KR20130118756A - Anode active materials and manufacturing method thereof, and anode and lithium battery using the same - Google Patents

Abstract

PURPOSE: A method for preparing an anode active material is provided to easily prepare titanium oxide with a size of several nanometers in a nitrogen-doped porous carbon nanotube, and allow an appropriate control of the nitrogen content, the titanium oxide content, the pore size, the diameter of the carbon nanotube, and the size of titanium oxide. CONSTITUTION: A method for preparing an anode active material comprises the following steps. An electro-spinning 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 nanotube precursor is dissolved, and an ionic liquid solution for nitrogen doping and forming of a porous structure (S10). The electro-spinning solution is electro-spun to prepare a composite material of metal oxide-nitrogen-porous carbon nanotube (S20). The composite material is thermally treated (S30). Further, an anode is formed by coating a current collector with a slurry in which the anode active material, a conducting agent, a binding agent, and a solvent are mixed. [Reference numerals] (AA) Start; (BB) End; (S10) Produce electro-spinning solution; (S20) Produce metal oxide-nitrogen-porous carbon nanofiber composite; (S30) Thermally treat composite

Description

A method of manufacturing a negative electrode active material, and a negative electrode and a lithium battery employing the same {ANODE ACTIVE MATERIALS AND MANUFACTURING METHOD THEREOF, AND ANODE AND LITHIUM BATTERY USING THE SAME}

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, and more particularly, a method for producing a negative electrode active material consisting of nitrogen-doped porous carbon nanofibers containing a nano-sized metal oxide. And a negative electrode and a lithium battery employing the same.

Recently, the application of lithium batteries has been expanded to electric vehicles and power storage devices beyond the main power source of small electronic devices such as mobile phones and laptops. As such, a lithium battery is widely used as an electrochemical energy storage body, and a lithium battery having a small capacity decrease is required even in frequent charging and discharging.

Currently, graphite, a carbon-based material having good lifespan, has been commercialized as a negative electrode active material used in lithium batteries, but the theoretical capacity is very low at 372 mAh / g, and the solid electrolyte membrane formed on the surface of the active material during charge and discharge is a lithium battery. It is causing safety problems. Many studies have been conducted to replace graphite having such low capacity and safety problems, and typically, TiO ₂ , Li ₄ Ti ₅ O ₁₂ , KNb ₅ O ₁₃ , Fe ₂ O ₃ , Co ₃ O ₄ , MnO ₂ , Research into using metal oxides in which an addition or conversion reaction of MoO ₂ , MoO ₃ , NiO, CuO, etc. occurs is used as a negative electrode active material.

However, metal oxides such as TiO ₂ , Li ₄ Ti ₅ O ₁₂ and KNb ₅ O ₁₃ have a limited theoretical capacity, while Fe ₂ O ₃ , Co ₃ O ₄ , MnO _2, etc. The transfer rate is limited and generates an active material which is electrically isolated in the electrode with volume expansion upon reaction with lithium, resulting in low rate characteristics.

In order to solve this problem, researches on nanostructured materials have been widely conducted. Such nanostructured materials refer to one, two, or three-dimensional structured nanomaterials, Nano Lett., 9, (2009) 1045, Angew. Chem., Int. Ed., 48 (2009) 1660, J. Phys. Chem. C, 112 (2008) 4836, Chem. Commun. (2006) 2783 proposes nanorods, nanowires, nanoflowers, or nanospheres. The nano structured material exhibited high capacity and high stability battery characteristics by alleviating the cracking and aggregation of the active material, thereby alleviating stress and volume change generated in the electrode during charging and discharging. However, due to the use of an electrode active material having a high surface area, the side reaction phenomenon with the electrolyte is increased, and the energy density per volume is reduced.

Therefore, the introduction of a negative electrode active material that can implement a lithium battery having a high capacity, high stability properties to solve this problem is required.

The present invention relates to a method for manufacturing a negative electrode active material for improving capacity and stability as well as improving conductivity in a lithium secondary battery. Specifically, electrospinning a metal oxide precursor / carbon fiber precursor solution / ionic liquid solution It is to provide a method for producing a negative electrode active material consisting of porous carbon nanofibers produced by heat treatment after the heat treatment, and a negative electrode and a lithium battery employing the same.

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

The method for producing a negative electrode active material of the present invention for realizing the above object is a first solution in which a metal oxide precursor is dissolved, a second solution in which a polymer that is a carbon fiber precursor is dissolved, and an ionic liquid for nitrogen doping and porous structure formation. Preparing an electrospinning solution by mixing a solution, preparing a metal oxide-nitrogen-porous carbon nanofiber composite material by electrospinning the electrospinning solution, 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 metal chloride.

The metal chloride salt is titanium isoprooxide (Ti (OCH (CH ₃ ) ₂ ) ₄ ), titanium chloride (TiCl ₄ , or TiCl ₃ ), tin hydrate (SnCl ₂ · H ₂ O) and iron chloride (FeCl ₃ ), Nickel chloride (NiCl ₂ ), copper chloride (CuCl ₂ ), magnesium chloride (MgCl ₂ ), palladium chloride (PdCl ₂ ), cobalt chloride (CoCl ₂ ), tantalum chloride (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 ) It may be any one selected from the group consisting of.

