Method for activating electrolyte surface of SOFC (solid oxide fuel cell) through ion polishing

Abstract

The invention discloses a surface treatment method for activating the electrolyte surface of a solid oxide fuel cell (SOFC) through ion polishing treatment and remarkably improving the electrochemical performance and durability of the SOFC. The method mainly comprises the following steps: preparing an anode / electrolyte double-layer structure half cell; carrying out ion polishing treatment on the electrolyte surface of the half cell by using an ion polishing instrument; and coating the surface of the treated electrolyte with the cathode slurry, and sintering to obtain the single cell. The surface of the electrolyte is subjected to ion polishing treatment, so that the surface of the electrolyte can be effectively activated and the surface roughness can be increased, the interface bonding strength and the effective contact area of the electrolyte / cathode are increased, and the electrochemical performance and the durability of the battery are remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the field of inorganic non-metallic ceramic materials and energy and power technology, and specifically relates to a new technology for surface treatment of solid oxide fuel cell (SOFC) electrolyte, namely, a method for activating the surface of SOFC electrolyte by ion polishing, which activates the surface of SOFC electrolyte by ion polishing, increases the electrolyte / cathode interface bonding strength and effective contact area, thereby significantly improving the electrochemical performance and durability of the battery. Background Art

[0002] Solid oxide fuel cell (SOFC) is a power generation device that directly converts chemical energy stored in fuel and oxidant into electrical energy with high efficiency. Its biggest feature is that the reaction process does not involve combustion, and the energy conversion efficiency is as high as 60~80%, which is 2~3 times that of ordinary internal combustion engines. It has the advantages of all-solid-state structure, fuel diversity, zero emissions, and no need for precious metals. In traditional SOFC, the ohmic resistance at the electrolyte and the polarization resistance at the cathode are the main sources that limit the performance and durability of SOFC. With the advancement of electrolyte film preparation technology and the continuous development of high-performance cathode materials, the resistance at the electrolyte and cathode has been significantly reduced. Correspondingly, the cathode / electrolyte interface bonding quality and interface resistance have become one of the key factors determining the low-temperature performance of SOFC. However, a large number of studies in recent years have shown that SOFC still has the inherent defect of weak cathode / electrolyte interface bonding, which seriously limits the development of SOFC. For example, some recent work by Choi et al. (Choi S, Kucharczyk CJ, Liang Y, et al. Exceptional power density and stability at intermediate temperatures in protonic ceramic fuel cells [J]. Nature Energy, 2018, 3 (3): 202-210.) has shown that electrolyte surface passivation (surface chemical segregation and weak bonding between electrolyte and cathode, etc.) will lead to larger interface contact (ohmic and polarization) resistance, affecting the performance of the single cell; and Bian et al. (Bian W, Wu W, Wang B, et al. Revitalizing interface in protonic ceramic cells by acid etch [J]. Nature, 2022, 604 (7906): 479-485) found that after working, obvious cracks appeared at the interface between the electrolyte layer and the cathode layer of the single cell, and the conductivity of the electrolyte could not be fully utilized in the single cell. The calcination temperature of the combined single cell is as high as 1400 ° C, while the calcination temperature of the single cell is only 1000 ° C. Bian et al. believed that the surface activity of the electrolyte after high-temperature annealing is low, which is not conducive to the bonding of the electrolyte / cathode interface during the secondary low-temperature calcination, and seriously limits the life and durability of SOFC.

[0003] In order to solve the above problems and enhance the cathode / electrolyte interface bonding, many strategies have been proposed and achieved remarkable results, which are mainly divided into two aspects: electrolyte surface structure design and electrolyte surface treatment. In terms of electrolyte surface structure design, the rough structure of the electrolyte surface is mainly designed through methods such as photolithography, 3D printing, atomic layer deposition, template method, physical cutting, etc., so as to enhance the effective contact area of ​​the cathode / electrolyte interface and achieve the purpose of enhancing SOFC performance (Zheng L, Xu R, Zhang J, et al. Enhanced electrochemical performance by structural design of electrolyte surface combining 3D printing technology with multi-physical modelling [J]. Chemical Engineering Journal, 2023, 451: 139038).In terms of electrolyte surface treatment, it mainly includes surface acid etching (Bian W, Wu W, Wang B, et al. Revitalizing interfacein protonic ceramic cells by acid etch[J]. Nature, 2022, 604(7906): 479-485), laser ablation (Si Xiaoqing, Xue Yuewen, Wang Xiaoyang, et al. Method for improving the interface between electrolyte and cathode based on femtosecond laser surface groove structure[P]. Chinese invention patent, CN117410535A), sandblasting (Konno A, Iwai H, InuyamaK, et al. Mesoscale-structure control at anode / electrolyte interface in solidoxide fuel cell[J]. Journal of Power Sources, 2011, 196(1): 98-109), mechanical polishing (Li C, Tong X, Yuan C, et al. Electrolyte-electrode interface: A key factorfor advanced protonic ceramic electrochemical cells[J]. CeramicsInternational, 2024, 50(3): 4656-4664.) and other methods, while removing inactive substances on the electrolyte surface, increasing the roughness of the electrolyte surface, thereby improving the cathode / electrolyte interface bonding strength and battery performance.

