which can prevent the supply of reaction gas to the catalyst layer 112 from being hindered.

[0057] Thus, according to this embodiment, adequate drainage can be obtained, allowing the fuel cell 1 and fuel cell cell 101 to function well over a wider operating range and suppressing the progression of deterioration.

[0058] Secondly, by providing an intermediate section 116c that extends to the end face of the gas diffusion layer 114 and faces the flow path C1 of the separator 102, in addition to the first surface section 116a and the second surface section 116b, the movement of generated water excluded by the first surface section 116a toward the flow path C1 is promoted, and the situation in which generated water accumulates in the gas diffusion layer 114 and causes blockage can be actively suppressed. In Figure 4, arrow f3 indicates the path of the movement of generated water promoted by the intermediate section 116c.

[0059] Thirdly, by extending the second surface portion 116b over the entire width W of the rib 102a, the edge of the second surface portion 116b faces the flow path C1 of the separator 102, promoting contact between the generated water discharged into the flow path C1 through the second surface portion 11b and the reaction gas, thereby ensuring more reliable discharge from the separator 102.

[0060] The above effects can be obtained not only from the fuel cell cell 101 alone, but from the entire fuel cell stack, thereby improving the power generation performance of the fuel cell 1 and suppressing the progression of degradation.

[0061] Figure 8 is a plan view of a first modified example of the microporous layer 116 according to this embodiment, and schematically shows the arrangement of the second surface portion 116b in particular, as viewed from a direction perpendicular to the surface of the gas diffusion layer 114. As in Figure 7, only the outer contour of the rib 102a is shown by a dashed line.

[0062] In the first modified example, the second surface portion 116b extends across the entire surface of the gas diffusion layer 114 in the width direction W of the rib 102a, spanning between adjacent ribs 102a, 102a, and is continuously formed across multiple parallel channels C1, C1 of the separator 102. Furthermore, the second surface portion 116b has discontinuous portions g2 between adjacent second surface portions 116b, 116b in the length direction L of the rib 102a, and a portion of the surface of the gas diffusion layer 114 is exposed from the microporous layer 116 through these discontinuous portions g2 and exposed to the channels C1 between adjacent separators 102, 102. The pitch or center-to-center distance pl in the length direction L of the rib 102a is equal for the second surface portions 116b.

[0063] In this way, by forming the second surface portion 116b of the microporous layer 116 across the space between adjacent ribs 102a, the generated water present on the underside of the ribs 102a and its vicinity is moved through the second surface portion 116b to a position closer to the center of the flow path C1 of the separator 102, thereby promoting contact with the reaction gas flowing through the flow path C1 and facilitating discharge from the separator 102.

[0064] Figure 9 is a plan view of a second modified example of the microporous layer 116 according to this embodiment, and schematically shows the arrangement of the second surface portion 116b in particular, as viewed from a direction perpendicular to the surface of the gas diffusion layer 114. As in Figure 7, only the outer contour of the rib 102a is shown by a dashed line.

[0065] In the second modified example, the second surface portion 116b extends along the length L of the rib 102a, over the entire flow channel C1 defined by the rib 102a, and is formed continuously from the upstream end to the downstream end. The second surface portion 116b has discontinuous portions g1 between adjacent second surface portions 116b, 116b in the width direction W of the rib 102a, and a portion of the surface of the gas diffusion layer 114 is exposed from the microporous layer 116 to the flow channel C1 through these discontinuous portions g1. The pitch or center-to-center distance pw in the width direction W of the rib 102a is equal for the second surface portions 116b.

[0066] In this way, by forming the second surface portion 116b of the microporous layer 116 along the length L of the rib 102a over the entire flow path C1 of the separator 102, the discharge of generated water from the lower surface of the rib 102a and its vicinity, where drainage performance tends to be particularly poor, can be promoted over the entire flow path C1, and the accumulation of generated water below the rib 102a can be more reliably suppressed.

[0067] The following describes embodiments of the present invention other than those described above. In the following description, the difference from the previous embodiments lies in the configuration of the intermediate portion 116b of the microporous layer 116 provided on the cathode side of the fuel cell cell 101, while the configuration of other elements of the fuel cell cell 101, the stacking structure of the cell 101 in the fuel cell 1, and the overall configuration of the fuel cell system S are the same as in the previous embodiments.

[0068] Figure 5 is a cross-sectional view showing the configuration of the cathode electrode and its surrounding region of a fuel cell cell 101 according to another embodiment of the present invention.

[0069] In this embodiment, the intermediate portion (referred to as the "first intermediate portion" to distinguish it from the second intermediate portion described below) 116c extends below the rib 102a of the separator 102 from the first surface portion 116a in a direction perpendicular to the surface of the gas diffusion layer 114 to the end face position of the gas diffusion layer 114 directly below the rib 102a, and is connected to the second surface portion 116b. In other words, in this embodiment, the first surface portion 116a and the second surface portion 116b of the microporous layer 116 are connected to each other via the first intermediate portion 116c, and the microporous layer 116 is in a continuous state from the region near the surface of the catalyst layer 112 to the end face position of the gas diffusion layer 114.

