WO2019074305A2 - Positive electrode active material for lithium secondary battery, preparing method therefor, positive electrode, comprising same, for lithium secondary battery, and lithium secondary battery - Google Patents

Positive electrode active material for lithium secondary battery, preparing method therefor, positive electrode, comprising same, for lithium secondary battery, and lithium secondary battery Download PDF

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Publication number
WO2019074305A2
WO2019074305A2 PCT/KR2018/011984 KR2018011984W WO2019074305A2 WO 2019074305 A2 WO2019074305 A2 WO 2019074305A2 KR 2018011984 W KR2018011984 W KR 2018011984W WO 2019074305 A2 WO2019074305 A2 WO 2019074305A2
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lithium
nickel
active material
positive electrode
transition metal
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PCT/KR2018/011984
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French (fr)
Korean (ko)
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WO2019074305A3 (en
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김원태
신선식
윤여준
박홍규
강성훈
유종열
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주식회사 엘지화학
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Priority claimed from KR1020180120667A external-priority patent/KR102213174B1/en
Application filed by 주식회사 엘지화학 filed Critical 주식회사 엘지화학
Priority to CN201880047150.4A priority Critical patent/CN110892565B/en
Priority to US16/630,720 priority patent/US11362332B2/en
Priority to JP2019572655A priority patent/JP7051184B2/en
Publication of WO2019074305A2 publication Critical patent/WO2019074305A2/en
Publication of WO2019074305A3 publication Critical patent/WO2019074305A3/en

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/90—Carbides
    • C01B32/914—Carbides of single elements
    • C01B32/991—Boron carbide
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G51/00—Compounds of cobalt
    • C01G51/04—Oxides; Hydroxides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a positive electrode active material for a lithium secondary battery, a method for producing the positive electrode active material, a positive electrode for a lithium secondary battery including the positive electrode active material, and a lithium secondary battery.
  • lithium secondary batteries having a high energy density and voltage, a long cycle life, and a low self-discharge rate are commercially available and widely used.
  • Lithium transition metal complex oxides are used as the positive electrode active material of lithium secondary batteries, and lithium cobalt composite metal oxides such as LiCoO 2 having a high operating voltage and excellent capacity characteristics are mainly used.
  • LiCoO 2 has very poor thermal properties due to the destabilization of the crystal structure due to the depolymerization.
  • LiCoO 2 is expensive, it can not be used in large quantities as a power source for fields such as electric vehicles and the like.
  • Lithium manganese composite metal oxides such as LiMnO 2 or LiMn 2 O 4
  • lithium iron phosphate compounds such as LiFePO 4
  • lithium nickel composite metal oxides such as LiNiO 2
  • LiNiO 2 has a lower thermal stability than LiCoO 2
  • a lithium nickel cobalt metal oxide in which a part of Ni is substituted with Co and Mn or Al has been developed as a method for improving low thermal stability while maintaining excellent reversible capacity of LiNiO 2 .
  • the lithium nickel cobalt metal oxide containing lithium nickel cobalt metal oxide containing a high content of Ni exhibiting a high capacity characteristic is excellent in the structural stability of the lithium nickel cobalt metal oxide, and development of a cathode active material capable of producing a high capacity and high- .
  • a first technical object of the present invention is to provide a lithium transition metal oxide containing nickel in a high content, wherein a surface of the lithium transition metal oxide is coated using a specific raw material, And a method for producing a cathode active material having improved structural stability.
  • a second object of the present invention is to provide a cathode active material having a Co-containing coating material formed in a specific amount.
  • a third object of the present invention is to provide a positive electrode for a lithium secondary battery comprising the positive electrode active material.
  • a fourth aspect of the present invention is to provide a lithium secondary battery including the positive electrode for a lithium secondary battery.
  • the present invention relates to a process for preparing a nickel-containing lithium transition metal oxide by a first heat treatment of a nickel-containing hydroxide precursor and a lithium-raw material containing 65 mol% or more of nickel relative to the total number of moles of the transition metal; Mixing the B-containing and C-containing raw material and the Co-containing raw material with the nickel-containing lithium transition metal oxide to form a mixture; And a second heat treatment of the mixture to form a coating material containing B and Co on the surface of the lithium-transition metal oxide.
  • the present invention also relates to a nickel-containing lithium transition metal oxide comprising at least 65 mol% of nickel based on the total moles of transition metals except lithium; And a coating material distributed on the surface of the nickel-containing lithium-transition metal oxide, wherein the coating material comprises B and Co, and the coating material contains Co in an amount of 1,000 to 5,000 ppm. Thereby providing an active material.
  • a positive electrode for a lithium secondary battery comprising the positive electrode active material according to the present invention.
  • a lithium secondary battery comprising a positive electrode according to the present invention.
  • the present invention by forming a coating material containing B and Co using a specific raw material on the surface of a lithium transition metal oxide containing nickel in a high content, it is possible to prevent oxygen escape due to oxidation of Ni.
  • side reactions between the positive electrode active material and the electrolyte can be suppressed, and the structural stability of the positive electrode active material can be improved.
  • the secondary battery can be provided with improved output characteristics and lifetime characteristics in battery manufacturing.
  • FIG. 1 is a scanning electron micrograph of the cathode active material prepared in Example 1.
  • FIG. 2 is a scanning electron microscope (SEM) image of the cathode active material prepared in Comparative Example 1.
  • FIG. 3 is a scanning electron micrograph of the cathode active material prepared in Comparative Example 2.
  • Example 6 is a graph showing discharge capacities of a lithium secondary battery manufactured in Example 1 and Comparative Examples 1 and 3 to 4 under a condition of 1.0 C constant current discharge.
  • FIG. 7 is a graph showing the discharge capacities of the lithium secondary batteries manufactured in Example 1 and Comparative Examples 1 and 3 to 4 under a condition of 2.0 C constant current discharge.
  • the positive electrode active material according to the present invention is a nickel-containing lithium transition metal oxide containing at least 65 mol% of nickel based on the total moles of transition metals except lithium. And a coating material formed on the surface of the nickel-containing lithium transition metal oxide, wherein the coating material comprises B and Co, and the coating material contains Co in an amount of 1,000 to 5,000 ppm.
  • the cathode active material may include a nickel-containing lithium transition metal oxide containing at least 65 mol% of nickel based on the total moles of transition metals other than lithium, more preferably nickel -Containing lithium transition metal oxide.
  • Me is at least one selected from the group consisting of Mn and Al.
  • the nickel-containing lithium transition metal oxide may more preferably be LiNi a Co b Al 1 - (a + b) O 2 or LiNi a Co b Mn 1 - (a + b) O 2 , LiNi 0 . 65 Co 0 . 2 Al 0 . 15 O 2 , LiNi 0.7 Co 0.15 Al 0.15 O 2 , LiNi 0 . 8 Co 0 . 1 Al 0 . 1 O 2 , LiNi 0 . 9 Co 0 . 05 A1 0 . 05 O 2 , LiNi 0 . 65 Co 0 . 2 Mn 0 .
  • the nickel-containing lithium transition metal oxide having a nickel content of 65 mol% or more with respect to the total number of moles of transition metals other than lithium can be used to achieve high capacity of the battery during the production of the battery.
  • the positive electrode active material includes a coating material including Co element B and Co formed on the surface of the positive electrode active material. Since the contact between the positive electrode active material and the electrolyte contained in the lithium secondary battery is blocked by the coating material, occurrence of side reaction is suppressed, so that it is possible to improve the lifetime characteristics when applied to a battery and increase the filling density of the positive electrode active material have. Particularly, when B is contained as a coating element, it is possible to reduce the initial resistance and the rate of increase in resistance due to securing excellent electrical conductivity, achieve the effect of reducing lithium impurities remaining on the surface of the cathode material, The rate characteristics can be improved and the initial resistance and the rate of increase in resistance can be reduced due to securing excellent electrical conductivity.
  • the coating material may contain B in an amount of 100 ppm to 500 ppm, preferably 200 ppm to 300 ppm, and the Co may include 1,000 ppm to 5,000 ppm, preferably 2,000 ppm to 4,500 ppm.
  • B and Co are included in the above-mentioned coating material, the effect of suppressing the corrosion and side reaction on the surface of the cathode active material by hydrogen fluoride occurs more effectively, and the rate characteristics and lifetime characteristics when applied to a battery can be further improved.
  • the content of Co contained in the coating material can be measured using a transmission electron microscope and X-ray spectrometry.
  • the content of Co present in a coating material can be measured using electron dispersive X-ray spectroscopy (EDS) of a JEM-2010F transmission electron microscope (TEM).
  • EDS electron dispersive X-ray spectroscopy
  • TEM JEM-2010F transmission electron microscope
  • the content of B contained in the coating material can be measured by, for example, ICP mass spectrometry.
  • ICP mass spectrometry Optima 7000 dv, PerkinElmer
  • Optima 7000 dv PerkinElmer
  • Optima 7000 dv PerkinElmer
  • Optima 7000 dv PerkinElmer
  • 0.2 mL of internal STD is added to the dissolved sample and diluted to 20 mL with ultrapure water.
  • the coating material may be uniformly distributed over the entire surface of the cathode active material, or may be distributed in the form of partially coherent islands. Specifically, when the coating material uniformly forms a coating layer over the entire surface of the cathode active material, for example, the thickness of the coating layer may be 1 nm to 50 nm, preferably 7 nm to 25 nm. When the coating material is distributed on the surface of the cathode active material in the island shape, the coating material may be distributed to occupy 20% to 90% of the total surface area of the cathode active material. When the area of the coating material is less than 20% of the total surface area of the cathode active material, the effect of improving the structural stability due to the formation of the coating material may be insignificant. When the coating material is uniformly formed over the entire surface of the cathode active material, the structural stability of the cathode active material surface can be further improved.
  • the method for producing a positive electrode active material comprises mixing a nickel-containing hydroxide precursor containing at least 65 mol% of nickel relative to the total moles of transition metals and a lithium-source material and subjecting the mixture to a first heat treatment to form a nickel- Producing a metal oxide; Mixing the B-containing and C-containing raw material and the Co-containing raw material with the nickel-containing lithium transition metal oxide to form a mixture; And forming a coating material containing B and Co on the surface of the lithium-transition metal oxide by secondary heat treatment of the mixture.
  • a nickel-containing transition metal hydroxide precursor and a lithium-source material are mixed and subjected to a first heat treatment to prepare a nickel-containing lithium transition metal oxide.
  • the nickel-containing transition metal hydroxide precursor may have a nickel content of 65 mol% or more based on the total number of moles of the transition metal, and Ni a1 Co b1 Me 1 - (a 1 + b 1 ) OH 2 wherein 0.65? A1? , 0.05? B1? 0.2, 0.85? A1 + b1? 0.95, and Me is at least one selected from the group consisting of Mn and Al).
  • the nickel cobalt manganese hydroxide precursor is Ni 0 . 65 Co 0 . 2 Al 0 .15 (OH) 2 , Ni 0. 7 Co 0 . 15 Al 0 .15 (OH) 2 , Ni 0. 8 Co 0 .
  • the lithium-source material is not particularly limited as long as it is a compound containing a lithium source, but lithium carbonate (Li 2 CO 3 ), lithium hydroxide (LiOH), LiNO 3 , CH 3 COOLi and Li 2 COO) 2 may be used.
  • the nickel-containing transition metal hydroxide precursor and the lithium-source material are mixed so that the molar ratio of Li to metal (Li / metal ratio) is 1 to 1.3, preferably 1.05 to 1.1, more preferably 1.07 to 1.09 .
  • the nickel-containing transition metal hydroxide precursor and the lithium-source material are mixed in the above range, a cathode active material exhibiting excellent capacity characteristics can be produced.
  • a mixture of the nickel-containing transition metal hydroxide precursor and the lithium-source material is subjected to a first heat treatment to prepare a cathode active material containing a nickel-containing lithium transition metal oxide.
  • the primary heat treatment may be performed at a temperature of 700 ° C to 900 ° C.
  • the first heat treatment may be performed in an oxidizing atmosphere.
  • a residual lithium impurity to such an extent that a coating material can be sufficiently formed can be obtained, and a positive electrode nickel-containing lithium transition metal oxide having excellent crystal grains can be obtained.
  • the primary heat treatment is performed in an inactive atmosphere such as a nitrogen atmosphere, the amount of residual lithium impurities increases, so that metal oxides are not synthesized and formation of a coating material may be difficult.
  • the primary heat treatment may be carried out in an oxidizing atmosphere at 600 ° C to 800 ° C for 4 hours to 5 hours in one step and then at 800 ° C to 900 ° C for 8 hours to 10 hours in two steps.
  • the particle strength of the cathode active material can be improved.
  • the primary heat treatment temperature and time satisfy the above range, the raw material does not remain in the particles and the high-temperature stability of the battery can be improved. As a result, the bulk density and crystallinity are improved, The structural stability can be improved.
  • the nickel-containing lithium transition metal oxide is mixed with the B- and C-containing raw material and the Co-containing raw material to form a mixture.
  • the C- and B-containing source material B 4 C, (C 3 H 7 O) 3 B, (C 6 H 5 O) 3 B, [CH 3 (CH 2) 3 O] 3 B, And C 6 H 5 B (OH) 2 , and may be at least one of B 4 C, preferably B 4 C.
  • the B and C-containing raw materials are B 4 C
  • B 4 C since B 4 C has a high melting point, it is advantageous to apply it as a raw material for performing a high-temperature heat treatment.
  • the C included in the B and C-containing raw materials is easily oxidized by the strong reducing action, and oxidation of the coating raw material can be easily suppressed.
  • the B and C-containing raw material may be mixed in an amount of 0.02 parts by weight to 0.04 parts by weight based on 100 parts by weight of the nickel-containing lithium transition metal oxide.
  • the Co-containing raw material can be used without limitation as long as it can coat the surface of the lithium transition metal oxide particles and does not deteriorate the electrochemical performance.
  • Co (OH) 2 , Co 2 O 3 , Co 3 (PO 4) 2, CoF 3, CoOOH, Co (OCOCH 3) 2 ⁇ 4H 2 O, Co (NO 3) ⁇ 6H 2 O, Co 3 O 4, Co (SO 4) 2 ⁇ 7H 2 O and CoC at least one may be at least selected from the group consisting of 2 O 4.
  • Co (OH) 2 when used as the Co-containing raw material, its structural stability can be further improved when applied to a battery.
  • the Co (OH) 2 when the Co (OH) 2 is thermally treated in an oxidizing atmosphere at a temperature of 300 ° C or higher, it is oxidized to Co 3 O 4 to act as a resistance during electrochemical reaction, Thereby causing a problem that the resistance characteristic is poor.
  • the Co-containing raw material as well as the B and C-containing raw materials are included together as the coating material according to the present invention, the B and C-containing raw materials are generated during the dissociation process at high temperature heat treatment Carbon can act as a reducing agent. Accordingly, the Co (OH 2 ) can be prevented from being oxidized to the metal oxide, so that the Co content in the coating material is preferably about 1,000 to 5,000 ppm.
  • the Co-containing raw material may be mixed with 0.5 part by weight to 1.0 part by weight with respect to 100 parts by weight of the nickel-containing lithium transition metal oxide.
  • the mixture is subjected to a secondary heat treatment at 500 ° C to 750 ° C to form a coating material containing B and Co on the surface of the lithium transition metal oxide.
  • the secondary heat treatment may be performed at 500 ° C to 750 ° C for 3 hours to 8 hours, more preferably at 500 ° C to 650 ° C for 4 hours to 6 hours.
  • the secondary heat treatment temperature is in the above range, the surface of the cathode active material is easily modified due to the formation of the coating material without changing the surface of the cathode active material by forming the coating material at a high temperature, It is possible to produce a cathode active material having an excellent and high capacity.
  • capacity and lifetime characteristics may be reduced due to excessive lithium borate compound formation.
  • the cathode for a secondary battery includes a cathode current collector, a cathode active material layer formed on the cathode current collector, and the cathode active material layer includes the cathode active material according to the present invention.
  • cathode active material is the same as that described above, a detailed description thereof will be omitted and only the remaining constitution will be specifically described below.
  • the positive electrode current collector is not particularly limited as long as it has conductivity without causing chemical changes in the battery.
  • carbon, nickel, titanium, , Silver or the like may be used.