The polymer is polyvinylpyrrolidone (PVP), polymethylmethacrylate (PMMA), polyvinyl alcohol (PVA), polyvinylacetate (PVAC), polyacrylonitrile PAN, polyfurfuryl alcohol, cellulose, glucose, polyvinylchloride (PVC), polyacrylic acid, polylactic acid, polyethylene oxide oxide; PEO, polypyrrole, polyimide, polyamideimide, polyaramid, polyaniline, polyaniline, PANI, phenol resin, and pitch Can be.

The ionic liquid solution is ethyl methyl imidazolium chloride (EMIM Cl), ethyl methyl imidazolium dicyanamid (EMIM DCA), ethyl methyl imidazolium trifluoromethanesulfonate (EMIM Otf), ethyl methyl imidazolium Trifluoromethylsulfonylimide (EMIM TFSI), ethylmethylimidazolium acetate (EMIM Ac), ethylmethylimidazolium hydrate (EMIM OH), ethylmethylimidazolium diethylphosphate (EMIM DEP), ethylmethyl Midazolium methyl carbonate (EMIM MeOCO ₂ ), ethylmethylimidazolium lactate (EMIM Lactate), butylmethylimidazolium chloride (BMIM Cl), butylmethylimidazolium methylcarbonate solution (BMIM MeOCO ₂ ), butylmethyl Midazolium trifluoromethanesulfonate (BMIM Otf), butylmethylimidazolium trifluoromethylsulfonylimide (EMIM TFSI), butylmethylimidazolium trifluoroacetate (BM IM CF ₃ CO ₂ ), and dimethylimidazolium methanesulfonate (MMIM CH ₃ SO ₃ ).

In the preparing of the composite material, the electrospinning solution is maintained at 70 ° C. or less, the electrospinning solution is supplied at a flow rate of 0.1 to 1 mL / h, and at the same time, the electrospinning is performed by applying a voltage of 10 to 25 kV. Can be.

The heat treatment may include: firstly raising the composite material to 280 ° C., heat treating the composite material in an air atmosphere for 3 to 5 hours after the first temperature increase, and then heat treating the air in the air atmosphere. And heating the composite material to 500 ° C. for a second time, and heat treating the composite material under an argon (Ar) atmosphere for 1 to 5 hours after the second temperature increase. The step and the step of raising the second temperature may be performed immediately after.

In addition, a negative electrode employing the negative electrode active material prepared by the above method can be prepared. Specifically, the negative electrode of the present invention for realizing the above object is a negative electrode formed by coating a slurry formed by mixing a negative electrode active material, a conductive material, a binder, and a solvent on a current collector, wherein the negative electrode active material contains a metal oxide It may be made of a porous carbon nanofiber doped with nitrogen.

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

The metal oxide may be titanium oxide.

In addition, it is possible to manufacture a lithium battery employing the negative electrode active material prepared by the above method. Specifically, the lithium battery of the present invention for realizing the above object, in the lithium battery comprising a positive electrode, a negative electrode, and a separator, the negative electrode is made of a porous carbon nanofiber doped with nitrogen containing a metal oxide Can be.

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

The metal oxide may be titanium oxide.

According to the manufacturing method of the negative electrode active material described above, it is possible to easily produce a few nano titanium oxide inside the nitrogen-doped porous carbon nanofibers, nitrogen content, titanium oxide content, pore size, carbon fiber The diameter and the size of the titanium oxide can be appropriately controlled.

In addition, 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 may provide excellent electrical characteristics.

In addition, by applying an extremely fast electron transfer speed of the negative electrode active material of the present invention, it is possible to produce electrode materials and catalysts such as solar cells, fuel cells, lithium air batteries and the like.

1 is a flowchart showing a method of manufacturing a negative electrode active material of the present invention in order.
2 is a conceptual diagram showing an electrospinning device for producing a negative electrode active material of the present invention.
Figure 3 is a flow chart illustrating in detail the step of heat treatment in the manufacturing method of the negative electrode active material of the present invention.
4A to 4C are scanning electron microscope (SEM) photographs of negative electrode active materials prepared in Examples.
Figure 4d is a scanning electron microscope (SEM) photograph of the negative electrode active material prepared in Comparative Example 1.
Figure 5a is a transmission electron microscope (TEM) photograph of the negative electrode active material prepared in Example 2.
5B is a selected area diffraction pattern (SADP) photograph of a transmission electron microscope of a negative electrode active material.
Figure 5c is an energy dispersive x-ray spectroscopy (EDS) elemental analysis of the negative electrode active material prepared in Example 2.
6 is a transmission electron microscope (TEM) photograph of the negative electrode active material prepared in Comparative Example 1. FIG.
7 is an X-ray diffraction (XRD) graph of each negative electrode active material prepared in Example 2 and Comparative Example 1.
8 is an X-ray photoelectron spectroscopy (XPS) graph of the anode active material prepared in Example 2. FIG.
Figure 9a is a graph of the BET surface area analysis of each negative electrode active material prepared in Example 1, Example 2, Example 3, and Comparative Example 1.
9B is a graph of BJH pore size analysis of the negative electrode active material prepared in Example 2. FIG.
10 shows the results of charge and discharge experiments of the lithium batteries prepared in Examples 4, 5, 6, and 2, respectively.
11 is a result of the rate characteristic of each lithium battery prepared in Example 5 and Comparative Example 2.
12 is an impedance result of each lithium battery prepared in Example 5 and Comparative Example 2.

