Electrolyte powder for thermally sprayed solid oxide fuel cell or electrolytic cell, and preparation method and application thereof

Abstract

The invention discloses electrolyte powder for a thermally sprayed solid oxide fuel cell or electrolytic cell as well as a preparation method and application of the electrolyte powder, and belongs to the technical field of electrolyte powder. The preparation method of the electrolyte powder comprises the following steps: preparing micron-sized electrolyte powder by adopting a spray drying method; carrying out densification treatment on the micron-sized electrolyte powder in a plasma spheroidizing or high-temperature sintering-crushing manner; and screening the densified powder to obtain the electrolyte powder with the particle size of 5-50 microns. According to the method, the particle size, sphericity, fluidity and density of the electrolyte powder are improved, the density and uniformity of an electrolyte coating as well as electrochemical and mechanical properties and the like of a battery can be improved, and the requirement of SOFC / SOEC on a high-performance electrolyte coating can be met.

Description

Technical Field

[0001] The present invention relates to the technical field of electrolyte powders, and in particular, to an electrolyte powder for a solid oxide fuel cell or electrolyzer for thermal spraying, a preparation method thereof, and an application thereof. Background Art

[0002] As an emerging power generation technology, a solid oxide fuel cell (SOFC) directly converts the chemical energy of fuel into electrical energy through an electrochemical reaction, and has the following remarkable advantages: high energy conversion efficiency (the combined heat and power efficiency can reach more than 80%), environmental friendliness, wide fuel applicability, etc., and has broad application prospects in the fields of distributed energy systems, backup power supplies, and integrated energy systems. On the other hand, as the reverse process technology of SOFC, a solid oxide electrolysis cell (SOEC) decomposes water and carbon dioxide into renewable fuel chemicals such as hydrogen and carbon monoxide by driving with electrical energy, providing a potential solution for achieving the carbon neutrality goal. SOFC and SOEC constitute a two-way system for efficient energy conversion and storage, and are of great significance in improving energy utilization efficiency, reducing emissions and carbon, and promoting the development of green energy.

[0003] Both SOFC and SOEC contain a core component, an electrolyte layer, whose main function is to conduct ions and physically separate the gases on both sides of the electrodes at the same time. Therefore, the electrolyte structure needs to be dense and thin, which can not only ensure sufficient ion conduction, but also reduce the internal resistance of the battery and improve the power density. The traditional SOFC / SOEC electrolyte layer is usually prepared by wet chemical methods such as tape casting and screen printing. The original particle size of the electrolyte powder is 0.1 μm to 1 μm. The electrolyte powder with this particle size has poor fluidity and is difficult to be directly used in the thermal spraying process.

[0004] To solve this problem, in the field of thermal spraying, the spray drying process is usually used to agglomerate nano / micron electrolyte powders into electrolyte powders with good fluidity of 10 μm to 100 μm. However, the particle size of this agglomerated electrolyte powder is large (median diameter D 50 >50 μm), resulting in insufficient melting during thermal spraying, reducing the density, deposition efficiency, and bonding strength of the electrolyte coating. In addition, there are many fine pores inside the agglomerated electrolyte powder, which will remain in the coating after thermal spraying, further reducing the density (<90%) and bonding strength of the electrolyte coating, making it difficult to meet the requirements of SOFC / SOEC for the airtightness and conductivity of the electrolyte coating.

[0005] In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] The object of the present invention is to provide an electrolyte powder for a solid oxide fuel cell or electrolyzer for thermal spraying, and a preparation method and application thereof, so as to solve or improve the problems of large particle size and many internal pores of the SOFC / SOEC electrolyte powder, and provide a preparation method for an SOFC / SOEC electrolyte powder with a small particle size and a dense internal structure.

[0007] The present invention can be realized as follows:

[0008] In a first aspect, the present invention provides a preparation method for an electrolyte powder for a solid oxide fuel cell or electrolyzer for thermal spraying, comprising the following steps: preparing a micron-sized electrolyte powder by spray drying; densifying the micron-sized electrolyte powder by plasma spheroidization or high-temperature sintering-crushing, and screening the densified powder to obtain an electrolyte powder with a particle size of 5 μm to 50 μm.

[0009] In an optional embodiment, the preparation of the micron-sized electrolyte powder includes: mixing an electrolyte raw material powder with a dispersant, a binder and a solvent, and then performing ball milling to obtain an electrolyte slurry; spray drying and granulating the electrolyte slurry.

[0010] In an optional embodiment, the particle size of the micron-sized electrolyte powder is 5 μm to 100 μm.

[0011] In an optional embodiment, the electrolyte raw material powder has at least one of the following characteristics:

[0012] Characteristic 1: The particle size of the electrolyte raw material powder is 10 nm to 5 μm, preferably 50 nm to 1 μm;

[0013] Characteristic 2: The electrolyte raw material powder is an oxide ceramic material with a melting point of 1000 °C to 3500 °C; preferably includes at least one of ZrO2-based materials, CeO2-based materials and perovskite-type materials.

[0014] In an optional embodiment, the ZrO2-based material includes at least one of yttria-stabilized zirconia and scandia-stabilized zirconia;

[0015] And / or, the CeO2-based material includes at least one of gadolinium-doped ceria and samarium-doped ceria;

[0016] And / or, the perovskite-type material includes La 1-x Sr x Ga 1-y Mg y O3, BaCe 1-z M z O3 and BaZr 1-z M zAt least one of O3; wherein, 0 < x ≤ 0.2, 0 < y ≤ 0.2, 0 < z ≤ 0.2, and M is at least one of Y, Yb, and Gd.

[0017] In an alternative embodiment, yttria-stabilized zirconia contains 3 mol% to 8 mol% of Y2O3.

[0018] In an alternative embodiment, scandia-stabilized zirconia contains 8 mol% to 10 mol% of Sc2O3.

[0019] In an alternative embodiment, gadolinium-doped ceria contains 10 mol% to 20 mol% of Gd2O3.

[0020] In an alternative embodiment, samarium-doped ceria contains 10 mol% to 20 mol% of Sm2O3.

