KR100960139B1 - Negative active material for lithium secondary battery, method of preparing thereof, and lithium secondary battery comprising the same - Google Patents

Abstract

The present invention relates to a negative electrode active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same. The negative electrode active material includes low crystalline graphite modified particles having an average particle diameter of 1 μm or less, and a low crystalline carbon material.

The negative electrode active material solves the problem of low charge output compared to the discharge output when designing the electrode using a conventional crystalline graphite-based carbon material, the lithium secondary battery comprising the same has a high current density and output characteristics during charging and discharging.

Low Crystalline, Graphite, Carbon Material, Output

Description

A negative electrode active material for a lithium secondary battery, a method of manufacturing the same, and a lithium secondary battery including the same {NEGATIVE ACTIVE MATERIAL FOR LITHIUM SECONDARY BATTERY, METHOD OF PREPARING THEREOF, AND LITHIUM SECONDARY BATTERY COMPRISING THE SAME}

The present invention relates to a negative electrode active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same. More specifically, a negative electrode active material for a lithium secondary battery having a high current density and output characteristics during charge and discharge, and a method for manufacturing the same It relates to a lithium secondary battery.

Carbonaceous materials used as negative electrode active materials for lithium secondary batteries are classified into crystalline carbon materials and amorphous carbon materials, and the crystalline carbon materials are further subdivided into graphite and carbon materials.

The graphite system includes natural graphite and artificial graphite. Among them, natural graphite has low cost and high electrochemical properties similar to artificial graphite, and thus has high utility as a negative electrode active material. However, since natural graphite has a plate-like shape, when it is manufactured as an electrode plate, the graphite active material is flattened and oriented on the current collector, so that impregnation of the electrolyte is not easy, and thus high rate charge / discharge characteristics are degraded.

In order to solve the problem of the natural graphite according to the shape of the plate-shaped particles, the scale-like natural graphite particles can be granulated into a sphere to improve the charge and discharge characteristics as a negative electrode active material of the lithium secondary battery (Korea Patent Publication 2003-2003). 87986, Republic of Korea Patent Publication No. 1999-76535, Republic of Korea Patent Publication No. 2005-9245).

In addition, in Korean Patent Laid-Open Publication No. 2000-0019113, crystalline carbon particles made of natural graphite and artificial graphite are spherically granulated with amorphous carbon to have good charge and discharge characteristics as a negative electrode active material of a lithium secondary battery, and have good propylene carbonate, diethyl carbonate, or propyl acetate. By using an electrolyte solution containing a low temperature characteristics and excellent anode active material excellent in safety.

However, in the case of crystalline graphite carbon materials such as natural graphite or artificial graphite, and Korean Patent Publication No. 2000-0019113, the charge output is very low compared to the discharge output when designing an electrode for high rate charging and discharging due to low voltage flatness compared to a lithium electrode. When the propylene carbonate (PC) electrolyte having excellent low temperature characteristics is used at a high ratio, the carbon layer may be peeled off, making it difficult to insert and detach lithium ions, making it difficult to use as an electrode.

Therefore, carbon materials having an amorphous structure such as hard carbon can use propylene carbonate (PC) electrolyte and have high output characteristics, but hard carbon is expensive to manufacture and exhibits sensitivity to moisture in the air. Therefore, it is necessary to develop a new amorphous carbon material exhibiting charge and discharge characteristics similar to those of hard carbon.

In order to solve the above problems, an object of the present invention is to provide a negative electrode active material for a lithium secondary battery excellent in capacity and high rate charge-discharge characteristics, a method of manufacturing the same.

Another object of the present invention is to provide a lithium secondary battery including the above.

In order to achieve the above object, the present invention

Low crystalline graphite modified particles having an average particle diameter of 1 μm or less, and

It provides a negative electrode active material for a lithium secondary battery comprising the graphite modified particles and a low crystalline carbon material.

The low crystalline graphite modified particles have a Raman peak intensity ratio (ID / IG) of 0.5 or more, preferably 0.5 to 2.

The low crystalline graphite modified particles have an average particle diameter of 1 μm or less, preferably 0.01 to 0.9 μm, more preferably 0.03 to 0.1 μm.

The negative active material for a lithium secondary battery may include 0.1 to 60 parts by weight of a low crystalline carbon material based on 100 parts by weight of low crystalline graphite modified particles.

