Fuel battery and fuel battery system

Abstract

To provide a fuel battery having impact resistance and effectively exhibiting a function of an internal humidification system.SOLUTION: According to an embodiment, a fuel battery 100 includes a fuel battery stack 102 in which a fuel battery cell 101 is stacked. The fuel battery cell 101 includes a solid polymer electrolyte membrane 105, a fuel electrode 110 and an oxidizer electrode 120 respectively provided adjacent to both surfaces 105a and 105b thereof, a fuel electrode separator 113 having a fuel electrode separator flow path 113a for supplying a fuel gas to the fuel electrode 110, and an oxidizer electrode separator 123 having an oxidizer electrode separator flow path 123a for supplying an oxidizer gas to the oxidizer electrode 120. The fuel electrode separator 113 or the oxidizer electrode separator 123 has a porous separator 150 in which a cooling water flow path 131 for cooling water is formed on a back surface thereof and in which a plurality of pores communicating from the cooling water flow path to the fuel electrode 110 or the oxidizer electrode 120 are formed.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] FIELD OF THE INVENTION Embodiments of the present invention relate to fuel cells and fuel cell systems. [Background technology]

[0002] Fuel cells are a clean power source that can convert hydrogen into electricity with high efficiency. Fuel cells are also useful as distributed power sources in environments where commercial power grids are unavailable.

[0003] In particular, fuel cells using a hydrogen ion-conducting polymer electrolyte membrane, ie, polymer electrolyte fuel cells (PEFCs), are characterized by their low operating temperature, light weight, and compact size.

[0004] For this reason, polymer electrolyte fuel cells have been attracting attention and being developed in recent years. Polymer electrolyte fuel cells are fuel cells that can be widely used in, for example, portable power sources, automotive power sources, cogeneration systems, and the like.

[0005] A typical fuel cell using a solid polymer electrolyte membrane is composed of an electrolyte membrane, catalyst layers on both sides of the membrane, a gas diffusion section on the outside of the catalyst layer, and a separator, which is a flow path plate in contact with the gas diffusion section. Here, the separator also includes a flow path for cooling water that recovers waste heat generated by the fuel cell's power generation.

[0006] The most commonly used electrolyte membrane today is a perfluorosulfonic acid ion-exchange membrane. It is known that if the electrolyte membrane dries out, the voltage of the fuel cell drops significantly during power generation, reducing the efficiency of the fuel cell system. Therefore, a means of humidifying the electrolyte membrane is necessary.

[0007] A common method for humidifying the electrolyte membrane is an external humidification method in which a humidifier is provided and the fuel gas and oxidant gas are humidified by the humidifier before being supplied to the fuel cell.

[0008] On the other hand, an internal humidification system is known in which the separator, which is a porous plate for passage of cooling water that recovers waste heat generated by power generation in the fuel cell, is used to humidify the electrolyte membrane using the cooling water inside the separator. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 3515161 Summary of the Invention [Problem to be solved by the invention]

[0010] In the case of the internal humidification method described above, a specific example of the porous separator is generally a porous carbon substrate using a carbon material.

[0011] On the other hand, when polymer electrolyte fuel cells are used in mobile devices such as portable power sources and automotive power sources, ensuring impact resistance of the polymer electrolyte fuel cell is an important requirement. It is considered difficult to ensure impact resistance with separators made of conventional carbon materials. Therefore, there is a demand for polymer electrolyte fuel cells that are impact resistant and allow the internal humidification system to function effectively.

[0012] In porous separators, if the wet seal is insufficient, the pressure difference between the gas and cooling water channels will cause gas to be sucked into the cooling water channel. This can result in problems such as the cooling water flow being stopped due to the intrusion of oxygen-containing gas (oxidizer gas) into the cooling water circulation system, or a decrease in power generation efficiency due to a drop in oxygen and hydrogen partial pressure. There is also a risk of the hydrogen-containing gas (fuel gas) igniting due to the mixing of hydrogen gas and oxidizer gas.

[0013] Furthermore, if the water permeability coefficient of a porous separator is low, the liquid water absorption rate in the gas flow path and the gas diffusion area will be insufficient, resulting in gas flow problems such as plugging and flooding, which will lead to problems such as a drop in cell voltage and a decrease in power generation efficiency.

[0014] For these reasons, when using impact-resistant materials for the separator and an internal humidification system, it is important to operate the fuel cell under conditions that allow the internal humidification system to function properly. Furthermore, ensuring cost competitiveness is also important for solid polymer fuel cells to be widely adopted in industry.

[0015] The problem to be solved by the present invention is to provide a fuel cell and a fuel cell system that are shock resistant and effectively exhibit the function of an internal humidification system. [Means for solving the problem]

[0016] In order to achieve the above-mentioned object, the fuel cell according to this embodiment is a fuel cell including a fuel cell stack in which a plurality of fuel cell units that generate electricity using a fuel gas and an oxidant gas are stacked, and each of the plurality of fuel cell units comprises: a solid polymer electrolyte membrane having hydrogen ion conductivity; an anode provided adjacent to a first surface of the solid polymer electrolyte membrane; an oxidant electrode provided adjacent to a second surface of the solid polymer electrolyte membrane; an anode separator adjacent to the anode and having an anode separator flow path formed therein for supplying the fuel gas to the anode; and an oxidant electrode separator adjacent to the oxidant electrode and having an oxidant electrode separator flow path formed therein for supplying the oxidant gas to the oxidant electrode, wherein at least one of the anode separator and the oxidant electrode separator has a cooling water flow path formed on its back surface and is a porous separator manufactured using metal powder and having a plurality of pores formed therein that communicate from the cooling water flow path to at least one of the anode and the oxidant electrode and are capable of retaining water. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a block diagram showing the configuration of a fuel cell system according to an embodiment; [Figure 2] 1 is a cross-sectional view showing the configuration of a fuel cell stack according to an embodiment, taken in a direction perpendicular to the stacking direction of fuel cell units. [Figure 3] 1 is a conceptual cross-sectional view of a metal powder processed body used in a fuel cell of a fuel cell according to an embodiment. [Figure 4] 3 is a front view showing an example of a cooling water flow path formed on the back surface of an oxidizer electrode separator of a fuel cell according to an embodiment. FIG. [Figure 5] 1 is a first comparison table showing a comparison between a fuel cell according to an embodiment and a first comparative example. [Figure 6] 10 is a second comparison table showing a comparison between the fuel cell according to the embodiment and a second comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, a fuel cell and a fuel cell system according to an embodiment of the present invention will be described with reference to the drawings. Hereinafter, identical or similar parts will be denoted by common reference numerals, and overlapping descriptions will be omitted.

