KR101978415B1 - Mesoporous three-dimensional nickel electrode, and high-performance flexible supercapacitor comprising same - Google Patents
Mesoporous three-dimensional nickel electrode, and high-performance flexible supercapacitor comprising same Download PDFInfo
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- KR101978415B1 KR101978415B1 KR1020170027674A KR20170027674A KR101978415B1 KR 101978415 B1 KR101978415 B1 KR 101978415B1 KR 1020170027674 A KR1020170027674 A KR 1020170027674A KR 20170027674 A KR20170027674 A KR 20170027674A KR 101978415 B1 KR101978415 B1 KR 101978415B1
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- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 title claims abstract description 471
- 229910052759 nickel Inorganic materials 0.000 title claims abstract description 293
- 238000000034 method Methods 0.000 claims abstract description 26
- 238000001027 hydrothermal synthesis Methods 0.000 claims abstract description 22
- 230000009467 reduction Effects 0.000 claims abstract description 13
- 238000010438 heat treatment Methods 0.000 claims abstract description 9
- BFDHFSHZJLFAMC-UHFFFAOYSA-L nickel(ii) hydroxide Chemical compound [OH-].[OH-].[Ni+2] BFDHFSHZJLFAMC-UHFFFAOYSA-L 0.000 claims description 88
- AMWRITDGCCNYAT-UHFFFAOYSA-L hydroxy(oxo)manganese;manganese Chemical compound [Mn].O[Mn]=O.O[Mn]=O AMWRITDGCCNYAT-UHFFFAOYSA-L 0.000 claims description 45
- 239000011149 active material Substances 0.000 claims description 40
- 239000000843 powder Substances 0.000 claims description 22
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- 238000004070 electrodeposition Methods 0.000 claims description 9
- 229910000000 metal hydroxide Inorganic materials 0.000 claims description 7
- 150000004692 metal hydroxides Chemical class 0.000 claims description 7
- 229910044991 metal oxide Inorganic materials 0.000 claims description 7
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- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 4
- 238000002441 X-ray diffraction Methods 0.000 description 4
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- VKYKSIONXSXAKP-UHFFFAOYSA-N hexamethylenetetramine Chemical compound C1N(C2)CN3CN1CN2C3 VKYKSIONXSXAKP-UHFFFAOYSA-N 0.000 description 4
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 4
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- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
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- 150000002500 ions Chemical class 0.000 description 3
- 229910000480 nickel oxide Inorganic materials 0.000 description 3
- AOPCKOPZYFFEDA-UHFFFAOYSA-N nickel(2+);dinitrate;hexahydrate Chemical compound O.O.O.O.O.O.[Ni+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O AOPCKOPZYFFEDA-UHFFFAOYSA-N 0.000 description 3
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- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
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- 229920005830 Polyurethane Foam Polymers 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
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- 229940082328 manganese acetate tetrahydrate Drugs 0.000 description 2
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- NDVLTYZPCACLMA-UHFFFAOYSA-N silver oxide Chemical compound [O-2].[Ag+].[Ag+] NDVLTYZPCACLMA-UHFFFAOYSA-N 0.000 description 2
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- 101100317222 Borrelia hermsii vsp3 gene Proteins 0.000 description 1
- 229910002483 Cu Ka Inorganic materials 0.000 description 1
- 229910021607 Silver chloride Inorganic materials 0.000 description 1
- MQRWBMAEBQOWAF-UHFFFAOYSA-N acetic acid;nickel Chemical compound [Ni].CC(O)=O.CC(O)=O MQRWBMAEBQOWAF-UHFFFAOYSA-N 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
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- 239000000446 fuel Substances 0.000 description 1
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- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- CESXSDZNZGSWSP-UHFFFAOYSA-L manganese(2+);diacetate;tetrahydrate Chemical compound O.O.O.O.[Mn+2].CC([O-])=O.CC([O-])=O CESXSDZNZGSWSP-UHFFFAOYSA-L 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 1
- 229910000474 mercury oxide Inorganic materials 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 229940078494 nickel acetate Drugs 0.000 description 1
- LGQLOGILCSXPEA-UHFFFAOYSA-L nickel sulfate Chemical compound [Ni+2].[O-]S([O-])(=O)=O LGQLOGILCSXPEA-UHFFFAOYSA-L 0.000 description 1
- 229910000363 nickel(II) sulfate Inorganic materials 0.000 description 1
- KBJMLQFLOWQJNF-UHFFFAOYSA-N nickel(ii) nitrate Chemical compound [Ni+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O KBJMLQFLOWQJNF-UHFFFAOYSA-N 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
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- 238000000926 separation method Methods 0.000 description 1
- HKZLPVFGJNLROG-UHFFFAOYSA-M silver monochloride Chemical compound [Cl-].[Ag+] HKZLPVFGJNLROG-UHFFFAOYSA-M 0.000 description 1
- 229910001923 silver oxide Inorganic materials 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
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Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-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
- H01G11/26—Electrodes characterised by their structure, e.g. multi-layered, porosity or surface features
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-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
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Chemical & Material Sciences (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Electric Double-Layer Capacitors Or The Like (AREA)
Abstract
Electrodes in which the interior is three-dimensionally structured and a plurality of mesoporous nickel layers are formed directly on the nickel film can have high electrochemical properties by having a large number of active sites as well as a fast charge transfer path. In addition, the electrode can be manufactured by a simple method such as a hydrothermal reaction and heating and reduction, and can be formed as a thin film, so that it can be used as an electrode of a supercapacitor because it has high flexibility.
Description
The present invention relates to a mesoporous nickel-based electrode, and a high performance flexible super capacitor comprising the same.