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 a nitrogen-doped porous carbon nanofibers containing metal oxides (particularly titanium oxides) as a negative electrode active material, and the negative electrode active material has excellent initial efficiency and excellent capacity retention characteristics, and thus, a lithium battery negative electrode and its corresponding It can be usefully used for a lithium battery employing an electrode.

The negative electrode active material according to the embodiment of the present invention is composed of titanium oxide (TiO ₂ ), carbon (C), nitrogen (N), these titanium oxide is present in a form evenly distributed on the nitrogen-doped porous carbon Good initial efficiency and capacity retention characteristics.

Here, the titanium oxide can be stably removed / inserted lithium ions without modification of the crystal structure, but there is a disadvantage of low electrical conductivity, there is a problem of high rate characteristics. However, since nitrogen is doped into the carbon nanofibers and the carbon nanofibers have a porous structure, the cycle characteristics and the high-rate characteristics are improved as these problems are solved.

Specifically, in the negative electrode active material of the present invention, it is preferable that at least one or more of nitrogen or porous carbon, which is a member, is combined with titanium oxide. That is, by combining the nitrogen-doped porous carbon nanofibers with titanium oxide, not only can the degradation of cycle characteristics resulting from the low electrical conductivity of titanium oxide be prevented, but rather the electrical conductivity is improved.

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

Such carbon may be present in amorphous form, particularly in amorphous form at grain boundaries between titanium oxide components.

Such a negative electrode active material of the present invention can be produced by the electrospinning method.

Specifically, as shown in the flowchart of FIG. 1, the method of preparing a negative electrode active material includes preparing an electrospinning solution (S10), preparing a metal oxide-nitrogen-porous carbon nanofiber composite material (S20), and It comprises a step (S30) of heat treating the composite material.

First, an electrospinning solution is prepared by mixing a first solution in which a metal oxide precursor is dissolved, a second solution in which a polymer that is 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 is used. In addition, titanium butoxide (TBO) or metal chloride is used as the metal oxide precursor. Here, the metal chloride salt is titanium isoprooxide (Ti (OCH (CH ₃ ) ₂ ) ₄ ), titanium chloride (TiCl ₄ , or TiCl ₃ ), tin hydrate (SnCl ₂ · H ₂ O) and iron chloride (FeCl ₃ ), Nickel chloride (NiCl ₂ ), copper chloride (CuCl ₂ ), magnesium chloride (MgCl ₂ ), palladium chloride (PdCl ₂ ), cobalt chloride (CoCl ₂ ), tantalum chloride (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 ) It may be any one selected from the group consisting of.

The polymers serving as carbon fiber precursors include polyvinylpyrrolidone (PVP), polymethylmethacrylate (PMMA), polyvinyl alcohol (PVA), and polyvinylacetate (PVAC). ), Polyacrylonitrile (PAN), polyfurfuryl alcohol, cellulose, glucose, polyvinylchloride (PVC), polyacrylic acid, polylactic acid ( polylactic acid, polyethylene oxide (PEO), polypyrrole, polyimide, polyamideimide, polyaramid, polyanimid, polyaniline (PANI), phenol resins, and pitches Any one selected from the group consisting of is used.

The ionic liquid solution mixed for the preparation of the electrospinning solution is ethyl methyl imidazolium chloride (EMIM Cl), ethyl methyl imidazolium dicyanamid (EMIM DCA), ethyl methyl imidazolium trifluoromethanesulfonate (EMIM Otf), ethylmethylimidazolium trifluoromethylsulfonylimide (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, the metal oxide-nitrogen-porous carbon nanofiber composite material is obtained by electrospinning the electrospinning solution prepared using the electrospinning device configured as shown in FIG. 2 (S20). Here, the metal oxide-nitrogen-porous carbon. The nanofiber composite material may specifically be in the form of nitrogen-doped porous carbon nanofibers containing metal oxides.

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

And, electrospinning can be carried out by maintaining the temperature of the chamber containing the electrospinning solution at 70 ℃ or less and applying a voltage of 10 to 25kV while supplying the electrospinning solution at a flow rate of 0.1 to 1mL / h. Here, when the magnitude of the applied voltage is less than 10 kV, the carbon nanofibers of the present invention are difficult to be produced because the voltage is low, and when the magnitude of the voltage is greater than 25 kV, the carbon nanofibers produced 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 Figure 3, after the composite material is first heated up (S31), the first heat treatment (S33) for 3 to 5 hours in an air atmosphere, and then the second temperature (S35), argon (Ar) is made according to the order of the second heat treatment (S37) for 1 to 5 hours under the atmosphere, wherein the first heat treatment (S33) and the second temperature rise (S35) in the air atmosphere is characterized in that the immediately following without a time interval. to be.

