An easily dispersible SOFC cathode powder and its preparation method and application

Abstract

The present invention provides an easily dispersible SOFC cathode powder and a preparation method and application thereof, comprising the following steps: mixing nitrate, urea, water-soluble starch and water, stirring until completely dissolved, and obtaining a mixed solution; immersing wood fiber in the mixed solution until absorption is saturated, and obtaining saturated wood fiber; drying the saturated wood fiber, calcining, and ball milling to obtain an easily dispersible SOFC cathode powder. In the present invention, the wood fiber is immersed in the mixed solution until absorption is saturated, and the mixed solution is evenly impregnated in the wood fiber. The wood fiber is loose and porous, and the heat generated in the combustion reaction can be effectively dissipated during calcination, so as to avoid grain growth and facilitate the synthesis of nanopowders; in addition, the wood fiber burns during calcination, and after calcination, it is evenly distributed around the powder particles in the form of residual carbon powder, effectively isolating the powder particles, and the powder particles are easy to disperse when preparing the cathode, and no large agglomerates are generated.

Description

Technical Field

[0001] The present invention relates to the technical field of solid oxide fuel cells, and in particular to an easily dispersible SOFC cathode powder and a preparation method and application thereof. Background Art

[0002] Solid oxide fuel cell (SOFC) is a power generation device that directly converts the chemical energy of fuel into electrical energy. It has the advantages of high energy conversion efficiency, wide fuel applicability, and low pollutant emissions. It can be used in power generation, thermal power recovery, transportation, space aerospace and other fields, and is known as the green energy of the 21st century.

[0003] The cathode is one of the important components of a solid oxide fuel cell. It provides an electrochemical reaction site for the reduction of oxygen, and its performance directly affects the performance of the entire battery. The cathode of a solid oxide fuel cell has strict requirements on the particle size, crystal structure, micromorphology and electrochemical performance of its raw material cathode powder. The most ideal cathode powder should have small and uniform particles, no impurity phase in the phase composition, complete and clear lattice boundaries, uniform and regular arrangement, and little or no agglomeration. At present, the commonly used methods for preparing cathode powders generally include sol-gel method, coprecipitation method, electrospinning, glycine-nitrate method, high temperature solid phase reaction method, etc. However, the cathode powders prepared by these methods generally have the problem that the powder particles are not easy to disperse and agglomerate more in the process of preparing the cathode, resulting in unsatisfactory cathode structure uniformity and performance. Therefore, there is an urgent need in the art for a method for preparing cathode powders, so that the prepared cathode powders are not easy to agglomerate and have good dispersibility in the process of preparing the cathode. Summary of the invention

[0004] The present invention provides an easily dispersible SOFC cathode powder and a preparation method and application thereof, in order to solve the common problem that the cathode powder prepared by the prior art is difficult to disperse and has a lot of agglomeration in the process of preparing the cathode. The cathode powder prepared by the preparation method of the present invention is not easy to agglomerate and has good dispersibility in the process of preparing the cathode.

[0005] On the one hand, the present invention provides a method for preparing an easily dispersible SOFC cathode powder, comprising the following steps: mixing nitrate, urea, water-soluble starch and water, and stirring until completely dissolved to obtain a mixed solution; immersing wood fiber in the mixed solution until absorption is saturated to obtain saturated wood fiber; drying the saturated wood fiber, calcining and ball milling to obtain the easily dispersible SOFC cathode powder.

[0006] In some embodiments of the present invention, in the mixed solution, by weight, water-soluble starch accounts for 0.1-0.5 parts, and water accounts for 70-90 parts; the concentration of nitrate in the mixed solution is not greater than 2 mol / l, and the mass ratio of nitrate to urea is (0.5-1):1.

[0007] In some embodiments of the present invention, the nitrate comprises at least two of lanthanum nitrate, iron nitrate, strontium nitrate, cobalt nitrate, beryllium nitrate, bismuth nitrate, nickel nitrate, and copper nitrate. Preferably, the purity of lanthanum nitrate, iron nitrate, strontium nitrate, cobalt nitrate, beryllium nitrate, bismuth nitrate, nickel nitrate, and copper nitrate is above 99%.

[0008] In some embodiments of the present invention, preferably, the purity of urea is above 99%.

[0009] In some embodiments of the present invention, the water-soluble starch is a modified starch having carboxyl and hydroxyl groups, and the viscosity of the water-soluble starch at a concentration of 4 wt % and a temperature of 25° C. is 500-1000 mPa.s.

