WO2016018023A1 - Graphite secondary particle, and lithium secondary battery comprising same - Google Patents

Graphite secondary particle, and lithium secondary battery comprising same Download PDF

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Publication number
WO2016018023A1
WO2016018023A1 PCT/KR2015/007820 KR2015007820W WO2016018023A1 WO 2016018023 A1 WO2016018023 A1 WO 2016018023A1 KR 2015007820 W KR2015007820 W KR 2015007820W WO 2016018023 A1 WO2016018023 A1 WO 2016018023A1
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Prior art keywords
primary particles
graphite
negative electrode
active material
particles
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PCT/KR2015/007820
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French (fr)
Korean (ko)
Inventor
송준혁
김은경
정동섭
우상욱
김예리
정주호
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주식회사 엘지화학
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Priority claimed from KR1020150105325A external-priority patent/KR101685832B1/en
Application filed by 주식회사 엘지화학 filed Critical 주식회사 엘지화학
Priority to CN201580002768.5A priority Critical patent/CN105794027B/en
Priority to JP2017500385A priority patent/JP6464252B2/en
Priority to EP15827495.1A priority patent/EP3054509B1/en
Priority to US15/035,635 priority patent/US10361426B2/en
Publication of WO2016018023A1 publication Critical patent/WO2016018023A1/en

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    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00Carbon; Compounds thereof
    • C01B32/20Graphite
    • C01B32/21After-treatment
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/05Accumulators with non-aqueous electrolyte
    • H01M10/052Li-accumulators
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00Carbon; Compounds thereof
    • C01B32/20Graphite
    • C01B32/205Preparation
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/13Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/36Selection of substances as active materials, active masses, active liquids
    • H01M4/58Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10Energy storage using batteries

Definitions

  • the present invention is a graphite secondary particles capable of high density of natural graphite primary particles having a high capacity output characteristics and artificial graphite primary particles having excellent cycle characteristics and swelling characteristics are excellent in the rolling property, which is aggregated, bonded or granulated, It relates to a negative electrode used as a negative electrode active material and a lithium secondary battery comprising the negative electrode.
  • lithium secondary batteries having high energy density and voltage, long cycle life, and low self discharge rate have been commercially used.
  • a lithium secondary battery includes a positive electrode including a positive electrode active material capable of inserting / desorbing lithium ions, a negative electrode containing a negative electrode active material capable of inserting / removing lithium ions, and a microporous separator interposed between the positive electrode and the negative electrode. It means a battery that contains a non-aqueous electrolyte containing lithium ions in the electrode assembly.
  • Examples of the positive electrode active material of a lithium secondary battery include transition metal oxides such as lithium cobalt oxide (LiCoO 2 ), lithium-manganese oxide (LiMn 2 O 4 ), or lithium-nickel oxide (LiNiO 2 ), and some of these transition metals are different. Composite oxides substituted with transition metals are used.
  • transition metal oxides such as lithium cobalt oxide (LiCoO 2 ), lithium-manganese oxide (LiMn 2 O 4 ), or lithium-nickel oxide (LiNiO 2 ), and some of these transition metals are different.
  • Composite oxides substituted with transition metals are used.
  • Lithium metal is used as the negative electrode active material, but when lithium metal is used, there is a risk of explosion due to battery short circuit due to dendrite formation, and recently, it has been replaced with a carbon-based material instead of lithium metal.
  • crystalline carbon such as natural graphite and artificial graphite
  • amorphous carbon such as soft carbon and hard carbon
  • Amorphous carbon has an advantage of large capacity, but has a disadvantage of large irreversibility in the charging and discharging process.
  • Natural graphite which is a representative crystalline carbon, has a low cost and excellent initial capacity and a relatively high theoretical limit capacity. However, since it has a plate shape, when it is manufactured as a pole plate, it is compressed and oriented flat on the current collector, so that impregnation of the electrolyte is not easy. Its high rate of charge and discharge characteristics is low, the service life is severely degraded, and cycle capacity is low.
  • the inventors of the present invention while researching a negative electrode active material having excellent rolling property, high density, high rate charge / discharge characteristics, cycle characteristics, and swelling characteristics, are coated with amorphous carbonaceous primary particles and
  • the present invention is made by preparing graphite secondary particles prepared by aggregating, bonding, or granulating artificial graphite primary particles, and confirming that a lithium secondary battery using the same as an anode active material exhibits excellent high rate charge / discharge characteristics, cycle characteristics, and swelling characteristics.
  • the present invention is made by preparing graphite secondary particles prepared by aggregating, bonding, or granulating artificial graphite primary particles, and confirming that a lithium secondary battery using the same as an anode active material exhibits excellent high rate charge / discharge characteristics, cycle characteristics, and swelling characteristics.
  • An object of the present invention is the natural graphite primary particles coated with amorphous carbon material having high capacity and excellent output characteristics, and the artificial graphite primary particles excellent in cycle characteristics and swelling characteristics are excellent in the rolling property in which the aggregated, bonded or granulated It is to provide a graphite secondary particle capable of densification.
  • Another object of the present invention is to provide a negative electrode for a lithium secondary battery, wherein the negative electrode active material slurry containing the graphite secondary particles is coated on a current collector.
  • Still another object of the present invention is to provide a lithium secondary battery having excellent high rate charge / discharge characteristics, cycle characteristics, and swelling characteristics, including the negative electrode, the positive electrode, and a separator and an electrolyte interposed between the negative electrode and the positive electrode.
  • the present invention is natural graphite primary particles coated with an amorphous carbon material; And a form in which artificial graphite primary particles are aggregated, bonded, or granulated, and the crystallites in the a-axis direction by powder state X-ray diffraction analysis of the natural graphite primary particles are 45 nm to 55 nm, and the c-axis direction
  • the crystallite has a size of 25 nm to 35 nm, the crystallite size in the a-axis direction of the artificial graphite primary particles is 35 nm to 45 nm, the crystallite size in the c-axis direction is 15 nm to 30 nm
  • Graphite secondary particles are provided.
  • the present invention provides a negative electrode for a secondary battery in which the negative electrode active material slurry for a lithium secondary battery including the graphite secondary particles is coated on a current collector.
  • the present invention provides a lithium secondary battery including the separator and the electrolyte interposed between the negative electrode and the positive electrode, the negative electrode and the positive electrode for the secondary battery.
  • Graphite secondary particles according to the present invention is a natural graphite primary particles exhibiting high capacity and high output characteristics but relatively low cycle characteristics and swelling characteristics, and artificial cycles exhibiting high cycle characteristics and swelling characteristics but relatively low capacity characteristics.
  • the graphite primary particles are aggregated, bonded or granulated, not only the high capacity and high output characteristics of the natural graphite primary particles can be exhibited, but also the high cycle characteristics and swelling characteristics of the artificial graphite primary particles can be obtained. Can be represented.
  • the graphite secondary particles may be excellent in rollability due to the fine pores present therein, and thus may be densified.
  • the lithium secondary battery including the graphite secondary particles as a negative electrode active material has an effect of improving high rate charge / discharge characteristics, cycle characteristics, and swelling characteristics.
  • FIG. 1 is a graph illustrating a result of comparing and analyzing swelling characteristics of a coin-type half cell according to an embodiment of the present invention.
  • FIG. 2 is a graph showing a result of comparing and analyzing the capacity characteristics of a coin-type half cell according to an embodiment of the present invention.
  • Figure 3 shows a result of a comparative analysis of the input and output characteristics of a monocell according to an embodiment of the present invention.
  • FIG. 4 is a graph illustrating a result of comparing and analyzing the swelling characteristics according to the heat treatment temperature of the coin-type half cell according to an embodiment of the present invention.
  • the present invention is a natural graphite primary particles coated with an amorphous carbon material having a high capacity and excellent output characteristics, easy to use as a negative electrode active material for lithium secondary batteries and artificial graphite primary particles excellent in cycle characteristics and swelling characteristics, Provided graphite secondary particles that can be densified due to excellent rolling or granulated rollability.
  • the graphite secondary particles according to an embodiment of the present invention is natural graphite primary particles coated with an amorphous carbon material; And the artificial graphite primary particles are aggregated, bonded or granulated form, the size of crystallites (La) in the a-axis direction by the powder state X-ray diffraction analysis of the natural graphite primary particles is 45 nm to 55 nm, The crystallites in the c-axis direction are 25 nm to 35 nm, the crystallites in the a-axis direction of the artificial graphite primary particles are 35 nm to 45 nm, and the crystallites in the c-axis direction are 15 nm. To 30 nm.
  • initial particle refers to an original particle when another type of particle is formed from a particle, and a plurality of primary particles are aggregated, bonded or granulated to form secondary particles. Can be formed.
  • secondary paricles refers to physically discernible large particles formed by the aggregation, bonding or granulation of individual primary particles.
  • the term “powder state X-ray diffraction analysis” refers to X-ray diffraction analysis using powders (powders) of particles (eg, natural graphite primary particles, artificial graphite primary particles, or graphite secondary particles). It means to carry out.
  • electrode state X-ray diffraction analysis means that the particles (eg, natural graphite primary particles, artificial graphite primary particles, or graphite secondary particles) are prepared in an electrode state and subjected to X-ray diffraction analysis. do.
  • assembly of primary particles refers to a process in which primary particles spontaneously or artificially aggregate or aggregate to form secondary aggregates by forming an aggregate composed of a plurality of primary particles.
  • the terms may be used interchangeably with the same meaning as a set or a combination.
  • the natural graphite primary particles coated with the amorphous carbon material may be in a flat form in which an amorphous carbon material is attached or coated on the surface of the natural graphite primary particles, and the natural graphite primary particles
  • the method of attaching or coating the amorphous carbon material on the surface is not particularly limited and may be carried out through a method commonly known in the art. For example, it may be prepared by attaching or coating an amorphous carbonaceous precursor material to the flat natural graphite primary particles, followed by heat treatment.
  • the amorphous carbon material precursor material is petroleum-based heavy oil and pitch It may be at least one selected from the group consisting of oils. That is, the amorphous carbon material may be derived from at least one material selected from the group consisting of petroleum heavy oil and pitch oil.
  • the coating amount of the amorphous carbon material may be more than 0% and 30% or less, and the coating amount may be calculated through Equation 1 below. If the coating amount of the amorphous carbon material is within the above range, in particular, 1% to 5%, as the carbon coating amount increases, the irreversibility of the graphite edge surface may be reduced, thereby including a lithium secondary battery including the negative electrode active material. The characteristics of can be improved. On the other hand, when the coating amount of the amorphous carbon material exceeds 30%, the amount of amorphous carbon compared to natural graphite is too large, making it difficult to easily charge and discharge a lithium secondary battery using the negative electrode active material and insert lithium into the negative electrode during charging. The absolute amount of space that can be reduced may cause a problem that the capacity of the secondary battery is reduced.
  • the natural graphite primary particles coated with the amorphous carbon material may be suppressed in shape deformation during rolling by an amorphous carbon material attached or coated on the surface of the natural graphite primary particles, and the natural graphite primary particles and the electrolyte described later Direct contact may be prevented, so that the reaction between the natural graphite primary particles and the electrolyte may be suppressed, thereby improving cycle characteristics of the lithium secondary battery including the negative active material.
  • the coating layer is microscopically the primary graphite. It may serve to support the swelling phenomenon of the particle core, the initial swelling characteristics of the lithium secondary battery including this as a negative electrode active material can be improved.
  • the natural graphite primary particles coated with the amorphous carbon material may have high crystallinity.
  • the crystallinity may be represented by an X-ray diffraction analysis. Specifically, the size of crystallites (La) in the a-axis direction is 45 nm to 55 nm when measuring the powder state of the natural graphite primary particles coated with the amorphous carbon material.
  • the size of the crystallite Lc in the c-axis direction may be 25 nm to 35 nm
  • the plane spacing d 002 of the (002) plane by X-ray diffraction may be 0.3355 nm to 0.3365 nm
  • the electrode state X The peak intensity ratio (I 002 / I 110 ) between the (002) plane and the (110) plane is 550 to 650
  • the peak intensity ratio (I 004 / I 110 ) between the (004) plane and the (110) plane by line diffraction analysis. ) May be from 25 to 35.
  • the natural graphite primary particles coated with the amorphous carbon material have excellent crystal characteristics such as the crystallite size in the a-axis direction, the crystallite size in the c-axis direction, the interplanar spacing and / or the peak intensity ratio. Dose characteristics can be expressed.
  • each X-ray diffraction analysis showing the crystallinity was measured using Cu-K ⁇ ray using the X-ray diffractometer Bruker D4 Endeavor, and the numerical value was corrected through the Topas3 fitting program. It was measured using high-purity silicon as an internal standard sample, and was calculated according to the school method (measurement method set forth by the 17th Committee of the Japan Academic Association).
  • the capacity of the natural graphite primary particles coated with the amorphous carbon material may be 355 mAh / g to 365 mAh / g.
  • the capacity represents the discharge capacity of the lithium secondary battery (Half-cell) produced using the natural graphite primary particles as a negative electrode active material.
  • the average particle diameter of the natural graphite primary particles coated with the amorphous carbon material may be 2 ⁇ m to 10 ⁇ m, and when the average particle diameter is within the above range, the rapid filling property or the cycle characteristic may be excellent.
  • the artificial graphite primary particles according to an embodiment of the present invention may be a flat form prepared by heat-treating coal-based heavy oil, petroleum-based heavy oil, tars, pitches, cokes and the like in a temperature range of 500 to 3000. .
  • the artificial graphite primary particles may be prepared by heat-treating one or more selected from the group consisting of needle cokes, moxa cokes, and coal tar pitch. That is, the artificial graphite primary particles may be at least one of needle coke-based artificial graphite primary particles, mosaic coke-based artificial graphite primary particles and coal tar pitch artificial graphite primary particles, preferably mosaic coke-based artificial graphite It may be at least one of primary particles and coal tar pitch-based artificial graphite primary particles.
  • the coal tar pitch artificial graphite may be MCMB (meso-carbon microbeads) artificial graphite.
  • the artificial graphite primary particles may be one having high crystallinity.
  • the crystallinity may be expressed by an X-ray diffraction analysis. Specifically, when the powder state of the artificial graphite primary particles is measured, the size (La) of the crystallites in the a-axis direction is 35 nm to 45 nm, and the crystallites in the c-axis direction.
  • the size Lc may be 15 nm to 30 nm, and the artificial graphite primary particles may have a plane spacing (d 002 ) of the (002) plane by X-ray diffraction of 0.3365 nm to 0.3380 nm.
  • the peak intensity ratio (I 002 / I 110 ) between the (002) plane and the (110) plane by the X-ray diffraction is 50 to 150 in the electrode state
  • the peak intensity ratio (the (004) plane and the (110) plane ( I 004 / I 110 ) may be 5 to 15.
  • the X-ray diffraction analysis value can be measured through the same method as the above-mentioned method.
  • the artificial graphite primary particles have excellent crystallinity characteristics such as crystallite size in the a-axis direction, crystallite size in the c-axis direction, interplanar spacing and / or peak intensity ratio, and thus have excellent capacity characteristics and high c-axis direction. Swelling properties can be expressed.
  • the artificial graphite primary particles may have a capacity of 320 mAh / g to 340 mAh / g.
  • the capacity represents the discharge capacity of a half-cell produced using the artificial graphite primary particles as a negative electrode active material.
  • the average particle diameter of the artificial graphite primary particles may be 2 ⁇ m to 10 ⁇ m, preferably may be the same as or smaller than the natural graphite primary particles coated with the amorphous carbon material. When the average particle diameter is within the above range, the rapid filling property or the cycle characteristic may be excellent.
  • the graphite secondary particles according to the present invention include natural graphite primary particles and artificial graphite primary particles coated with the amorphous carbon material, and specifically, natural graphite primary particles coated with the amorphous carbon material. Artificial graphite primary particles may be aggregated, bonded or granulated to form a single mass.
  • the weight ratio may be 4: 6 to 6: 4.
  • the method of gathering, combining, or granulating the natural graphite primary particles and artificial graphite primary particles coated with the amorphous carbon material is not particularly limited and may be performed by a method commonly known in the art, but for example, heterogeneous A binder, a catalyst, and the like may be mixed with the primary particles and subjected to heat treatment to prepare graphite secondary particles in which the heterogeneous primary particles are aggregated, bonded, or granulated.
