Three-phase composite solid electrolyte material and solid oxide fuel cell having the same

Abstract

The application discloses a kind of three-phase composite solid electrolyte material and solid oxide fuel cell with it, belong to solid oxide fuel cell technical field;Wherein electrolyte material includes BZCY, NaAlO2And NaOH;BZCY and NaAlO2Mass ratio is 1~9:1, the mass of NaOH is the total mass of BZCY and NaAlO2After 5~20% compound;It is also provided to obtain the material of BZCY, NaAlO2And NaOH mixing as electrolyte solid oxide fuel cell.The application improves the ion transport capacity of electrolyte, while reducing the minimum operating temperature of battery device, the solid-liquid interface created under the in-situ condition of solid electrolyte is beneficial to maintain the activated state of proton, so that fuel cell has the operating capacity of 320 DEG C;While improving the steady-state existence of electrolyte internal solid-liquid interface, it is beneficial to the improvement of fuel cell performance and stability at low temperature.

Description

Technical Field

[0001] This invention relates to the field of solid oxide fuel cell technology, and more specifically, to a three-phase composite solid electrolyte material and its synthesis and preparation, as well as a solid oxide fuel cell having the same. Background Technology

[0002] The development of fuel cells began in the mid-20th century. They are efficient, low-pollution, and widely applicable green energy devices that directly convert the chemical energy of clean fuels into electrical energy through electrochemical reactions. Initially used in aerospace and military applications, their applications have gradually expanded to transportation, portable power sources, and stationary power stations with technological advancements. Among the many types of fuel cells, solid oxide fuel cells (SOFCs) have attracted attention due to their high efficiency, low emissions, and ability to utilize multiple fuels. In recent years, SOFC technology has made significant progress, including breakthroughs in materials science and optimization of system design, leading to improved performance and reliability at high temperatures. However, traditional SOFCs operate at temperatures as high as 800 to 1000 °C, and still face challenges such as material degradation due to high temperatures, high costs, and stringent fuel requirements.

[0003] Lowering the operating temperature of solid oxide fuel cells (SOFCs) offers several significant advantages. Operating at lower temperatures helps reduce heat loss, improves energy conversion efficiency by optimizing electrochemical reaction kinetics, and enhances overall system performance. Lower temperatures reduce the energy demand for maintaining high temperatures, decrease energy consumption of auxiliary heating systems, effectively reduce operating costs, and improve the economic viability of the system. Lower temperatures generate less heat, significantly reducing thermal stress and overheating risks, thus improving system stability and safety. At lower temperatures, aging mechanisms such as thermal expansion mismatch, interfacial reactions, and microstructure degradation of key materials are mitigated, significantly delaying battery performance degradation, extending lifespan, and reducing maintenance frequency and related costs. Low-temperature SOFC systems are easier to design compactly and enable rapid start-up and shutdown, exhibiting greater environmental adaptability. Therefore, they are more suitable for various applications such as portable power supplies, mobile devices, and transportation, providing broader development space for the large-scale promotion and commercial application of fuel cell technology.

[0004] Currently, semiconductor ionic fuel cells (SIFCs), a novel type of low-temperature solid oxide fuel cell using NCAL as the symmetrical electrode and semiconductor heterostructure composite material as the electrolyte, have attracted much attention due to their high performance at low temperatures. This type of electrolyte, by combining different types of semiconductor materials and aligning the energy bands between the two phases, achieves a localized field effect at the electrolyte heterojunction caused by the differential distribution of electron charges. This field effect accelerates ions and suppresses electrons at the heterojunction, thereby improving ionic conductivity and increasing the open-circuit voltage of the cell, resulting in excellent battery performance in the 450-550℃ temperature range. Another key factor in achieving high performance at low temperatures in this type of fuel cell is the construction of a molten hydroxide conductive network within the electrolyte, which maintains rapid ionic conductivity at the heterojunction surface, thus enabling the cell to achieve high electrochemical output performance at low temperatures.

[0005] However, when the operating temperature of the battery is further reduced (<400℃), studies have shown that the molten hydroxide conductive network inside the SIFC electrolyte will change from a molten state to a condensed state. The destruction of the liquid phase fast ion transport network will directly lead to a significant deterioration of the ion transport capacity at the electrolyte interface, resulting in an irreparable deterioration of the battery's OCV and serious problems such as the inability of the fuel cell device to operate.

