JP4213515B2 - Polymer electrolyte fuel cell - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel cell useful as a consumer cogeneration system, a mobile body, a mobile energy source, and the like.
[0002]
[Prior art]
A polymer electrolyte fuel cell using a hydrogen ion conductive polymer membrane as an electrolyte is a gas in which an electrolyte selectively transports hydrogen ions, and a gas having a catalyst layer such as platinum for a fuel gas such as hydrogen and an oxidizing gas such as air. Electrochemical reaction is caused by the diffusion electrode to generate electricity and heat simultaneously.
The power generation unit of the polymer electrolyte fuel cell includes a hydrogen ion conductive electrolyte membrane, a carbon powder carrying a platinum group metal catalyst disposed in close contact with both surfaces thereof, and a polymer mixed to cover the carbon powder. It consists of a catalyst layer containing an electrolyte as a main component and a pair of gas diffusion layers having both gas permeability and conductivity, which are disposed in close contact with the outer surface of the catalyst layer. The gas diffusion electrode and the catalyst layer constitute a gas diffusion electrode. A combination of the above electrolyte membrane, catalyst layer, and gas diffusion layer is called an electrolyte membrane electrode assembly (hereinafter referred to as MEA). A gasket is disposed at the peripheral edge of the MEA to avoid gas leakage.
[0003]
On the outside of the gas diffusion electrode, the MEAs are mechanically fixed, adjacent MEAs are electrically connected to each other in series, and the reaction gas is supplied to the electrodes, and water and surplus gas generated by the reaction are supplied. A separator plate provided with a gas flow path for carrying away is disposed. Generally, a carbon material is used for the separator plate. Although the gas flow path can be provided separately from the separator plate, a method of providing a gas flow path by providing a groove on the surface of the separator plate is generally used.
[0004]
Many fuel cells have a stacked structure in which a large number of unit cells having the above-described structure are stacked. In the polymer electrolyte fuel cell stack as described above, in order to reduce the contact resistance between the laminated components such as the separator plate and the gas diffusion layer, and to maintain the gas sealing performance, the entire battery is placed in the stacking direction. Tightened constantly.
Pure hydrogen is suitable as the fuel supplied to the anode side, but there are problems in terms of infrastructure and storage. Therefore, in many cases, a fuel gas containing hydrogen as a main component is supplied to the fuel cell using a reformer that generates hydrogen gas by catalytic reaction from a hydrogen-containing compound such as hydrocarbon. The reformer can generate hydrogen gas from hydrocarbons such as methane, butane and natural gas, alcohols such as methanol, dimethyl ether and gasoline.
[0005]
[Problems to be solved by the invention]
Among various fuel cells, the polymer electrolyte fuel cell can be said to be a power generation system that is relatively easy to start and stop from an operating temperature as low as 100 ° C. or less. The start-up of the stack, which is the power generation unit, is performed by raising the temperature from 70 ° C. to a steady temperature of about 80 ° C. by heat transfer from the cooling water circulated for heat recovery and temperature control of the stack. Power generation is started by supplying an oxidant gas (usually using air). In a low-temperature state that does not reach the steady temperature, the gaps in the catalyst layer and the gas diffusion layer are blocked by condensed water, and the power generation characteristics of the stack are significantly deteriorated due to a decrease in gas diffusivity. Further, when the fuel gas supplied to the anode side is generated from a hydrogen-containing compound by a reforming reaction, carbon monoxide (CO) is contained in the fuel gas in a small amount. CO has the property of adsorbing on the surface of the platinum catalyst. When CO is contained in the anode side supply gas, it adsorbs to the platinum catalyst of the anode side catalyst layer of the battery unit, It inhibits the smooth oxidation reaction on the platinum surface and reduces the output of the fuel cell. This is called CO poisoning. Since CO poisoning becomes more conspicuous at lower temperatures, in order to avoid CO poisoning, the fuel stack and the oxidant gas are supplied to the stack after the stack has been heated to a steady temperature, and power generation is started. preferable.
