fuel cell

Abstract

To provide a fuel battery cell in which an amount of gas not contributing to power generation is reduced.SOLUTION: A fuel battery cell 10 comprises: a membrane-electrode assembly 11 which is obtained by forming catalyst layers 11b on both surfaces of an electrolyte membrane 11a; gas diffusion layers (GDLs) 21 which are disposed on both surfaces of the membrane-electrode assembly 11; a pair of separators 17 which sandwich the membrane-electrode assembly 11 via the GDLs 21 on both surfaces, and have gas passages 18 on contact surfaces with the GDLs 21; cell seals 19 which are annularly disposed on the separators 17 so as to surround the GDLs 21; gap grooves 26 which are formed between the GDLs 21 and the cell seals 19 along a passage direction α of the gas passages 18; and projecting ridge parts 28 which are provided between the gap grooves 26 and end sides of the catalyst layers 11b along the passage direction α, and protrude from the separators 17 toward the GDLs 21 so as to push the GDLs 21.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a fuel cell that generates electricity by electrochemically reacting a fuel gas in a membrane electrode assembly. [Background technology]

[0002] A fuel cell device is composed of a large number of fuel cell units called single cells stacked together. A single cell is composed of an anode separator, an anode gas diffusion layer (GDL), a membrane electrode assembly (MEA), a cathode GDL, and a cathode separator stacked in this order. Hydrogen gas supplied to the anode separator is pressurized by a pump external to the single cell and circulated within the fuel cell device. Oxidant gas such as oxygen supplied to the cathode separator is supplied at an increased flow rate by a compressor external to the single cell. Some of the water produced by the electrochemical reaction of these gases is pushed out by the supplied hydrogen gas and discharged to the outside of the single cell.

[0003] To prevent the leakage of these gases, a ring-shaped cell seal is disposed on the separator so as to surround the GDL, and the cell seal is made of a material such as a thermoplastic resin or a rubber material. However, cell seals made of thermoplastic resins can be thermally deformed by the application of heat and pressure during assembly, which can block the gas flow paths formed in the separators. Therefore, depending on the application or type of fuel cell device, rubber materials with high heat resistance are used for the separators. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-225477 Summary of the Invention [Problem to be solved by the invention]

[0005] However, rubber cell seals only undergo slight thermal deformation when heated and pressurized, which poses the problem of small gaps remaining unfilled due to the tolerances between the cell seal and GDL. Gas that flows into these gaps from the gas diffusion layer is discharged without contributing to power generation, reducing the power generation performance of the fuel cell device. This is because extra energy is required to supply gas to the MEA with sufficient pressure and to expel the generated water from the single cell.

[0006] The present invention has been made in consideration of the above circumstances, and has an object to provide a fuel cell in which gases that do not contribute to power generation are reduced. [Means for solving the problem]

[0007] a pair of separators sandwiching the membrane electrode assembly via the gas diffusion layers on both sides thereof and having gas flow paths on their contact surfaces with the gas diffusion layers; a cell seal arranged in a ring shape on the separators and surrounding the gas diffusion layers; a clearance groove formed between the gas diffusion layers and the cell seal along the flow path direction of the gas flow path; and a protruding ridge portion provided as a molding portion of the separator between the clearance groove and an edge of the catalyst layer along the flow path direction, the protruding ridge portion protruding from the separator toward the gas diffusion layer and pressing the gas diffusion layer. The anode-side protrusion and the cathode-side protrusion are arranged such that the centers of loads applied when pressed are offset from each other when viewed from above. It is something. [Effects of the Invention]

[0008] The present invention provides a fuel cell in which gases that do not contribute to power generation are reduced. [Brief explanation of the drawings]

[0009] [Figure 1]1 is a perspective view of a fuel cell device in which fuel cell devices according to an embodiment of the present invention are stacked; [Figure 2] FIG. 2 is a top view of a separator of a fuel cell according to an embodiment. [Figure 3] 2. FIG. 3 is a cross-sectional side view of the fuel cell according to the embodiment, taken along line II-II in FIG. [Figure 4] FIG. 10 is a partial top view of an end portion of a separator according to a modified example of the embodiment. [Figure 5] FIG. 10 is a partial top view of an end portion of a separator according to a second modified example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0011] First, a fuel cell device 50 according to an embodiment and a fuel cell 10 constituting this fuel cell device 50 will be outlined with reference to FIG. As shown in FIG. 1, the fuel cell device 50 has a plurality of stacked unit cells 10. The stack of unit cells 10 is fixed together by end plates 51 that sandwich the stack from both ends in the stacking direction and are bolted together with connecting bars (not shown).

