KR20040084114A - Method of Fabricating Electrode of Lithium Secondary Battery and Lithium Secondary Battery with the Electrode - Google Patents

Abstract

PURPOSE: Provided is a lithium secondary battery using an electrode comprising a multi-walled carbon nanotube which has high specific capacity and improved energy characteristic by the reversible adsorption and desorption of lithium ion. A method for manufacturing the electrode is also provided. CONSTITUTION: The method for manufacturing an electrode of a lithium secondary battery comprises the first step of mixing a multi-walled carbon nanotube material with a binder and a dispersion medium to prepare an electrode mix; and the second step of applying the electrode mix onto a collector and drying. Further, the lithium secondary battery includes an anode composed of the above obtained electrode; a cathode comprising a transition metal compound material; a multiporous separator which is lithium ion-conductible and electron-nonconductible; and a lithium salt conduction medium.

Description

Electrode manufacturing method of lithium secondary battery and lithium secondary battery using same {Method of Fabricating Electrode of Lithium Secondary Battery and Lithium Secondary Battery with the Electrode}

The present invention relates to a lithium secondary battery, and more particularly, to an electrode manufacturing method of a lithium secondary battery (Lithium Secondary Battery) exhibiting high capacity characteristics using a multi-layered carbon nanotubes as an electrode active material and a lithium secondary battery using the same.

As the weight and size of portable devices have increased due to the development of electronic technology, the proportion of batteries in the weight of devices has been relatively increased.In the case of mobile phones, the total weight was about 800g in 1988, but decreased to about 70g in 1999. It was. The mobile phone is about 70 ~ 80g as of 2002. Compared to 1999, various functions such as e-mail, web surfing, and MP3 player have been added. In the case of PDA, a personal information communication terminal, it is rapidly expanding in 2002 after the initial introduction stage. The performance of the PDA has been technologically advanced to the point of having a personal digital assistant with video (PDAV) function that integrates a video function including navigation with a function as a basic personal information communication terminal.

Therefore, there is a need for a high-performance secondary battery having the characteristics of smaller, lighter, and higher energy than the energy source of these high performance portable electronic devices. Lithium secondary battery shows high battery voltage of 3 ~ 4V, and specific energy has improved from 89Wh / kg in 1992 to 189Wh / kg as of 2002, resulting in 100% performance improvement for 8 years. 10-2002-0030748). As of 2002, the lithium secondary battery achieved an energy density of 494 Wh / L with a specific energy of 189 Wh / kg.

This development is the result of the steady development of electrode materials and battery manufacturing technology of the positive and negative electrodes. In the early days of 1992, the cathode had a specific capacity of 200 mAh / g or less using a pitch-based carbon material. At present, a high capacity graphite-based carbon material is used to use a specific amount of about 330mAh / g based on the graphite material.

In general, a lithium _secondary battery is a transition metal compound including a composition change thereof, such as LiCoO ₂ , LiMn ₂ O ₄ , LiCo _x Ni _1-x O ₂ (0 ≦ _x ≦ 1), V ₂ O _5, or LiFePO ₄ . It consists of a positive electrode (or positive electrode), a lithium salt containing organic electrolyte solution, and a carbon negative electrode (or negative electrode). In the early stages of research and development, negative electrodes for lithium secondary batteries were carried out on lithium metal and lithium-aluminum (Li-Al) alloys. However, as the research progressed, carbon-based negative electrode development proceeded due to life and safety issues. The development of a carbon-based negative electrode realized the commercialization of lithium secondary batteries. At the beginning of commercialization in 192, coke carbon material was used and the specific capacity was less than 200mAh / g. Currently, high-capacity graphite-based carbon materials having specific capacities of about 330mAh / g are used. In terms of capacity density, graphite materials and pitch-based carbon materials correspond to 726mAh / cm ³ and 380mAh / cm ³ , respectively.

