KR20120086113A - Anode for solid oxide fuel cell and fabrication method thereof - Google Patents

Abstract

PURPOSE: A manufacturing method of a negative electrode material is provided to use zirconium compound or nickel compound as a porogen, thereby capable of obtaining a negative electrode material satisfying porosity, contraction percentage, strength, electric conductivity, gas permeability of a negative electrode. CONSTITUTION: A manufacturing method of a negative electrode material comprises a step of mixing a porogen and a solvent; a step of molding a negative electrode support by using the mixture; a step of sintering the molded product; and a step of reducing the sintered product. The pore-forming agent is one or two more selected from a group consisting of a zirconium compound, and a nickel compound. The negative electrode material is one of a negative electrode support or a negative electrode functional layer.

Description

Anode for solid oxide fuel cell and manufacturing method thereof {Anode for solid oxide fuel cell and fabrication method

The present invention relates to a method for producing a negative electrode material for a solid oxide fuel cell, and more particularly, using a zirconium compound or a nickel compound as a new pore-forming agent, and wants the porosity and shrinkage of the negative electrode support or negative electrode functional layer, which is a negative electrode material for a solid oxide fuel cell. It relates to a method for producing a negative electrode material of a solid oxide fuel cell that can be adjusted to a level.

A fuel cell is a device that generates electricity by reacting fuel such as hydrogen or natural gas with oxygen, and is recognized as one of the main energy technologies of the future because of its high efficiency, pollution-free, and noise-free characteristics.

There are many types of fuel cells, among which solid oxide fuel cells (SOFC) use zirconia ceramics (ZrO ₂ ), ceria (CeO ₂ ) or lanthanum-strontium-gadolinium-magnesium oxide (LSGM) as solid electrolytes. I mean. The solid oxides are generally yttria (Y ₂ O ₃ ), ceria (CeO ₂ ), scandia (Sc ₂ O ₃ ) gadolinium oxide (Gd ₂ O ₃ ) for the purpose of improving thermal stability and ion conductivity at high temperature. And an appropriate amount of stabilizer.

The unit cell of the solid oxide fuel cell (SOFC) is made of the solid electrolytes in the center, with a cathode material on one side and an anode material on the other side. As a conventional cathode material, a mixture of nickel oxide (NiO) and stabilized zirconia is used, and as the anode material, lanthanum-strontium-manganese oxide (LSM), lanthanum-strontium-cobalt-iron oxide (LSCF), or the like is used.

In the conventional method of manufacturing a unit cell of a solid oxide fuel cell (SOFC), first, a dense electrolyte sintered body of a suitable thickness (about 200 μm) is manufactured by sintering in a conventional furnace, and then a negative electrode material is formed on one side and the other side. Known is a method (electrolyte support type) produced by coating and heat treatment of a positive electrode material.

As another method, first, a mixture of NiO and zirconia powder, which is a negative electrode material, is molded to a suitable thickness (about 1 mm) according to a conventional ceramic molding process, and firstly sintered at a relatively low temperature, for example, 1300 to 1400 ° C. After the solid oxide electrolyte was coated on it with a thin layer (approximately 5-20㎛), for example, by slurry coating or spray coating, a solid oxide electrolyte was applied at a temperature range of 1400-1500 ° C. in a sintering furnace. Secondary sintering is carried out by the method of holding for about 1 to 5 hours, and then a cathode material such as LSM or LSCF is coated on the upper surface of the electrolyte layer, and third sintering is carried out by a method similar to the above to produce a sintered body. (Cathode support type) is known.

The negative electrode material used in the negative electrode-supported solid oxide fuel cell has a moderate strength to support the unit cell structure, and is a fuel gas, and mainly has high porosity and gas permeability so that hydrogen or natural gas can sufficiently penetrate and react. Must have The manufacturing method of the negative electrode material mainly follows the conventional ceramics manufacturing method, that is, an additive that prevents the densification phenomenon during the sintering in the mixture of NiO and stabilized zirconia powder, so that the pores remain, that is, mainly graphite or carbon or starch forming agent such as starch A method of sintering after addition by molding is known.

The electrochemical reaction of the anode material in the solid oxide fuel cell occurs at the three-phase interface called TPB (Triple-Phase Boundary) where the three phases of the pore-YSZ-Ni meet. Will increase performance. Although it is advantageous to form a large number of large pores with sufficient porosity for fast fuel supply to the three phase interface, the amount of the three phase interface at which the electrochemical reaction of the supplied fuel takes place is rather reduced and as a result the performance of the fuel cell is reduced. Will be degraded. On the other hand, if the pores are formed by only micropores in order to increase the amount of the three-phase interface per unit volume, the fuel supply speed is lowered, which also lowers the performance of the fuel cell.

In the existing technology, for the sake of sufficient porosity, coarse particles are used to suppress densification or pore formers to secure porosity. Pores using coarse particles generally have a large pore size, resulting in a small three-phase interface. In addition, the use of pore formers such as starch, activated carbon or carbon creates a non-uniform microstructure due to cohesion and dispersibility of the pore formers, and to solve this problem, the amount of dispersant and solvent is increased and the mixing time is increased. Should be. In addition, the use of many pore formers requires the addition of a long time degreasing process. This not only takes a lot of time in the drying and degreasing process of the negative electrode material but also generates deformation and cracks as a result of uneven shrinkage.

