WO2017074124A1 - Conductive material dispersed liquid and lithium secondary battery manufactured using same - Google Patents

Conductive material dispersed liquid and lithium secondary battery manufactured using same Download PDF

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Publication number
WO2017074124A1
WO2017074124A1 PCT/KR2016/012301 KR2016012301W WO2017074124A1 WO 2017074124 A1 WO2017074124 A1 WO 2017074124A1 KR 2016012301 W KR2016012301 W KR 2016012301W WO 2017074124 A1 WO2017074124 A1 WO 2017074124A1
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Prior art keywords
conductive material
carbon nanotubes
dispersant
carbon
electrode
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PCT/KR2016/012301
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French (fr)
Korean (ko)
Inventor
김예린
설종헌
강경연
최상훈
우지희
조동현
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주식회사 엘지화학
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Application filed by 주식회사 엘지화학 filed Critical 주식회사 엘지화학
Priority to PL16860307T priority Critical patent/PL3301745T3/en
Priority to JP2018525334A priority patent/JP6749703B2/en
Priority to CN201680042062.6A priority patent/CN107851801B/en
Priority to US15/741,676 priority patent/US11050061B2/en
Priority to EP16860307.4A priority patent/EP3301745B1/en
Priority claimed from KR1020160142055A external-priority patent/KR101954430B1/en
Publication of WO2017074124A1 publication Critical patent/WO2017074124A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—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 conductive material dispersion having excellent conductivity and dispersibility, and a lithium secondary battery manufactured using the same.
  • lithium secondary batteries having high energy density and voltage, long cycle life, and low self discharge rate have been commercialized and widely used.
  • an electrode for a high capacity lithium secondary battery research is being actively conducted on a method for improving an electrode density to produce an electrode having a higher energy density per unit volume.
  • the high-density electrode is formed by molding electrode active material particles having a size of several micrometers to several tens of micrometers by a high pressure press, so that the particles are deformed, the space between the particles is reduced, and electrolyte permeability is easily degraded.
  • the electrically conductive material which has the intensity
  • the conductive material is dispersed between the compressed electrode active material to maintain fine pores between the active material particles to facilitate penetration of the electrolyte, and to reduce the resistance in the electrode with excellent conductivity.
  • the use of carbon nanotubes, which are fibrous carbon-based conductive materials, which can further reduce electrode resistance by forming an electrically conductive path in the electrode, is increasing.
  • Carbon nanotubes which are a kind of fine carbon fibers, are tubular carbons having a diameter of 1 ⁇ m or less, and are expected to be applied to various fields due to their high conductivity, tensile strength and heat resistance due to their specific structure.
  • carbon nanotubes have limited use due to their low solubility and dispersibility.
  • the carbon nanotubes were predispersed in a dispersion medium, and then used to prepare a composition for forming an electrode.
  • carbon nanotubes do not achieve a stable dispersion state in the dispersion medium due to strong van der Waals attraction between each other, there is a problem that agglomeration phenomenon occurs.
  • the first problem to be solved by the present invention is to provide a conductive material dispersion having excellent conductivity and dispersibility.
  • a second object of the present invention is to provide a composition for forming an electrode of a lithium secondary battery including the conductive material dispersion.
  • Another object of the present invention is to provide a lithium secondary battery manufactured using the conductive material dispersion.
  • the present invention comprises a conductive material, a dispersant and a dispersion medium, the conductive material has a bulk density of 10 to 50kg / m3 and a conductivity that meets the conditions of the following equation (1) It provides a conductive material dispersion comprising a bundle-type carbon nanotube having.
  • composition for forming an electrode of a lithium secondary battery comprising the conductive material dispersion.
  • a lithium secondary battery including an electrode made of the electrode forming composition.
  • the conductive material dispersion according to the present invention may exhibit excellent conductivity and dispersibility due to uniform dispersion of carbon nanotubes having excellent conductivity in the dispersion. Accordingly, when forming the electrode of the lithium secondary battery, it is possible to exhibit excellent dispersibility of the conductive material in the electrode, and to increase the conductivity in the electrode, thereby improving battery performance during battery application, particularly at low temperatures.
  • the conductive material dispersion is useful for the production of batteries requiring high output characteristics, such as automotive batteries.
  • Example 1 to 3 are photographs of the carbon nanotubes of Example 1-1 observed at various observation magnifications using a scanning electron microscope.
  • Example 10 is a graph showing the results of observing the change in powder resistance according to the powder density of the carbon nanotubes of Example 1-1, Comparative Example 1-1 and Comparative Example 1-2.
  • FIG. 11 is a photograph of the conductive material dispersion of Example 2-1 observed using a scanning electron microscope.
  • FIG. 11 is a photograph of the conductive material dispersion of Example 2-1 observed using a scanning electron microscope.
  • Example 12 is a photograph of the conductive material dispersion of Example 2-2 observed using a scanning electron microscope.
  • FIG. 13 is a photograph of the conducting material dispersion of Example 2-3 using a scanning electron microscope.
  • Example 14 is a photograph of the conductive material dispersion of Example 2-4 using a scanning electron microscope.
  • FIG. 15 is a photograph of the conducting material dispersion of Example 2-5 using a scanning electron microscope.
  • FIG. 15 is a photograph of the conducting material dispersion of Example 2-5 using a scanning electron microscope.
  • Example 16 is a photograph of a conductive material dispersion of Example 2-6 using a scanning electron microscope.
  • FIG. 17 is a photograph of a conductive material dispersion of Comparative Example 2-1 observed using a scanning electron microscope.
  • non-bundle type a plurality of carbon nanotube strands, ie, carbon nanotube units, are arranged side by side in an orientation substantially identical in the axis of the unit length direction, or It refers to a secondary shape in the form of a bundle or rope twisted spirally.
  • non-bundle type entangled type
  • entangled type entangled type
  • entangled type entangled type
  • carbon nanotubes In general, carbon nanotubes (CNTs) have physical properties depending on the crystallinity, structure, form, and structure and shape of secondary particles composed of the monomers, and components contained in carbon nanotubes including impurities. Can vary. Accordingly, by controlling any one or two or more of the above factors, it is possible to have the physical properties required according to the use of the carbon nanotubes.
  • the present invention by simultaneously controlling the bulk density and the powder resistance of the carbon nanotubes used in the production of the conductive material dispersion, to exhibit excellent dispersibility and conductivity, and consequently to increase the conductivity in the electrode when applied to electrode production Battery performance, especially the output characteristics of a battery at low temperatures can be greatly improved.
  • the conductive material dispersion includes a conductive material, a dispersant and a dispersion medium, the conductive material has a bulk density of 10 to 50 kg / m3 and a conductivity that meets the conditions of the following formula (1) Bundle-type carbon nanotubes having:
  • Equation 1 X is the bulk density of the carbon nanotubes, R is the powder resistance of the carbon nanotubes under a pressure of 10 to 65 MPa.
  • the bulk density of the carbon nanotubes may be determined according to Equation 2 below.
  • the carbon nanotubes have a bulk density of 20 to 35 kg / m 3; And a powder resistance of 0.013 ⁇ ⁇ cm or less, more specifically 0.001 to 0.01 ⁇ ⁇ cm under a pressure of 10 to 65 MPa.
  • the carbon nanotubes are secondary structures formed by gathering carbon nanotube units in whole or part in bundle form, and the carbon nanotube units are graphite surfaces.
  • sheet has the shape of a cylinder of nano size diameter and has a sp 2 bond structure.
  • the graphite surface may exhibit characteristics of a conductor or a semiconductor depending on the angle and structure of the surface.
  • Carbon nanotube units are single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs) and multi-walled carbon nanotubes (MWCNTs). walled carbon nanotube), the thinner the wall thickness, the lower the resistance.
  • the carbon nanotubes may include any one or two or more of carbon nanotube units of a single wall, a double wall and a multi-wall.
  • the average diameter of the carbon nanotube units in the carbon nanotubes usable in the present invention may be 5 to 30 nm, and the effect of improving the dispersibility of the conductive material and reducing the resistance in the electrode by controlling the diameter of the carbon nanotube units. In consideration of the above, the average diameter of the carbon nanotube unit may be 10 to 20nm.
  • the carbon nanotube unit means a strand of carbon nanotubes.
  • the longer the length of the carbon nanotube unit can improve the electrical conductivity, strength and electrolyte storage retention of the electrode.
  • the length of the carbon nanotube unit when the length of the carbon nanotube unit is too long, the dispersibility may decrease.
  • the length of the carbon nanotube unit in the carbon nanotubes usable in the present invention may be 0.5 to 200 ⁇ m.
  • the carbon nanotube unit in consideration of the diameter of the carbon nanotube unit, may have an aspect ratio defined as a ratio of the length and the diameter of the carbon nanotube unit, 5 to 50,000, and more specifically, 10 to 20,000. .
  • the length of the carbon nanotube unit means the length of the long axis passing through the center of the carbon nanotube unit
  • the diameter means the length of the short axis perpendicular to the long axis passing through the center of the carbon nanotube unit.
  • the carbon nanotubes including the carbon nanotube unit may have a ratio (TD / BD ratio) of true density (TD) and bulk density (BD) of 70 to 120.
  • the true density of the carbon nanotubes is measured using a Pycnometer (AccuPycII 1340), which is different from the bulk density in that the density of the particle itself except the pores in the porous solid. Accordingly, the internal structure of the carbon nanotubes can be predicted from the TD / BD ratio. If the TD / BD ratio is too large, the content of the carbon nanotube units in the carbon nanotubes is low, which may lower the capacity characteristics of the battery. If the / BD ratio is too small, the dispersibility of the carbon nanotubes may be lowered.
  • the TD / BD ratio of the carbon nanotubes usable in the present invention may be more specifically 70 to 100.
  • the true density of the carbon nanotubes usable in the present invention may be 1,800 to 2,200 kg / m3 under the conditions that meet the TD / BD ratio.
  • the carbon nanotube has a high BET specific surface area and excellent dispersibility because the carbon nanotube has a small average diameter of the unit as described above and a large TD / BD ratio.
  • the BET specific surface area of the carbon nanotubes usable in the present invention may be 180 to 300 m 2 / g, more specifically 230 to 280 m 2 / g.
  • the specific surface area of the carbon nanotubes is measured by the BET method, specifically, it is calculated from the nitrogen gas adsorption amount under the liquid nitrogen temperature (77K) using BELSORP-mino II by BEL Japan. Can be.
  • the carbon nanotubes have a maximum peak intensity (IG) of a G band at 1580 ⁇ 50 cm ⁇ 1 obtained by Raman spectroscopy using a laser of 532 nm wavelength.
  • the average value of the ratio (ID / IG) of the maximum peak intensity (ID) of the D-band at 1,360 ⁇ 50 cm ⁇ 1 ) is 0.75 to 1.05, specifically 0.95 to 1.04, and the standard deviation value is 1.3 to 2.0%. Specifically, the content may be 1.5 to 2.0%.
  • Raman spectroscopy is a method for analyzing the structure of carbon nanotubes, which is useful for analyzing the surface state of carbon nanotubes.
  • the peak present in the region near the wavenumber of 1,580 cm ⁇ 1 in the Raman spectrum of the carbon nanotubes is called a G band, which is a peak indicating sp 2 bond of the carbon nanotubes, indicating a carbon crystal without structural defects.
  • the peak present in the region near the wave number 1360 cm -1 of the Raman spectrum is called the D-band, which is a peak representing the sp 3 bond of the carbon nanotubes, the atomic bond consisting of sp 2 bonds are broken to become sp 3 bonds If it increases.
  • This D band is increased when a disorder or defect existing in the carbon nanotube is generated, so that the maximum peak intensity (ID) of the D band with respect to the maximum peak intensity (IG) of the G band is increased.
  • the ratio (ID / IG) can be calculated to quantitatively assess the degree of disorder to defect generation.
  • the G band of the Raman spectrum for the carbon nanotube may be a peak present in the wavenumber of 1,580 ⁇ 50 cm ⁇ 1 region
  • the D band may be a peak present in the wavenumber of 1,360 ⁇ 50 cm ⁇ 1 region.
  • the wave range for the G band and the D band corresponds to a range that can be shifted according to the laser light source used in the Raman analysis.
  • Raman values used in the present invention are not particularly limited, but may be measured at a laser wavelength of 532 nm using DXR Raman Microscope (Thermo Electron Scientific Instruments LLC).
  • the BET specific surface area is increased and the bundle structure As a result of the secondary shape, the crystallinity of the carbon nanotubes is good, but the average value and standard deviation of ID / IG are as described above.
  • the carbon nanotubes are 50 ppm or less of metal elements derived from a main catalyst or cocatalyst, such as Co, Mo, V, or Cr, used in the manufacturing process.
  • the content may be included in an amount of 5 ppm or less, and more specifically, may not include Fe.
  • the metal content as impurities remaining in the carbon nanotubes is significantly reduced, and in particular, it does not contain Fe in the carbon nanotubes, thereby exhibiting better conductivity without concern for side reactions in electrode application.
  • the content of the metal impurities remaining in the carbon nanotubes can be analyzed by using a high frequency inductively coupled plasma (ICP).
  • ICP inductively coupled plasma
  • Such carbon nanotubes may be manufactured using conventional methods such as arc discharge, laser evaporation, or chemical vapor deposition, and control the firing temperature and type and content of the catalyst during the manufacturing process, or perform impurity removal processes.
  • arc discharge laser evaporation
  • chemical vapor deposition control the firing temperature and type and content of the catalyst during the manufacturing process, or perform impurity removal processes.
  • the above-described physical properties can be implemented.
  • the carbon nanotubes are prepared by contacting a supported catalyst having a metal catalyst on a support under heating with a carbon source to produce carbon nanotubes, and optionally the carbon as necessary. It may be prepared by a manufacturing method comprising the step of removing metal impurities in the nanotubes.
  • the carbon is in the temperature range above the thermal decomposition temperature of the carbon source to below the melting point of the supported metal catalyst.
  • Source or by injecting a mixed gas of the carbon source, a reducing gas (for example, hydrogen) and a carrier gas (for example, nitrogen, etc.) to grow the carbon nanotubes by chemical vapor phase synthesis through decomposition of the carbon source.
  • a reducing gas for example, hydrogen
  • carrier gas for example, nitrogen, etc.
  • Carbon nanotubes prepared by the above chemical vapor phase synthesis method have a crystal growth direction of the crystal structure is substantially parallel to the longitudinal direction of the carbon nanotube unit and the graphite structure in the carbon nanotube unit longitudinal direction. As a result, the diameter of the unit is small, and the electrical conductivity and strength are high.
  • the heating process in the production of the carbon nanotube may be specifically carried out at a temperature of more than 550 °C 800 °C, more specifically at 550 °C to 700 °C.
  • a temperature of more than 550 °C 800 °C more specifically at 550 °C to 700 °C.
  • the weight is reduced while maintaining the bulk size, that is, the volume of the carbon nanotubes generated while minimizing the generation of amorphous carbon, the dispersibility may be further improved by reducing the bulk density.
  • a heat source for the heating process induction heating, radiant heat, laser, IR, microwave, plasma or surface plasmon heating may be used as a heat source for the heating process.
  • carbon when the carbon nanotubes are manufactured, carbon may be supplied as a carbon source, and may be used without particular limitation as long as it can exist in the gas phase at a temperature of 300 ° C. or higher.
  • the carbon source may be a carbon-based compound having 6 or less carbon atoms, and more specifically, carbon monoxide, methane, ethane, ethylene, ethanol, acetylene, propane, propylene, butane, butadiene, pentane, pentene, cyclopentadiene, and hexane , Cyclohexane, benzene, toluene, and the like, and any one or a mixture of two or more thereof may be used.
  • the carbon nanotube units may be grown by the chemical vapor phase synthesis method as described above, and then a cooling process may be selectively performed to align the arrangement of the carbon nanotube units more regularly. Specifically, the cooling process may be performed using natural cooling or a cooler according to the removal of the heat source.
  • the metal impurity removal process for the prepared carbon nanotubes may be performed according to conventional methods such as washing, acid treatment.
  • the supported catalyst used in the production of the carbon nanotubes is a metal catalyst supported on the support of the inorganic oxide
  • the inorganic oxide may be specifically alumina, more specifically spherical ⁇ -alumina.
  • ⁇ -alumina has a very low porosity compared with ⁇ -alumina, and thus has low utility as a catalyst support.
  • the calcination temperature at which the supported catalyst is formed it is possible to increase the diameter by reducing the specific surface area while suppressing the generation of amorphous carbon when synthesizing carbon nanotubes.
  • the bulk density of carbon nanotubes can be reduced to improve dispersibility.
  • the ⁇ -alumina usable as a support in the present invention may have an average particle diameter (D 50 ) of 20 to 200 ⁇ m and a BET specific surface area of 1 to 50 m 2 / g.
  • the ⁇ -alumina may have a very low porosity, specifically, a porosity of 0.001 to 0.1 cm 3 / g.
  • the supported catalyst may be prepared by baking the metal catalyst on a support. Specifically, after the support, specifically, alumina is added and mixed with the metal catalyst precursor solution prepared by dissolving the above-described metal catalyst precursor in water, it is 600 ° C. or less, more specifically 300 ° C. to 500 ° C. By firing at temperature.
  • the metal catalyst serves to help the carbon components present in the gaseous carbon source combine with each other to form a six-membered ring structure.
  • a main catalyst such as nickel or cobalt may be used alone, or the main catalyst may be It may be used in the form of a main catalyst-catalyst complex catalyst with a promoter such as molybdenum, vanadium or chromium.
  • the metal catalyst may be CoMo or CoV, and any one or a mixture of two or more thereof may be used.
  • the cocatalyst may be used in an amount of 0.01 to 1 mol, more specifically 0.05 to 0.5 mol with respect to 1 mol of the main catalyst.
  • a metal salt or metal oxide soluble in water may be used as a precursor of the metal catalyst usable in the preparation of the supported catalyst.
  • a metal salt or metal oxide soluble in water may be used.
  • it may be a metal salt, a metal oxide or a metal halide including any one or two or more metal elements selected from Fe, Ni, Co, Mo, V, and Cr, and any one or a mixture of two or more thereof may be used.
  • the precursor of the metal catalyst may be used in an aqueous solution dissolved in water.
  • the concentration of the metal catalyst precursor in the aqueous solution may be appropriately adjusted in consideration of the impregnation efficiency.
  • the concentration of the metal catalyst precursor in the aqueous solution may be 0.1 to 0.4 g / ml.
  • the mixing process of the metal catalyst precursor solution and the support may be performed according to a conventional method, specifically, it may be carried out by rotating or stirring at a temperature of 45 °C to 80 °C.
  • the metal catalyst precursor and the support may be mixed in consideration of the content of the metal catalyst in the final supported catalyst during the mixing.
  • the supported amount of the metal catalyst increases in the supported catalyst, the bulk density of the carbon nanotubes produced using the supported catalyst tends to increase.
  • the metal catalyst may be mixed in an amount of 5 to 30% by weight based on the total weight of the supported catalyst.
  • an acid may optionally be further used during addition and mixing of the support in the metal catalyst precursor solution.
  • the metal catalyst precursor solution when the acid is further added, may be used in an amount corresponding to 3 to 40 moles, more specifically 5 to 30 moles, of the metal catalyst per mole of acid.
  • the acid may specifically be citric acid and the like, and any one or a mixture of two or more thereof may be used.
  • a drying process may be optionally further performed prior to the subsequent firing process.
  • the drying process may be performed according to a conventional method, specifically, may be carried out by rotary evaporation under vacuum at a temperature of 40 °C to 100 °C for 3 minutes to 1 hour.
  • firing is performed on the mixture of the metal catalyst precursor and the support prepared in the above manner.
  • the firing can be carried out under air or an inert atmosphere at temperatures of up to 600 ° C, specifically 400 ° C to 600 ° C.
  • a preliminary firing process may be optionally further performed at a temperature of 250 ° C. to 400 ° C. after the drying process and before the firing process.
  • up to 50% of the mixture of the metal catalyst precursor and the support may be impregnated into the support immediately before the preliminary firing, and the remainder of the mixture may be impregnated into the support immediately after the preliminary firing. have.
  • Carbon nanotubes prepared according to the manufacturing method as described above may have low bulk density and powder resistance, and thus may exhibit excellent dispersibility and conductivity when preparing a conductive material dispersion.
  • the conductivity in the electrode can be increased to improve battery performance when the battery is applied, particularly the output characteristics of the battery at low temperatures.
  • the dispersing agent may be a nitrile-based rubber, more specifically may be a nitrile butadiene-based rubber hydrogenated in part or whole. Even more specifically, the dispersing agent includes a structural unit derived from conjugated diene, a structural unit derived from hydrogenated conjugated diene, and a structural unit derived from ⁇ , ⁇ -unsaturated nitrile, and the ⁇ , ⁇ -unsaturated nitrile derived structural unit with respect to the total weight of rubber. It may be a partially hydrogenated nitrile butadiene rubber containing 20 to 65% by weight.
  • the polymerization reaction process and the hydrogenation process may be performed according to a conventional method.
  • ⁇ , ⁇ -unsaturated nitriles that can be used in the production of the partially hydrogenated nitrile butadiene-based rubber include acrylonitrile or methacrylonitrile, and one or a mixture of two or more of them may be used. have.
  • the other copolymerizable terpolymers optionally used may include, for example, aromatic vinyl monomers (eg, styrene, ⁇ -methylstyrene, vinylpyridine, fluoroethyl vinyl ether, etc.), ⁇ , ⁇ -unsaturated carboxylic acids.
  • aromatic vinyl monomers eg, styrene, ⁇ -methylstyrene, vinylpyridine, fluoroethyl vinyl ether, etc.
  • ⁇ , ⁇ -unsaturated carboxylic acids eg, styrene, ⁇ -methylstyrene, vinylpyridine, fluoroethyl vinyl ether, etc.
  • esters or amides of ⁇ , ⁇ -unsaturated carboxylic acids eg methyl (meth) acrylate, ethyl (meth) acrylate, n-dodecyl (meth) acrylate, methoxymethyl (meth) acrylate, hydroxyethyl (meth) acrylate, or polyethylene glycol (meth) acrylate
  • anhydrides of ⁇ , ⁇ -unsaturated dicarboxylic acids (For example, maleic anhydride, itaconic anhydride, citraconic anhydride, etc.), but is not limited thereto.
  • ⁇ , ⁇ -unsaturated nitrile derived structural units, conjugated diene derived structural units, hydrogenated conjugated diene derived structural units, and optionally other copolymerizable terpolymers derived from The content ratio of the structural units may vary within a wide range, and in each case the sum of the structural units is 100% by weight.
  • the content of the ⁇ , ⁇ -unsaturated nitrile-derived structural unit in the partially hydrogenated nitrile butadiene-based rubber is the total weight of the partially hydrogenated nitrile-butadiene rubber. 20% to 65% by weight, specifically 30% to 60% by weight.
  • the ⁇ , ⁇ -unsaturated nitrile structure-containing repeating unit is included in the above content range, the dispersibility of the carbon nanotubes can be increased, and even if the amount of the carbon nanotubes is small, high conductivity can be given.
  • the content of the nitrile structure-containing repeating unit in the partially hydrogenated nitrile butadiene-based rubber is a weight ratio of the entire rubber of the structural unit derived from ⁇ , ⁇ -unsaturated nitrile, and the measurement of the content is JIS K According to the mill oven method of 6364, the amount of nitrogen which generate
  • the content of the hydrogenated conjugated diene-based structural unit in the partially hydrogenated nitrile butadiene rubber may be 1 to 30% by weight, more specifically 1 to 15% by weight relative to the total weight of the partially hydrogenated nitrile butadiene rubber.
  • the miscibility to the dispersion medium can be increased to increase the dispersibility of the carbon nanotubes.
  • the partially hydrogenated acrylonitrile-butadiene rubber may have a weight average molecular weight of 10,000 g / mol to 700,000 g / mol, more specifically 10,000 g / mol to 300,000 g / mol.
  • the partially hydrogenated acrylonitrile-butadiene rubber has a polydispersity index PDI (ratio of Mw / Mn, Mw is a weight average molecular weight and Mn is in the range of 2.0 to 6.0, specifically, 2.0 to 4.0). Number average molecular weight).
  • the carbon nanotubes may be uniformly dispersed in the dispersion medium.
  • the weight average molecular weight and the number average molecular weight are polystyrene reduced molecular weights analyzed by gel permeation chromatography (GPC).
  • the dispersion medium is dimethylformamide (DMF), diethyl formamide, dimethyl acetamide (DMAc), N-methyl pyrrolidone (NMP), or the like.
  • Amide polar organic solvents Methanol, ethanol, 1-propanol, 2-propanol (isopropyl alcohol), 1-butanol (n-butanol), 2-methyl-1-propanol (isobutanol), 2-butanol (sec-butanol), 1-methyl Alcohols such as 2-propanol (tert-butanol), pentanol, hexanol, heptanol or octanol; Glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, or hexylene glycol; Polyhydric alcohols such as glycerin, trimetholpropane, pentaerythritol, or sorbitol; Ethylene glycol mono methyl ether, diethylene glycol mono methyl ether, triethylene glyco
  • the content of the dispersant, the carbon nanotubes and the dispersion medium may be appropriately determined according to the use of the dispersion.
  • the dispersant may be included in an amount of 1 part by weight to 50 parts by weight based on 100 parts by weight of carbon nanotubes for uniform dispersion of the carbon nanotubes in the dispersion. If the content of the dispersant is less than 1 part by weight, it is difficult to uniformly disperse the carbon nanotubes in the dispersion. If the content of the dispersant is more than 50 parts by weight, the viscosity of the dispersion may increase, leading to a decrease in processability. More specifically, it may be included in 5 to 20 parts by weight.
  • the carbon nanotubes may be included in an amount of 1.0 wt% to 33 wt% based on the total weight of the conductive material dispersion.
  • the carbon nanotubes When the carbon nanotubes are included in the content of the above range, it can exhibit a good balance of electronic conductivity and dispersibility.
