Preparation Method of a Porous SiC@PANI Core / Shell Nanowire Quasi-Array and Its Application in Supercapacitors

Abstract

The present invention relates to a preparation method of a porous SiC@PANI core / shell nanowire quasi-array and its application in supercapacitors, belonging to the technical field of energy manufacturing. The present invention discloses a preparation method of a porous SiC@PANI core / shell nanowire quasi-array, characterized in that the preparation method includes: mixing powders of polysilazane and melamine and placing them in a crucible covered with a carbon substrate, and loading SiC nanowires on the carbon substrate by chemical vapor deposition; then using the carbon substrate loaded with SiC nanowires as the anode, a platinum sheet electrode as the cathode, and an aniline acidic solution as the electrolyte, and obtaining a porous SiC@PANI core / shell nanowire quasi-array by pulse electrodeposition. The present invention also discloses a porous SiC@PANI core / shell nanowire quasi-array and its application in supercapacitors.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy manufacturing, and relates to a preparation method of porous SiC@PANI core / shell nanowire quasi-arrays and their application in supercapacitors. Background Art

[0002] Currently, the demand for energy storage devices such as lithium-ion batteries, fuel cells, and supercapacitors is increasing continuously, forcing researchers to search for sustainable energy storage technologies. Among various candidate energy storage devices, supercapacitors have attracted great interest due to their attractive characteristics, such as high power, excellent cycle stability, fast charge and discharge, environmental friendliness, and long lifespan. These important properties remain applicable to the requirements of portable storage systems in today's rapidly growing electronics industry. However, despite the above excellent characteristics, the main obstacle to their practical application is the low energy density. So far, the common method to enhance the performance of supercapacitors is to optimize the inherent properties of materials and adopt appropriate electrode structure design. Therefore, it has become an urgent task to develop energy storage active materials with excellent electrochemical properties and structures to rapidly increase the energy density of supercapacitors.

[0003] Polyaniline (PANI), as a pseudocapacitive material, has been widely studied in recent decades due to its high theoretical capacitance, low cost, easy synthesis, and can be used as a coating on various substrates, etc. However, PANI still has obvious problems in terms of its stability and utilization as a supercapacitor electrode active material, including: i) the expansion and contraction of the polyaniline backbone during the energy storage process damage the material structure, ii) the utilization rate of PANI during the rapid energy storage process is relatively low, which limits the loading amount of the electrode energy storage active substance. Therefore, it is very necessary to further seek simple and effective methods to design and prepare PANI electrodes with a stable structure and high loading amount.

[0004] Recently, to overcome the above problems, an effective method is to incorporate PANI into conductive materials, such as carbon and carbides, to improve the electrochemical performance. The composite material also limits the volume expansion and contraction of PANI, while improving the overall electron transfer efficiency of the composite material. Another method is to form oriented PANI, that is, to form a good nanostructure array on a conductive substrate instead of in powder form, which can promote the rapid penetration of the electrolyte into the gaps of the nanowires, thus fully utilizing the electrode surface area and resulting in a high specific capacitance and excellent rate performance.

[0005] Although significant progress has been made in polyaniline materials so far, it remains a formidable challenge to design and fabricate advanced polyaniline-based composite electrode materials with intelligent nanostructures to improve overall performance. Therefore, based on the above discussion, if an effective method for preparing supercapacitors can be explored, it is expected to solve the main problems existing in current supercapacitors and strongly promote their application in the field of microcircuits. Summary of the Invention

[0006] The object of the present invention is to address the above-mentioned problems existing in the prior art and propose a method for preparing porous SiC@PANI quasi-arrays by in-situ synthesis and applying them to supercapacitors.

[0007] The object of the present invention can be achieved by the following technical solutions:

[0008] A method for preparing a porous SiC@PANI core / shell nanowire quasi-array, the preparation method comprising: mixing powders of polysilazane and melamine and placing them in a crucible covered with a carbon substrate, and obtaining SiC nanowires by chemical vapor deposition; then using the carbon substrate loaded with SiC nanowires as the anode, a platinum sheet electrode as the cathode, and an aniline acidic solution as the electrolyte, and obtaining the SiC@PANI core / shell nanowire quasi-array by pulse electrodeposition.

