Heterojunction-based SOFC composite electrolyte material, preparation method and application

Abstract

The application relates to the technical field of fuel cell electrolyte, in particular to a SOFC composite electrolyte material based on a heterojunction, a preparation method and application, and the preparation method comprises the following steps: after a p-type semiconductor oxide phase and an n-type semiconductor oxide phase are ground and mixed, a p-type semiconductor oxide-n-type semiconductor oxide composite powder is obtained; the p-type semiconductor oxide-n-type semiconductor oxide composite powder and an oxygen ion conductor phase are compounded and mixed to obtain a multi-phase composite powder; the multi-phase composite powder is formed and heat-treated to obtain the SOFC composite electrolyte material based on the heterojunction. According to the application, a space charge region and a built-in electric field are formed at the interface through the heterojunction, ion migration activation energy is reduced, a multi-channel ion conduction network is constructed, and an electrolyte material capable of improving low-temperature ion conduction and blocking electron transmission is obtained.

Description

Technical Field

[0001] This invention relates to the field of fuel cell electrolyte technology, and in particular to a heterojunction-based SOFC composite electrolyte material, its preparation method, and its application. Background Technology

[0002] Solid oxide fuel cells (SOFCs) have attracted much attention due to their advantages such as strong fuel adaptability, high energy conversion efficiency, and low emissions. However, traditional SOFCs typically operate in a high-temperature range of 800–1000°C, which easily leads to significant thermal stress and thermal cycling failure. This also imposes stringent requirements on the thermal expansion matching, chemical compatibility, and sealing materials among the electrolyte, electrodes, and interconnects, thereby increasing system manufacturing and operating costs. Lowering the SOFC operating temperature to the mid-to-low temperature range (e.g., 300°C–800°C) can significantly alleviate the thermal management burden and material constraints, improve system reliability and lifespan, and create conditions for the application of metal interconnects, sealing materials, and low-cost packaging solutions. However, in the mid-to-low temperature range, the bulk ionic conductivity of conventional oxygen ion conductors (such as rare-earth-doped cerium oxide and stabilized zirconium oxide) decreases significantly, electrolyte ohmic losses increase, electrode reaction kinetics slow down, and interfacial polarization resistance increases, making it difficult to simultaneously achieve high battery output power density and energy efficiency.

[0003] In recent years, semiconductor composite electrolytes have been developed to form space charge regions and built-in electric fields (BIEF) at heterojunction interfaces, thereby enhancing oxygen ion migration, reducing apparent activation energy, and weakening grain boundary blocking effects at lower temperatures, achieving "low-temperature high conductivity" conductivity. However, semiconductor components may also introduce electron / hole conduction channels, causing electron leakage and a decrease in open-circuit voltage. In addition, heterojunction interfaces may undergo phase transitions, element diffusion, or interface degradation under long-term thermochemical conditions, thus affecting stability and reproducibility.

[0004] Therefore, there is a need for a method for preparing SOFC composite electrolyte materials that can improve low-temperature ion conduction while effectively blocking electron transport and ensuring the material structure and electrochemical stability, as well as their applications. Summary of the Invention

[0005] The main objective of this invention is to provide a heterojunction-based SOFC composite electrolyte material, its preparation method, and its application, aiming to solve the problems of poor low-temperature conductivity, poor material stability, and poor electrochemical performance of SOFC in existing technologies.

[0006] To achieve the above objectives, this invention proposes a heterojunction-based SOFC composite electrolyte material, wherein the electrolyte material is a multiphase composite electrolyte comprising:

[0007] p-type semiconductor oxide phase;

[0008] n-type semiconductor oxide phase;

[0009] Oxygen ion conductor phase;

[0010] In this process, the p-type semiconductor oxide phase and the n-type semiconductor oxide phase form a pn heterojunction interface. The electrolyte material uses oxygen ions as the main charge carriers in the temperature range of 300℃ to 800℃. The p-type semiconductor oxide phase and the n-type semiconductor oxide phase form a heterojunction interface and a space charge region with the oxygen ion conductor phase, respectively. The relative content of the p-type semiconductor oxide phase and the n-type semiconductor oxide phase is expressed as a molar ratio of (1~10):(1~10).

[0011] Furthermore, the p-type semiconductor oxide phase is at least one of NiO, CoO, and CuO.

[0012] Furthermore, the n-type semiconductor oxide phase is SnO2 doped with an alkali metal element, namely M. x Sn 1-x O 2-δ , wherein M is at least one of Li and Na;

[0013] Where x is 0.001~0.30 and δ is 0~0.2, in order to enhance oxygen vacancy formation and regulate band structure.

[0014] Furthermore, the oxygen ion conductor phase is a fluorite-structured oxide, i.e., Ce. 1-y Re y O 2-δ (where Re is one or more of Sm, Gd, Y, and Yb), where y is 0.02~0.40 and δ is 0~0.2.

[0015] Furthermore, the electrolyte material also includes a fourth phase, which is an electron-blocking phase and / or a structurally reinforcing phase. The fourth phase is at least one of Al2O3, SiO2, MgO, ZrO2, and TiO2, and the content of the fourth phase is 0.1~10wt%.

[0016] This invention also proposes a method for preparing SOFC composite electrolyte materials based on heterojunctions, comprising the following steps:

[0017] The p-type semiconductor oxide phase and the n-type semiconductor oxide phase are ground and mixed to obtain a mixed product. The mixed product is calcined and kept at a temperature for 0.5~2h to obtain a composite powder in which the p-type semiconductor oxide and the n-type semiconductor oxide interface are in full contact. This is denoted as p-type semiconductor oxide-n-type semiconductor oxide composite powder.

[0018] The p-type semiconductor oxide-n-type semiconductor oxide composite powder is compounded and mixed with an oxygen ion conductor phase to obtain a multiphase composite powder;

[0019] Multiphase composite powder is shaped and heat-treated at 400℃~1500℃ for 0.1~20h to obtain SOFC composite electrolyte material based on heterojunction.

