JP5694103B2 - Fuel cell and fuel cell - Google Patents

Description

  The present invention relates to a fuel cell used for a fuel cell.

  In general, a cell of a fuel cell such as a polymer electrolyte fuel cell (PEFC) includes a membrane electrode membrane electrode assembly (MEA) in which an electrode catalyst is applied to an electrolyte membrane, and a pair of diffusion layers sandwiching the membrane electrode assembly. And a pair of separators that further sandwich the diffusion layer. A fuel cell stack is formed from a laminate in which a plurality of cells are laminated. As disclosed in FIG. 4 of Patent Document 1, the separator is provided with, for example, ribs that divide a flow path through which a reaction gas such as a fuel gas or an oxidizing gas flows. The rib is in contact with the diffusion layer, and a so-called serpentine type flow path is formed by the rib.

  Since the diffusion layer is formed of a porous material, a so-called pass cut may occur in which the reaction gas passes through the rib through the pores of the diffusion layer in the region where the rib is in contact. In order to prevent this pass cut, the rib and the diffusion layer are fixed with a liquid sealing material. This liquid sealing material is impregnated in the diffusion layer to reduce the porosity of the diffusion layer, thereby suppressing the path cut by the amount that clogs the through holes through which the reaction gas can pass. As a result, since the reaction gas flows along the gas flow path, the power generation performance can be improved.

JP 2008-4478 A

  However, in such a cell, it is assumed that excessive liquid sealing material leaks around the ribs, or the power generation area decreases due to the formation of the liquid sealing material reservoir. Moreover, an extra process is required for the impregnation of the liquid sealing material and the formation of the liquid sealing material reservoir.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a fuel cell and a fuel cell that can reduce a path cut with a simple configuration without reducing the power generation area.

In order to achieve the above object, according to the present invention,
In the fuel cell having the first and second separators that sandwich the diffusion layer between both surfaces of the electrolyte membrane,
A first flow path of a reactive gas formed on an inward surface of the first separator facing one of the diffusion layers;
A second flow path for the reaction gas formed on the inward surface of the second separator facing the other diffusion layer;
A rib formed on the second separator and partitioning the second flow path;
A protrusion formed on the contact surface of the rib that contacts the diffusion layer and protruding from the contact surface;
A fuel cell is provided.

  According to such a fuel cell, when the protrusion protrudes from the contact surface of the rib that contacts the diffusion layer, the protrusion bites into the diffusion layer, and the porosity of the diffusion layer can be reduced. In this way, it is possible to suppress the occurrence of a pass cut with a simple configuration in which only the protrusion is provided on the contact surface of the rib. In addition, a reduction in the power generation area due to leakage of the liquid sealing material into the diffusion layer can be avoided, and no extra work such as impregnation of the liquid sealing material is required.

  In this fuel cell, the protrusion is partially formed with respect to the entire length of the rib. According to such a configuration, the reaction gas path cut is partially suppressed and partially allowed to establish an appropriate flow of the reaction gas along the second flow path, and the reaction gas can Moisture can be appropriately transported throughout, and drying can be suppressed throughout the electrolyte membrane. In this way, it is possible to suppress a decrease in gas stoichiometry in the power generation region of the fuel battery cell, and to suppress a decrease in power generation performance.

In these fuel cells,
The first separator is a cathode separator and the second separator is an anode separator;
The first flow path extends in a first direction from the lower end of the first separator toward the upper end,
The second flow path extends by meandering in a second direction orthogonal to the first direction from the upper end to the lower end of the second separator by being partitioned by the ribs,
The protrusion extends from the proximal end of the rib adjacent to the turn portion of the second flow path toward the distal end of the rib.