Therefore, there is a need to improve the problem of the lack of electrochemical activity of the gas reaction (electrochemical reaction) by improving the microstructure of the anode material for a solid oxide fuel cell developed so far.

The present invention has been made to solve the above problems, the characteristics of the negative electrode of the desired solid oxide fuel cell using a zirconium compound or a nickel compound as a pore-forming agent, for example, porosity, shrinkage, strength, electrical conductivity, gas permeability An object of the present invention is to provide a method for producing a negative electrode material for a solid oxide fuel cell, which can be obtained.

In order to achieve the above object, the present invention is a solid oxide fuel cell for a solid oxide fuel cell, characterized in that in the method for producing a negative electrode material, one or more pore formers selected from the group consisting of a zirconium compound and a nickel compound. Provided is a method for producing a negative electrode material.

The anode material for a solid oxide fuel cell may be any one of a cathode support and a cathode functional layer.

The negative electrode support may include mixing any one or two or more pore formers and a solvent selected from the group consisting of nickel oxide, stabilized zirconia, zirconium compound, and nickel compound; Molding an anode support using the mixture; Sintering the molded body; And reducing the sintered body.

The sintering process is a step of pre-sintering for 0.5 to 2 hours at 1000 ℃ ~ 1200 ℃ at a temperature rising rate of 1 ~ 10 ℃ / min after heating up to a rate of 0.5 ~ 2 ℃ / min to 600 ℃; And it may include the step of co-sintering for 0.5 to 5 hours at 1300 ~ 1450 ℃ at a temperature rising rate of 1 ~ 10 ℃ / min.

The negative electrode functional layer is formed by coating the slurry on the negative electrode support through deep coating before co-sintering the pre-sintered negative electrode support, the slurry being any selected from the group consisting of nickel oxide, stabilized zirconia, zirconium compound and nickel compound. It can be prepared by mixing one or more pore formers and a solvent.

The zirconium compound used in the present invention may be any one or two or more selected from the group consisting of zirconium hydroxide, zirconium carbonate, zirconium sulfate and zirconium oxychloride.

The nickel compound used in the present invention may be any one or two or more selected from the group consisting of nickel hydroxide, nickel carbonate, nickel acetate, nickel chloride, nickel nitrate and nickel sulfamate.

The stabilized zirconia used in the present invention may be zirconia containing 3 to 10 mol% of yttria.

In addition, the pore-forming agent used in the present invention may further include any one or two or more selected from the group consisting of starch, carbon black, graphite and spherical polymer.

The spherical polymer may be any one of 1 to 10 μm of polymethylmethacrylate (PMMA) or polyvinyl alcohol (PVA).

In order to prepare a negative electrode support or a negative functional layer in the present invention, any one selected from the group consisting of a zirconium compound and a nickel compound, based on 100 parts by weight of a negative electrode material consisting of 30 to 60% by weight of nickel oxide and 40 to 70% by weight of stabilized zirconia 0.01 to 50 parts by weight of one or more pore formers may be mixed and used.

At this time, when the content of nickel oxide is out of the range, the Ni metal is disconnected, thereby lowering the electrical conductivity, which may cause a problem in the generated charge transfer, and when the content of the stabilized zirconia is out of the range, It may cause a problem in the movement of oxygen ions due to the disconnection, and if the content of the pore-forming agent is out of the above range, the performance of the fuel cell due to the delay of fuel supply due to the decrease in the strength and electrical conductivity of the negative electrode support or the lack of porosity May cause degradation.

The molding process may be performed by any one of press molding or extrusion molding, and a pressure of 20 to 40 MPa may be applied during the extrusion molding. In addition, the reduction process may be performed by heat-treating the sintered body at 800 to 1000 ℃ for 2 to 4 hours in the presence of argon containing 5% by volume hydrogen.

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

First, in the negative electrode supported solid oxide fuel cell, the negative electrode support must serve as a support of the multi-layered unit cell, and thus must have mechanical properties, and at the same time, satisfy the electrochemical properties for the oxidation reaction of the fuel. In addition, electrical conductivity or gas permeability should be excellent.

The mechanical properties of the negative electrode should be within the range of not only the strength of the support itself but also the thermal expansion coefficient with the electrolyte layer rising on the support to prevent the occurrence of defects during the heat cycle during manufacturing or operation. Since the cathode should not only serve as a carrier for extracting electricity, but also enable the oxidation reaction of the fuel in the cathode, a simple metal material cannot be used as the cathode.

In order to activate the oxidation reaction of the fuel, not only the catalyst component having high activity should be included in the cathode, but also the concentration of the active reaction point must be kept high in the cathode. In addition, the anode support in the anode support unit cell smoothly supplies fuel to the reaction point at which the electrochemical reaction of the fuel occurs and smoothly discharges water vapor generated during the oxidation reaction of the fuel. It must have a porous structure that includes pores as a passageway.

