A cerium oxide-based discrete interfacial functional layer, a single cell and a preparation method thereof

Abstract

The application discloses a cerium oxide-based discrete interface functional layer, a single cell and a preparation method thereof. Non-continuous cerium oxide-based particle clusters in island distribution are grown on the surface of a zirconium oxide-based ceramic electrolyte through a hydrothermal in-situ self-crystallization method. The cerium oxide-based discrete functional layer prepared by the method is discretely distributed in the form of nanoparticle clusters between the electrolyte and the cathode, effectively increases the cathode three-phase interface, accelerates the oxygen ion conduction on the cathode side, improves the cathode and electrolyte interface bonding strength, improves the comprehensive performance of the solid oxide fuel cell, and reduces the working temperature.

Description

Technical Field

[0001] This invention relates to a cerium oxide-based discrete interface functional layer and a single cell, belonging to the field of solid oxide fuel cells / electrolytes. Background Technology

[0002] The high operating temperature (800–1000℃) of traditional SOFCs places stringent demands on materials and technologies, making the development of low-temperature (500–800℃) SOFCs a current research hotspot. Improving the cathode electrocatalytic activity or optimizing the interfacial microstructure is key to enhancing the performance of low-temperature SOFCs. The electrochemical activity of the cathode is influenced by the intrinsic properties and microstructure of the materials, with the area of ​​the three-phase interface (TPB) between the cathode, electrolyte, and gas phase significantly affecting the cathode's electrochemical activity. However, mismatches in the physical, chemical, and mechanical properties between the cathode and electrolyte can easily lead to poor interfacial contact and hindered charge transport, thereby reducing battery performance.

[0003] La 1-x Sr x MnO3 (LSM) is a purely electronic conductor and lacks ionic conductivity; therefore, its operating temperature is typically above 800℃, which limits the use of LSM cathodes in medium-temperature SOFCs. However, LSM possesses excellent thermal and chemical stability, as well as good compatibility with yttrium-stabilized zirconia (YSZ). 1-x Sr x CoO3 possesses high oxygen ion conductivity and electronic conductivity, but its coefficient of thermal expansion is incompatible with that of the common electrolyte material YSZ, which can easily lead to electrode peeling during long-term operation at high temperatures. 0.6 Sr 0.4 Co 0.2 Fe 0.8 Although LCS3 (LSCF) exhibits good electrocatalytic activity at intermediate temperatures, its chemical compatibility with YSZ electrolyte is poor. It readily forms insulating phases such as SrZrO3 at the LSCF / YSZ interface, increasing interfacial impedance. Therefore, relying solely on a single cathode material is insufficient to simultaneously achieve high electrocatalytic activity, interfacial stability, and thermal matching. Optimizing the cathode-electrolyte interface becomes an effective strategy for improving SOFC performance.

[0004] Introducing a functional interfacial layer with high ionic conductivity at the cathode-electrolyte interface has proven to be an effective method. This functional interfacial layer helps optimize the contact between the cathode and electrolyte, promotes interfacial charge transfer, thereby increasing the exchange current density and improving the electrochemical performance of the cathode. For example, dense nanocomposite films such as gadolinium oxide-doped cerium oxide (GDC), LSCF-GDC, LSCF, and erbium oxide-stabilized bismuth oxide (ESB) can be added between a zirconia-based electrolyte and a perovskite cathode to optimize the interface. Currently, pulsed laser deposition (PLD) technology is commonly used to prepare nanoscale cathode interfacial functional layers. PLD technology can obtain highly dense and uniform films, but its equipment is expensive, the process is complex, and it is difficult to prepare on a large scale.