As portable electronic devices such as bendable displays, implantable heart sensors, curved laptops, and flexible mobile phones continue to be developed, there is a growing demand for improved energy storage systems of various structures, such as batteries and supercapacitors. Flexible supercapacitors with fast charge / discharge rates, high output densities and good cycle stability can be very useful in these applications.
In order to easily and economically manufacture an electrode for a flexible supercapacitor, a carbon-based material is conventionally coated on a paper-based flexible substrate. For example, it is known that carbon nanotube ink is deposited on cellulose paper to produce a flexible supercapacitor having an electrostatic capacity of 270 F / g and an energy density of 37 Wh / kg. As another useful method for manufacturing a flexible supercapacitor, a solventless drawing method of drawing an electrode pattern on a cellulose paper with a pencil is also known.
In order to further improve the performance of the paper-based flexible substrate, graphene, which is excellent in conductivity and large in area, is used as a current collector. For example, polyaniline / graphene electrodes have been reported to exhibit excellent flexibility, conductivity, cycle stability and high capacitance. In addition, manganese oxide-based flexible supercapacitors coated with graphene foam have been reported to provide a high capacitance of 1.4 F / cm2 (He, Y. et al., ACS nano 2012, 7 (1) 174-182). However, such conventional flexible supercapacitors have a problem of low capacitance and energy / output density as compared with a supercapacitor based on a metal current collector.
Accordingly, nickel films and nickel foams are now widely used in energy storage devices including batteries, supercapacitors and fuel cells. Among them, the nickel film has a disadvantage in that it is inexpensive and flexible, but its surface area is small and its electrochemical characteristics are not high. In addition, the nickel foams have a large number of active sites and are directly connected between the active material and the current collector, so that they are excellent in electrochemical characteristics, but they have a disadvantage in that they are difficult to manufacture because they are thin films of 1 mm or less. In addition, in the case of the nickel foam, a complex manufacturing process of coating the nickel with the polyurethane foam as a framework and finally removing the polyurethane foam is performed, and thus the process cost is high.
Therefore, in order to realize a next-generation high-performance energy storage system, it is required to develop a new nickel-based electrode that can be manufactured at a reasonable cost with a large number of active sites in a continuous network with flexibility.
Accordingly, it is an object of the present invention to provide a nickel-based new electrode capable of exhibiting high performance while having flexibility.
Another object of the present invention is to produce the nickel-based electrode by a simple and efficient method.
It is still another object of the present invention to provide a supercapacitor including the nickel-based electrode.
According to this object, the present invention provides a nickel film, and a nickel layer directly formed on the nickel film, wherein the nickel layer is three-dimensionally structured inside and has a plurality of mesopores.
According to another aspect of the present invention, there is provided a process for preparing a nickel hydroxide precursor solution, comprising the steps of: (1) directly forming a nickel hydroxide layer on a nickel film in a precursor solution of nickel hydroxide by hydrothermal reaction; And (2) reducing the nickel hydroxide layer to obtain an electrode having a nickel layer formed on a nickel film, wherein the nickel layer is three-dimensionally structured inside and has a plurality of mesopores, / RTI >
According to another aspect of the present invention, there is provided a supercapacitor including the electrode, the electrolyte, and the separator.
The electrode according to the present invention has a high charge transport path as well as a large number of active sites due to a three-dimensionally structured inner portion of the nickel layer having a large number of mesopores, so that it can have high electrochemical characteristics.
In addition, the electrode of the present invention can be manufactured by a simple method such as a hydrothermal reaction and heating and reduction, and can be formed into a thin film, unlike an electrode using a conventional nickel foam, and thus can have high flexibility.
Therefore, the electrode of the present invention can be usefully utilized in various fields including a wearable sensor and a curved electronic device which are required to have flexibility and high electrochemical performance including a super capacitor field.
BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described more fully hereinafter with reference to the accompanying drawings, in which: FIG.
The meanings of the abbreviations in the following description of the drawings are as defined in the specific embodiments to be described later.
1 is a schematic view of a method for manufacturing a mesoporous 3D-nickel / nickel film, in which (a) is a 3D-nickel hydroxide / nickel film And 3D-nickel / nickel films and SEM images); (b) is a photograph of the 3D-nickel / nickel film produced (insert image is enlarged SEM image); (c) and (d) are photographs showing the flexibility and curling characteristics of a 3D-nickel / nickel film, respectively.
Figure 2 shows the thermal durability and physical durability of a 3D-nickel electrode, wherein (a) and (b) are XRD curves of a 3D-nickel / nickel film after storage for several weeks immediately after manufacture and at room temperature, respectively; (c) is the TGA curve of the 3D-nickel / nickel film under atmospheric conditions (the inset image is the XRD curve after annealing the 3D-nickel / nickel film at 300 ° C for one hour); (d) a photograph of the 3D-nickel before and after the tape test (using commercially available 3M Scotch tape); (e) and (f) are SEM images (the numbers in the image are the weights of the electrodes) of the 3D-nickel / nickel films before and after the tape test and before and after blowing the nitrogen gas, respectively.
FIG. 3 is an SEM image of an active material in a 3D-nickel state, wherein (a) a nickel hydroxide / 3D-nickel electrode, (b) a 3D-nickel electrode where no active material is deposited, and (c) Respectively.
Figure 4 shows the electrochemical behavior of 3D-nickel electrodes in 1M KOH, where (a) and (b) show the same amount of nickel hydroxide on different collectors (nickel film, nickel foam, 3D- CV curves at 20 mV / s measured after deposition and non-volatile capacities at various current densities; (c) and (d) show CV curves and dynamic characteristics (the inserted image is a constant current curve at various current densities) at various scan rates measured for nickel hydroxide / 3D-nickel electrodes; (e) and (f) show CV curves and dynamic characteristics (the inserted image is a constant current curve at various current densities) measured at various scan rates for manganese oxide / 3D-nickel electrodes.
