JP5347456B2 - FUEL CELL STACK AND VEHICLE HAVING FUEL CELL STACK - Google Patents

Description

  The present invention relates to a fuel cell stack and a vehicle having the fuel cell stack.

  In recent years, solid polymer fuel cells have attracted attention as clean energy supply sources. A solid polymer fuel cell has a basic unit of a single cell in which a catalyst layer and a gas diffusion layer are arranged on both surfaces of an electrolyte membrane and these are sandwiched by a separator having a gas flow path. In order to obtain a high voltage, a plurality of single cells are generally stacked and electrically connected to be used as a fuel cell stack.

  The separator allows a fuel gas such as hydrogen or methanol or an oxidant gas such as air to flow into the fuel cell stack and electrically connects the single cells. For this reason, a separator excellent in corrosion resistance, strength, and conductivity is preferable. For example, the inventors of Patent Document 1 apply diamond-like carbon (Diamond-Like Carbon, hereinafter simply to a substrate formed of a metal such as an aluminum alloy). The separator is produced by forming a film (referred to as DLC).

The electric power of the plurality of single cells electrically connected by the separator is taken out through the current collector provided in the fuel cell stack. The current collector is generally positioned in the stacking direction of the single cells, and is in contact with the separator provided in the single cell positioned at the end in the stacking direction among the plurality of single cells. In order to improve conductivity, the current collector has, for example, a gold plating on the surface.
International Publication No. WO01 / 006585 Pamphlet

  However, for example, when a separator having a DLC film formed on an aluminum base as mentioned above is in contact with a current collector with gold plating, that is, when dissimilar metals are in contact with each other, one of them becomes base and corrosion occurs. The fuel cell stack may not be able to exhibit good current collecting performance.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a fuel cell stack capable of exhibiting good current collecting performance, and a vehicle having such a fuel cell stack. .

In order to achieve the above object, a fuel cell stack of the present invention includes a plurality of stacked single cells, and is arranged in the stacking direction of the single cells, and is electrically connected to a separator included in the single cells to extract the power of the single cells. A current collector. In the current collector, the surface is formed of a metal different from the surface material of the separator. In addition, the fuel cell stack includes a separator provided in a single cell located at an end in the stacking direction among a plurality of single cells, and a buffer member that is sandwiched between current collectors and prevents contact between different metals in the separator and current collectors Have In the buffer member, the standard electrode potential of the first contact portion in contact with the separator is equal to the standard electrode potential of the separator surface in contact with the first contact portion. In the buffer member, the standard electrode potential of the second contact portion in contact with the current collector is equal to the standard electrode potential of the current collector surface in contact with the second contact portion.

  In order to achieve the above object, a vehicle of the present invention has the fuel cell stack described above.

  According to the present invention, the buffer member prevents contact between different metals in the current collector and the separator, thereby suppressing corrosion of the both and exhibiting good current collecting performance.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that, in the embodiments and modifications described below, members having a common function are denoted by similar reference numerals, and redundant description is omitted.

<Fuel cell stack>
1 is a schematic cross-sectional view showing a fuel cell stack, FIG. 2 is an enlarged cross-sectional view showing a portion surrounded by reference numeral 2 in FIG. 1, and FIG. 3 is a schematic cross-sectional view showing another example of the fuel cell stack.

  As outlined in FIG. 1, the fuel cell stack 100 has a plurality of stacked single cells 140, 150, 160. The fuel cell stack 100 is also arranged in the stacking direction of the single cells 140, 150, 160 and is electrically connected to the separators 142, 143, 162 included in the single cells 140, 150, 160 and connected to the single cells 140, 150, 160. Current collector plate 120 (corresponding to a current collector) for taking out the power of the current. In the current collector plate 120, the surface is formed of a metal different from the metal on the surfaces of the separators 142, 143, and 162.

  The fuel cell stack 100 also includes a buffer member 130 that prevents contact between different metals in the separators 142 and 162 and the current collector plate 120. Separators 142 and 162 and current collector plate 120 provided in single cells 140 and 160 located at the end in the stacking direction among the plurality of single cells 140, 150 and 160 sandwich buffer member 130.

  The fuel cell stack 100 further includes an end plate 110 that sandwiches the single cells 140, 150, 160, the buffer member 130, and the current collector plate 120 from the stacking direction. The material forming the end plate 110 is, for example, an insulating resin.

  The single cell 140 includes a membrane electrode assembly 141 that promotes an electrochemical reaction of fuel gas and oxidant gas, and separators 142 and 143 that sandwich the membrane electrode assembly 141. The membrane electrode assembly 141 includes an electrolyte membrane 144 made of a polymer electrolyte, and electrodes 145 and 146 disposed on both surfaces of the electrolyte membrane 144. The electrodes 145 and 146 include a gas diffusion layer for diffusing the fuel gas or the oxidant gas, and a catalyst layer containing a catalyst.

