KR20150136959A - Methods for Preparing Inverse Opal Structure and anode active and Seconday Battery by Using Same - Google Patents

Abstract

The present invention relates to a method for producing inverse opal structure, a negative electrode active material using the same, and a lithium secondary battery using the same. The inverse opal structure of the present invention is produced by comprising metal powder. Battery performance is improved by using the inverse opal structure as the negative electrode active material, thereby providing a secondary battery having excellent cycle property.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an inverse opal structure, an anode active material using the same, and a secondary battery using the anode active material,

The present invention relates to a method for manufacturing an inverse opal structure, an anode active material using the same, and a secondary battery using the same.

The three-dimensional photonic crystal structure generally has regularly arranged dielectric constant and refractive index. When the length of the periodically arranged spatial structure corresponds to the wavelength of the visible light, it is possible to realize various colors depending on the angle of view . A representative material with this phenomenon is opal, a natural gem.

There are a variety of ways to artificially fabricate three-dimensional opal structures and fabricate inverted structures from them. Specifically, a method of producing opaque opal according to an opal template is determined. The precursor of the opal opal to be obtained on a colloidal crystal form mold is subjected to sol-gel chemistry, salt precipitation ), Chemical conversion, chemical vapor deposition (CVD), nanocrystal deposition, and the like.

There are several drawbacks to the way in which such processes are used, especially in the liquid phase. Synthesis, and aging. Therefore, it takes a long time and additionally generates a large amount of contaminated wastewater.

In addition, since the reaction takes place in the liquid phase, it requires a lot of energy while being subjected to a drying process and includes various non-environmentally friendly elements.

In addition, there is a limitation in the use of the inverse opal silicon structure using CVD (Adv. Funct. Mater. 2009, 19, 1999-2010).

Therefore, there is a high need for development of an opaque structure that is easy to manufacture and environmentally friendly.

Adv. Funct. Mater. 2009, 19, 1999-2010

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and provides a secondary battery having excellent capacity and cycle characteristics by manufacturing a reverse opal structure by applying metal powder to a precursor of an inverse opal structure, .

According to an aspect of the present invention, there is provided an inverse opal structure,

Dispersing polymer nanoparticles in a first organic solvent, and removing the first organic solvent to prepare a template; Coating a mold formed of the polymer nanoparticles with a mixed solution and subjecting the mold to a first heat treatment to produce a precursor of the inverse opal structure; And reducing the precursor of the inverse opal structure.

Wherein reducing the precursor of the inverse opal structure comprises applying a metal powder to the precursor of the inverse opal structure and performing a second heat treatment, wherein the precursor of the inverse opal structure and the metal powder have a volume ratio of 0.5: 1.5 to 1.5: Can be mixed.

The metal powder may be at least one selected from the group consisting of aluminum (Al), titanium (Ti), zirconium (Zr), cesium (Cs), and magnesium (Mg).

The first heat treatment may be performed at 450 to 650 ° C for 4 to 6 hours, and the second heat treatment may be performed at 600 to 1500 ° C for 10 to 14 hours.

The mixed solution includes a second organic solvent, an acid catalyst, and a silica precursor, and the acid catalyst may be at least one selected from the group consisting of nitric acid, sulfuric acid, hydrochloric acid, and acetic acid.

The first organic solvent and the second organic solvent are selected from the group consisting of alcohols, glycols, ethers, esters, ketones, and formic acid. And may be at least one selected from the group consisting of.

The polymer nanoparticles may also be selected from the group consisting of polystyrene, polymethylmethacrylate, polyphenylmethacrylate, polyacrylate, polyaramethylstyrene, poly (1-methylcyclohexylmethacrylate), polycyclohexylmethacrylate, poly (1-phenylcyclohexyl methacrylate), poly (1-phenylethyl methacrylate), polyperfuryl methacrylate, poly (1,2-diphenylethyl methacrylate) Or more.

The precursor of the inverse opal structure may be an inverse opal silica, and the inverse opal structure may be an inverse opal silicon structure.

According to another aspect of the present invention, there is provided a method of manufacturing an anode active material,

Preparing an inverse opal silicon structure using reverse opal silica; Dispersing the inverse opal silicon structure in a third organic solvent; Stirring an emulsifier in a third organic solvent in which the inverse opal silicon structure is dispersed; And carbonizing and carbonizing the mixture after the stirring, wherein the inverse opal silicon structure can be manufactured by applying a metal powder to the inverse opal silica and performing a second heat treatment.

