Gas diffusion member

Abstract

Provided is a rollable gas diffusion member. This gas diffusion member is made of a flexible material and is disposed between a separator and a catalyst layer in a fuel cell. The gas diffusion member comprises: a gas diffusion part that comprises a plurality of first grooves which are formed in a first direction and which serve as gas flow paths in a surface on the separator side, and a first rib which is formed between adjacent first grooves; and an introduction part that connects the gas diffusion part and a manifold for supplying gas to be introduced into the gas diffusion part. The introduction part comprises: a plurality of second grooves having a second direction different from the first direction in the first grooves; a second rib formed between adjacent second grooves; and a third groove having the same direction as the first direction.

Description

Gas diffusion material

[0001] The present disclosure relates to a gas diffusion member.

[0002] In a gas supply diffusion layer for a fuel cell that allows gas permeation and diffusion, a configuration has been proposed in which the separator-side surface of the porous layer is provided with a gas flow channel groove extending from the gas inlet side to the gas outlet side (e.g., Patent Documents 1 and 2).

[0003] Re-tabulation 2019 / 207811 publication Re-tabulation 2019 / 239605 publication

[0004] Conventional gas supply diffusion layers for fuel cells are generally manufactured from nonwoven carbon fiber composite materials and distributed as rolled products. However, gas diffusion layers with gas flow channel grooves, including those of the prior art described above, have the problem of being difficult to roll in a specific direction depending on the direction of the grooves. In particular, when gas flow channel grooves are formed in multiple different directions, it is difficult to distribute them as rolled products. Furthermore, when such gas diffusion layers are cut to a predetermined size and made into individual sheet-like products, problems arise, such as increased costs.

[0005] The present disclosure has been made in consideration of the above-mentioned problem as an example, and the object of the present disclosure is to provide a gas diffusion member that can be distributed as a roll-shaped product even if it has flow path grooves formed in multiple directions.

[0006] In order to solve the above problems, according to one aspect of the present disclosure, there is provided a gas diffusion member made of a flexible material and arranged between a separator and a catalyst layer of a fuel cell, the gas diffusion member comprising: a gas diffusion section having a plurality of first grooves formed in a first direction on the surface facing the separator, which serve as gas flow paths, and first ribs formed between adjacent first grooves; a manifold for supplying gas to be introduced into the gas diffusion section; and an introduction section connecting the gas diffusion section, the introduction section comprising a plurality of second grooves having a second direction different from the first direction of the first grooves, second ribs formed between adjacent second grooves, and a third groove having the same direction as the first direction.

[0007] According to the present disclosure, even if flow path grooves are formed in multiple directions in each region, a rollable gas diffusion member can be provided, which can contribute to efficiency in terms of productivity, storage, logistics, etc.

[0008] 10 is a schematic diagram showing a configuration example of a fuel cell vehicle having a fuel cell according to an embodiment of the present disclosure. FIG. 11 is a schematic diagram showing a configuration example of a fuel cell according to an embodiment of the present disclosure. FIG. 12 is a schematic diagram showing a configuration example of a fuel cell cell constituting a fuel cell according to an embodiment of the present disclosure. FIG. 13 is a schematic diagram showing a configuration example of a gas diffusion member having easy rolling properties in the X-axis direction according to an embodiment of the present disclosure. FIG. 14 is a perspective view from the AA' cross section of FIG. 4 in the Y-axis direction. FIG. 15 is a perspective view from the BB' cross section of FIG. 4 in the Y-axis direction. FIG. 16 is a perspective view from the CC' cross section of FIG. 4 in the Y-axis direction. FIG. 17 is a schematic diagram showing a configuration example of a gas diffusion member having easy rolling properties in the X-axis direction according to a modified example. FIG. 18 is a schematic diagram showing a configuration example of a gas diffusion member having easy rolling properties in the X-axis direction according to another modified example. FIG. 19 is a perspective view from the DD' cross section of FIG. 10 in the Y-axis direction. FIG. 19 is a schematic diagram showing a configuration example of a gas diffusion member having easy rolling properties in the X-axis direction according to another modified example.

[0009] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functions are designated by the same reference numerals, and redundant description will be omitted. Furthermore, for configurations other than those described in detail below, publicly known technologies, including those described in the patent documents listed above, and vehicle configurations may be appropriately applied.