In order to satisfy these properties at the same time, the cathode mainly uses a metal composite having an electrical conductivity while having an electrochemical activity with an ion conductive oxide, wherein the composition of the oxide and the metal is adjusted to adjust the mechanical strength and the coefficient of thermal expansion. The composition is adjusted to optimize the combination of electrical conductivity and gas permeability, which are opposite properties. In addition, the porosity of the composite is determined in consideration of mechanical properties and gas permeability, and should be adjusted to maximize the active reaction point of the fuel in the allowable porosity range.

1 shows the sintering shrinkage rate of the support and the porosity after reduction according to the amount of the pore-forming agent in the composite powder used as the negative electrode material, there was no additional sintering shrinkage rate with the addition of the spherical polymer such as PMMA, spherical polymer As porosity increased, the porosity and shrinkage were 40.9% and 20.7%, respectively, when 9 wt% of PMMA was used. In addition, the sinter shrinkage rate of the anode support should be similar to that of the electrolyte layer (22%). For this purpose, the high sintering shrinkage rate of the P10_C5 support, which is the support containing PMMA and carbon black, needs to be lowered by increasing the sintering temperature. Therefore, by increasing the sintering temperature from 1100 ° C. (P10_C5) to 1150 ° C. (P10_C5 ^* ), the sinter shrinkage was reduced, and the sinter shrinkage of P10_C5 could be lowered to 22.4% without changing the porosity.

Figure 2 shows the microstructure of the negative electrode support obtained by changing the composition of the composite powder used as the negative electrode material, a and b are the microstructure of the negative electrode support prepared by adding 9% by weight of the spherical PMMA, sphere is approximately diameter It is homogeneous at 5 micrometers, it is distributed uniformly inside a support body, and pores are mutually connected. c and d are the microstructure of the negative electrode support prepared by adding 4% by weight of carbon black to the composition of a and b, and produced and increased micropores between large pores compared to a and b. In other words, the addition of carbon black caused the increase in PMMA, but the porosity did not have a significant influence, but the shrinkage was increased, and there were more micropores between large pores than the support without carbon black. In addition, the large pores resulting from the structure of the PMMA reduced the average size as a whole. This has no effect on the change in porosity even though the support with carbon black added a pore-forming agent in addition to that of the support without carbon black.

Due to the high hydrophobic surface properties and large surface area of carbon black, dispersion of carbon black is very difficult, especially in water-based operations. Carbon black is generally composed of many aggregates composed of bonds between the initial nano-sized particles. Because of this structure, carbon black is very porous and therefore has a very large surface area. The surface properties of these carbon black particles are very different from those of other oxide particles. These points hinder the slurry mixing of the carbon black and the oxide particles, and particularly, the carbon black of the slurry is nanometer in size and has a high solids content because of high water absorption.

In this respect, a zirconium compound or nickel compound was used in the present invention as a new pore forming agent as a carbon black substitute. The advantages of the new pore formers are that they have better surface properties than carbon black, are similar to the surface properties of the oxide particles used for the support, are larger than the particles of carbon black, and are non-porous. In addition, the pore-forming agent is composed of Zr or Ni, which is a component constituting the support body, and changes to zirconia or nickel oxide upon sintering.

When 4% by weight of zirconium hydroxide was added to the 9% by weight PMMA support instead of 4% by weight of carbon black, the effect of addition of zirconium hydroxide on the shrinkage and porosity was observed to be similar to that with carbon black. Due to the volume change caused by the zirconium hydroxide to zirconia phase change during sintering, fine pores were formed in the place of the zirconium hydroxide particles, which is the role of carbon black. As shown in e and f in FIG. 2, the microstructures between the large pores are more porous than those of the support (a and b in FIG. 2) using only PMMA pore formers.

In addition, the large pores generated by PMMA decreased during sintering and its average size also slightly decreased. This is almost the same as the support (P10_C5) prepared by adding PMMA and carbon black. Therefore, the microstructure of the support of the support (P10_Z5) prepared by adding PMMA and zirconium hydroxide, porosity (38.8%), and sintering shrinkage (21.7%) can be sufficiently satisfied as a high-performance support.

Figure 3a shows the electrical conductivity of the support, Figure 3b shows the change in the biaxial strength of the support according to the content of the pore-forming agent. As described in FIG. 1, the electrical conductivity and biaxial strength were constantly reduced by increasing the content of PMMA, which contributes to increasing porosity. On the contrary, as shown in FIG. 3, the addition of carbon black to the PMMA support has little effect on the electrical conductivity and biaxial strength. These additional additives rarely change the porosity as mentioned above. The addition of carbon black is less sensitive to electrical conductivity and mechanical strength.

Similar behaviors in electrical conductivity and mechanical strength were also observed in supports using zirconium hydroxide as an additive. However, zirconium hydroxide is believed to be better as a pore-forming agent. The electrical conductivity and the mechanical strength of the zirconium hydroxide-added negative electrode support (P10_Z5) are 3337 S / cm and 148 MPa, respectively, and these physical properties are higher than those of other NiO-YSZ composite supports having the same porosity. In addition, the gas permeability was also 0.047 cm ² / (cm H ₂ O) min, which was higher than that of the general support.

