Electrode current collecting powder with thermal expansion adjusting function and high conductivity for solid oxide electrolytic cell and preparation method of electrode current collecting powder

Abstract

The invention provides an application of LaCo < 0.6 > Ni < 0.4 > O < 3-delta > (LCN) and a negative thermal expansion material in a solid oxide electrolytic tank. The LCN and the negative thermal expansion material are used in the solid oxide electrolytic tank, the overall thermal expansion coefficient of the composite powder can be accurately adjusted through the cooperative regulation effect of positive expansion and negative expansion, the composite powder is matched with a galvanic pile assembly, the problem of interface thermal stress is solved, adverse reaction between the composite powder and the LCN can be effectively avoided, and the service life of the solid oxide electrolytic tank is prolonged. And the long-term performance stability of the composite powder is ensured. Positive expansion of LCN is compensated by utilizing the thermal shrinkage and cold expansion characteristics of the negative thermal expansion material, and the overall thermal expansion behavior is regulated and controlled through the stress containment effect of a two-phase interface, so that the thermal expansion coefficient of the composite powder is regulated and controlled to be matched with the thermal expansion coefficient of an SOEC electrolyte and other components, and then thermal stress is reduced; and the structural stability and reliability in the high-temperature operation process are improved.

Description

Technical Field

[0001] This invention belongs to the technical field of electronic ceramics, and relates to a LaCo... 0.6 Ni 0.4 O 3-δ The application of LCN (Liquid Ceramic Nuclei) and negative thermal expansion materials in solid oxide electrolytic cells, and the preparation method of mixed powder of LCN and negative thermal expansion materials, especially the electrode current collector powder for solid oxide electrolytic cells with both thermal expansion regulation function and high conductivity, and the preparation method thereof. Background Technology

[0002] With the global push for "dual carbon" goals accelerating and traditional fossil fuels becoming increasingly depleted, the efficient conversion and storage of clean energy has become a core issue in the energy sector. From electric vehicles essential for daily travel to hydrogen supply indispensable for industrial production, various energy applications rely on efficient energy conversion devices. Among them, solid oxide electrolyzers (SOECs), as key equipment for the efficient conversion of electrical and chemical energy, are gradually becoming a research focus in the energy field due to their outstanding advantages in areas such as hydrogen production through water electrolysis and carbon dioxide resource utilization.

[0003] The core function of SOEC (Solar Electrolytic Cell) is to achieve efficient electrolysis at high temperatures of 600-900℃. The electron current collector, as the core channel for electron transport within the SOEC, directly determines the battery's conductivity and long-term operational stability. If the performance of the electron current collector is mismatched with other SOEC components, it can easily lead to battery malfunctions and even significantly shorten its lifespan. Therefore, developing high-performance SOEC electron current collector materials is not only a key breakthrough for promoting the industrial application of SOEC technology, but also the core technical field of this invention.

[0004] The core structure of an SOEC fuel cell stack consists of individual solar cells, an electron current collector, bipolar plates, and electrode metal plates. During the water electrolysis process to produce hydrogen, the hydrogen electrode reacts to form H₂O → H₂ + O. 2- The reduction reaction occurs at the oxygen electrode, where O2 is generated. 2- →The oxidation reaction of O2 occurs, and the electron current collector plays a crucial role in efficiently transferring electrons generated by the electrodes to the external circuitry, thus forming a complete current loop. Insufficient conductivity of the electron current collector directly leads to increased internal resistance of the battery, significantly reducing energy conversion efficiency. Furthermore, if its thermal expansion characteristics are mismatched with the electrolyte, interfacial thermal stress will occur at high temperatures, causing component cracking or delamination, ultimately leading to battery failure. LCN, as a typical perovskite oxide, owes its excellent electronic conductivity to Co. 3+ / Co 4+ with Ni 3 + / Ni 4+The valence cycle mechanism of LCN enables rapid electron transport at high temperatures. Simultaneously, LCN exhibits excellent high-temperature chemical stability and is not prone to chemical reactions with the core components of SOEC. Therefore, due to its good electronic conductivity, superior catalytic activity, and chemical compatibility with the metal casing of SOEC stacks, LCN is frequently used as a powder in the air electrode current collector layer of solid oxide electrolyzers.

[0005] However, it is important to point out that the high coefficient of thermal expansion is a core drawback of LCN as an electron current collector material, severely limiting its practical application. LCN itself has a high coefficient of thermal expansion (TEC), typically reaching 19 × 10⁻⁶. -6 / ℃), and commonly used metal connectors (such as the Crofer22APU's TEC approximately 13×10). -6 / ℃, Haynes 230's TEC is approximately 15×10 -6 The significant mismatch between the materials used in SOEC (Solar Energy Storage and Electrode) and the electrode functional layer has become a core bottleneck restricting its stable application in SOEC. In SOEC, differences in the thermal expansion coefficients of different components can lead to problems such as interface peeling and breakage, affecting battery performance and lifespan. This thermal expansion mismatch causes significant thermal stress at the interface during high-temperature operation (typically 600~900℃) and repeated start-stop operation. When the thermal stress exceeds the bonding strength and fracture toughness of the materials, it directly leads to peeling and cracking between the current collector and the metal interconnect, and in extreme cases, even damage to the air electrode functional layer. The generation of interface defects not only significantly increases electron transport resistance, causing a sharp rise in battery ohmic losses, but also damages the sealing performance between the electrode and the current collector, causing air leakage and exacerbating high-temperature oxidation corrosion of the metal interconnect, forming a vicious cycle of "stress-leakage-corrosion." Under long-term operation, this mismatch will cause the battery output power to continuously decrease, shortening the lifespan from thousands of hours to hundreds of hours, seriously hindering the industrialization of SOEC towards high stability and long lifespan.

