KR101676085B1 - Silicon based anode active material and lithium secondary battery comprising the same - Google Patents

Abstract

The present invention relates to a silicone-based particle; And carbon particles, wherein the carbon particles include fine carbon particles and granulated carbon particles having different average particle diameters.
The negative electrode active material according to an embodiment of the present invention includes both silicon-based particles and fine and assembled carbon particles having different average particle diameters. It is possible to increase the contact property between the silicon-based particles and the carbon particles, thereby further improving the efficiency and lifetime characteristics of the lithium secondary battery.

Description

TECHNICAL FIELD [0001] The present invention relates to a silicon-based negative electrode active material and a lithium secondary battery comprising the same. BACKGROUND ART [0002]

The present invention relates to a silicon-based anode active material, and more specifically, to a silicon-based anode active material. And a silicon-based negative electrode active material including fine particle carbon particles and granulated carbon particles having different average particle diameters, and a lithium secondary battery comprising the same.

BACKGROUND ART [0002] With the recent development of the information communication industry, as electronic devices have become smaller, lighter, thinner, and portable, there is a growing demand for higher energy density of batteries used as power sources for such electronic devices. Lithium secondary batteries are the ones that can best meet these demands, and researches on them are actively under way.

Various types of carbon-based materials including artificial graphite, natural graphite, or hard carbon capable of lithium insertion / removal have been applied to the anode active material of the lithium secondary battery. The carbon-based graphite provides advantages in terms of energy density of a lithium battery and is most widely used because it guarantees a long life of a lithium secondary battery with excellent reversibility.

However, graphite has a problem in that its capacity is low in terms of energy density per unit volume of electrodes, and a high side discharge voltage tends to cause a side reaction with the organic electrolytic solution to be used, and there is a risk of ignition or explosion due to malfunction or overcharge of the battery.

Accordingly, metal-based negative electrode active materials such as silicon (Si) have been studied. Si metal anode active material is known to exhibit a high lithium capacity of about 4200 mAh / g. However, it causes a volume change of up to 300% or more before and after the reaction with lithium, that is, during charging and discharging. As a result, there is a phenomenon that the conductive network in the electrode is damaged and the contact resistance between particles is increased, thereby deteriorating the performance of the cell.

Accordingly, there has been studied an electrode in which a graphite particle surrounds a silicon anode active material to improve the conductivity of a silicon based anode active material.

However, in the case of the negative electrode active material, the contact between the graphite-based particles and the silicon-based particles deteriorates due to the volume change of up to 300% of the silicon-based negative active material at the time of charge reversal. Particularly, in the case of a silicon-based negative active material, short-circuiting between the silicon-based particles and the graphite particles at the time of charging and discharging is intensified, and battery performance may be deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems of the prior art.

The first technical problem to be solved by the present invention is to improve the efficiency and lifetime characteristics of the secondary battery by solving the problem of contact deterioration and short circuit between the anode active material during the conventional charge and discharge while using the mixed anode active material of silicon particles and carbon particles And a negative electrode active material.

A second aspect of the present invention is to provide a negative electrode and a lithium secondary battery including the negative electrode active material.

In order to solve the above-mentioned problems, And carbon particles, wherein the carbon particles include fine carbon particles and granulated carbon particles having different average particle diameters.

The present invention also provides a negative electrode comprising the negative active material.

Further, the present invention provides a lithium secondary battery including the negative electrode.

The negative electrode active material according to an embodiment of the present invention includes silicon-based particles and fine and coarse carbon particles having different average particle diameters together to increase the contact between the silicon-based particles and the carbon particles, The efficiency and lifetime characteristics of the battery can be further improved.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments of the invention and, together with the description of the invention, It should not be construed as limited.
1 shows a schematic view of a conventional negative electrode (a), a negative electrode (b) upon charging and a negative electrode (c) upon discharging.
FIG. 2 is a schematic view of a cathode at the time of discharging according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail in order to facilitate understanding of the present invention.

