WO2019177338A1 - Amorphous silicon-carbon composite, preparation method therefor, and lithium secondary battery comprising same - Google Patents

Amorphous silicon-carbon composite, preparation method therefor, and lithium secondary battery comprising same Download PDF

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Publication number
WO2019177338A1
WO2019177338A1 PCT/KR2019/002843 KR2019002843W WO2019177338A1 WO 2019177338 A1 WO2019177338 A1 WO 2019177338A1 KR 2019002843 W KR2019002843 W KR 2019002843W WO 2019177338 A1 WO2019177338 A1 WO 2019177338A1
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Prior art keywords
amorphous silicon
carbon composite
carbon
silicon
composite
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PCT/KR2019/002843
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French (fr)
Korean (ko)
Inventor
김장배
박수진
채종현
양지혜
복태수
홍동기
류재건
유석근
Original Assignee
주식회사 엘지화학
울산과학기술원
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Priority claimed from KR1020190026971A external-priority patent/KR102207529B1/en
Application filed by 주식회사 엘지화학, 울산과학기술원 filed Critical 주식회사 엘지화학
Priority to JP2020531992A priority Critical patent/JP7062212B2/en
Priority to EP19767922.8A priority patent/EP3718969A4/en
Priority to US16/769,909 priority patent/US11616233B2/en
Priority to CN201980006152.3A priority patent/CN111433154B/en
Publication of WO2019177338A1 publication Critical patent/WO2019177338A1/en
Priority to US18/110,153 priority patent/US20230197957A1/en

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/02—Silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • 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
    • 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
    • H01M4/58—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
    • 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 an amorphous silicon-carbon composite, a method of manufacturing the same, and a negative electrode and a lithium secondary battery for a lithium secondary battery comprising the same.
  • Lithium secondary batteries for example, lithium ion batteries
  • nickel hydride batteries and other secondary batteries are becoming increasingly important as power supplies for on-board power supplies or portable terminals such as notebook computers.
  • a lithium secondary battery capable of obtaining high energy density at a light weight can be used as a high output power source for mounting a vehicle, and thus it is expected to continuously increase demand in the future.
  • the lithium secondary battery is manufactured by using a material capable of inserting and detaching lithium ions as an active material of a negative electrode, installing a porous separator between the positive electrode and the negative electrode, and then injecting a liquid electrolyte. Electricity is generated or consumed by redox reactions following insertion and desorption.
  • the lithium secondary battery various types of carbon-based materials including artificial graphite, natural graphite, hard carbon, and soft carbon capable of inserting and detaching lithium have been applied as a negative electrode active material.
  • the carbon-based graphites the graphite not only exhibits a high discharge voltage of 3.6 V, but also provides an advantage in terms of energy density of the lithium secondary battery, and guarantees the long life of the lithium secondary battery with excellent reversibility. It is widely used.
  • the graphite active material has a low graphite density (theoretical density of 2.2 g / cc) in the production of the electrode plate, which has a low capacity in terms of energy density per unit volume of the electrode plate, and easily generates side reactions with the organic electrolyte used at high voltages. There was a problem of capacity reduction.
  • the carbon-based negative electrode active material In order to solve such a problem of the carbon-based negative electrode active material, a Si-based negative electrode active material having a much higher capacity than graphite has been developed and studied.
  • the high-capacity Si-based negative electrode material is accompanied by a severe volume change during charging and discharging, which causes a breakdown of particles and thus has a disadvantage of poor life characteristics.
  • the silicon or silicon oxide (SiO x , 0 ⁇ x ⁇ 2) -based negative electrode active material capable of alloying and dealloying lithium ions has a volume expansion of up to 300%. During such volume expansion and contraction, the SiO x -based negative active material is subjected to severe physical stress and collapses.
  • the result is a breakdown of the existing SEI layer and the creation of a new interface, forming a new SEI layer.
  • This causes continuous electrolyte decomposition and consumption of lithium ions, thereby degrading the cycle characteristics of the battery.
  • the conductive structure is destroyed by the volume expansion and contraction of the SiO x -based negative electrode active material, and durability of the electrode decreases, thereby deteriorating battery life.
  • SiO x in the form of nanotubes has been developed.
  • An object of the present invention is to provide an amorphous silicon-carbon composite having a small volume change and no fragmentation during charging and discharging of a lithium secondary battery.
  • an object of the present invention is to provide a method for producing an amorphous silicon-carbon composite having a simple manufacturing process using a pyrolysis method.
  • an object of the present invention is to provide a negative electrode and a lithium secondary battery of a lithium secondary battery including the amorphous silicon-carbon composite to improve the electrical conductivity and life characteristics of the battery.
  • the present invention is an amorphous silicon-carbon composite in which silicon (Si) and carbon (C) are mixed at the molecular level,
  • the composite provides a composite having a diameter of 10 nm to 1 ⁇ m.
  • the present invention comprises the steps of a) preparing a mixed solution by mixing a silane compound containing a hydrocarbon with an organic solvent;
  • the present invention is an active material; Conductive material; In the negative electrode for a lithium secondary battery comprising a binder,
  • the active material provides a negative electrode for a lithium secondary battery comprising the amorphous silicon-carbon composite of the present invention.
  • the present invention is an anode; cathode; A separator interposed between the anode and the cathode; And lithium secondary battery comprising an electrolyte,
  • the negative electrode provides a lithium secondary battery, characterized in that the negative electrode of the present invention.
  • silicon and carbon are mixed in a molecular unit, and thus have a small volume change and no fragmentation during charging and discharging of a battery.
  • the method of manufacturing the amorphous silicon-carbon composite of the present invention has the advantage of a simple process.
  • the lithium secondary battery including the amorphous silicon-carbon composite of the present invention has an excellent electrical conductivity and life characteristics.
  • FIG. 1 is a schematic diagram of an amorphous silicon-carbon composite of the present invention.
  • Example 2 is a transmission electron microscope (TEM) image of the amorphous silicon-carbon composite prepared in Example 1-1.
  • TEM transmission electron microscope
  • Example 3 is a photograph measured using a transmission electron microscope (TEM) energy dispersive spectroscopy of the amorphous silicon-carbon composite (Si-C) prepared in Example 1-1.
  • TEM transmission electron microscope
  • TEM 7 is a transmission electron microscope (TEM) photograph of the amorphous silicon-carbon composite prepared in Comparative Example 3-1.
  • FIG. 8 is an X-ray diffraction graph of Experimental Example 1.
  • Example 10 is an initial charge and discharge graph of Example 1-3, Comparative Example 1-3, and Comparative Example 2-3.
  • Example 11 is an initial charge and discharge graph of Example 1-3 and Comparative Example 3-3.
  • Silicon has a capacity of about 10 times that of graphite, but there is a problem in that the lifespan characteristics of the battery are deteriorated due to volume change and fragmentation occurring during charging and discharging of the battery.
  • the present invention has been made to provide an amorphous silicon-carbon composite in which silicon (Si) and carbon (C) are mixed on a molecular basis.
  • silicon and carbon are mixed in a molecular unit, thereby solving the above problems.
  • the present invention relates to an amorphous silicon-carbon composite in which silicon (Si) and carbon (C) are mixed at the molecular level, and the diameter of the composite is 10 nm to 1 ⁇ m.
  • the amorphous silicon-carbon composite is formed by a pyrolytic deposition process for a silicon source and a carbon source, and the composite includes silicon-carbon covalent bonds, silicon-silicon covalent bonds, and carbon-carbon covalent bonds. Is irregularly present in the complex.
  • the amorphous silicon-carbon composite may further include a hetero atom, in which case the complex may further include one or more bonds among hetero atom-carbon covalent bonds and hetero atom-silicone covalent bonds, and the covalent Bonds are irregularly present in the complex.
  • the hetero atom may be at least one selected from the group consisting of boron (B), phosphorus (P), nitrogen (N) and sulfur (S).
  • the amorphous silicon-carbon composite is formed by a pyrolytic deposition process of a silane compound including a hydrocarbon, and when the compound is pyrolyzed, a part or the entire bond of the compound is broken to form an amorphous silicon-carbon composite.
  • the silicon source and carbon source may be a silane compound comprising a hydrocarbon. Therefore, the composite of the present invention is a silicon and carbon is distributed without a concentration gradient it can minimize the volume expansion problem when applied to a lithium secondary battery, it is possible to improve the life characteristics of the battery.
  • the amorphous silicon-carbon composite includes silicon and carbon in a weight ratio of 3: 7 to 7: 3.
  • the silicon is included below the range may reduce the capacity of the battery, if included beyond the range may reduce the life of the battery.
  • the life of the battery may be reduced, and when the above range is exceeded, the capacity of the battery may be reduced.
  • the amorphous silicon-carbon composite may include trace amounts of hydrogen and oxygen.
  • the amorphous silicon-carbon composite is in the form of particles, the diameter of the composite may be 10nm to 1 ⁇ m, preferably 100 to 500nm. If the diameter of the composite is less than 10nm, not only the density of the composite is significantly lowered, but also difficult to manufacture the electrode. If the diameter exceeds 1 ⁇ m, the electrical conductivity of the composite is greatly reduced, thereby deteriorating battery life and rate characteristics.
  • the density of the amorphous silicon-carbon composite is 0.2 to 0.6 g / cc, preferably 0.3 to 0.5 g / cc. If the density is less than 0.2g / cc, the electrode density is low, that is, the thickness of the electrode becomes thicker compared to the same loading amount, so that the energy density of the battery is lowered. If the density exceeds 0.6g / cc, the resistance of the electrode is increased, thereby decreasing the rate characteristic. do.
  • the amorphous silicon-carbon composite of the present invention is a mixture of silicon and carbon at a molecular level, and consists of a plurality of silicon atoms, a plurality of carbon atoms, and covalent bonds thereof, and may be used as a negative electrode active material of a lithium secondary battery.
  • the amorphous silicon-carbon composite of the present invention When the amorphous silicon-carbon composite of the present invention is used in a lithium secondary battery, problems such as volume change and fragmentation of silicon generated during battery charging and discharging may be solved, and the battery may exhibit excellent electrical conductivity and lifespan characteristics.
  • the present invention comprises the steps of a) preparing a mixed solution by mixing a silane compound containing a hydrocarbon with an organic solvent;
  • Step a) is a step of preparing a mixed solution by mixing a silane compound containing a hydrocarbon with an organic solvent.
  • the silane compound containing the hydrocarbon is a compound containing a hydrocarbon as a functional group in the silane structure, and the kind thereof is not particularly limited, but in the present invention, tetramethylsilane, dimethylsilane, methylsilane, triethylsilane, and phenylsilane are preferred. And it may include one or more selected from the group consisting of diphenylsilane.
  • silane compound including the hydrocarbon may be a compound further comprising a hetero atom.
  • the kind of the compound is not particularly limited as long as the hetero atom can form a covalent bond with silicon and carbon.
  • the hetero atom may be at least one selected from the group consisting of boron (B), phosphorus (P), nitrogen (N) and sulfur (S).
  • the organic solvent may be used without particular limitation as long as it can dissolve the silane compound containing hydrocarbon, preferably, the boiling point is about 100 ° C. or higher, the viscosity is not high, and carbonization is performed at a temperature of 600 ° C. or higher.
  • Organic solvents that do not occur may be used, and in the present invention may specifically include one or more selected from the group consisting of, for example, toluene, benzene, ethylbenzene, xylene, mesitylene, heptane and octane.
  • the organic solvent is used as a dilution to compensate for the boiling point of the silane compound including a hydrocarbon having a relatively low boiling point, and when the pyrolysis temperature is 800 ° C. or higher, thermal decomposition of the organic solvent may occur together. It can serve to control the ratio of silicon and carbon by providing additional carbon within.
  • Mixing of the compound and the organic solvent is preferably performed for about 10 to 30 minutes at room temperature.
  • step b) the mixed solution is thermally decomposed in an inert atmosphere and deposited on a substrate.
  • the pyrolysis is performed by a process of bubbling by supplying an inert gas to the mixed solution, and the inert atmosphere is preferably an argon (Ar) gas atmosphere.
  • the inert atmosphere is preferably an argon (Ar) gas atmosphere.
  • the pyrolysis temperature is 600 to 900 °C, if the pyrolysis temperature is less than 600 °C can not produce an amorphous silicon-carbon composite due to the thermal decomposition of the silane compound containing a hydrocarbon, Above 900 ° C., direct decomposition of the organic solvent may occur to escape the desired mixing ratio of silicon and carbon, as well as to control its content.
  • the pyrolysis temperature is within the above temperature range, the higher the temperature, the lower the content of hydrogen in the amorphous silicon-carbon composite, so the pyrolysis temperature is preferably 700 to 800 ° C.
  • the pyrolysis is made for 10 minutes to 1 hour, preferably 30 minutes to 1 hour.
  • the amorphous silicon-carbon composite produced by the pyrolysis is deposited on a substrate, and further comprising the step of separating the deposited composite can finally produce an amorphous silicon-carbon composite in the form of particles.
  • the method for separating the deposited composite is not particularly limited in the present invention, but preferably, a ball-mill process may be used.
  • the diameter of the deposited composite has a size of more than 1 ⁇ m, the diameter of the amorphous silicon-carbon composite having a particle form separated from the substrate is 10nm to 1 ⁇ m, preferably 100 to 500nm. If the diameter of the composite is less than 10nm, not only the density of the composite is significantly lowered, but also difficult to manufacture the electrode. If the diameter exceeds 1 ⁇ m, the electrical conductivity of the composite is greatly reduced, thereby deteriorating battery life and rate characteristics.
  • the kind of the substrate is not particularly limited in the present invention, and preferably, a silicon or alumina substrate can be used.
  • a mixed solution of the compound and the organic solvent at room temperature is prepared.
  • an inert gas is flowed into the furnace to make it inert atmosphere and heated to adjust the temperature inside the furnace at a constant temperature.
  • the mixture is poured into a furnace to pyrolyze a silane compound including a hydrocarbon to prepare an amorphous silicon-carbon composite, and the composite is deposited on a substrate.
