JP2009037977A - Seal for fuel cell, separator for fuel cell and manufacturing method of fuel cell with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid blister between a seal and a separator in a fuel cell. <P>SOLUTION: In a first separator 20 and a second separator 22 for the fuel cell, each of a first gas inlet passage 30, a first gas outlet passage 32, a second gas inlet passage 34, a second gas outlet passage 36, a refrigerant inlet passage 38, a refrigerant outlet passage 40, a branched passage 52 and a converged passage 54 has a first seal 56 and a second seal 58. A DLC film 60 is formed on a surface of each of the first seal 56 and the second seal 58. For example, after formation of the first seal 56 and the second seal 58 on the surface of each of the first separator 20 and the second separator 22, the DLC film 60 is formed on the surface of each of the first seal 56 and the second seal 58 by a plasma ion implantation method. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell seal for preventing a reaction gas or the like from leaking from the inside of the fuel cell, a fuel cell separator provided with the fuel cell seal, and a fuel comprising the fuel cell separator The present invention relates to a battery manufacturing method.

  A fuel cell usually includes a single cell configured by sandwiching an electrolyte / electrode assembly between a pair of separators. In the single cell having such a configuration, seals are formed on both side edges of the separator (see, for example, Patent Document 1). During operation of the fuel cell, a fuel gas containing hydrogen is supplied to the anode side electrode constituting the electrolyte-electrode assembly, and an oxidant gas containing oxygen is supplied to the cathode side electrode. The The seal is for preventing these fuel gas and oxidant gas from leaking out of the fuel cell.

  Moreover, as described in Patent Document 2, the seal may be provided in a refrigerant flow passage portion through which the refrigerant flows. Alternatively, a seal may be provided in the oxidant gas flow passage portion or the fuel gas flow passage portion through which the oxidant gas or fuel gas in a humidified state is circulated. In the oxidant gas flow passage and the fuel gas flow passage, there is a possibility that the oxidant gas and the fuel gas may condense and the generated water generated during the operation (power generation) of the fuel cell may stay. is there. Of course, seals may be provided in all of the refrigerant flow passage portion, the oxidant gas flow passage portion, and the fuel gas flow passage portion.

  As this type of seal (seal composition), silicone resins are widely used. This is because the silicone resin is rich in elasticity and easily follows expansion / contraction of the stack accompanying the operation / stop of the fuel cell. In addition, since elasticity is maintained even below the freezing point, it is possible to prevent the reaction gas from leaking even in cold districts and the like, and therefore, it is suitable for use in an automobile fuel cell.

  However, it is difficult to say that the silicone resin has sufficient acid resistance. On the other hand, it has been pointed out that the electrolyte membrane constituting the electrolyte / electrode assembly generally has high acidity, and therefore there is a concern that the silicone resin in the vicinity of the electrolyte membrane is deteriorated and the elasticity is lowered. Similarly, since the primer that is interposed between the silicone resin and the separator and adheres the silicone resin and the separator is also deteriorated by the acid, there is a concern that the seal may peel from the separator due to this.

  Therefore, Patent Document 3 proposes that a predetermined liquid is subjected to a cross-linking reaction to thereby obtain a fuel cell packing material (seal) made of addition-type silicone having excellent acid resistance. Patent Document 4 proposes to improve acid resistance by using a primer compound containing an organic compound having a chelate ring and / or an alkoxyl group in a resol type phenol resin.

JP 2004-207071 A Japanese Patent Laid-Open No. 2005-2222764 JP 2002-83616 A JP 2006-206616 A

When the fuel cell is operated, the temperature of the fuel cell is raised to a predetermined operating temperature. As is well known, H ₂ O (mainly water vapor) is generated with the operation of the fuel cell. The H ₂ O is discharged from the flow passage together with the fuel gas that has passed through the anode side electrode or the oxidant gas that has passed through the cathode side electrode.

  As can be understood from the above, high temperature and high humidity gas comes into contact with the fuel cell seal. Here, although silicone rubber has a gas shielding property sufficient to seal fuel gas and oxidant gas, gas permeability is higher than that of rubber such as fluorine rubber or ethylene / propylene / diene copolymer (EPDM). On the other hand, water permeability is extremely low due to water repellency. Therefore, when the primer is made of silicone rubber, when water vapor (gas) permeates through the silicone rubber and condenses into a liquid state at the interface between the silicone rubber and the separator, blisters called blisters may occur. When such a situation occurs in the vicinity of the flow passage, the cross-sectional area of the flow passage portion becomes narrow, and thus a problem that the pressure loss increases is caused.

