CN107833755A - A kind of high-performance SiC@Fe2O3Hybrid supercapacitor negative material - Google Patents

Abstract

The present invention adopts hydrothermal method to prepare SiC@Fe ₂ O ₃ composite nanomaterials, the inner core is SiC nanowires, they are entangled with each other to form a special network structure, and the outer shell is an array composed of Fe ₂ O ₃ nano needles , the diameter of Fe ₂ O ₃ nanoneedles is 50-80nm, and the length is 200-300nm, and the nanoneedle array is neatly arranged and uniformly dispersed, and sufficient free spaces are formed between adjacent nanoneedles; the SiC@ The Fe ₂ O ₃ composite material has excellent electrochemical performance, and its maximum mass specific capacitance value is 721F g ^‑1 , and after 3000 cycles, its specific capacitance can still maintain 90.7% of the original specific capacitance, which is a great opportunity for building a new generation High-performance supercapacitors provide excellent candidate anode materials.

Description

A High Performance SiC@Fe2O3 Composite Supercapacitor Anode Material

technical field

The invention relates to the field of new energy storage, in particular to a high _- performance SiC@ _Fe2O3 composite supercapacitor negative electrode material.

technical background

Supercapacitor is a new type of energy storage device developed in recent years. It has the advantages of high power density, fast charging speed, long cycle life, wide operating temperature range, good safety performance and environmental protection. It is used in new energy vehicles, micro communication equipment , heavy machinery, aerospace and other fields have broad application prospects (Chinese invention patent, application number 201310326357.4; Chinese invention patent, application number 201610024861.2). However, the mismatch between the positive and negative electrodes of supercapacitors often leads to a decrease in the specific energy density of supercapacitors, especially in recent years, carbon materials (such as activated carbon, carbon nanotubes and graphene) are often used as supercapacitor anode materials (Journal of Power Sources ,2015,283,270-278; NPG Asia Materials,2015,7,e165), due to its low theoretical specific capacitance, this problem is more prominent, which seriously restricts its industrial production process. Therefore, it is necessary to design and build a new type and Anode materials that have a good match with the cathode are of great significance for improving the specific energy density of supercapacitors. At present, researchers are trying to replace traditional carbon materials with transition metal oxides such as V ₂ O ₅ , MoO ₃ , Fe ₂ O ₃ and Bi ₂ O ₃ to improve their specific capacitance, among which Fe ₂ O ₃ has attracted the most attention. Mainly because Fe ₂ O ₃ has high theoretical specific capacitance, excellent redox characteristics and electrochemical activity, and has the advantages of abundant raw materials, environmental friendliness and low price (J.Mater.Chem.A, 2016, 4, 12289 -12295; Chemical Engineering Journal, 2016, 306, 193-203). However, like other transition metal oxides, Fe ₂ O ₃ has the disadvantages of poor conductivity and cycle stability, and is prone to agglomeration on the substrate (Chinese invention patent, application number 201110150179.5; Chinese invention patent, application number 201610024861.2), which The specific surface of the active material will be reduced, resulting in the actual specific capacitance much lower than its theoretical value. In order to overcome the above problems, researchers often use carbon materials with good conductivity and large specific surface area, inorganic semiconductors or conductive polymers as the skeleton to compound with Fe ₂ O ₃ , which effectively improves the agglomeration of active materials and poor capacitance characteristics. Defects (J. Mater. Chem. A, 2016, 4, 9977-9985; ACS Appl. Mater. Interfaces 2015, 7, 27518-27525). Although the composite electrode materials prepared above have good electrochemical properties, they still cannot meet the requirements of high specific capacitance and rate characteristics in the charging and discharging process of new supercapacitors. Therefore, it is imperative to develop an ideal framework material. Row. As we all know, SiC nanowires not only have good mechanical properties and physical and chemical stability, large aspect ratio and specific surface area, excellent electrical conductivity and anti-corrosion and anti-oxidation properties, but also they are entangled with each other to form a special network. structure. Therefore, the network structure composed of SiC nanowires not only makes the active materials uniformly dispersed, but also provides a variety of transport channels for electron conduction during the charge and discharge process, and can also solve the collapse of the electrode structure caused by the volume expansion/shrinkage of the active materials, This makes them very competitive skeleton materials for composite electrodes of supercapacitors; in addition, SiC nanowire electrode materials can also exhibit high area specific capacitance, long-term cycle stability, excellent resistance to electrochemical corrosion and excellent flexibility Performance characteristics of supercapacitor electrodes made of silicon carbide nanowires grown on carbon fabric. Journal of Power Sources 2013,243,648-653. Alper, et al.Silicon carbide nanowires as highly robust electrodes of formicrosupercapa 230, 298-302). Therefore, when SiC nanowires are used as a skeleton to compound with nano Fe ₂ O ₃ , the capacitive properties of the composite negative electrode material can be greatly improved. So far, there is no report on Fe ₂ O ₃ nanoneedle array-coated SiC nanowire composite supercapacitor anode materials.

