A SOFC fuel electrode, its preparation method and application

Abstract

This invention discloses an SOFC fuel electrode, its preparation method, and its application, belonging to the field of fuel electrode technology. The SOFC fuel electrode of this invention has a three-layer structure, including a first layer, a second layer, and a third layer. By increasing the proportion of plate-like NiO in the second layer, the contact area between the electrode and the reacting gas can be increased, thereby improving the reaction rate. By increasing the proportion of particulate NiO in the first and third layers, the gas diffusion rate can be improved. The SOFC fuel electrode prepared using the method described in this invention exhibits good stability, durability, fuel utilization rate, and maximum power density.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and in particular to an SOFC fuel electrode, its preparation method, and its application. Background Technology

[0002] Solid oxide fuel cells (SOFCs) are a highly efficient and environmentally friendly energy conversion technology. In an SOFC, the fuel electrode is one of the key components of the cell, and its function is to transfer electrons from the fuel gas to the cell, where they react with oxygen to produce water and carbon dioxide.

[0003] Fuel electrodes are typically fabricated using composite materials of metallic phases or metallic precursors and ceramic phases, resulting in a porous composite layer structure. Current research often improves fuel electrode performance by employing gradient design to alter the content, purity, particle size, and pore-forming agent of YSZ and NiO. However, this approach suffers from problems such as increased interfacial contact resistance and gas-phase diffusion impedance due to increased thickness. Other studies have explored replacing traditional Ni / YSZ fuel electrode materials with novel materials such as perovskite oxides, or using methods like electrodeposition to control the microstructure and chemical composition of fuel electrode materials. However, these methods also have drawbacks, including poor stability of the resulting fuel electrodes, high fabrication costs, and complex fabrication processes, significantly limiting the practical application and production of SOFCs. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide an SOFC fuel electrode, its preparation method and application; the SOFC fuel electrode has good stability and excellent gas conversion efficiency, and its preparation method is relatively simple and suitable for industrial production.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] An SOFC fuel electrode comprises three layers: a first layer, a second layer, and a third layer, wherein the second layer is located between the first layer and the third layer.

[0007] The weight ratio of sheet-like NiO to granular NiO in the first layer is lower than that in the second layer.

[0008] The weight ratio of plate-like NiO to granular NiO in the third layer is lower than that in the second layer.

[0009] Flaky NiO possesses a large specific surface area and an open porous structure. Compared to granular NiO, the increased specific surface area is beneficial for improving the gas reaction rate. Sintering and reducing flaky NiO yields a greater number of anodic active sites, allowing for controllable adjustment of the active site distribution, increasing the three-phase linear density, and improving electrical performance. Simultaneously, flaky NiO tends to align parallel to the functional layer layers, increasing Ni continuity and reducing anodic diffusion resistance compared to granular NiO. The flaky structure also reduces the influence of the coefficient of thermal expansion, decreasing the likelihood of battery degradation due to inconsistent thermal expansion during operation, thereby enhancing the stability of the fuel electrode and extending its service life.

[0010] In addition, the main components of the fuel electrode include electron transport carriers, ion transport carriers and interconnected pores. Because it needs to undergo a three-phase reaction involving ions, electrons and gas and a process of generating gas discharge during operation, from the perspective of single-layer structure, when the content of plate-like NiO is high, the surface area of ​​the electrode layer pores is larger, the contact area with the reaction fuel is larger, the number of active sites per unit reaction is greater, and the reaction rate is faster.

[0011] Designing the fuel electrode as a three-layer composite structure, from the perspective of interlayer gas diffusion and reaction rate, the middle layer has a large proportion of plate-like NiO, resulting in a slow gas diffusion rate perpendicular to the interface. Compared to the upper and lower layers, it increases the number of effective three-phase points in the lateral direction, further improving the reaction rate. The upper and lower layers have a higher proportion of particulate matter, which is conducive to fuel gas diffusion. The particulate powder facilitates the formation of a longitudinally interconnected pore structure, resulting in a fast gas diffusion rate, allowing it to quickly diffuse to the middle layer in the direction perpendicular to the interface per unit time. In addition, the multi-layer structure design can also improve the stability and durability of the fuel electrode. Under the same experimental conditions, the maximum power density of this fuel electrode is much higher than that of a single-layer fuel electrode.

