KR101605146B1 - Cnt-lto complex for lithium secondary battery, and preparing method of the same, and lithium secondary battery including the same - Google Patents

Abstract

Provided are a method for manufacturing a CNT-LTO complex for a lithium secondary battery, a CNT-LTO complex for a lithium secondary battery manufactured by the manufacturing method, and a lithium secondary battery comprising the CNT-LTO complex. The method for manufacturing the CNT-LTO complex for a lithium secondary battery comprises the following steps: dispersing a carbon nanotube (CNT) in a solvent; and adding lithium-titanium oxide in the solvent, mixing, and sintering the same.

Description

TECHNICAL FIELD [0001] The present invention relates to a CNT-LTO composite for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including a CNT-LTO composite. BACKGROUND OF THE INVENTION 1. Field of the Invention [0002]

A CNT-LTO composite for a lithium secondary battery, and a lithium secondary battery comprising the CNT-LTO composite.

Recently, energy storage materials are being studied in order to improve the output characteristics of secondary batteries and to apply them to hybrid vehicles or to utilize high output capacitors as auxiliary output devices to improve fuel efficiency. A secondary battery for an automobile refers to a nickel-metal hydride battery and a lithium battery that can be charged and discharged. A supercapacitor is a capacitor having a capacity of about 1,000 times higher than that of a conventional electrostatic capacitor.

Electrochemical devices such as a secondary battery or a supercapacitor use a transition metal compound having an electrochemical activity by an oxidation-reduction reaction as an electrode active material. In order to effectively exhibit the theoretical capacity and voltage characteristics of such electrode active materials, It is necessary to adjust or complement the physico-chemical properties such as electrochemical characteristics, corrosion resistance, and dispersibility, and so on.

Examples of such efforts include nano-particleization of transition metal compound particles, employment of hetero elements, formation of a protective film on the surface of particles, and mixing of electrically conductive materials. As the substance coated on the surface of the transition metal compound particles, a carbon material or a ceramic material which is excellent in corrosion resistance and chemical resistance and improves the electric conductivity of the electrode material is often used.

Particularly, since the carbon material has advantages such as high electric conductivity, chemical and physical stability, it is necessary to mix or compound the carbon material with the transition metal compound or to coat the surface of the transition metal compound particle A number of methods have been proposed. As a method, carbon is simply mixed with a transition metal compound using a mechanical mixing method, or carbon is coated on the surface of a transition metal compound particle by a chemical vapor deposition method or the like. It is generally known that covering individual particle surfaces rather than mixing carbon materials is more effective in protecting the surface of particles and imparting electrical conductivity. Advantages of the carbon material include the improvement of the electrical conductivity of the electrode material, the protection of the transition metal compound particles from the external physico-chemical effects, and the restriction of the excessive growth of the transition metal compound particles in the heat treatment.

In recent years, a method of applying a fibrous carbon material such as carbon nanotube (CNT) has been proposed as a method capable of achieving an effect comparable to coating of a carbon material on particles.

Korean Patent No. 10-1103606 relates to a composite comprising an aggregate of primary particles of a transition metal compound, which is an electrode active material, and a carbon material. However, in order to increase the electrical conductivity of the active material, such a composite is a form of mixing a carbon material and has a limitation in surface functionalization. In addition, since it is difficult to uniformly disperse the carbon material, the yield and productivity may be lowered when applied to processes such as spray drying.

The present invention relates to a method for producing a carbon nanotube-lithium titanium oxide (CNT-LTO) composite for a lithium secondary battery, a CNT-LTO composite for a lithium secondary battery produced by the manufacturing method, and a lithium secondary battery including the CNT- .

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

According to a first aspect of the present invention, there is provided a method for producing a carbon nanotube, comprising: dispersing a carbon nanotube (CNT) in a solvent; And a step of adding and mixing lithium-titanium oxide and titanium oxide on the solvent, and firing the mixture, wherein a lithium-titanium-oxide (LTO) Wherein the CNT-LTO composite is grown on a nanotube.

