Method for improving cathode side interface bonding force and electrical property of solid oxide fuel cell

Abstract

The invention provides a method for improving cathode side interface bonding force and electrical performance of a solid oxide fuel cell, and belongs to the field of fuel cells. The method for improving the cathode side interface bonding force and the electrical property of the solid oxide fuel cell comprises the following steps of: carrying out silk-screen printing on cathode transition layer slurry on a half cell with a barrier layer, then drying, printing a layer of cathode slurry, drying, and then discharging glue and sintering; wherein the cathode transition layer slurry comprises the following components in percentage by mass: 20-60wt% of transition layer powder, 40-75wt% of a silk-screen printing solvent and 5wt% of a dispersing agent; the cathode slurry comprises the following components in percentage by mass: 60-90wt% of cathode powder, 40-75wt% of a silk-screen printing solvent and 5wt% of a dispersing agent; each of the transition layer powder and the cathode powder comprises a cathode material and a barrier layer material; the transition layer powder and the cathode powder further comprise a composite negative thermal expansion material; the composite negative thermal expansion material is obtained by forming neodymium oxide on nitrogen-doped graphene in situ and then compounding with manganese oxide through a solid phase method.

Description

Technical Field

[0001] This invention relates to the field of fuel cells, specifically to a method for improving the bonding strength and electrical performance of the cathode side interface in solid oxide fuel cells. Background Technology

[0002] Solid oxide fuel cells (SOFCs), as a highly efficient energy conversion device, face a significant challenge in their commercial development: thermomechanical instability. This instability primarily stems from the mismatch in the coefficients of thermal expansion (TEC) between different fuel cell components, leading to internal stress gradients. These stress gradients can cause problems such as cell degradation, delamination, or fracture, severely impacting the lifespan and performance of SOFCs.

[0003] Among the various components of commercially available SOFCs, the performance of the air electrode, i.e., the cathode, is one of the key factors determining the overall performance of the battery. The most commonly used cathode materials include cobalt-containing perovskites such as (La,Sr)(Co,Fe)O. 3–δ (LSCF) and LaSrCoO 3–δ These materials, such as..., are highly favored due to their excellent oxygen reduction activity and high electrical conductivity. However, the coefficient of thermal expansion of these materials is typically between 17 and 20 × 10... -6 K -1 Within this range, the TEC is significantly higher than that of yttrium-stabilized zirconium oxide (YSZ) in commercial SOFC electrolytes (10~11 × 10⁻⁶). -6 K -1 This poses a severe challenge to the stability of the battery structure.

[0004] To mitigate this mismatch, current commercial SOFCs add a barrier layer to the cathode side, such as gadolinium-doped cerium dioxide (GDC) or samarium-doped cerium dioxide (SDC). These barrier layers not only suppress Sr diffusion in the cathode material but also act as a TEC buffer layer to some extent. However, due to the high TEC of the cathode material itself, to enhance the interfacial bonding, it is generally necessary to dope the cathode with a portion of the barrier layer material, with common ratios being LSCF:GDC = 6:4 or 5:5. Although this method effectively reduces the overall coefficient of thermal expansion and enhances interfacial bonding, it comes at the cost of sacrificing the electronic conductivity of the cathode material, thereby reducing the battery's electrical performance.

[0005] Furthermore, the cathode thickness is strictly limited to prevent delamination between the cathode and the barrier layer, or between the barrier layer and the electrolyte layer. While an excessively thick cathode can increase the number of three-phase interfaces and help improve electrochemical reaction efficiency, it also increases the risk of delamination between the aforementioned layers, ultimately affecting the overall performance of the battery. Therefore, there is an urgent need to develop methods to improve the interfacial bonding and electrical performance of the cathode side in solid oxide fuel cells, enhancing the bonding strength without sacrificing or even improving electrical performance, and overcoming the negative impacts of cathode thickness limitations. Summary of the Invention

[0006] The purpose of this invention is to provide a method for improving the bonding strength and electrical performance of the cathode side interface of a solid oxide fuel cell, so as to solve the technical problems mentioned in the background art.

