CN110136989B - Anode, preparation method thereof and prepared super capacitor - Google Patents
Anode, preparation method thereof and prepared super capacitor Download PDFInfo
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- CN110136989B CN110136989B CN201910498609.9A CN201910498609A CN110136989B CN 110136989 B CN110136989 B CN 110136989B CN 201910498609 A CN201910498609 A CN 201910498609A CN 110136989 B CN110136989 B CN 110136989B
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- 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
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Abstract
The invention relates to a positive electrode which is a flexible electrode and comprises a graphene sheet and a bimetallic sulfide attached to the graphene sheet. Compared with the single metal sulfide in the prior art, the conductivity of the double metal sulfide electrode material is several times or even dozens of times of that of the single metal sulfide, and the defects of poor cycle performance and poor rate characteristic of the single metal sulfide electrode material are overcome. In addition, the two components can be subjected to redox reaction, so that larger specific capacitance can be provided, and the high-ion-diffusion bimetallic sulfide and the high-conductivity flexible graphene sheet are cooperatively combined to prepare the high-specific-surface-area high-conductivity graphene sheet, which shows that the high-specific-surface-area high-conductivity graphene sheet has larger application potential in the fields of high power, high safety and power.
Description
Technical Field
The invention belongs to the field of energy materials, and particularly relates to an anode, a preparation method thereof and a prepared super capacitor.
Background
With the development of portable electronic products such as mobile phones, notebooks and tablet computers, people have raised higher-level challenges of being lighter, thinner, foldable, wearable, etc., in addition to the needs for their most basic application functions. In order to meet the energy requirements of these novel flexible electronic products, the research and development of novel flexible energy storage devices, such as flexible lithium ion batteries, flexible supercapacitors, etc., become one of the research focuses in the field of energy storage. The all-solid-state flexible supercapacitor has a good development space and a good application prospect due to high power density, fast charge and discharge rate, wide working temperature, good stability, long service life and low later maintenance cost, and particularly due to the fact that the graphene-based all-solid-state flexible supercapacitor is rapidly developed in recent years. However, the energy storage performance of most all-solid-state flexible supercapacitors developed at present still cannot meet daily requirements of people, such as the specific capacitance is still small, the energy density is still not high, the rate capability is relatively poor, and the like.
CN107342173B discloses a flexible supercapacitor electrode, which includes graphene paper and three-dimensional porous graphene compounded on the graphene paper. The preparation method of the flexible supercapacitor electrode comprises the following steps: (1) mixing and stirring the organic dispersion phase of the magnetic nanoparticles subjected to surface modification and the aqueous dispersion phase of graphene oxide, carrying out reaction, then carrying out centrifugal washing to obtain graphene oxide modified by the magnetic nanoparticles, and dispersing the graphene oxide modified by the magnetic nanoparticles in an ethanol solution to obtain a graphene oxide ethanol dispersion liquid modified by the magnetic nanoparticles; (2) coating graphene oxide gel on the surface of a substrate, then placing the substrate in an ethanol solution, applying a magnetic field below the graphene oxide gel, adding a magnetic nanoparticle modified graphene oxide ethanol dispersion liquid into the ethanol solution, and carrying out enrichment, arrangement and assembly on the graphene oxide gel surface by the magnetic nanoparticle modified graphene oxide under the action of the magnetic field to obtain a flexible supercapacitor electrode precursor; (3) and reducing the flexible supercapacitor electrode precursor and cleaning with deionized water to obtain the flexible supercapacitor electrode. The preparation method is complex in preparation process, the obtained electrode is poor in conductivity, and the electrochemical performance of the electrode cannot meet the requirements of excellent super capacitor electrodes.
CN108597905A discloses a preparation method of a fiber/graphene/cobalt nickel sulfide flexible electrode material, which comprises the following steps: A. dipping the pretreated fiber fabric into a graphene oxide suspension and drying, and repeating the step for a plurality of times to obtain a fiber/graphene oxide material, wherein the graphene oxide suspension is prepared by ultrasonically dispersing graphene oxide powder into deionized water; B. carrying out in-situ reduction on the fiber/graphene oxide material to obtain a fiber/graphene material; C. and D, immersing the fiber/graphene material obtained in the step B into a hydrothermal reaction kettle containing nickel salt, cobalt salt and a sulfur-containing precursor solution, and carrying out heating reaction to synthesize the fiber/graphene/cobalt nickel sulfide flexible electrode material. The electrode prepared by the method has poor conductivity and poor electrochemical performance.