[0012] Preferably, the weight ratio of each component in the first layer is: flake NiO: granular NiO: 8YSZ = (10-30): (20-50): (30-70); the weight ratio of each component in the second layer is: flake NiO: granular NiO: 8YSZ = (20-40): (20-40): (20-60); and the weight ratio of each component in the third layer is: flake NiO: granular NiO: 8YSZ = (10-30): (20-50): (30-70).

[0013] More preferably, the weight ratio of each component in the first layer is: flake NiO: granular NiO: 8YSZ = (10-20): (30-40): (30-70); the weight ratio of each component in the second layer is: flake NiO: granular NiO: 8YSZ = (20-35): (20-30): (20-60); and the weight ratio of each component in the third layer is: flake NiO: granular NiO: 8YSZ = (10-20): (30-40): (30-70). When the content of flake NiO is too high, the continuity of Ni is poor, and the performance of the SOFC fuel electrode will decrease. When the content of granular NiO is too high, the NiO powder is prone to agglomeration during sintering, which will also lead to a decrease in performance. By further optimizing the composition of the three components, the stability and electrical performance of the SOFC fuel electrode can be effectively improved.

[0014] Preferably, the length of the flake-shaped NiO is 1-10 μm, the width is 0.1-10 μm, and the thickness is 0.01-1 μm, wherein the thickness is 0.1 to 0.2 times the width, and the particle size of the granular NiO is 0.1 to 10 μm; the thickness ratio of the first layer, the second layer, and the third layer is (1-2):(1-3):(1-2).

[0015] More preferably, the sheet-like NiO has a length of 1-5 μm, a width of 1-5 μm, and a thickness of 0.1-0.5 μm; the thickness ratio of the first layer, the second layer, and the third layer is 1:(2-3):1. Increasing the thickness of the intermediate layer can improve fuel utilization and increase the maximum power density.

[0016] Preferably, the overall thickness of the SOFC fuel electrode is 3-35 μm, and the first and third layers have the same composition and thickness. Controlling the composition and thickness of the first and third layers to be the same can improve the stability of the fuel electrode and enhance its electrochemical performance.

[0017] Preferably, the 8YSZ is a granular powder with a particle size of 0.1 to 10 μm; the morphology of the granular NiO is at least one of spherical, near-spherical, ellipsoidal, flower-shaped, and star-shaped.

[0018] More preferably, the particle size of the granular NiO is 0.1–5 μm, and the particle size of the 8YSZ is 0.1–5 μm. By limiting the particle size as described above, the fuel utilization rate and electrical performance of the SOFC fuel electrode can be further improved.

[0019] Furthermore, the present invention also discloses a method for preparing the SOFC fuel electrode, the method comprising the following steps:

[0020] (1) Weigh flake NiO, granular NiO, and 8YSZ according to the weight ratio of each component in the first layer, add binder and solvent to prepare a slurry, and prepare the first film tape by casting; weigh flake NiO, granular NiO, and 8YSZ according to the weight ratio of each component in the second layer, add binder and solvent to prepare a slurry, and prepare the second film tape by casting; weigh flake NiO, granular NiO, and 8YSZ according to the weight ratio of each component in the third layer, add binder and solvent to prepare a slurry, and prepare the third film tape by casting.

[0021] (2) The first membrane strip, the second membrane strip, and the third membrane strip are stacked in sequence and stamped to obtain the SOFC fuel electrode; the stamping pressure is 15-20 MPa.

[0022] Meanwhile, this invention also discloses the application of the SOFC fuel electrode in a solid oxide fuel cell, wherein the preparation method of the solid oxide fuel cell includes the following steps:

[0023] (1) Assemble the electrolyte layer with the SOFC fuel electrode according to any one of claims 1-7, and perform hydrostatic pressing to obtain a combined membrane; the hydrostatic pressing conditions are: pressure 80-100MPa, time 30-40min;

[0024] (2) The membrane is debonded and sintered, and then the cathode layer is printed on one side of the electrolyte layer of the membrane to obtain the solid oxide fuel cell.

