KR20110107211A - Preparation method of li4ti5o12 nanofibers with fast rechargeable characteristics, and lithium ion batteries thereof - Google Patents

Abstract

The present invention comprises the steps of (a) mixing the source material of lithium (Li) and the source material of titanium (Ti) appropriately to enable the electrospinning to prepare an intermediate mixture, (b) the two kinds of the intermediate mixture and the electrospinning possible Preparing an intermediate compound by mixing the above-described high molecular material, (c) producing the nanofiber-shaped web in which the intermediate compound is adjusted to a diameter of about 5 to 1000 nm through electrospinning under appropriate voltage and flow conditions. And (d) heat treating the web to produce lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) in the form of nanofibers having a diameter in the range of about 5 to 1000 nm. It provides a lithium secondary battery having a lithium titanium oxide nanofiber prepared as a negative electrode active material.
The present invention can implement the nanofiber form of the diameter size is controlled by using the electrospinning when manufacturing the lithium titanium oxide nanofibers, through which the charge exchange reaction on the surface to activate a high charge and discharge rate (charge / discharge) rate) property can be maintained.

Description

A method of manufacturing lithium titanium oxide nanofibers having improved charge and discharge characteristics at high charge and discharge rates, and a lithium secondary battery comprising the same {Preparation method of Li4Ti5O12 nanofibers with fast rechargeable characteristics, and lithium ion batteries

The present invention relates to a method for producing lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) nanofibers and a lithium secondary battery comprising the same, and more particularly, as a negative electrode active material of a lithium secondary battery, high energy density in a fast charge and discharge environment, The present invention relates to a method for producing lithium titanium oxide nanofibers having high capacity retention rate and long cycle characteristics, and a lithium secondary battery including the same.

In recent years, as the issues such as fossil fuels, global warming caused by carbon dioxide, and environmental pollution, which are being exhausted, electric vehicles (EVs) and hybrids that can replace automobiles using fossil fuels as energy sources Interest in hybrid electric vehicles (HEVs) is exploding. Lead-acid batteries, lithium secondary batteries, solar cells, hydrogen batteries, and the like have been studied as energy sources of such electric vehicles, and among them, interest in lithium secondary batteries having high energy density, high output, and good cycle characteristics is the greatest. (Nature 2001, 414, 359) Despite these advantages, however, the US Department of Energy (DOE) does not support the use of commercially available lithium secondary batteries as energy sources for electric and hybrid electric vehicles. There is not enough to satisfy the criteria suggested by.

The lithium secondary battery is composed of a positive electrode and a negative electrode active material capable of reversible insertion and desorption of lithium ions, a separator to prevent electrical contact between the electrode, and an organic electrolyte and a polymer electrolyte as a medium for the movement of lithium ions between the active material of the electrode, Electrical energy is stored or released by a change in chemical potential upon reversible insertion / desorption of lithium ions at the electrode.

Various lithium transition metal compounds (LiCoO ₂ , LiMnO ₂ , LiMn ₂ O _4, etc.) are used as the positive electrode active material of the lithium secondary battery. (Nature 2001, 414, 359 .; Nature Materials 2005, 4, 336 .; Mat. Sci. Eng. R 2001, 33, 109)

On the other hand, as a negative electrode active material of a lithium secondary battery, various carbon-based materials such as mesocarbon microbeads (MCMB), natural graphite, hard carbon, and soft carbon are used. (Carbon 2000, 38, 183) In the carbon-based material, graphite is widely commercialized and used because of its low price, high capacity retention, and theoretical capacity of 372 mAh / g. In the case of the graphite, since the charge and discharge reaction occurs at 0.1 ~ 0.2V compared to the oxidation / reduction chemical potential of lithium / lithium ions, it can exhibit a high discharge voltage of 3.5V or more.

