KR101494715B1 - Negative active material for rechargeable lithium battery, method of preparing the same, and negative electrode and rechargeable lithium battery including the same - Google Patents

Negative active material for rechargeable lithium battery, method of preparing the same, and negative electrode and rechargeable lithium battery including the same Download PDF

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KR101494715B1
KR101494715B1 KR20120138461A KR20120138461A KR101494715B1 KR 101494715 B1 KR101494715 B1 KR 101494715B1 KR 20120138461 A KR20120138461 A KR 20120138461A KR 20120138461 A KR20120138461 A KR 20120138461A KR 101494715 B1 KR101494715 B1 KR 101494715B1
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particles
silicon
carbon
si
active material
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KR20140070227A (en
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이성만
신민선
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강원대학교산학협력단
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50Manufacturing or production processes characterised by the final manufactured product
    • Y02P70/54Manufacturing of lithium-ion, lead-acid or alkaline secondary batteries

Abstract

Wherein the composite particle comprises a plurality of composite particles and porous agglomerated particles including pores between the composite particles, wherein the composite particle includes silicon (Si) based particles, carbon fine particles and amorphous carbon, and the amorphous carbon is soft carbon and hard carbon And the carbon particles are dispersed in the amorphous carbon, a method for producing the same, and a negative electrode and a lithium secondary battery including the same, wherein the silicon particles and the carbon fine particles are dispersed in the amorphous carbon.

Description

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

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

2. Description of the Related Art In recent years, portable electronic devices have been required to have a higher capacity of a lithium secondary battery as a power source due to miniaturization and multifunctionalization. However, since graphite has a theoretical capacity of 372 mAh / g, which is currently commercialized as an anode active material, it is urgent to develop a new high capacity anode active material.

Silicon (Si) and its compounds have been studied as novel materials that can replace graphite. Silicon reversibly intercalates and deintercalates lithium through compound formation reaction with lithium, and its theoretical maximum capacity is 4020 mAh / g (9800 mAh / g, specific gravity: 2.23), which is very large compared to graphite and is therefore promising as a high capacity cathode material.

But charging? During the discharge, the volume change occurs due to the reaction with lithium, which leads to the undifferentiation of the silicon active material powder and the electrical contact failure between the silicon active material powder and the current collector. As a result, as the charge / discharge cycle of the battery progresses, the battery capacity sharply decreases, shortening the cycle life.

An embodiment of the present invention is to provide a negative electrode active material for a lithium secondary battery having a high capacity and excellent cycle life characteristics and high rate charge / discharge characteristics.

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

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

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

One embodiment of the present invention includes a porous granular particle comprising a plurality of composite particles and pores between the composite particles, wherein the composite particle comprises silicon (Si) based particles, carbon fine particles and amorphous carbon, The carbon includes at least one selected from soft carbon and hard carbon, and the silicon-based particles and the carbon fine particles are dispersed in the amorphous carbon.

The soft carbon may be obtained from at least one selected from coal-based pitch, petroleum pitch, polyvinyl chloride, mesophase pitch, tar and low molecular weight heavy oil, and the hard carbon may be selected from phenol resin, naphthalene resin, furfuryl alcohol alcohol resin, a polyamide resin, a furan resin, a polyimide resin, an epoxy resin and a vinyl chloride resin.

The silicon-based particles may include at least one selected from the group consisting of silicon (Si), silicon (Si) -containing alloy, and silicon (Si) -containing oxide.

The silicon-containing alloy may be silicon (Si), and at least one of silicon (Si), and at least one of Ge, Sn, Al, Sb, B, P, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Ru, Rh, Pd, Ag, Ta and W.

The silicon (Si) -containing oxide may be selected from the group consisting of silicon (Si), Ge, Sn, Al, Sb, B, P, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Ru, Rh, Pd, Ag, Ta and W.

The average particle diameter (D50) of the silicon (Si) -based particles may be 0.005 to 1 탆.

The carbon microparticles may include carbon black, acetylene black, Ketjen black, Super P, or a combination thereof.

The average particle diameter (D50) of the carbon fine particles may be 0.002 to 1 mu m.

The silicon (Si) based particles and the carbon fine particles may be contained in a weight ratio of 1: 5 to 5: 1.