  • the content of the carbon nanotubes out of the range of less than 1% by weight for example, when forming the electrode of a lithium secondary battery, the composition for forming an electrode includes a large amount of organic solvent, and as a result, the voids in the electrode increase, and the active material The battery capacity may be lowered by lowering the filling rate.
  • the drying time for removing the organic solvent may be long.
  • the content of the carbon nanotube is more than 30% by weight, the viscosity is high, the dispersion is not properly, there is a fear that the electrode resistance is increased.
  • the conductive material dispersion according to an embodiment of the present invention may include 1 to 50 parts by weight of the dispersant, and 200 to 9,900 parts by weight of the dispersion medium based on 100 parts by weight of the carbon nanotubes.
  • Carbon nanotubes can be uniformly dispersed in the dispersion medium in the above range.
  • the dispersant may include 5 to 20 parts by weight and 1,000 to 3,500 parts by weight of the dispersion medium based on 100 parts by weight of the carbon nanotubes.
  • the conductive material dispersion according to an embodiment of the present invention may further include a dispersion stabilizer for increasing the dispersion stability.
  • the dispersion stabilizer may prevent the agglomeration of the carbon nanotubes by adsorbing on the surface of the carbon nanotubes and exhibiting a lapping effect surrounding the carbon nanotubes. Accordingly, as the dispersion stabilizer, it may be preferable to have excellent affinity for carbon nanotubes and excellent compatibility for the dispersant and the dispersion medium.
  • the dispersion stabilizer may be a fluorine-based polymer such as polyvinylidene fluoride, polyvinylpyrrolidone, any one or more of these Mixtures can be used.
  • the dispersion stabilizer may be a weight average molecular weight of 20,000 g / mol to 5,000,000 g / mol. If the molecular weight of the dispersion stabilizer is too small, less than 20,000 g / mol, it is difficult to exhibit a sufficient lapping effect on the carbon nanotubes, and if the molecular weight is too large, exceeding 5,000,000 g / mol, the molecular motion of the dispersion stabilizer in the dispersion medium is lowered. As a result, it is difficult to sufficiently wrap the carbon nanotubes. More specifically, the dispersion stabilizer may be a weight average molecular weight of 70,000 g / mol to 2,000,000 g / mol.
  • the dispersion stabilizer may be used in 1 part by weight to 10 parts by weight with respect to 100 parts by weight of carbon nanotubes. If the content of the dispersion stabilizer is too low compared to the content of the carbon nanotubes, it is difficult to obtain a sufficient lapping effect, and as a result, there is a fear that aggregation of the carbon nanotubes occurs.
  • the conductive material dispersion according to an embodiment of the present invention having the configuration as described above comprises the steps of preparing a slurry containing carbon nanotubes by mixing carbon nanotubes and a dispersion medium (step 1); And it may be prepared by a manufacturing method comprising the step (step 2) of mixing the dispersant in the slurry.
  • step 1 a manufacturing method comprising the step (step 2) of mixing the dispersant in the slurry.
  • step 2 the type and the amount of the carbon nanotubes, the dispersant and the dispersion medium are the same as described above.
  • mixing of the carbon nanotubes and the dispersion medium using a conventional mixing method, specifically, homogenizer, bead mill, ball mill, basket mill, treatment mill, universal stirrer, clear mixer or TK mixer Can be performed.
  • the cavitation dispersion treatment may be performed to increase the mixability of the carbon nanotubes and the dispersion medium, or the dispersibility of the carbon nanotubes in the dispersion medium.
  • the cavitation dispersion treatment is a dispersion treatment method using a shock wave generated by the rupture of the vacuum bubbles generated in water when high energy is applied to the liquid, and can be dispersed without damaging the properties of the carbon nanotubes by the above method.
  • the cavitation dispersion treatment may be performed by ultrasonic wave, jet mill, or shear dispersion treatment.
  • the dispersion treatment process may be appropriately performed according to the amount of carbon nanotubes and the type of dispersant. Specifically, when the ultrasonic treatment is performed, the frequency is in the range of 10 Hz to 150 Hz, the amplitude is in the range of 5 ⁇ m to 100 ⁇ m, and the irradiation time may be 1 minute to 300 minutes. As an ultrasonic generator for performing the ultrasonic treatment process, for example, an ultrasonic homogenizer may be used. In addition, when the jet mill treatment is performed, the pressure may be 20 MPa to 250 MPa, and may be performed one or more times, specifically, two or more times. Moreover, a high pressure wet jet mill etc. can be used as said jet mill dispersion apparatus.
  • the temperature in the cavitation dispersion treatment process is not particularly limited, but may be performed at a temperature at which there is no fear of change in viscosity of the dispersion due to evaporation of the dispersion medium. Specifically, the temperature may be performed at a temperature of 50 ° C. or lower, more specifically 15 ° C. to 50 ° C.
  • the mixing process of the dispersant may be carried out by a conventional mixing or dispersing method, specifically, milling (ball mill), bead mill (basket mill), basket mill (basket mill), etc. Method, or by homogenizer, beads mill, ball mill, basket mill, attrition mill, universal stirrer, clear mixer or TK mixer. More specifically, it may be performed by a milling method using a bead mill. At this time, the size of the bead mill may be appropriately determined according to the type and amount of carbon nanotubes and the type of dispersant, specifically, the diameter of the bead mill may be 0.5mm to 2mm.
  • the dispersion stabilizer when a dispersion stabilizer is optionally further used in the preparation of the dispersion, the dispersion stabilizer may be added together during the mixing process of the dispersion.
  • the manufacturing method of the conductive material dispersion according to an embodiment of the present invention may further include a dispersion stabilizer addition process. The type and the amount of the dispersion stabilizer are the same as described above.
  • a dispersion in which carbon nanotubes are uniformly dispersed in a dispersion medium may be prepared.
  • the carbon nanotubes and the dispersant in the form of a carbon nanotube-dispersant composite wherein the dispersant is introduced through a physical or chemical bond to the surface of the carbon nanotubes It may be included in a uniform dispersion, more specifically the composite in the conductive material dispersion is more excellent by showing a narrow particle size distribution of less than 10, more specifically 2 to 6.5 according to the following equation (3) Uniform dispersibility.
  • D 10 , D 50, and D 90 refer to particle sizes at 10%, 50%, and 90% of the particle size distribution of the carbon nanotube-dispersant composite, respectively.
  • D 10 of the particle size distribution of the composite may be 1 to 5 ⁇ m, D 50 to 3 to 15 ⁇ m, and D 90 to 10 to 100 ⁇ m, More specifically, D 10 may be 1 to 3 ⁇ m, D 50 may be 4 to 15 ⁇ m, and D 90 may be 10 to 30 ⁇ m.
  • the particle sizes D 10 , D 50 and D 90 of the composite can be measured using a laser diffraction method, more specifically, after dispersing the complex in a solvent, it is commercially available. Introduced into a laser diffraction particle size measuring device (e.g., Microtrac MT 3000), an ultrasonic wave of about 28 kHz is irradiated at an output of 60 W, and the average particle diameter at 10, 50% and 90% of the particle size distribution in the measuring device is measured. Each can be calculated.
  • a laser diffraction particle size measuring device e.g., Microtrac MT 3000
  • the conductive material dispersion may have a viscosity of 1,000 to 20,000 mPa ⁇ s when measuring the viscosity at a rate of 10 rpm using a Brookfield viscometer. As described above, by having a lower viscosity characteristic than in the prior art, it is possible to exhibit more excellent dispersion characteristics when applied for electrode production.
  • the conductive material dispersion according to the present invention may exhibit more excellent electrical, thermal, and mechanical properties by uniform dispersion of carbon nanotubes, and workability is also improved by maintaining low viscosity, thereby enabling application and practical use in various fields.
  • the conductive material dispersion may be used for the production of a lithium secondary battery electrode.
  • a composition for forming an electrode for a lithium secondary battery including the conductive material dispersion together with an electrode active material, and an electrode manufactured using the same.
  • the electrode may be an anode or a cathode, and more specifically, may be an anode.
  • the composition for forming an electrode of the lithium secondary battery may include the conductive material dispersion, the electrode active material and the binder.
  • the conductive material dispersion may be included in 1% by weight to 50% by weight relative to the total weight of the composition for forming the electrode of the lithium secondary battery. If the content of the conductive material dispersion is less than 1% by weight, there is a fear of deterioration of battery output characteristics due to a decrease in conductivity and an increase in resistance in the electrode active material layer. There is.
  • the electrode active material may be used as a positive electrode or negative electrode active material of a secondary battery.
  • the electrode active material is a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound), specifically, cobalt and manganese. It may be a positive electrode active material of a lithium transition metal oxide including a transition metal and lithium, such as nickel or aluminum.
  • the electrode active material may be used as a positive electrode or negative electrode active material of a secondary battery.
  • the electrode active material is a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound), specifically, cobalt and manganese. It may be a positive electrode active material of a lithium transition metal oxide including a transition metal and lithium, such as nickel or aluminum.
  • the electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and includes carbon such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon.
  • Vaginal materials Metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys or Al alloys; Metal oxides capable of doping and undoping lithium such as SiO x (0 ⁇ x ⁇ 2), SnO 2 , vanadium oxide, lithium vanadium oxide; Or an anode active material such as a composite including the metallic compound and a carbonaceous material, such as a Si-C composite or a Sn-C composite, and any one or a mixture of two or more thereof may be used. In addition, a metal lithium thin film may be used as the anode active material. As the carbon material, both low crystalline carbon and high crystalline carbon can be used.
  • Soft crystalline carbon and hard carbon are typical low crystalline carbon, and high crystalline carbon is amorphous, plate, scaly, spherical or fibrous natural graphite or artificial graphite, Kish graphite (Kish) graphite, pyrolytic carbon, mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches and petroleum or coal tar pitch High-temperature calcined carbon such as derived cokes is typical.
  • the electrode active material may be included in 70 to 99.5% by weight based on the total weight of the composition for forming an electrode based on the solid content. If the content of the electrode active material is less than 70% by weight, there is a fear of lowering the capacity, and when the content of the electrode active material exceeds 99.5% by weight, the relative content of the binder and the conductive material is reduced, there is a concern such as lowering the adhesion to the electrode current collector, lowering the conductivity.
  • the binder may be included to improve adhesion between the electrode active material particles and adhesion between the electrode active material and the current collector.
  • the binder is specifically polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene Butadiene rubber (SBR), fluorine rubber, or various copolymers thereof, and the like, and one or more of these may be used.
  • the binder may be included in an amount of 0.09 to 30% by weight based on the total weight of the composition for forming an electrode.
  • the electrode forming composition may further include a solvent for mixing and dispersing the electrode active material, a binder, and the like.
  • the solvent may be a solvent generally used in the art, and may include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone or acetone. Water, and the like, one of these alone or a mixture of two or more thereof may be used.
  • the amount of the solvent may be sufficient to dissolve or disperse the electrode active material and the binder in consideration of the coating thickness of the slurry and the production yield, and to have a viscosity capable of exhibiting excellent thickness uniformity during application of the electrode.
  • the electrode according to an embodiment of the present invention manufactured using the composition for forming an electrode, except that the electrode active material layer is formed using the composition for forming an electrode to be manufactured according to a conventional method. Can be.
  • the electrode is applied to the current-coating composition for forming the electrode on the current collector and dried, or casting the electrode-forming composition on a separate support, then the film obtained by peeling from the support lamination on the current collector It can be manufactured by.
  • the current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery.
  • copper, stainless steel, aluminum, nickel, titanium, calcined carbon, or carbon, nickel, The surface-treated with titanium, silver, etc. can be used.
  • the current collector may generally have a thickness of 3 to 500 ⁇ m, and may form fine irregularities on the surface of the current collector to increase the adhesion of the positive electrode active material.
  • it can be used in various forms, such as a film, a sheet, a foil, a net, a porous body, a foam, a nonwoven body.
  • an electrochemical device including the electrode is provided.
  • the electrochemical device may be specifically a battery, a capacitor, or the like, and more specifically, a lithium secondary battery.
  • the separator is to separate the negative electrode and the positive electrode and to provide a passage for the movement of lithium ions, if it is usually used as a separator in a lithium secondary battery can be used without particular limitation, in particular to the ion movement of the electrolyte It is desirable to have a low resistance against the electrolyte and excellent electrolytic solution-moisture capability.
  • a porous polymer film for example, a porous polymer film made of a polyolefin-based polymer such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer and ethylene / methacrylate copolymer or the like Laminate structures of two or more layers may be used.
  • a porous nonwoven fabrics such as nonwoven fabrics made of high melting point glass fibers, polyethylene terephthalate fibers and the like may be used.
  • a coated separator containing a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength, and may be optionally used as a single layer or a multilayer structure.
  • examples of the electrolyte used in the present invention include an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, and the like, which can be used in manufacturing a lithium secondary battery. It doesn't happen.
  • the electrolyte may include an organic solvent and a lithium salt.
  • the organic solvent may be used without particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move.
  • the organic solvent may be an ester solvent such as methyl acetate, ethyl acetate, ⁇ -butyrolactone or ⁇ -caprolactone; Ether solvents such as dibutyl ether or tetrahydrofuran; Ketone solvents such as cyclohexanone; Aromatic hydrocarbon solvents such as benzene and fluorobenzene; Dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), propylene carbonate, Carbonate solvents such as PC); Alcohol solvents such as ethyl alcohol and isopropyl alcohol; Nitriles such as R-CN (R is a C2 to C20 linear, branched or cyclic hydrocarbon group, which may include a
  • carbonate-based solvents are preferable, and cyclic carbonates having high ionic conductivity and high dielectric constant (for example, ethylene carbonate or propylene carbonate) that can improve the charge and discharge performance of a battery, and low viscosity linear carbonate compounds (for example, a mixture of ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate and the like is more preferable.
  • the cyclic carbonate and the chain carbonate may be mixed and used in a volume ratio of about 1: 1 to about 1: 9, so that the performance of the electrolyte may be excellent.
  • the lithium salt may 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 is 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 and the like can be used.
  • the concentration of the lithium salt is preferably used within the range of 0.1 to 2.0M. When the concentration of the lithium salt is included in the above range, since the electrolyte has an appropriate conductivity and viscosity, it can exhibit excellent electrolyte performance, and lithium ions can move effectively.
  • the electrolyte includes, for example, haloalkylene carbonate-based compounds such as difluoro ethylene carbonate, pyridine, tri, etc. for the purpose of improving battery life characteristics, reducing battery capacity, and improving discharge capacity of the battery.
  • haloalkylene carbonate-based compounds such as difluoro ethylene carbonate, pyridine, tri, etc.
  • Ethyl phosphite triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphate triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N, N-substituted imida
  • One or more additives such as zolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxy ethanol or aluminum trichloride may be included. In this case, the additive may be included in 0.1 to 5% by weight based on the total weight of the electrolyte.
  • the lithium secondary battery including the electrode manufactured using the conductive material dispersion according to the present invention may stably exhibit excellent discharge capacity, output characteristics, and capacity retention rate due to the uniform dispersion of the conductive material in the electrode.
  • portable devices such as a mobile telephone, a notebook computer, a digital camera, and the electric vehicle field
  • HEV hybrid electric vehicle
  • a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.
  • the battery module or the battery pack is a power tool (Power Tool); Electric vehicles including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); Or it can be used as a power source for any one or more of the system for power storage.
  • Power Tool Electric vehicles including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); Or it can be used as a power source for any one or more of the system for power storage.
  • Example 1-1, Comparative Example 1-1 and Comparative Example 1-2 Preparation of Carbon Nanotubes
  • citric acid was added so that Co was 1 mole of citric acid to 1 mole of citric acid, and the weight of the resulting mixture was measured, and stirred for 5 minutes in a 60 ° C. constant temperature bath in order to sufficiently support the graphitized catalyst metal precursor. I was. While maintaining the temperature, the aged mixture was vacuum dried while rotating at 80 rpm, and the weight after drying was measured to determine the water removal amount (about 14.1 wt%). The resulting dry reactant was secondary calcined for 4 hours at the temperature shown in Table 1 below to prepare a supported catalyst.
  • Carbon nanotube synthesis was performed in a laboratory scale fixed bed reactor using the supported catalyst for carbon nanotube synthesis prepared above. Specifically, the supported catalyst for synthesizing carbon nanotubes prepared above was mounted at the center of a quartz tube having an inner diameter of 55 mm, and then heated up to 670 ° C. in a nitrogen atmosphere and maintained therein, and mixed with nitrogen, hydrogen, and ethylene gas. The volume ratio was reacted for 1 hour while flowing 180 ml per minute in the same ratio of 1: 1: 1 to synthesize bundle carbon nanotubes.
  • Example 1-1 The carbon nanotubes of Example 1-1, Comparative Example 1-1 and Comparative Example 1-2 were observed using a scanning electron microscope (SEM).
  • SEM scanning electron microscope
  • the observation results of the carbon nanotubes of Example 1-1 are shown in FIGS. 1 to 3.
  • the observation results of the carbon nanotubes of Comparative Example 1-1 are shown in FIGS. 4 to 6.
  • Carbon nanotubes prepared in Comparative Examples 1-2 are shown in FIGS. 7 to 9.
  • the carbon nanotubes of Example 1-1 and the carbon nanotubes of Comparative Example 1-1 and Comparative Example 1-2 were bundled structures having an average particle diameter (D 50 ) of equivalent level of 100 ⁇ m or less.
  • D 50 average particle diameter
  • the carbon nanotube unit of Example 1-1 has a longer length and a higher linearity than the carbon nanotubes of Comparative Example 1-1 and Comparative Example 1-2.
  • Powder resistance The powder was filled into an insulating mold with a diameter of 1 mm and pressurized to measure the surface current and voltage with four probes, and a volumetric resistance value at 62 MPa was calculated by applying a correction factor. .
  • BET specific surface area BELSORP-mino II by BEL Japan Co., Ltd. was calculated from the amount of nitrogen gas adsorption under liquid nitrogen temperature (77K).
  • the carbon nanotubes of Example 1-1 were higher in purity and specific surface area than the carbon nanotubes of Comparative Examples 1-1 and 1-2, but their bulk density and powder resistance were low. .
  • the carbon nanotubes of Example 1-1 satisfy the above Equation 1, but the carbon nanotubes of Comparative Example 1-1 and Comparative Example 1-2 did not satisfy the above Equation 1.
  • Example 1-1 Comparative Example 1-1 and Comparative Example 1-2 were observed a change in powder resistance according to the powder density, the results are shown in Table 3 and FIG.
  • the carbon nanotube powder was filled into an insulating mold with a diameter of 1 mm and pressurized, and the surface current and voltage were measured by four probes. The powder density and powder resistance were calculated by applying a correction factor. It was.
  • the carbon nanotubes of Example 1-1 have a powder resistance of 0.0080 ⁇ ⁇ cm to 0.0357 ⁇ ⁇ cm when the pressure is 13 to 62 MPa, and satisfies Equation 1 described above. It can be seen that. Carbon nanotubes of Example 1-1 showed a lower powder resistance than carbon nanotubes of Comparative Examples 1-1 and 1-2 in the same powder density section. On the other hand, the carbon nanotubes of Comparative Example 1-1 and Comparative Example 1-2 did not satisfy all of the above-described equations.
  • Example 2-1 to Example 2-6, Comparative Example 2-1 and Comparative Examples 2-2 Preparation of the conductive material dispersion
  • NMP N-methylpyrrolidone
  • Example 1-1 54 63 0 260,000 2.9
  • Example 2-2 Example 1-1 37 63 0 200,000 2.7
  • Example 2-3 Example 1-1 37 63 0 300,000 3.3
  • Example 2-4 Example 1-1 37 44 35 400,000 0.3
  • Example 2-5 Example 1-1 21 63 10 480,000 2.2
  • Example 2-6 Example 1-1 Polyvinylpyrrolidone 400,000 - Comparative Example 2-1 Comparative Example 1-1 37 63 0 260,000 2.9 Comparative Example 2-2 Comparative Example 1-2 37 63 0 260,000 2.9
  • Particle size distribution The average particle size D based on 10% of the particle size distribution in the measuring device after being introduced into a laser diffraction particle size measuring device (e.g., Microtrac MT 3000) was irradiated with an output of 60 W at about 28 Hz. 10 , the average particle size D 50 at the 50% basis of the particle size distribution and the average particle size D 90 at the 90% basis of the particle size distribution were calculated, respectively.
  • a laser diffraction particle size measuring device e.g., Microtrac MT 3000
  • BF viscosity The viscosity at 10 rpm was measured using a Brookfield viscometer.
  • the carbon nanotube-dispersant composite in the conductive material dispersion of Examples 2-1 to 2-6 was found to satisfy the particle size distribution according to the equation (3).
  • the carbon nanotube-dispersant composites in the conductive material dispersions of Comparative Example 2-1 and Comparative Example 2-2 did not satisfy the particle size distribution according to Equation 3.
  • the conductive material dispersions of Examples 2-1 to 2-2, Comparative Example 2-1 and Comparative Example 2-2 were observed using a scanning electron microscope (SEM).
  • SEM scanning electron microscope
  • the observation result of the electrically conductive material dispersion liquid of Example 2-1 is shown in FIG. 11,
  • the observation result of the electrically conductive material dispersion liquid of Example 2-2 is shown in FIG. 12, and the observation result of the electrically conductive material dispersion liquid of Example 2-3 is shown in FIG.
  • the observation result of the electrically conductive material dispersion liquid of Example 2-4 is shown in FIG. 14,
  • the observation result of the electrically conductive material dispersion liquid of Example 2-5 is shown in FIG. Shown in The observation result of the electrically conductive material dispersion of Comparative Example 2-1 is shown in FIG. 17.
  • the observation result of the electrically conductive material dispersion prepared in Comparative Example 2-2 is shown in FIG. 18.
  • the total weight of the composition for forming a positive electrode 23.35% by weight of the conductive material dispersion described in Table 6 below, the positive electrode active material LiNi 0 . 6 Mn 0 . 2 Co 0 .
  • BF viscosity The viscosity at 10 rpm was measured using a Brookfield viscometer.
  • Example 3-1 Example 2-1 LiNi 0.6 Mn 0.2 Co 0.2 O 2 Polyvinylidene fluoride 15,000
  • Example 3-2 Example 2-2 13,800
  • Example 3-3 Example 2-3 16,800
  • Example 3-4 Example 2-4 17,900
  • Example 3-5 Example 2-5 21,000
  • Example 3-6 Example 2-6 11,000 Comparative Example 3-1 Comparative Example 2-1 12.000 Comparative Example 3-2 Comparative Example 2-2 21,000
  • Powder resistance The powder which removed all solvents of anode composition was filled and pressurized into an insulating mold with a diameter of 1mm and the surface current and voltage were measured with four probes. The value was calculated.
  • Example 3-1 35.9 29.6 25.4 22.2 19.8
  • Example 3-3 37.7 32.8 27.3 23.1 21.9
  • Example 3-4 39.9 34.4 28.4 25.3 23.1
  • Example 3-5 41.2 37.1 30.3 27.4 25.3
  • Example 3-6 43.1 39.2 33.4 30.4 27.8 Comparative Example 3-1 101.0 82.5 71.8 63.2 57.0 Comparative Example 3-2 55.2 48.5 42.9 39.2 36.4
  • the composition for positive electrode formation of Examples 3-1 to 3-6 had a powder resistance of 34.2 ⁇ ⁇ cm to 43.1 ⁇ ⁇ cm when the pressure was 13 MPa, and powder resistance of 27.8 when the pressure was 25 MPa.
  • ⁇ ⁇ cm to 39.2 ⁇ ⁇ cm powder pressure is 24.4 ⁇ ⁇ cm to 33.4 ⁇ ⁇ cm when the pressure is 37 MPa
  • powder resistance is 21.9 ⁇ ⁇ cm to 30.4 ⁇ ⁇ cm when the pressure is 50 MPa
  • the pressure was 62 MPa
  • the powder resistance was 18.7 ⁇ ⁇ cm to 27.8 ⁇ ⁇ cm.
  • the composition for forming a positive electrode shown in Table 8 below was applied to an aluminum current collector, dried at 130 ° C., and then rolled to prepare a positive electrode. Also, 97% by weight of graphite as a negative electrode active material, 1% by weight of carbon black as a conductive material, 1% by weight of styrene-butadiene rubber (SBR) as a binder, and 1% by weight of carboxymethyl cellulose (CMC) as a thickener based on the total weight of the mixture. 353 g of the mixed mixture was mixed in 250 ml of water to prepare a composition for forming a negative electrode, which was applied to a copper current collector to prepare a negative electrode.
  • SBR styrene-butadiene rubber
  • CMC carboxymethyl cellulose
  • An electrode assembly was manufactured by interposing a separator of porous polyethylene between the positive electrode and the negative electrode prepared as described above, the electrode assembly was placed in a case, and an electrolyte solution was injected into the case to prepare a lithium secondary battery.
  • the lithium secondary batteries of Examples 4-1 to 4-4, Comparative Examples 4-1 and 4-4 were discharged at a low temperature ( ⁇ 10 ° C.) at a temperature of 6.5C based on 50% SOC.
  • the voltage change along each was measured (cut off voltage: 1.9V). The results are shown in Table 9 and FIG. 20.
  • Example 4-1 2.716 2.579 2.434 2.249
  • Example 4-2 2.706 2.575 2.435 2.275
  • Example 4-3 2.630 2.482 2.315 2.105
  • Example 4-4 2.585 2.429 2.255 2.029
  • Example 4-5 2.634 2.471 2.281 2.005
  • Example 4-6 2.611 2.438 2.229 1.915
  • the lithium secondary batteries of Examples 4-1 to 4-6 exhibited excellent low-temperature output characteristics compared to the lithium secondary batteries of Comparative Examples 4-1 to 4-4. .
  • the discharge could not be continued until 20 seconds.

