WO2014103893A1 - Batterie secondaire au lithium et son procédé de sélection - Google Patents

Batterie secondaire au lithium et son procédé de sélection Download PDF

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WO2014103893A1
WO2014103893A1 PCT/JP2013/084154 JP2013084154W WO2014103893A1 WO 2014103893 A1 WO2014103893 A1 WO 2014103893A1 JP 2013084154 W JP2013084154 W JP 2013084154W WO 2014103893 A1 WO2014103893 A1 WO 2014103893A1
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positive electrode
negative electrode
secondary battery
charge transfer
lithium secondary
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PCT/JP2013/084154
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Japanese (ja)
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加藤　有光
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日本電気株式会社
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • 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
    • H01M10/058—Construction or manufacture
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M2010/4292—Aspects relating to capacity ratio of electrodes/electrolyte or anode/cathode
    • 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
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to a lithium secondary battery and a selection method thereof.
  • Lithium secondary batteries are widely used for portable electronic devices and personal computers because of their small size and large capacity. However, since the characteristics deteriorate due to repeated charge and discharge, there is a lifetime. In recent years, the use of batteries for large capacity devices such as household storage batteries and electric vehicles has been realized, so it is not desirable to replace batteries in the short term. It has become.
  • a decomposition reaction occurs at the time of charge / discharge at the contact portion between the positive electrode or the negative electrode and the electrolytic solution, and a reaction product is formed on the electrode surface, or the crystallinity changes in a part of the electrode. Is considered.
  • a 5 V class operating potential can be realized by using, as an active material, a spinel compound in which Mn of lithium manganate is substituted with Ni, Co, Fe, Cu, Cr or the like.
  • spinel compounds such as LiNi 0.5 Mn 1.5 O 4 exhibit a potential plateau in the region of 4.5 V or higher.
  • Mn exists in a tetravalent state, and the operating potential is defined by oxidation and reduction of Ni 2+ ⁇ ⁇ Ni 4+ instead of oxidation reduction of Mn 3+ ⁇ ⁇ Mn 4+ .
  • LiNi 0.5 Mn 1.5 O 4 has a capacity of 130 mAh / g or more and an average operating voltage of 4.6 V or more with respect to metallic lithium. Although the capacity is smaller than LiCoO 2 , the energy density of the battery is higher than LiCoO 2 . Furthermore, spinel type lithium manganese oxide has an advantage that it has a three-dimensional lithium diffusion path, has excellent thermodynamic stability, and is easy to synthesize. For these reasons, LiNi 0.5 Mn 1.5 O 4 is promising as a future positive electrode material.
  • Patent Document 1 discloses the diameter of a semicircular arc drawn when impedance is measured in a frequency region of 10 kHz to 10 mHz and a result is described on a complex plane in an electrochemical cell using a positive electrode as a working electrode and lithium metal as a game.
  • an electrochemical cell using R1 and a negative electrode plate as the working electrode and lithium metal as the counter electrode when impedance is measured in the frequency range from 10 kHz to 10 mHz and the result is described on the complex plane, the diameter of the semicircular arc drawn as R2 It is stated that the deterioration in the charge / discharge cycle can be suppressed by setting the value of R2 / R1 to 0.01 to 15.
  • Patent Document 2 describes an increase rate of a negative electrode resistance component (impedance), an increase rate of a positive electrode resistance component (impedance), and the like of a lithium ion battery subjected to charge / discharge cycles.
  • Patent Document 3 describes the ratio of the charge transfer resistance between the early discharge stage and the late discharge stage of the electrode plate for a nonaqueous electrolyte secondary battery.
  • Patent Document 4 shows a comparison between the charge transfer resistance of the positive electrode and the charge transfer resistance of the negative electrode for a plurality of unused lithium ion batteries of the same type and a plurality of lithium ion batteries of the same type different in use state. Has been.
  • FIG. 7 shows a result of evaluating the relationship between R2 / R1 in a state where the battery is once charged after the trial manufacture and the amount of change ⁇ Rall of the internal resistance of the battery due to 50 cycles of charge / discharge.
  • the data is experimental data of examples and comparative examples in the present specification, and conditions will be described later.
  • the evaluation of R1 and R2 was obtained by fitting an AC impedance measurement between the electrodes and an equivalent circuit as described later.
  • the lithium secondary battery of the present invention aims to realize excellent charge / discharge cycle characteristics.
  • a lithium secondary battery having a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, and an electrolytic solution including a nonaqueous electrolytic solvent, A change amount ( ⁇ Rct) of the positive electrode charge transfer resistance before and after a predetermined stress application on a plane having two axes orthogonal to each other, the change amount of the charge transfer resistance of the positive electrode and the change amount of the charge transfer resistance of the negative electrode ) And a point ( ⁇ Rct2, ⁇ Rct) representing the amount of change ( ⁇ Rct2) in the charge transfer resistance of the negative electrode is projected to a point ( ⁇ Ra , ⁇ Rc) A point ( ⁇ Ra, ⁇ Rc) is defined with respect to a straight line passing through the origin on a plane having two axes orthogonal to each other.
  • the lithium secondary battery is characterized in that the distance from the vertically projected point to the origin is within a predetermined range.
  • a secondary battery having excellent cycle characteristics can be provided.
  • a positive electrode active material that operates at a potential of 4.5 V or higher with respect to lithium is used, a secondary battery having excellent cycle characteristics can be provided.
  • the lithium secondary battery of the present embodiment has a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, and an electrolytic solution including a nonaqueous electrolytic solvent.
  • Charge transfer resistances Rct and Rct2 exist in the positive electrode and the negative electrode, respectively.
  • the amount of change in the charge transfer resistance of the positive electrode before and after the predetermined stress application [(charge transfer resistance value of the positive electrode after stress application) ⁇ (charge transfer resistance value of the positive electrode before stress application)] is ⁇ Rct
  • the amount of change in the charge transfer resistance of the negative electrode [(charge transfer resistance value of negative electrode after applying stress) ⁇ (charge transfer resistance value of negative electrode before applying stress)] is represented by ⁇ Rct2.
  • the circle centered on the origin from the point ( ⁇ Rct2, ⁇ Rct) is 1 ⁇ .
  • the point on the circle after normalization is defined as a point ( ⁇ Ra, ⁇ Rc).
