CN111986931B - Manganese oxide nano-structure electrode material and preparation method and application thereof - Google Patents

Manganese oxide nano-structure electrode material and preparation method and application thereof Download PDF

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CN111986931B
CN111986931B CN202010722698.3A CN202010722698A CN111986931B CN 111986931 B CN111986931 B CN 111986931B CN 202010722698 A CN202010722698 A CN 202010722698A CN 111986931 B CN111986931 B CN 111986931B
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electrode material
manganese oxide
manganese
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oxide nano
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CN111986931A (en
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黄洪
孙贤
司徒粤
曹树坤
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South China University of Technology SCUT
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/48—Conductive polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/24—Electrodes characterised by structural features of the materials making up or comprised in the electrodes, e.g. form, surface area or porosity; characterised by the structural features of powders or particles used therefor
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/84—Processes for the manufacture of hybrid or EDL capacitors, or components thereof
    • H01G11/86—Processes for the manufacture of hybrid or EDL capacitors, or components thereof specially adapted for electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/13—Energy storage using capacitors

Abstract

The invention discloses a manganese oxide nano-structured electrode material and a preparation method and application thereof. The method comprises the following steps: 1) oxidizing the carbon fiber; 2) placing the oxidized carbon fibers in a potassium permanganate solution for high-temperature hydrothermal reaction to obtain electrode plates; 3) and (3) soaking the electrode slice in a manganese acetate solution, performing high-temperature hydrothermal reaction, washing and drying to obtain the manganese oxide nano-structure electrode material. The manganese oxide nano-structured electrode material prepared by the invention has the characteristics of large specific capacitance, excellent cycle performance, high coulombic efficiency and the like, the specific capacitance reaches 1709F/g when the current density is 1A/g, the capacitance retention rate reaches 91.9 percent of the initial value after 6000 charge-discharge cycles under 10A/g, and the coulombic efficiency reaches 100 percent.

Description

Manganese oxide nano-structure electrode material and preparation method and application thereof
Technical Field
The invention belongs to the technical field of supercapacitors, and particularly relates to a manganese oxide nano-structured electrode material and a preparation method and application thereof.
Background
Energy and environmental crisis have become two major problems faced in the world today, and in order to solve this problem, scientists are constantly searching for new renewable energy sources capable of replacing fossil energy, and solar energy, wind energy, hydrogen energy and other related environment-friendly energy sources are just in charge of. Since the beginning of the new century, the development and utilization of energy based on electrochemistry are rapidly developed, and most typically, the development and application of rechargeable lithium ion batteries lay a solid foundation for the development of later mobile electronic equipment, thereby facilitating the life of people. Meanwhile, another green environment-friendly electrochemical energy storage device supercapacitor is also rapidly developed. The lithium ion battery has the characteristics of fast charging time, high power density, high reversible cycle stability, low price and the like, and is considered to be a candidate device for replacing the lithium battery in the future. Since supercapacitors are mainly based on electric double layers and pseudocapacitances, mainly charge adsorption and reversible electron transfer, their energy density is not very high compared to lithium batteries. In order to improve the electrochemical performance of the supercapacitor mainly based on energy density, a great deal of research on electrode materials is continuously carried out, wherein the research on the electrode materials comprises transition metal oxides, fluorides, nitrides and sulfides, carbon materials (represented by graphene), metal organic framework MOF, organic covalent structure COF, MXene materials, lithium-containing battery-like materials and the like. Transition metal oxides are electrode materials which have been studied more extensively, in addition to carbon materials, and comprise bisElectrical layers, pseudocapacitors, and hybrid materials. Initially as RuO2The pseudocapacitance electrode material represented by the pseudocapacitance becomes the research heat tide of the electrode material of the super capacitor at one time, but because of RuO2The oxides of other transition metals are gradually replaced due to lack of resources, high price and harm to the environment, and the most representative oxides of manganese are used. Due to its low price, environmental protection and high theoretical capacitance, the related research in recent years is very common, such as MnO2，CNT/MnO2，grapheme/MnO2，MnMo4·H2O@MnO2，Mn3O4，Mn2O3And the like. However, the manganese oxide has poor conductivity, is easy to fall off when being compounded with other electrode materials, has relatively small specific capacitance when being prepared, and the like, and is a bottleneck and challenge for scientific research and marketization application.