[0006] Therefore, finding a more suitable method to overcome the existing shortcomings of LCN as an electron current collector material has become one of the focal points of attention for many cutting-edge researchers in the field. Summary of the Invention

[0007] In view of this, the technical problem to be solved by the present invention is to provide an application of LCN and negative thermal expansion materials in solid oxide electrolytic cells, and a method for preparing a mixed powder of LCN and negative thermal expansion materials, particularly an electrode current collector powder for solid oxide electrolytic cells that combines thermal expansion regulation function and high conductivity. The present invention uses a negative thermal expansion material to compensate for the positive expansion of LCN, which allows for precise control of the thermal expansion coefficient of the composite powder, making it compatible with the thermal expansion characteristics of commonly used metal components, ultimately achieving a synergistic effect of thermal expansion regulation and high conductivity. Furthermore, the preparation conditions are simple and easy to control, the cost is low, it is safe and environmentally friendly, and the efficiency is high, making it more suitable for industrial promotion and application.

[0008] This invention provides LaCo 0.6 Ni 0.4 O 3-δ Application of negative thermal expansion materials in solid oxide electrolytic cells.

[0009] Preferably, the LaCo 0.6 Ni 0.4 O 3-δ and negative thermal expansion materials including LaCo 0.6 Ni 0.4 O 3-δ Mixed powder of materials with negative thermal expansion;

[0010] The solid oxide electrolytic cell includes an air electrode electron current collector layer.

[0011] Preferably, the LaCo 0.6 Ni 0.4 O 3-δ The mass ratio of the material with negative thermal expansion is (9.5~5):(0.5~5).

[0012] Preferably, the negative thermal expansion material includes Sm 0.85 Zn 0.15 MnO3, ZrW2O8, Y2W3O 12 One or more of NdMnO3.

[0013] Preferably, the LaCo 0.6 Ni 0.4 O 3-δ The negative thermal expansion material is specifically a composite system of a highly conductive positive expansion phase and a negative thermal expansion regulating phase;

[0014] The applications include reducing interfacial thermal stress in solid oxide electrolytic cells.

[0015] The present invention also provides a LaCo application in any of the above-described technical solutions. 0.6 Ni 0.4 O3-δ A method for preparing a mixed powder of a material with negative thermal expansion includes the following steps:

[0016] 1) After premixing LCN powder and negative thermal expansion material powder, a premixed powder is obtained;

[0017] 2) Place the premixed powder and dispersion medium obtained in the above steps into a ball mill for ball milling, and after drying, obtain a mixed powder.

[0018] Preferably, the LCN powder comprises LCN powder synthesized by the sol-gel method;

[0019] The negative thermal expansion material powder includes negative thermal expansion material powder synthesized at high temperature solid phase.

[0020] Preferably, the dispersion medium includes ethanol;

[0021] The ball milling time is 4 to 10 hours.

[0022] Preferably, the ball-to-material ratio in the ball mill is (5~20):1;

[0023] The ball mill rotates at a speed of 300-600 rpm.

[0024] Preferably, the particle size of the mixed powder is 0.2~1μm.

[0025] This invention provides LaCo 0.6 Ni 0.4 O 3-δ The application of negative thermal expansion materials in solid oxide electrolyzers (SOECs). Compared with existing technologies, single-component LCN materials have a high coefficient of thermal expansion, resulting in poor thermal expansion matching with other components. Significant thermal stress easily forms at the interface, making it difficult to meet the requirements of long-term high-temperature operation of SOECs. Under thermal stress, microcracks easily appear in the current collector, causing interruption of electron transport paths and leading to a rapid increase in the battery's internal resistance. Negative thermal expansion materials are a class of materials with special functions; their coefficient of thermal expansion is negative (i.e., volume shrinks when temperature rises and expands when temperature falls). Typical examples include Sm... 0.85 Zn 0.15 MnO3, ZrW2O8, Y2W3O 12 And compounds such as NdMnO3. The negative thermal expansion characteristics of these materials originate from special changes in the crystal structure, such as rigid framework rotation, phase transition and other microscopic mechanisms.

[0026] Based on this, the present invention specifically incorporates LaCo 0.6 Ni 0.4 O 3-δWhen negative thermal expansion materials are used in solid oxide electrolytic cells (SOECs), the overall thermal expansion coefficient of the composite powder can be precisely adjusted through the synergistic regulation effect of "positive expansion + negative expansion," ensuring its compatibility with the stack components and resolving interfacial thermal stress issues. Simultaneously, selecting negative thermal expansion materials with excellent chemical stability effectively prevents adverse reactions with LCN, guaranteeing the long-term performance stability of the composite powder. This invention can regulate the thermal expansion matching between the current collector powder of SOEC electrodes and the metal components of the stack, reducing thermal stress and improving the stability and long-term operating performance of the SOEC stack. This invention prepares SOEC electron current collector powder through the synergistic composite of a "highly conductive phase (LCN) + a negative thermal expansion regulating phase," achieving the dual functions of "precise thermal expansion regulation + high electronic conductivity."

[0027] This invention employs a composite powder design, combining LCN with powders exhibiting negative thermal expansion characteristics. The "thermal contraction and cold expansion" properties of the negative thermal expansion material are used to compensate for the positive expansion of LCN. The overall thermal expansion behavior is controlled through the stress restraint effect at the two-phase interface, thereby regulating the thermal expansion coefficient of the composite powder to match that of SOEC electrolytes and other components. This reduces thermal stress and improves the structural stability and reliability of SOEC during high-temperature operation. Attached Figure Description

[0028] Figure 1 LaCo prepared for embodiments of the present invention 0.6 Ni 0.4 O 3-δ XRD pattern of sol-gel precursor of (LCN);

[0029] Figure 2 LaCo prepared for embodiments of the present invention 0.6 Ni 0.4 O 3-δ XRD pattern of sol-gel precursor of (LCN) after high-temperature sintering;

[0030] Figure 3 Sm prepared for embodiments of the present invention 0.85 Zn 0.15 The XRD pattern of MnO3 (SZM) powder changes with temperature;

[0031] Figure 4 The sintering curve is obtained using the multi-segment temperature control program employed in this embodiment of the invention.