(B) CV curves at various refresh rates of the flexible supercapacitors; (c) graphs of the CV curves at various scan rates of the flexible supercapacitors; (c) the schematic diagrams of the flexible supercapacitors (nickel hydroxide / 3D-nickel / manganese oxide / A CV curve at 50 mV / s bending conditions of a flexible super capacitor, (d) a cycle stability after 100 cycles of a flexible super capacitor, and (e) a Ragone graph compared to a (e) high performance flexible supercapacitor.
Figure 6 is an XRD curve of (a) the 3D-nickel hydroxide / nickel film electrode before reduction, and (b) the XRD curve of the reduced 3D-nickel / nickel film electrode.
7 is a photograph showing the difference in thickness and flexibility of a nickel film, a nickel foam, and a 3D-nickel / nickel film.
8 is a photograph of a
9 is a TGA curve of a 3D-nickel electrode.
10 is a photograph before and after rubbing the 3D-nickel electrode.
Figure 11 is a SEM image of a cross section showing weak bonding between 3D-nickel hydroxide and nickel film prior to reduction and formation of strong bonds between 3D-nickel and nickel film after reduction.
12 is (a) an SEM image of a commercially available nickel foam, and (b) an SEM image of a 3D-nickel electrode.
FIG. 13 shows the surface characteristics of a 3D-nickel electrode, showing (a) adsorption / desorption isotherm curves of 3D-nickel and (b) pore size distribution of 3D-nickel.
14 shows XRD curves of (a) a nickel hydroxide / 3D-nickel electrode and (b) an XRD curve of a manganese oxide / 3D-nickel electrode.
15 shows a SEM image of a nickel hydroxide / nickel film, a nickel hydroxide / nickel foam, and a nickel hydroxide / 3D-nickel electrode.
16 is a photograph of the relative electrical resistance of each electrode measured by a digital instrument.
17 is an electrochemical impedance curve measured on the same volume basis for the various current collectors (nickel film, nickel foam, and 3D-nickel) deposited with nickel hydroxide.
Figure 18 shows the cycle stability after 1000 cycles of the asymmetric supercapacitor (nickel hydroxide / 3D-nickel / manganese oxide / 3D-nickel).
According to one aspect of the present invention, there is provided an electrode comprising a nickel film and a nickel layer formed directly on the nickel film, the nickel layer being structured three-dimensionally in the interior to have a plurality of mesopores.
The nickel film used in the electrode may be a conventional nickel film.
Preferably, the nickel film may be a flexible nickel film.
The nickel film may have a thickness in the range of, for example, 10 to 1000 占 퐉, or 10 to 100 占 퐉.
At the electrode, the nickel layer is formed directly on the nickel film. That is, the nickel layer may be formed on the nickel film without a binder or an adhesive.
The nickel layer is three-dimensionally structured inside and has a large number of mesopores.
The mesopores may have a size of, for example, 10 to 200 nm. The mesopores may have an average size of 10 to 50 nm, or 10 to 30 nm.
In the nickel layer, nickel may be connected in the form of a three-dimensional network to form a plurality of mesopores. These mesopores may be closely connected to each other to form a continuous channel.
Such a mesopore not only provides a large surface area, but also provides an effective diffusion channel through which electrolyte ions can access the inner surface, thereby improving the performance of the energy storage device.
The nickel layer may be formed by directly forming a nickel hydroxide layer on the nickel film and then reducing, preferably by heating and reducing. The nickel hydroxide layer may be formed directly on the nickel film by a hydrothermal reaction. In addition, the nickel hydroxide layer may be formed of nickel hydroxide powders having petal shape.
The electrode according to the present invention may further comprise at least one powder of a metal hydroxide powder and a metal oxide powder as an active material. As a specific example, the electrode may further include a nickel hydroxide powder, a manganese oxide powder, or a mixed powder thereof as an active material.
The active material may be formed on the outer surface and the inner surface (i.e., mesopore surface) of the nickel layer. The active material may be deposited on the nickel layer without a separate adhesive or binder. For example, the active material may be formed by electrodeposition on the electrode.
According to a preferred example, the nickel layer is formed by directly forming a nickel hydroxide layer on the nickel film by a hydrothermal reaction followed by heating and reducing; The electrode may further include a nickel hydroxide powder as an active material.
The electrode is excellent in flexibility such as bending property, curling property, and folding property (see Figs. 1 (c) and (d)).
In addition, the electrode can maintain excellent electrochemical characteristics even under bending conditions. For example, the electrode can maintain at least 85%, at least 90%, or at least 95% of its initial capacitance after 100 repeated bend tests. In addition, the electrode can maintain 85% or more, or 90% or more of the initial capacitance after a 180 ° bend test.
In addition, the electrode according to the present invention has excellent thin film characteristics. For example, the electrode may have a total thickness ranging from 0.01 to 1 mm, from 0.03 to 0.5 mm, or from 0.03 to 0.1 mm.
The electrode according to the present invention has a large surface area due to the numerous mesopores formed therein. Specifically, the electrode has a surface area ranging from 3 to 20
According to a preferred embodiment, the electrode has a total thickness in the range of 0.01 to 1 mm; And can have a surface area of 3 to 20
The electrode according to the present invention has excellent electrochemical properties.
