JP4239695B2 - Fuel cell separator and method of manufacturing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel cell separator and a method for producing the same.
[0002]
[Prior art]
2. Description of the Related Art A fuel cell, for example, a solid polymer electrolyte fuel cell includes a laminate of a membrane-electrode assembly (MEA) and a separator.
In a separator for a fuel cell, it is known to improve conductivity and corrosion resistance by plating or vapor-depositing gold or the like on the surface of a separator base material (stainless steel) (for example, JP 2002-367434 A). ).
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-367434
[Problems to be solved by the invention]
However, the separator fuel gas has a flow path for supplying an oxidizing gas to the MEA, therefore it has an uneven for the flow path, it is difficult to uniformly form the surface treatment layer. In order to solve this problem, according to the invention of Japanese Patent Application Laid-Open No. 2002-367434, after the surface treatment layer is formed, irregularities are formed by press working or the like.
However, if the surface treatment layer is formed by plating or vapor deposition, etc., and unevenness is applied by pressing or the like, the surface treatment layer may be cracked or the surface treatment layer may be peeled off, reducing the electrical conductivity and corrosion resistance. is there.
In addition, in the method of forming irregularities first and then forming the surface treatment layer by plating, vapor deposition or the like, it is difficult to form the surface treatment layer on the corners of the irregularities or the vertical walls of the grooves. good beauty, predetermined thickness to form a surface treatment layer of it is difficult corrosion resistance and abrasion resistance of the site is lowered to a predetermined site, a problem occurs.
The object of the present invention is to form a surface treatment layer on any part of the surface of the separator on which the irregularities are formed (also on the corners of the irregularities and the vertical walls of the grooves), and have a predetermined thickness, conductivity, An object of the present invention is to provide a fuel cell separator capable of forming a surface treatment layer having good corrosion resistance and a method for producing the same.
[0005]
[Means for Solving the Problems]
The present invention for achieving the above object is as follows.
(1) It has a base material of a separator and a surface treatment layer formed on the surface of the base material, and the surface treatment layer contains metal ultrafine particles having a particle diameter of 3 to 10 nm , and at the time of sintering progress and termination The metal ultrafine particles are bonded and fused together, and the resin is cured to form a solid layer,
The surface treatment layer discharges a solution containing conductive metal ultrafine particle paste containing the ultrafine metal particles, a scavenger, a binder and a dispersant onto the surface of the separator substrate by an ink jet method to form a coated surface. Thereafter, a separator for a fuel cell, which is manufactured by annealing.
(2) The fuel cell separator according to (1), wherein the surface treatment layer is formed in a single layer or multiple layers, and the material of the surface treatment layer is changed depending on a site.
(3) A solution containing conductive ultra-fine metal particle paste containing ultra-fine metal particles having a particle diameter of 3 to 10 nm , a scavenger, a binder, and a dispersant is ejected onto the surface of the separator substrate by an ink jet method. After the formation of the film, the metal ultrafine particles having a particle diameter of 3 to 10 nm are bonded and fused to each other when the sintering proceeds and ends , and the resin is cured to form a solid layer . A method for producing a fuel cell separator for forming a surface treatment layer.
[0006]
In the fuel cell separator according to (1) to ( 2 ) and the fuel cell separator according to ( 3 ), the number of nozzles, the inclination (coating direction), and the coating are applied because the layer is coated by an ink jet method. By appropriately selecting or changing the amount etc., it is possible to form a surface treatment layer with corrosion resistance on any part of the uneven separator (even on the corners of the unevenness and the vertical wall of the groove ) , by varying according to the injection amount of fine droplets of Lee inkjet to a site, the predetermined thickness to the predetermined portion, it is possible to form a good surface treatment layer of anti-corrosion. Further, a coating layer of metallic particulate paste, to anneal after the inkjet, the metal ultrafine particles each other fused, conductive surface treatment layer is ensured.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Below, the separator for fuel cells of this invention and its manufacturing method are demonstrated with reference to FIGS.
The fuel cell to which the separator of the present invention is assembled is, for example, a solid polymer electrolyte fuel cell 10. The fuel cell 10 is mounted on, for example, a fuel cell vehicle. However, it may be used other than an automobile.
[0008]
As shown in FIGS. 3 and 4, the solid polymer electrolyte fuel cell 10 is composed of a laminate of a membrane-electrode assembly (MEA) and a separator 18. The membrane-electrode assembly includes an electrolyte membrane 11 made of an ion exchange membrane, an electrode (anode, fuel electrode) 14 having a catalyst layer 12 disposed on one surface of the electrolyte membrane, and a catalyst disposed on the other surface of the electrolyte membrane 11. It comprises an electrode (cathode, air electrode) 17 having a layer 15. Between the catalyst layers 12 and 15 and the separator 18, diffusion layers 13 and 16 are provided on the anode side and the cathode side, respectively.
