JP3854682B2 - Fuel cell separator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a separator for a fuel cell, and particularly relates to a separator having a small contact resistance between a separator and an electrode of a unit cell.
[0002]
[Prior art]
Examples of fuel cells include solid polymer fuel cells, phosphoric acid fuel cells, and molten carbonate fuel cells. These fuel cells include a unit cell that generates an electromotive force due to an electrochemical reaction between an oxygen-containing gas and a hydrogen-containing gas, and a unit cell that is interposed between adjacent unit cells of the stacked unit cells. A separator that contacts the electrodes to electrically connect the unit cells and separates the reaction gas. As the separator, solid polymer fuel cells and phosphoric acid fuel cells include dense carbon. The material is used, and Ni / SUS clad material is used for molten carbonate fuel cells.
[0003]
[Problems to be solved by the invention]
However, the separator using the dense carbon material and the separator using the Ni / SUS clad material have a problem that the contact resistance with the electrode of the unit battery is large.
Therefore, the present invention has been made to solve such problems, and an object of the present invention is to provide a fuel cell separator having a low contact resistance with an electrode of a unit cell.
[0004]
[Means for Solving the Problems]
The fuel cell separator of the first invention is interposed between adjacent unit cells of the stacked unit cells, contacts both electrodes of the adjacent unit cells to electrically connect the unit cells, and reacts with the reaction gas. Is a separator made of a metal member and directly plated with gold only on the contact surfaces of the electrodes of both adjacent unit cells without applying base plating, so that the thickness of the gold plating is 0. A plurality of partial plating layers having a thickness of 01 to 0.06 μm are formed on both sides .
A fuel cell separator according to a second aspect of the present invention is the fuel cell separator according to claim 1, wherein the metal member is stainless steel.
The fuel cell separator of the third aspect of the present invention, in the fuel cell separator according to claim 1 or 2, wherein, you characterized by defining a reaction gas passage so as to face the said electrode.
[0005]
By applying gold plating directly only to the contact surface of the separator with the electrode without applying base plating, the contact resistance between the separator and the electrode is reduced, and electrons between the separator and the electrode are reduced. Conduction is performed well. Further, since the thickness of the gold plating for forming a plurality of partial plating layers on both sides of the fuel cell separator is set to 0.01 to 0.06 μm , there is no occurrence of pinholes as a starting point of corrosion in the gold plating . The contact resistance between the separator and the electrode of the unit cell becomes smaller and constant, the output voltage of the fuel cell is improved, and the amount of gold used per separator can be reduced, thereby reducing the cost.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Aluminum, titanium, Ni-iron alloy, stainless steel, etc. can be used for the metal member, but it is desirable to use stainless steel from the viewpoint of corrosion resistance.
The reaction gas passage formed between the separator and the electrode may be defined by forming a groove in the electrode, or may be defined by providing unevenness in the separator, particularly when the electrode is made of carbon. it is desirable to define a reaction gas passage irregularities provided on a metal separator.
Since the thickness of the gold plating applied to the separator, the results of experiments, it became clear that no particularly small becomes and the pinhole contact resistance when the 0.01~0.06μm the said thickness, the the thickness of the gold plating shall be the 0.01~0.06μm.
This separator can be employed in various fuel cells such as solid polymer fuel cells, phosphoric acid fuel cells, and molten carbonate fuel cells.
[0007]
【Example】
Hereinafter, as an example of the present invention, a fuel cell separator employed in a polymer electrolyte fuel cell will be described with reference to FIGS.
As shown in FIG. 1, the fuel cell separator 1 of this embodiment is made of stainless steel (SUS304), and the outer peripheral portion 2 has a reaction gas introduction flow hole 3, a reaction gas outflow flow hole 4, and A cooling water circulation hole 5 is formed, and a bulge forming portion 7 having a large number of irregularities is formed in the inner peripheral portion 6 by press molding. A gold plating layer 9 having a thickness of 0.01 to 0.02 μm is formed on the bulging tip side end face 8 of the bulging molded part 7.
As shown in FIG. 2, when forming a fuel cell, the separator 1 is interposed between the stacked unit cells 10, 11, and the electrodes 12, 13 of the unit cells 10, 11 and the bulging formed portion 7 are expanded. A gold plating layer 9 formed on the leading end side end face 8 is disposed so as to abut , and a reaction gas passage 14 is defined between the separator 1 and the electrodes 12 and 13 .
[0008]
The gold plating layer 9 of the separator 1 is subjected to a degreasing process, a cleaning process, a surface activation process, a cleaning process, a partial gold plating process, a cleaning process, and a drying process in this order without performing base plating on the press-molded separator material. Formed.
In the degreasing step, the fat and oil adhering to the surface of the separator material is removed using a strong alkaline degreasing agent.
In the surface activation step, an inorganic mixed acid and an organic inhibitor are used as treatment agents to activate and smooth the surface of the separator material.
In the partial gold plating process, a sparger method is used in which a plating treatment liquid is ejected from a nozzle to which a voltage is applied to the separator material to a portion to be plated to form a partial plating layer, and a cyan gold potassium solution is used as the plating treatment liquid. Partial plating is performed on the end surface 8 of the bulging tip side of the bulge forming portion 7 of the material.
[0009]
