JP2010186685A - Fuel battery and fuel battery system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain electric contact resistance between a collector and a separator of a fuel battery for a long period of time. <P>SOLUTION: The fuel battery includes a laminated body 19 laminating a plurality of layers of unit cells 31 each equipped with an electrolyte film 10, a fuel electrode 38 and an oxidant electrode 39 pinching the electrolyte film 10 from either side, and conductive separators 11, 18 having a fuel gas circulation channel 12 supplying fuel gas to the fuel electrode 38 as well as an oxidant gas circulation channel 13 supplying oxidant gas to the oxidant electrode 39. The fuel battery is further provided with a collector plate 32 arranged at an outside face of the separator 18 at an end part of the laminated body 19 for extracting power generation current of the laminated body 19 outside, and a clamping plate 33 arranged outside the collector plate 32 for clamping the laminated body 19 in its lamination direction. The collector plate 32 includes a rugged part formed on a face of the separator 18 in contact with an outside face of the laminated body 19. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell and a system thereof having a laminate in which unit cells are laminated and a current collector plate, and in particular, a contact electric resistance between the current collector plate and a separator (hereinafter simply referred to as “contact resistance”). The present invention relates to a fuel cell that can be controlled over a long period of time and a system thereof.

  A fuel cell is a power generator that supplies fuel such as hydrogen and an oxidant such as air to the fuel cell body and reacts them electrochemically, thereby converting the chemical energy of the fuel directly into electrical energy and taking it out. It is.

  In a conventional fuel cell using a typical solid polymer membrane, a laminate in which a plurality of unit cells (unit cells) are laminated is formed. Each unit cell has a fuel electrode (anode electrode) and an oxidant electrode (cathode electrode) coated with a catalyst on both ends of the solid polymer membrane, and has a fuel gas flow path and an oxidant gas flow path on both sides thereof. It consists of a fuel electrode flow path plate and an oxidant electrode flow path plate. A plurality of unit cells are stacked, current collector plates and clamping plates are positioned at both ends of the stacked body, and the stacked body is tightened with studs, nuts, and disc springs (see Patent Document 1).

  This polymer electrolyte fuel cell stack is generally configured by inserting a separator for each cell. This separator has a cooling and heat removal function for removing heat generated by cell power generation, a conductive function for electrically connecting cells in series, and a fuel flowing to the separator side of one of the cells arranged via the separator. It has a reactive gas blocking function for preventing the mixing of the oxidant gas flowing to the separator side of the other one cell arranged via the separator same as the gas.

  On the other hand, the extraction of the electric energy from the polymer electrolyte fuel cell to the outside is performed through current collecting plates installed at both ends of the laminate in which a plurality of unit cells are laminated. This current collector plate needs to function as a function of stably and efficiently extracting current from the contacting cells in the power generation environment of the fuel cell or supplying the current to the contacting cells. The energy loss at the current collector can be shown as the voltage loss of the current collector, and it is important to reduce it. In order to reduce the voltage loss, it is necessary to reduce the resistance of the current collector plate itself and the contact resistance between the current collector plate and the separator in contact with the current collector plate. It is important to reduce the contact resistance between separators and prevent an increase over time.

  This contact resistance is determined by the material of the current collector plate and the separator, and the tightening contact pressure of both materials. Further, the relationship between the tightening contact pressure and the contact resistance generally shows a substantially constant contact resistance above a certain predetermined contact pressure, but when the pressure falls below a certain predetermined contact pressure, the contact resistance rapidly increases with the decrease. Increased insulation properties.

  From these facts, in order to reduce the contact resistance and keep it low, the contact resistance with the separator material is small, and the total tightening force is reduced due to the plastic deformation of the laminate under battery operation, and the accompanying contact. It is necessary to make the material / structure less sensitive to contact pressure against in-plane contact pressure drop and surface pressure distribution change (generation of contact pressure distribution due to concentration of surface pressure).

  In order to realize these, as a method for preventing contact resistance increase due to corrosion of the current collector plate, a method of coating a noble metal that is stable against corrosion (Patent Document 2), or plastic deformation of the laminate under battery operation As a result, there is known a method (Patent Document 1) or the like that suppresses a decrease in contact pressure as a result of tightening the laminated body via a spring for reducing the tightening force.