[0007] The technical solution to achieve the objective of this invention is: This invention provides a method for improving the bonding strength and electrical performance of the cathode side interface of a solid oxide fuel cell. The steps include: first, screen printing a cathode transition layer paste on a half-cell with a barrier layer and drying it; then printing another layer of cathode paste and drying it; and finally debinding and sintering to obtain the cell.

[0008] Further, the cathode transition layer slurry comprises, by mass fraction: 20-60 wt% transition layer powder, 40-75 wt% screen printing solvent, and 5 wt% dispersant; the cathode slurry comprises, by mass fraction: 60-90 wt% cathode powder, 5-35 wt% screen printing solvent, and 5 wt% dispersant.

[0009] Furthermore, both the transition layer powder and the cathode powder include cathode material and barrier layer material.

[0010] Further, the mass ratio of cathode material to barrier layer material in the transition layer powder is (0~50):(50~100); the mass ratio of cathode material to barrier layer material in the cathode powder is (50~100):(0~50); preferably, the mass ratio of cathode material to barrier layer material in the transition layer powder is 20:80; the mass ratio of cathode material to barrier layer material in the cathode powder is 80:20.

[0011] Furthermore, the transition layer powder and the cathode powder also include a composite negative thermal expansion material; the amount of the composite negative thermal expansion material added is 0~10wt%; the composite negative thermal expansion material is first formed in situ on nitrogen-doped graphene to form neodymium oxide, and then combined with manganese oxide by solid-state method.

[0012] Further, the preparation steps of the composite negative thermal expansion material are as follows: Neodymium trioxide and manganese oxide are mixed evenly in an agate mortar at a mass ratio of (38.7~193.5):1, thoroughly ground, and poured into a clean tableting mold. The mixture is then kept at 11~13 MPa for 1~3 min, and then calcined in a muffle furnace at 950~1050℃ for 9~11 h. After calcination, the mixture is removed, placed in an agate mortar, crushed, and ground into a fine powder. The fine powder is then calcined in a muffle furnace at 1200~1250℃ for 23~25 h to obtain the composite negative thermal expansion material.

[0013] Further, the preparation steps of the composite neodymium trioxide are as follows: 0.0122~0.0608 parts by mass of neodymium nitrate hexahydrate are dissolved in 30 parts by mass of deionized water, and then 0.4 parts by mass of nitrogen-doped graphene are added and ultrasonically dispersed evenly. Then, under sealed conditions and at 68~72℃, the mixture is continuously stirred for 5~7 hours. Next, the sealed conditions are removed and the mixture is heated at 68~72℃ to completely evaporate the solid powder. Finally, the solid powder is calcined at 500~600℃ for 3~5 hours under nitrogen protection to obtain the composite neodymium trioxide.

[0014] Furthermore, the screen printing solvent includes a binder and a mixed solvent; the binder includes one of ethyl cellulose, polyvinyl butyral, and polymethyl methacrylate.

[0015] Furthermore, the mixed solvent comprises, by mass fraction, 0-100% turpentine percolate, 0-50% butyl carbitol, and 0-30% dodecyl alcohol ester.

[0016] Furthermore, the dispersant is one of triethanolamine, herring oil, phosphate ester, and polypropylene.

[0017] By adopting the above technical solution, the present invention has the following beneficial effects: (1) The present invention provides a method for improving the bonding force and electrical performance of the cathode side interface of a solid oxide fuel cell: First, a cathode transition layer slurry is screen-printed on a half cell with a barrier layer and dried, then another cathode slurry is printed on it and dried, and finally the adhesive is removed and sintered. By introducing a cathode transition layer between the cathode layer and the barrier layer, this method not only effectively enhances the bonding force of the cathode side interface, but also avoids the sacrifice of electrical performance, and helps to improve it, and further overcomes the negative impacts such as the reduction of the number of three-phase interfaces caused by the limited cathode thickness.

[0018] (2) In this invention, both the transition layer powder in the cathode transition layer slurry and the cathode powder in the cathode slurry include cathode material and barrier layer material. The mass ratio of cathode material to barrier layer material in the transition layer powder is 20:80; the cathode material to barrier layer material in the cathode powder is 80:20. Thanks to the buffering effect of the cathode transition layer, the interface between the cathode and the barrier layer is well bonded and no delamination occurs. Under the same working voltage conditions, the battery performance with the cathode transition layer is significantly improved compared to the battery without the layer, and it also exhibits excellent thermal cycling resistance and high stability.

