KR20130107892A - Negative active material for rechargeable lithium battery, method of preparing the same, and rechargeable lithium battery including the same - Google Patents

Abstract

PURPOSE: A lithium secondary battery is provided to have high charging and discharging capacity, to have high cycle lifetime, and to have excellent charging and discharging performance at high voltage density. CONSTITUTION: A negative electrode active material (1) includes a core particle (2) which includes at least one selected from hard carbon and soft carbon and a shell layer located on the surface of the core particle. The shell layer includes a carbon microparticle crystalline graphite microparticle, graphene, carbon black, and carbon nanotubes; silicon or silicon alloy microparticle (4); and an amorphous or semi-crystalline carbon (5). The average particle diameter (D_50) of the core particle is 2-20 micron. The average particle diameter (D_50) of the carbon microparticle is 0.003-5 micron.

Description

TECHNICAL FIELD The present invention relates to a negative active material for a lithium secondary battery, a method for producing the negative active material, and a lithium secondary battery including the same. [0001] The present invention relates to a negative active material for a lithium secondary battery,

The present invention provides a negative electrode active material for a lithium secondary battery, a method for producing the same, and a lithium secondary battery comprising the same.

Recently, as the application of lithium secondary batteries to medium and large-sized lithium secondary batteries such as electric vehicles as well as portable electronic devices, high capacity and charge / discharge output characteristics are required to be improved.

However, graphite as a commercially available negative active material is limited to a theoretical capacity of about 372 mAh / g, so it is urgent to develop a new high capacity negative active material.

As a material which can replace graphite, silicon (Si) or its compound has been studied conventionally. Silicon reversibly occludes and releases lithium through compound formation reaction with lithium and is promising as a high capacity cathode material because its theoretical maximum capacity is about 4200 mAh / g (9800 mAh / cc, specific gravity 2.23), which is much larger than graphite.

However, during charging and discharging, a volume change occurs due to reaction with lithium, which causes micronization 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 and discharge cycles of the battery proceed, the battery capacity is drastically reduced, which causes the cycle life to be shortened.

Accordingly, in order to improve charge and discharge cycle characteristics, a method of forming silicon (Si) or a compound particle thereof or using a composite active material of these compound particles and carbon has been studied. However, there is still not enough improvement in capacity, cycle characteristics, and output characteristics for use as a negative electrode active material for lithium secondary batteries.

One embodiment of the present invention is to provide a negative active material for a lithium secondary battery having a large charge and discharge capacity, excellent cycle life characteristics, excellent charge and discharge output characteristics at a high current density.

Another embodiment of the present invention is to provide a method for manufacturing the negative electrode active material for a lithium secondary battery.

Another embodiment of the present invention is to provide a lithium secondary battery including the negative electrode active material for the lithium secondary battery.

One embodiment of the present invention includes a core particle comprising at least one selected from hard carbon and soft carbon, and a shell layer located on the surface of the core particle, wherein the shell layer comprises crystalline graphite fine particles, graphene, carbon At least one carbon fine particle selected from black and carbon nanotubes; Silicon or silicon alloy fine particles; And it provides a negative electrode active material for a lithium secondary battery containing amorphous or semi-crystalline carbon.

The average particle diameter (D50) of the core particles may be 2 to 20 ㎛.

The core particles may be included in 5 to 97% by weight based on the total amount of the negative electrode active material.

The carbon fine particles may have an average particle diameter (D50) of 0.003 to 5 ㎛.

The crystalline graphite fine particles may be obtained by separating or pulverizing at least one selected from artificial graphite, natural graphite and fibrous carbon, and specifically, may be obtained by separating or pulverizing soil graphite.

The carbon fine particles may be included in 1 to 90% by weight based on the total amount of the negative electrode active material.

The silicon or silicon alloy fine particles may have an average particle diameter (D50) of 0.005 to 2 ㎛.

The silicon alloy fine particles are Si phase in the particle; And Si, Li, Ge, Sn, Al, Sb, B, P, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd Compound phases comprising at least one element selected from Ag, Ta, W and O may be present in admixture.

The silicon or silicon alloy fine particles may be included in 1 to 90% by weight based on the total amount of the negative electrode active material.

The carbon fine particles and the silicon or silicon alloy fine particles may be mixed in a weight ratio of 5 to 90:10 to 95.

The amorphous or semicrystalline carbon may be sucrose, phenol resin, naphthalene resin, polyvinyl alcohol, polyvinyl chloride, furfuryl alcohol, polyacrylonitrile, polyamide, furan resin, cellulose, styrene, polyyi It may be formed from a carbon precursor including at least one selected from the group consisting of mid, epoxy resin, vinyl chloride resin, coal-based pitch, petroleum-based pitch, mesoface pitch, tar and low molecular weight heavy oil.

The amorphous or semicrystalline carbon may be included in an amount of 1 to 93% by weight based on the total amount of the negative electrode active material.

The mixture of the carbon fine particles and the silicon or silicon alloy fine particles and the amorphous or semicrystalline carbon may be mixed in a weight ratio of 10 to 95: 5 to 90.

The ratio of the average particle diameter (D50) of the core particles and the thickness of the shell layer may be 17 to 99.5: 0.5 to 83.

The anode active material may further include a coating layer disposed on the surface of the shell layer and including the amorphous or semicrystalline carbon, and the thickness of the coating layer may be 0.01 to 5 μm.

The anode active material is located on the surface of the shell layer and the amorphous or semicrystalline carbon; And a coating layer including at least one carbon fine particle selected from the crystalline graphite fine particles, the graphene, the carbon black, and the carbon nanotubes, and the thickness of the coating layer may be 0.01 to 5 μm. .

The average particle diameter (D50) of the negative electrode active material may be 2 to 40 ㎛.

The negative electrode active material includes the core particle including at least one selected from the hard carbon and the soft carbon, and the shell layer located on the surface of the core particle, wherein the shell layer separates or grinds the earth graphite. The crystalline graphite fine particles obtained by The silicon or silicon alloy fine particles; And the amorphous or semicrystalline carbon.

The negative electrode active material includes the core particle including at least one selected from the hard carbon and the soft carbon, and the shell layer located on a surface of the core particle, wherein the shell layer comprises the carbon black; The silicon or silicon alloy fine particles; And the amorphous or semicrystalline carbon.

According to another embodiment of the present invention, the surface of the core particle including at least one selected from hard carbon and soft carbon may include at least one carbon fine particle selected from crystalline graphite fine particles, graphene, carbon black, and carbon nanotubes; Silicon or silicon alloy fine particles; And coating with a mixture of amorphous or semicrystalline carbon precursors to obtain composite particles; And heat treating the composite particles. The present invention also provides a method for manufacturing a negative electrode active material for a lithium secondary battery.