[0006] Therefore, the key to further developing SIFC at lower temperatures lies in how to regulate the melting point of the molten hydroxide inside the electrolyte to make it lower and more stable in the molten state for a longer period of time, as well as determining the phase structure evolution process at the solid-liquid interface and the key role of the molten hydroxide network in improving ionic conductivity. Summary of the Invention

[0007] In view of this, one of the objectives of this invention is to provide a preparation technology for a three-phase composite solid electrolyte, which can construct a solid-liquid coexistence system of a solid framework and molten hydroxide under the in-situ operating environment of a fuel cell. This technology can significantly improve the ionic conductivity and long-term operational stability of the electrolyte, while reducing the minimum operating temperature of the fuel cell to 320°C, effectively promoting the development of fuel cells towards lower temperatures, thereby enhancing their technological advantages and application prospects as a green energy source.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] A three-phase composite solid electrolyte material includes BZCY, NaAlO2 and NaOH, wherein BZCY and NaAlO2 are mixed at a two-phase material mass ratio of 1 to 9:1 to obtain a precursor composite material; the mass of NaOH is 5 to 20% of the total mass of the precursor composite material.

[0010] BZCY is a zirconium-yttrium co-doped barium cerate perovskite oxide with the molecular formula BaZr. 0.2 Ce 0.7 Y 0.1 O 3-δ .

[0011] Furthermore, the mass ratio of BZCY to NaAlO2 is 2~3:1.

[0012] Furthermore, the mass ratio of BZCY to NaAlO2 is 7:3. During the experiment, it was found that when the mass ratio of BZCY to NaAlO2 is 7:3, the prepared battery has higher ionic conductivity, power density and stability.

[0013] Furthermore, the mass of the NaOH is 10% of the total mass of the preceding composite material. During the experiment, it was found that when the mass of NaOH is 10% of the total mass of the preceding composite material, the resulting battery has higher ionic conductivity, power density, and stability.

[0014] In this invention, a three-phase composite solid electrolyte obtained by combining NaAlO2 and NaOH in BZCY undergoes in-situ testing under the conditions of high temperature and continuous hydrogen supply in a fuel cell testing environment. The NaAlO2 hydrolysis and the directly introduced NaOH melt into a liquid state and are uniformly distributed in the pores of BZCY, forming a solid-liquid system. Simultaneously, in an environment where H2 and liquid NaOH coexist, strong reducing conditions break down the structure of BZCY, promoting a phase transition and completing a surface reconstruction effect rich in defect states. Furthermore, free hydroxide ions in the liquid phase are adsorbed onto defect sites, serving as relay stations for proton transport within the electrolyte, thus supporting rapid proton transport at low temperatures (520℃–320℃). Ultimately, a functional solid electrolyte material capable of long-term, high-efficiency operation at ultra-low temperatures is obtained. This design paradigm and the clarification of the rapid proton transfer mechanism at the interface in the solid-liquid system provide insights and new ideas for the development of high-performance, low-cost clean power sources based on hydrogen energy utilization.

[0015] The second objective of this invention is to provide a method for preparing the above-mentioned solid electrolyte material, comprising the following steps:

[0016] 1) Weigh out BZCY, NaAlO2, and NaOH according to the formula ratio;

[0017] 2) Disperse BZCY and NaAlO2 in a solvent, and first sonicate them in a water bath at room temperature (20-30℃) to form a complex solution.

[0018] The solid was then transferred to a microwave reactor for microwave treatment to obtain a loose complex solid.

[0019] After grinding, powder is obtained;

[0020] The obtained powder was placed in a tube furnace for pre-activation treatment. Under the protection of an inert gas (such as argon), the temperature was raised at a low rate to the non-decomposition temperature of NaAlO2. After cooling to room temperature, it was ball-milled thoroughly to obtain the preceding composite material.

[0021] 3) The obtained composite material was dispersed in a composite solvent and a suspension a was prepared by ultrasonication. Then, NaOH was dissolved in deionized water to obtain solution b. Solution b was then slowly added dropwise to suspension a through a medical intravenous infusion set. At the same time, the mixture was stirred at an appropriate temperature to form a uniform coating layer of NaOH on the surface of the BZCY / NaAlO2 composite material. The mixture was then dried in a gradient temperature vacuum drying oven and finally ground thoroughly to obtain composite electrolyte powder, denoted as BZCY / NaAlO2@NaOH.

[0022] In this invention, the microwave treatment in step (2) can utilize the instantaneous heating characteristics of microwaves to promote the complexation reaction to proceed fully and form a more stable complex system; the pre-activation treatment in step (2) can remove adsorbed water on the surface of the BZCY / NaAlO2 composite material and improve its specific surface area and reactivity.

[0023] Further, in step 2), the ultrasonic treatment time is 30-60 min, preferably 40 min; the ultrasonic frequency is 40-60 kHz, preferably 50 kHz; the solvent is ethanol; the microwave reactor processing power is 300-500 W, preferably 400 W; and the microwave treatment time is 20-40 min, preferably 30 min.

