JP2009181713A - Polymer electrolyte fuel cell and power generation system loading the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polymer electrolyte fuel cell with a seal structure so made to secure enough gas tightness while preventing entry of impurities from cooling water into electrodes and an electrolyte film. <P>SOLUTION: The polymer electrolyte fuel cell, provided with cells structured to pinch a solid polymer electrolyte film and electrodes between a pair of separators having a cooling water manifold circulating cooling water and a gas manifold circulating gas, further includes a gas seal going around a gas flow channel face and a cooling water seal going around a periphery of the cooling water manifold. Moreover, the cooling water seal is fitted further outside than an outer edge of the solid polymer electrolyte film, so that the electrolyte film is not to be in direct contact with the cooling water. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polymer electrolyte fuel cell and a power generation system equipped with the same.

  The polymer electrolyte fuel cell has features such as high output density, high power generation efficiency, and low start-up time because the operation temperature is as low as about 70 ° C to 80 ° C. Therefore, a wide range of applications such as electric vehicle power supplies, commercial distributed power supplies, and home distributed power supplies are expected.

  Among these applications, a distributed power supply equipped with a polymer electrolyte fuel cell, such as a cogeneration power generation system, takes out electricity from the polymer electrolyte fuel cell and at the same time collects heat generated from the cell as hot water during power generation. By doing so, it is a system that tries to use energy effectively.

  A distributed power source equipped with a polymer electrolyte fuel cell is required to have a long life of 50,000 to 100,000 hours. For this reason, improvements are being made to membrane-electrode assemblies (hereinafter abbreviated as MEA), cell configuration, power generation conditions, and the like. In such a power generation system with an emphasis on life, a technique for eliminating factors that cause a decrease in battery output is required.

  As one of the factors that decrease the battery output, it is conceivable that the catalyst is deactivated due to impurities contained in the gas or cooling water or air pollutants and the resistance of the electrolyte membrane is increased.

  When carbon monoxide contained in the fuel gas or nitrogen oxide of the reformed gas is taken into the battery, the catalyst inactivation of the electrode and the resistance of the electrolyte membrane increase, which causes the battery output to gradually decrease. To do. Depending on the installation environment of the fuel cell, it may contain a relatively small amount of air pollutants such as nitrogen oxides and sulfur oxides in the atmosphere, and dust. The catalytic activity is reduced.

  In addition, a small amount of impurities are taken into the battery from the cooling water, and the impurities may permeate the electrolyte membrane or adhere to the catalyst layer, thereby increasing the resistance of the electrolyte membrane and reducing the catalytic activity. In particular, it becomes a problem when the water quality deteriorates during long-term storage or when antifreeze is used as cooling water in a cold region. In the latter case, the additive in the antifreeze becomes a pollutant.

  In addition, not only water but also a low freezing point solvent such as ethylene glycol or a refrigerant containing an aqueous solution thereof may be used for the cooling water. In the present invention, the case where these are used is included. This is called cooling water. In many cases, water is often used as a refrigerant in the polymer electrolyte fuel cell, so the following description will be made taking an example of using water.

  In the present invention, it is intended to prevent a decrease in battery output due to impurities in cooling water or substances added to prevent freezing. The reason is as follows.

  It is easy to reduce the amount of impurities in the gas by precise control of the reforming reaction, the use of a filter, etc., and since the gas is not supplied when power is not generated as in the shutdown period, Contamination from gas can be avoided.

  However, in the case of cooling water, contamination is likely to occur due to residual water inside the battery even when power generation is stopped, and the electrolyte membrane may be contaminated by additives when using antifreeze. Although it is conceivable to provide a mechanism for discharging the refrigerant from the battery when power generation is stopped, the system becomes complicated and it is not easy to completely remove the refrigerant from the battery. As described above, the impurities contained in the cooling water remaining inside the battery gradually affect the performance of the electrolyte membrane and the catalyst by repeatedly stopping the power generation. Therefore, the prevention of contamination derived from cooling water is technically more difficult than the prevention of contamination from gas.

  As a conventional technique related to contamination prevention, a method for enhancing the reliability of a seal (Patent Document 1), a method for providing a mechanism for maintaining water quality in the system (Patent Document 2), and the like are disclosed.

Japanese Patent No. 3292670 JP-A-2005-183109

  In the case of preventing the entry of impurities by a sealing method using an elastic body such as rubber, the entry of impurities cannot be prevented unless a high pressure is applied to the seal. This is because an elastic body such as rubber has a characteristic of causing deformation due to permanent strain, and the pressure of the seal is reduced by the deformation. If pressure is applied to the seal so that a compression amount exceeding the permanent strain is obtained and a seal having the same configuration is provided in the passage of cooling water and gas, the sealing performance can be secured initially.

  However, such a sealing method creates the following new problems in the long term. That is, if the pressure applied to the seal is increased, a local pressure is generated on the electrolyte membrane, which causes new problems such as damage to the electrolyte membrane. In particular, if a pressure that greatly exceeds the pressure required to ensure gas tightness is applied to a part of the electrolyte membrane, the electrolyte membrane is damaged at the portion where the pressure is applied, and the gas from the damaged portion to the outside of the battery Leak (external leak) or gas exchange (internal leak) between the fuel and the oxidant through the electrolyte membrane occurs.