  • the composite deposited on the substrate may be obtained through a process such as a ball mill to obtain an amorphous silicon-carbon composite in the form of particles.
  • the amorphous silicon-carbon composite is manufactured in the form of particles through a process of separating a complex such as a ball mill after substrate deposition, the amorphous silicon-carbon composite is in the form of particles, the diameter of the amorphous silicon-carbon composite in the form of particles Is 10 nm to 1 ⁇ m, and preferably 100 nm to 500 nm.
  • the production method of the present invention is to prepare an amorphous silicon-carbon composite through a simple pyrolysis method, the manufacturing process has a simple advantage.
  • the present invention is an active material; Conductive material; And it relates to a negative electrode for a lithium secondary battery comprising a binder, the active material comprises the amorphous silicon-carbon composite of the present invention.
  • the negative electrode includes a negative electrode active material formed on the negative electrode current collector, the negative electrode active material uses an amorphous silicon-carbon composite prepared according to the present invention.
  • the negative electrode current collector may be specifically selected from the group consisting of copper, stainless steel, titanium, silver, palladium, nickel, alloys thereof, and combinations thereof.
  • the stainless steel may be surface treated with carbon, nickel, titanium, or silver, and an aluminum-cadmium alloy may be used as the alloy.
  • calcined carbon, a nonconductive polymer surface-treated with a conductive material, or a conductive polymer may be used.
  • the said conductive material is used in order to improve the electroconductivity of an electrode active material further.
  • a conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery, and examples thereof include graphite such as natural graphite and artificial graphite; Carbon blacks such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black and summer black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride powder, aluminum powder and nickel powder; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Polyphenylene derivatives and the like can be used.
  • the binder is used for bonding the electrode active material and the conductive material to the current collector.
  • binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polyacrylic acid (PAA), polymethacrylic acid (PMA), polymethyl methacrylate (PMMA) polyacrylamide (PAM), polymethacrylamide, polyacrylonitrile (PAN), polymethacrylonitrile, polyimide (PI), alginic acid, alginate, chitosan, carboxymethylcellulose (CMC) ), Starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber (SBR) , Fluororubbers, various copolymers thereof, and the like.
  • PVDF polyvinyliden
  • the negative electrode may further include a filler and other additives.
  • the present invention is an anode; cathode; A separator interposed between the anode and the cathode; And a lithium secondary battery comprising an electrolyte, the negative electrode relates to a lithium secondary battery characterized in that the negative electrode of the present invention described above.
  • the configuration of the positive electrode, the negative electrode, the separator and the electrolyte of the lithium secondary battery is not particularly limited in the present invention, and is known in the art.
  • the positive electrode includes a positive electrode active material formed on a positive electrode current collector.
  • the positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery, and for example, carbon, nickel on the surface of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel Surface treated with titanium, silver, or the like can be used.
  • the positive electrode current collector may use various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric having fine irregularities formed on a surface thereof so as to increase the adhesion with the positive electrode active material.
  • cathode active material any cathode active material available in the art may be used.
  • the electrode layer may further include a binder, a conductive material, a filler, and other additives in addition to the positive electrode active material, and the binder and the conductive material are the same as described above for the negative electrode for the lithium secondary battery.
  • the separator may be made of a porous substrate, and the porous substrate may be used as long as it is a porous substrate that is typically used in an electrochemical device.
  • a porous substrate that is typically used in an electrochemical device.
  • a polyolefin-based porous membrane or a nonwoven fabric may be used. It is not.
  • the separator is polyethylene, polypropylene, polybutylene, polypentene, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyether ether ketone, polyether sulfone, It may be a porous substrate composed of any one selected from the group consisting of polyphenylene oxide, polyphenylene sulfide, and polyethylene naphthalate or a mixture of two or more thereof.
  • the electrolyte of the lithium secondary battery is a non-aqueous electrolyte containing lithium salt and is composed of a lithium salt and a solvent, and a non-aqueous organic solvent, an organic solid electrolyte and an inorganic solid electrolyte are used as the solvent.
  • the lithium salt is a material that is easy to dissolve in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO 4 , LiBF 4 , LiB 10 Cl 10 , LiPF 6 , LiAsF 6 , LiSbF 6 , LiAlCl 4 , LiSCN, LiC 4 BO 8 , LiCF 3 CO 2 , LiCH 3 SO 3 , LiCF 3 SO 3 , LiN (SO 2 CF 3 ) 2 , LiN (SO 2 C 2 F 5 ) 2 , LiC 4 F 9 SO 3 , LiC (CF 3 SO 2 ) 3 , (CF 3 SO 2 ) .2NLi, lithium chloroborane, lower aliphatic lithium carbonate, lithium tetraphenyl borate imide and the like can be used.
  • the non-aqueous organic solvent is, for example, N-methyl-2-pyrrolidone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, gamma-butyrolactone, 1,2 Dimethoxy ethane, 1,2-diethoxy ethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, 4-methyl-1,3-dioxene, Diethyl ether, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxy methane, dioxolane derivatives, sulfolane, methylsulforane, 1,3- Aprotic organic solvents such as dimethyl-2-imidazolidinone, propylene carbonate
  • organic solid electrolytes examples include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate ester polymers, polyagitation lysine, polyester sulfides, polyvinyl alcohol, polyvinylidene fluoride, Polymers including secondary dissociation groups and the like can be used.
  • Examples of the inorganic solid electrolyte include 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 , Nitrides, halides, sulfates and the like of Li, such as Li 4 SiO 4 -LiI-LiOH, Li 3 PO 4 -Li 2 S-SiS 2 , and the like, may be used.
  • the non-aqueous electrolyte may further include other additives for the purpose of improving charge / discharge characteristics, flame retardancy, and the like.
  • the additives include pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexa phosphate triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazoli Dinon, N, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride, fluoroethylene carbonate (FEC), propene sultone (PRS), vinylene carbonate ( VC) etc. are mentioned.
  • FEC fluoroethylene carbonate
  • PRS propene sultone
  • VC vinylene carbonate
  • Lithium secondary battery according to the present invention in addition to the winding (winding) which is a general process, it is possible to lamination (stacking) and folding (folding) of the separator and the electrode.
  • the battery case may be cylindrical, square, pouch type, or coin type.
  • TMS tetramethylsilane
  • argon (Ar) gas purity 99.999%) was flowed at a rate of 500 cc / min to make the inside of the furnace in an inert atmosphere. Thereafter, the furnace was heated at a temperature rising rate of 10 ° C./min and heated up to 750 ° C. After the furnace temperature reached 750 ° C., the temperature was maintained for 10 to 30 minutes to keep the temperature inside the furnace constant.
  • the mixed solution was injected into the furnace at a rate of 100 cc / min, and argon gas was flowed and bubbled to thermally decompose the mixed solution.
  • the furnace temperature is lowered to room temperature to obtain an amorphous silicon-carbon composite decomposed on the substrate inside the furnace, and the composite is passed through a ball mill to form silicon (Si) and carbon (C) in the form of particles.
  • Amorphous silicon-carbon composites (Si-C) mixed at the molecular level were prepared (FIGS. 2 and 3).
  • the silicon-carbon composite had a diameter of about 200 nm and a density of 0.42 g / cc.
  • the amorphous silicon-carbon composite prepared in Example 1-1 was used as a negative electrode active material.
  • 80 wt% of the negative electrode active material, 10 wt% of the binder (PAA / CMC, 1: 1 weight ratio), and 10 wt% of the conductive material (super-P) were dispersed in water to form a negative electrode slurry, and the electrode plate was manufactured by coating on a copper electrode.
  • the electrode plate prepared in Example 1-2 was used as the negative electrode.
  • Lithium metal was used as a counter electrode and a polyethylene separator was interposed between the cathode and the counter electrode, and then a mixed solvent of ethylene carbonate and dimethyl carbonate (EC / DEC, 3: 7, volume ratio) using 1.3 M LiPF 6 was used as an electrolyte.
  • Coin cells were prepared using 10% by weight of FEC as an additive.
  • the silicon-carbon composites (Si) were simply mixed by inducing about 15wt% of Si (about 3500mAh / g) and about 85wt% of graphite (about 372mAh / g) to meet 600mAh / g of discharge capacity.
  • -Graphite was prepared (FIG. 4).
  • a coin cell was manufactured in the same manner as in Example 1-3, except that the cathode plate prepared in Comparative Example 1-2 was used as a cathode.
  • silicone oil silicone oil
  • SiOC silicon-oxygen-carbon composite
  • a coin cell was manufactured in the same manner as in Example 1-3, except that the cathode plate prepared in Comparative Example 2-2 was used as the cathode.
  • Si-C amorphous silicon-carbon composite
  • a coin cell was manufactured in the same manner as in Example 1-3, except that the cathode plate prepared in Comparative Example 3-2 was used as a cathode.
  • the silicon-carbon composite (Si-C) of Example 1-1 showed a wide area peak at 32 degrees and 60 degrees. Since the silicon of the silicon-carbon composite (Si-Graphite) of Comparative Example 1-1 is not amorphous, the six silicon peaks (approximately 28 degrees, 47 degrees, 56 degrees, 69 degrees, 76 degrees, and 88 degrees) are clear. The peaks of Graphite appeared at about 26 degrees, 35 degrees, and 44 degrees. In addition, the silicon-oxygen-carbon composite (SiOC) of Comparative Example 2-1 showed a wide area peak at 30 degrees and 42 degrees.
  • Example 1-2 The electrode plates prepared in Example 1-2, Comparative Example 1-2, and Comparative Example 2-2 were measured for electrical conductivity using a four-point probe (Four-point probe) (Fig. 9).
  • the electrode plate of Example 1-2 had excellent electrical conductivity and showed low resistance value.
  • the electrode plate of Comparative Example 1-2 had a low resistance value due to its excellent electrical conductivity because Graphite had a very good electrical conductivity in the form of stacked carbon layers.
  • the electrode plate of Comparative Example 2-3 contained a silicon-oxygen-carbon composite (SiOC), which is a ceramic material, and thus exhibited low electrical conductivity, thereby showing a very high resistance.
  • SiOC silicon-oxygen-carbon composite
  • the charge and discharge rate of the coin cells prepared in Example 1-3, Comparative Example 1-3 and Comparative Example 2-3 is fixed to 0.05 C-rate And, the operating voltage was set to 0.005 ⁇ 2.5V to measure the charge and discharge characteristics of the coin cell (Fig. 10).
  • Example 1-3 having a smaller diameter of the silicone composite has superior charge and discharge characteristics than Comparative Example 3-3, which has a diameter of the silicone composite exceeding 1 ⁇ m.
  • the coin cell of Example 1-3 showed excellent life characteristics because the capacity of the battery hardly decreased even after the cycle progressed.
  • the coin cell of Comparative Examples 1-3 is a very unstable connection because silicon is in contact with the graphite particles with dots, and as the cycle progresses, the volume expansion of the silicon causes the capacity of the battery to decrease, resulting in poor life characteristics. I could not.
  • the coin cell of Comparative Example 2-3 also had a poor battery life as the capacity of the battery decreased as the cycle progressed.
  • Example 1-3 showed a saturation capacity and stable life characteristics before 50cylce, while Comparative Example 3-3 did not saturate for 100 cycles and showed a low capacity.
  • the charge and discharge rates of the coin cells prepared in Examples 1-3, Comparative Examples 1-3 and Comparative Examples 2-3 were 20 cycles at 0.2 C-rate, 10 cycles at 0.5 C-rate, and then 5 Each cycle, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 C-rate was adjusted to charge and discharge rate, and finally returned to 0.2-rate to check whether it is restored normally (Fig. 14).

Abstract

The present invention relates to an amorphous silicon-carbon composite, a method for preparing an amorphous silicon-carbon composite by using a pyrolysis method, and a lithium secondary battery anode and a lithium secondary battery, both of which comprise same.

Description

비정질 실리콘-탄소 복합체, 이의 제조방법 및 이를 포함하는 리튬 이차전지Amorphous silicon-carbon composite, a method of manufacturing the same, and a lithium secondary battery comprising the same
본 출원은 2018년 3월 14일자 한국 특허출원 제10-2018-0029924호 및 2019년 3월 8일자 한국 특허출원 10-2019-0026971호에 기초한 우선권의 이익을 주장하며, 해당 한국 특허 출원의 문헌에 개시된 모든 내용을 본 명세서의 일부로서 포함한다.This application claims the benefit of priority based on Korean Patent Application No. 10-2018-0029924 dated March 14, 2018 and Korean Patent Application No. 10-2019-0026971 dated March 8, 2019, and the documents of the Korean patent application It is intended to include all of the content disclosed herein as part of this specification.
본 발명은 비정질 실리콘-탄소 복합체, 이의 제조방법, 이를 포함하는 리튬 이차전지용 음극 및 리튬 이차전지에 관한 것이다.The present invention relates to an amorphous silicon-carbon composite, a method of manufacturing the same, and a negative electrode and a lithium secondary battery for a lithium secondary battery comprising the same.
리튬 이차전지(예를 들면, 리튬 이온전지), 니켈 수소전지 및 그 외의 이차전지는 차량 탑재용 전원, 또는 노트북 등의 휴대 단말기의 전원으로서 중요성이 높아지고 있다. 특히, 경량으로 고에너지 밀도를 얻을 수 있는 리튬 이차전지는 차량 탑재용 고출력 전원으로 이용될 수 있어서, 향후 계속적인 수요 증대가 전망되고 있다.Lithium secondary batteries (for example, lithium ion batteries), nickel hydride batteries, and other secondary batteries are becoming increasingly important as power supplies for on-board power supplies or portable terminals such as notebook computers. In particular, a lithium secondary battery capable of obtaining high energy density at a light weight can be used as a high output power source for mounting a vehicle, and thus it is expected to continuously increase demand in the future.
