KR101491092B1 - Anode active material for rechargeable battery, rechargeable battery, and method for manufacturing the same - Google Patents

Abstract

Disclosed is a negative electrode active material for a secondary battery. An anode active material according to an embodiment of the present invention includes a first particle sphericalized by a first particle precursor serving as a flaky graphite flute, And a second particle dispersed between scaly graphite sections in the first particles and the second particles, (i) SiO _x, Si _1-x M _x O _y, and from the group consisting of At least one selected; (ii) SiO _x And Si; And (iii) a combination of Si _{1 - x} M _x O _y and Si.

Description

TECHNICAL FIELD The present invention relates to a negative electrode active material for a secondary battery, a secondary battery having the negative electrode active material for the secondary battery, and a method of manufacturing the same. BACKGROUND ART < RTI ID = 0.0 >

The present invention relates to a negative electrode active material for a secondary battery, a negative electrode and a secondary battery for the same, and a method of manufacturing the same. More specifically, the present invention relates to a negative electrode active material for realizing a high capacity lithium secondary battery having excellent cycle life, and a lithium secondary battery comprising the same.

Lithium secondary batteries have a high energy density and are widely used in portable electronic devices such as notebook computers, digital cameras, and mobile phones because they have less self-discharge and memory effect than other batteries. However, with the recent miniaturization and multifunctionalization of portable electronic devices, it is required to increase the capacity of a lithium secondary battery as a power source. Current theoretical capacity of graphite commercialized as an anode active material is limited to 372 mAh / g, and it is urgent to develop a new high capacity anode active material.

Conventionally, silicon (Si) or a compound thereof has been studied as a substitute for graphite. Silicon reversibly intercalates and deintercalates lithium through a compound formation reaction with lithium. The silicon has a theoretical maximum capacity of 4020 mAh / g (9800 mAh / cm3, specific gravity: 2.23) However, the volume change occurs due to the reaction with lithium during charging and discharging, resulting in undifferentiation of the silicon active material powder and poor electrical contact between the silicon active material powder and the current collector. As a result, as the charge / discharge cycle of the battery progresses, the battery capacity sharply decreases and the cycle life is shortened.

In order to solve such a problem, Korean Patent Registration No. 10-0830612 discloses a method for producing a graphite first particle, which is a sphered first particle precursor which is a flaky graphite flake; And at least one elementary particle selected from the group consisting of Si, Sn, Al, Ge, Pb and combinations thereof dispersed between the flaky graphite flakes in the spherical graphite first particles; At least one element compound particle selected from the group consisting of Si, Sn, Al, Ge, Pb and combinations thereof; At least one element-containing composite particle selected from the group consisting of Si, Sn, Al, Ge, Pb and combinations thereof; At least one element-containing carbon composite particle selected from the group consisting of Si, Sn, Al, Ge, Pb and combinations thereof; And at least one second particle selected from the group consisting of a combination of these particles, wherein the peeled scaly graphite slice is such that in the spherical graphite first particle, the scraped scaly graphite slice is concentrically oriented The anode active material for a lithium secondary battery has been proposed as a laminated and assembled particle.

It is desirable to minimize the size of the silicon-containing alloy particles to 0.1 mu m or less in order to effectively control the volume change of the silicon phase during charging and discharging. However, if the size of the particles is too small, there is a problem that the manufacturing cost is high and uniform dispersion is difficult during the production of the composite. In the case of increasing the size of the silicon-containing alloy particles, the manufacturing cost of the silicon-containing alloy particles is low, and the composite using the same is easy to manufacture. However, the volume change due to the volume expansion of the silicon phase during the lithium- Effective control can be difficult.

On the other hand, according to recent research results, in the state where silicon oxide (SiO _x ) is distributed in the amorphous Si-O matrix with a Si phase of 2 to 3 nm size, the volume of existing Si due to lithium insertion and desorption during charging / The problem of change can be greatly alleviated.

Further, when a silicon composite oxide (Si _{1 - x} M _x O _y ) doped and doped with another element to SiO _x is used as a negative electrode active material for a lithium secondary battery, electrical conductivity and structural stability can be improved. However, development of an anode active material for a lithium secondary battery which can further cushion the volume change of an oxide due to a reaction with lithium during charging and discharging is desired.

