Solid oxide cell separator and monocell and method of manufacture

Abstract

The application discloses a solid oxide cell isolation layer and a single cell and a preparation method. A solid oxide cell electrolyte is immersed in an aqueous solution, reacts for a certain time at a certain temperature to form an isolation layer, an electrode is prepared on the surface of the isolation layer by using a screen printing method, and then co-sintering is performed to form a single cell. The isolation layer prepared by the application can effectively inhibit the chemical reaction and element diffusion of the electrode / electrolyte interface, prevent the mutual reaction of the electrode and the electrolyte, and has the advantages of simple process flow, low cost, controllable composition and thickness, easy scale production, and suitability for various configurations of solid oxide cells.

Description

Technical Field

[0001] This invention relates to a solid oxide battery separator, a single cell, and a preparation method thereof, for use in solid oxide fuel cells / electrolytes, and belongs to the field of new energy technology. Background Technology

[0002] In solid oxide fuel cells, zirconia-based electrolytes (such as 8YSZ) maintain good chemical stability under both reducing and oxidizing atmospheres, and are therefore widely used as electrolyte materials. However, they also have certain drawbacks, such as poor chemical compatibility with many highly active perovskite anion and anode materials; and a tendency to react during high-temperature preparation and long-term operation, generating low-conductivity phases such as La₂Zr₂O₇, SrZrO₃, and Sr₂ZrO₄, which severely affect battery performance and lifespan. Currently, to address this issue, a common method is to add a layer of CeO₂-doped ceramic film (such as GDC, gadolinium oxide-doped cerium oxide) between the electrode and the electrolyte. 0.1 Ce 0.9 O 1.95 As an insulating layer, it can not only suppress electrode / electrolyte interface reactions and element diffusion, and prevent the formation of high-resistivity products, but its expansion coefficient is located between the electrode and the electrolyte, which can also improve the thermal expansion matching between the two.

[0003] Although the GDC insulating layer can prevent the electrolyte from reacting with the active electrode during high-temperature preparation and long-term operation, gadolinium oxide-doped cerium oxide (GDC) sintered using conventional methods only achieves a density of over 95% at 1550℃. Furthermore, co-sintering GDC with YSZ films is difficult, and the temperature can be significantly lower at ~1200℃. o Reactions above C will also occur to form the insulating phase SrZrO3, thus affecting the battery performance. A denser GDC separator can effectively reduce the ohmic impedance of fuel cells, but separators prepared by conventional sintering methods have low density, which significantly increases the ohmic impedance of solid oxide batteries.

[0004] Currently, there are many methods for preparing GDC insulating layers. Pulsed laser deposition, chemical vapor deposition, electrochemical deposition, and reactive sputtering can produce relatively dense CeO2 insulating layers, but these methods involve complex production processes, expensive equipment, and high costs. For example, electrophoretic deposition on SSZ electrolyte and La... 0.6 Sr 0.4 CoO 3-δA ~2 μm GDC separator layer was prepared between the (LSC) cathode and the cathode. Thicker GDC may be beneficial in suppressing the reaction between SSZ and LSC, but when its thickness is increased to ≥5 μm, cracks will appear during co-sintering; GDC separator layers prepared by precipitation deposition with a thickness between 3-6 μm will exhibit a porous structure; GDC separator layers prepared by the most commonly used screen printing method will form a porous structure after high-temperature sintering.

[0005] Therefore, the aforementioned problems stem from the high production cost, expensive equipment, complex processes, and difficulty in large-area fabrication of high-density GDC separators, as well as the tendency to form porous structures and cracks after sintering. Furthermore, they exhibit poor adaptability to irregularly shaped electrolyte surfaces, such as tubular, conical, and corrugated structures. Therefore, achieving low-cost fabrication of large-area dense separators at low temperatures is a pressing issue for the solid oxide battery industry. Summary of the Invention

[0006] This invention provides a novel method for preparing a solid oxide battery separator layer and a single cell. The separator layer is grown on the surface of the solid oxide battery electrolyte using an in-situ growth method, and then co-sintered with an electrode prepared by screen printing to achieve the fabrication of a high-density cerium oxide-based ceramic thin film separator layer and a single cell.

[0007] The technical solution proposed by the present invention to solve the problems of the prior art is as follows: a solid oxide battery separator layer and its preparation method, wherein the solid oxide battery electrolyte is immersed in an aqueous solution and reacted at a certain temperature for a certain time to form a separator layer.

[0008] A solid oxide single cell and its preparation method include two steps: in-situ growth of the separator layer and co-sintering it with a screen-printed electrode, as detailed below: (1) The solid oxide battery electrolyte is immersed in an aqueous solution and reacted at a certain temperature for a certain time to form an isolation layer; (2) Electrodes are prepared on the surface of the insulating layer by screen printing and then co-sintered to form a single cell.

[0009] Preferably, the configuration of the solid oxide battery includes any one of electrolyte support, anode (hydrogen electrode) support, cathode (oxygen electrode) support, support body support, and metal support, and its shape is any one of flat plate, cylindrical tube, flat tube, series tube or corrugated.

