KR20160133212A - Preparing method of layered double hydroxide - Google Patents

Abstract

The present invention relates to a preparation method of layered double hydroxide using a reverse micelle method. The preparation method can easily prepare layered double hydroxide with high yield within a short period of time. According to the present invention, the preparation method of layered double hydroxide comprises the following steps of: obtaining a first solution by mixing a first metal precursor and a second metal precursor in a first solvent; obtaining a second solution by mixing a second solvent and a surfactant; obtaining a third solution by injecting the first solution to the second solution; and making the third solution react by heat-treating the same.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for producing a layered double hydroxide,

The present invention relates to a process for preparing a layered double hydroxide using a reverse micelle method.

Colloidal ultra-thin inorganic nanosheets of metal oxides or hydroxides having a thickness of approximately a few nanometers have received much attention for their application in energy storage, electronic devices, and catalysis as well as for studying basic physical properties. Layered double hydroxide (LDH) is a lamella compound consisting of a host layer filled by a positive charge and an inserted anion for charge balancing. Generally, the LDH has the _formula [M ^{2 +} _{1 x} M ^{3 +} _x (OH) ₂ ] (A ^n- ) _{x / n}揃_m H ₂ O where M ^{2 +} and M ³⁺ are 2 And A < ^n- > is a charge balanced anion. LDH has received much attention recently due to its rapid redox reaction and their excellent pseudocapacitive properties associated with large active surface area. The colloidal LDH nanosheets can also be used as components in the production of functional films.

Typically, coprecipitation is one of the most widely used methods for producing stratiform double hydroxides. This method has the disadvantage of requiring a very long reaction time and high pH. In addition, since the nanosheets are formed by laminating particles, the nanosheets have a disadvantage in that additional peeling steps are required due to their structural characteristics in order to obtain a single crystalline nanosheet.

Peeling is one of the most widely used methods of making colloidal stacked solids. However, as compared to other stacked solids, the exfoliation of LDH is quite difficult due to strong interlayer electrostatic interaction, which is due to the high charge density of the LDH layer and the high content of incorporated anions. Recently, the reverse micelle method has been used for the synthesis of colloidal LDH nanoplateles, which is a self-assembled process, including the injection of an aqueous phase, which generally contains a metal precursor in the oil phase. assembled droplets surrounded by surfactant molecules. The droplet serves as a nanoreactor with limited space for controlled growth of the LDH. The reverse micelle method has enabled the production of LDH nanoparticles with controlled thicknesses and diameters.

The reverse micelle synthesis of conventional LDH nanosheets is generally performed using sodium dodecyl sulfate (SDS) as a surfactant and 1-butanol as an auxiliary surfactant to form iso-octane as an oil phase isooctane). For example, colloidal Mg-Al, Ca-Al, and Co-Al LDH nanosheets have been synthesized by the reverse-micelle method based on isooctane. However, most of the above synthesis requires a long reaction time (1 to 4 days) and a pH value adjustment of the reaction solution (usually 10 or more).

On the other hand, Chengle J. Wang discloses the reverse micelle synthesis of Co-Al layered double hydroxides (LDH) and also discloses that the particle size and magnetic properties are controlled through the above synthesis (CJ Wang , YA Wu, RMJ Jacobs, JH Warner, GR Williams, D. O'Hare, Chem.Mater., 2011, 23, 171-180.).

The present invention provides a process for preparing a layered double hydroxide using a reverse micelle method.

However, the problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

One aspect of the present invention is directed to a process for preparing a first metal precursor, comprising: mixing a first metal precursor and a second metal precursor in a first solvent to obtain a first solution; Mixing a second solvent and a surfactant to obtain a second solution; Injecting the first solution into the second solution to obtain a third solution; And heat treating the third solution to react. The present invention also provides a method for producing a layered double hydroxide.

According to one embodiment of the present invention, it is possible to provide a method for producing a layered double hydroxide using a reverse micelle method at a high yield in a short time compared with the conventional method, and the layered double hydroxide produced by the method according to the present invention can be used such as an electrode material of a pseudo capacitor, a water decomposition catalyst, a lithium ion battery, or a solar battery. In addition, the process according to the present invention can produce layered double hydroxides without pH adjustment, and the layered double hydroxides according to the present invention can exhibit high non-discharge capacity and excellent stability.

