WO2016085282A1 - Silicon-based negative electrode active material and method for manufacturing same - Google Patents

Silicon-based negative electrode active material and method for manufacturing same Download PDF

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Publication number
WO2016085282A1
WO2016085282A1 PCT/KR2015/012815 KR2015012815W WO2016085282A1 WO 2016085282 A1 WO2016085282 A1 WO 2016085282A1 KR 2015012815 W KR2015012815 W KR 2015012815W WO 2016085282 A1 WO2016085282 A1 WO 2016085282A1
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Prior art keywords
active material
silicon
negative electrode
electrode active
water
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PCT/KR2015/012815
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French (fr)
Korean (ko)
Inventor
김현철
이용주
강윤아
김은경
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주식회사 엘지화학
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Priority to US15/521,532 priority Critical patent/US10873071B2/en
Priority claimed from KR1020150166965A external-priority patent/KR101888230B1/en
Publication of WO2016085282A1 publication Critical patent/WO2016085282A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • Y—GENERAL 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a negative electrode active material including silicon-based nanoparticles in which polymer carbide is distributed on a surface thereof, and a method of manufacturing the same.
  • Lithium metal oxide is used as a positive electrode active material of a lithium secondary battery, and lithium metal, a lithium alloy, crystalline or amorphous carbon or a carbon composite material is used as a negative electrode active material.
  • the active material is applied to a current collector with a suitable thickness and length, or the active material itself is applied in a film shape to form an electrode group by winding or laminating together with a separator, which is an insulator, and then put it in a can or a similar container, and then injecting an electrolyte solution.
  • a secondary battery is manufactured.
  • graphite is mainly used as a negative electrode material of a lithium secondary battery, graphite has a small capacity per unit mass of 372 mAh / g, and it is difficult to increase the capacity of a lithium secondary battery.
  • the material which forms intermetallic compound with lithium such as silicon, tin, and these oxides, is promising, for example.
  • these materials cause a change in the crystal structure when absorbing and storing lithium, causing a problem of expansion of the volume.
  • silicon-based materials which are being studied as high-capacity materials, have a high capacity of about 3600 mAh / g, which is about 10 times higher than the theoretical capacity of carbon-based materials, and thus are attracting attention as high-capacity secondary battery materials.
  • Li 4 . 4 Si For silicon, the maximum amount of lithium absorbed and stored, Li 4 . 4 Si is converted to volume expansion by charging, in which case the rate of volume increase by charging can be expanded up to about 4.12 times the volume of silicon before volume expansion, resulting in cracks between particles and short-lived electrodes. There is a problem that deterioration of characteristics occurs.
  • An object of the present invention is to provide a silicon-based anode active material 10 times higher theoretical capacity than a carbon-based anode active material, to distribute the polymer carbide on the surface of the silicon-based nanoparticles to improve the electrical conductivity and control the volume expansion It is to provide a non-carbon negative electrode active material.
  • the negative electrode active material silicon-based nanoparticles; And a carbide of the water-soluble polymer distributed on the nanoparticles, wherein the size of the silicon-based nanoparticles in which the polymer carbide is distributed on the surface is 30 to 800 nm.
  • the silicon-based nanoparticles may be any one material selected from the group consisting of Si, SiO, SiM, and combinations thereof, wherein M is Ni, Co, B, Cr, Cu, Fe, Mn, Ti, Y And combinations thereof may be any one selected from the group consisting of.
  • the water-soluble polymer may include any one selected from the group consisting of carboxy methyl cellulose (CMC), sucrose (sucrose), polyacrylonitrile (polyacrylonitrile, PAN), and combinations thereof.
  • CMC carboxy methyl cellulose
  • sucrose sucrose
  • PAN polyacrylonitrile
  • the water-soluble polymer may have a weight average molecular weight of 90,000 to 2,000,000.
  • the negative electrode active material may include 3 to 20% by weight of polymer carbide, based on the total weight of the silicon-based nanoparticles.
  • the carbonization may be performed in a two step process including a low temperature carbonization process and a high temperature carbonization process.
  • the low temperature carbonization process may be performed using a spray drying apparatus, and may include injecting the suspension into a chamber in the spray drying apparatus and spraying the suspension in the chamber to dry it.
  • the low temperature carbonization process may be performed at a temperature of 80 to 300 °C.
  • the high temperature carbonization process may be heat treatment at a temperature of 800 to 1100 °C.
  • the method for preparing a negative electrode active material of the present invention can easily disperse nano-sized silicon-based particles using ultrasonic waves, and distribute the polymer carbide on the surface of the silicon-based nanoparticles through a simple method such as spray drying. In this way, aggregation between nanoparticles can be prevented, conductivity can be ensured, and additional conductivity can be provided by forming a shell layer with a water-soluble polymer.
  • the volume expansion coefficient is significantly lower, and an anode active material having excellent electrical conductivity can be provided.
  • Method for producing a negative electrode active material the dispersion of the silicon-based nanoparticles and the water-soluble polymer added to the solvent using ultrasonic waves; And carbonizing the water-soluble polymer to form polymer carbide on the surface of the silicon-based nanoparticles.
  • Preparation and dispersion of the suspension may include adding silicon-based nanoparticles and a water-soluble polymer to a solvent to prepare a suspension, and dispersing the nanoparticles having cohesive properties by irradiating ultrasonic waves to the suspension to vibrate the particles in the suspension.
  • a solvent to prepare a suspension
  • the solvent may be easily volatilized in a subsequent carbonization process, and may be applied without particular limitation as long as it is a solvent that does not react with the water-soluble polymer. Solvents and the like can be used.
  • the silicon-based nanoparticles may be nanoparticles of a silicon compound and nanoparticles having an oxide film formed on a surface thereof.
  • it may be a particle composed of silicon single element, silicon oxide, silicon nitride, a compound of silicon and metal, and the like, specifically, for example, Si, SiO, SiM or a mixture thereof may be applied, and in the SiM M may be Ni, Co, B, Cr, Cu, Fe, Mn, Ti, Y, or a combination thereof, and Si and the powder of M may be alloyed by a mechanical alloying method, but lithium ions as a negative electrode active material It may be preferable if the particles are composed of Si single elements so as to be easily occluded and released.
  • the water-soluble polymer can be applied without limitation as long as it can be well dispersed in the aqueous solvent used, for example, may be a cellulose-based polymer, a polymer containing a nitrile group.
  • a cellulose-based polymer for example, carboxy methyl cellulose (CMC), sucrose (sucrose) or a mixture thereof may be applied.
  • the polymer containing a nitrile group for example, polyacrylonitrile (polyacrylonitrile, PAN) and the like may be applied, and functional groups which are easily oxidized such as carboxyl groups or nitrile groups may be easily carbonized, and thus, it may be desirable to apply a water-soluble polymer including such functional groups.
  • the water-soluble polymer may have a weight average molecular weight of 90,000 to 2,000,000, for example, 1,400,000 or more, 1,800,000 or less, and most preferably 90,000 to 700,000. If the molecular weight of the water-soluble polymer is less than 90,000 may be advantageous in terms of solubility, but the amount of carbonization is disadvantageous in terms of securing the conductivity, it may be disadvantageous in terms of economics and fairness because the excessive amount should be injected, if the molecular weight is greater than 2,000,000 Dispersibility of the sub-type nanoparticles is reduced, and uniformity of carbides located on the surface may be reduced.
  • the content of the silicon-based nanoparticles and the water-soluble polymer added to the solvent may be preferably added in consideration of a relative ratio, and the silicon-based nanoparticles and the water-soluble polymer may be formed of the polymer carbide formed on the surface of the silicon-based nanoparticles.
  • Excessive amounts can form a coating structure that completely covers the outside, such as a coating layer, which can interfere with the occlusion and release of lithium ions into the silicon crystal structure, and the amount of polymer carbide on the surface of the silicon-based nanoparticles It is necessary to properly consider and adjust both aspects such as low electrical conductivity problems that may occur due to too little, problems of inhibiting volume expansion, or the effect of preventing aggregation.
  • the silicon-based nanoparticles and the water-soluble polymer need to be present in a uniformly dispersed state in the suspension.
  • carbonization of the water-soluble polymer may not be distributed on the surface of all silicon-based nanoparticles and may be distributed only on some particles, thereby causing problems of electrical conductivity or volume expansion of the silicon-based anode active material. May not be resolved.
  • ultrasonic waves can be used as a method for this uniform dispersion, and by irradiating the ultrasonic waves, the energy in the ultrasonic waves causes the particles in the suspension to vibrate, causing the distance between particles to be far apart. So that uniform dispersion can be achieved.
  • the ultrasonic waves can be adjusted appropriately, and the frequency is considered in consideration of the dispersibility of silicon-based nanoparticles and water-soluble polymers, and the aspects of concern about deformation or reaction of silicon-based nanoparticles or water-soluble polymers due to high energy. Can be adjusted.
  • a two-step carbonization process may be performed, and the two-step carbonization process may include a low temperature carbonization process and a high temperature carbonization process.
  • the low temperature carbonization process may be a method using a spray drying apparatus, carbonization of the water-soluble polymer using the spray drying apparatus is to inject the suspension into the chamber in the spray drying apparatus, and drying the suspension while spraying in the chamber It may be to include.
  • the spray drying apparatus that can be applied to the spray drying process, for example, ultrasonic spray drying apparatus, air nozzle spray drying apparatus, ultrasonic nozzle spray drying apparatus, filter expansion droplet generator, electrostatic spray drying apparatus or a combination thereof There may be.
  • the silicon-based nanoparticles in which the water-soluble polymer is carbonized on the surface by injecting a suspension in which the silicon-based nanoparticles and the water-soluble polymer are uniformly dispersed into a chamber provided in the spray drying apparatus, and spraying the suspension in the chamber, followed by drying.
  • a core containing can be formed.
  • Low temperature carbonization carried out through the spray drying method may be performed at a temperature of 80 to 300 °C.
  • the temperature of the spray drying is less than 80 ° C, moisture may remain in the particles, and when the temperature exceeds 300 ° C, particle growth may occur due to aggregation between nanoparticles. Therefore, it is necessary to control the appropriate temperature, it may be desirable to adjust the temperature to about 100 to 200 °C.
  • the high temperature carbonization process may be performed by putting a Si material produced by the spray drying method into a furnace and performing heat treatment under an inert atmosphere.
  • the heat treatment temperature may be 800 to 1100 °C, when the heat treatment temperature is less than 800 °C low graphitization degree may lower the electrical conductivity, when it exceeds 1100 °C nano Si crystals grow and crystal grains Problems such as deterioration of life characteristics and / or occurrence of swelling of the electrode due to coarsening may occur.
  • the silicon-based active material has the advantage that the theoretical capacity of the negative electrode active material is about 10 times larger than that of the carbon-based active material, but on the contrary, after lithium ions are initially occluded and released, the silicon-based active material shows a volume expansion rate of nearly 4 times that of the carbon-based active material. . Thus, if you want to use a silicon-based active material should be used as nanoparticles to greatly reduce the scale.
  • the nanoparticles have a large surface energy inherently agglomerating properties, it is difficult to manufacture the active material particles due to this agglomeration property, and thus has difficulty in commercializing a silicon-based active material.
  • the method for preparing a negative electrode active material according to an embodiment of the present invention is a silicon-based polymer carbide formed on the surface by dispersing the silicon-based nanoparticles by ultrasonic and carbonizing the water-soluble polymer on the surface of the silicon-based nanoparticles
  • the core containing the nanoparticles can prevent aggregation between the nanoparticles and at the same time solve the problem of low electrical conductivity of the silicon-based active material.