Disclosure of Invention
In order to overcome the defects and shortcomings in the prior art, the invention mainly aims to provide a preparation method of a manganese oxide nano-structure electrode material. Firstly, carbon fibers are used as a substrate material, and oxidation of the carbon substrate is carried out at high temperature to provide compact and uniform carbon gaps and surface oxidation functional groups; then carrying out hydrothermal growth of manganese dioxide nanosheets in a potassium permanganate solution at a high temperature; taking the electrode slice obtained by the reaction as a substrate material, carrying out hydrothermal reaction at high temperature in a manganese acetate solution to grow manganese oxides with different crystal forms, and finally repeatedly cleaning and drying by deionized water to obtain the high-performance manganese oxide nano-structure electrode material.
The invention also aims to provide a manganese oxide nano-structured electrode material prepared by the method.
The invention further aims to provide application of the manganese oxide nano-structured electrode material in a super capacitor.
The purpose of the invention is realized by the following technical scheme:
a preparation method of a manganese oxide nano-structured electrode material comprises the following steps:
(1) oxidizing the carbon fiber at 200-600 ℃ for 1-8 h to obtain oxidized carbon fiber;
(2) adding oxidized carbon fibers into a potassium permanganate solution, carrying out hydrothermal reaction for 2-8 h at the temperature of 140-190 ℃, washing, and drying to obtain an electrode plate;
(3) soaking the electrode slice in a manganese acetate solution for 1-5 days to enable manganese acetate to be buried in a manganese oxide nano layer of the electrode slice; and carrying out hydrothermal reaction for 1-10 h at 150-210 ℃, growing manganese oxides with different crystal forms, washing and drying to obtain the manganese oxide nano-structure electrode material.
Preferably, before the oxidation treatment, the carbon fiber in the step (1) is further subjected to washing and drying treatment, wherein the washing refers to that the carbon fiber is placed in ethanol, washed under the ultrasonic action and then cleaned by deionized water; the drying is carried out according to the conventional drying operation.
Preferably, the temperature of the oxidation treatment in the step (1) is 300-600 ℃, and the time is 3-8 h; more preferably 3 to 7 hours.
Preferably, the oxidation treatment in step (1) is performed in an air atmosphere.
Preferably, the mass ratio of the oxidized carbon fibers to the potassium permanganate in the step (2) is 1-4: 1-5.
Preferably, the mass concentration of the potassium permanganate solution in the step (2) is 1-10 mg/mL; more preferably 2-8 mg/mL; the solvent is water.
Preferably, the temperature of the hydrothermal reaction in the step (2) is 150-170 ℃ and the time is 3-8 h. Preferably, the washing in step (2) is water washing, and the drying is conventional drying.
Preferably, the mass concentration of the manganese acetate solution in the step (3) is 0.5-20 mg/mL; more preferably 0.6-8 mg/mL; the solvent is a mixture of ethanol, glycol and water, wherein the volume ratio of the ethanol to the glycol to the water is 1-4: 2-8: 1; more preferably 1 to 4: 5-8: 1.
preferably, the manganese acetate solution in the step (3) is prepared by the following method: adding manganese acetate into the ethanol solution, stirring at a high speed for 0.1-1 h to uniformly disperse the manganese acetate, then adding the glycol solution and deionized water, and stirring at a high speed for 0.3-1.5 h to uniformly mix the manganese acetate and the deionized water.
Preferably, the soaking time in the step (3) is 2-4 days.
Preferably, the temperature of the hydrothermal reaction in the step (3) is 150-180 ℃ and the time is 3-9 h.
Preferably, the washing in step (3) is water washing, and the drying is conventional drying.
The manganese oxide nano-structure electrode material prepared by the method.
The carbon fiber in the manganese oxide nano-structured electrode material loads two manganese oxides with different crystal forms.
The manganese oxide nano-structure electrode material is applied to a super capacitor.
Compared with the prior art, the invention has the following advantages and beneficial effects:
the preparation method is simple, the surface of the manganese oxide nano-structured electrode material prepared by the invention has a high-density manganese oxide nano-sphere structure with the size of 20-50nm, and the manganese oxide nano-structured electrode material has larger specific capacitance compared with other manganese oxide nano-materials or composite materials, and the specific capacitance reaches 1709F/g when the current density is 1A/g; compared with other manganese oxide electrode materials, the manganese oxide nano-structure electrode material prepared by the invention has more excellent cycle performance, the capacitance retention rate reaches 91.9% of the initial value after 6000 times of charge-discharge cycle at 10A/g, the capacitance retention rate reaches 71.7% of the initial value after 20000 times of cycle, and the coulombic efficiency reaches 100%.
Drawings
Fig. 1 and 2 are scanning electron micrographs of the electrode sheet obtained in step (2) in example 1.
FIG. 3 is a scanning electron micrograph of the electrode material obtained in step (4) of example 1.
FIGS. 4 and 5 are transmission electron micrographs of the electrode material obtained in step (4) in example 1.
