WO2019050203A2 - Anode for lithium secondary battery, and lithium secondary battery comprising same - Google Patents

Anode for lithium secondary battery, and lithium secondary battery comprising same Download PDF

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Publication number
WO2019050203A2
WO2019050203A2 PCT/KR2018/009882 KR2018009882W WO2019050203A2 WO 2019050203 A2 WO2019050203 A2 WO 2019050203A2 KR 2018009882 W KR2018009882 W KR 2018009882W WO 2019050203 A2 WO2019050203 A2 WO 2019050203A2
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WIPO (PCT)
Prior art keywords
active material
negative electrode
weight
mixture
electrode active
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PCT/KR2018/009882
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French (fr)
Korean (ko)
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WO2019050203A3 (en
Inventor
이주성
이희원
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주식회사 엘지화학
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Priority claimed from KR1020180038717A external-priority patent/KR102434067B1/en
Application filed by 주식회사 엘지화학 filed Critical 주식회사 엘지화학
Priority to US16/634,712 priority Critical patent/US20200212438A1/en
Priority to CN201880047349.7A priority patent/CN110892560B/en
Priority to EP18854898.6A priority patent/EP3644412B1/en
Publication of WO2019050203A2 publication Critical patent/WO2019050203A2/en
Publication of WO2019050203A3 publication Critical patent/WO2019050203A3/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
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a negative electrode for a high capacity lithium secondary battery and a lithium secondary battery comprising the same, and more particularly, to a high capacity negative electrode having a negative electrode active material layer using silicon nanoparticles and having improved stability, and a lithium secondary battery comprising the same.
  • the negative electrode of the conventional lithium secondary battery is mainly composed of a carbonaceous compound which can reversibly intercalate and desorb lithium ions while maintaining the structural and electrical properties of the negative electrode active material.
  • the chemical potential of the carbon-based compound in the insertion and desorption of lithium ions is similar to that of metallic lithium, so that even at a slight high charging current, lithium precipitation occurs due to overpotential, As the number of repetitions increases, the capacity is accelerated, resulting in a decrease in capacity and a short circuit due to dendrites. Thus, the safety can be greatly influenced.
  • the amount of lithium exceeding the amount of lithium If the battery is charged, the temperature rises, causing an exothermic reaction, which may cause ignition and explosion of the battery. .
  • the theoretical capacity is about 10 times higher than that of a conventional carbon-based anode material.
  • the swelling phenomenon may occur and the volume of silicon may increase sharply.
  • Such a swelling phenomenon may cause structural stress on the negative electrode, which may result in damage to the battery.
  • the negative electrode material of a pouch-type lithium secondary battery which is greatly affected by stability as the volume expands, There is a problem that it is difficult.
  • Japanese Patent Application Laid-Open No. 10-2016-0039982 discloses a composition for forming an anode comprising a silicon oxide, wherein the composition for forming an anode is not limited to the swelling phenomenon in which silicon oxide swells up, When the conductive path is broken due to expansion, a binder having a high binding force is used in order to compensate for this.
  • the silicon oxide is generally a micro-sized compound, there is a problem in safety when mass-producing an anode material using the above composition for a lithium secondary battery.
  • the silicon oxide has a relatively lower theoretical capacity than silicon, and even when the same mass is used, there is a problem that the battery capacity is low and the efficiency of the battery is low.
  • an object of the present invention is to provide a negative electrode for a lithium secondary battery and a lithium secondary battery including the negative electrode.
  • the present invention is a negative electrode for a lithium secondary battery comprising a negative electrode collector and a negative electrode active material layer disposed on the negative electrode collector, wherein the negative electrode active material layer has an average particle diameter (D 50 ) To 50 ⁇ ⁇ , silicon nanoparticles having an average particle diameter (D50) of 70 nm to 300 nm, a first conductive material; And a negative electrode for a lithium secondary battery comprising two or more kinds of cellulose-based compounds having different weight average molecular weights.
  • D 50 average particle diameter
  • D50 average particle diameter
  • the present invention provides a process for producing a silicon nanocrystal by mixing silicon nanoparticles having an average particle diameter (D 50 ) of 70 nm to 300 nm, a first conductive material, a first cellulose compound having a weight average molecular weight of 10,000 to 500,000, Forming a first mixture; Forming a second mixture by mixing a graphite-based active material having an average particle diameter (D 50 ) of 5 ⁇ to 50 ⁇ , a second cellulosic compound having a weight average molecular weight of 1,000,000 to 2,500,000, and a solvent; Mixing the first mixture and the second mixture to form a negative electrode active material slurry; And coating the surface of the negative electrode current collector with the negative electrode active material slurry to form a negative electrode active material layer.
  • D 50 average particle diameter
  • the present invention provides a lithium secondary battery including the negative electrode for a lithium secondary battery according to the present invention.
  • the negative electrode for a lithium secondary battery according to the present invention includes silicon nanoparticles and a graphite-based active material satisfying a specific particle size range in a negative electrode active material layer so that silicon nanoparticles can be arranged in the gap between the graphite- The swelling phenomenon of the silicon particles can be effectively suppressed.
  • both the silicon nanoparticles having different average particle diameters (D 50 ) and the graphite-based active materials can be uniformly dispersed in the negative electrode active material layer.
  • FIG. 1 is a cross-sectional view of a negative electrode active material layer for a lithium secondary battery according to the present invention.
  • the average particle diameter (D 50 ) can be measured using a laser diffraction method or a scanning electron microscope (SEM) photograph, and the average particle diameter (D 50 ) % Volume standard (based on volumetric amount).
  • the negative electrode for a lithium secondary battery comprises a negative electrode collector and a negative electrode active material layer disposed on the negative electrode collector, wherein the negative electrode active material layer has a mean particle diameter (D 50 ) of 5 ⁇ to 50 ⁇ , Active material; Silicon nanoparticles having an average particle diameter (D 50 ) of 70 nm to 300 nm; A first conductive material; And two or more kinds of cellulose-based compounds having different weight average molecular weights.
  • the negative electrode active material layer When the graphite-based active material, the silicon nanoparticles, the first conductive material, and two kinds of cellulose-based compounds having different weight average molecular weights are contained in the negative electrode active material layer, the negative electrode active material layer is swollen The anode active material layer having improved lifetime characteristics can be formed.
  • a silicone compound used as an anode active material has a theoretical capacity higher than that of a carbon-based compound, but a swelling phenomenon occurs when lithium ions are inserted.
  • the swelling phenomenon occurs, the total volume of the negative electrode including the negative electrode active material layer becomes large, and cracks are generated in the inside and the surface of the negative electrode, resulting in a large amount of consumption of the electrolyte, The lifetime characteristics of the battery may be deteriorated.
  • the average particle diameter (D 50) for having silicon nano-particles and the average particle size diameter is small silicon nanoparticles in the case of mixing to prepare a negative electrode coating portion to the graphite-based active material having a (D 50) within the range in the range It is confirmed that swelling of the entire anode active material layer is effectively suppressed even when the silicon nano-particles are partially swollen due to the position between the pores formed between the graphite active materials.
  • the negative electrode collector may be used without particular limitation, as long as it has high conductivity without causing chemical changes in the battery.
  • Specific examples thereof include copper, stainless steel, aluminum, nickel, titanium, A surface of copper or stainless steel surface-treated with carbon, nickel, titanium or silver, an aluminum-cadmium alloy, or the like can be used.
  • the negative electrode current collector may have various shapes, and may be in the form of a film, a sheet, a foil, a net, a porous body, a foam, a nonwoven fabric, or the like.
  • the negative electrode collector may have a thickness of 3 ⁇ to 500 ⁇ , or 4 ⁇ to 400 ⁇ , more preferably 5 ⁇ to 300 ⁇ .
  • the thickness of the negative electrode current collector is not necessarily limited to the above range, and the range may vary depending on the total capacity of the negative electrode for a lithium secondary battery.
  • the negative electrode collector may be formed with fine irregularities or patterns on the surface of the negative electrode collector in order to enhance the bonding force with the negative electrode active material layer.
  • the graphite-based active material contained in the negative electrode active material layer preferably has an average particle diameter (D 50 ) of 5 ⁇ to 50 ⁇ , preferably 10 ⁇ to 40 ⁇ , more preferably 15 ⁇ to 30 ⁇ Lt; / RTI >
  • silicon nanoparticles may be positioned between voids formed between the graphite-based active materials.
  • the silicon nanoparticles When the silicon nanoparticles are positioned between the voids formed between the graphite-based active materials, the graphite-based active material can prevent the silicon nanoparticles from swelling more than the volume inside the voids.
  • FIG. 1 is a cross-sectional view of an anode active material layer in which the silicon nanoparticles 20 are located between the voids of the graphite-based active material 10, and it is confirmed that the silicon nanoparticles are not swelled in the voids .
  • the silicon nanoparticles contained in the negative electrode active material layer positioned on the negative electrode collector preferably have an average particle diameter (D 50 ) of 70 nm to 300 nm, 80 nm to 300 nm, more preferably 90 Nm to 300 nm.
  • the silicon nanoparticles When the silicon nanoparticles have an average particle diameter (D 50 ) of less than the above range, the theoretical capacity of the battery may not be maintained above a certain level, and the average particle diameter (D 50 ) ,
  • the silicon nanoparticles When the lithium ion is inserted into the negative electrode active material layer during the charging and discharging process, the silicon nanoparticles may swell more rapidly and may not be located within the gap formed between the negative electrode active materials. As a result, the total volume of the negative electrode including the negative active material layer becomes large, and cracks are generated in the inside and the surface of the negative electrode. As a result, the amount of consumption of the electrolyte is increased, mechanical detachment occurs in the electrode, and the lifetime characteristics of the battery may be deteriorated.
  • the silicon nanoparticles contained in the negative active material layer may be added in an amount of 1 to 100 parts by weight, 5 to 50 parts by weight, more preferably 10 to 30 parts by weight, 30 parts by weight.
  • the content of the silicon nanoparticles satisfies the above range, most of the silicon nanoparticles are located between the voids formed between the graphite-based active materials, so that the swelling of the silicon nanoparticles during charging and discharging can be effectively suppressed.
  • the first conductive material may be included in the active material layer of the negative electrode for a lithium secondary battery.
  • the first conductive material is used for imparting conductivity to the negative electrode, and can be used without particular limitation as long as it does not cause chemical change and has electronic conductivity.
  • the first conductive material may exist independently of the anode active material layer, but may exist in a state attached to the surface of the silicon nanoparticles. When the first conductive material is adhered to the surface of the silicon nanoparticles, A passageway is formed and a more excellent conductivity can be realized.
  • the first conductive material for example, at least one compound selected from the group consisting of carbon nanoparticles, carbon nanofibers, carbon nanotubes, and carbon nanorods may be used.
  • the first conductive material has a nano size. This is because the first conductive material can be smoothly adhered to the surface of the silicon nanoparticles.
  • the average particle diameter (D 50 ) of the first conductive material may be 5 nm to 40 nm, preferably 10 nm to 35 nm, and more preferably 15 nm to 30 nm.
  • the particle shape is not limited to a specific shape, but refers to a shape that can be formed by aggregation or aggregation of carbon or the like. More specifically, it may have a spherical shape, a spherical shape, .
  • the present invention is not limited to the above-mentioned form, but may be included in the case of the aggregated particle form.
  • the width of the fibers is preferably smaller than the average particle diameter (D 50 ) of the silicon nanoparticles.
  • the width of the first conductive material may be 5 nm to 40 nm, preferably 10 nm to 35 nm, and more preferably 15 nm to 30 nm.
  • the width may be defined as the diameter of the cross section of the cylindrical conductive member when the conductive member is in the form of a fiber and the unit form of the fiber in a cylindrical form.
  • the first conductive material contained in the negative electrode active material layer may be added in an amount of 0.01 to 2.0 parts by weight, preferably 0.05 to 1.0 part by weight, more preferably 0.1 to 0.8 parts by weight, based on 100 parts by weight of the graphite- Weight part may be included.
  • the negative electrode active material layer may contain two or more kinds of cellulose compounds having different weight average molecular weights.
  • the cellulosic compound may include a first cellulosic compound and a second cellulosic compound having a weight average molecular weight higher than that of the first cellulosic compound.
  • the first cellulosic compound may have a weight average molecular weight of 10,000 to 500,000, preferably 15,000 to 500,000, more preferably 20,000 to 500,000, and even more preferably 20,000 to 400,000.
  • the second cellulosic compound may have a weight average molecular weight of 1,000,000 to 2,500,000, preferably 1,100,000 to 25,000,000, more preferably 1,200,000 to 20,000,000, and still more preferably 1,500,000 to 20,000,000.
  • the weight average molecular weight (Mw) means a polystyrene reduced weight average molecular weight (Mw) measured by gel permeation chromatography (GPC).
  • the cellulosic compound is for uniformly dispersing components such as a negative electrode active material and a conductive material contained in the negative electrode active material layer.
  • components such as a negative electrode active material and a conductive material contained in the negative electrode active material layer.
  • the cellulose compound When the cellulose compound is mixed with other components constituting the negative electrode active material layer, it is present in the form of a negatively charged ion. As a result, an electrostatic repulsive force is generated between the cellulosic compounds, so that the components can be uniformly dispersed in the negative active material layer.
  • the cellulose-based compound has a different chain length depending on the weight-average molecular weight, and the miscibility of the silicon nanoparticles with the graphite-based active material varies depending on the chain length. Therefore, when only one kind of cellulose compound is used in the negative electrode according to the present invention, it is difficult to uniformly disperse both the silicon nanoparticles and the graphite-based active material.
  • the silicone nanoparticles having a relatively small average particle diameter (D 50 ) are mixed with a cellulose-based compound having a long chain length, the cellulose-based compound and the silicon nanoparticles can not be uniformly mixed, Coagulation phenomena may occur between the compounds.
  • relatively average particle diameter (D 50) the case where the mixing and short cellulosic compounds if the chain length of the large graphite-based active material, the cellulose-based average particle diameter of the chain length of the graphite-based active material of the compound (D 50)
  • the electrostatic repulsive force of the cellulose compound is weak and it is difficult to uniformly mix the graphite-based active material.
  • the amount of the first cellulosic compound may be 0.01 part by weight to 1 part by weight, preferably 0.05 part by weight to 0.5 part by weight, more preferably 0.1 part by weight to 0.3 part by weight based on 100 parts by weight of the graphite-based active material.
  • the second cellulosic compound may be added in an amount of 0.1 to 5.0 parts by weight, preferably 0.1 to 3.0 parts by weight, more preferably 0.5 to 3.0 parts by weight based on 100 parts by weight of the graphite-based active material .
  • the negative electrode active material layer may further include a binder, if necessary.
  • the binder can be used without particular limitation as long as it is used for binding inside the anode active material layer and for improving the adhesion between the anode active material layer and the anode current collector.
  • Specific examples of the binder include polyvinylidene fluoride (PVDF), polyvinyl alcohol, starch, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM) -EPDM, styrene-butadiene rubber (SBR), acrylic copolymer, fluorocarbon rubber or various copolymers thereof. One or more of these may be used alone or as a mixture of two or more thereof.
  • the binder may be included in an amount of 0.1 to 5 parts by weight, preferably 0.1 to 4 parts by weight, more preferably 0.2 to 4 parts by weight based on 100 parts by weight of the graphite-based active material.
  • the negative electrode active material layer may further include a second conductive material, if necessary.
  • the second conductive material is used for imparting conductivity to the cathode, such as the first conductive material.
  • the second conductive material can be used without any particular limitation as long as it has electron conductivity without causing chemical change. Do.
  • the second conductive material may be attached to the surface of the graphite-based active material, or may be located inside the negative active material layer without being attached to any compound constituting the negative active material layer.
  • the second conductive material may be a carbon-based material such as super C65, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, Metal powder or metal fibers such as copper, nickel, aluminum and silver;
  • the conductive whiskers such as zinc oxide whiskers, calcium carbonate whiskers, titanium dioxide whiskers, silicon oxide whiskers, silicon carbide whiskers, aluminum borate whiskers, magnesium borate whiskers, potassium titanate whiskers, silicon nitride whiskers, silicon carbide whiskers, alumina whiskers, (Whisker); Conductive metal oxides such as titanium oxide; And polyphenylene derivatives. These may be used alone or in admixture of two or more.
  • the second conductive material may be included in an amount of 0.1 to 5 parts by weight, preferably 0.1 to 3 parts by weight, more preferably 0.5 to 3 parts by weight based on 100 parts by weight of the graphite-based active material.