1 is a schematic diagram illustrating the structure of a layered double hydroxide (LDH) nanosheet according to one embodiment of the present invention.
2 is a photograph showing a first solution and a third solution (c) mixed with a second solution (a), a third solution (b), and ethanol, respectively, in one embodiment of the present invention.
Figure 3 shows, in one embodiment of the invention, a scanning transmission electron microscopy (STEM) image (a) of a colloidal metal LDH, a surface HRTEM image of a single metal LDH and a Fourier transform (b) (Atomic force microscopy) image and line profile (c) of the LDH, and the thickness distribution (d) of the single colloidal metal LDH.
4 (a) and 4 (b) are SEM (scanning electron microscope) images of metal LDH nanosheets obtained after ethanol treatment in one embodiment of the present invention, and FIGS. 4 (c) and 4 , In one embodiment of the present application, is a TEM image of a metal LDH nanosheet obtained after ethanol treatment.
5 (a) to 5 (d) are graphs showing the X-ray diffraction (XRD) pattern, the energy dispersive X-ray spectroscopy (EDS) spectrum of the metal LDH nanosheets, the Ni 2p XPS X-ray photoelectron spectroscopy core level spectra, and Mn 2p XPS core level spectra.
Figures 6 (a) and 6 (b) are TEM images and powder XRD patterns of the Ni precursor solution, respectively, in one embodiment of the invention, and Figures 6 (c) and 6 (d) Are an SEM image of the Mn precursor solution and a powder XRD pattern, respectively.
Figures 7 (a) and 7 (e) show a comparison of the CV (cyclic voltammetry) curves and non-breakdown capacity for metal LDH nanosheets, Ni (OH) ₂ , and Mn ₃ O ₄ , 7 (b) to 7 (d) are constant current charge-discharge curves of metal LDH nanosheets, Ni (OH) ₂ and Mn ₃ O ₄ , respectively, in the embodiment of the present invention, (F) shows the cycling performance of metal LDH nanosheets and Ni (OH) ₂ in one embodiment of the present invention.

Hereinafter, embodiments and examples of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art to which the present invention pertains. It should be understood, however, that the present invention may be embodied in many different forms and is not limited to the embodiments and examples described herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout this specification, when a part is referred to as being "connected" to another part, it is not limited to a case where it is "directly connected" but also includes the case where it is "electrically connected" do.

Throughout this specification, when a member is "on " another member, it includes not only when the member is in contact with the other member, but also when there is another member between the two members.

Throughout this specification, when an element is referred to as "including " an element, it is understood that the element may include other elements as well, without departing from the other elements unless specifically stated otherwise.

As used herein, the terms "about," " substantially, "and the like are used herein to refer to or approximate the numerical value of manufacturing and material tolerances inherent in the stated sense, Accurate or absolute numbers are used to prevent unauthorized exploitation by unauthorized intruders of the mentioned disclosure.

The term " step " or " step of ~ " as used throughout the specification does not imply " step for.

Throughout this specification, the term "combination (s) thereof " included in the expression of the machine form means a mixture or combination of one or more elements selected from the group consisting of the constituents described in the expression of the form of a marker, Quot; means at least one selected from the group consisting of the above-mentioned elements.

Throughout this specification, the description of "A and / or B" means "A or B, or A and B".

Throughout this specification, the term "alkyl group" is typically an alkyl group having from 1 to 20 carbon atoms, from 1 to 10 carbon atoms, from 1 to 8 carbon atoms, from 1 to 5 carbon atoms, or from 1 to 3 carbon atoms , A linear or branched alkyl group and an isomer thereof. When the alkyl group is substituted with an alkyl group, it is also used interchangeably as a "branched alkyl group ". Examples of the substituent which may be substituted on the alkyl group include halo (for example, F, Cl, Br or I), haloalkyl (for example, CCl ₃ or CF ₃ ), alkoxy, alkylthio, [-C (O) -OH], alkyloxycarbonyl [-C (O) -OR], alkylcarbonyloxy [-OC (O) -R], amino (-NH _2), carbamoyl [- At least one member selected from the group consisting of NHC (O) OR- or -OC (O) NHR-], urea [-NH-C (O) -NHR-], thiol (-SH) But is not limited thereto. In addition, the alkyl group having 2 or more carbon atoms in the alkyl group described above may include, but not limited to, at least one carbon to carbon double bond or at least one carbon to carbon triple bond. For example, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, , Eicosyl, or any of the possible isomers thereof, but is not limited thereto.