[0010] In some embodiments of the present invention, when preparing the mixed solution, nitrate and urea are first added to water and stirred until completely dissolved, and then water-soluble starch is added and stirred until completely dissolved to obtain the mixed solution.

[0011] In some embodiments of the present invention, the wood fiber is a spherical wood fiber, and the spherical wood fiber is prepared by pelletizing wood fibers.

[0012] In some embodiments of the present invention, the diameter of the spherical wood fiber is 2-5 mm, and the pore diameter is 10-40 μm.

[0013] In some embodiments of the present invention, the drying temperature of the saturated wood fiber is 80-100° C.; after the saturated wood fiber is dried, the temperature is kept at 350-450° C. for 30-60 min to complete calcination.

[0014] On the other hand, the present invention further provides an easily dispersible SOFC cathode powder, wherein the easily dispersible SOFC cathode powder is prepared according to any one of the preparation methods described above.

[0015] On the other hand, the present invention also provides an application of the above-mentioned easily dispersible SOFC cathode powder, wherein the easily dispersible SOFC cathode powder is ball-milled with water as a medium to obtain SOFC cathode slurry, and the SOFC cathode slurry is loaded on an electrolyte layer to obtain a SOFC cathode.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) The mixed liquid of the present invention is a mixture of nitrate, urea, water-soluble starch and water. After the wood fiber is immersed in the mixed liquid until it is saturated with absorption, the mixed liquid is evenly immersed in the porous channels of the wood fiber itself. After the saturated wood fiber is taken out from the mixed liquid, due to the presence of the water-soluble starch, the mixed liquid immersed in the wood fiber is more easily hung in the wood fiber, and the mixed liquid will not be separated from the saturated wood fiber. After the water is removed from the dried saturated wood fiber, the mixed liquid is still evenly distributed in the porous channels of the wood fiber, which is convenient for the subsequent calcination to proceed smoothly. Nitrate and urea induce low-temperature combustion to generate Ultrafine powder products, because wood fiber has a loose and porous structure, the heat generated in the combustion reaction during calcination can be effectively dissipated, avoiding grain growth, which is conducive to the synthesis of nano powders. In addition, during calcination, wood fiber and water-soluble starch burn, and become carbon powder after calcination. Since the mixed liquid in the dried saturated wood fiber is still evenly distributed in the porous channels of the wood fiber after removing water, the residual carbon powder formed by the combustion of wood fiber and water-soluble starch after calcination is evenly distributed around the powder particles, effectively isolating the powder particles. When preparing the cathode, the powder particles are easy to disperse, and no large agglomerates will be generated. The prepared cathode has good structural uniformity and excellent performance. In addition, the preparation method of the present invention is simple in process, safe in operation, low in cost, can be mass-produced, and the prepared cathode powder has a uniform microstructure.

[0018] (2) The nitrate concentration in the mixed solution of the present invention is not more than 2 mol / l, which meets the requirements of the solid oxide fuel cell for the cathode component composition; the mass ratio of nitrate to urea is (0.5-1):1, which can ensure that the combustion flame temperature of the low-temperature combustion reaction occurring during calcination is sufficiently low, thereby making the particle size of the generated ultrafine powder sufficiently low, thereby meeting the solid oxide fuel cell cathode's requirements for the cathode powder nanoparticle size; the water-soluble starch accounts for 0.1-0.5 parts by weight, which can ensure that the mixed solution immersed in the wood fiber is fully hung in the wood fiber, and the phenomenon of the mixed solution being separated from the saturated wood fiber will not occur, thereby ensuring that after subsequent drying, the mixed solution is still evenly distributed in the porous channels of the wood fiber after removing the water; water accounts for 70-90 parts by weight, which can ensure that the prepared mixed solution is easy to be immersed in the wood fiber.

[0019] (3) The water-soluble starch of the present invention is a modified starch with carboxyl and hydroxyl groups. The viscosity of the water-soluble starch measured at a concentration of 4wt% and a temperature of 25°C is 500-1000mPa.s. It has good solubility in cold water. The carboxyl and hydroxyl groups achieve compatibility between the wood fiber and the mixed solution, that is, the modified starch has carboxyl and hydroxyl groups, which makes it easier for the mixed solution to be fixed to the wood fiber, which is beneficial to the absorption of the mixed solution by the porous channels of the wood fiber, and the mixed solution is not easy to separate from the wood fiber. In addition, when preparing the mixed solution, the present invention first dissolves nitrate and urea in water and then adds the water-soluble starch. Since the water-soluble starch itself has a certain viscosity, this addition order can ensure the dissolution rate of nitrate and prevent the starch from slowing down the dissolution of nitrate when the nitrate is added together or added first.