[0032] Figure 5 The electrical conductivity of the LCN / SZM composite material prepared in this embodiment of the invention varies with temperature.

[0033] Figure 6The thermal expansion properties of SZM prepared in this embodiment of the invention vary with temperature;

[0034] Figure 7 The change of thermal expansion coefficient of LCN / SZM prepared in the embodiments of the present invention with temperature;

[0035] Figure 8 The thermal expansion coefficient of LCN / NMO prepared in Comparative Example 1 of this invention varies with temperature. Detailed Implementation

[0036] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention and not for limiting the claims of the present invention.

[0037] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0038] There are no particular restrictions on the purity of any raw materials used in this invention. Preferably, analytical grade or conventional purity in the field of solid oxide electrolytic cell materials is sufficient.

[0039] This invention provides LaCo 0.6 Ni 0.4 O 3-δ Application of negative thermal expansion materials in solid oxide electrolytic cells.

[0040] In this invention, the LaCo 0.6 Ni 0.4 O 3-δ Materials with negative thermal expansion are preferably LaCo 0.6 Ni 0.4 O 3-δ Mixed powder of materials with negative thermal expansion.

[0041] In this invention, the solid oxide electrolytic cell preferably includes an air electrode electron current collector layer of the solid oxide electrolytic cell.

[0042] In this invention, the LaCo 0.6 Ni 0.4 O 3-δ The preferred mass ratio of the material to the negative thermal expansion material is (9.5~5):(0.5~5), more preferably (8.5~6):(1.5~4), and even more preferably (7.5~7):(2.5~3.0).

[0043] In this invention, the negative thermal expansion material preferably includes Sm 0.85 Zn 0.15 MnO3, ZrW2O8, Y2W3O12 and one or more of NdMnO3, more preferably Sm 0.85 Zn 0.15 MnO3, ZrW2O8, Y2W3O 12 or NdMnO 3。

[0044] In this invention, the LaCo 0.6 Ni 0.4 O 3-δ The preferred material for negative thermal expansion is a composite system of a highly conductive positive expansion phase and a negative thermal expansion regulating phase.

[0045] In this invention, the preferred application direction includes applications in reducing interfacial thermal stress in solid oxide electrolytic cells.

[0046] This invention provides a LaCo solution in any of the above-described technical solutions. 0.6 Ni 0.4 O 3-δ A method for preparing a mixed powder of a material with negative thermal expansion includes the following steps:

[0047] 1) After premixing LCN powder and negative thermal expansion material powder, a premixed powder is obtained;

[0048] 2) Place the premixed powder and dispersion medium obtained in the above steps into a ball mill for ball milling, and after drying, obtain a mixed powder.

[0049] The present invention first premixes LCN powder and negative thermal expansion material powder to obtain premixed powder.

[0050] In this invention, the LCN powder preferably includes LCN powder synthesized by the sol-gel method.

[0051] In this invention, the negative thermal expansion material powder preferably includes negative thermal expansion material powder synthesized at high temperature solid phase.

[0052] Finally, the premixed powder and dispersion medium obtained in the above steps are placed in a ball mill for ball milling, and after drying, a mixed powder is obtained.

[0053] In this invention, the dispersion medium preferably includes ethanol.

[0054] In this invention, the ball milling time is preferably 4 to 10 hours, more preferably 5 to 9 hours, even more preferably 6 to 8 hours, and specifically 6 hours.

[0055] In this invention, the ball-to-material ratio of the ball mill is preferably (5~20):1, more preferably (8~17):1, even more preferably (10~14):1, and specifically can be 10:1.

[0056] In this invention, the rotational speed of the ball mill is preferably 300~600 rpm, more preferably 350~550 rpm, even more preferably 400~500 rpm, and specifically 400 rpm.

[0057] In this invention, the particle size of the mixed powder is preferably 0.2~1μm, more preferably 0.35~0.85μm, and even more preferably 0.5~0.7μm.

[0058] This invention specifically uses LaCo 0.6 Ni 0.4 O 3-δ When negative thermal expansion materials are used in solid oxide electrolytic cells (SOECs), the overall thermal expansion coefficient of the composite powder can be precisely adjusted through the synergistic regulation effect of "positive expansion + negative expansion," ensuring its compatibility with the stack components and resolving interfacial thermal stress issues. Simultaneously, selecting negative thermal expansion materials with excellent chemical stability effectively prevents adverse reactions with LCN, guaranteeing the long-term performance stability of the composite powder. This invention can regulate the thermal expansion matching between the current collector powder of SOEC electrodes and the metal components of the stack, reducing thermal stress and improving the stability and long-term operating performance of the SOEC stack. This invention prepares SOEC electron current collector powder through the synergistic composite of a "highly conductive phase (LCN) + a negative thermal expansion regulating phase," achieving the dual functions of "precise thermal expansion regulation + high electronic conductivity."

[0059] This invention employs a composite powder design, combining LCN with powders exhibiting negative thermal expansion characteristics. The "thermal contraction and cold expansion" properties of the negative thermal expansion material are used to compensate for the positive expansion of LCN. The overall thermal expansion behavior is controlled through the stress restraint effect at the two-phase interface, thereby regulating the thermal expansion coefficient of the composite powder to match that of SOEC electrolytes and other components. This reduces thermal stress and improves the structural stability and reliability of SOEC during high-temperature operation.

[0060] This invention aims to complete and refine the overall technical solution, better ensure the stability and uniformity of the mixed powder, and further improve the electrochemical performance of the mixed powder in the air electrode electron current collector layer of a solid oxide electrolytic cell. Specifically, the aforementioned electrode current collector powder for a solid oxide electrolytic cell, which combines thermal expansion regulation and high conductivity, and its preparation method may include the following:

[0061] LaCo 0.6 Ni 0.4 O 3-δ Sol-gel synthesis process of (LCN)

[0062] This invention uses the sol-gel method to prepare LCN powder, with polyvinyl alcohol (PVA), lanthanum nitrate, cobalt nitrate, and nickel nitrate as raw materials. The specific synthesis steps are as follows:

[0063] 1) Preparation of PVA aqueous solution

[0064] Accurately weigh the PVA powder and distilled water, then slowly add the powder to the water. After stirring and dispersing, seal the beaker containing the mixture to prevent water evaporation during heating, which could lead to concentration deviations.

