CN113497266B - Electrolyte layer, preparation method and application thereof - Google Patents
Electrolyte layer, preparation method and application thereof Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
- H01M8/124—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte characterised by the process of manufacturing or by the material of the electrolyte
- H01M8/1246—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte characterised by the process of manufacturing or by the material of the electrolyte the electrolyte consisting of oxides
- H01M8/126—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte characterised by the process of manufacturing or by the material of the electrolyte the electrolyte consisting of oxides the electrolyte containing cerium oxide
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- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
- H01M2008/1293—Fuel cells with solid oxide electrolytes
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Abstract
The invention discloses an electrolyte layer, a preparation method and application thereof. The method comprises the following steps: (1) preparing electrolyte slurry: mixing electrolyte powder with a binder and then grinding to obtain electrolyte slurry; (2) screen printing of electrolyte: screen printing the electrolyte paste to a support surface by at least two times; (3) sintering of electrolyte: and sintering the support body printed with the electrolyte slurry in air, wherein the sintering is carried out at least 5 times at different heating rates, the temperature is kept for 30-90 minutes before the heating rate is changed each time, the temperature is kept for 4-8 hours after the temperature is raised to the maximum temperature of 1500-1600 ℃, then the temperature is reduced at least 3 times at different cooling rates, and the temperature is kept for 30-90 minutes before the cooling rate is changed each time, so that the electrolyte layer with the thickness of less than 10 micrometers and the density of more than 70 percent is obtained. The technical problems of large loss and low power when the electrolyte layer prepared by screen printing is applied to a fuel cell/an electrolytic cell are solved.
Description
Technical Field
The invention belongs to the field of solid oxide fuel cells/electrolytic cells, and particularly relates to an electrolyte layer, a preparation method and application thereof.
Background
The solid oxide fuel cell/electrolytic cell is directly inactivated due to diffusion and reaction between an electrolyte material and an electrode material, agglomeration and growth of the electrode material and reaction between the electrode material and an external environment (including a gas environment and a pile connector material) in the high-temperature (800-1000 ℃) operation process, and the commercialization process of the solid oxide fuel cell/electrolytic cell is seriously influenced. In order to improve the operational life of the battery and to achieve rapid start-up of the battery, many developments have been focused in recent years on reducing the operating temperature from a high temperature to a medium-low temperature (500 to 650 ℃). However, the problem of thermodynamically determined slower ion transport at medium and low temperature ranges makes battery power less than commercially desirable. In order to solve the problem, researchers propose two technical routes, namely, a thin film technology is used for reducing the thickness of an electrolyte and shortening the transmission distance of oxygen ions; and secondly, an electrolyte material, an electrode material and a catalyst material with better performance are researched, and the rapid transmission and conversion of substances at the three-phase interface of the electrolyte layer and the electrode are realized.
In the oxygen ion conductor material, inDoped CeO at the same temperature 2 The conductivity of the base electrolyte material (DCO) is higher than that of the conventional ZrO 2 The base electrolyte material is higher by one order of magnitude, the DCO has better high-temperature chemical compatibility with most of the existing electrode materials, and an additional barrier layer material is not required to be introduced to block the substance diffusion between the DCO and the electrode materials, so that the difficulty of the preparation process of the battery/electrolytic cell is reduced. Therefore, DCO is preferred as an electrolyte material in a medium-low temperature range; meanwhile, the thickness of the electrolyte layer is expected to be reduced, namely the transmission distance of oxygen ions is shortened, and the rapid transmission and conversion of substances can be realized, so that the power density of the battery is greatly improved, and the use of the SOFC/SOEC in a medium-low temperature range is realized.
At present, the thickness of an electrolyte layer prepared by screen printing, whether YSZ or GDC/SDC, is approximately distributed between 10 and 30 mu m, and the measured ohmic resistance is higher after the electrolyte layer is applied to a battery, so that the power density of the battery is lower. The thickness of the electrolyte layer prepared by adopting methods such as laser pulse deposition, physical/chemical vapor deposition and the like can be as low as 1-3 mu m, and the density can also meet the requirement, but the preparation cost is high, and the commercial application is influenced. Related researchers try to reduce the thickness of the electrolyte to be less than 10 microns by screen printing, but through holes exist in the electrolyte layer after sintering, or the electrolyte has a porous structure, and the compactness of the electrolyte does not meet the practical application requirement.