[0019] FIG. 1 is a block diagram showing the configuration of a fuel cell system 1 according to an embodiment.

[0020] The fuel cell system 1 has a fuel cell 100 and a service system. The service system has a fuel gas supply device 2, an oxidant gas supply device 3, and a cooling water circulation device 4. Although FIG. 1 illustrates an example in which the fuel cell system 1 has one fuel cell 100, the fuel cell system 1 may have multiple fuel cells 100. In this case, there may be one service system common to the multiple fuel cells 100.

[0021] The fuel cell 100 has a fuel cell stack 102 and a connection to a service system. The interior of the fuel cell stack 102 will be described in detail later with reference to FIG.

[0022] The fuel cell stack 102 is connected to a fuel gas supply device 2 as a service system via a fuel gas inlet 115 and a fuel gas outlet 116. The fuel cell stack 102 is connected to an oxidizing gas supply device 3 as a service system via an oxidizing gas inlet 125 and an oxidizing gas outlet 126. The fuel cell stack 102 is also connected to a cooling water circulator 4 as a service system via a cooling water inlet 135 and a cooling water outlet 136. The cooling water inlet 135 is provided on the vertically lower side of the fuel cell stack 102, and the cooling water outlet 136 is provided on the vertically upper side of the fuel cell stack 102.

[0023] The fuel gas supply device 2 has a liquefied fuel gas tank 2b that stores fuel gas, a fuel gas pipe 2a extending from the liquefied fuel gas tank 2b, and a pressure reducing valve 2c provided on the fuel gas pipe 2a. Here, the fuel gas is a raw material gas supplied to the anode 110 (FIG. 2) of the fuel cell 100, and is, for example, a hydrogen-containing gas. Note that instead of the liquefied fuel gas tank 2b, a system in which multiple gas cylinders are used by sequentially switching between them may be used. Alternatively, fuel gas may be supplied from an infrastructure system such as city gas.

[0024] The fuel gas supply device 2 including the pressure reducing valve 2c can set the fuel gas pressure at the inlet of the fuel cell 100 to a value that falls within the range of the fuel gas inlet pressure conditions on the fuel cell 100 side described below, under the operating conditions of the fuel cell 100.

[0025] The oxidant gas supply device 3 includes an oxidant gas pipe 3a, a blower 3b provided in the oxidant gas pipe 3a, and an outside air filter 3c provided at the intake port of the oxidant gas pipe 3a. Note that a compressor may be used instead of the blower 3b as long as the pressure resistance conditions of the fuel cell system 1 are ensured. Here, it is preferable to select a low-cost blower 3b or compressor that is basically a catalog product, or a catalog product that has been modified to a small extent.

[0026] The oxidant gas supply device 3 including the blower 3b can set the pressure of the oxidant gas at the inlet of the fuel cell 100 to a value that falls within the range of the oxidant gas inlet pressure conditions on the fuel cell 100 side described below, under the operating conditions of the fuel cell 100.

[0027] Note that catalog products, or catalog products that have been modified to a small extent, are referred to as "standard products." Using standard products can help reduce costs.

[0028] The cooling water circulation device 4 has an open tank 4a, a suction-side cooling water pipe 4g, a pump 4d, a discharge-side cooling water pipe 4e, and a cooler 4f, which form a cooling water circulation flow path. The fuel cell 100 is provided in the suction-side cooling water pipe 4g. The part of the suction-side cooling water pipe 4g upstream of the fuel cell 100 will be referred to as the suction-side upstream cooling water pipe 4b, and the part downstream of the fuel cell 100 will be referred to as the suction-side downstream cooling water pipe 4c.

[0029] The suction-side upstream cooling water pipe 4b connects the open tank 4a and the fuel cell 100. The suction-side downstream cooling water pipe 4c connects the fuel cell 100 and the suction side of the pump 4d. The discharge-side cooling water pipe 4e connects the discharge side of the pump 4d and the open tank 4a. The cooler 4f is provided on the discharge-side cooling water pipe 4e. The pump 4d circulates the cooling water within the cooling water circulation flow path. The cooler 4f is a heat exchanger for exchanging heat between the cooling water for cooling the fuel cell 100 and the antifreeze on the heat dissipation source side. The cooler 4f cools the cooling water whose temperature has risen in the fuel cell 100. Here, it is preferable to similarly select standard products for the pump 4d and the cooler 4f.

[0030] The cooling water used in the fuel cell 100 is supplied from the suction-side upstream cooling water piping 4b to the cooling water inlet 135 of the fuel cell 100, and is discharged from the cooling water outlet 136 of the fuel cell 100 to the suction-side downstream cooling water piping 4c. At this time, as shown in Figure 1, the cooling water flows in from the bottom side of the fuel cell 100 and is discharged from the top side of the fuel cell 100. In order to make the pressure of the cooling water in the fuel cell 100 negative at this time, the fuel cell 100 is provided on the suction-side cooling water piping 4g, which is the suction side of the pump 4d.