[0065] The above system was placed in a constant temperature water bath environment. The temperature was first set to 50°C and stirred at this temperature for 3 hours to ensure that the PVA was fully swollen. Then the water bath temperature was raised to 90°C and stirred continuously until the solution was completely clear and transparent, thus obtaining a 4% PVA aqueous solution for later use.

[0066] 2) Preparation of metal ion / PVA sol

[0067] Based on the stoichiometry of LCN, accurately weigh La(NO3)3·6H2O, Co(NO3)2·6H2O and Ni(NO3)2·6H2O crystals, and slowly add them sequentially to the above PVA aqueous solution.

[0068] Remove the beaker seal and place the system in an 80°C oil bath environment, stirring at a constant temperature for 10 hours. Continue to evaporate moisture during the process. Stop heating and stirring when the system transforms into a uniform, viscous, reddish-brown gel.

[0069] 3) Preparation and calcination of precursors

[0070] The aforementioned reddish-brown gel was transferred to a clean porcelain boat and dried in a 100°C oven for 24 hours to remove residual moisture, yielding a fluffy caramel-colored solid precursor. The caramel-colored precursor was then removed and thoroughly ground into a fine powder using a mortar and pestle, and transferred to a corundum crucible. The crucible was placed in a high-temperature muffle furnace and calcined at 1100°C for 3 hours to complete the phase transformation and impurity removal. After natural cooling to room temperature, the LCN target product powder was obtained.

[0071] Sm 0.85 Zn 0.15 High-temperature solid-state synthesis process of MnO3 (SZM)

[0072] This experiment used a high-temperature solid-state synthesis method to prepare SZM powder. High-purity Sm2O3, ZnO, and MnO2 were used as raw materials. The product synthesis was completed through steps including ball milling, molding, and high-temperature sintering. The specific process is as follows:

[0073] 1) Raw material weighing and pretreatment

[0074] Calculate the theoretical amount of each raw material based on the chemical composition of SZM, accurately weigh the high-purity raw material powder, and reduce the adverse effects on the product structure and performance.

[0075] 2) High-energy ball milling mixing

[0076] Place all weighed raw materials into the ball mill jar of a high-energy ball mill, and add anhydrous ethanol as a dispersion solvent. The volume of solvent should be sufficient to completely cover the powder (the specific amount can be adjusted slightly according to the porosity of the raw materials). Set the ball-to-material mass ratio to 10:1 and the rotation speed to ≥400 rpm. Start the ball mill and grind continuously for ≥6 hours to fully refine and uniformly mix the raw material particles, laying the foundation for the subsequent solid-phase reaction.

[0077] 3) Powder drying and molding

[0078] After ball milling, the solid-liquid turbid system in the ball mill jar was removed and transferred to a clean beaker. The beaker was then placed in an 80°C oven for constant temperature drying for 6 hours to completely remove the ethanol solvent. The dried powder was collected and pressed into tablets using a tablet press to form cylindrical blanks with a diameter of 14 mm and a height of 6-8 mm. This molding process improves the powder density, reduces porosity during sintering, and promotes efficient solid-phase reactions.

[0079] 4) High-temperature sintering and post-treatment

[0080] The shaped green body was placed in a corundum crucible and sent into a high-temperature muffle furnace. The sintering temperature was set to 1100℃, and after reaching the target temperature, it was held for 6 hours to allow the raw material components to undergo a full solid-phase reaction and form the SZM target crystalline phase. After sintering, the power to the muffle furnace was turned off, and the sample was allowed to cool naturally to room temperature before being removed. Finally, the cooled sample was ground and sieved to obtain SZM product powder with uniform particle size.

[0081] Powder mixing process

[0082] The LCN and SZM powders, which have undergone the above-mentioned calcination treatment, were physically premixed at mass ratios of 9.5:0.5, 9.0:1.0, 8.5:1.5, and 8.0:2.0, respectively. The premixed powders were then reloaded into a ball mill jar, and ethanol was added as a dispersion medium. The mixture was continuously ball-milled to ensure uniform mixing. Finally, the ball-milled slurry was dried to achieve a more thorough mechanical mixing of the two powders, providing a homogenized powder for subsequent processes.

[0083] Sample preparation process for conductivity testing

[0084] The strip-shaped bulk samples for conductivity testing were prepared by a method combining dry pressing and subsequent sintering. The specific steps are as follows:

[0085] 1) Powder pretreatment and binder mixing: To improve the dry pressing effect, the dried mixed powder is first modified with a binder. Based on the total mass of the powder, the mixed powder and 4% PVA aqueous solution (binder) are weighed at a mass ratio of 96:4. The mixed powder is first placed in an agate mortar, and then the corresponding amount of PVA aqueous solution is added. The mixture is continuously ground for 30 minutes to ensure that the binder and powder are fully impregnated and mixed evenly, resulting in a powder with excellent molding performance to be pressed.

[0086] 2) Dry pressing: Accurately weigh 3g of the pretreated uniform powder and place it into the dry pressing mold. Gently agitate the mold to ensure the powder is evenly distributed within the cavity, avoiding localized density differences. Then, slowly apply pressure to 8MPa and hold for 60 seconds to ensure the compactness of the blank. Afterward, release the pressure. Apply an appropriate ejection force using the mold's release mechanism to smoothly remove the pressed strip-shaped blank from the mold.

[0087] 3) Drying and sintering treatment: Place the strip-shaped green body in an 80℃ oven to dry until all residual moisture in the green body has evaporated, to avoid cracking or deformation of the green body due to moisture evaporation during sintering. Place the dried green body in a high-temperature furnace for sintering.

