KR100942091B1 - Stacked Structure of Flat Solid Oxide Fuel Cell - Google Patents

Abstract

An object of the present invention is to provide a stack structure of a plate-type solid oxide fuel cell which improves the power generation efficiency of a fuel cell by increasing the contact area between the bottom surface of the anode and the fuel gas.

In order to achieve the above object, the technical configuration of the present invention includes a flat fuel electrode 3, an electrolyte 2, and an air electrode 1 which are stacked in this order to form a unit cell, and two or more of the stages arranged vertically. In the laminated structure of a flat solid oxide fuel cell in which a connecting member 4 is inserted between cells, and a sealing material 5 is sealed on both sides of the unit cell, the fuel electrode 3 in contact with the connecting member 4. The fuel tunnel 3a is formed at regular intervals on the lower surface of the bottom, and the air tunnel 4b is formed on the lower surface of the connecting member 4 in contact with the cathode 1.

Flat panel, solid oxide fuel cell, anode, connector, fuel tunnel,

Description

Stacking structure of planar solid oxide fuel cell

The present invention relates to a laminated structure of a flat-plate solid oxide fuel cell, and more particularly, a flat plate that improves the power generation efficiency of a fuel cell by increasing the contact area between the bottom surface of the anode constituting the cathode of the fuel cell and the fuel gas. It relates to a laminated structure of a solid oxide fuel cell.

A fuel cell is called a 3rd generation battery following a 1st generation battery (battery) and a 2nd generation battery (charger), and is a battery which directly converts chemical energy generated by oxidation of fuel into electrical energy. This fuel cell is characterized by high energy efficiency because it can produce electricity semi-permanently as the reactants are continuously supplied from the outside and the reaction products are continuously removed to the outside of the system, and there is no loss in mechanical conversion. . It uses various fuels such as fossil fuel, liquid fuel and gaseous fuel, and is divided into low temperature type and high temperature type according to operating temperature.

Among these, the solid oxide fuel cell (SOFC) is a fuel cell that uses a solid oxide having oxygen or hydrogen ion conductivity as an electrolyte, and operates at the highest temperature (600-1000 ℃) among the existing fuel cells. Because all components are solid, the structure is simpler than other fuel cells, and there is no problem of loss, replenishment and corrosion of electrolyte, no precious metal catalyst, and easy fuel supply through direct internal reforming.

In addition, it has the advantage that thermal combined cycle power generation using waste heat is possible because the high-temperature gas is discharged. Because of these advantages, research on solid oxide fuel cells has been actively conducted in advanced countries such as the United States and Japan, aiming to commercialize in the early 21st century.

The solid oxide fuel cell is classified into a flat plate type and a cylindrical type according to the stacked structure thereof. FIGS. 1 and 2 illustrate a unit cell structure and a stacked structure of the plate type solid oxide fuel cell according to the present invention.

As shown in FIG. 1, the unit cell of the planar solid oxide fuel cell has a structure in which a cathode (cathode, 3), an electrolyte (2), and an anode (anode, 1), which are planar components having a rectangular cross section, are sequentially stacked. consist of. The working principle is that oxygen ions produced by the reduction reaction of oxygen in the cathode 1 move to the anode 3 through the oxygen ion conductive electrolyte 2 and then react with the hydrogen supplied from the anode 3 to generate water. In this process, electrons are generated at the anode 3 and electrons are consumed at the cathode 1, and when the two electrodes are connected to each other, electricity flows.

2 shows a stacked structure of a unit cell of the fuel electrode 3, the electrolyte 2, and the air electrode 1. The connecting member 4 is sandwiched between two or more unit cells arranged up and down, and the connecting member 4 serves to collect electrons generated from the battery and to separate each stacked cell. Also called a separator.

In addition, the upper and lower surfaces of the connecting member 4 are formed with a fuel tunnel 4a in contact with the fuel electrode 3 and an air tunnel 4b in contact with the air electrode 1, respectively. When fuel gas (hydrogen) and air gas flow through the fuel tunnel 4a and the air tunnel 4b, an electrochemical reaction occurs through the electrolyte 2.

On the other hand, the left and right sides of the unit cell are sealed by a sealant 5, which seals the unit cell so that fuel gas and air gas are not mixed or leaked.