  • the method for manufacturing a negative electrode for a lithium secondary battery according to the present invention includes the steps of (1) forming a first mixture, (2) forming a second mixture, (3) mixing the first mixture and the second mixture to form a negative electrode active material Forming a slurry, and (4) forming a negative electrode active material layer.
  • each step will be described in detail.
  • the first mixture is formed by mixing the silicon nanoparticles, the first conductive material, the first cellulosic compound, and the solvent.
  • the specific contents of the silicon nanoparticles, the first conductive material, and the first cellulosic compound are the same as those described above.
  • the silicon nanoparticles may be silicon nanoparticles having an average particle diameter (D 50 ) of 70 nm to 300 nm, preferably 80 nm to 300 nm, more preferably 90 nm to 300 nm,
  • the first cellulosic compound may have a weight average molecular weight of 10,000 to 500,000, preferably 15,000 to 500,000, more preferably 20,000 to 500,000, and even more preferably 20,000 to 400,000.
  • the solvent examples include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, and the like. Water and the like, and one kind or a mixture of two or more kinds can be used.
  • the solvent may be contained in an amount such that the solvent has an appropriate viscosity in consideration of the applicability and processability of the negative electrode active material slurry.
  • the first mixture contains the silicon nanoparticles, the first conductive material and the first cellulose compound in a weight ratio of (1 to 100): (0.01 to 2.0): (0.01 to 2.0) More preferably from (97 to 99): (0.5 to 1.5): (0.5 to 1.5) by weight, in terms of the weight ratio of (0.01 to 1.5): (0.01 to 1.5).
  • the silicon nanoparticles may be uniformly dispersed in the first mixture.
  • the graphite-based active material, the second cellulosic compound, and the solvent are mixed to form a second mixture.
  • the second mixture forming step is not necessarily performed after the first mixture forming step, and may be performed before the first mixture forming step or simultaneously with the first mixture forming step.
  • the specific contents of the graphite-based active material and the second cellulosic compound are the same as those described above.
  • the solvent mixed in the step of forming the second mixture is the same as the solvent used in the step of forming the first mixture.
  • the graphite-based active material may have an average particle diameter (D 50 ) of 5 ⁇ m to 50 ⁇ m, preferably 10 ⁇ m to 40 ⁇ m, more preferably 15 ⁇ m to 30 ⁇ m,
  • the second cellulosic compound may have a weight average molecular weight of 1,000,000 to 2,500,000, preferably 1,100,000 to 25,000,000, more preferably 1,200,000 to 20,000,000, still more preferably 1,500,000 to 20,000,000.
  • the second mixture may further include a second conductive material.
  • the specific content of the second conductive material is the same as described above.
  • the second mixture contains the graphite-based active material, the second cellulosic compound and the second conductive material in a weight ratio of (1 to 100): (0.1 to 5) :( 0.1 to 5) (0.5 to 3): (0.5 to 3) weight ratio, more preferably (94 to 99) :( 0.5 to 3) :( 0.5 to 3) weight ratio.
  • the graphite-based active material can be uniformly dispersed in the second mixture.
  • the first and second mixture are mixed to form a negative electrode active material slurry.
  • the first mixture and the second mixture are prepared by dividing the steps and then finally mixed.
  • cohesion may occur between the silicon nanoparticles or the graphite-based active material.
  • the silicon nanoparticles may not be positioned between the spaces between the graphite-based active materials.
  • the first cellulose compound having a short chain length is mixed to uniformly disperse the silicon nanoparticles to form a first mixture
  • a second cellulose compound having a long chain length is mixed to uniformly disperse the graphite- 2 mixture.
  • the components constituting the negative electrode active material slurry are uniformly dispersed by mixing the first and second mixture, and the silicon nanoparticles may be positioned between the spaces between the graphite-based active materials.
  • the first mixture and the second mixture may contain (5-15) :( 85-95), preferably (7-13) :( 87-93), more preferably (9-11) 91). ≪ / RTI > When the first and second mixtures are mixed so as to satisfy the above range, it can be confirmed that the capacity characteristics and the swelling suppressing performance of the finally formed lithium secondary battery are excellent.
  • the content of the solid content in the first mixture is preferably equal.
  • the solvent during the preparation of the negative electrode is finally removed, and only the graphite-based active material, the first and second conductive materials, and the first and second cellulose-based compounds that constitute the solid component remain. It is preferable that the solid content of the mixture and the second mixture are equally contained.
  • the respective components contained in the negative electrode active material slurry produced by mixing the first and second mixture may be mixed at a certain ratio.
  • a binder may be further added.
  • the binder may be added to improve the adhesion between the anode active material layer and the anode active material layer and the anode current collector, and the specific content of the binder is the same as described above.
  • the binder may be added in an amount of 0.1 to 5 parts by weight, preferably 0.1 to 4 parts by weight, more preferably 0.2 to 4 parts by weight based on 100 parts by weight of the graphite-based active material.
  • the negative electrode active material slurry thus formed is coated on the negative electrode collector to form a negative electrode active material layer.
  • the application can be accomplished through conventional slurry coating methods known in the art. Examples of the slurry coating method include, but are not limited to, bar coating, spin coating, roll coating, slot die coating, or spray coating.
  • the negative electrode active material slurry is coated on the negative electrode current collector, followed by drying and rolling to form a negative electrode active material layer, thereby manufacturing a negative electrode for a lithium secondary battery.
  • the lithium secondary battery according to the present invention comprises a negative electrode, a positive electrode, a separator interposed between the negative electrode and the positive electrode, and a nonaqueous electrolyte, wherein the negative electrode is the negative electrode according to the present invention. Since the details of the cathode are the same as those described above, the remaining components will be described below.
  • the positive electrode includes a positive electrode collector and a positive electrode active material layer formed on the positive electrode collector and including a positive electrode active material.
  • the positive electrode may be produced according to a conventional anodizing method known in the art. For example, a positive electrode active material slurry containing a positive electrode active material, a conductive material, a binder, and a solvent is applied on a positive electrode collector , ≪ / RTI > dried and rolled.
  • the positive electrode current collector may be any one of stainless steel, aluminum, nickel, titanium, sintered carbon or aluminum, and may be made of stainless steel, carbon, Nickel, titanium or silver, or the like may be used.
  • the cathode current collector may have a thickness of 3 ⁇ to 500 ⁇ , or 4 ⁇ to 400 ⁇ , more preferably 5 ⁇ to 300 ⁇ .
  • the thickness of the positive electrode current collector is not necessarily limited to the above range, but the range may vary depending on the total capacity of the positive electrode for a lithium secondary battery and the like.
  • the positive electrode active material it is possible to increase the adhesion of the positive electrode active material by forming fine irregularities on the surface of the positive electrode current collector and it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams and nonwoven fabrics.
  • a compound capable of reversibly intercalating and deintercalating lithium (a lithium intercalation compound) may be used.
  • a lithium intercalation compound a compound capable of reversibly intercalating and deintercalating lithium
  • M and M ' are independently Fe, Ni, Co, Mn, Cr, Zr, Nb, Cu, V, Mo, Ti, Zn, Al, Ga, Mg, B, 0 ⁇ y ⁇ 1, 0 ⁇ z ⁇ 1, 0 < x + y + z? 2.
  • the positive electrode active material may be contained in an amount of 69 to 98% by weight based on the total weight of the positive electrode active material layer.
  • the conductive material is used for imparting conductivity to the anode.
  • the conductive material is not particularly limited as long as it has electron conductivity without causing chemical change. Specific examples thereof include graphite such as natural graphite and artificial graphite; Carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, summer black and carbon fiber; Metal powder or metal fibers such as copper, nickel, aluminum and silver;
  • the conductive whiskers such as zinc oxide whiskers, calcium carbonate whiskers, titanium dioxide whiskers, silicon oxide whiskers, silicon carbide whiskers, aluminum borate whiskers, magnesium borate whiskers, potassium titanate whiskers, silicon nitride whiskers, silicon carbide whiskers, alumina whiskers, (Whisker); Conductive metal oxides such as titanium oxide; And polyphenylene derivatives. These may be used alone or in admixture of two or more.
  • the conductive material may be contained in an amount of 30% by weight or less, or 1 to 30% by weight based on the total weight of the cathode active material layer.
  • the binder serves to improve the adhesion between the positive electrode active material particles and the adhesion between the positive electrode active material and the current collector.
  • specific examples include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, There may be mentioned polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, fluorine rubber or various copolymers thereof. Can be used.
  • the binder may be contained in an amount of 30% by weight or less, or 1% by weight to 30% by weight based on the total weight of the positive electrode active material layer.
  • the separator is not particularly limited as long as it is used as a separator in a lithium secondary battery.
  • the separator is low in resistance against ion movement of the electrolyte and excellent in electrolyte wettability.
  • porous polymer films such as porous polymer films made of polyolefin-based polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers and ethylene / methacrylate copolymers, May be used.
  • a nonwoven fabric made of a conventional porous nonwoven fabric, for example, glass fiber of high melting point, polyethylene terephthalate fiber, or the like may be used.
  • Examples of the electrolyte used in the present invention include an organic-based liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, and a molten inorganic electrolyte that can be used in the production of a lithium secondary battery. no.
  • the electrolyte may include an organic solvent and a lithium salt.
  • the organic solvent may be used without limitation as long as it can act as a medium through which ions involved in the electrochemical reaction of the battery can move.
  • examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate,? -Butyrolactone and?
  • Ether solvents such as dibutyl ether or tetrahydrofuran
  • Ketone solvents such as cyclohexanone
  • Aromatic hydrocarbon solvents such as benzene and fluorobenzene
  • Dimethyl carbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), propylene carbonate PC) and the like can be used.
  • a carbonate-based solvent is preferable, and a cyclic carbonate (for example, ethylene carbonate or propylene carbonate) having a high ionic conductivity and a high dielectric constant, for example, such as ethylene carbonate or propylene carbonate, For example, ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate) is more preferable.
  • a cyclic carbonate for example, ethylene carbonate or propylene carbonate
  • ethylene carbonate or propylene carbonate having a high ionic conductivity and a high dielectric constant
  • ethylene carbonate or propylene carbonate for example, ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate
  • the lithium salt can be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery.
  • the lithium salt LiPF 6, LiClO 4, LiAsF 6, LiBF 4, LiSbF 6, LiAl0 4, LiAlCl 4, LiCF 3 SO 3, LiC 4 F 9 SO 3, LiN (C 2 F 5 SO 3) 2 , LiN (C 2 F 5 SO 2) 2, LiN (CF 3 SO 2) 2.
  • LiCl, LiI, or LiB (C 2 O 4 ) 2 may be used.
  • the lithium salt is preferably contained in the electrolyte at a concentration of about 0.6 mol% to 2 mol%.
  • the electrolytes include, for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, n-propylamine, and the like for the purpose of improving lifetime characteristics of the battery, N, N-substituted imidazolidine, ethylene glycol dialkyl ethers, ammonium salts, pyrroles, 2-ethylhexyl glycols, glycols such as glyme, hexa phosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, - methoxyethanol or aluminum trichloride may be further included.
  • the additive may be included in an amount of 0.1 wt% to 5 wt% based on the total weight of the electrolyte.
  • the lithium secondary battery having the above structure can be manufactured by manufacturing an electrode assembly with a separator interposed between the positive electrode and the negative electrode, positioning the electrode assembly in the case, and injecting an electrolyte into the case .
  • the lithium secondary battery including the negative electrode according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, it can be used in portable devices such as mobile phones, notebook computers, digital cameras, and hybrid electric vehicles And the like.
  • a battery module including the lithium secondary battery as a unit cell and a battery pack including the same.
  • the battery module or the battery pack may include a power tool; An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), and a plug-in hybrid electric vehicle (PHEV); Or a power storage system, as shown in FIG.
  • Silicone nanoparticles having an average particle diameter (D 50 ) of 110 nm, carbon nanotubes having a width of 20 nm, and CMC (GL CHEM, SG-L02, weight average molecular weight: 300,000) were mixed in a weight ratio of 98.0:
  • a first slurry the solid content of the first slurry is 45 wt%).
  • a mixture of artificial graphite (LC1) (Shanshan, LC1) having an average particle diameter (D 50 ) of 20 ⁇ and conductive super C65 and CMC (Daicel, 2200, weight average molecular weight 1,260,000)
  • LC1 artificial graphite
  • the first slurry and the second slurry were mixed at a weight ratio of 10:90 and 2.5 parts by weight of a binder (Zeon Co., BM-L301) was added to a total weight of 100 parts by weight of the first and second slurries to prepare an anode active material slurry .
  • a binder Zeon Co., BM-L301
  • the prepared negative electrode active material slurry was applied to a copper metal thin film as an anode current collector having a thickness of 8 ⁇ ⁇ by setting the circulating air temperature at 80 ⁇ ⁇ and dried. Then, the resultant was rolled and dried in a vacuum oven at 60 DEG C for 24 hours to prepare a negative electrode.
  • An anode based on NCM523 (L & F Advanced Materials Co., NE-X10S) corresponding to the prepared cathode was prepared, and a bicell was formed between a cathode and an anode through a ceramic coating separator (LG Chem, B12) having a thickness of 12 ⁇ m. stack & folding cell. This was injected into a 88 .mu.m thick pouch and an electrolyte was injected to complete the lithium secondary battery. The design capacity of the completed battery was 3200 mAh.
  • Silicon nanoparticles having an average particle diameter (D 50 ) of 300 nm, carbon nanotubes having a width of 20 nm, and CMC (Daiichi Co., H1496A, weight average molecular weight 500,000) were mixed in a ratio of 98.0: 1.0: 1.0
  • a negative electrode and a lithium secondary battery were prepared in the same manner as in Example 1, except that water was mixed with a solvent to prepare a first slurry.
  • Example 1 was repeated except that CMC (Daicel Co., 2200, weight average molecular weight: 1,260,000) was used in place of CMC (GL CHEM, SG-L02, weight average molecular weight 300,000) in the step of preparing the first slurry in Example 1 After the negative electrode active material slurry was prepared in the same manner, a negative electrode and a lithium secondary battery were produced in the same manner.
  • CMC Disicel Co., 2200, weight average molecular weight: 1,260,000
  • CMC GL CHEM, SG-L02, weight average molecular weight 300,000
  • a negative electrode active material slurry was prepared in the same manner as in Example 1, except that silicon particles having an average particle diameter (D 50 ) of 10 ⁇ m were used instead of the silicon nanoparticles having an average particle diameter (D 50 ) of 110 nm in Example 1 After that, a negative electrode and a lithium secondary battery were produced in the same manner.
  • Silicone nanoparticles having an average particle diameter (D 50 ) of 110 nm and a width of 20 nm were used without using CMC (GL CHEM, SG-L02, weight average molecular weight 300,000) in the step of preparing the first slurry in Example 1
  • Carbon nanotubes were mixed with water at a weight ratio of 99.0: 1.0 with a solvent to prepare a first slurry (the solid content of the first slurry was 45 wt%).
  • Example 1 Except that CMC (GL Chem, SG-L02, weight average molecular weight 300,000) was used without using CMC (Daicel Co., 2200, weight average molecular weight 1,260,000) in the step of preparing the second slurry in Example 1
  • the negative electrode active material slurry was prepared in the same manner as in Example 1, and then a negative electrode and a lithium secondary battery were prepared in the same manner.
  • the batteries of Examples 1 to 5 and Comparative Examples 1 to 4 were subjected to charging and discharging at a rate of 1 C / 1 C at 3.0 to 4.2 V to evaluate the initial capacity, capacity after 50 cycles, , which is shown in Table 1 below.
  • Comparative Example 4 a cellulosic compound having a low molecular weight was used in the preparation of the second slurry, and the slurry of the negative electrode active material according to Comparative Example 4 was also precipitated so fast that uniform electrode coating could not be performed.

Abstract

The present invention provides an anode for a lithium secondary battery, a method for preparing the same, and a lithium secondary battery comprising the same, the anode for a lithium secondary battery comprising: an anode current collector; and an anode active material layer disposed on the anode current collector, wherein the anode active material layer comprises: a graphite-based active material having an average particle diameter (D50) of 5 ㎛ to 50 ㎛; silicon nanoparticles having an average particle diameter (D50) of 70 ㎚ to 300 ㎚; a first conductive material; and two or more kinds of cellulose-based compounds having different weight average molecular weights.

