WO2018182343A1 - Binder composition for secondary battery, and electrode for secondary battery and lithium secondary battery comprising same - Google Patents

Binder composition for secondary battery, and electrode for secondary battery and lithium secondary battery comprising same Download PDF

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Publication number
WO2018182343A1
WO2018182343A1 PCT/KR2018/003746 KR2018003746W WO2018182343A1 WO 2018182343 A1 WO2018182343 A1 WO 2018182343A1 KR 2018003746 W KR2018003746 W KR 2018003746W WO 2018182343 A1 WO2018182343 A1 WO 2018182343A1
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weight
acrylate
secondary battery
methacrylate
parts
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PCT/KR2018/003746
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French (fr)
Korean (ko)
Inventor
윤지희
유정우
김제영
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주식회사 엘지화학
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Priority claimed from KR1020180035834A external-priority patent/KR102290957B1/en
Application filed by 주식회사 엘지화학 filed Critical 주식회사 엘지화학
Priority to JP2019548849A priority Critical patent/JP7034407B2/en
Priority to US16/325,500 priority patent/US11024851B2/en
Priority to PL18776291T priority patent/PL3483964T3/en
Priority to EP18776291.9A priority patent/EP3483964B1/en
Priority to CN201880003405.7A priority patent/CN109716566B/en
Publication of WO2018182343A1 publication Critical patent/WO2018182343A1/en

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L25/00—Compositions of, homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring; Compositions of derivatives of such polymers
    • C08L25/02—Homopolymers or copolymers of hydrocarbons
    • C08L25/04—Homopolymers or copolymers of styrene
    • C08L25/08—Copolymers of styrene
    • C08L25/10—Copolymers of styrene with conjugated dienes
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L29/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal or ketal radical; Compositions of hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Compositions of derivatives of such polymers
    • C08L29/02—Homopolymers or copolymers of unsaturated alcohols
    • C08L29/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L33/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides or nitriles thereof; Compositions of derivatives of such polymers
    • C08L33/04—Homopolymers or copolymers of esters
    • C08L33/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, which oxygen atoms are present only as part of the carboxyl radical
    • C08L33/08—Homopolymers or copolymers of acrylic acid esters
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L33/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides or nitriles thereof; Compositions of derivatives of such polymers
    • C08L33/24—Homopolymers or copolymers of amides or imides
    • C08L33/26—Homopolymers or copolymers of acrylamide or methacrylamide
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a secondary battery binder composition, and a secondary battery electrode and a lithium secondary battery comprising the same, and more particularly to a binder composition having a suitable wet strength, a secondary battery electrode and a lithium secondary battery comprising the same.
  • An electrode of a lithium secondary battery is prepared by mixing a positive electrode active material or a negative electrode active material with a binder resin component and dispersing it in a solvent to make a slurry, and applying this to the surface of an electrode current collector to form a mixture layer after drying.
  • the binder is used to secure adhesion or binding force between the active material and the active material, and between the active material and the electrode current collector, but an excess binder is required to improve the adhesion between the electrode current collector and the active material.
  • the excess binder has a problem of lowering the electrode capacity and conductivity.
  • insufficient adhesive force causes the electrode peeling phenomenon in the process of electrode drying, pressing, etc., thereby increasing the electrode defect rate.
  • an electrode with low adhesive force may be peeled off by an external impact, and this electrode peeling may increase contact resistance between the electrode material and the current collector, which may cause deterioration of electrode output performance.
  • the binder and the use of the present invention can provide a secondary battery having improved performance by providing better adhesion and solving an electrochemical performance deterioration problem due to electrode peeling, detachment of the active material from the current collector, or a change in contact interface between the active materials.
  • the problem to be solved by the present invention is to provide a binder composition for a secondary battery that can improve the life performance of the battery by maintaining a high mechanical properties even after the electrolyte solution impregnation while providing more excellent adhesion.
  • Another object of the present invention is to provide a secondary battery electrode comprising the secondary battery binder composition.
  • Another object of the present invention is to provide a lithium secondary battery including the secondary battery electrode.
  • the present invention to solve the above problems, (a) from a unit derived from a vinyl monomer, (b) a unit derived from a conjugated diene monomer or a conjugated diene polymer, and (c) from a (meth) acrylic acid ester monomer
  • a copolymer binder comprising at least one unit selected from the group consisting of derived units, and (D) units derived from water-soluble polymers, wherein the copolymer binder has a wet modulus of at least 0.02 MPa. It provides a binder composition for secondary batteries.
  • the present invention provides a negative electrode for a lithium secondary battery comprising the silicon-based negative electrode active material and the secondary battery binder composition in order to solve the other problem.
  • the present invention provides a lithium secondary battery comprising the electrode for a lithium secondary battery, in order to solve the another problem.
  • the binder composition for a secondary battery according to the present invention includes a copolymer binder including a hydrophilic functional group, and because the copolymer binder has a wet modulus of a predetermined value or more, the copolymer binder exhibits improved adhesion and In addition, high mechanical properties can be maintained even after the electrolyte is impregnated to improve the life performance of the battery.
  • Figure 2 is a graph showing the results of measuring the change in the discharge capacity up to 30 cycles in the charge and discharge current density 0.5 C conditions for the lithium secondary batteries prepared in Example 4 and Comparative Examples 3 and 4.
  • Example 4 is a graph showing the results of measuring the change in the discharge capacity of up to 200 cycles in the charge and discharge current density 0.33 C conditions for the lithium secondary batteries prepared in Example 8 and Comparative Example 5.
  • the binder composition for a lithium secondary battery comprises (a) a unit derived from a vinyl monomer, (b) a unit derived from a conjugated diene monomer or a conjugated diene polymer, and (c) a (meth) acrylic acid ester monomer.
  • a copolymer binder comprising at least one unit selected from the group consisting of derived units, and (D) units derived from water-soluble polymers, wherein the copolymer binder has a wet modulus of at least 0.02 MPa. will be.
  • the copolymer binder may have a wet strength of 0.02 MPa or more, specifically 0.1 MPa or more, more specifically 0.3 MPa to 0.5 MPa, and when the copolymer binder has a wet strength in the above range, swelling by an electrolyte solution This may be appropriately suppressed, and the life characteristics of the electrode and the secondary battery including the same may be improved by maintaining appropriate mechanical properties.
  • the wet strength is obtained by impregnating the copolymer binder in a conventional electrolyte solution used as a lithium secondary battery, and then applying a load to the copolymer binder to generate the inside of the copolymer binder through a stress-strain curve. It can be measured by grasping the relationship between tensile strength (Stress) and tensile strain (Strain).
  • the wet strength indicates the strength of the copolymer binder in the state of being impregnated with the electrolyte as in the actual driving environment of the lithium secondary battery, and thus the dry strength of the copolymer binder in the driving environment of the actual lithium secondary battery. Compared with the dry modulus, it has a different meaning from the higher dry strength.
  • the wet strength value of the copolymer binder can be achieved by controlling the content of the hydrophilic functional group of the copolymer binder, and specifically by appropriately adjusting the content of units derived from the (d) water-soluble polymer included in the copolymer binder.
  • the copolymer binder may have an appropriate wet strength value.
  • the copolymer has a total weight of 100 parts by weight based on (a) 1 to 70 parts by weight of units derived from vinyl monomers, (b) 10 to parts by weight of units derived from conjugated diene monomers or conjugated diene polymers. 97 parts by weight, (C) 1 to 30 parts by weight of the unit derived from the (meth) acrylic acid ester monomer, and (D) 1 to 70 parts by weight of the unit derived from the water-soluble polymer.
  • the copolymer may be based on a total weight of 100 parts by weight of (a) 20 parts by weight to 70 parts by weight of a unit derived from a vinyl monomer, (b) a unit derived from a conjugated diene monomer or a conjugated diene polymer. 10 parts by weight to 60 parts by weight, (c) 1 part by weight to 20 parts by weight of a unit derived from a (meth) acrylic acid ester monomer, and (d) 1 part by weight to 60 parts by weight of a unit derived from a water-soluble polymer. have.
  • the copolymer may be derived from (a) 30 parts by weight to 60 parts by weight of a unit derived from a vinyl monomer, (b) a conjugated diene monomer or a conjugated diene polymer based on a total weight of 100 parts by weight. 15 to 30 parts by weight of the unit, (c) 4 to 8 parts by weight of the unit derived from the (meth) acrylic acid ester monomer, and (d) 2 to 50 parts by weight of the unit derived from the water-soluble polymer.
  • a) 30 parts by weight to 60 parts by weight of a unit derived from a vinyl monomer a conjugated diene monomer or a conjugated diene polymer based on a total weight of 100 parts by weight. 15 to 30 parts by weight of the unit, (c) 4 to 8 parts by weight of the unit derived from the (meth) acrylic acid ester monomer, and (d) 2 to 50 parts by weight of the unit derived from the water-soluble polymer.
  • the copolymer is a unit derived from the (a) vinyl monomer, (b) a unit derived from a conjugated diene monomer or a conjugated diene polymer, and (c) a unit derived from a (meth) acrylic acid ester monomer.
  • the copolymer binder can exhibit excellent adhesion and strength.
  • the copolymer binder may have an excellent wet strength value.
  • the copolymer binder may have a particle shape and have an average particle diameter (D 50 ) of 100 nm to 1 ⁇ m, specifically 300 nm to 500 nm.
  • the copolymer binder has the average particle diameter (D 50 ), it can exhibit an appropriate adhesion, the electrolyte swelling phenomenon is small, and exhibits the proper elasticity to accommodate the change in the thickness of the electrode and reduce the gas generation phenomenon have.
  • the average particle diameter (D 50 ) can be defined as the particle size at 50% of the particle size distribution.
  • the average particle diameter is not particularly limited, but may be measured using, for example, a laser diffraction method or a scanning electron microscope (SEM) photograph.
  • the laser diffraction method can measure a particle diameter of about several mm from the submicron region, and a result having high reproducibility and high resolution can be obtained.
  • the units contained in the copolymer binder are as follows.
  • the vinyl monomer may be at least one selected from the group consisting of styrene, ⁇ -methylstyrene, ⁇ -methylstyrene, p-t-butylstyrene, and divinylbenzene.
  • the conjugated diene monomer is 1,3-butadiene, isoprene, chloroprene or piperylene
  • the conjugated diene polymer is 1,3- Polymers of two or more monomers selected from the group consisting of butadiene, isoprene, chloroprene, and piperylene, styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, styrene-isoprene copolymers, acrylate-butadiene rubbers, acrylo Nitrile-butadiene-styrene rubber, ethylene-propylene-diene based polymers, and these may be at least one selected from the group consisting of partially hydrogenated, epoxidized, or brominated polymers.
  • the (c) (meth) acrylic acid ester monomers are methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate.
  • the water-soluble polymer is a unit derived from a (meth) acrylic acid ester monomer, a unit derived from a (meth) acryl amide monomer, an unsaturated carboxylic acid monomer and a vinyl acetate monomer. It may be a copolymer including one or more units selected from the group consisting of derived units, and the production method is not particularly limited, but may be prepared according to, for example, suspension polymerization, emulsion polymerization, seed polymerization, or the like.
  • the (meth) acrylic acid ester monomer is methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n- amyl acrylate, iso amyl acrylate, n- Ethylhexyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl Methacrylate, n-amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, n-ethylhexyl methacrylate, 2-ethylhexyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl
  • the (meth) acryl amide monomer is a group consisting of acryl amide, n-methylol acrylamide, n-butoxy methylacrylamide, methacrylamide, n-methylol methacrylamide, n-butoxy methyl methacrylamide It may be one or more selected from.
  • the unsaturated carboxylic acid monomer may be at least one selected from the group consisting of maleic acid, fumaric acid, methacrylic acid, acrylic acid, glutaric acid, itaconic acid, tetrahydrophthalic acid, crotonic acid, isocrotonic acid and nadic acid.
  • the water-soluble polymer may be at least one selected from the group consisting of polyvinyl alcohol (PVA), polyacrylic acid (PAA), and polyacrylamide (PAM), and more specifically, polyacrylic acid (PAA).
  • PVA polyvinyl alcohol
  • PAA polyacrylic acid
  • PAM polyacrylamide
  • the copolymer binder is not particularly limited, but may be prepared by, for example, suspension polymerization, emulsion polymerization, seed polymerization, or the like, and specifically, may be prepared by emulsion polymerization.
  • the copolymer binder may include one or more other components such as a polymerization initiator, a crosslinking agent, a buffer, a molecular weight modifier, an emulsifier, and the like as necessary.
  • the vinyl-based monomer, the conjugated diene-based monomer or the conjugated diene-based may be added thereto, prepared by emulsion polymerization using the water-soluble polymer and the crosslinking agent.
  • the particle size of the copolymer binder may be adjusted according to the content of the emulsifier, and in particular, when the content of the emulsifier is increased, the average particle size of the particles may be reduced, and when the content of the emulsifier is decreased, the average particle size of the particles is greatly increased. can do.
  • the polymerization temperature and the polymerization time may be appropriately determined according to the kind of polymerization method polymerization initiator, etc., for example, the polymerization temperature may be 50 ° C to 300 ° C, and the polymerization time may be 1 hour to 20 hours, but is not particularly limited.
  • Inorganic or organic peroxides may be used as the polymerization initiator, and for example, water-soluble initiators including potassium persulfate, sodium persulfate, ammonium persulfate, and the like, or oil-soluble initiators including cumene hydroperoxide, benzoyl peroxide, and the like. Can be.
  • an activator may be used together to promote the initiation reaction of the polymerization initiator, the activator is selected from the group consisting of sodium formaldehyde sulfoxylate, sodium ethylenediamine tetraacetate, ferrous sulfate and dextrose 1 or more types are mentioned.
  • the crosslinking agent may be used to promote crosslinking of the binder, for example, amines such as diethylenetriamine, triethylene tetraamine, diethylamino propylamine, xylene diamine, isophorone diamine, dodecyl succinic anhydride acid anhydrides such as dodecyl succinic anhydride, phthalic anhydride, polyamide resins, polysulfide resins, phenol resins, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, trimethylol propane trimethacrylate, trimethylol methane triacrylate, glycidyl meta Acrylates and the like.
  • the grafting agent may be used together, such as aryl methacryl
  • buffer examples include NaHCO 3 , NaOH, or NH 4 OH.
  • molecular weight regulator examples include mercaptans, terpins such as terbinolene, dipentene, t-terpyene, and halogenated hydrocarbons such as chloroform and carbon tetrachloride.
  • the emulsifier may be an anionic emulsifier, a nonionic emulsifier, or a mixture thereof, and when the nonionic emulsifier is used in combination with the anionic emulsifier, in addition to the electrostatic stabilization of the anionic emulsifier, the colloidal form may be formed through the van der Waals force of the polymer particles. It may provide additional stabilization.
  • anionic emulsifier examples include phosphate, carboxylate, sulfate, succinate, sulfosuccinate, sulfonate, or disulfonate emulsifiers.
  • nonionic emulsifiers include ester type, ether type, and ester-ether type emulsifiers, and although not particularly limited, polyoxyethylene glycol, polyoxyethylene glycol methyl ether, polyoxyethylene monoallyl ether, poly Oxyethylene bisphenol-A ether, polypropylene glycol, polyoxyethylene neopentyl ether, polyoxyethylene cetyl ether, polyoxyethylene lauryl ether, polyoxyethyl oleyl ether, polyoxyethylene stearyl ether, polyoxyethylene decyl Ether and polyoxyethylene octyl ether.
  • the secondary battery binder composition may be used as a binder in the production of a lithium secondary battery electrode, and particularly useful when a silicon-based negative electrode active material is used as the negative electrode active material.
  • the present invention provides a negative electrode for a lithium secondary battery including the silicon-based negative active material and the binder composition for the secondary battery.
  • the silicon-based negative active material for example, a group consisting of Si, silicon oxide particles (SiO x , 0 ⁇ x ⁇ 2), Si-metal alloy, and an alloy of Si and silicon oxide particles (SiO x , 0 ⁇ x ⁇ 2) It may include one or more selected from the above, the silicon oxide particles (SiO x , 0 ⁇ x ⁇ 2) may be a composite composed of crystalline SiO 2 and amorphous Si.
  • a carbon material, lithium metal, tin, or the like, which may normally occlude and release lithium ions may be used.
  • a carbon material may be used, and as the carbon material, both low crystalline carbon and high crystalline carbon may be used.
  • Soft crystalline carbon and hard carbon are typical low crystalline carbon, and high crystalline carbon is natural graphite, kish graphite, pyrolytic carbon, liquid crystal pitch carbon fiber.
  • High-temperature calcined carbon such as (mesophase pitch based carbon fiber), meso-carbon microbeads, mesophase pitches and petroleum or coal tar pitch derived cokes.
  • the negative electrode for a lithium secondary battery may further include a carbon-based negative electrode active material, wherein the silicon-based negative electrode active material is 1% to 30% by weight of the total negative electrode active material, specifically 5 wt% to 10 wt% may be included.