[0009]
In each cell, a reaction for converting hydrogen into hydrogen ions (protons) and electrons is performed on the anode side, and the hydrogen ions move through the electrolyte membrane to the cathode side. On the cathode side, oxygen, hydrogen ions, and electrons (neighboring MEA) Next, the following reaction is performed to generate water from electrons generated at the anode of the first electrode through the separator or electrons generated at the anode of the cell at one end in the cell stacking direction through the external circuit to the cathode of the other cell.
Anode side: H ₂ → 2H ⁺ + 2e ⁻
Cathode side: 2H ⁺ + 2e ⁻ + (1/2) O ₂ → H ₂ O
[0010]
As shown in FIG. 3, the film - to overlap the electrode assembly and the separator 18 constitute a cell 19, constitute a module from at least one cell, the cell stack by stacking modules, cell stack of the cell stack Terminals 20, insulators 21 and end plates 22 are arranged at both ends in the direction, the cell stack is clamped in the cell stacking direction, a fastening member (for example, tension plate 24) extending in the cell stacking direction outside the cell stack, bolt, The stack 23 is configured by fixing with the nut 25.
[0011]
In order to perform the above reaction, the separator 18 is formed with a fuel gas flow path 27 for supplying fuel gas (hydrogen) to the anode 14, and for supplying oxidizing gas (oxygen, usually air) to the cathode 17. The oxidizing gas flow path 28 is formed. Further, in order to take heat generated by the above reaction, the separator is also formed with a refrigerant flow path 26 for flowing a refrigerant (usually cooling water).
In FIG. 4, 40 is a rubber gasket, and 33 is a seal adhesive.
[0012]
The separator 18 is made of carbon, metal, metal and resin (metal separator and resin frame), resin imparted with conductivity, or a combination thereof. FIG. 4 shows the case of a metal separator (for example, a stainless steel separator). However, the separator 18 is not limited to a metal separator.
[0013]
As shown in FIG. 1 and FIG. 2, adjacent cells on the surface of the separator 18 in which the projections and depressions are in contact with the refrigerant (the surface on the back side of the surface in contact with the reaction gas such as fuel gas and oxidizing gas). In order to maintain good conductivity with the 19 separators 18, to suppress the corrosion of the separators by cooling water, and to be worn by rubbing against the separators 18 of the adjacent cells 19 during assembly into the stack. In order to suppress it, the surface treatment layer 18b having conductivity and corrosion resistance is formed. The surface treatment layer 18 b is formed on the surface of the base material 18 a of the separator 18. The base material 18a of the separator 18 is a metal when the separator 18 is a metal separator, and is carbon when the separator 18 is a carbon separator.
[0014]
The surface treatment layer 18b having electrical conductivity and corrosion resistance is formed by an ultra-fine inkjet device 50 (a device capable of ejecting ultra-fine droplets of 1/1000 or less of the conventional inkjet, droplets having a diameter of 1 micron or less with a dot interval of about 3 microns capable of ejecting apparatus) using a conductive metal particulate paste 52 (metal ultrafine particles out ejection of the solution particle size containing 3 to 10 nm) on the surface of the base material 18a of the separator 18, the coated surface After the formation, it is manufactured by annealing (heat treatment at about 200 ° C.) .
[0015]
As shown in FIG. 2, the conductive metal ultrafine particle paste 52 is a viscous paste containing metal ultrafine particles (for example, silver ultrafine particles, particle diameter is 5 nm, for example) 52a, a scavenger 52b, a binder 52c, a dispersant 52d, and the like. Yes, it is diluted with an organic solvent to form a low-viscosity solution, and the solution is applied by an inkjet method. During annealing (heat treatment), the scavenger removes the dispersant at the start of sintering, and when the sintering progresses and ends, the ultrafine metal particles are bonded and fused together to ensure conductivity, and the resin is cured and solid. It is a layer. In general, the conductive droplets ensure electrical conductivity through contact between particles, whereas in the case of ultrafine particle pastes, electrical conductivity is ensured by fusion and integration between metal ultrafine particles.
[0016]
The surface treatment layer 18b is composed of a layer in which the conductive metal ultrafine particle paste 52 is applied in a planar shape and annealed (heat treated and cured). The surface treatment layer 18b is formed in one layer or multiple layers. In the case of forming in multiple layers, the upper layer is applied and annealed after the lower layer is cured. The surface treatment layer 18b is made of a uniform material in the in-plane direction and the thickness direction, or the material is changed according to the portions in the in-plane direction and the thickness direction. Since it is an ink jet system, it is possible to change the nozzle or the paste mixing ratio according to the application site, and the material can be changed according to the site.
[0017]
The method for forming the surface treatment layer 18b is as follows.
First, a step of forming a coating surface by discharging a solution obtained by diluting the conductive metal ultrafine particle paste 52 onto the surface of the base material 18a of the separator 18 having the unevenness, and then annealing (heat treatment). And a step of forming a surface treatment layer 18b having conductivity and corrosion resistance.