Japanese Patent No. 2566757 JP-A-5-182679

  However, while the noble metal coating current collector plate itself has high reliability against corrosion, it is very expensive and has become a bottleneck for commercialization. In order to maintain the battery clamping pressure, it is effective from the point of absorbing the plastic deformation of the laminate with a spring and mitigating the reduction in clamping force, that is, mitigating the reduction in contact pressure between the current collector and separator. Since a special large spring is required, it is similarly a bottleneck for commercialization from the viewpoint of cost.

  Further, even in a general fuel cell including the above laminate, the current collector plate and the separator are generally in surface contact since the contact surfaces thereof are both smooth surfaces. On the other hand, the various components of the laminate have differences in mechanical strength and compression elastic properties, and the surface pressure distribution due to the tightening method and the mechanical strength / compressive elastic properties of these components under tightening of the laminate have. The initial tightening force of the laminate is set so that the minimum pressure in the generated surface pressure distribution is equal to or higher than a predetermined surface pressure at which the contact resistance depending on the material of the current collector plate and the separator increases rapidly.

  However, as the battery is operated for a long period of time, plastic deformation of the laminate components is inevitable due to the temperature and operating environment, resulting in a change in the initial surface pressure distribution. The change in surface pressure distribution due to this plastic deformation is in the direction in which the surface pressure is concentrated, and the contact surface pressure increases in the portion where the plastic deformation is small, and the surface pressure decreases more in the large portion. When the surface pressure value of the surface pressure reduction portion is lower than a certain value, the resistance of the current collector plate as a whole increases and the voltage loss increases, which causes a problem of reducing the power generation efficiency as a battery.

  This invention is made | formed in view of the above, The objective is to suppress the contact electrical resistance between the collector plate of a fuel cell and a separator over a long period of time.

  In order to achieve the above object, a fuel cell according to the present invention supplies an electrolyte membrane, a fuel electrode and an oxidant electrode arranged so as to sandwich the electrolyte membrane from both sides, and a fuel gas to the fuel electrode. A stack of unit cells having a plurality of unit cells each including a fuel gas flow passage for supplying a conductive gas and a conductive plate separator having an oxidant gas flow passage for supplying an oxidant gas to the oxidant electrode; The laminate, wherein the separator disposed at the end of the laminate is disposed in contact with the outer surface of the laminate, and an uneven portion is formed on a surface of the separator that is in contact with the outer surface of the laminate. It has an electroconductive current collection board which takes out the generated current of a body outside, and a clamping board which is arranged outside the current collection board and clamps the layered product in the layering direction.

  ADVANTAGE OF THE INVENTION According to this invention, the contact electrical resistance between the collector plate of a fuel cell and a separator can be suppressed over a long period of time.

The typical fragmentary longitudinal cross-section which shows the current collection part vicinity of the laminated body of one Embodiment of the fuel cell which concerns on this invention. The elevation view which shows the main body of the state which removed the manifold of one embodiment of the fuel cell concerning the present invention. The typical plane sectional view of one embodiment of the fuel cell concerning the present invention. FIG. 4 is a partial vertical sectional view taken along line IV-IV in FIG. 3. The partial perspective view which looked at the current collecting plate of one Embodiment of the fuel cell which concerns on this invention from the edge part separator side which contact | connects this. The table | surface which shows the test result of the time-dependent change of the voltage loss of the current collecting plate in one Embodiment of the fuel cell which concerns on this invention.

  Hereinafter, an embodiment of a fuel cell according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic partial longitudinal sectional view showing the vicinity of a current collecting portion of a laminated body of an embodiment of a fuel cell according to the present invention, and FIG. 2 is a state in which a manifold of an embodiment of the fuel cell according to the present invention is removed. It is an elevation view which shows the main body. 3 is a schematic plan sectional view of one embodiment of the fuel cell according to the present invention, and FIG. 4 is a partial vertical sectional view taken along line IV-IV in FIG. FIG. 5 is a partial perspective view of the current collector plate of one embodiment of the fuel cell according to the present invention as viewed from the end separator side in contact with the current collector plate. However, in FIG. 1, studs, nuts, disc springs and the like for tightening the laminate are omitted. Further, FIG. 1 shows only one side of the current collecting structure at both ends of the laminate.

