CN115385333A - Potato seedling-based activated carbon and preparation method and application thereof - Google Patents
Potato seedling-based activated carbon and preparation method and application thereof Download PDFInfo
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 208
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- C01B32/00—Carbon; Compounds thereof
- C01B32/30—Active carbon
- C01B32/312—Preparation
- C01B32/318—Preparation characterised by the starting materials
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
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- H01G11/22—Electrodes
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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 belongs to the technical field of comprehensive utilization of agricultural wastes and preparation of supercapacitors, and particularly relates to potato seedling-based activated carbon and a preparation method and application thereof. After the potato seedlings are carbonized as the carbon precursors, the corresponding electrode materials are successfully prepared and processed into the super capacitor by screening and optimizing related process conditions by adopting a KOH chemical activation method, and tests prove that the super capacitor has the advantages of high charging and discharging speed, high power density, long cycle life, wide working temperature range and the like, so that the super capacitor has good electrochemical performance and has good practical popularization and application values.
Description
Technical Field
The invention belongs to the technical field of comprehensive utilization of agricultural wastes and preparation of supercapacitors, and particularly relates to potato seedling-based activated carbon and a preparation method and application thereof.
Background
The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.
Clean energy, i.e., green energy, refers to energy that does not emit pollutants and can be directly used for production and living, and includes such energy as hydroelectric power, wind power, solar energy, bio-energy (biogas), geothermal energy (including ground sources and water sources), and sea tide energy. However, in view of the problems of instability of new energy sources such as wind energy, solar energy and the like, the development of an energy storage technology is urgently needed; the super capacitor has the advantages of high power, short charging time, long service life and the like, and is widely applied to the aspects of household appliances, electric energy storage, intelligent start-stop control systems in the automobile industry, hybrid power and the like. However, the low energy density of the supercapacitor is a major factor that restricts the wide application of the supercapacitor, and the electrode material is a key that affects the performance of the supercapacitor.
Earlier stage researches find that the biomass activated carbon as an electrode material of the supercapacitor has the characteristics of rich yield, reproducibility, low cost and the like, realizes the reutilization of agricultural and forestry wastes, improves the application value of the agricultural and forestry wastes, and relieves the environmental pressure. Potato seedling is the aerial part of the potato plant and is a by-product remaining after harvesting of the potato tubers. Taking our country as an example only, the annual yield of the potato seedlings reaches over 9000 ten thousand, and a large amount of potato seedlings are not fully utilized and become agricultural wastes. However, among many agricultural wastes, studies on the preparation of activated carbon from potato seedlings and the application of the activated carbon as an electrode material in a supercapacitor are rarely reported.
Disclosure of Invention
Based on the defects of the prior art, the invention provides the potato seedling-based activated carbon, the preparation method and the application thereof. The present invention has been completed based on the above results.
In order to achieve the technical purpose, the invention relates to the following technical scheme:
in a first aspect of the invention, a preparation method of potato seedling-based activated carbon is provided, which comprises the following steps:
taking potato seedlings as a carbon precursor, carbonizing after pretreatment, and then preparing the potato seedling-based activated carbon by using a KOH chemical activation method;
wherein, the KOH chemical activation method is to soak the carbonized potato seedlings in saturated KOH solution;
controlling the activation temperature to be 700-850 ℃, the activation time to be 90-180min, and the impregnation ratio (w/w) to be 3.0-4.5.
In a second aspect of the invention, the potato seedling-based activated carbon obtained by the preparation method is provided. The potato seedling-based activated carbon prepared by the method has good electrochemical characteristics.
In a third aspect of the invention, an electrode material is provided, and the electrode material is the potato seedling-based activated carbon.
In a fourth aspect of the invention, a supercapacitor is provided, which contains potato seedling-based activated carbon or the above electrode material. The super capacitor can be prepared by adopting a conventional method.