리튬 이차전지는 리튬 이온의 삽입 및 탈리가 가능한 물질을 음극의 활물질로 사용하고, 상기 양극과 음극 사이에 다공성 분리막을 설치한 후 액체 전해질을 주입시켜 제조되며, 상기 음극 및 양극에서의 리튬 이온의 삽입 및 탈리에 따른 산화 환원반응에 의해 전기가 생성 또는 소비된다.The lithium secondary battery is manufactured by using a material capable of inserting and detaching lithium ions as an active material of a negative electrode, installing a porous separator between the positive electrode and the negative electrode, and then injecting a liquid electrolyte. Electricity is generated or consumed by redox reactions following insertion and desorption.
구체적으로, 리튬 이차전지에 있어서 음극 활물질로는 리튬의 삽입 및 탈리가 가능한 인조 흑연, 천연 흑연, 하드 카본, 소프트 카본을 포함한 다양한 형태의 탄소계 재료가 적용되어 왔다. 상기 탄소 계열 중 흑연은 흑연을 음극 활물질로 사용한 전지는 3.6V의 높은 방전 전압을 나타낼 뿐만 아니라, 리튬 이차전지의 에너지 밀도 면에서도 이점을 제공하며, 뛰어난 가역성으로 리튬 이차전지의 장수명을 보장하여 가장 널리 사용되고 있다. 그러나 흑연 활물질은 극판 제조시 흑연의 밀도(이론 밀도 2.2g/cc)가 낮아 극판의 단위 부피당 에너지 밀도 측면에서는 용량이 낮고, 높은 전압에서는 사용되는 유기 전해액과의 부반응이 일어나기 쉬워 가스 발생 및 이에 따른 용량 저하의 문제가 있었다.Specifically, in the lithium secondary battery, various types of carbon-based materials including artificial graphite, natural graphite, hard carbon, and soft carbon capable of inserting and detaching lithium have been applied as a negative electrode active material. Among the carbon-based graphites, the graphite not only exhibits a high discharge voltage of 3.6 V, but also provides an advantage in terms of energy density of the lithium secondary battery, and guarantees the long life of the lithium secondary battery with excellent reversibility. It is widely used. However, the graphite active material has a low graphite density (theoretical density of 2.2 g / cc) in the production of the electrode plate, which has a low capacity in terms of energy density per unit volume of the electrode plate, and easily generates side reactions with the organic electrolyte used at high voltages. There was a problem of capacity reduction.
이같은 탄소계 음극 활물질의 문제점을 해결하기 위해, 흑연 대비 용량이 매우 높은 Si계 음극 활물질이 개발, 연구되고 있다. 그러나, 고용량의 Si계 음극소재는 충·방전시 극심한 부피 변화가 수반되며 이로 인해 입자의 쪼개짐이 발생하여 수명 특성이 불량하다는 단점이 있다. 구체적으로 리튬 이온과 합금 및 탈합금화가 가능한 실리콘 또는 실리콘 산화물(SiOx, 0<x<2)계 음극 활물질은 최대 300%까지 부피팽창을 한다. 이와 같은 부피 팽창 및 수축시 SiOx계 음극 활물질은 물리적으로 심한 스트레스를 받게 되고 붕괴(pulverization)되어 버린다. 그 결과로 기존 SEI 층이 파괴되고 새로운 계면이 발생하면서 새로운 SEI층을 형성하게 된다. 이로 인해 지속적인 전해액 분해 및 리튬 이온의 소모가 발생하게 됨으로써 전지의 사이클 특성이 열화된다. 또, 지속적인 충·방전시 SiOx계 음극 활물질의 부피팽창 및 수축에 의해 도전구조가 파괴되어 전극의 내구성이 저하됨으로써 전지 수명이 열화된다.In order to solve such a problem of the carbon-based negative electrode active material, a Si-based negative electrode active material having a much higher capacity than graphite has been developed and studied. However, the high-capacity Si-based negative electrode material is accompanied by a severe volume change during charging and discharging, which causes a breakdown of particles and thus has a disadvantage of poor life characteristics. Specifically, the silicon or silicon oxide (SiO x , 0 <x <2) -based negative electrode active material capable of alloying and dealloying lithium ions has a volume expansion of up to 300%. During such volume expansion and contraction, the SiO x -based negative active material is subjected to severe physical stress and collapses. The result is a breakdown of the existing SEI layer and the creation of a new interface, forming a new SEI layer. This causes continuous electrolyte decomposition and consumption of lithium ions, thereby degrading the cycle characteristics of the battery. In addition, during continuous charging and discharging, the conductive structure is destroyed by the volume expansion and contraction of the SiO x -based negative electrode active material, and durability of the electrode decreases, thereby deteriorating battery life.
이를 해결하기 위해 부피팽창을 완충할 수 있는 공극을 포함하는 복합체가 제안되었다. 그러나 공극 구조를 포함하는 복합체의 경우 전극 제조 중 수반되는 압연과정에서 복합체가 파쇄되어 버리기 쉽고, 밀도가 낮아 높은 로딩량의 전극을 제조하는 것이 어렵다는 문제가 있다.In order to solve this problem, a composite including pores capable of buffering volume expansion has been proposed. However, in the case of a composite including a pore structure, the composite tends to be broken during the rolling process involved in electrode manufacturing, and it is difficult to manufacture an electrode having a high loading amount due to its low density.
또한, 이를 해결하기 위한 방법으로 나노튜브 형태의 SiOx가 개발되었으나, 제조 공정이 어렵고 단가가 높아 상용화가 어렵다는 문제가 있다.In addition, as a method for solving this problem, SiO x in the form of nanotubes has been developed.
[선행기술문헌][Preceding technical literature]
[특허문헌][Patent Documents]
대한민국 등록특허 제10-1612603호, 탄소-실리콘 복합체, 이를 포함하는 이차전지용 음극 활물질 및 탄소-실리콘 복합체를 제조하는 방법Republic of Korea Patent No. 10-1612603, carbon-silicon composite, a method for manufacturing a negative electrode active material and carbon-silicon composite for a secondary battery comprising the same
본 발명은 리튬 이차전지의 충·방전시 부피 변화가 작고, 파편화가 발생하지 않는 비정질 실리콘-탄소 복합체를 제공하는 것을 목적으로 한다.An object of the present invention is to provide an amorphous silicon-carbon composite having a small volume change and no fragmentation during charging and discharging of a lithium secondary battery.
또한, 본 발명은 열분해 방법을 이용하여 제조 공정이 단순한 비정질 실리콘-탄소 복합체 제조방법을 제공하는 것을 목적으로 한다.In addition, an object of the present invention is to provide a method for producing an amorphous silicon-carbon composite having a simple manufacturing process using a pyrolysis method.
또한, 본 발명은 상기 비정질 실리콘-탄소 복합체를 포함하여 전지의 전기 전도도 및 수명 특성을 향상시킬 수 있는 리튬 이차전지의 음극 및 리튬 이차전지를 제공하는 것을 목적으로 한다.In addition, an object of the present invention is to provide a negative electrode and a lithium secondary battery of a lithium secondary battery including the amorphous silicon-carbon composite to improve the electrical conductivity and life characteristics of the battery.
상기 목적을 달성하기 위하여,In order to achieve the above object,
본 발명은 실리콘(Si) 및 탄소(C)가 분자 수준에서 혼합된 비정질 실리콘-탄소 복합체로,The present invention is an amorphous silicon-carbon composite in which silicon (Si) and carbon (C) are mixed at the molecular level,
상기 복합체의 직경은 10nm 내지 1μm인 복합체를 제공한다.The composite provides a composite having a diameter of 10 nm to 1 μm.
또한, 본 발명은 a)탄화수소를 포함하는 실란 화합물을 유기 용매와 혼합하여 혼합액을 제조하는 단계; 및In addition, the present invention comprises the steps of a) preparing a mixed solution by mixing a silane compound containing a hydrocarbon with an organic solvent; And
b)상기 혼합액을 비활성 분위기에서 열분해시켜 기판상에 증착시키는 단계;를 포함하는 비정질 실리콘-탄소 복합체 제조방법 을 제공한다.b) thermally decomposing the mixed solution in an inert atmosphere and depositing the same on a substrate.
또한, 본 발명은 활물질; 도전재; 및 바인더를 포함하는 리튬 이차전지용 음극에 있어서,In addition, the present invention is an active material; Conductive material; In the negative electrode for a lithium secondary battery comprising a binder,
상기 활물질은 상기 본 발명의 비정질 실리콘-탄소 복합체를 포함하는 것을 특징으로 하는 리튬 이차전지용 음극을 제공한다.The active material provides a negative electrode for a lithium secondary battery comprising the amorphous silicon-carbon composite of the present invention.
또한, 본 발명은 양극; 음극; 상기 양극과 음극 사이에 개재되는 분리막; 및 전해액을 포함하는 리튬 이차전지로,In addition, the present invention is an anode; cathode; A separator interposed between the anode and the cathode; And lithium secondary battery comprising an electrolyte,
상기 음극은 상기 본 발명의 음극인 것을 특징으로 하는 리튬 이차전지를 제공한다.The negative electrode provides a lithium secondary battery, characterized in that the negative electrode of the present invention.
본 발명의 비정질 실리콘-탄소 복합체는 실리콘 및 탄소가 분자 단위로 혼합되어 있어 전지의 충·방전시 부피 변화가 작고, 파편화가 발생하지 않는 장점을 지니고 있다.In the amorphous silicon-carbon composite of the present invention, silicon and carbon are mixed in a molecular unit, and thus have a small volume change and no fragmentation during charging and discharging of a battery.
또한, 본 발명의 비정질 실리콘-탄소 복합체의 제조방법은 공정이 단순한 장점을 지니고 있다.In addition, the method of manufacturing the amorphous silicon-carbon composite of the present invention has the advantage of a simple process.
또한, 본 발명의 비정질 실리콘-탄소 복합체를 포함하는 리튬 이차전지는 전기 전도도 및 수명 특성이 우수한 효과를 지니고 있다.In addition, the lithium secondary battery including the amorphous silicon-carbon composite of the present invention has an excellent electrical conductivity and life characteristics.
도 1은 본 발명의 비정질 실리콘-탄소 복합체의 모식도이다.1 is a schematic diagram of an amorphous silicon-carbon composite of the present invention.
도 2는 실시예 1-1에서 제조한 비정질 실리콘-탄소 복합체의 투과 전자 현미경(TEM) 사진이다.2 is a transmission electron microscope (TEM) image of the amorphous silicon-carbon composite prepared in Example 1-1.
도 3은 실시예 1-1에서 제조한 비정질 실리콘-탄소 복합체(Si-C)의 투과 전자 현미경(TEM) 에너지 분산형 분광 분석법을 이용하여 측정한 사진이다.3 is a photograph measured using a transmission electron microscope (TEM) energy dispersive spectroscopy of the amorphous silicon-carbon composite (Si-C) prepared in Example 1-1.
도 4는 비교예 1-1에서 제조한 실리콘-탄소 복합체(Si-Graphite)의 주사 전자 현미경(SEM) 사진이다.4 is a scanning electron microscope (SEM) photograph of the silicon-carbon composite (Si-Graphite) prepared in Comparative Example 1-1.
도 5는 비교예 2-1에서 제조한 실리콘-산소-탄소 복합체(SiOC)의 주사 전자 현미경(SEM) 사진이다.5 is a scanning electron microscope (SEM) photograph of the silicon-oxygen-carbon composite (SiOC) prepared in Comparative Example 2-1.
도 6은 비교예 3-1에서 제조한 비정질 실리콘-탄소 복합체의 주사 전자 현미경(SEM) 사진이다.6 is a scanning electron microscope (SEM) photograph of the amorphous silicon-carbon composite prepared in Comparative Example 3-1.
도 7은 비교예 3-1에서 제조한 비정질 실리콘-탄소 복합체의 투과 전자 현미경(TEM) 사진이다.7 is a transmission electron microscope (TEM) photograph of the amorphous silicon-carbon composite prepared in Comparative Example 3-1.
도 8은 실험예 1의 X선 회절 그래프이다.8 is an X-ray diffraction graph of Experimental Example 1. FIG.
도 9는 실험예 2의 전기 전도도 그래프이다.9 is a graph of electrical conductivity of Experimental Example 2.
도 10는 실시예 1-3, 비교예 1-3 및 비교예 2-3의 초기 충·방전 그래프이다.10 is an initial charge and discharge graph of Example 1-3, Comparative Example 1-3, and Comparative Example 2-3.
도 11은 실시예 1-3 및 비교예 3-3의 초기 충·방전 그래프이다.11 is an initial charge and discharge graph of Example 1-3 and Comparative Example 3-3.
도 12는 실시예 1-3, 비교예 1-3 및 비교예 2-3의 충·방전 수명 특성 그래프이다.12 is a graph showing charge and discharge life characteristics of Examples 1-3, Comparative Examples 1-3, and Comparative Examples 2-3.
도 13은 실시예 1-3 및 비교예 3-3의 충·방전 수명 특성 그래프이다.13 is a graph showing charge and discharge life characteristics of Examples 1-3 and Comparative Examples 3-3.
도 14는 실시예 1-3, 비교예 1-3 및 비교예 2-3의 C-rate에 따른 충·방전 특성 그래프이다.14 is a graph showing charge and discharge characteristics according to C-rate of Examples 1-3, Comparative Examples 1-3, and Comparative Examples 2-3.
이하, 본 발명을 보다 자세히 설명한다.Hereinafter, the present invention will be described in more detail.
실리콘은 흑연 대비 약 10배의 용량을 가지고 있으나, 전지의 충·방전 중에 부피 변화 및 파편화가 발생하여 전지의 수명 특성이 저하되는 문제가 있다.Silicon has a capacity of about 10 times that of graphite, but there is a problem in that the lifespan characteristics of the battery are deteriorated due to volume change and fragmentation occurring during charging and discharging of the battery.
이에, 상기 문제점을 개선하고자 실리콘과 탄소를 단순 혼합하거나, 실리콘 표면에 탄소를 코팅한 후 이를 흑연과 혼합하는 방법 등이 제안되었으나, 상기의 종래 기술들은 실리콘과 탄소간의 접촉이 원활하게 이루어지지 않아 이온 전도도 및 전기 전도도가 우수하지 못할 뿐만 아니라, 실리콘과 탄소의 분포가 고르지 못하여 여전히 상기의 문제점을 해결하지 못하였다.Thus, in order to improve the problem, a method of simply mixing silicon and carbon, or coating carbon on a silicon surface and then mixing it with graphite has been proposed, but the above-described conventional technologies do not facilitate contact between silicon and carbon. Not only are the ionic conductivity and the electrical conductivity not good, but the distribution of silicon and carbon is uneven, which still does not solve the above problem.
