Method of preparing electrode for solid oxide fuel cell and solid oxide fuel cell

Abstract

According to embodiments of the present disclosure, a pre-electrolyte layer is formed, a pre-electrode active layer is formed on top of the pre-electrolyte layer, and a pre-support layer is formed on top of the pre-electrode active layer to manufacture a pre-electrode laminate, and the pre-electrode laminate is sintered to manufacture an electrode for a solid oxide fuel cell. In addition, an electrode for a solid oxide fuel cell formed by the manufacturing method described above may be provided. Accordingly, a solid oxide fuel cell having excellent performance and stability, comprising the electrode for a solid oxide fuel cell described above, may be provided.

Description

Technology Field

[0001] The present disclosure relates to a method for manufacturing an electrode for a solid oxide fuel cell and a solid oxide fuel cell. Background Technology

[0003] A Solid Oxide Fuel Cell (SOFC) is a highly efficient energy conversion device that directly converts chemical energy into electrical energy. Since the SOFC operates at high temperatures, it does not require a precious metal catalyst, and it can achieve high power generation efficiency as oxygen ions are transported within the fuel cell through a solid oxide electrolyte.

[0004] The unit cell of the above solid oxide fuel cell can be manufactured by attaching a positive electrode (air electrode) and a negative electrode (fuel electrode) to each side of an oxygen ion-conducting solid electrolyte. Oxygen ions generated by the reduction reaction of oxygen at the positive electrode can be transferred to the negative electrode through the solid electrolyte. The negative electrode can react with the supplied hydrogen and the transferred oxygen ions, and electrons are generated along with the oxidation reaction to produce electricity. During the manufacturing and operation of the above solid oxide fuel cell, the positive electrode and the solid electrolyte may react with each other as they are exposed to high temperatures for a long time, and a composite oxide layer with low ion conductivity may be formed at the interface between the positive electrode and the solid electrolyte. To suppress the formation of the composite oxide, a metal oxide layer with relatively high ion conductivity may be introduced into the solid oxide fuel cell.

[0005] To form a metal oxide layer, deposition methods under high vacuum conditions, such as sputtering and pulsed laser deposition, can be used, but economic efficiency and processability may be reduced. The problem to be solved

[0007] One objective of the present disclosure is to provide a method for manufacturing an electrode for a solid oxide fuel cell with improved electrical properties.

[0008] One objective of the present disclosure is to provide an electrode for a solid oxide fuel cell with improved lifespan characteristics and safety.

[0009] One objective of the present disclosure is to provide a solid oxide fuel cell comprising the electrode for the solid oxide fuel cell. means of solving the problem

[0011] A method for manufacturing an electrode for a solid oxide fuel cell according to the present disclosure comprises the steps of: forming a preliminary electrolyte layer; forming a preliminary electrode active layer on top of the preliminary electrolyte layer; forming a preliminary support layer on top of the preliminary electrode active layer to manufacture a preliminary electrode laminate; and sintering the preliminary electrode laminate.

[0012] According to exemplary embodiments, the step of forming the preliminary electrolyte layer may include the step of applying an electrolyte layer slurry to a substrate and the step of drying the applied electrolyte layer slurry.

[0013] According to exemplary embodiments, the electrolyte layer slurry may comprise a solid electrolyte oxide powder, a binder, and a solvent.

[0014] According to exemplary embodiments, the step of forming the preliminary electrode active layer may include the step of applying an electrode active layer slurry onto the preliminary electrolyte layer; and the step of drying the applied electrode active layer slurry.

[0015] According to exemplary embodiments, the electrode active layer slurry may comprise a solid electrolyte oxide powder, a binder, and a solvent.

[0016] According to exemplary embodiments, components within the pre-electrode active layer can penetrate into the pre-electrolyte layer.

[0017] According to exemplary embodiments, the step of forming the preliminary support layer may include the step of applying a support layer slurry onto the preliminary electrode active layer and the step of drying the applied support layer slurry.

[0018] According to exemplary embodiments, the support layer slurry may comprise solid electrolyte oxide powder, a binder, and a solvent.

[0019] According to exemplary embodiments, a component within the preliminary support layer can penetrate into the preliminary electrode active layer.

[0020] According to exemplary embodiments, the electrolyte layer slurry, the electrode active layer slurry, or the support layer slurry each independently further comprise a dispersant, a first plasticizer, and a second plasticizer, and the volume ratio of the dispersant, the binder, the first plasticizer, and the second plasticizer may be 4 to 6: 21 to 25: 16 to 20: 2 to 6.

[0021] According to exemplary embodiments, the thickness of the electrolyte layer may be 6 μm or less.

[0022] According to exemplary embodiments, the thickness of the electrode active layer may be 8 μm to 20 μm.

[0023] An electrode for a solid oxide fuel cell according to the present disclosure is manufactured by sintering the above-mentioned pre-electrode stack.

[0024] A solid oxide fuel cell according to the present disclosure may include the electrode for the solid oxide fuel cell described above, an air electrode facing the electrode for the solid oxide fuel cell, and a diffusion barrier layer interposed between the electrode for the solid oxide fuel cell and the air electrode. Effects of the invention

[0026] According to the method for manufacturing an electrode for a solid oxide fuel cell according to embodiments of the present invention, a preliminary electrode active layer is formed on top of a preliminary electrolyte layer, and a preliminary support layer is formed on top of the preliminary electrode active layer to manufacture a preliminary electrode laminate, and the preliminary electrode laminate can be sintered. An electrode for a solid oxide fuel cell with improved electrical characteristics can be manufactured.

