A symmetric reversible solid oxide cell with dual gradient electrodes and a method of making the same

Abstract

The application provides a symmetrical reversible solid oxide battery with a double-gradient electrode and a preparation method thereof, which comprises an electrolyte layer in the middle and electrode layers symmetrically arranged on both sides of the electrolyte layer; the electrode layer comprises a first gradient electrode layer and a second gradient electrode layer, and the first gradient electrode layer is close to the electrolyte layer; the electrolyte layer comprises dense 10ScSZ; the electrode layer comprises any one of SmBa 0.5 Sr 0.5 Co2O 5‑δ , PrBaCo2O 5+δ , Sr2Fe 1.5 Mo 0.5 O 6‑δ , and the porosity of the second gradient electrode layer is greater than that of the first gradient electrode layer. The battery disclosed by the application can not only operate in the SOFC mode, but also operate in the SOEC mode. The materials of the fuel electrode and the air electrode are the same, which not only simplifies the battery preparation process, but also reduces the preparation cost of the battery.

Description

Technical Field

[0001] This invention relates to the field of solid oxide battery technology, specifically to a symmetrical reversible solid oxide battery with dual gradient electrodes and its preparation method. Background Technology

[0002] Reversible solid oxide fuel cells (RSOCs) integrate solid oxide fuel cells (SOFCs) and solid oxide electrolyzers (SOECs). They can generate electricity from fuel in SOFC mode and produce hydrogen by electrolyzing water using waste heat and excess electricity from other renewable energy sources (such as solar and wind power) in SOEC mode, without producing byproducts. Therefore, RSOCs are considered one of the most promising energy conversion devices for solving hydrogen production and power generation problems. Due to their high conversion efficiency and clean operation, RSOCs have attracted significant attention in recent years for hydrogen production and power generation.

[0003] Reversible solid oxide fuel cells (RSOCs) face numerous limitations in electrode material selection and single-cell fabrication due to their multifunctional nature. This is especially true given that RSOCs are still in their early stages of development, and consequently, many technical challenges remain.

[0004] 1. Due to the immaturity of current RSOC technology, and the fact that most RSOCs are improvements on SOFC technology, there has been no significant improvement in electrode materials, resulting in insufficient performance of dual-functional batteries.

[0005] 2. Due to the complex operating conditions of RSOC, especially the thermal matching problem between the fuel electrode, electrolyte and fuel electrode, stress differences can occur between different layers, which can easily lead to battery delamination and cracking, resulting in performance degradation.

[0006] 3. Since RSOC evolved from traditional SOFC, its preparation process is still very complex and expensive.

[0007] To address the above technical problems, this invention proposes a novel symmetrical reversible solid oxide fuel cell with a dual-functional gradient electrode structure. Summary of the Invention

[0008] In order to solve the above technical problems, the present application provides a symmetrical reversible solid oxide cell with double gradient electrodes and a preparation method thereof. In order to solve the problem of poor electrode performance of the electrode material of the dual-function cell, the present application proposes to use a dual-function material as the electrode of the RSOC to prepare a single cell, so that the single cell has the performance of power generation and electrolysis. In order to solve the problem that the thermal matching between the fuel electrode, the electrolyte and the air electrode causes stress difference between different layers, leading to delamination and cracking of the cell, the present application proposes a design scheme of a symmetrical cell structure with a double gradient function electrode, in which the same electrode material is used for the two electrodes of the cell. In this way, the problem of thermal matching between the electrolyte and the electrode can be well solved to prevent delamination of the cell, and the double gradient function electrode can also enhance the strength of the entire single cell to prevent the cell from cracking. In order to solve the problem of complex preparation process and high cost of the RSSOC, the present application proposes a symmetrical cell, i.e. a preparation method in which the same material is used for the fuel electrode and the oxygen electrode and sintered at one time to simplify the preparation process and reduce the cost.

[0009] The technical means adopted by the present application are as follows:

[0010] A symmetrical reversible solid oxide cell (RSSOC) with double gradient electrodes comprises an electrolyte layer in the middle and electrode layers symmetrically arranged on both sides of the electrolyte layer;

[0011] The electrode layer comprises a first gradient electrode layer and a second gradient electrode layer, and the first gradient electrode layer is close to the electrolyte layer;

[0012] The electrolyte layer uses a dense 10ScSZ electrolyte with a density of 95% as a support;

[0013] Since the dual-function material has the functions of catalyzing hydrogen and catalyzing oxygen, the dual-function material can be used as the fuel electrode and the air electrode of the RSSOC. The material with the double gradient function electrode comprises SmBa 0.5 Sr 0.5 Co2O 5-δ (SBSC), PrBaCo2O 5+δ (PBCO), Sr2Fe 1.5 Mo 0.5 O 6-δ (SFMO). Therefore, the material of the electrode layer in the present application uses any one of SmBa 0.5 Sr 0.5 Co2O 5-δ , PrBaCo2O 5+δ , Sr2Fe 1.5 Mo 0.5 O 6-δ .