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

Through the first heat treatment and the first heat treatment and the first heat treatment (S31, S33), the carbon nanofiber form of the metal oxide-nitrogen-porous carbon nanofiber composite material is stably maintained. The second heat treatment process, the second temperature increase and the second heat treatment (S35, S37), converts the metal oxide precursor into the metal oxide while the form of the carbon nanofibers is maintained. In this case, when the heat treatment process of the nitrogen-doped porous carbon nanofibers containing the metal oxide is performed in excess of 700 ° C., deformation of the nanofiber form may occur or carbon may be exhausted during the heat treatment process.

In addition, in the preparation of the negative electrode active material, it is also possible to change the processing conditions appropriately to change the average size of the metal oxide, the size of the pores and the thickness of the carbon fiber. In addition, the metal oxide used to prepare the negative electrode active material is preferably titanium oxide.

The negative electrode active material thus prepared and a conductive material, a binder, a solvent and the like are mixed together to prepare a slurry, and then coated on a current collector and dried to prepare a negative electrode.

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

On the other hand, as the current collector constituting the negative electrode, a copper, nickel or SUS current collector can be used, of which the copper current collector having the best electrical conductivity is preferable. The negative electrode active material layer formed on the current collector is prepared by mixing a negative electrode active material, a conductive material, a binder, and a solvent to prepare a negative electrode active material composition, and then coating it directly on the current collector, or casting on a separate support and peeling from the support. The obtained negative electrode active material film is obtained by laminating on a current collector.

In addition, as the conductive material used to form the negative electrode active material layer, carbon black, graphite fine particles and the like may be used, but are not limited thereto, and any material that can be used as the conductive material in the art may be used. .

In addition, the binder includes vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethylmethacrylate, polytetrafluoroethylene (PTFE), and mixtures thereof; Or styrene butadiene rubber-based polymer (SBR) and the like can be used, but is not limited to these may be used as long as it can be used as a binder in the art.

As the solvent, N-methylpyrrolidone, ethanol, acetone or water may be used, but not limited thereto, and any solvent may be used as long as it can be used in the art.

When manufacturing a lithium battery using the present invention, the content of the negative electrode active material, the conductive material, the binder, and the solvent can be mixed to the level commonly used in lithium batteries, and the conductive material according to the use and configuration of the lithium battery. At least one of the binder, the solvent, and the solvent may be omitted and mixed.

Meanwhile, the lithium battery may be manufactured by the following method.

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

Then, similarly to the negative electrode, a positive electrode active material composition is prepared by mixing a positive electrode active material, a conductive material, a binder, and a solvent. The positive electrode active material composition is directly coated and dried on an aluminum current collector to prepare a positive electrode, or the positive electrode active material composition is cast on a separate support, and the film obtained by peeling from the support is laminated on the aluminum current collector. It is also possible to produce a positive electrode.

Herein, the positive electrode active material is LiCoO ₂ , LiMn _x O _2x (x = 1, 2), LiNi _{1- x} Mn _x O ₂ (0 <x <1), LiNi _{1- xy} Co _x Mn _y O ₂ (0 = x = 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 to these can be used as long as it can be used as a positive electrode active material in the art.

In addition, the amounts of the positive electrode active material, the conductive material, the binder, and the solvent are mixed at levels commonly used in lithium batteries, and at least one of the conductive material, the binder, and the solvent may be omitted and mixed according to the use and configuration of the lithium battery. Can be.

In some cases, a plasticizer may be 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 may be used as long as it is commonly used in lithium batteries. It is desirable to have low resistance to the ion migration of the electrolyte and excellent electrolytic solution-wetting ability. For example, it is selected from glass fiber, polyester, teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof, and may be in the form of nonwoven or woven fabric.

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

For example, an organic electrolyte may be prepared as an electrolyte of a lithium battery. Such an organic electrolyte is prepared by dissolving a lithium salt in an organic solvent. In this case, any organic solvent may be used as long as it can be used as an organic solvent in the art. For example, propylene carbonate, ethylene carbonate, fluoroethylene carbonate, diethyl carbonate, methylethyl carbonate, methylpropyl carbonate, butylene carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ- Butyrolactone, dioxolane, 4-methyldioxolane, N, N-dimethylformamide, dimethylacetamide, dimethylsulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene , Nitrobenzene, dimethyl carbonate, methyl isopropyl carbonate, ethyl propyl carbonate, dipropyl carbonate, dibutyl carbonate, diethylene glycol, dimethyl ether, or a mixture thereof. In addition, any lithium salt dissolved therein may be used as long as it can be used as a lithium salt in the 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 , LiN (C _x F _{2x + 1} SO ₂ ) (CyF _{2y + 1} SO ₂ ) (where x and y are natural numbers), LiCl, LiI, or mixtures thereof.

