CN107959036A - A kind of preparation method of the solid oxide fuel cell of flat structure - Google Patents

Abstract

The present invention provides a kind of solid oxide fuel cell preparation method of flat structure.For the solid oxide fuel cell using anode layer as supporting layer, the barrier material between electrolyte and cathode is GDC；The present invention is used anode support, electrolyte and barrier layer green compact co-sintering, it not only enormously simplify preparation process, and can may be such that electrolyte and barrier layer reach fine and close effect well when sintering temperature is 1300 DEG C, while can be worked well with the interface cohesion between electrolyte and barrier layer.In view of thermal stress and the smooth sex chromosome mosaicism of sintering, preparation method of the invention is particularly suitable for the solid oxide fuel cell with the hollow flat structure of distribution up and down.

Description

A kind of preparation method of solid oxide fuel cell with planar structure

technical field

The invention belongs to the technical field of solid oxide fuel cells, and in particular relates to a preparation method of a solid oxide fuel cell with a planar structure.

Background technique

Constrained by climate change and fossil energy, solid oxide fuel cell technology has received extensive attention. The basic structure of a solid oxide fuel cell includes an electrolyte, a porous anode, and a porous cathode. The fuel is fed into the anode, and the oxidant gas is fed into the cathode. Electrons are generated through the electrochemical reaction at the three-phase interface between the electrolyte and the electrode to form an external electronic circuit. Eventually electricity and heat are generated.

In recent years, Ni-YSZ, YSZ and LSM are the high-temperature anode, electrolyte and cathode materials that have been studied more and are relatively mature in solid oxide fuel cells. However, as the operating temperature of high-temperature solid oxide fuel cells decreases from 800-1000 °C to 500-800 °C, compared with the pure electron conductor cathode material LSM, the catalytic activity of the mixed ion conductor LSCF for oxygen is higher, making the battery discharge performance better. However, when operating at a high temperature greater than or equal to 1200 °C, the LSCF cathode material is prone to interfacial reactions with the electrolyte material YSZ, forming insulating phases SrZrO ₃ and La ₂ Zr ₂ O ₇ , etc., and causing problems such as mismatching expansion coefficients, cause battery instability.

To solve this problem, the researchers introduced a barrier layer between LSCF and YSZ, which should satisfy: 1) Good chemical compatibility with electrolyte YSZ and cathode LSCF, which can prevent the chemical The reaction produces a high impedance phase;

2) The expansion coefficient of the barrier layer material is between the electrolyte YSZ and the cathode LSCF, improving the thermal expansion coefficient between the cathode and the electrolyte;

3) The barrier layer material has good compactness and high oxygen ion conductivity at medium and low temperatures.

By doping an appropriate concentration of rare earth metal oxide Gd ₂ O ₃ in cerium oxide (CeO ₂ )-based materials, its oxygen ion vacancies can be greatly increased, and its ionic conductivity can be significantly improved, thus becoming a good oxygen ion conductor. This doped CeO2 _- based material is called GDC, and it can be prepared as a dense thin film layer, which can meet the above barrier requirements.

At this stage, the preparation steps of solid oxide fuel cells with Ni-YSZ, YSZ, LSCF and GDC as the anode, electrolyte, cathode material and barrier layer are generally as follows: after the anode functional layer and electrolyte layer are co-fired at 1300 ° C , screen-print GDC paste on the surface of the dense electrolyte substrate for sintering, the GDC barrier layer is generally sintered at 1200°C, and finally screen-print the cathode paste on the surface of the GDC barrier layer and sinter at about 1100°C.

The shortcomings of this method are: (1) the second sintering of the sintered half-cell increases the complexity of battery preparation; The cross-sectional SEM image of the GDC barrier layer is shown in Figure 1, which shows that its compaction effect is poor, it is difficult to meet the requirements of the barrier layer’s compactness, and the interface bonding effect with the electrolyte is poor, which will cause a large interface resistance. It is not conducive to avoiding the diffusion reaction between the cathode material and the electrolyte, and affects the operation stability of the battery.