[0027] Instead of manufacturing the electrolyte layer, electrode active layer, and support layer independently and then stacking them, a pre-electrode active layer is formed on top of a pre-electrode active layer, and a pre-support layer is formed on top of the pre-electrode active layer. This allows components within the pre-electrode active layer to penetrate into the pre-electrode active layer, thereby forming interlayer bonding without a pressure process for bonding between the pre-electrode active layer and the pre-electrode active layer. Additionally, components within the pre-support layer can penetrate into the pre-electrode active layer, allowing interlayer bonding to be formed without a compression process, such as hot isotropic pressing, for bonding between the pre-electrode active layer and the pre-support layer. Consequently, production can be further simplified, interfacial voids are reduced to form a smooth bond, and this improves ion diffusion pathways, contributing to enhanced fuel cell performance.

[0028] According to embodiments of the present invention, voids at the interfaces of the pre-electrolyte layer, the pre-electrode active layer, and the pre-support layer can be reduced, thereby improving electrical characteristics and lifespan characteristics. Accordingly, the solid oxide fuel cell manufactured by the method of the present invention can have improved energy density and chemical stability. Brief explanation of the drawing

[0030] FIG. 1 is a schematic flowchart illustrating a method for manufacturing an electrode for a solid oxide fuel cell according to exemplary embodiments. FIG. 2 is a schematic cross-sectional view of a solid oxide fuel cell according to one embodiment of the present invention. FIGS. 3a to 3e are SEM images of cross-sections of solid oxide fuel cells according to Example 1, Examples 4 to 6 and Comparative Example 1. FIG. 4a is a graph showing the impedance of solid oxide fuel cells according to Example 1 and Comparative Example 1 in fuel cell mode. FIG. 4b is a graph showing the impedance of solid oxide fuel cells according to Example 1 and Comparative Example 1 in electrolysis mode. FIG. 4c is a graph showing the impedance of solid oxide fuel cells according to Examples 1 to 3 in fuel cell mode. FIG. 4d is a graph showing the impedance of solid oxide fuel cells according to Examples 1 to 3 in electrolysis mode. Referring to FIG. 5a, this is a graph showing the Distribution of Relaxation Times (DRT) measured according to Example 1 and Comparative Example 1 in fuel cell mode. Referring to FIG. 5b, this is a graph showing the Distribution of Relaxation Times (DRT) measured according to Example 1 and Comparative Example 1 in electrolysis mode. Referring to FIG. 5c, this is a graph showing the Distribution of Relaxation Times (DRT) measured according to Examples 1 to 3 in fuel cell mode. Referring to FIG. 5d (5i), this is a graph showing the Distribution of Relaxation Times (DRT) measured according to Examples 1 to 3 in electrolysis mode. Figure 6a is a graph of current density-voltage-power density in the fuel cell mode of solid oxide fuel cells according to Example 1 and Comparative Example 1. FIG. 6b is a graph of current density-voltage-power density in the fuel cell mode of solid oxide fuel cells according to Example 1 and Comparative Example 1 in the electrolysis mode. FIG. 6c is a graph of current density-voltage-power density in the fuel cell mode of solid oxide fuel cells according to Examples 1 to 3. FIG. 6d is a graph of current density-voltage-power density in the fuel cell mode of solid oxide fuel cells according to Examples 1 to 3 in the electrolysis mode. Specific details for implementing the invention

[0031] According to embodiments of the present invention, a method for manufacturing an electrode for a solid oxide fuel cell is provided.

[0032] In addition, according to embodiments of the present invention, an electrode for a solid oxide fuel cell and a solid oxide fuel cell including the same are provided.

[0033] Hereinafter, the present disclosure will be described in detail with reference to the attached drawings. However, this is merely illustrative and the present disclosure is not limited to the specific embodiments described illustratively.

[0034] Method for manufacturing electrodes for solid oxide fuel cells

[0035] FIG. 1 is a schematic flowchart illustrating a method for manufacturing an electrode for a solid oxide fuel cell according to exemplary embodiments.

[0036] According to exemplary embodiments, the pre-electrode laminate may include a laminated structure of a pre-electrolyte layer, a pre-electrode active layer, and a pre-support layer. For example, the pre-electrolyte layer, the pre-electrode active layer, and the pre-support layer may be formed sequentially while in contact with each other.

[0037] Referring to FIG. 1, the pre-electrolyte layer can be formed on a substrate (e.g., step S10).

[0038] According to exemplary embodiments, the step of forming the pre-electrolyte layer may include the step of applying an electrolyte layer slurry to a substrate; and the step of drying the applied electrolyte layer slurry.

[0039] In some embodiments, the pre-electrolyte layer may be formed on a substrate by a tape casting process and dried for about 1 minute to 60 minutes at room temperature conditions (about 20 °C to 25 °C). For example, the pre-electrolyte layer may be coated on the substrate to a thickness of 10 μm or less by a tape casting process.

[0040] In some embodiments, the electrolyte layer slurry may include solid electrolyte oxide powder, a binder, and a solvent.

[0041] In some embodiments, the electrolyte layer slurry may comprise yttria-stabilized zirconia (YSZ), zirconia-based oxide (ZrO2), ceria-based oxide (CeO2), and lanthanum-strontium-gadolinium-magnesium oxide (LSGM). For example, the pre-electrolyte layer may comprise a complex of YSZ.

[0042] For example, the binder of the electrolyte layer slurry may include at least one of a copolymer of poly(butyl methacrylate) (PBMA) and poly(2-ethylhexyl methacrylate) (PEHMA) (PBMA-PEHMA), ethyl cellulose (EC), polyvinylisobutyral (PViB), and poly(2-ethylhexyl acrylate) (PEHA).