[0005] Furthermore, existing research has largely focused on continuous, dense cerium oxide-based thin films, while studies on discretely distributed, island-like cathode interface functional layers are relatively limited. Compared to continuous, dense films, cerium oxide-based discrete interface functional layers have potential advantages in optimizing interface microstructure, improving gas diffusion, and regulating interfacial reactivity. Island-like cerium oxide-based discrete interface functional layers may form multi-scale active sites, which could help improve the kinetics of the oxygen reduction reaction (ORR). Summary of the Invention

[0006] The purpose of this invention is to provide a cerium oxide-based discrete interface functional layer and a method for preparing a single cell, by introducing a functional layer with high ionic conductivity to expand the three-phase reaction interface, reduce the cell polarization impedance, and improve performance.

[0007] The technical solution proposed by this invention to solve the problems of the prior art is as follows:

[0008] In a first aspect, the present invention provides a cerium oxide-based discrete interface functional layer, which is discretely distributed in the form of island-like nanoparticle clusters between the electrolyte and cathode interfaces.

[0009] Preferably, the size of the nanoparticle clusters is 5-20 nm.

[0010] Preferably, the functional layer has a coverage of less than 50% between the electrolyte and cathode interfaces.

[0011] In a second aspect, the present invention provides a single cell based on a cerium oxide-based discrete interface functional layer, which includes the cerium oxide-based discrete interface functional layer described in the first aspect.

[0012] A method for fabricating a single cell based on a cerium oxide-based discrete interface functional layer includes the following steps:

[0013] (1) The half-cell of the high-temperature pre-sintered doped ZrO2-based electrolyte is immersed in a soluble salt solution of Ce and lanthanide metal X, and a discontinuous cerium oxide-based particle cluster distributed in an island-like manner is formed by hydrothermal in-situ self-crystallization, i.e., the functional layer.

[0014] (2) A cathode is prepared on the surface of the functional layer by screen printing and then co-sintered to form a single cell.

[0015] Preferably, the high-temperature pre-sintered doped ZrO2-based electrolyte refers to the electrolyte that is sintered at 1320°C for 3 hours.

[0016] Preferably, in the half-cell doped with ZrO2-based electrolyte, the electrolyte includes, but is not limited to, Y-doped ZrO2, Sc-doped ZrO2, and Ce-doped ZrO2.

[0017] Preferably, in the soluble salt solution of Ce and lanthanide metal X, X includes one or more of La, Sm, Pr, and Gd, and the molar ratio of Ce to X is not less than 1:9 and not more than 4:6.

[0018] Preferably, the hydrothermal temperature is 170℃ and the hydrothermal time is not less than 2 hours and not more than 12 hours, and island-shaped nanoparticle clusters are obtained under the specified temperature and time.

[0019] Preferably, the cathode has good chemical compatibility with the electrolyte, including but not limited to lanthanum strontium manganate.

[0020] Preferably, the co-sintering temperature with the cathode is not higher than 1250℃ and the time is not greater than 6 hours.

[0021] Compared with the prior art, the advantages of the present invention are:

[0022] (1) Compared with continuous dense functional layers, cerium oxide-based discrete functional layers effectively optimize the electrolyte cathode interface and increase the active sites for redox reactions at the three-phase interface.

[0023] (2) The cerium oxide-based discrete functional layer exhibits high ionic conductivity, which makes the ion migration path shorter and the resistance smaller, which helps to improve the efficiency of ions passing through the interface and thus improves the battery performance.

[0024] (3) This method uses a one-step hydrothermal method, which is simple and convenient to operate and has low cost.

[0025] (4) The cerium oxide-based discrete functional layer prepared by this method does not have problems such as continuous dense film defects. Attached Figure Description

[0026] Figure 1These are schematic diagrams of cross-sections of solid oxide fuel cells with different structures. (a) is a cerium oxide-based discrete functional layer structure; (b) is a cerium oxide-based continuous dense ceramic thin film structure; (c) is a blank sample structure; and the magnified part is a schematic diagram of the oxygen ion conduction process on the cathode side.