Description

리튬 이차전지용 음극, 및 이를 포함하는 리튬 이차전지Cathode for lithium secondary battery, and lithium secondary battery comprising same
관련출원과의 상호인용Mutual citation with related application
본 출원은 2017년 09월 08일자 한국특허출원 제10-2017-0115099호 및 2018년 04월 03일자 한국특허출원 제 10-2018-0038717호에 기초한 우선권의 이익을 주장하며, 해당 한국특허출원의 문헌에 개시된 모든 내용은 본 명세서의 일부로서 포함된다.This application claims the benefit of priority based on Korean Patent Application No. 10-2017-0115099 dated September 08, 2017 and Korean Patent Application No. 10-2018-0038717 dated April 03, 2018, The entire contents of which are incorporated herein by reference.
기술분야Technical field
본 발명은 고용량 리튬 이차전지용 음극 및 이를 포함하는 리튬 이차전지에 관한 것으로서, 더욱 상세하게는 실리콘 나노 입자를 이용한 음극 활물질 층을 가지면서 안정성이 향상된 고용량 음극 및 이를 포함하는 리튬 이차전지에 관한 것이다.The present invention relates to a negative electrode for a high capacity lithium secondary battery and a lithium secondary battery comprising the same, and more particularly, to a high capacity negative electrode having a negative electrode active material layer using silicon nanoparticles and having improved stability, and a lithium secondary battery comprising the same.
모바일 기기에 대한 기술 개발과 수요가 증가함에 따라 에너지원으로서 이차전지의 수요가 급격히 증가하고 있고, HEV, PHEV 및 EV 자동차가 미래형 자동차로 각광받으면서 그에 따라 다양한 요구에 부응할 수 있는 전지에 대한 연구가 다양하게 행해지고 있다. 특히, 이러한 장치의 전원으로 높은 에너지 밀도를 가지면서 우수한 수명 및 사이클 특성을 가지는 리튬 이차전지에 대한 연구가 활발히 진행되고 있다.As technology development and demand for mobile devices have increased, demand for secondary batteries has increased sharply, and HEVs, PHEVs, and EVs have been widely recognized as future vehicles, Are carried out in various ways. Particularly, research on a lithium secondary battery having a high energy density and excellent lifetime and cycle characteristics as a power source of such a device is actively under way.
이와 관련하여, 종래의 리튬 이차전지의 음극은 음극 활물질로 구조적, 전기적 성질을 유지하면서 가역적인 리튬 이온의 삽입(intercalation) 및 탈리가 가능한 탄소계 화합물이 주로 사용되고 있으나, 이러한 탄소계 화합물로 이루어지는 음극은 탄소계 화합물의 리튬 이온의 삽입 및 탈리시 화학적 전위(chemical potential)가 금속 리튬과 비슷하여 약간의 높은 충전전류에서도 과전압(overpotential)에 의한 리튬 석출이 발생하고, 한번 석출된 리튬은 충방전을 반복할수록 더욱 가속화되어 용량 감퇴는 물론 수지상 결정(dendrite)를 통한 단락(short)를 유발하여 안전성에 지대한 영향을 미칠 수 있으며, 전지의 과충전 등에 의해서 음극에서 받을 수 있는 리튬의 양보다 많은 양의 리튬이 충전될 경우 온도가 상승하며 발열반응을 일으켜 전지의 발화 폭발 등을 일으킬 수 있다.In this regard, the negative electrode of the conventional lithium secondary battery is mainly composed of a carbonaceous compound which can reversibly intercalate and desorb lithium ions while maintaining the structural and electrical properties of the negative electrode active material. However, The chemical potential of the carbon-based compound in the insertion and desorption of lithium ions is similar to that of metallic lithium, so that even at a slight high charging current, lithium precipitation occurs due to overpotential, As the number of repetitions increases, the capacity is accelerated, resulting in a decrease in capacity and a short circuit due to dendrites. Thus, the safety can be greatly influenced. The amount of lithium exceeding the amount of lithium If the battery is charged, the temperature rises, causing an exothermic reaction, which may cause ignition and explosion of the battery. .
상기 문제를 해결하기 위해 최근에는 종래의 탄소계 음극재에서 벗어나 실리콘(Si), 주석(Sn)을 이용한 Li 합금계(alloy) 반응에 의한 음극재 및 Li4Ti5O12에 대한 연구가 많이 진행되고 있다.In order to solve the above problems, researches on Li 4 Ti 5 O 12 and Li 4 Ti 5 O 12 by a Li alloy reaction using silicon (Si), tin (Sn) and the like have been carried out much from the conventional carbonaceous anode materials.
탄소계 음극재를 대체하기 위한 물질 중 하나인 실리콘을 음극재로 사용하는 경우, 기존의 탄소계 음극재보다 이론 용량이 약 10배 가량 더 높지만, 실리콘이 리튬을 저장함에 따라 부풀어오르게 되는 팽윤 현상(swelling 현상)이 발생되어 실리콘의 부피가 급격하게 증가할 수 있다. 상기와 같은 팽윤 현상은 음극에 구조적 스트레스를 야기할 수 있고, 결과적으로는 전지의 훼손을 초래할 수 있으며, 특히 부피가 팽창함에 따라 안정성에 큰 영향을 받는 파우치 형태의 리튬 이차전지의 음극재로서는 적용하기 어렵다는 문제점이 있다. When silicon, which is one of the materials for replacing carbon-based anode materials, is used as an anode material, the theoretical capacity is about 10 times higher than that of a conventional carbon-based anode material. However, the swelling phenomenon (swelling phenomenon) may occur and the volume of silicon may increase sharply. Such a swelling phenomenon may cause structural stress on the negative electrode, which may result in damage to the battery. Particularly, as the negative electrode material of a pouch-type lithium secondary battery which is greatly affected by stability as the volume expands, There is a problem that it is difficult.
이와 관련하여, 특허출원공개 제10-2016-0039982호는 실리콘 산화물을 포함하는 음극 형성용 조성물을 개시하고 있는데, 상기 음극 형성용 조성물은 실리콘 산화물이 부풀어오르는 팽윤 현상을 억제하기보다는 음극의 부피가 팽창하여 도전 경로가 끊기는 경우, 이를 보완하기 위하여 결착력이 높은 바인더를 사용하는 것이다. 다만, 상기 실리콘 산화물은 일반적으로 마이크로 사이즈의 화합물이므로 상기 조성물을 사용하는 음극재를 리튬 이차전지에 사용하여 양산화하기에는 안전성의 문제가 있다. 또한, 실리콘 산화물의 경우에는 실리콘 보다는 상대적으로 이론용량이 적은 화합물로, 동일한 질량을 사용하는 경우에도 전지 용량이 적어 전지의 효율이 낮다는 문제점이 존재한다.In this connection, Japanese Patent Application Laid-Open No. 10-2016-0039982 discloses a composition for forming an anode comprising a silicon oxide, wherein the composition for forming an anode is not limited to the swelling phenomenon in which silicon oxide swells up, When the conductive path is broken due to expansion, a binder having a high binding force is used in order to compensate for this. However, since the silicon oxide is generally a micro-sized compound, there is a problem in safety when mass-producing an anode material using the above composition for a lithium secondary battery. In addition, the silicon oxide has a relatively lower theoretical capacity than silicon, and even when the same mass is used, there is a problem that the battery capacity is low and the efficiency of the battery is low.
[선행기술문헌][Prior Art Literature]
[특허문헌][Patent Literature]
한국 특허공개공보 제10-2016-0039982호 (2016.04.12. 공개)Korean Patent Laid-Open Publication No. 10-2016-0039982 (published on April 12, 2016)
본 발명은 상기와 같은 문제점을 해결하기 위한 것으로, 높은 용량을 구현하면서도 팽윤 현상이 억제될 수 있는 리튬 이차전지용 음극 및 이를 포함하는 리튬 이차전지를 제공하고자 한다.Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made to solve the above problems, and an object of the present invention is to provide a negative electrode for a lithium secondary battery and a lithium secondary battery including the negative electrode.
일 구현예에 따르면, 본 발명은, 음극 집전체 및 상기 음극 집전체 상에 위치하는 음극 활물질 층을 포함하는 리튬 이차전지용 음극이며, 상기 음극 활물질 층은, 평균 입자 직경(D50)이 5 ㎛ 내지 50 ㎛인 흑연계 활물질, 평균 입자 직경(D50)이 70 ㎚ 내지 300 ㎚인 실리콘 나노 입자, 제1 도전재; 및 중량 평균 분자량이 서로 다른 2종 이상의 셀룰로오스계 화합물을 포함하는 리튬 이차전지용 음극을 제공한다.According to one embodiment, the present invention is a negative electrode for a lithium secondary battery comprising a negative electrode collector and a negative electrode active material layer disposed on the negative electrode collector, wherein the negative electrode active material layer has an average particle diameter (D 50 ) To 50 占 퐉, silicon nanoparticles having an average particle diameter (D50) of 70 nm to 300 nm, a first conductive material; And a negative electrode for a lithium secondary battery comprising two or more kinds of cellulose-based compounds having different weight average molecular weights.
다른 구현예에 따르면, 본 발명은 평균 입자 직경(D50)이 70 ㎚ 내지 300 ㎚인 실리콘 나노 입자, 제1 도전재, 중량 평균 분자량이 10,000 내지 500,000 인 제1 셀룰로오스계 화합물 및 용매를 혼합하여 제1 혼합물을 형성하는 단계; 평균 입자 직경(D50)이 5 ㎛ 내지 50 ㎛인 흑연계 활물질, 중량 평균 분자량이 1,000,000 내지 2,500,000 인 제2 셀룰로오스계 화합물 및 용매를 혼합하여 제2 혼합물을 형성하는 단계; 상기 제1 혼합물 및 상기 제2 혼합물을 혼합하여 음극 활물질 슬러리를 형성하는 단계; 및 상기 음극 활물질 슬러리를 음극 집전체의 표면에 도포하여 음극 활물질 층을 형성하는 단계를 포함하는 리튬 이차전지용 음극 제조방법을 제공한다.According to another embodiment, the present invention provides a process for producing a silicon nanocrystal by mixing silicon nanoparticles having an average particle diameter (D 50 ) of 70 nm to 300 nm, a first conductive material, a first cellulose compound having a weight average molecular weight of 10,000 to 500,000, Forming a first mixture; Forming a second mixture by mixing a graphite-based active material having an average particle diameter (D 50 ) of 5 탆 to 50 탆, a second cellulosic compound having a weight average molecular weight of 1,000,000 to 2,500,000, and a solvent; Mixing the first mixture and the second mixture to form a negative electrode active material slurry; And coating the surface of the negative electrode current collector with the negative electrode active material slurry to form a negative electrode active material layer.
또 다른 측면에서, 본 발명은 상기 본 발명의 리튬 이차 전지용 음극을 포함하는 리튬 이차전지를 제공한다.In another aspect, the present invention provides a lithium secondary battery including the negative electrode for a lithium secondary battery according to the present invention.
본 발명에 따른 리튬 이차전지용 음극은 음극 활물질층 내에 특정한 입경 범위를 만족하는 실리콘 나노 입자 및 흑연계 활물질을 함께 포함하여 흑연계 활물질들 사이의 공극에 실리콘 나노 입자가 배치될 수 있도록 함으로써 고용량의 실리콘을 사용하면서도, 실리콘 입자의 팽윤 현상을 효과적으로 억제할 수 있다.The negative electrode for a lithium secondary battery according to the present invention includes silicon nanoparticles and a graphite-based active material satisfying a specific particle size range in a negative electrode active material layer so that silicon nanoparticles can be arranged in the gap between the graphite- The swelling phenomenon of the silicon particles can be effectively suppressed.
또한, 중량 평균 분자량이 서로 다른 2종 이상의 셀룰로오스계 화합물을 사용하므로, 서로 평균 입자 직경(D50)이 상이한 실리콘 나노 입자와 흑연계 활물질이 모두 음극 활물질 층 내에 균일하게 분산될 수 있다.In addition, since two or more kinds of cellulose compounds having different weight average molecular weights are used, both the silicon nanoparticles having different average particle diameters (D 50 ) and the graphite-based active materials can be uniformly dispersed in the negative electrode active material layer.
도 1은 본 발명의 리튬 이차전지용 음극 활물질 층의 단면을 나타낸 것이다.1 is a cross-sectional view of a negative electrode active material layer for a lithium secondary battery according to the present invention.
이하, 본 발명에 대한 이해를 돕기 위해 본 발명을 더욱 상세하게 설명한다.Hereinafter, the present invention will be described in detail in order to facilitate understanding of the present invention.
본 발명의 설명 및 청구범위에서 사용된 용어나 단어는, 통상적이거나 사전적인 의미로 한정해서 해석되어서는 아니 되며, 발명자는 그 자신의 발명을 가장 최선의 방법으로 설명하기 위해 용어의 개념을 적절하게 정의할 수 있다는 원칙에 입각하여, 본 발명의 기술적 사상에 부합하는 의미와 개념으로 해석되어야만 한다.The terms and words used in the description of the present invention and in the claims should not be construed to be limited to ordinary or dictionary terms and the inventor should appropriately interpret the concept of the term appropriately The present invention should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention.
본 발명에 있어서, 평균 입자 직경(D50)은 레이저 회절법(laser diffraction method) 또는 주사전자현미경(SEM) 사진을 이용하여 측정할 수 있으며, 평균 입자 직경(D50)은 입자 직경 분포의 50% 체적 기준(체적 누적량 기준)에서의 입경으로 정의할 수 있다.In the present invention, the average particle diameter (D 50 ) can be measured using a laser diffraction method or a scanning electron microscope (SEM) photograph, and the average particle diameter (D 50 ) % Volume standard (based on volumetric amount).
음극cathode
이하, 본 발명에 따른 리튬 이차전지용 음극에 대하여 설명한다.Hereinafter, a negative electrode for a lithium secondary battery according to the present invention will be described.
본 발명에 따른 리튬 이차전지용 음극은 음극 집전체 및 상기 음극 집전체 상에 위치하는 음극 활물질 층을 포함하고, 상기 음극 활물질 층은, 평균 입자 직경(D50)이 5 ㎛ 내지 50 ㎛인 흑연계 활물질; 평균 입자 직경(D50)이 70 ㎚ 내지 300 ㎚인 실리콘 나노 입자; 제1 도전재; 및 중량 평균 분자량이 서로 다른 2종 이상의 셀룰로오스계 화합물을 포함한다.The negative electrode for a lithium secondary battery according to the present invention comprises a negative electrode collector and a negative electrode active material layer disposed on the negative electrode collector, wherein the negative electrode active material layer has a mean particle diameter (D 50 ) of 5 탆 to 50 탆, Active material; Silicon nanoparticles having an average particle diameter (D 50 ) of 70 nm to 300 nm; A first conductive material; And two or more kinds of cellulose-based compounds having different weight average molecular weights.
음극 활물질 층 내에 상기 흑연계 활물질, 상기 실리콘 나노 입자, 상기 제1 도전재, 상기 중량 평균 분자량이 서로 다른 2종의 셀룰로오스계 화합물이 포함되는 경우, 고용량 특성을 가지면서도, 음극 활물질 층이 팽윤되는 것을 억제하여 수명특성이 개선되는 음극 활물질 층을 형성할 수 있다. When the graphite-based active material, the silicon nanoparticles, the first conductive material, and two kinds of cellulose-based compounds having different weight average molecular weights are contained in the negative electrode active material layer, the negative electrode active material layer is swollen The anode active material layer having improved lifetime characteristics can be formed.
일반적으로 음극 활물질로 사용되는 실리콘계 화합물은 이론용량이 탄소계 화합물보다 더 우수하지만, 리튬 이온이 삽입되는 경우 팽윤 현상이 발생된다는 문제점이 있다. 팽윤 현상이 발생하게 되면, 음극 활물질 층을 비롯한 음극 전체 부피가 커지게 되면서, 음극의 내부 및 표면에 균열(crack)이 발생하게 되고, 그 결과로 전해액 소모량이 커지며, 전극 내 기계적 탈리가 발생되어 전지의 수명 특성이 저하될 수 있다.Generally, a silicone compound used as an anode active material has a theoretical capacity higher than that of a carbon-based compound, but a swelling phenomenon occurs when lithium ions are inserted. When the swelling phenomenon occurs, the total volume of the negative electrode including the negative electrode active material layer becomes large, and cracks are generated in the inside and the surface of the negative electrode, resulting in a large amount of consumption of the electrolyte, The lifetime characteristics of the battery may be deteriorated.
