Composite electrolyte buffer layer for solid oxide electrolytic cell and preparation method of composite electrolyte buffer layer

Abstract

The invention discloses a composite electrolyte buffer layer for a solid oxide electrolytic cell and a preparation method, and relates to the technical field of SOFC (solid oxide fuel cell) electrolyte, an electrolyte sputtering compact layer I, an electrolyte sputtering compact layer II and an anode sputtering layer are sequentially sputtered on the surface of an electrolyte layer of the solid oxide electrolytic cell, the thickness of the electrolyte sputtering compact layer I is 10 nanometers to 1 micrometer, the thickness of the electrolyte sputtering compact layer II is 50 nanometers to 500 nanometers, and the thickness of the anode sputtering layer is 5 nanometers to 30 nanometers. The composite electrolyte nano buffer layer prepared by a magnetron sputtering method has the advantages of blocking electrons, improving open-circuit voltage, enhancing ionic conductivity to reduce ohmic resistance, enhancing chemical compatibility and thermal matching with electrodes to improve long-term stability and the like; the problem of electric leakage in a traditional low-temperature electrolyte is solved, the open-circuit voltage is increased to 1.00 V or above (600 DEG C), the output power and stability of the solid oxide electrolytic cell are improved, and the application range of the solid oxide electrolytic cell is widened.

Description

Technical Field

[0001] The present invention relates to the technical field of solid oxide fuel cell electrolytes, and in particular to a composite electrolyte buffer layer for a solid oxide electrolyzer and a preparation method thereof. Background Art

[0002] Traditional solid oxide fuel cells use zirconium-based oxides as electrolytes, which can meet the performance and stability requirements at relatively high operating temperatures (800°C - 1000°C). However, at medium and low temperatures, due to relatively low ionic conductivity and excessive ohmic resistance, more performance losses occur; in addition, zirconium-based electrolytes are prone to react with electrode materials to form high-resistance phases, resulting in problems such as stability during long-term operation.

[0003] Cerium-based electrolytes have high ionic conductivity and thus become potential electrolytes for medium and low temperature solid oxide cells. However, their existing electronic conductivity will cause serious internal leakage, resulting in a low open-circuit voltage and serious internal power consumption of the battery, making it difficult to be applied to electrolyzers. To address the problems such as internal leakage of cerium-based electrolytes, on the one hand, new electrolyte components are developed. By doping oxides in the fluorite phase or designing new phase structures, the internal electronic conductivity is reduced. However, under the actual test redox atmosphere, the cerium-based electrolyte still has long-term stability problems. On the other hand, the internal leakage problem is improved by adding a separation layer. For example, adding a YSZ layer on the surface of GDC can alleviate the internal leakage problem; however, some commonly used electrode catalyst materials, such as lanthanum-based perovskite oxide electrodes, will react with YSZ at the interface during long-term operation to form a lanthanum zirconate barrier phase, resulting in performance degradation. Further, sputtering GDC on the surface of the YSZ separation layer can alleviate the harmful interfacial reaction caused by chemical compatibility problems, but there will still be a mismatch between the thermal expansion coefficient of GDC (~12×10 -6 K -1 ) and that of some commonly used high-performance cathode materials, such as barium cobalt-based perovskite oxides (>20×10 -6 K -1 ), resulting in problems such as the electrode peeling off from the electrolyte surface during the preparation and testing processes, generating a large interfacial resistance, etc.

[0004] In summary, the present invention urgently needs to design a method for improving the internal leakage and stability of high-performance cerium-based electrolytes at medium and low temperatures for solid oxide electrolyzers. Summary of the Invention

[0005] To solve the above technical problems, the present invention discloses a composite electrolyte buffer layer for a solid oxide electrolyzer and a preparation method thereof. The composite electrolyte buffer layer is composed of an electrolyte sputtering dense layer I, an electrolyte sputtering dense layer II, and an anode sputtering layer. The electrolyte sputtering dense layer I functions to conduct ions, isolate electrons, and increase the open-circuit voltage. The electrolyte sputtering dense layer II functions to increase the conductivity of the electrolyte and improve the chemical compatibility of the interface between the electrolyte and the anode. The anode sputtering layer functions to conduct electrons, improve the thermal matching and interface connectivity between the electrolyte and the anode.