That is, the pitch type and specific capacity of the graphite-based carbon materials in the conventional negative electrode material were 200mAh / g and 330mAh / g, and, In terms of the capacity density indicates the capacity of a unit volume of coke carbon material and the graphite material are each 380mAh / cm ³ And 726 mAh / cm ³ , there is a problem that the specific energy and energy density of the battery are also limited in proportion when a carbonaceous material having a low specific capacity and low capacity density is used as a negative electrode for a lithium secondary battery.

In order to improve the performance of the battery, new materials are being developed that surpass the specific capacity of graphite materials, and polypara-phenylene (PPP) and polyacene (PAS) materials and tin are representative high specific-cost materials. Research is underway on metal oxides such as oxide (SnOx) systems. Although there are active researches on various electrode active materials that overcome the limitations of the basic commercial product and have a higher specific amount, the electrode material that can replace the existing materials with stable cycle characteristics with high capacity Is not yet developed.

The present invention has been made in view of the above-mentioned conventional circumstances, and basically, carbon nanotubes, which are composed of carbon elements, can be structural isomers of graphite, and have structurally nanoscale diameters, are used as electrode materials. An object of the present invention is to provide a lithium secondary battery negative electrode having a high specific capacity and to provide a lithium secondary battery constituted using the present carbon nanotube negative electrode.

In order to achieve the above object, the present invention is to prepare a well-dispersed electrode mixture by stirring a multi-layer carbon nanotubes together with a binder and a dispersion medium, the electrode mixture is applied to the current collector of the thin film as a thin film to form an electrode, dried To prepare a negative electrode for a lithium secondary battery, using a carbon nanotube electrode to be wound together with a lithium relative electrode and a porous separator to prepare a jelly roll core for a half-cell, and the prepared jelly core with a lithium salt-based organic electrolyte It provides a manufactured lithium secondary battery.

In addition, the binder in the electrode manufacturing method may include polyvinylidene fluor, polyvinyl chloride, teflon emulsion, polytetrafluoroethylene, or carboxymethyl cellulose.

In addition, the dispersion medium for preparing the electrode mixture in the electrode manufacturing method may include N-methylpyrrolidone (N-methylpyrrolidone), DMF (dimethyl formamide), DMSO (dimethyl sulfoxide), ethanol, isopropanol, water.

The current collector is a copper or nitel thin film, and a foam of copper and nickel may be used.

In addition, the lithium salt-based organic electrolyte used is a solution of a lithium salt electrolyte in an aprotic organic solvent. In order to solidify the lithium secondary battery, a solid polymer electrolyte may be prepared as a lithium secondary battery, and in this case, the polymer may include both a medium of a polymer capable of conducting lithium salts and a polymer medium mixed with a polymer and an organic solvent.

At this time, the organic solvent is propylene carbonate, ethylene carbonate, dimethyl carbonate, ethylmethyl carbonate, methylpropyl carbonate, diethyl carbonate, It includes a single or complex organic solvent, such as 1,2-dimethoxyethane (1,2-dimethoxyethane).

The single or complex organic solvent may include an electrolyte additive for the purpose of protecting and preventing overcharge or improving safety.

As the anode, a transition metal compound material containing LiCoO ₂ , LiMn ₂ O ₄ , LiCo _x Ni _1-x O ₂ (0 ≦ _x ≦ 1), V ₂ O ₅ , LiFePO _4, or a composition change thereof may be used. And a cathode for a lithium secondary battery, which is prepared by preparing an electrode mixture, applying a thin film on an aluminum thin film, drying and pressing as shown in the cathode production.

According to the present invention, the multi-layered carbon nanotubes can store a large amount of lithium ions, and thus have a high specific cost, and thus, adsorption and desorption of lithium ions can be reversible to provide significantly improved energy characteristics than conventional lithium secondary batteries.

1 is a schematic view of a lithium secondary battery manufactured by applying a multilayer carbon nanotube material manufactured by chemical vacuum deposition.

FIG. 2 is a graph showing the X-ray diffraction trends of multilayer carbon nanotube materials prepared by chemical vacuum deposition.

