Isolating layer of solid oxide electrolytic cell and preparation method of isolating layer

Abstract

The invention relates to a solid oxide electrolytic cell isolation layer and a preparation method thereof, and belongs to the technical field of solid oxide electrolytic cells. According to the preparation method, a polyvinyl butyral (PVB)-terpilenol system is adopted as an organic carrier, then the organic carrier and SDC powder are subjected to ball milling treatment, slurry is coated on an electrolyte sheet through a screen printing process, and a sintering process is combined, so that the Sm0. 2Ce0. 8O2 (SDC) isolating layer with higher ionic conductivity and lower interface resistance is prepared. The isolation layer obtained by the invention effectively improves the overall electrochemical performance of the solid oxide electrolytic cell.

Description

Technical Field

[0001] This invention belongs to the field of solid oxide electrolytic cell technology, and relates to an isolation layer for solid oxide electrolytic cells and its preparation method. Background Technology

[0002] Solid oxide electrolyzers (SOECs), as efficient and environmentally friendly electrochemical energy conversion devices, can efficiently convert electrical energy into chemical energy in both directions, and have broad application prospects in fields such as hydrogen economy, carbon dioxide conversion, and renewable energy storage. Their core component is a multi-layered ceramic structure consisting of a fuel electrode, an electrolyte, an air electrode, and a crucial functional layer—an insulating layer—located between the electrodes and the electrolyte.

[0003] The isolation layer is typically made of doped cerium oxide (such as Sm). 0.2 Ce 0.8 Made of plasma conductor materials such as O2 and SDC, the SOEC plays multiple key roles: preventing interdiffusion of elements between electrode materials (especially the cathode) and electrolyte materials (such as YSZ) during high-temperature sintering and operation, thus preventing the formation of high-resistivity impurity phases; acting as a physical barrier layer to protect the electrolyte from mechanical or chemical damage; and providing more active sites for electrode reactions. Therefore, the performance of the barrier layer, especially its ionic conductivity and interfacial characteristics, directly determines the ohmic resistance and polarization resistance of the SOEC, playing a decisive role in the overall energy conversion efficiency and long-term operational stability of the battery.

[0004] Currently, the isolation layer of SOEC is mainly screen-printed onto the electrolyte sheet. The key to screen printing lies in preparing a paste with suitable rheological properties, stability, and film-forming properties. The paste is usually composed of functional powders, organic solvents, and binders. Among these, the selection and content of the binder are the core parameters for controlling the properties of the paste, which directly affect the uniformity and density of the printed film, as well as the microstructure and electrochemical performance of the final sintered isolation layer.

[0005] In existing technologies, ethyl cellulose (EC) is a widely used traditional binder. However, EC has many inherent defects in the preparation of high-performance insulating layers, mainly manifested in the following ways: (1) Poor uniformity and film-forming properties of the slurry: Slurries using EC as a binder often exhibit poor rheological properties, making them prone to flocculation or sedimentation, resulting in uneven powder dispersion. This leads to problems such as uneven thickness and numerous micro-defects in the release film obtained by screen printing. After sintering, these defects evolve into pores, cracks, or loose microstructures, becoming obstacles to ion transport.

[0006] (2) Weak interfacial bonding strength: Due to the high rigidity of EC binder, the interfacial bonding strength between the separator layer prepared with EC binder and the electrolyte substrate is weak. This weak interfacial bonding will introduce additional interfacial contact resistance and is prone to causing the separator layer to peel off during long-term thermal cycling of the battery.