Thus, the large pores in the site of PMMA formed during sintering contribute to gas permeation, while the micropores formed of zirconium hydroxide or carbon black are additionally formed during the reduction process and significantly increase the three-phase interface which is critical to the performance of the cell. The interaction of these large and small pores can significantly improve the performance of fuel cells.

Figure 4 shows the electrical conductivity according to the temperature of the NiO-YSZ cathode support prepared according to the embodiment, since the negative electrode needs a sufficiently high electrical conductivity for the flow of electrons at the operating temperature of the reducing atmosphere, as shown in Figure 4, At a typical operating temperature of 750 ° C, the electrical conductivity of 1000 S / cm or more is higher than that of other literatures with the same porosity.

5 is a graph showing changes in sinter shrinkage and porosity of a cathode functional layer depending on the amount of zirconium hydroxide added to a composite powder having a composition of 56 wt% NiO- (44-x) wt% YSZ-x wt% Zr (OH) ₄ In the case of addition of a small amount of zirconium hydroxide, the porosity increased as the amount of zirconium hydroxide increased, but as the addition, the porosity decreased and the porosity was saturated. The increase in porosity affected by the addition of zirconium hydroxide can contribute to the formation of pores resulting from the phase change of zirconium hydroxide to zirconia during the sintering process. On the other hand, the sinter shrinkage rate was small due to the addition of zirconium hydroxide, and the sinter shrinkage rate was maintained at approximately 22%, which is related to the sinter shrinkage rate of the electrolyte layer and the support. The porosity and sinter shrinkage of the cathode functional layer using 4.4% by weight of zirconium hydroxide were 31.8% and 21.6%, respectively. In particular, it is determined that the high electrical conductivity 4045 S / cm of the support P10_Z5 will be beneficial to fuel cell operation by preventing polarization activity.

Figure 6 shows the interfacial polarization resistance of the negative electrode support and the negative electrode functional layer prepared according to the present invention, by configuring the negative electrode functional layer on the negative electrode support to reduce the polarization due to the interface resistance by introducing an increase in the three-phase interface.

7A and 7B illustrate the microstructure of a cathode functional layer prepared by adding various amounts of zirconium hydroxide, wherein pores having a thickness of about 1 μm are uniformly distributed throughout the functional layer and connected to each other to form a pore path network. It is. The porosity of the functional layer prepared without the addition of zirconium hydroxide was 22.8% after the reduction treatment, and the pore contribution was 9% due to the addition of 4.4% by weight of zirconium hydroxide. That is, the porosity after reduction of the functional layer using 4.4 wt% zirconium hydroxide was 31.8%. These microporous cathode functional layers provide a highly chemically active reaction surface and improve cell performance.

FIG. 8 shows a cross section of the electrolyte layer / functional layer / support layer sintered at 1400 ° C. for 3 hours and then reduced at 900 ° C. in a hydrogen atmosphere. The electrolyte layer was approximately 3 μm and was completely compact without defects. The production of a completely dense YSZ electrolyte layer free of defects on the porous support is still a major challenge, with the functional layer smoothing the surface of the rough support due to the presence of large pores therein and improving the roughness of the surface on which the electrolyte layer will sit. Improved surface roughness reduces the likelihood of defects created in the electrolyte layer. In addition, the functional layer has a uniform and fine pore structure to tightly bond the electrolyte layer and the support.

In the method of manufacturing a negative electrode material for a solid oxide fuel cell according to the present invention, the transport of gas through large pores produced by a spherical polymer such as PMMA, and the length of a three-phase junction (TPB) through micropores using a zirconium compound or a nickel compound Compared with the negative electrode material using only spherical polymer such as PMMA as the pore forming agent, the negative electrode material made of the composite pore forming agent using zirconium compound or nickel compound together with PMMA can adjust the overall shrinkage rate and at the same time The strength, electrical conductivity and gas permeability, which are the weak points of anode materials for solid oxide fuel cells, are also very good.

Figure 1 shows the pore and sintered shrinkage change of the negative electrode support prepared by using various pore-forming agent ( ^* means a plastic support sintered at 1150 ℃).
Figure 2 is a SEM photograph showing the microstructure of the negative electrode support prepared using various pore-forming agents, a and b is 9% by weight PMMA (P10), c and d is 9% by weight PMMA and 4% by weight carbon black ( P10_C5), e and f mean 9% by weight PMMA and 4% by weight zirconium hydroxide (P10_Z5).
Figure 3 shows the electrical conductivity (a) and biaxial strength (b) of the negative electrode support prepared using various pore-forming agents ( ^* refers to the negative electrode support sintered at 1150 ℃).
Figure 4 shows the electrical conductivity change according to the temperature of the negative electrode support prepared by using various pore-forming agent ( ^* means a negative electrode support sintered at 1150 ℃).
Figure 5 shows the change in pore (a) and sintering shrinkage (b) of the negative electrode support according to the zirconium hydroxide content changes.
Figure 6 shows the interfacial polarization resistance of the negative electrode support and the negative electrode functional layer prepared using a variety of pore-forming agent ( ^* means 97% by volume H ₂ -3% by volume H ₂ O atmosphere).
7 is a SEM photograph showing the microstructure of a cathode functional layer to which 4.4 wt% of zirconium hydroxide is added.
8 is a SEM photograph of a negative electrode support coated with a negative electrode functional layer and an electrolyte layer.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the present invention is not limited by these examples.