[0014] The porosity of the second gradient electrode layer is greater than the porosity of the first gradient electrode layer.

[0015] The electrolyte layer is a dense 10ScSZ with a density of 95%.

[0016] The porosity of the first gradient electrode layer is 15-25%, preferably 20%, and the porosity of the second gradient electrode layer is 35-45%, preferably 40%.

[0017] The RSSOC has good adaptability to carbon-based fuels between 600-900 DEG C, so that the fuel gas types applicable to the RSSOC are more diversified, and the work has good stability.

[0018] The application further discloses a preparation method of the symmetrical reversible solid oxide cell with the double-gradient electrode.

[0019] S1: preparing a dense 10ScSZ electrolyte layer with a density of 95%; 10ScSZ electrolyte slurry is prepared by mixing zirconium oxide and scandium acetate tetrahydrate according to a molar ratio of 9:1 and then ball milling; the 10ScSZ electrolyte slurry is processed by a flow casting method to obtain an electrolyte green body, and the electrolyte green body is sintered at 1200-1300 DEG C for 5-7 h to obtain the dense electrolyte layer with a density of 95%.

[0020] S2: selecting preparation materials of the electrode layer and preparing the electrode layer powder from the materials; any one of SmBa 0.5 Sr 0.5 Co2O 5-δ , PrBaCo2O 5+δ , Sr2Fe 1.5 Mo 0.5 O 6-δ is selected as the electrode material for preparing the electrode layer; and the corresponding nitrate is weighed according to the molar ratio of the chemical formula of the selected electrode material (for example, if SmBa 0.5 Sr 0.5 Co2O 5-δ is selected as the electrode material, the molar mass ratio of Sm (NO3) 3.6H2O, Ba (NO3) 3.6H2O, Sr (NO3) 2 and Co (NO3) 2.6H2O is 2:1:1:4, and the above materials are weighed), and the nitrate is dissolved in deionized water, a precursor is obtained by using a sol-gel preparation method, and then the precursor is sintered in a muffle furnace at 1000 DEG C for 5 h to obtain the black electrode layer powder.

[0021] S3: preparing a first gradient electrode layer slurry and a second gradient electrode layer slurry from the electrode layer powder;

[0022] In the porous electrode of the fuel cell, the diffusion of fuel at the fuel electrode and oxygen at the air electrode are both affected by the concentration gradient, so a gradient electrode is designed according to the formula of the concentration gradient (formula 1) to better match the gas diffusion, optimize the diffusion of the gas, reduce the influence of the concentration gradient, and improve the performance of the cell.

[0023]

[0024] where C (mol m 3 ) is the oxygen concentration in the electrode. S represents the oxygen reduction reaction rate (W m -3 s -1 ). The effective diffusion coefficient of oxygen in the porous medium is represented by D. Therefore, the electrode adopts a gradient electrode, wherein the first gradient electrode is a relatively dense electrode with a porosity of 15-25%, and the second gradient electrode has a relatively large porosity of 35-45%. In the step S3, two equal weights of the electrode material powder are weighed, one of which is weighed with terpineol, ethyl cellulose and starch according to a mass ratio of 100:75:2, then put into a ball mill jar, then drop in a dispersing agent and add an appropriate amount of ball milling beads for ball milling to obtain the first gradient electrode slurry; the other is weighed with terpineol, ethyl cellulose and starch according to a mass ratio of 100:75:2:35-45, then put into a ball mill jar, then drop in a dispersing agent and add an appropriate amount of ball milling beads for ball milling to obtain the second gradient electrode slurry.

[0025] S4: The first gradient electrode slurry and the second gradient electrode slurry are respectively screen printed on both sides of the electrolyte layer by a screen printing method, and sintering is carried out at 1200-1300 DEG C to obtain the symmetrical reversible solid oxide cell of the double gradient electrode, wherein the dense 10ScSZ electrolyte with a density of 95% is used as a support in the middle, and the first gradient electrode with a porosity of 15-25% and the second gradient electrode with a porosity of 35-45% are provided on both sides.

[0026] The present application selects materials, because 10ScSZ has a high ionic conductivity, so it is used as an electrolyte material. SmBa 0.5 Sr 0.5 Co2O 5-δ (SBSC), PrBaCo2O 5+δ (PBCO), Sr2Fe 1.5 Mo 0.5 O 6-δ(SFMO) perovskite is a mixed ionic and electronic conductor (MIEC) and a bifunctional material, which exhibits good ionic and electronic conductivity and excellent electrocatalytic activity in the temperature range of 600-800 ℃. The advantage is that the electrochemical reaction of the traditional electrode occurs at the three-phase boundary, while the electrochemical reaction of the MIEC electrode can occur on the entire surface of the MIEC particles. Therefore, any one of the SBSC, PBCO and SFMO electrode material systems can be selected.

[0027] Compared with the prior art, the present application has the following advantages:

[0028] 1. The high-performance bifunctional perovskite electrode material is used, so that the battery has multiple functional characteristics and good performance.