CN108597906A discloses a preparation method of a fiber/graphene/copper sulfide flexible electrode material, which comprises the following steps: A. dipping the pretreated fiber fabric into a graphene oxide suspension and drying, and repeating the step for a plurality of times to obtain a fiber/graphene oxide material, wherein the graphene oxide suspension is prepared by ultrasonically dispersing graphene oxide powder into deionized water; B. carrying out in-situ reduction on the fiber/graphene oxide material to obtain a fiber/graphene material; C. and D, immersing the fiber/graphene material obtained in the step B into a hydrothermal reaction kettle containing copper salt and sulfur-containing precursor solution, and carrying out heating reaction to synthesize the fiber/graphene/copper sulfide flexible electrode material. The electrode prepared by the method has poor conductivity and poor electrochemical performance.
Therefore, how to prepare a self-supporting flexible thin film with good conductivity by a simple and effective method and further construct an all-solid-state flexible supercapacitor with excellent electrochemical behavior becomes the key point in the field of the current supercapacitors.
Disclosure of Invention
The invention aims to provide a positive electrode, a preparation method thereof and a prepared super capacitor.
In order to achieve the purpose, the invention adopts the following technical scheme:
one of the objects of the present invention is to provide a positive electrode, which is a flexible electrode and includes a graphene sheet and a bimetallic sulfide attached to the graphene sheet.
The conductivity of the bimetallic sulfide electrode material is several times or even dozens of times of that of a single metal sulfide, and the defects of poor cycle performance and poor rate characteristic of the single metal sulfide electrode material are overcome.
According to the invention, the flexible electrode is self-assembled by the bimetallic sulfide and the graphene to form a 3D flower-shaped structure, so that the current collector has a larger specific surface area, higher conductivity and high conductivity, and the energy density and the power density of the super capacitor are improved. Indicating that the high-power high-safety high-power high-safety high-power high-safety high-power high-safety high-power high-safety high-power high-safety high-power high-safety high-power high-safety high-power high-safety high-power high.
Preferably, the bimetallic sulfide is FeCo2S4。
Preferably, the diameter of the bimetallic sulfide is 3-4 μm, such as 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm or 3.9 μm.
FeCo of the invention2S4Compared with other bimetallic sulfides in the prior art, compared with other bimetallic sulfides, the iron element endows the bimetallic sulfide with higher conductivity, the cobalt element provides excellent specific capacity, the sulfur element provides sufficient conductivity and a richer redox state, and both the components can undergo redox reaction, so that larger specific capacitance can be provided, and therefore, the bimetallic sulfide pseudocapacitance electrode material shows excellent electrochemical performance.
The positive electrode is green and environment-friendly, and the high-specific-surface-area and high-conductivity bimetallic sulfide and the high-conductivity flexible graphene sheet are cooperatively combined to prepare the composite material with high specific surface area and high conductivity, and compared with other electrode materials grown in situ, the composite material has high power density and high area specific capacity, so that the composite material has great application potential in the fields of high power, high safety and power.
Preferably, the content of sulfur element in the bimetallic sulfide is 10 wt% to 50 wt%, such as 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt% or 50 wt%.
When the mass percentage of sulfur element in the bimetallic sulfide is less than 10 wt%, the specific capacity and the cycling stability of the material are reduced because the electrochemical active substance cannot be fully utilized in the electrochemical reaction process; when the mass percentage of sulfur element in the bimetallic sulfide is more than 50 wt%, the sulfide excessively reduces the specific surface area of the material, reduces the active site of electrochemical reaction, and reduces the specific capacity and the cycling stability of the material.
Preferably, the morphology of the bimetallic sulfide is a flower-like structure formed by stacking sheets.
The flower-like structure of the invention refers to a structure similar to a flower formed by building and stacking the bimetallic sulfide sheets mutually and not overlapping the sheets, and the typical but limiting example of the flower-like structure is shown in figure 1.
Preferably, the flower-like structure size of the bimetallic sulfide is 4-5 μm, such as 4.1 μm, 4.2 μm, 4.3 μm, 4.4 μm, 4.5 μm, 4.6 μm, 4.7 μm, 4.8 μm or 4.9 μm.
Preferably, the graphene sheets have a thickness of 10 μm to 100 μm, such as 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, or 90 μm.
Preferably, the content of the graphene sheets in the positive electrode is 30 wt% to 50 wt%, such as 32 wt%, 35 wt%, 38 wt%, 40 wt%, 42 wt%, 45 wt%, or 48 wt%, etc.
Another object of the present invention is to provide a method for producing the positive electrode according to the first object, the method comprising the steps of:
(1) mixing a mixed solution containing a metal source, a fluoride and an alkaline material with a graphene sheet, and then carrying out hydrothermal reaction to obtain a precursor;
(2) and mixing the precursor with a sulfide solution, and carrying out hydrothermal treatment to obtain the anode material.
According to the invention, the flower-shaped structure formed by stacking the lamellar bimetallic sulfides is obtained in a manner of growing the bimetallic sulfides on the graphene sheet in situ, the specific surface area of the electrode can be effectively increased by the structure, and the preparation method of the positive electrode is simple and easy, and is very beneficial to large-scale preparation, development and application of the positive electrode.
