WO2020149665A1 - Electrode for rechargeable battery, manufacturing method of same, and rechargeable battery including same - Google Patents

Electrode for rechargeable battery, manufacturing method of same, and rechargeable battery including same Download PDF

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Publication number
WO2020149665A1
WO2020149665A1 PCT/KR2020/000801 KR2020000801W WO2020149665A1 WO 2020149665 A1 WO2020149665 A1 WO 2020149665A1 KR 2020000801 W KR2020000801 W KR 2020000801W WO 2020149665 A1 WO2020149665 A1 WO 2020149665A1
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Prior art keywords
electrode
binder
active material
conductive material
secondary battery
Prior art date
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PCT/KR2020/000801
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French (fr)
Korean (ko)
Inventor
손정만
류동조
한선희
한정섭
강민아
최철훈
Original Assignee
주식회사 엘지화학
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Priority claimed from KR1020200005491A external-priority patent/KR102421113B1/en
Application filed by 주식회사 엘지화학 filed Critical 주식회사 엘지화학
Priority to JP2020562679A priority Critical patent/JP7222586B2/en
Priority to CN202080003144.6A priority patent/CN112236888A/en
Priority to EP20740821.2A priority patent/EP3780190A4/en
Priority to US17/055,845 priority patent/US20210226219A1/en
Publication of WO2020149665A1 publication Critical patent/WO2020149665A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • 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
    • H01M4/04—Processes of manufacture in general
    • 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
    • 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
    • H01M4/139—Processes of manufacture
    • 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 an electrode for a secondary battery, a method for manufacturing the same, and a secondary battery including the same.
  • a representative example of an electrochemical device using such electrochemical energy is a secondary battery, and its use area is gradually expanding.
  • Lithium secondary batteries are also used as power sources for electric vehicles and hybrid electric vehicles.
  • the specific gravity of the active material in the electrode must be large, but when the specific gravity of the active material is increased, the problem of desorption of the electrode is further accelerated due to low adhesion to the electrode current collector, and at the same time, the active material slurry is During the process of manufacturing the electrode using, an excessive amount of active material is used, but due to low adhesion, it causes process problems such as contamination of the rolling roll, and there is a problem in that production efficiency is delayed due to low process efficiency such as washing more frequently.
  • the present invention is to provide a secondary battery electrode that simultaneously secures binding properties to a conductive material and an active material, and has improved mechanical properties, including an improved discharge capacity and a reduced electrode expansion rate.
  • the electrode for a secondary battery having two types of binders having different particle diameters but having different distribution patterns of each binder in the electrode mixture layer is provided.
  • a binder having a relatively small particle diameter is first mixed with a conductive material to prepare a conductive material dispersion, and a binder and an electrode active material having a relatively large particle diameter are mixed with the conductive material dispersion to form an active material slurry.
  • a method of manufacturing an electrode for a secondary battery of the above embodiment is provided using the active material slurry composition.
  • a secondary battery including the electrode for a secondary battery of the one embodiment.
  • Increasing the adhesive force as described above has the effect of improving the mechanical properties of the electrode itself, increasing the discharge capacity of the battery including the electrode, and lowering the expansion coefficient of the electrode during driving of the battery.
  • At least one surface of the current collector a plurality of electrode active material particles; A plurality of conductive material particles distributed between the different electrode active material particles; A first binder having a particle diameter of 100 nm or less, which are respectively distributed between the different conductive material particles and between the conductive material particles and the current collector; A second binder having a particle diameter of 120 nm or more distributed between the different electrode active material particles, between the electrode active material particles and the conductive material particles, and between the electrode active material particles and the current collector; It provides an electrode for a secondary battery, the electrode mixture layer is included.
  • the particle diameter of each binder represents the particle diameter of the individual particles identified in the cross section of the electrode mixture layer and the like.
  • the electrode active material and the conductive material may have different distribution shapes in the electrode mixture layer according to the particle diameter.
  • the binding properties to the electrode active material and the conductive material may vary depending on the particle diameter of the binder.
  • the particle diameter of the electrode active material is larger than that of the conductive material, and the electrode active material particles are uniformly distributed in the electrode assembly layer, and the conductive material may be distributed between different electrode active material particles.
  • a binder having a particle diameter similar to the size of the conductive material If only a binder having a particle diameter similar to the size of the conductive material is used, a relatively large amount of the binder is distributed in the electrode of the same volume, which may help to bind the conductive material. However, a binder whose particle diameter is similar to the size of a conductive material, it may be difficult to bind an active material having a larger particle diameter.
  • the binding property of the binder to the conductive material is high compared to the electrode active material, and the electrode active material may be detached even when the conductive material is stably attached during battery operation. It is very likely.
  • the binder when using a binder whose particle diameter is similar to the size of the electrode active material, it may be helpful to bind the active material. However, a relatively small amount of the binder is distributed in the electrode of the same volume, and it may be difficult to bind an active material having a larger particle diameter than the binder.
  • the binding property of the binder to the electrode active material is high, and even when the electrode active material is stably attached during the electrode manufacturing process or during battery operation, the conductive material is likely to be detached.
  • the electrode for a secondary battery having two types of binders having different particle diameters but having different distribution types of the binders in the electrode mixture layer is provided.
  • a binder having a relatively small particle diameter is present on the surface portion of the conductive material, and a binder having a relatively large particle size is present on the surface portion of the active material, so that binding properties to the conductive material and the active material can be simultaneously secured.
  • the first binders having a relatively small particle diameter may be distributed between the conductive material particles, and between the conductive material particles and the current collector, to bind to each other.
  • the second binder having a relatively large particle diameter may be distributed between the electrode active material particles different from each other, and between the electrode active material particle and the current collector, to bind to each other.
  • the binder of the relatively small particle diameter is present on the surface portion of the conductive material, and the binder of the relatively large particle size is present on the surface portion of the active material, binding properties to the conductive material and the active material can be simultaneously secured.
  • increasing the adhesion of the electrode has the effect of improving the mechanical properties of the electrode itself, increasing the discharge capacity of the battery containing the electrode, and lowering the expansion coefficient of the electrode during operation of the battery.
  • the first binder is 60% by weight or more relative to the total weight of the first binder is located on the surface of the conductive material particles to bind the conductive material particles
  • the second binder is 60% by weight or more relative to the total weight of the second binder, Located on the surface of the electrode active material particles, the active material particles may be bound.
  • the surface portion may mean up to 1 ⁇ m in the vertical direction from the particle surface to the particle surface, and may be confirmed on the surface, cross-section, etc. of the electrode mixture layer .
  • a particle diameter may be represented based on D50.
  • the D50 is a particle diameter at a point of 50% of the cumulative distribution of particle number according to particle size, and can be measured using a laser diffraction method. Specifically, after the powder to be measured is dispersed in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (for example, Microtrac S3500) to measure the difference in diffraction pattern according to the particle diameter when particles pass through the laser beam, and thus the particle size distribution. Calculate D50 can be measured by calculating the particle diameter at a point at which 50% of the cumulative distribution of the number of particles according to the particle diameter in the measuring device is obtained.
  • a laser diffraction particle size measuring device for example, Microtrac S3500
  • the particle diameters of the components of the electrode mixture layer are as follows.
  • particles having a particle diameter (D50) in the range of 10 nm to 2 ⁇ m may be used.
  • the particle diameter (D50) is specifically 20 nm to 1 ⁇ m, for example, it can be used in the range of 30 to 100 nm as the conductive material.
  • a particle diameter of 100 nm or less specifically, 40 nm to 100 nm, such as 50 nm to 80 nm, may be used.
  • a particle diameter (D50) of 500 nm to 50 ⁇ m may be used as the electrode active material.
  • a particle diameter (D50) of 1 ⁇ m to 40 ⁇ m, such as 5 ⁇ m to 30 ⁇ m may be used as the electrode active material.
  • the particle diameter is 120 nm or more, specifically 150 nm To 600 nm, for example, within 160 to 300 nm.
  • the first binder and the second binder may be the same type, but may have different particle diameters.
  • the first binder and the second binder are commonly, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, recycled cellulose, poly Vinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene butadiene latex, fluorine latex, etc. may be one of polymers, specifically, water-based binder As it may be a styrene-butadiene-based latex having excellent binding force, such as styrene-butadiene-acrylic polymer.
  • Such a binder may be usually included in an amount of 0.1 to 30% by weight based on the total weight of the electrode mixture layer, and specifically 1 to 10% by weight.
  • the weight ratio of the first binder and the second binder may be 1:2 to 1:20, specifically 1:5 to 1:15.
  • the range may be appropriately determined by the content of the conductive material and the active material, and in general, the content of the second binder is high because the content of the active material is larger than that of the conductive material.
  • the electrode of the embodiment may be any one of an anode and a cathode, and accordingly The type of the electrode active material may be determined as either a positive electrode active material or a negative electrode active material.
  • the negative active material includes, for example, carbon such as non-graphitized carbon and graphite-based carbon; Li x Fe 2 O 3 (0 ⁇ x ⁇ 1), Li x WO 2 (0 ⁇ x ⁇ 1), Sn x Me 1-x Me' y O z (Me: Mn, Fe, Pb, Ge; Me' : Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen, metal composite oxides such as 0 ⁇ x ⁇ 1;1 ⁇ y ⁇ 3;1 ⁇ z ⁇ 8); Lithium metal; Lithium alloys; Silicon-based alloys; Tin-based alloys; SnO, SnO 2 , PbO, PbO 2 , Pb 2 O 3 , Pb 3 O 4 , Sb 2 O 3 , Sb 2 O 4 , Sb 2 O 5 , GeO, GeO 2 , Bi 2 O 3 , Bi 2 O 4 , and Bi 2 O 5 ; Conductive polymers such as polyacetylene; Li-Co-N
  • the electrode active material based on the total weight of the electrode mixture layer, may be included in 60 to 99% by weight, specifically, may be included in 80 to 98% by weight.
  • the electrode of the embodiment may be a negative electrode, and thus, a negative electrode active material may be applied as the electrode active material.
  • the discharge capacity of the secondary battery including the negative electrode of this embodiment is improved, and expansion of the negative electrode can be suppressed.
  • the conductive material that improves the conductivity between the electrode active material particles is not conventionally known, and is not particularly limited as long as it has conductivity without causing a chemical change in the battery.
  • carbon black, acetylene black, Carbon black such as ketjen black, channel black, furnace black, lamp black, and summer black For example, carbon black, acetylene black, Carbon black such as ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride powder, aluminum powder, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.
  • Such a conductive material may be usually included in an amount of 0.1 to 30% by weight based on the total weight of the electrode mixture layer, specifically, it may be included in 1 to 10% by weight.
  • a filler may be further included in the electrode mixture layer.
  • the filler is optionally used as a component that inhibits the expansion of the positive electrode, and is not particularly limited as long as it is a fibrous material without causing chemical changes in the battery, and includes, for example, olipine polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used, and the content may be included in an amount of 0 to 10% by weight based on the total weight of the electrode mixture layer.
  • the electrode of the embodiment may be either an anode or a cathode, and accordingly, a current collector on which the electrode mixture layer is formed may be determined as either a positive electrode current collector or a negative electrode current collector.
  • the positive electrode current collector is generally made to a thickness of 3 to 200 ⁇ m, and is not particularly limited as long as it has high conductivity without causing chemical changes in the battery.
  • stainless steel, aluminum, nickel, Titanium and aluminum or stainless steel may be selected from carbon, nickel, titanium, or silver surfaces, and aluminum may be used.
  • the current collector may also increase the adhesion of the positive electrode active material by forming fine irregularities on its surface, and various forms such as a film, sheet, foil, net, porous body, foam, and nonwoven fabric are possible.
  • the negative electrode current collector is generally manufactured to a thickness of 3 to 200 ⁇ m, and is not particularly limited as long as it has conductivity without causing a chemical change in the battery.
  • copper, stainless steel, aluminum, nickel, Surfaces made of carbon, nickel, titanium, silver, etc. on the surface of titanium, calcined carbon, copper or stainless steel, aluminum-cadmium alloy, or the like can be used.
  • it is also possible to form a fine unevenness on the surface to enhance the bonding force 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.
  • a binder having a relatively small particle diameter is first mixed with a conductive material to prepare a conductive material dispersion, and a binder and an electrode active material having a relatively large particle diameter are mixed with the conductive material dispersion.
  • the electrode of one embodiment described above can be obtained.
  • an electrode having excellent mechanical properties and electrochemical properties is obtained, as well as preventing electrode contamination and defects in the process, and at the same time, washing the roll by reducing contamination of the rolling roll during the manufacturing process It has the effect of reducing the process time or simplifying the process, such as reducing the frequency.
  • the first binder and the second binder can be produced using a generally known emulsion polymerization method.
  • the first binder and the second binder each independently, in the presence of an emulsifier, a polymerization initiator, and a solvent, may be prepared by including the step of polymerizing the monomer.
  • the content of the emulsifier in the total amount of the monomer, emulsifier, polymerization initiator, and solvent may be adjusted.
  • the content of the emulsifier is higher, a binder having a smaller particle diameter can be produced.
  • the content of the emulsifier in the total amount of the monomer, emulsifier, polymerization initiator, and solvent may be further increased.
  • the content of the emulsifier for preparing the first binder may be greater than 0.9 parts by weight, specifically 1 part by weight to 5 parts by weight, and an emulsifier for preparing the second binder
  • the content of may be 0.9 parts by weight or less, specifically 0.3 parts by weight to 0.8 parts by weight.
  • the emulsifier is used for emulsion polymerization, and for example, oleic acid, stearic acid, lauric acid, fatty acid salts represented by sodium or potassium salts of mixed fatty acids, and general anionic emulsifiers such as rosin and the like can be used.
  • a reactive emulsifier for improving the stability of the polymer may be added, and the emulsifier may be used alone or in combination of two or more.
  • the monomers may be monomers that are the basis of a binder to be produced, and for example, to produce styrene butadiene latex, which is one example of a first binder and a second binder, acrylic acid that imparts hydrophilicity with styrene and butadiene. Monomers can be used.
  • the polymerization initiator, inorganic or organic peroxide may be used, for example, water-soluble initiators including potassium persulfate, sodium persulfate, ammonium persulfate, and the like, cumene hydroperoxide, benzoyl peroxide, etc.
  • water-soluble initiators including potassium persulfate, sodium persulfate, ammonium persulfate, and the like, cumene hydroperoxide, benzoyl peroxide, etc.
  • the oil-soluble initiator can be used.
  • the polymerization initiator may be included in an amount of 0.01 to 2 parts by weight based on 100 parts by weight of the monomers.
  • an activator may be further included to accelerate the initiation reaction of the peroxide together with the polymerization initiator, and such activators include sodium formaldehyde sulfoxylate, sodium ethylenediaminetetraacetate, ferrous sulfate and dextrose One or more selected from the group consisting of can be used.
  • the solvent may be an organic solvent or water, specifically water.
  • the polymerization temperature and polymerization time for emulsion polymerization of each of the binders can be appropriately determined according to a polymerization method or the type of polymerization initiator used, for example, the polymerization temperature may be about 50°C to 200°C, and the polymerization time is It may be about 1 to 20 hours.
  • a first binder which is a binder for improving the binding property of the conductive material
  • a thickener can be optionally added.
  • the thickener is to adjust the viscosity, for example, cellulose-based polymer, polyethylene glycol, polyacrylamide, poly (N-vinyl amide) and poly (N-vinylpyrrolidone), the cellulose-based polymer Silver, carboxy methyl cellulose (CMC), methyl cellulose (MC), hydroxypropyl cellulose (HPC), methyl hydroxypropyl cellulose (MHPC), ethyl hydroxyethyl It may be at least one selected from the group consisting of cellulose (ethyl hydroxyethyl cellulose, EHEC), methyl ethylhydroxyethyl cellulose (MEHEC) and cellulose gum, and more specifically, carboxymethyl cellulose (carboxy) methyl cellulose, CMC).
  • CMC carboxy methyl cellulose
  • MC methyl cellulose
  • HPC hydroxypropyl cellulose
  • MHPC methyl hydroxypropyl cellulose
  • EHEC ethyl hydroxyethy
  • the thickener solution may be a solution containing these materials at a concentration of 0.5% to 20%.
  • the thickener may be included in an amount of 50 to 100 parts by weight based on 100 parts by weight of the conductive agent and the first binder.
  • the content ratio of the conductive material and the first binder may be 10:1 to 1:1. Outside the above range, if the content of the conductive material is too large, it is not preferable because the binder is not sufficient to secure the binding property of the conductive material, and if it is too small, the content of the conductive material itself decreases and secondary battery performance decreases, which is preferable Does not.
  • an electrode active material, a solvent, and a second binder are added to the conductive material dispersion and stirred to complete the active material slurry composition.
  • the electrode active material is added to have the content as described above in the electrode mixture layer, and the second binder is also added to have a content ratio as described above, compared to the content of the first binder.