Disclosure of Invention
Aiming at the defects or improvement requirements of the prior art, the invention provides an electrolyte layer, a preparation method and application thereof, and aims to prepare an ultrathin electrolyte layer doped with cerium oxide base (DCO, including GDC, SDC and the like) by means of adjusting the proportion of slurry, changing the mesh number of a printing screen, adjusting the sintering process curve and the like and applying the traditional screen printing process, so that the technical problems of large consumption and low power of a fuel cell/electrolytic cell in a medium-low temperature range due to the fact that through holes are formed in the sintered ultrathin electrolyte layer prepared by screen printing and the density is low are solved.
To achieve the above object, according to one aspect of the present invention, there is provided a method for preparing an electrolyte layer, the method comprising the steps of:
(1) Preparing electrolyte slurry: mixing electrolyte powder with a binder and then grinding to obtain electrolyte slurry;
(2) Screen printing of electrolyte: screen printing the electrolyte paste to a support surface by at least two times;
(3) Sintering of electrolyte: and sintering the support body printed with the electrolyte slurry in air at least 5 times at different heating rates, preserving heat for 30-90 minutes before changing the heating rate each time, preserving heat for 4-8 hours after heating to the maximum temperature of 1500-1600 ℃, then reducing the temperature at least 3 times at different cooling rates, and preserving heat for 30-90 minutes before changing the cooling rate each time to obtain an electrolyte layer with the thickness of less than 10 microns and the density of more than 70%.
Preferably, the electrolyte obtained by sintering at 1550 ℃ for 6 hours has the thickness of 4.5 μm and the compactness of 93%.
Preferably, the screen printing is performed by 200-380 meshes, the screen printing is performed twice, and the second screen printing is performed after the electrolyte layer after the first screen printing is dried.
Preferably, the height of the screen printing die (i.e. the distance between the screen printing die and the support) during screen printing is 0.5-1mm.
Preferably, the mass ratio of the electrolyte powder to the binder in the electrolyte slurry is 1:1-3:2; preferably, 1 to 3mol.% of Fe is also added to the electrolyte slurry 2 O 3 Or Al 2 O 3 As a sintering aid.
Preferably, the mass ratio of the electrolyte powder to the binder in the electrolyte slurry is 1:1, an electrolyte layer having a thickness of about 4.5 μm can be obtained.
Preferably, the method further comprises, prior to sintering, pre-sintering the support printed with the electrolyte slurry in air. The pre-sintering process can be as follows: heating to 600 ℃ according to the heating rate of more than 3 ℃/min, and preserving the heat for 30-90 minutes; heating to 900 ℃ according to the heating rate of 2-3 ℃/min, and preserving the heat for 30-90 minutes; heating to 1050 ℃ according to the heating rate of 2-3 ℃/min, preserving heat for 3 hours, cooling to 600 ℃ according to the cooling rate of 2-3 ℃/min, and then cooling to room temperature along with the furnace. The pre-sintering function is to remove starch in the support body and organic matters in the electrolyte layer, and avoid that a great amount of gas overflows to break the electrolyte film in the final sintering process.
Preferably, the sintering is specifically: heating to 600 ℃ according to the heating rate of more than 3 ℃/min, and preserving the heat for 30-90 minutes; heating to 900 ℃ according to the heating rate of 2-3 ℃/min, and preserving the heat for 30-90 minutes; heating to 1100 ℃ according to the heating rate of 2-3 ℃/min, and preserving the heat for 30-90 minutes; heating to 1400 ℃ according to the heating rate of 1-2 ℃/min, and keeping the temperature for 30-90 minutes; heating to 1500-1600 ℃ according to the heating rate of 0.5-1 ℃/min and preserving the heat for 4-8 hours; cooling to 1200 ℃ according to the cooling rate of 0.5-1 ℃/min, preserving the heat for 30-90 minutes, cooling to 600 ℃ according to the cooling rate of 1-2 ℃/min, and finally cooling to room temperature along with the furnace.