[0027] Figure 2 These are schematic diagrams of the surface structure of a half-cell before and after hydrothermal treatment, without high-temperature sintering. In this diagram, (a) shows a cerium oxide-based discrete functional layer grown on the electrolyte surface after hydrothermal treatment, (b) shows a cerium oxide-based continuous dense film grown on the electrolyte surface after hydrothermal treatment, and (c) shows the electrolyte surface before hydrothermal treatment.

[0028] Figure 3 These are SEM images of the surface of half-cells that were not sintered at high temperatures, as shown in Example 1 and Comparative Examples 1-3.

[0029] Figure 4 The current and power density curves of the single cells in Example 1 and Comparative Examples 1 and 2 at 800°C are shown.

[0030] Figure 5 The electrochemical impedance spectroscopy of the single cells of Example 1, Comparative Examples 1 and 2 at 800°C is shown.

[0031] Figure 6 The current and power density curves of the single cells in Example 1 and Comparative Examples 1 and 3 at 800°C are shown.

[0032] Figure 7 The electrochemical impedance spectroscopy of the single cells of Example 1, Comparative Examples 1 and 3 at 800°C is shown.

[0033] Figure 8 These are SEM images of the microstructure cross-sections of Example 1 and Comparative Example 1. Detailed Implementation

[0034] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings.

[0035] This invention proposes a low-cost hydrothermal in-situ growth method to introduce a cerium oxide-based discrete interface functional layer between YSZ and LSM, which effectively increases the three-phase interface of the cathode, accelerates oxygen ion conduction on the cathode side, and improves battery performance.

[0036] This invention controls the time and temperature of hydrothermal in-situ growth to form a cerium oxide-based discrete functional layer on the electrolyte surface. Compared with continuous dense ceramic films, this cerium oxide-based discrete functional layer can effectively expand the three-phase interface of the reaction, improve the oxygen ion transport rate, and better reduce battery performance loss.

[0037] The electrolyte material of the solid oxide battery thin film electrolyte in the following embodiments is Y-doped ZrO2 (YSZ). The method described in this invention is not limited to YSZ electrolyte thin films, and other types of electrolyte thin films are also applicable.

[0038] The following examples use Ce, Gd hydrated nitrate electrolyte precursor solutions. In fact, the methods described in this invention are not limited to Ce, Gd nitrate solutions. Soluble salts include, but are not limited to, common trivalent nitrates, oxalates, acetates, chlorides, etc., such as La, Gd, Sm, and Pr.

[0039] The following embodiments use Sr-doped LaMnO3 to form La0.8Sr0.2MnO3 (LSM). In fact, the method described in this invention is not limited to optimizing the LSM cathode interface, and is also applicable to other existing types of cathode interfaces.

[0040] The following embodiments employ a one-step hydrothermal reaction to grow a GDC functional layer in situ on the sintered solid oxide battery electrolyte film, optimizing the electrolyte-cathode interface, increasing the three-phase interface, accelerating oxygen ion conduction on the cathode side, and effectively improving the overall output performance of a single cell.

[0041] This invention employs a single hydrothermal method to in-situ self-crystallize a cerium oxide-based discrete functional layer on the surface of the electrolyte in an anode-supported half-cell. The functional layer is discretely distributed on the electrolyte surface in the form of nanoparticle aggregates. Furthermore, a cathode is fabricated on the surface of the functional layer using screen printing, followed by co-firing to form a single cell. Comparing cerium oxide-based discrete functional layers with different coverage rates, continuous dense cerium oxide-based ceramic films, and a blank sample, the cerium oxide-based discrete functional layer prepared in this invention can increase the three-phase interface between the electrolyte and the cathode, accelerate oxygen ion conduction on the cathode side, and effectively improve the overall output performance of the single cell.