In the negative electrode active material for lithium secondary battery, low crystalline graphite modified particles having an average particle diameter of 1 μm or less are spherically granulated by a low crystalline carbon material, so that the average particle size is 1.0 to 40 μm, preferably 5 to 30 μm. Have

Also,

Grinding the crystalline graphite particles to prepare low crystalline graphite modified particles having an average particle diameter of 1 μm or less;

It provides a method for producing a negative electrode active material for a lithium secondary battery comprising the step of spherical granulation by mixing the low crystalline graphite modified particles and the low crystalline carbon precursor, and heat treatment.

In another aspect, the present invention provides a lithium secondary battery comprising the negative electrode active material.

The present invention solves the problem of low charge output compared to the discharge output when designing an electrode using a conventional crystalline graphite carbon material, and can be used in a propylene carbonate (PC) -based electrolyte having excellent low temperature characteristics. Lithium secondary batteries have high current density and output characteristics during charging and discharging.

The negative electrode active material according to the present invention solves the problem of low charge output compared to the discharge output when designing electrodes using a conventional graphite-based carbon material, so that the lithium secondary battery including the same has a high current density and output characteristics during charge and discharge. .

The negative electrode active material includes low crystalline graphite modified particles having an average particle diameter of 1 μm or less, and the low crystalline graphite modified particles and a low crystalline carbon material.

The low crystalline graphite modified particles have an average particle diameter of 1 μm or less, preferably 0.01 to 0.9 μm, more preferably 0.03 to 0.1 μm. These finely sized low crystalline graphite modified particles have an increase in specific surface area to shorten the moving distance of lithium, thereby improving output characteristics of the battery. When the average particle diameter of the graphite-modified particles exceeds 1 μm, a problem arises in that the output characteristics decrease due to an increase in the diffusion distance of lithium ions during charging and discharging.

The low crystalline graphite modified particles have a crystalline portion and an amorphous portion, and has a Raman peak intensity ratio (ID / IG) of 0.5 or more, preferably 0.6 to 2, which shows a low degree of crystallinity. In the Raman peak intensity ratio, IG means peak of crystalline portion (G-peak, 1573 cm-1), and ID means peak of amorphous portion (D-peak, 1309 cm-1), where ID / It is an IG value. The larger this value, the lower the crystallinity.

If the Raman peak intensity ratio (ID / IG) is less than 0.5, the low voltage flatness of the graphite is maintained, so it is difficult to expect the effect of improving the output characteristics. On the contrary, if the Raman peak intensity ratio (ID / IG) exceeds 2, It is not easy to manufacture because very strong milling energy and long modification time are required to produce low crystalline graphite modified particles.

The negative electrode active material according to the present invention contains 0.1 to 60 parts by weight of the low crystalline carbon material with respect to 100 parts by weight of the low crystalline graphite modified particles. If the content of the low crystalline carbon material is less than the above range, it is difficult to sufficiently coat the surface of the low crystalline graphite modified particles, it is difficult to expect the surface modification effect according to the initial efficiency improvement. On the contrary, if the content exceeds the above range, the low crystalline carbon material is excessively coated on the low crystalline graphite modified particles, thereby lowering the reversible capacity characteristics and output characteristics of the battery.

The negative electrode active material including the low crystalline graphite modified particles and the low crystalline carbon material has an average particle diameter of 1.0 to 40 µm, preferably 5 to 30 µm. If the average particle diameter of the negative electrode active material is less than the above range, the area where the SEI film is generated during the initial charging reaction increases due to the increase in the specific surface area of the negative electrode active material particles, and as a result, the initial irreversible capacity is increased, and the binding to the current collector There is a problem of causing an increase in the amount of the binder (binder) to reduce the current density per unit volume of the electrode. On the contrary, if the average particle diameter exceeds the above range, the gap between particles increases during manufacturing of the electrode, resulting in a decrease in current density per unit volume of the battery, and a large particle size causes a long diffusion distance of lithium ions, resulting in a decrease in output characteristics. do.