[0029] 2. The gradient electrode is used, which can increase the electrochemical reaction of the electrode while considering the gas diffusion, slow down the delamination and cracking of the battery, and improve the performance of the battery.

[0030] (1) The battery can not only operate in SOFC mode, but also operate in SOEC mode.

[0031] (2) The three-phase interfaces of the fuel electrode and the air electrode are the same, so that the battery has a close thermal expansion coefficient between the electrode and the electrolyte, and the battery has good thermal matching, which slows down the delamination and cracking of the battery.

[0032] (3) The carbon deposition problem that occurs in long-term operation of the carbon-based fuel in SOFC mode can be slowed down, and the operation life is increased.

[0033] 3. The materials of the fuel electrode and the air electrode are the same, which simplifies the battery preparation process and reduces the preparation cost of the battery.

[0034] Based on the above reasons, the present application can be widely popularized in the field of solid oxide batteries and the like. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0036] Figure 1 It is a structure schematic diagram of a symmetrical reversible solid oxide battery with a double-gradient electrode according to the present application.

[0037] Figure 2 It is a structure schematic diagram of a symmetrical reversible solid oxide battery with a double-gradient electrode according to the present application. 0.5 Sr 0.5 Co2O5-δ Specific procedure of material preparation.

[0038] Figure 3 Schematic diagram of screen printing technology of the present application.

[0039] Figure 4 Discharge test comparison chart (SBSC) of the present application.

[0040] Figure 5 Discharge test comparison chart (PBCO) of the present application.

[0041] Figure 6 Discharge test comparison chart (SFMO) of the present application.

[0042] Figure 7 Electrolytic stability comparison chart (SBSC) of the present application.

[0043] Figure 8 Electrolytic stability comparison chart (PBCO) of the present application.

[0044] Figure 9 Electrolytic stability comparison chart (SFMO) of the present application. DETAILED DESCRIPTION

[0045] It should be noted that the embodiments and features of the present application can be combined with each other in the case of no conflict. The present application will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0046] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be described clearly and completely below in conjunction with the drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, but not all the embodiments. The description of the at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0047] It should be noted that the terms used herein are only for describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present application. As used herein, the singular form is intended to include the plural form unless the context clearly indicates otherwise, and it should also be understood that when the terms "comprise" and / or "include" are used in the specification, there is a feature, step, operation, device, component and / or combination thereof.

[0048] The foregoing is considered as illustrative only of the principles of the application. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the application to the exact construction and practice described. Accordingly, all such variations are intended to be included within the scope of the present application as defined in the following claims, along with full equivalents thereof.

[0049] In the description of the present application, it is to be understood that the orientation or positional relationships indicated by terms such as "front", "back", "up", "down", "left", "right", "lateral", "vertical", "horizontal", "top", "bottom", and the like are based on the orientation or positional relationships shown in the drawings, and are merely intended to facilitate the description and simplify the description, and do not indicate or imply that the device or element referred to must have a particular orientation or be constructed and operated in a particular orientation, and therefore cannot be construed as limiting the scope of protection of the present application. The orientation terms "inner", "outer" refer to the inner and outer relative to the contour of the components themselves.

[0050] For the convenience of description, spatial relative terms such as "over", "above", "upper surface", "upper", and the like can be used herein to describe the spatial positional relationship of one device or feature with respect to other devices or features as shown in the drawings. It should be understood that the spatial relative terms are intended to include different orientations in use or operation in addition to the orientation of the device as described in the drawings. For example, if the device in the drawings is inverted, the device described as "above" or "over" other devices or structures will be positioned "below" or "under" the other devices or structures. Thus, the exemplary term "above" can include both "above" and "below" orientations. The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein are interpreted accordingly.

[0051] In addition, it should be noted that the use of the terms "first", "second", and the like do not have a special meaning, and are used only to facilitate the distinction of the corresponding components, and therefore cannot be construed as limiting the scope of protection of the present application.

[0052] As Figure 1As shown, a symmetrical reversible solid oxide cell (RSSOC) with a double gradient electrode includes an electrolyte layer 1 in the middle and electrode layers symmetrically arranged on both sides of the electrolyte layer 1; the electrode layer includes a first gradient electrode layer 2 and a second gradient electrode layer 3, and the first gradient electrode layer 2 is close to the electrolyte layer 1; the electrolyte layer 1 uses a dense 10ScSZ electrolyte with a density of 95% as a support; since the double functional material has the functions of catalyzing hydrogen and catalyzing oxygen, the double functional material can be selected as both the fuel electrode and the air electrode of the RSSOC. The material with a double functional gradient electrode includes SmBa 0.5 Sr 0.5 Co2O 5-δ (SBSC)、PrBaCo2O 5+δ (PBCO)、Sr2Fe 1.5 Mo 0.5 O 6-δ (SFMO), so the material of the electrode layer is any one of SmBa 0.5 Sr 0.5 Co2O 5-δ 、PrBaCo2O 5+δ 、Sr2Fe 1.5 Mo 0.5 O 6-δ , and the porosity of the second gradient electrode layer 3 is greater than that of the first gradient electrode layer 2. The electrolyte layer 1 is a dense 10ScSZ with a density of 95%. The porosity of the first gradient electrode layer 2 is 15-25%, and the porosity of the second gradient electrode layer 3 is 35-45%.

