WO2008082048A1 - Nonaqueous electrolyte for li-secondary battery and li secondary battery thereby - Google Patents

Nonaqueous electrolyte for li-secondary battery and li secondary battery thereby Download PDF

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Publication number
WO2008082048A1
WO2008082048A1 PCT/KR2007/002918 KR2007002918W WO2008082048A1 WO 2008082048 A1 WO2008082048 A1 WO 2008082048A1 KR 2007002918 W KR2007002918 W KR 2007002918W WO 2008082048 A1 WO2008082048 A1 WO 2008082048A1
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Prior art keywords
carbonate
electrolyte solution
secondary battery
lithium secondary
aqueous electrolyte
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PCT/KR2007/002918
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French (fr)
Inventor
Jung Kang Oh
Young Jai Cho
Kab Youl Lee
Hak Soo Kim
Ho Seok Yang
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Cheil Industries Inc.
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Publication of WO2008082048A1 publication Critical patent/WO2008082048A1/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M1/00—Substation equipment, e.g. for use by subscribers
    • H04M1/02—Constructional features of telephone sets
    • H04M1/21—Combinations with auxiliary equipment, e.g. with clocks or memoranda pads
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0569—Liquid materials characterised by the solvents
    • A—HUMAN NECESSITIES
    • A45—HAND OR TRAVELLING ARTICLES
    • A45C—PURSES; LUGGAGE; HAND CARRIED BAGS
    • A45C11/00—Receptacles for purposes not provided for in groups A45C1/00-A45C9/00
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H01M4/1315—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx containing halogen atoms, e.g. 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M1/00—Substation equipment, e.g. for use by subscribers
    • H04M1/02—Constructional features of telephone sets
    • H04M1/0202—Portable telephone sets, e.g. cordless phones, mobile phones or bar type handsets
    • 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 non-aqueous electrolyte solution for a lithium secondary battery and a lithium secondary battery comprising the same. More specifically, the present invention relates to a non-aqueous electrolyte solution for improving lifespan and aging properties of a lithium secondary battery while enabling construction of battery exhibiting performance comparable to those using conventional non-aqueous electrolyte solutions, and a lithium secondary battery comprising the non-aqueous electrolyte solution.
  • Secondary batteries are different from primary batteries in that they are rechargeable and semi-permanently usable.
  • portable electronic devices e.g., notebook computers, mobile communication terminals and digital cameras
  • secondary batteries have joined semiconductors and displays as one the three leading and rapidly developing component industries in the 21 st century.
  • secondary batteries include lead acid batteries, nickel cadmium (Ni-Cd) batteries, nickel-metal hydride (Ni-MH) batteries, lithium (Li) batteries, etc.
  • the electrical potential and energy density of secondary batteries may depend upon inherent characteristics of electrode materials.
  • lithium secondary batteries exhibit a high energy density due to low oxidation/reduction electrical potential and a low molecular weight, and thus are commonly used as a power source in portable electronic devices .
  • lithium secondary batteries employing a non-aqueous electrolyte solution may include a positive electrode composed of a metal coated with a positive active material (e.g., mixed oxide of lithium metal), a negative electrode made of a metal coated with a negative active material (e.g., a carbonaceous material or lithium metal), and an electrolyte solution, in which a lithium salt is dissolved in an organic solvent, arranged between the positive electrode and negative electrode.
  • a positive active material e.g., mixed oxide of lithium metal
  • a negative electrode made of a metal coated with a negative active material (e.g., a carbonaceous material or lithium metal)
  • an electrolyte solution in which a lithium salt is dissolved in an organic solvent, arranged between the positive electrode and negative electrode.
  • lithium ions (Li + ) present in the electrolyte solution move from the positive electrode to the negative electrode.
  • the lithium ions (Li + ) move from the negative electrode to the positive electrode to generate electricity.
  • electrons move in the opposite direction of the lithium ions through a wire connecting the positive electrode to the negative electrode.
  • lithium ions (Li + ) released from the lithium metal oxide positive electrode are transferred to a carbon negative electrode and are intercalated into the negative electrode.
  • the lithium ions react with the carbon negative electrode, because of their high reactivity, to produce a compound such as Li 2 C ⁇ 3 , LiO or LiOH, thereby forming a thin film composed of the compound on the surface of the negative electrode.
  • This film is referred to as a "solid electrolyte interface (SEI) film".
  • SEI film functions as a kind of passivation film that passivates the surface of the negative electrode.
  • the SEI film may limit the reaction between the lithium ions and the negative electrode or other materials, and may also act as an ion tunnel, allowing the passage of only lithium ions .
  • the ion tunnel prevents disintegration of the structure of the negative electrode that may be caused by co- intercalation into the negative electrode, along with solvated lithium ions, of an organic solvent having a high molecular weight in the electrolyte solution (e.g. ethylene carbonate, dimethyl carbonate and diethyl carbonate) .
  • an organic solvent having a high molecular weight in the electrolyte solution e.g. ethylene carbonate, dimethyl carbonate and diethyl carbonate
  • the SEI film may prevent further reaction of the lithium ions with the negative electrode or other materials.
  • the initial amount of lithium ions can be reversibly maintained.
  • the carbonaceous material constituting the negative electrode reacts with an electrolyte solution during overcharging, thus forming a passivation film such as the SEI film on the surface of the negative electrode such that decomposition of the electrolyte solution is avoided and stable charging and discharging are maintained.
  • Lithium secondary batteries have an average discharge voltage of about 3.6 to 3.7 V), thus exhibiting an electric power higher than those of other secondary batteries such as alkaline, nickel-metal hydride (Ni-MH) and nickel-cadmium (Ni- Cd) batteries .
  • an electrolyte composition that is electrochemically stable at a charge/discharge voltage ranging from 0 to 4.2 V.
  • an organic electrolyte solution e.g., in which a lithium salt is dissolved in an organic solvent
  • the organic solvent it is preferable to use an organic solvent that has a high ionic conductivity, a high dielectric constant and a low viscosity.
  • U.S. Patent Nos . 6,114,070 and 6,048,637 disclose a method for improving an ionic conductivity of an organic solvent by employing a mixture of dimethyl carbonate or diethyl carbonate, and ethylene carbonate or propylene carbonate, as a mixed solvent of a chain carbonate and a cyclic carbonate.
  • Such a mixed solvent may be used at 120 0 C or below, but it may be unsuitable for use at a temperature exceeding 120 0 C, because gases may be generated due to vapor pressure, such that problems, e.g., battery swelling, may result.
  • U.S. Patent Nos. 5,352,548, 5,712,059 and 5,714,281 disclose an electrolyte solution comprising an organic solvent containing 20 wt% or more of vinylene carbonate (VC) .
  • Vinylene carbonate (VC) has a low dielectric constant, as compared to ethylene carbonate, propylene carbonate and ⁇ -butyrolactone. Therefore, a battery in which vinylene carbonate (VC) is used as a main solvent may have disadvantages such as deterioration in charging/discharging and loss of efficiency.
  • the use of the thin-film forming additive induces formation of a low-conductivity, high-resistance SEI composed of lithium ions on the negative electrode, the discharging characteristics of the battery may be significantly deteriorated.
  • the additive may undergo oxidative decomposition on the positive electrode upon aging at a high temperature, and gases may thus be generated. As a result, serious problems of battery swelling may result due to an increased internal pressure.
  • Japanese Patent Publication No. 1992-087156 discloses that battery lifespan may be improved via addition of vinyl ethylene carbonate (VEC) .
  • VEC vinyl ethylene carbonate
  • 1% or more of VEC is used, decreased battery capacity may become a problem due to an increase in thin film resistance.
  • Japanese Patent Publication suggests use of a mixture of vinyl ethylene carbonate (VEC) and vinyl carbonate (VC) to improve battery lifespan.
  • VEC vinyl ethylene carbonate
  • VC vinyl carbonate
  • Japanese Patent Publication No. 1995-006786 discloses a method for improving battery lifespan by using fluoroethylene carbonate (FEC) .
  • FEC fluoroethylene carbonate
  • the method may decrease battery lifespan at a high temperature, which is disadvantageous.
  • FEC Fluoroethylene carbonate
  • PC propylene carbonate
  • PC polystyrene
  • ionic conductivity of the electrolyte solution may be low (i.e., about 7 mS/cm) and battery performance may thus be deteriorated.