Example 1 Preparation of Anode Support Using Zirconium Hydroxide

For the preparation of the NiO-YSZ negative electrode support, first commercially available nickel oxide (NiO-FP, Sumitomo Metal Mining Co., LTD., Tokyo, Japan) and YSZ containing 8 mol% yttria (TZ-8YS, Tosho Co., Shunan, Japan). At this time, the average particle diameters of the YSZ and NiO powders measured by a particle size analyzer (LS 13 320, Porous Material Inc., Brea, CA, USA) were 0.2 and 0.3 μm, respectively. And PMMA (LDX-50, Sunjin Chem. Co., Ltd., Ansan, Korea), carbon black (HIBLACK 170, Evonik Carbon Korea, Incheon, Korea), zirconium hydroxide (97%, Sigma-Aldrich Co., St. Louis, MO, USA) powder was used as pore-forming agent. At this time, PMMA was spherical and the average particle diameter was 5 micrometers.

The composition of the composite powder for preparing the negative electrode support is shown in Table 1 below, and each composite powder was ball milled for 6 hours in a polyethylene bottle containing methanol as a solvent, wherein EFKA 4401 (Ciba Canada Ltd., Mississauga, Canada) was used as a dispersant. ) Was dried overnight at 50 ° C. and then ground in an agate mortar and then molded.

Classification Methanol
(g) EFKA 4401 (g) NiO (g) 8YSZ (g) PMMA (g) Carbon black (g) Zr (OH) ₄
(g) cathode
Support P0 40 One 56 44 0 P2 40 One 56 44 2 P6 40 One 56 44 6 P8 40 One 56 44 8 P10 40 One 56 44 10 P10_C5 40 One 56 44 10 5 P10_Z5 40 One 56 44 10 5 cathode
Functional layer Z4.4 40 One 56 39.6 4.4

This composite powder was pressed at a pressure of 30 MPa on a 20 mm diameter disk. The powder compact obtained was presintered at 1100 ° C. for 1 hour so as to have sufficient mechanical strength to facilitate handling. The powder compact was heated to a presintering temperature at a rate of 2 ° C./min up to 600 ° C., at a rate of 5 ° C./min up to 600 ° C. to 1100 ° C., and then 1 hour at 160 ° C., 3 hours at 350 ° C., and 600 ° C. Was maintained for 1 hour. The presintered molded body was measured and weighed, and then sintered by heating to 1400 ° C. at a rate of 5 ° C./min, and maintained at 1400 ° C. for 3 hours. After the sintered compact was dimensioned and weighed, NiO in the sintered compact was reduced to Ni by heat treatment at 900 ° C. for 3 hours in the presence of argon containing 5% by volume hydrogen. Thereafter, the dimensions and weighings of the reducing disks were carried out again. These measurements are intended to measure the shrinkage and porosity of the disks that occur during each heat treatment process.

Experimental Example 1 Evaluation of Sintering Shrinkage and Porosity

The porosity of the negative electrode support prepared in Example was measured by the Archimedes method.

1 shows the sinter shrinkage rate of the negative electrode support and the porosity after reduction according to the amount of the pore-forming agent in the composite powder. Here, the axis of abscissas means the type of pore-forming agent and the amount of PMMA from 0 to 10, and the porosity was increased with the increase of the spherical polymer. However, shrinkage remained at 22% without any significant change. In other words, the change in sinter shrinkage rate with the increase of spherical polymer was negligible. In addition, the spherical polymer formed large pores of the spherical shape and was fairly stable through the entire sintering process, and most of them remained pores after sintering.

From these results, there was no additional sintering shrinkage according to the addition of the spherical polymer. As the spherical polymer was increased, the porosity increased to 40.9% and 20.7%, respectively, when the PMMA was 9% by weight.

On the other hand, as is known, the sinter shrinkage rate of the negative electrode support should be similar to that of the electrolyte layer (22%). In view of this, the high sintering shrinkage rate of the P10C5 support (the support containing PMMA and carbon black) needs to be lowered by increasing the sintering temperature. By increasing the sintering temperature from 1100 ° C to 1150 ° C, the sintering shrinkage was reduced, and the sintering shrinkage of P10_C5 could be lowered to 22.4% as in Figure 1 without changing the porosity. Porosity (40.1%), sinter shrinkage rate (22.4%), and the microstructure of the negative electrode support sufficiently satisfy the requirements of high performance negative electrode material.

Experimental Example 2 Evaluation of Microstructure

The microstructure of the negative electrode support prepared in Example was observed with a scanning electron microscope (SEM, S-4200, Hitachi High-technologies Co., Ltd., Tokyo, Japan).