The amorphous carbon may be included in an amount of 2 to 90 parts by weight based on 100 parts by weight of the total amount of the silicon (Si) based particles and the carbon fine particles.

The average particle size (D50) of the composite particles may be 0.1 to 10 mu m.

The porous granulated particle may further include an aqueous binder which binds the composite particles together.

The aqueous binder may be selected from the group consisting of polyvinyl alcohol (PVA), triton, citric acid, stearic acid, sucrose, polyvinylidene fluoride, carboxymethylcellulose (CMC), hydroxypropylcellulose, regenerated cellulose, (EPDM), polyacrylic acid, polyacrylic sodium, polyacrylonitrile, cellulose, styrene, polyvinyl alcohol, sucrose, glucose, gelatin, saccharides, or combinations thereof. .

The average particle size (D50) of the porous granulated particles may be 3 to 30 탆.

The porosity of the porous assembled particles may be 1 to 50% by volume.

The negative electrode active material may further include a coating layer positioned on the surface of the porous assembled particles, and the coating layer may include at least one selected from soft carbon and hard carbon.

The thickness of the coating layer may be 0.01 to 3 탆.

According to another embodiment of the present invention, there is provided a method of manufacturing a semiconductor device, comprising: preparing a mixed solution by adding silicon (Si) based particles and carbon fine particles to a solution containing an amorphous carbon precursor and an organic solvent; Mixing an aqueous solution containing an aqueous binder and the mixed solution to obtain an emulsion solution; Removing the organic solvent from the emulsion solution to obtain a suspension in which the composite particle precursor is dispersed; Spray drying the suspension to obtain a porous granulated particle precursor; And heat treating the porous assembled particle precursor to obtain porous assembled particles. The present invention also provides a method for manufacturing a negative active material for a lithium secondary battery.

Wherein the amorphous carbon precursor is at least one soft carbon source selected from coal-based pitch, petroleum pitch, polyvinyl chloride, mesophase pitch, tar and low molecular weight heavy oil; At least one hard carbon raw material selected from phenol resin, naphthalene resin, furfuryl alcohol resin, polyamide resin, furan resin, polyimide resin, epoxy resin and vinyl chloride resin; Or a combination thereof.

The organic solvent may include N-methylpyrrolidone, dimethylformamide, toluene, ethylene, dimethylacetamide, acetone, methyl ethyl ketone, hexane, tetrahydrofuran, decane or combinations thereof.

The step of removing the organic solvent from the emulsion solution may be performed at a temperature of 50 to 100 ° C.

The spray drying may be performed at a temperature of 50 to 300 ° C, and the spray drying may be performed by a drying method including rotary spraying, nozzle spraying, ultrasonic spraying, or a combination thereof.

The heat treatment may be performed at a temperature of 500 to 1500 ° C, and the heat treatment may be performed in an atmosphere containing nitrogen, argon, hydrogen or a mixed gas thereof, or under vacuum.

Adding the porous granulated particles to a solution containing at least one selected from a soft carbon raw material and a hard carbon raw material and an organic solvent to obtain a mixed solution; And heat treating the mixed solution.

Another embodiment of the present invention provides a negative electrode for a lithium secondary battery comprising the negative active material.

According to another embodiment of the present invention, 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 high capacity and excellent cycle life characteristics and high rate charge / discharge characteristics can be realized.

FIG. 1 is a schematic view showing a structure of a negative electrode active material according to one embodiment.
2 is a schematic view schematically showing the structure of a negative electrode active material according to another embodiment.
3 is a low magnification scanning electron microscope (SEM) photograph of the negative electrode active material according to Example 1. Fig.
4 is a high magnification scanning electron microscope (SEM) photograph of the negative electrode active material according to Example 1. Fig.
5 is a high-magnification transmission electron microscope (SEM) photograph of the negative electrode active material according to Comparative Example 1. Fig.
6 is a low magnification transmission electron microscope (TEM) photograph of the negative electrode active material according to Example 1. Fig.
7 is a high-magnification transmission electron microscope (TEM) photograph of the negative electrode active material according to Example 1. Fig.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

The anode active material for a lithium secondary battery according to an embodiment may be a porous granulated particle including a plurality of composite particles including silicon (Si) based particles, carbon fine particles and amorphous carbon, and pores between the composite particles.

The structure of the negative electrode active material is specifically shown in Figs. 1 and 2.