The method of manufacturing the negative active material may further include coating the surface of the composite particle with the amorphous or semicrystalline carbon precursor.

Method for producing the negative electrode active material is a surface of the composite particles of the amorphous or semi-crystalline carbon precursor; And coating the at least one carbon fine particle selected from the crystalline graphite fine particles, the graphene, the carbon black, and the carbon nanotubes.

The heat treatment may be performed under an atmosphere containing nitrogen, argon, hydrogen or a mixed gas thereof, or under vacuum, and may be performed at a temperature of 500 to 2500 ° C.

Another embodiment of the present invention is a negative electrode comprising the negative electrode active material; anode; And a lithium secondary battery comprising the electrolyte.

Other details of the embodiments of the present invention are included in the following detailed description.

A lithium secondary battery having a large charge and discharge capacity, excellent cycle life characteristics, and excellent charge and discharge output characteristics at a high current density can be implemented.

1 is a schematic cross-sectional view of a negative electrode active material according to an embodiment.
2 is a schematic cross-sectional view of a negative electrode active material according to another embodiment.
3 is a schematic cross-sectional view of a negative electrode active material according to another embodiment.
4 to 10 are scanning electron microscope (SEM) photographs of negative electrode active materials according to Examples 1 to 7, respectively.
11 and 12 are scanning electron microscope (SEM) photographs of the negative electrode active materials according to Comparative Examples 1 and 2, respectively.
FIG. 13 is a scanning electron microscope (SEM) photograph of the silicon fine particles used for forming the shell layer in Examples 1 to 7. FIG.
14 is an energy dispersive X-ray spectroscopy (EDS) mapping photograph of silicon fine particles in a negative active material according to Example 3. FIG.
15 is a particle size distribution diagram of soil graphite fine particles used in Examples 1 to 3 and 6. FIG.
16 shows X-ray diffraction patterns (XRD) of the negative electrode active materials according to Example 1 and Comparative Example 1. FIG.
17 shows X-ray diffraction patterns (XRD) of the negative electrode active materials according to Example 2 and Comparative Example 2. FIG.
18 shows X-ray diffraction patterns (XRD) of the negative electrode active materials according to Example 3 and Example 6. FIG.

Hereinafter, embodiments of the present invention will be described in detail. However, this is presented as an example, by which the present invention is not limited and the present invention is defined only by the scope of the claims to be described later.

The negative electrode active material according to one embodiment can be explained with reference to FIG.

1 is a schematic cross-sectional view of a negative electrode active material according to one embodiment.

Referring to FIG. 1, the negative electrode active material 1 according to the embodiment may include a core particle 2 and a shell layer located on the surface of the core particle 2. Specifically, the shell layer may have a form surrounding the core particles 2.

The core particles 2 may include at least one selected from hard carbon and soft carbon. Specifically, the hard carbon may be amorphous hard carbon, and the soft carbon may be specifically semicrystalline or low crystalline soft carbon.

The shell layer may include carbon fine particles 3, silicon or silicon alloy fine particles 4, and amorphous or semicrystalline carbon 5. The amorphous or semicrystalline carbon 5 may bond the carbon fine particles 3 and the silicon or silicon alloy fine particles 4 to each other, and the carbon fine particles 3 and the silicon or silicon alloy fine particles 4 may be bonded to each other. The surface may also be coated. In addition, the amorphous or semi-crystalline carbon (5) may coat the surface of the core particles (2) while bonding the carbon particles (3) and the silicon or silicon alloy particles (4) and the core particles (2) to each other. have.

In this case, the carbon fine particles 3 may use at least one selected from crystalline graphite fine particles, graphene, carbon black, and carbon nanotubes, and among them, at least one selected from the crystalline graphite fine particles and carbon black may be used. Can be.

Hard carbon or soft carbon used as the core particles has good output characteristics of the battery when used as a negative electrode material, but has low initial efficiency and low storage capacity of lithium ions.

In addition, when the carbon fine particles are used as the negative electrode material, the initial efficiency is low due to the high specific surface area, and the electrode manufacturing process is poor due to the small size, making it difficult to manufacture an electrode having excellent initial efficiency and output characteristics.

In addition, when the silicon or silicon alloy fine particles are used as the negative electrode material, the capacity of the battery is high, but the initial efficiency is low, and the volume change occurs, which causes micronization of the silicon active material powder and poor electrical contact between the silicon active material powder and the current collector. Can be. As a result, as the charge and discharge cycle of the battery proceeds, the battery capacity is drastically reduced, which causes the cycle life to be shortened.

According to one embodiment, by using the hard carbon or the soft carbon as a core particle and having a structure for coating the surface of the core particle with the carbon fine particles, the silicon or silicon alloy fine particles, and the amorphous or semicrystalline carbon In addition, the lithium storage capacity is large, the capacity retention rate is high, the initial efficiency is improved, the lithium ion is easily moved during charging and discharging, and thus the output characteristics are excellent, and the charging and discharging efficiency may be high.

The average particle diameter (D50) of the core particles may be 2 to 20 ㎛, specifically 5 to 15 ㎛. When the core particles have an average particle diameter (D50) in the above range, the coating for forming the shell layer with the carbon fine particles is well made, and thus can be usefully applied to a lithium secondary battery having a high capacity and excellent output characteristics. At this time, the average particle diameter (D50) refers to the diameter of the particles corresponding to the cumulative volume 50% by volume in the particle size distribution.

The hard carbon may be sucrose, phenol resin, furan resin, furfuryl alcohol, polyacrylonitrile, polyimide, epoxy resin. ), Cellulose, styrene, citric acid, stearic acid, polyvinylidene fluoride, carboxymethyl cellulose (CMC), hydroxypropyl cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene At least one carbonaceous material selected from ethylene-propylene-diene monomer (EPDM), sulfonated ethylene-propylene-diene monomer (EPDM), starch, glucose, gelatin and saccharides may be used.

The soft carbon may be formed by carbonizing at least one carbonaceous material selected from polyvinyl alcohol, polyvinyl chloride, coal-based pitch, petroleum-based pitch, mesoface pitch, and low molecular weight heavy oil.

The core particles may be included in an amount of 5 to 97% by weight, and specifically 20 to 80% by weight, based on the total amount of the negative electrode active material. When the core particles are included in the above range, the shell layer may be formed at an appropriate ratio around the core particles to exhibit excellent output characteristics and to improve capacity.

