KR101610772B1 - Anode active materials and manufacturing method thereof, and anode and lithium battery using the same - Google Patents

Abstract

The present invention relates to a process for producing an electrospinning liquid by mixing a first solution in which a metal oxide precursor is dissolved, a second solution in which a polymer as a carbon fiber precursor is dissolved, and an ionic liquid solution for nitrogen doping and porous structure formation, A step of electrospinning the electrospinning liquid to produce a metal oxide-nitrogen-porous carbon nanofiber composite material, and a step of heat-treating the composite material; and a method of manufacturing a negative electrode and a lithium battery .

Description

TECHNICAL FIELD [0001] The present invention relates to a method for producing a negative electrode active material, and a negative electrode and a lithium battery employing the same. BACKGROUND ART < RTI ID = 0.0 >

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a carbon nanofiber negative electrode active material, and a negative electrode and a lithium battery employing the same. More particularly, the present invention relates to a method for manufacturing a negative electrode active material comprising nitrogen-doped porous carbon nanofibers And a negative electrode and a lithium battery employing the same.

In recent years, the use of lithium batteries has been expanding into electric vehicles and electric power storage devices beyond the main power sources of small electronic devices such as mobile phones and notebook computers. As the electrochemical energy storage material, the lithium battery has been used in a wide range of uses, and a lithium battery having a small capacity reduction with frequent charge and discharge is required.

At present, graphite, which is a carbon-based material having good life characteristics, has been commercialized as a negative electrode active material used in a lithium battery. However, the theoretical capacity of the graphite material is very low at 372 mAh / g, Causing safety problems. In order to overcome the problems of low capacity and safety, many studies have been carried out to replace graphite. Typical examples are TiO ₂ , Li ₄ Ti ₅ O ₁₂ , KNb ₅ O ₁₃ , Fe ₂ O ₃ , Co ₃ O ₄ , MnO ₂ , Studies have been made on the use of metal oxides in which an additional or conversion reaction such as MoO ₂ , MoO ₃ , NiO, CuO or the like occurs, as an anode active material.

However, metal oxides such as TiO ₂ , Li ₄ Ti ₅ O ₁₂ , and KNb ₅ O ₁₃ have limited theoretical capacity, and Fe ₂ O ₃ , Co ₃ O ₄ , MnO ₂ , It has a limited transfer rate and volumetric expansion upon reaction with lithium generates electrically isolated active materials in the electrode, resulting in a low rate characteristic.

As a method for solving such problems, researches on nanostructured materials have been extensively conducted. These nanostructured materials refer to 1, 2, or 3-dimensional structured nanomaterials and are described in Nano Lett., 9, (2009) 1045, Angew. Chem., Int. Ed., 48 (2009) 1660, J. Phys. Chem. C, 112 (2008) 4836, Chem. Commun. (2006) 2783 proposes a nanorod, a nanowire, a nanoflower, or a nanosphere. These nanostructured materials mitigate cracking and agglomeration of the active material, thereby alleviating stress and volume changes in the electrodes during charging and discharging, thereby exhibiting high capacity and high stability of battery characteristics. However, due to the use of an electrode active material having a high surface area, a side reaction with an electrolyte increases and energy density per volume decreases.

Therefore, it is required to introduce a negative electrode active material capable of realizing a lithium battery having characteristics of a high capacity and high stability to solve such a problem.

The present invention relates to a method for preparing an anode active material for improving the capacity and stability as well as improving the conductivity of a lithium secondary battery. More specifically, the present invention relates to a method for preparing a metal oxide precursor / carbon fiber precursor solution / And then subjecting the porous carbon nanofibers to heat treatment, thereby providing a negative electrode and a lithium battery employing the same.

The technical objects to be achieved by the present invention are not limited to the above-mentioned technical problems.

In order to achieve the above object, the present invention provides a method for producing an anode active material, comprising the steps of: preparing a first solution in which a metal oxide precursor is dissolved, a second solution in which a polymer as a carbon fiber precursor is dissolved and an ionic liquid Mixing the solution to prepare an electrospinning liquid, electrospinning the electrospinning liquid to produce a metal oxide-nitrogen-porous carbon nanofiber composite material, and heat-treating the composite material.

Specifically, the solvent of the first solution and the second solution may be any one selected from the group consisting of distilled water, dimethylformamide, phenol, toluene, ethanol, methanol, and propanol.

The metal oxide precursor may be titanium butoxide (TBO) or a metal salt flame.

The metal salt flame, titanium iso-proxy-side _{(Ti (OCH (CH 3)} 2) 4), titanium chloride (TiCl _4, or TiCl _3), tin hydrate (SnCl ₂ · H ₂ O) and ferric chloride (FeCl _3), nickel chloride (NiCl _2), copper chloride (CuCl _2), magnesium chloride (MgCl _2), palladium chloride (PdCl _2), cobalt chloride (CoCl _2), chloride, tantalum (TaCl _2), manganese chloride (MnCl _2), nitric acid iron _{(Fe (NO 3) 2,} Fe (NO 3) 3), nickel nitrate _{(Ni (NO 3) 2)} , copper nitrate _{(Cu (NO 3) 2)} , magnesium nitrate _{(Mg (NO 3) 2)} , cobalt nitrate _{(Co (NO 3) 2)} , manganese nitrate _{(Mn (NO 3) 2)} , manganese acetate _{(Mn (CO 2 CH 3)} 2), iron acetate _{(Fe (CO 2 CH 3)} 2), nickel acetate _{(Ni (CO 2 CH 3)} 2), cobalt acetate _{(Co (CO 2 CH 3)} 2), zinc acetate _{(Zn (CO 2 CH 3)} 2), and copper acetate _{(Cu (CO 2 CH 3)} 2) And the like.