[0043] For example, the solvent of the electrolyte layer slurry may be one or more mixed solvents selected from the group consisting of water, isopropanol, toluene, anhydrous ethanol, n-propanol, n-butyl acetate, ethylene glycol, butyl carbitol, and butyl carbitol acetate.

[0044] In some embodiments, the electrolyte layer slurry may further include a dispersant, a first plasticizer, and a second plasticizer.

[0045] For example, the plasticizer of the electrolyte layer slurry may be at least one of di-n-butylphthalate (DBP), di-2-ethylhexylphthalate (DOP), di-isononylphthalate (DINP), di-isodecylphthalate (DIDP), and butylbenzylphthalate (BBP).

[0046] For example, the dispersant of the electrolyte layer slurry is not particularly limited as long as it is known in the art, and may be, for example, fish oil, or dibutyl phthalate (DBP), or KD-2 (Polyoxyalkalene Amine Derivative Dispersant).

[0047] In some embodiments, the volume ratio of the dispersant, the binder, the first plasticizer, and the second plasticizer of the electrolyte layer slurry may be 4 to 6: 21 to 25: 16 to 20: 2 to 6.

[0048] For example, the volume ratio of the dispersant, the binder, the first plasticizer, and the second plasticizer of the electrolyte layer slurry may be 4:21 to 25:16 to 20:2 to 6. Within this range, the preparation of the electrolyte layer slurry containing the oxide powder may be easy.

[0049] In some embodiments, the process may be performed by setting the height of the doctor blade to 30 μm to 60 μm when forming the pre-electrolyte layer.

[0050] Referring to FIG. 1, a preliminary electrode active layer can be formed on top of the preliminary electrolyte layer (e.g., step S20).

[0051] According to exemplary embodiments, the step of forming the preliminary electrode active layer may include the step of applying an electrode active layer slurry onto the preliminary electrolyte layer and the step of drying the applied electrode active layer slurry.

[0052] In some embodiments, the pre-electrode active layer may be formed on the pre-electrolyte layer by a tape casting process and dried for about 5 minutes to 120 minutes under room temperature conditions (about 20°C to 25°C). For example, the pre-electrode active layer may be coated on the pre-electrolyte layer by a tape casting process to a thickness of 8 μm to 25 μm.

[0053] In some embodiments, the electrode active layer slurry may include solid electrolyte oxide powder, a binder, and a solvent.

[0054] In some embodiments, the electrode active layer slurry may comprise yttria-stabilized zirconia (YSZ), zirconia-based oxide (ZrO2), ceria-based oxide (CeO2), and lanthanum-strontium-gadolinium-magnesium oxide (LSGM).

[0055] In some embodiments, the electrode active layer slurry may include NiO (Nickel Oxide) with a surface area different from that of the preliminary support layer. For example, the preliminary electrode active layer may include a composite of NiO and the preliminary electrolyte.

[0056] For example, the electrode active layer slurry may use NiO with a larger surface area than the NiO used in the preliminary support layer. Accordingly, the reaction area between the solid electrolyte layers increases, thereby improving power density.

[0057] For example, the binder of the electrode active layer slurry may be the binder described above.

[0058] For example, the solvent of the electrode active layer slurry may be the solvent described above.

[0059] In some embodiments, the electrode active layer slurry may further include a dispersant, a first plasticizer, and a second plasticizer.

[0060] For example, the plasticizer of the electrode active layer slurry may be the plasticizer described above.

[0061] For example, the dispersant of the electrode active layer slurry may be the dispersant described above.

[0062] The volume ratio of the above dispersant, the above binder, the above first plasticizer, and the above second plasticizer may be 4 to 6: 21 to 25: 16 to 20: 2 to 6.

[0063] For example, the volume ratio of the dispersant, the binder, the first plasticizer, and the second plasticizer of the electrode active layer slurry may be 6:21 to 25:16 to 20:2 to 6. Within this range, the preparation of the electrode active layer slurry containing the oxide powder may be easy.

[0064] Within the above range, voids are not excessively formed in the electrolyte layer, and the interface between the electrolyte layer and the electrode active layer can be smooth.

[0065] In some embodiments, the components within the pre-electrode active layer may penetrate into the pre-electrolyte layer.

[0066] For example, components within the pre-electrode active layer can promote smooth interfacial bonding by redissolving the surface of the pre-electrolyte layer. Accordingly, additional lamination or hot pressing steps are not required, and production can be further simplified by improving adhesion between layers; additionally, visually observable voids can be reduced, thereby providing an improved ion diffusion pathway.

[0067] In some embodiments, the process may be performed by setting the height of the doctor blade to 80 μm, 100 μm, or 180 μm when forming the pre-electrode active layer.

[0068] Referring to FIG. 1, a preliminary support layer can be formed on top of the preliminary electrode active layer (e.g., step S30).

[0069] According to exemplary embodiments, the step of forming the preliminary support layer may include the step of applying a support layer slurry onto the preliminary electrode active layer and the step of drying the applied support layer slurry.

[0070] In some embodiments, the pre-support layer may be formed on the pre-electrode active layer by a tape casting process and may be dried for about 3 to 24 hours under conditions of 10°C to 100°C.

[0071] For example, the above pre-support layer can be dried for about 3 to 15 hours under conditions of 10 ℃ to 40 ℃.

[0072] In some embodiments, the support layer slurry may include solid electrolyte oxide powder, a binder, and a solvent.

[0073] In some embodiments, the support layer slurry may comprise yttria-stabilized zirconia (YSZ), zirconia-based oxide (ZrO2), ceria-based oxide (CeO2), and lanthanum-strontium-gadolinium-magnesium oxide (LSGM).

[0074] In some embodiments, the support layer slurry may include NiO (Nickel Oxide). For example, the support layer slurry may include a complex of NiO and the pre-electrolyte.

