Method for preparing ultrathin electrolyte film through natural deposition

Abstract

The invention provides a method for preparing an ultrathin electrolyte film through natural deposition, and belongs to the technical field of fuel cells. The method comprises the steps that a reaction solution containing YSZ powder, ethyl cellulose and terpilenol is prepared, polyvinylpyrrolidone is added to obtain a coating solution, the coating solution is subjected to ball milling to obtain a uniform deposition solution, a novel substrate with a fixed-size frame is prepared based on an anode substrate, ultrasonic dispersion work is conducted in advance, and the novel substrate with the fixed-size frame is prepared. The deposition liquid is applied to the prepared novel substrate, the coating layer is naturally volatilized and deposited under specific conditions, the electrolyte layer and the substrate are dried, warm isostatic pressing is carried out, and finally a blank with the deposited ultrathin electrolyte layer is obtained through press burning. The method has the advantages of simple process, low cost, large-scale production and the like, and the prepared ultrathin electrolyte film has high density, excellent chemical stability and good electrochemical performance and is suitable for the field of fuel cells.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a method for preparing an ultrathin electrolyte film by natural deposition. Background Art

[0002] Solid Oxide Cells (SOCs) are one of the cleanest and most efficient energy conversion devices in the 21st century. It can achieve efficient conversion between hydrogen energy and electrical energy and has two working modes. In the fuel cell mode, it is a device that continuously converts the chemical energy of fuel into electrical energy through an electrochemical reaction; in the electrolyzer mode, it can convert new energy such as solar energy and wind energy into electrical energy for storage and use in electrolysis. Currently, the vast majority of commercial products of SOCs are successively three generations of products: electrolyte-supported type, fuel electrode-supported type, and metal-supported type. For electrolyte-supported SOCs, the thickness of their electrolytes is often ≥200 μm. The ceramic electrolyte material has low thermal conductivity, slow battery startup time, and can only reach a relatively high working performance at high temperatures. Secondly, the costs of seals, connectors, and thermal insulation materials are also relatively high; for fuel electrode-supported SOCs, the thickness of the fuel electrode is ≧400 μm. Compared with electrolyte-type SOCs, they have a thinner electrolyte thickness and a lower working temperature, but the overall mechanical strength of the battery is relatively low, the sealing difficulty is high, and the cost of electrode materials is high; for metal-supported SOCs, the thickness of their electrolytes is about 10 - 50 μm. Their excellent thermal conductivity enables them to have a relatively high startup rate, but due to the presence of the metal support, their preparation is difficult, the support is prone to oxidation, and element diffusion is likely to occur between the anode and the support. For SOCs, whether they are protonic SOCs, ionic SOCs, or mixed ion conductor SOCs, the conduction of protons and ions needs to pass through the electrolyte. The greater the thickness of the electrolyte, the longer the path of proton and ion conduction, and the ohmic impedance increases as the electrolyte thickness increases. That is, the thinner the electrolyte layer, the higher the power generation efficiency. The preparation methods of SOC electrolytes mainly include low-temperature sintering method, tape casting method, screen printing method, thermal spraying method, vacuum plasma spraying method, chemical vapor deposition method, etc. In these preparation methods, the following problems exist: (1) The commercial methods for preparing electrolytes cannot prepare an electrolyte layer with a sufficiently thin thickness; (2) The sizes of the electrolytes and barrier layers produced by laboratory preparation methods are limited by the instrument specifications, and the production cost is relatively high, making large-scale production impossible.

[0003] Therefore, there is an urgent need to provide a new method for preparing SOC battery electrolytes, which can not only realize the thinning of the electrolyte film but also stably control the thickness of the deposited electrolyte and be applied to large-scale production. Summary of the Invention

[0004] The object of the present invention is to provide a method for preparing an ultrathin electrolyte film by natural deposition, which has the advantages of simple process, low cost, and large-scale production. The prepared ultrathin electrolyte film has high density, excellent chemical stability, and good electrochemical performance, and is applicable to the field of fuel cells.