  • the solvent added in the process (d) may be the same as the solvent used when preparing the conductive material dispersion, for example, an organic solvent or water, and specifically, the first binder and the second binder are water-based binders. In the case, for example, in the case of a styrene-butadiene-acrylic polymer, it may be water.
  • a binder having a relatively small particle diameter has a surface portion of the conductive material. Binders having a relatively large particle diameter may be present on the surface of the active material, respectively.
  • an electrode having an electrode mixture layer formed on at least one surface of the current collector can be obtained.
  • the coating, drying, and rolling process methods may follow generally known methods, and detailed descriptions are omitted.
  • the thickness of the electrode mixture layer is not limited, but may be 20 ⁇ m to 200 ⁇ m on one side.
  • the manufacturing method of one embodiment may be a method of manufacturing an anode or a cathode.
  • a negative electrode may be manufactured using the negative electrode active material as the electrode active material.
  • a secondary battery including the electrode for a secondary battery described above is provided.
  • the electrode assembly including the electrode (anode or cathode), the counter electrode (cathode or anode) of the electrode, and a separator interposed between the electrodes is embedded in a battery case together with an electrolyte. It can be made of a structure.
  • the separator an insulating thin film having high ion permeability and mechanical strength is used.
  • the pore diameter of the separator is generally 0.01 to 10 ⁇ m, and the thickness is generally 5 to 300 ⁇ m.
  • the separator include olefin-based polymers such as polypropylene, which are chemically resistant and hydrophobic; Sheets or non-woven fabrics made of glass fiber or polyethylene are used.
  • a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as a separator.
  • an SRS separator in which a mixture of inorganic particles and a binder is coated on at least one surface of an oliphine-based polymer (Safety Reinforced Separator) may be used.
  • an SRS separator in which a mixture of inorganic particles and a binder is coated on at least one surface of an oliphine-based polymer (Safety Reinforced Separator) may be used.
  • the specific content of the SRS separator the applicant's application number 10-2008-0005527 is included as a reference.
  • the electrolyte may be a lithium salt-containing non-aqueous electrolyte, and the lithium salt-containing non-aqueous electrolyte is composed of a non-aqueous electrolyte and a lithium salt, and the non-aqueous electrolyte includes a non-aqueous organic solvent, an organic solid electrolyte, and an inorganic solid electrolyte. It is not limited to.
  • non-aqueous organic solvent examples include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and gamma.
  • -Butyl lactone 1,2-dimethoxy ethane, tetrahydroxyfuran, 2-methyl tetrahydrofuran, dimethylsulfoxide, 1,3-dioxorun, formamide, dimethylformamide, dioxorun, acetonitrile , Nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxy methane, dioxoren derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, Aprotic organic solvents such as tetrahydrofuran derivatives, ethers, methyl pyropionate, and ethyl propionate can be used.
  • organic solid electrolyte examples include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphoric acid ester polymers, poly agitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, and ions.
  • a polymerization agent containing a sex dissociating group and the like can be used.
  • the inorganic solid electrolyte for example, Li 3 N, LiI, Li 5 NI 2 , Li 3 N-LiI-LiOH, LiSiO 4 , LiSiO 4- LiI-LiOH, Li 2 SiS 3 , Li 4 SiO 4 , Li 4 nitrides such as Li 4 SiO 4- LiI-LiOH, Li 3 PO 4- Li 2 S-SiS 2 , halides, sulfates and the like can be used.
  • the lithium salt is a material that is soluble in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO 4 , LiBF 4 , LiB 10 Cl 10 , LiPF 6 , LiCF 3 SO 3 , LiCF 3 CO 2 , LiAsF 6 , LiSbF 6 , LiAlCl 4 , CH 3 SO 3 Li, (CF 3 SO 2 ) 2 NLi, lithium chloroborane, lower aliphatic lithium carboxylate, lithium 4-phenyl borate, imide, and the like.
  • non-aqueous electrolytes are used for the purpose of improving charge/discharge characteristics, flame retardancy, etc., for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphate triamide, Nitrobenzene derivatives, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxy ethanol, aluminum trichloride, etc. may be added. have.
  • a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride may be further included, or carbon dioxide gas may be further included to improve high temperature storage properties, and FEC (Fluoro-Ethylene) Carbonate), PRS (Propene sultone), etc. may be further included.
  • lithium salts such as LiPF 6 , LiClO 4 , LiBF 4 , and LiN(SO 2 CF 3 ) 2 are formed of a cyclic carbonate of EC or PC as a highly dielectric solvent and DEC, DMC or EMC of a low viscosity solvent.
  • a lithium salt-containing nonaqueous electrolyte may be prepared by adding it to a mixed solvent of linear carbonate.
  • the present invention also provides a battery pack including such a secondary battery as a unit cell, and a device including such a battery pack as a power source.
  • the device includes, for example, a notebook computer, a netbook, a tablet PC, a mobile phone, an MP3, wearable electronic devices, a power tool, an electric vehicle (EV), and a hybrid electric vehicle (HEV). It can be a plug-in hybrid electric vehicle (PHEV), electric bike (E-bike), electric scooter (E-scooter), electric golf cart, or power storage system. However, it goes without saying that these are not limited to these.
  • Butadiene (52 g) and styrene (46 g) and acrylic acid (2 g) as monomers were added to water containing sodium lauryl sulfate (1 g) as emulsifier and potassium persulfate (0.2 g) as polymerization initiator, These were mixed and polymerized at 70° C. for about 5 hours to prepare binder A having a solid content of 40% having a particle diameter of the polymerized binder of 80 nm (measured by dynamic light scattering (DLS) equipment).
  • DLS dynamic light scattering
  • Example 1 polymerization was performed under the same reaction conditions, except that the emulsifier was used at 0.7 g, and the binder of 40% of solid content having a particle diameter of the polymerized binder of 160 nm (measured by dynamic light scattering (DLS) equipment) C was prepared.
  • the emulsifier was used at 0.7 g
  • the binder of 40% of solid content having a particle diameter of the polymerized binder of 160 nm (measured by dynamic light scattering (DLS) equipment) C was prepared.
  • CMC carboxymethylcellulose
  • the slurry composition was coated on a copper foil having a thickness of 20 ⁇ m with a loading of 8.2 mg/cm 2 , dried, and rolled to a thickness of 80 ⁇ m to prepare a negative electrode.
  • CMC carboxymethylcellulose
  • Super-P conductive material
  • the slurry composition was coated on a copper foil having a thickness of 20 ⁇ m with a loading of 8.2 mg/cm 2 , dried, and rolled to a thickness of 80 ⁇ m to prepare a negative electrode.
  • CMC carboxymethylcellulose
  • Super-P conductive material
  • the slurry composition was coated on a copper foil having a thickness of 20 ⁇ m with a loading of 8.2 mg/cm 2 , dried, and rolled to a thickness of 80 ⁇ m to prepare a negative electrode.
  • CMC carboxymethylcellulose
  • the slurry composition was coated on a copper foil having a thickness of 20 ⁇ m with a loading of 8.2 mg/cm 2 , dried, and rolled to a thickness of 80 ⁇ m to prepare a negative electrode.
  • the process procedure was the same as in Example 1, but after preparing a conductive material dispersion without using binder A, an active material slurry composition and a negative electrode were prepared.
  • CMC carboxymethylcellulose
  • D50 30 nm, Super-P
  • the slurry composition was coated on a copper foil having a thickness of 20 ⁇ m with a loading of 8.2 mg/cm 2 , dried, and rolled to a thickness of 80 ⁇ m to prepare a negative electrode.
  • the process sequence is the same as in Example 1, but the binder A is replaced as follows to prepare a conductive material dispersion, but the binder A and B are mixed with the prepared conductive material dispersion to prepare an active material slurry composition, and a cathode is prepared. It was prepared.
  • binder A (0.5 g) prepared in Preparation Example 1 and binder B (5.75 g) prepared in Preparation Example 2 were mixed to prepare a mixed binder.
  • a 1% CMC solution 100 g
  • a conductive material 1.5 g
  • the slurry composition was coated on a copper foil having a thickness of 20 ⁇ m with a loading of 8.2 mg/cm 2 , dried, and rolled to a thickness of 80 ⁇ m to prepare a negative electrode.
  • the process sequence was the same as in Example 1, but after replacing the binder A as follows to prepare a dispersion, an active material slurry composition and a negative electrode were prepared.
  • binder C 0.5 g was used to prepare a conductive material dispersion.
  • Example 2 The other matters were the same as in Example 1 to prepare an active material slurry composition and a negative electrode.
  • a conductive material dispersion composition was not prepared separately, and a conductive material, an active material, and binders A and B were mixed together to prepare an active material slurry composition, and a negative electrode was prepared.
  • the binder A (0.5 g) prepared in Preparation Example 1 and the binder B (5.75 g) prepared in Preparation Example 2 were mixed to prepare a mixed binder.
  • the slurry composition was coated on a copper foil having a thickness of 20 ⁇ m with a loading of 8.2 mg/cm 2 , dried, and rolled to a thickness of 80 ⁇ m to prepare a negative electrode.
  • the negative electrode prepared in the above Examples and Comparative Examples was cut into 60 mm (length) x 25 mm (width) to obtain test specimens.
  • a clean SUS rolled roll has a color difference value of 80, and as it gets contaminated, the value decreases.
  • each negative electrode of Example 1 and Comparative Example 2 By treating each negative electrode of Example 1 and Comparative Example 2 with OsO 4 , the binder contained in each negative electrode was stained with OsO 4 . Thereafter, each cathode surface was observed by SEM.
  • an average can be obtained from the particle diameters of the individual particles identified on the negative electrode surface (ie, the cross-section of the negative electrode mixture layer) to represent the particle diameter of each binder based on the average particle diameter.
  • 1, 3, and 5 are SEM images of the cathode surface of Example 1 at different magnifications.
  • 2, 4, and 6 are SEM images of the cathode surface of Comparative Example 2 at different magnifications.
  • FIGS. 1, 3, and 5 it is confirmed that a binder having a small average particle diameter of 100 nm or less is mainly distributed around the conductive material.
  • FIGS. 2, 4, and 6 it is confirmed that a binder having a large average particle diameter of 200 nm is mainly distributed around the conductive material.
  • the distribution form of the binder in the final cathode may vary depending on the timing of supplying each binder in the active material slurry manufacturing process. .
  • a relatively small particle size binder is first mixed with a conductive material to prepare a conductive material dispersion, and then a relatively large particle size binder and an active material are introduced into the conductive material dispersion and mixed to form an active material slurry.
  • a negative electrode in which a binder having a relatively small particle diameter is distributed around the conductive material can be finally obtained.
  • Comparative Example 2 after preparing a dispersion of a conductive material that does not contain a binder, two types of binders and active materials having different particle diameters are collectively introduced into the conductive material dispersion and mixed to prepare an active material slurry composition. In the case of, a negative electrode in which two kinds of binders are randomly distributed irrespective of their particle size can be finally obtained.
  • the negative electrode produced in the above Examples and Comparative Examples was used as a working electrode, a lithium metal sheet having a thickness of 150 ⁇ m was used as a reference electrode, and a polyethylene separator (thickness: 20 ⁇ m) between the working electrode and the reference electrode. , Porosity: 40%) was inserted into the battery container, the electrolyte solution was injected, and then the other matters were prepared in a lithium secondary battery in the form of a 2032 half-cell according to a conventional manufacturing method.
  • EC ethylene carbonate
  • PC propylene carbonate
  • DEC diethyl carbonate
  • LiPF 6 ethylene carbonate
  • FEC additive fluoroethylene carbonate
  • Discharge characteristics of the battery in a constant temperature chamber at 25°C, after discharging each lithium ion half battery three times in CC/CV mode from 1.5V to 5mV at 0.1C to 0.1C, and then to 0.1C in CC mode The cycle of charging up to 1.5V was repeated three times, but there was a rest period of 20 minutes between charging and discharging. Accordingly, the charged battery was finally discharged in 1C CC/CV mode, and the discharge capacity of the CC section compared to the total discharge capacity was converted to a percentage according to the following equation.
  • each cell was disassembled to recover the negative electrode.
  • Each recovered negative electrode was washed with DMC (dimethyl carbonate) solvent, naturally dried for 10 minutes at room temperature, and then the thickness was measured. The measured thickness was substituted into the following equation to calculate the expansion coefficient of the negative electrode.
  • DMC dimethyl carbonate
  • [Cathode expansion rate] 100%* ⁇ (thickness of discharge cathode of battery)-(thickness of rolled cathode) ⁇ / ⁇ (thickness of rolled cathode)-(thickness of copper foil) ⁇
  • Discharge negative electrode thickness of battery negative electrode thickness for one discharge of lithium ion battery
  • Thickness of copper foil thickness of cathode current collector among rolled electrodes

Abstract

The present invention relates to an electrode for a rechargeable battery, a manufacturing method of same, and a rechargeable battery including same. Specifically, provided, according to one embodiment of the present invention, is an electrode for a rechargeable battery, the electrode comprising two types of binders having different particle diameters from each other, wherein the respective distribution patterns of the binders in an electrode mixture layer are different.

Description

이차전지용 전극, 이의 제조방법, 및 이를 포함하는 이차전지Electrode for secondary battery, manufacturing method thereof, and secondary battery including the same
관련 출원(들)과의 상호 인용Cross-citation with relevant application(s)
본 출원은 2019년 1월 17일자 한국 특허 출원 제10-2019-0006227호 및 2020년 1월 15일자 한국 특허 출원 제10-2020-0005491호에 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. 10-2019-0006227 dated January 17, 2019 and Korean Patent Application No. 10-2020-0005491 dated January 15, 2020. All content disclosed in the literature is incorporated as part of this specification.
본 발명은 이차전지용 전극, 이의 제조방법, 및 이를 포함하는 이차전지에 관한 것이다.The present invention relates to an electrode for a secondary battery, a method for manufacturing the same, and a secondary battery including the same.
화석연료 사용의 급격한 증가로 인하여 대체 에너지나 청정에너지의 사용에 대한 요구가 증가하고 있으며, 그 일환으로 가장 활발하게 연구되고 있는 분야가 전기화학을 이용한 발전, 축전 분야이다.Due to the rapid increase in the use of fossil fuels, the demand for the use of alternative or clean energy is increasing, and as a part, the most actively researched field is the field of electricity generation and electricity storage using electrochemistry.
현재 이러한 전기화학적 에너지를 이용하는 전기화학 소자의 대표적인 예로 이차전지를 들 수 있으며, 점점 더 그 사용 영역이 확대되고 있는 추세이다.At present, a representative example of an electrochemical device using such electrochemical energy is a secondary battery, and its use area is gradually expanding.
더욱이, 최근에 환경 문제에 대한 관심이 커짐에 따라 대기오염의 주요 원인의 하나인 가솔린 차량, 디젤 차량 등 화석연료를 사용하는 차량을 대체할 수 있는 전기자동차, 하이브리드 전기자동차 등에 대한 연구가 많이 진행되고 있으며, 리튬 이차전지는 이러한 전기자동차, 하이브리드 전기자동차 등의 동력원으로도 사용되고 있다.Moreover, as interest in environmental issues has recently increased, many studies have been conducted on electric vehicles, hybrid electric vehicles, etc., which can replace fossil fuel vehicles such as gasoline vehicles and diesel vehicles, which are one of the main causes of air pollution. Lithium secondary batteries are also used as power sources for electric vehicles and hybrid electric vehicles.
이와 같이 리튬 이차전지의 응용 분야가 넓어짐에 따라 부족한 공급량을 제조 속도를 올려 해결하려는 노력이 한편에서 진행 중이다.As the application fields of lithium secondary batteries are widened, efforts are being made to solve the insufficient supply by increasing the manufacturing speed.
또한, 상기와 같은 전기자동차는 1회 충전으로 이동할 수 있는 거리를 늘이기 위해 이차전지 용량을 키우는 노력을 하고 있지만, 자동차 내 이차전지를 탑재할 수 있는 공간이 한정되어 있어 이차전지의 에너지 밀도를 최대화 하려는 노력도 동시에 진행 중이다.In addition, although the electric vehicle as described above is trying to increase the capacity of the secondary battery to increase the distance that can be moved by one charge, the space for mounting the secondary battery in the vehicle is limited, thereby maximizing the energy density of the secondary battery. Efforts are being made at the same time.
