Fuel battery cell

Abstract

To compensate for a decrease in gas supply due to partial compression of a gas diffusion layer.SOLUTION: A fuel battery cell includes: a membrane electrode assembly; a gas diffusion layer bonded to the membrane electrode assembly; a separator in which a plurality of gas flow paths and a non-flow-path portion in contact with the gas diffusion layer while separating the gas flow paths from one another are formed on a surface facing the gas diffusion layer; and at least one throttle portion formed in at least one of the plurality of gas flow paths to narrow a flow-path cross-sectional area. The throttle portion has a slit extending from the gas flow path to the non-flow-path portion on a surface on the gas diffusion layer side.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a fuel cell. [Background technology]

[0002] Patent Document 1 discloses a plurality of fuel cell units that constitute a fuel cell stack. Each fuel cell unit includes a membrane electrode gas diffusion layer assembly and a pair of separators that sandwich the membrane electrode gas diffusion layer assembly from the anode side and the cathode side. The membrane electrode gas diffusion layer assembly includes an electrolyte membrane, an anode electrode catalyst layer and a cathode electrode catalyst layer bonded to both sides of the electrolyte membrane, and a pair of gas diffusion layers bonded to the surfaces of the anode electrode catalyst layer and the cathode electrode catalyst layer opposite the electrolyte membrane.

[0003] The separator has a surface facing the gas diffusion layer that is formed with multiple gas flow channels and non-channel sections that separate adjacent gas flow channels. The non-channel sections are in contact with the gas diffusion layer. Furthermore, a throttle section is formed in a portion of the gas flow channel of the separator to reduce the cross-sectional area of ​​the channel in order to efficiently supply gas to the membrane-electrode-gas diffusion layer assembly. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-228482 A Summary of the Invention [Problem to be solved by the invention]

[0005] The gas diffusion layer is formed of a porous substrate to efficiently diffuse gas toward a membrane electrode assembly having an electrolyte membrane and anode and cathode electrode catalyst layers. However, when a portion of the gas diffusion layer near the non-channel portion is compressed and crushed by the pressure from the non-channel portion of the separator, the gas permeability and diffusibility of gas in the gas diffusion layer are partially reduced, which may lead to a decrease in gas supply through the gas diffusion layer and even a decrease in power generation performance. In view of these issues, this specification presents a technology that makes it possible to compensate for the decrease in gas supply through the gas diffusion layer even if part of the gas diffusion layer is compressed due to pressure from the non-flow path portion of the separator. [Means for solving the problem]

[0006] This specification discloses a fuel cell. The fuel cell includes a membrane electrode assembly, a gas diffusion layer bonded to the membrane electrode assembly, a separator having a surface facing the gas diffusion layer, on which a plurality of gas flow channels and a non-channel portion that contacts the gas diffusion layer and separates the gas flow channels, and at least one throttle portion formed in at least one of the plurality of gas flow channels to reduce the cross-sectional area of ​​the gas flow channel. The throttle portion has a slit on the surface facing the gas diffusion layer, extending from the gas flow channel toward the non-channel portion.

[0007] According to the above configuration, the slits in the throttle section ensure a gas supply path to the gas diffusion layer near the non-flow-path section, so that even if a part of the gas diffusion layer is compressed by the pressure from the non-flow-path section, the decrease in gas supply through the gas diffusion layer can be compensated for. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing a schematic configuration of a fuel cell stack according to an embodiment of the present invention; [Figure 2] FIG. 3 is a simplified view showing a part of the surface of the separator facing the gas diffusion layer. [Figure 3] 10A and 10B are diagrams showing other examples of slits in the throttle portion. [Figure 4] 10A and 10B are diagrams showing other examples of slits in the throttle portion. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present embodiment will be described with reference to the drawings. Each drawing is merely an example, and the present embodiment is not limited to the contents shown in the drawings. Furthermore, since each drawing is an example, the shapes shown in the drawings may not necessarily be accurate, and some parts may be omitted.

[0010] FIG. 1 shows a schematic configuration of a fuel cell stack 100 in this embodiment. For a general explanation of fuel cell stacks and fuel cell systems including fuel cell stacks, reference can be made to known technologies such as Patent Document 1 as appropriate, so a brief explanation will be given here. The fuel cell stack 100 is configured to include a plurality of fuel cell units 10 stacked in a stacking direction Z. A single fuel cell unit 10 is also referred to as a single cell 10. Two directions that are perpendicular to the stacking direction Z and perpendicular to each other are referred to as a first direction X and a second direction Y.