[0075] For example, the binder of the support layer slurry may be the binder described above.

[0076] For example, the solvent of the support layer slurry may be the solvent described above.

[0077] In some embodiments, the support layer slurry may further include a dispersant, a first plasticizer, and a second plasticizer.

[0078] For example, the plasticizer of the support layer slurry may be the plasticizer described above.

[0079] For example, the dispersant of the support layer slurry may be the dispersant described above.

[0080] The volume ratio of the above dispersant, the above binder, the above first plasticizer, and the above second plasticizer may be 4 to 6: 21 to 25: 16 to 20: 2 to 6.

[0081] For example, the volume ratio of the dispersant, the binder, the first plasticizer, and the second plasticizer of the support layer slurry may be 6:21 to 25:16 to 20:2 to 6. Within this range, it may be easy to manufacture the support layer slurry containing the oxide powder.

[0082] In some embodiments, components within the pre-support layer may penetrate into the pre-electrode active layer. For example, components within the pre-support layer may promote smooth interfacial bonding by re-dissolving the surface of the pre-electrode active layer. Accordingly, additional lamination or hot pressing steps are not required, and production can be further simplified by improving adhesion between layers.

[0083] In some embodiments, the process may be performed by setting the height of the doctor blade to 1000 μm when forming the preliminary support layer.

[0084] According to exemplary embodiments, the thickness of the electrolyte layer may be 6 μm or less. For example, it may be 6 μm, 5 μm, or 4 μm or less. Within this range, the resistance of the electrolyte may be lowered, thereby lowering the operating temperature of the fuel cell.

[0085] According to exemplary embodiments, the thickness of the electrode active layer may be 8 μm to 20 μm. For example, it may be 9 μm to 19 μm, 10 μm to 18 μm, or 11 μm to 17 μm or less. Within the above range, sufficient reaction sites can be provided in the electrode active layer.

[0086] Referring to FIG. 1, an electrode for a solid oxide fuel cell can be manufactured by sintering the above-mentioned pre-electrode stack (e.g., step S40).

[0087] In some embodiments, the step of sintering the pre-electrode laminate is,

[0088] The step of sintering at conditions of 1000 ℃ to 1800 ℃ for 3 to 12 hours may be included. For example, the step of sintering the pre-electrode laminate may further include pre-sintering at conditions of 800 ℃ to 1200 ℃ for 1 to 6 hours before sintering.

[0089] For example, when a pre-electrode laminate is sintered, the laminated pre-electrolyte layer, pre-electrode active layer, and pre-support layer can be simultaneously formed as an electrolyte layer, an electrode active layer, and a support layer.

[0090] In some embodiments, a preliminary diffusion barrier layer may be formed on top of the electrolyte layer of the electrode for a solid oxide fuel cell, and an air electrode may be formed on top of the preliminary diffusion barrier layer.

[0091] In one embodiment, the step of forming the preliminary diffusion barrier layer can be formed by screen printing a slurry comprising a ceria-based solid oxide electrolyte (GDC) and an organic binder.

[0092] In one embodiment, the step of sintering the preliminary diffusion barrier layer may include sintering for 1 to 6 hours under conditions of 900 ℃ to 1500 ℃.

[0093] In one embodiment, the step of forming the air electrode may include screen printing the air electrode onto a sintered GDC layer and then heat treating it at a temperature of 900°C to 1500°C for 1 to 3 hours.

[0094] Solid oxide fuel cell

[0095] Referring to FIG. 2, a support layer (200), an electrode active layer (220), an electrolyte layer (300), a diffusion barrier layer (110), and an air electrode (100) can be sequentially stacked.

[0096] FIG. 3a is a schematic cross-sectional view of a solid oxide fuel cell according to one embodiment of the present invention.

[0097] The electrode active layer (220) can function as a fuel electrode in a solid oxide fuel cell. For example, electrons can be generated as the fuel is electrochemically oxidized by oxygen ions in the electrode active layer (220).

[0098] The electrode active layer (220) may include a material that oxidizes oxygen ions.

[0099] In some embodiments, the electrode active layer (220) may include NiO.

[0100] In some embodiments, the electrode active layer (220) may comprise a composite of NiO and an electrolyte. For example, the electrode active layer (220) may comprise a composite of NiO and YSZ.

[0101] Oxygen ions generated at the air electrode (100) can be transferred to the electrode active layer (220) through the electrolyte layer (300). The electrolyte layer (300) may use a material with high ion conductivity so that oxygen ions can be transferred between the air electrode (100) and the electrode active layer (220). For example, the electrolyte layer (300) may be a zirconia-based oxide (ZrO2), a ceria-based oxide (CeO2), or a lanthanum-strontium-gadolinium-magnesium oxide (LSGM).

[0102] The electrolyte layer (300) may further include a composite metal oxide. For example, the composite metal oxide may include at least one of a zirconium oxide-based material, a cerium oxide-based material, a lanthanum oxide-based material, a titanium oxide-based material, and a bismuth oxide-based material.

[0103] In one embodiment, the electrolyte layer (300) may be yttria-stabilized zirconia (YSZ).

[0104] The air electrode (100) can be generated as oxygen ions as oxygen in the air is electrochemically reduced in a solid oxide fuel cell.

[0105] The air electrode (100) may include a material that reduces oxygen gas into oxygen ions. For example, the air electrode (100) may include lanthanum strontium manganese oxide (LSM), lanthanum strontium cobalt ferrite oxide (LSCF), lanthanum strontium cobalt oxide (LSC), lanthanum strontium ferrite oxide (LSF), or a complex of these with an electrolyte material.

[0106] For example, the air electrode (100) may include precious metals such as platinum, ruthenium, and palladium. These may be included individually or in combination of two or more.