Abstract

The present invention provides: a conductive material dispersed liquid containing a conductive material, a dispersant, and a dispersion medium, wherein the conductive material comprises bundle-type carbon nanotubes having a bulk density of 10-50 kg/m3 and a conductivity satisfying the conditions of mathematical expression 1 below, thereby exhibiting excellent dispersibility and conductivity; and a lithium secondary battery, which is manufactured using the conductive material dispersed liquid and thus can exhibit excellent battery functions, especially, excellent output characteristics at lower temperatures: [Mathematical Expression 1] -X ≤ 10log R ≤ -0.6X (in mathematical expression 1 above, X is the bulk density of the carbon nanotubes, and R is the powder resistance of the carbon nanotubes under a pressure of 10-65 MPa.)

Description

도전재 분산액 및 이를 이용하여 제조한 리튬 이차전지Dispersion of Conductive Material and Lithium Secondary Battery Prepared Using the Same
[관련출원과의 상호인용][Citations with Related Applications]
본 출원은 2015.10.28자 한국 특허 출원 제10-2015-0149938호 및 2016.10.28자 한국 특허 출원 제10-2016-0142055호에 기초한 우선권의 이익을 주장하며, 해당 한국 특허 출원의 문헌에 개시된　모든 내용은 본 명세서의 일부로서 포함된다.This application claims the benefit of priority based on Korean Patent Application No. 10-2015-0149938, filed on October 28, 2015 and Korean Patent Application No. 10-2016-0142055, filed on October 28, 2016. The contents are included as part of this specification.
[기술분야][Technical Field]
본 발명은 우수한 전도성 및 분산성을 갖는 도전재 분산액 및 이를 이용하여 제조한 리튬 이차전지에 관한 것이다. The present invention relates to a conductive material dispersion having excellent conductivity and dispersibility, and a lithium secondary battery manufactured using the same.
모바일 기기에 대한 기술 개발과 수요가 증가함에 따라 에너지원으로서 이차전지의 수요가 급격히 증가하고 있다. 이러한 이차전지 중 높은 에너지 밀도와 전압을 가지며, 사이클 수명이 길고, 자기방전율이 낮은 리튬 이차전지가 상용화되어 널리 사용되고 있다. 또, 이 같은 고용량 리튬 이차전지용 전극으로서, 전극 밀도를 향상시켜 단위 체적 당 에너지 밀도가 더 높은 전극을 제조하기 위한 방법에 대해 연구가 활발히 진행되고 있다. As technology development and demand for mobile devices increase, the demand for secondary batteries as a source of energy is rapidly increasing. Among such secondary batteries, lithium secondary batteries having high energy density and voltage, long cycle life, and low self discharge rate have been commercialized and widely used. In addition, as an electrode for a high capacity lithium secondary battery, research is being actively conducted on a method for improving an electrode density to produce an electrode having a higher energy density per unit volume.
일반적으로, 고밀도 전극은 수㎛ 내지 수십㎛의 크기를 갖는 전극 활물질 입자를 고압 프레스에 의해 성형하여 형성되므로, 입자들이 변형되고, 입자들 사이에 공간이 감소되며, 전해액 침투성이 저하되기 쉽다. In general, the high-density electrode is formed by molding electrode active material particles having a size of several micrometers to several tens of micrometers by a high pressure press, so that the particles are deformed, the space between the particles is reduced, and electrolyte permeability is easily degraded.
이 같은 문제를 해결하기 위해, 전극의 제조시 우수한 전기전도성과 함께 강도를 갖는 도전재를 사용하고 있다. 전극 제조시 도전재를 사용할 경우 도전재가 압축된 전극 활물질 사이에 분산됨으로써 활물질 입자들 사이에 미세기공을 유지하여 전해액의 침투가 용이하며, 또 우수한 전도성으로 전극 내 저항을 감소시킬 수 있다. 이와 같은 도전재 중에서도 전극 내 전기적 도전 경로를 형성함으로써 전극 저항을 더욱 감소시킬 수 있는 섬유형 탄소계 도전재인 탄소 나노튜브의 사용이 증가하고 있다.In order to solve such a problem, the electrically conductive material which has the intensity | strength with the outstanding electrical conductivity at the time of manufacturing an electrode is used. When the conductive material is used in electrode production, the conductive material is dispersed between the compressed electrode active material to maintain fine pores between the active material particles to facilitate penetration of the electrolyte, and to reduce the resistance in the electrode with excellent conductivity. Among such conductive materials, the use of carbon nanotubes, which are fibrous carbon-based conductive materials, which can further reduce electrode resistance by forming an electrically conductive path in the electrode, is increasing.
미세 탄소섬유의 일종인 탄소 나노튜브는 직경 1㎛이하 굵기의 튜브형 탄소로서, 그 특이적 구조에 기인한 높은 도전성, 인장 강도 및 내열성 등으로 인해 다양한 분야로의 적용 및 실용화가 기대되고 있다. 그러나, 이와 같은 탄소 나노튜브의 유용성에도 불구하고, 탄소 나노튜브는 낮은 용해성과 분산성으로 인해 그 사용에 한계가 있다. 이에 탄소 나노튜브를 이용한 전극 제조시, 탄소 나노튜브를 분산매에 선분산시킨 후 전극 형성용 조성물을 제조하여 사용하였다. 그러나, 탄소 나노튜브는 서로 간의 강한 반데르발스 인력에 의해 분산매 중에 안정적인 분산 상태를 이루지 못하고 응집 현상이 일어나는 문제가 있다.Carbon nanotubes, which are a kind of fine carbon fibers, are tubular carbons having a diameter of 1 μm or less, and are expected to be applied to various fields due to their high conductivity, tensile strength and heat resistance due to their specific structure. However, despite the usefulness of such carbon nanotubes, carbon nanotubes have limited use due to their low solubility and dispersibility. In preparing the electrode using the carbon nanotubes , the carbon nanotubes were predispersed in a dispersion medium, and then used to prepare a composition for forming an electrode. However, carbon nanotubes do not achieve a stable dispersion state in the dispersion medium due to strong van der Waals attraction between each other, there is a problem that agglomeration phenomenon occurs.
이러한 문제점을 해결하기 위하여 다양한 시도가 있어 왔다. 구체적으로 초음파 처리 등의 기계적 분산 처리를 통해 탄소 나노튜브를 분산매 중에 분산시키는 방법이 제안된 바 있다. 그러나, 이 방법의 경우 초음파를 조사하고 있는 동안은 분산성이 우수하지만, 초음파 조사가 종료되면 탄소 나노튜브의 응집이 시작되는 문제가 있다. 또, 다양한 분산제를 이용하여 탄소 나노튜브를 분산 안정화하는 방법이 제안되고 있다. 그러나, 이들 방법 역시 탄소 나노튜브를 분산매 중에 고농도로 분산시킬 경우, 점도 상승으로 인해 취급이 어렵게 되는 문제가 있다.Various attempts have been made to solve this problem. Specifically, a method of dispersing carbon nanotubes in a dispersion medium through mechanical dispersion treatment such as ultrasonication has been proposed. However, this method is excellent in dispersibility while irradiating ultrasonic waves, but there is a problem that aggregation of carbon nanotubes starts when ultrasonic irradiation ends. In addition, a method of dispersion stabilization of carbon nanotubes using various dispersants has been proposed. However, these methods also have a problem in that when the carbon nanotubes are dispersed in a high concentration in the dispersion medium, handling becomes difficult due to the increase in viscosity.
이에 따라, 도전성의 저하없이 전극 내 탄소 나노튜브의 분산성을 향상시킬 수 있는 방법 및 이를 이용하여 전극 제조에 유용한 탄소 나노튜브 분산액을 제조하는 방법의 개발이 필요하다. Accordingly, there is a need for development of a method for improving the dispersibility of carbon nanotubes in an electrode without deterioration of conductivity and a method of preparing carbon nanotube dispersions useful for electrode production using the same.
본 발명이 해결하고자 하는 제1 과제는 우수한 전도성 및 분산성을 갖는 도전재 분산액을 제공하는 것이다.The first problem to be solved by the present invention is to provide a conductive material dispersion having excellent conductivity and dispersibility.
본 발명이 해결하고자 하는 제2 과제는 상기 도전재 분산액을 포함하는 리튬 이차전지의 전극 형성용 조성물을 제공하는 것이다.A second object of the present invention is to provide a composition for forming an electrode of a lithium secondary battery including the conductive material dispersion.
또, 본 발명이 해결하고자 하는 제3 과제는, 상기 도전재 분산액을 이용하여 제조한 리튬 이차전지를 제공하는 것이다.Another object of the present invention is to provide a lithium secondary battery manufactured using the conductive material dispersion.
상기 과제를 해결하기 위하여 본 발명의 일 실시예에 따르면, 도전재, 분산제 및 분산매를 포함하며, 상기 도전재는 10 내지 50㎏/㎥의 벌크밀도와, 하기 수학식 1의 조건을 충족하는 전도성을 갖는 번들형(bundle-type) 탄소 나노튜브를 포함하는 것인 도전재 분산액을 제공한다.According to an embodiment of the present invention to solve the above problems, it comprises a conductive material, a dispersant and a dispersion medium, the conductive material has a bulk density of 10 to 50kg / ㎥ and a conductivity that meets the conditions of the following equation (1) It provides a conductive material dispersion comprising a bundle-type carbon nanotube having.
[수학식 1][Equation 1]
-X ≤ 10log R ≤ -0.6X-X ≤ 10log R ≤ -0.6X
(상기 수학식 1에서 X는 상기 탄소 나노튜브의 벌크밀도이고, R은 10 내지 65㎫의 압력 하에서의 상기 탄소 나노튜브의 분체저항이다)(Wherein X is the bulk density of the carbon nanotubes, and R is the powder resistance of the carbon nanotubes under a pressure of 10 to 65 MPa)
본 발명의 다른 일 실시예에 따르면, 상기 도전재 분산액을 포함하는 리튬 이차전지의 전극 형성용 조성물을 제공하는 것이다.According to another embodiment of the present invention, to provide a composition for forming an electrode of a lithium secondary battery comprising the conductive material dispersion.
본 발명의 또 다른 일 실시예에 따르면, 상기 전극 형성용 조성물로 제조한 전극을 포함하는 리튬 이차전지를 제공한다.According to another embodiment of the present invention, there is provided a lithium secondary battery including an electrode made of the electrode forming composition.
기타 본 발명의 실시예들의 구체적인 사항은 이하의 상세한 설명에 포함되어 있다.Other specific details of the embodiments of the present invention are included in the following detailed description.
본 발명에 따른 도전재 분산액은 분산액내 우수한 전도성을 갖는 탄소 나노튜브의 균일 분산으로 인해 우수한 전도성 및 분산성을 나타낼 수 있다. 이에 따라 리튬 이차전지의 전극 형성시 전극 내에서 우수한 도전재의 분산성을 나타낼 수 있으며, 전극 내 전도성을 높여 전지 적용시 전지 성능, 특히 저온에서의 출력 특성을 향상시킬 수 있다. 상기 도전재 분산액은 자동차용 전지 등과 같이 고출력 특성이 요구되는 전지의 제조에 유용하다.The conductive material dispersion according to the present invention may exhibit excellent conductivity and dispersibility due to uniform dispersion of carbon nanotubes having excellent conductivity in the dispersion. Accordingly, when forming the electrode of the lithium secondary battery, it is possible to exhibit excellent dispersibility of the conductive material in the electrode, and to increase the conductivity in the electrode, thereby improving battery performance during battery application, particularly at low temperatures. The conductive material dispersion is useful for the production of batteries requiring high output characteristics, such as automotive batteries.
본 명세서에 첨부되는 다음의 도면들은 본 발명의 바람직한 실시예를 예시하는 것이며, 전술한 발명의 내용과 함께 본 발명의 기술사상을 더욱 이해시키는 역할을 하는 것이므로, 본 발명은 그러한 도면에 기재된 사항에만 한정되어 해석되어서는 아니 된다.The following drawings, which are attached to this specification, illustrate preferred embodiments of the present invention, and together with the contents of the present invention serve to further understand the technical spirit of the present invention, the present invention is limited to the matters described in such drawings. It should not be construed as limited.
도 1 내지 도 3은 실시예 1-1의 탄소 나노튜브를 주사전자 현미경을 이용하여 다양한 관찰 배율로 관찰한 사진이다.1 to 3 are photographs of the carbon nanotubes of Example 1-1 observed at various observation magnifications using a scanning electron microscope.
도 4 내지 도 6은 비교예 1-1의 탄소 나노튜브를 주사전자 현미경을 이용하여 다양한 관찰 배율로 관찰한 사진이다.4 to 6 are photographs of the carbon nanotubes of Comparative Example 1-1 observed at various observation magnifications using a scanning electron microscope.
도 7 내지 도 9는 비교예 1-2의 탄소 나노튜브를 주사전자 현미경을 이용하여 다양한 관찰 배율로 관찰한 사진이다.7 to 9 are photographs of the carbon nanotubes of Comparative Examples 1-2 observed at various observation magnifications using a scanning electron microscope.
도 10은 실시예 1-1, 비교예 1-1 및 비교예 1-2의 탄소 나노튜브의 분체밀도에 따른 분체저항 변화를 관찰한 결과를 나타낸 그래프이다.10 is a graph showing the results of observing the change in powder resistance according to the powder density of the carbon nanotubes of Example 1-1, Comparative Example 1-1 and Comparative Example 1-2.
도 11은 실시예 2-1의 도전재 분산액을 주사전자 현미경을 이용하여 관찰한 사진이다.FIG. 11 is a photograph of the conductive material dispersion of Example 2-1 observed using a scanning electron microscope. FIG.
도 12는 실시예 2-2의 도전재 분산액을 주사전자 현미경을 이용하여 관찰한 사진이다.12 is a photograph of the conductive material dispersion of Example 2-2 observed using a scanning electron microscope.
도 13은 실시예 2-3의 도전재 분산액을 주사전자 현미경을 이용하여 관찰한 사진이다.FIG. 13 is a photograph of the conducting material dispersion of Example 2-3 using a scanning electron microscope. FIG.
도 14는 실시예 2-4의 도전재 분산액을 주사전자 현미경을 이용하여 관찰한 사진이다.14 is a photograph of the conductive material dispersion of Example 2-4 using a scanning electron microscope.
도 15는 실시예 2-5의 도전재 분산액을 주사전자 현미경을 이용하여 관찰한 사진이다.FIG. 15 is a photograph of the conducting material dispersion of Example 2-5 using a scanning electron microscope. FIG.
도 16는 실시예 2-6의 도전재 분산액을 주사전자 현미경을 이용하여 관찰한 사진이다.16 is a photograph of a conductive material dispersion of Example 2-6 using a scanning electron microscope.
도 17은 비교예 2-1의 도전재 분산액을 주사전자 현미경을 이용하여 관찰한 사진이다.17 is a photograph of a conductive material dispersion of Comparative Example 2-1 observed using a scanning electron microscope.
도 18은 비교예 2-2의 도전재 분산액을 주사전자 현미경을 이용하여 관찰한 사진이다.18 is a photograph of a conductive material dispersion of Comparative Example 2-2 observed using a scanning electron microscope.
도 19는 실시예 3-1 내지 실시예 3-6, 비교예 3-1 및 비교예 3-2에서 제조한 양극 형성용 조성물의 용매를 제거한 후, 분체저항을 관찰한 결과를 나타낸 그래프이다.19 is a graph showing the results of observing powder resistance after removing the solvent of the positive electrode forming composition prepared in Examples 3-1 to 3-3, Comparative Example 3-1, and Comparative Example 3-2.
도 20은 실시예 4-1 내지 실시예 4-6, 비교예 4-1 및 비교예 4-2의 리튬 이차전지의 저온(-10℃)에서의 방전시 출력 특성을 관찰한 결과를 나타낸 그래프이다.20 is a graph illustrating results of observing output characteristics during discharge at low temperature (-10 ° C) of the lithium secondary batteries of Examples 4-1 to 4-4, Comparative Examples 4-1, and Comparative Example 4-2. to be.
이하, 본 발명에 대한 이해를 돕기 위하여 본 발명을 더욱 상세하게 설명한다.Hereinafter, the present invention will be described in more detail to aid in understanding the present invention.
본 명세서 및 청구범위에 사용된 용어나 단어는 통상적이거나 사전적인 의미로 한정해서 해석되어서는 아니 되며, 발명자는 그 자신의 발명을 가장 최선의 방법으로 설명하기 위해 용어의 개념을 적절하게 정의할 수 있다는 원칙에 입각하여 본 발명의 기술적 사상에 부합하는 의미와 개념으로 해석되어야만 한다.The terms or words used in this specification and claims are not to be construed as limiting in their usual or dictionary meanings, and the inventors may appropriately define the concept of terms in order to best explain their invention in the best way possible. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that the present invention.
본 발명에서 사용하는 용어 '번들형(bundle type)'이란 달리 언급되지 않는 한, 복수 개의 탄소 나노튜브 가닥, 즉 탄소 나노튜브 단위체가 단위체 길이 방향의 축이 실질적으로 동일한 배향으로 나란하게 배열되거나 또는 나선형으로 꼬인 다발(bundle) 혹은 로프(rope) 형태의 2차 형상을 지칭한다. 또 '비번들형(non-bundle type) 또는 인탱글(entangled type)'이란 복수 개의 탄소 나노튜브 단위체가 특정 배향에 한정되지 않고 일정한 형상이 없이 뒤엉켜 있는 형태를 의미한다.As used herein, unless the term 'bundle type' is used, a plurality of carbon nanotube strands, ie, carbon nanotube units, are arranged side by side in an orientation substantially identical in the axis of the unit length direction, or It refers to a secondary shape in the form of a bundle or rope twisted spirally. In addition, "non-bundle type" (entangled type) or "entangled type" (entangled type) refers to a form in which a plurality of carbon nanotube units are not confined to a specific orientation and tangled without a certain shape.
통상 탄소 나노튜브(CNT)는 탄소 나노튜브를 구성하는 단위체의 결정성과 구조, 형태, 그리고 상기 단위체로 이루어진 2차 입자의 구조와 형태, 불순물을 포함하여 탄소 나노튜브 내 포함된 성분 등에 따라 물성이 달라질 수 있다. 이에 따라 상기한 요인들 중 어느 하나 또는 둘 이상을 조합적으로 제어함으로써, 탄소 나노튜브의 용도에 따라 요구되는 물성을 갖도록 할 수 있다.In general, carbon nanotubes (CNTs) have physical properties depending on the crystallinity, structure, form, and structure and shape of secondary particles composed of the monomers, and components contained in carbon nanotubes including impurities. Can vary. Accordingly, by controlling any one or two or more of the above factors, it is possible to have the physical properties required according to the use of the carbon nanotubes.
이에 따라, 본 발명에서는 도전재 분산액의 제조시 사용되는 탄소 나노튜브의 벌크밀도와 분체저항을 동시에 제어함으로써, 우수한 분산성 및 전도성을 나타내도록 하고, 결과적으로 전극 제조에 적용시 전극 내 전도성을 높여 전지 성능, 특히 저온에서의 전지의 출력 특성을 크게 향상시킬 수 있다.Accordingly, in the present invention, by simultaneously controlling the bulk density and the powder resistance of the carbon nanotubes used in the production of the conductive material dispersion, to exhibit excellent dispersibility and conductivity, and consequently to increase the conductivity in the electrode when applied to electrode production Battery performance, especially the output characteristics of a battery at low temperatures can be greatly improved.
구체적으로, 본 발명의 일 실시예에 따른 도전재 분산액은, 도전재, 분산제 및 분산매를 포함하고, 상기 도전재는 10 내지 50㎏/㎥의 벌크밀도와, 하기 수학식 1의 조건을 충족하는 전도성을 갖는 번들형(bundle-type) 탄소 나노튜브를 포함한다:Specifically, the conductive material dispersion according to an embodiment of the present invention includes a conductive material, a dispersant and a dispersion medium, the conductive material has a bulk density of 10 to 50 kg / ㎥ and a conductivity that meets the conditions of the following formula (1) Bundle-type carbon nanotubes having:
[수학식 1][Equation 1]
-X ≤ 10log R ≤ -0.6X-X ≤ 10log R ≤ -0.6X
상기 수학식 1에서 X는 상기 탄소 나노튜브의 벌크밀도이고, R은 10 내지 65㎫의 압력 하에서의 상기 탄소 나노튜브의 분체저항이다.In Equation 1, X is the bulk density of the carbon nanotubes, R is the powder resistance of the carbon nanotubes under a pressure of 10 to 65 MPa.
또, 본 발명에 있어서 탄소 나노튜브의 벌크밀도는 하기 수학식 2에 따라 결정될 수 있다.In addition, in the present invention, the bulk density of the carbon nanotubes may be determined according to Equation 2 below.
[수학식 2][Equation 2]
벌크밀도(㎏/㎥)= 탄소 나노튜브의 중량(㎏)/ 탄소 나노튜브의 부피(㎥)Bulk density (㎏ / ㎥) = weight of carbon nanotubes (㎏) / volume of carbon nanotubes (㎥)
보다 구체적으로 벌크밀도와 분체저항을 동시 제어에 따른 탄소 나노튜브의 전도성 및 분산성 개선 효과의 현저함을 고려할 때, 상기 탄소 나노튜브는 20 내지 35㎏/㎥의 벌크밀도; 및 10 내지 65㎫의 압력 하에서 0.013 Ω·㎝ 이하, 보다 구체적으로는 0.001 내지 0.01Ω·㎝의 분체저항을 갖는 것일 수 있다.More specifically, considering the remarkable effect of improving the conductivity and dispersibility of the carbon nanotubes by simultaneous control of bulk density and powder resistance, the carbon nanotubes have a bulk density of 20 to 35 kg / m 3; And a powder resistance of 0.013 Ω · cm or less, more specifically 0.001 to 0.01 Ω · cm under a pressure of 10 to 65 MPa.
본 발명의 일 실시예에 따른 상기 도전재 분산액에 있어서, 탄소 나노튜브는 탄소 나노튜브 단위체가 전체 또는 부분적으로 번들형을 이루도록 집합되어 형성된 2차 구조물로서, 상기 탄소 나노튜브 단위체는 흑연면(graphite sheet)이 나노 크기 직경의 실린더 형태를 가지며, sp2 결합 구조를 갖는다. 이때 상기 흑연면이 말리는 각도 및 구조에 따라서 도체 또는 반도체의 특성을 나타낼 수 있다. 탄소 나노튜브 단위체는 벽을 이루고 있는 결합수에 따라서 단일벽 탄소 나노튜브(SWCNT, single-walled carbon nanotube), 이중벽 탄소 나노튜브(DWCNT, doublewalled carbon nanotube) 및 다중벽 탄소 나노튜브(MWCNT, multi-walled carbon nanotube)로 분류될 수 있으며, 벽 두께가 얇을수록 저항이 낮다. 이에 따라 본 발명의 일 실시예에 따른 상기 도전재 분산액에 있어서, 상기 탄소 나노튜브는 단일벽, 이중벽 및 다중벽의 탄소 나노튜브 단위체 중 어느 하나 또는 둘 이상을 포함할 수 있다. In the conductive material dispersion according to an embodiment of the present invention, the carbon nanotubes are secondary structures formed by gathering carbon nanotube units in whole or part in bundle form, and the carbon nanotube units are graphite surfaces. sheet) has the shape of a cylinder of nano size diameter and has a sp 2 bond structure. In this case, the graphite surface may exhibit characteristics of a conductor or a semiconductor depending on the angle and structure of the surface. Carbon nanotube units are single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs) and multi-walled carbon nanotubes (MWCNTs). walled carbon nanotube), the thinner the wall thickness, the lower the resistance. Accordingly, in the conductive material dispersion according to an embodiment of the present invention, the carbon nanotubes may include any one or two or more of carbon nanotube units of a single wall, a double wall and a multi-wall.
또, 리튬 이차전지용 도전재로서 탄소 나노튜브 단위체의 직경이 지나치게 크면, 전극의 기공 직경 또한 크게 증가하게 되어 전극 밀도가 오히려 저하될 수 있다. 또, 탄소 나노튜브 단위체의 직경이 지나치게 작으면, 분산된 탄소 나노튜브 단위체 또는 탄소 나노튜브가 전극활물질 입자 사이의 공간에 매몰되어, 전극층 내 충분한 기공이 형성되기 어렵다. 이에 따라, 본 발명에서 사용 가능한 탄소 나노튜브에 있어서의 탄소 나노튜브 단위체의 평균 직경은 5 내지 30㎚일 수 있으며, 탄소 나노튜브 단위체의 직경 제어에 따른 도전재의 분산성 향상 및 전극 내 저항 감소 효과를 고려할 때, 상기 탄소 나노튜브 단위체의 평균 직경은 10 내지 20㎚일 수 있다. 상기 탄소 나노튜브 단위체는 탄소 나노튜브 한 가닥을 의미한다.In addition, when the diameter of the carbon nanotube unit is too large as the conductive material for a lithium secondary battery, the pore diameter of the electrode may also increase greatly, and thus the electrode density may be lowered. In addition, if the diameter of the carbon nanotube unit is too small, the dispersed carbon nanotube unit or carbon nanotube is embedded in the space between the electrode active material particles, it is difficult to form sufficient pores in the electrode layer. Accordingly, the average diameter of the carbon nanotube units in the carbon nanotubes usable in the present invention may be 5 to 30 nm, and the effect of improving the dispersibility of the conductive material and reducing the resistance in the electrode by controlling the diameter of the carbon nanotube units. In consideration of the above, the average diameter of the carbon nanotube unit may be 10 to 20nm. The carbon nanotube unit means a strand of carbon nanotubes.