3 is a graph showing the particle size distribution of multilayer carbon nanotube materials prepared by chemical vacuum deposition;

4 is a scanning electron micrograph of a multilayer carbon nanotube material prepared by chemical vacuum deposition;

FIG. 5 is a graph illustrating a change in voltage over time of a GCSOC (gradual control test of state of charge) result of a lithium secondary battery half cell using multilayer carbon nanotubes prepared by chemical vacuum deposition.

FIG. 6 shows the voltage axis subdivided to show a small change in potential over time of a GCSOC result of a lithium secondary battery half cell using multilayer carbon nanotubes prepared by chemical vacuum deposition.

FIG. 7 is a graph illustrating the correlation between the charge capacity, the discharge capacity, the irreversible capacity, and the cumulative non-reversible capacity by analyzing the results of FIGS. 5 and 6.

8 is a graph showing the X-ray diffraction trends of multilayer carbon nanotube materials prepared by the arc discharge method,

FIG. 9 is a graph illustrating a change in voltage over time of a GCSOC result of a lithium secondary battery half cell using multilayer carbon nanotubes prepared by the arc discharge method.

FIG. 10 shows subdivided voltage axes to show a small change in potential over time of a GCSOC result of a lithium secondary battery half cell using multilayer carbon nanotubes prepared by the arc discharge method.

FIG. 11 is a graph illustrating the correlation between the charge capacity, the discharge capacity, the irreversible capacity, and the cumulative non-reversible capacity by analyzing the results of FIGS. 9 and 10.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art, and the shape of the elements in the drawings are exaggerated for clarity.

An embodiment of the present invention proposes to use an electrode made of a multi-walled carbon nanotube material as an electrode of a lithium secondary battery.

Multi-layered carbon nanotubes are basically composed of carbon elements, and each carbon element basically has an SP2 hybrid orbit, and can be referred to as a structural isomer of graphite together with fullerene, and has isomers of various structures and forms. Cylindrical tube material, which is usually nano-sized in diameter, exists as a bundle and contains lithium ions doped in the interior of the tube, interstitial channels, and inter-layer of graphite sheets. Since there are many reaction sites, the lithium doping specific amount is very large, indicating a high specific capacity, and enables the production of high energy lithium secondary batteries. In addition, in the embodiment of the present invention, the electrode mixture is prepared using a binder containing polyvinylidene fluoride, and the multilayer carbon nanotube of the lithium secondary battery using the prepared composite carbon nanotube negative electrode material. A multilayer carbon nanotube cathode electrode is prepared.

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

Example 1

A schematic configuration diagram of a half cell for performance test of a multilayer carbon nanotube electrode as an electrode for a lithium secondary battery is as shown in Korean Patent Application No. 10-2002-0030748, and the multilayer carbon prepared by the embodiment of the present invention. A schematic illustration is shown in FIG. 1 to explain the configuration of a lithium secondary battery using nanotubes.

Specifically, a lithium _secondary battery according to an embodiment of the present invention is a negative electrode comprising a multi-layered carbon nanotube and LiCoO ₂ , LiMn ₂ O ₄ , LiCo _x Ni _1-x O ₂ (0≤x≤1), V ₂ A cathode comprising a transition metal compound material containing O ₅ , LiFePO ₄ or a composition change thereof, a porous separator, a lithium reference electrode, and a lithium salt, which are capable of conducting lithium ions and making electronic conductivity difficult It consists of Lithium salt based organic electrolyte.

Multi-layered carbon nanotubes were manufactured by chemical vapor deposition (CVD) in "ILJIN Nanotech" and subjected to particle size analysis to show an average particle size of 35 micrometers as shown in FIG. 2.

As shown in FIG. 3, the multilayer carbon nanotubes exhibited an X-ray diffraction trend, and the 2 theta of the d002 peak representing the interplanar distance information of the multiple graphite layers was 25.61 degrees, and the lambda value was 1.5405 according to the formula of nλ = 2d · sinθ. Application of, the interplanar distance of the graphite layer was 3.475 Å. The interplanar spacing of the graphite layers was 2.3 degrees F2 for the the maximum width of half maximum of peak (FWHM) of the peaks. The lower and higher two thetas were 24.61 degrees and 26.91 degrees, respectively. The interplanar distance values corresponded to 3.614Å and 3.403Å, respectively. The peak of d002 peak was about 3.888Å and the end was about 3.034Å, which shows that the graphite layer had low graphitization degree with various interplanar distances. 4 shows a 10,000x magnification photograph of an electron scanning microscope of a multilayer carbon nanotube material.