[0020] (4) The wood fiber of the present invention is spherical wood fiber. During the calcination process, in addition to the porous channels unique to the wood fiber itself, that is, the loose porous structure, which can effectively dissipate the heat generated in the combustion reaction during calcination, multiple spherical wood fibers in contact with each other will form channels between the spherical wood fibers, which is convenient for further heat dissipation, further avoiding grain growth, and is beneficial to the synthesis of nanopowders. The diameter of the spherical wood fiber of the present invention is 2-5mm, and the channel diameter is 10-40μm, which is more conducive to heat dissipation. The mass loss after calcination is 80-90%, that is, the carbon powder content of the wood fiber combustion residue accounts for 10%-20% of the mass of the wood fiber. On the one hand, the powder particles are effectively isolated, and on the other hand, the dispersant and pore-forming agent can be replaced. When preparing the cathode slurry, there is no need to add dispersant and pore-forming agent. It is only necessary to add water to the cathode powder prepared by the present invention to obtain the cathode slurry, and the cathode is obtained after being loaded on the electrolyte layer. The process is simple.

[0021] (5) The present invention immerses the wood fiber in the absorption mixed liquid until saturated, and then dries the saturated wood fiber, which can fully remove moisture, open the pores of the wood fiber, and prevent the problem of water boiling due to direct calcination and then bringing the mixed liquid components out of the wood fiber; the drying temperature is 80-100°C to ensure the drying efficiency, and the calcination is completed at 350-450°C for 30-60 minutes to ensure the full combustion of the wood fiber and the water-soluble starch, thereby obtaining powder particles separated by carbon powder, that is, obtaining easily dispersible cathode powder.

[0022] (6) The cathode powder prepared by the preparation method of the present invention can be mixed evenly at the molecular level, the composition is more uniform, the particle diameter is small, and the residual carbon powder from the combustion of wood fiber and water-soluble starch fully isolates the powder particles. The obtained cathode powder is easy to disperse when preparing the cathode and will not produce large agglomerates. In addition, when the cathode powder prepared by the preparation method of the present invention is used to prepare the cathode, the carbon powder that isolates the powder particles acts as a dispersant and a pore-forming agent, and there is no need to add additional dispersants and pore-forming agents. The cathode powder is ball-milled with water as the medium. After the ball milling is completed, the ball milling beads are taken out to obtain the SOFC cathode slurry. The SOFC cathode slurry is loaded on the electrolyte layer to obtain the SOFC cathode. DETAILED DESCRIPTION

[0023] In order to make the objectives, technical solutions and advantages of the present invention more clear, various aspects of the present invention will be described in detail below in conjunction with specific embodiments. However, these specific embodiments are only used to illustrate the present invention and do not constitute any limitation on the scope of protection and essential content of the present invention.

[0024] The invention provides a method for preparing an easily dispersible SOFC cathode powder, comprising the following steps: mixing nitrate, urea, water-soluble starch and water, and stirring until completely dissolved to obtain a mixed solution; immersing wood fiber in the mixed solution until absorption is saturated to obtain saturated wood fiber; and drying the saturated wood fiber, calcining and ball milling to obtain an easily dispersible SOFC cathode powder.

[0025] In the present invention, in the mixed solution, by weight, water-soluble starch accounts for 0.1-0.5 parts, and water accounts for 70-90 parts; the concentration of nitrate in the mixed solution is not greater than 2 mol / l, and the mass ratio of nitrate to urea is (0.5-1):1.

[0026] In the present invention, the nitrate includes at least two of lanthanum nitrate, iron nitrate, strontium nitrate, cobalt nitrate, beryllium nitrate, bismuth nitrate, nickel nitrate, and copper nitrate. Preferably, the purity of lanthanum nitrate, iron nitrate, strontium nitrate, cobalt nitrate, beryllium nitrate, bismuth nitrate, nickel nitrate, and copper nitrate is above 99%.

[0027] In the present invention, preferably, the purity of urea is above 99%.

[0028] In the present invention, the water-soluble starch is a modified starch with carboxyl and hydroxyl groups, and the viscosity of the water-soluble starch at a concentration of 4 wt% and a temperature of 25° C. is 500-1000 mPa.s.