[0031] The cooling water circulation device 4 including the pump 4d can set the pressure of the cooling water at the inlet of the fuel cell 100 to a value within the range of the inlet pressure conditions of the fuel cell 100 described below under the operating conditions of the fuel cell 100.

[0032] In order to ensure the suction pressure of the pump 4d and prevent the occurrence of cavitation, the pump 4d is installed at a position sufficiently lower than the installation height of the open tank 4a.

[0033] As described above, standard products can be used for the service system equipment of the fuel cell system 1. In other words, the fuel cell 100 can be operated using fuel gas, oxidant gas, and coolant supplied by a service system configured with standard products. As a result, the cost competitiveness of the fuel cell 100 and the fuel cell system 1 can be improved.

[0034] FIG. 2 is a cross-sectional view in a direction perpendicular to the stacking direction of fuel cell units 101, showing the configuration of a fuel cell stack 102 according to this embodiment.

[0035] The fuel cell stack 102 has a plurality of fuel cell units 101 stacked one on top of the other.

[0036] Each fuel cell 101 includes a solid polymer electrolyte membrane 105, a fuel electrode 110 disposed adjacent to a first surface 105a of the solid polymer electrolyte membrane 105, an oxidizer electrode 120 disposed adjacent to a second surface 105b of the solid polymer electrolyte membrane 105, a fuel electrode separator 113, and an oxidizer electrode separator 123.

[0037] The fuel gas passes from the fuel electrode separator flow path 113a through the fuel electrode diffusion layer 112 and is supplied to the fuel electrode catalyst layer 111. The oxygen-containing gas passes from the oxidizer electrode separator flow path 123a through the oxidizer electrode diffusion layer 122 and is supplied to the oxidizer electrode catalyst layer 121. The reactions shown in the following formulas (1) and (2) take place at the fuel electrode 110 and the oxidizer electrode 120. Anode reaction: H2 → 2H + + 2e - ···(1) Oxidant electrode reaction: 2H + + 2e - + (1 / 2)O2 → H2O (2)

[0038] The solid polymer electrolyte membrane 105 is a polymer electrolyte membrane having hydrogen ion conductivity, and is, for example, an electrolyte membrane containing a fluorosulfonic acid-based ion exchange resin as a main component.

[0039] Anode 110 has anode catalyst layer 111 and anode diffusion layer 112 .

[0040] Anode catalyst layer 111 is, for example, a platinum alloy such as platinum-cobalt in powder form.

[0041] Anode diffusion layer 112 is located between anode catalyst layer 111 and anode separator 113, and covers anode catalyst layer 111. Anode diffusion layer 112 is made of, for example, carbon paper. Anode diffusion layer 112 also has the function of holding anode catalyst layer 111 in powder form.

[0042] The oxidant electrode 120 has an oxidant electrode catalyst layer 121 and an oxidant electrode diffusion layer 122 .

[0043] The oxidizer electrode catalyst layer 121 is, for example, a platinum alloy such as platinum-ruthenium in powder form.

[0044] The oxidant electrode diffusion layer 122 is located between the oxidant electrode catalyst layer 121 and the oxidant electrode separator 123, and covers the oxidant electrode catalyst layer 121. The oxidant electrode diffusion layer 122 is made of, for example, carbon paper. The oxidant electrode diffusion layer 122 also functions to hold the powdered oxidant electrode catalyst layer 121.

[0045] Next, we will explain the fuel electrode separator 113 and the oxidizer electrode separator 123. The fuel electrode separator 113 and the oxidizer electrode separator 123 are porous separators 150 that have impact resistance, desired sealing properties, and water permeability.

[0046] Anode separator 113 is disposed adjacent to anode 110. A plurality of anode separator channels 113a that supply fuel gas to anode 110 are formed in parallel on the surface of anode separator 113 facing anode 110. Anode diffusion layer 112 is formed to allow the fuel gas flowing through anode separator channels 113a to permeate anode catalyst layer 111.

[0047] Anode separator ribs 113b with convex cross sections are formed between adjacent anode separator channels 113a. The anode separator ribs 113b are pressed against the anode diffusion layer 112. The anode separator ribs 113b also serve as paths for current that contributes to the catalytic reaction. The anode separator ribs 113b also serve as paths for absorbing liquid water inside the anode diffusion layer 112.

[0048] The oxidant electrode separator 123 is disposed adjacent to the oxidant electrode 120. A plurality of oxidant electrode separator channels 123a that supply oxidant gas to the oxidant electrode 120 are formed in parallel on the surface of the oxidant electrode separator 123 facing the oxidant electrode diffusion layer 122. The oxidant gas is, for example, an oxygen-containing gas such as air. The oxidant electrode diffusion layer 122 is formed so that the oxidant gas flowing through the oxidant electrode separator channels 123a can permeate the oxidant electrode catalyst layer 121.

[0049] Oxidant electrode separator ribs 123b with convex cross sections are formed in parallel and sandwiched between adjacent oxidant electrode separator channels 123a. The oxidant electrode separator ribs 123b are pressed against the oxidant electrode diffusion layer 122. The oxidant electrode separator ribs 123b also serve as paths for current that contributes to the catalytic reaction. The oxidant electrode separator ribs 123b also serve as paths for absorbing liquid water inside the oxidant electrode diffusion layer 122.

[0050] 3 is a conceptual cross-sectional view of a metal powder processed body 160 used in the fuel cell 101 of the fuel cell 100 according to this embodiment. That is, FIG. 3 conceptually shows the metal powder processed body 160 used as a material for the porous separator 150.