  • the point ( ⁇ Ra, ⁇ Rc) is set to the origin on a plane having two axes perpendicular to the amount of change in charge transfer resistance of the positive electrode after normalization and the amount of change in charge transfer resistance of the negative electrode after normalization. Project perpendicular to the straight line that passes through.
  • the cycle characteristics of the lithium ion secondary battery are compared to when the distance ⁇ Rx is not within the predetermined range.
  • the vertical axis represents the amount of change in charge transfer resistance of the positive electrode
  • the horizontal axis represents the amount of change in charge transfer resistance of the negative electrode
  • the vertical axis represents the change amount of the charge transfer resistance of the positive electrode after normalization according to FIG. 4
  • the horizontal axis represents the change amount of the charge transfer resistance of the negative electrode after normalization according to FIG. 4.
  • ⁇ Rx may be referred to as “projection value”.
  • Examples of the stress include charge / discharge cycles, high temperature storage (for example, storage at 45 ° C. or higher for 5 minutes or longer), high voltage application (for example, a value higher by 0.05 V or more than the voltage on the higher potential side of the battery), and the like. Can be mentioned.
  • an increase in the internal resistance of the battery can be suppressed, and a lithium secondary battery with good charge / discharge cycle resistance can be realized.
  • the present invention is more effective when the resistance increase due to stress is large, such as a lithium secondary battery using a positive electrode active material that operates at a potential of 4.5 V or higher with respect to lithium. .
  • ⁇ Rct2 and ⁇ Rct change in a substantially proportional relationship
  • the values change in a radiation direction centered on the origin. Increase or decrease. Therefore, in the present embodiment, as described above, the point ( ⁇ Rct2, ⁇ Rct) is set to the origin on the plane with the change amount of the charge transfer resistance of the positive electrode on the vertical axis and the change amount of the charge transfer resistance of the negative electrode on the horizontal axis.
  • a straight line passing through the origin is set as a new axis on a plane with the vertical axis representing the amount of change in charge transfer resistance of the positive electrode after normalization and the horizontal axis representing the amount of change in charge transfer resistance of the negative electrode after normalization.
  • the projection is perpendicular to the straight line from the point ( ⁇ Ra, ⁇ Rc).
  • the slope of the straight line passing through the origin can be set from the measurement results of the charge transfer resistances of a plurality of lithium ion secondary batteries.
  • the distance from the point ( ⁇ Ra, ⁇ Rc) to the origin when projected perpendicularly to the straight line passing through the origin is assumed to be ⁇ Rx.
  • the value ⁇ Rx obtained by projecting perpendicularly to the straight line passing through the origin is in the range of 0 ⁇ 1 ⁇ .
  • a predetermined range of ⁇ Rx is determined, and a lithium secondary battery having excellent cycle characteristics can be obtained.
  • the predetermined range ⁇ Rx is not particularly limited, but is preferably within 0 ⁇ 0.5 ⁇ , and more preferably within 0 ⁇ 0.3 ⁇ .
  • Rct and Rct2 there is a method of measuring and evaluating an impedance between a positive electrode and a negative electrode by an AC impedance method.
  • the measurement result is plotted on the complex plane, two arcs or elliptical arcs are observed.
  • the actual resistance side diameter (or elliptical diameter) of the high frequency side arc (or elliptical arc) is Rct2
  • the actual resistance side diameter or elliptical diameter of the low frequency side arc (or elliptical arc) is It may be regarded as Rct (see FIG. 3).
  • Rct2 and Rct are interchanged, one of them may satisfy the condition that ⁇ Rx is within a predetermined range. In addition, when there are three or more arcs, the larger one is considered.
  • fitting to an equivalent circuit may be performed to extract Rct2 and Rct.
  • fitting with an equivalent circuit as shown in FIG. 2 may be performed to extract Rct2 and Rct.
  • the AC impedance method an AC voltage is applied between terminals whose impedance is to be evaluated, a response current and its phase are evaluated, and real resistance and imaginary resistance at that frequency are extracted.
  • Another method for measuring Rct and Rct2 includes the following method. First, a conductive electrode made of lithium or the like is provided on the battery, and the impedance between the conductive electrode and the positive electrode is measured and evaluated by an AC impedance method. When the measurement result is plotted on a complex surface, an arc or an elliptical arc is observed. The actual resistance side diameter (or elliptical diameter) is Rct. Similarly, Rct2 is obtained from the impedance measurement result between the conductive electrode and the negative electrode.
  • This embodiment can be used as a means for selecting a cell having high resistance to stress and a cell having low resistance from a plurality of lithium ion secondary batteries (cells). For example, when the projection value ⁇ Rx deviates from the design range or the amount of difference (standard deviation) from the distribution of other cells, the cell may be selected as a cell that is likely to become defective due to an abnormality. It becomes possible. Thus, the technology of the present invention can also be used as a means for selecting a lithium ion secondary battery.
  • the electrolytic solution includes a supporting salt and a nonaqueous electrolytic solvent.
  • the composition of the nonaqueous electrolytic solvent of the present invention can be adjusted as appropriate. For example, it preferably contains a fluorine-containing phosphate ester, and more preferably contains a cyclic sulfonate ester as an additive.
  • the oxidation resistance of the electrolytic solution can be enhanced, and the compatibility with other solvent components and the ionic conductivity of the electrolytic solution can be enhanced.
  • a fluorine-containing phosphate compound is used as an electrolyte solution solvent for a battery including a positive electrode that operates at a high potential, decomposition of the electrolyte solution at a high potential is suppressed, which is preferable.
  • fluorine-containing phosphate ester examples include tris phosphate (trifluoromethyl), tris phosphate (trifluoroethyl), tris phosphate (tetrafluoropropyl), tris phosphate (pentafluoropropyl), tris phosphate ( Heptafluorobutyl), tris phosphate (octafluoropentyl) and the like.
  • examples of the fluorine-containing phosphate ester include trifluoroethyl dimethyl phosphate, bis (trifluoroethyl) methyl phosphate, bistrifluoroethyl ethyl phosphate, pentafluoropropyl dimethyl phosphate, heptafluorobutyl dimethyl phosphate, Trifluoroethylmethyl ethyl phosphate, pentafluoropropylmethyl ethyl phosphate, heptafluorobutylmethyl ethyl phosphate, trifluoroethyl methyl propyl phosphate, pentafluoropropyl methyl propyl phosphate, heptafluorobutyl methyl propyl phosphate, phosphoric acid Trifluoroethylmethylbutyl, pentafluoropropylmethylbutyl phosphate, heptafluorobutylmethylbutyl
  • Examples of tris (tetrafluoropropyl) phosphate include tris (2,2,3,3-tetrafluoropropyl) phosphate.
