JPH0629024A - Solid electrolyte fuel cell - Google Patents

Abstract

PURPOSE:To equip a fuel cell of solid electrolyte type with a high output capacity, long lifetime, and high reliability by decreasing the electric resistance of fuel cell electrode, and reducing micro-crack initiation and exfoliation of each layer due to thermal hysteresis. CONSTITUTION:A fuel cell with solid electrolyte includes a base tube (plate) 2, fuel electrode (or air electrode) 4 in lamination, solid electrolyte (YSZ) 6, and air electrode (or fuel electrode) 8. The electrodes 4, 8 are made of porous material selected among NiCrAl series, NiCrFe series and NiCrFeAl series and NiCrAl+YSZ series, NiCrFe+ YSZ series and NiCrFeAl+YSZ series. It is possible to form the solid electrolyte (YSZ) through plasma fusion spray and each electrode film by flame fusion spray. Also it is acceptable that the base tube (plate) is fabricated from the mentioned material to allow working also as electrode 4. This heat resistant alloy whether used as fuel electrode or air electrode, excels in the durability, electroconductivity, and the matching capability with the YSZ, and its laminate structure and execution of constructing are simplified because of the possibility of working as the base tube (plate) and electrode at the same time. The factor to generate thermal distortion is decreased, and the fuel electrode and air electrode can be formed from the materials in the same series.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid electrolyte fuel cell, and more particularly to a cylindrical or flat plate solid electrolyte fuel cell using yttria-stabilized zirconia as a solid electrolyte, in which the air electrode or the fuel electrode has a specific heat resistance. To a solid electrolyte fuel cell, characterized in that the base tube or base plate is made of an alloy or cermet, or the base tube or base plate is made of the alloy or cermet, and the base tube or base plate itself is also used as an air electrode or a fuel electrode. It is a thing.

[0002]

2. Description of the Related Art Solid electrolyte fuel cells have higher power generation efficiency (about 60%) and are more economical than other fuel cells, and have a high exhaust heat temperature, which enables efficient use such as combined cycle power generation. Since all the battery materials are solid and stable performance and long life can be expected without fear of corrosion and evaporation, they are being developed as a power source for future electric utilities.

A solid electrolyte fuel cell is based on a structure in which a solid electrolyte is sandwiched between electrode plates having good gas permeability. As the solid electrolyte, a fluorite type cubic crystal structure is maintained from room temperature to high temperature. And yttria-stabilized zirconia (YSZ), which is a chemically stable composite oxide, has been used. Yttria-stabilized zirconia (YSZ)
Is (Y ₂ O ₃ ) _x (ZrO ₂ ) _1-x (x = 8 to
Has a composition of 10 moles). Since YSZ has a solution of trivalent yttrium oxide in tetravalent zirconium oxide, it has oxide ion vacancies in the crystal. At high temperature, these vacancies move freely in the crystal. To do. When gas permeable electrodes are attached to both sides and oxygen concentration difference is given to both sides, high concentration side (cathode, generally called air electrode)
From this, oxygen becomes O ²⁻ and enters YSZ, and moves to the low oxygen side (anode, generally called a fuel electrode) by a concentration difference and carries electrons. The O ²⁻ ions reaching the anode release electrons and react with the fuel. The emitted electrons flow through an external electric circuit and work on the load. The anode (fuel electrode) promotes the reaction between the fuel and oxygen and plays a role of supplying electrons to the load, while the cathode (air electrode) plays a role of supplying oxygen and electrons to YSZ as O ²⁻ ions. .

At present, there are a solid electrolyte fuel cell of a cylindrical type and a flat plate type, and FIG. 6 shows the operating principle of the cylindrical solid electrolyte fuel cell. Cylindrical solid electrolyte fuel cell 2
0 is inserted into the protective tube 24 equipped with the electric furnace 22 on the outer periphery, the fuel gas (or oxygen source gas) is passed through the internal passage of the cell, and the oxygen source gas (or fuel gas) is passed around the cell. Passed through. The source of oxygen gas is usually air.
A plurality of power generation units 26 connected in series are formed at intervals along the length of the battery, and electricity generated from these power generation units is collected through the collector electrode 28 to generate power. Ammeter 3
0, voltmeter 32 and load 34 are connected as shown.

FIG. 7 is an enlarged partial sectional view of a part of the solid oxide fuel cell 20 of FIG. The solid electrolyte fuel cell has a base tube 36, and a plurality of power generation sections 26 are shown along the length thereof, one of which is shown in cross section. Power generation unit 26
Is composed of a fuel electrode 38, an electrolyte 40 and an air electrode 42. A first airtight layer 44 and a second airtight layer 46 are provided to keep the battery airtight.

