KR100945619B1 - Negative active material used for secondary battery, secondary battery including the same, and method thereof - Google Patents

Abstract

The present invention discloses a negative electrode active material for a secondary battery, a secondary battery comprising the same, and a method of manufacturing the same. In the negative electrode active material for a secondary battery according to the present invention, a part or all of the edges of the core carbon material having a particle shape is covered by a coated carbon material composed of a carbide layer, and d ₁ and d _max of the Particle Size Distribution (PSD) are respectively It is 0.5 micrometer or more and 60 micrometers or less, It is characterized by the bulk density of 1.0-1.3 g / cm <^3> .

When the negative electrode of the secondary battery is manufactured using the negative electrode active material for the secondary battery according to the present invention, processability and compressibility may be improved, and the discharge capacity, efficiency, and discharge capacity retention rate of the secondary battery may be improved.

Anode active material, core carbon material, carbide layer, PSD, bulk density, tap density, specific surface area

Description

Negative active material used for secondary battery, secondary battery including the same, and method

The present invention relates to a negative electrode active material for a secondary battery, and more particularly, a negative electrode active material for a secondary battery made of a core carbon material in which part or all of an edge is covered by a coated carbon material, a secondary battery including the same, and a manufacturing method thereof It is about.

Recently, with the rapid spread of electronic devices using batteries such as mobile phones, notebook computers, and electric vehicles, the demand for small, lightweight, and relatively high capacity secondary batteries is rapidly increasing. In particular, lithium secondary batteries have attracted attention as a driving power source for portable devices due to their light weight and high energy density. Accordingly, research and development efforts for improving the performance of lithium secondary batteries have been actively conducted.

Lithium secondary batteries are used when lithium ions are inserted / desorbed from the positive electrode and the negative electrode in a state in which an organic or polymer electrolyte is charged between a negative electrode and a positive electrode made of an active material capable of intercalations and deintercalation of lithium ions. Produces electrical energy by oxidation and reduction reactions.

As a cathode active material of a lithium secondary battery, transition metal compounds such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), lithium manganese oxide (LiMnO ₂ ), and the like are mainly used.

The negative active material is generally a crystalline carbon material such as natural graphite or artificial graphite having a high softening degree, or a pseudo-graphite structure obtained by carbonizing a hydrocarbon or a polymer at a low temperature of 1000 to 1500 ° C or A low crystalline carbon material having a turbostatic structure is used.

The crystalline carbon material has a high true density, which is advantageous for packing the active material and has excellent potential flatness, initial capacity, and charge / discharge reversibility. However, the more the battery is used, the lower the charge / discharge efficiency and cycle capacity are. have. This problem is analyzed to be due to the electrolytic solution decomposition reaction at the edge portion of the crystalline carbon material as the charge and discharge cycle of the battery increases.

Japanese Laid-Open Patent Publication No. 2002-348109 discloses a carbon-based negative electrode active material coated with a carbide layer in order to prevent the decomposition reaction of the electrolyte from occurring at the edge portion of the crystalline carbon material. In the carbon material-based negative active material, the carbide layer is formed by coating a coating material (coal or petroleum-based heavy oil including pitch) on the surface of the carbon material and performing heat treatment at 1000 ° C. or higher. When the carbide layer is coated on the carbon material, the initial capacity of the secondary battery is reduced by a small amount, but the charging and discharging efficiency and the cycle capacity characteristics are improved. In particular, when artificial graphitization of the coating material coating layer through high temperature heat treatment, it is possible to effectively suppress the decomposition reaction of the electrolyte solution while reducing the amount of initial capacity reduction.

The prior art is a mass ratio of carbon material and carbide layer required to effectively inhibit the decomposition reaction of the electrolyte, the coating and firing conditions of the carbide layer, the crystallographic properties of the carbide layer through XRD and Raman analysis, the specific surface area conditions of the carbide layer, etc. It is described in detail.

However, the inventors of the present invention, although the formation conditions of the carbide layer itself and various physical conditions of the carbide layer is important when forming the negative electrode of the secondary battery with a carbon-based negative electrode active material, the particle size distribution and bulk density of the negative electrode active material powder Newly discovered that the properties greatly affect the electrochemical properties of the secondary battery.