The multi-layered carbon nanotube negative electrode is prepared by preparing an electrode mixture in which a multi-walled carbon nanotube material is stirred together with a binder and a dispersion medium, and applying the electrode mixture as a thin film on a current collector of a thin film to form an electrode, drying and pressing to form lithium. A negative electrode for a secondary battery was prepared, and a half roll jelly roll core was manufactured by winding together with a lithium counter electrode and a porous separator using the prepared carbon nanotube electrode, and the prepared jelly roll core was used as a lithium salt-based organic electrolyte and a lithium reference electrode. In addition, a lithium secondary battery half cell was produced, and the performance of the nanotube electrode as a lithium secondary battery negative electrode was revealed.

The binder in the electrode manufacturing method may include polyvinylidene fluoride, polyvinyl chloride, teflon emulsion, polyethylene tetrafluoride, or carboxylic acid methyl cellulose. The content of the electrode binder can be used from 1% by weight to 15% by weight.

In the manufacture of multilayer carbon nanotube electrodes, conductive materials such as carbon black, vapor-grown carbon fiber, graphite nanofiber, and the like may be added by adding 1 wt% to 10 wt% in order to improve electron conduction characteristics of the electrode.

In addition, the dispersion medium for preparing the electrode mixture in the electrode manufacturing method may include N-methylpyrrolidone (N-methylpyrrolidone), DMF (dimethyl formamide), DMSO (dimethyl sulfoxide), ethanol, isopropanol, water.

In order to improve the density of the dry multilayer carbon nanotube electrode and to reduce the roughness, the electrode is pressed by using a compactor to increase the density and lower the roughness of the electrode surface. The density of the crimped electrode composite was 0.6 g / cm ³ .

The current collector is a thin film of copper or nickel, and a foam of copper and nickel may be used.

The lithium counter electrode was used by laminating lithium metal on a current collector of a copper or nickel thin film.

An electrode leader, which is an access passage of electrons by an electrochemical reaction, was ultrasonically welded to the manufactured multilayer carbon nanotube electrode and the lithium relative electrode.

The lithium reference electrode was used by pressing lithium metal on a nickel lead (lead).

In addition, the lithium salt-based organic electrolyte used is a solution of a lithium salt electrolyte in an aprotic organic solvent. In order to solidify the lithium secondary battery, a solid polymer electrolyte may be prepared as a lithium secondary battery, and in this case, may include both a polymer-only medium capable of conducting lithium salts and a polymer medium mixed with a polymer and an organic solvent.

In this case, the electrolyte of the lithium salt may include all of ionic compounds including lithium, such as LiPF ₆ , LiB (OOCCOO) ₂ , LIBF ₄ , LiClO ₄ , LiAsF ₆ , and LiCF ₃ SO ₃ . The lithium salt organic electrolyte in this example was a 1 M LiPF ₆ solution, and the organic solvent was a composition in which the ethylene carbonate (EC), the diethyl carbonate (DEC), and the dimethyl carbonate (DMC) were mixed at a volume ratio of 3: 5: 5, respectively. .

The organic solvent may be propylene carbonate, ethylene carbonate, dimethyl carbonate, ethylmethyl carbonate, methylpropyl carbonate, diethyl carbonate, It includes a single or complex organic solvent, such as 1,2-dimethoxyethane (1,2-dimethoxyethane).

The single or complex organic solvent may include an electrolyte additive for the purpose of protecting and preventing overcharge or improving safety.