또, 탄소 나노튜브 단위체의 길이가 길수록 전극의 전기전도성, 강도 및 전해액 보관유지성이 향상될 수 있다. 그러나, 탄소 나노튜브 단위체의 길이가 지나치게 길면 분산성이 저하될 우려가 있다. 이에 따라, 본 발명에서 사용 가능한 탄소 나노튜브에 있어서의 탄소 나노튜브 단위체의 길이는 0.5 내지 200㎛일 수 있다. 또, 상기 탄소 나노튜브 단위체의 직경을 고려할 때, 상기 탄소 나노튜브 단위체는 탄소 나노튜브 단위체의 길이와 직경의 비로 정의되는 종횡비가 5 내지 50,000일 수 있으며, 보다 구체적으로는 10 내지 20,000일 수 있다. In addition, the longer the length of the carbon nanotube unit can improve the electrical conductivity, strength and electrolyte storage retention of the electrode. However, when the length of the carbon nanotube unit is too long, the dispersibility may decrease. Accordingly, the length of the carbon nanotube unit in the carbon nanotubes usable in the present invention may be 0.5 to 200㎛. In addition, in consideration of the diameter of the carbon nanotube unit, the carbon nanotube unit may have an aspect ratio defined as a ratio of the length and the diameter of the carbon nanotube unit, 5 to 50,000, and more specifically, 10 to 20,000. .
본 발명에 있어서, 탄소 나노튜브 단위체의 길이는 탄소 나노튜브 단위체의 중심을 지나는 장축의 길이를 의미하고, 직경은 탄소 나노튜브 단위체의 중심을 지나는 장축에 수직한 단축의 길이를 의미한다.In the present invention, the length of the carbon nanotube unit means the length of the long axis passing through the center of the carbon nanotube unit, the diameter means the length of the short axis perpendicular to the long axis passing through the center of the carbon nanotube unit.
한편, 상기 탄소 나노튜브 단위체를 포함하는 탄소 나노튜브는 진밀도(TD)와 벌크밀도(BD)의 비(TD/BD 비)가 70 내지 120인 것일 수 있다.Meanwhile, the carbon nanotubes including the carbon nanotube unit may have a ratio (TD / BD ratio) of true density (TD) and bulk density (BD) of 70 to 120.
본 발명에 있어서, 탄소 나노튜브의 진밀도는 Pycnometer (AccuPycⅡ 1340)을 이용하여 측정되는 것으로, 다공성 고체에서 기공을 제외한 입자 자체만의 부피에 대한 밀도라는 점에서 벌크밀도와는 차이가 있다. 이에 따라 TD/BD비로부터 탄소 나노튜브의 내부 구조를 예측할 수 있는데, TD/BD 비가 지나치게 크면 탄소 나노튜브 내 탄소 나노튜브 단위체의 함량이 낮기 때문에 전지의 용량 특성이 저하될 우려가 있고, 또 TD/BD 비가 지나치게 작으면 탄소 나노튜브의 분산성이 저하될 우려가 있다. 벌크밀도와 진밀도의 비 제어에 따른 개선 효과의 현저함을 고려할 때, 본 발명에서 사용 가능한 탄소 나노튜브의 TD/BD 비는 보다 구체적으로 70 내지 100일 수 있다. 또, 본 발명에서 사용 가능한 상기 탄소 나노튜브의 진밀도는 상기한 TD/BD 비를 충족하는 조건 하에서 1,800 내지 2,200㎏/㎥일 수 있다.In the present invention, the true density of the carbon nanotubes is measured using a Pycnometer (AccuPycII 1340), which is different from the bulk density in that the density of the particle itself except the pores in the porous solid. Accordingly, the internal structure of the carbon nanotubes can be predicted from the TD / BD ratio. If the TD / BD ratio is too large, the content of the carbon nanotube units in the carbon nanotubes is low, which may lower the capacity characteristics of the battery. If the / BD ratio is too small, the dispersibility of the carbon nanotubes may be lowered. Considering the remarkable effect of the improvement effect of the ratio of the bulk density and the true density, the TD / BD ratio of the carbon nanotubes usable in the present invention may be more specifically 70 to 100. In addition, the true density of the carbon nanotubes usable in the present invention may be 1,800 to 2,200 kg / ㎥ under the conditions that meet the TD / BD ratio.
또, 본 발명의 일 실시예에 따른 상기 도전재 분산액에 있어서, 상기 탄소 나노튜브는 그 단위체의 평균 직경이 앞서 설명한 바와 같이 작고, TD/BD 비가 크기 때문에 높은 BET 비표면적을 가지며 우수한 분산성을 나타낼 수 있다. 구체적으로 본 발명에서 사용 가능한 상기 탄소 나노튜브의 BET 비표면적은 180 내지 300㎡/g일 수 있으며, 보다 구체적으로는 230 내지 280㎡/g일 수 있다. In addition, in the conductive material dispersion according to an embodiment of the present invention, the carbon nanotube has a high BET specific surface area and excellent dispersibility because the carbon nanotube has a small average diameter of the unit as described above and a large TD / BD ratio. Can be represented. Specifically, the BET specific surface area of the carbon nanotubes usable in the present invention may be 180 to 300 m 2 / g, more specifically 230 to 280 m 2 / g.
본 발명에 있어서, 상기 탄소 나노튜브의 비표면적은 BET법에 의해 측정한 것으로서, 구체적으로는 BEL Japan 사 BELSORP-mino Ⅱ를 이용하여 액체 질소 온도 하(77K)에서의 질소가스 흡착량으로부터 산출할 수 있다.In the present invention, the specific surface area of the carbon nanotubes is measured by the BET method, specifically, it is calculated from the nitrogen gas adsorption amount under the liquid nitrogen temperature (77K) using BELSORP-mino II by BEL Japan. Can be.
또, 본 발명의 일 실시예에 따른 상기 도전재 분산액에 있어서, 상기 탄소 나노튜브는 532nm 파장의 레이저를 이용한 라만 분광 분석법에 의해 얻어진 1580±50㎝-1에서의 G 밴드의 최대 피크 강도(IG)에 대한 1,360±50㎝-1 에서의 D 밴드의 최대 피크 강도(ID)의 비(ID/IG)의 평균값이 0.75 내지 1.05, 구체적으로는 0.95 내지 1.04이고, 표준편차값이 1.3 내지 2.0%, 구체적으로는 1.5 내지 2.0%인 것일 수 있다. In the conductive material dispersion according to the embodiment of the present invention, the carbon nanotubes have a maximum peak intensity (IG) of a G band at 1580 ± 50 cm −1 obtained by Raman spectroscopy using a laser of 532 nm wavelength. The average value of the ratio (ID / IG) of the maximum peak intensity (ID) of the D-band at 1,360 ± 50 cm −1 ) is 0.75 to 1.05, specifically 0.95 to 1.04, and the standard deviation value is 1.3 to 2.0%. Specifically, the content may be 1.5 to 2.0%.
라만 분광 분석법은 탄소 나노튜브의 구조를 분석하는 방법으로서, 탄소 나노튜브의 표면 상태 분석에 유용한 방법이다. 탄소 나노튜브의 라만 스펙트럼 중 파수 1,580cm-1 부근의 영역에 존재하는 피크를 G 밴드라고 하며, 이는 탄소 나노튜브의 sp2 결합을 나타내는 피크로서, 구조결함이 없는 탄소 결정을 나타내는 것이다. 한편, 라만 스펙트럼 중 파수 1360㎝-1 부근의 영역에 존재하는 피크를 D밴드라고 하며, 이는 탄소 나노튜브의 sp3 결합을 나타내는 피크로서, sp2 결합으로 이루어진 원자 결합이 끊어져 sp3 결합이 되는 경우 증가한다. 이와 같은 D밴드는 상기 탄소 나노튜브 내에 존재하는 무질서(disorder) 내지 결함(defect)이 생성될 경우 증가하게 되므로, G 밴드의 최대 피크 강도(IG)에 대한 D 밴드의 최대 피크 강도(ID)의 비(ID/IG)를 계산하여 무질서(disorder) 내지 결함(defect)의 생성 정도를 정량적으로 평가할 수 있다. Raman spectroscopy is a method for analyzing the structure of carbon nanotubes, which is useful for analyzing the surface state of carbon nanotubes. The peak present in the region near the wavenumber of 1,580 cm −1 in the Raman spectrum of the carbon nanotubes is called a G band, which is a peak indicating sp 2 bond of the carbon nanotubes, indicating a carbon crystal without structural defects. On the other hand, the peak present in the region near the wave number 1360 cm -1 of the Raman spectrum is called the D-band, which is a peak representing the sp 3 bond of the carbon nanotubes, the atomic bond consisting of sp 2 bonds are broken to become sp 3 bonds If it increases. This D band is increased when a disorder or defect existing in the carbon nanotube is generated, so that the maximum peak intensity (ID) of the D band with respect to the maximum peak intensity (IG) of the G band is increased. The ratio (ID / IG) can be calculated to quantitatively assess the degree of disorder to defect generation.
본 발명에 있어서 탄소 나노튜브에 대한 라만 스펙트럼의 G 밴드는 파수 1,580±50㎝-1 영역에 존재하는 피크일 수 있고, D 밴드는 파수 1,360±50㎝-1 영역에 존재하는 피크일 수 있다. 상기 G 밴드 및 D 밴드에 대한 파수 범위는 라만 분석법에 사용한 레이저 광원에 따라 시프트 될 수 있는 범위에 해당하는 것이다. 본 발명에서 사용하는 라만 값은 특별히 제한되는 것은 아니지만, DXR Raman Microscope(Thermo Electron Scientific Instruments LLC)을 이용하여 레이저 파장 532㎚ 에서 측정할 수 있다.In the present invention, the G band of the Raman spectrum for the carbon nanotube may be a peak present in the wavenumber of 1,580 ± 50 cm −1 region, and the D band may be a peak present in the wavenumber of 1,360 ± 50 cm −1 region. The wave range for the G band and the D band corresponds to a range that can be shifted according to the laser light source used in the Raman analysis. Raman values used in the present invention are not particularly limited, but may be measured at a laser wavelength of 532 nm using DXR Raman Microscope (Thermo Electron Scientific Instruments LLC).
통상 G 밴드 피크 적분치와 D 밴드 피크 적분치의 비율이 클 수록 비정질 탄소가 다량 함유되어 있거나 탄소 나노튜브의 결정성이 불량함을 의미하는 것이나, 본 발명에서는 BET 비표면적이 증가하고 번들형 구조의 2차 형상을 가짐에 따라 탄소 나노튜브의 결정성이 양호하면서도 상기와 같은 ID/IG의 평균값 및 표준편차값을 갖게 된다.In general, the larger the ratio of the G band peak integral to the D band peak integral, the higher the amount of amorphous carbon or the poorer crystallinity of the carbon nanotubes. However, in the present invention, the BET specific surface area is increased and the bundle structure As a result of the secondary shape, the crystallinity of the carbon nanotubes is good, but the average value and standard deviation of ID / IG are as described above.
본 발명의 일 실시예에 따른 상기 도전재 분산액에 있어서, 상기 탄소 나노튜브는 그 제조과정에서 사용된 Co, Mo, V, 또는 Cr 등과 같은 주 촉매 또는 조촉매 유래의 금속 원소를 50ppm 이하, 보다 구체적으로는 5ppm 이하의 함량으로 포함할 수 있으며, 보다 더 구체적으로는 Fe를 포함하지 않는 것일 수 있다. 이와 같이, 탄소 나노튜브 내 잔류하는 불순물로서의 금속 함량이 현저히 감소되고, 특히 탄소 나노튜브 내 Fe를 포함하지 않음으로써 전극 적용시 부반응에 대한 우려없이 보다 우수한 전도성을 나타낼 수 있다. In the conductive material dispersion according to an embodiment of the present invention, the carbon nanotubes are 50 ppm or less of metal elements derived from a main catalyst or cocatalyst, such as Co, Mo, V, or Cr, used in the manufacturing process. Specifically, the content may be included in an amount of 5 ppm or less, and more specifically, may not include Fe. As such, the metal content as impurities remaining in the carbon nanotubes is significantly reduced, and in particular, it does not contain Fe in the carbon nanotubes, thereby exhibiting better conductivity without concern for side reactions in electrode application.
본 발명에 있어서, 탄소 나노튜브 내 잔류하는 금속불순물의 함량은 고주파 유도 결합 플라즈마(inductively coupled plasma, ICP)를 이용하여 분석할 수 있다. In the present invention, the content of the metal impurities remaining in the carbon nanotubes can be analyzed by using a high frequency inductively coupled plasma (ICP).
상기와 같은 탄소 나노튜브는 아크방전법, 레이저 증발법 또는 화학기상 증착법 등의 통상의 방법을 이용하여 제조될 수 있으며, 제조 과정에서의 소성 온도 및 촉매의 종류와 함량 제어, 또는 불순물 제거 공정 실시 등을 통해 상기한 물성을 구현할 수 있다. Such carbon nanotubes may be manufactured using conventional methods such as arc discharge, laser evaporation, or chemical vapor deposition, and control the firing temperature and type and content of the catalyst during the manufacturing process, or perform impurity removal processes. The above-described physical properties can be implemented.
구체적으로, 화학적 기상 합성법에 따라 제조할 경우, 상기 탄소 나노튜브는 지지체에 금속촉매가 담지된 담지촉매를 탄소 공급원과 가열 하에 접촉시켜 탄소 나노튜브를 제조하는 단계, 및 필요에 따라 선택적으로 상기 탄소 나노튜브 내 금속불순물을 제거하는 단계를 포함하는 제조방법에 의해 제조될 수 있다.Specifically, when prepared by chemical vapor phase synthesis, the carbon nanotubes are prepared by contacting a supported catalyst having a metal catalyst on a support under heating with a carbon source to produce carbon nanotubes, and optionally the carbon as necessary. It may be prepared by a manufacturing method comprising the step of removing metal impurities in the nanotubes.
상기 화학적 기상 합성법에 따른 탄소 나노튜브의 제조는, 보다 구체적으로 상기 담지촉매를 고정층 반응기 또는 유동층 반응기 내에 투입한 후, 탄소 공급원의 열분해 온도 이상 내지 상기 담지된 금속촉매의 융점 이하의 온도 범위에서 탄소 공급원; 또는 상기 탄소 공급원과 환원가스(예를 들면 수소 등) 및 운반가스(예를 들면 질소 등)의 혼합가스를 주입하여 탄소 공급원의 분해를 통해 화학적 기상 합성법으로 탄소 나노튜브를 성장시킴으로써 수행될 수 있다. 상기와 같은 화학적 기상 합성법에 의해 제조되는 탄소 나노튜브는 결정의 성장방향이 탄소 나노튜브 단위체의 길이 방향과 거의 평행하고 또 탄소 나노튜브 단위체 길이 방향으로의 흑연 구조의 결정성이 높다. 그 결과, 단위체의 직경이 작고, 전기전도성 및 강도가 높다. In the preparation of the carbon nanotubes according to the chemical vapor phase synthesis method, more specifically, after the supported catalyst is introduced into a fixed bed reactor or a fluidized bed reactor, the carbon is in the temperature range above the thermal decomposition temperature of the carbon source to below the melting point of the supported metal catalyst. Source; Or by injecting a mixed gas of the carbon source, a reducing gas (for example, hydrogen) and a carrier gas (for example, nitrogen, etc.) to grow the carbon nanotubes by chemical vapor phase synthesis through decomposition of the carbon source. . Carbon nanotubes prepared by the above chemical vapor phase synthesis method have a crystal growth direction of the crystal structure is substantially parallel to the longitudinal direction of the carbon nanotube unit and the graphite structure in the carbon nanotube unit longitudinal direction. As a result, the diameter of the unit is small, and the electrical conductivity and strength are high.
또, 상기 탄소 나노튜브의 제조시 가열 공정은 구체적으로는 550℃ 이상 800℃ 미만의 온도, 보다 구체적으로는 550℃ 내지 700℃에서 수행될 수 있다. 상기 온도 범위 내에서는 비결정성 탄소의 발생을 최소화하는 동시에 생성되는 탄소 나노튜브의 벌크 크기, 즉 부피를 그대로 유지하면서 중량이 낮아지므로, 벌크밀도 감소에 따른 분산성이 더욱 향상될 수 있다. 또, 상기 가열 공정을 위한 열원으로서는 유도 가열(induction heating), 복사열, 레이저, IR, 마이크로파, 플라즈마 또는 표면 플라즈몬 가열 등이 이용될 수 있다. In addition, the heating process in the production of the carbon nanotube may be specifically carried out at a temperature of more than 550 ℃ 800 ℃, more specifically at 550 ℃ to 700 ℃. Within the above temperature range, since the weight is reduced while maintaining the bulk size, that is, the volume of the carbon nanotubes generated while minimizing the generation of amorphous carbon, the dispersibility may be further improved by reducing the bulk density. In addition, as a heat source for the heating process, induction heating, radiant heat, laser, IR, microwave, plasma or surface plasmon heating may be used.
또, 상기 탄소 나노튜브의 제조시 탄소 공급원으로는 탄소를 공급할 수 있으며, 300℃ 이상의 온도에서 기상으로 존재할 수 있는 것이라면 특별한 제한없이 사용가능하다. 구체적으로 상기 탄소 공급원은 탄소수 6 이하의 탄소계 화합물일 수 있으며, 보다 구체적으로는 일산화탄소, 메탄, 에탈, 에틸렌, 에탄올, 아세틸렌, 프로판, 프로필렌, 부탄, 부타디엔, 펜탄, 펜텐, 사이클로펜타디엔, 헥산, 사이클로헥산, 벤젠 또는 톨루엔 등을 들 수 있으며, 이들 중 어느 하나 또는 둘 이상의 혼합물이 사용될 수 있다.In addition, when the carbon nanotubes are manufactured, carbon may be supplied as a carbon source, and may be used without particular limitation as long as it can exist in the gas phase at a temperature of 300 ° C. or higher. Specifically, the carbon source may be a carbon-based compound having 6 or less carbon atoms, and more specifically, carbon monoxide, methane, ethane, ethylene, ethanol, acetylene, propane, propylene, butane, butadiene, pentane, pentene, cyclopentadiene, and hexane , Cyclohexane, benzene, toluene, and the like, and any one or a mixture of two or more thereof may be used.
또, 상기 탄소 나노튜브의 제조시, 상기와 같은 화학적 기상 합성법에 의해 탄소 나노튜브 단위체를 성장시킨 후, 탄소 나노튜브 단위체의 배열을 보다 규칙적으로 정렬하기 위한 냉각공정을 선택적으로 더 수행할 수도 있다. 상기 냉각공정은 구체적으로 열원의 제거에 따른 자연냉각 또는 냉각기 등을 이용하여 수행될 수 있다.In addition, when the carbon nanotubes are manufactured, the carbon nanotube units may be grown by the chemical vapor phase synthesis method as described above, and then a cooling process may be selectively performed to align the arrangement of the carbon nanotube units more regularly. . Specifically, the cooling process may be performed using natural cooling or a cooler according to the removal of the heat source.
또, 이후 제조된 탄소 나노튜브에 대한 금속불순물 제거 공정은 세척, 산처리 등의 통상의 방법에 따라 수행될 수 있다.In addition, the metal impurity removal process for the prepared carbon nanotubes may be performed according to conventional methods such as washing, acid treatment.
한편, 상기 탄소 나노튜브의 제조에 사용되는 담지촉매는 무기산화물의 지지체에 금속촉매가 담지된 것으로, 상기 무기산화물은 구체적으로 알루미나, 보다 구체적으로는 구형의 α-알루미나일 수 있다. α-알루미나는 γ-알루미나에 비해 다공성이 매우 낮아 촉매 지지체로서의 활용성이 매우 낮다. 그러나, 담지촉매가 형성되는 소성 온도를 제어함으로써, 이를 이용하여 탄소 나노튜브 합성시 비결정성 탄소의 발생을 억제하면서도 비표면적을 감소시켜 직경을 증가시킬 수 있다. 동시에 탄소 나노튜브의 벌크밀도를 감소시켜 분산성을 개선할 수 있다.On the other hand, the supported catalyst used in the production of the carbon nanotubes is a metal catalyst supported on the support of the inorganic oxide, the inorganic oxide may be specifically alumina, more specifically spherical α-alumina. α-alumina has a very low porosity compared with γ-alumina, and thus has low utility as a catalyst support. However, by controlling the calcination temperature at which the supported catalyst is formed, it is possible to increase the diameter by reducing the specific surface area while suppressing the generation of amorphous carbon when synthesizing carbon nanotubes. At the same time, the bulk density of carbon nanotubes can be reduced to improve dispersibility.
구체적으로 본 발명에서 지지체로서 사용 가능한 상기 α-알루미나는 평균 입경(D50)이 20 내지 200㎛이고, 1 내지 50㎡/g의 BET 비표면적을 갖는 것일 수 있다. 또, 상기 α-알루미나는 표면이 매끄러워 매우 낮은 기공도, 구체적으로는 0.001 내지 0.1㎤/g의 기공도를 갖는 것일 수 있다. Specifically, the α-alumina usable as a support in the present invention may have an average particle diameter (D 50 ) of 20 to 200 μm and a BET specific surface area of 1 to 50 m 2 / g. In addition, the α-alumina may have a very low porosity, specifically, a porosity of 0.001 to 0.1 cm 3 / g.
상기 담지촉매는 지지체에 금속촉매의 담지 후 소성함으로써 제조될 수 있다. 구체적으로는, 상기한 금속촉매의 전구체를 물 중에 용해시켜 제조한 금속촉매 전구체 용액에, 지지체, 구체적으로는 알루미나를 첨가하여 혼합한 후, 600℃ 이하, 보다 구체적으로는 300℃ 내지 500℃의 온도에서 소성시킴으로써 수행될 수 있다.The supported catalyst may be prepared by baking the metal catalyst on a support. Specifically, after the support, specifically, alumina is added and mixed with the metal catalyst precursor solution prepared by dissolving the above-described metal catalyst precursor in water, it is 600 ° C. or less, more specifically 300 ° C. to 500 ° C. By firing at temperature.
상기 금속촉매는 기상 탄소 공급원에 존재하는 탄소 성분들이 서로 결합하여 6원환 구조를 형성하도록 도와주는 역할을 하는 것으로, 구체적으로 니켈 또는 코발트 등의 주촉매가 단독으로 사용될 수도 있고, 또는 상기 주촉매가 몰리브덴, 바나듐 또는 크롬 등의 조촉매와 함께 주촉매-조촉매 복합촉매의 형태로 사용될 수도 있다. 구체적으로 상기 금속촉매는 CoMo 또는 CoV 등일 수 있으며, 이들 중 어느 하나 또는 둘 이상의 혼합물이 사용될 수 있다. 또, 상기 조촉매는 주촉매 1몰에 대하여 0.01 내지 1몰, 보다 구체적으로는 0.05 내지 0.5몰의 양으로 사용될 수 있다.The metal catalyst serves to help the carbon components present in the gaseous carbon source combine with each other to form a six-membered ring structure. Specifically, a main catalyst such as nickel or cobalt may be used alone, or the main catalyst may be It may be used in the form of a main catalyst-catalyst complex catalyst with a promoter such as molybdenum, vanadium or chromium. Specifically, the metal catalyst may be CoMo or CoV, and any one or a mixture of two or more thereof may be used. In addition, the cocatalyst may be used in an amount of 0.01 to 1 mol, more specifically 0.05 to 0.5 mol with respect to 1 mol of the main catalyst.
상기 담지촉매의 제조시 사용 가능한 금속촉매의 전구체로는 물에 용해 가능한 금속염 또는 금속 산화물 등이 사용될 수 있다. 구체적으로는, Fe, Ni, Co, Mo, V 및 Cr 중에서 선택되는 어느 하나 또는 둘 이상의 금속원소를 포함하는 금속염, 금속산화물 또는 금속할로겐화물일 수 있으며, 이들 중 어느 하나 또는 둘 이상의 혼합물이 사용될 수 있다. 보다 구체적으로는 Co(NO3)2·6H2O, Co2(CO)8, [Co2(CO)6(t-BuC=CH)], Cu(OAc)2, Ni(NO3)2·6H2O, (NH4)6Mo7O24·4H2O, Mo(CO)6, (NH4)MoS4 및 NH4VO3로 이루어진 군에서 선택되는 어느 하나 또는 둘 이상의 혼합물이 사용될 수 있다.As a precursor of the metal catalyst usable in the preparation of the supported catalyst, a metal salt or metal oxide soluble in water may be used. Specifically, it may be a metal salt, a metal oxide or a metal halide including any one or two or more metal elements selected from Fe, Ni, Co, Mo, V, and Cr, and any one or a mixture of two or more thereof may be used. Can be. More specifically Co (NO 3 ) 2 · 6H 2 O, Co 2 (CO) 8 , [Co 2 (CO) 6 (t-BuC = CH)], Cu (OAc) 2 , Ni (NO 3 ) 2 6H 2 O, (NH 4 ) 6 Mo 7 O 24 4H 2 O, Mo (CO) 6 , (NH 4 ) MoS 4 and NH 4 VO 3 Any one or mixture of two or more selected from the group consisting of Can be.
상기 금속촉매의 전구체는 물에 용해된 수용액 상태로 사용될 수 있으며, 이때, 함침 효율 등을 고려하여 수용액 중의 금속촉매 전구체의 농도가 적절히 조절될 수 있다. 구체적으로, 수용액 중에서의 금속촉매 전구체의 농도는 0.1 내지 0.4g/㎖일 수 있다. The precursor of the metal catalyst may be used in an aqueous solution dissolved in water. In this case, the concentration of the metal catalyst precursor in the aqueous solution may be appropriately adjusted in consideration of the impregnation efficiency. Specifically, the concentration of the metal catalyst precursor in the aqueous solution may be 0.1 to 0.4 g / ㎖.
또, 상기한 금속촉매 전구체 용액과 상기 지지체의 혼합 공정은 통상의 방법에 따라 수행될 수 있으며, 구체적으로는 45℃ 내지 80℃ 온도 하에서 회전 또는 교반에 의해 수행될 수 있다.In addition, the mixing process of the metal catalyst precursor solution and the support may be performed according to a conventional method, specifically, it may be carried out by rotating or stirring at a temperature of 45 ℃ to 80 ℃.