  • the content of the polymer carbide relative to the total weight of the silicon-based nanoparticles may be about 3 to 20% by weight. That is, it may be important to control the ratio of the polymer carbide to the total weight of the silicon-based nanoparticles by appropriately adjusting various process conditions and content ratios.
  • Silicon-based nanoparticles in which the polymer carbide which is the carbonized water-soluble polymer are distributed on the surface may be applied to the anode active material as such, but after the carbonization, to surround the outside of the manufactured anode active material to secure conductivity, etc.
  • a carbon coating layer containing a water soluble polymer may be further formed.
  • the carbon coating layer may include a conductive material, and complement the low electrical conductivity, which is a disadvantage of the silicon-based active material, with the polymer carbide distributed on the surface of the silicon-based nanoparticles, and the life of the lithium secondary battery including the active material. Properties can also be improved.
  • the carbon coating layer may be a general method of coating the particles, it may be formed by a chemical method or a mechanical method.
  • the carbon coating layer may be formed by mixing the powder of the core and the powder of the water-soluble polymer, and then coating by a mechanical method, the mechanical method may be applied, for example, milling, etc., when using a milling process.
  • the carbon coating layer may be formed using a physicochemical method such as chemical vapor deposition, and may form a coating layer by depositing a precursor of a water-soluble polymer on the core.
  • the precursor of the material forming the carbon coating layer may be achieved by dispersing in a solvent such as tetrahydrofuran (THF), alcohol, and the like, and mixing it with the silicon-based negative electrode active material, followed by drying and heat treatment.
  • the heat treatment temperature may be, for example, 300 °C to 1400 °C, it may be coated by heat treatment in this temperature range.
  • a pitch or a hydrocarbon-based material may be used as a precursor of the material forming the carbon coating layer.
  • the hydrocarbon-based material include furfuryl alcohol, phenol resins, and the like.
  • a mechanical method, a physicochemical method or a heat treatment method can be appropriately selected according to the advantages and disadvantages of each.
  • the electrical conductivity that can be improved by the carbon coating layer may be sufficiently achieved even with a polymer carbide distributed on the surface of the silicon-based nanoparticles, in which case the carbon coating layer may be unnecessary. Therefore, the carbon coating layer may coexist or may not be properly formed depending on the physical properties of the manufactured silicon-based negative electrode active material.
  • a negative electrode active material silicon-based nanoparticles and water-soluble polymer carbide distributed on the nanoparticles; includes.
  • the core may have a size of 30 to 800 nm, preferably 50 to 300 nm, or 50 to 100 nm.
  • size of the core is less than 30 nm, it may be difficult to control the aggregation between nanoparticles even by carbonization or the formation of a shell layer due to the high surface energy.
  • core size is larger than 800 nm, it may cause volume expansion of the finally manufactured cell. Can be.
  • a negative electrode for a lithium secondary battery includes a negative electrode slurry including the negative electrode active material, a binder, and a solvent, and optionally including a conductive material and a thickener, and a negative electrode current collector to which the negative electrode slurry is applied. It may include.
  • the present invention also provides a positive electrode comprising a positive electrode slurry comprising a positive electrode active material, a binder and a solvent, optionally including a conductive material and a thickener, a positive electrode current collector coated with the positive electrode slurry, and
  • a lithium secondary battery having a separator interposed between a positive electrode and a negative electrode, and an electrolyte including a lithium salt, an additive, and a nonaqueous solvent.
  • the binder is generally applicable to any binder that can be used in the art without limitation, for example, polyvinylidene fluoride (PVdF), a copolymer of polyhexafluoropropylene-polyvinylidene fluoride ( PVdF / HFP), poly (vinylacetate), polyvinyl alcohol, polyethylene oxide, polyvinylpyrrolidone, alkylated polyethylene oxide, polyvinyl ether, poly (methyl methacrylate), poly (ethyl acrylate), polytetrafluoro Low ethylene (PTFE), polyvinylchloride, polyacrylonitrile, polyvinylpyridine, styrene-butadiene rubber, acrylonitrile-butadiene rubber, ethylene propylene diene monomer (EPDM) or mixtures thereof and the like can be applied.
  • PVdF polyvinylidene fluoride
  • PVdF / HFP polyhexafluoropropylene-
  • the conductive material may be included to improve conductivity, and the conductive material may include natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, summer black, carbon nanotube, fullerene, and carbon.
  • the negative electrode may include a thickener for viscosity control.
  • the thickener may be a cellulose-based material, for example, any one selected from the group consisting of carboxymethyl cellulose (CMC), hydroxymethyl cellulose, hydroxy ethyl cellulose, and hydroxy propyl cellulose, or a mixture of two or more thereof. have.
  • the thickener may be preferably carboxymethyl cellulose (CMC), and the negative electrode active material and the binder may be dispersed in water together with the carboxymethyl cellulose and applied to the negative electrode.
  • Solvents for forming the negative electrode slurry include an organic solvent such as NMP (N-methyl pyrrolidone), DMF (dimethyl formamide), acetone, dimethyl acetamide or water, and these solvents alone or two The above can be mixed and used.
  • organic solvent such as NMP (N-methyl pyrrolidone), DMF (dimethyl formamide), acetone, dimethyl acetamide or water, and these solvents alone or two The above can be mixed and used.
  • the negative electrode may include a current collector, and non-limiting examples of the negative electrode current collector include a foil made of copper, gold, nickel, or a copper alloy, or a combination thereof.
  • the lithium secondary battery according to the exemplary embodiment of the present invention may include all conventional lithium secondary batteries, such as a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.
  • the lithium secondary battery of the present invention can be prepared according to conventional methods known in the art. For example, a porous separator may be inserted between the positive electrode and the negative electrode, and an electrolyte in which lithium salt is dissolved may be added.
  • the positive electrode can be prepared by conventional methods known in the art.
  • a slurry may be prepared by mixing and stirring a solvent, a binder, a conductive material, and a dispersant in a positive electrode active material, and then applying (coating) to a current collector of a metal material, compressing, and drying the positive electrode to prepare a positive electrode.
  • the positive electrode is prepared by applying a positive electrode slurry on a positive electrode current collector and then drying.
  • the current collector of the metal material is a metal having high conductivity, and any metal can be used as long as the slurry of the electrode active material is a metal that can be easily adhered.
  • Non-limiting examples of the positive electrode current collector include a foil made of aluminum, nickel, or a combination thereof.
  • the solvent for forming the positive electrode includes an organic solvent such as NMP (N-methyl pyrrolidone), DMF (dimethyl formamide), acetone, dimethyl acetamide or water, and these solvents alone or in combination of two or more. Can be mixed and used.
  • organic solvent such as NMP (N-methyl pyrrolidone), DMF (dimethyl formamide), acetone, dimethyl acetamide or water, and these solvents alone or in combination of two or more. Can be mixed and used.
  • the amount of the solvent used is sufficient to dissolve and disperse the electrode active material, the binder, and the conductive agent in consideration of the coating thickness of the slurry and the production yield.
  • porous polymer films conventionally used as separators for example, polyolefins such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer and ethylene / methacrylate copolymer, etc.
  • the porous polymer film made of the polymer may be used alone or by laminating them, or a conventional porous nonwoven fabric, for example, a non-woven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, or the like may be used. It is not.
  • the lithium salt that may be included as the electrolyte can be used without limitation, those which are commonly used in a lithium secondary battery electrolyte, such as is in the lithium salt anion F -, Cl -, Br - , I -, NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) 2 PF 4 -, (CF 3) 3 PF 3 -, (CF 3) 4PF 2 -, (CF 3) 5PF -, (CF 3) 6P - , F 3 SO 3 -, CF 3 CF 2 SO 3 -, (CF 3 SO 2) 2N -, (FSO 2) 2N -, CF 3 CF 2 (CF 3) 2CO -, (CF 3 SO 2) 2CH - , (SF 5) 3C -, (CF 3 SO 2) 3C -, CF 3 (CF 2) 7SO 3 -, CF 3 CO 2 -, CH 3 CO 2 -, SCN
  • Examples of the electrolyte include an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, and the like that can be used in manufacturing a lithium secondary battery, but are not limited thereto.
  • the external shape of the lithium secondary battery of the present invention is not particularly limited, but may be cylindrical, square, pouch type, or coin type using a can.
  • the lithium secondary battery of the present invention can be used as a power source for various electronic products.
  • the present invention may be used in a portable telephone, a mobile phone, a game console, a portable television, a laptop computer, a calculator, and the like, but is not limited thereto.
  • Si nanoparticles as silicon-based nanoparticles and carboxymethylcellulose (hereinafter, CMC) having a weight average molecular weight of about 100,000 as water-soluble polymers are added to deionized water to prepare a suspension, and ultrasonic waves are applied to the suspension using an ultrasonic irradiation device. Irradiation induced dispersion of the particles.
  • CMC carboxymethylcellulose
  • a negative electrode slurry was prepared by mixing the core as a negative electrode active material, carbon black as a conductive material, and SBR-based rubber as a binder in N-methyl-2-pyrrolidone (NMP) as a solvent.
  • NMP N-methyl-2-pyrrolidone
  • the negative electrode slurry was applied to a thin copper (Cu) thin film, which is a negative electrode current collector having a thickness of 10 ⁇ m, dried to prepare a negative electrode, and then subjected to roll press to process a negative electrode.
  • Cu thin copper
  • a coin-type half cell (2016 R-type half cell) was prepared in a helium-filled glove box using the negative electrode, the lithium counter electrode, the microporous polyethylene separator, and the electrolyte.
  • the electrolyte 1 M LiPF 6 was dissolved in a solvent in which ethylene carbonate and dimethyl carbonate were mixed at a volume ratio of 50:50.
  • a negative electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1-1, except that the temperature of performing secondary carbonization after spray drying was 800 ° C.
  • a negative electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that CMC having a weight average molecular weight of about 3,000,000 was used as the water-soluble polymer.
  • Heat treatment was performed in place of the spray drying process, the heat treatment temperature was 600 °C, and other processes to produce a negative electrode active material and a lithium secondary battery in the same manner as in Example 1.
  • Example 1 In order to determine the initial discharge capacity of the coin-type half-cells prepared in Example 1 and Comparative Example 1, the half-cells prepared at 25 ° C. were charged and discharged once at 0.1 C at 0 V to 1.5 V. , Initial discharge capacity, initial charge capacity, and coulombic efficiency were measured. In addition, the capacity retention rate (life characteristics) of the half cell prepared at 25 ° C. after charging and discharging at 50 ° C. at 50 ° C. at 50 ° C. at 0.5 ° C. was confirmed. Table 1 shows the measurement results of the initial discharge capacity, initial efficiency, and lifetime characteristics measured by the above method.
  • Example 1 using a low molecular weight CMC it can be seen that the life characteristics are significantly superior to Comparative Example 1 using a high molecular weight CMC. Furthermore, even though a low molecular weight was used, it was confirmed that there was no loss in performance in terms of initial discharge capacity or efficiency compared to a high molecular weight. Thus, as compared with using a high molecular weight which causes dispersibility problems or uniformity problems during carbonization. It can be seen that it is advantageous to use low molecular weight CMC.

Abstract

A negative electrode active material of the present invention comprises a core containing: a silicon-based nanoparticle; and a polymer carbide distributed on the nanoparticle, wherein the core has a size of 30-300 nm. The negative electrode active material is prepared by a preparation method comprising: dispersing a suspension, which is obtained by adding silicon-based nanoparticles and a water-soluble polymer to a solvent, using ultrasonic waves; and carbonizing the water-soluble polymer to prepare a core, which comprises a silicon-based nanoparticle having a polymer carbide formed on a surface of the silicon-based nanoparticle. Therefore, a negative electrode active material can be provided that has a significantly low volume expansion rate and excellent electric conductivity compared with general non-carbon-based negative electrode active materials.

