JPS61131369A - Fuel cell - Google Patents

Abstract

PURPOSE:To prevent the increase of contact resistance and the lowering of conductivity to maintain the stable performance through a long time without causing the lowering of strength and the buckling by using carbon fibers which are made high purity by the processing of chlorine gas at high temperatures as the material of electrodes with ribs. CONSTITUTION:A unit cell is constituted by laminating a matrix 1 impregnating electrolyte, electrodes 2, 3 with ribs which have flow passages 4, 5 for fluid fuel and fluid oxidizing agent and to which catalyst is added and a separator 6. Carbon fibers which are made high purity are used as the material of electrodes 2, 3 with ribs. Carbon fibers which is reduced in impurity content are obtained by raising the temperature of the carbon fibers by the use of a graphitization furnace, and blowing chlorine gas at the temperature of 1,500 deg.C, and raising the temperature of it to 2,300 deg.C to scatter and eliminate impurities as chloride. A carbon porous plate of the electrode with ribs is obtained by carrying out the hot press forming of the mixture of the obtained carbon fibers and phenol series resin, and carrying out the processing of hardening, and carrying out the processing of carbonization for the resin, and carrying out the processing of graphitization.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a fuel cell, and more particularly to a fuel cell with an improved VF-equipped electrode having a function of diffusing fluid fuel or fluid oxidizer into a reaction field. .

[Technical background of the invention and its problems]

2. Description of the Related Art Fuel cells are conventionally known as devices that directly convert energy contained in fuel into electrical 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 surface of one electrode, and a fluid oxidizer such as oxygen is brought into contact with the back surface of the other electrode. (The electrochemical reaction that occurs at this time is used to extract electrical energy from between the electrodes.) As long as the fuel and oxidizer are supplied, electricity can be extracted with high conversion efficiency. It is something that can extract energy.

A unit cell of a fuel cell based on the above-mentioned principle, especially using sour/acid as an electrolyte, is constructed as shown in Fig. 1, and a plurality of these unit cells are stacked. As a result, the entire fuel cell device is configured as shown in FIG.

That is, in FIG. 1, the unit cell has ribbed electrodes 2 and 3 (usually made of carbon material) formed of a porous material and provided with a catalyst on both sides of a matrix 1 impregnated with an electrolyte. Further, the ribbed electrodes 2, 3 have flow passages 4, 5 for fluid fuel or fluid oxidant, respectively, on the opposite side of the catalyst application surface. Furthermore, both electrodes 2.3
On the back of the matori, opposite to Kusu 1, there are seven 74, respectively.
A controller 6 is installed. In this way, matrix 1
, the electrodes 2 and 3 with ribs and the separator 6 are stacked, and in this state, only the openings at both ends of the fluid fuel flow passage and the fluid oxidant flow passage of the ribbed electrodes 2 and 3 are left, and one part of each stacked end is opened. are hermetically sealed to form a unit cell.

A plurality of unit cells configured as shown in Fig. 1 are stacked,
As shown in FIG. 2, after being tightened with a predetermined pressure by a fastener 10 in order to obtain electrical continuity between the unit cells, a fuel supply port 11 is provided at one of the opposing end faces of the stack. a manifold 12 having a fuel outlet 13, and a manifold 14 having a fuel outlet 13, and a manifold 16 having an oxidizer supply port 15 on one of its opposite end faces;
A w manifold 18 having an oxidizing agent outlet 17 is applied to the other side, and these manifolds 12, 14, 16, 18 are tightened with a bolt or the like to maintain airtightness, thereby forming a fuel cell device 19. There is. Therefore, according to this fuel cell device 19, when fluid fuel is supplied from the fuel supply port II, this fuel branches through the flow path 4 of each unit cell, flows while contacting the back surface of the porous electrode 2, and then The fuel is discharged from the fuel discharge port 13. Also, oxidant supply port 1
When a fluid oxidizer is supplied from 5, this oxidant flows through the flow path 5 of each unit cell, flows while contacting the back surface of the porous ribbed electrode 3, and is then discharged from the oxidizer outlet 1r. Otherwise, the fluid fuel and the fluid oxidant are then supplied by diffusion into the porous ribbed electrodes 2, 3, respectively, to generate electrical energy as a fuel cell.

