Composite electrode, method of preparation and use thereof in solid oxide fuel cells

Abstract

The present application relates to the field of solid oxide fuel cell, and especially relates to a composite electrode, a preparation method and application thereof in solid oxide fuel cell. The composite electrode is mainly composed of layered perovskite and spinel; the mass ratio of the layered perovskite and the spinel is 0.5-2.0:1. By compounding the layered perovskite with high thermal expansion coefficient and the spinel with low thermal expansion coefficient in a certain mass ratio, and by optimizing the ratio of the two, the thermal expansion coefficient of the composite electrode can be matched with the thermal expansion coefficient of the electrolyte, so that the mechanical failure problems such as interface delamination and micro-cracks caused by thermal stress are fundamentally eliminated, and the structural stability of the cell in the process of thermal cycle and long-term operation is significantly improved.

Description

Technical Field

[0001] This invention relates to the field of solid oxide fuel cells, and more particularly to a composite electrode, its preparation method, and its application in solid oxide fuel cells. Background Technology

[0002] Solid oxide fuel cells (SOFCs), as efficient and clean energy conversion devices, can directly convert the chemical energy in fuel into electrical energy, and have attracted widespread attention. However, SOFCs typically operate in high-temperature environments, placing stringent requirements on the thermal stability of the materials. Among these, the matching of the coefficients of thermal expansion (TEC) of the cathode, electrolyte, and their interface is a core factor determining the structural integrity and long-term operational stability of the battery during thermal cycling.

[0003] Currently, layered perovskite cathode materials (such as PrBaCo2O) are available. 5+δ Cobalt (BZCYYb) is considered a highly promising cathode material due to its excellent oxygen reduction reaction (ORR) catalytic activity and mixed ion-electron conductivity. However, these materials typically contain a high proportion of cobalt, resulting in a significantly higher intrinsic coefficient of thermal expansion than commonly used proton-conducting electrolytes (such as BZCYYb). This significant difference in thermal expansion coefficients leads to substantial thermal stress at the electrode-electrolyte interface during long-term temperature cycling of the battery. This stress can cause electrode delamination, interfacial microcracks, and even mechanical failure of the battery structure, severely limiting the practical application of highly active cathode materials.

[0004] To address the TEC mismatch issue, existing technologies typically employ elemental doping to reduce the intrinsic TEC of the cathode material, or introduce a second phase to form a composite material to regulate the overall thermal expansion behavior. However, elemental doping often comes at the cost of sacrificing the material's electrochemical activity; while simple physical compositing can adjust the overall expansion coefficient to some extent, during high-temperature operation, if there is a lack of effective chemical interaction between the two composite phases, it is often difficult to guarantee long-term phase stability and interface continuity, and may even reduce the electrode's power output due to high contact resistance between the two phases.

[0005] Therefore, existing technologies need to be improved. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this invention is to provide a composite electrode, a preparation method and its application in solid oxide fuel cells, aiming to solve the problem that the thermal expansion coefficient (TEC) of layered perovskite cathode materials (such as PBC) is too high and does not match that of proton conductor electrolytes (such as BZCYYb) in existing solid oxide fuel cells (SOFCs).

[0007] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a composite electrode, mainly composed of layered perovskite and spinel; the mass ratio of the layered perovskite to spinel is 0.5~2.0:1.

[0008] Optionally, the layered perovskite is PrBaCo2O 5+δ PrBaFe2O 5+δ PrBaMn2O 5+δ .

[0009] Optionally, the spinel is NiFe2O4, ZnFe2O4, LiMn2O4, or LaFe2O4.

[0010] Secondly, the present invention provides a method for preparing a composite electrode, comprising the following steps: S1. Preparation of layered perovskite powder and spinel powder; S2. Mix layered perovskite powder and spinel powder, add an organic carrier, and grind into a slurry; S3. The prepared slurry is coated onto the support substrate and then sintered to form the composite electrode. The mass ratio of the layered perovskite to spinel is 0.5~2.0:1.

[0011] Optionally, in step S1, perovskite powder and spinel powder are prepared by sol-gel method.

[0012] Specifically, the method for preparing perovskite powder includes the following steps: The perovskite nitrate precursor was dissolved in water and stirred until dissolved to obtain a perovskite precursor solution. Ethylenediaminetetraacetic acid and citric acid were added to the perovskite precursor solution, and the pH was adjusted to 7-9 using ammonia water to obtain mixed solution one. The mixed solution was stirred and heated to a sol-gel state, and then dried at 160~200℃ for more than 6 hours to obtain the perovskite precursor (black powder). The obtained perovskite precursor was calcined in air at 900~1000℃ for 4-6 hours to obtain the desired perovskite powder.

[0013] Specifically, the preparation method of spinel powder includes the following steps: The spinel nitrate precursor was dissolved in water and stirred until dissolved to obtain a spinel precursor solution. Ethylenediaminetetraacetic acid and citric acid were added to the spinel precursor solution, and the pH was adjusted to 7-9 using ammonia water to obtain mixed solution two. The mixed solution was stirred and heated to a sol-gel state, and then dried at 160~200℃ for more than 6 hours to obtain spinel precursor (black powder). The obtained spinel precursor was calcined in air at 900~1000℃ for 4-6 hours to obtain the desired spinel powder.

[0014] Optionally, in step S2, ball milling is used for grinding.

[0015] Optionally, in step S3, the sintering temperature is 900~1100℃; the sintering time is 1~5 hours.