[0020] Furthermore, in the step of molding the multiphase composite powder and heat-treating it at 400℃~1500℃ for 0.1~20h to obtain the SOFC composite electrolyte material based on heterojunction, the molding method includes at least one of the following: dry pressing, cold isostatic pressing, hot pressing, spark plasma sintering, tape casting, scraping, spraying, dip coating, spin coating, and the molding pressure is 50~800Mpa.

[0021] Further, the step of grinding and mixing the p-type semiconductor oxide phase and the n-type semiconductor oxide phase, calcining the mixture, and holding the calcined product at a temperature of 0.5~2h to obtain the p-type semiconductor oxide-n-type semiconductor oxide composite powder includes:

[0022] The p-type semiconductor oxide phase and the n-type semiconductor oxide phase were weighed and dried, crushed and sieved in sequence to obtain the sieved p-type semiconductor oxide phase and n-type semiconductor oxide phase.

[0023] The sieved p-type semiconductor oxide phase and n-type semiconductor oxide phase are mixed according to a set ratio. The mixing is carried out in any mixed solution of ethanol, isopropanol, acetone, water or the above components, and wet milling is performed with zirconium oxide balls and / or alumina balls at a ball-to-material mass ratio of (0.5~3):1, ball milling time of 6~48h, and rotation speed of 100~600rpm.

[0024] The present invention also proposes a medium-low temperature solid oxide fuel cell, wherein the medium-low temperature solid oxide fuel cell includes the heterojunction-based SOFC composite electrolyte material as described in any of the above technical solutions.

[0025] This invention constructs a multi-channel ion conduction network by forming a space charge region and a built-in electric field at the interface through a heterojunction, and reduces the ion migration activation energy, thereby obtaining an electrolyte material that improves low-temperature ion conduction and blocks electron transport. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the processes shown in these drawings without creative effort.

[0027] Figure 1 This is a schematic flowchart of a method for preparing a heterojunction-based SOFC composite electrolyte material according to an embodiment of the present invention.

[0028] Figure 2 (a) A powder particle diagram of the NLS-SDC composite electrolyte material provided in an embodiment of the present invention; Figure 2 (b) is a cross-sectional SEM image of a low-temperature solid oxide fuel cell;

[0029] Figure 3 The XRD patterns of the composite electrolytes in Examples 1-3, Comparative Examples 1-3, and NiO, LS, and SDC control materials of this invention are shown below.

[0030] Figure 4 The current-voltage (IV) and current-power (IP) data of typical single cells prepared in Examples 1-3 and Comparative Examples 1-3 provided for this invention are shown in the figure at the optimal operating temperature (550°C).

[0031] Figure 5 (a) is a graph showing the current-voltage (IV) and current-power (IP) data of a typical single cell assembled in Example 1 of the present invention at operating temperatures of 450°C, 500°C and 550°C. Figure 5 (b) is a graph showing the current-voltage (IV) and current-power (IP) data of a typical single cell assembled in Example 2 of the present invention at operating temperatures of 450°C, 500°C, and 550°C; Figure 5 (c) is a graph showing the current-voltage (IV) and current-power (IP) data of a typical single cell assembled in Example 3 of the present invention at operating temperatures of 450°C, 500°C and 550°C; Figure 5 (d) is a graph showing the current-voltage (IV) and current-power (IP) data of a typical single cell assembled in Comparative Example 1 of this invention at operating temperatures of 450°C, 500°C, and 550°C. Figure 5 (e) is a graph showing the current-voltage (IV) and current-power (IP) data of a typical single cell assembled in Comparative Example 2 of this invention at operating temperatures of 450°C, 500°C, and 550°C. Figure 5(f) is a graph showing the current-voltage (IV) and current-power (IP) data of a typical single cell assembled in Comparative Example 3 of this invention at operating temperatures of 450°C, 500°C, and 550°C.

[0032] Figure 6 (a) A typical single cell assembled in Example 1 of this invention at 450°C to 550°C (i.e., 723 to 823 K, corresponding to a 1000 / T of approximately 1.215 to 1.384 K). -1 The relationship between ionic conductivity and temperature (σ) within the operating temperature range ion -T) Data chart; Figure 6 (b) A typical single cell assembled in Example 2 of this invention at 450°C to 550°C (i.e., 723 to 823 K, corresponding to a 1000 / T of approximately 1.215 to 1.384 K). -1 The relationship between ionic conductivity and temperature (σ) within the operating temperature range ion -T) Data chart; Figure 6 (c) A typical single cell assembled in Example 3 of this invention at 450°C~550°C (i.e., 723~823K, corresponding to a 1000 / T of approximately 1.215~1.384 K). -1 The relationship between ionic conductivity and temperature (σ) within the operating temperature range ion -T) Data chart; Figure 6 (d) A typical single cell assembled in Comparative Example 1 of this invention at 450°C~550°C (i.e., 723~823K, corresponding to a 1000 / T of approximately 1.215~1.384 K). -1 The relationship between ionic conductivity and temperature (σ) within the operating temperature range ion -T) Data chart; Figure 6 (e) A typical single cell assembled in Comparative Example 2 of this invention at 450°C~550°C (i.e. 723~823K, corresponding to a 1000 / T of approximately 1.215~1.384 K). -1 The relationship between ionic conductivity and temperature (σ) within the operating temperature range ion -T) Data chart; Figure 6 (f) A typical single cell assembled in Comparative Example 3 of this invention at 450°C~550°C (i.e., 723~823K, corresponding to 1000 / T of approximately 1.215~1.384 K). -1 The relationship between ionic conductivity and temperature (σ) within the operating temperature range ion -T) Data chart;