  In order to suppress the intrusion of impurities from the cooling water, the pressure applied to the seal must be increased. On the other hand, the electrolyte membrane is easily damaged. Conversely, if the pressure is lowered so as to avoid damage to the electrolyte membrane, impurity contamination from the cooling water tends to occur. Thus, the prevention of impurity intrusion from cooling water and the prevention of damage to the electrolyte membrane are in a trade-off relationship with respect to pressure.

  An object of the present invention is to provide a polymer electrolyte fuel cell having a seal structure capable of ensuring sufficient gas tightness while preventing intrusion of impurities from cooling water into an electrode or an electrolyte membrane. .

  The present invention relates to a solid polymer fuel comprising a cell having a structure in which a solid polymer electrolyte membrane and an electrode are sandwiched between a pair of separators each having a cooling manifold for passing a coolant such as cooling water and a gas manifold for passing a gas. The battery includes a gas seal that circulates around the gas flow path surface of the separator and a refrigerant seal that circulates around the cooling manifold, the refrigerant seal is provided outside the outer edge of the solid polymer electrolyte membrane, and the electrolyte membrane The polymer electrolyte fuel cell has a structure that does not come into direct contact with cooling water. The cooling water can be replaced with a refrigerant other than water (low melting point liquid such as ethylene glycol and a solution or an aqueous solution thereof).

  In the present invention, the gas seal is preferably provided in the plane of the solid polymer electrolyte membrane, and the gas seal and the refrigerant seal are preferably not in contact with each other. The gas seal can be integrally formed by applying and drying a liquid gasket on the electrolyte membrane. Silicon rubber, ethylene / propylene rubber, or the like can be selected as the material for the liquid gasket.

  The gas seal is formed on the electrolyte membrane. However, if the part in contact with the separator is semicircular or convex (also called lip or bead), the gas seal can be compressed with a low clamping pressure. Airtightness is easily obtained, which is preferable. In particular, the electrolyte membrane has a thickness of several tens of μm and may be damaged due to the pressure of the seal. Therefore, it is preferable to use a gas seal having the above-described shape. If the gas seal front end portion in contact with the separator is made slightly flat, the pressure applied to the electrolyte membrane by the front end portion becomes uniform, which is more preferable in preventing breakage of the electrolyte membrane. In order to make the pressure on the electrolyte membrane uniform while making the width of the gas seal as small as possible, the width of the flat portion is suitably in the range of 0.5 mm to 10 mm, particularly 1 mm to 1.5 mm.

  As another form, the gas seal may be a resin frame having a square cross-sectional shape, and the frame may be bonded to the separator surface. An adhesive such as an epoxy resin is used as the adhesive. When such a resin gasket is used, the area of the flat portion of the frame to be pressure-bonded to the electrolyte membrane can be easily increased, and it is not necessary to apply excessive pressure to the electrolyte membrane. As will be described later, this is effective when a rubber gasket is used for the refrigerant seal. The resin-based gasket may be formed on the separator by a mold forming method.

  The gas seal is desirably insulative in any of the above cases. This is because when the electrolyte membrane is broken, the gas seals or the gas seals and the separators are short-circuited if they have good conductivity. If the gas seal having such properties is formed integrally with the electrolyte membrane, it is possible to reduce variations in cell voltage due to component misalignment.

  As for the refrigerant seal, by forming the seal in the separator surface, it is possible to assemble the battery with high accuracy and reduce the voltage variation between the cells. For example, after forming the seal portion by applying the above-described liquid gasket by mechanical application such as a dispenser, the solvent seal is dried to adhere the refrigerant seal in the separator surface. Further, a refrigerant seal may be formed by forming a thermoplastic gasket material on the separator surface by a mold forming method. In addition to such a rubber-based gasket, it is also possible to produce a resin-based gasket by using a thermosetting adhesive such as an epoxy resin and applying it on a separator surface with a dispenser to form a seal portion. A single cell can be manufactured by laminating two separators via the MEA and performing an optical curing process such as a thermosetting process or an ultraviolet ray.

  Further, when one of the gas seal and the refrigerant seal is made of an elastic body, the other is made of an inelastic body. For example, when one is made of rubber, the other is made of resin. In this way, it is possible to configure with materials having different elasticity (compressibility against pressure).

  When a thermosetting resin seal is used as the refrigerant seal, when the MEA is sandwiched between two separators, the separator interval is substantially fixed. In such a case, a resin-based gasket may be used for the gas seal. Since the distance between the separators is constant, excessive pressure is not applied to the electrolyte membrane as long as the dimensional accuracy of the resin-based gasket or separator can be sufficiently secured.

  As a more desirable form, a rubber-based gasket having a high compressibility is used for the gas seal. In this case, since the allowable range of the dimensional accuracy of the gas seal is relaxed, the gas seal can be performed even if the dimensional accuracy such as the flatness and the parallelism of the separator is slightly low. According to this configuration, although the tightening load is low, a large compression amount can be secured by the rubber gasket, and gas tightness can be secured. Since it is easy to avoid application of excessive pressure to the electrolyte membrane, it is advantageous for preventing damage to the electrolyte membrane.