FIG. 6 is a cyclic voltammogram at scan rates of 5mV/s, 10mV/s, 20mV/s, 50mV/s, and 100mV/s for the electrode material obtained in step (4) of example 1.
FIG. 7 is a Raman spectrum of the electrode material obtained in step (4) in example 1.
FIG. 8 is an XRD pattern of the electrode material obtained in step (4) of example 1.
FIG. 9 is a graph showing charge and discharge curves of the electrode material obtained in step (4) of example 1 at current densities of 1A/g, 2A/g, 4A/g, 8A/g, 16A/g, and 20A/g.
FIG. 10 is a graph showing the charge/discharge cycle characteristics of the electrode material obtained in step (4) of example 1 at a current density of 10A/g.
Fig. 11 is a scanning electron micrograph of the electrode sheet obtained in step (2) in example 2.
FIG. 12 is a cyclic voltammogram at scan rates of 5mV/s, 10mV/s, 20mV/s, 50mV/s, and 100mV/s for the electrode material obtained in step (4) of example 2.
FIG. 13 is a graph showing charge and discharge curves of the electrode material obtained in step (4) of example 2 at current densities of 1A/g, 2A/g, 4A/g, 8A/g, 16A/g, and 20A/g.
FIG. 14 is a Raman spectrum of the electrode material obtained in step (4) in example 3.
FIG. 15 is a cyclic voltammogram at scan rates of 5mV/s, 10mV/s, 20mV/s, 50mV/s, and 100mV/s for the electrode material obtained in step (4) of example 3.
FIG. 16 is a graph showing charge and discharge curves of the electrode material obtained in step (4) of example 3 at current densities of 1A/g, 2A/g, 4A/g, 8A/g, 16A/g, and 20A/g.
Fig. 17 is a scanning electron micrograph of the electrode sheet obtained in step (2) of example 4.
FIG. 18 is a SEM image of the electrode material obtained in step (4) of example 4.
FIG. 19 is a cyclic voltammogram at scan rates of 5mV/s, 10mV/s, 20mV/s, 50mV/s, and 100mV/s for the electrode material obtained in step (4) in example 4.
FIG. 20 is a graph showing charge and discharge curves of the electrode material obtained in step (4) of example 4 at current densities of 1A/g, 2A/g, 4A/g, 8A/g, 16A/g, and 20A/g.
FIG. 21 is an XRD pattern of the electrode material obtained in step (4) of example 5.
FIG. 22 is a cyclic voltammogram at a scan rate of 5mV/s, 10mV/s, 20mV/s, 50mV/s, 100mV/s for the electrode obtained in step (4) of example 5.
FIG. 23 is a graph showing charge and discharge curves of the electrode material obtained in step (4) of example 5 at current densities of 1A/g, 2A/g, 4A/g, 8A/g, 16A/g, and 20A/g.
FIG. 24 is a SEM image of the electrode material obtained in step (4) of example 6.
FIG. 25 is a cyclic voltammogram at scan rates of 5mV/s, 10mV/s, 20mV/s, 50mV/s, and 100mV/s for the electrode material obtained in step (4) of example 6.
FIG. 26 is a graph showing charge and discharge curves of the electrode material obtained in step (4) of example 6 at current densities of 1A/g, 2A/g, 4A/g, 8A/g, 16A/g, and 20A/g.
FIG. 27 is a plot of cyclic voltammetry versus scan rate of 50mV/s for the electrode material obtained in step 4) of example 1, the electrode material obtained in step 5) of comparative example 1, and the electrode material obtained in step 3) of comparative example 2.
FIG. 28 shows the current density of 1Ag for the electrode material obtained in step 4) of example 1, the electrode material obtained in step 5) of comparative example 1, and the electrode material obtained in step 3) of comparative example 2-1The following charge and discharge curves are compared.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but the embodiments of the present invention are not limited thereto.
Those who do not specify specific conditions in the examples of the present invention follow conventional conditions or conditions recommended by the manufacturer. The raw materials, reagents and the like which are not indicated for manufacturers are all conventional products which can be obtained by commercial purchase.
The high-temperature heat treatment of the carbon fibers described in the examples and comparative examples of the present application was carried out in an air atmosphere.
Example 1
1) Placing the carbon fiber in absolute ethyl alcohol for ultrasonic washing, then washing with deionized water and drying; and (3) heating the dried carbon fiber in air at 500 ℃ for 4 h.
2) And placing the oxidized carbon fiber in a potassium permanganate aqueous solution of 4mg/mL according to the mass ratio of the carbon fiber to the potassium permanganate of 1.1:1 for hydrothermal reaction at 160 ℃ for 6 hours, repeatedly washing with deionized water, and drying to obtain the electrode plate.