[0019] (3) The transition layer powder and cathode powder of the present invention also include a composite negative thermal expansion material; the amount of composite negative thermal expansion material added is 0~10wt%; the composite negative thermal expansion material is first generated in situ by using nitrogen-doped graphene as a carrier to form a "flexible nano-mesh" with extremely high flexibility, excellent mechanical strength and chemical stability. When encountering thermal stress, the flexible nano-mesh can absorb and dissipate energy through bending and wrinkling, thereby avoiding stress directly concentrating on the interface between the barrier layer and the electrolyte, playing a preliminary stress buffering role, and significantly reducing the risk of interface tearing. Even without macroscopic peeling, insufficient contact between the cathode and the electrolyte will increase ohmic impedance, hinder ion transport and reduce overall performance; in addition, the composite negative thermal expansion material also utilizes two-dimensional nitrogen The large specific surface area and lightweight properties of doped graphene expose a large number of active sites, promoting effective contact with the electrolyte. By combining neodymium trioxide and manganese oxide through a solid-state method, a negative thermal expansion material NdMnO3 phase is formed. The NdMnO3 phase shrinks in volume when heated. Since the cathode and electrolyte usually exhibit positive thermal expansion, the introduction of NdMnO3 into the transition layer can effectively counteract the excessive expansion of the cathode during heating, thus effectively resisting cathode expansion during thermal cycling. At the same time, the lightweight and high specific surface area composite negative thermal expansion material efficiently fills the microscopic voids between cathode powders, improves the connectivity of the conductive pathways inside the electrode, optimizes the transport path of oxygen ions in the cathode, and reduces transport resistance, thereby synergistically improving the electrochemical performance and long-term operational stability of the battery. Attached Figure Description

[0020] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein... Figure 1 This is a diagram of the interface between the battery electrolyte and the barrier layer GDC in Embodiment 1 of the present invention.

[0021] Figure 2 This is a diagram of the interface between the battery electrolyte and the barrier layer GDC in Comparative Example 1 of the present invention.

[0022] Figure 3The battery performance graphs for Example 1 and Comparative Example 1 are shown under the same cathode conditions. Detailed Implementation

[0023] To better understand the above technical solution, the following will provide a detailed explanation of the technical solution in conjunction with specific implementation methods.

[0024] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0025] The following embodiments are only used to illustrate the technical solutions of the present invention more clearly, and should not be used to limit the scope of protection of the present invention.

[0026] The preparation steps of nitrogen-doped graphene are as follows: 1 mL of 10 mg / mL graphene oxide and 500 mg of urea were stirred in 20 mL of deionized water for 20 min; the water was removed by vacuum drying in a freeze dryer for 2 days, and after grinding, the graphene was placed in a tube furnace and heated to 600 °C at a heating rate of 3 °C / min under a flowing Ar atmosphere and held for 1 h. Then the temperature was increased to 900 °C at a heating rate of 5 °C / min and held for 3 h. The graphene was then naturally cooled to room temperature and removed from the tube furnace to obtain nitrogen-doped graphene.

[0027] The cathode powder used is LSCF powder (La0.6Sr0.4)0.95Co0.2Fe0.8O3-δ.

[0028] The barrier layer material is GDC powder Gd0.8Ce0.2O1.9.

[0029] The adhesive used is ethyl cellulose.

[0030] The dispersant used is triethanolamine.

[0031] Example 1 A method for improving the interface bonding and electrical performance of the cathode side of a solid oxide fuel cell includes the following steps: First, a cathode transition layer paste is screen-printed onto a half-cell with a barrier layer using a 200-mesh screen. After drying at 90°C for 30 minutes and cooling to room temperature, a second layer of cathode paste is printed using a 150-mesh screen. This is then dried at 90°C for 30 minutes and cooled to room temperature before being sent to a debinding furnace for debinding and sintering. The temperature is increased from room temperature to 450°C at a rate of 2°C / min and held for 2 hours. Then, the temperature is increased to 1000°C at a rate of 1°C / min and held for 2 hours. Finally, the cell is allowed to cool naturally to room temperature to obtain the battery.