As used herein, the expression "nanosheet" means a state in which each layer of a metal layered double hydroxide having a layered structure, a metal having a laminated structure, or a metal oxide is dispersed in a single state in a solvent.

Hereinafter, embodiments of the present invention are described in detail, but the present invention is not limited thereto.

One aspect of the present invention is directed to a process for preparing a first metal precursor, comprising: mixing a first metal precursor and a second metal precursor in a first solvent to obtain a first solution; Mixing a second solvent and a surfactant to obtain a second solution; Injecting the first solution into the second solution to obtain a third solution; And heat treating the third solution to react. The present invention also provides a method for producing a layered double hydroxide.

In one embodiment of the invention, the process for preparing the layered double hydroxides comprises a reverse micelle process. When the surfactant is dissolved in an organic solvent, the hydrophilic part of the surfactant forms a nucleus and the lipophilic part touches an organic solvent to form a surface to form a reverse micelle structure. .

In one embodiment, the first solvent is selected from the group consisting of deionized water, glycerol, ethylene glycol, polyethylene glycol, diethyleneglycol, triethylene glycol, triethylene glycol, tetraethylene glycol, formamide, N-methylformamide, dimethyl formamide, dimethyl acetylamide, dimethylsulfoxide, 2-pyrrolidinone, acetamide, acrylamide, N-methylurea, urea, and the like), methanol, acetonitrile, , And combinations thereof, but the present invention is not limited thereto, and the first solvent may be a water-soluble aqueous phase material.

In one embodiment of the present invention, the step of obtaining the first solution may include, but is not limited to, mixing the first metal precursor and the second metal precursor respectively after being dissolved in the first solvent .

In one embodiment, the first metal precursor is selected from the group consisting of nickel (Ni), manganese (Mn), iron (Fe), cobalt (Co), zinc (Zn), vanadium (V), copper (Cr), titanium (Ti), iridium (Ir), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), silver (Ag), gold (Au), platinum (Al), and combinations thereof. ≪ / RTI >

In one embodiment, the second metal precursor is selected from the group consisting of nickel (Ni), manganese (Mn), iron (Fe), cobalt (Co), zinc (Zn), vanadium (Cr), titanium (Ti), iridium (Ir), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), silver (Ag), gold (Au), platinum (Al), and combinations thereof. ≪ / RTI >

In one embodiment of the invention, the second solvent is selected from the group consisting of xylene, heptane, hexane, octane, toluene, isooctane, dodecane, hexadecane, ethylbenzene, cyclohexane, divinylbenzene, styrene, But the present invention is not limited thereto, and the second solvent may be a lipophilic oil phase material.

In one embodiment of the present invention, the surfactant may be selected from the group consisting of C _{1 -20} alkylamines, C _{1 -20} fatty acids, mixtures thereof, and combinations thereof, but is not limited thereto. In the surfactant, the C _{1 -20} alkylamine may be used as a main surfactant, and the C _{1 -20} fatty acid may be used as an auxiliary surfactant, but is not limited thereto, The surfactant may be a mixture of a main surfactant and an auxiliary surfactant, but is not limited thereto.

For example, the C _{1 -20} alkylamine may be selected from the group consisting of methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, undecylamine, dodecylamine, But are not limited to, those including, but not limited to, tridecylamine, tetradecylamine, pentadecylamine, hexadecylamine, heptadecylamine, octadecylamine, nonadecylamine, oleylamine, eicosylamine, It is not.

For example, the C _{1 -20} fatty acid may be selected from the group consisting of oleic acid, methanoic acid, ethanoic acid, propanoic acid, butanoic acid, pentanoic acid, Hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, dodecanoic acid, Trimellitic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, nonanoic acid, But are not limited to, nonadecanoic acid, eicosanoic acid, or isomers thereof.