  For this reason, as a fuel cell seal, it is desired that the blister resistance is sufficient, but it is not easy to ensure the blister resistance in the conventional technology as described above.

  The present invention has been made in order to solve the above-mentioned problems, and it is difficult to separate and firmly bond to the separator. For this reason, moisture can be prevented from entering between the separator and blister resistance can be improved. It is an object of the present invention to provide a fuel cell seal that can be used, a fuel cell separator provided with the seal, and a method of manufacturing a fuel cell including the separator.

In order to achieve the above object, according to the present invention, an electrolyte / electrode assembly in which an anode side electrode and a cathode side electrode are arranged via an electrolyte is interposed between a first separator and a second separator. A fuel cell seal used for the first separator and the second separator of a fuel cell comprising a single cell,
Provided between the first separator and the second separator and / or between the first separator or the second separator and the electrolyte-electrode assembly, or on the first separator and the second separator. A diamond-like carbon (hereinafter also referred to as DLC) film is provided on the surface of the reaction gas flow path and / or the refrigerant flow path.

  In the seal provided with the DLC film, the gas permeability is extremely small. That is, it becomes difficult for water vapor to enter the inside of the seal and thus between the seal and the separator, thereby making it difficult to generate blisters. In short, the blister resistance is improved.

  Moreover, due to the presence of the DLC film on the surface, the seal exhibits extremely excellent acid resistance. After all, according to the present invention, it is possible to greatly improve acid resistance and blister resistance.

The present invention also provides a first separator and a first separator constituting a single cell of a fuel cell by interposing an electrolyte-electrode assembly in which an anode side electrode and a cathode side electrode are disposed via an electrolyte between each other. A set of fuel cell separators having two separators,
Provided between the first separator and the second separator and / or between the first separator or the second separator and the electrolyte / electrode assembly, or on the first separator and the second separator. A seal disposed in the reaction gas flow path and / or the refrigerant flow path is formed, and the seal has a diamond-like carbon film on a surface thereof.

  That is, this separator is provided with the above-described seal. For this reason, it is very difficult to generate blisters in the flow passage through which the fuel gas and the oxidant gas are circulated. As a result, it is avoided that the flow passage is narrowed, thereby preventing pressure loss when the fuel gas or the oxidant gas is circulated.

Furthermore, the present invention provides a fuel cell comprising a single cell in which an electrolyte-electrode assembly in which an anode side electrode and a cathode side electrode are disposed via an electrolyte is interposed between a first separator and a second separator. A manufacturing method of
Reaction gas between the first separator and the second separator and / or between the first separator or the second separator and the electrolyte / electrode assembly, or at the first separator or the second separator Providing a seal in the flow passage and / or the refrigerant flow passage;
Forming a diamond-like carbon film on the surface of the seal;
Forming the single cell by interposing the electrolyte-electrode assembly between the separators;
It is characterized by having.

  Through such a process, a seal excellent in blister resistance can be easily obtained. Therefore, it is possible to avoid the narrowing of the flow passage through which the fuel gas and the oxidant gas are circulated, and it is possible to obtain a fuel cell in which the pressure loss when the fuel gas and the oxidant gas are circulated is prevented.

  An example of a method for forming the DLC film is a plasma ion implantation method.

  According to the present invention, since the diamond-like carbon film is provided on the surface of the seal, it is avoided that water vapor or the like permeates into the seal by the diamond-like carbon film. Thereby, the blister resistance is greatly improved. In addition, the acid resistance of the seal is improved.

  In a fuel cell having a fuel cell separator provided with such a seal, it is possible to avoid the formation of blisters in the flow passage for circulating the reaction gas, and therefore the flow passage may be narrowed. Avoided. Eventually, it is possible to prevent the occurrence of pressure loss when fuel gas or oxidant gas is circulated.

  Preferred embodiments of a fuel cell seal, a fuel cell separator, and a fuel cell manufacturing method according to the present invention will be described below in detail with reference to the accompanying drawings. In the following description, the fuel cell seal and the fuel cell separator may be simply referred to as a seal and a separator, respectively.

  First, the configuration of the fuel cell will be outlined.

  FIGS. 1 and 2 are an exploded perspective view and a vertical cross-sectional view of a main part of a stack 10 included in the fuel cell, respectively.

  The stack 10 includes an electrolyte / electrode assembly 18 configured by sandwiching an electrolyte 16 between an anode side electrode 12 and a cathode side electrode 14, and a first separator 20 and a second separator that sandwich the electrolyte / electrode assembly 18. And a single cell 24 composed of 22. In the present embodiment, the first separator 20 and the second separator 22 are made of stainless steel such as SUS304 or SUS316.