Preferably, the metal source of step (1) comprises an iron source and a cobalt source.
Preferably, the molar ratio of the iron source, the cobalt source and the alkaline material in the mixed solution in the step (1) is 1: 1-4: 2-8, such as 1:2:6, 1:3:4, 1:2:5, 1:2:6, 1:3:5, 1:4:3, 1:3:7, 1:2:8, 1:3:6, 1:1:5 or 1:4: 8.
Preferably, the molar ratio of the fluoride and the alkaline material in step (1) is 1:1 to 3, such as 1:1.2, 1:1.4, 1:1.5, 1:1.6, 1:1.8, 1:2, 1:2.1, 1:2.3, 1:2.5, 1:2.6, 1:2.7, 1:2.8, or 1: 2.9.
When the molar ratio of the fluoride to the alkaline material is more than 1:1, a complete flower-shaped electrode material cannot be formed due to insufficient amount of the precipitant, so that the cycle performance of the capacitor is influenced; when the molar ratio of the fluoride to the alkaline material is less than 1:3, the flower-like structure generated by excessive precipitator is too thick, which is not beneficial to the full reaction of the electrode material and the reduction of the specific capacity of the electrode material.
Preferably, the mass ratio of the graphene sheet to the metal source in step (1) is 1:1 to 3, such as 1:1.2, 1:1.4, 1:1.5, 1:1.6, 1:1.8, 1:2, 1:2.1, 1:2.3, 1:2.5, 1:2.6, 1:2.7, 1:2.8, or 1: 2.9.
When the mass ratio of the graphene sheet to the metal source is less than 1:3, the formed graphene film is thin, so that the flexibility of the electrode material is reduced; when the mass ratio of the graphene sheet to the metal source is greater than 1:1, the mass of the formed graphene film is larger than that of the electrode active material, and the specific capacity of the whole electrode is reduced.
Preferably, the iron source in step (1) is Fe (NO)3)2。
Preferably, the cobalt source in step (1) is Co (NO)3)2。
Preferably, the fluoride in step (1) is ammonium fluoride.
Preferably, the alkaline material of step (1) is urea.
Preferably, the hydrothermal temperature in step (1) is 100 to 140 ℃, for example 105 ℃, 110 ℃, 115 ℃, 120 ℃, 125 ℃, 130 ℃ or 135 ℃.
When the hydrothermal temperature is less than 100 ℃, the size of the electrode material is reduced, the surface energy is too large or the amount of the end-capped molecules is insufficient, so that the conductivity of the material is reduced; when the hydrothermal temperature is higher than 140 ℃, due to the excessively fast reaction speed, the initial crystal nucleus is increased by increasing the temperature to form agglomeration, so that the specific surface area of the electrode material is reduced, and the specific capacity and the cycling stability of the electrode material are reduced.
Preferably, the hydrothermal time in the step (1) is 6-10 h, such as 7h, 8h or 9 h.
When the hydrothermal time is less than 6h, a complete flower-shaped structure morphology cannot be formed to influence the cycle performance of the electrode material; when the hydrothermal time is longer than 10h, the morphology of the flower-shaped structure collapses to be unfavorable for full reaction of the electrode material, and the specific capacity of the material is reduced.
Preferably, the hydrothermal process of step (1) further comprises a washing and drying process.
Preferably, the drying temperature is 40-80 ℃, such as 45 ℃, 50 ℃, 55 ℃, 60 ℃, 65 ℃, 70 ℃ or 75 ℃.
Preferably, the drying time is 2-4 h, such as 2.2h, 2.5h, 2.8h, 3h, 3.2h, 3.5h or 3.8 h.
Preferably, the preparation process of the graphene sheet in step (1) comprises: graphene oxide is prepared by a Hummers method, and then thermal treatment is carried out to obtain graphene sheets.
Preferably, the temperature of the heat treatment is 200 to 400 ℃, for example, 220 ℃, 250 ℃, 280 ℃, 300 ℃, 320 ℃, 350 ℃ or 380 ℃.
The method comprises the steps of placing a dry graphene oxide sheet in an environment of 200-400 ℃ for rapid heating to enable the graphene oxide sheet to undergo rapid reduction reaction to generate a graphene sheet, and decomposing functional groups of the graphene oxide to generate CO in the reduction reaction process2CO and H2And O gas, wherein the graphene oxide is stripped in the generation process of the gas to obtain the flexible substrate graphene sheet.
Preferably, the time of the heat treatment is 2-6 h, such as 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h or 6 h.
Preferably, the ratio of the sulfide compound in step (2) to the total molar amount of the iron source and the cobalt source in step (1) is 1-2: 1, such as 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 5:3, 1.7:1, 1.8:1, or 1.9: 1.