본 발명자들의 연구에 따르면, 실리콘계 화합물로서, 평균 입자 직경(D50)이 상기 범위 내인 실리콘 나노 입자를 사용하는 경우, 동일한 질량의 평균 입자 직경(D50)이 10㎛ 이상인 실리콘 입자를 사용하는 경우보다 부풀어오르는 현상이 확연하게 감소하는 것을 확인할 수 있어, 팽윤 현상(swelling)이 방지되는 것을 확인할 수 있었다.According to the studies of the present inventors, when silicon nanoparticles having an average particle diameter (D 50 ) within the above range are used as the silicone compound, and silicon particles having an average particle diameter (D 50 ) It was confirmed that the swelling phenomenon was significantly reduced, and swelling was prevented.
또한, 상기 범위 내의 평균 입자 직경(D50)을 가지는 실리콘 나노 입자와 상기 범위 내의 평균 입자 직경(D50)을 가지는 흑연계 활물질을 혼합하여 음극 활물질 층을 제조하는 경우 입경이 작은 실리콘 나노 입자가 흑연계 활물질 간에 형성되는 공극 사이에 위치하게 되어 상기 실리콘 나노 입자가 일부 팽윤되는 경우에도, 상기 음극활물질층 전체가 팽윤되는 것은 효과적으로 억제되는 것을 확인할 수 있었다.Further, the average particle diameter (D 50) for having silicon nano-particles and the average particle size diameter is small silicon nanoparticles in the case of mixing to prepare a negative electrode coating portion to the graphite-based active material having a (D 50) within the range in the range It is confirmed that swelling of the entire anode active material layer is effectively suppressed even when the silicon nano-particles are partially swollen due to the position between the pores formed between the graphite active materials.
본 발명에 있어서, 상기 음극집전체로는 전지에 화학적 변화를 유발하지 않으면서 높은 도전성을 가지는 것이라면 특별히 제한없이 사용될 수 있으며, 구체적으로는, 구리, 스테인레스 스틸, 알루미늄, 니켈, 티탄, 소성 탄소, 구리나 스테인레스 스틸의 표면에 탄소, 니켈, 티탄 또는 은 등으로 표면처리한 것, 알루미늄-카드뮴 합금 등이 사용될 수 있다.In the present invention, the negative electrode collector may be used without particular limitation, as long as it has high conductivity without causing chemical changes in the battery. Specific examples thereof include copper, stainless steel, aluminum, nickel, titanium, A surface of copper or stainless steel surface-treated with carbon, nickel, titanium or silver, an aluminum-cadmium alloy, or the like can be used.
상기 음극집전체는 다양한 형태를 가질 수 있으며, 구체적으로는 필름, 시트, 호일, 네트, 다공질체, 발포체, 부직포체 등의 형태일 수 있다.The negative electrode current collector may have various shapes, and may be in the form of a film, a sheet, a foil, a net, a porous body, a foam, a nonwoven fabric, or the like.
또한, 상기 음극집전체는 3 ㎛ 내지 500 ㎛, 또는 4 ㎛ 내지 400 ㎛, 보다 바람직하게는 5 ㎛ 내지 300 ㎛의 두께를 가질 수 있다. 상기 음극집전체의 두께는 상기 범위에 반드시 한정되는 것은 아니고, 리튬 이차전지용 음극의 전체 용량 등에 따라서 그 범위가 달라질 수 있다.Further, the negative electrode collector may have a thickness of 3 탆 to 500 탆, or 4 탆 to 400 탆, more preferably 5 탆 to 300 탆. The thickness of the negative electrode current collector is not necessarily limited to the above range, and the range may vary depending on the total capacity of the negative electrode for a lithium secondary battery.
한편, 상기 음극집전체는 음극 활물질 층과의 결합력을 강화시킬 수 있도록, 음극집전체의 표면에 미세한 요철 또는 패턴이 형성될 수도 있다.On the other hand, the negative electrode collector may be formed with fine irregularities or patterns on the surface of the negative electrode collector in order to enhance the bonding force with the negative electrode active material layer.
본 발명에 있어서, 상기 음극 활물질 층에 포함되는 상기 흑연계 활물질은 평균 입자 직경(D50)이 5 ㎛ 내지 50㎛, 바람직하게는 10 ㎛ 내지 40 ㎛, 보다 바람직하게는 15 ㎛ 내지 30 ㎛인 것일 수 있다.In the present invention, the graphite-based active material contained in the negative electrode active material layer preferably has an average particle diameter (D 50 ) of 5 탆 to 50 탆, preferably 10 탆 to 40 탆, more preferably 15 탆 to 30 탆 Lt; / RTI >
상기 범위의 평균 입자 직경(D50)을 가지는 흑연계 활물질을 사용하는 경우, 상기 흑연계 활물질 간에 형성되는 공극 사이에 실리콘 나노 입자가 위치할 수 있다. 상기 흑연계 활물질 간에 형성되는 공극 사이에 실리콘 나노 입자가 위치하게 되면, 상기 흑연계 활물질이 상기 실리콘 나노 입자가 상기 공극 내부의 부피보다 팽윤하는 것을 저지할 수 있다.When a graphite-based active material having an average particle diameter (D 50 ) in the above range is used, silicon nanoparticles may be positioned between voids formed between the graphite-based active materials. When the silicon nanoparticles are positioned between the voids formed between the graphite-based active materials, the graphite-based active material can prevent the silicon nanoparticles from swelling more than the volume inside the voids.
도 1은 상기 흑연계 활물질(10)의 공극 사이에 상기 실리콘 나노 입자(20)가 위치한 음극 활물질 층의 단면을 나타낸 것으로, 상기 실리콘 나노 입자가 상기 공극 내에서 팽윤되지 않도록 위치하는 것을 확인할 수 있다.1 is a cross-sectional view of an anode active material layer in which the silicon nanoparticles 20 are located between the voids of the graphite-based active material 10, and it is confirmed that the silicon nanoparticles are not swelled in the voids .
본 발명에 있어서, 상기 음극 집전체 상에 위치하는 상기 음극 활물질 층에 포함되는 상기 실리콘 나노 입자는 평균 입자 직경(D50)이 70 ㎚ 내지 300 ㎚, 80 ㎚ 내지 300 ㎚, 보다 바람직하게는 90 ㎚ 내지 300 ㎚인 것일 수 있다.In the present invention, the silicon nanoparticles contained in the negative electrode active material layer positioned on the negative electrode collector preferably have an average particle diameter (D 50 ) of 70 nm to 300 nm, 80 nm to 300 nm, more preferably 90 Nm to 300 nm.
상기 실리콘 나노 입자가 상기 범위 미만의 평균 입자 직경(D50)을 가지는 경우, 전지의 이론용량이 일정 수준 이상으로 유지되지 못할 수 있으며, 상기 범위를 초과하는 평균 입자 직경(D50)을 가지는 경우에는, 충방전 과정에서 음극 활물질 층에 리튬 이온이 삽입될 때, 실리콘 나노 입자가 더욱 급격하게 팽윤할 수 있고, 상기 음극 활물질 간에 형성되는 공극 내부에 위치하지 못할 수 있다. 이에 따라, 상기 음극 활물질 층을 비롯한 음극 전체 부피가 커지게 되면서, 음극의 내부 및 표면에 균열(crack)이 발생하게 된다. 그 결과로 전해액 소모량이 커지며, 전극 내 기계적 탈리가 발생되어 전지의 수명 특성이 저하될 수 있다.When the silicon nanoparticles have an average particle diameter (D 50 ) of less than the above range, the theoretical capacity of the battery may not be maintained above a certain level, and the average particle diameter (D 50 ) , When the lithium ion is inserted into the negative electrode active material layer during the charging and discharging process, the silicon nanoparticles may swell more rapidly and may not be located within the gap formed between the negative electrode active materials. As a result, the total volume of the negative electrode including the negative active material layer becomes large, and cracks are generated in the inside and the surface of the negative electrode. As a result, the amount of consumption of the electrolyte is increased, mechanical detachment occurs in the electrode, and the lifetime characteristics of the battery may be deteriorated.
본 발명에 있어서, 상기 음극 활물질 층에 포함된 상기 실리콘 나노 입자는 상기 흑연계 활물질 100 중량부에 대하여 1 중량부 내지 100 중량부, 5 중량부 내지 50 중량부, 보다 바람직하게는 10 중량부 내지 30 중량부로 포함될 수 있다.In the present invention, the silicon nanoparticles contained in the negative active material layer may be added in an amount of 1 to 100 parts by weight, 5 to 50 parts by weight, more preferably 10 to 30 parts by weight, 30 parts by weight.
상기 실리콘 나노 입자의 함량이 상기 범위를 만족하는 경우, 대부분의 실리콘 나노 입자가 흑연계 활물질 간에 형성되는 공극 사이에 위치하게 되므로, 충방전 시에 실리콘 나노 입자가 팽윤되는 것을 효과적으로 억제할 수 있다.When the content of the silicon nanoparticles satisfies the above range, most of the silicon nanoparticles are located between the voids formed between the graphite-based active materials, so that the swelling of the silicon nanoparticles during charging and discharging can be effectively suppressed.
본 발명에 있어서, 리튬 이차전지용 음극의 활물질 층에는 제1 도전재가 포함될 수 있다. In the present invention, the first conductive material may be included in the active material layer of the negative electrode for a lithium secondary battery.
상기 제1 도전재는 음극에 도전성을 부여하기 위해 사용되는 것으로서, 화학변화를 야기하지 않고 전자 전도성을 갖는 것이면 특별한 제한없이 사용 가능하다. 제1 도전재는 음극 활물질 층에 독립적으로 존재할 수도 있지만, 상기 실리콘 나노 입자의 표면에 부착된 상태로 존재할 수 있으며, 실리콘 나노 입자의 표면에 상기 제1 도전재가 부착되는 경우, 활물질 입자들 사이의 전기적 통로가 형성되어 보다 우수한 도전성을 구현할 수 있다.The first conductive material is used for imparting conductivity to the negative electrode, and can be used without particular limitation as long as it does not cause chemical change and has electronic conductivity. The first conductive material may exist independently of the anode active material layer, but may exist in a state attached to the surface of the silicon nanoparticles. When the first conductive material is adhered to the surface of the silicon nanoparticles, A passageway is formed and a more excellent conductivity can be realized.
구체적으로는, 상기 제1 도전재로는, 예를 들면, 카본나노입자, 카본나노파이버, 카본나노튜브 및 카본나노로드로 이루어진 군에서 선택되는 적어도 하나 이상의 화합물이 사용될 수 있다.Specifically, as the first conductive material, for example, at least one compound selected from the group consisting of carbon nanoparticles, carbon nanofibers, carbon nanotubes, and carbon nanorods may be used.
한편, 상기 제1 도전재는 나노 사이즈를 갖는 것이 바람직하다. 이 경우, 실리콘 나노 입자의 표면에 제1 도전재가 원활하게 부착될 수 있기 때문이다.Meanwhile, it is preferable that the first conductive material has a nano size. This is because the first conductive material can be smoothly adhered to the surface of the silicon nanoparticles.
예를 들면, 제1 도전재가 카본나노입자와 같은 입자 형태인 경우, 상기 제1 도전재의 평균 입자 직경(D50)은, 실리콘 나노 입자의 평균 입자 직경(D50)보다 작은 것이 바람직하며, 예를 들면, 상기 제1 도전재의 평균 입자 직경(D50)은 5 ㎚ 내지 40 ㎚, 바람직하게는 10 ㎚ 내지 35 ㎚, 보다 바람직하게는 15 ㎚ 내지 30 ㎚일 수 있다. 한편, 상기 입자 형태는 특정 형태로 한정되는 것은 아니고, 카본 등이 응집 또는 집합되면서 형성될 수 있는 형태를 의미하는 것으로, 보다 구체적으로 구 형태, 구형에 가까운 형태, 판(상) 형태 등이 있을 수 있다. 다만, 상기 형태로 한정되는 것은 아니고, 응집된 입자 형태인 경우에는 모두 포함될 수 있다.For example, the first conductive material in the case of particulate form, such as carbon nanoparticles, wherein the first conductive material having an average particle diameter (D 50) is preferably smaller than the average particle diameter (D 50) of the silicon nano-particles, for example, For example, the average particle diameter (D 50 ) of the first conductive material may be 5 nm to 40 nm, preferably 10 nm to 35 nm, and more preferably 15 nm to 30 nm. On the other hand, the particle shape is not limited to a specific shape, but refers to a shape that can be formed by aggregation or aggregation of carbon or the like. More specifically, it may have a spherical shape, a spherical shape, . However, the present invention is not limited to the above-mentioned form, but may be included in the case of the aggregated particle form.
한편, 제1 도전재가 카본나노파이버, 카본나노튜브 및 카본나노로드와 같이 섬유 형태인 경우, 상기 섬유의 너비가 실리콘 나노 입자의 평균 입자 직경(D50)보다 작은 것이 바람직하며, 예를 들면, 상기 제1 도전재의 너비가 5 ㎚ 내지 40 ㎚, 바람직하게는 10 ㎚ 내지 35 ㎚, 보다 바람직하게는 15 ㎚ 내지 30 ㎚일 수 있다. On the other hand, when the first conductive material is in the form of fibers such as carbon nanofibers, carbon nanotubes and carbon nanorods, the width of the fibers is preferably smaller than the average particle diameter (D 50 ) of the silicon nanoparticles. For example, The width of the first conductive material may be 5 nm to 40 nm, preferably 10 nm to 35 nm, and more preferably 15 nm to 30 nm.
상기 너비란, 도전재가 섬유 형태인 경우, 섬유 형태의 단위체를 원통형으로 볼 때, 상기 원통형 도전재의 단면의 지름으로 정의할 수 있다.The width may be defined as the diameter of the cross section of the cylindrical conductive member when the conductive member is in the form of a fiber and the unit form of the fiber in a cylindrical form.
상기 음극 활물질 층에 포함된 상기 제1 도전재는 상기 흑연계 활물질 100 중량부에 대하여, 0.01 중량부 내지 2.0 중량부, 바람직하게는 0.05 중량부 내지 1.0 중량부, 보다 바람직하게는 0.1 중량부 내지 0.8 중량부 포함될 수 있다. The first conductive material contained in the negative electrode active material layer may be added in an amount of 0.01 to 2.0 parts by weight, preferably 0.05 to 1.0 part by weight, more preferably 0.1 to 0.8 parts by weight, based on 100 parts by weight of the graphite- Weight part may be included.
본 발명에 있어서, 상기 음극 활물질 층에는 중량 평균 분자량이 서로 다른 2종 이상의 셀룰로오스계 화합물이 포함될 수 있다. 예를 들면, 상기 셀룰로오스계 화합물은 제1셀룰로오스계 화합물과, 상기 제1셀룰로오스계 화합물보다 높은 중량평균분자량을 갖는 제2셀룰로오스계 화합물을 포함할 수 있다. In the present invention, the negative electrode active material layer may contain two or more kinds of cellulose compounds having different weight average molecular weights. For example, the cellulosic compound may include a first cellulosic compound and a second cellulosic compound having a weight average molecular weight higher than that of the first cellulosic compound.
보다 구체적으로, 상기 제1 셀룰로오스계 화합물은 중량평균 분자량이 10,000 내지 500,000, 바람직하게는 15,000 내지 500,000, 보다 바람직하게는 20,000 내지 500,000, 보다 더 바람직하게는 20,000 내지 400,000 일 수 있다.More specifically, the first cellulosic compound may have a weight average molecular weight of 10,000 to 500,000, preferably 15,000 to 500,000, more preferably 20,000 to 500,000, and even more preferably 20,000 to 400,000.
또한, 상기 제2 셀룰로오스계 화합물은 중량 평균 분자량이 1,000,000 내지 2,500,000, 바람직하게는 1,100,000 내지 25,000,000, 보다 바람직하게는 1,200,000 내지 20,000,000, 보다 더 바람직하게는 1,500,000 내지 20,000,000 일 수 있다. The second cellulosic compound may have a weight average molecular weight of 1,000,000 to 2,500,000, preferably 1,100,000 to 25,000,000, more preferably 1,200,000 to 20,000,000, and still more preferably 1,500,000 to 20,000,000.
이때, 상기 중량평균 분자량(Mw)은 겔 투과 크로마토그래피(GPC)로 측정한 폴리스티렌 환산 중량 평균 분자량(Mw)을 의미한다. Herein, the weight average molecular weight (Mw) means a polystyrene reduced weight average molecular weight (Mw) measured by gel permeation chromatography (GPC).