  • Examples of tris (pentafluoropropyl) phosphate include tris (2,2,3,3,3-pentafluoropropyl) phosphate.
  • Examples of tris (trifluoroethyl) phosphate include tris (2,2,2-trifluoroethyl) phosphate (hereinafter also abbreviated as PTTFE).
  • Examples of tris phosphate (heptafluorobutyl) include tris phosphate (1H, 1H-heptafluorobutyl).
  • Examples of lintris (octafluoropentyl) include trisphosphate (1H, 1H, 5H-octafluoropentyl) and the like. These fluorine-containing phosphate esters can be used alone or in combination of two or more.
  • the content of the fluorine-containing phosphate ester is preferably in the range of 0.1 to 95% by volume, more preferably 0.2% by volume or more, and more preferably 0.5% by volume or more in the total nonaqueous electrolytic solvent. Preferably, 5 volume% or more is more preferable, it is more preferable that it is larger than 10 volume%, 20 volume% or more is further more preferable, 90 volume% or less is more preferable, and 80 volume% or less is further more preferable. When the content of the fluorine-containing phosphate is within this range, a lithium secondary battery excellent in cycle characteristics can be obtained.
  • the nonaqueous electrolytic solvent preferably contains a cyclic carbonate and / or a chain carbonate.
  • cyclic carbonate or chain carbonate has a large relative dielectric constant, the addition of these improves the dissociation property of the supporting salt and makes it easy to impart sufficient conductivity.
  • cyclic carbonates and chain carbonates are suitable for mixing with fluorine-containing phosphate esters because of their high voltage resistance and electrical conductivity. Furthermore, it is possible to improve the ion mobility in the electrolytic solution by selecting a material having an effect of lowering the viscosity of the electrolytic solution.
  • the cyclic carbonate is not particularly limited, and examples thereof include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and vinylene carbonate (VC).
  • the cyclic carbonate includes a fluorinated cyclic carbonate. Examples of the fluorinated cyclic carbonate include compounds in which some or all of the hydrogen atoms such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), or vinylene carbonate (VC) are substituted with fluorine atoms. Can be mentioned.
  • fluorinated cyclic carbonate examples include, for example, 4-fluoro-1,3-dioxolan-2-one, (cis or trans) 4,5-difluoro-1,3-dioxolan-2-one, 4,4-difluoro-1,3-dioxolan-2-one, 4-fluoro-5-methyl-1,3-dioxolan-2-one, and the like can be used.
  • ethylene carbonate, propylene carbonate, or a compound obtained by fluorinating a part thereof is preferable, and ethylene carbonate is more preferable, from the viewpoint of voltage resistance and conductivity.
  • a cyclic carbonate can be used individually by 1 type or in combination of 2 or more types.
  • the chain carbonate is not particularly limited, and examples thereof include dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and dipropyl carbonate (DPC).
  • the chain carbonate includes a fluorinated chain carbonate.
  • a fluorinated chain carbonate for example, a part or all of hydrogen atoms such as ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC) and the like are substituted with fluorine atoms. Examples include compounds having a structure.
  • examples of the fluorinated chain carbonate include bis (fluoroethyl) carbonate, 3-fluoropropyl methyl carbonate, 3,3,3-trifluoropropyl methyl carbonate, and 2,2,2-trifluoro.
  • dimethyl carbonate 2,2,2-trifluoroethyl methyl carbonate, monofluoromethyl methyl carbonate, methyl 2,2,3,3-tetrafluoropropyl carbonate and the like are preferable from the viewpoint of voltage resistance and conductivity.
  • a linear carbonate can be used individually by 1 type or in combination of 2 or more types.
  • the nonaqueous electrolytic solvent may contain a carboxylic acid ester.
  • the carboxylate ester is not particularly limited, and examples thereof include ethyl acetate, methyl propionate, ethyl formate, ethyl propionate, methyl butyrate, ethyl butyrate, methyl acetate, and methyl formate.
  • the carboxylic acid ester also includes a fluorinated carboxylic acid ester. Examples of the fluorinated carboxylic acid ester include ethyl acetate, methyl propionate, ethyl formate, ethyl propionate, methyl butyrate, ethyl butyrate, methyl acetate, or formic acid.
  • Examples thereof include compounds having a structure in which part or all of the hydrogen atoms of methyl are substituted with fluorine atoms.
  • Specific examples of the fluorinated carboxylic acid ester include, for example, ethyl pentafluoropropionate, ethyl 3,3,3-trifluoropropionate, methyl 2,2,3,3-tetrafluoropropionate, and acetic acid.
  • the carboxylic acid esters include ethyl propionate, methyl acetate, methyl 2,2,3,3-tetrafluoropropionate, 2,2,3,3 trifluoroacetic acid. -Tetrafluoropropyl is preferred.
  • Carboxylic acid esters have the effect of reducing the viscosity of the electrolytic solution in the same manner as chain carbonates. Therefore, for example, the carboxylic acid ester can be used in place of the chain carbonate, and can also be used in combination with the chain carbonate.
  • the nonaqueous electrolytic solvent can contain an alkylene biscarbonate represented by the following formula (1) in addition to the fluorine-containing phosphate ester. Since the oxidation resistance of the alkylene biscarbonate is equal to or slightly higher than that of the chain carbonate, the voltage resistance of the electrolytic solution can be improved.
  • R 4 and R 6 each independently represents a substituted or unsubstituted alkyl group.
  • R 5 represents a substituted or unsubstituted alkylene group).
  • the alkyl group includes linear or branched ones, preferably having 1 to 6 carbon atoms, and more preferably 1 to 4 carbon atoms.
  • the alkylene group is a divalent saturated hydrocarbon group, including a linear or branched chain group, preferably having 1 to 4 carbon atoms, and more preferably 1 to 3 carbon atoms. .
  • alkylene biscarbonate represented by the formula (1) examples include 1,2-bis (methoxycarbonyloxy) ethane, 1,2-bis (ethoxycarbonyloxy) ethane, and 1,2-bis (methoxycarbonyloxy).
