FUEL CELL SEPARATOR

Abstract

Separator for a fuel cell, which is used in a fuel cell (10) with a membrane electrode assembly (11), wherein the membrane electrode assembly (11) comprises an electrolyte membrane (12) and electrode layers (13, 14) which are connected in a thickness direction to opposite sides of the electrolyte membrane (12), The separator for a fuel cell includes the following: a metallic separator base part (22, 32) which is arranged in the thickness direction on an outside of the membrane electrode assembly (11) and has conductivity; a plurality of comb sections (23, 33) provided in the separator base (22, 32) and projecting towards the membrane electrode unit (11); and a plurality of depression sections (24, 34) provided in the separator base section (22, 32) and projecting in a direction opposite to the direction in which the ridge sections (23, 33) project, the comb sections (23, 33) and the sink sections (24, 34) are arranged alternately in one direction along a plane of the membrane electrode unit (11) and extend parallel to each other and Areas surrounded by the respective sink sections (24, 34) and a corresponding electrode layer (13, 14) each form a passage (25, 35) which supplies oxidation gas or fuel gas to the electrode layer, a first thin film (41, 51) is placed over entire surfaces of the comb sections (23, 33) and the sink sections (24, 34) facing the corresponding electrode layer (13, 14), which has a conductivity and corrosion resistance higher than that of the separator base part (22, 32) and on parts of the first thin film (41, 51) that are placed on the upper surfaces of the comb sections (23, 33), a second thin film (42, 52) is placed which has conductivity, characterized by the fact that a part of the second thin film (42, 52), which is placed on the top of each comb section (23, 33), has a groove (43, 53) extending linearly in a direction that intersects a direction in which the comb sections (23, 33) extend, and at least one end of the groove (43, 53) is connected to the passage (25, 35).

Description

BACKGROUND 1. Area

[0001] The present invention relates to a separator for a fuel cell, which is arranged in a fuel cell between membrane electrode units. 2. Description of the state of the art

[0002] Fig. Figure 4 shows a conventional fuel cell 70 disclosed in JP 2016-66531A. The fuel cell 70 comprises membrane electrode assemblies (MEAs) 71 and separators 75. The separators 75 are oriented in the thickness direction (from top to bottom). Fig. 4) on opposite sides of each membrane electrode assembly 71, centering the membrane electrode assembly 71. The membrane electrode assembly 71 comprises an electrolyte membrane 72 and two electrode layers arranged in the thickness direction on opposite sides of the electrolyte membrane 72. One of the electrode layers forms a cathode electrode layer 73, and the other electrode layer forms an anode electrode layer 74. In the fuel cell 70, the membrane electrode assemblies 71 are separated by the separators 75 such that each membrane electrode assembly 71 is centered in the thickness direction between the separators 75 on opposite sides.

[0003] Each separator 75 has a separator base 76 made of conductive metal. Each separator base 76 has several comb sections 77 projecting towards the membrane electrode assembly 71 and several sink sections 78 receding in the opposite direction to the projecting direction of the comb sections 77. The comb sections 77 and the sink sections 78 are oriented in one direction along the plane of the membrane electrode assembly 71 (in the left-to-right direction). Fig. 4) arranged alternately and extending parallel to each other.

[0004] Areas surrounded by the respective sink sections 78 and the cathode electrode layer 73 each form a passage 81 that supplies oxidation gas to the cathode electrode layer 73. Areas surrounded by the respective sink sections 78 and the anode electrode layer 74 each form a passage 82 that supplies fuel gas to the anode electrode layer 74.

[0005] A thin, conductive film 85 is placed on the upper surface of each comb section 77. These thin films 85 serve to suppress any increase in contact resistance between the membrane electrode assembly 71 and the separator base 76 of each separator 75, thereby reducing the influence of contact resistance on the reaction of fuel gas and oxidizer gas in the membrane electrode assembly 71. Contact resistance refers to the electrical resistance in the area comprising the interface between two objects when the objects are brought into contact and a current flows through them.