Disclosure of the Invention The present invention has been conceived to solve the problems described above, and it is an object of the present invention to provide a negative electrode active material for a high capacity lithium secondary battery, which uses Si-based oxide particles having a relatively large size, . ≪ / RTI >

The negative electrode active material for a secondary battery according to an embodiment of the present invention includes a first graphite particle having a sphered first particle precursor as a flaky graphite segment, And a second particle dispersed between the flake graphite flakes in the first particle, wherein the second particle is selected from the group consisting of (i) SiO _x , Si _{1 - x} M _x O _y , and combinations thereof At least one being; (ii) SiO _x And Si; And (iii) a combination of Si _{1 - x} M _x O _y and Si.

A method for manufacturing a negative electrode active material for a secondary battery according to an embodiment of the present invention includes: preparing a first particle precursor as a flaky graphite flake by peeling flake graphite; Mixing the first particle precursor and the second particle to produce a mixture; And assembling the mixture, wherein the second particles are at least one selected from the group consisting of (i) SiO _x , Si _{1 - x} M _x O _y , and combinations thereof; (ii) SiO _x And Si; And (iii) a combination of Si _{1 - x} M _x O _y and Si.

A method for manufacturing a negative electrode active material for a secondary battery according to an embodiment of the present invention includes: preparing a first particle precursor as a flaky graphite flake by peeling flake graphite; Mixing the first particle precursor, the second particle, and the amorphous carbon precursor or soft carbon precursor to produce a mixture; Assembling the mixture to produce an assembly in which the second particles and the amorphous carbon precursor or soft carbon precursor are dispersed; And heat-treating the assembly, and comprising the step of carbonizing the amorphous carbon or soft carbon precursor, wherein the second particles (i) SiO _x, Si _{1 -x} M _x O _y, and selected from the group consisting of At least one being; (ii) SiO _x And Si; And (iii) a combination of Si _{1 - x} M _x O _y and Si.

The negative electrode active material for a secondary battery according to the present invention is particularly suitable for a negative electrode for a lithium secondary battery.

The present invention uses Si oxide particles having relatively large sizes as negative electrode active materials for secondary batteries. In the case of the Si-based oxide, since the size of the Si phase in the oxide is dispersed to a size of several nm, even when the oxide particles are large, the buffering effect of the volume change of the silicon oxide is excellent by the reaction with lithium during charging and discharging, Can be improved.

Further, since the anode active material according to the present invention uses Si-based oxide particles having a relatively large size and excellent dispersibility, the composite manufacturing process is easy and the production cost can be reduced.

1 is a cross-sectional view of an anode active material according to an embodiment of the present invention.
2 is a cross-sectional view of an anode active material according to another embodiment of the present invention.
3 is a cross-sectional view of a negative electrode active material according to another embodiment of the present invention.
4 is a graph showing the results of measurement of particle size distribution of laser diffraction scattering with respect to particle size distribution of silicon oxide powder produced according to an embodiment of the present invention.
5 is a graph showing the results of measurement of the particle size distribution of the laser diffraction scattering type particle size distribution of the silicon powder produced according to the comparative example.
6 is a scanning electron micrograph of a silicon oxide powder prepared according to an embodiment of the present invention.
7 is a scanning electron micrograph of the silicon powder prepared according to the comparative example.
8 to 10 are SEM micrographs of the negative electrode active materials prepared according to Examples and Comparative Examples of the present invention, respectively.
11 is a diagram showing the results of X-ray diffraction pattern analysis on the crystallinity of silicon oxide produced according to an embodiment of the present invention.
12 is a diagram showing the X-ray diffraction pattern analysis results on the crystallinity of silicon produced in the comparative example.
13 is a graph showing the results of X-ray diffraction pattern analysis of each of the negative electrode active materials prepared according to Examples and Comparative Examples of the present invention.
FIGS. 14 and 15 are views showing evaluation results of initial charge / discharge characteristics of a test cell manufactured according to an embodiment of the present invention. FIG.
16 is a diagram showing the evaluation results of initial charging and discharging characteristics of a test cell manufactured according to a comparative example

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. However, it is to be understood that the present invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. It is intended that the disclosure of the present invention be limited only by the terms of the appended claims. Like reference numerals refer to like elements throughout the specification.