Description

규소계 음극활물질 및 이의 제조방법Silicon negative electrode active material and preparation method thereof
관련출원과의 상호인용Citation with Related Applications
본 출원은 2014년 11월 27일자 한국 특허 출원 제10-2014-0167760호 및 2015년 11월 27일자 한국 특허 출원 제10-2015-0166965호에 기초한 우선권의 이익을 주장하며, 해당 한국 특허 출원의 문헌에 개시된 모든 내용은 본 명세서의 일부로서 포함된다.This application claims the benefit of priority based on Korean Patent Application No. 10-2014-0167760 filed on November 27, 2014 and Korean Patent Application No. 10-2015-0166965 filed on November 27, 2015. All content disclosed in the literature is included as part of this specification.
기술분야Technical Field
본 발명은 고분자 탄화물이 표면상에 분포된 규소계 나노입자를 포함하는 음극활물질과, 이를 제조하는 방법에 관한 것이다. The present invention relates to a negative electrode active material including silicon-based nanoparticles in which polymer carbide is distributed on a surface thereof, and a method of manufacturing the same.
모바일 기기에 대한 기술 개발과 수요가 증가함에 따라 에너지원으로서의 이차 전지의 수요가 급격히 증가하고 있고, 이러한 이차 전지 중 높은 에너지 밀도와 전압을 가지는 리튬 이차전지가 상용화되어 널리 사용되고 있다.As technology development and demand for mobile devices increase, the demand for secondary batteries as energy sources is rapidly increasing, and lithium secondary batteries having high energy density and voltage are commercially used in these secondary batteries.
리튬 이차전지의 양극 활물질로는 리튬 금속 산화물이 사용되고, 음극 활물질로는 리튬 금속, 리튬 합금, 결정질 또는 비정질 탄소 또는 탄소 복합체가 사용되고 있다. 상기 활물질을 적당한 두께와 길이로 집전체에 도포하거나 또는 활물질 자체를 필름 형상으로 도포하여 절연체인 분리막과 함께 감거나 적층하여 전극군을 만든 다음, 캔 또는 이와 유사한 용기에 넣은 후, 전해액을 주입하여 이차 전지를 제조한다.Lithium metal oxide is used as a positive electrode active material of a lithium secondary battery, and lithium metal, a lithium alloy, crystalline or amorphous carbon or a carbon composite material is used as a negative electrode active material. The active material is applied to a current collector with a suitable thickness and length, or the active material itself is applied in a film shape to form an electrode group by winding or laminating together with a separator, which is an insulator, and then put it in a can or a similar container, and then injecting an electrolyte solution. A secondary battery is manufactured.
리튬 이차 전지의 음극 재료로서는 흑연이 주로 이용되고 있지만, 흑연은 단위 질량당의 용량이 372 mAh/g로 작고, 리튬 이차 전지의 고용량화가 어렵다.Although graphite is mainly used as a negative electrode material of a lithium secondary battery, graphite has a small capacity per unit mass of 372 mAh / g, and it is difficult to increase the capacity of a lithium secondary battery.
흑연보다도 고용량을 나타내는 음극재로서는, 예를 들면 실리콘, 주석 및 이들의 산화물 등의 리튬과 금속간 화합물을 형성하는 재료가 유망하다. 그러나 이들 재료는 리튬을 흡수 저장할 때에 결정구조의 변화를 야기시켜 체적이 팽창하는 문제점이 있다.As an anode material which shows higher capacity than graphite, the material which forms intermetallic compound with lithium, such as silicon, tin, and these oxides, is promising, for example. However, these materials cause a change in the crystal structure when absorbing and storing lithium, causing a problem of expansion of the volume.
최근 고용량 소재로 연구되고 있는 실리콘계 물질은 탄소계 물질이 가지는 이론 용량 보다 약 10 배 이상 높은 약 3600 mAh/g의 고용량을 가지고 있어 고용량 이차 전지 소재로 각광을 받고 있다.Recently, silicon-based materials, which are being studied as high-capacity materials, have a high capacity of about 3600 mAh / g, which is about 10 times higher than the theoretical capacity of carbon-based materials, and thus are attracting attention as high-capacity secondary battery materials.
실리콘의 경우 리튬을 최대량 흡수 저장하면, Li4 . 4Si로 전환되어, 충전에 의한 부피 팽창이 이루어지며, 이 경우 충전에 의한 체적 증가율은 부피 팽창 전 실리콘의 부피에 비해 약 4.12배까지 팽창할 수 있어 입자간 크랙 발생 및 전극간 단락에 의한 수명특성 저하가 발생된다는 문제가 있다.For silicon, the maximum amount of lithium absorbed and stored, Li 4 . 4 Si is converted to volume expansion by charging, in which case the rate of volume increase by charging can be expanded up to about 4.12 times the volume of silicon before volume expansion, resulting in cracks between particles and short-lived electrodes. There is a problem that deterioration of characteristics occurs.
이를 개선하고자, 실리콘 입자로서 나노크기 수준의 입자를 사용하거나, 실리콘이 다공성을 가지게 하여 부피변화에 대한 완충효과를 갖게 하는 연구가 진행되었으나, 나노입자의 경우 서로간에 응집 현상이 강하게 발생하여 수명 특성 개선에 큰 이점이 없었고, 도전성이 낮아 전지 성능을 제대로 구현하지 못한다는 문제도 함께 안고 있었다.In order to improve this, studies have been made to use nano-sized particles as silicon particles or to make silicon have a porosity to have a buffering effect against volume change. There was no significant advantage in the improvement, and the problem was that the low conductivity did not properly implement the battery performance.
본 발명의 목적은 탄소계 음극활물질보다 이론용량이 10 배 가까이 높은 규소계 음극활물질을 제공하고자, 규소계 나노입자의 표면상에 고분자 탄화물을 분포시켜 전기전도성을 향상시키고 부피팽창을 제어할 수 있는 비탄소계 음극활물질을 제공하고자 함이다.An object of the present invention is to provide a silicon-based anode active material 10 times higher theoretical capacity than a carbon-based anode active material, to distribute the polymer carbide on the surface of the silicon-based nanoparticles to improve the electrical conductivity and control the volume expansion It is to provide a non-carbon negative electrode active material.
상기 과제를 해결하기 위하여, 본 발명의 일 실시예에 따른 음극활물질은, 규소계 나노입자; 및 상기 나노입자상에 분포된 수용성 고분자의 탄화물;을 포함하고, 고분자 탄화물이 표면에 분포된 규소계 나노입자의 크기는 30 내지 800 nm인 것이다.In order to solve the above problems, the negative electrode active material according to an embodiment of the present invention, silicon-based nanoparticles; And a carbide of the water-soluble polymer distributed on the nanoparticles, wherein the size of the silicon-based nanoparticles in which the polymer carbide is distributed on the surface is 30 to 800 nm.
상기 규소계 나노입자는 Si, SiO, SiM 및 이들의 조합으로 이루어진 군에서 선택된 어느 하나의 물질일 수 있고, 상기 M은 M은 Ni, Co, B, Cr, Cu, Fe, Mn, Ti, Y 및 이들의 조합으로 이루어진 군에서 선택된 어느 하나일 수 있다.The silicon-based nanoparticles may be any one material selected from the group consisting of Si, SiO, SiM, and combinations thereof, wherein M is Ni, Co, B, Cr, Cu, Fe, Mn, Ti, Y And combinations thereof may be any one selected from the group consisting of.
상기 수용성 고분자는 카르복시메틸셀룰로오스(carboxy methyl cellulose, CMC), 수크로오스(sucrose), 폴리아크릴로니트릴(polyacrylonitrile, PAN) 및 이들의 조합으로 이루어진 군에서 선택된 어느 하나를 포함할 수 있다.The water-soluble polymer may include any one selected from the group consisting of carboxy methyl cellulose (CMC), sucrose (sucrose), polyacrylonitrile (polyacrylonitrile, PAN), and combinations thereof.
상기 수용성 고분자는 중량평균분자량이 90,000 내지 2,000,000 일 수 있다.The water-soluble polymer may have a weight average molecular weight of 90,000 to 2,000,000.
상기 음극활물질은 규소계 나노입자의 총중량 대비, 3 내지 20 중량%의 고분자 탄화물을 포함할 수 있다.The negative electrode active material may include 3 to 20% by weight of polymer carbide, based on the total weight of the silicon-based nanoparticles.
용매에 규소계 나노입자 및 수용성 고분자를 첨가한 현탁액을 초음파를 이용하여 분산시키고; 상기 수용성 고분자를 탄화시켜 규소계 나노입자의 표면에 고분자 탄화물을 형성시키는 것을 포함한다.Dispersing the suspension in which the silicon-based nanoparticles and the water-soluble polymer are added to the solvent using ultrasonic waves; And carbonizing the water-soluble polymer to form polymer carbide on the surface of the silicon-based nanoparticles.
상기 탄화는 저온 탄화 공정 및 고온 탄화 공정을 포함하는 두 단계 공정으로 수행될 수 있다.The carbonization may be performed in a two step process including a low temperature carbonization process and a high temperature carbonization process.
상기 저온 탄화 공정은 분무건조 장치를 이용하여 수행될 수 있으며, 상기 현탁액을 분무건조 장치 내 챔버에 주입하고, 현탁액을 챔버 내에서 분무하여 건조하는 것을 포함할 수 있다.The low temperature carbonization process may be performed using a spray drying apparatus, and may include injecting the suspension into a chamber in the spray drying apparatus and spraying the suspension in the chamber to dry it.
상기 저온 탄화 공정은 80 내지 300℃의 온도에서 수행될 수 있다.The low temperature carbonization process may be performed at a temperature of 80 to 300 ℃.
상기 고온 탄화 공정은 800 내지 1100℃의 온도에서 열처리가 수행되는 것일 수 있다.The high temperature carbonization process may be heat treatment at a temperature of 800 to 1100 ℃.
본 발명의 음극활물질의 제조방법은 초음파를 이용하여 나노 크기의 규소계 입자들을 용이하게 분산시킬 수 있고, 분무건조 등의 방법과 같은 단순한 방법을 통해 규소계 나노입자의 표면상에 고분자 탄화물을 분포시킴으로써, 나노입자간의 응집을 방지하고, 도전성을 확보할 수 있으며, 수용성 고분자로 쉘 층을 형성함으로써 추가의 도전성을 제공할 수 있다. 이에 일반적인 비탄소계 음극활물질에 비하여 부피팽창율이 현저히 낮고, 우수한 전기전도성을 갖는 음극활물질을 제공할 수 있다.The method for preparing a negative electrode active material of the present invention can easily disperse nano-sized silicon-based particles using ultrasonic waves, and distribute the polymer carbide on the surface of the silicon-based nanoparticles through a simple method such as spray drying. In this way, aggregation between nanoparticles can be prevented, conductivity can be ensured, and additional conductivity can be provided by forming a shell layer with a water-soluble polymer. Thus, compared with the general non-carbon negative electrode active material, the volume expansion coefficient is significantly lower, and an anode active material having excellent electrical conductivity can be provided.