[0010] <Fuel Cell Vehicle 200> Figure 1 is a schematic diagram showing an example of the configuration of a fuel cell vehicle 200 equipped with a fuel cell 100 according to this embodiment. This fuel cell vehicle 200 is configured as a four-wheel drive vehicle in which a driving torque output from a driving force source that generates driving torque for the vehicle is transmitted to the wheels. In this embodiment, the driving force source can be, for example, a well-known electric motor disposed on the front wheel side. Note that in addition to the electric motor described above, the driving force source may also include an internal combustion engine such as a gasoline engine, a diesel engine, or a gas turbine engine.

[0011] A power supply system that supplies the desired electric power to such a driving force source includes a fuel cell 100, the detailed structure of which will be described later, a hydrogen gas supply unit including a known hydrogen tank 23 and piping, an air supply unit including a known compressor 31 and piping, a known secondary battery such as a lithium ion secondary battery or a lead storage battery, a known converter, and a control unit CU that controls these. In this power supply system, the fuel cell 100 and the secondary battery can each supply electric power to a load including the electric motor described above.

[0012] In addition, in the hydrogen gas supply section for supplying fuel (hydrogen) gas to the fuel cell 100, the hydrogen gas stored in the hydrogen tank 23 is supplied to the anode side flow path of the above-mentioned fuel cell 100 via a hydrogen intake valve 32a having a known structure installed in the hydrogen supply flow path.

[0013] A portion of the hydrogen gas discharged from the fuel cell 100 may be returned to the hydrogen supply flow path by a circulation flow path and a known circulation pump. The remainder of the hydrogen gas discharged from the fuel cell 100 is diluted by a diluter 35 at predetermined timings under the control of the control unit CU via the opening and closing operation of a known hydrogen exhaust valve 32b, and then released (exhausted) to the atmosphere.

[0014] On the other hand, the air supply unit for supplying oxygen gas (air) to the fuel cell 100 is configured to include, in addition to the above-mentioned compressor 31, a known air supply valve 32c and an air exhaust valve (back pressure valve) 32d that adjust the amount of oxygen (air) supplied to the fuel cell 1. In addition, this air supply unit may further include a known flow rate sensor (not shown) that can measure the flow rate of air supplied to the fuel cell 100.

[0015] The air taken in by the compressor 31 is supplied to the cathode-side flow path in the fuel cell 100 via an air supply valve 32c and a known humidifier (not shown). The air supplied to the fuel cell 100 is also supplied to the diluter 35 as cathode off-gas under the control of an oxygen exhaust valve (back pressure valve) 32d by the control unit CU.

[0016] The control device CU is configured to include one or more processors (CPUs (Central Processing Units)) and one or more memories communicatively connected to the one or more processors. The control device CU may be configured to be connectable to a known external network such as the Internet via various known communication devices, such as a smartphone.

[0017] The control unit CU is electrically connected to the compressor 31, the valves 32 (hydrogen intake valve 32a, hydrogen exhaust valve 32b, air supply valve 32c, and oxygen exhaust valve 32d), temperature sensors, speed sensors, and other known on-board sensors (not shown), either directly or via communication means such as a CAN (Controller Area Network) or LIN (Local Internet).

[0018] <Fuel Cell 100, Fuel Cell Unit 70> Next, a fuel cell 100 in which fuel cell units 70 of this embodiment are stacked will be described with reference to Figures 2 and 3. The fuel cell 100 has a stack structure in which a plurality of fuel cell units 70, each having an electromotive force of about 1 V, are connected in series and stacked. As an example, the fuel cell 100 of this embodiment can be a polymer electrolyte fuel cell (PEFC) in which the fuel cell units 70 are connected in series within a pair of known end plates 60 (a first end plate 60A and a second end plate 60B) that pressurize and hold the fuel cell at both ends so as to provide the system voltage required by the fuel cell vehicle 200.