  • natural graphite primary particles, artificial graphite primary particles, binders and catalysts coated with an amorphous carbon material are introduced into a vacuum reactor under a nitrogen or argon atmosphere, mixed, and heat treated at 1000 to 2800 to produce graphite secondary particles. can do.
  • the catalyst may be removed to form pores in the finally produced graphite secondary particles, and the graphite secondary particles having extremely low defects and high crystallinity may be obtained. That is, when heat treatment at a temperature of less than 1000 there is a fear that the capacity does not occur because the graphitization is not normally performed, and if it exceeds 2800, the swelling characteristics may be degraded, if possible in the range of 1000 to 2800 It may be desirable to perform.
  • the graphite secondary particles may have a total pore volume of 3 cm 3 / g to 30 cm 3 / g, and a specific surface area of 1 m 2 / g to 10 m 2 / g.
  • a lithium secondary battery using the graphite secondary particles having such a specific surface area and / or pore volume as a negative electrode active material can secure a structure having many pores in the negative electrode, thereby improving input / output characteristics and improving swelling characteristics.
  • the charge and discharge capacity characteristics can be improved.
  • the binder is not particularly limited, and for example, petroleum, coal, artificial pitch, tar, or the like may be used.
  • carbides such as silicon, iron, nickel, titanium, and boron, oxides, nitrides, and the like may be used.
  • the amount of the catalyst is not particularly limited, but is 1 to 50 parts by weight based on 100 parts by weight of the total amount of the primary particles and the binder. Can be used.
  • the graphite secondary particles according to the present invention may be preferably spherical, the aspect ratio may be 1 to 1.5. If the aspect ratio is out of the above range, when the negative electrode is manufactured using the negative electrode active material including the graphite secondary particles, problems such as deformation, stretching, and breakage of the current collector may occur, thereby reducing the density of the active material layer. Can be. In addition, when the graphite secondary particles deviate largely out of the spherical shape outside of the aspect ratio, the orientation in the c-axis direction may be increased, thereby reducing the swelling characteristics of the lithium secondary battery including the negative electrode active material. The negative electrode active material including the graphite secondary particles may adversely affect the distribution of large pores, and as a result, the input / output characteristics of the lithium secondary battery including the graphite secondary particles may also be degraded.
  • the average particle diameter of the graphite secondary particles may be 10 ⁇ m to 30 ⁇ m, the peak intensity ratio (I 002 / I 110 ) of the (002) plane and (110) plane by electrode state X-ray diffraction analysis is 200 to 400
  • the peak intensity ratio (I 004 / I 110 ) of the (004) plane and the (110) plane may be 10 to 25.
  • the peak intensity ratio may be obtained through X-ray diffraction analysis, and X-ray diffraction analysis may be performed by the same method as mentioned above.
  • the graphite secondary particles according to the present invention includes natural graphite primary particles coated with a high-capacity, high-output amorphous carbon material in the graphite secondary particles, and artificial graphite primary particles having high cycle characteristics and excellent swelling characteristics. It not only shows high capacity and high power characteristics but also shows excellent cycle characteristics and swelling characteristics.
  • the fine pores in the graphite secondary particles can act as a microscopic buffer, so that even when the graphite secondary particles are relatively strong compared to the negative electrode active material using a mixture of different types of graphite May have excellent rollability without being deformed or decomposed, thereby enabling higher density of the active material layer.
  • the graphite secondary particles according to the present invention may be included in the negative electrode active material for a secondary battery, and the method for manufacturing the negative electrode active material may be as follows.
  • the amorphous carbon material precursor material and the natural graphite primary particles are mixed and heat-treated to prepare natural graphite primary particles coated with the amorphous carbon material; At least one selected from the group consisting of coal-based heavy oil, fibrous heavy oil, tars, pitches, and coke powder is graphitized by heat treatment at 500 to 3000 ° C. to prepare artificial graphite primary particles; Mixing natural graphite primary particles, artificial graphite primary particles, a binder, and a catalyst coated with an amorphous carbon material; It may be prepared including a process of producing a graphite secondary particles by heat treatment at 1000 to 2800 °C.
  • the method for producing the negative electrode active material including the graphite secondary particles according to the present invention is not limited to the above method, other methods can be applied, one of the other methods, natural graphite primary particles and digraphitization Mixing the soft carbon particles and assembling them into secondary particles; There may be a method comprising a; to prepare a graphite secondary particles by powder graphitization of the assembled secondary particles by heat treatment at 3000 to 3200 °C.
  • the negative electrode active material including the graphite secondary particles manufactured by the two methods exemplified above is composed of natural graphite primary particles, artificial graphite primary particles, and graphite secondary particles coated with an amorphous carbon material as its constituent materials.
  • the particles can express excellent capacity characteristics, and can provide a secondary battery with improved swelling characteristics.
  • the present invention provides a negative electrode for a secondary battery in which the negative electrode active material slurry for a lithium secondary battery including the graphite secondary particles is coated on a current collector.
  • the negative electrode according to an embodiment of the present invention may be prepared by applying a negative electrode active material including the graphite secondary particles to a negative electrode current collector, drying and rolling.
  • the negative electrode current collector may be generally used having a thickness of 3 ⁇ m to 500 ⁇ m, and is not particularly limited as long as it has a high conductivity without causing chemical changes in 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.
  • the negative electrode active material may be prepared by adding and mixing an additive such as a binder, a conductive material, and a filler to the graphite secondary particles.
  • an additive such as a binder, a conductive material, and a filler to the graphite secondary particles.
  • a dispersing agent can be added further at the time of organic mixing.
  • the binder is a component that assists the bonding of the graphite secondary particles and the conductive material and the bonding to the current collector, and may be generally added in an amount of 1 wt% to 30 wt% based on the total amount of the graphite secondary particles.
  • Such binders are not particularly limited and may be conventional ones known in the art, but for example, vinylidene fluoride-hexafluoropropylene copolymer (PVBF-co-HEP), polyvinylidenefluoride, polyacryl Ronitrile (polyacrylonitrile), polymethyl methacrylate (polymethaylmethacrylate), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, poly Propylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butyrene rubber (SBR) and fluorine rubber, and may be selected from the group consisting of two or more, especially carboxymethylcellulose (CMC) and styrene-butylene rubber (SBR) can be used in combination.
  • the conductive material may typically be added in an amount of 0.05 wt% to 5 wt% based on the total weight of the graphite secondary particles.
  • the conductive material is not particularly limited and is not particularly limited as long as it is conductive without causing side reactions with other elements of the battery. Examples thereof include graphite such as natural graphite and artificial graphite; Carbon blacks such as carbon black (super-p), acetylene black, ketjen black, channel black, furnace black, lamp black and summer black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride powder, aluminum powder and nickel powder; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives.
  • the filler is a component for inhibiting the expansion of the negative electrode and can be used or not as necessary. If the filler is a fibrous material without causing chemical changes in the battery, it is not particularly limited, for example, an olefin polymer such as polyethylene or polypropylene. ; It may be a fibrous material such as glass fiber, carbon fiber.
  • the dispersant is not particularly limited, but may be, for example, isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or the like.
  • the coating may be performed by a method commonly known in the art, but for example, the negative electrode active material may be distributed on an upper surface of one side of the negative electrode current collector, and then uniformly dispersed using a doctor blade or the like. have.
  • the method may be performed by a die casting method, a comma coating method, a screen printing method, or the like.
  • the drying is not particularly limited, but may be performed within one day in a vacuum oven of 50 to 200.
  • the present invention provides a lithium secondary battery including the separator and the electrolyte interposed between the negative electrode and the positive electrode, the negative electrode and the positive electrode for the secondary battery.
  • the lithium secondary battery according to an embodiment of the present invention is coated with a negative electrode active material including graphite secondary particles formed by the aggregation, bonding or granulation of natural graphite primary particles and artificial graphite primary particles coated with an amorphous carbon material And a separator and an electrolyte interposed between the negative electrode and the positive electrode, the negative electrode and the positive electrode.
  • a negative electrode active material including graphite secondary particles formed by the aggregation, bonding or granulation of natural graphite primary particles and artificial graphite primary particles coated with an amorphous carbon material
  • a separator and an electrolyte interposed between the negative electrode and the positive electrode, the negative electrode and the positive electrode.
  • the positive electrode is not particularly limited, but may be prepared by coating a positive electrode active material on one surface of a positive electrode current collector and then drying the positive electrode active material.
  • the positive electrode active material may include additives such as a binder, a conductive material, a filler, and a dispersant.
  • the positive electrode current collector may be the same as or included in the aforementioned negative electrode current collector.
  • Additives such as binders, conductive materials, fillers, and dispersants used in the positive electrode may be the same as or included in the aforementioned negative electrode.
  • the positive electrode active material is not particularly limited and may be a conventional one known in the art, for example, a layered compound such as lithium cobalt oxide (LiCoO 2 ), lithium nickel oxide (LiNiO 2 ), or one or more transition metals.
  • the separator may be an insulating thin film having high ion permeability and mechanical strength, and may generally have a pore diameter of 0.01 ⁇ m to 10 ⁇ m and a thickness of 5 ⁇ m to 300 ⁇ m.
  • a porous polymer film such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer and an ethylene / methacrylate copolymer, may be used.
  • these may be laminated and used, or a nonwoven fabric made of a conventional porous nonwoven fabric, for example, a high melting glass fiber, polyethylene terephthalate fiber, or the like may be used, but is not limited thereto.
  • the electrolyte may include an organic solvent and a lithium salt commonly used in the electrolyte, and are not particularly limited.
  • lithium salt of the anion is F -, Cl -, I - , NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) 2 PF 4 -, (CF 3 ) 3 PF 3 -, (CF 3) 4 PF 2 -, (CF 3) 5 PF -, (CF 3) 6 P -, CF 3 SO 3 -, CF 3 CF 2 SO 3 -, (CF 3 SO 2 ) 2 N -, (FSO 2 ) 2 N -, CF 3 CF 2 (CF 3) 2 CO -, (CF 3 CO 2) 2 CH -, (SF 5) 3 C -, (CF 3 SO 2) 3 C -, CF 3 (CF 2 ) 7 SO 3 -, CF 3 CO 2 -, CH 3 CO 2 -, SCN - , and (CF 3 CF 2 SO 2) 2 N - may be at least one member selected from the group consisting of .
  • Typical organic solvents include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, methylpropyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane and vinylene. It may be one or more selected from the group consisting of carbonate, sulfolane, gamma-butyrolactone, propylene sulfite and tetrahydrofuran.
  • ethylene carbonate and propylene carbonate which are cyclic carbonates among the carbonate-based organic solvents, are highly viscous organic solvents, and thus may be preferably used because they dissociate lithium salts in the electrolyte well.
  • Such cyclic carbonate dimethylcarboniate and di When a low viscosity, low dielectric constant linear carbonate such as ethyl carbonate is mixed and used in an appropriate ratio, an electrolyte having high electrical conductivity can be prepared, and thus it can be more preferably used.
  • the electrolyte may be pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexa phosphate triamide, nitrobenzene to improve charge / discharge characteristics, flame retardancy characteristics, etc. as necessary.
  • Derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrroles, 2-methoxy ethanol, aluminum trichloride, and the like. have.
  • the solvent may further include a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride to impart nonflammability, may further include carbon dioxide gas to improve high temperature storage characteristics, and may further include fluoro-ethylene carbonate. ), PRS (propene sultone), FPC (fluoro-propylene carbonate) may further include.
  • a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride to impart nonflammability
  • PRS propene sultone
  • FPC fluoro-propylene carbonate
  • an electrode assembly is formed by disposing a separator between a positive electrode and a negative electrode, and the electrode assembly may be manufactured by putting an electrolyte into a cylindrical battery case or a square battery case. Alternatively, after stacking the electrode assembly, it may be prepared by impregnating it in an electrolyte and sealing the resultant obtained in a battery case.
  • the battery case used in the present invention may be adopted that is commonly used in the art, there is no limitation on the appearance according to the use of the battery, for example, cylindrical, square, pouch type or coin using a can (coin) type and the like.
  • the lithium secondary battery according to the present invention may not only be used in a battery cell used as a power source for a small device, but also preferably used as a unit battery in a medium-large battery module including a plurality of battery cells.
  • Preferred examples of the medium and large devices include, but are not limited to, electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, power storage systems, and the like.
  • Natural graphite coated with amorphous carbon having a grain size of 50 nm in the a-axis direction, 30 nm in the c-axis direction, and a plane spacing (d 002 ) of the (002) plane of 0.3360 nm and a particle diameter of 5 ⁇ m. 50% by weight of the secondary particles (coating amount: 2%) and the crystallite size in the a-axis direction are 30 nm, the crystallite size in the c-axis direction is 20 nm, and the plane spacing (d 002 ) of the (002) plane is 0.3370 nm.
  • a binder and a catalyst were added to a mixture composed of 50 wt% of artificial graphite primary particles having a particle diameter of 5 ⁇ m, mixed, and heat-treated at 2800 under a nitrogen atmosphere to prepare graphite secondary particles.
  • the artificial graphite primary particles used coke artificial graphite.
  • a negative electrode active material slurry was prepared by mixing 96 wt% of the prepared graphite secondary particles with 1 wt% of carbon black conductive material, 1.5 wt% of carboxymethyl cellulose (CMC), and 1.5 wt% of styrene-butadiene rubber (SBR).
  • the negative electrode was prepared by coating the copper foil with a thickness of 150 ⁇ m, followed by rolling and drying.
  • Graphite secondary particles were prepared in the same manner as in Preparation Example 1, except that artificial graphite primary particles were mother-based artificial graphite, to prepare a negative electrode.
  • Graphite secondary particles were prepared in the same manner as in Preparation Example 1, except that the artificial graphite primary particles were MCMB-type artificial graphite, to prepare a negative electrode.
  • An anode was manufactured in the same manner as in Preparation Example 1, except that natural graphite coated with amorphous carbon material and artificial graphite were mixed at a weight ratio of 5: 5 instead of the graphite secondary particles.
  • a negative electrode was manufactured in the same manner as in Preparation Example 1, except that graphite secondary particles were manufactured using a plurality of artificial graphite primary particles (single material) instead of the natural graphite primary particles coated with an amorphous carbon material. It was.
  • a graphite secondary particle was produced in the same manner as in Preparation Example 1 except that the heat treatment temperature was 2500 ° C., and a negative electrode was prepared.
  • a graphite secondary particle was prepared in the same manner as in Preparation Example 1 except that the heat treatment temperature was 800 ° C., and a negative electrode was prepared.
  • a graphite secondary particle was prepared in the same manner as in Preparation Example 1 except that the heat treatment temperature was 3000 ° C., and a negative electrode was prepared.
  • Lithium metal foil was used as a counter electrode, and the counter electrode and the negative electrode prepared in Preparation Example 1-1 were punched into a coin shape, and LiPF6 was 1 mol and 2 wt% of VC (vinyl).
  • a coin-type half cell was prepared by injecting a carbonate-based electrolyte solution containing chloride).
  • a positive electrode active material slurry was prepared by mixing 96% by weight of LiCoO 2, 2 % by weight of carbon black and 2% by weight of polyfluorovinylidene as a positive electrode active material, and further adding and mixing N-methyl-2-pyrrolidone (NMP). Then, it was coated on an aluminum foil with a thickness of 130 ⁇ m, then rolled and dried to prepare a positive electrode.
  • NMP N-methyl-2-pyrrolidone
  • a coin-type half cell and a monocell were prepared in the same manner as in Example 1-1, except that the negative electrode prepared in Preparation Example 2 was used as the negative electrode.
  • a coin-type half cell and a monocell were prepared in the same manner as in Example 1-1, except that the negative electrode prepared in Preparation Example 3 was used as the negative electrode.
  • a coin-type half cell and a monocell were prepared in the same manner as in Example 1-1, except that the negative electrode prepared in Comparative Preparation Example 1 was used as the negative electrode.
  • a coin-type half cell and a monocell were prepared in the same manner as in Example 1-1, except that the negative electrode prepared in Comparative Preparation Example 2 was used as the negative electrode.
  • a coin-type half cell and a monocell were prepared in the same manner as in Example 1-1, except that the negative electrode prepared in Preparation Example 4 was used as the negative electrode.
  • a coin-type half cell and a monocell were manufactured in the same manner as in Example 1-1, except that the negative electrode prepared in Comparative Preparation Example 3 was used as the negative electrode.
  • a coin-type half cell and a monocell were prepared in the same manner as in Example 1-1, except that the negative electrode prepared in Comparative Preparation Example 4 was used as the negative electrode.
