JPH08250131A - Layered phosphoric acid type fuel cell - Google Patents

Abstract

PURPOSE: To operate a fuel cell stably for a long time by limiting the electrochemical corrosion of a cooling pipe, embedded in a cooling plate of a cell layered body, and moreover restraining the occurrence of the coating defect of the cooling pipe. CONSTITUTION: A metallic cooling pipe 1, provided with an insulative corrosion resistant coating, is embedded between cooling base plates 3A and 3B composed of a pair of carbon materials via conductive filling members 2. In the vicinity of the end surface of a cooling plate, formed by fastening; insulaing members 4 composed of fluororesin are arranged, so that tips can be protruded from the end surfaces of the plates 3A and 3B, in a portion facing the pipe 1 of the members 2, and are assembled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated phosphoric acid fuel cell formed by using an electrolyte layer which holds phosphoric acid, and more particularly to the structure of a cooling plate inserted in a cell stack.

[0002]

2. Description of the Related Art FIG. 3 is an exploded perspective view showing a general structure of a cell stack of a conventionally used stacked phosphoric acid fuel cell. As shown in the figure, an electrolyte layer 11 for holding phosphoric acid, a fuel electrode 12 having a fuel catalyst layer formed on one surface and a plurality of fuel gas flow grooves formed on the other surface,
A single cell 15 is formed by being sandwiched by an air electrode 13 having an air catalyst layer formed on one surface and a plurality of air passage grooves orthogonal to the fuel gas passage grooves on the other surface. The cell stack is formed by alternately stacking the single cells 15 and the separators 14, and further inserting and cooling the cooling plates 20 as appropriate and tightening them with a uniform pressure. The cooling plate 20 includes a refrigerant supply header 22 and a refrigerant discharge header 23.
A plurality of cooling pipes 1 that connect to and are buried, and by passing a coolant through the cooling pipes 1, the battery stack is cooled, and heat generated by power generation is removed.

FIG. 4 is a partial cross-sectional view in the stacking direction showing the structure near the end face of the cooling plate 20. The cooling pipe 1 made of metal for flowing the refrigerant has two cooling substrates 3A made of carbon.
3 and 3B, a conductive filling member 2 made of expandable graphite having good adhesion is interposed and buried while maintaining conductivity. Further, in order to prevent corrosion by the fuel gas containing phosphoric acid vapor and reaction air generated inside the unit cell 15 due to the power generation reaction, the surface of the cooling pipe 1 is provided with an insulating corrosion-resistant coating made of a fluororesin (not shown). Has been done. A current flows between the cooling substrates 3A and 3B during power generation, but no current flows through the cooling pipe 1 because the insulating and corrosion resistant coating is applied.

[0004]

DISCLOSURE OF THE INVENTION Cooling plate 2 for battery stack
As described above, the fluorocarbon resin is usually used for the insulating and corrosion-resistant coating of the cooling pipe 1 of No. 0. Fluororesin has excellent electrical insulation and corrosion resistance at use temperatures, but has a drawback in that it has weak mechanical strength and is susceptible to defects. Since there is a difference in the thermal expansion coefficient between the cooling plates 3A and 3B made of carbon and the conductive filling member 2 made of expandable graphite, which form the cooling plate 20, and the cooling pipe 1 made of metal, there is a difference in power generation. When the operation is repeated, friction is generated due to the heat cycle, and defects are likely to occur in the insulating and corrosion-resistant coating of the fluororesin having weak mechanical strength. When a defect occurs in the insulating and corrosion-resistant coating, phosphoric acid permeates from the defective portion and the metal cooling pipe 1 is corroded.

At the end portions of the cooling substrates 3A and 3B from which the cooling pipe 1 projects, not only the insulating and corrosion-resistant coating of the cooling pipe 1 is liable to cause defects due to friction with the conductive filling member 2, but also
Since the protruding portion of the cooling pipe 1 is directly exposed to the gas containing phosphoric acid, it is in a condition where it is more likely to be corroded. In particular, at this end, in addition to corrosion by phosphoric acid penetrating through the defects of the insulating and corrosion resistant coating, electrochemical corrosion is caused by the current flowing between the conductive filling member 2 and the cooling pipe 1 through the defects of the insulating and corrosion resistant coating. Therefore, there is a problem that the corrosion progresses rapidly.