[0088] 4) Post-processing: The sintered dense strip-shaped blocks are sanded with sandpaper to make the surface flat and the size regular, so as to meet the sample requirements for subsequent conductivity characterization tests.

[0089] The above description of the present invention provides a LaCo 0.6 Ni 0.4 O 3-δ Applications of negative thermal expansion materials in solid oxide electrolyzers and LaCo 0.6 Ni 0.4 O 3-δ A method for preparing a mixed powder of a high-conductivity positive expansion phase (LCN) and a negative thermal expansion regulating phase (SZM). This invention provides a composite system of "highly conductive positive expansion phase (LCN) + negative thermal expansion regulating phase (SZM)," utilizing the high electronic conductivity of LCN (pure phase conductivity reaches 1159.12 S·cm at 800℃). -1 It is chemically compatible with SOEC electrolyte, ensuring the core conductivity of the current collector; SZM is selected as the negative expansion regulating phase, which maintains orthorhombic stability without phase transition in the range of 30~900℃, and exhibits significant negative thermal expansion characteristics after 400℃ (macroscopic contraction after 710℃), which can accurately compensate for the positive expansion of LCN and solve the problem of thermal expansion mismatch.

[0090] The composite powder system composed of LCN and SZM provided by this invention is particularly useful in the air electrode electron current collector of SOEC, serving as a highly conductive phase and a negative thermal expansion regulating phase, respectively, which is more conducive to the use of SOEC in related scenarios such as high-temperature water electrolysis for hydrogen production and CO2 resource utilization.

[0091] The composite powder system provided by this invention can improve the structural stability and lifespan of SOEC. The precise matching of the composite powder and the metal connector avoids interfacial thermal stress during high-temperature preparation (800~1000℃) and start-up / shutdown processes, preventing current collector peeling, cracking, and damage to the air electrode functional layer. It also balances high conductivity and thermal expansion regulation, preserving the core conductive function: at the optimal ratio (LCN:SZM=9:1), the conductivity reaches 750 S·cm⁻¹ at 800℃, exceeding the conductivity threshold of the SOEC current collector, avoiding an increase in ohmic losses due to composite adjustment. By adjusting the SZM dosage, the composite powder TEC can be achieved at 14.8 × 10⁻¹. -6 / ℃~18×10 -6 The temperature range is adjustable to adapt to the TEC requirements of different SOEC modules, offering high flexibility. Simultaneously, the process is mature and easily industrialized, with controllable costs and readily available raw materials and equipment: LCN uses conventional raw materials such as nitrates and PVA, while SZM uses common high-purity powders such as Sm2O3 and ZnO, requiring no special or rare materials; the preparation process uses general-purpose equipment such as ball mills, muffle furnaces, and tablet presses, eliminating customization requirements; the process has strong scalability: the entire process (sol-gel, high-temperature solid phase, ball milling and mixing) uses mature technologies in the materials field, with controllable parameters and high repeatability, allowing for rapid transition from small-batch laboratory preparation to industrial mass production, resulting in significant cost advantages. Furthermore, this invention has advantages over other negative expansion materials; compared to other negative expansion materials such as NdMnO3 (NMO), SZM has a superior adjustment effect: when the mass ratio of LCN:NMO = 8:2, the TEC is still as high as 17.4 × 10⁻⁶. -6 / ℃, which cannot be matched with metal connectors; while SZM only requires 10% doping to reduce TEC to 14.8×10 -6 It has a lower temperature of ℃ and a smaller impact on the conductivity of LCN, resulting in better overall performance.

[0092] To further illustrate the present invention, the following embodiments demonstrate a LaCo method provided by the present invention. 0.6 Ni 0.4 O 3-δ Applications of negative thermal expansion materials in solid oxide electrolyzers and LaCo 0.6 Ni 0.4 O 3-δ The preparation method of the mixed powder of negative thermal expansion material is described in detail. However, it should be understood that these embodiments are implemented under the premise of the technical solution of the present invention. Detailed implementation methods and specific operation processes are given only to further illustrate the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention. The scope of protection of the present invention is not limited to the following embodiments.

[0093] Example

[0094] 1. LaCo0.6 Ni 0.4 O 3-δ Sol-gel synthesis process of (LCN)

[0095] 1) Preparation of 4% polyvinyl alcohol (PVA) aqueous solution

[0096] Polyvinyl alcohol (PVA) of type 1788 was used as a dispersant. PVA was precisely weighed according to a mass ratio of 4:96 to distilled water, with 9.43 g of PVA powder and 230 mL of deionized water respectively. The weighed PVA powder was slowly added to the distilled water while stirring to achieve initial dispersion. The beaker containing the mixture was then sealed with sealing film to prevent concentration fluctuations caused by water evaporation during subsequent heating.

[0097] The sealed mixture system is placed in a constant temperature water bath. First, the water bath temperature is adjusted to 50°C. Under this temperature condition, the mixture is stirred for 3 hours to ensure that the PVA particles can fully swell. After the swelling process is completed, the water bath temperature is raised to 90°C and the stirring is continued until the mixture becomes a completely clear and transparent liquid. At this point, a 4% PVA aqueous solution is obtained and placed in a cool place for later use.

[0098] 2) Preparation of metal ion / PVA sol

[0099] According to LaCo 0.6 Ni 0.4 O 3-δ According to the stoichiometric ratio, accurately weigh 17.62 g of La(NO3)3·6H2O, 7.10 g of Co(NO3)2·6H2O, and 4.74 g of Ni(NO3)2·6H2O, and slowly add them sequentially to the above PVA aqueous solution. Remove the beaker seal and place the system in an 80℃ oil bath environment, stirring at a constant temperature for 10 h. During the process, continue to evaporate water until the system transforms into a uniform, viscous, reddish-brown gel, then stop heating and stirring.