In one embodiment of the invention, the heat treatment may be performed at a temperature ranging from about 5 ° C to about 100 ° C, but is not limited thereto. For example, the temperature may range from about 5 ° C to about 100 ° C, from about 10 ° C to about 100 ° C, from about 20 ° C to about 100 ° C, from about 30 ° C to about 100 ° C, To about 100 캜, from about 60 캜 to about 100 캜, from about 70 캜 to about 100 캜, from about 80 캜 to about 100 캜, from about 90 캜 to about 100 캜, from about 5 캜 to about 90 캜, About 80 占 폚, about 20 占 폚 to about 70 占 폚, about 30 占 폚 to about 60 占 폚, or about 40 占 폚 to about 50 占 폚. In addition, the heat treatment may include a step of heating slowly at a constant rate and then maintaining a constant temperature, and cooling the third solution, which has been reacted by the heat treatment, at room temperature.

In one embodiment of the present invention, the step of washing and drying the produced layered double hydroxide may further include, but is not limited to, the step of heat-treating and reacting. The washing may be carried out using hexane; Tolune; Aceton; Chloroform; Examples of the alcohol include alcohols such as methanol, ethanol, propanol, benzyl alcohol, butanol, octanol, diacetone alcohol, furfuryl alcohol, isoamyl alcohol, isobutyl alcohol, isooctyl alcohol, isopropyl Alcohol, lauryl alcohol, polyvinyl alcohol, n-propyl alcohol; But are not limited to, a solution selected from the group consisting of water, ethanol, and combinations thereof.

In one embodiment of the present invention, the layered double hydroxide may include, but is not limited to, a single crystalline nanosheet. In addition, the layered double hydroxides may include, but are not limited to, those in a colloidal state. In addition, the nanosheet may have a lattice pattern, and may have a thickness ranging from about 1 nm to about 30 nm, but is not limited thereto. For example, the thickness of the nanosheet may range from about 1 nm to about 30 nm, from about 2 nm to about 30 nm, from about 3 nm to about 30 nm, from about 4 nm to about 30 nm, from about 5 nm to about 30 nm, From about 6 nm to about 30 nm, from about 7 nm to about 30 nm, from about 8 nm to about 30 nm, from about 9 nm to about 30 nm, from about 10 nm to about 30 nm, from about 15 nm to about 30 nm, From about 1 nm to about 25 nm, from about 3 nm to about 20 nm, from about 5 nm to about 15 nm, or from about 7 nm to about 10 nm, from about 25 nm to about 30 nm, from about 25 nm to about 30 nm, But is not limited to.

In one embodiment of the invention, the layered double hydroxide may have a size ranging from about 10 nm to about 1 탆, but is not limited thereto. For example, the size of the layered double hydroxide may be from about 10 nm to about 1 탆, from about 50 nm to about 1 탆, from about 100 nm to about 1 탆, from about 150 nm to about 1 탆, from about 200 nm to about 1 탆 About 500 nm to about 1 μm, about 600 nm to about 1 μm, about 700 nm to about 1 μm, about 800 nm to about 1 μm, about 300 nm to about 1 μm, about 400 nm to about 1 μm, about 500 nm to about 1 μm, From about 10 nm to about 500 nm, from about 10 nm to about 500 nm, from about 10 nm to about 800 nm, from about 10 nm to about 700 nm, from about 10 nm to about 600 nm, from about 10 nm to about 500 nm, From about 10 nm to about 300 nm, from about 10 nm to about 200 nm, from about 10 nm to about 150 nm, from about 10 nm to about 100 nm, or from about 10 nm to about 50 nm, But is not limited to.