Since the plate-type solid oxide fuel cell configured as described above usually operates at a high temperature of 1000 ° C. or more, a ceramic material that can withstand high temperatures is mainly used. That is, yttria stabilized zirconia (YSZ, Yttria-Stabilized-ZrO ₂ ) is used as the electrolyte ₂ , Ni-ZrO ₂ is used as the anode 3, and Sr-LaMnO is used as the cathode 1. ₃ is used a lot.

The consolidated 4 also ceramic materials of Sr-doped LaCrO ₃ has been mainly used, in recent years while the development is low and medium on the solid oxide fuel cell operating at 600 ~ 800 ℃ CrFe alloy _{(Cr 5 FeY 2 O 3)} , ferrite Metallic materials such as Ferritic Stainless Steel are also used. Using such a metal connecting material 4 has the advantage that the manufacturing cost is relatively lower than the ceramic material.

However, in the conventional connecting member 4, several tunnels 4a and 4b are processed on the upper and lower surfaces thereof so that fuel gas and air gas can flow to a portion contacting the anode or the cathode regardless of the material thereof, and thus the work maneuver. This is increased, which requires a very precise operation due to the limitation on thinning the overall thickness of the connecting member (4) has a problem that the processing cost is greatly increased.

In addition, in the form of the conventional fuel tunnel 4a, the area where the fuel gas is in contact with the anode 3 is too small, so the power generation efficiency is low, and the contact resistance between the anode 3 and the connecting member 4 is long when used for a long time. There was a problem that the output is reduced by increasing. To solve this problem, as shown in FIG. 2, a mesh metal plate 6 made of expensive metal is inserted between the anode 3 and the connecting member 4 to directly connect electricity generated from the anode 3 to the connecting member 4. It has been configured to deliver the fuel cell, which has been the main reason for increasing the manufacturing cost by making the fuel cell stack more complicated.

The present invention has been developed to solve this problem, by forming a fuel tunnel directly on the lower surface of the anode used as a cathode of the flat-plate solid oxide fuel cell components to increase the contact area between the fuel gas and the anode to generate electricity The purpose is to provide a new type of laminated structure with improved efficiency.

According to the technical configuration of the present invention for achieving the above object, a flat fuel electrode, an electrolyte, and an air electrode are sequentially stacked to form a unit cell, and a connecting member is inserted between the unit cells in which two or more are arranged vertically. In the laminated structure of the flat-type solid oxide fuel cell is provided, both sides of the unit cell is provided with a sealing material,

Fuel tunnels are formed at regular intervals on the lower surface of the anode contacting the connecting member, and air tunnels are formed at regular intervals on the lower surface of the connecting member contacting the cathode.

Preferably, the fuel electrode is configured such that the height of the fuel tunnel is 20 to 80% of the thickness of the entire anode and the contact area with the connecting member is 20 to 80% of the lower area of the entire anode.

According to the laminated structure of the planar solid oxide fuel cell according to the present invention configured as described above, the contact area between the fuel gas and the anode is increased, and the current collecting characteristics and power generation efficiency are greatly improved. In addition, there is no need to install a separate mesh-shaped metal plate in order to transfer the generated electricity to the connecting material, and the labor cost for processing the connecting material can be simplified to reduce the production cost.

Hereinafter, with reference to the accompanying drawings will be described in more detail with respect to the laminated structure of a flat solid oxide fuel cell according to the present invention. 3 shows a single cell structure according to the present invention, and FIG. 4 shows a laminated structure of the single cell. For the sake of clarity, the same reference numerals are used for the same components as those of FIGS. 1 and 2 described above.

In the unit cell structure according to the present invention, a flat fuel electrode 3, an electrolyte 2, and an air electrode 1 are sequentially stacked to form a unit cell, and two or more of the unit cells are arranged up and down. (4) is inserted and is the same as the conventional one in that the sealant 5 is sealedly installed on both sides of the unit cell.

The biggest technical feature of the present invention is that the fuel tunnel 3a is formed at regular intervals on the lower surface of the anode 3 in contact with the connecting member 4. The fuel tunnel 3a is formed in a convex concave-convex shape, and the cross section may be any of a rectangle, a trapezoid, and an arc.