[0033] Figure 7(a) A typical single cell assembled in Example 1 of this invention at 450°C to 550°C (i.e., 723 to 823 K, corresponding to a 1000 / T of approximately 1.215 to 1.384 K). -1 Plot of apparent diffusion activation energy (Ea) data for operating temperatures within the range of ) Figure 7 (b) A typical single cell assembled in Example 2 of this invention at 450°C to 550°C (i.e., 723 to 823 K, corresponding to a 1000 / T of approximately 1.215 to 1.384 K). -1 Plot of apparent diffusion activation energy (Ea) data for operating temperatures within the range of ) Figure 7 (c) A typical single cell assembled in Example 3 of this invention at 450°C~550°C (i.e., 723~823K, corresponding to a 1000 / T of approximately 1.215~1.384 K). -1 Plot of apparent diffusion activation energy (Ea) data for operating temperatures within the range of ) Figure 7 (d) A typical single cell assembled in Comparative Example 1 of this invention at 450°C~550°C (i.e., 723~823K, corresponding to a 1000 / T of approximately 1.215~1.384 K). -1 Plot of apparent diffusion activation energy (Ea) data for operating temperatures within the range of ) Figure 7 (e) A typical single cell assembled in Comparative Example 2 of this invention at 450°C~550°C (i.e. 723~823K, corresponding to a 1000 / T of approximately 1.215~1.384 K). -1 Plot of apparent diffusion activation energy (Ea) data for operating temperatures within the range of ) Figure 7 (f) A typical single cell assembled in Comparative Example 3 of this invention at 450°C~550°C (i.e., 723~823K, corresponding to 1000 / T of approximately 1.215~1.384 K). -1 Plot of apparent diffusion activation energy (Ea) data for operating temperatures within the range of ) Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0035] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0036] Furthermore, the use of terms such as "first" and "second" in this invention is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this invention.

[0037] Semiconductor composite electrolytes, by constructing heterojunction interfaces, can form space charge regions and built-in electric fields (BIEF) at the interface. This enhances oxygen ion migration, lowers the apparent activation energy, and weakens the grain boundary blocking effect at lower temperatures, achieving "low-temperature high conductivity" conduction characteristics. However, the semiconductor components may also introduce electron / hole conduction channels, causing electron leakage and a decrease in open-circuit voltage. Furthermore, heterojunction interfaces may undergo phase transitions, element diffusion, or interface degradation under long-term thermochemical conditions, thus affecting stability and reproducibility.

[0038] Based on this, embodiments of this application provide a heterojunction-based SOFC composite electrolyte material. It is understood that the composite electrolyte material of this invention includes at least phase A and phase B, and phase A and phase B form a continuous or semi-continuous contact interface within the material. Furthermore, the heterojunction interface between phase A and phase B is distributed in multiple points or three dimensions within the material to improve the effective coverage of the space charge region and the built-in electric field. Even further, the composite electrolyte material of this invention can also improve the heterojunction interface density through nano-sizing, layering / gradient, or core-shell / skeleton impregnation.

[0039] The electrolyte material of the present invention uses p-type semiconductor oxide phase (hereinafter referred to as phase A) and n-type semiconductor oxide phase (hereinafter referred to as phase B) as core components. By constructing a contact interface between phase A and phase B inside the material to form a pn heterojunction, an oxygen ion conductor phase (hereinafter referred to as phase C) is introduced to construct a three-dimensional through ion conduction network, thereby improving the apparent ion conduction capability in the medium and low temperature range, while taking into account airtightness and stability.

[0040] The surface of phase A can form a continuous heterojunction network with phase B through coating or in-situ growth. The coating method is selected from impregnation-calcination, deposition-reduction, solution wetting, in-situ precipitation or a combination thereof.

[0041] Furthermore, phase A is selected from one or more of the following: NiO (nickel oxide), CoO (cobalt oxide), and CuO (copper oxide). Among them, phase A is preferably NiO (nickel oxide) or a Ni-containing p-type composite oxide.

[0042] Phase B is SnO2 doped with alkali metal elements to enhance oxygen vacancy formation and regulate band positions. The doping element is selected from one or more of Li and Na. The doping amount (based on phase B) is preferably 0.1~30 mol%, and the doping amount is more preferably 10~25 mol%.

[0043] Phase C is a fluorite-structured oxide, which is preferably a rare earth element doped with cerium oxide. It is understood that phase C can also be a rare earth element doped with one or more of Sm, Gd, Y, and Yb. The doping amount is preferably 5-30 mol%, more preferably 10-25 mol%, and even more preferably 15-20 mol% (based on Ce sites), serving only as an ionic conductor to provide ionic conductivity.

[0044] Preferably, the ratio (molar ratio) of phase A to phase B is (1~10):(1~10); more preferably (6~10):(7~10); preferably, phase C accounts for 0~80wt% of the total mass (mass of phase A + phase B + phase C); more preferably 10~70wt%; and even more preferably 10~60wt%.

[0045] In this invention, the particle size of phases A, B, and C is 5-500 nm, and the relative density of the electrolyte layer is ≥85% to ensure airtightness and stable open-circuit voltage. It is understood that within the target operating temperature range, the material should meet the requirement of "dominant ion conduction and controlled electron leakage," that is, the preferred ionic conductivity is ≥10. -3 S·cm -1 Furthermore, electron transport (or electron leakage) is preferably at least one order of magnitude lower than ion conduction to ensure higher open-circuit voltage and long-term stability.

[0046] The SOFC composite electrolyte material based on heterojunctions involved in this invention can be any one of a single-layer uniform structure, a layered structure, a gradient structure, or a core-shell structure. If it is a layered structure, it includes a stack of phase A / B layers and an ion conductor layer containing phase C. If it is a gradient structure, at least one of phases A, B, and C is continuously or segmentedly distributed along the thickness direction.

[0047] This invention also proposes a method for preparing SOFC composite electrolyte materials based on heterojunctions, referring to... Figure 1 As shown, the preparation method involves the following steps:

[0048] Step S10: The p-type semiconductor oxide phase and the n-type semiconductor oxide phase are ground and mixed to obtain a mixed product. The mixed product is calcined and kept at a temperature for 0.5~2h to obtain a composite powder in which the p-type semiconductor oxide and n-type semiconductor oxide interfaces are in full contact. This is referred to as p-type semiconductor oxide-n-type semiconductor oxide composite powder.