  • Example 4 The swelling characteristics of the coin-type half cells produced in Example 4 and Comparative Examples 3 and 4 were compared and analyzed. The thickness of each cell was measured using a coin-type real-time thickness measurement equipment. The results are shown in FIG.
  • the coin-type half cell of Example 4 fabricated using a negative electrode including graphite secondary particles according to the present invention was compared with the coin-type half cells of Comparative Examples 3 and 4. It confirmed that the swelling characteristic was excellent.
  • Each battery was charged at a rate of 0.1 C at 25 CC / CV, and then discharged at a rate of 0.1 C at CC up to 1.5 V, thereby measuring charge and discharge capacity, and analyzing charge and discharge efficiency and discharge rate characteristics. The results are shown in FIG.
  • the coin type half cells of Examples 1 to 3 manufactured using the negative electrode including the graphite secondary particles according to the present invention are compared with the coin type half cells of Comparative Examples 1 and 2. Overall, the capacity characteristics were somewhat better or similar.
  • Each monocell was repeatedly charged and recharged at 25C, 0.2C / 0.2C, 0.2C / 0.5C, 0.2C / 1.0C, and 0.2C / 2.0C under 25 conditions, and the capacity retention rate according to the charge / discharge rate was analyzed. . The results are shown in FIG.
  • the monocells of Examples 1 to 3 produced using a negative electrode containing the graphite secondary particles according to the present invention as a negative electrode active material overall capacity compared to the monocells of Comparative Examples 1 and 2 It was confirmed that the retention rate was rather excellent.

Abstract

The present invention relates to a graphite secondary particle, an anode using the same as an anode active material, and a lithium secondary battery comprising the anode, the graphite secondary particle being able to be densified by having excellent rolling properties due to comprising a high-capacity natural graphite primary particle having excellent output characteristics aggregated, combined or assembled with an artificial graphite primary particle having excellent cycle characteristics and swelling characteristics. A lithium secondary battery comprising the graphite secondary particle according to the present invention as an anode active material has an effect of improving high-rate charging and discharging characteristics, cycle characteristics and swelling characteristics.

Description

흑연 2차 입자 및 이를 포함하는 리튬 이차전지Graphite secondary particles and lithium secondary battery comprising same
관련출원과의 상호인용Citation with Related Applications
본 출원은 2014년07월29일자 한국 특허 출원 제10-2014-0096737호 및 2015년07월24일자 한국 특허 출원 제10-2015-0105325호에 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. 10-2014-0096737 dated July 29, 2014 and Korean Patent Application No. 10-2015-0105325 dated July 24, 2015. All content disclosed in the literature is included as part of this specification.
기술분야Technical Field
본 발명은 고용량의 출력 특성이 우수한 천연흑연 1차 입자와 사이클 특성과 스웰링 특성이 우수한 인조흑연 1차 입자가 집합, 결합 또는 조립화된 압연성이 우수하여 고밀도화가 가능한 흑연 2차 입자, 이를 음극 활물질로 이용한 음극 및 상기 음극을 포함하는 리튬 이차전지에 관한 것이다.The present invention is a graphite secondary particles capable of high density of natural graphite primary particles having a high capacity output characteristics and artificial graphite primary particles having excellent cycle characteristics and swelling characteristics are excellent in the rolling property, which is aggregated, bonded or granulated, It relates to a negative electrode used as a negative electrode active material and a lithium secondary battery comprising the negative electrode.
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. 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 commercially used.
또한, 환경문제에 대한 관심이 커짐에 따라 대기오염의 주요 원인의 하나인 가솔린 차량, 디젤 차량 등 화석연료를 사용하는 차량을 대체할 수 있는 전기자동차, 하이브리드 전기자동차에 대한 관심이 높아지고 있으며, 이러한 전기자동차, 하이브리드 전기자동차 등의 동력원으로서 리튬 이차전지를 사용하기 위한 연구가 활발히 진행되고 있다. In addition, as interest in environmental problems increases, interest in electric vehicles and hybrid electric vehicles, which can replace vehicles using fossil fuel, such as gasoline and diesel vehicles, which are one of the main causes of air pollution, is increasing. Research into using lithium secondary batteries as a power source for electric vehicles and hybrid electric vehicles is being actively conducted.
한편, 리튬 이차전지는 리튬 이온의 삽입/탈리가 가능한 양극 활물질을 포함하고 있는 양극과, 리튬 이온의 삽입/탈리가 가능한 음극 활물질을 포함하고 있는 음극, 상기 양극과 음극 사이에 미세 다공성 분리막이 개재된 전극 조립체에 리튬 이온을 함유한 비수 전해질이 포함되어 있는 전지를 의미한다. Meanwhile, a lithium secondary battery includes a positive electrode including a positive electrode active material capable of inserting / desorbing lithium ions, a negative electrode containing a negative electrode active material capable of inserting / removing lithium ions, and a microporous separator interposed between the positive electrode and the negative electrode. It means a battery that contains a non-aqueous electrolyte containing lithium ions in the electrode assembly.
리튬 이차전지의 양극 활물질로는, 리튬 코발트 산화물(LiCoO2), 리튬-망간계 산화물(LiMn2O4) 또는 리튬-니켈 산화물(LiNiO2) 등의 전이금속 산화물, 이들 전이금속의 일부가 다른 전이금속으로 치환된 복합 산화물 등이 사용되고 있다. Examples of the positive electrode active material of a lithium secondary battery include transition metal oxides such as lithium cobalt oxide (LiCoO 2 ), lithium-manganese oxide (LiMn 2 O 4 ), or lithium-nickel oxide (LiNiO 2 ), and some of these transition metals are different. Composite oxides substituted with transition metals are used.
음극 활물질로는 리튬 금속을 사용하였으나, 리튬 금속을 사용할 경우 덴드라이트(dendrite) 형성으로 인한 전지 단락이 발생하여 폭발의 위험성이 있어, 최근에는 리튬 금속 대신 탄소계 물질로 대체되고 있다. Lithium metal is used as the negative electrode active material, but when lithium metal is used, there is a risk of explosion due to battery short circuit due to dendrite formation, and recently, it has been replaced with a carbon-based material instead of lithium metal.
리튬 이차전지의 음극 활물질로 사용되는 탄소계 물질에는 천연흑연 및 인조흑연과 같은 결정질계 탄소와 소프트 카본(soft carbon) 및 하드 카본(hard carbon)과 같은 비정질계 탄소가 사용되고 있다.As the carbon-based material used as a negative electrode active material of a lithium secondary battery, crystalline carbon such as natural graphite and artificial graphite and amorphous carbon such as soft carbon and hard carbon are used.
비정질계 탄소는 용량이 큰 장점이 있으나, 충방전 과정에서 비가역성이 크다는 단점이 있다.Amorphous carbon has an advantage of large capacity, but has a disadvantage of large irreversibility in the charging and discharging process.
대표적인 결정질계 탄소인 천연흑연은 저가이면서도 초기 용량이 우수하고 이론 한계 용량이 비교적 높으나, 판상의 형상을 갖기 때문에 이를 극판으로 제조할 경우 집전체 상에 납작하게 압착 배향되어 전해액의 함침이 용이하지 않아 고율 충방전 특성이 낮으며 수명 열화가 심하고 사이클 용량이 떨어지는 단점이 있다. Natural graphite, which is a representative crystalline carbon, has a low cost and excellent initial capacity and a relatively high theoretical limit capacity. However, since it has a plate shape, when it is manufactured as a pole plate, it is compressed and oriented flat on the current collector, so that impregnation of the electrolyte is not easy. Its high rate of charge and discharge characteristics is low, the service life is severely degraded, and cycle capacity is low.
이에, 판상의 천연흑연을 기계적으로 구형화하여 사용하거나, 다른 흑연과 혼합하여 사용하는 방안이 제시되었으나, 압연시 흑연 표면의 균열이나 코어의 노출이 발생할 수 있어 전해액과의 부반응이 증가하여 사이클 특성이나 스웰링 특성이 저하되는 문제점이 있다. 또한, 상기의 단점을 보완하기 위하여 용량은 천연흑연에 비하여 조금 낮으나, 사이클 특성 및 스웰링 특성이 우수한 인조흑연을 사용하는 방법이 연구되어 왔다. 그러나, 인조흑연을 사용하기 위해서는 흑연화 공정이 필수적으로 필요하며, 이에 천연흑연에 비해 고가이며, PC가 포함된 전해액에 취약하고 출력 특성 또한 떨어지는 단점이 있다. Therefore, the method of using the spherical natural graphite to mechanically spherical or mixed with other graphite has been proposed, but the cracking of the graphite surface or the exposure of the core may occur during rolling, resulting in increased side reactions with the electrolyte, resulting in cycle characteristics. However, there is a problem that the swelling characteristic is lowered. In addition, in order to compensate for the above disadvantages, although the capacity is slightly lower than that of natural graphite, a method of using artificial graphite having excellent cycle characteristics and swelling characteristics has been studied. However, in order to use artificial graphite, a graphitization process is necessary, which is expensive compared to natural graphite, and is vulnerable to electrolytes containing PC and also having poor output characteristics.
상기와 같은 배경 하에, 본 발명자들은 압연성이 우수하여 고밀도화가 가능하고 고율 충방전 특성, 사이클 특성 및 스웰링 특성이 우수한 음극 활물질을 연구하던 중, 비정질계 탄소재가 코팅된 천연흑연 1차 입자 및 인조흑연 1차 입자를 집합, 결합 또는 조립화하여 제조된 흑연 2차 입자를 제조하고 이를 음극 활물질로 사용한 리튬 이차전지가 우수한 고율 충방전 특성, 사이클 특성 및 스웰링 특성을 나타내는 것을 확인함으로써 본 발명을 완성하였다.Under the background as described above, the inventors of the present invention, while researching a negative electrode active material having excellent rolling property, high density, high rate charge / discharge characteristics, cycle characteristics, and swelling characteristics, are coated with amorphous carbonaceous primary particles and The present invention is made by preparing graphite secondary particles prepared by aggregating, bonding, or granulating artificial graphite primary particles, and confirming that a lithium secondary battery using the same as an anode active material exhibits excellent high rate charge / discharge characteristics, cycle characteristics, and swelling characteristics. Was completed.
본 발명의 목적은 고용량의 우수한 출력 특성을 갖는 비정질계 탄소재가 코팅된 천연흑연 1차 입자와 사이클 특성 및 스웰링 특성이 우수한 인조흑연 1차 입자가 집합, 결합 또는 조립화된 압연성이 우수하여 고밀도화가 가능한 흑연 2차 입자를 제공하는 것이다. An object of the present invention is the natural graphite primary particles coated with amorphous carbon material having high capacity and excellent output characteristics, and the artificial graphite primary particles excellent in cycle characteristics and swelling characteristics are excellent in the rolling property in which the aggregated, bonded or granulated It is to provide a graphite secondary particle capable of densification.
본 발명의 다른 목적은 상기의 흑연 2차 입자를 포함하는 음극 활물질 슬러리가 집전체 상에 도포된 리튬 이차전지용 음극을 제공하는 것이다. Another object of the present invention is to provide a negative electrode for a lithium secondary battery, wherein the negative electrode active material slurry containing the graphite secondary particles is coated on a current collector.
본 발명의 또 다른 목적은 상기의 음극, 양극 및 상기 음극과 양극 사이에 개재된 분리막 및 전해질을 포함하는, 고율 충방전 특성, 사이클 특성 및 스웰링 특성이 우수한 리튬 이차전지를 제공하는 것이다.Still another object of the present invention is to provide a lithium secondary battery having excellent high rate charge / discharge characteristics, cycle characteristics, and swelling characteristics, including the negative electrode, the positive electrode, and a separator and an electrolyte interposed between the negative electrode and the positive electrode.
상기의 과제를 해결하기 위하여, 본 발명은 비정질계 탄소재가 코팅된 천연흑연 1차 입자; 및 인조흑연 1차 입자가 집합, 결합 또는 조립화된 형태이고, 상기 천연흑연 1차 입자의 분체 상태 X선 회절 분석에 의한 a축 방향의 결정자의 크기가 45 nm 내지 55 nm이고, c축 방향의 결정자의 크기가 25 nm 내지 35 nm 이며, 상기 인조흑연 1차 입자의 a축 방향의 결정자의 크기가 35 nm 내지 45 nm이고, c축 방향의 결정자의 크기가 15 nm 내지 30 nm인 것을 특징으로 하는 흑연 2차 입자를 제공한다.In order to solve the above problems, the present invention is natural graphite primary particles coated with an amorphous carbon material; And a form in which artificial graphite primary particles are aggregated, bonded, or granulated, and the crystallites in the a-axis direction by powder state X-ray diffraction analysis of the natural graphite primary particles are 45 nm to 55 nm, and the c-axis direction The crystallite has a size of 25 nm to 35 nm, the crystallite size in the a-axis direction of the artificial graphite primary particles is 35 nm to 45 nm, the crystallite size in the c-axis direction is 15 nm to 30 nm Graphite secondary particles are provided.
또한, 본 발명은 상기의 흑연 2차 입자를 포함하는 리튬 이차전지용 음극 활물질 슬러리가 집전체 상에 도포된 이차전지용 음극을 제공한다.In addition, the present invention provides a negative electrode for a secondary battery in which the negative electrode active material slurry for a lithium secondary battery including the graphite secondary particles is coated on a current collector.
아울러, 본 발명은 상기의 이차전지용 음극과 양극, 상기 음극과 양극 사이에 개재된 분리막 및 전해질을 포함하는 리튬 이차전지를 제공한다.In addition, the present invention provides a lithium secondary battery including the separator and the electrolyte interposed between the negative electrode and the positive electrode, the negative electrode and the positive electrode for the secondary battery.
본 발명에 따른 흑연 2차 입자는 고용량 및 고출력 특성을 나타내나 상대적으로 사이클 특성 및 스웰링 특성이 낮은 천연흑연 1차 입자와 높은 사이클 특성과 스웰링 특성을 나타내나 상대적으로 낮은 용량 특성을 나타내는 인조흑연 1차 입자가 집합, 결합 또는 조립화되어 있음으로써, 상기 천연흑연 1차 입자가 가지는 고용량, 고출력 특성을 나타낼 수 있을 뿐 아니라, 상기 인조흑연 1차 입자가 가지는 높은 사이클 특성 및 스웰링 특성을 나타낼 수 있다.Graphite secondary particles according to the present invention is a natural graphite primary particles exhibiting high capacity and high output characteristics but relatively low cycle characteristics and swelling characteristics, and artificial cycles exhibiting high cycle characteristics and swelling characteristics but relatively low capacity characteristics. As the graphite primary particles are aggregated, bonded or granulated, not only the high capacity and high output characteristics of the natural graphite primary particles can be exhibited, but also the high cycle characteristics and swelling characteristics of the artificial graphite primary particles can be obtained. Can be represented.
또한, 상기 흑연 2차 입자는 내부에 존재하는 미세 세공에 의하여 압연성이 우수할 수 있어 고밀도화가 가능할 수 있다.In addition, the graphite secondary particles may be excellent in rollability due to the fine pores present therein, and thus may be densified.
따라서, 상기 흑연 2차 입자를 음극 활물질로 포함하는 리튬 이차전지는 고율 충방전 특성, 사이클 특성 및 스웰링 특성이 개선되는 효과가 있다. Therefore, the lithium secondary battery including the graphite secondary particles as a negative electrode active material has an effect of improving high rate charge / discharge characteristics, cycle characteristics, and swelling characteristics.
본 명세서에 첨부되는 다음의 도면은 본 발명의 바람직한 실시예를 예시하는 것이며, 전술한 발명의 내용과 함께 본 발명의 기술 사상을 더욱 이해시키는 역할을 하는 것이므로, 본 발명은 그러한 도면에 기재된 사항에만 한정되어 해석되어서는 안된다.The following drawings, which are attached to this specification, illustrate exemplary embodiments of the present invention, and together with the contents of the present invention serve to further understand the technical idea 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, 본 발명의 일 실시예에 따른 코인형 반쪽 전지의 재료에 따른 스웰링 특성을 비교분석한 결과 그래프를 나타낸 것이다.1 is a graph illustrating a result of comparing and analyzing swelling characteristics of a coin-type half cell according to an embodiment of the present invention.