  Next, when a rubber-based gasket having a large compression rate is used for the refrigerant seal, the tightening load is increased in order to obtain a sufficient compression amount. In this case, a resin frame having a square cross section is used for the gas seal so that an excessive pressure is not applied to the gas seal in contact with the electrolyte membrane. As a result, the area of the flat portion of the frame to be pressure-bonded to the electrolyte membrane can be easily increased, and an excessive pressure is not applied to the electrolyte membrane.

  A combination as described above can be selected according to the service life of the product on which the fuel cell is mounted. As a basic idea, the refrigerant seal is selected first, and the gas seal is determined so as to match it.

  That is, when high load tightening is performed to prevent impurity leakage from the refrigerant seal, a rubber gasket is used for the refrigerant seal. In this case, since the separator interval can change, it is necessary to apply a uniform pressure to the electrolyte membrane. Therefore, a resin gasket is selected for the gas seal.

  On the other hand, a resin gasket is used for the refrigerant seal when low load tightening is performed to prevent leakage of impurities from the refrigerant seal. In this case, since the tightening pressure is small, the range of selection of the gas seal is expanded. That is, either rubber or resin gaskets may be used.

  Among these, a combination using a thermosetting resin seal as a refrigerant seal and a rubber gasket or a resin gasket as a gas seal is advantageous for a fuel cell that requires long-term durability. This is because airtightness can be sufficiently secured by tightening with a low load, so that airtight failure due to deformation of the gasket, and hence impurity leakage can be avoided.

  The polymer electrolyte fuel cell of the present invention has a refrigerant seal and a gas seal separately, and has a structure in which the outer edge of the electrolyte membrane does not come into direct contact with the refrigerant, so that impurities from the refrigerant are transferred to the electrodes and the electrolyte membrane. Intrusion can be prevented. Further, by providing the refrigerant seal and the gas seal separately, it becomes possible to combine seals having different functions, and sufficient gas tightness can be secured.

  As a result of studies, the present inventors have provided a manifold seal through which cooling water flows outside the outer edge of the electrolyte membrane in order to protect the electrolyte membrane and electrodes from impurities in the refrigerant, and the electrolyte membrane is directly on the refrigerant. It came to the idea that it would be effective to make the structure untouchable. The present invention is based on this idea. In other words, the present invention intends to provide a fuel cell having a new seal structure in which a refrigerant seal and a gas seal are functionally separated.

  Below, the content of this invention is demonstrated based on the typical Example when pure water is used for a refrigerant | coolant.

  The cooling water passes through the cooling manifold and is supplied to the separator having a flow path through which the cooling water flows. After the heat generated during power generation is taken from the separator surface, the cooling water is discharged out of the battery from another manifold.

  A power generation cell (also referred to as a single cell) has a fuel gas manifold and a separator having a flow path thereof, an oxidant gas manifold, a separator having the flow path and an MEA, and the MEA is sandwiched between a pair of separators. It has the structure made. A voltage of 0.5 to 0.8 V is usually generated in this power generation cell.

  Further, a cooling cell is generally provided on the surface opposite to the fuel gas channel surface or the oxidant gas channel surface of the power generation cell, that is, the back surface, and heat of the power generation cell is removed.

  In the present invention, in order to avoid contamination of the electrolyte membrane due to impurities in the cooling water, the outer edge of the electrolyte membrane is not extended to the cooling manifold, and the electrolyte membrane is not in direct contact with the cooling water seal. In this way, the electrolyte membrane is shortened so that the electrolyte membrane does not exist on the refrigerant seal. This is because if a refrigerant seal is provided on the electrolyte membrane, the coolant gradually immerses the seal due to creep (permanent strain) of the seal and eventually reaches the catalyst layer.

  In addition, a coolant seal that circulates around the cooling manifold is provided so that cooling water does not flow into the MEA side. The cooling water seal plays a role of a kind of shielding wall that does not allow impurities in the cooling water to permeate to the MEA side. Thereby, contamination of the electrolyte membrane and the electrode due to impurities in the cooling water can be prevented.

  In the polymer electrolyte fuel cell of the present invention, since the electrolyte membrane does not protrude from the refrigerant seal to the cooling manifold side, the electrolyte membrane is not damaged by the refrigerant seal. Therefore, the selection range of the material for the refrigerant seal and the range of the clamping pressure are also expanded.

  The material of the refrigerant seal needs to be water resistant. In addition, when the cooling water is other than pure water, for example, when it is an organic liquid such as ethylene glycol, a material that does not change such as swelling when contacting the liquid is desirable. As a sealing material that satisfies such requirements, for example, there are thermosetting resins typified by epoxy resins and phenol resins, or rubber materials that are adhesive to separators. Suitable rubber materials include, for example, liquid gaskets mainly composed of fluorine rubber, ethylene / propylene rubber, silicon rubber and the like. However, the material is not limited to these materials as long as the material does not deteriorate with respect to the refrigerant (water or organic substance) and impurities in the refrigerant.

  Adhesive thermosetting resin is used as a material for the cooling water seal, and by joining the separators, the separators are difficult to peel off even if there is an external impact or vibration. This is extremely effective in preventing leakage.