[0025] Preferably, in step (2), the sintering conditions are: temperature 1350-1400℃, time 4-6h.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] This invention designs the structure of an SOFC fuel electrode by selectively varying the proportions of its components to create a three-layer structure. In the second layer, the proportion of sheet-like NiO is higher than that of particulate NiO, while in the first and third layers, the proportion of sheet-like NiO is lower than that of particulate NiO. This design ensures rapid and efficient diffusion of fuel gas within the electrode, while also allowing for sufficient reaction in the intermediate layer, the second layer, resulting in excellent electrical performance of the SOFC fuel electrode. Furthermore, by optimizing the size of the sheet-like NiO, the composition of each layer, and its thickness, this invention improves the thermal stability of the SOFC fuel electrode, reduces losses caused by thermal stress, and further enhances its electrical performance. Attached Figure Description

[0028] Figure 1This is a schematic diagram of the SOFC fuel electrode described in Example 1;

[0029] In the diagram, horizontal lines represent flake-shaped NiO, circles represent granular NiO, and the remaining part represents 8YSZ. Detailed Implementation

[0030] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0031] The performance parameters of some components in the examples and comparative examples are as follows:

[0032] Granular NiO: 1μm spherical particles;

[0033] 8YSZ: 0.01μm irregular particles;

[0034] Electrolyte layer: 8YSZ;

[0035] Cathode layer: LSCF.

[0036] Examples 1-16

[0037] The formulations and structures of the SOFC fuel electrode of the present invention, Examples 1-16, are shown in Tables 1-3, and the preparation methods are as follows:

[0038] (1) Weigh flake NiO, granular NiO and 8YSZ according to the weight ratio of each component in the first layer, add a mixed solvent of anhydrous ethanol and toluene and binder PVB to make a slurry, and prepare the first film tape by casting.

[0039] Weigh flake NiO, granular NiO and 8YSZ according to the weight ratio of each component in the second layer, add a mixed solvent of anhydrous ethanol and toluene and binder PVB to make a slurry, and prepare the second film tape by casting.

[0040] Weigh flake NiO, granular NiO and 8YSZ according to the weight ratio of each component in the third layer, add a mixed solvent of anhydrous ethanol and toluene and binder PVB to make a slurry, and prepare the third film tape by casting.

[0041] The third membrane strip has the same composition as the first membrane strip; the mass of the mixed solvent in each layer is 50% of the total mass of flake NiO, granular NiO, and 8YSZ, and the mass of the binder PVB is 13% of the total mass of flake NiO, granular NiO, and 8YSZ.

[0042] (2) The first membrane strip, the second membrane strip, and the third membrane strip are stacked in sequence and stamped at a pressure of 20 MPa to obtain the SOFC fuel electrode.

[0043] Figure 1 This is a schematic diagram of the SOFC fuel electrode described in Example 1; the horizontal lines in the figure represent sheet-like NiO, the circles represent granular NiO, and the remaining part represents 8YSZ.

[0044] The difference between Examples 1 to 7 is that the proportions of the components in the first and second layers are different, as shown in Table 1.

[0045] The difference between Examples 1 and Examples 8-16 is that the size of the sheet-like NiO used is different, as shown in Table 2.

[0046] The difference between Examples 1 and Examples 17-21 is that at least one of the first, second, and third layers has a different thickness, as shown in Table 3.

[0047] Comparative Example 1

[0048] Comparative Example 1 is an SOFC fuel electrode, which differs from Example 1 only in the different proportions of the components in the first and second layers, as shown in Table 1.

[0049] Comparative Example 2

[0050] Comparative Example 2 is a SOFC fuel electrode, which differs from Comparative Example 1 only in that the sheet-like NiO used has a length of 0.5 μm, a width of 0.5 μm, and a thickness of 0.1 μm.

[0051] Comparative Example 3

[0052] Comparative Example 3 is a SOFC fuel electrode, which differs from Comparative Example 1 only in that the sheet-like NiO used has a length of 12 μm, a width of 12 μm, and a thickness of 1 μm.

[0053] Comparative Example 4

[0054] Comparative Example 4 is a SOFC fuel electrode, which differs from Comparative Example 1 only in that the sheet-like NiO used has a length of 3μm, a width of 3μm, and a thickness of 1.5μm.

