Cr-poisoning-resistant composite current collecting layer for solid oxide fuel cell and preparation method and application of Cr-poisoning-resistant composite current collecting layer

Abstract

The invention belongs to the technical field of electrochemical materials, and particularly relates to an anti-Cr poisoning composite current collecting layer for a solid oxide fuel cell as well as a preparation method and application of the anti-Cr poisoning composite current collecting layer. The Cr poisoning resistant composite current collecting layer is a composite current collecting layer constructed by adopting two perovskite materials LCN and LSCN, and the problem of cathode failure caused by volatilization of metal connector Cr is successfully solved by combining the physical barrier characteristic of strontium-free LCN and the chemical capture characteristic of strontium-containing LSCN. The invention aims at an SOFC system using an iron-based alloy as a connector, and aims at solving the technical problem that the catalytic activity of a cathode is attenuated due to chromium species volatilized by a metal connector in a high-temperature oxygen-enriched environment, so that the long-term operation stability of a cell stack is remarkably improved, and the service life of the cell stack is remarkably prolonged. According to the invention, through specific material combination and layered structure design, the contradiction that a single current collecting layer is difficult to give consideration to Cr volatilization blocking and low contact resistance maintaining is solved, and the polarization impedance growth rate of the cell is significantly reduced.

Description

Technical Field

[0001] This invention belongs to the technical field of electrochemical materials, specifically relating to a Cr-resistant composite current collector for solid oxide fuel cells, its preparation method, and its application. Background Technology

[0002] Among numerous new energy technologies, fuel cells, as a device that directly converts the chemical energy in fuel into electrical energy through electrochemical reactions, have significant advantages such as high energy conversion efficiency, environmental friendliness, and strong modularity because they are not limited by the efficiency of Carnot cycle heat engines.

[0003] Solid oxide fuel cells (SOFCs), as a third-generation fuel cell technology, employ an all-solid-state ceramic structure, avoiding the corrosion and leakage problems associated with liquid electrolytes. SOFCs typically operate at high temperatures ranging from 600°C to 1000°C, giving them exceptional fuel flexibility and high-quality waste heat utilization value. Therefore, SOFCs are widely recognized as a promising green power generation technology, with broad applications in stationary power plants, distributed combined heat and power systems, transportation auxiliary power, and military power.

[0004] The output voltage of a single SOFC cell is typically only around 1V, which cannot meet the high voltage and high power requirements of practical applications. Therefore, in practical applications, multiple single cells are usually assembled into a battery stack by connecting them in series using "connectors". The main functions of the connectors include: physically connecting the anode and cathode of adjacent single cells, collecting and conducting current, and spatially separating the fuel gas on the anode side from the oxidant gas on the cathode side.

[0005] As SOFC technology moves towards medium-temperature operating ranges (600-800℃), traditional ceramic connectors are gradually being replaced by metal connectors due to their difficult processing, high cost, and brittleness. Iron-based alloys have become the mainstream material for IT-SOFC connectors because of their excellent electronic conductivity, good thermal conductivity, lower raw material costs, and mature processing technology. To protect the substrate from rapid oxidation and corrosion in high-temperature oxidizing atmospheres, these alloys must contain sufficient chromium to form a dense chromium oxide protective film on the surface. However, it is precisely this Cr2O3 protective film that triggers one of the most challenging failure mechanisms in SOFC technology—cathode Cr poisoning.

[0006] To suppress Cr volatilization and poisoning, the current mainstream strategy is to prepare conductive ceramic coatings on the surface of metal interconnects. Common coating materials include spinel and perovskite. While spinel coatings can effectively reduce Cr volatilization, their coefficient of thermal expansion is not well matched with some interconnects, making them prone to detachment during long-term thermal cycling, and their preparation process is costly. Perovskite coatings, on the other hand, offer higher conductivity. However, single-component perovskite coatings face a dilemma: if they contain Sr, although they have good conductivity, they are prone to reacting with Cr to form a high-resistivity layer; if they do not contain Sr, they may have a high contact resistance with the cathode and cannot actively adsorb the trace amounts of volatilized Cr.