[0011] FIG. 1 also shows a partial cross-sectional view of one fuel cell 10. The fuel cell 10 includes a membrane electrode assembly 30, two gas diffusion layers 20, and a pair of separators, i.e., an anode-side separator 50 and a cathode-side separator 40. The membrane electrode assembly 30 is abbreviated as MEA 30. The MEA 30 is configured by bonding an anode electrode catalyst layer 31 and a cathode electrode catalyst layer 32 to either side of an electrolyte membrane. A gas diffusion layer 20 is bonded to either side of the MEA 30. A membrane electrode gas diffusion layer assembly 21, which is a combination of the MEA 30 and the two gas diffusion layers 20 sandwiching it, is abbreviated as MEGA 21.

[0012] The surface of each gas diffusion layer 20 opposite to the surface bonded to the MEA 30 faces the separators 40, 50. The two separators 40, 50 have uneven surfaces. Gas flow channels 42, 52 recessed in a direction away from the opposing gas diffusion layer 20 are formed by convex portions 46, 56 on the uneven surfaces of the separators 40, 50 contacting the gas diffusion layer 20. In other words, the surface of the separator 40 facing the gas diffusion layer 20 is formed with a plurality of gas flow channels 42 and convex portions 46 that contact the gas diffusion layer 20 with the gas flow channels 42 spaced apart. Similarly, the surface of the separator 50 facing the gas diffusion layer 20 is formed with a plurality of gas flow channels 52 and convex portions 56 that contact the gas diffusion layer 20 with the gas flow channels 52 spaced apart.

[0013] Gas flows through the recesses (gas flow channels 42, 52) on the uneven surfaces of the separators 40, 50, but almost no gas flows through the protrusions 46, 56 that contact the gas diffusion layer 20. Therefore, these protrusions 46, 56 are an example of a "non-flow channel portion." The gas flow channels 52 of the separator 50 supply hydrogen gas as an anode gas to the anode side of the MEGA 21. The multiple gas flow channels 52 extend along the first direction X and are arranged in the second direction Y, separated from each other by the protrusions 56. In other words, the separator 50 has gas flow channels 52 and protrusions 56 alternately in the second direction Y. The gas flow channels 42 of the separator 40 supply air as a cathode gas to the cathode side of the MEGA 21. The multiple gas flow channels 42 extend along the first direction X and are arranged in the second direction Y, separated from each other by the protrusions 46. That is, the separator 40 has the gas flow channels 42 and the protrusions 46 arranged alternately in the second direction Y.

[0014] The separator 50 has a coolant flow field 54 formed on the opposite side of the protrusion 56. The separator 40 has a coolant flow field 44 formed on the opposite side of the protrusion 46. That is, the coolant flow field 54 of the separator 50 of the fuel cell 10 shown in FIG. 1 faces and combines with the coolant flow field 44 of the separator 40 of another fuel cell 10 stacked on the + side of the fuel cell 10 in the stacking direction Z, thereby forming a single coolant flow field. Similarly, the coolant flow field 44 of the separator 40 of the fuel cell 10 shown in FIG. 1 faces and combines with the coolant flow field 54 of the separator 50 of another fuel cell 10 stacked on the − side of the fuel cell 10 in the stacking direction Z, thereby forming a single coolant flow field. A coolant for cooling the fuel cell stack 100 flows through these coolant flow fields.

[0015] The separators 40 and 50 are made of a material that is gas-impermeable and electron-conductive, and may be made of metal plates such as stainless steel, titanium, etc. The separators 40 and 50 are press-molded plates made by pressing metal plates.

[0016] FIG. 2 shows a simplified view of a portion of the surface of the cathode-side separator 40 facing the gas diffusion layer 20, viewed from the MEGA 21 side. As can be seen from FIG. 2, in the separator 40, multiple gas flow channels 42 extend along the first direction X and are arranged side by side in the second direction Y, separated by protrusions 46. As described above, the protrusions 46 are in contact with the gas diffusion layer 20. The arrows in the gas flow channels 42 generally indicate the direction of gas flow. At least one of the multiple gas flow channels 42 has at least one throttle section 43 formed therein that narrows the cross-sectional area of ​​the gas flow channel 42. The throttle section 43 narrows the cross-sectional area of ​​the gas flow channel 42 compared to the portion other than the throttle section 43.

[0017] 2, the constricted portion 43 protrudes into the gas flow path 42 so as to narrow the flow path width in the second direction Y. The side plates that define the gas flow path 42 in the second direction Y are shared with the convex portions 46 on both sides of the gas flow path 42 in the second direction Y. Therefore, the constricted portion 43 may be understood as a portion where the thickness of such a side plate that is shared by the gas flow path 42 and the convex portions 46 is locally increased to narrow the flow path width of the gas flow path 42 in the second direction Y. Furthermore, although not shown, the constricted portion 43 may be designed so that the height of the gas flow path 42 in the stacking direction Z is lower than the portion other than the constricted portion 43.