The low crystalline carbon material means carbonized by heat treatment from an amorphous carbon precursor. The negative electrode active material according to the present invention contains 0.1 to 60 parts by weight of low crystalline carbon material based on 100 parts by weight of low crystalline graphite modified particles. If the content of low crystalline carbon is less than the above range, it is difficult to sufficiently coat the surface of the low crystalline graphite modified particles, it is difficult to expect the surface modification effect such as the irreversible capacity reduction. On the contrary, if the content exceeds the above range, since the low active carbon contains a lot of low crystalline carbon in the negative electrode active material, the reversible capacity of the battery is lowered, and the low crystalline carbon layer is formed inside and on the surface of the negative electrode active material. There is a problem that the thickness is formed to reduce the output characteristics.

The negative electrode active material for a lithium secondary battery,

Grinding the crystalline graphite particles in an oxygen atmosphere to produce low crystalline graphite modified particles;

The low crystalline graphite-modified particles and the low crystalline carbon precursor are mixed and spherical granulated, and then subjected to a heat treatment.

First, crystalline graphite particles are pulverized in an oxygen atmosphere to produce low crystalline modified graphite modified particles.

The graphite particles are crystalline carbonaceous materials, and may be one selected from the group consisting of natural graphite, artificial graphite, and mixtures thereof. At this time, the shape of the graphite particles is not limited in the present invention, typically fibrous, flaky or spherical graphite is possible, preferably inexpensive and economically advantageous use of flaky natural graphite.

The crystalline graphite particles are converted to low crystalline graphite modified particles by grinding, the crystal structure of the graphite particles is affected by the grinding conditions, and through the grinding, the crystal structure of the graphite particles is converted from crystalline to low-density do.

The grinding is carried out by a conventional milling process, for example, ball mill (attrition mill), vibration mill (vibration mill), disk mill (disk mill), jet mill (jet mill), Or using a milling apparatus such as a rotor mill. At this time, the grinding speed (rpm) and the grinding time for the grinding can be appropriately adjusted by those skilled in the art according to the type of milling apparatus, the content of the material to be treated and the like.

In particular, in the present invention, the grinding of the crystalline graphite particles is performed in an oxygen atmosphere, for example, by injecting oxygen or air containing oxygen. The low crystalline graphite modified particles obtained by pulverizing in an oxygen atmosphere are strongly adsorbed between the graphite structures in which oxygen is destroyed so that recrystallization of the low crystalline graphite modified particles is suppressed in the subsequent heat treatment step.

However, when the milling is carried out in an inert atmosphere, incomplete recrystallization of the low crystalline graphite particles occurs during the subsequent heat treatment process. As a result, when this is used as a negative electrode active material of the battery, incomplete recrystallization occurs on the surface during charging and discharging of the battery, the electrolyte is co-calated with lithium to the low crystalline graphite modified particles, and the graphite particles are peeled off, or the irreversible reaction associated with the SEI film. This increase increases the initial irreversible capacity of the battery.

For example, in the case of pulverizing using a ball mill, the pulverization using the ball mill is a high energy milling process, and refers to a dry ball milling process in which graphite powder is charged into a container together with a plurality of balls and stirred at high mechanical energy.

At this time, each graphite powder during the ball milling process is subjected to repeated compressive and shear stresses between the balls to make the graphite powder particles fine and rearrangement of carbon atoms to proceed, thereby making nanocrystalline particles having a submicron particle size. It is possible to produce particles in which -crystalline and disordered regions are present.

The ball mill ball is performed using a metal alloy of stainless steel and alloy tool steel (eg, SKD-11), and ceramic balls such as zirconia and alumina.

The low crystalline graphite modified particles obtained through the pulverization in this way have an average particle diameter of 1 µm or less, preferably 0.01 to 0.9 µm, more preferably 0.03 to 0.1 µm. When the average particle diameter of the graphite-modified particles exceeds 1 μm, the diffusion distance of lithium ions is increased to reduce the output characteristics of the battery.

Next, the low crystalline graphite modified particles and the low crystalline carbon precursor are mixed, spherical granulated, and then heat treated to prepare a negative electrode active material.

The amorphous carbonaceous precursor is not particularly limited in the present invention, typically a soft carbon precursor such as polyvinyl alcohol (PVA), polyvinyl chloride (PVC), coal-based pitch, petroleum-based pitch, mesophase pitch, low molecular weight heavy oil and Sucrose, phenol resin, furan resin, furfuryl alcohol, polyacrylonitrile, cellulose, styrene, polyimide At least one carbon precursor selected from polymer resins, such as epoxy resins, is possible.