[0021] In an alternative embodiment, the dispersant includes at least one of polyvinylpyrrolidone, polyacrylic acid, citric acid, and polyethylene glycol;

[0022] and / or, the binder includes a water-soluble or alcohol-soluble polymer binder; preferably, the binder includes at least one of polyvinylpyrrolidone, polyvinyl alcohol, hydroxypropyl methylcellulose, polyethylene glycol, and ethyl cellulose;

[0023] and / or, the solvent includes at least one of deionized water, ethanol, and isopropanol;

[0024] and / or, the mass ratio of the electrolyte raw material powder, the dispersant, and the solvent is 100:(2 - 15):(200 - 500); the mass of the binder is 0.5% - 5% of the electrolyte raw material powder.

[0025] In an alternative embodiment, ball milling is carried out under the conditions of 180 rpm to 250 rpm for 2 h to 6 h;

[0026] and / or, spray drying granulation includes at least one of the following features:

[0027] Feature 3: The inlet temperature is 180°C to 220°C, preferably 190°C to 210°C;

[0028] Feature 4: The outlet temperature is 80°C to 110°C, preferably 90°C to 100°C;

[0029] Feature 5: The atomization pressure is 0.3 MPa to 0.6 MPa, preferably 0.35 MPa to 0.5 MPa.

[0030] In an alternative embodiment, plasma spheroidization includes at least one of the following features:

[0031] Feature 6: The plasma gas includes argon or nitrogen;

[0032] Feature 7: Flow rate of the plasma gas: The flow rate of argon or nitrogen is 10 L / min to 60 L / min, and the flow rate of the auxiliary hydrogen is 2 L / min to 10 L / min;

[0033] Feature 8: The output power is 30 kW to 120 kW, preferably 40 kW to 100 kW;

[0034] Feature 9: The powder feeding rate is 5 g / min to 20 g / min.

[0035] In an alternative embodiment, the high-temperature sintering-crushing includes at least one of the following features:

[0036] Feature 10: The sintering temperature is 1200 °C to 1700 °C;

[0037] Feature 11: The sintering time is 2 h to 12 h;

[0038] Feature 12: The heating and cooling rates are independently 1 °C / min to 10 °C / min;

[0039] Feature 13: The crushing form includes crushing using a jaw crusher, a ball mill, a vibration mill or a jet mill.

[0040] In a second aspect, the present invention provides an electrolyte powder, which is prepared by the preparation method of any one of the foregoing embodiments.

[0041] In an alternative embodiment, the particle size of the electrolyte powder is 5 μm to 50 μm.

[0042] In an alternative embodiment, the particle size of the electrolyte powder is 5 μm to 30 μm.

[0043] In a third aspect, the present invention provides an application of the electrolyte powder of any one of the foregoing embodiments, for example, it can be used to prepare a solid oxide fuel cell or an electrolytic cell by thermal spraying.

[0044] The beneficial effects of the present invention include:

[0045] The present invention creatively densifies the micron-scale electrolyte prepared by spray drying, such as plasma spheroidization or high-temperature sintering-crushing. Subsequently, the densified powder is screened to obtain electrolyte powder with small particle size, high sphericity, good fluidity, and high density. This electrolyte powder is easy to be stably and uniformly fed into the center of the thermal spraying flame, and is particularly suitable for preparing a structurally uniform electrolyte coating by thermal spraying technology. It can significantly reduce the porosity inside the electrolyte coating, improve the density (>95%) and bonding strength of the electrolyte coating, and ensure the effective separation of the gases on both sides of the electrodes of SOFC / SOEC without subsequent densification processes such as high-temperature or impregnation sintering. This dense electrolyte coating can provide a continuous ion transport path, increase the ionic conductivity, and thus improve the battery output power. In addition, the dense structure is conducive to thinning the electrolyte thickness, reducing the ohmic impedance of the battery, and increasing the battery output power. Moreover, the dense electrolyte coating has good mechanical strength and durability, can resist thermal cycling and mechanical stress, reduce the risk of electrolyte cracking and spalling, protect the internal structure of the battery from high temperature and chemically active environments, and extend the service life of SOFC / SOEC. Description of the Drawings

[0046] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and thus should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0047] Figure 1 SEM image of the non-dense electrolyte powder provided as a control example;

[0048] Figure 2 SEM image of the dense electrolyte powder prepared by plasma spheroidization in Example 1;

[0049] Figure 3 SEM image of the dense electrolyte powder prepared by high-temperature sintering-crushing in Example 4;

[0050] Figure 4 SEM image of the electrolyte coating prepared from the electrolyte powder provided as a control example;

[0051] Figure 5 SEM image of the electrolyte coating prepared from the electrolyte powder provided in Example 1;

[0052] Figure 6 SEM image of the electrolyte coating prepared from the electrolyte powder provided in Example 4;

[0053] Figure 7 The performance results of the battery prepared from the electrolyte powder provided by the control example;

[0054] Figure 8 The performance results of the battery prepared from the electrolyte powder provided by Example 6;

[0055] Figure 9 The performance results of the battery prepared from the electrolyte powder provided by Example 7. Detailed implementation manners

[0056] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. For those not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are followed. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0057] The electrolyte powder for a solid oxide fuel cell or electrolytic cell for thermal spraying provided by the present invention, its preparation method, and applications will be specifically described below.

[0058] In terms of improving the poor fluidity of the electrolyte powder, the commonly used method in the thermal spraying field is to use the spray drying process to agglomerate nano / micron electrolyte powder into electrolyte powder with a particle size of 10 μm to 100 μm. However, the particle size of this agglomerated electrolyte powder is large (median diameter D 50 > 50 μm), resulting in insufficient melting during thermal spraying, which will reduce the density, deposition efficiency, and bonding strength of the electrolyte coating. In addition, there are many fine pores inside the agglomerated electrolyte powder, which will remain in the coating after thermal spraying, further reducing the density (<90%) and bonding strength of the electrolyte coating, making it difficult to meet the requirements of SOFC / SOEC for the airtightness and conductivity of the electrolyte coating.