[0100] 3) Preparation and calcination of precursors

[0101] The aforementioned reddish-brown gel was transferred to a clean porcelain boat, and the powder was subjected to X-ray diffraction analysis, as follows: Figure 1 As shown, the spectrum indicates an amorphous phase. The gel powder was then dried in a 100℃ oven for 24 hours to remove residual moisture, yielding a fluffy caramel-colored solid precursor. The caramel-colored precursor was removed and thoroughly ground into a fine powder using a mortar and pestle, then transferred to a corundum crucible. The crucible was placed in a high-temperature muffle furnace at 1100℃ and calcined for 10 hours to complete the phase transformation and impurity removal. After natural cooling to room temperature, the LCN target product powder was obtained. X-ray diffraction analysis of the powder was performed, as shown... Figure 2 As shown, it is a pure phase with good crystallinity and no impurities were observed.

[0102] See Figure 1 , Figure 1 LaCo prepared for embodiments of the present invention 0.6 Ni 0.4 O 3-δ XRD pattern of the sol-gel precursor of (LCN).

[0103] See Figure 2 , Figure 2 LaCo prepared for embodiments of the present invention 0.6 Ni 0.4 O 3-δ XRD pattern of sol-gel precursor of (LCN) after high-temperature sintering.

[0104] 2. Sm 0.85 Zn 0.15 High-temperature solid-state synthesis process of MnO3 (SZM) powder

[0105] 1) Raw material weighing and pretreatment

[0106] 9.74 g of Sm₂O₃, 0.80 g of ZnO, and 5.72 g of MnO₂ powder were weighed using an electronic analytical balance. Before weighing, the raw materials were dried in a 120°C oven for 2 hours to remove adsorbed moisture from the air and prevent powder agglomeration during ball milling.

[0107] 2) High-energy ball milling for refining and homogenization

[0108] The three pretreated raw material powders were loaded into a 50mL agate ball mill jar, and anhydrous ethanol was added as a dispersion medium. The amount of solvent was sufficient to completely submerge the powder (30mL, which can be adjusted flexibly according to the looseness of the powder). To improve grinding efficiency and mixing uniformity, the ball-to-powder mass ratio was set to 10:1 (using 5mm diameter agate grinding balls), and the ball mill speed was adjusted to 600rpm for continuous grinding for 6 hours. This process can refine the raw material particle size to below 1μm and achieve uniform mixing of each component, creating thermodynamic conditions for the full occurrence of subsequent solid-phase reactions.

[0109] 3) Powder drying and tableting

[0110] After ball milling, the solid-liquid suspension in the milling jar was transferred to a beaker and dried in an 80°C oven for 8 hours to ensure complete evaporation of the anhydrous ethanol. The dried loose powder was then gently ground in a mortar to break up any clumps, and then transferred to a tablet press mold. It was pressed at 10 MPa for 30 seconds to form cylindrical blanks with a diameter of 14 mm and a height of 6–8 mm. This molding process significantly improves the powder's bulk density and reduces gas phase channels during sintering, thereby promoting efficient solid-phase diffusion reactions.

[0111] 4) High-temperature sintering and post-processing of products

[0112] The pressed blanks were placed in a corundum crucible, separated by zinc oxide powder to prevent adhesion, and then fed into a high-temperature muffle furnace. The heating program was set to increase the temperature from room temperature to 1100℃ at a rate of 5℃ / min. After reaching the target temperature, the temperature was held for 6 hours to allow Sm, Zn, and Mn to fully react through solid-phase diffusion to form the SZM perovskite structure. After sintering, the heating power was turned off, and the sample was cooled to room temperature with the furnace (cooling rate approximately 2℃ / min) to avoid sudden temperature changes that could cause cracking. Finally, the cooled block sample was ground in an agate mortar and sieved through a 100-mesh standard sieve to obtain uniformly sized SZM target powder.

[0113] 5) Performance Testing

[0114] The synthesized SZM powder was subjected to in-situ temperature-variable X-ray diffraction analysis at temperatures ranging from 30 to 900℃. Figure 3 As shown, no phase transition occurred throughout the entire test temperature range as the temperature increased, maintaining the orthorhombic crystal structure.

[0115] See Figure 3 , Figure 3 Sm prepared for embodiments of the present invention 0.85 Zn 0.15 The XRD pattern of MnO3 (SZM) powder changes with temperature.

[0116] 3. Powder mixing process

[0117] The LCN powder and SZM powder prepared by the aforementioned process were physically mixed according to a preset ratio. Four mass ratio gradients were set: LCN:SZM = 9.5:0.5, 9.0:1.0, 8.5:1.5, and 8.0:2.0. Each group of powders was premixed by manual stirring. The premixed composite powder was transferred to an agate ball mill jar, and anhydrous ethanol was added as a dispersion medium (the amount should be just enough to submerge the powder). Using the parameters of a ball-to-powder mass ratio of 10:1 and 5mm diameter agate grinding balls, the ball mill was started and continuously ground at 400 rpm for 6 hours to achieve deep homogenization of the two powders through mechanical force. After ball milling, the slurry mixture in the jar was transferred to a clean beaker and dried in an 80℃ forced-air oven to constant weight to remove residual ethanol solvent, finally obtaining a uniformly distributed LCN / SZM composite powder.

[0118] Strip-shaped dense block samples were prepared using a combined "dry pressing-high temperature sintering" process. By controlling the pressing pressure and sintering temperature, the dimensional regularity and structural density of the samples were ensured. Based on the total mass of the mixed powder, the amounts of powder and binder (4% PVA aqueous solution by mass) were determined at a ratio of 96:4. During the process, the weighed mixed powder was first poured into an agate mortar, and then the corresponding amounts of PVA aqueous solution were added in batches. Continuous grinding was then carried out for 30 minutes to ensure that the binder uniformly wetted each powder particle, ultimately yielding a well-dispersed powder with excellent molding properties.

[0119] Accurately weigh 3g of the modified mixed powder using an electronic balance and place it into the cavity of a strip-shaped dry-pressing mold. Gently tap and vibrate the mold to evenly spread the powder within the cavity, eliminating density differences caused by uneven local accumulation. Start the tablet press and slowly apply pressure until it reaches 8MPa, maintaining this pressure for 60 seconds to achieve sufficient powder densification, then slowly release the pressure. Using the mold's ejection mechanism, apply a uniform ejection force to smoothly eject the formed strip-shaped preform, avoiding breakage due to uneven force during demolding.