The carbon fine particles constituting the shell layer may use an average particle diameter (D50) of 0.003 to 5 ㎛, specifically 0.003 to 3 ㎛, more specifically 0.003 to 2 ㎛. When using carbon fine particles having an average particle diameter (D50) of the above range, the carbon fine particles facilitate the dispersion of the silicon or silicon alloy fine particles can exhibit excellent cycle characteristics, that is, the silicon by the carbon fine particles Alternatively, since the efficiency of buffering the volume expansion of the silicon alloy fine particles increases, it may have an excellent capacity retention rate. In addition, as the diffusion distance of lithium ions is shortened during charging and discharging, high rate characteristics are improved as diffusion is easy inside. In other words, the insertion and desorption reactions of lithium ions are rapidly generated between the graphite layers of the carbon fine particles. Can be represented.

The crystalline graphite fine particles used as the carbon fine particles may be those obtained by separating or pulverizing at least one selected from artificial graphite, natural graphite and fibrous carbon, and among them, those obtained by separating or pulverizing natural graphite may be used. have. Specifically, one obtained by separating or pulverizing soil graphite can be used among the above kinds of natural graphite.

The natural graphite is largely divided into soil graphite and impression graphite, and the soil graphite may also be referred to as microcrystalline graphite. The earth graphite is a state in which fine particles are aggregated, and the aggregated graphite mass has an average particle diameter (D50) of about 0.1 to 50 μm. It has an average particle diameter (D50). In addition, when the ground graphite and the impression graphite are pulverized by the milling process, the soil graphite uses the term "pulverization", but the structure is close to the concept of "separating" the aggregated state. Graphite is distinguished from each other in that the crystallinity may be lowered in the crushing process as the crushed flat plate particles.

The grinding may be performed by a conventional milling process. Specifically, the milling process may include a ball mill, an attention mill, a vibration mill, a disk mill, a jet mill, a rotor mill, and the like. Can be carried out using a milling apparatus.

The grinding speed (rpm) and grinding time for the grinding may 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.

The fibrous carbon may be at least one selected from polyacrylonitrile-based carbon fibers, rayon-based carbon fibers, pitch-based carbon fibers, carbon nanotubes, and vapor-grown carbon fibers (VGCF).

The fibrous carbon may have a diameter of 1 to 1000 nm and a length of 0.5 to 20 um.

The crystalline graphite fine particles may have at least one shape selected from amorphous, flaky, plate, spherical and fibrous.

The crystalline graphite fine particles may be non-(I ₁₃₆₀ / I ₁₅₈₀₎ of 0.1 to 0.5 of the peak intensity (I ₁₃₆₀₎ of 1360㎝ ^-1 to a peak intensity (I ₁₅₈₀₎ of one 1580㎝ ^-1 in Raman spectrum, specifically It may be from 0.1 to 0.3. In this case, the ratio of the peak intensity (I ₁₃₆₀ / I ₁₅₈₀₎ to find the surface crystallinity of the graphite fine particles bar, the ratio of the peak intensity (I ₁₃₆₀ / I _1580), which through is within the range of crystallinity is excellently maintained The initial charge and discharge efficiency is excellent.

The graphene used as the carbon fine particles may be one obtained by at least one method selected from mechanical peeling of graphite and chemical peeling of graphite.

The carbon black used as the fine carbon particles may be one obtained by at least one method selected from a method of producing a hydrocarbon by incomplete combustion and a pyrolysis method of a hydrocarbon.

The carbon fine particles may be included in an amount of 1 to 90% by weight, and specifically 5 to 70% by weight, based on the total amount of the negative electrode active material. When the carbon fine particles are included in the above range, the carbon fine particles may form a shell layer at an appropriate ratio around the core particles to exhibit excellent output characteristics, and may properly buffer the volume expansion of the silicon or silicon alloy fine particles to provide excellent cycle characteristics. Can be represented.

The silicon or silicon alloy fine particles constituting the shell layer may have an average particle diameter (D50) of 0.005 to 2 ㎛, specifically, may have an average particle diameter (D50) of 0.005 to 1 ㎛. When the silicon or silicon alloy fine particles have an average particle diameter (D50) in the above range, it is possible to implement a lithium secondary battery having improved cycle life characteristics.

 The silicon alloy fine particles are Si phase in the particle; And Si, Li, Ge, Sn, Al, Sb, B, P, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd Compound phases comprising at least one element selected from Ag, Ta, W and O may be present in admixture.

The silicon or silicon alloy fine particles may be included in 1 to 90% by weight, specifically, 5 to 80% by weight based on the total amount of the negative electrode active material. When the silicon or silicon alloy fine particles are included in the range, the silicon or silicon alloy fine particles may form a shell layer at an appropriate ratio around the core particles, thereby exhibiting excellent output characteristics and improving capacity.

The carbon fine particles and the silicon or silicon alloy fine particles may be mixed in a weight ratio of 5 to 90:10 to 95, and specifically, may be mixed in a weight ratio of 20 to 80:20 to 80. When the carbon fine particles and the silicon or silicon alloy fine particles are mixed in the ratio, the capacity increase is large, and the buffer life efficiency of the volume expansion caused by the carbon fine particles is increased, thereby improving cycle life characteristics.

The amorphous or semicrystalline carbon constituting the shell layer may include sucrose, phenol resin, naphthalene resin, polyvinyl alcohol, polyvinyl chloride, furfuryl alcohol, polyacrylonitrile, polyamide, furan resin, One formed from a carbon precursor comprising at least one selected from cellulose, styrene, polyimide, epoxy resin, vinyl chloride resin, coal-based pitch, petroleum-based pitch, mesoface pitch, tar and low molecular weight heavy oil can be used.

The amorphous or semicrystalline carbon may be included in an amount of 1 to 93% by weight, specifically, 15 to 75% by weight based on the total amount of the negative electrode active material. When the amorphous or semicrystalline carbon is included in the above range, the lithium secondary battery having a high capacity may be realized by sufficiently combining the carbon fine particles with the silicon or silicon alloy fine particles.

The mixture of the carbon fine particles and the silicon or silicon alloy fine particles and the amorphous or semicrystalline carbon may be mixed in a weight ratio of 10 to 95: 5 to 90, specifically, in a weight ratio of 20 to 80: 20 to 80. Can be. When mixed in the ratio, the capacity increase is large, the bonding degree of the silicon or silicon alloy fine particles and the carbon fine particles is excellent, the adhesion of the shell layer and the core particles can be improved.

The ratio of the average particle diameter (D50) of the core particles and the thickness of the shell layer may be 17 to 99.5: 0.5 to 83, specifically 30 to 90: 70 to 10. The negative electrode active material having a ratio in the above range may have a high capacity and exhibit excellent high rate output characteristics.

The negative electrode active material 1 may be manufactured by the following method.

The surface of the core particles may be coated with a mixture of the carbon fine particles, the silicon or silicon alloy fine particles, and an amorphous or semi-crystalline carbon precursor to obtain composite particles, and then the composite particles may be heat-treated to prepare the negative electrode active material. .