[0032] The preparation steps of the cathode transition layer slurry are as follows: 50wt% of transition layer powder, 45wt% of screen printing solvent and 5wt% of dispersant are added to a vacuum mixer according to the mass percentage. After mixing for 5 minutes under the conditions of -100kPa, 400rpm revolution and 1000rpm rotation, the mixture is added to a three-roll mill to prepare the slurry until the slurry fineness reaches 3μm. Then, it is added to a vacuum mixer and mixed for 5 minutes under the conditions of -100kPa, 500rpm revolution and 1500rpm rotation to obtain the cathode transition layer slurry.

[0033] The preparation steps of the cathode paste are as follows: 75wt% cathode powder, 20wt% screen printing solvent and 5wt% dispersant are added to a vacuum mixer according to the mass percentage. After mixing for 5 minutes under the conditions of -100kPa, 400rpm revolution and 1000rpm rotation, the paste is added to a three-roll mill to prepare the paste until the paste fineness reaches 3μm. Then, it is added to a vacuum mixer and mixed for 5 minutes under the conditions of -100kPa, 500rpm revolution and 1500rpm rotation to obtain the cathode paste.

[0034] The preparation steps of screen printing solvent are as follows: (1) Take 60wt% turpentine percolate, 20wt% butyl carbitol and 20wt% dodecyl alcohol ester, and mix them in a mixer at 800rpm and 1500rpm for 5min. (2) Add 4 wt% of adhesive to 96 wt% mixed solvent, stir at 80°C, and cool to room temperature after the adhesive has dissolved completely.

[0035] The mass ratio of cathode material to barrier layer material in the transition layer powder is 20:80; the mass ratio of cathode material to barrier layer material in the cathode powder is 80:20.

[0036] Example 2 A method for improving the interface bonding and electrical performance of the cathode side of a solid oxide fuel cell includes the following steps: First, a cathode transition layer paste is screen-printed onto a half-cell with a barrier layer using a 200-mesh screen. After drying at 90°C for 30 minutes and cooling to room temperature, a second layer of cathode paste is printed using a 150-mesh screen. This is then dried at 90°C for 30 minutes and cooled to room temperature before being sent to a debinding furnace for debinding and sintering. The temperature is increased from room temperature to 450°C at a rate of 2°C / min and held for 2 hours. Then, the temperature is increased to 1000°C at a rate of 1°C / min and held for 2 hours. Finally, the cell is allowed to cool naturally to room temperature to obtain the battery.

[0037] The preparation steps of the cathode transition layer slurry are as follows: 50wt% of transition layer powder, 45wt% of screen printing solvent and 5wt% of dispersant are added to a vacuum mixer according to the mass percentage. After mixing for 5 minutes under the conditions of -100kPa, 400rpm revolution and 1000rpm rotation, the mixture is added to a three-roll mill to prepare the slurry until the slurry fineness reaches 3μm. Then, it is added to a vacuum mixer and mixed for 5 minutes under the conditions of -100kPa, 500rpm revolution and 1500rpm rotation to obtain the cathode transition layer slurry.

[0038] The preparation steps of the cathode paste are as follows: 75wt% cathode powder, 20wt% screen printing solvent and 5wt% dispersant are added to a vacuum mixer according to the mass percentage. After mixing for 5 minutes under the conditions of -100kPa, 400rpm revolution and 1000rpm rotation, the paste is added to a three-roll mill to prepare the paste until the paste fineness reaches 3μm. Then, it is added to a vacuum mixer and mixed for 5 minutes under the conditions of -100kPa, 500rpm revolution and 1500rpm rotation to obtain the cathode paste.

[0039] The preparation steps of screen printing solvent are as follows: (1) Take 60wt% turpentine percolate, 20wt% butyl carbitol and 20wt% dodecyl alcohol ester, and mix them in a mixer at 800rpm and 1500rpm for 5min. (2) Add 4 wt% of adhesive to 96 wt% mixed solvent, stir at 80°C, and cool to room temperature after the adhesive has dissolved completely.