The inverse opal silica may be prepared by dispersing polymer nanoparticles in a fourth organic solvent and then removing the fourth organic solvent to prepare a template; And a step of coating a mold formed of the polymer nanoparticles with a mixed solution and performing a first heat treatment.

Wherein the third organic solvent and the fourth organic solvent are selected from the group consisting of alcohols, glycols, ethers, esters, ketones, formic acid, ≪ / RTI >

In addition, the present invention may be a secondary battery including a negative electrode active material.

As described above, the present invention can form an inverse opal structure having a nanometer-sized hollow by using a simple process.

In addition, when the inverse opal structure manufactured according to the present invention is carbonized and used as a negative electrode active material, the charge transfer resistance is reduced, and insertion and desorption of Li ⁺ ions are improved. Therefore, the carbon coated inverse opal structure manufactured according to the present invention has excellent cycle characteristics, and the performance of the battery can be improved.

1 is a process diagram according to an embodiment of the present invention;
2 is a SEM photograph of a reverse opal silicon structure according to an embodiment of the present invention and Comparative Example 1;
3 is a TEM photograph of an inverse opal silicon structure according to an embodiment of the present invention;
4 is a graph showing a cyclic voltammogram of an electrode according to Experimental Example 1;
FIG. 5 is a graph showing the results of evaluation of capacity characteristics by the C-rate according to Experimental Example 2 of the present invention;
FIG. 6 shows the results of the capacity characteristic evaluation by the C-rate according to Comparative Example 2; And
7 is a Nyquist plot of an electrode according to Experimental Example 2 of the present invention.

Hereinafter, the present invention will be described in more detail with reference to examples and the like, but the following examples are intended to illustrate the present invention, and the scope of the present invention is not limited thereto.

Accordingly, the present invention provides a method of making an inverse opal structure.

In one preferred embodiment, the polymer nanoparticles are dispersed in a first organic solvent, and then the first organic solvent is removed to prepare a template. Coating a mold formed of the polymer nanoparticles with a mixed solution and subjecting the mold to a first heat treatment to produce a precursor of the inverse opal structure; And reducing the precursor of the inverse opal structure to form the inverse opal structure.

As described above, since the inverse opal structure manufactured according to the present invention can omit the process of using CVD as in the conventional art, the inverse opal structure can be generated more quickly.

The term "first organic solvent", "second organic solvent", "third organic solvent", and "fourth organic solvent" used in the present invention mean a liquid organic compound capable of dissolving solid, do. The 'first organic solvent', the 'second organic solvent', the 'third organic solvent' and the 'fourth organic solvent' are not particularly limited but include alcohols, glycols, ethers ethers, ethers, esters, ketones, and formic acid may be used as the solvent.

In order to carry out the present invention, polymer nanoparticles can be first dispersed in the first organic solvent for 20 to 50 minutes.

The polymer nanoparticles may be any polymer known in the art. For example, the polymer nanoparticles may include polystyrene, polymethacrylate, Polyacrylate, poly (alpha-methylstyrene), poly (1-methylcyclohexylmetacrylate), polycyclohexylmetacrylate, poly (1-phenylcyclohexylmethacrylate), poly (1-phenylethylmethacrylate), polyfurfurylmethacrylate, and poly (1-phenylethylmethacrylate) , 2-diphenylethyl methacrylate), poly (1,2-, diphenylethyl methacrylate), but is not limited thereto. Preferably, , Polystyrene, polymethyl methacrylate or polyacrylate, and most preferably polystyrene.

The first organic solvent is not particularly limited as long as it can be dissolved and mixed uniformly, and then the solvent or dispersion medium can be easily removed.

After the polymer nanoparticles are dispersed in the first organic solvent, a template may be prepared using a paper filter to remove the first organic solvent.

A precursor of the inverse opal structure can be manufactured through a first heat treatment by applying a mold formed of the polymer nanoparticles with a mixed solution.

In order to produce the precursor of the inverse opal structure, a mold is applied to the mixed solution as described above, and the mixed solution may be prepared by including a second organic solvent, an acid catalyst, and a silica precursor.

The precursors of the silica may be selected from the group consisting of tetraethyl orthosilicate (TEOS), tetramethyl orthosilicate (TMOS), sodium silicate, tetramethoxysilane (TMS), tetraethoxysilane , TES), and preferably TEOS can be used.