[0006] When fuel gas is supplied to the anode electrode layer 74 and oxidation gas to the cathode electrode layer 73 of the fuel cell 70 described above, current is generated in the membrane electrode assembly 71 based on the reaction of the fuel gas and the oxidation gas. At this point, water is produced by the reaction in the cathode electrode layer 73. Some of the water is located between the cathode electrode layer 73 and each thin film 85. A portion of the water located near the openings 81 flows together with the oxidation gas, which flows through the openings 81 at a high velocity, and is discharged to the outside of the fuel cell 70.

[0007] However, some of the water located away from the passages 81 is not carried away by the flow of oxidation gas through the passages 81 to the outside of the fuel cell 70, but remains between the cathode electrode layer 73 and the thin film 85. This remaining water can lead to insufficient diffusion of oxidation gas. This can reduce the reaction between fuel gas and oxidation gas.

[0008] Power generation efficiency can be improved by impregnating the cathode electrode layer 73 and the anode electrode layer 74 with a specific amount of water. In this respect, the thickness of the membrane electrode assembly 71 can be reduced. This allows the water generated in the cathode electrode layer 73 to move easily along the electrolyte membrane 72 towards the anode electrode layer 74. However, if more water than necessary is retained between the respective thin films 85 and the anode electrode layer 74, and excess water remains in the vicinity of the anode electrode layer 74, fuel gas cannot easily make contact with the anode electrode layer 74. This can reduce the reaction between fuel gas and oxidizer gas.

[0009] Furthermore, a separator for a fuel cell is known from JP 2010 - 129 464 A, which has the features specified in the preamble of claim 1. SUMMARY

[0010] The invention, particularly with regard to JP 2016 - 66 531 A, is based on the objective of providing a separator for a fuel cell that improves the removal capacity for water produced during power generation.

[0011] In a general embodiment, a separator for a fuel cell is provided which has the features specified in claim 1.

[0012] Further features and designs will be revealed in the following detailed description, drawings and claims. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a partial sectional view of a fuel cell according to an exemplary embodiment. Fig. Figure 2 is a partial perspective view of a first separator according to the embodiment. Fig. 3 is a partial perspective view showing a first separator according to a modification in which grooves are provided in a second thin film, differing from those in Fig. They are two different things. Fig. Figure 4 is a diagram of a conventional fuel cell, schematically representing a state in which a membrane electrode assembly is taken into the center from opposite sides in the thickness direction by separators.

[0013] In all drawings and the detailed description, identical reference numbers denote identical elements. The drawings need not be to scale, and the relative size, proportions, and representation of elements in the drawings may be exaggerated for the sake of clarity, presentation, and convenience. DETAILED DESCRIPTION

[0014] With reference to the Fig. 1 and Fig. 2. A separator for a fuel cell according to an exemplary embodiment is now described.

[0015] As in Fig. As shown in Figure 1, a fuel cell has 10 membrane electrode assemblies 11. Each membrane electrode assembly 11 is oriented in the thickness direction (in the direction from top to bottom). Fig. 1) from opposite sides, separated into the center by separators for a fuel cell. To distinguish between the two separators for a fuel cell, the one located above each membrane electrode assembly 11 (in the thickness direction on one of the outer sides) is referred to as a first separator 21, and the other located below (in the thickness direction on the other outer side) is referred to as a second separator 31.

[0016] The membrane electrode units 11 are separated from each other by the first separator 21 and the second separator 31, which are arranged between them. Each membrane electrode unit 11 has an electrolyte membrane 12 and two electrode layers that are connected in the thickness direction to opposite sides of the electrolyte membrane 12. One (in Fig. 1 the upper) of the electrode layers forms a cathode electrode layer 13, and the other electrode layer (in Fig. 1 the lower one) forms an anode electrode layer 14.

[0017] On the side opposite the electrolyte membrane 12 (in Fig. On the upper side (1) of the cathode electrode layer 13, a gas diffusion layer 15 is arranged. The gas diffusion layer 15 consists of carbon fibers or the like and promotes the diffusion of oxidation gas, which will be discussed below. On the side opposite the electrolyte membrane 12 (in Fig. A gas diffusion layer 16 is arranged on the underside (1) of the anode electrode layer 14. The gas diffusion layer 16 consists of carbon fibers or the like and promotes the diffusion of fuel gas, which will be discussed below.