도 2는, 본 발명의 일 실시예에 따른 코인형 반쪽 전지의 용량 특성을 비교분석한 결과 그래프를 나타낸 것이다. 2 is a graph showing a result of comparing and analyzing the capacity characteristics of a coin-type half cell according to an embodiment of the present invention.
도 3은, 본 발명의 일 실시예에 따른 모노셀의 입출력 특성을 비교분석한 결과 그래프를 나타낸 것이다.Figure 3 shows a result of a comparative analysis of the input and output characteristics of a monocell according to an embodiment of the present invention.
도 4는, 본 발명의 일 실시예에 따른 코인형 반쪽 전지의 열처리 온도에 따른 스웰링 특성을 비교분석한 결과 그래프를 나타낸 것이다.4 is a graph illustrating a result of comparing and analyzing the swelling characteristics according to the heat treatment temperature of the coin-type half cell according to an embodiment of the present invention.
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 발명은 리튬 이차전지용 음극 활물질로 사용이 용이한, 고용량의 우수한 출력 특성을 갖는 비정질계 탄소재로 코팅된 천연흑연 1차 입자 및 사이클 특성 및 스웰링 특성이 우수한 인조흑연 1차 입자가 집합, 결합 또는 조립화된 압연성이 우수하여 고밀도화가 가능한 흑연 2차 입자를 제공한다. The present invention is a natural graphite primary particles coated with an amorphous carbon material having a high capacity and excellent output characteristics, easy to use as a negative electrode active material for lithium secondary batteries and artificial graphite primary particles excellent in cycle characteristics and swelling characteristics, Provided graphite secondary particles that can be densified due to excellent rolling or granulated rollability.
본 발명의 일 실시예에 따른 상기 흑연 2차 입자는 비정질계 탄소재가 코팅된 천연흑연 1차 입자; 및 인조흑연 1차 입자가 집합, 결합 또는 조립화된 형태이고, 상기 천연흑연 1차 입자의 분체 상태 X선 회절 분석에 의한 a축 방향의 결정자(La)의 크기가 45 nm 내지 55 nm이고, c축 방향의 결정자(Lc)의 크기가 25 nm 내지 35 nm 이며, 상기 인조흑연 1차 입자의 a축 방향의 결정자의 크기가 35 nm 내지 45 nm이고, c축 방향의 결정자의 크기가 15 nm 내지 30 nm인 것을 특징으로 한다. The graphite secondary particles according to an embodiment of the present invention is natural graphite primary particles coated with an amorphous carbon material; And the artificial graphite primary particles are aggregated, bonded or granulated form, the size of crystallites (La) in the a-axis direction by the powder state X-ray diffraction analysis of the natural graphite primary particles is 45 nm to 55 nm, The crystallites in the c-axis direction are 25 nm to 35 nm, the crystallites in the a-axis direction of the artificial graphite primary particles are 35 nm to 45 nm, and the crystallites in the c-axis direction are 15 nm. To 30 nm.
본 발명에서 사용되는 용어 "1차 입자(initial particle)"는 어떤 입자로부터 다른 종류의 입자가 형성될 때 원래의 입자를 의미하며, 복수의 1차 입자가 집합, 결합 또는 조립화하여 2차 입자를 형성할 수 있다. As used herein, the term "initial particle" refers to an original particle when another type of particle is formed from a particle, and a plurality of primary particles are aggregated, bonded or granulated to form secondary particles. Can be formed.
본 발명에서 사용되는 용어 "2차 입자(secondary paricles)"는 개개의 1차 입자가 집합, 결합 또는 조립화하여 형성된, 물리적으로 분별할 수 있는 큰 입자를 의미한다. The term "secondary paricles" as used herein refers to physically discernible large particles formed by the aggregation, bonding or granulation of individual primary particles.
본 발명에서 사용되는 용어 "분체 상태 X선 회절 분석"은 입자(예컨대, 천연흑연 1차 입자, 인조흑연 1차 입자 또는 흑연 2차 입자)의 분체(분말, powder)를 이용하여 X선 회절 분석을 실시한 것을 의미한다.As used herein, the term “powder state X-ray diffraction analysis” refers to X-ray diffraction analysis using powders (powders) of particles (eg, natural graphite primary particles, artificial graphite primary particles, or graphite secondary particles). It means to carry out.
본 발명에서 사용되는 용어 "전극 상태 X선 회절 분석"은 입자(예컨대, 천연흑연 1차 입자, 인조흑연 1차 입자 또는 흑연 2차 입자)를 전극 상태로 제조하고 X선 회절 분석을 실시한 것을 의미한다.As used herein, the term "electrode state X-ray diffraction analysis" means that the particles (eg, natural graphite primary particles, artificial graphite primary particles, or graphite secondary particles) are prepared in an electrode state and subjected to X-ray diffraction analysis. do.
본 발명에서 사용되는 용어 "1차 입자의 조립"은 1차 입자들이 자발적으로 혹은 인위적으로 응집하거나 뭉치어 보다 복수 개의 1차 입자로 이루어진 집합체를 이룸으로써 2차 입자화 되는 과정을 의미하는 것으로, 집합 또는 결합 등의 용어와 동일한 의미로 혼용될 수 있다.As used herein, the term "assembly of primary particles" refers to a process in which primary particles spontaneously or artificially aggregate or aggregate to form secondary aggregates by forming an aggregate composed of a plurality of primary particles. The terms may be used interchangeably with the same meaning as a set or a combination.
본 발명의 일 실시예에 따른 상기 비정질계 탄소재가 코팅된 천연흑연 1차 입자는 천연흑연 1차 입자 표면에 비정질계 탄소재가 부착되거나 피복되어 있는 편평상 형태일 수 있으며, 상기 천연흑연 1차 입자 표면에 비정질계 탄소재를 부착 또는 피복하는 방법은 특별히 한정되지 않고 당분야에 통상적으로 공지된 방법을 통하여 수행할 수 있다. 예컨대, 편평상 천연흑연 1차 입자에 비정질계 탄소재 전구체 물질을 부착 또는 피복한 후 열처리하여 제조할 수 있다. The natural graphite primary particles coated with the amorphous carbon material according to an embodiment of the present invention may be in a flat form in which an amorphous carbon material is attached or coated on the surface of the natural graphite primary particles, and the natural graphite primary particles The method of attaching or coating the amorphous carbon material on the surface is not particularly limited and may be carried out through a method commonly known in the art. For example, it may be prepared by attaching or coating an amorphous carbonaceous precursor material to the flat natural graphite primary particles, followed by heat treatment.
구체적으로, 비정질계 탄소재 전구체 물질에 편평상 천연흑연 1차 입자를 혼합 또는 침지한 후 500 내지 1500의 온도범위에서 열처리하여 제조할 수 있으며, 상기 비정질계 탄소재 전구체 물질은 석유계 중질유 및 피치오일로 이루어진 군으로부터 선택된 1종 이상일 수 있다. 즉, 상기 비정질계 탄소재는 석유계 중질유 및 피치오일로 이루어진 군으로부터 선택된 1종 이상의 물질로부터 유래된 것일 수 있다.Specifically, after mixing or immersing flat natural graphite primary particles in an amorphous carbon material precursor material, it can be prepared by heat treatment at a temperature range of 500 to 1500, the amorphous carbon material precursor material is petroleum-based heavy oil and pitch It may be at least one selected from the group consisting of oils. That is, the amorphous carbon material may be derived from at least one material selected from the group consisting of petroleum heavy oil and pitch oil.
상기 비정질계 탄소재의 코팅량은 0% 초과, 30% 이하인 것이 바람직할 수 있으며, 상기 코팅량은 하기의 수학식 1을 통하여 계산할 수 있다. 만약, 상기 비정질계 탄소재의 코팅량이 상기 범위 내, 특히 1% 내지 5%일 경우에는 탄소 코팅량이 증가할수록 흑연 에지(edge)면의 비가역을 감소시킬 수 있어 이를 음극 활물질로 포함하는 리튬 이차전지의 특성이 향상될 수 있다. 반면에, 상기 비정질계 탄소재의 코팅량이 30%를 초과하는 경우에는 천연흑연 대비 비정질계 탄소량이 너무 많아져 이를 음극 활물질로 사용한 리튬 이차전지의 용이한 충방전이 어렵고 충전 시 음극에 리튬이 삽입될 수 있는 공간의 절대량이 줄어들어 상기 이차전지의 용량이 감소되는 문제가 발생할 수 있다.The coating amount of the amorphous carbon material may be more than 0% and 30% or less, and the coating amount may be calculated through Equation 1 below. If the coating amount of the amorphous carbon material is within the above range, in particular, 1% to 5%, as the carbon coating amount increases, the irreversibility of the graphite edge surface may be reduced, thereby including a lithium secondary battery including the negative electrode active material. The characteristics of can be improved. On the other hand, when the coating amount of the amorphous carbon material exceeds 30%, the amount of amorphous carbon compared to natural graphite is too large, making it difficult to easily charge and discharge a lithium secondary battery using the negative electrode active material and insert lithium into the negative electrode during charging. The absolute amount of space that can be reduced may cause a problem that the capacity of the secondary battery is reduced.
[수학식 1][Equation 1]
Figure PCTKR2015007820-appb-I000001
Figure PCTKR2015007820-appb-I000001
상기 비정질계 탄소재가 코팅된 천연흑연 1차 입자는 천연흑연 1차 입자 표면에 부착 또는 피복된 비정질계 탄소재에 의하여 압연시 형상 변형이 억제될 수 있으며, 천연흑연 1차 입자와 후술하는 전해액의 직접적인 접촉이 방지될 수 있어 상기 천연흑연 1차 입자와 전해액과의 반응이 억제되어 이를 음극 활물질로써 포함하는 리튬 이차전지의 사이클 특성이 개선될 수 있다.The natural graphite primary particles coated with the amorphous carbon material may be suppressed in shape deformation during rolling by an amorphous carbon material attached or coated on the surface of the natural graphite primary particles, and the natural graphite primary particles and the electrolyte described later Direct contact may be prevented, so that the reaction between the natural graphite primary particles and the electrolyte may be suppressed, thereby improving cycle characteristics of the lithium secondary battery including the negative active material.
또한, 비교적 큰 평균입경(15 ㎛ 내지 20 ㎛)의 구형화 천연흑연에 비하여 작은 평균입경을 갖는 상기 천연흑연 1차 입자 표면에 비정질계 탄소재가 코팅되는 경우, 코팅층이 미시적으로 상기 천연흑연 1차 입자 코어의 스웰링 현상을 지지해주는 역할을 할 수 있어, 이를 음극 활물질로 포함하는 리튬 이차전지의 초기 스웰링 특성이 향상될 수 있다. In addition, when an amorphous carbon material is coated on the surface of the natural graphite primary particles having a smaller average particle diameter than that of spherical natural graphite having a relatively large average particle diameter (15 μm to 20 μm), the coating layer is microscopically the primary graphite. It may serve to support the swelling phenomenon of the particle core, the initial swelling characteristics of the lithium secondary battery including this as a negative electrode active material can be improved.
또한, 상기 비정질계 탄소재가 코팅된 천연흑연 1차 입자는 높은 결정성을 가질 수 있다. 상기 결정성은 X선 회절 분석치로 나타낼 수 있으며, 구체적으로는 상기 비정질계 탄소재가 코팅된 천연흑연 1차 입자의 분체 상태의 측정시 a축 방향의 결정자(La)의 크기가 45 nm 내지 55 nm이고, c축 방향의 결정자(Lc)의 크기가 25 nm 내지 35 nm일 수 있으며, X선 회절에 의한 (002)면의 면간격(d002)이 0.3355 nm 내지 0.3365 nm일 수 있고, 전극 상태 X선 회절 분석에 의한 (002)면과 (110)면의 피크강도비(I002/I110)가 550 내지 650이고, (004)면과 (110)면의 피크강도비(I004/I110)가 25 내지 35인 것일 수 있다. In addition, the natural graphite primary particles coated with the amorphous carbon material may have high crystallinity. The crystallinity may be represented by an X-ray diffraction analysis. Specifically, the size of crystallites (La) in the a-axis direction is 45 nm to 55 nm when measuring the powder state of the natural graphite primary particles coated with the amorphous carbon material. , the size of the crystallite Lc in the c-axis direction may be 25 nm to 35 nm, the plane spacing d 002 of the (002) plane by X-ray diffraction may be 0.3355 nm to 0.3365 nm, and the electrode state X The peak intensity ratio (I 002 / I 110 ) between the (002) plane and the (110) plane is 550 to 650, and the peak intensity ratio (I 004 / I 110 ) between the (004) plane and the (110) plane by line diffraction analysis. ) May be from 25 to 35.
상기 비정질계 탄소재가 코팅된 천연흑연 1차 입자가, 상기한 a축 방향의 결정자 크기, c축 방향의 결정자의 크기, 면간격 및/또는 피크강도비 등의 결정 특성을 가짐으로써, 이로 인해 우수한 용량 특성을 발현시킬 수 있다. The natural graphite primary particles coated with the amorphous carbon material have excellent crystal characteristics such as the crystallite size in the a-axis direction, the crystallite size in the c-axis direction, the interplanar spacing and / or the peak intensity ratio. Dose characteristics can be expressed.
여기에서, 상기 결정성을 나타내는 각 X선 회절 분석치는 X선 회절 분석기 Bruker D4 Endeavor를 이용하여 Cu-Kα선을 사용하여 측정되었으며, Topas3 fitting program을 통하여 수치를 보정하였다. 고순도 실리콘을 내부표준시료로 사용하여 측정하고, 학진법(일본 학술 진흥회 제17 위원회가 정한 측정법)에 따라 산출하였다. Here, each X-ray diffraction analysis showing the crystallinity was measured using Cu-Kα ray using the X-ray diffractometer Bruker D4 Endeavor, and the numerical value was corrected through the Topas3 fitting program. It was measured using high-purity silicon as an internal standard sample, and was calculated according to the school method (measurement method set forth by the 17th Committee of the Japan Academic Association).
또한, 상기 비정질계 탄소재가 코팅된 천연흑연 1차 입자의 용량은 355 mAh/g 내지 365 mAh/g일 수 있다. 이때, 상기 용량은 상기 천연흑연 1차 입자를 음극 활물질로 사용하여 제작한 리튬 이차전지(Half-cell)의 방전 용량을 나타낸다. In addition, the capacity of the natural graphite primary particles coated with the amorphous carbon material may be 355 mAh / g to 365 mAh / g. In this case, the capacity represents the discharge capacity of the lithium secondary battery (Half-cell) produced using the natural graphite primary particles as a negative electrode active material.
상기 비정질계 탄소재가 코팅된 천연흑연 1차 입자의 평균입경은 2 ㎛ 내지 10 ㎛일 수 있으며, 평균입경이 상기 범위 내일 경우에는 급속 충전성이나 사이클 특성이 우수할 수 있다. The average particle diameter of the natural graphite primary particles coated with the amorphous carbon material may be 2 μm to 10 μm, and when the average particle diameter is within the above range, the rapid filling property or the cycle characteristic may be excellent.
본 발명의 일 실시예에 따른 상기 인조흑연 1차 입자는 석탄계 중질유, 석유계 중질유, 타르류, 피치류, 코크스류 등을 500 내지 3000의 온도범위에서 열처리하여 제조한 편평상 형태인 것일 수 있다.The artificial graphite primary particles according to an embodiment of the present invention may be a flat form prepared by heat-treating coal-based heavy oil, petroleum-based heavy oil, tars, pitches, cokes and the like in a temperature range of 500 to 3000. .
바람직하게는, 상기 인조흑연 1차 입자는 니들 코크스(needle cokes), 모자익 코크스(mosaic cokes) 및 콜타르피치(coaltar pitch)로 이루어진 군으로부터 선택된 1종 이상을 열처리하여 제조한 것일 수 있다. 즉, 상기 인조흑연 1차 입자는 니들 코크스계 인조흑연 1차 입자, 모자익 코크스계 인조흑연 1차 입자 및 콜타르피치계 인조흑연 1차 입자 중 1종 이상일 수 있으며, 바람직하게는 모자익 코크스계 인조흑연 1차 입자 및 콜타르피치계 인조흑연 1차 입자 중 1종 이상일 수 있다. Preferably, the artificial graphite primary particles may be prepared by heat-treating one or more selected from the group consisting of needle cokes, moxa cokes, and coal tar pitch. That is, the artificial graphite primary particles may be at least one of needle coke-based artificial graphite primary particles, mosaic coke-based artificial graphite primary particles and coal tar pitch artificial graphite primary particles, preferably mosaic coke-based artificial graphite It may be at least one of primary particles and coal tar pitch-based artificial graphite primary particles.