[0059] The present invention creatively proposes a preparation method for an electrolyte powder for a solid oxide fuel cell or electrolytic cell for thermal spraying. The method includes the following steps: preparing micron-sized electrolyte powder by spray drying; densifying the micron-sized electrolyte powder by plasma spheroidization or high-temperature sintering-crushing, and screening the densified powder to obtain electrolyte powder with a particle size of 5 μm to 50 μm.

[0060] In some alternative embodiments, the preparation of the micron-sized electrolyte powder includes: mixing the electrolyte raw material powder with a dispersant, a binder, and a solvent, followed by ball milling to obtain an electrolyte slurry; and spray drying and granulating the electrolyte slurry.

[0061] Among them, the particle size of the electrolyte raw material powder can be 10 nm to 5 μm, preferably 50 nm to 1 μm. Spraying and drying and agglomerating the electrolyte raw material powder within the above particle size range helps to optimize the treatment effects of subsequent plasma spheroidization and high-temperature sintering-crushing processes. During the plasma spheroidization process, the raw material powder with a smaller particle size is more likely to be fully melted, ensuring high density and excellent fluidity of the spheroidized powder, thereby improving the deposition efficiency and coating uniformity of subsequent thermal spraying. In the high-temperature sintering-crushing process, fine powder has a large specific surface area and high sintering activity, and is more likely to form a dense structure, resulting in fewer internal defects and better particle uniformity after crushing. In addition, the raw material powder with a smaller particle size can also improve the mixing uniformity of the powder and the uniformity of element distribution, thereby optimizing the microstructure and ionic conduction performance of the electrolyte. These optimizations not only improve the density and airtightness of the SOFC / SOEC electrolyte coating, but also reduce the ohmic impedance of the electrolyte layer and enhance the electrochemical performance and long-term stability of the fuel cell / electrolyzer.

[0062] The electrolyte raw material powder is an oxide ceramic material with a melting point of 1000 °C to 3500 °C, and can, for example, include at least one of ZrO2-based materials, CeO2-based materials, and perovskite-type materials. Using the oxide ceramic material with the above melting point is beneficial to ensuring the stable phase structure and chemical stability of the electrolyte in a high-temperature environment, and avoiding performance deterioration caused by thermal expansion mismatch or high-temperature decomposition. In addition, these materials have high ionic conductivity, can effectively enhance the electrochemical performance of SOFC / SOEC, and at the same time have excellent mechanical strength, corrosion resistance, and chemical compatibility, enabling them to operate stably for a long time in the harsh working environment of fuel cells or electrolyzers.

[0063] Among them, the ZrO2-based material can, for example, include at least one of yttria-stabilized zirconia and scandia-stabilized zirconia. Preferably, the yttria-stabilized zirconia contains 3 mol% to 8 mol% (such as 3 mol%, 4 mol%, 5 mol%, 6 mol%, 7 mol%, or 8 mol%, etc.) of Y2O3. The scandia-stabilized zirconia contains 8 mol% to 10 mol% (such as 8 mol%, 8.5 mol%, 9 mol%, 9.5 mol%, or 10 mol%, etc.) of Sc2O3.

[0064] The CeO₂-based materials may exemplarily include at least one of gadolinium-doped cerium oxide and samarium-doped cerium oxide. Preferably, the gadolinium-doped cerium oxide contains 10 mol% to 20 mol% (such as 10 mol%, 12 mol%, 15 mol%, 18 mol% or 20 mol%, etc.) of Gd₂O₃. The samarium-doped cerium oxide contains 10 mol% to 20 mol% (such as 10 mol%, 12 mol%, 15 mol%, 18 mol% or 20 mol%, etc.) of Sm₂O₃.

[0065] The perovskite-type materials may exemplarily include La 1-x Sr x Ga 1-y Mg y O₃, BaCe 1-z M z O₃ and BaZr 1-z M z O₃, where 0 < x ≤ 0.2, 0 < y ≤ 0.2, 0 < z ≤ 0.2, and M is at least one of Y, Yb, and Gd.

[0066] In some alternative embodiments, the dispersant may exemplarily include at least one of polyvinylpyrrolidone (PVP), polyacrylic acid (PAA), citric acid, and polyethylene glycol (PEG).

[0067] In some alternative embodiments, the binder includes a water-soluble or alcohol-soluble polymer binder. For example, the binder may exemplarily include at least one of polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), hydroxypropyl methylcellulose (HPMC), polyethylene glycol (PEG), and ethyl cellulose (EC).

[0068] In some alternative embodiments, the solvent includes at least one of deionized water, ethanol, and isopropanol.

[0069] In some alternative embodiments, the mass ratio of the electrolyte raw material powder, the dispersant, and the solvent may be 100:(2 - 15):(200 - 500). For example, the mass ratio of the electrolyte raw material powder to the dispersant may be 100:2, 100:5, 100:8, 100:10, 100:12, or 100:15, etc., or other values within the range of 100:(2 - 15). The mass ratio of the electrolyte raw material powder to the solvent may be 100:200, 100:250, 100:300, 100:350, 100:400, 100:450, or 100:500, etc., or other values within the range of 100:(200 - 500).

[0070] If the mass ratio of the electrolyte raw material powder to the dispersant is less than 100:2 (such as 100:1), it is likely to result in poor dispersion of the powder in the slurry, severe particle agglomeration, uneven particle size distribution of the powder after spray drying, and affect the uniformity of the subsequent spheroidization or sintering-crushing process; if the mass ratio of the electrolyte raw material powder to the dispersant is greater than 100:15 (such as 100:20), it is likely to cause too high viscosity of the slurry, difficult to grind evenly during the ball milling process, and even affect the fluidity of spray drying, making the structure of the dried powder loose and not conducive to subsequent densification treatment.

[0071] In some alternative embodiments, the mass of the binder can be 0.5% - 5% of the electrolyte raw material powder, such as 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, etc., or other values within the range of 0.5% - 5%.