  Among these, the anode side electrode 12 and the cathode side electrode 14 each have a gas diffusion layer facing the electrolyte 16 side and an electrode catalyst layer joined to the gas diffusion layer. Such configurations of the anode-side electrode 12 and the cathode-side electrode 14 are known, and therefore are not shown here and will not be described in detail.

  On the other hand, in FIG.1 and FIG.2, the 1st gas inlet channel 30 for distribute | circulating oxidizing gas is provided in each upper left corner part of the 1st separator 20 and the 2nd separator 22, The diagonal A first gas outlet passage 32 for circulating used oxidant gas is provided at the lower right corner, which is the position. Similarly, a second gas inlet passage 34 for allowing fuel gas to pass therethrough is provided in the upper right corner, and in the lower left corner, which is the diagonal position, used fuel gas is allowed to pass. The second gas outlet passage 36 is provided. The first separator 20 and the second separator 22 are further provided with a refrigerant inlet passage 38 extending from the first gas inlet passage 30 toward the second gas inlet passage 34, while the second gas outlet passage 36 extends from the first separator 20 and the second separator 22. A refrigerant outlet passage 40 extending toward the one gas outlet passage 32 is provided.

  A wave-like fuel gas passage portion 42 in which peaks and valleys are alternately formed on the surface of the first separator 20 facing the anode side electrode 12 in order to supply and discharge fuel gas to and from the anode side electrode 12. Is curved and extends. As shown in FIG. 2, the top surface of the fuel gas passage 42 is separated from the anode side electrode 12. As a result, a hollow portion 44 is formed between the fuel gas passage portion 42 and the anode electrode 12, and the fuel gas is circulated through the hollow portion 44.

  On the other hand, the second separator 22 is provided with a wavy oxidant gas passage 46 that protrudes on the opposite side to the fuel gas passage 42 of the first separator 20. The surface protrudes toward the first separator 20. Accordingly, a hollow portion 48 is formed between the oxidant gas passage portion 46 and the cathode side electrode 14 as the top surface is separated from the cathode side electrode 14, and the oxidant gas is contained in the hollow portion 48. Distributed.

  Further, since the top surfaces of the fuel gas passage portion 42 of the first separator 20 and the oxidant gas passage portion 46 of the second separator 22 protrude on opposite sides, the fuel gas passage portion 42 and the oxidant gas passage portion 46 The top surfaces are separated from each other. A communication passage 50 is formed by this separation, and the refrigerant introduced from the refrigerant inlet passage 38 flows through the communication passage 50 and reaches the refrigerant outlet passage 40.

  In each of the first separator 20 and the second separator 22, a branch path 52 that branches from the refrigerant inlet passage 38 toward the communication path 50, and a focusing path for condensing the refrigerant from the communication path 50 to the refrigerant outlet passage 40. 54 is provided.

  The first gas inlet passage 30, the first gas outlet passage 32, the second gas inlet passage 34, the second gas outlet passage 36, the refrigerant inlet passage 38, and the refrigerant outlet are provided on both surfaces of the first separator 20 and the second separator 22. A first seal 56 and a second seal 58 are provided around the passage 40, the branch path 52, and the focusing path 54, respectively. A suitable material for the first seal 56 and the second seal 58 is silicone rubber.

  The first seal 56 and the second seal 58 are formed after the seal composition provided on the first separator 20 and the seal composition provided on the second separator 22 are overlapped, as will be described later. It is formed by curing. Therefore, as shown in FIG. 2, in the actual stack 10, the first seal 56 and the second seal 58 are integrally joined, but for convenience, the seal composition provided in the first separator 20 is used. The cured portion is designated as a first seal 56, the cured portion of the seal composition provided on the second separator 22 is designated as a second seal 58, and the first seal 56 and the second seal 58 in FIG. A broken line is attached between the two to indicate a boundary portion before the integration of the two.

  Further, a DLC film 60 is formed on the surfaces of the first seal 56 and the second seal 58. As will be described later, the DLC film 60 is preferably provided by a plasma ion implantation method, and a suitable thickness thereof is set to 10 to 5000 mm. If it is less than 10 mm, the effect of reducing gas permeability is poor. Further, if it exceeds 5000 mm, there is a concern that cracks occur in the hard DLC film 60 when an external force is applied when the stack 10 is formed.