상기 콜타르피치계 인조흑연은 MCMB(meso-carbon microbeads)형 인조흑연인 것일 수 있다.The coal tar pitch artificial graphite may be MCMB (meso-carbon microbeads) artificial graphite.
또한, 상기 인조흑연 1차 입자는 높은 결정성을 갖는 것 일수 있다. 상기 결정성은 X선 회절 분석치로 나타낼 수 있으며, 구체적으로는 상기 인조흑연 1차 입자의 분체 상태의 측정시 a축 방향의 결정자의 크기(La)가 35 nm 내지 45 nm이고, c축 방향의 결정자의 크기(Lc)가 15 nm 내지 30 nm일 수 있으며, 상기 인조흑연 1차 입자는 X선 회절에 의한 (002)면의 면간격(d002)이 0.3365 nm 내지 0.3380 nm일 수 있다. 또한, 전극 상태에 X선 회절에 의한 (002)면과 (110)면의 피크강도비(I002/I110)가 50 내지 150이고, (004)면과 (110)면의 피크강도비(I004/I110)가 5 내지 15인 것일 수 있다. 여기에서, 상기 X선 회절 분석치는 앞서 언급한 방법과 동일한 방법을 통하여 측정할 수 있다. In addition, the artificial graphite primary particles may be one having high crystallinity. The crystallinity may be expressed by an X-ray diffraction analysis. Specifically, when the powder state of the artificial graphite primary particles is measured, the size (La) of the crystallites in the a-axis direction is 35 nm to 45 nm, and the crystallites in the c-axis direction. The size Lc may be 15 nm to 30 nm, and the artificial graphite primary particles may have a plane spacing (d 002 ) of the (002) plane by X-ray diffraction of 0.3365 nm to 0.3380 nm. In addition, the peak intensity ratio (I 002 / I 110 ) between the (002) plane and the (110) plane by the X-ray diffraction is 50 to 150 in the electrode state, and the peak intensity ratio (the (004) plane and the (110) plane ( I 004 / I 110 ) may be 5 to 15. Here, the X-ray diffraction analysis value can be measured through the same method as the above-mentioned method.
상기 인조흑연 1차 입자가, 상기한 a축 방향의 결정자 크기, c축 방향의 결정자의 크기, 면간격 및/또는 피크강도비 등의 결정 특성을 가짐으로써 우수한 용량 특성과 c축 방향으로의 높은 스웰링 특성을 발현할 수 있다.The artificial graphite primary particles have excellent crystallinity characteristics such as crystallite size in the a-axis direction, crystallite size in the c-axis direction, interplanar spacing and / or peak intensity ratio, and thus have excellent capacity characteristics and high c-axis direction. Swelling properties can be expressed.
상기 인조흑연 1차 입자의 용량은 320 mAh/g 내지 340 mAh/g일 수 있다. 여기에서, 상기 용량은 상기 인조흑연 1차 입자를 음극 활물질로 사용하여 제작한 이차전지(Half-cell)의 방전 용량을 나타낸다. The artificial graphite primary particles may have a capacity of 320 mAh / g to 340 mAh / g. Here, the capacity represents the discharge capacity of a half-cell produced using the artificial graphite primary particles as a negative electrode active material.
상기 인조흑연 1차 입자의 평균입경은 2 ㎛ 내지 10 ㎛일 수 있으며, 바람직하게는 상기 비정질계 탄소재가 코팅된 천연흑연 1차 입자와 같거나 작을 수 있다. 평균입경이 상기 범위 내일 경우에는 급속 충전성이나 사이클 특성이 우수할 수 있다.The average particle diameter of the artificial graphite primary particles may be 2 ㎛ to 10 ㎛, preferably may be the same as or smaller than the natural graphite primary particles coated with the amorphous carbon material. When the average particle diameter is within the above range, the rapid filling property or the cycle characteristic may be excellent.
본 발명에 따른 상기 흑연 2차 입자는 앞서 언급한 비정질계 탄소재가 코팅된 천연흑연 1차 입자와 인조흑연 1차 입자를 포함하는 것으로, 구체적으로는 비정질계 탄소재가 코팅된 천연흑연 1차 입자와 인조흑연 1차 입자가 집합, 결합 또는 조립화되어 하나의 덩어리로 형성된 것일 수 있다. 이때, 상기 흑연 2차 입자는 비정질계 탄소재가 코팅된 천연흑연 1차 입자와 인조흑연 1차 입자를 3:7 내지 7:3의 중량비(비정질계 탄소재가 코팅된 천연흑연 1차 입자:인조흑연 1차 입자=7:3 내지 3:7)로 포함하는 것일 수 있다. 바람직하게는, 4:6 내지 6:4의 중량비일 수 있다. The graphite secondary particles according to the present invention include natural graphite primary particles and artificial graphite primary particles coated with the amorphous carbon material, and specifically, natural graphite primary particles coated with the amorphous carbon material. Artificial graphite primary particles may be aggregated, bonded or granulated to form a single mass. In this case, the graphite secondary particles are a natural graphite primary particles coated with amorphous carbon material and artificial graphite primary particles in a weight ratio of 3: 7 to 7: 3 (natural graphite primary particles coated with amorphous carbon material: artificial graphite Primary particles = 7: 3 to 3: 7). Preferably, the weight ratio may be 4: 6 to 6: 4.
상기 비정질계 탄소재가 코팅된 천연흑연 1차 입자와 인조흑연 1차 입자를 집합, 결합 또는 조립화하는 방법은 특별히 한정되지 않고 당업계에 통상적으로 공지된 방법에 의하여 수행할 수 있으나, 예컨대 이종의 1차 입자에 바인더, 촉매 등을 혼합하고 열처리하여 상기 이종의 1차 입자가 집합, 결합 또는 조립화된 흑연 2차 입자를 제조할 수 있다. The method of gathering, combining, or granulating the natural graphite primary particles and artificial graphite primary particles coated with the amorphous carbon material is not particularly limited and may be performed by a method commonly known in the art, but for example, heterogeneous A binder, a catalyst, and the like may be mixed with the primary particles and subjected to heat treatment to prepare graphite secondary particles in which the heterogeneous primary particles are aggregated, bonded, or granulated.
구체적으로는, 질소 또는 아르곤 분위기하 진공 반응기에 비정질계 탄소재가 코팅된 천연흑연 1차 입자, 인조흑연 1차 입자, 바인더 및 촉매를 투입하여 혼합하고 1000 내지 2800에서 열처리하여 흑연 2차 입자를 제조할 수 있다. 상기의 온도 범위에서 열처리함으로써 촉매가 제거되어 최종 생성된 흑연 2차 입자 내에 세공이 형성될 수 있으며, 결점이 극히 적고, 높은 결정성을 갖는 흑연 2차 입자를 수득할 수 있다. 즉, 1000 미만의 온도로 열처리할 경우에는 흑연화가 정상적으로 이루어지지 않아 용량 발현이 이루어지지 않을 우려가 있고, 2800를 초과하게 되면 스웰링 특성이 열화될 우려가 있어, 가능하면 1000 내지 2800의 범위로 수행하는 것이 바람직할 수 있다.Specifically, natural graphite primary particles, artificial graphite primary particles, binders and catalysts coated with an amorphous carbon material are introduced into a vacuum reactor under a nitrogen or argon atmosphere, mixed, and heat treated at 1000 to 2800 to produce graphite secondary particles. can do. By heat treatment in the above temperature range, the catalyst may be removed to form pores in the finally produced graphite secondary particles, and the graphite secondary particles having extremely low defects and high crystallinity may be obtained. That is, when heat treatment at a temperature of less than 1000 there is a fear that the capacity does not occur because the graphitization is not normally performed, and if it exceeds 2800, the swelling characteristics may be degraded, if possible in the range of 1000 to 2800 It may be desirable to perform.
상기 흑연 2차 입자는 총 세공용적이 3 cm3/g 내지 30 cm3/g일 수 있으며, 비표면적이 1 m2/g 내지 10 m2/g일 수 있다. 이에, 이러한 비표면적 및/또는 세공용적을 갖는 상기 흑연 2차 입자를 음극 활물질로 사용한 리튬 이차전지는 음극 내에 기공이 많은 구조를 확보할 수 있어 입출력 특성이 개선됨과 동시에 스웰링 특성이 향상될 수 있으며, 또한 충방전 용량 특성이 향상될 수 있다.The graphite secondary particles may have a total pore volume of 3 cm 3 / g to 30 cm 3 / g, and a specific surface area of 1 m 2 / g to 10 m 2 / g. Thus, a lithium secondary battery using the graphite secondary particles having such a specific surface area and / or pore volume as a negative electrode active material can secure a structure having many pores in the negative electrode, thereby improving input / output characteristics and improving swelling characteristics. In addition, the charge and discharge capacity characteristics can be improved.
상기 바인더는 특별히 한정되지 않으나, 예컨대 석유, 석탄, 인조피치, 타르 등을 사용할 수 있다. The binder is not particularly limited, and for example, petroleum, coal, artificial pitch, tar, or the like may be used.
상기 촉매는 규소, 철, 니켈, 티탄, 붕소 등의 탄화물, 산화물, 질화물 등을 사용할 수 있으며, 사용량은 특별히 한정되지 않으나 전체 1차 입자 및 바인더 합계량 100 중량부에 대하여 1 중량부 내지 50 중량부를 사용할 수 있다. As the catalyst, carbides such as silicon, iron, nickel, titanium, and boron, oxides, nitrides, and the like may be used. The amount of the catalyst is not particularly limited, but is 1 to 50 parts by weight based on 100 parts by weight of the total amount of the primary particles and the binder. Can be used.
또한, 본 발명에 따른 상기 흑연 2차 입자는 구형상인 것이 바람직할 수 있으며, 어스팩트비가 1 내지 1.5인 것일 수 있다. 만약, 어스팩트비가 상기의 범위를 벗어날 경우에는 상기 흑연 2차 입자를 포함하는 음극 활물질을 사용하여 음극을 제조할 때 집전체의 변형, 연신, 파단과 같은 문제를 발생시켜 활물질층의 고밀도화가 저하될 수 있다. 또한, 상기 흑연 2차 입자가 상기의 어스팩트비를 벗어나 구형상에서 크게 벗어 나게 되면 c축 방향으로의 배향성이 증가될 수 있어 이를 음극 활물질로서 포함하는 리튬 이차전지의 스웰링 특성이 저하될 수 있고, 상기 흑연 2차 입자를 포함하는 음극 활물질을 이용하여 음극을 제작 할시 큰 기공의 분포에 악영향을 주게되고 결과적으로 상기 흑연 2차 입자를 포함하는 리튬 이차전지의 입출력 특성 또한 저하될 수 있다. In addition, the graphite secondary particles according to the present invention may be preferably spherical, the aspect ratio may be 1 to 1.5. If the aspect ratio is out of the above range, when the negative electrode is manufactured using the negative electrode active material including the graphite secondary particles, problems such as deformation, stretching, and breakage of the current collector may occur, thereby reducing the density of the active material layer. Can be. In addition, when the graphite secondary particles deviate largely out of the spherical shape outside of the aspect ratio, the orientation in the c-axis direction may be increased, thereby reducing the swelling characteristics of the lithium secondary battery including the negative electrode active material. The negative electrode active material including the graphite secondary particles may adversely affect the distribution of large pores, and as a result, the input / output characteristics of the lithium secondary battery including the graphite secondary particles may also be degraded.
상기 흑연 2차 입자의 평균입경은 10 ㎛ 내지 30 ㎛일 수 있으며, 전극 상태 X선 회절 분석에 의한 (002)면과 (110)면의 피크강도비(I002/I110)가 200 내지 400이고, (004)면과 (110)면의 피크강도비(I004/I110)가 10 내지 25일 수 있다. 이때, 상기 피크강도비는 X선 회절 분석을 통하여 수득할 수 있으며, X선 회절 분석은 앞서 언급한 방법과 동일한 방법을 통하여 수행할 수 있다. The average particle diameter of the graphite secondary particles may be 10 ㎛ to 30 ㎛, the peak intensity ratio (I 002 / I 110 ) of the (002) plane and (110) plane by electrode state X-ray diffraction analysis is 200 to 400 The peak intensity ratio (I 004 / I 110 ) of the (004) plane and the (110) plane may be 10 to 25. In this case, the peak intensity ratio may be obtained through X-ray diffraction analysis, and X-ray diffraction analysis may be performed by the same method as mentioned above.
본 발명에 따른 상기 흑연 2차 입자는 상기 흑연 2차 입자 내에 고용량, 고출력의 비정질계 탄소재가 코팅된 천연흑연 1차 입자와 높은 사이클 특성과 우수한 스웰링 특성을 갖는 인조 흑연 1차 입자를 포함하고 있어 고용량 및 고출력 특성을 나타낼 뿐 아니라 우수한 사이클 특성 및 스웰링 특성을 나타낼 수 있다. 뿐만 아니라, 상기 흑연 2차 입자를 음극 활물질로 사용할 경우, 상기 흑연 2차 입자 내에 미세 세공이 미시적인 버퍼 역할을 수행할 수 있어 단순히 이종의 흑연을 혼합 사용한 음극 활물질에 비하여 상대적으로 강한 압연에도 형태가 변형되거나 분해되지 않고 우수한 압연성을 가질 수 있으며, 이에 활물질층의 고밀도화를 가능하게 할 수 있다. The graphite secondary particles according to the present invention includes natural graphite primary particles coated with a high-capacity, high-output amorphous carbon material in the graphite secondary particles, and artificial graphite primary particles having high cycle characteristics and excellent swelling characteristics. It not only shows high capacity and high power characteristics but also shows excellent cycle characteristics and swelling characteristics. In addition, when the graphite secondary particles are used as a negative electrode active material, the fine pores in the graphite secondary particles can act as a microscopic buffer, so that even when the graphite secondary particles are relatively strong compared to the negative electrode active material using a mixture of different types of graphite May have excellent rollability without being deformed or decomposed, thereby enabling higher density of the active material layer.
전술한 바와 같이, 본 발명에 따른 상기 흑연 2차 입자는 이차전지용 음극 활물질에 포함되는 것일 수 있고, 상기 음극 활물질을 제조하는 방법을 정리해 보면 다음과 같을 수 있다.As described above, the graphite secondary particles according to the present invention may be included in the negative electrode active material for a secondary battery, and the method for manufacturing the negative electrode active material may be as follows.
먼저, 비정질계 탄소재 전구체 물질과 천연흑연 1차 입자를 혼합하고 열처리하여 비정질계 탄소재가 코팅된 천연흑연 1차 입자를 제조하고; 석탄계 중질유, 섬유계 중질유, 타르류, 피치류 및 코크스류로 이루어진 군에서 선택된 1 종 이상을 500 내지 3000℃의 열처리로 분체 흑연화하여 인조흑연 1차 입자를 제조하고; 비정질계 탄소재가 코팅된 천연흑연 1차 입자, 인조흑연 1차 입자, 바인더 및 촉매를 혼합한 후; 1000 내지 2800℃로 열처리하여 흑연 2차 입자를 제조하는 과정을 포함하여 제조될 수 있다.First, the amorphous carbon material precursor material and the natural graphite primary particles are mixed and heat-treated to prepare natural graphite primary particles coated with the amorphous carbon material; At least one selected from the group consisting of coal-based heavy oil, fibrous heavy oil, tars, pitches, and coke powder is graphitized by heat treatment at 500 to 3000 ° C. to prepare artificial graphite primary particles; Mixing natural graphite primary particles, artificial graphite primary particles, a binder, and a catalyst coated with an amorphous carbon material; It may be prepared including a process of producing a graphite secondary particles by heat treatment at 1000 to 2800 ℃.
한편, 본 발명에 따른 흑연 2차 입자를 포함하는 음극 활물질을 제조하는 방법이 상기 방법으로 국한 되는 것은 아니고, 다른 방법이 적용될 수 있으며, 그 다른 방법 중 하나로는, 천연흑연 1차 입자 및 이흑연화 탄소(soft carbon) 입자를 혼합하여 2차 입자로 조립하는 단계; 상기 조립된 2차 입자를 3000 내지 3200℃의 열처리로 분체 흑연화 하여 흑연 2차 입자를 제조하는 단계;를 포함하는 방법이 있을 수 있다. On the other hand, the method for producing the negative electrode active material including the graphite secondary particles according to the present invention is not limited to the above method, other methods can be applied, one of the other methods, natural graphite primary particles and digraphitization Mixing the soft carbon particles and assembling them into secondary particles; There may be a method comprising a; to prepare a graphite secondary particles by powder graphitization of the assembled secondary particles by heat treatment at 3000 to 3200 ℃.