[0006] The composite electrolyte buffer layer for the solid oxide electrolyzer can break through the internal leakage of traditional low-temperature electrolytes, increase the open-circuit voltage to above 1.00 V (at 600 °C), and at the same time, the composition of the uppermost layer is similar to that of the electrode, which can greatly enhance the chemical compatibility and thermal matching with the electrode, thereby effectively improving the long-term stability of the solid oxide electrolyzer and promoting its development and application.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A composite electrolyte buffer layer for a solid oxide electrolyzer, comprising an electrolyte sputtering dense layer I, an electrolyte sputtering dense layer II, and an anode sputtering layer that are sequentially sputtered on the surface of the electrolyte layer of the solid oxide electrolyzer;

[0009] Wherein:

[0010] The electrolyte sputtering dense layer I has a thickness of 10 nm to 1 μm and is used for ion conduction, electron isolation, and increasing the open-circuit voltage;

[0011] The electrolyte sputtering dense layer II has a thickness of 50 nm to 500 nm and is used for increasing the conductivity of the electrolyte and improving the chemical compatibility of the interface between the electrolyte and the anode;

[0012] The anode sputtering layer has a thickness of 5 nm to 30 nm and is used for electron conduction, improving the thermal matching and interface connectivity between the electrolyte and the anode.

[0013] Further, the composition of the electrolyte sputtering dense layer I is one of scandium-stabilized zirconia (ScSZ), yttrium-stabilized zirconia (YSZ), cerium-doped zirconia (CCZ), and yttrium-doped barium zirconate (BZY).

[0014] Further, the composition of the electrolyte sputtering dense layer II is one of gadolinium-doped ceria (GDC), samarium-doped ceria (SDC), and yttrium-doped barium cerate (BCY).

[0015] Further, the composition of the anode sputtering layer is one of barium cobaltate (BC), barium ferrite (BF), and iron-doped barium cobaltate oxide (BCF).

[0016] The present invention also discloses a preparation method of a composite electrolyte buffer layer for a solid oxide electrolyzer. The electrolyte sputtering dense layer I, the electrolyte sputtering dense layer II and the anode sputtering layer are sequentially sputtered on the surface of the electrolyte layer of the solid oxide electrolyzer by magnetron sputtering to form a composite electrolyte buffer layer.

[0017] Furthermore, the process of sputtering to prepare the electrolyte sputtering dense layer I is as follows:

[0018] The alloy target used is one of scandium zirconium alloy, yttrium zirconium alloy, cerium zirconium alloy, yttrium zirconium barium alloy. The sputtering temperature is 300 - 600 °C, the sputtering power is 90 - 180 W, the sputtering time is 30 - 800 minutes, the sputtering atmosphere is a mixed gas of argon and oxygen, where the argon flow rate is 1 - 10 sccm and the oxygen flow rate is 0.1 - 5 sccm. After sputtering, annealing is carried out at 800 °C to 950 °C for 1 h to 10 h, and the sputtering process can be repeated 1 - 3 times.

[0019] Furthermore, the process of sputtering to prepare the electrolyte sputtering dense layer II is as follows:

[0020] The alloy target used is one of gadolinium cerium alloy, samarium cerium alloy, yttrium cerium barium alloy. The sputtering temperature is 100 - 350 °C, the sputtering power is 100 - 180 W, the sputtering time is 30 - 120 minutes, the sputtering atmosphere is a mixed gas of argon and oxygen, where the argon flow rate is 1 - 10 sccm and the oxygen flow rate is 0.1 - 5 sccm. After sputtering, annealing is carried out at 900 °C to 950 °C for 1 h to 10 h, and the sputtering process can be repeated 1 - 3 times.

[0021] Furthermore, the process of sputtering to prepare the anode sputtering layer is as follows:

[0022] The alloy target used is one of cobalt barium alloy, iron barium alloy, iron cobalt barium alloy. The sputtering temperature is 10 - 300 °C, the sputtering power is 50 - 120 W, the sputtering time is 5 - 30 minutes, the sputtering atmosphere is a mixed gas of argon and oxygen, where the argon flow rate is 1 - 10 sccm and the oxygen flow rate is 0.1 - 5 sccm. After sputtering, annealing is carried out at 300 °C to 800 °C for 0.5 h to 5 h.

[0023] The beneficial effect of the present invention is that, compared with the prior art,

[0024] The present invention uses physical vapor deposition to prepare the electrolyte sputtering dense layer I on the surface of the cerium-based electrolyte micron layer. This nano diaphragm can effectively block the internal electron conduction problem, and at the same time, the formed nano film layer and the interface will also form high ionic conductivity, which can not only improve the internal leakage and increase the open circuit voltage, but also enhance the ionic conductivity, so as to achieve the purpose of reducing the ohmic loss.