이하, 본 발명에 대한 이해를 돕기 위해 본 발명을 더욱 상세하게 설명한다. 본 명세서 및 청구범위에 사용된 용어나 단어는 통상적이거나 사전적인 의미로 한정해서 해석되어서는 아니 되며, 발명자는 그 자신의 발명을 가장 최선의 방법으로 설명하기 위해 용어의 개념을 적절하게 정의할 수 있다는 원칙에 입각하여 본 발명의 기술적 사상에 부합하는 의미와 개념으로 해석되어야만 한다. Hereinafter, the present invention will be described in more detail to aid in understanding the present invention. The terms or words used in this specification and claims are not to be construed as limiting in their usual or dictionary meanings, and the inventors may appropriately define the concept of terms in order to best explain their invention in the best way possible. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that the present invention.
본 발명의 일 실시예에 따른 음극활물질의 제조방법은, 용매에 규소계 나노입자 및 수용성 고분자를 첨가한 현탁액을 초음파를 이용하여 분산시키고; 상기 수용성 고분자를 탄화시켜 규소계 나노입자의 표면에 고분자 탄화물을 형성시키는 것을 포함한다.Method for producing a negative electrode active material according to an embodiment of the present invention, the dispersion of the silicon-based nanoparticles and the water-soluble polymer added to the solvent using ultrasonic waves; And carbonizing the water-soluble polymer to form polymer carbide on the surface of the silicon-based nanoparticles.
상기 현탁액의 제조 및 분산은 용매에 규소계 나노입자와 수용성 고분자를 첨가하여 현탁액을 제조하고, 이 현탁액에 초음파를 조사하여 현탁액 내의 입자를 진동시킴으로써 응집 특성이 있는 나노입자를 분산시키는 과정을 포함할 수 있다.Preparation and dispersion of the suspension may include adding silicon-based nanoparticles and a water-soluble polymer to a solvent to prepare a suspension, and dispersing the nanoparticles having cohesive properties by irradiating ultrasonic waves to the suspension to vibrate the particles in the suspension. Can be.
상기 용매는 이후 수행되는 탄화 공정에서 휘발되기가 용이하고, 수용성 고분자와 반응하지 않는 용매이면 특별한 제한 없이 적용이 가능하고, 예컨대, 탈이온수나 증류수 등의 물, 에테르나 아세톤과 같은 탄소수가 적은 유기 용매 등을 사용할 수 있다.The solvent may be easily volatilized in a subsequent carbonization process, and may be applied without particular limitation as long as it is a solvent that does not react with the water-soluble polymer. Solvents and the like can be used.
상기 규소계 나노입자는 규소화합물의 나노입자일 수 있고, 그 표면에 산화피막이 형성되어 있는 나노입자일 수 있다. 예를 들면, 규소 단일원소로 이루어진 입자, 규소산화물, 규소질화물, 규소와 금속의 화합물 등일 수 있으며, 구체적으로 예를 들면, Si, SiO, SiM 또는 이들의 혼합물 등이 적용될 수 있으며, 상기 SiM에서 M은 Ni, Co, B, Cr, Cu, Fe, Mn, Ti, Y 또는 이들의 조합일 수 있고, Si와 상기 M의 분말이 기계적인 합금법으로 합금화 한 것일 수 있으나, 음극활물질로서 리튬 이온이 흡장 및 방출되기 용이하도록 Si 단일 원소로 이루어진 입자인 경우가 바람직할 수 있다.The silicon-based nanoparticles may be nanoparticles of a silicon compound and nanoparticles having an oxide film formed on a surface thereof. For example, it may be a particle composed of silicon single element, silicon oxide, silicon nitride, a compound of silicon and metal, and the like, specifically, for example, Si, SiO, SiM or a mixture thereof may be applied, and in the SiM M may be Ni, Co, B, Cr, Cu, Fe, Mn, Ti, Y, or a combination thereof, and Si and the powder of M may be alloyed by a mechanical alloying method, but lithium ions as a negative electrode active material It may be preferable if the particles are composed of Si single elements so as to be easily occluded and released.
상기 수용성 고분자는 사용되는 수계 용매에 잘 분산될 수 있는 것이라면 제한 없이 적용이 가능하며, 예를 들면, 셀룰로오스계 고분자일 수 있으며, 니트릴기를 포함하는 고분자일 수 있다. 셀룰로오스계 고분자로는, 예컨대, 카르복시메틸셀룰로오스(carboxy methyl cellulose; CMC), 수크로오스(sucrose) 또는 이들의 혼합물 등이 적용될 수 있고, 니트릴기를 포함하는 고분자로는, 예컨대, 폴리아크릴로니트릴(polyacrylonitrile, PAN) 등이 적용될 수 있으며, 카르복실기 또는 니트릴기 등의 산화되기 쉬운 관능기들은 탄화시키기도 용이할 수 있어 이러한 관능기를 포함하는 수용성 고분자를 적용하는 것이 바람직할 수 있다.The water-soluble polymer can be applied without limitation as long as it can be well dispersed in the aqueous solvent used, for example, may be a cellulose-based polymer, a polymer containing a nitrile group. As the cellulose-based polymer, for example, carboxy methyl cellulose (CMC), sucrose (sucrose) or a mixture thereof may be applied. As the polymer containing a nitrile group, for example, polyacrylonitrile (polyacrylonitrile, PAN) and the like may be applied, and functional groups which are easily oxidized such as carboxyl groups or nitrile groups may be easily carbonized, and thus, it may be desirable to apply a water-soluble polymer including such functional groups.
상기 수용성 고분자는, 중량평균분자량이 90,000 내지 2,000,000 일 수 있고, 예를 들면, 1,400,000 이상일 수 있으며, 1,800,000 이하일 수 있으며, 가장 바람직하게는 90,000 내지 700,000일 수 있다. 상기 수용성 고분자의 분자량이 90,000 보다도 작을 경우 용해도 측면에서는 유리할 수 있으나, 탄화량이 적어 도전성 확보 측면에서 불리하며, 과량을 투입하여야 하므로 경제성 및 공정성 측면에서 불리할 수 있고, 분자량이 2,000,000 보다도 클 경우에는 규소계 나노입자의 분산성이 저하되며, 표면에 위치되는 탄화물의 균일성이 떨어질 수 있다.The water-soluble polymer may have a weight average molecular weight of 90,000 to 2,000,000, for example, 1,400,000 or more, 1,800,000 or less, and most preferably 90,000 to 700,000. If the molecular weight of the water-soluble polymer is less than 90,000 may be advantageous in terms of solubility, but the amount of carbonization is disadvantageous in terms of securing the conductivity, it may be disadvantageous in terms of economics and fairness because the excessive amount should be injected, if the molecular weight is greater than 2,000,000 Dispersibility of the sub-type nanoparticles is reduced, and uniformity of carbides located on the surface may be reduced.
상기 용매에 첨가되는 상기 규소계 나노입자 및 수용성 고분자의 함량은 상대적인 비율을 고려하여 첨가하는 것이 바람직할 수 있고, 규소계 나노입자와 수용성 고분자는 규소계 나노입자의 표면상에 형성되는 고분자 탄화물의 양이 과도하여 코팅층과 같이 외부를 완전히 덮는 피막 구조를 형성할 수 있어 규소 결정구조 내부로 리튬 이온이 흡장 및 방출되는 것을 방해할 수 있다는 점과, 규소계 나노입자의 표면상의 고분자 탄화물의 양이 너무 적음으로 인해 발생할 수 있는 낮은 전기전도성 문제, 부피팽창의 억제 문제, 또는 응집을 방지하려는 효과 등의 양 측면을 적절하게 고려하여 조절할 필요가 있다.The content of the silicon-based nanoparticles and the water-soluble polymer added to the solvent may be preferably added in consideration of a relative ratio, and the silicon-based nanoparticles and the water-soluble polymer may be formed of the polymer carbide formed on the surface of the silicon-based nanoparticles. Excessive amounts can form a coating structure that completely covers the outside, such as a coating layer, which can interfere with the occlusion and release of lithium ions into the silicon crystal structure, and the amount of polymer carbide on the surface of the silicon-based nanoparticles It is necessary to properly consider and adjust both aspects such as low electrical conductivity problems that may occur due to too little, problems of inhibiting volume expansion, or the effect of preventing aggregation.
상기 규소계 나노입자와 수용성 고분자는 현탁액 내에서 균일하게 분산된 상태로 존재할 필요가 있다. 균일하게 분산되지 않을 경우, 수용성 고분자의 탄화시 모든 규소계 나노입자의 표면상에 분포되지 않을 수 있고 일부 입자에만 분포될 수 있어, 규소계 음극활물질이 갖고 있는 전기전도성의 문제나 부피팽창의 문제가 해결되지 않을 수 있다.The silicon-based nanoparticles and the water-soluble polymer need to be present in a uniformly dispersed state in the suspension. When not uniformly dispersed, carbonization of the water-soluble polymer may not be distributed on the surface of all silicon-based nanoparticles and may be distributed only on some particles, thereby causing problems of electrical conductivity or volume expansion of the silicon-based anode active material. May not be resolved.
따라서, 현탁액을 균일하게 분산시킬 필요가 있으며, 이 균일한 분산을 위한 방법으로서 초음파가 이용될 수 있고, 초음파를 조사함으로써, 초음파에 의한 에너지로 인해 현탁액 내 입자가 진동하면서 입자간 간격이 멀어질 수 있고, 이에 따라 균일한 분산이 이루어질 수 있다Therefore, it is necessary to uniformly disperse the suspension, and ultrasonic waves can be used as a method for this uniform dispersion, and by irradiating the ultrasonic waves, the energy in the ultrasonic waves causes the particles in the suspension to vibrate, causing the distance between particles to be far apart. So that uniform dispersion can be achieved.
상기 초음파는 그 주파수를 적절하게 조절할 수 있으며, 규소계 나노입자와 수용성 고분자의 분산성 측면과, 높은 에너지로 인한 규소계 나노입자나 수용성 고분자의 변형 또는 반응 등에 대한 우려의 측면을 고려하여 그 주파수를 조절할 수 있다.The ultrasonic waves can be adjusted appropriately, and the frequency is considered in consideration of the dispersibility of silicon-based nanoparticles and water-soluble polymers, and the aspects of concern about deformation or reaction of silicon-based nanoparticles or water-soluble polymers due to high energy. Can be adjusted.
상기 현탁액을 분산시키고, 수용성 고분자를 규소계 나노입자상에 탄화시키는 방법으로서 두 단계의 탄화 공정이 이루어는 것일 수 있고, 상기 두 단계의 탄화 공정은 저온 탄화 공정과 고온 탄화 공정을 포함할 수 있다.As a method of dispersing the suspension and carbonizing the water-soluble polymer on the silicon-based nanoparticles, a two-step carbonization process may be performed, and the two-step carbonization process may include a low temperature carbonization process and a high temperature carbonization process.
상기 저온 탄화 공정은 분무건조 장치를 이용한 방법이 이용될 수 있으며, 상기 분무건조 장치를 이용한 수용성 고분자의 탄화는 상기 현탁액을 분무건조 장치 내 챔버에 주입하고, 현탁액을 챔버 내에서 분무하면서 건조시키는 것을 포함하는 것일 수 있다. The low temperature carbonization process may be a method using a spray drying apparatus, carbonization of the water-soluble polymer using the spray drying apparatus is to inject the suspension into the chamber in the spray drying apparatus, and drying the suspension while spraying in the chamber It may be to include.
이러한 분무건조 공정에 적용될 수 있는 상기 분무건조 장치로는, 예컨대, 초음파 분무건조 장치, 공기노즐 분무건조 장치, 초음파노즐 분무건조 장치, 필터 팽창 액적 발생장치, 정전분무건조 장치 또는 이들의 조합 등이 있을 수 있다.The spray drying apparatus that can be applied to the spray drying process, for example, ultrasonic spray drying apparatus, air nozzle spray drying apparatus, ultrasonic nozzle spray drying apparatus, filter expansion droplet generator, electrostatic spray drying apparatus or a combination thereof There may be.