Preferably, the sulfide of step (2) is sodium sulfide and/or thiourea.
Preferably, the hydrothermal temperature in step (2) is 140 to 180 ℃, for example, 145 ℃, 150 ℃, 155 ℃, 160 ℃, 165 ℃, 170 ℃ or 175 ℃, and the like.
When the hydrothermal temperature is lower than 140 ℃, the size of the electrode material is reduced, the surface energy is too large or the amount of the end-capped molecules is insufficient, so that the conductivity of the material is reduced; when the hydrothermal temperature is higher than 180 ℃, the reaction speed is too high, the temperature is increased, initial crystal nuclei are increased to form agglomerates, the specific surface area of the electrode material is reduced, and the specific capacity and the cycling stability of the electrode material are reduced.
Preferably, the temperature of the hydrothermal of step (2) is > the temperature of the hydrothermal of step (1).
Preferably, the hydrothermal time in the step (2) is 6-10 h, such as 6.5h, 7h, 7.5h, 8h, 8.5h, 9h or 9.5 h.
When the hydrothermal time is less than 6h, the bimetallic sulfide cannot be sufficiently formed due to insufficient reaction time, so that the specific capacity and the use efficiency of the material are reduced; when the hydrothermal time is more than 10 hours, the thickening of the flower-shaped lamellar layer reduces the specific surface area of the material and reduces the cycling stability of the material.
Preferably, the step (2) further comprises a washing and drying process after the hydrothermal process.
Preferably, the drying temperature is 40-80 ℃, such as 45 ℃, 50 ℃, 55 ℃, 60 ℃, 65 ℃, 70 ℃ or 75 ℃.
Preferably, the drying time is 4-8 h, such as 4.5h, 5h, 5.5h, 6h, 6.5h, 7h or 7.5 h.
As a preferred technical scheme, the preparation method of the positive electrode comprises the following steps:
(1) preparing graphene oxide by adopting a Hummers method, and then carrying out heat treatment at 200-400 ℃ for 2-6 h to obtain graphene sheets;
(2) will contain Fe (NO)3)2、Co(NO3)2A mixed solution of ammonium fluoride and urea, in which Fe (NO) is mixed, is mixed with the graphene sheet3)2、Co(NO3)2The molar ratio of the ammonium fluoride to the urea is 1: 1-4: 2-8, the molar ratio of the ammonium fluoride to the urea is 1: 1-3, the thickness of the graphene sheet is 10-100 microns, the mass ratio of the graphene sheet to the metal source is 1: 1-3, then carrying out hydrothermal reaction at 100-140 ℃ for 6-10 h, cleaning, and drying at 40-80 ℃ for 2-4 h to obtain a precursor;
(3) mixing the precursor with a sodium sulfide solution, the sodium sulfide being in contact with the Fe (NO) in step (1)3)2And Co (NO)3)2The total molar weight ratio of the positive electrode to the negative electrode is 1-2: 1, hydrothermal is carried out at 140-180 ℃ for 6-10 h, cleaning is carried out, and drying is carried out at 40-80 ℃ for 4-8 h, so as to obtain the positive electrode.
It is a further object of the present invention to provide a supercapacitor including the positive electrode according to one of the objects.
Preferably, the supercapacitor further comprises a negative electrode and a gel electrolyte.
The specific capacitance of the super capacitor obtained by the invention under the current density of 1A/g, 2A/g, 5A/g, 8A/g and 10A/g can reach 247.93F/g, 228.32F/g, 197.11F/g, 175.85F/g and 149.72F/g, the energy density can reach 88.2Wh/kg, the power density can reach 8001Wh/kg, and the cycle performance of 5000 cycles can reach 85.1%. And basically does not influence the electrochemical behavior in the bending and twisting state, has the advantages of larger energy density and power density, portability, foldability and the like, and can be applied to some special fields, such as wearable and foldable electronic devices and the like.
The super capacitor constructed in the invention can be used in series or in parallel, for example, a plurality of devices connected in series can drive small electronic equipment such as LED lamp beads to normally work after being fully charged.
The fourth purpose of the invention is to provide a preparation method of the supercapacitor, which comprises the following steps: and separating the anode and the cathode by adopting a diaphragm, and then injecting electrolyte to obtain the super capacitor.
Preferably, the preparation process of the negative electrode comprises: mixing the activated carbon and the adhesive to prepare slurry, coating the slurry on carbon cloth, and drying to obtain the cathode.
Preferably, the preparation process of the electrolyte comprises: polyvinyl alcohol was mixed with hot water, stirred until a clear gel appeared, cooled, and then the gel was mixed with KOH to obtain an electrolyte.
Preferably, the temperature of the hot water is 80-100 ℃, such as 85 ℃, 90 ℃ or 95 ℃.