The present invention has been made in view of the above problems, and an object thereof is to suppress electrochemical corrosion of a cooling pipe embedded in a cooling plate of a battery laminate, and further to cool the cooling pipe. Another object of the present invention is to provide a laminated phosphoric acid fuel cell capable of stably operating over a long period of time by preventing the occurrence of defects in the dielectric and corrosion resistant coating.

[0007]

In order to achieve the above object, in the present invention, an electrolyte layer holding phosphoric acid is sandwiched between a fuel electrode and an air electrode and alternately laminated with a separator to form a cooling plate. In a laminated phosphoric acid fuel cell including a cell stack formed by appropriately inserting, a cooling pipe made of a metal material having an insulating and corrosion-resistant coating, for example, a carbon material via a conductive filling member made of expandable graphite. Insulation partly protruding from the end surface of the cooling board, between the conductive filling member near the end surface of the cooling board and the cooling pipe of the cooling plate embedded between the pair of cooling boards It shall be provided with members.

Further, in a laminated phosphoric acid fuel cell including a cell stack formed in the same manner as described above, a pair of cooling pipes made of a metal material having an insulating and corrosion resistant coating and made of a carbon material with a conductive filling member interposed therebetween. Of the cooling plate, which is embedded between the cooling substrates, between the cooling substrate near the end face of the cooling substrate and the cooling pipe, and the insulating member, a part of which protrudes from the end face of the cooling substrate. Are provided in abutment with the conductive filling member.

Further, the insulating member is made of fluororesin. Further, the above-mentioned seal member is made of fluororesin.

[0010]

In a cooling plate formed by embedding a cooling pipe made of a metal material having an insulating and corrosion-resistant coating between a pair of cooling substrates made of a carbon material via a conductive filling member made of expandable graphite, for example. If the insulating member is provided between the conductive filling member near the end surface of the cooling substrate and the cooling pipe, and a part of the insulating member is projected from the end surface of the cooling substrate, the cooling substrate and the conductive filling member are provisionally provided. The difference in the coefficient of thermal expansion between the cooling pipe and the cooling pipe causes friction, and even if the corrosion-resistant coating of fluororesin with weak mechanical strength becomes defective, the cooling pipe protruding to the end surface of the cooling substrate is insulated. Since it is covered by the member, the insulating member is interposed in the conduction path that connects the cooling pipe and the end surface of the cooling substrate or the conductive filling member through the defective portion of the insulating and corrosion resistant coating, and the electrical insulation is substantially maintained. . Therefore, even if a defect occurs in the insulating and corrosion-resistant coating, the flow of current is blocked, so that electrochemical corrosion, which has been a problem in conventional cooling plates, is suppressed, and rapid corrosion of cooling tubes is prevented. To be prevented. In addition,
Since the insulating member is arranged only in the vicinity of the end surface of the cooling substrate, the pair of cooling substrates are connected via the conductive filling member except for this part, and the conductivity between the cooling substrates is sufficiently maintained. It

A cooling pipe formed of a metal material having an insulating and corrosion resistant coating is embedded between a pair of cooling substrates made of a carbon material via a conductive filling member made of expandable graphite. In the plate, between the cooling substrate near the end face of the cooling substrate and the cooling pipe, a laminated body of a seal member and an insulating member, a part of which protrudes from the end face of the cooling substrate, is provided in abutment with the conductive filling member. If so, since the cooling pipe protruding to the end surface portion of the cooling substrate is covered with the insulating member as in the above case, even if a defect occurs in the insulating corrosion-resistant coating, the occurrence of electrochemical corrosion is suppressed, and cooling is performed. Rapid corrosion of tubes is prevented. Further, since the insulating member and the sealing member are laminated, there is an advantage that the force applied to the cooling plate can be suppressed so as not to be excessive when the battery laminated body is tightened to be formed. Even in this configuration, the laminated body of the seal member and the insulating member is arranged only near the end surface of the cooling substrate, and except for a part of this, the pair of cooling substrates are connected via the conductive filling member. Therefore, the conductivity between the cooling substrates is sufficiently maintained.