The amorphous or semi-crystalline carbon precursor may be sucrose, phenol resin, naphthalene resin, polyvinyl alcohol, polyvinyl chloride, furfuryl alcohol, polyacrylonitrile, polyamide, furan resin, cellulose, styrene, At least one selected from polyimide, epoxy resin, vinyl chloride resin, coal pitch, petroleum pitch, mesoface pitch, tar and low molecular weight heavy oil can be used.

The coating method for obtaining the composite particles may be a mechanochemical method such as a blade, mechano-fusion, etc. which can give a shear force, and also spray drying or emulsion method May be used, but is not limited thereto.

For example, the core particles, the carbon fine particles, the silicon or silicon alloy fine particles, and the amorphous or semi-crystalline carbon precursor are introduced into a rotor blade mill, so that the temperature of the softening point of the amorphous or semi-crystalline carbon precursor is higher. It can be coated by giving a strong mechanical shear force at.

The heat treatment may be performed in an atmosphere containing nitrogen, argon, hydrogen or a mixed gas thereof, or under a vacuum.

In addition, the heat treatment may be carried out at a temperature of 500 to 2500 ℃, specifically, may be carried out at a temperature of 700 to 1800 ℃. When the heat treatment is performed in the temperature range, the fine pores of the hard carbon are maintained, the crystallinity of the soft carbon is maintained, so that the capacity and output characteristics are excellent, and carbonization of the amorphous or semicrystalline carbon precursor may occur sufficiently.

The negative electrode active material according to another embodiment may be described with reference to FIGS. 2 and 3.

2 is a schematic cross-sectional view of a negative electrode active material according to another embodiment, and FIG. 3 is a schematic cross-sectional view of a negative electrode active material according to another embodiment.

Referring to FIG. 2, the negative electrode active material 10 may include a core particle 2, a shell layer positioned on the surface of the core particle 2, and a coating layer 6 positioned on the surface of the shell layer. Referring to FIG. 3, the negative active material 20 may include a core particle 2, a shell layer positioned on the surface of the core particle 2, and a coating layer 7 positioned on the surface of the shell layer. In detail, the shell layer may have a form surrounding the core particles 2, and the coating layers 6 and 7 may have a form surrounding the shell layer.

The shell layer may include carbon fine particles 3, silicon or silicon alloy fine particles 4, and amorphous or semicrystalline carbon 5.

Details of the core particles and the shell layer are as described above.

The coating layer 6 may include amorphous or semicrystalline carbon. In addition, the coating layer 7 may include the carbon fine particles and the amorphous or semicrystalline carbon.

The carbon fine particles and the amorphous or semicrystalline carbon are as described above.

When the carbon fine particles and the silicon or silicon alloy fine particles are coated with the amorphous or semicrystalline carbon and coated on the surface of the core particles to form a shell layer, the capacity may be improved. In addition, when the amorphous or semicrystalline carbon is further coated on the shell layer, or when the carbon fine particles and the amorphous or semicrystalline carbon are further coated on the shell layer, the exposure of the graphite edge surface and the surface of the silicon or silicon alloy fine particles is reduced and hard. Exposure of the surface of the core particles of carbon or soft carbon may be reduced to improve initial charge and discharge efficiency, and the cycle life characteristics may be improved by appropriately buffering the volume expansion of the silicon or silicon alloy fine particles.

The coating layers 6 and 7 may have a thickness of 0.01 to 5 μm, specifically 0.1 to 3 μm. When the thickness of the coating layer is formed in the above range, the exposure of the graphite edge surface and the surface of the silicon or silicon alloy fine particles is reduced, and the exposure of the core particle surface of the hard carbon or soft carbon is reduced, thereby increasing initial charge and discharge efficiency, The output characteristics are excellent and a lithium secondary battery having a high capacity can be realized.

The negative electrode active material 10 may be manufactured by the following method. The surface of the core particles is coated with a mixture of the carbon fine particles, the silicon or silicon alloy fine particles, and an amorphous or semicrystalline carbon precursor to obtain a composite particle, and then the surface of the composite particle is coated with the amorphous or semicrystalline carbon precursor. After coating, the negative electrode active material may be prepared by heat-treating the coated composite particles.

In addition, the negative electrode active material 20 may be manufactured by the following method. The surface of the core particles is coated with a mixture of the carbon fine particles, the silicon or silicon alloy fine particles, and an amorphous or semicrystalline carbon precursor to obtain a composite particle, and then the surface of the composite particle is coated with the amorphous or semicrystalline carbon precursor. After coating with the carbon fine particles, the coated composite particles may be heat-treated to prepare the negative electrode active material.

The carbon fine particles, the silicon or silicon alloy fine particles, and the amorphous or semicrystalline carbon precursor are as described above, and the atmosphere and temperature of the heat treatment are also as described above.

The shape of the negative active material according to the exemplary embodiment illustrated through FIGS. 1 to 3 may be spherical, but is not limited thereto.

The average particle diameter (D50) of the negative electrode active material may be 2 to 40 ㎛, specifically, may be 5 to 30 ㎛. When the negative electrode active material has an average particle diameter (D50) in the above range it can be obtained an excellent electrode manufacturing process efficiency and electrode density.

According to another embodiment of the present invention, there is provided a lithium secondary battery including a cathode including a cathode active material capable of intercalating and deintercalating lithium ions, a cathode including the anode active material, and an electrolyte solution .

The lithium secondary battery can be classified into a lithium ion battery, a lithium ion polymer battery, and a lithium polymer battery according to the type of the separator and electrolyte used. The lithium secondary battery can be classified into a cylindrical shape, a square shape, a coin shape, Depending on the size, it can be divided into bulk type and thin type. The structure and the manufacturing method of these cells are well known in the art, and detailed description thereof will be omitted.

The negative electrode may be prepared by mixing the above-described negative electrode active material, a binder and optionally a conductive material to prepare a composition for forming the negative electrode active material layer, and then applying the composition to the negative electrode current collector.

Examples of the binder include polyvinyl alcohol, carboxymethylcellulose / styrene-butadiene rubber, hydroxypropylene cellulose, diacetylene cellulose, polyvinyl chloride, polyvinylpyrrolidone, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene Polypropylene and the like can be used, but the present invention is not limited thereto.

The binder may be mixed in an amount of 1 to 30% by weight based on the total weight of the composition for forming the negative electrode active material layer.

The conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, and specifically includes graphite such as natural graphite and artificial graphite; Carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskeys 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 conductive material may be mixed in an amount of 0.1 to 30% by weight based on the total amount of the composition for forming the negative electrode active material layer.

The negative electrode current collector may have a thickness of 3 to 500 mu m. Examples of the negative electrode current collector may include stainless steel, aluminum, nickel, titanium, sintered carbon, or a surface treated with carbon, nickel, titanium, silver or the like on the surface of aluminum or stainless steel. The negative electrode current collector may have fine irregularities on its surface to increase the adhesive force of the negative electrode active material, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric are possible.