이때, 상기 에너지 밀도를 높이기 위해서는 전극 내에서 활물질의 비중이 커야 하지만, 상기 활물질의 비중이 높아지면, 전극 집전체에 대한 낮은 접착력으로 인해 전극의 탈리의 문제가 더욱 가속화되고, 이와 동시에 활물질 슬러리를 사용하여 전극을 제조하는 공정 중, 과량의 활물질이 사용되는 반면 낮은 접착력으로 인해 압연롤에 대한 오염 등 공정 문제를 야기하여, 세척을 보다 자주 해야하는 등 공정 효율성이 낮아져 생산이 지연되는 문제가 있다.At this time, in order to increase the energy density, the specific gravity of the active material in the electrode must be large, but when the specific gravity of the active material is increased, the problem of desorption of the electrode is further accelerated due to low adhesion to the electrode current collector, and at the same time, the active material slurry is During the process of manufacturing the electrode using, an excessive amount of active material is used, but due to low adhesion, it causes process problems such as contamination of the rolling roll, and there is a problem in that production efficiency is delayed due to low process efficiency such as washing more frequently.
따라서, 에너지 밀도를 상승시키기 위해 활물질의 비중을 크게 하더라도 높은 수준의 접착력을 확보함과 동시에, 압연롤에 대한 오염을 줄일 수 있는 기술에 대한 필요성이 높은 실정이다.Therefore, even if the specific gravity of the active material is increased to increase the energy density, there is a high need for a technology capable of securing a high level of adhesion and reducing contamination on a rolling roll.
본 발명은, 도전재 및 활물질에 대한 결착성을 동시에 확보하고, 기계적 물성이 개선된 이차전지용 전극을 제공하며, 이를 포함하여 방전 용량이 개선되고 전극 팽창률은 저감된 이차전지를 제공하기 위한 것이다.The present invention is to provide a secondary battery electrode that simultaneously secures binding properties to a conductive material and an active material, and has improved mechanical properties, including an improved discharge capacity and a reduced electrode expansion rate.
또한, 그러한 이차전지용 전극을 제조함에 있어서, 공정 시간, 비용 등을 절감하는 방법을 제공하기 위한 것이다.In addition, in manufacturing such an electrode for a secondary battery, it is intended to provide a method for reducing process time, cost, and the like.
구체적으로, 본 발명의 일 구현예에서는, 입자 직경이 서로 다른 2종의 바인더를 포함하되, 전극 합제층 내에서 각 바인더의 분포 형태를 상이하게 한 이차전지용 전극을 제공한다.Specifically, in one embodiment of the present invention, the electrode for a secondary battery having two types of binders having different particle diameters but having different distribution patterns of each binder in the electrode mixture layer is provided.
본 발명의 다른 일 구현예에서는, 상대적으로 입자 직경이 작은 바인더는 도전재와 먼저 혼합하여 도전재 분산액을 제조하고, 상대적으로 입자 직경이 큰 바인더 및 전극 활물질을 상기 도전재 분산액과 혼합하여 활물질 슬러리 조성물을 제조한 뒤, 상기 활물질 슬러리 조성물을 사용하여 상기 일 구현예의 이차전지용 전극을 제조하는 방법을 제공한다.In another embodiment of the present invention, a binder having a relatively small particle diameter is first mixed with a conductive material to prepare a conductive material dispersion, and a binder and an electrode active material having a relatively large particle diameter are mixed with the conductive material dispersion to form an active material slurry. After preparing the composition, a method of manufacturing an electrode for a secondary battery of the above embodiment is provided using the active material slurry composition.
본 발명의 또 다른 일 구현예에서는, 상기 일 구현예의 이차전지용 전극을 포함하는 이차전지를 제공한다.In another embodiment of the present invention, there is provided a secondary battery including the electrode for a secondary battery of the one embodiment.
상기 일 구현예의 이차전지용 전극에 있어서, 상대적으로 작은 입경의 바인더는 도전재의 표면부에, 상대적으로 큰 입경의 바인더는 활물질의 표면부에 각각 존재하므로, 상기 도전재 및 상기 활물질에 대한 결착성을 동시에 확보할 수 있다.In the electrode for a secondary battery of the above embodiment, since a binder with a relatively small particle diameter is present on a surface portion of a conductive material, and a binder with a relatively large particle diameter is present on a surface portion of an active material, binding property to the conductive material and the active material is obtained. It can be secured at the same time.
이처럼 접착력을 높이는 것은, 전극 그 자체의 기계적 물성을 개선하고, 그러한 전극을 포함하는 전지의 방전 용량을 높이며, 전지의 구동 중 전극의 팽창률은 낮추는 효과가 있다.Increasing the adhesive force as described above has the effect of improving the mechanical properties of the electrode itself, increasing the discharge capacity of the battery including the electrode, and lowering the expansion coefficient of the electrode during driving of the battery.
공정 상으로는, 전극 오염 및 불량을 예방함과 동시에, 그 제조 공정 중 압연롤의 오염을 감소시킴으로써 롤 세척 빈도를 줄이는 등 공정 시간 단축 또는 공정 단순화 효과가 있다.In the process, there is an effect of shortening the process time or simplifying the process, such as reducing the frequency of roll cleaning by preventing contamination and defects of the electrode and reducing the contamination of the rolling roll during the manufacturing process.
도 1, 3, 및 5는, 배율을 달리 하여 실시예 1의 음극 표면을 촬영한 SEM 이미지들이다.1, 3, and 5 are SEM images of the cathode surface of Example 1 at different magnifications.
도 2, 4, 및 6은, 배율을 달리 하여 비교예 2의 음극 표면을 촬영한 SEM 이미지들이다.2, 4, and 6 are SEM images of the cathode surface of Comparative Example 2 at different magnifications.
본 명세서에서 사용되는 용어는 단지 예시적인 실시예들을 설명하기 위해 사용된 것으로, 본 발명을 한정하려는 의도는 아니다. 단수의 표현은 문맥상 명백하게 다르게 뜻하지 않는 한, 복수의 표현을 포함한다. 본 명세서에서, "포함하다", "구비하다" 또는 "가지다" 등의 용어는 실시된 특징, 단계, 구성 요소 또는 이들을 조합한 것이 존재함을 지정하려는 것이지, 하나 또는 그 이상의 다른 특징들이나 단계, 구성 요소, 또는 이들을 조합한 것들의 존재 또는 부가 가능성을 미리 배제하지 않는 것으로 이해되어야 한다.The terms used in this specification are only used to describe exemplary embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, the terms "include", "have" or "have" are intended to indicate that an implemented feature, step, component, or combination thereof exists, one or more other features or steps, It should be understood that the existence or addition possibilities of the components, or combinations thereof, are not excluded in advance.
본 발명은 다양한 변경을 가할 수 있고 여러 가지 형태를 가질 수 있는 바, 특정 실시예들을 예시하고 하기에서 상세하게 설명하고자 한다. 그러나, 이는 본 발명을 특정한 개시 형태에 대해 한정하려는 것이 아니며, 본 발명의 사상 및 기술 범위에 포함되는 모든 변경, 균등물 내지 대체물을 포함하는 것으로 이해되어야 한다.The present invention can be applied to various changes and may have various forms, and specific embodiments will be illustrated and described in detail below. However, this is not intended to limit the present invention to a specific disclosure form, and it should be understood that all modifications, equivalents, and substitutes included in the spirit and scope of the present invention are included.
이하 발명의 구체적인 구현예에 따른 이차전지용 전극 및 이의 제조방법에 관하여 보다 상세하게 설명하기로 한다.Hereinafter, an electrode for a secondary battery according to a specific embodiment of the present invention and a manufacturing method thereof will be described in more detail.
이차전지용 전극Electrode for secondary battery
본 발명의 일 구현예에서는, 집전체의 적어도 일면에, 복수의 전극 활물질 입자; 서로 다른 상기 전극 활물질 입자 사이에 분포된, 복수의 도전재 입자; 서로 다른 상기 도전재 입자 사이, 그리고 상기 도전재 입자 및 상기 집전체 사이에 각각 분포된, 입자 직경이 100 nm 이하인 제1 바인더; 서로 다른 상기 전극 활물질 입자 사이, 상기 전극 활물질 입자 및 상기 도전재 입자 사이, 그리고 상기 전극 활물질 입자 및 상기 집전체 사이에 각각 분포된, 입자 직경이 120 nm 이상인 제2 바인더; 포함하는 전극 합제층이 위치하는, 이차전지용 전극을 제공한다.In one embodiment of the present invention, at least one surface of the current collector, a plurality of electrode active material particles; A plurality of conductive material particles distributed between the different electrode active material particles; A first binder having a particle diameter of 100 nm or less, which are respectively distributed between the different conductive material particles and between the conductive material particles and the current collector; A second binder having a particle diameter of 120 nm or more distributed between the different electrode active material particles, between the electrode active material particles and the conductive material particles, and between the electrode active material particles and the current collector; It provides an electrode for a secondary battery, the electrode mixture layer is included.
여기서, 각 바인더의 입자 직경은, 전극 합제층의 단면 등에서 확인되는 개별 입자의 입경을 나타낸 것이다.Here, the particle diameter of each binder represents the particle diameter of the individual particles identified in the cross section of the electrode mixture layer and the like.
전극 활물질 및 도전재는, 그 입자 직경에 따라 전극 합제층 내 분포 형태가 달라질 수 있다. 또한, 바인더의 입자 직경에 따라, 전극 활물질 및 도전재에 대한 결착성이 달라질 수 있다.The electrode active material and the conductive material may have different distribution shapes in the electrode mixture layer according to the particle diameter. In addition, depending on the particle diameter of the binder, the binding properties to the electrode active material and the conductive material may vary.
구체적으로, 도전재에 대비하여 전극 활물질의 입자 직경이 큰 것이 일반적이며, 전극 활물질 입자가 전극 합체층 내 균일하게 분포되고, 서로 다른 전극 활물질 입자 사이에 도전재가 분포될 수 있다. Specifically, it is common that the particle diameter of the electrode active material is larger than that of the conductive material, and the electrode active material particles are uniformly distributed in the electrode assembly layer, and the conductive material may be distributed between different electrode active material particles.
만약 입자 직경이 도전재의 크기와 유사한 바인더만 사용한다면, 같은 부피의 전극 내 상대적으로 많은 양의 바인더가 분포되고, 도전재를 결착시키는 데 도움이 될 수 있다. 다만, 입자 직경이 도전재의 크기와 유사한 바인더는, 그보다 입자 직경이 큰 활물질을 결착시키기는 어려울 수 있다. If only a binder having a particle diameter similar to the size of the conductive material is used, a relatively large amount of the binder is distributed in the electrode of the same volume, which may help to bind the conductive material. However, a binder whose particle diameter is similar to the size of a conductive material, it may be difficult to bind an active material having a larger particle diameter.
다시 말해, 입자 직경이 도전재의 크기와 유사한 바인더만 사용하는 경우에는, 전극 활물질에 대비하여 도전재에 대한 바인더의 결착성이 높고, 전지 구동 중 도전재는 안정적으로 결착되어 있어라도 전극 활물질은 탈리될 가능성이 높다.In other words, when only a binder having a particle diameter similar to the size of the conductive material is used, the binding property of the binder to the conductive material is high compared to the electrode active material, and the electrode active material may be detached even when the conductive material is stably attached during battery operation. It is very likely.
이와 달리, 입자 직경이 전극 활물질의 크기와 유사한 바인더를 사용하는 경우, 활물질을 결착시키는 데에는 도움이 될 수 있다. 다만, 같은 부피의 전극 내 상대적으로 적은 양의 바인더가 분포되고, 그 바인더보다 입자 직경이 큰 활물질을 결착시키기는 어려울 수 있다.Alternatively, when using a binder whose particle diameter is similar to the size of the electrode active material, it may be helpful to bind the active material. However, a relatively small amount of the binder is distributed in the electrode of the same volume, and it may be difficult to bind an active material having a larger particle diameter than the binder.
다시 말해, 도전재에 대비하여 전극 활물질에 대한 바인더의 결착성이 높고, 전극 제조 공정 중이나 전지 구동 중 전극 활물질이 안정적으로 결착되어 있어라도 도전재는 탈리될 가능성이 높다.In other words, compared to the conductive material, the binding property of the binder to the electrode active material is high, and even when the electrode active material is stably attached during the electrode manufacturing process or during battery operation, the conductive material is likely to be detached.
위와 같은 문제를 고려하여, 본 발명의 일 구현예에서는, 입자 직경이 서로 다른 2종의 바인더를 포함하되, 전극 합제층 내에서 각 바인더의 분포 형태를 상이하게 한 이차전지용 전극을 제공한다.In consideration of the above problems, in one embodiment of the present invention, the electrode for a secondary battery having two types of binders having different particle diameters but having different distribution types of the binders in the electrode mixture layer is provided.
상대적으로 작은 입경의 바인더는 도전재의 표면부에, 상대적으로 큰 입경의 바인더는 활물질의 표면부에 각각 존재하여, 상기 도전재 및 상기 활물질에 대한 결착성을 동시에 확보할 수 있다.A binder having a relatively small particle diameter is present on the surface portion of the conductive material, and a binder having a relatively large particle size is present on the surface portion of the active material, so that binding properties to the conductive material and the active material can be simultaneously secured.
구체적으로, 서로 다른 상기 도전재 입자 사이, 그리고 상기 도전재 입자 및 상기 집전체 사이에 각각, 상대적으로 작은 입경의 상기 제1 바인더가 분포하여 상호 결착시킬 수 있다.Specifically, the first binders having a relatively small particle diameter may be distributed between the conductive material particles, and between the conductive material particles and the current collector, to bind to each other.
또한, 서로 다른 상기 전극 활물질 입자 사이, 그리고 상기 전극 활물질 입자 및 상기 집전체 사이에 각각, 상대적으로 큰 입경의 상기 제2 바인더가 분포하여 상호 결착시킬 수 있다.In addition, the second binder having a relatively large particle diameter may be distributed between the electrode active material particles different from each other, and between the electrode active material particle and the current collector, to bind to each other.
이에 따라, 상대적으로 작은 입경의 바인더는 도전재의 표면부에, 상대적으로 큰 입경의 바인더는 활물질의 표면부에 각각 존재하므로, 상기 도전재 및 상기 활물질에 대한 결착성을 동시에 확보할 수 있다.Accordingly, since the binder of the relatively small particle diameter is present on the surface portion of the conductive material, and the binder of the relatively large particle size is present on the surface portion of the active material, binding properties to the conductive material and the active material can be simultaneously secured.
나아가, 전극의 접착력을 높이는 것은, 전극 그 자체의 기계적 물성을 개선하고, 그러한 전극을 포함하는 전지의 방전 용량을 높이며, 전지의 구동 중 전극의 팽창률은 낮추는 효과가 있다.Furthermore, increasing the adhesion of the electrode has the effect of improving the mechanical properties of the electrode itself, increasing the discharge capacity of the battery containing the electrode, and lowering the expansion coefficient of the electrode during operation of the battery.
공정 상으로는, 전극 오염 및 불량을 예방함과 동시에, 그 제조 공정 중 압연롤의 오염을 감소시킴으로써 롤 세척 빈도를 줄이는 등 공정 시간 단축 또는 공정 단순화 효과가 있다.In the process, there is an effect of shortening the process time or simplifying the process, such as reducing the frequency of roll cleaning by preventing contamination and defects of the electrode and reducing the contamination of the rolling roll during the manufacturing process.
이하, 상기 일 구현예의 이차전지용 전극을 상세히 설명한다.Hereinafter, the electrode for a secondary battery of one embodiment will be described in detail.
전극 합제층 구성 성분들의 분포 형태Distribution pattern of the components of the electrode mixture layer
상기 제 1 바인더는 제 1 바인더 총 중량 대비 60 중량% 이상이 상기 도전재 입자들 표면부에 위치하여 도전재 입자들을 결착시키고, 상기 제 2 바인더는 제 2 바인더 총 중량 대비 60 중량% 이상이, 상기 전극 활물질 입자들 표면부에 위치하여 활물질 입자들을 결착시킬 수 있다.The first binder is 60% by weight or more relative to the total weight of the first binder is located on the surface of the conductive material particles to bind the conductive material particles, the second binder is 60% by weight or more relative to the total weight of the second binder, Located on the surface of the electrode active material particles, the active material particles may be bound.
여기서, 상기 표면부란, 입자 표면에서부터 입자 표면으로부터 수직 방향으로 1 ㎛ 까지를 의미할 수 있고, 전극 합제층의 표면, 단면 등에서 확인될 수 있다 . Here, the surface portion may mean up to 1 µm in the vertical direction from the particle surface to the particle surface, and may be confirmed on the surface, cross-section, etc. of the electrode mixture layer .