[0007] Therefore, developing a low-cost composite current collector that combines high conductivity, excellent barrier capability, and the ability to actively capture Cr species is the key to solving the problem of Cr poisoning in SOFC cathodes. Summary of the Invention

[0008] To address the aforementioned problems, the present invention aims to provide a Cr-resistant composite current collector for solid oxide fuel cells, its preparation method, and its application.

[0009] The technical content of this invention is as follows:

[0010] The present invention provides a Cr poisoning resistant composite current collector for solid oxide fuel cells. The composite current collector is disposed between the cathode and the metal connector of the solid oxide fuel cell, and is intended to block the volatilization of chromium in the metal connector and its diffusion to the cathode side.

[0011] The composite current collector layer comprises at least two layers of conductive ceramic material with a perovskite structure.

[0012] The conductive ceramic material with a perovskite structure includes LCN material or LSCN material;

[0013] The general chemical formula of the LCN material is LaCo. 1-x Ni x O 3-δ LaCo is preferred. 0.6 Ni 0.4 O 3-δ It is a strontium-free perovskite oxide. Since it does not contain the alkaline earth metal Sr, it does not produce surface Sr segregation at high temperatures, thus exhibiting strong chemical inertness to Cr. Meanwhile, the B-site doping of Ni and Co endows it with extremely high electronic conductivity. In the composite layer, LCN mainly undertakes the function of connecting and conducting electricity with the metal interconnect, and provides a certain physical barrier to the Cr volatilized from the metal interconnect.

[0014] The general chemical formula of the LSCN material is La. 1-y Sr y Co1-z Ni z O 3-δ La is preferred. 0.8 Sr 0.2 Co 0.6 Ni 0.4 O 3-δ The invention introduces an appropriate amount of Sr doping into the LCN layer material. Although the introduction of Sr is traditionally considered to be the cause of Cr poisoning, it is cleverly used as a "Cr trap" in the design of this invention. The LSCN layer located in the inner layer (cathode surface) uses the Sr component on its surface to actively react with the volatilized Cr gas to fix Cr in the current collector structure, thereby sacrificing its own surface to protect the deep cathode active sites.

[0015] The above x, y, and z are 0.3≤x≤0.5, 0.1≤y≤0.3, and 0.3≤z≤0.5, respectively.

[0016] The present invention also provides a method for preparing the above-mentioned Cr-resistant composite current collector for solid oxide fuel cells, comprising the following steps:

[0017] 1) Preparation of flow layer powder material: Hydrated metal nitrates are dissolved in sol aqueous solution and heated to evaporate water, increase solution viscosity, and gradually change color from pink to dark purple to obtain a viscoelastic gel precursor. The gel precursor is dried and ground into powder, and the powder is sintered at high temperature to obtain pure phase perovskite powder.

[0018] The sol-water solution includes a PVA aqueous solution, which is prepared by adding PVA particles to deionized water and heating to dissolve them to obtain a PVA aqueous solution with a mass fraction of 2-10%. As a sol carrier, PVA not only acts as a dispersant to prevent metal ion aggregation, but the hydroxyl groups on its molecular chain can also complex with metal ions to achieve uniform mixing at the atomic scale.

[0019] The ratio of the total molar number of metal ions after the hydrated metal nitrate is dissolved in the sol aqueous solution to the molar number of PVA monomer units is approximately 1:(1~5).