[0040] The transition layer powder comprises, by mass percentage, 5 wt% composite negative thermal expansion material, 19 wt% cathode material, and 76 wt% barrier layer material; the cathode powder comprises 5 wt% composite negative thermal expansion material, 76 wt% cathode material, and 19 wt% barrier layer material.

[0041] The preparation steps of the composite negative thermal expansion material are as follows: Neodymium trioxide and manganese oxide are mixed evenly in an agate mortar at a mass ratio of 38.7:1, ground thoroughly, poured into a clean tableting mold, kept at 11 MPa for 3 min, and then calcined in a muffle furnace at 950℃ for 11 h. After that, the mixture is taken out, placed in an agate mortar and crushed and ground into fine powder. The fine powder is then calcined in a muffle furnace at 1200℃ for 25 h to obtain the composite negative thermal expansion material.

[0042] The preparation steps of the composite neodymium trioxide are as follows: 0.0608 parts by mass of neodymium nitrate hexahydrate are dissolved in 30 parts by mass of deionized water, and then 0.4 parts by mass of nitrogen-doped graphene are added and ultrasonically dispersed evenly. Then, under sealed conditions and at 68°C, the mixture is continuously stirred for 5 hours. Next, the sealed conditions are removed and the mixture is heated at 68°C to completely evaporate the solid powder. Finally, the solid powder is calcined at 500°C for 3 hours under nitrogen protection to obtain the composite neodymium trioxide.

[0043] Example 3 A method for improving the interface bonding and electrical performance of the cathode side of a solid oxide fuel cell includes the following steps: First, a cathode transition layer paste is screen-printed onto a half-cell with a barrier layer using a 200-mesh screen. After drying at 90°C for 30 minutes and cooling to room temperature, a second layer of cathode paste is printed using a 150-mesh screen. This is then dried at 90°C for 30 minutes and cooled to room temperature before being sent to a debinding furnace for debinding and sintering. The temperature is increased from room temperature to 450°C at a rate of 2°C / min and held for 2 hours. Then, the temperature is increased to 1000°C at a rate of 1°C / min and held for 2 hours. Finally, the cell is allowed to cool naturally to room temperature to obtain the battery.

[0044] The preparation steps of the cathode transition layer slurry are as follows: 50wt% of transition layer powder, 45wt% of screen printing solvent and 5wt% of dispersant are added to a vacuum mixer according to the mass percentage. After mixing for 5 minutes under the conditions of -100kPa, 400rpm revolution and 1000rpm rotation, the mixture is added to a three-roll mill to prepare the slurry until the slurry fineness reaches 3μm. Then, it is added to a vacuum mixer and mixed for 5 minutes under the conditions of -100kPa, 500rpm revolution and 1500rpm rotation to obtain the cathode transition layer slurry.

[0045] The preparation steps of the cathode paste are as follows: 75wt% cathode powder, 20wt% screen printing solvent and 5wt% dispersant are added to a vacuum mixer according to the mass percentage. After mixing for 5 minutes under the conditions of -100kPa, 400rpm revolution and 1000rpm rotation, the paste is added to a three-roll mill to prepare the paste until the paste fineness reaches 3μm. Then, it is added to a vacuum mixer and mixed for 5 minutes under the conditions of -100kPa, 500rpm revolution and 1500rpm rotation to obtain the cathode paste.

[0046] The preparation steps of screen printing solvent are as follows: (1) Take 60wt% turpentine percolate, 20wt% butyl carbitol and 20wt% dodecyl alcohol ester, and mix them in a mixer at 800rpm and 1500rpm for 5min. (2) Add 4 wt% of adhesive to 96 wt% mixed solvent, stir at 80°C, and cool to room temperature after the adhesive has dissolved completely.

[0047] The transition layer powder comprises, by mass percentage, 10 wt% composite negative thermal expansion material, 18 wt% cathode material, and 72 wt% barrier layer material; the cathode powder comprises 10 wt% composite negative thermal expansion material, 72 wt% cathode material, and 18 wt% barrier layer material.

