JP2009259743A - Fuel cell, its edge seal member, and method of manufacturing edge seal member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive fuel cell satisfying the performance requirement of an edge seal member, and to provide its edge seal member. <P>SOLUTION: Edge seal members 10a, 10b, 10c, 10d are arranged so that each gas does not leak to a counter electrode in extension parts parallel to gas passages of porous carbon plates 40a, 40b, 40c, 40d. The edge seal members 10a, 10b, 10c, 10d are formed by inserting a body 11 such as an expanded graphite sheet into a shrinkable resin tube 12, sealing both ends by heat seal, opening a vent hole 15a in a part, and then shrinking the tube. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell, an end seal member thereof, and a manufacturing method of the end seal member, and in particular, an electrolyte layer holding an electrolyte is sandwiched between a fuel electrode catalyst layer and an air electrode catalyst layer, and fuel gas is contained in the fuel electrode catalyst layer. Production of a fuel cell in which a unit cell in which a porous material having a gas flow path and a porous material having a gas flow path for an oxidant gas are arranged on an air electrode catalyst layer is laminated, and its end seal member and end seal member Regarding the method.

In recent years, fuel cells are expected to be widely used for various purposes because they can directly convert chemical energy of fuel into electrical energy and thus have high power generation efficiency and are environmentally friendly.
FIG. 5 is a schematic configuration diagram showing a state in which two unit cells of the fuel cell are stacked.

  In the fuel cell, porous carbon plates 93a and 93b having gas flow paths and electrode portions 94a and 94b constituting a counter electrode are sandwiched between separators 91a and 91b. An electrolyte layer (not shown) is formed between the electrodes 94a and 94b. Similarly, porous carbon plates 93c and 93d and electrode portions 94c and 94d constituting a counter electrode are sandwiched between separators 91b and 91c. End seal members 92a, 92b, 92c, and 92d are arranged in the extended portions parallel to the gas flow paths of the porous carbon plates 93a, 93b, 93c, and 93d so that the respective gases do not leak to the counter electrode.

  The end seal members 92a, 92b, 92c, and 92d are required to have corrosion resistance to the electrolyte as well as gas impermeability. Moreover, since it is necessary to ensure the height of a gas flow path, the thickness of about 2 mm is also required. Furthermore, if a large amount of electrolyte is contained, there is a possibility that a problem such as electrolyte migration between the upper and lower cells may occur due to electrolyte leakage between the upper and lower cells at the end surfaces of the end seal members 92a, 92b, 92c, and 92d. For this reason, it was required that the electrolyte does not have a liquid junction at the end face. As end seal members 92a, 92b, 92c, and 92d that satisfy these conditions, conventionally, a dense carbon material that has been graphitized or a separator is cut into the width of the end seal member and laminated through a fluororesin film. What was used was expensive.

Thus, a technique has been proposed in which an inexpensive expanded graphite sheet is subjected to water-repellent treatment with a perfluoroethylene-based resin to form an end seal member (see, for example, Patent Document 1).
In order to simplify the gas sealing process at the side end, there is also a technique of sealing the end by covering a porous carbon plate with a resin-based shrink tube (for example, see Patent Document 2).
Japanese Patent No. 3838403 Japanese Patent Laid-Open No. 3-20564

However, the configuration of the end seal member of the fuel cell as described above has the following problems.
Although the technology of using an expanded graphite sheet for water-repellent treatment as an end seal member can constitute an end seal member at a low cost, the water repellent treatment with a perfluoroethylene resin deteriorates with the operation time. There is a point. Although the impermeability to the electrolyte is maintained in the operation for several thousand hours, a decrease in the impermeability is observed in the operation time of tens of thousands of hours.

  Further, in the technique of coating the porous carbon plate with a resin-based shrink tube to form an end seal member, both ends of the shrink tube are in an open state, and there is a problem that a separate process is required. In order to make the open portion gas-permeable and electrolyte impervious, for example, a process of separately impregnating the open end face with resin or fusing another resin film to the end face is required. Therefore, it was a factor of cost increase.