Preferably, in the mixed solution of the polyvinyl alcohol and the hot water, the concentration of the polyvinyl alcohol is 0.05-0.2 g/mL, such as 0.06g/mL, 0.08g/mL, 0.1g/mL, 0.12g/mL, 0.15g/mL, or 0.18 g/mL.
Preferably, the mass ratio of KOH to polyvinyl alcohol is 0.5-1.5: 1, such as 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, or 1.4: 1.
Compared with the prior art, the invention has the following beneficial effects:
(1) the conductivity of the bimetallic sulfide electrode material is several times or even dozens of times of that of the monometal sulfide, and the defects of poor cycle performance and poor rate characteristic of the monometal sulfide electrode material are overcome. In addition, both components can undergo redox reaction, thereby providing larger specific capacitance, and therefore, the bimetallic sulfide pseudocapacitance electrode material shows excellent electrochemical performance.
(2) The positive electrode is green and environment-friendly, and the high-specific-surface-area and high-conductivity bimetallic sulfide and the high-conductivity flexible graphene sheet are cooperatively combined to prepare the composite material with high specific surface area and high conductivity, and compared with other electrode materials grown in situ, the composite material has high power density and high area specific capacity, so that the composite material has great application potential in the fields of high power, high safety and power.
(3) The specific surface area of the super capacitor constructed in the invention is more than or equal to 50m2g, the corresponding specific capacitance under the current density of 1A/g, 2A/g, 5A/g, 8A/g and 10A/g can reach 247.93F/g, 228.32F/g, 197.11F/g, 175.85F/g and 149.72F/g, the energy density can reach 88.2Wh/kg, the power density can reach 8001Wh/kg, the cycle performance of 5000 cycles can reach 85.1 percent, the electrochemical behavior of the material is not basically influenced in the bending and twisting states, the material has the advantages of larger energy density and power density, portability, foldability and the like, can be applied to some special fields such as wearable and foldable electronic devices and the like, meanwhile, the super capacitor constructed in the invention can be used in series or in parallel, for example, a plurality of devices connected in series can drive small electronic equipment such as LED lamp beads to normally work after being fully charged.
Drawings
Fig. 1 is an SEM image of a positive electrode obtained in embodiment 1 of the present invention;
fig. 2 is an XRD spectrum of the positive electrode obtained in embodiment 1 of the present invention;
FIG. 3 is an XPS spectrum of a positive electrode obtained in embodiment 1 of the present invention;
fig. 4 is a constant current charging and discharging curve of the super capacitor obtained in embodiment 1 of the present invention;
fig. 5 is a diagram of the structure and performance test of the super capacitor obtained in embodiment 1 of the present invention.
Detailed Description
For the purpose of facilitating an understanding of the present invention, the present invention will now be described by way of examples. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
Example 1
The preparation method of the supercapacitor comprises the following steps:
(1) preparing a 5mg/mL graphene oxide solution by adopting a Hummers method, and then carrying out heat treatment at 300 ℃ for 2h to obtain graphene sheets;
(2) will contain Fe (NO)3)2、Co(NO3)2A mixed solution of ammonium fluoride and urea, in which Fe (NO) is mixed, is mixed with the graphene sheet3)2、Co(NO3)2The molar ratio of the ammonium fluoride to the urea is 1:2:6, the molar ratio of the ammonium fluoride to the urea is 1:2, the thickness of the graphene sheet is 20 micrometers, the mass ratio of the graphene sheet to the metal source is 1:2, then carrying out hydrothermal reaction at 120 ℃ for 8 hours, cleaning, and drying at 60 ℃ for 3 hours to obtain a precursor;
(3) mixing the precursor with a sodium sulfide solution, the sodium sulfide being in contact with the Fe (NO) in step (1)3)2And Co (NO)3)2The total molar weight ratio of the raw materials is 5:3, hydrothermal is carried out for 8 hours at 160 ℃, cleaning is carried out, and drying is carried out for 6 hours at 60 ℃ to obtain a positive electrode;
the appearance of the positive electrode is shown in FIG. 1, and FeCo can be seen in the figure2S4Successfully loaded on the surface of a graphene sheet, and the composite material keeps the flower-shaped array morphology and has the diameter of about 3-4 mu m; the XRD spectrum of the positive electrode is shown in fig. 2, from which it can be seen that 30.8 °, 36.1 °, 43.2 °, 58.1 ° and 63.9 ° respectively correspond to crystal planes (220), (311), (400), (511) and (440) corresponding to Co in PDF card3O4(PDF 42-1467), after vulcanization, the crystal planes at 21.9 °, 31.2 °, 37.9 °, 49.9 ° and 55.3 ° are (220), (311), (400), (511) and (440) corresponding to Co in PDF cards3S4(PDF47-1738), from which FeCo is known2S4Successfully loaded on the surface of a graphene sheet; the XPS spectrum of the positive electrode is shown in FIG. 3, and the specific connection of Fe, Co and S can be seenFeCo is known from nearly 1:2:42S4Successfully loaded on the surface of a graphene sheet;
(4) mixing activated carbon and a binder to prepare slurry, coating the slurry on carbon cloth, and drying to obtain a negative electrode;
(5) mixing polyvinyl alcohol with hot water at 90 ℃ according to the concentration of the polyvinyl alcohol of 0.1g/mL, stirring until clear gel appears, cooling, and then mixing the gel with KOH, wherein the mass ratio of the KOH to the polyvinyl alcohol is 1:1, so as to obtain an electrolyte;
(6) separating the anode and the cathode by adopting a diaphragm, and then injecting the electrolyte to obtain the super capacitor; the structure and performance test chart of the supercapacitor is shown in FIG. 5, the constant current charging and discharging chart of the supercapacitor is shown in FIG. 4, and it can be seen from the chart that the corresponding values under the conditions of current density of 1A/g, 2A/g, 5A/g, 8A/g and 10A/g are 247.93F/g, 228.32F/g, 197.11F/g, 175.85F/g and 149.72F/g respectively.