  In this fuel cell, the generated water generated by the power generation reaction is carried from the lower end of the cathode separator toward the upper end by the reaction gas flowing through the first flow path, so that the reaction gas is near the upper end of the cathode separator in the first flow path. The water vapor inside is saturated. As a result, the electrolyte membrane is kept in a high wet state near the upper end. On the other hand, in the second flow path of the anode separator, the reaction gas flows while meandering from the upper end to the lower end of the anode separator. At this time, the gas pressure of the reaction gas decreases as it is consumed from the upstream to the downstream of the second flow path. As a result, the largest differential pressure is generated across the region of the proximal end of the rib adjacent to the turn portion of the second flow path. As a result of the path cut being suppressed by the protrusion in the region where the differential pressure is large, an appropriate amount of reaction gas flows through the second flow path. Moreover, as a result of the pass cut being allowed in the region where the protrusion is not formed, the reaction gas can be shortcut even if there is a rib. In this way, the reaction gas containing moisture is appropriately diffused into the second flow path, so that it is possible to carry moisture entirely from the upper end to the lower end in the second flow path.

  In such a fuel cell, it is preferable that the length of the protrusion is set to be approximately equal to the width of the turn portion. Moreover, according to this invention, a fuel cell provided with the laminated body which laminated | stacked multiple such fuel battery cells as mentioned above is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel cell and fuel cell which reduce a path cut with a simple structure, without reducing an electric power generation area can be provided.

1 is a perspective view schematically showing a structure of a fuel cell according to an embodiment of the present invention. 1 is an exploded perspective view schematically showing a structure of a fuel cell according to an embodiment of the present invention. It is a front view which shows the structure of an anode separator roughly. FIG. 4 is a partially enlarged cross-sectional view taken along line 4-4 of FIG. FIG. 5 is a partially enlarged cross-sectional view taken along line 5-5 in FIG. It is a graph which shows the relationship between the operating temperature of a fuel cell, and a cell voltage. FIG. 6 is a partial enlarged cross-sectional view schematically showing a structure of a protrusion according to a specific example corresponding to FIG. 5. FIG. 6 is a partial enlarged cross-sectional view schematically showing a structure of a protrusion according to a specific example corresponding to FIG. 5. FIG. 6 is a partial enlarged cross-sectional view schematically showing a structure of a protrusion according to a specific example corresponding to FIG. 5. FIG. 6 is a partial enlarged cross-sectional view schematically showing a structure of a protrusion according to a specific example corresponding to FIG. 5.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a perspective view schematically showing the structure of a fuel cell 11 according to an embodiment of the present invention. The fuel cell 11 constitutes a polymer electrolyte fuel cell (PEFC), for example. The fuel cell 11 can be used as, for example, an in-vehicle power generation system for a fuel cell vehicle (FCHV), and can be a mobile body such as a ship or an airplane, or a self-propelled mobile body such as a robot. It can be used as a power generation system mounted on the vehicle, or as a stationary power generation system.

  The fuel cell 11 includes a cell stack 13 formed by stacking a plurality of fuel cells 12 and a pair of end plates 14 and 14 that sandwich the cell stack 13 in the stacking direction of the fuel cells 12. I have. A current collector plate with an output terminal and an insulating plate are sandwiched between the cell stack 13 and the end plate 14 (none is shown). A pair of plate-like members 15 and 15 are arranged between the cell stack 13 and one end plate 14. The plate-like members 15 and 15 sandwich an elastic module such as a coil spring, for example, and apply a predetermined fastening force (compression load) in the stacking direction of the cell stack 13 by the elastic restoring force of the elastic module.

  The fuel cell 11 includes a pair of tension plates 16 and 16 that connect the end plates 14 and 14 to each other. The cell stack 13 is disposed between the tension plates 16 and 16. The tension plates 16 and 16 maintain a state in which a predetermined fastening force (compression load) is applied in the stacking direction of the cell stack 13. On the inward surface of the tension plate 16 facing the cell stack 13, an insulating film (not shown) that prevents leakage and sparks is formed. The insulating film includes an insulating tape attached to the inward surface and a resin coating applied to the inward surface.

  In the end plate 14, for example, three inflow ports 17 and three outflow ports 18 used for supply and discharge of the reaction gas (oxidizing gas) to the cell stack 13 are formed. Similarly, in the end plate 14, for example, one inflow port 19 and an outflow port 20 that are used for supplying and discharging a reaction gas (fuel gas) such as hydrogen gas to the cell stack 13 are formed. The inlets 17 and 19 and the outlets 18 and 20 are connected to the cell stack 13, respectively. In this way, oxidizing gas and hydrogen gas are supplied to each fuel battery cell 12, and electricity is generated by the electrochemical reaction between the oxidizing gas and hydrogen gas via each fuel battery cell 12.