In one embodiment herein, the layered double hydroxide may have a non-reactive capacity ranging from about 100 F / g to about 2,000 F / g, but is not limited thereto. For example, the non-electrochemical capacity of the layered double hydroxide may be from about 100 F / g to about 2,000 F / g, from about 200 F / g to about 2,000 F / g, from about 300 F / g to about 2,000 F / g, From about 500 F / g to about 2,000 F / g, from about 600 F / g to about 2,000 F / g, from about 700 F / g to about 2,000 F / g, from about 800 F / g to about 2,000 F / g, from about 900 F / g to about 2,000 F / g, from about 1,000 F / g to about 2,000 F / g, from about 1,200 F / About 100 F / g to about 1,600 F / g, about 2,000 F / g, about 1,600 F / g to about 2,000 F / g, about 1,800 to about 2,000 F / From about 100 F / g to about 900 F / g, from about 100 F / g to about 1,400 F / g, from about 100 F / g to about 1,200 F / g, from about 100 F / g to about 800 F / g, from about 100 F / g to about 700 F / g, from about 100 F / g to about 600 F / From about 100 F / g to about 400 F / g, from about 100 F / g to about 300 F / g, or from about 100 F / g to about 200 F / g Or, without being limited thereto.

The process for producing a layered double hydroxide according to an embodiment of the present invention can produce a layered double hydroxide using a reverse micelle method at a high yield in a short time in comparison with a conventional method, The double hydroxides can be used in various fields such as electrode materials of pseudocapacitors, water decomposition catalysts, lithium ion batteries, or solar cells. In addition, the process according to the present invention can produce layered double hydroxides without pH adjustment, and the layered double hydroxides according to the present invention can exhibit high non-discharge capacity and excellent stability.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto.

[ Example ]

Interlayer double hydroxide  Produce

For the synthesis of Ni-Mn LDH nanosheets, oleylamine (sigma-aldrich, 1.25 mmol) and oleic acid (sigma-aldrich, 0.5 mmol) xylene, samchun, 15 mL).

Meanwhile, nickel (II) chloride hydrate (nickel (II) chloride hydrate; NiCl ₂ .xH ₂ O, sigma-aldrich, 1 mmol] and manganese (II) acetate tetrahydrate; Mn (CH ₃ COO) ₂ .H ₂ O, sigma-aldrich, 0.5 mmol] was dissolved in demineralized water (deionized water, 3 mL).

Next, an aqueous solution (3 mL) containing the nickel (II) chloride and manganese (II) acetate was injected into a xylene solution (15 mL) containing oleylamine and oleic acid using a pipette, The reaction was continued for 2 hours while maintaining the stirring speed at rpm.

The reaction solution, which was reacted at room temperature for 2 hours, was slowly heated to 90 ° C at a constant rate of 7 ° C for 5 minutes while maintaining the stirring speed. Thereafter, the reaction solution was maintained at 90 ° C for 12 hours. After the reaction, the reaction solution was cooled to room temperature.

A 1: 1 mixed solution of ethanol and acetone was added to wash the nickel-manganese layered double hydroxide monocrystalline nanosheet obtained through the above-described process, and the mixture was precipitated at 8,000 rpm for 10 minutes using a centrifugal separator . Nickel-manganese layered double hydroxides precipitated and the remaining solution was removed, and a small amount of xylene and ethanol-acetone mixed solution was added. After stirring for 10 minutes, the mixture was centrifuged for 10 minutes and then dried . The above washing procedure was repeated three times.

The Ni-Mn LDH nanosheets contain oleylamine as a surfactant and manganese (II) acetate as an auxiliary surfactant in an oleic acid and an oil phase of xylene in an aqueous phase, manganese (II) acetate] and nickel (II) chloride [nickel (II) chloride] The aqueous droplets surrounded by oleylamine and oleic acid are formed and dispersed in xylene and serve as a nanoreactor for the growth of Ni-Mn LDH nanosheets. Without the surfactant, the aqueous phase and the oil phase are present separately (Fig. 2 (a)). After the synthesis, in this embodiment, no precipitate could be observed in the state where the water / xylene suspension of Ni-Mn LDH nanosheets (FIG. 2 (b)) was produced, Lt; RTI ID = 0.0 > colloidal < / RTI >

[ Experimental Example  One]

In the preparation of samples for transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) studies of colloidal LDH nanosheets, samples of the nanosheet suspension were coated on a carbon-coated copper grid Lt; / RTI > and dried at room temperature. After drying, the grid was washed with ethanol and dried again in air at ambient temperature. TEM, HRTEM, and scanning transmission electron microscopy (STEM) images were taken using a JEOL JEM-2100F microscope operated at 200 kV. Atomic force microscopy (AFM) images were obtained using XE-100 (Park system). Scanning electron microscope (SEM) images were obtained using a JEOL JSM-6701F microscope operated at 15 kV. Powder X-ray diffraction (XRD) patterns were obtained using a D8-Focus (Bruker AXS) diffractometer equipped with a rotating anode and a CuKa radiation source (lambda = 0.15418 nm). X-ray photoelectron spectroscopy (XPS) data was obtained using ECSA 2000 (VG Microtech).