FIG. 1 is a schematic view schematically showing a structure of an anode active material according to one embodiment, and specifically, a schematic diagram showing a structure of the composite particle. FIG. 2 is a schematic view schematically showing a structure of a negative electrode active material according to another embodiment, and specifically, it is a schematic diagram showing a structure of the porous assembled particles.

1 and 2, the negative electrode active material according to one embodiment, specifically, the porous granulated particles 20 includes a plurality of composite particles 10 and pores (not shown) between the composite particles 10 can do. The composite particles 10 may include silicon (Si) based particles 1, carbon fine particles 2, and amorphous carbon 3. The silicon (Si) based particles 1 and the carbon fine particles 2 may be dispersed in the amorphous carbon 3. When the negative electrode active material having such a structure is used, the carbon fine particles in the composite particles improve dispersibility of the nano-sized silicon-based particles and can serve as a buffer against volume expansion of the silicon-based particles. In addition, since the porous structure of the porous granulated particles alleviates the volume expansion due to the composite particles during charging and discharging and facilitates the impregnation of the electrolyte, the lithium secondary battery having a high capacity and excellent cycle life characteristics and high rate charge- Can be implemented.

The porous granulated particles may be formed by assembling the composite particles together. In other words, the composite particles corresponding to the primary particles may be granulated to form the porous granulated particles corresponding to the secondary particles.

The amorphous carbon may be at least one selected from soft carbon and hard carbon.

The soft carbon may be obtained from at least one selected from coal-based pitch, petroleum pitch, polyvinyl chloride, mesophase pitch, tar and low molecular weight heavy oil.

The hard carbon may be obtained from at least one selected from a phenol resin, a naphthalene resin, a furfuryl alcohol resin, a polyamide resin, a furan resin, a polyimide resin, an epoxy resin and a vinyl chloride resin.

The silicon-based particles may be at least one selected from silicon (Si), silicon (Si) -containing alloy, and silicon (Si) -containing oxide.

The silicon (Si) -containing alloy may be selected from the group consisting of Si, Ge, Sn, Al, Sb, B, P, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Ru, Rh, Pd, Ag, Ta and W.

The silicon (Si) -containing oxide may be selected from the group consisting of silicon (Si), Ge, Sn, Al, Sb, B, P, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Ru, Rh, Pd, Ag, Ta and W.

The average particle size (D50) of the silicon-based particles may be 0.005 to 1 mu m, and may be specifically 0.01 to 0.1 mu m. In this case, the average particle diameter (D50) means the particle diameter corresponding to the cumulative volume of 50 vol% in the particle size distribution. When the average particle diameter of the silicon-based particles is within the above-mentioned range, volume expansion during charging and discharging is small and excellent cycle life characteristics and high rate charge / discharge characteristics can be obtained.

The carbon fine particles may be carbon black, acetylene black, Ketjen black, Super P, or a combination thereof.

The average particle diameter (D50) of the carbon fine particles may be 0.002 to 1 mu m, and may be specifically 0.005 to 0.5 mu m. When the average particle diameter of the carbon fine particles is within the above range, aggregation does not occur when mixed with the silicon-based particles, excellent dispersibility into the amorphous carbon, and excellent bufferability against volume expansion of the silicone- .

When the silicon-based particles and the carbon fine particles are dispersed in the amorphous carbon, the silicon-based particles and the carbon fine particles may be dispersed in a weight ratio of 1: 5 to 5: 1, specifically 1: 3 to 3: 1 Can be dispersed in a weight ratio. When the weight ratio is dispersed within the above range, the capacity is increased and the volume expansion of the silicon-based particles is suppressed at the time of charge / discharge, thereby improving cycle life characteristics.

The amorphous carbon may be included in an amount of 2 to 90 parts by weight, specifically 10 to 80 parts by weight, based on 100 parts by weight of the total amount of the silicon-based particles and the carbon fine particles. When the amorphous carbon is contained in the above content range, the composite particles corresponding to the primary particles can be easily formed and the capacity can be increased.

The average particle diameter (D50) of the composite particles may be 0.1 to 10 mu m, and may be 0.5 to 5 mu m. When the average particle diameter of the composite particles is within the above range, the buffering property against the volume expansion of the silicon-based particles during charging and discharging is improved, the diffusion distance of lithium ions is shortened, and the high rate charging / discharging characteristics can be improved.