  • the cathode current collector may have a thickness of 3 to 500 ⁇ , and fine unevenness may be formed on the surface of the current collector to increase the adhesive force of the cathode active material.
  • it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.
  • the cathode active material layer may include a conductive material and, optionally, a binder optionally together with the cathode active material.
  • the cathode active material may be contained in an amount of 80 to 99% by weight, more specifically 85 to 98.5% by weight based on the total weight of the cathode active material layer. When included in the above content range, excellent capacity characteristics can be exhibited.
  • the conductive material is used for imparting conductivity to the electrode.
  • the conductive material is not particularly limited as long as it has electron conductivity without causing chemical change. Specific examples thereof include graphite such as natural graphite and artificial graphite; Carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, summer black and carbon fiber; Metal powder or metal fibers such as copper, nickel, aluminum and silver; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; And polyphenylene derivatives. These may be used alone or in admixture of two or more.
  • the conductive material may be included in an amount of 0.1 to 15% by weight based on the total weight of the cathode active material layer.
  • the binder serves to improve the adhesion between the positive electrode active material particles and the adhesion between the positive electrode active material and the current collector.
  • Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose ), Starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, and various copolymers thereof.
  • the binder may be included in an amount of 0.1 to 15% by weight based on the total weight of the cathode active material layer.
  • the positive electrode may be manufactured according to a conventional positive electrode manufacturing method, except that the positive electrode active material described above is used. Specifically, the cathode active material and optionally the binder and the conductive material may be dissolved or dispersed in a solvent to prepare a composition for forming a cathode active material layer, which is then applied onto the cathode current collector, followed by drying and rolling.
  • the solvent examples include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, and the like. Water and the like, and one kind or a mixture of two or more kinds can be used.
  • the amount of the solvent to be used is sufficient to dissolve or disperse the cathode active material, the conductive material and the binder in consideration of the coating thickness of the slurry and the yield of the slurry, and then to have a viscosity capable of exhibiting excellent thickness uniformity Do.
  • the positive electrode may be produced by casting the composition for forming the positive electrode active material layer on a separate support, and then laminating a film obtained by peeling from the support onto the positive electrode collector.
  • the present invention can produce an electrochemical device including the positive electrode.
  • the electrochemical device may be specifically a battery, a capacitor, or the like, and more specifically, it may be a lithium secondary battery.
  • the lithium secondary battery includes a positive electrode, a negative electrode disposed opposite to the positive electrode, and a separation membrane and an electrolyte interposed between the positive electrode and the negative electrode.
  • the positive electrode is the same as that described above, Only the remaining configuration will be described in detail below.
  • the lithium secondary battery may further include a battery container for housing the electrode assembly of the anode, the cathode, and the separator, and a sealing member for sealing the battery container.
  • the negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector.
  • the negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery.
  • the negative electrode current collector may be formed on the surface of copper, stainless steel, aluminum, nickel, titanium, sintered carbon, Carbon, nickel, titanium, silver or the like, aluminum-cadmium alloy, or the like may be used.
  • the negative electrode collector may have a thickness of 3 to 500 ⁇ , and similarly to the positive electrode collector, fine unevenness may be formed on the surface of the collector to enhance the binding force of the negative electrode active material.
  • it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.
  • the anode active material layer optionally includes a binder and a conductive material together with the anode active material.
  • a compound capable of reversible intercalation and deintercalation of lithium may be used.
  • Specific examples thereof include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber and amorphous carbon;
  • Metal compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys or Al alloys; SiO ⁇ (0 ⁇ ⁇ 2 ), SnO 2, vanadium oxide, which can dope and de-dope a lithium metal oxide such as lithium vanadium oxide;
  • a composite containing the metallic compound and the carbonaceous material such as Si-C composite or Sn-C composite, and any one or a mixture of two or more thereof may be used.
  • a metal lithium thin film may be used as the negative electrode active material.
  • the carbon material may be both low-crystalline carbon and high-crystallinity carbon.
  • Examples of the low-crystalline carbon include soft carbon and hard carbon.
  • Examples of the highly crystalline carbon include natural graphite, artificial graphite, artificial graphite or artificial graphite, Kish graphite graphite, pyrolytic carbon, mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches and petroleum or coal tar coke derived cokes).
  • the negative electrode active material may include 80% by weight to 99% by weight based on the total weight of the negative electrode active material layer.
  • the binder is a component for assisting the bonding between the conductive material, the active material and the current collector, and is usually added in an amount of 0.1% by weight to 10% by weight based on the total weight of the negative electrode active material layer.
  • binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene
  • PVDF polyvinylidene fluoride
  • CMC carboxymethylcellulose
  • EPDM ethylene-propylene-diene polymer
  • sulfonated-EPDM styrene-butadiene rubber
  • fluorine rubber various copolymers thereof.
  • the conductive material may be added in an amount of 10 wt% or less, preferably 5 wt% or less, based on the total weight of the negative electrode active material layer, as a component for further improving the conductivity of the negative electrode active material.
  • a conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, for example, graphite such as natural graphite or artificial graphite; Carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.
  • the negative electrode active material layer is prepared by applying and drying a composition for forming a negative electrode active material layer, which is prepared by dissolving or dispersing a negative electrode active material on a negative electrode current collector, and optionally a binder and a conductive material in a solvent, Casting a composition for forming an active material layer on a separate support, and then laminating a film obtained by peeling from the support onto a negative electrode current collector.
  • a composition for forming a negative electrode active material layer which is prepared by dissolving or dispersing a negative electrode active material on a negative electrode current collector, and optionally a binder and a conductive material in a solvent, Casting a composition for forming an active material layer on a separate support, and then laminating a film obtained by peeling from the support onto a negative electrode current collector.
  • the negative electrode active material layer may be formed by applying and drying a composition for forming a negative electrode active material layer prepared by dissolving or dispersing a negative electrode active material on a negative electrode collector and optionally a binder and a conductive material in a solvent, Casting the composition on a separate support, and then peeling the support from the support to laminate a film on the negative electrode current collector.
  • the separation membrane separates the cathode and the anode and provides a passage for lithium ion.
  • the separation membrane can be used without any particular limitation as long as it is used as a separation membrane in a lithium secondary battery. Particularly, It is preferable to have a low resistance and an excellent ability to impregnate the electrolyte.
  • porous polymer films such as porous polymer films made of polyolefin-based polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers and ethylene / methacrylate copolymers, May be used.
  • a nonwoven fabric made of a conventional porous nonwoven fabric for example, glass fiber of high melting point, polyethylene terephthalate fiber, or the like may be used.
  • a coated separator containing a ceramic component or a polymer material may be used, and the separator may be selectively used as a single layer or a multilayer structure.
  • Examples of the electrolyte used in the present invention include an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, and a molten inorganic electrolyte that can be used in the production of a lithium secondary battery. It is not.
  • the electrolyte may include an organic solvent and a lithium salt.
  • the organic solvent may be used without limitation as long as it can act as a medium through which ions involved in the electrochemical reaction of the battery can move.
  • examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate,? -Butyrolactone and?
  • Ether solvents such as dibutyl ether or tetrahydrofuran; Ketone solvents such as cyclohexanone; Aromatic hydrocarbon solvents such as benzene and fluorobenzene; Dimethyl carbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), propylene carbonate PC) and the like; Alcohol solvents such as ethyl alcohol and isopropyl alcohol; R-CN (R is a linear, branched or cyclic hydrocarbon group having 2 to 20 carbon atoms, which may contain a double bond aromatic ring or an ether bond); Amides such as dimethylformamide; Dioxolanes such as 1,3-dioxolane; Or sulfolane may be used.
  • Ether solvents such as dibutyl ether or tetrahydrofuran
  • Ketone solvents such as cyclohex
  • a carbonate-based solvent is preferable, and a cyclic carbonate (for example, ethylene carbonate or propylene carbonate) having a high ionic conductivity and a high dielectric constant, for example, such as ethylene carbonate or propylene carbonate, For example, ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate) is more preferable.
  • a cyclic carbonate for example, ethylene carbonate or propylene carbonate
  • ethylene carbonate or propylene carbonate for example, ethylene carbonate or propylene carbonate
  • ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate
  • the lithium salt can be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery.
  • the lithium salt LiPF 6, LiClO 4, LiAsF 6, LiBF 4, LiSbF 6, LiAl0 4, LiAlCl 4, LiCF 3 SO 3, LiC 4 F 9 SO 3, LiN (C 2 F 5 SO 3) 2 , LiN (C 2 F 5 SO 2) 2, LiN (CF 3 SO 2) 2.
  • LiCl, LiI, or LiB (C 2 O 4 ) 2 may be used.
  • the concentration of the lithium salt is preferably in the range of 0.1 to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte has an appropriate conductivity and viscosity, so that it can exhibit excellent electrolyte performance and the lithium ion can effectively move.
  • the electrolyte may contain, for example, a haloalkylene carbonate-based compound such as difluoroethylene carbonate or the like, pyridine, triethanolamine, or the like for the purpose of improving lifetime characteristics of the battery, Ethyl phosphite, triethanol amine, cyclic ether, ethylenediamine, glyme, hexametriamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, At least one additive such as benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, The additive may be included in an amount of 0.1 to 5% by weight based on the total weight of the electrolyte.
  • the lithium secondary battery including the cathode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics and life characteristics, it can be used in portable devices such as mobile phones, notebook computers, digital cameras, and hybrid electric vehicles hybrid electric vehicle (HEV)).
  • portable devices such as mobile phones, notebook computers, digital cameras, and hybrid electric vehicles hybrid electric vehicle (HEV)).
  • HEV hybrid electric vehicles hybrid electric vehicle
  • a battery module including the lithium secondary battery as a unit cell and a battery pack including the same.
  • the battery module or the battery pack may include a power tool; An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); Or a power storage system, as shown in FIG.
  • a power tool including an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); Or a power storage system, as shown in FIG.
  • EV electric vehicle
  • PHEV plug-in hybrid electric vehicle
  • the external shape of the lithium secondary battery of the present invention is not particularly limited, but may be a cylindrical shape, a square shape, a pouch shape, a coin shape, or the like using a can.
  • the lithium secondary battery according to the present invention can be used not only in a battery cell used as a power source of a small device but also as a unit cell in a middle- or large-sized battery module including a plurality of battery cells.
  • the cathode active material prepared above was pulverized using induction. 0.02 parts by weight and 0.8 parts by weight of B 4 C and Co (OH) 2 as coating element-containing raw materials were added to the crushed cathode active material, respectively, and mixed with 100 parts by weight of the cathode active material. Subsequently, heat treatment was performed at 600 ⁇ ⁇ for 5 hours in an air atmosphere. The heat treated powder was pulverized by induction and classified by using 325 mesh to prepare a cathode active material in which coating materials containing B and Co were distributed on the surface in an island shape.
  • a lithium secondary battery was prepared from the positive electrode active material by the same method as in Example 1.
  • the cathode active material was prepared in the same manner as in Example 1 above.
  • Example 1 the surface was relatively smooth as in Comparative Example 1 (see FIG. 2) in which a coating material was formed at a relatively low temperature.
  • Comparative Example 5 the surface was relatively smooth as in Example 1 and Comparative Example 1, but the Co content was small compared with Example 1 and Comparative Examples 1 and 2 It was because.
  • a lithium secondary battery was fabricated using the cathode active materials prepared in Examples 1 and 2 and Comparative Examples 1 and 3 to 5, respectively, and capacity characteristics were confirmed using the same.
  • the positive electrode active material, the carbon black conductive material, and the carbon black conductive material prepared in Examples 1 and 2 and Comparative Examples 1 and 3 to 5 were mixed at a weight ratio of 95: 2.5: 2.5, and the mixture was mixed in N-methylpyrrolidone solvent to prepare a composition for forming a positive electrode.
  • the composition for forming an anode was applied to an Al foil having a thickness of 20 ⁇ , dried, and rolled to produce a positive electrode.
  • a lithium metal electrode having a diameter of 16 pi was used as the negative electrode active material.
  • the positive electrode and the negative electrode prepared above were laminated together with a polypropylene separator to prepare an electrode assembly.
  • the electrode assembly was placed in a battery case, and 1 M of LiPF 6 was dissolved in a mixed solvent of ethyl methyl carbonate: ethylene carbonate in a ratio of 7: 3 And an electrolyte was injected thereinto to prepare lithium secondary batteries of Examples 1 and 2 and Comparative Examples 1 and 3 to 5.
  • Each of the lithium secondary batteries of Examples 1 and 2 and Comparative Examples 1 and 3 to 5 prepared above was charged to 4.3 V at a constant current of 0.1 C at 25 ⁇ and discharged at a constant current of 0.1 C until the voltage reached 3 V Charging and discharging characteristics were observed in the first cycle, and the results are shown in Table 1 and FIG. 5 below. Thereafter, discharge capacities at 1.0 C and 2.0 C were measured at different discharge conditions of 1.0 C and 2.0 C, respectively. These discharge capacities were shown in FIG. 6 and FIG. 7, respectively. The efficiency at 2.0 C is shown in Table 2 below.
  • the secondary batteries prepared in Examples 1 and 2 exhibited efficiencies of 90% or more at 1.0 C-rate, 89% at 2.0 C-rate Efficiency, and the discharge capacity was the most improved.
  • the lithium secondary batteries of Examples 1 to 2 and Comparative Examples 1 to 5 were charged at a constant current of 0.5 C at a temperature of 25 ⁇ until the voltage reached 4.3 V, allowed to stand for 20 minutes, and then become 3 V at a constant current of 1.0 C .
  • the charge and discharge behaviors were taken as one cycle. After repeating this cycle 50 times, the resistance increase rate according to this example and the comparative example was measured, and the results are shown in Table 3 below.
  • Example 3 As shown in Table 3, it was confirmed that the resistance of the secondary battery manufactured in Example 1 showed a resistance increase rate of less than 1.5% as compared with the initial resistance in the resistance measurement after 50 cycles. Meanwhile, it was confirmed that the secondary battery according to Example 2 had relatively low structural stability of the cathode active material as the Co content in the coating material was lowered, and that the resistance characteristic was improved when the battery was applied to the battery.
  • the B and C-containing raw materials may act as a reducing agent to prevent oxidation of the Co-containing raw material during the heat treatment after forming a coating material containing B and Co on the surface of the metal oxide.
  • Co is not reduced and remains in the coating material to achieve the effect of the present invention.

Abstract

The present invention relates to a method for preparing a positive electrode active material, the method comprising the steps of: mixing a nickel-containing hydroxide precursor containing 65 mol% or more of nickel relative to the total number of moles of transition metals and a lithium raw material, followed by primary thermal treatment, to prepare a nickel-containing lithium transition metal oxide; mixing a B and C-containing raw material and a Co-containing raw material with the nickel-containing lithium transition metal oxide to form a mixture; and subjecting the mixture to secondary thermal treatment to form a coating material containing B and Co on a surface of the lithium-transition metal oxide, to a positive electrode active material prepared by the preparation method and having a coating material containing a particular content of Co, to a positive electrode, containing the positive electrode active material, for a lithium secondary battery, and to a lithium secondary battery.

Description

리튬 이차전지용 양극 활물질, 이의 제조방법, 이를 포함하는 리튬 이차전지용 양극 및 리튬 이차전지Cathode active material for lithium secondary battery, production method thereof, anode and lithium secondary battery for lithium secondary battery containing same
관련출원과의 상호 인용Mutual citation with related application
본 출원은 2017년 10월 12일자 한국특허출원 제2017-0132681호 및 2018년 10월 10일자 한국특허출원 제2018-0120667호에 기초한 우선권의 이익을 주장하며, 해당 한국특허출원의 문헌에 개시된 모든 내용은 본 명세서의 일부로서 포함된다.This application claims the benefit of priority based on Korean Patent Application No. 2017-0132681 of October 12, 2017 and Korean Patent Application No. 2018-0120667 of October 10, 2018, and all of the contents disclosed in the Korean patent application publication The contents of which are incorporated herein by reference.
기술분야Technical field
본 발명은 리튬 이차전지용 양극 활물질, 상기 양극 활물질의 제조 방법, 상기 양극 활물질을 포함하는 리튬 이차전지용 양극 및 리튬 이차전지에 관한 것이다. The present invention relates to a positive electrode active material for a lithium secondary battery, a method for producing the positive electrode active material, a positive electrode for a lithium secondary battery including the positive electrode active material, and a lithium secondary battery.