따라서, 본 발명에서는 상기의 문제점을 해결하고자 실리콘(Si) 및 탄소(C)가 분자 단위로 혼합된 비정질 실리콘-탄소 복합체를 제공하고자 하였다.Accordingly, the present invention has been made to provide an amorphous silicon-carbon composite in which silicon (Si) and carbon (C) are mixed on a molecular basis.
상기 본 발명의 비정질 실리콘-탄소 복합체는 실리콘 및 탄소가 분자 단위로 혼합되어 있어 상기의 문제점을 해결할 수 있다.In the amorphous silicon-carbon composite of the present invention, silicon and carbon are mixed in a molecular unit, thereby solving the above problems.
비정질 실리콘-탄소 복합체Amorphous silicon-carbon composite
본 발명은 실리콘(Si) 및 탄소(C)가 분자 수준에서 혼합된 비정질 실리콘-탄소 복합체에 관한 것으로, 상기 복합체의 직경은 10nm 내지 1μm이다.The present invention relates to an amorphous silicon-carbon composite in which silicon (Si) and carbon (C) are mixed at the molecular level, and the diameter of the composite is 10 nm to 1 μm.
상기 비정질 실리콘-탄소 복합체는 실리콘 공급원 및 탄소 공급원에 대한 열분해 증착 공정에 의해 형성된 것으로, 상기 복합체는 실리콘-탄소 공유결합, 실리콘-실리콘 공유결합 및 탄소-탄소 공유결합을 포함하고 있으며, 상기 공유 결합은 복합체 내에 불규칙적으로 존재하고 있다.The amorphous silicon-carbon composite is formed by a pyrolytic deposition process for a silicon source and a carbon source, and the composite includes silicon-carbon covalent bonds, silicon-silicon covalent bonds, and carbon-carbon covalent bonds. Is irregularly present in the complex.
또한, 상기 비정질 실리콘-탄소 복합체는 헤테로 원자를 더 포함할 수 있으며, 이 경우 상기 복합체는 헤테로 원자-탄소 공유결합 및 헤테로 원자-실리콘 공유결합 중에서 1종 이상의 결합을 더 포함할 수 있으며, 상기 공유 결합은 복합체 내에 불규칙적으로 존재하고 있다.In addition, the amorphous silicon-carbon composite may further include a hetero atom, in which case the complex may further include one or more bonds among hetero atom-carbon covalent bonds and hetero atom-silicone covalent bonds, and the covalent Bonds are irregularly present in the complex.
이 때 상기 헤테로 원자는 붕소(B), 인(P), 질소(N) 및 황(S)으로 이루어진 군으로부터 선택되는 1종 이상일 수 있다.At this time, the hetero atom may be at least one selected from the group consisting of boron (B), phosphorus (P), nitrogen (N) and sulfur (S).
본 발명에서 상기 비정질 실리콘-탄소 복합체는 탄화수소를 포함하는 실란 화합물의 열분해 증착 공정으로 형성된 것으로, 상기 화합물이 열분해될 때 화합물의 일부분 또는 전체 결합이 끊어져 비정질 실리콘-탄소 복합체가 형성되는 것이다. 즉, 상기 실리콘 공급원 및 탄소 공급원은 탄화수소를 포함하는 실란 화합물일 수 있다. 따라서, 본 발명의 복합체는 농도 구배가 없이 실리콘 및 탄소가 분포되어 있어 이를 리튬 이차전지에 적용시 부피 팽창 문제를 최소화할 수 있으며, 전지의 수명 특성을 향상시킬 수 있다.In the present invention, the amorphous silicon-carbon composite is formed by a pyrolytic deposition process of a silane compound including a hydrocarbon, and when the compound is pyrolyzed, a part or the entire bond of the compound is broken to form an amorphous silicon-carbon composite. That is, the silicon source and carbon source may be a silane compound comprising a hydrocarbon. Therefore, the composite of the present invention is a silicon and carbon is distributed without a concentration gradient it can minimize the volume expansion problem when applied to a lithium secondary battery, it is possible to improve the life characteristics of the battery.
상기 비정질 실리콘-탄소 복합체는 실리콘 및 탄소를 3:7 내지 7:3의 중량비로 포함하고 있다.The amorphous silicon-carbon composite includes silicon and carbon in a weight ratio of 3: 7 to 7: 3.
상기 실리콘이 상기 범위 미만으로 포함되면 전지의 용량이 감소할 수 있으며, 상기 범위를 초과하여 포함되면 전지의 수명이 감소할 수 있다. If the silicon is included below the range may reduce the capacity of the battery, if included beyond the range may reduce the life of the battery.
또한, 상기 탄소가 상기 범위 미만으로 포함되면 전지의 수명이 감소할 수 있으며, 상기 범위를 초과하면 전지의 용량이 감소할 수 있다.In addition, when the carbon is included below the above range, the life of the battery may be reduced, and when the above range is exceeded, the capacity of the battery may be reduced.
상기 비정질 실리콘-탄소 복합체는 극소량의 수소 및 산소를 포함할 수도 있다. The amorphous silicon-carbon composite may include trace amounts of hydrogen and oxygen.
상기 비정질 실리콘-탄소 복합체는 입자 형태로 이루어져 있으며, 상기 복합체의 직경은 10nm 내지 1μm이며, 바람직하게는 100 내지 500nm 일 수 있다. 만약 상기 복합체의 직경이 10nm 미만이면 복합체의 밀도가 크게 낮아질 뿐 아니라 전극의 제조에 어려움이 있고, 1μm를 초과하면 복합체의 전기 전도도가 크게 감소하여 전지의 수명 및 율속 특성이 저하될 수 있다.The amorphous silicon-carbon composite is in the form of particles, the diameter of the composite may be 10nm to 1μm, preferably 100 to 500nm. If the diameter of the composite is less than 10nm, not only the density of the composite is significantly lowered, but also difficult to manufacture the electrode. If the diameter exceeds 1μm, the electrical conductivity of the composite is greatly reduced, thereby deteriorating battery life and rate characteristics.
또한, 상기 비정질 실리콘-탄소 복합체의 밀도는 0.2 내지 0.6g/cc이며, 바람직하게는 0.3 내지 0.5g/cc이다. 상기 밀도가 0.2g/cc 미만이면 전극의 밀도가 낮아져, 즉 동일한 로딩량 대비 전극의 두께가 두꺼워져 전지의 에너지 밀도가 저하되고, 0.6g/cc를 초과하면 전극의 저항이 높아져 율속 특성이 감소된다.In addition, the density of the amorphous silicon-carbon composite is 0.2 to 0.6 g / cc, preferably 0.3 to 0.5 g / cc. If the density is less than 0.2g / cc, the electrode density is low, that is, the thickness of the electrode becomes thicker compared to the same loading amount, so that the energy density of the battery is lowered. If the density exceeds 0.6g / cc, the resistance of the electrode is increased, thereby decreasing the rate characteristic. do.
상기 본 발명의 비정질 실리콘-탄소 복합체는 실리콘 및 탄소가 분자 수준으로 혼합된 것으로 복수의 실리콘 원자, 복수의 탄소 원자 및 이들의 공유 결합으로 이루어져 있으며, 이를 리튬 이차전지의 음극 활물질로 사용 가능하다. The amorphous silicon-carbon composite of the present invention is a mixture of silicon and carbon at a molecular level, and consists of a plurality of silicon atoms, a plurality of carbon atoms, and covalent bonds thereof, and may be used as a negative electrode active material of a lithium secondary battery.
상기 본 발명의 비정질 실리콘-탄소 복합체를 리튬 이차전지에 사용하면 전지 충·방전시 발생하는 실리콘의 부피 변화 및 파편화 등의 문제점을 해결할 수 있으며, 전지의 우수한 전기 전도도 및 수명 특성을 나타낼 수 있다.When the amorphous silicon-carbon composite of the present invention is used in a lithium secondary battery, problems such as volume change and fragmentation of silicon generated during battery charging and discharging may be solved, and the battery may exhibit excellent electrical conductivity and lifespan characteristics.
비정질 실리콘-탄소 복합체 제조방법Method for preparing amorphous silicon-carbon composite
또한, 본 발명은 a)탄화수소를 포함하는 실란 화합물을 유기 용매와 혼합하여 혼합액을 제조하는 단계; 및In addition, the present invention comprises the steps of a) preparing a mixed solution by mixing a silane compound containing a hydrocarbon with an organic solvent; And
b)상기 혼합액을 비활성 분위기에서 열분해시켜 기판상에 증착시키는 단계;를 포함하는 비정질 실리콘-탄소 복합체 제조방법에 관한 것이다.and b) depositing the mixed solution on a substrate by pyrolysis in an inert atmosphere.
상기 a)단계는 탄화수소를 포함하는 실란 화합물을 유기 용매와 혼합하여 혼합액을 제조하는 단계이다.Step a) is a step of preparing a mixed solution by mixing a silane compound containing a hydrocarbon with an organic solvent.
상기 탄화수소를 포함하는 실란 화합물은 실란 구조에 작용기로 탄화수소를 포함하는 화합물로 그 종류를 특별히 한정하는 것은 아니나, 본 발명에서는 바람직하게는 테트라메틸실란, 디메틸실란, 메틸실란, 트리에틸실란, 페닐실란 및 디페닐실란으로 이루어진 군으로부터 선택되는 1종 이상을 포함할 수 있다.The silane compound containing the hydrocarbon is a compound containing a hydrocarbon as a functional group in the silane structure, and the kind thereof is not particularly limited, but in the present invention, tetramethylsilane, dimethylsilane, methylsilane, triethylsilane, and phenylsilane are preferred. And it may include one or more selected from the group consisting of diphenylsilane.
또한, 상기 탄화수소를 포함하는 실란 화합물은 헤테로 원자를 더 포함하는 화합물일 수 있다.In addition, the silane compound including the hydrocarbon may be a compound further comprising a hetero atom.
본 발명에서는 헤테로 원자가 실리콘 및 탄소와 공유결합을 이룰 수 있는 것이라면 화합물의 종류를 특별히 한정하지는 않는다. 상기 헤테로 원자는 붕소(B), 인(P), 질소(N) 및 황(S)으로 이루어진 군으로부터 선택되는 1종 이상일 수 있다.In the present invention, the kind of the compound is not particularly limited as long as the hetero atom can form a covalent bond with silicon and carbon. The hetero atom may be at least one selected from the group consisting of boron (B), phosphorus (P), nitrogen (N) and sulfur (S).
상기 유기 용매는 탄화수소를 포함하는 실란 화합물을 용해시킬 수 있는 것이라면 그 종류를 특별히 한정하지 않고 사용할 수 있으며, 바람직하게는 끓는점이 약 100℃ 이상이며, 점도가 높지 않고, 600℃ 이상의 온도에서 탄화가 일어나지 않는 유기 용매가 사용될 수 있으며, 본 발명에서는 구체적으로 예를 들어 톨루엔, 벤젠, 에틸벤젠, 자일렌, 메시틸렌, 헵탄 및 옥탄으로 이루어진 군으로부터 선택되는 1종 이상을 포함할 수 있다. The organic solvent may be used without particular limitation as long as it can dissolve the silane compound containing hydrocarbon, preferably, the boiling point is about 100 ° C. or higher, the viscosity is not high, and carbonization is performed at a temperature of 600 ° C. or higher. Organic solvents that do not occur may be used, and in the present invention may specifically include one or more selected from the group consisting of, for example, toluene, benzene, ethylbenzene, xylene, mesitylene, heptane and octane.
상기 유기 용매는 끓는점이 비교적 낮은 탄화수소를 포함하는 실란 화합물의 끓는점을 보완하기 위한 희석 용도로 사용되는 것이며, 열분해 온도가 800℃ 이상이면 유기 용매의 열분해도 함께 일어날 수 있어 제조되는 비정질 실리콘-탄소 복합체 내 추가적인 탄소를 제공하여 실리콘 및 탄소의 비율을 조절하는 역할을 수행할 수 있다.The organic solvent is used as a dilution to compensate for the boiling point of the silane compound including a hydrocarbon having a relatively low boiling point, and when the pyrolysis temperature is 800 ° C. or higher, thermal decomposition of the organic solvent may occur together. It can serve to control the ratio of silicon and carbon by providing additional carbon within.
상기 화합물 및 유기 용매의 혼합은 상온에서 약 10 내지 30분 동안 이루어지는 것이 바람직하다.Mixing of the compound and the organic solvent is preferably performed for about 10 to 30 minutes at room temperature.
상기 b)단계는 상기 혼합액을 비활성 분위기에서 열분해시켜 기판 상에 증착시키는 단계이다.In step b), the mixed solution is thermally decomposed in an inert atmosphere and deposited on a substrate.
구체적으로 상기 열분해는 상기 혼합액에 비활성 가스를 공급하여 버블링시키는 공정에 의해 수행되는 것이며, 상기 비활성 분위기는 바람직하게는 아르곤(Ar) 가스 분위기이다.Specifically, the pyrolysis is performed by a process of bubbling by supplying an inert gas to the mixed solution, and the inert atmosphere is preferably an argon (Ar) gas atmosphere.
상기 열분해 온도는 600 내지 900℃이며, 상기 열분해 온도가 600℃ 미만이면 탄화수소를 포함하는 실란 화합물의 열분해가 이루어지지 않아 비정질 실리콘-탄소 복합체를 제조할 수 없고, 900℃를 초과하면 유기 용매의 직접적인 분해가 일어나 실리콘 및 탄소의 바람직한 혼합비를 벗어날 수 있을 뿐만 아니라, 그 함량을 조절하는 것이 어렵다.The pyrolysis temperature is 600 to 900 ℃, if the pyrolysis temperature is less than 600 ℃ can not produce an amorphous silicon-carbon composite due to the thermal decomposition of the silane compound containing a hydrocarbon, Above 900 ° C., direct decomposition of the organic solvent may occur to escape the desired mixing ratio of silicon and carbon, as well as to control its content.