The lithium battery thus manufactured 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. Subsequently, the organic electrolyte is injected into the battery case and sealed with a cap assembly to complete the lithium battery. Such a battery case may be cylindrical, rectangular, thin film, or the like. Characteristically, the lithium battery of the present invention may be a thin film battery or a lithium ion battery.

On the other hand, it is possible to manufacture a lithium ion polymer battery 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 negative electrode and a positive electrode employing the negative electrode active material of the present invention to form a battery structure. Next, the battery structure is laminated in a bi-cell structure, impregnated in an organic electrolyte, and finally, the resultant is accommodated in a pouch and sealed to complete a lithium ion polymer battery.

Alternatively, the battery pack may be formed by stacking a plurality of battery structures previously formed in order to manufacture a lithium ion polymer battery, and the battery pack thus manufactured may be used in all devices requiring high capacity and high power.

According to the nitrogen-doped porous carbon nanofibers containing the metal oxide described above and a method of manufacturing the same, it is possible to easily produce several nano titanium oxides inside the nitrogen-doped porous carbon nanofibers, and the nitrogen content and the metal oxide content , The size and content of the pores, the diameter of the carbon fiber, and the size of the metal oxide can be controlled appropriately. As the metal oxide of the present invention, it may be most effective to use titanium oxide.

In addition, since the nitrogen-doped porous carbon nanofibers containing the metal oxide of the present invention exhibit improved capacity and cycle characteristics, the negative electrode and the lithium battery employing the metal oxide can provide excellent electrical properties.

In addition, nitrogen-doped porous carbon nanofibers containing metal oxides are characterized by a very fast electron transfer speed. By applying this, electrode materials and catalysts such as solar cells, fuel cells and lithium air batteries can be prepared. have.

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

Example 1 Anode Material

0.5 g of polyvinylpyrrolidone (PVP) and 0.54 g of polyvinylpyrrolidone (PVP) prepared by mixing 1.5 g of titanium butoxide (TBO) and 3 mL of acetic acid with 3 mL of ethanol were mixed for 30 minutes. A solution prepared by dissolving in (second solution) and an ionic liquid solution containing 0.1 mL of ethyl methyl imidazolium dicyanamid (EMIM DCA) were homogeneously mixed for 30 minutes to prepare an electrospinning solution. (S10)

The electrospinning liquid thus prepared was placed in a syringe, and the electrospinning was performed by applying a voltage of 20 kV while supplying the inside of the electrospinning apparatus at a flow rate of 0.5 mL / h using a syringe pump. At this time, the distance from the tip of the nozzle to the collecting part was fixed at 20 cm, and nitrogen-doped porous carbon nanofibers were obtained using the drum type collecting part for uniform collection.

Nitrogen doped porous carbon nanofibers obtained through this process were oxidized at 280 ° C. for 5 hours under an air atmosphere to stabilize the structure, and carbonization was performed at 550 ° C. under an argon atmosphere for 3 hours to carry out nitrogen doping containing metal oxides. The prepared porous carbon nanofiber negative electrode active material was prepared. (S30)

Example 2 Anode Material

1.5 g of titanium butoxide (TBO) and 3 mL of acetic acid were added to 3 mL of ethanol, followed by mixing for 30 minutes to dissolve 0.514 g of polyvinylpyrrolidone (PVP), 0.514 g, of polyvinylpyrrolidone (PVP). An electrospinning solution was prepared by homogeneously mixing a prepared solution (second solution) and an ionic liquid solution containing 0.3 mL of ethylmethylimidazolium dicyanamid (EMIM DCA) for 30 minutes.

The electrospinning liquid thus prepared was placed in a syringe, and the electrospinning was performed by applying a voltage of 20 kV while supplying the inside of the electrospinning apparatus at a flow rate of 0.5 mL / h using a syringe pump. At this time, the distance from the tip of the nozzle to the collecting part was fixed to 20 cm, and nitrogen-doped porous carbon nanofibers were obtained using the drum type collecting part for uniform collecting.

Nitrogen doped porous carbon nanofibers obtained through this process were oxidized at 280 ° C. for 5 hours under an air atmosphere to stabilize the structure, and carbonization was performed at 550 ° C. under an argon atmosphere for 3 hours to carry out nitrogen doping containing metal oxides. The prepared porous carbon nanofiber negative electrode active material was prepared.

Example 3 Anode Material

1.5 g of titanium butoxide (TBO) and 3 mL of acetic acid were added to 3 mL of ethanol, followed by mixing for 30 minutes. The prepared solution (second solution) and the ionic liquid solution containing 0.5 mL of ethyl methyl imidazolium dicyanamid (EMIM DCA) were homogeneously mixed for 30 minutes to prepare an electrospinning solution.

The electrospinning liquid thus prepared was placed in a syringe, and the electrospinning was performed by applying a voltage of 20 kV while supplying the inside of the electrospinning apparatus at a flow rate of 0.5 mL / h using a syringe pump. At this time, the distance from the tip of the nozzle to the collecting part was fixed to 20 cm, and nitrogen-doped porous carbon nanofibers were obtained using the drum type collecting part for uniform collecting.