[0010] Preferably, the isolation layer formed is composed of cerium oxide-doped material with the general formula Ce. n X 1-n O 2-δ X can be one of the lanthanide rare earth elements such as Gd, Sm, La, and Pr, and n = 0.6~1.

[0011] Preferably, the aqueous solution is a soluble salt solution of Ce and X, with a molar ratio of Ce:X = 0.6-1:0.4-0.

[0012] Preferably, the concentration of the aqueous solution is 0.01-1 mol / L.

[0013] Preferably, the reaction temperature is 100-250℃ and the reaction time is 1-100 h.

[0014] Preferably, the pH value of the aqueous solution before the reaction is not higher than 7.

[0015] Preferably, when co-sintering to form a single cell, the co-sintering temperature is not higher than 1200℃ and the time is not longer than 10 hours.

[0016] Compared with the preparation of traditional CeO2-based separators (GDC) / single cells, its advantages are: (1) This method only requires co-sintering with the electrode, which simplifies the process flow, while the traditional preparation method requires separate high-temperature sintering.

[0017] (2) This method achieves co-sintering with the electrode, which effectively reduces the sintering temperature of the isolation layer, which is far lower than the reaction temperature of CeO2 and ZrO2, and will not generate (Ce,Zr)O2 solid solution.

[0018] (3) This method immerses the electrolyte in the solution, and the electrolyte is in contact with the solution. The concentration of reactants and the force on the electrolyte surface are uniform, which can achieve uniform growth.

[0019] (4) This method is applicable to multi-configuration solid oxide batteries and can achieve in-situ growth on electrolyte surfaces of various battery shapes, such as corrugated and tubular curved surfaces.

[0020] (5) This method has low equipment and operating costs, simple and controllable process, obvious effect and can be mass-produced. Attached Figure Description

[0021] Figure 1 It is the traditional single-cell preparation process and the preparation process proposed in this invention patent.

[0022] Figure 2 These are comparative examples 1-2 and schematic diagrams of the battery structure of this invention patent.

[0023] Figure 3 The electrochemical impedance spectroscopy spectra of single cells from Comparative Examples 1-2 and Examples 1-2 at 750°C are shown.

[0024] Figure 4 The curves show the current and power density of single cells in Comparative Examples 1-2 and Examples 1-2 at 750°C.

[0025] Figure 5 These are the electrochemical impedance spectroscopy spectra of the single cells in Examples 1, 3, and 4 at 750°C.

[0026] Figure 6 These are the current and power density curves of the single cells in Examples 1, 3, and 4 at 750°C.

[0027] Figure 7 The X-ray diffraction patterns of the electrolyte surface before and after the reaction of the half-cell NiO-YSZ||YSZ in Example 1 are shown.

[0028] Figure 8 These are scanning electron microscope (SEM) images of the cross-sectional microstructure of a single cell from Comparative Example 1 and Example 1.

[0029] Figure 9 The single cell in Example 1 is at 0.42 A / cm 2 Stability curves of long-term operation for 300 hours under constant current density. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings.

[0031] The solid oxide battery configuration used in the following embodiments is an anode-supported structure, the electrolyte material is yttrium-stabilized zirconium oxide (8YSZ), and the aqueous solution is a soluble salt solution of Ce and Gd (not limited to Gd, but also lanthanide rare earth elements such as Sm, La, and Pr).

[0032] Comparative Example 1 An LSCF-GDC-LSCF cathode with an area of ​​0.5 cm² was directly screen-printed onto the calcined half-cell NiO-YSZ||YSZ. 2 The anode-supported single cell was prepared by calcining at 1075℃ for 2 hours.

[0033] Comparative Example 2 A GDC separator layer was screen-printed on the calcined NiO-YSZ||YSZ half-cell, and then calcined at 1250℃ for 3 hours. An LSCF-GDC||LSCF cathode with an area of ​​0.5 cm² was screen-printed on the GDC. 2 The anode-supported single cell was prepared by calcining at 1075℃ for 2 hours.

[0034] Example 1 A 0.05 mol / L, 60 ml solution was prepared using a Gd(NO3)3·6H2O:Ce(NO3)3·6H2O ratio of 0.1:0.9. The pH of the solution was adjusted to 6-7, and after thorough stirring, the calcined half-cell NiO-YSZ||YSZ (with the YSZ electrolyte side facing up) was placed in a reactor containing the aqueous solution and reacted at 180℃ for 24 h. After the reaction, the pH of the solution decreased, and then an LSCF-GDC||LSCF cathode with an area of ​​0.5 cm² was screen-printed. 2 The anode-supported single cell was prepared by calcining (co-sintering) at 1075℃ for 2 hours.

[0035] Example 2 Prepare a 0.02 mol / L, 60 ml aqueous solution by mixing Gd(NO3)3·6H2O and Ce(NO3)3·6H2O in a ratio of 0.1:0.9, and keep all other conditions unchanged.

[0036] Example 3 The reaction time in the reactor in Example 1 was changed to 36 hours, while the other conditions remained unchanged.