However, since the carbon yield after carbonization of each carbon precursor is different, the amount of low crystalline carbon material after carbonization should be adjusted so that the amount of the low crystalline carbon material is 0.1 to 60 parts by weight based on the carbon precursor. If the content of the low crystalline carbon material is less than the above range, it is difficult to sufficiently coat the surface of the low crystalline graphite modified particles, it is difficult to expect a surface modification effect such as reducing irreversible capacity. On the contrary, if the content exceeds the above range, since the low active carbon contains a lot of low crystalline carbon in the negative electrode active material, the reversible capacity of the battery is lowered, and the low crystalline carbon layer is formed inside and on the surface of the negative electrode active material. There is a problem that the thickness is formed to reduce the output characteristics.

At this time, the heat treatment is carried out at a temperature of 700 to 2000 ℃, preferably 900 to 1500 ℃. If the heat treatment temperature is less than the above range, the removal of impurity dissimilar elements will not be sufficient. On the contrary, if the above is exceeded, recrystallization of low crystalline graphite modified particles occurs, or a problem of graphitization of a low crystalline carbon precursor occurs.

In this case, the heat treatment may be performed under an inert atmosphere by injecting nitrogen, argon, hydrogen, and a mixed gas thereof, and may be performed under vacuum in some cases.

In addition, the spherical granulation step is performed in the spherical granulation step after mixing the low crystalline graphite modified particles with the low crystalline carbon precursor. The spheroidization process is performed by applying a rotational friction force with equipment such as a blade rotor mill, and through such spherical granulation, the anode active material has a spherical shape and a particle size of a constant size. As a result, the dispersion degree of the composition for forming a negative electrode may be increased when introduced into the negative electrode active material using the same, and the tap density in the negative electrode may be increased.

The negative electrode active material thus prepared is introduced into the negative electrode of the lithium secondary battery.

The lithium secondary battery includes a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, and an electrolyte located between the positive electrode and the negative electrode. In this case, an active material including low crystalline graphite modified particles and a low crystalline carbon material according to the present invention is used as the negative electrode active material. Since the negative active material has a nanocrystalline or disordered microstructure of the main active particles, the negative active material exhibits an inclined voltage curve similar to that of hard carbon, thereby obtaining high output characteristics during charge and discharge, and high current density during charge and discharge. do. As a result, the conventional graphite-based carbon material solves the problem that the charging output is very low compared to the discharge output when designing the electrode for high rate charging and discharging due to the low voltage flatness of the lithium electrode.

 When using a crystalline carbon material such as natural graphite or artificial graphite as a negative electrode active material, propylene carbonate (PC) electrolyte having excellent low temperature characteristics may be used, resulting in a peeling phenomenon of the carbon layer, making it difficult to insert and detach lithium ions. Difficult to use In Korean Patent Laid-Open Publication No. 2000-0019113, a propylene carbonate (PC) is included in a limited range of a battery made of a negative active material of a lithium secondary battery by spherical granulation of crystalline carbon particles composed of natural graphite and artificial graphite with amorphous carbon. Only the electrolyte shows its properties. However, according to the present invention, when the active material including the low crystalline graphite modified particles and the low crystalline carbon material is used, the propylene carbonate (PC) is 100 Vol% because the main active particles have a nanocrystalline or disordered arrangement of microstructures. Even when phosphorus electrolyte is used, it is possible to manufacture a battery having excellent low-temperature characteristics because the peeling phenomenon of the carbon layer does not occur and there is no reduction in initial efficiency and capacity.

Hereinafter, preferred examples and comparative examples of the present invention are described. However, the following examples are only one preferred embodiment of the present invention and the present invention is not limited to the following examples.

(Example 1)

Low-crystalline graphite-modified particles having an average particle diameter of 0.19 μm by performing natural milling having a particle diameter of 200 μm and performing planetary milling for 2 hours at 1300 rpm at a weight ratio of 1:20 in the air with graphite particles and ball particles. Was prepared.