비정질 실리콘-탄소 복합체 내에 수소의 함량이 높으면 전지 작동 시 수소 가스가 발생하여 전지 용량이 저하되는 문제가 발생한다. 열분해 온도가 상기 온도 범위 내일지라도 온도가 높을수록 비정질 실리콘-탄소 복합체 내 수소의 함량을 감소시킬 수 있으므로 열분해 온도는 700 내지 800℃인 것이 바람직하다.When the content of hydrogen in the amorphous silicon-carbon composite is high, hydrogen gas is generated during operation of the battery, resulting in a problem that the battery capacity is lowered. Even if the pyrolysis temperature is within the above temperature range, the higher the temperature, the lower the content of hydrogen in the amorphous silicon-carbon composite, so the pyrolysis temperature is preferably 700 to 800 ° C.
또한, 상기 열분해는 10분 내지 1시간 동안 이루어지며, 바람직하게는 30분 내지 1시간 동안 이루어진다.In addition, the pyrolysis is made for 10 minutes to 1 hour, preferably 30 minutes to 1 hour.
상기 혼합액에 포함된 화합물, 또는 화합물 및 유기 용매가 열분해됨으로써 최종적으로 실리콘(Si) 및 탄소(C)가 분자 수준으로 혼합된 비정질 실리콘-탄소 복합체를 제조할 수 있다.By thermal decomposition of the compound, or the compound and the organic solvent contained in the mixture, it is possible to prepare an amorphous silicon-carbon composite in which silicon (Si) and carbon (C) is finally mixed at the molecular level.
보다 자세하게는, 상기 열분해로 생성된 비정질 실리콘-탄소 복합체는 기판 위에 증착되며, 상기 증착된 복합체를 분리하는 단계를 더 포함하여 최종적으로 입자 형태의 비정질 실리콘-탄소 복합체를 제조할 수 있다. 상기 증착된 복합체의 분리 방법을 본 발명에서 특별히 한정하는 것은 아니나, 바람직하게는 볼밀(ball-mill) 공정을 사용할 수 있다.More specifically, the amorphous silicon-carbon composite produced by the pyrolysis is deposited on a substrate, and further comprising the step of separating the deposited composite can finally produce an amorphous silicon-carbon composite in the form of particles. The method for separating the deposited composite is not particularly limited in the present invention, but preferably, a ball-mill process may be used.
상기 증착된 복합체의 직경은 1μm를 초과하는 크기를 가지며, 기판으로부터 분리되어 입자 형태를 가지는 비정질 실리콘-탄소 복합체의 직경은 10nm 내지 1μm이며, 바람직하게는 100 내지 500nm 일 수 있다. 만약 상기 복합체의 직경이 10nm 미만이면 복합체의 밀도가 크게 낮아질 뿐 아니라 전극의 제조에 어려움이 있고, 1μm를 초과하면 복합체의 전기 전도도가 크게 감소하여 전지의 수명 및 율속 특성이 저하될 수 있다.The diameter of the deposited composite has a size of more than 1μm, the diameter of the amorphous silicon-carbon composite having a particle form separated from the substrate is 10nm to 1μm, preferably 100 to 500nm. If the diameter of the composite is less than 10nm, not only the density of the composite is significantly lowered, but also difficult to manufacture the electrode. If the diameter exceeds 1μm, the electrical conductivity of the composite is greatly reduced, thereby deteriorating battery life and rate characteristics.
상기 기판의 종류는 본 발명에서 특별히 한정하는 것은 아니며, 바람직하게는 실리콘 또는 알루미나 기판 등을 사용할 수 있다.The kind of the substrate is not particularly limited in the present invention, and preferably, a silicon or alumina substrate can be used.
본 발명의 일 구현예로, 상기 화합물과 유기 용매를 상온에서 혼합한 혼합액을 준비한다. 퍼니스에 기판을 넣어준 후 퍼니스 내부에 비활성 기체를 흘려주어 비활성 분위기로 만든 뒤 가열하여 퍼니스 내부의 온도를 일정하게 맞춰준다. 그 후 상기 혼합액을 퍼니스로 흘려주어 탄화수소를 포함하는 실란 화합물을 열분해하여 비정질 실리콘-탄소 복합체를 제조하며, 상기 복합체는 기판 위에 증착된다. 상기 기판 위에 증착된 복합체를 볼밀 등의 공정을 통하여 입자 형태의 비정질 실리콘-탄소 복합체를 수득할 수 있다.In one embodiment of the present invention, a mixed solution of the compound and the organic solvent at room temperature is prepared. After placing the substrate in the furnace, an inert gas is flowed into the furnace to make it inert atmosphere and heated to adjust the temperature inside the furnace at a constant temperature. Thereafter, the mixture is poured into a furnace to pyrolyze a silane compound including a hydrocarbon to prepare an amorphous silicon-carbon composite, and the composite is deposited on a substrate. The composite deposited on the substrate may be obtained through a process such as a ball mill to obtain an amorphous silicon-carbon composite in the form of particles.
상기 비정질 실리콘-탄소 복합체는 기판 증착 후 볼밀 등의 복합체를 분리하는 공정을 통하여 입자 형태로 제조되며, 상기 비정질 실리콘-탄소 복합체는 입자 형태로 이루어져 있으며, 상기 입자 형태의 비정질 실리콘-탄소 복합체의 직경은 10nm 내지 1μm이며, 바람직하게는 100nm 내지 500nm 일 수 있다. The amorphous silicon-carbon composite is manufactured in the form of particles through a process of separating a complex such as a ball mill after substrate deposition, the amorphous silicon-carbon composite is in the form of particles, the diameter of the amorphous silicon-carbon composite in the form of particles Is 10 nm to 1 μm, and preferably 100 nm to 500 nm.
본 발명의 제조방법은 단순 열분해 방법을 통하여 비정질 실리콘-탄소 복합체를 제조하는 것으로, 제조 공정이 단순한 장점을 지니고 있다. The production method of the present invention is to prepare an amorphous silicon-carbon composite through a simple pyrolysis method, the manufacturing process has a simple advantage.
리튬 이차전지용 음극Cathode for Lithium Secondary Battery
본 발명은 활물질; 도전재; 및 바인더를 포함하는 리튬 이차전지용 음극에 관한 것으로, 상기 활물질은 상기 본 발명의 비정질 실리콘-탄소 복합체를 포함한다.The present invention is an active material; Conductive material; And it relates to a negative electrode for a lithium secondary battery comprising a binder, the active material comprises the amorphous silicon-carbon composite of the present invention.
구체적으로, 상기 음극은 음극 집전체 상에 형성된 음극 활물질을 포함하며, 상기 음극 활물질은 본 발명에 따라 제조된 비정질 실리콘-탄소 복합체를 사용한다. Specifically, the negative electrode includes a negative electrode active material formed on the negative electrode current collector, the negative electrode active material uses an amorphous silicon-carbon composite prepared according to the present invention.
상기 음극 집전체는 구체적으로 구리, 스테인리스스틸, 티타늄, 은, 팔라듐, 니켈, 이들의 합금 및 이들의 조합으로 이루어진 군에서 선택되는 것일 수 있다. 상기 스테인리스스틸은 카본, 니켈, 티탄 또는 은으로 표면 처리될 수 있으며, 상기 합금으로는 알루미늄-카드뮴 합금이 사용될 수 있다. 그 외에도 소성 탄소, 도전재로 표면 처리된 비전도성 고분자, 또는 전도성 고분자 등이 사용될 수도 있다.The negative electrode current collector may be specifically selected from the group consisting of copper, stainless steel, titanium, silver, palladium, nickel, alloys thereof, and combinations thereof. The stainless steel may be surface treated with carbon, nickel, titanium, or silver, and an aluminum-cadmium alloy may be used as the alloy. In addition, calcined carbon, a nonconductive polymer surface-treated with a conductive material, or a conductive polymer may be used.
상기 도전재는 전극 활물질의 도전성을 더욱 향상시키기 위해 사용한다.　이러한 도전재는 당해 전지에 화학적 변화를 유발하지 않으면서 도전성을 가진 것이라면 특별히 제한되는 것은 아니며, 예를 들어, 천연 흑연이나 인조 흑연 등의 흑연; 카본블랙, 아세틸렌 블랙, 케첸 블랙, 채널 블랙, 퍼니스 블랙, 램프 블랙, 서머 블랙 등의 카본블랙; 탄소 섬유나 금속 섬유 등의 도전성 섬유; 불화 카본, 알루미늄, 니켈 분말 등의 금속 분말; 산화아연, 티탄산 칼륨 등의 도전성 휘스커; 산화티탄 등의 도전성 금속 산화물; 폴리페닐렌 유도체 등이 사용될 수 있다.The said conductive material is used in order to improve the electroconductivity of an electrode active material further. Such a conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery, and examples thereof include graphite such as natural graphite and artificial graphite; Carbon blacks such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black and summer black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride powder, aluminum powder and nickel powder; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Polyphenylene derivatives and the like can be used.
상기 바인더는 전극 활물질과 도전재의 결합과 집전체에 대한 결합을 위해 사용한다. 이러한 바인더의 비제한적인 예로는, 폴리비닐리덴플로라이드(PVDF), 폴리비닐알코올(PVA), 폴리아크릴산(PAA), 폴리메타크릴산(PMA), 폴리메틸메타크릴레이트(PMMA) 폴리아크릴아미드(PAM), 폴리메타크릴아미드, 폴리아크릴로니트릴(PAN), 폴리메타크릴로니트릴, 폴리이미드(PI), 알긴산(Alginic acid), 알지네이트(Alginate), 키토산(Chitosan), 카르복시메틸셀룰로오스(CMC), 전분, 하이드록시프로필셀룰로오스, 재생 셀룰로오스, 폴리비닐피롤리돈, 테트라플루오로에틸렌, 폴리에틸렌, 폴리프로필렌, 에틸렌-프로필렌-디엔 폴리머(EPDM), 술폰화-EPDM, 스티렌-부타디엔 고무(SBR), 불소 고무, 이들의 다양한 공중합체 등을 들 수 있다.The binder is used for bonding the electrode active material and the conductive material to the current collector. Non-limiting examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polyacrylic acid (PAA), polymethacrylic acid (PMA), polymethyl methacrylate (PMMA) polyacrylamide (PAM), polymethacrylamide, polyacrylonitrile (PAN), polymethacrylonitrile, polyimide (PI), alginic acid, alginate, chitosan, carboxymethylcellulose (CMC) ), Starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber (SBR) , Fluororubbers, various copolymers thereof, and the like.
또한, 상기 음극은 충진제 및 기타 첨가제 등을 추가로 포함할 수 있다.In addition, the negative electrode may further include a filler and other additives.
리튬 이차전지Lithium secondary battery
또한, 본 발명은 양극; 음극; 상기 양극과 음극 사이에 개재되는 분리막; 및 전해액을 포함하는 리튬 이차전지로, 상기 음극은 상술한 상기 본 발명의 음극인 것을 특징으로 하는 리튬 이차전지에 관한 것이다.In addition, the present invention is an anode; cathode; A separator interposed between the anode and the cathode; And a lithium secondary battery comprising an electrolyte, the negative electrode relates to a lithium secondary battery characterized in that the negative electrode of the present invention described above.
상기 리튬 이차전지의 양극, 음극, 분리막 및 전해액의 구성은 본 발명에서 특별히 한정하지 않으며, 이 분야에서 공지된 바를 따른다.The configuration of the positive electrode, the negative electrode, the separator and the electrolyte of the lithium secondary battery is not particularly limited in the present invention, and is known in the art.
양극은 양극 집전체 상에 형성된 양극 활물질을 포함한다.The positive electrode includes a positive electrode active material formed on a positive electrode current collector.
양극 집전체는 당해 전지에 화학적 변화를 유발하지 않으면서 높은 도전성을 가지는 것이라면 특별히 제한되지 않으며, 예를 들면 스테인리스 스틸, 알루미늄, 니켈, 티탄, 소성 탄소, 또는 알루미늄이나 스테인리스 스틸의 표면에 카본, 니켈, 티탄, 은 등으로 표면 처리한 것 등이 사용될 수 있다. 이때, 상기 양극 집전체는 양극 활물질과의 접착력을 높일 수도 있도록, 표면에 미세한 요철이 형성된 필름, 시트, 호일, 네트, 다공질체, 발포체, 부직포체 등 다양한 형태를 사용할 수 있다.The positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery, and for example, carbon, nickel on the surface of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel Surface treated with titanium, silver, or the like can be used. In this case, the positive electrode current collector may use various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric having fine irregularities formed on a surface thereof so as to increase the adhesion with the positive electrode active material.