[0016] Optionally, in step S3, the supporting substrate is a substrate made of an electrolyte; the electrolyte is BaZr. 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ YSZ (ZrO2 doped with Y2O3), La 0.8 Sr 0.2 Ga 0.9 Mg 0.1 O 3-δ GDC (Gd-doped CeO2) and SDC (Sm-doped CeO2).

[0017] Thirdly, the present invention provides an application of the composite electrode described above as a cathode electrode in a solid oxide fuel cell.

[0018] Fourthly, the present invention provides a solid oxide fuel cell, comprising an anode, an electrolyte, and a cathode, wherein the cathode is the composite electrode described above.

[0019] Optionally, the electrolyte is BaZr. 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ YSZ (ZrO2 doped with Y2O3), La 0.8 Sr 0.2 Ga 0.9 Mg 0.1 O 3-δ GDC (Gd-doped CeO2) and SDC (Sm-doped CeO2).

[0020] Beneficial Effects: This invention provides a composite electrode, its preparation method, and its application in solid oxide fuel cells. This invention combines layered perovskite (such as PBC) with spinel (such as NiFe2O4) of high thermal expansion coefficient in a certain mass ratio. By optimizing the ratio of the two, it is possible to make their thermal expansion coefficient comparable to that of the electrolyte (such as BaZr). 0.1Ce 0.7 Y 0.1 Yb 0.1 O 3-δ The coefficient of thermal expansion is matched, which fundamentally eliminates mechanical failure problems such as interface delamination and microcracks caused by thermal stress, and significantly improves the structural stability of the battery during thermal cycling and long-term operation. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating the preparation process of the composite electrode in an embodiment of the present invention; Figure 2 This is a comparison diagram of the thermal expansion coefficients of the composite electrodes prepared in the embodiments of the present invention; Figure 3 This is a comparison chart of the EIS test results of single cells prepared in the comparative example (pure PBC cathode) and the example (PBC-NiFeO composite cathode) of this invention at 600°C. Figure 4 This is a comparison chart of the long-term stability test (constant current discharge voltage versus time curve) of single cells prepared in the comparative example (pure PBC cathode) and the example (PBC-NiFeO composite cathode) of the present invention at 550℃. Detailed Implementation

[0022] This invention provides a composite electrode, its preparation method, and its application in solid oxide fuel cells. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0023] The commercialization of solid oxide fuel cells (SOFCs) has consistently been hampered by the challenge of balancing the thermomechanical stability and electrochemical performance of materials under high-temperature operating conditions. While layered perovskite cathode materials (such as PBCs) have emerged as key candidates for overcoming the performance bottlenecks of traditional cathodes due to their excellent oxygen reduction reaction (ORR) catalytic activity and mixed ion-electron conductivity, the high cobalt content results in a significantly higher intrinsic coefficient of thermal expansion (TEC), which is inconsistent with commonly used proton conductor electrolytes (such as BaZr). 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ There is an irreconcilable TEC difference between the spinel materials (BZCYYb, abbreviated as BZCYYb), and this core contradiction has become a major technical barrier restricting the practical application of highly active cathode materials. The spinel materials, such as nickel-iron spinel (NiFe2O4), have a low coefficient of thermal expansion (typically around 10 × 10⁻⁶). -6 K -1It has good chemical stability and certain catalytic activity at medium and high temperatures (around 1000-1000 ppm).

[0024] Existing solutions to the TEC mismatch problem all have significant limitations: while elemental doping strategies can reduce the intrinsic TEC of layered perovskites to some extent, they often disrupt the integrity of the material's crystal structure, leading to a decrease in ORR catalytic activity and ion-electron conduction efficiency, resulting in a dilemma of "increased stability at the expense of increased activity"; simple physical composite methods can regulate overall thermal expansion behavior by introducing a low-thermal-expansion second phase, but the lack of effective chemical interaction between the two phases makes them prone to phase separation and interface delamination during long-term high-temperature operation of SOFCs. This not only fails to guarantee long-term phase stability and interface continuity but may also lead to a decrease in electrode power output due to increased contact resistance between the two phases, making it difficult to simultaneously improve thermomechanical stability and electrochemical performance. Existing research has shown that the interfacial effect of proportional control in composite systems is key to determining the synergy between thermal expansion matching and electrochemical performance. However, existing composite schemes have not achieved precise synergistic optimization of both, and cannot fundamentally solve mechanical failure problems such as electrode delamination and microcracks caused by thermal stress.

[0025] Based on this, this embodiment provides a composite electrode, mainly composed of layered perovskite and spinel; the mass ratio of the layered perovskite to spinel is 0.5~2.0:1.

[0026] It should be noted that this embodiment combines layered perovskite (such as PBC) with a certain mass ratio of high thermal expansion coefficient and spinel (such as NiFe2O4, NiFeO). By optimizing the ratio of the two, it is possible to make its thermal expansion coefficient similar to that of the electrolyte (such as BaZr). 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ The thermal expansion coefficients of the composite electrode (such as BaZr, BZCYYb) are matched, fundamentally eliminating mechanical failure problems such as interface delamination and microcracks caused by thermal stress, and significantly improving the structural stability of the battery during thermal cycling and long-term operation. By adjusting the composite ratio, the average thermal expansion coefficient of the composite electrode in this embodiment can be made to match that of the corresponding electrolyte (such as BaZr) within the room temperature operating range. 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ The difference in the average coefficient of thermal expansion is controlled within ±5×10. -6 K -1 Within this range. For example, when the mass ratio of PBC to NiFeO is 1:1, the TEC of the composite electrode can be tuned to 14.0 × 10⁻⁶. -6 K -1It is well-matched with the TEC of BZCYYb electrolyte.