[0020] The pure phase perovskite powder includes LCN or LSCN powder;

[0021] In the preparation of the LCN powder, the hydrated metal nitrates used include La(NO3)3·6H2O, Co(NO3)2·6H2O, and Ni(NO3)2·6H2O, and their mixing ratio is based on the stoichiometric ratio La:Co:Ni=1:(1-x):x, where 0.3≤x≤0.5. The resulting LCN has the general chemical formula LaCo. 1-x Ni x O 3-δ ;

[0022] Preferably, the hydrated metal nitrates in the LCN powder are mixed according to a stoichiometric ratio of La:Co:Ni = 1:0.6:0.4, which is LaCo 0.6 Ni 0.4 O 3-δ ;

[0023] In the preparation of the LSCN powder, the hydrated metal nitrates used include La(NO3)3·6H2O, Sr(NO3)2, Co(NO3)2·6H2O, and Ni(NO3)2·6H2O. Their mixing ratio is based on the stoichiometric ratio La:Sr:Co:Ni = (1-y):y:(1-z):z, where 0.1≤y≤0.3 and 0.3≤z≤0.5. The resulting LSCN has the general chemical formula La. 1-y Sr y Co 1-z Ni z O 3-δ ;

[0024] Preferably, the hydrated metal nitrates in the LSCN powder are mixed according to a stoichiometric ratio of La:Sr:Co:Ni = 0.8:0.2:0.6:0.4, which is La 0.8 Sr 0.2 Co 0.6 Ni 0.4 O 3-δ ;

[0025] The high-temperature calcination is carried out at a temperature of 500~800℃ for 3~5 hours.

[0026] Powder sintered at high temperature has high sintering activity, which is conducive to the formation of dense coatings at lower temperatures;

[0027] 2) Preparation of Cr poisoning resistant composite current collector: First, a layer of LSCN slurry is coated on the cathode surface of a solid oxide fuel cell and dried. Then, a layer of LCN slurry is coated and dried to form a double ceramic layer with good interfacial bonding, thus obtaining the Cr poisoning resistant composite current collector.

[0028] The LSCN slurry or LCN slurry is prepared by mixing LSCN powder or LCN powder with an organic binder, respectively, and its solid content is 30~60 wt%.

[0029] The organic binder includes an ethyl cellulose terpineol solution or an aqueous solution of polyvinyl alcohol;

[0030] The thickness of the coating layer is controlled between 10 and 50 μm.

[0031] The coating process includes screen printing, spraying, or manual brushing.

[0032] In the Cr poisoning-resistant composite current collector, the LCN layer is the outer layer (in direct contact with the metal connector), which has certain gaps for gas transport and physically blocks gaseous Cr emitted from the metal connector. At the same time, since the LCN does not contain Sr, it will not undergo harmful solid-phase reactions with the metal connector, ensuring a good electron transport channel at the interface. The LSCN layer is the inner layer (in direct contact with the cathode material). When the Cr oxide film on the surface of the connector releases gaseous CrO2(OH)2, the LSCN layer captures it through chemical adsorption, generating SrCrO4 deposits. Although this increases the local resistance of the layer, it prevents gaseous Cr from diffusing to the cathode.

[0033] This invention also provides the application of the above-mentioned Cr-resistant composite current collector in the preparation of solid oxide fuel cells;

[0034] The solid oxide fuel cell is composed of a structure consisting of a half cell, an LSCN layer, an LCN layer, and a metal connector in sequence.

[0035] The half-cell includes an electrolyte and a cathode, with the cathode linked to an LSCN layer;

[0036] The cathode material includes La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) and Gd 0.1 Ce 0.9 O 1.95 A complex composed of (GDC);

[0037] The electrolyte material includes Gd 0.1 Ce 0.9 O 1.95 (GDC) or yttrium-stabilized zirconium oxide (YSZ);

[0038] The material of the metal connector includes Fe-Cr based ferritic stainless steel.

[0039] The present invention also provides a La 0.8 Sr 0.2 Co 0.6 Ni 0.4 O 3-δ The material is used as a cathode Cr scavenger. It is placed on the surface of the LSCF-GDC cathode material. The SrO segregated phase on its surface reacts with volatile CrO2(OH)2 or CrO3 to generate SrCrO4, thereby protecting the cathode from poisoning by gaseous Cr.