전극층을 구성하는 양극 활물질은 당해 기술분야에서 이용 가능한 모든 양극 활물질이 사용 가능하다. 이러한 양극 활물질의 구체적인 예로서, 리튬 금속; LiCoO2 등의 리튬 코발트계 산화물; Li1+xMn2-xO4(여기서, x는 0 내지 0.33임), LiMnO3, LiMn2O3, LiMnO2 등의 리튬 망간계 산화물; Li2CuO2 등의 리튬 구리산화물; LiV3O8, LiFe3O4, V2O5, Cu2V2O7 등의 바나듐 산화물; LiNi1-xMxO2 (여기서, M=Co, Mn, Al, Cu, Fe, Mg, B 또는 Ga 이고, x=0.01 내지 0.3임)으로 표현되는 리튬 니켈계 산화물; LiMn2-xMxO2(여기서, M=Co, Ni, Fe, Cr, Zn 또는 Ta 이고, x=0.01 내지 0.1임) 또는 Li2Mn3MO8(여기서, M=Fe, Co, Ni, Cu 또는 Zn 임)으로 표현되는 리튬 망간 복합산화물; Li(NiaCobMnc)O2(여기에서, 0＜a＜1, 0＜b＜1, 0＜c＜1, a+b+c=1)으로 표현되는 리튬-니켈-망간-코발트계 산화물; LiV3O8, LiFe3O4, V2O5, Cu2V2O7 등의 바나듐 산화물; 황 또는 디설파이드 화합물; LiFePO4, LiMnPO4, LiCoPO4, LiNiPO4 등의 인산염; Fe2(MoO4)3 등을 들 수 있지만, 이들만으로 한정되는 것은 아니다.As the cathode active material constituting the electrode layer, any cathode active material available in the art may be used. Specific examples of such a cathode active material include lithium metal; Lithium cobalt oxides such as LiCoO 2 ; Lithium manganese oxides such as Li 1 + x Mn 2-x O 4 (where x is 0 to 0.33), LiMnO 3 , LiMn 2 O 3 , LiMnO 2, and the like; Lithium copper oxides such as Li 2 CuO 2 ; Vanadium oxides such as LiV 3 O 8 , LiFe 3 O 4 , V 2 O 5 , Cu 2 V 2 O 7 and the like; Lithium nickel-based oxides represented by LiNi 1-x M x O 2 , wherein M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3; LiMn 2-x M x O 2 , where M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 to 0.1, or Li 2 Mn 3 MO 8 , where M = Fe, Co, Ni , Lithium manganese composite oxide represented by Cu or Zn; Lithium-nickel-manganese-cobalt represented by Li (Ni a Co b Mn c ) O 2 (wherein 0 <a <1, 0 <b <1, 0 <c <1, a + b + c = 1) Type oxides; Vanadium oxides such as LiV 3 O 8 , LiFe 3 O 4 , V 2 O 5 , Cu 2 V 2 O 7 and the like; Sulfur or disulfide compounds; Phosphates such as LiFePO 4 , LiMnPO 4 , LiCoPO 4 , LiNiPO 4 and the like; Fe 2 (MoO 4 ) 3 and the like, but are not limited to these.
이 때, 상기 전극층은 양극 활물질 이외에 바인더, 도전재, 충진제 및 기타 첨가제 등을 추가로 포함할 수 있으며, 상기 바인더 및 도전재는 상기 리튬 이차전지용 음극에 상술한 내용과 동일하다.In this case, the electrode layer may further include a binder, a conductive material, a filler, and other additives in addition to the positive electrode active material, and the binder and the conductive material are the same as described above for the negative electrode for the lithium secondary battery.
상기 분리막은 다공성 기재로 이루어질 수 있는데, 상기 다공성 기재는, 통상적으로 전기화학소자에 사용되는 다공성 기재라면 모두 사용이 가능하고, 예를 들면 폴리올레핀계 다공성 막 또는 부직포를 사용할 수 있으나, 이에 특별히 한정되는 것은 아니다.The separator may be made of a porous substrate, and the porous substrate may be used as long as it is a porous substrate that is typically used in an electrochemical device. For example, a polyolefin-based porous membrane or a nonwoven fabric may be used. It is not.
상기 분리막은, 폴리에틸렌, 폴리프로필렌, 폴리부틸렌, 폴리펜텐, 폴리에틸렌 테레프탈레이트, 폴리부틸렌 테레프탈레이트, 폴리에스테르, 폴리아세탈, 폴리아마이드, 폴리카보네이트, 폴리이미드, 폴리에테르에테르케톤, 폴리에테르설폰, 폴리페닐렌 옥사이드, 폴리페닐렌 설파이드, 및 폴리에틸렌 나프탈레이트로 이루어진 군으로부터 선택된 어느 하나 또는 이들 중 2종 이상의 혼합물로 이루어진 다공성 기재일 수 있다.The separator is polyethylene, polypropylene, polybutylene, polypentene, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyether ether ketone, polyether sulfone, It may be a porous substrate composed of any one selected from the group consisting of polyphenylene oxide, polyphenylene sulfide, and polyethylene naphthalate or a mixture of two or more thereof.
상기 리튬 이차전지의 전해액은 리튬염을 함유하는 비수계 전해액으로서 리튬염과 용매로 구성되어 있으며, 용매로는 비수계 유기용매, 유기 고체 전해질 및 무기 고체 전해질 등이 사용된다.The electrolyte of the lithium secondary battery is a non-aqueous electrolyte containing lithium salt and is composed of a lithium salt and a solvent, and a non-aqueous organic solvent, an organic solid electrolyte and an inorganic solid electrolyte are used as the solvent.
상기 리튬염은 상기 비수계 전해액에 용해되기 좋은 물질로서, 예를 들어, LiCl, LiBr, LiI, LiClO4, LiBF4, LiB10Cl10, LiPF6, LiAsF6, LiSbF6, LiAlCl4, LiSCN, LiC4BO8, LiCF3CO2, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC4F9SO3, LiC(CF3SO2)3, (CF3SO2)·2NLi, 클로로 보란 리튬, 저급 지방족 카르본산 리튬, 4 페닐 붕산 리튬 이미드 등이 사용될 수 있다.The lithium salt is a material that is easy to dissolve in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO 4 , LiBF 4 , LiB 10 Cl 10 , LiPF 6 , LiAsF 6 , LiSbF 6 , LiAlCl 4 , LiSCN, LiC 4 BO 8 , LiCF 3 CO 2 , LiCH 3 SO 3 , LiCF 3 SO 3 , LiN (SO 2 CF 3 ) 2 , LiN (SO 2 C 2 F 5 ) 2 , LiC 4 F 9 SO 3 , LiC (CF 3 SO 2 ) 3 , (CF 3 SO 2 ) .2NLi, lithium chloroborane, lower aliphatic lithium carbonate, lithium tetraphenyl borate imide and the like can be used.
비수계 유기용매는, 예를 들어, N-메틸-2-피롤리돈, 프로필렌 카보네이트, 에틸렌 카보네이트, 부틸렌 카보네이트, 디메틸 카보네이트, 디에틸 카보네이트, 에틸메틸 카보네이트, 감마-부티로락톤, 1,2-디메톡시 에탄, 1,2-디에톡시 에탄, 테트라하이드록시 프랑(franc), 2-메틸 테트라하이드로푸란, 디메틸술폭시드, 1,3-디옥솔란, 4-메틸-1,3-디옥센, 디에틸에테르, 포름아마이드, 디메틸포름아마이드, 디옥솔란, 아세토니트릴, 니트로메탄, 포름산메틸, 초산메틸, 인산 트리에스테르, 트리메톡시 메탄, 디옥솔란 유도체, 설포란, 메틸설포란, 1,3-디메틸-2-이미다졸리디논, 프로필렌 카보네이트 유도체, 테트라하이드로푸란 유도체, 에테르, 프로피온산 메틸, 프로피온산 에틸 등의 비양자성 유기용매가 사용될 수 있다.The non-aqueous organic solvent is, for example, N-methyl-2-pyrrolidone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, gamma-butyrolactone, 1,2 Dimethoxy ethane, 1,2-diethoxy ethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, 4-methyl-1,3-dioxene, Diethyl ether, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxy methane, dioxolane derivatives, sulfolane, methylsulforane, 1,3- Aprotic organic solvents such as dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate and ethyl propionate can be used.
상기 유기 고체 전해질로는, 예를 들어, 폴리에틸렌 유도체, 폴리에틸렌 옥사이드 유도체, 폴리프로필렌 옥사이드 유도체, 인산 에스테르 폴리머, 폴리 에지테이션 리신(agitation lysine), 폴리에스테르 술파이드, 폴리비닐알코올, 폴리 불화 비닐리덴, 이차성 해리기를 포함하는 중합체 등이 사용될 수 있다.Examples of the organic solid electrolytes include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate ester polymers, polyagitation lysine, polyester sulfides, polyvinyl alcohol, polyvinylidene fluoride, Polymers including secondary dissociation groups and the like can be used.
상기 무기 고체 전해질로는, 예를 들어, Li3N, LiI, Li5NI2, Li3N-LiI-LiOH, LiSiO4, LiSiO4-LiI-LiOH, Li2SiS3, Li4SiO4, Li4SiO4-LiI-LiOH, Li3PO4-Li2S-SiS2 등의 Li의 질화물, 할로겐화물, 황산염 등이 사용될 수 있다.Examples of the inorganic solid electrolyte include 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 , Nitrides, halides, sulfates and the like of Li, such as Li 4 SiO 4 -LiI-LiOH, Li 3 PO 4 -Li 2 S-SiS 2 , and the like, may be used.
또한, 비수계 전해액에는 충방전 특성, 난연성 등의 개선을 목적으로 기타 첨가제를 더 포함할 수 있다. 상기 첨가제의 예시로는 피리딘, 트리에틸포스파이트, 트리에탄올아민, 환상 에테르, 에틸렌 디아민, n-글라임(glyme), 헥사 인산 트리 아마이드, 니트로벤젠 유도체, 유황, 퀴논 이민 염료, N-치환 옥사졸리디논, N,N-치환 이미다졸리딘, 에틸렌 글리콜 디알킬 에테르, 암모늄염, 피롤, 2-메톡시에탄올, 삼염화 알루미늄, 플루오로에틸렌 카보네이트(FEC), 프로펜 설톤(PRS), 비닐렌 카보네이트(VC) 등을 들 수 있다.In addition, the non-aqueous electrolyte may further include other additives for the purpose of improving charge / discharge characteristics, flame retardancy, and the like. Examples of the additives include pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexa phosphate triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazoli Dinon, N, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride, fluoroethylene carbonate (FEC), propene sultone (PRS), vinylene carbonate ( VC) etc. are mentioned.
본 발명에 따른 리튬 이차전지는, 일반적인 공정인 권취(winding) 이외에도 분리막과 전극의 적층(lamination, stack) 및 접음(folding) 공정이 가능하다. 그리고 상기 전지케이스는 원통형, 각형, 파우치(pouch)형 또는 코인(coin)형 등이 될 수 있다.Lithium secondary battery according to the present invention, in addition to the winding (winding) which is a general process, it is possible to lamination (stacking) and folding (folding) of the separator and the electrode. The battery case may be cylindrical, square, pouch type, or coin type.
이하 본 발명의 이해를 돕기 위하여 바람직한 실시예를 제시하나, 하기 실시예는 본 발명을 예시하는 것일 뿐 본 발명의 범주 및 기술사상 범위 내에서 다양한 변경 및 수정이 가능함은 당업자에게 있어서 명백한 것이며, 이러한 변경 및 수정이 첨부된 특허청구범위에 속하는 것도 당연한 것이다.Hereinafter, preferred examples are provided to help the understanding of the present invention, but the following examples are merely for exemplifying the present invention, and various changes and modifications within the scope and spirit of the present invention are apparent to those skilled in the art. It goes without saying that changes and modifications belong to the appended claims.
실시예 1.Example 1.
1-1. 비정질 실리콘-탄소 복합체 제조1-1. Amorphous Silicon-Carbon Composites
10mL의 테트라메틸실란(tetramethylsilane, TMS)을 10mL의 톨루엔에 용해시킨 뒤 상온에서 10 내지 30분 동안 혼합하여 혼합액을 제조하였다. 10 mL of tetramethylsilane (TMS) was dissolved in 10 mL of toluene and mixed at room temperature for 10 to 30 minutes to prepare a mixed solution.
퍼니스에 비정질 실리콘-탄소 복합체가 증착될 실리콘 웨이퍼(wafer)를 넣어준 후, 500cc/min 속도로 아르곤(Ar) 가스(순도 99.999%)를 흘려주어 퍼니스 내부를 비활성 분위기로 만들었다. 이 후 10℃/min의 승온 속도로 퍼니스를 가열하여 750℃까지 가열시켰다. 퍼니스의 온도가 750℃로 도달한 후 10 내지 30분 동안 상기 온도를 유지하여 퍼니스 내부의 온도를 일정하게 맞추었다. After the silicon wafer (a wafer) on which the amorphous silicon-carbon composite is to be deposited was placed in the furnace, argon (Ar) gas (purity 99.999%) was flowed at a rate of 500 cc / min to make the inside of the furnace in an inert atmosphere. Thereafter, the furnace was heated at a temperature rising rate of 10 ° C./min and heated up to 750 ° C. After the furnace temperature reached 750 ° C., the temperature was maintained for 10 to 30 minutes to keep the temperature inside the furnace constant.
그 후 상기 혼합액을 100cc/min의 속도로 퍼니스 내부에 주입하고, 아르곤 가스를 흘려 버블링 시켜 상기 혼합액을 열분해 시켰다. Thereafter, the mixed solution was injected into the furnace at a rate of 100 cc / min, and argon gas was flowed and bubbled to thermally decompose the mixed solution.
열분해 후 퍼니스의 온도를 상온까지 떨어뜨린 후 퍼니스 내부의 기판 위에 분해된 비정질 실리콘-탄소 복합체를 수득하며, 상기 복합체를 볼밀(ball-mill)을 통하여 입자 형태의 실리콘(Si) 및 탄소(C)가 분자 수준에서 혼합된 비정질 실리콘-탄소 복합체(Si-C)를 제조하였다(도 2 및 도 3). 상기 실리콘-탄소 복합체의 직경은 약 200nm이었으며, 밀도는 0.42g/cc이었다.After pyrolysis, the furnace temperature is lowered to room temperature to obtain an amorphous silicon-carbon composite decomposed on the substrate inside the furnace, and the composite is passed through a ball mill to form silicon (Si) and carbon (C) in the form of particles. Amorphous silicon-carbon composites (Si-C) mixed at the molecular level were prepared (FIGS. 2 and 3). The silicon-carbon composite had a diameter of about 200 nm and a density of 0.42 g / cc.
1-2. 극판 제조1-2. Pole plate manufacturing
상기 실시예 1-1에서 제조한 비정질 실리콘-탄소 복합체를 음극 활물질로 사용하였다. 음극 활물질 80 중량%, 바인더 (PAA/CMC, 1:1 중량비) 10 중량%, 도전재(super-P) 10 중량% 를 물에 분산시켜 음극 슬러리를 만들고 구리 전극에 도포하여 극판을 제조하였다.The amorphous silicon-carbon composite prepared in Example 1-1 was used as a negative electrode active material. 80 wt% of the negative electrode active material, 10 wt% of the binder (PAA / CMC, 1: 1 weight ratio), and 10 wt% of the conductive material (super-P) were dispersed in water to form a negative electrode slurry, and the electrode plate was manufactured by coating on a copper electrode.