As such, when the fuel tunnel 3a, which is cut into the groove shape, is directly formed on the lower surface of the anode 3, the power generation efficiency of the fuel cell is greatly improved by the following two mechanisms.

First, as shown in FIG. 2, the fuel gas (hydrogen) injected into the fuel tunnel 3a is in contact with the anode as compared with the case where the fuel tunnel 4a is formed on the upper surface of the connecting member 4. The unit area is greatly increased. This increases the amount of hydrogen ions bonded to the oxygen ions that have migrated through the electrolyte 2.

Second, the fuel gas flowing through the fuel tunnel 3a is uniformly supplied over the entire lower surface of the anode 3. As a result, an electrochemical reaction is induced over the entire fuel electrode 3, so that the amount of electricity generated is greatly increased.

The microstructure of the anode 3 composed of approximately 50:50 wt% of Ni and ZrO ₂ is formed differently in the thickness direction. That is, the upper surface contacting the electrolyte 2 has a dense structure, while the lower surface contacting the connecting material 4 has a coarse structure with a lot of large particles and pores. Therefore, when the area in contact with the fuel gas in the lower surface in contact with the connecting member 4 becomes wider, a larger amount of hydrogen ions are supplied into the anode through the surface having a higher porosity, which contributes to an increase in power generation efficiency. . In view of this, according to the present invention, when the fuel gas is designed at an appropriate flow rate, a much larger amount of fuel gas can be supplied into the fuel electrode 3.

As such, when the fuel tunnel 3a is directly formed on the lower surface of the anode 3, a larger amount of fuel can be supplied through the fuel tunnel 3a. In other words, the fuel tunnel 3a having a smaller area can generate power of equal or more. Therefore, when fuel gas can be supplied through the fuel tunnel 3a of a smaller area, all the other parts can be made to contact the connecting material 4. As a result, when the contact area is increased, the electrical resistance between the anode 3 and the connecting member 4 is reduced, so that the output does not decrease even when used for a long time.

Furthermore, when the contact area between the anode 3 and the connecting member 4 is increased, the electricity generated from the anode can be directly transmitted to the connecting member 4, so that a separate mesh-shaped metal plate 6 is inserted as shown in FIG. 2. There is no need to install it. This makes the stacking structure of the solid oxide fuel cell according to the present invention simpler and reduces the manufacturing cost.

As described above, according to the present invention, since the fuel tunnel 3a is directly formed on the lower surface of the anode 3, it is not necessary to form a separate gas passage on the upper surface of the connecting member 4 unlike the conventional art. Therefore, in the connecting member 4 according to the present invention, since the air tunnels 4b are formed at regular intervals only on the lower surface of the connecting member 4 in contact with the air electrode 1, the shape of the connecting member 4 is very simple. Since the connecting member 4 requires a very precise machining due to the limitation of the thickness, the connecting member 4 of the present invention greatly reduces the processing cost.

In the fuel electrode 3 according to the present invention, the supply efficiency of the fuel gas varies depending on the height of the fuel tunnel 3a formed on the lower surface thereof and the contact area between the connecting member 4, thereby affecting the current collecting characteristics of the fuel cell. The inventors have made several experiments. The fuel electrode 3 has a height t of the fuel tunnel 3a of 20 to 80% of the thickness of the entire fuel electrode 3, and the contact area with the connecting member 4 is increased. It was found that the best current collection characteristics are shown when 20 to 80% of the lower area of the entire anode 3 is present.

In more detail, the height t of the fuel tunnel 3a is less than 20% of the thickness of the entire anode 3, or the contact area with the connecting member 4 represents 80% of the lower area of the entire anode 3. When it exceeds, it will not fully secure a fuel gas supply passage and battery performance will fall. On the contrary, when the height t of the fuel tunnel 3a exceeds 80% of the thickness of the entire anode 3 or the contact area with the connecting member 4 is less than 20% of the lower area of the entire anode 3, The current collecting performance deteriorates and the output becomes unstable when used for a long time.

EXAMPLE

The inventors conducted the experiment as follows to find out the optimum shape of the fuel tunnel 3a showing excellent current collecting characteristics.