In Figure 2 a and b is a microstructure of the negative electrode support prepared by adding 9% by weight of PMMA, the spheres are homogeneously approximately 5㎛ in diameter, uniformly distributed inside the support, the pores were connected to each other.

In Figure 2 c and d is a microstructure of the negative electrode support prepared by adding 4% by weight of carbon black to the a and b composition, compared to a, b to generate and increase the micropores between large pores. In other words, the addition of carbon black caused the increase of PMMA, but the porosity did not have a significant influence, but it increased the shrinkage rate and more micropores between the large pores than the support without carbon black. In addition, the large pores resulting from the structure of PMMA reduced the average size as a whole. This had no effect on the change in porosity even though the carbon black added support added additional pore formers than that of the carbon black free support.

On the other hand, Figure 2 e and f is a microstructure of the negative electrode support prepared by adding 4% by weight of zirconium hydroxide instead of 4% by weight of carbon black in the c and d composition, the effect of shrinkage and porosity according to the addition of zirconium hydroxide It was observed to be similar to the support with carbon black. Due to the volume change resulting from the zirconium hydroxide to zirconia phase change during sintering, fine pores are formed in the place of the zirconium hydroxide particles, which is the role of carbon black. That is, the microstructure between the large pores appeared to be more porous than that of the support (FIG. 2a and b) using only the PMMA pore former.

In addition, the large pores generated by PMMA were reduced during sintering and its average size was also slightly reduced. This is almost the same as the support (P10C5) prepared by adding PMMA and carbon black. Therefore, the results of microstructure, porosity (38.8%), and sintering shrinkage (21.7%) of P10Z5 support were judged to be sufficient as high-performance supports.

Experimental Example 3 Electrical Conductivity, Mechanical Strength, and Gas Permeability Evaluation

The electrical conductivity of the negative electrode support prepared in Example was measured using a 4-point probe surface resistance meter (CMT-SR1000N, Chang Min Co., Ltd., Sungnam, Korea) and DC voltage (UP-3005D, Unicorn Tech Co., Ltd.). , Anyang, Korea) and a digital multimeter (Model 2000 6-1 / 2-Digit DMM, Keithley Instruments Inc., Cleveland, OH, USA), and the mechanical strength was measured using biaxial strength (ISO6872: 2008E, AG 500E, Shimadzu Co., Kyoto, Japan).

Figure 3a shows the electrical conductivity of the negative electrode support, Figure 3b shows the change in the biaxial strength of the negative electrode support according to the content of the pore-forming agent. As shown in FIG. 1, the electrical conductivity and biaxial strength were constantly decreased by increasing the content of PMMA, which contributes to increasing porosity. On the other hand, the addition of carbon black to the PMMA support as shown in Figure 3 did not have a significant effect on the electrical conductivity and biaxial strength. The addition of such carbon black caused little change in porosity as mentioned above. The addition of carbon black was found to be less sensitive to electrical conductivity and mechanical strength.

Similar behaviors in electrical conductivity and mechanical strength were also observed in the support using zirconium hydroxide as an additive, but zirconium hydroxide was found to be better as a pore-forming agent. The electrical conductivity and mechanical strength of the zirconium hydroxide-added negative electrode support (P10Z5) are 3337 S / cm and 148 MPa, respectively, and these physical properties are higher than those of other NiO-YSZ composite supports having the same porosity.

In addition, the gas permeability of the support, measured using a permeability meter (CFP-1500 AEL, Porous Material Inc., Ithaca, NY, USA), was also 0.047 cm ² / (cm H ₂ O) min, which was higher than that of a typical support. .

Experimental Example 4 Evaluation of Electrical Conductivity Change According to Temperature

Electrical conductivity according to the temperature of the negative electrode support prepared in Example was measured in the same manner as in Experiment 3.

Since the negative electrode requires a sufficiently high electrical conductivity for the flow of electrons at the operating temperature of the reducing atmosphere, as shown in FIG. 4, the electrical conductivity of 1000 S / cm or more at a general operating temperature of 750 ° C. is higher than that of the negative electrode support of other documents having the same porosity. High (J. Solid State Electrochem. 11 (2007) 1295-1301). This conducting behavior follows the behavior of typical metals. Electrical conductivity decreases with increasing temperature, and conduction appears to occur through the connection of Ni. Therefore, it was confirmed that the negative electrode support of the example is sufficiently high in electrical conductivity and can be used as the negative electrode support in terms of porosity and mechanical strength.

Example 2 Preparation of Cathode Functional Layer and Electrolyte Layer Using Zirconium Hydroxide

The anode functional layer and the YSZ electrolyte layer were prepared by sintering the pre-sintered support using a slurry dip-coating method and co-sintered in air at 1400 ° C. for 3 hours. A more detailed process for preparing the functional layer and the electrolyte layer on the negative electrode support is as follows.

