JPH04245167A - Manufacture of solid electrolytic fuel cell - Google Patents

Abstract

PURPOSE:To lengthen the life of a solid electrolytic fuel cell by suppressing the increase in the contact resistance at a collecting part such as a bipolar plate, or the contact resistance between a solid electrolyte and electrodes for a long term. CONSTITUTION:A manufacture of a solid electrolytic fuel cell comprising; the first step for producing a layered product in such a way that a fuel pole is disposed on one plane of a solid electrolyte, and the second step for heat-treating the layered product while applying a predetermined load in a reducing atmosphere of 1000 deg.C or higher (the operating temperature of a battery).

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a solid oxide fuel cell, and more particularly to a method for manufacturing a flat solid oxide fuel cell.

0002

2. Description of the Related Art Fuel cells directly convert the chemical energy of supplied gas into electrical energy, and are therefore expected to have high power generation efficiency. In particular, solid oxide fuel cells (SOF)
C) is attracting attention as a third generation fuel cell following phosphoric acid type and molten carbonate type fuel cells.

Specifically, the solid electrolyte fuel cell is made of solid oxides (Y2 O3 stabilized ZrO2, etc.) and can avoid evaporation and creepage of the electrolyte, thereby eliminating electrolyte loss. Since it operates at a high temperature of about 1000°C, it has the advantage of increasing power generation efficiency when waste heat is included.

0004

[Problems to be Solved by the Invention] By the way, various wet methods and dry methods have been proposed as methods for manufacturing the solid electrolyte fuel cell, but no matter which method is used, electrodes may not be produced during battery operation. is sintered, and the thickness of the electrode (particularly the fuel electrode), which plays the role of electrical conduction, is reduced. As a result, the contact between the electrode and the current collector such as a bipolar plate and the solid electrolyte deteriorates, resulting in an increase in contact resistance.

The present invention has been made in view of the current situation, and is an object of the present invention to suppress the increase in contact resistance between a current collector such as a bipolar plate and a solid electrolyte and an electrode over a long period of time, thereby producing a long-life solid state. The purpose of the present invention is to provide a method for manufacturing an electrolyte fuel cell.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a first step of preparing a stack by arranging a fuel electrode on one side of a solid electrolyte, and a first step of fabricating a stack by disposing a fuel electrode on one side of a solid electrolyte.
The method is characterized by comprising a second step of performing heat treatment while applying a predetermined load in a reducing atmosphere at 0° C. or higher.

[0007]

[Operation] If a stack with a fuel electrode arranged on one side of a solid electrolyte is heat-treated in a reducing atmosphere of 1000°C or higher while applying a predetermined load, the fuel electrode will be sintered during the heat treatment. It shrinks. Therefore, creep of the fuel electrode is suppressed during operation, and it becomes possible to suppress reduction in the thickness of the fuel electrode.

[0008] It is desirable that the load during firing is greater than the clamping pressure during operation, but even if it is smaller, the same effect can be expected by increasing the firing time. In addition, if heat treatment is performed again while applying a predetermined load in an oxidizing atmosphere at 1000°C or higher after cell formation, the creep of the oxidizer electrode can be suppressed, and therefore the decrease in the thickness of the oxidizer electrode can also be suppressed. can.

[0009]

[Embodiment] An embodiment of the present invention will be described below based on FIG. 1 and Table 1. [Example 1] The cell consisted of a fuel electrode made of Ni-ZrO2 cermet, an oxidizer electrode made of La0.9 Sr0.1 MnO3, and a solid electrolyte mainly composed of Y2 O3 stabilized ZrO2 interposed between the two electrodes. It has a board.

[0010] Here, a cell having the above structure was manufactured as follows. First, a fuel electrode material and an oxidizer electrode material shown below are thoroughly mixed in a ball mill, and minute air bubbles contained in the slurry are stirred and removed under reduced pressure. (1) Fuel electrode material NiO powder
70 parts by weight Y2 O3 Stabilized ZrO
2 30 parts by weight Binder (polyvinyl butyral resin) 20 parts by weight Plasticizer (dioctyl phthalate) 10 parts by weight Solvent (ethanol)
200 parts by weight (2) Oxidizer electrode material La0.9 Sr0.1 MnO3 powder
100 parts by weight Binder (polyvinyl butyral resin) 30 parts by weight Plasticizer (dioctyl phthalate)
20 parts by weight solvent (ethanol)
300 parts by weight Next, a slurry for fuel electrodes was applied to a thickness of 100 μm on one side of a commercially available partially stabilized ZrO2 plate (a solid electrolyte plate, 200 μm thick), and then heated at 1200°C for 4 hours (in the atmosphere). Medium) Baking. After this, at a load of 4 kg/cm2, 100
Heat treatment is performed at 0° C. for 4 hours (in a hydrogen atmosphere). After that,
On the other side of the solid electrolyte, 100 μm of slurry for the oxidizer electrode was applied, and then heated at 1100°C for 4 hours (in air).
Firing is performed to produce a flat cell. Finally, using five of these flat cells, a stack with an effective area of 100 cm2 was fabricated.