[0019] The fuel cell 70 includes a pair of known separators 80 (a cathode-side separator 80A and a fuel-side separator 80B) disposed on the fuel electrode side and the air electrode side, respectively, and a membrane electrode assembly 90 interposed between them. The membrane electrode assembly 90 includes at least a cathode catalyst layer 20, a known anode catalyst layer 30 disposed opposite the cathode catalyst layer 20, and a known polymer electrolyte membrane 10 disposed between the cathode catalyst layer 20 and the anode catalyst layer 30. The membrane electrode assembly 90 further includes a cathode-side gas diffusion layer (first GDL) 40 and a fuel-side gas diffusion layer (second GDL) 50. The cathode-side gas diffusion layer (first GDL) 40 is disposed between the cathode-side separator 80A and the cathode catalyst layer 20, and the fuel-side gas diffusion layer (second GDL) 50 is disposed between the fuel-side separator 80B and the anode catalyst layer 30.

[0020] 4 and 6, a gas diffusion member for a fuel cell according to the present disclosure will be described below using an air electrode-side gas diffusion layer (first GDL) 40 as an example. Note that the gas diffusion member for a fuel cell according to the present disclosure is not limited to the above. That is, the gas diffusion member for a fuel cell according to the present disclosure can also be applied to a fuel electrode-side gas diffusion layer (second GDL) 50 arranged on the anode gas side of the fuel cell.

[0021] The cathode-side gas diffusion layer (first GDL) 40 is made of a material that is both electrically conductive and gas permeable. More specifically, the cathode-side gas diffusion layer (first GDL) 40 is made of a porous and flexible substrate such as a carbon material. The cathode-side gas diffusion layer (first GDL) 40 includes a gas diffusion section 41 that is in contact with the cathode catalyst layer 20 and through which air is diffused, and an inlet section 43 that connects the gas diffusion section 41 to a manifold MF that supplies gas to the gas diffusion section 41. The gas diffusion section 41 and the inlet section 43 may be molded integrally.

[0022] Generally, in a fuel cell, a fuel gas or an oxidant gas is introduced into a manifold on the gas inlet side, passes through a gas flow path, and is discharged from a manifold on the outlet side. When a gas, such as air, is introduced into the manifold on the inlet side, the introduced air diffuses through the gas diffusion layer.

[0023] The air electrode-side gas diffusion layer (first GDL) 40 of the present disclosure is disposed between the air electrode-side separator 80A and the cathode catalyst layer 20, and includes a gas flow path for gas diffusion on the surface facing the air electrode-side separator 80A. More specifically, the air electrode-side gas diffusion layer (first GDL) 40 includes a plurality of first ribs 413 extending linearly in the Y direction shown in FIG. 4 within the gas diffusion section 41. The air electrode-side gas diffusion layer (first GDL) 40 further includes a plurality of first grooves 411 formed between adjacent first ribs 413 and extending linearly in the Y direction. Two adjacent first ribs 413 and the first grooves 411 formed therebetween form a gas flow path GF １ This gas flow path GF １ has the function of diffusing the air supplied from the manifold MF into the gas diffusion section 41 .

[0024] 5 , the heights (Ha) of the multiple first ribs 413 may be the same. Furthermore, the depth of the first grooves 411 corresponds to the height (Ha) of the first ribs 413. The multiple first ribs 413 and the multiple first grooves 411 arranged therebetween are arranged alternately and at equal intervals in the X direction of the gas diffusion section 41. Note that hereinafter, the Y direction is defined as the direction in which the first grooves 411 extend linearly, the X direction is defined as the direction perpendicular to the Y direction, and the Z direction is defined as the thickness direction of the air electrode-side gas diffusion layer (first GDL) 40.

[0025] 5, the widths of the first rib 413 and the first groove 411 in the X direction are generally the same, but this is not limiting and a person skilled in the art can appropriately set the optimum width. Specifically, if the width of the first rib 413 is larger than that of the first groove 411, the strength of the entire gas diffusion section 41 can be improved. Furthermore, if the width of the first groove 411 is larger than that of the first rib 413, the pressure loss during gas diffusion can be reduced, and the power generation efficiency of the fuel cell can be improved.

[0026] 4, the first rib 413 and the first groove 411 extend in the Y direction without changing their width, but this is not limited to this. Specifically, by increasing the width of the first groove 411 with increasing distance from the inlet 43, it is possible to reduce pressure loss during gas diffusion and improve the power generation efficiency of the fuel cell.