Nitrogen doped porous carbon nanofibers obtained through this process were oxidized at 280 ° C. for 5 hours under an air atmosphere to stabilize the structure, and carbonization was performed at 550 ° C. under an argon atmosphere for 3 hours to carry out nitrogen doping containing metal oxides. The prepared porous carbon nanofiber negative electrode active material was prepared.

Example 4 Anode and Lithium Battery (Coin Cell)

A slurry was prepared by mixing 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) in agate mortar. The slurry thus prepared was coated with a doctor blade to a thickness of about 80 μm on a copper foil, and dried at room temperature for 2 hours, and then dried once again for 2 hours at a vacuum atmosphere and 120 ° C. to prepare a negative electrode.

On the other hand, after preparing a cathode prepared in this way, and a cathode made of lithium metal, using a polypropylene separator (Celgard 2400) as a separator, 1M LiPF ₆ is EC (ethylene carbonate) + DEC (diethylene carbonate) (1: 1 volume ratio) to prepare a lithium battery (coin cell) of the CR-2032 standard using a solution dissolved in the electrolyte.

Example 5 Anode and Lithium Battery

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

Example 6 Anode and Lithium Battery

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

&Lt; Comparative Example 1 &

1.5 g of titanium butoxide (TBO) and 3 mL of acetic acid were added to 3 mL of ethanol and mixed for 30 minutes to prepare a solution (first solution) and 0.536 g of polyvinylpyrrolidone (PVP) in 7 mL of ethanol. An electrospinning solution was prepared by homogeneously mixing the solution (second solution) for 30 minutes.

The electrospinning liquid thus prepared was placed in a syringe, and the electrospinning was performed by applying a voltage of 20 kV while supplying the inside of the electrospinning apparatus at a flow rate of 0.5 mL / h using a syringe pump. At this time, the distance from the tip of the nozzle to the collecting part was fixed at 20 cm, and nitrogen-doped carbon nanofibers were obtained using the drum type collecting part for uniform collecting.

Nitrogen-doped carbon nanofibers obtained through this process were oxidized at 280 ° C. for 5 hours under an air atmosphere to stabilize the structure, and carbonization was performed at 550 ° C. under an argon atmosphere for 3 hours to carry out nitrogen doping containing metal oxides. A carbon nanofiber negative electrode active material was prepared.

&Lt; Comparative Example 2 &

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

In summary, the preferred embodiments of the present invention prepared as described above are shown in Table 1 below.

division material Ionic Liquid (IL) PVP / Ethanol Example 1 Anode active material TiO ₂ + PVP + Ionic Liquid 0.1mL 0.529g / 7.4mL 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 0.5g / 7mL Example 4 Cathode and
Lithium battery A negative electrode produced using the negative electrode active material of Example 1,
And lithium batteries employing the same Example 5 Cathode and
Lithium battery A negative electrode manufactured using the negative electrode active material of Example 2,
And lithium batteries employing the same Example 6 Cathode and
Lithium battery A negative electrode manufactured using the negative electrode active material of Example 3,
And lithium batteries employing the same Comparative Example 1 Anode active material TiO ₂ + PVP - 0.536g / 7.5mL Comparative Example 2 Cathode and
Lithium battery A negative electrode manufactured using the negative electrode active material of Comparative Example 1,
And lithium batteries employing the same

4A to 4C are scanning electron microscope (SEM) photographs of the negative electrode active materials prepared in Examples 1, 2, and 3, and FIG. 4D is a scanning electron microscope of the negative electrode active materials prepared in Comparative Example 1. FIG. (SEM) picture. As shown in the photographs of FIGS. 4A to 4D, both the porous carbon nanofibers prepared by adding the ionic liquid (FIGS. 4A to 4C) and the carbon nanofibers prepared without adding the ionic liquid (FIG. 4D) are fibers. The diameter of is in the range of 200 to 300 um, showing a fibrous one-dimensional form. Thus, it can be confirmed that the addition of the ionic liquid does not affect the shape and size (diameter) of the carbon nanofibers forming the negative electrode active material.

Figure 5a is a transmission electron microscope (TEM) photograph of the negative electrode active material prepared in Example 2. Here, looking at the high-magnification TEM photograph of the negative electrode active material of Example 2, it can be seen that not only metal oxides but also pores are formed inside the carbon nanofibers forming the negative electrode active material. In addition, in the selected area diffraction pattern (SADP) photograph of Example 2 anode active material of FIG. 5B, in Example 2 anode active material using an ionic liquid, the average size of the crystal region is 10 nm and the lattice distance is 0.189 nm. It can be seen that the fringe of the (200) plane of the anatase titanium oxide is well represented. This is because the polyvinylpyrrolidone (PVP) used as the ionic liquid and the carbon fiber precursor has different carbonization temperatures, which creates pores during the heat treatment process, so that the carbon nanofibers maintain the porous form. Because.

As such, when the carbon nanofibers are formed in a porous form, lithium ions can be easily diffused in a direction perpendicular to the long axis direction of the carbon nanofibers, thereby improving high rate characteristics. In addition, carbon and titanium oxides are organically connected, thereby providing a good electrical connection between the particles, thereby reducing the resistance between grain boundaries. In addition, since the carbon fiber has a porous form, the reaction area of titanium oxide and lithium ions is increased to increase the effective amount.