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 energy sources is rapidly increasing. Among such secondary batteries, lithium secondary batteries having a high energy density and voltage, a long cycle life, and a low self-discharge rate are commercially available and widely used.
리튬 이차전지의 양극활물질로는 리튬 전이금속 복합 산화물이 이용되고 있으며, 이중에서도 작용전압이 높고 용량 특성이 우수한 LiCoO2 등의 리튬 코발트 복합금속 산화물이 주로 사용되고 있다. 그러나, LiCoO2는 탈리튬에 따른 결정 구조의 불안정화 때문에 열적 특성이 매우 열악하다. 또한, 상기 LiCoO2는 고가이기 때문에 전기 자동차 등과 같은 분야의 동력원으로서 대량 사용하기에는 한계가 있다. Lithium transition metal complex oxides are used as the positive electrode active material of lithium secondary batteries, and lithium cobalt composite metal oxides such as LiCoO 2 having a high operating voltage and excellent capacity characteristics are mainly used. However, LiCoO 2 has very poor thermal properties due to the destabilization of the crystal structure due to the depolymerization. In addition, since LiCoO 2 is expensive, it can not be used in large quantities as a power source for fields such as electric vehicles and the like.
상기 LiCoO2를 대체하기 위한 재료로서, 리튬 망간 복합금속 산화물(LiMnO2 또는 LiMn2O4 등), 리튬 인산철 화합물(LiFePO4 등) 또는 리튬 니켈 복합금속 산화물(LiNiO2 등) 등이 개발되었다. 이 중에서도 약 200 mAh/g의 높은 가역용량을 가져 대용량의 전지 구현이 용이한 리튬 니켈 복합금속 산화물에 대한 연구 개발이 보다 활발히 연구되고 있다. 그러나, 상기 LiNiO2는 LiCoO2와 비교하여 열안정성이 열위하고, 충전 상태에서 외부로부터의 압력 등에 의해 내부 단락이 생기면 양극 활물질 그 자체가 분해되어 전지의 파열 및 발화를 초래하는 문제가 있었다. 이에 따라 상기 LiNiO2의 우수한 가역용량은 유지하면서도 낮은 열안정성을 개선하기 위한 방법으로서, Ni의 일부를 Co 및 Mn 또는 Al로 치환한 리튬 니켈코발트금속 산화물이 개발되었다.Lithium manganese composite metal oxides (such as LiMnO 2 or LiMn 2 O 4 ), lithium iron phosphate compounds (such as LiFePO 4 ), or lithium nickel composite metal oxides (such as LiNiO 2 ) have been developed as materials for replacing LiCoO 2 . Among them, research and development on a lithium nickel composite metal oxide having a high reversible capacity of about 200 mAh / g and facilitating the realization of a large capacity battery has been actively researched. However, LiNiO 2 has a lower thermal stability than LiCoO 2, and if an internal short circuit occurs due to external pressure or the like in a charged state, the cathode active material itself is decomposed to cause rupture and ignition of the battery. Accordingly, a lithium nickel cobalt metal oxide in which a part of Ni is substituted with Co and Mn or Al has been developed as a method for improving low thermal stability while maintaining excellent reversible capacity of LiNiO 2 .
그러나, 상기 리튬 니켈코발트금속 산화물의 경우, 구조 안정성이 낮고 용량이 낮으며, 특히 용량 특성을 높이기 위해 니켈의 함량을 높일 경우, 충방전 공정이 진행됨에 따라 상기 니켈이 Ni2 +에서 Ni3 + 또는 Ni4 +로 산화하고, 이에 따라 급격한 산소 탈리가 진행되어, 구조 안정성이 더욱 저하된다는 문제점이 있었다.However, in the case of the lithium-nickel-cobalt metal oxide structure it was reliability is low and the capacity is low, particularly when increasing the content of Ni to improve the capacity characteristics, Ni wherein the nickel is in the Ni 2 + in accordance with the charge-discharge process progresses 3 + Or Ni < 4 + > so that rapid oxygen desorption proceeds, resulting in a further reduction in the structural stability.
따라서, 고용량 특성을 나타내는 고함량의 Ni을 포함하는 리튬 니켈코발트금속 산화물을 포함하되, 이때 상기 리튬 니켈코발트금속 산화물의 구조 안정성이 우수하여, 고용량 및 고수명 전지를 제조할 수 있는 양극 활물질의 개발이 요구되고 있다.Therefore, the lithium nickel cobalt metal oxide containing lithium nickel cobalt metal oxide containing a high content of Ni exhibiting a high capacity characteristic is excellent in the structural stability of the lithium nickel cobalt metal oxide, and development of a cathode active material capable of producing a high capacity and high- .
상기와 같은 문제점을 해결하기 위하여, 본 발명의 제 1 기술적 과제는 니켈을 고함량으로 포함하는 리튬 전이금속 산화물을 포함하되, 특정 원료 물질을 이용하여 상기 리튬 전이금속 산화물의 표면을 코팅함으로써 고용량 특성을 나타내며 구조적 안정성이 개선된 양극 활물질의 제조 방법을 제공하는 것이다.In order to solve the above problems, a first technical object of the present invention is to provide a lithium transition metal oxide containing nickel in a high content, wherein a surface of the lithium transition metal oxide is coated using a specific raw material, And a method for producing a cathode active material having improved structural stability.
본 발명의 제 2 기술적 과제는 특정 함량으로 Co를 포함하는 코팅 물질이 형성된 양극 활물질을 제공하는 것이다.A second object of the present invention is to provide a cathode active material having a Co-containing coating material formed in a specific amount.
본 발명의 제 3 기술적 과제는 상기 양극 활물질을 포함하는 리튬 이차전지용 양극을 제공하는 것이다.A third object of the present invention is to provide a positive electrode for a lithium secondary battery comprising the positive electrode active material.
본 발명의 제 4 기술적 과제는 상기 리튬 이차전지용 양극을 포함하는 리튬 이차전지를 제공하는 것이다.A fourth aspect of the present invention is to provide a lithium secondary battery including the positive electrode for a lithium secondary battery.
본 발명은 전이금속의 총 몰수에 대하여 65몰% 이상의 니켈을 포함하는 니켈-함유 수산화물 전구체 및 리튬-원료물질을 1차 열처리하여, 니켈-함유 리튬 전이금속 산화물을 제조하는 단계; 상기 니켈-함유 리튬 전이금속 산화물에 B 및 C-함유 원료 물질 및 Co-함유 원료 물질을 혼합하여 혼합물을 형성하는 단계; 및, 상기 혼합물을 2차 열처리하여, 상기 리튬-전이금속 산화물 표면에 B 및 Co를 포함하는 코팅 물질을 형성하는 단계;를 포함하는 양극 활물질의 제조 방법을 제공한다. The present invention relates to a process for preparing a nickel-containing lithium transition metal oxide by a first heat treatment of a nickel-containing hydroxide precursor and a lithium-raw material containing 65 mol% or more of nickel relative to the total number of moles of the transition metal; Mixing the B-containing and C-containing raw material and the Co-containing raw material with the nickel-containing lithium transition metal oxide to form a mixture; And a second heat treatment of the mixture to form a coating material containing B and Co on the surface of the lithium-transition metal oxide.
또한, 본 발명은 리튬을 제외한 전이금속의 총 몰수에 대하여 65몰% 이상의 니켈을 포함하는 니켈-함유 리튬 전이금속 산화물; 및, 상기 니켈-함유 리튬 전이금속 산화물의 표면에 분포된 코팅 물질;을 포함하며, 상기 코팅 물질은 B 및 Co를 포함하고, 상기 코팅 물질 내에 1,000 내지 5,000 ppm의 Co를 포함하는 것인, 양극 활물질을 제공한다.The present invention also relates to a nickel-containing lithium transition metal oxide comprising at least 65 mol% of nickel based on the total moles of transition metals except lithium; And a coating material distributed on the surface of the nickel-containing lithium-transition metal oxide, wherein the coating material comprises B and Co, and the coating material contains Co in an amount of 1,000 to 5,000 ppm. Thereby providing an active material.
또한, 본 발명에 따른 양극 활물질을 포함하는, 리튬 이차전지용 양극을 제공한다.Also, there is provided a positive electrode for a lithium secondary battery comprising the positive electrode active material according to the present invention.
또한, 본 발명에 따른 양극을 포함하는, 리튬 이차전지를 제공한다.Further, there is provided a lithium secondary battery comprising a positive electrode according to the present invention.
본 발명에 따르면, 니켈을 고함량으로 포함하는 리튬 전이금속 산화물의 표면에 특정 원료물질을 이용하여 B 및 Co를 포함하는 코팅 물질을 형성함으로써, Ni의 산화에 따른 산소 탈리를 방지할 수 있다. 이에 따라, 양극 활물질과 전해액 간의 부반응을 억제하여, 양극 활물질의 구조 안정성을 개선할 수 있다. 이를 이용하여 전지 제조 시 출력 특성 및 수명 특성이 향상된 이차전지를 제공할 수 있다. According to the present invention, by forming a coating material containing B and Co using a specific raw material on the surface of a lithium transition metal oxide containing nickel in a high content, it is possible to prevent oxygen escape due to oxidation of Ni. Thus, side reactions between the positive electrode active material and the electrolyte can be suppressed, and the structural stability of the positive electrode active material can be improved. The secondary battery can be provided with improved output characteristics and lifetime characteristics in battery manufacturing.
특히, 코팅 원료 물질로서 특정 화합물을 사용함에 따라, Co의 산화에 따른 저항 특성의 저하를 방지할 수 있다.Particularly, by using a specific compound as a coating material, deterioration of the resistance characteristic due to oxidation of Co can be prevented.
도 1은 실시예 1에서 제조한 양극 활물질의 주사전자현미경 사진이다.1 is a scanning electron micrograph of the cathode active material prepared in Example 1. Fig.
도 2는 비교예 1에서 제조한 양극 활물질의 주사전자현미경 사진이다.2 is a scanning electron microscope (SEM) image of the cathode active material prepared in Comparative Example 1. Fig.
도 3은 비교예 2에서 제조한 양극 활물질의 주사전자현미경 사진이다.3 is a scanning electron micrograph of the cathode active material prepared in Comparative Example 2. Fig.
도 4는 비교예 5에서 제조한 양극 활물질의 주사전자현미경 사진이다.4 is a scanning electron micrograph of the cathode active material prepared in Comparative Example 5. Fig.
도 5는 실시예 1~2 및 비교예 1, 3~4에서 제조한 리튬 이차전지의 충방전 특성을 나타낸 그래프이다.5 is a graph showing the charging / discharging characteristics of the lithium secondary batteries manufactured in Examples 1 and 2 and Comparative Examples 1 and 3 to 4.
도 6은 실시예 1 및 비교예 1, 3~4에서 제조한 리튬 이차전지의 1.0C 정전류 조건으로 방전하였을 때의 방전 용량을 나타낸 그래프이다. 6 is a graph showing discharge capacities of a lithium secondary battery manufactured in Example 1 and Comparative Examples 1 and 3 to 4 under a condition of 1.0 C constant current discharge.
도 7은 실시예 1 및 비교예 1, 3~4에서 제조한 리튬 이차전지의 2.0C 정전류 조건으로 방전하였을 때의 에서의 방전 용량을 나타낸 그래프이다.FIG. 7 is a graph showing the discharge capacities of the lithium secondary batteries manufactured in Example 1 and Comparative Examples 1 and 3 to 4 under a condition of 2.0 C constant current discharge. FIG.
이하, 본 발명을 더욱 상세하게 설명한다. Hereinafter, the present invention will be described in more detail.
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 and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.
본 발명에 따른 양극 활물질은 리튬을 제외한 전이금속의 총 몰수에 대하여 65몰% 이상의 니켈을 포함하는 니켈-함유 리튬 전이금속 산화물; 및, 상기 니켈-함유 리튬 전이금속 산화물의 표면에 형성된 코팅 물질;을 포함하며, 상기 코팅 물질은 B 및 Co를 포함하고, 상기 코팅 물질 내에 1,000 내지 5,000 ppm의 Co를 포함하는 것이다.The positive electrode active material according to the present invention is a nickel-containing lithium transition metal oxide containing at least 65 mol% of nickel based on the total moles of transition metals except lithium. And a coating material formed on the surface of the nickel-containing lithium transition metal oxide, wherein the coating material comprises B and Co, and the coating material contains Co in an amount of 1,000 to 5,000 ppm.
구체적으로, 상기 양극 활물질은 리튬을 제외한 전이금속의 총 몰수에 대하여 65몰% 이상의 니켈을 포함하는 니켈-함유 리튬 전이금속 산화물을 포함하는 것일 수 있으며, 보다 바람직하게는 하기 화학식 1로 표시되는 니켈-함유 리튬 전이금속 산화물을 포함할 수 있다.Specifically, the cathode active material may include a nickel-containing lithium transition metal oxide containing at least 65 mol% of nickel based on the total moles of transition metals other than lithium, more preferably nickel -Containing lithium transition metal oxide.
[화학식 1][Chemical Formula 1]
Li1+x(NiaCobMe1-(a+b))1-xO2 Li 1 + x (Ni a Co b Me 1- (a + b) ) 1-x O 2
상기 화학식 1에서, 0≤x≤0.3, 0.65≤a≤0.9, 0.05≤b≤0.2, 0.7≤a+b<1, 바람직하게는 0≤x≤0.3, 0.65≤a≤0.8, 0.1≤b≤0.2, 0.75≤a+b≤0.95, Me는 Mn 및 Al으로 이루어진 군에서 선택된 적어도 하나 이상임.In the above formula 1, 0? X? 0.3, 0.65? A? 0.9, 0.05? B? 0.2, 0.7? A + b <1, preferably 0? X? 0.3, 0.65? A? 0.8, 0.2, 0.75? A + b? 0.95, and Me is at least one selected from the group consisting of Mn and Al.
상기 니켈-함유 리튬 전이금속 산화물은 보다 바람직하게는 LiNiaCobAl1 -(a+b)O2 또는 LiNiaCobMn1 -(a+b)O2일 수 있으며, 가장 바람직하게는 LiNi0 . 65Co0 . 2Al0 . 15O2, LiNi0.7Co0.15Al0.15O2, LiNi0 . 8Co0 . 1Al0 . 1O2, LiNi0 . 9Co0 . 05Al0 . 05O2, LiNi0 . 65Co0 . 2Mn0 . 15O2, LiNi0.7Co0.15Mn0.15O2, LiNi0 . 8Co0 . 1Mn0 . 1O2, 및 LiNi0 . 9Co0 . 05Mn0 . 05O2로 이루어진 군에서 선택되는 적어도 하나일 수 있다. 상기와 같이 리튬을 제외한 전이금속 전체 몰수에 대하여 니켈의 함량이 65몰% 이상인 니켈-함유 리튬 전이금속 산화물을 이용하여 전지 제조 시 전지의 고용량화를 달성할 수 있다.The nickel-containing lithium transition metal oxide may more preferably be LiNi a Co b Al 1 - (a + b) O 2 or LiNi a Co b Mn 1 - (a + b) O 2 , LiNi 0 . 65 Co 0 . 2 Al 0 . 15 O 2 , LiNi 0.7 Co 0.15 Al 0.15 O 2 , LiNi 0 . 8 Co 0 . 1 Al 0 . 1 O 2 , LiNi 0 . 9 Co 0 . 05 A1 0 . 05 O 2 , LiNi 0 . 65 Co 0 . 2 Mn 0 . 15 O 2 , LiNi 0.7 Co 0.15 Mn 0.15 O 2 , LiNi 0 . 8 Co 0 . 1 Mn 0 . 1 O 2 , and LiNi 0 . 9 Co 0 . 05 Mn 0 . 05 O &lt; 2 &gt;. As described above, the nickel-containing lithium transition metal oxide having a nickel content of 65 mol% or more with respect to the total number of moles of transition metals other than lithium can be used to achieve high capacity of the battery during the production of the battery.