[0049] Step S20: The p-type semiconductor oxide-n-type semiconductor oxide composite powder and the oxygen ion conductor phase are composite mixed to obtain a multiphase composite powder;

[0050] Step S30: The multiphase composite powder is shaped and heat-treated at 400℃~1500℃ for 0.1~20h to obtain SOFC composite electrolyte material based on heterojunction.

[0051] Furthermore, in one embodiment, step S10 further includes:

[0052] Step S11: Weigh the p-type semiconductor oxide phase and the n-type semiconductor oxide phase and dry, crush and sieve them in sequence to obtain the sieved p-type semiconductor oxide phase and n-type semiconductor oxide phase.

[0053] Step S12: The sieved p-type semiconductor oxide phase and n-type semiconductor oxide phase are mixed according to a set ratio. The mixing is carried out in any mixed solution of ethanol, isopropanol, acetone, water or the above components, and wet-milled with zirconium oxide balls and / or alumina balls at a ball-to-material mass ratio of (0.5~3):1, a ball milling time of 6~48h, and a rotation speed of 100~600rpm.

[0054] In detail, in this invention, steps S11 and S12 are solid-state methods, namely, sequentially performing drying, wet ball milling, calcination, composite ball milling, drying and sieving, molding, and heat treatment. The SOFC composite electrolyte material prepared by this invention is as follows: Figure 2 As shown, where, Figure 2 (a) is a cross-sectional SEM image of the composite electrolyte material powder particles in this invention. Figure 2 (b) is a cross-sectional SEM image of a low-temperature solid oxide fuel cell.

[0055] The present invention also discloses the following three sets of embodiments and three sets of comparative examples, and the specific implementation of each embodiment is as follows:

[0056] Example 1

[0057] The chemical composition of the electrolyte material prepared in this embodiment is: NiO-Li 0.25 Sn 0.75 O 2-δ -Sm 0.2 Ce 0.8 O 2-δ Among them, Li 0.25 Sn 0.75 O 2-δ Abbreviated as LS (i.e., phase B), NiO-Li 0.25 Sn 0.75 O 2-δ Abbreviated as NLS (i.e., p-type semiconductor oxide-n-type semiconductor oxide composite powder), Sm 0.2 Ce 0.8 O 2-δ Abbreviated as SDC (i.e., phase C), therefore, NiO-Li 0.25 Sn 0.75 O 2-δ -Sm 0.2 Ce 0.8 O 2-δ Abbreviated as NLS-SDC, NLS-SDC is used as the electrolyte material for the fuel cell in this embodiment.

[0058] The specific preparation steps are as follows:

[0059] Step S1, pretreatment: NiO raw material, raw material for preparing LS and SDC are vacuum dried at 120℃ and then ground for ≥2h to achieve particle size refinement and homogenization.

[0060] Step S2: Weigh the raw materials for preparing LS according to the target stoichiometry and perform wet ball milling for 24 hours using acetone as the medium.

[0061] Step S3: The ball-milled mixture is calcined at 950°C for 4 hours in air atmosphere to obtain LS powder, and then the LS powder is ground for 2 hours.

[0062] Step S4: NiO and LS are compounded in a molar ratio of 8:9 to obtain a mixed powder of NiO and LS. The mixed powder of NiO and LS is then mixed with acetone as a medium to form a first slurry. Zirconia balls with a diameter of 0.5~2mm are added to the first slurry. The mass ratio of the added zirconia balls to the mass of the mixed powder of NiO and LS is 1:1. The first slurry with added zirconia balls is ball-milled at 300rpm for 12h. The ball-milled first slurry is dried at 120℃ and then ball-milled again for 30min. It is then passed through a 400-mesh sieve and calcined at 950℃ for 1h in an air atmosphere to obtain a uniform composite NLS powder.

[0063] Step S5: Composite NLS powder and SDC powder are compounded at a mass ratio of 6:4 to obtain a mixed powder of NLS and SDC. The mixed powder of NLS and SDC is then mixed with ethanol as a medium to form a second slurry. Zirconia balls with a diameter of 0.5~2mm are added to the second slurry. The mass ratio of zirconia balls to NLS and SDC mixed powder is 1:1. The second slurry with added zirconia balls is ball-milled at 300rpm for 12h. The ball-milled second slurry is dried at 120℃ and then ball-milled again for 30min. The slurry is then passed through a 400-mesh sieve to obtain the NLS-SDC composite material at a mass ratio of 6:4, which is denoted as NLS-SDC 6:4 material.

[0064] Step S6: The obtained NLS-SDC 6:4 material is used as the composite electrolyte powder. The composite electrolyte powder is dry-pressed in a mold to obtain an electrolyte preform. A symmetrical electrode structure is then used for co-pressing and sintering assembly. The electrolyte layer thickness is 50~800μm, and the effective reaction area is 0.5cm². 2 .

[0065] Example 2:

[0066] The chemical composition of the electrolyte material prepared in this embodiment is: NiO-Li 0.25 Sn 0.75 O 2-δ -Sm 0.2 Ce 0.8 O 2-δ Among them, Li 0.25 Sn 0.75 O 2-δ Abbreviated as LS (i.e., phase B), NiO-Li 0.25 Sn 0.75 O 2-δ Abbreviated as NLS (i.e., p-type semiconductor oxide-n-type semiconductor oxide composite powder), Sm 0.2 Ce 0.8 O 2-δ Abbreviated as SDC (i.e., phase C), therefore, NiO-Li 0.25 Sn 0.75 O 2-δ -Sm 0.2 Ce 0.8 O 2-δ Abbreviated as NLS-SDC, NLS-SDC is used as the electrolyte material for the fuel cell in this embodiment.

