WO2017099481A1 - Cathode for secondary battery and secondary battery comprising same - Google Patents

Cathode for secondary battery and secondary battery comprising same Download PDF

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Publication number
WO2017099481A1
WO2017099481A1 PCT/KR2016/014352 KR2016014352W WO2017099481A1 WO 2017099481 A1 WO2017099481 A1 WO 2017099481A1 KR 2016014352 W KR2016014352 W KR 2016014352W WO 2017099481 A1 WO2017099481 A1 WO 2017099481A1
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Prior art keywords
positive electrode
active material
secondary battery
carbon nanotubes
weight
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PCT/KR2016/014352
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French (fr)
Korean (ko)
Inventor
설종헌
이민희
김동규
김재웅
김예린
최상훈
김제영
김선규
Original Assignee
주식회사 엘지화학
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Priority claimed from KR1020160166124A external-priority patent/KR102101006B1/en
Application filed by 주식회사 엘지화학 filed Critical 주식회사 엘지화학
Priority to CN201680047594.9A priority Critical patent/CN107925056B/en
Priority to JP2018524817A priority patent/JP7027626B2/en
Priority to US15/747,367 priority patent/US11171322B2/en
Priority to EP16873346.7A priority patent/EP3319151B1/en
Publication of WO2017099481A1 publication Critical patent/WO2017099481A1/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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • 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 positive electrode for a secondary battery exhibiting excellent electrolyte wetting property through improved pore structure and a secondary battery including 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 structures.
  • carbon nanotubes have limited use due to their low solubility and dispersibility.
  • the carbon nanotubes were predispersed in a solvent to prepare a composition for forming an electrode.
  • carbon nanotubes do not achieve a stable dispersion state in a solvent due to strong van der Waals attraction between each other, and there is a problem in that agglomeration occurs.
  • the first problem to be solved by the present invention is to provide a secondary battery positive electrode exhibiting excellent electrolyte wettability through improved pore structure.
  • a second object of the present invention is to provide a lithium secondary battery, a battery module, and a battery pack including the positive electrode.
  • a cathode active material layer including a cathode active material, a conductive material and a dispersant
  • the conductive material is a bundle (average strand diameter of 15 nm or less of carbon nanotube units) -type) carbon nanotubes, the carbon nanotubes being 1360 ⁇ 50 cm -1 for the maximum peak intensity (IG) of the 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 is 0.7 to 1.7, and the standard deviation value is 1.3 to 2.0%
  • the positive electrode active material layer has a packing density of 3.0 g / cc or more.
  • it provides a secondary battery positive electrode having an average pore diameter of 0.1 ⁇ m to 0.5 ⁇ m according to the following equation 1 when measuring the pore size distribution according to the mercury intrusion method at
  • V is the pore volume
  • A is the pore area
  • a lithium secondary battery a battery module and a battery pack including the positive electrode, respectively.
  • the secondary battery positive electrode according to the present invention has an improved pore structure in the positive electrode active material layer can exhibit excellent electrolyte wettability. As a result, when the battery is applied, the positive electrode wetting period is shortened, and the electrolyte unfilled area is reduced, thereby improving battery performance.
  • Example 1 is a graph showing the results of evaluating propylene carbonate (PC) for the batteries of Example 1 and Comparative Example 1.
  • PC propylene carbonate
  • Figure 3 is a graph showing the results of observing the pore size distribution in the positive electrode of Example 2 and Comparative Example 2.
  • Example 4 is a graph showing the resistance characteristics evaluation results for the battery of Example 2 and Comparative Example 2.
  • Example 5 is a graph showing the cycle characteristics evaluation results for the battery of Example 2 and Comparative Example 2.
  • non-bundle type a plurality of carbon nanotube strands, that is, carbon nanotube units are arranged side by side in an orientation substantially the same axis in the longitudinal direction of the unit 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
  • the thickness of the electrode becomes thicker and the packing density (or rolling density) increases.
  • the electrolyte wettability of the electrode is lowered.
  • the decrease in the electrolyte wettability at the electrode causes a nonuniform wetting of the electrolyte with an increase in the electrode wetting time, and as a result, there is a problem that the charging is not performed in the electrolyte nonwetting region and the battery characteristics are deteriorated.
  • the carbon nanotubes are used as the conductive material, and the carbon nanotubes are optimized for dispersibility in the cathode active material layer by optimizing the characteristics of the carbon nanotubes without fear of deterioration of the discharge pulse resistance characteristics and cycle characteristics of the battery.
  • the carbon nanotubes are optimized for dispersibility in the cathode active material layer by optimizing the characteristics of the carbon nanotubes without fear of deterioration of the discharge pulse resistance characteristics and cycle characteristics of the battery.
  • the positive electrode for a secondary battery includes a positive electrode active material layer including a positive electrode active material, a conductive material and a dispersant, and the conductive material includes bundle carbon having an average strand diameter of carbon nanotube units of 15 nm or less.
  • the carbon nanotubes having a D band at 1360 ⁇ 50cm ⁇ 1 for a maximum peak intensity (IG) of G band at 1580 ⁇ 50cm ⁇ 1 obtained by Raman spectroscopy with a laser of 532 nm wavelength
  • the average value of the ratio (ID / IG) of the maximum peak intensity (ID) is 0.7 to 1.7, the standard deviation value is 1.3 to 2.0%, and the positive electrode active material layer has a packing density of 3.0 g / cc or more, the filling
  • the average pore diameter P according to Equation 1 is 0.1 ⁇ m to 0.5 ⁇ m.
  • V is the pore volume
  • A is the pore area
  • Equation 1 is obtained by modeling from the pore volume and the pore area obtained from the pore size distribution measurement value by the mercury porosimetry.
  • the positive electrode active material layer has a packing density of 3.0g / cc to 4.3g / cc, the average according to the formula 1 in the filling density
  • the pore diameter may be 0.1 ⁇ m to 0.5 ⁇ m, and more specifically 0.1 ⁇ m to 0.3 ⁇ m.
  • the secondary battery positive electrode according to the present invention has a large pore size even at a high filling density as described above. Furthermore, since the positive electrode active material layer has a pore size distribution within the above range, the electrolyte solution can quickly and easily penetrate into the positive electrode active material layer, and can uniformly penetrate into the active material layer without generation of the electrolyte wetting portion. As a result, charging may occur throughout the positive electrode active material layer, thereby further improving battery characteristics.
  • the required packing density in the active material layer may vary depending on the type of the positive electrode active material used. Accordingly, specifically in the secondary battery positive electrode according to an embodiment of the present invention, when the positive electrode active material layer contains lithium nickel manganese cobalt-based oxide as the positive electrode active material, the positive electrode active material layer is more than 3.0g / cc, Specifically, it may have a packing density of 3.1 g / cc to 3.6 g / cc, and may have an average pore diameter of 0.1 ⁇ m to 0.3 ⁇ m, more specifically 0.1 ⁇ m to 0.2 ⁇ m at the filling density.
  • the cathode active material layer contains lithium cobalt oxide as the cathode active material
  • the cathode active material layer is 3.0 g / cc or more, more specifically 3.9 g / cc to 4.3 g / cc, and more specifically 3.9 g It has a packing density of / cc to 4.2g / cc, it may have an average pore diameter of 0.1 ⁇ m to 0.3 ⁇ m, more specifically 0.1 ⁇ m to 0.2 ⁇ m in the filling density.
  • the positive electrode active material layer exhibits a peak in the pore diameter range of 30 nm to 2500 nm under the above-described filling density condition when pore size distribution is measured by mercury porosimetry.
  • the positive electrode active material layer exhibits a maximum peak in the pore diameter range of 250 nm to 330 nm under the packing density condition.
  • the cathode active material layer in the positive electrode for secondary batteries according to the present invention has large pores even under high packing density. May have a size. As a result, the electrolyte solution may quickly and uniformly penetrate into the cathode active material layer.
  • the pore size and pore size distribution (PSD) in the cathode active material layer can be measured from the pressure and volume at the time when Hg is filled in the pores by mercury (Hg) indentation.
  • the improved pore structure in the active material layer in the positive electrode for a secondary battery according to the embodiment of the present invention is further controlled through the control of the conductive material constituting the positive electrode active material layer, and furthermore, together with the conductive material, the positive electrode active material, the dispersant and the selective material.
  • This can be implemented by controlling the content and type of binder, physical properties or mixing ratio.
  • the positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound) And lithium composite metal oxides including lithium with one or more metals such as cobalt, manganese, nickel or aluminum.
  • the lithium composite metal oxide is a lithium-manganese oxide (eg, LiMnO 2 , LiMn 2 O Etc.), lithium-cobalt-based oxides (e.g., LiCoO 2, etc.), lithium-nickel-based oxides (e.g., LiNiO 2, etc.), lithium-nickel-manganese-based oxides (e.g., LiNi 1 - Y Mn Y O 2 (where, 0 ⁇ Y ⁇ 1), LiMn 2-z Ni z O 4 (where, 0 ⁇ z ⁇ 2) and the like), lithium-nickel-cobalt-based oxide (for example, LiNi 1- Y Co Y O 2 (where, 0 ⁇ Y ⁇ 1) and the like), lithium-manganese-cobalt oxide (e.g., LiCo 1-Y Mn Y O 2 (where, 0 ⁇ Y ⁇ 1), LiMn 2-z Co z O 4 (where, 0 ⁇ Z ⁇
  • the metal elements except lithium is selected from the group consisting of Al, Cu, Fe, V, Cr, Ti, Zr, Zn, Ta, Nb, Mg, B, W, and Mo. It may be doped by any one or two or more elements selected. As described above, when the above metal element is further doped into the lithium composite metal oxide of the lithium defect, the structural stability of the cathode active material may be improved, and as a result, the output characteristics of the battery may be improved. In this case, the content of the doping element included in the lithium composite metal oxide may be appropriately adjusted within a range that does not lower the characteristics of the positive electrode active material, specifically, may be 0.02 atomic% or less.
  • the lithium composite metal oxide may be to include a compound of formula (1).
  • M is Al, Cu, Fe, V, Cr, Ti, Zr, Zn, Ta, Nb, Mg, B, W and Mo containing any one or two or more elements selected from the group consisting of A, x, y, z and w are each independently the atomic fraction of the corresponding elements, -0.5 ⁇ a ⁇ 0.5, 0 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 1, 0 ⁇ z ⁇ 1, 0 ⁇ w ⁇ 1 and 0 ⁇ x + y + z ⁇ 1)
  • the positive electrode active material is 0 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 1, 0 ⁇ z ⁇ 1, y + z in Chemical Formula 1 It may include a lithium composite metal oxide of ⁇ x.
  • the lithium composite metal oxide is more specifically LiCoO 2 or lithium nickel manganese cobalt oxide (eg, Li (Ni 0.6 Mn 0.2 Co 0.2 ) O) in that the capacity characteristics and stability of the battery can be improved.
  • LiNi 0 . 5 Mn 0 . 3 Co 0 . 2 O 2, or LiNi 0.8 Mn 0.1 Co 0.1 O 2, and so on) may be, given the remarkable also in the improvement according to the kind and content ratio control of constituent elements forming the lithium composite metal oxide, wherein the lithium composite metal oxide has LiNi 0 . 6 Mn 0 . 2 Co 0 . 2 O 2 , LiNi 0 . 5 Mn 0 . 3 Co 0 .
  • the positive electrode active material is not particularly limited in form, and specifically, may have various forms such as spherical, polyhedral, fibrous, plate, and flaky.
  • the positive electrode active material may be one of the 2 ⁇ m to 30 ⁇ m Specifically, the average particle diameter (D 50). If the average particle size of the positive electrode active material is less than 2 ⁇ m, dispersibility in the composition may decrease due to aggregation between the active materials, and if it exceeds 30 ⁇ m, there is a fear of deterioration of activity due to a decrease in specific surface area. Considering the remarkable improvement effect of the optimization of the average particle diameter of the positive electrode active material, the positive electrode active material may have an average particle diameter (D 50 ) of 5 ⁇ m to 20 ⁇ m.
  • the cathode active material may have a bimodal type particle size distribution within the above average particle diameter range.
  • the packing density of the positive electrode active material in the active material layer can be further increased, and as a result, the capacity characteristics can be further improved when the battery is applied.
  • the cathode active material may include a mixture of two or more active materials having different shapes or different particle sizes.
  • the positive electrode active material may include a mixture of the average particle diameter (D 50) is 2 ⁇ m 10 ⁇ m to the first positive electrode active material and, 10 ⁇ m 30 ⁇ m less than the second cathode active material.
  • D 50 average particle diameter
  • the packing density of the positive electrode active material in the active material layer may be increased, and as a result, capacity characteristics may be further improved when the battery is applied.
  • the positive electrode active material has a mean particle diameter (D 50) 2 ⁇ m 10 ⁇ m to the first positive electrode active material and ,
  • the second positive electrode active material of more than 10 ⁇ m 30 ⁇ m or less may be included in a mixed weight ratio of 50:50 to 80:20, more specifically 50:50 to 70:30.
  • the average particle diameter (D 50 ) of the positive electrode active material may be defined as the particle size at 50% of the particle size distribution.
  • the average particle diameter (D 50 ) of the positive electrode active material may be measured using, for example, a laser diffraction method. Specifically, after dispersing the particles of the positive electrode active material in a solvent, it is introduced into a commercially available laser diffraction particle size measuring device (for example, Microtrac MT 3000) and irradiated with an ultrasonic wave of about 28 kHz at an output of 60 W, and the particle diameter in the measuring device. The average particle diameter (D 50 ) at 50% of the distribution can be calculated.
  • the cathode active material may be included in an amount of 70 to 99.5% by weight based on the total weight of the cathode active material layer based on the solid content. If the content of the positive electrode active material is less than 70% by weight, there is a fear of lowering the capacity. If the amount of the positive electrode active material is higher than 99.5% by weight, the relative content of the binder and the conductive material is reduced, thereby reducing the adhesion to the electrode current collector, the conductivity, and the like.
  • the positive electrode active material layer includes a conductive material.
  • the conductive material may be carbon nanotubes, and more specifically, carbon nanotube units may be bundle-type carbon nanotubes having an average strand diameter of 15 nm or less.
  • the carbon nanotubes are secondary structures formed by gathering carbon nanotube units in whole or in part in bundles.
  • the carbon nanotube units have a graphite sheet having a nano-size diameter cylinder, and sp 2 Has a bonding 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. 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.
  • the carbon nanotubes may have different physical properties depending on crystallinity and structure, form, and structure and form of secondary particles including the monomers, and components included in the carbon nanotubes including impurities. 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 diameter of the carbon nanotube unit is excessively large as the secondary battery conductive material, the number of strands per volume decreases and the amount of the conductive material increases, so that the production of electrodes having high energy density is disadvantageous, and the pore diameter of the electrode is also greatly increased. The electrode density may be lowered.
  • the diameter of the carbon nanotube unit is too small, it is difficult to disperse and thus the dispersion manufacturing processability may be reduced, and the dispersed carbon nanotube unit or the carbon nanotube is buried in the space between the particles of the positive electrode active material, thereby forming sufficient pores. It's hard to be.
  • the average strand diameter of the carbon nanotube units in the carbon nanotubes usable in the present invention may be 15 nm or less, and the effect of improving the dispersibility and solid-like properties of the conductive material by controlling the diameter of the unit, and as a result, the electrode
  • the average strand diameter of the carbon nanotube unit may be 1nm to 15nm, more specifically may be 3nm to 12nm.
  • the longer the length of the carbon nanotube unit can improve the electrical conductivity, strength and life characteristics of the anode at room temperature and high temperature. If the length of the carbon nanotube unit is short, it is difficult to form the conductive paths efficiently, and thus the electrical conductivity may be lowered. On the other hand, if the length of the carbon nanotube unit is too long, there is a fear that the dispersibility is lowered. Accordingly, the length of the unit in the carbon nanotubes usable in the present invention may be 0.5 ⁇ m to 200 ⁇ m.
  • the carbon nanotube unit has a length (length of long axis passing through the center of the unit) and a diameter (length of the unit passing through the center of the unit and perpendicular to the long axis).
  • the aspect ratio defined as the ratio of the length of the short axis, may be 10 to 80,000, and more specifically 20 to 50,000.
  • the strand diameter and length of the carbon nanotube unit can be measured by using a field emission scanning electron microscope.
  • the carbon nanotubes have a high BET specific surface area and exhibit excellent dispersibility because the carbon nanotubes have a small average diameter as described above and a high aspect ratio.
  • the BET specific surface area of the carbon nanotubes usable in the present invention may be 200m 2 / g to 330m 2 / g, and more specifically 240m 2 / g to 280m 2 / g.
  • the specific surface area of the carbon nanotubes is measured by the BET method, and specifically, it can be calculated from the nitrogen gas adsorption amount under the liquid nitrogen temperature (77K) using BELSORP-mino II manufactured by BEL Japan. have.
  • the carbon nanotubes have a maximum peak intensity (IG) of a G band at 1580 ⁇ 50cm ⁇ 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 1360 ⁇ 50 cm ⁇ 1 to may be 0.7 to 1.7, and the standard deviation may be 1.3 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 1580 cm ⁇ 1 in the Raman spectrum of the carbon nanotubes is called a G band, which is a peak indicating sp2 bond of the carbon nanotubes, indicating a carbon crystal without structural defects.
  • the peak present in the region near the wave number 1360cm -1 of the Raman spectrum is called the D band, which is a peak indicating the sp3 bond of the carbon nanotube, and increases when the atomic bond formed by the sp2 bond is broken and becomes the sp3 bond.
  • This D band is increased when a disorder or defect present in the carbon nanotubes is generated, so that the ratio of the maximum peak intensity (ID) of the D band to the maximum peak intensity (IG) of the G band is increased. (ID / IG) can be calculated to quantitatively assess the degree of disorder or defect generation.
  • the G band of the Raman spectrum for the carbon nanotubes may be a peak present in the wavenumber 1580 ⁇ 50cm ⁇ 1 region, and the D band may be a peak present in the wavenumber 1360 ⁇ 50cm ⁇ 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.
  • the Raman value used in the present invention is 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 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 nanotube includes a metal element derived from a main catalyst or a promoter such as Co, Mo, V, or Cr used in the manufacturing process as impurities. can do.
  • the carbon nanotubes may include 3 mg / kg or less, more specifically, 2 mg / kg or less, as a total amount of metal elements of Fe, Ni, and Mo, among catalyst-derived metal elements, and more specifically,
  • the metal element that is, at least one of Fe, Ni and Mo, in particular may be one containing no Fe.
  • 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 obtained commercially or used directly.