[0042] Example 1

[0043] A 0.1 mol / L, 60 ml aqueous solution was prepared by mixing Gd(NO3)3·6H2O and Ce(NO3)3·6H2O at a ratio of 0.2:0.8. After thorough stirring, the calcined (1320℃ / 3 hours) half-cell NiO-YSZ||YSZ was placed in a reactor containing the aqueous solution and reacted at 170℃ for 3 hours. This process resulted in the formation of discontinuous cerium oxide-based particle clusters, i.e., the functional layer, through hydrothermal in-situ self-crystallization. During this process, the YSZ electrolyte layer was ensured to be completely exposed to the solution, while other non-critical components, such as the anode support, were protected by a mold. After the reaction, the sample was removed, the surface was rinsed with deionized water, and then an LSM cathode with an area of ​​0.5 cm² was screen-printed. 2 The cells were calcined (co-sintered) at 1200℃ for 2 hours, and silver meshes were screen-printed on the anode and cathode sides as current collectors to form an anode-supported single cell.

[0044] Comparative Example 1

[0045] LSM was screen-printed onto the calcined NiO-YSZ||YSZ half-cell after calcination (calcination temperature 1320℃ / 3 hours), with an area of ​​0.5 cm². 2 The cells were calcined at 1200℃ for 2 hours; silver mesh was screen-printed on the anode and cathode sides as current collector layers to form an anode-supported single cell.

[0046] Comparative Example 2

[0047] In Example 1, the hydrothermal time was changed to 12 hours, while the other conditions remained the same, and the same steps were repeated.

[0048] Comparative Example 3

[0049] In Example 1, the hydrothermal temperature was changed to 180°C, while the other conditions remained the same, and the same steps were repeated.

[0050] Figure 1 These are schematic diagrams of cross-sections of solid oxide fuel cells with different structures. Figure 1 (a) shows the cerium oxide-based discrete functional layer structure; (b) shows the cerium oxide-based continuous dense ceramic thin film structure; (c) shows the structure of the blank sample; the magnified part is a schematic diagram of the oxygen ion conduction process on the cathode side. It can be observed that the cerium oxide-based discrete functional layer structure can increase the three-phase interface, accelerate the oxygen ion conduction process on the cathode side, and effectively modify the electrolyte-cathode interface.

[0051] Figure 2 This is a schematic diagram of the surface structure of a half-cell before and after hydrothermal treatment, without high-temperature sintering. Figure 2 (a) shows a cerium oxide-based discrete functional layer grown on the electrolyte surface after hydrothermal treatment; (b) shows a cerium oxide-based continuous dense film grown on the electrolyte surface after hydrothermal treatment; and (c) shows the electrolyte surface before hydrothermal treatment. Figure 3 Example 1 shows SEM images of the surface of half-cells from Comparative Examples 1-3 that were not sintered at high temperatures. It can be seen that the YSZ crystal structure and grains on the electrolyte surface changed significantly before and after hydrothermal treatment. Before hydrothermal treatment, the electrolyte surface of Comparative Example 1 showed smooth, clearly defined YSZ grains. After hydrothermal treatment at 170°C for 3 hours, numerous GDC nanoparticles grew on the YSZ crystal faces of the electrolyte in Example 1, distributed in serrated clusters. This structure is a functional layer, discretely distributed on the electrolyte surface in the form of nanoparticle clusters. Using ImageJ software, the coverage of the discrete functional layer was calculated. In Example 1, the coverage of the functional layer between the electrolyte and cathode interface was 46%. With increasing hydrothermal time, a continuous and dense GDC film covered the electrolyte surface of Comparative Example 2. With increasing hydrothermal temperature, the GDC grain size on the electrolyte surface of Comparative Example 3 increased, and the GDC structure showed a larger continuous area, with a coverage of 59%.

[0052] Figure 4 These are the current and power density curves of the single cells in Example 1, and Comparative Examples 1 and 2, at 800°C. The open-circuit voltage of all single cells is approximately 1.07V, indicating good battery sealing. Example 1 achieved a maximum power density of 660 mW / cm³. 2 Compared to Comparative Examples 1 and 2, the battery's output performance was improved.