[0007] In summary, traditional EC adhesives, due to their inherent material properties, have become a technical bottleneck restricting further improvements in the performance of SOEC isolation layers, severely hindering breakthroughs in SOEC performance. Summary of the Invention

[0008] To address the aforementioned problems, this invention provides a solid oxide electrolytic cell isolation layer and its preparation method. This invention uses a polyvinyl butyral (PVB)-terpineol system as an organic carrier, which is then ball-milled with SDC powder. The slurry is then coated onto the electrolyte sheet using a screen printing process. Combined with the sintering process of this invention, a Sm... 0.2 Ce 0.8 O2 (SDC) isolation layer. The technical solution of the present invention is as follows: A method for preparing an isolation layer for a solid oxide electrolytic cell, comprising the following specific steps: (1) Preparation and ball milling of organic carrier: Using terpineol as organic solvent, PVB powder is slowly added to terpineol to make the mass concentration of PVB 1-5 wt.%, and placed in a ball mill jar, controlling the ball-to-material ratio to be 2:1; the ball mill jar is fixed on the ball mill, the rotation speed is set to 400-450 rpm, and the ball milling time is 15-20 hours, so that PVB is fully dissolved in terpineol to prepare SB organic carrier; the preferred mass concentration of PVB is 3 wt.%; the ball mill jar is fixed on the ball mill, the rotation speed is set to 450 rpm, and the ball milling time is 15 hours.

[0009] (2) Preparation and ball milling of the isolation layer slurry: Weigh the organic carrier prepared in step (1) and SDC powder at a mass ratio of (1-3):1. Place the powder in a ball mill jar and control the ball-to-powder ratio to be 1:1. Fix the ball mill jar on the ball mill and set the rotation speed to 350-450 rpm for 5-10 hours. Disperse the SDC powder evenly in the organic carrier to form a slurry for screen printing. Weigh the SB1 organic carrier and SDC powder at a mass ratio of 1.5:1 and place them in a ball mill jar, controlling the ball-to-powder ratio to be 1:1. Fix the ball mill jar on the ball mill and set the rotation speed to 450 rpm for 10 hours.

[0010] (3) Vacuum degassing: Transfer the slurry obtained in step (2) to a degassing tank and place it in a vacuum stirring degassing machine for degassing. Set the parameters as follows: set the stirring speed to 2000 rad / min and stir for 10 min; set the vacuum degassing speed to 2200 rad / min and degas for 15 min, and set the vacuum degree to -(0.05-0.1) MPa, preferably -0.1 MPa. This step is to remove the air bubbles that are trapped inside the slurry during the ball milling process, thereby obtaining the isolation layer green body.

[0011] (4) Screen printing: The isolation layer green blank obtained in step (3) is printed onto both sides of the electrolyte sheet through a 200-300 mesh screen, preferably 300 mesh; the number of printing passes is controlled to be 1-3 passes, preferably 2 passes; thereby obtaining an isolation layer green blank film with uniform thickness.

[0012] (5) High-temperature sintering: The screen-printed electrolyte sheet is placed in a high-temperature sintering furnace and heated to 1150-1350℃ at a heating rate of 2-5°C / min. The temperature is held for 2-5 hours to allow the SDC particles to be fully sintered and densified, forming an isolation layer with high strength and high ionic conductivity, and forming a strong chemical bonding interface with the electrolyte. The preferred sintering temperature is 1250℃, and the holding time is 3 hours.

[0013] The present invention also includes a solid oxide electrolytic cell isolation layer obtained by the above preparation method.

[0014] The advantages of this invention compared to the prior art are as follows: Traditional ethyl cellulose exhibits poor bonding properties, resulting in low cross-linking between ceramic particles in the separator slurry. Excessive ethyl cellulose content also reduces the density of the separator. In contrast, the separator slurry prepared using high-viscosity polyvinyl butyral as a binder exhibits high cross-linking between ceramic particles, requiring a lower polyvinyl butyral content. This results in good interfacial contact between the separator, electrolyte, and electrode. The battery obtained in Example 3 exhibits the lowest ohmic resistance. Furthermore, the electrode polarization resistance in these examples is lower than that in Comparative Example 1, indicating improved electrocatalytic activity of the electrode. Attached Figure Description

[0015] Figure 1 The bar chart shows the comparison of the ohmic resistance of the symmetrical cells tested in Examples 1-4 and Comparative Example 1. Figure 2 This is a comparative bar chart of the polarization resistance of the symmetrical cells tested in Examples 1-4 and Comparative Example 1; Figure 3 Electron micrograph of the isolation layer obtained in Embodiment 1 of the present invention. Detailed Implementation

[0016] The technical solution of the present invention will be described in detail below through specific embodiments. It should be understood that the following specific embodiments are merely exemplary, and any modifications or changes that do not depart from the technical solution design of the present invention should be within the scope of protection of the claims of the present invention. The present invention will be described in detail below with reference to embodiments.