In a fifth aspect of the invention, there is provided the use of the above potato seedling-based activated carbon, electrode material and/or supercapacitor in fields including, but not limited to, aerospace, automotive industry, consumer electronics, power and communications.
The beneficial technical effects of one or more technical schemes are as follows:
the technical scheme provides the potato seedling activated carbon and the preparation method and application thereof, the agricultural waste potato seedlings with rich yield are used as the raw materials for preparing the activated carbon electrode material for the first time, the activated carbon electrode material of the potato seedlings is prepared by changing the conditions of activation reaction, the surface characteristics of the electrode material and the electrochemical characteristics of a super capacitor are analyzed systematically, and the optimal performance of the electrode material is finally prepared.
The potato seedlings are used as agricultural wastes, the cost is low, the source is wide, the price is low, the electrode material with excellent electrochemical characteristics and surface characteristics can be obtained through a simple preparation process, tests prove that the active carbon prepared from the potato seedlings has the advantages of high charging and discharging speed, high power density, long cycle life, wide working temperature range and the like, and the active carbon is used as the electrode material and further used for preparing the super capacitor, so that the active carbon has good practical popularization and application values.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.
FIG. 1 is a flow chart of a preparation process of potato seedling-based activated carbon in the embodiment of the invention.
FIG. 2 is a graph showing the effect of activation temperature on surface area in examples of the present invention.
FIG. 3 is a graph showing the effect of activation time on surface area in examples of the present invention.
FIG. 4 shows the effect of specific surface area on impregnation in examples of the present invention.
FIG. 5 is an SEM microscopic characterization of an example of the invention.
FIG. 6 is a graph showing pore size distribution of potato seedling-based activated carbon in an embodiment of the present invention.
FIG. 7 is a constant current discharge curve in accordance with an embodiment of the present invention.
FIG. 8 shows the rate capability of activated carbon with different specific surface areas in the examples of the present invention.
FIG. 9 is a graph showing the relationship between the mass specific capacitance and the specific surface area of activated carbon in the examples of the present invention.
FIG. 10 is a graph showing rate capability of activated carbon with different specific surface areas in examples of the present invention.
FIG. 11 shows that the activated carbon AC3187 in the example of the invention is 0.5Ag -1 Charge and discharge efficiency under the conditions.
Detailed Description
It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
As mentioned above, a large amount of potato seedlings are not fully utilized and become agricultural wastes, and researches on preparation of activated carbon from potato seedlings and application of the activated carbon as an electrode material in a super capacitor are rarely reported.
In view of the above, in one exemplary embodiment of the present invention, there is provided a method for preparing potato seedling-based activated carbon, the method comprising:
taking potato seedlings as a carbon precursor, pretreating, carbonizing, and preparing the potato seedling-based activated carbon by using a KOH chemical activation method;
wherein, the KOH chemical activation method is to soak the carbonized potato seedlings in saturated KOH solution;
in another embodiment of the invention, the activation temperature is controlled to be 700-850 ℃, the activation time is 90-180min, and the impregnation ratio (w/w) is 3.0-4.5.
In another embodiment of the present invention, the carbonization temperature is 550-650 ℃, preferably 600 ℃, and the carbonization time is controlled to be 100-150min, preferably 120min; it should be noted that the temperature and time of carbonization directly affect the pore structure and strength of the carbonized product. According to the invention, researches show that the carbonization temperature is too low, and the carbonization time is too short, so that the carbonized product can not form enough mechanical strength, the mechanical property of the finally prepared potato seedling-based activated carbon is poor, and the service life of the finally prepared potato seedling-based activated carbon is influenced, while the carbonization temperature is too high, and the carbonization time is too long, so that the microcrystals in the carbonized product can be promoted to change orderly, the pores among the microcrystals are reduced, and the pore-forming process is influenced, so that the physical and chemical properties of the finally prepared activated carbon are also adversely influenced.