[0018] The first and second separators 21, 31 enclose the membrane electrode assembly 11 and the gas diffusion layers 15, 16 in the thickness direction from opposite sides (the outer sides) towards the center. The membrane electrode assembly 11, the gas diffusion layers 15, 16, the first separator 21, and the second separator 31 form a cell unit 20. Several cell units 20 are stacked in the thickness direction to form the cell stack of the fuel cell 10.

[0019] As in the Fig. 1 and Fig. As shown in Figure 2, the basic structure of each first separator 21 is formed by a separator base 22 made of conductive metal. In the present embodiment, each separator base 22 consists of a stainless steel sheet with a thickness of approximately 100 µm.

[0020] Each separator base 22 has several comb sections 23 that project towards the membrane electrode assembly 11, and several sink sections 24 that retract in the opposite direction to the projecting direction of the comb sections 23. In the Fig. 1 and Fig. 2. The comb sections 23 jump downwards, and the sink sections 24 jump upwards. The comb sections 23 and the sink sections 24 are oriented in one direction along the plane of the membrane electrode assembly 11 (in the left-to-right direction). Fig. 1) are arranged alternately and extend parallel to each other. Areas surrounded by the respective sink sections 24 and the cathode electrode layer 13 each form a passage 25 that supplies oxidation gas (for example, air) to the cathode electrode layer 13.

[0021] As in Fig. As shown in Figure 1, the basic structure of each second separator 31 is formed by a separator base 32 made of conductive metal. In the present embodiment, each separator base 32, as in the case of the separator base 22 described above, consists of a stainless steel sheet with a thickness of approximately 100 µm.

[0022] Each separator base 32 has several comb sections 33 that project towards the membrane electrode assembly 11, and several sink sections 34 that retract in the direction opposite to the projections towards the comb sections 33. Fig. 1. The comb sections 33 jump upwards, and the sink sections 34 jump downwards. The comb sections 33 and the sink sections 34 are oriented in one direction along the plane of the membrane electrode assembly 11 (in the left-to-right direction). Fig. 1) are arranged alternately and extend parallel to each other. Areas surrounded by the respective sink sections 34 and the anode electrode layer 14 each form a passage 35 that supplies fuel gas (for example, hydrogen) to the anode electrode layer 14.

[0023] As described above, the fuel cell stack 10 has several cell units 20 stacked in the thickness direction. As indicated by the once long and twice short dashed lines in Fig. As shown in Figure 1, the second separator 31 of the upper cell unit 20 is located in the downward direction. Fig. 1. The first separator 21 of the centrally located cell unit 20 is arranged above it. An intermediate layer 26 is arranged between the bottom of each sink section 24 of the first separator 21 and the bottom 34 of the upper second separator 31. The intermediate layers 26 are configured to suppress an increase in contact resistance between the sink sections 24 and 34. The intermediate layers 26 consist of a material that has a higher conductivity (a lower electrical resistance) than the separator base parts 22 and 32. The intermediate layers 26 consist, for example, of carbon, gold, or platinum. In addition, a passage 27 is defined between each comb section 23 of the first separator 21 and the corresponding comb section 33 of the upper second separator 31. Coolant (for example, cooling water) flows through the passage 27.

[0024] As indicated by the lines with one long and two short dashed lines in Fig. Figure 1 shows the first separator 21 of the cell unit 20 located below in the downward direction. Fig. 1 is arranged below the second separator 31 of the centrally located cell unit 20. An intermediate layer 26 is arranged between the bottom of each sink section 34 of the second separator 31 and the bottom of the corresponding sink section 24 of the lower separator 21. A passage 27 is also defined between each comb section 33 of the second separator 31 and the corresponding comb section 23 of the lower first separator 21. Coolant flows through the passage 27.

[0025] As in the Fig. 1 and Fig. As shown in Figure 2, a first thin film 41 is provided on the separator base 22 of the first separator 21 of each cell unit 20. Specifically, the first thin film 41 is placed over the entire surfaces of the comb sections 23 and the sink sections 24 facing the cathode electrode layer 13. The first thin film 41 has a conductivity and corrosion resistance that is higher than that of the separator base 22. In the present embodiment, the first thin film 41 consists of a material obtained by mixing conductive particles such as titanium nitride (TiN) in plastic.