[Configuration of the embodiment]
In this fuel cell, as shown in FIG. 2, a plurality of unit cells (unit cells) 31 are stacked to form a stacked body (stack) 19, and two current collectors are disposed at both ends of the stacked body 19 in the stacking direction. A plate 32 is arranged, and two clamping plates 33 are arranged so as to sandwich the current collecting plates 32 from the outside. A plurality of studs 34 extending in the laminating direction are arranged around the fastening plates 33, whereby the laminated body 19 is clamped in the laminating direction by nuts and disc springs. The fastening plate 33 is made of an insulating material such as plastic.

  As shown in FIG. 4 and the like, this fuel cell uses a solid polymer electrolyte membrane 10, and each unit cell 31 has an anode electrode (fuel electrode) in which a catalyst is applied to both surfaces of the solid polymer membrane 10, respectively. ) 38 and a cathode electrode (oxidizer electrode) 39, and the separator 11 is disposed on both sides of the cathode electrode (oxidant electrode) 39. The separator 11 has a plate shape made of a conductive material such as carbon. The separator 11 has a groove that forms the fuel gas flow passage 12 formed on the surface in contact with the anode 38, and the oxidant gas flow passage on the surface in contact with the cathode 39. 13 is formed. Furthermore, in the example shown in FIGS. 1, 3, and 4, a cooling water flow passage 22 is formed in the separator 11.

  As illustrated in FIG. 3, in order to supply fuel gas, oxidant gas, and cooling water to the fuel gas flow path 12, the oxidant gas flow path 13, and the cooling water flow path 22 of each unit cell 31, respectively, A fuel gas supply gas manifold 14, an air supply gas manifold 15, and a cooling water supply manifold 41 are disposed around 19. Further, in order to discharge the fuel gas, the oxidant gas, and the cooling water from the fuel gas flow path 12, the oxidant gas flow path 13, and the cooling water flow path 22 of each unit cell 31, respectively, a fuel gas discharge gas manifold 16 and air An exhaust gas manifold 17 and a cooling water discharge manifold 42 are arranged around the laminate 19.

  In addition, a fuel gas supply device for supplying fuel gas to the fuel cell, a cooling water circulation facility for supplying cooling water, a control device for controlling various devices, etc. (not shown) are arranged to constitute a fuel cell system. ing.

  As shown in FIG. 1, the current collector plate terminal portion 21 is disposed through a hole penetrating the fastening plate 33. The current collector terminal portion 21 is made of a conductive material, and one end is fixed to the current collector plate 32. The current collecting plate 32 is made of a conductive material such as oxygen-free copper, and a surface 50 in contact with the end separator 18 is provided with a rough surface formed by machining embossing as shown in FIG. Is given. In forming the concavo-convex surface, for example, one surface of a flat plate may be cut to form a plurality of grooves 51 in the vertical and horizontal directions, and these may be used as concave portions, and the remaining portions may be used as convex portions 52. In this case, the tip of the convex portion 52 is preferably a flat surface. The thickness of the current collector plate 32 is, for example, 5 mm, and the height of the unevenness is, for example, 0.5 mm. The area ratio with respect to the entire convex portion 52 is preferably about 30 to 60%.

  Around the current collector plate 32, a peripheral seal portion 20 is disposed so as to surround the current collector plate 32 by being sandwiched between the end separator 18 and the fastening plate 33 disposed at the end portion of the laminate 19. Yes. The peripheral seal portion 20 has a function of preventing moisture from entering the current collector plate 32 from the side surface during operation and stop of the fuel cell.

  The size of the current collecting portion of the current collecting plate 32 is preferably larger than the reaction portion of each unit cell 31 and the same as or smaller than the inside of the peripheral seal portion 20.

[Operation of the embodiment]
Next, the operation of the fuel cell of this embodiment will be described.