3) Preparing a manganese acetate solution with the mass concentration of 5mg/mL according to the volume ratio of the ethanol to the glycol to the water solvent of 2:7: 1; firstly, weighing 0.1g of manganese acetate, adding the manganese acetate into 4mL of ethanol solution, stirring at a high speed for dissolving for 0.5h at normal temperature, then sequentially adding 14mL of ethylene glycol solution and 2mL of deionized water, and stirring for 1h at normal temperature to form uniform mixed solution; and then soaking the electrode slice obtained in the step 2) in the solution for 2 days to finish the electrode seed crystal burying.
4) Transferring the system obtained in the step 3) into a hydrothermal kettle, reacting for 5 hours at 180 ℃, removing the electrode when the system is cooled to normal temperature, repeatedly cleaning with deionized water, and drying to obtain the high-performance manganese oxide nano electrode material.
Fig. 1 and 2 are scanning electron micrographs of the electrode sheet obtained in step (2) in this example, and as can be seen from fig. 1, manganese dioxide is distributed more uniformly on the surface of carbon fiber and grows more densely; as can be seen from fig. 2, manganese dioxide is petal-shaped and has relatively significant voids.
FIG. 3 is a scanning electron micrograph of the electrode material obtained in step (4) in this example, from which MnO was observed2/Mn3O4The nanoparticles are uniformly distributed on the carbon fibers and have a particle size of about 5 to 50 nm.
FIGS. 4 and 5 are transmission electron micrographs of the electrode material obtained in step (4) in this example, and as can be seen from FIG. 4, the nanoparticles have different lattice sizes, indicating that the nanoparticles are composed of several different substances, mainly Mn3O4And MnO2(ii) a As can be seen from fig. 5, the thickness of the manganese dioxide nanolayer around the manganese oxide nanospheres is about 3-12 nm.
FIG. 6 is a cyclic voltammogram graph of the electrode material obtained in step (4) at scan rates of 5mV/s, 10mV/s, 20mV/s, 50mV/s, and 100mV/s, and it can be seen that the scan curve is trapezoidal-like, indicating thatThe capacitance is mainly in the form of double layer capacitance, and the specific capacitance is 905.2F g at scan rates of 5mV/s and 20mV/s-1And 469.4F g-1(ii) a The curve has a more pronounced rise near 0.8V, which is associated with Mn during the scan3O4Is involved in the oxidation phase transition.
FIG. 7 is a Raman spectrum of the electrode material obtained in step (4) in this example, from which it can be seen that there is a peak located at 571cm in addition to the distinct peaks D, G and 2D of the carbon fiber-1MnO of2Peak sum 650cm-1MnO ofxPeak, wherein MnOxMainly Mn3O4。
FIG. 8 is an XRD pattern of the electrode material obtained in step (4) in this example, and from the peak positions in the pattern, it can be seen that the composite mainly contains amorphous carbon and MnO2And Mn3O4。
FIG. 9 is a charging and discharging curve diagram of the electrode material obtained in step (4) in the embodiment, wherein the current density is 1A/g, 2A/g, 4A/g, 8A/g, 16A/g, and 20A/g, and as can be seen from the diagram, the charging and discharging curve is in a quasi-symmetrical triangular shape, which indicates that the electrode has good ion and charge transport capabilities; according to the formula C ═ It/(mV) (I represents the current density, t represents the discharge time, m represents the load mass, and V represents the voltage range), at a current density of 1Ag-1Capacitance of 1709F g-1The value is large.
Fig. 10 is a test chart of the charge-discharge cycle performance of the electrode material obtained in step (4) at a current density of 10A/g in this example, and it can be seen from the test chart that the capacitance retention rate reaches 91.9% of the initial value after 6000 cycles of charge-discharge at 10A/g, the capacitance retention rate reaches 71.7% of the initial value after 20000 cycles, and the coulombic efficiency reaches 100%.
Example 2
1) Placing the carbon fiber in absolute ethyl alcohol for ultrasonic washing, then washing with deionized water and drying; and (3) heating the dried carbon fiber in air at 400 ℃ for 5 h.
2) And placing the oxidized carbon fiber in a 2mg/mL aqueous solution of potassium permanganate at 150 ℃ for hydrothermal reaction for 7h according to the mass ratio of the carbon fiber to the potassium permanganate of 2.2:1, repeatedly washing with deionized water, and drying to obtain the electrode plate.
