JP2010086695A - Fuel battery separator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel battery capable of reducing the number of components and thinning. <P>SOLUTION: In a fuel battery made by laminating one or more of a fuel battery unit cell in which an anode oxidizing fuel and a cathode reducing oxidant gas are formed through a proton conductive solid polymer film, a separator supplying the fuel and the oxidant gas to the fuel battery cells, and a sealing material for sealing the fuel and the oxidant gas, flow channels formed on the face of the separator are structured of three steps of a concave part, a convex part and a flat part of an intermediate height, and fluid flow paths are formed of a combination of the three steps of height. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell and a separator. More specifically, a fuel cell and separator in which fuel is oxidized at the anode of a membrane / electrode assembly (MEA) composed of an anode, an electrolyte membrane, a cathode, and a diffusion layer, and oxygen is reduced at the cathode. Related to structural improvements.

With recent advances in electronic technology, portable electronic devices such as telephones, notebook computers, audio-visual devices, camcorders, and personal information terminal devices are rapidly spreading.
Conventionally, such portable electronic devices are systems driven by secondary batteries, and new high-energy dense secondary batteries such as sealed lead-acid batteries, Ni / Cd batteries, Ni / hydrogen batteries, and even Li-ion secondary batteries. With the advent, portable devices have become smaller and lighter. On the other hand, higher functionality of portable devices has been attempted. In order to further increase the energy density of various secondary batteries, especially Li-ion secondary batteries, the development of battery active materials and the development of high-capacity battery structures have been promoted, realizing a power source that lasts longer in one charge. Efforts have been made.

  However, secondary batteries always require a charging operation after using a certain amount of power, and charging equipment and a relatively long charging time are required, so that mobile devices can be used continuously at any time and anywhere for a long time. There are many problems left to drive. In the future, portable devices are moving toward a direction that requires a higher power density and higher energy density power source, that is, a power source with a longer continuous drive time, in response to the increasing amount of information and its higher speed and higher functionality . Therefore, there is an increasing need for a small generator that does not require charging, that is, a small generator that can be easily refueled.

  From such a background, a fuel cell power supply can be considered as one that can meet the above-mentioned demand. A fuel cell is a generator that consists of at least a solid or liquid electrolyte and two electrodes that induce a desired electrochemical reaction, an anode and a cathode, and converts the chemical energy of the fuel directly into electrical energy with high efficiency. . As the fuel, pure hydrogen, hydrogen chemically converted from fossil fuel or water, methanol, which is a liquid or solution in a normal environment, alkali hydride, hydrazine, dimethyl ether which is a pressurized liquefied gas, and the like are used. Air or oxygen gas is used as the oxidant gas. The fuel is electrochemically oxidized at the anode and oxygen is reduced at the cathode, resulting in a difference in electrical potential between the electrodes. At this time, if a load is applied between the two electrodes as an external circuit, ion movement occurs in the electrolyte, and electric energy is extracted from the external load. For this reason, various types of fuel cells are highly expected to be used as large-scale power generation systems that replace thermal power equipment, small distributed cogeneration systems, and electric vehicle power supplies that replace engine generators.

  Among these fuel cells, solid polymer fuel cells and direct methanol fuel cells are membrane / electrode assemblies in which a polymer-like solid electrolyte membrane is composed of a carbon electrode carrying a catalyst such as platinum. The main feature is that (MEA: Membrane Electrode Assembly) is used. A pair of separators having a flow path for supplying fuel and oxidant gas to this MEA and having a current collecting action sandwiching the MEA through a sealing material that prevents leakage of fuel and oxidant gas It is called a single cell, and the fuel cell stack is formed by stacking a plurality of such single cells.

  Among these members, the separator is a member for efficiently supplying fuel and oxidant gas as an electrode, and is made of a carbon-based or metal-based conductive material.