  FIG. 2 is an exploded perspective view schematically showing the structure of the fuel cell 12 according to one embodiment of the present invention. The fuel cell 12 includes a membrane electrode assembly (MEA) 21 and a cathode separator 22 and an anode separator 23 that sandwich the membrane electrode assembly 21 from both sides. The membrane electrode assembly 21, the cathode separator 22, and the anode separator 23 are formed in a rectangular plate shape. The membrane electrode assembly 21 includes an electrolyte membrane 24. A pair of diffusion layers 25 and 25 are disposed between the membrane electrode assembly 21 and the separators 22 and 23.

  The electrolyte membrane 24 is formed of an ion exchange membrane made of a polymer material. The contour of the electrolyte membrane 24 is formed to be slightly larger than the contour of the diffusion layer 25. A diffusion layer 25 is bonded to the electrolyte membrane 24 by, for example, a hot press method. The diffusion layer 25 is formed of a conductor such as a porous carbon material that allows fluid (oxidizing gas, hydrogen gas, and generated water) to pass therethrough. A catalyst layer (not shown) is disposed on the electrolyte membrane 24 facing the inward surface of the diffusion layer 25. The catalyst layer includes, for example, a solid electrolyte, carbon particles, and a catalyst supported on the carbon particles. For example, platinum or a platinum alloy is preferably used as the catalyst.

  The separators 22 and 23 are made of a gas impermeable conductive material. Examples of the conductive material include carbon and a hard resin having conductivity, and a metal material such as aluminum and stainless steel. The separators 22 and 23 of the present embodiment are formed of, for example, a metal plate, and are so-called metal separators. A film excellent in corrosion resistance (for example, a film formed by gold plating) is formed on the inward surfaces of the separators 22 and 23 facing the membrane electrode assembly 21.

  As is apparent from FIG. 2, a first flow path 26 for oxidizing gas is formed on the inward surface of the cathode separator 22 facing the membrane electrode assembly 21. The first flow path 26 is formed from a recess formed, for example, by press molding on the inward surface of the cathode separator 22. Outside the first flow path 26, a plurality of oxidizing gas inflow manifolds 27 a and outflow side manifolds 27 b are formed on the outer periphery of the cathode separator 22. The manifold 27 a is arranged adjacent to the lower end of the cathode separator 22, while the manifold 27 b is arranged adjacent to the upper end of the cathode separator 22.

  The manifold 27a communicates with the inlet 17 of the end plate 14, while the manifold 27b communicates with the outlet 18 of the end plate 14. By connecting the first flow path 26 to the manifolds 27a and 27b, the oxidizing gas flows through the first flow path 26. Here, as shown by the arrows in FIG. 2, the oxidizing gas flows from the manifold 27a into the first flow path 26 and out of the manifold 27b, so that the cell stack 13 is directed in the first direction from the lower end toward the upper end. Flowing. The oxidizing gas flowing through the first flow path 26 is supplied to the electrolyte membrane 24 through the diffusion layer 25.

  On the other hand, a second flow path 28 of hydrogen gas is formed on the inward surface of the anode separator 23 facing the membrane electrode assembly 21. The second flow path 28 is formed from a recess formed, for example, by press molding on the inward surface of the anode separator 23. Outside the second flow path 28, a hydrogen gas inflow side manifold 29 a and an outflow side manifold 29 b are formed on the outer periphery of the anode separator 23. The manifold 29a is disposed adjacent to the upper left end of the anode separator 23, while the manifold 29b is disposed adjacent to the lower right end of the anode separator 23.

  The manifold 29a communicates with the inlet 19 of the end plate 14, while the manifold 29b communicates with the outlet 20 of the end plate 14. By connecting the second flow path 28 to the manifolds 29a and 29b, hydrogen gas flows through the second flow path 28. As shown in FIG. 2, the second flow path 28 is partitioned by a plurality of ribs 30a and 30b, for example. The ribs 30a and 30b extend in parallel to each other, for example. Each rib 30a, 30b is connected to the outer periphery of the anode separator 23 at its base end. Thus, the second flow path 28 is formed as a so-called serpentine-type flow path, and extends while meandering in a second direction orthogonal to the first direction.