[0040] The beneficial effects of this invention are as follows:

[0041] This invention relates to a Cr-poisoning-resistant composite current collector for solid oxide fuel cells (SOFCs). The current collector is constructed using two perovskite materials: LCN (as the outer layer) and LSCN (as the inner layer). These materials have complementary properties. By combining the interface-friendly characteristics of strontium-free LCN with the metal interconnect with the chemical capture properties of strontium-containing LSCN for gaseous Cr, the problem of cathode failure caused by Cr volatilization from the metal interconnect is successfully solved. Experimental results show that this composite coating can reduce the polarization decay rate of the battery to about 10% of that in the unprotected state, while maintaining extremely low ohmic contact resistance. This invention is specifically designed for SOFC systems using iron-based alloys as interconnects, aiming to solve the technical challenge of chromium species volatilized from the metal interconnect causing cathode catalytic activity decay under high-temperature, oxygen-rich environments, thereby significantly improving the long-term operational stability and lifespan of the fuel cell stack. This invention, through specific material combinations and layered structure design, resolves the contradiction between blocking Cr volatilization and maintaining low contact resistance in a single current collector, significantly reducing the rate of increase in polarization impedance of the battery.

[0042] This invention employs a low-cost sol-gel method to synthesize powders combined with a coating process. The process is simple, easily scaled up for industrial use, and requires no expensive vacuum coating equipment; conventional screen printing and muffle furnace sintering are sufficient for preparation, making it suitable for large-scale industrial production. This invention is significant for advancing the commercialization of intermediate-temperature solid oxide fuel cells, particularly for stack systems using inexpensive stainless steel interconnects. This current collector layer can significantly extend its lifespan and reduce total lifespan costs. Future work could further optimize the thickness ratio of each sublayer or explore the application of this coating technology in the fabrication of metal-supported SOFCs. Attached Figure Description

[0043] Figure 1 XRD pattern of LCN powder;

[0044] Figure 2 To compare the ohmic impedance (R) of the current collector assembly and the composite current collector assembly of the present invention during heat preservation at 700°C for 50 hours. Ω A comparison chart of trends over time;

[0045] Figure 3 To compare the current collector array and the composite current collector array of the present invention, the polarization resistance (R) during the heat treatment at 700°C for 50 hours is measured. p A comparison chart of trends over time. Detailed Implementation

[0046] The present invention will be further described in detail below through specific implementation examples and accompanying drawings. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of protection of the present invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art fall within the scope of the appended claims.

[0047] Unless otherwise specified, all raw materials and reagents used in this invention are from the conventional market.

[0048] Example 1

[0049] Synthesis of Powder Materials for Heating Layer

[0050] 1. LaCo 0.6 Ni 0.4 O 3-δ Preparation of (LCN) powder

[0051] 1) Sol preparation: Weigh an appropriate amount of PVA particles and add them to deionized water. Heat to 95°C and stir at a constant temperature until the PVA is completely dissolved. Prepare a 5% PVA aqueous solution as a carrier.

[0052] 2) Metal ion complexation: Accurately weigh La(NO3)3·6H2O, Co(NO3)2·6H2O, and Ni(NO3)2·6H2O according to the stoichiometric ratio La:Co:Ni = 1:0.6:0.4. Dissolve the weighed nitrates in the above PVA solution. The ratio of the total moles of metal ions to the moles of PVA monomer units is approximately 1:2.

[0053] 3) Gelation: The mixed solution is placed in an 80℃ oil bath and stirred continuously. As water evaporates, the viscosity of the solution increases, and the color gradually changes from pink to dark purple, eventually forming a viscoelastic gel;

[0054] 4) Precursor drying and decomposition: The gel was placed in a forced-air drying oven and dried at 180°C for 12 hours to obtain a dry gel. The dry gel was then ground into powder.

[0055] 5) High-temperature synthesis: The precursor powder was placed in a high-temperature sintering furnace and heated to 800°C at a heating rate of 5°C / min under air atmosphere, and held at that temperature for 3 hours. During this process, the PVA framework combusts and decomposes, and the metal oxide crystallizes to form a perovskite structure. After natural cooling, it was ground to obtain black LCN ultrafine powder;

[0056] 6) Phase characterization: XRD analysis ( Figure 1 The results showed that the synthesized LCN powder had sharp diffraction peaks that matched the standard card, and no impurity phase peaks, proving the effectiveness of the sol-gel method.