다시 말해서, 상기 예시한 두 가지의 방법을 통해서 제조되는 흑연 2차 입자를 포함하는 음극 활물질은 그 구성 물질로서 비정질계 탄소재가 코팅된 천연흑연 1차 입자와 인조흑연 1차 입자, 그리고 흑연 2차 입자가 전술한 결정 특성을 가짐으로써, 우수한 용량 특성을 발현할 수 있고, 스웰링 특성이 향상된 이차전지를 제공할 수 있다.In other words, the negative electrode active material including the graphite secondary particles manufactured by the two methods exemplified above is composed of natural graphite primary particles, artificial graphite primary particles, and graphite secondary particles coated with an amorphous carbon material as its constituent materials. By having the above-described crystal characteristics, the particles can express excellent capacity characteristics, and can provide a secondary battery with improved swelling characteristics.
또한, 본 발명은 상기의 흑연 2차 입자를 포함하는 리튬 이차전지용 음극 활물질 슬러리가 집전체 상에 도포된 이차전지용 음극을 제공한다. In addition, the present invention provides a negative electrode for a secondary battery in which the negative electrode active material slurry for a lithium secondary battery including the graphite secondary particles is coated on a current collector.
본 발명의 일 실시예에 따른 상기 음극은 상기 흑연 2차 입자를 포함하는 음극 활물질을 음극 집전체에 도포하고 건조 및 압연하여 제조할 수 있다. The negative electrode according to an embodiment of the present invention may be prepared by applying a negative electrode active material including the graphite secondary particles to a negative electrode current collector, drying and rolling.
상기 음극 집전체는 일반적으로 3 ㎛ 내지 500 ㎛의 두께인 것을 사용할 수 있으며, 당해 전지에 화학적 변화를 유발하지 않으면서 높은 도전성을 가지는 것이라면 특별히 제한되는 것은 아니나, 예컨대 구리, 스테인레스 스틸, 알루미늄, 니켈, 티탄, 소성 탄소 또는 알루미늄이나 스테인레스 스틸의 표면에 카본, 니켈, 티탄 또는 은 등으로 표면 처리한 것 등이 사용될 수 있다. The negative electrode current collector may be generally used having a thickness of 3 ㎛ to 500 ㎛, and is not particularly limited as long as it has a high conductivity without causing chemical changes in 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.
상기 음극 활물질은 상기 흑연 2차 입자에 바인더와 도전재 및 충진제등의 첨가제를 첨가하고 혼합하여 제조한 것일 수 있다. 또한, 유기계 혼합 시에는 분산제를 추가로 첨가할 수 있다.The negative electrode active material may be prepared by adding and mixing an additive such as a binder, a conductive material, and a filler to the graphite secondary particles. In addition, a dispersing agent can be added further at the time of organic mixing.
상기 바인더는 상기 흑연 2차 입자와 도전재의 결합과 집전체에 대한 결합에 조력하는 성분으로서, 통상적으로 흑연 2차 입자 총량을 기준으로 1 중량% 내지 30 중량%로 첨가될 수 있다. 이러한 바인더는 특별히 한정되지 않고 당업계에 공지된 통상적인 것을 사용할 수 있으나, 예컨대 비닐리덴플루오라이드-헥사플로우로프로필렌 코폴리머(PVBF-co-HEP), 폴리비닐리덴플루오라이드(polyvinylidenefluoride), 폴리아크릴로니트릴(polyacrylonitrile), 폴리메틸메타크릴레이트(polymethaylmethacrylate), 폴리비닐알코올, 카르복시메틸셀룰로오스(CMC), 전분, 히드록시프로필셀룰로오스, 재생 셀룰로오스, 폴리비닐피롤리돈, 테트라플루오로에틸렌, 폴리에틸렌, 폴리프로필렌, 폴리아크릴산, 에틸렌-프로필렌-디엔 모노머(EPDM), 술폰화 EPDM, 스티렌-부티렌 고무(SBR) 및 불소 고무로 이루어진 군으로부터 선택된 1종 또는 2종 이상의 혼합물일 수 있으며, 특히 카르복시메틸셀룰로오스(CMC) 및 스티렌-부티렌 고무(SBR)을 혼합하여 사용할 수 있다. The binder is a component that assists the bonding of the graphite secondary particles and the conductive material and the bonding to the current collector, and may be generally added in an amount of 1 wt% to 30 wt% based on the total amount of the graphite secondary particles. Such binders are not particularly limited and may be conventional ones known in the art, but for example, vinylidene fluoride-hexafluoropropylene copolymer (PVBF-co-HEP), polyvinylidenefluoride, polyacryl Ronitrile (polyacrylonitrile), polymethyl methacrylate (polymethaylmethacrylate), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, poly Propylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butyrene rubber (SBR) and fluorine rubber, and may be selected from the group consisting of two or more, especially carboxymethylcellulose (CMC) and styrene-butylene rubber (SBR) can be used in combination.
상기 도전재는 통상적으로 흑연 2차 입자 전체 중량을 기준으로 0.05 중량% 내지 5 중량%로 첨가될 수 있다. 이러한 도전재는 특별히 한정되지 않고 전지의 기타 요소들과 부반응을 유발하지 않으면서 도전성을 가진 것이라면 특별히 제한되는 것은 아니나, 예컨대 천연흑연이나 인조흑연 등의 흑연; 카본 블랙(super-p), 아세틸렌 블랙, 케첸 블랙, 채널 블랙, 퍼네이스 블랙, 램프 블랙, 서머 블랙 등의 카본 블랙; 탄소 섬유나 금속 섬유 등의 도전성 섬유; 불화 카본, 알루미늄, 니켈 분말 등의 금속 분말; 산화아연, 티탄산 칼륨 등의 도전성 위스커; 산화 티탄 등의 도전성 금속 산화물; 폴리페닐렌 유도체 등의 도전성 소재 등일 수 있다. The conductive material may typically be added in an amount of 0.05 wt% to 5 wt% based on the total weight of the graphite secondary particles. The conductive material is not particularly limited and is not particularly limited as long as it is conductive without causing side reactions with other elements of the battery. Examples thereof include graphite such as natural graphite and artificial graphite; Carbon blacks such as carbon black (super-p), acetylene black, ketjen black, channel black, furnace black, lamp black and summer black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride powder, aluminum powder and nickel powder; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives.
상기 충진제는 음극의 팽창을 억제하는 성분으로서 필요에 따라 사용 여부를 정할 수 있으며, 당해 전지에 화학적 변화를 유발하지 않으면서 섬유상 재료라면 특별히 제한되는 것은 아니나, 예컨대 폴리에틸렌, 폴리프로필렌 등의 올레핀계 중합체; 유리섬유, 탄소섬유 등의 섬유상 물질일 수 있다. The filler is a component for inhibiting the expansion of the negative electrode and can be used or not as necessary. If the filler is a fibrous material without causing chemical changes in the battery, it is not particularly limited, for example, an olefin polymer such as polyethylene or polypropylene. ; It may be a fibrous material such as glass fiber, carbon fiber.
상기 분산제(분산액)로는 특별히 한정되는 것은 아니나, 예컨대 이소프로필알코올, N-메틸피로릴돈(NMP), 아세톤 등일 수 있다.The dispersant (dispersion liquid) is not particularly limited, but may be, for example, isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or the like.
상기 도포는 당업계에 통상적으로 공지된 방법에 의하여 수행할 수 있으나, 예컨대 상기 음극 활물질을 상기 음극 집전체 일측 상면에 분배시킨 후 닥터 블레이드(doctor blade) 등을 사용하여 균일하게 분산시켜 수행할 수 있다. 이외에도, 다이 캐스팅(die casting), 콤마 코팅(comma coating), 스크린 프린팅(screen printing) 등의 방법을 통하여 수행할 수 있다. The coating may be performed by a method commonly known in the art, but for example, the negative electrode active material may be distributed on an upper surface of one side of the negative electrode current collector, and then uniformly dispersed using a doctor blade or the like. have. In addition, the method may be performed by a die casting method, a comma coating method, a screen printing method, or the like.
상기 건조는 특별히 한정되는 것은 아니나 50 내지 200의 진공오븐에서 1일 이내로 수행하는 것일 수 있다. The drying is not particularly limited, but may be performed within one day in a vacuum oven of 50 to 200.
아울러, 본 발명은 상기의 이차전지용 음극과 양극, 상기 음극과 양극 사이에 개재된 분리막 및 전해질을 포함하는 리튬 이차전지를 제공한다. In addition, the present invention provides a lithium secondary battery including the separator and the electrolyte interposed between the negative electrode and the positive electrode, the negative electrode and the positive electrode for the secondary battery.
본 발명의 일 실시예에 따른 상기 리튬 이차전지는 비정질계 탄소재가 코팅된 천연흑연 1차 입자와 인조흑연 1차 입자가 집합, 결합 또는 조립화되어 형성된 흑연 2차 입자를 포함하는 음극 활물질이 도포된 음극과 양극, 상기 음극과 양극 사이에 개재된 분리막 및 전해질을 포함하는 것을 특징으로 한다. The lithium secondary battery according to an embodiment of the present invention is coated with a negative electrode active material including graphite secondary particles formed by the aggregation, bonding or granulation of natural graphite primary particles and artificial graphite primary particles coated with an amorphous carbon material And a separator and an electrolyte interposed between the negative electrode and the positive electrode, the negative electrode and the positive electrode.
상기 양극은 특별히 한정되는 것은 아니나, 양극 집전체 일측 상면에 양극 활물질을 도포한 후 건조하여 제조할 수 있으며, 상기 양극활물질은 바인더, 도전재, 충진제 및 분산제와 같은 첨가제를 포함할 수 있다. The positive electrode is not particularly limited, but may be prepared by coating a positive electrode active material on one surface of a positive electrode current collector and then drying the positive electrode active material. The positive electrode active material may include additives such as a binder, a conductive material, a filler, and a dispersant.
상기 양극 집전체는 앞서 언급한 음극 집전체와 동일한 것이거나, 포함되는 것일 수 있다. The positive electrode current collector may be the same as or included in the aforementioned negative electrode current collector.
상기 양극에 사용되는 바인더, 도전재, 충진제 및 분산제와 같은 첨가제는 앞서 언급한 음극 제조에 사용된 것과 동일하거나, 포함되는 것일 수 있다. Additives such as binders, conductive materials, fillers, and dispersants used in the positive electrode may be the same as or included in the aforementioned negative electrode.
상기 양극 활물질은 특별히 한정되지 않고 당업계에 공지된 통상적인 것을 사용할 수 있으나, 예컨대 리튬 코발트 산화물(LiCoO2), 리튬 니켈 산화물(LiNiO2) 등의 층상 화합물이나, 하나 또는 그 이상의 전이금속으로 치환된 화합물; 리튬망간 산화물(LiMnO2); 리튬 동 산화물(Li2CuO2); 바나듐 산화물; 니켈 사이트형 리튬 니켈 산화물(Lithiated nickel oxide); 리튬 망간 복합 산화물, 디설파이드 화합물 또는 이들 조합에 의해 형성되는 복합 산화물 등과 같이 리튬 흡착 물질(lithium intercalation material)을 주성분으로 하는 화합물일 수 있다. The positive electrode active material is not particularly limited and may be a conventional one known in the art, for example, a layered compound such as lithium cobalt oxide (LiCoO 2 ), lithium nickel oxide (LiNiO 2 ), or one or more transition metals. Compound; Lithium manganese oxide (LiMnO 2 ); Lithium copper oxide (Li 2 CuO 2 ); Vanadium oxide; Nickel site type lithium nickel oxide; It may be a compound containing a lithium intercalation material as a main component, such as a lithium manganese composite oxide, a disulfide compound, or a composite oxide formed by a combination thereof.
상기 분리막으로는 높은 이온 투과도와 기계적 강도를 가지는 절연성의 얇은 박막일 수 있으며, 일반적으로 0.01 ㎛ 내지 10 ㎛의 기공직경, 5 ㎛ 내지 300 ㎛의 두께를 갖는 것일 수 있다. 이러한 분리막으로는 다공성 고분자 필름, 예컨대 에틸렌 단독 중합체, 프로필렌 단독중합체, 에틸렌/부텐 공중합체, 에틸렌/헥센 공중합체 및 에틸렌/메타크릴레이트 공중합체 등과 같은 폴리올레핀계 고분자로 제조한 다공성 고분자 필름을 단독으로 또는 이들을 적층하여 사용할 수 있으며, 또는 통상적인 다공성 부직포, 예를 들어 고융점의 유리 섬유, 폴리에틸렌테레프탈레이트 섬유 등으로 된 부직포를 사용할 수 있으나, 이에 제한되는 것은 아니다. The separator may be an insulating thin film having high ion permeability and mechanical strength, and may generally have a pore diameter of 0.01 μm to 10 μm and a thickness of 5 μm to 300 μm. As such a separator, a porous polymer film, such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer and an ethylene / methacrylate copolymer, may be used. Alternatively, these may be laminated and used, or a nonwoven fabric made of a conventional porous nonwoven fabric, for example, a high melting glass fiber, polyethylene terephthalate fiber, or the like may be used, but is not limited thereto.
또한, 상기 전해질은 전해질에 통상적으로 사용되는 유기용매 및 리튬염을 포함할 수 있으며, 특별히 제한되는 것은 아니다. In addition, the electrolyte may include an organic solvent and a lithium salt commonly used in the electrolyte, and are not particularly limited.
상기 리튬염의 음이온으로는 F-, Cl-, I-, NO3 -, N(CN)2 -, BF4 -, ClO4 -, PF6 -, (CF3)2PF4 -, (CF3)3PF3 -, (CF3)4PF2 -, (CF3)5PF-, (CF3)6P-, CF3SO3 -, CF3CF2SO3 -, (CF3SO2)2N-, (FSO2)2N-, CF3CF2(CF3)2CO-, (CF3CO2)2CH-, (SF5)3C-, (CF3SO2)3C-, CF3(CF2)7SO3 -, CF3CO2 -, CH3CO2 -, SCN- 및 (CF3CF2SO2)2N-로 이루어진 군으로부터 선택된 1종 이상일 수 있다. With the lithium salt of the anion is F -, Cl -, I - , NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) 2 PF 4 -, (CF 3 ) 3 PF 3 -, (CF 3) 4 PF 2 -, (CF 3) 5 PF -, (CF 3) 6 P -, CF 3 SO 3 -, CF 3 CF 2 SO 3 -, (CF 3 SO 2 ) 2 N -, (FSO 2 ) 2 N -, CF 3 CF 2 (CF 3) 2 CO -, (CF 3 CO 2) 2 CH -, (SF 5) 3 C -, (CF 3 SO 2) 3 C -, CF 3 (CF 2 ) 7 SO 3 -, CF 3 CO 2 -, CH 3 CO 2 -, SCN - , and (CF 3 CF 2 SO 2) 2 N - may be at least one member selected from the group consisting of .
상기 유기용매로는 대표적으로는 프로필렌 카보네이트, 에틸렌 카보네이트, 디에틸카보네이트, 디메틸카보네이트, 에틸메틸카보네이트, 메틸프로필카보네이트, 디프로필카보네이트, 디메틸술폭사이드, 아세토니트릴, 디메톡시에탄, 디에톡시에탄, 비닐렌카보네이트, 술포란, 감마-부티로락톤, 프로필렌설파이트 및 테트라하이드로퓨란으로 이루어진 군으로부터 선택된 1종 이상인 것일 수 있다. Typical organic solvents include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, methylpropyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane and vinylene. It may be one or more selected from the group consisting of carbonate, sulfolane, gamma-butyrolactone, propylene sulfite and tetrahydrofuran.