FIG. 8 is a sectional view taken along the line AA of FIG. The mode that the power generation part 26 is comprised from the base | substrate tube 36 and the fuel electrode 38, the electrolyte 40, and the air electrode 42 which were laminated | stacked on it is shown.

As shown in FIG. 9, a flat plate type solid electrolyte fuel cell is constructed by integrating a plurality of flat plate-shaped battery unit cells 48 each composed of two electrodes sandwiching a solid electrolyte with a separator 50 interposed therebetween. By supplying the fuel gas or the oxygen source gas alternately, the same effect as described above can be obtained.
Alternatively, as shown in FIG. 10, a single cell structure 56 in which an electrode-solid electrolyte-electrode layer laminated body 54 is laminated on the upper surface of a base plate (separator) 52 having a gas passage may be integrated. .

The conventional solid electrolyte fuel cell has Al ₂ O ₃
Alternatively, a porous base tube or base plate made of calcia-stabilized zirconium (CSZ) is provided with a porous air electrode made of a lanthanum-based perovskite complex oxide (LaCoO ₃ , LaMnO ₃ or LaSrMnO ₃ ), Y
The porous fuel electrode made of the SZ solid electrolyte and NiO was laminated in this order or in the order of the porous fuel electrode, the YSZ solid electrolyte and the porous air electrode. The solid electrolyte is currently Y due to the need to secure its performance.
It is confirmed as SZ. The materials of the other base tube (plate) and the electrode component element are selected for the intended function while considering the compatibility with YSZ. It was recognized that these materials were not entirely satisfactory, but at present they have been regarded as the best materials. These were formed on a porous substrate tube or substrate plate by a thermal spraying method (acetylene flame spraying, plasma spraying, etc.), an electrochemical vapor deposition method (CVD / EVD), and an extrusion-slurry method.

[0009]

In the above configuration,
Especially, the electric resistance of the air electrode is high and the fuel cell is operating.
Ionic electron conduction occurs in the high temperature operating region between the solid electrolyte YSZ and the porous fuel electrode and between the solid electrolyte YSZ and the porous air electrode. At this time, due to the difference in thermal expansion between the two, thermal stress is generated in the discontinuous portion of the welded surface in the laminated boundary surface, resulting in microcracks and peeling. For this reason,
Electric resistance increased, which was a major factor in battery output loss. Furthermore, the stability of the battery operating characteristics of the air electrode is impaired, and there is a problem in extending the life of the battery. For example, conventionally used LaCoO ₃ has a drawback that La and Co which are structural constituent elements are selectively evaporated at a power generation operating temperature of about 1000 ° C., the chemical structure is changed, and the conductivity is lowered. In manufacturing a fuel cell, a large number of elements are connected in series and parallel in order to obtain a large output, so that it can be manufactured by a simple process in a short time, the material cost is low, and the gas permeability is good. It must be taken into consideration that an electrode film having good adhesion to the solid electrolyte YSZ can be formed.

An object of the present invention is to reduce the electrical resistance of electrodes, particularly air electrodes, during power generation at high temperatures, and to reduce the occurrence of microcracks and peeling of each layer due to thermal history.
In addition to achieving high output, long life and high reliability of the battery,
It is to simplify the battery configuration as compared with the conventional one.

[0011]

As a result of repeated studies aimed at solving the above problems, the present inventor has found that the air electrode and the fuel electrode, which were conventionally made of different materials, are made of the same material. As a result of trying various materials, assuming (NiCrA
1) system, (NiCrFe) system and (NiCrFeAl)
System and (NiCrAl + YSZ) system, (NiCrFe
+ YSZ) system and (NiCrFeAl + YSZ) system have been found to be feasible by adopting a heat resistant alloy or cermet selected from the group. Based on this finding,
The present invention provides a solid electrolyte fuel cell comprising yttria-stabilized zirconia as a solid electrolyte and an air electrode and a fuel electrode in contact with the solid electrolyte, wherein the air electrode and the fuel electrode are porous, (NiCrAl) system, NiC
rFe) -based and (NiCrFeAl) -based heat-resistant alloys and (NiCrAl + YSZ) -based, (NiCrFe + YS)
A solid electrolyte fuel cell characterized by being made of a heat resistant alloy or cermet selected from the group of Z) type and (NiCrFeAl + YSZ) type cermets.