  • the carbon-based negative electrode active material may be natural graphite, artificial graphite, or a mixture thereof.
  • the secondary battery binder used to form the negative electrode active material layer of the negative electrode has a wetness of 0.02 MPa or more, specifically 0.1 MPa or more, more specifically 0.3 MPa to 0.5 MPa.
  • a wetness 0.02 MPa or more, specifically 0.1 MPa or more, more specifically 0.3 MPa to 0.5 MPa.
  • the lithium secondary battery may include a separator interposed between the negative electrode, the positive electrode, and the negative electrode and the positive electrode.
  • the negative electrode may be manufactured by a conventional method known in the art, and for example, a negative electrode active material slurry is prepared by mixing and stirring additives such as the negative electrode active material, the above-described binder, and a conductive material, and then apply the negative electrode active material to the negative electrode current collector. It can be prepared by drying and compressing.
  • the solvent for forming the negative electrode includes an organic solvent such as NMP (N-methyl pyrrolidone), DMF (dimethyl formamide), acetone, dimethyl acetamide or water, and these solvents alone or in combination of two or more. Can be mixed and used. The amount of the solvent used is sufficient to dissolve and disperse the negative electrode active material, the binder, and the conductive material in consideration of the coating thickness of the slurry and the production yield.
  • NMP N-methyl pyrrolidone
  • DMF dimethyl formamide
  • acetone dimethyl acetamide or water
  • the secondary battery binder composition may be included in less than 10% by weight of the total weight of the slurry for the negative electrode active material, specifically 0.1 to 10% by weight, more specifically 0.5 to 4% by weight may be included. If the content of the binder is less than 0.1% by weight, the effect of using the binder is insignificant and undesirable. If the content of the binder exceeds 10% by weight, the capacity per volume may decrease due to the decrease in the relative content of the active material due to the increase in the content of the binder. Not desirable
  • the conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery.
  • Examples of the conductive material include graphite such as natural graphite and artificial graphite; Carbon blacks such as acetylene black, Ketjen black, channel black, furnace black, lamp black and thermal 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; Or conductive materials such as polyphenylene derivatives.
  • the conductive material may be used in an amount of 1% by weight to 9% by weight based on the total weight of the slurry for the negative electrode active material.
  • the negative electrode current collector used for the negative electrode according to an embodiment of the present invention may have a thickness of 3 ⁇ m to 500 ⁇ m.
  • the negative electrode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery.
  • the negative electrode current collector may be formed on the surface of copper, gold, stainless steel, aluminum, nickel, titanium, calcined carbon, copper, or stainless steel. Surface-treated with carbon, nickel, titanium, silver and the like, aluminum-cadmium alloy and the like can be used.
  • fine concavities and convexities may be formed on the surface to enhance the bonding strength of the negative electrode active material, and may be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.
  • the active material slurry may include a viscosity modifier and / or fillers as needed.
  • the viscosity adjusting agent may be carboxymethyl cellulose, polyacrylic acid, or the like, and the viscosity of the active material slurry may be adjusted to facilitate the preparation of the active material slurry and the coating process on the electrode current collector by addition.
  • the filler is an auxiliary component that suppresses the expansion of the electrode, and is not particularly limited as long as it is a fibrous material that does not cause chemical change in the battery.
  • the filler is fibrous such as olefin-based polymers such as polyethylene and polypropylene, glass fibers, and carbon fibers. It may be a substance.
  • the positive electrode can be prepared by conventional methods known in the art.
  • a slurry may be prepared by mixing and stirring a solvent, the above-described binder, a conductive material, and a dispersant in a positive electrode active material, and then applying the coating (coating) to a current collector of a metal material, compressing it, and drying the same to prepare a positive electrode.
  • the current collector of the metal material is a metal having high conductivity, and is a metal to which the slurry of the positive electrode active material can be easily adhered, and is particularly limited as long as it has high conductivity without causing chemical change in the battery in the voltage range of the battery.
  • surface treated with carbon, nickel, titanium, silver, or the like on the surface of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel may be used.
  • fine unevenness may be formed on the surface of the current collector to increase the adhesion of the positive electrode active material.
  • the current collector may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a nonwoven fabric, and may have a thickness of 3 to 500 ⁇ m.
  • the solvent for forming the positive electrode includes an organic solvent such as NMP (N-methyl pyrrolidone), DMF (dimethyl formamide), acetone, dimethyl acetamide or water, and these solvents alone or in combination of two or more. Can be mixed and used. The amount of the solvent used is sufficient to dissolve and disperse the positive electrode active material, the binder, and the conductive material in consideration of the coating thickness of the slurry and the production yield.
  • NMP N-methyl pyrrolidone
  • DMF dimethyl formamide
  • acetone dimethyl acetamide or water
  • the conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery.
  • Examples of the conductive material include graphite such as natural graphite and artificial graphite; Carbon blacks such as acetylene black, Ketjen black, channel black, farnes black, lamp black and thermal black; Conductive fibers such as carbon fibers and metal fibers; Conductive tubes such as carbon nanotubes; Metal powders such as fluorocarbon, aluminum and nickel powders; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.
  • the conductive material may be used in an amount of 1 wt% to 20 wt% with respect to the total weight of the positive electrode slurry.
  • the dispersant may be an aqueous dispersant or an organic dispersant such as N-methyl-2-pyrrolidone.
  • separator conventional porous polymer films conventionally used as separators, such as polyolefin-based polymers such as ethylene homopolymer, propylene homopolymer, ethylene-butene copolymer, ethylene-hexene copolymer and ethylene-methacrylate copolymer
  • the porous polymer film prepared by using a single or a lamination thereof may be used, or a conventional porous nonwoven fabric, such as a high melting point glass fiber, polyethylene terephthalate fiber, etc. may be used, but is not limited thereto.
  • organic solvent included in the electrolyte solution those conventionally used in the electrolyte for secondary batteries may be used without limitation, and typically propylene carbonate (PC), ethylene carbonate (ethylene carbonate, EC ), Diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), methylpropyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane , Vinylene carbonate, sulfolane, gamma-butyrolactone, propylene sulfite, tetrahydrofuran, any one selected from the group consisting of, or mixtures of two or more thereof may be representatively used.
  • PC propylene carbonate
  • EC ethylene carbonate
  • DEC Diethyl carbonate
  • DMC dimethyl carbonate
  • EMC ethylmethyl carbonate
  • methylpropyl carbonate dipropyl carbon
  • ethylene carbonate and propylene carbonate which are cyclic carbonates among the carbonate-based organic solvents, may be preferably used because they have high dielectric constants to dissociate lithium salts in the electrolyte, and may be preferably used in such cyclic carbonates.
  • a low viscosity, low dielectric constant linear carbonate such as ethyl carbonate is mixed and used in an appropriate ratio, an electrolyte having high electrical conductivity can be prepared, and thus it can be used more preferably.
  • the electrolyte solution stored according to the present invention may further include additives such as an overcharge inhibitor included in a conventional electrolyte solution.
  • the external shape of the lithium secondary battery of the present invention is not particularly limited, but may be cylindrical, square, pouch type, or coin type using a can.
  • the lithium secondary battery according to the present invention may not only be used in a battery cell used as a power source for a small device, but also preferably used as a unit battery in a medium-large battery module including a plurality of battery cells.
  • a copolymer binder having an average particle diameter (D 50 ) of 350 nm was obtained in the same manner as in Example 1, except that polyacrylic acid was used in an amount of 42 g.
  • a copolymer binder having an average particle diameter (D 50 ) of 450 nm was obtained in the same manner as in Example 1, except that polyacrylic acid was used in an amount of 98 g.
  • a copolymer binder having an average particle diameter (D 50 ) of 200 nm was obtained in the same manner as in Comparative Example 1, except that 1,3-butadiene and butyl acrylate were changed to the amounts of 50 g and 10 g, respectively. .
  • Artificial graphite natural graphite: silicon-based negative electrode active material (SiO) mixed in a weight ratio of 84.5: 10.5: 5 mixed negative electrode active material, a thickener (carboxy methyl cellulose), carbon black as a conductive material, the binder prepared in Example 2 98
  • a negative electrode slurry was prepared by mixing using a TK mixer at a weight ratio of 1: 1: 2. The negative electrode slurry was coated on a copper foil of 20 ⁇ m to a thickness of 120 ⁇ m, dried at 100 ° C. for 12 hours in a vacuum oven, and then rolled to a suitable thickness to prepare a negative electrode.
  • 96 g of LiCoO 2 , 2 g of acetylene black, and 2 g of polyvinylidene fluoride (PVdF) as a positive electrode active material were added to N-methyl-2-pyrrolidone (NMP) as a solvent to prepare a slurry for the positive electrode.
  • NMP N-methyl-2-pyrrolidone
  • the anode slurry was coated on an aluminum (Al) thin film to a thickness of 350 ⁇ m, dried to prepare a cathode, and then roll-rolled to prepare a cathode.
  • the anode prepared above was punched out to have a surface area of 13.33 cm 2 , and the anode prepared above was punched out to have a surface area of 12.60 cm 2 to prepare a mono-cell.
  • a tap was attached to the upper part of the positive electrode and the negative electrode, and the resultant was loaded into an aluminum pouch through a separator made of a polyolefin microporous membrane between the negative electrode and the positive electrode, and 500 mg of the electrolyte was injected into the pouch.
  • the pouch was sealed using a vacuum packaging machine and maintained at room temperature for 12 hours, followed by a constant current charging process to maintain a constant current at a rate of about 0.05 C and maintain a voltage until about 1/6 of the current. .
  • a constant current charging process to maintain a constant current at a rate of about 0.05 C and maintain a voltage until about 1/6 of the current.
  • Example 4 Except that the copolymer binder of Example 1 was used as the binder in the preparation of the negative electrode in Example 4, and the artificial negative electrode: natural graphite: silicon-based negative active material was mixed mixed active material in a weight ratio of 80:10:10. Through the same process as in Example 4, a negative electrode, a positive electrode, and a lithium secondary battery were prepared.
  • Example 4 Preparation of the negative electrode in Example 4
  • the artificial graphite natural graphite: silicon-based negative electrode active material using a mixed negative electrode active material mixed in a weight ratio of 80:10:10, and using the copolymer binder of Examples 2 and 3, respectively Except, a negative electrode, a positive electrode and a lithium secondary battery were prepared through the same process as in Example 4.
  • Example 4 except that the artificial graphite: silicone-based negative active material was mixed in a weight ratio of 70:30 and the copolymer binder of Example 3 was used to prepare the negative electrode in Example 4, Through the same process as to prepare a negative electrode, a positive electrode and a lithium secondary battery.
  • a negative electrode, a positive electrode and a lithium secondary battery were manufactured through the same process as in Example 4, except that the copolymer binders prepared in Comparative Examples 1 and 2 were used as binders in preparing the negative electrode in Example 4. .
  • Example 4 Except that the artificial graphite: silicone-based negative active material was mixed in a weight ratio of 70:30, and the copolymer binder prepared in Comparative Example 1 was used in the preparation of the negative electrode in Example 4, A negative electrode, a positive electrode, and a lithium secondary battery were manufactured through the same process as in Example 4.
  • the charge and discharge current density was 0.5 C
  • the charge end voltage was 4.2 V (Li / Li + )
  • the discharge end voltage was 3 V (Li / Charge and discharge tests with Li + ) were performed 30 times.
  • the charging and discharging current density was 1 C
  • the charging end voltage was 4.2 V (Li / Li + )
  • the discharge end voltage was 3 V (Li / Li + ). Charge and discharge tests were performed 130 times.
  • the charge and discharge current density was 0.33 C
  • the charge end voltage was 4.2 V (Li / Li + )
  • the discharge end voltage was 3 V (Li / Li + ). 200 charge and discharge tests were conducted.
  • the copolymer binders of Comparative Examples 1 and 2 having low wet strength were significantly swelled by the electrolyte solution compared to the copolymer binder of Example 2 having high wet strength ( swelling).
  • the negative electrode and the secondary battery of Comparative Examples 3 and 4 prepared using the same have poor capacity retention compared to the negative electrode and the secondary battery of Example 4 prepared using the copolymer binder of Example 2.
  • Figure 3 can be confirmed the capacity retention rate of the secondary battery according to the wet strength of the copolymer binder used. Referring to FIG.
  • Figure 4 shows the experimental results for comparing the difference in effect according to the type of the copolymer binder when the negative electrode was prepared using a negative electrode active material mixed with artificial graphite and a silicon-based negative active material in a weight ratio of 70:30 have.
  • the negative electrode and the secondary battery of Example 4 including the copolymer binder of Example 3 exhibit excellent capacity retention ratios compared to the negative electrode and the secondary battery of Comparative Example 5 including the copolymer binder of Comparative Example 1. It can be confirmed that.
  • the copolymer binder of the present invention having a wet strength of 0.02 MPa or more is applied to a negative electrode including a silicon-based negative active material having a large volume change due to charging and discharging, the copolymer binder exhibits improved adhesion and high mechanical strength. Since physical properties were maintained, it was confirmed that the life performance of the secondary battery could be improved.

Abstract

The present invention relates to a binder composition for a secondary battery, and a lithium secondary battery anode and a lithium secondary battery comprising the binder composition, wherein the binder composition comprises a copolymer binder comprising (a) a unit derived from a vinyl-based monomer, (b) a unit derived from a conjugated diene-based monomer or a conjugated diene-based polymer, (c) at least one unit selected from the group consisting of units derived from a (meth)acrylic acid ester-based monomer, and (d) a unit derived from a water-soluble polymer, wherein the copolymer binder has a wet modulus of 0.02 MPa or higher.

Description

이차전지용 바인더 조성물, 이를 포함하는 이차전지용 전극 및 리튬 이차전지Binder composition for secondary batteries, electrodes for secondary batteries and lithium secondary batteries comprising same
[관련출원과의 상호 인용][Cross-cited with Related Applications]
본 출원은 2017년 03월 31일자 한국 특허 출원 제10-2017-0042131호 및 2018년 03월 28일자 한국 특허 출원 제10-2018-0035834호에 기초한 우선권의 이익을 주장하며, 해당 한국 특허 출원의 문헌에 개시된 모든 내용은 본 명세서의 일부로서 포함된다.This application claims the benefit of priority based on Korean Patent Application No. 10-2017-0042131 dated March 31, 2017 and Korean Patent Application No. 10-2018-0035834 dated March 28, 2018. All content disclosed in the literature is included as part of this specification.
[기술분야][Technical Field]
본 발명은 이차전지용 바인더 조성물, 및 이를 포함하는 이차전지용 전극 및 리튬 이차전지에 관한 것으로, 보다 자세하게는 적절한 습윤강도를 가지는 바인더 조성물, 이를 포함하는 이차전지용 전극 및 리튬 이차전지에 관한 것이다.The present invention relates to a secondary battery binder composition, and a secondary battery electrode and a lithium secondary battery comprising the same, and more particularly to a binder composition having a suitable wet strength, a secondary battery electrode and a lithium secondary battery comprising the same.
모바일 기기에 대한 기술 개발과 수요가 증가함에 따라 에너지원으로서의 이차전지에 대한 수요가 급격히 증가하고 있고, 그러한 이차전지 중에서도 높은 에너지 밀도와 작동 전위를 나타내고, 사이클 수명이 길며, 자기방전율이 낮은 리튬 이차전지가 상용화되어 널리 사용되고 있다.As the development and demand for mobile devices increases, the demand for secondary batteries as energy sources is rapidly increasing. Among them, lithium secondary batteries exhibiting high energy density and operating potential, long cycle life, and low self-discharge rate. Batteries have been commercialized and widely used.
리튬 이차전지의 전극은 양극 활물질 또는 음극 활물질과 바인더(binder) 수지 성분을 혼합하여 용매에 분산시켜 슬러리(slurry)를 만들고, 이것을 전극 집전체 표면에 도포하여 건조 후 합제층을 형성시켜 제작된다.An electrode of a lithium secondary battery is prepared by mixing a positive electrode active material or a negative electrode active material with a binder resin component and dispersing it in a solvent to make a slurry, and applying this to the surface of an electrode current collector to form a mixture layer after drying.
바인더는 활물질과 활물질 간, 활물질과 전극 집전체 간의 접착력 또는 결착력 확보를 위하여 사용되나, 전극 집전체와 활물질 간의 접착력을 향상시키기 위해서는 과량의 바인더가 요구된다. 그러나 과량의 바인더는, 전극의 용량 및 전도성을 낮추게 되는 문제가 있다. 반면에, 충분하지 않은 접착력은 전극 건조, 압연(pressing) 등의 공정에서 전극 박리 현상을 유발하여 전극 불량률을 높이는 원인이 된다. 또한, 접착력이 낮은 전극은 외부 충격에 의해서 박리될 수 있고, 이러한 전극 박리는 전극 물질과 집전체 간 접촉 저항을 키워, 전극 출력 성능 저하의 원인이 될 수 있다.The binder is used to secure adhesion or binding force between the active material and the active material, and between the active material and the electrode current collector, but an excess binder is required to improve the adhesion between the electrode current collector and the active material. However, the excess binder has a problem of lowering the electrode capacity and conductivity. On the other hand, insufficient adhesive force causes the electrode peeling phenomenon in the process of electrode drying, pressing, etc., thereby increasing the electrode defect rate. In addition, an electrode with low adhesive force may be peeled off by an external impact, and this electrode peeling may increase contact resistance between the electrode material and the current collector, which may cause deterioration of electrode output performance.