  The present invention has been made in view of these points, and provides an inexpensive fuel cell having sufficient performance required for an end seal member, and an end seal member and a method for manufacturing the end seal member. With the goal.

  In order to solve the above problems, an electrolyte layer holding an electrolyte is sandwiched between a fuel electrode catalyst layer and an air electrode catalyst layer, and a porous material having a fuel gas gas passage in the fuel electrode catalyst layer and an air electrode catalyst layer are provided. In a fuel cell in which a unit cell having a porous material having a gas flow path for an oxidant gas is stacked, a predetermined end including an expanded graphite sheet at an end parallel to the gas flow path formed in the porous material A fuel cell is provided in which a part sealing material is covered with a shrinkable resin tube, both ends of the shrinkable resin tube are sealed by thermal fusion, and a contracted end part seal member is disposed.

  According to such a fuel cell, the end seal member in which the predetermined end seal material including the expanded graphite sheet is covered with the shrinkable resin tube, and both ends of the shrinkable resin tube are sealed by thermal fusion, It arrange | positions at the edge part parallel to the gas flow path of the fuel cell formed in a porous material.

  Further, in order to solve the above problems, the end seal member is disposed in the fuel cell, and a predetermined end seal member is covered with a shrinkable resin tube, and both ends of the shrinkable resin tube are thermally fused. An end seal member is provided that is sealed by attachment.

  Furthermore, in order to solve the above-mentioned problem, a method for manufacturing the above-described end seal member, which is a procedure of covering a predetermined end seal material with a shrinkable resin tube, and heat-bonding the end of the shrinkable resin tube Is provided with a method for fusing and sealing, and a method for shrinking the shrinkable resin tube.

  According to the disclosed fuel cell, the end seal member thereof, and the end seal member manufacturing method, the end seal member is covered with the shrinkable resin tube, and both ends of the shrinkable resin tube are heat-sealed and sealed. Is done. Thereby, since the whole surface including both ends of the end seal member is covered with the resin, gas impermeability and corrosion resistance to the electrolyte can be provided. Moreover, since both ends of the end seal member are covered by heat-sealing both ends of the shrinkable resin tube, it is possible to omit a process such as fusing another resin film for sealing at both ends. As a result, an inexpensive fuel cell sufficiently equipped with the required performance of the end seal member and the end seal member can be obtained.

Hereinafter, a first embodiment of the present invention will be described. FIG. 1 is a diagram showing a single end seal member of the fuel cell according to the first embodiment.
The end seal member 10 has a main body 11 covered with a shrinkable resin tube 12.

  The main body 11 is represented by a dotted line in the figure, and is formed of a predetermined end seal material including an expanded graphite sheet. In addition, although there exists a clearance gap between the shrinkable resin tubes 12 in the figure for the sake of explanation, they are actually in close contact. The predetermined end seal material includes a material used as an end seal material, and includes, for example, a porous carbon plate and a calcined carbon plate in addition to the expanded graphite sheet.

  The shrinkable resin tube 12 is made of a fluororesin in a tube shape, and shrinks when heated to cover the main body 11 inserted therein. Examples of the fluororesin used include tetrafluoroethylene resin (abbreviation PTFE, melting point 327 ° C.), fluorinated alkyloxyethylene resin (abbreviation PFA, melting point 300 to 310 ° C.), and fluoroethylenepropylene resin (abbreviation TFP, Melting point 290-300 ° C.). The tube end 14 is sealed by heat-sealing at the fusing portions 13 on both end surfaces in the longitudinal direction of the end seal member 10. Here, the tube end 14 and the fusing part 13 are the same. Further, a degassing hole (hereinafter referred to as a degassing hole) 15 is opened at an arbitrary position of the shrinkable resin tube 12. The gas vent holes 15 are provided for preventing the shrinkable resin tube 12 from being damaged by the volume change of the gas in the tube, and an arbitrary number of the gas vent holes 15 are provided with a necessary and sufficient size. For example, one gas vent hole 15 is formed on each of both end faces of the end seal member 10 in the longitudinal direction so that the gas is uniformly vented.