특히, 상기 카보네이트계 유기용매 중 고리형 카보네이트인 에틸렌카보네이트 및 프로필렌카보네이트는 고점도의 유기용매로서 유전율이 높아 전해질 내의 리튬염을 잘 해리시키므로 바람직하게 사용될 수 있으며, 이러한 고리형 카보네이트 디메틸카보니에트 및 디에틸카보네이트와 같은 저점도, 저유전율 선형 카보네이트를 적당한 비율로 혼합하여 사용하면 높은 전기 전도율을 갖는 전해액을 만들 수 있어 더욱 바람직하게 사용될 수 있다. In particular, ethylene carbonate and propylene carbonate, which are cyclic carbonates among the carbonate-based organic solvents, are highly viscous organic solvents, and thus may be preferably used because they dissociate lithium salts in the electrolyte well. Such cyclic carbonate dimethylcarboniate and di When a low viscosity, low dielectric constant linear carbonate such as ethyl carbonate is mixed and used in an appropriate ratio, an electrolyte having high electrical conductivity can be prepared, and thus it can be more preferably used.
또한, 상기 전해질은 필요에 따라 충방전 특성, 난연성 특성 등의 개선을 위하여 피리딘, 트리에틸포스파이트, 트리에탄올아민, 환상에테르, 에틸렌 디아민, n-글라임(glyme), 헥사 인산 트리 아미드, 니트로벤젠 유도체, 유황, 퀴논 이민 염료, N-치환 옥사졸리디논, N,N-치환 이미다졸리딘, 에틸렌 글리콜 디알킬 에테르, 암모늄염, 피롤, 2-메톡시 에탄올, 삼염화 알루미늄 등을 추가로 포함할 수 있다. 경우에 따라서는, 불연성을 부여하기 위하여 사염화탄소, 삼불화에틸렌 등의 할로겐 함유 용매를 더 포함할 수 있으며, 고온 보존 특성을 향상시키기 위하여 이산화탄산 가스를 더 포함할 수도 있고, FEC(fluoro-ethylene carbonate), PRS(propene sultone), FPC(fluoro-propylene carbonate) 등을 더 포함할 수 있다. In addition, the electrolyte may be pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexa phosphate triamide, nitrobenzene to improve charge / discharge characteristics, flame retardancy characteristics, etc. as necessary. Derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrroles, 2-methoxy ethanol, aluminum trichloride, and the like. have. In some cases, the solvent may further include a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride to impart nonflammability, may further include carbon dioxide gas to improve high temperature storage characteristics, and may further include fluoro-ethylene carbonate. ), PRS (propene sultone), FPC (fluoro-propylene carbonate) may further include.
본 발명의 리튬 이차전지는 양극과 음극 사이에 분리막을 배치하여 전극 조립체를 형성하고, 상기 전극 조립체는 원통형 전지 케이스 또는 각형 전지 케이스에 넣은 다음 전해질을 주입하여 제조할 수 있다. 또는, 상기 전극 조립체를 적층한 후, 이를 전해질에 함침시키고 얻어진 결과물을 전지 케이스에 넣어 밀봉하여 제조할 수도 있다. In the lithium secondary battery of the present invention, an electrode assembly is formed by disposing a separator between a positive electrode and a negative electrode, and the electrode assembly may be manufactured by putting an electrolyte into a cylindrical battery case or a square battery case. Alternatively, after stacking the electrode assembly, it may be prepared by impregnating it in an electrolyte and sealing the resultant obtained in a battery case.
본 발명에서 사용되는 전지 케이스는 당분야에서 통상적으로 사용되는 것이 채택될 수 있고, 전지의 용도에 따른 외형에 제한이 없으며, 예를 들면, 캔을 사용한 원통형, 각형, 파우치(pouch)형 또는 코인(coin)형 등이 될 수 있다. The battery case used in the present invention may be adopted that is commonly used in the art, there is no limitation on the appearance according to the use of the battery, for example, cylindrical, square, pouch type or coin using a can (coin) type and the like.
본 발명에 따른 리튬 이차전지는 소형 디바이스의 전원으로 사용되는 전지셀에 사용될 수 있을 뿐만 아니라, 다수의 전지셀들을 포함하는 중대형 전지모듈에 단위전지로도 바람직하게 사용될 수 있다. 상기 중대형 디바이스의 바람직한 예로는 전기자동차, 하이브리드 전기자동차, 플러그-인 하이브리드 전기자동차, 전력 저장용 시스템 등을 들 수 있지만, 이들 만으로 한정되는 것은 아니다. The lithium secondary battery according to the present invention may not only be used in a battery cell used as a power source for a small device, but also preferably used as a unit battery in a medium-large battery module including a plurality of battery cells. Preferred examples of the medium and large devices include, but are not limited to, electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, power storage systems, and the like.
실시예Example
이하, 하기 실시예 및 실험예에 의하여 본 발명을 더욱 상세하게 설명하고자 한다. 그러나, 하기 실시예 및 실험예는 본 발명을 예시하기 위한 것으로 이들 만으로 본 발명의 범위가 한정되는 것은 아니다.Hereinafter, the present invention will be described in more detail with reference to the following examples and experimental examples. However, the following Examples and Experimental Examples are provided to illustrate the present invention, and the scope of the present invention is not limited only to these examples.
제조예Production Example 1 One
a축 방향의 결정자 크기가 50 nm, c축 방향의 결장자 크기가 30 nm, (002)면의 면간격(d002)가 0.3360 nm이고 입경이 5 ㎛인 비정질계 탄소가 코팅된 천연흑연 1차 입자(코팅량: 2%) 50 중량% 와 a축 방향의 결정자의 크기가 30 nm, c축 방향의 결정자의 크기가 20 nm, (002)면의 면간격(d002)가 0.3370 nm이고 입경이 5 ㎛인 인조흑연 1차 입자 50 중량%로 구성된 혼합물에 바인더 및 촉매를 투입하고 혼합한 후 질소 분위기 하에서 2800로 열처리하여 흑연 2차 입자를 제조하였다. 이때, 상기 인조흑연 1차 입자는 코크스계 인조흑연을 사용하였다. Natural graphite coated with amorphous carbon having a grain size of 50 nm in the a-axis direction, 30 nm in the c-axis direction, and a plane spacing (d 002 ) of the (002) plane of 0.3360 nm and a particle diameter of 5 μm. 50% by weight of the secondary particles (coating amount: 2%) and the crystallite size in the a-axis direction are 30 nm, the crystallite size in the c-axis direction is 20 nm, and the plane spacing (d 002 ) of the (002) plane is 0.3370 nm. A binder and a catalyst were added to a mixture composed of 50 wt% of artificial graphite primary particles having a particle diameter of 5 μm, mixed, and heat-treated at 2800 under a nitrogen atmosphere to prepare graphite secondary particles. At this time, the artificial graphite primary particles used coke artificial graphite.
제조된 흑연 2차 입자 96 중량%에 카본블랙계 도전재 1 중량%, 카르복시메틸셀룰로스(CMC) 1.5 중량%, 스티렌-부타디엔 고무(SBR) 1.5 중량%를 혼합하여 음극 활물질 슬러리를 제조하고, 이를 구리 호일에 150 ㎛ 두께로 도포한 후 압연 및 건조하여 음극을 제조하였다. A negative electrode active material slurry was prepared by mixing 96 wt% of the prepared graphite secondary particles with 1 wt% of carbon black conductive material, 1.5 wt% of carboxymethyl cellulose (CMC), and 1.5 wt% of styrene-butadiene rubber (SBR). The negative electrode was prepared by coating the copper foil with a thickness of 150 μm, followed by rolling and drying.
제조예Production Example 2 2
인조흑연 1차 입자가 모자익계 인조흑연인 것을 제외하고는 상기 제조예 1과 동일한 방법을 통하여 흑연 2차 입자를 제조하고, 음극을 제작하였다.Graphite secondary particles were prepared in the same manner as in Preparation Example 1, except that artificial graphite primary particles were mother-based artificial graphite, to prepare a negative electrode.
제조예Production Example 3 3
인조흑연 1차 입자가 MCMB형 인조흑연인 것을 제외하고는 상기 제조예 1과 동일한 방법을 통하여 흑연 2차 입자를 제조하고, 음극을 제작하였다.Graphite secondary particles were prepared in the same manner as in Preparation Example 1, except that the artificial graphite primary particles were MCMB-type artificial graphite, to prepare a negative electrode.
비교제조예Comparative Production Example 1 One
흑연 2차 입자 대신에 비정질계 탄소재가 코팅된 천연흑연과 인조흑연을 5:5의 중량비로 혼합하여 사용한 것을 제외하고는 상기 제조예 1과 동일한 방법을 통하여 음극을 제작하였다. An anode was manufactured in the same manner as in Preparation Example 1, except that natural graphite coated with amorphous carbon material and artificial graphite were mixed at a weight ratio of 5: 5 instead of the graphite secondary particles.
비교제조예Comparative Production Example 2 2
비정질계 탄소재가 코팅된 천연흑연 1차 입자 대신에 복수의 인조흑연 1차 입자(단일 물질)를 사용하여 흑연 2차 입자를 제조한 것을 제외하고는 상기 제조예 1과 동일한 방법을 통하여 음극을 제작하였다.A negative electrode was manufactured in the same manner as in Preparation Example 1, except that graphite secondary particles were manufactured using a plurality of artificial graphite primary particles (single material) instead of the natural graphite primary particles coated with an amorphous carbon material. It was.
제조예Production Example 4 4
열처리 온도를 2500℃로 한 것을 제외하고는 상기 제조예 1과 동일한 방법을 통하여 흑연 2차 입자를 제조하고, 음극을 제작하였다.A graphite secondary particle was produced in the same manner as in Preparation Example 1 except that the heat treatment temperature was 2500 ° C., and a negative electrode was prepared.
비교제조예Comparative Production Example 3 3
열처리 온도를 800℃로 한 것을 제외하고는 상기 제조예 1과 동일한 방법을 통하여 흑연 2차 입자를 제조하고, 음극을 제작하였다.A graphite secondary particle was prepared in the same manner as in Preparation Example 1 except that the heat treatment temperature was 800 ° C., and a negative electrode was prepared.
비교제조예Comparative Production Example 4 4
열처리 온도를 3000℃로 한 것을 제외하고는 상기 제조예 1과 동일한 방법을 통하여 흑연 2차 입자를 제조하고, 음극을 제작하였다.A graphite secondary particle was prepared in the same manner as in Preparation Example 1 except that the heat treatment temperature was 3000 ° C., and a negative electrode was prepared.
실시예Example 1 One
1) 코인형 반쪽 전지 제작1) coin type half cell
상대 전극(counter electrode)으로 리튬 금속 호일(foil)을 사용하였으며, 상기 상대 전극 및 상기 제조예 1-1에서 제조한 음극을 코인 모양으로 타발하고, LiPF6가 1 mol 및 2 중량%의 VC(vinyl chloride)가 녹아있는 카보네이트계 전해액을 주입하여 코인형 반쪽 전지를 제조하였다. Lithium metal foil was used as a counter electrode, and the counter electrode and the negative electrode prepared in Preparation Example 1-1 were punched into a coin shape, and LiPF6 was 1 mol and 2 wt% of VC (vinyl). A coin-type half cell was prepared by injecting a carbonate-based electrolyte solution containing chloride).
2) 모노셀 제작2) Monocell production
양극 활물질로서 LiCoO2 96 중량%와 카본블랙 2 중량% 및 폴리플루오로비닐리덴 2 중량%를 혼합하고 N-메틸-2-피롤리돈(NMP)를 추가로 첨가하고 혼합하여 양극 활물질 슬러리를 제조하고, 이를 알루미늄 호일에 130 ㎛ 두께로 도포한 후 압연 및 건조하여 양극을 제조하였다. A positive electrode active material slurry was prepared by mixing 96% by weight of LiCoO 2, 2 % by weight of carbon black and 2% by weight of polyfluorovinylidene as a positive electrode active material, and further adding and mixing N-methyl-2-pyrrolidone (NMP). Then, it was coated on an aluminum foil with a thickness of 130 ㎛, then rolled and dried to prepare a positive electrode.
상기 양극 및 상기 제조예 1에서 제조한 음극을 34 cm2 크기로 타발한 후 LiPF6가 1 mol 및 2 중량%의 VC(vinyl chloride)가 녹아있는 카보네이트계 전해액을 주입하여 폴리머 셀 타입의 모노셀을 제작하였다. After the cathode and the anode prepared in Preparation Example 1 were punched out to a size of 34 cm 2 , a carbonate-based electrolyte in which LiPF 6 was dissolved in 1 mol and 2 wt% of VC (vinyl chloride) was injected to form a polymer cell-type monocell. Produced.
실시예Example 2 2
음극으로 상기 제조예 2에서 제조한 음극을 사용한 것을 제외하고는 상기 실시예 1-1과 동일하게 코인형 반쪽 전지 및 모노셀을 제작하였다.A coin-type half cell and a monocell were prepared in the same manner as in Example 1-1, except that the negative electrode prepared in Preparation Example 2 was used as the negative electrode.
실시예Example 3 3
음극으로 상기 제조예 3에서 제조한 음극을 사용한 것을 제외하고는 상기 실시예 1-1과 동일하게 코인형 반쪽 전지 및 모노셀을 제작하였다.A coin-type half cell and a monocell were prepared in the same manner as in Example 1-1, except that the negative electrode prepared in Preparation Example 3 was used as the negative electrode.
비교예Comparative example 1 One
음극으로 상기 비교제조예 1에서 제조한 음극을 사용한 것을 제외하고는 상기 실시예 1-1과 동일하게 코인형 반쪽 전지 및 모노셀을 제작하였다.A coin-type half cell and a monocell were prepared in the same manner as in Example 1-1, except that the negative electrode prepared in Comparative Preparation Example 1 was used as the negative electrode.
비교예Comparative example 2 2
음극으로 상기 비교제조예 2에서 제조한 음극을 사용한 것을 제외하고는 상기 실시예 1-1과 동일하게 코인형 반쪽 전지 및 모노셀을 제작하였다.A coin-type half cell and a monocell were prepared in the same manner as in Example 1-1, except that the negative electrode prepared in Comparative Preparation Example 2 was used as the negative electrode.
실시예Example 4 4
음극으로 상기 제조예 4에서 제조한 음극을 사용한 것을 제외하고는 상기 실시예 1-1과 동일하게 코인형 반쪽 전지 및 모노셀을 제작하였다.A coin-type half cell and a monocell were prepared in the same manner as in Example 1-1, except that the negative electrode prepared in Preparation Example 4 was used as the negative electrode.
비교예Comparative example 3 3
음극으로 상기 비교제조예 3에서 제조한 음극을 사용한 것을 제외하고는 상기 실시예 1-1과 동일하게 코인형 반쪽 전지 및 모노셀을 제작하였다.A coin-type half cell and a monocell were manufactured in the same manner as in Example 1-1, except that the negative electrode prepared in Comparative Preparation Example 3 was used as the negative electrode.
비교예Comparative example 4 4
음극으로 상기 비교제조예 4에서 제조한 음극을 사용한 것을 제외하고는 상기 실시예 1-1과 동일하게 코인형 반쪽 전지 및 모노셀을 제작하였다.A coin-type half cell and a monocell were prepared in the same manner as in Example 1-1, except that the negative electrode prepared in Comparative Preparation Example 4 was used as the negative electrode.
실험예Experimental Example 1: 재료에 따른  1: according to the material 스웰링Swelling 특성 평가 Property evaluation
상기 실시예 1 내지 3 및 비교예 1 내지 2에서 제작한 각 코인형 반쪽 전지의 스웰링 특성을 비교 분석하였다. 각 전지의 두께는 코인 형태의 실시간 두께 측정 장비를 이용하여 측정하였다. 결과를 도 1에 나타내었다.The swelling characteristics of the coin-type half cells produced in Examples 1 to 3 and Comparative Examples 1 to 2 were analyzed. The thickness of each cell was measured using a coin-type real-time thickness measurement equipment. The results are shown in FIG.
도 1에 나타난 바와 같이, 본 발명에 따른 흑연 2차 입자를 음극 활물질로 포함하는 음극을 이용하여 제작된 실시예 1 내지 3의 코인형 반쪽 전지가 비교예 1 및 2의 코인형 반쪽 전지와 비교하여 전반적으로 스웰링 특성이 우수한 것을 확인하였다. As shown in FIG. 1, the coin type half cells of Examples 1 to 3 manufactured using the negative electrode including the graphite secondary particles according to the present invention as compared with the coin type half cells of Comparative Examples 1 and 2 Overall, it was confirmed that the swelling characteristics are excellent.