상기 양극 활물질은, 상기 양극 활물질의 표면에 형성된 코팅 원소 B 및 Co를 포함하는 코팅 물질을 포함한다. 상기 코팅 물질에 의해 상기 양극 활물질과 리튬 이차전지에 포함되는 전해액과의 접촉이 차단되어 부반응 발생이 억제되므로, 전지에 적용시 수명 특성을 향상시킬 수 있고, 더불어 양극활물질의 충진 밀도를 증가시킬 수 있다. 특히, 코팅 원소로서 B를 포함할 경우, 우수한 전기 전도성 확보로 인해 초기 저항 및 저항 증가율을 감소시킬 수 있고, 양극재 표면에 잔류하는 리튬 불순물을 저감하는 효과를 달성할 수 있고, 코팅 원소 Co를 포함할 경우, 율 특성을 개선할 수 있고, 우수한 전기 전도성 확보로 인해 초기 저항 및 저항 증가율을 감소시킬 수 있다.The positive electrode active material includes a coating material including Co element B and Co formed on the surface of the positive electrode active material. Since the contact between the positive electrode active material and the electrolyte contained in the lithium secondary battery is blocked by the coating material, occurrence of side reaction is suppressed, so that it is possible to improve the lifetime characteristics when applied to a battery and increase the filling density of the positive electrode active material have. Particularly, when B is contained as a coating element, it is possible to reduce the initial resistance and the rate of increase in resistance due to securing excellent electrical conductivity, achieve the effect of reducing lithium impurities remaining on the surface of the cathode material, The rate characteristics can be improved and the initial resistance and the rate of increase in resistance can be reduced due to securing excellent electrical conductivity.
상기 코팅 물질은 상기 B를 100 ppm 내지 500 ppm, 바람직하게는 200 ppm 내지 300 ppm로 포함할 수 있고, 상기 Co를 1,000 ppm 내지 5,000 ppm, 바람직하게는 2,000 ppm 내지 4,500 ppm으로 포함할 수 있다. 상기 코팅 물질 내에 상기 B 및 Co가 상기 범위로 포함될 경우, 불화수소에 의한 양극 활물질 표면의 부식 및 부반응 억제 효과가 더욱 효과적으로 발생하여, 전지에 적용 시 율 특성 및 수명 특성이 더욱 향상될 수 있다. The coating material may contain B in an amount of 100 ppm to 500 ppm, preferably 200 ppm to 300 ppm, and the Co may include 1,000 ppm to 5,000 ppm, preferably 2,000 ppm to 4,500 ppm. When the above-mentioned B and Co are included in the above-mentioned coating material, the effect of suppressing the corrosion and side reaction on the surface of the cathode active material by hydrogen fluoride occurs more effectively, and the rate characteristics and lifetime characteristics when applied to a battery can be further improved.
상기 코팅 물질에 포함되는 Co의 함량은 투과전자현미경 및 X선 분광 분석법을 이용하여 측정할 수 있다. 예를 들면, JEOL 社의 JEM-2010F 모델(transmission electron microscope, TEM)의 electron dispersive X-ray spectroscopy(EDS)를 이용하여 코팅 물질 내 존재하는 Co의 함량을 측정할 수 있다. The content of Co contained in the coating material can be measured using a transmission electron microscope and X-ray spectrometry. For example, the content of Co present in a coating material can be measured using electron dispersive X-ray spectroscopy (EDS) of a JEM-2010F transmission electron microscope (TEM).
상기 코팅 물질에 포함되는 B의 함량은 예를 들어, ICP 질량 분석법을 이용하여 측정할 수 있다. 예를 들면, 상기 ICP 질량 분석은 (Optima 7000 dv, PerkinElmer 社)을 이용하여, 시료를 유리병(vial)에 0.05g이 되도록 분취하여 무게를 측정하고, 염산 2mL 및 과산화수소 0.5mL를 가한 후, 130℃에서 3 시간 동안 가열하여 시료를 용해시킨다. 이어서 용해된 시료에 internal STD 0.2mL를 첨가하고, 초순수 용액으로 20mL가 되도록 희석함으로써 측정할 수 있다. The content of B contained in the coating material can be measured by, for example, ICP mass spectrometry. For example, the ICP mass spectrometry (Optima 7000 dv, PerkinElmer) was used to collect the sample in a vial of 0.05 g, weigh the sample, add 2 ml of hydrochloric acid and 0.5 ml of hydrogen peroxide, Heat the sample at 130 ° C for 3 hours to dissolve the sample. Subsequently, 0.2 mL of internal STD is added to the dissolved sample and diluted to 20 mL with ultrapure water.
상기 코팅 물질은 양극 활물질의 표면 전체에 걸쳐 균일하게 분포될 수도 있고, 부분적으로 뭉친 아일랜드(island) 형태로 분포될 수도 있다. 구체적으로, 상기 코팅 물질이 상기 양극 활물질의 표면 전체에 걸쳐 균일하게 코팅층을 형성할 경우, 예를 들면 상기 코팅층의 두께는 1 nm 내지 50 nm, 바람직하게는 7 nm 내지 25 nm일 수 있다. 상기 양극 활물질의 표면에 상기 코팅 물질이 아일랜드 형태로 분포할 경우, 상기 코팅 물질은 양극 활물질의 전체 표면적 중 20% 이상 내지 90% 이하의 면적을 차지하도록 분포될 수 있다. 상기 코팅 물질의 면적이 양극 활물질의 전체 표면적 중 20% 미만일 경우, 코팅 물질의 형성에 따른 구조적 안정성 개선 효과가 미미할 수 있다. 상기 코팅 물질이 양극 활물질의 표면 전체에 걸쳐 균일하게 형성될 경우 양극 활물질 표면의 구조 안정성을 더욱 개선시킬 수 있다. The coating material may be uniformly distributed over the entire surface of the cathode active material, or may be distributed in the form of partially coherent islands. Specifically, when the coating material uniformly forms a coating layer over the entire surface of the cathode active material, for example, the thickness of the coating layer may be 1 nm to 50 nm, preferably 7 nm to 25 nm. When the coating material is distributed on the surface of the cathode active material in the island shape, the coating material may be distributed to occupy 20% to 90% of the total surface area of the cathode active material. When the area of the coating material is less than 20% of the total surface area of the cathode active material, the effect of improving the structural stability due to the formation of the coating material may be insignificant. When the coating material is uniformly formed over the entire surface of the cathode active material, the structural stability of the cathode active material surface can be further improved.
한편, 본 발명에 따른 양극 활물질의 제조 방법은 전이금속의 총 몰수에 대하여 65몰% 이상의 니켈을 포함하는 니켈-함유 수산화물 전구체 및 리튬-원료물질을 혼합하고 1차 열처리하여, 니켈-함유 리튬 전이금속 산화물을 제조하는 단계; 상기 니켈-함유 리튬 전이금속 산화물에 B 및 C-함유 원료 물질 및 Co-함유 원료 물질을 혼합하여 혼합물을 형성하는 단계; 및, 상기 혼합물을 2차 열처리하여, 상기 리튬-전이금속 산화물 표면에 B 및 Co를 포함하는 코팅 물질을 형성하는 단계;를 포함한다.In the meantime, the method for producing a positive electrode active material according to the present invention comprises mixing a nickel-containing hydroxide precursor containing at least 65 mol% of nickel relative to the total moles of transition metals and a lithium-source material and subjecting the mixture to a first heat treatment to form a nickel- Producing a metal oxide; Mixing the B-containing and C-containing raw material and the Co-containing raw material with the nickel-containing lithium transition metal oxide to form a mixture; And forming a coating material containing B and Co on the surface of the lithium-transition metal oxide by secondary heat treatment of the mixture.
이하, 본 발명의 양극 활물질의 제조 방법을 구체적으로 설명한다.Hereinafter, a method for producing the positive electrode active material of the present invention will be described in detail.
먼저, 니켈-함유 전이금속 수산화물 전구체 및 리튬-원료물질을 혼합하고 1차 열처리하여, 니켈-함유 리튬 전이금속 산화물을 제조한다.First, a nickel-containing transition metal hydroxide precursor and a lithium-source material are mixed and subjected to a first heat treatment to prepare a nickel-containing lithium transition metal oxide.
상기 니켈-함유 전이금속 수산화물 전구체는 전이금속의 총 몰수에 대하여 니켈의 함량이 65몰% 이상인 것일 수 있으며, Nia1Cob1Me1 -(a1+b1)OH2(이때, 0.65≤a1≤0.8, 0.05≤b1≤0.2, 0.85≤a1+b1≤0.95, Me는 Mn 및 Al으로 이루어진 군에서 선택된 적어도 하나 이상임)인 것일 수 있다. 바람직하게는, 상기 니켈코발트망간 수산화물 전구체는 Ni0 . 65Co0 . 2Al0 .15(OH)2, Ni0 . 7Co0 . 15Al0 .15(OH)2, Ni0 . 8Co0 . 1Al0 .1(OH)2, Ni0.9Co0.05Al0.05(OH)2, Ni0 . 65Co0 . 2Mn0 .15(OH)2, Ni0 . 7Co0 . 15Mn0 .15(OH)2, Ni0 . 8Co0 . 1Mn0 .1(OH)2, 및 Ni0 . 9Co0 . 05Mn0 .05(OH)2로 이루어진 군에서 선택되는 적어도 하나 이상일 수 있다. 상기와 같이 양극 활물질용 전구체의 전체 몰수에 대하여 니켈의 함량이 65몰% 이상일 경우, 이를 이용하여 전지 제조 시 전지의 고용량화를 달성할 수 있다.The nickel-containing transition metal hydroxide precursor may have a nickel content of 65 mol% or more based on the total number of moles of the transition metal, and Ni a1 Co b1 Me 1 - (a 1 + b 1 ) OH 2 wherein 0.65? A1? , 0.05? B1? 0.2, 0.85? A1 + b1? 0.95, and Me is at least one selected from the group consisting of Mn and Al). Preferably, the nickel cobalt manganese hydroxide precursor is Ni 0 . 65 Co 0 . 2 Al 0 .15 (OH) 2 , Ni 0. 7 Co 0 . 15 Al 0 .15 (OH) 2 , Ni 0. 8 Co 0 . 1 Al 0 .1 (OH) 2 , Ni 0.9 Co 0.05 Al 0.05 (OH) 2 , Ni 0 . 65 Co 0 . 2 Mn 0 .15 (OH) 2 , Ni 0. 7 Co 0 . 15 Mn 0 .15 (OH) 2 , Ni 0. 8 Co 0 . 1 0 .1 Mn (OH) 2, and Ni 0. 9 Co 0 . 05 Mn 0 .05 (OH) 2 . When the content of nickel is 65 mol% or more with respect to the total number of moles of the precursor for a cathode active material as described above, it is possible to achieve a high capacity of the battery during the production of the battery.
또한, 상기 리튬-원료 물질은, 리튬 소스를 포함하는 화합물이라면 특별히 한정되지 않으나, 바람직하게는, 탄산리튬(Li2CO3), 수산화리튬(LiOH), LiNO3, CH3COOLi 및 Li2(COO)2로 이루어진 군에서 선택되는 적어도 하나를 사용할 수 있다.The lithium-source material is not particularly limited as long as it is a compound containing a lithium source, but lithium carbonate (Li 2 CO 3 ), lithium hydroxide (LiOH), LiNO 3 , CH 3 COOLi and Li 2 COO) 2 may be used.
또한, 상기 니켈-함유 전이금속 수산화물 전구체 및 리튬-원료물질은 Li과 금속의 몰비(Li/금속 ratio)가 1 내지 1.3, 바람직하게는 1.05 내지 1.1, 보다 바람직하게는 1.07 내지 1.09가 되도록 혼합할 수 있다. 상기 니켈-함유 전이금속 수산화물 전구체 및 리튬-원료물질이 상기 범위로 혼합될 경우, 우수한 용량 특성을 나타내는 양극 활물질을 제조할 수 있다.The nickel-containing transition metal hydroxide precursor and the lithium-source material are mixed so that the molar ratio of Li to metal (Li / metal ratio) is 1 to 1.3, preferably 1.05 to 1.1, more preferably 1.07 to 1.09 . When the nickel-containing transition metal hydroxide precursor and the lithium-source material are mixed in the above range, a cathode active material exhibiting excellent capacity characteristics can be produced.
상기 니켈-함유 전이금속 수산화물 전구체 및 리튬-원료물질의 혼합물을 1차 열처리하여, 니켈-함유 리튬 전이금속 산화물을 포함하는 양극 활물질을 제조한다. 상기 1차 열처리는 700℃ 내지 900℃의 온도로 수행될 수 있다.A mixture of the nickel-containing transition metal hydroxide precursor and the lithium-source material is subjected to a first heat treatment to prepare a cathode active material containing a nickel-containing lithium transition metal oxide. The primary heat treatment may be performed at a temperature of 700 ° C to 900 ° C.
이때, 상기 1차 열처리는 산화 분위기에서 수행할 수 있다. 상기 1차 열처리를 산화 분위기에서 수행할 경우, 코팅 물질을 충분히 형성할 수 있을 정도의 잔류 리튬 불순물을 얻을 수 있으며, 결정립의 발달이 우수한 양극 니켈-함유 리튬 전이금속 산화물을 얻을 수 있다. 예를 들면, 상기 1차 열처리를 질소 분위기 등의 비활성화 분위기에서 수행할 경우, 잔류 리튬 불순물의 양이 많아져 금속 산화물이 합성되지 않아 코팅 물질의 형성이 어려울 수 있다. At this time, the first heat treatment may be performed in an oxidizing atmosphere. When the primary heat treatment is performed in an oxidizing atmosphere, a residual lithium impurity to such an extent that a coating material can be sufficiently formed can be obtained, and a positive electrode nickel-containing lithium transition metal oxide having excellent crystal grains can be obtained. For example, when the primary heat treatment is performed in an inactive atmosphere such as a nitrogen atmosphere, the amount of residual lithium impurities increases, so that metal oxides are not synthesized and formation of a coating material may be difficult.
상기 1차 열처리는 산화 분위기에서 600℃ 내지 800℃에서 4시간 내지 5시간 동안 1단계로 수행한 후, 800℃ 내지 900℃에서 8시간 내지 10시간 동안 2단계로 수행하는 것일 수 있다. 상기 1차 열처리를 2단계로 수행할 경우, 양극 활물질의 입자 강도를 향상시킬 수 있다. 또한, 상기 1차 열처리 온도 및 시간이 상기 범위를 만족할 경우, 입자 내에 원료 물질이 잔류하지 않아, 전지의 고온 안정성이 향상될 수 있고, 이에 따라 부피 밀도 및 결정성이 향상되어 결과적으로 양극 활물질의 구조 안정성이 향상될 수 있다. The primary heat treatment may be carried out in an oxidizing atmosphere at 600 ° C to 800 ° C for 4 hours to 5 hours in one step and then at 800 ° C to 900 ° C for 8 hours to 10 hours in two steps. When the primary heat treatment is performed in two steps, the particle strength of the cathode active material can be improved. In addition, when the primary heat treatment temperature and time satisfy the above range, the raw material does not remain in the particles and the high-temperature stability of the battery can be improved. As a result, the bulk density and crystallinity are improved, The structural stability can be improved.
이어서, 상기 니켈-함유 리튬 전이금속 산화물에 B 및 C-함유 원료 물질 및 Co-함유 원료 물질을 혼합하여, 혼합물을 형성한다.Next, the nickel-containing lithium transition metal oxide is mixed with the B- and C-containing raw material and the Co-containing raw material to form a mixture.
구체적으로, 상기 B 및 C-함유 원료 물질은, B4C, (C3H7O)3B, (C6H5O)3B, [CH3(CH2)3O]3B, 및 C6H5B(OH)2로 이루어진 군에서 선택되는 적어도 하나 이상일 수 있으며, 바람직하게는 B4C일 수 있다.Specifically, the C- and B-containing source material, B 4 C, (C 3 H 7 O) 3 B, (C 6 H 5 O) 3 B, [CH 3 (CH 2) 3 O] 3 B, And C 6 H 5 B (OH) 2 , and may be at least one of B 4 C, preferably B 4 C.