  When a rubber material is used for the cooling water seal, it is desirable to apply a high pressure to the seal so as to obtain a compression amount equal to or greater than the deformation amount of the rubber due to permanent strain. Further, when sealing is performed using the elasticity of the rubber material, it is desirable to reduce the area where the rubber contacts the separator as much as possible and increase the pressure of the sealed portion. For example, if it is convex (also referred to as a lip shape or a bead shape), the pressure can be increased at the apex portion of the seal (the portion that is compressed to exhibit the sealing function). Here, it is effective to reduce the seal space and reduce the load on the entire seal by forming the apex of the refrigerant seal so as to have a small line width of 0.1 to 1 mm when it is crimped to the separator. It is.

  By using the water-resistant refrigerant seal having the above configuration, it is possible to prevent the electrolyte membrane and the like from being contaminated by impurities contained in the cooling water, and to avoid a decrease in battery output.

  Next, the gas seal will be described.

  The gas seal is provided at a position where it does not interfere with the cooling water seal within the separator surface, and has a functionally separated structure. The gas seal is brought into close contact with the electrolyte membrane. This is because the fuel is supplied to one surface of the electrolyte membrane and the oxidant is supplied to the other surface, so that a gas seal is essential on the electrolyte membrane. At this time, around the fuel manifold or the oxidant manifold, the seal is pressure-bonded to the electrolyte membrane to obtain airtightness, or the seal is bonded on the electrolyte membrane and pressure-bonded to the separator surface for airtightness. obtain.

  About a gas seal, it is desirable to take the following two structures according to the material of a cooling water seal.

  When a thermosetting resin is used for the cooling water seal, the separator interval can be kept constant, so that the pressure applied to the electrolyte membrane by the gas seal can be adjusted. As a result, damage to the electrolyte membrane can be avoided. In this case, since the compression amount of the gas seal material can be defined, a rubber material may be used.

  On the other hand, when an elastic material such as a rubber material is used for the cooling water seal, the separator cannot be fixed at a constant value, and the battery should be operated at a high pressure to prevent leakage of impurities from the cooling water. Because of the tightening, it is necessary to adopt another method for the gas seal. That is, when an elastic material (for example, rubber seal) is used for the gas seal in the same manner as the cooling water seal, when the load applied to the two separators is increased and the cooling water seal is compressed, the compression amount of the gas seal is simultaneously increased. Will also increase. If the amount of compression exceeds the limit value of the mechanical strength of the electrolyte membrane, the electrolyte membrane may be damaged. Therefore, when an elastic material is used for the cooling water seal, a new gas sealing method using a swelling property of the electrolyte membrane is applied by using a material having no elasticity for the gas seal, for example, a resin material such as a thermosetting resin. , Avoid damaging the electrolyte membrane.

  The electrolyte membrane contains a certain amount of water during power generation, and has the property of retaining water in the electrolyte membrane for a long time once power generation is performed. The electrolyte membrane containing water expands slightly and is inserted into and closely adhered to a portion where gas leakage is to be stopped, for example, the outer peripheral portion of the flow path of the separator, thereby exhibiting gas sealing properties. Utilizing the swelling action of the electrolyte membrane, gas tightness is enhanced.

  When gas sealing is performed by utilizing the swelling action of the electrolyte membrane, it is preferable to form a protrusion on the gas seal so as to be in close contact with the electrolyte membrane. Since the tip of the protrusion is in contact with the electrolyte membrane, it is desirable that the protrusion be as flat as possible. The flatness is preferably within ± 20 μm. If it is larger than this, the amount of increase in the thickness due to the swelling of the electrolyte membrane is exceeded, so that a gap is formed in the closely contacted portion, and gas leakage tends to occur.

  The above-mentioned protrusion is preferably formed so as to go around the electrode formed at the center of the electrolyte membrane. As the material of the protrusion, any material can be used as long as it is chemically and physically stable in the temperature range where the battery is operated. For example, polyethylene terephthalate, tetrafluoroethylene, polyimide, polyether ether ketone, polyphenylene sulfide and the like can be applied.

  When the gas seal having the above configuration is used, when the electrolyte membrane contains generated water during power generation, the electrolyte membrane expands and gas tightness can be secured. Due to the swelling of the electrolyte membrane by the generated water, the electrolyte membrane can act as a cushion, and gas can be prevented from leaking between the separator and the electrolyte membrane. In this method, it is possible to keep the separator interval constant, so that the pressure on the electrolyte membrane can be relaxed and breakage of the electrolyte membrane can be prevented.

  In addition to the above-described configuration, the gas sealing performance can be further improved by employing the following method.

  In one method, the width of the flat apex portion of the gas seal is set to 1 mm or more, and is larger than the width of the apex portion of the cooling water rubber seal (0.1 to 1 mm when pressurized). The upper limit of the width of the gas seal is suitably within 10 mm so as not to provide an extra seal area in the separator surface.

  In one method, a gas seal is bonded in advance in the separator surface before the MEA is assembled between two separators.

  One method uses two types of seals having different flat widths of gas seals for two separators facing each other through an electrolyte membrane. In this way, even if there is a slight misalignment between the two separators, the two gas seals come into close contact via the electrolyte membrane.