[0027] In some embodiments, the layered perovskite is PrBaCo2O 5+δ PrBaFe2O 5+δ PrBaMn2O 5+δ .

[0028] In some embodiments, the spinel is NiFe2O4, ZnFe2O4, LiMn2O4, or LaFe2O4.

[0029] This embodiment also provides a method for preparing a composite electrode, such as... Figure 1 As shown, it includes the following steps: S1. Preparation of layered perovskite powder and spinel powder; S2. Mix layered perovskite powder and spinel powder, add an organic carrier, and grind into a slurry; S3. The prepared slurry is coated onto the support substrate and then sintered to form the composite electrode. The mass ratio of the layered perovskite to spinel is 0.5~2.0:1.

[0030] It should be noted that in this embodiment, layered perovskite powder with a high coefficient of thermal expansion and spinel powder with a low coefficient of thermal expansion are physically mixed in a preset ratio. The mixed powder is then made into a slurry, coated onto the surface of a supporting substrate (proton conductor electrolyte), and calcined at high temperature to induce an in-situ ion exchange reaction at the interface between the layered perovskite phase and the spinel phase, thus preparing a composite electrode with thermal expansion matching characteristics. This embodiment utilizes high-temperature calcination to induce ion exchange between the two phases (layered perovskite and spinel). This in-situ reaction not only optimizes the phase structure of the material at the microscopic level but also constructs a strong chemical bond at the phase interface, reducing the interfacial contact resistance and improving the phase stability of the composite electrode under medium and high temperature conditions. The ion-exchanged composite electrode not only retains the high conductivity of the layered perovskite but also the introduction of the spinel phase increases the active sites at the three-phase interface (TPB), synergistically promoting the oxygen reduction reaction kinetics and ensuring that the applied battery still has excellent power output under thermal matching conditions. Moreover, the method of this invention adopts traditional physical mixing and ceramic preparation processes, which do not require complex equipment or expensive processes, and are easy to achieve large-scale production and widespread application.

[0031] In one embodiment, in step S1, perovskite powder and spinel powder are prepared by sol-gel method.

[0032] Specifically, the method for preparing perovskite powder includes the following steps: The perovskite nitrate precursor was dissolved in water and stirred until dissolved to obtain a perovskite precursor solution. Ethylenediaminetetraacetic acid and citric acid were added to the perovskite precursor solution, and the pH was adjusted to 7-9 using ammonia water to obtain mixed solution one. The mixed solution was stirred and heated to a sol-gel state, and then dried at 160~200℃ for more than 6 hours to obtain the perovskite precursor (black powder). The obtained perovskite precursor was calcined in air at 900~1000℃ for 4-6 hours to obtain the desired perovskite powder.

[0033] Specifically, the preparation method of spinel powder includes the following steps: The spinel nitrate precursor was dissolved in water and stirred until dissolved to obtain a spinel precursor solution. Ethylenediaminetetraacetic acid and citric acid were added to the spinel precursor solution, and the pH was adjusted to 7-9 using ammonia water to obtain mixed solution two. The mixed solution was stirred and heated to a sol-gel state, and then dried at 160~200℃ for more than 6 hours to obtain spinel precursor (black powder). The obtained spinel precursor was calcined in air at 900~1000℃ for 4-6 hours to obtain the desired spinel powder.

[0034] In one embodiment, in step S2, ball milling or ultrasonic dispersion is used for grinding. This mixing method includes, but is not limited to, mechanical ball milling, ultrasonic dispersion, etc., as long as it can ensure that the two phases are evenly distributed.

[0035] In one embodiment, the organic carrier may be a mixture of isopropanol, ethylene glycol, and glycerol.

[0036] In one embodiment, in step S3, the sintering temperature is 900~1100℃ (e.g., 900℃, 910℃, 920℃, 930℃, 940℃, 950℃, 960℃, 970℃, 980℃, 990℃, 1000℃, 1010℃, 1020℃, 1030℃, 1040℃, 1050℃, 1060℃, 1070℃, 1080℃, 1090℃, 1100℃); the sintering time is 1~5 hours (e.g., 1 hour, 2 hours, 3 hours, 4 hours, 5 hours). This embodiment needs to ensure a good interfacial bond between the composite electrode and the electrolyte, while allowing the composite electrode material to exchange, enabling ion exchange between PBC and NiFeO to form a porous composite cathode.

[0037] In one embodiment, in step S3, the supporting substrate is a substrate made of an electrolyte; the electrolyte is BaZr. 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ YSZ (ZrO2 doped with Y2O3), La 0.8 Sr 0.2 Ga 0.9 Mg 0.1 O 3-δ GDC (Gd-doped CeO2) and SDC (Sm-doped CeO2).

[0038] This embodiment also provides an application of the aforementioned composite electrode as a cathode electrode in a solid oxide fuel cell.

[0039] This embodiment also provides a solid oxide fuel cell, including an anode, an electrolyte, and a cathode, wherein the cathode is the composite electrode described above.