예를 들면, 상기 B 및 C-함유 원료 물질이 B4C일 경우, 상기 B4C는 높은 녹는점을 가지기 때문에 고온 열처리를 수행하는 경우의 원료 물질로서 적용하기 유리하다. 또한, 상기 B 및 C-함유 원료 물질 에 포함되는 C는 강력한 환원 작용으로 인해 상기 C의 산화가 용이하며, 동시에 코팅 원료 물질의 산화를 용이하게 억제할 수 있다. For example, when the B and C-containing raw materials are B 4 C, since B 4 C has a high melting point, it is advantageous to apply it as a raw material for performing a high-temperature heat treatment. In addition, the C included in the B and C-containing raw materials is easily oxidized by the strong reducing action, and oxidation of the coating raw material can be easily suppressed.
상기 B 및 C-함유 원료 물질은 니켈-함유 리튬 전이금속 산화물 100 중량부에 대하여 0.02 중량부 내지 0.04 중량부로 혼합할 수 있다. 상기 B 및 C-함유 원료 물질을 상기 범위로 혼합함으로써, 우수한 전기 전도성 확보로 인해 초기 저항 및 저항 증가율을 감소시킬 수 있고, 양극재 표면에 잔류하는 리튬 불순물을 저감하는 효과를 달성할 수 있다.The B and C-containing raw material may be mixed in an amount of 0.02 parts by weight to 0.04 parts by weight based on 100 parts by weight of the nickel-containing lithium transition metal oxide. By mixing the B and C-containing raw material in the above range, it is possible to reduce the initial resistance and the rate of increase in resistance due to the excellent electrical conductivity and to reduce the lithium impurities remaining on the surface of the cathode material.
상기 Co-함유 원료 물질은, 리튬 전이금속 산화물의 입자 표면을 피복 처리할 수 있고, 전기화학적 성능을 저하시키지 않는 것이라면 제한 없이 사용할 수 있으며, 구체적으로 Co(OH)2, Co2O3, Co3(PO4)2, CoF3, CoOOH, Co(OCOCH3)2·4H2O, Co(NO3)·6H2O, Co3O4, Co(SO4)2·7H2O 및 CoC2O4로 이루어진 군에서 선택되는 적어도 하나 이상일 수 있다.The Co-containing raw material can be used without limitation as long as it can coat the surface of the lithium transition metal oxide particles and does not deteriorate the electrochemical performance. Specifically, Co (OH) 2 , Co 2 O 3 , Co 3 (PO 4) 2, CoF 3, CoOOH, Co (OCOCH 3) 2 · 4H 2 O, Co (NO 3) · 6H 2 O, Co 3 O 4, Co (SO 4) 2 · 7H 2 O and CoC at least one may be at least selected from the group consisting of 2 O 4.
예를 들면, 상기 Co-함유 원료 물질로서 Co(OH)2를 사용할 경우, 이를 전지에 적용시 구조 안정성이 더욱 개선될 수 있다. 그러나, 상기 Co(OH)2를 산화 분위기에서 300℃ 이상으로 열처리 시, Co3O4로 산화되어 전기 화학 반응 시 저항으로 작용하거나, 전극 제조 과정 중 또는 충방전 사이클 중 외부의 물리적인 영향에 의해 양극재 표면에서 탈리되어 저항 특성이 열위하다는 문제점이 있었다. 그러나, 본 발명과 같이 코팅 물질로서 Co-함유 원료 물질뿐만 아니라, B 및 C-함유 원료 물질을 함께 포함할 경우, 상기 B 및 C-함유 원료 물질은 고온 열처리 시, 해리(dissociation) 과정에서 발생하는 탄소에 의하여 환원제 역할을 수행할 수 있다. 이에 따라, 상기 Co(OH2)가 금속 산화물로 산화되는 것을 방지하여, 코팅 물질 내 Co가 바람직하게는 1,000 내지 5,000 ppm 정도로 잔존하는 것일 수 있다.For example, when Co (OH) 2 is used as the Co-containing raw material, its structural stability can be further improved when applied to a battery. However, when the Co (OH) 2 is thermally treated in an oxidizing atmosphere at a temperature of 300 ° C or higher, it is oxidized to Co 3 O 4 to act as a resistance during electrochemical reaction, Thereby causing a problem that the resistance characteristic is poor. However, when the Co-containing raw material as well as the B and C-containing raw materials are included together as the coating material according to the present invention, the B and C-containing raw materials are generated during the dissociation process at high temperature heat treatment Carbon can act as a reducing agent. Accordingly, the Co (OH 2 ) can be prevented from being oxidized to the metal oxide, so that the Co content in the coating material is preferably about 1,000 to 5,000 ppm.
상기 Co-함유 원료 물질은 니켈-함유 리튬 전이금속 산화물 100 중량부에 대하여 0.5 중량부 내지 1.0 중량부로 혼합할 수 있다. 상기 Co-함유 원료 물질을 상기 범위로 혼합함으로써, 율 특성을 개선할 수 있다.The Co-containing raw material may be mixed with 0.5 part by weight to 1.0 part by weight with respect to 100 parts by weight of the nickel-containing lithium transition metal oxide. By mixing the above-mentioned Co-containing raw material in the above range, the rate characteristics can be improved.
다음으로, 상기 혼합물을 500℃ 내지 750℃에서 2차 열처리하여, 리튬 전이금속 산화물의 입자 표면에 B 및 Co를 포함하는 코팅 물질을 형성한다.Next, the mixture is subjected to a secondary heat treatment at 500 ° C to 750 ° C to form a coating material containing B and Co on the surface of the lithium transition metal oxide.
상기 2차 열처리는 500℃ 내지 750℃에서 3 시간 내지 8 시간, 보다 바람직하게는 500℃ 내지 650℃에서 4시간 내지 6시간 동안 수행하는 것일 수 있다. 상기 2차 열처리 온도가 상기 범위를 만족할 경우, 고온에서 코팅 물질을 형성함으로써 양극 활물질 표면의 변화 없이, 코팅 물질의 형성으로 인한 양극 활물질의 표면 개질이 용이하게 발생하여 4.3V 이상의 고전압에서도 구조적 안정성이 우수하고, 고용량을 가지는 양극 활물질을 제조할 수 있다. 예를 들면, 상기 2차 열처리 온도 및 시간이 상기 범위를 벗어날 경우, 과도한 리튬 보레이트 화합물 형성으로 인해 용량 및 수명 특성이 감소할 수 있다. The secondary heat treatment may be performed at 500 ° C to 750 ° C for 3 hours to 8 hours, more preferably at 500 ° C to 650 ° C for 4 hours to 6 hours. When the secondary heat treatment temperature is in the above range, the surface of the cathode active material is easily modified due to the formation of the coating material without changing the surface of the cathode active material by forming the coating material at a high temperature, It is possible to produce a cathode active material having an excellent and high capacity. For example, when the temperature and time of the second heat treatment are out of the above ranges, capacity and lifetime characteristics may be reduced due to excessive lithium borate compound formation.
또한, 본 발명에 따른 양극 활물질을 포함하는, 리튬 이차전지용 양극을 제공한다. 구체적으로, 상기 이차전지용 양극은, 양극 집전체, 상기 양극 집전체 상에 형성된 양극 활물질층을 포함하며, 상기 양극 활물질층은 본 발명에 따른 양극 활물질을 포함하는, 리튬 이차전지용 양극을 제공한다. Also, there is provided a positive electrode for a lithium secondary battery comprising the positive electrode active material according to the present invention. Specifically, the cathode for a secondary battery includes a cathode current collector, a cathode active material layer formed on the cathode current collector, and the cathode active material layer includes the cathode active material according to the present invention.
이때, 상기 양극 활물질은 상술한 바와 동일하므로, 구체적인 설명을 생략하고, 이하 나머지 구성에 대해서만 구체적으로 설명한다.Since the cathode active material is the same as that described above, a detailed description thereof will be omitted and only the remaining constitution will be specifically described below.
상기 양극 집전체는 전지에 화학적 변화를 유발하지 않으면서 도전성을 가진 것이라면 특별히 제한되는 것은 아니며, 예를 들어 스테인리스 스틸, 알루미늄, 니켈, 티탄, 소성 탄소 또는 알루미늄이나 스테인레스 스틸 표면에 탄소, 니켈, 티탄, 은 등으로 표면 처리한 것 등이 사용될 수 있다. 또, 상기 양극 집전체는 통상적으로 3 내지 500㎛의 두께를 가질 수 있으며, 상기 집전체 표면 상에 미세한 요철을 형성하여 양극 활물질의 접착력을 높일 수도 있다. 예를 들어 필름, 시트, 호일, 네트, 다공질체, 발포체, 부직포체 등 다양한 형태로 사용될 수 있다.The positive electrode current collector is not particularly limited as long as it has conductivity without causing chemical changes in the battery. For example, carbon, nickel, titanium, , Silver or the like may be used. In addition, the cathode current collector may have a thickness of 3 to 500 탆, and fine unevenness may be formed on the surface of the current collector to increase the adhesive force of the cathode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.
상기 양극 활물질층은 상기 양극 활물질과 함께, 도전재 및 필요에 따라 선택적으로 바인더를 포함할 수 있다. The cathode active material layer may include a conductive material and, optionally, a binder optionally together with the cathode active material.
이때 상기 양극 활물질은 양극 활물질층 총 중량에 대하여 80 내지 99중량%, 보다 구체적으로는 85 내지 98.5중량%의 함량으로 포함될 수 있다. 상기한 함량범위로 포함될 때 우수한 용량 특성을 나타낼 수 있다.At this time, the cathode active material may be contained in an amount of 80 to 99% by weight, more specifically 85 to 98.5% by weight based on the total weight of the cathode active material layer. When included in the above content range, excellent capacity characteristics can be exhibited.
상기 도전재는 전극에 도전성을 부여하기 위해 사용되는 것으로서, 구성되는 전지에 있어서, 화학변화를 야기하지 않고 전자 전도성을 갖는 것이면 특별한 제한 없이 사용 가능하다. 구체적인 예로는 천연 흑연이나 인조 흑연 등의 흑연; 카본 블랙, 아세틸렌블랙, 케첸블랙, 채널 블랙, 퍼네이스 블랙, 램프 블랙, 서머 블랙, 탄소섬유 등의 탄소계 물질; 구리, 니켈, 알루미늄, 은 등의 금속 분말 또는 금속 섬유; 산화아연, 티탄산 칼륨 등의 도전성 위스키; 산화 티탄 등의 도전성 금속 산화물; 또는 폴리페닐렌 유도체 등의 전도성 고분자 등을 들 수 있으며, 이들 중 1종 단독 또는 2종 이상의 혼합물이 사용될 수 있다. 상기 도전재는 양극 활물질층 총 중량에 대하여 0.1 내지 15 중량%로 포함될 수 있다.The conductive material is used for imparting conductivity to the electrode. The conductive material is not particularly limited as long as it has electron conductivity without causing chemical change. Specific examples thereof include graphite such as natural graphite and artificial graphite; Carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, summer black and carbon fiber; Metal powder or metal fibers such as copper, nickel, aluminum and silver; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; And polyphenylene derivatives. These may be used alone or in admixture of two or more. The conductive material may be included in an amount of 0.1 to 15% by weight based on the total weight of the cathode active material layer.
상기 바인더는 양극 활물질 입자들 간의 부착 및 양극 활물질과 집전체와의 접착력을 향상시키는 역할을 한다. 구체적인 예로는 폴리비닐리덴플로라이드(PVDF), 비닐리덴플루오라이드-헥사플루오로프로필렌 코폴리머(PVDF-co-HFP), 폴리비닐알코올, 폴리아크릴로니트릴(polyacrylonitrile), 카르복시메틸셀룰로우즈(CMC), 전분, 히드록시프로필셀룰로우즈, 재생 셀룰로우즈, 폴리비닐피롤리돈, 테트라플루오로에틸렌, 폴리에틸렌, 폴리프로필렌, 에틸렌-프로필렌-디엔 폴리머(EPDM), 술폰화-EPDM, 스티렌 부타디엔 고무(SBR), 불소 고무, 또는 이들의 다양한 공중합체 등을 들 수 있으며, 이들 중 1종 단독 또는 2종 이상의 혼합물이 사용될 수 있다. 상기 바인더는 양극 활물질층 총 중량에 대하여 0.1 내지 15 중량%로 포함될 수 있다.The binder serves to improve the adhesion between the positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose ), Starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, and various copolymers thereof. One kind or a mixture of two or more kinds of them may be used. The binder may be included in an amount of 0.1 to 15% by weight based on the total weight of the cathode active material layer.
상기 양극은 상기한 양극 활물질을 이용하는 것을 제외하고는 통상의 양극 제조방법에 따라 제조될 수 있다. 구체적으로, 상기한 양극 활물질 및 선택적으로, 바인더 및 도전재를 용매 중에 용해 또는 분산시켜 제조한 양극 활물질층 형성용 조성물을 양극집전체 상에 도포한 후, 건조 및 압연함으로써 제조할 수 있다. The positive electrode may be manufactured according to a conventional positive electrode manufacturing method, except that the positive electrode active material described above is used. Specifically, the cathode active material and optionally the binder and the conductive material may be dissolved or dispersed in a solvent to prepare a composition for forming a cathode active material layer, which is then applied onto the cathode current collector, followed by drying and rolling.
상기 용매로는 당해 기술분야에서 일반적으로 사용되는 용매일 수 있으며, 디메틸셀폭사이드(dimethyl sulfoxide, DMSO), 이소프로필 알코올(isopropyl alcohol), N-메틸피롤리돈(NMP), 아세톤(acetone) 또는 물 등을 들 수 있으며, 이들 중 1종 단독 또는 2종 이상의 혼합물이 사용될 수 있다. 상기 용매의 사용량은 슬러리의 도포 두께, 제조 수율을 고려하여 상기 양극 활물질, 도전재 및 바인더를 용해 또는 분산시키고, 이후 양극제조를 위한 도포시 우수한 두께 균일도를 나타낼 수 있는 점도를 갖도록 하는 정도면 충분하다.Examples of the solvent include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, and the like. Water and the like, and one kind or a mixture of two or more kinds can be used. The amount of the solvent to be used is sufficient to dissolve or disperse the cathode active material, the conductive material and the binder in consideration of the coating thickness of the slurry and the yield of the slurry, and then to have a viscosity capable of exhibiting excellent thickness uniformity Do.
또한, 다른 방법으로, 상기 양극은 상기 양극 활물질층 형성용 조성물을 별도의 지지체 상에 캐스팅한 다음, 이 지지체로부터 박리하여 얻은 필름을 양극 집전체 상에 라미네이션함으로써 제조될 수도 있다.Alternatively, the positive electrode may be produced by casting the composition for forming the positive electrode active material layer on a separate support, and then laminating a film obtained by peeling from the support onto the positive electrode collector.
또한, 본 발명은 상기 양극을 포함하는 전기화학소자를 제조할 수 있다. 상기 전기화학소자는 구체적으로 전지, 커패시터 등일 수 있으며, 보다 구체적으로는 리튬 이차전지일 수 있다.In addition, the present invention can produce an electrochemical device including the positive electrode. The electrochemical device may be specifically a battery, a capacitor, or the like, and more specifically, it may be a lithium secondary battery.
상기 리튬 이차전지는 구체적으로, 양극, 상기 양극과 대향하여 위치하는 음극, 및 상기 양극과 음극 사이에 개재되는 분리막 및 전해질을 포함하고, 상기 양극은 앞서 설명한 바와 동일하므로, 구체적인 설명을 생략하고, 이하 나머지 구성에 대해서만 구체적으로 설명한다. Specifically, the lithium secondary battery includes a positive electrode, a negative electrode disposed opposite to the positive electrode, and a separation membrane and an electrolyte interposed between the positive electrode and the negative electrode. The positive electrode is the same as that described above, Only the remaining configuration will be described in detail below.
또한, 상기 리튬 이차전지는 상기 양극, 음극, 분리막의 전극 조립체를 수납하는 전지용기, 및 상기 전지용기를 밀봉하는 밀봉 부재를 선택적으로 더 포함할 수 있다.The lithium secondary battery may further include a battery container for housing the electrode assembly of the anode, the cathode, and the separator, and a sealing member for sealing the battery container.
상기 리튬 이차전지에 있어서, 상기 음극은 음극 집전체 및 상기 음극 집전체 상에 위치하는 음극 활물질층을 포함한다.In the lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector.