[0053] The preparation method comprises:

[0054] S1: preparing a dense 10ScSZ electrolyte layer with a density of 95%; mixing zirconium oxide and scandium acetate tetrahydrate according to a molar ratio of 9:1, and then ball milling to prepare a 10ScSZ electrolyte slurry; processing the 10ScSZ electrolyte slurry by tape casting to obtain an electrolyte green body, and sintering at 1200-1300 ℃ for 5-7 h to obtain a dense electrolyte layer with a density of 95%.

[0055] S2: selecting the preparation material of the electrode layer, and preparing the material into an electrode layer powder; selecting SmBa 0.5 Sr 0.5 Co2O 5-δ 、PrBaCo2O 5+δ 、Sr2Fe 1.5 Mo 0.5 O 6-δany one of Sm(NO3)3·6H2O, Ba(NO3)3·6H2O, Sr(NO3)2, Co(NO3)2·6H2O as electrode material for preparing the electrode layer; and according to the molar ratio of the chemical formula of the selected electrode material, the corresponding nitrate salt is weighed (for example, if Sm(NO3)3·6H2O, Ba(NO3)3·6H2O, Sr(NO3)2, Co(NO3)2·6H2O are selected, the molar mass ratio of Sm(NO3)3·6H2O, Ba(NO3)3·6H2O, Sr(NO3)2, Co(NO3)2·6H2O is 2:1:1:4, and the above materials are weighed), and the nitrate salt is dissolved in deionized water, a precursor is obtained by using a sol-gel preparation method, and then the precursor is placed in a muffle furnace and sintered at 1000°C for 5 h to obtain a black electrode layer powder. 0.5 Sr 0.5 Co2O 5-δ As the electrode material is calculated according to the molar mass ratio of Sm(NO3)3·6H2O, Ba(NO3)3·6H2O, Sr(NO3)2, Co(NO3)2·6H2O is 2:1:1:4, and the above materials are weighed), and the nitrate salt is dissolved in deionized water, a precursor is obtained by using a sol-gel preparation method, and then the precursor is placed in a muffle furnace and sintered at 1000°C for 5 h to obtain a black electrode layer powder.

[0056] S3: using the electrode layer powder to prepare a first gradient electrode layer slurry and a second gradient electrode layer slurry, respectively;

[0057] In the porous electrode of the fuel cell, the diffusion of fuel at the fuel electrode and oxygen at the air electrode is affected by the concentration gradient, so a gradient electrode designed according to the formula of the concentration gradient (formula 1) can better match the gas diffusion, optimize the gas diffusion and reduce the influence of the concentration gradient, thereby improving the performance of the battery.

[0058]

[0059] where C (mol m 3 ) is the oxygen concentration in the electrode. S represents the oxygen reduction reaction rate (Wm -3 s -1 ). represents the effective diffusion coefficient of oxygen in the porous medium. Therefore, the electrode adopts a gradient electrode, wherein the first gradient electrode is a relatively dense electrode with a porosity of 15-25%, and the second gradient electrode has a relatively large porosity of 35-45%. In the step S3, two equal weights of the electrode material powder are weighed from the electrode layer powder, one of which is weighed with terpineol, ethyl cellulose and starch according to a mass ratio of 100:75:2, then put into a ball mill jar, then drop in a dispersing agent and add an appropriate amount of ball milling beads for ball milling to obtain the first gradient electrode slurry; the other is weighed with terpineol, ethyl cellulose and starch according to a mass ratio of 100:75:2:35-45, then put into a ball mill jar, then drop in a dispersing agent and add an appropriate amount of ball milling beads for ball milling to obtain the second gradient electrode slurry.

[0060] S4: the first gradient electrode slurry and the second gradient electrode slurry are respectively screen-printed on both sides of the electrolyte layer by a screen printing method, and sintering is performed at 1200-1300 ℃ to obtain the symmetrical reversible solid oxide cell with a double gradient electrode, which has a dense 10ScSZ electrolyte with a density of 95% as a support in the middle, and a first gradient electrode with a porosity of 15-25% and a second gradient electrode with a porosity of 35-45% on both sides.