The second organic solvent is not particularly limited as long as it is a liquid organic compound capable of dissolving a solid, a gas and a liquid as described above. The acid catalyst is preferably a strong acid. Examples thereof include nitric acid, sulfuric acid, And acetic acid.

As one preferred example, the mixed solution may contain TEOS, methanol, and hydrochloric acid, and the mixing ratio of TEOS: methanol: hydrochloric acid may be mixed in a volume ratio of 10: 5: 1. If the mixing ratio is exceeded, the physical properties of TEOS, methanol, and hydrochloric acid may be deteriorated and the mold may not be removed. As a result, the precursor of the hollow inverted opal structure desired by the present invention may not be formed.

Next, the mixed solution mixed at the above ratio may be applied to the mold and the first heat treatment may be performed.

Specifically, the reaction time and the reaction temperature are also important variables that affect the stability of the inverse opal structure. If the reaction time is too long, the stability becomes poor. Therefore, the first heat treatment may be performed at 450 to 650 ° C for 4 to 6 hours, preferably at 500 to 550 ° C for about 5 hours to form a precursor of a more stable inverse opal structure can do.

That is, when the mixed solution is applied to the mold and then subjected to the first heat treatment, the precursor of the hollow inverted opal structure can be manufactured while removing the polymer nanoparticles. Preferably, the precursor of the hollow inverse opal structure may be hollow inverse opal silica (SiO ₂ ).

Next, to reduce the precursor of the inverse opal structure, a metal powder may be applied and a second heat treatment may be performed.

When the hollow inverted opal silica and the metal powder are mixed, the metal powder coats the outer layer of the opal opal silica to widen the surface area, and firmly adhere to the opal opal silica to improve the durability against temperature change. In addition, when the mixed inverse opal silica and the metal powder are subjected to the second heat treatment, the inverse opal silica is reduced to obtain pure silicon (SiO ₂ + M? Si + MO (M: metal powder)).

At this time, the reverse opal silica and the metal powder are mixed at a volume ratio of 0.5: 1.5 to 1.5: 0.5, more preferably 1: 1.

When the metal powder is added below the mixing ratio, a part of the inverse opal silica may not be reduced, which is undesirable. On the other hand, when the metal powder is added in excess of the mixing ratio, a large amount of metal powder that has not reacted with the inverse opal silica may remain. If the metal powder is applied to the electrode, , Which is undesirable.

As described above, the second heat treatment is performed on the reversed opal silica and the metal powder mixed at a specific ratio to reduce the reverse opal silica. It is noted that, while reducing the opal silica, the metal powders are completely melted Be careful not to combine them.

In order to carry out the second heat treatment, the metal powder needs to be heat-treated at a temperature of 600 to 1500 ° C. for 10 to 14 hours in a reducing atmosphere or an inert atmosphere, preferably at a temperature of 700 to 1000 ° C. for 11 to 13 hours have. When the heat treatment is performed at a temperature higher than 1500 ° C, there is a possibility that the metal powder is melted. When the heat treatment is performed at a temperature lower than 600 ° C, it is difficult to reduce the inverse opal silica.

The metal powder used in the present invention may be at least one selected from the group consisting of aluminum (Al), titanium (Ti), zirconium (Zr), cesium (Cs), and magnesium (Mg) .

(HF), phosphoric acid (H ₃ PO ₄ ), ammonium fluoride (NH ₄ F), hydrogen peroxide (H ₂ O ₂ ), hydrochloric acid (HCl), and the like, to remove metal oxides and other impurities remaining in the product. , Nitric acid (HNO ₃ ) and sulfuric acid (H ₂ SO ₄ ), or a mixture thereof. More preferably, the product is supported on hydrochloric acid for 10 to 14 hours and then dried to produce the desired inverse opal structure according to the present invention. As a preferred example, the inverse opal structure may be an inverse opal silicon structure .

That is, the reverse opal silicon structure manufactured according to the present invention has a hollow structure inside the reverse opal silicon structure. The hollow is a space where the polymer nanoparticles are located, and the hollow is formed while the nanoparticles are removed. As such, it is possible to form more efficient structural features for the transfer of protons when used in fuel cells, as a non-limiting example.

The size of the hollow formed inside the reverse opal silicon structure may be about 1 to 100 탆, but is not limited thereto.

The present invention also provides a method for producing a negative electrode active material comprising the above method.