  In the present embodiment, the longitudinal and lateral dimensions of the electrolyte / electrode assembly 18 are slightly larger than the fuel gas passage portion 42 of the first separator 20 and the oxidant gas passage portion 46 of the second separator 22. Is set. Therefore, as shown in FIG. 2, a part of the first seal 56 is pressed against the anode side electrode 12 and hardens in a shape along the shape of the anode side electrode 12, while a part of the second seal 58 is It is pressed by the cathode side electrode 14 and cured in a shape along the shape of the cathode side electrode 14. Eventually, a part of the first seal 56 is located between the anode side electrode 12 and the first separator 20, and a part of the second seal 58 is located between the cathode side electrode 14 and the second separator 22.

  When operating the fuel cell configured as described above, after the temperature of the fuel cell is raised to a predetermined temperature, a fuel gas such as a hydrogen-containing gas passes through the second gas inlet passage 34 from the hollow portion 44 to the anode. While being supplied to the side electrode, an oxidant gas such as air is supplied from the hollow portion 48 to the cathode side electrode via the first gas inlet passage 30. In the presence of these reaction gases, an electrode reaction occurs at each of the electrodes 12 and 14. During the operation of the fuel cell, the single cell 24, that is, the electrolyte / electrode assembly 18, the first separator 20, and the second separator 22 are supplied via the refrigerant inlet passage 38 and the branch passage 52, and the communication passage 50. It is cooled by a refrigerant (cooling water or the like) that passes through.

  The spent fuel gas and the oxygen-containing gas are discharged to the outside of the stack 10 through the second gas outlet passage 36 and the first gas outlet passage 32, respectively. The refrigerant that has cooled the single cell 24 by flowing from the branch path 52 via the communication path 50 is collected in the refrigerant outlet path 40 via the converging path 54, and finally flows through the refrigerant outlet path 40. Then, it is discharged outside the stack 10.

During the operation of the fuel cell in this way, H ₂ O (mainly water vapor) is generated by the electrode reaction. This H ₂ O reaches the second gas outlet passage 36 or the first gas outlet passage 32 along with the used oxidant gas or fuel gas.

  Here, in the first separator 20 and the second separator 22, the first gas inlet passage 30, the first gas outlet passage 32, the second gas inlet passage 34, the second gas outlet passage 36, the refrigerant inlet passage 38, and the refrigerant outlet passage. The DLC film 60 is present on the surface of the first seal 56 or the second seal 58 provided so as to surround each of the 40 as described above. For this reason, the entry of water vapor into the first seal 56 or the second seal 58 is significantly hindered. For this reason, it becomes extremely difficult for water vapor to reach between the first seal 56 and the first separator 20 and between the second seal 58 and the second separator 22, and thus the occurrence of blistering is avoided. The Eventually, the blister resistance is improved.

  Moreover, the DLC film 60 is excellent in acid resistance. Therefore, the durability of the first seal 56 and the second seal 58 is improved, and the sealing performance can be ensured over a long period of time.

  This fuel cell can be manufactured as follows.

  First, predetermined positions of the first separator 20, that is, the first gas inlet passage 30, the first gas outlet passage 32, the second gas inlet passage 34, the second gas outlet passage 36, the refrigerant inlet passage 38, and the refrigerant outlet passage 40. A seal composition is provided at a site surrounding each of the components.

In the present invention, the “step of providing the fuel cell seal composition on the separator” includes all means for applying the fuel cell seal composition to the separator, such as spraying, pressure bonding, and injection, as well as coating. Shall.

  Next, the seal composition is cured by heating to form the first seal 56 and the second seal 58.

  Next, the DLC film 60 is provided on the surfaces of the first seal 56 and the second seal 58 by performing plasma ion implantation on each of the first seal 56 and the second seal 58. The plasma ion implantation method can be performed at a low temperature at which the first seal 56 mainly composed of silicone rubber is not softened or decomposed. The obtained DLC film 60 is robust to the first seal 56. There is an advantage that the DLC film 60 can be formed without unevenness even if the shape of the first seal 56 is complicated, which is difficult to adhere and peel off.

  That is, by performing the plasma ion implantation method, the DLC film 60 that easily deforms following the first seal 56 and the second seal 58 without changing the quality of the first seal 56 and the second seal 58 is substantially uniform. Can get to.

  The film formation by plasma ion implantation may be performed, for example, by connecting a negative pulse power source with the seal side as a negative electrode and introducing a source gas into the vacuum chamber while energizing in this state. . Note that Si ions are preferably implanted into the first seal 56 prior to the implantation of C ions. This is because the bonding force between the first seal 56 and the DLC film 60 is increased in this case.

  The single cell 24 is configured by interposing the electrolyte / electrode assembly 18 between the first separator 20 in which the first seal 56 is formed in this way and the second separator 22 in which the second seal 58 is formed. In addition, if the single cells 24 are stacked, the stack 10 is formed.