[0006]
Therefore, in order to shorten the start-up time of the power generation system using the polymer electrolyte fuel cell, it is indispensable to shorten the temperature raising time to the steady temperature of the stack. In order to shorten the stack heating time, it is necessary to suppress heat dissipation from the stack body to the surroundings. Since the side surface of the separator plate whose main component is carbon having a large thermal conductivity is exposed on the side surface of the stack, the amount of heat that the stack should hold during startup is easily dissipated. In order to suppress this, it is often used to suppress heat dissipation by bonding a heat insulating plate or the like to the side surface of the stack (see Patent Document 1). However, the heat insulating plate cannot be said to have sufficient adhesion to the side surface of the separator plate, and there is a problem that the heat insulating plate is peeled off during long-time power generation.
[0007]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-231273
[Means for Solving the Problems]
In view of the problems as described above, the present invention has a structure in which the gasket at the peripheral edge of the MEA is larger than the outer peripheral size of the separator plate and covers the side surface of the separator plate integrally from the portion larger than the separator plate. In this way, the side of the separator plate is covered with a gasket made of resin, elastomer or rubber with low thermal conductivity to suppress heat release from the stack and to shorten the startup time of the polymer electrolyte fuel cell. is there. That is, the gasket that is a constituent member of the MEA also serves as a heat insulating material that suppresses heat dissipation from the side surface of the stack.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The polymer electrolyte fuel cell of the present invention includes a hydrogen ion conductive polymer electrolyte membrane, a pair of electrodes sandwiching the hydrogen ion conductive polymer electrolyte membrane, and the hydrogen ion conductive polymer electrolyte membrane at a peripheral portion of the electrode A unit cell comprising a pair of gaskets, an anode side separator plate having a gas flow path for supplying fuel gas to one electrode, and a cathode side separator plate having a gas flow path for supplying oxidant gas to the other electrode A plurality of polymer electrolyte fuel cells laminated, wherein the gasket has a flat gasket main body and a rib extending vertically from an outer peripheral portion of the gasket main body, and the rib includes a rib of an adjacent gasket. Adhering to each other, one of the rib of the anode side gasket and the rib of the cathode side gasket has a protrusion formed at the tip, the other, Has a recess or notch formed in the end, said projection, said recess or notch and is fitted, completely covers the side surface of the anode-side separator plate and the cathode-side separator plate It is characterized by that.
[0010]
In a preferred embodiment of the present invention, the gasket has a rib extending to cover a side surface of the separator plate, which is connected to the peripheral portion, and a recess for fitting the separator plate is formed by the rib. ing.
With reference to the drawings below describing the embodiments of the present invention.
[0011]
Reference-type state
The cross-sectional view of a fuel cell of the present reference embodiment shown in FIG. FIG. 2 is a plan view of the anode side gasket.
The MEA includes a polymer electrolyte membrane 11, and an anode 12 and a cathode 13 that sandwich the membrane. The polymer electrolyte membrane 11 exposed on the outer periphery of the electrode is sandwiched between a pair of gaskets 22 and 23. The anode side separator plate 14 has a gas flow path 16 for supplying fuel gas to the anode 12, and a groove 18 constituting a flow path of cooling water on the opposite side. The cathode side separator plate 15 has a gas flow path 17 for supplying an oxidant gas to the cathode 13, and has a groove 19 constituting a flow path of cooling water on the opposite side.
[0012]
As shown in FIG. 2, the anode-side gasket 22 includes a flat gasket main body 24 and ribs 26 extending vertically from the outer peripheral portions of the four sides thereof and connected to each other. The gasket body 24 has the same structure as that of the conventional gasket except that the size of the rib 26 is larger than that of the separator plate. The gasket body 24 has a notch portion 31 into which the electrode is fitted, A pair of fuel gas manifold holes 32, an oxidant gas manifold hole 33, a cooling water manifold hole 34, and four holes 35 for passing bolts for fastening the fuel cell are provided.
[0013]
The anode-side gasket 22 configured as described above has a recess formed by a rib 26 on the separator plate side, and the gasket 22 and the separator plate 14 are integrated by fitting the anode-side separator plate 14 into the recess. Assembled into.