The negative electrode active material produced according to the present invention includes: an inverse opal silicon structure; Dispersing the inverse opal silicon structure in a third organic solvent; Stirring an emulsifier in a third organic solvent in which the inverse opal silicon structure is dispersed; And a step of carbonizing and carbonizing the mixture after the stirring, wherein the inverse opal silicon structure may include a second heat treatment by applying a metal powder to the inverse opal silica.

Here, the inverse opal silica may be prepared by dispersing polymer nanoparticles in a fourth organic solvent and then removing a fourth organic solvent to prepare a template; And a step of applying a mold formed of the polymer nanoparticles with a mixed solution and performing a first heat treatment. As described above, a detailed description thereof will be omitted.

1 is a process diagram according to an embodiment of the present invention.

Referring to FIG. 1, a hollow inverse opal silicon structure is manufactured by preparing a mold using polystyrene, which is a polymer nanoparticle, and dropping the mixed solution into the mold by one drop. The hollow inverse opal silicon structure thus produced can be carbonized to produce a carbon-coated inverted opal silicon structure, which can be used as an anode active material.

As described above, the negative electrode active material manufactured according to the present invention can realize a lithium secondary battery improved in capacity and cycle characteristics by carbonizing an inverse opal silicon structure produced by mixing inverse opal silica and a metal powder to use as an anode active material .

As described above, the negative electrode active material according to the present invention may include a carbon-coated inverse opal silicon structure (hereinafter referred to as a carbon structure), and the carbon structure has a hollow structure inside.

In order to produce the negative electrode active material according to the present invention, the prepared hollow inverse opal silicon structure can be dispersed in an appropriate third organic solvent.

The third organic solvent may be a solvent containing an alcohol, preferably be dispersed in isopropyl alcohol, and may further contain water.

At this time, an emulsifier may be further added to the solution in which the inverse opal silicon structure is dispersed in order to prevent agglomeration of the nano-sized inverted opal silicon structure and disperse it in the solvent uniformly.

Wherein the emulsifier is at least one selected from stearic acid, palmitic acid, oleic acid, lauric acid, tridecylic acid, pentadecanoic acid, myristic acid, nonadecanoic acid, arachic acid, behenic acid, linolic acid, linolenic acid, Species. For example, stearic acid, palmitic acid, oleic acid, glycerin and the like can be used, and these emulsifiers can be used singly or in combination of two or more kinds.

The solution containing the emulsifier and the reverse opal silicon structure is stirred for 1 to 2 hours and then fired to obtain a carbon-coated inverted opal silicon structure.

The carbonization may be performed in an atmosphere containing a reducing atmosphere containing no oxygen, that is, an inert gas such as He or Ne, hydrogen, nitrogen, or SF6 gas, and may be included in the inverse opal structure Carbonized precursor may be carbonized to produce a carbon-coated inverse opal structure. The time required for the calcination in the reducing atmosphere is not particularly limited and may be appropriately selected within a time range sufficient for carbonizing the carbon precursor material. As a preferred example, the firing temperature in the reducing atmosphere may be 500 to 1200 캜, preferably 700 to 1000 캜, more preferably 800 to 1000 캜, and the firing time is preferably about 1 hour, But it is not limited thereto.

By such a method for producing the negative electrode active material, a negative electrode active material having a high capacity and excellent cycle characteristics can be produced.

The present invention also provides a negative electrode material mixture containing the negative electrode active material.

The negative electrode mixture according to the present invention may contain a binder in an amount of 1 to 20% by weight based on the total weight of the composition, and optionally a conductive material in an amount of 0 to 20% by weight.

Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), cellulose, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, Polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluorine rubber, various copolymers, high molecular weight polyolefins such as polyolefin, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, Vinyl alcohol, and the like.

The conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, for example, graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used. Concrete examples of commercially available conductive materials include acetylene black series such as Chevron Chemical Company, Denka Singapore Private Limited, Gulf Oil Company, etc.), Ketjenblack, EC (Armak Company), Vulcan XC-72 (Cabot Company), and Super P (Timcal).

In some cases, a filler may be optionally added as a component to suppress the expansion of the negative electrode. Such a filler is not particularly limited as long as it is a fibrous material without causing a chemical change in the battery, and examples thereof include olefin polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

In addition, other components such as a viscosity adjusting agent, an adhesion promoter and the like may be further included as a selective or a combination of two or more.