[0048] The preparation steps of the composite negative thermal expansion material are as follows: Neodymium trioxide and manganese oxide are mixed evenly in an agate mortar at a mass ratio of 64.5:1, and then thoroughly ground. The mixture is poured into a clean tableting mold and kept at 12 MPa for 2 minutes. Then, it is placed in a muffle furnace and calcined at 1000℃ for 10 hours. After that, it is taken out and placed in an agate mortar to be crushed and ground into fine powder. The fine powder is then placed in a muffle furnace and calcined at 1250℃ for 24 hours to obtain the composite negative thermal expansion material.

[0049] The preparation steps of the composite neodymium trioxide are as follows: 0.0365 parts by mass of neodymium nitrate hexahydrate are dissolved in 30 parts by mass of deionized water, and then 0.4 parts by mass of nitrogen-doped graphene are added and ultrasonically dispersed evenly. Then, under sealed conditions and at 70°C, the mixture is continuously stirred for 6 hours. Next, the sealed conditions are removed and the mixture is heated at 70°C to completely evaporate the solid powder. Finally, the solid powder is calcined at 550°C for 3 hours under nitrogen protection to obtain the composite neodymium trioxide.

[0050] Example 4 A method for improving the interface bonding and electrical performance of the cathode side of a solid oxide fuel cell includes the following steps: First, a cathode transition layer paste is screen-printed onto a half-cell with a barrier layer using a 200-mesh screen. After drying at 90°C for 30 minutes and cooling to room temperature, a second layer of cathode paste is printed using a 150-mesh screen. This is then dried at 90°C for 30 minutes and cooled to room temperature before being sent to a debinding furnace for debinding and sintering. The temperature is increased from room temperature to 450°C at a rate of 2°C / min and held for 2 hours. Then, the temperature is increased to 1000°C at a rate of 1°C / min and held for 2 hours. Finally, the cell is allowed to cool naturally to room temperature to obtain the battery.

[0051] The preparation steps of the cathode transition layer slurry are as follows: 50wt% of transition layer powder, 45wt% of screen printing solvent and 5wt% of dispersant are added to a vacuum mixer according to the mass percentage. After mixing for 5 minutes under the conditions of -100kPa, 400rpm revolution and 1000rpm rotation, the mixture is added to a three-roll mill to prepare the slurry until the slurry fineness reaches 3μm. Then, it is added to a vacuum mixer and mixed for 5 minutes under the conditions of -100kPa, 500rpm revolution and 1500rpm rotation to obtain the cathode transition layer slurry.

[0052] The preparation steps of the cathode paste are as follows: 75wt% cathode powder, 20wt% screen printing solvent and 5wt% dispersant are added to a vacuum mixer according to the mass percentage. After mixing for 5 minutes under the conditions of -100kPa, 400rpm revolution and 1000rpm rotation, the paste is added to a three-roll mill to prepare the paste until the paste fineness reaches 3μm. Then, it is added to a vacuum mixer and mixed for 5 minutes under the conditions of -100kPa, 500rpm revolution and 1500rpm rotation to obtain the cathode paste.

[0053] The preparation steps of screen printing solvent are as follows: (1) Take 60wt% turpentine percolate, 20wt% butyl carbitol and 20wt% dodecyl alcohol ester, and mix them in a mixer at 800rpm and 1500rpm for 5min. (2) Add 4 wt% of adhesive to 96 wt% mixed solvent, stir at 80°C, and cool to room temperature after the adhesive has dissolved completely.

[0054] The transition layer powder comprises, by mass percentage, 10 wt% composite negative thermal expansion material, 18 wt% cathode material, and 72 wt% barrier layer material; the cathode powder comprises 10 wt% composite negative thermal expansion material, 72 wt% cathode material, and 18 wt% barrier layer material.

[0055] The preparation steps of the composite negative thermal expansion material are as follows: Neodymium trioxide and manganese oxide are mixed evenly in an agate mortar at a mass ratio of 193.5:1, and then thoroughly ground. The mixture is poured into a clean tableting mold and kept at 13 MPa for 1 minute. Then, it is placed in a muffle furnace and calcined at 1050°C for 9 hours. After that, it is taken out and placed in an agate mortar to be crushed and ground into fine powder. The fine powder is then placed in a muffle furnace and calcined at 1250°C for 23 hours to obtain the composite negative thermal expansion material.