특히, 리튬 이차전지의 충방전시에는 리튬과의 반응에 의한 음극 활물질의 부피 변화가 발생하고, 계속적인 충방전시 음극 활물질이 집전체로부터 탈리되거나, 활물질 상호간 접촉 계면의 변화에 따른 저항 증가로 인해, 충방전 사이클이 진행됨에 따라 용량이 급격하게 저하되어 사이클 수명이 짧아지는 문제점을 가지고 있다. 또한, 방전 용량의 증대를 위하여 실리콘, 주석, 실리콘-주석 합금 등과 같은 재료를 복합하여 사용하는 경우, 실리콘, 주석 등이 리튬과의 반응에 의해 보다 큰 부피 변화를 일으키므로, 이러한 문제점이 더욱 두드러지게 된다. In particular, during charging and discharging of a lithium secondary battery, a volume change of the negative electrode active material occurs due to reaction with lithium, and during continuous charging and discharging, the negative electrode active material is detached from the current collector, or the resistance increases due to the change of the contact interface between the active materials. As a result, as the charge and discharge cycle proceeds, the capacity is drastically lowered and the cycle life is shortened. In addition, when using a material such as silicon, tin, silicon-tin alloy, etc. in order to increase the discharge capacity, this problem is more prominent because silicon, tin, etc. cause a larger volume change by reaction with lithium. You lose.
따라서, 더욱 우수한 접착력을 제공하여 전극 박리, 활물질의 집전체로부터의 탈리, 또는 활물질 간의 접촉 계면 변화로 인한 전기화학적 성능 저하 문제를 해결하여, 성능이 향상된 이차전지를 제공할 수 있는 바인더 및 이를 사용하여 제조된 이차전지용 전극의 개발이 지속적으로 요구되고 있다.Therefore, the binder and the use of the present invention can provide a secondary battery having improved performance by providing better adhesion and solving an electrochemical performance deterioration problem due to electrode peeling, detachment of the active material from the current collector, or a change in contact interface between the active materials. There is a continuous demand for the development of a secondary battery electrode manufactured by.
본 발명의 해결하고자 하는 과제는 더욱 우수한 접착력을 제공하면서 전해액 함침 후에도 높은 기계적 물성을 유지하여 전지의 수명 성능을 향상시킬 수 있는 이차전지용 바인더 조성물을 제공하는 것이다. The problem to be solved by the present invention is to provide a binder composition for a secondary battery that can improve the life performance of the battery by maintaining a high mechanical properties even after the electrolyte solution impregnation while providing more excellent adhesion.
본 발명의 다른 해결하고자 하는 과제는 상기 이차전지용 바인더 조성물을 포함하는 이차전지용 전극을 제공하는 것이다. Another object of the present invention is to provide a secondary battery electrode comprising the secondary battery binder composition.
본 발명의 또 다른 해결하고자 하는 과제는 상기 이차전지용 전극을 포함하는 리튬 이차전지를 제공하는 것이다.Another object of the present invention is to provide a lithium secondary battery including the secondary battery electrode.
본 발명은 상기 과제를 해결하기 위하여, (가) 비닐계 단량체로부터 유도되는 단위, (나) 공액 디엔계 단량체 또는 공액 디엔계 중합체로부터 유도되는 단위, 및 (다) (메타)아크릴산 에스테르계 단량체로부터 유도되는 단위로 이루어진 군에서 선택되는 1종 이상의 단위, 및 (라) 수용성 중합체로부터 유도되는 단위를 포함하는 공중합체 바인더를 포함하고, 상기 공중합체 바인더가 0.02 MPa 이상의 습윤강도(wet modulus)를 가지는, 이차전지용 바인더 조성물을 제공한다.The present invention to solve the above problems, (a) from a unit derived from a vinyl monomer, (b) a unit derived from a conjugated diene monomer or a conjugated diene polymer, and (c) from a (meth) acrylic acid ester monomer A copolymer binder comprising at least one unit selected from the group consisting of derived units, and (D) units derived from water-soluble polymers, wherein the copolymer binder has a wet modulus of at least 0.02 MPa. It provides a binder composition for secondary batteries.
본 발명은 상기 다른 과제를 해결하기 위하여, 실리콘계 음극 활물질 및 상기 이차전지용 바인더 조성물을 포함하는 리튬 이차전지용 음극을 제공한다. The present invention provides a negative electrode for a lithium secondary battery comprising the silicon-based negative electrode active material and the secondary battery binder composition in order to solve the other problem.
본 발명은 상기 또 다른 과제를 해결하기 위하여, 상기 리튬 이차전지용 전극을 포함하는 리튬 이차전지를 제공한다.The present invention provides a lithium secondary battery comprising the electrode for a lithium secondary battery, in order to solve the another problem.
본 발명에 따른 이차전지용 바인더 조성물은 친수성 작용기를 포함하는 공중합체 바인더를 포함하고, 상기 공중합체 바인더가 일정 값 이상의 습윤강도(wet modulus)를 가지므로, 상기 공중합체 바인더가 향상된 접착력을 발휘함과 함께, 전해액 함침 후에도 높은 기계적 물성을 유지하여 전지의 수명 성능을 향상시킬 수 있다.The binder composition for a secondary battery according to the present invention includes a copolymer binder including a hydrophilic functional group, and because the copolymer binder has a wet modulus of a predetermined value or more, the copolymer binder exhibits improved adhesion and In addition, high mechanical properties can be maintained even after the electrolyte is impregnated to improve the life performance of the battery.
도 1은 실험예 1에서 사용된 시편의 도안 및 규격을 나타낸 그림이다. 1 is a diagram showing the design and specification of the specimen used in Experimental Example 1.
도 2는 실시예 4, 및 비교예 3 및 4에서 제조된 리튬 이차전지에 대해 충방전 전류밀도 0.5 C 조건에서 30 사이클까지의 방전 용량의 변화를 측정한 결과를 나타낸 그래프이다. Figure 2 is a graph showing the results of measuring the change in the discharge capacity up to 30 cycles in the charge and discharge current density 0.5 C conditions for the lithium secondary batteries prepared in Example 4 and Comparative Examples 3 and 4.
도 3은 실시예 5 내지 7에서 제조된 리튬 이차전지에 대해 충방전 전류 밀도 1 C 조건에서 130 사이클까지의 방전 용량의 변화를 측정한 결과를 나타낸 그래프이다.3 is a graph showing the results of measuring the change of the discharge capacity up to 130 cycles under the charge and discharge current density 1 C conditions for the lithium secondary battery prepared in Examples 5 to 7.
도 4는 실시예 8 및 비교예 5에서 제조된 리튬 이차전지에 대해 충방전 전류 밀도 0.33 C 조건에서 200 사이클까지의 방전 용량의 변화를 측정한 결과를 나타낸 그래프이다.4 is a graph showing the results of measuring the change in the discharge capacity of up to 200 cycles in the charge and discharge current density 0.33 C conditions for the lithium secondary batteries prepared in Example 8 and Comparative Example 5.
이하, 본 발명에 대한 이해를 돕기 위해 본 발명을 더욱 상세하게 설명한다.Hereinafter, the present invention will be described in more detail to aid in understanding the present invention.
본 명세서 및 청구범위에 사용된 용어나 단어는 통상적이거나 사전적인 의미로 한정해서 해석되어서는 아니 되며, 발명자는 그 자신의 발명을 가장 최선의 방법으로 설명하기 위해 용어의 개념을 적절하게 정의할 수 있다는 원칙에 입각하여 본 발명의 기술적 사상에 부합하는 의미와 개념으로 해석되어야만 한다.The terms or words used in this specification and claims are not to be construed as limiting in their usual or dictionary meanings, and the inventors may appropriately define the concept of terms in order to best explain their invention in the best way possible. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that the present invention.
본 발명에 따른 리튬 이차전지용 바인더 조성물은 (가) 비닐계 단량체로부터 유도되는 단위, (나) 공액 디엔계 단량체 또는 공액 디엔계 중합체로부터 유도되는 단위, 및 (다) (메타)아크릴산 에스테르계 단량체로부터 유도되는 단위로 이루어진 군에서 선택되는 1종 이상의 단위, 및 (라) 수용성 중합체로부터 유도되는 단위를 포함하는 공중합체 바인더를 포함하고, 상기 공중합체 바인더가 0.02 MPa 이상의 습윤강도(wet modulus)를 가지는 것이다. The binder composition for a lithium secondary battery according to the present invention comprises (a) a unit derived from a vinyl monomer, (b) a unit derived from a conjugated diene monomer or a conjugated diene polymer, and (c) a (meth) acrylic acid ester monomer. A copolymer binder comprising at least one unit selected from the group consisting of derived units, and (D) units derived from water-soluble polymers, wherein the copolymer binder has a wet modulus of at least 0.02 MPa. will be.
상기 공중합체 바인더는 0.02 MPa 이상, 구체적으로 0.1 MPa 이상, 더욱 구체적으로 0.3 MPa 내지 0.5 MPa의 습윤강도를 가질 수 있으며, 상기 공중합체 바인더가 상기 범위의 습윤강도를 가질 경우, 전해액에 의한 스웰링이 적절히 억제될 수 있으며, 적절한 기계적 물성을 유지하여 이를 포함하는 전극 및 이차전지의 수명특성이 개선될 수 있다. The copolymer binder may have a wet strength of 0.02 MPa or more, specifically 0.1 MPa or more, more specifically 0.3 MPa to 0.5 MPa, and when the copolymer binder has a wet strength in the above range, swelling by an electrolyte solution This may be appropriately suppressed, and the life characteristics of the electrode and the secondary battery including the same may be improved by maintaining appropriate mechanical properties.
상기 습윤강도는 상기 공중합체 바인더를 리튬 이차전지로 사용되는 통상의 전해액에 함침시킨 후, 상기 공중합체 바인더에 하중을 가하여 응력 변형 곡선(Stress-Strain curve)을 통해 상기 공중합체 바인더의 내부에 생기는 인장 강도(Stress)와 인장 변형(Strain) 관계를 파악함으로써 측정할 수 있다. The wet strength is obtained by impregnating the copolymer binder in a conventional electrolyte solution used as a lithium secondary battery, and then applying a load to the copolymer binder to generate the inside of the copolymer binder through a stress-strain curve. It can be measured by grasping the relationship between tensile strength (Stress) and tensile strain (Strain).
상기 습윤강도는 상기 공중합체 바인더가 실제 리튬 이차전지의 구동환경과 같이 전해액에 함침된 상태에서의 강도를 나타내므로, 실제 리튬 이차전지의 구동 환경에서 상기 공중합체 바인더가 어떠한 강도를 나타낼지를 건조강도(dry modulus)에 비해 보다 직접적으로 반영한다는 점에서, 상기 건조강도가 높은 것과는 또 다른 의미를 가진다.The wet strength indicates the strength of the copolymer binder in the state of being impregnated with the electrolyte as in the actual driving environment of the lithium secondary battery, and thus the dry strength of the copolymer binder in the driving environment of the actual lithium secondary battery. Compared with the dry modulus, it has a different meaning from the higher dry strength.
상기 공중합체 바인더의 습윤강도 값은 공중합체 바인더의 친수성 작용기의 함량을 조절함으로써 달성될 수 있으며, 구체적으로 상기 공중합체 바인더에 포함되는 상기 (라) 수용성 중합체로부터 유도되는 단위의 함량을 적절히 조절함으로써, 상기 공중합체 바인더가 적절한 습윤강도 값을 가질 수 있도록 할 수 있다. The wet strength value of the copolymer binder can be achieved by controlling the content of the hydrophilic functional group of the copolymer binder, and specifically by appropriately adjusting the content of units derived from the (d) water-soluble polymer included in the copolymer binder. In addition, the copolymer binder may have an appropriate wet strength value.
상기 공중합체는 총 중량 100 중량부를 기준으로, (가) 비닐계 단량체로부터 유도되는 단위 1 중량부 내지 70 중량부, (나) 공액 디엔계 단량체 또는 공액 디엔계 중합체로부터 유도되는 단위 10 중량부 내지 97 중량부, (다) (메타)아크릴산 에스테르계 단량체로부터 유도되는 단위 1 중량부 내지 30 중량부, 및 (라) 수용성 중합체로부터 유도되는 단위 1 중량부 내지 70 중량부를 포함할 수 있다. The copolymer has a total weight of 100 parts by weight based on (a) 1 to 70 parts by weight of units derived from vinyl monomers, (b) 10 to parts by weight of units derived from conjugated diene monomers or conjugated diene polymers. 97 parts by weight, (C) 1 to 30 parts by weight of the unit derived from the (meth) acrylic acid ester monomer, and (D) 1 to 70 parts by weight of the unit derived from the water-soluble polymer.
또한, 구체적으로 상기 공중합체는 총 중량 100 중량부를 기준으로, (가) 비닐계 단량체로부터 유도되는 단위 20 중량부 내지 70 중량부, (나) 공액 디엔계 단량체 또는 공액 디엔계 중합체로부터 유도되는 단위 10 중량부 내지 60 중량부, (다) (메타)아크릴산 에스테르계 단량체로부터 유도되는 단위 1 중량부 내지 20 중량부, 및 (라) 수용성 중합체로부터 유도되는 단위 1 중량부 내지 60 중량부를 포함할 수 있다. In addition, specifically, the copolymer may be based on a total weight of 100 parts by weight of (a) 20 parts by weight to 70 parts by weight of a unit derived from a vinyl monomer, (b) a unit derived from a conjugated diene monomer or a conjugated diene polymer. 10 parts by weight to 60 parts by weight, (c) 1 part by weight to 20 parts by weight of a unit derived from a (meth) acrylic acid ester monomer, and (d) 1 part by weight to 60 parts by weight of a unit derived from a water-soluble polymer. have.
또한, 더욱 구체적으로 상기 공중합체는 총 중량 100 중량부를 기준으로, (가) 비닐계 단량체로부터 유도되는 단위 30 중량부 내지 60 중량부, (나) 공액 디엔계 단량체 또는 공액 디엔계 중합체로부터 유도되는 단위 15 중량부 내지 30 중량부, (다) (메타)아크릴산 에스테르계 단량체로부터 유도되는 단위 4 중량부 내지 8 중량부, 및 (라) 수용성 중합체로부터 유도되는 단위 2 중량부 내지 50 중량부를 포함할 수 있다.More specifically, the copolymer may be derived from (a) 30 parts by weight to 60 parts by weight of a unit derived from a vinyl monomer, (b) a conjugated diene monomer or a conjugated diene polymer based on a total weight of 100 parts by weight. 15 to 30 parts by weight of the unit, (c) 4 to 8 parts by weight of the unit derived from the (meth) acrylic acid ester monomer, and (d) 2 to 50 parts by weight of the unit derived from the water-soluble polymer. Can be.
상기 공중합체가 상기 (가) 비닐계 단량체로부터 유도되는 단위, (나) 공액 디엔계 단량체 또는 공액 디엔계 중합체로부터 유도되는 단위, 및 (다) (메타)아크릴산 에스테르계 단량체로부터 유도되는 단위를 각각 상기 범위로 포함할 경우, 상기 공중합체 바인더가 우수한 접착력 및 강도를 발휘할 수 있다.The copolymer is a unit derived from the (a) vinyl monomer, (b) a unit derived from a conjugated diene monomer or a conjugated diene polymer, and (c) a unit derived from a (meth) acrylic acid ester monomer. When included in the above range, the copolymer binder can exhibit excellent adhesion and strength.
또한, 상기 공중합체가 상기 (라) 수용성 중합체로부터 유도되는 단위를 상기 함량 범위로 포함할 경우, 상기 공중합체 바인더가 우수한 습윤강도 값을 가질 수 있다. In addition, when the copolymer includes a unit derived from the (d) water-soluble polymer in the content range, the copolymer binder may have an excellent wet strength value.
상기 공중합체 바인더는 입자 형상이고, 100 nm 내지 1 ㎛, 구체적으로 300 nm 내지 500 nm의 평균 입경(D50)을 가질 수 있다. The copolymer binder may have a particle shape and have an average particle diameter (D 50 ) of 100 nm to 1 μm, specifically 300 nm to 500 nm.