[0027] The top surface of the first rib 413 and the bottom surface of the first groove 411 may or may not be flat and parallel to the air electrode side separator 80A.

[0028] The cathode-side gas diffusion layer (first GDL) 40 of the present disclosure has the gas flow path GF １ The provision of the first rib 413 and the first groove 411 provides the following advantages: The cathode-side gas diffusion layer (first GDL) 40 has irregularities on the surface facing the cathode-side separator 80A, which increases the surface area and improves gas diffusion efficiency. Furthermore, the surface facing the cathode-side separator 80A does not need to have a gas flow path, which reduces the separator processing costs.

[0029] Furthermore, the cathode-side gas diffusion layer (first GDL) 40 includes an inlet 43 between the gas diffusion section 41 and the manifold MF. The inlet 43 serves to introduce gas supplied from the manifold MF into the gas diffusion section 41. As shown in FIG. 4 , the inlet 43 includes grooves extending in two different directions. More specifically, the inlet 43 includes a plurality of third grooves 431 extending in the Y direction on extensions of the first grooves 411 of the gas diffusion section 41, and a second groove 433 extending in the same plane as the third grooves 431 and in a direction intersecting the Y direction (the direction of arrow P in FIG. 4 ). Furthermore, the inlet 43 may include a plurality of second ribs 435 between two adjacent second grooves 433. As shown in FIG. 4 , the second ribs 435 of the inlet 43 are interspersed between the second grooves 433 and the third grooves 431 extending in two different directions.

[0030] Fig. 6 is a cross-sectional view taken along the line B-B' in Fig. 4, and Fig. 7 is a cross-sectional view taken along the line C-C'. Figs. 6 and 7 show the cross-sectional shape of the second rib 435 in the introduction portion 43. As shown in Figs. 6 and 7, when different cross sections in the Y direction are observed, the second ribs 435 are arranged to protrude at different positions in the X direction. When viewed in a plan view as in Fig. 4, the second ribs 435 are arranged in a regularly dispersed manner on at least a portion of the surface of the introduction portion 43 facing the air electrode-side separator 80A.

[0031] As shown in FIG. 4, the third groove 431 (W １ The width of the third groove 431 is generally the same as the width of the first groove 411, but is not limited to this. In other words, the width of the third groove 431 can be made narrower than the width of the first groove 411, and in this case, the overall strength of the introduction portion 43 can be improved.

[0032] The top surface of the second rib 435 in the introduction portion 43 contacts and supports the surface on the air electrode side separator 80A side. In this way, the second groove 433, the third groove 431, and the second rib 435 form the gas flow path GF ２ The gas flow path GF is formed. ２ represents the gas flow path GF in the gas diffusion section 41. １ It is connected to.

[0033] 5 to 7, the heights (Ha) of the multiple second ribs 435 may be the same as each other. The height (Hb) of the second ribs 435 may be the same as the height (Ha) of the first rib 413. The depths of the second grooves 433 and the third grooves 431 correspond to the height (Hb) of the second ribs 435.

[0034] As shown in FIG. 4 , the second grooves 433 extend linearly in a direction inclined at approximately 30 to 60 degrees with respect to the Y direction. The multiple second grooves 433 are arranged parallel to one another within the introduction section 43. Furthermore, the multiple second grooves 433 intersect with the multiple third grooves 431, resulting in multiple second ribs 435 arranged in a staggered pattern within the introduction section 43. While the shape of each second rib 435 is shown as a parallelogram in FIG. 4 , this is not limiting. That is, the shape of each second rib 435 may be a diamond, a circle, or the like. The arrangement and shape of the second ribs 435 are preferably such that gas supplied from the manifold MF can be introduced into the gas diffusion section 41 and that the air electrode-side gas diffusion layer (first GDL) 40 can roll around its axis in the Y direction.

[0035] In this embodiment, the cathode-side gas diffusion layer (first GDL) 40 has a gas flow path GF ２ By providing the introduction portion 43, for example, the following effects can be achieved: Because the third grooves 431 are formed on the extensions of the first grooves 411, it is possible to roll the cathode-side gas diffusion layer (first GDL) 40 around the Y direction as an axis. In other words, the grooves and ribs of the introduction portion 43 do not unnecessarily hinder the rolling around the Y direction as an axis.