For example, the electrode may have a capacitance of greater than 2000 F / g, greater than 2500 F / g, or greater than 3000 F / g at a current density of 10 A / g. More specifically, the electrode may have a capacitance of 2500-4000 F / g, 3000-3800 F / g, or 3300-3700 F / g at a current density of 10 A / g.
The electrode according to the present invention is excellent in stability. For example, the electrode can maintain 70%, 75%, or 80% or more of its initial capacitance after 1000 cycles. Also, the electrode can maintain a capacitance of 70%, 75%, or 80% or more of the capacitance at a current density of 10 A / g even at a current density of 200 A / g.
According to a preferred embodiment, the mesopores have an average size of 10 to 50 nm, the electrodes have a total thickness of 0.03 to 0.5 mm; A surface area of 5 to 10 m < 2 > / g; A capacitance of 3000 to 3800 F / g at a current density of 10 A / g; It can be used as an electrode of a super capacitor.
Also, at this time, the electrode can maintain 90% or more of the initial capacitance even after the 180 ° bending test and the 100 repeated bending test.
The electrode according to the present invention can be used as an electrode in a supercapacitor and exhibit excellent electrochemical performance. The excellent electrochemical performance of the electrode of the present invention is due to the synergistic effect of numerous active sites and the reduced resistance due to the direct contact between the active material and the mesoporous 3D-nickel current collector, Fast transport of charge / ions is possible.
Although commercially available low cost nickel films have flexibility, they do not have a large number of active sites. In addition, commercially available nickel foams have a large area and a fast charge transfer path due to the three-dimensional network structure, but they generally do not bend because the thickness exceeds 1 mm. On the other hand, the electrode according to the present invention can make the thickness of the current collector thinner without changing the amount of the deposited active material, thereby improving both flexibility and electrochemical characteristics.
In addition, the electrode according to the present invention can be manufactured in a large area (see Fig. 8).
Accordingly, the electrode according to the present invention can be advantageously used in various fields including a wearable sensor and a curved electronic device requiring flexibility and high electrochemical performance.
According to another aspect of the present invention, there is provided a method for preparing a nickel hydroxide precursor solution, comprising the steps of: (1) directly forming a nickel hydroxide layer by hydrothermal reaction on a nickel film in a precursor solution of nickel hydroxide; And (2) reducing the nickel hydroxide layer to obtain an electrode having a nickel layer formed on a nickel film, wherein the nickel layer is three-dimensionally structured inside and has a plurality of mesopores, / RTI >
In addition, the method of manufacturing the electrode may further include the step of (3) electro-depositing a metal hydroxide or a metal oxide powder on the electrode in a precursor solution of metal hydroxide or metal oxide after the step (2) .
The electrode manufactured by the above method can have the above-described physical properties and electrochemical characteristics.
Hereinafter, the manufacturing method will be described in detail for each step.
In the step (1), a nickel hydroxide layer is directly formed on the nickel film in the precursor solution of nickel hydroxide by a hydrothermal reaction.
First, the nickel film is immersed in a precursor solution of nickel hydroxide.
A typical nickel film may be used for the nickel film, and a detailed description of the thickness range and the like is as described above. Further, the nickel film may be one produced by a method such as electro-deposition, rolling, or the like.
The precursor solution of nickel hydroxide can be, for example, a solution of nickel nitrate hexahydrate, nickel sulfate, nickel nitrate, nickel acetate or the like. At this time, the solvent of the precursor solution may be water, ethanol, methanol or the like.
Thereafter, a nickel hydroxide layer is formed directly on the nickel film by a hydrothermal reaction. The hydrothermal reaction may be carried out at a temperature in the range of 60 to 150 ° C, or in the range of 80 to 120 ° C. The hydrothermal reaction may be performed for 0.5 to 10 hours, or for 2 to 6 hours.
After the hydrothermal reaction, a nickel hydroxide layer consisting of three-dimensional shaped nickel hydroxide powders can be formed directly on the nickel film. Preferably, the nickel hydroxide layer may be composed of nickel hydroxide powders having a petal shape. In addition, the nickel hydroxide powder may be a hierarchical Ni (OH) 2 .
The thickness of the nickel hydroxide layer may be proportional to the time and temperature of the hydrothermal reaction.
In addition, prior to the hydrothermal reaction, the step of physically polishing the nickel film with sandpaper may be further performed, thereby removing impurities such as oxide layer and dust on the nickel film, The bonding force between the formed nickel hydroxide layer and the nickel film can be further increased.
In the step (2), the nickel hydroxide layer is reduced to obtain an electrode in which a nickel layer is formed on a nickel film.
Preferably, the reduction is performed by thermal reduction. For example, the nickel hydroxide layer / nickel film produced in step (1) may be placed in a heating furnace and annealed in a hydrogen atmosphere.
Specifically, the reduction may be performed at a temperature in the range of 300 to 800 ° C, or in the range of 300 to 500 ° C. In addition, the reduction may be performed for 0.5 to 4 hours, or for 1 to 2 hours. In addition, the reduction may be performed in an argon gas, a hydrogen gas, or a mixed gas atmosphere thereof.
When the nickel hydroxide layer is heated and reduced, water molecules in the nickel hydroxide layer evaporate and the interior is three-dimensionally structured so that a nickel layer having many mesopores can be obtained directly on the nickel film.
A method and a method for manufacturing an electrode according to an example are shown in Fig. 1 (a).
As shown in FIG. 1 (a), according to the above example, (1) forming a nickel hydroxide layer made of a petal-shaped nickel hydroxide powder by a hydrothermal reaction on a nickel film; And (2) heating and reducing the obtained nickel hydroxide layer / nickel film to produce an electrode of a mesoporous nickel layer / nickel film structure.