[0004] The above electrolyte surface treatment methods have effectively enhanced the performance and durability of SOFC, but there are still some problems. For example, the sandpaper mechanical polishing method is simple and low-cost, but it is easy to damage the electrolyte and cause gas leakage. As for the simple and effective surface acid etching treatment method, this research group has developed a new method for the surface treatment of oxygen ion conductor electrolyte Ce. 0.8 Sm 0.2 O 2-δ (SDC) surface acid etching treatment (Wang X, Lu F, Liang Q, et al. Improved Performance of Solid Oxide Fuel Cells with the BaCo 0.4 Fe 0.4 Zr 0.1 Y 0.1 O 3−δCathode by a Modified Acid Etch ofCe 0.8 Sm 0.2 O 2-δ Electrolyte[J]. Energy&Fuels, 2025.) found that simple acid etching can effectively activate the SDC surface and increase the surface roughness, significantly enhancing the battery performance and durability, but it also has problems such as poor parameter stability, easy excessive corrosion and accompanying environmental pollution. Therefore, a new method is urgently needed to achieve precise, effective and environmentally friendly SOFC electrolyte surface treatment. Summary of the invention

[0005] In order to solve the problems existing in the above-mentioned prior art, the present invention provides a novel method for activating the electrolyte surface of a solid oxide fuel cell (SOFC) by ion polishing, which activates the electrolyte surface of the SOFC by ion polishing, and can significantly improve the electrochemical performance and durability of the SOFC; that is, by accurately setting the working voltage and working time, the degree of polishing treatment of the electrolyte surface is precisely controlled, the electrolyte surface is effectively activated and its roughness is increased, thereby significantly improving the cathode / electrolyte interface bonding and battery performance.

[0006] To achieve the above object, the present invention adopts the following technical solutions: A method for activating the surface of a SOFC electrolyte by ion polishing, the method specifically comprising: performing ion polishing on the electrolyte surface of the SOFC half-cell before coating the cathode. The method can significantly improve the electrochemical performance and durability of the SOFC.

[0007] Specifically, the ion polishing process is achieved by an ion polishing instrument, which includes the following working parameters: the working vacuum degree of the instrument chamber is 1×10 -2 -1×10 -4 , the operating voltage is 2-6 kV, and the operating current is 1-4.5 mA.

[0008] Furthermore, when the ion polishing instrument performs ion polishing, the ion source used may be argon ions, and the ion polishing process may take 5-40 minutes. Preferably, the model of the ion polishing instrument may be Leica EM Res102.

[0009] Specifically, the configuration of the SOFC half-cell is an anode|electrolyte structure, wherein the electrolyte is a classic oxygen ion conductor electrolyte--cerium oxide-based electrolyte SDC, and the anode is composed of nickel oxide+electrolyte.

[0010] The present invention provides a method for preparing SOFC by activating the surface of SOFC electrolyte through ion polishing, which specifically comprises the following steps: S1: Prepare a SOFC half-cell with anode|electrolyte configuration, with a heat treatment temperature of 1350-1700 °C and a heat treatment time of 5-10 h; S2: The electrolyte surface of the half-cell obtained in S1 was ion polished using an ion polisher. The treatment time was 5-40 min. The ion source used was argon ions. The working vacuum degree of the instrument chamber was 1×10 -2 -1×10 -4 , the operating voltage is 2-6 kV, and the operating current is 1-4.5 mA; S3: prepare cathode slurry, evenly apply the cathode slurry on the surface of the electrolyte treated by S2, and heat treat it at 900-1000°C for 1-3 h.

[0011] The present invention provides a solid oxide fuel cell SOFC prepared by the above preparation method.