구체적으로, 규소계 나노입자와 수용성 고분자가 균일하게 분산된 현탁액을 분무건조 장치 내에 구비된 챔버 내에 주입하고, 챔버에서 상기 현탁액을 분무하면서, 건조시킴으로써 표면상에 수용성 고분자가 탄화된 규소계 나노입자를 함유하는 코어를 형성할 수 있다.Specifically, the silicon-based nanoparticles in which the water-soluble polymer is carbonized on the surface by injecting a suspension in which the silicon-based nanoparticles and the water-soluble polymer are uniformly dispersed into a chamber provided in the spray drying apparatus, and spraying the suspension in the chamber, followed by drying. A core containing can be formed.
상기 분무건조 방법을 통해 수행되는 저온 탄화는 80 내지 300℃의 온도에서 수행될 수 있다. 상기 분무건조시의 온도가 80℃ 미만일 경우, 입자 내에 수분이 잔류하고 있을 수 있으며, 300℃를 초과할 경우, 나노입자간 응집으로 인해 입자 성장이 일어날 수 있다. 따라서, 적절한 온도의 조절이 필요하며, 100 내지 200℃ 정도로 온도를 조절하는 것이 바람직할 수 있다.Low temperature carbonization carried out through the spray drying method may be performed at a temperature of 80 to 300 ℃. When the temperature of the spray drying is less than 80 ° C, moisture may remain in the particles, and when the temperature exceeds 300 ° C, particle growth may occur due to aggregation between nanoparticles. Therefore, it is necessary to control the appropriate temperature, it may be desirable to adjust the temperature to about 100 to 200 ℃.
상기 고온 탄화 공정은 상기 분무 건조 방법을 통해 생성된 Si 소재를 퍼니스에 넣어 불활성 분위기 하에서 열처리를 하는 것으로 수행될 수 있다. 이 때에 수행되는 열처리 온도는 800 내지 1100℃일 수 있으며, 열처리 온도가 800℃ 미만일 경우 흑연화도가 낮아 전기전도성이 저하될 우려가 있으며, 1100℃를 초과할 경우에는 나노 Si의 결정이 성장하여 결정립 조대화로 인한 수명 특성 저하 및/또는 전극의 스웰링 현상 발생 등의 문제가 발생될 수 있다.The high temperature carbonization process may be performed by putting a Si material produced by the spray drying method into a furnace and performing heat treatment under an inert atmosphere. At this time, the heat treatment temperature may be 800 to 1100 ℃, when the heat treatment temperature is less than 800 ℃ low graphitization degree may lower the electrical conductivity, when it exceeds 1100 ℃ nano Si crystals grow and crystal grains Problems such as deterioration of life characteristics and / or occurrence of swelling of the electrode due to coarsening may occur.
이러한 규소계 활물질은 음극활물질 중 이론 용량이 탄소계 활물질에 비하여 10 배 가까이 크다는 장점을 갖지만, 반대로 리튬 이온이 초기에 한번 흡장되고 방출된 후에는 탄소계 활물질에 비해 4 배 가까이 큰 부피팽창율을 나타낸다. 이에, 규소계 활물질을 사용하고자 한다면 스케일을 크게 축소하여 나노입자로써 사용하여야 한다.The silicon-based active material has the advantage that the theoretical capacity of the negative electrode active material is about 10 times larger than that of the carbon-based active material, but on the contrary, after lithium ions are initially occluded and released, the silicon-based active material shows a volume expansion rate of nearly 4 times that of the carbon-based active material. . Thus, if you want to use a silicon-based active material should be used as nanoparticles to greatly reduce the scale.
한편, 나노입자는 본질적으로 큰 표면에너지를 갖고 있기 때문에 응집하려는 특성이 있어, 이러한 응집특성으로 인해 활물질 입자로 제조하기가 까다로워, 결국 규소계 활물질을 상용화 시키는 데에 어려움을 겪고 있다.On the other hand, since the nanoparticles have a large surface energy inherently agglomerating properties, it is difficult to manufacture the active material particles due to this agglomeration property, and thus has difficulty in commercializing a silicon-based active material.
그러나, 본 발명의 일 실시예에 따른 음극활물질의 제조방법은 초음파를 통해 규소계 나노입자를 분산시키고 규소계 나노입자의 표면상에 수용성 고분자를 탄화시킴으로써 제조된 고분자 탄화물이 표면상에 형성된 규소계 나노입자를 함유하는 코어는, 나노입자 간의 응집을 방지할 수 있고, 동시에 규소계 활물질의 낮은 전기전도성 문제도 해결할 수 있다.However, the method for preparing a negative electrode active material according to an embodiment of the present invention is a silicon-based polymer carbide formed on the surface by dispersing the silicon-based nanoparticles by ultrasonic and carbonizing the water-soluble polymer on the surface of the silicon-based nanoparticles The core containing the nanoparticles can prevent aggregation between the nanoparticles and at the same time solve the problem of low electrical conductivity of the silicon-based active material.
전술한 효과적인 측면을 전반적으로 고려하여 음극활물질을 제조할 경우에는, 규소계 나노입자의 총중량 대비, 고분자 탄화물의 함량이 약 3 내지 20 중량%가 될 수 있다. 즉, 여러 가지 공정 조건 및 함량 비율 등을 적절하게 조절하여 규소계 나노입자의 총중량 대비 고분자 탄화물이 차지하는 비율을 제어하는 것이 중요할 수 있다.When preparing the negative electrode active material in consideration of the above-described effective aspects as a whole, the content of the polymer carbide relative to the total weight of the silicon-based nanoparticles may be about 3 to 20% by weight. That is, it may be important to control the ratio of the polymer carbide to the total weight of the silicon-based nanoparticles by appropriately adjusting various process conditions and content ratios.
상기 탄화된 수용성 고분자인 고분자 탄화물이 표면에 분포된 규소계 나노입자는 그 자체로도 음극활물질에 적용될 수 있지만, 도전성 등을 확보하기 위해, 상기 탄화 이후에, 제조된 음극활물질의 외부를 감싸도록 수용성 고분자를 함유하는 탄소코팅층을 더 형성할 수 있다. Silicon-based nanoparticles in which the polymer carbide which is the carbonized water-soluble polymer are distributed on the surface may be applied to the anode active material as such, but after the carbonization, to surround the outside of the manufactured anode active material to secure conductivity, etc. A carbon coating layer containing a water soluble polymer may be further formed.
상기 탄소코팅층은 도전성 재료를 포함할 수 있고, 규소계 나노입자 표면상에 분포된 고분자 탄화물과 더불어 규소계 활물질의 단점인 낮은 전기전도성을 보완할 수 있으며, 이러한 활물질을 구비하는 리튬 이차전지의 수명특성도 함께 개선할 수 있다. The carbon coating layer may include a conductive material, and complement the low electrical conductivity, which is a disadvantage of the silicon-based active material, with the polymer carbide distributed on the surface of the silicon-based nanoparticles, and the life of the lithium secondary battery including the active material. Properties can also be improved.
상기 탄소코팅층은 입자를 코팅하는 일반적인 방법이 적용될 수 있으며, 화학적인 방법 또는 기계적인 방법에 의하여 형성될 수 있다.The carbon coating layer may be a general method of coating the particles, it may be formed by a chemical method or a mechanical method.
상기 탄소코팅층은 상기 코어의 분말 및 수용성 고분자의 분말을 혼합한 후, 기계적인 방법을 통해 코팅하여 형성될 수 있고, 상기 기계적인 방법으로는 예컨대, 밀링 등이 적용될 수 있으며, 밀링 공정을 이용할 경우에는 공업적 규모의 생산에 있어서 비용 측면, 공정 운용 측면 등에서 이점이 있을 수 있다. The carbon coating layer may be formed by mixing the powder of the core and the powder of the water-soluble polymer, and then coating by a mechanical method, the mechanical method may be applied, for example, milling, etc., when using a milling process There may be advantages in terms of cost, process operation, etc. in industrial scale production.
상기 탄소코팅층은 화학기상증착법과 같은 물리화학적인 방법을 이용하여 형성되는 것일 수 있고, 상기 코어상에 수용성 고분자의 전구체를 이용하여 증착함으로써 코팅층을 형성할 수 있다.The carbon coating layer may be formed using a physicochemical method such as chemical vapor deposition, and may form a coating layer by depositing a precursor of a water-soluble polymer on the core.
또한, 탄소코팅층을 형성하는 물질의 전구체를 테트라하이드로퓨란(THF), 알코올 등의 용매에 분산시키고, 이를 상기 규소계 음극활물질과 혼합한 후, 건조 및 열처리 함으로써 달성될 수 있다. 상기 열처리 온도는 예를 들어 300 ℃ 내지 1400 ℃일 수 있고, 이 온도 범위에서 열처리하여 코팅할 수 있다.In addition, the precursor of the material forming the carbon coating layer may be achieved by dispersing in a solvent such as tetrahydrofuran (THF), alcohol, and the like, and mixing it with the silicon-based negative electrode active material, followed by drying and heat treatment. The heat treatment temperature may be, for example, 300 ℃ to 1400 ℃, it may be coated by heat treatment in this temperature range.
상기 탄소코팅층을 형성하는 물질의 전구체로는, 예컨대, 핏치(pitch) 또는 탄화수소계 물질 등을 사용할 수 있다. 상기 탄화수소계 물질로는 푸르푸릴 알코올(furfuryl alcohol)이나 페놀계 수지 등을 예로 들 수 있다.As a precursor of the material forming the carbon coating layer, for example, a pitch or a hydrocarbon-based material may be used. Examples of the hydrocarbon-based material include furfuryl alcohol, phenol resins, and the like.
따라서, 상기 규소계 나노입자 및 고분자 탄화물을 함유하는 음극활물질 상에 탄소코팅층을 형성함에 있어서는, 필요에 따라 각각의 장단점에 맞추어 기계적인 방법 또는 물리화학적인 방법 또는 열처리 방법을 적절하게 선택할 수 있다.Therefore, in forming the carbon coating layer on the negative electrode active material containing the silicon-based nanoparticles and polymer carbide, a mechanical method, a physicochemical method or a heat treatment method can be appropriately selected according to the advantages and disadvantages of each.
다만, 이러한 탄소코팅층에 의해 향상될 수 있는 전기전도성은 규소계 나노입자의 표면상에 분포된 고분자 탄화물로도 충분히 달성할 수 있는 경우가 있고, 그러한 경우에는 탄소코팅층은 불필요할 수 있다. 따라서, 탄소코팅층은 제조된 규소계 음극활물질의 물성에 따라 적절하게 형성하거나, 또는 형성하지 않는 경우가 공존할 수 있다.However, the electrical conductivity that can be improved by the carbon coating layer may be sufficiently achieved even with a polymer carbide distributed on the surface of the silicon-based nanoparticles, in which case the carbon coating layer may be unnecessary. Therefore, the carbon coating layer may coexist or may not be properly formed depending on the physical properties of the manufactured silicon-based negative electrode active material.
본 발명의 다른 일 실시예에 따른 음극활물질은, 규소계 나노입자 및 상기 나노입자상에 분포된 수용성 고분자 탄화물;을 포함한다.A negative electrode active material according to another embodiment of the present invention, silicon-based nanoparticles and water-soluble polymer carbide distributed on the nanoparticles; includes.