  There are many types of separators. An internal manifold type in which fuel and oxidant gas are supplied to adjacent separators through through holes provided in the separator, and there are no through holes for gas ventilation in the separator, and fuel and oxidant gas are supplied from the side of the separator. Each is divided into external manifold types to be supplied. In addition, the separator is classified into some types depending on the structure of the surface in contact with the electrode or the diffusion layer. For example, there is a separator having an uneven shape on the electrode (diffusion layer) contact surface, or a separator combining a flat plate and an intercollector having an uneven shape or groove shape. Separator materials are broadly classified into carbon and metal. Carbon-based carbon materials such as graphite can be blended with a resin material such as a phenol-based resin as a binder and molded to form a plate material, which makes it easy to form a flow path to the plate material by cutting or the like. High degree of freedom in road shape.

  However, since the graphite separator material is brittle, a certain thickness or more is required from the viewpoint of strength. On the other hand, metal has a higher strength than graphite and has a merit that it can be made compact and lightweight because a metal thin plate is used. However, metal materials have battery degradation due to corrosion and growth of passive films, an increase in internal resistance, and restrictions on flow path formability due to metal plastic processing. Solutions to problems due to corrosion and passive film growth have been proposed previously, and in order to compensate for the drawbacks of flow path formability, they are dealt with by combining an intercollector and multiple metal plates with flow grooves. . On the other hand, Patent Document 1 discloses a technique for configuring a separator with a single metal plate. These separators according to the prior art have a structure in which a single metal plate having a channel groove and a frame structure surrounding the metal plate are provided. Since these use a single metal plate, the number of parts can be reduced, which is advantageous in terms of cost.

  In the metal separator, the flow path is formed by a method of imparting an uneven shape by pressing a thin metal plate. Therefore, if a serpentine-shaped flow path having a folded portion is provided on one surface of the metal separator, there is a risk that the flow path cannot be formed on the other surface due to a location where the flow path does not communicate. There is. Therefore, in order to solve this problem, a structure in which a plurality of protrusions are installed on the folded portion is disclosed (Patent Documents 2 to 4).

Japanese Patent Application Laid-Open No. 08-222237 JP 2005-108505 A JP 2007-165257 A JP 2007-73192 A

  The above-described conventional technique is composed of a linear concavo-convex portion having a corrugated cross section and a dimple portion having a plurality of protrusions, but a partition portion needs to be provided in order to form a folded portion. According to Patent Document 2, when the partition portion is integrally provided by press molding or the like, the partition portion is formed on the surface opposite to the surface on which the folded portion is provided, so that the partition portion can be formed. It cannot be done, and it is shown that the whole flow path becomes a linear shape. Further, when both surfaces are configured as folded portions as in Patent Document 3, it is difficult to achieve the above-described reason by a method such as press molding. Therefore, it is necessary to provide another member, and the number of parts increases. .

  The present invention solves these problems, and an object of the present invention is to provide a fuel cell in which the number of parts can be reduced and the thickness can be reduced.

  According to the present invention, a fuel cell single cell in which an anode for oxidizing fuel and a cathode for reducing oxidant gas are formed via a proton conductive solid polymer membrane, and the fuel and the oxidant gas are supplied to the fuel cell. In the fuel cell in which one or more separators to be supplied to each single cell and one or more sealing materials for sealing the fuel and the oxidant gas are laminated, the flow path formed on the surface of the separator has a recess and There is provided a fuel cell characterized in that it is composed of three stages of a convex part and a flat part which is the height between them, and a fluid flow path is formed by a combination of the three stages.

  In addition, according to the present invention, there is provided a fuel cell comprising a flow path in which a fuel that flows on one side of a separator and an oxidant gas that flows on the other side flow independently.

  In addition, according to the present invention, there is provided a fuel cell characterized in that a partial cross section of the separator has a corrugated shape.

  In addition, according to the present invention, there is provided a fuel cell characterized in that when the fuel cells are stacked and configured, the separators are stacked upside down.