The porous granulated particle may further include an aqueous binder in addition to the composite particle and the pore. The aqueous binder binds a plurality of the composite particles to each other, thereby assisting in assembling.

The aqueous binder may be selected from the group consisting of polyvinyl alcohol (PVA), triton, citric acid, stearic acid, sucrose, polyvinylidene fluoride, carboxymethylcellulose (CMC), hydroxypropylcellulose, regenerated cellulose, (EPDM), polyacrylic acid, polyacrylic sodium, polyacrylonitrile, cellulose, styrene, polyvinyl alcohol, sucrose, glucose, gelatin, saccharides, or combinations thereof. Can be used.

The average particle size (D50) of the porous granulated particles may be 3 to 30 탆, specifically 5 to 20 탆. When the average particle diameter of the porous granulated particles is within the above range, it is possible to obtain a high electrode density with high efficiency in the electrode manufacturing process.

The porous granulated particles may be formed by combining the composite particles with each other by the aqueous binder, and pores may be formed between the composite particles. The porosity of the porous granulated particles may be 1 to 50% by volume, and may be 5 to 40% by volume. When the porosity of the porous granulated particles is within the above range, the porous granulated particles are excellent in the electrolyte impregnability inside the granulated particles, so that the high rate charging / discharging characteristics are excellent, and the high density of the porous granulated particles can provide a high electrode energy density .

The porous assembled particles may be spherical.

The anode active material according to an embodiment may further include a coating layer positioned on the surface of the porous assembled particles. The coating layer may be composed of at least one selected from soft carbon and hard carbon. The substance content of the soft carbon and the hard carbon is as described above.

The thickness of the coating layer may be 0.01 to 3 탆, and may be 0.100 to 2 탆. When the thickness of the coating layer is within the above range, the silicone-based particles are excellent in bufferability against volume expansion upon charging and discharging.

The anode active material according to one embodiment can be manufactured by the following method.

(Si) -based particles and the carbon fine particles to a solution containing an amorphous carbon precursor and an organic solvent to obtain a mixed solution, mixing an aqueous solution containing an aqueous binder and the mixed solution to prepare an emulsion solution Removing the organic solvent from the emulsion solution to prepare a suspension in which the composite particle precursor is dispersed, spray-drying the suspension to obtain a porous granulated particle precursor, and drying the porous granulated particle precursor And the above-mentioned porous assembled particles can be obtained by heat treatment.

Wherein the amorphous carbon precursor is at least one soft carbon source selected from coal-based pitch, petroleum pitch, polyvinyl chloride, mesophase pitch, tar and low molecular weight heavy oil; At least one hard carbon raw material selected from phenol resin, naphthalene resin, furfuryl alcohol resin, polyamide resin, furan resin, polyimide resin, epoxy resin and vinyl chloride resin; Or a combination thereof.

The organic solvent may be N-methylpyrrolidone, dimethylformamide, toluene, ethylene, dimethylacetamide, acetone, methyl ethyl ketone, hexane, tetrahydrofuran, decane or a combination thereof.

The aqueous binder may be selected from the group consisting of polyvinyl alcohol (PVA), triton, citric acid, stearic acid, sucrose, polyvinylidene fluoride, carboxymethylcellulose (CMC), hydroxypropylcellulose, regenerated cellulose, (EPDM), polyacrylic acid, polyacrylic sodium, polyacrylonitrile, cellulose, styrene, polyvinyl alcohol, sucrose, glucose, gelatin, saccharides, or combinations thereof.

The aqueous binder serves as a surfactant in the step of obtaining the emulsion, and the size of the pores in the porous granular particle precursor formed after the spray drying and the size of the primary particle precursor can be appropriately controlled.

The aqueous solution containing the aqueous binder may contain ethylene glycol.

In order to obtain the primary particle precursor in the process of preparing the porous granulated particle precursor, the spherical primary particle precursor can be effectively prepared, and a process for preparing the porous granulated particle based on the aqueous solution It is possible.

The step of removing the organic solvent from the emulsion solution may be carried out at a temperature of 50 to 100 ° C, and specifically at a temperature of 60 to 90 ° C. The stability of the emulsion solution can be ensured when it is carried out within the above temperature range.

The granulation for forming the porous granulated particles may be performed through the spray drying.