Meanwhile, the research of the invention discovers that the parameter conditions in the activation process have obvious influence on the physical and chemical properties of the final activated carbon, mainly including the specific surface area, the pore size distribution, the total volume of micropores and the like of the activated carbon, and the analysis research discovers that when the high-temperature activation temperature is controlled to be 800 ℃, the high-temperature activation time is 180min and the impregnation ratio is controlled to be 1, the physical and chemical properties of the finally prepared activated carbon are optimal, so that the activated carbon can have large surface area based on the adjustment of the pore structure of the activated carbon, and the pore structure can meet the adsorption requirement conditions of adsorbing electrolyte ions to the maximum extent, and a super capacitor with the optimal performance can be obtained.
In another embodiment of the invention, the pre-treatment comprises drying and crushing the potato seedlings; the potato seedling powder is obtained by drying and crushing, so that the subsequent carbonization and activation processes are facilitated. Wherein, the drying can be carried out by any known drying method, in a specific embodiment of the invention, the drying is carried out by a high-temperature drying method, and specifically, the drying can be carried out by oven drying, such as drying at 100-150 ℃ (preferably 120 ℃), then carrying out crushing treatment, and sieving the crushed particles with the particle size not more than 0.125mm.
In another embodiment of the invention, the potato seedling-based activated carbon obtained by the preparation method is provided. The invention is preparedThe obtained potato seedling-based activated carbon has good electrochemical properties. Proved by verification, under the optimized preparation conditions, the surface area of the potato seedling activated carbon electrode material is 2871m 2 (ii)/g, at a current density of 0.2A/g, has a mass specific capacitance of 265F/g. Under the condition of higher current density, the active carbon electrode material not only keeps higher capacitance, but also greatly shortens the charge-discharge time of the super capacitor, and has no obvious voltage drop in the charge-discharge moment. Meanwhile, compared with other known active carbon electrode materials, the active carbon electrode material has the advantages of high mass specific capacitance, high energy density, high power density and the like, and has good practical application and popularization values.
Therefore, in another embodiment of the invention, an electrode material is provided, wherein the electrode material is the potato seedling-based activated carbon.
In yet another embodiment of the present invention, a supercapacitor is provided, which comprises potato seedling-based activated carbon or the above electrode material. It should be noted that, the preparation process of the supercapacitor is not particularly limited in the present invention, and the supercapacitor can be prepared by a conventional method. In order to facilitate understanding of the technical personnel in the field, in one embodiment of the invention, the super capacitor is obtained by putting the first electrode plate, the diaphragm and the second electrode plate into a battery and then adding an alkaline electrolyte.
The first electrode plate and the second electrode plate are both prepared by the following method:
and coating the slurry obtained by mixing the activated carbon, the polytetrafluoroethylene emulsion and the conductive graphite on a foamed nickel current collector and drying to obtain the finished product.
The alkaline electrolyte can be KOH electrolyte, and the concentration is 3-8mol/L, preferably 6mol/L.
Wherein the mass ratio of the potato seedling-based activated carbon to the polytetrafluoroethylene emulsion to the conductive graphite is 6-10.
In yet another embodiment of the present invention, there is provided the use of the above-described potato seedling-based activated carbon, electrode material and/or supercapacitor in fields including, but not limited to, aerospace, automotive industry, consumer electronics, power and communications.
The invention is further illustrated by the following examples, which are not to be construed as limiting the invention thereto. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention.
Examples
1. Preparation process of potato seedling-based activated carbon
The preparation process of the potato seedling-based activated carbon electrode material is shown in figure 1 (wherein the carbonization temperature is 600 ℃, and the carbonization time is 120 min), different component experiment groups are additionally arranged on the basis of the experiment of a standard group, and the experiment conditions have great influence on the physicochemical characteristics of the activated carbon, particularly the activation temperature, the activation time and the impregnation ratio. The experiment adopts a three-factor four-level orthogonal test to explore the influence of the three factors on the physical and chemical properties of the activated carbon. The factors and levels of the orthogonality test are shown in Table 1.
