KR100775949B1 - Carbon nanofibrils, preparation method thereof, and uses thereof - Google Patents

Abstract

The present invention relates to carbon nanofibrils and aggregates thereof, a method for producing the same, and a use thereof, which have high crystallinity and very high crimping properties and entanglement, which can easily diffuse and transfer ions or molecules. The carbon nanofibrils have a three-dimensional network type higher order structure. The carbon nanofibrils are a) a carbon precursor and a catalyst or a catalyst compound selected from the group consisting of metals and semimetals to prepare a uniform carbon precursor / catalyst hybrid precursor, b) heat the precursor to the inside It may be prepared by the process of preparing a carbon in the form of nanofibrils containing a catalyst or a catalyst compound, c) removing the catalyst or catalyst compound from the prepared carbon.

High crystallinity, entanglement, high crimpability, carbon nanofibrils and aggregates thereof, lithium battery negative electrode material, energy storage material

Description

Carbon nanofibrils, preparation methods thereof and uses thereof {CARBON NANOFIBRILS, PREPARATION METHOD THEREOF, AND USES THEREOF}

1 is an X-ray diffraction spectrum of carbon nanofibrils aggregate prepared according to Example 2 of the present invention.

Figure 2a is a graph showing the nitrogen adsorption and desorption isotherm of the carbon nanofibrils aggregate prepared according to Example 2 of the present invention.

Figure 2b is a graph showing the pore size distribution of the carbon nanofibrils aggregate prepared according to Example 2 of the present invention.

Figure 3a is a low magnification transmission electron micrograph of carbon nanofibrils prepared according to Example 1 of the present invention.

3B is an enlarged transmission electron micrograph of carbon nanofibrils prepared according to Example 1 of the present invention.

FIG. 3C is a picture showing a fibrill aggregate photograph of cotton existing in nature and a microfibrils structure which is a component of the cotton.

4A is a transmission electron micrograph of carbon nanofibrils prepared according to Example 2 of the present invention.

4B is a high resolution transmission electron micrograph of carbon nanofibrils prepared according to Example 2 of the present invention.

5A is a charge / discharge graph showing lithium storage characteristics of carbon nanofibrils prepared according to Example 2 of the present invention.

5B is a graph showing cycle characteristics of carbon nanofibrils prepared according to Example 2 of the present invention.

The present invention relates to carbon nanofibrils, aggregates thereof, methods for preparing the same, and uses thereof, which have high crystallinity and have very high crimping properties and entanglement, which can facilitate diffusion and migration of ions and molecules. .

Carbon nanomaterials have been used as a storage or catalyst support for storing ions or molecules in various applications, that is, batteries, capacitors and fuel cells, and also used as membranes for removing contaminants [J. Lee, S. Yoon, S. M. Oh, C. Shin, H. T. Hyeon, Adv. Mater. 2000, 12, 359 .; G. Che, B. B. Lakshmi, E. R. C. Fisher, R. Martin, Nature 1998, 393, 346 .; J. Jang, B. Lim, Adv. Mater. 2002, 14, 1390.].

The use of carbon as a cathode material for lithium ion batteries was first attempted by Sony in Japan in early 1990. The material properties required for the carbon material to act as a lithium ion reservoir include: high crystallinity for stable voltage characteristics and cycle characteristics, adequate surface area for high charge and discharge times, and short lithium ion diffusion passages for high charge and discharge efficiency. to be. Common carbon materials are largely divided into graphite or this graphitizable carbon and egg graphitizable carbon. Graphite or this graphitizable carbon shows high crystallinity but low surface area, while non-graphitizable carbon has high surface area and moderate pores but low crystallinity. Therefore, graphite or this graphitizable carbon shows stable voltage characteristics and high charge and discharge efficiency, but graphitized carbon having limited capacity shows high storage capacity but unstable voltage characteristic and low charge and discharge efficiency.

Since the advent of nano carbon materials such as carbon nanotubes and fullerenes [S. Iijima, Nature 1991, 354, 56 .; K. Komatsu, M. Murata, Y. Murata , Science 2005, 307, 238] Recently, carbon nano-cage and carbon nano-horn have been reported. Has not been reported. However, carbon nanotubes have a reasonable surface area, inner tube space, high crystallinity, and an open structure that allows easy access to lithium ions, which is why we expect great expectations as lithium storage materials, but the initial charge and discharge efficiency is less than 50%. Inferior results [TP Kumar, R. Ramesh, YY Lin, GTK Fey, Electrochem. Commun. 2004, 6, 520.].