The viscosity modifier may be added up to 30% by weight based on the total weight of the negative electrode mixture as a component for adjusting the viscosity of the electrode mixture so that the mixing process of the electrode mixture and the coating process on the current collector may be easy. Examples of such viscosity modifiers include carboxymethylcellulose, polyvinylidene fluoride and the like, but are not limited thereto. In some cases, the above-described solvent may play a role as a viscosity adjusting agent.

The adhesion promoter may be added in an amount of 10% by weight or less based on the binder, for example, oxalic acid, adipic acid, Formic acid, acrylic acid derivatives, itaconic acid derivatives, and the like.

The present invention also provides a negative electrode for a secondary battery in which the negative electrode material mixture is applied on a current collector.

The negative electrode may be prepared by adding a negative electrode material including a negative electrode active material and a binder to a solvent such as NMP to prepare a slurry, applying the slurry on a current collector, and drying and compressing the slurry.

The negative electrode collector is generally made to have a thickness of 3 to 500 mu m. Such an anode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery, and may be formed of a material such as copper, stainless steel, aluminum, nickel, titanium, fired carbon, surface of copper or stainless steel A surface treated with carbon, nickel, titanium, silver or the like, an aluminum-cadmium alloy, or the like can be used. The current collector may have fine irregularities on the surface thereof to increase the adhesive force of the negative electrode active material, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric are possible.

The present invention also provides a secondary battery comprising the negative electrode, wherein the battery is preferably a lithium secondary battery.

Such a lithium secondary battery has a structure in which a lithium salt-containing non-aqueous electrolyte is impregnated in an electrode assembly having a separator interposed between a positive electrode and a negative electrode.

The anode may be formed by coating a cathode active material on a cathode current collector, drying and applying the anode active material, and may further include other components such as a binder, a conductive material, and the like.

The cathode current collector generally has a thickness of 3 to 500 mu m. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery, and may be formed of a material such as stainless steel, aluminum, nickel, titanium, sintered carbon, or a surface of aluminum or stainless steel Treated with carbon, nickel, titanium, silver or the like may be used. The positive electrode current collector may have fine unevenness formed on the surface thereof to increase the adhesive force of the positive electrode active material as in the case of the negative electrode current collector. Alternatively, the positive electrode current collector may have various properties such as a film, sheet, foil, net, porous body, Form is possible.

The cathode active material is a material capable of causing an electrochemical reaction. Examples of the lithium transition metal oxide include lithium cobalt oxide (LiCoO ₂ ) containing two or more transition metals and substituted with one or more transition metals, lithium Layered compounds such as nickel oxide (LiNiO ₂ ); Lithium manganese oxide substituted with one or more transition metals; Formula _{LiNi 1-y M y O 2} ( where, M = Co, Mn, Al , Cu, Fe, Mg, B, Cr, Zn or Ga and Lim, 0.01≤y≤0.7 include one or more elements of the element) A lithium nickel-based oxide represented by the following formula: _{Li 1 + z Ni 1/3 Co 1/3} Mn 1/3 O 2, Li 1 + z Ni 0.4 Mn 0.4 Co 0.2 O 2 , such as _{Li 1 + z Ni b Mn c} Co 1- (b + c + d _{) M d O (2-e} ) A e ( where, -0.5≤z≤0.5, 0.1≤b≤0.8, 0.1≤c≤0.8, 0≤d≤0.2 , 0≤e≤0.2, b + c + d <1, M = Al, Mg, Cr, Ti, Si or Y, and A = F, P or Cl; lithium nickel cobalt manganese composite oxide; And the formula _{Li 1 + x M 1-y} M 'y PO 4-z X z ( wherein, M = a transition metal, preferably Fe, Mn, Co or Ni, M' = Al, Mg or Ti, X = F, S or N, and -0.5? X? +0.5, 0? Y? 0.5, and 0? Z? 0.1), but the present invention is not limited thereto.

The binder, the conductive material, and the components added as necessary are the same as those in the negative electrode.

The separator is an insulating thin film interposed between the anode and the cathode and having high ion permeability and mechanical strength. The hollow diameter of the separator is generally 0.01 to 10 mu m and the thickness is generally 5 to 300 mu m. As such a separation membrane, for example, a sheet or a nonwoven fabric made of an olefin-based polymer such as polypropylene which is chemically resistant and hydrophobic, glass fiber, polyethylene or the like is used.