상기 공중합체 바인더가 상기 평균 입경(D50)을 가질 경우, 적절한 접착력을 발휘할 수 있고, 전해액 스웰링 현상이 작으며, 적절한 탄력성을 발휘하여 전극의 두께 변화를 수용하고 가스 발생 현상을 감소시킬 수 있다. When the copolymer binder has the average particle diameter (D 50 ), it can exhibit an appropriate adhesion, the electrolyte swelling phenomenon is small, and exhibits the proper elasticity to accommodate the change in the thickness of the electrode and reduce the gas generation phenomenon have.
본 발명에 있어서, 상기 평균 입경(D50)은 입경 분포의 50% 기준에서의 입경으로 정의할 수 있다. 상기 평균 입경은 특별히 제한되지 않지만, 예컨대 레이저 회절법(laser diffraction method) 또는 주사전자현미경(SEM) 사진을 이용하여 측정할 수 있다. 상기 레이저 회절법은 일반적으로 서브미크론(submicron) 영역에서부터 수 mm 정도의 입경의 측정이 가능하며, 고 재현성 및 고 분해성을 가지는 결과를 얻을 수 있다.In the present invention, the average particle diameter (D 50 ) can be defined as the particle size at 50% of the particle size distribution. The average particle diameter is not particularly limited, but may be measured using, for example, a laser diffraction method or a scanning electron microscope (SEM) photograph. In general, the laser diffraction method can measure a particle diameter of about several mm from the submicron region, and a result having high reproducibility and high resolution can be obtained.
상기 공중합체 바인더가 포함하는 단위들은 이하와 같다. The units contained in the copolymer binder are as follows.
상기 (가) 비닐계 단량체로부터 유도되는 단위에서, 상기 비닐계 단량체는 스티렌, α-메틸스티렌, β-메틸스티렌, p-t-부틸스티렌 및 디비닐벤젠으로 이루어진 군으로부터 선택되는 1종 이상일 수 있다. In the unit derived from the (a) vinyl monomer, the vinyl monomer may be at least one selected from the group consisting of styrene, α-methylstyrene, β-methylstyrene, p-t-butylstyrene, and divinylbenzene.
상기 (나) 공액 디엔계 단량체 또는 공액 디엔계 중합체로부터 유도되는 단위에서, 상기 공액 디엔계 단량체는 1,3-부타디엔, 이소프렌, 클로로프렌, 또는 피페릴렌이고, 상기 공액 디엔계 중합체는 1,3-부타디엔, 이소프렌, 클로로프렌, 및 피페릴렌으로 이루어진 군에서 선택되는 2종 이상의 단량체들의 중합체, 스티렌-부타디엔 공중합체, 아크릴로니트릴-부타디엔 공중합체, 스티렌-이소프렌 공중합체, 아크릴레이트-부타디엔 고무, 아크릴로니트릴-부타디엔-스티렌 고무, 에틸렌-프로필렌-디엔계 중합체, 및 이들이 부분적으로 수소화, 에폭시화, 또는 브롬화된 중합체로 이루어진 군으로부터 선택된 1종 이상일 수 있다. In the unit derived from the (b) conjugated diene monomer or conjugated diene polymer, the conjugated diene monomer is 1,3-butadiene, isoprene, chloroprene or piperylene, and the conjugated diene polymer is 1,3- Polymers of two or more monomers selected from the group consisting of butadiene, isoprene, chloroprene, and piperylene, styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, styrene-isoprene copolymers, acrylate-butadiene rubbers, acrylo Nitrile-butadiene-styrene rubber, ethylene-propylene-diene based polymers, and these may be at least one selected from the group consisting of partially hydrogenated, epoxidized, or brominated polymers.
상기 (다) (메타)아크릴산 에스테르계 단량체는 메틸아크릴레이트, 에틸아크릴레이트, 프로필아크릴레이트, 이소프로필아크릴레이트, n-부틸아크릴레이트, 이소부틸아크릴레이트, n-아밀아크릴레이트, 이소아밀아크릴레이트, n-에틸헥실아크릴레이트, 2-에틸헥실아크릴레이트, 2-히드록시에틸아크릴레이트, 메틸메타크릴레이트, 에틸메타크릴레이트, 프로필메타크릴레이트, 이소프로필메타크릴레이트, n-부틸메타크릴레이트, 이소부틸메타크릴레이트, n-아밀메타크릴레이트, 이소아밀메타크릴레이트, n-헥실메타크릴레이트, n-에틸헥실 메타크릴레이트, 2-에틸헥실 메타크릴레이트, 히드록시에틸 메타크릴레이트, 히드록시프로필 메타크릴레이트, 메타아크릴록시 에틸에틸렌우레아, β-카르복시에틸아크릴레이트, 알리파틱 모노아크릴레이트, 디프로필렌 디아크릴레이트, 디트리메틸로프로판 테트라아크릴레이트, 하이드록시에틸 아크릴레이트, 디펜타에리트리톨 헥사아크릴레이트, 펜타에리트리톨 트리아크릴레이트, 펜타에리트리톨 테트라아크릴레이트, 라우릴 아크릴레이트, 세릴 아크릴레이트, 스테아릴 아크릴레이트, 라우릴 메타 아크릴레이트, 세틸 메타 아크릴레이트 및 스테아릴 메타 아크릴레이트로 이루어진 군으로부터 선택되는 1종 이상일 수 있다. The (c) (meth) acrylic acid ester monomers are methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate. , n-ethylhexyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate Isobutyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, n-ethylhexyl methacrylate, 2-ethylhexyl methacrylate, hydroxyethyl methacrylate, Hydroxypropyl methacrylate, methacryloxy ethylethylene urea, β-carboxyethyl acrylate, aliphatic monoacrylate, dipro Lene diacrylate, ditrimethyllopropane tetraacrylate, hydroxyethyl acrylate, dipentaerythritol hexaacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, lauryl acrylate, seryl acrylate, It may be at least one selected from the group consisting of stearyl acrylate, lauryl methacrylate, cetyl methacrylate and stearyl methacrylate.
상기 (라) 수용성 중합체로부터 유도되는 단위에서, 상기 수용성 중합체는 (메타)아크릴산 에스테르계 단량체로부터 유도되는 단위, (메타)아크릴 아미드계 단량체로부터 유도되는 단위, 불포화 카르본산계 단량체 및 비닐 아세테이트 단량체로부터 유도되는 단위로 이루어진 군에서 선택되는 1종 이상의 단위를 포함하는 공중합체일 수 있으며, 제조방법은 특별히 제한되지 않지만, 예컨대 현탁 중합법, 유화 중합법, 또는 시드 중합법 등에 따라 제조될 수 있다. In the unit derived from the (d) water-soluble polymer, the water-soluble polymer is a unit derived from a (meth) acrylic acid ester monomer, a unit derived from a (meth) acryl amide monomer, an unsaturated carboxylic acid monomer and a vinyl acetate monomer. It may be a copolymer including one or more units selected from the group consisting of derived units, and the production method is not particularly limited, but may be prepared according to, for example, suspension polymerization, emulsion polymerization, seed polymerization, or the like.
상기 (메타)아크릴산 에스테르계 단량체는 메틸아크릴레이트, 에틸아크릴레이트, 프로필아크릴레이트, 이소프로필아크릴레이트, n-부틸아크릴레이트, 이소부틸아크릴레이트, n-아밀아크릴레이트, 이소아밀아크릴레이트, n-에틸헥실아크릴레이트, 2-에틸헥실아크릴레이트, 2-히드록시에틸아크릴레이트, 메틸메타크릴레이트, 에틸메타크릴레이트, 프로필메타크릴레이트, 이소프로필메타크릴레이트, n-부틸메타크릴레이트, 이소부틸메타크릴레이트, n-아밀메타크릴레이트, 이소아밀메타크릴레이트, n-헥실메타크릴레이트, n-에틸헥실 메타크릴레이트, 2-에틸헥실 메타크릴레이트, 히드록시에틸 메타크릴레이트, 히드록시프로필 메타크릴레이트, 메타아크릴록시 에틸에틸렌우레아, β-카르복시에틸아크릴레이트, 알리파틱 모노아크릴레이트, 디프로필렌 디아크릴레이트, 디트리메틸로프로판 테트라아크릴레이트, 하이드록시에틸 아크릴레이트, 디펜타에리트리톨 헥사아크릴레이트, 펜타에리트리톨 트리아크릴레이트, 펜타에리트리톨 테트라아크릴레이트, 라우릴 아크릴레이트, 세릴 아크릴레이트, 스테아릴 아크릴레이트, 라우릴 메타 아크릴레이트, 세틸 메타 아크릴레이트 및 스테아릴 메타 아크릴레이트로 이루어진 군으로부터 선택되는 1종 이상일 수 있다. The (meth) acrylic acid ester monomer is methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n- amyl acrylate, iso amyl acrylate, n- Ethylhexyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl Methacrylate, n-amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, n-ethylhexyl methacrylate, 2-ethylhexyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl Methacrylate, methacryloxy ethylethylene urea, β-carboxyethyl acrylate, aliphatic monoacrylate, dipropylene Acrylate, ditrimethyllopropane tetraacrylate, hydroxyethyl acrylate, dipentaerythritol hexaacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, lauryl acrylate, seryl acrylate, stearyl It may be at least one selected from the group consisting of acrylate, lauryl methacrylate, cetyl methacrylate and stearyl methacrylate.
상기 (메타)아크릴 아미드계 단량체는 아크릴 아미드, n-메틸올 아크릴아미드, n-부톡시 메틸아크릴아미드, 메타크릴아미드, n-메틸올 메타크릴아미드, n-부톡시 메틸메타크릴아미드로 이루어진 군으로부터 선택되는 1종 이상일 수 있다. The (meth) acryl amide monomer is a group consisting of acryl amide, n-methylol acrylamide, n-butoxy methylacrylamide, methacrylamide, n-methylol methacrylamide, n-butoxy methyl methacrylamide It may be one or more selected from.
상기 불포화카르본산계 단량체는 말레인산, 푸마르산, 메타크릴산, 아크릴산, 글루타르산, 이타콘산, 테트라하이드로프탈산, 크로톤산, 이소크로톤산 및 나딕산으로 이루어진 군에서 선택되는 1종 이상일 수 있다. The unsaturated carboxylic acid monomer may be at least one selected from the group consisting of maleic acid, fumaric acid, methacrylic acid, acrylic acid, glutaric acid, itaconic acid, tetrahydrophthalic acid, crotonic acid, isocrotonic acid and nadic acid.
상기 수용성 중합체는, 구체적으로 폴리비닐 알코올(PVA), 폴리아크릴산(PAA) 및 폴리아크릴아미드(PAM)로 이루어지는 군으로부터 선택되는 1종 이상일 수 있으며, 더욱 구체적으로 폴리아크릴산(PAA)일 수 있다. Specifically, the water-soluble polymer may be at least one selected from the group consisting of polyvinyl alcohol (PVA), polyacrylic acid (PAA), and polyacrylamide (PAM), and more specifically, polyacrylic acid (PAA).
상기 공중합체 바인더는 특별히 제한되지 않지만, 예컨대 현탁 중합법, 유화 중합법, 또는 시드 중합법 등에 따라 제조될 수 있으며, 구체적으로 유화 중합법에 의해 제조될 수 있다. The copolymer binder is not particularly limited, but may be prepared by, for example, suspension polymerization, emulsion polymerization, seed polymerization, or the like, and specifically, may be prepared by emulsion polymerization.
한편, 상기 공중합체 바인더는 필요에 따라 중합개시제, 가교제, 버퍼, 분자량 조절제, 유화제 등의 기타의 성분들을 하나 이상 포함할 수 있다. Meanwhile, the copolymer binder may include one or more other components such as a polymerization initiator, a crosslinking agent, a buffer, a molecular weight modifier, an emulsifier, and the like as necessary.
본 발명의 일례에 따른 이차전지용 바인더 조성물을 제조하는 방법에 있어서, 예컨대 상기 공중합체 바인더를 유화 중합법에 의해 제조할 경우를 들어 설명하면, 상기 비닐계 단량체, 상기 공액 디엔계 단량체 또는 공액 디엔계 중합체, 및 상기 수용성 중합체와 가교제를 이용하여 유화 중합법에 의해 제조하면서 중합 과정 중 중합개시제, 버퍼, 분자량 조절제, 유화제 등의 기타의 성분들을 이에 첨가할 수 있다. 상기 공중합체 바인더의 입자 크기는 유화제의 함량에 따라 조절될 수 있으며, 구체적으로 유화제의 함량이 증가할 경우 입자의 평균 입경을 작게할 수 있고, 유화제의 함량이 감소할 경우 입자의 평균 입경을 크게할 수 있다. In the method for producing a secondary battery binder composition according to an example of the present invention, for example, when the copolymer binder is produced by an emulsion polymerization method, the vinyl-based monomer, the conjugated diene-based monomer or the conjugated diene-based The polymer and other components such as a polymerization initiator, a buffer, a molecular weight regulator, an emulsifier and the like during the polymerization process may be added thereto, prepared by emulsion polymerization using the water-soluble polymer and the crosslinking agent. The particle size of the copolymer binder may be adjusted according to the content of the emulsifier, and in particular, when the content of the emulsifier is increased, the average particle size of the particles may be reduced, and when the content of the emulsifier is decreased, the average particle size of the particles is greatly increased. can do.
중합 온도 및 중합 시간은 중합 방법 중합 개시제의 종류 등에 따라 적절히 결정할 수 있으며, 예컨대 중합 온도는 50℃ 내지 300℃일 수 있고, 중합 시간은 1 시간 내지 20 시간일 수 있지만, 특별히 제한되지 않는다. The polymerization temperature and the polymerization time may be appropriately determined according to the kind of polymerization method polymerization initiator, etc., for example, the polymerization temperature may be 50 ° C to 300 ° C, and the polymerization time may be 1 hour to 20 hours, but is not particularly limited.
상기 중합 개시제로는 무기 또는 유기 과산화물이 사용될 수 있으며, 예컨대 포타슘 퍼설페이트, 소듐 퍼설페이트, 암모늄 퍼설페이트 등을 포함하는 수용성 개시제, 또는 큐멘 하이드로 퍼옥사이드, 벤조일 퍼옥사이드 등을 포함하는 유용성 개시제를 들 수 있다. 한편, 상기 중합개시제의 개시 반응을 촉진시키기 위해 활성화제가 함께 사용될 수 있으며, 상기 활성화제로는 소듐 포름알데히드 설폭실레이트, 소듐 에틸렌디아민 테트라아세테이트, 황산 제1철 및 덱스트로오스로 이루어진 군으로부터 선택되는 1종 이상을 들 수 있다. Inorganic or organic peroxides may be used as the polymerization initiator, and for example, water-soluble initiators including potassium persulfate, sodium persulfate, ammonium persulfate, and the like, or oil-soluble initiators including cumene hydroperoxide, benzoyl peroxide, and the like. Can be. On the other hand, an activator may be used together to promote the initiation reaction of the polymerization initiator, the activator is selected from the group consisting of sodium formaldehyde sulfoxylate, sodium ethylenediamine tetraacetate, ferrous sulfate and dextrose 1 or more types are mentioned.
상기 가교제는 상기 바인더의 가교를 촉진시키기 위해 사용될 수 있으며, 예컨대 디에틸렌트리아민, 트리에틸렌 테트라아민, 디에틸아미노 프로필아민, 자일렌 디아민, 이소포론 디아민 등의 아민류, 도데실 석시닉 언하이드리드(dodecyl succinic anhydride), 프탈릭 언하이드리드 등의 산무수물, 폴리아미드 수지, 폴리설파이드 수지, 페놀수지, 에틸렌 글리콜 디메타크릴레이트, 디에틸렌 글리콜 디메타크릴레이트, 트리에틸렌 글리콜 디메타크릴레이트, 1,3-부탄디올 디메타크릴레이트, 1,6-헥산디올 디메타크릴레이트, 네오펜틸 글리콜 디메타크릴레이트, 트리 메틸롤 프로판 트리메타크릴레이트, 트리 메틸롤 메탄 트리아크릴레이트, 글리시딜 메타 아크릴레이트 등을 들 수 있다. 한편, 그라프팅제가 함께 사용될 수 있으며, 예컨대 아릴 메타크릴레이트(AMA), 트리아릴 이소시아누레이트(TAIC), 트리아릴 아민(TAA), 또는 디아릴 아민(DAA) 등을 들 수 있다. The crosslinking agent may be used to promote crosslinking of the binder, for example, amines such as diethylenetriamine, triethylene tetraamine, diethylamino propylamine, xylene diamine, isophorone diamine, dodecyl succinic anhydride acid anhydrides such as dodecyl succinic anhydride, phthalic anhydride, polyamide resins, polysulfide resins, phenol resins, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, trimethylol propane trimethacrylate, trimethylol methane triacrylate, glycidyl meta Acrylates and the like. On the other hand, the grafting agent may be used together, such as aryl methacrylate (AMA), triaryl isocyanurate (TAIC), triaryl amine (TAA), or diaryl amine (DAA).