  One method forms a thin elastic body (rubber such as silicon rubber or ethylene / propylene rubber or a liquid gasket) on the flat portion of the gas seal. In this way, even if there is uneven thickness of the separator, and the separator spacing varies, gas leakage can be prevented by compression of the elastic body. For this purpose, the elastic body is provided in the flat part of the gas seal in the form of a lip or bead. The compression amount of the lip or bead portion is preferably set within the range of the thickness variation of the separator (usually ± 20 to ± 50 μm) or more.

  As a first embodiment, FIG. 1A shows a separator 107 having a fuel gas flow path surface, and a gas seal 103 and a refrigerant seal 106 formed thereon. FIG. 1B shows a separator 107 having an oxidant gas flow path surface and a gas seal 103 formed thereon. 1A and 1B, as a typical example, a bipolar separator in which a fuel gas flow path surface 104 is formed on one surface and an oxidant gas flow path surface 109 is formed on the back surface of a single plate is shown. . When two such separators are prepared and a membrane-electrode assembly (MEA) is sandwiched between the fuel gas channel surface and the oxidant gas channel surface, a power generation cell is configured as shown in FIG. A separator provided with a fuel gas channel surface and a separator provided with an oxidant gas channel surface may be prepared separately.

  One of the two fuel gas manifolds 101 provided in each separator 107 is a supply manifold for introducing fuel gas before power generation into the cell, and the other is after hydrogen is consumed in the cell. This is a discharge manifold for discharging the exhaust gas. The supply side manifold and the discharge side manifold are determined by the design conditions of the battery. In this embodiment, referring to FIG. 1A, fuel is supplied from the fuel gas manifold 101 on the upper right side of the fuel gas flow path surface 104 and discharged from the fuel gas manifold 101 on the lower left side. The fuel gas manifold 101 provided in the separator 107 having the oxidant gas flow path surface 109 in FIG. 1B is used only for passing the fuel gas.

  Further, the oxidant is supplied from the oxidant gas manifold 102 located at the lower left of the oxidant gas flow path surface 109 of the separator 107 shown in FIG. 1B, and is discharged from the oxidant gas manifold 102 at the upper right. did. The oxidant gas manifold 102 provided in the separator 107 having the fuel gas flow path surface 104 is used only for passing the oxidant gas.

  The gas seal 103 is formed on both the fuel gas channel surface 104 and the oxidant gas channel surface 109. Here, in order to show an embodiment in which a liquid gasket made of fluorine rubber or silicon rubber is used as the refrigerant seal 106, the gas seal 103 has a planar shape and a frame structure. Further, an opening window is provided in the center of the gas seal 103, and the fuel gas flow path surface 104 is exposed in the separator 107 having the fuel gas flow path surface under the opening window, and the oxidant gas in the separator 107 having the oxidant gas flow path surface. The flow path surface 109 was exposed. The electrode layer of the MEA is in close contact with the gas flow path from the opening window of the gas seal 103, the hydrogen oxidation reaction shown in the following formula 1 occurs on the fuel gas flow path surface 104, and the oxidant gas flow path surface 109 shows the formula 2 Oxygen reduction occurs.

H ₂ ⇒ 2H ⁺ ... Formula 1
2H ⁺ +1/2 O ₂ + 2e ⁻ ⇒ H ₂ O Formula 2
As an example of the gas seal 103, a polyethylene terephthalate (PET) sheet was used. A PET sheet (thickness 0.2 mm, tolerance ± 0.01 mm) was cut into the shape of the gas seal 103 shown in FIGS. 1A and 1B and adhered to the separator 107. A fluororubber sealant was used as the adhesive. An adhesive was applied to the separator surface in an extremely thin shape, and a gas seal 103 made of a PET sheet was pressed and adhered. The overall dimensions were measured after bonding, and the average thickness of the adhesive layer was determined by subtracting the thickness of the separator before bonding and the thickness of PET. The thickness was 0.05 mm (measurement error ± 0.01 mm).

  Any material other than PET can be used as long as the material has high thickness accuracy and does not cause thermal deformation at the operating temperature of the fuel cell. For example, polyparaphenylene sulfide (PPS) can also be used. The glass transition temperature of PPS is higher than the glass transition temperature of PET, and is several tens of degrees higher than the operating temperature (70 to 80 ° C.) of the fuel cell. Therefore, it is more desirable because it is more resistant to thermal deformation than PET. If the glass transition temperature is higher than the operating temperature of the fuel cell, a polymer resin material other than PET can be selected.

  The cooling manifold 105 is formed to allow cooling water to pass in a direction perpendicular to the plane of the separator 107. One of the two cooling manifolds 105 formed on the separator 107 is a supply manifold for passing low-temperature water, and the other is for passing high-temperature water after removing heat from the power generation cell. This is a discharge manifold. Leakage of the cooling water to the electrolyte membrane side is suppressed by the refrigerant seal 106. The outer edge of the electrolyte membrane is inside the refrigerant seal 106 and does not extend from the refrigerant seal 106 to the cooling manifold 105 side.

  A liquid gasket made of fluorine rubber or silicon rubber was provided as a refrigerant seal 106 on the outer periphery adjacent to the cooling manifold 105. The liquid gasket had a lip shape (semicircular shape) with a line width of 1 mm and a height of 0.8 mm. The liquid gasket is cured by drying at room temperature and can be used as a refrigerant seal. The separator manufactured in this way is referred to as a separator S1.