3) Preparing a manganese acetate solution with the mass concentration of 7mg/mL according to the volume ratio of ethanol to glycol to water solvent of 1:8: 1; firstly, weighing 0.14g of manganese acetate, adding the manganese acetate into 2mL of ethanol solution, stirring at a high speed for dissolving for 0.5h at normal temperature, then sequentially adding 16mL of ethylene glycol solution and 2mL of deionized water, and stirring for 1h at normal temperature to form uniform mixed solution; and then soaking the electrode slice obtained in the step 2) in the solution for 3 days to finish the electrode seed crystal burying.
4) Transferring the system obtained in the step 3) into a hydrothermal kettle, reacting for 7 hours at 170 ℃, removing the electrode when the system is cooled to normal temperature, repeatedly cleaning with deionized water, and drying to obtain the high-performance manganese oxide nano electrode material.
Fig. 11 is a scanning electron microscope image of the electrode sheet obtained in step (2) in this example, and it can be seen from the image that manganese dioxide nanosheets are crosslinked with each other, and the layer gap is small.
FIG. 12 is a cyclic voltammogram graph of the electrode material obtained in step (4) in this example at scan rates of 5mV/s, 10mV/s, 20mV/s, 50mV/s, and 100mV/s, and a specific capacitance of 831.1F g at scan rates of 5mV/s and 20mV/s-1And 481.3F g-1(ii) a As can be seen, the scan curve is in the shape of a horn, indicating Mn during the scan3O4The oxidation of (a) is significant.
FIG. 13 is a graph showing the charging and discharging curves of the electrode material obtained in step (4) at current densities of 1A/g, 2A/g, 4A/g, 8A/g, 16A/g and 20A/g in this example, and it can be seen from the graph that the curves are symmetrically triangular, indicating that the electrode has better ion and charge transport properties, but the shorter discharging time indicates that the electrode has relatively smaller capacitance.
Example 3
1) Placing the carbon fiber in absolute ethyl alcohol for ultrasonic washing, then washing with deionized water and drying; and (3) heating the dried carbon fiber in the air at 600 ℃ for 3 h.
2) And placing the oxidized carbon fiber in a potassium permanganate aqueous solution of 4mg/mL according to the mass ratio of the carbon fiber to the potassium permanganate of 1.1:1 for hydrothermal reaction at 170 ℃ for 6 hours, repeatedly washing with deionized water, and drying to obtain the electrode plate.
3) Preparing a manganese acetate solution with the mass concentration of 7.5mg/mL according to the volume ratio of the ethanol to the glycol to the water solvent of 2:7: 1; firstly, 0.15g of manganese acetate is weighed and added into 4mL of ethanol solution to be stirred and dissolved for 1h at a high speed at normal temperature, then 14mL of ethylene glycol solution and 2mL of deionized water are sequentially added to be stirred for 1h at normal temperature, and uniform mixed solution is formed; and then soaking the electrode slice obtained in the step 2) in the solution for 3 days to finish the electrode seed crystal burying.
4) Transferring the system obtained in the step 3) into a hydrothermal kettle to react for 3 hours at 180 ℃, removing the electrode when the system is cooled to normal temperature, repeatedly cleaning with deionized water, and drying to obtain the high-performance manganese oxide nano electrode material.
FIG. 14 is a Raman spectrum of the electrode material obtained in step (4) in this example, from which it can be seen that, in addition to the significant carbon fiber D, G and 2D peaks, there is a peak at 571cm-1MnO of2Peak sum 650cm-1MnO ofxPeak, wherein MnOxMainly Mn3O4。
FIG. 15 is a graph showing cyclic voltammetry curves of the electrode material obtained in step (4) at scan rates of 5mV/s, 10mV/s, 20mV/s, 50mV/s, and 100mV/s, and a specific capacitance of 604.1F g at scan rates of 5mV/s and 20mV/s in this example-1And 361.2F g-1(ii) a As can be seen, the scanning curve is trapezoidal-like, indicating that the capacitance type of the electrode is mainly double layer capacitance.
FIG. 16 is a charging/discharging curve diagram of the electrode material obtained in step (4) in the embodiment, wherein the current densities are 1A/g, 2A/g, 4A/g, 8A/g, 16A/g and 20A/g, and as can be seen from the diagram, the curve is in a quasi-symmetric triangular shape, which shows that the electrode has better ion and charge transport performance.
Example 4
1) Placing the carbon fiber in absolute ethyl alcohol for ultrasonic washing, then washing with deionized water and drying; and (3) heating the dried carbon fiber in air at 300 ℃ for 4 h.
2) And placing the oxidized carbon fibers in 8mg/mL aqueous solution of potassium permanganate according to the mass ratio of the carbon fibers to the potassium permanganate of 1.1:2 for hydrothermal reaction at 160 ℃ for 3 hours, repeatedly washing with deionized water, and drying to obtain the electrode plate.