  FIG. 3 is a front view of the anode separator 23. The second flow path 28 includes a first straight portion 31 extending from the base end of the rib 30a toward the tip, a first turn portion 32 connected to the first straight portion 31 and extending around the tip of the rib 30a, and a first A second straight portion 33 connected to the turn portion 32 and extending from the tip of the rib 30a toward the proximal end; a second turn portion 34 connected to the second straight portion 33 and extending around the tip of the rib 30b; And a third straight portion 35 connected to the turn portion 34 and extending from the distal end of the rib 30b toward the proximal end. The second straight portion 33 extends from the proximal end of the rib 30b toward the distal end.

  A manifold 29 a is connected to one end of the first straight portion 31, and a manifold 29 b is connected to the other end of the third straight portion 35. As a result, as shown by the arrow in FIG. 2, the hydrogen gas passes through the first straight part 31, the first turn part 32, the second straight part 33, the second turn part 34, and the third straight part 35 in order. Flowing. Accordingly, hydrogen gas flows in the opposite direction between the first straight portion 31 and the second straight portion 33. Similarly, hydrogen gas flows in the opposite direction between the second straight portion 33 and the third straight portion 35. Thus, the hydrogen gas meanders and flows in a second direction orthogonal to the first direction from the upper end to the lower end of the anode separator 23.

  Projections 36a and 36b are partially formed on the ribs 30a and 30b, respectively. The protrusions 36 a and 36 b protrude from the ribs 30 a and 30 b toward the membrane electrode assembly 21. In the present embodiment, the length of the protrusion 36a defined in the direction from the proximal end to the distal end of the rib 30a is set substantially equal to the width of the second turn portion 34. Similarly, the length of the protrusion 36b defined in the direction from the proximal end to the distal end of the rib 30b is set substantially equal to the width of the first turn portion 32. The lengths of the protrusions 36a and 36b are not limited to this size, and are set to an appropriate size according to the air permeability of the diffusion layer 25 and the like.

  4 is a partially enlarged sectional view taken along line 4-4 of FIG. The rib 30a (30b) has a rectangular parallelepiped outline, for example, and the cross section is formed in a rectangle. The rib 30a (30b) is in contact with the diffusion layer 25 of the membrane electrode assembly 21 at its tip surface. FIG. 5 is a partially enlarged sectional view taken along line 5-5 in FIG. On the rib 30a (30b), a protrusion 36a (36b) is formed on the tip surface, that is, the contact surface of the rib 30a (30b). In this embodiment, the protrusion 36a (36b) has a rectangular parallelepiped outline, for example, and the cross section is formed in the rectangle.

  As shown in FIG. 5, the protrusion 36 a (36 b) protrudes from the rib 30 a (30 b) toward the diffusion layer 25 and bites into the diffusion layer 25. As a result, the diffusion layer 25 is partially compressed, so that the number of pores through which hydrogen gas can permeate is reduced at the locations where the protrusions 36a (36b) are formed, and the porosity (air permeability) of the diffusion layer 25 decreases. . As a result, it is possible to suppress the passage of hydrogen gas through the diffusion layer 25, that is, the occurrence of a pass cut, at the location where the protrusion 36a (36b) is formed. The effects of suppressing the occurrence of pass cut will be described later.

  In the present embodiment, it is preferable that the protruding amounts of the protrusions 36 a and 36 b from the contact surfaces of the ribs 30 a and 30 b are set to about 20 to 50% of the thickness of the diffusion layer 25, for example. However, if the protruding amounts of the protrusions 36a and 36b are too small, the effect of reducing the porosity is poor. On the other hand, if the protruding amount is too large, the surface pressure on the diffusion layer 25 of the ribs 30a and 30b other than the protruding portions 36a and 36b cannot be secured. Furthermore, if the protruding amount is too large, the electrolyte membrane 24 may be damaged by the fibers forming the diffusion layer 25. Therefore, the protrusion amount is preferably adjusted as appropriate according to the width of the ribs 30a and 30b, the thickness of the diffusion layer 25, the strength of the electrolyte membrane 24, and the like.