That is, to prepare a functional layer on the negatively sintered negative electrode support at 1150 ° C. for 1 hour, zirconium hydroxide was added to the NiO-YSZ composite powder to prepare a dip-coating slurry. At this time, the composition of the NiO-YSZ composite powder was composed of 56% by weight NiO, 39.6% by weight YSZ and 4.4% by weight Zr (OH) ₄ , the composite powder is a zirconia ball in methanol containing 1% by weight of EFKA 4401 dispersant. Wet ball mill was performed for 18 hours. This includes 3% by weight of polyvinyl butyral resin binder (Butvar B-98, Solutia Inc., St. Louis, MO, USA) and 2% by weight of dioctyl phthalate (DOP, 99.0%, Samchun Pure Chem. , Ltd., Pyongtack, Korea)) additional ball mill was performed for 5 hours after the addition of the plasticizer. After the ball mill was finished, the solid content of the dip coating slurry was diluted to 10% by weight. The functional layer Z4.4 was formed twice on the slurry for 30 seconds using a dip coating machine to form a sintered support.

The negative electrode support coated with the functional layer was dried (or sintered) at room temperature for 1 hour to prepare an electrolyte layer through a dip coating process on the functional layer. The slurry used for coating the electrolyte layer was prepared by the same process as the slurry used for coating the functional layer. The negative electrode support coated with the functional layer was immersed twice in an electrolyte slurry for 30 seconds and dried at room temperature for 1 hour.

The negative electrode support coated with the functional layer and the electrolyte layer was co-sintered at 1400 ° C. for 3 hours. To form a uniform and thin YSZ electrolyte layer and cathode functional layer, dip coating was performed twice for two purposes. One is to ensure the strength of the functional and electrolyte layers and the other is to prevent the formation of tiny holes in the electrolyte layer during the sintering process and drying.

Experimental Example 5 Investigation of Changes in Sintering Shrinkage and Porosity of Anode Functional Layer According to Zirconium Hydroxide Addition

In the same manner as in Experimental Example 1, the change of the sinter shrinkage rate and the porosity of the anode functional layer according to the addition amount of zirconium hydroxide was examined.

5 is a graph showing changes in sinter shrinkage and porosity of a cathode functional layer depending on the amount of zirconium hydroxide added to a mixed powder having a composition of 56 wt% NiO- (44-x) wt% YSZ-x wt% Zr (OH) ₄ In the case of addition of a small amount of zirconium hydroxide, the porosity increased as the amount of zirconium hydroxide increased, but as the addition, the porosity decreased and the porosity was saturated. The increase in porosity influenced by the addition of zirconium hydroxide may contribute to the formation of pores resulting from the phase change of zirconium hydroxide to zirconia during sintering. On the other hand, the sinter shrinkage rate was small due to the addition of zirconium hydroxide, and the sinter shrinkage rate was maintained at approximately 22%, which was related to the sinter shrinkage rate of the electrolyte layer and the support. The functional layer using 4.4% by weight of zirconium hydroxide has porosity and sinter shrinkage of 31.8% and 21.6%, respectively. In particular, high electrical conductivity (4045 S / cm) compared to 3337 S / cm of the support P10Z5 was determined to be beneficial for fuel cell operation by preventing polarization activity.

Experimental Example 6 Evaluation of Interface Resistance of Anode Support and Anode Functional Layer

In order to measure the interface resistance between the negative electrode support and the negative electrode functional layer prepared in Example, an impedance impedance was measured using an impedance analyzer (1260A Impedance / Gain-Phase Analyzer, AMETEK Solartron, Farnborough, United Kingdom). Linear reaction using an excitation voltage of 50 mV over a frequency range of 0.1 to 105 Hz in a wet hydrogen atmosphere (3 vol% H ₂ O-97 or 5 vol% H ₂ -balance Ar) at 800 ° C. It was confirmed.

As shown in FIG. 6, the interfacial resistance of the negative electrode support was improved by the formation of the negative electrode functional layer. In addition, when the hydrogen concentration was increased from 5% to 97% by volume in the wet atmosphere, it was judged that the polarization phenomenon was caused by the charge transfer reaction at the cathode as the intermediate frequency arc almost disappeared.

Experimental Example 7 Microstructure of Cathodic Functional Layer

In the same manner as in Experimental Example 2, the change in the microstructure of the anode functional layer according to the addition amount of zirconium hydroxide was examined.

7a and 7b show the microstructure of the cathode functional layer prepared by adding 0 to 4.4% by weight of zirconium hydroxide, the pores of approximately 1㎛ are uniformly distributed throughout the functional layer and form a pore path network with each other Is connected to The porosity of the functional layer prepared without the addition of zirconium hydroxide was 22.8% after the reduction treatment, and the pore contribution was 9% due to the addition of 4.4% by weight of zirconium hydroxide. As shown in FIG. 5, the porosity after reduction of the functional layer using 4.4 wt% zirconium hydroxide was 31.8%. These microporous cathode functional layers provide an electrochemically active reaction surface and can improve cell performance.

8 shows a cross section of the electrolyte layer / functional layer / support layer sintered at 1400 ° C. for 3 hours and then reduced at 900 ° C. in a hydrogen atmosphere. The electrolyte layer was approximately 3 μm and was completely compact without defects.