Petroleum pitch was carbonized with the low crystalline graphite modified particles and the amorphous carbon precursor, mixed by dry milling, and spherical granulated. Subsequently, heat treatment was performed at 1,200 ° C. for 1 hour while injecting Ar gas, followed by grinding to prepare a negative electrode active material having an average particle diameter of 20 μm. In the prepared negative active material, the weight ratio of the low crystalline graphite modified particles to the low crystalline carbon material was 70:30.

(Example 2)

, Except that dissolved to a concentration of the LiClO ₄ 1 (mol / L) in propylene carbonate (PC) (100 vol.% ) Was carried out in the same manner as in Example 1 as an electrolyte.

(Example 3)

Polyvinyl alcohol (PVA) was carbonized on the low crystalline graphite modified particles, and wet milled at a carbon material weight ratio of 97: 3, followed by 1 hour at 600 ° C while injecting Ar gas, which was then petroleum pitch and dry milling. The same process as in Example 1 was carried out except that the mixture was mixed by a method and spherical granulated. In the prepared negative active material, the weight ratio of the low crystalline graphite modified particles to the low crystalline carbon material was 70:30.

(Example 4)

, Except that dissolved to a concentration of the LiClO ₄ 1 (mol / L) in propylene carbonate (PC) (100 vol.% ) Was carried out in the same manner as in Example 3 as an electrolyte.

(Comparative Example 1)

Hard carbon particles having a particle diameter of 10 μm were used as the negative electrode active material.

Experimental Example 1

In order to investigate the shape change of the particles by the ball milling treatment, the natural graphite particles used as starting materials in Example 1 and the low crystalline graphite modified particles obtained after the ball milling were measured using a scanning electron microscope, and the results obtained. It is shown in Figure 1a and 1b below.

Figure 1a is a scanning electron micrograph of the natural graphite particles used as a starting material, Figure 1b is a scanning electron micrograph of the low crystalline graphite modified particles. 1A and 1B, it can be seen that the size of the particles becomes very fine as compared with FIG. 1A, which is an electron micrograph before modification.

Experimental Example 2

In order to determine the particle size of the low crystalline graphite modified particles obtained after the ball milling of Example 1 was measured using a particle size analyzer, the results obtained are shown in FIG.

FIG. 2 is a graph of particle size analysis of the low crystalline graphite modified particles obtained in Example 1. Referring to FIG. 2, the low crystalline graphite modified particles may be 1 μm or less, specifically 20 nm and 30 nm, by a milling process. It can be seen that it has a submicron level.

Experimental Example 3

In order to determine the crystal state of the low crystalline graphite modified particles, natural graphite and low crystalline graphite particles as starting materials were measured using an X-ray diffraction analyzer, and the obtained results are shown in FIGS. 3A and 3B.

3A is an X-ray diffraction pattern of natural graphite as a starting material, and FIG. 3B is an X-ray diffraction pattern of low crystalline graphite modified particles of Example 1. FIG.

3A-3B, the low crystalline graphite modified particles of Example 1 (FIG. 3B) which have undergone grinding compared to FIG. 3A showing natural graphite have a very high intensity of (002) diffraction peak which is the main peak. It is smaller and the width of the peak is wider, which shows that the crystallinity is lower than that of natural graphite.

Experimental Example 4

It was measured using a scanning electron microscope of the negative electrode active material particles prepared in Example 1, and the results obtained are shown in FIG.

Referring to FIG. 4, since the negative electrode active material prepared according to Example 1 was manufactured through a spherical granulation process, it can be seen that it has a spherical shape and a particle size of a certain size.

Experimental Example 5

In order to investigate the crystallinity change of the graphite by the ball milling treatment, the Raman spectra of the natural graphite used as the starting material in Example 1 and the low crystalline graphite modified particles obtained after the ball milling were measured, and the results obtained were as follows. 5 is shown.

FIG. 5 compares the Raman spectra of natural graphite used as a starting material in Example 1 and low crystalline graphite modified particles obtained after ball milling, and graphite after ball milling has a wider Raman spectrum D peak and G peak. The larger D peak and the higher ID / IG value indicate that the crystallinity is lower than that of untreated natural graphite.

Experimental Example 7

(Manufacture of Test Cell)

A negative electrode slurry was prepared by mixing the negative electrode active materials prepared in Examples 1, 3 and Comparative Example 1 with CMC / SBR (carboxymethyl cellulose / styrene-butadiene rubber) in distilled water at a weight ratio of 95: 5.