[0009] Compared with ordinary arrays with neat arrangements, the silicon carbide nanowires of the present invention are arranged in a nearly vertical manner on the fibers of the carbon cloth, so they are called quasi-arrays.

[0010] Preferably, the pulse electrodeposition process sets the AC mode of the pulse power supply, the duty cycle is 45 - 55%, the voltage is 0 - 1.5V, the frequency is 45 - 55Hz, and the time is 40 - 75min.

[0011] More preferably, the voltage of the pulse electrodeposition process is 0 - 1.2V and the time is 50 - 70min.

[0012] Pulse electrodeposition can control parameters such as waveform, frequency, on-off ratio, and average current density, and the grain size obtained is smaller than that of direct current electrodeposition; and when using pulsed current, due to the existence of pulse intervals, the growing crystals are hindered, reducing epitaxial growth and changing the growth trend, so it is not easy to form large and thick crystals.

[0013] Preferably, the mass ratio of polysilazane to melamine is (2 - 4):1.

[0014] More preferably, the polysilazane is heated and cured at 250 - 270°C and then ground into fine powder in a ball mill.

[0015] Preferably, the carbon substrate includes one or more of carbon fiber cloth and carbon paper.

[0016] More preferably, the carbon substrate needs to be pretreated. The pretreatment process includes immersing the carbon substrate in a cobalt nitrate ethanol solution with a concentration of 0.01 - 0.1 mol / L to load the catalyst, and then drying it after taking it out.

[0017] Preferably, the chemical vapor deposition method includes heating and depositing in a high-temperature atmosphere sintering furnace.

[0018] More preferably, the heating process includes segmented heating in an argon atmosphere, rising from room temperature to the first-stage temperature in 45 - 50 min, then rising to the second-stage temperature in 9 - 13 min, and then dropping to the third-stage temperature in 8 - 12 min; where the first-stage temperature is 1380 - 1420 °C, the second-stage temperature is 1510 - 1590 °C, and the third-stage temperature is 1270 - 1310 °C.

[0019] Even more preferably, the second-stage temperature is 1540 - 1560 °C.

[0020] In the present invention, the loading amount of SiC is controlled by controlling the heating temperature. If the temperature is too high, the generated nanowire structure is irregular; if the temperature is too low, the loading amount is smaller. An excessive loading amount is not conducive to the subsequent deposition process, and a too small loading amount is not conducive to ion migration. Therefore, it is necessary to control the temperature so that an appropriate amount of SiC nanowires is loaded on the carbon substrate, which is beneficial to the performance of the material.

[0021] Preferably, the aniline acidic solution includes aniline monomer and an acidic solvent.

[0022] More preferably, in the aniline acidic solution, the concentration of aniline monomer is 0.005 - 0.02 mol / L, and the concentration of the acidic solvent is 0.4 - 0.7 mol / L.

[0023] Even more preferably, the aniline monomer is obtained by secondary distillation; the acidic solvent includes one or more of hydrochloric acid and sulfuric acid.

[0024] Aniline itself is insoluble in water and common organic solvents, and can form a salt with HCl, which is a very effective method for storing aniline, can prevent aniline oxidation, and at the same time, aniline hydrochloride is easily soluble in water. Aniline needs to be purified before use to improve the quality of polyaniline.

[0025] The present invention also provides a porous SiC@PANI core / shell nanowire quasi-array.

[0026] The present invention also provides an application of the porous SiC@PANI core / shell nanowire quasi-array in supercapacitors.

[0027] Preferably, the supercapacitor includes a positive electrode, a negative electrode, a separator, and an electrolyte. The positive and negative electrodes are carbon substrates loaded with porous SiC@PANI core / shell nanowire quasi-arrays, the separator is a polypropylene film, and the electrolyte is 1-3M H2SO4.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The supercapacitor assembled from the carbon substrate loaded with the prepared porous SiC@PANI core / shell nanowire quasi-arrays by the pulse electrodeposition method in the present invention has good specific capacitance, cycle stability, and energy density.

[0030] 2. The present invention uses the pulse electrodeposition method to deposit PANI on the surface of SiC nanowires to form a core-shell structure, and N and O elements are distributed in the shell layer, while Si elements are evenly distributed in the core layer.