In the step (3), the active material is deposited on the previously prepared electrode.
Specifically, a metal hydroxide or a metal oxide powder may be deposited on the electrode in a precursor solution of a metal hydroxide or a metal oxide.
The electrodeposition may be performed in the range of -20 mA to 10 mA, or in the range of -10 mA to 0 mA. In addition, the above electrical deposition can be performed for 1 to 20 minutes, or for 1 to 5 minutes.
As a result, the active material can be uniformly deposited on the outer and inner surfaces of the nickel layer.
In addition to electrodeposition, the active material can be deposited on the electrode through a hydrothermal reaction.
According to the manufacturing method of the present invention, it is possible to manufacture a high-performance flexible nickel-based electrode by a simple method such as hydrothermal reaction, heating reduction, and electrodeposition.
According to still another aspect of the present invention, there is provided a supercapacitor including an electrode, an electrolyte, and a separator according to the present invention.
The electrode used in the supercapacitor is an electrode having a mesoporous nickel layer as described above, and can be used, for example, as a working electrode.
The electrode according to the present invention may include an active material, and the specific types of the active material are as described above.
The electrolyte may be a solid electrolyte or a liquid electrolyte. Examples of the solid electrolyte include PVA / KOH gel, PVA / H 3 PO 4 gel, PVA / TEABF 4 gel, and the like. In addition, the liquid electrolyte may include KOH, H 3 PO 4 , NaCl, TEABF 4 (tetraethylammonium tetrafluoroborate), and the like.
The separation membrane may be a filter membrane, paper, filter paper, or the like.
The supercapacitor may further include a counter electrode, and examples of the counter electrode include platinum mesh, carbon, and conductive metal.
The supercapacitor may further include a reference electrode, and examples of the reference electrode include Ag / AgCl, Hg / HgO, and the like.
The supercapacitor may be a two-electrode system or a three-electrode system.
Also, the supercapacitor may be a solid state battery, for example, a solid state asymmetric battery. At this time, the flexible supercapacitor can be constituted by the electrode of the present invention.
In addition, the supercapacitor may be sealed with a sealing material, and may be sealed with a flexible polymer film such as polyethylene terephthalate (PET).
The supercapacitor of the present invention can exhibit satisfactory performance in terms of energy density and output density. For example, the energy density of the supercapacitor may be 50-90 Wh / kg, 60-85 Wg / kg or 70-80 Wg / kg, and the output density may be 600-7000 W / kg, 1000-6500 W / kg, 3000 to 6000 W / kg, 4000 to 6000 W / kg, or 5000 to 5500 W / kg.
Hereinafter, the present invention will be described in more detail with reference to examples.
The following examples are illustrative of the present invention, but the scope of the present invention is not limited to these examples.
The meanings of the abbreviations used in the following examples are as follows:
- 3D-nickel hydroxide: Nickel hydroxide made of petal powder
- 3D-Nickel: Nickel with three-dimensionally structured interior and numerous mesopores
- 3D-Nickel Electrode: An electrode with a structure (3D-nickel / nickel film) in which 3D-nickel is directly formed on the nickel film
- Nickel hydroxide / 3D-nickel electrode: 3D-nickel electrode with nickel hydroxide as active material
- Manganese oxide / 3D-nickel electrode: 3D-nickel electrode using manganese oxide as active material
- BET: Brunauer-Emmett-Teller
- CV: cyclic voltammetry
- FE-SEM: field emission scanning electron microscopy
- SEM: scanning electron microscopy
- TGA: thermogravimetric analysis
- XRD: X-ray diffraction
The materials and equipment used in the following examples are as follows:
- Nickel film: nickle foil, Alfa Aesar, 20 x 30 cm, 99%
Nickel foam, 49 x 150 mm, thickness 1.6 mm, bulk density 0.45 g /
- Nickel nitrate hexahydrate, nickel nitrate hexahydrate, Samcheon chem, 98%
- manganese acetate tetrahydrate, Sigma Aldrich,> 99%
- Sodium sulfate anhydrous: sodium sulfate anhydrous, Sigma Aldrich, ACS reagent,> 99%
- The structure of the electrodes was analyzed using FE-SEM (SEM FEI / USA nanonova 230).
- The crystallinity of the electrode was measured by X-ray diffraction (XRD, Ragaku Co. high power X-ray diffractometer D / MAZX 2500V / PC, Cu Ka radiation, λ = 1.5406 Å) at 1 ° / s < / RTI >
The surface area, pore size, and pore volume of the electrode were measured using a measuring device (Belsorp max, Bel Japan) according to the BET (Brunauer-Emmett-Teller) method.
Example 1: Preparation of 3D-nickel electrode
100 mM of Ni (NO) 3 .6H 2 O and 100 mM of hexamethylenetetramine (HMTA) were dissolved in deionized water and stirred for 1 hour at atmospheric pressure, and then 40 mL of the obtained solution was placed in a 70 mL vial. Nickel film made of petal powder was directly synthesized and grown on the nickel film by a hydrothermal reaction in which the nickel film was immersed in the solution and heated at 100 캜 for 4 hours. The obtained 3D-nickel hydroxide / nickel film was naturally cooled. The film was thoroughly washed with distilled water and ethanol and dried at 120 캜 under vacuum for 12 hours. Then, the film was further annealed for 2 hours while flowing hydrogen gas under a vacuum of 400 캜 to reduce nickel hydroxide, thereby finally obtaining an electrode (i.e., a 3D-nickel / nickel film) on which a 3D-nickel film was formed on the nickel film Respectively.