[0017] Example 1: A solid oxide electrolytic cell isolation layer and its preparation method The steps are as follows: (1) Preparation and ball milling of organic carrier: PVB powder was slowly added to terpineol as an organic solvent to achieve a PVB mass concentration of 1 wt.%, and placed in a ball mill jar with a ball-to-powder ratio of 2:1. The ball mill jar was fixed on a ball mill, the rotation speed was set to 450 rpm, and the ball milling time was 15 hours to allow PVB to be fully dissolved in terpineol, thereby obtaining SB1 organic carrier.

[0018] (2) Preparation and ball milling of the isolation layer slurry: Weigh the SB1 organic carrier and SDC powder prepared in step (1) at a mass ratio of 1.5:1 and place them in a ball mill jar, controlling the ball-to-material ratio to be 1:1. Fix the ball mill jar on the ball mill, set the rotation speed to 450 rpm, and the ball milling time to 10 hours. This allows the SDC powder to be uniformly dispersed in the organic carrier, forming a high-quality slurry with good stability, no agglomeration, and suitable for screen printing.

[0019] (3) Vacuum degassing: The slurry obtained in step (2) is transferred to a degassing tank using a dropper and placed in a vacuum stirring degassing machine for degassing. The parameters are set as follows: the stirring process is set to a speed of 2000 rad / min for 10 min; the vacuum degassing process is set to a speed of 2200 rad / min for 15 min, and the vacuum degree is -0.1 MPa. This step is to remove the air bubbles that are trapped inside the slurry during the ball milling process, thereby obtaining a dense, defect-free isolation layer green body.

[0020] (4) Screen printing: The green isolation layer prepared in step (3) is printed onto both sides of the YSZ electrolyte sheet through a 300-mesh screen. The number of printing passes is controlled to be 2, so as to obtain a green isolation layer film with uniform thickness.

[0021] (5) High-temperature sintering: The screen-printed electrolyte sheet with the isolation layer is placed in a high-temperature sintering furnace and heated to 1250°C at a heating rate of 3°C / min, and held for 3 hours. This allows the SDC particles to be fully sintered and densified, forming an isolation layer with high strength and high ionic conductivity, and forming a strong chemical bonding interface with the electrolyte.

[0022] (6) Performance testing and characterization: The prepared isolation layer samples were assembled into symmetrical cells (LSCF|SDC|YSZ|SDC|LSCF), and electrochemical impedance spectroscopy (EIS) was performed using an electrochemical workstation to evaluate their ohmic and polarization resistance.

[0023] Example 2: A solid oxide electrolytic cell isolation layer and its preparation method The steps are as follows: The difference between the experimental steps in this embodiment and those in Example 1 is that in step (1), PVB powder is slowly added to terpineol to make the mass concentration of PVB 2wt.%, thereby preparing SB2 organic colloid.

[0024] Example 3: A solid oxide electrolytic cell isolation layer and its preparation method The steps are as follows: The difference between the experimental steps in this embodiment and those in Example 1 is that in step (1), PVB powder is slowly added to terpineol to make the mass concentration of PVB 3wt.%, thereby preparing SB3 organic colloid.

[0025] Example 4: A solid oxide electrolytic cell isolation layer and its preparation method The steps are as follows: The difference between the experimental steps in this embodiment and those in Example 1 is that in step (1), PVB powder is slowly added to terpineol to make the mass concentration of PVB 4wt.%, thereby preparing SB4 organic colloid.

[0026] Example 5: A solid oxide electrolytic cell isolation layer and its preparation method The steps are as follows: The difference between the experimental steps in this embodiment and those in Example 1 is that in step (1), PVB powder is slowly added to terpineol to make the mass concentration of PVB 5wt.%, thereby preparing SB5 organic colloid.