On the other hand, most of the carbon nanomaterials reported until recently were manufactured using a carbon source of the gas phase by a method such as arc discharge and laser evaporation [Y. Saito, T. Matsumoto, Nature 1998, 392, 237 .; A. Krishnan, E. Dujardin, MMJ Treacy, J. Hugdah, S. Lynum, TW Ebbesen, Nature 1997, 388, 452.]. However, these synthesis methods have great limitations in mass production due to the harsh synthesis conditions and low yields. Chemical vapor deposition, another manufacturing method, produces nanostructured carbon materials by thermal decomposition of hydrocarbon precursors in the gas phase in the presence of transition metal catalysts such as iron, cobalt, and nickel. This method is relatively economical but has the disadvantage of low purity of the manufactured carbon nanomaterials.

It is well known that the graphitization catalysts, such as iron, cobalt and nickel, or semimetals such as silicon, can be used in the carbon production to vary the microstructure of carbon materials. However, studies on the production of carbon materials with new structures using carbon precursors in solid phases such as polymers or liquids dissolved in solutions as carbon sources are insignificant. In effectiveness in terms of performance [M. Inagaki, K. Fujita, Y. Takeuchi, K. Oshida, H. Iwata, H. Konno, Carbon 2001, 39, 921 .; W. Cho, E. Hanada, Y. Kondo, K. Takayanagi, Appl. Phys. Lett. 1996, 69, 278; N. A. Kiselev, J. Sloan, D. N. Zakharov, E. F. Kudovitskii, J. L. Hutchison, J. Hammer, A. S. Kotosonov, Carbon 1998, 36, 1149.].

For example, U.S. Patent Publication No. 2005-0008562 discloses a carbon material having nanostructures of high crystallinity and high specific surface area using a ternary system, that is, a polymer carbon precursor, a metal catalyst, and an inorganic oxide, and utilizes it as a catalyst carrier. It is written about. However, in order to obtain a high specific surface area, an inorganic oxide must be added and the structure of the carbon material formed is crystalline, but has a closed structure, so that the specific surface area is similar to that of activated carbon, but the diffusion of ions and molecules is limited. Structure.

The present invention is to provide a carbon nanofibrils and aggregates thereof having high crystallinity and very high crimpability and entanglement, which can easily diffuse and move ions or molecules.

Another object of the present invention is to provide a method for producing the carbon nanofibrils.

Another object of the present invention is to provide a use of the carbon nanofibrils.

In order to achieve the above object, the present invention provides carbon nanofibrils and aggregates thereof having a three-dimensional network-like higher order structure.

The invention also provides a uniform carbon precursor / catalyst hybrid precursor by a) mixing a carbon precursor with a carbon precursor and a catalyst or catalyst compound selected from the group consisting of carbon precursors and metals and semimetals,

b) heat treating the precursor to prepare nanofibrils in carbon containing a catalyst or a catalyst compound,

c) providing a method for producing carbon nanofibrils comprising the step of removing a catalyst or a catalyst compound from the carbon prepared above.

The present invention also provides a lithium battery comprising a positive electrode capable of reversible occlusion and release of lithium, a negative electrode including the carbon nanofibrils as a negative electrode active material, and an electrolyte impregnated with the positive electrode and the negative electrode.

The present invention also provides an energy storage or catalyst carrier comprising the carbon nanofibrils or aggregates thereof.

Hereinafter, the present invention will be described in more detail.

The present invention provides carbon nanofibrils and aggregates thereof having a three-dimensional network-like higher order structure.

The carbon nanofibrils have a (002) interlayer distance (d002) in the range of 3.34 to 3.50 kPa, preferably 3.34 to 3.40 kPa.

The carbon nanofibrils also show peaks of (100), (004) and (101) in X-ray diffraction analysis. Samples prepared during X-ray diffraction analysis were powdered, the scan rate was adjusted to 5 ° per minute, and the X-ray radiation used was 50 kV, 100 mA of nickel-filtered Cu K _a ray with a wavelength of 1.54 Å. Was used.

In addition, the carbon nanofibrils preferably have a size (L _c ) of crystallites perpendicular to the base surface in the range of 5 to 15 nm (50 to 150 Hz), and the surface area measured by BET is 170 to 250 cm ² / g. It is in the range, and the average pore size is in the range of 5 to 60 nm.