[0018] FIG. 2 further illustrates an enlarged view of one of the throttle portions 43. According to this embodiment, the throttle portion 43 has slits 48 extending from the gas flow paths 42 toward the protruding portions 46 on the surface facing the gas diffusion layer 20. In FIG. 2 and FIGS. 3 and 4 described below, each of the multiple slits 48 is indicated by a simple solid line. The slits 48 may also be referred to as grooves. According to FIG. 2, the slits 48 extend substantially parallel to the second direction Y and open toward the gas flow paths 42 and the gas diffusion layer 20. The slits 48 also extend to the vicinity of the boundary between the throttle portion 43 and the protruding portions 46. However, the boundary between the throttle portion 43 and the protruding portions 46 does not necessarily have to be clear. The slits 48 do not penetrate the plate thickness of the protruding portions 46 to open into the coolant flow paths 44, including the examples shown in FIGS. 3 and 4. The surface of the throttle portion 43 shown in FIG. 2 can be considered to be in contact with the gas diffusion layer 20, similar to the protruding portions 46.

[0019] As described above, according to this embodiment, the fuel cell 10 includes an MEA 30, a gas diffusion layer 20 bonded to the MEA 30, a separator 40 having a plurality of gas flow paths 42 and non-flow path portions (protrusions 46) that are formed on a surface facing the gas diffusion layer 20 and that separate the gas flow paths 42 and are in contact with the gas diffusion layer 20, and at least one throttle portion 43 that is formed in at least one of the plurality of gas flow paths 42 and narrows the cross-sectional area of ​​the flow path. The throttle portion 43 has a slit 48 that extends from the gas flow path 42 toward the non-flow path portion on the surface facing the gas diffusion layer 20.

[0020] According to the above configuration, the slits 48 formed on the surface of the throttle section 43 facing the gas diffusion layer 20 ensure a gas supply path to the gas diffusion layer 20 near the non-flow path section. As a result, even if a portion of the gas diffusion layer 20 near the non-flow path section is compressed due to pressure from the non-flow path section, causing a decrease in gas permeability or diffusibility in that portion, the decrease in gas supply to the MEA 30 through the gas diffusion layer 20 can be compensated for. This makes it possible to avoid a decrease in the power generation performance of the fuel cell 10.

[0021] 3 and 4 each show an example of the slits 48 of the throttle portion 43, which is different from that shown in FIG. 2. For FIGS. 3 and 4, explanations that are common to those given with reference to FIG. 2 will be omitted. As shown in FIG. 3, the slits 48 may reach near the center of the protrusions 46 in the second direction Y. By forming the slits 48 longer in this way, it is possible to reliably supply gas to the area of ​​the gas diffusion layer 20 that contacts the protrusions 46.

[0022] As shown in Fig. 4, the extension direction of the slit 48 may not be parallel to the second direction Y but may be inclined. According to Fig. 4, the extension direction of the slit 48 is inclined with respect to the second direction Y so that the end of the slit 48 on the gas flow path 42 side faces the upstream side of the gas flow path 42. With this configuration, the gas flowing through the gas flow path 42 can easily flow into the slit 48. It is also possible to combine the various aspects of the slit 48 disclosed in Figs. 2, 3, and 4.

[0023] The feature of this embodiment in which the throttle portion 43 of the gas flow path has the slit 48 on the surface facing the gas diffusion layer 20 can be similarly applied to the gas flow path on the anode side, that is, the gas flow path 52 of the separator 50.

[0024] Note that the thickness of the gas diffusion layer 20 when the separators 40, 50 are assembled to the MEGA 21 may be measured in advance through experiments or simulations to determine the air permeability within the gas diffusion layer 20, and the number or length of the slits 48 may be increased in the narrowed portions 43 at positions corresponding to the areas with low air permeability when the separators 40, 50 are manufactured. The slits 48 may be formed when the separators 40, 50 are press-molded, or may be formed by laser processing.

[0025] Although specific examples of the technology disclosed in this specification have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. Furthermore, the technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings simultaneously achieves multiple objectives, and achieving one of those objectives itself has technical utility. [Explanation of symbols]

[0026] 10: fuel cell, 20: gas diffusion layer, 30: membrane electrode assembly (MEA), 21: membrane electrode gas diffusion layer assembly (MEGA), 40: separator, 42: gas flow path, 43: restriction portion, 46: convex portion, 48: slit, 50: separator, 52: gas flow path, 56: convex portion, 100: fuel cell stack

Claims

[Claim 1] a membrane electrode assembly; a gas diffusion layer joined to the membrane electrode assembly; a separator having a surface facing the gas diffusion layer, the separator having a plurality of gas flow channels and non-flow channel portions that are in contact with the gas diffusion layer and separate the gas flow channels from each other; a fuel cell including at least one throttle portion formed in at least one of the plurality of gas flow paths, the throttle portion narrowing a cross-sectional area of ​​the flow path, The throttle portion has a slit on the surface facing the gas diffusion layer, the slit extending from the gas flow path toward the non-flow path portion.

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