또, 상기 혼합시 최종 제조되는 담지촉매에서의 금속촉매의 함량을 고려하여 금속촉매 전구체와 지지체를 혼합할 수 있다. 담지촉매에 있어서 금속촉매의 담지량이 증가할수록, 담지촉매를 이용하여 제조되는 탄소 나노튜브의 벌크밀도가 증가하는 경향이 있다. 이에 따라 제조되는 탄소 나노튜브의 벌크밀도를 고려하여, 최종 제조되는 담지촉매 총 중량에 대하여 금속촉매가 5 내지 30중량%의 양으로 담지될 수 있도록 혼합할 수 있다.In addition, the metal catalyst precursor and the support may be mixed in consideration of the content of the metal catalyst in the final supported catalyst during the mixing. As the supported amount of the metal catalyst increases in the supported catalyst, the bulk density of the carbon nanotubes produced using the supported catalyst tends to increase. In consideration of the bulk density of the carbon nanotubes thus prepared, the metal catalyst may be mixed in an amount of 5 to 30% by weight based on the total weight of the supported catalyst.
또, 최종 제조되는 탄소 나노튜브의 벌크밀도 제어를 위해, 상기 금속촉매 전구체 용액 중에 지지체의 첨가 및 혼합시 산이 선택적으로 더 사용될 수 있다. In addition, in order to control the bulk density of the carbon nanotubes to be finally prepared, an acid may optionally be further used during addition and mixing of the support in the metal catalyst precursor solution.
이와 같이 산이 더 첨가될 경우 상기 금속촉매 전구체 용액은 산 1 몰에 대해 금속촉매 3 내지 40몰, 보다 구체적으로는 5 내지 30몰에 해당하는 함량으로 사용될 수 있다. 상기 산은 구체적으로 시트르산 등일 수 있으며, 이들 중 어느 하나 또는 둘 이상의 혼합물이 사용될 수 있다.As such, when the acid is further added, the metal catalyst precursor solution may be used in an amount corresponding to 3 to 40 moles, more specifically 5 to 30 moles, of the metal catalyst per mole of acid. The acid may specifically be citric acid and the like, and any one or a mixture of two or more thereof may be used.
또, 상기 금속촉매 전구체 용액과 상기 지지체의 혼합 후, 이후의 소성 공정에 앞서 건조 공정이 선택적으로 더 수행될 수 있다. 상기 건조 공정은 통상의 방법에 따라 수행될 수 있으며, 구체적으로는 40℃ 내지 100℃ 온도에서 진공 하에 3분 내지 1시간 동안 회전 증발시킴으로써 수행될 수도 있다.In addition, after the metal catalyst precursor solution and the support are mixed, a drying process may be optionally further performed prior to the subsequent firing process. The drying process may be performed according to a conventional method, specifically, may be carried out by rotary evaporation under vacuum at a temperature of 40 ℃ to 100 ℃ for 3 minutes to 1 hour.
이어서, 상기한 방법으로 준비된 금속촉매 전구체 및 지지체의 혼합물에 대해 소성이 수행된다. 상기 소성은 600℃ 이하, 구체적으로는 400℃ 내지 600℃의 온도에서 공기 또는 불활성 대기 하에 수행될 수 있다. Subsequently, firing is performed on the mixture of the metal catalyst precursor and the support prepared in the above manner. The firing can be carried out under air or an inert atmosphere at temperatures of up to 600 ° C, specifically 400 ° C to 600 ° C.
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또, 상기한 건조 공정 후, 그리고 소성 공정 전에 250℃ 내지 400℃의 온도에서 예비 소성 공정이 선택적으로 더 수행될 수 있다.In addition, a preliminary firing process may be optionally further performed at a temperature of 250 ° C. to 400 ° C. after the drying process and before the firing process.
이때, 반응의 효율성을 고려할 때 상기 예비 소성 직전에, 상기 금속촉매 전구체 및 지지체의 혼합물 중 최대 50%를 상기 지지체에 함침시켜 사용하고, 상기 예비 소성 직후 잔부의 상기 혼합물을 지지체에 함침시켜 사용할 수 있다.In this case, in consideration of the efficiency of the reaction, up to 50% of the mixture of the metal catalyst precursor and the support may be impregnated into the support immediately before the preliminary firing, and the remainder of the mixture may be impregnated into the support immediately after the preliminary firing. have.
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상기와 같은 제조방법에 따라 제조된 탄소 나노튜브는 낮은 벌크밀도와 분체저항을 가져 도전재 분산액 제조시 우수한 분산성과 전도성을 나타낼 수 있다. 또 고순도로, 전극 내 전도성을 높여 전지 적용시 전지 성능, 특히 저온에서의 전지의 출력특성을 향상시킬 수 있다.Carbon nanotubes prepared according to the manufacturing method as described above may have low bulk density and powder resistance, and thus may exhibit excellent dispersibility and conductivity when preparing a conductive material dispersion. In addition, with high purity, the conductivity in the electrode can be increased to improve battery performance when the battery is applied, particularly the output characteristics of the battery at low temperatures.
한편, 본 발명의 일 실시예에 따른 도전재 분산액에 있어서, 상기 분산제는 니트릴계 고무일 수 있으며, 보다 구체적으로는 부분 또는 전체로 수소화된 니트릴부타디엔계 고무일 수 있다. 보다 더 구체적으로는 상기 분산제는 공액 디엔 유래 구조 단위, 수소화된 공액 디엔 유래 구조 단위 및 α,β-불포화 니트릴 유래 구조 단위를 포함하고, 고무 총 중량에 대해 상기 α,β-불포화 니트릴 유래 구조 단위를 20 내지 65중량%로 포함하는 부분 수소화된 니트릴부타디엔계 고무일 수 있다.On the other hand, in the conductive material dispersion according to an embodiment of the present invention, the dispersing agent may be a nitrile-based rubber, more specifically may be a nitrile butadiene-based rubber hydrogenated in part or whole. Even more specifically, the dispersing agent includes a structural unit derived from conjugated diene, a structural unit derived from hydrogenated conjugated diene, and a structural unit derived from α, β-unsaturated nitrile, and the α, β-unsaturated nitrile derived structural unit with respect to the total weight of rubber. It may be a partially hydrogenated nitrile butadiene rubber containing 20 to 65% by weight.
상기 부분 수소화된 니트릴부타디엔계 고무는 α,β-불포화 니트릴, 공액 디엔 및 선택적으로 기타 공중합 가능한 삼원단량체(termonomer)를 공중합시킨 후, 공중합체 내 C=C 이중결합을 수소화시킴으로써 제조될 수 있다. 이때 상기 중합 반응 공정 및 수소화 공정은 통상의 방법에 따라 수행될 수 있다.The partially hydrogenated nitrile butadiene-based rubbers may be prepared by copolymerizing α, β-unsaturated nitriles, conjugated dienes and optionally other copolymerizable termonomers, followed by hydrogenation of C = C double bonds in the copolymer. In this case, the polymerization reaction process and the hydrogenation process may be performed according to a conventional method.
상기 부분 수소화된 니트릴부타디엔계 고무의 제조시 사용 가능한 α,β-불포화 니트릴로는 구체적으로 아크릴로니트릴 또는 메타크릴로니트릴 등을 들 수 있으며, 이들 중 1종 단독 또는 2종 이상의 혼합물이 사용될 수 있다. Specific examples of α, β-unsaturated nitriles that can be used in the production of the partially hydrogenated nitrile butadiene-based rubber include acrylonitrile or methacrylonitrile, and one or a mixture of two or more of them may be used. have.
상기 부분 수소화된 니트릴부타디엔계 고무의 제조시 사용 가능한 공액 디엔으로는 구체적으로 1,3-부타디엔, 이소프렌, 2,3-디메틸-1,3-부타디엔 등의 탄소수 4~6의 공액 디엔을 들 수 있으며, 이들 중 어느 하나 또는 둘 이상의 혼합물이 사용될 수 있다.Specific examples of the conjugated diene that can be used in the production of the partially hydrogenated nitrile butadiene rubber include conjugated dienes having 4 to 6 carbon atoms such as 1,3-butadiene, isoprene and 2,3-dimethyl-1,3-butadiene. Any one or a mixture of two or more of these may be used.
또, 상기 선택적으로 사용 가능한 기타 공중합가능한 삼원단량체로는 구체적으로 방향족 비닐 단량체(예를 들면, 스티렌, α-메틸스티렌, 비닐피리딘, 플루오로에틸 비닐 에테르 등), α,β-불포화 카르복실산(예를 들면, 아크릴산, 메타크릴산, 말레산, 푸마르산, 등), α,β-불포화 카르복실산의 에스테르 또는 아미드(예를 들면, 메틸 (메트)아크릴레이트, 에틸 (메트)아크릴레이트, n-도데실 (메트)아크릴레이트, 메톡시메틸 (메트)아크릴레이트, 히드록시에틸 (메트)아크릴레이트, 또는 폴리에틸렌 글리콜 (메트)아크릴레이트 등), α,β-불포화 디카르복실산의 무수물(예를 들면, 말레산 무수물, 이타콘산 무수물, 시트라콘산 무수물 등)을 들 수 있으나, 이에 한정되는 것은 아니다. In addition, the other copolymerizable terpolymers optionally used may include, for example, aromatic vinyl monomers (eg, styrene, α-methylstyrene, vinylpyridine, fluoroethyl vinyl ether, etc.), α, β-unsaturated carboxylic acids. (Eg, acrylic acid, methacrylic acid, maleic acid, fumaric acid, etc.), esters or amides of α, β-unsaturated carboxylic acids (eg methyl (meth) acrylate, ethyl (meth) acrylate, n-dodecyl (meth) acrylate, methoxymethyl (meth) acrylate, hydroxyethyl (meth) acrylate, or polyethylene glycol (meth) acrylate), and anhydrides of α, β-unsaturated dicarboxylic acids (For example, maleic anhydride, itaconic anhydride, citraconic anhydride, etc.), but is not limited thereto.
상기와 같은 방법에 따라 제조된 부분 수소화된 니트릴부타디엔계 고무에 있어서, α,β-불포화 니트릴 유래 구조 단위, 공액 디엔 유래 구조 단위, 수소화된 공액 디엔 유래 구조단위 및 선택적으로 기타 공중합 가능한 삼원단량체 유래 구조 단위의 함량비는 넓은 범위 내에서 다양할 수 있으며, 각 경우에 있어서 상기 구조단위들의 총 합은 100중량%가 된다.In the partially hydrogenated nitrile butadiene rubber prepared according to the above method, α, β-unsaturated nitrile derived structural units, conjugated diene derived structural units, hydrogenated conjugated diene derived structural units, and optionally other copolymerizable terpolymers derived from The content ratio of the structural units may vary within a wide range, and in each case the sum of the structural units is 100% by weight.
또, 탄소 나노튜브에 대한 분산성 향상 및 분산매와의 혼화성을 고려할 때, 상기 부분 수소화된 니트릴부타디엔계 고무 내 α,β-불포화 니트릴 유래 구조단위의 함량은 부분 수소화된 니트릴부타디엔계 고무 총 중량에 대하여 20중량% 내지 65중량%, 구체적으로는 30중량% 내지 60중량%일 수 있다. 상기한 함량 범위로 α,β-불포화 니트릴 구조 함유 반복단위를 포함할 경우, 탄소 나노튜브의 분산성을 높일 수 있어, 탄소 나노튜브의 첨가량이 적더라도 높은 도전성을 부여할 수 있다. In addition, considering the dispersibility of the carbon nanotubes and the miscibility with the dispersion medium, the content of the α, β-unsaturated nitrile-derived structural unit in the partially hydrogenated nitrile butadiene-based rubber is the total weight of the partially hydrogenated nitrile-butadiene rubber. 20% to 65% by weight, specifically 30% to 60% by weight. When the α, β-unsaturated nitrile structure-containing repeating unit is included in the above content range, the dispersibility of the carbon nanotubes can be increased, and even if the amount of the carbon nanotubes is small, high conductivity can be given.
본 발명에 있어서, 부분 수소화된 니트릴부타디엔계 고무 내 니트릴 구조 함유 반복단위의 함량은, α,β-불포화 니트릴에서 유래하는 구조 단위의 고무 전체에 대한 중량 비율로, 당해 함량의 측정은, JIS K 6364의 밀 오븐법에 따라서, 발생한 질소량을 측정하고 아크릴로니트릴 분자량으로부터 그의 결합량을 환산하여, 정량되는 값의 중앙값이다. In the present invention, the content of the nitrile structure-containing repeating unit in the partially hydrogenated nitrile butadiene-based rubber is a weight ratio of the entire rubber of the structural unit derived from α, β-unsaturated nitrile, and the measurement of the content is JIS K According to the mill oven method of 6364, the amount of nitrogen which generate | occur | produced is measured, it is the median of the value quantified by converting the amount of its binding from the acrylonitrile molecular weight.
또, 상기 부분 수소화된 니트릴부타디엔계 고무내 수소화된 공액 디엔 유래 구조 단위의 함량은 부분 수소화된 니트릴부타디엔계 고무 총 중량에 대하여 1 내지 30중량%, 보다 구체적으로는 1 내지 15중량%일 수 있다. 상기와 같은 함량으로 포함될 때, 분산매에 대한 혼화성이 증가되어 탄소 나노튜브의 분산성을 높일 수 있다.In addition, the content of the hydrogenated conjugated diene-based structural unit in the partially hydrogenated nitrile butadiene rubber may be 1 to 30% by weight, more specifically 1 to 15% by weight relative to the total weight of the partially hydrogenated nitrile butadiene rubber. . When included in the amount as described above, the miscibility to the dispersion medium can be increased to increase the dispersibility of the carbon nanotubes.
또, 상기 부분 수소화된 아크릴로니트릴-부타디엔 고무(H-NBR)는 중량평균 분자량이 10,000g/㏖ 내지 700,000g/㏖, 보다 구체적으로는 10,000g/㏖ 내지 300,000g/㏖인 것일 수 있다. 또, 상기 부분 수소화 아크릴로니트릴-부타디엔 고무(H-NBR)는 2.0 내지 6.0의 범위, 구체적으로는 2.0 내지 4.0 범위의 다분산지수 PDI(Mw/Mn의 비, Mw는 중량평균 분자량이고 Mn은 수평균 분자량임)을 갖는 것일 수 있다. 상기 H-NBR이 상기한 범위의 중량평균 분자량 및 다분산 지수를 가질 때, 상기 탄소 나노튜브를 분산매 중에 균일하게 분산시킬 수 있다. 본 발명에 있어서, 상기 중량평균 분자량 및 수평균 분자량은 겔 투과형 크로마토그래피(GPC)로 분석되는 폴리스티렌 환산 분자량이다. In addition, the partially hydrogenated acrylonitrile-butadiene rubber (H-NBR) may have a weight average molecular weight of 10,000 g / mol to 700,000 g / mol, more specifically 10,000 g / mol to 300,000 g / mol. Further, the partially hydrogenated acrylonitrile-butadiene rubber (H-NBR) has a polydispersity index PDI (ratio of Mw / Mn, Mw is a weight average molecular weight and Mn is in the range of 2.0 to 6.0, specifically, 2.0 to 4.0). Number average molecular weight). When the H-NBR has a weight average molecular weight and a polydispersity index in the above-described range, the carbon nanotubes may be uniformly dispersed in the dispersion medium. In the present invention, the weight average molecular weight and the number average molecular weight are polystyrene reduced molecular weights analyzed by gel permeation chromatography (GPC).
한편, 본 발명의 일 실시예에 따른 상기 도전재 분산액에 있어서, 상기 분산매는 디메틸포름아미드(DMF), 디에틸 포름아미드, 디메틸 아세트아미드(DMAc), N-메틸 피롤리돈(NMP) 등의 아미드계 극성 유기 용매; 메탄올, 에탄올, 1-프로판올, 2-프로판올(이소프로필 알코올), 1-부탄올(n-부탄올), 2-메틸-1-프로판올(이소부탄올), 2-부탄올(sec-부탄올), 1-메틸-2-프로판올(tert-부탄올), 펜탄올, 헥산올, 헵탄올 또는 옥탄올 등의 알코올류; 에틸렌글리콜, 디에틸렌글리콜, 트리에틸렌 글리콜, 프로필렌 글리콜, 1,3-프로판디올, 1,3-부탄디올, 1,5-펜탄디올, 또는 헥실렌글리콜 등의 글리콜류; 글리세린, 트리메티롤프로판, 펜타에리트리톨, 또는 소르비톨 등의 다가 알코올류; 에틸렌글리콜모노 메틸에테르, 디에틸렌글리콜모노 메틸에테르, 트리에틸렌글리콜 모노 메틸에테르, 테트라 에틸렌글리콜모노 메틸에테르, 에틸렌글리콜모노 에틸에테르, 디에틸렌글리콜모노 에틸에테르, 트리에틸렌글리콜 모노 에틸에테르, 테트라 에틸렌글리콜모노 에틸에테르, 에틸렌글리콜모노 부틸 에테르, 디에틸렌글리콜모노 부틸 에테르, 트리에틸렌글리콜 모노 부틸 에테르, 또는 테트라 에틸렌글리콜모노 부틸 에테르 등의 글리콜 에테르류; 아세톤, 메틸 에틸 케톤, 메틸프로필 케톤, 또는 사이클로펜타논 등의 케톤류; 초산에틸, γ-부틸 락톤, 및 ε-프로피오락톤 등의 에스테르류 등을 들 수 있으며, 이들 중 어느 하나 또는 둘 이상의 혼합물이 사용될 수 있다. 보다 구체적으로, 상기 탄소 나노튜브 및 분산제에 대한 분산성 향상 효과를 고려할 때 상기 분산매는 아미드계 극성 유기용매일 수 있다. Meanwhile, in the conductive material dispersion according to an embodiment of the present invention, the dispersion medium is dimethylformamide (DMF), diethyl formamide, dimethyl acetamide (DMAc), N-methyl pyrrolidone (NMP), or the like. Amide polar organic solvents; Methanol, ethanol, 1-propanol, 2-propanol (isopropyl alcohol), 1-butanol (n-butanol), 2-methyl-1-propanol (isobutanol), 2-butanol (sec-butanol), 1-methyl Alcohols such as 2-propanol (tert-butanol), pentanol, hexanol, heptanol or octanol; Glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, or hexylene glycol; Polyhydric alcohols such as glycerin, trimetholpropane, pentaerythritol, or sorbitol; Ethylene glycol mono methyl ether, diethylene glycol mono methyl ether, triethylene glycol mono methyl ether, tetra ethylene glycol mono methyl ether, ethylene glycol mono ethyl ether, diethylene glycol mono ethyl ether, triethylene glycol mono ethyl ether, tetra ethylene glycol Glycol ethers such as mono ethyl ether, ethylene glycol mono butyl ether, diethylene glycol mono butyl ether, triethylene glycol mono butyl ether, or tetra ethylene glycol mono butyl ether; Ketones such as acetone, methyl ethyl ketone, methylpropyl ketone, or cyclopentanone; Ester, such as ethyl acetate, (gamma) -butyl lactone, (epsilon) -propiolactone, etc. are mentioned, Any one or a mixture of two or more of these may be used. More specifically, when considering the effect of improving the dispersibility of the carbon nanotubes and dispersant, the dispersion medium may be an amide polar organic solvent.
상기와 같은 구성을 갖는 본 발명의 일 실시예에 따른 상기 도전재 분산액에 있어서, 상기 분산제, 탄소 나노튜브 및 분산매의 함량은 분산액의 용도에 따라 적절히 결정될 수 있다. In the conductive material dispersion according to an embodiment of the present invention having the above configuration, the content of the dispersant, the carbon nanotubes and the dispersion medium may be appropriately determined according to the use of the dispersion.
구체적으로, 분산액 중의 탄소 나노튜브의 균일 분산을 위해 상기 분산제는 탄소 나노튜브 100중량부에 대하여 1중량부 내지 50중량부로 포함될 수 있다. 분산제의 함량이 1중량부 미만이면 분산액 중 탄소 나노튜브의 균일 분산이 어렵고, 50중량부를 초과하면 분산액의 점도 증가로 가공성 저하 등의 우려가 있다. 보다 구체적으로는 5 내지 20중량부로 포함될 수 있다. Specifically, the dispersant may be included in an amount of 1 part by weight to 50 parts by weight based on 100 parts by weight of carbon nanotubes for uniform dispersion of the carbon nanotubes in the dispersion. If the content of the dispersant is less than 1 part by weight, it is difficult to uniformly disperse the carbon nanotubes in the dispersion. If the content of the dispersant is more than 50 parts by weight, the viscosity of the dispersion may increase, leading to a decrease in processability. More specifically, it may be included in 5 to 20 parts by weight.
또, 상기 탄소 나노튜브는 도전재 분산액 총 중량에 대하여 1.0중량% 내지 33중량%로 포함될 수 있다. 탄소 나노튜브가 상기 범위의 함량으로 포함될 때 전자 전도성과 분산성을 발란스 좋게 나타낼 수 있다. 만약 탄소 나노튜브의 함량이 상기 범위를 벗어나 1중량% 미만일 경우, 일례로 리튬 이차전지의 전극 제조시 전극 형성용 조성물이 다량의 유기용제를 포함하게 되고, 그 결과 전극 내 공극이 증가하고, 활물질 충전율이 저하됨으로써 전지 용량이 저하될 수 있다. 또, 유기용제 제거를 위한 건조시간이 길어질 수 있다. 또, 탄소 나노튜브의 함량이 30중량%를 초과할 경우, 점도가 높아 분산이 제대로 되지 않아 전극의 저항이 높아질 우려가 있다.The carbon nanotubes may be included in an amount of 1.0 wt% to 33 wt% based on the total weight of the conductive material dispersion. When the carbon nanotubes are included in the content of the above range, it can exhibit a good balance of electronic conductivity and dispersibility. If the content of the carbon nanotubes out of the range of less than 1% by weight, for example, when forming the electrode of a lithium secondary battery, the composition for forming an electrode includes a large amount of organic solvent, and as a result, the voids in the electrode increase, and the active material The battery capacity may be lowered by lowering the filling rate. In addition, the drying time for removing the organic solvent may be long. In addition, when the content of the carbon nanotube is more than 30% by weight, the viscosity is high, the dispersion is not properly, there is a fear that the electrode resistance is increased.
보다 구체적으로, 본 발명의 일 실시예에 따른 상기 도전재 분산액은 상기 탄소 나노튜브 100 중량부에 대하여, 상기 분산제 1 내지 50중량부, 및 상기 분산매 200 내지 9,900중량부를 포함할 수 있다. 상기 범위에서 탄소 나노튜브를 분산매에 균일하게 분산시킬 수 있다. 보다 구체적으로는 상기 탄소 나노튜브 100중량부에 대하여 상기 분산제 5 내지 20중량부 및 상기 분산매 1,000 내지 3,500중량부를 포함할 수 있다. More specifically, the conductive material dispersion according to an embodiment of the present invention may include 1 to 50 parts by weight of the dispersant, and 200 to 9,900 parts by weight of the dispersion medium based on 100 parts by weight of the carbon nanotubes. Carbon nanotubes can be uniformly dispersed in the dispersion medium in the above range. More specifically, the dispersant may include 5 to 20 parts by weight and 1,000 to 3,500 parts by weight of the dispersion medium based on 100 parts by weight of the carbon nanotubes.
또, 본 발명의 일 실시예에 따른 상기 도전재 분산액은 분산액 안정성을 높이기 위한 분산 안정화제를 더 포함할 수 있다. In addition, the conductive material dispersion according to an embodiment of the present invention may further include a dispersion stabilizer for increasing the dispersion stability.
상기 분산 안정화제는 탄소 나노튜브의 표면에 흡착해 탄소 나노튜브를 둘러싸는 랩핑 효과를 나타냄으로써 탄소 나노튜브의 응집을 방지할 수 있다. 이에 따라 상기 분산 안정화제로는 탄소 나노튜브에 대한 친화성이 우수한 동시에, 분산제 및 분산매에 대한 혼화성이 우수한 것이 바람직할 수 있다. 구체적으로, 본 발명의 일 실시예에 따른 상기 도전재 분산액에 있어서, 상기 분산 안정화제는 폴리비닐리덴 플루오라이드, 또는 폴리비닐피롤리돈 등의 불소계 고분자일 수 있으며, 이들 중 어느 하나 또는 둘 이상의 혼합물이 사용될 수 있다.The dispersion stabilizer may prevent the agglomeration of the carbon nanotubes by adsorbing on the surface of the carbon nanotubes and exhibiting a lapping effect surrounding the carbon nanotubes. Accordingly, as the dispersion stabilizer, it may be preferable to have excellent affinity for carbon nanotubes and excellent compatibility for the dispersant and the dispersion medium. Specifically, in the conductive material dispersion according to an embodiment of the present invention, the dispersion stabilizer may be a fluorine-based polymer such as polyvinylidene fluoride, polyvinylpyrrolidone, any one or more of these Mixtures can be used.
또, 상기 분산 안정화제는 중량평균 분자량이 20,000g/㏖ 내지 5,000,000g/㏖인 것일 수 있다. 분산 안정화제의 분자량이 20,000g/㏖ 미만으로 지나치게 작으면, 탄소 나노튜브에 대해 충분한 랩핑 효과를 나타내기 어렵고, 또 분자량이 5,000,000g/㏖를 초과하여 지나치게 크면 분산매 중 분산 안정화제의 분자 운동 저하로, 탄소 나노튜브를 충분히 랩핑하기 어렵다. 보다 구체적으로 상기 분산 안정화제는 중량평균 분자량이 70,000g/㏖ 내지 2,000,000g/㏖인 것일 수 있다.In addition, the dispersion stabilizer may be a weight average molecular weight of 20,000 g / mol to 5,000,000 g / mol. If the molecular weight of the dispersion stabilizer is too small, less than 20,000 g / mol, it is difficult to exhibit a sufficient lapping effect on the carbon nanotubes, and if the molecular weight is too large, exceeding 5,000,000 g / mol, the molecular motion of the dispersion stabilizer in the dispersion medium is lowered. As a result, it is difficult to sufficiently wrap the carbon nanotubes. More specifically, the dispersion stabilizer may be a weight average molecular weight of 70,000 g / mol to 2,000,000 g / mol.