  2A and 2B show another embodiment of the gas seal and the refrigerant seal. FIG. 2A shows a separator 107 having a fuel gas flow path surface 104 and a gas seal 103 and a refrigerant seal 106 formed thereon. FIG. 2B shows the separator 107 having the oxidant gas flow path surface 109 on the back surface of the separator of FIG.

  In this embodiment, a thermosetting resin such as an epoxy resin is used for the cooling water seal 106 around the cooling water manifold 105. The cooling water seal 106 was preliminarily heat-treated in order to apply the epoxy resin in a linear shape using a dispenser and to make the application part semi-cured. The treatment temperature was 80 to 90 ° C.

  On the other hand, the gas seal 203 is formed in a polygonal shape on the fuel gas flow path surface 104 of the separator 107. The material of the gas seal 203 was a fluorine-based or silicon rubber liquid gasket. This gasket is cured by drying at room temperature and can be used as a gas seal. Since the cooling water seal is a thermosetting seal material, an elastic gas seal can be used.

  Although the gas seal is not provided on the oxidant gas flow path surface, a seal wider than the seal on the fuel gas flow path surface may be provided. In this way, even if the position of the convex portion of the gas seal formed on the fuel gas flow path surface is slightly shifted, the oxidant gas flow path surface is not deviated from the gas seal surface. The separator having the seal structure described above is referred to as a separator S2.

  After preparing these two types of separators S1 and S2, the MEA was inserted between the two separators S1 or the two separators S2, and the power generation cell having the structure shown in FIG. 4 was assembled. In addition, when separator S2 was used, the heat processing for the main hardening of an epoxy resin was performed, and separators were joined.

  Next, the structure of the cooling cell which consists of a separator which has a cooling water flow path is demonstrated.

  FIGS. 3A and 3B show the separator surfaces constituting the cooling cell. A cooling cell is made by these separator surfaces facing each other. The cooling cell separator 307 of FIG. 3A has a cooling water flow path, and FIG. 3B is the back surface of FIG. 3A, which is a flat surface having no cooling water flow path.

  The cooling water is supplied from either one of the two cooling manifolds 305 to the cooling cell separator 307, passes through the cooling water passage 303, and is discharged from the other cooling water manifold 305. The cooling cell separator 307 is formed on the back surface of the fuel gas channel surface 104 of the separator 107 shown in FIG. 1A or on the back surface of the oxidant gas channel surface 109 of the separator 107 shown in FIG.

  The compact cell structure combining the cooling cell and the power generation cell is preferably a structure as described below. The cooling cell can also be made by combining the following two types of separators.

  One is to prepare a separator having a flat surface in FIG. 3B on the back surface of the oxidant gas flow path surface 109 in FIG. This is referred to as separator A.

  One is to prepare a separator B having the cooling water flow path surface of FIG. 3A on the back surface of the fuel gas flow path surface 109 of FIG.

  When the flat surface of the cooling cell separator is opposed to the cooling water flow path surface, the cooling cell can be configured.

  By installing the cooling cell on the back surface of the fuel gas or oxidant gas flow path of the power generation cell, the back surface of the fuel gas flow path surface of the adjacent power generation cell or the oxidant gas flow while passing through the cooling water flow path 303. Excess heat can be removed from the back of the road surface.

  The cooling water channel 303 is delimited by ribs (convex portions) 304 in the separator surface. Electricity flows in the direction perpendicular to the drawing through the ribs (convex portions) 304 so that each power generation cell can generate power simultaneously.

  The refrigerant seal 306 of the cooling cell separator 307 is provided so as to surround the entire outer periphery of the cooling water flow path 303 and the cooling manifold 305 so that the cooling water does not leak to the outside. In the cooling cell, it is not necessary to consider a seal (gas seal) of the electrolyte membrane, and therefore, the entire cooling water flow path surface can be manufactured with the same seal as shown in FIG. That is, since the fuel and the oxidant only pass through the cooling cell, there is no problem even if a gas seal is formed around the fuel gas manifold 301 and the oxidant gas manifold 302 with the same material as the refrigerant seal.

  Next, the configuration of the power generation cell will be described with reference to FIG.

  FIG. 4 is an example of a cross-sectional shape of a power generation cell in which a separator 407 having an oxidant gas flow path surface and a separator 401 having a fuel gas flow path surface are combined. In FIG. 4, the shape of the back surface of each separator may be a gas flow path or a cooling water flow path, and therefore the shape of the back surface is omitted.

  An MEA in which an electrode 403 composed of an electrode layer and a gas diffusion layer and an electrolyte membrane 402 are integrated is inserted between these separators.

  The separator 401 has the fuel gas flow path surface 104, the gas seal 103, and the cooling water seal 106 shown in FIG. The separator 407 has an oxidant gas flow path surface 109 and a gas seal 103 as shown in FIG. The refrigerant seal 406 on the separator 401 having the fuel gas flow path surface 104 is pressure-bonded or bonded to a flat portion around the cooling water manifold 405 of the opposing separator 407.

  Therefore, the height of the refrigerant seal 406 is at least twice the thickness of one gas seal 403 so that the cooling manifold 405 is surrounded by the cooling water seal 406 when the two separators are brought into close contact with each other. I made it. In this way, leakage of cooling water was prevented.