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

The negative electrode active material according to one embodiment of the present invention includes silicon-based particles; And carbon particles, wherein the carbon particles include fine carbon particles and granulated carbon particles having different average particle diameters.

1 (a) to 1 (c) are schematic diagrams showing the shapes of a conventional negative electrode a, a negative electrode b during charging, and a negative electrode c during discharging.

In general, the negative electrode active material containing silicon-based particles has a disadvantage of low conductivity. Thus, as shown in Fig. 1, a method of improving the conductivity by mixing the silicon particles 110 and the carbon particles 120 has been studied. However, as shown in FIGS. 1 (b) and 1 (c), a short circuit may occur due to deterioration of contact between the silicon-based particles and the carbon particles due to the volume change of the silicon-based particles during charging and discharging.

Accordingly, in the present invention, as shown in FIG. 2, the silicon particles 210 and the granules 230 and the granules 220 having different average particle diameters are included together. The contact between the silicon-based particles and the carbon particles is increased to prevent a short circuit, thereby further improving the efficiency and lifetime characteristics of the lithium secondary battery.

According to one embodiment of the present invention, the average particle diameter (D ₅₀ ) of the fine carbon particles may be 1 μm to 5 μm, preferably 1 μm to 4 μm.

According to an embodiment of the present invention, when the average particle diameter of the fine carbon particles has an average particle size within the above range, the fine carbon particles can be uniformly formed between the silicon particles and the assembled carbon particles, The contactability with the silicon-based particles and the carbon particles can be improved and the problem of short-circuit due to volume expansion during charging and discharging can be solved.

In addition, the average particle diameter (D ₅₀ ) of the assembled carbon particles may be 10 μm to 30 μm, preferably 10 μm to 20 μm.

When the average particle diameter of the assembled carbon particles is less than 10 탆, the size difference with respect to the particulate carbon particles is small and the effect of improving the conductivity by mixing the heterogeneous carbon particles may be insignificant. When the average particle diameter is more than 30 탆, There may be a problem of lowering the speed-rate characteristic due to the increase of the capacitance and a problem of the capacity drop of the electrode at the optimum density.

In the negative active material according to an embodiment of the present invention, the fine carbon particles may be contained in an amount of 1 wt% to 30 wt%, preferably 10 wt% to 20 wt% with respect to the total weight of the carbon particles. When the amount of the fine carbon particles is less than 1% by weight, the effects of preventing the short-circuiting of the desired silicon-based particles and carbon particles of the present invention and the lifetime characteristics of the secondary battery may be insignificant. On the other hand, if the amount of the fine carbon particles is more than 30% by weight, the specific surface area may increase due to excess of the fine carbon particles, which may result in an increase in side reaction and deterioration of the life characteristics.

In the negative electrode active material according to an embodiment of the present invention, the granulated carbon particles are preferably 70 wt% to 99 wt%, and preferably 80 wt% to 90 wt% with respect to the total weight of the carbon particles. When the assembled carbon particles are in the above range, the conductivity of the silicon based negative electrode active material can be sufficiently improved.

If the amount of the assembled carbon particles is less than 70% by weight, the specific surface area may increase due to excess of the fine carbon particles, which may result in an increase in side reaction and deterioration of lifetime characteristics. On the other hand, when the amount of the assembled carbon particles is more than 99% by weight, the amount of the mixed carbon particles is too small, so that the effect of preventing the short-circuiting of the intended silicone particles and carbon particles of the present invention and the lifetime characteristics of the secondary battery is insignificant .

According to an embodiment of the present invention, the mixture ratio of the fine carbon particles and the assembled carbon particles is preferably 1: 4 to 9 by weight.