The anode active material for a lithium secondary battery according to an embodiment of the present invention includes a spherical graphite first particle having a first particle precursor, which is a flake graphite slice, And a second particle dispersed between the flaky graphite flakes in the spherical graphite first particle.

The second particles preferably have a size of 5 nm to 5000 nm, more preferably 20 nm to 1000 nm. When the size of the elemental grains exceeds 5,000 nm, the elemental grains are hardly uniformly dispersed in the spherical graphite first grains within the first graphite grains, and when the size of the elemental grains is less than 5 nm, Dispersion is difficult.

The second particle according to an embodiment of the present invention contains SiO _x . Here, x is preferably 0 < x < 1.5, more preferably 0.001 x 1. When x is 1.5 or more, the amount of Si, which is an active element for lithium, decreases, and the reversible capacity per unit weight decreases.

The second particle according to an embodiment of the present invention contains Si _{1 - x} M _x O _y . Here, x is preferably 0 < x < 1.0, more preferably 0.001 x 0.5. When x is 0.5 or more, the amount of Si, which is an active element for lithium, decreases, and the reversible capacity per unit weight decreases. M is at least one element selected from Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, La, Hf, Ta, W, At least one element selected from the group consisting of Ca, B, P, Al, Ge, Sn, Sb, Bi, Li and combinations thereof. Y is preferably 0.1? Y? 1.7, more preferably 0.3? Y? 1.5. When y is 0.3 or less, the cycle life characteristics are degraded. When y is 1.5 or more, the amount of the inactive phase to lithium in the composite silicon oxide powder containing Si _{1 -x} M _x O _y is large, and the lithium storage capacity is decreased.

In a composite silicon oxide containing Si _{1 - x} M _x O _y according to an embodiment of the present invention, the second element M is doped into SiO _x oxide to form an amorphous matrix of Si - OM or form a crystalline compound can do. Here, the amorphous matrix and the crystalline compound made of the formed Si-OM are structurally stable and can improve the conductivity.

In one embodiment of the present invention, the first particle precursor, which is a flaky graphite flake, is corrugated in a cabbage shape, and the second particles are dispersed between the flaked graphite flakes. Also, voids exist between the flaky graphite flakes to provide a buffer space for volume expansion of the second flakes, and a buffering effect can be obtained by sliding the graphite flake particles.

The carbon has a strong covalent bond in a direction parallel to the surface of the first particle precursor, which is a flake graphite flake, so that the toughness of the first particle precursor, which is a graphite flake, . In addition, since the first particle precursor, which is a flaky graphite flake, is thin, it provides flexibility in the volume expansion of the second particles, and more improved cycle characteristics can be obtained.

1 is a cross-sectional view of an anode active material according to an embodiment of the present invention.

Referring to FIG. 1, the negative electrode active material 1 is formed of a first particle precursor 11, which is a flaky graphite piece, and has a shape of cabbage. The second particles (12) are dispersed among the first particle precursors (11) which are flaky graphite pieces.

The spherical graphite first particles may include voids between the flake graphite flakes. The voids in the vertical or horizontal direction formed between the flaky graphite flakes in the spheronized graphite first particles further improve the buffering action against the volume expansion of the second particles.

The negative electrode active material preferably contains 1 to 70% by weight, more preferably 5 to 30% by weight, of the second particles relative to the total weight of the spherical graphite first particles. When the second particles are less than 1 wt%, the capacity increasing effect is insignificant. When the second particles are more than 70 wt%, it is difficult to expect a buffering effect due to excessive volume expansion when lithium is occluded.

The thickness of the first particle precursor which is the flaky graphite flake is desirably 2 탆 or less, more preferably 0.1 탆 or less, and more preferably 0.01 탆 to 0.1 탆. When the thickness of the first particle precursor as the flaky graphite section exceeds 2 탆, it is difficult to sufficiently disperse the second particles between the flake graphite flakes and the volume expansion of the second particles during charging / The buffering effect is insufficient.