상기 셀룰로오스계 화합물은 음극 활물질층에 포함되는 음극 활물질, 도전재 등의 성분들을 균일하게 분산시키기 위한 것이다. 셀룰로오스계 화합물이 음극 활물질 층을 구성하는 다른 성분들과 혼합되면, 음전하를 띄는 이온형태로 존재하게 된다. 이에 따라 셀룰로오스계 화합물 사이에 정전기적 척력이 발생하게 되어 음극 활물질 층 내에 각 성분들이 균일하게 분산될 수 있다. 다만, 셀룰로오스계 화합물은 중량평균분자량에 따라 상이한 사슬 길이를 가지는데, 사슬 길이에 따라 실리콘 나노 입자와 흑연계 활물질과의 혼화성에 차이가 발생한다. 따라서, 본 발명에 따른 음극에서 한 종류의 셀룰로오스계 화합물만을 사용할 경우, 실리콘 나노 입자와 흑연계 활물질이 모두 균일하게 분산되기 어렵다는 문제점이 있다.The cellulosic compound is for uniformly dispersing components such as a negative electrode active material and a conductive material contained in the negative electrode active material layer. When the cellulose compound is mixed with other components constituting the negative electrode active material layer, it is present in the form of a negatively charged ion. As a result, an electrostatic repulsive force is generated between the cellulosic compounds, so that the components can be uniformly dispersed in the negative active material layer. However, the cellulose-based compound has a different chain length depending on the weight-average molecular weight, and the miscibility of the silicon nanoparticles with the graphite-based active material varies depending on the chain length. Therefore, when only one kind of cellulose compound is used in the negative electrode according to the present invention, it is difficult to uniformly disperse both the silicon nanoparticles and the graphite-based active material.
구체적으로는 상대적으로 평균 입자 직경(D50)이 작은 상기 실리콘 나노 입자를 사슬길이가 긴 셀룰로오스계 화합물과 혼합하는 경우, 상기 셀룰로오스계 화합물과 상기 실리콘 나노 입자가 균일하게 혼합되지 못하고, 상기 셀룰로오스계 화합물 간에 응집 현상이 발생할 수 있다.Specifically, when the silicone nanoparticles having a relatively small average particle diameter (D 50 ) are mixed with a cellulose-based compound having a long chain length, the cellulose-based compound and the silicon nanoparticles can not be uniformly mixed, Coagulation phenomena may occur between the compounds.
또한, 상대적으로 평균 입자 직경(D50)이 큰 흑연계 활물질의 경우 사슬길이가 짧은 셀룰로오스계 화합물과 혼합되는 경우, 상기 셀룰로오스계 화합물의 사슬 길이가 상기 흑연계 활물질의 평균 입자 직경(D50) 보다 짧아 셀룰로오스계 화합물의 정전기적 척력이 약하게 발생하여 상기 흑연계 활물질이 균일하게 혼합되기 어렵다.In addition, relatively average particle diameter (D 50) the case where the mixing and short cellulosic compounds if the chain length of the large graphite-based active material, the cellulose-based average particle diameter of the chain length of the graphite-based active material of the compound (D 50) The electrostatic repulsive force of the cellulose compound is weak and it is difficult to uniformly mix the graphite-based active material.
따라서, 본 발명에서는 서로 다른 중량 평균 분자량을 가지는 2종 이상의 셀룰로오스계 화합물을 사용함으로써, 실리콘 나노 입자와 흑연계 활물질 모두에 대해서 우수한 분산성을 구현할 수 있도록 하였다. Therefore, in the present invention, by using two or more kinds of cellulose compounds having different weight average molecular weights, excellent dispersibility can be realized for both silicon nanoparticles and graphite-based active materials.
상기 제1 셀룰로오스계 화합물은 상기 흑연계 활물질 100 중량부에 대하여 0.01 중량부 내지 1 중량부, 바람직하게는 0.05 중량부 내지 0.5 중량부, 보다 바람직하게는 0.1 중량부 내지 0.3 중량부 포함될 수 있다.The amount of the first cellulosic compound may be 0.01 part by weight to 1 part by weight, preferably 0.05 part by weight to 0.5 part by weight, more preferably 0.1 part by weight to 0.3 part by weight based on 100 parts by weight of the graphite-based active material.
상기 제2 셀룰로오스계 화합물은 상기 흑연계 활물질 100 중량부에 대하여, 0.1 중량부 내지 5.0 중량부, 바람직하게는 0.1 중량부 내지 3.0 중량부, 보다 바람직하게는 0.5 중량부 내지 3.0 중량부 포함될 수 있다.The second cellulosic compound may be added in an amount of 0.1 to 5.0 parts by weight, preferably 0.1 to 3.0 parts by weight, more preferably 0.5 to 3.0 parts by weight based on 100 parts by weight of the graphite-based active material .
한편, 본 발명에 있어서, 상기 음극 활물질 층은, 필요에 따라, 바인더를 더 포함할 수 있다.Meanwhile, in the present invention, the negative electrode active material layer may further include a binder, if necessary.
상기 바인더는　음극 활물질 층 내부의 결착, 그리고 음극 활물질 층과 음극집전체와의 접착력 향상을 위해 사용되는 것이라면 특별한 한정없이 사용가능하다. 구체적인 예로는 상기 바인더로는 폴리비닐리덴플로라이드(PVDF), 폴리비닐알코올, 전분, 폴리비닐피롤리돈, 테트라플루오로에틸렌, 폴리에틸렌, 폴리프로필렌, 에틸렌-프로필렌-디엔 폴리머(EPDM), 술폰화-EPDM, 스티렌-부타디엔 고무(styrene-butadiene rubber, SBR), 아크릴계 공중합체, 불소계 고무 또는 이들의 다양한 공중합체 등을 들 수 있으며, 이들 중 1종 단독 또는 2종 이상의 혼합물이 사용될 수 있다. 상기 바인더는 상기 흑연계 활물질 100 중량부에 대하여 0.1 중량부 내지 5 중량부, 바람직하게는 0.1 중량부 내지 4 중량부, 보다 바람직하게는 0.2 중량부 내지 4 중량부로 포함되는 것일 수 있다.The binder can be used without particular limitation as long as it is used for binding inside the anode active material layer and for improving the adhesion between the anode active material layer and the anode current collector. Specific examples of the binder include polyvinylidene fluoride (PVDF), polyvinyl alcohol, starch, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM) -EPDM, styrene-butadiene rubber (SBR), acrylic copolymer, fluorocarbon rubber or various copolymers thereof. One or more of these may be used alone or as a mixture of two or more thereof. The binder may be included in an amount of 0.1 to 5 parts by weight, preferably 0.1 to 4 parts by weight, more preferably 0.2 to 4 parts by weight based on 100 parts by weight of the graphite-based active material.
본 발명에 있어서, 상기 음극 활물질 층은, 필요에 따라, 제2 도전재를 더 포함할 수 있다. 상기 제2 도전재는 상기 제1 도전재와 같이 음극에 도전성을 부여하기 위해 사용되는 것으로서, 본 발명에 따라 제조되는 리튬 이차전지에 있어서, 화학변화를 야기하지 않고 전자 전도성을 갖는 것이면 특별한 제한없이 사용 가능하다. 다만, 상기 제2 도전재는 상기 흑연계 활물질의 표면에 부착되거나, 음극 활물질 층을 구성하는 어떠한 화합물에도 부착되지 않고 음극 활물질 층 내부에 위치하는 것일 수도 있다. In the present invention, the negative electrode active material layer may further include a second conductive material, if necessary. The second conductive material is used for imparting conductivity to the cathode, such as the first conductive material. In the lithium secondary battery produced according to the present invention, the second conductive material can be used without any particular limitation as long as it has electron conductivity without causing chemical change. Do. However, the second conductive material may be attached to the surface of the graphite-based active material, or may be located inside the negative active material layer without being attached to any compound constituting the negative active material layer.
예를 들어, 상기 제2 도전재는 super C65, 카본 블랙, 아세틸렌블랙, 케첸블랙, 채널 블랙, 퍼네이스 블랙, 램프 블랙, 서머 블랙, 탄소섬유 등의 탄소계 물질; 구리, 니켈, 알루미늄, 은 등의 금속 분말 또는 금속 섬유; 산화아연 휘스커, 탄산칼슘 휘스커, 이산화티탄 휘스커, 산화규소 휘스커, 탄화규소 휘스커, 붕산 알루미늄 휘스커, 붕산 마그네슘 휘스커, 티탄산 칼륨 휘스커, 질화 규소 휘스커, 실리콘 카바이드 휘스커, 알루미나 휘스커 등의 침상 또는 가지상의 도전성 휘스커(Whisker); 산화티탄 등의 도전성 금속 산화물; 또는 폴리페닐렌 유도체 등의 전도성 고분자 등을 들 수 있으며, 이들 중 1종 단독 또는 2종 이상의 혼합물이 사용될 수 있다. For example, the second conductive material may be a carbon-based material such as super C65, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, Metal powder or metal fibers such as copper, nickel, aluminum and silver; The conductive whiskers such as zinc oxide whiskers, calcium carbonate whiskers, titanium dioxide whiskers, silicon oxide whiskers, silicon carbide whiskers, aluminum borate whiskers, magnesium borate whiskers, potassium titanate whiskers, silicon nitride whiskers, silicon carbide whiskers, alumina whiskers, (Whisker); Conductive metal oxides such as titanium oxide; And polyphenylene derivatives. These may be used alone or in admixture of two or more.
상기 제2 도전재는 상기 흑연계 활물질 100 중량부에 대하여 0.1 중량부 내지 5 중량부, 바람직하게는 0.1 중량부 내지 3 중량부, 보다 바람직하게는 0.5 중량부 내지 3 중량부로 포함될 수 있다. The second conductive material may be included in an amount of 0.1 to 5 parts by weight, preferably 0.1 to 3 parts by weight, more preferably 0.5 to 3 parts by weight based on 100 parts by weight of the graphite-based active material.
다음으로, 본 발명의 리튬 이차전지용 음극 제조방법에 대하여 설명한다.Next, a method of manufacturing a negative electrode for a lithium secondary battery of the present invention will be described.
음극 제조 방법Cathode manufacturing method
본 발명에 따른 리튬 이차전지용 음극 제조방법은, (1) 제1 혼합물을 형성하는 단계, (2) 제2 혼합물을 형성하는 단계, (3) 상기 제1 혼합물 및 제2 혼합물을 혼합하여 음극 활물질 슬러리를 형성하는 단계 및 (4) 음극 활물질 층을 형성하는 단계를 포함한다. 이하에서 각 단계들에 대해 구체적으로 설명하기로 한다. The method for manufacturing a negative electrode for a lithium secondary battery according to the present invention includes the steps of (1) forming a first mixture, (2) forming a second mixture, (3) mixing the first mixture and the second mixture to form a negative electrode active material Forming a slurry, and (4) forming a negative electrode active material layer. Hereinafter, each step will be described in detail.
(1) 제1 혼합물을 형성하는 단계(1) forming a first mixture
먼저, 실리콘 나노 입자, 제1 도전재, 제1 셀룰로오스계 화합물 및 용매를 혼합하여 제1 혼합물을 형성한다. 이때, 상기 실리콘 나노 입자, 제1 도전재, 제1 셀룰로오스계 화합물의 구체적인 내용은 상술한 바와 동일하다. First, the first mixture is formed by mixing the silicon nanoparticles, the first conductive material, the first cellulosic compound, and the solvent. Here, the specific contents of the silicon nanoparticles, the first conductive material, and the first cellulosic compound are the same as those described above.
즉, 상기 실리콘 나노 입자는 평균 입자 직경(D50)이 70 ㎚ 내지 300 ㎚, 바람직하게는 80 ㎚ 내지 300 ㎚, 보다 바람직하게는 90 ㎚ 내지 300 ㎚ 인 실리콘 나노 입자일 수 있으며, That is, the silicon nanoparticles may be silicon nanoparticles having an average particle diameter (D 50 ) of 70 nm to 300 nm, preferably 80 nm to 300 nm, more preferably 90 nm to 300 nm,
상기 제1 셀룰로오스계 화합물은 중량 평균 분자량이 10,000 내지 500,000, 바람직하게는 15,000 내지 500,000, 보다 바람직하게는 20,000 내지 500,000, 보다 더 바람직하게는 20,000 내지 400,000 인 것일 수 있다. The first cellulosic compound may have a weight average molecular weight of 10,000 to 500,000, preferably 15,000 to 500,000, more preferably 20,000 to 500,000, and even more preferably 20,000 to 400,000.
상기 용매로는 당해 기술분야에서 일반적으로 사용되는 용매일 수 있으며, 디메틸셀폭사이드(dimethyl sulfoxide, DMSO), 이소프로필 알코올(isopropyl alcohol), N-메틸피롤리돈(NMP), 아세톤(acetone) 또는 물 등을 들 수 있으며, 이들 중 1종 단독 또는 2종 이상의 혼합물이 사용될 수 있다. 상기 용매는 음극　활물질 슬러리의 도포성 및 공정성을 고려하여 적절한 점도를 갖도록 하는 양으로 포함되는 것이 바람직할 수 있다. Examples of the solvent include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, and the like. Water and the like, and one kind or a mixture of two or more kinds can be used. The solvent may be contained in an amount such that the solvent has an appropriate viscosity in consideration of the applicability and processability of the negative electrode active material slurry.
상기 제1 혼합물은 상기 실리콘 나노입자, 상기 제1 도전재 및 상기 제1 셀룰로오스계 화합물을 (1~100):(0.01~2.0):(0.01~2.0) 중량비로, 바람직하게는 (10~100):(0.01~1.5):(0.01~1.5) 중량비로, 보다 바람직하게는 (97~99):(0.5~1.5):(0.5~1.5) 중량비로 포함하는 것일 수 있다. 상기 중량비로 포함되는 경우, 상기 실리콘 나노입자가 상기 제1 혼합물 내에서 균일하게 분산될 수 있다. Wherein the first mixture contains the silicon nanoparticles, the first conductive material and the first cellulose compound in a weight ratio of (1 to 100): (0.01 to 2.0): (0.01 to 2.0) More preferably from (97 to 99): (0.5 to 1.5): (0.5 to 1.5) by weight, in terms of the weight ratio of (0.01 to 1.5): (0.01 to 1.5). When included in the weight ratio, the silicon nanoparticles may be uniformly dispersed in the first mixture.
(2) 제2 혼합물을 형성하는 단계(2) forming a second mixture
다음으로, 흑연계 활물질, 제2 셀룰로오스계 화합물 및 용매를 혼합하여 제2 혼합물을 형성한다. 이때, 상기 제2 혼합물 형성 단계는 제1 혼합물 형성단계 이후에 실시되어야 하는 것은 아니며, 제1 혼합물 형성단계 전 또는 제1 혼합물 형성단계와 동시에 실시되어도 무방하다. Next, the graphite-based active material, the second cellulosic compound, and the solvent are mixed to form a second mixture. At this time, the second mixture forming step is not necessarily performed after the first mixture forming step, and may be performed before the first mixture forming step or simultaneously with the first mixture forming step.
한편, 상기 흑연계 활물질, 제2 셀룰로오스계 화합물의 구체적인 내용은 상술한 바와 동일하다. 또한, 상기 제2 혼합물을 형성하는 단계에서 혼합되는 용매는 상기 제1 혼합물을 형성하는 단계에서 사용된 용매와 동일하다.The specific contents of the graphite-based active material and the second cellulosic compound are the same as those described above. In addition, the solvent mixed in the step of forming the second mixture is the same as the solvent used in the step of forming the first mixture.
즉, 상기 흑연계 활물질은 평균 입자 직경(D50)이 5㎛ 내지 50㎛, 바람직하게는 10㎛ 내지 40㎛, 보다 바람직하게는 15㎛ 내지 30㎛인 것일 수 있으며,That is, the graphite-based active material may have an average particle diameter (D 50 ) of 5 μm to 50 μm, preferably 10 μm to 40 μm, more preferably 15 μm to 30 μm,
상기 제2 셀룰로오스계 화합물은 중량 평균 분자량이 1,000,000 내지 2,500,000, 바람직하게는 1,100,000 내지 25,000,000, 보다 바람직하게는 1,200,000 내지 20,000,000, 보다 더 바람직하게는 1,500,000 내지 20,000,000 일 수 있다. The second cellulosic compound may have a weight average molecular weight of 1,000,000 to 2,500,000, preferably 1,100,000 to 25,000,000, more preferably 1,200,000 to 20,000,000, still more preferably 1,500,000 to 20,000,000.
상기 제2 혼합물은 제2 도전재를 더 포함할 수 있다. 이때, 상기 제2 도전재의 구체적인 내용은 상술한 바와 동일하다.The second mixture may further include a second conductive material. At this time, the specific content of the second conductive material is the same as described above.