[0056] The preparation steps of the composite neodymium trioxide are as follows: 0.0122 parts by mass of neodymium nitrate hexahydrate are dissolved in 30 parts by mass of deionized water, and then 0.4 parts by mass of nitrogen-doped graphene are added and ultrasonically dispersed evenly. Then, under sealed conditions and at 72°C, the mixture is continuously stirred for 7 hours. Next, the sealed conditions are removed and the mixture is heated at 72°C to completely evaporate the solid powder. Finally, the solid powder is calcined at 600°C for 3 hours under nitrogen protection to obtain the composite neodymium trioxide.

[0057] Comparative Example 1 The preparation method of the battery in Comparative Example 1 is as follows: First, a layer of cathode paste is screen-printed on the half-cell with a barrier layer. The screen number is 150 mesh. After drying at 90°C for 30 min, it is cooled to room temperature and then sent to the debinding furnace for debinding and sintering. The temperature is increased from room temperature to 450°C at 2°C / min and held for 2 h. Then, the temperature is increased to 1000°C at 1°C / min and held for 2 h. After naturally cooling to room temperature, the battery is obtained.

[0058] The preparation steps of the cathode paste are as follows: 75wt% cathode powder, 20wt% screen printing solvent and 5wt% dispersant are added to a vacuum mixer according to the mass percentage. After mixing for 5 minutes under the conditions of -100kPa, 400rpm revolution and 1000rpm rotation, the paste is added to a three-roll mill to prepare the paste until the paste fineness reaches 3μm. Then, it is added to a vacuum mixer and mixed for 5 minutes under the conditions of -100kPa, 500rpm revolution and 1500rpm rotation to obtain the cathode paste.

[0059] The preparation steps of screen printing solvent are as follows: (1) Take 60wt% turpentine percolate, 20wt% butyl carbitol and 20wt% dodecyl alcohol ester, and mix them in a mixer at 800rpm and 1500rpm for 5min. (2) Add 4 wt% of adhesive to 96 wt% mixed solvent, stir at 80°C, and cool to room temperature after the adhesive has dissolved completely.

[0060] The cathode powder contains cathode material in a 60:40 ratio with barrier layer material.

[0061] Comparative Example 2 The only difference between Comparative Example 2 and Example 3 is that the composite negative thermal expansion material used is NdMnO3.

[0062] Comparative Examples 3-4 The only difference between Comparative Examples 3 and 4 and Example 3 is that the amount of composite negative thermal expansion material added to the transition layer powder and cathode powder is 15 wt% and 20 wt%, respectively.

[0063] Example of effect from Figure 1 As can be seen, in Example 1, the battery with the added cathode transition layer has a tight interface between the electrolyte and the barrier layer, and no delamination occurs; conversely, Figure 2 The battery in Comparative Example 1 without a cathode transition layer was shown, and obvious delamination appeared at the interface between the electrolyte and the barrier layer. It can be seen that adding a cathode transition layer significantly improves the interfacial bonding between the battery electrolyte and the barrier layer, making it more robust and stable.

[0064] Table 1 below shows the battery performance test results of Examples 1-4 and Comparative Examples 1-4 at 750°C: Table 1

[0065] Table 1 shows that the batteries in Examples 2-4 have lower polarization resistance at 800°C and higher power density at the same current density.

[0066] Combined with Table 1 Figure 3 The data shows that the battery with the cathode transition layer added in Example 1 has a slightly lower open-circuit voltage than the battery without the cathode transition layer in Comparative Example 1, and a higher power density at the same current density. In particular, under the operating condition of 0.76V, the battery performance of Example 1 is 27% higher than that of Comparative Example 1, showing a significant performance advantage.

[0067] The only difference between Comparative Example 2 and Example 3 is that the composite negative thermal expansion material uses NdMnO3, which has a larger polarization resistance and a lower power density at the same current density. This indicates that the composite negative thermal expansion material first forms neodymium trioxide in situ on nitrogen-doped graphene, and then combines it with manganese oxide through a solid-state method to obtain a battery with better performance.