The polymer may be selected from the group consisting of polyvinylpyrrolidone (PVP), polymethylmethacrylate (PMMA), polyvinyl alcohol (PVA), polyvinylacetate (PVAC), polyacrylonitrile PAN, polyfurfuryl alcohol, cellulose, glucose, polyvinylchloride (PVC), polyacrylic acid, polylactic acid, polyethylene oxide (polyethylene) (PEI), polypyrrole, polyimide, polyamideimide, polyaramid, polyaniline (PANI), phenol resin, and pitch. .

Wherein the ionic liquid solution is selected from the group consisting of ethylmethylimidazolium chloride (EMIM Cl), ethylmethylimidazolium dicyanamide (EMIM DCA), ethylmethylimidazolium trifluoromethanesulfonate (EMIM Otf), ethylmethylimidazolium (EMIM TFSI), ethylmethylimidazolium acetate (EMIM Ac), ethylmethylimidazolium hydrate (EMIM OH), ethylmethylimidazolium diethylphosphate (EMIM DEP), ethylmethylimidazolium iodide imidazolium methyl carbonate (EMIM MeOCO _2), ethyl methyl imidazolium lactate (EMIM lactate), butyl-methyl-imidazolium chloride (BMIM Cl), butyl methyl imidazolium methyl carbonate solution (BMIM MeOCO _2), butyl methyl (BMIM Otf), butylmethylimidazolium trifluoromethylsulfonylimide (EMIM TFSI), butylmethylimidazolium trifluoroacetate (BM (methylimidazolium trifluoromethanesulfonate) IM CF ₃ CO ₂ ), and dimethylimidazolium methanesulfonate (MMIM CH ₃ SO ₃ ).

In the step of preparing the composite material, the electric spinning solution is maintained at 70 ° C or lower, the electric spinning solution is supplied at a flow rate of 0.1 to 1 mL / h, and electrospinning is performed by applying a voltage of 10 to 25 kV .

The step of heat-treating may include a step of heating the composite material up to 280 ° C, a step of heat-treating the composite material for 3 to 5 hours under an air atmosphere after the primary temperature-rise, a step of heat- A second step of heating the composite material to 500 ° C, and a second step of heat-treating the composite material for 1 to 5 hours in an argon (Ar) atmosphere, And the step of raising the secondary temperature may be carried out consecutively.

In addition, a negative electrode employing the negative electrode active material produced by the above method can be produced. Specifically, the negative electrode of the present invention for realizing the above object is a negative electrode in which a slurry in which a negative electrode active material, a conductive material, a binder, and a solvent are mixed is coated on the current collector, and the negative electrode active material contains a metal oxide Doped porous carbon nanofibers.

The porous carbon nanofibers may have an average particle diameter of 0.1 to 1 μm.

The metal oxide may be titanium oxide.

In addition, a lithium battery employing the negative electrode active material produced by the above method can be produced. Specifically, the lithium battery of the present invention for realizing the above object is a lithium battery comprising a positive electrode, a negative electrode and a separator, wherein the negative electrode is made of a nitrogen-doped porous carbon nanofiber containing a metal oxide .

The porous carbon nanofibers may have an average particle diameter of 0.1 to 1 μm.

The metal oxide may be titanium oxide.

According to the method of manufacturing the anode active material as described above, it is possible to easily produce titanium oxide of several nanometers in the inside of the nitrogen-doped porous carbon nanofiber, and the nitrogen content, the content of the titanium oxide, the size of the pore, The diameter and the size of the titanium oxide can be appropriately controlled.

Further, since the negative electrode active material of the present invention exhibits improved capacity and cycle characteristics, the negative electrode and the lithium battery employing the negative electrode active material can provide excellent electrical characteristics.

In addition, electrode materials and catalysts for solar cells, fuel cells, lithium air cells, etc. can be manufactured by applying a very fast electron transfer rate of the negative electrode active material of the present invention.

1 is a flowchart showing a method of manufacturing the negative electrode active material of the present invention in order.
2 is a conceptual diagram showing an electrospinning apparatus for producing the negative electrode active material of the present invention.
FIG. 3 is a flowchart specifically showing a step of heat-treating the negative active material of the present invention.
4A to 4C are scanning electron microscope (SEM) photographs of the negative electrode active material prepared in Examples.
FIG. 4D is a scanning electron microscope (SEM) photograph of the negative electrode active material prepared in Comparative Example 1. FIG.
FIG. 5A is a transmission electron microscope (TEM) photograph of the negative electrode active material prepared in Example 2. FIG.
5B is a SADP (selected area diffraction pattern) photograph of a transmission electron microscope of the negative active material of Example 2.
FIG. 5C is a result of EDS (energy dispersive x-ray spectroscopy) analysis of the negative electrode active material prepared in Example 2. FIG.
6 is a transmission electron microscope (TEM) photograph of the negative electrode active material prepared in Comparative Example 1. Fig.
FIG. 7 is an X-ray diffraction (XRD) graph of each of the negative electrode active materials prepared in Example 2 and Comparative Example 1. FIG.
8 is an X-ray photoelectron spectroscopy (XPS) graph of the negative electrode active material prepared in Example 2. Fig.
FIG. 9A is a BET surface area analysis graph of each of the negative electrode active materials prepared in Examples 1, 2, 3, and Comparative Example 1. FIG.
FIG. 9B is a BJH pore size analysis graph of the negative electrode active material prepared in Example 2. FIG.
10 is a graph showing the results of charging and discharging tests of the respective lithium batteries prepared in Examples 4, 5, 6 and Comparative Example 2. FIG.
FIG. 11 shows the results of the rate characteristics of the respective lithium batteries manufactured in Example 5 and Comparative Example 2. FIG.
12 shows the impedance results of the respective lithium batteries manufactured in Example 5 and Comparative Example 2. Fig.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same components are denoted by the same reference symbols whenever possible. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

The present invention provides nitrogen-doped porous carbon nanofibers containing a metal oxide (particularly titanium oxide) as a negative electrode active material. Since the negative electrode active material has excellent initial efficiency and excellent capacity retention characteristics, And can be usefully used for a lithium battery employing an electrode.