Example 2: Preparation of nickel hydroxide / 3D-nickel electrode
The 3D-nickel electrode prepared in Example 1 was placed in a 100 mM nickel nitrate hexahydrate solution, and a current of -5 mA was supplied at 25 캜 for 5 minutes to electroplath the nickel hydroxide powder on the 3D-nickel electrode. The resulting nickel hydroxide / 3D-nickel electrode was carefully washed with distilled water and ethanol and dried under vacuum at 120 ° C for 12 hours.
Example 3: Preparation of manganese oxide / 3D-nickel electrode
The 3D-nickel electrode prepared in Example 1 was placed in a 100 mM manganese acetate tetrahydrate and 100 mM sodium sulfate anhydrous, and a current of -5 mA was supplied at 25 DEG C for 5 minutes to deposit manganese oxide powder on the 3D- Respectively. The resulting manganese oxide / 3D-nickel electrode was carefully washed with distilled water and ethanol and dried under vacuum at 120 ° C for 12 hours.
Example 4: Preparation of super capacitor
A three electrode supercapacitor was prepared by connecting mercury / silver oxide as a working electrode in Examples 2 and 3, a platinum mesh as a counter electrode, and a reference electrode, and immersing it in a beaker containing a 1 M KOH electrolyte.
Example 5: Manufacture of super capacitor
Using the nickel hydroxide / 3D-nickel electrode prepared in Example 2 and the manganese oxide / 3D-nickel electrode prepared in Example 3 as the anode, a PVA / KOH gel electrolyte was applied to each electrode and dried for 10 minutes . After separating the separator between the electrodes, the two electrodes were sealed with a PET film to produce an asymmetric two-electrode solid supercapacitor.
Comparative Example
As a comparative example, a nickel film and a nickel foam were used as an electrode, and nickel hydroxide was vapor-deposited as an active material.
Experimental Example 1: Structural Analysis
1A and 1B are photographs and enlarged views of a nickel film, a 3D-nickel hydroxide / nickel film, and a 3D-nickel / nickel film according to the sequential manufacturing process of Example 1. FIG.
The 3D-nickel hydroxide / nickel film produced exhibited a light green color, which turned black after being reduced to a 3D-nickel / nickel film.
From the XRD results of each electrode shown in Fig. 6, it can be seen that the 3D-nickel hydroxide / nickel film completely changed into a 3D-nickel / nickel film without any impurities.
15 is a SEM image of a nickel hydroxide / nickel film electrode and a nickel hydroxide / nickel foam electrode and a nickel hydroxide / 3D-nickel electrode according to Example 2 as a comparative example. As shown in FIG. 15, when the active material was deposited in the same amount (1.0 mg) on each current collector, the active material was deposited thicker when the collector had a low surface area. The relative thickness of the active material deposited on the surface of the collector was greater in the order of 3D-nickel, nickel foam, and nickel film. Thick active materials deposited on nickel films and nickel foams cracked during the drying process, which degrades the electrical performance of the electrodes. On the contrary, the active material on the 3D-nickel current collector was uniformly coated and did not crack.
Experimental Example 2: Evaluation of thermal stability
FIG. 2 (a) shows XRD data of a 3D-nickel / nickel film obtained by high temperature annealing a 3D-nickel hydroxide / nickel film under hydrogen gas according to Example 1, indicating that the nickel hydroxide was reduced to nickel. The 2θ peaks (44.5 °, 51 ° and 77 °) of the XRD curve corresponded to the (111), (200) and (220) planes of nickel (see JCPDS card 04-0850).
Further, in order to check the physical and thermal stability of the 3D-nickel / nickel film, the XRD peak change and the weight loss of the thermogravimetric analysis (TGA) curve were observed under various conditions. FIG. 2 (b) shows that the crystallinity of the 3D-nickel / nickel film was maintained for 2 months as the XRD data measured after storing the 3D-nickel / nickel film at room temperature for several weeks.
TGA was performed from 100 DEG C to 800 DEG C for the 3D-nickel electrode, and the results are shown in Fig.
As shown in FIG. 9 and Table 1, the TGA curve of the 3D-nickel / nickel film under atmospheric conditions was measured and showed almost no change in weight up to 300 ° C. From these, it can be seen that these electrodes have thermal stability, which is also confirmed by the XRD curve ( see the inset of FIG. 2 (c) ). On the other hand, the weight increase of 25% observed at 400 ° C appears to be due to the transformation of 3D-nickel into NiO in air.
Experimental Example 3: Physical Stability Evaluation
The physical durability of the 3D-nickel structure was confirmed by the detachment test.
Even after the commercially available 3M Scotch tape was attached to the surface of the 3D-nickel / nickel film prepared in Example 1 and the blow test was performed using a nitrogen gas gun, the 3D-nickel did not fall off from the nickel film and the original shape Respectively. In particular, 3D-nickel / nickel films showed only a slight weight loss from 137.651 mg to 137.647 mg after the blowing test (see Fig. 2 (d) to (f)).
Also, as shown in FIG. 10, the physical stability of the 3D-nickel / nickel film could be confirmed since no significant change was observed when the 3D-nickel / nickel film was rubbed with the finger.
Figure 11 shows SEM images of 3D-nickel / nickel films after annealing and annealing 3D-nickel hydroxide / nickel films according to Example 1. The high mechanical stability of the 3D-nickel is due to the tight bonding between the reduced 3D-nickel and the constituents of the nickel film by being partially melted / solidified under high temperature reduction / cooling conditions.
Experimental Example 4: Pore Evaluation
The 3D-nickel electrode prepared in Example 1 was observed by SEM and is shown in Fig. 3 (b). As shown in FIG. 3 (b), in the 3D-nickel electrode, nickel is connected in the form of a three-dimensional network to form many mesopores, and these mesopores are closely connected to each other to form a continuous channel.