A second aspect of the present invention provides a CNT-LTO composite for a lithium secondary battery produced by the method according to the first aspect of the present invention.

A third aspect of the present invention is directed to a CNT-LTO composite according to the second aspect of the present invention, comprising a cathode, a cathode, a separator, and an organic electrolyte, wherein the anode comprises a lithium-metal thin film, The lithium secondary battery, which is included, is provided.

According to one embodiment of the present invention, a carbon nanotube (CNT) is dispersed and lithium-titanium-oxide (LTO) is deposited on the CNT during mixing and firing of the dispersed CNT, lithium-titanium oxide, Since the composite grows directly, excellent surface functionalization can be achieved. In addition, since the LTO is grown on the CNT during the firing process, the drying process can be omitted, and the time and cost required for the reaction can be reduced.

In addition, according to one embodiment of the present invention, a CNT-LTO composite is used as a negative electrode active material for a lithium secondary battery. Since the CNT has a very strong strength, resistance against fracture is high, It is possible to manufacture a lithium secondary battery having high stability.

1 is a schematic diagram of a CNT-LTO complex according to one embodiment of the present invention.
Figure 2 is an image of a scanning electron microscope in one embodiment of the invention.
3 is a graph of Raman spectroscopy of a carbon nanotube and a vapor-phase synthetic carbon fiber (VGCF) according to an embodiment of the present invention.
4 is a graph of Raman spectroscopy according to an embodiment of the present invention.
FIG. 5 is a graph showing a change in capacity with respect to the lifetime of a lithium secondary battery according to an embodiment of the present invention.
FIG. 6 is a graph illustrating the evaluation of a high-rate characteristic (C-rate) of a lithium secondary battery according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. It should be understood, however, that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, the same reference numbers are used throughout the specification to refer to the same or like parts.

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

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

Throughout this specification, when an element is referred to as " including " an element, it is understood that the element may include other elements as well, without departing from the other elements unless specifically stated otherwise. The terms " about ", " substantially ", etc. used to the extent that they are used throughout the specification are intended to be taken to mean the approximation of the manufacturing and material tolerances inherent in the stated sense, Accurate or absolute numbers are used to help prevent unauthorized exploitation by unauthorized intruders of the referenced disclosure. The word " step (or step) " or " step " used to the extent that it is used throughout the specification does not mean " step for.

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

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

Hereinafter, embodiments and examples of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to these embodiments and examples and drawings.

According to a first aspect of the present invention, there is provided a method for producing a carbon nanotube, comprising the steps of: dispersing carbon nanotubes (CNT) in a solvent; and adding lithium-titanium oxide and titanium oxide to the solvent, And a lithium-titanium-oxide (LTO) composite is grown on the carbon nanotube. The present invention also provides a method for producing a CNT-LTO composite for a lithium secondary battery.

According to one embodiment of the present invention, the solvent is a nonionic dispersant, which may include, but is not limited to, a nonionic hydrophilic group such as a hydroxyl group or ether in the molecule. The nonionic dispersant may include, but is not limited to, a polyoxyethylene glycol type and a polyhydric alcohol type dispersant depending on the type of the hydrophilic group. For example, the solvent may include, but is not limited to, those selected from the group consisting of polyoxyethylene glycols, glycols, glycerol, and combinations thereof.

In one embodiment of the present invention, the carbon nanotube provides a path through which the titanium oxide included in the electrode can easily move electronically, and can improve the intrinsic characteristics of the lithium secondary battery. In addition, the carbon nanotubes have a very strong strength, which has a high resistance to breakage, and can prevent deformation of the collector and prevention of oxidation by charging and discharging, thereby enhancing the stability of the lithium secondary battery.