전극 합제층 구성 성분들의 입자 직경Particle diameter of the components of the electrode mixture layer
상기 전극 활물질 및 상기 도전재의 경우, D50을 기준으로 입자 직경을 나타낼 수 있다. 상기 D50은 입경에 따른 입자 개수 누적 분포의 50% 지점에서의 입경이며, 레이저 회절법(laser diffraction method)을 이용하여 측정할 수 있다. 구체적으로, 측정 대상 분말을 분산매 중에 분산시킨 후, 시판되는 레이저 회절 입도 측정 장치(예를 들어 Microtrac S3500)에 도입하여 입자들이 레이저빔을 통과할 때 입자 직경에 따른 회절패턴 차이를 측정하여 입도 분포를 산출한다. 측정 장치에 있어서의 입경에 따른 입자 개수 누적 분포의 50%가 되는 지점에서의 입자 직경을 산출함으로써, D50을 측정할 수 있다.In the case of the electrode active material and the conductive material, a particle diameter may be represented based on D50. The D50 is a particle diameter at a point of 50% of the cumulative distribution of particle number according to particle size, and can be measured using a laser diffraction method. Specifically, after the powder to be measured is dispersed in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (for example, Microtrac S3500) to measure the difference in diffraction pattern according to the particle diameter when particles pass through the laser beam, and thus the particle size distribution. Calculate D50 can be measured by calculating the particle diameter at a point at which 50% of the cumulative distribution of the number of particles according to the particle diameter in the measuring device is obtained.
한편, 상기 제1 바인더 및 상기 제2 바인더의 경우, 고분자 입자로서 D50을 구하기 어렵기에, 전극 합제층의 단면 등에서 확인되는 개별 입자의 입경으로부터 평균을 구하여, 그 평균 입경을 기준으로 입자 직경을 나타낼 수 있다.On the other hand, in the case of the first binder and the second binder, since it is difficult to obtain D50 as a polymer particle, an average is obtained from the particle diameters of individual particles identified on the cross-section of the electrode mixture layer, etc., and the particle diameter is displayed based on the average particle diameter. Can.
이와 같은 정의를 기준으로, 전극 합제층 구성 성분들의 입자 직경을 설명하면 다음과 같다.Based on this definition, the particle diameters of the components of the electrode mixture layer are as follows.
상기 도전재는, 입자 직경(D50)이 10 nm 내지 2㎛ 범위 내인 것을 사용할 수 있다. 구체적으로, 입자 직경(D50)이 구체적으로는 20 nm 내지 1 ㎛, 예컨대 30 내지 100 nm 범위 내인 것을 상기 도전재로 사용할 수 있다.As the conductive material, particles having a particle diameter (D50) in the range of 10 nm to 2 μm may be used. Specifically, the particle diameter (D50) is specifically 20 nm to 1 μm, for example, it can be used in the range of 30 to 100 nm as the conductive material.
상기 도전재 입자 및 상기 집전체 사이에 각각 분포되는 제1 바인더로는, 입자 직경이 100 nm 이하, 구체적으로 40 nm 내지 100 nm, 예컨대 50 nm 내지 80 nm 범위 내인 것을 사용할 수 있다.As the first binder distributed between the conductive material particles and the current collector, a particle diameter of 100 nm or less, specifically, 40 nm to 100 nm, such as 50 nm to 80 nm, may be used.
상기 범위를 벗어나 너무 작은 경우 공정상 핸들링이 어렵고 안정적인 바인더 구현이 어려운 문제가 있다. 상기 범위를 벗어나 너무 큰 경우, 제 2 바인더와 구분되지 않고 소망하는 정도의 도전재 결착성의 향상이 어려울 수 있다. If it is too small outside the above range, it is difficult to handle in the process and difficult to implement a stable binder. If it is too large outside the above range, it may be difficult to improve the binding property of the conductive material to a desired degree without being distinguished from the second binder.
한편, 상기 전극 활물질로는, 입자 직경(D50)이 500 nm 내지 50 ㎛의 범위 내인 것을 사용할 수 있다. 구체적으로, 용량, 공정성 등을 고려하여, 입자 직경(D50)이 1 ㎛ 내지 40 ㎛, 예컨대 5 ㎛ 내지 30 ㎛ 범위 내인 것을 상기 전극 활물질로 사용할 수 있다.Meanwhile, as the electrode active material, a particle diameter (D50) of 500 nm to 50 μm may be used. Specifically, in consideration of capacity, processability, and the like, a particle diameter (D50) of 1 μm to 40 μm, such as 5 μm to 30 μm, may be used as the electrode active material.
서로 다른 상기 전극 활물질 입자 사이, 상기 전극 활물질 입자 및 상기 도전재 입자 사이, 그리고 상기 전극 활물질 입자 및 상기 집전체 사이에 각각 분포되는 제2 바인더로는, 입자 직경이 120 nm 이상, 구체적으로 150 nm 내지 600 nm, 예컨대 160 내지 300 nm 내인 것을 사용할 수 있다.As a second binder distributed between the different electrode active material particles, between the electrode active material particles and the conductive material particles, and between the electrode active material particles and the current collector, the particle diameter is 120 nm or more, specifically 150 nm To 600 nm, for example, within 160 to 300 nm.
상기 범위를 벗어나 너무 작은 경우, 제 1 바인더와 구분되지 않고, 보다 큰 입자 직경을 가지는 전극 활물질의 결착성 향상이 어려울 수 있다. 상기 범위를 벗어나 너무 큰 경우에는, 활물질의 결착에 필요한 절대적인 입자 수가 적어서 우수한 결착력을 구현하기 힘들 수 있다.If it is too small outside the above range, it is not distinguishable from the first binder, and it may be difficult to improve the binding property of the electrode active material having a larger particle diameter. If it is too large outside the above range, the absolute number of particles required for binding of the active material may be small, and thus it may be difficult to realize excellent binding force.
바인더의 종류 및 함량Type and content of binder
상기 제1 바인더 및 상기 제2 바인더는 동종이되, 입자 직경만 서로 다른 것일 수 있다.The first binder and the second binder may be the same type, but may have different particle diameters.
예를 들어, 상기 제1 바인더 및 상기 제2 바인더는 공통적으로, 폴리불화비닐리덴, 폴리비닐알코올, 카르복시메틸셀룰로우즈(CMC), 전분, 히드록시프로필셀룰로우즈, 재생 셀룰로우즈, 폴리비닐피롤리돈, 테트라플루오로에틸렌, 폴리에틸렌, 폴리프로필렌, 에틸렌-프로필렌-디엔 테르 폴리머(EPDM), 술폰화 EPDM, 스티렌 부타디엔 라텍스, 불소 라텍스 등의 중합체 중 1종일 수 있고, 구체적으로, 수계 바인더로서 결착력이 우수한 스티렌-부타디엔계 라텍스, 예컨대 스티렌-부타디엔-아크릴계 중합체일 수 있다.For example, the first binder and the second binder are commonly, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, recycled cellulose, poly Vinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene butadiene latex, fluorine latex, etc. may be one of polymers, specifically, water-based binder As it may be a styrene-butadiene-based latex having excellent binding force, such as styrene-butadiene-acrylic polymer.
이러한 바인더는, 통상적으로 전극 합제층 전체 중량을 기준으로 0.1 내지 30 중량%로 포함될 수 있고, 구체적으로 1 내지 10 중량%로 포함될 수 있다.Such a binder may be usually included in an amount of 0.1 to 30% by weight based on the total weight of the electrode mixture layer, and specifically 1 to 10% by weight.
상기 제 1 바인더와 제 2 바인더의 중량비는, 1:2 내지 1:20, 구체적으로 1:5 내지 1:15일 수 있다.The weight ratio of the first binder and the second binder may be 1:2 to 1:20, specifically 1:5 to 1:15.
상기 범위는 도전재와 활물질의 함량에 의해 적절히 정해질 수 있고, 일반적으로 활물질의 함량이 도전재의 함량보다 크기 때문에 제 2 바인더의 함량이 높다.The range may be appropriately determined by the content of the conductive material and the active material, and in general, the content of the second binder is high because the content of the active material is larger than that of the conductive material.
전극 활물질의 종류 및 함량Type and content of electrode active material
상기 일 구현예의 전극은 양극과 음극 중 어느 하나일 수 있고, 그에 따라 상기 전극 활물질의 종류가 양극 활물질과 음극 활물질 중 어느 하나로 결정될 수 있다.The electrode of the embodiment may be any one of an anode and a cathode, and accordingly The type of the electrode active material may be determined as either a positive electrode active material or a negative electrode active material.
상기 양극 활물질은, 예를 들어, 리튬 코발트 산화물(LiCoO 2), 리튬 니켈 산화물(LiNiO 2) 등의 층상 화합물이나 1 또는 그 이상의 전이금속으로 치환된 화합물; 화학식 Li 1+xMn 2-xO 4 (여기서, x 는 0 ~ 0.33 임), LiMnO 3, LiMn 2O 3, LiMnO 2 등의 리튬 망간 산화물; 리튬 동 산화물(Li 2CuO 2); LiV 3O 8, LiV 3O 4, V 2O 5, Cu 2V 2O 7 등의 바나듐 산화물; 화학식 LiNi 1-xM xO 2 (여기서, M = Co, Mn, Al, Cu, Fe, Mg, B 또는 Ga 이고, x = 0.01 ~ 0.3 임)으로 표현되는 Ni 사이트형 리튬 니켈 산화물; 화학식 LiMn 2-xM xO 2 (여기서, M = Co, Ni, Fe, Cr, Zn 또는 Ta 이고, x = 0.01 ~ 0.1 임) 또는 Li 2Mn 3MO 8 (여기서, M = Fe, Co, Ni, Cu 또는 Zn 임)으로 표현되는 리튬 망간 복합 산화물; 화학식의 Li 일부가 알칼리토금속 이온으로 치환된 LiMn 2O 4; 디설파이드 화합물; Fe 2(MoO 4) 3 등을 들 수 있지만, 이들만으로 한정되는 것은 아니다.The positive electrode active material may include, for example, a layered compound such as lithium cobalt oxide (LiCoO 2 ) or lithium nickel oxide (LiNiO 2 ), or a compound substituted with one or more transition metals; Lithium manganese oxides such as the formula Li 1+x Mn 2-x O 4 (where x is 0 to 0.33), LiMnO 3 , LiMn 2 O 3 , LiMnO 2 ; Lithium copper oxide (Li 2 CuO 2 ); Vanadium oxides such as LiV 3 O 8 , LiV 3 O 4 , V 2 O 5 and Cu 2 V 2 O 7 ; Ni-site type lithium nickel oxide represented by the formula LiNi 1-x M x O 2 (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3); Formula LiMn 2-x M x O 2 (where M = Co, Ni, Fe, Cr, Zn or Ta, x = 0.01 to 0.1) or Li 2 Mn 3 MO 8 (where M = Fe, Co, Lithium manganese composite oxide represented by Ni, Cu or Zn); LiMn 2 O 4 in which part of Li in the formula is substituted with alkaline earth metal ions; Disulfide compounds; Fe 2 (MoO 4 ) 3 and the like, but are not limited to these.
상기 음극 활물질은, 예를 들어, 난흑연화 탄소, 흑연계 탄소 등의 탄소; Li xFe 2O 3(0≤x≤1), Li xWO 2(0≤x≤1), Sn xMe 1-xMe' yO z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, 주기율표의 1족, 2족, 3족 원소, 할로겐; 0<x≤1; 1≤y≤3; 1≤z≤8) 등의 금속 복합 산화물; 리튬 금속; 리튬 합금; 규소계 합금; 주석계 합금; SnO, SnO 2, PbO, PbO 2, Pb 2O 3, Pb 3O 4, Sb 2O 3, Sb 2O 4, Sb 2O 5, GeO, GeO 2, Bi 2O 3, Bi 2O 4, and Bi 2O 5 등의 금속 산화물; 폴리아세틸렌 등의 도전성 고분자; Li-Co-Ni 계 재료 등을 사용할 수 있다.The negative active material includes, for example, carbon such as non-graphitized carbon and graphite-based carbon; Li x Fe 2 O 3 (0≤x≤1), Li x WO 2 (0≤x≤1), Sn x Me 1-x Me' y O z (Me: Mn, Fe, Pb, Ge; Me' : Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen, metal composite oxides such as 0<x≤1;1≤y≤3;1≤z≤8); Lithium metal; Lithium alloys; Silicon-based alloys; Tin-based alloys; SnO, SnO 2 , PbO, PbO 2 , Pb 2 O 3 , Pb 3 O 4 , Sb 2 O 3 , Sb 2 O 4 , Sb 2 O 5 , GeO, GeO 2 , Bi 2 O 3 , Bi 2 O 4 , and Bi 2 O 5 ; Conductive polymers such as polyacetylene; Li-Co-Ni based materials and the like can be used.
통상적으로, 상기 전극 활물질은 전극 합제층 전체 중량을 기준으로, 60 내지 99 중량%로 포함될 수 있고, 구체적으로, 80 내지 98 중량%로 포함될 수 있다. Typically, the electrode active material, based on the total weight of the electrode mixture layer, may be included in 60 to 99% by weight, specifically, may be included in 80 to 98% by weight.
상기 일 구현예의 전극은 음극일 수 있고, 이에 전극 활물질로는 음극 활물질을 적용할 수 있다. 이러한 일 구현예의 음극을 포함하는 이차전지의 방전 용량이 개선되고, 음극의 팽창이 억제될 수 있다.The electrode of the embodiment may be a negative electrode, and thus, a negative electrode active material may be applied as the electrode active material. The discharge capacity of the secondary battery including the negative electrode of this embodiment is improved, and expansion of the negative electrode can be suppressed.
도전재의 종류 및 함량Type and content of conductive material
한편, 상기 전극 활물질 입자들 사이의 도전성을 향상시키는 도전재는, 종래 공지된 것으로서 당해 전지에 화학적 변화를 유발하지 않으면서 도전성을 가진 것이라면 특별히 제한되는 것은 아니며, 예를 들어, 카본블랙, 아세틸렌 블랙, 케첸 블랙, 채널 블랙, 퍼네이스 블랙, 램프 블랙, 서머 블랙 등의 카본블랙; 탄소 섬유나 금속 섬유 등의 도전성 섬유; 불화 카본, 알루미늄, 니켈 분말 등의 금속 분말; 산화아연, 티탄산 칼륨 등의 도전성 위스키; 산화 티탄 등의 도전성 금속 산화물; 폴리페닐렌 유도체 등의 도전성 소재 등이 사용될 수 있다. On the other hand, the conductive material that improves the conductivity between the electrode active material particles is not conventionally known, and is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, carbon black, acetylene black, Carbon black such as ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride powder, aluminum powder, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.
이러한 도전재는, 통상적으로 전극 합제층 전체 중량을 기준으로 0.1 내지 30 중량%로 포함될 수 있고, 구체적으로, 1 내지 10 중량%로 포함될 수 있다.Such a conductive material may be usually included in an amount of 0.1 to 30% by weight based on the total weight of the electrode mixture layer, specifically, it may be included in 1 to 10% by weight.
기타 전극 합제층의 구성 성분Components of other electrode mixture layer
한편, 상기 전극 합제층에는 충진제가 더 포함될 수 있다.Meanwhile, a filler may be further included in the electrode mixture layer.
상기 충진제는 양극의 팽창을 억제하는 성분으로서 선택적으로 사용되며, 당해 전지에 화학적 변화를 유발하지 않으면서 섬유상 재료라면 특별히 제한되는 것은 아니며, 예를 들어, 폴리에틸렌, 폴리프로필렌 등의 올리핀계 중합체; 유리섬유, 탄소섬유 등의 섬유상 물질이 사용되며, 함량은 전극 합제층 전체 중량을 기준으로 0 내지 10 중량%로 포함될 수 있다.The filler is optionally used as a component that inhibits the expansion of the positive electrode, and is not particularly limited as long as it is a fibrous material without causing chemical changes in the battery, and includes, for example, olipine polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used, and the content may be included in an amount of 0 to 10% by weight based on the total weight of the electrode mixture layer.
집전체Whole house
앞서 언급한 바와 같이, 상기 일 구현예의 전극은 양극과 음극 중 어느 하나일 수 있고, 그에 따라 상기 전극 합제층이 형성되는 집전체는 양극 집전체와 음극 집전체 중 어느 하나로 결정될 수 있다.As mentioned above, the electrode of the embodiment may be either an anode or a cathode, and accordingly, a current collector on which the electrode mixture layer is formed may be determined as either a positive electrode current collector or a negative electrode current collector.
상기 양극 집전체는, 일반적으로 3 ~ 200 ㎛의 두께로 제조되며, 당해 전지에 화학적 변화를 유발하지 않으면서 높은 도전성을 가지는 것이라면 특별히 제한되는 것은 아니며, 예를 들어, 스테인레스 스틸, 알루미늄, 니켈, 티타늄, 및 알루미늄이나 스테인레스 스틸의 표면에 카본, 니켈, 티타늄 또는 은으로 표면처리 한 것 중에서 선택되는 하나를 사용할 수 있고, 상세하게는 알루미늄이 사용될 수 있다. 집전체는 그것의 표면에 미세한 요철을 형성하여 양극 활물질의 접착력을 높일 수도 있으며, 필름, 시트, 호일, 네트, 다공질체, 발포체, 부직포체 등 다양한 형태가 가능하다.The positive electrode current collector is generally made to a thickness of 3 to 200 μm, and is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, stainless steel, aluminum, nickel, Titanium and aluminum or stainless steel may be selected from carbon, nickel, titanium, or silver surfaces, and aluminum may be used. The current collector may also increase the adhesion of the positive electrode active material by forming fine irregularities on its surface, and various forms such as a film, sheet, foil, net, porous body, foam, and nonwoven fabric are possible.