  According to the present invention, each of the folded portions is provided by combining three types of the concave and convex portions having a corrugated cross section and a flat portion having a height between the concave portions and the convex portions, which serve as separator flow paths. The flow paths on the surface are formed independently. Therefore, even if a meandering channel is provided on one side of the separator, a straight channel can be provided on the back side of the serpentine channel on the other side. Since these flow paths can be formed integrally by press molding or the like, the number of parts does not increase, and a manufacturing method similar to the conventional one can be applied for molding. In addition, the separator can be made thin by corrugated plate shape and can be composed of one type of separator, so the number of parts can be reduced, a compact fuel cell can be manufactured, and it is suitable as a power source for portable devices. Yes.

  Embodiments according to the present invention will be described below, but the present invention is not limited to the following embodiments.

  In the fuel cell of this embodiment, an anode for oxidizing the fuel and a cathode for reducing the oxidant gas are disposed via the proton conductive solid polymer membrane. The anode and the cathode are respectively disposed in contact with a separator that supplies the fuel and the oxidant gas to the fuel battery cell, and a sealing material that seals the fuel and the oxidant gas. The separator is formed with a flow path for supplying fuel and oxidant gas to the anode and the cathode, for example, a groove, and a manifold and an introduction portion formed between the flow path and the manifold.

  There is no particular limitation on the material of the separator, and a carbon-based or metal-based material can be used. However, since the separator can be thinned, the thickness of the separator is 0 by using a relatively strong metal-based material. A thickness of about 0.1 to 0.2 mm is possible.

Example 1
A first aspect of the present invention will be described with reference to FIGS. FIG. 1 is a perspective view of a single fuel cell according to an embodiment of the present invention. The MEA 1 is sandwiched between two separators 3a and 3b. The separator is composed of only one type, and the separator 3b is the same type of separator as the separator 3a turned upside down. The separator 3 is made of SUS316L stainless steel metal plate with a thickness of 0.2 mm, and is formed by press molding at four corners for each of the oxidant inlet manifold 10a, the oxidant outlet manifold 10b, the fuel inlet manifold 11a, and the fuel outlet manifold 11b. Is provided.

  Flow channel grooves 12 project from the front and back of the central portion of the metal plate, and the back side of each flow channel groove 12 is a flow channel projection 13. An introduction portion 9 is formed between the manifolds 10 a, 10 b, 11 a, 11 b and the flow channel 12. The sealing material 2 has an outer diameter equivalent to that of the separator 3 and has a planar structure in which the surfaces of the separator 3 that are in contact with the manifolds 10 a, 10 b, 11 a, 11 b and the flow channel 12 are removed.

  The fuel and the oxidant flow like the flow paths 31 and 32 on the separator, respectively. That is, the fuel passes from the fuel inlet manifold 11a through the introduction portion 9 through the flow channel 12 and reaches the fuel outlet manifold 11b through the introduction portion 9 through two folded portions. Similarly, the oxidant passes from the oxidant inlet manifold 10a through the introduction part 9 through the flow channel 12 and reaches the oxidant outlet manifold 10b through the introduction part 9 through two folded portions.

As shown in FIG. 2, the separator 3 includes a plurality of flow channel grooves 12 and flow channel projections 13 that are provided by molding into a corrugated plate shape. FIG. 4 shows a cross section at the AA position shown in FIG. 2 in which a plurality of the single cells shown in FIG. 1 are stacked. The separator 3 sandwiches the MEA 1 and the channel groove 12 serves as a channel. The fuel flow path 31 and the oxidant flow path 32 are formed.
By separating the separators 3 while being turned over, the phase of the flow paths can be shifted between the odd-numbered cells and the even-numbered cells in the stacking order, and the flow path positions of the fuel flow path 31 and the oxidant flow path 32 are the same. Since it becomes a layer, the thickness of the fuel cell in the stacking direction can be reduced. Further, the flow path protrusions 13 of the separator 3 that sandwich the MEA 1 support the MEA 1 at the same place, and it is difficult for shear stress to be applied to the MEA.

  On the other hand, the folded fuel flow path 31a includes a flat portion 16 that is provided without molding a part of the flow path protrusion 13. In the folded portion, as shown in FIG. 5, adjacent flow channel grooves 12 are connected via the flat portion 16, and the fuel flow channel 31 a of the folded portion constitutes a continuous flow channel.