  • a non-aqueous electrolyte solution for a lithium secondary battery comprising: a basic electrolyte solution consisting of a non-aqueous organic solvent and a lithium salt dissolved in the nonaqueous organic solvent; and a vinyl ethylene carbonate-based compound represented by the following Formula 1 and a halogenated ethylene carbonate- based compound represented by the following Formula 2, wherein the non-aqueous organic solvent includes at least one selected from the group consisting of carbonate- based solvents, ester-based solvents, ether-based solvents and ketone-based solvents:
  • the non-aqueous electrolyte solution for a lithium secondary battery and a lithium secondary battery comprising the same may enable an improvement in lifespan and aging properties while maintaining battery performance upon application of a high voltage.
  • FIG. 1 is a schematic diagram illustrating a lithium secondary battery in which aluminum (Al) is used as a metal for a positive electrode, copper (Cu) is used as a metal for a negative electrode, LiCo ⁇ 2 is used as a positive active material, carbon (C) is used as a negative active material, and the non-aqueous electrolyte solution of the present invention is used as an electrolyte solution;
  • FIGs . 2A and 2B are graphs showing the room-temperature cycle lifespan property of lithium secondary batteries produced in Example 3 and Comparative Examples 1, 2, 5 and 6; and
  • FIG. 3 is a graph showing a high-temperature cycle lifespan property of lithium secondary batteries produced in Example 3 and Comparative Example 3.
  • the present invention is directed to a non-aqueous electrolyte solution for a lithium secondary battery comprising: a basic electrolyte solution consisting of a non-aqueous organic solvent and a lithium salt dissolved in the non-aqueous organic solvent; and a vinyl ethylene carbonate-based compound represented by the following Formula 1 and a halogenated ethylene carbonate-based compound represented by the following Formula 2, wherein the nonaqueous organic solvent includes at least one selected from the group consisting of carbonate-based solvents, ester-based solvents, ether-based solvents and ketone-based solvents.
  • the present invention is directed to a lithium secondary battery comprising: the non-aqueous electrolyte solution of the present invention; an electrode part consisting of a positive electrode and a negative electrode that face each other at opposite sides of the nonaqueous electrolyte solution; and a separator electrically separating the positive electrode from the negative electrode.
  • the non-aqueous electrolyte solution for a lithium secondary battery of the present invention contains no water (H 2 O) and uses only an organic solvent as a solvent, as apparent from the definition of the term "non-aqueous".
  • the non-aqueous electrolyte solution may comprise additives to improve lifespan and aging properties of the lithium secondary battery, in addition to the basic electrolyte solution in which a lithium salt is dissolved in the nonaqueous organic solvent .
  • the basic electrolyte solution consists of a non-aqueous organic solvent and a lithium salt.
  • the non-aqueous organic solvent functions as a medium, allowing migration of ions involved in an electrochemical reaction of a battery.
  • solvents that have a high dielectric constant (polarity) and a low viscosity.
  • polarity polarity
  • a mixed solvent consisting of at least one solvent with a high dielectric constant and a high viscosity and at least one solvent with a low dielectric constant and a low viscosity.
  • the non-aqueous organic solvent used in the present invention includes at least one selected from the group consisting of carbonate-based solvents, ester-based solvents, ether-based solvents and ketone-based solvents .
  • the carbonate-based solvent may be a mixture of at least one cyclic carbonate-based organic solvent selected from ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1, 2-pentylene carbonate and 2, 3-pentylene carbonate; and at least one chain carbonate-based organic solvent selected from dimethyl carbonate (DMC) , diethyl carbonate (DEC) , dipropyl carbonate (DPC), ethylmethyl carbonate (EMC), methylpropyl carbonate (MPC) and ethylpropyl carbonate (EPC) .
  • DMC dimethyl carbonate
  • DEC diethyl carbonate
  • DPC dipropyl carbonate
  • EMC ethyl
  • the cyclic carbonate-based organic solvent and the chain carbonate-based organic solvent may be mixed in a volume ratio of 1 : 1 to 1 : 9, preferably, 1 : 1.5 to 1 : 4, in view of the lifespan and aging properties of the battery.
  • cyclic carbonate-based organic solvents preferred is the use of ethylene carbonate and propylene carbonate, both of which have a high dielectric constant.
  • ethylene carbonate preferred is the use of ethylene carbonate.
  • chain carbonate-based organic solvents preferred is the use oE dimethyl carbonate (DMC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) , all of which have a low viscosity.
  • the ester-based solvents may include at least one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, ⁇ -butyrolactone, ⁇ -valerolactone, ⁇ -caprolactone, ⁇ -valerolactone and ⁇ -caprolactone.
  • the ether-based solvents may include at least one selected from the group consisting of tetrahydrofuran, 2-methyltetrahydrofuran and dibutyl ether.
  • the ketone-based solvents may include polymethylvinylketone.
  • the non-aqueous organic solvent may further include an aromatic hydrocarbon-based organic solvent represented by Formula 3 below: wherein R is halogen or Ci-Cio alkyl; and q is an integer of 0 to 6.
  • the aromatic hydrocarbon-based organic solvent may include at least one selected from benzene, fluorobenzene, bromobenzene, chlorobenzene, toluene, xylene, mesitylene, fluorotoluene, difluorotoluene and trifluorotoluene .
  • the aromatic hydrocarbon-based solvent and the carbonate-based solvent may be used in a volume ratio of 1 : 1 to 1 : 30.
  • the basic electrolyte solution may be prepared by dissolving a lithium salt in the non-aqueous organic solvent.
  • the lithium salt acts as a feed source of lithium ions and enables fundamental operation of a lithium battery.
  • the lithium salt may include at least one selected from LiPF 6 , LiClO 4 , LiAsF 6 , LiBF 4 , LiN (C 2 F 5 SO 3 ) 2 , LiN(C 2 F 5 SO 2 ) ?
  • the concentration of the lithium salt in the electrolyte solution is preferably 0.6 to 2.0 M, more preferably, 0.7 to 1.6 M.
  • Ri, R 2 , R 3 and R 4 are each independently hydrogen or C2-C 6 hydrocarbon having a double bond; and at least one of Ri, R 2 , R 3 and R 4 is C 2 -C 6 hydrocarbon having a double bond, and O
  • the vinyl ethylene carbonate-based compound may be added in an amount of 0.1 to 5 parts by weight, based on 100 parts of the basic electrolyte solution.
  • the halogenated ethylene carbonate-based compound may be added in an amount of 0.1 to 20% by weight, based on 100 parts of the basic electrolyte solution.
  • the vinyl ethylene carbonate compound and the halogenated ethylene carbonate compound must be mixed in amounts within the range as defined above.
  • the vinyl ethylene carbonate compound is used alone for the basic electrolyte solution
  • the low-temperature aging property of the battery is deteriorated.
  • the halogenated ethylene carbonate compound is used alone for the basic electrolyte solution
  • the room-temperature lifespan property of the battery, in particular, the high-temperature lifespan property is deteriorated.
  • the non-aqueous electrolyte solution of the present invention may further comprise propyl acetate methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate, etc.
  • the non-aqueous electrolyte solution of the present invention may exhibit superior aging property and long lifespan in a temperature range of -20 to 60 0 C, thus improving stability and reliability of the battery.
  • the nonaqueous electrolyte solution of the present invention may be applied to all lithium secondary batteries including lithium ion batteries, lithium polymer batteries, etc.
  • FIG. 1 is a schematic diagram illustrating a lithium secondary battery in which aluminum (Al) is used as a metal for a positive electrode 100, copper (Cu) is used as a metal for a negative electrode 110, LiCoC> 2 is used as a positive active material, carbon (C) is used as a negative active material, and the non-aqueous electrolyte solution of the present invention is used as an electrolyte solution 130.
  • the lithium secondary battery comprises the positive electrode 100, the negative electrode 110, the electrolyte solution 130 and a separator 140.
  • non-aqueous electrolyte solution used as the electrolyte solution 130 for the lithium secondary battery has been explained above, a further description thereof is omitted.
  • the positive electrode 100 and the negative electrode 100 are arranged such that they face each other at opposite sides of the non-aqueous electrolyte solution 130.
  • the positive electrode 100 may be composed of a metal coated with a positive active material.
  • the positive active material may include at least one selected from Li x Mni- y M y A 2 , Li x Mn 2 ⁇ 4 - z X z , Li x Mn 2 - y M y M' z A 4 , Li x C ⁇ i- y M y A 2 , Li x C ⁇ i- y M y 0 2 - z X z , Li x Nii_ y M y O 2 - z X z , Li x Nii- y Co y 0 2 - z X z , Li x Nii_ y - z Co y M z A ⁇ , Li x Nii_ y - z Co y M z 0
  • carbon crystalline or amorphous carbon
  • the negative electrode 110 may be coated with at least one active material ' selected from a carbon composite, a carbon fiber, a lithium metal, a lithium alloy and a lithium composite.
