A low-temperature cerium-based composite electrolyte film with high ionic conductivity and a preparation process thereof

Abstract

The application belongs to the technical field of solid oxide electrochemical devices, and particularly relates to a low-temperature cerium-based composite electrolyte film with high ionic conductivity and a preparation process thereof. The film has a gradient function integrated structure and sequentially comprises a transmission layer composed of dense gadolinium-doped ceria, a functional layer constructed thereon, which is composed of a porous gadolinium-doped ceria skeleton and a lanthanum-strontium-gallium-magnesium oxide-alkali carbonate eutectic composite phase filled in the pores, and a SmNiO3 or SmCoO3 ultrathin interface modification layer covering the surface of the functional layer. The preparation process involves transmission layer forming sintering, functional layer slurry coating and step-by-step eutectic reaction heat treatment, and atomic layer deposition of the interface layer. The composite film can realize high oxygen ion conductivity and low electronic conductivity in a medium-low temperature range of 400-650 DEG C, significantly improves the battery efficiency and stability, and reduces the system operating temperature and cost.

Description

Technical Field

[0001] This invention belongs to the field of solid oxide electrochemical device technology, specifically relating to a low-temperature cerium-based composite electrolyte thin film with high ionic conductivity and its preparation process. Background Technology

[0002] Solid oxide fuel cells (SOFCs) and solid oxide electrolyzers (SOECs) are considered core devices for future clean energy conversion and storage due to their high efficiency, fuel flexibility, and environmental friendliness. SOFCs can directly convert the chemical energy of fuels (such as hydrogen and natural gas) into electrical energy, while SOECs can efficiently electrolyze water vapor into hydrogen under electrified conditions, achieving the storage and conversion of renewable energy. The core component of both types of devices is a ceramic-based solid oxide electrolyte, whose core function is to selectively conduct oxygen ions and isolate electrons between the cathode and anode, thereby driving the reversible electrochemical reaction.

[0003] Currently, yttrium-stabilized zirconia (YSZ) is the most widely commercialized or researched solid oxide electrolyte material. YSZ possesses sufficient oxygen ion conductivity and good chemical and mechanical stability at high temperatures, thus forming the technological basis of traditional SOFC / SOEC. However, this heavy reliance on high temperatures also brings insurmountable systemic drawbacks. First, the extremely high operating temperature leads to accelerated aging and degradation of key components in the battery stack, severely limiting the long-term operational life and reliability of the system. Second, the stringent requirements of high-temperature environments necessitate the use of expensive high-temperature alloys, significantly increasing system manufacturing costs. Furthermore, achieving high-temperature operation requires complex and time-consuming heating and holding processes, resulting in slow start-up speeds that cannot meet the demands of rapid-response applications. In addition, high-temperature operation also limits the system's application potential in mobile or small-scale distributed scenarios. Therefore, reducing the operating temperature of SOFC / SOEC to achieve medium- and low-temperature operation has become a key breakthrough for promoting the large-scale commercial application of this technology.

[0004] To lower operating temperatures, researchers have turned their attention to alternative electrolyte materials with higher intrinsic oxygen ion conductivity in the mid-to-low temperature range, among which doped cerium oxide is one of the most promising material systems. These cerium-based electrolytes exhibit ionic conductivity at 500-600℃ that is an order of magnitude higher than YSZ at the same temperature, offering material science possibilities for achieving efficient mid-to-low temperature operation. However, pure-phase doped cerium oxide, under low oxygen partial pressure conditions, partially loses its Ce2+ content. 4+ It will be reduced to Ce 3+This results in significant electronic conductivity. This "electronic conductivity" creates a short-circuit current inside the battery, leading to a drop in open-circuit voltage and a huge loss in energy conversion efficiency, severely weakening its practical application value. On the other hand, obtaining a dense electrolyte layer that can completely block gases usually requires extremely high sintering temperatures, which contradicts the original intention of reducing system manufacturing costs. Furthermore, high-temperature sintering may lead to interfacial reactions with other battery components.