The negative electrode active material according to this embodiment may further include amorphous carbon or soft carbon dispersed among the graphite pieces in the spherical graphite first particles. Here, the amorphous carbon means a hard carbon in which carbon atoms are randomly arranged and can not be changed into crystalline graphite even when the temperature is raised. Soft carbon, on the other hand, is a low-crystalline carbon in which changes to crystalline graphite occur when heated to high temperatures. When the soft carbon precursor is heat-treated at 2000 ° C or less, the soft carbon precursor is present in a low crystalline state with a lower crystallinity than pure graphite.

The negative electrode active material according to another embodiment of the present invention includes a first graphite particle having a sphered first particle precursor of a flake graphite slice; The second particles dispersed between the flaky graphite flakes in the spherical graphite first particles; And amorphous carbon or soft carbon dispersed between the first particle precursor which is a flake graphite flake in the spheronized graphite first particle.

As shown in FIG. 2, the negative electrode active material 2 is formed of a first particle precursor 11 of a flaky graphite flute, and has a cabbage shape. The second particles 12 and the amorphous carbon or soft carbon 14 are dispersed between the first particle precursors 11, which are flaky graphite pieces.

The negative electrode active material 2 according to the embodiment shown in FIG. 2 may include a microporous channel formed on amorphous carbon or soft carbon dispersed between scaly graphite slices in spherical graphite first particles. The microporous channel is formed by carbonizing an amorphous carbon precursor or a soft carbon precursor in a heat treatment process of a spherical graphite first particle containing an amorphous carbon precursor or a soft carbon precursor.

The amorphous carbon or soft carbon is preferably contained in an amount of 1 to 50% by weight based on the total weight of the negative electrode active material. When amorphous carbon or soft carbon is contained in an amount of less than 1% by weight based on the total weight of the negative electrode active material, it is difficult to expect sufficient effect to include amorphous carbon or soft carbon, and when it exceeds 50% by weight, A large amount of amorphous carbon or soft carbon is present in the first particle, so that the ionic conductivity and the electric conductivity are lowered and the charging / discharging rate is lowered.

According to an embodiment of the present invention, the negative electrode active material may be coated with amorphous carbon or soft carbon material on the spherical graphite first particle surface. 3, the negative electrode active material 3 includes a coating film 13 made of amorphous carbon or soft carbon surrounding spherical graphite first particles, and this coating film can improve the reactivity with the electrolyte have. Therefore, when the negative electrode active material 3 according to the present embodiment is used, the charge / discharge efficiency of the lithium secondary battery increases.

It is preferable that the coating film 13 made of amorphous carbon or soft carbon material has a thickness of 0.01 탆 to 1 탆. When the thickness of the coating film is less than 0.01 탆, a reaction occurs between the surface of the spheroidized graphite first particles and the electrolyte, so that the electrolyte is decomposed and side reactions such as co-intercalation occur are not sufficiently suppressed. On the other hand, when the thickness of the coating film is more than 1 탆, the amount of amorphous carbon or soft carbon is increased, the capacity increasing effect is lowered, and the electrical characteristics are lowered and the charge and discharge characteristics are decreased.

On the other hand, the negative electrode active material 2 shown in Fig. 2 can also be coated with amorphous carbon or soft carbon material on the spherical graphite first particle surface.

In the embodiment shown in FIG. 2, in order to strengthen the bond between the first particle precursor, which is a flake graphite slice, and the second particle, and to increase the internal packing density of the spheroidized graphite composite in the formation of the spherical graphite composite, Soft carbon precursor. In this case, the amorphous carbon precursor is subjected to carbonization heat treatment at 600 to 2000 ° C. to produce an anode active material for a lithium secondary battery.

Examples of the amorphous carbon precursor include sucrose, polyvinyl alcohol (PVA), phenol resin, furan resin, furfuryl alcohol, polyacrylonitrile It is preferable to use a hard carbon precursor such as epoxy resin, cellulose, styrene, polyimide, or epoxy resin.

As the soft carbon precursor, it is preferable to use soft carbon precursors such as petroleum pitch, coal pitch, polyvinyl chloride (PVC), mesophase pitch, and low molecular weight heavy oil.

The microporous channel is formed in the amorphous carbon or the soft carbon through the carbonization heat treatment process. The microporous channel formed in the amorphous carbon or soft carbon formed in the carbonization heat treatment process of the amorphous carbon precursor or the soft carbon precursor not only plays a buffer against the volume change of the second particles during charge and discharge, And the like.