[0061] Example 1

[0062] A symmetrical reversible solid oxide cell (RSSOC) with a double gradient electrode and a preparation method thereof, comprising:

[0063] S1: preparation of 10ScSZ electrolyte

[0064] Zirconium hydroxide is calcined at 450-550 ℃ for 2 h to obtain zirconium oxide, which is mixed with scandium acetate tetrahydrate at a molar ratio of 9:1, then ball-milled for 12 h, dried at 400 ℃ for 4 h and crushed, and then calcined at 1050-1250 ℃ for 2 h, and after cooling, 10ScSZ powder is obtained; 2-butanone acid and ethanol are mixed at a volume ratio of 1-3:1 to obtain a uniform mixed solvent; finally, the prepared 10ScSZ powder and mixed solvent are mixed with polyvinyl butyral and dibutyl phthalate at a mass ratio of 100:50-70:2-4:1-3, and ball-milled for 12-20 h to prepare an electrolyte slurry; part of the electrolyte slurry is used to prepare a green body of a dense 10ScSZ electrolyte substrate with a thickness of 30 μm and a structure density of 95% by a flow casting method. Then the green body is calcined at 1200-1300 ℃ in an air atmosphere for 5-7 h to obtain a dense electrolyte sheet with a density of 95%.

[0065] S2: preparation of SBSC electrode material

[0066] As Figure 2As shown, first, Sm(NO3)3.6H2O, Sr(NO3)2, Ba(NO3)3.6H2O, Co(NO3)2.6H2O were weighed according to the stoichiometric ratio of 2:1:1:4, dissolved in an appropriate amount of deionized water to make it completely dissolved, and recorded as A liquid. Then, anhydrous citric acid and EDTA (Shanghai Yongchuan Biological Technology Co., Ltd.) were weighed according to the ratio of 1:1:1.5 of metal ions, and an appropriate amount of deionized water was added, continuously stirred in a magnetic stirrer, and then an appropriate amount of ammonia water was added until the solution became clear, recorded as B liquid. Pour A liquid into B liquid, stir evenly, and add ammonia water to adjust the pH to 4-5, then heat in a water bath at 80 ℃ until the solution forms a sol-gel. The sol-gel is dried in an oven at 180 ℃ for 10 h, then preliminary grinding is performed using a mortar to prepare a precursor powder. The precursor powder after the mortar is moved to a ceramic square boat, then placed in a muffle furnace at 1000 ℃ for 5 h, with a heating rate of 2 ℃ / min to prepare black SBSC finished powder.

[0067] S3, Preparation of SBSC electrode slurry

[0068] Preparation of the first gradient electrode slurry: First, prepare the SBSC powder dry. Then weigh 10 g of SBSC material with an electronic balance and place it in a ball mill jar. The weighed SBSC powder, terpineol, ethyl cellulose are weighed according to the mass ratio of 100:75:2 and then placed in the ball mill jar, then the dispersant is added dropwise and an appropriate amount of ball milling beads is added. Finally, the well-proportioned ball mill jar is placed in a ball mill at 500 rpm / min for 24 h to prepare a viscous SBSC first gradient electrode slurry.

[0069] Preparation of the second gradient electrode slurry: First, prepare the SBSC powder dry. Then weigh 10 g of SBSC material with an electronic balance and place it in a ball mill jar. The weighed SBSC powder, terpineol, ethyl cellulose, starch are weighed according to the mass ratio of 100:75:2:35-45 and then placed in the ball mill jar, then the dispersant is added dropwise and an appropriate amount of ball milling beads is added. Finally, the well-proportioned ball mill jar is placed in a ball mill at 500 rpm / min for 24 h to prepare a viscous SBSC second gradient electrode slurry.

[0070] S4, Preparation of RSSOC single cell of dual-function gradient SBSC electrode

[0071] The preparation of the RSSOC single cell with 10ScSZ as electrolyte and SBSC as fuel electrode and air electrode is as follows: first, take the above prepared 10ScSZ electrolyte circular substrate with a diameter of 20 mm, wipe both sides of the substrate with alcohol, then screen print the SBSC first gradient electrode slurry to both sides of the electrolyte sheet once (such asFigure 3 The first gradient electrode slurry was coated to 20 μm, and then the SBSC second gradient electrode slurry was screen-printed on both sides of the electrolyte sheet once, which was dried in an oven at 80 °C, and the above steps were repeated to coat to 40 μm. Finally, the symmetrical cell with the gradient electrode material coated on both sides was placed on an alumina sheet and sintered in a muffle furnace at 1250 °C for 5 h to obtain an RSSOC single cell with an electrolyte thickness of 20 μm, and the first gradient thickness of 15 μm and the second gradient thickness of 30 μm on both sides of the electrode.

[0072] Example 2

[0073] A symmetrical reversible solid oxide cell (RSSOC) with a double gradient electrode and a preparation method thereof, comprising:

[0074] S1, Preparation of 10ScSZ electrolyte

[0075] Zirconium hydroxide was calcined at 450-550 °C for 2 h to obtain zirconium oxide, which was mixed with scandium acetate tetrahydrate at a molar ratio of 9:1 and then ball-milled for 12 h, dried at 400 °C for 4 h and crushed, and then calcined at 1050-1250 °C for 2 h, and after cooling, 10ScSZ powder was obtained; 2-butanone acid and ethanol were mixed at a volume ratio of 1-3:1 to obtain a uniform mixed solvent; finally, the prepared 10ScSZ powder and mixed solvent were mixed with polyvinyl butyral and dibutyl phthalate at a mass ratio of 100:50-70:2-4:1-3, and ball-milled for 12-20 h to prepare an electrolyte slurry; part of the electrolyte slurry was taken to prepare a dense 10ScSZ electrolyte substrate green body with a thickness of 30 μm and a structure density of 95% by tape casting. Then the green body was calcined at 1200-1300 °C in an air atmosphere for 5-7 h to obtain a dense electrolyte sheet with a density of 95%.