Preferably, the electrolyte slurry is specifically formulated as: adopting alcohol as a solvent, ball-milling electrolyte powder in a high-energy ball mill at a rotating speed of 350-400 r/min for 24-48 h, drying, placing in an agate mortar, and grinding for 1-2h to obtain ground powder, wherein the average particle size of the ground powder is 2-3 mu m, mixing the ground powder with a binder, and placing in the agate mortar for grinding for 1-2h to obtain the electrolyte slurry.
Preferably, the electrolyte powder includes Gd 0.1 Ce 0.9 O 2-δ (GDC) powder or Sm 0.2 Ce 0.8 O 2-δ (SDC) powder; the adhesive is obtained by the following steps: adding 2-4% of ethyl cellulose by mass into terpineol, adding 2.5wt.% of fish oil as a dispersing agent, and stirring in an oil bath kettle at 90 ℃ for 24-48 h to mix uniformly, thereby obtaining the binder.
Preferably, the support body is a support body piece obtained by sintering after dry pressing or a support body green blank obtained by tape casting, degreasing and presintering, and the support body piece and the support body green blank comprise NiO and GDC or NiO and SDC.
According to another aspect of the present invention, there is provided an electrolyte layer prepared by the method described above, wherein the material of the electrolyte layer comprises alkaline earth metal doped ceria or rare earth element doped ceria, the thickness of the electrolyte layer is less than 10 μm, the electrolyte layer is obtained by screen printing on a support, and the density of the electrolyte layer is greater than 70%.
Preferably, the electrolyte layer has a thickness of less than 5 μm.
According to a further aspect of the present invention there is provided the use of an electrolyte layer for a solid oxide fuel cell/electrolyser, the cell comprising the electrolyte layer and an air electrode material supported on the electrolyte surface.
In general, the above technical solutions conceived by the present invention have advantages over the prior art in that:
(1) In the prior art, the electrolyte layer with the thickness less than 10 microns, which is obtained by screen printing, cannot be directly used, because through holes which penetrate through the electrolyte layer with the thickness less than 10 microns are formed in the electrolyte layer after the electrolyte layer with the thickness less than 10 microns is obtained by screen printing and sintered, or the electrolyte has a porous structure, and the density of the electrolyte cannot meet the requirement of practical application. At present, the electrolyte layer prepared by screen printing can have higher density only by reaching at least 10 micrometers, and can be applied to batteries.
In the preparation method provided by the invention, the electrolyte layer with the thickness of less than 10 microns and the density of more than 70% is obtained by adjusting the sintering process curve, so that the compactness of the ultrathin electrolyte layer is ensured, and the ultrathin electrolyte layer prepared by screen printing can be applied to a solid fuel cell. And after the thickness of the electrolyte layer is reduced, the transmission distance of oxygen ions is shortened, and the rapid transmission and conversion of substances can be realized, so that the power density of the battery is greatly improved. In addition, the electrolyte layer can be directly exposed in the air for sintering in a single piece, and obvious bending cannot be generated after sintering, so that the problems of cracking, difficulty in separation, rough surface and the like caused by opposite pressure sintering in the traditional electrolyte sintering process are solved.
Specifically, in the process of sintering the electrolyte at a high temperature, the temperature rise rate is adjusted for more than five times by the method provided by the invention along with the continuous rise of the temperature, and the temperature is kept for 30-90 min at the temperature point of adjusting the temperature rise rate, because the volume of the electrolyte shrinks in the continuous solidification process, and then thermal stress is inevitably generated, and the higher the temperature is, the larger the thermal stress is. By adopting the sintering process, the thermal stress in the battery can be released in time so as to prevent the battery from bending and even cracking. Meanwhile, the single electrolyte layer can be directly sintered by adopting the sintering process, so that the problem of battery cracking caused by counter pressure sintering adopted in the prior art during sintering is avoided.
