JPS6139458A - Fuel cell and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent a fluid from leaking as well as to aim at improvements in the prolongation of service lide in a cell and its reliability, by superposing two types of heat resistant and electrolyte-proof fluorocarbon resin films different in a fusing point each, on a side end part in parallel with a fluid flow passage of a ribbed electrode, while heating these films and pressing them inside upon fusion. CONSTITUTION:First a film of heat resistant and electrolyte-proof first fluorocarbon resin 20 different in a fusing point each is put between in a U-shaped form into a side end part in parallel with grooves 7 and 8 of a ribbed electrode 19, and heated and pressed in upon fusion, then an impregnation layer is formed up. Next, a film of heat resistant and electrolyte-proof second fluorocarbon resin 21 having a higher fusing point T2 than the first fluorocarbon resin 20 is also put between thereinto, and heated and pressed in upon fusion, then an impregnation layer is formed up whereby a double-layered end seal layer is constituted. With this constitution, characteristics of each film coexists within one, thus a fluid leakage from the electrode side is preventable from occurring with certainty.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention provides a fuel cell that has stable performance over a long period of time, has a long service life, and has improved reliability, and a method for manufacturing the same. Regarding.

[Technical background of the invention and its problems]

Conventionally, the energy possessed by fuel was directly converted into electricity -r4
A fuel cell is known as a device for converting energy into energy. This fuel cell usually has a pair of porous electrodes sandwiching an electrolyte between them, and a fluid fuel such as hydrogen is brought into contact with the back of one of the fuel electrodes, and the other electrode, the oxidizer electrode, is placed in contact with the back of the fuel electrode. A fluid oxidizing agent such as oxygen is brought into contact with the back surface, and the electrochemical reaction that occurs at this time is utilized to extract electrical energy from between the electrodes.The fuel and oxidizing agent are supplied. Electrical energy can be extracted with the highest conversion efficiency possible.

By the way, the unit cell of a fuel cell based on the above principle, especially using phosphoric acid as an electrolyte, is usually constructed as shown in FIG. As a result, the entire fuel cell device is constructed as shown in FIG.

That is, in FIG. 3 (&), a unit cell has an electrolyte layer (hereinafter referred to as a matrix) 1 impregnated with an electrolyte as a boundary, and electrodes 2 and 3 formed of a porous material and having a catalyst added on both sides. (usually made of carbon material), and a plate 6 (generally made of a mixed bond of graphite and thermosetting resin) with ribs 4.5 on each of the matrices 1 and 4. (hereinafter referred to as interconnectors) are arranged. On the surface of the interconnector 6 located on the side of each electrode 2, 3, a plurality of grooves 7, 8 are regularly provided in parallel in directions perpendicular to each other by ribs 4, 5, respectively. 7 and 8 constitute flow paths for fluid fuel and fluid oxidizer, respectively. Further, on the opposite surface of the interconnector 6, grooves 7.8 are similarly formed by the ribs 4 and 5, and the grooves 7.8 serve as flow paths for the fluid fuel and the fluid oxidizer in the adjacent unit cells in a direction perpendicular to each other. ing. In this way, the matrix 1, electrodes 2, 3, and interconnector 6 are stacked, and in this state, the end faces of each stack are hermetically sealed, leaving only the openings at both ends of the grooves 78 of the interconnector 6, to form a unit cell. are doing.

A plurality of unit cells configured as shown in FIG. 3(,) are stacked, and as shown in FIG. 4, a manifold 10 having a fuel supply port 9 on one of the opposing end faces of the stacked body,
A manifold 12 having a fuel discharge port 11 is applied to the other end, and an oxidizer supply port 13 is applied to the other opposing end face.
A manifold 14 having an oxidant discharge port 15 on the other side and a manifold 16 having an oxidizing agent outlet 15 on the other side are fitted, and these manifolds 10, 12, 14, 16 are tightened with bolts or the like to maintain airtightness. is configured. Therefore, according to this fuel cell device 17, when fluid fuel is supplied from the fuel supply port 9, this fuel flows through the plurality of grooves 7, which are the flow paths of each unit cell, and is in contact with the back surface of the porous electrode 2. The fuel flows and is then discharged from the fuel discharge port 11. Furthermore, when a fluid oxidant is supplied from the oxidant supply port 13, the oxidant flows through the plurality of grooves 8, which are the flow paths of each unit cell, and flows while contacting the back surface of the porous electrode 3, and then the oxidant It will be discharged from the discharge port 15. The fluid fuel and the fluid oxidant are supplied into the porous electrodes 2 and 3 by diffusion, respectively, to generate electrical energy as a fuel cell. Note that the output terminal is omitted in the figure.