  • active material ' selected from a carbon composite, a carbon fiber, a lithium metal, a lithium alloy and a lithium composite.
  • Specific examples of the amorphous carbon include hard carbon, cokes, mesocarbon microbeads (MCMBs) calcinated at 1,500 0 C or below, mesophase pitch-based carbon fibers (MPCFs), etc.
  • the crystalline carbon may include, e.g., graphite-based materials, specific examples of which include natural graphite, graphitized cokes, graphitized MCMBs, graphitized MPCFs, etc. It is preferable that the carbonaceous material has a doo 2 interplanar distance of 3.35 to 3.38 A, and a crystallite size (Lc) of 20 nm or more as measured by X-ray diffraction.
  • graphite-based materials specific examples of which include natural graphite, graphitized cokes, graphitized MCMBs, graphitized MPCFs, etc. It is preferable that the carbonaceous material has a doo 2 interplanar distance of 3.35 to 3.38 A, and a crystallite size (Lc) of 20 nm or more as measured by X-ray diffraction.
  • the lithium alloy may include alloys of lithium and a metal selected from aluminum (Al), Zinc (Zn), bismuth (Bi) , cadmium (Cd) , antimony (Sb) , silicon (Si) , lead (Pb) , tin (Sn) , gallium (Ga) and indium (In) .
  • Positive and negative electrodes may be fabricated by preparing an electrode slurry composition and applying the composition to an electrode collector. The preparation of the composition may be carried out by dispersing a thickening agent (if necessary) , along with the electrode active materials, a binder and a conductive agent, in a solvent.
  • a positive electrode collector may be composed of aluminum (Al) or an aluminum-containing alloy.
  • a negative electrode collector may be composed of copper (Cu) or a copper-containing alloy.
  • the positive and negative electrode collectors may have a shape such as a foil, a film, a sheet, a punched metal, a porous metal and an expanded metal.
  • the binder contributes to pestelization of active materials, co-adhesion between active materials, adhesion of active materials to collectors, and may offset swelling and contraction of active materials.
  • the binder include polyvinylidene fluoride, polyhexafluoropropylene- polyvinylidene fluoride (P(VdF/HFP)) copolymers, poly (vinylacetate) , polyvinyl alcohol, polyethylene oxide, polyvinyl pyrrolidone, alkylated polyethylene oxide, polyvinyl ether, poly (methylmethacrylate) , poly (ethylacrylate) , polytetrafluoroethylene, polyvinylchloride, polyacrylonitrile, polyvinyl pyridine, styrene-butadiene rubbers, acrylonitrile- butadiene rubbers, etc.
  • the amount of the binder may be 0.1 to 30% by weight, preferably, 1 to 10% by weight, with respect to the electrode active material.
  • the amount of the binder is excessively low, the adhesion of the electrode active material to the collector may be insufficient.
  • the amount of the binder is excessively high, the adhesion force may be excellent but the amount of the electrode active material may be correspondingly decreased, which may be disadvantageous with respect to increasing battery capacity.
  • the conductive agent may contribute to an improvement in electrical conductivity.
  • the conductive agent may include at least one selected from graphite-based conductive agents, carbon black-based conductive agents, and metal- or metallic compound-based conductive agents.
  • graphite-based conductive agents include artificial graphite and natural graphite.
  • carbon black-based conductive agents include acetylene black, ketjen black, denka black, thermal black, channel black, etc.
  • the metal- or metallic compound-based conductive agents include tin (Sn) , tin oxide, tin phosphate (SnPC ⁇ ) , titanium oxide, potassium titanate, and perovskite such as LaSrCoC> 3 or LaSrMnO 3 .
  • the present invention is not limited to the above- mentioned examples of the conductive agent.
  • the amount of the conductive agent is preferably 0.1 to 10% by weight, with respect to the electrode active material.
  • the amount of the conductive agent is lower than 0.1 wt%, the electrochemical property of the electrolyte solution may be deteriorated.
  • the content of the conductive agent exceeds 10 wt%, the energy density per unit weight may be reduced.
  • any thickening agent may be used without particular limitation so long as it can control the viscosity of the active material slurry.
  • Specific examples of the thickening agent include carboxymethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose and hydroxypropyl cellulose.
  • the solvent in which the electrode active materials, the binder and the conductive agent are dispersed may be a nonaqueous solvent or an aqueous solvent .
  • the non- aqueous solvent include N-methyl-2-pyrrolidone (NMP) , dimethylformamide, dimethylacetamide,
  • the metals for the positive electrode 100 and the negative electrode 110 receive a voltage from an external source during charging, and discharge the voltage to the outside during discharging.
  • the positive active material serves as a collector for collecting positive charges
  • the negative active material serves as a collector for collecting negative charges .
  • the separator 140 maintains the positive electrode 100 electrically separated from the negative electrode 110, thereby preventing occurrence of a short phenomenon, while allowing for the passage of lithium ions.
  • the separator 140 may be a polyethylene or polypropylene mono-layered separator, a polyethylene/polypropylene double- layered separator, or a polyethylene/polypropylene/polyethylene or polypropylene/polyethylene/polypropylene triple-layered separator.
  • the separator 140 may have a shape of a multilayer film, a microporous film, a woven fabric or a non-woven fabric. Alternatively, a porous polyolefin film coated with a highly stable resin may be used as the separator.
  • An electrode assembly fabricated as mentioned above and the electrolyte solution may be injected into a can-type case, followed by sealing an upper part of the case with a cap assembly, to complete production of a lithium secondary battery.
  • the cap assembly may include a cap plate, an insulating plate, a terminal plate and an electrode terminal.
  • the cap assembly may be combined with an insulating case, thereby sealing the can.
  • a terminal hole, into which an electrode terminal can be inserted may be arranged in the center of the cap plate.
  • a tube-type gasket provided at the external surface of the electrode terminal, may also be inserted into the terminal hole so that the electrode terminal can be insulated from the cap plate.
  • the electrolyte solution may be injected through an electrolyte injection hole and the electrolyte injection hole may then be sealed with a sealing means.
  • the electrode terminal may be coupled to a negative electrode tap of the negative electrode or a positive electrode tap of the positive electrode, thus operating as a negative or positive electrode terminal.
  • a non-aqueous electrolyte solution for a lithium secondary battery according to embodiments of the present invention is capable of improving lifespan and aging properties of a lithium secondary battery will be demonstrated from the following detailed description taken in conjunction with specific Examples and Comparative Examples .
  • Features and procedures whose implementations are well known to those skilled in the art may be omitted for brevity.
  • LiCo ⁇ 2 as a positive active material, polyvinylidene fluoride (PVDF) as a binder, and carbon as a conductive agent were mixed in a weight ratio of 92 : 4 : 4. Then, the mixture was dispersed in N-methyl-2-pyrrolidone to prepare a positive electrode slurry. The slurry was coated on an aluminum foil with a thickness of 20 ⁇ m, followed by drying and compressing, to fabricate a positive electrode.
  • PVDF polyvinylidene fluoride
  • Artificial graphite as a negative active material, a styrene-butadiene rubber as a binder, and carboxymethyl cellulose as a thickening agent were mixed in a weight ratio of 96 : 2 : 2. Then, the mixture was dispersed in water to prepare a negative electrode slurry. The slurry was coated on a copper foil with a thickness of 15 ⁇ m, followed by drying and compressing, to fabricate a negative electrode.
  • a polyethylene (PE) film separator having a thickness of 20 ⁇ m was interposed between the positive and negative electrodes, wound and pressed, then inserted into a cylindrical can.
  • An electrolyte solution was added to the cylindrical can, thereby producing a lithium secondary battery.
  • the electrolyte solution was prepared by dissolving
  • the vinyl ethylene carbonate and fluoroethylene carbonate were added in an amount of 0.5% by weight and 1% by weight, respectively, with respect to the weight of the organic solvent .
  • a lithium secondary battery was produced in the same manner as in Example 1, except that vinyl ethylene carbonate and fluoroethylene carbonate were added in an amount of 0.5% by weight and 10% by weight, respectively.
  • a lithium secondary battery was produced in the same manner as in Example 1, except that vinyl ethylene carbonate and fluoroethylene carbonate were added in an amount of 1% by weight and 3% by weight, respectively.
  • Example 4 A lithium secondary battery was produced in the same manner as in Example 1, except that vinyl ethylene carbonate and fluoroethylene carbonate were added in an amount of 1% by weight and 5% by weight, respectively.
  • a lithium secondary battery was produced in the same manner as in Example 1, except that vinyl ethylene carbonate and fluoroethylene carbonate were added in an amount of 1% by weight and 7% by weight, respectively.