[0036] In this embodiment, the inlet portion 43 is formed with a second groove 433 extending from the manifold MF toward the gas diffusion portion 41. This makes it possible to make the flow velocity distribution uniform when introducing gas.

[0037] In the present embodiment, the inlet portion 43 includes second ribs 435 between adjacent second grooves 433. Therefore, the gas introduced from the manifold MF into the inlet portion 43 flows between the second ribs 435 and is introduced into the gas diffusion portion 41. Note that a portion of the gas flowing between the second ribs 435 may branch off and flow into the third groove 431.

[0038] [Modification 1] The cathode-side gas diffusion layer (first GDL) 40a of Modification 1 will be described with reference to Figure 8. The cathode-side gas diffusion layer (first GDL) 40a of Modification 1 basically has the same configuration as the fuel cell gas supply diffusion layer 40 according to the first embodiment, but differs from the first embodiment in the shape of the second rib, etc. Therefore, the differences will be mainly described, and the same reference numerals will be used to designate common features, and their description will be omitted.

[0039] The shape of the second rib 435a in Modification 1 is longer in the P direction in FIG. 8 than the second rib 435 in the first embodiment described above. As a result, the number of second ribs 435a in the introduction portion 43 is fewer than the number of second ribs 435 in the first embodiment. Furthermore, the number of third grooves 431a in Modification 1 is fewer than the number of third grooves 431 in the first embodiment. In other words, in this modification, the distance between adjacent third grooves 431a is wider than the distance between adjacent first grooves 411. The configuration of Modification 1 increases the area of ​​the second rib 435a in the introduction portion 43 compared to the first embodiment, which has the effect of improving the strength of the introduction portion 43.

[0040] 8, the third grooves 431a are formed linearly on the extension of the first grooves 411, but this is not limiting. That is, the third grooves 431a may be formed discontinuously in the Y direction, as shown in FIG. 9. In this case, it can be said that the multiple third grooves 431a formed on adjacent second grooves 431a have an offset as shown in the figure.

[0041] [Modification 2] The cathode-side gas diffusion layer (first GDL) 40b of Modification 2 will be described using Figures 10 and 11. Figure 10 is a schematic diagram showing an example of the structure of a gas diffusion member having easy rollability in the X-axis direction according to this modification, and Figure 11 is a schematic diagram showing a cross section taken along line D-D' in Figure 10. The cathode-side gas diffusion layer (first GDL) 40b of Modification 2 differs from the first embodiment in the depth of the grooves in the inlet portions 43. Therefore, these differences will be mainly described, and common features will be denoted by the same reference numerals and will not be described again.

[0042] As shown in FIG. 11 , the depth (Hc) of the second groove 433b and the third groove 431b in Modification 2 is deeper than the depth (Hb) of the second groove 433 and the third groove 431 in the first embodiment. Therefore, compared to the first embodiment, this provides the effect of reducing pressure loss when introducing gas into the introduction portion 43. In this modification, the width or depth of the second groove 433b and the width or depth of the third groove 431b may be different from each other. For example, if the depth of the second groove 433b is deeper than the third groove 431b, this can contribute to reducing pressure loss when gas travels in the P direction. In this modification, the width or depth of the third groove 431b may be different from the width or depth of the first groove 411. Furthermore, the width or depth of the second groove 433b may be different from the width or depth of the first groove 411. If the width of the second groove 433b or the third groove 431b is wider, this can contribute to reducing pressure loss. Similarly, if the second groove 433b or the third groove 431b is deep, it can contribute to reducing pressure loss.

[0043] [Variation 3] A cathode-side gas diffusion layer (first GDL) 40c of Variation 3 will be described with reference to FIGS. 12 and 13. FIG. 12 is a plan view of Variation 3, and FIG. 13 is a perspective view of the Y-axis direction from the E-E' cross section in FIG. 12. As shown in FIGS. 12 and 13, Variation 3 differs from the above-described embodiment and variations in the shape of the second ribs 435c. More specifically, the length of the second ribs 435c in Variation 3 in the P direction is the same as that of Variation 1. Meanwhile, with regard to the height of the second ribs 435c, the highest point (Ha) is the same as that of the first ribs 413, while a recess 436 is provided in the center of each second rib 435c in the P direction. As shown in FIG. 11, this recess 436 is provided on an extension of the first groove 411 of the gas diffusion section 41. As shown in FIG. 13, the height Hd of the recess 436 is smaller than the height (Ha) of the first ribs 413.