However, the prior art does not mention that the particle size distribution and the bulk density characteristics of the carbon material powder have a close correlation with the electrochemical characteristics of the secondary battery.

The present invention has been made to solve the above-mentioned problems of the prior art, and provides a carbon-based negative electrode active material and a method for producing the carbon material-based negative electrode material with optimized particle size distribution and volume density characteristics to derive good electrochemical characteristics of a secondary battery. Its purpose is to.

Another object of the present invention is to provide an electrode made of a carbon material-based negative electrode active material having optimized particle size distribution and volume density characteristics, and a secondary battery including the same.

In order to achieve the above technical problem, the anode active material for a secondary battery according to the present invention is coated with a carbon material comprising a carbide layer in which part or all of the edges of the core carbon material having a particle shape are formed of a PSD (Particle Size Distribution) d ₁ and d _max are 0.5 µm or more and 60 µm or less, respectively, and have a bulk density of 1.0 to 1.3 g / cm ³ .

Here, PSD refers to the size distribution of the particles when the negative electrode active material powders are arranged in order of the particle size. PSD was measured using CILAS 'CILAS920, France' and MARVERN's 'Mastersizer2000, USA'. 'CILAS920, France' was used to measure the PSD of the fine powder in the negative electrode active material powder, 'Mastersizer2000, USA' was used to measure the coarse PSD of the negative electrode active material powder. d ₁ is the size of particles in the PSD within 1%, d _max is the size of the largest particle in the PSD. The volume density refers to the density of the carbonaceous-based negative active material filled in the tapping cell when the negative active material powder is dropped into a 20cc tapping cell through a 200 μm sieve to fill the tapping cell.

It is preferable that the negative electrode active material according to the present invention has a lower crystallinity of the coated carbon material than the core carbon material.

Preferably, the tap density of the negative electrode active material is 0.7 g / cm ³ or more, and the specific surface area is 5 m ² / g or less.

Here, tap density was measured according to JIS-K5101 using the "powder tester PT-R" by Hosokawa Micron. That is, the carbonaceous anode active material powder is dropped into a tapping cell of 20 cc capacity through a sieve having a graduation interval of 200 μm, and the tapping cell is fully filled, followed by 3000 strokes of 18 mm stroke length once per second. The tap density is measured by measuring the density of the negative electrode active material. In addition, the specific surface area of a negative electrode active material is measured using the nitrogen adsorption BET specific surface area measuring apparatus ASAP2400 manufactured by Micromeritex.

In order to achieve the above technical problem, a method of manufacturing a negative active material for a secondary battery according to the present invention includes firing a core carbon material coated with a first stage raw material coated with a core carbon material having a particle form and coating a raw material of a coated carbon material. In the second step of forming a coated carbon material consisting of a carbide layer on part or all of the edges of the core carbon material, and the core carbon material formed with the coated carbon material such that d1 and d _max are 0.5 µm or more and 60 µm or less, respectively, based on the PSD. It characterized in that it comprises a third step of classifying.

Preferably, the core carbon material coated with the raw material in the second step is fired for 1 to 48 hours at a temperature of 1000 ~ 2500 ℃.

Preferably, the third step is to classify the negative electrode active material by a classifier using an air cyclone method, to remove the fine powder so that d1 of the PSD is 0.5㎛ or more under a blower pressure of 10 ~ 200mmHg, in the blower, the pressure is 400 ~ 800mmHg condition is a step of classifying the negative active material is less than or equal to d _max is 60㎛.

Still another technical problem of the present invention can be achieved by the electrode manufactured by using the carbon material-based negative electrode active material for the secondary battery and the secondary battery including the same.

When the negative electrode of the secondary battery is manufactured using the negative electrode active material for the secondary battery according to the present invention, processability and compressibility may be improved, and the discharge capacity, efficiency, and discharge capacity retention rate of the secondary battery may be improved.