In one embodiment of the present invention, the carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes or multi-walled carbon nanotubes. The single-walled carbon nanotube is a single-walled carbon nanotube. The single-walled carbon nanotube is a carbon nanotube having one wall (graphite surface) , And the multi-walled carbon nanotube refers to a carbon nanotube having a plurality of walls (graphite surfaces). In one embodiment of the present invention, the single-walled carbon nanotube exhibits excellent electrical characteristics due to a one-dimensional structure, and exhibits various electrical characteristics depending on the molecular asymmetric structure of a hexagonal honeycomb structure and its diameter. In one embodiment of the present invention, the carbon nanotubes may be linear or curved, and the aspect ratio of the carbon nanotubes may be about 40 to about 6,000, but the present invention is not limited thereto. For example, when the aspect ratio of the carbon nanotubes is less than about 40, the inherent physical properties (electrical conductivity, etc.) of the carbon nanotubes may not be realized. According to one embodiment of the present invention, the length of the carbon nanotubes may be about 3 탆 to about 20 탆, but the present invention is not limited thereto. For example, the length of the carbon nanotubes may range from about 3 microns to about 20 microns, from about 3 microns to about 15 microns, from about 3 microns to about 10 microns, from about 3 microns to about 5 microns, from about 5 microns to about 20 microns , From about 10 microns to about 20 microns, or from about 15 microns to about 20 microns.

According to an embodiment of the present invention, the diameter of the carbon nanotubes may be about 20 nm to about 80 nm, but the present invention is not limited thereto. For example, the diameter of the carbon nanotubes may range from about 20 nm to about 80 nm, from about 20 nm to about 70 nm, from about 20 nm to about 60 nm, from about 20 nm to about 50 nm, from about 20 nm to about 40 nm , About 20 nm to about 30 nm, about 30 nm to about 80 nm, about 40 nm to about 80 nm, about 50 nm to about 80 nm, about 60 nm to about 80 nm, or about 70 nm to about 80 nm But may not be limited thereto.

According to one embodiment of the present invention, zirconia balls may be added as a catalyst when the lithium-titanium oxide and the titanium oxide are added to the solvent, but the present invention is not limited thereto. For example, when the lithium-titanium oxide and the titanium oxide are added to the solvent, they may be added to plastic and zirconia containers filled with zirconia balls, milled and mixed, but the present invention is not limited thereto. For example, the plastic may be polypropylene (PP) or polyethylene (PE).

According to one embodiment of the present invention, the mixing of the lithium-titanium oxide and the titanium oxide on the solvent may be performed by a ball mill method, but the present invention is not limited thereto.

In one embodiment of the present invention, the carbon nanotubes, lithium-titanium oxide, and titanium oxide dispersed in the solvent may include, but are not limited to, baking for a sufficient temperature and time. For example, the carbon nanotubes, lithium-titanium oxide, and titanium oxide dispersed in the solvent may be calcined at a temperature of about 400 ° C. to about 650 ° C. for about 6 hours to about 8 hours, . In one embodiment of the present invention, when the calcination temperature is about 400 ° C or lower, the carbon nanotubes may not be synthesized because lithium-titanium oxide and titanium oxide are not bonded to each other. In this case, the electrical conductivity of the oxide is affected The battery performance is reduced.

According to one embodiment of the present application, the firing may be performed at a temperature of about 400 ° C. to about 650 ° C., but may not be limited thereto. For example, the firing may be performed at a temperature of about 400 캜 to about 650 캜, about 400 캜 to about 600 캜, about 400 캜 to about 550 캜, about 400 캜 to about 500 캜, To about 650 占 폚, from about 500 占 폚 to about 650 占 폚, from about 550 占 폚 to about 650 占 폚, or from about 600 占 폚 to about 650 占 폚. For example, the higher the firing temperature, the higher the rate at which the lithium-titanium-oxide (LTO) composite is grown on the carbon nanotube during the firing step.