  The fuel gas containing hydrogen is supplied from the fuel gas supply gas manifold 14 to the fuel gas flow passage 12 of each unit cell 31 and is discharged through the fuel gas exhaust gas manifold 16. Similarly, air, which is an oxidant gas containing oxygen, is supplied from the air supply gas manifold 15 to the oxidant gas flow passage 13 of each unit cell 31 and is discharged through the air exhaust gas manifold 17. The cooling water is supplied from the cooling water supply manifold 41 to the cooling water flow passage 22 and is discharged through the cooling water discharge manifold 42. As a result, power is generated in each unit cell 31 and cooling is performed.

  The battery reaction consumes hydrogen in the fuel gas and oxygen in the oxidant gas, and the reaction product water is discharged as water vapor.

  Electrical energy from the polymer electrolyte fuel cell is taken out through the current collector plate 32. Since irregularities are formed on the surface 50 of the current collector plate 32 facing the end separators 18 located at both ends of the laminate 19, the convex portions 52 of the surface 50 and the end separators 18 are pressed against each other. This ensures electrical contact. Moreover, the current collecting plate 32 can stably and efficiently take out current from the cells in contact with each other in the power generation environment of the fuel cell. The energy loss at the current collector plate 32 can be shown as the voltage loss of the current collector plate 32, but this can be reduced. Moreover, it is possible to prevent the contact resistance between the current collector plate 32 and the end separator 18 in contact with the current collector plate 32 from increasing with time.

  According to this embodiment, the contact resistance between the end separator 18 and the current collector plate 32 is small, and the total tightening force is reduced due to the plastic deformation of the laminate 19 under battery operation, and the contact pressure in the contact surface is reduced accordingly. A structure having a small contact pressure sensitivity to a change in the contact pressure distribution (generation of contact pressure distribution due to concentration of contact pressure) can be achieved. Thereby, contact resistance reduction and maintenance are realizable.

  That is, in this embodiment, by reducing the contact area between the current collector plate 32 and the end separator 18, the contact pressure between the current collector plate 32 and the end separator 18 is increased under the same tightening force. can do. In addition, with respect to changes in the surface pressure distribution due to the individual plastic deformation differences of the laminate 19 components under battery operation, the surface pressure of the contact surface is reduced even at the portion where the surface pressure is the lowest. It can be maintained higher than the contact surface pressure. That is, even if the flat current collector 32 has the same surface pressure distribution that causes an increase in contact resistance, the surface pressure of the contact surface can be maintained at a predetermined surface pressure or higher, at which the contact resistance increases rapidly. Thereby, it is possible to realize a stable fuel cell having a stable contact resistance for a long period of time, that is, without an increase in voltage loss and energy loss.

[Testing of Examples]
A battery was assembled with the above configuration, and a power generation test was performed to confirm the effect of the embodiment of the present invention. Further, as a comparison, a current collecting plate 32 having the same shape as the copper current collecting plate 32 without embossing and the copper current collecting plate 32 without nickel plating embossing was assembled, and each battery was assembled in the same manner as described above, and a power generation test was performed. The test results are shown in FIG. Here, the current collector plate A is a conventional type using a smooth copper plate (no plating), and the current collector plate B is a conventional type in which the surface of the current collector plate A is subjected to nickel plating, and the current collector plate C Is a current collector plate (nickel-plated embossed copper plate) of an embodiment of the present invention.

  The effect of the embodiment of the present invention was evaluated by the voltage loss between the gold wire terminals embedded in the end separator 18 in contact with the current collector plate terminal portion 21 when a constant generated current was taken out. In addition, a start / stop test was performed, and the change in voltage loss due to this was measured. In FIG. 6, the voltage loss is 1.0 as the voltage loss under a predetermined extraction current in the first power generation test of the current collector plate (oxygen-free copper plate), and the other test results are relative values. Indicated.

  As shown in the results of FIG. 6, it was confirmed that the voltage loss of the current collector plate A using the conventional copper plate increased rapidly with the number of start / stop operations. Further, the conventional current collector plate B subjected to nickel plating shows an increasing tendency although the increase in voltage loss is smaller than that of the conventional copper current collector due to the effect of preventing the formation of the copper surface oxide film. In the nickel-plated embossed current collector plate C according to the example of the present invention, although the initial voltage loss was large, the increase in the voltage loss due to start / stop was small and confirmed to be stable.