Example 2
The difference from the example 1 is that the hydrothermal time of the step (2) is 6 h.
Example 3
The difference from the example 1 is that the hydrothermal time of the step (2) is 10 h.
Example 4
The difference from the example 1 is that the hydrothermal time of the step (2) is 5 h.
Example 5
The difference from the example 1 is that the hydrothermal time of the step (2) is 12 h.
Example 6
The difference from example 1 is that the sodium sulfide in step (3) is Fe (NO) in step (1)3)2And Co (NO)3)2The ratio of the total molar amount of (a) is 1.2: 1.
Example 7
The difference from example 1 is that the molar ratio of ammonium fluoride and urea in step (2) is 2: 1.
Example 8
The difference from example 1 is that the molar ratio of ammonium fluoride and urea in step (2) is 1: 4.
Example 9
The preparation method of the supercapacitor comprises the following steps:
(1) preparing a 5mg/mL graphene oxide solution by adopting a Hummers method, and then carrying out heat treatment at 200 ℃ for 2h to obtain graphene sheets;
(2) will contain Fe (NO)3)2、Co(NO3)2A mixed solution of ammonium fluoride and urea, in which Fe (NO) is mixed, is mixed with the graphene sheet3)2、Co(NO3)2The molar ratio of the graphene sheet to the urea is 1:4:8, the molar ratio of the ammonium fluoride to the urea is 1:2, the mass ratio of the graphene sheet to the metal source is 1:1.5, then carrying out hydrothermal reaction at 100 ℃ for 8h, cleaning, and drying at 40 ℃ for 4h to obtain a precursor;
(3) mixing the precursor with a sodium sulfide solution, the sodium sulfide being in contact with the Fe (NO) in step (1)3)2And Co (NO)3)2The total molar weight ratio of the anode to the cathode is 2:1, hydrothermal is carried out for 10 hours at 140 ℃, cleaning is carried out, and drying is carried out for 8 hours at 40 ℃ to obtain an anode;
(4) mixing activated carbon and a binder to prepare slurry, coating the slurry on carbon cloth, and drying to obtain a negative electrode;
(5) mixing polyvinyl alcohol with hot water at the temperature of 80 ℃ according to the concentration of the polyvinyl alcohol of 0.05g/mL, stirring until clear gel appears, cooling, and then mixing the gel with KOH, wherein the mass ratio of the KOH to the polyvinyl alcohol is 1.5:1, so as to obtain an electrolyte;
(6) and separating the positive electrode and the negative electrode by adopting a diaphragm, and then injecting the electrolyte to obtain the super capacitor.
Example 10
The preparation method of the supercapacitor comprises the following steps:
(1) preparing a 5mg/mL graphene oxide solution by adopting a Hummers method, and then carrying out heat treatment at 400 ℃ for 2h to obtain graphene sheets;
(2) will contain Fe (NO)3)2、Co(NO3)2A mixed solution of ammonium fluoride and urea, and graphiteMixing the olefinic sheets, and adding Fe (NO) in the mixed solution3)2、Co(NO3)2The molar ratio of the graphene sheet to the urea is 1:1:2, the molar ratio of the ammonium fluoride to the urea is 1:2, the mass ratio of the graphene sheet to the metal source is 1:3, then carrying out hydrothermal reaction at 130 ℃ for 8h, cleaning, and drying at 80 ℃ for 2h to obtain a precursor;
(3) mixing the precursor with a sodium sulfide solution, the sodium sulfide being in contact with the Fe (NO) in step (1)3)2And Co (NO)3)2The total molar weight ratio of the raw materials is 5:3, hydrothermal is carried out for 6 hours at 180 ℃, cleaning is carried out, and drying is carried out for 4 hours at 80 ℃ to obtain a positive electrode;
(4) mixing activated carbon and a binder to prepare slurry, coating the slurry on carbon cloth, and drying to obtain a negative electrode;
(5) mixing polyvinyl alcohol with hot water at 100 ℃ according to the concentration of the polyvinyl alcohol of 0.2g/mL, stirring until clear gel appears, cooling, and then mixing the gel with KOH, wherein the mass ratio of the KOH to the polyvinyl alcohol is 0.5:1, so as to obtain an electrolyte;
(6) and separating the positive electrode and the negative electrode by adopting a diaphragm, and then injecting the electrolyte to obtain the super capacitor.