[0067] The specific preparation steps are as follows:

[0068] Step S1, pretreatment: NiO raw material, raw material for preparing LS and SDC are vacuum dried at 120℃ and then ground for ≥2h to achieve particle size refinement and homogenization.

[0069] Step S2: Weigh the raw materials for preparing LS according to the target stoichiometry and perform wet ball milling for 24 hours using acetone as the medium.

[0070] Step S3: The ball-milled mixture is calcined at 950°C for 4 hours in air atmosphere to obtain LS powder, and then the LS powder is ground for 2 hours.

[0071] Step S4: NiO and LS are compounded in a molar ratio of 8:9 to obtain a mixed powder of NiO and LS. The mixed powder of NiO and LS is then mixed with acetone as a medium to form a first slurry. Zirconia balls with a diameter of 0.5~2mm are added to the first slurry. The mass ratio of the added zirconia balls to the mass of the mixed powder of NiO and LS is 1:1. The first slurry with added zirconia balls is ball-milled at 300rpm for 12h. The ball-milled first slurry is dried at 120℃ and then ball-milled again for 30min. It is then passed through a 400-mesh sieve and calcined at 950℃ for 1h in an air atmosphere to obtain a uniform composite NLS powder.

[0072] Step S5: The composite NLS powder and SDC powder are compounded at a mass ratio of 7:3 to obtain a mixed NLS-SDC powder. The mixed NLS and SDC powder is then mixed with ethanol as a medium to form a second slurry. Zirconia balls with a diameter of 0.5~2mm are added to the second slurry. The mass ratio of the zirconia balls to the mixed NLS and SDC powder is 1:1. The second slurry with added zirconia balls is ball-milled at 300rpm for 12h. The ball-milled second slurry is dried at 120℃ and then ball-milled again for 30min. The slurry is then passed through a 400-mesh sieve to obtain the NLS-SDC composite material at a mass ratio of 7:3, which is denoted as NLS-SDC 7:3 material.

[0073] Step S6: The obtained NLS-SDC 7:3 material is used as the composite electrolyte powder. The composite electrolyte powder is dry-pressed in a mold to obtain an electrolyte preform. A symmetrical electrode structure is then used for co-pressing and sintering assembly. The electrolyte layer thickness is 50~800μm, and the effective reaction area is 0.5cm². 2 .

[0074] It is understandable that, compared to Example 1, in Example 2, the NLS:SDC composite material ratio is adjusted from 6:4 to 7:3 in step S5.

[0075] Example 3:

[0076] The chemical composition of the electrolyte material prepared in this embodiment is: NiO-Li 0.25 Sn 0.75 O 2-δ -Sm 0.2 Ce0.8 O 2-δ Among them, Li 0.25 Sn 0.75 O 2-δ Abbreviated as LS (i.e., phase B), NiO-Li 0.25 Sn 0.75 O 2-δ Abbreviated as NLS (i.e., p-type semiconductor oxide-n-type semiconductor oxide composite powder), Sm 0.2 Ce 0.8 O 2-δ Abbreviated as SDC (i.e., phase C), therefore, NiO-Li 0.25 Sn 0.75 O 2-δ -Sm 0.2 Ce 0.8 O 2-δ Abbreviated as NLS-SDC, NLS-SDC is used as the electrolyte material for the fuel cell in this embodiment.

[0077] The specific preparation steps are as follows:

[0078] Step S1, pretreatment: NiO raw material, raw material for preparing LS and SDC are vacuum dried at 120℃ and then ground for ≥2h to achieve particle size refinement and homogenization.

[0079] Step S2: Weigh the raw materials for preparing LS according to the target stoichiometry and perform wet ball milling for 24 hours using acetone as the medium.

[0080] Step S3: The ball-milled mixture is calcined at 950°C for 4 hours in air atmosphere to obtain LS powder, and then the LS powder is ground for 2 hours.

[0081] Step S4: NiO and LS are compounded in a molar ratio of 8:9 to obtain a mixed powder of NiO and LS. The mixed powder of NiO and LS is then mixed with acetone as a medium to form a first slurry. Zirconia balls with a diameter of 0.5~2mm are added to the first slurry. The mass ratio of the added zirconia balls to the mass of the mixed powder of NiO and LS is 1:1. The first slurry with added zirconia balls is ball-milled at 300rpm for 12h. The ball-milled first slurry is dried at 120℃ and then ball-milled again for 30min. It is then passed through a 400-mesh sieve and calcined at 950℃ for 1h in an air atmosphere to obtain a uniform composite NLS powder.

[0082] Step S5: Composite NLS powder and SDC powder are compounded at a mass ratio of 5:5 to obtain a mixed powder of NLS and SDC. The mixed powder of NLS and SDC is then mixed with ethanol as a medium to form a second slurry. Zirconia balls with a diameter of 0.5~2mm are added to the second slurry. The mass ratio of zirconia balls to NLS and SDC mixed powder is 1:1. The second slurry with added zirconia balls is ball-milled at 300rpm for 12h. The ball-milled second slurry is dried at 120℃ and then ball-milled again for 30min. The slurry is then passed through a 400-mesh sieve to obtain the NLS-SDC composite material at a mass ratio of 5:5, which is denoted as NLS-SDC 5:5 material.

[0083] Step S6: The obtained NLS-SDC 5:5 material is used as the composite electrolyte powder. The composite electrolyte powder is dry-pressed in a mold to obtain an electrolyte preform. A symmetrical electrode structure is then used for co-pressing and sintering assembly. The electrolyte layer thickness is 50~800μm, and the effective reaction area is 0.5cm². 2 .

[0084] It is understandable that, compared to Example 1, in Example 3, the NLS:SDC composite material ratio is adjusted from 6:4 to 5:5 in step S5.