In order to investigate the influence of the gold plating layer 9 on the contact resistance between the separator 1 and the electrodes 12 and 13 of the unit cells 10 and 11, electrons are transferred from the separator 15 to the separator 17 through the electrode base 16 as shown in FIG. The conduction resistance when conducting was measured.
Hereinafter, the measurement of the conduction resistance will be described in detail. As shown in FIG. 3, an electrode base material 16 made of the same constituent material as the electrodes 12 and 13 of the unit cells 10 and 11 is sandwiched between a separator 15 and a separator 17 made of the same structure and material as the separator 1, The separator 15 and the separator 17 are sandwiched between a pair of current collector plates 19 and 20 connected to a constant current power source 18, and a potential difference generated between the separators 15 and 17 when a constant current is supplied between the separators 15 and 17 It detects with the potentiometer 21 connected in series between 15 and 17, converts this potential difference into resistance value, and acquires conduction | electrical_connection resistance. At this time, the current collecting plates 19 and 20 are held by the pressing plates 24 and 25 via the insulating plates 22 and 23, and the pressing plates 24 and 25 are pressed by a pressing device (not shown) to expand the separators 15 and 17. A predetermined surface pressure is applied to the leading end side end faces 26 and 27.
[0010]
FIG. 4 shows the relationship between the conduction resistance and the thicknesses of the gold plating layers 28 and 29 formed on the bulging tip side end surfaces 26 and 27 of the separators 15 and 17 under a constant surface pressure.
As can be seen from FIG. 4, the conduction resistance decreases as the thickness of the gold plating layers 28 and 29 decreases, and it becomes clear that the conduction resistance becomes substantially constant when the thickness is smaller than 0.06 μm.
[0011]
FIG. 5 shows the relationship between the conduction resistance and the surface pressure when the surface pressure applied to the bulging tip side end surfaces 26 and 27 of the separators 15 and 17 is changed (described as “Example” in the figure).
For comparison, a dense carbon separator and a Ni / SUS clad separator are prepared, and the electrode substrate 16 is sandwiched by the dense carbon separator instead of the separators 15 and 17, and the surface pressure is changed. The electrode substrate 16 is sandwiched between Ni / SUS clad separators instead of the separators 15 and 17 and the relationship between the conduction resistance and the surface pressure when the conduction resistance is measured (described as “Comparative Example 1” in the figure). Then, the relationship between the conduction resistance and the surface pressure (measured as “Comparative Example 2” in the figure) when the conduction resistance is measured while changing the surface pressure is also shown in FIG. In any separator, the apparent contact area with the electrode substrate 16 is the same.
[0012]
As is clear from FIG. 5, the tendency that the conduction resistance decreases as the surface pressure increases is the same for the separators 15 and 17, the dense carbon separator, and the Ni / SUS clad separator. As for the magnitude of the resistance, the separators 15 and 17 were the smallest.
[0013]
In order to investigate the corrosion resistance of the separator 1, a nitric acid aeration test (JIS H8621) was performed to confirm whether or not pinholes that would cause corrosion were present in the gold plating layer 9. As a result, it was confirmed that no elution of Cr was observed and no pinholes were formed when the thickness of the gold plating layer 9 was 0.01 μm or more.
[0014]
【The invention's effect】
According to the first invention, the fuel cell separator is formed of a metal member, and the gold plating is directly applied only to the contact surfaces of the electrodes of both adjacent unit cells without applying the base plating. Since the contact resistance with the electrode is reduced and the conduction of electrons from the separator to the electrode is improved, the output voltage of the fuel cell is increased. Further, since the thickness of the gold plating for forming a plurality of partial plating layers on both sides of the fuel cell separator is set to 0.01 to 0.06 μm, there is no occurrence of pinholes as a starting point of corrosion in the gold plating. The contact resistance between the separator and the electrode of the unit cell becomes smaller and constant, the output voltage of the fuel cell is improved, and the amount of gold used per separator can be reduced, thereby reducing the cost.
According to the second invention, since the metal member is made of stainless steel, the corrosion resistance is improved, and the durability is improved.
According to the third invention, since the separator faces the electrode and defines the reaction gas passage, the reaction gas passage can be defined by a metal separator that is easy to mold. it improves the productivity of the fuel cell.
[Brief description of the drawings]
FIG. 1 is a plan view of a fuel cell separator according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a contact state between the fuel cell separator and a unit cell.
FIG. 3 is a diagram showing a means for measuring conduction resistance.
FIG. 4 is a graph showing the relationship between the thickness of the gold plating layer and the conduction resistance.
FIG. 5 is a graph showing the relationship between surface pressure and conduction resistance.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fuel cell separator 8 Swelling front end side surface 9 Gold plating layer 10 Unit battery 11 Unit battery 12 Electrode 13 Electrode 14 Reactive gas passage

Claims (3)

A separator that is interposed between adjacent unit cells of the stacked unit cells, contacts both electrodes of the adjacent unit cells, electrically connects both unit cells, and separates the reaction gas;
A partial plating layer made of a metal member and directly plated with gold only on the contact surfaces of the electrodes of both adjacent unit cells without applying base plating, and having a gold plating thickness of 0.01 to 0.06 μm. A fuel cell separator , wherein a plurality of separators are formed on both sides . The fuel cell separator according to claim 1, wherein the metal member is made of stainless steel. The fuel cell separator according to claim 1 or 2, wherein a reaction gas passage is defined facing the electrode.

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