상기 음극 집전체는 일반적으로 3 ~ 200 ㎛의 두께로 제조되며, 당해 전지에 화학적 변화를 유발하지 않으면서 도전성을 가진 것이라면 특별히 제한되는 것은 아니며, 예를 들어, 구리, 스테인레스 스틸, 알루미늄, 니켈, 티탄, 소성 탄소, 구리나 스테인레스 스틸의 표면에 카본, 니켈, 티탄, 은 등으로 표면처리한 것, 알루미늄-카드뮴 합금 등이 사용될 수 있다. 또한, 양극 집전체와 마찬가지로, 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 is generally manufactured to a thickness of 3 to 200 μm, and is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, copper, stainless steel, aluminum, nickel, Surfaces made of carbon, nickel, titanium, silver, etc. on the surface of titanium, calcined carbon, copper or stainless steel, aluminum-cadmium alloy, or the like can be used. In addition, like the positive electrode current collector, it is also possible to form a fine unevenness on the surface to enhance the bonding force 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.
이차전지용 전극의 제조 방법Method for manufacturing electrodes for secondary batteries
본 발명의 또 다른 일 구현예에서는, 입자 직경이 100 nm 이하인 제 1 바인더 및 도전재를 혼합하여, 도전재 분산액을 제조하는 단계; 상기 도전재 분산액; 입자 직경이 120 nm 이상인 제 2 바인더 및 전극 활물질을 혼합하여, 활물질 슬러리 조성물을 제조하는 단계; 집전체의 적어도 일면에 상기 활물질 슬러리 조성물을 도포하고, 건조 및 압연하여, 전극을 수득하는 단계를 포함하는, 이차전지용 전극의 제조방법을 제공한다.In another embodiment of the present invention, mixing a first binder and a conductive material having a particle diameter of 100 nm or less to prepare a conductive material dispersion; The conductive material dispersion; Mixing a second binder and an electrode active material having a particle diameter of 120 nm or more to prepare an active material slurry composition; It provides a method of manufacturing an electrode for a secondary battery, comprising the step of applying the active material slurry composition to at least one surface of the current collector, drying and rolling to obtain an electrode.
이는, 활물질 슬러리 조성물 제조 공정 중 제 1 바인더와 제 2 바인더의 공급 시점을 통제함에 따라, 최종적으로 수득되는 전극 내 제 1 바인더와 제 2 바인더의 분포 형태를 제어하는 방법에 해당된다. This corresponds to a method of controlling the distribution pattern of the first binder and the second binder in the electrode finally obtained by controlling the supply timings of the first binder and the second binder during the manufacturing process of the active material slurry composition.
구체적으로, 상기 일 구현예의 제조 방법에서는, 상대적으로 입자 직경이 작은 바인더는 도전재와 먼저 혼합하여 도전재 분산액을 제조하고, 상대적으로 입자 직경이 큰 바인더 및 전극 활물질을 상기 도전재 분산액과 혼합하여 제조한 활물질 슬러리 조성물을 사용함으로써, 전술한 일 구현예의 전극을 수득할 수 있따. Specifically, in the manufacturing method of the above embodiment, a binder having a relatively small particle diameter is first mixed with a conductive material to prepare a conductive material dispersion, and a binder and an electrode active material having a relatively large particle diameter are mixed with the conductive material dispersion. By using the prepared active material slurry composition, the electrode of one embodiment described above can be obtained.
상기 일 구현예의 제조 방법에 따르면, 기계적 물성, 전기화학적 특성 등이 두루 우수한 전극이 수득됨은 물론, 공정 상 전극 오염 및 불량을 예방함과 동시에, 그 제조 공정 중 압연롤의 오염을 감소시킴으로써 롤 세척 빈도를 줄이는 등 공정 시간 단축 또는 공정 단순화 효과가 있다.According to the manufacturing method of the above embodiment, an electrode having excellent mechanical properties and electrochemical properties is obtained, as well as preventing electrode contamination and defects in the process, and at the same time, washing the roll by reducing contamination of the rolling roll during the manufacturing process It has the effect of reducing the process time or simplifying the process, such as reducing the frequency.
이하, 상기 일 구현예의 이차전지용 전극 제조방법을 상세히 설명한다.Hereinafter, a method of manufacturing an electrode for a secondary battery according to the embodiment will be described in detail.
바인더의 제조 공정Binder manufacturing process
상기 제 1 바인더 및 상기 제 2 바인더는, 일반적으로 알려진 유화 중합법을 이용하여 제조할 수 있다. 구체적으로, 상기 제 1 바인더 및 상기 제 2 바인더는, 각각 독립적으로, 유화제, 중합 개시제, 및 용매의 존재 하에, 단량체를 중합시키는 단계를 포함하여 제조할 수 있다.The first binder and the second binder can be produced using a generally known emulsion polymerization method. Specifically, the first binder and the second binder, each independently, in the presence of an emulsifier, a polymerization initiator, and a solvent, may be prepared by including the step of polymerizing the monomer.
다만, 상기 제1 바인더 및 상기 제2 바인더의 입자 직경을 다르게 형성하기 위하여, 상기 단량체, 유화제, 중합 개시제, 및 용매의 총량 중 유화제의 함량을 조절 할 수 있다.However, in order to form different particle diameters of the first binder and the second binder, the content of the emulsifier in the total amount of the monomer, emulsifier, polymerization initiator, and solvent may be adjusted.
보다 구체적으로, 유화제의 함량이 높을 수록, 입자 직경이 상대적으로 더 작은 바인더가 제조될 수 있다. 이와 관련하여, 상기 제 2 바인더에 대비하여, 상기 제 1 바인더의 제조 시, 상기 단량체, 유화제, 중합 개시제, 및 용매의 총량 중 유화제의 함량을 더 높일 수 있다.More specifically, as the content of the emulsifier is higher, a binder having a smaller particle diameter can be produced. In this regard, compared to the second binder, in the preparation of the first binder, the content of the emulsifier in the total amount of the monomer, emulsifier, polymerization initiator, and solvent may be further increased.
구체적으로, 상기 제 1 바인더를 제조하기 위한 유화제의 함량은, 단량체들 100 중량부를 기준으로, 0.9 중량부 초과, 구체적으로는 1 중량부 내지 5 중량부일 수 있고, 제 2 바인더를 제조하기 위한 유화제의 함량은 0.9 중량부 이하, 구체적으로는 0.3 중량부 내지 0.8 중량부일 수 있다.Specifically, the content of the emulsifier for preparing the first binder, based on 100 parts by weight of the monomers, may be greater than 0.9 parts by weight, specifically 1 part by weight to 5 parts by weight, and an emulsifier for preparing the second binder The content of may be 0.9 parts by weight or less, specifically 0.3 parts by weight to 0.8 parts by weight.
상기 유화제는 유화 중합에 사용하는 것으로서, 예를 들어, 올레인산, 스테아린산, 라우린산, 혼합 지방산의 소듐 또는 포타슘 염 등으로 대표되는 지방산 염 계통이나, 로진산 등의 일반적인 음이온성 유화제 등이 사용될 수 있고, 구체적으로는 중합체의 안정성을 향상시키는 반응형 유화제가 첨가될 수도 있는데, 상기 유화제는 단독 또는 2종 이상으로 혼합하여 사용할 수도 있다. The emulsifier is used for emulsion polymerization, and for example, oleic acid, stearic acid, lauric acid, fatty acid salts represented by sodium or potassium salts of mixed fatty acids, and general anionic emulsifiers such as rosin and the like can be used. Specifically, a reactive emulsifier for improving the stability of the polymer may be added, and the emulsifier may be used alone or in combination of two or more.
상기 단량체들은 제조하고자 하는 바인더의 기본이 되는 단량체들일 수 있으며, 예를 들어, 제 1 바인더 및 제 2 바인더의 하나의 예인, 스티렌 부타디엔 라텍스를 제조하기 위해서는 스티렌, 부타디엔과 함께 친수성을 부여하는 아크릴산의 단량체를 사용할 수 있다. The monomers may be monomers that are the basis of a binder to be produced, and for example, to produce styrene butadiene latex, which is one example of a first binder and a second binder, acrylic acid that imparts hydrophilicity with styrene and butadiene. Monomers can be used.
또한, 상기 중합 개시제는, 무기 또는 유기 과산화물이 사용될 수 있으며, 예를 들어, 포타슘 퍼설페이트, 소듐 퍼설페이트, 암모늄 퍼설페이트 등을 포함하는 수용성 개시제와, 큐멘 하이드로 퍼옥사이드, 벤조일 퍼옥사이드 등을 포함하는 유용성 개시제를 사용할 수 있다. In addition, the polymerization initiator, inorganic or organic peroxide may be used, for example, water-soluble initiators including potassium persulfate, sodium persulfate, ammonium persulfate, and the like, cumene hydroperoxide, benzoyl peroxide, etc. The oil-soluble initiator can be used.
상기 중합 개시제는 단량체들 100 중량부를 기준으로 0.01 중량부 내지 2 중량부로 포함될 수 있다.The polymerization initiator may be included in an amount of 0.01 to 2 parts by weight based on 100 parts by weight of the monomers.
더 나아가, 상기 중합 개시제와 함께 과산화물의 개시반응을 촉진시키기 위해 활성화제를 더 포함할 수 있으며, 이러한 활성화제로는 소듐 포름알데히드 설폭실 레이트, 소듐 에틸렌디아민테트라아세테이트, 황산 제 1 철 및 덱스트로오스로 이루어진 군으로부터 선택되는 1 종 이상이 사용될 수 있다.Furthermore, an activator may be further included to accelerate the initiation reaction of the peroxide together with the polymerization initiator, and such activators include sodium formaldehyde sulfoxylate, sodium ethylenediaminetetraacetate, ferrous sulfate and dextrose One or more selected from the group consisting of can be used.
상기 용매는, 유기 용매 또는 물일 수 있으며, 구체적으로는 물일 수 있다.The solvent may be an organic solvent or water, specifically water.
상기 각 바인더의 유화 중합을 위한 중합 온도 및 중합 시간은 중합 방법이나 사용하는 중합 개시제의 종류 등에 따라 적절히 결정할 수 있으며, 예를 들어, 중합 온도는 약 50℃ 내지 200℃ 일 수 있고, 중합 시간은 약 1 내지 20 시간일 수 있다.The polymerization temperature and polymerization time for emulsion polymerization of each of the binders can be appropriately determined according to a polymerization method or the type of polymerization initiator used, for example, the polymerization temperature may be about 50°C to 200°C, and the polymerization time is It may be about 1 to 20 hours.
도전재 분산액의 제조 공정Manufacturing process of conductive material dispersion
상기 도전재 분산액을 제조할 때, 도전재의 결착성을 향상시키는 바인더인 제1 바인더를 함께 혼합하며, 선택적으로 증점제를 첨가할 수 있다.When preparing the dispersion of the conductive material, a first binder, which is a binder for improving the binding property of the conductive material, is mixed together, and a thickener can be optionally added.
상기 증점제는, 점도를 조절하는 것으로, 예를 들어, 셀룰로오스계 고분자, 폴리에틸렌 글리콜, 폴리아크릴아미드, 폴리(N-비닐 아미드) 및 폴리(N-비닐피롤리돈)일 수 있으며, 상기 셀룰로오스계 고분자는, 카복시메틸셀룰로오스(carboxy methyl cellulose, CMC), 메틸 셀룰로오스(methyl cellulose, MC), 하이드록시프로필 셀룰로오스(hydroxypropyl cellulose, HPC), 메틸 하이드록시프로필 셀룰로오스(methyl hydroxypropyl cellulose, MHPC), 에틸 하이드록시에틸 셀룰로오스(ethyl hydroxyethyl cellulose, EHEC), 메틸 에틸 하이드록시에틸 셀룰로오스(methyl ethylhydroxyethyl cellulose, MEHEC) 및 셀룰로오스 검(cellulose gum)으로 이루어진 군으로부터 선택되는 하나 이상일 수 있고, 보다 상세하게는, 카복시메틸셀룰로오스(carboxy methyl cellulose, CMC)일 수 있다.The thickener is to adjust the viscosity, for example, cellulose-based polymer, polyethylene glycol, polyacrylamide, poly (N-vinyl amide) and poly (N-vinylpyrrolidone), the cellulose-based polymer Silver, carboxy methyl cellulose (CMC), methyl cellulose (MC), hydroxypropyl cellulose (HPC), methyl hydroxypropyl cellulose (MHPC), ethyl hydroxyethyl It may be at least one selected from the group consisting of cellulose (ethyl hydroxyethyl cellulose, EHEC), methyl ethylhydroxyethyl cellulose (MEHEC) and cellulose gum, and more specifically, carboxymethyl cellulose (carboxy) methyl cellulose, CMC).
상기 증점제 용액은 이들 물질이 0.5% 내지 20%의 농도로 포함된 용액일 수 있다.The thickener solution may be a solution containing these materials at a concentration of 0.5% to 20%.
상기 증점제는 실질적인 증점제의 함량이 도전재 및 제 1 바인더 100 중량부를 기준으로 50 중량부 내지 100 중량부로 포함될 수 있다.The thickener may be included in an amount of 50 to 100 parts by weight based on 100 parts by weight of the conductive agent and the first binder.
이때, 상기 도전재와 상기 제1 바인더의 함량비는 10:1 내지 1:1일 수 있다. 상기 범위를 벗어나, 도전재의 함량이 지나치게 많은 경우, 바인더가 도전재의 결착성을 확보할 만큼 충분하지 않으므로 바람직하지 않고, 너무 적은 경우, 도전재 자체의 함량이 적어져 이차전지 성능 저하가 나타나므로 바람직하지 않다.At this time, the content ratio of the conductive material and the first binder may be 10:1 to 1:1. Outside the above range, if the content of the conductive material is too large, it is not preferable because the binder is not sufficient to secure the binding property of the conductive material, and if it is too small, the content of the conductive material itself decreases and secondary battery performance decreases, which is preferable Does not.
활물질 슬러리 조성물의 제조 공정Manufacturing process of active material slurry composition
이후, 상기 도전재 분산액에 전극 활물질, 용매, 및 제 2 바인더를 첨가하고 교반하여, 활물질 슬러리 조성물을 완성할 수 있다.Thereafter, an electrode active material, a solvent, and a second binder are added to the conductive material dispersion and stirred to complete the active material slurry composition.
이때, 상기 전극 활물질은, 전극 합제층 내에서 앞서 설명한 바와 같은 함량을 갖도록 추가되며, 제 2 바인더도 제 1 바인더 함량과 비교하여, 상기에서 설명한 바와 같은 함량비를 가지도록 추가된다.At this time, the electrode active material is added to have the content as described above in the electrode mixture layer, and the second binder is also added to have a content ratio as described above, compared to the content of the first binder.
상기 과정(d)에서 추가되는 용매는 도전재 분산액 제조시 사용되는 용매와 동일할 수 있고, 예를 들어, 유기 용매 또는 물일 수 있으며, 구체적으로는, 제 1 바인더와 제 2 바인더가 수계 바인더인 경우, 예를 들어, 스티렌-부타디엔-아크릴계 중합체인 경우, 물일 수 있다. The solvent added in the process (d) may be the same as the solvent used when preparing the conductive material dispersion, for example, an organic solvent or water, and specifically, the first binder and the second binder are water-based binders. In the case, for example, in the case of a styrene-butadiene-acrylic polymer, it may be water.
본 발명과 같이 제 1 바인더와 제 2 바인더의 투입 시점을 다르게 하고 도전재 분산액을 먼저 제조한 후, 슬러리를 제조함에 따라, 앞서 설명한 바와 같이, 상대적으로 작은 입경의 바인더는 도전재의 표면부에, 상대적으로 큰 입경의 바인더는 활물질의 표면부에 각각 존재하게 할 수 있다.As in the present invention, as the first binder and the second binder have different input timings, and a conductive material dispersion is prepared first, and then a slurry is prepared, as described above, a binder having a relatively small particle diameter has a surface portion of the conductive material. Binders having a relatively large particle diameter may be present on the surface of the active material, respectively.
활물질 슬러리 조성물의 도포, 건조, 및 압연 공정Application, drying, and rolling processes of the active material slurry composition
상기 전극 슬러리 조성물을 집전체의 적어도 일면에 도포하고, 건조 및 압연함으로써, 전극 합제층이 집전체의 적어도 일면에 형성된 전극을 수득할 수 있다.By applying the electrode slurry composition to at least one surface of the current collector, drying and rolling, an electrode having an electrode mixture layer formed on at least one surface of the current collector can be obtained.