[0040] In one embodiment, the electrolyte is BaZr. 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ YSZ (ZrO2 doped with Y2O3), La 0.8 Sr 0.2 Ga 0.9 Mg 0.1 O 3-δ GDC (Gd-doped CeO2) and SDC (Sm-doped CeO2).

[0041] It should be noted that the electrolyte material BaZr in this embodiment 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ It is a high-performance proton-conducting electrolyte with high conductivity in the medium temperature range (500-700℃), but its coefficient of thermal expansion (approximately 8~10×10⁻⁶) is relatively low. -6 K -1 The composite electrode in this embodiment is incompatible with existing PBCs (within the specified range). By optimizing the ratio of PBC to NiFeO spinel, the difference between the average coefficient of thermal expansion of the composite electrode and the average coefficient of thermal expansion of the BZCYYb electrolyte is controlled within 5 × 10⁻⁶ °C in the range from room temperature to SOFC operating temperature (e.g., 600-800 °C). -6 K -1 Within this range. For example, when the mass ratio of PBC to NiFeO is 1:1, the TEC of the composite electrode can be tuned to 14.0 × 10⁻⁶. -6K -1 It is well-matched with the TEC of BZCYYb electrolyte.

[0042] The present invention will be further described below through specific embodiments.

[0043] Example 1 1. Layered perovskite powder (PrBaCo2O) was prepared using the solvent gelation method. 5+δ The preparation method of layered perovskite powder (PBC) includes the following steps: 0.01 mol of Pr(NO3)3, Ba(NO3)2, and Co(NO3)2 raw materials are weighed and dissolved in pure water to obtain a perovskite precursor solution; 0.04 mol of ethylenediaminetetraacetic acid and 0.08 mol of citric acid are added, and the pH is adjusted to 7 with ammonia to obtain mixed solution one; mixed solution one is stirred and heated to a sol-gel state, and dried at 160℃ for 6 hours to obtain perovskite precursor (black powder); the obtained perovskite precursor is calcined in air at 1000℃ for 5 hours to obtain the desired PBC powder. The preparation method of spinel powder (NiFe2O4, NiFeO) includes the following steps: 0.01 mol of NiNO3 and Fe(NO3)3 raw materials are weighed and dissolved in pure water to obtain a NiFeO precursor solution; 0.02 mol of ethylenediaminetetraacetic acid and 0.04 mol of citric acid are added, and the pH value is adjusted to 7 with ammonia water to obtain a mixed solution two; the mixed solution two is stirred and heated to a sol-gel state, and dried at 160℃ for 6 hours to obtain the NiFeO precursor (black powder); the obtained NiFeO precursor is calcined in air at 1000℃ for 5 hours to obtain NiFeO powder.

[0044] 2. Composite Electrode Preparation: The obtained PBC powder and NiFeO powder were mixed at a mass ratio of 1:1, and anhydrous ethanol was added as a medium. The mixture was ball-milled at 400 rpm for 10 hours in a high-energy ball mill to ensure uniform mixing. The ball-milled slurry was dried to obtain PBC-NiFeO composite powder. The PBC-NiFeO composite powder was then ball-milled again with an organic carrier (a mixture of isopropanol, ethylene glycol, and glycerol) to prepare a slurry of suitable viscosity.

[0045] 3. First, a NiO-BZCYYb anode support is prepared. This involves pre-combining a BZCYYb electrolyte substrate (approximately 18 μm thick) with NiO to form the NiO-BZCYYb anode support. Then, the resulting cathode slurry is sprayed onto one side of the dense BZCYYb electrolyte substrate. After spraying, the green body is dried at 180°C on a heating table and then sintered in a muffle furnace at 1000°C for 2 hours to form a porous cathode layer, ultimately obtaining a single cell with a NiO-BZCYYb anode support / BZCYYb dense electrolyte / 1PBC-1NiFeO porous cathode. During this process, the high temperature provides kinetic conditions that induce in-situ ion exchange reactions between the PBC phase and the NiFeO phase at the contact interface.

[0046] Example 2 1. Layered perovskite powder (PrBaCo2O) was prepared using the solvent gelation method. 5+δ The preparation method of layered perovskite powder (PBC) includes the following steps: 0.01 mol of Pr(NO3)3, Ba(NO3)2, and Co(NO3)2 raw materials are weighed and dissolved in pure water to obtain a perovskite precursor solution; 0.04 mol of ethylenediaminetetraacetic acid and 0.08 mol of citric acid are added, and the pH is adjusted to 7 with ammonia to obtain mixed solution one; mixed solution one is stirred and heated to a sol-gel state, and dried at 160℃ for 6 hours to obtain perovskite precursor (black powder); the obtained perovskite precursor is calcined in air at 1000℃ for 5 hours to obtain the desired PBC powder. The preparation method of spinel powder (NiFe2O4, NiFeO) includes the following steps: Weigh 0.01 mol of NiNO3 and Fe(NO3)3 raw materials, dissolve them in pure water to obtain a NiFeO precursor solution; add 0.02 mol of ethylenediaminetetraacetic acid and 0.04 mol of citric acid, and adjust the pH value to 7 with ammonia water to obtain mixed solution two; stir mixed solution two and heat it to a sol-gel state, and dry it at 160℃ for 6 hours to obtain NiFeO precursor (black powder); calcine the obtained NiFeO precursor in air at 1000℃ for 5 hours to obtain NiFeO powder.