[0027] Example 6: A solid oxide electrolytic cell isolation layer and its preparation method The steps are as follows: The difference between the experimental steps in this embodiment and those in embodiment 3 is that the mass ratio of SB3 organic carrier to SDC powder in step (2) is 1.2:1. Example 7: A solid oxide electrolytic cell isolation layer and its preparation method The steps are as follows: The difference between the experimental steps in this embodiment and those in Example 3 is that the mass ratio of the SB3 organic carrier to the SDC powder in step (2) is 1:1.

[0028] Example 8: A solid oxide electrolytic cell isolation layer and its preparation method The steps are as follows: The difference between the experimental steps in this embodiment and those in Example 3 is that the mass ratio of SB3 organic carrier to SDC powder in step (2) is 2.5:1.

[0029] Comparative Example 1 (1) Preparation and ball milling of organic carrier: Using terpineol as the organic solvent, ethyl cellulose (EC) powder was slowly added to terpineol to control the mass percentage concentration at 4 wt.%, and placed in a ball mill jar with a ball-to-powder ratio of 2:1. The ball mill jar was fixed on a ball mill, the rotation speed was set to 450 rpm, and the ball milling time was 20 hours to allow EC to be fully dissolved in terpineol, thereby obtaining a 4 wt.% EC organic carrier.

[0030] (2) Preparation and ball milling of the isolation layer slurry: Weigh the 4wt.% EC colloid and SDC powder prepared in step (1) at a mass ratio of 1.5:1 and place them in a ball mill jar, controlling the ball-to-material ratio to be 1:1. Fix the ball mill jar on the ball mill, set the rotation speed to 450 rpm, and the ball milling time to 10 hours. This allows the SDC powder to be uniformly dispersed in the organic carrier, forming a high-quality slurry with good stability, no agglomeration, and suitable for screen printing.

[0031] (3) Vacuum degassing: The isolation layer slurry obtained in step (2) is transferred to a degassing tank using a dropper and placed in a vacuum stirring degassing machine for degassing. The parameters are set as follows: the stirring process is set to a speed of 2000 rad / min and a stirring time of 10 min; the vacuum degassing process is set to a speed of 2200 rad / min and a degassing time of 15 min, with a vacuum degree of -0.08 MPa. This step is to remove the air bubbles that are trapped inside the slurry during the ball milling process, thereby obtaining a dense and defect-free isolation layer green body.

[0032] (4) Screen printing: The separator slurry prepared in step (3) is precisely printed onto both sides of the YSZ electrolyte sheet through a 300-mesh screen. The number of printing passes is controlled to be 2, so as to obtain a separator green film with uniform thickness.

[0033] (5) High-temperature sintering: The screen-printed electrolyte sheet is placed in a high-temperature sintering furnace and heated to 1250°C at a heating rate of 3°C / min, and held for 2 hours. This allows the SDC particles to be fully sintered and densified, forming an isolation layer with high strength and high ionic conductivity, and forming a strong chemical bonding interface with the electrolyte.

[0034] (6) Performance testing and characterization: The prepared isolation layer samples were assembled into symmetrical cells (LSCF|SDC|YSZ|SDC|LSCF), and electrochemical impedance spectroscopy (EIS) was performed using an electrochemical workstation to evaluate their ohmic and polarization resistance.

[0035] Comparative Example 2 The experimental steps of this comparative example differ from those of comparative example 1 in that the mass ratio of organic colloid to SDC powder in step (2) is 1.5:1.

[0036] The electrochemical performance results for Examples 1-8, Comparative Examples 1 and 2 are shown in Table 1: ; As shown in Table 1, the ohmic resistance of the solid oxide electrolytic cell isolation layer prepared by using PVB as a binder in this invention is all below 0.13 Ωcm at 750℃. 2 The following values ​​are all lower than the ohmic resistance in Comparative Example 1 (0.165 Ωcm). 2 PVB molecules have stronger adhesion than ethyl cellulose, and the binder is also more flexible. Therefore, the interfacial contact between the separator membrane and the electrolyte and electrodes is better, resulting in faster ion conduction in the separator and lower ohmic resistance of the battery. Meanwhile, the polarization resistance of the electrodes in the embodiments is less than 0.079 Ωcm. 2 The resistance of the electrodes was also lower than that of the comparative example, and the total resistance of the electrodes was also lower than that of the comparative example, thus the electrodes exhibited superior electrochemical performance. This indicates that the isolation layer slurry prepared using polyvinyl butyral as a binder has a more excellent effect.