  The separator 142 has a flow path 148 through which fuel gas flows and a flow path 147 through which cooling water flows. The separator 143 has a flow path 149 for flowing an oxidant gas and a flow path 147 for flowing cooling water.

  The flow path 148 communicates with a manifold (not shown) through which fuel gas flows. The flow path 149 communicates with a manifold (not shown) through which the oxidant gas flows. The flow path 147 communicates with a manifold (not shown) through which cooling water flows. The fuel gas is, for example, hydrogen or methanol. The oxidant gas is, for example, air.

  As shown in FIG. 2, the separators 142 and 143 include a base material 20 made of aluminum and a hard carbon film 22 that covers the entire surface of the base material 20. Aluminum is preferable from the viewpoints of weight, versatility, cost performance, or processability. The hard carbon film 22 contains hard carbon. The single cells 150 and 160 are substantially the same as the single cell 140.

  The current collecting plate 120 includes a base material 121 formed of aluminum and a layer 122 that covers the entire surface of the base material 121. The layer 122 is gold-plated (hereinafter, the layer 122 is referred to as a gold-plated layer 122). Gold is preferable because of its excellent conductivity.

  The buffer member 130 includes a base material 131 made of aluminum, and hard carbon and gold covering the surface of the base material 131. The layer 133 (corresponding to the first contact portion) in contact with the separator 142 in the buffer member 130 includes hard carbon. The layer 132 (corresponding to the second contact portion) in contact with the current collector plate 120 in the buffer member 130 includes gold.

  That is, the hard carbon film is formed on the surface of the separator 133 in contact with the layer 133 and the layer 133. Further, the layer 132 and the surface of the current collector plate 120 in contact with the layer 132 contain gold (hereinafter, the layer 133 is referred to as a hard carbon film 133 and the layer 132 is referred to as a gold plating layer 132).

  Therefore, the standard electrode potential of the hard carbon film 133 is equal to the standard electrode potential of the separator surface in contact with the hard carbon film 133, the standard electrode potential of the gold plating layer 132, and the standard electrode of the current collector plate surface in contact with the gold plating layer 132. The potential is equal. “Standard electrode potentials are equal” includes not only the state where the standard electrode potentials are exactly the same, but also the state where the standard electrode potentials approximate, and it is sufficient that corrosion can be suppressed even if they are not the same metal.

  Since the hard carbon film 22 and the hard carbon film 133 contain graphitized DLC, the corrosion resistance can be improved as compared with the case of only the base materials 20 and 121 while ensuring conductivity.

The hard carbon film 22 and the hard carbon film 133 are determined by the intensity ratio R (I _D / I _G ) between the D band peak intensity (I _D ) and the G band peak intensity (I _G ), which is measured by Raman scattering spectroscopy. It is prescribed. Specifically, the intensity ratio R (I _D / I _G ) is 1.3 or more.

When the carbon material is analyzed by Raman spectroscopy, peaks are usually generated around 1350 cm ⁻¹ and 1584 cm ⁻¹ . Highly crystalline graphite has a single peak near 1584 cm ⁻¹ , and this peak is usually referred to as the “G band”. On the other hand, a peak near 1350 cm ⁻¹ appears as the crystallinity decreases (crystal structure defects increase). This peak is usually referred to as the “D band” (note that the peak of diamond is strictly 1333 cm ⁻¹ and is distinct from the D band). The intensity ratio R (I _D / I _G ) between the D band peak intensity (I _D ) and the G band peak intensity (I _G ) is the graphite cluster size of the carbon material and the disorder of the graphite structure (crystal structure defect), It is used as an indicator such as sp2 bond ratio. That is, in the present invention, it can be used as an index of contact resistance between the hard carbon film 22 and the hard carbon film 133 and can be used as a film quality parameter for controlling the conductivity of the hard carbon film 22 and the hard carbon film 133.

The R (I _D / I _G ) value is calculated by measuring the Raman spectrum of the carbon material using a microscopic Raman spectrometer. Specifically, the peak intensity of 1300～1400Cm ^-1 called the D band _{(I D),} the relative intensity ratio of the peak intensity of 1500～1600Cm ^-1 called G band _{(I G)} (peak area ratio ( I _D / I _G )).

  As described above, in this embodiment, the R value is 1.3 or more. Moreover, in preferable embodiment, the said R becomes like this. Preferably it is 1.4-2.0, More preferably, it is 1.4-1.9, More preferably, it is 1.5-1.8. If the R value is 1.3 or more, sufficient conductivity in the stacking direction can be secured. Moreover, if R value is 2.0 or less, the reduction | decrease of a graphite component can be suppressed. Furthermore, the increase in internal stress of the hard carbon film 22 and the hard carbon film 133 itself can be suppressed, and the adhesion to the base materials 20 and 131 as the base can be further improved.