  • examples include propane and 1-ethoxycarbonyloxy-2-methoxycarbonyloxyethane. Of these, 1,2-bis (methoxycarbonyloxy) ethane is preferred.
  • Alkylene biscarbonate is a material with a low dielectric constant. Therefore, for example, it can be used instead of the chain carbonate, or can be used in combination with the chain carbonate.
  • the nonaqueous electrolytic solvent may contain a chain ether.
  • the chain ether is not particularly limited, and examples thereof include 1,2-ethoxyethane (DEE) and ethoxymethoxyethane (EME).
  • the chain ether also includes fluorinated chain ether.
  • the fluorinated chain ether is preferably used in the case of a positive electrode having high oxidation resistance and operating at a high potential.
  • Examples of the fluorinated chain ether include compounds having a structure in which some or all of the hydrogen atoms of 1,2-ethoxyethane (DEE) or ethoxymethoxyethane (EME) are substituted with fluorine atoms.
  • fluorinated chain ether examples include 2,2,3,3,3-pentafluoropropyl 1,1,2,2-tetrafluoroethyl ether, 1,1,2,2 and the like.
  • -Tetrafluoroethyl 2,2,2-trifluoroethyl ether 1H, 1H, 2'H, 3H-decafluorodipropyl ether, 1,1,1,2,3,3-hexafluoropropyl-2,2 -Difluoroethyl ether
  • isopropyl 1,1,2,2-tetrafluoroethyl ether, propyl 1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl 2,2,3 3-tetrafluoropropyl ether 1H, 1H, 5H-perfluoropentyl-1,1,2,2-tetrafluoroethyl ether, 1H, 1H, 2′H-per Fluo
  • 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether 1H, 1H, 2′H, 3H-decafluoro Dipropyl ether, 1H, 1H, 2′H-perfluorodipropyl ether, ethyl nonafluorobutyl ether and the like are preferable.
  • the chain ether has the effect of reducing the viscosity of the electrolytic solution, like the chain carbonate. Therefore, for example, a chain ether can be used in place of a chain carbonate or carboxylic acid ester, and can also be used in combination with a chain carbonate or carboxylic acid ester.
  • the nonaqueous electrolytic solvent may contain the following in addition to the above.
  • Nonaqueous electrolytic solvents include, for example, ⁇ -lactones such as ⁇ -butyrolactone, chain ethers such as 1,2-ethoxyethane (DEE) or ethoxymethoxyethane (EME), and cyclic rings such as tetrahydrofuran or 2-methyltetrahydrofuran. Ethers and the like can be included. Moreover, what substituted some hydrogen atoms of these materials by the fluorine atom may be included.
  • an aprotic organic solvent such as dimethyl-2-imidazolidinone, 3-methyl-2-oxazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ethyl ether, 1,3-propane sultone, anisole,
  • Examples of the supporting salt include LiPF 6 , LiAsF 6 , LiAlCl 4 , LiClO 4 , LiBF 4 , LiSbF 6 , LiCF 3 SO 3 , LiC 4 F 9 CO 3 , LiC (CF 3 SO 2 ) 2 , LiN (CF 3 Examples thereof include lithium salts such as SO 2 ) 2 , LiN (C 2 F 5 SO 2 ) 2 , and LiB 10 Cl 10 .
  • Other examples of the supporting salt include lower aliphatic lithium carboxylate carboxylate, lithium chloroborane, lithium tetraphenylborate, LiBr, LiI, LiSCN, LiCl, and the like.
  • the supporting salt can be used alone or in combination of two or more.
  • the concentration of the supporting salt is preferably 0.5 to 1.5 mol / l in the electrolyte solution of the lithium salt.
  • the lithium secondary battery of the present invention may contain a cyclic sulfonate ester in the electrolytic solution.
  • cyclic sulfonic acid ester which can be used for this invention, the cyclic sulfonic acid ester represented by following formula (2) is mentioned, for example.
  • a and B each independently represent an alkylene group or a fluorinated alkylene group, and X represents a C—C single bond or —OSO 2 — group.
  • the number of carbon atoms of the alkylene group is, for example, 1 to 8, preferably 1 to 6, and more preferably 1 to 4.
  • a and B are each independently an alkylene group or a fluoroalkylene group, and X is a C—C single bond or —OSO 2 — group).
  • the fluorinated alkylene group represents a substituted alkylene group having a structure in which at least one hydrogen atom of the unsubstituted alkylene group is substituted with a fluorine atom.
  • the carbon number of the fluorinated alkylene group is, for example, 1 to 8, preferably 1 to 6, and more preferably 1 to 4.
  • the -OSO 2 -group may be in any direction.
  • the cyclic sulfonic acid ester is a cyclic monosulfonic acid ester, and the cyclic monosulfonic acid ester is preferably a compound represented by the following formula (4). .
  • R 101 and R 102 each independently represent a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 4 carbon atoms.
  • N is 0, 1, 2, 3, or 4. .
  • the cyclic sulfonic acid ester is a cyclic disulfonic acid ester
  • the cyclic disulfonic acid ester is preferably a compound represented by the following formula (5) .
  • R 201 to R 204 each independently represents a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 4 carbon atoms, and n is 1, 2, 3, or 4. , N is 2, 3, or 4, n R 203s may be the same or different from each other, and n R 204s may be the same or different from each other. May be.
  • Examples of the cyclic sulfonate ester include 1,3-propane sultone, 1,2-propane sultone, 1,4-butane sultone, 1,2-butane sultone, 1,3-butane sultone, 2,4-butane sultone, 1,3 -Monosulfonic acid esters such as pentansultone (when X in formula (2) is a single bond), methylenemethane disulfonic acid ester (1,5,2,4-dioxadithian-2,2,4,4-tetraoxide ), Disulfonic acid esters such as ethylenemethane disulfonic acid ester (when X in the formula (2) is —OSO 2 — group), and the like.
  • 1,3-propane sultone, 1,4-butane sultone, and methylene methane disulfonic acid ester are preferable from the viewpoint of film forming effect, availability, and cost.
  • the content of the cyclic sulfonic acid ester in the electrolytic solution is preferably 0.01 to 10% by mass, and more preferably 0.1 to 5% by mass.
  • a coating can be more effectively formed on the positive electrode surface to suppress decomposition of the electrolytic solution.
  • an ion conductive polymer may be added to the nonaqueous electrolytic solvent.
  • the ion conductive polymer include polyethers such as polyethylene oxide and polypropylene oxide, and polyolefins such as polyethylene and polypropylene.