  When the separator is in close contact, the height of the refrigerant seal 406 is the sum of the thickness of the gas seal 404 and the thickness of the MEA, like the refrigerant seal 406 shown in FIG.

  The gas seal 404 is provided on the separators 401 and 407 and outside the electrode 403 so as to crimp the outer edge of the electrolyte membrane. Note that the electrode 403 exists in the opening of the gas seal shown in FIGS. 1A and 1B and is in contact with the gas flow path surface of the separator 401 or the separator 407.

  The cooling manifold 405 passes through positions outside the ends of the gas seal 404 and the electrolyte membrane 402. A refrigerant seal 406 is provided around the cooling manifold 405. Thereby, water leakage and impurity leakage to the MEA side are suppressed.

  In addition, since the outer edge of the electrolyte membrane 402 is inside the refrigerant seal 406, the electrolyte membrane is not contaminated by impurities of the cooling water, and is firmly fixed in the gap between the two separators 401 and 407. The refrigerant seal 406 is not easily damaged or peeled off. As a result, leakage of impurities from the seal can be suppressed even after long-term power generation.

  The refrigerant seal 406 can be formed by applying a thermosetting resin such as an epoxy resin on the separator and performing a heat treatment after the formation. In order to prevent thermal oxidation of the separator material and the electrolyte membrane, it is desirable to select a sealing material that is cured at a temperature at which the separator and the like are not oxidized. That is, it is possible to use an epoxy resin that starts to cure in a low temperature zone (80 to 90 ° C.) where the fluorine-based electrolyte membrane is not oxidized, or a liquid gasket (silicon rubber or the like dispersed in a solvent). In addition, a gas atmosphere is effective in preventing oxidation in an inert gas, but in order to simplify the manufacturing process, it is preferable to select a sealing material that can be cured in the air. Epoxy resin is also excellent for this.

  When a material having a fluidity such as an epoxy resin is used as the material for the refrigerant seal, a coating method using a dispenser or a coating method using screen printing can be employed. In the case of a sealing material with low fluidity, it is also possible to form the sealing material on the separator using a mold under high pressure.

  When the heat treatment is performed after the sealing material is formed and cured, the two separators 401 and 407 are bonded. Note that the final treatment step of the sealing material may be any method in which the sealing material is cured, not heat treatment.

  Since the voltage of the power generation cell alone is as low as less than 1 V, a configuration of the power generation cell and the cooling cell suitable for the cell stack in which these are connected in series will be described.

  As a typical example, if a separator as shown in the following (1) to (3) is used, a cell stack can be assembled from several types of separators.

  (1) The “surface” of the separator is the oxidant gas flow path surface of FIG. 1B, and the “back surface” is the flat surface of FIG. This is designated as separator A.

  (2) The “front surface” of the separator is the cooling water flow path surface of FIG. 3A, and the “back surface” is the fuel gas flow path surface of FIG. This is designated as separator B.

  (3) The “front surface” of the separator is the oxidant gas flow path surface of FIG. 1B, and the “back surface” is the fuel gas flow path surface of FIG. This is designated as separator C.

  Here, when the separator arrangement is described so that the surface of the separator is on the right side, two cells connected in series with the configuration of A // C // B can be made using each separator one by one. it can. However, double-slashed // indicates that the MEA is inserted.

  This separator arrangement (A // C // B) can be made the cooling cell shown in FIG. 3 by adding B on the right side (surface of C). ) Can be connected repeatedly. Therefore, if this unit unit is used, the number of cells can be increased.

  Another form is a cell stack combining the power generation cell (FIG. 4) and the cooling cell (FIG. 3) of the present invention, as shown in FIG.

  As shown in the enlarged view, the power generation cell 501 of the present invention includes an electrolyte membrane 502, a fuel side and oxidant side catalyst layer 503, and a gas diffusion layer 506.

  The gas seals 550 and 551 pressurize a part of the electrolyte membrane 502 to prevent gas leakage. The refrigerant seal 505 is formed outside the electrolyte membrane 502 and seals the outer periphery of the cooling manifold (not shown in FIG. 5). The cooling cell 508 is installed for every two power generation cells 501 and is arranged so that heat can be removed from the back surface of the separator 504 of the power generation cell 501. As described above, the current collector plates 513 and 514 are placed outside the stacked body of the plurality of power generation cells 501 and the cooling cells 508, and the insulating plates 507 and the end plates 509 are further installed. Finally, a load is applied to the end plate by bolts 516, springs 517, and nuts 518 to fix the laminate.

  When the fuel gas and the oxidant gas are supplied from the fuel gas pipe connector 510 and the oxidant gas pipe connector 512 provided on the end plate, electric power can be taken out from the external power line 519 through the current collecting plates 513 and 514. This electric power is supplied to a load 521 installed outside via a DC-DC converter or an inverter 520. The gas after power generation is discharged from the connector 522 for fuel gas piping and the connector 523 for oxidant gas piping.

  The cooling water is supplied from a cooling water pipe connector 511 provided on the end plate, and after passing through the cooling cell, is discharged from the cooling water pipe connector 524 to the outside of the battery. In general, after the cooling water is radiated by a heat exchanger, the cooling water is re-supplied to the cooling water pipe connector 511, and the cooling water is generally used as circulating water.