When the amorphous carbon precursor or the soft carbon precursor is added, the additive material may be added in solid or liquid form. In the case of solid phase addition, the first particle precursor, the second particle, and the powdery amorphous carbon precursor or the soft carbon precursor, which are the flaky graphite flakes, are mixed, and the mixture is put into an equipment for spheronization, The first particle precursor as a section is cut into a cabbage shape to produce an assembly, and the assembly is heat treated at a temperature in the range of 600 to 2000 ° C to carbonize the amorphous carbon precursor or soft carbon precursor.

When the amorphous carbon precursor or soft carbon precursor is added in a liquid phase, the first particle precursor, the second particle, and the amorphous carbon precursor or the soft carbon precursor, which are the flaky graphite flakes, are uniformly mixed in a solvent, , Drying the mixture to a suitable size, adding the processed mixture to an appropriate size into the sphering machine, assembling a first particle precursor, which is a flaky graphite piece, in a cabbage shape to form an assembly, The assembly is heat treated at a temperature in the range of 600 to 2000 ° C to carbonize the amorphous carbon precursor or soft carbon precursor.

According to an embodiment of the present invention, there is provided a method of manufacturing a graphite particle, comprising the steps of: preparing a spheroidized graphite particle before a heat treatment step of an amorphous carbon precursor or a soft carbon precursor so as to improve contactability between the first particle precursor, Can be isotropically pressed. Here, isotropic pressing refers to pressing the assembly uniformly and three-dimensionally. As a method of isotropically pressing, for example, cold isotropic pressing treatment in which water or argon is used as a medium at room temperature or isotropically is pressed at room temperature can be used. In the isotropic pressing process, the pressure is not particularly limited, but is preferably 50 to 100 atm, more preferably 100 to 200 atm.

The assembly of the first particle precursor and the second particles, which are the flaky graphite flakes, is assembled into a granulated mixture. However, the assembly is not limited to a specific one. For example, a conventional apparatus for producing spherical graphite -263612, Korean Patent Publication No. 2003-0087986) or by a similar method.

The first particle precursor and the second particle, which are flaky graphite flakes, are simultaneously injected into the production apparatus to form an assembly by making the first particle precursor, which is flaky graphite flake, into a cabbage shape so as to form an assembly, Thereby uniformly dispersing the second particles.

Those skilled in the art will be able to fabricate a negative electrode for a lithium secondary battery based on the negative electrode active material according to the embodiments described above and also to prepare a negative electrode for intercalating and deintercalating lithium ions A lithium secondary battery can be manufactured in combination with a positive electrode containing a positive electrode active material capable of being activated, and an electrolyte.

Example  One

Silicon oxide (SiO) having an average particle diameter (D50) of 11.9 占 퐉 was pulverized by a ball milling method to prepare silicon oxide (SiO) having an average particle diameter (D50) of 0.91 占 퐉. The prepared silicon oxide (SiO) was mixed with natural graphite having a particle size of about 3 탆 at a weight ratio of 60:40 to prepare a mixture.

The mixture was mixed with a tetrahydrofuran solution in which a petroleum pitch (carbon yield: 38 mass%), which is an amorphous or quasi-crystalline carbon precursor of 30% by weight of the mixture weight, was dissolved and stirred by a ball milling method, Lt; / RTI &gt; for 12 hours to form a composite.

The prepared composite was put into a rotor blade mill (rotated at a speed of 5000 to 20000 rpm in a few seconds to several minutes) to obtain spherical primary particles by the rotational force and the frictional force of the blades. The prepared primary particles and a petroleum pitch (carbon yield: 38% by mass) which is an amorphous or quasi-crystalline carbon precursor were mixed at a weight ratio of 85:15, and the mixture was introduced into a rotor blade mill (rotated at a speed of 5000 to 20000 rpm in a few seconds to several minutes) Secondary spherical particles were obtained by blade rotational force and frictional force. The secondary particles were heat-treated at a temperature of 1,000 ° C under an argon atmosphere to prepare an anode active material.