[0047] 2. Composite Electrode Preparation: The obtained PBC powder and NiFeO powder were mixed at a mass ratio of 2:1, and anhydrous ethanol was added as a medium. The mixture was ball-milled at 400 rpm for 10 hours in a high-energy ball mill to ensure uniform mixing. The ball-milled slurry was dried to obtain PBC-NiFeO composite powder. The PBC-NiFeO composite powder was then ball-milled again with an organic carrier (a mixture of isopropanol, ethylene glycol, and glycerol) to prepare a cathode slurry of suitable viscosity.

[0048] 3. First, a NiO-BZCYYb anode support is prepared. This involves pre-combining a BZCYYb electrolyte substrate (approximately 18 μm thick) with NiO to form the NiO-BZCYYb anode support. Then, the resulting cathode slurry is sprayed onto one side of the dense BZCYYb electrolyte substrate. After spraying, the green body is dried at 180°C on a heating table and then sintered in a muffle furnace at 1000°C for 2 hours to form a porous cathode layer, ultimately obtaining a single cell with a NiO-BZCYYb anode support / BZCYYb dense electrolyte / 1PBC-1NiFeO porous cathode. During this process, the high temperature provides kinetic conditions that induce in-situ ion exchange reactions between the PBC phase and the NiFeO phase at the contact interface.

[0049] The difference between this embodiment and Embodiment 1 is that the mass ratio of PBC to NiFeO in step 2 is adjusted to 2:1.

[0050] Example 3 1. Layered perovskite powder (PrBaCo2O) was prepared using the solvent gelation method. 5+δ The preparation method of layered perovskite powder (PBC) includes the following steps: 0.01 mol of Pr(NO3)3, Ba(NO3)2, and Co(NO3)2 raw materials are weighed and dissolved in pure water to obtain a perovskite precursor solution; 0.04 mol of ethylenediaminetetraacetic acid and 0.08 mol of citric acid are added, and the pH is adjusted to 7 with ammonia to obtain mixed solution one; mixed solution one is stirred and heated to a sol-gel state, and dried at 160℃ for 6 hours to obtain perovskite precursor (black powder); the obtained perovskite precursor is calcined in air at 1000℃ for 5 hours to obtain the desired PBC powder. The preparation method of spinel powder (NiFe2O4, NiFeO) includes the following steps: Weigh 0.01 mol of NiNO3 and Fe(NO3)3 raw materials, dissolve them in pure water to obtain a NiFeO precursor solution; add 0.02 mol of ethylenediaminetetraacetic acid and 0.04 mol of citric acid, and adjust the pH value to 7 with ammonia water to obtain mixed solution two; stir mixed solution two and heat it to a sol-gel state, and dry it at 160℃ for 6 hours to obtain NiFeO precursor (black powder); calcine the obtained NiFeO precursor in air at 1000℃ for 5 hours to obtain NiFeO powder.

[0051] 2. Composite Electrode Preparation: The obtained PBC powder and NiFeO powder were mixed at a mass ratio of 1:2, and anhydrous ethanol was added as a medium. The mixture was ball-milled at 400 rpm for 10 hours in a high-energy ball mill to ensure uniform mixing. The ball-milled slurry was dried to obtain PBC-NiFeO composite powder. The PBC-NiFeO composite powder was then ball-milled again with an organic carrier (a mixture of isopropanol, ethylene glycol, and glycerol) to prepare a cathode slurry with suitable viscosity.

[0052] 3. First, a NiO-BZCYYb anode support is prepared. This involves pre-combining a BZCYYb electrolyte substrate (approximately 18 μm thick) with NiO to form the NiO-BZCYYb anode support. Then, the resulting cathode slurry is sprayed onto one side of the dense BZCYYb electrolyte substrate. After spraying, the green body is dried at 180°C on a heating table and then sintered in a muffle furnace at 1000°C for 2 hours to form a porous cathode layer, ultimately obtaining a single cell with a NiO-BZCYYb anode support / BZCYYb dense electrolyte / 1PBC-1NiFeO porous cathode. During this process, the high temperature provides kinetic conditions that induce in-situ ion exchange reactions between the PBC phase and the NiFeO phase at the contact interface.

[0053] The difference between this embodiment and Embodiment 1 is that the mass ratio of PBC to NiFeO in step 2 is adjusted to 1:2.

[0054] Comparative Example 1 1. Layered perovskite powder (PrBaCo2O) was prepared using the solvent gelation method. 5+δ The preparation method of layered perovskite powder (PBC) includes the following steps: 0.01 mol of Pr(NO3)3, Ba(NO3)2, and Co(NO3)2 raw materials are weighed and dissolved in pure water to obtain a perovskite precursor solution; ethylenediaminetetraacetic acid and citric acid are added, and the pH value is adjusted to 7 using ammonia water to obtain mixed solution one; mixed solution one is stirred and heated to a sol-gel state, and dried at 160℃ for 6 hours to obtain a perovskite precursor (black powder); the obtained perovskite precursor is calcined in air at 1000℃ for 5 hours to obtain the desired PBC powder.

[0055] 2. Electrode Preparation: The obtained PBC powder was mixed with anhydrous ethanol as a medium and ball-milled at 400 rpm for 10 hours in a high-energy ball mill to ensure uniform mixing. The ball-milled slurry was dried to obtain PBC powder. The PBC powder was then ball-milled again with an organic carrier (such as a mixture of isopropanol, ethylene glycol, and glycerol) to prepare a cathode slurry of suitable viscosity.