[0025] In the present invention, an electrolyte sputtering dense layer II is further designed and prepared on the surface of the electrolyte partition layer as an electrode nano-buffer layer. On the one hand, the electrode nano-buffer layer has high compatibility and matching with the substrate film; on the other hand, it has high ionic conductivity.

[0026] The components of the anode nano-buffer layer further prepared on the electrolyte sputtering dense layer II are close to those of the electrode material. During the preparation and testing processes, it has high compatibility and matching with the electrode layer; in addition, the nano-structure in the electrode nano-buffer layer helps to improve the internal ionic and electronic conductivities, and certain catalytic active sites are also formed on the surface, thus greatly enhancing the electrode activity.

[0027] The composite electrolyte buffer layer prepared in the present invention is applicable to both oxygen ion type solid oxide electrolytic cells and proton type solid oxide electrolytic cells. By improving and optimizing the electrolyte layer structure, medium and low temperature high-performance battery systems are applied to efficient electrolysis systems.

[0028] This method can realize the application of high-performance solid oxide batteries with cerium-based fluorite phase or perovskite phase oxides as electrolytes in the electrolysis field. By using the magnetron sputtering method to prepare the composite electrolyte nano-buffer layer, it has the advantages of blocking electrons to increase the open circuit voltage, enhancing ionic conductivity to reduce the ohmic resistance, and enhancing the chemical compatibility and thermal matching with the electrode to improve the long-term stability, which is beneficial to promoting the development and application of high-performance solid oxide electrolytic cells in electrolysis. Description of the Drawings

[0029] Figure 1 It is the cross-section (upper figure) and surface (lower figure) structure diagrams of the YSZ buffer layer prepared in Example 1 of the present invention;

[0030] Figure 2 It is the cross-section (upper figure) and surface (lower figure) structure diagrams of the YSZ and GDC double buffer layers prepared in Example 1 of the present invention;

[0031] Figure 3 It is the I-V curve of the battery prepared in Example 1 of the present invention;

[0032] Figure 4 It is the stability test of the battery prepared in Example 1 of the present invention;

[0033] Figure 5 It is the cross-section (upper figure) and surface (lower figure) structure diagrams of the YSZ buffer layer prepared in Example 2 of the present invention. Detailed Embodiments

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0035] Example 1

[0036] A preparation method of a composite electrolyte buffer layer for a solid oxide electrolyzer uses magnetron sputtering to sequentially sputter and prepare an electrolyte sputtered dense layer I, an electrolyte sputtered dense layer II, and an anode sputtered layer on the surface of the solid oxide electrolyzer electrolyte layer. The specific process is as follows:

[0037] Use magnetron sputtering to prepare the electrolyte sputtered dense layer I, whose composition is yttria-stabilized zirconia (YSZ). Use a yttrium-zirconium alloy target, the sputtering temperature is 500 °C, the sputtering power is 180 W, the sputtering time is 35 minutes, the sputtering atmosphere is a mixed gas of argon and oxygen, where the argon flow rate is 10 sccm and the oxygen flow rate is 5 sccm. After sputtering, anneal at 900 °C for 2 h; as Figure 1 shown, a surface-dense electron isolation buffer layer with a thickness of 60 - 70 nanometers is obtained.

[0038] Use magnetron sputtering to continue preparing the electrolyte dense layer II, whose composition is gadolinium-doped ceria (GDC). Use a gadolinium-ceria alloy target, the sputtering temperature is 300 °C, the sputtering power is 90 W, the sputtering time is 50 minutes, the sputtering atmosphere is a mixed gas of argon and oxygen, where the argon flow rate is 10 sccm and the oxygen flow rate is 5 sccm. After sputtering, anneal at 900 °C for 2 h; as Figure 2 shown, a surface-dense compatibility buffer layer with a thickness of 70 - 80 nanometers is obtained.

[0039] Use magnetron sputtering to prepare the anode sputtered layer, whose composition is barium cobaltate (BC). Use a specific cobalt-barium alloy target, the sputtering temperature is 300 °C, the sputtering power is 120 W, the sputtering time is 5 minutes, the sputtering atmosphere is a mixed gas of argon and oxygen, where the argon flow rate is 10 scmm and the oxygen flow rate is 5 sccm. After sputtering, anneal at 800 °C for 2 h to obtain a thermal matching buffer layer with a thickness of 5 - 10 nanometers; a composite electrolyte buffer layer is made.

[0040] Assemble the prepared composite electrolyte buffer layer into a battery for performance testing, as Figure 3 and Figure 4 shown, the open circuit voltage reaches 1.086 V at 600 °C, and the electrolysis current reaches 1.5 A cm-2 above, and the electrolytic stability can be improved.