  • the method may be manufactured using a conventional method such as an arc discharge method, a laser evaporation method or a chemical vapor deposition method, and the aforementioned physical properties may be controlled by controlling the type of catalyst, heat treatment temperature, and impurity removal method in the manufacturing process. Can be implemented.
  • the carbon nanotubes are prepared by contacting a supported catalyst having a metal catalyst supported on a spherical ⁇ -alumina support under heating with a carbon source to produce carbon nanotubes, and According to the present invention may optionally be prepared by a manufacturing method comprising the step of removing metal impurities in the carbon nanotubes.
  • the supported catalyst is introduced into a horizontal fixed bed reactor or a fluidized bed reactor, and at a temperature above the thermal decomposition temperature of the gaseous carbon source to below the melting point of the supported metal catalyst.
  • Carbon 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
  • a carrier gas for example, nitrogen, etc.
  • the production of the carbon nanotubes may be specifically carried out at a temperature of less than 500 °C 800 °C, more specifically at 550 °C to 700 °C.
  • a temperature of less than 500 °C 800 °C more specifically at 550 °C to 700 °C.
  • dispersibility may be further improved due to the decrease in bulk density.
  • a heat source for the heat treatment induction heating, radiant heat, laser, IR, microwave, plasma, surface plasmon heating and the like can be used.
  • carbon may be supplied to the 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.
  • it 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, hexane, cyclohexane, Benzene, toluene, and the like, and any one or a mixture of two or more thereof may be used.
  • a cooling process for more regularly aligning the arrangement of the carbon nanotubes may optionally be further performed.
  • the cooling process may be performed using natural cooling or a cooler according to the removal of the heat source.
  • the supported catalyst used for the production of the conductive material is a metal catalyst supported on a spherical ⁇ -alumina support.
  • ⁇ -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 because the surface is smooth.
  • the supported catalyst comprising the spherical ⁇ -alumina as a support may be prepared by baking the metal catalyst on the spherical ⁇ -alumina support. Specifically, the supported catalyst is carried out by adding and mixing the spherical ⁇ -alumina support to a metal catalyst precursor solution prepared by dissolving the precursor of the metal catalyst in water, followed by calcining at a temperature of 600 ° C. or lower. Can be.
  • the metal catalyst supported on the support 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 iron, nickel or cobalt may be used alone, or the main catalyst may be used in the form of a main catalyst-catalyst complex catalyst together with a promoter such as molybdenum, vanadium or chromium.
  • the complex catalyst may be FeCO, CoMo, CoV, FeCoMo, FeMoV, FeV or FeCoMoV, etc. 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. 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, Cr, and any one or a mixture of two or more thereof. Can be used.
  • 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
  • Any one or a mixture of two or more selected from the group consisting of 2 O, (NH 4 ) 6 Mo 7 O 24 4H 2 O, Mo (CO) 6 , (NH 4 ) MoS 4 and NH 4 VO 3 can 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 content of the spherical ⁇ -alumina support mixed with the metal catalyst precursor may be appropriately determined in consideration of the content of the support in the supported catalyst to be finally prepared.
  • an acid may optionally be further used during support addition and mixing in the metal catalyst precursor solution for bulk density control of the carbon nanotubes.
  • the metal catalyst precursor solution may be used in an amount corresponding to 3 to 40 mol, more specifically, 5 to 30 mol of the metal catalyst with respect to 1 mol of the 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.
  • the mixing process of the metal catalyst precursor solution and the spherical ⁇ -alumina support may be performed according to a conventional method, and specifically, may be performed by rotating or stirring under 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 supported on the finally prepared supported catalyst.
  • the supported amount of the metal catalyst in the supported catalyst increases, the bulk density of the carbon nanotubes produced using the supported catalyst tends to increase.
  • the metal catalyst may be mixed to be supported in an amount of 5% by weight to 30% by weight based on the total weight of the supported catalyst.
  • a drying process may be optionally further performed prior to the 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.
  • a removal process for removing metal impurities derived from the metal catalyst remaining in the carbon nanotubes may be selectively performed with respect to the carbon nanotubes prepared by the above-described manufacturing process, wherein the metal impurities removal process may include washing, It may be carried out in accordance with conventional methods such as acid treatment.
  • Carbon nanotubes prepared according to the above manufacturing method has a bundle type, and since the carbon nanotube unit has a small strand diameter, it may exhibit excellent dispersibility and conductivity during electrode production. 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.
  • the positive electrode active material layer includes a dispersant to increase the dispersibility of the conductive material.
  • the dispersant may be a nitrile rubber, and more specifically, may be a nitrile butadiene rubber hydrogenated in part or in whole.
  • the hydrogenated nitrile butadiene-based rubber 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 hydrogenated conjugated diene derived structure with respect to the total weight of rubber. It may be to include the unit in 20% by weight to 80% by weight. When included in the content as described above, the miscibility to the solvent is increased to increase the dispersibility of the carbon nanotubes and at the same time increase the solid-like properties of the conductive material dispersion, and as a result improve the coating stability of the electrode forming composition You can. More specifically, the hydrogenated conjugated diene-derived structural unit may include 40 wt% to 70 wt%.
  • the content of the ⁇ , ⁇ -unsaturated nitrile-derived structural unit in the partially hydrogenated nitrile butadiene-based rubber is 10% by weight to the total weight of the rubber. It may be 50% by weight, specifically 20% to 40% 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 hydrogenated nitrile butadiene-based rubber is based on the total weight of the rubber 10% to 50% by weight of a structural unit derived from conjugated diene; 20% to 80% by weight of structural units derived from hydrogenated conjugated diene; And a partially hydrogenated nitrile butadiene-based rubber comprising 10 wt% to 50 wt% of ⁇ , ⁇ -unsaturated nitrile derived structural units.
  • the content of the nitrile structure-containing repeating unit in the hydrogenated nitrile butadiene-based rubber is a weight ratio with respect to the entire rubber of the structural unit derived from ⁇ , ⁇ -unsaturated nitrile, and the measurement of the content is JIS K 6364 According to the mill oven method of this, the amount of nitrogen which generate
  • 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 hydrogenated nitrile butadiene-based rubber include acrylonitrile or methacrylonitrile, and one or a mixture of two or more of them may be used. .
  • the conjugated diene which can be used at the time of manufacture of the said hydrogenated nitrile butadiene type rubber specifically contains conjugated diene of 4-6 carbon atoms, such as 1, 3- butadiene, isoprene, and 2, 3-methylbutadiene, among these. Either one or a mixture of two or more may be used.
  • 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 terpolymer-derived structures The content ratio of units can vary within a wide range, in each case the total sum of the structural units is 100% by weight.
  • the hydrogenated acrylonitrile-butadiene rubber may have a weight average molecular weight of 10,000g / mol to 700,000g / mol, more specifically 10,000g / mol to 300,000g / 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 can be uniformly dispersed in a solvent.
  • the weight average molecular weight and the number average molecular weight are polystyrene reduced molecular weights analyzed by gel permeation chromatography (GPC).
  • the dispersant may be included in 1 to 50 parts by weight based on 100 parts by weight of carbon nanotubes. 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 10 to 25 parts by weight.
  • the positive electrode active material layer is A binder may be further included to improve adhesion between the active material particles and adhesion between the positive 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 0.1 to 30% by weight based on the total weight of the positive electrode active material layer.
  • a secondary battery positive electrode having the configuration as described above, the positive electrode active material layer composition prepared by dispersing a positive electrode active material, a conductive material, a dispersant and optionally a binder in a solvent is applied on the positive electrode current collector And rolling after drying or casting the composition for forming the positive electrode active material layer on a separate support, and then laminating the film obtained by peeling from the support onto a current collector and rolling.
  • the composition for forming the positive electrode active material layer may be prepared by dispersing carbon nanotubes and a dispersant in a solvent to prepare a conductive material dispersion, and then mixing the positive electrode active material and a binder, and, if necessary, further adding a solvent. .
  • the carbon nanotubes and the dispersant are as described above.
  • the solvent may be an amide polar organic solvent such as dimethylformamide (DMF), diethyl formamide, dimethyl acetamide (DMAc) or N-methyl pyrrolidone (NMP); 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 g
  • the conductive material dispersion may include 1 to 50 parts by weight of the dispersant, and 200 to 9900 parts by weight of the solvent based on 100 parts by weight of the carbon nanotubes.
  • Carbon nanotubes can be uniformly dispersed in the solvent in the above range. More specifically, it may include 10 to 25 parts by weight of the dispersant and 4000 to 7000 parts by weight of the solvent based on 100 parts by weight of the carbon nanotubes.
  • the mixing of the carbon nanotubes and the solvent 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.
  • cavitation dispersion treatment may be performed to increase the carbon nanotubes and the solvent or the dispersibility of the carbon nanotubes in the solvent.
  • 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 depending on 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 kHz to 150 kHz, 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 changing the viscosity of the dispersion by evaporation of the solvent. 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, bead mill, ball mill, basket mill, treatment 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 solvent 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 (2) 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 size D 10, D 50 and D 90 of the composite can be measured using a laser diffraction method (laser diffraction method), more specifically, after dispersing the composite in a solvent, a 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 Can be calculated respectively.
  • laser diffraction method laser diffraction method
  • a 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
  • the average particle diameter at 10%, 50% and 90% of the particle size distribution in the measuring device Can be calculated respectively.
  • the conductive material dispersion may have a viscosity of 1,000 mPa ⁇ s to 20,000 mPa ⁇ s when the viscosity is measured at a speed 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.
  • a positive electrode active material a binder and optionally a solvent are added and mixed to prepare a composition for forming a positive electrode active material layer.
  • the cathode active material and the binder are as described above.
  • the solvent may be a solvent generally used in the art, dimethyl sulfoxide (DMSO), isopropyl alcohol (isopropyl alcohol), N-methylpyrrolidone (NMP), acetone (acetone ) Or water, and one kind alone or a mixture of two or more kinds thereof may be used.
  • the amount of the solvent is sufficient to dissolve or disperse the positive electrode active material and the binder in consideration of the coating thickness of the slurry, the production yield, and to have a viscosity capable of exhibiting excellent thickness uniformity during application for electrode production.
  • the positive electrode active material layer prepared above is coated on a positive electrode current collector, dried and rolled, or the composition for forming the positive electrode active material layer is cast on a separate support, and then the film obtained by peeling from the support is obtained.
  • a positive electrode is manufactured by laminating and rolling on an electrical power collector.
  • the positive electrode current collector is not particularly limited as long as it has conductivity without causing chemical changes to the battery.
  • copper, stainless steel, aluminum, nickel, titanium, calcined carbon, or a surface treated with carbon, nickel, titanium, silver or the like on the surface of aluminum or stainless steel may be used.
  • the current collector may have a thickness of typically 3 ⁇ m to 500 ⁇ m, and may form fine irregularities on the surface of the current collector to increase 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, or a nonwoven body.
  • composition for forming a positive electrode active material layer on the positive electrode current collector may be performed according to a conventional method.
  • the coating process may be performed by a coating method such as spray coating or bar coating.
  • the drying process may be performed according to conventional methods such as natural drying, hot air drying, heat drying.
  • process conditions such as the application rate and drying temperature during the coating and drying process may affect the packing density in the cathode active material layer to be manufactured.
  • the coating process may be specifically carried out at a coating speed of 5 to 50m / min, more specifically 10 to 40m / min composition for forming the positive electrode active material layer.
  • the drying process may be carried out at 120 to 150 °C, more specifically may be carried out at 130 to 150 °C.
  • the rolling process may be performed according to a conventional method, except to have the filling density described above. Specifically, the rolling process may be performed according to a roll press method for rolling the anode thickness by adjusting the roll up / down gap. Can be.
  • 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 lithium secondary battery includes a positive electrode, a negative electrode positioned to face the positive electrode, a separator and an electrolyte interposed between the positive electrode and the negative electrode, and at least one of the positive electrode and the negative electrode includes the conductive material dispersion. It may be prepared by.
  • the lithium secondary battery may further include a battery container for accommodating the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member for sealing the battery container.
  • the separator separates the negative electrode and the positive electrode and provides a movement path of lithium ions, and can be used without particular limitation as long as it is usually used as a separator in a lithium secondary battery. It is preferable that it is resistance and excellent in electrolyte solution moisture-wetting ability.
  • 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.
  • 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 by 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.
  • NMP N-methylpyrrolidone
  • ⁇ ⁇ -unsaturated nitrile-derived structural unit content
  • PDI polydispersity index
  • the prepared positive electrode composition was applied to an aluminum current collector at a rate of 10 m / min, dried at 130 ° C., and then rolled in a roll press under conditions of a target packing density of 3.427 g / cc to prepare a positive electrode.
  • the packing density in the prepared positive electrode active material layer was 3.4 g / cc.
  • a positive electrode was prepared in the same manner as in Example 1, except that roll pressing was performed.
  • the packing density in the prepared cathode active material layer was 3.1 g / cc.
  • the positive electrode was manufactured in the same manner as in Example 1, except that the mixture was mixed with and roll-pressed at a target filling density of 4.1 g / cc during the rolling process.
  • the packing density in the prepared anode active material layer was 4.1 g / cc.
  • a positive electrode was manufactured in the same manner as in Example 1, except that the roll press was carried out. The packing density in the prepared positive electrode active material layer was 3.4 g / cc.
  • Carbon black instead of carbon nanotubes in Example 1, and the mixture is carried out in the same manner as in Example 2 except for using a mixture of the positive electrode active material: carbon black: binder 95: 3: 2: To prepare a positive electrode.
  • Example 1 Except for using carbon nanotubes of the physical properties described below instead of the carbon nanotubes in Example 1 was carried out in the same manner as in Example 1 to prepare a positive electrode.
  • BET specific surface area BELSORP-mino II, manufactured by BEL Japan, was calculated from the amount of nitrogen gas adsorption under liquid nitrogen temperature (77K).
  • Example 1 Comparative Example 3 CNT secondary structure shape Bundled Bundled Average diameter of CNT monomer (nm) 8 20 Crystallinity (IG / ID Ratio) Average 0.95 0.72 Standard Deviation(%) 1.64 2.12 Purity (wt%) 100 99.5 BET specific surface area (m 2 / g) 249 245
  • ICP-OEB Optima-7300 was used to analyze the metal element content through ICP analysis.
  • each sample containing CNTs used in Example 1 and Comparative Example 3 was accurately measured in about 0.5 g vials.
  • 2 ml of concentrated sulfuric acid was added to the vial containing the sample.
  • Samples were heated on a hot plate, carbonized and dried.
  • 3 ml of hydrochloric acid / 1 ml of nitric acid / one drop of hydrogen peroxide were added to the carbonized sample to decompose.
  • 200 ⁇ l of 1000 mg / kg internal standard was added and diluted with 20 ml of ultrapure water. Analysis by ICP-OEB. The results are shown in Table 2 below.
  • Example 1 Comparative Example 3 Metal content (unit: mg / kg) Al - - Co ⁇ 10 - Fe - 500 Mo - - Ni - 260 V ⁇ 1 -
  • Electrolyte wetting experiments were performed for the positive electrodes prepared in Example 1 and Comparative Example 1.
  • Example 1 and Comparative Example 1 were placed on a flat plate so as to be horizontal, respectively, in a space with light and fixed with an adhesive tape.
  • the syringe was filled with propylene carbonate solvent or the corresponding electrolyte solution up to 10 ⁇ l so as not to bubble inside.
  • a syringe filled with propylene carbonate or electrolyte was fixed perpendicularly to the fixed stand and placed in the center of the sample fixed to the plate.
  • the syringe scale was checked and pushed out by an amount of 1 ⁇ l, and it was visually checked whether a propylene carbonate solvent or electrolyte was formed at the end of the syringe nozzle.
  • the syringe was lowered slowly until the PC solvent or electrolyte formed on the tip of the syringe nozzle reached the sample surface using the height adjuster of the syringe holding stand. As soon as the PC solvent or electrolyte reached the sample surface, the measurement was started using the stopwatch. The syringe was lifted at least 30 mm from the sample using the height adjuster of the syringe holding stand. Samples were covered with a transparent casserole lid for isolation from the external environment. The time when the dark contrast part (impregnation area of PC solvent and electrolyte solution) disappears completely was recorded and confirmed.
  • the packing density was calculated using the true density of the material used in the positive electrode production and the thickness / weight of the electrode.
  • Example 2 the positive electrode prepared in Example 2 and Comparative Example 2 was carried out in the same manner as described above to determine the filling density and propylene carbonate wetting time. The results are shown in Table 4 below.
  • Pore size distribution was measured for the cathodes prepared in Example 2 and Comparative Example 2 using a mercury intrusion method.
  • the average pore diameter P in each active material layer in each electrode was determined according to the following equation. The results are shown in Table 5 and FIG. 3 together with the packing density in the cathode active material layer of each electrode.
  • V is the pore volume
  • A is the pore area
  • the positive electrode active material layer of Example 2 showed a significantly larger average pore diameter than that of Comparative Example 2.
  • the maximum peak (maximum pore size) of the pore diameter in the positive electrode active material layer of Comparative Example 2 is 166.6 nm
  • the maximum peak (maximum pore size) in the positive electrode active material layer of Example 2 is It increased to 311.1 nm, and the overall graph hierarchy was also shifted towards larger pores.
  • a lithium secondary battery was manufactured using the positive electrodes prepared in Examples 1 and 2.
  • graphite, a carbon black conductive material, a styrene butadiene rubber (SBR) binder and a carboxymethyl cellulose (CMC) thickener are mixed in water at a weight ratio of 97: 1: 1: 1 as a negative electrode active material to prepare a composition for forming a negative electrode. Then, this was applied to a copper current collector to prepare a negative electrode.
  • SBR styrene butadiene rubber
  • CMC carboxymethyl cellulose
  • LiPF 6 lithium hexafluorophosphate
  • a lithium secondary battery was manufactured by the same method as described above with respect to the positive electrode prepared in Comparative Examples 1 to 4.
  • Mono-cells having the same capacity were prepared using positive electrodes (Examples 2 and 3 and 4) prepared using the carbon nanotube dispersions of Examples 2 and Comparative Examples 2, respectively, and 25 ° C.
  • the resistance was measured for 10 seconds at 150A based on 50% SOC at cut off voltage of 1.9V. The results are shown in FIG.
  • the battery including the positive electrode prepared in Example 2 exhibits a lower resistance than the battery containing the positive electrode prepared in Comparative Example 2, it can be expected to exhibit a better output characteristics.
  • Example 2 The lithium secondary batteries of Example 2 and Comparative Example 2 were charged and discharged 300 times under conditions of 1C / 1C at a high temperature (45 ° C) within a 2.7V to 3.8V driving voltage range.
  • Cycle capacity retention which is the ratio of the discharge capacity at the 300th cycle of charge / discharge, was measured. The results are shown in FIG. 5.