In some cases, a gel polymer electrolyte may be coated on the separation membrane to improve the stability of the cell. Representative examples of such gel polymers include polyethylene oxide, polyvinylidene fluoride, and polyacrylonitrile. When a solid electrolyte such as a polymer is used as an electrolyte, the solid electrolyte may also serve as a separation membrane.

The lithium salt-containing non-aqueous electrolyte is composed of an organic solvent electrolyte and a lithium salt.

Examples of the electrolytic solution include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, 4 Methyl-1,3-dioxane, diethyl ether, formamide, dimethyl formamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivative An aprotic organic solvent such as sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ether, methyl pyrophosphate and ethyl propionate can be used have.

Examples of the organic solid electrolyte include a polymer electrolyte such as a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, an agitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride, A polymer containing an ionic dissociation group and the like may be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Nitrides, halides and sulfates of Li such as Li ₄ SiO ₄ -LiI-LiOH and Li ₃ PO ₄ -Li ₂ S-SiS ₂ can be used.

The lithium salt is a material that is readily soluble in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO 4, LiBF 4, LiB 10 Cl 10, LiPF 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF _{6, LiSbF 6, LiAlCl 4,} CH 3 SO 3 Li, CF 3 SO 3 Li, LiSCN, LiC (CF 3 SO 2) 3, (CF 3 SO 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, 4-phenylborate, imide, and the like can be used.

For the purpose of improving the charge / discharge characteristics and the flame retardancy, the electrolytic solution is preferably mixed with an organic solvent such as pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, glyme, Benzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, . In some cases, halogen-containing solvents such as carbon tetrachloride and ethylene trifluoride may be further added to impart nonflammability. In order to improve the high-temperature storage characteristics, carbon dioxide gas may be further added. FEC (Fluoro-Ethylene Carbonate, PRS (Propene sultone), and the like.

In a preferred _{embodiment, LiPF 6, LiClO 4, LiBF} 4, LiN (SO 2 CF 3) 2 , such as a lithium salt, a highly dielectric solvent of DEC, DMC or EMC Fig solvent cyclic carbonate and a low viscosity of the EC or PC of And then adding it to a mixed solvent of linear carbonate to prepare a lithium salt-containing non-aqueous electrolyte.

[Example 1: Preparation of reverse opal silicone]

1) Manufacture of mold

A colloidal crystal solution is synthesized to prepare the mold. In the present invention, polystyrene (polystyrene) was used as a mold. 1 占 퐉 polystyrene is dispersed in ethanol for 30 minutes.

2) Manufacture of Inverse Opal

In order to prepare the reverse opal, the mixed solution was dropwise added to the polystyrene mold one by one using a syringe and then sintered (first heat treatment) to obtain the inverse opal silica. At this time, the mixed solution can be prepared by mixing 12 ml of TEOS, 6 ml of methanol, and 1.2 ml of hydrochloric acid, and the heat treatment was carried out at 550 ° C. for 5 hours.

The obtained reverse opal silica and Mg powder were mixed at a volume ratio of 1: 1 and sintered (second heat treatment) in an argon atmosphere. At this time, the heat treatment was carried out at 800 DEG C for 12 hours. The 2M HCl was then carried for 12 hours and dried in an oven to form an inverse opal silicon structure.

[Example 2: Preparation of negative electrode active material]

To prepare the negative electrode active material, the reverse opal silicon structure prepared according to Example 1 was dispersed in isopropyl alcohol for 30 minutes. The dissolved stearic acid was added to isopropyl alcohol in which the reverse opal silicon structure was dispersed, and the mixture was stirred for 1 hour. After stirring, it was dried and then carbonized under a nitrogen atmosphere at 800 ° C to produce a carbon-coated inverse opal silicon structure.

[Comparative Example 1]

The commercially available silicon nanoparticles (Panax Ethec) were used.

[Comparative Example 2]

An inverse opal silicon structure was produced using the same method as in Example 1, except that Mg powder was not used in Example 1.

{evaluation}

[Experimental Example 1]

Structures formed in Example 1, Example 2, and Comparative Example 1 were observed through SEM, and the results are shown in FIG. 2 and FIG.

FIG. 2 is a SEM image of an inverse opal silicon structure according to an embodiment of the present invention and Comparative Example 1, and FIG. 3 is a TEM photograph of an inverse opal silicon structure according to an embodiment of the present invention.

Specifically, FIG. 2 (a) is a SEM image of a silicon nanocrystal of Comparative Example 1, (b) is an SEM image of an inverse opal silicon structure manufactured according to Example 1, 2 is an SEM photograph of a carbon coated reverse opal silicon structure.