  • the ion conductive polymer include polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl fluoride, polyvinyl chloride, polyvinylidene chloride, polymethyl methacrylate, polymethyl acrylate, polyvinyl alcohol, polymethacrylonitrile, and polyvinyl chloride.
  • Examples thereof include acetate, polyvinyl pyrrolidone, polycarbonate, polyethylene terephthalate, polyhexamethylene acipamide, polycaprolactam, polyurethane, polyethyleneimine, polybutadiene, polystyrene, or polyisoprene, or derivatives thereof.
  • An ion conductive polymer can be used individually by 1 type or in combination of 2 or more types. Moreover, you may use the polymer containing the various monomers which comprise the said polymer.
  • fluoroethylene carbonate may be included as an additive in the nonaqueous electrolytic solvent.
  • the positive electrode includes a positive electrode active material.
  • the positive electrode is formed, for example, by binding a positive electrode active material so as to cover the positive electrode current collector with a positive electrode binder.
  • the positive electrode of the lithium secondary battery according to the present embodiment preferably contains a positive electrode active material capable of inserting or extracting lithium ions at a potential of 4.5 V or higher with respect to lithium metal from the viewpoint of obtaining a high energy density.
  • the positive electrode active material that operates at a potential of 4.5 V or higher with respect to lithium can be selected by the following method, for example. First, a positive electrode containing a positive electrode active material and Li metal are placed in a state of facing each other with a separator interposed therebetween, and an electrolytic solution is injected to produce a battery. When charging / discharging is performed at a constant current of, for example, 5 mAh / g per positive electrode active material mass in the positive electrode, a charge / discharge capacity of 10 mAh / g or more per mass of active material is a potential of 4.5 V or more with respect to lithium. Can be a positive electrode active material that operates at a potential of 4.5 V or higher with respect to lithium.
  • the charge / discharge capacity per active material mass at a potential of 4.5 V or higher with respect to lithium is 20 mAh / g or higher. It is preferable that it is 50 mAh / g or more, and it is further more preferable that it is 100 mAh / g or more.
  • the shape of the battery can be, for example, a coin type.
  • positive electrode active materials examples include spinel materials, layered materials, and olivine materials.
  • spinel-based materials include LiNi 0.5 Mn 1.5 O 4 , LiCr x Mn 2-x O 4 (0.4 ⁇ x ⁇ 1.1), LiFe x Mn 2-x O 4 (0.4 ⁇ x ⁇ 1.1), LiCu x Mn 2-x O 4 (0.3 ⁇ x ⁇ 0.6), LiCo x Mn 2-x O 4 (0.4 ⁇ x ⁇ 1.1), and the like
  • a material that operates at a high potential of 4.5 V or higher with respect to lithium such as LiCoMnO 4 , LiCrMnO 4 , LiFeMnO 4 , LiCu 0.5 Mn 1.5 O 4 ; LiMn 2 O 4 a part of Mn increased the substituted to life with another element, LiM1 x Mn 2-x- y M2 y O 4 (M1 represents at least one selected Ni, Fe, Co, Cr, and Cu, 0 .4 ⁇ x ⁇ 1.1 and M2 is Li, Al , B, Mg, Si and transition
  • the spinel material a material represented by the following formula is particularly preferable.
  • M is Co
  • Y is at least one selected from the group consisting of Cr and Cu
  • Y is at least one selected from the group consisting of Li, B, Na, Al, Mg, Ti, Si, K, and Ca.
  • M preferably contains Ni, and preferably only Ni. This is because when M contains Ni, a high-capacity active material can be obtained relatively easily.
  • x is preferably 0.4 or more and 0.6 or less from the viewpoint of obtaining a high-capacity active material.
  • the positive electrode active material is LiNi 0.5 Mn 1.5 O 4 because a high capacity of 130 mAh / g or more can be obtained.
  • the lifetime may be improved by replacing a part of the Mn portion of these active materials with Li, B, Na, Al, Mg, Ti, SiK, Ca, or the like.
  • the life when 0 ⁇ y, the life may be improved.
  • Y when Y is Al, Mg, Ti, or Si, the life improvement effect is high.
  • Y when Y is Ti, it is more preferable because it provides a life improvement effect while maintaining a high capacity.
  • the range of y is preferably greater than 0 and less than or equal to 0.3. By setting y to 0.3 or less, it becomes easy to suppress a decrease in capacity.
  • Layered materials have the general formula: LiMO 2 (In the formula, M is at least one of Co and Ni.) Specifically, LiCoO 2 , LiNi 1-x M x O 2 (M is an element containing at least Co or Al, 0.05 ⁇ x ⁇ 0.3), Li (Ni x Co y Mn 2-x- y) O 2 (0.1 ⁇ x ⁇ 0.7,0 ⁇ y ⁇ 0.5), Li (M 1-z Mn z ) O 2 (8) (In formula (8), 0.7 ⁇ z ⁇ 0.33, and M is at least one of Li, Co, and Ni).
  • Li (M1 x M2 y Mn 1-xy ) O 2 (M1: at least one selected from the group consisting of Ni, Co and Fe, M2: at least one selected from the group consisting of Li, Mg and Al, 0.1 ⁇ x ⁇ 0.5, 0.05 ⁇ y ⁇ 0.3) and the like.
  • Li (Li x M 1-x -z Mn z) O 2 (9) (In Formula (9), 0 ⁇ x ⁇ 0.3, 0.33 ⁇ z ⁇ 0.7, M is at least one of Co and Ni) Is particularly preferred.
  • X in the formula of this material is preferably 0.1 ⁇ x ⁇ 0.3.
  • the olivine-based material has the general formula: LiMPO 4 (7) Specifically, LiFePO 4 , LiMnPO 4 , LiCoPO 4 , and LiNiPO 4 may be mentioned. Those in which a part of these transition metals is replaced with another element or the oxygen part is replaced with fluorine can also be used.
  • examples of the active material that operates at a potential of 4.5 V or more with respect to lithium include Si composite oxide.
  • examples of the Si composite oxide include Li 2 MSiO 4 (M: Mn, Fe, Co). At least one of them).
  • NASICON type lithium transition metal silicon composite oxide, and the like can be used.