Contents of the invention

Aiming at the technical status of the above-mentioned solid oxide fuel cell, the present invention provides a preparation method of the solid oxide fuel cell, which has a simple process and low cost, and the prepared GDC barrier layer not only has good compactness, but also has a good gap between the solid oxide fuel cell and the electrolyte. The interface binding is good.

For this reason, the inventors found after a lot of experiments and explorations that using a flat plate structure with the anode layer as the support layer to co-sinter the anode layer, the electrolyte layer and the barrier layer green body can not only simplify the preparation process and save costs, but also when When the sintering temperature rises to 1300°C, the GDC barrier layer and the electrolyte layer can achieve a dense effect, and the interface between the GDC barrier layer and the electrolyte layer has a good bonding effect.

That is, the technical solution of the present invention is: a method for preparing a flat solid oxide fuel cell, the solid oxide fuel cell uses the anode layer as the support layer, the anode layer material is Ni-YSZ, and the electrolyte material is YSZ , the cathode material is LSCF, the barrier layer material between the electrolyte and the cathode is GDC, and it is characterized in that: the barrier layer is made by sintering, and the anode layer, the electrolyte layer and the barrier layer green body are co-sintered, and the sintering temperature is greater than or Equal to 1300°C.

As an implementation manner, the electrolyte slurry and the barrier layer GDC slurry are coated, impregnated, or screen-printed on the surface of the anode layer, and then co-sintered.

Preferably, the thickness of the electrolyte layer is 1-10 μm, more preferably 5 μm.

Preferably, the barrier layer has a thickness of 1-5 μm, more preferably 3 μm.

Preferably, the co-sintering procedure is as follows: heat up to 600°C at 0.5°C/min-3°C/min, keep warm for 0.5h-3h, then heat up to sintering temperature at 0.5°C/min-3°C/min, keep warm for 1h -5h, and finally cooled down to room temperature naturally.

After the above-mentioned anode layer, electrolyte layer and barrier layer green bodies are co-sintered, the cathode paste is coated or screen-printed on the surface of the barrier layer, and then sintered. The sintering temperature is the cathode sintering temperature. The cathode sintering temperature is 1000°C to 1200°C.

At present, one problem of solid oxide fuel cells with a planar structure is that the cell structure is asymmetric. When the battery is operated at a higher temperature, the introduction of fuel, electrochemical reaction and electron transfer all generate heat, and the coexistence of these heat causes the internal heat balance to be extremely uneven, especially when the battery structure is asymmetrical due to this uneven heat generation The thermal stress of the battery is even more serious, and it can cause cracks between the thin electrolyte and the electrodes, which can destroy the battery and cause operational failure. In addition, when the battery structure is asymmetric, denaturation is likely to occur during the sintering process of preparing the battery, which affects the flatness of the battery.

For this reason, in the present invention, the solid oxide fuel cell with flat plate structure is preferably designed as an upper and lower distribution type with the anode support layer as the center, that is, the electrolyte layer is divided into two layers, which are respectively located on the upper and lower surfaces of the anode support layer; the barrier layer is also divided into two layers: The cathode layer is also divided into two layers, which are respectively located on the surfaces of the two barrier layers; and the anode support layer is provided with holes for gas passage, and the holes are on the side of the anode support layer Has an open end. The design takes the anode support layer as the center, and the gas passes through the side opening into the internal pores of the anode support layer, and then diffuses to the upper and lower sides. The three-phase interface where the electrochemical reaction occurs is located on the upper and lower sides of the support electrode layer, so the Thermal stress is effectively counteracted, thereby greatly reducing thermal stress. In addition, during the battery preparation process, since the battery structure is distributed up and down, it is beneficial to maintain the flatness of the battery during the battery sintering process.