[0005] Therefore, developing a novel electrolyte material system and its suitable preparation process, which can simultaneously achieve high ionic conductivity, low electronic conductivity, good low-temperature sintering activity, and excellent structural and chemical stability, is of great significance for promoting the practical application of low-temperature SOFC / SOEC technology. Summary of the Invention

[0006] The purpose of this invention is to provide a low-temperature cerium-based composite electrolyte thin film with high ionic conductivity and its preparation process, which solves the key problems of traditional electrolyte materials being highly dependent on high temperatures and having difficulty in balancing efficiency and stability, thereby improving the overall performance and practicality of solid oxide electrochemical devices.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A low-temperature cerium-based composite electrolyte film with high ionic conductivity comprises the following three-layer structure: The transport layer is composed of gadolinium-doped cerium oxide with a relative density of not less than 99%. A functional layer is constructed on one side surface of the transport layer. The functional layer consists of a porous gadolinium-doped cerium oxide framework and a composite ionic conductor filling the pores of the framework. The composite ionic conductor is a continuous phase formed by lanthanum strontium gallium magnesium oxide and alkali metal carbonate through a eutectic reaction. An interface modification layer, which is SmNiO3 or SmCoO3, covers the surface of the functional layer.

[0008] Furthermore, the general chemical formula of the gadolinium-doped cerium oxide in the transport layer is Ce. 1-x Gd x O 2-δ Where x = 0.15-0.20, δ represents the oxygen vacancy concentration; the thickness of the transport layer is 3-10 μm.

[0009] Furthermore, the porosity of the porous gadolinium-doped cerium oxide framework in the functional layer is 40%-60%; the general chemical formula of gadolinium-doped cerium oxide is Ce. 1-x Gd x O 2-δ Where x = 0.15-0.20, δ represents the oxygen vacancy concentration; the thickness of the functional layer is 5-15 μm.

[0010] Furthermore, the general chemical formula of the lanthanum-strontium-gallium-magnesium oxide in the functional layer is La. 1-a Sr a Ga 1-b Mg b O 3-δ Where 0.7≤a≤0.9, 0.1≤b≤0.2, and δ represents the oxygen vacancy concentration; the alkali metal carbonate is at least one of lithium carbonate, sodium carbonate, and potassium carbonate.

[0011] Furthermore, the molar ratio of lanthanum strontium gallium magnesium oxide to alkali metal carbonate in the functional layer is 1:1.5-1:2.5.

[0012] Furthermore, the thickness of the interface modification layer is 5-50 nm.

[0013] The composite electrolyte film of this invention systematically solves the inherent contradictions of traditional solid electrolytes through the synergistic design of gradient structure and interface. To achieve sufficiently high oxygen ion conductivity, traditional electrolytes often require high operating temperatures or the selection of materials with high intrinsic ion conductivity at medium to low temperatures (such as cerium oxide doping). However, high-temperature operation brings durability and cost issues; while medium-to-low temperature high ion conductivity materials are prone to electron leakage under reducing atmospheres, reducing efficiency.

[0014] In the composite electrolyte film of this invention, a dense GDC (Gross Dioxide) bottom layer ensures mechanical support and gas isolation; the middle layer uses porous GDC as a framework, with LSGM-carbonate eutectic phase filling the pores, providing a faster ion channel than pure GDC at medium and low temperatures, while the three-dimensional porous structure greatly expands the reaction interface. The outermost ultrathin SmNiO3 / SmCoO3 modification layer, uniformly covered by atomic layer deposition, effectively blocks electron migration from the reducing atmosphere to the GDC framework, but hardly hinders oxygen ion transport. This structure avoids the dilemma of developing a single material, achieving high ion conductivity, low electron leakage, and efficient interface reaction simultaneously at medium and low temperatures through precise synergy of the "dense layer - composite fast ion channel layer - ultrathin electron blocking layer," providing a feasible material path for reducing system operating temperature.