[0037] Example 4 The reaction time in the reactor in Example 1 was changed to 48 hours, while the other conditions remained unchanged.

[0038] Figure 1 The traditional single-cell fabrication process and the fabrication process proposed in this invention are different. The isolation layer is grown on the surface of the electrolyte through in-situ growth, and then co-sintered with the cathode to achieve the fabrication of the isolation layer and the single cell.

[0039] Figure 2 These are schematic diagrams of the battery structures of Comparative Examples 1-2 and the present invention. The battery structure of Comparative Example 1 is an anode support || electrolyte || cathode, and the battery structures of Comparative Example 2 and the present invention are an anode support || electrolyte || separator || cathode.

[0040] Figure 3 The electrochemical impedance spectroscopy spectra of the single cells of Comparative Examples 1-2 and Examples 1-2 at 750°C are shown. The ohmic impedances of the cells in Comparative Examples 1 and 2 are 0.112 Ω·cm. 2 and 0.163Ω･cm 2 Furthermore, the polarization impedance of Comparative Example 1 is 2.487 Ω·cm. 2 The polarization impedance is more than twice that of the batteries in other embodiments; the ohmic impedances of batteries in embodiments 1 and 2 are 0.103 Ω·cm. 2 and 0.102Ω･cm 2Compared with the comparative example, the ohmic impedance is significantly reduced. This is because the addition of the insulating layer suppresses the interfacial reaction and element diffusion of the electrode / electrolyte, prevents the formation of high-impedance products, and proves the feasibility of the technical solution described in this invention. Moreover, the electrochemical performance of the prepared single cell is better than that of the screen printing method.

[0041] Figure 4 The figures show the current and power density curves of single cells from Comparative Examples 1-2 and Examples 1-2 at 750°C. The maximum power density of the cell in Comparative Example 1 is only 0.079 W / cm². 2 The output performance was extremely poor because the LSCF cathode and YSZ electrolyte reacted during sintering, forming an insulating solid solution; the maximum power density of the comparative example 2 cell was 0.898 W / cm³. 2 The maximum power density of the batteries in Examples 1 and 2 was 1.013 W / cm², respectively. 2 and 1.092W / cm 2 Compared to the comparative example, the output performance is significantly improved.

[0042] Figure 5 These are the electrochemical impedance spectroscopy spectra of the single cells from Examples 1, 3, and 4 at 750°C. The ohmic and polarization impedances of the cells are 0.103 Ω·cm. 2 0.103Ω·cm 2 0.099Ω･cm 2 and 0.871Ω･cm 2 0.636Ω·cm 2 0.52Ω·cm 2 .

[0043] Figure 6 These are the current and power density curves of the single cells in Examples 1, 3, and 4 at 750°C. The maximum power density of the cells is 1.013 W / cm³, respectively. 2 1.214W / cm 2 1.177W / cm 2 .

[0044] Figure 7 The X-ray diffraction spectra of the electrolyte surface before and after the reaction of the half-cell NiO-YSZ||YSZ in Example 1 show that GDC is generated on the electrolyte surface after the reaction.

[0045] Figure 8 The images show the cross-sectional microstructure of the single cells in Comparative Example 1 and Example 1 using scanning electron microscopy. It can be observed that the thickness of the separator prepared by this invention is ~600 nm, which is thinner than the separator prepared by screen printing. At the same time, it achieves low-cost densification of the separator.

[0046] Figure 9 The single cell in Example 1 is at 0.42 A / cm 2 The stability curves obtained from the long-term operation of the isolation layer and single cell under constant current density for 300 hours show that the method of preparing the isolation layer and single cell of the present invention can achieve stable operation for 300 hours.

Claims

1. A method for preparing a solid oxide battery separator layer, characterized in that, The electrolyte of the solid oxide battery is immersed in an aqueous solution and reacted at 180°C for 24-48 hours to form an isolation layer. The aqueous solution is a soluble salt solution of Ce and X, with a molar ratio of Ce:X = 0.6-1:0.4-0, where X is not 0 and X is one of the lanthanide rare earth elements Gd, Sm, La, and Pr.

2. The method as described in claim 1, characterized in that, Solid oxide batteries can be configured in any of the following ways: electrolyte support, anode support, cathode support, support body support, or metal support. Their shape can be any of the following: flat plate, cylindrical tube, flat tube, series tube, or corrugated.

3. The method as described in claim 1, characterized in that, The concentration of the aqueous solution is 0.01-1 mol / L.

4. The method as described in claim 1, characterized in that, The pH value of the aqueous solution is not higher than 7.

5. The solid oxide battery separator layer prepared by the method according to any one of claims 1-4.

6. A method for preparing a solid oxide single cell, characterized in that, include: Electrodes are fabricated on the surface of the solid oxide battery separator layer prepared by any one of the methods described in claims 1-4 using screen printing, and then co-sintered to form a single cell.

7. The method as described in claim 6, characterized in that, When co-sintering to form a single cell, the co-sintering temperature shall not exceed 1200℃ and the time shall not exceed 10 h.

8. A solid oxide single cell prepared by the method of claim 6 or 7.

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