[0057] 2. La 0.8Sr 0.2 Co 0.6 Ni 0.4 O 3-δ Preparation of (LSCN) powder

[0058] The preparation steps are the same as above, except that strontium nitrate (Sr(NO3)2)2 is added to the raw materials in step 2), and the molar ratio of metal ions is adjusted to La:Sr:Co:Ni = 0.8:0.2:0.6:0.4. Pure-phase LSCN powder is obtained by calcination at 800℃ for 3 hours.

[0059] Example 2

[0060] Synthesis of Powder Materials for Heating Layer

[0061] 1. LaCo 0.7 Ni 0.3 O 3-δ Preparation of (LCN) powder

[0062] 1) Sol preparation: Weigh an appropriate amount of PVA particles and add them to deionized water. Heat to 95°C and stir at a constant temperature until the PVA is completely dissolved. Prepare an 8% PVA aqueous solution as a carrier.

[0063] 2) Metal ion complexation: Accurately weigh La(NO3)3·6H2O, Co(NO3)2·6H2O, and Ni(NO3)2·6H2O according to the stoichiometric ratio La:Co:Ni = 1:0.7:0.3. Dissolve the weighed nitrates in the above PVA solution. The ratio of the total molar number of metal ions to the molar number of PVA monomer units is approximately 1:3.

[0064] 3) Gelation: The mixed solution is placed in an 80℃ oil bath and stirred continuously. As water evaporates, the viscosity of the solution increases, and the color gradually changes from pink to dark purple, eventually forming a viscoelastic gel;

[0065] 4) Precursor drying and decomposition: The gel was placed in a forced-air drying oven and dried at 180°C for 12 hours to obtain a dry gel. The dry gel was then ground into powder.

[0066] 5) High-temperature synthesis: The precursor powder was placed in a high-temperature sintering furnace and heated to 600°C at a heating rate of 5°C / min under air atmosphere, and held at that temperature for 4 hours. During this process, the PVA framework combusts and decomposes, and the metal oxide crystallizes to form a perovskite structure. After natural cooling, it was ground to obtain black LCN ultrafine powder.

[0067] 2. La 0.7 Sr 0.3 Co 0.5 Ni 0.5 O 3-δPreparation of (LSCN) powder

[0068] The preparation steps are the same as above, except that strontium nitrate (Sr(NO3)2)2 is added to the raw materials in step 2), and the molar ratio of metal ions is adjusted to La:Sr:Co:Ni = 0.7:0.3:0.5:0.5. Pure-phase LSCN powder is obtained by calcination at 600℃ for 4 hours.

[0069] Example 3

[0070] Synthesis of Powder Materials for Heating Layer

[0071] 1. LaCo 0.5 Ni 0.5 O 3-δ Preparation of (LCN) powder

[0072] 1) Sol preparation: Weigh an appropriate amount of PVA particles and add them to deionized water. Heat to 95°C and stir at a constant temperature until the PVA is completely dissolved. Prepare a 10% PVA aqueous solution as a carrier.

[0073] 2) Metal ion complexation: Accurately weigh La(NO3)3·6H2O, Co(NO3)2·6H2O, and Ni(NO3)2·6H2O according to the stoichiometric ratio La:Co:Ni = 1:0.5:0.5. Dissolve the weighed nitrates in the above PVA solution. The ratio of the total molar number of metal ions to the molar number of PVA monomer units is approximately 1:5.

[0074] 3) Gelation: The mixed solution is placed in an 80℃ oil bath and stirred continuously. As water evaporates, the viscosity of the solution increases, and the color gradually changes from pink to dark purple, eventually forming a viscoelastic gel;

[0075] 4) Precursor drying and decomposition: The gel was placed in a forced-air drying oven and dried at 180°C for 12 hours to obtain a dry gel. The dry gel was then ground into powder.