The negative electrode slurry was coated on a copper foil (Cu-foil) to form a thin electrode plate, dried at 180 ° C. for at least 15 hours, and then pressed to prepare a negative electrode plate having a thickness of 40 μm.

With the cathode as the working electrode and the metal lithium foil as the counter electrode, a separator made of a porous polypropylene film is inserted between the working electrode and the counter electrode, and a mixed solvent of diethyl carbonate (DEC) and ethylene carbonate (EC) as an electrolyte solution ( DEC: EC = 1: 1) was used to dissolve LiPF6 to a concentration of 1 (mole / L) to prepare a half coin (half cell) of the 2016 coin type.

Experimental Example 8

(Manufacture of Test Cell)

The negative electrode active material prepared in Examples 2 and 4 was mixed with CMC / SBR (carboxymethyl cellulose / styrene-butadiene rubber) in distilled water at a weight ratio of 95: 5 to prepare a negative electrode slurry.

The negative electrode slurry was coated on a copper foil (Cu-foil) to form a thin electrode plate, dried at 180 ° C. for at least 15 hours, and then pressed to prepare a negative electrode plate having a thickness of 40 μm.

With the cathode as the working electrode and the metal lithium foil as the counter electrode, a separator made of a porous polypropylene film is inserted between the working electrode and the counter electrode, and LiClO ₄ is dissolved in a propylene carbonate (PC) (100 vol.%) Solvent as an electrolyte. A half cell of a 2016 coin type was prepared using the solution dissolved to a concentration of 1 (mol / L).

Experimental Example 9

In order to find out whether the negative electrode active material prepared according to Example 1 was operated in the propylene carbonate (PC) electrolyte, a test half cell was prepared according to Experimental Example 7 and Experimental Example 8 to evaluate the cycle characteristics. 6a and 6b.

Figure 6a shows the cycle characteristics of the half cell prepared according to Experimental Example 7 (Example 1), Figure 6b shows the cycle characteristics of the half cell prepared according to Experimental Example 8 (Example 2).

6A and 6B, since the same capacity and excellent cycle characteristics are exhibited regardless of the type of electrolyte, it can be seen that the peeling phenomenon does not occur with respect to the PC electrolyte.

(Charge and discharge characteristic test)

The charge and discharge characteristics were measured using the half cells prepared above, and the results obtained are shown in Table 1 below.

Discharge Capacity [mAh / g] Initial Efficiency [%] High rate characteristic [5C capacity / 0.2C capacity * 100] (%) Example 1 317 81.8 91 Example 2 316 81.8 92 Example 3 295 83.8 91.1 Example 4 290 83 91 Comparative Example 1 310 80.4 78.8

Referring to Table 1, in the case of a battery including the negative electrode active material prepared in Examples 1 to 4, compared with the battery containing the negative electrode active material of Comparative Example 1, the initial efficiency is high, and high rate characteristics (output characteristics) also It can be seen that high.

In the case of the battery including the negative electrode active material prepared by Examples 2 and 4, even in an electrolyte solution having a propylene carbonate (PC) of 100 Vol%, the capacity reduction and the difference in high rate characteristics (output characteristics) compared to the batteries of Examples 1 and 3 You can see that there is no.

The battery according to the embodiment shows that it is possible to use a propylene carbonate electrolyte and thus to manufacture a battery having excellent low temperature characteristics.

The present invention is not limited to the above embodiments, but may be manufactured in various forms, and a person skilled in the art to which the present invention pertains has another specific form without changing the technical spirit or essential features of the present invention. It will be appreciated that the present invention may be practiced as. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

1A is a scanning electron microscope photograph of natural graphite particles used as starting materials.

1B is a scanning electron micrograph of low crystalline graphite modified particles.

2 is a particle size analysis graph of the low crystalline graphite modified particles obtained in Example 1.

3A is an X-ray diffraction pattern of natural graphite as a starting material.

3B is an X-ray diffraction pattern of the low crystalline graphite modified particles of Example 1. FIG.

Figure 4 is a scanning electron microscope photograph of the negative electrode active material prepared in Example 1.

5 is a Raman spectrum graph of raw natural graphite before ball milling and low crystalline graphite modified particles after ball milling of Example 1. FIG.