[0005] To achieve the above object, the present invention provides a method for preparing an ultrathin electrolyte film by natural deposition, comprising the following steps: Step S1: Prepare a reaction solution with a mass ratio of 55-65% yttria-stabilized zirconia ceramic powder (Yttria-Stabilized Zirconia, abbreviated as YSZ), 2% ethyl cellulose, and 25-35% terpineol. Step S2: Add polyvinylpyrrolidone to the reaction solution to obtain a coating solution. Step S3: Ball-mill the obtained coating solution in sequence to obtain a uniform deposition solution. Step S4: Prepare a new substrate with a fixed-size frame based on the anode substrate. Step S5: Perform ultrasonic dispersion work in advance before dropping the deposition solution. Step S6: Apply the deposition solution to the prepared new substrate. Step S7: Perform natural volatilization deposition on the coating layer. Step S8: Dry the electrolyte layer and the substrate, and perform warm isostatic pressing. Step S9: Sinter by pressing to finally obtain a green body with a deposited ultrathin electrolyte layer.

[0006] Preferably, in step S1, the particle size of the YSZ powder is 0.1-0.5 μm.

[0007] Preferably, in step S2, the polyvinylpyrrolidone accounts for 5% of the total mass of the reaction solution.

[0008] Preferably, in step S3, it specifically includes: using a horizontal ball mill to ball-mill the coating solution in step S2 at a rotation speed of 800 r / min.

[0009] Preferably, in step S4, it specifically includes: Step S41: Prepare a frame, and the frame is made of plastic. Step S42: Adhere the frame and the anode substrate together with silicone rubber. Step S43: Wait for the silicone rubber substrate to volatilize and dry. Step S44: Obtain a substrate with a fixed size that can carry the deposition solution.

[0010] Preferably, in step S5, during ultrasonic dispersion, the temperature is 30 °C and it lasts for 15 min.

[0011] Preferably, in step S7, it specifically includes: Step S71: Place the substrate after applying the deposition solution in an environment with a constant temperature of 26°C and a constant humidity of 60%; Step S72: Place the substrate on a hollow frame; Step S73: Accelerate the volatilization under the action of a blower in a fume hood.

[0012] Preferably, in step S8, it specifically includes: Step S81: Separate the frame from the substrate body by cutting to obtain a substrate with a fixed size; Step S82: Place the deposited substrate in a high-temperature furnace; Step S83: Keep the temperature at 80°C and the heat preservation time at 15 min; Step S84: Put the dried sample into a warm isostatic press and perform warm isostatic pressing at 80°C and 20 MPa.

[0013] Preferably, in step S9, it specifically includes: Step S91: Place the billet after warm isostatic pressing between two zirconium plates with porcelain chips; Step S92: Place it in a muffle furnace, set the maximum temperature at 1400°C, and perform pressure sintering.

[0014] Preferably, in step S9, the thickness of the ultra-thin electrolyte film is less than or equal to 5 μm.

[0015] Therefore, the present invention adopts the above method for preparing an ultra-thin electrolyte film by natural deposition, and the beneficial technical effects are as follows: (1) By introducing a brand-new method of natural volatilization deposition, the present invention can prepare electrolytes on substrate materials of any size, meeting the production of various specifications of products; (2) The deposition method of the present invention does not require expensive instruments used in deposition methods such as laser deposition and spraying, which can reduce production costs; (3) By adding the prepared coating solution to a substrate with a fixed size for deposition, the present invention can control the thickness of the electrolyte film by adjusting the amount of the coating solution, and at the same time solves the problems of difficult low-cost preparation of traditional deposited electrolyte layers and difficult control of their size and thickness. Description of the Drawings

[0016] Figure 1 It is a flowchart of the method for preparing an ultra-thin electrolyte film by natural deposition according to the present invention; Figure 2 It is a surface image of the obtained electrolyte film in Embodiment 1 of the present invention taken by a scanning electron microscope (SEM); Figure 3 This is a cross-sectional image of the substrate on which the thin film electrolyte is deposited obtained in Example 3 of the present invention, taken using a scanning electron microscope (SEM); Figure 4 This is a local enlarged X-ray diffraction (XRD) image of the electrolyte film obtained in Example 2 of the present invention. DETAILED DESCRIPTION