[0024] The inert gas atmosphere is argon, the heating rate is 5℃ / min, the heating termination temperature is 200~300℃, preferably 250℃, and the ball milling time is 3~5 h, preferably 4 h.

[0025] In step 3), the composite solvent is obtained by mixing ethanol and ethylene glycol in a volume ratio of 2:1; the constant temperature stirring temperature is 30~60℃, preferably 40℃; the stirring time is 1~3h, preferably 2h; the gradient heating and heat preservation step is 50℃—120℃—200℃, and each stage is kept at 1h.

[0026] The third objective of this invention is to provide a low-temperature solid oxide fuel cell containing the above-mentioned three-phase composite solid electrolyte material.

[0027] Furthermore, the anode and / or cathode material of the battery is obtained by mixing γ-Al2O3 with NCAL.

[0028] NCAL is a commonly used electrode material in solid oxide fuel cells, with a specific chemical composition of Ni. 0.8 Co 0.15 Al 0.05 LiO 2-δ For materials, δ is the value that keeps the compound electrically neutral.

[0029] In this invention, a composite electrode is obtained by combining active gamma alumina, i.e., γ-Al2O3, in NCAL. While still providing electron rectification characteristics, the active γ-Al2O3 itself possesses catalyst support and product unblocking properties, which improves the electrocatalytic activity of SIFC electrode materials. At the same time, it enhances the generation and unblocking of anode-side derivative hydroxides, allowing more concentrated hydroxides to penetrate into the electrolyte, which is beneficial to improving the performance and stability of fuel cells at low temperatures.

[0030] Furthermore, in the anode and / or cathode materials, the mass of γ-Al2O3 is 5% to 15%; through experiments, the present invention has found that the performance is optimal when the mass ratio of γ-Al2O3 is 5% to 15% of NCAL, especially 10%.

[0031] Furthermore, the method for preparing the anode and / or cathode materials is as follows:

[0032] S1. Weigh out γ-Al2O3 and NCAL according to the mass ratio of γ-Al2O3;

[0033] S2. Disperse NCAL in a solvent, then add γ-Al2O3 and mix thoroughly.

[0034] S3. The solution obtained from step S2 is ball-milled and sintered to obtain the γ-Al2O3 / NCAL electrode.

[0035] Further, in step S2, the solvent is ethanol;

[0036] In step S3, the ball milling time is 1.5~2.5 h, the ball milling speed is 60~100 rad / min, the sintering temperature is 500~600 ℃, and the sintering time is 1.5~2.5 h.

[0037] Furthermore, when preparing the anode and / or cathode plate using the aforementioned anode and / or cathode material, the following steps are included: mixing the prepared anode and / or cathode material with terpineol in alcohol at a solid-liquid ratio of 10:3 (g / ml), grinding thoroughly to form a slurry, uniformly coating the obtained slurry onto a nickel foam mesh, and then placing the coated nickel foam sheet in a forced-air drying oven and drying at 120 °C for 30 minutes. The above operation is repeated twice to finally obtain a porous symmetrical electrode.

[0038] The beneficial effects of this invention are as follows:

[0039] 1) A three-phase composite solid electrolyte was constructed by combining NaAlO2 and NaOH in BZCY. Since NaAlO2 can hydrolyze to produce NaOH in the in-situ environment of fuel cell testing, the directly combined NaOH exists in a molten state on the surface of BZCY, forming a solid-liquid composite system with BZCY as the solid framework and molten NaOH as the molten liquid phase. The proton transport mode in the solid-liquid system changes from the original single-phase transport mode in BZCY to a three-dimensional proton conductivity involving the BZCY bulk phase, solid-liquid interface, and molten liquid phase, significantly improving ionic conductivity. Simultaneously, the presence of NaOH lowers the initial melting temperature of the liquid-phase hydroxide to 325℃. Ultimately, this enables the fuel cell device to achieve an ultra-low temperature operation capability of 320℃.

[0040] 2) This invention introduces NaAlO2 and NaOH. Under in-situ testing conditions of a fuel cell, in a strong reducing environment where hydrogen and molten hydroxide coexist, a destructive reaction occurs at the solid-liquid interface of BZCY. The surface BZCY is reconstructed from a perovskite structure to a fluorite CeO2 structure. Simultaneously, the reconstructed CeO2 undergoes CeO2 degradation due to the strong reducing environment. 4+ To Ce 3+ The reaction leads to the formation of a reconstructed CeO2 / CeO rich in defect sites. 2-x Furthermore, a large number of free hydroxide ions in the molten hydroxide will be adsorbed on the defective oxygen vacancies. In the test environment, the hydroxide ions that recombine with the oxygen vacancies at the solid-liquid interface will act as carriers for proton migration, greatly reducing the activation energy of proton migration and accelerating proton transport, thereby enabling the battery device to obtain high electrochemical power output. Attached Figure Description

[0041] Figure 1 This is a power density diagram of battery devices constructed using BZCY / NaAlO2 pre-composite electrolytes prepared in various composite ratios according to the present invention at 520-320 °C.