또, 상기 분산 안정화제는 탄소 나노튜브 100중량부에 대하여 1중량부 내지 10중량부로 사용될 수 있다. 탄소 나노튜브의 함량에 비해 분산 안정화제의 함량이 지나치게 낮으면, 충분한 랩핑 효과를 얻기 어렵고, 그 결과 탄소 나노튜브 끼리의 응집이 발생할 우려가 있다.In addition, the dispersion stabilizer may be used in 1 part by weight to 10 parts by weight with respect to 100 parts by weight of carbon nanotubes. If the content of the dispersion stabilizer is too low compared to the content of the carbon nanotubes, it is difficult to obtain a sufficient lapping effect, and as a result, there is a fear that aggregation of the carbon nanotubes occurs.
상기와 같은 구성을 갖는 본 발명의 일 실시예에 따른 도전재 분산액은, 탄소 나노튜브와 분산매를 혼합하여 탄소 나노튜브 포함 슬러리를 제조하는 단계(단계 1); 및 상기 슬러리에 상기한 분산제를 혼합하는 단계(단계 2)를 포함하는 제조방법에 의해 제조될 수 있다. 이때 탄소 나노튜브, 분산제 및 분산매의 종류 및 사용량은 앞서 설명한 바와 동일하다. The conductive material dispersion according to an embodiment of the present invention having the configuration as described above comprises the steps of preparing a slurry containing carbon nanotubes by mixing carbon nanotubes and a dispersion medium (step 1); And it may be prepared by a manufacturing method comprising the step (step 2) of mixing the dispersant in the slurry. At this time, the type and the amount of the carbon nanotubes, the dispersant and the dispersion medium are the same as described above.
또, 상기 탄소 나노튜브와 분산매의 혼합은, 통상의 혼합 방법, 구체적으로는 호모게나이져, 비즈밀, 볼밀, 바스켓밀, 어트리션밀, 만능 교반기, 클리어 믹서 또는 TK믹서 등과 같은 혼합 장치를 이용하여 수행될 수 있다. In addition, mixing of the carbon nanotubes and the dispersion medium, using a conventional mixing method, specifically, homogenizer, bead mill, ball mill, basket mill, treatment mill, universal stirrer, clear mixer or TK mixer Can be performed.
또, 상기 탄소 나노튜브와 분산매의 혼합시, 탄소 나노튜브와 분산매의 혼합성, 또는 분산매 중 탄소 나노튜브의 분산성을 높이기 위하여 캐비테이션 분산 처리가 수행될 수도 있다. 상기 캐비테이션 분산 처리는 액체에 고에너지를 인가했을 때 물에 생긴 진공 기포가 파열되는 것에 의해 생긴 충격파를 이용한 분산 처리방법으로서, 상기 방법에 의해 탄소 나노튜브의 특성을 손상시키는 일 없이 분산시킬 수 있다. 구체적으로 상기 캐비테이션 분산 처리는 초음파, 제트 밀, 또는 전단 분산 처리에 의해 수행될 수 있다.In addition, when the carbon nanotubes and the dispersion medium are mixed, the cavitation dispersion treatment may be performed to increase the mixability of the carbon nanotubes and the dispersion medium, or the dispersibility of the carbon nanotubes in the dispersion medium. The cavitation dispersion treatment is a dispersion treatment method using a shock wave generated by the rupture of the vacuum bubbles generated in water when high energy is applied to the liquid, and can be dispersed without damaging the properties of the carbon nanotubes by the above method. . Specifically, the cavitation dispersion treatment may be performed by ultrasonic wave, jet mill, or shear dispersion treatment.
상기 분산처리 공정은 탄소 나노튜브의 양 및 분산제의 종류에 따라 적절히 수행될 수 있다. 구체적으로는 초음파 처리를 수행할 경우, 주파수 10㎑ 내지 150㎑의 범위이며, 진폭은 5㎛ 내지 100㎛의 범위이며, 조사 시간은 1분 내지 300분일 수 있다. 상기 초음파 처리 공정 수행을 위한 초음파 발생 장치로서는, 예를 들면 초음파 호모지나이저 등을 이용할 수 있다. 또, 제트 밀 처리를 수행할 경우, 압력은 20㎫ 내지 250㎫일 수 있으며, 1회 이상, 구체적으로는 2회 이상 복수 회 수행될 수 있다. 또, 상기 제트 밀 분산 장치로는 고압 습식 제트 밀 등을 이용할 수 있다.The dispersion treatment process may be appropriately performed according to the amount of carbon nanotubes and the type of dispersant. Specifically, when the ultrasonic treatment is performed, the frequency is in the range of 10 Hz to 150 Hz, the amplitude is in the range of 5 µm to 100 µm, and the irradiation time may be 1 minute to 300 minutes. As an ultrasonic generator for performing the ultrasonic treatment process, for example, an ultrasonic homogenizer may be used. In addition, when the jet mill treatment is performed, the pressure may be 20 MPa to 250 MPa, and may be performed one or more times, specifically, two or more times. Moreover, a high pressure wet jet mill etc. can be used as said jet mill dispersion apparatus.
상기 캐비테이션 분산 처리 공정시 온도는 특별히 한정되지 않으나, 분산매의 증발에 의한 분산액의 점도 변화의 우려가 없는 온도 하에서 수행될 수 있다. 구체적으로는 50℃ 이하, 보다 구체적으로는 15℃ 내지 50℃의 온도에서 수행될 수 있다.The temperature in the cavitation dispersion treatment process is not particularly limited, but may be performed at a temperature at which there is no fear of change in viscosity of the dispersion due to evaporation of the dispersion medium. Specifically, the temperature may be performed at a temperature of 50 ° C. or lower, more specifically 15 ° C. to 50 ° C.
또, 상기 분산제의 혼합 공정은 통상의 혼합 또는 분산 방법에 의해 수행될 수 있으며, 구체적으로는, 볼 밀(ball mill), 비드 밀(bead mill), 바스켓 밀(basket mill) 등의 밀링(milling)방법, 또는 호모게나이져, 비즈밀, 볼밀, 바스켓밀, 어트리션밀, 만능 교반기, 클리어 믹서 또는 TK믹서 에 의해 수행될 수 있다. 보다 구체적으로는 비드 밀을 이용한 밀링 방법에 의해 수행될 수 있다. 이때 비드 밀의 크기는 탄소 나노튜브의 종류와 양, 그리고 분산제의 종류에 따라 적절히 결정될 수 있으며, 구체적으로는 상기 비드 밀의 직경은 0.5mm 내지 2mm일 수 있다.In addition, the mixing process of the dispersant may be carried out by a conventional mixing or dispersing method, specifically, milling (ball mill), bead mill (basket mill), basket mill (basket mill), etc. Method, or by homogenizer, beads mill, ball mill, basket mill, attrition mill, universal stirrer, clear mixer or TK mixer. More specifically, it may be performed by a milling method using a bead mill. At this time, the size of the bead mill may be appropriately determined according to the type and amount of carbon nanotubes and the type of dispersant, specifically, the diameter of the bead mill may be 0.5mm to 2mm.
또, 상기 분산액의 제조시 분산 안정화제가 선택적으로 더 사용되는 경우, 상기 분산 안정화제는 상기 분산제의 혼합 공정시에 함께 첨가될 수 있다. 이 경우 본 발명의 일 실시예에 따른 도전재 분산액의 제조방법은 분산 안정화제 첨가 공정을 더 포함할 수 있다. 상기 분산 안정화제의 종류 및 사용량은 앞서 설명한 바와 동일하다.In addition, when a dispersion stabilizer is optionally further used in the preparation of the dispersion, the dispersion stabilizer may be added together during the mixing process of the dispersion. In this case, the manufacturing method of the conductive material dispersion according to an embodiment of the present invention may further include a dispersion stabilizer addition process. The type and the amount of the dispersion stabilizer are the same as described above.
상기와 같은 제조방법에 따라 분산매 중에 탄소 나노튜브가 균일 분산된 분산액이 제조될 수 있다. According to the above production method, a dispersion in which carbon nanotubes are uniformly dispersed in a dispersion medium may be prepared.
구체적으로, 본 발명의 일 실시예에 따른 상기 도전재 분산액에 있어서, 상기 탄소 나노튜브와 분산제는, 분산제가 탄소 나노튜브의 표면에 물리적 또는 화학적 결합을 통해 도입된 탄소 나노튜브-분산제 복합체의 형태로 균일 분산되어 포함될 수 있으며, 보다 구체적으로 상기 도전재 분산액 내에서 상기 복합체는 하기 수학식 3에 따른 입자 크기 분포가 10 이하, 보다 구체적으로는 2 내지 6.5로 좁은 입자 크기 분포를 나타냄으로써 보다 우수한 균일 분산성을 나타낼 수 있다. Specifically, in the conductive material dispersion according to an embodiment of the present invention, the carbon nanotubes and the dispersant, in the form of a carbon nanotube-dispersant composite wherein the dispersant is introduced through a physical or chemical bond to the surface of the carbon nanotubes It may be included in a uniform dispersion, more specifically the composite in the conductive material dispersion is more excellent by showing a narrow particle size distribution of less than 10, more specifically 2 to 6.5 according to the following equation (3) Uniform dispersibility.
[수학식 3][Equation 3]
탄소 나노튜브-분산제 복합체의 입자 크기 분포=(D90-D10)/D50 Particle size distribution of the carbon nanotube-dispersant composite = (D 90 -D 10 ) / D 50
(상기 수학식 3에서, D10, D50 및 D90은 각각 탄소 나노튜브-분산제 복합체의 입자 크기 분포의 10%, 50% 및 90% 기준에서의 입자 크기를 의미한다)(In Equation 3, D 10 , D 50, and D 90 refer to particle sizes at 10%, 50%, and 90% of the particle size distribution of the carbon nanotube-dispersant composite, respectively.)
보다 더 구체적으로는 상기한 입자 크기 분포를 충족하는 조건하에서, 복합체의 입자 크기 분포의 D10이 1 내지 5 ㎛, D50이 3 내지 15㎛, 그리고 D90이 10 내지 100㎛일 수 있으며, 보다 구체적으로는 D10이 1 내지 3㎛, D50이 4 내지 15㎛, 그리고 D90이 10 내지 30㎛일 수 있다. More specifically, under conditions satisfying the particle size distribution described above, D 10 of the particle size distribution of the composite may be 1 to 5 μm, D 50 to 3 to 15 μm, and D 90 to 10 to 100 μm, More specifically, D 10 may be 1 to 3 μm, D 50 may be 4 to 15 μm, and D 90 may be 10 to 30 μm.
본 발명에 있어서, 상기 복합체의 입자 크기 D10, D50 및 D90은 레이저 회절법(laser diffraction method)을 이용하여 측정할 수 있으며, 보다 구체적으로는, 상기 복합체를 용매에 분산시킨 후, 시판되는 레이저 회절 입도 측정 장치(예를 들어 Microtrac MT 3000)에 도입하여 약 28kHz의 초음파를 출력 60W로 조사하고, 측정 장치에 있어서의 입자 크기 분포의 10, 50% 및 90% 기준에서의 평균 입경을 각각 산출할 수 있다.In the present invention, the particle sizes D 10 , D 50 and D 90 of the composite can be measured using a laser diffraction method, more specifically, after dispersing the complex in a solvent, it is commercially available. Introduced into a laser diffraction particle size measuring device (e.g., Microtrac MT 3000), an ultrasonic wave of about 28 kHz is irradiated at an output of 60 W, and the average particle diameter at 10, 50% and 90% of the particle size distribution in the measuring device is measured. Each can be calculated.
또, 상기 도전재 분산액은 브룩필드 점도계를 이용하여 10rpm의 속도로 점도 측정시 1,000 내지 20,000m㎩·s의 점도를 갖는 것일 수 있다. 상기한 바와 같이 종래에 비해 낮은 점도 특성을 가짐으로써, 전극 제조를 위한 적용시 보다 우수한 분산 특성을 나타낼 수 있다. In addition, the conductive material dispersion may have a viscosity of 1,000 to 20,000 mPa · s when measuring the viscosity at a rate of 10 rpm using a Brookfield viscometer. As described above, by having a lower viscosity characteristic than in the prior art, it is possible to exhibit more excellent dispersion characteristics when applied for electrode production.
이와 같이 본 발명에 따른 도전재 분산액은 탄소 나노튜브의 균일 분산으로 보다 우수한 전기적, 열적, 기계적 특성을 나타낼 수 있고, 또 저점도 유지로 작업성 또한 향상되어 다양한 분야에서의 적용 및 실용화가 가능하다. 구체적으로 상기 도전재 분산액은 리튬 이차전지용 전극의 제조에 이용될 수 있다. As described above, the conductive material dispersion according to the present invention may exhibit more excellent electrical, thermal, and mechanical properties by uniform dispersion of carbon nanotubes, and workability is also improved by maintaining low viscosity, thereby enabling application and practical use in various fields. . Specifically, the conductive material dispersion may be used for the production of a lithium secondary battery electrode.
이에 따라 본 발명의 또 다른 일 실시예에 따르면, 전극활물질과 함께 상기한 도전재 분산액을 포함하는 리튬 이차전지용 전극 형성용 조성물 및 이를 이용하여 제조된 전극을 제공한다. 이때 상기 전극은 양극 또는 음극일 수 있으며, 보다 구체적으로는 양극일 수 있다.Accordingly, according to another embodiment of the present invention, there is provided a composition for forming an electrode for a lithium secondary battery including the conductive material dispersion together with an electrode active material, and an electrode manufactured using the same. In this case, the electrode may be an anode or a cathode, and more specifically, may be an anode.
구체적으로, 상기 리튬 이차전지의 전극 형성용 조성물은 상기한 도전재 분산액, 전극 활물질 및 바인더를 포함할 수 있다.Specifically, the composition for forming an electrode of the lithium secondary battery may include the conductive material dispersion, the electrode active material and the binder.
상기 리튬 이차전지의 전극 형성용 조성물에 있어서, 상기 도전재 분산액은 상기 리튬 이차전지의 전극 형성용 조성물 총 중량에 대하여 1중량% 내지 50중량%로 포함될 수 있다. 상기 도전재 분산액의 함량이 1중량% 미만이면 전극활물질층 내 전도성 저하 및 저항의 증가로 전지 출력 특성 저하의 우려가 있고, 50중량%를 초과할 경우 상대적인 활물질 함량의 저하로 용량 특성 저하의 우려가 있다. In the composition for forming an electrode of the lithium secondary battery, the conductive material dispersion may be included in 1% by weight to 50% by weight relative to the total weight of the composition for forming the electrode of the lithium secondary battery. If the content of the conductive material dispersion is less than 1% by weight, there is a fear of deterioration of battery output characteristics due to a decrease in conductivity and an increase in resistance in the electrode active material layer. There is.
상기 전극 형성용 조성물에 있어서, 전극활물질은 통상 이차전지의 양극 또는 음극 활물질로서 사용되는 것일 수 있다.In the composition for forming an electrode, the electrode active material may be used as a positive electrode or negative electrode active material of a secondary battery.
구체적으로는 상기 전극 형성용 조성물이 양극 형성용일 경우, 상기 전극 활물질은 리튬의 가역적인 인터칼레이션 및 디인터칼레이션이 가능한 화합물(리티에이티드 인터칼레이션 화합물)로서, 구체적으로는 코발트, 망간, 니켈 또는 알루미늄과 같은 전이금속과 리튬을 포함하는 리튬전이금속 산화물의 양극 활물질일 수 있다.Specifically, when the composition for forming an electrode is for forming an anode, the electrode active material is a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound), specifically, cobalt and manganese. It may be a positive electrode active material of a lithium transition metal oxide including a transition metal and lithium, such as nickel or aluminum.
상기 전극 형성용 조성물에 있어서, 전극활물질은 통상 이차전지의 양극 또는 음극 활물질로서 사용되는 것일 수 있다.In the composition for forming an electrode, the electrode active material may be used as a positive electrode or negative electrode active material of a secondary battery.
구체적으로는 상기 전극 형성용 조성물이 양극 형성용일 경우, 상기 전극 활물질은 리튬의 가역적인 인터칼레이션 및 디인터칼레이션이 가능한 화합물(리티에이티드 인터칼레이션 화합물)로서, 구체적으로는 코발트, 망간, 니켈 또는 알루미늄과 같은 전이금속과 리튬을 포함하는 리튬전이금속 산화물의 양극 활물질일 수 있다.Specifically, when the composition for forming an electrode is for forming an anode, the electrode active material is a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound), specifically, cobalt and manganese. It may be a positive electrode active material of a lithium transition metal oxide including a transition metal and lithium, such as nickel or aluminum.
또, 상기 전극 형성용 조성물이 음극 형성용일 경우, 상기 전극 활물질은 리튬의 가역적인 인터칼레이션 및 디인터칼레이션이 가능한 화합물로서, 인조흑연, 천연흑연, 흑연화 탄소섬유, 비정질탄소 등의 탄소질 재료; Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si합금, Sn합금 또는 Al합금 등 리튬과 합금화가 가능한 금속질 화합물; SiOx(0 < x < 2), SnO2, 바나듐 산화물, 리튬 바나듐 산화물과 같이 리튬을 도프 및 탈도프할 수 있는 금속산화물; 또는 Si-C 복합체 또는 Sn-C 복합체과 같이 상기 금속질 화합물과 탄소질 재료를 포함하는 복합물 등의 음극활물질일 수 있으며, 이들 중 어느 하나 또는 둘 이상의 혼합물이 사용될 수 있다. 또한, 상기 음극활물질로서 금속 리튬 박막이 사용될 수도 있다. 또, 탄소재료는 저결정 탄소 및 고결정성 탄소 등이 모두 사용될 수 있다. 저결정성 탄소로는 연화탄소 (soft carbon) 및 경화탄소 (hard carbon)가 대표적이며, 고결정성 탄소로는 무정형, 판상, 인편상, 구형 또는 섬유형의 천연 흑연 또는 인조 흑연, 키시흑연 (Kish graphite), 열분해 탄소 (pyrolytic carbon), 액정피치계 탄소섬유 (mesophase pitch based carbon fiber), 탄소 미소구체 (meso-carbon microbeads), 액정피치 (Mesophase pitches) 및 석유와 석탄계 코크스 (petroleum or coal tar pitch derived cokes) 등의 고온 소성탄소가 대표적이다.In addition, when the composition for forming an electrode is for forming a negative electrode, the electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and includes carbon such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon. Vaginal materials; Metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys or Al alloys; Metal oxides capable of doping and undoping lithium such as SiO x (0 <x <2), SnO 2 , vanadium oxide, lithium vanadium oxide; Or an anode active material such as a composite including the metallic compound and a carbonaceous material, such as a Si-C composite or a Sn-C composite, and any one or a mixture of two or more thereof may be used. In addition, a metal lithium thin film may be used as the anode active material. As the carbon material, both low crystalline carbon and high crystalline carbon can be used. Soft crystalline carbon and hard carbon are typical low crystalline carbon, and high crystalline carbon is amorphous, plate, scaly, spherical or fibrous natural graphite or artificial graphite, Kish graphite (Kish) graphite, pyrolytic carbon, mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches and petroleum or coal tar pitch High-temperature calcined carbon such as derived cokes is typical.
상기한 전극활물질은 고형분 함량을 기준으로 전극 형성용 조성물 총 중량에 대하여 70 내지 99.5중량%로 포함될 수 있다. 전극활물질의 함량이 70중량% 미만이면 용량 저하의 우려가 있고, 99.5중량%를 초과할 경우 바인더 및 도전재의 상대적인 함량 감소로 전극 집전체에 대한 접착력 저하, 도전성 저하 등의 우려가 있다.The electrode active material may be included in 70 to 99.5% by weight based on the total weight of the composition for forming an electrode based on the solid content. If the content of the electrode active material is less than 70% by weight, there is a fear of lowering the capacity, and when the content of the electrode active material exceeds 99.5% by weight, the relative content of the binder and the conductive material is reduced, there is a concern such as lowering the adhesion to the electrode current collector, lowering the conductivity.
또, 상기 바인더는 전극 활물질 입자들 간의 부착 및 전극 활물질과 집전체와의 접착력을 향상시키기 위해 포함되는 것일 수 있다.In addition, the binder may be included to improve adhesion between the electrode active material particles and adhesion between the electrode active material and the current collector.
상기 바인더는 구체적으로 폴리비닐리덴플로라이드(PVDF), 비닐리덴플루오라이드-헥사플루오로프로필렌 코폴리머(PVDF-co-HFP), 폴리비닐알코올, 폴리아크릴로니트릴(polyacrylonitrile), 카르복시메틸셀룰로우즈(CMC), 전분, 히드록시프로필셀룰로우즈, 재생 셀룰로우즈, 폴리비닐피롤리돈, 테트라플루오로에틸렌, 폴리에틸렌, 폴리프로필렌, 에틸렌-프로필렌-디엔 폴리머(EPDM), 술폰화-EPDM, 스티렌 부타디엔 고무(SBR), 불소 고무, 또는 이들의 다양한 공중합체 등을 들 수 있으며, 이들 중 1종 단독 또는 2종 이상의 혼합물이 사용될 수 있다. 상기 바인더는 전극 형성용 조성물 총 중량에 대하여 0.09 내지 30중량%로 포함될 수 있다.The binder is specifically polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene Butadiene rubber (SBR), fluorine rubber, or various copolymers thereof, and the like, and one or more of these may be used. The binder may be included in an amount of 0.09 to 30% by weight based on the total weight of the composition for forming an electrode.
또, 상기 전극 형성용 조성물은 상기한 전극 활물질, 바인더 등의 혼합 및 분산을 위해 용매를 더 포함할 수 있다.In addition, the electrode forming composition may further include a solvent for mixing and dispersing the electrode active material, a binder, and the like.
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 용매의 사용량은 슬러리의 도포 두께, 제조 수율을 고려하여 상기 전극 활물질 및 바인더를 용해 또는 분산시키고, 이후 전극 제조를 위한 도포시 우수한 두께 균일도를 나타낼 수 있는 점도를 갖도록 하는 정도면 충분하다.The solvent may be a solvent generally used in the art, and may include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone or acetone. Water, and the like, one of these alone or a mixture of two or more thereof may be used. The amount of the solvent may be sufficient to dissolve or disperse the electrode active material and the binder in consideration of the coating thickness of the slurry and the production yield, and to have a viscosity capable of exhibiting excellent thickness uniformity during application of the electrode.
한편, 상기한 전극 형성용 조성물을 이용하여 제조되는 본 발명의 일 실시예에 따른 전극은, 상기한 전극 형성용 조성물을 이용하여 전극 활물질층을 형성하는 것을 제외하고는 통상의 방법에 따라 제조될 수 있다.On the other hand, the electrode according to an embodiment of the present invention manufactured using the composition for forming an electrode, except that the electrode active material layer is formed using the composition for forming an electrode to be manufactured according to a conventional method. Can be.
구체적으로, 상기 전극은 상기한 전극 형성용 조성물을 집전체에 도포하고 건조하거나, 또는 상기 전극 형성용 조성물을 별도의 지지체 상에 캐스팅한 다음, 이 지지체로부터 박리하여 얻은 필름을 집전체 상에 라미네이션함으로써 제조될 수 있다.Specifically, the electrode is applied to the current-coating composition for forming the electrode on the current collector and dried, or casting the electrode-forming composition on a separate support, then the film obtained by peeling from the support lamination on the current collector It can be manufactured by.
상기 집전체는 전지에 화학적 변화를 유발하지 않으면서 도전성을 가진 것이라면 특별히 제한되는 것은 아니며, 예를 들어 구리, 스테인리스 스틸, 알루미늄, 니켈, 티탄, 소성 탄소 또는 알루미늄이나 스테인레스 스틸 표면에 탄소, 니켈, 티탄, 은 등으로 표면 처리한 것 등이 사용될 수 있다. 또, 상기 집전체는 통상적으로 3 내지 500㎛의 두께를 가질 수 있으며, 상기 집전체 표면 상에 미세한 요철을 형성하여 양극활물질의 접착력을 높일 수도 있다. 예를 들어 필름, 시트, 호일, 네트, 다공질체, 발포체, 부직포체 등 다양한 형태로 사용될 수 있다.The current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, or carbon, nickel, The surface-treated with titanium, silver, etc. can be used. In addition, the current collector may generally have a thickness of 3 to 500㎛, and may form fine irregularities on the surface of the current collector to increase the adhesion of the positive electrode active material. For example, it can be used in various forms, such as a film, a sheet, a foil, a net, a porous body, a foam, a nonwoven body.
본 발명의 또 다른 일 실시예에 따르면, 상기 전극을 포함하는 전기화학소자가 제공된다. 상기 전기화학소자는 구체적으로 전지, 커패시터 등일 수 있으며, 보다 구체적으로는 리튬 이차전지일 수 있다.According to another embodiment of the present invention, an electrochemical device including the electrode is provided. The electrochemical device may be specifically a battery, a capacitor, or the like, and more specifically, a lithium secondary battery.
한편, 상기 리튬 이차전지에 있어서, 세퍼레이터는 음극과 양극을 분리하고 리튬 이온의 이동 통로를 제공하는 것으로, 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. 또, 내열성 또는 기계적 강도 확보를 위해 세라믹 성분 또는 고분자 물질이 포함된 코팅된 세퍼레이터가 사용될 수도 있으며, 선택적으로 단층 또는 다층 구조로 사용될 수 있다.On the other hand, in the lithium secondary battery, the separator is to separate the negative electrode and the positive electrode and to provide a passage for the movement of lithium ions, if it is usually used as a separator in a lithium secondary battery can be used without particular limitation, in particular to the ion movement of the electrolyte It is desirable to have a low resistance against the electrolyte and excellent electrolytic solution-moisture capability. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin-based polymer such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer and ethylene / methacrylate copolymer or the like Laminate structures of two or more layers may be used. In addition, conventional porous nonwoven fabrics such as nonwoven fabrics made of high melting point glass fibers, polyethylene terephthalate fibers and the like may be used. In addition, a coated separator containing a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength, and may be optionally used as a single layer or a multilayer structure.
또, 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. In addition, examples of the electrolyte used in the present invention include an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, and the like, which can be used in manufacturing a lithium secondary battery. It doesn't happen.