3) Preparing a manganese acetate solution with the mass concentration of 8mg/mL according to the volume ratio of ethanol to glycol to water solvent of 4:5: 1; firstly, weighing 0.16g of manganese acetate, adding the manganese acetate into 8mL of ethanol solution, stirring at a high speed for dissolving for 0.7h at normal temperature, then sequentially adding 10mL of ethylene glycol solution and 2mL of deionized water, and stirring for 1.2h at normal temperature to form uniform mixed solution; and then soaking the electrode slice obtained in the step 2) in the solution for 2 days to finish the electrode seed crystal burying.
4) Transferring the system obtained in the step 3) into a hydrothermal kettle to react for 9 hours at 160 ℃, removing the electrode when the system is cooled to normal temperature, repeatedly cleaning with deionized water, and drying to obtain the high-performance manganese oxide nano electrode material.
Fig. 17 is a scanning electron microscope image of the electrode sheet obtained in step (2) in this example, and it can be seen from the image that the manganese dioxide layer is mainly composed of thicker nanowires, and the nanosheets are thinner.
FIG. 18 is a scanning electron micrograph of the electrode material obtained in step (4) in this example, from which it can be seen that the nanosphere size is between 20-50 nm.
FIG. 19 is a cyclic voltammogram graph of the electrode material obtained in step (4) in this example at scan rates of 5mV/s, 10mV/s, 20mV/s, 50mV/s, and 100mV/s, and a specific capacitance of 533.1F g at scan rates of 5mV/s and 20mV/s-1And 317.4F g-1(ii) a As can be seen, the scan curve is trapezoidal-like and the scan curve area at 100mV/s is significantly increased over other scan rates, which is mainly related to the Mn of the electrode under different scan conditions3O4The degree of oxidation of (c).
FIG. 20 is a graph showing the charging and discharging curves of the electrode material obtained in step (4) at current densities of 1A/g, 2A/g, 4A/g, 8A/g, 16A/g and 20A/g in this example, and it can be seen from the graph that the curves are in a triangle-like symmetrical shape, but the curve symmetry at 1A/g is poor, which indicates that the electrode has relatively poor ion and charge transport properties at the current density.
Example 5
1) Placing the carbon fiber in absolute ethyl alcohol for ultrasonic washing, then washing with deionized water and drying; and (3) heating the dried carbon fiber in air at 500 ℃ for 6 h.
2) And placing the oxidized carbon fiber in a potassium permanganate solution of 4.5mg/mL according to the mass ratio of the carbon fiber to the potassium permanganate of 1:1 for hydrothermal reaction at 150 ℃ for 8 hours, repeatedly washing with deionized water, and drying to obtain the electrode plate.
3) Preparing a manganese acetate solution with the mass concentration of 6mg/mL according to the volume ratio of ethanol to glycol to water solvent of 4:5: 1; firstly, weighing 0.12g of manganese acetate, adding the manganese acetate into 8mL of ethanol solution, stirring at a high speed for dissolving for 0.6h at normal temperature, then sequentially adding 10mL of ethylene glycol solution and 2mL of deionized water, and stirring for 0.5h at normal temperature to form uniform mixed solution; and then soaking the electrode slice obtained in the step 2) in the solution for 4 days to finish the electrode seed crystal burying.
4) Transferring the system obtained in the step 3) into a hydrothermal kettle to react for 5 hours at the temperature of 150 ℃, removing the electrode when the system is cooled to the normal temperature, repeatedly cleaning with deionized water, and drying to obtain the high-performance manganese oxide nano electrode material.
FIG. 21 is an XRD pattern of the electrode material obtained in step (4) in this example, and it can be seen from the figure that the composite material mainly contains amorphous carbon and MnO2And Mn3O4。
FIG. 22 is a graph showing cyclic voltammetry curves of the electrode material obtained in step (4) at scan rates of 5mV/s, 10mV/s, 20mV/s, 50mV/s, and 100mV/s, and specific capacitances of 351.1F g at scan rates of 5mV/s and 20mV/s-1And 242.2F g-1(ii) a As can be seen, the scan curve is in the shape of a horn, indicating Mn during the scan3O4The oxidation of (a) is significant.
FIG. 23 is a graph showing the charging and discharging curves of the electrode material obtained in step (4) at current densities of 1A/g, 2A/g, 4A/g, 8A/g, 16A/g and 20A/g in this example, and it can be seen from the graph that the curve has a quasi-symmetric triangular shape, which indicates better ion transport performance of the electrode, and the shorter discharging time indicates that the electrode has a relatively smaller specific capacitance.