[0051] Here, the metal powder processed body 160 refers to an integrated body manufactured using metal powder 161. First, the metal powder 161 used in the metal powder processed body is, for example, a metal powder having an average particle size of 10 to 20 μm and including particles having a particle size of less than 10 μm, or a metal powder having a particle size of 10 to 20 μm as the main component and including particles having a particle size of less than 10 μm. By using the metal powder processed body 160, it is possible to ensure the impact resistance of the porous separator 150 while also ensuring the desired sealing properties and water permeability.

[0052] A plurality of pores 163 are formed inside the metal powder processed body 160. These pores 163 communicate from one surface to the other surface of the metal powder processed body 160 and are gas impermeable at least when wet. In detail, when retaining moisture, these pores 163 can retain moisture that does not allow gas to pass through under a differential pressure that does not exceed the wet seal pressure described below.

[0053] The metal powder processed body 160 can be manufactured, for example, by placing the metal powder 161 in a mold, solidifying it, and baking it at a temperature lower than the melting point of the metal powder 161. Alternatively, the metal powder processed body 160 may be manufactured by plating or sputtering a foamed resin, and then removing the foamed resin by heat treatment. The metal powder processed body 160 may also be manufactured by compressing the metal powder 161, metal fibers, etc. Alternatively, the metal powder processed body 160 may be manufactured by mixing the metal powder 161 with a resin binder, compressing it, and then degreasing it with heat treatment or a solvent.

[0054] Examples of metals that can be used include austenitic stainless steel (e.g., SUS304, SUS316, SUS316L), titanium, and the like. In this case, it is not necessary to mix a resin binder with the metal powder before heat treatment. Stainless steel and titanium exhibit low ion elution and are resistant to corrosion in the power generation environment of the fuel cell 100. For example, in stainless steel, chromium (Cr) oxidizes before iron (Fe), forming an oxide film that covers the surface, preventing the elution of Fe ions. This prevents the fuel electrode separator 113 and the oxidizer electrode separator 123 from deteriorating, causing holes that make them unable to be sealed. In this way, the use of stainless steel or titanium improves the durability of the fuel cell 100.

[0055] As described above, the metal powder processed body 160 has a plurality of pores 163 that communicate between both surfaces and are gas impermeable at least when wet, i.e., capable of retaining moisture. Note that hereinafter, the pores 163 will include the spaces between the metal powder particles 161. By using metal powder 161 with a fine particle size, the metal powder processed body 160 has improved hydrophilicity, and can simultaneously improve the wet seal pressure and water permeability described below.

[0056] In addition to the metal powder 161, fibers with a diameter of 5 to 15 μm may be mixed into the metal powder processed body 160 and then sintered. Since the fuel electrode separator 113 and the oxidizer electrode separator 123 are stacked in the fuel cell 100, flatness is important. By mixing the metal fibers into the metal powder 161, the metal powder processed body 160 can be made thin and less prone to distortion, and flatness can be improved.

[0057] It is preferable to provide a coating portion 162 on the inner walls of the pores 163 of the metal powder processed body 160, i.e., on the surface portion of the metal powder 161 that comes into contact with a fluid such as cooling water. The coating portion 162 is mainly composed of chromium (Cr) and nickel (Ni). By providing the coating portion 162, it is possible to prevent the iron (Fe) component from coming into direct contact with the fluid. Alternatively, when the powdered metal is heat-treated together with a resin binder, the coating portion 162 may be formed by heating the powdered metal to a degree that leaves the resin on the inner walls of the porous material. Note that in addition to or instead of the coating portion 162, the hydrophilicity may be improved by surface treatment with tin chloride or the like.

[0058] The main component of stainless steel is Fe, and if Fe ions are eluted, the solid polymer electrolyte membrane 105 will deteriorate due to the Fenton reaction. For this reason, as described above, Cr and Ni contained in the stainless steel are placed on the inner walls of the pores 163 of the metal powder processed body through which the cooling water flows. The effect of Cr and Ni ions adhering to the catalyst surface is less damaging than the deterioration of the solid polymer electrolyte membrane 105 due to the Fenton reaction.

[0059] 3, the fuel electrode separator flow path 113a and the oxidizer electrode separator flow path 123a can be maintained in a humidified atmosphere. As a result, even when dry fuel gas and oxidizer gas are supplied to the fuel cell 100, these gases are easily humidified, and drying of the solid polymer electrolyte membrane 105 can be prevented.

[0060] Furthermore, when cooling water is held in the pores 163, even if liquid water occurs in the fuel electrode separator flow path 113a and the oxidizer electrode separator flow path 123a, the liquid water can be absorbed due to the pressure difference with the low-pressure cooling water flow path 131. As a result, accumulation of fuel gas and oxidizer gas due to plugging or flooding can be prevented, and a drop in cell voltage can be prevented.

[0061] As described above, the case where the metal powder processed body 160 is used as the material for both the fuel electrode separator 113 and the oxidizer electrode separator 123 has been described as an example, but the present invention is not limited to this. That is, the metal powder processed body 160 may be used for only one of the fuel electrode separator 113 and the oxidizer electrode separator 123. In this case, the separator that does not include the metal powder processed body 160 is also made of an impact-resistant material such as metal or silicon carbide (SiC).

[0062] A cooling water channel 131 is formed on the back surface of at least one of the fuel electrode separator 113 and the oxidizer electrode separator 123. Fig. 2 shows an example in which the cooling water channel 131 is formed on the back surface of the oxidizer electrode separator 123, i.e., the surface behind the side on which the oxidizer electrode separator channel 123a is formed. However, the cooling water channel 131 may also be formed on the back surface of the fuel electrode separator 113.

[0063] The cooling water flow path 131 is adjacent to the oxidizer electrode separator flow path 123a in the stacking direction, via the main body of the oxidizer electrode separator 123. The cooling water flow path 131 is also adjacent to the anode separator flow path 113a in the stacking direction, via the main body of the anode separator 113.