상기 제2 혼합물은 상기 흑연계 활물질, 상기 제2 셀룰로오스계 화합물 및 상기 제2 도전재를 (1~100):(0.1~5):(0.1~5) 중량비로, 바람직하게는 (1~100):(0.5~3):(0.5~3) 중량비로, 보다 바람직하게는 (94~99):(0.5~3):(0.5~3) 중량비로 포함하는 것일 수 있다. 포함할 수 있다. 상기 중량비로 혼합되는 경우, 상기 흑연계 활물질이 상기 제2 혼합물 내에서 균일하게 분산될 수 있다.The second mixture contains the graphite-based active material, the second cellulosic compound and the second conductive material in a weight ratio of (1 to 100): (0.1 to 5) :( 0.1 to 5) (0.5 to 3): (0.5 to 3) weight ratio, more preferably (94 to 99) :( 0.5 to 3) :( 0.5 to 3) weight ratio. . When mixed in the weight ratio, the graphite-based active material can be uniformly dispersed in the second mixture.
(3) 음극 활물질 슬러리를 형성하는 단계(3) Step of forming a negative electrode active material slurry
다음으로, 상기 제1, 2 혼합물을 혼합하여 음극 활물질 슬러리를 형성한다.Next, the first and second mixture are mixed to form a negative electrode active material slurry.
상기 제1 혼합물 및 상기 제2 혼합물은 단계를 나누어 제조한 후에 최종적으로 혼합한다. 상기 실리콘 나노 입자 및 상기 흑연계 활물질을 동시에 혼합시키면, 상기 실리콘 나노 입자간 또는 상기 흑연계 활물질 간 응집 현상이 발생할 수 있다. 또한, 상기 실리콘 나노 입자는 상기 흑연계 활물질 간의 공극 사이에 위치하지 못하게 될 수 있다.The first mixture and the second mixture are prepared by dividing the steps and then finally mixed. When the silicon nanoparticles and the graphite-based active material are mixed at the same time, cohesion may occur between the silicon nanoparticles or the graphite-based active material. In addition, the silicon nanoparticles may not be positioned between the spaces between the graphite-based active materials.
따라서, 실리콘 나노 입자가 균일하게 분산되도록 사슬 길이가 짧은 제1 셀룰로오스계 화합물을 혼합하여 제1 혼합물을 형성하고, 흑연계 활물질이 균일하게 분산되도록 사슬 길이가 긴 제2 셀룰로오스계 화합물을 혼합하여 제2 혼합물을 형성하는 단계를 나누어 진행한다.Therefore, the first cellulose compound having a short chain length is mixed to uniformly disperse the silicon nanoparticles to form a first mixture, and a second cellulose compound having a long chain length is mixed to uniformly disperse the graphite- 2 mixture. ≪ / RTI >
이후, 상기 제1, 2 혼합물을 혼합하여, 음극 활물질 슬러리를 구성하는 성분들이 균일하게 분산되고, 상기 실리콘 나노 입자는 상기 흑연계 활물질 간의 공극 사이에 위치할 수 있다.Thereafter, the components constituting the negative electrode active material slurry are uniformly dispersed by mixing the first and second mixture, and the silicon nanoparticles may be positioned between the spaces between the graphite-based active materials.
상기 제1 혼합물 및 상기 제2 혼합물은 (5~15):(85~95), 바람직하게는 (7~13):(87~93), 보다 바람직하게는 (9~11):(89~91)의 중량비로 혼합될 수 있다. 상기 범위를 만족하도록 제1, 2 혼합물을 혼합하는 경우, 최종 형성되는 리튬 이차전지의 용량 특성 및 팽윤 억제 성능이 우수한 것을 확인할 수 있다.The first mixture and the second mixture may contain (5-15) :( 85-95), preferably (7-13) :( 87-93), more preferably (9-11) 91). ≪ / RTI > When the first and second mixtures are mixed so as to satisfy the above range, it can be confirmed that the capacity characteristics and the swelling suppressing performance of the finally formed lithium secondary battery are excellent.
상기 제1 혼합물 및 제2 혼합물은 혼합시, 상기 제1 혼합물에 포함된 고형분의 함량은 동등한 것이 바람직하다. 상기 제1, 2 혼합물이 혼합된 이후 음극 제조시 용매는 최종적으로 제거되고, 고형분을 이루는 흑연계 활물질, 제1, 2 도전재 및 제1, 2 셀룰로오스계 화합물만 잔류하게 되는데, 이때 상기 제1 혼합물 및 제2 혼합물의 고형분 함량은 동등하게 포함되어 있는 것이 바람직하다. 상기 제1, 2 혼합물의 고형분 함량이 동등하게 포함되어 있는 경우, 제1, 2 혼합물을 혼합하여 제조되는 음극 활물질 슬러리 내에 포함되는 각 성분들이 일정한 비율로 혼합될 수 있다.When the first mixture and the second mixture are mixed, the content of the solid content in the first mixture is preferably equal. After the first and second mixture are mixed, the solvent during the preparation of the negative electrode is finally removed, and only the graphite-based active material, the first and second conductive materials, and the first and second cellulose-based compounds that constitute the solid component remain. It is preferable that the solid content of the mixture and the second mixture are equally contained. When the solid contents of the first and second mixture are equally contained, the respective components contained in the negative electrode active material slurry produced by mixing the first and second mixture may be mixed at a certain ratio.
상기 음극 활물질 슬러리를 형성하는 단계에서 바인더를 더 첨가할 수 있다. 바인더는 음극 활물질 층 내부, 상기 음극 활물질 층와 상기 음극 집전체 간의 접착력을 향상시키기 위해 첨가될 수 있으며, 바인더의 구체적인 내용은 상술한 바와 동일하다.In the step of forming the negative electrode active material slurry, a binder may be further added. The binder may be added to improve the adhesion between the anode active material layer and the anode active material layer and the anode current collector, and the specific content of the binder is the same as described above.
상기 바인더는 상기 흑연계 활물질 100 중량부에 대하여 0.1 중량부 내지 5 중량부, 바람직하게는 0.1 중량부 내지 4 중량부, 보다 바람직하게는 0.2 중량부 내지 4 중량부 범위로 첨가될 수 있다. The binder may be added in an amount of 0.1 to 5 parts by weight, preferably 0.1 to 4 parts by weight, more preferably 0.2 to 4 parts by weight based on 100 parts by weight of the graphite-based active material.
(4) 음극 활물질 층 형성단계(4) Negative electrode active material layer formation step
다음으로, 음극 활물질 층을 형성한다.Next, a negative electrode active material layer is formed.
상기와 같이 형성된 음극 활물질 슬러리를 음극 집전체 상에 도포하여 음극 활물질층을 형성한다. 상기 도포는, 당해 기술 분야에 알려져 있는 통상적인 슬러리 코팅법을 통해 이루어질 수 있다. 상기 슬러리 코팅법의 예로는 바 코팅, 스핀코팅, 롤 코팅, 슬롯다이 코팅, 또는 스프레이 코팅 등을 들 수 있으나, 이에 한정되는 것은 아니다.The negative electrode active material slurry thus formed is coated on the negative electrode collector to form a negative electrode active material layer. The application can be accomplished through conventional slurry coating methods known in the art. Examples of the slurry coating method include, but are not limited to, bar coating, spin coating, roll coating, slot die coating, or spray coating.
상기 음극 활물질 슬러리가 음극집전체 상에 도포된 후, 건조 및 압연함으로써 음극 활물질 층을 형성하여 리튬 이차전지용 음극이 제조될 수 있다.The negative electrode active material slurry is coated on the negative electrode current collector, followed by drying and rolling to form a negative electrode active material layer, thereby manufacturing a negative electrode for a lithium secondary battery.
리튬 이차 전지Lithium secondary battery
다음으로 본 발명에 따른 리튬 이차전지에 대해 설명한다.Next, a lithium secondary battery according to the present invention will be described.
본 발명에 따른 리튬 이차전지는 음극, 양극, 상기 음극과 양극 사이에 개재되어 위치하는 세퍼레이터 및 비수전해질을 포함하며, 이때, 상기 음극은 상술한 본 발명에 따른 음극이다. 음극에 대한 구체적인 내용은 상술한 바와 동일하므로, 이하에서는 나머지 구성요소들에 대해서 설명한다. The lithium secondary battery according to the present invention comprises a negative electrode, a positive electrode, a separator interposed between the negative electrode and the positive electrode, and a nonaqueous electrolyte, wherein the negative electrode is the negative electrode according to the present invention. Since the details of the cathode are the same as those described above, the remaining components will be described below.
상기 양극은 양극집전체 및 상기 양극집전체 상에 형성되며, 양극 활물질을 포함하는 양극 활물질 층을 포함한다. The positive electrode includes a positive electrode collector and a positive electrode active material layer formed on the positive electrode collector and including a positive electrode active material.
상기와 같은 양극은 당해 기술 분야에 알려진 통상의 양극 제조방법에 따라 제조될 수 있으며, 예를 들면, 양극 활물질, 도전재, 바인더, 용매가 포함된 양극 활물질 슬러리를 양극집전체 상에 도포한 후, 건조 및 압연함으로써 제조될 수 있다.The positive electrode may be produced according to a conventional anodizing method known in the art. For example, a positive electrode active material slurry containing a positive electrode active material, a conductive material, a binder, and a solvent is applied on a positive electrode collector , ≪ / RTI > dried and rolled.
이때. 상기 양극집전체로는 전지에 화학적 변화를 유발하지 않으면서 도전성을 가진 것이라면 특별한 제한없이 사용가능하며, 예를 들어 스테인리스 스틸, 알루미늄, 니켈, 티탄, 소성 탄소 또는 알루미늄이나, 스테인레스 스틸 표면에 탄소, 니켈, 티탄 또는 은 등으로 표면 처리한 것 등이 사용될 수 있다.At this time. The positive electrode current collector may be any one of stainless steel, aluminum, nickel, titanium, sintered carbon or aluminum, and may be made of stainless steel, carbon, Nickel, titanium or silver, or the like may be used.
또, 상기 양극집전체는 3㎛ 내지 500㎛, 또는 4㎛ 내지 400㎛, 보다 바람직하게는 5㎛ 내지 300㎛의 두께를 가질 수 있다. 상기 양극집전체의 두께는 상기 범위에 반드시 한정되는 것은 아니고, 리튬 이차전지용 양극의 전체 용량 등에 따라서 그 범위가 달라질 수 있다.The cathode current collector may have a thickness of 3 탆 to 500 탆, or 4 탆 to 400 탆, more preferably 5 탆 to 300 탆. The thickness of the positive electrode current collector is not necessarily limited to the above range, but the range may vary depending on the total capacity of the positive electrode for a lithium secondary battery and the like.
상기 양극집전체 표면 상에 미세한 요철을 형성하여 양극 활물질의 접착력을 높일 수도 있으며, 예를 들어 필름, 시트, 호일, 네트, 다공질체, 발포체, 부직포체 등 다양한 형태로 사용될 수 있다.It is possible to increase the adhesion of the positive electrode active material by forming fine irregularities on the surface of the positive electrode current collector and it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams and nonwoven fabrics.
또, 상기 양극 활물질로는 리튬의 가역적인 인터칼레이션 및 디인터칼레이션이 가능한 화합물(리티에이티드 인터칼레이션 화합물)이 사용될 수 있다. 구체적으로는 코발트, 망간, 니켈 또는 이들의 조합의 금속과 리튬과의 복합 산화물 중 1종 이상의 것을 사용할 수 있으며, 보다 구체적인 예로는 하기 화학식 1로 표시되는 리튬 금속 화합물이 사용될 수 있다.As the cathode active material, a compound capable of reversibly intercalating and deintercalating lithium (a lithium intercalation compound) may be used. Concretely, it is possible to use at least one of complex oxides of metal and lithium of cobalt, manganese, nickel or a combination thereof. More specific examples thereof may be lithium metal compounds represented by the following formula (1).
[화학식 1][Chemical Formula 1]
LixMyM'zO2 LixMyM'zO 2
(상기 화학식 1에서, 상기 M 및 M'은 각각 독립적으로 Fe, Ni, Co, Mn, Cr, Zr, Nb, Cu, V, Mo, Ti, Zn, Al, Ga, Mg, B 및 이들의 조합으로 이루어진 군에서 선택되는 원소이고, 상기 x, y, z는 각각 독립적인 산화물 조성 원소들의 원자분율로서, 0<x≤1, 0<y≤1, 0<z≤1, 0<x+y+z≤2이다.)M and M 'are independently Fe, Ni, Co, Mn, Cr, Zr, Nb, Cu, V, Mo, Ti, Zn, Al, Ga, Mg, B, 0 < y < 1, 0 < z < 1, 0 &lt; x + y + z? 2.)
이중에서도 전지의 용량 특성 및 안정성을 높일 수 있다는 점에서 상기 양극 활물질은 LiCoO2, LiMnO2, LiNiO2, 리튬니켈망간코발트 산화물(예를 들면, Li(Ni0.6Mn0.2Co0.2)O2, LiNi0.5Mn0.3Co0.2O2, 또는 LiNi0.8Mn0.1Co0.1O2　등), 또는 리튬니켈코발트알루미늄 산화물(예를 들면, LiNi0.8Co0.15Al0.05O2　등) 및 이들의 혼합물로 이루어진 군에서 선택되는 것이 바람직할 수 있다.LiCoO 2 , LiMnO 2 , LiNiO 2 , lithium nickel manganese cobalt oxide (for example, Li (Ni 0.6 Mn 0.2 Co 0.2 ) O 2 , LiNi 0.5 Mn 0.3 Co 0.2 O 2 , or LiNi 0.8 Mn 0.1 Co 0.1 O 2 ), or lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 0.15 Al 0.05 O 2 ), and mixtures thereof. May be desirable.
상기 양극 활물질은 상기 양극 활물질층 총 중량에 대하여 69 내지 98중량%로 포함될 수 있다.The positive electrode active material may be contained in an amount of 69 to 98% by weight based on the total weight of the positive electrode active material layer.
상기 도전재는 양극에 도전성을 부여하기 위해 사용되는 것으로서, 구성되는 전지에 있어서, 화학변화를 야기하지 않고 전자 전도성을 갖는 것이면 특별한 제한없이 사용가능하다. 구체적인 예로는 천연 흑연이나 인조 흑연 등의 흑연; 카본 블랙, 아세틸렌블랙, 케첸블랙, 채널 블랙, 퍼네이스 블랙, 램프 블랙, 서머 블랙, 탄소섬유 등의 탄소계 물질; 구리, 니켈, 알루미늄, 은 등의 금속 분말 또는 금속 섬유; 산화아연 휘스커, 탄산칼슘 휘스커, 이산화티탄 휘스커, 산화규소 휘스커, 탄화규소 휘스커, 붕산 알루미늄 휘스커, 붕산 마그네슘 휘스커, 티탄산 칼륨 휘스커, 질화 규소 휘스커, 실리콘 카바이드 휘스커, 알루미나 휘스커 등의 침상 또는 가지상의 도전성 휘스커(Whisker); 산화티탄 등의 도전성 금속 산화물; 또는 폴리페닐렌 유도체 등의 전도성 고분자 등을 들 수 있으며, 이들 중 1종 단독 또는 2종 이상의 혼합물이 사용될 수 있다.The conductive material is used for imparting conductivity to the anode. The conductive material is not particularly limited as long as it has electron conductivity without causing chemical change. Specific examples thereof include graphite such as natural graphite and artificial graphite; Carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, summer black and carbon fiber; Metal powder or metal fibers such as copper, nickel, aluminum and silver; The conductive whiskers such as zinc oxide whiskers, calcium carbonate whiskers, titanium dioxide whiskers, silicon oxide whiskers, silicon carbide whiskers, aluminum borate whiskers, magnesium borate whiskers, potassium titanate whiskers, silicon nitride whiskers, silicon carbide whiskers, alumina whiskers, (Whisker); Conductive metal oxides such as titanium oxide; And polyphenylene derivatives. These may be used alone or in admixture of two or more.
상기 도전재는 상기 양극 활물질층 총 중량에 대하여 30중량% 이하, 혹은 1 내지 30중량%로 포함될 수 있다.The conductive material may be contained in an amount of 30% by weight or less, or 1 to 30% by weight based on the total weight of the cathode active material layer.