A method for manufacturing such an end seal member 10 will be described.
A main body 11 formed of an expanded graphite sheet or the like is inserted into the shrinkable resin tube 12. Next, the tube end 14 is melted and cut off with a sealer (hot wire heat fusion device) or the like, and both ends are sealed. As a result, the entire surface of the main body 11 is covered with the resin and sealed. Next, a gas vent hole 15 having a diameter of about 0.5 μm is formed in a part of the shrinkable resin tube 12. Thereby, the internal degassing at the time of tube contraction can be performed. Next, the end seal member 10 whose entire surface of the main body 11 is covered with the shrinkable resin tube 12 is heated to shrink the shrinkable resin tube 12, and the end seal member 10 is manufactured.

  In such a manufacturing method of the end seal member 10, after inserting the main body 11 into the shrinkable resin tube 12, both ends of the tube are sealed by heat sealing, whereby the manufacturing process can be simplified. And the manufactured end seal member 10 can ensure gas seal and electrolytic impermeability at both ends. Further, by opening the gas vent hole 15 in a part of the shrinkable resin tube 12, damage due to a change in the volume of gas in the shrinkable resin tube 12 can be prevented.

FIG. 2 is a diagram showing a state in which two unit cells of the fuel cell according to the first embodiment are stacked.
The fuel cell in the figure shows a state in which a unit cell formed between the separator 30a and the separator 30b and a unit cell formed between the separator 30b and the separator 30c are stacked in two layers.

  The separators 30a, 30b, and 30c satisfy gas impermeability and corrosion resistance to the electrolyte. For example, a paper made of cellulose fiber is impregnated with a thermosetting resin, dried, laminated, pressed, and further fired.

  The unit cell sandwiched between the separators 30a and 30b includes a fuel electrode catalyst layer having a porous carbon plate 40a in which a fuel gas flow path is formed and an electrode part (fuel electrode) 50a on both surfaces of an electrolyte layer (not shown), A porous carbon plate 40b on which an oxidant gas or air channel (hereinafter referred to as an air channel) is formed and an air electrode catalyst layer having an electrode part (air electrode) 50b are disposed. In the example of the figure, the fuel gas channel and the air channel are overlapped so as to be orthogonal to each other. Similarly, the unit cell sandwiched between the separators 30b and 30c has the fuel electrode catalyst layer having the porous carbon plate 40c and the electrode portion 50c on both surfaces of the electrolyte layer, and the porous carbon plate 40d and the electrode portion 50d. An air electrode catalyst layer is disposed.

  End seal members 10a, 10b, 10c, and 10d are arranged in the extended portions parallel to the gas flow paths of the porous carbon plates 40a, 40b, 40c, and 40d so that the respective gases do not leak to the counter electrode. For example, end seal members 10a are disposed at both ends of the porous carbon plate 40a in the gas flow path direction (the depth direction of the fuel cell in the drawing). The same applies to the other end seal members 10b, 10c, and 10d. The end seal members 10a, 10b, 10c, and 10d are formed in the same manner as the end seal member 10 shown in FIG. That is, the entire surface of the main body 11 such as an expanded graphite sheet is covered with the shrinkable resin tube 12. Further, both ends of the shrinkable resin tube 12 are sealed by heat fusion, and a gas vent hole is formed in a part thereof. Such an end seal member is placed at the end of the separators 30a, 30b, and 30c with a resin film having a melting point lower than that of the shrinkable resin tube 12 used for the end seal member, and heat fusion is performed by hot pressing. To wear. Thereby, the end seal member of the fuel cell is formed. For example, in the end seal member 10a that is heat-sealed to the separator 30a, both ends of the tube are heat-sealed at the end seal member end surfaces 16a at both ends in the longitudinal direction of the end seal member 10a, and the end seal member end surface 16a A vent hole 15a is formed at a position opposite to the porous carbon plate 40a.