Carbon nanofibrils according to the present invention is excellent in crimping properties and entanglement.

Crimp property can be calculated by the following equation:

[Equation 1]

Where l _c means the length of the straight state and ㅣ means the length of the tortuous state.

Carbon nanofibrils of the present invention exhibits a crimping property of 40% or more (40-100%).

Referring to the manufacturing method of carbon nanofibrils having the characteristics as described above in detail.

First, in the first process, the carbon precursor / catalyst hybrid carbon precursor is mixed by uniformly mixing a catalyst or catalyst compound selected from the group consisting of a carbon precursor having excellent thermal stability and high carbon yield, and a metal or semimetal. Manufacture.

Any carbon precursor may be used as long as the material has excellent thermal stability and excellent carbon yield. Preferred examples of carbon precursors include sugars and celluloses including derivatives such as sucrose, polysucrose, lignocellulose, rayon and cellulose acetate; Polyacrylonitrile (Poly (acrylonitrile)); Poly (vinyl alcohol); Poly (furfuryl alcohol); Poly (vinyl dibenzene); Polyacrylamide; Polyacrylic acid; Vinyl polymers including polyvinyl chloride, polyvinylpiridine, and polyvinylpyrollidone; Wholly aromatic polyesters; Pitches such as wholly aromatic polyamide and petroleum pitch may also be used.

The catalyst or catalyst compound selected from the group consisting of metals and semimetals plays a very large role in lowering the temperature of the stabilization reaction during heat treatment and changing the amorphous precursor structure into a regular structure, and has a high crystalline carbon structure. It plays a very important role in the introduction.

The catalyst may include transition metals or internal transition metals corresponding to Groups 3-11 of 4-7 cycles of the periodic table; Group 13 element; Group 14 elements; Compounds containing an element belonging to group 1 or 2 can be preferably used.

Specific examples thereof include titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), iridium (Y), Zirconium (Zr), niobium (Nb), molybdenum (Mo), lanthanum (La), hafnium (Hf), tantalum (Ta), tungsten (W), and aluminum (Al), sodium (Na), potassium (Ca) Or silicon (Si). Compound containing said metal fluoride (F ^-), chloride (Cl ^-), bromine (Br ^-), hydroxide (OH ^-), oxide (O ^{2 -),} acetate bit (CH ₃ COO ^-) and such as carboxylate, acetylacetonate _{(CH 3 COCH = C (O} -) CH 3), nitrate (NO ₃ ^-), sulfate (SO ₄ ^{2 -),} disulfide (S ^{2 -),} perchlorate (ClO ₄ ^- ), phosphate (PO ₄ ^-), oxalate (COO ^-), and alkoxide (RO ^-) (wherein R is preferably includes an anion selected from the group consisting of alkyl of 1 to 10.

 The carbon precursor and the catalyst are preferably used in a molar ratio of 10: 1 to 2: 1. If the molar ratio of the carbon precursor is more than 10, there is a problem that the effect of the catalyst is very poor, if less than 2 there is a problem that the catalyst does not melt any more is not preferred.

As a solvent used in the solution blending method, a solvent such as dimethylformaldehyde, dimethylsulfoxide, or the like may be used, but is not limited thereto.

In the present invention, unlike the conventional method, since the solution blending method of mixing under a solvent instead of powder mixing is used, the carbon precursor and the catalyst are dispersed very uniformly, thereby obtaining a uniform composite mixture at proton or atomic level. This property also has a good influence on the properties of the final carbon fibrillated material. The solution blending method can also be mixed through conventional mixers, in particular magnetic stirrers.

The solvent is removed to prepare a carbon precursor / catalyst hybrid precursor. The solvent is preferably removed by a vacuum drying process, the drying process is preferably carried out at a temperature of 25 ℃ to 90 ℃. If the drying temperature is less than 25 ° C, drying of the solvent is insufficient, and if it exceeds 90 ° C, there is a problem of precipitation of the catalyst, which is not preferable.

In the second process, the precursor is heat-treated to carbonize a carbon precursor to produce nanofibrils in the form of carbon containing a catalyst or a catalyst compound therein. The heat treatment is preferably carried out at a temperature of 200 to 2800 ℃. If the heat treatment temperature is less than 200 ℃ carbon precursor is not made, if the temperature exceeds 2800 ℃ carbonization effect is not large compared to the previous temperature is not preferable. In addition, the temperature increase rate during the heat treatment is preferably 2 to 20 ℃ / min.