[0042] Figure 2This is a power density diagram of the battery device constructed using the BZCY / NaAlO2@NaOH electrolyte prepared in this invention at 520-320 °C.

[0043] Figure 3 This is a comparison of the conductivity and activation energy of the BZCY / NaAlO2@NaOH composite electrolyte fuel cell prepared in this invention and the pure BZCY electrolyte fuel cell at 520-320 °C.

[0044] Figure 4 These are the stability test results of the battery device constructed using the BZCY / NaAlO2@NaOH composite electrolyte prepared in this invention at 520 °C.

[0045] Figure 5 These are the stability test results of the battery device constructed using the BZCY electrolyte prepared in this invention at 520 °C.

[0046] Figure 6 This is an AC-STEM image of the powder of the BZCY / NaAlO2@NaOH electrolyte prepared in this invention after in-situ reconstruction.

[0047] Figure 7 This is the XANES image of the powder of the BZCY / NaAlO2@NaOH electrolyte prepared in this invention after in-situ reconstruction.

[0048] Figure 8 Figure 1 shows the EELS line scan results of the BZCY / NaAlO2@NaOH electrolyte powder after in-situ reconstruction. Figure 2a shows the HAADF-STEM image of the three-phase composite electrolyte sample after testing, from the BZCY bulk to the reconstructed surface. The Ce oxidation state can be quantitatively determined using the M5 / M4 ratio. The M5 / M4 peak intensities at random 1 nm intervals along the straight line are shown in Figures 2b and 2c (1-10). Positions 1-5 are located inside the BZCY bulk phase. In this region, the peak intensity of M5 is lower than that of M4, that is, the M5 / M4 ratio is less than 1, indicating that the bulk phase is entirely Ce. 4+ Existence; while positions 6-10 are located in the surface reconstruction region, and among these sites, the positions where the M5 / M4 ratio is greater than 1 are Ce. 3+ The location of its existence indicates that this region is Ce. 3+ / Ce 4+ Coexistence indicates the construction of defective states after reconstruction.

[0049] Figure 9 The results of thermogravimetric-differential calorimetry (TGC) tests on the electrolyte material of the BZCY / NaAlO2@NaOH composite electrolyte fuel cell prepared in this invention are shown after electrochemical testing.

[0050] Figure 10The results are O2-TPD / MS tests performed on the electrolyte material after electrochemical testing of the BZCY / NaAlO2@NaOH composite electrolyte prepared in this invention.

[0051] Figure 11 This is a power density diagram of a battery device constructed with the BZCY / NaAlSiO4@NaOH composite electrolyte compared to the present invention, at 520-320 °C.

[0052] Figure 12 This is a power density diagram of a battery device constructed with the BZCY / SiO2@NaOH composite electrolyte compared to that of the present invention, at 550-350 °C.

[0053] Figure 13 This is a power density diagram of a battery device constructed with the BZY / SiO2@Zn(OH)2 composite electrolyte compared to the present invention, at 550-400 °C. Detailed Implementation

[0054] Numerous specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many other ways different from those described herein, and similar modifications can be made by those skilled in the art without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0055] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0056] Example 1

[0057] Using barium nitrate Ba(NO3)2, zirconium nitrate pentahydrate Zr(NO3)4·5H2O, cerium nitrate hexahydrate Ce(NO3)3·6H2O, and yttrium nitrate hexahydrate Y(NO3)3·6H2O as raw materials, and ethylenediaminetetraacetic acid (EDTA) and citric acid (CA) as chelating agents, 0.05 mol BZCY was synthesized by the sol-gel method. At room temperature, 13.067 g Ba(NO3)2, 2.1466 g Zr(NO3)4·5H2O, 15.1977 g Ce(NO3)3·6H2O, and 3.83 g Y(NO3)3·6H2O were accurately weighed and placed in a beaker. An appropriate amount of deionized water was added, and the mixture was magnetically stirred until completely dissolved, yielding a clear solution of the mixed metal salts. To the above mixed metal salt solution, EDTA (29.24 g) solution and CA (31.521 g) solid, dissolved in a small amount of ammonia (to promote dissolution), were added sequentially. Under continuous vigorous stirring, ammonia was added dropwise to the system to precisely adjust the pH of the mixed solution to 7.0. The pH-adjusted solution was placed in a constant-temperature 80°C water bath, and after approximately 4-6 hours, it transformed into a dark brown, homogeneous wet gel. This wet gel was transferred to a forced-air drying oven and dried at 200°C for 5 hours to obtain a fluffy, porous, and brittle dark brown dry gel precursor. Subsequently, it was heated to 600°C at a heating rate of 3°C / min and held at this temperature for 5 hours. Finally, the pre-calcined powder was ground again to eliminate possible agglomeration, and then heated to 1200°C to obtain BZCY powder.