[0026] As in Fig. As shown in Figure 1, a first thin film 51 is provided on the separator base 32 of the second separator 31 of each cell unit 20. Specifically, the first thin film 51 is placed over the entire surfaces of the comb sections 33 and the sink sections 34 facing the anode electrode layer 14. The first thin film 51 has a conductivity and high corrosion resistance that is higher than that of the separator base 32.

[0027] As in the Fig. 1 and Fig. As shown in Figure 2, a second thin film 42 is placed on the portions of the first thin film 41 that are positioned on the upper surfaces of the comb sections 23 in each first separator 21. The second thin films 42 serve to suppress an increase in contact resistance between the membrane electrode assembly 11 and the separator bases 22, thereby reducing the influence of contact resistance on the reaction of fuel gas and oxidizer gas in the membrane electrode assembly 11. The second thin films 42 are made of the same material as the intermediate layers 26 and are formed by inkjet printing, giving them a thickness of, for example, several hundred nm to several hundred µm. The second thin films 42 have a higher hydrophilicity than the separator bases 22. Each first separator 21 contacts the gas diffusion layer 15 on the second thin films 42.In other words, every second thin film 42 of the first separator 21 indirectly touches the cathode electrode layer 13 via the gas diffusion layer 15.

[0028] Every second thin film 42 has grooves 43 extending in a direction that intersects the direction in which the comb sections 23 extend. In the present embodiment, the grooves 43 extend in a direction perpendicular to the direction in which the comb sections 23 extend (in the left-to-right direction). Fig. 1) The grooves 43 are separated from each other in the direction in which the comb sections 23 extend. The depth of the grooves 43 is set so that it is the same as the thickness of the second thin film 42. Thus, the first thin film 41 is exposed at the points where the grooves 43 are provided.

[0029] The openings 25 are located on opposite sides of each comb section 23, on which the second thin films 42 with the grooves 43 are provided. In the second thin film 42 on the top side of each comb section 23, one end of each groove 43 is connected to one of the openings 25 located on opposite sides of the comb section 23, and the other end is connected to the other opening 25. Thus, the openings 25 on opposite sides of each comb section 23 are continuously connected to each other via the grooves 43.

[0030] As in Fig. As shown in Figure 1, a second thin film 52 is placed on each portion of the first thin film 51 located on the upper surfaces of the comb sections 33 in each second separator 31. Each second thin film 52 serves the same purpose and is produced by the same process from the same material, thickness, and hydrophilicity as the second thin films 42 on the first separator 21. The second separator 31 contacts the gas diffusion layer 16 on the second thin films 52 located on the respective comb sections 33. Each second thin film 52 has grooves 53 extending in the same direction as the grooves 43 of the first separator 21.In the second thin film 52 on the upper surface of each comb section 33, one end of each groove 53 is connected to one of the openings 35 located on opposite sides of the comb section 33, and the other end is connected to the other opening 35. The openings 35 on opposite sides of each comb section 33 are thus continuously connected to one another via the grooves 53.

[0031] The first separator 21 described above is manufactured as follows. First, a flat stainless steel sheet is prepared. On one side of the stainless steel sheet, a material obtained by mixing conductive particles such as titanium nitride (TiN) in plastic is applied over the entire surface to form a first thin film 41. The stainless steel sheet on which the first thin film 41 has been formed in the manner described above is stamped to form a separator base 22 having comb sections 23 and depression sections 24. On portions of the first thin film 41 that are placed on the upper surfaces of the comb sections 23, a material having a higher conductivity than the separator base 22 is applied by inkjet printing to form second thin films 42 with grooves 43. The second separator 31 is manufactured by the same steps as the first separator 21.

[0032] The functionality and advantages of the embodiment described above will now be described.

[0033] In the fuel cell 10, oxidation gas (air) flows through the openings 25, and fuel gas (hydrogen) flows through the openings 35. The oxidation gas flowing through each opening 25 is supplied to the cathode electrode layer 13 via the gas diffusion layer 15. The fuel gas flowing through each opening 35 is supplied to the anode electrode layer 14 via the gas diffusion layer 16. In the membrane electrode assembly 11, electricity is generated based on the reaction of the supplied fuel gas and oxidation gas. This reaction also produces water in the cathode electrode layer 13, to which the oxidation gas has been supplied.