The heat treatment step is possible in an active atmosphere such as air or in an inert atmosphere such as nitrogen, and the heat treatment atmosphere is not particularly limited, but is preferably performed in an inert atmosphere. The inert atmosphere is preferably nitrogen (N ₂ ) or argon (Ar) atmosphere.

The structure and crystallinity, crimpability, entanglement, and specific surface area of the carbon nanofibrils formed by controlling the molar ratio of the carbon precursor and the catalyst and the heat treatment temperature can be controlled to a desired range.

In the third step, the carbon nanofibrils or aggregates thereof are prepared by removing the catalyst or catalyst compound and having high crystallinity, very high crimpability and entanglement, and facilitating diffusion and migration of ions and molecules.

The catalyst or catalyst compound is removed by acid or alkali treatment in a temperature range of 25 to 100 占 폚. The acid or alkali used for the removal of the catalyst or catalyst compound is preferably used at a concentration of 0.01 M to 10 M. If the concentration of the acid or alkali is less than 0,01M, the catalyst or catalyst compound may not be sufficiently removed, and if the concentration exceeds 10M, there is a problem causing decomposition of the produced carbon material.

The acid or alkali treatment time is preferably 5 to 48 hours. The acid is one selected from the group consisting of sulfuric acid (H ₂ SO ₄ ), hydrogen chloride (HCl), nitric acid (HNO ₃ ), phosphoric acid (H ₃ PO ₄ ), acetic acid (CH ₃ COOH), hydrofluoric acid (HF) Or mixtures thereof may be preferably used. As the base, sodium hydroxide (NaOH) or the like may be used.

It is then preferable to perform a second heat treatment of the obtained carbon nanofibrils. The secondary heat treatment temperature is preferably carried out in the temperature range of 500 to 1200 ℃. If the secondary heat treatment temperature is less than 500 ° C., the carbon precursor is not carbonized, and if the secondary heat treatment temperature is higher than 1200 ° C., the effect of the secondary heat treatment process is not great. It is preferable that secondary heat processing time is 1 to 5 hours, and isothermal heat processing in the range of 2-20 degreeC / min is preferable.

In the present invention, it is possible to produce high crystalline carbon having a structure in which the carbon layers are arranged like graphite even at a relatively low temperature.

The secondary heat treatment process can be carried out in a variety of atmospheric gases, nitrogen (N ₂ ), argon (Ar), carbon dioxide (CO ₂ ), steam, hydrogen (H ₂ ), methane (CH ₄ ), ethylene It is preferable to carry out in one or more atmospheres selected from (CH ₂ CH ₂ ) and acetylene (CHCH).

When the secondary heat treatment is performed, carbon nanofibrils having high crystalline, high crimping, high entanglement properties and excellent lamination completion of the carbon layer can be obtained. Such carbon nanofibrils can be used as a negative electrode active material exhibiting excellent performance in lithium batteries.

These carbon nanofibrils have a nanostructured property, which facilitates the diffusion of ions, atoms, or molecules such as lithium ions, and is particularly excellent as a negative electrode material of a lithium ion battery.

When applied to a lithium ion battery, carbon nanofibrils or aggregates prepared as described above may be mixed with a binder and an organic solvent to prepare a paste, and then coated on a current collector, compressed, and dried to prepare a negative electrode. .

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by the following Examples.

< Example  1>

Polyacrylonitrile (Polyacrylonitrile) and iron (III) chloride (FeCl ₃ ) were dissolved in dimethylformaldehyde (Dimethylformaldehyde) at 55 ° C., respectively, and the mixture was mixed to obtain a yellow transparent solution. In particular, iron chloride was hygroscopic and dissolved in a reactor where nitrogen was injected. The solution thus prepared was sufficiently dried in a vacuum oven at 55 ° C. for 96 hours to prepare a polyacrylonitrile / iron chloride hybrid precursor. This was subjected to a first heat treatment at 1100 ° C. under a nitrogen atmosphere at a rate of 5 ° C./min. The heat treated carbon / catalyst hybrid precursor was treated with 5M HCl at 60 ° C. to remove the catalyst. Then, sufficiently dried in a vacuum oven at 55 ℃ for 24 hours. The carbon material thus obtained was subjected to secondary heat treatment at 800 ° C. for 2 hours at a temperature increase rate of 10 ° C./min in a hydrogen atmosphere to prepare carbon nanofibrils with further improved crystallinity.