The heat preservation temperature of the final densification of the electrolyte in the method is 1500-1600 ℃, and the heat preservation time is 4-8 h. Compared with other electrolyte sintering processes, the invention selects higher sintering temperature because the electrolyte layer is thinner, and needs to realize grain growth at higher temperature while the battery shrinks, so as to prevent the electrolyte layer from generating fine through holes at lower temperature. The compactness is one of the key factors influencing the performance of the battery, and the low compactness reduces the open-circuit voltage of the battery, so that the power density of the battery is low. The density of the electrolyte layer obtained by sintering of the invention reaches more than 70 percent, and the requirement of the fuel cell/electrolytic cell on the electrolyte is greatly met.
(2) According to the invention, the DCO ultrathin electrolyte layer with the thickness of less than 5 mu m is obtained by controlling the height of the screen printing die and changing the mesh number of the screen printing, so that the thickness of the electrolyte layer is further reduced, namely the transmission distance of oxygen ions is shortened, and the rapid transmission and conversion of substances can be realized, thereby greatly improving the power density of the battery.
(3) The invention reduces the thickness of the electrolyte layer and ensures the density of the electrolyte layer by adjusting the slurry proportion, adding the sintering aid, controlling the height of the screen printing mould, changing the mesh number of the printing screen and adjusting the synergistic action among all parameters of the sintering process curve. The method provided by the invention has the advantages of low cost, rapidness, high repeatability, good controllability and excellent performance. And after the prepared electrolyte is assembled into a battery, the prepared electrolyte shows excellent and stable electrochemical performance no matter in a fuel cell mode or an electrolytic cell mode, is an excellent method for preparing a medium-low temperature solid oxide fuel cell/electrolytic cell, and is suitable for popularization and application.
Drawings
Fig. 1 (a) is a degreasing process profile of a cast support according to a preferred embodiment of the present invention, fig. 1 (b) is a pre-sintering process profile of an electrolyte layer according to a preferred embodiment of the present invention, and fig. 1 (c) is a sintering process of an electrolyte according to a preferred embodiment of the present invention;
FIG. 2 is a SEM image of a cross-section of an electrolyte obtained by sintering using the sintering process curve shown in (c) of FIG. 1;
fig. 3 is a cross-sectional SEM characterization picture of a full cell after reduction, manufactured using the sintering process shown in fig. 1 (c);
fig. 4 (a) shows an impedance spectrum of the cell provided in example 1 of the present invention measured in the SOFC mode, and fig. 4 (b) shows an I-V-P curve of the cell provided in example 1 of the present invention measured in the SOFC mode;
fig. 5 (a) is an impedance spectrum of the battery provided in example 1 of the present invention measured in the SOEC mode, and fig. 5 (b) is an I-V curve of the battery provided in example 1 of the present invention measured in the SOEC mode.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Example 1
1. Preparation of the support
In this embodiment, the support body is prepared by dry pressing and sintering. In the battery support body, niO and pore-forming agent (starch) respectively account for 60% and 10% of the total mass of NiO and GDC/SDC, required powder is subjected to ball milling and mixing uniformly in a high-energy ball mill at the rotating speed of 300r/min, and then drying and grinding are carried out. During preparation, 0.4g of dried powder is weighed each time and is dried and pressed for 1min under the pressure of 12MPa, and then the formed support body sheet is obtained. Then presintering for 3h at 1050 ℃, wherein the specific sintering process can be referred to as (b) in figure 1. After sintering, a 0.6mm thick support piece was obtained.
2. Preparation of the Binder
Adding ethyl cellulose into terpineol, stirring in an oil bath kettle at 90 ℃ for 24 hours, and fully and uniformly mixing to obtain the binder, wherein the content of the ethyl cellulose is 4 wt%, and in addition, 2.5 wt% of fish oil is added as a dispersing agent.
3. Screen printing electrolyte
The powder needed by the electrolyte is as fine as possible so as to shorten the diffusion distance of the powder in the high-temperature sintering process and reduce the sintering difficulty of the electrolyte. Therefore, firstly, alcohol is used as a solvent, commercial GDC powder is ball-milled in a high-energy ball mill for 24 hours at the rotating speed of 350r/min, and then the drying and grinding are carried out to obtain the powder for preparing the electrolyte.