Meanwhile, as a result of elemental analysis of EDS (energy dispersive x-ray spectroscopy) of the negative electrode active material of FIG. 5C, titanium (Ti), oxygen (O), carbon (C), and nitrogen (N) are uniform in the porous carbon nanofibers. It can be confirmed that the distribution.

On the other hand, in Comparative Example 1 in which the ionic liquid was not used, as shown in the TEM photograph of FIG. 6, the carbon nanofibers showed a dense form without pores in the fibers.

That is, in the present invention, by appropriately adjusting and adding the ionic liquid, a nitrogen-doped porous carbon nanofiber containing a metal oxide is prepared, and the effective amount can be increased and fast charge and discharge by using this as a negative electrode material of a lithium secondary battery. It was made.

7 is an X-ray diffraction (XRD) graph of Example 2 and Comparative Example 1. FIG. In Example 2, crystalline anatase-type titanium oxide was formed in nitrogen-doped amorphous carbon nanofibers, and 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. As a result, when preparing the nitrogen-doped carbon nanofibers containing the metal oxide by adding the ionic liquid, it can be seen that the ionic liquid serves to increase the crystallinity 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 are clearly seen in the nitrogen-doped porous carbon fibers containing metal oxides. 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 carbon-carbon bonds (CC 285.1 eV), carbon-nitrogen bonds (C = N 286.7 eV, CN 288 eV) and carbon-oxygen bonds (CO 289.5 eV). The N 1s peak appears as a mixed bond due to various oxidation states of nitrogen as shown in the C 1s peak. The CN bond, the single bond of the carbon-nitrogen bonds, is seen at 398.5 eV, and the double bond C = N is shown at 400.8 eV. This is an effect that occurs when nitrogen is doped in the carbon, when the carbon containing nitrogen can have a higher electrical conductivity than carbon containing no nitrogen, thereby enabling high-speed charging and discharging.

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

10 shows the results of charge and discharge experiments of Example 4, Example 5, Example 6, and Comparative Example 2. FIG.

Specifically, each of the negative electrode active materials of Examples 1, 2, 3, and Comparative Example 1 included in the lithium batteries of Examples 4, 5, and 6, and the lithium batteries of Comparative Example 2, respectively. The battery was discharged at a current of 30 mA per gram until the voltage reached 1.0 V (vs. Li), and again charged at the same current until the voltage reached 3.0 V (vs. Li). Subsequently, charging and discharging were repeated a total of 30 times in the same current and voltage section. The room temperature charge and discharge test results of FIG. 10 are shown in the following [Table 2].

Initial Capacity
(mAh / g) After 28 charge / discharge cycles
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 is confirmed that the lithium battery of Example 5 has a smaller decrease in lithium battery capacity after room temperature charge / discharge experiments than the decrease in lithium battery capacity after room temperature charge / discharge experiments of the lithium battery of Comparative Example 2. Can be. That is, the lithium battery of Example 5 not only showed a slightly higher initial capacity than the lithium battery of Comparative Example 2, but also shows that the capacity retention rate was remarkably improved.

11 shows results of room temperature rate characteristics of lithium batteries of Example 5 and Comparative Example 2. FIG. Specifically, while maintaining the same voltage of the lithium battery of Example 5 and Comparative Example 2, the current value during charging was the same, while the current value during discharge was differently repeated 10 times for each charge and discharge step. At this time, the current value during charging is 30mA, 150mA, 300mA, 900mA, 1500mA for each charge / discharge repeating step, and the current value per discharge of 1g of negative electrode active material included in each lithium battery reaches 1.0V (vs. Li). The battery was discharged until the current value was charged to 30 V at a current of 30 mA until the voltage reached 3.0 V (vs. Li). Referring to this graph, it can be seen that the rate characteristic of the lithium battery of Example 5 is superior to that of the lithium battery of Comparative Example 2.

12 shows impedance test results of lithium batteries of Example 5 and Comparative Example 2. FIG. Specifically, the battery was discharged at a current of 30 mA per 1 g of each negative electrode active material included in each of the lithium batteries of Example 5 and Comparative Example 2 until the voltage reached 1.0 V (vs. Li), and the voltage was again generated at the same current. Charged to 3.0 V (vs. Li). Subsequently, charging and discharging were repeated 20 times in the same current and voltage section, and then impedance analysis was performed while the voltage was 3.0V (vs. Li). Referring to this graph, it can be seen that the lithium battery of Example 2 is more stable than the lithium battery of Comparative Example 2.

According to the manufacturing method of the negative electrode active material as described above, it is possible to easily prepare a nitrogen-doped porous carbon nanofibers in which the nano-sized metal oxide is dispersed, the nitrogen content, the titanium oxide content, the diameter of the carbon fiber and the titanium oxide Size can be controlled appropriately.

In addition, by employing a nitrogen-doped porous carbon fiber containing the metal oxide of the present invention as a negative electrode active material, it is possible to manufacture a negative electrode and a lithium battery having excellent electrical properties, stability, and lifespan characteristics.