  Next, a case where the fuel cell 11 is operated will be described. An oxidizing gas, which is a dry gas, is supplied to the first flow path 26 of the cathode separator 22, while hydrogen gas is supplied to the second flow path 28 of the anode separator 23. As a result, an oxidation reaction occurs in the anode electrode, while a reduction reaction occurs in the cathode electrode, and an electromotive reaction occurs in the entire cell stack 13. The generated water generated by this electromotive reaction is carried from the lower end to the upper end of the cathode separator 22 by the oxidizing gas flowing through the first flow path 26. Thus, in the first flow path 26, the amount of water vapor in the oxidizing gas is saturated at the upper end of the cathode separator 22, that is, in the vicinity of the manifold 27b. As a result, the electrolyte membrane 24 is kept in a high wet state near the upper end of the fuel cell 12.

  On the other hand, in the second flow path 28 of the anode separator 23, the hydrogen gas flows while meandering from the upper end to the lower end of the anode separator 23. At this time, the gas pressure of the hydrogen gas decreases as the hydrogen gas is consumed from the upstream to the downstream of the second flow path 28. As a result, the largest differential pressure is generated across the base end region of the rib 30 a adjacent to the second turn portion 34 and the base end region of the rib 30 b adjacent to the first turn portion 32. In the present invention, since the protrusions 36a and 36b that partition the region where the differential pressure is large are formed, the pass cut is suppressed in the region where the differential pressure is large. As a result, for example, an appropriate differential pressure is generated between the gas pressure of the first turn portion 32 and the gas pressure of the second turn portion 34, so An appropriate amount of hydrogen gas flows to the portion 35.

  As described above, since a high wet state is maintained near the upper end of the electrolyte membrane 24 adjacent to the first straight portion 31 disposed at the upper end of the anode separator 23, the hydrogen gas flowing through the first straight portion 31 is electrolyte. A relatively large amount of moisture is supplied from the membrane 24. In a region where the protrusion 36a is not formed, a pass cut is allowed from the first straight portion 31 to the second straight portion 33 via the diffusion layer 25 below the rib 30a. As a result, hydrogen gas can be short-cut from the first straight portion 31 to the second straight portion 33 and from the second straight portion 33 to the third straight portion 35. Thus, since the hydrogen gas containing moisture is appropriately diffused into the second flow path 28, the second flow path 28 can carry moisture entirely from the upper end to the lower end.

  In particular, although the electrolyte membrane 24 is easily dried on the lower end side of the fuel battery cell 12 into which the dry gas flows from the manifold 27a, according to the present invention, the moisture is transported from the upper end to the lower end on the second channel 28 side. The electrolyte membrane 24 can be appropriately humidified from the upper end to the lower end. As a result, an appropriate wet state can be secured in the entire electrolyte membrane 24 including the lower end that is easy to dry. In general, when the electrolyte membrane 24 is dried, its resistance value is increased, so that the power generation performance is reduced. However, according to the present invention, an increase in the resistance value is avoided by appropriately humidifying the entire electrolyte membrane 24. The power generation performance of the fuel cell 12 can be improved.

  On the other hand, if the formation of the protrusions 36a and 36b is omitted and the path cut is allowed in the entire ribs 30a and 30b, the ribs 30a and 30b adjacent to the first turn part 32 and the second turn part 34 are used. Hydrogen gas is short-cut in a region where the differential pressure at the base end is large. As a result, for example, only a small differential pressure is generated between the gas pressure of the first turn portion 32 and the gas pressure of the second turn portion 34 as compared with the present invention, and the hydrogen gas smoothly flows along the second flow path 28. Can't establish a good flow. As a result, power generation performance is reduced due to partial hydrogen shortage. Moreover, the water | moisture content supplied by the 1st linear part 31 cannot be conveyed to the 3rd linear part 35, but electric power generation performance will fall.