[0107] In one embodiment, the air electrode (100) may be lanthanum strontium cobalt iron oxide (LSCF).

[0108] According to exemplary embodiments, the diffusion barrier layer (110) may include a material that does not react with the air electrode (100) or the electrolyte layer (300). For example, the diffusion barrier layer (110) may include a ceria-based oxide.

[0109] In some embodiments, the ceria-based oxide may further include a doping element. For example, the doping element may include a rare earth metal.

[0110] Examples of the above rare earth metals include gadolinium (Gd), samarium (Sm), lanthanum (La), scandium (Sc), yttrium (Y), neodymium (Nd), praseodymium (Pr), europium (Eu), terbium (Tb), dysprosium (Dy), holmium (Ho), thulium (Tm), ytterbium (Yb), ruthenium (Lu), erbium (Er), etc. These may be used individually or in combination of two or more.

[0111] In one embodiment, the diffusion barrier layer (110) may include a gadolinium-doped ceria-based oxide (Gd-doped CeO2, GDC).

[0112] According to exemplary embodiments, the diffusion barrier layer (110) includes a chelating agent and may have a density of 90% or more.

[0113] According to exemplary embodiments, the density of the diffusion barrier layer (110) may be 90% or more. For example, the density of the diffusion barrier layer (110) may be 95% or more and 99% or less.

[0114] The above density is the ratio of the metal oxide layer to the total space in the diffusion barrier layer (110) and can be defined as '1-porosity'. If the density is lower than the above range, the ion conductivity may be reduced. The above porosity can be measured through SEM image analysis.

[0115] Hereinafter, experimental examples including specific embodiments and comparative examples are presented to aid in understanding the present invention; however, these are merely illustrative of the invention and do not limit the appended claims. It is obvious to those skilled in the art that various changes and modifications to the embodiments are possible within the scope and spirit of the present invention, and that such variations and modifications fall within the scope of the appended claims.

[0117] Example 1

[0118] (1) Preparation of electrodes for solid oxide fuel cells

[0119] 1) Preparation of electrolyte layer slurry

[0120] YSZ powder (surface area 16±2 m²) in a mixed solvent in which toluene (Daejeong, South Korea) and anhydrous ethanol (Daejeong, South Korea) were mixed in a 1:1 weight ratio 2 ·g -1 (Tosoh, Japan) was added. Subsequently, fish oil (Sigma Aldrich, USA) was added as a dispersant. YSZ powder and zirconia balls were added at a weight ratio of 1:4, and ball milling was performed at 80 RPM for 24 hours.

[0121] Polyvinyl butyral (PVB79, Victor Chem, South Korea) binder, di-n-butyl phthalate (DBP, Thermo Fisher Scientific, South Korea) as a first plasticizer, and polyethylene glycol (PEG) as a second plasticizer, molecular weight 8000 g·mol -1 , Acros Organics, USA) was added.

[0122] Oxide powder: Additives (dispersant, binder, first plasticizer, and second plasticizer) were mixed in a volume ratio of 1:1, and a slurry was prepared such that the solvent accounted for 80 volume% of the total volume of the electrolyte layer slurry.

[0123] Of the total volume of additives, the dispersant was prepared at 12 volume%, the binder at 45 volume%, the first plasticizer at 35 volume%, and the second plasticizer at 8 volume%.

[0124] Immediately after mixing, a degassing process was performed under vacuum for 1 to 2 hours to remove air bubbles inside the slurry.

[0126] 2) Preparation of electrode active layer slurry

[0127] oxide powder NiO-AFL (surface area 8-10 m²) 2 ·g -1 , Kceracell, South Korea) and YSZ powder (surface area 16±2 m²) 2 ·g -1 Except for using (Tosoh, Japan), it was prepared in the same way as the above electrolyte layer slurry.

[0129] 3) Preparation of support layer slurry

[0130] as oxide powder NiO powder (surface area 0.35 m²) 2 ·g -1 , Terra Fuel Cell, South Korea) and 8 mol% Y2O3-doped ZrO2 (8YSZ) powder (surface area 7±2 m²) 2 ·g -1 Except for using (Tosoh, Japan), it was prepared in the same way as the above electrolyte layer slurry.

[0132] 4) Preparation of electrodes for solid oxide fuel cells

[0133] An electrolyte slurry was applied to a substrate using a tape caster (model STC-14A, Hansung system, South Korea) and by adjusting the doctor blade height to 30 μm, and dried for 5 minutes in a 20 ℃ environment to form a pre-electrolyte layer.

[0134] Subsequently, the electrode active layer slurry was applied onto the pre-electrolyte layer by a tape casting process with the doctor blade height adjusted to 80 μm, and the pre-electrolyte active layer was formed by drying at 20°C for 10 minutes.

[0135] The above preliminary support layer was formed by adjusting the doctor blade height to 1000 μm and using the support layer slurry on top of the above preliminary electrode active layer by a tape casting process, and dried for about 12 hours under conditions of about 30 ℃.

[0137] (2) Manufacturing of solid oxide fuel cells

[0138] The dried electrode laminate was pre-sintered at 900°C for 2 hours to form a circular half-paper by punching and to remove organic material.

[0139] An electrode laminate with an electrolyte approximately 3 μm thick was prepared by sintering a pre-sintered half-paper at 1400°C for 5 hours.

[0140] The 10 mol% Gd-doped CeO2 (GDC) diffusion barrier layer is GDC (GDC10-HP, surface area 11.3 m²) 2 ·g -1 A GDC slurry prepared by mixing a , Fuel Cell Materials, USA) and an organic binder (ESL, Ferro Corporation, USA) was screen printed onto the electrolyte layer of an electrode laminate. The weight ratio of GDC to ESL was 1:1.