In addition, by applying an extremely fast electron transfer speed of the negative electrode active material of the present invention, it is possible to produce electrode materials and catalysts such as solar cells, fuel cells, lithium air batteries and the like.

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

1: chamber 2: electrospinning nozzle
3: collector 4: power supply
5: collector controller

Claims (14)

Preparing an electrospinning solution by mixing a first solution in which a metal oxide precursor is dissolved, a second solution in which a polymer that is a carbon fiber precursor is dissolved, and an ionic liquid solution for forming a porous structure with nitrogen doping;
Electrospinning the electrospinning solution to prepare a metal oxide-nitrogen-porous carbon nanofiber composite material; And
And heat treating the composite material.
The method according to claim 1,
The solvent of the first solution and the second solution is any one selected from the group consisting of distilled water, dimethylformamide, phenol, toluene, ethanol, methanol, and propanol.
The method according to claim 1,
The metal oxide precursor is a titanium butoxide (TBO) or a metal chloride salt manufacturing method of the negative electrode active material.
The method according to claim 3,
The metal chloride salt is titanium isoprooxide (Ti (OCH (CH ₃ ) ₂ ) ₄ ), titanium chloride (TiCl ₄ , or TiCl ₃ ), tin hydrate (SnCl ₂ · H ₂ O) and iron chloride (FeCl ₃ ), Nickel chloride (NiCl ₂ ), copper chloride (CuCl ₂ ), magnesium chloride (MgCl ₂ ), palladium chloride (PdCl ₂ ), cobalt chloride (CoCl ₂ ), tantalum chloride (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 ) Method for producing a negative electrode active material any one selected from the group consisting of.
The method according to claim 1,
The polymer is polyvinylpyrrolidone (PVP), polymethylmethacrylate (PMMA), polyvinyl alcohol (PVA), polyvinylacetate (PVAC), polyacrylonitrile PAN, polyfurfuryl alcohol, cellulose, glucose, polyvinylchloride (PVC), polyacrylic acid, polylactic acid, polyethylene oxide oxide; PEO, polypyrrole, polyimide, polyamideimide, polyaramid, polyaniline, polyaniline, PANI, phenol resin, and pitch Method for producing a negative electrode active material.
The method according to claim 1,
The ionic liquid solution is ethyl methyl imidazolium chloride (EMIM Cl), ethyl methyl imidazolium dicyanamid (EMIM DCA), ethyl methyl imidazolium trifluoromethanesulfonate (EMIM Otf), ethyl methyl imidazolium Trifluoromethylsulfonylimide (EMIM TFSI), ethylmethylimidazolium acetate (EMIM Ac), ethylmethylimidazolium hydrate (EMIM OH), ethylmethylimidazolium diethylphosphate (EMIM DEP), ethylmethyl Midazolium methyl carbonate (EMIM MeOCO ₂ ), ethylmethylimidazolium lactate (EMIM Lactate), butylmethylimidazolium chloride (BMIM Cl), butylmethylimidazolium methylcarbonate solution (BMIM MeOCO ₂ ), butylmethyl Midazolium trifluoromethanesulfonate (BMIM Otf), butylmethylimidazolium trifluoromethylsulfonylimide (EMIM TFSI), butylmethylimidazolium trifluoroacetate (BM IM CF ₃ CO ₂ ), and dimethylimidazolium methanesulfonate (MMIM CH ₃ SO ₃ ) any one selected from the group consisting of negative electrode active material.
The method according to claim 1,
Preparing the composite material,
The electrospinning solution is maintained at 70 ° C. or lower, the electrospinning solution is supplied at a flow rate of 0.1 to 1 mL / h, and at the same time, the electrospinning method is performed by applying a voltage of 10 to 25 kV.
The method according to claim 1,
The heat treatment step,
Firstly raising the composite material to 280 ° C;
Heat treating the composite material in an air atmosphere for 3 to 5 hours after the first temperature increase;
Heating up the composite material to 500 ° C. after the heat treatment in the air atmosphere; And
Heat treating the composite material in an argon (Ar) atmosphere for 1 to 5 hours after the second temperature increase,
The step of heat treatment under the air atmosphere and the step of raising the secondary temperature is a method for producing a negative electrode active material immediately after.
In the negative electrode formed by coating a slurry mixed with a negative electrode active material, a conductive material, a binder, and a solvent on a current collector,
The negative electrode active material is a negative electrode made of porous carbon nano fibers doped with nitrogen containing a metal oxide.
The method of claim 9,
The porous carbon nanofibers have an average particle diameter of 0.1 to 1μm or less.
The method of claim 9,
The metal oxide is a titanium oxide anode.
In a lithium battery comprising a positive electrode, a negative electrode, and a separator,
The negative electrode is a lithium battery formed of a negative electrode active material consisting of porous carbon nanofibers doped with nitrogen containing a metal oxide.
The method of claim 12,
The porous carbon nanofibers have an average particle diameter of 0.1 or more and 1μm or less.
The method of claim 12,
The metal oxide is a titanium oxide lithium battery.

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