When the above-mentioned fine carbon particles are smaller than the above-mentioned weight ratio, the effect of preventing the short-circuiting of the desired silicon-based particles and carbon particles of the present invention and the lifetime characteristics of the secondary battery may be insignificant, and when the fine carbon particles are excessively contained The specific surface area may increase, resulting in an increase in side reaction and deterioration in lifetime characteristics.

According to an embodiment of the present invention, the carbon particles may be at least one selected from the group consisting of artificial graphite, natural graphite, mesocarbon, amorphous hard carbon, low crystalline soft carbon, carbon black, acetylene black, Ketjen black, super P, graphene, , Fibrous carbon, and surface-coated graphite, or a mixture of two or more thereof.

According to an embodiment of the present invention, the fine carbon particles and the assembled carbon particles may be the same or different from each other.

The carbon particles may be in the form of amorphous, flaky, angular, plate-like, spherical, fiber-like, point-like, or a mixture thereof. Specifically, the shape of the fine carbon particles may be, for example, spherical, angular, scaly, plate-like, point-like, or a mixture thereof, more preferably spherical, . The shape of the assembled carbon may be, for example, an amorphous shape, a scaly shape, a plate shape, a fiber shape, a spherical shape or a mixture thereof, more preferably a spherical shape, a scaly shape, a plate shape, .

According to an embodiment of the present invention, the silicon-based particles may be SiOx (where 0? X <2) or a silicon-based compound of the following formula (1)

&Lt; Formula 1 >

MySi

M is at least one element selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, La, Hf, , Os, Mg, Ca, B, P, Al, Ge, Sn, Sb, Bi and Li, or two or more of these elements,

y is from 0.001 to 0.4.

The silicon-based particles preferably have a specific surface area (BET-SSA) of 0.5 m 2 / g to 20 m 2 / g. If the specific surface area of the silicone-based particles is less than 0.5 m 2 / g, the effect of improving the contact with carbon particles may be insignificant. If the specific surface area exceeds 20 m 2 / g, it may be difficult to reduce side reactions with the electrolyte.

According to one embodiment of the present invention, the specific surface area of the silicon-based particles can be measured by a BET (Brunauer-Emmett-Teller) method. For example, it can be measured by a BET 6-point method by a nitrogen gas adsorption / distribution method using a porosimetry analyzer (Bell Japan Inc, Belsorp-II mini).

In addition, the average particle diameter (D ₅₀ ) of the silicon-based particles according to an embodiment of the present invention may be 0.01 μm to 20 μm, preferably 0.01 μm to 10 μm.

When the average particle diameter of the silicon-based particles is less than 0.01 탆, dispersion in the negative electrode active material slurry may be difficult. When the average particle diameter exceeds 20 탆, the particle expansion due to the charging of lithium ions becomes severe, The bondability between the particles and the current collector is deteriorated and the life characteristic can be greatly reduced.

In the present invention, the average particle diameter of the particles can be defined as the particle diameter at the 50% of the particle diameter distribution of the particles. The average particle diameter (D ₅₀ ) of the particles according to an embodiment of the present invention can be measured using, for example, a laser diffraction method. The laser diffraction method generally enables measurement of a particle diameter of several millimeters from a submicron region, resulting in high reproducibility and high degradability.

On the other hand, the mixing ratio of the silicon particles: carbon particles including fine particles and coarse carbon particles is preferably 1: 1 to 50, more preferably 1:10 to 1:30 in terms of weight ratio.

If the content of the carbon particles is less than the above mixing ratio, the effect of improving the electrical conductivity of the negative electrode active material may be insignificant. If the mixing ratio is exceeded, the content of silicon is decreased and it is difficult to achieve high capacity.

The silicon-based particles may be silicon-based particles containing a carbon coating layer on the surface of the silicon-based particles.

The carbon coating layer may be formed by a conventional coating method using a carbon precursor. For example, the outer wall of the silicon-based particle may be coated with carbon by mixing the silicon-based particle with a carbon precursor and then performing heat treatment.