상기 음극 집전체는 전지에 화학적 변화를 유발하지 않으면서 높은 도전성을 가지는 것이라면 특별히 제한되는 것은 아니며, 예를 들어, 구리, 스테인레스 스틸, 알루미늄, 니켈, 티탄, 소성 탄소, 구리나 스테인레스 스틸의 표면에 탄소, 니켈, 티탄, 은 등으로 표면처리한 것, 알루미늄-카드뮴 합금 등이 사용될 수 있다. 또, 상기 음극 집전체는 통상적으로 3㎛ 내지 500㎛의 두께를 가질 수 있으며, 양극 집전체와 마찬가지로, 상기 집전체 표면에 미세한 요철을 형성하여 음극활물질의 결합력을 강화시킬 수도 있다. 예를 들어, 필름, 시트, 호일, 네트, 다공질체, 발포체, 부직포체 등 다양한 형태로 사용될 수 있다.The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, the negative electrode current collector may be formed on the surface of copper, stainless steel, aluminum, nickel, titanium, sintered carbon, Carbon, nickel, titanium, silver or the like, aluminum-cadmium alloy, or the like may be used. In addition, the negative electrode collector may have a thickness of 3 to 500 탆, and similarly to the positive electrode collector, fine unevenness may be formed on the surface of the collector to enhance the binding force of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.
상기 음극 활물질층은 음극 활물질과 함께 선택적으로 바인더 및 도전재를 포함한다.The anode active material layer optionally includes a binder and a conductive material together with the anode active material.
상기 음극 활물질로는 리튬의 가역적인 인터칼레이션 및 디인터칼레이션이 가능한 화합물이 사용될 수 있다. 구체적인 예로는 인조흑연, 천연흑연, 흑연화 탄소섬유, 비정질탄소 등의 탄소질 재료; Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si합금, Sn합금 또는 Al합금 등 리튬과 합금화가 가능한 금속질 화합물; SiOβ(0<β<2), SnO2, 바나듐 산화물, 리튬 바나듐 산화물과 같이 리튬을 도프 및 탈도프할 수 있는 금속산화물; 또는 Si-C 복합체 또는 Sn-C 복합체과 같이 상기 금속질 화합물과 탄소질 재료를 포함하는 복합물 등을 들 수 있으며, 이들 중 어느 하나 또는 둘 이상의 혼합물이 사용될 수 있다. 또한, 상기 음극활물질로서 금속 리튬 박막이 사용될 수도 있다. 또, 탄소재료는 저결정 탄소 및 고결정성 탄소 등이 모두 사용될 수 있다. 저결정성 탄소로는 연화탄소 (soft carbon) 및 경화탄소 (hard carbon)가 대표적이며, 고결정성 탄소로는 무정형, 판상, 인편상, 구형 또는 섬유형의 천연 흑연 또는 인조 흑연, 키시흑연 (Kish graphite), 열분해 탄소 (pyrolytic carbon), 액정피치계 탄소섬유 (mesophase pitch based carbon fiber), 탄소 미소구체 (meso-carbon microbeads), 액정피치 (Mesophase pitches) 및 석유와 석탄계 코크스 (petroleum or coal tar pitch derived cokes) 등의 고온 소성탄소가 대표적이다.As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples thereof include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber and amorphous carbon; Metal compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys or Al alloys; SiO β (0 <β <2 ), SnO 2, vanadium oxide, which can dope and de-dope a lithium metal oxide such as lithium vanadium oxide; Or a composite containing the metallic compound and the carbonaceous material such as Si-C composite or Sn-C composite, and any one or a mixture of two or more thereof may be used. Also, a metal lithium thin film may be used as the negative electrode active material. The carbon material may be both low-crystalline carbon and high-crystallinity carbon. Examples of the low-crystalline carbon include soft carbon and hard carbon. Examples of the highly crystalline carbon include natural graphite, artificial graphite, artificial graphite or artificial graphite, Kish graphite graphite, pyrolytic carbon, mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches and petroleum or coal tar coke derived cokes).
상기 음극활물질은 음극 활물질층의 전체 중량을 기준으로 80 중량% 내지 99중량%로 포함될 수 있다.The negative electrode active material may include 80% by weight to 99% by weight based on the total weight of the negative electrode active material layer.
상기 바인더는 도전재, 활물질 및 집전체 간의 결합에 조력하는 성분으로서, 통상적으로 음극 활물질층의 전체 중량을 기준으로 0.1 중량% 내지 10 중량%로 첨가된다.　이러한 바인더의 예로는, 폴리비닐리덴플루오라이드(PVDF), 폴리비닐알코올, 카르복시메틸셀룰로우즈(CMC), 전분, 히드록시프로필셀룰로우즈, 재생 셀룰로우즈, 폴리비닐피롤리돈, 테트라플루오로에틸렌, 폴리에틸렌, 폴리프로필렌, 에틸렌-프로필렌-디엔 폴리머(EPDM), 술폰화-EPDM, 스티렌-부타디엔 고무, 니트릴-부타디엔 고무, 불소 고무, 이들의 다양한 공중합체 등을 들 수 있다.The binder is a component for assisting the bonding between the conductive material, the active material and the current collector, and is usually added in an amount of 0.1% by weight to 10% by weight based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene Examples thereof include ethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluorine rubber and various copolymers thereof.
상기 도전재는 음극활물질의 도전성을 더욱 향상시키기 위한 성분으로서, 음극 활물질층의 전체 중량을 기준으로 10 중량% 이하, 바람직하게는 5 중량% 이하로 첨가될 수 있다. 이러한 도전재는 당해 전지에 화학적 변화를 유발하지 않으면서 도전성을 가진 것이라면 특별히 제한되는 것은 아니며, 예를 들어, 천연 흑연이나 인조 흑연 등의 흑연; 아세틸렌 블랙, 케첸 블랙, 채널 블랙, 퍼네이스 블랙, 램프 블랙, 서멀 블랙 등의 카본블랙; 탄소 섬유나 금속 섬유 등의 도전성 섬유; 불화 카본, 알루미늄, 니켈 분말 등의 금속 분말; 산화아연, 티탄산 칼륨 등의 도전성 위스키; 산화티탄 등의 도전성 금속 산화물; 폴리페닐렌 유도체 등의 도전성 소재 등이 사용될 수 있다.The conductive material may be added in an amount of 10 wt% or less, preferably 5 wt% or less, based on the total weight of the negative electrode active material layer, as a component for further improving the conductivity of the negative electrode active material. Such a conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, for example, graphite such as natural graphite or artificial graphite; Carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.
예를 들면, 상기 음극 활물질층은 음극 집전체 상에 음극 활물질, 및 선택적으로 바인더 및 도전재를 용매 중에 용해 또는 분산시켜 제조한 음극 활물질층 형성용 조성물을 도포하고 건조함으로써 제조되거나, 또는 상기 음극 활물질층 형성용 조성물을 별도의 지지체 상에 캐스팅한 다음, 이 지지체로부터 박리하여 얻은 필름을 음극 집전체 상에 라미네이션함으로써 제조될 수 있다.For example, the negative electrode active material layer is prepared by applying and drying a composition for forming a negative electrode active material layer, which is prepared by dissolving or dispersing a negative electrode active material on a negative electrode current collector, and optionally a binder and a conductive material in a solvent, Casting a composition for forming an active material layer on a separate support, and then laminating a film obtained by peeling from the support onto a negative electrode current collector.
상기 음극 활물질층은 일례로서 음극 집전체 상에 음극 활물질, 및 선택적으로 바인더 및 도전재를 용매 중에 용해 또는 분산시켜 제조한 음극 활물질층 형성용 조성물을 도포하고 건조하거나, 또는 상기 음극 활물질층 형성용 조성물을 별도의 지지체 상에 캐스팅한 다음, 이 지지체로부터 박리하여 얻은 필름을 음극 집전체 상에 라미네이션함으로써 제조될 수도 있다.The negative electrode active material layer may be formed by applying and drying a composition for forming a negative electrode active material layer prepared by dissolving or dispersing a negative electrode active material on a negative electrode collector and optionally a binder and a conductive material in a solvent, Casting the composition on a separate support, and then peeling the support from the support to laminate a film on the negative electrode current collector.
한편, 상기 리튬 이차전지에 있어서, 분리막은 음극과 양극을 분리하고 리튬 이온의 이동 통로를 제공하는 것으로, 통상 리튬 이차전지에서 분리막으로 사용되는 것이라면 특별한 제한 없이 사용가능하며, 특히 전해질의 이온 이동에 대하여 저저항이면서 전해액 함습 능력이 우수한 것이 바람직하다. 구체적으로는 다공성 고분자 필름, 예를 들어 에틸렌 단독중합체, 프로필렌 단독중합체, 에틸렌/부텐 공중합체, 에틸렌/헥센 공중합체 및 에틸렌/메타크릴레이트 공중합체 등과 같은 폴리올레핀계 고분자로 제조한 다공성 고분자 필름 또는 이들의 2층 이상의 적층 구조체가 사용될 수 있다. 또 통상적인 다공성 부직포, 예를 들어 고융점의 유리 섬유, 폴리에틸렌테레프탈레이트 섬유 등으로 된 부직포가 사용될 수도 있다. 또, 내열성 또는 기계적 강도 확보를 위해 세라믹 성분 또는 고분자 물질이 포함된 코팅된 분리막이 사용될 수도 있으며, 선택적으로 단층 또는 다층 구조로 사용될 수 있다.Meanwhile, in the lithium secondary battery, the separation membrane separates the cathode and the anode and provides a passage for lithium ion. The separation membrane can be used without any particular limitation as long as it is used as a separation membrane in a lithium secondary battery. Particularly, It is preferable to have a low resistance and an excellent ability to impregnate the electrolyte. Specifically, porous polymer films such as porous polymer films made of polyolefin-based polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers and ethylene / methacrylate copolymers, May be used. Further, a nonwoven fabric made of a conventional porous nonwoven fabric, for example, glass fiber of high melting point, polyethylene terephthalate fiber, or the like may be used. In order to secure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer material may be used, and the separator may be selectively used as a single layer or a multilayer structure.
또한, 본 발명에서 사용되는 전해질로는 리튬 이차전지 제조시 사용 가능한 유기계 액체 전해질, 무기계 액체 전해질, 고체 고분자 전해질, 겔형 고분자 전해질, 고체 무기 전해질, 용융형 무기 전해질 등을 들 수 있으며, 이들로 한정되는 것은 아니다. Examples of the electrolyte used in the present invention include an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, and a molten inorganic electrolyte that can be used in the production of a lithium secondary battery. It is not.
구체적으로, 상기 전해질은 유기 용매 및 리튬염을 포함할 수 있다. Specifically, the electrolyte may include an organic solvent and a lithium salt.
상기 유기 용매로는 전지의 전기 화학적 반응에 관여하는 이온들이 이동할 수 있는 매질 역할을 할 수 있는 것이라면 특별한 제한 없이 사용될 수 있다. 구체적으로 상기 유기 용매로는, 메틸 아세테이트(methyl acetate), 에틸 아세테이트(ethyl acetate), γ-부티로락톤(γ-butyrolactone), ε-카프로락톤(ε-caprolactone) 등의 에스테르계 용매; 디부틸 에테르(dibutyl ether) 또는 테트라히드로퓨란(tetrahydrofuran) 등의 에테르계 용매; 시클로헥사논(cyclohexanone) 등의 케톤계 용매; 벤젠(benzene), 플루오로벤젠(fluorobenzene) 등의 방향족 탄화수소계 용매; 디메틸카보네이트(dimethylcarbonate, DMC), 디에틸카보네이트(diethylcarbonate, DEC), 메틸에틸카보네이트(methylethylcarbonate, MEC), 에틸메틸카보네이트(ethylmethylcarbonate, EMC), 에틸렌카보네이트(ethylene carbonate, EC), 프로필렌카보네이트(propylene carbonate, PC) 등의 카보네이트계 용매; 에틸알코올, 이소프로필 알코올 등의 알코올계 용매; R-CN(R은 탄소수 2 내지 20의 직쇄상, 분지상 또는 환 구조의 탄화수소기이며, 이중결합 방향 환 또는 에테르 결합을 포함할 수 있다) 등의 니트릴류; 디메틸포름아미드 등의 아미드류; 1,3-디옥솔란 등의 디옥솔란류; 또는 설포란(sulfolane)류 등이 사용될 수 있다. 이중에서도 카보네이트계 용매가 바람직하고, 전지의 충방전 성능을 높일 수 있는 높은 이온전도도 및 고유전율을 갖는 환형 카보네이트(예를 들면, 에틸렌카보네이트 또는 프로필렌카보네이트 등)와, 저점도의 선형 카보네이트계 화합물(예를 들면, 에틸메틸카보네이트, 디메틸카보네이트 또는 디에틸카보네이트 등)의 혼합물이 보다 바람직하다. 이 경우 환형 카보네이트와 사슬형 카보네이트는 약 1:1 내지 약 1:9의 부피비로 혼합하여 사용하는 것이 전해액의 성능이 우수하게 나타날 수 있다. The organic solvent may be used without limitation as long as it can act as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate,? -Butyrolactone and? -Caprolactone; Ether solvents such as dibutyl ether or tetrahydrofuran; Ketone solvents such as cyclohexanone; Aromatic hydrocarbon solvents such as benzene and fluorobenzene; Dimethyl carbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), propylene carbonate PC) and the like; Alcohol solvents such as ethyl alcohol and isopropyl alcohol; R-CN (R is a linear, branched or cyclic hydrocarbon group having 2 to 20 carbon atoms, which may contain a double bond aromatic ring or an ether bond); Amides such as dimethylformamide; Dioxolanes such as 1,3-dioxolane; Or sulfolane may be used. Among these, a carbonate-based solvent is preferable, and a cyclic carbonate (for example, ethylene carbonate or propylene carbonate) having a high ionic conductivity and a high dielectric constant, for example, such as ethylene carbonate or propylene carbonate, For example, ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate) is more preferable. In this case, when the cyclic carbonate and the chain carbonate are mixed in a volume ratio of about 1: 1 to about 1: 9, the performance of the electrolytic solution may be excellent.
상기 리튬염은 리튬 이차전지에서 사용되는 리튬 이온을 제공할 수 있는 화합물이라면 특별한 제한 없이 사용될 수 있다. 구체적으로 상기 리튬염은, LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2 . LiCl, LiI, 또는 LiB(C2O4)2 등이 사용될 수 있다. 상기 리튬염의 농도는 0.1 내지 2.0M 범위 내에서 사용하는 것이 좋다. 리튬염의 농도가 상기 범위에 포함되면, 전해질이 적절한 전도도 및 점도를 가지므로 우수한 전해질 성능을 나타낼 수 있고, 리튬 이온이 효과적으로 이동할 수 있다.The lithium salt can be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt, LiPF 6, LiClO 4, LiAsF 6, LiBF 4, LiSbF 6, LiAl0 4, LiAlCl 4, LiCF 3 SO 3, LiC 4 F 9 SO 3, LiN (C 2 F 5 SO 3) 2 , LiN (C 2 F 5 SO 2) 2, LiN (CF 3 SO 2) 2. LiCl, LiI, or LiB (C 2 O 4 ) 2 may be used. The concentration of the lithium salt is preferably in the range of 0.1 to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte has an appropriate conductivity and viscosity, so that it can exhibit excellent electrolyte performance and the lithium ion can effectively move.
상기 전해질에는 상기 전해질 구성 성분들 외에도 전지의 수명특성 향상, 전지 용량 감소 억제, 전지의 방전 용량 향상 등을 목적으로 예를 들어, 디플루오로 에틸렌카보네이트 등과 같은 할로알킬렌카보네이트계 화합물, 피리딘, 트리에틸포스파이트, 트리에탄올아민, 환상 에테르, 에틸렌 디아민, n-글라임(glyme), 헥사인산 트리아미드, 니트로벤젠 유도체, 유황, 퀴논 이민 염료, N-치환 옥사졸리디논, N,N-치환 이미다졸리딘, 에틸렌 글리콜 디알킬 에테르, 암모늄염, 피롤, 2-메톡시 에탄올 또는 삼염화 알루미늄 등의 첨가제가 1종 이상 더 포함될 수도 있다. 이때 상기 첨가제는 전해질 총 중량에 대하여 0.1 내지 5 중량%로 포함될 수 있다.In addition to the electrolyte components, the electrolyte may contain, for example, a haloalkylene carbonate-based compound such as difluoroethylene carbonate or the like, pyridine, triethanolamine, or the like for the purpose of improving lifetime characteristics of the battery, Ethyl phosphite, triethanol amine, cyclic ether, ethylenediamine, glyme, hexametriamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, At least one additive such as benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, The additive may be included in an amount of 0.1 to 5% by weight based on the total weight of the electrolyte.