[0058] NaOH and NaAlO2 were commercially available laboratory reagents.

[0059] First, weigh the BCZY to be synthesized and commercially available NaAlO2 according to a mass ratio of 7:3, i.e., weigh 0.7 g of BCZY and 0.3 g of NaAlO2 respectively. Place the BZY and NaAlO2 in 200 mL of ethanol and sonicate for 40 minutes to form a complex (ultrasonic frequency 40 kHz; the purpose of sonication is to break up the physical agglomeration of the powder materials, aiming to make the composite material more uniformly mixed). Rapidly transfer the resulting complex to a microwave reactor for microwave treatment (400 W power, 30 min) to obtain a loose complex solid. After grinding, place it in a tube furnace for pre-activation treatment. Under argon protection, heat to 250 °C at a low rate of 5 °C / min, then cool to room temperature. After thorough ball milling for 4 h, a uniform BCZY / NaAlO2 precursor composite material is obtained.

[0060] The obtained BCZY / NaAlO2 precursor composite material was dispersed in 200 ml of composite solvent (ethanol: ethylene glycol = 2:1) and ultrasonically treated for 30 min to obtain suspension a. Commercial NaOH particles were weighed at a ratio of 10% of the precursor composite material mass and dissolved in deionized water to obtain solution b. Solution b was then slowly added dropwise to suspension a through a medical intravenous infusion set, while stirring at a constant temperature of 40℃ to form a uniform coating layer of NaOH on the surface of the BZCY / NaAlO2 composite material. After gradient heating (50℃—120℃—200℃, each stage held for 1 h) and drying in a vacuum drying oven, the three-phase composite solid electrolyte powder was obtained by thorough grinding and denoted as BZCY / NaAlO2@NaOH.

[0061] The γ-Al₂O₃ / NCAL electrode was prepared according to the following method:

[0062] The composite electrode material was prepared using a solid-state method: commercially purchased active γ-Al2O3 was mixed with LiNi produced by Tianjin Bamo Technology Co., Ltd. 0.8 Co 0.15 Al 0.05 O 2-δ Weigh out 0, 5, 10, and 15 wt% of NCAL in a composite ratio for later use. First, dissolve 10 g of NCAL in 100 mL of ethanol solution. Transfer the beaker to an ultrasonicator and sonicate for 30 min (dispersion). After sonication, add γ-Al2O3 while stirring thoroughly. Then, transfer the resulting dispersion to a ball mill jar and ball mill at 80 rad / min for 2 h. Dry the resulting liquid with an oven lamp. After all the ethanol has evaporated, place the resulting powder in a muffle furnace and rapidly heat to 550 °C. Calcinate at 550 °C for 2 h. After natural cooling, a black γ-Al2O3 / NCAL composite electrode material with scattered and uniformly distributed white γ-Al2O3 is obtained.

[0063] γ-Al₂O₃ / NCAL and terpineol were mixed in a specific ratio (10 g γ-Al₂O₃ / NCAL with 3 mL terpineol) and thoroughly ground with alcohol as a dispersant to form a slurry. The resulting slurry was then uniformly coated onto a surface with an area of ​​0.64 cm². 2 A nickel foam mesh with a thickness of 1.2 mm was applied. The coated nickel foam sheet was then placed in a forced-air drying oven and dried at 120 °C for 30 minutes. This process was repeated twice to obtain a porous symmetric electrode material, Ni-γ-Al₂O₃ / NCAL, with an effective working area of ​​0.64 cm². 2 .

[0064] Fuel cell devices were fabricated using a dry pressing method. The prepared γ-Al₂O₃ / NCAL electrode was used as the symmetrical electrode. The obtained BZCY / NaAlO₂@NaOH was used as the electrolyte, and 0.25 g of electrolyte powder was weighed and compacted between the two composite electrodes under a load pressure of 400 MPa for 90 s. The resulting SIMFC device has a γ-Al₂O₃ / NCAL‖BZCY / NaAlO₂@NaOH‖γ-Al₂O₃ / NCAL sandwich structure, with a fuel cell diameter of 13 mm and an active area of ​​0.64 cm². 2 The fuel cell was then preheated at 550 °C for 30 minutes before electrochemical testing was conducted.