However, when the carbon-based material is used as the negative electrode active material, the non-conductive layer formed between the electrode and the electrolyte at about 0.7 V relative to the oxidation / reduction chemical potential of lithium / lithium ion is used for the SEI layer (Solid Electrolyte Interphase layer). The capacity and charge and discharge characteristics of the lithium secondary battery can not be prevented and the performance is rapidly reduced at high charge and discharge speeds. Therefore, the lithium secondary battery can be used as an anode active material for an electric vehicle or a hybrid electric vehicle in which high speed charge and discharge performance is essential. Is impossible. (Electrochem. Solid. St. 2001, 4, A109)

Li ₄ Ti ₅ O ₁₂ is a representative material that is being actively researched as a negative electrode active material that can replace the carbon-based material, the most characteristic of this material is the spinel structure and lock in the lithium insertion / desorption process Changes between the rock-chair structure maintains a space in which lithium ions can move with little change in the volume of the material itself, and the charge-discharge reaction occurs around 1.55V relative to the oxidation / reduction chemical potential of lithium / lithium ions. will be. In addition, since the chemical potential section in which the charge-discharge reaction occurs is very narrow, it is possible to manufacture a lithium secondary battery having a very stable output characteristics. Due to this feature, the insertion and desorption process of lithium can be faster than the carbon-based material, and at the same time has a better cycle characteristics because there is little volume change. In addition, since the solid electrolyte interfacial layer (SEI layer) has a higher charge-discharge reaction potential than the chemical potential to be produced, it is possible to prevent the performance degradation that can occur by preventing the generation of the solid electrolyte interfacial layer (SEI layer). (J. Electrochem. Soc. 1999, 146, 4348 .; Adv. Mater. 2006, 18, 3169 .; J. Power Sources 2004, 129, 38)

Currently, research is being conducted to prepare Li ₄ Ti ₅ O ₁₂ by various methods (hydrothermal method, ball-milling method, etc.) (J. Electrochem. Soc. 1995, 142, 1431; J. Power Sources 1999, 81 , 300; Electrochem.Comm. 2005, 7, 894; Adv. Mater. 2005, 17, 865)

However, in the case of Li ₄ Ti ₅ O ₁₂ manufacturing method known through the existing research, it is difficult to produce a Li ₄ Ti ₅ O ₁₂ having a uniform or small size is impossible or continuous production or mass production. In addition, since the metal oxide has a low electrical conductivity of about 10 ^-8 S / cm, the charging and discharging performance is deteriorated at a very high charge and discharge rate as in the case of a carbon-based material (J Eur Ceram Soc 2007, 27, 909)

In order to overcome the problems described above, by using a composite electrospinning method, continuous production and mass production are possible, and have a uniform thickness having improved capacity and cycle characteristics compared to the existing Li ₄ Ti ₅ O ₁₂ at high charge and discharge rates. There is a need for a new method for manufacturing Li ₄ Ti ₅ O ₁₂ nanofibers and lithium secondary batteries using the same.

The present invention relates to a lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) nanofiber of uniform thickness, and relates to a negative electrode active material of a lithium secondary battery having stable cycle characteristics at a fast charge and discharge rate.

Lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) nanofiber of the present invention (a) step of preparing an intermediate mixture by appropriately mixing the source material of lithium (Li) and the source material of titanium (Ti) to enable electrospinning (b) mixing the intermediate mixture with two or more polymer materials capable of electrospinning to prepare an intermediate compound, and (c) the intermediate compound at an appropriate voltage and flow rate, through electrospinning, having a diameter of about 5 to Preparing a nanofiber-shaped web controlled to a range of 1000 nm and (d) heat treating the web to form lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) in a nanofiber form having a diameter of about 5 to 1000 nm. It can be obtained through a method comprising the step of preparing.

A more detailed description of the invention will be described later in detail with reference to the drawings in the Examples section.

The present invention provides a novel method for producing lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) nanofibers of uniform thickness. That is, the present invention by using the electrospinning in the production of lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ), it is possible to implement a nanofiber-type tissue of the diameter size controlled, thereby activating the charge exchange reaction on the surface To maintain a high charge / discharge rate characteristic.