The anode active material according to an embodiment of the present invention is composed of titanium oxide (TiO ₂ ), carbon (C), and nitrogen (N), and titanium oxide is present in a uniformly distributed form in the nitrogen-doped porous carbon Excellent initial efficiency and capacity retention characteristics.

Here, titanium oxide is capable of stably intercalating / deintercalating lithium ions without deforming the crystal structure, but has a disadvantage of low electrical conductivity and high-rate characteristics. However, since nitrogen is doped in the carbon nanofibers and the carbon nanofibers have a porous structure, such problems are solved, and the cycle characteristics and the high-rate characteristics are improved.

Specifically, in the negative electrode active material of the present invention, it is preferable that at least one of nitrogen, which is a constituent element, or porous carbon is bonded to titanium oxide. That is, by bonding the nitrogen-doped porous carbon nanofibers with the titanium oxide, it is possible not only to prevent deterioration of the cycle characteristics caused by the low electrical conductivity of the titanium oxide, but also to improve the electric conductivity.

In addition, the carbon fiber of the porous structure leads to rapid diffusion of lithium, thereby improving the high-rate characteristics.

These carbons can exist in the amorphous form, especially in the amorphous form at the grain boundary between the titanium oxide components.

The negative electrode active material of the present invention can be produced by electrospinning.

Specifically, as shown in the flowchart of FIG. 1, a method of manufacturing an anode active material includes the steps of (S10) manufacturing an electrospinning liquid, (S20) producing a metal oxide-nitrogen-porous carbon nanofiber composite material, and And heat treating the composite material (S30).

First, an electrolytic solution is prepared by mixing a first solution in which a metal oxide precursor is dissolved, a second solution in which a polymer as a carbon fiber precursor is dissolved, and an ionic liquid solution for nitrogen doping and forming a porous structure.

As the solvent of the first solution and the second solution, any one selected from the group consisting of distilled water, dimethylformamide, phenol, toluene, ethanol, methanol, and propanol may be used. As the metal oxide precursor, titanium butoxide (TBO) or a metal salt flame is used. Here, the metal salt flame is titanium iso-proxy-side _{(Ti (OCH (CH 3)} 2) 4), titanium chloride (TiCl _4, or TiCl _3), tin hydrate (SnCl ₂ · H ₂ O) and ferric chloride (FeCl _3), nickel chloride (NiCl _2), copper chloride (CuCl _2), magnesium chloride (MgCl _2), palladium chloride (PdCl _2), cobalt chloride (CoCl _2), chloride, tantalum (TaCl _2), manganese chloride (MnCl _2), nitric acid iron _{(Fe (NO 3) 2,} Fe (NO 3) 3), nickel nitrate _{(Ni (NO 3) 2)} , copper nitrate _{(Cu (NO 3) 2)} , magnesium nitrate _{(Mg (NO 3) 2)} , cobalt nitrate _{(Co (NO 3) 2)} , manganese nitrate _{(Mn (NO 3) 2)} , manganese acetate _{(Mn (CO 2 CH 3)} 2), iron acetate _{(Fe (CO 2 CH 3)} 2), nickel acetate _{(Ni (CO 2 CH 3)} 2), cobalt acetate _{(Co (CO 2 CH 3)} 2), zinc acetate _{(Zn (CO 2 CH 3)} 2), and copper acetate _{(Cu (CO 2 CH 3)} 2) And the like.

Polymers acting as carbon fiber precursors include polyvinylpyrrolidone (PVP), polymethylmethacrylate (PMMA), polyvinyl alcohol (PVA), polyvinylacetate (PVA) ), Polyacrylonitrile (PAN), polyfurfuryl alcohol, cellulose, glucose, polyvinylchloride (PVC), polyacrylic acid, polylactic acid polylactic acid, polyethylene oxide (PEO), polypyrrole, polyimide, polyamideimide, polyaramid, polyaniline (PANI), phenolic resin, Is used.

The ionic liquid solution to be mixed for the preparation of the electrical spinning solution is ethylmimidazolium chloride (EMIM Cl), ethylmethylimidazolium dicyanamide (EMIM DCA), ethylmethylimidazolium trifluoromethanesulfonate (EMIM (EMIM TFSI), ethylmethylimidazolium acetate (EMIM Ac), ethylmethylimidazolium hydrate (EMIM OH), ethylmethylimidazolium diethylphosphate (EMIM DEP), ethyl methyl imidazolium methyl carbonate (EMIM MeOCO ₂ ), ethyl methyl imidazolium lactate (EMIM Lactate), butyl methyl imidazolium chloride (BMIM Cl), butyl methyl imidazolium methyl carbonate solution BMIM MeOCO _2), butyl methyl imidazolium trifluoro methane sulfonate (BMIM Otf), butyl methyl imidazolium trifluoro methylsulfonyl a polyimide (EMIM TFSI), butyl methyl already Imidazolium trifluoro acetate (BMIM CF ₃ CO _2), and the dimethyl use any one selected from the group consisting of imidazolium methane sulfonate (MMIM CH ₃ SO _3).

Next, a metal oxide-nitrogen-porous carbon nanofiber composite material is obtained by electrospinning an electrospinning liquid prepared by using the electrospinning device configured as shown in FIG. 2. (S20) Here, the metal oxide-nitrogen- The nanofiber composite material may specifically be in the form of nitrogen-doped porous carbon nanofibers containing a metal oxide.

On the other hand, the electrospinning device used at this time may utilize a known device or utilize a device that has been modified to improve the yield of a known device. However, the metal oxide-nitrogen-porous carbon nanofiber composite material of the present invention is obtained in a drum-type collector portion spaced 20 to 30 cm from the tip of the electrospinning nozzle formed inside the electrospinning device.