[0065] By adjusting the composite ratio of the two materials (BZCY and NaAlO2) in this embodiment (the mass ratios of BZCY and NaAlO2 were 9:1, 8:2, 7:3, 6:4, and 5:5, respectively), the BZCY / NaAlO2 biphase electrolyte fuel cell was preheated at 550 °C for 30 minutes, followed by electrochemical testing. The test results are as follows: Figure 1 As shown, the power density of the battery is optimal when the ratio of BZCY to NaAlO2 is 7:3. Subsequent devices all use a BZCY to NaAlO2 ratio of 7:3.

[0066] The device γ-Al₂O₃ / NCAL‖BZCY / NaAlO₂@NaOH‖γ-Al₂O₃ / NCAL was tested. The test results are as follows: Figure 2 As shown, the battery still has operational capability when the temperature drops to 320 ℃.

[0067] Figure 3 This is a comparison of the conductivity of the BZCY / NaAlO2@NaOH composite electrolyte fuel cell and the pure BZCY electrolyte fuel cell in this embodiment at 520-320 °C. As can be seen, the BZCY / NaAlO2@NaOH composite electrolyte prepared in this embodiment can significantly improve the ionic conductivity of the fuel cell.

[0068] To further verify the stability of the fuel cell device constructed with the BZCY / NaAlO2@NaOH composite electrolyte, the battery fabricated in this embodiment was tested under fuel cell operating conditions at 100 mA / cm². 2 The results of a 320-hour long-term stability test on the current density are shown in the figure. Figure 4 As shown; BZCY exhibits poor stability, and the results are for repeated validation data. Figure 5The results show the stability test results at 550℃ for two battery devices constructed using the same pure BZCY electrolyte prepared in the same manner. It can be seen that, compared to batteries constructed using pure BZCY as the electrolyte, the BZCY / NaAlO2@NaOH composite electrolyte designed in this embodiment can significantly improve battery stability, with a stability time exceeding 320 h, demonstrating excellent electrochemical stability.

[0069] After undergoing electrochemical testing, the three-layer structure of the battery was laterally cut along the electrolyte layer, and the collected electrolyte blocks were thoroughly ground using a mortar and pestle to finally obtain in-situ reconstructed BZCY / NaAlO2@NaOH electrolyte powder.

[0070] Figure 6 The AC-STEM image of the in-situ reconstructed BZCY / NaAlO2@NaOH electrolyte shows a 4 nm thick surface reconstruction layer on the surface of the fine atomic structure of BZCY.

[0071] Figure 7 and Figure 8 The EXNFS and EELS line scan results for the in-situ reconstructed BZCY / NaAlO2@NaOH electrolyte are shown below. It can be seen that the valence state of Ce in the BZCY / NaAlO2@NaOH powder after testing is Ce. 4+ With Ce3 + The coexistence of these elements indicates the reconstructed CeO2 / CeO 2-x A large number of defect sites are generated due to the decrease in the valence state of Ce.

[0072] Figure 9 The results of thermogravimetric-differential calorimetry (TGC) tests on the electrolyte material of the prepared BZCY / NaAlO2@NaOH composite electrolyte fuel cell after electrochemical testing are shown in the figure. As can be seen from the figure, the electrolyte material begins to exhibit a melting endothermic peak at approximately 327℃, accompanied by mass loss. The endothermic peak appears at 350℃, which is the melting point of the hydroxide complex. When the test temperature is higher than the initial melting temperature, a solid-liquid coexistence is widespread in the electrolyte, proton migration is accelerated, and battery performance is improved.

[0073] Figure 10 The results are O2-TPD / MS measurements of the prepared BZCY / NaAlO2@NaOH composite electrolyte after electrochemical testing. Figure 9 The results shown corroborate each other. The O2-TPD / MS results presented in this figure indicate that when the temperature exceeds approximately 325℃, significant O desorption begins to occur in the tested composite electrolyte powder, and it reacts with OH groups with a relative molecular mass of 17 observed in the MS results.- The desorption curves showed a good match, indicating that the substance that began to melt and decompose at this temperature was an alkaline hydroxide, i.e., a hydroxide complex present in the electrolyte.

[0074] Comparative Example 1

[0075] The difference between this comparative example and Example 1 is that NaAlO2 is replaced with an equal amount of NaAlSiO4, and the prepared electrolyte is a BZCY / NaAlSiO4@NaOH composite electrolyte, wherein the mass ratio of BZCY to NaAlSiO4 is also 7:3.

[0076] Similarly, the SIFC device with a γ-Al2O3 / NCAL‖BZCY / NaAlSiO4@NaOH‖γ-Al2O3 / NCAL sandwich structure was prepared according to the method in Example 1.

[0077] After testing, such as Figure 11 As shown, the performance of the battery prepared in this comparative example at 520-320℃ is significantly reduced compared to Example 2, and its OCV at 320℃ shows obvious degradation.