[0031] 3. The SiC@PANI nanowires prepared by the chemical vapor deposition method and the pulse electrodeposition method in the present invention have a porous structure, which is beneficial to the progress of the electrochemical reaction.

[0032] 4. The present invention controls the temperature in the process of the chemical vapor deposition method to load an appropriate amount of SiC nanowires on the carbon substrate.

[0033] 5. The preparation method of the present invention is simple and controllable, and has high repeatability. Description of the Drawings

[0034] Figure 1 It is the scanning electron microscope image of the SiC@PANI core / shell nanowire quasi-array prepared in Example 1 of the present invention.

[0035] Figure 2 It is the EDS image of the SiC@PANI core / shell nanowire quasi-array prepared in Example 1 of the present invention.

[0036] Figure 3 It is the specific capacitance image of the SiC@PANI symmetric supercapacitor prepared in Example 1 of the present invention.

[0037] Figure 4 It is the cycle performance image of the SiC@PANI symmetric supercapacitor prepared in Example 1 of the present invention.

[0038] Figure 5 It is the Ragone image of the SiC@PANI symmetric supercapacitor prepared in Example 1 of the present invention.

[0039] Figure 6 It is the scanning electron microscope image of the SiC@PANI core / shell nanowire quasi-array prepared in Example 2 of the present invention.

[0040] Figure 7 This is the scanning electron microscope image of the SiC@PANI core / shell nanowire quasi-array prepared in Example 3 of the present invention.

[0041] Figure 8 This is the scanning electron microscope image of the SiC nanowires prepared in Example 5 of the present invention.

[0042] Figure 9 This is the scanning electron microscope image of PANI grown on carbon cloth prepared in Comparative Example 2 of the present invention. Detailed implementation manners

[0043] The following are specific examples of the present invention to further describe the technical solutions of the present invention, but the present invention is not limited to these examples.

[0044] Example 1

[0045] First, poly(silazane) is heated and cured at 260 °C, and then ground into fine powder in a ball mill; the carbon cloth is immersed in a 0.05 mol / L cobalt nitrate ethanol solution to load the catalyst, and then taken out and dried. The poly(silazane) and melamine powder with a mass ratio of 3:1 are mixed evenly and placed in a crucible covered with carbon cloth. The crucible is placed in a high-temperature atmosphere sintering furnace. Under an argon atmosphere, it is heated from room temperature to the first-stage temperature of 1400 °C in 48 min, then raised to the second-stage temperature of 1550 °C in 10 min, and then lowered to the third-stage temperature of 1300 °C in 8 min and then naturally cooled to obtain carbon cloth loaded with SiC nanowires. 0.005 mol of aniline monomer is dispersed in 500 ml of a 0.5 mol / L hydrochloric acid solution; then the above carbon cloth is placed in an electrolytic cell containing 15 ml of aniline acidic solution. The carbon cloth loaded with SiC nanowires is used as the anode, and a platinum sheet is used as the cathode. The pulse power supply is set in the AC mode, the duty cycle is 50%, the voltage is 0 - 1.2 V, the frequency is 50 Hz, and the time is 60 min. After deposition, it is taken out and dried to obtain the SiC@PANI core / shell nanowire quasi-array. The scanning electron microscope image of the prepared material is as Figure 1 shown, and there is a rough PANI layer on the surface of the nanorods; the EDS image is as Figure 2 shown, and N and O elements are mainly distributed in the shell layer, and Si elements are evenly distributed in the core layer, confirming the core / shell structure of SiC@PANI. The prepared SiC@PANI electrode material is tested with three electrodes in 1 M H2SO4, and the performance data are shown in Table 1. Then, two SiC@PANI electrode materials with the same area are used as the positive electrode and the negative electrode respectively, a polypropylene film is used as the separator, and 1 M H2SO4 is used as the electrolyte to assemble a symmetric button supercapacitor for two-electrode performance testing. The performance graph is as Figure 3 - 4 shown. When the current density is from 0.5 mA / cm 2Increased to 5 mA / cm 2 , the capacitance retention rate after being magnified by 10 times is as Figure 3 shown; after cycling 5000 times at a current density of 5 mA / cm 2 , the cycling performance graph is as Figure 4 shown; the energy density at a power density of 0.25 mW / cm 2 and the energy density at a power density of 2.5 mW / cm after being magnified by 10 times 2 are as Figure 5 shown, and the specific data is shown in Table 2.