[0141] The compositions were mixed and degassed for 5 minutes each using a centrifugal mixer (Thinky, USA). The barrier layer was sintered at 1250°C for 2 hours.

[0142] Afterwards, an area of ​​0.5 cm 2 The air electrode was screen printed onto the sintered GDC layer and then heat-treated at 1100° for 1 hour.

[0143] The air electrode slurry is (La 0.6 Sr 0.4 ) 0.97 Co 0.2 Fe 0.8 O3(LSCF) (K-Ceracell, Korea, 5-10 m²·g -1 ) and GDC were mixed in a volume ratio of 6:4, and then the LSCF-GDC composite powder and ESL were mixed in a weight ratio of 1:1 using a centrifuge to prepare the product.

[0145] Example 2

[0146] A solid oxide fuel cell was manufactured in the same manner as in Example 1, except that the height of the doctor blade was changed when manufacturing the preliminary cathode active layer so that the thickness of the cathode active layer was 17 μm.

[0148] Example 3

[0149] A solid oxide fuel cell was manufactured in the same manner as in Example 1, except that the height of the doctor blade was changed when manufacturing the preliminary cathode active layer so that the thickness of the cathode active layer was 38 μm.

[0151] Example 4

[0152] A solid oxide fuel cell was prepared in the same manner as in Example 1, except that the oxide powder and additives (dispersant, binder, first plasticizer, and second plasticizer) were mixed in a volume ratio of 39:61 and the solvent was prepared in such a way that the solvent accounted for 75 volume% of the total volume of the electrolyte layer slurry.

[0153] Of the total volume of additives, the dispersant was prepared at 30 volume%, the binder at 35 volume%, the first plasticizer at 27 volume%, and the second plasticizer at 8 volume%.

[0155] Example 5

[0156] A solid oxide fuel cell was manufactured in the same manner as in Example 1, except that the solvent was used to prepare a slurry of 75 volume% of the total volume of the electrolyte layer slurry.

[0157] Of the total volume of additives, the dispersant was prepared at 22 volume%, the binder at 35 volume%, the first plasticizer at 35 volume%, and the second plasticizer at 8 volume%.

[0159] Example 6

[0160] A solid oxide fuel cell was prepared in the same manner as in Example 1, except that the solvent used to prepare the slurry was a mixture of ethanol and toluene in a mass ratio of 1:4.

[0161] Of the total volume of additives, the dispersant was prepared at 12 volume%, the binder at 45 volume%, the first plasticizer at 35 volume%, and the second plasticizer at 8 volume%.

[0163] Comparative Example 1

[0164] (1) Preparation of electrodes for solid oxide fuel cells

[0165] The electrode active layer and the electrolyte layer were prepared separately by dip coating and spin coating, respectively, and the pre-support layer was applied onto the electrode active layer and dried in the same manner as in Example 1.

[0166] Then, the dried pre-support layer was formed into a circular shape using a 22Φ punch and pre-sintered at 900°C for 2 hours. One side of the support layer featured a NiO-YSZ electrode active layer (AFL) prepared via dip coating technology, and the opposite side was covered with Parafilm. After drying, an electrolyte slurry was spin-coated to form a pre-electrolyte layer on top of the electrode active layer.

[0167] The fabricated pre-electrode laminate was pre-sintered at 900°C for 2 hours to remove organic material, and then sintered at 1430°C for 5 hours to produce an electrode laminate containing an electrolyte with a thickness of about 3 μm.

[0169] (2) Manufacturing of solid oxide fuel cells

[0170] A solid oxide fuel cell was manufactured using the same method as in Example 1, except for the method of manufacturing the electrode for the solid oxide fuel cell.

[0172] Experimental Example

[0173] (1) Microstructure analysis

[0174] In the Examples and Comparative Example 1, the microstructure of the solid oxide fuel cell was investigated using a field emission scanning electron microscope (FE-SEM, Hitachi High-Tech S-4700, Japan). The Examples and Comparative Example were sputter-coated with a platinum thin film to prevent localized electric charging during investigation. Additionally, the thickness of the electrode active layer was measured using a digital vernier caliper (Mitutoyo, Japan).

[0175] FIGS. 3a to 3e are SEM images of cross-sections of solid oxide fuel cells according to Example 1, Examples 4 to 6 and Comparative Example 1.

[0176] Referring to FIGS. 3a and 3e, compared to Comparative Example 1, Example 1 includes an improved interface between the electrode active layer and the electrolyte, and the number of pores observed visually was smaller.

[0177] FIGS. 3a, FIGS. 3b to 3d are SEM images of cross-sections of solid oxide fuel cells of Example 1, Example 4 to Example 6.

[0178] Referring to FIG. 3a, in Example 1, the solvent mixture is formed as an azeotropic mixture, so the pre-electrode laminate evaporates uniformly, thereby reducing the occurrence of defects during the manufacturing process of the electrode laminate.

[0179] Referring to Fig. 3b, in Example 4, there were no defects in the manufacturing process required for operation, but pores were observed visually in the electrolyte layer due to a relatively large amount of dispersant.

[0180] Referring to Fig. 3c, in Example 5, the oxide powder and additive were adjusted to a volume ratio of 1:1 to maintain a low-viscosity slurry, but pores were visually observed in the electrolyte layer due to the interaction between the dispersant and the binder.

[0181] Referring to FIG. 3d, in Example 6, the volume percentage of the binder was increased instead of the dispersant, and the volume percentage of the solvent was increased to maintain a low-viscosity slurry, but the drying speed was uneven due to the increased solvent content, resulting in defects or non-uniformity in the tape.