특히, 인조흑연으로 모자익계 인조흑연을 사용한 실시예 2와 MCMB계 인조흑연을 사용한 실시예 3의 코인형 반쪽 전지의 경우, 단순 1차 입자 혼합을 사용한 비교예 1 및 동일한 복수의 인조흑연 1차 입자를 사용하여 제조한 흑연 2차 입자를 사용한 비교예 2의 코인형 반쪽 전지와 비교하여 현저히 우수한 스웰링 특성을 나타내었다. In particular, in the case of the coin-type half-cell of Example 2 using the mother-scale artificial graphite as the artificial graphite and Example 3 using the MCMB artificial graphite, Comparative Example 1 using simple primary particle mixing and the same plurality of artificial graphite primary Compared with the coin-type half cell of Comparative Example 2 using graphite secondary particles prepared using the particles, the swelling characteristics were remarkably excellent.
실험예Experimental Example 2: 열처리 온도에 따른  2: according to the heat treatment temperature 스웰링Swelling 특성 평가 Property evaluation
상기 실시예 4 및 비교예 3과 4에서 제작한 각 코인형 반쪽 전지의 스웰링 특성을 비교 분석하였다. 각 전지의 두께는 코인 형태의 실시간 두께 측정 장비를 이용하여 측정하였다. 결과를 도 4에 나타내었다.The swelling characteristics of the coin-type half cells produced in Example 4 and Comparative Examples 3 and 4 were compared and analyzed. The thickness of each cell was measured using a coin-type real-time thickness measurement equipment. The results are shown in FIG.
도 4에 나타난 바와 같이, 본 발명에 따른 흑연 2차 입자를 음극 활물질로 포함하는 음극을 이용하여 제작된 실시예 4의 코인형 반쪽 전지가 비교예 3 및 4의 코인형 반쪽 전지와 비교하여 전반적으로 스웰링 특성이 우수한 것을 확인하였다. As shown in FIG. 4, the coin-type half cell of Example 4 fabricated using a negative electrode including graphite secondary particles according to the present invention was compared with the coin-type half cells of Comparative Examples 3 and 4. It confirmed that the swelling characteristic was excellent.
즉, 열처리 온도를 1000 내지 2800℃ 가량으로 맞추어 수행한 경우에 스웰링 특성이 우수하게 나타났으며, 상기 온도 범위를 벗어나는 경우에는 스웰링 특성이 열화됨을 확인할 수 있었다.That is, when the heat treatment temperature was adjusted to about 1000 to 2800 ° C., the swelling characteristics were excellent, and when the temperature was out of the above temperature range, the swelling characteristics were deteriorated.
실험예Experimental Example 3: 용량 특성 평가 3: Capacity Characterization
상기 실시예 1 내지 3 및 비교예 1 내지 2에서 제작한 각 코인형 반쪽 전지의 용량 특성을 비교 분석하였다. The capacity characteristics of the coin-type half cells produced in Examples 1 to 3 and Comparative Examples 1 and 2 were compared and analyzed.
상기 각 전지를 25에서 CC/CV로 0.1 C의 속도로 충전한 후, 1.5 V까지 CC로 0.1C의 속도로 방전하여 충전 및 방전 용량을 측정하고 이를 통하여 충방전 효율 및 방전율 특성을 분석하였다. 결과를 도 2에 나타내었다. Each battery was charged at a rate of 0.1 C at 25 CC / CV, and then discharged at a rate of 0.1 C at CC up to 1.5 V, thereby measuring charge and discharge capacity, and analyzing charge and discharge efficiency and discharge rate characteristics. The results are shown in FIG.
도 2에 나타난 바와 같이, 본 발명에 따른 흑연 2차 입자를 음극 활물질로 포함하는 음극을 이용하여 제작된 실시예 1 내지 3의 코인형 반쪽 전지가 비교예 1 및 2의 코인형 반쪽 전지와 비교하여 전반적으로 다소 우수하거나 유사한 정도의 용량 특성을 나타내었다.As shown in FIG. 2, the coin type half cells of Examples 1 to 3 manufactured using the negative electrode including the graphite secondary particles according to the present invention are compared with the coin type half cells of Comparative Examples 1 and 2. Overall, the capacity characteristics were somewhat better or similar.
실험예Experimental Example 4: 사이클 특성 평가 4: Cycle characteristic evaluation
상기 실시예 1 내지 3 및 비교예 1 내지 2에서 제작한 각 모노셀의 입출력 특성을 비교 분석하였다.The input and output characteristics of the monocells prepared in Examples 1 to 3 and Comparative Examples 1 to 2 were compared and analyzed.
각 모노셀을 25에서 충반전 0.2C/0.2C, 0.2C/0.5C, 0.2C/1.0C, 0.2C/2.0C 조건으로 차례로 충반전을 반복하고, 충방전 속도에 따른 용량 유지율을 분석하였다. 결과를 도 3에 나타내었다. Each monocell was repeatedly charged and recharged at 25C, 0.2C / 0.2C, 0.2C / 0.5C, 0.2C / 1.0C, and 0.2C / 2.0C under 25 conditions, and the capacity retention rate according to the charge / discharge rate was analyzed. . The results are shown in FIG.
도 3에 나타난 바와 같이, 본 발명에 따른 흑연 2차 입자를 음극 활물질로 포함하는 음극을 이용하여 제작된 실시예 1 내지 3의 모노셀이 비교예 1 및 2의 모노셀과 비교하여 전반적으로 용량 유지율이 다소 우수한 것을 확인하였다.As shown in Figure 3, the monocells of Examples 1 to 3 produced using a negative electrode containing the graphite secondary particles according to the present invention as a negative electrode active material overall capacity compared to the monocells of Comparative Examples 1 and 2 It was confirmed that the retention rate was rather excellent.

Claims (23)

  1. 비정질계 탄소재가 코팅된 천연흑연 1차 입자 및 인조흑연 1차 입자가 조립된 흑연 2차 입자를 포함하고,Natural graphite primary particles coated with an amorphous carbon material and graphite secondary particles assembled with artificial graphite primary particles,
    상기 천연흑연 1차 입자의 분체 상태 X선 회절 분석에 의한 a축 방향의 결정자의 크기가 45 nm 내지 55 nm이고, c축 방향의 결정자의 크기가 25 nm 내지 35 nm 이며,The size of crystallites in the a-axis direction is 45 nm to 55 nm, the size of the crystallites in the c-axis direction is 25 nm to 35 nm by powder state X-ray diffraction analysis of the natural graphite primary particles,
    상기 인조흑연 1차 입자의 a축 방향의 결정자의 크기가 35 nm 내지 45 nm이고, c축 방향의 결정자의 크기가 15 nm 내지 30 nm인 것인 음극 활물질.The size of the crystallites in the a-axis direction of the artificial graphite primary particles is 35 nm to 45 nm, the size of the crystallites in the c-axis direction is 15 nm to 30 nm.
  2. 청구항 1에 있어서,The method according to claim 1,
    상기 흑연 2차 입자는 총 세공용적이 3 cm3/g 내지 30 cm3/g인 것인 음극 활물질.The graphite secondary particles have a total pore volume of 3 cm 3 / g to 30 cm 3 / g.
  3. 청구항 1에 있어서,The method according to claim 1,
    상기 흑연 2차 입자는 비표면적이 1 m2/g 내지 10 m2/g인 것인 음극 활물질.The graphite secondary particles have a specific surface area of 1 m 2 / g to 10 m 2 / g negative electrode active material.
  4. 청구항 1에 있어서,The method according to claim 1,
    상기 천연흑연 1차 입자의 용량은 355 mAh/g 내지 365 mAh/g인 것인 음극 활물질.The capacity of the natural graphite primary particles is a negative electrode active material is 355 mAh / g to 365 mAh / g.
  5. 청구항 1에 있어서,The method according to claim 1,
    상기 천연흑연 1차 입자는 분체 상태 X선 회절 분석에 의한 (002)면의 면간격(d002)이 0.3355 nm 내지 0.3365 nm인 것인 음극 활물질.The natural graphite primary particles have a surface spacing (d 002 ) of the (002) plane by powder state X-ray diffraction analysis of 0.3355 nm to 0.3365 nm.
  6. 청구항 1에 있어서,The method according to claim 1,
    상기 천연흑연 1차 입자는 전극 상태 X선 회절 분석에 의한 (002)면과 (110)면의 피크강도비(I002/I110)가 550 내지 650이고, (004)면과 (110)면의 피크강도비(I004/I110)가 25 내지 35인 것인 음극 활물질.The natural graphite primary particles have a peak intensity ratio (I 002 / I 110 ) of (550) to (650) and (110) plane of (002) plane and (110) plane by electrode state X-ray diffraction analysis. The negative electrode active material having a peak intensity ratio (I 004 / I 110 ) of 25 to 35.
  7. 청구항 1에 있어서,The method according to claim 1,
    상기 천연흑연 1차 입자는 평균입경이 2 ㎛ 내지 10 ㎛인 것인 음극 활물질.The natural graphite primary particles are negative active material having an average particle diameter of 2 ㎛ to 10 ㎛.
  8. 청구항 1에 있어서,The method according to claim 1,
    상기 인조흑연은 니들 코크스계 인조흑연, 모자익 코크스계 인조흑연 및 MCMB(meso-carbon microbeads)형 인조흑연으로 이루어진 군으로부터 선택된 1종 이상인 것인 음극 활물질.The artificial graphite is at least one selected from the group consisting of needle coke-based artificial graphite, mosaic coke-based artificial graphite and MCMB (meso-carbon microbeads) artificial graphite.
  9. 청구항 1에 있어서,The method according to claim 1,
    상기 인조흑연은 모자익 코크스계 인조흑연 및 MCMB형 인조흑연으로 이루어진 군으로부터 선택된 1종 이상인 것인 음극 활물질.The artificial graphite is at least one selected from the group consisting of mosaic coke-based artificial graphite and MCMB artificial graphite.
  10. 청구항 1에 있어서,The method according to claim 1,
    상기 인조흑연 1차 입자의 용량은 320 mAh/g 내지 340 mAh/g인 것인 음극 활물질.The capacity of the artificial graphite primary particles is 320 mAh / g to 340 mAh / g of the negative electrode active material.
  11. 청구항 1에 있어서,The method according to claim 1,
    상기 인조흑연 1차 입자는 분체 상태 X선 회절 분석에 의한 (002)면의 면간격(d002)이 0.3365 nm 내지 0.3380 nm인 것인 음극 활물질.The artificial graphite primary particles have a surface spacing (d 002 ) of the (002) plane by powder state X-ray diffraction analysis of 0.3365 nm to 0.3380 nm.
  12. 청구항 1에 있어서,The method according to claim 1,
    상기 인조흑연 1차 입자는 전극 상태 X선 회절 분석에 의한 (002)면과 (110)면의 피크강도비(I002/I110)가 50 내지 150이고, (004)면과 (110)면의 피크강도비(I004/I110)가 5 내지 15인 것인 음극 활물질.The artificial graphite primary particles have a peak intensity ratio (I 002 / I 110 ) of 50 to 150 between (002) plane and (110) plane by electrode state X-ray diffraction analysis, and (004) plane and (110) plane. The negative electrode active material having a peak intensity ratio (I 004 / I 110 ) of 5 to 15.
  13. 청구항 1에 있어서,The method according to claim 1,
    상기 인조흑연 1차 입자는 평균입경이 2 ㎛ 내지 10 ㎛인 것인 음극 활물질.The artificial graphite primary particles have an average particle diameter of 2 ㎛ to 10 ㎛.
  14. 청구항 1에 있어서,The method according to claim 1,
    상기 흑연 2차 입자의 평균입경은 10 ㎛ 내지 30 ㎛인 것인 음극 활물질.The average particle diameter of the graphite secondary particles is 10 ㎛ to 30 ㎛ negative active material.
  15. 청구항 1에 있어서,The method according to claim 1,
    상기 흑연 2차 입자의 어스팩트비는 1 내지 1.5인 것인 음극 활물질.An aspect ratio of the graphite secondary particles is 1 to 1.5 negative electrode active material.
  16. 청구항 1에 있어서,The method according to claim 1,
    상기 흑연 2차 입자는 전극 상태 X선 회절 분석에 의한 (002)면과 (110)면의 피크강도비(I002/I110)가 200 내지 400이고, (004)면과 (110)면의 피크강도비(I004/I110)가 10 내지 25인 것인 음극 활물질.The graphite secondary particles have a peak intensity ratio (I 002 / I 110 ) between (002) and (110) planes of 200 to 400, and (004) and (110) planes by electrode state X-ray diffraction analysis. The peak active material ratio (I 004 / I 110 ) is 10 to 25 negative electrode active material.
  17. 비정질계 탄소재 전구체 물질과 천연흑연 1차 입자를 혼합하고 열처리하여 비정질계 탄소재가 코팅된 천연흑연 1차 입자를 제조하는 단계;Mixing the amorphous carbon material precursor material with the natural graphite primary particles and heat-treating them to prepare natural graphite primary particles coated with the amorphous carbon material;
    석탄계 중질유, 섬유계 중질유, 타르류, 피치류 및 코크스류로 이루어진 군에서 선택된 1 종 이상을 500 내지 3000℃의 열처리로 분체 흑연화하여 인조흑연 1차 입자를 제조하는 단계;Preparing artificial graphite primary particles by powder-graphitizing one or more selected from the group consisting of coal-based heavy oil, fibrous heavy oil, tars, pitches, and coke by heat treatment at 500 to 3000 ° C;
    비정질계 탄소재가 코팅된 천연흑연 1차 입자, 인조흑연 1차 입자, 바인더 및 촉매를 혼합하는 단계; 및Mixing the natural graphite primary particles, artificial graphite primary particles, a binder, and a catalyst coated with an amorphous carbon material; And
    1000 내지 2800℃로 열처리하여 흑연 2차 입자를 제조하는 단계;를 포함하는 음극 활물질의 제조방법.Method of manufacturing a negative electrode active material comprising a; step of producing a graphite secondary particles by heat treatment at 1000 to 2800 ℃.
  18. 청구항 17에 있어서,The method according to claim 17,
    상기 비정질계 탄소재는 석유계 중질유 및 피치오일유로 이루어진 군으로부터 선택된 1종 이상으로 제조되는 것인 음극 활물질의 제조방법.The amorphous carbon material is a method for producing a negative electrode active material is prepared from at least one selected from the group consisting of petroleum-based heavy oil and pitch oil oil.
  19. 청구항 17에 있어서,The method according to claim 17,
    상기 천연흑연 1차 입자에 코팅되는 비정질계 탄소재의 코팅량은 0% 초과 및 30% 이하인 것인 음극 활물질의 제조방법.The coating amount of the amorphous carbon material coated on the natural graphite primary particles is greater than 0% and 30% or less.
  20. 청구항 17에 있어서,The method according to claim 17,
    상기 흑연 2차 입자는 비정질계 탄소재로 코팅된 천연흑연 1차 입자와 인조흑연 1차 입자가 3:7 내지 7:3의 중량비를 갖도록 포함하는 것인 음극 활물질의 제조방법.The graphite secondary particles are a method for producing a negative electrode active material comprising a natural graphite primary particles and an artificial graphite primary particles coated with an amorphous carbon material to have a weight ratio of 3: 7 to 7: 3.
  21. 천연흑연 1차 입자 및 이흑연화 탄소(soft carbon) 입자를 혼합하여 2차 입자로 조립하는 단계;Mixing the natural graphite primary particles and soft carbon particles into granulated secondary particles;
    상기 조립된 2차 입자를 3000 내지 3200℃의 열처리로 분체 흑연화 하여 흑연 2차 입자를 제조하는 단계;를 포함하는 음극 활물질의 제조방법.Preparing graphite secondary particles by powder graphitizing the assembled secondary particles by heat treatment at 3000 to 3200 ° C .;
  22. 청구항 1에 기재된 음극 활물질을 포함하는 음극 슬러리가 집전체 상에 도포된 이차전지용 음극.The negative electrode for secondary batteries which the negative electrode slurry containing the negative electrode active material of Claim 1 apply | coated on the electrical power collector.
  23. 청구항 22에 기재된 이차전지용 음극과 양극, 상기 음극과 양극 사이에 개재된 분리막 및 전해질을 포함하는 리튬 이차전지.A lithium secondary battery comprising a separator and an electrolyte interposed between the negative electrode and the positive electrode for a secondary battery according to claim 22, the negative electrode and the positive electrode.
PCT/KR2015/007820 2014-07-29 2015-07-27 Graphite secondary particle, and lithium secondary battery comprising same WO2016018023A1 (en)

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