상기 버퍼로는, 예컨대 NaHCO3, NaOH, 또는 NH4OH를 들 수 있다. Examples of the buffer include NaHCO 3 , NaOH, or NH 4 OH.
상기 분자량 조절제로는, 예컨대 머캅탄류 또는 터비놀렌, 디펜텐, t-테르피엔 등의 테르핀류나 클로로포름, 사염화탄소 등의 할로겐화 탄화수소를 들 수 있다. Examples of the molecular weight regulator include mercaptans, terpins such as terbinolene, dipentene, t-terpyene, and halogenated hydrocarbons such as chloroform and carbon tetrachloride.
상기 유화제는 음이온성 유화제, 비이온성 유화제 또는 이들의 혼합물일 수 있으며, 음이온성 유화제에 비이온성 유화제를 함께 사용할 경우 음이온성 유화제의 정전기적 안정화에 더하여 고분자 입자의 반데르발스 힘을 통한 콜로이드 형태의 추가적인 안정화를 제공할 수 있다. The emulsifier may be an anionic emulsifier, a nonionic emulsifier, or a mixture thereof, and when the nonionic emulsifier is used in combination with the anionic emulsifier, in addition to the electrostatic stabilization of the anionic emulsifier, the colloidal form may be formed through the van der Waals force of the polymer particles. It may provide additional stabilization.
상기 음이온성 유화제로는, 예컨대 포스페이트계, 카르복실레이트계, 설페이트계, 석시네이트계, 설포석시네이트계, 설포네이트계, 또는 디설포네이트계 유화제를 들 수 있고, 특별히 제한되지 않지만 구체적으로 소듐 알킬 설페이트, 소듐 폴리옥시에틸렌 설페이트, 소듐 로릴 에테르 설페이트(Sodium lauryl ether sulfate), 소듐 폴리옥시에틸렌 로릴 에테르 설페이트, 소듐 로릴 설페이트, 소듐 알킬 설포네이트, 소듐 알킬 에테르 설포네이트, 소듐 알킬벤젠 설포네이트, 소듐 리니어 알킬벤젠 설포네이트, 소듐 알파-올레핀 설포네이트, 소듐 알코올 폴리옥시에틸렌 에테르 설포네이트, 소듐 디옥틸설포석시네이트, 소듐 퍼플루오로옥탄설포네이트, 소듐 퍼플루오로부탄설포네이트, 알킬디페닐옥사이드 디설포네이트, 소듐 디옥틸 설포석시네이트, 소듐 알킬-아릴 포스페이트, 소듐 알킬 에테르 포스테이트, 또는 소듐 라우오릴 사르코시네이트를 들 수 있다. Examples of the anionic emulsifier include phosphate, carboxylate, sulfate, succinate, sulfosuccinate, sulfonate, or disulfonate emulsifiers. Sodium alkyl sulfate, sodium polyoxyethylene sulfate, sodium lauryl ether sulfate, sodium polyoxyethylene lauryl ether sulfate, sodium lauryl sulfate, sodium alkyl sulfonate, sodium alkyl ether sulfonate, sodium alkylbenzene sulfonate, Sodium linear alkylbenzene sulfonate, sodium alpha-olefin sulfonate, sodium alcohol polyoxyethylene ether sulfonate, sodium dioctylsulfosuccinate, sodium perfluorooctanesulfonate, sodium perfluorobutanesulfonate, alkyldiphenyloxide Disulfonate, Sodium Dioctyl Sulfosuccinate, Sodium Al - there may be mentioned aryl phosphates, sodium alkyl ether four-state, or sodium laurate ohril sarcoidosis upon carbonate.
상기 비이온성 유화제로는, 예컨대 에스테르형, 에테르형, 에스테르-에테르형 유화제를 들 수 있고, 특별히 제한되지 않지만 구체적으로 폴리옥시에틸렌글리콜, 폴리옥시에틸렌글리콜메틸에테르, 폴리옥시에틸렌모노알릴에테르, 폴리옥시에틸렌비스페놀-A 에테르, 폴리프로필렌글 리콜, 폴리옥시에틸렌네오펜틸에테르, 폴리옥시에틸렌세틸에테르, 폴리옥시에틸렌로릴에테르, 폴리옥시에틸올레일에테르, 폴리옥시에틸렌스테아릴 에테르, 폴리옥시에틸렌데실에테르, 폴리옥시에틸렌옥틸에테르를 들 수 있다. Examples of the nonionic emulsifiers include ester type, ether type, and ester-ether type emulsifiers, and although not particularly limited, polyoxyethylene glycol, polyoxyethylene glycol methyl ether, polyoxyethylene monoallyl ether, poly Oxyethylene bisphenol-A ether, polypropylene glycol, polyoxyethylene neopentyl ether, polyoxyethylene cetyl ether, polyoxyethylene lauryl ether, polyoxyethyl oleyl ether, polyoxyethylene stearyl ether, polyoxyethylene decyl Ether and polyoxyethylene octyl ether.
상기 이차전지용 바인더 조성물은 리튬 이차전지용 전극의 제조에 있어서 바인더로 사용될 수 있으며, 특히 음극 활물질로서 실리콘계 음극 활물질이 사용될 경우 유용하게 사용될 수 있다. The secondary battery binder composition may be used as a binder in the production of a lithium secondary battery electrode, and particularly useful when a silicon-based negative electrode active material is used as the negative electrode active material.
따라서, 본 발명은 실리콘계 음극 활물질 및 상기 이차전지용 바인더 조성물을 포함하는 리튬 이차전지용 음극을 제공한다. Accordingly, the present invention provides a negative electrode for a lithium secondary battery including the silicon-based negative active material and the binder composition for the secondary battery.
상기 실리콘계 음극 활물질로는, 예컨대 Si, 실리콘 산화물 입자(SiOx, 0<x≤2), Si-금속합금, 및 Si와 실리콘 산화물 입자(SiOx, 0<x≤2)의 합금으로 이루어진 군으로부터 선택된 1종 이상을 포함하는 것을 들 수 있고, 상기 실리콘 산화물 입자(SiOx, 0<x<2)는 결정형 SiO2 및 비정형 Si로 구성된 복합물일 수 있다. 또한, 상기 음극 활물질로는 상기 실리콘계 음극 활물질 이외에 통상적으로 리튬 이온이 흡장 및 방출될 수 있는 탄소재, 리튬 금속 또는 주석 등을 사용할 수 있다. 바람직하게는 탄소재를 사용할 수 있는데, 탄소재로는 저결정 탄소 및 고결정성 탄소 등이 모두 사용될 수 있다. 저결정성 탄소로는 연화탄소(soft carbon) 및 경화탄소(hard carbon)가 대표적이며, 고결정성 탄소로는 천연 흑연, 키시흑연(kish graphite), 열분해 탄소(pyrolytic carbon), 액정피치계 탄소섬유(mesophase pitch based carbon fiber), 탄소 미소구체(meso-carbon microbeads), 액정피치(mesophase pitches) 및 석유와 석탄계 코크스(petroleum or coal tar pitch derived cokes) 등의 고온 소성탄소가 대표적이다.As the silicon-based negative active material, for example, a group consisting of Si, silicon oxide particles (SiO x , 0 <x≤2), Si-metal alloy, and an alloy of Si and silicon oxide particles (SiO x , 0 <x≤2) It may include one or more selected from the above, the silicon oxide particles (SiO x , 0 <x <2) may be a composite composed of crystalline SiO 2 and amorphous Si. In addition, as the negative electrode active material, in addition to the silicon-based negative electrode active material, a carbon material, lithium metal, tin, or the like, which may normally occlude and release lithium ions, may be used. Preferably, a carbon material may be used, and as the carbon material, both low crystalline carbon and high crystalline carbon may be used. Soft crystalline carbon and hard carbon are typical low crystalline carbon, and high crystalline carbon is natural graphite, kish graphite, pyrolytic carbon, liquid crystal pitch carbon fiber. High-temperature calcined carbon such as (mesophase pitch based carbon fiber), meso-carbon microbeads, mesophase pitches and petroleum or coal tar pitch derived cokes.
본 발명의 일례에 따른 리튬 이차전지용 음극에 있어서, 상기 리튬 이차전지용 음극은 탄소계 음극 활물질을 더 포함할 수 있고, 이때 상기 실리콘계 음극 활물질은 전체 음극 활물질 중 1 중량% 내지 30 중량%, 구체적으로 5 중량% 내지 10 중량% 포함되어 있을 수 있다. 상기 탄소계 음극 활물질은 구체적으로 천연 흑연, 인조 흑연, 또는 이들의 혼합물일 수 있다. In the negative electrode for a lithium secondary battery according to an embodiment of the present invention, the negative electrode for a lithium secondary battery may further include a carbon-based negative electrode active material, wherein the silicon-based negative electrode active material is 1% to 30% by weight of the total negative electrode active material, specifically 5 wt% to 10 wt% may be included. Specifically, the carbon-based negative electrode active material may be natural graphite, artificial graphite, or a mixture thereof.
상기 리튬 이차전지용 음극이 실리콘계 음극 활물질을 포함할 경우, 상기 음극의 음극 활물질 층의 형성에 사용되는 상기 이차전지용 바인더가 0.02 MPa 이상, 구체적으로 0.1 MPa 이상, 더욱 구체적으로 0.3 MPa 내지 0.5 MPa의 습윤강도를 가질 경우, 전해액에 의한 스웰링이 적절히 억제될 수 있으며, 적절한 기계적 물성을 유지하여 이를 포함하는 음극 및 이차전지의 수명특성이 개선될 수 있다. When the negative electrode for a lithium secondary battery includes a silicon-based negative electrode active material, the secondary battery binder used to form the negative electrode active material layer of the negative electrode has a wetness of 0.02 MPa or more, specifically 0.1 MPa or more, more specifically 0.3 MPa to 0.5 MPa. When having strength, swelling by the electrolyte may be appropriately suppressed, and life characteristics of the negative electrode and the secondary battery including the same may be improved by maintaining appropriate mechanical properties.
상기 리튬 이차전지는 상기 음극, 양극 및 상기 음극과 양극 사이에 개재된 세퍼레이터를 포함하는 것일 수 있다.The lithium secondary battery may include a separator interposed between the negative electrode, the positive electrode, and the negative electrode and the positive electrode.
상기 음극은 당 분야에 알려져 있는 통상적인 방법으로 제조될 수 있으며, 예컨대 음극 활물질 및 전술한 바인더, 및 도전재 등의 첨가제들을 혼합 및 교반하여 음극 활물질 슬러리를 제조한 후, 이를 음극 집전체에 도포하고 건조한 후 압축하여 제조할 수 있다.The negative electrode may be manufactured by a conventional method known in the art, and for example, a negative electrode active material slurry is prepared by mixing and stirring additives such as the negative electrode active material, the above-described binder, and a conductive material, and then apply the negative electrode active material to the negative electrode current collector. It can be prepared by drying and compressing.
상기 음극을 형성하기 위한 용매로는 NMP(N-메틸 피롤리돈), DMF(디메틸 포름아미드), 아세톤, 디메틸 아세트아미드 등의 유기 용매 또는 물 등이 있으며, 이들 용매는 단독으로 또는 2종 이상을 혼합하여 사용할 수 있다. 용매의 사용량은 슬러리의 도포 두께, 제조 수율을 고려하여 상기 음극 활물질, 바인더, 도전재를 용해 및 분산시킬 수 있는 정도이면 충분하다.The solvent for forming the negative electrode includes an organic solvent such as NMP (N-methyl pyrrolidone), DMF (dimethyl formamide), acetone, dimethyl acetamide or water, and these solvents alone or in combination of two or more. Can be mixed and used. The amount of the solvent used is sufficient to dissolve and disperse the negative electrode active material, the binder, and the conductive material in consideration of the coating thickness of the slurry and the production yield.
상기 이차전지용 바인더 조성물은 음극 활물질용 슬러리 전체 중량 중에 10 중량% 이하로 포함될 수 있으며, 구체적으로 0.1 중량% 내지 10 중량%, 더욱 구체적으로 0.5 중량% 내지 4 중량% 포함될 수 있다. 상기 바인더의 함량이 0.1 중량% 미만이면 바인더의 사용에 따른 효과가 미미하여 바람직하지 않고, 10 중량%를 초과하면 바인더의 함량 증가에 따른 활물질의 상대적인 함량 감소로 인해 체적당 용량이 저하될 우려가 있어 바람직하지 않다.The secondary battery binder composition may be included in less than 10% by weight of the total weight of the slurry for the negative electrode active material, specifically 0.1 to 10% by weight, more specifically 0.5 to 4% by weight may be included. If the content of the binder is less than 0.1% by weight, the effect of using the binder is insignificant and undesirable. If the content of the binder exceeds 10% by weight, the capacity per volume may decrease due to the decrease in the relative content of the active material due to the increase in the content of the binder. Not desirable
상기 도전재는 당해 전지에 화학적 변화를 유발하지 않으면서 도전성을 가진 것이라면 특별히 제한되는 것은 아니며, 상기 도전재의 예로서는 천연 흑연이나 인조 흑연 등의 흑연; 아세틸렌 블랙, 케첸 블랙, 채널 블랙, 퍼네이스 블랙, 램프 블랙, 서멀 블랙 등의 카본블랙; 탄소 섬유나 금속 섬유 등의 도전성 섬유; 불화 카본, 알루미늄, 니켈 분말 등의 금속 분말; 산화아연, 티탄산 칼륨 등의 도전성 위스커; 산화 티탄 등의 도전성 금속 산화물; 또는 폴리페닐렌 유도체 등의 도전성 소재 등을 들 수 있다. 상기 도전재는 음극 활물질용 슬러리 전체 중량에 대해 1 중량% 내지 9 중량%의 양으로 사용될 수 있다.The conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery. Examples of the conductive material include graphite such as natural graphite and artificial graphite; Carbon blacks such as acetylene black, Ketjen black, channel black, furnace black, lamp black and thermal 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; Or conductive materials such as polyphenylene derivatives. The conductive material may be used in an amount of 1% by weight to 9% by weight based on the total weight of the slurry for the negative electrode active material.
본 발명의 일 실시예에 따른 상기 음극에 사용되는 음극 집전체는 3 ㎛ 내지 500 ㎛의 두께를 갖는 것일 수 있다. 상기 음극 집전체는, 당해 전지에 화학적 변화를 유발하지 않으면서 도전성을 가진 것이라면 특별히 제한되는 것은 아니며, 예컨대 구리, 금, 스테인리스 스틸, 알루미늄, 니켈, 티탄, 소성 탄소, 구리나 스테인리스 스틸의 표면에 카본, 니켈, 티탄, 은 등으로 표면처리한 것, 알루미늄-카드뮴 합금 등이 사용될 수 있다. 또한, 표면에 미세한 요철을 형성하여 음극 활물질의 결합력을 강화시킬 수도 있으며, 필름, 시트, 호일, 네트, 다공질체, 발포체, 부직포체 등 다양한 형태로 사용될 수 있다.The negative electrode current collector used for the negative electrode according to an embodiment of the present invention may have a thickness of 3 ㎛ to 500 ㎛. The negative electrode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery. For example, the negative electrode current collector may be formed on the surface of copper, gold, stainless steel, aluminum, nickel, titanium, calcined carbon, copper, or stainless steel. Surface-treated with carbon, nickel, titanium, silver and the like, aluminum-cadmium alloy and the like can be used. In addition, fine concavities and convexities may be formed on the surface to enhance the bonding strength of the negative electrode active material, and may be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.
상기 활물질 슬러리에는 필요에 따라 점도 조절제 및/또는 충진제가 포함될 수 있다.The active material slurry may include a viscosity modifier and / or fillers as needed.
상기 점도 조절제는 카르복시메틸셀룰로우즈, 또는 폴리아크릴산 등일 수 있으며, 첨가에 의해 상기 활물질 슬러리의 제조와 상기 전극 집전체 상의 도포 공정이 용이하도록 활물질 슬러리의 점도가 조절될 수 있다. The viscosity adjusting agent may be carboxymethyl cellulose, polyacrylic acid, or the like, and the viscosity of the active material slurry may be adjusted to facilitate the preparation of the active material slurry and the coating process on the electrode current collector by addition.
상기 충진제는 전극의 팽창을 억제하는 보조성분으로서, 당해 전지에 화학적 변화를 유발하지 않는 섬유상 재료라면 특별히 제한되는 것은 아니며, 예컨대 폴리에틸렌, 폴리프로필렌 등의 올레핀계 중합체, 유리섬유, 탄소섬유 등의 섬유상 물질일 수 있다.The filler is an auxiliary component that suppresses the expansion of the electrode, and is not particularly limited as long as it is a fibrous material that does not cause chemical change in the battery. For example, the filler is fibrous such as olefin-based polymers such as polyethylene and polypropylene, glass fibers, and carbon fibers. It may be a substance.