[0120] The demolded strip-shaped green bodies are placed in an 80℃ forced-air drying oven for constant temperature drying until the green body mass is constant. This thoroughly removes residual moisture and prevents internal stress caused by rapid moisture evaporation during subsequent sintering, which could lead to cracking or deformation of the green body. After drying, the green bodies are transferred to a high-temperature sintering furnace and sintered using... Figure 4 The sintering process is carried out using a multi-stage temperature control program. This program achieves the full decomposition and elimination of PVA binder through slow heating in the low-temperature stage, and precisely controls the temperature in the high-temperature stage to inhibit excessive growth of powder particles, ultimately ensuring the morphological integrity and structural stability of the sintered green body.

[0121] See Figure 4 , Figure 4 The sintering curve is obtained using the multi-segment temperature control program used in the embodiments of the present invention.

[0122] After sintering, the strip-shaped blocks are cooled to room temperature in the furnace and then removed. Their surfaces are then polished step by step using metallographic sandpaper. During the polishing process, the polishing force must be controlled to ensure that the sample surface is flat, smooth, and free of scratches. At the same time, the sample size is calibrated to the test standard range so that the sample meets the requirements for geometric morphology and dimensional accuracy for electrical conductivity and thermal expansion tests, providing a high-quality sample for subsequent characterization.

[0123] 4. Performance Testing

[0124] The electrical conductivity of the composite material was tested using the four-electrode method, and the test results are as follows: Figure 5 As shown, the horizontal axis represents temperature (unit: °C), and the vertical axis represents electrical conductivity (unit: S·cm). -1 The figure contains curves for six different samples: the pure-phase LCN exhibits the highest conductivity, at 1159.12 S·cm at 800℃. -1 The electrical conductivity of the composite material decreases with increasing composite ratio. Furthermore, the electrical conductivity of pure-phase SZM material is significantly lower than that of LCN, reaching only 40 S·cm over the specified temperature range. -1 The conductivity of LCN / SZM composite materials gradually decreases with increasing doping concentration, reaching 750 S·cm at 5% doping. -1 The conductivity is around 80 S·cm, while when LCN:SZM=8:2, the conductivity is only 80 S·cm. -1 about.

[0125] See Figure 5 , Figure 5 The electrical conductivity of the LCN / SZM composite material prepared in the embodiments of the present invention changes with temperature.

[0126] See Figure 6 , Figure 6 The thermal expansion properties of the SZM prepared in this embodiment of the invention vary with temperature.

[0127] Depend on Figure 6 The thermal expansion curves of pure phase SZM in the range of room temperature to 1000℃ show that the thermal expansion curve of SZM reverses at around 400℃, changing from the conventional thermal expansion characteristics to negative thermal expansion, that is, thermal contraction occurs. At around 710℃, the thermal expansion change value of the SZM sample drops to zero, and then the sample undergoes macroscopic contraction, indicating the application prospects of this type of material in thermal expansion sensitive fields.

[0128] Meanwhile, the LSC / SZM composite material also exhibited the expected thermal expansion mitigation effect. With an LCN:SZM ratio of 9:1, the average coefficient of thermal expansion (TEC) of the composite material in the range of room temperature to 900℃ was successfully reduced to 14.8 × 10⁻⁶. -6 / ℃. This value is similar to that of the commonly used metal connector Crofer22APU (13×10). -6 / ℃), Haynes 230 (15×10 -6 The values ​​( / ℃) are close to those of the values ​​of the two points.

[0129] See Figure 7 , Figure 7 The thermal expansion coefficient of LCN / SZM prepared for the embodiments of the present invention varies with temperature.

[0130] Considering both thermal expansion and conductivity, LCN:SZM = 9:1 exhibits lower thermal expansion behavior, meeting the requirements of both thermal expansion regulation and high conductivity solid oxide electrolytic cell air electrode current collector powder.

[0131] Comparative Example 1

[0132] The negative thermal expansion powder was replaced with NdMnO3 (NMO), while the same LCN was still used as the main powder. After different proportions of doping and mixing, the electrical conductivity and thermal expansion behavior were compared.

[0133] 1. Solid-state synthesis of NdMnO3

[0134] 1) Raw material weighing and pretreatment

[0135] 6.9 g of Nd₂O₃ and 3.6 g of MnO₂ powder were weighed using an electronic analytical balance. Before weighing, the raw materials were dried in a 120°C oven for 2 hours to remove adsorbed moisture from the air and prevent powder agglomeration during ball milling.

[0136] 2) High-energy ball milling for refining and homogenization

[0137] The two pretreated raw material powders were placed together into a 50mL agate ball mill jar, and anhydrous ethanol was added as a dispersion medium. The amount of solvent was sufficient to completely submerge the powder (30mL, which can be adjusted flexibly according to the looseness of the powder). To improve grinding efficiency and mixing uniformity, the ball-to-powder mass ratio was set to 10:1 (using 5mm diameter agate grinding balls), and the ball mill speed was adjusted to 600rpm for continuous grinding for 6 hours. This process can refine the raw material particle size to below 1μm and achieve uniform mixing of all components, creating thermodynamic conditions for the full occurrence of subsequent solid-phase reactions.

[0138] 3) Powder drying and tableting

[0139] After ball milling, the solid-liquid suspension in the milling jar was transferred to a beaker and dried in an 80°C oven for 8 hours to ensure complete evaporation of the anhydrous ethanol. The dried loose powder was then gently ground in a mortar to break up any clumps, and then transferred to a tablet press mold. It was pressed at 10 MPa for 30 seconds to form cylindrical blanks with a diameter of 14 mm and a height of 6–8 mm. This molding process significantly improves the powder's bulk density and reduces gas phase channels during sintering, thereby promoting efficient solid-phase diffusion reactions.