상기 도포, 건조, 및 압연 공정 방식은 일반적으로 알려진 방식에 따를 수 있어, 상세한 설명을 생략한다.The coating, drying, and rolling process methods may follow generally known methods, and detailed descriptions are omitted.
전극 합제층의 두께는 한정되지 아니하나, 일면에서 20 ㎛ 내지 200 ㎛일 수 있다.The thickness of the electrode mixture layer is not limited, but may be 20 μm to 200 μm on one side.
상기 일 구현예의 제조 방법은, 양극 또는 음극을 제조하는 방법일 수 있다. 구체적으로, 이차전지의 방전 용량을 개선하고, 음극의 팽창을 억제하고자 할 경우, 상기 전극 활물질로 음극 활물질을 사용하여 음극을 제조할 수 있다.The manufacturing method of one embodiment may be a method of manufacturing an anode or a cathode. Specifically, in order to improve the discharge capacity of the secondary battery and suppress the expansion of the negative electrode, a negative electrode may be manufactured using the negative electrode active material as the electrode active material.
이차전지Secondary battery
본 발명의 또 다른 일 구현예에서는, 전술한 이차전지용 전극을 포함하는 이차전지를 제공한다.In another embodiment of the present invention, a secondary battery including the electrode for a secondary battery described above is provided.
더욱 구체적으로, 상기 이차전지는, 상기 전극(양극 또는 음극), 상기 전극의 대향 전극(음극 또는 양극), 및 상기 전극들 사이에 개재되는 분리막을 포함하는 전극조립체가 전해액과 함께 전지케이스에 내장되어 있는 구조로 이루어질 수 있다.More specifically, in the secondary battery, the electrode assembly including the electrode (anode or cathode), the counter electrode (cathode or anode) of the electrode, and a separator interposed between the electrodes is embedded in a battery case together with an electrolyte. It can be made of a structure.
이하, 상기 이차전지의 기타 성분에 대해서 설명한다.Hereinafter, other components of the secondary battery will be described.
상기 분리막은, 높은 이온 투과도와 기계적 강도를 가지는 절연성의 얇은 박막이 사용된다. 분리막의 기공 직경은 일반적으로 0.01 ~ 10 ㎛이고, 두께는 일반적으로 5 ~ 300 ㎛이다. 이러한 분리막으로는, 예를 들어, 내화학성 및 소수성의 폴리프로필렌 등의 올레핀계 폴리머; 유리섬유 또는 폴리에틸렌 등으로 만들어진 시트나 부직포 등이 사용된다. 전해질로서 폴리머 등의 고체 전해질이 사용되는 경우에는 고체 전해질이 분리막을 겸할 수도 있다.As the separator, an insulating thin film having high ion permeability and mechanical strength is used. The pore diameter of the separator is generally 0.01 to 10 μm, and the thickness is generally 5 to 300 μm. Examples of the separator include olefin-based polymers such as polypropylene, which are chemically resistant and hydrophobic; Sheets or non-woven fabrics made of glass fiber or polyethylene are used. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as a separator.
또는, 올리핀계 폴리머의 적어도 일면에 무기물 입자와 바인더의 혼합물이 코팅되어 있는 형태의 SRS 분리막(Safety Reinforced Separator)을 사용할 수 있다. 여기서, SRS 분리막의 구체적인 내용은, 본 출원인의 출원번호 10-2008-0005527가 참조로서 포함된다.Alternatively, an SRS separator in which a mixture of inorganic particles and a binder is coated on at least one surface of an oliphine-based polymer (Safety Reinforced Separator) may be used. Here, the specific content of the SRS separator, the applicant's application number 10-2008-0005527 is included as a reference.
상기 전해액은 리튬염 함유 비수 전해질일 수 있고, 상기 리튬염 함유 비수 전해질은 비수 전해액과 리튬염으로 이루어져 있으며, 상기 비수 전해액으로는 비수계 유기용매, 유기 고체 전해질, 무기 고체 전해질 등이 사용되지만 이들만으로 한정되는 것은 아니다.The electrolyte may be a lithium salt-containing non-aqueous electrolyte, and the lithium salt-containing non-aqueous electrolyte is composed of a non-aqueous electrolyte and a lithium salt, and the non-aqueous electrolyte includes a non-aqueous organic solvent, an organic solid electrolyte, and an inorganic solid electrolyte. It is not limited to.
상기 비수계 유기용매로는, 예를 들어, N-메틸-2-피롤리디논, 프로필렌 카르보네이트, 에틸렌 카르보네이트, 부틸렌 카르보네이트, 디메틸 카르보네이트, 디에틸 카르보네이트, 감마-부틸로 락톤, 1,2-디메톡시 에탄, 테트라히드록시푸란, 2-메틸 테트라하이드로푸란, 디메틸술폭시드, 1,3-디옥소런, 포름아미드, 디메틸포름아미드, 디옥소런, 아세토니트릴, 니트로메탄, 포름산 메틸, 초산메틸, 인산 트리에스테르, 트리메톡시 메탄, 디옥소런 유도체, 설포란, 메틸 설포란, 1,3-디메틸-2-이미다졸리디논, 프로필렌 카르보네이트 유도체, 테트라하이드로푸란 유도체, 에테르, 피로피온산 메틸, 프로피온산 에틸 등의 비양자성 유기용매가 사용될 수 있다.Examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and gamma. -Butyl lactone, 1,2-dimethoxy ethane, tetrahydroxyfuran, 2-methyl tetrahydrofuran, dimethylsulfoxide, 1,3-dioxorun, formamide, dimethylformamide, dioxorun, acetonitrile , Nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxy methane, dioxoren derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, Aprotic organic solvents such as tetrahydrofuran derivatives, ethers, methyl pyropionate, and ethyl propionate can be used.
상기 유기 고체 전해질로는, 예를 들어, 폴리에틸렌 유도체, 폴리에틸렌 옥사이드 유도체, 폴리프로필렌 옥사이드 유도체, 인산 에스테르 폴리머, 폴리 에지테이션 리신(agitation lysine), 폴리에스테르 설파이드, 폴리비닐 알코올, 폴리 불화 비닐리덴, 이온성 해리기를 포함하는 중합제 등이 사용될 수 있다.Examples of the organic solid electrolyte include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphoric acid ester polymers, poly agitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, and ions. A polymerization agent containing a sex dissociating group and the like can be used.
상기 무기 고체 전해질로는, 예를 들어, Li 3N, LiI, Li 5NI 2, Li 3N-LiI-LiOH, LiSiO 4, LiSiO 4-LiI-LiOH, Li 2SiS 3, Li 4SiO 4, Li 4SiO 4-LiI-LiOH, Li 3PO 4-Li 2S-SiS 2 등의 Li의 질화물, 할로겐화물, 황산염 등이 사용될 수 있다.As the inorganic solid electrolyte, for example, Li 3 N, LiI, Li 5 NI 2 , Li 3 N-LiI-LiOH, LiSiO 4 , LiSiO 4- LiI-LiOH, Li 2 SiS 3 , Li 4 SiO 4 , Li 4 nitrides such as Li 4 SiO 4- LiI-LiOH, Li 3 PO 4- Li 2 S-SiS 2 , halides, sulfates and the like can be used.
상기 리튬염은 상기 비수 전해질에 용해되기 좋은 물질로서, 예를 들어, LiCl, LiBr, LiI, LiClO 4, LiBF 4, LiB 10Cl 10, LiPF 6, LiCF 3SO 3, LiCF 3CO 2, LiAsF 6, LiSbF 6, LiAlCl 4, CH 3SO 3Li, (CF 3SO 2) 2NLi, 클로로 보란 리튬, 저급 지방족 카르본산 리튬, 4 페닐 붕산 리튬, 이미드 등이 사용될 수 있다.The lithium salt is a material that is soluble in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO 4 , LiBF 4 , LiB 10 Cl 10 , LiPF 6 , LiCF 3 SO 3 , LiCF 3 CO 2 , LiAsF 6 , LiSbF 6 , LiAlCl 4 , CH 3 SO 3 Li, (CF 3 SO 2 ) 2 NLi, lithium chloroborane, lower aliphatic lithium carboxylate, lithium 4-phenyl borate, imide, and the like.
또한, 비수 전해질에는 충방전 특성, 난연성 등의 개선을 목적으로, 예를 들어, 피리딘, 트리에틸포스파이트, 트리에탄올아민, 환상 에테르, 에틸렌 디아민, n-글라임(glyme), 헥사 인산 트리 아미드, 니트로벤젠 유도체, 유황, 퀴논 이민 염료, N-치환 옥사졸리디논, N,N-치환 이미다졸리딘, 에틸렌 글리콜 디알킬 에테르, 암모늄염, 피롤, 2-메톡시 에탄올, 삼염화 알루미늄 등이 첨가될 수도 있다. 경우에 따라서는, 불연성을 부여하기 위하여, 사염화탄소, 삼불화에틸렌 등의 할로겐 함유 용매를 더 포함시킬 수도 있고, 고온 보존 특성을 향상시키기 위하여 이산화탄산 가스를 더 포함시킬 수도 있으며, FEC(Fluoro-Ethylene Carbonate), PRS(Propene sultone) 등을 더 포함시킬 수 있다.In addition, non-aqueous electrolytes are used for the purpose of improving charge/discharge characteristics, flame retardancy, etc., for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphate triamide, Nitrobenzene derivatives, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxy ethanol, aluminum trichloride, etc. may be added. have. In some cases, in order to impart non-flammability, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride may be further included, or carbon dioxide gas may be further included to improve high temperature storage properties, and FEC (Fluoro-Ethylene) Carbonate), PRS (Propene sultone), etc. may be further included.
하나의 구체적인 예에서, LiPF 6, LiClO 4, LiBF 4, LiN(SO 2CF 3) 2 등의 리튬염을, 고유전성 용매인 EC 또는 PC의 환형 카보네이트와 저점도 용매인 DEC, DMC 또는 EMC의 선형 카보네이트의 혼합 용매에 첨가하여 리튬염 함유 비수 전해질을 제조할 수 있다.In one specific example, lithium salts such as LiPF 6 , LiClO 4 , LiBF 4 , and LiN(SO 2 CF 3 ) 2 are formed of a cyclic carbonate of EC or PC as a highly dielectric solvent and DEC, DMC or EMC of a low viscosity solvent. A lithium salt-containing nonaqueous electrolyte may be prepared by adding it to a mixed solvent of linear carbonate.
본 발명은 또한, 이러한 이차전지를 단위전지로서 포함하는 전지팩, 및 이러한 전지팩을 전원으로서 포함하는 디바이스를 제공한다.The present invention also provides a battery pack including such a secondary battery as a unit cell, and a device including such a battery pack as a power source.
상기 디바이스는, 예를 들어, 노트북 컴퓨터, 넷북, 태블릿 PC, 휴대폰, MP3, 웨어러블 전자기기, 파워 툴(power tool), 전기자동차(Electric Vehicle, EV), 하이브리드 전기자동차(Hybrid Electric Vehicle, HEV), 플러그-인 하이브리드 전기자동차(Plug-in Hybrid Electric Vehicle, PHEV), 전기 자전거(E-bike), 전기 스쿠터(E-scooter), 전기 골프 카트(electric golf cart), 또는 전력저장용 시스템일 수 있지만, 이들만으로 한정되지 않음은 물론이다.The device includes, for example, a notebook computer, a netbook, a tablet PC, a mobile phone, an MP3, wearable electronic devices, a power tool, an electric vehicle (EV), and a hybrid electric vehicle (HEV). It can be a plug-in hybrid electric vehicle (PHEV), electric bike (E-bike), electric scooter (E-scooter), electric golf cart, or power storage system. However, it goes without saying that these are not limited to these.
이러한 디바이스의 구조 및 제작 방법은 당업계에 공지되어 있으므로, 본 명세서에서는 그에 대한 자세한 설명을 생략한다.Since the structure and manufacturing method of such a device are known in the art, detailed description thereof is omitted in this specification.
이하에서는, 본 발명의 실시예를 참조하여 설명하지만, 이는 본 발명의 더욱 용이한 이해를 위한 것으로, 본 발명의 범주가 그것에 의해 한정되는 것은 아니다.In the following, description will be made with reference to examples of the present invention, but this is for easier understanding of the present invention, and the scope of the present invention is not limited thereto.
제조예 1Preparation Example 1
단량체로서 부타디엔(52 g)와 스티렌(46 g) 및 아크릴산(2 g)을, 유화제로서 소듐 라우릴 설페이트(1g), 중합개시제로서 포타슘 퍼설페이트(0.2g)가 포함되어 있는 물에 첨가하고, 이들을 혼합하여, 70℃에서 약 5 시간 동안 중합하여, 중합된 바인더의 입자 직경이 80 nm(동적 광 산란(DLS) 장비에 의한 측정 값) 인 고형분 40%의 바인더 A를 준비하였다.Butadiene (52 g) and styrene (46 g) and acrylic acid (2 g) as monomers were added to water containing sodium lauryl sulfate (1 g) as emulsifier and potassium persulfate (0.2 g) as polymerization initiator, These were mixed and polymerized at 70° C. for about 5 hours to prepare binder A having a solid content of 40% having a particle diameter of the polymerized binder of 80 nm (measured by dynamic light scattering (DLS) equipment).
제조예 2Preparation Example 2
상기 제조예 1에서 유화제를 0.5g으로 사용한 것을 제외하고는 동일한 반응 조건으로 중합하여, 중합된 바인더의 입자 직경이 200 nm(동적 광 산란(DLS) 장비에 의한 측정 값)인 고형분 40%의 바인더 B를 준비하였다.A binder having a solid content of 40% having a particle diameter of 200 nm (measured value by dynamic light scattering (DLS) equipment) by polymerizing under the same reaction conditions, except that the emulsifier in Preparation Example 1 was used as 0.5 g. B was prepared.
제조예 3Preparation Example 3
상기 제조예 1에서 유화제를 0.7g으로 사용한 것을 제외하고는 동일한 반응 조건으로 중합하여, 중합된 바인더의 입자 직경이 160 nm (동적 광 산란(DLS) 장비에 의한 측정 값)인 고형분 40%의 바인더 C를 준비하였다.In Example 1, polymerization was performed under the same reaction conditions, except that the emulsifier was used at 0.7 g, and the binder of 40% of solid content having a particle diameter of the polymerized binder of 160 nm (measured by dynamic light scattering (DLS) equipment) C was prepared.
제조예 4 Preparation Example 4
상기 제조예 1에서 유화제를 2.5g으로 사용한 것을 제외하고는 동일한 반응 조건으로 중합하여, 중합된 바인더의 입자 직경이 50 nm (동적 광 산란(DLS) 장비에 의한 측정 값)인 고형분 40%의 바인더 D를 준비하였다.A binder having a solid content of 40% having a particle diameter of 50 nm (measured by dynamic light scattering (DLS) equipment) by polymerization under the same reaction conditions, except that the emulsifier in Preparation Example 1 was used in 2.5 g. D was prepared.
실시예 1Example 1
도전재 분산액 제조Conductive material dispersion
1% 카복시메틸셀룰로오스(CMC) 용액(100g), 도전재(D50: 30 nm, Super-P)(1.5g), 제조예 1의 바인더 A(0.5g)을 상온에서 1시간 동안 교반하여 도전재 분산액을 제조하였다.1% carboxymethylcellulose (CMC) solution (100 g), conductive material (D50: 30 nm, Super-P) (1.5 g), and stirring the binder A (0.5 g) of Preparation Example 1 at room temperature for 1 hour, conductive material Dispersions were prepared.
활물질 슬러리 조성물 제조Preparation of active material slurry composition
상기에서 제조된 도전재 분산액에 인조흑연(D50: 18 ㎛, 95g), 증류수(20g), 제조예 2의 바인더 B(5.75g)을 추가하여 상온에서 1시간동안 교반하여 슬러리 조성물을 완성하였다.Artificial graphite (D50: 18 μm, 95 g), distilled water (20 g), and binder B (5.75 g) of Preparation Example 2 were added to the conductive material dispersion prepared above and stirred at room temperature for 1 hour to complete a slurry composition.
음극의 제조Preparation of cathode
상기 슬러리 조성물을 두께 20 ㎛의 구리 호일 위에 8.2 mg/cm 2의 로딩량으로 코팅하고 건조한 후, 80 ㎛ 두께로 압연하여 음극을 제조하였다. The slurry composition was coated on a copper foil having a thickness of 20 μm with a loading of 8.2 mg/cm 2 , dried, and rolled to a thickness of 80 μm to prepare a negative electrode.
실시예 2Example 2
도전재 분산액 제조Conductive material dispersion
1% 카복시메틸셀룰로오스(CMC) 용액(100g), 도전재(Super-P)(D50: 30 nm, 1.5g), 제조예 1의 바인더 A(1.0g)을 상온에서 1시간 동안 교반하여 도전재 분산액을 제조하였다.1% carboxymethylcellulose (CMC) solution (100 g), conductive material (Super-P) (D50: 30 nm, 1.5 g), the conductive material by stirring the binder A (1.0 g) of Preparation Example 1 at room temperature for 1 hour Dispersions were prepared.