[0015] The second aspect of this invention provides a process for preparing the aforementioned low-temperature cerium-based composite electrolyte thin film with high ionic conductivity, comprising the following steps: (1) The gadolinium-doped cerium oxide powder is formed into a green body through a molding process and sintered at 1350-1500℃ to obtain a transport layer with a relative density of not less than 99%; (2) Gadolinium-doped cerium oxide powder, lanthanum strontium gallium magnesium oxide powder, alkali metal carbonate powder and organic solvent are mixed to form a slurry, which is coated on the surface of the transport layer and dried before being subjected to staged heat treatment; in the first stage, the alkali metal carbonate is melted and impregnated by holding at 600-800℃, and in the second stage, the lanthanum strontium gallium magnesium oxide and alkali metal carbonate undergo a eutectic reaction by holding at 1100-1300℃ to form a functional layer with a porous framework and a continuous eutectic phase in the pores; (3) Using atomic layer deposition process, a metal-organic precursor containing samarium, nickel or cobalt and an oxygen source are alternately introduced into the surface of the functional layer to deposit an interface modification layer of SmNiO3 or SmCoO3.

[0016] Further, the molding process in step (1) is tape casting or dry pressing; the sintering time is 2-10 hours.

[0017] Further, in step (2), the molar ratio of lanthanum strontium gallium magnesium oxide powder to alkali metal carbonate powder is 1:1.5-1:2.5; the first stage heat preservation time is 0.5-3 hours, and the second stage heat preservation time is 1-6 hours.

[0018] Step (2) begins by melting alkali metal carbonates into a liquid phase at a relatively low temperature of 600-800℃. This liquid phase is then uniformly impregnated into the pores of the solid oxide powder aggregate through capillary action, achieving uniform mixing at the molecular scale. Subsequently, the temperature is raised to a high temperature range of 1100-1300℃, where the molten salt undergoes a eutectic reaction at the solid-liquid interface with the solid LSGM particles. This directly generates a uniform and continuous eutectic composite phase in situ within the pores of the pre-formed porous GDC framework. This process simultaneously achieves the integrated construction of the porous framework through sintering strengthening and the fast ion conductor channel.

[0019] Further, in step (3), the samarium-containing precursor is tris(ethylcyclopentadienyl)samarium, the nickel-containing precursor is nickel acetylacetonate, the cobalt-containing precursor is cobalt acetylacetonate, and the oxygen source is ozone; the reaction temperature of the atomic layer deposition is 200-400℃.

[0020] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: 1. Achieved high-efficiency operation at medium and low temperatures: By introducing an LSGM-alkali metal carbonate eutectic composite phase as a second fast ion conductor into the porous GDC framework, this composite electrolyte film can achieve a speed higher than 0.1 S cm⁻¹ at 550℃. -1 The high ionic conductivity significantly reduces the operating temperature of solid oxide electrochemical devices, thereby alleviating problems such as material degradation, sealing difficulties, and cost increases caused by high temperatures.

[0021] 2. Effectively suppresses electron leakage, improving output voltage and efficiency: An ultrathin, dense SmNiO3 or SmCoO3 interface modification layer with extremely low intrinsic electronic conductivity was constructed on a complex porous surface using atomic layer deposition (ALD) technology. This layer fundamentally blocks the erosion of the GDC framework by the reducing atmosphere and suppresses Ce... 4+ The reduction and generation of electronic conductivity result in an electron transfer number greater than 0.99 in the thin film, which greatly reduces the internal short-circuit current and ensures high open-circuit voltage and energy conversion efficiency.

[0022] 3. Excellent structural stability and thermal cycling performance: The thin film uses a mechanically stable dense GDC layer as a supporting substrate, and the functional layers are firmly bonded together through optimized processes, forming a gradient structure with matched thermal expansion. This integrated structure effectively resists thermal stress, enabling the device to maintain excellent electrochemical performance stability and structural integrity during repeated heating and cooling cycles.