[0140] 4) High-temperature sintering and post-processing of products

[0141] The pressed green body was placed in a corundum crucible and then fed into a high-temperature muffle furnace. The heating program was set to increase the temperature from room temperature to 1200°C at a rate of 5°C / min. After reaching the target temperature, it was held for 10 hours to allow for complete reaction and NMO formation through solid-phase diffusion. After sintering, the heating power was turned off, and the sample was cooled to room temperature with the furnace (cooling rate approximately 2°C / min). Finally, the cooled block sample was ground in an agate mortar and sieved through a 100-mesh standard sieve to obtain uniformly sized target powder.

[0142] 2. Powder mixing and performance testing

[0143] The synthesized NMO powder and LCN powder were mixed at mass ratios of 9:1 and 8:2 (LCN:NMO = 8:1 and 8:2 respectively). The premixed composite powder was transferred to an agate ball mill jar, and anhydrous ethanol was added as a dispersion medium (the amount should just cover the powder). Using a ball-to-powder mass ratio of 10:1 and 5mm diameter agate grinding balls, the ball mill was started and continuously ground at 400 rpm for 6 hours to achieve deep homogenization of the two powders through mechanical force. After ball milling, the slurry mixture in the jar was transferred to a clean beaker and dried in an 80℃ forced-air oven to constant weight to remove residual ethanol solvent, finally obtaining a composite powder with uniform component distribution, providing high-quality raw materials for subsequent molding and sintering processes.

[0144] Strip-shaped dense bulk samples were prepared using a combined "dry pressing-high temperature sintering" process. Precise control of the molding pressure and sintering regime ensured the dimensional regularity and structural density of the samples. Based on the total mass of the mixed powder, the ratio of powder to binder (4% PVA aqueous solution by mass) was determined to be 96:4. 3g of the modified mixed powder was weighed and placed into the mold cavity of the strip-shaped dry pressing mold. The mold was gently tapped and vibrated to ensure uniform powder distribution within the cavity, eliminating density differences caused by uneven local accumulation. The tablet press was started and pressure was slowly applied until it reached 8MPa. This pressure was maintained for 60 seconds to achieve sufficient powder densification, followed by slow pressure release. Using the mold's ejector plate, a uniform ejection force was applied to smoothly eject the formed strip-shaped blank, preventing breakage due to uneven force during demolding.

[0145] The demolded strip-shaped green bodies are placed in an 80℃ forced-air drying oven for constant temperature drying until the green body mass is constant. This thoroughly removes residual moisture and prevents internal stress caused by rapid moisture evaporation during subsequent sintering, which could lead to cracking or deformation of the green body. After drying, the green bodies are transferred to a high-temperature sintering furnace for sintering using a multi-stage temperature control program. The sintering curve is consistent with... Figure 4 Consistent. After sintering, surface treatment is performed to remove surface stains and unevenness. The thermal expansion coefficient of the strip sample is tested, and the test results are as follows. Figure 8 As shown.

[0146] See Figure 8 , Figure 8 The thermal expansion coefficient of LCN / NMO prepared in Comparative Example 1 of this invention varies with temperature.

[0147] The results show that when LCN:NMO = 8:2, the coefficient of thermal expansion is 17.4 × 10⁻⁶. -6 Although the thermal expansion behavior is somewhat mitigated at ℃, it is still far higher than the thermal expansion value of the metal connector. Prolonged high-temperature operation will lead to interface delamination, which is detrimental to the stability of the interface.

[0148] The foregoing provides a detailed description of the electrode current collector powder for solid oxide electrolytic cells that combines thermal expansion regulation and high conductivity, as well as its preparation method. Specific examples have been used to illustrate the principles and implementation methods of the invention. The descriptions of these embodiments are merely illustrative of the method and core ideas of the invention, including the best mode, and are intended to enable any person skilled in the art to practice the invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. LaCo 0.6 Ni 0.4 O 3-δ Application of negative thermal expansion materials in solid oxide electrolytic cells.

2. The application according to claim 1, characterized in that, The LaCo 0.6 Ni 0.4 O 3-δ and negative thermal expansion materials including LaCo 0.6 Ni 0.4 O 3-δ Mixed powder of materials with negative thermal expansion; The solid oxide electrolytic cell includes an air electrode electron current collector layer.

3. The application according to claim 1, characterized in that, The LaCo 0.6 Ni 0.4 O 3-δ The mass ratio of the material with negative thermal expansion is (9.5~5):(0.5~5).

4. The application according to claim 1, characterized in that, The negative thermal expansion material includes Sm 0.85 Zn 0.15 MnO3, ZrW2O8, Y2W3O 12 One or more of NdMnO3.

5. The application according to claim 1, characterized in that, The LaCo 0.6 Ni 0.4 O 3-δ The negative thermal expansion material is specifically a composite system of a highly conductive positive expansion phase and a negative thermal expansion regulating phase; The applications include reducing interfacial thermal stress in solid oxide electrolytic cells.

6. A LaCo in any of the applications described in claims 2 to 5 0.6 Ni 0.4 O 3-δ A method for preparing a mixed powder of a material with negative thermal expansion, characterized in that, Includes the following steps: 1) After premixing LCN powder and negative thermal expansion material powder, a premixed powder is obtained; 2) Place the premixed powder and dispersion medium obtained in the above steps into a ball mill for ball milling, and after drying, obtain a mixed powder.

7. The preparation method according to claim 6, characterized in that, The LCN powder includes LCN powder synthesized by the sol-gel method; The negative thermal expansion material powder includes negative thermal expansion material powder synthesized at high temperature solid phase.

8. The preparation method according to claim 6, characterized in that, The dispersion medium includes ethanol; The ball milling time is 4 to 10 hours.

9. The preparation method according to claim 6, characterized in that, The ball-to-material ratio of the ball mill is (5~20):1; The ball mill rotates at a speed of 300-600 rpm.

10. The preparation method according to claim 6, characterized in that, The particle size of the mixed powder is 0.2~1μm.

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