[0017] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0018] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0019] Embodiment 1 Step S1: preparing a reaction solution containing 55% YSZ, 2% ethyl cellulose and 35% terpineol; Step S2: adding 5% polyvinyl pyrrolidone to the reaction solution to obtain a coating solution; Step S3: bottle the coating liquid and place it on a horizontal ball mill for ball milling at a speed of 800 r / min for 24 hours to obtain a deposition liquid; Step S4: connecting a square polyvinyl chloride (PVC) frame with a side length of 3 cm to the blank using organic silicone; Step S5: pre-ultrasonic dispersion of the deposition liquid, setting the temperature to 30°C and the time to 15 minutes; Step S6: using a pipette to measure a fixed amount of the deposition liquid being ultrasonically dispersed and slowly dripping and smearing it on the blank with the frame; Step S7: placing the green body coated with the electrolyte solution in a fume hood and placing the green body in the air to prevent deformation caused by volatilization of the deposition solution (to improve the electrolyte deposition effect); Step S8: placing the coating in a high temperature furnace and drying it at 80°C for 15 minutes, placing the dried sample in a warm isostatic press and performing warm isostatic pressing at 80°C and 20 MPa for 5 minutes; Step S9: The green body is placed between two zirconium plates padded with 0.9 cm ceramic sheets for pressure firing at a maximum temperature of 1400°C.

[0020] Get as Figure 2 The dense electrolyte film shown has a thickness of 5 μm.

[0021] Embodiment 2 Step S1: preparing a reaction solution containing 57.5% YSZ, 2% ethyl cellulose and 32.5% terpineol; Step S2: adding 5% polyvinyl pyrrolidone to the reaction solution to obtain a coating solution; Step S3: bottle the coating liquid and place it on a horizontal ball mill for ball milling at a speed of 800 r / min for 24 hours to obtain a deposition liquid; Step S4: Connecting a square PVC frame with a side length of 3 cm to the blank using organic silicone; Step S5: pre-ultrasonic dispersion of the deposition liquid, setting the temperature to 30°C and the time to 15 minutes; Step S6: using a pipette to measure a fixed amount of the deposition liquid being ultrasonically dispersed and slowly dripping and smearing it on the blank with the frame; Step S7: placing the green body coated with the electrolyte solution in a fume hood and placing the green body in the air to prevent deformation caused by volatilization of the deposition solution (to improve the electrolyte deposition effect); Step S8: placing the coating in a high temperature furnace and drying it at 80°C for 15 minutes, placing the dried sample in a warm isostatic press and performing warm isostatic pressing at 80°C and 20 MPa for 5 minutes; Step S9: The green body is placed between two zirconium plates padded with 0.9 cm ceramic sheets for pressure firing at a maximum temperature of 1400°C.

[0022] An electrolyte film with a thickness of about 4 μm is obtained; Figure 4 As shown, the thin film electrolyte prepared by natural volatilization deposition is consistent with the characteristic peaks of the standard spectrum, proving that it is YSZ.

[0023] Embodiment 3 Step S1: preparing a reaction solution containing 60% YSZ, 2% ethyl cellulose and 30% terpineol; Step S2: adding 5% polyvinyl pyrrolidone to the reaction solution to obtain a coating solution; Step S3: bottle the coating liquid and place it on a horizontal ball mill for ball milling at a speed of 800 r / min for 24 hours to obtain a deposition liquid; Step S4: Connecting a square PVC frame with a side length of 3 cm to the blank using organic silicone; Step S5: pre-ultrasonic dispersion of the deposition liquid, setting the temperature to 30°C and the time to 15 minutes; Step S6: using a pipette to measure a fixed amount of the deposition liquid being ultrasonically dispersed and slowly dripping and smearing it on the blank with the frame; Step S7: placing the green body coated with the electrolyte solution in a fume hood and placing the green body in the air to prevent deformation caused by volatilization of the deposition solution (to improve the electrolyte deposition effect); Step S8: placing the coating in a high temperature furnace and drying it at 80°C for 15 minutes, placing the dried sample in a warm isostatic press and performing warm isostatic pressing at 80°C and 20 MPa for 5 minutes; Step S9: Place the green body between two zirconium plates with 0.9 cm thick ceramic chips and perform pressure sintering at a maximum temperature of 1400 °C.

[0024] Obtain an electrolyte film with a thickness of about Figure 3 3 μm as shown.