상기 양극은 당 분야에 알려져 있는 통상적인 방법으로 제조할 수 있다. 예를 들면, 양극 활물질에 용매, 전술한 바인더, 도전재, 분산제를 혼합 및 교반하여 슬러리를 제조한 후 이를 금속 재료의 집전체에 도포(코팅)하고 압축한 뒤 건조하여 양극을 제조할 수 있다.The positive electrode can be prepared by conventional methods known in the art. For example, a slurry may be prepared by mixing and stirring a solvent, the above-described binder, a conductive material, and a dispersant in a positive electrode active material, and then applying the coating (coating) to a current collector of a metal material, compressing it, and drying the same to prepare a positive electrode. .
상기 금속 재료의 집전체는 전도성이 높은 금속으로서, 상기 양극 활물질의 슬러리가 용이하게 접착될 수 있는 금속으로 전지의 전압 범위에서 당해 전지에 화학적 변화를 유발하지 않으면서 높은 도전성을 가지는 것이라면 특별히 제한되는 것은 아니며, 예컨대 스테인레스 스틸, 알루미늄, 니켈, 티탄, 소성 탄소, 또는 알루미늄이나 스테리인레스 스틸의 표면에 카본, 니켈, 티탄, 은 등으로 표면 처리한 것 등이 사용될 수 있다. 또한, 집전체 표면에 미세한 요철을 형성하여 양극 활물질의 접착력을 높일 수도 있다. 집전체는 필름, 시트, 호일, 네트, 다공질체, 발포체, 부직포체 등 다양한 형태로 사용 가능하며, 3 내지 500 ㎛의 두께를 갖는 것일 수 있다. The current collector of the metal material is a metal having high conductivity, and is a metal to which the slurry of the positive electrode active material can be easily adhered, and is particularly limited as long as it has high conductivity without causing chemical change in the battery in the voltage range of the battery. For example, surface treated with carbon, nickel, titanium, silver, or the like on the surface of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel may be used. In addition, fine unevenness may be formed on the surface of the current collector to increase the adhesion of the positive electrode active material. The current collector may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a nonwoven fabric, and may have a thickness of 3 to 500 μm.
상기 양극 활물질은, 예컨대 리튬 코발트 산화물(LiCoO2); 리튬 니켈 산화물(LiNiO2); Li[NiaCobMncM1 d]O2(상기 식에서, M1은 Al, Ga 및 In으로 이루어진 군에서 선택되는 어느 하나 또는 이들 중 2종 이상의 원소이고, 0.3≤a<1.0, 0≤b≤0.5, 0≤c≤0.5, 0≤d≤0.1, a+b+c+d=1이다); Li(LieM2 f-e-f'M3 f')O2 - gAg(상기 식에서, 0≤e≤0.2, 0.6≤f≤1, 0≤f'≤0.2, 0≤g≤0.2이고, M2는 Mn과, Ni, Co, Fe, Cr, V, Cu, Zn 및 Ti로 이루어진 군에서 선택되는 1종 이상을 포함하며, M3은 Al, Mg 및 B로 이루어진 군에서 선택되는 1종 이상이고, A는 P, F, S 및 N로 이루어진 군에서 선택되는 1종 이상이다) 등의 층상 화합물이나 1 또는 그 이상의 전이금속으로 치환된 화합물; Li1 + hMn2 - hO4(상기 식에서 0≤h≤0.33), LiMnO3, LiMn2O3, LiMnO2 등의 리튬 망간 산화물; 리튬 동 산화물(Li2CuO2); LiV3O8, V2O5, Cu2V2O7 등의 바나듐 산화물; 화학식 LiNi1 - iM4 iO2(상기 식에서, M4는 Co, Mn, Al, Cu, Fe, Mg, B 또는 Ga이고, 0.01≤i≤0.3)로 표현되는 Ni 사이트형 리튬 니켈 산화물; 화학식 LiMn2 - jM5 jO2 (상기 식에서, M5는 Co, Ni, Fe, Cr, Zn 또는 Ta이고, 0.01≤j≤0.1) 또는 Li2Mn3M6O8(상기 식에서, M6는 Fe, Co, Ni, Cu 또는 Zn)로 표현되는 리튬 망간 복합 산화물; 화학식의 Li 일부가 알칼리토금속 이온으로 치환된 LiMn2O4; 디설파이드 화합물; LiFe3O4, Fe2(MoO4)3 등을 들 수 있지만, 이들만으로 한정되는 것은 아니다. The positive electrode active material may be, for example, lithium cobalt oxide (LiCoO 2 ); Lithium nickel oxide (LiNiO 2 ); Li [Ni a Co b Mn c M 1 d ] O 2 (wherein M 1 is any one selected from the group consisting of Al, Ga, and In or two or more elements thereof, and 0.3 ≦ a <1.0, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.1, a + b + c + d = 1); Li (Li e M 2 fe-f ' M 3 f' ) O 2 - g A g (wherein 0≤e≤0.2, 0.6≤f≤1, 0≤f'≤0.2, 0≤g≤0.2 , M 2 includes at least one selected from the group consisting of Mn, Ni, Co, Fe, Cr, V, Cu, Zn and Ti, M 3 is 1 selected from the group consisting of Al, Mg and B At least one species, and A is at least one species selected from the group consisting of P, F, S and N), or a compound substituted with one or more transition metals; Li 1 + h Mn 2 - h O 4 ( wherein 0≤h≤0.33), LiMnO 3, the lithium manganese oxide such as LiMn 2 O 3, LiMnO 2; Lithium copper oxide (Li 2 CuO 2 ); Vanadium oxides such as LiV 3 O 8 , V 2 O 5 , Cu 2 V 2 O 7, and the like; Formula LiNi 1 - i M 4 i O 2 Ni site type lithium nickel oxides represented by (wherein, M 4 is a Co, Mn, Al, Cu, Fe, Mg, B or Ga, 0.01≤i≤0.3); LiMn 2 - j M 5 j O 2 (wherein M 5 is Co, Ni, Fe, Cr, Zn or Ta, 0.01 ≦ j ≦ 0.1) or Li 2 Mn 3 M 6 O 8 (wherein 6 is a lithium manganese composite oxide represented by Fe, Co, Ni, Cu or Zn); LiMn 2 O 4 in which a part of Li in the formula is substituted with alkaline earth metal ions; Disulfide compounds; LiFe 3 O 4 , Fe 2 (MoO 4 ) 3, etc. may be mentioned, but is not limited thereto.
상기 양극을 형성하기 위한 용매로는 NMP(N-메틸 피롤리돈), DMF(디메틸 포름아미드), 아세톤, 디메틸 아세트아미드 등의 유기 용매 또는 물 등이 있으며, 이들 용매는 단독으로 또는 2종 이상을 혼합하여 사용할 수 있다. 용매의 사용량은 슬러리의 도포 두께, 제조 수율을 고려하여 상기 양극 활물질, 바인더, 도전재를 용해 및 분산시킬 수 있는 정도이면 충분하다.The solvent for forming the positive electrode includes an organic solvent such as NMP (N-methyl pyrrolidone), DMF (dimethyl formamide), acetone, dimethyl acetamide or water, and these solvents alone or in combination of two or more. Can be mixed and used. The amount of the solvent used is sufficient to dissolve and disperse the positive electrode active material, the binder, and the conductive material in consideration of the coating thickness of the slurry and the production yield.
상기 도전재는 당해 전지에 화학적 변화를 유발하지 않으면서 도전성을 가진 것이라면 특별히 제한되는 것은 아니며, 예컨대 천연 흑연이나 인조 흑연 등의 흑연; 아세틸렌 블랙, 케첸 블랙, 채널 블랙, 파네스 블랙, 램프 블랙, 서멀 블랙 등의 카본블랙; 탄소 섬유나 금속 섬유 등의 도전성 섬유; 탄소 나노 튜브 등의 도전성 튜브; 플루오로카본, 알루미늄, 니켈 분말 등의 금속 분말; 산화아연, 티탄산 칼륨 등의 도전성 위스커; 산화 티탄 등의 도전성 금속 산화물; 폴리페닐렌 유도체 등의 도전성 소재 등이 사용될 수 있다. 상기 도전재는 양극 슬러리 전체 중량에 대해 1 중량% 내지 20 중량%의 양으로 사용될 수 있다. The conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery. Examples of the conductive material include graphite such as natural graphite and artificial graphite; Carbon blacks such as acetylene black, Ketjen black, channel black, farnes black, lamp black and thermal black; Conductive fibers such as carbon fibers and metal fibers; Conductive tubes such as carbon nanotubes; Metal powders such as fluorocarbon, aluminum and nickel powders; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used. The conductive material may be used in an amount of 1 wt% to 20 wt% with respect to the total weight of the positive electrode slurry.
상기 분산제는 수계 분산제 또는 N-메틸-2-피롤리돈 등의 유기 분산제를 사용할 수 있다. The dispersant may be an aqueous dispersant or an organic dispersant such as N-methyl-2-pyrrolidone.
한편, 세퍼레이터로는 종래에 세퍼레이터로 사용된 통상적인 다공성 고분자 필름, 예컨대 에틸렌 단독중합체, 프로필렌 단독중합체, 에틸렌-부텐 공중합체, 에틸렌-헥센 공중합체 및 에틸렌-메타크릴레이트 공중합체 등과 같은 폴리올레핀계 고분자로 제조한 다공성 고분자 필름을 단독으로 또는 이들을 적층하여 사용할 수 있으며, 또는 통상적인 다공성 부직포, 예컨대 고융점의 유리 섬유, 폴리에틸렌테레프탈레이트 섬유 등으로 된 부직포를 사용할 수 있으나, 이에 한정되는 것은 아니다.On the other hand, as the separator, conventional porous polymer films conventionally used as separators, such as polyolefin-based polymers such as ethylene homopolymer, propylene homopolymer, ethylene-butene copolymer, ethylene-hexene copolymer and ethylene-methacrylate copolymer The porous polymer film prepared by using a single or a lamination thereof may be used, or a conventional porous nonwoven fabric, such as a high melting point glass fiber, polyethylene terephthalate fiber, etc. may be used, but is not limited thereto.
본 발명에서 사용되는 전해질로서 포함될 수 있는 리튬염은 리튬 이차전지용 전해질에 통상적으로 사용되는 것들이 제한 없이 사용될 수 있으며, 예컨대 상기 리튬염의 음이온으로는 F-, Cl-, Br-, I-, NO3 -, N(CN)2 -, BF4 -, ClO4 -, PF6 -, (CF3)2PF4 -, (CF3)3PF3 -, (CF3)4PF2 -, (CF3)5PF-, (CF3)6P-, CF3SO3 -, CF3CF2SO3 -, (CF3SO2)2N-, (FSO2)2N-, CF3CF2(CF3)2CO-, (CF3SO2)2CH-, (SF5)3C-, (CF3SO2)3C-, CF3(CF2)7SO3 -, CF3CO2 -, CH3CO2 -, SCN- 및 (CF3CF2SO2)2N-로 이루어진 군에서 선택된 어느 하나일 수 있다. A lithium salt which can be included as an electrolyte used in the present invention can be used without limitation, those which are commonly used in a lithium secondary battery electrolyte, for example the lithium salt of the anion is F -, Cl -, Br - , I -, NO 3 -, N (CN) 2 - , BF 4 -, ClO 4 -, PF 6 -, (CF 3) 2 PF 4 -, (CF 3) 3 PF 3 -, (CF 3) 4 PF 2 -, (CF 3) 5 PF -, (CF 3) 6 P -, CF 3 SO 3 -, CF 3 CF 2 SO 3 -, (CF 3 SO 2) 2 N -, (FSO 2) 2 N -, CF 3 CF 2 (CF 3) 2 CO -, (CF 3 SO 2) 2 CH -, (SF 5) 3 C -, (CF 3 SO 2) 3 C -, CF 3 (CF 2) 7 SO 3 -, CF 3 CO 2 may be any one selected from the group consisting of -, CH 3 CO 2 -, SCN - , and (CF 3 CF 2 SO 2) 2 N.
본 발명에서 사용되는 전해액에 있어서, 전해액에 포함되는 유기 용매로는 이차 전지용 전해액에 통상적으로 사용되는 것들이 제한 없이 사용될 수 있으며, 대표적으로 프로필렌 카보네이트(propylene carbonate, PC), 에틸렌 카보네이트(ethylene carbonate, EC), 디에틸 카보네이트(diethyl carbonate, DEC), 디메틸 카보네이트(dimethyl carbonate, DMC), 에틸메틸 카보네이트(EMC), 메틸프로필 카보네이트, 디프로필 카보네이트, 디메틸 설퍼옥사이드, 아세토니트릴, 디메톡시에탄, 디에톡시에탄, 비닐렌 카보네이트, 설포란, 감마-부티로락톤, 프로필렌 설파이트 및 테트라하이드로푸란으로 이루어진 군에서 선택되는 어느 하나 또는 이들 중 2종 이상의 혼합물 등이 대표적으로 사용될 수 있다. 구체적으로, 상기 카보네이트계 유기용매 중 고리형 카보네이트인 에틸렌 카보네이트 및 프로필렌 카보네이트는 고점도의 유기용매로서 유전율이 높아 전해질 내의 리튬염을 잘 해리시키므로 바람직하게 사용될 수 있으며, 이러한 고리형 카보네이트에 디메틸 카보네이트 및 디에틸 카보네이트와 같은 저점도, 저유전율 선형 카보네이트를 적당한 비율로 혼합하여 사용하면 높은 전기 전도율을 갖는 전해액을 만들 수 있어 더욱 바람직하게 사용될 수 있다.In the electrolyte solution used in the present invention, as the organic solvent included in the electrolyte solution, those conventionally used in the electrolyte for secondary batteries may be used without limitation, and typically propylene carbonate (PC), ethylene carbonate (ethylene carbonate, EC ), Diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), methylpropyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane , Vinylene carbonate, sulfolane, gamma-butyrolactone, propylene sulfite, tetrahydrofuran, any one selected from the group consisting of, or mixtures of two or more thereof may be representatively used. Specifically, ethylene carbonate and propylene carbonate, which are cyclic carbonates among the carbonate-based organic solvents, may be preferably used because they have high dielectric constants to dissociate lithium salts in the electrolyte, and may be preferably used in such cyclic carbonates. When a low viscosity, low dielectric constant linear carbonate such as ethyl carbonate is mixed and used in an appropriate ratio, an electrolyte having high electrical conductivity can be prepared, and thus it can be used more preferably.
선택적으로, 본 발명에 따라 저장되는 전해액은 통상의 전해액에 포함되는 과충전 방지제 등과 같은 첨가제를 더 포함할 수 있다.Optionally, the electrolyte solution stored according to the present invention may further include additives such as an overcharge inhibitor included in a conventional electrolyte solution.
본 발명의 리튬 이차전지의 외형은 특별한 제한이 없으나, 캔을 사용한 원통형, 각형, 파우치(pouch)형 또는 코인(coin)형 등이 될 수 있다.The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be cylindrical, square, pouch type, or coin type using a can.
본 발명에 따른 리튬 이차전지는 소형 디바이스의 전원으로 사용되는 전지셀에 사용될 수 있을 뿐만 아니라, 다수의 전지셀들을 포함하는 중대형 전지모듈에 단위전지로도 바람직하게 사용될 수 있다.The lithium secondary battery according to the present invention may not only be used in a battery cell used as a power source for a small device, but also preferably used as a unit battery in a medium-large battery module including a plurality of battery cells.
실시예Example
이하, 본 발명을 구체적으로 설명하기 위해 실시예 및 실험예를 들어 더욱 상세하게 설명하나, 본 발명이 이들 실시예 및 실험예에 의해 제한되는 것은 아니다. 본 발명에 따른 실시예는 여러 가지 다른 형태로 변형될 수 있으며, 본 발명의 범위가 아래에서 상술하는 실시예에 한정되는 것으로 해석되어서는 안 된다. 본 발명의 실시예는 당업계에서 평균적인 지식을 가진 자에게 본 발명을 보다 완전하게 설명하기 위해서 제공되는 것이다.Hereinafter, the present invention will be described in more detail with reference to Examples and Experimental Examples, but the present invention is not limited to these Examples and Experimental Examples. Embodiments according to the present invention can be modified in many different forms, the scope of the invention should not be construed as limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.
공중합체 바인더의 제조Preparation of Copolymer Binder
실시예 1Example 1
스티렌 60 g, 1,3-부타디엔 30 g, 부틸아크릴레이트 8 g, 폴리아크릴산 2 g과 함께, 중합 개시제로서 포타슘 퍼설페이트 및 유화제로서 소듐 로릴 설페이트 소량을 증류수에 첨가하고, 5시간 동안 70℃를 유지하면서 반응시켜 평균 입경(D50)이 200 nm인 공중합체 바인더를 얻었다. Along with 60 g of styrene, 30 g of 1,3-butadiene, 8 g of butylacrylate, and 2 g of polyacrylic acid, a small amount of potassium persulfate as a polymerization initiator and sodium lauryl sulfate as an emulsifier was added to distilled water and 70 ° C for 5 hours. reacting while keeping the average particle diameter (D 50) to obtain a 200 nm a copolymer binder.