  • a lithium secondary battery was produced in the same manner as in Example 1, except that vinyl ethylene carbonate and fluoroethylene carbonate were added in an amount of 2% by weight and 3% by weight, respectively.
  • a lithium secondary battery was produced in the same manner as in Example 1, except that vinyl ethylene carbonate and fluoroethylene carbonate were added in an amount of 2% by weight and 5% by weight, respectively.
  • Example 1 A lithium secondary battery was produced in the same manner as in Example 1, except that vinyl ethylene carbonate was added exclusively in an amount of 3% by weight.
  • Example 3 A lithium secondary battery was produced in the same manner as in Example 1, except that vinylene carbonate was added exclusively in an amount of 3% by weight.
  • Comparative Examples 1 to 4 were charged under constant current-constant voltage (CC-CV) conditions of 0.5C/4.2V for 3 hours.
  • CC-CV constant current-constant voltage
  • the batteries produced in Examples 1 to 7 and Comparative Examples 1 to 4 were charged under CC-CV conditions of 0.5C/4.2V at 25 0 C for 3 hours, and were discharged at 1C CC to a cut off voltage of 3 V. A series of the charging and discharging was repeated 300 times.
  • the capacity maintenance ratio (%) at a 300 th cycle of each battery was calculated by the following Equation and the result is shown in Tables 1 and 2.
  • Capaci ty maintenance ra tio at 300th cycle (%) (discharge capaci ty a t 300 th cycle) / (discharge capaci ty a t 1 st cycle) X 100
  • Example 3 The batteries produced in Example 3, and Comparative Examples 3 and 4 were charged under CC-CV conditions of 0.5C/4.2V at 60 0 C for 3 hours, and were discharged at 1C CC to a cut off voltage of 3 V. A series of the charging and discharging was repeated 300 times. The capacity maintenance ratio (%) at a 300 th cycle and 60 0 C of each battery was calculated and the result is shown in Table 2.
  • the batteries produced in Examples 1 to 7, and Comparative Examples 1 and 2 were charged under CC-CV conditions of 0.5C/4.2V at 25 0 C for 3 hours and were then left at 0 0 C for 4 hours.
  • the batteries were discharged at 0.5 C CC to a cut off voltage of 3 V.
  • the batteries produced in Examples 1 to 7, and Comparative Examples 1 and 2 were charged under CC-CV conditions of 0.5C/4.2V at 25 0 C for 3 hours and were then left at 85 0 C for 24 hours.
  • the batteries were discharged at 0.5 C CC to a cut off voltage of 3 V.
  • the discharge capacity recovery ratio (%) after high-temperature aging of each battery was calculated by the following Equation and the result is shown in Table 1.
  • Discharge capacity recovery ratio after high- temperature aging (0.5 C discharge capacity after high- temperature aging) / (0.5 C discharge capacity before high- temperature aging) x 100
  • VEC vinyl ethylene carbonate
  • FEC fluoroethylene carbonate
  • VC vinylene carbonate
  • the electrolyte solutions of Examples 1 to 7, comprising 0.1 to 5% by weight of vinyl ethylene carbonate and 0.1 to 20% by weight of fluoroethylene carbonate provide good lifespan and aging properties for the battery.
  • the electrolyte solution of Comparative Example 1 comprising only vinyl ethylene carbonate, shows poor low- temperature aging properties.
  • the electrolyte solution of Comparative Example 6 comprising vinylene carbonate instead of vinyl ethylene carbonate and fluoroethylene carbonate exhibits substantially equivalent room-temperature lifespan property, but shows poor low-temperature property, as compared to the electrolyte solution of Comparative Example 3 comprising vinyl ethylene carbonate and fluoroethylene carbonate.

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Abstract

Disclosed herein is a non-aqueous electrolyte solution for a lithium secondary battery capable of imparting superior aging property and prolonged lifespan to a lithium secondary battery while maintaining battery performance upon application of a high voltage. The non-aqueous electrolyte solution comprises a basic electrolyte solution consisting of a non-aqueous organic solvent and a lithium salt dissolved in the non-aqueous organic solvent, and a vinyl ethylene carbonate- based compound represented by the following Formula 1 and a halogenated ethylene carbonate-based compound represented by the following Formula 2, wherein the non-aqueous organic solvent includes at least one selected from the group consisting of carbonate-based solvents, ester-based solvents, ether-based solvents and ketone-based solvents. Disclosed herein is further a lithium secondary battery comprising the non-aqueous electrolyte solution.

Description

[DESCRIPTION] [Invention Title]
NONAQUEOUS ELECTROLYTE FOR LI-SECONDARY BATTERY AND LI SECONDARY BATTERY THEREBY
[Technical Field]
The present invention relates to a non-aqueous electrolyte solution for a lithium secondary battery and a lithium secondary battery comprising the same. More specifically, the present invention relates to a non-aqueous electrolyte solution for improving lifespan and aging properties of a lithium secondary battery while enabling construction of battery exhibiting performance comparable to those using conventional non-aqueous electrolyte solutions, and a lithium secondary battery comprising the non-aqueous electrolyte solution.
[Background Art]
Secondary batteries are different from primary batteries in that they are rechargeable and semi-permanently usable. The increasing popularity of portable electronic devices, e.g., notebook computers, mobile communication terminals and digital cameras, has brought about an exponential increase in the size of the market for secondary batteries. As a result, secondary batteries have joined semiconductors and displays as one the three leading and rapidly developing component industries in the 21st century.
Classified by the materials used for negative or positive electrodes, secondary batteries include lead acid batteries, nickel cadmium (Ni-Cd) batteries, nickel-metal hydride (Ni-MH) batteries, lithium (Li) batteries, etc. The electrical potential and energy density of secondary batteries may depend upon inherent characteristics of electrode materials. Among these batteries, lithium secondary batteries exhibit a high energy density due to low oxidation/reduction electrical potential and a low molecular weight, and thus are commonly used as a power source in portable electronic devices .
In particular, lithium secondary batteries employing a non-aqueous electrolyte solution may include a positive electrode composed of a metal coated with a positive active material (e.g., mixed oxide of lithium metal), a negative electrode made of a metal coated with a negative active material (e.g., a carbonaceous material or lithium metal), and an electrolyte solution, in which a lithium salt is dissolved in an organic solvent, arranged between the positive electrode and negative electrode.
The mechanism of operation of such a lithium secondary battery will now be briefly explained. During charging of the lithium secondary battery, lithium ions (Li+) present in the electrolyte solution move from the positive electrode to the negative electrode. Conversely, during discharging of the lithium secondary battery, the lithium ions (Li+) move from the negative electrode to the positive electrode to generate electricity. At this time, electrons move in the opposite direction of the lithium ions through a wire connecting the positive electrode to the negative electrode.
During the charging of the lithium secondary battery, lithium ions (Li+) released from the lithium metal oxide positive electrode are transferred to a carbon negative electrode and are intercalated into the negative electrode. At this time, the lithium ions react with the carbon negative electrode, because of their high reactivity, to produce a compound such as Li2Cθ3, LiO or LiOH, thereby forming a thin film composed of the compound on the surface of the negative electrode. This film is referred to as a "solid electrolyte interface (SEI) film". The SEI film functions as a kind of passivation film that passivates the surface of the negative electrode. Specifically, during charging/discharging of the battery, the SEI film may limit the reaction between the lithium ions and the negative electrode or other materials, and may also act as an ion tunnel, allowing the passage of only lithium ions .
The ion tunnel prevents disintegration of the structure of the negative electrode that may be caused by co- intercalation into the negative electrode, along with solvated lithium ions, of an organic solvent having a high molecular weight in the electrolyte solution (e.g. ethylene carbonate, dimethyl carbonate and diethyl carbonate) .
Once the SEI film is formed, it may prevent further reaction of the lithium ions with the negative electrode or other materials. Thus, the initial amount of lithium ions can be reversibly maintained.
That is, the carbonaceous material constituting the negative electrode reacts with an electrolyte solution during overcharging, thus forming a passivation film such as the SEI film on the surface of the negative electrode such that decomposition of the electrolyte solution is avoided and stable charging and discharging are maintained.
Lithium secondary batteries have an average discharge voltage of about 3.6 to 3.7 V), thus exhibiting an electric power higher than those of other secondary batteries such as alkaline, nickel-metal hydride (Ni-MH) and nickel-cadmium (Ni- Cd) batteries .