1 is a field emission scanning electron microscopy (FE-SEM) image of a web of lithium source material-titanium source material-composite polymeric nanofibers prepared according to the method of the present invention.
FIG. 2 is a lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) nanofiber field emission scanning electron microscope (FE-SEM) image prepared according to the method of the present invention.
FIG. 3 is a diagram illustrating structure analysis data using an X-ray diffraction pattern (XRD) of lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) nanofibers prepared according to the method of the present invention.
4 is a graph of charge and discharge curves at 1 V to 2.5 V of a battery using lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) nanofibers prepared according to the method of the present invention.
5 to 7 are graphs showing cycle characteristics according to various charge and discharge rates at 1 V to 2.5 V of a battery using lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) nanofibers prepared according to the method of the present invention. .

Simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

Meanwhile, in describing the first to third embodiments according to the present invention with reference to the accompanying drawings, the identification number required for describing the result according to the embodiment uses three digits and the number of units of the day is the same. It means the same embodiment. That is, 101, 201, and 301 mean Embodiment 1, 102, 202, and 302 mean Embodiment 2, and 103, 203, and 303 mean Embodiment 3.

Lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) nanofibers of the uniform size according to the present invention is (a) the intermediate material by appropriately mixing the source material of lithium (Li) and the source material of titanium (Ti) to enable electrospinning Preparing a mixture, (b) mixing the intermediate mixture with two or more polymer materials capable of electrospinning to prepare an intermediate compound, and (c) subjecting the intermediate compound to electrospinning at suitable voltage and flow rate conditions. Preparing a nanofiber-shaped web having a diameter adjusted to a range of about 5 to 1000 nm, and (d) heat treating the web to form a nanofiber type lithium titanium oxide (Li ₄ Ti) having a diameter of about 5 to 1000 nm. ₅ O ₁₂ ) can be obtained through a method comprising the step of preparing.

A detailed description of each of these steps follows. Firstly, the source material of lithium and the titanium source material are mixed properly to enable electrospinning. At this time, the source material of lithium used is not limited to any organic metal material containing lithium, such as lithium acetate (Lithium Acetate), lithium hydroxide (Lithium Hydroixde). The titanium source material is not limited as long as it is an organometallic material including titanium, such as titanium iso-propoxide, titanium butoxide, and the like. The solvent used when mixing the lithium source material and the titanium source material is N, N-dimethylformamide (DMF), N, N-diethylformamide (N, N-diethylformamide; DEF ), Dimethyl sulphoxide (DMSO), N-methylpyrrolidone (N-methylpyrrolidone; NMP) and the like, any polar solvent is not limited. In addition, in the case of the source material of lithium, since the mixing in the organic solvent is not smooth, mixing using a weak acid such as acetic acid, benzoic acid, formic acid, etc. can do.

In order to enable electrospinning, a composite polymer solution that can be mixed with the lithium and titanium source mixed solution is prepared. At this time, the polymer used is poly-acrylonitrile (PAN), poly-methylmethacrylate (PMMA), poly-ethylene oxide (Poly-ethyleneoxide) well dissolved in the solvent of the mixed solution. ; PEO) and the like, but are not limited to any. More specifically, in order to facilitate the electrospinning and secure thermal stability at the same time to prepare a composite polymer solution using two or more polymers.

The lithium, titanium source mixed solution and the composite polymer solution is stirred at room temperature for 12 hours or more (500 to 1000 rpm) to prepare a solution capable of electrospinning.

Using a lithium, titanium source-composite polymer solution prepared by the above method, it is possible to produce a web consisting of nanofibers with a diameter adjusted in the range of 5 to 1000 nm through electrospinning, and keep the diameter at 200 nm or less. It is desirable to. When the electrospinning is carried out, a voltage of about 20 kV to 30 kV is applied to the nozzle and the current collector is grounded to form an electric field.

The nanofiber-form web prepared by the above method may be heat-treated in an inert gas atmosphere to prepare nanofiber-type lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) having a diameter adjusted in the range of 5 to 1000 nm. It is desirable to keep the size below 200 nm.

The lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) nanofibers obtained through the present invention may be usefully used as a negative electrode active material of a lithium secondary battery. The lithium secondary battery is composed of a negative electrode, a positive electrode, an electrolyte, and a separator.

 The negative electrode used in the lithium secondary battery is prepared using a negative electrode active material according to the present invention, a conductive agent to improve the electrical conductivity, a current collector, a binder to support the negative electrode constituent material to be bonded to the current collector, wherein The proportion of the negative electrode active material, the conductive agent, and the binder is in accordance with the ratio usually used in the production of a lithium secondary battery. More specifically, the negative electrode is prepared by mixing the negative electrode active material, the conductive agent, and the binder using a solvent and then applying the current to the current collector to completely remove the solvent, and the thickness of the coating is maintained at a thickness of 10 μm to 50 μm. desirable. The current collector used at this time is usually copper, but is not limited thereto.

The conductive agent may include carbon black, acetylene carbon, carbon nanotubes (CNT), carbon nanofibers (CNF), and the like, but are not limited thereto.

The binder is poly-vinylidene fluoride (PVDF), poly-vinylidene fluoride / hexafluoroethylne copolymer (PVDF-HFP), poly-tetrafluoro Ethylene (Poly-tetrafluoroethylene; PTFE) and mixtures thereof, and the like, but is not limited thereto.

The solvent includes N-methylpyrrolidone (NMP), acetone, tetra hydrofuran (THF), n-hexane (n-Hexane), and the like. Anything is not limited.

The cathode is manufactured through the same process as the fabrication of the anode, using a cathode active material, a conductive agent to improve electrical conductivity, a current collector, and a binder to support the current-carrying material to bond with the current collector. In this case, the current collector used is usually aluminum, but is not limited thereto.

The conductive agent may include carbon black, acetylene carbon, carbon nanotubes (CNT), carbon nanofibers (CNF), and the like, but are not limited thereto.

The binder is poly-vinylidene fluoride (PVDF), poly-vinylidene fluoride / hexafluoroethylne copolymer (PVDF-HFP), poly-tetrafluoro Ethylene (Poly-tetrafluoroethylene; PTFE) and mixtures thereof, and the like, but is not limited thereto.

The solvent includes N-methylpyrrolidone (NMP), acetone, tetra hydrofuran (THF), n-hexane (n-Hexane), and the like. Anything is not limited.

The separator used in the lithium secondary battery may include poly-vinylidene fluoride (PVDF), poly-propylene (PP), poly-ethylene (PE), and multilayer films thereof. Mixed membranes and mixed multilayer membranes may be used, but any is not limited.

As the electrolyte used in the lithium secondary battery, a non-aqueous solvent containing a lithium salt and a solid electrolyte in which they are known are used.

Lithium salts used in the electrolyte may include LiAlCl ₄ , LiAlO ₄ , LiAsF ₆ , LiBF ₄ , LiCl, LiClO ₄ , LiPF ₆ , but are not limited thereto.

The non-aqueous solvent used in the electrolyte is ethylene carbonate (Ethylene Carbonate; EC), propylene carbonate (Prophylene Carbonate; PC), butylene carbonate (Buthylene Carbonate; BC), dimethyl carbonate (Dimethyl Carbonate; DMC), methyl ethyl carbonate ( Methylethyl Carbonate (MEC), Diethyl Carbonate (DEC), and the like, and these may be used alone or in plurality. However, it is not limited to this. In addition, the non-aqueous solvent including the lithium salt is a known polymer such as poly-acrylonitrile (PAN), poly-ethyleneoxide (PEO) and solids such as LiI and Li ₃ N. Electrolytes can also be used.

Lithium secondary batteries produced using the negative electrode, the positive electrode, the separator and the electrolyte can be classified into cylindrical, coin type, pouch type, etc. according to their shape, and lithium ion battery, lithium ion polymer battery, lithium according to the electrolyte and the separator. It can be classified as a polymer battery. Since the manufacturing method and structure of each battery are well known in the art, detailed description thereof will be omitted.