  In the fuel cell having such a configuration, the gas vent hole prevents the tube from being damaged due to the volume change of the gas inside the tube, which occurs even during operation of the fuel cell. Further, an end seal member made of an end seal material whose both ends are heat-sealed and whose entire surface is covered with a shrinkable resin tube has gas impermeability and electrolyte impermeability that satisfy required performance.

  Example 1 An expanded graphite sheet (PF250, thickness 2.5 mm, bulk density 0.65 g / cc) manufactured by Toyo Tanso Co., Ltd. cut to 18 × 130 mm was used as a heat shrinkable tube made by Gunze PFA. Insert into SMT (thickness 50 μm). The heat-shrinkable tube end is fused with a heat sealer FV-801 manufactured by Hakuko. Then, a gas vent hole having a diameter of about 0.5 μm is formed in the melted portion. Thereafter, the heat-shrinkable tube is shrunk by holding at 180 ° C. for 2 hours in an electric furnace.

  Subsequently, a glassy carbon plate (SG-3, thickness 0.6 mm) manufactured by Showa Denko KK is cut into 130 × 130 mm to obtain a separator. An expanded graphite sheet with a heat-shrinkable tube adhered thereto was placed at both ends of the separator through a 25 μm thick FEP film cut to 180 × 130 mm, and pressurized at 0.5 MPa for 10 minutes at 320 ° C. An end seal member is obtained.

In the fuel cell manufactured according to Example 1, the amount of gas leakage through the end seal member was 0.1 ml / min or less when the differential pressure was 10 kPa. In addition, there was no increase in leakage after 2000 hours of operation at a current density of 300 mA / cm ² . Further, as a result of the disassembling investigation after the operation, the electrolyte did not enter the end seal member, and neither corrosion nor liquid junction of the electrolyte at the end seal member end surface occurred. In general, it was confirmed that the fuel cell having a favorable end seal member configuration can be obtained by Example 1. In Example 1, it was confirmed that there was no increase in leakage after 2000 hours of operation, but the end seal member of the structure covered with the resin film was recognized to be electrolyte impervious for 40000 hours or more. The same electrolyte impervious performance is expected to be obtained for Example 1 as well.

  Next, a second embodiment will be described. In the first embodiment, the position at which the gas vent hole is opened is arbitrary, but in the second embodiment, it is assumed that the upper end is formed above the center position in the thickness direction of the end seal member.

FIG. 3 is a diagram showing a single end seal member of the fuel cell according to the second embodiment. The same parts as those in the end seal member shown in FIG.
The end seal member 20 is formed by inserting the main body 11 into the shrinkable resin tube 12, fusing the tube end 14 to seal both ends, and then forming a gas vent hole 21 to be opened in the shrinkable resin tube 12. 20 is opened above the center position in the thickness direction. The size of the gas vent hole 21 is the same as that of the gas vent hole 15 of the first embodiment. For example, a hole having a diameter of about 0.5 μm is formed. Except that the position of the gas vent hole 21 is different, the material and manufacturing process of the end seal member 20 are the same as those in the first embodiment.

Thus, by forming the gas vent hole 21, it is possible to prevent the shrinkable resin tube 12 from being damaged due to the volume change of the gas in the shrinkable resin tube 12.
Further, by opening the vent hole 21 above the center of the thickness of the end seal member 20, the condensed water is prevented from dripping from the shrinkable resin tube 12 when the condensed water is accumulated in the tube. be able to.

  Resin-based shrinkable tubes have water vapor permeability, and water vapor that has permeated into the tube during operation may condense when stopped and accumulate as condensed water in the tube. If the gas vent hole 21 is opened in the lower part of the end seal member 20 in this state, the condensed water in the tube hangs down from the gas vent hole 21 and causes rusting of the structural member and a decrease in insulation of the electrical component. . Therefore, by opening the vent hole 21 in the upper part of the end seal member 20, it is possible to prevent dripping of the condensed water, and to prevent the rust of the structural member and the insulation deterioration of the electrical component.