[0056] 3. First, a NiO-BZCYYb anode support is prepared. This involves pre-combining a BZCYYb electrolyte substrate (approximately 18 μm thick) with NiO to form the NiO-BZCYYb anode support. Then, the resulting cathode slurry is sprayed onto one side of the dense BZCYYb electrolyte substrate. After spraying, the green body is dried at 180°C on a heating table and then sintered in a muffle furnace at 1000°C for 2 hours to form a porous cathode layer, ultimately obtaining a single cell with a NiO-BZCYYb anode support / BZCYYb dense electrolyte / 1PBC-1NiFeO porous cathode. During this process, the high temperature provides kinetic conditions that induce in-situ ion exchange reactions between the PBC phase and the NiFeO phase at the contact interface.

[0057] The difference between this comparative example and Example 1 is that a pure PBC cathode cell was used in step 1, without the addition of NiFeO spinel.

[0058] Test results: The electrode materials obtained in Examples 1, 2, 3, and Comparative Example 1 were tested using a thermal expansion tester, and the results are as follows: Figure 2 As shown, the average TEC of pure PBC (Comparative Example 1) is as high as 22.8 × 10⁻⁶. -6 K -1 This is significantly higher than the 9.0 × 10⁻⁶ of BZCYYb electrolyte. -6 K -1 The PBC-NiFeO composite material prepared in Example 1, due to the introduction of a spinel phase with a low coefficient of thermal expansion and the adjustment of the crystal lattice by ion exchange, had an average TEC reduced to 14.0 × 10⁻⁶. -6 K -1 At this point, the difference in thermal expansion coefficients between the composite electrode and the BZCYYb electrolyte decreases, thus effectively alleviating interfacial thermal stress. Similarly, in Examples 2 and 3, due to the introduction of the low-expansion-coefficient spinel phase and the adjustment of the crystal lattice by ion exchange, the average TEC decreased to 17.0 × 10⁻⁶. -6 K -1 14.0×10 -6 K -1 This can also reduce the difference in the coefficient of thermal expansion between the composite electrode and the BZCYYb electrolyte.

[0059] At an operating temperature of 600°C, electrochemical impedance spectroscopy (EIS) tests were performed on the single cell prepared in Example 1 (PBC:NFO = 2:1 composite cathode) and the single cell in Comparative Example 1 (pure PBC cathode). The results are as follows: Figure 3As shown, the impedance semicircle diameter of the composite cathode is significantly smaller than that of the pure PBC cathode, and the high-frequency ohmic intercepts of the two are basically the same, indicating that the ohmic impedances are similar. The difference mainly comes from the kinetic resistance of the oxygen reduction reaction on the cathode side. This directly proves that the introduction of NFO effectively optimizes the oxygen reduction reaction kinetics, increases the catalytic active sites and improves the ion-electron transport network, significantly reduces charge transfer and concentration polarization losses, and thus improves the electrochemical performance of the single cell.

[0060] At 550℃ and 550mAcm -2 Under constant current density and an air atmosphere containing 3% water vapor, the single cell (PBC:NFO=2:1 composite cathode) prepared in Example 2 exhibited excellent long-term operational stability, as shown in the results. Figure 4 As shown, after 300 hours of continuous constant current discharge, its operating voltage remained consistently within the range of approximately 1.35–1.40V, with no significant voltage decay or fluctuations throughout the process. The curve was smooth and stable, indicating that the battery performance maintained a high degree of consistency under long-term operating conditions. In contrast, the single cell prepared in Comparative Example 1 (pure PBC cathode) exhibited significant voltage fluctuations and an inability to maintain stable output due to severe mismatch in the coefficient of thermal expansion (TEC) between the cathode and electrolyte, resulting in microcracks forming at the interface after high-temperature sintering. This comparison directly demonstrates that the present invention, by introducing an NFO composite phase, effectively improves the thermal matching and interfacial chemical stability of the cathode material, significantly suppresses the generation and deterioration of interfacial microcracks, and greatly enhances the long-term service life and operational reliability of the single cell.

[0061] Example 4 1. Layered perovskite powder PrBaFe2O was prepared by solvent gelation method. 5+δAnd spinel powder (NiFe2O4, NiFeO). The preparation method of layered perovskite powder PBC includes the following steps: Weigh 0.01 mol of Pr(NO3)3, Ba(NO3)2, and Fe(NO3)2 raw materials respectively, dissolve them in pure water to obtain a perovskite precursor solution; add 0.04 mol of ethylenediaminetetraacetic acid and 0.08 mol of citric acid, and adjust the pH value to 7 with ammonia water to obtain mixed solution one; stir mixed solution one and heat it to a sol-gel state, and dry it at 160℃ for 6 hours to obtain perovskite precursor (black powder); calcine the obtained perovskite precursor in air at 900℃ for 5 hours to obtain the desired PBC powder. The preparation method of spinel powder (NiFe2O4, NiFeO) includes the following steps: Weigh 0.01 mol of NiNO3 and Fe(NO3)3 raw materials, dissolve them in pure water to obtain a NiFeO precursor solution; add 0.02 mol of ethylenediaminetetraacetic acid and 0.04 mol of citric acid, and adjust the pH value to 7 with ammonia water to obtain mixed solution two; stir mixed solution two and heat it to a sol-gel state, and dry it at 160℃ for 6 hours to obtain NiFeO precursor (black powder); calcine the obtained NiFeO precursor in air at 900℃ for 5 hours to obtain NiFeO powder.