The spray drying can be carried out at a temperature of 50 to 300 캜, specifically at a temperature of 80 to 200 캜. When spray drying is performed in the temperature range described above, drying of the emulsion solution is stably performed, so that the structure and shape of the porous granulated particle precursor can be easily controlled.

The spray drying may be carried out by a drying method comprising rotary spraying, nozzle spraying, ultrasonic spraying or a combination thereof.

The heat treatment may be performed at a temperature of 500 to 1500 ° C, specifically, at a temperature of 700 to 1200 ° C. When the heat treatment is performed in the temperature range, the silicon-based particles and the amorphous carbon precursor react with each other to inhibit the formation of silicon carbide (SiC), thereby increasing the lithium storage capacity, and the silicon-based particles are excellent in reactivity with lithium The charge and discharge characteristics of the amorphous carbon precursor are excellent and the carbonization process of the amorphous carbon precursor occurs sufficiently to improve the electrode characteristics upon charge and discharge.

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

In order to form the above-mentioned coating layer on the surface of the prepared porous granulated particles, the porous granulated particles are added to a solution containing at least one selected from a soft carbon raw material and a hard carbon raw material and an organic solvent to obtain a mixed liquid, The mixed solution can be heat-treated.

The soft carbon raw material may be at least one selected from coal-based pitch, petroleum pitch, polyvinyl chloride, mesophase pitch, tar and low molecular weight heavy oil, and the hard carbon raw material may be at least one selected from the group consisting of phenol resin, naphthalene resin, furfuryl alcohol alcohol resin, polyamide resin, furan resin, polyimide resin, epoxy resin, and vinyl chloride resin.

The organic solvent is the same as the above-mentioned organic solvent.

The heat treatment may be performed in the same manner as the heat treatment conditions for obtaining the porous assembled particles.

Another embodiment provides a negative electrode for a lithium secondary battery including the negative active material, and another embodiment provides a lithium secondary battery including the negative electrode.

The lithium secondary battery may 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 may 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.

A lithium secondary battery according to an embodiment includes an electrode assembly including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode. The electrode assembly includes a sealing member that is housed in a battery container, impregnates the electrolyte, and seals the battery container.

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 an anode current collector such as copper.

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 amount 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 whiskey 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 anode active material layer.

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

As the cathode active material, a compound capable of reversibly intercalating and deintercalating lithium (a lithiated intercalation compound) can be used. Concretely, at least one of complex oxides of lithium and at least one kind selected from cobalt, manganese and nickel can be used.

The electrolyte solution may be a lithium salt, a non-aqueous organic solvent, an organic solid electrolyte, or an inorganic solid electrolyte.

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 pyrophonate, 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, and the like can 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 embodiments and comparative examples of the present invention will be described. However, the following embodiments are merely preferred embodiments of the present invention, and the present invention is not limited to the following embodiments.

(Preparation of negative electrode active material)

Example  One

(Si) particles having an average particle diameter (D50) of 20 to 30 nm and carbon black particles were mixed in a weight ratio of 1: 1 to a mixture of 60 ml of tetrahydrofuran (THF) dissolved in 40 ml of petroleum pitch in an amount of 60 Parts by weight were added and stirred to prepare a mixed solution. Thereafter, the mixed solution was dripped into an aqueous solution containing 5 parts by weight of polyvinyl alcohol at a rate of 10 ml / min to prepare an aging solution, followed by stirring at 60 ° C to remove the tetrahydrofuran solvent. Thus, a suspension of the composite particle precursor . The suspension was spray-dried at a hot air temperature of 160 ° C to obtain a porous granulated particle precursor powder. The porous granulated particle precursor powder was heat-treated at 1000 ° C under argon atmosphere and then furnace cooled to prepare porous granulated particles having an average particle diameter (D50) of 10 μm. The obtained porous assembled particles were used as a negative electrode active material.

Example  2

50 parts by weight of a mixture of silicon particles having an average particle diameter (D50) of 20 to 30 nm and carbon black particles at a weight ratio of 1: 1 was added to 100 ml of a tetrahydrofuran (THF) solution in which 50 parts by weight of petroleum pitch was dissolved And stirring to prepare a mixed solution. Porous granulated particles were prepared in the same manner as in Example 1,

Example  3

The porous granulated particles prepared in Example 1 were added to 40 parts by weight of a tetrahydrofuran solution in which 20 parts by weight of the petroleum pitch was dissolved, and then heat-treated at 1000 ° C under an argon atmosphere and then subjected to furnace cooling to obtain an average particle size ) Was 15 mu m. The obtained porous assembled particles were used as a negative electrode active material.