  According to the configuration of the cell stack of the present invention, even if cooling water in which a low melting point material such as ethylene glycol is added to water is used, the refrigerant seal 106 shown in FIG. Can be prevented. As a result, even if the low melting point substance is a substance that acts as an impurity that causes deterioration of the electrode or the electrolyte membrane, contact with the electrode etc. can be almost completely suppressed, and high output for a long time can be maintained. Become.

  For fuel cells for cold districts, the freezing point should be lower than the cold district temperature, so a liquid in which a second component (alcohol such as ethylene glycol) is added to water, or the second component itself (anhydride) May be used.

(A) shows an example of the fuel gas flow path surface side of the separator and a seal structure, and (b) is a plan view showing an example of the oxidant gas flow path surface side and the seal structure. (A) shows the fuel gas channel surface side of the separator and another example of the seal structure, and (b) is a plan view showing another example of the oxidant gas channel surface side and the seal structure. (A) shows the separator which has a cooling water flow path, (b) is a top view which shows the back surface. 1 is a cross-sectional view of a power generation cell according to an embodiment of the present invention. The schematic block diagram of the cell stack which laminated | stacked several power generation cells of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 101 ... Fuel gas manifold, 102 ... Oxidant gas manifold, 103 ... Gas seal, 104 ... Fuel gas flow path surface, 105 ... Cooling manifold, 106 ... Refrigerant seal, 107 ... Separator, 109 ... Oxidant gas flow path surface, 203 ... Gas Seal: 301 ... Fuel gas manifold, 302 ... Oxidant gas manifold, 303 ... Cooling water flow path, 304 ... Rib (convex part), 305 ... Cooling manifold, 306 ... Refrigerant seal, 307 ... Cooling cell separator, 401 ... Separator, 402 DESCRIPTION OF SYMBOLS ... Electrolyte membrane, 403 ... Laminated body of electrode layer and gas diffusion layer, 404 ... Gas seal, 405 ... Cooling manifold, 406 ... Refrigerant seal, 407 ... Separator, 501 ... Power generation cell, 502 ... Electrolyte membrane, 503 ... Catalyst layer, 504 ... Separator, 505 ... Refrigerant seal, 506 ... Gas diffusion layer 507 ... Insulating plate, 508 ... Cooling cell, 509 ... End plate, 510 ... Connector for fuel gas piping, 511 ... Connector for cooling water piping, 512 ... Connector for oxidant gas piping, 513 ... Current collector plate, 514 ... Current collector Plate, 516 ... Bolt, 517 ... Spring, 518 ... Nut, 519 ... External power line, 520 ... DC-DC converter or inverter, 521 ... Load installed outside, 522 ... Connector for fuel gas piping, 523 ... Oxidant gas piping Connector, 524 ... Connector for cooling water piping, 550 ... Gas seal, 551 ... Gas seal.

Claims (14)

  In a polymer electrolyte fuel cell comprising a cell having a structure in which a solid polymer electrolyte membrane and an electrode are sandwiched between a pair of separators each having a cooling manifold through which a refrigerant passes and a gas manifold through which gas passes, the gas flow of the separator A gas seal that circulates around the road surface and a refrigerant seal that circulates around the cooling manifold, wherein the refrigerant seal is provided outside the outer edge of the solid polymer electrolyte membrane, and the electrolyte membrane does not directly contact the refrigerant. A polymer electrolyte fuel cell characterized by comprising:   2. The polymer electrolyte fuel cell according to claim 1, wherein the gas seal is provided in a plane of the solid polymer electrolyte membrane.   2. The polymer electrolyte fuel cell according to claim 1, wherein the gas seal and the refrigerant seal are provided in a non-contact manner.   2. The polymer electrolyte fuel cell according to claim 1, wherein the gas seal is bonded to the separator.   3. The polymer electrolyte fuel cell according to claim 2, wherein the gas seal has a protrusion, and the protrusion is in contact with the solid polymer electrolyte membrane.   6. The polymer electrolyte fuel cell according to claim 5, wherein a tip of the projection of the gas seal is a flat surface.   2. The polymer electrolyte fuel cell according to claim 1, wherein the refrigerant seal is made of an elastic material, and the gas seal is made of an inelastic material.   2. The polymer electrolyte fuel cell according to claim 1, wherein the refrigerant seal is made of a thermosetting material, and the gas seal is made of rubber.   2. The polymer electrolyte fuel cell according to claim 1, wherein the refrigerant seal is made of an inelastic material, and the gas seal is made of an elastic material.   2. The polymer electrolyte fuel cell according to claim 1, wherein the refrigerant seal is made of rubber, and the gas seal is made of a thermosetting material.   3. The polymer electrolyte fuel cell according to claim 2, wherein the gas seal is a sheet having an insulating property and is pressure-bonded by the solid polymer electrolyte membrane.   12. The polymer electrolyte fuel cell according to claim 11, wherein a surface of the gas seal that is pressure-bonded by the solid polymer electrolyte membrane is a smooth surface.   The polymer electrolyte fuel cell according to claim 1, wherein separators are joined by the refrigerant seal.   A power generation system on which the polymer electrolyte fuel cell according to any one of claims 1 to 13 is mounted.

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