[0034] When fuel gas (hydrogen) is supplied to the anode electrode layer 14, electrons are removed from the hydrogen atoms and delivered to the anode electrode layer 14. These electrons flow from the anode electrode layer 14 through conducting wires of an (not shown) external circuit to the cathode electrode layer 13. The removal of electrons from the hydrogen atoms in the anode electrode layer 14 generates positively charged hydrogen ions (protons), which then move across the electrolyte membrane 12 to the cathode electrode layer 13. Meanwhile, in the cathode electrode layer 13, to which the oxidation gas (air) is supplied, oxygen atoms accept electrons, thus becoming oxygen ions.Furthermore, hydrogen ions that have moved from the anode electrode layer 14 via the electrolyte membrane 12 to the cathode electrode layer 13 combine with the oxygen ions, so that water is produced in the cathode electrode layer 13.

[0035] Some of the generated water is located in the gas diffusion layer 15 between the cathode electrode layer 13 and every second thin film 42. Some of the water located near each vent 25 is, as indicated by the arrows in Fig. As indicated in Figure 2, the water is drawn towards the passage 25 by the oxidation gas flowing through the passage 25. Once it has moved into the passage 25, the water flows through the passage 25 along with the oxidation gas. A portion of the water in the gas diffusion layer 15, located near each groove 43, is drawn away, as indicated by the arrows in Figure 2. Fig. As shown in Figure 1, the water is also drawn towards the passage 25 by the oxidation gas through the groove 43. Once it has moved into the passage 25, this water also flows through the passage 25 along with the oxidation gas. As described above, the water flowing through the passage 25 together with the oxidation gas is ultimately discharged to the outside of the fuel cell 10.

[0036] Compared to the case where no grooves 43 are provided, the amount of water discharged to the outside of the fuel cell 10 is thus increased. This improves the water discharge capacity. Furthermore, unlike in the case where no grooves 43 are provided, the generated water is prevented from remaining in the gas diffusion layer 15. Insufficient diffusion of oxidation gas due to residual water is therefore avoided. Consequently, it is unlikely that the reaction between the fuel gas and the oxidation gas will be impaired.

[0037] In particular, in the present embodiment, one end of each groove 53 in the second thin film 42 on the upper surface of each comb section 23 is connected to one of the openings 25 located on opposite sides of the comb section 23, and the other end is connected to the other opening 25. Thus, some of the water in the gas diffusion layer 15 located near each groove 43 is drawn along the longitudinal direction of the groove 43 towards the opposite ends by the oxidation gas flowing through the openings 25 on opposite sides of the comb sections 23. Some of the water in the gas diffusion layer 15 located near the groove 43 is therefore readily carried away through the groove 43 to the openings 25, and the water is then readily carried away along with the flow of oxidation gas through the opening 25 to the outside of the fuel cell 10.

[0038] Power generation efficiency can be improved by impregnating the cathode electrode layer 13 and the anode electrode layer 14 with a specific amount of water. In this respect, the thickness of the membrane electrode assembly 11 can be reduced. This allows the water generated in the cathode electrode layer 13 to move easily along the electrolyte membrane 12 towards the anode electrode layer 14. However, if more water than necessary remains in the gas diffusion layer 16 and excess water remains in the vicinity of the anode electrode layer 14, the fuel gas (hydrogen) cannot easily come into contact with the anode electrode layer 14. This can reduce the reaction of the fuel gas and the oxidation gas in the membrane electrode assembly 11.

[0039] However, some of the water in the gas diffusion layer 16, located near each passage 35, is drawn towards the passage 35 by the fuel gas flowing through it. As it moves into the passage 35, the water flows through it along with the fuel gas.

[0040] Furthermore, in the present embodiment, the second thin films 52 of the second separator 31 also have grooves 53 that prevent more water than necessary from being retained in the gas diffusion layer 16. This means that some of the water in the gas diffusion layer 16, which is located near each groove 53, is drawn through the groove 53 towards the passage 35 and then flows into the passage 35 together with the fuel gas.

[0041] As described above, the water flowing through the passage 35 along with the fuel gas is eventually discharged to the outside of the fuel cell 10. This prevents excess water from remaining in the vicinity of the anode electrode layer 14.