실시예 2 Example 2
상기 실시예 1에서 폴리아크릴산을 42 g으로 달리하여 사용한 것을 제외하고는, 실시예 1과 마찬가지의 방법으로 평균 입경(D50)이 350 nm인 공중합체 바인더를 얻었다.A copolymer binder having an average particle diameter (D 50 ) of 350 nm was obtained in the same manner as in Example 1, except that polyacrylic acid was used in an amount of 42 g.
실시예 3 Example 3
상기 실시예 1에서 폴리아크릴산을 98 g으로 달리하여 사용한 것을 제외하고는, 실시예 1과 마찬가지의 방법으로 평균 입경(D50)이 450 nm인 공중합체 바인더를 얻었다.A copolymer binder having an average particle diameter (D 50 ) of 450 nm was obtained in the same manner as in Example 1, except that polyacrylic acid was used in an amount of 98 g.
비교예 1Comparative Example 1
스티렌 40 g, 1,3-부타디엔 40 g, 부틸아크릴레이트 20 g과 함께, 중합 개시제로서 포타슘 퍼설페이트 및 유화제로서 소듐 로릴 설페이트 소량을 증류수에 첨가하고, 5시간 동안 70℃를 유지하면서 반응시켜 평균 입경(D50)이 200 nm인 공중합체 바인더를 얻었다. Along with 40 g of styrene, 40 g of 1,3-butadiene and 20 g of butyl acrylate, a small amount of potassium persulfate as a polymerization initiator and sodium lauryl sulfate as an emulsifier was added to distilled water, and reacted while maintaining at 70 DEG C for 5 hours to average A copolymer binder having a particle diameter (D 50 ) of 200 nm was obtained.
비교예 2Comparative Example 2
1,3-부타디엔 및 부틸아크릴레이트를 각각 50 g 및 10 g의 양으로 변경한 것을 제외하고는, 상기 비교예 1과 마찬가지의 방법으로 평균 입경(D50)이 200 nm인 공중합체 바인더를 얻었다.A copolymer binder having an average particle diameter (D 50 ) of 200 nm was obtained in the same manner as in Comparative Example 1, except that 1,3-butadiene and butyl acrylate were changed to the amounts of 50 g and 10 g, respectively. .
음극 및 리튬 이차전지의 제조 Fabrication of negative electrode and lithium secondary battery
실시예 4 Example 4
<음극의 제조> <Production of Cathode>
인조흑연:천연흑연:실리콘계 음극 활물질(SiO)이 84.5:10.5:5의 중량비로 혼합된 혼합 음극 활물질, 증점제(카르복시 메틸셀룰로오즈), 도전재로서 카본블랙, 상기 실시예 2에서 제조된 바인더를 98:1:1:2의 중량비로 TK 믹서를 이용하여 혼합하여 음극 슬러리를 제조하였다. 상기 음극 슬러리를 20 ㎛의 구리 호일에 120 ㎛ 두께로 코팅한 후, 진공 오븐에서 100℃로 12시간 건조한 뒤, 적당한 두께로 압연하여 음극을 제조하였다.Artificial graphite: natural graphite: silicon-based negative electrode active material (SiO) mixed in a weight ratio of 84.5: 10.5: 5 mixed negative electrode active material, a thickener (carboxy methyl cellulose), carbon black as a conductive material, the binder prepared in Example 2 98 A negative electrode slurry was prepared by mixing using a TK mixer at a weight ratio of 1: 1: 2. The negative electrode slurry was coated on a copper foil of 20 μm to a thickness of 120 μm, dried at 100 ° C. for 12 hours in a vacuum oven, and then rolled to a suitable thickness to prepare a negative electrode.
<양극의 제조><Manufacture of Anode>
양극 활물질로서 LiCoO2 96 g, 아세틸렌 블랙 2 g, 바인더로 폴리비닐리덴 플루오라이드(PVdF) 2 g을 용매인 N-메틸-2-피롤리돈(NMP)에 첨가하여 양극용 슬러리를 제조한 후, 상기 양극용 슬러리를 알루미늄(Al) 박막에 350 ㎛ 두께로 코팅하고, 건조하여 양극을 제조한 후, 롤 프레스(roll press)를 실시하여 양극을 제조하였다.96 g of LiCoO 2 , 2 g of acetylene black, and 2 g of polyvinylidene fluoride (PVdF) as a positive electrode active material were added to N-methyl-2-pyrrolidone (NMP) as a solvent to prepare a slurry for the positive electrode. The anode slurry was coated on an aluminum (Al) thin film to a thickness of 350 μm, dried to prepare a cathode, and then roll-rolled to prepare a cathode.
<리튬 이차전지의 제조><Production of Lithium Secondary Battery>
상기에서 제조된 음극을 표면적 13.33 cm2가 되도록 펀칭하고, 상기에서 제조된 양극을 표면적 12.60 cm2가 되도록 펀칭하여 단일셀(mono-cell)을 제작하였다. 탭(tap)을 상기 양극 및 음극의 상부에 부착하고, 음극과 양극 사이에 폴리올레핀 미세 다공막으로 만들어진 분리막을 개재시켜 상기 결과물을 알루미늄 파우치에 적재한 후 전해액 500 mg을 파우치 내부에 주입하였다. 전해액은 EC(에틸렌 카보네이트):DEC(디에틸 카보네이트):PC(프로필렌 카보네이트)=4:3:3(체적비) 혼합 용매를 사용하여 LiPF6 전해질을 1 M의 농도로 용해시켜 제조하였다.The anode prepared above was punched out to have a surface area of 13.33 cm 2 , and the anode prepared above was punched out to have a surface area of 12.60 cm 2 to prepare a mono-cell. A tap was attached to the upper part of the positive electrode and the negative electrode, and the resultant was loaded into an aluminum pouch through a separator made of a polyolefin microporous membrane between the negative electrode and the positive electrode, and 500 mg of the electrolyte was injected into the pouch. The electrolyte was prepared by dissolving the LiPF 6 electrolyte at a concentration of 1 M using an EC (ethylene carbonate): DEC (diethyl carbonate): PC (propylene carbonate) = 4: 3: 3 (volume ratio) mixed solvent.
이후, 진공포장기를 이용하여 상기 파우치를 밀봉하고 상온에서 12시간 동안 유지시킨 후, 약 0.05 C 비율로 정전류 충전하고 전류의 약 1/6이 될 때까지 전압을 유지시켜주는 정접압 충전 과정을 거쳤다. 이때, 셀 내부에 가스가 발생하므로 탈가스(degassing)와 재실링(resealing) 과정을 수행하여 리튬 이차전지를 완성하였다.Thereafter, the pouch was sealed using a vacuum packaging machine and maintained at room temperature for 12 hours, followed by a constant current charging process to maintain a constant current at a rate of about 0.05 C and maintain a voltage until about 1/6 of the current. . At this time, since gas is generated inside the cell, degassing and resealing were performed to complete the lithium secondary battery.
실시예 5 Example 5
상기 실시예 4에서 음극의 제조시 바인더로서 실시예 1의 공중합체 바인더를 사용하고, 인조흑연:천연흑연:실리콘계 음극 활물질이 80:10:10의 중량비로 혼합된 혼합 음극 활물질을 사용한 것을 제외하고는, 상기 실시예 4와 마찬가지의 과정을 통하여 음극, 양극 및 리튬 이차전지를 제조하였다. Except that the copolymer binder of Example 1 was used as the binder in the preparation of the negative electrode in Example 4, and the artificial negative electrode: natural graphite: silicon-based negative active material was mixed mixed active material in a weight ratio of 80:10:10. Through the same process as in Example 4, a negative electrode, a positive electrode, and a lithium secondary battery were prepared.
실시예 6 및 7Examples 6 and 7
상기 실시예 4에서 음극의 제조서 인조흑연:천연흑연:실리콘계 음극 활물질이 80:10:10의 중량비로 혼합된 혼합 음극 활물질을 사용하고, 또한 각각 실시예 2 및 3의 공중합체 바인더를 사용한 것을 제외하고는, 상기 실시예 4와 마찬가지의 과정을 통하여 각각 음극, 양극 및 리튬 이차전지를 제조하였다. Preparation of the negative electrode in Example 4 The artificial graphite: natural graphite: silicon-based negative electrode active material using a mixed negative electrode active material mixed in a weight ratio of 80:10:10, and using the copolymer binder of Examples 2 and 3, respectively Except, a negative electrode, a positive electrode and a lithium secondary battery were prepared through the same process as in Example 4.
실시예 8Example 8
상기 실시예 4에서 음극의 제조시 인조흑연:실리콘계 음극 활물질이 70:30의 중량비로 혼합된 혼합 음극 활물질을 사용하고, 또한 실시예 3의 공중합체 바인더를 사용한 것을 제외하고는, 상기 실시예 4와 마찬가지의 과정을 통하여 음극, 양극 및 리튬 이차전지를 제조하였다. Example 4, except that the artificial graphite: silicone-based negative active material was mixed in a weight ratio of 70:30 and the copolymer binder of Example 3 was used to prepare the negative electrode in Example 4, Through the same process as to prepare a negative electrode, a positive electrode and a lithium secondary battery.
비교예 3 및 4Comparative Examples 3 and 4
상기 실시예 4에서 음극의 제조시 바인더로서 각각 비교예 1 및 2에서 제조된 공중합체 바인더를 사용한 것을 제외하고는, 상기 실시예 4와 마찬가지의 과정을 통하여 음극, 양극 및 리튬 이차전지를 제조하였다. A negative electrode, a positive electrode and a lithium secondary battery were manufactured through the same process as in Example 4, except that the copolymer binders prepared in Comparative Examples 1 and 2 were used as binders in preparing the negative electrode in Example 4. .
비교예 5Comparative Example 5
상기 실시예 4에서 음극의 제조시 인조흑연:실리콘계 음극 활물질이 70:30의 중량비로 혼합된 혼합 음극 활물질을 사용하고, 또한 비교예 1에서 제조된 공중합체 바인더를 사용한 것을 제외하고는, 상기 실시예 4와 마찬가지의 과정을 통하여 음극, 양극 및 리튬 이차전지를 제조하였다. Except that the artificial graphite: silicone-based negative active material was mixed in a weight ratio of 70:30, and the copolymer binder prepared in Comparative Example 1 was used in the preparation of the negative electrode in Example 4, A negative electrode, a positive electrode, and a lithium secondary battery were manufactured through the same process as in Example 4.
실험예Experimental Example
실험예 1 : 모듈러스(modulus) 및 전해액 스웰링 측정Experimental Example 1: Modulus and electrolyte swelling measurement
실시예 1 내지 3, 및 비교예 1 및 2에서 제조된 공중합체 바인더에 대해 UTM(universal testing machine) 장비를 이용하여 응력 변형 곡선(Stress-Strain curve)을 통해 바인더에 하중을 가해 내부에 생기는 인장 강도(Stress)와 인장 변형(Strain) 관계를 통해 건조 강도(dry modulus) 및 습윤 강도(wet modulus)를 측정하였다.Tensile generated by applying a load to the binder through a stress-strain curve using a universal testing machine (UTM) equipment for the copolymer binders prepared in Examples 1 to 3 and Comparative Examples 1 and 2 Dry modulus and wet modulus were measured through the relationship between stress and tensile strain.
구체적으로, 실시예 1 내지 3, 및 비교예 1 및 2에서 제조된 용매에 분산되어 있는 바인더를 테플론이 코팅되어 있는 접시(dish)에 일정 두께로 도포 및 건조 후, 바인더 필름을 하기 도 1에 나타낸 바와 같은 규격으로 잘라 시편을 제조하여 실험을 진행하였다.Specifically, after applying and drying the binder dispersed in the solvent prepared in Examples 1 to 3, and Comparative Examples 1 and 2 to a plate having a Teflon coated (dish) to a certain thickness, the binder film is shown in Figure 1 Experiments were carried out by cutting specimens to the specifications as shown.
건조 강도는 상기 시편을 이용하여 측정하였으며, 습윤강도는 EC/DEC/PC=3:2:5(체적비) 혼합 용매에 48시간 동안 함침 후 상온에서 5분 건조 한 시편을 이용하여 측정하였다. 이때, 상기 시편과 상기 함침 후의 시편의 길이를 비교하여, 함침 후의 길이 증가 정도를 계산하여 전해액 스웰링 정도를 평가하였다. 그 결과를 하기 표 1에 나타내었다. The dry strength was measured using the specimen, and the wet strength was measured using the specimen dried for 5 minutes at room temperature after impregnation for 48 hours in an EC / DEC / PC = 3: 2: 5 (volume ratio) mixed solvent. At this time, by comparing the length of the specimen and the specimen after the impregnation, the degree of increase in the length after the impregnation was calculated to evaluate the degree of electrolyte swelling. The results are shown in Table 1 below.
실험예 2 : 용량 유지율 측정Experimental Example 2 Measurement of Capacity Retention Rate
<0.5 C 용량 유지율 측정><0.5 C capacity retention measurement>
실시예 4, 및 비교예 3 및 4에서 제조된 리튬 이차전지에 대해 각각 충방전 전류 밀도를 0.5 C로 하고 충전 종지 전압을 4.2 V(Li/Li+), 방전 종지 전압을 3 V(Li/Li+)로 한 충방전 시험을 30회 시행하였다.For the lithium secondary batteries prepared in Example 4 and Comparative Examples 3 and 4, respectively, the charge and discharge current density was 0.5 C, the charge end voltage was 4.2 V (Li / Li + ), and the discharge end voltage was 3 V (Li / Charge and discharge tests with Li + ) were performed 30 times.
모든 충전은 정전류/정전압으로 행하고, 정전압 충전의 종지 전류는 0.05 C로 하였다. 총 30 사이클의 시험을 완료한 후, 초기 방전 용량을 100%로 했을 때 각 사이클에서 측정된 방전 용량을 도 2에 나타내었다. All the charges were performed at constant current / constant voltage, and the termination current of constant voltage charge was 0.05C. After completing a total of 30 cycles of testing, the discharge capacity measured in each cycle when the initial discharge capacity was 100% is shown in FIG. 2.
<1 C 용량 유지율 측정><1 C capacity retention measurement>
실시예 5 내지 7에서 제조된 리튬 이차전지에 대해 각각 충방전 전류 밀도를 1 C로 하고 충전 종지 전압을 4.2 V(Li/Li+), 방전 종지 전압을 3 V(Li/Li+)로 한 충방전 시험을 130회 시행하였다.For the lithium secondary batteries prepared in Examples 5 to 7, respectively, the charging and discharging current density was 1 C, the charging end voltage was 4.2 V (Li / Li + ), and the discharge end voltage was 3 V (Li / Li + ). Charge and discharge tests were performed 130 times.
모든 충전은 정전류/정전압으로 행하고, 정전압 충전의 종지 전류는 0.05 C로 하였다. 총 130 사이클의 시험을 완료한 후, 초기 방전 용량을 100%로 했을 때 각 사이클에서 측정된 방전 용량을 도 3에 나타내었다.All the charges were performed at constant current / constant voltage, and the termination current of constant voltage charge was 0.05C. After completing a total of 130 cycles of testing, the discharge capacity measured in each cycle when the initial discharge capacity was 100% is shown in FIG. 3.
<0.33 C 용량 유지율 측정><0.33 C capacity retention measurement>
실시예 8 및 비교예 5에서 제조된 리튬 이차전지에 대해 각각 충방전 전류 밀도를 0.33 C로 하고 충전 종지 전압을 4.2 V(Li/Li+), 방전 종지 전압을 3 V(Li/Li+)로 한 충방전 시험을 200회 시행하였다.For the lithium secondary batteries prepared in Example 8 and Comparative Example 5, respectively, the charge and discharge current density was 0.33 C, the charge end voltage was 4.2 V (Li / Li + ), and the discharge end voltage was 3 V (Li / Li + ). 200 charge and discharge tests were conducted.
모든 충전은 정전류/정전압으로 행하고, 정전압 충전의 종지 전류는 0.05 C로 하였다. 총 200 사이클의 시험을 완료한 후, 초기 방전 용량을 100%로 했을 때 각 사이클에서 측정된 방전 용량을 도 4에 나타내었다. All the charges were performed at constant current / constant voltage, and the termination current of constant voltage charge was 0.05C. After completing a total of 200 cycles of testing, the discharge capacity measured in each cycle when the initial discharge capacity was 100% is shown in FIG. 4.