In one embodiment of the present invention, the carbon nanotubes, lithium-titanium oxide, and titanium oxide dispersed in the solvent can be heated at an acceleration ratio of about 10 캜 or less per minute. The acceleration ratio can be selected according to the equipment to which a higher or lower acceleration ratio is available, the desired elapsed time, and other factors, and the carbon nanotubes, lithium-titanium oxide and titanium oxide dispersed in the solvent can be directly pre- Or by placing it in a heated oven. The carbon nanotubes, lithium-titanium oxide, and titanium oxide dispersed in the solvent are maintained at about 400 ° C to about 650 ° C for about 6 hours to about 8 hours. The calcination reaction may be heated at the final reaction temperature for several hours and the heating is preferably carried out in the presence of a non-oxidizing or inert gas, such as argon, vacuum, or a reducing atmosphere.

In one embodiment of the present invention, the mixing of the carbon nanotubes, the lithium-titanium oxide, and the titanium oxide dispersed in the solvent may be performed in oxygen or air, and the calcination reaction may include a reduction reaction occurring during the calcination reaction Is conducted in a non-oxidizing atmosphere. For example, the non-oxidizing atmosphere may include, but is not limited to, the presence of a vacuum or an inert gas. The inert gas may include argon or nitrogen.

In one embodiment of the present invention, in the firing reaction, when an oxidizing gas (oxygen or air) is present, the oxidizing gas may interfere with the thermal carbon reduction or reduce the quality of the reaction product. For example, in the firing reaction, the presence of the oxidizing gas reacts with reducing carbon and may lower the availability of carbon involved in the reaction, so that the firing reaction is preferably performed in a non-oxidizing atmosphere.

In one embodiment of the invention, the reducing atmosphere may be provided as a pure reducing gas, or as a mixture of another gas and the reducing gas. For example, the reducing atmosphere may include, but is not limited to, selected from the group consisting of hydrogen, argon, nitrogen, carbon monoxide, argon, and combinations thereof. In one embodiment of the present invention, the reducing gas may be provided in a stoichiometric excess, but it is not limited thereto.

In one embodiment of the invention, the reducing gas may be used at a partial pressure of from about 0.01 atmospheric pressure to a super-atmospheric pressure, depending on factors such as the size of the sample required for the reaction, the volume of the heating chamber, have.

In one embodiment of the present invention, the CNT-LTO product obtained may be cooled, but not limited thereto, after the firing reaction. For example, the cooling may be cooled at an acceleration rate of about 10 DEG C per minute or less. The acceleration ratio may be selected, but not limited, to higher or lower acceleration ratios depending on the equipment available, the desired duration, and other factors. Through the cooling process, the bonding structure of the CNT-LTO product may be more preferable. In order to obtain a high cooling rate of about 100 ° C / min or more, the CNT-LTO product obtained after the calcination reaction may be quenched, but may not be limited thereto.

Figure 1 is a schematic diagram of a CNT-LTO complex, according to one embodiment of the present invention. As shown in FIG. 1, the CNT-LTO composite according to the present invention is a lithium-titanium-oxide (100) grown on a carbon nanotube 200.

According to one embodiment of the present invention, the CNT-LTO composite for a lithium secondary battery may include about 1 wt% to about 5 wt% of carbon nanotubes, but the present invention is not limited thereto. For example, the CNT-LTO complex may comprise, but is not limited to, about 1 wt%, about 2 wt%, about 3 wt%, about 4 wt%, or about 5 wt% carbon nanotubes . In one embodiment of the present invention, when the content of the carbon nanotubes is about 5 wt% or more, the carbon nanotubes and the titanium oxide are not bonded to each other, thereby reducing battery performance.

The second aspect of the present invention provides a CNT-LTO composite for a lithium secondary battery produced by the method according to the first aspect of the present invention.

The second aspect of the present invention relates to a CNT-LTO composite for a lithium secondary battery, which is produced by the method for manufacturing a CNT-LTO composite for a lithium secondary battery according to the first aspect of the present invention, The detailed description of the first aspect of the present invention may be applied to the second aspect of the present invention.

The third aspect of the invention comprises a cathode, a cathode, a separator, and an organic electrolyte, wherein the anode comprises a lithium-metal thin film and the anode comprises a CNT-LTO composite according to the second aspect of the present invention as an anode active material Lithium secondary battery.