That is to say, preferably, the solid oxide fuel cell is a hollow planar structure distributed up and down, as shown in FIG. The direction is stacked up and down; the electrolyte layer includes a first electrolyte layer and a second electrolyte layer, the first electrolyte layer is located on the lower surface of the supporting anode layer, and the second electrolyte layer is located on the upper surface of the supporting anode layer; the barrier layer includes the first barrier layer and the second electrolyte layer Two barrier layers, the first barrier layer is located on the lower surface of the first electrolyte layer, the second barrier layer is located on the upper surface of the second electrolyte layer; the cathode layer includes a first cathode layer and a second cathode layer, and the first cathode layer is located on the first The lower surface of the barrier layer, the second cathode layer is located on the upper surface of the second barrier layer; the supporting anode layer is provided with a hollow channel (or hole), and the channel (or hole) has an inlet and outlet port on the side of the supporting anode layer.

Further preferably, centering on the supporting anode layer, when the first electrolyte layer and the second electrolyte layer are symmetrically distributed, that is, when the shape and thickness of the first electrolyte layer and the second electrolyte layer are completely consistent, the thermal stress reduction effect Better and more conducive to maintaining the flatness of the sintering process.

Further preferably, with the supporting anode layer as the center, when the first barrier layer and the second barrier layer are symmetrically distributed, that is, when the shape and thickness of the first barrier layer and the second barrier layer are completely consistent, the thermal stress reduction effect Better, more conducive to maintaining the flatness of the sintering process.

Further preferably, with the supporting anode layer as the center, when the first cathode layer and the second cathode layer are symmetrically distributed, that is, when the shape and thickness of the first cathode layer and the second cathode layer are completely consistent, the thermal stress reduction effect Better, more conducive to maintaining the flatness of the sintering process.

In the above-mentioned hollow anode support structure distributed up and down, as an implementation, the preparation method of the solid oxide fuel cell of the present invention is as follows:

(1) Use the anode support as the raw material, and fill it with a high-temperature volatile substance with a certain size as a pore-forming agent, and form a molded body through molding and sintering, in which the pore-forming agent volatilizes to obtain a supporting electrode layer with a pore structure , and the hole has an open end on the side of the supporting electrode layer;

The material of the pore forming agent is not limited, including carbon rods, graphite, carbon nanotubes and other carbon materials in other shapes.

The molding method is not limited, including hot pressing, casting and other methods.

(2) sequentially coating, dipping, or screen printing the first electrolyte slurry and the first barrier layer slurry on the lower surface of the anode support; sequentially coating, dipping, or screen printing on the upper surface of the anode support the second electrolyte slurry and the second barrier layer slurry; and then co-sintering.

(3) Coating or screen-printing the first cathode slurry on the lower surface of the first barrier layer; coating or screen-printing the second cathode slurry on the lower surface of the second barrier layer; and then sintering.

To sum up, in the preparation process of the solid oxide fuel cell with flat plate structure, the present invention adopts the co-sintering of the anode support body, the electrolyte and the barrier layer green body, which greatly simplifies the preparation process, and can be used at a sintering temperature of 1300°C It can make the electrolyte and the barrier layer achieve a good densification effect, and at the same time, the interface bonding effect between the electrolyte and the barrier layer can be good. Considering the problems of thermal stress and sintering flatness, the preparation method of the present invention is especially suitable for solid oxide fuel cells with a flat plate structure with hollows distributed up and down.

Description of drawings

Figure 1 is a cross-sectional SEM image of a GDC barrier layer obtained on the surface of an electrolyte substrate by secondary sintering;

Fig. 2 is a schematic structural view of a solid oxide fuel cell with a hollow flat plate structure distributed up and down in Example 1 of the present invention;

Fig. 3 (a) is the SEM image of the surface of the GDC barrier layer obtained by co-sintering on the surface of the electrolyte substrate in the preparation of the solid oxide fuel cell with a hollow up and down distributed planar structure in Example 1 of the present invention;