Example  4

The porous granular particles prepared in Example 2 were added to 40 parts by weight of a tetrahydrofuran solution in which 20 parts by weight of the petroleum pitch was dissolved, and then heat-treated at 1000 ° C under an argon atmosphere and then subjected to furnace cooling to obtain an average particle size ) Was 15 mu m. The obtained porous assembled particles were used as a negative electrode active material.

Comparative Example  One

A mixture of silicon particles having an average particle diameter (D50) of 20 to 30 nm and carbon black particles in a weight ratio of 1: 1 was added to an aqueous solution obtained by dissolving 5 parts by weight of polyvinyl alcohol, and the mixture was stirred at a speed of 300 rpm to disperse the particle precursor A suspension was prepared. The suspension was spray-dried at a hot air temperature of 160 DEG C, and the obtained powder was heat-treated at 1000 DEG C in an argon atmosphere and then subjected to furnace cooling to prepare granulated particles having an average particle diameter (D50) of 10 mu m. The resulting granulated particles were used as negative electrode active material.

Comparative Example  2

The granulated particles prepared in Comparative Example 1 were added to 40 parts by weight of a tetrahydrofuran solution in which 20 parts by weight of the petroleum pitch was dissolved, and then heat-treated at 1000 ° C under an argon atmosphere and then subjected to a furnace cooling to obtain an average particle size (D50) To prepare coarse particles having a particle diameter of 15 mu m. The resulting granulated particles were used as negative electrode active material.

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

FIG. 3 is a SEM photograph of a negative active material according to Example 1, FIG. 4 is a SEM photograph of a negative active material according to Example 1, and FIG. (SEM) photograph of a negative electrode active material.

Referring to FIGS. 3 and 4, it can be seen that in Example 1, a plurality of primary particles, that is, composite particles are granulated to form secondary particles having porosity, that is, porous granulated particles. On the other hand, referring to FIG. 5, it can be seen that nano-sized silicon particles and carbon fine particles are assembled in the case of Comparative Example 1, but it is different from the porous structure according to one embodiment.

Evaluation 2: Transmission electron microscope of the anode active material TEM ) analysis

FIG. 6 is a low magnification transmission electron microscope (TEM) photograph of the negative electrode active material according to Example 1, and FIG. 7 is a high magnification transmission electron microscope (TEM) photograph of the negative electrode active material according to Example 1.

Referring to FIG. 6, it can be seen that in Example 1, a plurality of primary particles, that is, composite particles, are granulated to form secondary particles having porosity, that is, porous granulated particles.

Referring to FIG. 7, it can be seen from (A) and (B) that the silicon-based particles are dispersed in the amorphous carbon in the composite particles.

(Production of lithium secondary battery)

Each of the negative electrode active materials prepared in Examples 1 to 4 and Comparative Examples 1 and 2 was mixed with carbon black and CMC / SBR (carboxymethylcellulose / styrene-butadiene rubber) in distilled water at a weight ratio of 85: 5: Slurry. The negative electrode slurry was coated on a copper foil having a thickness of 10 mu m using a doctor blade, dried at 180 DEG C for 12 hours or more, and pressed to produce a negative electrode plate having a thickness of 45 mu m .

A separator made of a porous polypropylene film was inserted between the working electrode and the counter electrode with the negative electrode serving as the working electrode and the metal lithium foil serving as the counter electrode and a mixed solvent of diethyl carbonate (DEC) and ethylene carbonate (EC) DEC: EC = 1: 1) so that the concentration of LiPF 6 was 1 mol / L, a 2032 coin type half cell was fabricated.

Evaluation 3: Cycle life characteristics of lithium secondary battery

The life characteristics of the lithium secondary batteries fabricated according to Examples 1 to 4 and Comparative Examples 1 and 2 were evaluated in the following manner, and the results are shown in Table 1 below.