[0076] S2, Preparation of PBCO electrode material

[0077] First, Pr(NO3)3·6H2O, Ba(NO3)3·6H2O, Co(NO3)2·6H2O were weighed according to the stoichiometric ratio of 1:1:2, dissolved in a proper amount of deionized water to make them completely dissolved, and recorded as A liquid. Then, anhydrous citric acid and EDTA (Shanghai Yongchuan Biological Technology Co., Ltd.) were weighed according to the ratio of metal ions to anhydrous citric acid and EDTA of 1:1:1.5, a proper amount of deionized water was added, and continuously stirred in a magnetic stirrer, then a proper amount of ammonia water was added until the solution became clear, recorded as B liquid. Pour A liquid into B liquid, stir evenly, and add ammonia water to adjust pH to 4-5, then perform water bath heating at 80 ℃ until the solution forms a sol-gel. The sol-gel is placed in an oven at 180 ℃ for 10 h, then preliminary grinding is performed using a mortar to prepare a precursor powder. The precursor powder after the mortar is moved to a ceramic square boat, then placed in a muffle furnace for sintering at 1000 ℃ for 5 h, with a heating rate of 2 ℃ / min to prepare black PBCO finished powder.

[0078] S3, Preparation of PBCO electrode slurry

[0079] Preparation of the first gradient electrode slurry: First, prepare PBCO powder drying. Then weigh 10 g of PBCO material with an electronic balance and place it in a ball mill jar. The weighed PBCO powder, terpineol, ethyl cellulose are weighed according to the mass ratio of 100:75:2 and then placed in the ball mill jar, then the dispersant is added dropwise and a proper amount of ball milling beads is added. Finally, the well-proportioned ball mill jar is placed in a ball mill to mill at 500 rpm / min for 24 h to prepare a viscous PBCO first gradient electrode slurry.

[0080] Preparation of the second gradient electrode slurry: First, prepare PBCO powder drying. Then weigh 10 g of PBCO material with an electronic balance and place it in a ball mill jar. The weighed PBCO powder, terpineol, ethyl cellulose, starch are weighed according to the mass ratio of 100:75:2:(35-45) and then placed in the ball mill jar, then the dispersant is added dropwise and a proper amount of ball milling beads is added. Finally, the well-proportioned ball mill jar is placed in a ball mill to mill at 500 rpm / min for 24 h to prepare a viscous PBCO second gradient electrode slurry.

[0081] S4, Preparation of RSSOC single cell of bifunctional gradient PBCO electrode

[0082] The preparation of the single cell of the RSSOC with 10ScSZ as electrolyte and PBCO as fuel electrode and air electrode is as follows: first, take the above prepared 10ScSZ electrolyte round substrate with a diameter of 20 mm, wipe both sides of the substrate with alcohol, then screen print PBCO first gradient electrode slurry to both sides of the electrolyte sheet each once, put it into an oven at 80 ℃ for drying, repeat the above steps, coat to 20 μm, then screen print PBCO second gradient electrode slurry to both sides of the electrolyte sheet each once, put it into an oven at 80 ℃ for drying, repeat the above steps, coat to 40 μm. Finally, place the symmetrical cell with gradient electrode material coated on both sides on an alumina sheet, sinter in a muffle furnace at 1250 ℃ for 5 h, and the RSSOC single cell with an electrolyte thickness of 20 μm, first gradient electrode thickness of 15 μm on both sides and second gradient electrode thickness of 30 μm on both sides is obtained.

[0083] Example 3

[0084] A symmetrical reversible solid oxide cell (RSSOC) with a double gradient electrode and a preparation method thereof, comprising:

[0085] S1, preparation of 10ScSZ electrolyte

[0086] Zirconium hydroxide is calcined at 450-550 ℃ for 2 h to obtain zirconium oxide, which is mixed with scandium acetate tetrahydrate at a molar ratio of 9:1, then ball milled for 12 h, dried at 400 ℃ for 4 h and crushed, and then calcined at 1050-1250 ℃ for 2 h, and after cooling, 10ScSZ powder is obtained; 2-butanone acid and ethanol are mixed at a volume ratio of 1-3:1 to obtain a uniform mixed solvent; finally, the prepared 10ScSZ powder and mixed solvent are mixed with polyvinyl butyral and dibutyl phthalate at a mass ratio of 100:50-70:2-4:1-3, and ball milled for 12-20 h to prepare an electrolyte slurry; part of the electrolyte slurry is used to prepare a green body of a dense 10ScSZ electrolyte substrate with a structure density of 95% and a thickness of 30 μm by tape casting. Then the green body is calcined at 1200-1300 ℃ in an air atmosphere for 5-7 h to obtain a dense electrolyte sheet with a density of 95%.

