JP2005222906A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To uniformalize the steam pressure in air electrode separators in fuel cells of a fuel cell system. <P>SOLUTION: On the air electrode separators 8, 14 of an adjacent pair of the fuel cells 2A, 2B in the stacking direction, air electrode gas flow grooves 8A, 14A to supply an air electrode gas are formed. In the air electrode gas flow grooves 8A, 14A, a plurality of steam passing holes 8C, 14C are formed. The air electrode separators 8, 14 are disposed such that they interpose a steam permeable membrane 15 to selectively permeate steam so as to mutually give and take steam. The air electrode gas flow directions in the air electrode gas flow grooves 8A, 14A interposing the steam permeable membrane 15 are set to be opposite to each other. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell, and more particularly to a fuel cell having a structure in which a solid polymer electrolyte membrane is sandwiched between a fuel electrode separator and an air electrode separator.

  In general, in a fuel cell using a solid polymer electrolyte membrane, it is necessary to use a gas with high humidity in order to keep the proton conductivity of the solid polymer electrolyte membrane in a good state. In the fuel cell, generation of water as a product and disappearance of gas as a reaction occur in the direction of gas flow in the polymer solid electrolyte membrane, and the saturation ratio of water vapor at the gas outlet It becomes higher than the saturation ratio. In other words, if the humidity of the gas is adjusted with an external humidifier so that the saturation ratio near the gas inlet is appropriate, the saturation ratio near the gas outlet will increase, reducing the partial pressure of the reaction gas and reducing the power generation performance of the fuel cell. Cause a decline.

On the other hand, if the humidity of the gas is adjusted with an external humidifier so that the saturation ratio near the gas outlet is appropriate, the saturation ratio near the gas inlet is lowered and the proton conductivity of the polymer solid electrolyte membrane is lowered, so that Of power generation performance. As described above, the humidity of the fuel cell is such that the water vapor is excessive in the vicinity of the gas outlet, whereas the water vapor is insufficient in the vicinity of the gas inlet. In order to alleviate such a state, it is known to make the humidity distribution in the gas flow direction uniform by making the upstream and downstream of the gas flow adjacent to promote the movement of water vapor (for example, Patent Document 1). reference.). In addition, there is a separator plate having electric conductivity that also has a function of a water vapor permeable membrane, and moves excess water vapor from the air electrode gas to the fuel electrode gas (see, for example, Patent Document 2).
JP 2001-126746 A (page 4, FIG. 1) Japanese Patent No. 3331117 (first page, FIG. 2)

  Generally, a static pressure difference due to pressure loss exists upstream and downstream of the gas flow. In addition, since the catalyst layer in contact with the separator plate must have gas diffusivity, the catalyst layer itself has a high porosity, or a porous material such as carbon having high porosity and conductivity. The body is sandwiched between the catalyst layer and the separator plate. In the configuration in which the upstream and downstream of the gas flow are adjacent to each other with the structure having a high porosity as the boundary as in Patent Document 1, there is a problem in that the reaction gas moves according to the static pressure difference.

  In the configuration in which water vapor is exchanged between the air electrode gas and the fuel electrode gas as in Patent Document 2, only a small amount of water moves at the fuel electrode having a relatively small gas flow rate. However, there is a problem that the saturation ratio increases. For this reason, the water vapor pressure difference, which is the driving force for the water vapor movement, gradually decreases, and the excessive water vapor in the air electrode may not be alleviated.

  An object of the present invention is to make the water vapor pressure uniform in a fuel battery cell.

  The present invention is characterized in that air electrode separators of fuel cells adjacent to each other in the stacking direction sandwich a water vapor permeable membrane that selectively transmits water vapor.

  According to the present invention, the air electrode separators sandwiching the water vapor permeable membrane can exchange water vapor through the water vapor permeable membrane to make the water vapor pressure uniform. For this reason, the power generation performance of the fuel cell can be improved.

  Next, the fuel cell of the present invention will be illustrated and described with reference to the drawings. However, it should be noted that the drawings are schematic and the thicknesses and thickness ratios of the material layers are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

[First Embodiment]
FIG. 1 is an explanatory cross-sectional view schematically showing a fuel cell 1 according to a first embodiment of the present invention, and shows an example in which a pair of fuel cells 2A and 2B are stacked. FIG. 1 shows a state in which the layers are separated by the interposition of the sealing material 30, but the sealing material 30 is finally compressed so that the layers are joined to each other.