Example  2

Silicon having an average particle diameter (D50) of 12.7 占 퐉 was pulverized by a ball milling method to produce silicon having an average particle diameter (D50) of 0.9 占 퐉. Silicon oxide (SiO) having an average particle diameter (D50) of 0.91 mu m prepared in Example 1 and natural graphite having a particle size of about 3 mu m were mixed at a weight ratio of 13:37:50 to prepare a mixture.

The prepared mixture was treated in the same manner as in Example 1 to prepare an anode active material.

Comparative Example  One

Silicon having an average particle diameter (D50) of 0.9 탆 prepared in Example 2 was mixed with natural graphite having a particle size of about 3 탆 at a ratio of 32:78 by weight to prepare a mixture.

The prepared mixture was treated in the same manner as in Example 1 to prepare an anode active material.

<Evaluation 1: Analysis of Particle Size Distribution of Silicon Oxide (SiO) and Silicon>

The particle size distribution of each of the silicon oxide (SiO 2) and silicon produced in Examples 1 and 2 and Comparative Example 1 was measured by a laser diffraction scattering particle size distribution measurement method, and the results are shown in FIG. 4 and FIG.

&Lt; Evaluation 2: Scanning electron microscope (SEM) photograph analysis of an anode active material >

Scanning electron micrographs of the silicon oxide (SiO) and silicon powder prepared in Examples 1 and 2 and Comparative Example 1 are shown in FIG. 6 and FIG.

Scanning electron micrographs of the negative electrode active materials prepared in Examples 1 and 2 and Comparative Example 1 are shown in FIG. 8 to FIG.

Referring to FIGS. 8 to 10, the negative electrode active materials prepared in Examples 1 and 2 and Comparative Example 1 have a smooth surface in a spherical form and show no difference in particle size and shape between them.

&Lt; Evaluation 3: Analysis of X-ray diffraction pattern of an anode active material >

The crystallinity of the silicon oxide (SiO) and silicon prepared in Examples 1 and 2 and Comparative Example 1 was measured using an X-ray diffraction pattern analyzer, and the results are shown in FIGS. 11 and 12.

The X-ray diffraction pattern analysis results of the negative electrode active materials prepared in Examples 1 and 2 and Comparative Example 1 are shown in FIG.

Fig. 11 shows X-ray diffraction patterns of the silicon oxide (SiO) used in Examples 1 and 2 before and after ball milling, showing that there is no difference even after pulverization by the ball milling method.

12 is an X-ray diffraction pattern before and after ball milling of the silicon used in Example 2 and Comparative Example 1, and it can be seen that there is no difference even after milling by ball milling method. FIG. 13 shows X-ray diffraction patterns of the negative electrode active materials prepared in Examples 1 and 2 and Comparative Example 1, showing that the crystallinity of silicon and graphite is well-formed without being damaged.

Manufacture of test cell

Each of the negative electrode active materials prepared in Examples 1 and 2 and Comparative Example 1 was mixed with distilled water at a weight ratio of carbon black and CMC / SBR (carboxymethylcellulose / styrene butadiene louver) of 85: 5: 10 to prepare an anode slurry . The negative electrode slurry was coated on a copper foil, followed by drying and rolling to prepare respective negative electrodes.

(DEC: EC = 1: 1) mixed with diethyl carbonate (DEC) and ethylene carbonate (EC) was added with 1M of LiPF 6 ₆ dissolved therein was added to prepare a test cell.

<Evaluation 4: Initial charge / discharge characteristics analysis>

Initial charging and discharging characteristics according to Examples 1 and 2 and Comparative Example 1 were evaluated by the following method using the prepared test cell, and the results are shown in the following Table 1 and FIGS. 14 to 16.

Charging was performed in CC / CV mode with a current density of 0.2 mA / cm ^2, the end voltage was maintained at 0.02 V, and the charge was terminated when the current was 0.02 mA. The discharge was performed in a CC mode with a current density of 0.2 mA / cm ² and the end voltage was maintained at 1.5V.

The battery including the negative electrode active material according to Examples 1 and 2 showed excellent capacity characteristics even after 30 cycles. From this, it can be seen that the negative electrode active materials according to Examples 1 and 2 have excellent capacity characteristics and cycle characteristics.

On the other hand, the negative electrode active material prepared in Comparative Example 1 has a cycle characteristic in which a large capacity decrease phenomenon occurs as the charge and discharge cycle progresses.