[0183] The results of measuring the thickness of the electrode active layer are shown in Table 1 below.

[0185] division Electrode active layer thickness (μm) Example 1 11 Example 2 17 Example 3 38 Comparative Example 1 11

[0187] (2) Analysis of electrochemical characteristics

[0188] In the Examples and Comparative Example 1, 250 sccm of air was injected into the anode and 250 sccm of H2-3%H2O into the cathode using a mass flow controller (MKS Instruments, USA), and electrochemical impedance spectroscopy (EIS) and current-voltage-power (IVP) characteristics were measured at 800°C using a PotentioStat / GalvanoStat (WonaTech, ZIVE MP5).

[0189] EIS was measured in a frequency range of 106-10-1 Hz with an amplitude of 10 mV at open circuit voltage (OCV), and the voltage loss with respect to an increase in current density is called polarization, and the ohmic area specific resistance (ASRohmic) corresponds to the intersection point of the high frequency crossover and the real axis of impedance, and the polarization resistance (ASRpolarization) can be calculated as the difference between the high frequency crossover and the low frequency crossover point on the real axis of impedance.

[0190] The IVP characteristic is also 10mA·s -1 To simulate fuel cell (FC) mode and electrolysis cell (EC) mode at scanning speeds, measurements were taken at negative and positive current biases. To prevent overload of the measured cells, the cutoff voltage was set to 0.35 V for FC mode and 1.45 V for EC mode.

[0191] In electrolysis cell mode and fuel cell mode, the current density was measured at 1.3 V.

[0192] To control the water vapor pressure of the solid oxide fuel cell electrode, H2 and O2 gases underwent combustion reactions via a Pt catalyst. A heating jacket and heating tape were used to prevent water vapor condensation on the electrode contour of the solid oxide fuel cell.

[0193] During the measurement, humidified hydrogen (pH2O = 0.03 atm) and air (pO2 = 0.21 atm) served as fuel and oxidizer, respectively, and both gases were supplied at a rate of 250 sccm.

[0194] In addition, the Distribution of Relaxation Times (DRT) was derived using data obtained through EIS measurements.

[0195] The measurement results of ohmic area specific resistance, polarization resistance per area, and peak power density are shown in Table 2 below.

[0197] division Ohmic area specific resistance (Ω·cm) 2 ) Polarization resistance per unit area (Ω·cm) 2 ) Peak power density (W·cm²) -2 ) 1.3V current density (A / cm²) 2 ) Example 1 0.056 0.2 2.52 2.48 Example 2 0.063 0.217 2.9 2.21 Example 3 0.052 0.259 2.54 1.61 Comparative Example 1 0.044 0.544 2.03 0.81

[0199] Referring to Table 2, as the ohmic area specific resistance of Example 1 decreases compared to Comparative Example 1, it can be confirmed that the bonding characteristics at the anode and electrolyte interface are improved and the internal resistance is reduced.

[0200] FIG. 4a is a graph showing the impedance of solid oxide fuel cells according to Example 1 and Comparative Example 1 in fuel cell mode.

[0201] FIG. 4b is a graph showing the impedance of solid oxide fuel cells according to Example 1 and Comparative Example 1 in electrolysis mode.

[0202] FIG. 4c is a graph showing the impedance of solid oxide fuel cells according to Examples 1 to 3 in fuel cell mode.

[0203] Referring to Figure 4c, the polarization resistance per unit area tends to increase with the thickness of the electrode active layer, which confirms that a thick electrode active layer can hinder charge transfer and exacerbate mass transport limitations.

[0204] FIG. 4d is a graph showing the impedance of solid oxide fuel cells according to Examples 1 to 3 in electrolysis mode.

[0205] FIG. 5a is a graph showing the Distribution of Relaxation Times (DRT) measured according to Example 1 and Comparative Example 1 in fuel cell mode.

[0206] Referring to Fig. 5a, it can be seen that the P2, P3, and P4 peaks of DRT in Example 1 showed lower values ​​compared to Comparative Example 1. The P2 and P3 peaks are associated with the mass transfer overpotential of the fuel electrode, and P4 is associated with a reduction in electrode activation loss.

[0207] The main factors in electrode activation loss are electrode reaction kinetics and oxygen ion transfer efficiency through the electrolyte interface, but the improved interface in Example 1 promoted better connectivity and distribution of ion diffusion pathways. Accordingly, overall fuel cell performance could be improved.

[0208] FIG. 5b is a graph showing the Distribution of Relaxation Times (DRT) measured according to Example 1 and Comparative Example 1 in electrolysis mode.

[0209] FIG. 5c is a graph showing the Distribution of Relaxation Times (DRT) measured according to Examples 1 to 3 in fuel cell mode.

[0210] Referring to Fig. 5c, it can be seen that the P2 peak of the DRT showed a higher value in Example 1 compared to Examples 2 to 3. This indicates that the change in thickness of the electrode active layer is highly correlated with the P2 region, and that the reaction sites in the electrode active layer of Example 1 are relatively insufficient, which may cause an excessive voltage drop at high current densities.

[0211] FIG. 5d is a graph showing the Distribution of Relaxation Times (DRT) measured according to Examples 1 to 3 in electrolysis mode.

[0212] Referring to Fig. 5d, it can be seen that Example 1 showed lower values ​​compared to Examples 2 to 3, including the P2 peak of DRT. This indicates that the thin thickness of the electrode active layer in Example 1 allowed larger water vapor molecules to easily access the reaction site due to its high permeability. Accordingly, the efficiency of decomposing water into hydrogen and oxygen was increased, providing superior electrolysis performance.