< Example  2>

Carbon nanofibrils were prepared in the same manner as in Example 1, except that the first heat treatment temperature was set to 1500 ° C.

In order to determine the crystallinity of the carbon nanofibrils prepared in Example 2, X-ray diffraction analysis (XRD) was performed and the results are shown in FIG. 1. The X-ray diffraction analysis was performed at a scan rate of 5 ° per minute using _a Cu K _a line having _a wavelength of 1.54 kHz with a filter of nickel of 50 kV and 100 mA.

As shown in FIG. 1, it was confirmed that the (002) interlayer distance ( d ₀₀₂ ) was 3.43 μs, and there were (100), (004) peaks, and (101) peaks having high crystallinity. Therefore, it was confirmed that the carbon nanofibrils prepared according to Example 1 were carbons having high crystallinity. The crystal size (L _c ) perpendicular to the base surface was measured to be about 18 nm.

In Example 2, nitrogen adsorption experiments were carried out at a temperature of 77 K using an automatic adsorption instrument (model ASAP 2010, USA) to measure the specific surface area and pore characteristics of carbon nanofibrils. The results obtained are shown in FIGS. 2A and 2B. Shown in

Figure 2a is a graph of nitrogen adsorption and desorption of carbon nanofibrils of Example 2. Some hysteresis was identified, indicating that mesopores were formed. The specific surface area calculated here was about 190 m ² / g and it was confirmed that the specific surface area was relatively high while the crystallinity was high. The pore size formed was found to be about 5-6 nm from Figure 2b.

The crimpability of the carbon nanofibrils prepared according to Example 2 was calculated according to Equation 1 above, and was found to be higher than 40%.

Transmission electron micrographs of the carbon nanofibrils prepared in Example 1 are shown in FIGS. 3A and 3B. Figures 3a and 3b is a photograph taken at low and high magnification, respectively, showing the overall appearance of the material produced in the present invention. From the photographs, it was confirmed that the nanofibrils having a very high crimpability and entanglement of the carbon material produced were well developed. It can also be seen from FIGS. 3A and 3B that the carbon material of Example 1 is formed in an open structure.

A transmission electron micrograph of a cotton present in nature is shown in FIG. 3C for comparison. 3a to 3c it can be seen that the structure of the carbon nanofibrils prepared according to the present invention is very similar to the three-dimensional aggregate structure of the surface. In fact, cotton is a reticulated material with fibrillated fibrils, which are also composed of highly crystalline and crimped microfibrils with a size of less than about 10 nm. Therefore, the carbon nanofibrils prepared in Example 1 are named carbon-cotton because the microfibrils having high crystallinity and crimping properties on the cotton are entangled with each other to form a reticulated high order structure.

A transmission electron micrograph showing the overall appearance of the carbon nanofibrils prepared in Example 2 is shown in Figure 4a and a high resolution transmission electron microscope photograph showing a (002) lattice image is shown in Figure 4b. It was confirmed that the material prepared in Example 2 eliminated many defects present in the carbon layer and developed crystallinity much better than the material prepared in Example 1, and the thickness became thicker from about 12 nm to about 18 nm. Could.

In order to measure the electrochemical performance of the carbon nanofibrils prepared in Examples 1 and 2, a lithium ion battery was manufactured as follows. The paste was prepared by mixing the carbon nanofibrils, acetylene black (conductive material) and the binder polytetrafluoroethylene (PTFE) prepared in Example 1 or Example 2 in a weight ratio of 75:10:15. Was coated on a copper current collector, compressed and dried in a vacuum oven at 120 ° C. for 3 hours to prepare a laminate electrode. Lithium was used as the counter electrode and the reference electrode. Electrolytes used in the production of ethylene carbonate: diethyl carbonate (volume ratio 1: 1) in 1 mole LiPF ₆ Polytetrafluoroethylene was used as a separator for the solution in which the electrolyte was dissolved.

The charge and discharge characteristics of the lithium ion battery using the carbon nanofibrils prepared in Example 2 as the negative electrode material are shown in FIG. 5A and the cycle characteristics are shown in FIG. 5B. 5a shows a voltage characteristic of about 0.4 to 0.5 V which is slightly higher than the charge and discharge potential of graphite (~ 0.2 V) and lower than that of amorphous carbon material (~ 0.8 V), and at the same time high capacity that can be seen in amorphous carbon material. (Up to 650 mAh / g) and excellent initial efficiency of about 70%. It also showed stable cycle characteristics of over 95% up to 35 times.