또, 상기 바인더는 양극 활물질 입자들 간의 부착 및 양극 활물질과 집전체와의 접착력을 향상시키는 역할을 한다. 구체적인 예로는 폴리비닐리덴플로라이드(PVDF), 폴리비닐알코올, 카르복시메틸셀룰로우즈(CMC), 전분, 히드록시프로필셀룰로우즈, 재생 셀룰로우즈, 폴리비닐피롤리돈, 테트라플루오로에틸렌, 폴리에틸렌, 폴리프로필렌, 에틸렌-프로필렌-디엔 폴리머(EPDM), 술폰화-EPDM, 스티렌-부타디엔 고무, 불소 고무 또는 이들의 다양한 공중합체 등을 들 수 있으며, 이들 중 1종 단독 또는 2종 이상의 혼합물이 사용될 수 있다. 상기 바인더는 양극 활물질층 총 중량에 대하여 30 중량% 이하, 혹은 1 중량% 내지 30 중량%로 포함될 수 있다.In addition, the binder serves to improve the adhesion between the positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, There may be mentioned polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, fluorine rubber or various copolymers thereof. Can be used. The binder may be contained in an amount of 30% by weight or less, or 1% by weight to 30% by weight based on the total weight of the positive electrode active material layer.
한편, 상기 리튬 이차전지에 있어서, 세퍼레이터는 통상 리튬 이차전지에서 세퍼레이터로 사용되는 것이라면 특별한 제한없이 사용가능하며, 특히 전해질의 이온 이동에 대하여 저저항이면서 전해액 함습 능력이 우수한 것이 바람직하다. 구체적으로는 다공성 고분자 필름, 예를 들어 에틸렌 단독중합체, 프로필렌 단독중합체, 에틸렌/부텐 공중합체, 에틸렌/헥센 공중합체 및 에틸렌/메타크릴레이트 공중합체 등과 같은 폴리올레핀계 고분자로 제조한 다공성 고분자 필름 또는 이들의 2층 이상의 적층 구조체가 사용될 수 있다. 또 통상적인 다공성 부직포, 예를 들어 고융점의 유리 섬유, 폴리에틸렌테레프탈레이트 섬유 등으로 된 부직포가 사용될 수도 있다.Meanwhile, in the lithium secondary battery, the separator is not particularly limited as long as it is used as a separator in a lithium secondary battery. In particular, it is preferable that the separator is low in resistance against ion movement of the electrolyte and excellent in electrolyte wettability. Specifically, porous polymer films such as porous polymer films made of polyolefin-based polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers and ethylene / methacrylate copolymers, May be used. Further, a nonwoven fabric made of a conventional porous nonwoven fabric, for example, glass fiber of high melting point, polyethylene terephthalate fiber, or the like may be used.
본 발명에서 사용되는 전해질로는 리튬 이차전지 제조시 사용 가능한 유기계 액체 전해질, 무기계 액체 전해질, 고체 고분자 전해질, 겔형 고분자 전해질, 고체 무기 전해질, 용융형 무기 전해질 등을 들 수 있으며, 이들로 한정되는 것은 아니다.Examples of the electrolyte used in the present invention include an organic-based liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, and a molten inorganic electrolyte that can be used in the production of a lithium secondary battery. no.
구체적으로, 상기 전해질은 유기 용매 및 리튬염을 포함할 수 있다.Specifically, the electrolyte may include an organic solvent and a lithium salt.
상기 유기용매로는 전지의 전기 화학적 반응에 관여하는 이온들이 이동할 수 있는 매질 역할을 할 수 있는 것이라면 특별한 제한없이 사용될 수 있다. 구체적으로 상기 유기 용매로는, 메틸 아세테이트(methyl acetate), 에틸 아세테이트(ethyl acetate), γ-부티로락톤(γ-butyrolactone), ε-카프로락톤(ε-caprolactone) 등의 에스테르계 용매; 디부틸 에테르(dibutyl ether) 또는 테트라히드로퓨란(tetrahydrofuran) 등의 에테르계 용매; 시클로헥사논(cyclohexanone) 등의 케톤계 용매; 벤젠(benzene), 플루오로벤젠(fluorobenzene) 등의 방향족 탄화수소계 용매; 디메틸카보네이트(dimethylcarbonate, DMC), 디에틸카보네이트(diethylcarbonate, DEC), 메틸에틸카보네이트(methylethylcarbonate, MEC), 에틸메틸카보네이트(ethylmethylcarbonate, EMC), 에틸렌카보네이트(ethylene carbonate, EC), 프로필렌카보네이트(propylene carbonate, PC) 등의 카보네이트계 용매 등이 사용될 수 있다.The organic solvent may be used without limitation as long as it can act as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate,? -Butyrolactone and? -Caprolactone; Ether solvents such as dibutyl ether or tetrahydrofuran; Ketone solvents such as cyclohexanone; Aromatic hydrocarbon solvents such as benzene and fluorobenzene; Dimethyl carbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), propylene carbonate PC) and the like can be used.
이중에서도 카보네이트계 용매가 바람직하고, 전지의 충방전 성능을 높일 수 있는 높은 이온전도도 및 고유전율을 갖는 환형 카보네이트(예를 들면, 에틸렌카보네이트 또는 프로필렌카보네이트 등)와, 저점도의 선형 카보네이트계 화합물(예를 들면, 에틸메틸카보네이트, 디메틸카보네이트 또는 디에틸카보네이트 등)의 혼합물이 보다 바람직하다.Among these, a carbonate-based solvent is preferable, and a cyclic carbonate (for example, ethylene carbonate or propylene carbonate) having a high ionic conductivity and a high dielectric constant, for example, such as ethylene carbonate or propylene carbonate, For example, ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate) is more preferable.
또, 상기 리튬염은 리튬 이차 전지에서 사용되는 리튬 이온을 제공할 수 있는 화합물이라면 특별한 제한없이 사용될 수 있다. 구체적으로 상기 리튬염은, LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2. LiCl, LiI, 또는 LiB(C2O4)2　등이 사용될 수 있다. 상기 리튬염은 상기 전해질 내에 대략 0.6mol% 내지 2mol%의 농도로 포함되는 것이 바람직하다.In addition, the lithium salt can be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt, LiPF 6, LiClO 4, LiAsF 6, LiBF 4, LiSbF 6, LiAl0 4, LiAlCl 4, LiCF 3 SO 3, LiC 4 F 9 SO 3, LiN (C 2 F 5 SO 3) 2 , LiN (C 2 F 5 SO 2) 2, LiN (CF 3 SO 2) 2. LiCl, LiI, or LiB (C 2 O 4 ) 2 may be used. The lithium salt is preferably contained in the electrolyte at a concentration of about 0.6 mol% to 2 mol%.
상기 전해질에는 상기 전해질 구성 성분들 외에도 전지의 수명특성 향상, 전지 용량 감소 억제, 전지의 방전 용량 향상 등을 목적으로 예를 들어, 피리딘, 트리에틸포스파이트, 트리에탄올아민, 환상 에테르, 에틸렌 디아민, n-글라임(glyme), 헥사인산 트리아미드, 니트로벤젠 유도체, 유황, 퀴논 이민 염료, N-치환 옥사졸리디논, N,N-치환 이미다졸리딘, 에틸렌 글리콜 디알킬 에테르, 암모늄염, 피롤, 2-메톡시 에탄올 또는 삼염화 알루미늄 등의 첨가제가 1종 이상 더 포함될 수도 있다. 이때 상기 첨가제는 전해질 총 중량에 대하여 0.1중량% 내지 5 중량%로 포함될 수 있다.The electrolytes include, for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, n-propylamine, and the like for the purpose of improving lifetime characteristics of the battery, N, N-substituted imidazolidine, ethylene glycol dialkyl ethers, ammonium salts, pyrroles, 2-ethylhexyl glycols, glycols such as glyme, hexa phosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, - methoxyethanol or aluminum trichloride may be further included. The additive may be included in an amount of 0.1 wt% to 5 wt% based on the total weight of the electrolyte.
상기와 같은 구성을 갖는 리튬 이차전지는, 상기 양극과 상기 음극 사이에 분리막을 개재하여 전극 조립체를 제조하고, 상기 전극 조립체를 케이스 내부에 위치시킨 후, 케이스 내부로 전해액을 주입함으로써 제조될 수 있다.The lithium secondary battery having the above structure can be manufactured by manufacturing an electrode assembly with a separator interposed between the positive electrode and the negative electrode, positioning the electrode assembly in the case, and injecting an electrolyte into the case .
상기한 바와 같이 본 발명에 따른 음극을 포함하는 리튬 이차전지는 우수한 방전 용량, 출력 특성 및 용량 유지율을 안정적으로 나타내기 때문에, 휴대전화, 노트북 컴퓨터, 디지털 카메라 등의 휴대용 기기, 및 하이브리드 전기자동차 등의 전기 자동차 분야 등에 유용하다.As described above, since the lithium secondary battery including the negative electrode according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, it can be used in portable devices such as mobile phones, notebook computers, digital cameras, and hybrid electric vehicles And the like.
이에 따라, 본 발명의 다른 일 구현예에 따르면, 상기 리튬 이차전지를 단위 셀로 포함하는 전지 모듈 및 이를 포함하는 전지팩을 제공한다.According to another aspect of the present invention, there is provided a battery module including the lithium secondary battery as a unit cell and a battery pack including the same.
상기 전지모듈 또는 전지팩은 파워 툴(Power Tool); 전기자동차(Electric Vehicle, EV), 하이브리드 전기자동차(Hybrid Electric Vehicle, HEV), 및 플러그인 하이브리드 전기자동차(Plug-in Hybrid Electric Vehicle, PHEV)를 포함하는 전기차; 또는 전력 저장용 시스템 중 어느 하나 이상의 중대형 디바이스 전원으로 이용될 수 있다.　The battery module or the battery pack may include a power tool; An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), and a plug-in hybrid electric vehicle (PHEV); Or a power storage system, as shown in FIG.
이하, 본 발명이 속하는 기술 분야에서 통상의 지식을 가진 자가 용이하게 실시할 수 있도록 본 발명의 실시예에 대하여 상세히 설명한다. 그러나 본 발명은 여러 가지 상이한 형태로 구현될 수 있으며 여기에서 설명하는 실시예에 한정되지 않는다.Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.
[실시예][Example]
실시예 1Example 1
<음극 활물질 슬러리 제조>&Lt; Preparation of negative electrode active material slurry &
평균 입자 직경(D50)이 110 ㎚인 실리콘 나노 입자, 너비가 20nm 카본나노튜브 및 CMC(GL CHEM 社, SG-L02, 중량평균 분자량 300,000)를 98.0:1.0:1.0의 중량비로 물을 용매로 혼합하여 제1 슬러리를 제조하였다(제1슬러리의 고형분 함량은 45wt% 이다). 이후, 평균 입자 직경(D50)이 20 ㎛인 인조흑연(Shanshan 社, LC1)과 도전재 Super C65, CMC(Daicel 社, 2200, 중량평균 분자량 1,260,000)을 98.0:0.8:1.2 중량비로 물을 용매로 혼합하여 제2 슬러리를 제조하였다(제2 슬러리의 고형분 함량은 45wt% 이다). 상기 제1 슬러리 및 제2 슬러리를 10:90 중량비로 혼합하고, 바인더(Zeon사, BM-L301)를 상기 제1, 2 슬러리를 혼합한 총 중량 100 중량부 대비 2.5 중량부로 후첨하여 음극 활물질 슬러리를 제조하였다. Silicone nanoparticles having an average particle diameter (D 50 ) of 110 nm, carbon nanotubes having a width of 20 nm, and CMC (GL CHEM, SG-L02, weight average molecular weight: 300,000) were mixed in a weight ratio of 98.0: To prepare a first slurry (the solid content of the first slurry is 45 wt%). Thereafter, a mixture of artificial graphite (LC1) (Shanshan, LC1) having an average particle diameter (D 50 ) of 20 탆 and conductive super C65 and CMC (Daicel, 2200, weight average molecular weight 1,260,000) To prepare a second slurry (the solid content of the second slurry is 45 wt%). The first slurry and the second slurry were mixed at a weight ratio of 10:90 and 2.5 parts by weight of a binder (Zeon Co., BM-L301) was added to a total weight of 100 parts by weight of the first and second slurries to prepare an anode active material slurry .
<음극 제조>&Lt; Preparation of negative electrode &
상기 제조된 음극 활물질 슬러리를, 8㎛인 음극 집전체인 구리 금속 박막에 순환공기의 온도를 80℃로 설정하여 도포, 건조하였다. 이어서, 압연(roll press)하고 60℃의 진공 오븐에서 24시간 동안 건조하여 음극을 제조하였다. The prepared negative electrode active material slurry was applied to a copper metal thin film as an anode current collector having a thickness of 8 占 퐉 by setting the circulating air temperature at 80 占 폚 and dried. Then, the resultant was rolled and dried in a vacuum oven at 60 DEG C for 24 hours to prepare a negative electrode.
<리튬이차전지 제조>&Lt; Preparation of lithium secondary battery &
제조된 음극과 대응되는 NCM523 (L&F신소재사, NE-X10S) 기반의 양극을 준비하고 양극과 음극 사이에 두께가 12 ㎛인 세라믹 코팅 분리막 (LG화학사, B12)를 개재하여 bicell을 만들고 이를 적층하여 stack & folding 셀을 제작하였다. 이를 88 ㎛두께의 파우치에 투입하고 전해액을 주입하여 리튬이차전지를 완성하였다. 완성된 전지의 설계 용량은 3200mAh였다.An anode based on NCM523 (L & F Advanced Materials Co., NE-X10S) corresponding to the prepared cathode was prepared, and a bicell was formed between a cathode and an anode through a ceramic coating separator (LG Chem, B12) having a thickness of 12 쨉 m. stack & folding cell. This was injected into a 88 .mu.m thick pouch and an electrolyte was injected to complete the lithium secondary battery. The design capacity of the completed battery was 3200 mAh.
실시예 2Example 2
음극 활물질 슬러리를 제조할 때, 인조흑연(Shanshan 社, LC1)과 도전재 Super C65 및 CMC(Nippon paper社, MAC800LC, 중량 평균 분자량 1,880,000)를 98.0:1.0:1.0 중량비로 물을 용매로 혼합하여 제2 슬러리를 제조한 것을 제외하고는, 실시예 1과 동일한 방법으로 음극 활물질 슬러리, 음극 및 리튬이차전지를 제조하였다.In preparing the negative electrode active material slurry, water was mixed with a solvent of synthetic graphite (Shanshan, LC1) and a conductive material Super C65 and CMC (Nippon paper, MAC800LC, weight average molecular weight 1,880,000) at a weight ratio of 98.0: 1.0: 2 slurry, a negative electrode active material slurry, a negative electrode, and a lithium secondary battery were prepared in the same manner as in Example 1. [
실시예 3Example 3
음극 활물질 슬러리를 제조할 때, 인조흑연(Shanshan 社, LC1)과 도전재 Super C65 및 CMC(GL Chem 社, GB-S01, 중량평균 분자량 1,450,000)를 98.0:0.8:1.2 중량비로 물을 용매로 혼합하여 제2 슬러리를 제조한 것을 제외하고는, 실시예 1과 동일한 방법으로 음극 활물질 슬러리, 음극 및 리튬이차전지를 제조하였다. In preparing the negative electrode active material slurry, water was mixed with a solvent of 98.0: 0.8: 1.2 by weight of artificial graphite (Shanshan, LC1) and conductive super C65 and CMC (GL Chem, GB- To prepare a negative electrode active material slurry, a negative electrode and a lithium secondary battery in the same manner as in Example 1, except that the second slurry was prepared.
실시예 4Example 4
음극 활물질 슬러리를 제조할 때, 평균 입자 직경(D50)이 300 ㎚인 실리콘 나노 입자, 너비가 20nm 카본나노튜브 및 CMC(Daiichi 社, H1496A, 중량평균 분자량 500,000)을 98.0:1.0:1.0의 비율로 물을 용매로 혼합하여 제1 슬러리를 제조한 것을 제외하고는, 실시예 1과 동일한 방법으로 음극 활물질 슬러리, 음극 및 리튬이차전지를 제조하였다.Silicon nanoparticles having an average particle diameter (D 50 ) of 300 nm, carbon nanotubes having a width of 20 nm, and CMC (Daiichi Co., H1496A, weight average molecular weight 500,000) were mixed in a ratio of 98.0: 1.0: 1.0 A negative electrode and a lithium secondary battery were prepared in the same manner as in Example 1, except that water was mixed with a solvent to prepare a first slurry.