[0023] 4. Superior overall performance and broad application prospects: This invention, through synergistic innovation in materials, structure, and process, simultaneously solves several key challenges in a single system, including low-temperature high ionic conductivity, electron blocking, and interface stability. The prepared electrolyte film is particularly suitable for medium- and low-temperature solid oxide fuel cells (SOFCs) and SOECs, providing a material basis for the development of efficient, long-life, and low-cost clean energy conversion and storage technologies. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Unless otherwise specified, all raw materials used in the embodiments are commercially available products. The following sources are illustrative examples.

[0026] Ce 0.8 Gd 0.2 O 1.9 Ce 0.85 Gd 0.15 O 1.925 Ce 0.95 Gd 0.05 O 1.975 Purchased from Ningbo Sofor Energy Technology Co., Ltd.; La 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 3-δ La 0.85 Sr 0.15Ga 0.9 Mg0.1O 3-δ Purchased from Wuhan Huake Fusai New Energy Co., Ltd.; Tri(ethylcyclopentadienyl)samarium was purchased from SAFC Hitech (USA).

[0027] Example 1 This embodiment provides a low-temperature cerium-based composite electrolyte thin film with high ionic conductivity, and its preparation method includes the following steps: (1) Using Ce 0.8 Gd 0.2 O 1.9 Using GDC powder as a raw material, the powder was mixed with a binder (polyvinyl butyral, PVB) and a plasticizer (polyethylene glycol, PEG) system with ethanol as a solvent, and ball-milled for 24 hours to prepare a uniform slurry. The slurry was then cast using a casting method, and after drying, a green sheet with a thickness of approximately 0.5 mm was obtained. This green sheet was placed in a high-temperature furnace and heated to 1400 °C at a rate of 2 °C / min, and held at this temperature for 4 hours. After furnace cooling, a dense GDC transport layer with a thickness of approximately 5 μm and a relative density greater than 99.5% was obtained.

[0028] (2) Weigh out Ce respectively 0.8 Gd 0.2 O 1.9 (GDC) powder, La 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 3-δ LSGM powder and Li2CO3 powder were weighed at a mass ratio of GDC:LSGM:Li2CO3 of 70:15:9 (corresponding to a molar ratio of LSGM to carbonate of approximately 1:1.9), mixed with ethanol and a small amount of PVB, and ball-milled for 48 hours to form a uniform and stable slurry. The slurry was uniformly coated onto the surface of the transport layer obtained in step (1) using screen printing technology, with the wet film thickness controlled at approximately 30 μm. After drying at 80℃, the sample was placed in a muffle furnace for heat treatment: first, the temperature was increased to 700℃ at 3℃ / min and held for 1 hour to allow the carbonate to fully melt and impregnate the solid particles; then, the temperature was increased to 1200℃ at 5℃ / min and held for 3 hours to allow LSGM to undergo a eutectic reaction with the molten carbonate and to complete the sintering of the GDC framework. Finally, a functional layer with a thickness of approximately 10 μm and a framework porosity of approximately 50% was obtained, in which the pores of the GDC framework were filled with an LSGM-carbonate eutectic composite phase.

[0029] (3) The sample prepared in step (2) was placed in an atomic layer deposition (ALD) reaction chamber. Tri(ethylcyclopentadienyl)samarium (Sm(EtCp)3) and nickel acetylacetonate (Ni(acac)2) were used as precursors, and ozone (O3) was used as the oxygen source. The deposition temperature was set to 300℃. One deposition cycle consisted of: Sm(EtCp)3 pulse for 0.5 seconds, nitrogen purging for 10 seconds, O3 pulse for 1 second, nitrogen purging for 10 seconds, Ni(acac)2 pulse for 1 second, nitrogen purging for 10 seconds, O3 pulse for 1 second, and nitrogen purging for 10 seconds. By controlling the number of deposition cycles to 150, an amorphous SmNiO3 interface modification layer with a thickness of about 15 nm was deposited on the surface of the functional layer.