[0029] In the present invention, when preparing the mixed solution, nitrate and urea are first added into water and stirred until completely dissolved, and then water-soluble starch is added and stirred until completely dissolved to obtain a mixed solution.

[0030] In the present invention, the wood fiber is a spherical wood fiber, which is obtained by granulating wood fibers. The diameter of the spherical wood fiber is 2-5 mm, and the pore diameter is 10-40 μm.

[0031] In the present invention, the drying temperature when drying the saturated wood fiber is 80-100° C.; after drying the saturated wood fiber, the calcination is completed by keeping the temperature at 350-450° C. for 30-60 minutes.

[0032] The present invention also provides an easily dispersible SOFC cathode powder, which is prepared according to the preparation method of the present invention.

[0033] The present invention also provides an application of the easily dispersible SOFC cathode powder of the present invention, wherein the easily dispersible SOFC cathode powder is ball-milled with water as a medium to obtain SOFC cathode slurry, and the SOFC cathode slurry is loaded on an electrolyte layer to obtain a SOFC cathode.

[0034] Embodiment 1:

[0035] This embodiment provides a method for preparing an easily dispersible SOFC cathode powder, comprising the following steps:

[0036] S1, adding nitrate and urea to 70 parts by weight of distilled water and stirring until completely dissolved, then gradually adding 0.1 parts by weight of water-soluble starch, stirring for 30 minutes until completely dissolved, to obtain a mixed solution; in step S1, the amount of nitrate added satisfies that the concentration of nitrate in the prepared mixed solution is 2 mol / l, and the amount of urea added satisfies that the mass ratio of urea to nitrate is 1:0.5;

[0037] S2, weighing 10 parts by weight of wood fiber, immersing the wood fiber in the mixed solution for 15 minutes, filtering with a sieve to screen out the wood fiber that absorbs the mixed solution to saturation, and obtaining saturated wood fiber; in step S2, after the wood fiber is immersed in the mixed solution, since the wood fiber itself has porous channels and a loose porous structure, it will absorb the mixed solution, and the wood fiber will gain weight due to absorbing the mixed solution. The saturated state refers to the state reached when the wood fiber no longer gains weight;

[0038] S3. After drying the saturated wood fiber at 80°C, calcining it at 350°C for 30 minutes in a rotary kiln or a roller kiln, and obtaining an easily dispersible SOFC cathode powder by ball milling.

[0039] In this embodiment, the nitrate includes at least two of lanthanum nitrate, iron nitrate, strontium nitrate, cobalt nitrate, beryllium nitrate, bismuth nitrate, nickel nitrate, and copper nitrate. Specifically, the selection of the nitrate is determined according to the cathode. For example, in this embodiment, the cathode pre-prepared from the cathode powder is LaFeO 3-δ, then the nitrate is selected as lanthanum nitrate and iron nitrate. The actual amount of lanthanum nitrate and iron nitrate in the nitrate is based on LaFeO 3-δ The stoichiometric ratio and the concentration of nitrate in the mixed solution are calculated to be 2 mol / l.

[0040] In this embodiment, the water-soluble starch is a modified starch with carboxyl and hydroxyl groups, and the viscosity of the water-soluble starch at a concentration of 4 wt % and a temperature of 25° C. is 500 mPa.s.

[0041] In this embodiment, the wood fiber is a spherical wood fiber, which is made from wood fiber by granulation, and the diameter of the spherical wood fiber is 2 mm, and the diameter of the pore is 10 μm. In this embodiment, after the saturated spherical wood fiber is dried, when it is calcined in a rotary kiln or a roller kiln, the spherical wood fiber will roll in the rotary kiln or the roller kiln, and the contact points between adjacent spherical wood fibers will change continuously, and the pores formed between the spherical wood fibers will change continuously, and there will be no points of constant contact, which is convenient for heat dissipation.

[0042] This embodiment also provides an easily dispersible SOFC cathode powder, which is prepared according to the preparation method of this embodiment.

[0043] This embodiment also provides an application of the easily dispersible SOFC cathode powder of this embodiment. The easily dispersible SOFC cathode powder is ball-milled with water as a medium. After the ball milling is completed, the ball milling beads are taken out to obtain SOFC cathode slurry (only water is added when the cathode powder of this embodiment is made into SOFC cathode slurry, and no additional dispersant and pore-forming agent can be added). The SOFC cathode slurry is loaded on the electrolyte layer to obtain the SOFC cathode. In this embodiment, for example, LaFeO 3-δ cathode.