활물질 슬러리 조성물 제조Preparation of active material slurry composition
상기에서 제조된 도전재 분산액에 인조흑연(D50: 18 ㎛, 95g), 증류수(20g), 제조예 2의 바인더 B(5.25g)을 추가하여 상온에서 1시간동안 교반하여 슬러리 조성물을 완성하였다.Artificial graphite (D50: 18 μm, 95 g), distilled water (20 g), and binder B (5.25 g) of Preparation Example 2 were added to the conductive material dispersion prepared above and stirred at room temperature for 1 hour to complete a slurry composition.
음극의 제조Preparation of cathode
상기 슬러리 조성물을 두께 20 ㎛의 구리 호일 위에 8.2 mg/cm 2의 로딩량으로 코팅하고 건조한 후, 80 ㎛ 두께로 압연하여 음극을 제조하였다. The slurry composition was coated on a copper foil having a thickness of 20 μm with a loading of 8.2 mg/cm 2 , dried, and rolled to a thickness of 80 μm to prepare a negative electrode.
실시예 3 Example 3
도전재 분산액 제조Conductive material dispersion
1% 카복시메틸셀룰로오스(CMC) 용액(100g), 도전재(Super-P)(D50: 30 nm, 1.5g), 제조예 4의 바인더 D(1.0g)을 상온에서 1시간 동안 교반하여 도전재 분산액을 제조하였다.1% carboxymethylcellulose (CMC) solution (100 g), conductive material (Super-P) (D50: 30 nm, 1.5 g), the conductive material by stirring the binder D (1.0 g) of Preparation Example 4 at room temperature for 1 hour Dispersions were prepared.
활물질 슬러리 조성물 제조Preparation of active material slurry composition
상기에서 제조된 도전재 분산액에 인조흑연(D50: 18 ㎛, 95g), 증류수(20g), 제조예 2의 바인더 B(5.25g)을 추가하여 상온에서 1시간동안 교반하여 슬러리 조성물을 완성하였다.Artificial graphite (D50: 18 μm, 95 g), distilled water (20 g), and binder B (5.25 g) of Preparation Example 2 were added to the conductive material dispersion prepared above and stirred at room temperature for 1 hour to complete a slurry composition.
음극의 제조Preparation of cathode
상기 슬러리 조성물을 두께 20 ㎛의 구리 호일 위에 8.2 mg/cm 2의 로딩량으로 코팅하고 건조한 후, 80 ㎛ 두께로 압연하여 음극을 제조하였다. The slurry composition was coated on a copper foil having a thickness of 20 μm with a loading of 8.2 mg/cm 2 , dried, and rolled to a thickness of 80 μm to prepare a negative electrode.
실시예 4 Example 4
도전재 분산액 제조Conductive material dispersion
1% 카복시메틸셀룰로오스(CMC) 용액(100g), 도전재(D50: 30 nm, Super-P)(1.5g), 제조예 4의 바인더 D(1.0g)을 상온에서 1시간 동안 교반하여 도전재 분산액을 제조하였다.1% carboxymethylcellulose (CMC) solution (100 g), conductive material (D50: 30 nm, Super-P) (1.5 g), and stirring the binder D (1.0 g) of Preparation Example 4 at room temperature for 1 hour to conduct the conductive material Dispersions were prepared.
활물질 슬러리 조성물 제조Preparation of active material slurry composition
상기에서 제조된 도전재 분산액에 인조흑연(D50: 18 ㎛, 95g), 증류수(20g), 제조예 3의 바인더 C(5.25g)을 추가하여 상온에서 1시간동안 교반하여 슬러리 조성물을 완성하였다.Artificial graphite (D50: 18 μm, 95 g), distilled water (20 g), and binder C (5.25 g) of Preparation Example 3 were added to the conductive material dispersion prepared above and stirred at room temperature for 1 hour to complete a slurry composition.
음극의 제조Preparation of cathode
상기 슬러리 조성물을 두께 20 ㎛의 구리 호일 위에 8.2 mg/cm 2의 로딩량으로 코팅하고 건조한 후, 80 ㎛ 두께로 압연하여 음극을 제조하였다. The slurry composition was coated on a copper foil having a thickness of 20 μm with a loading of 8.2 mg/cm 2 , dried, and rolled to a thickness of 80 μm to prepare a negative electrode.
비교예 1Comparative Example 1
공정 순서는 실시예 1과 동일하게 하되, 바인더 A 를 사용하지 않고 도전재 분산액을 제조한 뒤, 활물질 슬러리 조성물, 및 음극을 제조하였다.The process procedure was the same as in Example 1, but after preparing a conductive material dispersion without using binder A, an active material slurry composition and a negative electrode were prepared.
도전재 분산액 제조Conductive material dispersion
구체적으로, 1% 카복시메틸셀룰로오스(CMC) 용액(100g), 도전재(D50: 30 nm, Super-P)(1.5g)를 상온에서 1시간 동안 교반하여 도전재 분산액을 제조하였다.Specifically, a 1% carboxymethylcellulose (CMC) solution (100 g) and a conductive material (D50: 30 nm, Super-P) (1.5 g) were stirred at room temperature for 1 hour to prepare a conductive material dispersion.
활물질 슬러리 조성물 제조Preparation of active material slurry composition
상기에서 제조된 도전재 분산액에 인조흑연(D50: 18 ㎛, 95g), 증류수(20g), 제조예 2의 바인더 B(6.25g)을 추가하여 상온에서 1시간동안 교반하여 슬러리 조성물을 완성하였다.Artificial graphite (D50: 18 μm, 95 g), distilled water (20 g), and binder B (6.25 g) of Preparation Example 2 were added to the conductive material dispersion prepared above and stirred at room temperature for 1 hour to complete a slurry composition.
음극의 제조Preparation of cathode
상기 슬러리 조성물을 두께 20 ㎛의 구리 호일 위에 8.2 mg/cm 2의 로딩량으로 코팅하고 건조한 후, 80 ㎛ 두께로 압연하여 음극을 제조하였다. The slurry composition was coated on a copper foil having a thickness of 20 μm with a loading of 8.2 mg/cm 2 , dried, and rolled to a thickness of 80 μm to prepare a negative electrode.
비교예 2Comparative Example 2
공정 순서는 실시예 1과 동일하게 하되, 바인더 A 를 다음과 같이 교체하여 도전재 분산액을 제조하되, 이처럼 제조된 도전재 분산액에 바인더 A 와 B를 혼합하여 활물질 슬러리 조성물을 제조하고, 및 음극을 제조하였다.The process sequence is the same as in Example 1, but the binder A is replaced as follows to prepare a conductive material dispersion, but the binder A and B are mixed with the prepared conductive material dispersion to prepare an active material slurry composition, and a cathode is prepared. It was prepared.
상기 제조예 1에서 제조된 바인더 A(0.5g)와, 제조예 2에서 제조된 바인더 B(5.75g)를 혼합하여 혼합 바인더를 준비하였다. The binder A (0.5 g) prepared in Preparation Example 1 and binder B (5.75 g) prepared in Preparation Example 2 were mixed to prepare a mixed binder.
도전재 분산액 제조Conductive material dispersion
구체적으로, 1% CMC 용액(100g), 도전재(1.5g)을 상온에서 1시간동안 교반하여 도전재 분산액을 제조하였다.Specifically, a 1% CMC solution (100 g) and a conductive material (1.5 g) were stirred at room temperature for 1 hour to prepare a conductive material dispersion.
활물질 슬러리 조성물 제조Preparation of active material slurry composition
상기에서 제조된 도전재 분산액에 인조흑연(D50: 18 ㎛, 95g), 증류수(20g), 상기 혼합 바인더 A+B(6.25g)을 추가하여 상온에서 1시간동안 교반하여 슬러리 조성물을 완성하였다.Artificial graphite (D50: 18 μm, 95 g), distilled water (20 g), and the mixed binder A+B (6.25 g) were added to the conductive material dispersion prepared above, and stirred at room temperature for 1 hour to complete a slurry composition.
음극의 제조Preparation of cathode
상기 슬러리 조성물을 두께 20 ㎛의 구리 호일 위에 8.2 mg/cm 2의 로딩량으로 코팅하고 건조한 후, 80 ㎛ 두께로 압연하여 음극을 제조하였다. The slurry composition was coated on a copper foil having a thickness of 20 μm with a loading of 8.2 mg/cm 2 , dried, and rolled to a thickness of 80 μm to prepare a negative electrode.
비교예 3Comparative Example 3
공정 순서는 실시예 1과 동일하게 하되, 바인더 A 를 다음과 같이 교체하여 분산액을 제조한 뒤, 활물질 슬러리 조성물, 및 음극을 제조하였다.The process sequence was the same as in Example 1, but after replacing the binder A as follows to prepare a dispersion, an active material slurry composition and a negative electrode were prepared.
구체적으로, 바인더 A 대신 바인더 C(0.5g)을 사용하여 도전재 분산액을 제조하였다.Specifically, instead of binder A, a binder C (0.5 g) was used to prepare a conductive material dispersion.
이 외 사항은 실시예 1과 동일하게 하여 활물질 슬러리 조성물, 및 음극을 제조하였다.The other matters were the same as in Example 1 to prepare an active material slurry composition and a negative electrode.
비교예 4 Comparative Example 4
별도로 도전재 분산액 제조하지 않고, 도전재, 활물질, 바인더 A 와 B를 일괄 혼합하여 활물질 슬러리 조성물을 제조하고, 및 음극을 제조하였다.A conductive material dispersion composition was not prepared separately, and a conductive material, an active material, and binders A and B were mixed together to prepare an active material slurry composition, and a negative electrode was prepared.
활물질 슬러리 조성물 제조Preparation of active material slurry composition
구체적으로, 상기 제조예 1에서 제조된 바인더 A(0.5g)와, 제조예 2에서 제조된 바인더 B(5.75g)를 혼합하여 혼합 바인더를 준비하였다. Specifically, the binder A (0.5 g) prepared in Preparation Example 1 and the binder B (5.75 g) prepared in Preparation Example 2 were mixed to prepare a mixed binder.
1% CMC 용액(100g), 도전재(1.5g), 인조흑연(D50: 18 ㎛, 95g), 증류수(20g), 및 상기 혼합 바인더 A+B(6.25g)을 일괄 혼합하여 상온에서 1시간동안 교반하여 슬러리 조성물을 완성하였다.1% CMC solution (100 g), conductive material (1.5 g), artificial graphite (D50: 18 μm, 95 g), distilled water (20 g), and the mixed binder A+B (6.25 g) were mixed together for 1 hour at room temperature. Stir for a while to complete the slurry composition.
음극의 제조Preparation of cathode
상기 슬러리 조성물을 두께 20 ㎛의 구리 호일 위에 8.2 mg/cm 2의 로딩량으로 코팅하고 건조한 후, 80 ㎛ 두께로 압연하여 음극을 제조하였다. The slurry composition was coated on a copper foil having a thickness of 20 μm with a loading of 8.2 mg/cm 2 , dried, and rolled to a thickness of 80 μm to prepare a negative electrode.
실험예 1 (음극 접착력)Experimental Example 1 (cathode adhesion)
(1) 박리 시험(1) Peel test
상기 실시예들 및 비교예들에서 제조된 음극을 60mm(길이)x 25mm(폭)으로 절단하여 테스트용 시편을 수득하였다. The negative electrode prepared in the above Examples and Comparative Examples was cut into 60 mm (length) x 25 mm (width) to obtain test specimens.
슬라이드 글라스에 양면 테이프를 붙이고 그 위에 상기 테스트용 시편을 올려 2 kg 롤러로 3회 왕복하여 접착시킨 후, UTM(TA 社) 기기를 이용하여 5 mm/sec으로 당겨 슬라이드 글라스로부터 박리되는 힘을 측정하였다. 이때, 슬라이드 글라스와 전극의 측정각도는 180˚였다.After attaching the double-sided tape to the slide glass and placing the test specimen on it, reciprocating and bonding with a 2 kg roller three times, measure the force peeled from the slide glass by pulling at 5 mm/sec using a UTM (TA company) device. Did. At this time, the measurement angle of the slide glass and the electrode was 180 degrees.
그 결과를 하기 표 1에 나타내었다.The results are shown in Table 1 below.
(2) 압연 전후의 압연롤 표면 오염 정도 평가(2) Evaluation of the degree of contamination of the roll surface before and after rolling
에탄올로 세척 후 10분 이상 상온에서 건조된 SUS 재질의 압연롤을 사용하여 상기 각 음극 4m를 압연한 뒤, 휴대용 색차계 (코니카미놀타, Potable Spectrophotometer)로 압연롤의 색도 변화를 측정하여 표면 오염 정도를 확인하였다.After washing with ethanol, after rolling each cathode 4 m using a rolling roll made of SUS material dried at room temperature for at least 10 minutes, the color contamination of the rolling roll was measured with a portable color difference meter (Konica Minolta, Potable Spectrophotometer) to measure the degree of surface contamination. Was confirmed.
그 결과를 하기 표 1에 나타내었다.The results are shown in Table 1 below.
*깨끗한 SUS 재질의 압연롤은 그 색차계 수치가 80이며, 오염될 수록 수치가 낮아진다.*A clean SUS rolled roll has a color difference value of 80, and as it gets contaminated, the value decreases.
접착력(gf/cm)Adhesion (gf/cm) 4m 압연후 압연롤 색차계 수치Rolled roll color difference after 4m rolling
실시예 1Example 1 3636 7979
실시예 2Example 2 3434 7979
실시예 3Example 3 3333 7979
실시예 4Example 4 3232 7979
비교예 1Comparative Example 1 3232 7070
비교예 2Comparative Example 2 3030 7474
비교예 3Comparative Example 3 3232 7575
비교예 4Comparative Example 4 2727 7979
상기 표 1에 따르면 본 발명에 따라, 제조한 전극의 경우, 높은 접착력과 압연 롤 오염 정도가 작은 반면에, 그렇지 않은 경우, 접착력이 저하되고, 이에 따라 압연 롤 오염도 상당 부분 나타나는 것을 확인할 수 있다.According to the above Table 1, it can be seen that, according to the present invention, in the case of the manufactured electrode, the high adhesive strength and the degree of contamination of the rolling roll are small, but otherwise, the adhesive strength is lowered, and accordingly, the contamination of the rolling roll appears to a considerable extent.
실험예 2 (음극 내 각 바인더의 분포 형태 평가) Experimental Example 2 (Evaluation of the distribution of each binder in the cathode)
상기 실시예 1과 비교예 2의 각 음극을 OsO 4로 처리함으로써, 각 음극에 포함된 바인더가 OsO 4에 의해 염색되도록 하였다. 이후, 각 음극 표면을 SEM으로 관찰하였다.By treating each negative electrode of Example 1 and Comparative Example 2 with OsO 4 , the binder contained in each negative electrode was stained with OsO 4 . Thereafter, each cathode surface was observed by SEM.
앞서 언급한 바와 같이, 음극 표면(즉, 음극 합제층의 단면) 에서 확인되는 개별 입자의 입경으로부터 평균을 구하여, 그 평균 입경을 기준으로 각 바인더의 입자 직경을 나타낼 수 있다.As mentioned above, an average can be obtained from the particle diameters of the individual particles identified on the negative electrode surface (ie, the cross-section of the negative electrode mixture layer) to represent the particle diameter of each binder based on the average particle diameter.
도 1, 3, 및 5는, 배율을 달리 하여 실시예 1의 음극 표면을 촬영한 SEM 이미지들이다. 또한, 도 2, 4, 및 6은, 배율을 달리 하여 비교예 2의 음극 표면을 촬영한 SEM 이미지들이다.1, 3, and 5 are SEM images of the cathode surface of Example 1 at different magnifications. 2, 4, and 6 are SEM images of the cathode surface of Comparative Example 2 at different magnifications.
도 1, 3, 및 5에 따르면, 평균 입자 직경이 100 ㎚ 이하로 작은 바인더가 도전재 주변에 주로 분포하고 있는 것으로 확인된다. 그에 반면, 도 2, 4, 및 6에 따르면, 평균 입자 직경이 200 ㎚로 큰 바인더가 도전재 주변에 주로 분포하고 있는 것으로 확인된다.According to FIGS. 1, 3, and 5, it is confirmed that a binder having a small average particle diameter of 100 nm or less is mainly distributed around the conductive material. On the other hand, according to FIGS. 2, 4, and 6, it is confirmed that a binder having a large average particle diameter of 200 nm is mainly distributed around the conductive material.