[0072] If the dosage of the binder is less, it is likely to result in insufficient strength of the powder particles during the spray drying process, and the dried powder is easily broken into small particles, affecting the fluidity and uniformity of the powder, and further affecting the stability of subsequent plasma spheroidization or sintering-crushing; if the dosage of the binder is more, it is likely to cause too high viscosity of the slurry, resulting in uneven atomization during the spray drying process, affecting the morphology and size distribution of the particles, and at the same time, the decomposition of the binder during the subsequent spheroidization or sintering process may produce too many residues, affecting the purity of the powder and the performance of the final electrolyte coating.

[0073] In some alternative embodiments, ball milling can be carried out under the conditions of 180 rpm - 250 rpm (such as 180 rpm, 190 rpm, 200 rpm, 210 rpm, 220 rpm, 230 rpm, 240 rpm or 250 rpm, etc.) for 2 h - 6 h (such as 2 h, 3 h, 4 h, 5 h or 6 h, etc.).

[0074] In some alternative embodiments, the inlet temperature of spray drying granulation can be 180°C - 220°C, such as 180°C, 185°C, 190°C, 195°C, 200°C, 205°C, 210°C, 215°C or 220°C, etc., or other values within the range of 180°C - 220°C. In some preferred embodiments, the inlet temperature of spray drying granulation is 190°C - 210°C.

[0075] The inlet temperature determines the rapid evaporation efficiency of the slurry, affecting the sphericity, internal pore structure and strength of the powder. If it is lower than 180°C, the slurry cannot be dried quickly, resulting in a relatively high water content in the powder particles, which is prone to adhesion, agglomeration and even collapse, affecting the powder flowability and the stability of subsequent spheroidization or sintering-crushing processes. If it is higher than 220°C, the water evaporates too fast, which may cause a hard shell to form on the particle surface while there is still residual solvent inside, ultimately leading to an increase in the powder porosity and affecting subsequent densification treatment.

[0076] In some alternative embodiments, the outlet temperature of spray drying granulation can be 80°C to 110°C, such as 80°C, 85°C, 90°C, 95°C, 100°C, 105°C or 110°C, etc., or other values within the range of 80°C to 110°C. In some preferred embodiments, the outlet temperature of spray drying granulation is 90°C to 100°C.

[0077] The outlet temperature affects the final water content and mechanical strength of the powder, ensuring that the powder maintains stable physical properties during storage and subsequent processing. If it is lower than 80°C, the powder has too high a moisture content, is prone to moisture absorption and caking, reducing the powder flowability, being unfavorable for uniform feeding, and affecting the stability of subsequent densification processes. If it is higher than 110°C, it may cause the powder to be over-dried, the particles to become brittle, and fine powder to be easily generated during storage and transportation, resulting in an out-of-control particle size distribution and affecting the consistency of subsequent processes.

[0078] In some alternative embodiments, the atomization pressure can be 0.3 MPa to 0.6 MPa, such as 0.3 MPa, 0.35 MPa, 0.4 MPa, 0.45 MPa, 0.5 MPa, 0.55 MPa or 0.6 MPa, etc., or other values within the range of 0.3 MPa to 0.6 MPa. In some preferred embodiments, the atomization pressure is 0.35 MPa to 0.5 MPa.

[0079] The atomization pressure determines the particle size of the slurry atomization, affecting the particle size distribution and sphericity of the final powder. If it is lower than 0.3 MPa, the atomization is insufficient, the droplets formed by the slurry are larger, resulting in non-uniform particle size of the powder after spray drying, and larger pores are easily formed inside the particles, affecting subsequent densification. If it is higher than 0.6 MPa, the atomized particles are too small, resulting in a smaller particle size and an increased surface area of the powder, which is prone to moisture absorption and agglomeration, and at the same time, uneven particle sintering is more likely to occur during plasma spheroidization or sintering, affecting the final properties of the powder.

[0080] In some alternative embodiments, the particle size of the micron-scale electrolyte powder prepared by the above method is 5 μm to 100 μm.

[0081] In some alternative embodiments, the plasma gas used for plasma spheroidization may include argon or nitrogen. Flow rate of the plasma gas: The flow rate of argon or nitrogen can be 10 L / min to 60 L / min, such as 10 L / min, 15 L / min, 20 L / min, 25 L / min, 30 L / min, 35 L / min, 40 L / min, 45 L / min, 50 L / min, 55 L / min or 60 L / min, etc., and can also be other values within the range of 10 L / min to 60 L / min. The flow rate of the auxiliary hydrogen can be 2 L / min to 10 L / min, such as 2 L / min, 4 L / min, 6 L / min, 8 L / min or 10 L / min, etc., and can also be other values within the range of 2 L / min to 10 L / min.

[0082] If the flow rate of the plasma gas is less than 10 L / min, it is likely to cause insufficient plasma arc intensity and insufficient energy supply to the molten powder, affecting the spheroidization efficiency, and ultimately resulting in a lower powder sphericity and poorer fluidity; if the flow rate of the plasma gas is higher than 60 L / min, it is likely to cause the plasma flame flow field to be too dispersed, shortening the residence time of the powder in the high-temperature zone, resulting in incomplete melting of some powders, and affecting the spheroidization degree and uniformity of the final powder.

[0083] In some alternative embodiments, the output power used for plasma spheroidization can be 30 kW to 120 kW, such as 30 kW, 50 kW, 80 kW, 100 kW or 120 kW, etc., and can also be other values within the range of 30 kW to 120 kW. In some preferred embodiments, the output power used for plasma spheroidization is 40 kW to 100 kW.

[0084] If the output power is lower than 30 kW, it is not conducive to providing sufficient heat energy to completely melt the powder, resulting in poor spheroidization effect, rough powder surface, decreased fluidity, and being not conducive to the stability of the subsequent thermal spraying process; if the output power is higher than 120 kW, it is not conducive to controlling the over-melting of the powder, which may cause uneven segregation of the internal components of the powder, and even evaporation loss, affecting the chemical composition stability and the final conductivity performance of the electrolyte powder.

[0085] In some alternative embodiments, the powder feeding rate used for plasma spheroidization can be 5 g / min to 20 g / min, such as 5 g / min, 8 g / min, 10 g / min, 12 g / min, 15 g / min, 18 g / min or 20 g / min, etc., and can also be other values within the range of 5 g / min to 20 g / min.