When the metal becomes ultrafine particles, the melting point decreases due to the size effect (the band gap increases as the particle size is reduced), so that the fusion proceeds even at room temperature. Therefore, in the paste stage, the dispersion of ultrafine particles is suppressed by adding a dispersant. However, since the electrical conductivity cannot be obtained if the particles are separated from each other, a trapping agent is added, and during heating, the dispersant is trapped and removed so that the fusion of the ultrafine particles proceeds at a stretch. .
[0018]
【Example】
On the surface of the separator on the side of the stainless steel substrate 18a that is in contact with the coolant, a conductive, silver ultrafine particle paste (fine particle diameter: 5 nm) is ejected by ultrafine ink jet to form a conductive layer. One layer of the coating surface was formed with a droplet having a diameter of about 1 micron and a dot interval of about 3 microns. After repeating the discharge three times, annealing was performed at about 200 ° C. for 30 minutes to fuse the ultrafine particles of the discharge layer, and the coated surface was cured.
A conductive silver ultrafine particle paste (fine particle diameter: 5 nm) is ejected onto the above coated surface by conventional ink jet, and the conductive layer is coated with a droplet having a diameter of about 20 microns and a dot interval of about 20 microns. 1 layer was formed. After repeating the discharge twice, annealing was performed at about 200 ° C. for 30 minutes to fuse the ultrafine particles of the discharge layer, and the coated surface was cured.
Thus, a multi-layered conductive surface treatment layer 18b was formed. The surface treatment layer 18b can be formed on any part of the separator surface on which the irregularities are formed (even on the corners of the irregularities and the vertical walls of the grooves), and has a predetermined thickness, a predetermined thickness, and good conductivity and corrosion resistance. The surface treatment layer 18b could be formed.
[0019]
【The invention's effect】
According to the manufacturing method of the fuel cell separator of claims 1 and 2 and the fuel cell separator of claim 3 , the number of nozzles, the inclination (application direction), the application amount, etc., for the layer applied by the ink jet method. or suitably selected, or by varying (also the vertical wall corners or grooves of the irregularities) in any part of an uneven separator, capable of forming a surface treatment layer having corrosion resistance, also, Lee inkjet by varying according to the injection amount of fine droplets to the site, the predetermined thickness to the predetermined portion, it is possible to form a good surface treatment layer of anti-corrosion. Further, a coating layer of metallic particulate paste, to anneal after the inkjet, the metal ultrafine particles each other fused, conductive surface treatment layer is ensured.
[Brief description of the drawings]
FIG. 1 is a side view of an apparatus for manufacturing a fuel cell separator according to the present invention.
FIG. 2 is an enlarged sectional view of the structure of a heat treatment process of a fuel cell separator according to the present invention.
FIG. 3 is a side view of a stack of fuel cells.
4 is a cross-sectional view of a portion of the stack of FIG.
[Explanation of symbols]
10 (Solid Polymer Electrolyte Type) Fuel Cell 11 Electrolyte Membrane 12, 15 Catalyst Layer 13, 16 Diffusion Layer 14 Electrode (Anode, Fuel Electrode)
17 electrodes (cathode, air electrode)
18 Separator 18a Base material 18b Surface treatment layer 19 Cell 20 Terminal 21 Insulator 22 End plate 23 Stack 24 Fastening member (tension plate)
25 Bolt 26 Refrigerant flow path (cooling water flow path)
27 Fuel gas channel 28 Oxidizing gas channel 33 Seal adhesive 40 Rubber gasket 50 Ultrafine inkjet device 51 Normal inkjet device 52 Conductive metal ultrafine particle paste 52a Metal ultrafine particle 52b Capture agent 52c Binder 52d Dispersant

Claims (3)

A separator base material and a surface treatment layer formed on the surface of the base material, wherein the surface treatment layer contains metal ultrafine particles having a particle size of 3 to 10 nm , and the metal The ultrafine particles are bonded and fused together, and the resin is cured to form a solid layer.
The surface treatment layer discharges a solution containing conductive metal ultrafine particle paste containing the ultrafine metal particles, a scavenger, a binder and a dispersant onto the surface of the separator substrate by an ink jet method to form a coated surface. Thereafter, a separator for a fuel cell, which is manufactured by annealing.   2. The fuel cell separator according to claim 1, wherein the surface treatment layer is formed in one layer or multiple layers, and the material of the surface treatment layer is changed depending on a part. After forming a coated surface by discharging a solution containing conductive ultrafine metal particle paste containing ultrafine metal particles with a particle size of 3 to 10 nm , a scavenger, a binder, and a dispersant onto the surface of the separator substrate by an inkjet method. The surface treatment layer in which the metal ultrafine particles having a particle diameter of 3 to 10 nm are bonded and fused to each other at the time of sintering progress and termination by annealing , and the resin is cured to be a solid layer The manufacturing method of the separator for fuel cells which forms.

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