상기와 같이 본 발명에 따른 양극 활물질을 포함하는 리튬 이차전지는 우수한 방전 용량, 출력 특성 및 수명 특성을 안정적으로 나타내기 때문에, 휴대전화, 노트북 컴퓨터, 디지털 카메라 등의 휴대용 기기, 및 하이브리드 전기자동차(hybrid electric vehicle, HEV) 등의 전기 자동차 분야 등에 유용하다.As described above, since the lithium secondary battery including the cathode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics and life characteristics, it can be used in portable devices such as mobile phones, notebook computers, digital cameras, and hybrid electric vehicles hybrid electric vehicle (HEV)).
이에 따라, 본 발명의 다른 일 구현예에 따르면, 상기 리튬 이차전지를 단위 셀로 포함하는 전지 모듈 및 이를 포함하는 전지팩이 제공된다. According to another embodiment of the present invention, there is provided a battery module including the lithium secondary battery as a unit cell and a battery pack including the same.
상기 전지모듈 또는 전지팩은 파워 툴(Power Tool); 전기자동차(Electric Vehicle, EV), 하이브리드 전기자동차, 및 플러그인 하이브리드 전기자동차(Plug-in Hybrid Electric Vehicle, PHEV)를 포함하는 전기차; 또는 전력 저장용 시스템 중 어느 하나 이상의 중대형 디바이스 전원으로 이용될 수 있다.The battery module or the battery pack may include a power tool; An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); Or a power storage system, as shown in FIG.
본 발명의 리튬 이차전지의 외형은 특별한 제한이 없으나, 캔을 사용한 원통형, 각형, 파우치(pouch)형 또는 코인(coin)형 등이 될 수 있다.The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be a cylindrical shape, a square shape, a pouch shape, a coin shape, or the like using a can.
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. The lithium secondary battery according to the present invention can be used not only in a battery cell used as a power source of a small device but also as a unit cell in a middle- or large-sized battery module including a plurality of battery cells.
이하, 본 발명을 구체적으로 설명하기 위해 실시예를 들어 상세하게 설명한다. 그러나, 본 발명에 따른 실시예는 여러 가지 다른 형태로 변형될 수 있으며, 본 발명의 범위가 아래에서 상술하는 실시예에 한정되는 것으로 해석되어서는 안 된다. 본 발명의 실시예는 당업계에서 평균적인 지식을 가진 자에게 본 발명을 보다 완전하게 설명하기 위해서 제공되는 것이다.Hereinafter, the present invention will be described in detail by way of examples with reference to the following examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.
실시예Example
실시예Example 1 One
Ni0 . 65Co0 . 2Mn0 .15(OH)2 전구체와 Li2CO3를 전이금속:Li의 몰비가 1.0:1.07이 되도록 혼합하고, 이를 알루미나 도가니에 넣고 산소 분위기 하에서 750℃에서 5시간 동안 열처리를 진행한 후, 870℃에서 10 시간 동안 열처리하여 양극 활물질을 제조하였다. Ni 0 . 65 Co 0 . Then a solution such that 1.07, and was put into an alumina crucible proceeds to a heat treatment for 5 hours at 750 ℃ under an oxygen atmosphere: 2 Mn 0 .15 (OH) 2 precursor and the Li 2 CO 3 to the transition metal: the molar ratio of Li 1.0 , Followed by heat treatment at 870 ° C for 10 hours to prepare a cathode active material.
상기에서 제조한 양극 활물질을 유발을 이용해서 분쇄하였다. 분쇄된 양극 활물질에 코팅 원소-함유 원료 물질로서 B4C 및 Co(OH)2를 상기 양극 활물질 100 중량부에 대하여 각각 0.02 중량부 및 0.8 중량부를 첨가하여 혼합하였다. 이어서, 공기 분위기에서 600℃로 5시간 동안 열처리를 수행하였다. 열처리된 분말을 유발을 이용하여 분쇄 후, 325 mesh를 이용하여 분급함으로써 표면에 B 및 Co를 포함하는 코팅 물질이 아일랜드 형태로 분포된 양극 활물질을 제조하였다. The cathode active material prepared above was pulverized using induction. 0.02 parts by weight and 0.8 parts by weight of B 4 C and Co (OH) 2 as coating element-containing raw materials were added to the crushed cathode active material, respectively, and mixed with 100 parts by weight of the cathode active material. Subsequently, heat treatment was performed at 600 占 폚 for 5 hours in an air atmosphere. The heat treated powder was pulverized by induction and classified by using 325 mesh to prepare a cathode active material in which coating materials containing B and Co were distributed on the surface in an island shape.
실시예Example 2 2
분쇄된 양극 활물질 100 중량부에 대하여, 코팅 원소-함유 원료 물질로서 B4C 및 Co(OH)2를 각각 0.02 중량부 및 0.4 중량부를 혼합하는 것을 제외하고는, 상기 실시예 1과 동일한 방법을 이용하여 양극 활물질을 제조하였다. Except that 0.02 part by weight and 0.4 part by weight of B 4 C and Co (OH) 2 were respectively mixed as 100 parts by weight of the pulverized cathode active material as the coating element-containing raw material, To prepare a cathode active material.
비교예Comparative Example 1 One
코팅 원소-함유 원료 물질로서 H3BO3를 양극 활물질 100 중량부에 대하여 0.05 중량부 포함하고, 380℃로 8 시간 동안 열처리를 수행하는 것을 제외하고는, 상기 실시예 1과 동일한 방법을 이용하여 양극 활물질을 제조하였다. Except that 0.05 part by weight of H 3 BO 3 as a coating element-containing raw material was added to 100 parts by weight of the cathode active material and the heat treatment was performed at 380 ° C. for 8 hours, Thereby preparing a cathode active material.
비교예Comparative Example 2 2
코팅 원소-함유 원료물질로서 Co(OH)2를 양극 활물질 100 중량부에 대하여 0.5 중량부 포함하고, 600℃로 5 시간 동안 열처리를 수행하는 것을 제외하고는, 상기 실시예 1과 동일한 방법을 이용하여 양극 활물질을 제조하였다.Except that 0.5 parts by weight of Co (OH) 2 was used as a coating element-containing raw material with respect to 100 parts by weight of the cathode active material, and heat treatment was performed at 600 DEG C for 5 hours. To prepare a cathode active material.
비교예Comparative Example 3 3
코팅 원소-함유 원료 물질로서 B4C를 양극 활물질 100 중량부에 대하여 0.05 중량부 포함하고, 600℃로 5 시간 동안 열처리를 수행하는 것을 제외하고는, 상기 실시예 1과 동일한 방법을 이용하여 양극 활물질을 제조하였다.Except that 0.05 parts by weight of B 4 C as a coating element-containing raw material was added to 100 parts by weight of the positive electrode active material and the heat treatment was performed at 600 ° C for 5 hours, To prepare an active material.
비교예Comparative Example 4 4
코팅-원소 함유 원료 물질로서 H3BO3 및 WO3을 양극 활물질 100 중량부에 대하여 각각 0.02 중량부 및 0.6 중량부 포함하고, 380℃로 8 시간 동안 열처리를 수행하는 것을 제외하고는, 상기 실시예 1과 동일한 방법을 이용하여 양극 활물질을 리튬 이차전지를 제조하였다.Except that 0.02 part by weight and 0.6 part by weight of H 3 BO 3 and WO 3 as coating material-containing raw material were added to 100 parts by weight of the cathode active material, respectively, and the heat treatment was carried out at 380 ° C. for 8 hours. A lithium secondary battery was prepared from the positive electrode active material by the same method as in Example 1.
비교예Comparative Example 5 5
코팅-원소 함유 원료 물질로서 B2O3 및 Li2CO3을 양극 활물질 100 중량부에 대하여 각각 0.163 중량부 및 0.161 중량부 포함하고, 600℃로 5 시간 동안 열처리를 수행하는 것을 제외하고는, 상기 실시예 1과 동일한 방법을 이용하여 양극 활물질을 제조하였다.Except that 0.163 part by weight and 0.161 part by weight of B 2 O 3 and Li 2 CO 3 were added to 100 parts by weight of the cathode active material as the coating-element-containing raw material and the heat treatment was performed at 600 ° C. for 5 hours, The cathode active material was prepared in the same manner as in Example 1 above.
실험예Experimental Example 1 One
상기 실시예 1 및 비교예 1, 2, 5에서 제조한 양극 활물질 각각을 주사전자현미경을 이용하여 그 표면 특성을 확인하였고, 이를 도 1 내지 도 4에 나타내었다. Co만을 단독으로 코팅한 비교예 2의 양극 활물질의 경우(도 3 참조), 실시예 1의 양극 활물질(도 1 참조)에 비해 활물질 표면에 작은 알갱이들(Co 입자들)이 더 많이 분포하였다. 비교예 2와 같이 표면에 Co 입자들이 알갱이처럼 분포될 경우, 전극 제조 중 혼합 공정, 예컨대 배치식 반응기에서의 혼합 공정 또는 초음파를 이용한 혼합 공정 시, 표면에 알갱이처럼 분포된 Co 입자의 탈리가 발생할 수 있으며, 이 경우 충방전 특성의 향상 및 저항 특성 개선 효과를 달성할 수 없다.The surface characteristics of each of the cathode active materials prepared in Example 1 and Comparative Examples 1, 2, and 5 were confirmed using a scanning electron microscope and are shown in FIGS. 1 to 4. In the case of the cathode active material of Comparative Example 2 (see Fig. 3) coated with Co alone, the smaller particles (Co particles) were more distributed on the surface of the active material than the cathode active material of Example 1 (see Fig. 1). As in Comparative Example 2, when the Co particles are distributed on the surface like the granules, the desorption of the Co particles, which are distributed like particles, on the surface occurs in the mixing process during the electrode manufacturing process, for example, the mixing process in the batch type reactor or the ultrasonic wave mixing process In this case, the improvement of the charge / discharge characteristics and the improvement of the resistance characteristics can not be achieved.
이에 비해, 실시예 1에서 제조한 양극 활물질의 경우, 비교적 저온에서 코팅 물질을 형성한 비교예 1(도 2 참조)과 같이 표면이 상대적으로 매끄럽게 형성되는 것을 확인할 수 있었다. 또한, 비교예 5에서 제조한 양극 활물질의 경우, 상기 실시예 1 및 비교예 1과 같이 표면이 상대적으로 매끄럽게 보였으나, 이는 Co의 함량이 실시예 1 및 비교예 1~2에 비해 소량 포함되었기 때문이었다.In contrast, in the case of the cathode active material prepared in Example 1, the surface was relatively smooth as in Comparative Example 1 (see FIG. 2) in which a coating material was formed at a relatively low temperature. In addition, in the case of the cathode active material prepared in Comparative Example 5, the surface was relatively smooth as in Example 1 and Comparative Example 1, but the Co content was small compared with Example 1 and Comparative Examples 1 and 2 It was because.
실험예Experimental Example 2: 양극 활물질의 전기 화학적 특성 평가 2: Electrochemical Characterization of Cathode Active Materials
상기 실시예 1~2 및 비교예 1, 3~5에서 각각 제조한 양극 활물질을 이용하여, 리튬 이차전지를 제조하였고, 이를 이용하여 용량 특성을 확인하였다. A lithium secondary battery was fabricated using the cathode active materials prepared in Examples 1 and 2 and Comparative Examples 1 and 3 to 5, respectively, and capacity characteristics were confirmed using the same.
먼저, 실시예 1~2 및 비교예 1, 3~5에 따른 리튬 이차전지를 제조하기 위하여, 실시예 1~2 및 비교예 1, 3~5에서 각각 제조한 양극 활물질, 카본블랙 도전재, 및 폴리비닐리덴라이드(PVDF) 바인더를 95:2.5:2.5의 중량비로 혼합하고, 이를 N-메틸 피롤리돈 용매 중에서 혼합하여 양극 형성용 조성물을 제조하였다. 상기 양극 형성용 조성물을 두께가 20㎛인 Al 호일에 도포한 후, 건조하고, 롤 프레스를 실시하여 양극을 제조하였다. 한편, 음극 활물질로서 직경 16 파이의 리튬 금속 전극을 사용하였다. 상기에서 제조한 양극과 음극을 폴리프로필렌 분리막과 함께 적층하여 전극 조립체를 제조한 다음, 이를 전지 케이스에 넣고 에틸메틸카보네이트:에틸렌카보네이트를 7:3으로 혼합한 혼합 용매에 1M의 LiPF6를 용해시킨 전해액을 주입하여, 실시예 1~2 및 비교예 1, 3~5의 리튬 이차전지를 제조하였다.First, in order to produce lithium secondary batteries according to Examples 1 and 2 and Comparative Examples 1 and 3 to 5, the positive electrode active material, the carbon black conductive material, and the carbon black conductive material prepared in Examples 1 and 2 and Comparative Examples 1 and 3 to 5, And polyvinylidene (PVDF) binder were mixed at a weight ratio of 95: 2.5: 2.5, and the mixture was mixed in N-methylpyrrolidone solvent to prepare a composition for forming a positive electrode. The composition for forming an anode was applied to an Al foil having a thickness of 20 탆, dried, and rolled to produce a positive electrode. On the other hand, a lithium metal electrode having a diameter of 16 pi was used as the negative electrode active material. The positive electrode and the negative electrode prepared above were laminated together with a polypropylene separator to prepare an electrode assembly. The electrode assembly was placed in a battery case, and 1 M of LiPF 6 was dissolved in a mixed solvent of ethyl methyl carbonate: ethylene carbonate in a ratio of 7: 3 And an electrolyte was injected thereinto to prepare lithium secondary batteries of Examples 1 and 2 and Comparative Examples 1 and 3 to 5.
상기에서 제조한 실시예 1~2 및 비교예 1, 3~5의 리튬 이차전지 각각에 대하여 25℃에서 0.1C 정전류로 4.3V까지 충전을 실시하였고, 0.1C 정전류로 3V가 될때까지 방전을 실시한 후, 첫번째 사이클에서 충방전 특성을 관찰하였고, 그 결과를 하기 표 1 및 도 5에 나타내었다. 이후, 1.0C 및 2.0C로 방전 조건을 달리하여 1.0C 및 2.0C에서의 방전 용량을 측정하여 각각 도 6 및 도 7에 나타내었고, 상기 방전 용량 값을 초기 충전 용량으로 나누어 계산한 1.0C 및 2.0C에서의 효율은 하기 표 2에 나타내었다. Each of the lithium secondary batteries of Examples 1 and 2 and Comparative Examples 1 and 3 to 5 prepared above was charged to 4.3 V at a constant current of 0.1 C at 25 캜 and discharged at a constant current of 0.1 C until the voltage reached 3 V Charging and discharging characteristics were observed in the first cycle, and the results are shown in Table 1 and FIG. 5 below. Thereafter, discharge capacities at 1.0 C and 2.0 C were measured at different discharge conditions of 1.0 C and 2.0 C, respectively. These discharge capacities were shown in FIG. 6 and FIG. 7, respectively. The efficiency at 2.0 C is shown in Table 2 below.
충전용량(mAh/g)Charging capacity (mAh / g) 방전용량(mAh/g)Discharge capacity (mAh / g) 효율(%)efficiency(%)
실시예 1Example 1 204.65204.65 186.08186.08 90.990.9
실시예 2Example 2 203.82203.82 184.52184.52 90.590.5
비교예 1Comparative Example 1 204.46204.46 180.44180.44 88.388.3
비교예 3Comparative Example 3 203.21203.21 182.10182.10 89.689.6
비교예 4Comparative Example 4 203.62203.62 182.49182.49 89.689.6
비교예 5Comparative Example 5 203.41203.41 182.29182.29 89.689.6
상기 표 1 및 도 5에 나타난 바와 같이, 비교예 1, 3~5에서 제조한 리튬 이차전지의 경우, 0.1C-rate로 충전 시 90% 미만의 효율을 나타내는 것을 확인할 수 있었다. 반면, 실시예 1 및 2에서 제조한 리튬 이차전지의 경우, 0.1C-rate로 충방전할 경우 90% 이상의 효율을 나타내 본 발명에 따른 리튬 이차전지가 더욱 우수한 효율을 나타내는 것을 확인할 수 있었다.As shown in Table 1 and FIG. 5, it was confirmed that the lithium secondary batteries prepared in Comparative Examples 1 and 3 to 5 exhibited efficiencies of less than 90% when charged at 0.1 C-rate. On the other hand, in the case of the lithium secondary battery manufactured in Examples 1 and 2, it was confirmed that the lithium secondary battery according to the present invention exhibited higher efficiency when the battery was charged and discharged at a rate of 0.1 C-rate, which was more than 90%.