[0030] Example 2 This embodiment provides a low-temperature cerium-based composite electrolyte thin film with high ionic conductivity, and its preparation method includes the following steps: (1) Using Ce 0.85 Gd 0.15 O 1.925 Using GDC powder as raw material, the powder was mixed with a binder (polyvinyl butyral, PVB) and a plasticizer (dibutyl phthalate, DBP) system with ethanol as solvent, and ball-milled for 20 hours to prepare a homogeneous slurry. The powder was then pressed into green sheets using a dry pressing method at 200 MPa. These green sheets were placed in a high-temperature furnace and heated to 1380°C at a rate of 3°C / min, held at this temperature for 5 hours, and then cooled in the furnace. After polishing, a dense GDC transport layer with a thickness of approximately 8 μm and a relative density greater than 99.2% was obtained.

[0031] (2) Weigh out Ce respectively 0.85 Gd 0.15 O 1.925 (GDC) powder, La 0.85 Sr 0.15 Ga 0.9 Mg 0.1 O 3-δLSGM powder and Na2CO3 powder were weighed at a mass ratio of GDC:LSGM:Na2CO3 of 65:15:15 (the molar ratio of LSGM to Na2CO3 was calculated to be approximately 1:2.2). The mixture was then mixed with isopropanol and a small amount of hydroxypropyl cellulose and ball-milled for 36 hours to form a uniform slurry. The slurry was uniformly coated onto the surface of the transport layer obtained in step (1) using a spraying technique, with the wet film thickness controlled at approximately 25 μm. After drying at 70℃, the sample was placed in a muffle furnace for heat treatment: first, the temperature was increased to 650℃ at 5℃ / min and held for 1.5 hours to allow the carbonate to fully melt and impregnate the solid particles; then, the temperature was increased to 1180℃ at 4℃ / min and held for 4 hours to allow LSGM to undergo a eutectic reaction with the molten carbonate and to complete the sintering of the GDC framework. Finally, a functional layer with a thickness of approximately 8 μm and a framework porosity of approximately 45% was obtained, with the LSGM-carbonate eutectic composite phase filling the pores of the GDC framework.

[0032] (3) The sample prepared in step (2) was placed in the atomic layer deposition reaction chamber. Tri(ethylcyclopentadienyl)samarium and cobalt acetylacetonate were used as precursors, and ozone was used as the oxygen source. The deposition temperature was set to 250℃. One deposition cycle consisted of: Sm(EtCp)3 pulse for 0.6 seconds, nitrogen purging for 12 seconds, O3 pulse for 1.2 seconds, nitrogen purging for 12 seconds, Co(acac)3 pulse for 1.5 seconds, nitrogen purging for 12 seconds, O3 pulse for 1.2 seconds, and nitrogen purging for 12 seconds. By controlling the number of deposition cycles to 400, an SmCoO3 interface modification layer with a thickness of about 40 nm was deposited on the surface of the functional layer.

[0033] Comparative Example 1 The difference between this comparative example and Example 1 is that step (3) is replaced by placing the sample prepared in step (2) in a magnetron sputtering device. Using metallic nickel as the target material, a nickel oxide (NiO) film with a thickness of about 50 nm is obtained by sputtering and depositing at room temperature for 30 minutes in a mixed atmosphere of argon and oxygen with a volume ratio of 4:1.

[0034] Comparative Example 2 The difference between this comparative example and Example 1 is that the heat treatment process in step (2) is replaced by placing the sample in a muffle furnace and performing heat treatment only once: heating directly from room temperature to 1200°C at a rate of 5°C / min and holding at that temperature for 4 hours, followed by cooling with the furnace.

[0035] Comparative Example 3 The difference between this comparative example and Example 1 is that the “Li2CO3 powder” in step (2) is replaced with an equal mass of calcium carbonate (CaCO3) powder.