[0086] If the powder feeding rate is lower than 5 g / min, it is not conducive to improving production efficiency, and the energy absorbed by a single particle in the plasma is too high, which may cause some powders to melt excessively or even evaporate and be lost, affecting the particle size uniformity of the powders; if the powder feeding rate is higher than 20 g / min, it is not conducive to the full melting of the powders, resulting in a decrease in the spheroidization rate. At the same time, powder agglomeration or unmelted particle inclusions may occur, affecting the quality of the final powders.

[0087] By performing plasma spheroidization under the above conditions, the size, shape, and distribution of the electrolyte powders can be precisely controlled.

[0088] In some alternative embodiments, the sintering temperature for high-temperature sintering can be 1200°C to 1700°C, such as 1200°C, 1250°C, 1300°C, 1350°C, 1400°C, 1450°C, 1500°C, 1550°C, 1600°C, 1650°C, or 1700°C, etc., or other values within the range of 1200°C to 1700°C.

[0089] The sintering time for high-temperature sintering can be 2 h to 12 h, such as 2 h, 4 h, 6 h, 8 h, 10 h, or 12 h, etc., or other values within the range of 2 h to 12 h.

[0090] If the temperature of high-temperature sintering is too low or the sintering time is too short, it is not conducive to the complete formation of the sintering necks between powder particles, resulting in insufficient densification inside the powders and affecting the uniformity and mechanical strength of the particles after subsequent crushing; if the temperature of high-temperature sintering is too high or the sintering time is too long, it is not conducive to the phase stability inside the powder particles, which may cause abnormal grain growth, powder caking, excessive sintering shrinkage rate, and even lead to the volatilization and loss of some components, affecting the final performance of the electrolyte powders.

[0091] The heating and cooling rates during high-temperature sintering are independently 1°C / min to 10°C / min, such as 1°C / min, 2°C / min, 4°C / min, 6°C / min, 8°C / min, or 10°C / min, etc., or other values within the range of 1°C / min to 10°C / min.

[0092] In some alternative embodiments, the crushing forms include crushing using a jaw crusher, a ball mill, a vibration mill, or a jet mill.

[0093] After densification treatment, electrolyte powders with a particle size of 5 μm to 50 μm are screened out.

[0094] Correspondingly, the present invention also provides an electrolyte powder, which is prepared by the above preparation method.

[0095] In some alternative embodiments, the electrolyte powder is mainly spherical, with a particle size of 5 μm to 50 μm; in some preferred embodiments, the particle size of the electrolyte powder is 5 μm to 30 μm.

[0096] Continuing from the above, the electrolyte powder prepared by the present invention has regular shape, high sphericity, good fluidity, and is easy to be stably and uniformly fed into the center of the thermal spraying flame, laying a solid foundation for the subsequent coating structure uniformity and process stability. Moreover, the electrolyte powder prepared by the present invention has a small particle size, is more easily melted and bonded during the thermal spraying process, which helps to improve the density of the electrolyte coating. In addition, by densifying the electrolyte powder before thermal spraying, the internal and external structures of the electrolyte powder can be made dense with fewer pores, enhancing the density of the powder and providing a basis for the high density of the coating.

[0097] Furthermore, the present invention also provides an application of the above electrolyte powder. For example, it can be used to prepare a solid oxide fuel cell or electrolyzer by thermal spraying. For example, the electrolyte powder can be prepared into an electrolyte coating and then further prepared into a solid oxide fuel cell or electrolyzer.

[0098] By using the electrolyte powder provided by the present invention for thermal spraying, the internal porosity of the coating can be significantly reduced, the density (>95%) and bonding strength of the electrolyte coating can be improved, and effective separation of the gases on both sides of the electrodes of the SOFC / SOEC can be ensured without subsequent high-temperature or impregnation sintering densification processes. The high fluidity of the spherical powder and the small particle size distribution range contribute to the uniformity of the coating, reduce coating defects, and improve the overall performance of the coating. Further, the dense electrolyte coating can provide a continuous ion transport path, increase the ionic conductivity, and thus improve the battery output power. In addition, the dense structure is conducive to reducing the thickness of the electrolyte, lowering the battery ohmic impedance, and improving the battery output power. Moreover, the dense electrolyte coating has good mechanical strength and durability, can resist thermal cycling and mechanical stress, reduce the risk of electrolyte cracking and spalling, protect the internal structure of the battery from high temperature and chemically active environments, and extend the service life of the SOFC / SOEC.

[0099] The features and properties of the present invention will be further described in detail below in conjunction with examples.

[0100] Example 1

[0101] This example provides a method for preparing an electrolyte powder for a solid oxide fuel cell or electrolyzer for thermal spraying, including the following steps:

[0102] S1: Prepare micron-scale electrolyte powder.

[0103] The electrolyte raw material powder is mixed with a dispersant, a binder, and a solvent and then subjected to ball milling to obtain an electrolyte slurry; the electrolyte slurry is spray-dried and granulated.

[0104] Among them, the electrolyte raw material powder is yttria-stabilized zirconia (containing 8 mol% of Y2O3) with a particle size of 50 nm to 1 μm and a melting point of about 2700 °C. The dispersant is polyvinylpyrrolidone, the binder is polyvinyl alcohol, and the solvent is deionized water; the mass ratio of the electrolyte raw material powder, the dispersant, and the solvent is 100:10:350; the mass of the binder is 5% of the electrolyte raw material powder. The ball milling is carried out at 200 rpm for 4 h; the inlet temperature of the spray drying and granulation is 200 °C, the outlet temperature is 95 °C, and the atomization pressure is 0.4 MPa.

[0105] S2: The micron-sized electrolyte powder is densified by a plasma spheroidization method.

[0106] The plasma gas used for plasma spheroidization is argon, the flow rate of the plasma gas is 55 L / min, and the flow rate of the auxiliary hydrogen gas is 10 L / min; the output power is 70 kW; the powder feeding rate is 10 g / min.