The stack thus produced is hereinafter referred to as the (A1) stack. [Example 2] The above flat cell was again subjected to a load of 4 kg/
A stack was produced in the same manner as in Example 1 above, except that the stack was heat-treated at 1000° C. for 4 hours (in the atmosphere). The stack produced in this way is hereinafter referred to as the (A2) stack. [Comparative Example] A stack was produced in the same manner as in Example 1 above, except that no heat treatment was performed.

The stack thus produced is hereinafter referred to as an (X) stack. [Experiment] (A1) stack of the above invention, (A2)
The relationship between operating time and cell voltage in the stack and the (X) stack of Comparative Example was investigated, and the results are shown in FIG. The stack is tightened using an air cylinder method (ceramics are attached to the cylinder rod, and the stack is pressed by this ceramic), and the tightening pressure is 2 kg/cm.
2, and is controlled to always remain constant from room temperature to operating temperature (1000°C). In addition, the experiment used air as the oxidant gas and hydrogen as the fuel gas, and
The condition is to discharge at a constant current of 00 mA/cm2. Furthermore, the oxygen utilization rate (UOX) and fuel utilization rate (Uf) during constant current discharge of 300 mA/cm2 are both 3.
0%, and the cell voltage in FIG. 1 is a value per single cell.

As is clear from FIG. 1, (X) of the comparative example
While the stack has a significant initial voltage drop, the (A1) stack and (A2) stack of the present invention have only a slight voltage drop, and in particular, the (A2) stack has almost no voltage drop. It will be done. In this way, the characteristics of the (X) stack of the comparative example are the same as those of the (A1) stack of the present invention.
The decrease compared to the (A2) stack is considered to be due to an increase in the contact resistance between the bipolar plate and the solid electrolyte and the electrodes (particularly the fuel electrode). Therefore, after disassembling each stack (cell), changes in electrode thickness were investigated, and the results are shown in Table 1. In addition, in Table 1,
Each data is an average value of 5 cells, and the thickness of the oxidizer electrode before stack assembly is 100, and the thickness of the fuel electrode after reduction (data from outside the cell test) is 100.

[0014]

[Table 1]

As is clear from Table 1, (A1
) stack, (A2) stack has an extremely small decrease in the thickness of the fuel electrode compared to the comparative example (X) stack, and in particular, in the (A2) stack, the decrease in the thickness of the oxidizer electrode is also extremely small. It is recognized that there are This is because in the stacks (A1) and (A2) of the present invention, after the fuel electrode is formed, heat treatment is performed at a temperature equal to or higher than the cell operating temperature while applying a load at a pressure greater than the stack clamping pressure. During this heat treatment, the fuel electrode is sintered. Therefore, creep of the fuel electrode is suppressed during operation. On the other hand, in the stack of Comparative Example (X), since no heat treatment was performed after the fuel electrode was formed, this is considered to be due to the fact that creep of the fuel electrode occurs during operation.

In addition, (A2) in the stack, the decrease in the thickness of not only the fuel electrode but also the oxidizer electrode is extremely small because after cell fabrication, a load is applied at a pressure greater than the tightening pressure and the temperature is equal to or higher than the cell operating temperature. Since the heat treatment is performed at a temperature of , the oxidizer electrode is sintered during this heat treatment. Therefore, this is thought to be due to the fact that creep of the oxidizer electrode is also suppressed during operation. [Other matters] ■ Firing time, firing temperature, firing load, clamping pressure, etc. are not limited to the above examples,
It can be changed depending on usage conditions, etc. ■The method for manufacturing the fuel electrode, solid electrolyte, and oxidizer electrode is not limited to the method described in the above embodiments; for example, a green sheet for the fuel electrode, a green sheet for the solid electrolyte, and a green sheet for the oxidizer electrode are laminated. After that, it is also possible to use a method in which they are fired together.

[0017]

As explained above, according to the present invention, the creep of the fuel electrode is suppressed during operation, and therefore the reduction in the thickness of the electrode is suppressed. Therefore, an increase in contact resistance between the solid electrolyte and the fuel electrode can be suppressed, and excellent effects such as a longer battery life can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between operating time and cell voltage in the (A1) stack of the present invention, the (A2) stack, and the (X) stack of the comparative example.

Claims (1)

[Claims] Claim 1: A first step of fabricating a stack by arranging a fuel electrode on one side of a solid electrolyte;
A method for manufacturing a solid electrolyte fuel cell, comprising: a second step of performing heat treatment while applying a predetermined load in a reducing atmosphere at a temperature of 000° C. or higher.