Table 1 orthogonal test table
2. Preparation of super capacitor
Mixing the activated carbon, polytetrafluoroethylene emulsion and conductive graphite in a mass ratio of 8. And finally, sequentially putting the electrode plate, the diaphragm and the electrode plate into the battery, and dropwise adding KOH electrolyte to form the super capacitor.
3. Characterization test
Respectively using N 2 The method comprises the steps of adsorption-desorption, SEM analysis, XRD crystal phase analysis, fourier transform infrared spectrum test analysis and other test methods, the characteristics of the activated carbon such as pore size distribution, surface morphology, microcrystalline structure, surface functional groups and the like are represented, and the influence of activation temperature, activation time and impregnation ratio on the surface characteristics of the activated carbon is analyzed.
4. Electrochemical test assay
The electrochemical characteristics of the potato seedling activated carbon electrode material are tested by methods of constant current charging and discharging, cycle life testing and the like, and the influence rule of the activation temperature, the activation time and the impregnation ratio on the electrochemical characteristics is analyzed.
5. Analysis of Experimental results
5.1 influence of activation temperature on surface physical properties and electrochemical properties of activated carbon of potato seedlings
In the activation process of preparing the potato seedling activated carbon, KOH is used as an activating agent, variables are controlled, under the premise that the activation time and the impregnation ratio are kept unchanged, four activation temperatures of 700 ℃, 750 ℃, 800 ℃ and 850 ℃ are respectively adopted, the derivation rule of the pore structure of the activated carbon is researched at different activation temperatures (as shown in figure 2), four different activated carbons are obtained, and the surface characteristics of the activated carbon are analyzed through a series of characterization tests such as XRD, SEM, BET and the like (as shown in figure 5); and processed into super capacitors respectively. Along with the increase of the activation temperature, the specific surface area of the activated carbon is increased, and the increase trend is fast and then slow, which shows that the potato activated carbon has rich pore structures and large specific surface area, can improve the performance of the electrode material, further analyzes the conditions of the optimal preparation process, and provides support for the research of the supercapacitor.
5.2 Effect of activation time on surface physical characteristics and electrochemical properties of activated carbon of potato seedlings
In the activation process of preparing the potato seedling activated carbon, on the premise of keeping the activation temperature and the impregnation ratio unchanged, four activation times of 90min, 120min, 150min and 180min are respectively adopted, four different activated carbons are obtained according to the relation between the different activation times and the specific surface area (as shown in figure 3), and the surface characteristics of the activated carbon are analyzed through a series of characterization tests such as XRD, SEM, BET and the like (as shown in figure 5); and processed into super capacitors respectively.
5.3 influence of steeping ratio on surface physical properties and electrochemical properties of potato seedling activated carbon
In the activation process of preparing the potato seedling activated carbon, on the premise of keeping the activation time and the activation temperature unchanged, four impregnation ratios of 3; and processed into super capacitors respectively.
5.4 pore size distribution of Potato Rice seedling-based activated carbon
Fig. 6 shows that the pore structure of 0.4-1nm can provide a large effective adsorption surface area for electrolyte ions. The mesoporous structure of 2-4nm can provide a low-resistance transport channel for electrolyte ions. The pore structure of 0.5 to 0.8nm is more advantageous for the formation of the electric double layer capacitance than the pore structure of 0.4 to 0.5 nm.
5.5 analysis to obtain the optimal preparation technology
The activated carbon activation conditions were screened by experiments, and the results are shown in table 2. Experiments show that the activation temperature, the activation time and the impregnation ratio are important factors for determining the surface characteristics and the electrochemical characteristics of the activated carbon electrode material, and the three factors simultaneously influence the specific surface area, the pore size distribution and the total pore volume of the activated carbon material. As can be seen from table 1 and through further discussion, the high-temperature activation temperature is 800 ℃, the high-temperature activation time is 180min, and the impregnation ratio is 3.5, which is based on that the pore structure of the activated carbon is adjusted so that the activated carbon has a large surface area and the pore structure can maximally meet the adsorption requirement for adsorbing electrolyte ions.