In this experiment, a partial sample of the reaction solution was directly dropped on a carbon-coated copper grid, dried at room temperature, and then analyzed using TEM to characterize the synthesized Ni-Mn LDH nanosheet . 3 (a) shows a representative STEM image of the Ni-Mn LDH nanosheet in the synthesized state, and shows the formation of a colloidal nanoplate having a size of 50 nm to 150 nm. Some of the nanosheets exhibit self-folding, indicating that they are formed in solution rather than on the substrate. In Figure 3 (b) the HRTEM image shows a continuous lattice pattern on the top surface of a single LDH nanosheet. The HRTEM image shows a single crystallinity of the nanosheet corresponding to a Fourier transform (FT) pattern consisting of spots arranged in a hexagonal shape (an insertion view of FIG. 3 (b)). AFM analysis showed that the thickness of the single colloidal nanosheets ranged from 3 nm to 8 nm (FIGS. 3 (c) and 3 (d)). The results of this example demonstrate the feasibility of our method for colloid synthesis of Ni-Mn LDH nanosheets.

For further characterization, the product was obtained by precipitation with ethanol (Fig. 2 (c)). Figures 4 (a) and 4 (b) show representative SEM images of Ni-Mn LDH nanosheets, indicating that a three-dimensional network of nanosheets was formed during precipitation. It has been reported that the introduction of hydrophilic molecules into the reverse micelle system can lead to micelle aggregation, which is known as polar-mediated filtration. In this case, the partial stacking of the preformed LDH nanosheets can take place in the fused micelles, and it may also be the explanation of the formation of the three-dimensional network structure during precipitation with the ethanol observed here have. The TEM and HRTEM images in Figures 4 (c) and 4 (d) clearly show the stacked structure of Ni-Mn LDH nanosheets. From the HRTEM image, the space between adjacent layers was measured to be about 0.7 nm.

Further, the Ni-Mn LDH nanosheets were further characterized by powder XRD, energy dispersive X-ray spectroscopy (EDS), and XPS. The XRD patterns of the Ni-Mn LDH nanosheets show diffraction peaks at 2θ values of 11.3, 22.6, 34.2 and 38.78 (FIG. 5 (a)), which correspond to the diffraction peaks of (003) on hydrotalcite, , (006), (012), and (015) reflections. The interlamellar spacing measured by XRD was 0.78 nm (Fig. 1 a), which was in agreement with the results from HRTEM analysis. In this experimental example, no characteristic peaks of a metal oxide such as Mn ₃ O ₄ or NiO confirming the formation of the Ni-Mn LDH nanosheet structure were observed. The EDS analysis indicated that the Ni-Mn LDH nanosheets contained Cl ions (FIG. 5 (b)). This observation indicates that the Cl ions are released from the NiCl ₂ precursor during synthesis and serve as the counteranion of the Ni-Mn LDH host layer. As measured by EDS analysis, the molar ratio of Ni to Mn in the Ni-Mn LDH nanosheet was 3: 1. FIG Ni 2p XPS core level spectrum as shown in 5 (c) has had each including a Ni 2p _3/2 and the Ni 2p _1/2 peaks at 855.7 eV and 873.3 eV, which is consistent with Ni ^{2 +.} Mn 2p core level on the spectrum [in FIG. 5 (d)], Mn 2p 3/2 and Mn 2p _1/2 binding energy of 641.7 eV and 653.4 eV were, respectively, which were close to the literature value for the Mn ^{+ 3.} As shown in Fig. 1, these results indicate that the Ni-Mn LDH nanosheet has a pseudo hydrotalcite structure having a formula of [Ni ₃ Mn (OH) ₈ ] (Cl ^- ) nH ₂ O.