FIG. 4 is a diagram showing a state in which two unit cells of the fuel cell according to the second embodiment are stacked. The same parts as those shown in FIG.
End seal members 20a, 20b, 20c, and 20d are arranged in the extended portions parallel to the gas flow paths of the porous carbon plates 40a, 40b, 40c, and 40d so that the respective gases do not leak to the counter electrode. Except that the end seal members 10a, 10b, 10c, and 10d of the first embodiment shown in FIG. 2 are replaced with the end seal members 20a, 20b, 20c, and 20d, the other configurations are the first embodiment. It is the same as the form.

  End seal members 20a, 20b, 20c, and 20d are arranged in the extended portions parallel to the gas flow paths of the porous carbon plates 40a, 40b, 40c, and 40d so that the respective gases do not leak to the counter electrode. The end seal members 20a, 20b, 20c, and 20d are formed in the same manner as the end seal member 20 shown in FIG. That is, a gas vent hole 21 is formed above the center of the thickness of the shrinkable resin tube 12 that covers the main body 11 such as an expanded graphite sheet. Such an end seal member is placed at the end of the separators 30a, 30b, and 30c with a resin film having a melting point lower than that of the shrinkable resin tube 12 used for the end seal member, and heat fusion is performed by hot pressing. To wear. At this time, the end seal member is arranged in the direction in which the gas vent hole 21 is at the top. Thereby, the end seal member of the fuel cell is formed. For example, the end seal member 20a that is heat-sealed to the separator 30a is heat-sealed at both ends of the tube at the end seal member end surfaces 22a at both ends in the longitudinal direction of the end seal member 20a, and the end seal member end surface 22a A gas vent hole 21a is formed in the opposite direction to the porous carbon plate 40a and above the center in the thickness direction of the end seal member 20a.

  In the fuel cell having such a configuration, the gas vent hole prevents the tube from being damaged due to the volume change of the gas inside the tube, which occurs even during operation of the fuel cell. Further, by setting the position of the vent hole above the center of the thickness of the end seal member, when the condensed water is accumulated in the shrinkable resin tube 12, the condensed water is prevented from dripping from the tube. can do. Further, the end seal member made of the end seal material whose both ends are also heat-sealed and whose entire surface is covered with the shrinkable resin tube 12 has gas impermeability and electrolyte impermeability that satisfy the required performance.

  (Example 2) An expanded graphite sheet (PF250, thickness 2.5 mm, bulk density 0.65 g / cc) manufactured by Toyo Tanso Co., Ltd. cut to 18 × 130 mm was used as a heat shrinkable tube made by Gunze PFA. Insert into SMT (thickness 50 μm). The heat-shrinkable tube end is fused with a heat sealer FV-801 manufactured by Hakuko. Then, a vent hole having a diameter of about 0.5 μm is formed in the upper part of the melted part (above the center of the melted part). Thereafter, the heat-shrinkable tube is shrunk by holding at 180 ° C. for 2 hours in an electric furnace.

  Subsequently, a glassy carbon plate (SG-3, thickness 0.6 mm) manufactured by Showa Denko KK is cut into 130 × 130 mm to obtain a separator. An expanded graphite sheet with a heat-shrinkable tube adhered thereto was placed at both ends of the separator through a 25 μm thick FEP film cut to 180 × 130 mm, and pressurized at 0.5 MPa for 10 minutes at 320 ° C. Get an end seal. At that time, an end seal is installed so that a hole with a diameter of about 0.5 μm is at the top.

In the fuel cell manufactured according to Example 2, the amount of gas leakage through the end seal member was 0.1 ml / min or less when the differential pressure was 10 kPa. In addition, there was no increase in leakage after 2000 hours of operation at a current density of 300 mA / cm ² . Furthermore, the condensed water in the heat-shrinkable tube did not drip even when the operation was started and stopped repeatedly. As a result of the disassembling investigation after the operation, the electrolyte did not enter the end seal member, and neither corrosion nor liquid junction of the electrolyte at the end seal member end surface occurred. In general, it was confirmed that the fuel cell having a favorable end seal member configuration was obtained in Example 2.