[0064] Cooling water flow path ribs 131b with convex cross sections are formed between adjacent cooling water flow paths 131. Cooling water flow path ribs 131b are pressed against anode separator 113. Cooling water flow path ribs 131b also serve as paths for absorbing liquid water inside anode diffusion layer 112. Cooling water flow path ribs 131b also serve as paths for supplying cooling water for wetting solid polymer electrolyte membrane 105 via anode diffusion layer 112.

[0065] FIG. 4 is a front view showing an example of a cooling water flow path 131 formed on the back surface of the oxidizer electrode separator 123 of the fuel cell 100 according to this embodiment.

[0066] 4 is a front view of the contact surface 132 on the side where the cooling water flow paths 131 are formed of the oxidizer electrode separator 123. The contact surface 132 that comes into contact with the back surface of the fuel electrode separator 113 has multiple cooling water flow paths 131 formed in parallel.

[0067] The cooling water introduction section 135 provided below the fuel cell stack 102 is a manifold. This manifold receives cooling water from the suction-side upstream cooling water pipe 4b and distributes it to the multiple cooling water flow paths 131.

[0068] The cooling water flow path 131 is formed so as to extend from a vertically lower side to an upper side while repeatedly extending vertically upward and horizontally.

[0069] The cooling water discharge unit 136 provided above the fuel cell stack 102 is a manifold. This manifold collects the cooling water received from the multiple cooling water flow paths 131 and causes it to flow out into the suction-side downstream cooling water pipe 4c.

[0070] 4, the cooling water flow paths 131 are arranged in a serpentine, or meandering, shape, but this is not limiting. The cooling water flow paths 131 may have other shapes as long as they are formed so as to face vertically upward. By forming the cooling water flow paths 131 in this manner, even if air bubbles are sucked into the cooling water flow paths 131, the air bubbles do not remain in the cooling water flow paths 131 but are released into the atmosphere after reaching the open tank 4a.

[0071] <Physical properties of porous separator> Before describing the characteristics of the porous separator 150, the physical properties of the porous separator 150 using the metal powder processed body 160 will be described below. Specifically, the wet seal pressure, water permeability coefficient, and water creep-up velocity will be described as physical properties.

[0072] First, the wet seal pressure is an index that indicates gas sealing performance, i.e., airtightness against gas. In other words, it is the limit (upper limit) pressure that can hold cooling water so that gas does not pass through the pores 163 and between the metal powders 161. The wet seal pressure is determined by the capillary pressure, which is determined by the surface tension of the cooling water, the contact angle of the cooling water on the surface of the pores 163, and the diameter of the pores 163. Therefore, the wet seal pressure can be improved by making the surface of the pores 163 hydrophilic. Here, using fine metal powder 161 is effective for hydrophilization.

[0073] To measure the wet seal pressure, first, the porous separator 150 is immersed in pure water to fill the pores 163 of the metal powder processed body 160 with water. Next, the periphery of the side of the porous separator 150 is sealed with a sealant. Next, a predetermined gas pressure (air or test gas such as nitrogen) is applied to one side of the porous separator 150. In this state, the pressure of the gas leaking from the other side is measured. When the same test is performed while gradually increasing the differential pressure, the airflow rate between the two sides increases sharply at a certain differential pressure. The wet seal pressure is the maximum differential pressure at which the airflow rate between the two sides can be maintained within a predetermined value. Note that it may also be a value obtained by subtracting a measurement error from the maximum value. Note that the predetermined value may be, for example, approximately 0.1 L / min for a measurement object of 1 square meter.

[0074] Next, the water permeability coefficient is an index showing the ease of water permeation into the pores 163, that is, the water permeability. The water permeability coefficient k[m 2 / Pa·sec] can be calculated as follows:

[0075] First, the porous separator 150 is immersed in pure water to allow the pores 163 of the metal powder processed body 160 to absorb water. Next, the periphery of the side of the porous separator 150 is sealed with a sealant. Next, a predetermined water pressure is applied to one side of the porous separator 150. In this state, the amount of water permeating to the other side per unit time is measured. The amount of water permeating is defined as Q [m 3 / sec], the average thickness of the porous separator 150 is L [m], the pressure difference between both sides of the porous separator 150 is ΔP [Pa], and the permeation area is A [m 2 ], the water permeability coefficient k [m 2 / Pa·sec] can be calculated using the following formula (3): The average thickness L is the thickness when the unevenness is averaged, although there is a range of unevenness depending on whether or not there are grooves. k=Q L / (ΔP A) (3)

[0076] Next, the water creeping speed is an index of water permeability in the direction along the surface of the porous separator 150. A water absorption test can be used to evaluate localized water permeability. For example, a very small amount (e.g., 10 μL) of pure water is dropped onto a certain location on the porous separator 150, and the time it takes for the water to be absorbed is measured. In this case, the water absorption time serves as an index corresponding to the water creeping speed. A short water absorption time indicates sufficiently fast water permeation and excellent gas humidification. In other words, even when dry fuel gas and oxidant gas are supplied to the fuel cell 100, sufficient humidification can be achieved, preventing deterioration of the solid polymer electrolyte membrane 105 due to drying and improving the durability of the fuel cell 100. Furthermore, high water absorption capacity can prevent plugging and flooding, as well as cell voltage oscillations.

[0077] <Characteristic conditions for each separator> The following describes the characteristics of the fuel electrode separator 113 and the oxidizer electrode separator 123 in this embodiment. As described above, in this embodiment, both the fuel electrode separator 113 and the oxidizer electrode separator 123 are porous separators 150 using metal powder processed bodies 160.