TABLE 2 carbon yield, specific surface area, pore volume of electrode materials prepared under different conditions
5.6 specific capacitance Property of Potato Roots activated carbon electrode Material
FIG. 7 is a constant current discharge curve of 0.5A/g for samples ranging from 0 to 1V, and the constant current discharge curve of potato seedling activated carbon shows that a typical charge-discharge pair is in a symmetrical triangle, which shows that the samples after KOH activation have ideal double electric layer characteristics and excellent capacitance behavior. With the increase of the specific surface area of the activated carbon, the charging and discharging time is increased. Due to the influence of the internal resistance of the electrode material, the mass specific capacitance of the sample is reduced along with the increase of the current density, the mass specific capacitance of the potato seedling activated carbon is 226F/g under the current density of 0.5A/g, and no obvious voltage drop exists in the charging and discharging moments.
5.7 relationship between specific capacitance by mass and specific surface area of activated carbon
FIG. 8 is a mass specific capacitance curve of activated carbon with different specific surface areas under the current density ranging from 0A/g to 5A/g. The overall rule obtained by image analysis is that the mass specific capacitance of the activated carbon electrode material is increased and then reduced along with the increase of the specific surface area under the current density ranging from 0 to 5A/g; when the specific surface area reaches 2871, the mass specific capacitance of the electrode material is the maximum, and the maximum can reach 265F/g.
FIG. 9 is a graph showing the relationship between the specific capacitance by mass and the specific surface area of activated carbon under a constant current. It is found from the image that the mass specific capacitance of the activated carbon electrode material increases and then decreases with the increase of the specific surface area under the premise of constant current, and the maximum value of the mass specific capacitance is 2800 to 3000m in the specific surface area 2 (iv) g. At a current density of 0.2A/g, the activated carbon electrode material had a mass specific capacitance of 265F/g.
It can be seen from the observation of fig. 8 and 9 that at a higher current density, the activated carbon electrode material not only maintains a larger capacitance, but also greatly shortens the charge-discharge time of the supercapacitor, indicating the excellent quality specific capacitance performance of the electrode material.
5.8 Rate Performance
FIG. 10 is a graph of rate capability of activated carbon of different specific surface areas. From FIG. 10, the current density was 1Ag -1 Increased to 5Ag -1 And the capacity retention rate of the super capacitor exceeds 90%, which shows that the potato seedling super capacitor has excellent large-current charge and discharge characteristics.
5.9 Charge-discharge efficiency
FIG. 11 shows the charge-discharge efficiency of activated carbon AC3187 under the condition of 0.5 Ag-1. From the third cycle in fig. 11, the charge and discharge efficiency reaches nearly 100% and remains stable, which indicates that the potato seedling super capacitor has higher starting efficiency and stability.
5.10 comparative study with conventional electrode materials
Table 3 shows that the comparison between the electrode material with potato seedlings as a carbon precursor and carbon materials in other documents shows that the electrode material prepared from potato seedlings has high mass specific capacitance, large energy density and excellent power density, which indicates that the potato seedling activated carbon electrode material has excellent electrochemical properties, is of great significance in practical application and has high popularization value.
TABLE 3 Mass specific capacitance of each sample
In summary,
1) The method adopts agricultural waste potato seedlings with rich yield as the raw materials for preparing the activated carbon electrode material for the first time, prepares the activated carbon electrode material of the potato seedlings by changing the conditions of activation reaction (activation temperature, activation time and impregnation ratio), and systematically analyzes the surface characteristics of the electrode material and the electrochemical characteristics of the super capacitor.