It is the figure which showed the edge part sealing member single-piece | unit of the fuel cell of 1st Embodiment. It is the figure which showed the state which laminated | stacked two unit cells of the fuel cell of 1st Embodiment. It is the figure which showed the edge part sealing member simple substance of the fuel cell of 2nd Embodiment. It is the figure which showed the state which laminated | stacked two unit cells of the fuel cell of 2nd Embodiment. It is the schematic block diagram which showed the state which laminated | stacked two unit cells of the fuel cell.

Explanation of symbols

10, 10a, 10b, 10c, 10d End seal member 11 Main body 12 Shrinkable resin tube 13 Fusing part 14 Tube end 15, 15a Gas vent hole 16a End seal member end face 30a, 30b, 30c Separator 40a, 40b, 40c, 40d porous carbon plate 50a, 50b, 50c, 50d electrode part

Claims (10)

An electrolyte layer holding an electrolyte is sandwiched between a fuel electrode catalyst layer and an air electrode catalyst layer, a porous material having a fuel gas gas flow path in the fuel electrode catalyst layer, and a gas flow of oxidant gas in the air electrode catalyst layer In a fuel cell in which unit cells in which the porous material having a path is arranged are stacked,
A predetermined end seal material including an expanded graphite sheet is covered with a shrinkable resin tube at an end parallel to the gas flow path formed in the porous material, and both ends of the shrinkable resin tube are heat-sealed. A fuel cell, characterized in that an end seal member that is sealed and shrunk by is disposed.   2. The fuel cell according to claim 1, wherein a hole for degassing is formed in the shrinkable resin tube that seals the predetermined end seal material.   3. The fuel cell according to claim 2, wherein the degassing hole is formed above a center position in a thickness direction of the end seal member.   The end seal member is formed by inserting the predetermined end seal material into the shrinkable resin tube and fusing the end portion of the shrinkable resin tube by thermal fusion, and then shrinking the shrinkable resin tube. The fuel cell according to claim 1, wherein the fuel cell is formed. An electrolyte layer holding an electrolyte is sandwiched between a fuel electrode catalyst layer and an air electrode catalyst layer, a porous material having a fuel gas gas flow path in the fuel electrode catalyst layer, and a gas flow of oxidant gas in the air electrode catalyst layer In an end seal member disposed at an end portion parallel to the gas flow path formed in the porous material of the fuel cell in which the unit cell in which the porous material having a path is disposed is laminated,
An end seal member, wherein a predetermined end seal material including an expanded graphite sheet is covered with a shrinkable resin tube, and both ends of the shrinkable resin tube are sealed by heat sealing.   6. The end seal member according to claim 5, wherein a hole for degassing is formed in the shrinkable resin tube that seals the predetermined end seal material.   The end seal member according to claim 6, wherein the gas vent hole is formed above a center position in a thickness direction of the end seal member. An electrolyte layer holding an electrolyte is sandwiched between a fuel electrode catalyst layer and an air electrode catalyst layer, a porous material having a fuel gas gas flow path in the fuel electrode catalyst layer, and an oxidant gas in the air electrode catalyst layer. In a method of manufacturing an end seal member disposed at an end parallel to the gas flow path formed in the porous material of a fuel cell in which unit cells having the gas flow path disposed therein are stacked. ,
A procedure for coating a predetermined end seal material including an expanded graphite sheet with a shrinkable resin tube,
A procedure for fusing and sealing the end of the shrinkable resin tube by thermal fusion;
A procedure for shrinking the shrinkable resin tube;
The manufacturing method of the edge part sealing member characterized by having.   9. The method of manufacturing an end seal member according to claim 8, further comprising a step of opening a gas venting hole in the shrinkable resin tube sealed by heat sealing.   The method for manufacturing an end seal member according to claim 9, wherein the degassing hole is formed above a center position in a thickness direction of the end seal member.

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