The positive electrode includes a positive electrode active material, and as the positive electrode active material, a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound) may be used. Concretely, at least one of complex oxides of at least one kind selected from cobalt, manganese and nickel and lithium can be used.

The positive electrode may also be prepared by mixing the positive electrode active material, the binder and optionally a conductive material to form a composition for forming a positive electrode active material layer, and then applying the composition to a positive electrode current collector such as aluminum.

The electrolytic solution is a lithium salt; And non-aqueous organic solvents, organic solid electrolytes, inorganic solid electrolytes, and the like.

The lithium salt is _{LiCl, LiBr, LiI, LiClO 4} , LiBF 4, LiB 10 Cl 10, LiPF 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, LiAlCl 4, CH 3 SO 3 Li, CF ₃ SO ₃ Li, (CF ₃ SO ₂ ) ₂ NLi, chloroborane lithium, lower aliphatic carboxylate lithium, lithium 4-phenylborate, and imide.

Examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, But are not limited to, ricifrcr, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, An ether, a methyl ethyl pyrophosphate, an ethyl propionate, a methyl ethyl ketone derivative, a methyl ethyl ketone derivative, a methyl ethyl ketone derivative, Etc. may be used.

Examples of the organic solid electrolytic solution include a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, an agitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene and an ionic dissociation group And the like can be used.

As the inorganic solid electrolytic solution, Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Li ₄ SiO ₄ - Nitrides, halides and sulfates of Li such as LiI-LiOH and Li ₃ PO ₄ -Li ₂ S-SiS ₂ can be used.

For the purpose of improving the charge-discharge characteristics and the flame retardancy, the electrolyte solution is preferably used in the form of a solution containing at least one member selected from the group consisting of pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, glyme, hexaphosphoric triamide, N, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride, etc. may be added.

Further, a halogen-containing solvent such as carbon tetrachloride, ethylene trifluoride or the like may be further added to impart nonflammability, or a carbon dioxide gas may be further added to improve high-temperature storage characteristics.

Depending on the type of the lithium secondary battery, a separator may exist between the positive electrode and the negative electrode. As such a separator, an insulating thin film having high ion permeability and mechanical strength can be used. The pore diameter of the separator may be 0.01 to 10 mu m and the thickness may be 5 to 300 mu m.

The separator specifically includes an olefin-based polymer such as polypropylene having chemical resistance and hydrophobicity; A sheet or a nonwoven fabric made of glass fiber, polyethylene or the like can be used. When a solid electrolyte such as a polymer is used as the electrolytic solution, the solid electrolytic solution may also serve as a separation membrane.

Hereinafter, preferred examples and comparative examples of the present invention are described. However, the following embodiments are merely preferred embodiments of the present invention, and the present invention is not limited to the following embodiments.

Example  One

35% by weight of hard carbon having an average particle diameter (D50) of 9 μm, 15% by weight of earthy graphite having an average particle diameter (D50) of 1.7 μm, 20% by weight of silicon fine particles having an average particle diameter (D50) of 30 to 40 nm, and petroleum 30% by weight of the pitch was put into a rotor blade mill (rotated at 5000 to 20000 rpm in a few seconds to several minutes) so that the surface of the hard carbon was a mixture of the earthy graphite, the silicon fine particles and the petroleum pitch. To obtain a composite particle powder coated with. The obtained composite particle powder was heat-treated at 1000 ° C. for 1 hour at an elevated temperature rate of 5 ° C./min in argon atmosphere, and then cooled to prepare a negative electrode active material having an average particle diameter (D50) of 13.4 μm.

Example  2

35% by weight of soft carbon having an average particle diameter (D50) of 11 μm, 20% by weight of earthy graphite having an average particle diameter (D50) of 1.7 μm, 25% by weight of silicon fine particles having an average particle diameter (D50) of 30 to 40 nm, and petroleum 20 wt% pitch was fed into a rotor mill (rotated at 5000 to 20000 rpm in seconds to minutes), so that the surface of the soft carbon was coated with a mixture of the earthy graphite, the silicon fine particles and the petroleum pitch Composite particle powder was obtained. The obtained composite particle powder was heat-treated at 1000 ° C. for 1 hour at an elevated temperature rate of 5 ° C./min in argon atmosphere, and then cooled to prepare a negative electrode active material having an average particle diameter (D50) of 14.1 μm.

Example  3

30 wt% of hard carbon having an average particle diameter (D50) of 9 µm, 15 wt% of carbon black, 30 wt% of silicon fine particles having an average particle diameter (D50) of 30 to 40 nm, and 25 wt% of petroleum pitch mill) (rotated at 5000 to 20000 rpm in a few seconds to several minutes) to obtain a first composite particle powder having a surface of the hard carbon coated with a mixture of the carbon black, the silicon fine particles, and the petroleum pitch. 80% by weight of the obtained first composite particle powder, 10% by weight of earthy graphite having an average particle diameter (D50) of 1.7 μm, and 10% by weight of petroleum pitch were added to the mixer, and the surface of the first composite particles powder was And a second composite particle powder coated with the petroleum pitch. The obtained second composite particle powder was heat-treated at 1000 ° C. for 1 hour at an elevated temperature rate of 5 ° C./min in argon atmosphere, and then cooled to prepare a negative electrode active material having an average particle diameter (D50) of 15 μm.

Example  4

30 wt% of soft carbon having an average particle diameter (D50) of 11 µm, 25 wt% of carbon black, 20 wt% of silicon fine particles having an average particle diameter (D50) of 30 to 40 nm, and 25 wt% of a petroleum pitch are rotor mills. mill) (rotated at 5000 to 20000 rpm in a few seconds to several minutes) to obtain a composite particle powder having a surface of the soft carbon coated with a mixture of the carbon black, the silicon fine particles, and the petroleum pitch. The obtained composite particle powder was heat-treated at 1000 ° C. for 1 hour at an elevated temperature rate of 5 ° C./min in argon atmosphere, and then cooled to prepare a negative electrode active material having an average particle diameter (D50) of 14.4 μm.

Example  5

Rotor mill (30 wt% of soft carbon having an average particle diameter (D50) of 11 µm, 25 wt% of graphene, 20 wt% of silicon fine particles having an average particle diameter (D50) of 30 to 40 nm, and 25 wt% of a petroleum pitch) mill) (rotated at 5000 to 20000 rpm in a few seconds to several minutes) to obtain a composite particle powder having a surface of the hard carbon coated with a mixture of the earthy graphite, the silicon fine particles, and the petroleum pitch. The obtained composite particle powder was heat-treated at 1000 ° C. for 1 hour at an elevated temperature rate of 5 ° C./min in argon atmosphere, and then cooled to prepare a negative electrode active material having an average particle diameter (D50) of 14.2 μm.