상기 코어는 그 크기가 30 내지 800 nm일 수 있고, 50 내지 300 nm, 또는 50 내지 100 nm 인 것이 바람직할 수 있다. 상기 코어의 크기가 30 nm 미만일 경우 높은 표면 에너지로 인해 탄화나 쉘 층의 형성으로도 나노입자간의 응집을 제어하기가 어려울 수 있으며, 800 nm 보다 클 경우 최종적으로 제작된 전지의 부피 팽창을 야기할 수 있다.The core may have a size of 30 to 800 nm, preferably 50 to 300 nm, or 50 to 100 nm. When the size of the core is less than 30 nm, it may be difficult to control the aggregation between nanoparticles even by carbonization or the formation of a shell layer due to the high surface energy. If the core size is larger than 800 nm, it may cause volume expansion of the finally manufactured cell. Can be.
상기 규소계 나노입자의 종류, 외부 산화 피막의 형성 등 규소계 나노입자에 관한 일체의 설명, 수용성 고분자에 관한 일체의 설명, 코어에 관한 일체의 설명 및 수용성 고분자의 종류, 쉘의 존부, 두께 및 중량비 등 쉘에 관한 일체의 설명은 상기 음극활물질의 제조방법에 기재된 바와 중복되므로 그 기재를 생략한다.Types of the silicon-based nanoparticles, the whole description of the silicon-based nanoparticles, such as the formation of an external oxide film, the whole description of the water-soluble polymer, the whole description of the core and the type of the water-soluble polymer, the presence of the shell, the thickness and The entire description of the shell, such as the weight ratio, is the same as that described in the method for producing the negative electrode active material, and thus the description thereof is omitted.
본 발명의 또 다른 일 실시예에 따른 리튬 이차전지용 음극은, 전술한 음극활물질, 바인더 및 용매를 포함하고, 도전재와 증점제를 선택적으로 포함하는 음극 슬러리와, 이 음극 슬러리가 도포된 음극 집전체를 포함할 수 있다. A negative electrode for a lithium secondary battery according to another embodiment of the present invention includes a negative electrode slurry including the negative electrode active material, a binder, and a solvent, and optionally including a conductive material and a thickener, and a negative electrode current collector to which the negative electrode slurry is applied. It may include.
또한, 본 발명은 상기 음극을 이용하여, 양극활물질, 바인더 및 용매를 포함하고, 선택적으로 도전재와 증점제를 포함하는 양극 슬러리와, 이 양극 슬러리가 도포된 양극 집전체를 포함하는 양극과, 상기 양극과 음극 사이에 개재되는 분리막과, 리튬염, 첨가제 및 비수용매를 포함하는 전해질을 구비하는 리튬 이차전지를 제공한다.The present invention also provides a positive electrode comprising a positive electrode slurry comprising a positive electrode active material, a binder and a solvent, optionally including a conductive material and a thickener, a positive electrode current collector coated with the positive electrode slurry, and Provided is a lithium secondary battery having a separator interposed between a positive electrode and a negative electrode, and an electrolyte including a lithium salt, an additive, and a nonaqueous solvent.
상기 바인더는, 일반적으로 당업계에서 이용될 수 있는 바인더라면 제한 없이 적용이 가능하며, 예를 들면, 폴리비닐리덴플루오라이드 (PVdF), 폴리헥사플루오로프로필렌-폴리비닐리덴플루오라이드의 공중합체 (PVdF/HFP), 폴리(비닐아세테이트), 폴리비닐알코올, 폴리에틸렌옥사이드, 폴리비닐피롤리돈, 알킬화 폴리에틸렌옥사이드, 폴리비닐에테르, 폴리(메틸메타크릴레이트), 폴리(에틸아크릴레이트), 폴리테트라플루오로에틸렌 (PTFE), 폴리비닐클로라이드, 폴리아크릴로니트릴, 폴리비닐피리딘, 스티렌-부타디엔 고무, 아크릴로니트릴-부타디엔 고무, 에틸렌프로필렌디엔모노머 (EPDM) 또는 이들의 혼합물 등이 적용될 수 있다.The binder is generally applicable to any binder that can be used in the art without limitation, for example, polyvinylidene fluoride (PVdF), a copolymer of polyhexafluoropropylene-polyvinylidene fluoride ( PVdF / HFP), poly (vinylacetate), polyvinyl alcohol, polyethylene oxide, polyvinylpyrrolidone, alkylated polyethylene oxide, polyvinyl ether, poly (methyl methacrylate), poly (ethyl acrylate), polytetrafluoro Low ethylene (PTFE), polyvinylchloride, polyacrylonitrile, polyvinylpyridine, styrene-butadiene rubber, acrylonitrile-butadiene rubber, ethylene propylene diene monomer (EPDM) or mixtures thereof and the like can be applied.
상기 도전재는 도전성 향상을 위해 포함할 수 있고, 상기 도전재는 천연 흑연, 인조 흑연, 카본블랙, 아세틸렌 블랙, 케첸 블랙, 채널 블랙, 퍼네이스 블랙, 램프 블랙, 서머 블랙, 탄소 나노튜브, 플러렌, 탄소 섬유, 금속 섬유, 불화 카본, 알루미늄, 니켈 분말, 산화 아연, 티탄산 칼륨, 산화 티탄 및 폴리페닐렌 유도체로 이루어진 군에서 선택된 어느 하나 또는 이들 중 2종 이상의 혼합물일 수 있으며, 바람직하게는 카본블랙일 수 있다.The conductive material may be included to improve conductivity, and the conductive material may include natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, summer black, carbon nanotube, fullerene, and carbon. Fiber, metal fiber, carbon fluoride, aluminum, nickel powder, zinc oxide, potassium titanate, titanium oxide and polyphenylene derivatives, any one selected from the group consisting of, or a mixture of two or more thereof, preferably carbon blackyl Can be.
상기 음극은 점도조절을 위해 증점제를 포함할 수 있다. 상기 증점제는 셀룰로오스계 물질일 수 있으며, 예를 들어 카르복시메틸셀룰로오스(CMC), 하이드록시메틸셀룰로오스, 하이드록시 에틸 셀룰로오스 및 하이드록시 프로필 셀룰로오스로 이루어진 군에서 선택된 어느 하나 또는 이들 중 2 종 이상의 혼합물일 수 있다. 상기 증점제는 바람직하게는 카르복시메틸셀룰로오스(CMC)일 수 있으며, 상기 음극활물질 및 바인더를 카르복시메틸셀룰로오스와 함께 물에 분산시켜 음극에 적용할 수 있다.The negative electrode may include a thickener for viscosity control. The thickener may be a cellulose-based material, for example, any one selected from the group consisting of carboxymethyl cellulose (CMC), hydroxymethyl cellulose, hydroxy ethyl cellulose, and hydroxy propyl cellulose, or a mixture of two or more thereof. have. The thickener may be preferably carboxymethyl cellulose (CMC), and the negative electrode active material and the binder may be dispersed in water together with the carboxymethyl cellulose and applied to the negative electrode.
상기 음극 슬러리를 형성하기 위한 용매로는 NMP(N-메틸 피롤리돈), DMF(디메틸 포름아미드), 아세톤, 디메틸 아세트아미드 등의 유기 용매 또는 물 등이 있으며, 이들 용매는 단독으로 또는 2종 이상을 혼합하여 사용할 수 있다.Solvents for forming the negative electrode slurry include an organic solvent such as NMP (N-methyl pyrrolidone), DMF (dimethyl formamide), acetone, dimethyl acetamide or water, and these solvents alone or two The above can be mixed and used.
상기 음극은 집전체를 포함할 수 있고, 음극 집전체의 비제한적인 예로는 구리, 금, 니켈 또는 구리 합금 또는 이들의 조합에 의하여 제조되는 호일 등이 있다.The negative electrode may include a current collector, and non-limiting examples of the negative electrode current collector include a foil made of copper, gold, nickel, or a copper alloy, or a combination thereof.
본 발명의 일실시예에 따른 리튬 이차 전지는 리튬금속 이차 전지, 리튬이온 이차 전지, 리튬폴리머 이차 전지 또는 리튬이온폴리머 이차 전지 등, 통상적인 리튬 이차 전지들을 모두 포함할 수 있다.The lithium secondary battery according to the exemplary embodiment of the present invention may include all conventional lithium secondary batteries, such as a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.
본 발명의 리튬 이차전지는 당 기술 분야에 알려진 통상적인 방법에 따라 제조할 수 있다. 예를 들면, 양극과 음극 사이에 다공성의 분리막을 넣고 리튬염이 용해되어 있는 전해질을 투입하여 제조할 수 있다.The lithium secondary battery of the present invention can be prepared according to conventional methods known in the art. For example, a porous separator may be inserted between the positive electrode and the negative electrode, and an electrolyte in which lithium salt is dissolved may be added.
상기 양극은 당 분야에 알려져 있는 통상적인 방법으로 제조할 수 있다. 예를 들면, 양극활물질에 용매, 필요에 따라 바인더, 도전재, 분산제를 혼합 및 교반하여 슬러리를 제조한 후 이를 금속 재료의 집전체에 도포(코팅)하고 압축한 뒤 건조하여 양극을 제조할 수 있다.The positive electrode can be prepared by conventional methods known in the art. For example, a slurry may be prepared by mixing and stirring a solvent, a binder, a conductive material, and a dispersant in a positive electrode active material, and then applying (coating) to a current collector of a metal material, compressing, and drying the positive electrode to prepare a positive electrode. have.
상기 양극은 양극 슬러리를 양극 집전체 상에 도포한 후, 건조하는 단계에 의해 제조된다. 이때, 상기 양극활물질은 리튬함유 전이금속 산화물이 바람직하게 사용될 수 있으며, 예를 들면 LixCoO2(0.5<x<1.3), LixNiO2(0.5<x<1.3), LixMnO2(0.5<x<1.3), LixMn2O4(0.5<x<1.3), Lix(NiaCobMnc)O2(0.5<x<1.3, 0<a<1, 0<b<1, 0<c<1, a+b+c=1), LixNi1 - yCoyO2(0.5<x<1.3, 0<y<1), LixCo1 - yMnyO2(0.5<x<1.3, 0≤y<1), LixNi1 - yMnyO2(0.5<x<1.3, O≤y<1), Lix(NiaCobMnc)O4(0.5<x<1.3, 0<a<2, 0<b<2, 0<c<2, a+b+c=2), LixMn2 - zNizO4(0.5<x<1.3, 0<z<2), LixMn2 - zCozO4(0.5<x<1.3, 0<z<2), LixCoPO4(0.5<x<1.3) 및 LixFePO4(0.5<x<1.3)로 이루어진 군에서 선택되는 어느 하나 또는 이들 중 2종 이상의 혼합물을 사용할 수 있으며, 상기 리튬함유 전이금속 산화물은 알루미늄(Al) 등의 금속이나 금속산화물로 코팅될 수도 있다. 또한, 상기 리튬함유 전이금속 산화물(oxide) 외에 황화물(sulfide), 셀렌화물(selenide) 및 할로겐화물(halide) 등도 사용될 수 있다.The positive electrode is prepared by applying a positive electrode slurry on a positive electrode current collector and then drying. At this time, the positive electrode active material may be preferably a lithium-containing transition metal oxide, for example, Li x CoO 2 (0.5 <x <1.3), Li x NiO 2 (0.5 <x <1.3), Li x MnO 2 ( 0.5 <x <1.3), Li x Mn 2 O 4 (0.5 <x <1.3), Li x (Ni a Co b Mn c ) O 2 (0.5 <x <1.3, 0 <a <1, 0 <b < 1, 0 <c <1, a + b + c = 1), Li x Ni 1 - y Co y O 2 (0.5 <x <1.3, 0 <y <1), LixCo 1 - y Mn y O 2 ( 0.5 <x <1.3, 0 ≦ y <1), Li x Ni 1 - y Mn y O 2 (0.5 <x <1.3, O ≦ y <1), Li x (Ni a Co b Mn c ) O 4 ( 0.5 <x <1.3, 0 < a <2, 0 <b <2, 0 <c <2, a + b + c = 2), Li x Mn 2 - z Ni z O 4 (0.5 <x <1.3, 0 <z <2), Li x Mn 2 - z Co z O 4 (0.5 <x <1.3, 0 <z <2), Li x CoPO 4 (0.5 <x <1.3) and Li x FePO 4 (0.5 < x <1.3) may be used any one selected from the group consisting of or a mixture of two or more thereof, and the lithium-containing transition metal oxide may be coated with a metal or metal oxide such as aluminum (Al). In addition to the lithium-containing transition metal oxide, sulfide, selenide, halide, and the like may also be used.