  First, the configuration of the fuel battery cell 2A disposed in the lower part of FIG. 1 will be described. The fuel cell 2A includes an MEA (membrane electrode assembly) 6 in which gas diffusion layers 4 and 5 including catalyst layers are formed on both main surfaces of the polymer solid electrolyte membrane 3, and one of the MEA 6 (lower in FIG. 1). A fuel electrode separator (anode plate) 7 disposed along the main surface of the MEA 6 and an air electrode separator (cathode plate) 8 disposed along the other main surface of the MEA 6 (upper side in FIG. 1). It is configured.

  1 includes an MEA 12 in which gas diffusion layers 10 and 11 including a catalyst layer are formed on both main surfaces of the polymer solid electrolyte membrane 9, and one of the MEA 12 The fuel electrode separator 13 is disposed along the main surface (upper side in FIG. 1), and the air electrode separator 14 is disposed along the other main surface (lower side in FIG. 1) of the MEA 12. Yes.

  The pair of fuel cells 2A and 2B are arranged such that the air electrode separators 8 and 14 face each other, and a resin having water vapor permeability and electrical insulation between the air electrode separators 8 and 14. A water vapor permeable membrane 15 is interposed. The air electrode gas circulated by the air electrode separators 8 and 14 is set to flow in opposite directions as will be described later.

  Here, the water vapor permeable membrane 15 and the air electrode separators 8 and 14 sandwiching the water vapor permeable membrane 15 will be described with reference to FIGS. 2A to 2C are plan views of the air electrode separator 14, the water vapor permeable membrane 15, and the air electrode separator 8 as viewed from the upper surface side, respectively.

Each of the water vapor permeable membrane 15 and the air electrode separators 8 and 14 is formed with various manifolds described later at corresponding positions. 2A to 2C show a fuel electrode gas inlet manifold 22 of hydrogen (H ₂ ) that is a fuel electrode gas, an air electrode gas outlet manifold 25, an air electrode gas inlet manifold 26, and cooling water. The inlet manifold 28 is formed.

  As shown in FIG. 2 (c), on the surface (lower surface) opposite to the surface (upper surface) facing the water vapor permeable membrane 15 in the air electrode separator 8, a plurality of parallel air electrode gas flow grooves 8A, The air electrode gas flow grooves 8A merge to form a merge groove 8B that guides the air electrode gas to the air electrode gas outlet manifold 25. In the air electrode gas flow grooves 8A, a plurality of water vapor passage holes 8C penetrating in the thickness direction of the air electrode separator 8 are formed at predetermined intervals along the grooves.

  Further, as shown in FIG. 2A, on the surface (upper surface) opposite to the surface (lower surface) facing the water vapor permeable membrane 15 in the air electrode separator 14, a plurality of rows are formed in the same manner as the air electrode separator 8. The parallel air electrode gas flow grooves 14A and the dispersion grooves 14B for distributing the air electrode gas from the air electrode gas inlet manifold 26 to the air electrode gas flow grooves 14A and dispersing them are formed. In the air electrode gas circulation groove 14A, a plurality of water vapor passage holes 14C penetrating in the thickness direction of the air electrode separator 14 are formed at predetermined intervals along the groove.

  The water vapor permeable membrane 15 and the air electrode separators 8 and 14 sandwiching the water vapor permeable membrane 15 are respectively formed in an arrangement as shown in FIG. 3, the fuel electrode gas inlet manifold 22, the fuel electrode gas outlet manifold 23, the air electrode gas inlet manifold 24, The air electrode gas outlet manifold 25, the air electrode gas inlet manifold 26, the air electrode gas outlet manifold 27, the cooling water inlet manifold 28, and the cooling water outlet manifold 29 are stacked so as to match.

  Then, under the fuel electrode separator 7 of the fuel cell 2A, a current collecting plate 16, an insulating plate 17, and an end plate 18 having electrical conductivity are sequentially stacked. In addition, a current collecting plate 19, an insulating plate 20, and an end plate 21 having electrical conductivity are sequentially stacked on the fuel battery cell 2B. As shown in FIG. 1, such a laminate has a sealing material 30 interposed in a place where airtightness is required, and, as shown in FIG. 3, for example, each layer is press-contacted by four tie rods 31. It is fixed to. FIG. 3 is a view showing a state in which the end plate 18 is viewed from the lower surface.

  The end plate 18, the insulating plate 17, and the current collecting plate 16 are also provided with a fuel electrode gas inlet manifold 22, a fuel electrode gas outlet manifold 23, an air electrode gas inlet manifold 24, an air electrode gas outlet manifold 25, and an air electrode gas inlet manifold. 26, an air electrode gas outlet manifold 27, a cooling water inlet manifold 28, and a cooling water outlet manifold 29 are formed.