[0055] Comparative Example 5

[0056] Comparative Example 5 is an SOFC fuel electrode, which differs from Comparative Example 2 only in that the thickness of the first layer is 5 μm, the thickness of the second layer is 20 μm, and the thickness of the third layer is 5 μm.

[0057] Table 1 (by weight)

[0058]

[0059] Table 2

[0060]

[0061]

[0062] Table 3

[0063] Thickness / μm First layer Second floor Third layer Example 1 10 10 10 Example 17 5 10 5 Example 18 5 15 5 Example 19 10 5 10 Example 20 10 15 10 Example 21 5 20 5

[0064] Examples of Results 1-21 and Comparative Examples of Results 1-5

[0065] SOFC fuel cells were prepared using the SOFC fuel electrodes described in Examples 1-21 and Comparative Examples 1-5, respectively, and named Effect Examples 1-21 and Effect Comparative Examples 1-5. The preparation methods are as follows:

[0066] (1) The electrolyte layer and the SOFC fuel electrode are assembled in sequence, and then pressed together by hydrostatic pressure to obtain a combined membrane; the hydrostatic pressure is set to 100 MPa and the pressing time is 30 min.

[0067] (2) The membrane is debonded and sintered in an air atmosphere at a temperature of 1400°C for 5 hours. After sintering, the cathode layer is printed onto the electrolyte layer to obtain the solid oxide fuel cell.

[0068] Performance testing

[0069] The test methods and test standards are shown in Table 4, and the test results are shown in Table 5.

[0070] Table 4

[0071]

[0072]

[0073] Table 5

[0074]

[0075]

[0076] As shown in Table 5, Examples 1 to 21 exhibit good overall performance, with a maximum power density reaching 1.45 W / cm². 2 Fuel utilization rates were all above 92%, stability was good, and AC impedance was ≤0.3Ω·cm. 2 .

[0077] In Comparative Example 1, the weight ratio of the second layer of sheet-like NiO to granular NiO in the SOFC fuel electrode is lower than that in the first layer of sheet-like NiO to granular NiO, resulting in lower fuel utilization and higher impedance.

[0078] In the SOFC fuel electrodes described in Comparative Examples 2-4, the weight ratio of the second layer of sheet-like NiO to granular NiO is less than that of the first layer of sheet-like NiO to granular NiO. Furthermore, the size of the sheet-like NiO is not within the preferred range, resulting in a low maximum power density, high AC impedance, and poor electrical performance.

[0079] In Comparative Example 5, the weight ratio of the second layer of sheet-like NiO to particulate NiO in the SOFC fuel electrode is less than that in the first layer. The size of the sheet-like NiO is not within the preferred range, and the thickness ratio of the first, second, and third layers is not within the preferred range, resulting in extremely high impedance.

[0080] Furthermore, comparing the test results of Examples 1-7, it can be found that when the weight ratio of each component in the first layer is: flake NiO: granular NiO: 8YSZ = (10-30): (20-50): (30-70), the weight ratio of each component in the second layer is: flake NiO: granular NiO: 8YSZ = (20-40): (20-40): (20-60), and the weight ratio of each component in the third layer is: flake NiO: granular NiO: 8YSZ = (10-30): (20-50): (30-70), the maximum power is achieved. The density is significantly higher; in addition, when the weight ratio of each component in the first layer is flake NiO: granular NiO: 8YSZ = (10-20): (30-40): (30-70), the weight ratio of each component in the second layer is flake NiO: granular NiO: 8YSZ = (20-35): (20-30): (20-60), and the weight ratio of each component in the third layer is flake NiO: granular NiO: 8YSZ = (10-20): (30-40): (30-70), the SOFC fuel electrode has the best overall performance.

[0081] Comparing the test results of Examples 1, 8-16, it can be found that the preferred size of the flake NiO is: length 1-10 μm, width 0.1-10 μm, and thickness 0.01-1 μm, wherein the thickness is 0.1-0.2 times the width. When the above conditions are met, the maximum power density and fuel utilization rate are high, the stability is better, and the impedance is low, exhibiting good electrical performance. In addition, when the size of the flake NiO is further preferably 1-5 μm in length, 1-5 μm in width, and 0.1-0.5 μm in thickness, the AC impedance is significantly lower.