The results indicate that carbon nanofibrils and aggregates of the new nanostructures, which facilitate the diffusion and migration of highly crystalline, highly crimped and highly entangled ions and molecules prepared in the present invention as lithium storage bodies. It was confirmed that the material is very good. Such excellent lithium storage properties can be attributed to the new structure of the material produced in the present invention. In other words, the crimp property and entanglement can effectively accommodate the volume expansion when lithium ions are inserted and detached, thereby accepting more lithium, stable voltage characteristics due to high crystallinity, and open carbon nanofibrils due to high entanglement. The aggregate structure of, which facilitates the diffusion, desorption and insertion of lithium, and the shortened diffusion movement distance of lithium, plays a decisive role in showing high initial efficiency and stable cycle characteristics.

Carbon nanofibrils and aggregates according to the present invention have a high yield of high crystallinity, very high crimpability and entanglement, and can easily diffuse and move ions or molecules. The carbon nanofibrils and aggregates thereof are excellent in lithium storage characteristics as a negative electrode material for lithium ion batteries, and may be applied to various energy storage fields and catalyst carriers due to the inherent structural properties of the manufactured materials.

Claims (16)

It has a three-dimensional reticular high order structure with crimp property of 40 to 100%. Carbon nanofibrils in which the crystallite size (L _c ) perpendicular to the base surface is 5 to 15 nm. The carbon nanofibrils have a (002) interlayer distance ( d ₀₀₂ ) in the range of 3.34 to 3.50, and show peaks of (100), (004) and (101) in X-ray diffraction analysis. Carbon nanofibrils. delete a) preparing a uniform carbon precursor / catalyst hybrid precursor by mixing a carbon precursor with a catalyst or catalyst compound selected from the group consisting of metals and semimetals, b) heat treating the precursor to prepare nanofibrils in the form of carbon containing a catalyst or a catalyst compound therein; c) A method for producing carbon nanofibrils comprising the step of removing a catalyst or a catalyst compound from the prepared carbon. The method of claim 4, wherein the mixing of the carbon precursor and the catalyst or the catalyst compound is performed by solution blending. The method of claim 4, wherein the carbon precursor and the catalyst or catalyst compound are used in a molar ratio of 10: 1 to 2: 1. The method of claim 4, wherein the carbon precursor / catalyst hybrid precursor is prepared by vacuum drying at a temperature between 25-90 ° C. 6. The method of claim 4, wherein the carbon precursor is a pitch, sugars and cellulose and its derivatives; Polyacrylonitrile (Poly (acrylonitrile)); Poly (vinyl alcohol); Poly (furfuryl alcohol); Poly (vinyl dibenzene); Polyacrylamide; Polyacrylic acid; Vinyl polymers; Wholly aromatic polyesters; And at least one polymer selected from the group consisting of wholly aromatic polyamides. The method of claim 4, wherein the catalyst or catalyst compound is selected from the group consisting of transition metals or internal transition metals, Group 13 elements, Group 14 elements, and Group 1 elements corresponding to Groups 3-11 of the 4-7 cycle of the periodic table. A method for producing carbon nanofibrils which are at least one selected from the group consisting of elements and compounds containing these elements. The method of claim 4, wherein the heat treatment is performed under an inert atmosphere. The method of claim 4, wherein the heat treatment is performed at a temperature of 200 to 2800 ° C. 6. The method of claim 4, wherein the catalyst or catalyst compound is removed by acid or alkali treatment. The method of claim 12, wherein the acid or alkali is used in a concentration of 0.01 M to 10 M carbon nanofibrils. 13. The method of claim 12, wherein the acid comprises sulfuric acid (H ₂ SO ₄ ), hydrogen chloride (HCl), nitric acid (HNO ₃ ), phosphoric acid (H ₃ PO ₄ ), acetic acid (CH ₃ COOH), and hydrofluoric acid (HF). Method for producing carbon nanofibrils which is at least one selected from the group. The method of manufacturing carbon nanofibrils according to claim 4, further comprising the step of heat-treating the carbon nanofibrils. A cathode capable of reversible occlusion and release of lithium, A negative electrode comprising the carbon nanofibrils according to claim 1 or 2 as a negative electrode active material, and A lithium battery comprising an electrolyte impregnated in the positive electrode and the negative electrode.

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