As described above, the multilayer carbon nanotube electrode, the porous separator, and the lithium counter electrode were prepared using a jelly roll for a lithium secondary battery using a winding machine. Using a prepared jelly roll, a lithium reference electrode, and an organic electrolyte of 1M LiPF ₆ EC: DEC: DMC (3: 5: 5), a multi-layer carbon nanotube lithium secondary battery 3-electrode half cell in a dry box under high-purity argon flow Prepared.

The characteristics of the three-electrode half cell of the multilayer carbon nanotube lithium secondary battery were analyzed by a charge / discharge test. The charge / discharge test was performed at room temperature using a Toscat 3100K charge / discharge tester. The test current was based on C / 10 of each battery, and the primary charge / discharge of the GCSOC (gradual control test of state of charge) test was charged to C / 7.5mAh / g and the discharge end potential was 3V (lithium reference electrode). The second charge and discharge was charged up to (C / 7.5 × 2) mAh / g and discharged to the end of discharge potential, and the nth charge and discharge was charged up to (C / 7.5 × n) mAh / g and discharged The discharge was completed to the end potential. After each charge and discharge, a rest time of 0.5 hours was given.

In the test as described above, during charging, lithium cations in the organic electrolyte are doped with multilayer carbon nanotubes. During discharge, lithium cations doped into the multilayer carbon nanotube electrodes are dedoped into the organic electrolyte medium.

Figure 5 shows the GCSOC results of the lithium secondary battery three-electrode half cell prepared using a multi-layer carbon nanotube electrode as a change in potential with time. 6 shows subdivisions of the voltage axis to show a small change in potential. The multilayer carbon nanotube content in the test cell was 12.8mg (16cm ³ ), the test current was 0.476mA, and 49.6 mAh / g of electricity was charged per GCSOC step.

7 shows the charge capacity, the discharge capacity, the irreversible capacity, the cumulative non-reversible capacity using the results of FIG. 5, and the relationship between the discharge capacity, the irreversible capacity, the cumulative non-reversible capacity and the discharge according to the charge capacity. The relationship between cumulative non-reversible capacity and specific amount is shown. Each result implies an interrelationship. References (1) to (4) provide details on GCSOC testing, analysis and application.

(1) C.H.Doh, H.S. Kim and S.I. Moon; J. Power Sources, 101 (2001), 96

(2) C.H.Doh, S.I. Moon, M.S. Yun, C.S. Jin, B.S. Jin, and S.W.Eom: Carbon Science, 1 (2000), 36

(3) C.H.Doh, S.I. Moon, M.S. Yun, S.W.Eom and J.H. Roh, "A study on The Initial Irreversible Capacity of The Lithium Intercalation using The Gradual Control of State of Charge": The Abstract of IMLB11 (2002)

(4) C.H.Doh, E.G. Shim, S.J. Choi and S.I. Moon, "A study on Electrochemical Properties of Carbon Nanotube as an Anode of Lithium Rechargeable Battery Using by the Gradual Control of State of Charge": The Abstract of IMLB11 (2002)

The irreversible capacity of the electrode-electrolyte system can be precisely defined using the initial irreversible capacity (IIC). For this purpose, the irreversible capacity must be divided and expressed in detail. The irreversible specific capacity can be expressed by the lithium doping (intercalation) characteristics of the material and the irreversible reaction of the material surface and the electrolyte. The internal reaction characteristics of the material can be expressed as Equation 1 as the initial intercalation Ah efficiency (IIE), and the surface-electrolyte reaction characteristics can be expressed as the initial irreversible capacity at the surface (IICs). Can be. Surface irreversible capacitances (IICs) and intercalation efficiencies (IIEs) represent the irreversible specific capacitance characteristics of the electrode surface-electrolyte and the electrode interior, respectively, and their relationship is shown in Equation 2.

-------------------------------------- (One)

--------------------------- (2)

Surface irreversible specific capacities (IICs) and intercalation efficiencies (IIEs) are specified according to the type of electrode material, the composition of the electrode, and the composition of the electrolyte, and exhibit independent characteristics with respect to the state of charge change.