[0037] The bar charts comparing the ohmic resistance of the symmetrical cells tested in Examples 1-4 and Comparative Example 1 of this invention are shown below. Figure 1 As shown; the polarization resistance comparison bar charts of the symmetrical cells tested in Examples 1-4 and Comparative Example 1 of the present invention are shown below. Figure 2 As shown; the electron micrograph of the isolation layer prepared in Example 1 of the present invention is shown. Figure 3 As shown.

Claims

1. A method for preparing an isolation layer in a solid oxide electrolytic cell, characterized in that, The specific steps of the preparation method are as follows: (1) Preparation and ball milling of organic carrier: Using terpineol as organic solvent, PVB powder was slowly added to terpineol to make the mass concentration of PVB 1-5 wt.%, and placed in a ball mill jar, controlling the ball-to-material ratio to be 2:1; the ball mill jar was fixed on a ball mill, the rotation speed was set to 400-450 rpm, and the ball milling time was 15-20 hours, so that PVB was fully dissolved in terpineol, and SB organic carrier was prepared; (2) Preparation and ball milling of the isolation layer slurry: Weigh the colloid prepared in step (1) and SDC powder at a mass ratio of (1-3):

1. Place the powder in a ball mill jar, controlling the ball-to-powder ratio to be 1:1; fix the ball mill jar on the ball mill, set the rotation speed to 350-450 rpm, and the ball milling time to 5-10 hours; so that the SDC powder is uniformly dispersed in the organic carrier to form a slurry for screen printing; (3) Vacuum degassing: The slurry obtained in step (2) is transferred to a degassing tank and placed in a vacuum stirring degassing machine for degassing. The parameters are set as follows: the stirring process is set to a speed of 2000 rad / min and a stirring time of 10 min; the vacuum degassing process is set to a speed of 2200 rad / min and a degassing time of 15 min, with a vacuum degree of -(0.05-0.1) MPa, to obtain a green body with an isolation layer. (4) Screen printing: The isolation layer preform obtained in step (3) is printed onto both sides of the electrolyte sheet through a 200-300 mesh screen; the number of printing passes is controlled to be 1-3 times to obtain an isolation layer preform film with uniform thickness. (5) High-temperature sintering: The screen-printed electrolyte sheet is placed in a high-temperature sintering furnace and heated to 1150-1350°C at a heating rate of 2-5°C / min. The temperature is held for 2-5 hours to obtain a solid oxide electrolytic cell isolation layer.

2. The preparation method according to claim 1, characterized in that, The mass concentration of PVB in step (1) is 3 wt.%.

3. The preparation method according to claim 1, characterized in that, In step (1), the grinding jar is fixed on the ball mill, the rotation speed is set to 450 rpm, and the grinding time is 15 hours.

4. The preparation method according to claim 1, characterized in that, In step (2), the SB1 organic carrier and SDC powder are weighed at a mass ratio of 1.5:1 and placed in a ball mill jar, with the ball-to-material ratio controlled at 1:1; the ball mill jar is fixed on the ball mill, the rotation speed is set to 450 rpm, and the ball milling time is 10 hours.

5. The preparation method according to claim 1, characterized in that, The vacuum level in step (3) is -0.1 MPa.

6. The preparation method according to claim 1, characterized in that, In step (4), the isolation layer blank is printed onto both sides of the electrolyte sheet through a 300-mesh screen; the number of printing passes is controlled to be 2.

7. The preparation method according to claim 1, characterized in that, In step (5), the sintering temperature is 1250°C and the holding time is 3 hours.

8. The solid oxide electrolytic cell isolation layer obtained by the preparation method according to any one of claims 1-7.

9. The application of the solid oxide electrolytic cell isolation layer as described in claim 8 in a solid oxide electrolytic cell.

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