In order to manufacture the fuel electrode 3, first, a mold having a convex shape on one side thereof is prepared, and organic binder and NiO, YSZ and other raw material mixed powder, which forms pores and at the same time, serves as a binder, are placed in a mold. Mold is applied after adding pressure. The mold was manufactured to have an inner product of about 12 × 12 × 12 cm and 24 × 24 × 24 cm. The mold was designed to be pushed from one side in the form of a penetrating top and bottom to come out of the mold, and to adjust the thickness of the anode 3 according to the separation of the upper and lower plates.

The bottom mold is manufactured in the form of fuel tunnels 3a having different sizes and depths, to fabricate fuel electrodes 3 having various types of bottom surfaces, and after primary sintering, the electrolyte (2) according to the prior art. ) And a cathode (1) were formed to produce a unit cell. Using the mold, the total thickness of the anode 3 was set to 200 to 4000 µm, and the bottom area of the anode was made 10 × 10 cm (100 cm ² ) or 20 × 20 cm (400 cm ² ).

At this time, the height of the fuel tunnel 3a formed on the lower surface of the anode 3 is 10 to 90% of the total thickness, and the contact area between the anode 3 and the connecting member 4 is the entire anode 3. Each Example and Comparative Example was prepared so that the range of 10 to 90% relative to the lower area of the. For each of the examples and comparative examples thus prepared, the mechanical stability, electrical properties with the connecting member, fuel gas reaction characteristics and the like were evaluated, and the results are shown in Table 1 below.

Form of anode Properties Height of fuel panel (%) Contact area with connecting materials (%) Mechanical stability Electrical characteristics Fuel gas reactivity Example 1 20 50 ◎ ◎ ◎ Example 2 80 50 ◎ ◎ ◎ Example 3 50 20 ◎ ◎ ◎ Example 4 50 80 ◎ ◎ ◎ Comparative Example 1 10 50 ◎ ◎ × Comparative Example 2 90 50 × △ ◎ Comparative Example 3 50 10 △ × △ Comparative Example 4 50 90 △ ◎ △

◎: Excellent △: Normal ×: under

The mechanical stability represents the flatness of the battery after the unit cell is fabricated, and the better the better the unit cell is not twisted or bent after fabrication. The electrical characteristics indicate electrical conductivity with the connecting member 4 under the operating conditions after stacking of single cells, and the higher the electrical conductivity with the connecting member 4, the better. The fuel gas reactivity is indicative of fuel utilization under operating conditions, and the higher the amount of fuel gas participating in the electrochemical reaction when the flow rate of the supplied fuel gas is constant, the better.

As shown in Table 1, the shape of the anode 3 varies depending on the height of the fuel panel 3a formed on the lower surface thereof and the contact area between the connecting member 4 which is changed due to the fuel panel 3a. Any one out of the 20 to 80% range did not exhibit the required physical properties.

1 is a view showing a unit cell structure of a conventional planar solid oxide fuel cell;

2 is a view showing a laminated structure of a conventional planar solid oxide fuel cell;

3 is a view illustrating a unit cell structure of a plate-type solid oxide fuel cell according to the present invention;

4 is a diagram illustrating a laminated structure of a planar solid oxide fuel cell according to the present invention.

※ Explanation of code for main part of drawing ※

1: air cathode

2: electrolyte

3: fuel electrode

3a: fuel tunnel

4: connecting material

4a: fuel tunnel

4b: air tunnel

5: sealing material

6: mesh type metal plate

Claims (2)

The flat fuel electrode 3, the electrolyte 2, and the air electrode 1 are stacked in this order to form a unit cell, and a connecting member 4 is inserted between the unit cells in which two or more are arranged vertically. In the laminated structure of the flat-type solid oxide fuel cell, the sealing material 5 is sealed on both sides of the unit cell, Fuel tunnels 3a are formed on the lower surface of the anode 3 in contact with the connecting member 4 at regular intervals, and an air tunnel 4b is formed on the lower surface of the connecting member 4 in contact with the cathode 1. It is formed at regular intervals, the height of the fuel tunnel (3a) is 20 to 80% of the thickness of the entire fuel electrode (3), the contact area of the fuel tunnel (3a) with the connecting member (4) of the entire fuel electrode (3) Laminated structure of a planar solid oxide fuel cell, characterized in that 20 to 80% of the lower area. delete

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