[0070] In addition to the above, a second intermediate portion 116d is formed in this embodiment. The configuration of the second intermediate portion 116d is the same as the intermediate portion of the microporous layer 116 in the previous embodiment, that is, the intermediate portion shown by reference numeral 116c in Figure 4, but it is arranged alternately with respect to the second surface portion 116b.

[0071] Thus, in this embodiment, the microporous layer 116 extends continuously from the region near the surface of the catalyst layer 112 to the end face of the gas diffusion layer 114 via the first surface portion 116a, the first intermediate portion 116c, and the second surface portion 116b, thereby further promoting the discharge of generated water through the microporous layer 116. In particular, it is possible to actively promote the discharge of generated water from the region below the rib 102a.

[0072] Figure 6 is a cross-sectional view showing the configuration of the cathode electrode and its surrounding region of a fuel cell cell 101 according to yet another embodiment of the present invention.

[0073] In this embodiment, the microporous layer 116 comprises a first intermediate portion 116c and a second intermediate portion 116d as intermediate portions, similar to the example shown in Figure 5. In this embodiment, the first intermediate portion 116c has a smaller cross-sectional area in the portion closer to the first surface portion 116a than in the portion closer to the second surface portion 116b, in other words, the cross-sectional area increases as it approaches the second surface portion 116b from the first surface portion 116a. The first intermediate portion 116c is formed below the rib 102, and the microporous layer 116 is continuous from the region near the surface of the catalyst layer 112 to the end face position of the gas diffusion layer 114 via the first surface portion 116a, the first intermediate portion 116c, and the second surface portion 116b, similar to the example shown in Figure 5.

[0074] Thus, in this embodiment, while the second surface portion 116b enables the discharge of generated water from the lower surface of the rib 102a and its vicinity, the cross-sectional area of ​​the first intermediate portion 116c at a position close to the first surface portion 116a is reduced, thereby reducing the overall volume of the first intermediate portion 116c, avoiding excessive drainage through the microporous layer 116, and preventing unnecessary increases in costs. [Explanation of symbols]

[0075] S...Fuel cell system, 1...Fuel cell, 11...Fuel gas tank, 12...Fuel residual gas circulation pump, 13...Flow control valve, 14...Compressor, 15...Internal cooler, 16...Bypass control valve, 17...Pressure regulating valve, 21...Inverter, 22...Electric motor, P11...Fuel gas supply pipe, P12...Fuel residual gas discharge pipe, P21...Oxidizer gas supply pipe, P22...Oxidizer gas discharge pipe, P3...Fuel residual gas circulation path, P4...Bypass pipe, 101 ...fuel cell, 102...separator, 102a...rib, 103...end plate, 104...output terminal section, 111...electrolyte membrane, 112, 113...catalyst layer, 114, 115...gas diffusion layer, 116, 117...microporous layer, 116a...first surface section, 116b...second surface section, 116c...intermediate section, C...flow channel, g1, g2...intermittent section, W...width direction of the rib, L...length direction of the rib, f1, f2, f3...flow of generated water.

Claims

1. Electrolyte membrane, A catalyst layer formed on the surface of the electrolyte membrane, A gas diffusion layer is disposed on the opposite side of the catalyst layer from the electrolyte membrane, A microporous layer with a smaller pore size than the aforementioned gas diffusion layer, Equipped with, The aforementioned microporous layer is A first surface portion is formed between the catalyst layer and the gas diffusion layer and extends across the entire surface of the gas diffusion layer, A plurality of second surface portions are formed between the gas diffusion layer and the separator, facing the lower surface of the separator rib that defines the flow path of the reaction gas supplied to the catalyst layer, extending in the width direction of the rib and being intermittently formed in the width direction of the rib or in the length direction of the rib perpendicular thereto, It has, The second surface portion extends over its entire width relative to the rib, The gas diffusion layer is a fuel cell in which a portion of the surface facing the separator is exposed from the microporous layer between adjacent second surface portions.

2. The microporous layer extends from the first surface portion in a direction perpendicular to the surface of the gas diffusion layer, and further has an intermediate portion that terminates at the end face of the gas diffusion layer opposite to this surface. The fuel cell cell according to claim 1.

3. The intermediate portion terminates at the end face position directly below the rib and connects to the second surface portion. The fuel cell cell according to claim 2.

4. The intermediate portion has a smaller cross-sectional area in the portion closer to the first surface portion than in the portion closer to the second surface portion. The fuel cell cell according to claim 3.

5. The second surface portion extends across a plurality of adjacent ribs in the width direction of the ribs and is formed intermittently in the length direction of the ribs. A fuel cell cell according to any one of claims 1 to 4.

6. The second surface portion extends in the longitudinal direction of the rib over the entire flow channel defined by the rib and is formed intermittently in the width direction of the rib. A fuel cell cell according to any one of claims 1 to 4.

7. A plurality of fuel cell cells according to any one of claims 1 to 6, arranged in a stacked manner with respect to each other, Among the plurality of fuel cell cells, a separator is placed between adjacent fuel cell cells, A fuel cell comprising a pair of output terminals, a positive electrode and a negative electrode, configured to be able to apply the series output of the plurality of fuel cell cells.

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