  • the specific surface area of lithium-manganese composite oxide represented by the formula (6) is, for example, 0.01 ⁇ 5m 2 / g, preferably 0.05 ⁇ 4m 2 / g, 0.1 ⁇ 3m 2 / g Is more preferable, and 0.2 to 2 m 2 / g is more preferable.
  • the contact area with the electrolytic solution can be adjusted to an appropriate range. That is, when the specific surface area is 0.01 m 2 / g or more, lithium ions can be easily inserted and desorbed smoothly, and the resistance can be further reduced.
  • the center particle size of the lithium manganese composite oxide is preferably 0.1 to 50 ⁇ m, more preferably 0.2 to 40 ⁇ m.
  • the particle size can be measured by a laser diffraction / scattering particle size distribution measuring apparatus.
  • the positive electrode active material preferably includes an active material that operates at a potential of 4.5 V or more with respect to lithium, but may include a 4 V class active material.
  • the same negative electrode binder can be used.
  • polyvinylidene fluoride is preferable from the viewpoint of versatility and low cost.
  • the amount of the positive electrode binder used is preferably 2 to 10 parts by mass with respect to 100 parts by mass of the positive electrode active material from the viewpoints of “sufficient binding force” and “higher energy” which are in a trade-off relationship. .
  • the positive electrode binder other than polyvinylidene fluoride is not particularly limited, but polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer.
  • PVdF polyvinylidene fluoride
  • Polymers, styrene-butadiene copolymer rubber, polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamideimide and the like can also be used.
  • a conductive auxiliary material may be added to the positive electrode active material layer containing the positive electrode active material for the purpose of reducing impedance.
  • the conductive auxiliary material include carbonaceous fine particles such as graphite, carbon black, and acetylene black.
  • the positive electrode current collector for example, aluminum, nickel, silver, stainless steel (SUS), valve metal, or an alloy thereof can be used from the viewpoint of electrochemical stability.
  • the shape include foil, flat plate, and mesh.
  • an aluminum foil can be suitably used.
  • a negative electrode will not be specifically limited if the negative electrode active material contains the material which can occlude and discharge
  • the negative electrode active material is not particularly limited, and for example, a carbon material (a) that can occlude and release lithium ions, a metal that can be alloyed with lithium (b), or a metal that can occlude and release lithium ions.
  • An oxide (c) etc. are mentioned.
  • the carbon material (a) graphite, amorphous carbon, diamond-like carbon, carbon nanotube, or a composite thereof can be used.
  • graphite with high crystallinity has high electrical conductivity, and is excellent in adhesiveness and voltage flatness with a positive electrode current collector made of a metal such as copper.
  • amorphous carbon having low crystallinity has a relatively small volume expansion, it has a high effect of relaxing the volume expansion of the entire negative electrode, and deterioration due to non-uniformity such as crystal grain boundaries and defects hardly occurs.
  • the carbon material (a) can be used alone or in combination with other substances, but is preferably in the range of 2% by mass to 80% by mass in the negative electrode active material, and is preferably 2% by mass to 30% by mass. More preferably, it is in the range of% or less.
  • the metal (b) a metal mainly composed of Al, Si, Pb, Sn, Zn, Cd, Sb, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, La, or the like, or these Two or more kinds of alloys, or an alloy of these metals or alloys and lithium can be used.
  • silicon (Si) is preferably included as the metal (b).
  • the metal (b) can be used alone or in combination with other substances, but is preferably in the range of 5% by mass to 90% by mass in the negative electrode active material, and is 20% by mass to 50% by mass. The following range is more preferable.
  • silicon oxide, aluminum oxide, tin oxide, indium oxide, zinc oxide, lithium oxide, or a composite thereof can be used as the metal oxide (c).
  • silicon oxide is preferably included as the metal oxide (c). This is because silicon oxide is relatively stable and hardly causes a reaction with other compounds.
  • one or more elements selected from nitrogen, boron, and sulfur may be added to the metal oxide (c), for example, 0.1 to 5% by mass. By carrying out like this, the electrical conductivity of a metal oxide (c) can be improved.
  • the metal oxide (c) can be used alone or in combination with other substances, but is preferably in the range of 5% by mass or more and 90% by mass or less in the negative electrode active material, and is 40% by mass or more and 70% by mass. More preferably, it is in the range of mass% or less.
  • metal oxide (c) examples include, for example, LiFe 2 O 3 , WO 2 , MoO 2 , SiO, SiO 2 , CuO, SnO, SnO 2 , Nb 3 O 5 , Li x Ti 2-x O 4. (1 ⁇ x ⁇ 4/3), PbO 2 , Pb 2 O 5 and the like.
  • the negative electrode active material include metal sulfide (d) that can occlude and release lithium ions.
  • Metal sulfide as (d) are, for example, SnS and FeS 2 or the like.
  • Other examples of the negative electrode active material include metal lithium or lithium alloy, polyacene or polythiophene, or Li 5 (Li 3 N), Li 7 MnN 4 , Li 3 FeN 2 , Li 2.5 Co 0. Examples thereof include lithium nitride such as 5 N or Li 3 CoN.
  • These negative electrode active materials can be used alone or in admixture of two or more.
  • the negative electrode active material can include a carbon material (a), a metal (b), and a metal oxide (c).
  • this negative electrode active material will be described.
  • the amorphous metal oxide (c) can suppress the volume expansion of the carbon material (a) and the metal (b), and can suppress the decomposition of the electrolytic solution. This mechanism is presumed to have some influence on the film formation on the interface between the carbon material (a) and the electrolytic solution due to the amorphous structure of the metal oxide (c).
  • the amorphous structure is considered to have relatively few elements due to non-uniformity such as crystal grain boundaries and defects.
  • the metal oxide (c) does not have an amorphous structure, a peak specific to the metal oxide (c) is observed, but all or part of the metal oxide (c) is amorphous. In the case of having a structure, the intrinsic peak of the metal oxide (c) is broad and observed.
  • the metal oxide (c) is preferably a metal oxide constituting the metal (b).
  • the metal (b) and the metal oxide (c) are preferably silicon (Si) and silicon oxide (SiO), respectively.
  • the metal (b) is preferably dispersed entirely or partially in the metal oxide (c).
  • the metal (b) is preferably dispersed entirely or partially in the metal oxide (c).
  • the volume expansion of the whole negative electrode can be further suppressed, and the decomposition of the electrolytic solution can also be suppressed.