Contents of the invention

The purpose of the present invention is to overcome the disadvantages of agglomeration of single active materials, poor capacitance characteristics and easy corrosion of skeleton materials, and adopt a simple hydrothermal method to prepare a compound with high mass specific capacitance, rate performance and long-term cycle stability. Fe ₂ O ₃ nanoneedle arrays coated SiC nanowire composite supercapacitor anode materials, the specific preparation process includes: first, using SiC nanowires as the framework material, using a hydrothermal method to deposit Fe ₂ O ₃ precursors on the surface, and then The SiC@Fe ₂ O ₃ composite supercapacitor anode material was obtained after calcination.

The composite anode material prepared by this method exhibits excellent electrochemical performance. When the current density is 2Ag ^-1 , the mass specific capacitance value is 721F g ^-1 . When the current density increases to 12Ag ^-1 , the mass specific capacitance value It is 366F g ^-1 ; and after 3000 cycles, its specific capacitance can still maintain 90.7% of the original specific capacitance, which lays a theoretical foundation for the application of SiC nanowire-based functional nanocomposites in a new generation of high-performance supercapacitors. Experimental basis.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Figure 1 is a SEM photo of SiC nanowires and SiC@Fe ₂ O ₃ nanocomposites.

Fig. 2 is the XRD pattern of SiC@Fe ₂ O ₃ nanocomposite material.

Fig. 3 is the CV curve of SiC@Fe ₂ O ₃ nanocomposite material.

Fig. 4 is the galvanostatic charge-discharge curve of the SiC@Fe ₂ O ₃ nanocomposite material and the change curve of mass specific capacitance with current density.

Fig. 5 is the EIS curve of the SiC@Fe ₂ O ₃ nanocomposite material.

Figure 6 shows the cycle stability of SiC@Fe ₂ O ₃ nanocomposites.

Detailed ways

Example 1

Preparation of SiC nanowires

SiC nanowires were prepared on the carbon cloth by chemical vapor phase reaction, using the mixed powder of Si powder and graphite powder with a molar ratio of 1:1.5 as the raw material, and carbon cloth and nickel nitrate as the substrate and catalyst. The specific steps are: first, immerse the carbon cloth in the mixed solution of nickel nitrate and ethanol for 10 minutes, and then dry it in the air; Put it in the vacuum furnace and seal the vacuum furnace cover, connect the power supply and the circulating water system, then start the vacuum system, after evacuating for 30 minutes, close the valve to stop the vacuuming, and then pass high-purity Ar into the vacuum furnace to close to normal pressure, Close the Ar valve and vacuumize again, stop vacuuming after 30 minutes and fill Ar to close to normal pressure, repeat this operation 2-3 times to remove the air in the furnace as much as possible; then make the vacuum furnace heat up at a rate of 350-400°Ch ^-1 Rise from room temperature to 1250°C and keep it warm for 13-16 minutes, and finally turn off the power to let the vacuum furnace cool down to room temperature naturally. The SEM characterization results of SiC nanowires are shown in Figure 1a.