Comparative example 1
The difference from example 1 is that Fe (NO) in step (2)3)2By substitution with equimolar amounts of Co (NO)3)2。
Comparative example 2
The difference from example 1 is that Co (NO) in step (2)3)2Replacement with equimolar amounts of Fe (NO)3)2。
And (3) performance testing:
the prepared positive electrode and the prepared super capacitor were subjected to the following tests:
(1) and (3) morphology testing: and observing the surface appearance of the obtained anode by adopting a scanning electron microscope.
(2) Specific surface area test: and (4) carrying out specific surface area test by using a Behcet specific surface area tester.
(3) And (3) electrochemical performance testing: adopting Chenghua 660C electrochemical workstation to carry out electrochemistry by using the supercapacitorPerformance test, namely testing the specific capacity of the battery under the current densities of 1A/g, 2A/g, 5A/g, 8A/g and 10A/g respectively, and testing the specific capacity at 5A g-1And testing the energy density, the power density and the cycle performance of 5000 cycles of the battery under the current density.
TABLE 1
As can be seen from Table 1, the positive electrode obtained by the method has good electrochemical performance and the specific surface area is more than or equal to 50m2The specific capacitance of the capacitor can reach 247.93F/g, 228.32F/g, 197.11F/g, 175.85F/g and 149.72F/g under the current density of 1A/g, 2A/g, 5A/g, 8A/g and 10A/g, the energy density can reach 88.2Wh/kg, the power density can reach 8001Wh/kg, and the cycle performance of 5000 cycles can reach 85.1%.
As can be seen from table 1, the specific capacitance, the energy density, the power density and the cycle performance of the positive electrode obtained in example 4 of the present invention are lower than those obtained in example 1, and the specific capacitance, the energy density, the power density and the cycle performance of the positive electrode obtained in example 4 are lower than those obtained in example 1, because the hydrothermal time in example 4 is shorter, and thus a complete flower-like structure morphology cannot be formed, which affects the electrochemical performance of the electrode material, particularly the cycle performance is poorer.
As can be seen from table 1, the specific surface area, specific capacitance, energy density and power density of the positive electrode obtained in example 5 of the present invention are lower than those obtained in example 1, and since the hydrothermal time is longer in example 5, and the flower-like structure collapses, which is not favorable for the sufficient reaction of the electrode material, and reduces the specific capacity, energy density and power density of the material, the specific surface area, specific capacitance, energy density and power density of the positive electrode obtained in example 5 of the present invention are lower than those obtained in example 1.
As can be seen from table 1, the specific surface area, specific capacitance, energy density, power density and cycle performance of the positive electrode obtained in example 7 of the present invention are lower than those obtained in example 1, and since the molar ratio of ammonium fluoride to urea in example 7 is 2:1, and further, the urea is insufficient in amount to form a complete flower-shaped electrode material, which affects the electrochemical performance, particularly the cycle performance, of the capacitor, the specific surface area, specific capacitance, energy density, power density and cycle performance of the positive electrode obtained in example 7 are lower than those obtained in example 1.
As can be seen from table 1, the specific surface area, specific capacitance, energy density, power density and cycle performance of the positive electrode obtained in example 8 of the present invention are lower than those obtained in example 1, and since the molar ratio of ammonium fluoride to urea in example 8 is 1:4, and further the flower-like structure generated by excessive urea is too thick, which is not favorable for sufficient reaction of the electrode material and reduces the electrochemical performance, particularly the specific capacity, of the positive electrode, the specific surface area, specific capacitance, energy density, power density and cycle performance of the positive electrode obtained in example 8 are lower than those obtained in example 1.
As can be seen from table 1, comparative examples 1 and 2 according to the present invention obtained lower specific surface area, specific capacitance, energy density, power density and cycle performance of the positive electrode than example 1, and comparative examples 1 and 2 obtained lower specific surface area, specific capacitance, energy density, power density and cycle performance than example 1 because the positive electrodes obtained in comparative examples 1 and 2 were monometallic sulfide electrodes, and the monometallic sulfide electrodes had poor cycle performance and poor rate characteristics.