  • all or part of the metal (b) is dispersed in the metal oxide (c) because it is observed with a transmission electron microscope (general TEM observation) and energy dispersive X-ray spectroscopy (general). This can be confirmed by using a combination of a standard EDX measurement.
  • the cross section of the sample containing the metal (b) particles is observed, the oxygen concentration of the metal (b) particles dispersed in the metal oxide (c) is measured, and the metal (b) particles are configured. It can be confirmed that the metal being used is not an oxide.
  • each carbon material (a), metal (b), and metal oxide (c) with respect to the total of the carbon material (a), metal (b), and metal oxide (c) is these are preferably 2% by mass or more and 80% by mass or less, 5% by mass or more and 90% by mass or less, and 5% by mass or more and 90% by mass or less.
  • the content rate of each carbon material (a), metal (b), and metal oxide (c) with respect to the sum total of a carbon material (a), a metal (b), and a metal oxide (c) is respectively More preferably, they are 2 mass% or more and 30 mass% or less, 20 mass% or more and 50 mass% or less, and 40 mass% or more and 70 mass% or less.
  • a negative electrode active material in which all or part of the metal oxide (c) has an amorphous structure and all or part of the metal (b) is dispersed in the metal oxide (c) is disclosed in, for example, It can be produced by the method disclosed in 2004-47404. That is, by performing a CVD process on the metal oxide (c) in an atmosphere containing an organic gas such as methane gas, the metal (b) in the metal oxide (c) is nanoclustered and the surface is a carbon material (a ) Can be obtained. Moreover, the said negative electrode active material is producible also by mixing a carbon material (a), a metal (b), and a metal oxide (c) by mechanical milling.
  • the carbon material (a), the metal (b), and the metal oxide (c) are not particularly limited, but particulate materials can be used.
  • the average particle diameter of the metal (b) may be smaller than the average particle diameter of the carbon material (a) and the average particle diameter of the metal oxide (c).
  • the metal (b) having a large volume change during charging and discharging has a relatively small particle size
  • the carbon material (a) and the metal oxide (c) having a small volume change have a relatively large particle size. Therefore, dendrite formation and alloy pulverization are more effectively suppressed.
  • lithium is occluded and released in the order of small particle size, large particle size, and small particle size during the charge / discharge process. This also suppresses the occurrence of residual stress and residual strain. Is done.
  • the average particle diameter of the metal (b) can be, for example, 20 ⁇ m or less, and is preferably 15 ⁇ m or less.
  • the average particle diameter of a metal oxide (c) is 1/2 or less of the average particle diameter of a carbon material (a), and the average particle diameter of a metal (b) is an average of a metal oxide (c). It is preferable that it is 1/2 or less of a particle diameter. Furthermore, the average particle diameter of the metal oxide (c) is 1 ⁇ 2 or less of the average particle diameter of the carbon material (a), and the average particle diameter of the metal (b) is the average particle diameter of the metal oxide (c). It is more preferable that it is 1/2 or less.
  • the average particle diameter of the silicon oxide (c) is set to 1/2 or less of the average particle diameter of the graphite (a), and the average particle diameter of the silicon (b) is the average particle of the silicon oxide (c). It is preferable to make it 1/2 or less of the diameter. More specifically, the average particle diameter of silicon (b) can be, for example, 20 ⁇ m or less, and is preferably 15 ⁇ m or less.
  • the negative electrode active material graphite whose surface is covered with a low crystalline carbon material can be used.
  • the surface of the graphite is covered with a low crystalline carbon material, which suppresses the reaction between the negative electrode active material and the electrolyte even when high energy density and high conductivity graphite is used as the negative electrode active material. can do. Therefore, by using the graphite covered with the low crystalline carbon material as the negative electrode active material, the capacity retention rate of the battery can be improved, and the battery capacity can be improved.
  • the graphite covered with the low crystalline carbon material can be obtained, for example, by coating particulate graphite with the low crystalline carbon material.
  • the average particle diameter (volume average: D 50 ) of the graphite particles is preferably 5 ⁇ m or more and 30 ⁇ m or less.
  • the graphite preferably has crystallinity, and the I D / IG value of the graphite is more preferably 0.01 or more and 0.08 or less.
  • the thickness of the low crystalline carbon material is preferably 0.01 ⁇ m or more and 5 ⁇ m or less, and more preferably 0.02 ⁇ m or more and 1 ⁇ m or less.
  • the average particle diameter (D 50 ) can be measured using, for example, a laser diffraction / scattering particle diameter / particle size distribution measuring apparatus Microtrac MT3300EX (Nikkiso).
  • the low crystalline carbon material can be formed on the surface of graphite by using a vapor phase method in which hydrocarbons such as propane and acetylene are thermally decomposed to deposit carbon.
  • the low crystalline carbon material can be formed, for example, by using a method in which pitch or tar is attached to the surface of graphite and firing at 800 to 1500 ° C.
  • Graphite has a crystal structure in which the 002 plane layer spacing d 002 is preferably 0.33 nm or more and 0.34 nm or less, more preferably 0.333 nm or more and 0.337 nm or less, and still more preferably 0.336 nm. It is as follows. Such highly crystalline graphite has a high lithium storage capacity and can improve charge and discharge efficiency.
  • the interlayer distance of graphite can be measured by, for example, X-ray diffraction.
  • the specific surface area of the graphite covered with the low crystalline carbon material is, for example, 0.01 to 20 m 2 / g, preferably 0.05 to 10 m 2 / g, and 0.1 to 5 m 2 / g. More preferably, it is 0.2 to 3 m 2 / g.
  • the graphite used as the base material is preferably highly crystalline.
  • artificial graphite or natural graphite can be used, but is not particularly limited thereto.
  • As the material of low crystalline carbon for example, coal tar, pitch coke, phenol resin and mixed with high crystalline carbon can be used.
  • a mixture is prepared by mixing 5 to 50% by mass of low crystalline carbon material with high crystalline carbon. After the mixture is heated to 150 ° C. to 300 ° C., heat treatment is further performed in the range of 600 ° C. to 1500 ° C. As a result, surface-treated graphite having a surface coated with low crystalline carbon can be obtained.
  • the heat treatment is preferably performed in an inert gas atmosphere such as argon, helium, or nitrogen.
  • the negative electrode active material may contain other active materials besides graphite covered with the low crystalline carbon material.
  • the binder for the negative electrode is not particularly limited, but polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, styrene-butadiene copolymer.