The electrospinning can be carried out by maintaining the temperature of the chamber containing the electric spinning solution at 70 DEG C or lower and applying the voltage of 10 to 25 kV while supplying the electric spinning solution at a flow rate of 0.1 to 1 mL / h. When the applied voltage is less than 10 kV, the voltage is low, so that it is difficult to produce the carbon nanofibers of the present invention. If the voltage is more than 25 kV, the voltage is excessively high, so that the produced carbon nanofibers may be lost or deformed.

Thereafter, the metal oxide-nitrogen-porous carbon nanofiber composite material undergoes a heat treatment process (S30). As shown in the flow chart of FIG. 3, the heat treatment process is performed by first heating the composite material (S31), then performing a first heat treatment (S33) for 3 to 5 hours in an air atmosphere, (S37) in an atmosphere of argon (Ar) for 1 to 5 hours. Here, the first heat treatment (S33) and the second heat raising (S35) to be.

Specifically, the metal oxide-nitrogen-porous carbon nanofiber composite material is heated to 280 ° C (S31), heat-treated for 3 to 5 hours in an air atmosphere (S33), heated up to 550 ° C (S35) (S37) in an atmosphere of argon (Ar) for 1 to 5 hours.

The carbon nanofiber morphology of the metal oxide-nitrogen-porous carbon nanofiber composite material is stably maintained through the first heat treatment and the first heat treatment (S31, S33). The second heat treatment, the second heat-up and the second heat treatment (S35, S37), converts the metal oxide precursor into metal oxide while maintaining the shape of the carbon nanofibers. Here, when the heat treatment of the nitrogen-doped porous carbon nanofibers containing the metal oxide is performed at a temperature higher than 700 ° C., deformation of the nanofiber type may occur or carbon may be exhausted during the heat treatment process.

It is also possible to change the average size of the metal oxide, the pore size, and the thickness of the carbon fiber by suitably changing the processing conditions during the production of the negative electrode active material. The metal oxide used for producing the negative electrode active material is preferably titanium oxide.

The negative electrode active material thus prepared, the conductive material, the binder, the solvent, and the like may be mixed together to prepare a slurry, followed by coating on the current collector and drying the negative electrode.

The nitrogen-doped carbon nanofiber negative electrode active material containing the metal oxide of the present invention together with a conductive material, a binder and the like constitutes a negative electrode active material layer, and the negative electrode active material layer is formed on the current collector to form a negative electrode. Here, the metal oxide may be titanium oxide.

On the other hand, copper, nickel or SUS current collectors can be used as the current collector constituting the negative electrode, and a copper current collector having the best electric conductivity is preferable. The negative electrode active material layer formed on the current collector may be prepared by preparing a negative electrode active material composition by mixing a negative electrode active material, a conductive material, a binder and a solvent and then directly coating the negative electrode active material composition on the current collector, casting the same on a separate support, And then laminating the obtained negative electrode active material film on a current collector.

As the conductive material used for forming the anode active material layer, carbon black, graphite fine particles, or the like may be used. However, the conductive material is not limited thereto, and any conductive material can be used as long as it can be used as a conductive material in the related art .

The binder may also include vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethylmethacrylate, polytetrafluoroethylene (PTFE), and mixtures thereof, Or a styrene-butadiene rubber-based polymer (SBR) may be used, but not limited thereto, and any of them can be used as long as it can be used as a binder in the art.

As the solvent, N-methylpyrrolidone, ethanol, acetone, water, or the like may be used, but not limited thereto, and any of those that can be used in the technical field can be used.

The content of the negative electrode active material, the conductive material, the binder and the solvent in the production of the lithium battery according to the present invention can be mixed at a level commonly used in the lithium battery, , A binder, and a solvent may be omitted and mixed.

On the other hand, a lithium battery can be manufactured by the following method.

As described above, a negative electrode is prepared and prepared.

Next, the cathode active material composition, the conductive material, the binder, and the solvent are mixed together in the same manner as the cathode. Then, the positive electrode active material composition is coated directly on the aluminum current collector and dried to prepare a positive electrode. Alternatively, the positive electrode active material composition is cast on a separate support, and then a film obtained by peeling the support from the support is laminated on the aluminum current collector It is also possible to manufacture the anode.

Here, the cathode active material is LiCoO ₂ , LiMn _x O ₂ x (x = 1, 2), LiNi _{1 -x} Mn _x O ₂ (0 <x <1), LiNi _{1 -xy} Co _x Mn _y O ₂ = 0.5, 0 = y = 0.5), LiFeO ₂ , LiFePO ₄ V ₂ O ₅ , TiS, MoS and the like can be used, but not limited thereto, and any of them can be used as the cathode active material in the related art.

The content of the positive electrode active material, the conductive material, the binder and the solvent are mixed at a level commonly used in the lithium battery, and one or more of the conductive material, the binder and the solvent are omitted and mixed according to the use and configuration of the lithium battery. .

In some cases, a plasticizer is further added to the cathode active material composition and the anode active material composition to form pores inside the electrode plate.

Next, a separator to be inserted between the positive electrode and the negative electrode is prepared. The separator can be used as long as it is conventionally used in a lithium battery. It is preferable to have a low resistance to the ion movement of the electrolyte and an excellent ability to impregnate the electrolyte. For example, selected from glass fibers, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE) or a combination thereof, in the form of a nonwoven fabric or a woven fabric.

Alternatively, the electrolyte may be in a solid, liquid, or gel state. For example, organic electrolytic solution, boron oxide, lithium oxynitride, and the like, but not limited thereto, and can be used as long as it can be used as an electrolyte in liquid, solid, or gel form in the art. On the other hand, when the electrolyte is a solid electrolyte, it can be formed on the negative electrode by a method such as sputtering or vapor deposition.