Hereinafter, a preferred embodiment of the present invention will be described in detail. Prior to this, terms or words used in the specification and claims should not be construed as having a conventional or dictionary meaning, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, the configurations described in the embodiments of the present specification are only the most preferred embodiments of the present invention, and do not represent all of the technical ideas of the present invention, and various equivalents and modifications that may substitute them at the time of the present application may be made. It should be understood that there may be examples.

A negative active material for a secondary battery according to a preferred embodiment of the present invention includes a core carbon material whose part or all of the edges are covered by a carbide layer, and d ₁ and d _max are each 0.5 μm based on the PSD (Particle Size Distribution). It is characterized by the above-mentioned and 60 micrometers or less and volume density of 1.0-1.3 g / cm <^3> .

Preferably, the core carbon material is spherical high crystalline natural graphite. Alternatively, the core carbon material may be formed of natural graphite, artificial graphite, mesocarbon micro beads, mesopez pitch fine powder, isotropic pitch fine powder, resin charcoal, and pseudo-graphite having an oval shape, a crushed shape, a scale shape, a whisker shape, or the like. It may be any one selected from the group consisting of low crystalline carbon fine powder having a pseudo-graphite structure or a turbostrattic structure or a mixture thereof.

Preferably, the carbide layer is a low crystalline carbide layer formed by coating a core carbon material with pitch, tar or mixtures thereof derived from coal or petroleum and then carbonizing and firing the same. Here, low crystallinity means that the carbide layer has a lower crystallinity than the core carbon material. If the carbide layer is lower in crystallinity than the core carbon material, it is possible to effectively prevent the decomposition reaction of the electrolyte from occurring at the edge portion of the core carbon material. In addition, it is possible to improve processability such as compressibility in the electrode manufacturing process.

In the present invention, PSD refers to the size distribution of the particles when the carbon material-based negative electrode active material powders are arranged in order of particle size. PSD was measured using CILAS's CILAS920, France and MALVERN's Mastersizer2000, USA. 'CILAS920, France' was used to measure the PSD of the fine powder in the negative electrode active material powder, 'Mastersizer2000, USA' was used to measure the coarse PSD of the negative electrode active material powder. d ₁ is the size of particles in the PSD within 1%, d _max is the size of the largest particle in the PSD. In addition, the bulk density refers to the density of the negative electrode active material filled in the tapping cell when the negative active material powder is dropped into the tapping cell having a capacity of 20 μm through a sieve having a graduation interval of 20 μm to fill the tapping cell.

When d ₁ is smaller than 0.5 μm in relation to the numerical range of d ₁ , when the electrode is manufactured as a negative electrode active material, the binding force between the negative electrode active material and the current collector metal decreases, and the negative electrode active material peels from the current collector during charge and discharge of the secondary battery. Problems may arise. Peeling of such a negative electrode active material causes the charge / discharge capacity of a secondary battery to fall. In addition, the value d _max is greater than d _max range in relation to the 60㎛ of, after applying the negative electrode active material on the current collector when producing the electrode as a negative electrode active material is squeezed not been well there is a problem in that the electrodes are thickened.

The carbon material-based negative active material according to the present invention more preferably satisfies constant conditions for not only PSD and volume density but also tap density and specific surface area. That is, the tap density of the negative electrode active material according to the present invention is 0.7 g / cm ³ or more, and the specific surface area is 5 m ² / g or less.

Here, tap density is based on JIS-K5101, and it measures using the "powder tester PT-R" by Hosokawa Micron. That is, the carbonaceous anode active material powder is dropped into a 20cc tapping cell through a sieve having a graduation interval of 200 μm to fill the tapping cell with a full amount, followed by 3000 strokes of 18 mm stroke length once per second. The tap density is measured by measuring the density of the negative electrode active material.

The tap density is influenced by the diameter, cross-sectional shape, surface shape, etc. of the carbonaceous material negative electrode active material powder. Therefore, even if the average particle diameter of the negative electrode active material particles is the same, the tap density varies depending on the particle size distribution, that is, PSD. In general, the tap density is increased by the coating of the core carbon material. On the other hand, when there are many scale-shaped particles in the core carbon material powder or a fine powder having a size smaller than d ₁ based on the PSD, the tap density does not increase. The carbonaceous negative electrode active material according to the present invention has a relatively high tap density of 0.7 g / cm ³ or more because there is no fine powder of less than d ₁ and part or all of the edges of the core carbon material are covered by the carbide layer. When the tap density of the negative electrode active material satisfies the above conditions, the packing density can be increased when the negative electrode active material is pressed onto the current collector metal without interfering with the penetration of the electrolyte into the negative electrode active material.