  • the battery including the positive electrode prepared in Example 2 showed an equivalent level of life characteristics compared to Comparative Example 2.

Abstract

The present invention provides a cathode for a secondary battery and a secondary battery comprising the same, wherein the cathode comprises a cathode active material layer comprising a cathode active material, a conductive material, and a binder; the conductive material comprises bundle-type carbon nanotubes that have an average strand diameter of 15nm or less; the cathode active material layer has a packing density of 3.0g/cc or higher and exhibits an average pore diameter of 0.1μm to 0.5μm, when the pore size distribution is measured at the packing density using mercury intrusion porosimetry, such that an excellent electrolyte wetting property can be exhibited; and, as a result, the cathode wetting period is shortened, when applied to a battery, and the area, which is not filled with the electrolyte, is reduced, making it possible to improve the battery performance.

Description

이차전지용 양극 및 이를 포함하는 이차전지Anode for Secondary Battery and Secondary Battery Having Same
[관련출원과의 상호인용][Citations with Related Applications]
본 출원은 2015.12.10자 한국 특허 출원 제10-2015-0176255호 및 2016.12.07자 한국 특허 출원 제10-2016-0166124에 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. 10-2015-0176255 filed Dec. 10, 2015 and Korean Patent Application No. 10-2016-0166124 filed Dec. 7, 2016, and all contents disclosed in the documents of the Korean patent application. Is included as part of this specification.
[기술분야][Technical Field]
본 발명은 기공 구조 개선을 통해 우수한 전해액 젖음성(wetting property)을 나타내는 이차전지용 양극 및 이를 포함하는 이차전지에 관한 것이다.The present invention relates to a positive electrode for a secondary battery exhibiting excellent electrolyte wetting property through improved pore structure and a secondary battery including 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 전극내 저항을 감소시킬 수 있다. 이와 같은 도전재 중에서도 전극내 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 manufacturing the electrode, 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 용매에 선분산시킨 후 전극 형성용 조성물을 제조하여 사용하였다. 그러나, 탄소 나노튜브는 서로 간의 강한 반데르발스 인력에 의해 용매 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 structures. 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 solvent to prepare a composition for forming an electrode. However, carbon nanotubes do not achieve a stable dispersion state in a solvent due to strong van der Waals attraction between each other, and there is a problem in that agglomeration occurs.
이러한 문제점을 해결하기 위하여 다양한 시도가 있어 왔다. 구체적으로 초음파 처리 등의 기계적 분산 처리를 통해 탄소 나노튜브를 용매 중에 분산시키는 방법이 제안된 바 있다. 그러나, 이 방법의 경우 초음파를 조사하고 있는 동안은 분산성이 우수하지만, 초음파 조사가 종료되면 탄소 나노튜브의 응집이 시작되어 탄소 나노튜브의 농도가 높아지면 응집해 버리는 문제가 있다. 또, 다양한 분산제를 이용하여 탄소 나노튜브를 분산 안정화하는 방법이 제안되고 있다. 그러나, 이들 방법 역시 미세 탄소섬유를 용매 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 solvent through mechanical dispersion treatment such as ultrasonication has been proposed. However, this method is excellent in dispersibility while irradiating ultrasonic waves, but when the ultrasonic irradiation ends, agglomeration of the carbon nanotubes starts, and when the concentration of the carbon nanotubes becomes high, there is a problem of aggregation. 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 fine carbon fibers are dispersed in a high concentration in a solvent, handling becomes difficult due to a viscosity increase.
이에 따라, 도전성의 저하없이 전극내 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 deteriorating conductivity and a method of preparing carbon nanotube dispersions useful for electrode production using the same.
본 발명이 해결하고자 하는 제1 과제는 기공 구조 개선을 통해 우수한 전해액 젖음성을 나타내는 이차전지용 양극을 제공하는 것이다.The first problem to be solved by the present invention is to provide a secondary battery positive electrode exhibiting excellent electrolyte wettability through improved pore structure.
본 발명이 해결하고자 하는 제2 과제는 상기 양극을 포함하는 리튬 이차전지, 전지모듈 및 전지팩을 제공하는 것이다.A second object of the present invention is to provide a lithium secondary battery, a battery module, and a battery pack including the positive electrode.
상기 과제를 해결하기 위하여 본 발명의 일 실시예에 따르면, 양극활물질, 도전재 및 분산제를 포함하는 양극활물질층을 포함하고, 상기 도전재는 탄소 나노튜브 단위체의 평균 가닥직경이 15nm 이하인 번들형(bundle-type) 탄소 나노튜브를 포함하며, 상기 탄소 나노튜브는 532nm 파장의 레이저를 이용한 라만 분광 분석법에 의해 얻어진 1580±50cm-1 에서의 G 밴드의 최대 피크 강도(IG)에 대한 1360±50cm-1 에서의 D 밴드의 최대 피크 강도(ID)의 비(ID/IG)의 평균값이 0.7 내지 1.7이고, 표준편차값이 1.3 내지 2.0%인 것이고, 상기 양극활물질층은 3.0g/cc 이상의 충진 밀도를 가지고, 상기 충진 밀도에서 수은 압입법에 따른 기공 크기 분포 측정시 하기 수학식 1에 따른 평균 기공 직경이 0.1㎛ 내지 0.5㎛인 것인 이차전지용 양극을 제공한다.In order to solve the above problems, according to an embodiment of the present invention, a cathode active material layer including a cathode active material, a conductive material and a dispersant, the conductive material is a bundle (average strand diameter of 15 nm or less of carbon nanotube units) -type) carbon nanotubes, the carbon nanotubes being 1360 ± 50 cm -1 for the maximum peak intensity (IG) of the 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 is 0.7 to 1.7, and the standard deviation value is 1.3 to 2.0%, and the positive electrode active material layer has a packing density of 3.0 g / cc or more. In addition, it provides a secondary battery positive electrode having an average pore diameter of 0.1㎛ to 0.5㎛ according to the following equation 1 when measuring the pore size distribution according to the mercury intrusion method at the filling density.
[수학식 1][Equation 1]
평균 기공 직경(P)=4V/AAverage pore diameter (P) = 4V / A
(상기 수학식 1에서, V는 기공 부피이고, A는 기공 면적이다)(In Equation 1, V is the pore volume, A is the pore area)
또, 본 발명의 다른 일 실시예에 따르면, 상기한 양극을 포함하는 리튬 이차전지, 전지모듈 및 전지팩을 각각 제공한다.In addition, according to another embodiment of the present invention, there is provided a lithium secondary battery, a battery module and a battery pack including the positive electrode, respectively.
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 이차전지용 양극은, 양극활물질층내 개선된 기공 구조를 가져 우수한 전해액 젖음성을 나타낼 수 있다. 그 결과 전지 적용시 양극 젖음 기간이 단축되고, 전해액 미충전 영역이 감소됨으로써 전지 성능이 개선될 수 있다.The secondary battery positive electrode according to the present invention has an improved pore structure in the positive electrode active material layer can exhibit excellent electrolyte wettability. As a result, when the battery is applied, the positive electrode wetting period is shortened, and the electrolyte unfilled area is reduced, thereby improving battery performance.
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 1은 실시예 1 및 비교예 1의 전지에 대한 프로필렌카보네이트(PC) 젖음성 평가 결과를 나타낸 그래프이다.1 is a graph showing the results of evaluating propylene carbonate (PC) for the batteries of Example 1 and Comparative Example 1.
도 2는 실시예 2 및 비교예 2의 전지에 대한 프로필렌카보네이트(PC) 젖음성 평가 결과를 나타낸 그래프이다.2 is a graph showing the results of evaluating propylene carbonate (PC) for the batteries of Example 2 and Comparative Example 2.
도 3은 실시예 2 및 비교예 2의 양극 내 기공 크기 분포를 관찰한 결과를 나타낸 그래프이다.Figure 3 is a graph showing the results of observing the pore size distribution in the positive electrode of Example 2 and Comparative Example 2.
도 4는 실시예 2 및 비교예 2의 전지에 대한 저항 특성 평가 결과를 나타낸 그래프이다.4 is a graph showing the resistance characteristics evaluation results for the battery of Example 2 and Comparative Example 2.
도 5는 실시예 2 및 비교예 2의 전지에 대한 사이클 특성 평가 결과를 나타낸 그래프이다.5 is a graph showing the cycle characteristics evaluation results for the battery of Example 2 and Comparative Example 2.
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.The term 'bundle type' used in the present invention, unless stated otherwise, a plurality of carbon nanotube strands, that is, carbon nanotube units are arranged side by side in an orientation substantially the same axis in the longitudinal direction of the unit 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.
최근 이차전지에 대한 고용량화 및 고에너지 밀도화 요구에 따라 전극의 두께가 두꺼워지고, 충진 밀도(packing density)(또는 압연 밀도)가 증가하고 있다. 그러나 이와 같이 전극 두께가 두꺼워지고 충진 밀도가 증가할 경우 전극의 전해액 젖음성이 저하되게 된다. 전극에서의 전해액 젖음성 저하는 전극 젖음 시간의 증가와 함께, 전해액의 불균일 젖음을 초래하고, 그 결과 전해액 미젖음 영역에서 충전이 이루어지지 않게 되어 전지 특성이 악화되는 문제가 있다.In recent years, as the demand for high capacity and high energy density for secondary batteries increases, the thickness of the electrode becomes thicker and the packing density (or rolling density) increases. However, when the electrode thickness is increased and the filling density is increased in this way, the electrolyte wettability of the electrode is lowered. The decrease in the electrolyte wettability at the electrode causes a nonuniform wetting of the electrolyte with an increase in the electrode wetting time, and as a result, there is a problem that the charging is not performed in the electrolyte nonwetting region and the battery characteristics are deteriorated.
이에 대해 본 발명에서는 탄소 나노튜브를 도전재로 이용하여 양극 제조시, 전지의 방전 펄스 저항 특성 및 사이클 특성 저하에 대한 우려없이, 탄소 나노튜브의 특성을 최적화하여 양극활물질층내 분산성을 높이고, 이를 통해 활물질층 내 기공 구조를 개선함으로써 전해액에 대한 젖음성을 향상시켜, 전지 적용시 전지 특성을 크게 향상시킬 수 있다.On the other hand, in the present invention, the carbon nanotubes are used as the conductive material, and the carbon nanotubes are optimized for dispersibility in the cathode active material layer by optimizing the characteristics of the carbon nanotubes without fear of deterioration of the discharge pulse resistance characteristics and cycle characteristics of the battery. By improving the pore structure in the active material layer through to improve the wettability of the electrolyte, it is possible to significantly improve the battery characteristics when applying the battery.
구체적으로, 본 발명의 일 실시예에 따른 이차전지용 양극은, 양극활물질, 도전재 및 분산제를 포함하는 양극활물질층을 포함하고, 상기 도전재는 탄소 나노튜브 단위체의 평균 가닥직경이 15nm 이하인 번들형 탄소 나노튜브를 포함하며, 상기 탄소 나노튜브는 532nm 파장의 레이저를 이용한 라만 분광 분석법에 의해 얻어진 1580±50cm-1 에서의 G 밴드의 최대 피크 강도(IG)에 대한 1360±50cm-1 에서의 D 밴드의 최대 피크 강도(ID)의 비(ID/IG)의 평균값이 0.7 내지 1.7이고, 표준편차값이 1.3 내지 2.0%인 것이고, 상기 양극활물질층은 3.0g/cc 이상의 충진 밀도를 가지고, 상기 충진 밀도에서 수은 압입법에 따른 기공 크기 분포 측정시 하기 수학식 1에 따른 평균 기공 직경(P)이 0.1㎛ 내지 0.5㎛인 것이다.Specifically, the positive electrode for a secondary battery according to an embodiment of the present invention includes a positive electrode active material layer including a positive electrode active material, a conductive material and a dispersant, and the conductive material includes bundle carbon having an average strand diameter of carbon nanotube units of 15 nm or less. Including nanotubes, the carbon nanotubes having a D band at 1360 ± 50cm −1 for a maximum peak intensity (IG) of G band at 1580 ± 50cm −1 obtained by Raman spectroscopy with a laser of 532 nm wavelength The average value of the ratio (ID / IG) of the maximum peak intensity (ID) is 0.7 to 1.7, the standard deviation value is 1.3 to 2.0%, and the positive electrode active material layer has a packing density of 3.0 g / cc or more, the filling When measuring the pore size distribution according to the mercury intrusion method in the density, the average pore diameter P according to Equation 1 is 0.1 μm to 0.5 μm.
[수학식 1][Equation 1]
평균 기공 직경(P)(㎛)=4V/AAverage Pore Diameter (P) (μm) = 4V / A
(상기 수학식 1에서, V는 기공 부피이고, A는 기공 면적이다)(In Equation 1, V is the pore volume, A is the pore area)
이때, 상기 수학식 1은 수은 압입법에 의한 기공 크기 분포 측정값으로부터 얻어진 기공 부피와 기공 면적으로부터 모델링하여 얻어진 것이다. In this case, Equation 1 is obtained by modeling from the pore volume and the pore area obtained from the pore size distribution measurement value by the mercury porosimetry.
보다 구체적으로, 본 발명의 일 실시예에 따른 상기 이차전지용 양극에 있어서, 상기 양극활물질층은 3.0g/cc 내지 4.3g/cc의 충진 밀도를 가지고, 상기 충진 밀도에서 상기 수학식 1에 따른 평균 기공 직경이 0.1㎛ 내지 0.5㎛, 보다 더 구체적으로는 0.1㎛ 내지 0.3㎛인 것일 수 있다.More specifically, in the secondary battery positive electrode according to an embodiment of the present invention, the positive electrode active material layer has a packing density of 3.0g / cc to 4.3g / cc, the average according to the formula 1 in the filling density The pore diameter may be 0.1 μm to 0.5 μm, and more specifically 0.1 μm to 0.3 μm.
통상 양극활물질층내 충진 밀도가 증가할수록 활물질층내 기공 크기가 작아지는 경향을 나타낸다. 그러나, 본 발명에 따른 이차전지용 양극은, 상기한 바와 같이 고충진 밀도에서도 큰 기공 크기를 갖는다. 더욱이, 양극활물질층이 상기한 범위 내의 기공 크기 분포를 가짐으로써, 양극활물질층 내로 전해액이 빠르고 쉽게 침투할 수 있으며, 전해액 미젖음 부분의 발생 없이 균일하게 활물질층 내로 침투할 수 있다. 그 결과 양극활물질층 전체에 걸쳐 충전이 일어날 수 있으므로, 전지 특성을 더욱 개선시킬 수 있다.In general, as the packing density in the cathode active material layer increases, the pore size in the active material layer tends to decrease. However, the secondary battery positive electrode according to the present invention has a large pore size even at a high filling density as described above. Furthermore, since the positive electrode active material layer has a pore size distribution within the above range, the electrolyte solution can quickly and easily penetrate into the positive electrode active material layer, and can uniformly penetrate into the active material layer without generation of the electrolyte wetting portion. As a result, charging may occur throughout the positive electrode active material layer, thereby further improving battery characteristics.
또 이차전지용 양극에 있어서, 사용되는 양극활물질의 종류에 따라 요구되는 활물질층내 충진 밀도가 다를 수 있다. 이에 따라, 구체적으로 본 발명의 일 실시예에 따른 상기 이차전지용 양극에 있어서, 상기 양극활물질층이 양극활물질로서 리튬 니켈망간코발트계 산화물을 포함하는 경우, 양극활물질층은 3.0g/cc 이상, 보다 구체적으로는 3.1g/cc 내지 3.6g/cc의 충진 밀도를 가지고, 상기 충진 밀도에서 0.1㎛ 내지 0.3㎛, 보다 구체적으로는 0.1㎛ 내지 0.2㎛의 평균 기공 직경을 가질 수 있다. 또, 상기 양극활물질층이 양극활물질로서 리튬 코발트계 산화물을 포함하는 경우, 양극활물질층은 3.0g/cc 이상, 보다 구체적으로는 3.9g/cc 내지 4.3g/cc, 보다 더 구체적으로는 3.9g/cc 내지 4.2g/cc의 충진 밀도를 가지고, 상기 충진 밀도에서0.1㎛ 내지 0.3㎛, 보다 구체적으로는 0.1㎛ 내지 0.2㎛의 평균 기공 직경을 가질 수 있다.In the positive electrode for a secondary battery, the required packing density in the active material layer may vary depending on the type of the positive electrode active material used. Accordingly, specifically in the secondary battery positive electrode according to an embodiment of the present invention, when the positive electrode active material layer contains lithium nickel manganese cobalt-based oxide as the positive electrode active material, the positive electrode active material layer is more than 3.0g / cc, Specifically, it may have a packing density of 3.1 g / cc to 3.6 g / cc, and may have an average pore diameter of 0.1 μm to 0.3 μm, more specifically 0.1 μm to 0.2 μm at the filling density. In addition, when the cathode active material layer contains lithium cobalt oxide as the cathode active material, the cathode active material layer is 3.0 g / cc or more, more specifically 3.9 g / cc to 4.3 g / cc, and more specifically 3.9 g It has a packing density of / cc to 4.2g / cc, it may have an average pore diameter of 0.1 ㎛ to 0.3 ㎛, more specifically 0.1 ㎛ to 0.2 ㎛ in the filling density.
또, 본 발명의 일 실시예에 따른 상기 이차전지용 양극에 있어서, 상기 양극활물질층은 수은 압입법에 따른 기공 크기 분포 측정시 상기한 충진 밀도 조건 하에서 30nm 내지 2500nm의 기공 직경 범위에서 피크를 나타낸다.In addition, in the positive electrode for a secondary battery according to an embodiment of the present invention, the positive electrode active material layer exhibits a peak in the pore diameter range of 30 nm to 2500 nm under the above-described filling density condition when pore size distribution is measured by mercury porosimetry.
또, 상기 양극활물질층은 상기한 충진 밀도 조건 하에서 250nm 내지 330nm의기공 직경 범위에서 최대 피크(max peak)를 나타낸다. 통상적인 양극활물질층이 동일 수준의 충진 밀도에서 약 160nm 내지 170nm의 기공 직경 범위에서 최대 피크를 나타내는 것과 비교하여, 본 발명에 따른 이차전지용 양극에 있어서의 양극활물질층은 고충진 밀도 하에서도 큰 기공 크기를 가질 수 있다. 이에 따라 양극활물질층 내로 전해액이 보다 빠르고 균일하게 침투할 수 있다.In addition, the positive electrode active material layer exhibits a maximum peak in the pore diameter range of 250 nm to 330 nm under the packing density condition. Compared with the conventional cathode active material layer showing the maximum peak in the pore diameter range of about 160 nm to 170 nm at the same level of packing density, the cathode active material layer in the positive electrode for secondary batteries according to the present invention has large pores even under high packing density. May have a size. As a result, the electrolyte solution may quickly and uniformly penetrate into the cathode active material layer.