Preparation of SiC@Fe ₂ O ₃ Nanocomposite

First, measure 75ml of distilled water, and use it as a solvent to prepare a mixed solution of Fe(NO ₃ ) ₃ 6H ₂ O and Na ₂ SO ₄ with a concentration of 0.08M and 0.06M, respectively, and then mix it with the SiC nanowire deposited Put the carbon cloth (1×1cm ² ) into the autoclave together, seal it, keep it warm at 120°C for 8 hours, take it out after the autoclave is cooled to room temperature, rinse it with distilled water for 2-3 times, and dry it naturally in the air. The dried sample was placed in a muffle furnace, heated to 450°C at a heating rate of 2°C/min, kept for 2 hours, and cooled to room temperature naturally to obtain SiC@Fe ₂ O ₃ nanocomposites. The SEM and XRD characterization results of SiC@Fe ₂ O ₃ nanocomposites are shown in Figure 1b and Figure 2, respectively.

Electrochemical Performance Test of SiC@Fe ₂ O ₃ Nanocomposites

The SiC@Fe ₂ O ₃ nanocomposite electrode material was used as the working electrode, the saturated calomel electrode was used as the reference electrode, and the platinum wire electrode was used as the counter electrode to form a three-electrode system. In a 2mol L ^-1 KOH solution, the scan rate was controlled as 10～50mV s ^-1 , measure the cyclic voltammetry curve, see Figure 3, it can be seen from Figure 3 that there is redox reaction in the electrode during the charging and discharging process, and there is no obvious electrode polarization phenomenon; control the current The density is 2Ag ^-1 ~ 12Ag ^-1 , measure the constant current charge and discharge curve, see Figure 4, it can be seen from Figure 4 that when the current density is 2Ag ^-1 , the mass specific capacitance value is 721F g ^-1 , when the current When the density increases to 12Ag ^-1 , the mass specific capacitance value is 366F g ^-1 ; the frequency range is controlled from 0.01 to 100000Hz, and the AC impedance spectrum is measured, as shown in Figure 5. It can be seen from Figure 5 that the electrode material has a small The internal resistance and charge transfer resistance; the control current density is 12Ag ^-1 , and the cycle stability is measured, as shown in Figure 6. It can be seen from Figure 6 that after 3000 cycles, it can still maintain 90.7% of the original specific capacitance, which shows that This electrode material has excellent cycle stability.

Claims (3)

1. A kind of 1. high-performance SiC@Fe₂O₃Hybrid supercapacitor negative material, it is characterised in that：The combination electrode material Kernel is SiC nanowire, and shell is the Fe of proper alignment₂O₃Nano needle arrays, specific preparation process include：First, received with SiC Rice noodles are framework material, and Fe is deposited on its surface using hydro-thermal method₂O₃Presoma, then obtain SiC@Fe by calcination processing₂O₃ Hybrid supercapacitor negative material.
2. A kind of 2. high-performance SiC@Fe according to claim 1₂O₃Hybrid supercapacitor negative material, it is characterised in that： Kernel is SiC nanowire, and they are entangled to each other, constitutes a kind of special network structure；Shell is by Fe₂O₃Nanoneedle is formed Array, Fe₂O₃A diameter of 50-80nm of nanoneedle, length 200-300nm, and it is nano needle arrays proper alignment, scattered Uniformly, the free space of abundance is formd between adjacent nano pin.
3. A kind of 3. high-performance SiC@Fe according to claim 1₂O₃Hybrid supercapacitor negative material, it is characterised in that： The combination electrode material shows excellent chemical property, when current density is 2Ag^-1When, quality is than capacitance 721Fg^-1；And after 3000 circle circulations, its specific capacitance remains to keep the 90.7% of former specific capacitance.