The specific surface area of the negative electrode active material according to the present invention is measured using a nitrogen adsorption BET specific surface area measuring apparatus ASAP2400 manufactured by Micromeritex. The negative electrode active material according to the present invention has a specific surface area of 5 m ² / g or less because the pores of the core carbon material are blocked by adhesion or coating of carbon derived from coal or petroleum. When the specific surface area is small in this way, the sites at which the decomposition reaction of the electrolyte may occur may be reduced, and thus, deterioration of the long-term cycle characteristics of the secondary battery due to the decomposition reaction of the electrolyte may be prevented.

The negative electrode active material for a secondary battery according to the present invention described above is coated carbon material on the surface of the core carbon material by mixing the core carbon material in the form of particles with pitch, tar or mixture thereof derived from coal or petroleum by wet or dry. First step of coating the raw material of the second step of forming the core carbon material coated with the raw material material to form a part or all of the edge of the core carbon material of the coated carbon material consisting of a carbide layer and d ₁ based on the PSD And a third step of classifying the core carbon material coated with the coated carbon material such that d _max is 0.5 µm or more and 60 µm or less, respectively.

In the second step, it is preferable to control the process conditions so that the coated carbon material has lower crystallinity than the core carbon material by appropriately selecting the carbonization temperature, the carbonization time, the carbonization pressure, the type of carbonization atmosphere gas, and the like. .

For example, when the carbonization process is performed after coating pitch on natural graphite, the carbonization firing temperature is controlled to 1000 to 2500 ° C, the carbonization firing time is 1 to 48 hours, and the carbonization firing pressure is 2 to 10 mmH ₂ O. As the baking atmosphere gas, an inert atmosphere gas capable of forming a non-oxidizing atmosphere such as N ₂ or Ar can be used.

Preferably, in the third step, the negative electrode active material is classified using an air cyclone classifier. For example, by adjusting the blower pressure of the classifier to 10 ~ 200 mmHg to remove the fine powder such that d ₁ is 0.5㎛ or more based on the PSD, and adjust the blower pressure of the classifier to 400 ~ 800mmHg negative electrode active material The negative electrode active material is classified so that d _{max of} does not exceed 60 micrometers.

However, the present invention is not limited by the specific process conditions associated with the classification method and classification of the negative electrode active material.

The negative electrode active material for a secondary battery manufactured by the above-described method may be mixed with a conductive material, a binder, and an organic solvent to prepare an active material paste. Then, the active material paste may be applied to a metal current collector such as a copper foil, and then dried, heat treated, and pressed to prepare an electrode for a secondary battery (cathode).

In addition, the secondary battery electrode thus prepared can be used for the production of a lithium secondary battery. That is, a metal current collector in which the negative electrode active material is bound to a predetermined thickness and a metal current collector in which the Li-based transition metal compound is bound to a predetermined thickness are opposed to each other with a separator therebetween, and the separator is impregnated with an electrolyte for a lithium secondary battery. If possible, it is also possible to manufacture a lithium secondary battery that can be repeatedly charged and discharged. Since the secondary battery electrode and the secondary battery manufacturing method are well known to those skilled in the art to which the present invention pertains, a detailed description thereof will be omitted.

On the other hand, the present invention is characterized in the physical properties of the negative electrode active material for secondary batteries. Therefore, when manufacturing a secondary battery electrode and a secondary battery including the same using the negative electrode active material according to the present invention can be applied to a variety of methods known in the art. In addition, it is apparent that the type of secondary battery in which the negative electrode active material according to the present invention may be utilized is not limited to the lithium secondary battery.