In the following Examples will be described in more detail with respect to the present invention, the following examples do not limit the scope of the invention.

Example 1

Hereinafter, embodiments of the present invention will be described in detail. However, this is presented by way of example, the present invention is not limited by the embodiment, the present invention is defined by the scope of the claims described later.

In an embodiment of the present invention, lithium hydroxide (LiOH), titanium iso-propoxide, N, N-dimethylformamide (N, N-Dimethylformamide; DMF), acetic acid ), Pyridine, poly-acrylonitrile (PAN), and poly-methylmethacrylate (PMMA) were used as starting materials.

In this example, first, 0.1893 g of lithium hydroxide (manufactured by Aldrich) and 2.99 ml of titanium isopropoxide (manufactured by Aldrich) were used, 6 ml of N, N-dimethylformamide (from Daejeong Chemical), and acetic acid (from tablet). 0.5 ml of chemicals) and 0.001 g of pyridine (Aldrich) were mixed in a mixed solvent and stirred at room temperature for 12 hours to prepare a lithium and titanium source solution.

In addition, a composite polymer solution is prepared to electrospin the lithium and titanium source solution. 0.6 g of poly-acrylonitrile (Aldrich) and 1.4 g of poly-methyl methacrylate (Aldrich) were mixed with 10 ml of N, N-dimethylformamide (from Daejeong Chemical Co., Ltd.) Stirring for a time to prepare the composite polymer solution. Thereafter, the composite polymer solution cooled to room temperature in air is mixed with the lithium and titanium source solution and stirred for 1 hour to prepare a lithium, titanium-composite polymer mixed solution.

Next, the lithium, titanium-composite polymer mixed solution is electrospun. A voltage of 25 kV was applied to a 0.2 mm diameter nozzle about 21 cm away from the current collector and electrospun for about 2 hours at a rate of 1.5 ml / hr to obtain a web of lithium source material-titanium source material-composite polymer nanofiber form. .

Then, the lithium, titanium-composite polymer nanofiber type web is heated to 800 ° C. at a heating rate of 5 ° C./min in a tube-type electric furnace, and then heat treated for 6 hours to obtain lithium titanium oxide nanofibers.

Example 2

Except for 1.0g of poly-acrylonitrile (manufactured by Aldrich) and 1.0g of polymethyl methacrylate (manufactured by Aldrich) in Example 1, lithium titanium oxide nanofibers were obtained under the same conditions.

Example 3

The lithium titanium oxide nanofibers were obtained in the same manner as in Example 1 except for 1.4 g of poly-acrylonitrile (manufactured by Aldrich) and 0.6 g of poly-methyl methacrylate (manufactured by Aldrich).

Example 1  And test for 3 to 3

Field emission scanning electron microscope (FE-SEM) of the lithium source material-titanium source material-composite polymer nanofiber web obtained in the spinning process of Example 1 (101), Example 2 (102), and Example 3 (103) ). As can be seen in Figure 1 it can be seen that the nanofiber web of about 200 nm can be obtained through electrospinning.

The lithium titanium oxide nanofibers obtained through the heat treatment of Example 1 (201), Example 2 (202) and Example 3 (203) were analyzed by using a field emission scanning electron microscope (FE-SEM). As can be seen in Figure 2, in the case of Example 1, the nanofiber form was not well maintained after the heat treatment process, in the case of Example 2 and Example 3 it can be seen that the nanofiber form was well maintained. It can also be seen that the diameter is maintained at about 100-150 nm.

The lithium titanium oxide nanofibers prepared in Examples 1, 2, and 3 were analyzed using a X-ray diffractometer (XRD; X-ray diffraction). As can be seen in Figure 3, it can be confirmed that the lithium titanium oxide was prepared through the above embodiment.

In addition, a coin van battery was manufactured using the prepared lithium titanium oxide nanofibers as a negative electrode active material, and an electrochemical test was performed.