As an example, an organic electrolytic solution may be prepared as an electrolyte solution of a lithium battery. Such an organic electrolytic solution is prepared by dissolving a lithium salt in an organic solvent. The organic solvent may be any organic solvent that can be used in the art. Examples of the solvent include propylene carbonate, ethylene carbonate, fluoroethylene carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, butylene carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2- methyltetrahydrofuran, But are not limited to, butyrolactone, dioxolane, 4-methyldioxolane, N, N-dimethylformamide, dimethylacetamide, dimethylsulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, , Nitrobenzene, dimethyl carbonate, methyl isopropyl carbonate, ethyl propyl carbonate, dipropyl carbonate, dibutyl carbonate, diethylene glycol, dimethyl ether, or mixtures thereof. Also, the lithium salt dissolved at this time can be used as long as it can be used as a lithium salt in the related art. For example, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiAlO ₂ , LiAlCl ₄ , _x F _{2x + 1} SO ₂ ) (CyF _{2y + 1} SO ₂ ) (where x and y are natural numbers), LiCl, LiI, or a mixture thereof.

The thus-produced lithium battery includes a positive electrode, a negative electrode, and a separator. Specifically, the positive electrode, the negative electrode, and the separator are wound or folded to be accommodated in the battery case. Then, an organic electrolytic solution is injected into the battery case and sealed with a cap assembly to complete the lithium battery. The battery case may be cylindrical, square, thin film, or the like. Characteristically, the lithium battery of the present invention may be a thin film battery or a lithium ion battery.

Meanwhile, a lithium ion polymer battery can be manufactured using the negative electrode active material of the present invention. In order to manufacture such a lithium ion polymer battery, first, a separator is disposed between a cathode and an anode in which the anode active material of the present invention is employed to form a battery structure. Next, this battery structure is laminated with a bi-cell structure, then impregnated with an organic electrolyte solution, and finally the resultant is housed in a pouch and sealed to complete a lithium ion polymer battery.

Alternatively, a battery pack may be formed by laminating a plurality of the battery structures previously formed to manufacture a lithium ion polymer battery. The battery pack thus manufactured may be used for all devices requiring high capacity and high output.

According to the above-described nitrogen-doped porous carbon nanofibers containing a metal oxide and a method for producing the same, it is possible to easily produce titanium oxide nanosized in the inside of the nitrogen-doped porous carbon nanofiber, and the nitrogen content, the content of the metal oxide The size and content of the pores, the diameter of the carbon fibers, and the size of the metal oxide can be suitably controlled. The metal oxide of the present invention may be most effective to use titanium oxide.

Also, since the nitrogen-doped porous carbon nanofiber containing the metal oxide of the present invention exhibits improved capacity and cycle characteristics, the negative electrode and the lithium battery employing the same can provide excellent electrical characteristics.

In addition, the nitrogen-doped porous carbon nanofibers containing metal oxides are characterized in that they have a very high electron mobility and can be used to produce electrode materials and catalysts for solar cells, fuel cells, lithium air cells, etc. have.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

&Lt; Example 1: Negative electrode active material &

(First solution) and 0.529 g of polyvinylpyrrolidone (PVP) prepared by adding 1.5 g of titanium oxide butoxide (TBO) as a metal oxide precursor and 3 mL of acetic acid into 3 mL of ethanol and mixing for 30 minutes were mixed with 7.4 mL , And 0.1 mL of ethylmethylimidazolium dicyanamide (EMIM DCA) were homogeneously mixed for 30 minutes to prepare an electric discharge solution. (S10)

The electric discharge solution thus prepared was placed in a syringe and supplied with a syringe pump at a flow rate of 0.5 mL / h into the electrospinning apparatus while applying a voltage of 20 kV to electrospray. At this time, the distance from the tip of the nozzle to the trapping portion was fixed to 20 cm, and nitrogen-doped porous carbon nanofibers were obtained using a drum type trapping portion for uniform collection (S20).

The nitrogen-doped porous carbon nanofibers obtained through this process were oxidized at 280 ° C. for 5 hours in an air atmosphere to stabilize the structure. Carbonization was carried out at 550 ° C. for 3 hours under an argon atmosphere to obtain a nitrogen doping Thereby preparing a porous carbon nanofiber anode active material. (S30)

&Lt; Example 2: Anode active material &

0.514 g of a solution (first solution) and polyvinylpyrrolidone (PVP) prepared by adding 1.5 g of titanium butoxide (TBO) and 3 mL of acetic acid into 3 mL of ethanol and mixing them for 30 minutes were dissolved in 7.2 mL of ethanol An ionic liquid solution containing 0.3 mL of the prepared solution (the second solution) and ethylmethylimidazolium dicyanamide (EMIM DCA) was homogeneously mixed for 30 minutes to prepare an electric spinning solution.

The electric discharge solution thus prepared was placed in a syringe and supplied with a syringe pump at a flow rate of 0.5 mL / h into the electrospinning apparatus while applying a voltage of 20 kV to electrospray. At this time, the distance from the tip of the nozzle to the trapping portion was fixed to 20 cm, and nitrogen-doped porous carbon nanofibers were obtained using a drum-type trapping portion for uniform collection.

The nitrogen-doped porous carbon nanofibers obtained through this process were oxidized at 280 ° C. for 5 hours in an air atmosphere to stabilize the structure. Carbonization was carried out at 550 ° C. for 3 hours under an argon atmosphere to obtain a nitrogen doping Thereby preparing a porous carbon nanofiber anode active material.

&Lt; Example 3 Negative electrode active material >

Prepared by dissolving 0.5 g of polyvinylpyrrolidone (PVP) in 7 mL of ethanol, prepared by mixing 1.5 g of titanium butoxide (TBO) and 3 mL of acetic acid in 3 mL of ethanol and mixing for 30 minutes. And an ionic liquid solution containing 0.5 mL of ethylmethylimidazolium dicyanamide (EMIM DCA) were homogeneously mixed for 30 minutes to prepare an electric spinning solution.

The electric discharge solution thus prepared was placed in a syringe and supplied with a syringe pump at a flow rate of 0.5 mL / h into the electrospinning apparatus while applying a voltage of 20 kV to electrospray. At this time, the distance from the tip of the nozzle to the trapping portion was fixed to 20 cm, and nitrogen-doped porous carbon nanofibers were obtained using a drum-type trapping portion for uniform collection.