3 ^rd cycle discharge capacity (mAh / g) 30 ^th cycle Discharge capacity (mAh / g) 30 ^th discharge capacity / 3 ^rd discharge capacity (%) Example 1 607 612 100 Example 2 745 735 99 Comparative Example 1 655 374 57

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, You will understand.

1, 2, 3: negative electrode active material 11: first particle precursor
12: second particle 13: coating film
14: amorphous carbon / soft carbon

Claims (20)

A first particle spheroidized by a first particle precursor, which is a flaky graphite segment, And
And a second particle dispersed between the flaky graphite flakes in the first particle
, &Lt; / RTI &
Wherein the second particle comprises,
(i) SiO _a (0 < a &lt;1); And
(ii) a combination of SiO _x (0 &lt; x &lt; 1.5) and Si
And at least one material selected from the group consisting of: delete delete delete The method according to claim 1,
And the second particle has a size of 5 nm to 5000 nm. The method according to claim 1,
Further comprising amorphous carbon or soft carbon dispersed between the flaky graphite flakes in the first particles. The method according to claim 1,
Wherein the first particle precursor as the flaky graphite flake is peeled to a thickness of 2 mu m or less. The method according to claim 1,
Wherein the first particle precursor as the flaky graphite flake is peeled off at a thickness of 0.01 mu m to 0.1 mu m. The method according to claim 1,
Further comprising a coating film made of amorphous carbon or soft carbon on the surface of said spherical graphite first particles. 10. The method of claim 9,
Wherein the thickness of the coating film is 0.01 占 퐉 to 1 占 퐉. The method according to claim 1,
Wherein the negative electrode active material comprises 1 to 70% by weight of the second particles with respect to the total weight of the first particles. The method according to claim 6,
Wherein the amorphous carbon or soft carbon is contained in an amount of 1 to 50 wt% based on the total weight of the negative electrode active material. The method according to claim 6,
The precursor of the amorphous carbon is selected from the group consisting of sucrose, poly vinyl alcohol (PVA), phenol resin, furan resin, furfuryl alcohol, polyacrylonitrile ), A cellulose, a styrene, a polyimide, or an epoxy resin. The method according to claim 6,
Wherein the precursor of the soft carbon is a petroleum pitch, a coal pitch, a polyvinyl chloride (PVC), a mesophase pitch, or a low molecular weight heavy oil. Peeling the flaky graphite to produce a first particle precursor of flaky graphite flakes;
Mixing the first particle precursor and the second particle to produce a mixture; And
The step of granulating the mixture
, &Lt; / RTI &
Wherein the second particle comprises,
(i) SiO _a (0 < a &lt;1); And
(ii) a combination of SiO _x (0 &lt; x &lt; 1.5) and Si
And at least one material selected from the group consisting of lithium, lithium, and lithium. Peeling the flaky graphite to produce a first particle precursor of flaky graphite flakes;
Mixing the first particle precursor with a second particle, and an amorphous carbon precursor or a soft carbon precursor to produce a mixture;
Assembling the mixture to produce an assembly in which the second particles and the amorphous carbon precursor or soft carbon precursor are dispersed; And
And heating the assembly to carbonize the amorphous carbon precursor or soft carbon precursor
, &Lt; / RTI &
Wherein the second particle comprises,
(i) SiO _a (0 < a &lt;1); And
(ii) a combination of SiO _x (0 &lt; x &lt; 1.5) and Si
And at least one material selected from the group consisting of lithium, lithium, and lithium. 17. The method of claim 16,
Further comprising the step of isotropically pressing the graphite particles after preparing the assembly in which the second particles and the amorphous carbon precursor or the soft carbon precursor are dispersed. A negative electrode for a secondary battery comprising the negative electrode active material for a secondary battery according to any one of claims 1 to 15. A secondary transposition comprising a negative electrode for a secondary battery comprising the negative electrode active material for a secondary battery according to any one of claims 1 to 14. A positive electrode comprising a positive electrode active material capable of intercalating and deintercalating lithium ions;
A negative electrode comprising the negative active material according to any one of claims 1 to 14; And
Electrolyte
&Lt; / RTI &gt;

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