Further, it has been found that the base tube or the base plate may be made of the above-mentioned material, and the base plate itself may also serve as the air electrode or the fuel electrode, thereby greatly simplifying the cell structure. Based on this finding, the present invention also provides a solid electrolyte fuel cell comprising a yttria-stabilized zirconia as a solid electrolyte, and an air electrode and a fuel electrode in contact with the solid electrolyte on a base tube or a base plate. Alternatively, the base plate may be a porous (NiCrAl) -based
(NiCrFe) type and (NiCrFeAl) type heat resistant alloys and (NiCrAl + YSZ) type, (NiCrF)
e + YSZ) -based and (NiCrFeAl + YSZ) -based cermet made of a heat-resistant alloy or cermet, and the base tube or base plate itself is also used as an air electrode or fuel electrode adjacent to the base pipe or base plate. Further, the other air electrode or fuel electrode is made of the same material, and a solid electrolyte fuel cell is provided.

It is preferable that the solid electrolyte and the air electrode and the fuel electrode are sprayed films, especially the solid electrolyte is a plasma sprayed film, and each electrode is a flame sprayed film.

[0014]

The air electrode and the fuel electrode, and further the base tube or the base plate are porous (NiCrAl) type, (NiCrF) type.
e) system and (NiCrFeAl) system and (NiCrA)
1 + YSZ) system, (NiCrFe + YSZ) system and (N
(iCrFeAl + YSZ) group made of a heat-resistant alloy or cermet with excellent durability and good electrical conductivity, selected from the group This makes it possible to improve the compatibility with the solid electrolyte YSZ and to simplify the battery structure. For example, porous NiO ₂ conventionally used as a fuel electrode can be used as a fuel electrode but cannot be used as an air electrode.

More specifically, the porous heat-resistant alloy used in the present invention has, for example, 1 at an operating temperature of a battery of 1000.degree.
It has a coating thickness of about 1.6 kS / cm at a sprayed film thickness of 00 μm, while it has been used for a conventional air electrode, for example, LaCo.
Since the O ₃ ceramic has about 600 S / cm at the battery operating temperature of 1000 ° C., the electric resistance of the electrodes is significantly improved, and thus the power generation efficiency is improved by the decrease of the internal resistance. Regarding the coefficient of thermal expansion, for example, in the case of LaCoO ₃ , it is 20 × 10 ⁻⁶ K ⁻¹ , whereas, for example, NiCrA is used.
lY + YSZ is 14 to 15 × 10 ⁻⁶ K ^−1, which is closer to the thermal expansion coefficient of 10 × 10 ⁻⁶ K ⁻¹ of the electrolyte YSZ, and the consistency of thermal expansion with the electrolyte YSZ is further improved. Moreover, since the main material involved in the present invention is metallic,
Good malleability, which improves the adhesive strength of the laminated film and makes microcracks and peeling less likely to occur. Conventionally used L
Although aCoO ₃ has a defect that La and Co, which are structural constituent elements, are selectively evaporated at a power generation operating temperature of about 1000 ° C., the chemical structure is changed, and the conductivity is lowered, but the material of the present invention is a heat resistant alloy. Or, since it is a ceramic and shows stable and high conductivity even at high temperature, such a problem does not occur.

[0016]

EXAMPLE FIG. 1 is an enlarged view of a part of FIG. 8 showing a cross section of a cylindrical solid electrolyte battery (a cylinder is shown linearly). A base tube 2 and a fuel electrode (or an air electrode) 4, a solid electrolyte (YSZ) 6 and an air electrode (or a fuel electrode) 8 stacked on the base tube 2 are shown. FIG. 2 shows a fuel electrode (or an air electrode) 4, a solid electrolyte (YSZ) 6 and an air electrode (or a fuel electrode) 8 which constitute the battery unit cell of the flat plate type solid electrolyte battery shown in FIG. FIG. 3 shows the battery unit cell structure of FIG. A fuel electrode (or air electrode) 4, a solid electrolyte (YSZ) 6 and an air electrode (or fuel electrode) 8 are laminated on a base plate 10 having a separator function. According to the invention, these electrodes 4 and 8
Is a porous (NiCrAl) system, (NiCrFe)
Series and (NiCrFeAl) series heat resistant alloys and (NiC
It is made of a heat resistant alloy or cermet selected from the group of rAl + YSZ) type, (NiCrFe + YSZ) type and (NiCrFeAl + YSZ) type cermets. These heat-resistant alloys and cermets have excellent durability and malleability,
It has low electric resistance and improves the thermal compatibility with the solid electrolyte (YSZ).