  Moreover, as shown in FIG. 1, the air electrode separators 8 and 14 have one end portions extending laterally to form current collecting terminals 8D and 14D. In addition, current collecting plates 16 and 19 are also extended at one end to form current collecting terminals 16A and 19A.

  As shown in FIG. 3, the arrow A indicates the gas flow direction in the air electrode gas flow groove 14 </ b> A of the air electrode separator 14, and the arrow B indicates the gas flow direction in the air electrode gas flow groove 8 </ b> A of the air electrode separator 8. . As described above, in the air electrode separator 8 and the air electrode separator 14, gas flows in the reverse direction through the water vapor permeable membrane 15.

  4 shows the position of the direction along the arrow A shown in FIG. 3 as the horizontal axis and the vertical axis for each position, that is, from the air electrode gas inlet manifold 25 and the air electrode gas outlet manifold 25 side to the air electrode gas outlet. The water vapor partial pressure of the air electrode gas flow grooves 8A and 14A for each position over the manifold 27 and the air electrode gas inlet manifold 24 is shown.

  In FIG. 4, the broken line is a profile when there is no movement of water vapor, that is, when the air electrode gas flow grooves 8 </ b> A and 14 </ b> A between the air electrode separators 8 and 14 are independent without using the water vapor permeable membrane 15. . In this case, since the water vapor partial pressure monotonously increases from the air electrode gas inlet manifolds 26 and 24 toward the air electrode gas outlet manifolds 25 and 27, respectively, the water vapor pressure near the air electrode gas inlet manifolds 26 and 24 is increased. If it is going to be secured, the water vapor pressure becomes excessive in the vicinity of the air electrode gas outlet manifolds 25, 27, and there is a problem that the condensed water closes the flow path and a problem that hinders gas diffusion.

  On the other hand, if the water vapor pressure in the vicinity of the air electrode gas outlet manifolds 25 and 27 is suppressed to such a level that condensation does not occur, the water vapor pressure in the vicinity of the air electrode gas inlet manifolds 26 and 24 decreases, and the polymer solid electrolyte membranes 3 and 9 There is a problem of promoting the evaporation of moisture.

  A solid line shown in FIG. 4 is a profile when water vapor actually moves through the water vapor permeable membrane 15. Since the differential pressure between the two water vapor profiles indicated by the broken line in FIG. 4 is the driving force for the movement of the water vapor, it is generally flat except for the vicinity of the air electrode gas inlet manifolds 26 and 24 and the vicinity of the air electrode gas outlet manifolds 25 and 27. Profile.

  As described above, according to the present embodiment, water vapor flows from the plurality of water vapor passage holes 8C and 14C formed in the air electrode gas flow grooves 8A and 14A of the air electrode separators 8 and 14 in which the air electrode gas flows in opposite directions. Since the water vapor is exchanged through the permeable membrane 15, both the air electrode separators 8, 14 can exchange substantially the same amount of water vapor, while reducing the permeation amount of the reaction gas other than water vapor, It is possible to make the water vapor pressure of the gas uniform.

  FIG. 5 shows an equivalent circuit of the fuel cell 1 according to the present embodiment. In the present embodiment, since the water vapor permeable membrane 15 does not have electrical conductivity, two independent fuel cells 2A and 2B are formed. By appropriately connecting the current collecting plates 16 and 19 and the current collecting terminals 8D and 14D, series connection or parallel connection becomes possible.

[Second Embodiment]
FIG. 6 shows a fuel cell according to the second embodiment of the present invention. In the fuel cell according to the present embodiment, the same portions as those of the fuel cell 1 according to the first embodiment described above are denoted by the same reference numerals.

  The fuel cell 100 is configured by stacking, for example, eight fuel cells 101 to 108. In the present embodiment, a pair of adjacent fuel cells 102 and 103 sandwich the water vapor permeable membrane 15, and the two fuel cells of the fuel cell 1 according to the first embodiment described above. It corresponds to 2A and 2B. Similarly, the pair of fuel cells 104 and 105 adjacent to each other and the pair of fuel cells 106 and 107 adjacent to each other also have a water vapor permeable membrane 15 interposed therebetween, and the fuel according to the first embodiment described above. The configuration is the same as that of the fuel battery cells 2A and 2B of the battery 1. Also in this embodiment, the water vapor permeable membrane 15 has electrical insulation.

  In the present embodiment, the fuel battery cell 101 is stacked under the lower fuel battery cell 102 in the lowest position in FIG. A fuel cell 108 is stacked on the uppermost fuel cell 107.

  Then, both ends of one of the air electrode separators 8 and 14 sandwiching the water vapor permeable membrane 15 (the air electrode separator 14 in the present embodiment) are extended laterally, and the current collecting terminals 14D, 14E. Each terminal extended in this way is formed with a through hole (not shown).