[0078] The fuel electrode separator 113 having the fuel electrode metal powder processed body 113m has a wet seal pressure of 62 kPa or more. The water permeability coefficient of the fuel electrode separator 113 is 4×10 -13 [m 2 / Pa·sec] or more, and the water absorption time (when 10 μL is dropped) is 38 seconds or less. 24 %. The porosity is the volume of the pores 163 divided by the total volume of the separator.

[0079] The oxidizer electrode separator 123 having the oxidizer electrode metal powder processed body 123m has a wet seal pressure of 60 kPa or more. The water permeability coefficient of the oxidizer electrode separator 123 is 4×10 -13 [m 2 / Pa·sec] or more, and the water absorption time (when 10 μL is dropped) is 38 seconds or less. In addition, the porosity of the oxidizer electrode metal powder processed body 123 μm is 25%.

[0080] <Conditions for using the fuel cell 100> The following describes the conditions for using the fuel cell 100. The fuel gas supply device 2, oxidant gas supply device 3, and cooling water circulator 4, which serve as service systems for the fuel cell system 1, are basically catalog products, or even if they are catalog products that have been modified to a small extent, they are low-cost standard products. As mentioned above, the following conditions can be achieved using such standard products.

[0081] (1) Pressure conditions on the cooling water side The pressure of the cooling water at the inlet of the fuel cell 100 is (-20 kPaG) to (-10 kPaG). As mentioned above, this pressure is achievable by the cooling water circulation device 4 using standard products. In the fuel cell 100, the pressure loss of the cooling water flowing through the cooling water flow path 131 of the porous separator 150 is 15 kPa. Note that the pressure loss at the cooling water inlet 135 and the cooling water outlet 136 is negligibly small compared to the pressure loss in the cooling water flow path 131. As a result, the outlet pressure of the fuel cell stack 102 is (-35 kPaG) to (-25 kPaG). In other words, the pressure range of the cooling water in the fuel cell stack 102 is (-35 kPaG) to (-10 kPaG).

[0082] (2) Fuel gas pressure conditions In the fuel cell stack 102, the pressure of the fuel gas flowing through the anode separator flow path 113a of the anode separator 113 is (+6 kPaG) to (+27 kPaG). If the pressure loss of the fuel gas in the fuel cell stack 102 is approximately 5 kPa, the condition for the fuel gas inlet pressure on the fuel cell 100 side is (+11 kPaG) to (+27 kPaG). As mentioned above, this pressure is a pressure that can be achieved by the fuel gas supply device 2 using a standard product. The fuel gas pressure is higher than the pressure on the cooling water side, and the pressure difference with the cooling water side does not exceed the wet seal pressure of the anode separator 113. As a result, the fuel gas does not flow into the cooling water side.

[0083] (3) Oxidant gas pressure conditions In the fuel cell stack 102, the pressure of the oxidant gas flowing through the oxidant electrode separator flow path 123a of the oxidant electrode separator 123 is (+2 kPaG) to (+21 kPaG). However, the oxidant gas pressure is set to be lower than the fuel gas pressure. If the pressure loss of the oxidant gas in the fuel cell stack 102 is approximately 5 kPa, the condition for the oxidant gas inlet pressure on the fuel cell 100 side is (+7 kPaG) to (+21 kPaG). As mentioned above, this pressure is a pressure that can be achieved by the oxidant gas supply device 3 using a standard product. The oxidant gas pressure is higher than the pressure on the coolant side, and the pressure difference with the coolant side does not exceed the wet seal pressure of the oxidant electrode separator 123. As a result, the oxidant gas does not flow into the coolant side.

[0084] (4) Relationship between fuel gas pressure and oxidizer gas pressure In addition to the respective pressure conditions for the fuel gas and the oxidant gas, the fuel gas must be at a higher pressure than the oxidant gas, because the electrodes (fuel electrode 110 and oxidant electrode 120) are less likely to deteriorate when the fuel gas (hydrogen-containing gas) on the fuel electrode 110 side leaks into the oxidant electrode 120 side through the solid polymer electrolyte membrane 105 than when the oxidant leaks into the fuel electrode 110 side. <Explanation of action and effect>

[0085] The fuel cell 100 and fuel cell system 1 according to this embodiment configured as described above have the following functions and effects.

[0086] (1) By using impact-resistant metal powder processed bodies 160 for fuel electrode separator 113 and oxidizer electrode separator 123, they can be used without problems in mobile devices such as portable power sources and automotive power sources. In addition, stainless steel and titanium have low ion elution in the power generation environment of fuel cell 100. This makes it possible to prevent impurities such as metal ions from adhering to the catalyst of fuel cell 100, improving the durability of fuel cell 100. Because stainless steel and titanium are resistant to corrosion in the power generation environment of fuel cell 100, it is possible to prevent deterioration such as holes appearing in fuel electrode separator 113 and oxidizer electrode separator 123, making them unable to be airtight.

[0087] (2) By making service equipment such as the blower 3b and the pump 4d standard products, cost competitiveness is ensured.

[0088] (3) By using standard components such as the blower 3b and the pump 4d and by appropriately setting the operating conditions of the fuel cell 100, the internal humidification system can be effectively utilized as follows.

[0089] (3-1) Outflow from the cooling water side As described above, the pressure range of the cooling water flowing through the cooling water flow path 131 is (-35 kPaG) to (-10 kPaG), the pressure range of the fuel gas flowing through the fuel electrode separator flow path 113a is (+6 kPaG) to (+27 kPaG), and the pressure range of the oxidizer gas flowing through the oxidizer electrode separator flow path 123a is (+2 kPaG) to (+21 kPaG).

[0090] In this way, the pressure range of the cooling water is lower than the pressure ranges of the fuel gas and the oxidant gas, and therefore the cooling water does not flow into the anode separator flow channel 113a and the oxidant electrode separator flow channel 123a.