  In general, an insulating rubber (not shown) for preventing corrosion is provided between the branch paths 52 and 52 and between the converging paths 54 and 54. The DLC film 60 may be formed not only on the first seal 56 and the second seal 58 but also on each insulating rubber.

  A separator is formed from stainless steel, primer No101A / B (silicone rubber / metal adhesive containing a silane coupling agent) manufactured by Shin-Etsu Chemical Co., Ltd. is applied to the separator, and the primer is kept at 160 ° C. for 1 hour. Baked.

  Next, silicone rubber was injection-molded on the primer, pre-cured by holding at 150 ° C. for 40 seconds, and then cured by holding at 200 ° C. for 2 hours, and a seal was provided on the primer .

Further, plasma ion implantation was performed. Specifically, CH ₄ (methane) gas is introduced into the vacuum chamber at a flow rate of 70 SCCM, the atmospheric pressure is 0.5 Pa, the atmospheric temperature is 85 ° C., the trigger pulse voltage is −20 kV, and the number of repetition pulses is 700 pulses / A DLC film was formed on the seal under conditions of a second, a pulse width of 30 μm, and a maximum current of 40 A. The thickness of the DLC film was controlled by adjusting the treatment time. Thus, a separator provided with a seal having a DLC film was produced.

  This separator was brought into contact with a commercially available Nafion membrane (a product name manufactured by DuPont) and left in this state in an environment of 100 ° C. and a relative humidity of 95% for 500 hours to examine changes in appearance.

  On the other hand, the water permeability at 40 ° C. was examined using a moisture permeability test cup according to JIS Z 0208. Further, it was examined whether or not the DLC film was cracked when the seal was compressed to 50%. The above results are shown in FIG. 3 together with the thickness of the DLC film. It can be seen from FIG. 3 that by setting the thickness within an appropriate range, it is possible to provide a DLC film that is excellent in acid resistance, hardly permeates water, and easily deforms.

It is a principal part disassembled perspective explanatory drawing of the stack in the fuel cell which comprises the seal | sticker and separator which concern on this Embodiment. It is principal part longitudinal cross-section structure explanatory drawing of the stack | stuck of FIG. It is a chart which shows the characteristic of each seal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Stack 12 ... Anode side electrode 14 ... Cathode side electrode 16 ... Electrolyte 18 ... Electrolyte / electrode assembly 20, 22 ... Separator 24 ... Single cell 30, 34 ... Gas inlet passage 32, 36 ... Gas outlet passage 38 ... Refrigerant inlet Passage 40 ... Refrigerant outlet passage 42 ... Fuel gas passage 46 ... Oxidant gas passage 56, 58 ... Seal 60 ... DLC membrane

Claims (4)

The first separator of a fuel cell comprising a single cell in which an electrolyte-electrode assembly in which an anode side electrode and a cathode side electrode are disposed via an electrolyte is interposed between the first separator and the second separator; A fuel cell seal used for the second separator,
Provided between the first separator and the second separator and / or between the first separator or the second separator and the electrolyte / electrode assembly, or on the first separator and the second separator. A fuel cell seal, which is disposed in a reaction gas flow path and / or a refrigerant flow path and has a diamond-like carbon film on a surface thereof. 1 set which has the 1st separator and 2nd separator which comprise the electrolyte-electrode assembly by which an anode side electrode and a cathode side electrode are arrange | positioned through electrolyte between each other, and comprise the single cell of a fuel cell A fuel cell separator,
Provided between the first separator and the second separator and / or between the first separator or the second separator and the electrolyte / electrode assembly, or on the first separator and the second separator. A fuel cell separator, wherein a seal disposed in the reaction gas flow path and / or the refrigerant flow path is formed, and the seal has a diamond-like carbon film on a surface thereof. A method of manufacturing a fuel cell comprising a single cell in which an electrolyte / electrode assembly in which an anode side electrode and a cathode side electrode are disposed via an electrolyte is interposed between a first separator and a second separator, ,
Reaction gas flow between the first separator and the second separator and / or between the first separator or the second separator and the electrolyte / electrode assembly, or in the first separator or the second separator. Providing a seal in the passage and / or refrigerant flow passage;
Forming a diamond-like carbon film on the surface of the seal;
Forming the single cell by interposing the electrolyte-electrode assembly between the separators;
A method for producing a fuel cell, comprising:   4. The method of manufacturing a fuel cell according to claim 3, wherein the step of forming the diamond-like carbon film is performed by a plasma ion implantation method.

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