Further, if the above-mentioned insulating member which is in direct contact with the cooling pipe is made of fluororesin, the strength of fluororesin is weak, and when the insulating and corrosion resistant coating of the cooling pipe is made of fluororesin, Since the same material is used, even if friction occurs due to a difference in coefficient of thermal expansion, damage to the insulating and corrosion resistant coating of the cooling pipe is suppressed. Furthermore, if the sealing member is made of fluororesin, the pressure applied to the cooling plate when the battery stack is tightened is made uniform, and application of excessive stress is avoided.

[0013]

1 is a partial cross-sectional view in the stacking direction showing the structure near the end face of a cooling plate in the first embodiment of the stacked phosphoric acid fuel cell of the present invention. The cooling pipe 1 made of metal for flowing the refrigerant has an insulating and corrosion-resistant coating made of fluororesin (not shown) on the surface thereof, and except a part near the end face of the cooling plate, a cooling substrate 3A made of a pair of carbon materials. And 3
A conductive filling member 2 made of expandable graphite is interposed between B and embedded and tightened. In the vicinity of the end surface of the cooling plate, a thin insulating member 4 made of fluororesin having a tip protruding from the end surfaces of the cooling substrates 3A and 3B is incorporated in a portion of the conductive filling member 2 facing the cooling pipe 1.

In this structure, the insulating member 4 is arranged only in the vicinity of the end faces of the cooling substrates 3A and 3B. Except for a part thereof, the pair of cooling substrates 3A and 3B are connected via the conductive filling member 2. Therefore, as in the conventional example, the conductivity between the cooling substrates 3A and 3B is sufficiently maintained. Further, in the vicinity of the end faces of the cooling substrates 3A and 3B, the cooling pipe 1 is separated from the end faces of the cooling substrates 3A and 3B or the conductive filling member 2 by the insulating member 4, so that the insulation corrosion resistance of the cooling pipe 1 is temporarily assumed. Even if there is a defect in the coating, the flow of current is blocked, the occurrence of electrochemical corrosion is suppressed, and rapid corrosion of the cooling pipe 1 is prevented. Further, since the insulating member 4 is formed of a fluororesin like the insulating and corrosion-resistant coating of the cooling pipe 1, even if friction occurs between the cooling pipe 1 and the cooling pipe 1 due to the heat cycle, the insulating member near the end face is insulated. The corrosion-resistant coating is less likely to be damaged, and the occurrence of defects is suppressed.

FIG. 2 is a partial cross-sectional view in the stacking direction showing the structure near the end face of the cooling plate in the second embodiment of the stacked phosphoric acid fuel cell of the present invention. The feature of this embodiment is that, in the vicinity of the end face of the cooling plate, between the cooling substrates 3A and 3B made of a pair of carbon materials and the cooling pipe 1 made of metal, the seal member 5 made of fluororesin and a part thereof are cooled. This is because a laminate with a thin insulating member 4 made of fluororesin protruding from the end face of the substrate is abutted and incorporated with the conductive filling member 2 made of expandable graphite.

In this structure, the thin insulating member 4 made of fluororesin is provided only near the end faces of the cooling substrates 3A and 3B.
By arranging, like the first embodiment of FIG. 1,
The conductivity between the cooling substrates 3A and 3B is sufficiently maintained, the occurrence of electrochemical corrosion of the cooling pipe 1 is suppressed, and the occurrence of defects in the insulating and corrosion resistant coating of the cooling pipe 1 is suppressed, Further, a sealing material 5 made of fluororesin is laminated and arranged on the insulating member 4 made of fluororesin, and the cooling substrate 3
Since the gap between A and 3B is filled, the pressure applied to this portion when the battery stack is tightened is relieved, application of excessive stress is avoided, and damage is prevented.

[0017]

As described above, according to the present invention, the electrolyte layer holding phosphoric acid is sandwiched between the fuel electrode and the air electrode, alternately laminated with the separator, and the cooling plate is appropriately inserted. In a laminated phosphoric acid fuel cell comprising a cell stack comprising:
An end surface of a cooling plate of a cooling plate formed by embedding a cooling pipe made of a metal material having an insulating and corrosion-resistant coating between a pair of cooling substrates made of a carbon material via a conductive filling member made of expandable graphite, for example. Between the conductive filling member and the cooling pipe in the vicinity of, the insulating member is provided so as to partly project from the end surface of the cooling substrate, so that the conductivity between the cooling substrates is sufficiently maintained, and Even if there is a defect in the insulating and corrosion-resistant coating, the flow of current through the cooling pipe is blocked, and the occurrence of electrochemical corrosion is suppressed, so a laminated phosphoric acid fuel cell that can be stably operated for a long time is provided. It will be obtained.