In the present invention, NiCrAl-based means N
i = 64-69% by weight, Cr = 21-23% by weight and A
1 = 9 to 11% by weight, defined as being composed of 1 to about 1% by weight, and a small amount of additives can be included.
Further, the NiCrFe system has Ni> 72 wt% and Cr = 1.
It is defined as consisting of 4 to 17% by weight and Fe = 6 to 10% by weight. Similarly, the NiCrFeAl system is defined as being composed of Ni = 58 to 63% by weight, Cr = 21 to 25% by weight, Fe = 10 to 20% by weight and Al = 1 to 1.7% by weight. . NiCrAl
+ YSZ system means Ni = 64 to 69% by weight, Cr = 21
It is defined as a composite material (cermet) in which 10 to 50% by weight of YSZ is added to a NiCrAl alloy composed of ˜23% by weight and Al = 9 to 11% by weight. NiCr
Fe + YSZ system means Ni> 72 wt%, Cr = 14-
N composed of 17% by weight and Fe = 6 to 10% by weight
It is defined as a composite material (cermet) in which 10 to 50% by weight of YSZ is added to an iCrFe alloy. Similarly, N
iCrFeAl + YSZ system means Ni = 58-63% by weight, Cr = 21-25% by weight, Fe = 10-20% by weight
And NiCrF composed of Al = 1 to 1.7% by weight
It is defined as a composite material (cermet) in which 10 to 50% by weight of YSZ is added to an eAl alloy. These can also contain small amounts of additives, around 1% by weight.

The electrode-electrolyte-electrode laminated structure can be prepared by a thermal spraying method (acetylene flame spraying, plasma spraying, etc.), an electrochemical vapor deposition method (CVD / EVD) and an extrusion molding-slurry method. The solid electrolyte needs to have the ability to almost completely prevent gas permeation, and the most preferable method is plasma spraying. The electrodes need to have sufficiently large gas permeation characteristics that flame spraying is suitable. In any of the thermal spraying methods, material particles are melted and sprayed onto a base material (base tube, base plate) to form a film, but by controlling the particle size of the material particles and the spraying conditions, the desired density and porosity can be obtained. Can be produced.

A construction example of plasma spraying will be described.
In order to manufacture a cylindrical solid electrolyte fuel cell, it is manufactured by the following procedure. Attach the substrate tube to the rotator. In order to form the battery pattern shown in FIG. 7, masking is performed on a portion other than the portion to be formed (masking here is to cover a portion of the metal plate that is not desired to be sprayed and formed). Depending on the size of the part to be covered up, a vertical shape is erected between the spray gun and the spray body, or a copper tape shape is wound directly around the pipe side and fixed and covered. Can be used.). After masking is completed, the substrate tube is rotated, the spray gun is fed along the axial direction of the substrate tube, and sprayed to form a film. After film formation,
Move the masking attachment position to the next film formation pattern,
A battery is manufactured by stacking layers in the same manner.

Table 1 shows an example of a combination of materials of the cylindrical vertical stripe type cell stack structure.

[0021]

[Table 1]

FIG. 4 shows a structure in which the base tube 2 of FIG. 1 is made of the above-mentioned material and is also used as the electrode 4. Therefore, in this case, the battery is composed of the base tube / electrode 12 and the solid electrolyte (YSZ) 6 and the air electrode (or fuel electrode) 8 formed thereon. FIG. 5 shows FIG.
A structure is shown in which the base plate 10 having the function of the separator is made of the above-mentioned material and also serves as the electrode 4. Therefore, here, the battery is the base plate (separator) and electrode 1
4 and a solid electrolyte (YSZ) 6 and an air electrode (or a fuel electrode) 8 laminated on the electrode 4. By adopting the configuration of FIG. 4 and FIG. 5, the number of laminated layers is reduced,
Moreover, since it is possible to use the same or the same material other than the solid electrolyte (YSZ), it is obvious that the assembly is greatly simplified.

(Example 1) In the test facility outlined in FIG. 6, a solid electrolyte battery having a length of 500 mm and a width of 15 m was used.
m power generation parts were formed at three locations. 21m for the base tube
A CSZ perforated tube of m diameter was used. NiCrAl film as fuel electrode by flame spraying method, solid electrolyte YSZ film by plasma spraying method, and NiCrAl + 30% by weight as air electrode by flame spraying method in power generation part
YSZ films were sequentially stacked. The plasma and flame spraying conditions were as shown in Table 2 below:

[0024]

[Table 2]

When this was actually operated and the state of the laminated film was examined, cracks and peeling did not occur. As a result of evaluating the battery performance, the output current density of a single cell is 300 mmA.
The output voltage was 0.7 V or more, which was excellent.

(Example 2) In Example 1, a substrate tube was made of NiCrAl + 30 wt% YSZ, and a solid electrolyte YSZ film and an N electrode as an air electrode were similarly formed thereon.
iCrAlY films were sequentially laminated. Similar excellent performance was obtained.