[0087] S2, preparation of SFMO electrode material

[0088] First, Sr(NO3)2·6H2O, Fe(NO3)3·6H2O, M(NO3)2·6H2O were weighed according to the stoichiometric ratio of 4:3:1, dissolved in a proper amount of deionized water to make it completely dissolved, and recorded as A liquid. Then, anhydrous citric acid and EDTA (Shanghai Yongchuan Biological Technology Co., Ltd.) were weighed according to the ratio of 1:1:1.5 of metal ions to anhydrous citric acid and EDTA, a proper amount of deionized water was added, and the solution was continuously stirred in a magnetic stirrer, then a proper amount of ammonia water was added until the solution became clear, recorded as B liquid. Pour A liquid into B liquid, stir evenly, and add ammonia water to adjust pH to 4-5, then perform water bath heating at 80 ℃ until the solution forms a sol-gel. The sol-gel is placed in an oven at 180 ℃ for 10 h, then a mortar is used for preliminary grinding to prepare a precursor powder. The precursor powder after the mortar is moved to a ceramic square boat, then placed in a muffle furnace at 1000 ℃ for 5 h, with a heating rate of 2 ℃ / min to prepare black SFMO finished powder.

[0089] S3, Preparation of SFMO electrode slurry

[0090] Preparation of the first gradient electrode slurry: First, prepare SFMO powder drying. Then weigh 10 g of SFMO material with an electronic balance and place it in a ball mill jar. The weighed SFMO powder, terpineol, ethyl cellulose are weighed according to the mass ratio of 100:75:2 and then placed in the ball mill jar, then the dispersant is added dropwise and a proper amount of ball milling beads is added. Finally, the well-proportioned ball mill jar is placed in a ball mill at 500 rpm / min for 24 h to prepare a viscous SFMO first gradient electrode slurry.

[0091] Preparation of the second gradient electrode slurry: First, prepare SFMO powder drying. Then weigh 10 g of SFMO material with an electronic balance and place it in a ball mill jar. The weighed SFMO powder, terpineol, ethyl cellulose, starch are weighed according to the mass ratio of 100:75:2:35-45 and then placed in the ball mill jar, then the dispersant is added dropwise and a proper amount of ball milling beads is added. Finally, the well-proportioned ball mill jar is placed in a ball mill at 500 rpm / min for 24 h to prepare a viscous SFMO second gradient electrode slurry.

[0092] 4. Preparation of RSSOC single cell of bifunctional gradient SFMO electrode

[0093] The single cell of the RSSOC with 10ScSZ as electrolyte and SFMO as fuel electrode and air electrode was prepared as follows: first, the above prepared 10ScSZ electrolyte round substrate with a diameter of 20 mm was wiped on both sides with alcohol, then the SFMO first gradient electrode slurry was screen printed on both sides of the electrolyte sheet once, which was placed in an oven at 80 ℃ for drying, the above steps were repeated, and the coating was 20 μm, then the SFMO second gradient electrode slurry was screen printed on both sides of the electrolyte sheet once, which was placed in an oven at 80 ℃ for drying, the above steps were repeated, and the coating was 40 μm. Finally, the symmetrical cell coated with gradient electrode material on both sides was placed on an alumina sheet, and sintered at 1250 ℃ for 5 h in a muffle furnace, to obtain a RSSOC single cell with an electrolyte thickness of 20 μm, and the first gradient thickness of 15 μm and the second gradient thickness of 30 μm on both sides of the electrode.

[0094] Comparative Example 1

[0095] The present comparative example is a traditional solid oxide fuel cell (SOFC) which is composed of a traditional YSZ electrolyte, a Ni-YSZ anode and a LSM-YSZ cathode.

[0096] The symmetrical reversible solid oxide fuel cell (RSSOC) with bifunctional gradient electrode prepared in Examples 1-3 and the traditional cell of Comparative Example 1 were tested for discharge performance and electrolysis stability under the set conditions.

[0097] The linear sweep voltammetry method was used to test the voltammetric characteristics of the cell, and the power density of the cell was calculated according to the measured current and voltage parameters.

[0098] The test conditions of the cell were as follows:

[0099] In SOFC mode, the discharge test was carried out at 800 ℃. Hydrogen was introduced into the fuel electrode at 300 sccm, and air was introduced into the air electrode at 1 atm;

[0100] In SOEC mode, the water electrolysis test was carried out, and the introduced water vapor was 0.25 mL / min, and the record was collected.