[0062] 2. Composite Electrode Preparation: The obtained PBC powder and NiFeO powder were mixed at a mass ratio of 1:1, and anhydrous ethanol was added as a medium. The mixture was ball-milled at 400 rpm for 10 hours in a high-energy ball mill to ensure uniform mixing. The ball-milled slurry was dried to obtain PBC-NiFeO composite powder. The PBC-NiFeO composite powder was then ball-milled again with an organic carrier (such as a mixture of isopropanol, ethylene glycol, and glycerol) to prepare a cathode slurry with suitable viscosity.

[0063] 3. First, prepare the NiO-BZCYYb anode support, that is, to use BaZr... 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ A (BZCYYb) electrolyte substrate (approximately 18 μm thick) is pre-fused with NiO to form a NiO-BZCYYb anode support. The resulting cathode slurry is then sprayed onto one side of the dense BZCYYb electrolyte substrate. The sprayed green body is dried at 180°C on a heating table and then placed in a muffle furnace for sintering at 1000°C for 2 hours to form a porous cathode layer. Ultimately, this embodiment also yields a single cell with a NiO-BZCYYb anode support / BZCYYb dense electrolyte / 1PBC-1NiFeO porous cathode.

[0064] Example 5 1. Layered perovskite powder (PrBaCo2O) was prepared using the solvent gelation method. 5+δ The preparation method of layered perovskite powder (PBC) includes the following steps: 0.01 mol of Pr(NO3)3, Ba(NO3)2, and Co(NO3)2 raw materials are weighed and dissolved in pure water to obtain a perovskite precursor solution; 0.04 mol of ethylenediaminetetraacetic acid and 0.08 mol of citric acid are added, and the pH is adjusted to 7 with ammonia water to obtain mixed solution one; mixed solution one is stirred and heated to a sol-gel state, and dried at 160℃ for 6 hours to obtain perovskite precursor (black powder); the obtained perovskite precursor is calcined in air at 1100℃ for 5 hours to obtain the desired PBC powder. The preparation method of spinel powder (NiFe2O4, NiFeO) includes the following steps: Weigh 0.01 mol of NiNO3 and Fe(NO3)3 raw materials, dissolve them in pure water to obtain a NiFeO precursor solution; add 0.02 mol of ethylenediaminetetraacetic acid and 0.04 mol of citric acid, and adjust the pH value to 7 with ammonia water to obtain mixed solution two; stir mixed solution two and heat it to a sol-gel state, and dry it at 160℃ for 6 hours to obtain NiFeO precursor (black powder); calcine the obtained NiFeO precursor in air at 1100℃ for 5 hours to obtain NiFeO powder.

[0065] 2. Composite Electrode Preparation: The obtained PBC powder and NiFeO powder were mixed at a mass ratio of 1:1, and anhydrous ethanol was added as a medium. The mixture was ball-milled at 400 rpm for 10 hours in a high-energy ball mill to ensure uniform mixing. The ball-milled slurry was dried to obtain PBC-NiFeO composite powder. The PBC-NiFeO composite powder was then ball-milled again with an organic carrier (such as a mixture of isopropanol, ethylene glycol, and glycerol) to prepare a cathode slurry with suitable viscosity.

[0066] 3. First, a NiO-YSZ anode support is prepared. This involves pre-combining a ZrO2-doped Y2O3 (YSZ) electrolyte substrate (approximately 18 μm thick) with NiO to form a NiO-YSZ anode support. Then, the resulting cathode slurry is sprayed onto one side of the dense YSZ electrolyte substrate. After spraying, the green blank is dried at 180°C on a heating table and then placed in a muffle furnace for sintering at 1000°C for 2 hours to form a porous cathode layer. Ultimately, this embodiment also yields a single cell with a NiO-YSZ anode support / YSZ dense electrolyte / 1PBC-1NiFeO porous cathode.

[0067] Example 6 1. Layered perovskite powder (PrBaCo2O) was prepared using the solvent gelation method. 5+δThe preparation method of layered perovskite powder (PBC) includes the following steps: 0.01 mol of Pr(NO3)3, Ba(NO3)2, and Co(NO3)2 raw materials are weighed and dissolved in pure water to obtain a perovskite precursor solution; 0.04 mol of ethylenediaminetetraacetic acid and 0.08 mol of citric acid are added, and the pH is adjusted to 7 with ammonia to obtain mixed solution one; mixed solution one is stirred and heated to a sol-gel state, and dried at 160℃ for 6 hours to obtain perovskite precursor (black powder); the obtained perovskite precursor is calcined in air at 900℃ for 5 hours to obtain the desired PBC powder. The preparation method of spinel powder (ZnFe2O4, ZnFeO) includes the following steps: 0.01 mol of Zn(NO3)2 and Fe(NO3)3 raw materials are weighed and dissolved in pure water to obtain a ZnFeO precursor solution; 0.02 mol of ethylenediaminetetraacetic acid and 0.04 mol of citric acid are added, and the pH value is adjusted to 7 with ammonia water to obtain a mixed solution II; the mixed solution II is stirred and heated to a sol-gel state, and dried at 160℃ for 6 hours to obtain a ZnFeO precursor (black powder); the obtained ZnFeO precursor is calcined in air at 900℃ for 5 hours to obtain ZnFeO powder.