  The size of the buffer member 130, the separators 142 and 143, and the current collector plate 120 in the surface direction is substantially equal, and the buffer member 130 is interposed between the separator 142 and the current collector plate 120 so as not to directly contact them.

  Unlike this, for example, as shown in FIG. 3, when the current collecting plate 120A is smaller than the separator 142A, the size of the buffer member 130A in the surface direction may be smaller than the separator 142A and substantially equal to the current collecting plate 120A. With such a configuration, the buffer member 130A does not directly contact the separator 142A and the current collector 120A. The current collecting plate 120A is fitted in a recess 115A provided in the end plate 110A.

  The operational effects of the fuel cell stack 100 will be described.

  The fuel cell stack 100 prevents the dissimilar metals from contacting each other in the current collector 120 and the separators 142 and 162 by the buffer member 130, and the standard electrode potential of the hard carbon film 133 and the standard electrode potential on the surfaces of the separators 142 and 162. And are equal. Further, the standard electrode potential of the gold plating layer 132 is equal to the standard electrode potential of the surface of the current collector plate 120. Therefore, the fuel cell stack 100 can suppress corrosion (galvanic corrosion) of the current collector plate 120 and the separators 142 and 162, and can exhibit good current collection performance.

  Corrosion can also be suppressed by using gold plating on the surfaces of the separators 142 and 162 that are in contact with the current collector plate 120 without using the buffer member 130.

  However, if only some of the many separators are different from others, the effect of producing a large number of the same separators such as improvement in productivity is reduced. Also, when forming a fuel cell stack 100 by forming a module in which a plurality of single cells are stacked and stacking the modules, only a part of the many modules must be changed, and the same It is.

  However, in the fuel cell stack 100, in order to suppress corrosion by the buffer member 130, which is a member different from the separator, the same separator or the same module may be stacked, and the effect obtained by producing a large number of the same ones can be obtained. It is done.

  In the fuel cell stack 100, the base material 131 of the buffer member 130 and the base material 20 of the separator 142 are made of the same material. For this reason, even if defects occur in the hard carbon film 133 and the hard carbon film 22 on the surfaces of the separators 142 and 162, the fuel cell stack 100 can suppress the corrosion of the buffer member 130 and the separators 142 and 162.

<Modification 1>
FIG. 4 is an enlarged perspective view showing a main part of the fuel cell stack of the first modification.

  The fuel cell stack 200 of Modification 1 is substantially the same as the fuel cell stack 100, but the buffer member 230, the current collector plate 220, and the end plate 210 are different from the fuel cell stack 100.

  The end plate 210 is different from the end plate 110 in that the end plate 210 has a recess on the surface facing the buffer member 230. The current collecting plate 220 is different from the current collecting plate 120 in that the current collecting plate 220 is fitted in the recess of the end plate 210.

  The end plate 210 has a manifold 211 through which fuel gas, oxidant gas, or cooling water flows. The end plate 210 has a sealing material 212 for preventing leakage of gas or cooling water around the manifold 211.

  The buffer member 230 is substantially the same as the buffer member 130, and the surface 233 facing the separator (not shown) includes hard carbon, and the surface 232 facing the current collector plate includes gold. On the other hand, the buffer member 230 is different from the buffer member 110 in that the buffer member 230 has a layer 235 containing hard carbon on the side facing the end plate 210.

  The buffer member 230 has a layer 235 around the manifold 234 through which fuel gas and the like flow. That is, on the surface of the buffer member 230 on the side facing the end plate 210, the layer 235 around the manifold 234 contains hard carbon, and the other part is gold-plated.

  The fuel cell stack 200 has substantially the same configuration as the fuel cell stack 100 and has the same effects as the fuel cell stack 100. In addition, since the fuel cell stack 200 has the hard carbon-containing layer 235 around the manifold 234, in addition to the effects of the fuel cell stack 100, the corrosion resistance against fuel gas, oxidant gas, or cooling water flowing through the manifold 234 can be improved. .

<Modification 2>
FIG. 5 is an enlarged perspective view showing a main part of the fuel cell stack according to the second modification.

  The fuel cell stack 300 of Modification 2 is substantially the same as the fuel cell stack 100, but the buffer member 330, the current collecting plate 320, and the end plate 310 are different from the fuel cell stack 100.

  The end plate 310 is different from the end plate 110 in that the end plate 310 has a recess on the surface facing the buffer member 330. The current collecting plate 320 is different from the current collecting plate 120 in that the current collecting plate 320 is fitted in the recess of the end plate 310.