금속 재료의 집전체는 전도성이 높은 금속으로, 상기 전극 활물질의 슬러리가 용이하게 접착할 수 있는 금속으로 전지의 전압 범위에서 반응성이 없는 것이면 어느 것이라도 사용할 수 있다. 양극 집전체의 비제한적인 예로는 알루미늄, 니켈 또는 이들의 조합에 의하여 제조되는 호일 등이 있다.The current collector of the metal material is a metal having high conductivity, and any metal can be used as long as the slurry of the electrode active material is a metal that can be easily adhered. Non-limiting examples of the positive electrode current collector include a foil made of aluminum, nickel, or a combination thereof.
상기 양극을 형성하기 위한 용매로는 NMP(N-메틸 피롤리돈), DMF(디메틸 포름아미드), 아세톤, 디메틸 아세트아미드 등의 유기 용매 또는 물 등이 있으며, 이들 용매는 단독으로 또는 2종 이상을 혼합하여 사용할 수 있다.The solvent for forming the positive electrode includes an organic solvent such as NMP (N-methyl pyrrolidone), DMF (dimethyl formamide), acetone, dimethyl acetamide or water, and these solvents alone or in combination of two or more. Can be mixed and used.
용매의 사용량은 슬러리의 도포 두께, 제조 수율을 고려하여 상기 전극활물질, 바인더, 도전제를 용해 및 분산시킬 수 있는 정도이면 충분하다.The amount of the solvent used is sufficient to dissolve and disperse the electrode active material, the binder, and the conductive agent in consideration of the coating thickness of the slurry and the production yield.
또한, 분리막으로는 종래에 분리막으로 사용된 통상적인 다공성 고분자 필름, 예를 들어 에틸렌 단독중합체, 프로필렌 단독중합체, 에틸렌/부텐 공중합체, 에틸렌/헥센 공중합체 및 에틸렌/메타크릴레이트 공중합체 등과 같은 폴리올레핀계 고분자로 제조한 다공성 고분자 필름을 단독으로 또는 이들을 적층하여 사용할 수 있으며, 또는 통상적인 다공성 부직포, 예를 들어 고융점의 유리 섬유, 폴리에틸렌테레프탈레이트 섬유 등으로 된 부직포를 사용할 수 있으나, 이에 한정되는 것은 아니다.In addition, as the separator, conventional porous polymer films conventionally used as separators, for example, polyolefins such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer and ethylene / methacrylate copolymer, etc. The porous polymer film made of the polymer may be used alone or by laminating them, or a conventional porous nonwoven fabric, for example, a non-woven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, or the like may be used. It is not.
상기 전해질로서 포함될 수 있는 리튬염은 리튬 이차 전지용 전해질에 통상적으로 사용되는 것들이 제한 없이 사용될 수 있으며, 예를 들어 상기 리튬염의 음이온으로는 F-, Cl-, Br-, I-, NO3 -, N(CN)2 -, BF4 -, ClO4 -, PF6 -, (CF3)2PF4 -, (CF3)3PF3 -, (CF3)4PF2 -, (CF3)5PF-, (CF3)6P-, F3SO3 -, CF3CF2SO3 -, (CF3SO2)2N-, (FSO2)2N-, CF3CF2(CF3)2CO-, (CF3SO2)2CH-, (SF5)3C-, (CF3SO2)3C-, CF3(CF2)7SO3 -, CF3CO2 -, CH3CO2 -, SCN- 및 (CF3CF2SO2)2N-로 이루어진 군에서 선택된 어느 하나일 수 있다.The lithium salt that may be included as the electrolyte can be used without limitation, those which are commonly used in a lithium secondary battery electrolyte, such as is in the lithium salt anion F -, Cl -, Br - , I -, NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) 2 PF 4 -, (CF 3) 3 PF 3 -, (CF 3) 4PF 2 -, (CF 3) 5PF -, (CF 3) 6P - , F 3 SO 3 -, CF 3 CF 2 SO 3 -, (CF 3 SO 2) 2N -, (FSO 2) 2N -, CF 3 CF 2 (CF 3) 2CO -, (CF 3 SO 2) 2CH - , (SF 5) 3C -, (CF 3 SO 2) 3C -, CF 3 (CF 2) 7SO 3 -, CF 3 CO 2 -, CH 3 CO 2 -, SCN - and It may be any one selected from the group consisting of (CF 3 CF 2 SO 2 ) 2N − .
상기 전해질로는 리튬 이차 전지 제조시 사용 가능한 유기계 액체 전해질, 무기계 액체 전해질, 고체 고분자 전해질, 겔형 고분자 전해질, 고체 무기 전해질, 용융형 무기 전해질 등을 들 수 있으며, 이들로 한정되는 것은 아니다.Examples of the electrolyte include an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, and the like that can be used in manufacturing a lithium secondary battery, but are not limited thereto.
본 발명의 리튬 이차전지의 외형은 특별한 제한이 없으나, 캔을 사용한 원통형, 각형, 파우치 (pouch)형 또는 코인 (coin)형 등이 될 수 있다.The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be cylindrical, square, pouch type, or coin type using a can.
본 발명의 리튬 이차전지는 각종 전자제품의 전원으로 사용될 수 있다. 예를 들어 휴대용 전화기, 핸드폰, 게임기, 휴대용 텔레비전, 노트북 컴퓨터, 계산기 등에 사용할 수 있으며, 이에 한정되는 것은 아니다.The lithium secondary battery of the present invention can be used as a power source for various electronic products. For example, the present invention may be used in a portable telephone, a mobile phone, a game console, a portable television, a laptop computer, a calculator, and the like, but is not limited thereto.
실시예Example
이하, 본 발명이 속하는 기술 분야에서 통상의 지식을 가진 자가 용이하게 실시할 수 있도록 본 발명의 실시예 등에 대하여 첨부한 도면을 참고로 하여 상세히 설명한다. 그러나 본 발명은 여러 가지 상이한 형태로 구현될 수 있으며 여기에서 설명하는 실시예에 한정되지 않는다.Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.
실시예Example 1 One
1) One) 음극활물질의Of cathode active material 제조 Produce
규소계 나노입자로 Si 나노입자와, 수용성 고분자로 중량평균분자량이 약 100,000인 카르복시메틸셀룰로오스(이하, CMC)를 탈이온수에 첨가하여 현탁액을 제조하고, 초음파 조사 장치를 이용하여 상기 현탁액에 초음파를 조사하면서 입자들의 분산을 유도하였다.Si nanoparticles as silicon-based nanoparticles and carboxymethylcellulose (hereinafter, CMC) having a weight average molecular weight of about 100,000 as water-soluble polymers are added to deionized water to prepare a suspension, and ultrasonic waves are applied to the suspension using an ultrasonic irradiation device. Irradiation induced dispersion of the particles.
분무건조 장비에 상기 제조된 현탁액을 주입하여 온도 약 200℃에서 분무건조 공정(저온 탄화 공정)을 수행하였으며, 약 1000℃에서 고온 탄화 공정을 실시하였고, 표면에 고분자 탄화물이 형성된 규소계 나노입자를 얻었다.Injecting the prepared suspension into the spray drying equipment to perform a spray drying process (low temperature carbonization process) at a temperature of about 200 ℃, a high temperature carbonization process at about 1000 ℃, silicon-based nanoparticles with a polymer carbide formed on the surface Got it.
2) 리튬 이차전지의 제작2) Fabrication of Lithium Secondary Battery
상기 코어를 음극활물질로 하고, 도전재로 카본블랙, 그리고, 바인더로 SBR계 고무를 용매인 N-메틸-2-피롤리돈(NMP)에 혼합하여 음극 슬러리를 제조하였다. 상기 음극 슬러리를 두께가 10 ㎛의 음극 집전체인 구리(Cu) 박막에 도포하고, 건조하여 음극을 제조한 후, 롤 프레스(roll press)를 실시하여 음극을 가공하였다.A negative electrode slurry was prepared by mixing the core as a negative electrode active material, carbon black as a conductive material, and SBR-based rubber as a binder in N-methyl-2-pyrrolidone (NMP) as a solvent. The negative electrode slurry was applied to a thin copper (Cu) thin film, which is a negative electrode current collector having a thickness of 10 μm, dried to prepare a negative electrode, and then subjected to roll press to process a negative electrode.
상기 음극과 리튬 대극, 미세다공성 폴리에틸렌 세퍼레이터 및 전해질을 사용하여 헬륨 충진된 글로브 박스에서 코인 타입의 반쪽 셀(2016 R-type half cell)을 제조하였다. 상기 전해질은 에틸렌 카보네이트 및 디메틸 카보네이트를 50:50의 부피비로 혼합한 용매에 1 M LiPF6를 용해시킨 것을 사용하였다.A coin-type half cell (2016 R-type half cell) was prepared in a helium-filled glove box using the negative electrode, the lithium counter electrode, the microporous polyethylene separator, and the electrolyte. As the electrolyte, 1 M LiPF 6 was dissolved in a solvent in which ethylene carbonate and dimethyl carbonate were mixed at a volume ratio of 50:50.
실시예Example 2 2
분무 건조 공정 후 2차 탄화를 수행하는 온도를 800℃로 한 것을 제외하고는 상기 실시예 1-1과 동일한 방법으로 음극활물질 및 리튬 이차전지를 제작하였다.A negative electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1-1, except that the temperature of performing secondary carbonization after spray drying was 800 ° C.
비교예Comparative example 1 One
수용성 고분자로 중량평균분자량이 약 3,000,000인 CMC를 사용한 것을 제외하고는 상기 실시예 1과 동일한 방법으로 음극활물질 및 리튬 이차전지를 제작하였다.A negative electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that CMC having a weight average molecular weight of about 3,000,000 was used as the water-soluble polymer.
비교예Comparative example 2 2
분무 건조 공정 대신에 열처리를 수행하였고, 열처리 온도는 600℃이었으며, 이 외의 공정은 상기 실시예 1과 동일한 방법으로 음극활물질 및 리튬 이차전지를 제작하였다.Heat treatment was performed in place of the spray drying process, the heat treatment temperature was 600 ℃, and other processes to produce a negative electrode active material and a lithium secondary battery in the same manner as in Example 1.