  The channel grooves and channel projections molded into corrugated shapes become channel projections and channel grooves on the opposite side of the separator, respectively. FIG. 3 shows the opposite side of FIG. In FIG. 2, the place where the turn-back portion is provided is a straight flow path in the vicinity of the manifold entrance / exit in FIG. The portion formed by the combination of the flow path protrusion 12 and the flat portion 16 whose back surface is the folded portion constitutes the oxidant flow path 32 by the combination of the flow channel groove 13 and the flat portion 16 in FIG. . Further, the channel groove 12 in FIG. 2 forms the channel protrusion 13 in FIG. 3, and thus forms a straight channel. As shown in FIG. 5, the oxidant flow path 32 forms a flow path in a direction perpendicular to the fuel flow path 31 a of the folded portion, and a different flow path can be formed on each surface of the separator.

(Example 2)
The separator 3 used in Example 1 is formed by press-molding a thin metal plate to form the manifolds 10a, 10b, 11a, 11b, the flow channel 12, the flow channel projection 13, and the flat portion 16, but is carbon-based. There is no particular limitation on the material as long as it is a conductive material. Another embodiment of the present invention will be described with reference to FIGS. The carbon separator is a natural graphite compounded with a phenolic resin as a binder and processed into a 1 mm plate shape. By cutting, a manifold and a channel groove 12 having a depth of 0.5 mm, a flat portion 16 having a depth of 0.25 mm are obtained. And a serpentine flow path that folds back and forth 1.5 times was formed.

6 is a front view of the carbon-based separator, and FIG. 7 is a rear view of FIG. Since the degree of freedom of processing is high, in the separator of FIGS. 2 and 3, in the linear flow channel portion near the manifold, the portion constituted by the composite of the flow channel groove 12 and the flat portion 16 is shown in FIGS. , Only the flat portion 16 is configured. Also in this embodiment, by combining the flow channel groove 12, the flow channel projection portion 13, and the flat portion 16, the back surface of the portion that becomes the folded portion can form a straight flow channel.
(Example 3)
FIG. 8 shows an exploded perspective view of the fuel cell stack 21 using the configuration of the first embodiment. This battery is composed of a plurality of separator / seal components 20a, an inverted separator / seal component 20b, MEA 1 and other members. That is, the separator / seal structure 20a, the diffusion layer / MEA1 / diffusion layer, and the separator / seal structure 20b are laminated in this order. A stack of the separator 3, MEA 1, diffusion layer, sealing material 2, and sealing material 4 stacked in this way becomes the power generation unit 22 of the fuel cell stack 21. The fuel cell stack 21 is configured to be sandwiched between a current collecting plate 17 for extracting current and voltage from the power generation unit 22 and an end plate 19 for fixing the power generation unit 22. When generating electricity, the fuel cell stack 21 according to this embodiment supplies fuel and oxidant to the fuel inlet and the oxidant inlet provided in the end plate 19, respectively, and unreacted fuel from the opposite end plate 19. And oxidant gas is discharged.

The members used in the fuel cell stack 21 are as follows.
(1) MEA1 in which an electrode catalyst is applied to both sides of a solid polymer film having a thickness of 50 μm
(2) Diffusion layer not shown in the figure composed of carbon paper equal to the electrode area of MEA1 on both outer sides of MEA1 (3) Made of stainless steel with a plate thickness of 0.2 mm, both sides of the center part by press molding Separator 3 with concave and convex grooves on
(4) Seal material 2 formed by stamping an EPDM sheet
(5) Current collecting plate 17 with a terminal in which conductive plating is applied to a copper plate having a thickness of 1 mm
(6) Insulating plates (7) which are not shown in the figure in which a manifold is formed by cutting PPS (polyphenylene sulfide) having a thickness of 5 mm installed between the current collecting plate 17 and the end plate 19 An end plate 19 provided with a joint serving as an inlet and outlet for fuel, oxidant gas and cooling water on a stainless steel plate having a thickness of 10 mm sandwiching the member

  In this embodiment, the end plate is fastened and fixed using a bolt / nut made of stainless steel.