Fig. 3(b) is a cross-sectional SEM diagram of the GDC barrier layer obtained by co-sintering on the surface of the electrolyte substrate in the preparation of the solid oxide fuel cell with a hollow upper and lower distributed planar structure in Example 1 of the present invention;

Fig. 4 (a) is the surface SEM image of the GDC barrier layer obtained by secondary sintering on the surface of the electrolyte substrate in the preparation of the solid oxide fuel cell with a hollow flat plate structure distributed up and down in Comparative Example 1 of the present invention;

Fig. 4(b) is a cross-sectional SEM image of the GDC barrier layer obtained by secondary sintering on the surface of the electrolyte substrate in the preparation of the solid oxide fuel cell with a hollow and vertically distributed planar structure in Comparative Example 1 of the present invention.

Detailed ways

The present invention will be further described in detail below with reference to the embodiments of the accompanying drawings. It should be noted that the following embodiments are intended to facilitate the understanding of the present invention, but have no limiting effect on it.

The reference signs in Fig. 2 are: 1-anode support layer; 21-first electrolyte layer; 22-second electrolyte layer; 31-first barrier layer; 32-second barrier layer; 41-first cathode layer; 42 - second cathode layer; 5 - channel.

Example 1:

In this embodiment, the solid oxide fuel cell is a hollow flat plate structure distributed up and down, as shown in Figure 2, with the anode layer 1 as the supporting layer, the anode layer, electrolyte layer, barrier layer and cathode layer are stacked up and down along the thickness direction; The electrolyte layer includes a first electrolyte layer 21 and a second electrolyte layer 22, the first electrolyte layer 21 is located on the lower surface of the supporting anode layer 1, and the second electrolyte layer 22 is located on the upper surface of the supporting anode layer 1; the barrier layer includes a first barrier layer 31 and the second barrier layer 32, the first barrier layer 31 is located on the lower surface of the first electrolyte layer 21, the second barrier layer 32 is located on the upper surface of the second electrolyte layer 22; the cathode layer includes the first cathode layer 41 and the second cathode layer layer 42, the first cathode layer 41 is located on the lower surface of the first barrier layer 31, and the second cathode layer 42 is located on the upper surface of the second barrier layer 32; the supporting anode layer 1 is provided with a number of holes 4, and the holes are placed on the supporting anode layer 1 The sides have access ports.

With the supporting anode layer 1 as the center, the first electrolyte layer 21 and the second electrolyte layer 22 are symmetrically distributed, that is, the shape and thickness of the first electrolyte layer 21 and the second electrolyte layer 22 are completely consistent.

With the supporting anode layer 1 as the center, the first barrier layer 31 and the second barrier layer 32 are symmetrically distributed, that is, the shape and thickness of the first barrier layer 31 and the second barrier layer 32 are completely consistent.

With the supporting anode layer 1 as the center, the first cathode layer 41 and the second cathode layer 42 are symmetrically distributed, that is, the shape and thickness of the first cathode layer 41 and the second cathode layer 42 are completely consistent.

The material of supporting anode layer 1 is Ni-YSZ.

The material of the first electrolyte layer 21 and the second electrolyte layer 22 is YSZ which is the same.

The first barrier layer 31 is made of the same material as the second barrier layer 32 , which is GDC.

The first cathode layer 41 is made of the same material as the second cathode layer 42, which is LSCF.

The preparation method of the above-mentioned solid oxide fuel cell comprises the following steps:

(1) Using the supporting anode layer material as the raw material, burying carbon rods in the raw material, hot pressing the raw material, and then sintering, the sintering temperature is 1000°C, to obtain the supporting anode layer with the hole structure, and the hole is in The sides supporting the electrode layer have open ends;

(2) Screen-print the first electrolyte slurry and the first barrier layer slurry on the lower surface of the anode support layer sequentially; screen-print the second electrolyte slurry and the second barrier layer slurry on the upper surface of the anode support in sequence , to obtain the half-cell green body; then, the half-cell green body is placed in a resistance furnace for co-sintering (vertical firing), and the sintering procedure is: the temperature is raised to 600°C at 1°C/min, kept for 2h, and then the temperature is raised at 1°C/min to 1300°C, keep warm for 4 hours, and finally cool down to room temperature naturally. After the resistance furnace cools down to room temperature, take out the half-cell.