Figure 6a is a graph showing the cycle characteristics of the half cell prepared according to Experimental Example 7.

Figure 6b is a graph showing the cycle characteristics of the half cell prepared according to Experimental Example 8.

Claims (18)

A plurality of low crystalline graphite modified particles having an average particle diameter of 1 μm or less, and A low crystalline carbon material surrounding each of the low crystalline graphite modified particles, and spherically granulating a plurality of enclosed low crystalline graphite modified particles, respectively. A negative electrode active material for a lithium secondary battery comprising a. The method of claim 1, The low crystalline graphite modified particles have a Raman peak intensity ratio (ID / IG) of 0.5 or more negative active material for a lithium secondary battery. The method of claim 1, The low crystalline graphite modified particles have a Raman peak intensity ratio (ID / IG) of 0.6 to 2 negative electrode active material for a lithium secondary battery. The method of claim 1, The low crystalline graphite modified particles are negative active material for a lithium secondary battery having an average particle diameter of 0.01 to 0.9 ㎛. The method of claim 1, The low crystalline graphite modified particles are negative active material for a lithium secondary battery having an average particle diameter of 0.03 to 0.1 ㎛. The method of claim 1, The negative active material is a lithium secondary battery negative electrode active material having an average particle diameter of 1.0 to 40 ㎛. The method of claim 1, The negative active material is a negative active material for a lithium secondary battery containing 0.1 to 60 parts by weight of a low crystalline carbon material with respect to 100 parts by weight of low crystalline graphite modified particles. Pulverizing the crystalline graphite modified particles in an oxygen atmosphere to produce low crystalline graphite modified particles; Mixing the low crystalline graphite modified particles with the low crystalline carbon precursor to form a spherical granule and heat treatment, The low crystalline carbon precursor is polyvinyl alcohol (PVA), polyvinyl chloride (PVC), coal-based pitch, petroleum-based pitch, mesophase pitch, low molecular weight heavy oil, sucrose, phenol resin, furan resin (furan resin), furfuryl alcohol, polyacrylonitrile, cellulose, styrene, polyimide, epoxy resin and mixtures thereof Method for producing a negative electrode active material for a lithium secondary battery comprising one selected from. The method of claim 8, The crystalline graphite particles are a method for producing a negative electrode active material for a lithium secondary battery using one selected from the group consisting of natural graphite, artificial graphite and mixtures thereof. The method of claim 8, The grinding is a milling apparatus such as a ball mill, an attention mill, a vibration mill, a disk mill, a jet mill, or a rotor mill. Method of manufacturing a negative active material for a lithium secondary battery that is carried out using. The method of claim 8, The pulverization is a method of manufacturing a negative active material for a lithium secondary battery that is performed by injecting oxygen or air containing oxygen. delete The method of claim 8, The heat treatment is a method of manufacturing a negative electrode active material for a lithium secondary battery that is carried out at 700 to 2000 ℃. The method of claim 8, The heat treatment is a method for producing a negative active material for a lithium secondary battery that is carried out at 900 to 1500 ℃. The method of claim 8, The heat treatment is performed by injecting nitrogen, argon, hydrogen and a mixed gas thereof a method of manufacturing a negative electrode active material for a lithium secondary battery. The method of claim 8, In addition, the spherical granulation process is performed in the step of spherically granulating the low crystalline graphite modified particles with the low crystalline carbon precursor. A negative electrode comprising the negative electrode active material according to any one of claims 1 to 7; A positive electrode including a positive electrode active material; And Lithium secondary battery comprising an electrolyte located between the negative electrode and the positive electrode. 100 parts by weight of a plurality of low crystalline graphite modified particles having an average particle diameter of 1 μm or less, and 0.1 to 60 low crystalline carbon materials surrounding each of the low crystalline graphite modified particles and spherically granulating a plurality of the enclosed low crystalline graphite modified particles with respect to 100 parts by weight of the plurality of low crystalline graphite modified particles. Including parts by weight, The low crystalline graphite modified particles have a Raman peak intensity ratio (ID / IG) of 0.5 or more, The low crystalline graphite modified particles are those having an average particle diameter of 0.01 to 0.9 ㎛ Anode active material for lithium secondary battery.

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