Note that the output terminal is omitted in the figure.

By the way, the above-mentioned ribbed electrodes 2 and 3 are made by molding a mixture of force-generating fibers and a thermosetting resin into several sheets, and then heating the mixture to 900°C to 1100°C in an inert atmosphere. In addition to carbonizing hardening resin, it also improves heat resistance, corrosion resistance,
2100℃~2500℃ to improve electrothermal properties
When a predetermined gas flow passage is formed by machining on the graphitized material, a special result can be obtained.

Furthermore, the ribbed electrodes 2 and 3 are usually 0.00% in terms of reaction gas diffusion, electrolyte retention function, electronic conductivity, and lamination sealing pressure.
It is made to have a low density of 4 to 0.6 iP/lx'' and a small average pore diameter of about several tens of microns.

However, even in the ribbed electrodes 2 and 3 made of graphitized carbonaceous porous plates, the impurities contained in the raw material carbon fibers and thermosetting resin are not completely removed and a considerable portion remains. ing. This is particularly true for carbon fibers made from petroleum pitch and coal pitch. When such electrodes 2゜3 with rigs are assembled as a unit cell and the fuel cell is operated under high temperature and high pressure conditions, impurities remaining in the rigged electric grinders 2 and 3 react with the electrolyte, oxidizing agent, water vapor, etc. As a result, the strength of the electrodes 2 and 3 with ribs decreases, and in severe cases, buckling occurs, resulting in an increase in contact resistance, a decrease in electrical conductivity, and a decrease in thermal conductivity, resulting in a decrease in battery performance. This makes it difficult to operate stably for a long period of time. This is particularly a problem in phosphoric acid electrolyte type fuel cells. Therefore, the emergence of a technology for producing electrodes with reduced impurities has been strongly desired from the viewpoint of long-term stable operation of fuel cells.

[Purpose of the invention]

The present invention was made in consideration of the above circumstances, and
The purpose is to use electrodes with a ridge with a small amount of impurities), and to maintain stability over a long period of time by preventing an increase in contact resistance and a decrease in conductivity without causing a decrease in strength or buckling even under operating conditions of high temperature and high pressure. The object of the present invention is to provide a fuel cell that can maintain the desired performance.

[Summary of the invention]

In order to achieve the above object, the present invention forms a fluid fuel flow path and a fluid oxidant flow path that are in contact with a pair of electrodes containing an electrolyte, and has a function of diffusing the flowing fuel and fluid oxidant into the reaction field. A fuel cell K comprising a plurality of stacked unit cells each having a ribbed electrode and outputting electrical energy under conditions where fuel and oxidizer are flowing through each flow path.
The present invention is characterized in that carnon fibers highly purified by high-temperature chlorine gas treatment are used as the material of the ribbed electrode.

[Embodiments of the invention]

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

In this embodiment, as the material for the ribbed electrodes 2 and 3 in the fuel cell described above, carnon fibers which have been highly purified by chlorine gas treatment at high temperatures are used.

The present ribbed electrode 2.3 is obtained as follows.

That is, carbon fiber is heated using a graphitization furnace, and after the temperature reaches 1500°C, chlorine gas is blown in at a predetermined flow rate for a specified period of time, and the temperature is further raised to 2300°C to scatter impurities as chloride. After that, the remaining chlorine is removed by scattering, thereby obtaining carbon fibers with a low content of fine particles. The table below shows the elemental analysis values of the amount of impurities remaining in the carnon fibers obtained in this way, and also compares the content of impurities in the carnon fibers before high purification treatment with chlorine gas. Shown for. As is clear from the table, the amount of impurities in the carnon fibers according to this example is extremely small compared to the untreated case, indicating that the fibers are highly purified.