실험예Experimental Example 1: 수용성 고분자의 중량평균분자량에 따른 전지 특성 평가 1: Evaluation of Battery Characteristics According to Weight Average Molecular Weight of Water-soluble Polymer
상기 실시예 1 및 비교예 1에서 제조된 코인 타입의 반쪽 셀의 초기 방전용량을 알아보기 위해, 25 ℃에서 제조한 반쪽 셀을 0 V 내지 1.5 V에서, 0.1 C로 1회 충방전을 실시하여, 초기 방전 용량, 초기 충전 용량, 쿨롱 효율을 측정하였다. 또한 1회 충방전 종료 후 25 ℃에서 제조한 반쪽 셀을 0 V 내지 1.5 V에서, 0.5 C로 50회 충방전 후의 용량 유지율(수명 특성)을 확인하였다. 상기의 방법으로 측정한 초기 방전용량, 초기 효율 및 수명특성의 측정결과를 하기 표 1에 나타내었다.In order to determine the initial discharge capacity of the coin-type half-cells prepared in Example 1 and Comparative Example 1, the half-cells prepared at 25 ° C. were charged and discharged once at 0.1 C at 0 V to 1.5 V. , Initial discharge capacity, initial charge capacity, and coulombic efficiency were measured. In addition, the capacity retention rate (life characteristics) of the half cell prepared at 25 ° C. after charging and discharging at 50 ° C. at 50 ° C. at 50 ° C. at 0.5 ° C. was confirmed. Table 1 shows the measurement results of the initial discharge capacity, initial efficiency, and lifetime characteristics measured by the above method.
초기 방전용량(mAh/g)Initial discharge capacity (mAh / g) 초기 효율(%)Initial Efficiency (%) 수명 특성(%)Life Characteristics (%)
실시예 1Example 1 30003000 8686 4040
비교예 1Comparative Example 1 30003000 8585 2222
상기 표 1을 참조하면, 저분자량의 CMC를 사용한 실시예 1의 경우 고분자량의 CMC를 사용한 비교예 1에 비하여 수명 특성이 상당히 우수하다는 점을 확인할 수 있다. 나아가, 저분자량을 사용하였음에도, 고분자량에 비하여 초기 방전용량이나 효율에 있어서 성능 면에서 손해 보는 바가 없음을 확인하였고, 따라서, 분산성 문제나 탄화시 균일성 문제를 야기하는 고분자량을 이용하는 것에 비하여 저분자량의 CMC를 사용하는 것이 유리하다는 점을 확인할 수 있다.Referring to Table 1, in the case of Example 1 using a low molecular weight CMC it can be seen that the life characteristics are significantly superior to Comparative Example 1 using a high molecular weight CMC. Furthermore, even though a low molecular weight was used, it was confirmed that there was no loss in performance in terms of initial discharge capacity or efficiency compared to a high molecular weight. Thus, as compared with using a high molecular weight which causes dispersibility problems or uniformity problems during carbonization. It can be seen that it is advantageous to use low molecular weight CMC.
실험예Experimental Example 2: 수용성 고분자의 탄화 온도에 따른 전지 특성 평가 2: Evaluation of Battery Characteristics According to Carbonization Temperature of Water-Soluble Polymer
상기 실시예 2 및 비교예 2의 이차전지에 대하여 상기 실험예 1에서와 동일한 방법으로 그 성능을 평가하였고, 하기 표 2에 그 결과를 나타내었다.The performance of the secondary batteries of Example 2 and Comparative Example 2 was evaluated in the same manner as in Experimental Example 1, and the results are shown in Table 2 below.
초기 방전용량(mAh/g)Initial discharge capacity (mAh / g) 초기 효율(%)Initial Efficiency (%) 수명 특성(%)Life Characteristics (%)
실시예 1Example 1 30003000 8686 4040
실시예 2Example 2 30003000 8686 4040
비교예 2Comparative Example 2 28002800 8383 3232
상기 표 2를 참조하면, 고온 탄화 공정의 온도를 600℃로 하여 800℃에 미달되는 비교예 2의 경우에는 모두 고온 탄화 공정의 온도가 각각 800℃ 및 1000℃인 실시예 1 및 2에 비하여 초기 방전용량을 비롯하여 초기 효율이나 수명 특성이 떨어진다는 점을 확인할 수 있다. 이를 통하여, 고온 탄화 공정의 온도가 800 내지 1100℃인 경우에는 수용성 고분자의 규소계 나노입자 표면에의 탄화가 전체적으로 균일하게 이루어져 성능이 우수하게 발현되고 있다는 점을 알 수 있다.Referring to Table 2, in the case of Comparative Example 2 which is less than 800 ℃ with the temperature of the high temperature carbonization process 600 ℃ all compared to Examples 1 and 2, the temperature of the high temperature carbonization process is 800 ℃ and 1000 ℃, respectively In addition to the discharge capacity, it can be seen that the initial efficiency and life characteristics are poor. Through this, it can be seen that when the temperature of the high temperature carbonization process is 800 to 1100 ° C., the carbonization of the water-soluble polymer onto the surface of the silicon-based nanoparticles is uniform, resulting in excellent performance.
이상에서 본 발명의 바람직한 실시예에 대하여 상세하게 설명하였지만 본 발명의 권리범위는 이에 한정되는 것은 아니고 다음의 청구범위에서 정의하고 있는 본 발명의 기본 개념을 이용한 당업자의 여러 변형 및 개량 형태 또한 본 발명의 권리범위에 속하는 것이다.Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

Claims (13)

  1. 규소계 나노입자; 및 상기 나노입자상에 분포된 수용성 고분자의 탄화물;을 포함하고, 고분자 탄화물이 표면에 분포된 규소계 나노입자의 크기는 30 내지 800 nm인 것인 음극활물질.Silicon-based nanoparticles; And a carbide of the water-soluble polymer distributed on the nanoparticles, wherein the size of the silicon-based nanoparticles in which the polymer carbide is distributed on the surface is 30 to 800 nm.
  2. 제1항에 있어서,The method of claim 1,
    상기 규소계 나노입자는 그 표면에 산화피막을 포함하는 것인 음극활물질.The silicon-based nanoparticles are anode active material comprising an oxide film on the surface.
  3. 제1항에 있어서,The method of claim 1,
    상기 규소계 나노입자는 Si, SiO, SiM 및 이들의 조합으로 이루어진 군에서 선택된 어느 하나의 물질을 포함하는 것이고, The silicon-based nanoparticles include any one material selected from the group consisting of Si, SiO, SiM, and combinations thereof,
    상기 M은 Ni, Co, B, Cr, Cu, Fe, Mn, Ti, Y 및 이들의 조합으로 이루어진 군에서 선택된 어느 하나를 포함하는 것인 음극활물질.Wherein M is Ni, Co, B, Cr, Cu, Fe, Mn, Ti, Y and a negative electrode active material containing any one selected from the group consisting of a combination thereof.
  4. 제1항에 있어서,The method of claim 1,
    상기 수용성 고분자는 카르복시메틸셀룰로오스(carboxy methyl cellulose, CMC), 수크로오스(sucrose), 폴리아크릴로니트릴(polyacrylonitrile, PAN) 및 이들의 조합으로 이루어진 군에서 선택된 어느 하나를 포함하는 것인 음극활물질.The water-soluble polymer is a negative electrode active material comprising any one selected from the group consisting of carboxy methyl cellulose (CMC), sucrose (sucrose), polyacrylonitrile (polyacrylonitrile, PAN) and combinations thereof.
  5. 제1항에 있어서,The method of claim 1,
    상기 수용성 고분자는 중량평균분자량이 90,000 내지 2,000,000인 것인 음극활물질.The water-soluble polymer is a negative electrode active material having a weight average molecular weight of 90,000 to 2,000,000.
  6. 제1항에 있어서,The method of claim 1,
    상기 음극활물질은 규소계 나노입자의 총중량 대비, 3 내지 20 중량%의 고분자 탄화물을 포함하는 것인 음극활물질.The negative electrode active material is a negative electrode active material containing 3 to 20% by weight of the polymer carbide, relative to the total weight of the silicon-based nanoparticles.
  7. 용매에 규소계 나노입자 및 수용성 고분자를 첨가한 현탁액을 초음파를 이용하여 분산시키고;Dispersing the suspension in which the silicon-based nanoparticles and the water-soluble polymer are added to the solvent using ultrasonic waves;
    상기 수용성 고분자를 탄화시켜 규소계 나노입자의 표면에 고분자 탄화물을 형성시키는 것을 포함하는 음극활물질의 제조방법.And carbonizing the water-soluble polymer to form polymer carbide on the surface of the silicon-based nanoparticles.
  8. 제7항에 있어서,The method of claim 7, wherein
    상기 탄화는 저온 탄화 공정 및 고온 탄화 공정을 포함하는 두 단계 공정으로 수행되는 것인 음극 활물질의 제조방법.The carbonization is a method of producing a negative electrode active material is carried out in a two-step process including a low temperature carbonization process and a high temperature carbonization process.
  9. 제8항에 있어서,The method of claim 8,
    상기 저온 탄화 공정은 분무건조 장치를 이용하여 수행되는 것이며, 상기 현탁액을 분무건조 장치 내 챔버에 주입하고, 현탁액을 챔버 내에서 분무하여 건조하는 것을 포함하는 것인 음극활물질의 제조방법.The low temperature carbonization process is to be carried out using a spray drying apparatus, the suspension is injected into the chamber in the spray drying apparatus, and the method of producing a negative electrode active material comprising spraying the suspension in the chamber to dry.
  10. 제9항에 있어서,The method of claim 9,
    상기 분무건조 장치는 초음파 분무건조 장치, 공기노즐 분무건조 장치, 초음파노즐 분무건조 장치, 필터 팽창 액적 발생장치, 정전분무건조 장치 및 이들의 조합으로 이루어진 군에서 선택된 어느 하나를 포함하는 것인 음극활물질의 제조방법.The spray drying apparatus may include any one selected from the group consisting of an ultrasonic spray drying apparatus, an air nozzle spray drying apparatus, an ultrasonic nozzle spray drying apparatus, a filter expansion droplet generator, an electrostatic spray drying apparatus, and a combination thereof. Manufacturing method.
  11. 제8항에 있어서,The method of claim 8,
    상기 저온 탄화 공정은 80 내지 300℃의 온도에서 수행되는 것인 음극활물질의 제조방법.The low temperature carbonization process is a method for producing a negative electrode active material is carried out at a temperature of 80 to 300 ℃.
  12. 제8항에 있어서,The method of claim 8,
    상기 고온 탄화 공정은 800 내지 1100℃의 온도에서 열처리가 수행되는 것인 음극활물질의 제조방법.The high temperature carbonization process is a method for producing a negative electrode active material that the heat treatment is carried out at a temperature of 800 to 1100 ℃.
  13. 제7항에 있어서,The method of claim 7, wherein
    상기 용매는 물, 아세톤 및 이들의 조합으로 이루어진 군에서 선택된 어느 하나를 포함하는 것인 음극활물질의 제조방법.The solvent is a method for producing a negative electrode active material comprising any one selected from the group consisting of water, acetone and combinations thereof.
PCT/KR2015/012815 2014-11-27 2015-11-27 Silicon-based negative electrode active material and method for manufacturing same WO2016085282A1 (en)

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KR20090058505A (en) * 2006-08-22 2009-06-09 센젠시 뻬이터루이 신에너지 자재 주식유한공사 A silicon-carbon composite negative material for lithium ion battery and the preparation method of the same
KR20130004536A (en) * 2011-06-30 2013-01-11 삼성에스디아이 주식회사 Negative active material, manufacturing method thereof, and lithium battery containing the material
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KR20130071071A (en) * 2011-12-20 2013-06-28 한국과학기술원 Anode active material of silicon-carbon composite with core-shell structure, manufacturing method for the same and lithium secondary battery comprising the anode active material
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