[0036] Comparative Example 4 The difference between this comparative example and Example 1 is that the "La" in step (2) is changed. 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 3-δ Replace “(LSGM) powder” with an equal mass of 8 mol% Y2O3-stabilized ZrO2 (YSZ) powder.

[0037] Comparative Example 5 The difference between this comparative example and Example 1 is that the "Ce" in steps (1) and (2) is changed. 0.8 Gd 0.2 O 1.9 (GDC) powder was replaced with an equal mass of Ce. 0.95 Gd 0.05 O 1.975 Powder.

[0038] Performance testing To verify the overall performance of the composite electrolyte film described in this invention, the composite electrolyte films prepared in Examples 1-2 and Comparative Examples 1-5 were subjected to the following performance tests.

[0039] 1. Ionic conductivity test: The thin film sample was placed between two platinum electrodes and tested at 550℃ in an air atmosphere. The ionic conductivity of the thin film was calculated by analyzing the bulk resistance in the EIS spectrum using the formula σ = L / (R×A) (where L is the film thickness, R is the resistance, and A is the electrode area).

[0040] 2. Electron Transfer Number Assessment: The thin film sample to be tested is placed between platinum electrodes in air and wet hydrogen (3% H2O / H2) atmospheres on both sides, forming a symmetrical cell with an asymmetric oxygen partial pressure. A DC bias voltage of 0.5V is applied to this cell, and the electron transfer number (tion) is calculated by measuring the steady-state current. The closer the tion value is to 1, the stronger the electrolyte film's ability to block electrons and the less electron leakage.

[0041] 3. Thermal cycling stability test: Assemble the sample to be tested into a complete single cell and subject the cell to 10 rapid heating and cooling cycles between 550°C and room temperature. Compare the rate of change of electrolyte areal resistivity (ASR) at 550°C before and after the cycle, as measured by EIS, to evaluate the thermal cycling stability of the electrolyte film itself.

[0042] The test results are shown in Table 1.

[0043] Table 1 Performance Test Results As can be seen from the above performance test results, both Example 1 and Example 2 exhibit excellent comprehensive performance, achieving the goals of low temperature, high ionic conductivity, low electron leakage, and high stability.

[0044] Comparative Example 1 showed a significant decrease in electron transfer number and a sharp increase in ASR after thermal cycling. The conventional sputtered NiO layer on the surface could not effectively block electron conduction, and its physical bonding with the porous framework was also weak, making it prone to deterioration under thermal stress, thus compromising the stability and insulation of the system. Comparative Example 2 showed a significant decrease in ionic conductivity and a decline in thermal cycling stability. The reason for this may be that one-step sintering could not form a uniform and continuous eutectic fast ion channel, resulting in uneven ion conduction in the functional layer and structural defects, which exacerbated performance degradation during thermal cycling. Comparative Example 3 showed the lowest ionic conductivity and a significant decrease in ASR after thermal cycling. This was because CaCO3 could not form a low-temperature eutectic phase, but instead generated an inert impurity phase at high temperatures, blocking the pores, severely hindering ion transport and introducing structural vulnerabilities. Comparative Example 4 showed a much lower ionic conductivity than the examples. The insufficient low-temperature ionic conductivity of the YSZ-carbonate composite directly limited the overall performance, highlighting the unique advantage of LSGM as the core component of the eutectic phase in improving conductivity. The ionic conductivity of Comparative Example 5 was also low. Due to the insufficient ionic conductivity of the GDC framework itself, even if the other structures were intact, it would become a bottleneck in the entire ion transport chain and affect the sintering density to a certain extent, resulting in slightly poor stability. This confirms that optimizing the Gd doping amount is a prerequisite for ensuring the basic performance of the material.