1.0C1.0 C 2.0C2.0C
방전용량(mAh/g)Discharge capacity (mAh / g) 효율(%)efficiency(%) 방전용량(mAh/g)Discharge capacity (mAh / g) 효율(%)efficiency(%)
실시예 1Example 1 171.85171.85 9292 165.77165.77 8989
실시예 2Example 2 168.89168.89 91.591.5 164.25164.25 8989
비교예 1Comparative Example 1 162.63162.63 9090 155.79155.79 8686
비교예 3Comparative Example 3 166.10166.10 9191 159.19159.19 8787
비교예 4Comparative Example 4 164.15164.15 9090 156.97156.97 8686
비교예 5Comparative Example 5 167.54167.54 9090 163.52163.52 8686
또한, 상기 표 2 및 도 6~7에 나타난 바와 같이, 실시예 1~2에서 제조한 이차전지의 경우, 1.0C-rate에서 90% 이상의 효율을 나타내고, 2.0C-rate에서 89% 정도의 우수한 효율을 나타내며, 방전 용량 또한 가장 개선된 것을 확인할 수 있었다. As shown in Table 2 and FIGS. 6 to 7, the secondary batteries prepared in Examples 1 and 2 exhibited efficiencies of 90% or more at 1.0 C-rate, 89% at 2.0 C-rate Efficiency, and the discharge capacity was the most improved.
반면, 비교예 1, 3~5를 살펴보면, B 및 Co를 본원발명의 범위로 포함하는 실시예 1에 비해 1.0C, 2.0C 각각에서 율 특성이 열위한 것을 확인할 수 있었다.On the other hand, in Comparative Examples 1, 3 to 5, it was confirmed that the rate characteristics were improved at 1.0 C and 2.0 C, respectively, as compared with Example 1 including B and Co within the range of the present invention.
실험예Experimental Example 3: 리튬 이차전지의 저항 특성 3: Resistance characteristic of lithium secondary battery
상기 실험예 2에서 제조한 실시예 1~2 및 비교예 1~5의 리튬 이차전지에 대하여 저항 특성 평가를 실시하였다.The resistance characteristics of the lithium secondary batteries of Examples 1 and 2 and Comparative Examples 1 to 5 prepared in Experimental Example 2 were evaluated.
구체적으로, 상기 실시예 1~2 및 비교예 1~5의 리튬 이차 전지를 25℃에서 0.5C 정전류로 4.3 V가 될 때까지 충전하고, 20 분간 방치한 다음, 1.0C 정전류로 3 V가 될 때까지 방전하였다. 상기 충방전 거동을 1 사이클로 하며, 이러한 사이클을 50 회 반복 실시한 후, 본 실시예 및 비교예에 따른 저항 증가율을 측정하였고, 그 결과를 하기 표 3에 나타내었다.Specifically, the lithium secondary batteries of Examples 1 to 2 and Comparative Examples 1 to 5 were charged at a constant current of 0.5 C at a temperature of 25 캜 until the voltage reached 4.3 V, allowed to stand for 20 minutes, and then become 3 V at a constant current of 1.0 C . The charge and discharge behaviors were taken as one cycle. After repeating this cycle 50 times, the resistance increase rate according to this example and the comparative example was measured, and the results are shown in Table 3 below.
초기 저항(Ω)Initial resistance (Ω) 50회 사이클 후 저항(Ω)Resistance after 50 cycles (Ω) 저항 증가율 (%)Rate of resistance increase (%)
실시예 1Example 1 7.677.67 11.4011.40 1.481.48
실시예 2Example 2 7.517.51 11.8711.87 1.581.58
비교예 1Comparative Example 1 8.238.23 13.0313.03 1.581.58
비교예 2Comparative Example 2 7.357.35 12.1412.14 1.651.65
비교예 3Comparative Example 3 7.927.92 12.7712.77 1.611.61
비교예 4Comparative Example 4 7.857.85 12.5112.51 1.591.59
비교예 5Comparative Example 5 7.787.78 13.2113.21 1.691.69
상기 표 3에 나타난 바와 같이, 실시예 1에서 제조한 이차전지의 경우, 50회 사이클 후 저항 측정 시, 초기 저항에 대비하여 1.5% 미만의 저항 증가율을 나타내는 것을 확인할 수 있었다. 한편, 상기 실시예 2에서 제조한 이차전지는 코팅 물질 내 Co 함량 저하에 따라 상대적으로 양극 활물질의 구조 안정성이 저하되어 이를 전지에 적용 시 실시예 1에 비해 저항 특성이 열위한 것을 확인할 수 있었다.As shown in Table 3, it was confirmed that the resistance of the secondary battery manufactured in Example 1 showed a resistance increase rate of less than 1.5% as compared with the initial resistance in the resistance measurement after 50 cycles. Meanwhile, it was confirmed that the secondary battery according to Example 2 had relatively low structural stability of the cathode active material as the Co content in the coating material was lowered, and that the resistance characteristic was improved when the battery was applied to the battery.
또한, 비교예 1, 3~4에서 제조한 이차전지의 경우, 실시예 1에 비해 저항 증가율이 높은 것을 확인할 수 있었다. 이를 통해, B 및 Co를 모두 포함하는 코팅 물질이 형성될 경우, 이를 포함하는 양극 활물질의 저항 증가율을 감소시키는 것을 확인할 수 있었다. 한편, 비교예 2에서 제조한 이차전지의 경우, 코팅 물질 내 Co만을 포함함에 따라, 상기 코발트 산화물이 산화되어 양극 활물질의 표면에서 탈리되거나 또는 사이클이 진행됨에 따라 점차 저항으로 작용하여, 저항 특성이 열위한 것을 확인할 수 있었다.In addition, it was confirmed that the resistance increase rate of the secondary battery manufactured in Comparative Examples 1 and 3 to 4 was higher than that of Example 1. As a result, it was confirmed that when the coating material containing both B and Co is formed, the resistance increase rate of the cathode active material containing the coating material is reduced. On the other hand, in the case of the secondary battery manufactured in Comparative Example 2, since the cobalt oxide is oxidized and released from the surface of the cathode active material or contains only Co in the coating material, the cobalt oxide gradually acts as a resistance as the cycle progresses, I could confirm that it was open.
또한, 비교예 5에서 제조한 이차전지의 경우, B 및 Co를 동시에 포함함에 따른 용량 특성은 개선되었으나, B 원료 물질로서 본원발명의 탄소 함유 B 원료 물질을 사용하지 않아, Co 원료 물질이 산화되더라도 상기 B 원료 물질이 환원제로서 작용하지 못했기 때문에, Co 원료 물질의 산화되어 저항으로 작용함으로써 50회 사이클 후 저항이 증가한 것으로 확인되었다.In addition, in the case of the secondary battery manufactured in Comparative Example 5, although the capacity characteristics due to the simultaneous inclusion of B and Co were improved, the carbon containing B raw material of the present invention was not used as the B raw material, Since the raw material B did not act as a reducing agent, it was confirmed that the resistance increased after 50 cycles due to the oxidation of the raw material of the Co and acting as a resistance.
즉, 본원발명에 따르면, 리튬 전이금속 산화물의 표면에 B 및 Co를 포함하는 코팅 물질을 코팅할 경우, 상기 B 및 C-함유 원료 물질 및 Co-함유 원료 물질을 특정 화합물을 사용함으로써, 리튬 전이금속 산화물의 표면에 B 및 Co를 포함하는 코팅 물질을 형성한 후 열처리 시, B 및 C-함유 원료 물질이 환원제 역할을 수행하여 Co-함유 원료 물질의 산화를 방지할 수 있다. 이에 따라, 고온 열처리를 수행하더라도 Co가 환원되지 않고, 코팅 물질 내 잔존하여 본 발명에 따른 효과를 달성하는 것이다.That is, according to the present invention, when the coating material containing B and Co is coated on the surface of the lithium-transition metal oxide, the B and C-containing raw material and the Co- The B and C-containing raw materials may act as a reducing agent to prevent oxidation of the Co-containing raw material during the heat treatment after forming a coating material containing B and Co on the surface of the metal oxide. Thus, even if the high temperature heat treatment is performed, Co is not reduced and remains in the coating material to achieve the effect of the present invention.

Claims (14)

  1. 전이금속의 총 몰수에 대하여 65몰% 이상의 니켈을 포함하는 니켈-함유 수산화물 전구체 및 리튬-원료물질을 혼합한 후 1차 열처리하여, 니켈-함유 리튬 전이금속 산화물을 제조하는 단계;Comprising the steps of: mixing a nickel-containing hydroxide precursor containing 65 mol% or more of nickel with respect to the total number of moles of transition metal and a lithium-source material and then subjecting the mixture to a primary heat treatment to prepare a nickel-containing lithium transition metal oxide;
    상기 니켈-함유 리튬 전이금속 산화물에 B 및 C-함유 원료 물질 및 Co-함유 원료 물질을 혼합하여 혼합물을 형성하는 단계; 및, Mixing the B-containing and C-containing raw material and the Co-containing raw material with the nickel-containing lithium transition metal oxide to form a mixture; And
    상기 혼합물을 2차 열처리하여, 상기 리튬-전이금속 산화물 표면에 B 및 Co를 포함하는 코팅 물질을 형성하는 단계;를 포함하는, 양극 활물질의 제조 방법.Subjecting the mixture to a secondary heat treatment to form a coating material containing B and Co on the surface of the lithium-transition metal oxide.
  2. 제1항에 있어서,The method according to claim 1,
    상기 B 및 C-함유 원료 물질은 B4C, (C3H7O)3B, (C6H5O)3B, [CH3(CH2)3O]3B, 및 C6H5B(OH)2로 이루어진 군에서 선택되는 적어도 하나 이상을 포함하는 것인, 양극 활물질의 제조 방법.The C- and B-containing source material is B 4 C, (C 3 H 7 O) 3 B, (C 6 H 5 O) 3 B, [CH 3 (CH 2) 3 O] 3 B, and C 6 H 5 &lt; / RTI &gt; B (OH) &lt; RTI ID = 0.0 &gt; 2. &Lt; / RTI &gt;
  3. 제1항에 있어서,The method according to claim 1,
    상기 B 및 C-함유 원료 물질은 니켈-함유 리튬 전이금속 산화물 100 중량부에 대하여 0.02 중량부 내지 0.04 중량부로 혼합되는 것인, 양극 활물질의 제조 방법.Wherein the B and C-containing raw material are mixed in an amount of 0.02 parts by weight to 0.04 parts by weight based on 100 parts by weight of the nickel-containing lithium transition metal oxide.
  4. 제1항에 있어서,The method according to claim 1,
    상기 Co-함유 원료 물질은 Co(OH)2, Co2O3, Co3(PO4)2, CoF3, CoOOH, Co(OCOCH3)2·4H2O, Co(NO3)·6H2O, Co3O4, Co(SO4)2·7H2O 및 CoC2O4로 이루어진 군에서 선택되는 적어도 하나 이상을 포함하는 것인, 양극 활물질의 제조 방법.Co- containing the raw material is Co (OH) 2, Co 2 O 3, Co 3 (PO 4) 2, CoF 3, CoOOH, Co (OCOCH 3) 2 · 4H 2 O, Co (NO 3) · 6H 2 O, Co 3 O 4 , Co (SO 4 ) 2 .7H 2 O, and CoC 2 O 4 .
  5. 제1항에 있어서,The method according to claim 1,
    상기 Co-함유 원료 물질은 니켈-함유 리튬 전이금속 산화물 100 중량부에 대하여 0.5 중량부 내지 1.0 중량부로 혼합되는 것인, 양극 활물질의 제조 방법.Wherein the Co-containing raw material is mixed with 0.5 part by weight to 1.0 part by weight based on 100 parts by weight of the nickel-containing lithium transition metal oxide.
  6. 제1항에 있어서,The method according to claim 1,
    상기 1차 열처리는 700℃ 내지 900℃에서 수행되는 것인, 양극 활물질의 제조 방법.Wherein the primary heat treatment is performed at 700 ° C to 900 ° C.
  7. 제1항에 있어서,The method according to claim 1,
    상기 1차 열처리는 700℃ 내지 800℃에서 4시간 내지 6 시간 동안 수행한 후, 800℃ 내지 900℃에서 8시간 내지 12시간 동안 수행하는 것인, 양극 활물질의 제조 방법. Wherein the primary heat treatment is performed at 700 캜 to 800 캜 for 4 hours to 6 hours and then at 800 캜 to 900 캜 for 8 hours to 12 hours.
  8. 제1항에 있어서,The method according to claim 1,
    상기 1차 열처리는 산화 분위기에서 수행하는 것인, 양극 활물질의 제조 방법.Wherein the first heat treatment is performed in an oxidizing atmosphere.
  9. 제1항에 있어서,The method according to claim 1,
    상기 2차 열처리는 500℃ 내지 700℃에서 수행되는 것인, 양극 활물질의 제조 방법.Wherein the second heat treatment is performed at 500 ° C to 700 ° C.
  10. 리튬을 제외한 전이금속의 총 몰수에 대하여 65몰% 이상의 니켈을 포함하는 니켈-함유 리튬 전이금속 산화물; 및,A nickel-containing lithium transition metal oxide containing at least 65 mol% of nickel based on the total molar amount of transition metals except lithium; And
    상기 니켈-함유 리튬 전이금속 산화물의 표면에 분포된 코팅 물질;을 포함하며, And a coating material distributed on a surface of the nickel-containing lithium transition metal oxide,
    상기 코팅 물질은 B 및 Co를 포함하고,Wherein the coating material comprises B and Co,
    상기 코팅 물질 내에 1,000 내지 5,000 ppm의 Co를 포함하는 것인, 양극 활물질.Wherein the coating material contains from 1,000 to 5,000 ppm of Co.
  11. 제10항에 있어서,11. The method of claim 10,
    상기 양극 활물질은 코팅 물질 내에 100 내지 500 ppm의 B를 포함하는 것인, 양극 활물질.Wherein the positive electrode active material contains B in an amount of 100 to 500 ppm in the coating material.
  12. 제10항에 있어서,11. The method of claim 10,
    상기 니켈-함유 리튬 전이금속 산화물은 하기 화학식 1로 표시되는 것인, 양극 활물질:Wherein the nickel-containing lithium transition metal oxide is represented by the following formula (1): &lt; EMI ID =
    [화학식 1][Chemical Formula 1]
    Li1+x(NiaCobMe1-(a+b))1-xO2 Li 1 + x (Ni a Co b Me 1- (a + b) ) 1-x O 2
    상기 화학식 1에서, In Formula 1,
    0≤x≤0.3, 0.65≤a≤0.9, 0.05≤b≤0.2, 0.7≤a+b<1, Me는 Mn 및 Al으로 이루어진 군에서 선택된 적어도 하나 이상임. 0? X? 0.3, 0.65? A? 0.9, 0.05? B? 0.2, 0.7? A + b <1, and Me is at least one selected from the group consisting of Mn and Al.
  13. 제10항 내지 제12항 중 어느 한 항에 따른 양극 활물질을 포함하는, 리튬 이차전지용 양극. A positive electrode for a lithium secondary battery, comprising the positive electrode active material according to any one of claims 10 to 12.
  14. 제13항에 따른 양극을 포함하는, 리튬 이차전지.A lithium secondary battery comprising a positive electrode according to claim 13.
PCT/KR2018/011984 2017-10-12 2018-10-11 Positive electrode active material for lithium secondary battery, preparing method therefor, positive electrode, comprising same, for lithium secondary battery, and lithium secondary battery WO2019074305A2 (en)

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