실시예 5Example 5
음극활물질 슬러리를 제조할 때, 인조흑연(Shanshan 社, LC1)과 도전재 Super C65 및 CMC(Nippon paper社, MAC300LC, 중량평균 분자량 1,100,000)를 98.0:0.8:1.2 중량비로 물을 용매로 혼합하여 제2 슬러리를 제조한 것을 제외하고는, 실시예 1과 동일한 방법으로 음극 활물질 슬러리, 음극 및 리튬이차전지를 제조하였다.In preparing the negative electrode active material slurry, water was mixed with a solvent of 98.0: 0.8: 1.2 by weight of artificial graphite (Shanshan, LC1) and conductive super C65 and CMC (Nippon paper, MAC300LC, weight average molecular weight 1,100,000) 2 slurry, a negative electrode active material slurry, a negative electrode, and a lithium secondary battery were prepared in the same manner as in Example 1. [
[비교예][Comparative Example]
비교예 1Comparative Example 1
실시예 1에서 제1 슬러리를 제조하는 단계에서 CMC(GL CHEM사, SG-L02, 중량평균 분자량 300,000) 대신 CMC(Daicel 社, 2200, 중량평균 분자량 1,260,000)을 사용한 것을 제외하고는 실시예 1과 동일한 방법으로 음극 활물질 슬러리를 제조한 후, 동일한 방법으로 음극 및 리튬이차전지를 제조하였다.Example 1 was repeated except that CMC (Daicel Co., 2200, weight average molecular weight: 1,260,000) was used in place of CMC (GL CHEM, SG-L02, weight average molecular weight 300,000) in the step of preparing the first slurry in Example 1 After the negative electrode active material slurry was prepared in the same manner, a negative electrode and a lithium secondary battery were produced in the same manner.
비교예 2Comparative Example 2
실시예 1에서 평균 입자 직경(D50)이 110 ㎚인 실리콘 나노 입자 대신 평균 입자 직경(D50)이 10㎛인 실리콘 입자를 사용한 것을 제외하고는 실시예 1과 동일한 방법으로 음극 활물질 슬러리를 제조한 후, 동일한 방법으로 음극 및 리튬이차전지를 제조하였다.A negative electrode active material slurry was prepared in the same manner as in Example 1, except that silicon particles having an average particle diameter (D 50 ) of 10 μm were used instead of the silicon nanoparticles having an average particle diameter (D 50 ) of 110 nm in Example 1 After that, a negative electrode and a lithium secondary battery were produced in the same manner.
비교예 3Comparative Example 3
실시예 1에서 제1 슬러리를 제조하는 단계에서 CMC(GL CHEM사, SG-L02, 중량평균 분자량 300,000)를 사용하지 않고, 평균 입자 직경(D50)이 110 ㎚인 실리콘 나노 입자 및 너비가 20nm 카본나노튜브를 99.0:1.0의 중량비로 물을 용매로 혼합하여 제1 슬러리를 제조하였고(제1슬러리의 고형분 함량은 45wt% 이다), 제2 슬러리를 제조하는 단계에서 CMC(Daicel, 2200, 중량평균 분자량 1,260,000)를 사용하지 않고, 평균 입자 직경(D50)이 20 ㎛인 인조흑연(Shanshan 社, LC1)과 도전재 Super C65를 99.0:1.0 중량비로 물을 용매로 혼합하여 제2 슬러리를 제조하였다(제2슬러리의 고형분 함량은 45wt% 이다). 이를 제외하고는, 실시예 1과 동일한 방법으로 음극 활물질 슬러리를 제조한 후, 동일한 방법으로 음극 및 리튬이차전지를 제조하였다. Silicone nanoparticles having an average particle diameter (D 50 ) of 110 nm and a width of 20 nm were used without using CMC (GL CHEM, SG-L02, weight average molecular weight 300,000) in the step of preparing the first slurry in Example 1 Carbon nanotubes were mixed with water at a weight ratio of 99.0: 1.0 with a solvent to prepare a first slurry (the solid content of the first slurry was 45 wt%). In the step of preparing the second slurry, CMC (Daicel, 2200, weight Artificial graphite (Shanshan, LC1) having an average particle diameter (D 50 ) of 20 탆 and a conductive material Super C65 were mixed at a weight ratio of 99.0: 1.0 by weight in a solvent, (The solid content of the second slurry is 45 wt%). Except for this, the negative electrode active material slurry was prepared in the same manner as in Example 1, and then a negative electrode and a lithium secondary battery were produced in the same manner.
비교예 4Comparative Example 4
실시예 1에서 제2 슬러리를 제조하는 단계에서 CMC(Daicel 社, 2200, 중량평균 분자량 1,260,000)를 사용하지 않고, CMC(GL Chem사, SG-L02, 중량평균 분자량 300,000)을 사용한 것을 제외하고 실시예 1과 동일한 방법으로 음극 활물질 슬러리를 제조한 후, 동일한 방법으로 음극 및 리튬이차전지를 제조하였다.Except that CMC (GL Chem, SG-L02, weight average molecular weight 300,000) was used without using CMC (Daicel Co., 2200, weight average molecular weight 1,260,000) in the step of preparing the second slurry in Example 1 The negative electrode active material slurry was prepared in the same manner as in Example 1, and then a negative electrode and a lithium secondary battery were prepared in the same manner.
[실험예][Experimental Example]
실험예: 전지의 충방전 용량, 전극 두께 변화율의 평가. Experimental Example: Evaluation of charge / discharge capacity and electrode thickness change rate of a battery.
실시예 1 ~ 5 및 비교예 1 ~ 4의 전지에 대해 1C/1C로 3.0~4.2V 구간에서 충··방전을 수행하여, 초기 용량, 50 Cycle 후 용량, 50 Cycle 후 전지의 두께 증가율을 평가하였고, 이를 하기 표 1에 기재하였다.The batteries of Examples 1 to 5 and Comparative Examples 1 to 4 were subjected to charging and discharging at a rate of 1 C / 1 C at 3.0 to 4.2 V to evaluate the initial capacity, capacity after 50 cycles, , Which is shown in Table 1 below.
초기용량(mAh)Initial capacity (mAh) 50 cycle 후 용량 (mAh)Capacity after 50 cycles (mAh) 50 cycle 후 전지의 두께 증가율 (%)Cell growth rate after 50 cycles (%)
실시예 1Example 1 32083208 31063106 2.12.1
실시예 2Example 2 32043204 31113111 1.81.8
실시예 3Example 3 32053205 31043104 2.12.1
실시예 4Example 4 32003200 30973097 2.42.4
실시예 5Example 5 31983198 30943094 2.22.2
비교예 1Comparative Example 1 32053205 30013001 3.93.9
비교예 2Comparative Example 2 32033203 28372837 8.58.5
비교예 3Comparative Example 3 측정 불가Not measurable 측정 불가Not measurable 측정 불가Not measurable
비교예 4Comparative Example 4 측정 불가Not measurable 측정 불가Not measurable 측정 불가Not measurable
상기 표 1에 나타난 바와 같이, 실시예 1~5의 경우, 초기용량 대비 50 cycle 후 용량의 차이가 비교예 1~2에 비하여 현저히 작으며, 50cycle 후 전지의 두께의 증가율 또한 비교예 1~2에 비하여 현저히 낮은 것을 확인할 수 있다.As shown in Table 1, in the case of Examples 1 to 5, the difference in capacity after 50 cycles of the initial capacity was significantly smaller than those of Comparative Examples 1 and 2, As shown in FIG.
또한, 비교예 1과 같이 1종의 셀룰로오스계 화합물을 사용하는 경우, 전지의 cycle 용량이 급격하게 저하되고, 전지의 두께 증가율이 높아짐을 확인할 수 있다.In addition, when one type of cellulosic compound is used as in Comparative Example 1, it can be confirmed that the cycle capacity of the battery is rapidly lowered and the thickness increase rate of the battery is increased.
또한, 비교예 2와 같이 평균 입자 직경(D50)이 본 발명의 범위를 초과하는 실리콘 입자를 사용하는 경우, 50 cycle 이후 전지의 수명 특성이 저하되고, 전지의 두께 증가율이 상승함을 확인할 수 있다. In addition, when the silicone particles having an average particle diameter (D 50 ) exceeding the range of the present invention were used as in Comparative Example 2, the lifetime characteristics of the battery were degraded after 50 cycles and the increase rate of the thickness of the battery was ascertained have.
한편, 비교예 3의 경우, 셀룰로오스계 화합물을 사용하지 않고 슬러리를 제조한 것으로, 비교예 3에 따른 음극 활물질 슬러리는 침강이 빨라서 균일한 전극 코팅이 수행될 수 없어 전지를 제조할 수 없었다.On the other hand, in the case of Comparative Example 3, the slurry was prepared without using the cellulosic compound, and the negative electrode active material slurry according to Comparative Example 3 could not be uniformly coated with the electrode because the sedimentation was fast.
비교예 4의 경우, 제2슬러리 제조시 저분자량의 셀룰로오스계 화합물을 사용한 것으로, 비교예 4에 따른 음극 활물질 슬러리 또한 침강이 빨라서 균일한 전극 코팅이 수행될 수 없어 전지를 제조할 수 없었다.In the case of Comparative Example 4, a cellulosic compound having a low molecular weight was used in the preparation of the second slurry, and the slurry of the negative electrode active material according to Comparative Example 4 was also precipitated so fast that uniform electrode coating could not be performed.
[부호의 설명] 10: 흑연계 활물질 20: 실리콘 나노입자 [Description of Reference Numerals] 10: graphite active material 20: silicon nanoparticles

Claims (15)

  1. 음극 집전체; 및 상기 음극 집전체 상에 위치하는 음극 활물질 층을 포함하는 리튬 이차전지용 음극이며,Cathode collector; And a negative electrode active material layer positioned on the negative electrode current collector,
    상기 음극 활물질 층은, 평균 입자 직경(D50)이 5 ㎛ 내지 50 ㎛인 흑연계 활물질; 평균 입자 직경(D50)이 70 ㎚ 내지 300 ㎚인 실리콘 나노 입자; 제1 도전재; 및 중량 평균 분자량이 서로 다른 2종 이상의 셀룰로오스계 화합물을 포함하는 리튬 이차전지용 음극.Wherein the negative electrode active material layer comprises a graphite-based active material having an average particle diameter (D 50 ) of 5 탆 to 50 탆; Silicon nanoparticles having an average particle diameter (D 50 ) of 70 nm to 300 nm; A first conductive material; And at least two cellulosic compounds having different weight average molecular weights.
  2. 제1항에 있어서,The method according to claim 1,
    상기 음극 활물질 층은 상기 실리콘 나노 입자를 상기 흑연계 활물질 100 중량부에 대하여 1 중량부 내지 100 중량부로 포함하는 것인 리튬 이차전지용 음극.Wherein the negative electrode active material layer comprises 1 to 100 parts by weight of the silicon nano-particles in 100 parts by weight of the graphite-based active material.
  3. 제1항에 있어서,The method according to claim 1,
    상기 제1 도전재는 카본나노입자, 카본나노파이버, 카본나노튜브 및 카본나노로드로 이루어진 군에서 선택되는 적어도 하나 이상의 화합물을 포함하는 것인 리튬 이차전지용 음극.Wherein the first conductive material comprises at least one compound selected from the group consisting of carbon nanoparticles, carbon nanofibers, carbon nanotubes, and carbon nanorods.
  4. 제1항에 있어서,The method according to claim 1,
    상기 제1 도전재는 입자 형태이고, 평균 입자 직경(D50)은 5 ㎚ 내지 40 ㎚인 것인 리튬 이차전지용 음극.Wherein the first conductive material is in the form of particles and has an average particle diameter (D 50 ) of 5 nm to 40 nm.
  5. 제1항에 있어서,The method according to claim 1,
    상기 제1 도전재는 섬유 형태이고, 너비는 5 ㎚ 내지 40 ㎚인 것인 리튬 이차전지용 음극.Wherein the first conductive material is in the form of fibers and has a width of 5 nm to 40 nm.
  6. 제1항에 있어서,The method according to claim 1,
    상기 음극 활물질 층은 제2 도전재를 더 포함하는 것인 리튬 이차전지용 음극.Wherein the anode active material layer further comprises a second conductive material.
  7. 제6항에 있어서,The method according to claim 6,
    상기 제2 도전재는 탄소계 물질, 도전성 휘스커, 도전성 금속 산화물 및 전도성 고분자로 이루어진 군에서 선택되는 적어도 하나 이상의 화합물을 포함하는 것인 리튬 이차전지용 음극.Wherein the second conductive material comprises at least one compound selected from the group consisting of a carbon-based material, a conductive whisker, a conductive metal oxide, and a conductive polymer.
  8. 제1항에 있어서,The method according to claim 1,
    상기 셀룰로오스계 화합물은 중량 평균 분자량이 10,000 내지 500,000 인 제1 셀룰로오스계 화합물 및 중량 평균 분자량이 1,000,000 내지 2,500,000 인 제2 셀룰로오스계 화합물을 포함하는 것인 리튬 이차전지용 음극.Wherein the cellulose-based compound comprises a first cellulose-based compound having a weight-average molecular weight of 10,000 to 500,000 and a second cellulose-based compound having a weight-average molecular weight of 1,000,000 to 2,500,000.
  9. 제1항에 있어서,The method according to claim 1,
    상기 음극 활물질 층은 바인더를 더 포함하는 것인 리튬 이차전지용 음극.Wherein the negative electrode active material layer further comprises a binder.
  10. 제1항에 따른 음극을 포함하는 리튬 이차전지.A lithium secondary battery comprising a negative electrode according to claim 1.
  11. 평균 입자 직경(D50)이 70 ㎚ 내지 300 ㎚인 실리콘 나노 입자, 제1 도전재, 중량 평균 분자량이 10,000 내지 500,000 인 제1 셀룰로오스계 화합물 및 용매를 혼합하여 제1 혼합물을 형성하는 단계;Forming a first mixture by mixing silicone nanoparticles having an average particle diameter (D 50 ) of 70 nm to 300 nm, a first conductive material, a first cellulose compound having a weight average molecular weight of 10,000 to 500,000, and a solvent;
    평균 입자 직경(D50)이 5 ㎛ 내지 50 ㎛인 흑연계 활물질, 중량 평균 분자량이 1,000,000 내지 2,500,000 인 제2 셀룰로오스계 화합물 및 용매를 혼합하여 제2 혼합물을 형성하는 단계;Forming a second mixture by mixing a graphite-based active material having an average particle diameter (D 50 ) of 5 탆 to 50 탆, a second cellulosic compound having a weight average molecular weight of 1,000,000 to 2,500,000, and a solvent;
    상기 제1 혼합물 및 상기 제2 혼합물을 혼합하여 음극 활물질 슬러리를 형성하는 단계; 및Mixing the first mixture and the second mixture to form a negative electrode active material slurry; And
    상기 음극 활물질 슬러리를 음극 집전체 상에 도포하여 음극 활물질 층을 형성하는 단계를 포함하는 리튬 이차전지용 음극 제조방법.And coating the negative electrode active material slurry on the negative electrode current collector to form a negative electrode active material layer.
  12. 제11항에 있어서,12. The method of claim 11,
    상기 제1 혼합물 및 상기 제2 혼합물을 혼합한 후 바인더를 첨가하는 단계를 더 포함하는 것인 리튬 이차전지용 음극 제조방법.Further comprising adding a binder after mixing the first mixture and the second mixture.
  13. 제11항에 있어서,12. The method of claim 11,
    상기 제1 혼합물은 상기 실리콘 나노 입자, 상기 제1 도전재 및 상기 제1 셀룰로오스계 화합물을 (1~100):(0.01~2.0):(0.01~2.0) 중량비로 포함하는 것인 리튬 이차전지용 음극 제조방법.Wherein the first mixture contains the silicon nanoparticles, the first conductive material and the first cellulose compound in a weight ratio of (1 to 100): (0.01 to 2.0): (0.01 to 2.0) Gt;
  14. 제11항에 있어서,12. The method of claim 11,
    상기 제2 혼합물은 제2 도전재를 더 포함하는 것인 리튬 이차전지용 음극 제조방법.And the second mixture further comprises a second conductive material.
  15. 제14항에 있어서,15. The method of claim 14,
    상기 제2 혼합물은 상기 흑연계 활물질, 상기 제2 셀룰로오스계 화합물 및 상기 제2 도전재를 (1~100):(0.1~5):(0.1~5) 중량비로 포함하는 것인 리튬 이차전지용 음극 제조방법.Wherein the second mixture contains the graphite-based active material, the second cellulosic compound, and the second conductive material in a weight ratio of (1 to 100): (0.1 to 5): (0.1 to 5) Gt;
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