[0042] Furthermore, in the present embodiment, one end of each groove 53 is connected to a passage 35, as in the case of the grooves 43 described above, and the other end is connected to a different passage 35. Thus, for the same reason as with the grooves 43 described above, some of the water in the gas diffusion layer 16 between the second thin film 52 and the anode electrode layer 14, which is located close to the groove 53, is drawn along the longitudinal direction of the groove 53 towards the opposite ends. The water is thus easily carried away through the groove 53 to the passages 35. The water then flows together with the fuel gas through the passages 35 to be discharged to the outside of the fuel cell 10.

[0043] If acidic substances are generated as byproducts of the reaction in the electrolyte membrane 12, the separator components 22, 32, which consist of stainless steel sheets, can erode or corrode through an electrochemical reaction with the acidic substances. Iron ions are thereby leached from the separator components 22, 32. This can impair the performance of the components of the membrane electrode assembly 11, for example, the electrolyte membrane 12 and the catalyst (not shown).

[0044] However, in the present embodiment, the leaching of iron ions is suppressed by the first thin films 41, 51. Therefore, the first thin films 41, 51 prevent the performance of the components of the membrane electrode assembly 11 from deteriorating due to leached iron ions.

[0045] In addition to the advantages mentioned above, the present embodiment has the following advantages.

[0046] If the hydrophilicity of the second thin films 42 in the first separator 21 is low, it is likely that the water in the grooves 43 will be repelled by the inner surfaces of the grooves 43, and it is unlikely that it will move within the grooves 43. Therefore, it is unlikely that the water in the grooves 43 will move towards the passages 25.

[0047] Since the second films 42 in the present embodiment have a higher hydrophilicity than the separator base 22, it is likely that the water in the grooves 43 will be distributed on the inner surfaces of the grooves 43. This allows the water in the grooves 43 to move easily to the openings 25.

[0048] Furthermore, since the second thin films 52 of every second separator 31 have a higher hydrophilicity than the separator base 32, the water moves easily to the passages 35 in the grooves 53, as in the case of the first separator 21.

[0049] The second thin films 42, 52, which have the grooves 43, 53, are formed by inkjet printing. Thus, the shapes of the grooves 43, 53 in the second thin films 42, 52 can be easily changed by adjusting the inkjet printing pattern.

[0050] In the second thin films 42, 52, the first thin films 41, 51 are exposed at the sections where the grooves 43, 53 are provided. In other words, the second thin films 42, 52 are not provided on the corresponding sections in the first thin films 41, 51. Thus, no ink material needs to be applied to the sections in the first thin films 41, 51 where the grooves 43, 53 are formed. The grooves 43, 53 can therefore be easily formed.

[0051] The embodiment described above can be modified as follows. <Hinsichtlich Separatorgrundteile 22, 32>

[0052] The separator components 22, 32 can be made of any material other than stainless steel, as long as it is conductive. For example, the separator components 22, 32 can be made of titanium. <Hinsichtlich erster dünner Filme 41, 51 und zweiter dünner Filme 42, 52>

[0053] The second thin films 42, 52 can be made of the same material as the first thin films 41, 51.

[0054] The second thin films 42, 52 can be provided on other sections of the comb sections 23, 33 or, in addition to the upper surfaces of the comb sections 23, 33, on the sink sections 24, 34. However, considering the difficulties and costs involved in forming the second thin films 42, 52, they are preferably provided only on the upper surfaces of the comb sections 23, 33.

[0055] If the second thin films 42, 52 are provided on sections other than the upper surfaces of the comb sections 23, 33, the cross-sectional flow areas of the passages 25, 35 are reduced accordingly. Therefore, the second thin films 42, 52 are preferably provided only on the upper surfaces of the comb sections 23, 33 where the second thin films 42, 52 are required.

[0056] In the embodiment described above, the second thin films 42, 52 have a higher hydrophilicity than the separator bases 22, 32. However, the present invention is not limited to this.

[0057] One of the first thin film 41 on the first separator 21 and one of the first thin film 51 on the second separator 31 can be omitted.

[0058] One of the second thin film 42 on the first separator 21 and one of the second thin film 52 on the second separator 31 can be omitted. <Hinsichtlich Rillen 43, 53>

[0059] The grooves 43, 53 can extend in a direction that crosses diagonally with the direction in which the ridge sections 23, 33 extend.