The third aspect of the present invention relates to a lithium secondary battery including the CNT-LTO composite for a lithium secondary battery according to the second aspect of the present invention, and a detailed description of portions overlapping with the first and second aspects of the present invention Although the description of the first aspect and the second aspect of the present invention is omitted in the third aspect of the present application, the same can be applied.

In one embodiment of the present invention, the CNT-LTO composite, the conductive agent, and the binder may be mixed in a solvent, but the present invention is not limited thereto. For example, the negative electrode can be produced by suspending a conductive agent and a binder in an appropriate solvent in the CNT-LTO complex, applying the suspension to a current collector such as aluminum foil, drying, and pressing. For example, the conductive agent may be selected from the group consisting of a conductive metal, a conductive carbon, a conductive polymer, and combinations thereof. Specific examples thereof include Ketjen black, carbon black, acetylene black, graphite, activated carbon, P (super-P), a conductive polymer resin, and combinations thereof may be used, but the present invention is not limited thereto. For example, it is preferable to use vinylidene fluoride, polyacronitrile, or polyethylene oxide as the binder.

In one embodiment of the present invention, the organic electrolyte may include an organic solvent and a lithium salt. The organic solvent may be a material known in the art and may be one having a high dielectric constant (polarity), a low viscosity, and a low reactivity with a lithium metal in order to increase the degree of dissociation of ions and smooth the conduction of ions desirable.

In one embodiment of the invention, the organic solvent may include, but is not limited to, those selected from the group consisting of cyclic carbonates, linear carbonates, cyclic ethers, linear ethers, and combinations thereof . For example, the organic solvent may be at least one selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), vinylene carbonate, diethyl carbonate (DEC), dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), tetrahydrofuran , 2-methyltetrahydrofuran (2-Me THF), dioxolane (DOX), dimethoxyethane (DME), diethoxyethane (DEE), gamma -butyrolactone (GBL), acetonitrile But are not limited to, those selected from the group consisting of polystyrene, poly (SL), and combinations thereof.

In one embodiment of the present invention, the lithium salt may be a material known in the art, and it is preferable to use a material having a high degree of dissociation due to a small lattice energy, excellent ionic conductivity, and good thermal stability and oxidation resistance. The lithium salt may be, for example, lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ) (LiCF ₃ SO ₃ ), bis-trifluoromethylsulfonylimide lithium [LiN (CF ₃ SO ₂ ) ₂ ], and combinations thereof, but is limited thereto It is not. For example, as the lithium salt, it is preferable to use an electrolyte which is not easily oxidized even under a high electric potential, and it is most preferable to use LiPF ₆ as a lithium salt.

In one embodiment of the present invention, the lithium-metal thin film is formed of a lithium-nickel composite oxide, a lithium-cobalt composite oxide, a lithium-nickel-cobalt composite oxide, a spinel type lithium-manganese- But are not limited to, those selected from the group consisting of manganese-cobalt composite oxides, lithium-nickel-cobalt-manganese composite oxides, lithium-iron phosphates, and combinations thereof. For example, the lithium metal thin film is Li _x Mn ₂ O _4, Li _x NiO _2, Li _x CoO _2, Li _x Ni _1-y Co _y O _2, Li _x Mn _2-y Ni _y O _4, Li _{x Mn y Co 1-y O} 2, Li x Ni 1 - yz Co y Mn z O 2, Li x FePO 4, and, but could be to include those selected from the group consisting of the combinations thereof, is not limited to, (The molar ratios of x, y and z of the lithium metal thin film are 0? X? 1, 0? Y? 1, and 0? Z? 1). In one embodiment of the present invention, the negative electrode active material according to the present invention makes it possible to set the positive electrode voltage to a high voltage. In particular, it is preferable to use a compound represented by Li _a Ni _b Co _c Mn _d O ₂ as the lithium-metal thin film, wherein the molar ratio of each of a, b, c, and d is 0? A? The molar ratio of b, c, and d is preferably in the range of 0.3? B? 0.4, 0.3? C? 0.4, and 0.3? D? 0.4).