When screen printing is carried out on a support sheet formed by dry pressing, the required paste ratio is GDC (commercial, SOFCMAN): binder =1:1, placing the mixture in an agate mortar, fully mixing and grinding for 2 hours, adjusting the height of a screen printing mold, printing twice, wherein the height of the screen printing mold is 0.5mm, and placing the screen printing mold in an oven to dry for 15min after printing each time. The mesh number of the screen printing mesh is controlled to be 200 meshes.
In order to improve the particle size uniformity of the electrolyte after sintering and properly reduce the sintering temperature under the premise of ensuring the compactness, 1mol percent of Fe is added into the electrolyte slurry 2 O 3 As a sintering aid.
In addition, SDC and GDC have certain electronic conductivity under a reducing atmosphere, which causes electric leakage between the cathode and the anode of the battery, reduces open-circuit voltage OCV of the battery, and affects power density of the battery. In order to increase the open circuit voltage of the cell, this embodiment introduces a layer of YSZ between the support and the electrolyte layer to block electron transport. The preparation method can select screen printing or spin coating, and the thickness is controlled to be 3 μm. Because the densification temperature of YSZ is lower than that of GDC/SDC, the electron barrier layer is sintered after the electrolyte is brushed.
4. Sintering of electrolyte
When the battery of the ultrathin electrolyte is sintered, a corresponding sintering process needs to be adjusted, and the battery needs to be sintered at a higher temperature to reduce surface defects and ensure the compactness of the electrolyte. The sintering process can be referred to as (c) in fig. 1. When sintering, the two batteries are not required to be pressed oppositely. The sintering specifically comprises the following steps: heating to 600 ℃ according to the heating rate of more than 3 ℃/min, and keeping the temperature for 60 minutes; heating to 900 ℃ according to the heating rate of 2 ℃/min, and keeping the temperature for 60 minutes; heating to 1100 deg.C at a heating rate of 2 deg.C/min, and maintaining for 60 min; heating to 1400 ℃ according to the heating rate of 1 ℃/min, and preserving the heat for 60 minutes; heating to 1550 ℃ according to the heating rate of 0.75 ℃/min and preserving the heat for 6 hours; cooling to 1200 ℃ according to the cooling rate of 1 ℃/min, preserving heat for 60 minutes, cooling to 600 ℃ according to the cooling rate of 1 ℃/min, and finally cooling to room temperature along with the furnace.
Referring to fig. 2, an electrolyte layer having a thickness of 4.5 μm and a density of 93% was obtained.
5. Preparation of air electrode
The GDC/SDC has excellent compatibility with the air electrode material with better performance researched at present, and impurity phases can not be generated at high temperature and after long-time operation, so that the air electrode material is directly loaded on the surface of the sintered electrolyte. The adopted process methods comprise magnetron sputtering, atomic layer deposition, laser pulse deposition, spin coating, drop coating, screen printing and the like, and the thickness is 10 mu m.
The air electrode material with excellent performance is (La, sr) MnO 3 、La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF)、Ba 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3-δ (BSCF)、La 0.8 Sr 0.2 Co 0.8 Ni 0.2 O 3-δ (LSCN) and the like. In addition, the electrode material is mechanically mixed with a dielectric material as the electrode material, and the overall performance is more excellent, such as Sm 0.5 Sr 0.5 CoO 3-δ (SSC) -GDC, and the like.
In addition, after the electrode material is sintered, ORR/OER catalyst materials, such as noble metals Pd and Ru, or alkaline earth metals Co and Fe, are introduced by means of impregnation, ion implantation and the like, so that the material conversion rate at the three-phase interface of the electrode can be further improved.
In the present example, BSCF and GDC were mechanically mixed (mass ratio BSCF: GDC = 7:3) as the air electrode material, the electrode material was coated on the electrolyte surface by screen printing, and sintered at 900 ℃ for 2h to form the air electrode tightly bonded to the electrolyte, as shown in fig. 3.