<Examples and Comparative Examples>

Example 1

A spherical natural graphite was dry mixed at a high pitch of about 20% by weight with respect to the weight of natural graphite for about 10 minutes to obtain a mixture. The mixture was subjected to the first and second carbonization firing processes for 1 hour at 1100 ° C. and 2200 ° C., respectively, and then classified and finely divided to prepare a negative electrode active material. In the classification and removal process, d ₁ was 4.4 μm and d _max was 45 μm on the basis of PSD. 100 g of the prepared negative electrode active material was placed in a 500 ml reactor, and a small amount of N-methyl pitolidon (NMP) and a binder (PVDF) were added thereto, followed by mixing using a mixer to prepare a slurry for producing a negative electrode. The negative electrode slurry was uniformly applied to an 8 μm thick copper foil, vacuum dried at 120 ° C., and compressed to prepare a negative electrode for a secondary battery. Then, a coin cell of 2016 standard (diameter: 20 mm, height: 16 mm) was manufactured using the prepared negative electrode and lithium foil (relative electrode) by applying a conventional manufacturing process of a lithium secondary battery. A porous polyethylene membrane (Celgard 2300, thickness 20 μm) was used as a separator for producing a coin cell, and as a liquid electrolyte, ethylene carbonate: diethyl carbonate: ethyl-methyl carbonate = 1: 1: 1 (volume ratio) of mixed solvent 1 Molar LiPF ₆ solution was used.

Example 2

D ₁ is 2.0 μm and d _max is 56 μm in the classification and fine powder removal process of the negative electrode active material. Process conditions were set to be, and the rest of the process was carried out in the same manner as in Example 1 to prepare a negative electrode active material for a secondary battery. Then, a coin cell was fabricated to evaluate the charge and discharge characteristics of the negative electrode active material. The coin cell was produced by applying the same conditions as in Example 1.

Example 3

Cokes were calcined at 3000 ° C. for 24 hours to produce artificial graphite. Then, a classification and fine powder removal process was performed under conditions of d ₁ and d _max of 0.7 μm and 56 μm, respectively, based on the PSD to prepare a negative active material for a secondary battery. Then, a coin cell was fabricated to evaluate the charge and discharge characteristics of the negative electrode active material. The coin cell was produced by applying the same conditions as in Example 1.

Comparative Example 1

D ₁ is 0.3 μm and d _max is 56 μm in the classification and fine powder removal process of the negative electrode active material. Process conditions were set to be, and the rest of the process was carried out in the same manner as in Example 1 to prepare a negative electrode active material for a secondary battery. Then, a coin cell was fabricated to evaluate the charge and discharge characteristics of the negative electrode active material. The coin cell was produced by applying the same conditions as in Example 1.

Comparative Example 2

D ₁ is 0.9 µm and d _max is 85 µm in the classification and removal of the negative active material. Process conditions were set to be, and the rest of the process was carried out in the same manner as in Example 1 to prepare a negative electrode active material for a secondary battery. Then, a coin cell was fabricated to evaluate the charge and discharge characteristics of the negative electrode active material. The coin cell was produced by applying the same conditions as in Example 1.

Comparative Example 3

D ₁ is 0.4 µm and d _max is 86 µm in the classification and removal of the negative active material. Process conditions were set to be, and the rest of the process was carried out in the same manner as in Example 3 to prepare a negative electrode active material for a secondary battery. Then, a coin cell was fabricated to evaluate the charge and discharge characteristics of the negative electrode active material. The coin cell was produced by applying the same conditions as in Example 1.

Comparative Example 4

D ₁ is 4.7 µm and d _max is 90 µm in the classification and removal of the negative active material. Process conditions were set to be, and the rest of the process was carried out in the same manner as in Example 3 to prepare a negative electrode active material for a secondary battery. Then, a coin cell was fabricated to evaluate the charge and discharge characteristics of the negative electrode active material. The coin cell was produced by applying the same conditions as in Example 1.

<Characteristic evaluation of the negative electrode active material>

The following characteristics evaluation experiments were performed using samples of the negative active material for secondary batteries prepared according to Examples 1 to 3 and Comparative Examples 1 to 4 as samples.

1.Bulk density: g / cm ³

The negative electrode active material sample was passed through a sieve having a graduation interval of 200 μm to fill a 20 cc capacity tapping cell, and then the bulk density was measured.