[0044] Embodiment 2:

[0045] This embodiment provides a method for preparing an easily dispersible SOFC cathode powder, comprising the following steps:

[0046] S1, adding nitrate and urea to 75 parts by weight of distilled water and stirring until completely dissolved, then gradually adding 0.2 parts by weight of water-soluble starch, stirring for 30 minutes until completely dissolved, to obtain a mixed solution; in step S1, the amount of nitrate added satisfies that the concentration of nitrate in the prepared mixed solution is 1.5 mol / l, and the amount of urea added satisfies that the mass ratio of urea to nitrate is 1:0.6;

[0047] S2, weighing 10 parts by weight of wood fiber, immersing the wood fiber in the mixed solution for 15 minutes, filtering with a sieve to screen out the wood fiber that absorbs the mixed solution to saturation, and obtaining saturated wood fiber; in step S2, after the wood fiber is immersed in the mixed solution, since the wood fiber itself has porous channels and a loose porous structure, it will absorb the mixed solution, and the wood fiber will gain weight due to absorbing the mixed solution. The saturated state refers to the state reached when the wood fiber no longer gains weight;

[0048] S3. After drying the saturated wood fiber at 85°C, calcining it at 370°C for 40 minutes in a rotary kiln or a roller kiln, and obtaining an easily dispersible SOFC cathode powder by ball milling.

[0049] In this embodiment, the nitrate includes at least two of lanthanum nitrate, iron nitrate, strontium nitrate, cobalt nitrate, beryllium nitrate, bismuth nitrate, nickel nitrate, and copper nitrate. Specifically, the choice of nitrate is determined according to the cathode. For example, in this embodiment, the cathode pre-prepared from the cathode powder is Bi 0.5 Sr 0.5 FeO 3-δ , then the nitrate is selected as bismuth nitrate, strontium nitrate, and iron nitrate. The actual amount of bismuth nitrate, strontium nitrate, and iron nitrate in the nitrate is based on Bi 0.5 Sr 0.5 FeO 3-δ The stoichiometric ratio and the concentration of nitrate in the mixed solution are calculated to be 1.5 mol / l.

[0050] In this embodiment, the water-soluble starch is a modified starch with carboxyl and hydroxyl groups, and the viscosity of the water-soluble starch at a concentration of 4 wt % and a temperature of 25° C. is 600 mPa.s.

[0051] In this embodiment, the wood fiber is a spherical wood fiber, which is made from wood fiber by granulation, and the diameter of the spherical wood fiber is 3 mm, and the diameter of the pore is 20 μm. In this embodiment, after the saturated spherical wood fiber is dried, when it is calcined in a rotary kiln or a roller kiln, the spherical wood fiber will roll in the rotary kiln or the roller kiln, and the contact points between adjacent spherical wood fibers will change continuously, and the pores formed between the spherical wood fibers will change continuously, and there will be no points of constant contact, which is convenient for heat dissipation.

[0052] This embodiment also provides an easily dispersible SOFC cathode powder, which is prepared according to the preparation method of this embodiment.

[0053] This embodiment also provides an application of the easily dispersible SOFC cathode powder of this embodiment. The easily dispersible SOFC cathode powder is ball-milled with water as a medium. After the ball-milling is completed, the ball-milling beads are taken out to obtain SOFC cathode slurry (only water is added when the cathode powder of this embodiment is made into SOFC cathode slurry, and no additional dispersant and pore-forming agent can be added). The SOFC cathode slurry is loaded on the electrolyte layer to obtain the SOFC cathode. In this embodiment, for example, Bi 0.5 Sr 0.5 FeO 3-δ cathode.