For one and two cycles, charging was done in CC / CV mode, the termination voltage was maintained at 0.02V, and charging was terminated when the current was 0.02 mA. The discharge was done in CC mode and the termination voltage was maintained at 2V. The charging was performed in the CC mode from the third cycle, and the cadence voltage was maintained at 0.02V. The discharge was done in CC mode and the termination voltage was maintained at 2V.

In Table 1, the initial efficiency (%) can be obtained by the ratio of the charging capacity to the discharging capacity in one cycle. In the following Table 1, the reversible capacity retention rate (%) is the percentage value of the reversible capacity at the third cycle with respect to the reversible capacity at the 40th cycle.

Initial efficiency (%) Reversible capacity at 3 cycles (mAh / g) Reversible Capacity Retention Rate (%) Example 1 82 920 85 Example 2 84 891 88 Example 3 85 864 92 Example 4 87 828 92 Comparative Example 1 66 650 11 Comparative Example 2 71 556 15

As shown in Table 1, in the case of Examples 1 to 4, in which a plurality of composite particles were granulated according to an embodiment, and the porous granulated particles having porosity were used as an anode active material, compared with Comparative Examples 1 and 2, It can be seen that the cycle life characteristics are excellent as the efficiency and the reversibility capacity retention ratio are high.

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: silicon (Si) -based particles
2: Carbon particles
3: Amorphous carbon
10: Composite particle
20: porous assembled particles

Claims (31)