  In the fuel cell 100 according to the present embodiment, the gas flow directions in the air electrode separators 8 and 14 disposed via the water vapor permeable membrane 15 are set to be opposite to each other.

  With such a configuration, as shown in FIG. 7, in addition to the configuration shown in FIG. 6, the collar 32 as the first elastic body, the collar 33 as the second elastic body, and the non-electric A circuit can be formed by sandwiching a collar 34 made of a conductive elastic body. Then, by fastening these collars 32, 33, and 34 with insulated bolts 35 and 36 that pass through the separator plate in which these collars are sandwiched, the fuel cell 100 represented by an equivalent circuit as shown in FIG. 8 is obtained. It is configured. In this manner, a current extraction portion is provided in the air electrode separator or the like, and thereby, the lowest voltage plate and the highest voltage plate connected in series can be obtained.

  In the above-described second embodiment, a plurality of units each composed of a pair of fuel cells arranged opposite to each other with the water vapor permeable membrane 15 interposed therebetween are configured. For this reason, the air electrode separators having substantially the same potential in the repeating unit are connected by the collar 33 having electric conductivity, and the air electrode separator and the fuel electrode separator in the adjacent unit have the electric conductivity collar 34. As a result of the connection, the voltage can be increased by the serial connection as in the conventional case.

  In the second embodiment described above, the collars 32, 33, and 34 are formed of an elastic body. Therefore, when the layers are stacked and fastened with the bolts 35 and 36, damage on the plate side is prevented. However, electrical conduction and electrical insulation can be reliably achieved.

  The fuel cell according to the present invention can be applied not only to a vehicle fuel cell but also to household and configuration fuel cell applications.

It is side explanatory drawing which shows the fuel cell which concerns on the 1st Embodiment of this invention. (A) is a plan view of one air electrode separator sandwiching the water vapor permeable membrane constituting the fuel cell according to the first embodiment of the present invention, (b) is a plan view of the water vapor permeable membrane, and (c) is water vapor. It is a top view of the other air electrode separator which pinches | interposes a permeable membrane. It is a bottom view which shows the state which looked at the fuel cell which concerns on 1st Embodiment which concerns on this invention from the end plate side. It is a figure which shows the relationship between the water vapor partial pressure and the gas flow direction position of the air electrode separator of the fuel cell which concerns on 1st Embodiment. 1 is an equivalent circuit diagram of a fuel cell according to a first embodiment. It is side surface explanatory drawing of the fuel cell which concerns on the 2nd Embodiment of this invention. It is side explanatory drawing which shows the example of a connection of the fuel cell which concerns on the 2nd Embodiment of this invention. FIG. 4 is an equivalent circuit diagram of a fuel cell according to a second embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell 2A, 2B Fuel cell 3, 9 Polymer solid electrolyte membrane 8, 14 Air electrode separator 8A, 14A Air electrode gas distribution groove 8C, 14C Water vapor passage hole 8D, 14D Current collecting terminal 15 Water vapor permeable membrane 16 Current collection Plate 18, 21 End plate 24, 26 Air electrode gas inlet manifold 25, 27 Air electrode gas outlet manifold 33 Collar (first elastic body)
34 color (second elastic body)
DESCRIPTION OF SYMBOLS 100 Fuel cell 101-108 Fuel cell

Claims (5)

A fuel in which a fuel electrode separator having a groove for supplying a fuel electrode gas and an air electrode separator having a groove for supplying an air electrode gas are disposed so as to sandwich the polymer solid electrolyte. A fuel cell in which a plurality of battery cells are stacked,
A pair of the fuel cells adjacent to each other in the stacking direction are arranged so as to sandwich a water vapor permeable membrane that selectively allows water vapor to pass between the air electrode separators. A fuel cell.   The fuel cell according to claim 1, wherein the air electrode separators sandwiching the water vapor permeable membrane are set so that the flow directions of the air electrode gas are opposite to each other.   The fuel cell according to claim 1 or 2, wherein an opening penetrating in the thickness direction is formed in the groove in the air electrode separator.   The fuel cell according to any one of claims 1 to 3, wherein the water vapor permeable membrane is made of an electrically insulating resin. The air electrode separator is formed of a conductive material,
A plurality of pairs of fuel cells sandwiching the water vapor permeable membrane are provided, and a first elastic body having electrical conductivity is sandwiched between the air electrode separators of the fuel cells forming each pair,
5. The second elastic body having electrical conductivity is sandwiched between a pair of air electrode separators and fuel electrode separators adjacent to each other, according to claim 1. Fuel cell.

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