The surface and cross-section of the half-cell GDC were characterized by SEM. The structure is shown in Figure 3(a) and 3(b), which shows that the electrolyte layer and the barrier layer are highly dense, and the interface between the electrolyte and the barrier layer has a very good bonding effect. Only There are very few pores, which are closed pores, and the surface of the GDC barrier layer is fully dense.

(3) Screen-print the first cathode slurry on the lower surface of the first barrier layer; screen-print the second cathode slurry on the lower surface of the second barrier layer; then perform sintering, the sintering temperature is 1100°C.

During the above sintering process, due to the symmetrical structure, the fabricated battery is flat.

In the working state, the oxidant gas is passed into the lower surface of the first cathode layer 41 and the upper surface of the second cathode layer 42; the fuel is passed into the opening end of the side hole of the supporting anode 1, and the fuel is passed into the supporting anode 1 through the hole 4 inside, and then diffuse to the upper and lower sides; the oxidant gas diffuses to the first electrolyte layer 21 through the first barrier layer 31, and diffuses to the second electrolyte layer 22 through the second barrier layer 32; the electrochemical reaction occurs through the first electrolyte layer 21 to produce Electrical energy and thermal energy, while electrochemically reacting through the second electrolyte layer 22 to generate electrical energy and thermal energy. Since the three-phase interface where the electrochemical reaction occurs is located on the upper and lower sides of the supporting electrode layer 1 , the generated thermal stress is effectively offset and the thermal stress is greatly reduced.

Comparative Example 1:

This example is a comparative example of Example 1 above.

In this embodiment, the solid oxide fuel cell is a hollow plate-shaped structure distributed up and down, which is exactly the same as that in Embodiment 1.

In this embodiment, the preparation method of the solid oxide fuel cell includes the following steps:

(1) is identical with the step (1) in embodiment 1;

(2) screen-print the first electrolyte slurry on the lower surface of the supporting anode layer; screen-print the second electrolyte slurry on the upper surface of the anode support to obtain a half-cell green body; then, the half-cell green body

Then, screen-print the first barrier layer slurry on the lower surface of the first electrolyte layer; screen-print the second barrier layer slurry on the upper surface of the second electrolyte layer; then, place it in a resistance furnace for co-sintering (vertical firing) , The sintering procedure is: heating up to 600°C at 1°C/min, holding for 2 hours, then raising the temperature at 1°C/min to 1300°C, holding for 4 hours, and finally cooling down to room temperature naturally. After the resistance furnace cools down to room temperature, take out the half-cell.

The SEM characterization of the surface and cross-section of the half-cell GDC, as shown in Figure 4(a) and 4(b), shows that the barrier layer has a poor densification effect, a large number of voids on the surface and cross-section, and poor bonding with the electrolyte. It will cause a large interface resistance.

(3) same as step (3) in embodiment 1;

During the above sintering process, due to the symmetrical structure, the fabricated battery is flat.

The above-mentioned embodiments have systematically and detailedly described the technical solutions of the present invention. It should be understood that the above-mentioned examples are only specific embodiments of the present invention, and are not intended to limit the present invention. Any modification, supplement or equivalent replacement made within the principle scope of the present invention shall be included in the protection scope of the present invention.