6. Assembled battery testing
And coating a layer of platinum slurry on the surface of the air electrode material of the prepared battery to be used as a current collecting layer, and sintering at 800 ℃ for 1h to obtain the battery with a complete structure. After the cell was packaged, the impedance data and I-V curve of the cell were tested using a Solartron electrochemical workstation or a Zennium IM6 electrochemical workstation. During testing, firstly, hydrogen is introduced into one side of the hydrogen electrode at 600-700 ℃ for reduction, and after NiO is completely reduced into Ni, the electrochemical performance test is carried out, and the reduction is completed, and the open-circuit voltage is stabilized at a certain value.
In this example, the open circuit voltage of the 600 ℃ cell was stabilized in the range of 0.87 to 0.89V.
Referring to fig. 4 (a) and 4 (b), which are the impedance spectrum and I-V-P curve of the cell provided in this example measured in the SOFC mode, it can be seen that the ohmic impedances of the cell at 500 deg.c, 550 deg.c, 600 deg.c, 650 deg.c, and 700 deg.c are 0.224, 0.150, 0.104, 0.079, and 0.068 Ω · cm, respectively 2 Polarization impedances of 0.407, 0.148, 0.049, 0.019 and 0.010. Omega. Cm 2 The corresponding maximum output power density is 0.398, 0.674, 0.996, 1.229, 1.283W/cm 2 。
Referring to fig. 5 (a) and 5 (b), there are impedance spectrum and I-V curve measured in the SOEC mode of the battery provided in the present embodiment, respectively. In the process of CO 2 And H 2 CO-electrolysis of O (volume ratio of CO) 2 :H 2 O = 1:3), a current density as high as 1.2A/cm at 650 ℃ under an applied voltage of 1.1V 2 。
Example 2
1. Preparation of the support
In this embodiment, the support is prepared by tape casting, degreasing and presintering. Firstly, weighing mixed powder of 55wt.% NiO (standard type) and 45wt.% GDC/SDC (SOFCMAN) as powder, adding menhaden oil (dispersing agent), solvent (ethanol and dimethylbenzene with the same volume) and a certain amount of starch (pore forming agent), and ball-milling the mixture for 24 hours to uniformly mix the mixture. Then, PVB B-98, PAG, BBP and cyclohexanone were added, and ball milling was continued for 24 hours to mix the slurry uniformly. The slurry needs to be stirred for 27min under a vacuum degree of 0.08MPa before casting, and the defoaming process is completed. Subsequently, the slurry was poured onto a casting machine for casting at a flow rate of 4mm s -1 And the height of the cutter head is fixed to be 2mm. After 72h of air drying, the green body is taken down and cut into a wafer with the diameter of 16mm by a manual button punching machine, namely the final anode support body green body. Degreasing and presintering are carried out after the electrolyte printing is finished.
2. Preparation of the Binder
Adding ethyl cellulose into terpineol, stirring in an oil bath kettle at 90 ℃ for 24 hours, and fully and uniformly mixing to obtain the binder, wherein the content of the ethyl cellulose is 4 wt%, and in addition, 2.5 wt% of fish oil is added as a dispersing agent.
3. Screen printing electrolyte
The powder needed by the electrolyte is as fine as possible so as to shorten the diffusion distance of the powder in the high-temperature sintering process and reduce the sintering difficulty of the electrolyte. Therefore, firstly, alcohol is used as a solvent, commercial SDC powder is ball milled for 24 hours in a high-energy ball mill at the rotating speed of 350r/min, and then the powder is dried and ground to obtain powder for preparing electrolyte.
When screen printing is carried out on the support body green body formed by tape casting, the surface which is not directly exposed in the air is selected, the height of a screen printing mold is 0.5mm, the slurry proportion is consistent with the surface, the printing is carried out twice, and the printing is carried out twice after the first time of printing is finished and the natural air drying is carried out for two hours. The brushed half-cells were placed in an oven for degreasing, the degreasing process being shown in fig. 1 (a). And (3) pre-sintering the degreased half cell, wherein the sintering process is consistent with that of the dry pressing support body, and the step (b) is shown in figure 1.