2.Particle Size Distribution (PSD)

The PSD of the negative electrode active material sample was measured using CILAS 'CILAS920, France' and MALVERN's 'Mastersizer2000, USA'.

3. Specific surface area

 The specific surface area of the negative electrode active material sample was measured by using the nitrogen adsorption BET specific surface area measuring apparatus ASAP2400 manufactured by Micromeritex.

4. Tap Density

The tap density of the negative electrode active material sample was measured according to JIS-K5101 using the powder tester PT-R manufactured by Hosokawa Micro Co., Ltd., and a sieve having a 200 μm scale interval was used as a sieve for passing the sample powder. . The sample powder passed through the sieve was dropped into the tapping cell having a capacity of 20 cc, and then filled. Then, the tap density of the powder filled in the tapping cell was measured after 3000 tappings having a stroke length of 18 mm once per second.

5. Charge and discharge characteristics

In order to evaluate the charge and discharge characteristics of the negative electrode active material sample, a charge and discharge experiment of a coin cell was conducted over 25 cycles. The charge and discharge test of each cycle using the coin cell regulates the potential in the range of 0.01 to 1.5V, proceeds with charging until it becomes 0.01V at a charging current of 0.5mA / cm ² , and maintains a voltage of 0.01V. Charging was continued until the current became 0.02 mA / cm ² . The discharge current was discharged up to 1.5 V at 0.5 mA / cm ² . Through this charge and discharge cycle test, the discharge capacity retention rate of the 25th cycle was calculated based on the charge and discharge efficiency of the first cycle, the discharge capacity of the second cycle, and the discharge capacity of the second cycle.

6. Fairness

100 g of a negative electrode active material sample was placed in a 500 ml reactor, and a small amount of N-methyl pitolidon (NMP) and a binder (PVDF) were added thereto, followed by mixing using a mixer to prepare a slurry. 35 g of the slurry was passed through a sieve by vacuum pumping for a sufficient time after putting a 100 μm sieve. At this time, fairness was evaluated according to Out / In (%), which is the ratio between the slurry input amount and the discharge amount. Fairness evaluation criteria were judged that fairness is good when Out / In (%) is greater than 70%, fairness is common between 50 and 70%, and less than 50% is poor.

7. compressibility

100 g of the sample powder was put in a 500 ml reactor, and a small amount of N-methyl pitolidon (NMP) and a binder (PVDF) were added thereto, followed by mixing using a mixer to prepare a slurry. Then, the slurry was uniformly applied to 8 μm thick copper foil, and the slurry was vacuum dried at 120 ° C. to prepare an electrode before compression. The electrode was then pressed several times. At this time, the electrode density at a predetermined point according to the number of times of compression was obtained to evaluate the compressibility of the negative electrode active material. The crimpability evaluation criterion evaluated that the crimping property was good when the electrode density in the 1 to 3 compression section was 1.7 (g / cc) or more, and the crimping property was poor when it was less than 1.7 (g / cc).

Tables 1 and 2 show various characteristics evaluation results for the negative active material for secondary batteries manufactured according to Examples 1 to 3 and Comparative Examples 1 to 4 described above. In Tables 1 and 2 below, BD represents volume density, SSA represents specific surface area, and TD represents tap density.

Referring to Tables 1 and 2 above, it can be seen that the negative electrode active materials of Examples 1 to 3 have better processability and compressibility than the negative electrode active materials of Comparative Examples 1 to 4, and have a high discharge capacity retention rate at 25 cycles. . In addition, the negative electrode active materials of Examples 1 to 3 were found to have a higher volumetric density BD than the negative electrode active materials of Comparative Examples 2 to 4, which is due to the fact that fine powder and coarse powder are mixed at an appropriate ratio in the particle distribution of the negative electrode active material. It is analyzed that it is because the differential is filled in the space in between. In addition, in contrast to Example 3 and Comparative Example 2, only the d ₁ of the PSD is slightly different, but the negative electrode active material of Example 2 compared to the negative electrode active material of Comparative Example 2 because the d ₁ value satisfies the conditions proposed by the present invention It can be seen that the discharge capacity retention rate characteristic at 25 cycles is excellent. The excellent discharge capacity retention characteristics at 25 cycles support the fact that even if the secondary battery is used for a long time, the decomposition reaction of the electrolyte is effectively suppressed and the deterioration of the long-term characteristics of the secondary battery is not intensified.