1-3. 리튬 이차전지 제조1-3. Lithium Secondary Battery Manufacturing
상기 실시예 1-2에서 제조한 극판을 음극으로 사용하였다. 대극으로 리튬 메탈을 사용하고 상기 음극과 대극의 중간에 폴리에틸렌 분리막을 개재한 후, 1.3M LiPF6를 사용한 에틸렌카보네이트 및 디메틸카보네이트의 혼합 용매(EC/DEC, 3:7, 부피비)를 전해액으로 사용하였으며, 첨가제로 FEC 10 중량%를 사용하여 코인셀을 제조하였다.The electrode plate prepared in Example 1-2 was used as the negative electrode. Lithium metal was used as a counter electrode and a polyethylene separator was interposed between the cathode and the counter electrode, and then a mixed solvent of ethylene carbonate and dimethyl carbonate (EC / DEC, 3: 7, volume ratio) using 1.3 M LiPF 6 was used as an electrolyte. Coin cells were prepared using 10% by weight of FEC as an additive.
비교예 1.Comparative Example 1.
1-1. 실리콘-탄소 복합체 제조1-1. Silicon-Carbon Composites Manufacturing
수명특성 평가시 방전용량으로 600mAh/g에 맞추기 위하여 Si(이론용량 약 3500mAh/g) 약 15wt%, Graphite(이론용량 약 372mAh/g) 약 85wt% 를 유발로 단순 혼합하여 실리콘-탄소 복합체(Si-Graphite)를 제조하였다(도 4).When evaluating the lifespan characteristics, the silicon-carbon composites (Si) were simply mixed by inducing about 15wt% of Si (about 3500mAh / g) and about 85wt% of graphite (about 372mAh / g) to meet 600mAh / g of discharge capacity. -Graphite) was prepared (FIG. 4).
1-2. 극판 제조1-2. Pole plate manufacturing
상기 비교예 1-1에서 제조한 실리콘-탄소 복합체(Si-Graphite)를 음극 활물질로 사용한 것을 제외하고는 상기 실시예 1-2와 동일하게 실시하여 극판을 제조하였다.Except for using a silicon-carbon composite (Si-Graphite) prepared in Comparative Example 1-1 as a negative electrode active material was carried out in the same manner as in Example 1-2 to prepare a negative electrode plate.
1-3. 리튬 이차전지 제조1-3. Lithium Secondary Battery Manufacturing
상기 비교예 1-2에서 제조한 극판을 음극으로 사용한 것을 제외하고는 상기 실시예 1-3과 동일하게 실시하여 코인셀을 제조하였다.A coin cell was manufactured in the same manner as in Example 1-3, except that the cathode plate prepared in Comparative Example 1-2 was used as a cathode.
비교예 2. Comparative Example 2.
2-1. 실리콘-산소-탄소 복합체 제조2-1. Silicon-Oxygen-Carbon Composites
3g의 실리콘 오일(silicone oil)을 알루미나 용기에 담아 비활성 분위기의 퍼니스에서 900℃로 열처리 하였다. 그 후 퍼니스 내부의 온도를 상온으로 떨어뜨린 후, 실리콘-산소-탄소 복합체(SiOC)를 수득하였다(도 5).3g of silicone oil (silicone oil) was placed in an alumina container and heat-treated at 900 ° C. in an inert atmosphere furnace. After the temperature inside the furnace was dropped to room temperature, a silicon-oxygen-carbon composite (SiOC) was obtained (FIG. 5).
2-2. 극판 제조2-2. Pole plate manufacturing
상기 비교예 2-1에서 제조한 실리콘-탄소 복합체(Si-Graphite)를 음극 활물질로 사용한 것을 제외하고는 상기 실시예 1-2와 동일하게 실시하여 극판을 제조하였다.Except for using a silicon-carbon composite (Si-Graphite) prepared in Comparative Example 2-1 as a negative electrode active material was carried out in the same manner as in Example 1-2 to prepare a cathode plate.
2-3. 리튬 이차전지 제조2-3. Lithium Secondary Battery Manufacturing
상기 비교예 2-2에서 제조한 극판을 음극으로 사용한 것을 제외하고는 상기 실시예 1-3과 동일하게 실시하여 코인셀을 제조하였다.A coin cell was manufactured in the same manner as in Example 1-3, except that the cathode plate prepared in Comparative Example 2-2 was used as the cathode.
비교예 3.Comparative Example 3.
3-1. 비정질 실리콘-탄소 복합체 제조3-1. Amorphous Silicon-Carbon Composites
볼밀 단계를 실시하지 않은 것을 제외하고는 상기 실시예 1-1과 동일하게 실시하여 비정질 실리콘-탄소 복합체(Si-C)를 제조하였다(도 6 및 도 7). 상기 실리콘-탄소 복합체의 직경은 약 3μm이었으며, 밀도는 0.66g/cc이었다.An amorphous silicon-carbon composite (Si-C) was prepared in the same manner as in Example 1-1 except that the ball mill step was not performed (FIGS. 6 and 7). The diameter of the silicon-carbon composite was about 3 μm and the density was 0.66 g / cc.
3-2. 극판 제조3-2. Pole plate manufacturing
상기 비교예 3-1에서 제조한 실리콘-탄소 복합체(Si-Graphite)를 음극 활물질로 사용한 것을 제외하고는 상기 실시예 1-2와 동일하게 실시하여 극판을 제조하였다.Except for using a silicon-carbon composite (Si-Graphite) prepared in Comparative Example 3-1 as a negative electrode active material was carried out in the same manner as in Example 1-2 to prepare a negative electrode plate.
3-3. 리튬 이차전지 제조3-3. Lithium Secondary Battery Manufacturing
상기 비교예 3-2에서 제조한 극판을 음극으로 사용한 것을 제외하고는 상기 실시예 1-3과 동일하게 실시하여 코인셀을 제조하였다.A coin cell was manufactured in the same manner as in Example 1-3, except that the cathode plate prepared in Comparative Example 3-2 was used as a cathode.
실험예 1. 복합체의 결정 구조 분석Experimental Example 1. Crystal structure analysis of the complex
상기 실시예 1-1에서 제조한 비정질 실리콘-탄소 복합체(Si-C), 비교예 1-1에서 제조한 실리콘-탄소 복합체(Si-Graphite) 및 비교예 2-1에서 제조한 실리콘-산소-탄소 복합체(SiOC)의 XRD를 측정하였다(도 8).Amorphous silicon-carbon composite (Si-C) prepared in Example 1-1, silicon-carbon composite (Si-Graphite) prepared in Comparative Example 1-1 and silicon-oxygen- prepared in Comparative Example 2-1 XRD of the carbon composite (SiOC) was measured (FIG. 8).
실시예 1-1의 실리콘-탄소 복합체(Si-C)는 32도 및 60도에서 넓은 영역의 피크가 나타났다. 비교예 1-1의 실리콘-탄소 복합체(Si-Graphite)의 실리콘은 비정질이 아닌 결정질이므로 6개의 실리콘 피크(약 28도, 47도, 56도, 69도, 76도 및 88도)가 선명하게 나타났으며, 약 26도, 35도 및 44도 등에서 Graphite의 피크가 나타났다. 또한, 비교예 2-1의 실리콘-산소-탄소 복합체(SiOC)는 30도 및 42도에서 넓은 영역의 피크가 나타났다. The silicon-carbon composite (Si-C) of Example 1-1 showed a wide area peak at 32 degrees and 60 degrees. Since the silicon of the silicon-carbon composite (Si-Graphite) of Comparative Example 1-1 is not amorphous, the six silicon peaks (approximately 28 degrees, 47 degrees, 56 degrees, 69 degrees, 76 degrees, and 88 degrees) are clear. The peaks of Graphite appeared at about 26 degrees, 35 degrees, and 44 degrees. In addition, the silicon-oxygen-carbon composite (SiOC) of Comparative Example 2-1 showed a wide area peak at 30 degrees and 42 degrees.
따라서, 상기 실시예 1-1, 비교예 1-1 및 2-1에서 제조된 복합체는 서로 다른 물질 및 물성을 갖는 것을 확인할 수 있었다.Therefore, the composites prepared in Examples 1-1, Comparative Examples 1-1, and 2-1 were confirmed to have different materials and physical properties.
실험예 2. 극판의 전기 전도도 평가Experimental Example 2. Evaluation of the electrical conductivity of the electrode plate
상기 실시예 1-2, 비교예 1-2 및 비교예 2-2에서 제조한 극판을 4침법(Four-point probe)을 사용하여 전기 전도도를 측정하였다(도 9).The electrode plates prepared in Example 1-2, Comparative Example 1-2, and Comparative Example 2-2 were measured for electrical conductivity using a four-point probe (Four-point probe) (Fig. 9).
실시예 1-2의 극판은 전기 전도도가 우수하여 낮은 저항수치를 나타냈다. 비교예 1-2의 극판은 Graphite가 탄소층이 겹겹이 쌓여진 형태로 전기 전도도가 매우 우수한 물질이므로 전기 전도도가 우수하여 낮은 저항 수치를 나타냈다. 그러나 비교예 2-3의 극판은 세라믹 물질인 실리콘-산소-탄소 복합체(SiOC)를 포함하고 있어 낮은 전기 전도도를 나타내며, 이로 인하여 매우 높은 저항을 보였다.The electrode plate of Example 1-2 had excellent electrical conductivity and showed low resistance value. The electrode plate of Comparative Example 1-2 had a low resistance value due to its excellent electrical conductivity because Graphite had a very good electrical conductivity in the form of stacked carbon layers. However, the electrode plate of Comparative Example 2-3 contained a silicon-oxygen-carbon composite (SiOC), which is a ceramic material, and thus exhibited low electrical conductivity, thereby showing a very high resistance.
실험예 3. 전지 성능 평가 Experimental Example 3. Battery Performance Evaluation
상기 실시예 1-3, 비교예 1-3, 비교예 2-3 및 비교예 3-3에서 제조한 코인셀의 초기 충·방전 평가, 수명특성 평가 및 율속특성 평가를 실시하였다.Initial charge / discharge evaluation, life characteristic evaluation, and rate rate characteristic evaluation of the coin cells prepared in Examples 1-3, Comparative Example 1-3, Comparative Example 2-3, and Comparative Example 3-3 were performed.
(1)초기 충·방전 평가(1) Initial charge and discharge evaluation
실리콘 복합체의 종류에 따른 충·방전 특성을 관찰하기 위하여, 상기 실시예 1-3, 비교예 1-3 및 비교예 2-3에서 제조한 코인셀의 충·방전 속도를 0.05 C-rate로 고정하였으며, 작동전압을 0.005~2.5V로 설정하여 코인셀의 충·방전 특성을 측정하였다(도 10).In order to observe the charge and discharge characteristics according to the type of the silicon composite, the charge and discharge rate of the coin cells prepared in Example 1-3, Comparative Example 1-3 and Comparative Example 2-3 is fixed to 0.05 C-rate And, the operating voltage was set to 0.005 ~ 2.5V to measure the charge and discharge characteristics of the coin cell (Fig. 10).
실시예 1-3, 비교예 1-3 및 비교예 2-3의 코인셀 모두 C-rate가 증가함에 따라 용량이 감소하였으며, 마지막 0.2 C-rate 에서는 초기용량 수준으로 복원되는 결과를 보였다.The capacity of all of the coin cells of Examples 1-3, Comparative Examples 1-3, and Comparative Examples 2-3 decreased with increasing C-rate, and the final 0.2 C-rate showed a result of restoring to the initial dose level.
또한, 실리콘 복합체의 직경 크기에 따른 충·방전 특성을 관찰하기 위하여 실시예 1-3 및 비교예 3-3에서 제조한 코인셀의 충·방전 특성을 관찰하였으며, 실험 방법은 상기와 동일하게 실시하였다(도 11).In addition, in order to observe the charge and discharge characteristics according to the diameter size of the silicone composite, the charge and discharge characteristics of the coin cells prepared in Examples 1-3 and Comparative Example 3-3 were observed, and the experimental method was carried out as described above. (FIG. 11).
그 결과를 하기 표 1에 나타내었다.The results are shown in Table 1 below.
복합체 크기Composite size 충전 용량(mAh/g)Charge capacity (mAh / g) 방전 용량(mAh/g)Discharge Capacity (mAh / g) 효율(%)efficiency(%)
실시예 1-3Example 1-3 약 200nmAbout 200nm 11821182 892.4892.4 75.575.5
비교예 3-3Comparative Example 3-3 약 3μmAbout 3μm 927927 579.4579.4 62.562.5
상기 표 1의 결과에서, 실리콘 복합체의 직경이 작은 실시예 1-3이 실리콘 복합체의 직경이 1μm를 초과한 비교예 3-3 보다 충·방전 특성이 우수한 것을 확인할 수 있었다.In the results of Table 1, it can be seen that Example 1-3 having a smaller diameter of the silicone composite has superior charge and discharge characteristics than Comparative Example 3-3, which has a diameter of the silicone composite exceeding 1 μm.
이로부터 실리콘 복합체의 직경이 작을수록 우수한 충·방전 효과를 나타내는 것을 알 수 있다.It can be seen from this that the smaller the diameter of the silicone composite is, the better the charge and discharge effect is.
(2)수명특성 평가(2) Life characteristics evaluation
실리콘 복합체의 종류에 따른 수명 특성을 관찰하기 위하여, 상기 실시예 1-3, 비교예 1-3 및 비교예 2-3에서 제조한 코인셀의 충·방전 속도를 0.2 C-rate로 고정하였으며, 작동전압을 0.005~2.5V로 설정하여 50 cycle을 진행하여 코인셀의 수명특성을 측정하였으며, 결과를 하기 표 2 및 도 12에 나타내었다.In order to observe the life characteristics according to the type of the silicon composite, the charge and discharge rate of the coin cells prepared in Examples 1-3, Comparative Examples 1-3 and Comparative Examples 2-3 was fixed to 0.2 C-rate, The lifetime characteristics of the coin cell were measured by setting the operating voltage to 0.005 to 2.5V and performing 50 cycles, and the results are shown in Table 2 and FIG. 12.