The nitrogen-doped porous carbon nanofibers obtained through this process were oxidized at 280 ° C. for 5 hours in an air atmosphere to stabilize the structure. Carbonization was carried out at 550 ° C. for 3 hours under an argon atmosphere to obtain a nitrogen doping Thereby preparing a porous carbon nanofiber anode active material.

Example 4 Negative electrode and lithium battery (coin cell)

80 wt% of the negative electrode active material prepared in Example 1, 10 wt% of carbon powder (Super C65, Timcal) and 10 wt% of polyvinylidene fluoride (PVDF) were mixed in agate induction to prepare a slurry. The slurry thus prepared was coated on a copper foil to a thickness of about 80 μm using a doctor blade, dried at room temperature for 2 hours, and dried again in a vacuum atmosphere at 120 ° C. for 2 hours to form a negative electrode.

(Celgard 2400) was used as a separator, 1M LiPF ₆ was added to a mixture of EC (ethylene carbonate) + DEC (diethylene carbonate) (1: 1 volume ratio) was used as an electrolyte to prepare a CR-2032 lithium battery (coin cell).

&Lt; Example 5 Cathode and lithium battery >

A negative electrode and a lithium battery (coin cell) were prepared in the same manner as in Example 4 using the negative electrode active material prepared in Example 2.

&Lt; Example 6 Cathode and lithium battery >

A negative electrode and a lithium battery (coin cell) were prepared in the same manner as in Example 4, using the negative active material prepared in Example 3.

&Lt; Comparative Example 1 &

(First solution) prepared by dissolving 0.536 g of polyvinylpyrrolidone (PVP) in 7 mL of ethanol was prepared by adding 1.5 g of titanium butoxide (TBO) and 3 mL of acetic acid into 3 mL of ethanol and mixing for 30 minutes (Second solution) were homogeneously mixed for 30 minutes to prepare an electric discharge solution.

The electric discharge solution thus prepared was placed in a syringe and supplied with a syringe pump at a flow rate of 0.5 mL / h into the electrospinning apparatus while applying a voltage of 20 kV to electrospray. At this time, the distance from the tip of the nozzle to the trapping portion was fixed at 20 cm, and nitrogen-doped carbon nanofibers were obtained using a drum-type trapping portion for uniform collection.

The nitrogen-doped carbon nanofibers thus obtained were oxidized at 280 ° C. for 5 hours in an air atmosphere to stabilize the structure. Carbonization was carried out at 550 ° C. under an argon atmosphere for 3 hours to obtain a nitrogen-doped Carbon nanofiber anode active material was prepared.

&Lt; Comparative Example 2 &

A negative electrode and a lithium battery (coin cell) were prepared in the same manner as in Example 4, using the negative active material prepared in Comparative Example 1.

The preferred embodiments of the present invention thus produced are summarized in the following Table 1.

division material The ionic liquid (IL) PVP / ethanol Example 1 Anode active material TiO ₂ + PVP + ionic liquid 0.1 mL 0.529 g / 7.4 mL Example 2 Anode active material TiO ₂ + PVP + ionic liquid 0.3 mL 0.514 g / 7.2 mL Example 3 Anode active material TiO ₂ + PVP + ionic liquid 0.5 mL 0.5 g / 7 mL Example 4 Cathode and
Lithium battery A negative electrode prepared using the negative electrode active material of Example 1,
And a lithium battery employing the same Example 5 Cathode and
Lithium battery A negative electrode prepared using the negative electrode active material of Example 2,
And a lithium battery employing the same Example 6 Cathode and
Lithium battery A negative electrode prepared using the negative electrode active material of Example 3,
And a lithium battery employing the same Comparative Example 1 Anode active material TiO ₂ + PVP - 0.536 g / 7.5 mL Comparative Example 2 Cathode and
Lithium battery The negative electrode prepared using the negative electrode active material of Comparative Example 1,
And a lithium battery employing the same

4A to 4C are SEM photographs of each of the negative electrode active materials prepared in Example 1, Example 2 and Example 3, and FIG. 4D is a scanning electron microscope (SEM) image of each of the negative electrode active materials prepared in Example 1, (SEM) photo. As shown in the photographs of FIGS. 4A to 4D, both the porous carbon nanofibers (FIGS. 4A to 4C) prepared by adding the ionic liquid and the carbon nanofibers (FIG. 4D) Has a diameter in the range of 200 to 300 μm and shows a fibrous phase in a one-dimensional form. As a result, it can be confirmed that the addition of the ionic liquid does not affect the shape and size (diameter) of the carbon nanofibers constituting the negative electrode active material.

FIG. 5A is a transmission electron microscope (TEM) photograph of the negative electrode active material prepared in Example 2. FIG. Here, high-rate TEM photographs of the negative electrode active material of Example 2 reveal that pores are formed in the carbon nanofiber forming the negative electrode active material as well as the metal oxide. 5B, in the case of the SADP (selected area diffraction pattern) of the negative electrode active material of Example 2, in the case of the negative electrode active material of Example 2 using the ionic liquid, the mean size of the crystal region was 10 nm and the lattice distance was 0.189 nm (200) surface fringes of anatase-type titanium oxide are well visible. This is because the ionic liquid and the polyvinylpyrrolidone (PVP) used as the carbon fiber precursor have different carbonization temperatures, so that the pores are formed during the heat treatment process, so that the carbon nanofibers maintain the porous form Because.

When the carbon nanofibers are formed in a porous form, the lithium ions can be easily diffused in a direction perpendicular to the long axis direction of the carbon nanofibers, thereby improving the high-rate characteristics. And, carbon and titanium oxide are organically connected to each other to make a good electrical connection between the particles, which can reduce the resistance between the grain boundaries. In addition, since the carbon fiber has a porous form, the reaction area of the titanium oxide and the lithium ion is increased and the effective amount is increased.