In order to improve the particle size uniformity of the electrolyte after sintering and properly reduce the sintering temperature under the premise of ensuring the compactness, 1mol.% of Al can be added into the electrolyte slurry 2 O 3 As a sintering aid.
4. Sintering of electrolyte
When sintering, the two batteries are not required to be pressed oppositely. The sintering specifically comprises the following steps: heating to 600 ℃ according to the heating rate of about 3 ℃/min, and keeping the temperature for 60 minutes; heating to 900 ℃ according to the heating rate of 2 ℃/min, and keeping the temperature for 60 minutes; heating to 1100 deg.C at a heating rate of 2 deg.C/min, and maintaining for 60 min; heating to 1400 ℃ according to the heating rate of 1 ℃/min, and preserving the heat for 60 minutes; heating to 1550 ℃ according to the heating rate of 0.75 ℃/min and preserving the heat for 6 hours; cooling to 1200 ℃ according to the cooling rate of 1 ℃/min, preserving heat for 60 minutes, cooling to 600 ℃ according to the cooling rate of 1 ℃/min, and finally cooling to room temperature along with the furnace.
An electrolyte layer with a thickness of 5.0 μm and a compactness of 92% was obtained.
5. Preparation of air electrode
The GDC/SDC has excellent compatibility with the air electrode material with better performance researched at present, and impurity phases can not be generated at high temperature and after long-time operation, so that the air electrode material is directly loaded on the surface of the sintered electrolyte. The adopted process methods comprise magnetron sputtering, atomic layer deposition, laser pulse deposition, spin coating, drop coating, screen printing and the like, and the thickness is controlled to be 10-20 mu m optimally.
The air electrode material with excellent performance is (La, sr) MnO 3 、La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF)、Ba 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3-δ (BSCF)、La 0.8 Sr 0.2 Co 0.8 Ni 0.2 O 3-δ (LSCN) and the like. In addition, the electrode material is mechanically mixed with a dielectric material as the electrode material, and the overall performance is more excellent, such as Sm 0.5 Sr 0.5 CoO 3-δ (SSC) -GDC, and the like.
In addition, after the electrode material is sintered, ORR/OER catalyst materials, such as noble metals Pd and Ru, or alkaline earth metals Co and Fe, are introduced by means of impregnation, ion implantation and the like, so that the material conversion rate at the three-phase interface of the electrode can be further improved.
6. Assembled battery testing
Coating a layer of platinum slurry on the surface of the air electrode material of the prepared battery to be used as a current collecting layer, and then sintering at 800 ℃ for 1-2h to obtain the battery with a complete structure.
Examples 3 to 4
Examples 3 to 4 and comparative examples 1 to 2 electrolyte layers were prepared in the same manner as in example 1, but the sintering process was different, see table 1 for details, and the thickness and the density of the electrolyte layers prepared in examples 3 to 4 and comparative examples 1 to 2 are also shown in table 1.
TABLE 1 electrolyte thickness and compactness obtained under different sintering processes
| Maximum sintering temperature (. Degree. C.) | Incubation time (h) | Thickness (μm) | Compactness degree | |
| Example 1 | 1550 | 6 | 4.5 | 93％ |
| Comparison ofExample 1 | 1450 | 4 | 8.5 | 67％ |
| Comparative example 2 | 1450 | 8 | 7.3 | 72％ |
| Example 3 | 1500 | 4 | 7.1 | 70％ |
| Example 4 | 1500 | 8 | 6.5 | 82％ |
It can be seen that below the maximum sintering temperature of 1500 ℃ provided by the present invention, the density of the electrolyte layer will decrease; the heat preservation time is 6 hours at the highest sintering temperature of 1550 ℃, and 93 percent of compactness can be achieved.
Examples 5 to 6
Examples 5 to 6 electrolyte layers were prepared in the same manner as in example 1, except that electrolyte slurries having different compounding ratios were used. See table 2 for details.
Table 2 thickness and density of electrolyte layer obtained by sintering electrolyte slurries with different ratios under the same conditions
It can be seen that different electrolyte slurry ratios can adjust the thickness of the electrolyte layer.