[ Comparative Example  One]

In order to understand the role of cations in the synthesis of Ni-Mn LDH nanosheets, control experiments were conducted in this comparative example by performing synthesis in the absence of Ni precursors. The synthesis was carried out under the same conditions as in the above example except for the presence of NiCl ₂ , and Mn ₃ O ₄ nanocrystals having a spinel structure were prepared (FIG. 6 (a)). 80-0382, Fig. 6 (b)].

[ Comparative Example  2]

In order to understand the role of cations in the synthesis of Ni-Mn LDH nanosheets, control experiments were conducted in this comparative example by performing synthesis in the absence of a Mn precursor. The synthesis was carried out under the same conditions as in the above examples except for the absence of Mn (CH ₃ COO) ₂ . (OH) ₂ particles in the [beta] -Ni (OH) ₂ phase were obtained (Fig. 6 (c)), without addition of Mn precursor, 6 (d)).

The results according to Comparative Examples 1 and 2 show that the presence of both Ni cations and Mn cations aids in the formation of Ni-Mn LDH nanosheets.

[ Experimental Example  2]

Electrochemical measurements of the metal layered double hydroxides prepared according to the above examples were performed using a 3-electrode system in 1 M KOH aqueous solution. Pt wire and Ag / AgCl (saturated NaCl solution) electrodes were used as counter electrodes and reference electrodes, respectively. The working electrode was a sample, Super-P, and polytetrafluoroethylene (PTFE) binder (weight ratio 8: 1: 1) in N-methyl-2-pyrrolidone (NMP) . The slurry was coated on a 1 cm x 1 cm Ni-foam (current collector). After drying in a 120 [deg.] C vacuum oven, the electrode was pressed and then immersed in 1 M KOH solution for 1 day. Cyclic voltammetry (CV) measurements were performed using a Reference 600 (Gamry Instrument) at a potential range of 0 V to 0.5 V (vs. Ag / AgCl) at a scan rate of 1 mV / s.

The non-volatile capacity was calculated by the following formula 1:

[Formula 1]

.

.

Where C _s is the non-discharge capacity, I is the current,? T is the discharge time, m is the mass of the sample, and? V is the voltage range during discharge. WBCS-3000 (Xeno Co.) measures the constant current charge-discharge profile at various current densities (0.5 A / g to 10 A / g) within the potential range of 0 V to 0.49 V (vs. Ag / AgCl) Respectively.

The electrochemical behavior of the synthesized Ni-Mn LDH nanosheet (Example), Ni (OH) ₂ (Comparative Example 2), and Mn ₃ O ₄ (Comparative Example 1) samples was 1 M Was investigated by cyclic voltammetry (CV) in aqueous KOH solution. Ke clear redox peaks for nodik and cathodic sweeps is Ni-Mn LDH and Ni (OH) was observed for the _second sample [Fig. 7 (a) a], which Ni ^{2 +} and / or the general intention of Ni ^{3 +} This is due to the pseudocapacitive behavior. The redox peaks for the Ni-Mn LDH samples were observed at a lower potential than the Ni (OH) ₂ samples, which may be due to their different crystal structures. The Ni-Mn LDH nano-sheet has a crystal structure similar to the crystal structure of the α-Ni (OH) _2, which shows the oxidation and reduction peaks at a relatively low potential than β-Ni (OH) _2. Under basic conditions, the redox reaction of Mn ₃ O ₄ can occur on the Mn ^{2 +} site. Mn ₃ O ₄ has a spinel structure and thus contains only 33% of Mn ^{2 +} , which is Mn ₃ O ₄ May be due to the weak redox peak for the sample. The Ni-Mn LDH-electrode exhibits a CV curve with a significantly wider confinement region than the other two electrodes, indicating that the Ni-Mn LDH nanosheets have much higher pseudocapacitance.