Example 6
1) Placing the carbon fiber in absolute ethyl alcohol for ultrasonic washing, then washing with deionized water and drying; and (3) heating the dried carbon fiber in air at 400 ℃ for 7 h.
2) And (3) placing the oxidized carbon fiber in a 7mg/mL potassium permanganate aqueous solution according to the mass ratio of 4:5 of the carbon fiber to the potassium permanganate for hydrothermal reaction at 160 ℃ for 7h, repeatedly washing with deionized water, and drying to obtain the electrode plate.
3) Preparing a manganese acetate solution with the mass concentration of 0.6mg/mL according to the volume ratio of the ethanol to the glycol to the water solvent of 3:6: 1; firstly, 0.012g of manganese acetate is weighed and added into 6mL of ethanol solution to be stirred and dissolved at high speed for 0.9h at normal temperature, and then 12mL of glycol solution and 2mL of deionized water are added in sequence to be stirred for 1.5h at normal temperature to form uniform mixed solution; and then soaking the electrode slice obtained in the step 2) in the solution for 4 days to finish the electrode seed crystal burying.
4) Transferring the system obtained in the step 3) into a hydrothermal kettle to react for 9 hours at 180 ℃, removing the electrode when the system is cooled to normal temperature, repeatedly cleaning with deionized water, and drying to obtain the high-performance manganese oxide nano electrode material.
FIG. 24 is a scanning electron micrograph of the electrode material obtained in step (4) in this example, from which it can be seen that the nanoparticles grow more densely.
FIG. 25 is a graph showing cyclic voltammetry curves of the electrode material obtained in step (4) at scan rates of 5mV/s, 10mV/s, 20mV/s, 50mV/s, and 100mV/s, and specific capacitance of 532.6F g at scan rates of 5mV/s and 20mV/s in this example-1And 481.2F g-1(ii) a As can be seen, the scan curves are in the shape of horns, indicating Mn3O4The oxidation phase change of (2) is remarkable.
FIG. 26 is a graph showing the charging and discharging curves of the electrode material obtained in step (4) at current densities of 1A/g, 2A/g, 4A/g, 8A/g, 16A/g, and 20A/g in this example, and it can be seen from the graph that the curves mostly show a triangle-like symmetry, and the curve symmetry at 1A/g is poor, which indicates that the electrode has relatively poor ion and charge transport properties at the current density.
Comparative example 1
1) Placing the carbon fiber in absolute ethyl alcohol for ultrasonic washing, then washing with deionized water and drying; and (3) heating the dried carbon fiber in air at 500 ℃ for 4 h.
2) Dissolving potassium permanganate in deionized water, and stirring until the potassium permanganate is uniformly dispersed, wherein the mass concentration of the potassium permanganate is 4mg/mL, so as to obtain a solution A.
3) And dissolving manganese acetate in deionized water, and stirring until the manganese acetate is uniformly dispersed, wherein the mass concentration of the manganese acetate is 5mg/mL, so as to obtain a solution B.
4) Uniformly mixing and stirring the solution A in the step 2) and the solution B in the step 3), transferring the mixture into a polytetrafluoroethylene tank, and soaking the oxidized carbon fiber obtained in the step 1) in A, B mixed solution for 2 days according to the mass ratio of the carbon fiber to potassium permanganate of 1.1: 1.
5) Transferring the system obtained in the step 4) into a hydrothermal kettle, reacting for 5 hours at 180 ℃, repeatedly washing with deionized water, and drying to obtain the electrode material.
Comparative example 2
1) And (3) washing the foamed nickel in dilute hydrochloric acid, washing with deionized water and drying.
2) Preparing a manganese acetate solution with the mass concentration of 5mg/mL according to the volume ratio of the solvent of 2:7: 1; firstly, weighing 0.1g of manganese acetate, adding the manganese acetate into 4mL of ethanol solution, stirring at a high speed for dissolving for 0.5h at normal temperature, then sequentially adding 14mL of ethylene glycol solution and 2mL of deionized water, and stirring for 1h at normal temperature to form uniform mixed solution; and soaking the foamed nickel obtained in the step 1) in the solution for 2 days to finish the electrode seed crystal burying.
3) Transferring the system obtained in the step 2) into a hydrothermal kettle, reacting for 5 hours at 180 ℃, removing the electrode when the system is cooled to normal temperature, repeatedly cleaning with deionized water, and drying to obtain the foamed nickel loaded manganese oxide nano electrode material.