  1. And a porous granulated particle containing a plurality of composite particles and pores between the composite particles,
    The composite particle includes silicon (Si) based particles, carbon fine particles and amorphous carbon,
    Wherein the amorphous carbon comprises at least one selected from soft carbon and hard carbon,
    The silicon-based particles and the carbon fine particles are dispersed in the amorphous carbon
    Negative electrode active material for lithium secondary battery.
  2. The method according to claim 1,
    Wherein the soft carbon is obtained from at least one selected from coal-based pitch, petroleum pitch, polyvinyl chloride, mesophase pitch, tar and low molecular weight heavy oil,
    The hard carbon is obtained from at least one selected from phenol resin, naphthalene resin, furfuryl alcohol resin, polyamide resin, furan resin, polyimide resin, epoxy resin and vinyl chloride resin
    Negative electrode active material for lithium secondary battery.
  3. The method according to claim 1,
    Wherein the silicon-based particles comprise at least one selected from the group consisting of silicon (Si), silicon (Si) -containing alloy, and silicon (Si) -containing oxide.
  4. The method of claim 3,
    The silicon-containing alloy may be silicon (Si), and at least one of silicon (Si), and at least one of Ge, Sn, Al, Sb, B, P, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Ru, Rh, Pd, Ag, Ta and W. The negative active material for lithium secondary battery according to claim 1,
  5. The method of claim 3,
    The silicon (Si) -containing oxide may be selected from the group consisting of silicon (Si), Ge, Sn, Al, Sb, B, P, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Ru, Rh, Pd, Ag, Ta and W. The negative active material for lithium secondary battery according to claim 1,
  6. The method according to claim 1,
    The average particle size (D50) of the silicon (Si) -based particles is 0.005 to 1 占 퐉.
  7. The method according to claim 1,
    Wherein the carbon fine particles include carbon black, acetylene black, Ketjen black, Super P, or a combination thereof.
  8. The method according to claim 1,
    The average particle diameter (D50) of the carbon fine particles is 0.002 to 1 占 퐉.
  9. The method according to claim 1,
    Wherein the silicon (Si) based particles and the carbon fine particles are contained in a weight ratio of 1: 5 to 5: 1.
  10. The method according to claim 1,
    Wherein the amorphous carbon is contained in an amount of 2 to 90 parts by weight based on 100 parts by weight of the total amount of the silicon (Si) based particles and the carbon fine particles.
  11. The method according to claim 1,
    Wherein the average particle size (D50) of the composite particles is 0.1 to 10 mu m.
  12. The method according to claim 1,
    Wherein the porous granulated particle further comprises an aqueous binder for binding the composite particles to each other.
  13. 13. The method of claim 12,
    The aqueous binder may be selected from the group consisting of polyvinyl alcohol (PVA), triton, citric acid, stearic acid, sucrose, polyvinylidene fluoride, carboxymethylcellulose (CMC), hydroxypropylcellulose, regenerated cellulose, (EPDM), polyacrylic acid, polyacrylic sodium, polyacrylonitrile, cellulose, styrene, polyvinyl alcohol, sucrose, glucose, gelatin, saccharides, or combinations thereof. Containing negative active material for a lithium secondary battery.
  14. The method according to claim 1,
    The average particle size (D50) of the porous granulated particles is 3 to 30 占 퐉 for a negative electrode active material for a lithium secondary battery.
  15. The method according to claim 1,
    Wherein the porosity of the porous assembled particles is 1 to 50% by volume.
  16. The method according to claim 1,
    Wherein the negative electrode active material further comprises a coating layer positioned on a surface of the porous assembled particles,
    Wherein the coating layer comprises at least one selected from soft carbon and hard carbon.
  17. 17. The method of claim 16,
    Wherein the thickness of the coating layer is 0.01 to 3 占 퐉.
  18. Adding silicon (Si) based particles and carbon fine particles to a solution containing an amorphous carbon precursor and an organic solvent to obtain a mixed solution;
    Mixing an aqueous solution containing an aqueous binder and the mixed solution to obtain an emulsion solution;
    Removing the organic solvent from the emulsion solution to obtain a suspension in which the composite particle precursor is dispersed;
    Spray drying the suspension to obtain a porous granulated particle precursor; And
    And heat-treating the porous assembled particle precursor to obtain porous assembled particles
    And a negative electrode active material for lithium secondary batteries.
  19. 19. The method of claim 18,
    Wherein the amorphous carbon precursor is at least one soft carbon source selected from coal-based pitch, petroleum pitch, polyvinyl chloride, mesophase pitch, tar and low molecular weight heavy oil; At least one hard carbon raw material selected from phenol resin, naphthalene resin, furfuryl alcohol resin, polyamide resin, furan resin, polyimide resin, epoxy resin and vinyl chloride resin; Or a combination thereof. ≪ RTI ID = 0.0 > 11. < / RTI >
  20. 19. The method of claim 18,
    The organic solvent may be at least one selected from the group consisting of N-methylpyrrolidone, dimethylformamide, toluene, ethylene, dimethylacetamide, acetone, methyl ethyl ketone, hexane, tetrahydrofuran, decane, Gt;
  21. 19. The method of claim 18,
    Wherein the silicon-based particles comprise at least one selected from silicon (Si), silicon (Si) -containing alloy, and silicon (Si) -containing oxide.
  22. 19. The method of claim 18,
    Wherein the carbon microparticles include carbon black, acetylene black, Ketjenblack, Super P, or a combination thereof.
  23. 19. The method of claim 18,
    The aqueous binder may be selected from the group consisting of polyvinyl alcohol (PVA), triton, citric acid, stearic acid, sucrose, polyvinylidene fluoride, carboxymethylcellulose (CMC), hydroxypropylcellulose, regenerated cellulose, (EPDM), polyacrylic acid, polyacrylic sodium, polyacrylonitrile, cellulose, styrene, polyvinyl alcohol, sucrose, glucose, gelatin, saccharides, or combinations thereof. Wherein the negative electrode active material for lithium secondary battery is a lithium secondary battery.
  24. 19. The method of claim 18,
    Wherein the step of removing the organic solvent from the emulsion solution is performed at a temperature of 50 to 100 ° C.
  25. 19. The method of claim 18,
    Wherein the spray drying is performed at a temperature of 50 to 300 캜.
  26. 19. The method of claim 18,
    Wherein the spray drying is performed by a drying method including rotary spraying, nozzle spraying, ultrasonic spraying, or a combination thereof.
  27. 19. The method of claim 18,
    Wherein the heat treatment is performed at a temperature of 500 to 1500 ° C.
  28. 19. The method of claim 18,
    Wherein the heat treatment is performed in an atmosphere containing nitrogen, argon, hydrogen, or a mixed gas thereof, or under vacuum.
  29. 19. The method of claim 18,
    Adding the porous granulated particles to a solution containing at least one selected from a soft carbon raw material and a hard carbon raw material and an organic solvent to obtain a mixed liquid; And
    Heat-treating the mixed solution
    Wherein the negative electrode active material for lithium secondary battery is a lithium secondary battery.
  30. The negative electrode active material according to any one of claims 1 to 17
    And a negative electrode for a lithium secondary battery.
  31. A negative electrode of claim 30;
    anode; And
    Electrolyte
    ≪ / RTI >
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