  As is clear from the above test results, the current collecting plate of the fuel cell is obtained by using the current collecting plate 32 formed with the nickel-plated after forming the convex surface by the embossing of machining on the oxygen-free copper plate according to the embodiment of the present invention. It was confirmed that the power generation loss and energy loss of the part were reduced.

[Modification]
Although the embodiment of the fuel cell according to the present invention has been described above, this is merely an example, and the present invention is not limited to this.

  For example, in the description of the above embodiment, the unevenness of the current collector plate 32 is formed by embossing. However, other machining or chemical treatment may be used as long as the processing method can form the same unevenness.

  Furthermore, the uneven shape of the current collector plate 32 is not limited to a linear shape as shown in FIG. 5, but may be a curved shape, for example, a concentric or spiral groove or ridge. Good.

  Moreover, although the case where nickel plating was performed in order to suppress the oxide production | generation of the copper surface of the current collecting plate 32 was shown in description of the said embodiment, it is not necessary to limit to this and it has sufficient electroconductivity (formation) Any plating may be used as long as the decrease in conductivity due to the surface oxide layer is small), has sufficient strength, and can prevent oxygen diffusion to the base metal plate. That is, the same effect can be obtained by metal plating such as tin (Sn), silver (Ag), platinum (Pt), gold (Au), ruthenium (Ru), rhodium (Ro), iridium (Ir).

  In the above description, expressions such as “elevation” and “plan” are used for convenience of explanation, and how this fuel cell is arranged in the direction of gravity. May be.

10: Solid polymer electrolyte membrane 11: Separator 12: Fuel gas flow passage 13: Oxidant gas flow passage 14: Fuel gas supply gas manifold 15: Air supply gas manifold 16: Fuel gas discharge gas manifold 17: Air discharge gas manifold 18 : End separator 19: Laminate 20: Peripheral seal 21: Current collector terminal 22: Cooling water passage 31: Unit cell 32: Current collector 33: Fastening plate 34: Stud 38: Anode electrode (fuel electrode)
39: Cathode electrode (oxidizer electrode, air electrode)
41: Cooling water supply manifold 42: Cooling water discharge manifold 50: Surface 51: Groove 52: Convex

Claims (7)

An electrolyte membrane, a fuel electrode and an oxidant electrode arranged so as to sandwich the electrolyte membrane from both sides thereof, a fuel gas flow passage for supplying fuel gas to the fuel electrode, and an oxidant gas in the oxidant electrode A laminate obtained by laminating a plurality of unit cells each including a conductive plate-like separator having an oxidant gas flow passage for supplying;
The laminated body, which is disposed in contact with an outer surface of the laminated body of the separator disposed at an end portion of the laminated body, and an uneven portion is formed on a surface contacting the outer surface of the laminated body of the separator. A conductive current collector plate for extracting the generated current to the outside,
A clamping plate that is disposed outside the current collector plate and clamps the laminate in the laminating direction;
A fuel cell comprising:   2. The fuel cell according to claim 1, wherein conductive metal plating is applied to at least a surface of the convex portion of the concavo-convex portion.   3. The fuel cell according to claim 2, wherein a material of the metal plating is any one of tin, silver, platinum, gold, ruthenium, rhodium, iridium, or a combination thereof.   The fuel cell according to any one of claims 1 to 3, wherein a main material of the current collecting plate is any one of copper, iron, stainless steel, and aluminum. A peripheral seal portion disposed so as to surround the current collector plate sandwiched between the separator disposed at the end of the laminate and the fastening plate;
The size of the current collecting portion of the current collecting plate is larger than the reaction portion of each unit cell and is the same as or smaller than the inside of the peripheral seal portion. The fuel cell according to item.   6. The fuel cell according to claim 5, wherein the uneven portion of the current collector plate is formed by forming a plurality of linear grooves by cutting a flat surface to form a plurality of linear grooves.   A fuel cell system using the fuel cell according to any one of claims 1 to 5.

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