[0025] Example 4 Step S1: Prepare a reaction solution containing 62.5% YSZ, 2% ethyl cellulose, and 27.5% terpineol. Step S2: Add 5% polyvinylpyrrolidone to the reaction solution to obtain a coating solution. Step S3: Place the coating solution in a bottle and perform ball milling on a horizontal ball mill at a rotation speed of 800 r / min for 24 h to obtain a deposition solution. Step S4: Connect a square PVC frame with a side length of 4 cm to the green body with silicone rubber. Step S5: Ultrasonically disperse the deposition solution in advance, set the temperature at 30 °C, and the time at 15 min. Step S6: Measure a fixed amount of the ultrasonically dispersed deposition solution with a pipette and slowly drip and smear it on the green body with the frame. Step S7: Place the green body coated with the electrolyte solution in a fume hood and suspend the green body to prevent deformation caused by the evaporation of the deposition solution (improve the electrolyte deposition effect). Step S8: Place the coating in a high-temperature furnace and perform drying treatment at 80 °C for 15 min. Put the dried sample into a warm isostatic press and perform warm isostatic pressing at 80 °C and 20 MPa for 5 min. Step S9: Place the green body between two zirconium plates with 0.9 cm thick ceramic chips and perform pressure sintering at a maximum temperature of 1400 °C.

[0026] Obtain an electrolyte film with a thickness of about 2 μm.

[0027] Example 5 Step S1: Prepare a reaction solution containing 65% YSZ, 2% ethyl cellulose, and 25% terpineol. Step S2: Add 5% polyvinylpyrrolidone to the reaction solution to obtain a coating solution. Step S3: Place the coating solution in a bottle and perform ball milling on a horizontal ball mill at a rotation speed of 800 r / min for 24 h to obtain a deposition solution. Step S4: Connect a square PVC frame with a side length of 5 cm to the green body with silicone rubber. Step S5: Ultrasonically disperse the deposition solution in advance, set the temperature at 30 °C, and the time at 15 min. Step S6: Slowly pipette and apply a fixed amount of the deposition liquid being ultrasonically dispersed drop by drop onto the green body with a frame. Step S7: Place the green body coated with the electrolyte solution in a fume hood and suspend the green body to prevent deformation caused by the evaporation of the deposition liquid (to improve the electrolyte deposition effect). Step S8: Place the coating in a high-temperature furnace and perform a drying treatment at 80 °C for 15 min. Put the dried sample into a warm isostatic press and perform warm isostatic pressing at 80 °C and 20 MPa for 5 min. Step S9: Place the green body between two zirconium plates with 0.9 cm ceramic chips as pads and perform pressure sintering, with the maximum temperature being 1400 °C.

[0028] An electrolyte thin film with a thickness of about 1 μm is obtained.

[0029] It can be proved by the above five examples that an ultra-thin electrolyte thin film with a thickness within 5 μm can be prepared by using the natural evaporation deposition technique and the deposition liquid used in the present invention.

[0030] Next, the performance parameters of the ultra-thin electrolyte thin film are evaluated through test experiments, including thin film thickness, electrolyte density, and chemical stability tests.

[0031] Experimental steps: Prepare an ultra-thin electrolyte thin film and prepare five samples according to the above five examples respectively.

[0032] Measurement of thin film thickness: Use a scanning electron microscope to measure the thickness of the deposited thin film.

[0033] Electrolyte density test: Characterize the compactness of the thin film distribution by observing the surface morphology of the sample through a scanning electron microscope.

[0034] Chemical stability test: Prepare several YSZ wafers with a thickness of 5 mm by dry pressing.

[0035] Deposit an appropriate amount of the deposition liquid on the YSZ wafers respectively according to the methods of the above five examples as specimens for chemical stability tests.

[0036] Measure the initial mass of the sample.

[0037] Prepare a group of concentrated nitric acid solutions with a nitric acid content of 65 - 68%.

[0038] Immerse the specimen in a beaker containing the concentrated nitric acid solution and let it stand for 24 h.

[0039] Take out the sample from the concentrated nitric acid solution, wash it with deionized water, and then dry it.

[0040] Measure the sample mass again and record the change in its magnitude.

[0041] Record the experimental data: Save the pictures taken by the scanning electron microscope of the cross-section and surface morphology of the sample, and record the results of the chemical stability test.

[0042] Insert the pictures taken by the scanning electron microscope and create data tables to organize and analyze the experimental results.

[0043] The data analysis is shown in Table 1: Table 1 Analysis Results ;

[0044] The summary is as follows: Thickness: Example sample 1 has the smallest thickness of 1.45 μm, and the thicknesses of the other samples are 2.01 μm (Example 2), 3.13 μm (Example 3), 4.27 μm (Example 4), and 4.89 μm (Example 5) respectively.