[0076] 5) High-temperature synthesis: The precursor powder was placed in a high-temperature sintering furnace and heated to 500°C at a heating rate of 5°C / min under air atmosphere, and held at that temperature for 5 hours. During this process, the PVA framework combusts and decomposes, and the metal oxide crystallizes to form a perovskite structure. After natural cooling, it was ground to obtain black LCN ultrafine powder.

[0077] 2. La 0.9 Sr 0.1 Co 0.7 Ni 0.3 O 3-δ Preparation of (LSCN) powder

[0078] The preparation steps are the same as above, except that strontium nitrate (Sr(NO3)2)2 is added to the raw materials in step 2), and the molar ratio of metal ions is adjusted to La:Sr:Co:Ni = 0.9:0.1:0.7:0.3. Pure-phase LSCN powder is obtained by calcination at 500℃ for 5 hours.

[0079] Example 4

[0080] Preparation of solid oxide fuel cell

[0081] 1) Preparation of electrolyte tablets: Weigh 2.5g GDC (Gd) 0.1 Ce 0.9 O 1.95 The powder was mixed with 5wt% PVA solution as a binder, ground evenly, and then placed into a 20mm diameter stainless steel mold and pressed into a green blank under a pressure of 20MPa. After demolding, the green blank was sintered at 1550℃ for 6 hours to obtain a GDC electrolyte sheet with a density >98% and a thickness of about 500μm.

[0082] 2) Cathode preparation: LSCF (La) 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ Powder and GDC (Gd) 0.1 Ce 0.9 O 1.95 The powders were mixed in a 1:1 mass ratio, and a terpineol solution containing 10 wt% ethyl cellulose was added. The mixture was then ground in an agate mortar for 1 hour to form a cathode slurry with good thixotropic properties.

[0083] The paste was applied evenly to the central area of ​​the electrolyte sheet using a manual coating method (effective area 0.5 cm²). 2 After coating, the cathode is dried at 80°C and then sintered at 1000°C for 2 hours to form a porous LSCF-GDC composite cathode layer with a cathode thickness controlled at approximately 30-50 μm.

[0084] 3) Preparation of the counter electrode: Silver paste is coated on the other side of the electrolyte sheet to serve as the counter electrode and reference electrode of the test circuit.

[0085] Example 5

[0086] Coating and assembly of Cr poisoning accumulator

[0087] First, a layer of LSCN paste is coated on the surface of the LSCF cathode. After drying at 80°C, a layer of LCN paste is then coated.

[0088] Coating process: The LCN or LSCN powder prepared in Example 1 was mixed with terpineol binder to form a slurry. The thickness of a single coating layer was controlled at approximately 20-30 μm. After coating, the half-cell and Fe-Cr alloy connector were pressed together, placed in a ceramic fixture, and then placed in a tube furnace for testing. During the test, as the temperature rose to the operating temperature of 700°C, the current collector slurry sintered in situ to form a porous contact layer.

[0089] To systematically evaluate the effectiveness of different flow layers, the following comparative example was designed:

[0090] Comparative Example 1 (without a flow layer)

[0091] The performance of the Fe-Cr alloy connector in contact with the LSCF cathode was directly tested.

[0092] Comparative Example 2 (LCN+LCN)

[0093] Two layers of LCN paste were coated on the sintered LSCF cathode surface.

[0094] Comparative Example 3 (LSCN+LSCN)

[0095] Two layers of LSCN paste were coated on the sintered LSCF cathode surface.

[0096] Performance testing and in-depth analysis of results

[0097] Four sets of half-cells (Comparative Example 1, Comparative Example 2, Comparative Example 3, and Example 5) were subjected to isothermal aging tests at 700°C in air for 50 hours. During this period, AC impedance spectroscopy was performed every 5 hours using an electrochemical workstation. Under open-circuit conditions, the frequency range was 0.1Hz-100kHz, and the signal amplitude was 10mV.