To enable a high driving voltage for batteries, there is a need for an electrolyte composition that is electrochemically stable at a charge/discharge voltage ranging from 0 to 4.2 V. For these reasons, an organic electrolyte solution, e.g., in which a lithium salt is dissolved in an organic solvent, is commonly used as an electrolyte solution for a lithium secondary battery. As the organic solvent, it is preferable to use an organic solvent that has a high ionic conductivity, a high dielectric constant and a low viscosity.
However, in practice, there is currently no single nonaqueous organic solvent that satisfies these requirements. Therefore, a mixture of a high dielectric- and a low dielectric organic solvent may be used, or a mixture of a high dielectric organic solvent and a low-viscosity organic solvent may be used. Recently, high-voltage (i.e. 4.2 V or higher) batteries have been developed and the stability of an electrolyte solution in these batteries is correspondingly more significant.
U.S. Patent Nos . 6,114,070 and 6,048,637 disclose a method for improving an ionic conductivity of an organic solvent by employing a mixture of dimethyl carbonate or diethyl carbonate, and ethylene carbonate or propylene carbonate, as a mixed solvent of a chain carbonate and a cyclic carbonate.
Such a mixed solvent may be used at 120 0C or below, but it may be unsuitable for use at a temperature exceeding 120 0C, because gases may be generated due to vapor pressure, such that problems, e.g., battery swelling, may result.
U.S. Patent Nos. 5,352,548, 5,712,059 and 5,714,281 disclose an electrolyte solution comprising an organic solvent containing 20 wt% or more of vinylene carbonate (VC) . Vinylene carbonate (VC) has a low dielectric constant, as compared to ethylene carbonate, propylene carbonate and γ-butyrolactone. Therefore, a battery in which vinylene carbonate (VC) is used as a main solvent may have disadvantages such as deterioration in charging/discharging and loss of efficiency.
The U.S. patents noted above suggest that an improvement in battery lifespan may be achieved via addition of VC. However, as the content of VC increases, resistance of a thin film increases and resistance of a battery increases. As a result, the capacity of the battery may be decreased at a high efficiency as well as at a low temperature. Furthermore, as the content of VC increases, gas may be generated at a high temperature such that battery swelling problems may occur. In an attempt to inhibit reductive decomposition of a solvent or lithium on a negative electrode, a compound that is capable of forming a solid electrolyte interface (SEI) on the negative electrode may be added to the electrolyte solution, as disclosed in Japanese Patent Publication No. 2001-6729, etc.
However, since the use of the thin-film forming additive induces formation of a low-conductivity, high-resistance SEI composed of lithium ions on the negative electrode, the discharging characteristics of the battery may be significantly deteriorated. Furthermore, in a case where an excessive amount of thin-film forming additive is present in the electrolyte solution, the additive may undergo oxidative decomposition on the positive electrode upon aging at a high temperature, and gases may thus be generated. As a result, serious problems of battery swelling may result due to an increased internal pressure.
Japanese Patent Publication No. 1992-087156 discloses that battery lifespan may be improved via addition of vinyl ethylene carbonate (VEC) . However, when 1% or more of VEC is used, decreased battery capacity may become a problem due to an increase in thin film resistance.
In an attempt to solve these problems, Japanese Patent Publication suggests use of a mixture of vinyl ethylene carbonate (VEC) and vinyl carbonate (VC) to improve battery lifespan. However, when the mixture is used in an amount of 2% or more, the problem of decreased battery capacity due to an increase in thin film resistance still remains unsolved. Japanese Patent Publication No. 1995-006786 discloses a method for improving battery lifespan by using fluoroethylene carbonate (FEC) . However, the method may decrease battery lifespan at a high temperature, which is disadvantageous.
U.S. Patent No. 6,506,524 discloses that use of an electrolyte solvent consisting of fluoroethylene carbonate
(FEC) and propylene carbonate (PC) may enable formation of a stable passivation film with respect to the electrolyte solution on the surfaces of graphite-based negative electrode materials . Fluoroethylene carbonate (FEC) and propylene carbonate
(PC) have a high dielectric constant, but also have a high viscosity. Accordingly, when this mixed solvent is used for an electrolyte solution, the ionic conductivity of the electrolyte solution may be low (i.e., about 7 mS/cm) and battery performance may thus be deteriorated.
Therefore, there is an increasing need for research and development associated with a non-aqueous electrolyte solution for a lithium secondary battery capable of improving lifespan and aging properties while maintaining battery performance . [Technical Problem]
Therefore, it is an aspect of the present invention to provide a non-aqueous electrolyte solution for a lithium secondary battery capable of improving lifespan and aging properties via use of suitable additives.
It is another aspect of the present invention to provide a lithium secondary battery comprising the non-aqueous electrolyte solution. Details of other aspects and exemplary embodiments encompassed in the present invention will be more clearly understood from the following detailed description.
[Technical Solution]
In accordance with one aspect of the present invention, there is provided a non-aqueous electrolyte solution for a lithium secondary battery comprising: a basic electrolyte solution consisting of a non-aqueous organic solvent and a lithium salt dissolved in the nonaqueous organic solvent; and a vinyl ethylene carbonate-based compound represented by the following Formula 1 and a halogenated ethylene carbonate- based compound represented by the following Formula 2, wherein the non-aqueous organic solvent includes at least one selected from the group consisting of carbonate- based solvents, ester-based solvents, ether-based solvents and ketone-based solvents:
Figure imgf000012_0001
[Advantageous Effects]
The non-aqueous electrolyte solution for a lithium secondary battery and a lithium secondary battery comprising the same according to embodiments of the present invention may enable an improvement in lifespan and aging properties while maintaining battery performance upon application of a high voltage.
[Description of Drawings]
The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: FIG. 1 is a schematic diagram illustrating a lithium secondary battery in which aluminum (Al) is used as a metal for a positive electrode, copper (Cu) is used as a metal for a negative electrode, LiCoθ2 is used as a positive active material, carbon (C) is used as a negative active material, and the non-aqueous electrolyte solution of the present invention is used as an electrolyte solution; FIGs . 2A and 2B are graphs showing the room-temperature cycle lifespan property of lithium secondary batteries produced in Example 3 and Comparative Examples 1, 2, 5 and 6; and
FIG. 3 is a graph showing a high-temperature cycle lifespan property of lithium secondary batteries produced in Example 3 and Comparative Example 3.
[Best Mode]
In one aspect, the present invention is directed to a non-aqueous electrolyte solution for a lithium secondary battery comprising: a basic electrolyte solution consisting of a non-aqueous organic solvent and a lithium salt dissolved in the non-aqueous organic solvent; and a vinyl ethylene carbonate-based compound represented by the following Formula 1 and a halogenated ethylene carbonate-based compound represented by the following Formula 2, wherein the nonaqueous organic solvent includes at least one selected from the group consisting of carbonate-based solvents, ester-based solvents, ether-based solvents and ketone-based solvents. O
Figure imgf000014_0001
In another aspect, the present invention is directed to a lithium secondary battery comprising: the non-aqueous electrolyte solution of the present invention; an electrode part consisting of a positive electrode and a negative electrode that face each other at opposite sides of the nonaqueous electrolyte solution; and a separator electrically separating the positive electrode from the negative electrode.
[Mode for Invention]
The non-aqueous electrolyte solution for a lithium secondary battery of the present invention contains no water (H2O) and uses only an organic solvent as a solvent, as apparent from the definition of the term "non-aqueous". The non-aqueous electrolyte solution may comprise additives to improve lifespan and aging properties of the lithium secondary battery, in addition to the basic electrolyte solution in which a lithium salt is dissolved in the nonaqueous organic solvent . The basic electrolyte solution consists of a non-aqueous organic solvent and a lithium salt. The non-aqueous organic solvent functions as a medium, allowing migration of ions involved in an electrochemical reaction of a battery. To secure favorable migration of the ions by promoting the degree of dissociation of the ions, it is preferred to use solvents that have a high dielectric constant (polarity) and a low viscosity. Generally, it is preferable to use a mixed solvent consisting of at least one solvent with a high dielectric constant and a high viscosity and at least one solvent with a low dielectric constant and a low viscosity.
The non-aqueous organic solvent used in the present invention includes at least one selected from the group consisting of carbonate-based solvents, ester-based solvents, ether-based solvents and ketone-based solvents . The carbonate-based solvent may be a mixture of at least one cyclic carbonate-based organic solvent selected from ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1, 2-pentylene carbonate and 2, 3-pentylene carbonate; and at least one chain carbonate-based organic solvent selected from dimethyl carbonate (DMC) , diethyl carbonate (DEC) , dipropyl carbonate (DPC), ethylmethyl carbonate (EMC), methylpropyl carbonate (MPC) and ethylpropyl carbonate (EPC) . The cyclic carbonate-based organic solvent and the chain carbonate-based organic solvent may be mixed in a volume ratio of 1 : 1 to 1 : 9, preferably, 1 : 1.5 to 1 : 4, in view of the lifespan and aging properties of the battery. In particular, among cyclic carbonate-based organic solvents, preferred is the use of ethylene carbonate and propylene carbonate, both of which have a high dielectric constant. In a case where artificial graphite is used as a negative electrode active material, preferred is the use of ethylene carbonate. Among chain carbonate-based organic solvents, preferred is the use oE dimethyl carbonate (DMC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) , all of which have a low viscosity.