The 3D-nickel of the electrode differs in size from the porous nickel skeleton in comparison with commercially available nickel foams widely used in supercapacitors and current collectors of batteries. Nickel foams have a large number of macropores (300 μm to 1 mm), while 3D-nickel electrodes have many mesopores (pore
Specifically, the surface area of the nickel foam was less than 0.5
In addition, the mesoporous network of the 3D-nickel electrode increases the proportion of the active material deposited on the current collector, enables rapid electron transport through the network, and allows the electrolyte to easily access the active material under bending conditions.
The electrodes of Examples 2 and 3, in which nickel hydroxide and manganese oxide were electro-deposited as active materials on the 3D-nickel, respectively, were observed by SEM and are shown in Figs. 3 (a) and 3 (c), respectively. Nickel hydroxide was deposited on the mesoporous 3D-nickel electrode to form a more complex wrinkled surface structure, and manganese oxide was deposited as particles on the surface of the 3D-nickel. The majority of the pores were open after the deposition of the active material, which can provide a path through which the electrolyte can be rapidly transported to the electrode.
As a result of controlling the deposition amount of the active material by adjusting the deposition current and the deposition time at the time of the electrodeposition, the electrochemical performance was best when the electrodeposition conditions were -5 mA and 5 minutes. Further, as shown in the XRD results of FIG. 14, it was confirmed that nickel hydroxide and manganese oxide were successfully deposited on the 3D-nickel without impurities.
Experimental Example 5: Evaluation of electrochemical characteristics
The electrochemical characteristics of the electrodes were evaluated by applying a 3D-nickel electrode to the three-electrode system and the two-electrode system supercapacitor in the same manner as in Examples 4 and 5.
Specifically, capacitance was measured by a cyclic voltammetry method and a constant current charge / discharge method using an electrochemical interfacial method (VMP3 biologic) through computer control.
As a comparative example, electrochemical characteristics were compared by depositing a nickel hydroxide active material on nickel films and nickel foams, which are two representative collectors of the prior art, and applying the same to the three-electrode system and two-electrode system supercapacitor, The amount of the active material used in the comparison was the same (1.0 mg).
As shown in FIG. 4 (a), the integrated area of the CV curve of the nickel hydroxide / 3D-nickel electrode at 20 mV / s was the largest, indicating that the 3D-nickel electrode had the highest capacitance.
The electrostatic capacity of each electrode was calculated from the constant current charge / discharge curve. As a result, the electrostatic capacity of nickel hydroxide / 3D-nickel electrode, nickel hydroxide / nickel foam, and nickel hydroxide / nickel film was 3498 F / g , 1088 F / g, and 622 F / g, respectively. Thus, the nickel hydroxide / 3D-nickel electrode exhibited a capacitance three times and five times greater than that of the nickel hydroxide / nickel foam electrode and the nickel hydroxide / nickel film electrode, respectively.
In addition, the adsorption / desorption isotherm curves and the pore size distribution of 3D-nickel were measured and shown in FIG. 13 and Table 2 below.
As can be seen from Fig. 13 and Table 2, on the surface area of the current collector where the active material can be deposited directly, the 3D-nickel electrode is very wide (approximately 7 times as compared to the conventional known nickel-based electrode) .
Also, as shown in Figures 16 and 17, the 3D-nickel electrode showed faster charge transport than other nickel foam or nickel film electrodes. In particular, it was confirmed that the electrical resistance did not significantly increase at the interface between the 3D-nickel film and the nickel film at the 3D-nickel electrode. This is because, in the 3D-nickel electrode, no binder is used to generate electrical resistance at the interface.
In addition, the 3D-nickel electrode showed a more vertical curve than the nickel film and the nickel foam, demonstrating the ideal behavior of the 3D-nickel electrode because the nickel hydroxide was thinly deposited on the 3D-nickel current collector.
Figures 4 (c) and 4 (d) show CV curves and dynamic characteristics at various scan rates (1, 5, 10, 20, and 30 mV / s) of nickel hydroxide / 3D-nickel electrodes.
The nickel hydroxide / 3D-nickel electrode exhibited a symmetrical curve with a small gap between the anode peak and the cathode peak, indicating a good reversible redox reaction. Also, a high capacitance of about 3400 F / g was measured at a current density of 10 A / g, approaching the highest capacitance reported to date for nickel hydroxide based active materials. In addition, the nickel hydroxide / 3D-nickel electrode exhibited a high capacitance retention rate of 80% at a high current density of 200 A / g (see FIG. 4 (d)), and the dynamic characteristics of the electrode were excellent. The high capacitance and dynamic properties of the nickel hydroxide / 3D-nickel electrode can be attributed to the differentiated structure of the 3D-nickel and thus the inertness of the active material can be minimized by the numerous active sites provided.
The advantages of the 3D-nickel electrode in the supercapacitor were confirmed in the performance evaluation of the manganese oxide / 3D-nickel electrode. As a result of CV curve measurement from -0.2 V to 0.6 V, anode peak and cathode peak were observed near 0.5 V and 0.3 V due to redox reaction with manganese oxide electrolyte. The manganese oxide / 3D-nickel electrode according to an embodiment exhibited a high capacitance of about 1200 F / g, which is close to the theoretical capacitance of manganese oxide used as the active material.
The charge / discharge curve of manganese oxide / 3D-nickel was measured under the same conditions as that of nickel hydroxide / 3D-nickel electrode, and the current density was changed from 10 A / g to 200 A / g. As a result, the manganese oxide / 3D-nickel electrode showed 1,130 F / g at 200 A / g, and the electrostatic capacity retention rate reached 82%. The high electrostatic capacity and excellent dynamic characteristics of the electrode are due to the differentiated structure of the 3D-nickel electrode of the present invention and the large amount of active material deposited directly on the 3D-nickel phase without the binder.