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited thereto.

[ Example ]

[ CNT  Grown on LTO ( Example  1)

20.0 g of Li ₂ CO ₃ , 39.8 g of TiO ₂ and 3 wt% of dispersed CNT were charged into a cylindrical zirconia container having a volume of 0.5 L together with 200 g of a zirconia ball having a diameter of 10 mm, And then calcined at 650 ° C for 8 hours in an argon (Ar) atmosphere to finally prepare a CNT-LTO composite powder.

[pure LTO ( Comparative Example  1)

20.0 g of Li ₂ CO _{3 and} 39.8 g of TiO ₂ were placed in a cylindrical zirconia container having a volume of 0.5 L together with 200 g of a zirconia ball having a diameter of 10 mm and mixed for 3 hours using a ball mill, And calcined at 650 DEG C for 8 hours in a firing furnace to finally produce LTO powder.

[ CNT - LTO  Mixed powder ( Comparative Example  2)

20 g of the pure LTO prepared in Comparative Example 1 and 3 wt% of CNT were put into a cylindrical zirconia container having a volume of 0.5 L together with 200 g of a zirconia ball having a diameter of 10 nm and mixed for 3 hours using a ball mill, LTO mixed powder was prepared.

[Vapor synthesis Carbon fiber ( vapor grown carbon fiber , VGCF ) ≪ / RTI > LTO ( Comparative Example  3)

20.0 g of Li ₂ CO ₃ , 39.8 g of TiO ₂ and 3 wt% of dispersed VGCF were placed in a cylindrical zirconia container having a volume of 0.5 L together with 200 g of a zirconia ball having a diameter of 10 mm and mixed for 3 hours using a ball mill And then calcined at 650 DEG C for 8 hours in a firing furnace under an argon (Ar) atmosphere to finally prepare a VGCF-LTO composite powder.

[ For lithium secondary battery  The electrodes and Coin type  Manufacture of half-cell]

Using the final powder obtained in Example 1 and Comparative Examples 1 to 3 as an electrode active material, an electrode for a lithium secondary battery and a coin half cell were produced.

The ratio of the weight of the electrode material weight portion: super-P: KS 6 weight portion: polyvinylidenefluoride (PVDF) produced through Example 1 and Comparative Examples 1 to 3 was fixed at 89: 6: 5, Was added to N-methyl pyrrolidone (NMP) and mixed in a mixer to prepare an LTO mixture slurry. Among them, the super-P: KS6 ratio was 2: 8 and was used as a conductive agent, and the PVDF was used as a binder.

The LTO mixture slurry was coated on one side of an aluminum foil, dried, and then rolled using a pressing process to produce a negative electrode plate. The negative electrode plate was punched out with a circular specimen having a diameter of 1.11 cm and used as a negative electrode, and a lithium metal thin plate was used as a positive electrode. In addition, 1.2 M of LiPF ₆ was dissolved in a mixed solution of ethylene carbonate (EC): ethylmethyl carbonate (EMC): dimethyl carbonate (DMC) at a volume ratio of 15:50:30 and used as an electrolyte. -scope C500 film to prepare a lithium secondary battery. 0.5 C, 1.0 C, 2.0 C, 5.0 C, and 0.1 V, respectively, when charging and discharging were performed at a rate of 2.8 V and 1.5 V, respectively, Charge and discharge were performed at 10.0 C.

[Raman characteristic evaluation]

As shown in FIG. 3 and FIG. 4, when the crystal structure of a carbon material such as CNT is analyzed using a Raman spectrum, the analysis can be performed in a shorter time than the TEM analysis. In this embodiment, the crystal states of the CNTs, CNT-LTOs, VGCFs, and VGCF-LTOs were analyzed using the Raman analysis method to confirm the bonding state between the materials.

3 is a graph comparing Raman spectra of CNT and VGCF in one embodiment of the present invention. I _D / I _G values indicating the ratio of the D band having carbonaceous particles or defects of CNT and VGCF to the G band indicating a typical graphite structure are 0.289 for CNT, 0.097. As a result of the analysis, it was confirmed that CNTs are structurally more defective than VGCFs.