[0012] FIG. 2 is a top view of the separator 17 of the unit cell 10 according to the embodiment. In FIG. 2, the separator 17 is provided with a cell seal 19, and the GDL 21 is also shown by a dashed line (imaginary line). 2, each unit cell 10 is provided with a gas supply port 12 and a gas exhaust port 13 that communicate with the stack, thereby forming a fuel cell device 50. In a large-capacity fuel cell device 50 required for a fuel cell vehicle or the like, several tens or more of unit cells 10 are stacked. The unit cell 10 according to the embodiment can be applied to fuel cell devices 50 of either a water-cooled type or an air-cooled type.

[0013] The unit cell 10 according to the embodiment has an arrangement structure in which a membrane electrode assembly (MEA) 11 is sandwiched between separators 17 with a gas diffusion layer (GDL) 21 interposed therebetween. The MEA 11 is configured by disposing electrode catalyst layers (hereinafter simply referred to as "catalyst layers") 11b on either side of an electrolyte membrane 11a. The catalyst layers 11b are configured by electrodes on the anode and cathode sides, each supporting a catalyst.

[0014] It should be noted that the "MEA" in the embodiment does not include the GDL 21. Furthermore, the GDL 21 and separator 17 are generally referred to as the anode GDL and anode separator when placed on the fuel electrode catalyst layer side, and the cathode GDL and cathode separator when placed on the air electrode catalyst layer side, but no particular distinction is made in this embodiment. In other words, the structural features of separator 17 and cell seal 19 described below can be provided on either the fuel electrode side or the air electrode side, as appropriate. Furthermore, the separator 17 referred to here can also include end plates 51.

[0015] The separator 17 is made of a metal plate such as a steel plate, a stainless steel plate, an aluminum plate, a plated steel plate, or a titanium steel plate, or carbon. On the contact surface between the separator 17 and the GDL 21, numerous strip-shaped irregularities are formed along the longitudinal direction by press working or the like to form the gas flow paths 18. In addition to the oxidant gas or hydrogen gas supplied onto the surface of the separator 17 from the gas supply port 12, water vapor generated by the electrochemical reaction of these gases flows through these gas flow paths 18.

[0016] The GDL 21 is a porous, flexible sheet-like member made of carbon paper, carbon cloth, or the like. The GDL 21 diffuses the various gases flowing through each gas flow path 18 and supplies them uniformly to the MEA 11. The GDL 21 is surrounded by a cell seal 19 arranged in a ring shape on the separator 17. The rubber cell seal 19 adheres or bonds to the separator 17 and also adheres tightly to the MEA 11, ensuring the airtightness of the reaction space 30 (Figure 3). In other words, the cell seal 19 prevents gases such as hydrogen gas from leaking from the GDL 21 to the outside of the single cell 10. The water produced by the electrochemical reaction and unreacted gases are discharged from the gas outlet 13. 2, the gas supply port 12 and gas exhaust port 13 on one diagonal line are surrounded by a cell seal 19 and isolated from the reaction space 30. These gas supply port 12 and gas exhaust port 13 are connected to the reaction space 30 on the back side of the separator 17, and supply or exhaust hydrogen gas or oxygen gas.

[0017] 3 is a side cross-sectional view of the unit cell 10 according to this embodiment taken along line II-II in FIG. 2. As shown in FIGS. 2 and 3, the GDL 21 is cut to a size larger than the extension range of the gas flow channel 18, and is provided so as to completely cover the entire extension range. As shown in FIG. 3, the catalyst layer 11b is designed to be approximately the same as the extension range of the gas flow passage 18 or slightly narrower in the direction perpendicular to the flow passage direction.

[0018] It is desirable that the outer size of the GDL 21 match the inner periphery size of the cell seal 19. However, in reality, due to tolerances, the GDL 21 is often slightly smaller than the inner periphery of the cell seal 19. Therefore, a gap groove 26 is formed between the GDL 21 and the cell seal 19 along the flow path direction α of the gas flow path 18.