Similarly, the cathode-side gasket 23 has ribs 27 in the gasket body, and the separator plate 15 is fitted into a recess formed by the ribs 27 so that the gasket 23 and the separator plate 15 are assembled together.
[0014]
In the illustrated example, the ribs 26 and 27 of the adjacent gaskets 22 and 23 are in close contact with each other so as to completely cover the side surfaces of the separator plates 14 and 15, but a part of the side surfaces of the separator plate is exposed. There may be. When the ribs of the adjacent gaskets are brought into close contact with each other, the side face of the separator plate is completely covered, and the heat insulating effect is maximized.
The material of the gasket is preferably an elastic body such as fluorine-based rubber or silicon rubber, but is not limited to these as long as the effect of the present invention is exhibited. Further, instead of a single material, for example, a hard resin material coated with the elastic body as described above may be used.
[0015]
Embodiment 1
The fuel cell of the present embodiment is shown in FIG.
MEA and the separator plate are on purpose similar reference type. The present embodiment is the same as the first embodiment except that the rib 46 formed on the peripheral edge of the anode side gasket 42 and the rib 47 formed on the peripheral edge of the cathode side gasket 43 are different. That is, the rib 46 of the anode side gasket 42 has a protrusion 48 whose tip is slightly extended on the outer peripheral side. On the other hand, the rib 47 of the cathode side gasket 43 has a notch 49 on the outer peripheral side. If the protrusion is provided at the center of the rib, the other rib is provided with a recess that fits into the protrusion.
[0016]
Since the gaskets 42 and 43 have the structure as described above, when the fuel cell is assembled, the protrusion 48 at the rib tip of the adjacent gasket 42 and the notch 49 at the rib tip of the gasket 43 are fitted. . When the ribs are provided with steps at the tips of the ribs so that they are fitted together, positioning of the MEA and the separator plate fitted with the gasket is facilitated and assembly is improved. In addition, even if there is a margin in the dimensions of the protrusion and the notch, the side surface of the separator plate can be completely covered.
Further, in the conventional stack in which the side surface of the separator plate is exposed, there is a possibility that a short circuit may occur between adjacent MEAs due to adhesion of foreign matters. On the other hand, the effect which prevents the above short circuit is provided by covering the side surface of a separator plate with the gasket which is an insulator as mentioned above. Furthermore, since the side surface of the separator plate is covered with a gasket that is an original MEA component, the number of parts can be reduced.
[0017]
Embodiment 2
In the above example, a composite separator plate that combines the anode-side separator plate and the cathode-side separator plate to form a cooling water flow path between them is inserted between the MEAs. Instead of this composite separator plate, it has a fuel gas flow path on one side and an oxidant gas flow path on the other side, and serves as a single anode plate and cathode side separator plate. A separator plate can also be used in part. Such For a separator plate, it is a to Turkey to cover one separator plate side of the anode side gasket and cathode side gasket.
[0018]
FIG. 4 shows a reference form, in which a peripheral portion of a single separator plate 54 serving as both an anode side separator plate and a cathode side separator plate is covered with a gasket 56 in which an anode side gasket and a cathode side gasket are integrated. An example is shown.
FIG. 5 is also a reference embodiment, and the peripheral portion of a single separator plate 54 serving as both an anode side separator plate and a cathode side separator plate is covered with a gasket 66 in which an anode side gasket and a cathode side gasket are integrated. An example is shown. In this example, the protrusion 68 and the notch 69 are provided so that adjacent gaskets can be engaged.
[0019]
【Example】
Examples of the present invention will be described below. [0020]
<< Reference Example 1 >>
A 60-cell stacked fuel cell having the structure of Embodiment 1 was assembled using a 20 cm square polymer electrolyte membrane and a 12 cm square electrode. The cell laminate was sandwiched between end plates via current collectors and insulating plates and fastened using stud bolts and load springs. The gasket was made of fluorine-based rubber, the thickness of the gasket main body portion was 200 μm, the rib width was 2.5 mm, and the rib height was 2.5 mm including the thickness of the main body portion. The polymer electrolyte membrane where the manifold holes and bolt holes provided in the gasket overlap with each other was removed in advance. The separator plate is 20 cm square and 2.5 mm thick, and has a structure that fits into the gasket as shown in FIG.