4 is a graph comparing Raman spectra of the CNT-LTO composite prepared in Example 1 and the VGCF-LTO composite prepared in Comparative Example 3. FIG. It was confirmed that the I _D / I _G value of the CNT-LTO composite prepared in Example 1 was changed from 0.289 to 0.054. It is considered that this is due to the fact that the chemical bond with the lithium-titanium-oxide (LTO) in the defective portion of the CNT changes to a structurally stable form. However, the I _D / I _G value of the VGCF-LTO composite prepared in Comparative Example 3 was slightly decreased from 0.097 to 0.07. It was confirmed that almost no chemical bond with the titanium oxide oxide was observed because the defective portion of VGCF hardly existed.

[Measurement of Electrode Properties and Electrochemical Properties of Batteries]

The electrode characteristics and the electrochemical characteristics of the battery were compared using a lithium secondary battery electrode and a coin half cell manufactured using the final powder obtained in Example 1 and Comparative Examples 1 to 3 as an electrode active material Respectively.

5 is a graph showing a recovery rate of a battery with respect to a cycle after manufacturing a coin type half-cell using the above-described Example 1 and Comparative Examples 1 to 3. FIG.

The CNT-LTO composite of Example 1 exhibited an excellent capacity retention ratio of 92% after 200 cycles. In Comparative Example 1, Comparative Example 2 and Comparative Example 3, the capacity retention ratios of 84%, 88%, and 90% Respectively.

6 is a graph showing capacity characteristics of a battery at various C-ratios after manufacturing a coin type half-cell using the above-described Example 1 and Comparative Examples 1 to 3. The results are shown in Table 1 below. The electrochemical properties of the CNT-LTO composites show that LTO is grown on the CNT-deficient part of the CNT-LTO complex, increasing the conductivity of the CNT by increasing the structural stability and facilitating electron transfer in the LTO through chemical bonding It is considered that

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

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

100: Lithium titanium oxide
200: Carbon nanotube (CNT)

Claims (10)

Dispersing carbon nanotubes (CNTs) in a solvent; And
Adding lithium-titanium oxide and titanium oxide to the solvent, mixing them, and firing the mixture
/ RTI >
In the firing step, a lithium-titanium-oxide (LTO) composite is directly grown on the carbon nanotubes to form a CNT-LTO complex,
And cooling the CNT-LTO complex. ≪ RTI ID = 0.0 > 11. < / RTI >
The method according to claim 1,
Wherein the solvent comprises one selected from the group consisting of polyoxyethylene glycol, glycol, glycerol, and combinations thereof.
The method according to claim 1,
Wherein the length of the carbon nanotubes is from 3 mu m to 20 mu m.
The method according to claim 1,
Wherein the diameter of the carbon nanotubes is 20 nm to 80 nm.
The method according to claim 1,
Wherein a zirconia ball is added as a catalyst when the lithium-titanium oxide and the titanium oxide are added to the solvent.
The method according to claim 1,
Wherein the mixing of lithium-titanium oxide and titanium oxide on the solvent is performed by a ball mill method.
The method according to claim 1,
Wherein the calcination is performed at a temperature of 400 ° C to 650 ° C.
The method according to claim 1,
Wherein the CNT-LTO composite for a lithium secondary battery comprises 1 wt% to 5 wt% of carbon nanotubes.
8. A CNT-LTO composite for a lithium secondary cell, produced by the method according to any one of claims 1 to 8, wherein carbon nanotubes are directly grown on the lithium-titanium-oxide composite.
An anode, a cathode, a separator, and an organic electrolyte,
Wherein the anode comprises a lithium-metal thin film,
Wherein the negative electrode comprises a CNT-LTO composite in which carbon nanotubes are directly grown on the lithium-titanium-oxide composite according to claim 9 as an anode active material.
Lithium secondary battery.

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