Example  6

Rotor mill (30 wt% of soft carbon having an average particle diameter (D50) of 11 µm, 25 wt% of graphene, 20 wt% of silicon fine particles having an average particle diameter (D50) of 30 to 40 nm, and 25 wt% of a petroleum pitch) mill) (rotated at 5000 to 20000 rpm in seconds to minutes) to obtain a first composite particle powder having a surface of the hard carbon coated with a mixture of the earthy graphite, the silicon fine particles, and the petroleum pitch. 80% by weight of the obtained first composite particle powder, 10% by weight of earthy graphite having an average particle diameter (D50) of 1.7 μm, and 10% by weight of petroleum pitch were added to the mixer, and the surface of the first composite particle powder was petroleum-based. A pitch-coated second composite particle powder was obtained. The obtained second composite particle powder was heat-treated at 1000 ° C. for 1 hour at an elevated temperature rate of 5 ° C./min in argon atmosphere, and then cooled to prepare a negative electrode active material having an average particle diameter (D50) of 15.5 μm.

Example  7

30 wt% of hard carbon having an average particle diameter (D50) of 9 µm, 15 wt% of graphene, 30 wt% of silicon fine particles having an average particle diameter (D50) of 30 to 40 nm, and 25 wt% of a petroleum pitch (rotor mill) mill) (rotated at 5000 to 20000 rpm in seconds to minutes) to obtain a first composite particle powder having a surface of the hard carbon coated with a mixture of the earthy graphite, the silicon fine particles, and the petroleum pitch. 90 wt% of the obtained first composite particle powder and 10 wt% of petroleum pitch were fed to the mixer to obtain a second composite grain powder having the surface of the first composite grain powder coated with the petroleum pitch. The obtained second composite particle powder was heat-treated at 1000 ° C. for 1 hour at an elevated temperature rate of 5 ° C./min in argon atmosphere, and then cooled to prepare a negative electrode active material having an average particle diameter (D50) of 13.9 μm.

Comparative Example  One

A hard carbon anode active material having an average particle diameter (D50) of 9 µm.

Comparative Example  2

A soft carbon anode active material having an average particle diameter (D50) of 11 µm.

Evaluation 1: Scanning electron microscope of negative electrode active material SEM ) Photo analysis

Scanning electron microscope (SEM) photographs of the negative electrode active materials prepared in Examples 1 to 7 and Comparative Examples 1 and 2 are shown in FIGS. 4 to 12.

4 to 10 are scanning electron microscope (SEM) pictures of the negative electrode active materials according to Examples 1 to 7, respectively, and FIGS. 11 and 12 are scanning electron microscope (SEM) pictures of the negative electrode active materials according to Comparative Examples 1 and 2, respectively.

4 to 12, in Examples 1 to 7, the surface of the core particles, which are hard carbon or soft carbon, is coated with carbon microparticles, silicon microparticles, and semicrystalline carbon obtained by carbonizing a petroleum pitch to form a shell layer. It can be seen that it has a core-shell structure, and in Comparative Example 1 and 2 it can be seen that only the core particles are present without a coated shell layer, respectively.

FIG. 13 is a scanning electron microscope (SEM) photograph of the silicon fine particles used for forming the shell layer in Examples 1 to 7. FIG.

Referring to FIG. 13, it can be seen that the silicon fine particles constituting the shell layer located on the surface of the core particle have a size of about 30 to 40 nm.

Evaluation 2: of the negative electrode active material EDS ( energy dispersive  X- ray spectroscopy ) Mapping  analysis

14 is an energy dispersive X-ray spectroscopy (EDS) mapping photograph of silicon fine particles in a negative active material according to Example 3. FIG.

Referring to FIG. 14, it can be seen that the silicon fine particles are uniformly distributed in the negative electrode active material prepared in Example 3 by EDS Mapping analysis.

Evaluation 3: Analysis of Particle Size Distribution of Carbon Particles

In Examples 1 to 3 and 6, the particle size distribution of the earth graphite fine particles used to form the shell layer or the coating layer when preparing the negative electrode active material was measured by laser diffraction scattering particle size distribution measurement method, and the results are shown in FIG. 15.

15 is a particle size distribution diagram of soil graphite fine particles used in Examples 1 to 3 and 6. FIG.

Referring to FIG. 15, it can be seen that soil graphite particles having an average particle diameter (D50) of 0.003 to 5 μm were used in forming the shell layers in Examples 1 and 2 and the coating layers in Examples 3 and 6.

Evaluation 4: particle size distribution analysis of the negative electrode active material

The particle size distributions of the negative electrode active materials prepared in Examples 1 to 7 and Comparative Examples 1 and 2 were measured by laser diffraction scattering particle size distribution measurement method, and the results are shown in Table 1 below.

Example Comparative Example One 2 3 4 5 6 7 One 2 Average particle size (D50) (占 퐉) of the negative electrode active material 13.4 14.1 15 14.4 14.2 15.5 13.9 9 11

Referring to Table 1, compared with the case of the negative electrode active material of Comparative Examples 1 to 2 made of only soft carbon or hard carbon, it can be seen that the average particle diameter (D50) of the negative electrode active material of Examples 1 to 7 further increases. have. This is due to the fact that the surface of the active material particles used in Comparative Examples 1 and 2 in the negative electrode active materials of Examples 1 to 7 formed a core-shell structure with a shell layer composed of carbon fine particles, silicon fine particles and semicrystalline carbon.

Evaluation 5: X-ray of anode active material diffraction  Pattern analysis

Crystallinity of the negative active materials prepared in Example 1 and Comparative Example 1 was measured using an X-ray diffraction pattern analyzer, and the results are shown in FIG. 16.

16 shows X-ray diffraction patterns (XRD) of the negative electrode active materials according to Example 1 and Comparative Example 1. FIG.

Referring to FIG. 16, it can be seen that the peak (002), which is the main peak of graphite, was shown in Example 1, which is a structure coated with crystalline graphite fine particles having excellent crystallinity as compared with the case of only amorphous hard carbon. Due to having. In addition, in the case of Example 1, it can be seen that the (111) peak, which is the main peak of silicon, appeared in comparison with the case of Comparative Example 1, which is due to the presence of silicon in the shell layer of the negative electrode active material.

In addition, the crystallinity of the negative electrode active material prepared in Example 2 and Comparative Example 2 was measured using an X-ray diffraction pattern analyzer, the results are shown in FIG.

17 shows X-ray diffraction patterns (XRD) of the negative electrode active materials according to Example 2 and Comparative Example 2. FIG.