Further, in a laminated phosphoric acid fuel cell provided with a cell stack formed in the same manner as described above, a cooling pipe made of a metal material provided with an insulating and corrosion resistant coating, for example, a conductive filling member made of expandable graphite is provided. A sealing plate and a part of the cooling plate embedded between a pair of cooling substrates made of carbon material between the cooling substrate and the cooling pipe near the end face of the cooling substrate protrude from the end face of the cooling substrate. If a laminate with an insulating member is provided in abutment with the conductive filling member, the conductivity between the cooling substrates is sufficiently maintained, and even if a defect occurs in the insulating and corrosion-resistant coating film, the cooling pipe. The flow of the current is blocked, the occurrence of electrochemical corrosion is suppressed, and the stress due to the tightening of the battery stack is relaxed, and a cooling plate that is not damaged can be obtained, so that stable operation can be performed for a long period of time. Laminated phosphoric acid fuel So that the pond can be obtained.

Further, if the above-mentioned insulating member is made of fluororesin, a cooling plate in which damage to the insulating and corrosion-resistant coating film is suppressed can be obtained, so that the laminated phosphoric acid type can be stably operated for a long period of time. It is more suitable for a cell stack of a fuel cell. Furthermore, if the sealing member is made of fluororesin, the stress associated with tightening is appropriately relieved and damage due to excessive stress is prevented, so that the laminated phosphoric acid can be operated stably for a longer period of time. A type fuel cell will be obtained.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view in a stacking direction showing a configuration near an end surface of a cooling plate in a first embodiment of a stacked phosphoric acid fuel cell of the present invention.

FIG. 2 is a partial cross-sectional view in the stacking direction showing the structure near the end surface of the cooling plate in the second embodiment of the stacked phosphoric acid fuel cell of the present invention.

FIG. 3 is an exploded perspective view showing a general configuration of a cell stack of a conventionally used stacked phosphoric acid fuel cell.

FIG. 4 is a partial cross-sectional view in the stacking direction showing the configuration near the end surface of the cooling plate of the conventional stacked phosphoric acid fuel cell.

[Explanation of symbols]

 1 Cooling Pipe 2 Conductive Filling Member 3A Cooling Substrate 3B Cooling Substrate 4 Insulating Member 5 Sealing Member 11 Electrolyte Layer 12 Fuel Electrode 13 Air Electrode 14 Separator 15 Single Cell 20 Cooling Plate 22 Refrigerant Supply Header 23 Refrigerant Discharge Header

Claims (5)

[Claims] 1. A laminated phosphoric acid fuel comprising a battery laminate formed by sandwiching an electrolyte layer holding phosphoric acid between a fuel electrode and an air electrode and alternately laminating it with a separator, and appropriately inserting a cooling plate. In the battery, the cooling plate, a cooling pipe made of a metal material having an insulating and corrosion-resistant coating is embedded between a pair of cooling substrates made of a carbon material via a conductive filling member,
A laminated phosphoric acid fuel characterized in that an insulating member is provided between the conductive filling member near the end face of the cooling substrate and the cooling pipe so as to partially project from the end face of the cooling substrate. battery. 2. A laminated phosphoric acid fuel comprising a battery laminate formed by sandwiching an electrolyte layer holding phosphoric acid between a fuel electrode and an air electrode and alternately laminating it with a separator, and appropriately inserting a cooling plate. In the battery, the cooling plate is formed by embedding a cooling pipe made of a metal material having an insulating and corrosion resistant coating between a pair of cooling substrates made of a carbon material via a conductive filling member, and Between the cooling substrate and the cooling pipe in the vicinity of the end face, a laminate of a seal member and an insulating member partially protruding from the end face of the cooling substrate is provided in abutment with the conductive filling member. Laminated phosphoric acid fuel cell. 3. The laminated phosphoric acid fuel cell according to claim 1, wherein the conductive filling member is formed of expandable graphite. 4. The stacked phosphoric acid fuel cell according to claim 1, 2 or 3, wherein the insulating member is made of a fluororesin. 5. The laminated phosphoric acid fuel cell according to claim 1, 2, 3 or 4, wherein the seal member is made of fluororesin.