초기 용량(mAh/g)Initial capacity (mAh / g) 50 cycle 후 용량(mAh/g)Capacity after 50 cycles (mAh / g)
실시예 1-3Example 1-3 10361036 10331033
비교예 1-3Comparative Example 1-3 640640 556556
비교예 2-3Comparative Example 2-3 348348 281281
실시예 1-3의 코인셀은 사이클이 진행되어도 전지의 용량이 거의 감소하지 않아 수명특성이 우수한 결과를 보였다.The coin cell of Example 1-3 showed excellent life characteristics because the capacity of the battery hardly decreased even after the cycle progressed.
그러나, 비교예 1-3의 코인셀은 Graphite 입자에 실리콘이 점으로 접촉되어 있는 형태이기 때문에 매우 불안정한 연결이므로, 사이클이 진행됨에 따라 실리콘의 부피 팽창이 일어나 전지의 용량이 감소하여 수명 특성이 좋지 못하였다.However, the coin cell of Comparative Examples 1-3 is a very unstable connection because silicon is in contact with the graphite particles with dots, and as the cycle progresses, the volume expansion of the silicon causes the capacity of the battery to decrease, resulting in poor life characteristics. I could not.
또한, 비교예 2-3의 코인셀도 사이클이 진행될수록 전지의 용량이 감소하여 수명 특성이 좋지 못하였다.In addition, the coin cell of Comparative Example 2-3 also had a poor battery life as the capacity of the battery decreased as the cycle progressed.
또한, 실리콘 복합체의 직경 크기에 따른 수명 특성을 관찰하기 위하여 실시예 1-3 및 비교예 3-3에서 제조한 코인셀의 수명 특성을 관찰하였으며, 실험 방법은 100cycle을 진행한 것을 제외하고는 상기와 동일하게 실시하였다(도 13).In addition, in order to observe the life characteristics according to the diameter size of the silicone composite, the life characteristics of the coin cells prepared in Examples 1-3 and Comparative Examples 3-3 were observed, except that the experimental method was 100cycle It carried out similarly to (FIG. 13).
그 결과, 실시예 1-3은 50cylce 이전에 용량이 포화되며 안정적인 수명특성을 보였으나, 비교예 3-3은 100cycle 동안에 포화되지 못하고 낮은 용량을 보였다.As a result, Example 1-3 showed a saturation capacity and stable life characteristics before 50cylce, while Comparative Example 3-3 did not saturate for 100 cycles and showed a low capacity.
따라서, 실리콘 복합체의 직경이 작을수록 우수한 수명 특성 효과를 나타내는 것을 알 수 있다.Therefore, it can be seen that the smaller the diameter of the silicone composite exhibits an excellent life characteristic effect.
(3)율속특성 평가(3) evaluation of speed characteristics
상기 실시예 1-3, 비교예 1-3 및 비교예 2-3에서 제조한 코인셀의 충방전 속도를 0.2 C-rate로 20 cycle, 0.5 C-rate로 10 cycle을 진행하였으며, 그 후 5 cycle마다 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 C-rate로 충방전 속도를 조절하였으며, 마지막으로 0.2-rate로 돌아와 정상적으로 다시 복원되는지 확인하였다(도 14).The charge and discharge rates of the coin cells prepared in Examples 1-3, Comparative Examples 1-3 and Comparative Examples 2-3 were 20 cycles at 0.2 C-rate, 10 cycles at 0.5 C-rate, and then 5 Each cycle, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 C-rate was adjusted to charge and discharge rate, and finally returned to 0.2-rate to check whether it is restored normally (Fig. 14).
실시예 1-3 및 비교예 2-3의 코인셀 모두 사이클이 진행될수록 전지 용량이 감소하였으며, 마지막 0.2-rate에서 초기용량 수준으로 복원되는 결과를 보였다.Both cycles of the coin cells of Examples 1-3 and Comparative Examples 2-3 decreased as the cycle progressed, and the result was restored to the initial capacity level at the last 0.2-rate.
그러나, 비교예 1-3의 코인셀의 경우, Graphite 층과 층 사이에 리튬 이온을 인터칼레이션(intercalation) 형태로 저장하여 리튬 이온의 이동 속도가 매우 느리다. 따라서 비교예 1-3의 코인셀은 율속 특성이 우수하지 못한 결과를 보였다. 실시예 1-3의 코인셀의 경우, 합금(alloy) 형태로 리튬 이온을 저장하기 때문에 Graphite 보다 상대적으로 낮은 전기 전도도를 가지더라도 율속 특성이 우수한 것을 확인할 수 있었다.However, in the coin cell of Comparative Examples 1-3, lithium ions are stored in the form of intercalation between the graphite layer and the layer, and thus the movement speed of the lithium ions is very slow. Therefore, the coin cell of Comparative Example 1-3 showed a result in which the rate characteristic was not excellent. In the case of the coin cell of Example 1-3, because the lithium ions are stored in the alloy (alloy) form, it was confirmed that the rate-rate characteristics are excellent even though having a relatively low electrical conductivity than Graphite.
상기 결과로부터, 실리콘 및 탄소가 분자 수준에서 혼합되며, 직경이 10nm 내지 1μm인 비정질 실리콘-탄소 복합체는 전기 전도도, 충·방전 특성 및 수명 특성이 우수한 효과를 나타내는 것을 확인할 수 있었다.From the above results, it was confirmed that silicon and carbon are mixed at the molecular level, and the amorphous silicon-carbon composite having a diameter of 10 nm to 1 μm exhibits excellent electrical conductivity, charge / discharge characteristics, and lifetime characteristics.

Claims (18)

  1. 실리콘(Si) 및 탄소(C)가 분자 수준에서 혼합된 비정질 실리콘-탄소 복합체로,An amorphous silicon-carbon composite in which silicon (Si) and carbon (C) are mixed at the molecular level,
    상기 비정질 실리콘-탄소 복합체의 직경은 10nm 내지 1μm인 것을 특징으로 하는 비정질 실리콘-탄소 복합체.Amorphous silicon-carbon composite, characterized in that the diameter of the amorphous silicon-carbon composite is 10nm to 1μm.
  2. 청구항 1에 있어서, 상기 비정질 실리콘-탄소 복합체는 실리콘-탄소 공유결합, 실리콘-실리콘 공유결합 및 탄소-탄소 공유결합을 불규칙하게 포함하는 것을 특징으로 하는 비정질 실리콘-탄소 복합체.The amorphous silicon-carbon composite of claim 1, wherein the amorphous silicon-carbon composite includes irregularly silicon-carbon covalent bonds, silicon-silicon covalent bonds, and carbon-carbon covalent bonds.
  3. 청구항 2에 있어서, 상기 비정질 실리콘-탄소 복합체는 헤테로 원자를 더 포함하며, 헤테로 원자-탄소 공유결합 및 헤테로 원자-실리콘 공유결합 중에서 1종 이상의 결합을 더 포함하는 것을 특징으로 하는 비정질 실리콘-탄소 복합체.The amorphous silicon-carbon composite of claim 2, wherein the amorphous silicon-carbon composite further includes a hetero atom, and further includes one or more bonds among hetero atom-carbon covalent bonds and hetero atom-silicon covalent bonds. .
  4. 청구항 3에 있어서, 상기 헤테로 원자는 붕소, 인, 질소 및 황으로 이루어진 군으로부터 선택되는 1종 이상인 것을 특징으로 하는 비정질 실리콘-탄소 복합체.The amorphous silicon-carbon composite according to claim 3, wherein the hetero atom is at least one member selected from the group consisting of boron, phosphorus, nitrogen, and sulfur.
  5. 청구항 1에 있어서, 상기 비정질 실리콘-탄소 복합체는 실리콘 및 탄소를 3:7 내지 7:3의 중량비로 포함하는 것을 특징으로 하는 비정질 실리콘-탄소 복합체.The amorphous silicon-carbon composite according to claim 1, wherein the amorphous silicon-carbon composite includes silicon and carbon in a weight ratio of 3: 7 to 7: 3.
  6. 청구항 1에 있어서, 상기 비정질 실리콘-탄소 복합체의 밀도는 0.2 내지 0.6g/cc인 것을 특징으로 하는 비정질 실리콘-탄소 복합체.The amorphous silicon-carbon composite of claim 1, wherein the amorphous silicon-carbon composite has a density of 0.2 to 0.6 g / cc.
  7. 청구항 1에 있어서, 상기 비정질 실리콘-탄소 복합체는 실리콘(Si) 공급원 및 탄소(C) 공급원에 대한 열분해 증착 공정에 의해 형성되는 것을 특징으로 하는 비정질 실리콘-탄소 복합체.The amorphous silicon-carbon composite of claim 1, wherein the amorphous silicon-carbon composite is formed by a pyrolytic deposition process for a silicon (Si) source and a carbon (C) source.
  8. a)탄화수소를 포함하는 실란 화합물을 유기 용매와 혼합하여 혼합액을 제조하는 단계; 및a) mixing a silane compound containing hydrocarbon with an organic solvent to prepare a mixed solution; And
    b)상기 혼합액을 비활성 분위기에서 열분해시켜 기판 상에 증착시키는 단계;를 포함하는 비정질 실리콘-탄소 복합체 제조방법.b) thermally decomposing the mixed solution in an inert atmosphere and depositing the same on a substrate.
  9. 청구항 8에 있어서, 상기 탄화수소를 포함하는 실란 화합물은 테트라메틸실란, 디메틸실란, 메틸실란, 트리에틸실란, 페닐실란 및 디페닐실란으로 이루어진 군으로부터 선택되는 1종 이상을 포함하는 것을 특징으로 하는 비정질 실리콘-탄소 복합체 제조방법.The amorphous silane compound containing hydrocarbon according to claim 8, wherein the silane compound comprises at least one member selected from the group consisting of tetramethylsilane, dimethylsilane, methylsilane, triethylsilane, phenylsilane and diphenylsilane. Silicon-carbon composite production method.
  10. 청구항 8에 있어서, 상기 a)단계에서 탄화수소를 포함하는 실란 화합물은 헤테로 원자를 더 포함하는 화합물인 것을 특징으로 하는 비정질 실리콘-탄소 복합체 제조방법.The method of claim 8, wherein the silane compound containing a hydrocarbon in step a) is a compound further comprising a hetero atom.
  11. 청구항 10에 있어서, 상기 헤테로 원자는 붕소, 인, 질소 및 황으로 이루어진 군으로부터 선택되는 1종 이상인 것을 특징으로 하는 비정질 실리콘-탄소 복합체 제조방법.The method of claim 10, wherein the hetero atom is at least one member selected from the group consisting of boron, phosphorus, nitrogen, and sulfur.
  12. 청구항 8에 있어서, 상기 a)단계에서 유기 용매는 톨루엔, 벤젠, 에틸벤젠, 자일렌, 메시틸렌, 헵탄 및 옥탄으로 이루어진 군으로부터 선택되는 1종 이상을 포함하는 것을 특징으로 하는 비정질 실리콘-탄소 복합체 제조방법.The amorphous silicon-carbon composite according to claim 8, wherein the organic solvent in step a) comprises at least one member selected from the group consisting of toluene, benzene, ethylbenzene, xylene, mesitylene, heptane and octane. Manufacturing method.
  13. 청구항 8에 있어서, 상기 b)단계에서 열분해 온도는 600 내지 900℃인 것을 특징으로 하는 비정질 실리콘-탄소 복합체 제조방법.The method of claim 8, wherein the pyrolysis temperature in step b) is 600 to 900 ° C. 11.
  14. 청구항 8에 있어서, 상기 b)단계에서 열분해는 혼합액에 비활성 가스를 공급하여 버블링시키는 공정에 의해 수행되는 것을 특징으로 하는 비정질 실리콘-탄소 복합체 제조방법.The method of claim 8, wherein the pyrolysis in step b) is performed by supplying an inert gas to the mixed solution and bubbling.
  15. 청구항 8에 있어서, 상기 기판으로부터 증착된 비정질 실리콘-탄소 복합체를 분리하는 단계를 더 포함하는 것을 특징으로 하는 비정질 실리콘-탄소 복합체 제조방법.The method of claim 8, further comprising separating the amorphous silicon-carbon composite deposited from the substrate.
  16. 청구항 15에 있어서, 상기 분리된 비정질 실리콘-탄소 복합체의 직경은 10nm 내지 1μm인 것을 특징으로 하는 비정질 실리콘-탄소 복합체 제조방법.The method of claim 15, wherein the separated amorphous silicon-carbon composite has a diameter of 10 nm to 1 μm.
  17. 활물질; 도전재; 및 바인더를 포함하는 리튬 이차전지용 음극에 있어서,Active material; Conductive material; In the negative electrode for a lithium secondary battery comprising a binder,
    상기 활물질은 청구항 1 내지 7 중 어느 한 항의 비정질 실리콘-탄소 복합체를 포함하는 것을 특징으로 하는 리튬 이차전지용 음극.The active material is a lithium secondary battery negative electrode comprising the amorphous silicon-carbon composite of any one of claims 1 to 7.
  18. 양극; 음극; 상기 양극과 음극 사이에 개재되는 분리막; 및 전해액을 포함하는 리튬 이차전지로,anode; cathode; A separator interposed between the anode and the cathode; And lithium secondary battery comprising an electrolyte,
    상기 음극은 청구항 17의 음극인 것을 특징으로 하는 리튬 이차전지.The negative electrode is a lithium secondary battery, characterized in that the negative electrode of claim 17.
PCT/KR2019/002843 2018-03-14 2019-03-12 Amorphous silicon-carbon composite, preparation method therefor, and lithium secondary battery comprising same WO2019177338A1 (en)

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