FIG. 27 is a cyclic voltammogram at a scan rate of 50mV/s for the electrode material obtained in step 4) of example 1, the electrode material obtained in step 5) of comparative example 1, and the electrode material obtained in step 3) of comparative example 2. As can be seen from the figure, the area enclosed by the scanning curve of growing manganese oxide in the manganese acetate solution after manganese dioxide is grown by potassium permanganate is far larger than the area formed by the scanning curve of growing manganese oxide by using a mixed solution of potassium permanganate and manganese acetate and using foamed nickel as a base material, and the electrode obtained by growing manganese oxide in the manganese acetate solution after manganese dioxide is grown in potassium permanganate has more excellent specific capacitance.
FIG. 28 shows the current density of 1A g for the electrode obtained in step 4) of example 1, the electrode material obtained in step 5) of comparative example 1, and the electrode material obtained in step 3) of comparative example 2-1The following charge-discharge curve diagram. Obtained according to the formula C ═ It/(mV) (I denotes current density, t denotes discharge time, m denotes load mass, and V denotes voltage range), C1＝1709F g-1，C2＝112.7F g-1And C3＝20.8F g-1(C1、C2、C3Representing the capacitances of the electrode materials obtained in step 4 in example 1, step 5 in comparative example 1, and step 3 in comparative example 2), respectively). From the above, the electrode obtained by growing manganese dioxide in potassium permanganate and then growing manganese oxide in manganese acetate solution has better specific capacitance performance.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims (10)

1. A preparation method of a manganese oxide nano-structured electrode material is characterized by comprising the following steps:
(1) oxidizing the carbon fiber at 200-600 ℃ for 1-8 h to obtain oxidized carbon fiber;
(2) adding oxidized carbon fibers into a potassium permanganate solution, carrying out hydrothermal reaction for 2-8 h at the temperature of 140-190 ℃, washing, and drying to obtain an electrode plate;
(3) soaking the electrode slice in a manganese acetate solution for 1-5 days to enable manganese acetate to be buried in a manganese oxide nano layer of the electrode slice; and carrying out hydrothermal reaction for 1-10 h at 150-210 ℃, growing manganese oxides with different crystal forms, washing and drying to obtain the manganese oxide nano-structure electrode material.
2. The preparation method of the manganese oxide nanostructured electrode material according to claim 1, wherein the mass ratio of the oxidized carbon fiber to the potassium permanganate in the step (2) is 1-4: 1-5.
3. The preparation method of the manganese oxide nano-structured electrode material according to claim 1 or 2, wherein the mass concentration of the potassium permanganate solution in the step (2) is 1-10 mg/mL; and (4) the mass concentration of the manganese acetate solution in the step (3) is 0.5-20 mg/mL.
4. The preparation method of the manganese oxide nano-structured electrode material as claimed in claim 3, wherein the temperature of the oxidation treatment in the step (1) is 300-600 ℃ and the time is 3-8 h; the temperature of the hydrothermal reaction in the step (2) is 150-170 ℃, and the time is 3-8 h; the soaking time in the step (3) is 2-4 days; the temperature of the hydrothermal reaction in the step (3) is 150-180 ℃, and the time is 3-9 h.
5. The preparation method of the manganese oxide nano-structured electrode material according to claim 3, wherein the mass concentration of the potassium permanganate solution in the step (2) is 2-8 mg/mL; and (4) the mass concentration of the manganese acetate solution in the step (3) is 0.6-8 mg/mL.
6. The method for preparing the manganese oxide nano-structured electrode material according to claim 3, wherein the solvent of the potassium permanganate solution in the step (2) is water; and (3) the solvent of the manganese acetate solution in the step (3) is a mixture of ethanol, ethylene glycol and water, wherein the volume ratio of the ethanol to the ethylene glycol to the water is 1-4: 2-8: 1.
7. the method for preparing a manganese oxide nanostructured electrode material according to claim 3, wherein said oxidation treatment of step (1) is carried out in an air atmosphere or an oxygen atmosphere; the manganese acetate solution in the step (3) is prepared by the following method: adding manganese acetate into the ethanol solution, stirring at a high speed for 0.1-1 h to uniformly disperse the manganese acetate, then adding the glycol solution and deionized water, and stirring at a high speed for 0.3-1.5 h to uniformly mix the manganese acetate and the deionized water.
8. The method for preparing the manganese oxide nanostructured electrode material according to claim 6, wherein the solvent of the manganese acetate solution in the step (3) is a mixture of ethanol, ethylene glycol and water, wherein the volume ratio of ethanol to ethylene glycol to water is 1-4: 5-8: 1.
9. a nanostructured electrode material of manganese oxide obtainable by the process according to any one of claims 1 to 8.
10. Use of a manganese oxide nanostructured electrode material according to claim 9 in a supercapacitor.
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