본 발명에 있어서, 양극활물질층내 기공 크기 및 기공 크기 분포(pore size distribution, PSD)는 수은(Hg) 압입법에 의해 기공 내 Hg가 채워질 때의 압력과 그때의 부피로부터 측정할 수 있다.In the present invention, the pore size and pore size distribution (PSD) in the cathode active material layer can be measured from the pressure and volume at the time when Hg is filled in the pores by mercury (Hg) indentation.
상기한 바와 같이 본 발명의 일 실시예에 따른 이차전지용 양극에 있어서의 활물질층내 개선된 기공 구조는 양극활물질층을 구성하는 도전재의 제어를 통해, 더 나아가 상기 도전재와 함께 양극활물질, 분산제 및 선택적으로 바인더의 함량과 종류, 물성 또는 혼합비의 제어를 통해 구현될 수 있다.As described above, the improved pore structure in the active material layer in the positive electrode for a secondary battery according to the embodiment of the present invention is further controlled through the control of the conductive material constituting the positive electrode active material layer, and furthermore, together with the conductive material, the positive electrode active material, the dispersant and the selective material. This can be implemented by controlling the content and type of binder, physical properties or mixing ratio.
구체적으로, 본 발명의 일 실시예에 따른 이차전지용 양극의 양극활물질층에 있어서, 상기 양극활물질은 리튬의 가역적인 인터칼레이션 및 디인터칼레이션이 가능한 화합물(리티에이티드 인터칼레이션 화합물)로서, 코발트, 망간, 니켈 또는 알루미늄과 같은 1종 이상의 금속과 리튬을 포함하는 리튬 복합금속 산화물을 포함할 수 있다.Specifically, in the positive electrode active material layer of the secondary battery positive electrode according to an embodiment of the present invention, the positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound) And lithium composite metal oxides including lithium with one or more metals such as cobalt, manganese, nickel or aluminum.
보다 구체적으로, 상기 리튬 복합금속 산화물은 리튬-망간계 산화물(예를 들면, LiMnO2, LiMn2O 등), 리튬-코발트계 산화물(예를 들면, LiCoO2 등), 리튬-니켈계 산화물(예를 들면, LiNiO2 등), 리튬-니켈-망간계 산화물(예를 들면, LiNi1 - YMnYO2(여기에서, 0<Y<1), LiMn2 - zNizO4(여기에서, 0＜Z＜2) 등), 리튬-니켈-코발트계 산화물(예를 들면, LiNi1 - YCoYO2(여기에서, 0<Y<1) 등), 리튬-망간-코발트계 산화물(예를 들면, LiCo1 - YMnYO2(여기에서, 0<Y<1), LiMn2 - zCozO4(여기에서, 0＜Z＜2) 등), 리튬-니켈-코발트-망간계 산화물(예를 들면, Li(NiPCoQMnR)O2(여기에서, 0＜P＜1, 0＜Q＜1, 0＜R＜1, P+Q+R=1) 또는 Li(NiPCoQMnR)O4(여기에서, 0＜P＜2, 0＜Q＜2, 0＜R＜2, P+Q+R=2) 등), 또는 리튬-니켈-코발트-망간-기타금속(M) 산화물(예를 들면, Li(NiPCoQMnRMS)O2(여기에서, M은 Al, Cu, Fe, V, Cr, Ti, Zr, Zn, Ta, Nb, Mg, B, W 및 Mo로 이루어지는 군으로부터 선택되고, P, Q, R 및 S는 각각 독립적인 원소들의 원자분율로서, 0＜P＜1, 0＜Q＜1, 0＜R＜1, 0＜S＜1, P+Q+R+S=1이다) 등) 등을 들 수 있으며, 이들 중 어느 하나 또는 둘 이상의 화합물이 포함될 수 있다.More specifically, the lithium composite metal oxide is a lithium-manganese oxide (eg, LiMnO 2 , LiMn 2 O Etc.), lithium-cobalt-based oxides (e.g., LiCoO 2, etc.), lithium-nickel-based oxides (e.g., LiNiO 2, etc.), lithium-nickel-manganese-based oxides (e.g., LiNi 1 - Y Mn Y O 2 (where, 0 <Y <1), LiMn 2-z Ni z O 4 (where, 0 <z <2) and the like), lithium-nickel-cobalt-based oxide (for example, LiNi 1- Y Co Y O 2 (where, 0 <Y <1) and the like), lithium-manganese-cobalt oxide (e.g., LiCo 1-Y Mn Y O 2 (where, 0 <Y <1), LiMn 2-z Co z O 4 (where, 0 <Z <2), and the like), lithium-nickel-cobalt-manganese-based oxide (e.g., Li (Ni P Co Q Mn R) O 2 (here, 0 <P <1, 0 <Q <1, 0 <R <1, P + Q + R = 1) or Li (Ni P Co Q Mn R ) O 4 (where 0 <P <2, 0 <Q <2, 0 <R <2, P + Q + R = 2) or the like, or lithium-nickel-cobalt-manganese-other metal (M) oxide (for example, Li (Ni P Co Q Mn R M S O 2 (wherein M is selected from the group consisting of Al, Cu, Fe, V, Cr, Ti, Zr, Zn, Ta, Nb, Mg, B, W and Mo, and P, Q, R and S Are each As the atomic fraction of the grains, 0 <P <1, 0 <Q <1, 0 <R <1, 0 <S <1, P + Q + R + S = 1), etc.) Any one or two or more of these may be included.
또, 상기 리튬 복합금속 산화물에 있어서 리튬을 제외한 금속원소들 중 적어도 하나는 Al, Cu, Fe, V, Cr, Ti, Zr, Zn, Ta, Nb, Mg, B, W 및 Mo로 이루어지는 군으로부터 선택되는 어느 하나 또는 둘 이상의 원소에 의해 도핑될 수도 있다. 이와 같이 리튬 결함의 리튬 복합금속 산화물에 상기한 금속원소가 더 도핑될 경우, 양극활물질의 구조안정성이 개선되고, 그 결과 전지의 출력 특성이 향상될 수 있다. 이때, 리튬 복합금속 산화물 내 포함되는 도핑 원소의 함량은 양극활물질의 특성을 저하시키지 않는 범위내에서 적절히 조절될 수 있으며, 구체적으로는 0.02원자% 이하일 수 있다.In the lithium composite metal oxide, at least one of the metal elements except lithium is selected from the group consisting of Al, Cu, Fe, V, Cr, Ti, Zr, Zn, Ta, Nb, Mg, B, W, and Mo. It may be doped by any one or two or more elements selected. As described above, when the above metal element is further doped into the lithium composite metal oxide of the lithium defect, the structural stability of the cathode active material may be improved, and as a result, the output characteristics of the battery may be improved. In this case, the content of the doping element included in the lithium composite metal oxide may be appropriately adjusted within a range that does not lower the characteristics of the positive electrode active material, specifically, may be 0.02 atomic% or less.
보다 구체적으로, 본 발명의 일 실시예에 따른 양극활물질에 있어서, 상기 리튬 복합금속 산화물은 하기 화학식 1의 화합물을 포함하는 것일 수 있다.More specifically, in the positive electrode active material according to an embodiment of the present invention, the lithium composite metal oxide may be to include a compound of formula (1).
[화학식 1][Formula 1]
Li1+aNixCoyMnzMwO2 Li 1 + a Ni x Co y Mn z M w O 2
(상기 화학식 1에서, M은 Al, Cu, Fe, V, Cr, Ti, Zr, Zn, Ta, Nb, Mg, B, W 및 Mo로 이루어진 군에서 선택되는 어느 하나 또는 둘 이상의 원소를 포함하는 것일 수 있고, a, x, y, z 및 w는 각각 독립적으로 해당 원소들의 원자 분율로서, -0.5≤a≤0.5, 0≤x≤1, 0≤y≤1, 0≤z≤1, 0≤w≤1 및 0<x+y+z≤1이다)(In Formula 1, M is Al, Cu, Fe, V, Cr, Ti, Zr, Zn, Ta, Nb, Mg, B, W and Mo containing any one or two or more elements selected from the group consisting of A, x, y, z and w are each independently the atomic fraction of the corresponding elements, -0.5≤a≤0.5, 0≤x≤1, 0≤y≤1, 0≤z≤1, 0 ≤ w ≤ 1 and 0 <x + y + z ≤ 1)
상기한 도전재 및 바인더와의 혼합 사용에 따른 개선효과의 현저함을 고려할 때, 상기 양극활물질은 상기 화학식 1에서 0<x<1, 0<y<1, 0<z<1, y+z≤x인 리튬 복합금속 산화물을 포함할 수 있다.In consideration of the remarkable improvement effect of the mixed use with the conductive material and the binder, the positive electrode active material is 0 <x <1, 0 <y <1, 0 <z <1, y + z in Chemical Formula 1 It may include a lithium composite metal oxide of ≤ x.
상기한 화합물들 중에서도 전지의 용량 특성 및 안정성을 높일 수 있다는 점에서 상기 리튬 복합금속 산화물은 보다 구체적으로 LiCoO2, 또는 리튬 니켈망간코발트 산화물(예를 들면, Li(Ni0.6Mn0.2Co0.2)O2, LiNi0 . 5Mn0 . 3Co0 . 2O2, 또는 LiNi0.8Mn0.1Co0.1O2 등)일 수 있으며, 리튬 복합금속 산화물을 형성하는 구성원소의 종류 및 함량비 제어에 따른 개선 효과의 현저함을 고려할 때 상기 리튬 복합금속 산화물은 LiNi0 . 6Mn0 . 2Co0 . 2O2, LiNi0 . 5Mn0 . 3Co0 . 2O2, LiNi0 . 7Mn0 . 15Co0 . 15O2 또는 LiNi0.8Mn0.1Co0.1O2 등일 수 있으며, 이들 중 어느 하나 또는 둘 이상의 혼합물을 포함할 수 있다.Among the above compounds, the lithium composite metal oxide is more specifically LiCoO 2 or lithium nickel manganese cobalt oxide (eg, Li (Ni 0.6 Mn 0.2 Co 0.2 ) O) in that the capacity characteristics and stability of the battery can be improved. 2 , LiNi 0 . 5 Mn 0 . 3 Co 0 . 2 O 2, or LiNi 0.8 Mn 0.1 Co 0.1 O 2, and so on) may be, given the remarkable also in the improvement according to the kind and content ratio control of constituent elements forming the lithium composite metal oxide, wherein the lithium composite metal oxide has LiNi 0 . 6 Mn 0 . 2 Co 0 . 2 O 2 , LiNi 0 . 5 Mn 0 . 3 Co 0 . 2 O 2 , LiNi 0 . 7 Mn 0 . 15 Co 0 . 15 O 2 or LiNi 0.8 Mn 0.1 Co 0.1 O 2 , and the like, and may include any one or a mixture of two or more thereof.
또, 상기 양극활물질은 그 형태가 특별히 한정되지 않으며, 구체적으로 구형, 다면체, 섬유상, 판상, 인편상 등 다양한 형태를 가질 수 있다.In addition, the positive electrode active material is not particularly limited in form, and specifically, may have various forms such as spherical, polyhedral, fibrous, plate, and flaky.
또, 상기 양극활물질은 구체적으로 평균 입경(D50)이 2㎛ 내지 30㎛인 것일 수 있다. 양극활물질의 평균 입경이 2㎛ 미만이면 활물질간 응집으로 조성물 중 분산성이 저하될 우려가 있고, 30㎛를 초과하면 비표면적의 감소로 인해 활성 저하의 우려가 있다. 양극활물질의 평균 입경의 최적화에 따른 개선효과의 현저함을 고려할 때 상기 양극활물질은 평균 입경(D50)이 5㎛ 내지 20㎛인 것일 수 있다.In addition, the positive electrode active material may be one of the 2㎛ to 30㎛ Specifically, the average particle diameter (D 50). If the average particle size of the positive electrode active material is less than 2 μm, dispersibility in the composition may decrease due to aggregation between the active materials, and if it exceeds 30 μm, there is a fear of deterioration of activity due to a decrease in specific surface area. Considering the remarkable improvement effect of the optimization of the average particle diameter of the positive electrode active material, the positive electrode active material may have an average particle diameter (D 50 ) of 5 μm to 20 μm.
또, 상기 양극활물질은 상기한 평균 입경 범위 내에서 바이모달형(bimodal type) 입자 크기 분포를 갖는 것일 수 있다. 이와 같은 입자 크기 분포를 가짐으로써 활물질층내 양극활물질의 충진 밀도가 더욱 증가할 수 있고, 그 결과 전지 적용시 용량 특성을 더욱 개선시킬 수 있다.In addition, the cathode active material may have a bimodal type particle size distribution within the above average particle diameter range. By having such a particle size distribution, the packing density of the positive electrode active material in the active material layer can be further increased, and as a result, the capacity characteristics can be further improved when the battery is applied.
또, 상기 양극활물질은 서로 다른 형상 또는 서로 다른 입자 크기를 갖는 둘 이상의 활물질의 혼합물을 포함할 수도 있다. 구체적으로, 상기 양극활물질은 평균 입경(D50)이 2㎛ 내지 10㎛인 제1 양극활물질과, 10㎛ 초과 30㎛ 이하의 제2 양극활물질과의 혼합물을 포함할 수 있다. 이와 같이 서로 다른 입자 크기를 갖는 활물질의 혼합물을 포함할 경우, 활물질층내 양극활물질의 충진 밀도가 증가할 수 있고, 그 결과 전지 적용시 용량 특성을 더욱 개선시킬 수 있다.In addition, the cathode active material may include a mixture of two or more active materials having different shapes or different particle sizes. Specifically, the positive electrode active material may include a mixture of the average particle diameter (D 50) is 2㎛ 10㎛ to the first positive electrode active material and, 10㎛ 30㎛ less than the second cathode active material. As such, when the mixture of the active materials having different particle sizes is included, the packing density of the positive electrode active material in the active material layer may be increased, and as a result, capacity characteristics may be further improved when the battery is applied.
서로 다른 입자크기를 갖는 활물질의 혼합물 포함에 따른 양극내 충진 밀도 증가 및 전지의 용량 특성 개선 효과를 고려할 때, 상기 양극활물질은 평균 입경(D50)이 2㎛ 내지 10㎛인 제1 양극활물질과, 10㎛ 초과 30㎛ 이하의 제2 양극활물질을 50:50 내지 80:20의 혼합중량비, 보다 구체적으로는 50:50 내지 70:30의 혼합 중량비로 포함할 수 있다.When each other considering the capacity characteristic improvement of increased packing density within the cell and a positive electrode active material effects of the other particles of the mixture containing a size, the positive electrode active material has a mean particle diameter (D 50) 2㎛ 10㎛ to the first positive electrode active material and , The second positive electrode active material of more than 10㎛ 30㎛ or less may be included in a mixed weight ratio of 50:50 to 80:20, more specifically 50:50 to 70:30.
본 발명에 있어서, 상기 양극활물질의 평균 입경(D50)은 입경 분포의 50% 기준에서의 입경으로 정의할 수 있다. 또, 상기 양극활물질의 평균 입경(D50)은 예를 들어, 레이저 회절법(laser diffraction method)을 이용하여 측정할 수 있다. 구체적으로는 양극활물질의 입자를 용매 중에 분산시킨 후, 시판되는 레이저 회절 입도 측정 장치(예를 들어 Microtrac MT 3000)에 도입하여 약 28 kHz의 초음파를 출력 60W로 조사하고, 측정 장치에 있어서의 입경 분포의 50% 기준에서의 평균 입경(D50)을 산출할 수 있다.In the present invention, the average particle diameter (D 50 ) of the positive electrode active material may be defined as the particle size at 50% of the particle size distribution. In addition, the average particle diameter (D 50 ) of the positive electrode active material may be measured using, for example, a laser diffraction method. Specifically, after dispersing the particles of the positive electrode active material in a solvent, it is introduced into a commercially available laser diffraction particle size measuring device (for example, Microtrac MT 3000) and irradiated with an ultrasonic wave of about 28 kHz at an output of 60 W, and the particle diameter in the measuring device. The average particle diameter (D 50 ) at 50% of the distribution can be calculated.
상기한 양극활물질은 고형분 함량을 기준으로 양극활물질층 총 중량에 대하여 70 내지 99.5중량%로 포함될 수 있다. 양극활물질의 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 cathode active material may be included in an amount of 70 to 99.5% by weight based on the total weight of the cathode active material layer based on the solid content. If the content of the positive electrode active material is less than 70% by weight, there is a fear of lowering the capacity. If the amount of the positive electrode active material is higher than 99.5% by weight, the relative content of the binder and the conductive material is reduced, thereby reducing the adhesion to the electrode current collector, the conductivity, and the like.
또, 본 발명의 일 실시예에 따른 이차전지용 양극에 있어서, 양극활물질층은 도전재를 포함한다.In addition, in the positive electrode for a secondary battery according to an embodiment of the present invention, the positive electrode active material layer includes a conductive material.
상기 도전재는 구체적으로 탄소 나노튜브일 수 있으며, 보다 구체적으로는 탄소 나노튜브 단위체의 평균 가닥직경이 15nm 이하인 번들형(bundle-type) 탄소 나노튜브일 수 있다.Specifically, the conductive material may be carbon nanotubes, and more specifically, carbon nanotube units may be bundle-type carbon nanotubes having an average strand diameter of 15 nm or less.
상기 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.The carbon nanotubes are secondary structures formed by gathering carbon nanotube units in whole or in part in bundles. The carbon nanotube units have a graphite sheet having a nano-size diameter cylinder, and sp 2 Has a bonding 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.
통상 탄소 나노튜브는 구성 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, the carbon nanotubes may have different physical properties depending on crystallinity and structure, form, and structure and form of secondary particles including the monomers, and components included in the carbon nanotubes including impurities. 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.