It will be understood by those skilled in the art that the foregoing is only an exemplary embodiment of the present invention, and is not intended to limit the invention to the particular forms disclosed, since various modifications, substitutions and improvements within the spirit and scope of the invention are possible and within the scope of the appended claims.
Claims (7)
1. A method for producing an electrolyte layer, comprising the steps of:
(1) Preparing electrolyte slurry: mixing electrolyte powder with a binder and then grinding to obtain electrolyte slurry; the average particle size of the electrolyte powder is 2~3 μm; the electrolyte powder comprises GDC powder or SDC powder;
(2) Screen printing of electrolyte: screen printing the electrolyte paste to a support surface by at least two times;
(3) Sintering of electrolyte: sintering the support body printed with the electrolyte slurry in air, wherein the sintering is carried out for at least 5 times at different heating rates, the temperature is kept for 30-90 minutes before the heating rate is changed each time, the temperature is kept for 6-8 hours after the temperature is raised to the maximum temperature of 1500-1600 ℃, then the temperature is reduced for at least 3 times at different cooling rates, and the temperature is kept for 30-90 minutes before the cooling rate is changed each time, so that an electrolyte layer with the thickness of less than 10 micrometers and the density of more than 70 percent is obtained;
the silk screen for silk screen printing is 200-380 meshes, the silk screen printing is performed twice, and the second silk screen printing is performed after the electrolyte layer after the first silk screen printing is dried;
the mass ratio of the electrolyte powder to the binder in the electrolyte slurry is 1:1-3:2; 1 to 3mol.% of F is also added to the electrolyte slurrye 2 O 3 Or Al 2 O 3 As a combustion aid;
the sintering specifically comprises the following steps: heating to 600 ℃ according to the heating rate of more than 3 ℃/min, and keeping the temperature for 30 to 90 minutes; heating to 900 ℃ according to the heating rate of 2~3 ℃/min, and preserving the heat for 30 to 90 minutes; heating to 1100 ℃ according to the heating rate of 2~3 ℃/min, and preserving the heat for 30 to 90 minutes; heating to 1400 ℃ according to the heating rate of 1~2 ℃/min, and preserving the temperature for 30-90 minutes; heating to 1500-1600 ℃ according to the heating rate of 0.5-1 ℃/min, and preserving the heat for 4~8 hours; cooling to 1200 ℃ at the cooling rate of 0.5-1 ℃/min, preserving the heat for 30-90 minutes, cooling to 600 ℃ at the cooling rate of 1~2 ℃/min, and finally cooling to room temperature along with the furnace.
2. The method of claim 1, wherein the electrolyte slurry is formulated specifically as: adopting alcohol as a solvent, ball-milling electrolyte powder in a high-energy ball mill at a rotating speed of 350-400 r/min for 24-48 h, then drying, placing in an agate mortar for grinding for 1-2h to obtain ground powder, mixing the ground powder with an adhesive, placing in the agate mortar for grinding for 1-2h to obtain the electrolyte slurry.
3. The method of claim 1, wherein the adhesive is obtained by: adding ethyl cellulose with the mass fraction of 2~4% into terpineol, adding 2.5 wt% of fish oil serving as a dispersing agent, stirring in a 90-DEG C oil bath kettle for 24-48 h, and fully and uniformly mixing to obtain the binder.
4. The method according to claim 1, wherein the support is a support sheet obtained by dry pressing and sintering or a support green body obtained by tape casting, degreasing and presintering, and the support sheet and the support green body comprise NiO and GDC or NiO and SDC.
5. An electrolyte layer prepared by the method of any one of claims 1 to 4, wherein the material of the electrolyte layer comprises an alkaline earth metal doped ceria or a rare earth element doped ceria, wherein the thickness of the electrolyte layer is less than 10 μm, wherein the electrolyte layer is obtained by screen printing on a support, and wherein the density of the electrolyte layer is greater than 70%.
6. The electrolyte layer of claim 5 wherein the electrolyte layer has a thickness of less than 5 μm.
7. Use of the electrolyte layer according to any of claims 5-6 in a solid oxide fuel cell/electrolyser comprising said electrolyte layer and an air electrode material supported on the electrolyte surface.
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