[0041] Example 2

[0042] A preparation method of a composite electrolyte buffer layer for a solid oxide electrolytic cell, which sequentially sputters and prepares an electrolyte sputtering dense layer I, an electrolyte sputtering dense layer II, and an anode sputtering layer on the surface of the electrolyte layer of the solid oxide electrolytic cell by magnetron sputtering. Specifically:

[0043] The electrolyte sputtering dense layer I is prepared by magnetron sputtering, and its composition is yttria-stabilized zirconia (YSZ). A yttrium-zirconium alloy target is used, the sputtering temperature is 400 °C, the sputtering power is 120 W, the sputtering time is 770 minutes, and the sputtering atmosphere is a mixed gas of argon and oxygen, where the argon flow rate is 10 sccm and the oxygen flow rate is 5 sccm. After sputtering, annealing is carried out at 900 °C for 2 h; as Figure 5 shown, a surface-dense electron isolation buffer layer with a thickness of 600 - 650 nanometers is obtained.

[0044] The electrolyte dense layer II is continuously prepared by magnetron sputtering, and its composition is gadolinium-doped ceria (GDC). A gadolinium-ceria alloy target is used, the sputtering temperature is 300 °C, the sputtering power is 120 W, the sputtering time is 50 minutes, and the sputtering atmosphere is a mixed gas of argon and oxygen, where the argon flow rate is 10 sccm and the oxygen flow rate is 1 sccm. After sputtering, annealing is carried out at 950 °C for 2 h to obtain a surface-dense compatibility buffer layer with a thickness of 120 - 150 nanometers.

[0045] The anode sputtering layer is prepared by magnetron sputtering, and its composition is barium cobaltate (BC). A specific cobalt-barium alloy target is used, the sputtering temperature is 300 °C, the sputtering power is 120 W, the sputtering time is 5 minutes, and the sputtering atmosphere is a mixed gas of argon and oxygen, where the argon flow rate is 10 sccm and the oxygen flow rate is 1 sccm. After sputtering, annealing is carried out at 800 °C for 2 h to obtain a thermal matching buffer layer with a thickness of 5 - 10 nanometers; a composite electrolyte buffer layer is made.

[0046] The prepared composite electrolyte buffer layer is assembled into a battery for performance testing. The open-circuit voltage reaches 1.035 V at 650 °C, and the electrolysis current reaches 2.5 A cm -2 above and can stably electrolyze.

[0047] Example 3

[0048] A preparation method of a composite electrolyte buffer layer for a solid oxide electrolytic cell, which sequentially sputters and prepares an electrolyte sputtering dense layer I, an electrolyte sputtering dense layer II, and an anode sputtering layer on the surface of the electrolyte layer of the solid oxide electrolytic cell by magnetron sputtering. Specifically:

[0049] The electrolyte sputtering dense layer I is prepared by magnetron sputtering. Its composition is scandia-stabilized zirconia (SSZ). A scandium-zirconium alloy target is used. The sputtering temperature is 500 °C, the sputtering power is 120 W, the sputtering time is 35 minutes, and the sputtering atmosphere is a mixed gas of argon and oxygen. Among them, the argon flow rate is 10 sccm, and the oxygen flow rate is 5 sccm. After sputtering, it is annealed at 900 °C for 2 h to obtain a surface-dense electron isolation buffer layer with a thickness of 50 - 60 nanometers.

[0050] The electrolyte dense layer II is continuously prepared by magnetron sputtering. Its composition is gadolinium-doped ceria (GDC). A gadolinium-ceria alloy target is used. The sputtering temperature is 300 °C, the sputtering power is 180 W, the sputtering time is 50 minutes, and the sputtering atmosphere is a mixed gas of argon and oxygen. Among them, the argon flow rate is 10 sccm, and the oxygen flow rate is 1 sccm. After sputtering, it is annealed at 950 °C for 2 h to obtain a surface-dense compatibility buffer layer with a thickness of 280 - 300 nanometers.

[0051] The anode sputtering layer is prepared by magnetron sputtering. Its composition is barium cobaltate (BC). A specific barium-cobalt alloy target is used. The sputtering temperature is 300 °C, the sputtering power is 120 W, the sputtering time is 5 minutes, and the sputtering atmosphere is a mixed gas of argon and oxygen. Among them, the argon flow rate is 10 sccm, and the oxygen flow rate is 1 sccm. After sputtering, it is annealed at 900 °C for 2 h to obtain a thermal matching buffer layer with a thickness of 5 - 10 nanometers; a composite electrolyte buffer layer is made.