건조 강도(dry modulus)[MPa]Dry modulus [MPa] 습윤강도(wet modulus)[MPa]Wet modulus [MPa] 전해액 스웰링 (%)Electrolyte Swelling (%)
실시예 1Example 1 0.4170.417 0.0260.026 3838
실시예 2Example 2 0.1320.132 0.1050.105 1818
실시예 3Example 3 1.3601.360 0.3920.392 99
비교예 1Comparative Example 1 0.0770.077 측정불가Not measurable 120120
비교예 2Comparative Example 2 0.0510.051 0.0110.011 4545
표 1, 및 도 2를 참조하면, 습윤강도가 낮은 비교예 1 및 2의 공중합체 바인더는 습윤 강도가 높은 실시예 2의 공중합체 바인더에 비해, 공중합체 바인더 자체가 전해액에 의해 크게 스웰링(swelling) 되었음을 확인할 수 있다. 또한, 이를 이용하여 제조된 비교예 3 및 4의 음극 및 이차전지는 실시예 2의 공중합체 바인더를 사용하여 제조된 실시예 4의 음극 및 이차전지에 비해 용량 유지율이 좋지 않음을 확인할 수 있었다. 한편, 도 3을 통하여는 사용된 공중합체 바인더의 습윤강도에 따른 이차전지의 용량 유지율을 확인할 수 있다. 도 3을 참조하면, 공중합체 바인더의 습윤강도가 증가할수록 이를 사용하여 제조된 음극 및 이차전지의 용량유지율이 우수함을 확인할 수 있으며, 특히 습윤강도가 0.1 이상이면 우수한 이차전지의 용량유지율을 발휘할 수 있고, 0.3 이상에서 가장 우수한 이차전지의 용량유지율을 발휘할 수 있음을 확인할 수 있었다. Referring to Table 1 and FIG. 2, the copolymer binders of Comparative Examples 1 and 2 having low wet strength were significantly swelled by the electrolyte solution compared to the copolymer binder of Example 2 having high wet strength ( swelling). In addition, it can be seen that the negative electrode and the secondary battery of Comparative Examples 3 and 4 prepared using the same have poor capacity retention compared to the negative electrode and the secondary battery of Example 4 prepared using the copolymer binder of Example 2. On the other hand, through Figure 3 can be confirmed the capacity retention rate of the secondary battery according to the wet strength of the copolymer binder used. Referring to FIG. 3, it can be seen that as the wet strength of the copolymer binder increases, the capacity retention ratio of the negative electrode and the secondary battery manufactured using the same is excellent. Particularly, when the wet strength is 0.1 or more, the excellent capacity maintenance ratio of the secondary battery can be obtained. In addition, it was confirmed that the capacity maintenance ratio of the secondary battery which is the best at 0.3 or more.
또한, 도 4에는 인조흑연과 실리콘계 음극 활물질이 70:30의 중량비로 혼합된 음극 활물질을 이용하여 음극을 제조하였을 때, 공중합체 바인더의 종류에 따른 효과 상의 차이를 비교하기 위한 실험 결과가 도시되어 있다. 도 4를 참조하면, 실시예 3의 공중합체 바인더를 포함하는 실시예 4의 음극 및 이차전지는 비교예 1의 공중합체 바인더를 포함하는 비교예 5의 음극 및 이차전지에 비하여 우수한 용량유지율을 발휘하였음을 확인할 수 있다. 이를 통해 충방전에 따른 부피 변화가 큰 실리콘계 음극 활물질을 포함하는 음극에 대하여 0.02 MPa 이상의 습윤강도를 가지는 본 발명의 공중합체 바인더를 적용할 경우, 상기 공중합체 바인더가 향상된 접착력을 발휘하고, 높은 기계적 물성을 유지하므로, 이차전지의 수명 성능을 향상시킬 수 있음을 확인할 수 있었다. In addition, Figure 4 shows the experimental results for comparing the difference in effect according to the type of the copolymer binder when the negative electrode was prepared using a negative electrode active material mixed with artificial graphite and a silicon-based negative active material in a weight ratio of 70:30 have. Referring to FIG. 4, the negative electrode and the secondary battery of Example 4 including the copolymer binder of Example 3 exhibit excellent capacity retention ratios compared to the negative electrode and the secondary battery of Comparative Example 5 including the copolymer binder of Comparative Example 1. It can be confirmed that. Through this, when the copolymer binder of the present invention having a wet strength of 0.02 MPa or more is applied to a negative electrode including a silicon-based negative active material having a large volume change due to charging and discharging, the copolymer binder exhibits improved adhesion and high mechanical strength. Since physical properties were maintained, it was confirmed that the life performance of the secondary battery could be improved.

Claims (14)

  1. (가) 비닐계 단량체로부터 유도되는 단위, (나) 공액 디엔계 단량체 또는 공액 디엔계 중합체로부터 유도되는 단위, 및 (다) (메타)아크릴산 에스테르계 단량체로부터 유도되는 단위로 이루어진 군에서 선택되는 1종 이상의 단위, 및 (라) 수용성 중합체로부터 유도되는 단위를 포함하는 공중합체 바인더를 포함하고, 1) a unit derived from a vinyl monomer, (b) a unit derived from a conjugated diene monomer or a conjugated diene polymer, and (c) a unit derived from a (meth) acrylic acid ester monomer. A copolymer binder comprising at least one unit and (d) a unit derived from the water soluble polymer,
    상기 공중합체 바인더가 0.02 MPa 이상의 습윤강도(wet modulus)를 가지는, 이차전지용 바인더 조성물.The binder composition of claim 2, wherein the copolymer binder has a wet modulus of 0.02 MPa or more.
  2. 제 1 항에 있어서,The method of claim 1,
    상기 공중합체는 총 중량 100 중량부를 기준으로, (가) 비닐계 단량체로부터 유도되는 단위 1 중량부 내지 70 중량부, (나) 공액 디엔계 단량체 또는 공액 디엔계 중합체로부터 유도되는 단위 10 중량부 내지 97 중량부, (다) (메타)아크릴산 에스테르계 단량체로부터 유도되는 단위 1 중량부 내지 30 중량부, 및 (라) 수용성 중합체로부터 유도되는 단위 1 중량부 내지 70 중량부를 포함하는 이차전지용 바인더 조성물. The copolymer has a total weight of 100 parts by weight based on (a) 1 to 70 parts by weight of units derived from vinyl monomers, (b) 10 to parts by weight of units derived from conjugated diene monomers or conjugated diene polymers. A binder composition for secondary batteries comprising 97 parts by weight, (c) 1 part by weight to 30 parts by weight of a unit derived from a (meth) acrylic acid ester monomer, and (d) 1 part by weight to 70 parts by weight of a unit derived from a water-soluble polymer.
  3. 제 2 항에 있어서, The method of claim 2,
    상기 공중합체는 총 중량 100 중량부를 기준으로, (가) 비닐계 단량체로부터 유도되는 단위 30 중량부 내지 60 중량부, (나) 공액 디엔계 단량체 또는 공액 디엔계 중합체로부터 유도되는 단위 15 중량부 내지 30 중량부, (다) (메타)아크릴산 에스테르계 단량체로부터 유도되는 단위 4 중량부 내지 8 중량부, 및 (라) 수용성 중합체로부터 유도되는 단위 2 중량부 내지 50 중량부를 포함하는, 이차전지용 바인더 조성물. The copolymer has a total weight of 100 parts by weight based on (a) 30 parts by weight to 60 parts by weight of units derived from vinyl monomers, (b) 15 parts by weight to units derived from conjugated diene monomers or conjugated diene polymers. A binder composition for a secondary battery, comprising 30 parts by weight, 4 parts by weight to 8 parts by weight of a unit derived from (meth) acrylic acid ester monomer, and 2 parts by weight to 50 parts by weight of a unit derived from a water-soluble polymer. .
  4. 제 1 항에 있어서, The method of claim 1,
    상기 공중합체 바인더가 입자 형상이고, 100 nm 내지 1 ㎛의 평균 입경(D50)을 가지는, 이차전지용 바인더 조성물. The binder composition for secondary batteries, wherein the copolymer binder has a particle shape and has an average particle diameter (D 50 ) of 100 nm to 1 μm.
  5. 제 1 항에 있어서, The method of claim 1,
    상기 비닐계 단량체는 스티렌, α-메틸스티렌, β-메틸스티렌, p-t-부틸스티렌 및 디비닐벤젠으로 이루어진 군으로부터 선택되는 1종 이상인, 이차전지용 바인더 조성물.The vinyl monomer is at least one member selected from the group consisting of styrene, α-methylstyrene, β-methylstyrene, p-t-butylstyrene and divinylbenzene, binder composition for secondary batteries.
  6. 제 1 항에 있어서, The method of claim 1,
    상기 공액 디엔계 단량체는 1,3-부타디엔, 이소프렌, 클로로프렌, 또는 피페릴렌이고, The conjugated diene monomer is 1,3-butadiene, isoprene, chloroprene, or piperylene,
    상기 공액 디엔계 중합체는 1,3-부타디엔, 이소프렌, 클로로프렌, 및 피페릴렌으로 이루어진 군에서 선택되는 2종 이상의 단량체들의 중합체, 스티렌-부타디엔 공중합체, 아크릴로니트릴-부타디엔 공중합체, 스티렌-이소프렌 공중합체, 아크릴레이트-부타디엔 고무, 아크릴로니트릴-부타디엔-스티렌 고무, 에틸렌-프로필렌-디엔계 중합체, 및 이들이 부분적으로 수소화, 에폭시화, 또는 브롬화된 중합체로 이루어진 군으로부터 선택된 1종 이상인, 이차전지용 바인더 조성물.The conjugated diene polymer is a polymer of two or more monomers selected from the group consisting of 1,3-butadiene, isoprene, chloroprene, and piperylene, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, styrene-isoprene air Binder for secondary batteries, in which a copolymer, an acrylate-butadiene rubber, an acrylonitrile-butadiene-styrene rubber, an ethylene-propylene-diene-based polymer, and at least one selected from the group consisting of partially hydrogenated, epoxidized, or brominated polymers Composition.
  7. 제 1 항에 있어서,The method of claim 1,
    상기 수용성 중합체는 (메타)아크릴산 에스테르계 단량체로부터 유도되는 단위, (메타)아크릴 아미드계 단량체로부터 유도되는 단위, 불포화 카르본산계 단량체 및 비닐 아세테이트 단량체로부터 유도되는 단위로 이루어진 군에서 선택되는 1종 이상의 단위를 포함하는, 이차전지용 바인더 조성물.The water-soluble polymer is one or more selected from the group consisting of units derived from (meth) acrylic acid ester monomers, units derived from (meth) acryl amide monomers, units derived from unsaturated carboxylic acid monomers and vinyl acetate monomers. Binder composition for secondary batteries containing a unit.
  8. 제 1 항에 있어서,The method of claim 1,
    상기 수용성 중합체는 폴리비닐알코올(PVA), 폴리아크릴산(PAA) 및 폴리아크릴아미드(PAM)로 이루어지는 군으로부터 선택되는 1종 이상인, 이차전지용 바인더 조성물.The water-soluble polymer is a binder composition for secondary batteries, which is at least one member selected from the group consisting of polyvinyl alcohol (PVA), polyacrylic acid (PAA), and polyacrylamide (PAM).
  9. 제 7 항에 있어서,The method of claim 7, wherein
    상기 (메타)아크릴산 에스테르계 단량체는 메틸아크릴레이트, 에틸아크릴레이트, 프로필아크릴레이트, 이소프로필아크릴레이트, n-부틸아크릴레이트, 이소부틸아크릴레이트, n-아밀아크릴레이트, 이소아밀아크릴레이트, n-에틸헥실아크릴레이트, 2-에틸헥실아크릴레이트, 2-히드록시에틸아크릴레이트, 메틸메타크릴레이트, 에틸메타크릴레이트, 프로필메타크릴레이트, 이소프로필메타크릴레이트, n-부틸메타크릴레이트, 이소부틸메타크릴레이트, n-아밀메타크릴레이트, 이소아밀메타크릴레이트, n-헥실메타크릴레이트, n-에틸헥실 메타크릴레이트, 2-에틸헥실 메타크릴레이트, 히드록시에틸 메타크릴레이트, 히드록시프로필 메타크릴레이트, 메타아크릴록시 에틸에틸렌우레아, β-카르복시에틸아크릴레이트, 알리파틱 모노아크릴레이트, 디프로필렌 디아크릴레이트, 디트리메틸로프로판 테트라아크릴레이트, 하이드록시에틸 아크릴레이트, 디펜타에리트리톨 헥사아크릴레이트, 펜타에리트리톨 트리아크릴레이트, 펜타에리트리톨 테트라아크릴레이트, 라우릴 아크릴레이트, 세릴 아크릴레이트, 스테아릴 아크릴레이트, 라우릴 메타 아크릴레이트, 세틸 메타 아크릴레이트 및 스테아릴 메타 아크릴레이트로 이루어진 군으로부터 선택되는 1종 이상인, 이차전지용 바인더 조성물.The (meth) acrylic acid ester monomer is methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n- amyl acrylate, iso amyl acrylate, n- Ethylhexyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl Methacrylate, n-amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, n-ethylhexyl methacrylate, 2-ethylhexyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl Methacrylate, methacryloxy ethylethylene urea, β-carboxyethyl acrylate, aliphatic monoacrylate, dipropylene Acrylate, ditrimethyllopropane tetraacrylate, hydroxyethyl acrylate, dipentaerythritol hexaacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, lauryl acrylate, seryl acrylate, stearyl A binder composition for secondary batteries, which is at least one member selected from the group consisting of acrylate, lauryl methacrylate, cetyl methacrylate, and stearyl methacrylate.
  10. 제 7 항에 있어서,The method of claim 7, wherein
    상기 (메타)아크릴 아미드계 단량체는 아크릴 아미드, n-메틸올 아크릴아미드, n-부톡시 메틸아크릴아미드, 메타크릴아미드, n-메틸올 메타크릴아미드, n-부톡시 메틸메타크릴아미드로 이루어진 군으로부터 선택되는 1종 이상인, 이차전지용 바인더 조성물.The (meth) acryl amide monomer is a group consisting of acryl amide, n-methylol acrylamide, n-butoxy methylacrylamide, methacrylamide, n-methylol methacrylamide, n-butoxy methyl methacrylamide The binder composition for secondary batteries which is 1 or more types chosen from.
  11. 제 7 항에 있어서,The method of claim 7, wherein
    상기 불포화카르본산계 단량체는 말레인산, 푸마르산, 메타크릴산, 아크릴산, 글루타르산, 이타콘산, 테트라하이드로프탈산, 크로톤산, 이소크로톤산 및 나딕산으로 이루어진 군에서 선택되는 1종 이상인, 이차전지용 바인더 조성물.The unsaturated carboxylic acid monomer is at least one selected from the group consisting of maleic acid, fumaric acid, methacrylic acid, acrylic acid, glutaric acid, itaconic acid, tetrahydrophthalic acid, crotonic acid, isocrotonic acid and nadic acid, secondary battery binder Composition.
  12. 실리콘계 음극 활물질 및 제 1 항에 따른 이차전지용 바인더 조성물을 포함하는 리튬 이차전지용 음극.A lithium secondary battery negative electrode comprising a silicon-based negative active material and the secondary battery binder composition according to claim 1.
  13. 제 12 항에 있어서, The method of claim 12,
    상기 리튬 이차전지용 음극이 탄소계 음극 활물질을 더 포함하고, The negative electrode for a lithium secondary battery further includes a carbon-based negative electrode active material,
    상기 실리콘계 음극 활물질을 전체 음극 활물질 중 1 중량% 내지 30 중량% 포함하는, 리튬 이차전지용 음극.1 to 30% by weight of the negative electrode active material of the silicon-based negative electrode active material, a lithium secondary battery negative electrode.
  14. 제 12 항에 따른 리튬 이차전지용 음극을 포함하는 리튬 이차전지.A lithium secondary battery comprising the anode for lithium secondary battery according to claim 12.
PCT/KR2018/003746 2017-03-31 2018-03-29 Binder composition for secondary battery, and electrode for secondary battery and lithium secondary battery comprising same WO2018182343A1 (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114243022A (en) * 2022-02-24 2022-03-25 北京壹金新能源科技有限公司 Three-dimensional network water system binder for lithium ion battery, preparation and application thereof
KR20230087590A (en) 2020-12-15 2023-06-16 아사히 가세이 가부시키가이샤 Polymer composition for non-aqueous secondary battery and non-aqueous secondary battery
CN116376481A (en) * 2023-06-05 2023-07-04 宁德时代新能源科技股份有限公司 Negative electrode binder, negative electrode plate, battery cell, battery and electricity utilization device

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KR20230087590A (en) 2020-12-15 2023-06-16 아사히 가세이 가부시키가이샤 Polymer composition for non-aqueous secondary battery and non-aqueous secondary battery
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CN116376481A (en) * 2023-06-05 2023-07-04 宁德时代新能源科技股份有限公司 Negative electrode binder, negative electrode plate, battery cell, battery and electricity utilization device
CN116376481B (en) * 2023-06-05 2023-10-27 宁德时代新能源科技股份有限公司 Negative electrode binder, negative electrode plate, battery cell, battery and electricity utilization device

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