[0085] Comparative Example 1:

[0086] The chemical composition of the electrolyte material prepared in Comparative Example 1 is: NiO-Li 0.25 Sn 0.75 O 2-δ Among them, Li 0.25 Sn 0.75 O 2-δ Abbreviated as LS (i.e., phase B), NiO-Li 0.25 Sn 0.75 O 2-δ Abbreviated as NLS (i.e., p-type semiconductor oxide-n-type semiconductor oxide composite powder), only NLS was used as the electrolyte material for fuel cells in Comparative Example 1.

[0087] The specific preparation steps are as follows:

[0088] Step S1, pretreatment: The NiO raw material and the raw material for preparing LS are vacuum dried at 120℃ and then ground for ≥2h to achieve particle size refinement and homogenization.

[0089] Step S2: Weigh the raw materials for preparing LS according to the target stoichiometry and perform wet ball milling for 24 hours using acetone as the medium.

[0090] Step S3: The ball-milled mixture is calcined at 950°C for 4 hours in air atmosphere to obtain LS powder, and then the LS powder is ground for 2 hours.

[0091] Step S4: NiO and LS are compounded in a molar ratio of 8:9 to obtain a mixed powder of NiO and LS. The mixed powder of NiO and LS is then mixed with acetone as a medium to form a first slurry. Zirconia balls with a diameter of 0.5~2mm are added to the first slurry. The mass ratio of the added zirconia balls to the mass of the mixed powder of NiO and LS is 1:1. The first slurry with added zirconia balls is ball-milled at 300rpm for 12h. The ball-milled first slurry is dried at 120℃ and then ball-milled again for 30min. It is then passed through a 400-mesh sieve and calcined at 950℃ for 1h in an air atmosphere to obtain a uniform composite NLS powder.

[0092] Step S5: The obtained NLS material is used as a composite electrolyte powder. The composite electrolyte powder is dry-pressed in a mold to obtain an electrolyte preform. A symmetrical electrode structure is then used for co-pressing and sintering assembly. The electrolyte layer thickness is 50~800μm, and the effective reaction area is 0.5cm². 2 .

[0093] It can be seen that, compared with Example 1, Comparative Example 1 only uses NLS composite material as composite electrolyte material.

[0094] Comparative Example 2:

[0095] The chemical composition of the electrolyte material prepared in Comparative Example 2 is: NiO-Sm 0.2 Ce 0.8 O 2-δ , among which, Sm 0.2 Ce 0.8 O 2-δ Abbreviated as SDC (i.e., phase C), therefore, NiO-Sm 0.2 Ce 0.8 O 2-δ It is abbreviated as NiO-SDC, and NiO-SDC is used as the electrolyte material for fuel cells in Comparative Example 2.

[0096] The specific preparation steps are as follows:

[0097] Step S1, pretreatment: NiO raw material and SDC are vacuum dried at 120℃ and then ground for ≥2h to achieve particle size refinement and uniformity.

[0098] Step S2: NiO and SDC are mixed at a mass ratio of 6:4 to obtain a NiO-SDC mixed powder. The NiO-SDC mixed powder is mixed into a slurry using acetone as a medium. Zirconia balls with a diameter of 0.5~2mm are added to the slurry. The mass ratio of the added zirconia balls to the mass of the NiO-SDC mixed powder is 1:1. The mixture is ball-milled at 300rpm for 12h. The ball-milled slurry is dried at 120℃ and then ground again for 30min. It is then passed through a 400-mesh sieve and calcined at 950℃ for 1h in air atmosphere to obtain a uniform NiO-SDC 6:4 composite material.

[0099] Step S3: The obtained NiO-SDC 6:4 composite material is used as the composite electrolyte powder. The composite electrolyte powder is dry-pressed in a mold to obtain an electrolyte preform. A symmetrical electrode structure is then used for co-pressing and sintering assembly. The electrolyte layer thickness is 50~800μm, and the effective reaction area is 0.5cm². 2 .

[0100] It can be seen that, compared with Example 1, Comparative Example 2 uses NiO-SDC 6:4 composite material as the composite electrolyte material.

[0101] Comparative Example 3:

[0102] The chemical composition of the electrolyte material prepared in Comparative Example 3 is: Li 0.25 Sn 0.75 O 2-δ -Sm 0.2 Ce 0.8 O 2-δ Among them, Li 0.25 Sn 0.75 O 2-δ Abbreviated as LS (i.e., phase B), Sm 0.2 Ce 0.8 O 2-δ Abbreviated as SDC (i.e., phase C), therefore, Li 0.25 Sn 0.75 O 2-δ -Sm 0.2 Ce 0.8 O 2-δ It is abbreviated as LS-SDC. Comparative Example 3 uses LS-SDC as the electrolyte material for a fuel cell.

[0103] The specific preparation steps are as follows:

[0104] Step S1, pretreatment: The raw materials for preparing LS and SDC are vacuum dried at 120℃ and then ground for ≥2h to achieve particle size refinement and homogenization.

[0105] Step S2: Weigh the raw materials for preparing LS according to the target stoichiometry and perform wet ball milling for 24 hours using acetone as the medium.

[0106] Step S3: The ball-milled mixture is calcined at 950°C for 4 hours in air atmosphere to obtain LS powder, and then the LS powder is ground for 2 hours.

[0107] Step S4: Mix LS powder and SDC at a molar ratio of 6:4 to obtain LS-SDC mixed powder. Mix the LS-SDC mixed powder into a slurry using acetone as a medium. Add zirconia balls with a diameter of 0.5~2mm to the slurry. The mass ratio of the added zirconia balls to the mass of the LS-SDC mixed powder is 1:1. Ball mill at 300rpm for 12h. After ball milling, dry the slurry at 120℃ and grind it again for 30min. Pass it through a 400-mesh sieve and calcine it at 950℃ for 1h in air atmosphere to obtain a uniform composite LS-SDC 6:4 powder.