On the other hand, the energy dispersive X-ray spectroscopy (EDS) analysis of the anode active material of Example 2 of FIG. 5C showed that titanium (Ti), oxygen (O), carbon (C), and nitrogen (N) As shown in Fig.

On the other hand, in the case of Comparative Example 1 in which an ionic liquid is not used, as shown in the TEM photograph of FIG. 6, the carbon nanofibers are densely packed without pores in the fibers.

That is, in the present invention, the nitrogen-doped porous carbon nanofiber containing metal oxide is prepared by appropriately regulating and adding an ionic liquid, and it is possible to increase the effective amount and increase the charge / discharge rate by using the carbon nanofiber as a cathode material of a lithium secondary battery Respectively.

7 is an X-ray diffraction (XRD) graph of Example 2 and Comparative Example 1. Fig. In the case of Example 2, a crystalline anatase-type titanium oxide was formed in the nitrogen-doped amorphous carbon nanofiber, and the carbon was present in an amorphous state. However, in Comparative Example 1, crystalline anatase-type titanium oxide was not formed in addition to nitrogen-doped amorphous carbon. Thus, it can be confirmed that when the nitrogen-doped carbon nanofiber containing the metal oxide is put into an ionic liquid, the ionic liquid plays a role of increasing the degree of crystallization of the titanium oxide.

8 is an X-ray photoelectron spectroscopy (XPS) graph of Example 2. Fig. Titanium (Ti) 2p, oxygen (O) 1s, carbon (C) 1s and nitrogen (N) 1s peaks clearly appear in the nitrogen-doped porous carbon fiber containing the metal oxide. In the case of Ti 2p at 459.1 eV and 464.8 eV are shown the two main peaks associated with the Ti 2p _3/2 and Ti 2p _1/2. This is associated with Ti ^{4 +} in the octahedral (tahedral), Ti 2p peak may show a typical energy in the form of titanium oxide bonded. The C 1s peak shows a carbon-carbon bond (CC 285.1 eV), a carbon-nitrogen bond (C = N 286.7 eV, CN 288 eV) and a carbon-oxygen bond (CO 289.5 eV). The N 1s peak appears as a mixed state due to the various oxidation states of nitrogen, as shown in the C 1s peak. The CN bond as a single bond in the carbon-nitrogen bond is shown at 398.5 eV, and the double bond, C = N, appears at 400.8 eV. This is an effect that occurs when nitrogen is doped in the carbon, and when the carbon contains nitrogen, it can have a higher electrical conductivity than the carbon that does not contain nitrogen, thereby enabling high-speed charging and discharging.

9A is a BET surface area analysis graph of Example 1, Example 2, Example 3, and Comparative Example 1. Fig. Referring to this graph, it can be seen that the nitrogen-doped carbon nanofibers containing the metal oxide contain meso pores. The surface area of Example 1 is 11 m ² / g, the surface area of Example 2 is 191 m ² / g, the surface area of Example 3 is 90 m ² / g, and the surface area of Comparative Example 1 is 8 m ² / g. In particular, the maximum surface area was shown in Example 2. The shape of the nanofiber with a large BET surface area leads to a rapid diffusion of lithium during charging and discharging, thereby exhibiting improved high rate characteristics. FIG. 9B is a BJH pore size analysis graph of Example 2, wherein the average size of the analyzed pores was 10 nm.

10 shows the charge / discharge test results of Example 4, Example 5, Example 6, and Comparative Example 2. Fig.

Specifically, each of the negative electrode active materials of Example 1, Example 2, Example 3, and Comparative Example 1 contained in each of the lithium batteries of Examples 4, 5, and 6 and the lithium battery of Comparative Example 2 Discharge was performed until the voltage reached 1.0 V (vs. Li) at a current of 30 mA per 1 g, and then charged to the same current until the voltage reached 3.0 V (vs. Li). Subsequently, charging and discharging were repeated 30 times in total in the same current and voltage section. The results of the normal charge-discharge test at Fig. 10 are shown in Table 2 below.

Initial Capacity
(mAh / g) 28 times after charge / discharge
Capacity retention rate (%) Example 4 (Lithium battery using Example 1) 250 67 Example 5 (Lithium battery using Example 2) 352 73 Example 6 (Lithium battery using Example 3) 270 46 Comparative Example 2 (Lithium battery using Comparative Example 1) 282 65

Referring to Table 2, it was confirmed that the lithium battery of Example 5 had a reduced amount of the lithium battery capacity after the normal temperature charge-discharge test as compared with the decrease amount of the lithium battery capacity after the normal temperature charge and discharge test of the lithium battery of Comparative Example 2 . That is, it can be seen that the lithium battery of Example 5 exhibited somewhat higher initial capacity than the lithium battery of Comparative Example 2, and the capacity retention ratio was remarkably improved.

11 is a graph showing the results of experiments on the room temperature rate characteristics of the lithium batteries of Example 5 and Comparative Example 2. Fig. Specifically, while keeping the same voltage of the lithium battery of Example 5 and Comparative Example 2, the current value at the time of charging was kept the same, and the current value at the time of discharging was made different. At this time, the current value at the time of charging is 30 mA, 150 mA, 300 mA, 900 mA, 1500 mA, and the voltage is 1.0 V (vs. Li) for each 1 g of the negative electrode active material contained in each lithium battery , And the current value at the time of charging was charged at a current of 30 mA until the voltage reached 3.0 V (vs. Li). Referring to this graph, it is confirmed that the rate characteristic of the lithium battery of Example 5 is superior to the rate characteristic of the lithium battery of Comparative Example 2.