[0045] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A low-temperature cerium-based composite electrolyte thin film with high ionic conductivity, characterized in that, It contains the following three-layer structure: The transport layer is composed of gadolinium-doped cerium oxide with a relative density of not less than 99%. A functional layer is constructed on one side surface of the transport layer. The functional layer consists of a porous gadolinium-doped cerium oxide framework and a composite ionic conductor filling the pores of the framework. The composite ionic conductor is a continuous phase formed by lanthanum strontium gallium magnesium oxide and alkali metal carbonate through a eutectic reaction. An interface modification layer, which is SmNiO3 or SmCoO3, covers the surface of the functional layer.

2. The low-temperature cerium-based composite electrolyte film with high ionic conductivity according to claim 1, characterized in that, The general chemical formula of the gadolinium-doped cerium oxide in the transport layer is Ce. 1-x Gd x O 2-δ Where x = 0.15-0.20, δ represents the oxygen vacancy concentration; the thickness of the transport layer is 3-10 μm.

3. The low-temperature cerium-based composite electrolyte film with high ionic conductivity according to claim 1, characterized in that, The porosity of the porous gadolinium-doped cerium oxide framework in the functional layer is 40%-60%; the general chemical formula of gadolinium-doped cerium oxide is Ce. 1- x Gd x O 2-δ Where x = 0.15-0.20, δ represents the oxygen vacancy concentration; the thickness of the functional layer is 5-15 μm.

4. The low-temperature cerium-based composite electrolyte film with high ionic conductivity according to claim 1, characterized in that, The general chemical formula of the lanthanum-strontium-gallium-magnesium oxide in the functional layer is La. 1-a Sr a Ga 1-b Mg b O 3-δ Where 0.7≤a≤0.9, 0.1≤b≤0.2, and δ represents the oxygen vacancy concentration; the alkali metal carbonate is at least one of lithium carbonate, sodium carbonate, and potassium carbonate.

5. The low-temperature cerium-based composite electrolyte film with high ionic conductivity according to claim 1, characterized in that, The molar ratio of lanthanum strontium gallium magnesium oxide to alkali metal carbonate in the functional layer is 1:1.5-1:2.

5.

6. The low-temperature cerium-based composite electrolyte film with high ionic conductivity according to claim 1, characterized in that, The thickness of the interface modification layer is 5-50 nm.

7. The preparation process of the low-temperature cerium-based composite electrolyte thin film with high ionic conductivity according to any one of claims 1-6, characterized in that, Includes the following steps: (1) The gadolinium-doped cerium oxide powder is formed into a green body through a molding process and sintered at 1350-1500℃ to obtain a transport layer with a relative density of not less than 99%; (2) Gadolinium-doped cerium oxide powder, lanthanum strontium gallium magnesium oxide powder, alkali metal carbonate powder and organic solvent are mixed to form a slurry, which is coated on the surface of the transport layer and dried before being subjected to staged heat treatment; in the first stage, the alkali metal carbonate is melted and impregnated by holding at 600-800℃, and in the second stage, the lanthanum strontium gallium magnesium oxide and alkali metal carbonate undergo a eutectic reaction by holding at 1100-1300℃ to form a functional layer with a porous framework and a continuous eutectic phase in the pores; (3) Using atomic layer deposition process, a metal-organic precursor containing samarium, nickel or cobalt and an oxygen source are alternately introduced into the surface of the functional layer to deposit an interface modification layer of SmNiO3 or SmCoO3.

8. The preparation process according to claim 7, characterized in that, The molding process in step (1) is either tape casting or dry pressing; the sintering time is 2-10 hours.

9. The preparation process according to claim 7, characterized in that, The molar ratio of lanthanum strontium gallium magnesium oxide powder to alkali metal carbonate powder in step (2) is 1:1.5-1:2.5; the first stage heat preservation time is 0.5-3 hours, and the second stage heat preservation time is 1-6 hours.

10. The preparation process according to claim 7, characterized in that, In step (3), the samarium-containing precursor is tris(ethylcyclopentadienyl)samarium, the nickel-containing precursor is nickel acetylacetonate, the cobalt-containing precursor is cobalt acetylacetonate, and the oxygen source is ozone; the reaction temperature of the atomic layer deposition is 200-400℃.

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