[0052] The above-prepared composite electrolyte buffer layer is assembled into a battery for performance testing. The open-circuit voltage reaches 1.05 V at 600 °C, and the electrolysis current reaches 1.5 A cm -2 above, and the electrolysis stability can be improved.

[0053] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions, or substitutions made by those skilled in the art within the scope of the essence of the present invention should also fall within the protection scope of the present invention.

Claims

1. A composite electrolyte buffer layer for a solid oxide electrolytic cell, characterized in that: The invention comprises an electrolyte sputtering dense layer I, an electrolyte sputtering dense layer II and an anode sputtering layer which are sequentially sputtered on the surface of the electrolyte layer of the solid oxide electrolytic cell; in: The electrolyte sputtering dense layer I has a thickness of 10 nanometers to 1 micrometer and is used for ion conduction, electron isolation and increased open circuit voltage; The electrolyte sputtering dense layer II has a thickness of 50 nanometers to 500 nanometers and is used to increase the conductivity of the electrolyte and improve the chemical compatibility of the electrolyte and anode interface; The anode sputtering layer has a thickness of 5 nanometers to 30 nanometers and is used to conduct electrons and improve the thermal matching and interface connectivity between the electrolyte and the anode.

2. A composite electrolyte buffer layer for a solid oxide electrolytic cell according to claim 2, characterized in that: The electrolyte sputtering dense layer I is composed of one of scandium oxide stabilized zirconium oxide, yttria stabilized zirconium oxide, cerium oxide doped zirconium oxide, and yttrium doped barium zirconate.

3. A composite electrolyte buffer layer for a solid oxide electrolytic cell according to claim 2, characterized in that: The electrolyte sputtering dense layer II is composed of one of gadolinium oxide doped cerium oxide, samarium oxide doped cerium oxide, and yttrium doped barium ceria.

4. A composite electrolyte buffer layer for a solid oxide electrolytic cell according to claim 3, characterized in that: The anode sputtering layer is composed of one of barium cobaltate, barium ferrite, and iron-doped barium cobaltate.

5. The method for preparing a composite electrolyte buffer layer for a solid oxide electrolytic cell according to claim 4, characterized in that: The electrolyte sputtering dense layer I, the electrolyte sputtering dense layer II and the anode sputtering layer are sequentially prepared on the surface of the electrolyte layer of the solid oxide electrolytic cell by magnetron sputtering method to prepare a composite electrolyte buffer layer.

6. The method for preparing a composite electrolyte buffer layer for a solid oxide electrolytic cell according to claim 51, characterized in that: The process of preparing the electrolyte sputtering dense layer I by sputtering is as follows: The alloy target material used is one of scandium zirconium alloy, yttrium zirconium alloy, cerium zirconium alloy, and yttrium zirconium-barium alloy. The sputtering temperature is 300-600°C, the sputtering power is 90-180W, the sputtering time is 30-800 minutes, and the sputtering atmosphere is a mixture of argon and oxygen, wherein the argon flow rate is 1-10sccm, and the oxygen flow rate is 0.1-5sccm. After sputtering, annealing is performed at 800°C to 950°C for 1h to 10h, and the sputtering process is repeated 1-3 times.

7. The method for preparing a composite electrolyte buffer layer for a solid oxide electrolytic cell according to claim 6, characterized in that: The process of preparing the electrolyte sputtering dense layer II by sputtering is as follows: The alloy target material used is one of gadolinium-cerium alloy, samarium-cerium alloy, and yttrium-cerium-barium alloy. The sputtering temperature is 100-350°C, the sputtering power is 100-180W, the sputtering time is 30-120 minutes, and the sputtering atmosphere is a mixture of argon and oxygen, wherein the argon flow rate is 1-10sccm and the oxygen flow rate is 0.1-5sccm. After sputtering, annealing is performed at 900°C to 950°C for 1h to 10h, and the sputtering process is repeated 1-3 times.

8. The method for preparing a composite electrolyte buffer layer for a solid oxide electrolytic cell according to claim 7, characterized in that: The process of sputtering to prepare the anode sputtering layer is: The alloy target material used is one of cobalt-barium alloy, iron-barium alloy, and iron-cobalt-barium alloy. The sputtering temperature is 10-300°C, the sputtering power is 50-120W, the sputtering time is 5-30 minutes, and the sputtering atmosphere is a mixture of argon and oxygen, wherein the argon flow rate is 1-10sccm and the oxygen flow rate is 0.1-5sccm. After sputtering, annealing is performed at 300°C to 800°C for 0.5h to 5h.

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