The relationship between the irreversible specific capacity (IIC) and the discharge specific capacity (Qd, the discharge capacity) of the lithium secondary battery half cell of the multilayer carbon nanotube electrode was obtained as shown in Table 1. When divided into charging capacity or discharge capacity, the cumulative specific reversible capacity up to 991 mAh / g or 880 mAh / g, respectively, showed a linear relationship with the discharge capacity. This linear relationship can be divided into three regions according to the slope.

Table 1 shows the relationship between the cumulative irreversible capacity and the discharge capacity and the application area of the relationship. In Table 1, the [a] region shows an electrochemical reaction up to 0.8 V (lithium reference electrode) as shown in FIG. 6 and is due to the surface irreversible reaction. The IIE for the area [A] is 3.94%, which indicates that only 3.94% of the specific amount charged by the doping was discharged. The negative IICs resulted in 2.6 V (lithium reference electrode) of the half-cell open circuit voltage. This is the result of discharging up to a potential equal to or greater than the charging amount by discharging up to the lithium reference electrode.

In Table 1, the [b] region is an electrochemical reaction region by doping lithium cations on the multilayer carbon nanotube material. The [b] area is up to 545 mAh / g for the charge capacity and 447 mAh / g for the discharge capacity. The IIE and IICs for this area were 33.6% and 370mAh / g, respectively.

In Table 1, the [C] region corresponds to a region in which the voltage at the end of charging increases in the potential change diagram of FIG. 6, and the increase in potential with the progress of charging results in the deposition of lithium metal on the electrode and thus the electrical conductivity of the electrode. This is because an overvoltage (iR-drop) decreases due to an increase. The IIE in this section can be defined as the efficiency of lithium elution relative to lithium precipitation, not the exact intercalation efficiency.

From the above considerations, the effective discharge specific capacity of the multilayer carbon nanotube material electrode for lithium secondary battery can be confirmed up to about 447 mAh / g. The discharge capacity of about 447 mAh / g is higher than 120% of 372 mAh / g, which is the theoretical specific capacity of the graphite material, and 330 mAh / g and 200 mAh / g of the conventional graphite and pitch coke respectively 135 Higher doses above% and 223% can be identified.

Area classification Charge capacity (mAh / g) Discharge specific capacity (mAh / g) Relationship between Cumulative Reversible Capacity and Discharge Capacity (mAh / g) IIE (%) IICs (mAh / g) [end] 198 35 IICsum [A] = 24.3526Qd-474.96 3.94 474.96 [I] 545 447 IICsum [B] = 1.9756Qd + 370.361 33.6 (370.4) [All] 991 880 IICsum [C] = 1.7388Qd + 476.35 36.5 (476.4)

<Example 2>

In the lithium secondary battery of Example 1, a negative electrode was prepared by commercially using multilayer carbon nanotubes prepared by CVD. In Example 2, multilayer carbon nanotubes in which a negative electrode of a lithium secondary battery is manufactured by an arc discharge method are selected from LiCoO ₂ , LiMn ₂ O ₄ , LiCo _x Ni _1-x O ₂ (0 ≦ _x ≦ 1), A positive electrode comprising a transition metal compound material including V ₂ O ₅ , LiFePO ₄ or a composition change thereof, a porous separator, a lithium reference electrode configured to be capable of conducting lithium ions and making electronic conductivity difficult It consists of lithium salt-based organic electrolyte.

Multi-layered carbon nanotubes were manufactured by an arc discharge method in "ILJIN NanoTech" and showed X-ray diffraction trends as shown in FIG. 8. The electrode manufacturing method and the GCSOC test method are the same as in Example 1.

FIG. 9 illustrates the GCSOC results of a lithium secondary battery three-electrode half cell manufactured using a multilayer carbon nanotube electrode as a change in potential with time. FIG. 10 shows subdivided voltage axes to show small changes in potential. The content of multilayer carbon nanotubes in the test cell was 64mg (8cm ³ ), the test current was 2.374mA, and 49.6 mAh / g of electricity per GCSOC step was charged.