In FIGS. 2 (b) and 2 (c), an inverse opal silicon structure having a regular macropore size of 1 μm can be identified. Specifically, comparing the shell shapes of (b) and (c), it can be seen that the thickness of the shell is thicker because (c) the shell of the reverse opal silicon structure is further coated with carbon.

More specifically, referring to FIG. 3, it can be seen that particles of 10 to 20 nm in size are gathered to form an inverse opal silicon structure in FIGS. 3 (a) and 3 (b) Was coated with carbon of about 2 nm in thickness.

[Experimental Example 2]

Each of the materials prepared (or purchased) in Examples 1, 2, and Comparative Example 1 and Comparative Example 2 was used as a negative electrode active material to prepare a lithium secondary battery as described below, Respectively.

2-1. Slurry  And electrode manufacturing

The products of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 capable of intercalating and deintercalating lithium ions were charged to prepare negative electrode active materials, respectively. And a negative electrode active material: binder: conductive material = 80: 10: 10 in weight ratio.

2-2. Manufacture of lithium secondary battery

A coin-shaped half-cell (CR2016) was prepared in the argon-filled glove box using the negative electrodes prepared in 2-1, a lithium anode, a polyethylene separator, and an electrolyte. The electrolytic solution was LiPF ₆ (Panaxitec) dissolved in a concentration of 1 mol in a mixed solvent of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate in a volume ratio of 1: 1: 1.

2-3. characteristic

1) cyclic voltammogram

The cyclic voltammogram analysis of the cathodes prepared in Experimental Example 2-1 was performed, and the results are shown in FIG.

4 (b) and 4 (c), respectively, of the silicon nanoparticles (Comparative Example 1), the inverse opal silicon structure (Example 1) The CV of Example 2 is shown.

Referring to FIG. 4, it was confirmed that peaks were formed at approximately 0.6 V in both of FIGS. 4 (a), 4 (b), and 4 (c), and were not formed in the next cycle. This could be confirmed by peaks in which a solid electrolyte interface (SEI) was formed on the surface of the material. In addition, the peak of all the samples except the SEI formation peak is judged to be the peak caused by the redox reaction between silicon and silicon. Therefore, the oxidation and reduction reactions are reversible in the second and above cycles, and the reverse opal silicon structure and carbon-coated reverse opal silicon structure are electrochemically stable.

2) C- rate Capacity characteristics by

The lithium secondary battery manufactured in accordance with Experimental Example 2-2 was charged and discharged at a rate of 100 mA / g at 0.005 V and 1.5 V in galvanostacking 100 times, 6.

FIG. 5 is a graph showing the results of capacity characteristics according to Experimental Example 2 of the present invention, and FIG. 6 is a graph showing capacitance characteristics of C-rate according to Comparative Example 2. FIG.

Referring to FIG. 5, when the silicon nanoparticles of Comparative Example 1 are used as a negative electrode active material, charging and discharging are performed through a compound-forming reaction with lithium ions. Thus, it can be seen that the discharge capacity is much larger than that of normal graphite, As the insertion and desorption of lithium continue, the function as a lithium acceptor gradually becomes lost due to crystal deterioration. Therefore, as shown in FIG. 5, when the experiment was conducted with silicon nanoparticles, it was confirmed that the capacity was continuously decreased and the capacity did not show after 20 cycles. However, in the case of the inverse opal silicon structure (Example 1), it was confirmed that the capacity was maintained well as compared with the case of experimenting with silicon nano-particles. Further, it is considered that the inverse opal silicon structure coated with carbon (Example 2) exhibits a high capacity and excellent cycle characteristics because it functions as a buffer for the volume change of silicon in charge / discharge process by covering the silicon with carbon.

On the other hand, FIG. 6 shows that the inverse opal structure of Comparative Example 2 shows a similar reaction mechanism to silicon in general, although the theoretical discharge capacity (1965 mAh / g) of silica is smaller than that of normal silicon, It can be confirmed that the function as a lithium acceptor gradually disappears due to crystal deterioration as insertion and desorption continue. 5 and 6), it can be confirmed that the discharge capacity of Comparative Example 2 is relatively lowered and the capacity of the battery may be lowered.

3) Electrical resistance of electrode

7 is a Nyquist plot of electrodes according to Example 1, Example 2, and Comparative Example 1. Fig.