The applicant states that the present invention is illustrated by the above examples to show the detailed process equipment and process flow of the present invention, but the present invention is not limited to the above detailed process equipment and process flow, i.e. it does not mean that the present invention must rely on the above detailed process equipment and process flow to be implemented. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (12)
1. A positive electrode, characterized in that the positive electrode is a flexible electrode, and the positive electrode comprises a graphene sheet and a bimetallic sulfide attached to the graphene sheet; the bimetallic sulfide is FeCo2S4(ii) a What is needed isThe thickness of the graphene sheet is 10-100 μm, and the content of the graphene sheet in the positive electrode is 30-50 wt%;
the preparation method of the positive electrode comprises the following steps:
(1) preparing graphene oxide by adopting a Hummers method, and then carrying out heat treatment at 200-300 ℃ for 2-6 h to obtain graphene sheets;
(2) will contain Fe (NO)3)2、Co(NO3)2A mixed solution of ammonium fluoride and urea, in which Fe (NO) is mixed, is mixed with the graphene sheet3)2、Co(NO3)2The molar ratio of the ammonium fluoride to the urea is 1: 1-4: 2-8, the molar ratio of the ammonium fluoride to the urea is 1: 1-3, the mass ratio of the graphene sheet to the metal source is 1: 1-3, then carrying out hydrothermal reaction at 100-140 ℃ for 6-10 h, cleaning, and drying at 40-80 ℃ for 2-4 h to obtain a precursor;
(3) mixing the precursor with a sodium sulfide solution, the sodium sulfide being in contact with the Fe (NO) in step (2)3)2And Co (NO)3)2The total molar weight ratio of the positive electrode to the negative electrode is 1-2: 1, hydrothermal is carried out at 140-180 ℃ for 6-10 h, cleaning is carried out, and drying is carried out at 40-80 ℃ for 4-8 h, so as to obtain the positive electrode.
2. The positive electrode according to claim 1, wherein the diameter of the bimetallic sulfide is 3 to 4 μm.
3. The positive electrode of claim 1, wherein the bimetallic sulfide has a morphology that is a flower-like structure built up of lamellae.
4. The positive electrode according to claim 1, wherein the flower-like structure size of the bimetallic sulfide is 4 to 5 μm.
5. A method for producing a positive electrode according to any one of claims 1 to 4, comprising the steps of:
(1) preparing graphene oxide by adopting a Hummers method, and then carrying out heat treatment at 200-300 ℃ for 2-6 h to obtain graphene sheets;
(2) will contain Fe (NO)3)2、Co(NO3)2A mixed solution of ammonium fluoride and urea, in which Fe (NO) is mixed, is mixed with the graphene sheet3)2、Co(NO3)2The molar ratio of the ammonium fluoride to the urea is 1: 1-4: 2-8, the molar ratio of the ammonium fluoride to the urea is 1: 1-3, the thickness of the graphene sheet is 10-100 microns, the mass ratio of the graphene sheet to the metal source is 1: 1-3, then carrying out hydrothermal reaction at 100-140 ℃ for 6-10 h, cleaning, and drying at 40-80 ℃ for 2-4 h to obtain a precursor;
(3) mixing the precursor with a sodium sulfide solution, the sodium sulfide being in contact with the Fe (NO) in step (2)3)2And Co (NO)3)2The total molar weight ratio of the positive electrode to the negative electrode is 1-2: 1, hydrothermal is carried out at 140-180 ℃ for 6-10 h, cleaning is carried out, and drying is carried out at 40-80 ℃ for 4-8 h, so as to obtain the positive electrode.
6. An ultracapacitor comprising the positive electrode of any one of claims 1 to 4, further comprising a negative electrode and a gel electrolyte.
7. A method for preparing the supercapacitor according to claim 6, wherein the method comprises the following steps: and separating the positive electrode and the negative electrode by adopting a diaphragm, and then injecting gel electrolyte to obtain the super capacitor.
8. The method according to claim 7, wherein the negative electrode is prepared by a process comprising: mixing the activated carbon and the adhesive to prepare slurry, coating the slurry on carbon cloth, and drying to obtain the cathode.
9. The method of claim 7, wherein the gel electrolyte is prepared by a process comprising: polyvinyl alcohol was mixed with hot water, stirred until a clear gel appeared, cooled, and then the gel was mixed with KOH to obtain a gel electrolyte.
10. The method according to claim 9, wherein the temperature of the hot water is 80 to 100 ℃.
11. The method according to claim 9, wherein the concentration of the polyvinyl alcohol in the mixed solution of the polyvinyl alcohol and hot water is 0.05 to 0.2 g/mL.
12. The method according to claim 9, wherein the mass ratio of KOH to polyvinyl alcohol is 0.5 to 1.5: 1.
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