  The end plate 310 has a manifold 311 through which fuel gas, oxidant gas, or cooling water flows. The end plate 310 has a sealing material 312 for preventing leakage of gas or cooling water around the manifold 311 and the current collector plate 320.

  The buffer member 330 is substantially the same as the buffer member 130, and the surface 333 facing the separator (not shown) contains hard carbon. On the other hand, the buffer member 330 is different from the buffer member 130 in that not only the layer 332 containing gold but also the layer 335 containing hard carbon is provided on the side facing the end plate 310.

  The size of the layer 332 in the surface direction is substantially equal to the size of the current collector plate 320 in the surface direction. On the surface of the buffer member 330 on the side facing the end plate 310, the portion other than the layer 332 is a layer 335 containing hard carbon.

  The fuel cell stack 300 of Modification 2 has substantially the same configuration as the fuel cell stack 100 and has the same effects as the fuel cell stack 100. On the surface of the cushioning member 330 on the side facing the end plate 310, a portion other than the layer 332 includes hard carbon. Therefore, the fuel cell stack 300 can improve the corrosion resistance against the fuel gas, the oxidant gas, or the cooling water flowing through the manifold 334 in addition to the effects of the fuel cell stack 100.

<Vehicle>
FIG. 6 is a schematic view of a vehicle having a fuel cell stack.

  As shown in FIG. 6, the vehicle 400 travels by using the fuel cell stack 100 as a driving power source and driving a motor with electric power generated by the fuel cell stack 100. The vehicle 400 may be mounted with the fuel cell stack 200 or the fuel cell stack 300. Since the vehicle 400 is equipped with the fuel cell stack 100, it can exhibit good current collecting performance.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims.

  For example, in the embodiment, the buffer member 130 includes the base 131 formed of aluminum, the gold-plated layer 132, and the layer 133 containing hard carbon, but the present invention is not limited to this configuration.

  That is, the present invention includes a device that prevents contact between different metals and suppresses corrosion. The base material 131, the layer 132, and the layer 133 in the buffer member 130 are formed in accordance with the configurations of the separators 142 and 162 and the current collector plate 120. It can be designed as appropriate.

It is a schematic sectional drawing which shows a fuel cell stack. It is sectional drawing which expands and shows the part enclosed by the code | symbol 2 of FIG. It is a schematic sectional drawing which shows the other example of a fuel cell stack. 10 is an enlarged perspective view showing a main part of a fuel cell stack according to Modification 1. FIG. 10 is an enlarged perspective view showing a main part of a fuel cell stack according to Modification 2. FIG. 1 is a schematic view of a vehicle having a fuel cell stack.

Explanation of symbols

100, 200, 300 Fuel cell stack,
110, 110A, 210, 310 end plate,
120, 120A, 220, 320 current collector (current collector),
121 substrate,
122 gold plating layer,
130, 130A, 230, 330 cushioning member,
131 substrate,
132, 232, 332 gold plating layer (second contact portion),
133, 233, 333 hard carbon film (first contact portion),
140, 140A, 150, 160 single cell,
141 membrane electrode assembly,
142, 143, 162 separators,
211, 234, 311, 334 Manifold,
235, 335 hard carbon film,
400 vehicles.

Claims (6)

A plurality of stacked single cells;
A current collector having a surface formed of a metal different from the surface material of the separator, which is arranged in the stacking direction of the single cells and is electrically connected to a separator provided in the single cells to extract electric power of the single cells When,
A buffer member that is sandwiched between separators provided on the current collector and a single cell located at an end in the stacking direction among the plurality of single cells, and prevents contact between different metals in the separator and the current collector; , have a,
The standard electrode potential of the first contact portion in contact with the separator in the buffer member is equal to the standard electrode potential of the separator surface in contact with the first contact portion, and the second contact portion in contact with the current collector in the buffer member. A fuel cell stack in which the standard electrode potential is equal to the standard electrode potential of the current collector surface in contact with the second contact portion . The current collector is disposed on the outer side in the stacking direction with respect to the separator provided in the single cell positioned at the end of the stacking direction among the plurality of stacked single cells, and between the current collector and the separator. The fuel cell stack according to claim 1 , wherein the buffer member is disposed in the fuel cell stack. Has a hard carbon film on the first contact portion and the surface of the separator in contact with the first contact portion, claim 1 or claim wherein the second contact portion and the collector surface in contact with said second contact portion comprises gold 3. The fuel cell stack according to 2.   The separator and the buffer member each have a base material on which at least a part of the surface is coated, and the material of the base material of the separator and the material of the base material of the buffer member are the same. Item 4. The fuel cell stack according to any one of Items 3.   The fuel cell stack according to claim 4, wherein the base material is made of aluminum.   A vehicle having the fuel cell stack according to any one of claims 1 to 5.

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