FIG. 4 is a graph of charge and discharge curves at 1 V to 2.5 V of a coin panel battery using lithium titanium oxide nanofibers prepared in Examples 1 (401), 2 (402), and 3 (403). , Charging and discharging rate at this time is 50 mA / g. Through this, the charge and discharge capacity of the lithium titanium oxide prepared in Example 2 and Example 3 having a nanofiber form is more than the charge and discharge capacity of the lithium titanium oxide prepared in Example 1 does not have a nanofiber form It can be seen that it is large, and this value is confirmed to be close to 172 mAh / g, which is the theoretical charge / discharge capacity of lithium titanium oxide.

5 to 7 show coin cell batteries using lithium titanium oxide nanofibers prepared in Example 1 (301), Example 2 (302) and Example 3 (303), respectively, from 1 V to 2.5 V for 100 cycles. In the following, the cycle characteristics are graphs according to various charge and discharge rates, and the results are shown in Table 1. In order to evaluate the cycle characteristics of the battery, the initial specific specific capacity of each coin-ban battery and the Coulombic efficiency after 100 cycles were calculated, and the following equation was used.

Specific capacity = discharge capacity (mAh) / mass of negative electrode active material (g)

Specific capacity = charge capacity (mAh) / mass of negative electrode active material (g)

Coulombic efficiency (%) = discharge specific capacity (mAh / g) / charging specific capacity (mAh / g)

C ₁ : initial discharge specific capacity

C ₁₀₀ : discharge capacity after 100 cycles

CE ₁₀₀ : current efficiency after 100 cycles

Sample
Charge / discharge rate
50 ㎃ / g Charge / discharge rate
500 ㎃ / g Charge / discharge rate
1000㎃ / g Charge / discharge rate
2000㎃ / g C ₁ C ₁₀₀ CE ₁₀₀ C ₁ C ₁₀₀ CE ₁₀₀ C ₁ C ₁₀₀ CE ₁₀₀ C ₁ C ₁₀₀ CE ₁₀₀ Example 1 141
㎃h / g 126
㎃h / g 99.8% 68
㎃h / g 57
㎃h / g 99.2% 52
㎃h / g 43
㎃h / g 98.8% 41
㎃h / g 36
㎃h / g 98.5% Example 2 165
㎃h / g 70
㎃h / g 99.5% 132
㎃h / g 118
㎃h / g 99.4% 117
㎃h / g 99
㎃h / g 99.5% 86
㎃h / g 75
㎃h / g 99.4% Example 3 158
㎃h / g 152
㎃h / g 99.4% 142
㎃h / g 135
㎃h / g 99.5% 119
㎃h / g 112
㎃h / g 99.3% 115
㎃h / g 88
㎃h / g 99.1%

Through this, it can be seen that the lithium titanium oxide having a nanofiber form shows improved electrochemical properties at a fast charge and discharge rate, especially when the nanofiber form is well developed (Example 2, Example 3) Since the charge exchange reaction is more activated, it can be confirmed that the faster charge / discharge characteristics are better than the case where it is not (Example 1).

Claims (17)