As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited thereto and is intended by those skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of equivalents of the claims to be described.

Claims (15)

In the negative electrode active material comprising a core carbon material, part or all of the edge is covered by a carbide layer, A negative active material for a secondary battery, wherein d ₁ and d _max are 0.5 μm or more and 60 μm or less, respectively, and have a bulk density of 1.0 to 1.3 g / cm ³ based on a PSD (Particle Size Distribution). The method of claim 1, The crystallinity of the carbide layer is lower than the crystallinity of the core carbon material, the negative electrode active material for secondary batteries. The method of claim 1, The negative electrode active material for a secondary battery, wherein the tap density of the negative electrode active material is 0.7 g / cm ³ or more. The method of claim 1, The specific surface area of the negative electrode active material is a negative electrode active material for a secondary battery, characterized in that 5 m ² / g or less. The method of claim 1, The core carbon material is a high crystalline spherical natural graphite negative electrode active material, characterized in that. The method of claim 1, The core carbon material is natural graphite, artificial graphite, mesocarbon micro beads, mesopeze pitch fine powder, isotropic pitch fine powder, resin charcoal, and pseudo-graphite having elliptical shape, scale shape, whisker shape or crushed shape. A negative active material for a secondary battery, characterized in that any one or a mixture thereof selected from the group consisting of low crystalline carbon fine powder having a structure or a turbostratactic structure. The method of claim 1, The carbide layer is a negative active material for a secondary battery, characterized in that the low crystalline carbide layer formed by coating a carbon, petroleum-based pitch, tar or a mixture thereof and then carbonized. A secondary battery electrode comprising a metal current collector coated with the negative electrode active material according to any one of claims 1 to 7. The negative electrode current collector coated with the negative electrode active material according to any one of claims 1 to 7, a positive electrode current collector coated with a positive electrode active material, a separator interposed between the negative electrode current collector and the positive electrode current collector and filled in the separator A secondary battery comprising an electrolyte solution. First step of coating the raw material of the coated carbon material on the surface of the core carbon material having a particle shape A second step of firing the core carbon material coated with the raw material to form a coated carbon material including a carbide layer on part or all of the edges of the core carbon material; And a third step of classifying the core carbon material on which the coated carbon material is formed such that d1 and d _max are 0.5 µm or more and 60 µm or less, respectively, based on the PSD. The method of claim 10, In the second step, the method for producing a negative electrode active material for a secondary battery, characterized in that the firing the core carbon material coated with the raw material for 1 to 48 hours at a temperature of 1000 ~ 2500 ℃. The method of claim 10, The third step is to classify the negative electrode active material by a classifier using an air cyclone method. The fine powder is removed so that d ₁ of the PSD becomes 0.5 μm or more under a blower pressure of 10 to 200 mmHg, and the blower pressure is 400 A method for producing a negative electrode active material for a secondary battery, characterized in that the step of classifying the negative electrode active material so that d _max is 60㎛ or less under the condition of ~ 800mmHg. The method of claim 10, The core carbon material is a method for producing a negative electrode active material for a secondary battery, characterized in that the high crystalline spherical natural graphite. The method of claim 10, The core carbon material is natural graphite, artificial graphite, mesocarbon microbeads, mesopez pitch fine powder, isotropic pitch fine powder, resin charcoal, and pseudo-graphite having elliptical shape, particle shape, scale shape, whisker shape or crushed shape. A method for producing a negative electrode active material for a secondary battery, characterized in that any one or a mixture thereof selected from the group consisting of graphite (low-crystalline) carbon powder having a graphite) structure or a turbostratactic structure. The method of claim 10, The raw material of the coated carbon material is a pitch, tar or a mixture thereof derived from coal-based or petroleum-based negative electrode active material manufacturing method for a secondary battery.