[0045] Chemical stability: By observing the mass loss of the sample before and after soaking the sample in a concentrated nitric acid solution with a nitric acid content of 65 - 68% for a certain period of time.

[0046] The method for preparing the YSZ thin film of the present invention is also applicable to preparing a high-density barrier layer to prevent element diffusion.

[0047] It should be noted that the content not elaborated in detail in the present invention is all prior art and is well-known to those skilled in the art.

[0048] Therefore, the present invention adopts the above method for preparing an ultra-thin electrolyte film by natural deposition, which has the advantages of simple process, low cost, and large-scale production. The prepared ultra-thin electrolyte film has high density, excellent chemical stability, and good electrochemical performance, and is applicable to the fuel cell field.

[0049] Finally, it should be noted that: The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing an ultra-thin electrolyte film by natural deposition, characterized in that: The following steps are involved: Step S1, preparing a reaction solution containing 55-65% YSZ powder, 2% ethyl cellulose and 25-35% terpineol by weight; Step S2, adding polyvinyl pyrrolidone to the reaction solution to obtain a coating solution; Step S3, ball milling the obtained coating liquid in sequence to obtain a uniform deposition liquid; Step S4, preparing a new substrate with a fixed size frame based on the anode substrate; Step S5, performing ultrasonic dispersion before adding the deposition liquid; Step S6, applying the deposition liquid to the prepared novel substrate; Step S7, the coating layer is naturally volatilized and deposited; Step S8, drying the electrolyte layer and the substrate, and performing warm isostatic pressing; Step S9: pressing and sintering to finally obtain a green body with an ultra-thin electrolyte layer deposited thereon.

2. The method for preparing an ultra-thin electrolyte film by natural deposition according to claim 1, characterized in that: In step S1, the particle size of the YSZ powder is 0.1-0.5 μm.

3. The method for preparing an ultra-thin electrolyte film by natural deposition according to claim 1, characterized in that: In step S2, polyvinyl pyrrolidone accounts for 5% of the total mass of the reaction solution.

4. The method for preparing an ultra-thin electrolyte film by natural deposition according to claim 1, characterized in that: Step S3 specifically includes: using a horizontal ball mill to ball-mill the coating liquid in step S2 at a rotation speed of 800 r / min.

5. The method for preparing an ultra-thin electrolyte film by natural deposition according to claim 1, characterized in that: Step S4 specifically includes: Step S41, preparing a frame, the frame is made of plastic; Step S42, bonding the frame and the anode substrate together through organic silica gel; Step S43, waiting for the organic silica gel substrate to evaporate and dry; Step S44, obtaining a substrate of a fixed size capable of carrying the deposition liquid.

6. The method for preparing an ultra-thin electrolyte film by natural deposition according to claim 1, characterized in that: In step S5, the ultrasonic dispersion is carried out at a temperature of 30° C. for 15 min.

7. The method for preparing an ultra-thin electrolyte film by natural deposition according to claim 1, characterized in that: Step S7 specifically includes: Step S71, placing the substrate after the deposition liquid is applied in an environment with a constant temperature of 26° C. and a constant humidity of 60%; Step S72, placing the substrate on the hollow frame; Step S73, accelerating volatilization by using a fan in a fume hood.

8. The method for preparing an ultra-thin electrolyte film by natural deposition according to claim 1, characterized in that: Step S8 specifically includes: Step S81, separating the frame from the substrate body by cutting to obtain a substrate of a fixed size; Step S82, placing the deposited substrate in a high temperature furnace; Step S83, maintaining the temperature at 80°C for 15 minutes; Step S84: Place the dried sample into a warm isostatic press and perform warm isostatic pressing at 80° C. and 20 MPa.

9. The method for preparing an ultra-thin electrolyte film by natural deposition according to claim 1, characterized in that: Step S9 specifically includes: Step S91, placing the green body after warm isostatic pressing between two zirconium plates padded with ceramic sheets; Step S92, placing in a muffle furnace, setting the maximum temperature to 1400°C, and performing pressure sintering.

10. The method for preparing an ultra-thin electrolyte film by natural deposition according to claim 1, characterized in that: In step S9, the thickness of the ultra-thin electrolyte film is less than or equal to 5 μm.

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