Preparing an intermediate mixture by appropriately mixing the source material of lithium (Li) and the source material of titanium (Ti) to enable electrospinning;
Preparing an intermediate compound by mixing the intermediate mixture and two or more polymer materials capable of electrospinning,
Preparing the web in the form of nanofibers whose diameter is adjusted to a range of about 5 to 1000 nm by electrospinning the intermediate compound at appropriate voltage and flow conditions;
Heat-treating the web to produce lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) in the form of nanofibers having a diameter in the range of about 5 to 1000 nm. The method of claim 1, wherein the intermediate compound comprises a lithium source material-titanium source material mixture solution and a composite polymer solution, the composite polymer solution comprises a composite polymer material and a solvent capable of dissolving the composite polymer material Method for producing lithium titanium oxide nanofibers. The method of claim 2, wherein the lithium source material-titanium source material mixed solution comprises a lithium source material, a titanium source material, a solvent for dissolving the composite polymer, a weak acid, and a liquid weak base. . The lithium source material of claim 3, wherein the lithium source material is lithium acetate, lithium hydroxide, lithium nitrate, lithium chloride, and lithium carbonate. Method for producing lithium titanium oxide nanofibers, characterized in that selected from the group consisting of. The lithium titanium oxide of claim 3, wherein the titanium source material is selected from the group consisting of titanium iso-propoxide, titanium butoxide and titanium chloride. Method of making nanofibers. The method of claim 3, wherein the solvent for dissolving the composite polymer is N, N-dimethylformamide (DMF), N, N-diethylformamide (DEF), dimethyl sulfoxide Method for producing lithium titanium oxide nanofibers, characterized in that selected from the group consisting of dimethyl sulphoxide (DMSO), and N-methylpyrrolidone (NMP) The method of claim 3, wherein the weak acid is selected from the group consisting of acetic acid, benzoic acid, and formic acid. The lithium titanium oxide of claim 3, wherein the liquid weak base is selected from the group consisting of pyridine, ethanolamine, N-butylthamine, and triethanolamine. Method of making nanofibers. The method according to claim 3, wherein the molar ratio of the lithium source material and the titanium source material is maintained at 0.6 to 0.8, and the sum of the lithium source material and the titanium source material is 10 wt% to 20 wt% with respect to the solvent for dissolving the composite polymer. Method for producing a lithium titanium oxide nanofiber, characterized in that it is dissolved in. The method of claim 2, wherein the composite polymer material is poly-acrylonitrile (PAN), poly-vinylidene fluoride, poly-stylene, poly- Methyl methacrylate (Poly-methylmethacrylate; PMMA), poly-ethylene oxide (Poly-ethylene oxide; PEO) and poly-vinyl acetate (Poly-vinyl acetate), characterized in that consisting of one selected from the group consisting of Method for producing lithium titanium oxide nanofibers. The method of claim 2, wherein the solvent capable of dissolving the composite polymer material is N, N-dimethylformamide (DMF), N, N-diethylformamide (DEF). And dimethyl sulphoxide (DMSO) and N-methylpyrrolidone (N-methylpyrrolidone; NMP). A method for producing lithium titanium oxide nanofibers, characterized in that. The method of claim 2, wherein the composite polymer material is characterized in that dissolved in 5wt% to 20wt% with respect to the solvent capable of dissolving the composite polymer material Method for producing lithium titanium oxide nanofibers. The method of claim 1, wherein the electrospinning uses an electrospinning apparatus including a nozzle, a current collector, and a robot arm, and the electrospinning is performed on a large area using the robot arm. . The method of claim 13, wherein the voltage applied to the nozzle and the current collector is 20 kV to 30 kV, and the distance between the nozzle and the current collector is 5 cm to 30 cm. The method of claim 13, wherein the diameter of the nozzle is 0.1mm to 1.0mm, and the solution ejection rate of the nozzle is 0.1ml / hr to 1.5ml / hr. The method of claim 1, wherein the heat treatment is performed for 6 hours to 12 hours at a heat treatment temperature of 700 ° C. to 1000 ° C. in a gas atmosphere of at least one of argon and nitrogen. Preparing an intermediate mixture by appropriately mixing the source material of lithium (Li) and the source material of titanium (Ti) to enable electrospinning;
Preparing an intermediate compound by mixing the intermediate mixture and two or more polymer materials capable of electrospinning,
Preparing the web in the form of nanofibers whose diameter is adjusted to a range of about 5 to 1000 nm by electrospinning the intermediate compound at appropriate voltage and flow conditions;
Nanofibers having a diameter in the range of 5 to 1000 nm, produced by a method comprising the step of heat-treating the web in a gas atmosphere of at least one of argon and nitrogen for 6 hours to 12 hours at a temperature of 700 ° C to 1000 ° C. A lithium secondary battery comprising an electrode having a lithium titanium oxide nanofiber of the form as an active material.

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