Referring to FIG. 17, it can be seen that the (002) peak, which is the main peak of graphite, was shown in Example 2, which is more crystalline in Example 2 than in Comparative Example 2, which is composed of only semicrystalline soft carbon. It is due to having a structure coated with good crystalline graphite fine particles. In addition, in the case of Example 2, it can be seen that the (111) peak, which is the main peak of silicon, is displayed as compared with the case of Comparative Example 2, which is due to the presence of silicon in the shell layer of the negative electrode active material.

Crystallinity of the negative electrode active materials prepared in Examples 3 and 6 was measured using an X-ray diffraction pattern analyzer, and the results are shown in FIG. 18.

18 shows X-ray diffraction patterns (XRD) of the negative electrode active materials according to Example 3 and Example 6. FIG.

Referring to FIG. 18, in Example 3 and Example 6, it can be seen that the (002) peak, which is the main peak of graphite, and the (111) peak, which is the main peak of silicon, exist, and the graphite and silicon are hard carbon or soft. This is due to the presence on the surface of the carbon core particles.

(Manufacture of Test Cell)

Each negative electrode active material, carbon black, and CMC / SBR (carboxymethyl cellulose / styrene-butadiene rubber) prepared in Examples 1 to 7 were mixed in distilled water at a weight ratio of 80: 5: 15 to prepare a negative electrode slurry. Each negative electrode slurry was coated on a copper foil, followed by drying and pressing to prepare each negative electrode.

Each negative electrode active material prepared in Comparative Examples 1 and 2 and CMC / SBR (carboxymethyl cellulose / styrene-butadiene rubber) were mixed in distilled water at a weight ratio of 95: 5 to prepare a negative electrode slurry. Each negative electrode slurry was coated on a copper foil, followed by drying and pressing to prepare each negative electrode.

Each of the negative electrode and the lithium metal was used as the positive electrode, and the electrode assembly was manufactured by laminating the negative electrode and the positive electrode through a cell guard as a separator. Thereafter, an electrolytic solution in which 1 M of LiPF ₆ was dissolved in a mixed solvent of diethyl carbonate (DEC) and ethylene carbonate (EC) (DEC: EC = 1: 1) was added to prepare a test cell.

Evaluation 6: initial Charging and discharging  Character analysis

Using the prepared test cell was evaluated the initial charge and discharge characteristics according to Examples 1 to 7 and Comparative Examples 1 to 2 in the following manner, the results are shown in Table 2 below.

For cells prepared according to Examples 1-7, charging was done in CC / CV mode with a current density of 0.2 mA / cm ² , the termination voltage was maintained at 0.02 V and charging was terminated when the current was 0.02 mA. . Discharge was performed in CC mode with a current density of 0.2 mA / cm ² , and the termination voltage was maintained at 2V.

For the cells prepared according to Comparative Examples 1 and 2, charging was performed in CC / CV mode with a current density of 0.2 mA / cm ² , the termination voltage was maintained at 0.01 V, and charging was terminated when the current was 0.02 mA. . Discharge was performed in CC mode with a current density of 0.2 mA / cm ² , and the termination voltage was maintained at 2V.

Initial Reversible Capacity (mAh / g) Initial efficiency (%) Example 1 697 85.2 Example 2 871 87.7 Example 3 877 88.1 Example 4 678 85.0 Example 5 781 84.0 Example 6 661 88.7 Example 7 870 87.1 Comparative Example 1 225 80.8 Comparative Example 2 231 83.5

Through Table 2, in the case of Examples 1 to 7 using the negative electrode active material of the core-shell structure in which the silicon fine particles are present in the shell layer, compared to the case of Comparative Examples 1 and 2 in which the shell layer does not exist, the initial reversible It can be seen that the capacity and initial efficiency are increased.

From this, in the case of using the negative electrode active material according to one embodiment, it exhibits a high capacity by the carbon fine particles and silicon or silicon alloy fine particles to be coated, the carbon fine particles as well as the porous surface of the hard carbon or soft carbon by amorphous or semicrystalline carbon It can be seen that it is possible to implement a lithium secondary battery having excellent initial efficiency by reducing the exposed surface of the edge and the silicon or silicon alloy fine particles.

Evaluation 7: Characterization of High Rate Charging (Lithium Insertion)

Using the prepared test cell was evaluated the high rate charging characteristics according to Examples 1 to 7 and Comparative Examples 1 to 2 in the following manner, the results are shown in Table 3 below.

For cells prepared according to Examples 1-7, charging was done in CC mode in the current density range of 50 to 1300 mA / g, the termination voltage was maintained at 0.02 V, and the discharge was at a current density of 50 mA / g. It was performed in CC mode and the termination voltage was kept at 2V.

In the case of cells prepared according to Comparative Examples 1 and 2, charging was performed in CC mode in the current density range of 50 to 1300 mA / g, the termination voltage was maintained at 0.01 V, and the discharge was performed at the current density of 50 mA / g. It was performed in CC mode and the termination voltage was kept at 2V.

Charging capacity (mAh / g) 50 mA / g 300 mA / g 800 mA / g 1300 mA / g Example 1 560 494 409 319 Example 2 816 747 616 515 Example 3 819 751 609 497 Example 4 601 531 420 354 Example 5 703 654 541 450 Example 6 602 536 409 337 Example 7 719 619 470 378 Comparative Example 1 189 147 94 66 Comparative Example 2 184 146 94 79

Through Table 3, in the case of Examples 1 to 7 using the core-shell structure negative electrode active material in which the silicon fine particles are present in the shell layer, the high rate charging characteristics are compared with those of Comparative Examples 1 and 2 in which the shell layer does not exist. It can be confirmed that excellent.

From this, high charge capacity can be exhibited by the silicon fine particles having a short diffusion distance of lithium and high charge capacity during high rate charging, thereby realizing a lithium secondary battery having excellent high rate characteristics.

Evaluation 8: Cycle Life Characterization

The cycle life characteristics according to Examples 1 to 7 were evaluated in the following manner using the prepared test cell, and the results are shown in Table 4 below.

Charging was performed in CC mode at a current density of 0.2 mA / cm ² , and the termination voltage was maintained at 0.02V. Discharge was performed in CC mode with a current density of 0.2 mA / cm ² , and the termination voltage was maintained at 2V.

The following capacity retention rate is calculated as a percentage of 30 ^th cycle discharge capacity to 1 ^st cycle discharge capacity.