The carbon coating layer may include, for example, a pitch or a hydrocarbon-based material. Examples of the hydrocarbon-based material include furfuryl alcohol and phenol-based resins.

According to an embodiment of the present invention, the carbon coating amount contained in the carbon coating layer may be used in an amount of 1 wt% to 30 wt% with respect to the total weight of the silicon based particles.

If the carbon coating amount is less than 1 wt%, a uniform coating layer may not be formed and electrical conductivity may be lowered. If the carbon coating amount is more than 30 wt%, additional irreversible reaction may occur, There may be a problem of decrease.

For example, tetrahydrofuran (THF), alcohol, or the like can be used as the solvent for forming the carbon coating layer, and the heat treatment can be carried out at a temperature ranging from 300 ° C to 1400 ° C, for example.

The present invention also provides a negative electrode comprising the negative active material.

Further, the present invention provides a lithium secondary battery comprising a cathode, a cathode, a separator interposed between the cathode and the anode, and an electrolyte in which the lithium salt is dissolved.

The negative electrode active material prepared above may be produced by a method commonly used in the art. For example, a negative electrode may be manufactured by preparing a slurry by mixing and stirring a binder and a solvent, if necessary, a conductive agent and a dispersant in an anode active material according to an embodiment of the present invention, applying the slurry to a current collector, .

Examples of the binder include polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, Polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM) Sulfonated EPDM, styrene butadiene rubber (SBR), fluorine rubber, poly acrylic acid, and polymers in which hydrogen is substituted with Li, Na, or Ca, or Various kinds of binder polymers such as various copolymers can be used. As the solvent, N-methylpyrrolidone, acetone, water and the like can be used.

The conductive agent is not particularly limited as long as it has electrical conductivity without causing any chemical change in the battery, and examples thereof include graphite such as natural graphite and artificial graphite; Carbon black such as carbon black, acetylene black, Ketjen black, channel black, panes black, lamp black, and thermal black; Conductive fibers such as carbon fiber and metal fiber; Conductive tubes such as carbon nanotubes; Metal powders such as fluorocarbon, aluminum and nickel powder; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The dispersing agent may be an aqueous dispersing agent or an organic dispersing agent such as N-methyl-2-pyrrolidone.

The cathode active material, the conductive agent, the binder and the solvent are mixed to prepare a slurry, which is directly coated on the metal current collector or cast on a separate support, and the cathode active material film, which is peeled from the support, The positive electrode can be manufactured by lamination to the current collector.

Wherein the cathode active material is at least one selected from the group consisting of lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), Li [Ni _x Co _y Mn _z Mv] O ₂ (Li _a M _{b -a} (Li _a M _{b -a} ) wherein x < = x &lt; _{- b 'M' b ')} O 2-c a c ( wherein, 0≤a≤0.2, 0.6≤b≤1, 0≤b'≤0.2, 0≤c≤0.2 and; M is Mn and, Ni M, at least one selected from the group consisting of Al, Mg and B, A is at least one selected from the group consisting of P, F, S, and N), or a compound substituted with one or more transition metals; Lithium manganese oxides such as Li _{1 + y} Mn _2-y O ₄ (where y is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ and LiMnO ₂ ; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ and Cu ₂ V ₂ O ₇ ; Formula _{LiNi 1 - y M y O 2} ( where, the M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, y = 0.01 - 0.3 Im) Ni site type lithium nickel oxide which is represented by; Formula _{LiMn 2 - y M y O 2} ( where, M = Co, Ni, Fe , Cr, and Zn, or Ta, y = 0.01 - 0.1 Im) or Li ₂ Mn ₃ MO ₈ (where, M = Fe, Co, Ni, Cu, or Zn); LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with an alkaline earth metal ion; Disulfide compounds; Fe ₂ (MoO ₄ ) ₃ , and the like. However, the present invention is not limited to these.