[0213] Referring to Table 2, it was confirmed that the peak power density of the solid oxide fuel cell according to the embodiments of the present invention was increased compared to the peak power density of the solid oxide fuel cell according to Comparative Example 1.

[0214] Figure 6a is a graph of current density-voltage-power density in the fuel cell mode of solid oxide fuel cells according to Example 1 and Comparative Example 1.

[0215] Referring to Fig. 6a, Example 1 had a lower overvoltage and a higher current density compared to Comparative Example 1 at 800°C, as indicated by the IVP curve. For example, 1 A·cm -2 In this example, Example 1 showed a lower overvoltage of approximately 80 mV, and at 0.8 V, Example 1 had a higher current density of 1.98 A·cm² -2 While [it] achieved [it], Comparative Example 1 achieved 1.18 A·cm -2 It was.

[0216] The peak power density (PPD) of Comparative Example 1 is 2.03 W·cm² -2 In comparison, the peak power density of Example 1 is 2.52 W·cm² -2 It improved by about 25%.

[0217] In addition, it was confirmed that in Example 1 compared to Comparative Example 1, the region where the slope of the current density-voltage graph increases sharply appears in the higher current density region. That is, in Example 1, it was confirmed that as the mobility of oxygen ions at the electrode active layer and electrolyte interface increases, the resistance related to concentration polarization decreases.

[0218] FIG. 6b is a graph of current density-voltage-power density in the fuel cell mode of solid oxide fuel cells according to Example 1 and Comparative Example 1 in the electrolysis mode.

[0219] FIG. 6c is a graph of current density-voltage-power density in the fuel cell mode of solid oxide fuel cells according to Examples 1 to 3.

[0220] Referring to FIG. 6c, Example 1 was able to operate even at a low temperature of 750°C. In addition, at 800°C, Example 1 was 2.52 W·cm² -2 While showing a PPD of , Example 2, with an electrode active layer thickness of 17 μm, provides more reaction sites so that the voltage drop in the high current region can be mitigated, thus 2.9 W·cm 2 A higher PPD was achieved. Meanwhile, Example 3, with an electrode active layer thickness of 38 μm, achieved a relatively low PPD of 2.54 W·cm².

[0221] FIG. 6d is a graph of current density-voltage-power density in the fuel cell mode of solid oxide fuel cells according to Examples 1 to 3 in the electrolysis mode.

[0222] The above description is merely an example of applying the principles of the present disclosure, and other configurations may be included without departing from the scope of the present invention. Explanation of the symbols

[0224] 100: Air electrode 110: Diffusion barrier layer 220: Electrode active layer 300: Electrolyte layer

Claims

Claim 1 A method for manufacturing an electrode for a solid oxide fuel cell, comprising the steps of: forming a preliminary electrolyte layer; forming a preliminary electrode active layer on top of the preliminary electrolyte layer; forming a preliminary support layer on top of the preliminary electrode active layer to manufacture a preliminary electrode laminate; and sintering the preliminary electrode laminate. Claim 2 A method for manufacturing an electrode for a solid oxide fuel cell according to claim 1, wherein the step of forming the pre-electrolyte layer comprises: a step of applying an electrolyte layer slurry to a substrate; and a step of drying the applied electrolyte layer slurry. Claim 3 A method for manufacturing an electrode for a solid oxide fuel cell according to claim 2, wherein the electrolyte layer slurry comprises a solid electrolyte oxide powder, a binder, and a solvent. Claim 4 A method for manufacturing an electrode for a solid oxide fuel cell, wherein, in claim 1, the step of forming the preliminary electrode active layer comprises: applying an electrode active layer slurry onto the preliminary electrolyte layer; and drying the applied electrode active layer slurry. Claim 5 A method for manufacturing an electrode for a solid oxide fuel cell according to claim 4, wherein the electrode active layer slurry comprises a solid electrolyte oxide powder, a binder, and a solvent. Claim 6 A method for manufacturing an electrode for a solid oxide fuel cell according to claim 1, wherein a component within the pre-electrode active layer penetrates into the pre-electrode electrolyte layer. Claim 7 A method for manufacturing an electrode for a solid oxide fuel cell according to claim 1, wherein the step of forming the preliminary support layer comprises: applying a support layer slurry onto the preliminary electrode active layer; and drying the applied support layer slurry. Claim 8 A method for manufacturing an electrode for a solid oxide fuel cell according to claim 7, wherein the support layer slurry comprises a solid electrolyte oxide powder, a binder, and a solvent. Claim 9 A method for manufacturing an electrode for a solid oxide fuel cell according to claim 1, wherein a component within the preliminary support layer penetrates into the preliminary electrode active layer. Claim 10 A method for manufacturing an electrode for a solid oxide fuel cell according to any one of claims 3, 5, or 8, wherein the electrolyte layer slurry, the electrode active layer slurry, or the support layer slurry each independently further comprise a dispersant, a first plasticizer, and a second plasticizer, and the volume ratio of the dispersant, the binder, the first plasticizer, and the second plasticizer is 4 to 6: 21 to 25: 16 to 20: 2 to 6. Claim 11 A method for manufacturing an electrode for a solid oxide fuel cell according to claim 1, wherein the thickness of the electrolyte layer is 6 μm or less. Claim 12 A method for manufacturing an electrode for a solid oxide fuel cell according to claim 1, wherein the thickness of the electrode active layer is 8 μm to 20 μm. Claim 13 An electrode for a solid oxide fuel cell, manufactured by sintering the pre-electrode laminate of claim 1. Claim 14 A solid oxide fuel cell comprising: an electrode for a solid oxide fuel cell according to claim 13; an air electrode facing the electrode for the solid oxide fuel cell; and a diffusion barrier layer interposed between the electrode for the solid oxide fuel cell and the air electrode.

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