[0046] Example 2

[0047] Compared with Example 1, the difference is that the temperature in the second stage is 1570 °C, and the scanning electron microscope image of the prepared material is as Figure 6 shown; and three-electrode tests are carried out, and the performance data is shown in Table 1. The prepared material is assembled into a symmetric button supercapacitor for two-electrode performance tests, and the performance data is shown in Table 2.

[0048] Example 3

[0049] Compared with Example 1, the difference is that a pulsed power supply AC mode is set, the duty cycle is 50%, the voltage is 0 - 1.2 V, the frequency is 50 Hz, the time is 20 min, and after deposition is completed, it is taken out and dried to obtain SiC@PANI core / shell nanowire quasi-arrays. The scanning electron microscope image of the prepared material is as Figure 7 shown; and three-electrode tests are carried out, and the performance data is shown in Table 1. The prepared material is assembled into a symmetric button supercapacitor for two-electrode performance tests, and the performance data is shown in Table 2.

[0050] Example 4

[0051] Compared with Example 1, the difference is that a pulsed power supply AC mode is set, the duty cycle is 50%, the voltage is 0 - 1.2 V, the frequency is 50 Hz, the time is 80 min, and after deposition is completed, it is taken out and dried to obtain SiC@PANI core / shell nanowire quasi-arrays. And three-electrode tests are carried out, and the performance data is shown in Table 1. Then the prepared material is assembled into a symmetric button supercapacitor for two-electrode performance tests, and the performance data is shown in Table 2.

[0052] Example 5

[0053] Compared with Example 1, the difference is that the temperature in the second stage is 1600 °C, and the scanning electron microscope image of the carbon cloth loaded with SiC nanowires is as Figure 8 shown. The prepared SiC@PANI core / shell nanowire quasi-arrays are subjected to three-electrode tests, and the performance data is shown in Table 1. Then the prepared material is assembled into a symmetric button supercapacitor for two-electrode performance tests, and the performance data is shown in Table 2.

[0054] Example 6

[0055] Compared with Example 1, the difference lies in that the temperature in the second stage is 1500 °C. The prepared SiC@PANI core / shell nanowire quasi-arrays were tested by three electrodes, and the performance data are shown in Table 1. Then, the prepared materials were assembled into a symmetric button supercapacitor for two-electrode performance testing, and the performance data are shown in Table 2.

[0056] Comparative Example 1

[0057] Compared with Example 1, the difference lies in that PANI was not deposited, and the prepared carbon cloth material loaded with SiC nanowires was directly tested by three electrodes, and the performance data are shown in Table 1. Then, the prepared materials were assembled into a symmetric button supercapacitor for two-electrode performance testing, and the performance data are shown in Table 2.

[0058] Comparative Example 2

[0059] Compared with Example 1, the difference lies in that PANI was directly deposited on the surface of the carbon cloth. The pulse power supply was set in the AC mode, the duty cycle was 50%, the voltage was 0 - 1.2 V, the frequency was 50 Hz, and the time was 60 min. The scanning electron microscope image of the prepared material is as Figure 9 shown; and three-electrode tests were carried out, and the performance data are shown in Table 1.

[0060] Comparative Example 3

[0061] Compared with Example 1, the difference lies in that PANI was deposited on the surface of the carbon cloth loaded with SiC nanowires prepared in Example 1 of the present invention by using the segmented current deposition method used in (Weijun Li. Preparation of Low-Dimensional SiC Nanomaterials and Their Application in Supercapacitors. Jilin University.), that is, deposited at 0.08 mA / cm 2 for 2 min, then deposited at 0.06 mA / cm 2 for 10 min, and finally deposited at 0.04 mA / cm 2 for 80 min. The prepared materials were tested by three electrodes, and the performance data are shown in Table 1.