The separator may be a conventional porous polymer film used as a conventional separator, for example, a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer The prepared porous polymer film can be used alone or in a laminated form. The porous nonwoven fabric can be used as a porous nonwoven fabric, for example, a nonwoven fabric made of glass fiber, polyethylene terephthalate fiber or the like having high melting point, But is not limited thereto.

In the electrolyte solution used in the embodiment of the present invention, the lithium salt that can be included as the electrolyte may be used without limitation as long as it is commonly used in an electrolyte for a secondary battery. Examples of the anion of the lithium salt include F ^{- _{Cl -, I -, NO 3}} -, N (CN) 2 -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) 2 PF 4 -, (CF 3) 3 PF 3 -, (CF 3 ^{_{) 4 PF 2 -, (CF}} 3) 5 PF -, (CF 3) 6 P -, CF 3 SO 3 -, CF 3 CF 2 SO 3 -, (CF 3 SO 2) 2 N -, (FSO 2) _{^{2 N -, CF 3 CF 2}} (CF 3) 2 CO -, (CF 3 SO 2) 2 CH -, (SF 5) 3 C -, (CF 3 SO 2) 3 C -, CF 3 (CF 2) ₇ SO ₃ ^- , CF ₃ CO ₂ ^- , CH ₃ CO ₂ ^- , SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- can be used.

In the electrolyte solution used in the embodiment of the present invention, the organic solvent contained in the electrolytic solution may be any of those conventionally used, and examples thereof include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl But are not limited to, carbonate, methylpropyl carbonate, dipropyl carbonate, fluoro-ethylene carbonate, dimethylsulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, Methyl formate, methyl acetate, ethyl acetate, isopropyl acetate, isoamyl acetate, methyl propionate (methyl ethyl ketone, methyl isobutyl ketone, methyl isobutyl ketone, methyl propionate, ethyl propionate, It is possible to use any one selected from the group consisting of propyl propionate, butyl propionate, methyl butylate and ethyl butylate, or a mixture of two or more thereof have.

In particular, ethylene carbonate and propylene carbonate, which are cyclic carbonates in the carbonate-based organic solvent, can be preferably used because they have high permittivity as a high-viscosity organic solvent and dissociate the lithium salt in the electrolyte well. To such a cyclic carbonate, dimethyl carbonate and diethyl When a low viscosity, low dielectric constant linear carbonate such as carbonate is mixed in an appropriate ratio, an electrolyte having a high electric conductivity can be prepared, and thus it can be more preferably used.

Alternatively, the electrolytic solution stored in accordance with the present invention may further include an additive such as an overcharge inhibitor or the like contained in an ordinary electrolytic solution.

A separator is disposed between the positive electrode and the negative electrode to form an electrode assembly. The electrode assembly is inserted into a cylindrical battery case, a prismatic battery case, or an aluminum pouch, and then an electrolyte is injected. Alternatively, the electrode assembly is laminated, then impregnated with the electrolytic solution, and the resulting product is sealed in a battery case to complete the lithium secondary battery.

The lithium secondary battery according to the present invention can be used not only in a battery cell used as a power source of a small device but also as a unit cell in a middle- or large-sized battery module including a plurality of battery cells. Preferable examples of the above medium and large-sized devices include, but are not limited to, electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric power storage systems, and the like.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention may be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

Example

&Lt; Preparation of negative electrode active material &

Example  One

Si particles (a) having an average particle diameter (D ₅₀ ) of 5 탆; And graphite particles (b) in which incorporated graphite particles having an average particle diameter (D ₅₀ ) of 20 μm and fine graphite particles having an average particle diameter (D ₅₀ ) of 3.8 μm were mixed at a weight ratio of 80:20 were mixed to prepare an anode active material . At this time, the mixing ratio of the Si particles (a) and the graphite particles (b) was 5:95 by weight.