Example 3 Preparation of Anode Support and Anode Functional Layer Using Nickel Carbonate

It is the same as the manufacturing method of the negative electrode support and the negative electrode functional layer mentioned above, each composition is shown in Table 2 below.

Classification Methanol
(g) EFKA 4401 (g) NiO (g) 8YSZ (g) PMMA (g) NiCO ₃ -2Ni (OH) ₂ -4H ₂ O cathode
Support P10_NC5 40 One 56 44 10 5 NC 40 One 39.2 44 16.8 cathode
Functional layer NC 40 One 39.2 44 16.8

The total shrinkage, sintering shrinkage, and post-reduction porosity of the cathode support P10_NC5 using PMMA and nickel carbonate were 24.8%, 21.8%, and 44%, respectively. The total shrinkage and post-reduction porosity of the anode support NC using only nickel carbonate were 24.4% and 35%, respectively.

<Example 4> Preparation of negative electrode support and production of negative electrode functional layer using zirconium carbonate

It is the same as the manufacturing method of the negative electrode support and the negative electrode functional layer mentioned above, each composition is shown in Table 3 below.

Classification Methanol
(g) EFKA 4401 (g) NiO (g) 8YSZ (g) PMMA (g) [ZrO ₂ ] ₂ ? CO ₂ ? XH ₂ O cathode
Support P10_ZC5 40 One 56 44 10 5 ZC 40 One 56 17.6 26.4 cathode
Functional layer ZC 40 One 56 17.6 26.4

The total shrinkage, sintering shrinkage, and post-reduction porosity of the anode support P10_ZC5 using PMMA and zirconium carbonate were 26.1%, 21.1%, and 41.4%, respectively. The total shrinkage and post-reduction porosity of the negative electrode support ZC using only zirconium carbonate were 26.2% and 35%, respectively.

While the present invention has been particularly shown and described with reference to specific embodiments thereof, those skilled in the art will appreciate that such specific embodiments are merely preferred embodiments and that the scope of the present invention is not limited thereby. something to do. It is therefore intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

Claims (13)

A method for producing a negative electrode material for a solid oxide fuel cell, the method for producing a negative electrode material for a solid oxide fuel cell, characterized in that any one or two or more pore formers selected from the group consisting of a zirconium compound and a nickel compound are added. The method of claim 1, wherein the anode material for a solid oxide fuel cell is any one of a cathode support or a cathode functional layer. The method according to claim 2, wherein the negative electrode support,
Mixing one or two or more pore formers and a solvent selected from the group consisting of nickel oxide, stabilized zirconia, zirconium compound and nickel compound;
Molding an anode support using the mixture;
Sintering the molded body; And
Reducing the sintered body
Method for producing a negative electrode material for a solid oxide fuel cell comprising a. The method of claim 3, wherein the sintering is performed by heating at a rate of 0.5 to 2 ° C./min up to 600 ° C. and then sintering at 1000 ° C. to 1200 ° C. for 0.5 to 2 hours at a temperature rising rate of 1 to 10 ° C./min; And co-sintering at 1300 to 1450 ° C. for 0.5 to 5 hours at a temperature increase rate of 1 to 10 ° C./min. The method according to claim 4, wherein the cathode functional layer,
It is formed by coating the slurry on the negative electrode support through deep coating prior to co-sintering the pre-sintered negative electrode support, wherein the slurry is any one or two or more pores selected from the group consisting of nickel oxide, stabilized zirconia, zirconium compound and nickel compound A method for producing a negative electrode material for a solid oxide fuel cell, characterized in that a mixing agent and a solvent are mixed. The method of claim 1 or 2, wherein the zirconium compound is any one or two or more selected from the group consisting of zirconium hydroxide, zirconium carbonate, zirconium sulfate and zirconium oxychloride. The negative electrode material of claim 1 or 2, wherein the nickel compound is any one or two or more selected from the group consisting of nickel hydroxide, nickel carbonate, nickel acetate, nickel chloride, nickel nitrate, and nickel sulfamate. Manufacturing method. The method of claim 3, wherein the stabilized zirconia is a zirconia containing 3 to 10 mol% of yttria. The method of claim 1 or 2, wherein the pore-forming agent further comprises any one or two or more selected from the group consisting of starch, carbon black, graphite and spherical polymer. The method of claim 9, wherein the spherical polymer is any one of 1 to 10 μm of polymethyl methacrylate (PMMA) or polyvinyl alcohol (PVA). . The method according to claim 3, wherein the mixture is formed of one or two or more pores selected from the group consisting of a zirconium compound and a nickel compound with respect to 100 parts by weight of the negative electrode material consisting of 30 to 60% by weight nickel oxide and 40 to 70% by weight stabilized zirconia Method for producing a negative electrode material for a solid oxide fuel cell, characterized in that the mixture of 0.01 to 50 parts by weight. The method of manufacturing a negative electrode material for a solid oxide fuel cell according to claim 3, wherein the molding is any one of press molding and extrusion molding. The method of claim 3, wherein the reduction is performed by heating the sintered body at 800 to 1000 ° C. for 2 to 4 hours in the presence of argon containing 5% by volume of hydrogen.

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