70 ° C hot water is supplied to the cooling water channel of this fuel cell at a flow rate of 2.5 L / min, the time-dependent change in the temperature of the hot water discharged from the fuel cell is measured, and the rate at which the stack heats up is evaluated. The heat insulation performance of was evaluated. The result is shown in FIG. In the fuel cell of this reference example, the time until the outlet hot water reached 68 ° C. was 36 minutes.
[0021]
Example 1
In this example, the structure of the first embodiment is adopted. The anode side gasket 42 has a rib 48 having a protrusion 48 having a height of 0.5 mm, and the cathode side gasket 43 has a rib 47 having a notch 49 having a depth of 0.5 mm on the outer peripheral side. Others are the same as in Reference Example 1.
As in Reference Example 1, the heat insulation performance of the stack was evaluated by changing the temperature of the hot water discharged from the fuel cell by supplying hot water of 70 ° C. to the cooling water channel. The results are also shown in FIG. In the fuel cell of this example, the time until the outlet hot water reached 68 ° C. was 34 minutes.
[0022]
《Comparative example》
Reference Example 1 is the same as the gasket except that the gasket is a sheet having the same outer dimensions as the separator plate.
With respect to this fuel cell, the heat insulation performance of the stack was evaluated by supplying the hot water of 70 ° C. to the cooling water channel and changing the temperature of the hot water discharged from the fuel cell with time. The result is shown in FIG. In this fuel cell, the time until the outlet hot water reached 68 ° C. was 52 minutes.
Compared to the fuel cells of Reference Example 1 and Example 1, the fuel cell of the comparative example required a long time for temperature increase because the side surface of the separator plate having a large thermal conductivity was exposed on the side surface of the stack. This is thought to be the result of increased heat dissipation outside the stack.
[0023]
【The invention's effect】
According to the present invention, the heat insulating property of the polymer electrolyte fuel cell laminate is improved, and the startup time is greatly shortened. In addition, it is possible to prevent a short circuit between adjacent MEAs due to adhesion of foreign matter or the like.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a main part of a fuel cell according to a reference embodiment of the present invention.
FIG. 2 is a plan view of the gasket of the fuel cell.
FIG. 3 is a cross-sectional view of a main part of the fuel cell according to Embodiment 1 of the present invention.
FIG. 4 is a cross-sectional view of a main part of a fuel cell according to a reference embodiment of the present invention.
FIG. 5 is a cross-sectional view of a main part of a fuel cell according to a modification of the reference embodiment of the present invention.
FIG. 6 is a diagram showing a change with time of water discharged from fuel cells of Examples, Reference Examples and Comparative Examples of the present invention.

Claims (2)

Hydrogen ion conductive polymer electrolyte membrane, a pair of electrodes sandwiching the hydrogen ion conductive polymer electrolyte membrane, a pair of gaskets sandwiching the hydrogen ion conductive polymer electrolyte membrane at the periphery of the electrode, and a fuel in one electrode POLYMER ELECTROLYTE TYPE FUEL CELL LAMINATE WITH MULTILAYING SINGLE CELLS COMPRISING AN anodic separator plate having a gas channel for supplying gas and a Cathode side separator plate having a gas channel for supplying oxidizing gas to the other electrode Because
The gasket has a flat gasket body and a rib extending vertically from the outer periphery of the gasket body,
The rib is in close contact with the rib of the adjacent gasket,
One of the rib of the anode side gasket and the rib of the cathode side gasket has a protrusion formed at the tip, and the other has a recess or notch formed at the tip,
The polymer electrolyte fuel cell , wherein the protrusion and the recess or notch are fitted to completely cover the side surfaces of the anode-side separator plate and the cathode-side separator plate . 2. The polymer electrolyte fuel cell according to claim 1 , wherein the gasket main body and the rib form a recess that fits into the anode separator plate or the cathode separator plate .

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