[0019] When a thermoplastic resin cell seal 19 is used, this gap groove 26 is a gap that is lost when the cell seal 19 thermally deforms and expands during the manufacturing process. However, because the cell seal 19 according to the embodiment is made of rubber, this gap is not filled and remains, resulting in the gap groove 26 into which some of the gas flows. The gas that flows into the gap groove 26 does not come into contact with the catalyst layer 11b, and is therefore discharged from the gas outlet 13 without contributing to the electrochemical reaction. Therefore, it is necessary to supply more gas by the amount corresponding to the pressure of the gas flowing into the gap groove 26 to maintain the pressure at the specified value, which requires extra energy.

[0020] Therefore, in the unit cell 10 according to this embodiment, a ridge portion 28 is provided between the gap groove 26 and the edge of the catalyst layer 11b along the flow path direction α of the gas flow path 18. It is desirable that the ridge portion 28 extend beyond the inlet end and outlet end of the gas flow path 18 to both end edges of the GDL 21. In the cross-sectional view shown in FIG. 3, the protruding stripe 28 protrudes from the separator 17 toward the GDL 21 and presses against the GDL 21. At the portion of the GDL 21 where the ridge portion 28 presses the GDL 21, the pressure loss of the gas flowing inside the GDL 21 increases, and therefore the inflow of gas from the GDL 21 into the clearance groove 26 is suppressed.

[0021] It is desirable that the cross section of the ridge portion 28 taken along line II-II (FIG. 2) shown in FIG. 3 is triangular or semicircular. For example, if the ridge portion 28 is rectangular, when the ridge portion 28 presses against the GDL 21, the load is concentrated at the pressed point, reducing the load applied to other parts of the GDL 21 accordingly. If the load is unevenly distributed in this way and falls below the designed load value between the catalyst layer 11b and the GDL 21, the contact resistance within the unit cell 10 increases and the output decreases. Furthermore, if the load is concentrated at the pressed point, the load applied from the GDL 21 to the cell seal 19 also decreases, reducing the airtightness of the cell seal 19. If the airtightness of the cell seal 19 decreases, hydrogen gas may leak, reducing safety.

[0022] From the same perspective, to prevent load concentration, the anode-side ridge portion 28 and the cathode-side ridge portion 28 are positioned so that their load centers do not overlap when viewed from above when pressed. However, in order to utilize the fact that pressing with the ridge portion 28 increases the rigidity of the pressed portion of the GDL 21, it is desirable to position the anode-side ridge portion 28 and the cathode-side ridge portion 28 at positions that are not too far apart. The relative positions of the anode-side ridge portion 28 and the cathode-side ridge portion 28 are determined based on the load values ​​at the pressed portion and surrounding pressed portions.

[0023] The height of the ridge portion 28 is about 1 / 10 to 1 / 20 of the thickness of the GDL 21, which is about 200 μm to 300 μm, and is adjusted taking into account the load value on the GDL 21 at the pressing point. The number and width of the ridges 28 are also adjusted taking into consideration the load value on the GDL 21 at the pressing point. The ridges 28 can be formed, for example, by cutting a plate having a thickness equal to the thickness of the separator 17 plus the height of the ridges 28, or by pressing.

[0024] The edge of the GDL 21 forms one wall surface of the gap groove 26. A gas impermeable layer 29 may be formed by applying a resin or the like to one wall surface. By providing the impermeable layer 29, it is possible to prevent gas diffused in the GDL 21 from flowing into the gap groove 26, similar to the effect of the ridge portion 28.

[0025] 4 is a partial top view of the end of the separator 17 of the unit cell 10a (10) according to a modified embodiment. In FIG. 4 and FIG. 5 described later, the cell seal 19 and the GDL 21 shown by the dashed line are also shown on the separator 17, as in FIG. 2. In order to improve the effect of preventing gas from flowing into the gap groove 26, it is desirable to seal one of the opening ends 31 of the gap groove 26 with a cell seal 19a (19), as shown in Fig. 4. When laying the GDL 21 on the separator 17, the GDL 21 is slid so that one side thereof is brought into close contact with the cell seal 19a, thereby sealing one of the opening ends 31.