[0108] Step S5: The obtained LS-SDC 6:4 material is used as the composite electrolyte powder. The composite electrolyte powder is dry-pressed in a mold to obtain an electrolyte preform. A symmetrical electrode structure is then used for co-pressing and sintering assembly. The electrolyte layer thickness is 50~800μm, and the effective reaction area is 0.5cm². 2 .

[0109] It can be seen that, compared with Example 1, Comparative Example 3 uses LS-SDC 6:4 composite material as the composite electrolyte material.

[0110] The present invention also discloses the performance test results of the samples prepared according to Examples 1-3 and Comparative Examples 1-3, as follows:

[0111] Experiment 1

[0112] Phase structure analysis was performed on samples from Examples 1-3, Comparative Examples 1-3, and control samples (single NiO material, single SDC material, and single LS material) using a Rigaku D / MAX X-ray diffractometer (Japan). The results are as follows: Figure 3 As shown.

[0113] In detail, Figure 3 The XRD patterns are for Examples 1-3, Comparative Examples 1-3, and the control. In this experiment, CuKα radiation (λ = 1.5406 Å) was used, with tube voltage and current set to 40 kV and 150 mA, respectively. The scan range was 20°–90° (2θ), with a step size of 0.01°. Figure 3 The XRD patterns show that all prepared composite materials exhibit a standard multiphase structure, and no impurity phase peaks were observed.

[0114] Experiment 2

[0115] The electrochemical performance of the batteries assembled in Examples 1-3 and Comparative Examples 1-3 was systematically tested using an IT8500G+ electronic load. All tests were conducted within the temperature range of 450–550 °C, and the results are as follows: Figure 4 , Figure 5 As shown.

[0116] In detail, Figure 4 Comparative data on current density-voltage (IV) and current density-power density (IP) of the samples of Examples 1-3 and Comparative Examples 1-3 at the optimal operating temperature (550°C) are provided. Figure 5 The current density-voltage (IV) and current density-power density (IP) data of the batteries assembled from the samples of Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2 and Comparative Example 3 are given respectively at 450~550℃.

[0117] The maximum power density is defined as the maximum power density of the battery at that temperature. During the test, the anode hydrogen flow rate was maintained at 100–150 mL / min. -1 This is to ensure a stable gas supply and reliable data. For example... Figure 4 , Figure 5 As shown, across the entire test temperature range, the performance of the NLS-SDC composite samples (Examples 1-3) was significantly better than that of the corresponding comparative examples (Comparative Examples 1-3). Among them, Example 1 showed the most outstanding performance: its maximum power density reached 916 mW·cm at 550℃. -2 The corresponding open-circuit voltage (OCV) at 550℃ reaches 1.129V; and its maximum power density can still reach 621mW·cm at 450℃. -2 In contrast, when NLS was used as the electrolyte alone (Comparative Example 1), the power density was only 282 mW·cm⁻¹ at 550 °C and 450 °C, respectively. -2 With 447mW·cm -2 The composite electrolytes prepared in Examples 1-3 of this invention all exhibit an OCV of no less than 1.0V at 550℃, meeting the requirements of low electron leakage and good airtightness. It is noteworthy that although the electrolyte layer was not subjected to high-temperature densification sintering in this work, and its inherent porosity and thickness are not conducive to reducing ohmic polarization, the material still exhibits the aforementioned excellent output performance. This further confirms the effectiveness of improving electrolyte performance through intrinsic ion selectivity regulation and interface structure optimization.

[0118] Experiment 3

[0119] This experiment was conducted to systematically evaluate the ion transport characteristics of Examples 1-3 and Comparative Examples 1-3, using a combination of polarization curve analysis and Arrhenius analysis.

[0120] The results are as follows Figures 6-7 As shown, the ohmic resistance R is first extracted from the low-field linear region of the current density-voltage (IV) curve. ohm (=dV / dI), and then calculate the area resistance R using equations (1) and (2). ASR With ionic conductivity σ ion :

[0121] R ASR =R ohm ×S(1);

[0122] σ ion =L / (R ASR ×S)(2);

[0123] Among them, R ohm S represents the ohmic resistance in the low-field linear region of the IV curve, where L is the electrolyte thickness and S is the effective reaction area. The linear region was determined using the residual least squares method. All samples were tested under the same conditions to ensure comparability of results.

[0124] The results show (e.g.) Figures 6-7 As shown), where, Figure 6 The relationship between ionic conductivity and temperature (σ) of typical single cells assembled in Examples 1-3 and Comparative Examples 1-3 of this invention at an operating temperature of 450℃~550℃. ion -T) Data chart; Figure 7 The graph shows the apparent diffusion activation energy (Ea) of typical single cells assembled in Examples 1-3 and Comparative Examples 1-3 of this invention at an operating temperature of 450~550℃. It can be understood that the apparent diffusion activation energy (Ea) is derived from ln(σT) (i.e., ...). Figure 7 The (ionic conductivity·temperature) on the middle vertical axis is taken as the natural logarithm of 1000 / T (i.e., Figure 7 The slope of the graph plotted on the horizontal axis (1000 / T) is obtained by calculating the slope. 450~550℃ translates to 723~823K in Kelvin, corresponding to 1.215~1.384K for 1000 / T. -1 At 550℃ (i.e., 823K, corresponding to 1.215K per 1000T). -1 Under ) in Example 1, σ ion Reaching 0.348 S·cm -1This significantly outperforms other comparative systems. This advantage is attributed to the synergistic optimization of the interface and the percolation network. The pn heterojunction formed by p-type NiO and n-type LS and SDC generates a built-in electric field (BIEF), reducing the oxygen vacancy migration barrier. Simultaneously, the three-dimensional percolation network formed by the three phases shortens the ion transport path and reduces the interfacial impedance, thereby increasing R... ASR Reduce, σ ion Increase. Imminent 550℃ (i.e., 823K corresponds to 1.215K for 1000 / T). -1 When the open circuit voltage (OCV) of most batteries is ≥1.0V (1.129V in Example 1), it indicates that electron leakage is effectively suppressed and ion conduction is dominant.