또, 이차전지용 도전재로서 탄소 나노튜브 단위체의 직경이 지나치게 크면, 부피당 절대 가닥수가 감소하게 되어 도전재 사용량이 증가하기 때문에 고에너지 밀도의 전극 제작이 불리하고, 전극의 기공 직경 또한 크게 증가하게 되어 전극밀도가 저하될 수 있다. 또, 탄소 나노튜브 단위체의 직경이 지나치게 작으면, 분산이 어려워 분산액 제조 공정성이 저하될 수 있고, 분산된 탄소 나노튜브 단위체 또는 탄소 나노튜브가 양극활물질 입자 사이의 공간에 매몰되어, 충분한 기공이 형성되기 어렵다. 이에 따라, 본 발명에서 사용 가능한 탄소 나노튜브에 있어서의 탄소 나노튜브 단위체의 평균 가닥 직경은 15nm 이하일 수 있으며, 단위체의 직경 제어에 따른 도전재의 분산성 향상 및 고체 유사 특성 증가 효과, 그리고 결과로서 전극 형성용 조성물의 코팅안정성 개선 효과를 고려할 때, 상기 탄소 나노튜브 단위체의 평균 가닥 직경은 1nm 내지 15nm일 수 있으며, 보다 더 구체적으로는 3nm 내지 12nm일 수 있다.In addition, if the diameter of the carbon nanotube unit is excessively large as the secondary battery conductive material, the number of strands per volume decreases and the amount of the conductive material increases, so that the production of electrodes having high energy density is disadvantageous, and the pore diameter of the electrode is also greatly increased. The electrode density may be lowered. In addition, if the diameter of the carbon nanotube unit is too small, it is difficult to disperse and thus the dispersion manufacturing processability may be reduced, and the dispersed carbon nanotube unit or the carbon nanotube is buried in the space between the particles of the positive electrode active material, thereby forming sufficient pores. It's hard to be. Accordingly, the average strand diameter of the carbon nanotube units in the carbon nanotubes usable in the present invention may be 15 nm or less, and the effect of improving the dispersibility and solid-like properties of the conductive material by controlling the diameter of the unit, and as a result, the electrode When considering the effect of improving the coating stability of the composition for forming, the average strand diameter of the carbon nanotube unit may be 1nm to 15nm, more specifically may be 3nm to 12nm.
또, 탄소 나노튜브 단위체의 길이가 길수록 양극의 전기전도성, 강도 및 상온과 고온에서의 수명 특성이 향상될 수 있다. 만약 탄소 나노튜브 단위체의 길이가 짧으면 효율적으로 도전성 패스를 형성하기 어렵기 때문에 전기전도성이 저하될 우려가 있다. 반면, 탄소 나노튜브 단위체의 길이가 지나치게 길면 분산성이 저하될 우려가 있다. 이에 따라, 본 발명에서 사용 가능한 탄소 나노튜브에 있어서의 단위체의 길이는 0.5㎛ 내지 200㎛일 수 있다. 또, 상기한 탄소 나노튜브 단위체의 직경을 고려할 때, 상기 탄소 나노튜브 단위체는 탄소 나노튜브 단위체의 길이(단위체의 중심을 지나는 장축의 길이)와 직경(단위체의 중심을 지나며, 상기 장축에 수직하는 단축의 길이)의 비로 정의되는 종횡비가 10 내지 80,000일 수 있으며, 보다 구체적으로는 20 내지 50,000일 수 있다.In addition, the longer the length of the carbon nanotube unit can improve the electrical conductivity, strength and life characteristics of the anode at room temperature and high temperature. If the length of the carbon nanotube unit is short, it is difficult to form the conductive paths efficiently, and thus the electrical conductivity may be lowered. On the other hand, if the length of the carbon nanotube unit is too long, there is a fear that the dispersibility is lowered. Accordingly, the length of the unit in the carbon nanotubes usable in the present invention may be 0.5 μm to 200 μm. In addition, in consideration of the diameter of the carbon nanotube unit, the carbon nanotube unit has a length (length of long axis passing through the center of the unit) and a diameter (length of the unit passing through the center of the unit and perpendicular to the long axis). The aspect ratio, defined as the ratio of the length of the short axis, may be 10 to 80,000, and more specifically 20 to 50,000.
본 발명에 있어서, 탄소 나노튜브 단위체의 가닥 직경 및 길이는 전계 방사형 주사전자 현미경을 이용하여 측정할 수 있다.In the present invention, the strand diameter and length of the carbon nanotube unit can be measured by using a field emission scanning electron microscope.
또, 본 발명의 일 실시예에 따른 상기 도전재 분산액에 있어서, 상기 탄소 나노튜브는 그 단위체의 평균 직경이 앞서 설명한 바와 같이 작고, 종횡비가 크기 때문에 높은 BET 비표면적을 가지며 우수한 분산성을 나타낼 수 있다. 구체적으로 본 발명에서 사용 가능한 상기 탄소 나노튜브의 BET 비표면적은 200m2/g 내지 330m2/g일 수 있으며, 보다 구체적으로는 240m2/g 내지 280m2/g일 수 있다.In addition, in the conductive material dispersion according to an embodiment of the present invention, the carbon nanotubes have a high BET specific surface area and exhibit excellent dispersibility because the carbon nanotubes have a small average diameter as described above and a high aspect ratio. have. Specifically, the BET specific surface area of the carbon nanotubes usable in the present invention may be 200m 2 / g to 330m 2 / g, and more specifically 240m 2 / g to 280m 2 / g.
본 발명에 있어서, 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, and specifically, it can be calculated from the nitrogen gas adsorption amount under the liquid nitrogen temperature (77K) using BELSORP-mino II manufactured by BEL Japan. have.
또, 본 발명의 일 실시예에 따른 상기 도전재 분산액에 있어서, 상기 탄소 나노튜브는 532nm 파장의 레이저를 이용한 라만 분광 분석법에 의해 얻어진 1580±50cm-1에서의 G 밴드의 최대 피크 강도(IG)에 대한 1360±50 cm-1 에서의 D 밴드의 최대 피크 강도(ID)의 비(ID/IG)의 평균값이 0.7 내지 1.7이고, 표준편차값이 1.3 내지 2.0%인 것일 수 있다.In addition, in the conductive material dispersion according to an embodiment of the present invention, the carbon nanotubes have a maximum peak intensity (IG) of a G band at 1580 ± 50cm −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 1360 ± 50 cm −1 to may be 0.7 to 1.7, and the standard deviation may be 1.3 to 2.0%.
라만 분광 분석법은 탄소 나노튜브의 구조를 분석하는 방법으로서, 탄소 나노튜브의 표면 상태 분석에 유용한 방법이다. 탄소 나노튜브의 라만 스펙트럼 중 파수 1580cm-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 1360cm-1 부근의 영역에 존재하는 피크를 D 밴드라고 하며, 이는 탄소 나노튜브의 sp3 결합을 나타내는 피크로서, sp2 결합으로 이루어진 원자 결합이 끊어져 sp3 결합이 되는 경우 증가한다. 이와 같은 D 밴드는 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 1580 cm −1 in the Raman spectrum of the carbon nanotubes is called a G band, which is a peak indicating sp2 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 1360cm -1 of the Raman spectrum is called the D band, which is a peak indicating the sp3 bond of the carbon nanotube, and increases when the atomic bond formed by the sp2 bond is broken and becomes the sp3 bond. This D band is increased when a disorder or defect present in the carbon nanotubes is generated, so that the ratio of the maximum peak intensity (ID) of the D band to the maximum peak intensity (IG) of the G band is increased. (ID / IG) can be calculated to quantitatively assess the degree of disorder or defect generation.
본 발명에 있어서 탄소 나노튜브에 대한 라만 스펙트럼의 G 밴드는 파수 1580±50cm-1 영역에 존재하는 피크일 수 있고, D 밴드는 파수 1360±50cm-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 라만값은 특별히 제한되는 것은 아니지만, DXR Raman Microscope(Thermo Electron Scientific Instruments LLC)을 이용하여 레이저 파장 532nm 에서 측정할 수 있다.In the present invention, the G band of the Raman spectrum for the carbon nanotubes may be a peak present in the wavenumber 1580 ± 50cm −1 region, and the D band may be a peak present in the wavenumber 1360 ± 50cm −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. The Raman value used in the present invention is 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 카본이 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 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.
또, 본 발명의 일 실시예에 따른 이차전지용 양극에 있어서, 상기 탄소 나노튜브는 그 제조과정에서 사용된 Co, Mo, V, 또는 Cr 등과 같은 주 촉매 또는 조촉매 유래의 금속 원소를 불순물로서 포함할 수 있다. 구체적으로 상기 탄소 나노튜브는 촉매 유래 금속 원소 중에서도 Fe, Ni 및 Mo의 금속 원소를 총 합계량으로 3mg/kg 이하, 보다 구체적으로는 2mg/kg 이하의 함량으로 포함할 수 있으며, 보다 더 구체적으로는 상기한 금속원소, 즉 Fe, Ni 및 Mo 중 적어도 어느 하나, 특히 Fe를 포함하지 않는 것일 수 있다. 이와 같이, 탄소 나노튜브내 잔류하는 불순물로서의 상기 금속 원소들, 특히 Fe 금속 함량을 현저히 감소시킴으로써 전극내 부반응에 대한 우려없이 보다 우수한 전도성을 나타낼 수 있다.In addition, in the positive electrode for a secondary battery according to an embodiment of the present invention, the carbon nanotube includes a metal element derived from a main catalyst or a promoter such as Co, Mo, V, or Cr used in the manufacturing process as impurities. can do. Specifically, the carbon nanotubes may include 3 mg / kg or less, more specifically, 2 mg / kg or less, as a total amount of metal elements of Fe, Ni, and Mo, among catalyst-derived metal elements, and more specifically, The metal element, that is, at least one of Fe, Ni and Mo, in particular may be one containing no Fe. As such, by significantly reducing the content of the metal elements, especially the Fe metal, as impurities remaining in the carbon nanotubes, it is possible to exhibit better conductivity without concern for side reactions in the electrode.
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 상업적으로 입수하여 사용될 수도 있고, 또는 직접 제조하여 사용될 수도 있다. 제조할 경우, 아크방전법, 레이저 증발법 또는 화학기상 증착법 등의 통상의 방법을 이용하여 제조될 수 있으며, 제조 과정에서의 촉매의 종류, 열처리 온도 및 불순물 제거 방법 등의 제어를 통해 상기한 물성을 구현할 수 있다.Such carbon nanotubes may be obtained commercially or used directly. In the case of manufacturing, the method may be manufactured using a conventional method such as an arc discharge method, a laser evaporation method or a chemical vapor deposition method, and the aforementioned physical properties may be controlled by controlling the type of catalyst, heat treatment temperature, and impurity removal method in the manufacturing process. Can be implemented.
구체적으로, 화학적 기상 합성법에 따라 제조할 경우, 상기 탄소 나노튜브는 구형의 α-알루미나 지지체에 금속 촉매가 담지된 담지 촉매를 탄소 공급원과 가열하에 접촉시켜 탄소 나노튜브를 제조하는 단계, 및 필요에 따라 선택적으로 탄소 나노튜브내 금속 불순물을 제거하는 단계를 포함하는 제조방법에 의해 제조될 수 있다.Specifically, when prepared according to chemical vapor phase synthesis, the carbon nanotubes are prepared by contacting a supported catalyst having a metal catalyst supported on a spherical α-alumina support under heating with a carbon source to produce carbon nanotubes, and According to the present invention may optionally be prepared by a manufacturing method comprising the step of removing metal impurities in the carbon nanotubes.
상기 화학적 기상 합성법에 따른 탄소 나노튜브의 제조는, 보다 구체적으로 상기 담지 촉매를 수평 고정층 반응기 또는 유동층 반응기 내에 투입하고, 상기 기상 탄소 공급원의 열분해 온도 이상 내지 상기 담지된 금속 촉매의 융점 이하의 온도에서 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 튜브축과 거의 평행하고, 튜브 길이 방향으로 흑연 구조의 결정성이 높다. 그 결과, 단위체의 직경이 작고, 전기전도성 및 강도가 높다.In the preparation of carbon nanotubes according to the chemical vapor phase synthesis method, more specifically, the supported catalyst is introduced into a horizontal fixed bed reactor or a fluidized bed reactor, and at a temperature above the thermal decomposition temperature of the gaseous carbon source to below the melting point of the supported metal catalyst. Carbon 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. . The carbon nanotubes produced by the above chemical vapor phase synthesis method have a crystal growth direction substantially parallel to the tube axis and high crystallinity of the graphite structure in the tube length direction. As a result, the diameter of the unit is small, and the electrical conductivity and strength are high.
또, 상기 탄소 나노튜브의 제조는 구체적으로는 500℃ 이상 800℃ 미만의 온도, 보다 구체적으로는 550℃ 내지 700℃에서 수행될 수 있다. 상기 반응온도 범위내에서는 비결정성 탄소의 발생을 최소화하면서 생성되는 탄소 나노튜브의 벌크 크기를 그대로 유지하면서 중량이 낮아지므로, 벌크밀도 감소에 따른 분산성이 더욱 향상될 수 있다. 상기 열처리를 위한 열원으로서는 유도 가열(induction heating), 복사열, 레이저, IR, 마이크로파, 플라즈마, 표면 플라즈몬 가열 등이 이용될 수 있다.In addition, the production of the carbon nanotubes may be specifically carried out at a temperature of less than 500 ℃ 800 ℃, more specifically at 550 ℃ to 700 ℃. Within the reaction temperature range, since the weight is lowered while maintaining the bulk size of the carbon nanotubes generated while minimizing the generation of amorphous carbon, dispersibility may be further improved due to the decrease in bulk density. As a heat source for the heat treatment, induction heating, radiant heat, laser, IR, microwave, plasma, surface plasmon heating and the like can be used.
또, 상기 탄소 공급원으로는 탄소를 공급할 수 있으며, 300℃ 이상의 온도에서 기상으로 존재할 수 있는 것이라면 특별한 제한없이 사용가능하다. 구체적으로 탄소수 6 이하의 탄소계 화합물일 수 있으며, 보다 구체적으는 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, carbon may be supplied to the 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, it 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, hexane, cyclohexane, Benzene, toluene, and the like, and any one or a mixture of two or more thereof may be used.
상기와 같은 열처리에 의해 탄소 나노튜브를 성장시킨 후, 탄소 나노튜브의 배열을 보다 규칙적으로 정렬하기 위한 냉각공정이 선택적으로 더 수행될 수 있다. 상기 냉각공정은 구체적으로 열원의 제거에 따른 자연냉각 또는 냉각기 등을 이용하여 수행될 수 있다.After growing the carbon nanotubes by the heat treatment as described above, a cooling process for more regularly aligning the arrangement of the carbon nanotubes may optionally be further performed. Specifically, the cooling process may be performed using natural cooling or a cooler according to the removal of the heat source.
한편, 상기 도전재의 제조에 사용되는 담지 촉매는, 구형의 α-알루미나 지지체에에 금속 촉매가 담지된 것이다.On the other hand, the supported catalyst used for the production of the conductive material is a metal catalyst supported on a spherical α-alumina support.
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 벌크 밀도를 감소시켜 분산성을 개선할 수 있다.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 50m2/g의 BET 비표면적을 갖는 것일 수 있다. 또, 상기 α-알루미나는 표면이 매끄러워 매우 낮은 기공도, 구체적으로는 0.001 내지 0.1cm3/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 because the surface is smooth.
한편, 상기한 구형의 α-알루미나를 지지체로 포함하는 상기 담지 촉매는, 상기한 구형의 α-알루미나 지지체에 금속 촉매의 담지 후 소성함으로써 제조될 수 있다. 구체적으로는, 상기 담지 촉매는 상기한 금속 촉매의 전구체를 물 중에 용해시켜 제조한 금속 촉매 전구체 용액에, 상기 구형의 α-알루미나 지지체를 첨가하여 혼합한 후, 600℃ 이하의 온도에서 소성 시킴으로써 수행될 수 있다.On the other hand, the supported catalyst comprising the spherical α-alumina as a support may be prepared by baking the metal catalyst on the spherical α-alumina support. Specifically, the supported catalyst is carried out by adding and mixing the spherical α-alumina support to a metal catalyst precursor solution prepared by dissolving the precursor of the metal catalyst in water, followed by calcining at a temperature of 600 ° C. or lower. Can be.
상기 지지체에 담지되는 금속 촉매는 기상 탄소 공급원에 존재하는 탄소 성분들이 서로 결합하여 6원환 구조를 형성하도록 도와주는 역할을 한다. 상기 금속 촉매로는 철, 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 복합촉매는 FeCO, CoMo, CoV, FeCoMo, FeMoV, FeV 또는 FeCoMoV 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 수도 있다.The metal catalyst supported on the support serves to help the carbon components present in the gaseous carbon source combine with each other to form a six-membered ring structure. As the metal catalyst, a main catalyst such as iron, nickel or cobalt may be used alone, or the main catalyst may be used in the form of a main catalyst-catalyst complex catalyst together with a promoter such as molybdenum, vanadium or chromium. . Specifically, the complex catalyst may be FeCO, CoMo, CoV, FeCoMo, FeMoV, FeV or FeCoMoV, etc. 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, Cr 및 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)26H2O, Co2(CO)8, [Co2(CO)6(t-BuC=CH)], Cu(OAc)2, Ni(NO3)26H2O, (NH4)6Mo7O244H2O, 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, Cr, and any one or a mixture of two or more thereof. Can be used. 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 Any one or a mixture of two or more selected from the group consisting of 2 O, (NH 4 ) 6 Mo 7 O 24 4H 2 O, Mo (CO) 6 , (NH 4 ) MoS 4 and NH 4 VO 3 can be used.
상기 금속 촉매의 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/ml 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 / ml.
또, 상기 금속 촉매 전구체와 혼합되는 상기 구형의 α-알루미나 지지체의 함량을 최종 제조되는 담지 촉매에서의 지지체의 함량을 고려하여 적절히 결정될 수 있다.In addition, the content of the spherical α-alumina support mixed with the metal catalyst precursor may be appropriately determined in consideration of the content of the support in the supported catalyst to be finally prepared.
또, 탄소 나노튜브의 벌크 밀도 제어를 위해 상기 금속 촉매 전구체 용액 중에 지지체 첨가 및 혼합시 산이 선택적으로 더 사용될 수 있다. 이와 같이 산이 더 첨가될 경우 상기 금속 촉매 전구체 용액은 산 1 몰에 대해 금속 촉매 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.In addition, an acid may optionally be further used during support addition and mixing in the metal catalyst precursor solution for bulk density control of the carbon nanotubes. As such, when the acid is further added, the metal catalyst precursor solution may be used in an amount corresponding to 3 to 40 mol, more specifically, 5 to 30 mol of the metal catalyst with respect to 1 mol of the 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.
한편, 상기한 금속 촉매 전구체 용액과 상기 구형의 α-알루미나 지지체의 혼합 공정은 통상의 방법에 따라 수행될 수 있으며, 구체적으로는 45℃ 내지 80℃ 온도 하에서 회전 또는 교반에 의해 수행될 수 있다.Meanwhile, the mixing process of the metal catalyst precursor solution and the spherical α-alumina support may be performed according to a conventional method, and specifically, may be performed by rotating or stirring under a temperature of 45 ° C. to 80 ° C.