[0082] Comparing the test results of Example 1 and Examples 17-21, it can be found that when the thickness ratio of the first, second, and third layers is (1-2):(1-3):(1-2), the fuel utilization rate can reach over 92%, and the AC impedance can be controlled within 0.3 Ω·cm. 2Furthermore, when the thickness ratio of the first, second, and third layers is 1:(2-3):1, the resulting SOFC fuel electrode exhibits a higher maximum power density and a lower impedance.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A SOFC fuel electrode, characterized in that, The SOFC fuel electrode comprises three layers: a first layer, a second layer, and a third layer, with the second layer located between the first and third layers. The first, second, and third layers all contain plate-like NiO, spherical particle NiO, and 8YSZ; The weight ratio of plate-like NiO to spherical NiO in the first layer is lower than that in the second layer. The weight ratio of plate-like NiO to spherical NiO in the third layer is lower than that in the second layer. The weight ratio of each component in the first layer is: flake NiO: spherical NiO: 8YSZ = (10-30): (20-50): (30-70); the weight ratio of each component in the second layer is: flake NiO: spherical NiO: 8YSZ = (20-40): (20-40): (20-60); the weight ratio of each component in the third layer is: flake NiO: spherical NiO: 8YSZ = (10-30): (20-50): (30-70).

2. The SOFC fuel electrode as described in claim 1, characterized in that, The weight ratio of each component in the first layer is: flake NiO: spherical NiO: 8YSZ = (10-20): (30-40): (30-70); the weight ratio of each component in the second layer is: flake NiO: spherical NiO: 8YSZ = (20-35): (20-30): (20-60); the weight ratio of each component in the third layer is: flake NiO: spherical NiO: 8YSZ = (10-20): (30-40): (30-70).

3. The SOFC fuel electrode as described in claim 1, characterized in that, The length of the sheet-like NiO is 1-10 μm, the width is 0.1-10 μm, and the thickness is 0.01-1 μm, with the thickness being 0.1 to 0.2 times the width. The particle size of the spherical NiO particles is 0.1 to 10 μm. The thickness ratio of the first layer, the second layer, and the third layer is (1-2):(1-3):(1-2).

4. The SOFC fuel electrode as described in claim 3, characterized in that, The sheet-like NiO has a length of 1-5 μm, a width of 1-5 μm, and a thickness of 0.1-0.5 μm; the thickness ratio of the first layer, the second layer, and the third layer is 1:(2-3):

1.

5. The SOFC fuel electrode as described in claim 1, characterized in that, The SOFC fuel electrode has an overall thickness of 3-35 μm, and the first and third layers have the same composition and thickness.

6. The SOFC fuel electrode as described in claim 1, characterized in that, The 8YSZ is a spherical granular powder with a particle size of 0.1~10μm; the morphology of the spherical NiO particles is at least one of spherical, near-spherical, ellipsoidal, flower-shaped, and star-shaped.

7. A method for preparing an SOFC fuel electrode as described in any one of claims 1-6, characterized in that, Includes the following steps: (1) Weigh flake NiO, spherical NiO, and 8YSZ according to the weight ratio of each component in the first layer, add binder and solvent to prepare a slurry, and prepare the first film tape by casting; weigh flake NiO, spherical NiO, and 8YSZ according to the weight ratio of each component in the second layer, add binder and solvent to prepare a slurry, and prepare the second film tape by casting; weigh flake NiO, spherical NiO, and 8YSZ according to the weight ratio of each component in the third layer, add binder and solvent to prepare a slurry, and prepare the third film tape by casting. (2) The first membrane strip, the second membrane strip, and the third membrane strip are stacked in sequence and then stamped to obtain the SOFC fuel electrode.

8. The application of the SOFC fuel electrode as described in any one of claims 1-6 in a solid oxide fuel cell.

9. A solid oxide fuel cell, characterized in that, The preparation method of the solid oxide fuel cell includes the following steps: (1) Assemble the electrolyte layer with the SOFC fuel electrode according to any one of claims 1-6, and perform a pressing process by hydrostatic pressing to obtain a composite membrane; (2) The membrane is debonded and sintered, and then the cathode layer is printed on one side of the electrolyte layer of the membrane to obtain the solid oxide fuel cell.

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