[0068] 2. Composite Electrode Preparation: The obtained PBC powder and ZnFeO powder were mixed at a mass ratio of 1:1, and anhydrous ethanol was added as a medium. The mixture was ball-milled at 400 rpm for 10 hours in a high-energy ball mill to ensure uniform mixing. The ball-milled slurry was dried to obtain PBC-ZnFeO composite powder. The PBC-ZnFeO composite powder was then ball-milled again with an organic carrier (such as a mixture of isopropanol, ethylene glycol, and glycerol) to prepare a cathode slurry of suitable viscosity.

[0069] 3. First, prepare the NiO-BZCYYb anode support, that is, to use BaZr... 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ A (BZCYYb) electrolyte substrate (approximately 18 μm thick) is pre-fused with NiO to form a NiO-BZCYYb anode support. The resulting cathode slurry is then sprayed onto one side of the dense BZCYYb electrolyte substrate. The sprayed green body is dried at 180°C on a heating table and then placed in a muffle furnace for sintering at 1000°C for 2 hours to form a porous cathode layer. Ultimately, this embodiment also yields a single cell with a NiO-BZCYYb anode support / BZCYYb dense electrolyte / 1PBC-1ZnFeO porous cathode.

[0070] In summary, this invention provides a composite electrode, its preparation method, and its application in solid oxide fuel cells. This invention combines layered perovskite (such as PBC) with spinel (such as NiFe2O4) of a certain mass ratio, and by optimizing the ratio of the two, it can make their thermal expansion coefficient similar to that of the electrolyte (such as BaZr). 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ The coefficient of thermal expansion is matched, which fundamentally eliminates mechanical failure problems such as interface delamination and microcracks caused by thermal stress, and significantly improves the structural stability of the battery during thermal cycling and long-term operation.

[0071] This invention significantly improves the overall performance and service reliability of mid-temperature solid oxide fuel cells by introducing a composite electrode (PBC:NFO) formed by NFO into the PBC: First, the electrochemical activity is significantly enhanced. AC impedance testing at 600℃ shows that, compared to a pure PBC cathode, the composite cathode described in this invention exhibits a significantly reduced polarization impedance, resulting in a marked optimization of the oxygen reduction reaction kinetics. This effectively reduces charge transfer and concentration polarization losses, thereby improving the electrocatalytic performance of the cathode. Secondly, long-term operational stability has been significantly improved. (At 550℃ and 550mA) cm -2 Under constant current discharge conditions, the single cell prepared by this invention can operate stably for more than 300 hours without significant voltage decay; while the pure PBC cathode, due to thermal expansion coefficient mismatch, exhibits significant performance fluctuations in less than 50 hours. This invention effectively suppresses the generation and propagation of interfacial microcracks by improving the thermal matching and interfacial chemical stability between the cathode and electrolyte, thus significantly extending the service life of the battery. Third, its application adaptability is significantly improved. The composite cathode described in this invention simultaneously achieves optimized catalytic activity and enhanced interface stability, providing a reliable technical solution for the efficient and long-life operation of mid-temperature solid oxide fuel cells, and has significant industrial application value and promising prospects.

[0072] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A composite electrode for a solid oxide fuel cell, characterized in that, It is mainly prepared by high-temperature calcination of layered perovskite and spinel, inducing an in-situ ion exchange reaction between the layered perovskite and spinel at the contact interface; the mass ratio of layered perovskite to spinel is 0.5~2.0:1; the layered perovskite is PrBaCo2O 5+δ PrBaFe2O 5+δ PrBaMn2O 5+δ The spinel is NiFe2O4, ZnFe2O4, LiMn2O4, or LaFe2O4.

2. A method for preparing a composite electrode for a solid oxide fuel cell as described in claim 1, characterized in that, Includes the following steps: S1. Preparation of layered perovskite powder and spinel powder; S2. Mix layered perovskite powder and spinel powder, add an organic carrier, and grind into a slurry; S3. The prepared slurry is coated onto the support substrate and then sintered to form the composite electrode. The mass ratio of the layered perovskite to spinel is 0.5~2.0:

1.

3. The method for preparing a composite electrode for a solid oxide fuel cell according to claim 2, characterized in that, In step S1, layered perovskite powder and spinel powder are prepared by sol-gel method.

4. The method for preparing a composite electrode for a solid oxide fuel cell according to claim 2, characterized in that, In step S3, the sintering temperature is 900~1100℃; the sintering time is 1~5 hours.

5. The method for preparing a composite electrode for a solid oxide fuel cell according to claim 2, characterized in that, In step S3, the supporting substrate is a substrate made of an electrolyte; the electrolyte is BaZr. 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ ZrO2 doped with Y2O3 and La 0.8 Sr 0.2 Ga 0.9 Mg 0.1 O 3-δ Gd-doped CeO2, Sm-doped CeO2.

6. The application of a composite electrode of a solid oxide fuel cell as described in claim 1 as a cathode electrode in a solid oxide fuel cell.

7. A solid oxide fuel cell, comprising an anode, an electrolyte, and a cathode, characterized in that, The cathode is the composite electrode of the solid oxide fuel cell according to claim 1.

8. A solid oxide fuel cell according to claim 7, characterized in that, The electrolyte is BaZr. 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ ZrO2 doped with Y2O3 and La 0.8 Sr 0.2 Ga 0.9 Mg 0.1 O 3-δ Gd-doped CeO2, Sm-doped CeO2.

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