[0012] The present invention uses an ion polishing instrument to perform ion polishing treatment on the surface of the SOFC half-cell SDC for 5-40 minutes at a working voltage of 2-6 kV, thereby removing inactive substances on the SDC surface and obtaining a rough surface structure; the cathode is further connected to the treated SDC surface to prepare a corresponding SOFC single cell. The method of the present invention can effectively activate the electrolyte surface and increase the surface roughness by performing ion polishing treatment on the electrolyte surface, thereby increasing the electrolyte / cathode interface bonding strength and effective contact area, and significantly improving the electrochemical performance and durability of the battery.

[0013] Compared with the prior art, the method of ion polishing SOFC electrolyte surface of the present invention has the following advantages and beneficial effects: 1) The present invention uses an ion polisher to perform ion polishing on the electrolyte surface. The ion polisher has the characteristics of high peak power and low probability of destructive impact on the electrolyte. It can achieve polishing on the SDC without destroying its physical and chemical properties.

[0014] 2) The process parameters of the present invention are controllable and have good stability. The degree of polishing treatment on the electrolyte surface can be accurately controlled by accurately setting the working voltage and working time, thereby avoiding problems such as electrolyte leakage caused by excessive treatment.

[0015] 3) The ion polishing treatment technology of the present invention can remove inactive substances on the SDC surface, improve the surface activity of the electrolyte, and obtain a rough structure on the SDC surface, which is beneficial to the interface bonding between the cathode and the electrolyte.

[0016] 4) The process of the present invention is simple, easy to operate, and can effectively avoid environmental pollution problems associated with chemical methods such as acid etching. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The top view (a) and side view (b) SEM images of the microscopic morphology of the SDC prepared in Example 1 of the present invention before and after ion polishing treatment; Figure 2 AFM (a) and KPFM (b) test images of the SDC surface before and after ion polishing prepared in Example 1 of the present invention; Figure 3 The XPS spectra of the SDC surface before (a) and after (b) ion polishing treatment prepared in Example 1 of the present invention; Figure 4 SEM images (a, b) of the cathode / electrolyte interface before and after ion polishing treatment and the interface peeling strength test result (d) prepared in Example 1 of the present invention; (c) is a schematic diagram of a homemade peeling test device; Figure 5 IV (a), IP curve (b), and corresponding long-term stability (c) and thermal cycle stability (d) test results of the NiO-SDC|SDC|BSF-20NM configuration single cell before and after ion polishing treatment prepared in Example 1 of the present invention; Figure 6 EIS curves of a NiO-SDC|SDC|BSF-20NM configuration single cell (a) and a BSF-20NM|SDC|BSF-20NM configuration symmetric cell (b) before and after ion polishing prepared in Example 1 of the present invention; Figure 7 This is the process of preparing a NiO-SDC|SDC|BSF-20NM configuration single cell with ion polishing treatment according to Example 1 of the present invention. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is further described in detail below in conjunction with the embodiments, but the protection scope of the present invention is not limited thereto. In order to enable those skilled in the art to better understand that the technical solution of the present invention can be implemented, the present invention is further described below in conjunction with specific embodiments, but the embodiments are not intended to limit the present invention. Unless otherwise defined, all professional terms used hereinafter have the same meaning as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing the specific embodiments and are not intended to limit the protection scope of the present invention.

[0019] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be purchased from the market or prepared by existing methods.

[0020] Example 1 A method for preparing SOFC by ion polishing and activating the surface of SOFC electrolyte (the process is shown in Figure 7), which specifically includes the following steps: S1: Prepare a SOFC half-cell of anode|electrolyte configuration, i.e., NiO-SDC|SDC half-cell, with a heat treatment temperature of 1350-1700 °C and a heat treatment time of 5-10 h; the preparation process of NiO-SDC|SDC half-cell can be specifically referred to the method in the existing literature (Kang Liu, Fei Lu, et al. A highperformance thermal expansion offset composite cathode for IT-SOFCs†. Journal of Materials Chemistry A, 2022, 10,24410); S2: Electrolyte preparation: The electrolyte surface of the NiO-SDC|SDC half-cell obtained in S1 was ion polished by an ion polisher to remove the non-surface active substances on the SDC surface and obtain a rough surface structure. The treatment time was 20 min, the ion source used was argon ions, and the working vacuum degree of the instrument chamber was 1×10 -3 , the working voltage is 3 kV, the working current is 4 mA; S3: Preparation of cathode slurry: a. Weigh the BSF prepared by the sol-gel method and the NM powder prepared by the solid phase reaction method according to the mass ratio, and mix them evenly by ball milling to obtain a BSF-20NM composite cathode material; b. Further weighing BSF-20NM composite cathode material, ethyl cellulose and pinene alcohol according to the mass ratio, mixing and grinding to obtain cathode slurry; S4: single cell preparation: the cathode slurry prepared in S3 is coated on the surface of the electrolyte SDC treated by S2 to obtain a half-cell with the cathode slurry; the half-cell with the cathode slurry is placed in a muffle furnace and sintered in an air atmosphere to obtain a final single cell.