[0027]

INDUSTRIAL APPLICABILITY The heat-resistant alloy used in the present invention has excellent durability, electric conductivity, and compatibility with the solid electrolyte (YSZ) both as a fuel electrode and an air electrode, and also has excellent compatibility with the base tube (plate). Since it can be used also as an electrode, the laminated structure and its construction are simplified, and the production is facilitated. Factors that are subject to thermal strain are reduced, which results in longer battery life, improved reliability, and higher output. By using the same material for the fuel electrode and the air electrode, the manufacturing process of thermal spraying can be simplified and the cell stack structure can be further simplified.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a cylindrical solid electrolyte battery.

FIG. 2 is a cross-sectional view of a battery single cell of a flat plate type solid electrolyte battery.

FIG. 3 is a cross-sectional view of a battery single cell structure of a flat plate solid electrolyte battery.

FIG. 4 is a cross-sectional view showing a configuration in which the substrate tube of FIG. 1 also serves as one of the electrodes.

5 is a cross-sectional view showing a configuration in which the base plate (separator) of FIG. 3 also serves as one of the electrodes.

FIG. 6 is an explanatory diagram illustrating the operating principle of a cylindrical solid electrolyte fuel cell.

FIG. 7 is an enlarged view showing a partial cross section of a part of the cylindrical solid oxide fuel cell of FIG.

8 is a cross-sectional view taken along the line AA of FIG.

FIG. 9 is a perspective view of an example of a flat plate solid oxide fuel cell.

FIG. 10 is a perspective view of another example of a flat plate solid oxide fuel cell.

[Explanation of symbols]

 2 base tube 4 fuel electrode (or air electrode) 6 solid electrolyte (YSZ) 8 air electrode (or fuel electrode) 10 base plate 12 base tube / electrode 14 base plate / electrode 20 cylindrical solid electrolyte fuel cell 22 electric furnace 24 protection Tube 26 Power generation section 28 Collector electrode 30 Ammeter 32 Voltmeter 34 Load 36 Base tube 38 Fuel electrode 40 Solid electrolyte (YSZ) 42 Air electrode 44 First airtight layer 46 Second airtight layer 48 Battery unit cell 50 Separator 52 Base plate 54 Battery single cell stack 56 Battery single cell structure

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Futoshi Uchiyama 1-4 Umezono, Tsukuba-shi, Ibaraki Electronic Technology Research Institute, Industrial Technology Institute (72) Koichi Tsukamoto 1-4-1 Umezono, Tsukuba-shi, Ibaraki (72) Inventor, Yasuo Kaga, 1-4 Umezono, Tsukuba City, Ibaraki Prefecture (72) Inventor, Electronic Technology Research Institute (72) Hideo Horiuchi 1-3, Nagasu Nishidori, Amagasaki, Hyogo Prefecture −26 In Japan Coating Industry Co., Ltd. (72) Inventor Moto Kanazawa 5-7-4 Bunkura, Urawa City, Saitama Prefecture Japan Coating Industry Co., Ltd. Tokyo Plant

Claims (3)

[Claims] 1. A solid electrolyte fuel cell comprising yttria-stabilized zirconia as a solid electrolyte and comprising an air electrode and a fuel electrode in contact with the solid electrolyte, wherein the air electrode and the fuel electrode are porous (NiCrAl) -based, (N
(iCrFe) type and (NiCrFeAl) type heat resistant alloys and (NiCrAl + YSZ) type, (NiCrFe +)
A solid electrolyte fuel cell, characterized by being made of a heat resistant alloy or cermet selected from the group of YSZ) type and (NiCrFeAl + YSZ) type cermets. 2. A solid electrolyte fuel cell comprising yttria-stabilized zirconia as a solid electrolyte, and an air electrode and a fuel electrode in contact with the solid electrolyte on the base tube or the base plate, wherein the base tube or the base plate is porous. , (N
iCrAl) type, (NiCrFe) type and (NiCrF)
eAl) type heat resistant alloy and (NiCrAl + YSZ)
System, (NiCrFe + YSZ) system and (NiCrFeA)
1 + YSZ) cermet, made of a heat-resistant alloy or cermet, and the base tube or base plate itself is also used as an air electrode or fuel electrode adjacent to the base tube or base plate and the other air electrode. Alternatively, the solid electrolyte fuel cell is characterized in that the fuel electrode is made of a similar material. 3. The solid electrolyte fuel cell according to claim 1, wherein the solid electrolyte and the air electrode and the fuel electrode are sprayed films.