FIG. 11 shows the charge capacity, the discharge capacity, the irreversible capacity, the cumulative non-reversible capacity using the results of FIG. 9, and the relationship between the discharge capacity, the irreversible capacity, the cumulative non-reversible capacity and the discharge according to the charge capacity. The relationship between cumulative non-reversible capacity and specific amount is shown. Each result implies an interrelationship. The relationship between the irreversible specific capacity (IIC) and the discharge capacity (Qd, the discharge capacity) of the half-cell of the multilayer carbon nanotube electrode lithium secondary battery was obtained from the equations (1) and (2). The cumulative non-reversible capacity up to 989 mAh / g or 946 mAh / g, respectively, showed a linear relationship with the discharge capacity. This linear relationship can be largely divided into two regions according to the slope. The first area is the electrochemical reaction area by doping lithium cations on multilayer carbon nanotube materials. The IIE for the area is 81%, indicating that 81% of the specific amount charged by doping is discharged. The charge capacity of the first area was up to 197 mAh / g, and the discharge capacity was 181 mAh / g, and the IICs for this area were 63 mAh / g.

The second region corresponds to the region in which the voltage at the end of charging increases in the potential change diagram of FIG. 9, and the increase in electrical potential as the charging progresses results in the deposition of lithium metal on the electrode to increase the electronic conductivity of the electrode, thereby increasing the overvoltage ( iR-drop) is reduced. The IIE in this section can be defined as the efficiency of lithium elution relative to lithium precipitation, not the exact intercalation efficiency.

From the above considerations, the effective discharge specific capacity of the multilayer carbon nanotube material electrode for lithium secondary battery manufactured by the arc discharge method can be confirmed up to about 181 mAh / g.

Area classification Charge capacity (mAh / g) Discharge specific capacity (mAh / g) Relationship between Cumulative Reversible Capacity and Discharge Capacity (mAh / g) IIE (%) IICs (mAh / g) [end] 197 181 IICsum [A] = 0.2317Qd + 63.0 81.2 63 [I] 989 946 IICsum [B] = 0.8917Qd-86.8 52.9 (-86.8)

<Example 3>

In constructing a lithium secondary battery half cell using the multilayer carbon nanotube material electrodes shown in Examples 1 and 2, a lithium secondary battery using a multilayer carbon nanotube material electrode was formed by replacing the lithium relative electrode with a cathode for a lithium secondary battery. can do.

The carbon nanotube anode prepared according to Example 1 was wound together with a cathode and a porous separator for a lithium secondary battery to prepare a jelly roll core for a lithium secondary battery, and the prepared jelly roll core was combined with a lithium salt-based organic electrolyte in an overall manufacturing process. It provides a lithium ion battery through.

LiCoO ₂ , LiMn ₂ O ₄ , LiCo _x Ni _1-x O ₂ (0≤x≤1), V ₂ O ₅ , LiFePO ₄ which is a 4-5V class electrode material or these materials A transition metal compound material containing a composition change of may be used. As shown in the negative electrode preparation, an electrode mixture is prepared, a thin film is applied on an aluminum thin film, dried and compressed to prepare a positive electrode for a lithium secondary battery.

In the preparation of the positive electrode for a lithium secondary battery, the binder may include polyvinylidene fluoride, polyvinyl chloride, teflon emulsion, polyethylene tetrafluoride, or carboxylate methyl cellulose. The content of the electrode binder can be used from 1% by weight to 15% by weight. In the manufacture of a positive electrode for a lithium secondary battery, conductive materials such as carbon black, vapor-grown carbon fiber, graphite nanofiber, and the like may be added in an amount of 1% by weight to 10% by weight in order to improve the electronic conductivity of the electrode. The dispersion medium for preparing the electrode mixture may include N-methylpyrrolidone (N-methylpyrrolidone), dimethyl formamide (DMF), dimethyl sulfoxide (DMSO), ethanol, isopropanol, and water.

On the other hand, the present invention is not limited to the above-described typical preferred embodiments, but can be carried out in various ways without departing from the gist of the present invention various modifications, changes, substitutions or additions are common in the art. Those who have knowledge will easily understand. If the implementation by such improvement, change, replacement or addition falls within the scope of the appended claims below, the technical idea should also be regarded as belonging to the present invention.