[0101] During the experiment, the discharge test, water electrolysis test and stability test of the single cell were included. The test results are shown in FIGS. 4 to Figure 9

[0102] ​The discharge performance test results of the batteries are shown in FIGS. 4 to 6. The battery operating temperature is set to 800℃, and the three RSSOC batteries prepared in Examples 1 to 3 and the battery of Comparative Example 1 are tested under high-temperature conditions, with hydrogen at 300 sccm as fuel and air as oxidant for single-cell discharge test, and the test results are expressed by I-P-V curves, in which the flow ratio of hydrogen to air is kept at 1:3. The test results show that the open-circuit voltage of the three SSOFC batteries prepared in Examples 1 to 3 always remains above 1.05 V, and the maximum power densities of the single cells with SBSC, PBCO and SFMO as functional gradient electrodes are 0.291 W / cm 2 , 0.343 W / cm 2 and 0.346 W / cm 2 , respectively; while the maximum power density of the battery of Comparative Example 1 under the highest temperature is 0.242 W / cm 2 .

[0103] The test results of the water electrolysis cycle stability of the batteries are shown in FIGS. 7 to Figure 9 , and the cycle stability analysis of the batteries determines the durability of the batteries. The three RSSOC prepared in Examples 1 to 3 are subjected to constant-voltage electrolysis at a constant voltage of 1.3 V for cycle stability test, with water vapor at 0.25 mL / min, and the duration of charge and discharge is 8 h. As can be seen from FIGS. 7 to Figure 9 , the single cells with SBSC, PBCO and SFMO as functional gradient electrodes show good stability, and the electrolysis of Comparative Example 1 starts to decay at about the 4th hour. This shows that the RSSOC batteries with SBSC, PBCO and SFMO as functional gradient electrodes show good electrolysis stability.

[0104] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A symmetric reversible solid oxide cell with a dual- gradient electrode, characterized in that, The electrolyte layer is located in the middle, and the electrode layers are symmetrically arranged on both sides of the electrolyte layer; The electrode layer comprises a first gradient electrode layer and a second gradient electrode layer, and the first gradient electrode layer is close to the electrolyte layer; The electrolyte layer comprises dense 10ScSZ; The electrode layer includes any one of SmBa 0.5 Sr 0.5 Co2O 5-δ , PrBaCo2O 5+δ , Sr2Fe 1.5 Mo 0.5 O 6-δ ​ The porosity of the second gradient electrode layer is greater than that of the first gradient electrode layer.

2. A symmetric reversible solid oxide cell with a dual- gradient electrode according to claim 1, characterized in that, The electrolyte layer is dense 10ScSZ with a density of 95%.

3. A symmetric reversible solid oxide cell with a dual- gradient electrode according to claim 2, characterized in that, The porosity of the first gradient electrode layer is 15-25%, and the porosity of the second gradient electrode layer is 35-45%.

4. The method of claim 1 to 3, wherein the method is characterized by, The method comprises the following steps: S1: preparing the electrolyte layer; S2: selecting the preparation materials of the electrode layer and preparing the electrode layer powder; S3: using the electrode layer powder to prepare the first gradient electrode layer slurry and the second gradient electrode layer slurry respectively; S4: brushing the first gradient electrode layer slurry and the second gradient electrode layer slurry on the electrolyte layer in sequence, and sintering at 1200-1300 ℃ to obtain the symmetrical reversible solid oxide cell with a double gradient electrode.

5. The method of claim 4, wherein the method further comprises: In the step S1, 10ScSZ electrolyte slurry is prepared by ball milling after mixing zirconium oxide and scandium acetate tetrahydrate in a molar ratio of 9:1; the 10ScSZ electrolyte slurry is processed by a flow casting method to obtain an electrolyte sheet green body, and the electrolyte sheet green body is sintered at 1200-1300 ℃ for 5-7 h to obtain the electrolyte layer.

6. The method of claim 4, wherein the method further comprises: In the step S2, any one of SmBa 0.5 Sr 0.5 Co2O 5-δ , PrBaCo2O 5+δ , Sr2Fe 1.5 Mo 0.5 O 6-δ is selected as an electrode material for preparing the electrode layer. According to the molar ratio of the chemical formula of the selected electrode material, the corresponding nitrate salt is weighed and dissolved in deionized water, and a precursor is obtained by a sol-gel preparation method, and then the precursor is sintered at 1000 ℃ for 5 h to obtain the electrode layer powder.

7. The method of claim 4, wherein the method further comprises: In the step S3, two portions of the electrode material powder with the same weight are weighed, one portion is weighed with terpineol, ethyl cellulose and starch in a mass ratio of 100:75:2, then put into a ball milling tank, drop in a dispersing agent and add an appropriate amount of ball milling beads for ball milling to obtain the first gradient electrode layer slurry; the other portion is weighed with terpineol, ethyl cellulose and starch in a mass ratio of 100:75:2:35-45, then put into a ball milling tank, drop in a dispersing agent and add an appropriate amount of ball milling beads for ball milling to obtain the second gradient electrode layer slurry.

8. The method of claim 4, wherein the method further comprises: In the step S4, the first gradient electrode layer slurry and the second gradient electrode layer slurry are screen printed on both sides of the electrolyte layer by a screen printing method, and sintered at 1200-1300 ℃ to obtain the symmetrical reversible solid oxide cell with a double gradient electrode.

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