1 ^st cycle discharge capacity (mAh / g) 30 ^th cycle discharge capacity (mAh / g) Capacity retention rate (%) Example 1 630 624 99.0 Example 2 815 808 99.1 Example 3 817 812 99.4 Example 4 583 576 98.8 Example 5 639 632 98.9 Example 6 554 553 99.9 Example 7 770 765 99.4

Through Table 4, when using a core-shell structure negative electrode active material having a shell layer made of silicon or silicon alloy fine particles, carbon fine particles, and amorphous or semi-crystalline carbon on the surface of the core particles that are hard carbon or soft carbon, It can be seen that the cycle life characteristics.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. As will be understood by those skilled in the art. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

1, 10, 20: negative electrode active material
2: core particle
3: carbon fine particles
4: silicon or silicon alloy fine particles
5: amorphous or semicrystalline carbon
6, 7: coating layer

Claims (28)

A core particle comprising at least one selected from hard carbon and soft carbon, and
Shell layer located on the surface of the core particles
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The shell layer may include at least one carbon fine particle selected from crystalline graphite fine particles, graphene, carbon black, and carbon nanotubes; Silicon or silicon alloy fine particles; And containing amorphous or semicrystalline carbon
Negative electrode active material for lithium secondary battery.
The method of claim 1,
The average particle diameter (D50) of the core particles is 2 to 20 ㎛ negative electrode active material for a secondary battery.
The method of claim 1,
The core particle is a lithium secondary battery negative electrode active material is contained in 5 to 97% by weight based on the total amount of the negative electrode active material.
The method of claim 1,
The carbon fine particles are a negative active material for a lithium secondary battery having an average particle diameter (D50) of 0.003 to 5 ㎛.
The method of claim 1,
Said crystalline graphite fine particles are obtained by separating or pulverizing at least one selected from artificial graphite, natural graphite and fibrous carbon.
The method of claim 1,
Said crystalline graphite fine particles are negative electrode active materials for lithium secondary batteries obtained by separating or pulverizing soil graphite.
The method of claim 1,
The carbon fine particles are 1 to 90% by weight based on the total amount of the negative electrode active material negative electrode active material for a lithium secondary battery.
The method of claim 1,
The silicon or silicon alloy fine particles are a negative active material for a lithium secondary battery having an average particle diameter (D50) of 0.005 to 2 ㎛.
The method of claim 1,
The silicon alloy fine particles are Si phase in the particle; And Si, Li, Ge, Sn, Al, Sb, B, P, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd A negative electrode active material for a lithium secondary battery in which a compound phase including at least one element selected from Ag, Ta, W, and O is mixed.
The method of claim 1,
The silicon or silicon alloy fine particles are 1 to 90% by weight based on the total amount of the negative electrode active material negative electrode active material for a lithium secondary battery.
The method of claim 1,
The carbon fine particles and the silicon or silicon alloy fine particles are mixed in a weight ratio of 5 to 90: 10 to 95 negative electrode active material for a lithium secondary battery.
The method of claim 1,
The amorphous or semicrystalline carbon may be sucrose, phenol resin, naphthalene resin, polyvinyl alcohol, polyvinyl chloride, furfuryl alcohol, polyacrylonitrile, polyamide, furan resin, cellulose, styrene, polyyi A negative electrode active material for a lithium secondary battery formed from a carbon precursor comprising at least one selected from mead, epoxy resin, vinyl chloride resin, coal-based pitch, petroleum-based pitch, mesophase pitch, tar, and low molecular weight heavy oil.
The method of claim 1,
The amorphous or semi-crystalline carbon is 1 to 93% by weight based on the total amount of the negative electrode active material negative electrode active material for a lithium secondary battery.
The method of claim 1,
The negative electrode active material for a lithium secondary battery, wherein the mixture of the carbon fine particles and the silicon or silicon alloy fine particles and the amorphous or semicrystalline carbon are mixed in a weight ratio of 10 to 95: 5 to 90.
The method of claim 1,
The ratio of the average particle diameter (D50) of the core particles and the thickness of the shell layer is 17 to 99.5: 0.5 to 83 negative electrode active material for a lithium secondary battery.
The method of claim 1,
The negative active material is
The negative active material for a lithium secondary battery further comprises a coating layer on the surface of the shell layer and containing the amorphous or semi-crystalline carbon.
17. The method of claim 16,
The thickness of the coating layer is a negative active material for a lithium secondary battery of 0.01 to 5 ㎛.
The method of claim 1,
The negative active material is
The amorphous or quasicrystalline carbon located on the surface of the shell layer; And a coating layer comprising at least one carbon fine particle selected from the crystalline graphite fine particles, the graphene, the carbon black, and the carbon nanotubes.
A negative electrode active material for a lithium secondary battery further comprising.
19. The method of claim 18,
The thickness of the coating layer is a negative active material for a lithium secondary battery of 0.01 to 5 ㎛.
The method of claim 1,
An average particle diameter (D50) of the negative electrode active material is a negative active material for a lithium secondary battery having a 2 to 40 ㎛.
The method of claim 1,
The negative active material is
The core particle comprising at least one selected from the hard carbon and the soft carbon, and
The shell layer located on the surface of the core particles,
The shell layer may include the crystalline graphite fine particles obtained by separating or grinding the earth graphite; The silicon or silicon alloy fine particles; And the amorphous or semicrystalline carbon
Negative electrode active material for lithium secondary battery.
The method of claim 1,
The negative active material is
The core particle comprising at least one selected from the hard carbon and the soft carbon, and
The shell layer located on the surface of the core particles,
The shell layer is the carbon black; The silicon or silicon alloy fine particles; And the amorphous or semicrystalline carbon
Negative electrode active material for lithium secondary battery.
The surface of the core particle including at least one selected from hard carbon and soft carbon may include at least one carbon fine particle selected from crystalline graphite fine particles, graphene, carbon black and carbon nanotubes; Silicon or silicon alloy fine particles; And coating with a mixture of amorphous or semicrystalline carbon precursors to obtain composite particles; And
Heat treating the composite particles
And a negative electrode active material for lithium secondary batteries.
24. The method of claim 23,
Method for producing the negative electrode active material
Coating the surface of the composite particle with the amorphous or semicrystalline carbon precursor
The manufacturing method of the negative electrode active material for lithium secondary batteries containing further.
24. The method of claim 23,
Method for producing the negative electrode active material
A surface of the composite particle is an amorphous or semicrystalline carbon precursor; And coating with the at least one carbon fine particle selected from the crystalline graphite fine particles, the graphene, the carbon black, and the carbon nanotubes.
The manufacturing method of the negative electrode active material for lithium secondary batteries containing further.
24. The method of claim 23,
The heat treatment is a method for producing a negative electrode active material for a lithium secondary battery is carried out under an atmosphere containing nitrogen, argon, hydrogen or a mixed gas thereof, or under a vacuum.
24. The method of claim 23,
Wherein the heat treatment is performed at a temperature of 500 to 2500 ° C.
A negative electrode comprising the negative electrode active material of any one of claims 1 to 22;
anode; And
Electrolyte
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