[0054] Embodiment 3:

[0055] This embodiment provides a method for preparing an easily dispersible SOFC cathode powder, comprising the following steps:

[0056] S1, adding nitrate and urea to 80 parts by weight of distilled water and stirring until completely dissolved, then gradually adding 0.3 parts by weight of water-soluble starch, stirring for 30 minutes until completely dissolved, to obtain a mixed solution; in step S1, the amount of nitrate added satisfies that the concentration of nitrate in the prepared mixed solution is 1 mol / l, and the amount of urea added satisfies that the mass ratio of urea to nitrate is 1:0.7;

[0057] S2, weighing 10 parts by weight of wood fiber, immersing the wood fiber in the mixed solution for 15 minutes, filtering with a sieve to screen out the wood fiber that absorbs the mixed solution to saturation, and obtaining saturated wood fiber; in step S2, after the wood fiber is immersed in the mixed solution, since the wood fiber itself has porous channels and a loose porous structure, it will absorb the mixed solution, and the wood fiber will gain weight due to absorbing the mixed solution. The saturated state refers to the state reached when the wood fiber no longer gains weight;

[0058] S3. After drying the saturated wood fiber at 90° C., calcining it at 380° C. for 45 min in a rotary kiln or a roller kiln, and obtaining an easily dispersible SOFC cathode powder by ball milling.

[0059] In this embodiment, the nitrate includes at least two of lanthanum nitrate, iron nitrate, strontium nitrate, cobalt nitrate, beryllium nitrate, bismuth nitrate, nickel nitrate, and copper nitrate. Specifically, the choice of nitrate is determined according to the cathode. For example, in this embodiment, the cathode pre-prepared from the cathode powder is La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ , then the nitrate is selected from lanthanum nitrate, strontium nitrate, cobalt nitrate, and iron nitrate. The actual amount of lanthanum nitrate, strontium nitrate, cobalt nitrate, and iron nitrate in the nitrate is determined according to La 0.6 Sr 0.4 Co0.2 Fe 0.8 O 3-δ The stoichiometric ratio and the concentration of nitrate in the mixed solution are calculated as 1 mol / l.

[0060] In this embodiment, the water-soluble starch is a modified starch with carboxyl and hydroxyl groups, and the viscosity of the water-soluble starch at a concentration of 4 wt % and a temperature of 25° C. is 700 mPa.s.

[0061] In this embodiment, the wood fiber is a spherical wood fiber, which is made from wood fiber by granulation, and the diameter of the spherical wood fiber is 4 mm, and the diameter of the pore is 30 μm. In this embodiment, after the saturated spherical wood fiber is dried, when it is calcined in a rotary kiln or a roller kiln, the spherical wood fiber will roll in the rotary kiln or the roller kiln, and the contact points between adjacent spherical wood fibers will change continuously, and the pores formed between the spherical wood fibers will change continuously, and there will be no points of constant contact, which is convenient for heat dissipation.

[0062] This embodiment also provides an easily dispersible SOFC cathode powder, which is prepared according to the preparation method of this embodiment.

[0063] This embodiment also provides an application of the easily dispersible SOFC cathode powder of this embodiment. The easily dispersible SOFC cathode powder is ball-milled with water as a medium. After the ball-milling is completed, the ball-milling beads are taken out to obtain SOFC cathode slurry (only water is added when the cathode powder of this embodiment is made into SOFC cathode slurry, and no additional dispersant and pore-forming agent can be added). The SOFC cathode slurry is loaded on the electrolyte layer to obtain the SOFC cathode. In this embodiment, for example, La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ cathode.

[0064] Embodiment 4:

[0065] This embodiment provides a method for preparing an easily dispersible SOFC cathode powder, comprising the following steps:

[0066] S1, adding nitrate and urea to 85 parts by weight of distilled water and stirring until completely dissolved, then gradually adding 0.4 parts by weight of water-soluble starch, stirring for 30 minutes until completely dissolved, to obtain a mixed solution; in step S1, the amount of nitrate added satisfies that the concentration of nitrate in the prepared mixed solution is 0.5 mol / l, and the amount of urea added satisfies that the mass ratio of urea to nitrate is 1:0.8;

[0067] S2, weighing 10 parts by weight of wood fiber, immersing the wood fiber in the mixed solution for 15 minutes, filtering with a sieve to screen out the wood fiber that absorbs the mixed solution to saturation, and obtaining saturated wood fiber; in step S2, after the wood fiber is immersed in the mixed solution, since the wood fiber itself has porous channels and a loose porous structure, it will absorb the mixed solution, and the wood fiber will gain weight due to absorbing the mixed solution. The saturated state refers to the state reached when the wood fiber no longer gains weight;

[0068] S3. After drying the saturated wood fiber at 95° C., calcining it at 420° C. for 50 min in a rotary kiln or a roller kiln, and obtaining an easily dispersible SOFC cathode powder by ball milling.