[0062] Table 1. Data Sheet of Three-Electrode Performance Test

[0063] <![CDATA[Specific capacitance mF / cm 2 (1 mA / cm 2 )]]> Magnification performance % after magnifying 20 times Example 1 352.0 90.3 Example 2 275.6 87.4 Example 3 198.2 89.2 Example 4 179.4 80.5 Example 5 180.8 81.8 Example 6 197.0 86.3 Comparative Example 1 4.38 94.0 Comparative Example 2 243.8 32.1 Comparative Example 3 235.7 83.0

[0064] Table 2. Data Sheet of Two-Electrode Performance Test

[0065]

[0066] The present invention improves the material properties by controlling the heating deposition temperature, time, and the method of pulse electro-deposition. In Example 3, the pulse electro-deposition time is 20 min, and the deposition time is too short, resulting in poor performance; in Example 4, the pulse electro-deposition time is 80 min, and the deposition time is too long, resulting in excessive PANI covering on the surface, which is not conducive to ion exchange and leads to poor performance; in Example 5, the temperature in the second stage is too high, and the generated nanowire structure is irregular, which is not conducive to the occurrence of electrochemical reactions; in Example 6, the temperature in the second stage is too low, the loading amount is small, and the performance is reduced.

[0067] And in Comparative Example 3, according to the method of segment current deposition in (Weijun Li. Preparation of Low-Dimensional SiC Nanomaterials and Their Application in Supercapacitors. Jilin University.), PANI was deposited on the carbon cloth loaded with SiC nanowires prepared by the present invention. The three-electrode test results show that the performance of the material prepared by the present invention (the specific capacitance reaches 235.7 mF / cm 2 at 1 mA / cm 2 ; the retention rate of the specific capacitance is 83.0% at a current density of 20 mA / cm 2 ; the retention rate of the specific capacitance is 81.2% at a current density of 40 mA / cm 2 ) is higher than the data in the article (the specific capacitance reaches 225.6 mF / cm 2 at 1 mA / cm 2 ; the retention rate of the specific capacitance is 80.9% at a current density of 40 mA / cm 2 ).

[0068] In summary, the porous SiC@PANI core / shell nanowire quasi-arrays prepared by the present invention as the electrode material of a symmetric button supercapacitor can have good specific capacitance, cycle stability, and energy density; the preparation method of the present invention is simple and controllable, enabling the PANI layer on the surface of the prepared porous SiC@PANI core / shell nanowire quasi-arrays to be uniformly wrapped and form a core-shell structure.

[0069] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Those skilled in the art to which the present invention pertains can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, but will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A preparation method of a porous SiC@PANI core / shell nanowire quasi-array, characterized in that, The preparation method includes: Mixing polysilazane and melamine powder with a mass ratio of 3:1 evenly, placing them in a crucible covered with carbon cloth, putting the crucible into a high-temperature atmosphere sintering furnace, under an argon atmosphere, heating from room temperature to the first-stage temperature of 1400 °C in 48 min, then heating to the second-stage temperature of 1550 °C in 10 min, and then cooling to the third-stage temperature of 1300 °C in 8 min and then naturally cooling to obtain carbon cloth loaded with SiC nanowires; Dispersing 0.005 mol of aniline monomer in 500 ml of hydrochloric acid solution with a concentration of 0.5 mol / L; then placing the above carbon cloth in an electrolytic cell containing 15 ml of aniline acidic solution, using the carbon cloth loaded with SiC nanowires as the anode and a platinum sheet as the cathode, setting the pulse power supply in an alternating current mode, with a duty cycle of 50%, a voltage of 0 - 1.2 V, a frequency of 50 Hz, and a time of 60 min, taking it out and drying after deposition to obtain SiC@PANI core / shell nanowire quasi-arrays.

2. A porous SiC@PANI core / shell nanowire quasi-array, characterized in that, The porous SiC@PANI core / shell nanowire quasi-arrays are prepared by the preparation method described in claim 1.

3. Application of a porous SiC@PANI core / shell nanowire quasi-array as described in claim 2 in a supercapacitor.

4. The application according to claim 3, characterized in that, The supercapacitor includes a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode and the negative electrode are carbon substrates loaded with porous SiC@PANI core / shell nanowire quasi-arrays, the separator is a polypropylene membrane, and the electrolyte is 1M H2SO4.

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