The ester-based solvents may include at least one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-valerolactone and ε-caprolactone. The ether-based solvents may include at least one selected from the group consisting of tetrahydrofuran, 2-methyltetrahydrofuran and dibutyl ether. The ketone-based solvents may include polymethylvinylketone.
The non-aqueous organic solvent may further include an aromatic hydrocarbon-based organic solvent represented by Formula 3 below:
Figure imgf000017_0001
wherein R is halogen or Ci-Cio alkyl; and q is an integer of 0 to 6.
Specifically, the aromatic hydrocarbon-based organic solvent may include at least one selected from benzene, fluorobenzene, bromobenzene, chlorobenzene, toluene, xylene, mesitylene, fluorotoluene, difluorotoluene and trifluorotoluene .
The aromatic hydrocarbon-based solvent and the carbonate-based solvent may be used in a volume ratio of 1 : 1 to 1 : 30.
The basic electrolyte solution may be prepared by dissolving a lithium salt in the non-aqueous organic solvent.
The lithium salt acts as a feed source of lithium ions and enables fundamental operation of a lithium battery. the lithium salt may include at least one selected from LiPF6, LiClO4, LiAsF6, LiBF4, LiN (C2F5SO3) 2, LiN(C2F5SO2)?., LiN (CF3SO2) 2, LiSbF6, LiCF3SO3, LiC4F9SO3, LiAlO4, LiAlCl4, LiN(CxF2χ+iSθ2) (CyF2y+iSθ2) (wherein x and y are each independently a positive integer), LiCl and LiI.
Taking into consideration the properties associated with electrical conductivity of the electrolyte solution and the viscosity-related mobility of lithium ions, the concentration of the lithium salt in the electrolyte solution is preferably 0.6 to 2.0 M, more preferably, 0.7 to 1.6 M.
To the basic electrolyte solution, where the lithium salt is dissolved in the non-aqueous organic solvent, may be added a vinyl ethylene carbonate-based compound represented by the following Formula 1 and a halogenated ethylene carbonate- based compound represented by the following Formula 2 as additives :
O
Figure imgf000018_0001
wherein, in (1) , Ri, R2, R3 and R4 are each independently hydrogen or C2-C6 hydrocarbon having a double bond; and at least one of Ri, R2, R3 and R4 is C2-C6 hydrocarbon having a double bond, and O
Figure imgf000018_0002
-(x) (γ)» (2) wherein, in (2) X is halogen; Y is hydrogen or halogen; and n and m are each independently 1 or 2.
The vinyl ethylene carbonate-based compound may be added in an amount of 0.1 to 5 parts by weight, based on 100 parts of the basic electrolyte solution. The halogenated ethylene carbonate-based compound may be added in an amount of 0.1 to 20% by weight, based on 100 parts of the basic electrolyte solution.
To ensure desired lifespan and aging properties of the battery, the vinyl ethylene carbonate compound and the halogenated ethylene carbonate compound must be mixed in amounts within the range as defined above. In a case where the vinyl ethylene carbonate compound is used alone for the basic electrolyte solution, the low-temperature aging property of the battery is deteriorated. Meanwhile, in a case where the halogenated ethylene carbonate compound is used alone for the basic electrolyte solution, the room-temperature lifespan property of the battery, in particular, the high-temperature lifespan property is deteriorated. If necessary, the non-aqueous electrolyte solution of the present invention may further comprise propyl acetate methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate, etc.
The non-aqueous electrolyte solution of the present invention may exhibit superior aging property and long lifespan in a temperature range of -20 to 60 0C, thus improving stability and reliability of the battery. The nonaqueous electrolyte solution of the present invention may be applied to all lithium secondary batteries including lithium ion batteries, lithium polymer batteries, etc.
FIG. 1 is a schematic diagram illustrating a lithium secondary battery in which aluminum (Al) is used as a metal for a positive electrode 100, copper (Cu) is used as a metal for a negative electrode 110, LiCoC>2 is used as a positive active material, carbon (C) is used as a negative active material, and the non-aqueous electrolyte solution of the present invention is used as an electrolyte solution 130. As shown in FIG. 1, the lithium secondary battery comprises the positive electrode 100, the negative electrode 110, the electrolyte solution 130 and a separator 140.
As the non-aqueous electrolyte solution used as the electrolyte solution 130 for the lithium secondary battery has been explained above, a further description thereof is omitted.
The positive electrode 100 and the negative electrode 100 are arranged such that they face each other at opposite sides of the non-aqueous electrolyte solution 130. The positive electrode 100 may be composed of a metal coated with a positive active material. The positive active material may include at least one selected from LixMni-yMyA2, LixMn2θ4-zXz, LixMn2-yMyM'zA4, LixCθi-yMyA2, LixCθi-yMy02-zXz, LixNii_ yMyO2-zXz, LixNii-yCoy02-zXz, LixNii_y-zCoyMzAα, LixNii_y-zCoyMz02-αXα, LixNii-y-zMriyMzAα and LixNiι-y-JήnyMzO2-aXa (wherein 0.9 < x < 1.1, 0 < y < 0.5, 0 < z < 0.5, 0 < α <2; M and M' are same or different and are selected from the group consisting of Mg, Al, Co, K, Na, Ca, Si, Ti, Sn, V, Ge, Ga, B, As, Zr, Mn, Cr, Fe, Sr, V and rare earth elements; A is selected from the group consisting of 0, F, S and P; and X is selected from the group consisting of F, S and P) .
As shown in FIG. 1, carbon (crystalline or amorphous carbon) that can reversibly intercalate and deintercalate lithium ions may be used as an active material for the negative electrode 110. Alternatively, the negative electrode may be coated with at least one active material ' selected from a carbon composite, a carbon fiber, a lithium metal, a lithium alloy and a lithium composite. Specific examples of the amorphous carbon include hard carbon, cokes, mesocarbon microbeads (MCMBs) calcinated at 1,500 0C or below, mesophase pitch-based carbon fibers (MPCFs), etc.
The crystalline carbon may include, e.g., graphite-based materials, specific examples of which include natural graphite, graphitized cokes, graphitized MCMBs, graphitized MPCFs, etc. It is preferable that the carbonaceous material has a doo2 interplanar distance of 3.35 to 3.38 A, and a crystallite size (Lc) of 20 nm or more as measured by X-ray diffraction. The lithium alloy may include alloys of lithium and a metal selected from aluminum (Al), Zinc (Zn), bismuth (Bi) , cadmium (Cd) , antimony (Sb) , silicon (Si) , lead (Pb) , tin (Sn) , gallium (Ga) and indium (In) . Positive and negative electrodes may be fabricated by preparing an electrode slurry composition and applying the composition to an electrode collector. The preparation of the composition may be carried out by dispersing a thickening agent (if necessary) , along with the electrode active materials, a binder and a conductive agent, in a solvent.
A positive electrode collector may be composed of aluminum (Al) or an aluminum-containing alloy. A negative electrode collector may be composed of copper (Cu) or a copper-containing alloy. The positive and negative electrode collectors may have a shape such as a foil, a film, a sheet, a punched metal, a porous metal and an expanded metal.
The binder contributes to pestelization of active materials, co-adhesion between active materials, adhesion of active materials to collectors, and may offset swelling and contraction of active materials. Examples of the binder include polyvinylidene fluoride, polyhexafluoropropylene- polyvinylidene fluoride (P(VdF/HFP)) copolymers, poly (vinylacetate) , polyvinyl alcohol, polyethylene oxide, polyvinyl pyrrolidone, alkylated polyethylene oxide, polyvinyl ether, poly (methylmethacrylate) , poly (ethylacrylate) , polytetrafluoroethylene, polyvinylchloride, polyacrylonitrile, polyvinyl pyridine, styrene-butadiene rubbers, acrylonitrile- butadiene rubbers, etc. The amount of the binder may be 0.1 to 30% by weight, preferably, 1 to 10% by weight, with respect to the electrode active material. When the amount of the binder is excessively low, the adhesion of the electrode active material to the collector may be insufficient. Conversely, when the amount of the binder is excessively high, the adhesion force may be excellent but the amount of the electrode active material may be correspondingly decreased, which may be disadvantageous with respect to increasing battery capacity.