Example  2

Si particles (a) having an average particle diameter (D ₅₀ ) of 5 탆; And graphite particles (b) in which incorporated graphite particles having an average particle diameter (D ₅₀ ) of 20 μm and fine graphite particles having an average particle diameter (D ₅₀ ) of 5 μm were mixed at a weight ratio of 80:20 were mixed to prepare an anode active material . At this time, the mixing ratio of the Si particles (a) and the graphite particles (b) was 5:95 by weight.

Comparative Example  One

An anode active material was prepared in the same manner as in Example 1 except that only the granulated graphite particles having an average particle diameter (D ₅₀ ) of 20 탆 were used as the graphite particles (b).

Comparative Example  2

An anode active material was prepared in the same manner as in Example 1 except that fine graphite particles having an average particle diameter (D ₅₀ ) of 5.5 μm were used as the graphite particles (b).

Comparative Example  3

An anode active material was prepared in the same manner as in Example 1, except that fine graphite particles having an average particle diameter (D ₅₀ ) of 0.5 탆 were used as the graphite particles (b).

&Lt; Preparation of coin-shaped half-cell &

Example  3

The negative electrode active material prepared in Example 1, acetylene black, a conductive agent and polyvinylidene fluoride as a binder were mixed at a weight ratio of 70:10:20, and these were mixed in a solvent N-methyl-2-pyrrolidone To prepare a slurry. The prepared slurry was coated on one side of the copper current collector to a thickness of 30 탆, dried and rolled, and then punched to a predetermined size to prepare a negative electrode.

10% by weight of fluoroethylene carbonate was added to a mixed solvent comprising an organic solvent prepared by mixing ethylene carbonate and diethyl carbonate at a weight ratio of 30:70 and 1.0 M of LiPF ₆ based on the total weight of the electrolytic solution, Thereby preparing an electrolytic solution.

A lithium metal foil was used as a counter electrode. A polyolefin separator was interposed between both electrodes, and the electrolyte was injected into the coin type half cell.

Example  4

A coin-shaped half-cell was prepared in the same manner as in Example 3, except that the negative electrode active material prepared in Example 2 was used instead of the negative active material prepared in Example 1 as the negative electrode active material.

Comparative Example  4 to 6

A coin-shaped half-cell was prepared in the same manner as in Example 2, except that the negative electrode active material prepared in Comparative Examples 1 to 3 was used as the negative electrode active material instead of the negative active material prepared in Example 1 above.

Experimental Example  1: Analysis of life characteristics and capacity characteristics

In order to examine the capacity characteristics and lifespan characteristics of the coin-type half-cells manufactured in Examples 3 and 4 and Comparative Examples 4 to 6 according to the charging and discharging cycles, in Examples 3 and 4 and Comparative Examples 4 to 6 The coin-shaped half-cell was charged to 5 mV at a constant current / constant voltage (CC / CV) condition at 23 ° C and 0.1 C to 0.005 C at a temperature of 23 ° C. and discharged at 0.1 C to 1.5 V under a constant current (CC) .

Thereafter, the battery was charged at 0.5 C to 5 mV and 0.005 C at a constant current / constant voltage (CC / CV) condition, and discharged at 0.5 C to 1.0 V under a constant current (CC) condition. The results are shown in Table 1 below.

Yes Capacity (mAh / g) Efficiency (1 ^st Efficiency) Life characteristics (%) Example 3 420mAh / g 85.3% 97% Example 4 419mAh / g 85.5% 95% Comparative Example 4 420mAh / g 85.8% 87% Comparative Example 5 418mAh / g 85.4% 89% Comparative Example 6 411mAh / g 83.8% 86%

- Life characteristics: (49th cycle discharge capacity / first cycle discharge capacity) 100

As can be seen from the above Table 1, the secondary batteries of Examples 3 and 4 using the negative electrode active material obtained by mixing Si particles and carbon particles together with fine granules and assembled carbon particles having different average particle sizes, The capacity characteristics and the efficiency characteristics are similar to those of Comparative Example 4, which is mixed with the carbon particles containing only the assembled carbon particles, but the lifetime characteristics of the secondary battery are improved by about 10%.