또, 상기 혼합시 최종 제조되는 담지 촉매에서 담지되는 금속 촉매의 함량을 고려하여 금속 촉매 전구체와 지지체를 혼합할 수 있다. 담지 촉매에 있어서 금속 촉매의 담지량이 증가할수록, 담지 촉매를 이용하여 제조되는 탄소 나노튜브의 벌크밀도가 증가하는 경향이 있다. 이에 따라 제조되는 탄소 나노튜브의 벌크밀도를 고려하여, 최종 제조되는 담지 촉매 총 중량에 대하여 금속 촉매가 5중량% 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 supported on the finally prepared supported catalyst. As the supported amount of the metal catalyst in the supported catalyst increases, 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 to be supported in an amount of 5% by weight to 30% by weight based on the total weight of the supported catalyst.
또, 상기 금속 촉매 전구체 용액과 상기 구형의 α-알루미나 지지체의 혼합 후, 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 1 시간 동안 회전 증발시킴으로써 수행될 수도 있다.In addition, after mixing the metal catalyst precursor solution and the spherical α-alumina support, a drying process may be optionally further performed prior to the 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 금속 촉매 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.
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 금속 촉매 전구체 및 지지체의 혼합물 중 최대 50%를 상기 α-알루미나 지지체에 함침시켜 사용하고, 상기 예비 소성 직후 잔부의 상기 혼합물을 상기 α-알루미나 지지체에 함침시켜 사용할 수 있다.At this time, in consideration of the efficiency of the reaction, up to 50% of the mixture of the metal catalyst precursor and the support is impregnated into the α-alumina support immediately before the preliminary firing, and the mixture of the remainder immediately after the preliminary firing is applied to the α- It can be used by impregnating an alumina support body.
상기와 같은 제조 공정에 의해 제조된 탄소 나노튜브에 대해 탄소 나노튜브내에 잔류하는, 금속 촉매 유래 금속불순물을 제거하기 위한 제거 공정이 선택적으로 더 수행될 수 있으며, 이때 상기 금속불순물 제거 공정은 세척, 산처리 등의 통상의 방법에 따라 수행될 수 있다.A removal process for removing metal impurities derived from the metal catalyst remaining in the carbon nanotubes may be selectively performed with respect to the carbon nanotubes prepared by the above-described manufacturing process, wherein the metal impurities removal process may include washing, It may be carried out in accordance with conventional methods such as acid treatment.
상기와 같은 제조방법에 따라 제조된 탄소 나노튜브는 번들형을 가지며, 탄소 나노튜브 단위체가 작은 가닥 직경을 갖기 때문에 전극 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 above manufacturing method has a bundle type, and since the carbon nanotube unit has a small strand diameter, it may exhibit excellent dispersibility and conductivity during electrode production. 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 상기 이차전지용 양극에 있어서, 상기 양극활물질층은 상기한 도전재의 분산성을 높이기 위하여 분산제를 포함한다.On the other hand, in the secondary battery positive electrode according to an embodiment of the present invention, the positive electrode active material layer includes a dispersant to increase the dispersibility of the conductive material.
상기 분산제는 니트릴계 고무일 수 있으며, 보다 구체적으로는 부분 또는 전체로 수소화된 니트릴부타디엔계 고무일 수 있다.The dispersant may be a nitrile rubber, and more specifically, may be a nitrile butadiene rubber hydrogenated in part or in whole.
구체적으로는 상기 수소화된 니트릴부타디엔계 고무는 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 수소화된 공액 디엔 유래 구조 단위를 20중량% 내지 80중량%로 포함하는 것일 수 있다. 상기와 같은 함량으로 포함될 때, 용매에 대한 혼화성이 증가되어 탄소 나노튜브의 분산성을 높일 수 있는 동시에 도전재 분산액의 고체 유사 특성을 증가시키고, 그 결과로서 전극 형성용 조성물의 코팅안정성을 향상시킬 수 있다. 보다 구체적으로는 상기 수소화된 공액 디엔 유래 구조 단위를 40중량% 내지 70중량%로 포함하는 것일 수 있다.Specifically, the hydrogenated nitrile butadiene-based rubber 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 hydrogenated conjugated diene derived structure with respect to the total weight of rubber. It may be to include the unit in 20% by weight to 80% by weight. When included in the content as described above, the miscibility to the solvent is increased to increase the dispersibility of the carbon nanotubes and at the same time increase the solid-like properties of the conductive material dispersion, and as a result improve the coating stability of the electrode forming composition You can. More specifically, the hydrogenated conjugated diene-derived structural unit may include 40 wt% to 70 wt%.
또, 탄소 나노튜브에 대한 분산성 향상 및 용매와의 혼화성을 고려할 때, 상기 부분 수소화된 니트릴부타디엔계 고무내 α,β-불포화 니트릴 유래 구조단위의 함량은 고무 총 중량에 대하여 10중량% 내지 50중량%, 구체적으로는 20중량% 내지 40중량%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 solvent, the content of the α, β-unsaturated nitrile-derived structural unit in the partially hydrogenated nitrile butadiene-based rubber is 10% by weight to the total weight of the rubber. It may be 50% by weight, specifically 20% to 40% 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.
고무를 구성하는 반복 단위 구조의 함량 제어에 따른 도전재 분산액의 고체 유사 특성 개선 및 이를 포함하는 전극 형성용 조성물의 코팅 안정성 개선효과를 고려할 때, 상기 수소화된 니트릴부타디엔계 고무는 고무 총 중량에 대해, 공액 디엔 유래 구조 단위 10중량% 내지 50중량%; 수소화된 공액 디엔 유래 구조 단위 20중량% 내지 80중량%; 및 α,β-불포화 니트릴 유래 구조 단위를 10중량% 내지 50중량%로 포함하는 부분 수소화된 니트릴부타디엔계 고무일 수 있다.Considering the improvement of the solid-like properties of the conductive material dispersion according to the content control of the repeating unit structure constituting the rubber and the effect of improving the coating stability of the electrode-forming composition comprising the same, the hydrogenated nitrile butadiene-based rubber is based on the total weight of the rubber 10% to 50% by weight of a structural unit derived from conjugated diene; 20% to 80% by weight of structural units derived from hydrogenated conjugated diene; And a partially hydrogenated nitrile butadiene-based rubber comprising 10 wt% to 50 wt% of α, β-unsaturated nitrile derived structural units.
본 발명에 있어서, 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 hydrogenated nitrile butadiene-based rubber is a weight ratio with respect to the entire rubber of the structural unit derived from α, β-unsaturated nitrile, and the measurement of the content is JIS K 6364 According to the mill oven method of this, the amount of nitrogen which generate | occur | produced is measured, it is the median value of the value quantified by converting the amount of its binding from the acrylonitrile molecular weight.
또, 상기 수소화된 니트릴부타디엔계 고무는 α,β-불포화 니트릴, 공액 디엔 및 선택적으로 기타 공중합 가능한 삼원단량체(termonomer)를 공중합 시킨 후, 공중합체 내 C=C 이중결합을 수소화시킴으로써 제조될 수 있다. 이때 상기 중합 반응 공정 및 수소화 공정은 통상의 방법에 따라 수행될 수 있다.In addition, the hydrogenated nitrile butadiene rubber may be prepared by copolymerizing α, β-unsaturated nitrile, conjugated diene and optionally other copolymerizable termonomers, and then hydrogenating the C = C double bond in the copolymer. . In this case, the polymerization reaction process and the hydrogenation process may be performed according to a conventional method.
상기 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 hydrogenated nitrile butadiene-based rubber include acrylonitrile or methacrylonitrile, and one or a mixture of two or more of them may be used. .
또, 상기 수소화된 니트릴부타디엔계 고무의 제조시 사용 가능한 공액 디엔으로는 구체적으로 1,3-부타디엔, 이소프렌, 2,3-메틸부타디엔 등의 탄소수 4~6의 공액 디엔을 들 수 있으며, 이들 중 어느 하나 또는 둘 이상의 혼합물이 사용될 수 있다.Moreover, the conjugated diene which can be used at the time of manufacture of the said hydrogenated nitrile butadiene type rubber specifically contains conjugated diene of 4-6 carbon atoms, such as 1, 3- butadiene, isoprene, and 2, 3-methylbutadiene, among these. Either one or a mixture of two or more 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 수소화된 니트릴부타디엔계 고무에 있어서, α,β-불포화 니트릴 유래 구조 단위, 공액 디엔 유래 구조 단위, 수소화된 공액 디엔 유래 구조 단위 및 선택적으로 기타 공중합 가능한 삼원단량체 유래 구조 단위의 함량비는 넓은 범위 내에서 다양할 수 있으며, 각 경우에 있어서 상기 구조 단위들의 총 합은 100중량%가 된다.In the hydrogenated nitrile butadiene-based rubber produced 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 terpolymer-derived structures The content ratio of units can vary within a wide range, in each case the total sum of the structural units is 100% by weight.
또, 상기 수소화된 아크릴로니트릴-부타디엔 고무(H-NBR)는 중량평균 분자량이 10,000g/mol 내지 700,000g/mol, 보다 구체적으로는 10,000g/mol 내지 300,000g/mol인 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, 탄소 나노튜브를 용매 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 hydrogenated acrylonitrile-butadiene rubber (H-NBR) may have a weight average molecular weight of 10,000g / mol to 700,000g / mol, more specifically 10,000g / mol to 300,000g / 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 range, the carbon nanotubes can be uniformly dispersed in a solvent. 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).
상기 분산제는 탄소 나노튜브 100중량부에 대하여 1중량부 내지 50중량부로 포함될 수 있다. 분산제의 함량이 1중량부 미만이면 분산액 중 탄소 나노튜브 의 균일 분산이 어렵고, 50중량부를 초과하면 분산액의 점도 증가로 가공성 저하 등의 우려가 있다. 보다 구체적으로는 10 내지 25중량부로 포함될 수 있다.The dispersant may be included in 1 to 50 parts by weight based on 100 parts by weight of carbon nanotubes. 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 10 to 25 parts by weight.
또, 본 발명의 일 실시예에 따른 이차전지용 양극에 있어서, 상기 양극활물질층은 활물질 입자들 간의 부착 및 양극활물질과 집전체와의 접착력을 향상시키기 위하여 바인더를 더 포함할 수 있다.In addition, in the positive electrode for a secondary battery according to an embodiment of the present invention, the positive electrode active material layer is A binder may be further included to improve adhesion between the active material particles and adhesion between the positive 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 양극활물질층 총 중량에 대하여 0.1 내지 30 중량%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 0.1 to 30% by weight based on the total weight of the positive electrode active material layer.
상기와 같은 구성을 갖는 본 발명의 일 실시예에 따른 이차전지용 양극은, 양극활물질, 도전재, 분산제 및 선택적으로 바인더를 용매 중에 분산시켜 제조한 양극활물질층 형성용 조성물을 양극집전체 상에 도포 및 건조 후 압연하거나, 또는 상기 양극활물질층 형성용 조성물을 별도의 지지체 상에 캐스팅한 다음, 이 지지체로부터 박리하여 얻은 필름을 집전체 상에 라미네이션하고, 압연함으로써 제조될 수 있다.A secondary battery positive electrode according to an embodiment of the present invention having the configuration as described above, the positive electrode active material layer composition prepared by dispersing a positive electrode active material, a conductive material, a dispersant and optionally a binder in a solvent is applied on the positive electrode current collector And rolling after drying or casting the composition for forming the positive electrode active material layer on a separate support, and then laminating the film obtained by peeling from the support onto a current collector and rolling.
구체적으로, 상기 양극활물질층 형성용 조성물은 탄소 나노튜브 및 분산제를 용매 중에 분산시켜 도전재 분산액을 제조한 후, 여기에 양극활물질 및 바인더, 그리고 필요한 경우 용매를 더욱 첨가하여 혼합함으로써 제조될 수 있다.Specifically, the composition for forming the positive electrode active material layer may be prepared by dispersing carbon nanotubes and a dispersant in a solvent to prepare a conductive material dispersion, and then mixing the positive electrode active material and a binder, and, if necessary, further adding a solvent. .
상기 도전재 분산액에 있어서, 상기 탄소 나노튜브 및 분산제는 앞서 설명한 바와 같다.In the conductive material dispersion, the carbon nanotubes and the dispersant are as described above.
또, 상기 도전재 분산액에 있어서, 상기 용매는 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, 헥사놀, 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 용매는 아미드계 극성 유기용매일 수 있다.In the conductive material dispersion, the solvent may be an amide polar organic solvent such as dimethylformamide (DMF), diethyl formamide, dimethyl acetamide (DMAc) or N-methyl pyrrolidone (NMP); 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, the solvent may be an amide polar organic solvent when considering the effect of improving dispersibility for the carbon nanotubes and the dispersant.
보다 구체적으로, 상기 도전재 분산액은 상기 탄소 나노튜브 100 중량부에 대하여, 상기 분산제 1 내지 50중량부, 및 상기 용매 200 내지 9900중량부를 포함할 수 있다. 상기 범위에서 탄소 나노튜브를 용매에 균일하게 분산시킬 수 있다. 보다 구체적으로는 상기 탄소 나노튜브 100중량부에 대하여 분산제 10 내지 25중량부 및 용매 4000 내지 7000중량부를 포함할 수 있다.More specifically, the conductive material dispersion may include 1 to 50 parts by weight of the dispersant, and 200 to 9900 parts by weight of the solvent based on 100 parts by weight of the carbon nanotubes. Carbon nanotubes can be uniformly dispersed in the solvent in the above range. More specifically, it may include 10 to 25 parts by weight of the dispersant and 4000 to 7000 parts by weight of the solvent based on 100 parts by weight of the carbon nanotubes.
또, 상기 탄소 나노튜브와 용매의 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, the mixing of the carbon nanotubes and the solvent, 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 용매의 혼합시, 탄소 나노튜브와 용매의 혼합성, 또는 용매 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 solvent are mixed, cavitation dispersion treatment may be performed to increase the carbon nanotubes and the solvent or the dispersibility of the carbon nanotubes in the solvent. 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 분산 처리 공정은 탄소 나노튜브의 양 및 분산제의 종류에 따라 적절히 수행될 수 있다. 구체적으로는 초음파 처리를 수행할 경우, 주파수 10kHz 내지 150kHz의 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 20MPa 내지 250MPa일 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 depending on 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 kHz to 150 kHz, 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, 용매의 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 changing the viscosity of the dispersion by evaporation of the solvent. 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 TK믹서에 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, bead mill, ball mill, basket mill, treatment 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 용매 중에 탄소 나노튜브가 균일 분산된 분산액이 제조될 수 있다.According to the preparation method as described above, a dispersion in which carbon nanotubes are uniformly dispersed in a solvent 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 2에 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 (2) Uniform dispersibility.
[수학식 2][Equation 2]
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 2에서, D10, D50 및 D90은 각각 탄소 나노튜브-분산제 복합체의 입자 크기 분포의 10%, 50% 및 90% 기준에서의 입자 크기를 의미한다)(In Equation 2, 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 size D 10, D 50 and D 90 of the composite can be measured using a laser diffraction method (laser diffraction method), more specifically, after dispersing the composite in a solvent, a 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 Can be calculated respectively.
또, 상기 도전재 분산액은 브룩필드 점도계를 이용하여 10rpm의 속도로 점도 측정시 1,000mPa·s 내지 20,000mPa·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.The conductive material dispersion may have a viscosity of 1,000 mPa · s to 20,000 mPa · s when the viscosity is measured at a speed 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.
다음으로 상기에서 제조한 도전재 분산액에 대해, 양극활물질, 바인더 및 선택적으로 용매를 첨가하고 혼합하여 양극활물질층 형성용 조성물을 제조한다.Next, with respect to the conductive material dispersion prepared above, a positive electrode active material, a binder and optionally a solvent are added and mixed to prepare a composition for forming a positive electrode active material layer.
이때 상기 양극활물질 및 바인더는 앞서 설명한 바와 같다.In this case, the cathode active material and the binder are as described above.
또, 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 양극활물질 및 바인더를 용해 또는 분산시키고, 이후 전극 제조를 위한 도포시 우수한 두께 균일도를 나타낼 수 있는 점도를 갖도록 하는 정도면 충분하다.In addition, the solvent may be a solvent generally used in the art, dimethyl sulfoxide (DMSO), isopropyl alcohol (isopropyl alcohol), N-methylpyrrolidone (NMP), acetone (acetone ) Or water, and one kind alone or a mixture of two or more kinds thereof may be used. The amount of the solvent is sufficient to dissolve or disperse the positive electrode active material and the binder in consideration of the coating thickness of the slurry, the production yield, and to have a viscosity capable of exhibiting excellent thickness uniformity during application for electrode production.
다음으로, 상기에서 제조한 양극활물질층을 양극집전체 상에 도포하고, 건조한 후 압연하거나, 또는 상기 양극활물질층 형성용 조성물을 별도의 지지체 상에 캐스팅한 다음, 이 지지체로부터 박리하여 얻은 필름을 집전체 상에 라미네이션하고, 압연함으로써 양극을 제조한다.Next, the positive electrode active material layer prepared above is coated on a positive electrode current collector, dried and rolled, or the composition for forming the positive electrode active material layer is cast on a separate support, and then the film obtained by peeling from the support is obtained. A positive electrode is manufactured by laminating and rolling on an electrical power collector.
먼저, 양극활물질층 형성용 조성물을 양극집전체 상에 도포 및 건조 후 압연하여 제조하는 경우, 상기 양극집전체로는 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 또는 부직포체 등 다양한 형태로 사용될 수 있다.First, when the composition for forming the positive electrode active material layer is coated on a positive electrode current collector, dried, and then rolled, the positive electrode current collector is not particularly limited as long as it has conductivity without causing chemical changes to the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, or a surface treated with carbon, nickel, titanium, silver or the like on the surface of aluminum or stainless steel may be used. In addition, the current collector may have a thickness of typically 3 μm to 500 μm, and may form fine irregularities on the surface of the current collector to increase 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, or a nonwoven body.
상기한 양극집전체에 대한 양극활물질층 형성용 조성물의 도포 및 건조는 통상의 방법에 따라 수행될 수 있다.Application and drying of the composition for forming a positive electrode active material layer on the positive electrode current collector may be performed according to a conventional method.
구체적으로 상기 도포 공정은 분무 코팅 또는 바 코팅 등의 코팅 방법으로 수행될 수 있다. 또, 상기 건조 공정은 자연 건조, 열풍 건조, 가열 건조 등 통상의 방법에 따라 수행될 수 있다.Specifically, the coating process may be performed by a coating method such as spray coating or bar coating. In addition, the drying process may be performed according to conventional methods such as natural drying, hot air drying, heat drying.