The conductive agent may contribute to an improvement in electrical conductivity. The conductive agent may include at least one selected from graphite-based conductive agents, carbon black-based conductive agents, and metal- or metallic compound-based conductive agents. Examples of the graphite- based conductive agents include artificial graphite and natural graphite. Examples of the carbon black-based conductive agents include acetylene black, ketjen black, denka black, thermal black, channel black, etc. Examples of the metal- or metallic compound-based conductive agents include tin (Sn) , tin oxide, tin phosphate (SnPC^) , titanium oxide, potassium titanate, and perovskite such as LaSrCoC>3 or LaSrMnO3.
The present invention is not limited to the above- mentioned examples of the conductive agent. The amount of the conductive agent is preferably 0.1 to 10% by weight, with respect to the electrode active material. When the amount of the conductive agent is lower than 0.1 wt%, the electrochemical property of the electrolyte solution may be deteriorated. Conversely, when the content of the conductive agent exceeds 10 wt%, the energy density per unit weight may be reduced.
Any thickening agent may be used without particular limitation so long as it can control the viscosity of the active material slurry. Specific examples of the thickening agent include carboxymethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose and hydroxypropyl cellulose. The solvent in which the electrode active materials, the binder and the conductive agent are dispersed may be a nonaqueous solvent or an aqueous solvent . Examples of the non- aqueous solvent include N-methyl-2-pyrrolidone (NMP) , dimethylformamide, dimethylacetamide,
N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, etc. The metals for the positive electrode 100 and the negative electrode 110 receive a voltage from an external source during charging, and discharge the voltage to the outside during discharging. The positive active material serves as a collector for collecting positive charges, and the negative active material serves as a collector for collecting negative charges .
The separator 140 maintains the positive electrode 100 electrically separated from the negative electrode 110, thereby preventing occurrence of a short phenomenon, while allowing for the passage of lithium ions.
The separator 140 may be a polyethylene or polypropylene mono-layered separator, a polyethylene/polypropylene double- layered separator, or a polyethylene/polypropylene/polyethylene or polypropylene/polyethylene/polypropylene triple-layered separator. The separator 140 may have a shape of a multilayer film, a microporous film, a woven fabric or a non-woven fabric. Alternatively, a porous polyolefin film coated with a highly stable resin may be used as the separator.
An electrode assembly fabricated as mentioned above and the electrolyte solution may be injected into a can-type case, followed by sealing an upper part of the case with a cap assembly, to complete production of a lithium secondary battery.
The cap assembly may include a cap plate, an insulating plate, a terminal plate and an electrode terminal. The cap assembly may be combined with an insulating case, thereby sealing the can. In addition, a terminal hole, into which an electrode terminal can be inserted, may be arranged in the center of the cap plate. When the electrode terminal is inserted into the terminal hole, a tube-type gasket, provided at the external surface of the electrode terminal, may also be inserted into the terminal hole so that the electrode terminal can be insulated from the cap plate.
After the cap assembly is coupled to the top of the can, the electrolyte solution may be injected through an electrolyte injection hole and the electrolyte injection hole may then be sealed with a sealing means. At this time, the electrode terminal may be coupled to a negative electrode tap of the negative electrode or a positive electrode tap of the positive electrode, thus operating as a negative or positive electrode terminal.
Hereinafter, the fact that a non-aqueous electrolyte solution for a lithium secondary battery according to embodiments of the present invention is capable of improving lifespan and aging properties of a lithium secondary battery will be demonstrated from the following detailed description taken in conjunction with specific Examples and Comparative Examples . Features and procedures whose implementations are well known to those skilled in the art may be omitted for brevity.
EXAMPLES <Example 1>
LiCoθ2 as a positive active material, polyvinylidene fluoride (PVDF) as a binder, and carbon as a conductive agent were mixed in a weight ratio of 92 : 4 : 4. Then, the mixture was dispersed in N-methyl-2-pyrrolidone to prepare a positive electrode slurry. The slurry was coated on an aluminum foil with a thickness of 20 μm, followed by drying and compressing, to fabricate a positive electrode.
Artificial graphite as a negative active material, a styrene-butadiene rubber as a binder, and carboxymethyl cellulose as a thickening agent were mixed in a weight ratio of 96 : 2 : 2. Then, the mixture was dispersed in water to prepare a negative electrode slurry. The slurry was coated on a copper foil with a thickness of 15 μm, followed by drying and compressing, to fabricate a negative electrode.
A polyethylene (PE) film separator having a thickness of 20 μm was interposed between the positive and negative electrodes, wound and pressed, then inserted into a cylindrical can. An electrolyte solution was added to the cylindrical can, thereby producing a lithium secondary battery. The electrolyte solution was prepared by dissolving
LiPFε in a mixed organic solvent of ethylene carbonate (EC) , ethylmethyl carbonate (EMC) and dimethyl carbonate (DMC) in a volume ratio of 1 : 1 : 1 to prepare a basic electrolyte solution (concentration: 1.3 M) and adding vinyl ethylene carbonate and fluoroethylene carbonate to the basic electrolyte solution. The vinyl ethylene carbonate and fluoroethylene carbonate were added in an amount of 0.5% by weight and 1% by weight, respectively, with respect to the weight of the organic solvent .
<Example 2>
A lithium secondary battery was produced in the same manner as in Example 1, except that vinyl ethylene carbonate and fluoroethylene carbonate were added in an amount of 0.5% by weight and 10% by weight, respectively.
<Example 3>
A lithium secondary battery was produced in the same manner as in Example 1, except that vinyl ethylene carbonate and fluoroethylene carbonate were added in an amount of 1% by weight and 3% by weight, respectively.
<Example 4> A lithium secondary battery was produced in the same manner as in Example 1, except that vinyl ethylene carbonate and fluoroethylene carbonate were added in an amount of 1% by weight and 5% by weight, respectively.
<Example 5>
A lithium secondary battery was produced in the same manner as in Example 1, except that vinyl ethylene carbonate and fluoroethylene carbonate were added in an amount of 1% by weight and 7% by weight, respectively.
<Example 6>
A lithium secondary battery was produced in the same manner as in Example 1, except that vinyl ethylene carbonate and fluoroethylene carbonate were added in an amount of 2% by weight and 3% by weight, respectively.
<Example 7>
A lithium secondary battery was produced in the same manner as in Example 1, except that vinyl ethylene carbonate and fluoroethylene carbonate were added in an amount of 2% by weight and 5% by weight, respectively.
<Comparative Example 1> A lithium secondary battery was produced in the same manner as in Example 1, except that vinyl ethylene carbonate was added exclusively in an amount of 3% by weight.
<Comparative Example 2> A lithium secondary battery was produced in the same manner as in Example 1, except that fluoroethylene carbonate was added exclusively in an amount of 3% by weight.
<Comparative Example 3> A lithium secondary battery was produced in the same manner as in Example 1, except that vinylene carbonate was added exclusively in an amount of 3% by weight.
<Comparative Example 4> A lithium secondary battery was produced in the same manner as in Example 1, except that vinylene carbonate and fluoroethylene carbonate were added in an amount of 1% by weight and 3% by weight, respectively. <Standard capacity>
The batteries produced in Examples 1 to 7 and
Comparative Examples 1 to 4 were charged under constant current-constant voltage (CC-CV) conditions of 0.5C/4.2V for 3 hours. The standard capacity of each battery is shown in
Table 1.
<Room-temperature lifespan property>
The batteries produced in Examples 1 to 7 and Comparative Examples 1 to 4 were charged under CC-CV conditions of 0.5C/4.2V at 25 0C for 3 hours, and were discharged at 1C CC to a cut off voltage of 3 V. A series of the charging and discharging was repeated 300 times. The capacity maintenance ratio (%) at a 300th cycle of each battery was calculated by the following Equation and the result is shown in Tables 1 and 2.
* Capaci ty maintenance ra tio at 300th cycle (%) = (discharge capaci ty a t 300th cycle) / (discharge capaci ty a t 1st cycle) X 100
<High-temperature lifespan property>
The batteries produced in Example 3, and Comparative Examples 3 and 4 were charged under CC-CV conditions of 0.5C/4.2V at 60 0C for 3 hours, and were discharged at 1C CC to a cut off voltage of 3 V. A series of the charging and discharging was repeated 300 times. The capacity maintenance ratio (%) at a 300th cycle and 60 0C of each battery was calculated and the result is shown in Table 2.