[0098] By analyzing the Nyquist plot, the high-frequency intercept is extracted as the ohmic impedance (R0). Ω , Ω⋅cm 2 The difference between the high and low frequency intercepts is used as the polarization impedance (R). p , Ω⋅cm 2 ).

[0099] Table 1. Comparison of impedance data of each group of half-cells before and after 50-hour aging test.

[0100]

[0101] Based on Table 1 Figure 2 , Figure 3 visible:

[0102] Compared to the failure of the half-cell without a current collector layer in Comparative Example 1, the initial performance was acceptable, but within 50 hours, R... pIt increased by 7.5 times. This directly confirms the severity of Cr poisoning. Ω The increase (approximately 1.36 Ω·cm) 2 The main cause is the oxide scale formed on the surface of the connector and the low-conductivity SrCrO4 layer formed at the interface. The huge increase in polarization impedance indicates that the three-phase interface of the cathode has been severely blocked by Cr deposits, and the oxygen reduction catalytic activity has been completely lost.

[0103] In Comparative Example 2, although R Ω The increase was small (5.02%), indicating that the LCN, as a physical barrier layer, effectively prevented the deterioration of the interface resistance. However, R p The growth rate was still 109%, indicating that physical barriers alone cannot completely prevent gaseous Cr molecules from passing through the coating pores and reaching the cathode surface.

[0104] In Comparative Example 3, its initial R Ω The lower R is attributed to the better sintering activity and conductivity of Sr-containing perovskites. p The growth rate (182%) was higher than that of the LCN group. This may be because although LSCN adsorbs Cr, the products generated by its own reaction deposit between the metal and the current collector after a long period of time, causing R to... Ω This increases. The limitations of a single flow layer are evident.

[0105] The LCN+LSCN structure used in Embodiment 5 of this invention exhibits the best overall performance: lowest initial resistance: initial R Ω Only 2.91 Ω·cm 2 The polarization resistance was significantly lower than other groups, likely due to better contact between the LCN layer and the metal interconnect, and the absence of high-resistivity phase formation caused by Cr deposition at the interface. It exhibited the strongest resistance to poisoning: after 50 hours, the polarization resistance increased by only approximately 0.55 Ω·cm. 2 (Growth rate of 75%), only 1 / 8 of the increase without a current collector layer, proves that the composite layer not only blocks Cr but also maintains extremely stable electrical contact. It is evident that the combined effect of LCN+LSCN is superior to the simple superposition of single components. The stable contact interface between the outer LCN and the metal interconnect facilitates current transmission, while the inner LSCN has excellent Cr capture properties, thus protecting the cathode from Cr poisoning. The two achieve functional decoupling and complementarity, strongly demonstrating the effectiveness of the dual mechanism of "LCN conduction + LSCN capture." The LCN layer is in direct contact with the metal interconnect; while the inner LSCN layer chemically adsorbs gaseous Cr, and the generated SrCrO4 remains between the current collector LCN and LSCN, having minimal impact on the conductivity of the current collector layer. The current collector layer continuously provides protection and an electron channel for the cathode.

Claims

1. A Cr-resistant composite current collector for solid oxide fuel cells, characterized in that, The composite current collector layer comprises at least two layers of conductive ceramic material with a perovskite structure. The conductive ceramic material with a perovskite structure includes LCN material or LSCN material; The general chemical formula of the LCN material is LaCo. 1-x Ni x O 3-δ Where 0.3≤x≤0.5; The general chemical formula of the LSCN material is La. 1-y Sr y Co 1-z Ni z O 3-δ , where 0.1≤y≤0.3 and 0.3≤z≤0.

5.