In this experimental example, the capacitive performance of the samples was further investigated by a constant current charge-discharge measurement at different charge-discharge current densities (Fig. 7 (b) to (d)). The Ni-Mn LDH nanosheets exhibited higher non-electric capacity than Ni (OH) ₂ and Mn ₃ O ₄ within the entire current density range (FIG. 7 (e)). Based on the charge-discharge curves, the Ni-Mn LDH nanosheets have a current density of 881 F / g at a current density of 0.5 A / g, 1 A / g, 2 A / g, 5 A / g, 769 F / g, 664 F / g, 517 F / g, and 403 F / g. The non-ionic capacity of the Ni-Mn LDH nanosheets was twice the non-ionic capacity of the Ni (OH) ₂ sample at constant current density. It is believed that the improvement in the non-ionic capacity of the Ni-Mn LDH nanosheets is due to the lamination structure of Ni-Mn LDH nanosheets having a large surface area and thus an exposed active site. In addition, a laminated structure having a relatively large interlayer space can improve diffusion of ions. The measured non-electrostatic capacity (881 F / g at a current density of 0.5 A / g) of the Ni-Mn LDH sample according to this example was reported for Ni-Al LDH measured under similar experimental conditions (1 M KOH aqueous solution) (795 F / g at a current density of 0.5 / Ag).

In this experiment, a constant current charge-discharge cycle test was performed at a current density of 5 A / g (FIG. 7 (f)). After 500 cycles, the constant current charge-discharge measurements showed 12% loss in capacity and 24% loss in Ni (OH) ₂ sample for Ni-Mn LDH nanosheets, and Ni- ) ₂ samples. ≪ / RTI >

This example describes a simple method for synthesizing colloidal Ni-Mn LDH nanosheets with high yield based on the reverse micelle method using oleic acid as the oil phase and oleylamine as the surfactant. The synthesized Ni-Mn LDH nanosheets had a pseudo hydrotalcite structure with the formula [Ni ₃ Mn (OH) ₈ ] (Cl ^- ) .nH ₂ O and had a similar hydrotalcite structure as the pseudo- High performance. It is expected that the method of this embodiment can be extended to the colloid synthesis of other LDH nanosheets.

It will be understood by those of ordinary skill in the art that the foregoing description of the embodiments is for illustrative purposes and that those skilled in the art can easily modify the invention without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention .

Claims (9)

Mixing a first metal precursor and a second metal precursor in a first solvent to obtain a first solution;
Mixing a second solvent and a surfactant to obtain a second solution;
Injecting the first solution into the second solution to obtain a third solution; And
Heat treating the third solution to react
≪ / RTI >
The method according to claim 1,
Wherein the first solvent is selected from the group consisting of ultrapure water, glycerol, ethylene glycol, polyethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, formamide, N-methylformamide, dimethylformamide, dimethylacetylamide, dimethylsulfoxide, Wherein the solvent is selected from the group consisting of acetonitrile, 2-pyrrolidinone, acetamide, acrylamide, N-methylurea, urea, and combinations thereof.
The method according to claim 1,
Wherein the first metal precursor is selected from the group consisting of Ni, Mn, Fe, Co, Zn, V, Cu, Cr, Ti, Ir, Mo, Ru, Rh, Ag, Au, Pt, Pd, Al, ≪ / RTI > wherein the metal is selected from the group consisting of aluminum, aluminum, and combinations thereof.
The method according to claim 1,
Wherein the second metal precursor is one selected from the group consisting of Ni, Mn, Fe, Co, Zn, V, Cu, Cr, Ti, Ir, Mo, Ru, Rh, Ag, Au, Pt, Pd, Al, ≪ / RTI > wherein the metal is selected from the group consisting of aluminum, aluminum, and combinations thereof.
The method according to claim 1,
Wherein the second solvent is selected from the group consisting of xylene, heptane, hexane, octane, toluene, isooctane, dodecane, hexadecane, ethylbenzene, cyclohexane, divinylbenzene, styrene, A method for producing a layered double hydroxide.
The method according to claim 1,
Wherein the surfactant is selected from the group consisting of C _{1 -20} alkylamines, C _{1 -20} fatty acids, mixtures thereof, and combinations thereof.
The method according to claim 1,
Wherein the heat treatment is performed at a temperature ranging from 5 캜 to 100 캜.
The method according to claim 1,
Wherein the layered double hydroxide comprises a single crystalline nanosheet. ≪ RTI ID = 0.0 > 21. < / RTI >
9. The method of claim 8,
Wherein the layered double hydroxide has a size ranging from 10 nm to 1 < RTI ID = 0.0 > um. ≪ / RTI >

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