Furthermore, recently, from the point of view of weight reduction, an improved model has been introduced as shown in Fig. 3 (
A fuel cell unit cell configured as shown in b) has been considered. In FIG. 3(b), 18 is a separator;
Reference numeral 19 indicates a ribbed electrode, and other elements having the same functions as those in FIG. 3(a) are designated by the same reference numerals. That is, the interconnector 6 shown in FIG. has been done.

The feature of this improved type is that the separator 18 prevents mixing of the fluid fuel and the fluid oxidizer, and also serves as a current collector for unit cell stacking. In addition, this improved type of fuel cell has a weight that is about half that of the interconnector type shown in Figure 3 (,), and the ribs are porous and overflow from the matrix layer. The ribbed electrode 19 has a so-called "redaver machine" that absorbs the released phosphoric acid and replenishes the stored phosphoric acid when the phosphoric acid in the matrix layer decreases.In other words, the ribbed electrode 19 absorbs fluid fuel and fluid oxidation It has sufficient permeability for reaction fluids to reach the respective catalyst layers, has good electrical conductivity and thermal conductivity, and has strength to withstand stacking loads.

By the way, in the conventional improved fuel cell as described above, since the material of the ribbed electrode 19 is graphite based on carbon, it is extremely porous, and the fluid supplied to the ribbed electrode 19 is The fuel and fluid oxidizer pass through this and reach the matrix 1, as shown at A in FIG. 5, where an electrochemical reaction occurs. However, each fluid supplied to the ribbed electrode 19 also passes through the side surface of the ribbed electrode 19 and leaks, as shown by B in FIG.

When this fluid leakage occurs, the fluid partial pressure decreases and the current density of each unit cell becomes non-uniform, which causes a decrease or deterioration of the power generation performance of the battery. Furthermore, if the fuel and oxidizer fluids leak and their mixture occurs, a combustion reaction may occur, which is not desirable from a safety standpoint.

[Purpose of the invention]

The present invention was made to solve the above problems, and its purpose is to prevent fluid leakage from the side surface of the ribbed electrode, maintain stable power generation performance over a long period of time, and extend the life of the electrode. It is an object of the present invention to provide a fuel cell and a method for manufacturing the same, which can improve the efficiency and reliability of the fuel cell.

[Summary of the invention]

In order to achieve the above object, the present invention provides heat resistance having different melting points at the side end portion of the ribbed electrode parallel to the fluid flow path in the fuel cell described above.

It is characterized in that the side edges of the ribbed electrode are sealed by overlapping two types of electrolytic-resistant fluororesin films and press-fitting them by heating and melting.

[Embodiments of the invention]

An embodiment of the present invention shown in the drawings will be described below.

As shown in FIG. 1, the fuel cell according to this embodiment has a heat-resistant and electrolyte-resistant first electrode having a melting point of T1 at the end of the side surface parallel to the groove 7°8 of the ribbed electrode 19 described above. A 0.025-thick film of fluorine-based resin 20, such as tetrafluoroethylene-hexafluoropropylene copolymer resin (hereinafter referred to as FEP), is sandwiched in a U-shape, The impregnated layer is formed by applying a pressure of kg/cyy+ and heating and melting press-fitting at 290° C. for about 3 hours, and then a heat-resistant and resistant material having a melting point T2 (>Tt) higher than that of the first fluororesin 20 is formed. The thickness of the electrolytic second 7. thread resin 21, for example, 4-fluoroalkoxy resin (hereinafter referred to as Pi''A) is 0.0.
A 25 ms film was sandwiched in the same manner as described above, and this was heated and melted and press-fitted at 320°C for about 3 hours under a pressure of 60 to 70 kg/c1n2 to form an impregnated layer, as shown in Figure 2. ? EP impregnated layer 22 and Plt'A
Two layers of the impregnated layer 23 are stacked to form an end seal layer. Note that each melting point T1eTz is higher than the fuel cell operating temperature.