2) The invention researches the influence of physical and chemical properties such as specific surface area, pore size distribution and the like on the basic electrochemical performance of the potato seedling activated carbon, and obtains the optimal preparation process. Namely, the surface area of the potato seedling activated carbon electrode material prepared under the conditions of high temperature activation temperature of 800 ℃, high temperature activation time of 180min and dipping ratio of 3.5 2 (ii)/g, at a current density of 0.2A/g, has a mass specific capacitance of 265F/g. Under the condition of higher current density, the active carbon electrode material not only keeps higher capacitance, but also greatly shortens the charge-discharge time of the super capacitor, and has no obvious voltage drop in the charge-discharge moment.
From the above, the potato seedlings are used as the precursor to prepare the activated carbon, and by adjusting independent variables (activation temperature, activation time and activation time), the activated carbon shows obvious differences in the aspects of specific surface area, pore size distribution, mass specific capacitance and the like, and the most excellent performance of the electrode material is obtained. The potato seedlings are used as agricultural wastes, the cost is low, the source is wide, the price is low, the electrode material with excellent electrochemical characteristics and surface characteristics can be obtained through a simple preparation process, and the electrode material has the advantages of high charging and discharging speed, high power density, long cycle life, wide working temperature range and the like, so the potato seedlings have wide application prospects in various fields of aerospace, automobile industry, consumer electronics, electric power, communication and the like.
Finally, it should be noted that, although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments described in the foregoing embodiments, or equivalents may be substituted for elements thereof. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention. Although the present invention has been described with reference to the specific embodiments, it should be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.
Claims (10)
1. A preparation method of potato seedling-based activated carbon is characterized by comprising the following steps:
taking potato seedlings as a carbon precursor, carbonizing after pretreatment, and then preparing the potato seedling-based activated carbon by using a KOH chemical activation method;
wherein, the KOH chemical activation method is to soak the carbonized potato seedlings in saturated KOH solution;
controlling the activation temperature to be 700-850 ℃, the activation time to be 90-180min, and the impregnation ratio to be 3.0-4.5.
2. The preparation method according to claim 1, wherein the pre-treatment comprises drying and pulverizing the potato seedlings.
3. The preparation method according to claim 2, wherein the drying is performed in a high-temperature drying manner, and comprises drying in an oven at 100-150 ℃, then performing crushing treatment, and screening the crushed particles to have a particle size of not more than 0.125mm;
the carbonization temperature is 550-650 ℃, preferably 600 ℃; the carbonization time is controlled to be 100-150min, and is preferably 120min.
4. The process according to claim 1, wherein the activation temperature is 750 to 800 ℃, the activation time is 150 to 180min, and the impregnation ratio is 3.5 to 4.0; furthermore, the activation temperature is 800 ℃, the high-temperature activation time is 180min, and the impregnation ratio is 3.5.
5. A potato seedling-based activated carbon obtained by the production method as set forth in any one of claims 1 to 4.
6. An electrode material, characterized in that it is potato seedling based activated carbon as claimed in claim 5.
7. A supercapacitor, characterized in that it contains potato-based activated carbon as in claim 5 or electrode material as in claim 6.
8. The super capacitor according to claim 7, wherein the super capacitor is obtained by putting the first electrode plate, the diaphragm and the second electrode plate into a battery and then adding an alkaline electrolyte.
9. The supercapacitor according to claim 8, wherein the first electrode sheet and the second electrode sheet are both prepared by the following method:
coating the slurry obtained by mixing the activated carbon, the polytetrafluoroethylene emulsion and the conductive graphite on a foamed nickel current collector and drying to obtain the active carbon-conductive graphite composite material;
the mass ratio of the potato seedling-based activated carbon to the polytetrafluoroethylene emulsion to the conductive graphite is 6-10, and further is (1);
the alkaline electrolyte is KOH electrolyte, and the concentration is 3-8mol/L, and further 6mol/L.
10. Use of potato seedling based activated carbon as defined in claim 5, an electrode material as defined in claim 6 and/or a supercapacitor as defined in any one of claims 7 to 9 in the fields of aerospace, automotive industry, consumer electronics, electricity and communications.
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