[0091] (3-2) Outflow from the fuel gas side to the cooling water side The maximum differential pressure between the fuel gas, which has a pressure range of (+6 kPaG) to (+27 kPaG), and the cooling water, which has a pressure range of (-35 kPaG) to (-10 kPaG), is 62 kPa. Meanwhile, the wet seal pressure of the anode separator 113 is 62 kPa or higher. Therefore, a wet seal between the cooling water side and the fuel gas side via the porous separator 150 is ensured. As a result, there is no risk of fuel gas leaking to the cooling water side, which would lower the cell voltage of the fuel cell 100.

[0092] (3-3) Flow from the oxidizer gas side to the cooling water side The maximum differential pressure between the oxidant gas, which has a pressure range of (+2 kPaG) to (+21 kPaG), and the coolant, which has a pressure range of (-35 kPaG) to (-10 kPaG), is 56 kPa. On the other hand, the wet seal pressure of the oxidant electrode separator 123 is 60 kPa. Therefore, a wet seal between the coolant side and the oxidant gas side via the porous separator 150 is ensured. As a result, there is no risk of the oxidant gas leaking into the coolant side and lowering the cell voltage of the fuel cell 100.

[0093] (3-4) Fuel gas pressure and oxidizer gas pressure As described above, the fuel cell 100 is used under the condition that the pressure of the fuel gas is greater than the pressure of the oxidant gas, which results in less deterioration of the electrodes (fuel electrode 110 and oxidant electrode 120), and the health of the electrodes is maintained.

[0094] (4) Appropriate water permeability and wet sealing properties Because porous separator 150 is used for fuel electrode separator 113 and oxidizer electrode separator 123, liquid water in fuel electrode separator flow path 113a, fuel electrode diffusion layer 112, oxidizer electrode diffusion layer 122, and oxidizer electrode separator flow path 123a can be absorbed into the low-pressure cooling water. That is, it is possible to prevent plugging, in which liquid water accumulates in fuel electrode separator flow path 113a and oxidizer electrode separator flow path 123a, and flooding, in which liquid water accumulates in fuel electrode diffusion layer 112 and oxidizer electrode diffusion layer 122. As a result, it is possible to prevent events such as a decrease in oxidizer gas diffusion performance due to plugging or flooding, which results in a drop in cell voltage.

[0095] In this embodiment, by using a fine grain metal for the sintered metal, it is possible to simultaneously improve the wet seal pressure and water permeability, thereby eliminating problems such as the risk of ignition and a decrease in cell voltage.

[0096] The physical properties of the porous separator 150 require a balance between wet sealing and water permeability. That is, a small pore structure facilitates wet sealing, but makes it difficult for cooling water to pass through. From the perspective of pore structure, the two physical properties are essentially a trade-off. In this embodiment, hydrophilicity is improved by using a metal with a fine particle size for the sintered metal. As a result, wet sealing and water permeability can be improved simultaneously.

[0097] Furthermore, by setting the water absorption time (when 10 μL is dropped) to 38 seconds or less, water permeation is sufficiently fast, and sufficient humidification is possible even when dry fuel gas and oxygen-containing gas are supplied. As a result, deterioration due to drying of the solid polymer electrolyte membrane 105 can be suppressed, and durability can be improved.

[0098] <Comparison with the first comparative example> FIG. 5 is a first comparison table showing a comparison between the fuel cell 100 according to the embodiment and a first comparative example.

[0099] In the first comparative example, the wet seal pressure of the fuel electrode separator was 40 kPa, and the permeability coefficient was 5×10 -13 [m 2 / Pa·sec] and the porosity is 31%. The wet seal pressure of the oxidant electrode separator is 40 kPa, and the permeability coefficient is 5×10 -13 [m 2 / Pa·sec] and the porosity is 31%. The pressure range of the cooling water inside the fuel cell stack 102 is (-35 kPaG) to (-10 kPaG), as in this embodiment. The pressure on the fuel gas side is (+6 kPaG) to (+27 kPaG). Therefore, the maximum pressure difference between the cooling water and the fuel gas is 62 kPa.

[0100] On the other hand, the wet seal pressure of the anode separator is 40 kPa, as shown in FIG. 5. Furthermore, the porosity is 31%, which is larger than that of the present embodiment, and therefore the water permeability coefficient is also larger than that of the present embodiment. As a result, there is a possibility that the differential pressure between the cooling water and the fuel gas will exceed the wet seal pressure in some places. If the differential pressure between the cooling water and the fuel gas exceeds the wet seal pressure, the fuel gas will flow into the cooling water side, hindering the flow of the cooling water and further impeding the supply of fuel gas to the anode 110, causing malfunctions in the fuel cell 100.

[0101] As shown in FIG. 5, the oxidizer electrode separator also has similar characteristic values ​​to the fuel electrode separator, and therefore the same problems as those in the case of the fuel electrode separator occur.

[0102] <Comparison with the second comparative example> FIG. 6 is a second comparison table showing a comparison between the fuel cell 100 according to the embodiment and a second comparative example.

[0103] In the second comparative example, the wet seal pressure of the fuel electrode separator was 60 kPa, and the permeability coefficient was 3×10 -13 [m 2 / Pa·sec] and a porosity of 21%. Similarly, the wet seal pressure of the oxidant electrode separator is 70 kPa and the permeability coefficient is 3×10 -13 [m2 / Pa·sec] and the porosity is 21%.

[0104] The pressure range of the cooling water inside the fuel cell stack 102 is (-35 kPaG+α) to (-10 kPaG), as in this embodiment. The pressure on the fuel gas side is (+6 kPaG) to (+27 kPaG). Therefore, the maximum pressure difference between the cooling water and the fuel gas is 62 kPa.