구체적으로, 상기 전해질은 유기 용매 및 리튬염을 포함할 수 있다. Specifically, the electrolyte may include an organic solvent and a lithium salt.
상기 유기 용매로는 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; 에틸알코올, 이소프로필 알코올 등의 알코올계 용매; R-CN(R은 C2 내지 C20의 직쇄상, 분지상 또는 환 구조의 탄화수소기이며, 이중결합 방향 환 또는 에테르 결합을 포함할 수 있다) 등의 니트릴류; 디메틸포름아미드 등의 아미드류; 1,3-디옥솔란 등의 디옥솔란류; 또는 설포란(sulfolane)류 등이 사용될 수 있다. 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. 이 경우 환형 카보네이트와 사슬형 카보네이트는 약 1:1 내지 약 1:9의 부피비로 혼합하여 사용하는 것이 전해액의 성능이 우수하게 나타날 수 있다. The organic solvent may be used without particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may be an ester solvent such as methyl acetate, ethyl acetate, γ-butyrolactone or ε-caprolactone; Ether solvents such as dibutyl ether or tetrahydrofuran; Ketone solvents such as cyclohexanone; Aromatic hydrocarbon solvents such as benzene and fluorobenzene; Dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), propylene carbonate, Carbonate solvents such as PC); Alcohol solvents such as ethyl alcohol and isopropyl alcohol; Nitriles such as R-CN (R is a C2 to C20 linear, branched or cyclic hydrocarbon group, which may include a double bond aromatic ring or an ether bond); Amides such as dimethylformamide; Dioxolanes such as 1,3-dioxolane; Or sulfolanes may be used. Of these, carbonate-based solvents are preferable, and cyclic carbonates having high ionic conductivity and high dielectric constant (for example, ethylene carbonate or propylene carbonate) that can improve the charge and discharge performance of a battery, and low viscosity linear carbonate compounds ( For example, a mixture of ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate and the like is more preferable. In this case, the cyclic carbonate and the chain carbonate may be mixed and used in a volume ratio of about 1: 1 to about 1: 9, so that the performance of the electrolyte may be excellent.
상기 리튬염은 리튬 이차전지에서 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 리튬염의 농도는 0.1 내지 2.0M 범위 내에서 사용하는 것이 좋다. 리튬염의 농도가 상기 범위에 포함되면, 전해질이 적절한 전도도 및 점도를 가지므로 우수한 전해질 성능을 나타낼 수 있고, 리튬 이온이 효과적으로 이동할 수 있다.The lithium salt may 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 is 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 and the like can be used. The concentration of the lithium salt is preferably used within the range of 0.1 to 2.0M. When the concentration of the lithium salt is included in the above range, since the electrolyte has an appropriate conductivity and viscosity, it can exhibit excellent electrolyte performance, and lithium ions can move effectively.
상기 전해질에는 상기 전해질 구성 성분들 외에도 전지의 수명특성 향상, 전지 용량 감소 억제, 전지의 방전 용량 향상 등을 목적으로 예를 들어, 디플루오로 에틸렌카보네이트 등과 같은 할로알킬렌카보네이트계 화합물, 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 0.1 내지 5 중량%로 포함될 수 있다.In addition to the electrolyte components, the electrolyte includes, for example, haloalkylene carbonate-based compounds such as difluoro ethylene carbonate, pyridine, tri, etc. for the purpose of improving battery life characteristics, reducing battery capacity, and improving discharge capacity of the battery. Ethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphate triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N, N-substituted imida One or more additives such as zolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxy ethanol or aluminum trichloride may be included. In this case, the additive may be included in 0.1 to 5% by weight based on the total weight of the electrolyte.
상기와 같이 본 발명에 따른 도전재 분산액을 이용하여 제조된 전극을 포함하는 리튬 이차전지는 전극 내 도전재의 균일 분산으로 인해 우수한 방전 용량, 출력 특성 및 용량 유지율을 안정적으로 나타낼 수 있다. 그 결과, 휴대전화, 노트북 컴퓨터, 디지털 카메라 등의 휴대용 기기, 및 하이브리드 전기자동차(hybrid electric vehicle, HEV) 등의 전기 자동차 분야 등에 유용하다.As described above, the lithium secondary battery including the electrode manufactured using the conductive material dispersion according to the present invention may stably exhibit excellent discharge capacity, output characteristics, and capacity retention rate due to the uniform dispersion of the conductive material in the electrode. As a result, it is useful for portable devices, such as a mobile telephone, a notebook computer, a digital camera, and the electric vehicle field | area, such as a hybrid electric vehicle (HEV).
이에 따라, 본 발명의 다른 일 구현예에 따르면, 상기 리튬 이차전지를 단위 셀로 포함하는 전지 모듈 및 이를 포함하는 전지팩이 제공된다. Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.
상기 전지모듈 또는 전지팩은 파워 툴(Power Tool); 전기자동차(Electric Vehicle, EV), 하이브리드 전기자동차, 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 is a power tool (Power Tool); Electric vehicles including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); Or it can be used as a power source for any one or more of the system for power storage.
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 practice the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.
실시예 1-1, 비교예 1-1 및 비교예 1-2: 탄소 나노튜브의 제조Example 1-1, Comparative Example 1-1 and Comparative Example 1-2: Preparation of Carbon Nanotubes
Co와 V의 전구체 물질로서 Co(NO3)2 ·6H2O와 NH4Vo3(Co/V, 10:1몰비) 2,424g을 물 2,000㎖에 투입하여 맑은 수용액을 플라스크 A에 준비하였다. 별도로, 알루미늄계 지지체 전구체로서 수산화알루미늄(Al(OH)3)를 하기 표 1에 기재된 온도에서 4시간 동안 1차 소성하여 얻어진 알루미나 지지체 2,000g을 플라스크 B에 준비하였다. 상기 알루미나 지지체 2,000g을 몰 기준 100으로 환산하여, Co/V 30몰이 되도록 플라스크 B에 상기 플라스크 A 용액 4,424g을 첨가하였다. 또 시트르산 1몰 대비 Co가 하기 표 1에 기재된 몰이 되도록 시트르산을 첨가한 뒤, 결과로 수득된 혼합물의 중량을 측정하고, 그래파이트화 촉매금속 전구체를 충분히 담지시키기 위하여 60℃ 항온조에서 5분간 교반하여 숙성시켰다. 상기 온도를 유지하면서 숙성된 혼합물을 80rpm으로 회전시키며 진공 건조시키고, 건조 후 중량을 측정하여 수분 제거량을 측정하였다(약 14.1중량%). 결과로 수득된 건조 반응물을 하기 표 1에 기재된 온도에서 4시간 동안 2차 소성시켜 담지 촉매를 제조하였다. As precursor materials of Co and V Co (NO 3) 2 · 6H 2 O and NH 4 Vo 3: to a 2,424g (Co / V, 10 1 molar ratio) added to the water 2,000㎖ prepared a clear solution in the flask A. Separately, 2,000 g of an alumina support obtained by first calcining aluminum hydroxide (Al (OH) 3 ) as an aluminum-based support precursor at a temperature shown in Table 1 for 4 hours was prepared in Flask B. 4,424 g of the Flask A solution was added to Flask B such that 2,000 g of the alumina support was converted to 100 moles on a molar basis. Further, citric acid was added so that Co was 1 mole of citric acid to 1 mole of citric acid, and the weight of the resulting mixture was measured, and stirred for 5 minutes in a 60 ° C. constant temperature bath in order to sufficiently support the graphitized catalyst metal precursor. I was. While maintaining the temperature, the aged mixture was vacuum dried while rotating at 80 rpm, and the weight after drying was measured to determine the water removal amount (about 14.1 wt%). The resulting dry reactant was secondary calcined for 4 hours at the temperature shown in Table 1 below to prepare a supported catalyst.
상기에서 제조한 탄소 나노튜브 합성용 담지촉매를 이용하여 실험실 규모의 고정층 반응장치에서 탄소 나노튜브 합성을 수행하였다. 구체적으로 상기에서 제조된 탄소 나노튜브 합성용 담지촉매를 직경 55㎜의 내경을 갖는 석영관의 중앙부에 장착한 후 질소 분위기에서 670℃까지 승온한 다음 유지시키고, 질소와 수소, 그리고 에틸렌 가스의 혼합 부피비를 1:1:1의 동일 비율로 총 분당 180㎖ 흘리면서 1시간 동안 반응시켜 번들형의 탄소 나노튜브를 합성하였다. Carbon nanotube synthesis was performed in a laboratory scale fixed bed reactor using the supported catalyst for carbon nanotube synthesis prepared above. Specifically, the supported catalyst for synthesizing carbon nanotubes prepared above was mounted at the center of a quartz tube having an inner diameter of 55 mm, and then heated up to 670 ° C. in a nitrogen atmosphere and maintained therein, and mixed with nitrogen, hydrogen, and ethylene gas. The volume ratio was reacted for 1 hour while flowing 180 ml per minute in the same ratio of 1: 1: 1 to synthesize bundle carbon nanotubes.
1차 소성온도(℃)Primary firing temperature (℃) Co(몰)Co (Mall) 2차 소성온도(℃)Secondary firing temperature (℃)
실시예 1-1Example 1-1 450450 2323 650650
비교예 1-1Comparative Example 1-1 450450 5.85.8 650650
비교예 1-2Comparative Example 1-2 400400 2323 675675
실험예 1-1: 탄소 나노튜브의 형상 평가Experimental Example 1-1: Shape Evaluation of Carbon Nanotubes
상기 실시예 1-1, 비교예 1-1 및 비교예 1-2의 탄소 나노튜브를 주사전자 현미경(SEM)을 이용하여 관찰하였다. 실시예 1-1의 탄소 나노튜브의 관찰결과를 도 1 내지 도 3에 나타내었다. 비교예 1-1의 탄소 나노튜브의 관찰결과를 도 4 내지 도 6에 나타내었다. 비교예 1-2에서 제조한 탄소 나노튜브를 도 7 내지 도 9에 나타내었다.The carbon nanotubes of Example 1-1, Comparative Example 1-1 and Comparative Example 1-2 were observed using a scanning electron microscope (SEM). The observation results of the carbon nanotubes of Example 1-1 are shown in FIGS. 1 to 3. The observation results of the carbon nanotubes of Comparative Example 1-1 are shown in FIGS. 4 to 6. Carbon nanotubes prepared in Comparative Examples 1-2 are shown in FIGS. 7 to 9.
측정결과, 실시예 1-1의 탄소 나노튜브와 비교예 1-1 및 비교예 1-2의 탄소 나노튜브는 100㎛ 이하의 동등 수준의 평균 입자 직경(D50)을 갖는 번들형의 구조체이었다. 그러나, 실시예 1-1의 탄소 나노튜브 단위체는 비교예 1-1 및 비교예 1-2의 탄소 나노튜브와 비교하여 단위체의 길이가 길고, 직선도가 더 높음을 확인할 수 있다. As a result of the measurement, the carbon nanotubes of Example 1-1 and the carbon nanotubes of Comparative Example 1-1 and Comparative Example 1-2 were bundled structures having an average particle diameter (D 50 ) of equivalent level of 100 μm or less. . However, it can be seen that the carbon nanotube unit of Example 1-1 has a longer length and a higher linearity than the carbon nanotubes of Comparative Example 1-1 and Comparative Example 1-2.
실험예 1-2: 탄소 나노튜브의 특성 평가 (1)Experimental Example 1-2: Characterization of Carbon Nanotubes (1)
상기 실시예 1-1, 비교예 1-1 및 비교예 1-2의 탄소 나노튜브에 대해 하기와 같은 방법으로, 탄소 나노튜브 단위체의 평균 직경 및 길이, 탄소 나노튜브의 2차구조 형상, 입도, IG/ID비, 순도, 분체저항, BET 비표면적, 벌크밀도 및 진밀도를 각각 측정하고, 그 결과를 하기 표 2에 나타내었다.For the carbon nanotubes of Examples 1-1, Comparative Example 1-1 and Comparative Example 1-2, the average diameter and length of the carbon nanotube unit, secondary structure shape, particle size of the carbon nanotubes , IG / ID ratio, purity, powder resistance, BET specific surface area, bulk density and true density were measured, respectively, and the results are shown in Table 2 below.
1) 2차 구조 형상 및 입도: 주사전자 현미경을 이용하여 탄소 나노튜브의 입도 및 2차 구조의 형상을 관찰하였다.1) Secondary structure shape and particle size: The particle size and shape of the secondary structure of the carbon nanotubes were observed using a scanning electron microscope.
2) 탄소 나노튜브 단위체의 평균 직경: SEM 및 BET를 이용하여 측정하였다. 2) Average diameter of carbon nanotube units: measured using SEM and BET.
3) 탄소 나노튜브 단위체의 평균 길이: SEM 및 BET를 이용하여 측정하였다. 3) Average length of carbon nanotube units: measured using SEM and BET.
4) 결정화도(IG/ID비): 514.5㎚ 파장의 레이저를 이용한 라만 분광 분석법에 의해 얻어진 1,575㎝-1 내지 1,600㎝-1에서의 G 밴드의 최대 피크 강도(IG)에 대한 1,340㎝-1 내지 1,360㎝-1에서의 D 밴드의 최대 피크 강도(ID)의 비(ID/IG)로부터 평균값 및 표준편차를 구하였다. 4) The crystallinity (IG / ID ratio): 1,340㎝ -1 to a maximum peak intensity (IG) of G-band in a Raman 1,575㎝ -1 to 1,600㎝ -1 obtained by the spectroscopic analysis using a laser of wavelength to 514.5㎚ The average value and standard deviation were determined from the ratio (ID / IG) of the maximum peak intensity (ID) of the D band at 1,360 cm −1 .
5) 순도: 에쉬 테스트(ash test)에 의해 탄소 나노튜브의 순도를 측정하였다.5) Purity: The purity of the carbon nanotubes was measured by ash test.
6) 분체저항: 파우더를 직경이 1㎜인 절연 몰드에 충진하고 가압하여 표면의 전류와 전압을 4개의 탐침으로 측정하였고, 보정계수를 적용하여 압력이 62㎫일 때의 부피 저항값을 산출하였다. 6) Powder resistance: The powder was filled into an insulating mold with a diameter of 1 mm and pressurized to measure the surface current and voltage with four probes, and a volumetric resistance value at 62 MPa was calculated by applying a correction factor. .
7) BET 비표면적: BEL Japan 사 BELSORP-mino Ⅱ를 이용하여 액체 질소 온도 하(77K)에서의 질소가스 흡착량으로부터 산출하였다.7) BET specific surface area: BELSORP-mino II by BEL Japan Co., Ltd. was calculated from the amount of nitrogen gas adsorption under liquid nitrogen temperature (77K).
8) 벌크밀도: 무게를 알고 있는 25㎖ 용기에 파우더를 채우고 무게를 측정한 후, 밀도를 환산하는 방법으로 측정하였다. 8) Bulk Density: After filling the powder into 25ml container of known weight and weighing, it was measured by converting the density.
9) 진밀도: Pycnometer(AccuPyc Ⅱ 1340)을 이용하여 측정하였다.9) True Density: Measured using Pycnometer (AccuPyc II 1340).
실시예 1-1Example 1-1 비교예 1-1Comparative Example 1-1 비교예 1-2Comparative Example 1-2
탄소 나노튜브 단위체의 평균 직경(nm)Average diameter of carbon nanotube units (nm) 1111 1212 1111
탄소 나노튜브 단위체의 평균 길이(㎛)Average length of carbon nanotube units (µm) 100100 100100 100100
탄소 나노튜브 2차구조 형상Carbon nanotube secondary structure shape 번들형Bundled 번들형Bundled 번들형Bundled
탄소 나노튜브 2차구조 평균 입도(㎛)Carbon nanotube secondary structure average particle size (㎛) ≤100≤100 ≤100≤100 ≤100≤100
IG/ID 비IG / ID ratio 평균Average 0.950.95 0.720.72 1.631.63
표준편차(%)Standard Deviation(%) 1.641.64 2.122.12 4.714.71
분체저항(Ω·cm, @62㎫) Powder Resistance (Ωcm, @ 62MPa) 0.0080.008 0.02160.0216 0.01350.0135
BET 비표면적(m2/g)BET specific surface area (m 2 / g) 249249 245245 238238
벌크밀도(kg/m3)Bulk Density (kg / m 3 ) 2323 3535 3838
진밀도(kg/m3)True density (kg / m 3 ) 1,9371,937 2,0502,050 1,8721,872
-1.0 X (X: 벌크밀도)-1.0 X (X: bulk density) -23-23 -35-35 -38-38
10logR (R: 분체저항) 10logR (R: Powder Resistance) -20.969-20.969 -16.655-16.655 -18.696-18.696
-0.6 X (X: 벌크밀도)-0.6 X (X: bulk density) -13.8-13.8 -21-21 -22.8-22.8
상기 표 2에 나타난 바와 같이, 실시예 1-1의 탄소 나노튜브는 비교예 1-1 및 비교예 1-2의 탄소 나노튜브에 비해 순도 및 비표면적은 높은 반면, 벌크밀도와 분체저항은 낮았다. 또한, 실시예 1-1의 탄소 나노튜브는 상기 수학식 1을 만족하지만, 비교예 1-1 및 비교예 1-2의 탄소 나노튜브는 상기 수학식 1을 만족하지 못하였다.As shown in Table 2, the carbon nanotubes of Example 1-1 were higher in purity and specific surface area than the carbon nanotubes of Comparative Examples 1-1 and 1-2, but their bulk density and powder resistance were low. . In addition, the carbon nanotubes of Example 1-1 satisfy the above Equation 1, but the carbon nanotubes of Comparative Example 1-1 and Comparative Example 1-2 did not satisfy the above Equation 1.
실험예 1-3: 탄소 나노튜브의 특성 평가 (2)Experimental Example 1-3: Characterization of Carbon Nanotubes (2)
상기 실시예 1-1, 비교예 1-1 및 비교예 1-2의 탄소 나노튜브에 대해 분체밀도에 따른 분체저항의 변화를 관찰하였고, 그 결과를 표 3 및 도 10에 나타내었다. The carbon nanotubes of Example 1-1, Comparative Example 1-1 and Comparative Example 1-2 were observed a change in powder resistance according to the powder density, the results are shown in Table 3 and FIG.
※ 분체저항: 탄소 나노튜브의 파우더를 직경이 1㎜인 절연 몰드에 충진하고 가압하여 표면의 전류와 전압을 4개의 탐침으로 측정하였고, 보정계수를 적용하여 압력에 따른 분체밀도 및 분체저항을 산출하였다. ※ Powder Resistance: The carbon nanotube powder was filled into an insulating mold with a diameter of 1 mm and pressurized, and the surface current and voltage were measured by four probes. The powder density and powder resistance were calculated by applying a correction factor. It was.
구분division 압력(㎫)Pressure (MPa)
1313 2525 3737 5050 6262
실시예 1-1Example 1-1 분체저항(Ω·㎝)Powder resistance (Ωcm) 0.03570.0357 0.02030.0203 0.01430.0143 0.01070.0107 0.00800.0080
분체밀도(g/cc)Powder density (g / cc) 0.520.52 0.770.77 1.001.00 1.251.25 1.571.57
-1.0 X-1.0 X -23.0-23.0
10logR10logR -14.473-14.473 -16.925-16.925 -18.446-18.446 -19.706-19.706 -20.969-20.969
-0.6 X-0.6 X -13.8-13.8
비교예 1-1Comparative Example 1-1 분체저항(Ω·㎝)Powder resistance (Ωcm) 0.04730.0473 0.03570.0357 0.02950.0295 0.02350.0235 0.02160.0216
분체밀도(g/cc)Powder density (g / cc) 0.640.64 0.850.85 1.001.00 1.141.14 1.271.27
-1.0 X-1.0 X -34.0-34.0
10logR10logR -13.251-13.251 -14.473-14.473 -15.301-15.301 -16.289-16.289 -16.655-16.655
-0.6 X-0.6 X -21-21
비교예 1-2Comparative Example 1-2 분체저항(Ω·㎝)Powder resistance (Ωcm) 0.04890.0489 0.02770.0277 0.01950.0195 0.01570.0157 0.01350.0135
분체밀도(g/cc)Powder density (g / cc) 0.550.55 0.800.80 1.001.00 1.251.25 1.521.52
-1.0 X-1.0 X -38.0-38.0
10logR10logR -13.106-13.106 -15.575-15.575 -17.099-17.099 -18.041-18.041 -18.696-18.696
-0.6 X-0.6 X -22.8-22.8
※ R: 분체밀도, 10logR의 값 중 소수점 넷째자리는 버림※ R: powder density, 4th decimal place among 10logR
※ X: 벌크밀도※ X: Bulk Density
표 3 및 도 10을 참조하면, 실시예 1-1의 탄소 나노튜브는 압력이 13 내지 62㎫일 때, 분체저항이 0.0080 Ω·㎝ 내지 0.0357 Ω·㎝이고, 상술한 수학식 1을 만족하는 것을 알 수 있다. 실시예 1-1의 탄소 나노튜브는 동일 분체밀도 구간에서의 비교예 1-1 및 비교예 1-2의 탄소 나노튜브 보다 낮은 분체저항을 나타내었다. 반면, 비교예 1-1 및 비교예 1-2의 탄소 나노튜브는 상술한 수학식을 모두 만족하지 못하였다. Referring to Table 3 and FIG. 10, the carbon nanotubes of Example 1-1 have a powder resistance of 0.0080 Ω · cm to 0.0357 Ω · cm when the pressure is 13 to 62 MPa, and satisfies Equation 1 described above. It can be seen that. Carbon nanotubes of Example 1-1 showed a lower powder resistance than carbon nanotubes of Comparative Examples 1-1 and 1-2 in the same powder density section. On the other hand, the carbon nanotubes of Comparative Example 1-1 and Comparative Example 1-2 did not satisfy all of the above-described equations.
또한, 비교예 1-1 및 비교예 1-2의 경우, 인가되는 압력이 낮을 때는 실시예 1-1 보다 높은 분체밀도를 나타내다가, 인가되는 압력이 높아질 때는 분체밀도가 더 낮아진 것을 알 수 있었다. 이는 실시예 1-1, 비교예 1-1 및 비교예 1-2의 탄소 나노튜브의 재료특성의 차이로 보여진다.In addition, in the case of Comparative Example 1-1 and Comparative Example 1-2, the powder density was higher than in Example 1-1 when the applied pressure is low, the powder density was lower when the applied pressure is higher. . This is seen as a difference in the material properties of the carbon nanotubes of Example 1-1, Comparative Example 1-1 and Comparative Example 1-2.
실시예 2-1 내지 실시예 2-6, 비교예 2-1 및 비교예 2-2: 도전재 분산액의 제조 Example 2-1 to Example 2-6, Comparative Example 2-1 and Comparative Examples 2-2 Preparation of the conductive material dispersion
분산매인 N-메틸피롤리돈(NMP) 용매 94.0중량부에, 하기 표 4에 기재된 도전재 5중량부 및 하기 표 4에 기재된 분산제 1.0중량부를 첨가하고 균질혼합기(제조사: VMA 모델명: LC55, 임펠러 회전 속도: 3,000rpm)를 이용하여 60분 동안 혼합하여 혼합물을 제조하였다. 상기 혼합물을 네취 비드 밀(제조사: NETZSCH, 모델명: Minicer, 비드 크기: 1mm, 비드 회전 속도: 3,000rpm)을 이용하여 60분 동안 분산시켜 도전재 분산액을 수득하였다.To 94.0 parts of N-methylpyrrolidone (NMP) solvent as a dispersion medium, 5 parts by weight of the conductive material shown in Table 4 and 1.0 parts by weight of the dispersant shown in Table 4 were added thereto, and a homogeneous mixer (manufacturer: VMA model name: LC55, impeller Rotational speed: 3,000 rpm) was mixed for 60 minutes to prepare a mixture. The mixture was dispersed for 60 minutes using a NETZSCH bead mill (manufacturer: NETZSCH, model name: Minicer, bead size: 1 mm, bead rotation speed: 3,000 rpm) to obtain a conductive material dispersion.
구분division 도전재Conductive material 분산제Dispersant
수소화된 니트릴부타디엔계 고무Hydrogenated Nitrile Butadiene Rubber
α,β-불포화 니트릴 유래 구조의 반복 단위(중량%)Recurring units (wt%) of α, β-unsaturated nitrile-derived structures 수소화된 공액 디엔 유래 구조의 반복 단위(중량%)Recurring unit (wt%) of hydrogenated conjugated diene-derived structure 공중합 가능한 단량체 유래 반복 단위(중량%)Recurring unit derived from copolymerizable monomer (% by weight) 중량평균 분자량(g/㏖)Weight average molecular weight (g / mol) 다분산 지수(PDI)Polydispersity Index (PDI)
실시예 2-1Example 2-1 실시예 1-1Example 1-1 5454 6363 00 260,000260,000 2.92.9
실시예 2-2Example 2-2 실시예 1-1Example 1-1 3737 6363 00 200,000200,000 2.72.7
실시예 2-3Example 2-3 실시예 1-1Example 1-1 3737 6363 00 300,000300,000 3.33.3
실시예 2-4Example 2-4 실시예 1-1Example 1-1 3737 4444 3535 400,000400,000 0.30.3
실시예 2-5Example 2-5 실시예 1-1Example 1-1 2121 6363 1010 480,000480,000 2.22.2
실시예 2-6Example 2-6 실시예 1-1Example 1-1 폴리비닐피롤리돈Polyvinylpyrrolidone 400,000400,000 --
비교예 2-1Comparative Example 2-1 비교예 1-1Comparative Example 1-1 3737 6363 00 260,000260,000 2.92.9
비교예 2-2Comparative Example 2-2 비교예 1-2Comparative Example 1-2 3737 6363 00 260,000260,000 2.92.9
※ α,β-불포화 니트릴 유래 구조의 반복 단위:
Figure PCTKR2016012301-appb-I000001
※ Repeating unit of α, β-unsaturated nitrile derived structure:
Figure PCTKR2016012301-appb-I000001
수소화된 공액 디엔 유래 구조의 반복 단위:Recurring units of hydrogenated conjugated diene-derived structure:
Figure PCTKR2016012301-appb-I000002
Figure PCTKR2016012301-appb-I000002
공액 디엔 유래 구조 단위의 반복 단위:
Figure PCTKR2016012301-appb-I000003
Repeat units of conjugated diene-derived structural units:
Figure PCTKR2016012301-appb-I000003
실험예 2-1: 도전재 분산액의 특성 평가 (1)Experimental Example 2-1: Evaluation of Properties of Conductive Material Dispersion (1)
실시예 2-1 내지 실시예 2-6, 비교예 2-1 및 비교예 2-2에서 제조한 도전재 분산액 내 탄소 나노튜브-분산제 복합체의 입자 크기 분포 및 점도를 측정하였다. 그 결과를 하기 표 5에 나타내었다. The particle size distribution and viscosity of the carbon nanotube-dispersant composite in the conductive material dispersions prepared in Examples 2-1 to 2-2, Comparative Example 2-1 and Comparative Example 2-2 were measured. The results are shown in Table 5 below.