[0107] S3: The powder after densification treatment is sieved to obtain an electrolyte powder with a particle size of 5 μm to 50 μm.

[0108] Example 2

[0109] This example provides a method for preparing an electrolyte powder for a solid oxide fuel cell or electrolyzer for thermal spraying, including the following steps:

[0110] S1: Prepare a micron-sized electrolyte powder.

[0111] The electrolyte raw material powder is mixed with a dispersant, a binder, and a solvent and then subjected to ball milling to obtain an electrolyte slurry; the electrolyte slurry is spray-dried and granulated.

[0112] Among them, the electrolyte raw material powder is samarium-doped ceria (containing 10 mol% of Sm2O3) with a particle size of 10 nm to 5 μm and a melting point of about 2400 °C. The dispersant is citric acid, the binder is hydroxypropyl methylcellulose, and the solvent is ethanol; the mass ratio of the electrolyte raw material powder, the dispersant, and the solvent is 100:2:200; the mass of the binder is 0.5% of the electrolyte raw material powder. The ball milling is carried out at 180 rpm for 6 h; the inlet temperature of the spray drying and granulation is 180 °C, the outlet temperature is 80 °C, and the atomization pressure is 0.3 MPa.

[0113] S2: The micron-sized electrolyte powder is densified by a plasma spheroidization method.

[0114] The plasma gas used for plasma spheroidization is nitrogen, the flow rate of the plasma gas is 30 L / min, and the flow rate of the auxiliary hydrogen gas is 2 L / min; the output power is 30 kW; the powder feeding rate is 5 g / min.

[0115] S3: Screen the powder after densification treatment to obtain electrolyte powder with a particle size of 5 μm to 50 μm.

[0116] Example 3

[0117] This example provides a method for preparing electrolyte powder for a solid oxide fuel cell or electrolytic cell used in thermal spraying, including the following steps:

[0118] S1: Prepare micron-scale electrolyte powder.

[0119] Mix the electrolyte raw material powder with a dispersant, a binder, and a solvent, and then perform ball milling to obtain an electrolyte slurry; perform spray drying granulation on the electrolyte slurry.

[0120] Among them, the electrolyte raw material powder is BaZr 0.9 M 0.1 O3 with a particle size of 2 μm to 5 μm and a melting point of about 2600 °C. The dispersant is polyacrylic acid, the binder is polyvinyl alcohol, and the solvent is isopropyl alcohol; the mass ratio of the electrolyte raw material powder, the dispersant, and the solvent is 100:15:500; the mass of the binder is 5% of the electrolyte raw material powder. The ball milling is carried out at 250 rpm for 2 h; the inlet temperature of the spray drying granulation is 220 °C, the outlet temperature is 110 °C, and the atomization pressure is 0.6 MPa.

[0121] S2: Perform densification treatment on the micron-scale electrolyte powder by means of plasma spheroidization.

[0122] The plasma gas used for plasma spheroidization is argon, the flow rate of the plasma gas is 60 L / min, and the flow rate of the auxiliary hydrogen gas is 10 L / min; the output power is 120 kW; the powder feeding rate is 20 g / min.

[0123] S3: Screen the powder after densification treatment to obtain electrolyte powder with a particle size of 5 μm to 50 μm.

[0124] Example 4

[0125] This example provides a method for preparing electrolyte powder for a solid oxide fuel cell or electrolytic cell used in thermal spraying, including the following steps:

[0126] S1: Prepare micron-scale electrolyte powder.

[0127] The electrolyte raw material powder is mixed with a dispersant, a binder and a solvent and then subjected to ball milling to obtain an electrolyte slurry; the electrolyte slurry is spray-dried and granulated.

[0128] Among them, the electrolyte raw material powder is gadolinium-doped cerium dioxide (containing 10 mol% of Gd2O3) with a particle size of 50 nm to 1 μm and a melting point of about 2400 °C. The dispersant is polyvinylpyrrolidone, the binder is polyvinyl alcohol, and the solvent is deionized water; the mass ratio of the electrolyte raw material powder, the dispersant and the solvent is 100:8:300; the mass of the binder is 5% of the electrolyte raw material powder. The ball milling is carried out at 190 rpm for 5 h; the inlet temperature of the spray drying and granulation is 200 °C, the outlet temperature is 100 °C, and the atomization pressure is 0.35 MPa.

[0129] S2: The micron-sized electrolyte powder is densified by high-temperature sintering-crushing method.

[0130] The sintering temperature is 1400 °C; the sintering time is 12 h; the heating and cooling rates are both 1 °C / min; a jaw crusher is used for crushing.

[0131] S3: The densified powder is sieved to obtain an electrolyte powder with a particle size of 5 μm to 50 μm.

[0132] Example 5

[0133] This example provides a method for preparing an electrolyte powder for a solid oxide fuel cell or electrolyzer for thermal spraying, including the following steps:

[0134] S1: Prepare a micron-sized electrolyte powder.

[0135] The electrolyte raw material powder is mixed with a dispersant, a binder and a solvent and then subjected to ball milling to obtain an electrolyte slurry; the electrolyte slurry is spray-dried and granulated.

[0136] Among them, the electrolyte raw material powder is scandium-stabilized zirconia (containing 10 mol% of Sc2O3) with a particle size of 50 nm to 1 μm and a melting point of about 2700 °C. The dispersant is polyvinylpyrrolidone, the binder is polyvinyl alcohol, and the solvent is deionized water; the mass ratio of the electrolyte raw material powder, the dispersant and the solvent is 100:12:400; the mass of the binder is 4% of the electrolyte raw material powder. The ball milling is carried out at 220 rpm for 3 h; the inlet temperature of the spray drying and granulation is 210 °C, the outlet temperature is 100 °C, and the atomization pressure is 0.5 MPa.

[0137] S2: The micron-sized electrolyte powder is densified by high-temperature sintering-crushing method.

[0138] The sintering temperature is 1700 °C; the sintering time is 2 h; the heating and cooling rates are both 10 °C / min; jet milling is used for crushing.