[0069] In this embodiment, the nitrate includes at least two of lanthanum nitrate, iron nitrate, strontium nitrate, cobalt nitrate, beryllium nitrate, bismuth nitrate, nickel nitrate, and copper nitrate. Specifically, the choice of nitrate is determined according to the cathode. For example, in this embodiment, the cathode pre-prepared from the cathode powder is La 0.8 Be 0.2 Fe 0.6 Ni 0.4 O 3-δ , then the nitrate is selected from lanthanum nitrate, beryllium nitrate, iron nitrate, and nickel nitrate. The actual amount of lanthanum nitrate, beryllium nitrate, iron nitrate, and nickel nitrate in the nitrate is determined according to La 0.8 Be 0.2 Fe 0.6 Ni 0.4 O 3-δ The stoichiometric ratio and the concentration of nitrate in the mixed solution are calculated to be 0.5 mol / l.

[0070] In this embodiment, the water-soluble starch is a modified starch with carboxyl and hydroxyl groups, and the viscosity of the water-soluble starch at a concentration of 4 wt % and a temperature of 25° C. is 800 mPa.s.

[0071] In this embodiment, the wood fiber is a spherical wood fiber, which is made from wood fiber by granulation, and the diameter of the spherical wood fiber is 4.5 mm, and the diameter of the pore is 35 μm. In this embodiment, after the saturated spherical wood fiber is dried, when it is calcined in a rotary kiln or a roller kiln, the spherical wood fiber will roll in the rotary kiln or the roller kiln, and the contact points between adjacent spherical wood fibers will change continuously, and the pores formed between the spherical wood fibers will change continuously, and there will be no points of constant contact, which is convenient for heat dissipation.

[0072] This embodiment also provides an easily dispersible SOFC cathode powder, which is prepared according to the preparation method of this embodiment.

[0073] This embodiment also provides an application of the easily dispersible SOFC cathode powder of this embodiment. The easily dispersible SOFC cathode powder is ball-milled with water as a medium. After the ball-milling is completed, the ball-milling beads are taken out to obtain SOFC cathode slurry (only water is added when the cathode powder of this embodiment is made into SOFC cathode slurry, and no additional dispersant and pore-forming agent can be added). The SOFC cathode slurry is loaded on the electrolyte layer to obtain the SOFC cathode. In this embodiment, for example, La 0.8 Be 0.2 Fe 0.6 Ni 0.4 O 3-δ cathode.

[0074] Embodiment 5:

[0075] This embodiment provides a method for preparing an easily dispersible SOFC cathode powder, comprising the following steps:

[0076] S1. Add nitrate and urea to 90 parts by weight of distilled water and stir until completely dissolved, then gradually add 0.5 parts by weight of water-soluble starch and stir for 30 minutes until completely dissolved to obtain a mixed solution; in step S1, the amount of nitrate added satisfies that the concentration of nitrate in the prepared mixed solution is 0.2 mol / l, and the amount of urea added satisfies that the mass ratio of urea to nitrate is 1:1;

[0077] S2, weighing 10 parts by weight of wood fiber, immersing the wood fiber in the mixed solution for 15 minutes, filtering with a sieve to screen out the wood fiber that absorbs the mixed solution to saturation, and obtaining saturated wood fiber; in step S2, after the wood fiber is immersed in the mixed solution, since the wood fiber itself has porous channels and a loose porous structure, it will absorb the mixed solution, and the wood fiber will gain weight due to absorbing the mixed solution. The saturated state refers to the state reached when the wood fiber no longer gains weight;

[0078] S3. After drying the saturated wood fiber at 100° C., calcining it in a rotary kiln or roller kiln at 450° C. for 60 min, and ball milling to obtain an easily dispersible SOFC cathode powder.

[0079] In this embodiment, the nitrate includes at least two of lanthanum nitrate, iron nitrate, strontium nitrate, cobalt nitrate, beryllium nitrate, bismuth nitrate, nickel nitrate, and copper nitrate. Specifically, the choice of nitrate is determined according to the cathode. For example, in this embodiment, the cathode pre-prepared from the cathode powder is La 0.6 Be 0.2 Sr 0.2 Fe 0.8 Cu 0.2 O 3-δ, then the nitrate is selected from lanthanum nitrate, beryllium nitrate, strontium nitrate, iron nitrate, and copper nitrate. The actual amount of lanthanum nitrate, beryllium nitrate, strontium nitrate, iron nitrate, and copper nitrate in the nitrate is determined according to La 0.6 Be 0.2 Sr 0.2 Fe 0.8 Cu 0.2 O 3-δ The stoichiometric ratio and the concentration of nitrate in the mixed solution are calculated to be 0.2 mol / l.