As described in detail above, according to the present invention, a high-capacity lithium secondary battery negative electrode having an effective discharge specific capacity of 447 mAh / g was invented using a chemical vapor deposition multilayer carbon nanotube as a negative electrode material of a lithium secondary battery. In the case of the multilayer carbon nanotube material manufactured by the arc discharge method, it was possible to exhibit a discharge specific capacity of 181 mAh / g.

The high-capacity negative electrode material for lithium secondary batteries of multilayer carbon nanotubes manufactured by chemical vacuum deposition has a discharge cost of 447 mAh / g, which is 120% higher than the theoretical specific capacity of 372 mAh / g of graphite materials. Pitch coke can be identified with high specific capacities of 330 mAh / g and 200 mAh / g, respectively, exceeding 135% and 223%.

Claims (15)

A first step of preparing an electrode mixture by mixing a multilayer carbon nanotube material, a binder, and a dispersion medium; Lithium secondary battery electrode manufacturing method comprising the step of applying the electrode mixture to a current collector and dried. The method of claim 1, The multilayer carbon nanotube is a lithium secondary battery electrode manufacturing method, characterized in that produced by any one selected from chemical vapor deposition and arc discharge method. The method of claim 1, The binder is a lithium secondary battery electrode manufacturing method comprising at least one conductive material selected from carbon black, vapor-grown carbon fiber, graphite nanofibers in the range of 1% to 10% by weight. The method of claim 1, The dispersion medium is at least one selected from N-methylpyrrolidone (N-methylpyrrolidone), DMF (dimethyl formamide), DMSO (dimethyl sulfoxide), ethanol, isopropanol, water The method of claim 1, And further comprising a third step of pressing the metal thin film coated with the electrode mixture. The method of claim 1, The binder comprises at least one binder selected from polyvinylidene fluoride, polyvinyl chloride, teflon emulsion, polyethylene tetrafluoride and carboxylic acid methyl cellulose in the range of 1% to 20% by weight. Lithium secondary battery electrode manufacturing method The method of claim 1, The current collector is a lithium secondary battery electrode manufacturing method, characterized in that any one selected from a copper thin film, nickel thin film, copper foam (foam) and nickel foam. A negative electrode comprising an electrode prepared according to any one of claims 1 to 7; An anode comprising a transition metal compound material; A porous separator configured to be capable of conducting lithium ions and making electronic conductivity difficult; A lithium secondary battery comprising a lithium salt conductive medium for conducting lithium salts. The method of claim 8, The transition metal compound material of the positive electrode is at least one selected from LiCoO ₂ , LiMn ₂ O ₄ , LiCo _x Ni _1-x O ₂ (0 ≦ _x ≦ 1), V ₂ O ₅ , LiFePO ₄ and composition variations thereof Lithium secondary battery characterized by the above. The method of claim 8, The separator is a lithium secondary battery, characterized in that the porous separator of polyethylene, polypropylene, polyvinylidene fluoride series. The method of claim 8, The lithium salt conducting medium is a lithium secondary battery, characterized in that the lithium salt-containing organic electrolyte solution in which the electrolyte of the lithium salt dissolved in any one selected from aprotic single organic solvent and composite organic solvent. The method of claim 11, The lithium salt electrolyte is at least one selected from LiPF ₆ , LiB (OOCCOO) ₂ , LIBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ . The method of claim 8, The lithium salt conducting medium is a lithium secondary battery, characterized in that the polymer medium capable of conducting lithium salt. The method of claim 8, The lithium salt conductive medium is a lithium secondary battery, characterized in that the composite organic solvent mixed with a polymer capable of conducting lithium salt and an organic solvent. The method of claim 8, The lithium salt conducting medium is biphenyl (binphenyl), bibenzyl, stilbene, 1,2-diphenylacetylene (1,2-diphenylacetylene), diphenyl ether, vinyl ethylene tabo Lithium secondary battery comprising at least one electrolyte additive in a vinyl (ethylene carbonate).