  Further, as in Patent Document 1, when the ribs 30 a and 30 b are fixed to the diffusion layer 25 by the liquid sealing material as a whole, the path cut is suppressed in the entire second flow path 28. As a result, for example, a large differential pressure is generated between the gas pressure of the first turn portion 32 and the gas pressure of the second turn portion 34 as compared with the present invention, and the hydrogen gas flows smoothly in the second flow path 28. Can be secured. However, since there is no diffusion of hydrogen gas due to the pass cut, the moisture supplied by the first straight part 31 is consumed, for example, for humidification of the electrolyte membrane 24 in the second straight part 33, and the third straight part 35 is sufficiently obtained. Moisture cannot be spread over and the power generation performance is reduced.

  From the above, in the fuel cell 11 according to the present embodiment, it is possible to suppress the occurrence of a pass cut with a simple configuration in which only the protrusions 36a and 36b are provided on the ribs 30a and 30b. In addition, it is possible to avoid a reduction in power generation area due to leakage of the liquid sealing material to the diffusion layer 25 and unnecessary work such as impregnation of the liquid sealing material is unnecessary. Further, the formation of the protrusions 36a and 36b can partially suppress and partially allow the hydrogen gas path cut. As a result, an appropriate flow of hydrogen gas along the second flow path 28 is established, and moisture supplied at the upper end of the fuel cell 12 can be transported toward the lower end, and the entire electrolyte membrane 24 is dried. Can be suppressed. In this way, it is possible to suppress a decrease in gas stoichiometry in the power generation region of the fuel battery cell 11, and it is possible to suppress a decrease in power generation performance.

  Next, the performance of the fuel cell 11 during operation was compared. The fuel cell 11 according to the present invention was prepared as a specific example, and the fuel cell of Patent Document 1 was prepared as a comparative example. As shown in FIG. 6, although the cell voltage decreased as the operating temperature increased from 85 ° C. to 95 ° C., the decrease was suppressed in the specific example as compared with the comparative example. In general, as the operating temperature increases, the degree of drying of the electrolyte membrane increases and the resistance value of the electrolyte membrane increases, so the cell voltage decreases. In the specific example of the present invention, it was confirmed that the cell voltage can be suppressed from being lowered at a high temperature by appropriately humidifying the entire electrolyte membrane.

  In the fuel cell 11 as described above, the shape of the protrusions 36a and 36b is not limited to the shape described above. As shown in FIG. 7, a wire having a predetermined diameter may be bonded to the contact surface of the rib 30a when forming the protrusion 36a. Here, although the wire is cylindrical, the shape of the wire is not limited to this. Further, as shown in FIG. 8, the protrusion 36a may be formed, for example, from a dome-like protrusion that protrudes in a semi-cylindrical shape toward the diffusion layer 25, as shown in FIG. In addition, it may be formed from a triangular prism-shaped protrusion formed on the contact surface, or may be formed from a semi-cylindrical protrusion formed on the contact surface as shown in FIG. Such a shape is formed by, for example, a two-stage pressing process.

11 Fuel Cell 12 Fuel Cell 13 Stack (Cell Stack)
21 Membrane electrode assembly 22 Cathode separator 23 Anode separator 24 Electrolyte membrane 25 Diffusion layer 26 First flow path 28 Second flow path 30a Rib 30b Rib 36a Protrusion 36b Protrusion

Claims (3)

In a fuel cell having a cathode separator and an anode separator each sandwiching a diffusion layer between both surfaces of an electrolyte membrane,
A first flow path of a reaction gas formed on an inward surface of one of the cathode separators facing one of the diffusion layers and extending in a first direction from the lower end to the upper end of the cathode separator ;
A second flow path of a reaction gas formed on an inward surface of the other anode separator facing the other diffusion layer, and is partitioned by a rib formed on the anode separator; A second flow path extending while meandering in a second direction perpendicular to the first direction from the upper end toward the lower end ;
A projection projecting from said abutment surface is formed on the contact surface of the rib that abuts the front Symbol diffusion layer, the tip of the rib from the base end of the rib adjacent to the turn portions of the second flow path And a protrusion extending toward the
The protrusion is a fuel cell, wherein Rukoto partially formed over the full length of the rib. The length of the protrusion is a fuel cell according to claim 1, characterized in that approximately equal to the width of the turn portion. A fuel cell comprising a laminate in which a plurality of the fuel cells according to claim 1 or 2 are laminated.

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