[0125] Using Arrhenius's formula (3) to apply σ ion Fitting data using the T-data:

[0126] σ ion T = A × exp[-Ea / K] t T](3);

[0127] Where A is the pre-exponential factor, Ea is the apparent activation energy, and K... t Let be the Boltzmann constant, T be the absolute temperature, and exp represent an exponential function with the natural constant e as the base. The activation energy Ea of Example 1 was found to be 0.40 eV, significantly lower than that of conventional fluorite / zirconia electrolytes. This indicates that the interfacial electric field and defect chemistry jointly reduce ion migration resistance: the BIEF and space charge layer increase the oxygen vacancy concentration at the interface and lower its migration barrier, while interfacial distortion and the local electric field weaken phonon scattering during ion diffusion, thus achieving a synergistic improvement in high conductivity and low activation energy at 450–550 °C.

[0128] The above are merely preferred embodiments and parameter windows of the present invention, used to illustrate the technical solution of the present invention, and do not constitute a limitation on the scope of protection of the present invention. Those skilled in the art can make equivalent substitutions or modifications to the material composition, proportions, preparation conditions, and structural morphology without departing from the spirit of the present invention, and all such modifications should fall within the scope of protection of the present invention.

[0129] This invention constructs a multi-channel ion conduction network by forming a space charge region and a built-in electric field at the interface through a heterojunction, and reduces the ion migration activation energy, thereby obtaining an electrolyte material that improves low-temperature ion conduction and blocks electron transport.

[0130] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A SOFC composite electrolyte material based on a heterojunction, characterized in that, The electrolyte material is a multiphase composite electrolyte, comprising: p-type semiconductor oxide phase; n-type semiconductor oxide phase; Oxygen ion conductor phase; In this process, the p-type semiconductor oxide phase and the n-type semiconductor oxide phase form a pn heterojunction interface. The electrolyte material uses oxygen ions as the main charge carriers in the temperature range of 300℃ to 800℃. The p-type semiconductor oxide phase and the n-type semiconductor oxide phase respectively form a heterojunction interface and a space charge region. The relative content of the p-type semiconductor oxide phase and the n-type semiconductor oxide phase is expressed as a molar ratio of (1~10):(1~10).

2. The SOFC composite electrolyte material based on heterojunction as described in claim 1, characterized in that, The p-type semiconductor oxide phase is at least one of NiO, CoO, and CuO.

3. The SOFC composite electrolyte material based on heterojunction as described in claim 2, characterized in that, The n-type semiconductor oxide phase is SnO2 doped with an alkali metal element, namely M. x Sn 1-x O 2-δ , wherein M is at least one of Li and Na; Where x is 0.001~0.30 and δ is 0~0.2, in order to enhance oxygen vacancy formation and regulate band structure.

4. The SOFC composite electrolyte material based on heterojunction as described in claim 3, characterized in that, The oxygen ion conductor phase is a fluorite-structured oxide, i.e., Ce. 1-y Re y O 2-δ (in, Re is one or more of Sm, Gd, Y, and Yb, where y is 0.02 to 0.40 and δ is 0 to 0.

2.

5. The SOFC composite electrolyte material based on heterojunction as described in claim 4, characterized in that, The electrolyte material further includes a fourth phase, which is an electron-blocking phase and / or a structurally reinforcing phase. The fourth phase is at least one of Al2O3, SiO2, MgO, ZrO2, and TiO2, and the content of the fourth phase is 0.1~10wt%.

6. A method for preparing SOFC composite electrolyte material based on heterojunction, characterized in that, Includes the following steps: The p-type semiconductor oxide phase and the n-type semiconductor oxide phase are ground and mixed to obtain a mixed product. The mixed product is calcined and kept at a temperature for 0.5~2h to obtain a composite powder in which the p-type semiconductor oxide and the n-type semiconductor oxide interface are in full contact. This is denoted as p-type semiconductor oxide-n-type semiconductor oxide composite powder. The p-type semiconductor oxide-n-type semiconductor oxide composite powder is compounded and mixed with an oxygen ion conductor phase to obtain a multiphase composite powder; Multiphase composite powder is shaped and heat-treated at 400℃~1500℃ for 0.1~20h to obtain SOFC composite electrolyte material based on heterojunction.

7. The method for preparing SOFC composite electrolyte material based on heterojunction as described in claim 6, characterized in that, In the step of molding the multiphase composite powder and heat-treating it at 400℃~1500℃ for 0.1~20h to obtain the SOFC composite electrolyte material based on heterojunction, the molding method includes at least one of the following: dry pressing, cold isostatic pressing, hot pressing, spark plasma sintering, tape casting, scraping, spraying, dip coating, spin coating, and the molding pressure is 50~800Mpa.

8. The method for preparing SOFC composite electrolyte material based on heterojunction as described in claim 6, characterized in that, The steps of grinding and mixing the p-type semiconductor oxide phase and the n-type semiconductor oxide phase, calcining the mixture, and holding it at a temperature for 0.5-2 hours after calcination to obtain the p-type semiconductor oxide-n-type semiconductor oxide composite powder include: The p-type semiconductor oxide phase and the n-type semiconductor oxide phase were weighed and dried, crushed and sieved in sequence to obtain the sieved p-type semiconductor oxide phase and n-type semiconductor oxide phase. The sieved p-type semiconductor oxide phase and n-type semiconductor oxide phase are mixed according to a set ratio. The mixing is carried out in any mixed solution of ethanol, isopropanol, acetone, water or the above components, and wet milling is performed with zirconium oxide balls and / or alumina balls at a ball-to-material mass ratio of (0.5~3):1, ball milling time of 6~48h, and rotation speed of 100~600rpm.

9. A medium-low temperature solid oxide fuel cell, characterized in that, The medium- and low-temperature solid oxide fuel cell includes the heterojunction-based SOFC composite electrolyte material as described in any one of claims 1-5.

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