이를 통해, 서로 다른 입경을 가지는 2종의 바인더를 배합하는 비율이 동일하더라도, 활물질 슬러리 제조 공정에 있어서 각 바인더를 공급하는 시기에 따라, 최종 음극 내 바인더의 분포 형태가 달라질 수 있음을 알 수 있다.Through this, it can be seen that even if the proportions of the two binders having different particle diameters are the same, the distribution form of the binder in the final cathode may vary depending on the timing of supplying each binder in the active material slurry manufacturing process. .
구체적으로, 실시예 1과 같이, 상대적으로 작은 입경의 바인더는 도전재와 먼저 혼합하여 도전재 분산액을 제조한 뒤, 상대적으로 큰 입경의 바인더와 활물질을 상기 도전재 분산액에 투입하고 혼합함으로써 활물질 슬러리 조성물을 제조하는 경우, 상대적으로 입자 직경이 작은 바인더가 도전재 주위에 분포된 음극이 최종 수득될 수 있다.Specifically, as in Example 1, a relatively small particle size binder is first mixed with a conductive material to prepare a conductive material dispersion, and then a relatively large particle size binder and an active material are introduced into the conductive material dispersion and mixed to form an active material slurry. When preparing the composition, a negative electrode in which a binder having a relatively small particle diameter is distributed around the conductive material can be finally obtained.
여기서, 전극 합제층 구성 성분의 입자 직경을 고려하면, 서로 다른 상기 전극 활물질 입자 사이에 분포된, 복수의 도전재 입자가 분포될 것임은 자명하다. 이에, 서로 다른 상기 도전재 입자 사이, 그리고 상기 도전재 입자 및 상기 집전체 사이에 각각, 상대적으로 입자 직경이 작은 바인더가 분포되고; 서로 다른 상기 전극 활물질 입자 사이, 상기 전극 활물질 입자 및 상기 도전재 입자 사이, 그리고 상기 전극 활물질 입자 및 상기 집전체 사이에 각각, 상대적으로 입자 직경이 큰 분포된 것으로 볼 수 있다.Here, considering the particle diameters of the components of the electrode mixture layer, it is apparent that a plurality of conductive material particles, which are distributed between the different electrode active material particles, will be distributed. Thus, a binder having a relatively small particle diameter is distributed between the different conductive material particles and between the conductive material particles and the current collector, respectively; It can be seen that the particle diameters of the electrode active material particles are different from each other, between the electrode active material particles and the conductive material particles, and between the electrode active material particles and the current collector.
그에 반면, 비교예 2과 같이, 바인더를 포함하지 않는 도전재 분산액을 제조한 뒤, 서로 다른 입경을 가지는 2종의 바인더 및 활물질을 일괄하여 상기 도전재 분산액에 투입하고 혼합함으로써 활물질 슬러리 조성물을 제조하는 경우, 2종의 바인더가 그 입경에 무관하게 무질서하게(random) 분포된 음극이 최종 수득될 수 있다.On the other hand, as in Comparative Example 2, after preparing a dispersion of a conductive material that does not contain a binder, two types of binders and active materials having different particle diameters are collectively introduced into the conductive material dispersion and mixed to prepare an active material slurry composition. In the case of, a negative electrode in which two kinds of binders are randomly distributed irrespective of their particle size can be finally obtained.
실험예 3 (전지의 방전 특성, 및 음극 팽창률 평가) Experimental Example 3 (evaluation of discharge characteristics of batteries and expansion coefficient of cathode)
상기 실시예들과 비교예들에서 제작된 음극을 각각 작동 전극으로 사용하고, 150 ㎛ 두께의 리튬 메탈 시트를 기준 전극으로 사용하고, 상기 작동 전극과 상기 기준 전극 사이에 폴리에틸렌 세퍼레이터(두께: 20㎛, 기공도: 40%)를 삽입하여 전지 용기에 투입하고, 전해액을 주입한 다음, 이 외의 사항은 통상적인 제조방법에 따라 2032 하프셀(half-cell)의 형태로 리튬 이차 전지를 제작하였다.The negative electrode produced in the above Examples and Comparative Examples was used as a working electrode, a lithium metal sheet having a thickness of 150 μm was used as a reference electrode, and a polyethylene separator (thickness: 20 μm) between the working electrode and the reference electrode. , Porosity: 40%) was inserted into the battery container, the electrolyte solution was injected, and then the other matters were prepared in a lithium secondary battery in the form of a 2032 half-cell according to a conventional manufacturing method.
상기 전해액으로는, 에틸렌 카보네이트(ethylene carbonate, EC), 프로필렌 카르보네이트(propylene carbonate, PC)와 디에틸 카보네이트(diethyl carbonate, DEC)의 혼합 용매(EC:PC:DEC=3:2:5의 무게비)에 LiPF 6가 1.3M의 농도가 되도록 용해시키고, 전해액 총 중량에 대해 10 중량%의 첨가제 플루오로에틸렌 카보네이트(fluoroethylene carbonate, FEC)를 첨가시킨 것을 사용하였다.As the electrolyte, a mixed solvent of ethylene carbonate (EC), propylene carbonate (PC) and diethyl carbonate (DEC) (EC:PC:DEC=3:2:5) LiPF 6 was dissolved in a concentration of 1.3 M in a weight ratio), and 10 wt% of additive fluoroethylene carbonate (FEC) was added to the total weight of the electrolyte.
각각의 리튬 이차 전지를 다음과 같이 평가한 뒤, 그 평가 결과를 하기 표 2에 나타내었다:After evaluating each lithium secondary battery as follows, the evaluation results are shown in Table 2 below:
전지의 방전 특성: 25℃의 항온 챔버 내에서, 0.1 C로 1.5V에서 5mV 에 이르기까지 CC/CV 모드(mode)로 상기 각 리튬 이온 반쪽 전지를 3회 방전한 뒤, CC모드로 0.1 C로 1.5V까지 충전하는 사이클을 3회 반복하되, 충전과 방전 사이에는 20분 동안의 휴지 기간을 두었다. 이에 따라 충전된 전지를 1C CC/CV 모드(mode)로 최종 방전한 다음, 하기 식에 따라 전체 방전 용량 대비 CC 구간의 방전 용량을 백분율로 변환하였다. Discharge characteristics of the battery : in a constant temperature chamber at 25°C, after discharging each lithium ion half battery three times in CC/CV mode from 1.5V to 5mV at 0.1C to 0.1C, and then to 0.1C in CC mode The cycle of charging up to 1.5V was repeated three times, but there was a rest period of 20 minutes between charging and discharging. Accordingly, the charged battery was finally discharged in 1C CC/CV mode, and the discharge capacity of the CC section compared to the total discharge capacity was converted to a percentage according to the following equation.
[전지의 방전 특성] =100%*{(1.0C CC)})/{(1.0C CC/CV)} [Battery Discharge Characteristics] =100%*{(1.0C CC)})/{(1.0C CC/CV)}
음극 팽창률: 상기 방전 특성 평가 후, 각 전지를 분해하여 음극을 회수하였다. 각 회수된 음극을 DMC(디메틸 카보네이트) 용매로 세척하고 상온에서 10 분 동안 자연 건조시킨 뒤, 두께를 측정하였다. 이에 따라 측정된 두께를 다음과 같은 식에 대입하여, 음극의 팽창률을 계산하였다. Cathodic expansion rate : After evaluating the discharge characteristics, each cell was disassembled to recover the negative electrode. Each recovered negative electrode was washed with DMC (dimethyl carbonate) solvent, naturally dried for 10 minutes at room temperature, and then the thickness was measured. The measured thickness was substituted into the following equation to calculate the expansion coefficient of the negative electrode.
[음극 팽창률]= 100%*{(전지의 방전 음극 두께)-(압연 음극 두께)}/{(압연 음극 두께)-(구리 호일 두께)}[Cathode expansion rate] = 100%*{(thickness of discharge cathode of battery)-(thickness of rolled cathode)}/{(thickness of rolled cathode)-(thickness of copper foil)}
여기서, 각 용어의 정의는 다음과 같다:Here, the definition of each term is as follows:
전지의 방전 음극 두께 = 리튬 이온 전지의 1회 방전 시 음극 두께Discharge negative electrode thickness of battery = negative electrode thickness for one discharge of lithium ion battery
압연 음극 두께 = 리튬 이온 전지의 조립 전 음극의 두께Rolled negative electrode thickness = thickness of negative electrode before assembly of lithium ion battery
구리 호일의 두께 = 압연 전극 중 음극 집전체의 두께Thickness of copper foil = thickness of cathode current collector among rolled electrodes
100%*{((1.0C CC)})/{(1.0C CC/CV)100%*{((1.0C CC)})/{(1.0C CC/CV) 음극 팽창률Cathodic expansion rate
실시예 1Example 1 40 %40% 21 %21%
실시예 2Example 2 42 %42% 20 %20%
실시예 3Example 3 43 %43% 20 %20%
실시예 4Example 4 44 %44% 20 %20%
비교예 1Comparative Example 1 36 %36% 23 %23%
비교예 2Comparative Example 2 39 %39% 23 %23%
비교예 3Comparative Example 3 38 %38% 22 %22%
비교예 4Comparative Example 4 40 %40% 22 %22%
앞서 살펴본 표 1의 결과와 상기 표 2의 결과를 종합하여 보면, 실시예는 비교예 대비 음극 접착력, 압연 시 오염 정도, 음극 팽창률, 그리고 레이트(rate) 특성에서 우수한 성능을 동시에 확보하는 데 유리함을 알 수 있다. Comparing the results of Table 1 and the results of Table 2, the examples are advantageous in securing excellent performance simultaneously in the negative electrode adhesion, the degree of contamination during rolling, the negative electrode expansion rate, and rate characteristics compared to the comparative example. Able to know.
이상 본 발명의 실시예를 참조하여 설명하였지만, 본 발명이 속한 분야에서 통상의 지식을 가진 자라면 상기 내용을 바탕으로 본 발명의 범주 내에서 다양한 응용 및 변형을 행하는 것이 가능할 것이다.Although described above with reference to embodiments of the present invention, those skilled in the art to which the present invention pertains will be able to perform various applications and modifications within the scope of the present invention based on the above.

Claims (15)

  1. 집전체의 적어도 일면에, At least on one side of the current collector,
    복수의 전극 활물질 입자; A plurality of electrode active material particles;
    서로 다른 상기 전극 활물질 입자 사이에 분포된, 복수의 도전재 입자;A plurality of conductive material particles distributed between the different electrode active material particles;
    서로 다른 상기 도전재 입자 사이, 그리고 상기 도전재 입자 및 상기 집전체 사이에 각각 분포된, 입자 직경이 100 nm 이하인 제1 바인더;A first binder having a particle diameter of 100 nm or less, which are respectively distributed between the different conductive material particles and between the conductive material particles and the current collector;
    서로 다른 상기 전극 활물질 입자 사이, 상기 전극 활물질 입자 및 상기 도전재 입자 사이, 그리고 상기 전극 활물질 입자 및 상기 집전체 사이에 각각 분포된, 입자 직경이 120 nm 이상인 제2 바인더;A second binder having a particle diameter of 120 nm or more distributed between the different electrode active material particles, between the electrode active material particles and the conductive material particles, and between the electrode active material particles and the current collector;
    를 포함하는 전극 합제층이 형성된 것인, The electrode mixture layer containing is formed,
    이차전지용 전극.Electrode for secondary battery.
  2. 제1항에 있어서, According to claim 1,
    상기 도전재 입자는,The conductive material particles,
    D50 입경이 10 nm 내지 2㎛인 것인,D50 particle size is 10 nm to 2㎛,
    이차전지용 전극.Electrode for secondary battery.
  3. 제1항에 있어서, According to claim 1,
    상기 제 1 바인더는,The first binder,
    입자의 평균 직경이 40 nm 내지 100 nm인, The particles have an average diameter of 40 nm to 100 nm,
    이차전지용 전극.Electrode for secondary battery.
  4. 제1항에 있어서, According to claim 1,
    상기 전극 활물질 입자는,The electrode active material particles,
    D50 입경이 500 nm 내지 50 ㎛인 것인,D50 having a particle diameter of 500 nm to 50 μm,
    이차전지용 전극.Electrode for secondary battery.
  5. 제1항에 있어서, According to claim 1,
    상기 제 2 바인더는,The second binder,
    입자의 평균 직경이 150 nm 내지 600 nm인, The particles have an average diameter of 150 nm to 600 nm,
    이차전지용 전극.Electrode for secondary battery.
  6. 제1항에 있어서,According to claim 1,
    상기 도전재 입자 표면에서부터 입자 표면으로부터 수직 방향으로 1 ㎛까지의 거리 내에, Within a distance from the particle surface of the conductive material to 1 μm in the vertical direction from the particle surface,
    상기 제1 바인더의 총량(100 중량%) 중 60 중량% 이상이 분포하는 것인,More than 60% by weight of the total amount (100% by weight) of the first binder is distributed,
    이차전지용 전극.Electrode for secondary battery.
  7. 제1항에 있어서,According to claim 1,
    상기 전극 활물질 입자 표면에서부터 입자 표면으로부터 수직 방향으로 1 ㎛까지의 거리 내에, Within a distance from the electrode active material particle surface to the particle surface in a vertical direction to 1 μm,
    상기 제 2 바인더의 총량(100 중량%) 중, 60 중량% 이상이 상기 전극 활물질 입자의 표면부에 분포하는 것인,Of the total amount (100% by weight) of the second binder, 60% by weight or more is distributed over the surface portion of the electrode active material particles,
    이차전지용 전극.Electrode for secondary battery.
  8. 제1항에 있어서, According to claim 1,
    상기 제1 바인더 및 상기 제2 바인더는 모두, Both the first binder and the second binder,
    스티렌-부타디엔- 아크릴계 중합체인,Styrene-butadiene-acrylic polymer,
    이차전지용 전극.Electrode for secondary battery.
  9. 제1항에 있어서,According to claim 1,
    상기 제1 바인더 및 상기 제2 바인더의 중량비(제1 바인더:제2 바인더)는,The weight ratio of the first binder and the second binder (first binder:second binder) is
    1:2 내지 1:20인 것인,1:2 to 1:20,
    이차전지용 전극.Electrode for secondary battery.
  10. 제 1 항에 있어서, According to claim 1,
    상기 전극은 음극인 것인,The electrode is a cathode,
    이차전지용 전극.Electrode for secondary battery.
  11. 입자 직경이 100 nm 이하인 제 1 바인더 및 도전재를 혼합하여, 도전재 분산액을 제조하는 단계;Mixing a first binder and a conductive material having a particle diameter of 100 nm or less to prepare a conductive material dispersion;
    상기 도전재 분산액; 입자 직경이 120 nm 이상인 제 2 바인더 및 전극 활물질을 혼합하여, 활물질 슬러리 조성물을 제조하는 단계;The conductive material dispersion; Mixing a second binder and an electrode active material having a particle diameter of 120 nm or more to prepare an active material slurry composition;
    집전체의 적어도 일면에 상기 활물질 슬러리 조성물을 도포하고, 건조 및 압연하여, 전극을 수득하는 단계를 포함하는, 이차전지용 전극의 제조방법.A method of manufacturing an electrode for a secondary battery, comprising applying the active material slurry composition to at least one surface of a current collector, drying and rolling, to obtain an electrode.
  12. 제11항에 있어서,The method of claim 11,
    상기 제 1 바인더 및 상기 제 2 바인더는, 각각 독립적으로, The first binder and the second binder are each independently,
    유화제, 중합 개시제, 및 용매의 존재 하에, 단량체를 중합시키는 단계를 포함하여 제조된 것인,Prepared in the presence of an emulsifier, polymerization initiator, and solvent, comprising polymerizing the monomer,
    이차전지용 전극의 제조방법.Method for manufacturing a secondary battery electrode.
  13. 제12항에 있어서,The method of claim 12,
    상기 제 2 바인더에 대비하여, 상기 제 1 바인더의 제조 시,In preparation for the second binder, when manufacturing the first binder,
    상기 단량체, 유화제, 중합 개시제, 및 용매의 총량 중 유화제의 함량을 더 높이는 것인, To increase the content of the emulsifier in the total amount of the monomer, emulsifier, polymerization initiator, and solvent,
    이차전지용 전극의 제조방법.Method for manufacturing a secondary battery electrode.
  14. 제12항에 있어서,The method of claim 12,
    상기 단량체는, The monomer,
    부타디엔; 스티렌; 및 아크릴산을 포함하는 것인,butadiene; Styrene; And acrylic acid,
    이차전지용 전극의 제조방법.Method for manufacturing a secondary battery electrode.
  15. 제1항에 따른 전극을 포함하는 이차전지.A secondary battery comprising the electrode according to claim 1.
PCT/KR2020/000801 2019-01-17 2020-01-16 Electrode for rechargeable battery, manufacturing method of same, and rechargeable battery including same WO2020149665A1 (en)

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EP20740821.2A EP3780190A4 (en) 2019-01-17 2020-01-16 Electrode for rechargeable battery, manufacturing method of same, and rechargeable battery including same
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