입자 크기 분포: 레이저 회절 입도 측정 장치(예를 들어 Microtrac MT 3000)에 도입하여 약 28㎑의 초음파를 출력 60W로 조사한 후, 측정 장치에 있어서의 입자 크기 분포의 10% 기준에서의 평균 입자 크기 D10, 입자 크기 분포의 50% 기준에서의 평균 입자 크기 D50 및 입자 크기 분포의 90% 기준에서의 평균 입자 크기 D90을 각각 산출하였다.Particle size distribution: The average particle size D based on 10% of the particle size distribution in the measuring device after being introduced into a laser diffraction particle size measuring device (e.g., Microtrac MT 3000) was irradiated with an output of 60 W at about 28 Hz. 10 , the average particle size D 50 at the 50% basis of the particle size distribution and the average particle size D 90 at the 90% basis of the particle size distribution were calculated, respectively.
BF점도: 브룩필드 점도계를 이용하여 10rpm에서의 점도를 측정하였다.BF viscosity: The viscosity at 10 rpm was measured using a Brookfield viscometer.
탄소 나노튜브-분산제 복합체의 입자 크기 분포Particle Size Distribution of Carbon Nanotube-Dispersant Composites BF 점도(mPa·s)BF Viscosity (mPas)
(D90-D10)/D50 (D 90 -D 10 ) / D 50 D10(㎛)D 10 (㎛) D50(㎛)D 50 (㎛) D90(㎛)D 90 (㎛)
실시예 2-1Example 2-1 2.022.02 1.601.60 4.804.80 11.3011.30 12,80012,800
실시예 2-2Example 2-2 2.152.15 1.451.45 4.304.30 10.6910.69 10,20010,200
실시예 2-3Example 2-3 2.012.01 1.721.72 5.135.13 12.3112.31 13,60013,600
실시예 2-4Example 2-4 3.363.36 1.981.98 5.795.79 21.4321.43 16,50016,500
실시예 2-5Example 2-5 5.965.96 2.112.11 5.315.31 25.7925.79 18,90018,900
실시예 2-6Example 2-6 2.162.16 1.151.15 5.125.12 12.2412.24 4,5004,500
비교예 2-1Comparative Example 2-1 7.887.88 1.801.80 5.135.13 42.2442.24 12,00012,000
비교예 2-2Comparative Example 2-2 6.616.61 1.451.45 7.907.90 53.7053.70 21,00021,000
표 5를 참조하면, 실시예 2-1 내지 실시예 2-6의 도전재 분산액 내 탄소 나노튜브-분산제 복합체는 수학식 3에 따른 입자 크기 분포를 만족하는 것으로 나타났다. 하지만, 비교예 2-1 및 비교예 2-2의 도전재 분산액 내 탄소 나노튜브-분산제 복합체는 수학식 3에 따른 입자 크기 분포를 만족하지 못하였다. Referring to Table 5, the carbon nanotube-dispersant composite in the conductive material dispersion of Examples 2-1 to 2-6 was found to satisfy the particle size distribution according to the equation (3). However, the carbon nanotube-dispersant composites in the conductive material dispersions of Comparative Example 2-1 and Comparative Example 2-2 did not satisfy the particle size distribution according to Equation 3.
이와 같은 결과로, 실시예 2-1 내지 실시예 2-6의 도전재 분산액을 구성하는 탄소 나노튜브-분산제 복합체가 균일한 입자 크기를 갖는 것을 알 수 있었다. As a result, it was found that the carbon nanotube-dispersant composites constituting the conductive material dispersions of Examples 2-1 to 2-6 had a uniform particle size.
실험예 2-2: 도전재 분산액의 특성 평가 (2)Experimental Example 2-2: Characterization of the conductive material dispersion (2)
실시예 2-1 내지 실시예 2-6, 비교예 2-1 및 비교예 2-2의 도전재 분산액을 주사전자 현미경(SEM)을 이용하여 관찰하였다. 실시예 2-1의 도전재 분산액의 관찰 결과를 도 11에, 실시예 2-2의 도전재 분산액의 관찰 결과를 도 12에, 실시예 2-3의 도전재 분산액의 관찰 결과를 도 13에, 실시예 2-4의 도전재 분산액의 관찰 결과를 도 14에, 실시예 2-5의 도전재 분산액의 관찰 결과를 도 15에, 실시예 2-6의 도전재 분산액의 관찰결과를 도 16에 나타내었다. 비교예 2-1의 도전재 분산액의 관찰 결과를 도 17에 나타내었다. 비교예 2-2에서 제조한 도전재 분산액의 관찰 결과를 도 18에 나타내었다.The conductive material dispersions of Examples 2-1 to 2-2, Comparative Example 2-1 and Comparative Example 2-2 were observed using a scanning electron microscope (SEM). The observation result of the electrically conductive material dispersion liquid of Example 2-1 is shown in FIG. 11, The observation result of the electrically conductive material dispersion liquid of Example 2-2 is shown in FIG. 12, and the observation result of the electrically conductive material dispersion liquid of Example 2-3 is shown in FIG. The observation result of the electrically conductive material dispersion liquid of Example 2-4 is shown in FIG. 14, The observation result of the electrically conductive material dispersion liquid of Example 2-5 is shown in FIG. Shown in The observation result of the electrically conductive material dispersion of Comparative Example 2-1 is shown in FIG. 17. The observation result of the electrically conductive material dispersion prepared in Comparative Example 2-2 is shown in FIG. 18.
관찰 결과, 실시예 2-1 내지 실시예 2-6의 도전재 분산액의 경우, 구성 요소들이 균일하게 분산된 것을 확인할 수 있었다. 하지만, 비교예 2-1 및 비교예 2-2의 도전재 분산액의 경우, 실시예 2-1 내지 실시예 2-6의 도전재 분산액보다 구성 요소들이 균일하게 분산되지 못한 것을 확인할 수 있었다.As a result, it was confirmed that the components of the conductive material dispersions of Examples 2-1 to 2-6 were uniformly dispersed. However, in the conductive material dispersion of Comparative Example 2-1 and Comparative Example 2-2, it was confirmed that the components are not uniformly dispersed than the conductive material dispersion of Examples 2-1 to 2-6.
실시예 3-1 내지 3-6, 비교예 3-1 및 3-2: 양극 형성용 조성물의 제조 Examples 3-1 to 3-6, Comparative Examples 3-1 and 3-2: Preparation of Composition for Anode Formation
양극 형성용 조성물 총 중량에 대하여, 하기 표 6에 기재된 도전재 분산액 23.35중량%, 양극활물질 LiNi0 . 6Mn0 . 2Co0 . 2O2 75.49중량% 및 바인더 1.16중량%로 포함하는 양극 형성용 조성물을 제조하였고, 이의 점도를 하기 표 6에 기재하였다.Regarding the total weight of the composition for forming a positive electrode, 23.35% by weight of the conductive material dispersion described in Table 6 below, the positive electrode active material LiNi 0 . 6 Mn 0 . 2 Co 0 . A composition for forming a cathode, including 75.49 wt% of 2 O 2 and 1.16 wt% of a binder, was prepared, and the viscosity thereof is shown in Table 6 below.
BF점도: 브룩필드 점도계를 이용하여 10rpm에서의 점도를 측정하였다.BF viscosity: The viscosity at 10 rpm was measured using a Brookfield viscometer.
구분division 도전재 분산액Conductive Dispersion 양극활물질Cathode active material 바인더bookbinder 점도(m㎩·s)Viscosity (m㎩s)
실시예 3-1Example 3-1 실시예 2-1Example 2-1 LiNi0.6Mn0.2Co0.2O2 LiNi 0.6 Mn 0.2 Co 0.2 O 2 폴리비닐리덴 플루오라이드Polyvinylidene fluoride 15,00015,000
실시예 3-2Example 3-2 실시예 2-2Example 2-2 13,80013,800
실시예 3-3Example 3-3 실시예 2-3Example 2-3 16,80016,800
실시예 3-4Example 3-4 실시예 2-4Example 2-4 17,90017,900
실시예 3-5Example 3-5 실시예 2-5Example 2-5 21,00021,000
실시예 3-6Example 3-6 실시예 2-6Example 2-6 11,00011,000
비교예 3-1Comparative Example 3-1 비교예 2-1Comparative Example 2-1 12.00012.000
비교예 3-2Comparative Example 3-2 비교예 2-2Comparative Example 2-2 21,00021,000
실험예 3-1: 양극 형성용 조성물의 특성 평가Experimental Example 3-1: Characterization of the composition for forming a positive electrode
실시예 3-1 내지 실시예 3-6, 비교예 3-1 및 비교예 3-2의 양극 형성용 조성물의 분체밀도에 따른 분체저항(volume resistivity)의 변화를 관찰하였다. 그 결과를 표 7 및 도 19에 나타내었다.The change of the volume resistivity according to the powder density of the composition for positive electrode formation of Examples 3-1 to 3-3, Comparative Example 3-1, and Comparative Example 3-2 was observed. The results are shown in Table 7 and FIG. 19.
※ 분체저항: 양극 형성용 조성물의 용매를 모두 제거한 파우더를 직경이 1㎜인 절연 몰드에 충진하고 가압하여 표면의 전류와 전압을 4개의 탐침으로 측정하였고, 보정계수를 적용하여 압력에 따른 부피 저항값을 산출하였다. ※ Powder resistance: The powder which removed all solvents of anode composition was filled and pressurized into an insulating mold with a diameter of 1mm and the surface current and voltage were measured with four probes. The value was calculated.
구분division 압력(㎫)Pressure (MPa)
1313 2525 3737 5050 6262
분체밀도(g/cc)Powder density (g / cc)
2.32.3 2.42.4 2.52.5 2.62.6 2.72.7
분체저항(Ω·㎝)Powder resistance (Ωcm)
실시예 3-1Example 3-1 35.935.9 29.629.6 25.425.4 22.222.2 19.819.8
실시예 3-2Example 3-2 34.234.2 27.827.8 24.424.4 21.921.9 18.718.7
실시예 3-3Example 3-3 37.737.7 32.832.8 27.327.3 23.123.1 21.921.9
실시예 3-4Example 3-4 39.939.9 34.434.4 28.428.4 25.325.3 23.123.1
실시예 3-5Example 3-5 41.241.2 37.137.1 30.330.3 27.427.4 25.325.3
실시예 3-6Example 3-6 43.143.1 39.239.2 33.433.4 30.430.4 27.827.8
비교예 3-1Comparative Example 3-1 101.0101.0 82.582.5 71.871.8 63.263.2 57.057.0
비교예 3-2Comparative Example 3-2 55.255.2 48.548.5 42.942.9 39.239.2 36.436.4
그 결과, 실시예 3-1 내지 실시예 3-6의 양극 형성용 조성물은 압력이 13㎫일 때 분체저항이 34.2Ω·㎝ 내지 43.1Ω·㎝이고, 압력이 25㎫일 때 분체저항이 27.8Ω·㎝ 내지 39.2Ω·㎝이고, 압력이 37㎫일 때 분체저항이 24.4Ω·㎝ 내지 33.4Ω·㎝이고, 압력이 50㎫일 때 분체저항이 21.9Ω·㎝ 내지 30.4Ω·㎝이고, 압력이 62㎫일 때, 분체저항이 18.7Ω·㎝ 내지 27.8Ω·㎝이었다. As a result, the composition for positive electrode formation of Examples 3-1 to 3-6 had a powder resistance of 34.2Ω · cm to 43.1Ω · cm when the pressure was 13 MPa, and powder resistance of 27.8 when the pressure was 25 MPa. Ω · cm to 39.2Ω · cm, powder pressure is 24.4Ω · cm to 33.4Ω · cm when the pressure is 37 MPa, powder resistance is 21.9Ω · cm to 30.4Ω · cm when the pressure is 50 MPa, When the pressure was 62 MPa, the powder resistance was 18.7 Ω · cm to 27.8 Ω · cm.
이와 같이, 동일 압력일 때, 실시예 3-1 내지 실시예 3-6의 분체저항이 비교예 3-1 및 비교예 3-2의 분체저항보다 낮은 것을 알 수 있다. As described above, it can be seen that the powder resistances of Examples 3-1 to 3-6 were lower than those of Comparative Examples 3-1 and 3-2 at the same pressure.
실시예 4-1 내지 4-6, 비교예 4-1 및 4-2: 리튬 이차전지의 제조 Examples 4-1 to 4-6, Comparative Examples 4-1 and 4-2: Preparation of Lithium Secondary Battery
하기 표 8에 기재된 양극 형성용 조성물을 알루미늄 집전체에 도포한 후, 130℃에서 건조 후, 압연하여 양극을 제조하였다. 또, 혼합물 총 중량에 대하여, 음극활물질로서 흑연 97중량%, 도전재로서 카본블랙 1중량%, 바인더로서 스티렌부타디엔 고무(SBR) 1중량% 및 증점제로서 카르복시메틸셀룰로오스(CMC)를 1중량%로 혼합한 혼합물 353g을 물 250㎖에 혼합하여 음극 형성용 조성물을 제조하고, 이를 구리 집전체에 도포하여 음극을 제조하였다.The composition for forming a positive electrode shown in Table 8 below was applied to an aluminum current collector, dried at 130 ° C., and then rolled to prepare a positive electrode. Also, 97% by weight of graphite as a negative electrode active material, 1% by weight of carbon black as a conductive material, 1% by weight of styrene-butadiene rubber (SBR) as a binder, and 1% by weight of carboxymethyl cellulose (CMC) as a thickener based on the total weight of the mixture. 353 g of the mixed mixture was mixed in 250 ml of water to prepare a composition for forming a negative electrode, which was applied to a copper current collector to prepare a negative electrode.
상기와 같이 제조된 양극과 음극 사이에 다공성 폴리에틸렌의 세퍼레이터를 개재하여 전극 조립체를 제조하고, 상기 전극 조립체를 케이스 내부에 위치시킨 후, 케이스 내부로 전해액을 주입하여 리튬 이차전지를 제조하였다. 이때 전해액은 에틸렌카보네이트/ 디메틸카보네이트/ 에틸메틸카보네이트(EC/DMC/EMC의 혼합 부피비=3/4/3)로 이루어진 유기 용매에 1.0M 농도의 리튬헥사플루오로포스페이트(LiPF6)를 용해시켜 제조하였다. An electrode assembly was manufactured by interposing a separator of porous polyethylene between the positive electrode and the negative electrode prepared as described above, the electrode assembly was placed in a case, and an electrolyte solution was injected into the case to prepare a lithium secondary battery. At this time, the electrolyte is prepared by dissolving 1.0M concentration of lithium hexafluorophosphate (LiPF 6 ) in an organic solvent consisting of ethylene carbonate / dimethyl carbonate / ethyl methyl carbonate (mixed volume ratio of EC / DMC / EMC = 3/4/3). It was.
구분division 양극 형성용 조성물Anode Formation
실시예 4-1Example 4-1 실시예 3-1Example 3-1
실시예 4-2Example 4-2 실시예 3-2Example 3-2
실시예 4-3Example 4-3 실시예 3-3Example 3-3
실시예 4-4Example 4-4 실시예 3-4Example 3-4
실시예 4-5Example 4-5 실시예 3-5Example 3-5
실시예 4-6Example 4-6 실시예 3-6Example 3-6
비교예 4-1Comparative Example 4-1 비교예 3-1Comparative Example 3-1
비교예 4-2Comparative Example 4-2 비교예 3-2Comparative Example 3-2
실험예 4-1: 리튬 이차전지의 특성 평가Experimental Example 4-1: Characterization of the lithium secondary battery
실시예 4-1 내지 실시예 4-6, 비교예 4-1 및 비교예 4-2의 리튬 이차전지를 저온(-10℃)에서 SOC 50%를 기준으로 6.5C의 조건으로 방전시 시간에 따른 전압 변화를 각각 측정하였다(cut off 전압: 1.9V). 그 결과를 표 9 및 도 20에 나타내었다.The lithium secondary batteries of Examples 4-1 to 4-4, Comparative Examples 4-1 and 4-4 were discharged at a low temperature (−10 ° C.) at a temperature of 6.5C based on 50% SOC. The voltage change along each was measured (cut off voltage: 1.9V). The results are shown in Table 9 and FIG. 20.
구분division 시간(초)Time in seconds
55 1010 1515 2020
전압(V)Voltage (V)
실시예 4-1Example 4-1 2.7162.716 2.5792.579 2.4342.434 2.2492.249
실시예 4-2Example 4-2 2.7062.706 2.5752.575 2.4352.435 2.2752.275
실시예 4-3Example 4-3 2.6302.630 2.4822.482 2.3152.315 2.1052.105
실시예 4-4Example 4-4 2.5852.585 2.4292.429 2.2552.255 2.0292.029
실시예 4-5Example 4-5 2.6342.634 2.4712.471 2.2812.281 2.0052.005
실시예 4-6Example 4-6 2.6112.611 2.4382.438 2.2292.229 1.9151.915
비교예 4-1Comparative Example 4-1 2.4782.478 2.2292.229 2.0732.073 --
비교예 4-2Comparative Example 4-2 2.5372.537 2.3692.369 2.1682.168 1.9071.907
표 9 및 도 20을 참조하면, 실시예 4-1 내지 실시예 4-6의 리튬 이차전지는, 비교예 4-1 내지 비교예 4-2의 리튬 이차전지에 비해 우수한 저온 출력특성을 나타내었다. 한편, 비교예 4-1의 리튬 이차전지의 경우, 20초까지 방전을 지속할 수가 없었다.Referring to Table 9 and FIG. 20, the lithium secondary batteries of Examples 4-1 to 4-6 exhibited excellent low-temperature output characteristics compared to the lithium secondary batteries of Comparative Examples 4-1 to 4-4. . On the other hand, in the lithium secondary battery of Comparative Example 4-1, the discharge could not be continued until 20 seconds.

Claims (15)

  1. 도전재, 분산제 및 분산매를 포함하며,Including a conductive material, a dispersant and a dispersion medium,
    상기 도전재는 10 내지 50㎏/㎥의 벌크밀도와, 하기 수학식 1의 조건을 충족하는 전도성을 갖는 번들형(bundle-type) 탄소 나노튜브를 포함하는 것인 도전재 분산액.The conductive material is a conductive material dispersion containing a bundle-type carbon nanotube having a bulk density of 10 to 50 kg / ㎥, and conductivity to meet the conditions of the following equation (1).
    [수학식 1][Equation 1]
    -X ≤ 10log R ≤ -0.6X-X ≤ 10log R ≤ -0.6X
    (상기 수학식 1에서 X는 상기 탄소 나노튜브의 벌크밀도이고, R은 10 내지 65㎫의 압력 하에서의 상기 탄소 나노튜브의 분체저항이다)(Wherein X is the bulk density of the carbon nanotubes, and R is the powder resistance of the carbon nanotubes under a pressure of 10 to 65 MPa)
  2. 제1항에 있어서,The method of claim 1,
    상기 탄소 나노튜브는 20 내지 35㎏/㎥의 벌크밀도, 및 10 내지 65㎫의 압력 하에서 0.001 내지 0.01Ω·㎝의 분체저항을 갖는 것인 도전재 분산액.The carbon nanotubes have a bulk density of 20 to 35 kg / m 3 and a powder resistance of 0.001 to 0.01 Ω · cm under a pressure of 10 to 65 MPa.
  3. 제1항에 있어서, The method of claim 1,
    상기 탄소 나노튜브는 진밀도(TD)와 벌크밀도(BD)의 비(TD/BD 비)가 70 내지 120인 것인 도전재 분산액.The carbon nanotube has a ratio (TD / BD ratio) of true density (TD) and bulk density (BD) is 70 to 120 of the conductive material dispersion.
  4. 제1항에 있어서, The method of claim 1,
    상기 탄소 나노튜브의 진밀도가 1,800 내지 2,200㎏/㎥인 것인 도전재 분산액.Conductive material dispersion of the carbon nanotubes is 1,800 to 2,200kg / ㎥.
  5. 제1항에 있어서, The method of claim 1,
    상기 탄소 나노튜브의 BET 비표면적이 180 내지 300㎡/g인 것인 도전재 분산액.Conductive material dispersion of the carbon nanotubes having a BET specific surface area of 180 to 300 m 2 / g.
  6. 제1항에 있어서, The method of claim 1,
    상기 탄소 나노튜브는 10 내지 20㎚의 평균 직경을 갖는 탄소 나노튜브 단위체를 포함하는 것인 도전재 분산액.The carbon nanotube is a conductive material dispersion containing carbon nanotube units having an average diameter of 10 to 20nm.
  7. 제1항에 있어서,The method of claim 1,
    상기 탄소 나노튜브는 532㎚ 파장의 레이저를 이용한 라만 분광 분석법에 의해 얻어진 1,580±50㎝-1 에서의 G 밴드의 최대 피크 강도(IG)에 대한 1,360±50㎝-1 에서의 D 밴드의 최대 피크 강도(ID)의 비(ID/IG)의 평균값이 0.75 내지 1.05이고, 표준편차값이 1.3 내지 2.0%인 것인 도전재 분산액.The carbon nanotubes have a maximum peak of D band at 1,360 ± 50 cm −1 with respect to maximum peak intensity (IG) of G band at 1,580 ± 50 cm −1 obtained by Raman spectroscopy using a laser of 532 nm wavelength. The electrically conductive material dispersion liquid whose average value of ratio (ID / IG) of intensity | strength ID is 0.75-1.05, and a standard deviation value is 1.3-2.0%.
  8. 제1항에 있어서, The method of claim 1,
    상기 분산제는 니트릴계 고무를 포함하는 것인 도전재 분산액.The dispersant is a conductive material dispersion containing nitrile rubber.
  9. 제1항에 있어서, The method of claim 1,
    상기 분산제는 수소화된 니트릴부타디엔계 고무를 포함하는 것인 도전재 분산액.The dispersant is a conductive material dispersion that includes a hydrogenated nitrile butadiene rubber.
  10. 제1항에 있어서, The method of claim 1,
    상기 분산제는 총 중량에 대하여 α,β-불포화 니트릴 유래 구조 단위를 20 내지 65중량%로 포함하는 수소화된 니트릴부타디엔계 고무를 포함하는 것인 도전재 분산액.The dispersant comprises a hydrogenated nitrile butadiene rubber containing 20 to 65% by weight of the α, β-unsaturated nitrile-based structural units relative to the total weight.
  11. 제1항에 있어서, The method of claim 1,
    상기 분산제는 총 중량에 대하여 수소화된 공액 디엔 유래 구조 단위를 1 내지 30중량% 포함하는 수소화된 니트릴부타디엔계 고무를 포함하는 것인 도전재 분산액.The dispersant comprises a hydrogenated nitrile butadiene rubber containing 1 to 30% by weight of the hydrogenated conjugated diene-based structural units relative to the total weight.
  12. 제1항에 있어서, The method of claim 1,
    상기 분산제는 탄소 나노튜브 100중량부에 대하여 1중량부 내지 50중량부로 포함되는 것인 도전재 분산액.The dispersant is a conductive material dispersion that is contained in 1 to 50 parts by weight based on 100 parts by weight of carbon nanotubes.
  13. 제1항에 있어서,The method of claim 1,
    상기 분산제는 탄소 나노튜브의 표면에 도입되어 탄소 나노튜브-분산제 복합체를 형성하고, The dispersant is introduced to the surface of the carbon nanotubes to form a carbon nanotube-dispersant complex,
    상기 탄소 나노튜브-분산제 복합체는 하기 수학식 3에 따른 입자 크기 분포가 2 내지 6.5인 것인 도전재 분산액.The carbon nanotube-dispersant composite has a particle size distribution of 2 to 6.5 according to the following equation (3).
    [수학식 3][Equation 3]
    탄소 나노튜브-분산제 복합체의 입자 크기 분포=(D90-D10)/D50 Particle size distribution of the carbon nanotube-dispersant composite = (D 90 -D 10 ) / D 50
    (상기 수학식 3에서, D10, D50 및 D90은 각각 탄소 나노튜브-분산제 복합체의 입자 크기 분포의 10%, 50% 및 90% 기준에서의 입자 크기이다)(In Equation 3, D 10 , D 50 and D 90 are particle sizes at 10%, 50% and 90% of the particle size distribution of the carbon nanotube-dispersant composite, respectively)
  14. 전극 활물질; 및 Electrode active material; And
    제1항 내지 제13항 중 어느 한 항에 따른 도전재 분산액을 포함하는 리튬 이차전지의 전극 형성용 조성물.A composition for forming an electrode of a lithium secondary battery comprising the conductive material dispersion according to any one of claims 1 to 13.
  15. 양극; 음극; 세퍼레이터 및 전해질을 포함하며,anode; cathode; A separator and an electrolyte,
    상기 양극 및 음극 중 적어도 하나는 제14항에 따른 전극 형성용 조성물로 제조된 것인 리튬 이차전지.At least one of the positive electrode and the negative electrode is a lithium secondary battery made of a composition for forming an electrode according to claim 14.
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