[0060] As in Fig.As shown in Figure 3, each groove 43 of the first separator 21 can have one end connected to the passage 25 and another end not connected to the passage 25. In this case, the water located in the gas diffusion layer 15 is easily carried away through the groove 43 to the passage 25. The fact that one end of each groove 43 is closed is due to the likelihood that the water in the groove 43 is attracted by the oxidation gas flowing through the passage 25, thus facilitating the removal of water.

[0061] The same modification can be applied to the grooves 53 of the second separator 31 for the same reason as described above.

[0062] If each comb section 23 of the first separator 21 has several grooves 43 at various locations in the direction in which the comb section 23 extends as described above, each groove having only one end connected to a passage 25, then each adjacent pair of grooves 43 is preferably connected to different passages 25 on opposite sides of the comb section 23. This is because such a configuration allows the water near the grooves 43 in the gas diffusion layer 15 to be drawn substantially uniformly towards and flow to the passages 25 on the opposite sides.

[0063] The same modification can be applied to the grooves 53 of the second separator 31 for the same reason as described above.

[0064] Each pair of grooves 43 that lie side by side in the direction in which the comb section 23 extends can be connected to the same pair of openings 25 on the opposite sides of the comb section 23. The same modification can be applied to the grooves 53.

[0065] One of the grooves 43 in the first separator 21 and one of the grooves 53 in the second separator 31 can be omitted.

[0066] The depths of the grooves 43, 53 can be set to be less than the thickness of the second thin films 42, 52 in sections where the grooves 43, 53 are not provided. In this case, portions of the second thin films 42, 52 are provided in sections where the grooves 43, 53 are provided. Unlike in the embodiments described above, the first thin films 41, 51 are not exposed in the sections of the thin films 42, 52 where the grooves 43, 53 are not provided. Inkjet printing allows the formation of the second thin films 42, 52 that contain sections with a lesser thickness than the other parts. <Weitere Abwandlung>

[0067] The first and second separators 21, 31 can be used in a fuel cell that does not have the gas diffusion layers 15, 16.

Claims

A separator for a fuel cell, used in a fuel cell (10) with a membrane electrode assembly (11), wherein the membrane electrode assembly (11) has an electrolyte membrane (12) and electrode layers (13, 14) connected in a thickness direction to opposite sides of the electrolyte membrane (12), the separator for a fuel cell comprising: a metallic separator base (22, 32) arranged in the thickness direction on an outside of the membrane electrode assembly (11) and having conductivity; a plurality of comb sections (23, 33) provided in the separator base (22, 32) and projecting towards the membrane electrode assembly (11); and a plurality of recessed sections (24, 34) provided in the separator base (22, 32) and projecting in a direction opposite to the direction in which the ridge sections (23, 33) project, the ridge sections (23,33) and the sink sections (24, 34) are arranged alternately in one direction along a plane of the membrane electrode assembly (11) and extend parallel to each other, and areas surrounded by the respective sink sections (24, 34) and a corresponding electrode layer (13, 14) each form a passage (25, 35) that supplies oxidation gas or fuel gas to the electrode layer, a first thin film (41, 51) is placed over entire surfaces of the comb sections (23, 33) and the sink sections (24, 34) facing the corresponding electrode layer (13, 14), which has a conductivity and corrosion resistance higher than that of the separator base (22, 32), and a second thin film is placed on parts of the first thin film (41, 51) that are placed on the tops of the comb sections (23, 33). (42, 52) is placed, which has conductivity, characterized in that a part of the second thin film (42, 52),which is placed on the upper side of each comb section (23, 33), has a groove (43, 53) extending linearly in a direction that intersects a direction in which the comb sections (23, 33) extend, and at least one end of the groove (43, 53) is connected to the passage (25, 35). Separator for a fuel cell according to claim 1, wherein in the second thin film (42, 52) on the top of each comb section (23, 33) one end of the groove (43, 53) is connected to one of the openings (25, 35) located on opposite sides of the comb section (23, 33) and the other end of the groove (43, 53) is connected to the other opening (25, 35). Separator for a fuel cell according to claim 1 or 2, wherein the first thin film (41, 51) is exposed at locations where the grooves (43, 53) are provided.

Images