In a fuel cell equipped with a ribbed electrode 19 having such an end seal configuration, an anchor effect is provided by deeply impregnating the ribbed electrode 19 with FEP having a low melting point, and heat resistance and resistance are added from the outside. By press-fitting and impregnating PFA with high electrolytic properties, defects and defects in the FEP can be covered. For this,
The characteristics of the F'EP and PFA films coexist to form a highly reliable edge seal structure on the side surface of the ribbed electrode 19, thereby reliably preventing fluid leakage from the side surface of the electrode as described above. It becomes possible.

As a result, assuming that the current density in each unit cell is uniform,
It is possible to extend the life of the battery while stably maintaining the power generation performance of the battery. In addition, for the above reasons, the fuel and oxidizer fluids do not mix and cause a combustion reaction.
It is possible to improve reliability by making it safer.

In the above example, after impregnating the PEP film, PF
Although the A film was impregnated, each of these films may be impregnated at the same time by heating and melting press-fitting once.

Further, in the above embodiment, the first. Although FEP and PFk were used as the second fluororesin, other resins may be used.

Furthermore, although the thickness of each of the FEP and PFA films was set to 0.025 mm in the above example, it is not limited to this as long as it is within the range of 0.01 to 0.1 mm.

〔Effect of the invention〕

As explained above, according to the present invention, two types of fluororesin films having different melting points, heat resistant and electrolyte resistant, are superimposed on the side edge portion of the ribbed electrode parallel to the fluid flow path. The side edges of the ribbed electrode are sealed by heating and melting and press-fitting the ribbed electrode, thereby preventing fluid leakage from the side of the ribbed electrode and maintaining stable power generation performance over a long period of time. A fuel cell that can last for a long time and have improved reliability and a method for manufacturing the same can be provided.

[Brief explanation of drawings]

゛Figures 1 and 2 are block diagrams showing one embodiment of the present invention, Figures 3 (a) and (b) are exploded perspective views showing unit cells of a conventional fuel cell, and Figure 4 is a diagram showing a unit cell of a conventional fuel cell. FIG. 5, which is a perspective view showing the entire device, is a diagram for explaining the problems of the prior art. 1...Matrix, 7.8...Groove, 1B...Semi-quadrate, 19...Ribbed electrode, 20...FEP
Film, 21...PFA 74 Lum, 22...F
'EP impregnated layer, 23...PFA impregnated layer. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 (a) (b) Figure 4 Figure 5

Claims (4)

[Claims] (1) In a fuel cell constructed by stacking a plurality of unit cells in which an electrolyte layer is sandwiched between a pair of porous ribbed electrodes in which fluid flow paths for fluid fuel or fluid oxidizer are formed. , a heat-resistant and electrolyte-resistant first fluororesin film having a certain melting point, and a heat-resistant and electrolyte-resistant first fluororesin film having a melting point higher than that of the first fluororesin film;
Seal the side edges of the ribbed electrode parallel to the fluid flow path with a two-layer stack of electrolyte-resistant second fluororesin with the first fluororesin on the inside. A fuel cell characterized by: (2) As the first and second fluororesins, a tetrafluoroethylene hexafluoropropylene copolymer resin and a perfluoroalkoxy resin are used, respectively, as described in claim (1). fuel cell. (3) A fuel cell constructed by stacking a plurality of unit cells in which an electrolyte layer is sandwiched between a pair of porous ribbed electrodes in which fluid flow paths for fluid fuel or fluid oxidizer are formed. In the manufacturing method, a heat-resistant and electrolyte-resistant first fluororesin film having a melting point is placed on the inner side of the ribbed electrode at a side end parallel to the fluid flow path, and the first fluorine-based resin film is placed on the outside thereof. A sealing layer is formed by overlapping two layers of a heat-resistant, electrolyte-resistant second fluorine-based resin film that has a higher melting point than the fluorine-based resin film, and press-fitting the film by heating and melting it at a predetermined temperature and pressure. A method for manufacturing a fuel cell, characterized in that: (4) Claim (3) characterized in that the first and second fluororesins are a tetrafluoroethylene/hexafluoropropylene copolymer and a perfluoroalkoxy resin, respectively. 2. Method for manufacturing a fuel cell as described in Section 1.