[0078] Comparative Example 2

[0079] The difference between this comparative example and Example 1 is that NaAlO2 is replaced with an equal amount of SiO2, and the electrolyte prepared is a BZCY / SiO2@NaOH composite electrolyte, wherein the mass ratio of BZCY to SiO2 is still 7:3.

[0080] Similarly, the SIFC device with a γ-Al2O3 / NCAL‖BZCY / SiO2@NaOH‖γ-Al2O3 / NCAL sandwich structure was prepared according to the method in Example 1.

[0081] After testing, such as Figure 12 As shown, the performance of the battery prepared in this comparative example at 520-320℃ is significantly reduced compared to Example 2, and its minimum operating temperature can only reach 350℃.

[0082] Comparative Example 3

[0083] The difference between this comparative example and Example 2 is that BZCY is replaced with an equal amount of BZY (BaZr). 0.8 Y 0.2 O 3-δ The NaAlO2 was replaced with an equal amount of SiO2, and the NaOH was replaced with an equal amount of Zn(OH)2. The mass ratio of BZY to SiO2 was 7:3. Zn(OH)2 was also mixed with the first two phases at a ratio of 10% of the total mass of the first two phases.

[0084] Similarly, the SIFC device with a γ-Al2O3 / NCAL‖BZY / SiO2@Zn(OH)2‖γ-Al2O3 / NCAL sandwich structure was prepared according to the method in Example 1.

[0085] After testing, such as Figure 13 As shown, the battery prepared in this comparative example exhibits a significant decrease in battery performance, and its lowest operating temperature is only 400℃.

[0086] Comparative Example 4

[0087] The difference between this comparative example and Example 1 is that the amount of NaOH added is 3% and 25%, while the amount of BZCY and NaAlO2 added remains the same as in Example 1.

[0088] The SIFC device was prepared in accordance with the method described in Example 1.

[0089] Tests showed that when the amount of NaOH added was 3%, the low-temperature performance of the battery device was poor. The battery could not achieve performance output at temperatures below 350 ℃. This was because the amount of NaOH introduced was too small, which caused the hydroxide conductive network to fail to meet the requirements for Yu-Shen interconnection.

[0090] Tests showed that when 25% NaOH was added, the open-circuit voltage (OCV) of the battery device at 520 °C could not remain stable and continued to decrease, significantly reducing the performance of the battery device. The reason for this was that excessive NaOH was introduced, and the excess hydroxide inside the electrolyte was converted into carbonate. The premature solidification of carbonate would damage the proton conduction network, thus making it impossible to maintain the stable potential at both ends of the battery and causing it to continue to decline.

[0091] Comparative Example 5

[0092] The difference between this comparative example and Example 1 is that the preparation process of the three-phase composite solid electrolyte material is as follows:

[0093] BZCY and NaAlO2 were placed in 200 mL of ethanol and ultrasonically treated for 40 minutes (ultrasonic frequency 40 kHz) to form a complex. The resulting complex was rapidly transferred to a ball mill jar and ball-milled at 260 rad / min for 4 hours. The liquid was then dried at 120 °C using a heat lamp until the ethanol was completely evaporated. A homogeneous BCZY / NaAlO2 precursor composite material was then obtained through thorough grinding.

[0094] Then, 10% of the mass of the preceding composite material was weighed out as commercial NaOH particles. The preceding composite material and NaOH particles were mixed and dissolved in alcohol. After ultrasonic treatment for 30 minutes, the mixture was thoroughly ground in a ball mill jar. After the spherical NaOH particles were completely ground, the liquid was dried with a heat lamp to finally obtain BZCY / NaAlO2@NaOH three-phase composite electrolyte powder.

[0095] The three-phase composite electrolyte powder prepared using this comparative example was also prepared according to the method in Example 1 to obtain an SIFC device with a γ-Al2O3 / NCAL‖BZCY / NaAlO2@NaOH‖γ-Al2O3 / NCAL sandwich structure.

[0096] Tests showed that when the electrolyte materials synthesized in this proportion were assembled into battery devices, the maximum power density of the fuel cell decreased at each temperature within the 320-550 ℃ range, and the open-circuit voltage (OCV) continued to decay at 320 ℃. This is because the synthesis route combining ultrasonication, titration, and microwave treatment was not followed for the three-phase electrolyte materials. The resulting three-phase electrolyte materials had poor surface activity and failed to fully maintain and exist the solid-liquid interface under the in-situ operating environment of the battery. This led to poor establishment of the proton-proton-migrating infiltration network, resulting in a significant decrease in battery performance.