Further, in Examples 3 and 4 using fine carbon particles having an average particle diameter of 5 占 퐉 or less, the lifetime characteristics were increased by about 8% as compared with Comparative Example 5 using fine carbon particles having an average particle diameter of 5.5 占 퐉, The efficiency and lifetime characteristics showed an increase rate of about 10% or more as compared with Comparative Example 6 using particles.

Therefore, according to the present invention, the negative electrode active material obtained by mixing Si particles and carbon particles containing fine particulate and coarse carbon particles having different average particle diameters together is superior in life characteristic compared with the case of using single carbon particles, It was confirmed that the capacity characteristics and the efficiency characteristics were equal to or more than those of the case of using the fine carbon particles out of the above range and the lifetime characteristics were improved by about 7 to 10% .

Therefore, the negative electrode active material of the present invention having excellent capacity characteristics, efficiency characteristics, and life characteristics can be usefully used in a secondary battery.

110: Silicon-based particles
120: carbon particles
210: Silicon-based particles
220: assembled carbon particles
230: fine carbon particles

Claims (18)

Silicon-based particles; And carbon particles,
The carbon particles include fine carbon particles and granulated carbon particles having different average particle diameters,
The average particle diameter (D ₅₀ ) of the fine carbon particles is 1 탆 to 5 탆,
The mean particle diameter (D ₅₀ ) of the assembled carbon particles is 10 탆 to 30 탆,
Wherein the mixture ratio of the fine carbon particles to the assembled carbon particles is 1: 4 to 9 by weight.
delete delete The method according to claim 1,
Wherein the mixing ratio of the silicon-based particles to the carbon particles is 1: 1 to 50 by weight.
delete The method according to claim 1,
Wherein the fine carbon particles are contained in an amount of 1 to 30% by weight based on the total weight of the carbon particles.
The method according to claim 1,
Wherein the average particle diameter (D ₅₀ ) of the silicon-based particles is 0.01 μm to 20 μm.
8. The method of claim 7,
Wherein the average particle size (D ₅₀ ) of the silicon-based particles is 0.01 μm to 10 μm.
The method according to claim 1,
Wherein the silicon-based particles have a specific surface area (BET-SSA) of 0.5 m 2 / g to 20 m 2 / g.
The method according to claim 1,
Wherein the silicon-based particles are SiOx (0? X <2) or a silicon-based compound represented by the following formula (1):
&Lt; Formula 1 >
MySi
M is at least one element selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, La, Hf, , Os, Mg, Ca, B, P, Al, Ge, Sn, Sb, Bi and Li, or two or more of these elements,
y is from 0.001 to 0.4.
The method according to claim 1,
The carbon particles may be selected from the group consisting of artificial graphite, natural graphite, mesocarbon, amorphous hard carbon, low crystalline soft carbon, carbon black, acetylene black, Ketjen black, super P, graphene, fibrous carbon and surface- Or a mixture of two or more thereof.
The method according to claim 1,
Wherein the shape of the fine carbon is spherical, angular, flaky, plate-like, point-like, or a mixed form thereof.
The method according to claim 1,
Wherein the shape of the assembled carbon is amorphous, scaly, plate-like, fibrous, spherical, or mixed form thereof.
The method according to claim 1,
Wherein the silicon-based particles are silicon-based particles having a carbon coating layer on the surface thereof.
15. The method of claim 14,
Wherein the carbon coating amount contained in the carbon coating layer is 1 to 30 wt% based on the total weight of the silicon based particles.
15. The method of claim 14,
Wherein the carbon coating layer comprises a pitch or a hydrocarbon-based material.
An anode comprising the anode active material of claim 1.
A lithium secondary battery comprising the negative electrode of claim 17.

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