[0021] The BSF-20NM composite cathode material is a thermal expansion compensation composite cathode material Ba with excellent performance developed by the inventors. 0.5 Sr 0.5 FeO 3-δ -20NdMnO 3-δ(BSF-20NM), the specific preparation details of the composite cathode material, cathode slurry and single cell can be referred to the existing literature (Lu F, Shi Y, Shi L, et al. Improved SOFCperformance by enhancing cathode / electrolytebonding and grain refinement ofcathode with thermal expansion offset[J].Ceramics International, 2024, 50(22): 46318-46326.) and patents (Cai Bin, Lu Fei, Yang Mengjie, et al. A new composite cathode material containing negative thermal expansion material and its application in the preparation of SOFC[P]. Chinese invention patent, CN111403754B)).

[0022] Example 2 A method for preparing SOFC by ion polishing to activate the surface of SOFC electrolyte, the specific steps of which are shown in Example 1, except that the S2 electrolyte is prepared as follows: The electrolyte surface of the NiO-SDC|SDC half-cell obtained by S1 was ion polished by an ion polisher to remove the non-surface active substances on the SDC surface and obtain a rough surface structure for standby use. The treatment time was 10 min, the ion source used was argon ions, and the working vacuum degree of the instrument chamber was 1×10 -3 , the operating voltage is 3 kV and the operating current is 4 mA.

[0023] Example 3 A method for preparing SOFC by ion polishing to activate the surface of SOFC electrolyte, the specific steps of which are shown in Example 1, except that the S2 electrolyte is prepared as follows: The electrolyte surface of the NiO-SDC|SDC half-cell obtained by S1 was ion polished by an ion polisher to remove the non-surface active substances on the SDC surface and obtain a rough surface structure. The treatment time was 30 min, the ion source used was argon ions, and the working vacuum degree of the instrument chamber was 1×10 -3 , the operating voltage is 3 kV and the operating current is 4 mA.

[0024] Example 4 A method for preparing SOFC by ion polishing to activate the surface of SOFC electrolyte, the specific steps of which are shown in Example 1, except that the S2 electrolyte is prepared as follows: The electrolyte surface of the NiO-SDC|SDC half-cell obtained by S1 was ion polished by an ion polisher to remove the non-surface active substances on the SDC surface and obtain a rough surface structure for standby use. The treatment time was 40 min, the ion source used was argon ions, and the working vacuum degree of the instrument chamber was 1×10 -3 , the operating voltage is 3 and the operating current is 4 mA.

[0025] Figure 1 The top view (a) and side view (b) SEM images of the microscopic morphology of the SDC prepared in Example 1 of the present invention before and after ion polishing are given. It can be seen from the figure that compared with the untreated SDC, the surface grains of the SDC after 20 minutes of ion polishing are sharp, and the surface ups and downs (i.e., roughness) are significantly increased, indicating that ion polishing can effectively increase the surface roughness of the SDC, thereby improving the bonding strength between the SDC and the cathode interface.

[0026] Figure 2 The AFM (a) and KPFM (b) test images of the SDC surface before and after ion polishing prepared in Example 1 of the present invention are given. It can be seen from the figure that compared with the untreated SDC, after 20 minutes of ion polishing, the average surface roughness of SDC is increased from 59.3 nm to 152.2 nm, and the average surface potential is increased from 0.019 V to 0.076 V; this result quantitatively proves that ion polishing can significantly increase the surface roughness of SDC and effectively activate the surface; and both of these beneficial effects help to enhance the interface bonding between SDC and the cathode.

[0027] Figure 3 The XPS spectra of the SDC surface before (a) and after (b) ion polishing treatment prepared in Example 1 of the present invention are given. It can be seen from the figure that compared with the untreated SDC, the Ce on the SDC surface after 20 min ion polishing is 3+ and O II The relative contents have increased, indicating that the concentration of oxygen vacancies on the SDC surface has increased, which is beneficial to ion transport; it also confirms the activation effect of ion polishing on the SDC surface.