[0053] Figure 5 These are the electrochemical AC impedance spectra of single cells from Examples 1, 1, and 2 at 800°C. The polarization impedance of Comparative Example 1 at 800°C is 0.595 Ω·cm. 2 Comparative Example 2 has a polarization impedance of 0.487 Ω·cm. 2 The polarization impedance of Example 1 is 0.398 Ω·cm. 2 .

[0054] Figure 6 These are the current and power density curves of the single cells in Example 1, Comparative Examples 1 and 3, at 800°C. Compared to the single cells in Comparative Examples 1 and 3, the single cell in Example 1 has the highest maximum power density value, exhibiting the best performance.

[0055] Figure 7 This is the electrochemical AC impedance spectrum of the single cell from Example 1, Comparative Examples 1 and 3, at 800°C. At 800°C, the ohmic impedance of Example 1 drops to 0.057 Ω·cm. 2 Compared to 0.060 Ω·cm in Comparative Example 3 2 The polarization impedance decreased by 5%; it was 0.886 Ω·cm², compared to 0.994 Ω·cm² in Comparative Example 3. 2 It also decreased by 10.9%. Due to the reduction in hydrothermal temperature, the GDC grain size was reduced, agglomeration was reduced, and the growth of the GDC structure was dispersed. Therefore, the contact area of ​​the electrode / electrolyte interface was effectively expanded, more three-phase interfaces were added, and the polarization resistance of the battery was reduced.

[0056] Figure 8 These are SEM images of the cross-sectional microstructures of Example 1 and Comparative Example 1. In Example 1, the electrolyte membrane is dense and continuous without cracks. Due to its good chemical compatibility, the YSZ electrolyte and GDC functional layer are well sintered, making it difficult to distinguish the GDC grains from the YSZ electrolyte layer at the electrolyte / cathode interface. However, it can be observed that after introducing the functional layer between the electrolyte and the cathode, the contact interface exhibits a serrated morphology, which is significantly different from Comparative Example 1.

Claims

1. A cerium oxide-based discrete interface functional layer, characterized in that, This functional layer is discretely distributed in the form of island-like nanoparticle clusters between the electrolyte and cathode interfaces.

2. The cerium oxide-based discrete interface functional layer as described in claim 1, characterized in that, The size of the nanoparticle clusters is 5-20 nm.

3. The cerium oxide-based discrete interface functional layer as described in claim 1, characterized in that, The functional layer has a coverage of less than 50% between the electrolyte and cathode interfaces.

4. A single cell based on a cerium oxide-based discrete interface functional layer, characterized in that, It includes a cerium oxide-based discrete interface functional layer as described in any one of claims 1-3.

5. A method for preparing a single cell as described in claim 4, characterized in that, Includes the following steps: (1) The half-cell of the high-temperature pre-sintered ZrO2-based electrolyte was immersed in a soluble salt solution of Ce and lanthanide metal X, and a functional layer was formed by hydrothermal in-situ self-crystallization. (2) A cathode is prepared on the surface of the functional layer by screen printing and then co-sintered to form a single cell.

6. The method as described in claim 5, characterized in that, In a half-cell doped with ZrO2-based electrolyte, the electrolyte is Y-doped ZrO2, Sc-doped ZrO2, or Ce-doped ZrO2.

7. The method as described in claim 5, characterized in that, In a soluble salt solution of Ce and lanthanide metal X, where X includes one or more of La, Sm, Pr, and Gd, the molar ratio of Ce to X is not less than 1:9 and not more than 4:

6.

8. The method as described in claim 5, characterized in that, The hydrothermal temperature is 170℃, and the hydrothermal time is not less than 2 hours and not more than 12 hours.

9. The method as described in claim 5, characterized in that, The cathode is lanthanum strontium manganate.

10. The method as described in claim 5, characterized in that, The co-sintering temperature should not exceed 1250℃ and the time should not exceed 6 hours.

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