[0097] The batteries obtained in Example 1 and the comparative example are summarized below, and the results are shown in Table 1:

[0098] Table 1: Battery performance with different electrolytes

[0099]

[0100] Table 1 provides a direct comparison of battery power parameters between the examples and different comparative examples. The comparison criteria are: power density and open-circuit voltage are compared at the same temperature; a higher value indicates better performance; and a lower minimum operating temperature is better. Comparative Example 3 cannot operate below 400°C, but its open-circuit voltage is very high. This is because there is indeed a molten hydroxide conductive network inside the electrolyte. The internal molten material solidifies at this temperature, causing the electrolyte to exhibit insulating properties due to the large amount of carbonate production, thus increasing the open-circuit voltage to 1.18V. However, due to the lack of ion transport channels, it cannot operate at lower temperatures. Comparative Example 4-1 can only obtain 3 data points when discharging at 350°C. At least 5 data points are needed to plot the discharge curve, therefore it cannot operate at this temperature. This is because the molten conductive network inside the electrolyte is missing at this temperature; although species with lower melting points exist, their quantity is too low to meet the battery's operating requirements.

[0101] It should be noted that the test methods and conditions involved in this embodiment are as follows: Battery electrochemical performance test: The performance tests of all SIFC devices involved used an IT8500 electronic load. Discharge tests were performed within a temperature range of 320–520℃, after the open-circuit voltage of the battery stabilized at each test temperature. The scan rate was set to 0.05–0.1 A / s when saving data. The obtained test values ​​were divided by the effective area of ​​0.64 cm². 2 The power density, used to characterize the battery's performance, was then obtained. During the test, the hydrogen was supplied in real time by a hydrogen generator, with the flow rate set at 120 mL / min–130 mL / min. The gas supply was stable during operation, and the battery's performance was verified through multiple tests, demonstrating repeatability.

[0102] Conductivity testing: In the IV / IP test scan curve of a battery, the ohmic polarization from the electrolyte corresponds to the relatively stable linear portion in the middle of the curve. The slope of this straight line can be calculated as the ohmic resistance. R= V / I), and then the ionic conductivity of the electrolyte can be obtained by following the conductivity calculation formula.

[0103] Stability test: The hydrogen flow rate was stabilized at 125 mL / min, and the electron load maintenance current density was set to 100 mA / cm². 2 Record the relationship between battery voltage and time.

[0104] TG / DSC test: Weigh 15 mg of electrolyte powder from the BZCY / NaAlO2@NaOH composite electrolyte battery after testing and place it in a test crucible. Use N2 as protective gas and air as purge gas, both with a flow rate of 30 mL / min. Perform programmed heating at a heating rate of 10 ℃ / min to obtain the thermogravimetric / differential calorimetric test results of the sample.

[0105] O2-TPD / MS test: Take about 5 g of the electrolyte powder from the BZCY / NaAlO2@NaOH composite electrolyte battery after testing and place it in a test U-tube. Use argon as the purge gas at a flow rate of 40 mL / min and perform a programmed temperature increase at a rate of 10 ℃ / min to obtain the O2-TPD test results of the sample. Pass the test exhaust gas into the mass spectrometer to simultaneously obtain the MS results of the sample.

[0106] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0107] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A three-phase composite solid electrolyte material, characterized in that, Includes BZCY, NaAlO2, and NaOH, wherein BZCY is BaZr. 0.2 Ce 0.7 Y 0.1 O 3-δ The mass ratio of BZCY to NaAlO2 is 7:3; the mass of NaOH is 10% of the total mass of the composite of BZCY and NaAlO2.

2. The method for preparing the three-phase composite solid electrolyte material according to claim 1, characterized in that, Includes the following steps: 1) Weigh out BZCY, NaAlO2, and NaOH according to the formula ratio; 2) Dissolve BZCY and NaAlO2 in a solvent, and then treat them by ultrasound, microwave, pre-activation, and ball milling to obtain the preceding composite material; 3) The obtained composite material is combined with NaOH to obtain electrolyte powder.

3. The method for preparing the three-phase composite solid electrolyte material according to claim 2, characterized in that, In step 2), the ultrasonic treatment time is 30-60 min; the solvent is ethanol; and / or the microwave treatment power is 300-500W and the microwave treatment time is 20-40 min; and / or the ball milling time is 3-5 h.

4. The method for preparing the three-phase composite solid electrolyte material according to claim 2, characterized in that, In step 3), the obtained composite material is dispersed in a solvent and ultrasonically treated to obtain suspension a; NaOH is dissolved in deionized water to obtain solution b; then solution b is added dropwise to suspension a, and after stirring, gradient heating, vacuum drying, and thorough grinding, electrolyte powder is obtained.

5. A solid oxide fuel cell containing the three-phase composite solid electrolyte material of claim 1.

6. The solid oxide fuel cell according to claim 5, characterized in that, The anode and / or cathode material of the solid oxide fuel cell is γ-Al2O3 / NCAL.

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