[0080] In this embodiment, the water-soluble starch is a modified starch with carboxyl and hydroxyl groups, and the viscosity of the water-soluble starch at a concentration of 4 wt % and a temperature of 25° C. is 1000 mPa.s.

[0081] In this embodiment, the wood fiber is a spherical wood fiber, which is made from wood fiber by granulation, and the diameter of the spherical wood fiber is 5 mm, and the diameter of the pore is 40 μm. In this embodiment, after the saturated spherical wood fiber is dried, when it is calcined in a rotary kiln or a roller kiln, the spherical wood fiber will roll in the rotary kiln or the roller kiln, and the contact points between adjacent spherical wood fibers will change continuously, and the pores formed between the spherical wood fibers will change continuously, and there will be no points of constant contact, which is convenient for heat dissipation.

[0082] This embodiment also provides an easily dispersible SOFC cathode powder, which is prepared according to the preparation method of this embodiment.

[0083] This embodiment also provides an application of the easily dispersible SOFC cathode powder of this embodiment. The easily dispersible SOFC cathode powder is ball-milled with water as a medium. After the ball-milling is completed, the ball-milling beads are taken out to obtain SOFC cathode slurry (only water is added when the cathode powder of this embodiment is made into SOFC cathode slurry, and no additional dispersant and pore-forming agent can be added). The SOFC cathode slurry is loaded on the electrolyte layer to obtain the SOFC cathode. In this embodiment, for example, La 0.6 Be 0.2 Sr 0.2 Fe 0.8 Cu 0.2 O 3-δ cathode.

[0084] The present invention has been described above in conjunction with specific embodiments. These specific embodiments are merely exemplary and cannot be used to limit the scope of protection of the present invention. Those skilled in the art may make various modifications, changes or substitutions without departing from the essence of the present invention. Therefore, various equivalent changes made according to the present invention still fall within the scope covered by the present invention.

Claims

1. A method for preparing an easily dispersible SOFC cathode powder, characterized in that: The following steps are involved: Mix nitrate, urea, water-soluble starch and water, and stir until completely dissolved to obtain a mixed solution; The water-soluble starch accounts for 0.1-0.5 parts, and the water accounts for 70-90 parts; the concentration of nitrate in the mixed solution is not more than 2 mol / l, and the mass ratio of nitrate to urea is (0.5-0.7):1; The water-soluble starch is a modified starch with carboxyl and hydroxyl groups, and the viscosity of the water-soluble starch is 500-1000 mPa.s at a concentration of 4wt% and a temperature of 25°C; Immersing wood fibers in the mixed solution until the mixture is absorbed to saturation, thereby obtaining saturated wood fibers; The wood fiber is a spherical wood fiber, and the spherical wood fiber is prepared by granulating wood fibers; The diameter of the spherical wood fiber is 2-5 mm, and the pore diameter is 10-40 μm; The saturated wood fiber is dried, calcined, and ball-milled to obtain the easily dispersible SOFC cathode powder.

2. The method for preparing an easily dispersible SOFC cathode powder according to claim 1, characterized in that: The nitrate includes at least two of lanthanum nitrate, iron nitrate, strontium nitrate, cobalt nitrate, beryllium nitrate, bismuth nitrate, nickel nitrate and copper nitrate.

3. The method for preparing an easily dispersible SOFC cathode powder according to claim 1, characterized in that: When preparing the mixed solution, first add nitrate and urea into water and stir until they are completely dissolved, then add water-soluble starch and stir until they are completely dissolved to obtain the mixed solution.

4. The method for preparing an easily dispersible SOFC cathode powder according to claim 1, characterized in that: The drying temperature when drying the saturated wood fiber is 80-100° C.; after drying the saturated wood fiber, the calcination is completed by keeping the temperature at 350-450° C. for 30-60 minutes.

5. An easily dispersible SOFC cathode powder, characterized in that: The easily dispersible SOFC cathode powder is prepared according to the preparation method described in any one of claims 1 to 4.

6. The use of the easily dispersible SOFC cathode powder according to claim 5, characterized in that: The easily dispersible SOFC cathode powder is ball-milled with water as a medium to obtain SOFC cathode slurry. The SOFC cathode slurry is loaded on an electrolyte layer to obtain a SOFC cathode.