2. A method for preparing a Cr-poison-resistant composite current collector for a solid oxide fuel cell as described in claim 1, characterized in that, Includes the following steps: 1) Preparation of current collector layer powder material: Hydrated metal nitrates are dissolved in sol aqueous solution and heated. The color gradually changes from pink to dark purple to obtain a viscoelastic gel precursor. The gel precursor is dried and ground into powder. The powder is sintered at high temperature to obtain pure phase perovskite powder. The pure phase perovskite powder includes LCN or LSCN powder; In the preparation of the LCN powder, the hydrated metal nitrates used include La(NO3)3·6H2O, Co(NO3)2·6H2O, and Ni(NO3)2·6H2O, and their mixing ratio is based on the stoichiometric ratio La:Co:Ni=1:(1-x):x, where 0.3≤x≤0.

5. The resulting LCN has the general chemical formula LaCo. 1-x Ni x O 3-δ ; In the preparation of the LSCN powder, the hydrated metal nitrates used include La(NO3)3·6H2O, Sr(NO3)2, Co(NO3)2·6H2O, and Ni(NO3)2·6H2O. Their mixing ratio is based on the stoichiometric ratio La:Sr:Co:Ni = (1-y):y:(1-z):z, where 0.1≤y≤0.3 and 0.3≤z≤0.

5. The resulting LSCN has the general chemical formula La. 1-y Sr y Co 1-z Ni z O 3-δ ; 2) Preparation of Cr poisoning resistant composite current collector: First, a layer of LSCN slurry is coated on the cathode surface of a solid oxide fuel cell and dried. Then, a layer of LCN slurry is coated and dried to form a double-layer structure, thus obtaining the Cr poisoning resistant composite current collector.

3. The method for preparing the Cr-resistant composite current collector layer according to claim 2, characterized in that, The sol-aqueous solution includes a PVA aqueous solution, which is prepared by adding PVA particles to deionized water and heating to dissolve them to obtain a PVA aqueous solution with a mass fraction of 2-10%.

4. The method for preparing the Cr-resistant composite current collector layer according to claim 2, characterized in that, The ratio of the total molar number of metal ions after the hydrated metal nitrate is dissolved in the sol aqueous solution to the molar number of PVA monomer units is 1:(1~5).

5. The method for preparing the Cr-resistant composite current collector layer according to claim 2, characterized in that, The hydrated metal nitrates in the LCN powder are mixed according to a stoichiometric ratio of La:Co:Ni = 1:0.6:0.4, which is LaCo 0.6 Ni 0.4 O 3-δ .

6. The method for preparing the Cr-resistant composite current collector layer according to claim 2, characterized in that, The hydrated metal nitrates in the LSCN powder are mixed according to the stoichiometric ratio La:Sr:Co:Ni = 0.8:0.2:0.6:0.4, which is La 0.8 Sr 0.2 Co 0.6 Ni 0.4 O 3-δ .

7. The method for preparing the Cr-resistant composite current collector layer according to claim 2, characterized in that, The LSCN slurry or LCN slurry is prepared by mixing LSCN powder or LCN powder with an organic binder, and its solid content is 30~60wt%. The organic binder includes an ethyl cellulose terpineol solution or an aqueous solution of polyvinyl alcohol.

8. The method for preparing the Cr-resistant composite current collector layer according to claim 2, characterized in that, The high-temperature calcination is carried out at a temperature of 500~800℃ for 3~5 hours.

9. The application of the Cr-poisoning-resistant composite current collector as described in claim 1 in the preparation of solid oxide fuel cells, characterized in that, The solid oxide fuel cell is composed of a structure consisting of a half cell, an LSCN layer, an LCN layer, and a metal connector in sequence. The half-cell includes an electrolyte and a cathode, with the cathode connected to the LSCN layer; The cathode material includes La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ With Gd 0.1 Ce 0.9 O 1.95 The complex composed of; The electrolyte material includes Gd 0.1 Ce 0.9 O 1.95 (GDC) or yttrium-stabilized zirconium oxide (YSZ); The material of the metal connector includes Fe-Cr based ferritic stainless steel.

10. A La as described in claim 6 0.8 Sr 0.2 Co 0.6 Ni 0.4 O 3-δ Application of the material as a cathode Cr scavenger.

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