[0105] On the other hand, the wet seal pressure is 60 kPa as shown in FIG. 6, which is a level that corresponds almost to the maximum differential pressure, and the possibility that the differential pressure between the cooling water and the fuel gas will exceed the wet seal pressure is small. On the other hand, the porosity is 21%, which is smaller than that of this embodiment, and therefore the water permeability coefficient is also smaller than that of this embodiment. As a result, the water permeability coefficient is 3×10 -13 [m 2 / Pa·sec], the liquid water absorption function of the gas flow path and the gas diffusion portion is low. As a result, plugging and flooding cannot be suppressed, and the cell voltage of the fuel cell 100 oscillates. That is, the cell voltage drops while the fuel gas is prevented from reaching the anode 110, and rises when the liquid water is blown away by the fuel gas or otherwise expelled. Furthermore, a localized fuel gas shortage at the anode 110 corrodes and deteriorates the anode 110.

[0106] As shown in FIG. 6, the oxidizer electrode separator also has similar characteristic values ​​to the fuel electrode separator, and therefore the same problems as those in the case of the fuel electrode separator occur.

[0107] As described above, the first and second comparative examples do not have a good balance between the wet seal pressure and the water permeability coefficient, and therefore are unable to achieve the same functions and effects as the present embodiment.

[0108] According to the embodiments described above, it is possible to provide a fuel cell and a fuel cell system that are shock resistant and effectively exhibit the function of the internal humidification method.

[0109] [Other embodiments] Although the embodiments of the present invention have been described above, they are presented as examples and are not intended to limit the scope of the invention. Furthermore, features of each embodiment may be combined. Furthermore, the embodiments may be implemented in various other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. The embodiments and their modifications are intended to be included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims. [Explanation of symbols]

[0110] 1... fuel cell system, 2... fuel gas supply device, 2a... fuel gas piping, 2b... liquefied fuel gas tank, 2c... pressure reducing valve, 3... oxidant gas supply device, 3a... oxidant gas piping, 3b... blower, 3c... outside air filter, 4... cooling water circulation device, 4a... open tank, 4b... suction side upstream cooling water piping, 4c... suction side downstream cooling water piping, 4d... pump, 4e... discharge side cooling water piping, 4f... cooler, 4g... suction side cooling water piping, 100... fuel cell, 101... fuel cell cell, 102... fuel cell stack, 105... solid polymer electrolyte membrane, 105a... first surface, 105b... second surface, 110... fuel electrode, 111... fuel electrode catalyst layer, 112... fuel electrode diffusion layer, 113... fuel electrode separator, 113a... fuel electrode separator anode separator rib contact surface, 113b... anode separator rib contact surface, 113c... anode separator rib contact surface, 115... fuel gas inlet portion, 116... fuel gas outlet portion, 120... oxidizer electrode, 121... oxidizer electrode catalyst layer, 122... oxidizer electrode diffusion layer, 123... oxidizer electrode separator, 123a... oxidizer electrode separator flow path, 123b... oxidizer electrode separator rib, 123c... oxidizer electrode separator rib contact surface, 125... oxidizer gas inlet portion, 126... oxidizer gas outlet portion, 131... cooling water flow path, 132... contact surface, 133... cooling water flow path rib, 135... cooling water inlet portion, 136... cooling water outlet portion, 140... electrode outer periphery, 150... porous separator, 160... metal powder processed body, 161... metal powder, 162... coating portion, 163... pores

Claims

1. A fuel cell including a fuel cell stack in which a plurality of fuel cell units that generate electricity using a fuel gas and an oxidant gas are stacked, Each of the plurality of fuel cell units is a solid polymer electrolyte membrane having hydrogen ion conductivity; a fuel electrode provided adjacent to a first surface of the solid polymer electrolyte membrane; an oxidizer electrode provided adjacent to the second surface of the solid polymer electrolyte membrane; an anode separator adjacent to the anode and having an anode separator flow path formed therein for supplying the fuel gas to the anode; an oxidizer electrode separator adjacent to the oxidizer electrode, the oxidizer electrode separator having an oxidizer electrode separator flow path formed therein for supplying the oxidizer gas to the oxidizer electrode; Equipped with At least one of the fuel electrode separator and the oxidizer electrode separator has a cooling water flow path formed on its back surface for cooling water for cooling the fuel cell stack, and is a porous separator manufactured using metal powder and having a plurality of pores formed therein that are capable of retaining water and that communicate from the cooling water flow path to at least one of the fuel electrode and the oxidizer electrode. A fuel cell characterized by:

2. 2. The fuel cell according to claim 1, wherein the porous separator is made of a material containing at least one of stainless steel and titanium as a main component.

3. 2. The fuel cell according to claim 1, wherein a coating portion is provided on the surface of the inner wall of the porous separator that faces the plurality of pores.

4. 4. The fuel cell according to claim 3, wherein the material of the covering portion contains at least one of resin, nickel, and chromium.

5. 2. The fuel cell according to claim 1, wherein the porous separator is made of a sintered body of the metal powder or a sintered body of the metal powder and metal fibers.

6. The porous separator is 4×10 －１３ [m ２ 2. The fuel cell according to claim 1, wherein the fuel cell has a water permeability coefficient of at least 100 [kPa / Pa·sec] and a wet seal pressure of at least 60 [kPa].

7. 7. The fuel cell according to claim 6, wherein the pressure of the fuel gas and the oxidant gas is greater than the pressure of the cooling water, and the wet seal pressure is greater than the pressure difference between the fuel gas and the cooling water and the pressure difference between the oxidant gas and the cooling water.

8. A fuel cell according to any one of claims 1 to 7; a fuel gas supply device for supplying the fuel gas to the fuel cell; an oxidant gas supply device for supplying the oxidant gas to the fuel cell; a cooling water circulator that supplies the cooling water to the fuel cell; A fuel cell system comprising:

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