Claims (10)

1. A preparation method of a flat solid oxide fuel cell, wherein the solid oxide fuel cell takes the anode layer as a support layer, the anode layer material is Ni-YSZ, the electrolyte material is YSZ, the cathode material is LSCF, and the electrolyte The material of the barrier layer between the cathode and the cathode is GDC, which is characterized in that: the barrier layer is made by sintering, and the anode layer, the electrolyte layer and the barrier layer green body are co-sintered, and the sintering temperature is greater than or equal to 1300°C. 2. The method for preparing a flat solid oxide fuel cell as claimed in claim 1, characterized in that: the green body co-sintering process is: coating, impregnating, or screen-printing electrolyte slurry on the surface of the anode layer material and barrier layer GDC paste, followed by co-sintering. 3. The method for preparing a planar solid oxide fuel cell according to claim 1, characterized in that: the thickness of the electrolyte layer is 1-10 μm, preferably 5 μm. 4. The method for preparing a planar solid oxide fuel cell according to claim 1, characterized in that: the barrier layer has a thickness of 1-5 μm, preferably 3 μm. 5. The method for preparing a solid oxide fuel cell with flat plate structure as claimed in claim 1, characterized in that: the co-sintering procedure is: heating up to 600°C at 0.5°C/min-3°C/min, holding 0.5h-3h, then raise the temperature to the sintering temperature at 0.5°C/min-3°C/min, keep it warm for 1h-5h, and finally cool down to room temperature naturally. 6. The preparation method of the solid oxide fuel cell of flat structure as claimed in claim 1, it is characterized in that: after described anode layer, electrolyte layer and barrier layer green body are co-sintered, coating or The cathode paste is screen-printed, and then sintered. The sintering temperature is the cathode sintering temperature, and the cathode sintering temperature is 1000°C-1200°C. 7. The method for preparing a flat solid oxide fuel cell according to any one of claims 1 to 6, characterized in that: the solid oxide fuel cell is a hollow planar structure distributed up and down, The anode layer is used as the support layer, and the support anode layer, the electrolyte layer, the barrier layer and the cathode layer are stacked up and down along the thickness direction; the electrolyte layer includes a first electrolyte layer and a second electrolyte layer, and the first electrolyte layer is located on the lower surface of the support anode layer, The second electrolyte layer is located on the upper surface of the supporting anode layer; the barrier layer includes a first barrier layer and a second barrier layer, the first barrier layer is located on the lower surface of the first electrolyte layer, and the second barrier layer is located on the upper surface of the second electrolyte layer The cathode layer includes a first cathode layer and a second cathode layer, the first cathode layer is located on the lower surface of the first barrier layer, and the second cathode layer is located on the upper surface of the second barrier layer; supporting the anode layer is provided with a hollow channel (or hole) , the channel (or hole) has an inlet and outlet port on the side supporting the anode layer. 8. The method for preparing a flat solid oxide fuel cell as claimed in claim 7, wherein the first electrolyte layer and the second electrolyte layer are symmetrically distributed around the supporting anode layer; Preferably, with the supporting anode layer as the center, the first barrier layer and the second barrier layer are distributed symmetrically; Preferably, the first cathode layer and the second cathode layer are distributed symmetrically around the supporting anode layer. 9. The preparation method of the solid oxide fuel cell with flat structure as claimed in claim 6, characterized in that: the preparation method of the solid oxide fuel cell is as follows: (1) Use the anode support as the raw material, and fill it with a high-temperature volatile substance with a certain size as a pore-forming agent, and form a molded body through molding and sintering, in which the pore-forming agent volatilizes to obtain a supporting electrode layer with a pore structure , and the hole has an open end on the side of the supporting electrode layer; (2) sequentially coating, dipping, or screen printing the first electrolyte slurry and the first barrier layer slurry on the lower surface of the anode support; sequentially coating, dipping, or screen printing on the upper surface of the anode support a second electrolyte slurry and a second barrier layer slurry; then performing the co-sintering; (3) Coating or screen-printing the first cathode slurry on the lower surface of the first barrier layer; coating or screen-printing the second cathode slurry on the lower surface of the second barrier layer; and then sintering. 10. The method for preparing a planar solid oxide fuel cell according to claim 6, characterized in that: said pore-forming agent material comprises carbon rods, graphite and carbon nanotubes.