[0139] S3: Screen the powder after densification treatment to obtain electrolyte powder with a particle size of 5 μm to 50 μm.

[0140] Example 6

[0141] This example provides a method for preparing electrolyte powder for a solid oxide fuel cell or electrolyzer for thermal spraying, including the following steps:

[0142] S1: Prepare micron-scale electrolyte powder.

[0143] Mix the electrolyte raw material powder with a dispersant, a binder, and a solvent, and then perform ball milling to obtain an electrolyte slurry; perform spray drying granulation on the electrolyte slurry.

[0144] Among them, the electrolyte raw material powder is scandia-stabilized zirconia (containing 10 mol% of Sc2O3) with a particle size of 50 nm to 1 μm and a melting point of about 2700 °C. The dispersant is polyacrylic acid (PAA), the binder is polyvinylpyrrolidone (PVP), and the solvent is deionized water; the mass ratio of the electrolyte raw material powder, the dispersant, and the solvent is 100:10:350; the mass of the binder is 4% of the electrolyte raw material powder. Ball milling is carried out at 200 rpm for 4 h; the inlet temperature of spray drying granulation is 210 °C, the outlet temperature is 100 °C, and the atomization pressure is 0.4 MPa.

[0145] S2: Perform densification treatment on the micron-scale electrolyte powder by means of plasma spheroidization.

[0146] The plasma gas used for plasma spheroidization is argon, the flow rate of the plasma gas is 55 L / min, and the flow rate of the auxiliary hydrogen is 10 L / min; the output power is 70 kW; the powder feeding rate is 10 g / min.

[0147] S3: Screen the powder after densification treatment to obtain electrolyte powder with a particle size of 5 μm to 50 μm.

[0148] Example 7

[0149] This example provides a method for preparing electrolyte powder for a solid oxide fuel cell or electrolyzer for thermal spraying, including the following steps:

[0150] S1: Prepare micron-scale electrolyte powder.

[0151] Mix the electrolyte raw material powder with a dispersant, a binder, and a solvent, and then perform ball milling to obtain an electrolyte slurry; perform spray drying granulation on the electrolyte slurry.

[0152] Among them, the electrolyte raw material powder is scandium-stabilized zirconia (containing 10 mol% of Sc2O3) with a particle size of 50 nm to 1 μm and a melting point of about 2700°C. The dispersant is polyacrylic acid (PAA), the binder is polyvinylpyrrolidone (PVP), and the solvent is deionized water; the mass ratio of the electrolyte raw material powder, the dispersant and the solvent is 100:10:350; the mass of the binder is 4% of the electrolyte raw material powder. Ball milling is carried out under the condition of 200 rpm for 4 h; the inlet temperature of spray drying granulation is 210°C, the outlet temperature is 100°C, and the atomization pressure is 0.4 MPa.

[0153] S2: Densify the micron-sized electrolyte powder by means of high-temperature sintering-crushing.

[0154] The sintering temperature is 1400°C; the sintering time is 6 h; the heating and cooling rates are both 1°C / min; use a jaw crusher for crushing.

[0155] S3: Screen the powder after densification treatment to obtain electrolyte powder with a particle size of 5 μm to 50 μm.

[0156] Test Example

[0157] Taking the use of the traditional spray drying process to agglomerate nano / sub-micron electrolyte powder into electrolyte powder with a particle size of 10 μm to 100 μm as a control example, the SEM image is as Figure 1 shown. The SEM image of the electrolyte powder of Example 1 is as Figure 2 shown, and the SEM image of the electrolyte powder of Example 4 is as Figure 3 shown.

[0158] Furthermore, spray the electrolyte powder prepared in the control example, Example 1 and Example 4 onto the surface of a 430 stainless steel metal substrate by thermal spraying. The process conditions of thermal spraying are spraying power 54 kW to 60 kW, argon gas flow rate 50 L / min to 60 L / min, hydrogen gas flow rate 8 L / min to 12 L / min, powder feeding rate 5 g / min to 10 g / min, walking speed 500 mm / s to 800 mm / s, and a coating with a thickness of 5 μm to 50 μm is prepared. Test the density of each coating, and the density is measured by referring to the image analysis technology method. The results show that the density of the coating corresponding to the control group < 90%, the density of the coating corresponding to Example 1 > 95%, and the density of the coating corresponding to Example 1 > 97%.

[0159] The SEM image of the electrolyte coating prepared from the electrolyte powder provided by the control example is as Figure 4 shown, and by Figure 4It can be seen that the electrolyte coating is loose and porous, and the density is <90%. The SEM image of the electrolyte coating prepared from the electrolyte powder provided in Example 1 is as shown in Figure 5 shown, and from Figure 5 it can be seen that the electrolyte coating is very dense, and the density is >95%. The SEM image of the electrolyte coating prepared from the electrolyte powder provided in Example 4 is as shown in Figure 6 shown, and from Figure 6 it can be seen that the electrolyte coating is very dense, and the density is >97%. This shows that the electrolyte coatings prepared from the electrolyte powders obtained in Example 1 and Example 4 of the present invention have high density, which is beneficial to improving the performance of SOFC / SOEC and extending the service life of SOFC / SOEC.

[0160] Furthermore, the electrolyte powders prepared in the control group, Example 6, and Example 7 were made into batteries by the following method, and then the electrochemical performance of the batteries was tested. The results are as shown in Figures 7 to 9 shown.

[0161] Among them, the specific method for preparing the battery is as follows: A porous 430 stainless steel disc (diameter 19 mm, thickness 1 mm) is selected as the single-cell spraying substrate, and the NiO-GDC anode, ScSZ electrolyte, and LSCF cathode are sequentially sprayed on the porous metal substrate by plasma spraying technology. In the preparation of the control group and the batteries in the examples, the electrolyte powder raw material is the single variable, while the spraying parameters of the anode, electrolyte, and cathode are all the same.