[0028] Figure 4The SEM images (a, b) of the cathode / electrolyte interface before and after ion polishing treatment and the interface peeling strength test results (d) prepared in Example 1 of the present invention are given; Figure (c) is a schematic diagram of a homemade peeling test device, and a conventional peeling test device in the art can also be used. It can be seen from Figures (a, b) that there are small cracks at the interface between the SDC and the cathode of the untreated battery, while the SDC and cathode interfaces of the battery after 20 minutes of treatment are well bonded, and no obvious cracks can be observed, which intuitively proves that ion polishing treatment has an enhancing effect on the cathode / electrolyte interface bonding. It can be seen from Figure (d) that compared with the untreated battery, after 20 minutes of ion polishing, the peel strength (i.e., bonding strength) of the SDC / cathode interface is increased from 3.2 N∙cm -2 Increased to 6.1 N∙cm -2 , quantitatively proved that ion polishing treatment can effectively improve the interface bonding strength between SDC and cathode.

[0029] Figure 5 The IV (a), IP curve (b), and corresponding long-term stability (c) and thermal cycle stability (d) test results of the NiO-SDC|SDC|BSF-20NM configuration single cell prepared in Example 1 of the present invention before and after ion polishing are given. It can be seen from Figures (a, b) that at 450-650 °C, compared with the untreated single cell, the PPD of the single cell after 20 min ion polishing is 134-1266 mW∙cm -2 Increased to 161-1511 mW∙cm -2 , quantitatively proved that ion polishing can effectively improve the output performance of SOFC single cells. As can be seen from Figures (c, d): Compared with the untreated single cells, the performance attenuation rate of the single cells after 20 min of ion polishing after long-term operation and thermal cycle operation was reduced from 21.4% and 28.5% to 14.7% and 15.7%, respectively, proving that ion polishing can effectively improve the output performance of SOFC single cells while also effectively improving their long-term stability and thermal cycle stability.

[0030] Figure 6 The EIS curves of the NiO-SDC|SDC|BSF-20NM configuration single cell (a) and the BSF-20NM|SDC|BSF-20NM configuration symmetric cell (b) before and after ion polishing prepared in Example 1 of the present invention are given. It can be seen from the figure that at 450-650°C, compared with the untreated single cell, the polarization resistance of the single cell and the symmetric cell after 20 min ion polishing is significantly reduced, indicating that ion polishing can effectively reduce the polarization resistance, thereby improving the battery performance.

[0031] Figure 7This is the process of preparing a NiO-SDC|SDC|BSF-20NM configuration single cell with ion polishing treatment according to Example 1 of the present invention. It can be seen that the ion polishing treatment process is simple, easy to operate, and is conducive to large-scale production.

Claims

1. A method for activating the surface of a SOFC electrolyte by ion polishing, characterized in that: Before coating the cathode on the SOFC half-cell, the electrolyte surface of the half-cell is ion polished.

2. The method for activating the surface of a SOFC electrolyte by ion polishing according to claim 1, characterized in that: Ion polishing is achieved by an ion polisher, with the following working parameters: the vacuum degree of the instrument chamber is 1×10 -2 -1×10 -4 , the operating voltage is 2-6 kV, and the operating current is 1-4.5 mA.

3. The method for activating the surface of a SOFC electrolyte by ion polishing according to claim 2, characterized in that: When the ion polishing instrument performs ion polishing, the ion source used is argon ions, and the ion polishing process lasts for 5-40 minutes.

4. The method for activating the surface of a SOFC electrolyte by ion polishing according to claim 2, characterized in that: The model of the ion polisher is Leica EM Res102.

5. The method for activating the surface of a SOFC electrolyte by ion polishing according to claim 1, characterized in that: The configuration of the SOFC half-cell is an anode|electrolyte structure, wherein the electrolyte is a cerium oxide-based electrolyte and the anode is composed of nickel oxide+electrolyte.

6. A method for preparing SOFC by activating the surface of SOFC electrolyte by ion polishing, characterized in that: The specific steps include: S1: Prepare a SOFC half-cell with anode|electrolyte configuration, with a heat treatment temperature of 1350-1700 °C and a heat treatment time of 5-10 h; S2: The electrolyte surface of the half-cell obtained in S1 was ion polished using an ion polisher. The treatment time was 5-40 min. The ion source used was argon ions. The working vacuum degree of the instrument chamber was 1×10 -2 -1×10 -4 , the working voltage is 2-6kV, and the working current is 1-4.5 mA; S3: prepare cathode slurry, evenly apply the cathode slurry on the surface of the electrolyte treated by S2, and heat treat it at 900-1000 °C for 1-3 h.

7. SOFC prepared by the preparation method according to claim 6.

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