  In order to confirm the sealing performance of the fuel cell stack 21, a leak test using helium gas was performed. In the test, helium gas was sealed at 1 atm from the fuel inlet provided in the other end plate 19 with the fuel discharge port provided in the end plate 19 closed, and the oxidant gas Atmospheric pressure nitrogen gas was supplied from the inlet, and a helium gas detector was connected to the oxidant gas outlet. In the fuel cell stack 21 according to this example, helium was not detected by the helium detector, and it was confirmed that no leak occurred.

A power generation test was performed using the fuel cell stack 21. As the fuel, a 1 mol / L aqueous methanol solution was used, and air was supplied as an oxidant gas to the fuel cell stack 21 at an air utilization rate of 25%. In this example, only air was adjusted so that the dew point temperature was 30 ° C. The temperature of the fuel cell stack 21 during power generation was set to 60 ° C. by controlling the ambient temperature. When power was generated at a current density of 0.2 A / cm ² , the voltage was 2.1 V (0.42 V per single cell), and it was confirmed that power generation was good.

  The embodiment described above is a representative example, and in this embodiment, a serpentine shape having a 1.5-turn turn-up portion on both sides is shown as a representative. The configuration can be selected without depending on the configuration and shape of the concavo-convex portion and flat portion, and is not limited to this, and by combining the concavo-convex portion and flat portion in a desired shape, a uniform flow distribution can be obtained. What is necessary is just to make it the flow path shape which can be performed.

  According to the present invention, it contributes to thinning in the stacking direction, and the folded portion can be formed on each surface without providing a partition portion by a separate member, and the flow paths on each surface are formed independently. be able to. In addition, according to the present invention, it is possible to provide a separator that can supply one type of fuel to one side and supply an oxidant to the other side.

1 is an exploded perspective view of a single fuel cell according to an embodiment of the present invention. FIG. 2 is a plan view of the separator / seal structure of FIG. 1. FIG. 3 is a plan view of the back side of the separator / seal structure shown in FIG. 2. FIG. 3 is a cross-sectional view taken along line AA in FIG. 2 in which a plurality of fuel cell single cells are stacked. Sectional drawing which laminated | stacked multiple fuel cell single cells and followed the BB line of FIG. The separator top view by the Example of the other form of this invention. The top view of the back side of the separator shown in FIG. FIG. 3 is a developed perspective view of a fuel cell stack configured using a separator according to the present invention.

Explanation of symbols

1 MEA (membrane / electrode assembly)
2 Sealant 3, 3a, 3b Separator 8 Carbon separator 9 Introducing portion 10A Oxidant inlet manifold 10B Oxidant outlet manifold 11A Fuel inlet manifold 11B Fuel outlet manifold 12 Channel groove 13 Channel protrusion 16 Flat portion 17 Current collector plate 19 End plate 20a, 20b Separator / seal structure 21 Fuel cell stack 22 Power generation section 31 Fuel flow path 31a Fuel flow path 32 of turn-up section Oxidant flow path 32a Oxidant flow path of turn-up section

Claims (4)

  A fuel cell single cell in which an anode for oxidizing fuel and a cathode for reducing oxidant gas are formed via a proton conductive solid polymer membrane, and supplying the fuel and the oxidant gas to the single fuel cell, respectively In the fuel cell in which one or more separators and one or more sealing materials for sealing the fuel and the oxidant gas are laminated, the flow path formed on the surface of the separator has a concave portion and a convex portion and a height between them. A fuel cell comprising a three-stage flat portion and a fluid flow path formed by a combination of the three heights.   2. The fuel cell according to claim 1, further comprising a flow path in which the fuel that flows on one side of the separator and the oxidant gas that flows on the other side flow independently of each other.   3. The fuel cell according to claim 1, wherein a part of the cross section of the separator has a corrugated shape.   4. The fuel cell according to claim 1, wherein when the fuel cells are stacked, the separators are stacked while being turned over.

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