[0026] It is desirable that the opening end 31 to be sealed is on the gas inflow side. However, even if the opening end 31 on the gas outflow side is sealed, it is expected that a certain amount of pressure loss will be caused to prevent the gas from flowing into the gap groove 26. It is also possible to seal the opening end 31 of the gap groove 26 by bringing the end of the uneven protrusion 18a that forms the gas flow path 18 into close contact with the cell seal 19a.

[0027] FIG. 5 is a partial top view of an end portion of a separator 17 of a unit cell 10b (10) according to a second modified example of the embodiment. To prevent gas from flowing from the gas supply port 12 into the gap groove 26a (26), the gap groove 26a may be made serpentine, as shown in Fig. 5. Specifically, the gap groove 26a is made serpentine by providing irregularities on the opposing surfaces of the cell seal 19b (19) and the GDL 21a (21). By making the gap groove 26a serpentine, a pressure loss occurs in the gas that attempts to flow from the gas supply port 12 into the gap groove 26a, and therefore the flow of gas into the gap groove 26a is suppressed.

[0028] As described above, the unit cell 10 according to this embodiment can suppress the amount of hydrogen gas flowing into the gap groove 26, thereby reducing the flow rate of hydrogen gas that is pressurized to push out the generated water. Furthermore, the flow rate of the oxidant gas can also be reduced, thereby reducing the power consumption of the compressor. Therefore, the unit cell 10 can reduce gases that do not contribute to power generation.

[0029] Although an embodiment of the present invention has been described, this embodiment is presented as an example and is not intended to limit the scope of the invention. The embodiments may be embodied in various other forms, and various omissions, substitutions, modifications, and combinations may be made without departing from the spirit of the invention. The embodiments and their modifications are included in the scope of the inventions and their equivalents as defined in the claims, as well as in the scope and spirit of the inventions.

[0030] For example, in the embodiment, the gas flow passage of the separator is described as extending along the longitudinal direction of the separator, but the direction and shape of the gas flow passage are not particularly limited. Furthermore, although the embodiment has been described with reference to an example in which the cell seal is made of rubber, the present invention is applicable to a variety of unit cells in which gap grooves occur, regardless of the material of the cell seal. [Explanation of symbols]

[0031] 10 (10a, 10b)... fuel cell (single cell), 11... membrane electrode assembly (MEA), 11a (11)... electrolyte membrane, 11b (11)... catalyst layer, 12... gas supply port, 13... gas exhaust port, 14... alignment hole, 15... positioning pin, 17... separator, 18 (18a) ...gas flow path (convex portion of gas flow path), 19 (19a, 19b)...cell seal, 21 (21a)...gas diffusion layer (GDL), 26 (26a)...gap groove, 28...convex portion, 29...impermeable layer, 30...reaction space, 31...opening end, 50...fuel cell device, 51...end plate, α...flow path direction, GAS...gas (oxidant gas, hydrogen gas, water vapor).

Claims

1. a membrane electrode assembly formed by forming catalyst layers on both sides of an electrolyte membrane; gas diffusion layers disposed on both sides of the membrane electrode assembly and covering the catalyst layers; a pair of separators sandwiching the membrane electrode assembly via the gas diffusion layers on both sides, the separators having gas flow paths on the surfaces in contact with the gas diffusion layers; a cell seal disposed in a ring shape on the separator and surrounding the gas diffusion layer; a gap groove formed between the gas diffusion layer and the cell seal along a flow direction of the gas flow channel; a protruding ridge portion provided as a molding portion of the separator between the clearance groove and an edge of the catalyst layer along the flow path direction, the protruding ridge portion protruding from the separator toward the gas diffusion layer and pressing the gas diffusion layer, A fuel cell characterized in that the anode-side protruding portion and the cathode-side protruding portion are disposed such that the centers of load applied when pressed are offset from each other when viewed from above.

2. The fuel cell according to claim 1 , wherein the cell seal seals an open end of the clearance groove.

3. 3. The fuel cell according to claim 1, wherein the ridges extend to both ends of the gas diffusion layer in the flow path direction.

4. 4. The fuel cell according to claim 1, wherein a cross section of the ridge portion perpendicular to the flow path direction is triangular or semicircular.

5. 5. The fuel cell according to claim 1, wherein an impermeable layer is formed on an edge of the gas diffusion layer that forms one wall surface of the gap groove.

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