다만, 상기 도포 및 건조 공정시 도포 속도 및 건조 온도 등의 공정 조건은 제조되는 양극활물질층에서의 충진 밀도에 영향을 줄 수 있다.However, process conditions such as the application rate and drying temperature during the coating and drying process may affect the packing density in the cathode active material layer to be manufactured.
이에 따라 본 발명에 있어서, 상기 도포 공정은 구체적으로 양극활물질층 형성용 조성물을 5 내지 50m/min, 보다 구체적으로는 10 내지 40m/min 의 도포 속도로 수행될 수 있다. 또, 상기 건조 공정은 120 내지 150℃에서 수행될 수 있고, 보다 구체적으로는 130 내지 150℃에서 수행될 수 있다.Accordingly, in the present invention, the coating process may be specifically carried out at a coating speed of 5 to 50m / min, more specifically 10 to 40m / min composition for forming the positive electrode active material layer. In addition, the drying process may be carried out at 120 to 150 ℃, more specifically may be carried out at 130 to 150 ℃.
상기 도포 및 건조 공정시의 도포 속도 및 건조 온도 조건이 상기한 범위를 벗어날 경우, 형성되는 양극활물질층에 요구되는 충진 밀도를 이루기 어렵고, 또 용매 등을 비롯하여 물질의 잔류로 인해 부반응 발생 및 이에 따른 전지 성능 저하의 우려가 있다.If the application rate and drying temperature conditions during the application and drying process are out of the above ranges, it is difficult to achieve the required packing density in the positive electrode active material layer to be formed, and side reactions may occur due to the remaining of materials including solvents and the like. There is a risk of battery performance deterioration.
이후 건조된 양극활물질층 형성용 조성물의 도막에 대한 압연 공정이 수행된다.Thereafter, a rolling process is performed on the coating film of the dried cathode active material layer-forming composition.
상기 압연 공정은 상기한 충진 밀도를 갖도록 하는 것을 제외하고는, 통상의 방법에 따라 수행될 수 있으며, 구체적으로는 롤 상/하 간격 조절을 통해 양극 두께를 맞추어 압연하는 롤 프레스 방법에 따라 수행될 수 있다.The rolling process may be performed according to a conventional method, except to have the filling density described above. Specifically, the rolling process may be performed according to a roll press method for rolling the anode thickness by adjusting the roll up / down gap. Can be.
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.
상기 리튬 이차전지는 구체적으로 양극, 상기 양극과 대향하여 위치하는 음극, 상기 양극과 음극 사이에 개재되는 세퍼레이터 및 전해질을 포함하며, 상기 양극 및 음극 중 적어도 하나는 상기 도전재 분산액을 포함하는 전극 조성물에 의해 제조된 것일 수 있다. 또, 상기 리튬 이차전지는 상기 양극, 음극, 세퍼레이터의 전극 조립체를 수납하는 전지용기, 및 상기 전지용기를 밀봉하는 밀봉 부재를 선택적으로 더 포함할 수 있다.Specifically, the lithium secondary battery includes a positive electrode, a negative electrode positioned to face the positive electrode, a separator and an electrolyte interposed between the positive electrode and the negative electrode, and at least one of the positive electrode and the negative electrode includes the conductive material dispersion. It may be prepared by. The lithium secondary battery may further include a battery container for accommodating the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member for sealing the battery container.
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.In the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a movement path of lithium ions, and can be used without particular limitation as long as it is usually used as a separator in a lithium secondary battery. It is preferable that it is resistance and excellent in electrolyte solution moisture-wetting ability. 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 전극내 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 by 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]Example 1
N-메틸피롤리돈(NMP) 용매 97.6중량부에, 하기 표 1에 기재된 물성의 번들형 탄소 나노튜브 2중량부 및 수소화된 니트릴부타디엔계 고무(α,β-불포화 니트릴 유래 구조 단위 함량: 35중량%, 수소화된 공액 디엔 유래 구조 단위의 함량: 65중량%, 중량평균 분자량: 260,000g/mol, 다분산지수(PDI)=2.9) 1.0중량부를 첨가하고 균질혼합기(VMA LC55, Impeller/3000rpm)를 이용하여 1시간 동안 혼합하였다. 결과의 혼합물에 대해 네취 비드 밀(NETZSCH Mini-cer, 비드 크기: 1mm/3000rpm)를 이용하여 1시간 동안 순환하여 수행하여 탄소 나노튜브 분산액을 수득하였다.97.6 parts by weight of N-methylpyrrolidone (NMP) solvent, 2 parts by weight of bundled carbon nanotubes of the physical properties shown in Table 1, and a hydrogenated nitrile butadiene-based rubber (α, β-unsaturated nitrile-derived structural unit content: 35 % By weight, content of hydrogenated conjugated diene-derived structural unit: 65% by weight, weight average molecular weight: 260,000 g / mol, polydispersity index (PDI) = 2.9), and 1.0 part by weight of a homogeneous mixer (VMA LC55, Impeller / 3000 rpm) was added. Was mixed for 1 hour. The resulting mixture was circulated for 1 hour using a NETZSCH Mini-cer (bead size: 1 mm / 3000 rpm) to obtain a carbon nanotube dispersion.
상기에서 제조한 탄소 나노튜브 분산액에 양극활물질로서 LiNi0 . 8Mn0 . 1Co0 . 1O2 (D50=10㎛) 및 PVdF 바인더를 양극활물질:탄소나노튜브:바인더 = 98.1:0.4:1.5의 중량비로 혼합하여 양극 형성용 조성물(점도: 15,000mPa·s)을 제조하였다. 제조한 양극 형성용 조성물을 알루미늄 집전체에 10m/min 의 속도로 도포한 후, 130℃에서 건조 후, 타켓 충진 밀도 3.427g/cc의 조건으로 롤 프레스로 압연하여 양극을 제조하였다. 제조된 양극내 양극활물질층에서의 충진 밀도는 3.4g/cc였다.LiNi 0. As a cathode active material in the carbon nanotube dispersion prepared above . 8 Mn 0 . 1 Co 0 . 1 O 2 (D 50 = 10 μm) and PVdF binder were mixed at a weight ratio of positive electrode active material: carbon nanotube: binder = 98.1: 0.4: 1.5 to prepare a composition for forming a positive electrode (viscosity: 15,000 mPa · s). The prepared positive electrode composition was applied to an aluminum current collector at a rate of 10 m / min, dried at 130 ° C., and then rolled in a roll press under conditions of a target packing density of 3.427 g / cc to prepare a positive electrode. The packing density in the prepared positive electrode active material layer was 3.4 g / cc.
[실시예 2]Example 2
상기 실시예 1에서 양극활물질로서 D50=5㎛ 및 D50=11㎛의 서로 다른 입자 크기를 갖는 LiNi0 . 6Mn0 . 2Co0 . 2O2의 혼합물(혼합중량비=7:3)을 사용하고, 양극활물질:탄소나노튜브:바인더=97.8:0.8:1.4의 중량비로 혼합하며, 그리고 압연 공정시 타켓 충진 밀도 3.194g/cc의 조건으로 롤 프레스하는 것을 제외하고는 상기 실시예 1에서와 동일한 방법으로 실시하여 양극을 제조하였다. 제조된 양극내 양극활물질층에서의 충진 밀도는 3.1g/cc였다.LiNi 0 having different particle sizes of D 50 = 5 μm and D 50 = 11 μm as the positive electrode active material in Example 1 . 6 Mn 0 . 2 Co 0 . A mixture of 2 O 2 (mixed weight ratio = 7: 3) is used, mixed at a weight ratio of positive electrode active material: carbon nanotube: binder = 97.8: 0.8: 1.4, and a target packing density of 3.194 g / cc during the rolling process. A positive electrode was prepared in the same manner as in Example 1, except that roll pressing was performed. The packing density in the prepared cathode active material layer was 3.1 g / cc.
[실시예 3]Example 3
상기 실시예 1에서 양극활물질로서 LiCoO2(XD20A™, 유미코어사제, D50=16.5㎛, 바이모달형 입도 분포)을 사용하고, 양극활물질:탄소나노튜브:바인더=97.8:0.3:0.9의 중량비로 혼합하며, 그리고 압연 공정시 타켓 충진 밀도 4.1g/cc의 조건으로 롤 프레스하는 것을 제외하고는 상기 실시예 1에서와 동일한 방법으로 실시하여 양극을 제조하였다. 제조된 양극내 양극활물질층에서의 충진 밀도는 4.1g/cc였다.In Example 1, LiCoO 2 (XD20A ™, manufactured by Yumi Core, D 50 = 16.5 μm, bimodal particle size distribution) was used as the positive electrode active material, and a positive electrode active material: carbon nanotube: binder = 97.8: 0.3: 0.9 The positive electrode was manufactured in the same manner as in Example 1, except that the mixture was mixed with and roll-pressed at a target filling density of 4.1 g / cc during the rolling process. The packing density in the prepared anode active material layer was 4.1 g / cc.
[비교예 1]Comparative Example 1
상기 실시예 1에서 탄소 나노튜브 대신에 카본블랙을 사용하고, 양극활물질:카본블랙:바인더=96.7:1.6:1.7의 중량비로 혼합하여 사용하며, 그리고 공정시 타켓 충진 밀도 3.488g/cc의 조건으로 롤 프레스하는 것을 제외하고는 것을 제외하고는 상기 실시예 1에서와 동일한 방법으로 실시하여 양극을 제조하였다. 제조된 양극내 양극활물질층에서의 충진 밀도는 3.4g/cc였다.Carbon black is used instead of carbon nanotubes in Example 1, and a mixture of positive electrode active material: carbon black: binder = 96.7: 1.6: 1.7 is used, and the target packing density is 3.488 g / cc. A positive electrode was manufactured in the same manner as in Example 1, except that the roll press was carried out. The packing density in the prepared positive electrode active material layer was 3.4 g / cc.
[비교예 2]Comparative Example 2
상기 실시예 1에서 탄소 나노튜브 대신에 카본블랙을 사용하고, 양극활물질:카본블랙:바인더=95:3:2의 중량비로 혼합하여 사용하는 것을 제외하고는 상기 실시예 2에서와 동일한 방법으로 실시하여 양극을 제조하였다. 제조된 양극내 양극활물질층에서의 충진 밀도는 3.1g/cc였다.Carbon black instead of carbon nanotubes in Example 1, and the mixture is carried out in the same manner as in Example 2 except for using a mixture of the positive electrode active material: carbon black: binder = 95: 3: 2: To prepare a positive electrode. The packing density in the prepared cathode active material layer was 3.1 g / cc.
[비교예 3]Comparative Example 3
상기 실시예 1에서 탄소 나노튜브 대신에 하기 기재된 물성의 탄소 나노튜브를 사용하는 것을 제외하고는 상기 실시예 1에서와 동일한 방법으로 실시하여 양극을 제조하였다.Except for using carbon nanotubes of the physical properties described below instead of the carbon nanotubes in Example 1 was carried out in the same manner as in Example 1 to prepare a positive electrode.
[실험예 1]Experimental Example 1
상기 실시예 1 및 비교예 3에서 사용한 탄소 나노튜브(CNT)에 대하여 하기와 같은 방법으로, CNT의 2차 구조 형상, CNT 단위체의 평균 직경, 결정화도, 순도 및 BET 비표면적을 각각 측정하고, 그 결과를 하기 표 1에 나타내었다.With respect to the carbon nanotubes (CNT) used in Example 1 and Comparative Example 3, the secondary structure shape of the CNT, the average diameter of the CNT unit, the crystallinity, the purity and the BET specific surface area were respectively measured, and The results are shown in Table 1 below.
1) CNT의 2차 구조 형상 및 입도: 주사전자 현미경을 이용하여 탄소 나노튜브의 입도 및 2차 구조의 형상을 관찰하였다.1) Secondary structure shape and particle size of CNT: The particle size and shape of the secondary structure of the carbon nanotubes were observed using a scanning electron microscope.
2) CNT 단위체의 평균 직경: SEM 및 BET를 이용하여 측정하였다.2) Average diameter of CNT unit: measured using SEM and BET.
3) 결정화도(IG/ID비): 514.5nm 파장의 레이저를 이용한 라만 분광 분석법에 의해 얻어진 1575nm 내지 1600nm에서의 G 밴드의 최대 피크 강도(IG)에 대한 1340nm 내지 1360nm에서의 D 밴드의 최대 피크 강도(ID)의 비(ID/IG)로부터 평균값 및 표준편차를 구하였다.3) Crystallinity (IG / ID ratio): Maximum peak intensity of D band at 1340 nm to 1360 nm to maximum peak intensity (IG) of G band at 1575 nm to 1600 nm obtained by Raman spectroscopy using a laser of 514.5 nm wavelength. The average value and standard deviation were calculated from the ratio (ID / IG) of (ID).
4) 순도: 에쉬 테스트(ash test)에 의해 탄소 나노튜브의 순도를 측정하였다.4) Purity: The purity of the carbon nanotubes was measured by ash test.
5) BET 비표면적: BEL Japan 사 BELSORP-mino II를 이용하여 액체 질소 온도 하(77K)에서의 질소가스 흡착량으로부터 산출하였다.5) BET specific surface area: BELSORP-mino II, manufactured by BEL Japan, was calculated from the amount of nitrogen gas adsorption under liquid nitrogen temperature (77K).
실시예 1Example 1 비교예 3Comparative Example 3
CNT 2차구조 형상CNT secondary structure shape 번들형 Bundled 번들형Bundled
CNT 단위체의 평균 직경(nm)Average diameter of CNT monomer (nm) 88 2020
결정화도(IG/ID 비)Crystallinity (IG / ID Ratio) 평균Average 0.950.95 0.720.72
표준편차(%)Standard Deviation(%) 1.641.64 2.122.12
순도(wt%)Purity (wt%) 100100 99.599.5
BET 비표면적(m2/g)BET specific surface area (m 2 / g) 249249 245245
[[ 실험예Experimental Example 2] 2]
상기 실시예 1 및 비교예 3에서 사용한 CNT에 대해, ICP-OEB(Optima-7300)를 사용하여 ICP 분석을 통한 금속원소 함량 분석을 수행하였다.For CNTs used in Example 1 and Comparative Example 3, ICP-OEB (Optima-7300) was used to analyze the metal element content through ICP analysis.
상세하게는 실시예 1 및 비교예 3에서 사용한 CNT를 각각 포함하는 시료를 약 0.5g 바이알에 정확히 측정하여 넣었다. 시료가 담긴 바이알에 진한 황산 2ml를 넣었다. 시료를 핫 플레이트에서 가열하여 탄화시킨 후 건조하였다. 염산 3ml/질산 1ml/과산화수소 1방울을 탄화된 시료에 가하여 분해시켰다. 시료가 완전히 분해되면 1000mg/kg 내부 표준물 200㎕를 넣고 초순수 20ml로 희석하였다. ICP-OEB로 분석하였다. 그 결과를 하기 표 2에 나타내었다.In detail, each sample containing CNTs used in Example 1 and Comparative Example 3 was accurately measured in about 0.5 g vials. 2 ml of concentrated sulfuric acid was added to the vial containing the sample. Samples were heated on a hot plate, carbonized and dried. 3 ml of hydrochloric acid / 1 ml of nitric acid / one drop of hydrogen peroxide were added to the carbonized sample to decompose. When the sample was completely digested, 200 μl of 1000 mg / kg internal standard was added and diluted with 20 ml of ultrapure water. Analysis by ICP-OEB. The results are shown in Table 2 below.
실시예 1Example 1 비교예3Comparative Example 3
금속함량(단위: mg/kg)Metal content (unit: mg / kg) AlAl -- --
CoCo <10<10 --
FeFe -- 500500
MoMo -- --
NiNi -- 260260
VV <1<1 --
[실험예 3] Experimental Example 3
상기 실시예 1 및 비교예 1에서 제조한 양극에 대해 전해액 젖음 실험을 실시하였다.Electrolyte wetting experiments were performed for the positive electrodes prepared in Example 1 and Comparative Example 1.
상세하게는, 빛이 있는 공간에 상기 실시예 1 및 비교예 1에서 제조한 양극을 각각 수평이 되도록 평판 플레이트 위에 올려놓고 접착 테이프로 고정하였다. 주사기에 프로필렌 카보네이트 용매 또는 해당 전해액을 내부에 기포가 생기지 않도록 10㎕ 누금까지 채워 넣었다. 프로필렌 카보네이트 혹은 전해액이 채워진 주사기를 고정용 스탠드에 수직으로 고정시키고, 플레이트에 고정된 시료 중앙부에 위치시켰다. 주사기 눈금을 확인하여 1㎕ 양 만큼 밀어내고 주사기 노즐 끝에 프로필렌 카보네이트 용매 또는 전해액이 맺혀 있는지 육안으로 확인하였다.In detail, the anodes prepared in Example 1 and Comparative Example 1 were placed on a flat plate so as to be horizontal, respectively, in a space with light and fixed with an adhesive tape. The syringe was filled with propylene carbonate solvent or the corresponding electrolyte solution up to 10 μl so as not to bubble inside. A syringe filled with propylene carbonate or electrolyte was fixed perpendicularly to the fixed stand and placed in the center of the sample fixed to the plate. The syringe scale was checked and pushed out by an amount of 1 μl, and it was visually checked whether a propylene carbonate solvent or electrolyte was formed at the end of the syringe nozzle.
시간 측정용 스탑워치(stop-watch)의 영점을 맞춘 후, 주사기 고정용 스탠드의 높이 조절기를 이용하여 주사기 노즐 끝에 맺힌 PC용매 또는 전해액이 시료 표면까 닿을 때까지 주사기를 천천히 하강시켰다. PC 용매 또는 전해액이 시료 표면에 닿는 즉시 스탑워치를 이용하여 측정을 시작하였다. 주사기 고정용 스탠드의 높이 조절기를 이용하여 주사기를 시료에서 30mm 이상 상승시켰다. 외부 환경과의 차단을 위해 시료를 투명 샬레 뚜껑으로 덮어 두었다. 짙은 명암을 가진 부분(PC 용매 및 전해액의 함침 영역)이 완전히 없어지는 시간을 확인하여 기록하였다.After zeroing the stop-watch for time measurement, the syringe was lowered slowly until the PC solvent or electrolyte formed on the tip of the syringe nozzle reached the sample surface using the height adjuster of the syringe holding stand. As soon as the PC solvent or electrolyte reached the sample surface, the measurement was started using the stopwatch. The syringe was lifted at least 30 mm from the sample using the height adjuster of the syringe holding stand. Samples were covered with a transparent chalet lid for isolation from the external environment. The time when the dark contrast part (impregnation area of PC solvent and electrolyte solution) disappears completely was recorded and confirmed.