12 shows the impedance test results of the lithium batteries of Example 5 and Comparative Example 2. Fig. Specifically, discharging was performed until the voltage reached 1.0 V (vs. Li) at a current of 30 mA per 1 g of each negative electrode active material contained in each of the lithium batteries of Example 5 and Comparative Example 2, Lt; / RTI &gt; and then charged to 3.0 V (vs. Li). Subsequently, charging and discharging were repeated 20 times in the same current and voltage section, and impedance analysis was performed under the condition that the voltage was 3.0 V (vs. Li). Referring to this graph, it is confirmed that the lithium battery of Example 2 is more stable than the lithium battery of Comparative Example 2.

According to the method for manufacturing an anode active material as described above, it is possible to easily produce nitrogen-doped porous carbon nanofibers in which nano-sized metal oxide is dispersed. The nitrogen content, the content of titanium oxide, the diameter of carbon fiber, The size can be appropriately controlled.

Further, the nitrogen-doped porous carbon fiber containing the metal oxide of the present invention is employed as a negative electrode active material, and the rate characteristics, stability, and lifetime characteristics are improved, so that an excellent negative electrode and lithium battery can be produced.

In addition, electrode materials and catalysts for solar cells, fuel cells, lithium air cells, etc. can be manufactured by applying a very fast electron transfer rate of the negative electrode active material of the present invention.

The method of manufacturing the negative electrode active material as described above, and the negative electrode and the lithium battery employing the negative electrode active material are not limited to the configuration and operation of the embodiments described above. The embodiments may be configured so that all or some of the embodiments may be selectively combined so that various modifications may be made.

1: chamber 2: electrospinning nozzle
3: Collecting part 4: Power supply
5: Collector controller

Claims (14)

Preparing a first solution in which a metal oxide precursor is dissolved, a second solution in which a polymer as a carbon fiber precursor is dissolved, and an ionic liquid solution for nitrogen doping and forming a porous structure;
Preparing a metal oxide-nitrogen-porous carbon nanofiber composite material by electrospinning the electrorheological fluid; And
And heat treating the composite material,
The solvent of the first solution and the second solution may be any one selected from the group consisting of distilled water, dimethylformamide, phenol, toluene, ethanol, methanol, and propanol,
The metal oxide precursor may be titanium butoxide (TBO) or a metal salt flame,
The metal salt flame, titanium iso-proxy-side _{(Ti (OCH (CH 3)} 2) 4), titanium chloride (TiCl _4, or TiCl _3), tin hydrate (SnCl ₂ · H ₂ O) and ferric chloride (FeCl _3), nickel chloride (NiCl _2), copper chloride (CuCl _2), magnesium chloride (MgCl _2), palladium chloride (PdCl _2), cobalt chloride (CoCl _2), chloride, tantalum (TaCl _2), manganese chloride (MnCl _2), nitric acid iron _{(Fe (NO 3) 2,} Fe (NO 3) 3), nickel nitrate _{(Ni (NO 3) 2)} , copper nitrate _{(Cu (NO 3) 2)} , magnesium nitrate _{(Mg (NO 3) 2)} , cobalt nitrate _{(Co (NO 3) 2)} , manganese nitrate _{(Mn (NO 3) 2)} , manganese acetate _{(Mn (CO 2 CH 3)} 2), iron acetate _{(Fe (CO 2 CH 3)} 2), nickel acetate _{(Ni (CO 2 CH 3)} 2), cobalt acetate _{(Co (CO 2 CH 3)} 2), zinc acetate _{(Zn (CO 2 CH 3)} 2), and copper acetate _{(Cu (CO 2 CH 3)} 2) , &Lt; / RTI &gt;
The step of heat-
Heating the composite material to 280 ° C;
Heat-treating the composite material under an air atmosphere for 3 to 5 hours after the primary heating;
Heating the composite material to a temperature of 500 ° C after the heat treatment in the air atmosphere; And
Heat-treating the composite material for 1 to 5 hours in an argon (Ar) atmosphere after the secondary heating,
Wherein the step of heat-treating in the air atmosphere and the step of raising the secondary temperature are performed successively.
delete delete delete The method according to claim 1,
The polymer may be selected from the group consisting of polyvinylpyrrolidone (PVP), polymethylmethacrylate (PMMA), polyvinyl alcohol (PVA), polyvinylacetate (PVAC), polyacrylonitrile PAN, polyfurfuryl alcohol, cellulose, glucose, polyvinylchloride (PVC), polyacrylic acid, polylactic acid, polyethylene oxide (polyethylene) (PEI), polypyrrole, polyimide, polyamideimide, polyaramid, polyaniline (PANI), phenol resin, and pitches. A method for producing an anode active material.
The method according to claim 1,
Wherein the ionic liquid solution is selected from the group consisting of ethylmethylimidazolium chloride (EMIM Cl), ethylmethylimidazolium dicyanamide (EMIM DCA), ethylmethylimidazolium trifluoromethanesulfonate (EMIM Otf), ethylmethylimidazolium (EMIM TFSI), ethylmethylimidazolium acetate (EMIM Ac), ethylmethylimidazolium hydrate (EMIM OH), ethylmethylimidazolium diethylphosphate (EMIM DEP), ethylmethylimidazolium iodide imidazolium methyl carbonate (EMIM MeOCO _2), ethyl methyl imidazolium lactate (EMIM lactate), butyl-methyl-imidazolium chloride (BMIM Cl), butyl methyl imidazolium methyl carbonate solution (BMIM MeOCO _2), butyl methyl (BMIM Otf), butylmethylimidazolium trifluoromethylsulfonylimide (EMIM TFSI), butylmethylimidazolium trifluoroacetate (BM (methylimidazolium trifluoromethanesulfonate) IM CF ₃ CO ₂ ), and dimethylimidazolium methanesulfonate (MMIM CH ₃ SO ₃ ).
The method according to claim 1,
Wherein the step of preparing the composite material comprises:
Wherein the electric spinning solution is maintained at 70 占 폚 or lower, the electric spinning solution is supplied at a flow rate of 0.1 to 1 ml / h, and a voltage of 10 to 25 kV is applied to conduct electrospinning.
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