[Table] Elemental analysis value unit of residual impurities ppm・Next, a predetermined amount of the mixture with phenolic resin is weighed using the carnon fiber obtained as above, and a flat surface (e.g. 650 x 750 square) K arrangement. Then, the arranged material is made into a predetermined thickness of 160~
Hot pressure molding at a temperature of 170°C for 5 minutes, and further 180°C
A post-cure treatment is carried out at 0.degree. C. for 72 hours to complete the reaction. Thereafter, the resin component is carbonized at 1100 DEG C., and then graphitized at 2100 to 2400'C, to obtain a carbon porous plate of a ribbed electrode.

Grooves as reaction gas flow passages were formed in the carbon porous plate obtained in this way, and a catalyst and electrolyte layer were further added and integrated to form a unit cell, which was assembled as a battery (205).
It was evaluated by long-term operation at ℃. After approximately 3,000 hours of operation, the electrode with ribs was disassembled and the electrode with ribs was observed. The decrease in strength of the rib material, buckling of the ribs, etc. that occurred in conventional electrodes with ribs were not observed in this example at all. . Therefore, it is clear from this that the carbon porous plate for electrodes with ribs obtained in this example maintains stable characteristics in fuel cell operation under high temperature and high pressure conditions, and as a result, it can be used in batteries. By incorporating the fuel cell, it is possible to prevent the conventional decrease in strength, increase in contact resistance due to buckling, etc., decrease in battery performance due to decrease in conductivity, etc., and to obtain a fuel cell that can maintain stable performance over a long period of time. It is something that can be done.

In addition to the above, a mixture of carbon fiber and a 7-enol resin such as furfural (also commonly referred to as furfural resin) may be used as the mixture for obtaining the porous plate in the above.

〔Effect of the invention〕

As explained above, according to the present invention, a ribbed electrode with a small amount of impurities is used, which is made of highly purified carbon fiber (through chlorine gas treatment at high temperature). It is possible to provide an extremely reliable fuel cell that can maintain stable performance over a long period of time by preventing an increase in welding resistance and a decrease in conductivity without causing a decrease in strength or buckling even under various conditions. .

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing a unit cell of a fuel cell, and FIG. 2 is a perspective view showing a fuel cell device incorporating the same unit cell. DESCRIPTION OF SYMBOLS 1... Matrix, box, 2, 3... Ribbed electrode, 4° 5... Fluid flow path, 6... Separator, 10...
Fastener, 11...Fuel supply port, 12, 14.16゜1
8... Manifold, 13--Fuel outlet, 15-- Oxidizing agent supply port, 17... Oxidizing agent outlet, 19... Fuel cell device. Originator's representative Patent attorney Takehiko Suzue Procedural amendments Showa IpO, b, 23rd Patent Office Commissioner Manabu Shiga 1, Indication of case Patent application No. 59-253049 2, Name of invention fuel cell 3, Amendment Relationship with the case of a person who makes a patent application Patent applicant (307) Toshiba Corporation (and 2 others) 4. Agent 5. Voluntary amendment A. Contents of amendment

Claims (2)

[Claims] (1) Forming a fluid fuel flow path and a fluid oxidizer flow path in contact with a pair of electrodes containing an electrolyte, each of which includes a ribbed electrode having a function of diffusing the flowing fuel and fluid oxidizer into a reaction field; In a fuel cell formed by stacking a plurality of unit cells that output electrical energy under conditions where fuel and oxidizer are flowing through the flow path, carbon highly purified by chlorine gas treatment at high temperature is used as the material for the ribbed electrode. A fuel cell characterized by using fibers. (2) The temperature at which high purity is achieved by chlorine gas treatment is 1500
The fuel cell according to claim (1), characterized in that the temperature is 2500°C to 2500°C.