[0068] Data from the batteries in Examples 1-4 and Comparative Examples 3-4 show that as the amount of composite negative thermal expansion material added increases, the battery's electrical performance at 800°C first increases and then decreases. This indicates that adding 5% to 10 wt% of composite negative thermal expansion material helps optimize battery performance, but excessive amounts can have adverse effects due to factors such as diluting the highly conductive LSCF component in the cathode.

[0069] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for improving the interfacial bonding strength and electrical performance of a solid oxide fuel cell cathode, characterized in that, The steps include: First, a cathode transition layer paste is screen-printed onto a half-cell with a barrier layer and then dried. Then, another layer of cathode paste is printed and dried. Finally, the binder is removed and sintered to obtain the cell. The cathode transition layer slurry comprises, by mass fraction: 20-60 wt% transition layer powder, 40-75 wt% screen printing solvent, and 5 wt% dispersant; the cathode slurry comprises, by mass fraction: 60-90 wt% cathode powder, 5-35 wt% screen printing solvent, and 5 wt% dispersant; both the transition layer powder and the cathode powder comprise cathode material and barrier layer material; both the transition layer powder and the cathode powder also comprise composite negative thermal expansion material; the amount of composite negative thermal expansion material added is 0-10 wt%; the composite negative thermal expansion material is first formed in situ on nitrogen-doped graphene to form neodymium oxide, and then compounded with manganese oxide through a solid-state method.

2. The method for improving the interfacial bonding strength and electrical performance of the cathode side of a solid oxide fuel cell according to claim 1, characterized in that, The mass ratio of cathode material to barrier layer material in the transition layer powder is (0~50):(50~100); the mass ratio of cathode material to barrier layer material in the cathode powder is (50~100):(0~50).

3. The method for improving the interface bonding and electrical performance of the cathode side of a solid oxide fuel cell according to claim 1, characterized in that, The preparation steps of the composite negative thermal expansion material are as follows: Neodymium trioxide and manganese oxide are mixed evenly in an agate mortar at a mass ratio of (38.7~193.5):1, and then thoroughly ground. The mixture is poured into a clean tableting mold and kept at 11~13MPa for 1~3min. Then, it is placed in a muffle furnace and calcined at 950~1050℃ for 9~11h. After that, it is taken out and placed in an agate mortar to be crushed and ground into fine powder. The fine powder is then placed in a muffle furnace and calcined at 1200~1250℃ for 23~25h to obtain the composite negative thermal expansion material.

4. The method for improving the interface bonding and electrical performance of the cathode side of a solid oxide fuel cell according to claim 3, characterized in that, The preparation steps of the composite neodymium trioxide are as follows: 0.0122~0.0608 parts by mass of neodymium nitrate hexahydrate are dissolved in 30 parts by mass of deionized water, and then 0.4 parts by mass of nitrogen-doped graphene are added and ultrasonically dispersed evenly. Then, under sealed conditions and at 68~72℃, the mixture is continuously stirred for 5~7 hours. Next, the sealed conditions are removed and the mixture is heated at 68~72℃ to completely evaporate the solid powder. Finally, the solid powder is calcined at 500~600℃ for 3~5 hours under nitrogen protection to obtain the composite neodymium trioxide.

5. The method for improving the interfacial bonding strength and electrical performance of a solid oxide fuel cell cathode side according to claim 1, characterized in that, The screen printing solvent includes a binder and a mixed solvent; the binder includes one of ethyl cellulose, polyvinyl butyral, and polymethyl methacrylate.

6. The method for improving the interfacial bonding strength and electrical performance of a solid oxide fuel cell cathode according to claim 5, characterized in that, The mixed solvent comprises, by mass fraction, 0-100% turpentine percolate, 0-50% butyl carbitol, and 0-30% dodecyl alcohol ester.

7. The method for improving the interfacial bonding strength and electrical performance of a solid oxide fuel cell cathode side according to claim 1, characterized in that, The dispersant is one of triethanolamine, herring oil, phosphate ester, and polypropylene.

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