[0162] The test conditions for the electrochemical performance of the battery are as follows: The battery is tested on an electrochemical workstation by the DC four-terminal method. Before the test, the battery is placed in a tubular furnace and heated to 600 °C at a heating rate of 5 °C / min and held for 2 hours. During this period, wet H2 (mixed with 3 vol% H2O) is continuously introduced into the fuel side at 50 mL / min to fully reduce the NiO in the anode to metallic Ni. After the heat preservation is completed, between 600 and 800 °C, the battery is subjected to linear sweep voltammetry (LSV) every 50 °C to obtain the open-circuit voltage and output performance.

[0163] From Figures 7 to 9 it can be seen that the open-circuit voltages of the batteries at an operating temperature of 800 °C are 0.82 V, 0.92 V, and 1.0 V respectively, and the maximum power densities are 0.68 W / cm 2 , 0.88 W / cm 2 and 0.95 W / cm 2 . This shows that the performance of the batteries prepared with the plasma spheroidization / high-temperature sintering-crushing dense electrolyte powder is significantly better than that of the batteries prepared with the traditional agglomerated non-dense electrolyte powder.

[0164] In summary, by optimizing the preparation process of the electrolyte powder, the present invention improves the particle size, sphericity, fluidity and density of the powder, thereby achieving significant improvements in aspects such as the density and uniformity of the electrolyte coating, as well as the electrochemical and mechanical properties of the cell, meeting the requirements of SOFC / SOEC for high-performance electrolyte coatings.

[0165] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing electrolyte powder for a solid oxide fuel cell or electrolytic cell for thermal spraying, characterized in that: The method comprises the following steps: preparing micron-sized electrolyte powder by spray drying; densifying the micron-sized electrolyte powder by plasma spheroidization or high-temperature sintering-crushing, and sieving the densified powder to obtain electrolyte powder with a particle size of 5 μm to 50 μm.

2. The preparation method according to claim 1, characterized in that: The preparation of the micron-sized electrolyte powder comprises: mixing the electrolyte raw material powder with a dispersant, a binder and a solvent and then subjecting the mixture to ball milling to obtain an electrolyte slurry; spray drying and granulating the electrolyte slurry; Preferably, the particle size of the micron-sized electrolyte powder is 5 μm to 100 μm.

3. The preparation method according to claim 2, characterized in that: The electrolyte raw material powder has at least one of the following characteristics: Feature 1: The particle size of the electrolyte raw material powder is 10nm to 5μm, preferably 50nm to 1μm; Feature 2: The electrolyte raw material powder is an oxide ceramic material with a melting point of 1000°C to 3500°C; preferably includes at least one of a ZrO2-based material, a CeO2-based material and a perovskite-type material.

4. The preparation method according to claim 3, characterized in that: The ZrO2-based material includes at least one of yttria-stabilized zirconia and scandia-stabilized zirconia; and / or, the CeO2-based material comprises at least one of gadolinium oxide-doped ceria and samarium oxide-doped ceria; And / or, the perovskite material includes La 1-x Sr x Ga 1-y Mg y O3、BaCe 1-z M z O3 and BaZr 1-z M z At least one of O3; Wherein, 0<x≤0.2, 0<y≤0.2, 0<z≤0.2, M is at least one of Y, Yb and Gd; Preferably, the yttria-stabilized zirconia contains 3 mol% to 8 mol% of Y2O3; Preferably, the scandia-stabilized zirconia contains 8 mol% to 10 mol% of Sc2O3; Preferably, the gadolinium oxide-doped cerium dioxide contains 10 mol% to 20 mol% of Gd2O3; Preferably, the samarium oxide-doped cerium dioxide contains 10 mol% to 20 mol% of Sm2O3.

5. The preparation method according to claim 2, characterized in that: The dispersant comprises at least one of polyvinyl pyrrolidone, polyacrylic acid, citric acid and polyethylene glycol; And / or, the binder comprises a water-soluble or alcohol-soluble polymer binder; preferably, the binder comprises at least one of polyvinyl pyrrolidone, polyvinyl alcohol, hydroxypropyl methylcellulose, polyethylene glycol and ethyl cellulose; and / or, the solvent comprises at least one of deionized water, ethanol and isopropanol; And / or, the mass ratio of the electrolyte raw material powder, the dispersant and the solvent is 100:(2-15):(200-500); the mass of the binder is 0.5%-5% of the electrolyte raw material powder.

6. The preparation method according to claim 2, characterized in that: Ball milling was performed at 180 rpm to 250 rpm for 2 h to 6 h; And / or, the spray drying granulation comprises at least one of the following features: Feature 3: The inlet temperature is 180°C to 220°C, preferably 190°C to 210°C; Feature 4: The outlet temperature is 80°C to 110°C, preferably 90°C to 100°C; Feature 5: The atomization pressure is 0.3MPa to 0.6MPa, preferably 0.35MPa to 0.5MPa.

7. The preparation method according to claim 1, characterized in that: Plasma spheroidization includes at least one of the following features: Feature 6: The plasma gas includes argon or nitrogen; Feature 7: Plasma gas flow rate: argon or nitrogen flow rate is 10L / min to 60L / min, auxiliary hydrogen flow rate is 2L / min to 10L / min; Feature 8: The output power is 30kW to 120kW, preferably 40kW to 100kW; Feature 9: The powder feeding rate is 5g / min to 20g / min.

8. The preparation method according to claim 1, characterized in that: High temperature sintering-crushing includes at least one of the following features: Feature 10: Sintering temperature is 1200℃~1700℃; Feature 11: Sintering time is 2h to 12h; Feature 12: The heating and cooling rates are independently 1°C / min to 10°C / min; Feature 13: Crushing methods include using a jaw crusher, a ball mill, a vibration mill or a jet mill for crushing.

9. An electrolyte powder for a thermally sprayed solid oxide fuel cell or electrolytic cell, characterized in that: The electrolyte powder is prepared by the preparation method according to any one of claims 1 to 8; Preferably, the particle size of the electrolyte powder is 5 μm to 50 μm; More preferably, the particle size of the electrolyte powder is 5 μm to 30 μm.

10. Use of the electrolyte powder according to claim 9, characterized in that: The electrolyte powder is used for preparing solid oxide fuel cells or electrolysis by thermal spraying.

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