[0044] As in Modification 3, by providing a recess 436 in the center of the second rib 435c, this recess 436 assists the rolling of the air electrode-side gas diffusion layer (first GDL) 40 about the axis in the Y direction, thereby further improving the rolling properties. Furthermore, the height of the second rib 435c may be made different from the height of the first rib 413. In this case, the rib height may be adjusted depending on the difference in surface pressure acting on the rib in the introduction section and the power generation section.

[0045] [Modification 4] A cathode-side gas diffusion layer (first GDL) 40d of Modification 4 will be described with reference to Fig. 14. Fig. 14 is a plan view of Modification 4. As shown in Fig. 14, Modification 4 differs from the above-described embodiment and modifications in the arrangement of second grooves 433d, third grooves 431d, and second ribs 435d.

[0046] More specifically, in the fourth modification, the gas diffusion section 41 includes a plurality of first grooves 411d extending linearly in the X direction and a plurality of first ribs 413d disposed between two adjacent first grooves 411d. The gas diffusion section 41 further includes a plurality of fourth grooves 415d extending linearly in the Y direction. The first grooves 411d and the fourth grooves 415d intersect at right angles within the gas diffusion section 41.

[0047] On the other hand, in the introduction portion 43, the third groove 431d extends linearly in the X direction, and the second rib 435d is disposed between two adjacent third grooves 431d. The second groove 433d extends in a direction different from the X direction and the Y direction in the XY plane.

[0048] The above-described configuration of the air electrode-side gas diffusion layer (first GDL) 40d of Modification 4 provides the following advantages. When rolling around the X-direction, the grooves and ribs do not interfere with the rolling, improving the rolling properties. The second groove 433d and the fourth groove 415d are provided in the inlet section 43 and the gas diffusion section 41, respectively, making it possible to roll around the Y-direction. In other words, the air electrode-side gas diffusion layer (first GDL) 40d of Modification 4 can be used for both rolling around the X-direction and rolling around the Y-direction.

[0049] Although the preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings, the technology of the present disclosure is not limited to such examples. It is clear that a person skilled in the art of the technology to which the present disclosure pertains can conceive of various modified or altered examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure.

[0050] 100: fuel cell 100, 200: fuel cell vehicle, 10: polymer electrolyte membrane, 20: cathode catalyst layer, 30: anode catalyst layer, 40: air electrode side gas diffusion layer (first GDL), 41: gas diffusion portion, 411: first groove, 413: first rib, 43: inlet portion, 431: third groove, 433: second groove, 435: second rib, 50: fuel electrode side gas diffusion layer (second GDL), 60: end plate, 70: fuel cell, 80: separator, 90: membrane electrode assembly

Claims

1. A gas diffusion member made of a flexible material and arranged between a separator and a catalyst layer of a fuel cell, comprising: a gas diffusion section having a plurality of first grooves formed in a first direction on the surface facing the separator to form gas flow paths, and first ribs formed between adjacent first grooves; a manifold for supplying gas to be introduced into the gas diffusion section, and an introduction section connecting the gas diffusion section, wherein the introduction section has a plurality of second grooves having a second direction different from the first direction, second ribs formed between adjacent second grooves, and third grooves having the same direction as the first direction.

2. The gas diffusion member according to claim 1, wherein the groove depth of the second grooves and the groove depth of the first grooves are different from each other.

3. The gas diffusion member according to claim 1 or 2, wherein the height of at least a portion of the second ribs is different from the height of the first ribs.

4. The gas diffusion member according to claim 1 or 2, wherein the width or depth of the third groove is different from the width or depth of the first groove or the second groove.

5. The gas diffusion member according to claim 1 or 2, wherein the interval between adjacent third grooves is different from the interval between adjacent first grooves.

6. The gas diffusion member according to claim 1 or 2, wherein the third grooves are discontinuously formed, and the third grooves formed on adjacent second grooves have an offset.

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