The reason why the negative electrode active material prepared according to Example 2 exhibits excellent capacity when manufactured into an electrode is that lithium ions are free to move. Specifically, referring to FIG. 6, it can be seen that, when the electrode is manufactured using the negative electrode active material according to the second embodiment, the impregnation of the electrolyte is smooth and the lithium ion moves rapidly in the electrode. As a result, the insertion and desorption of Li ⁺ ions are improved, the charge transfer resistance is reduced, and the capacity is increased.

That is, when the carbon-coated inverse opal silicon structure is used as the negative active material, the electric resistance is lower than that in the case where the inverse opal silicon structure is used as the negative active material.

The embodiments of the present invention described above and shown in the drawings should not be construed as limiting the technical idea of the present invention. The scope of protection of the present invention is limited only by the matters described in the claims, and those skilled in the art will be able to modify the technical idea of the present invention in various forms. Accordingly, such improvements and modifications will fall within the scope of the present invention as long as they are obvious to those skilled in the art.

Claims (17)

Dispersing polymer nanoparticles in a first organic solvent, and removing the first organic solvent to prepare a template;
Coating a mold formed of the polymer nanoparticles with a mixed solution and subjecting the mold to a first heat treatment to produce a precursor of the inverse opal structure; And
Reducing the precursor of the inverse opal structure;
&Lt; / RTI &gt; The method according to claim 1,
Wherein reducing the precursor of the inverse opal structure comprises:
Applying a metal powder to a precursor of the inverse opal structure, and performing a second heat treatment. 3. The method of claim 2,
Wherein the precursor of the inverse opal structure and the metal powder are mixed at a volume ratio of 0.5: 1.5 to 1.5: 0.5. 3. The method of claim 2,
Wherein the metal powder is at least one selected from the group consisting of Al, Ti, Zr, Cs, and Mg. 3. The method of claim 2,
The first heat treatment is performed at 450 to 650 ° C for 4 to 6 hours,
Wherein the second heat treatment is performed at 600 to 1500 DEG C for 10 to 14 hours. The method according to claim 1,
Wherein the mixed solution comprises a second organic solvent, an acid catalyst, and a silica precursor. The method according to claim 6,
Wherein the acid catalyst is at least one selected from the group consisting of nitric acid, sulfuric acid, hydrochloric acid, and acetic acid. The method according to claim 6,
The first organic solvent and the second organic solvent may contain,
The production of an inverse opal silicon structure which is at least one selected from the group consisting of alcohols, glycols, ethers, esters, ketones, and formic acid. Way. The method according to claim 1,
The polymer nanoparticles may be selected from the group consisting of polystyrene, polymethylmethacrylate, polyphenylmethacrylate, polyacrylate, polyalphamethylstyrene, poly (1-methylcyclohexylmethacrylate), polycyclohexylmethacrylate, poly (1-phenylethyl methacrylate), poly (1-phenylethyl methacrylate), polyperfuryl methacrylate, and poly (1,2-diphenylethyl methacrylate) A method for manufacturing a reverse opal silicon structure. The method according to claim 6,
Wherein the precursor of the inverse opal structure is inverse opal silica. 11. The method of claim 10,
Wherein the inverse opal structure is an inverse opal silicon structure. 12. An inverse opal silicon structure produced by the method according to any one of the preceding claims. Preparing an inverse opal silicon structure using reverse opal silica;
Dispersing the inverse opal silicon structure in a third organic solvent;
Stirring an emulsifier in a third organic solvent in which the inverse opal silicon structure is dispersed; And
Stirring and carbonizing the mixture;
Lt; / RTI &gt;
Wherein the reverse opal silicon structure comprises:
Applying a metal powder to the inverse opal silica, and performing a second heat treatment. 14. The method of claim 13,
The inverse opal silica may comprise,
Dispersing the polymer nanoparticles in a fourth organic solvent, and removing the fourth organic solvent to prepare a template; And
Coating a template formed of the polymer nanoparticles with a mixed solution and performing a first heat treatment;
Wherein the negative electrode active material is produced by a method comprising the steps of: 15. The method of claim 14,
The third organic solvent, and the fourth organic solvent,
Wherein at least one selected from the group consisting of alcohols, glycols, ethers, esters, ketones, and formic acid is used. The negative electrode active material produced by any one of claims 13 to 15. A secondary battery comprising the negative electrode active material according to claim 16.

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