FIG. 5 (a) shows a structural view of a flexible supercapacitor to which a 3D-nickel electrode is applied according to Example 5 and an electrode photograph thereof.
FIG. 5 (b) is a CV curve of the flexible supercapacitor at various scans, showing the anode peak due to the oxidation reaction of the electrode and the cathode peak due to the reduction reaction of the electrode. No shape change was observed at increasing scan rate, which means that no further reaction occurs.
5 (c) and 5 (d), no particular change was observed in the CV curve of the supercapacitor even under various bending conditions (from 0 ° to 180 °) and 100 repetitive bending conditions, - Nickel-based asymmetric solid state supercapacitor is excellent in cycle stability and flexibility.
The cyclic stability was measured while charging and discharging the flexible supercapacitor over 1,000 cycles (see FIG. 18). As a result, the capacity was 74%, indicating excellent cycle stability. This excellent performance is due to the stable and robust structure of 3D-Nickel, as found in the flexibility and tape test. This is very useful in that it can extend the lifetime when it is actually used in flexible supercapacitors. Generally, when the structure of nickel hydroxide is changed from a-type to b-type, the theoretical capacitance is decreased, so that the electrostatic capacity gradually decreases as the electrochemical reaction continues. However, since the reaction of the a-type nickel hydroxide is reversible, the shape and the electrostatic capacity can be maintained, resulting in a synergistic effect of fast charge / electron transport and mechanical stability.
The 3D-nickel electrode of the present invention has a differentiated network structure and mesopores, providing numerous active sites through the active material in direct contact with the current collector, enabling rapid electron transport through the network and ion transport in the electrolyte. Specifically, the capacitance of asymmetric supercapacitors of nickel hydroxide / 3D-nickel / manganese oxide / 3D-nickel structure was calculated to be 290 F / g at 1 A / g and maximum energy density and power density of 78 Wh / kg And 5,340 W / kg, respectively. This is remarkably superior to that of the conventional flexible supercapacitors Ref 35 to 38 as shown in FIG. 5 (e), which exhibited a low energy density of about 40 Wh / kg or a low output density of about 500 W / kg .
In addition, a test was performed in which three flexible supercapacitors according to Example 5 were connected in series to vary the working voltage to emit various LEDs. As a result, the flexible supercapacitor emits all the LEDs, and the blue LED emits over 10 minutes, confirming excellent energy density and power density.
In addition, the application of the flexible supercapacitor to the wrist strap of the electronic wristwatch has resulted in normal operation, and the potential for wearable devices has been confirmed.
It has been found through the above experiments that a flexible 3D-nickel / nickel film can be provided at low cost, and the film can be applied to a super capacitor by simple hydrothermal reaction and electro-deposition. In particular, the 3D-nickel electrode of the present invention comprises a nickel hydroxide / 3D-nickel electrode with a high charge transport pathway as well as multiple active sites, resulting in a high electrostatic charge of about 3400 F / g at a current density of 10 A / g Capacity. In addition, 3D-nickel has a number of active sites in the active material, thus exhibiting excellent reversibility characteristics even at a high current density of 200 A / g while maintaining 80% of initial capacitance. In addition, the asymmetric supercapacitor using a 3D-nickel electrode showed an energy density of 78 Wh / kg similar to that of a battery at an output density of 5,340 W / kg, and due to the excellent flexibility, the function as an energy storage device faithfully Respectively.
Claims (15)
The inside of the nickel layer is three-dimensionally structured to have a large number of mesopores having an average size of 10 to 50 nm,
The electrode has a total thickness of 0.03 to 0.5 mm, a surface area of 5 to 10 m < 2 > / g and a capacitance of 3000 to 3800 F / g at a current density of 10 A / g and is used as an electrode of a supercapacitor.
Wherein the electrode maintains at least 90% of its initial capacitance after a 180 ° bend test and 100 repeat bend tests.
Wherein the nickel layer is formed by directly forming a nickel hydroxide layer on the nickel film and then heating and reducing the nickel layer.
Wherein the nickel hydroxide layer is formed directly on the nickel film by hydrothermal reaction.
Wherein the electrode further comprises a nickel hydroxide powder, a manganese oxide powder, or a mixed powder thereof as an active material.
The nickel layer is formed by directly forming a nickel hydroxide layer on the nickel film by a hydrothermal reaction followed by heating and reducing;
Wherein the electrode further comprises a nickel hydroxide powder as an active material.
(2) reducing the nickel hydroxide layer to obtain an electrode in which a nickel layer is formed on the nickel film,
The inside of the nickel layer is three-dimensionally structured to have a large number of mesopores having an average size of 10 to 50 nm,
The electrode has a total thickness of 0.03 to 0.5 mm, a surface area of 5 to 10 m < 2 > / g and a capacitance of 3000 to 3800 F / g at a current density of 10 A / g and is used as an electrode of a supercapacitor Gt;
Wherein the nickel hydroxide layer is made of a nickel hydroxide powder having a petal shape.
The hydrothermal reaction is carried out in a temperature range of 60 to 150 ° C,
Wherein the reduction is performed in a temperature range of 300 to 800 캜.
The method for producing an electrode according to claim 1, further comprising, after the step (2), electroplating a metal hydroxide or a metal oxide powder on the electrode in a precursor solution of a metal hydroxide or a metal oxide .
Wherein the electrodeposition is performed under a current condition of -10 mA to 0 mA.
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