추가적으로, 상기 실시예 1 및 비교예 1에서 제조한 양극에 대해, 양극 제조에 사용된 재료의 진밀도와 전극의 두께/무게를 이용하여 충진 밀도를 계산하였다.In addition, for the positive electrode prepared in Example 1 and Comparative Example 1, the packing density was calculated using the true density of the material used in the positive electrode production and the thickness / weight of the electrode.
그 결과를 하기 표 3에 나타내었다.The results are shown in Table 3 below.
비교예 1Comparative Example 1 실시예 1Example 1
충진 밀도(g/cc)Fill density (g / cc) 3.43.4 3.43.4
프로필렌카보네이트 젖음 시간(sec)Propylene Carbonate Wetting Time (sec) 271271 9494
추가적으로 실시예 2 및 비교예 2에서 제조한 양극에 대해서도 상기와 동일한 방법으로 실시하여 충진 밀도 및 프로필렌카보네이트 젖음 시간을 측정하였다. 그 결과를 하기 표 4에 나타내었다.In addition, the positive electrode prepared in Example 2 and Comparative Example 2 was carried out in the same manner as described above to determine the filling density and propylene carbonate wetting time. The results are shown in Table 4 below.
비교예 2Comparative Example 2 실시예 2Example 2
충진 밀도(g/cc)Fill density (g / cc) 3.13.1 3.13.1
프로필렌카보네이트 젖음 시간(sec)Propylene Carbonate Wetting Time (sec) 687687 149149
[실험예 4] Experimental Example 4
상기 실시예 2 및 비교예 2에서 제조한 양극에 대해 수은 압입법을 이용하여 기공 크기 분포를 측정하였다. 각 전극내 활물질층에서의 평균 기공 직경(P)는 하기 수학식 1에 따라 결정하였다. 그 결과를 각 전극의 양극활물질층에서의 충진 밀도와 함께 하기 표 5 및 도 3에 각각 나타내었다.Pore size distribution was measured for the cathodes prepared in Example 2 and Comparative Example 2 using a mercury intrusion method. The average pore diameter P in each active material layer in each electrode was determined according to the following equation. The results are shown in Table 5 and FIG. 3 together with the packing density in the cathode active material layer of each electrode.
[수학식 1][Equation 1]
평균 기공 직경(P)(㎛)=4V/AAverage Pore Diameter (P) (μm) = 4V / A
(상기 수학식 1에서, V는 기공 부피이고, A는 기공 면적이다)(In Equation 1, V is the pore volume, A is the pore area)
비교예 2Comparative Example 2 실시예 2Example 2
충진 밀도Filling density 3.1 g/cc3.1 g / cc 3.1 g/cc3.1 g / cc
부피 기준 중간 기공 직경Medium pore diameter by volume 0.15964㎛0.15964 μm 0.28705㎛0.28705㎛
표면적 기준 중간 기공 직경Mesopore diameter 0.04463㎛0.04463 μm 0.09059㎛0.09059 μm
평균 기공 직경(P)Average pore diameter (P) 0.09681㎛0.09681 μm 0.17114㎛0.17114 μm
측정결과, 실시예 2의 양극활물질층은 비교예 2에 비해 현저히 큰 평균 기공 직경을 나타내었다.As a result, the positive electrode active material layer of Example 2 showed a significantly larger average pore diameter than that of Comparative Example 2.
또, 도 3에 나타난 바와 같이 비교예 2의 양극활물질층에서의 기공 직경의 최대 피크(최대 기공 크기)는 166.6nm인 반면, 실시예 2의 양극활물질층에서의 최대 피크(최대 기공 크기)는 311.1nm로 증가하였으며, 전체적인 그래프 계형도 포어가 커지는 쪽으로 이동되었다.In addition, as shown in FIG. 3, the maximum peak (maximum pore size) of the pore diameter in the positive electrode active material layer of Comparative Example 2 is 166.6 nm, whereas the maximum peak (maximum pore size) in the positive electrode active material layer of Example 2 is It increased to 311.1 nm, and the overall graph hierarchy was also shifted towards larger pores.
이 같은 결과로부터, 고충진 밀도 하에서도 본 발명에 따른 양극활물질층에서 보다 개선된 기공 구조가 형성됨을 확인할 수 있다.From these results, it can be seen that the improved pore structure is formed in the positive electrode active material layer according to the present invention even under high packing density.
[제조예 : 리튬 이차전지의 제조]  Preparation Example: Fabrication of Lithium Secondary Battery
상기 실시예 1 및 2에서 제조한 양극을 이용하여 리튬 이차전지를 제조하였다. A lithium secondary battery was manufactured using the positive electrodes prepared in Examples 1 and 2.
상세하게는, 음극활물질로서 흑연, 카본블랙 도전재, 스티렌부타디엔 고무(SBR) 바인더 및 카르복시메틸셀룰로오스(CMC) 증점제를 물 중에서 97:1:1:1의 중량비로 혼합하여 음극 형성용 조성물을 제조하고, 이를 구리 집전체에 도포하여 음극을 제조하였다.Specifically, graphite, a carbon black conductive material, a styrene butadiene rubber (SBR) binder and a carboxymethyl cellulose (CMC) thickener are mixed in water at a weight ratio of 97: 1: 1: 1 as a negative electrode active material to prepare a composition for forming a negative electrode. Then, this was applied to a copper current collector to prepare a negative electrode.
상기 실시예 1, 2 및 비교예 1, 2에서 제조한 양극과 음극 사이에 다공성 폴리에틸렌의 세퍼레이터를 개재하여 전극 조립체를 제조하고, 상기 전극 조립체를 케이스 내부에 위치시킨 후, 케이스 내부로 전해액을 주입하여 리튬 이차 전지를 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 is manufactured by interposing a separator of porous polyethylene between the positive electrode and the negative electrode prepared in Examples 1 and 2 and Comparative Examples 1 and 2, the electrode assembly is placed in a case, and an electrolyte is injected into the case. To produce 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 (mixing volume ratio of EC / DMC / EMC = 3/4/3). It was.
상기 비교예 1 내지 4에서 제조한 양극에 대해서도 상기와 동일한 방법으로 실시하여 리튬 이차전지를 제조하였다.A lithium secondary battery was manufactured by the same method as described above with respect to the positive electrode prepared in Comparative Examples 1 to 4.
[실험예 5]Experimental Example 5
상기 실시예 2 및 비교예 2의 탄소 나노튜브 분산액을 각각 이용하여 제조한 양극(실시예 2 및 비교예 3, 4)을 이용하여 동일한 용량의 모노셀(mono-cell)을 제작하고, 25℃에서 SOC 50%를 기준으로 150A로 10초간 방전시 저항을 각각 측정하였다(cut off 전압: 1.9V). 그 결과를 도 4에 나타내었다.Mono-cells having the same capacity were prepared using positive electrodes (Examples 2 and 3 and 4) prepared using the carbon nanotube dispersions of Examples 2 and Comparative Examples 2, respectively, and 25 ° C. The resistance was measured for 10 seconds at 150A based on 50% SOC at cut off voltage of 1.9V. The results are shown in FIG.
실험결과, 실시예 2에서 제조한 양극을 포함하는 전지는 비교예 2에서 제조한 양극을 포함하는 전지에 비해 낮은 저항 특성을 나타내어, 보다 우수한 출력 특성을 나타냄을 예상할 수 있다.As a result of the experiment, the battery including the positive electrode prepared in Example 2 exhibits a lower resistance than the battery containing the positive electrode prepared in Comparative Example 2, it can be expected to exhibit a better output characteristics.
[실험예 6]Experimental Example 6
상기 실시예 2 및 비교예 2에서의 리튬 이차전지에 대해 고온(45℃)에서 2.7V 내지 3.8V 구동전압 범위내에서 1C/1C의 조건으로 300회 사이클 충방전을 실시하였다. 고온에서의 충방전 300사이클째의 방전용량의 비율인 사이클 용량유지율(capacity retention)을 각각 측정하였다. 그 결과를 하기 도 5에 나타내었다.The lithium secondary batteries of Example 2 and Comparative Example 2 were charged and discharged 300 times under conditions of 1C / 1C at a high temperature (45 ° C) within a 2.7V to 3.8V driving voltage range. Cycle capacity retention, which is the ratio of the discharge capacity at the 300th cycle of charge / discharge, was measured. The results are shown in FIG. 5.
실험결과, 실시예 2에서 제조한 양극을 포함하는 전지는 비교예 2와 비교하여 동등 수준의 수명 특성을 나타내었다. As a result, the battery including the positive electrode prepared in Example 2 showed an equivalent level of life characteristics compared to Comparative Example 2.

Claims (19)

  1. 양극활물질, 도전재 및 분산제를 포함하는 양극활물질층을 포함하고,Comprising a positive electrode active material layer containing a positive electrode active material, a conductive material and a dispersant,
    상기 도전재는 탄소 나노튜브 단위체의 평균 가닥직경이 15nm 이하인 번들형(bundle-type) 탄소 나노튜브를 포함하며,The conductive material includes bundle-type carbon nanotubes having an average strand diameter of carbon nanotube units of 15 nm or less,
    상기 탄소 나노튜브는 532nm 파장의 레이저를 이용한 라만 분광 분석법에 의해 얻어진 1580±50cm-1 에서의 G 밴드의 최대 피크 강도(IG)에 대한 1360±50cm-1 에서의 D 밴드의 최대 피크 강도(ID)의 비(ID/IG)의 평균값이 0.7 내지 1.7이고, 표준편차값이 1.3 내지 2.0%인 것이고,The carbon nanotubes have a maximum peak intensity (ID) of D band at 1360 ± 50 cm −1 to a maximum peak intensity (IG) of 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) is 0.7 to 1.7, and the standard deviation is 1.3 to 2.0%,
    상기 양극활물질층은 3.0g/cc 이상의 충진 밀도를 가지고, 상기 충진 밀도에서 수은 압입법에 따른 기공 크기 분포 측정시 하기 수학식 1에 따른 평균 기공 직경이 0.1㎛ 내지 0.5㎛인 것인 이차전지용 양극.The cathode active material layer has a packing density of 3.0 g / cc or more, and when the pore size distribution is measured by mercury intrusion at the packing density, the average pore diameter according to Equation 1 is 0.1 μm to 0.5 μm. .
    [수학식 1][Equation 1]
    평균 기공 직경(P)=4V/AAverage pore diameter (P) = 4V / A
    (상기 수학식 1에서, V는 기공 부피이고, A는 기공 면적이다)(In Equation 1, V is the pore volume, A is the pore area)
  2. 제1항에 있어서,The method of claim 1,
    상기 양극활물질은 리튬 니켈망간코발트계 산화물을 포함하고,The positive electrode active material includes a lithium nickel manganese cobalt-based oxide,
    상기 양극활물질층은 3.1g/cc 내지 3.6g/cc의 충진 밀도를 가지고, 상기 충진 밀도에서 상기 수학식 1에 따른 평균 기공 직경이 0.1㎛ 내지 0.3㎛인 것인 이차전지용 양극.The cathode active material layer has a filling density of 3.1 g / cc to 3.6 g / cc, and the average pore diameter according to Equation 1 in the filling density is 0.1 μm to 0.3 μm.
  3. 제1항에 있어서,The method of claim 1,
    상기 양극활물질은 리튬 코발트계 산화물을 포함하고,The positive electrode active material includes a lithium cobalt oxide,
    상기 양극활물질층은 3.9g/cc 내지 4.3g/cc의 충진 밀도를 가지고, 상기 충진 밀도에서 상기 수학식 1에 따른 평균 기공 직경이 0.1㎛ 내지 0.3㎛인 것인 이차전지용 양극.The cathode active material layer has a filling density of 3.9g / cc to 4.3g / cc, the average pore diameter according to the formula (1) in the filling density is 0.1 ㎛ to 0.3 ㎛.
  4. 제1항에 있어서,The method of claim 1,
    상기 양극활물질층은 3.0g/cc 이상의 충진 밀도에서 수은 압입법으로 측정하였을 때, 250nm 내지 330nm의 기공 직경 범위에서 최대 피크를 나타내는 것인 이차전지용 양극.The positive electrode active material layer is a secondary battery positive electrode that shows a maximum peak in the pore diameter range of 250nm to 330nm when measured by mercury intrusion at a packing density of 3.0g / cc or more.
  5. 제1항에 있어서,The method of claim 1,
    상기 탄소 나노튜브는 200m2/g 내지 330m2/g의 비표면적을 갖는 것인 이차전지용 양극.The CNT anode is a secondary battery having a specific surface area of 200m 2 / g to 330m 2 / g.
  6. 제1항에 있어서,The method of claim 1,
    상기 탄소 나노튜브는 Fe, Ni 및 Mo를 포함하는 금속원소를 총 합계량으로 3mg/kg 이하로 포함하는 것인 이차전지용 양극.Wherein the carbon nanotubes, the positive electrode for secondary batteries comprising a total amount of metal elements including Fe, Ni and Mo in 3mg / kg or less.
  7. 제1항에 있어서,The method of claim 1,
    상기 분산제는 수소화된 니트릴부타디엔계 고무를 포함하는 것인 이차전지용 양극.The dispersant is a positive electrode for a secondary battery comprising a hydrogenated nitrile butadiene rubber.
  8. 제1항에 있어서,The method of claim 1,
    상기 분산제는 고무 총 중량에 대하여 α,β-불포화 니트릴 유래 구조 단위를 10중량% 내지 50중량%로 포함하는 수소화된 니트릴부타디엔계 고무를 포함하는 것인 이차전지용 양극.The dispersant is a positive electrode for secondary batteries comprising a hydrogenated nitrile butadiene-based rubber containing 10 to 50% by weight of the α, β-unsaturated nitrile-based structural unit relative to the total weight of the rubber.
  9. 제1항에 있어서,The method of claim 1,
    상기 분산제는 고무 총 중량에 대하여 수소화된 공액 디엔 유래 구조 단위를 20중량% 내지 80중량%로 포함하는 수소화된 니트릴부타디엔계 고무를 포함하는 것인 이차전지용 양극.Wherein the dispersant is a positive electrode for a secondary battery comprising a hydrogenated nitrile butadiene-based rubber containing 20 to 80% by weight of the hydrogenated conjugated diene-based structural unit relative to the total weight of the rubber.
  10. 제1항에 있어서,The method of claim 1,
    상기 분산제는 공액 디엔 유래 구조 단위 10중량% 내지 50중량%; 수소화된 공액 디엔 유래 구조 단위 20중량% 내지 80중량%; 및 α,β-불포화 니트릴 유래 구조 단위 10중량% 내지 50중량%를 포함하는 부분 수소화된 니트릴부타디엔계 고무를 포함하는 것인 이차전지용 양극.The dispersing agent is 10 to 50% by weight of the structural unit derived from conjugated diene; 20% to 80% by weight of structural units derived from hydrogenated conjugated diene; And a partially hydrogenated nitrile butadiene-based rubber comprising 10 wt% to 50 wt% of α, β-unsaturated nitrile-based structural units.
  11. 제1항에 있어서,The method of claim 1,
    상기 분산제는 중량평균 분자량이 10,000g/mol 내지 700,000g/mol이고 다분산 지수가 2.0 내지 6.0의 범위인 수소화된 아크릴로니트릴-부타디엔 고무를 포함하는 것인 이차전지용 양극.The dispersant positive electrode for secondary batteries comprising a hydrogenated acrylonitrile-butadiene rubber having a weight average molecular weight of 10,000 g / mol to 700,000 g / mol and a polydispersity index of 2.0 to 6.0.
  12. 제1항에 있어서,The method of claim 1,
    상기 분산제는 탄소 나노튜브 100중량부에 대하여 1중량부 내지 50중량부로 포함되는 것인 이차전지용 양극.The dispersant is a positive electrode for a secondary battery 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 양극활물질은 코발트, 망간, 니켈 및 알루미늄으로 이루어진 군에서 선택되는 적어도 1종의 금속과 리튬을 포함하는 리튬 복합금속 산화물을 포함하는 것인 이차전지용 양극.The positive electrode active material is a positive electrode for a secondary battery comprising a lithium composite metal oxide containing at least one metal and lithium selected from the group consisting of cobalt, manganese, nickel and aluminum.
  14. 제13항에 있어서,The method of claim 13,
    상기 리튬 복합금속 산화물은 Al, Cu, Fe, V, Cr, Ti, Zr, Zn, Ta, Nb, Mg, B, W 및 Mo로 이루어지는 군으로부터 선택되는 어느 하나 또는 둘 이상의 원소에 의해 도핑된 것인 이차전지용 양극.The lithium composite metal oxide is doped with any one or two or more elements selected from the group consisting of Al, Cu, Fe, V, Cr, Ti, Zr, Zn, Ta, Nb, Mg, B, W and Mo. Positive electrode for secondary batteries.
  15. 제1항에 있어서,The method of claim 1,
    상기 양극활물질은 2㎛ 내지 30㎛의 평균 입경(D50)을 갖는 것인 이차전지용 양극.The cathode active material is a secondary battery positive electrode having an average particle diameter (D 50 ) of 2 ㎛ to 30 ㎛.
  16. 제1항에 있어서,The method of claim 1,
    상기 양극활물질은 서로 다른 평균 입경을 갖는 둘 이상의 양극활물질의 혼합물인 것인 이차전지용 양극.The cathode active material is a secondary battery positive electrode that is a mixture of two or more cathode active materials having different average particle diameters.
  17. 제1항에 있어서,The method of claim 1,
    상기 양극활물질은 평균 입경(D50)이 2㎛ 내지 10㎛인 제1 양극활물질과, 10㎛ 초과 30㎛ 이하인 제2 양극활물질과의 혼합물을 포함하는 것인 이차전지용 양극.The cathode active material includes a mixture of a first cathode active material having an average particle diameter (D 50 ) of 2 μm to 10 μm and a second cathode active material of more than 10 μm and 30 μm or less.
  18. 제1항에 있어서,The method of claim 1,
    상기 양극활물질은 바이모달형(bimodal type) 입도 분포를 갖는 것인 이차전지용 양극.The cathode active material is a secondary battery positive electrode having a bimodal type particle size distribution.
  19. 제1항 내지 제18항 중 어느 한 항에 따른 양극을 포함하는 리튬 이차전지.A lithium secondary battery comprising the positive electrode according to any one of claims 1 to 18.
PCT/KR2016/014352 2015-12-10 2016-12-08 Cathode for secondary battery and secondary battery comprising same WO2017099481A1 (en)

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US15/747,367 US11171322B2 (en) 2015-12-10 2016-12-08 Positive electrode having improved pore structure in positive electrode active material layer
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