<Low-temperature aging property>
The batteries produced in Examples 1 to 7, and Comparative Examples 1 and 2 were charged under CC-CV conditions of 0.5C/4.2V at 25 0C for 3 hours and were then left at 0 0C for 4 hours. The batteries were discharged at 0.5 C CC to a cut off voltage of 3 V. The discharge capacity recovery ratio (%) after low-temperature aging of each battery was calculated by the following Equation and the result is shown in Table 1. * Discharge capacity recovery ratio after low- temperature aging (%) = ( 0.5 C discharge capacity after low- temperature aging) / (0.5 C discharge capacity before low- temperature aging) x 100
<High-temperature aging property>
The batteries produced in Examples 1 to 7, and Comparative Examples 1 and 2 were charged under CC-CV conditions of 0.5C/4.2V at 25 0C for 3 hours and were then left at 85 0C for 24 hours. The batteries were discharged at 0.5 C CC to a cut off voltage of 3 V. The discharge capacity recovery ratio (%) after high-temperature aging of each battery was calculated by the following Equation and the result is shown in Table 1.
* Discharge capacity recovery ratio after high- temperature aging (%) = (0.5 C discharge capacity after high- temperature aging) / (0.5 C discharge capacity before high- temperature aging) x 100
TABLE 1
Figure imgf000033_0001
Figure imgf000034_0001
TABLE 2
Figure imgf000034_0002
(VEC: vinyl ethylene carbonate, FEC: fluoroethylene carbonate, VC: vinylene carbonate)
As can be seen from the data of Tables 1 and 2, the electrolyte solutions of Examples 1 to 7, comprising 0.1 to 5% by weight of vinyl ethylene carbonate and 0.1 to 20% by weight of fluoroethylene carbonate, provide good lifespan and aging properties for the battery.
The electrolyte solution of Comparative Example 1, comprising only vinyl ethylene carbonate, shows poor low- temperature aging properties. The electrolyte solution of Comparative Example 2, comprising only fluoroethylene carbonate, shows poor lifespan properties.
The electrolyte solutions of Comparative Examples 3 and
4, comprising an excessive amount of vinylethylene carbonate or fluoroethylene carbonate, show deteriorated low-temperature or high-temperature aging properties .
The electrolyte solution of Comparative Example 6 comprising vinylene carbonate instead of vinyl ethylene carbonate and fluoroethylene carbonate exhibits substantially equivalent room-temperature lifespan property, but shows poor low-temperature property, as compared to the electrolyte solution of Comparative Example 3 comprising vinyl ethylene carbonate and fluoroethylene carbonate.
Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims .

Claims

[CLAIMS]
[Claim 1]
A non-aqueous electrolyte solution for a lithium secondary battery comprising: a basic electrolyte solution consisting of a non-aqueous organic solvent and a lithium salt dissolved in the nonaqueous organic solvent; and a vinyl ethylene carbonate-based compound represented by the following Formula 1 and a halogenated ethylene carbonate- based compound represented by the following Formula 2, wherein the non-aqueous organic solvent includes at least one selected from the group consisting of a carbonate- based solvent, an ester-based solvent, an ether-based solvent and a ketone-based solvent:
O
Figure imgf000036_0001
wherein Ri, R.2, R3 and R4 are each independently hydrogen or C2-C6 hydrocarbon having a double bond; and at least one of Ri, R2, R3 and R4 is C2-C6 hydrocarbon having a double bond: O
Figure imgf000037_0001
wherein X is halogen; Y is hydrogen or halogen; and n and m are each independently 1 or 2.
[Claim 2]
The non-aqueous electrolyte solution for a lithium secondary battery according to claim 1, wherein the vinyl ethylene carbonate-based compound is added in an amount of 0.1 to 5 parts by weight, based on 100 parts by weight of the basic electrolyte solution.
[Claim 3]
The non-aqueous electrolyte solution for a lithium secondary battery according to claim 1, wherein the halogenated diphenyl ether compound is added in an amount of
0.1 to 20 parts by weight, based on 100 parts by weight of the basic electrolyte solution.
[Claim 4] The non-aqueous electrolyte solution for a lithium secondary battery according to claim 1, wherein the carbonate- based solvent is a mixture of: at least one cyclic carbonate- based organic solvent selected from ethylene carbonate (EC) , propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1, 2-pentylene carbonate and 2, 3-pentylene carbonate; and at least one chain carbonate-based organic solvent selected from dimethyl carbonate (DMC) , diethyl carbonate (DEC) , dipropyl carbonate (DPC) , ethylmethyl carbonate (EMC) , methylpropyl carbonate (MPC) and ethylpropyl carbonate (EPC) .
[Claim 5]
The non-aqueous electrolyte solution for a lithium secondary battery according to claim 4, wherein the cyclic carbonate-based organic solvent and the chain carbonate-based organic solvent are mixed in a volume ratio of 1 : 1 to 1 : 9.
[Claim 6]
The non-aqueous electrolyte solution for a lithium secondary battery according to claim 1, wherein the ester- based solvent includes at least one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-valerolactone and ε-caprolactone .
[Claim 7]
The non-aqueous electrolyte solution for a lithium secondary battery according to claim 1, wherein the ether- based solvent includes at least one selected from the group consisting of tetrahydrofuran, 2-methyltetrahydrofuran and dibutyl ether.
[Claim 8]
The non-aqueous electrolyte solution for a lithium secondary battery according to claim 1, wherein the ketone- based solvent is polymethylvinylketone.
[Claim 9]
The non-aqueous electrolyte solution for a lithium secondary battery according to claim 1, wherein the nonaqueous organic solvent further includes an aromatic hydrocarbon-based compound represented by Formula 3 below:
Figure imgf000039_0001
wherein R is halogen or a Cχ-Cio alkyl group; and q is an integer of 0 to 6.
[Claim 10] The non-aqueous electrolyte solution for a lithium secondary battery according to claim 9, wherein the aromatic hydrocarbon-based compound is benzene, fluorobenzene, bromobenzene, chlorobenzene, toluene, xylene, mesitylene, fluorotoluene, difluorotoluene or trifluorotoluene.
[Claim 11]
The non-aqueous electrolyte solution for a lithium secondary battery according to claim 9, wherein the aromatic hydrocarbon-based solvent and the carbonate-based solvent are mixed in a volume ratio of 1 : 1 to 1 : 30.
[Claim 12]
The non-aqueous electrolyte solution for a lithium secondary battery according to claim 9, wherein the lithium salt includes at least one selected from LiPF6, LiClC>4, LiAsF6, LiBF4, LiN (C2F5SO3) 2, LiN (C2F5SO2) 2, LiN (CF3SO2) 2, LiSbF6, LiCF3SO3, LiC4F9SO3, LiAlO4, LiAlCl4, LiN (CxF2x+iSO2) (CyF2y+iSO2) (wherein x and y are each independently a positive integer) , LiCl and LiI, and the concentration of the lithium salt in the electrolyte solution is 0.6 to 2.0 M.
[Claim 13]
A lithium secondary battery comprising: the non-aqueous electrolyte solution according to claim l; an electrode part consisting of a positive electrode and a negative electrode that face each other at opposite sides of the non-aqueous electrolyte solution; and a separator electrically separating the positive electrode from the negative electrode.
[Claim 14] The lithium secondary battery according to claim 13, wherein the positive electrode is composed of a metal coated with an active material, and the active material includes at least one selected from LixMni-yMyA2, LixMn2θ4-zXz, LixMn2-yMyM ' zA,j , LixCθi-yMyA2, LixCθi_yMy02-zXz, LixNii-yMyO2-zXz, LixNi i-yCoy02-zXz, LixNi1-^2COyM2A3, LixNii-y-zCoyMz02-αXα, LixNi i-y-zMnyMzAa and LixNii-y- zMnyMzO2-αXα (wherein 0 . 9 ≤ x < 1 . 1, 0 < y < 0 . 5, 0 < z < 0 . 5 , 0 ≤ α ≤2 ; M and M ' are same or different and are selected from the group consisting of Mg, Al , Co, K, Na, Ca, Si, Ti, Sn, V, Ge, Ga, B, As , Zr, Mn, Cr, Fe, Sr, V and rare earth elements; A is selected from the group consisting of O, F, S and P; and
X is selected from the group consisting of F, S and P) .
[Claim 15 ] The lithium secondary battery according to claim 13, wherein the negative electrode is composed of a metal coated with at least one active material selected from crystalline carbon, amorphous carbon, a carbon composite, a carbon fiber, a lithium metal, a lithium alloy and a lithium composite.
PCT/KR2007/002918 2007-01-05 2007-06-15 Nonaqueous electrolyte for li-secondary battery and li secondary battery thereby WO2008082048A1 (en)

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