  • PVdF polyvinylidene fluoride
  • Polymerized rubber, polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamideimide and the like can be mentioned.
  • the content of the negative electrode binder is preferably in the range of 1 to 30% by mass, more preferably 2 to 25% by mass with respect to the total amount of the negative electrode active material and the negative electrode binder.
  • the content is preferably in the range of 1 to 30% by mass, more preferably 2 to 25% by mass with respect to the total amount of the negative electrode active material and the negative electrode binder.
  • the negative electrode current collector is not particularly limited, but aluminum, nickel, copper, silver, and alloys thereof are preferable from the viewpoint of electrochemical stability.
  • Examples of the shape include foil, flat plate, and mesh.
  • the negative electrode can be produced by forming a negative electrode active material layer containing a negative electrode active material and a negative electrode binder on a negative electrode current collector.
  • Examples of the method for forming the negative electrode active material layer include a doctor blade method, a die coater method, a CVD method, and a sputtering method.
  • a thin film of aluminum, nickel, or an alloy thereof may be formed by a method such as vapor deposition or sputtering to form a negative electrode current collector.
  • the secondary battery can be composed of a combination of a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte as its configuration.
  • the separator include a woven fabric, a nonwoven fabric, a polyolefin such as polyethylene and polypropylene, a porous polymer film such as polyimide, a porous polyvinylidene fluoride film, and an ion conductive polymer electrolyte film. These can be used alone or in combination.
  • Examples of the shape of the battery include a cylindrical shape, a square shape, a coin shape, a button shape, and a laminate shape.
  • Examples of the battery outer package include stainless steel, iron, aluminum, titanium, alloys thereof, and plated products thereof. As the plating, for example, nickel plating can be used.
  • examples of the laminate resin film used for the laminate mold include aluminum, aluminum alloy, and titanium foil.
  • examples of the material of the heat-welded portion of the metal laminate resin film include thermoplastic polymer materials such as polyethylene, polypropylene, and polyethylene terephthalate.
  • the metal laminate resin layer and the metal foil layer are not limited to one layer, and may be two or more layers.
  • the exterior body can be appropriately selected as long as it is stable to the electrolyte and has a sufficient water vapor barrier property.
  • a laminated laminate type secondary battery a laminate film made of aluminum, silica-coated polypropylene, polyethylene, or the like can be used as the outer package.
  • an aluminum laminate film from the viewpoint of suppressing volume expansion.
  • FIG. 1 is a schematic diagram showing the configuration of a lithium secondary battery produced in this example.
  • a lithium secondary battery includes a positive electrode active material layer 1 containing a positive electrode active material on a positive electrode current collector 3 made of metal such as aluminum foil, and a negative electrode current collector made of metal such as copper foil. And a negative electrode active material layer 2 containing a negative electrode active material on the body 4.
  • the positive electrode active material layer 1 and the negative electrode active material layer 2 are disposed to face each other with a separator 5 made of an electrolytic solution, a nonwoven fabric containing the electrolyte, a polypropylene microporous film, and the like.
  • 6 and 7 are exterior bodies
  • 8 is a negative electrode tab
  • 9 is a positive electrode tab.
  • the positive electrode active material of this example was produced as follows.
  • a material is selected from MnO 2 , NiO, Fe 2 O 3 , TiO 2 , B 2 O 3 , CoO, Li 2 CO 3 , MgO, Al 2 O 3 , and LiF so as to have a desired metal composition ratio.
  • LiNi 0.5 Mn 1.5 O 4 was produced by firing the powder after mixing the raw materials at a firing temperature of 500 to 1000 ° C. for 8 hours.
  • LiNi 0.5 Mn 1.5 O 4 as a positive electrode active material, polyvinylidene fluoride (PVDF) (5 mass%) as a binder, and carbon black (5 mass%) as a conductive agent are mixed.
  • a positive electrode slurry was prepared by dispersing the positive electrode mixture in N-methyl-2-pyrrolidone. This positive electrode slurry was uniformly applied to one side of an aluminum current collector having a thickness of 20 ⁇ m. The thickness of the coating film was adjusted so that the initial charge capacity per unit area was 2.5 mAh / cm 2 . After drying, a positive electrode was produced by compression molding with a roll press.
  • a negative electrode slurry was prepared by dispersing in artificial graphite and N-methylpyrrolidone in which PVDF was dissolved as a binder. The mass ratio between the negative electrode active material and the binder was 90/10. This negative electrode slurry was uniformly coated on a 10 ⁇ m thick Cu current collector. After drying, a negative electrode was produced by compression molding with a roll press.
  • a positive electrode and a negative electrode cut out to 1.5 cm ⁇ 3 cm were arranged so as to face each other with a separator interposed therebetween. Five positive electrodes and six negative electrodes were alternately stacked.
  • As the separator a microporous polypropylene film having a thickness of 25 ⁇ m was used.
  • a solvent and a solvent containing 2% by volume of fluoroethylene carbonate (FEC) as an additive were used.
  • the above positive electrode, negative electrode, separator, and electrolyte were placed in a laminate outer package, the laminate was sealed, and a lithium secondary battery was produced.
  • the positive electrode and the negative electrode were connected to a tab and electrically connected from the outside of the laminate.
  • Charging conditions constant current constant voltage method, charging end voltage 4.75 V, charging current 10 mA, total charging time 10 hours
  • Charging conditions constant current constant voltage method, charging end voltage 4.75 V, charging current 50 mA, total charging time 2.5 hours
  • the actual resistance measured by the AC impedance method at 100 mHz increased by 0.59 ⁇ .
  • the high frequency side negative charge transfer resistance Rct2 obtained by fitting to the circuit model is 0.22 ⁇ from 0.28 ⁇ to 0.50 ⁇ , and the low frequency side positive charge transfer resistance Rct is 0.90 ⁇ to 0.97 ⁇ from 0.90 ⁇ . Changed by 07 ⁇ .
  • the projection value ⁇ Rx is 0.36 ⁇ .
  • LiPF 6 is 0.8 mol / l
  • EC / TFETFPE / PTTFE / propylene carbonate (PC) 2/2/5/1
  • the additive is cyclic disulfonate (1,5,2,4-dioxodithiane-2,2 , 4,4-tetraoxide)
  • a lithium secondary battery was prepared and measured in the same manner as in Example 1 except that 0.8 wt% electrolytic solution was used. The actual resistance measured by the AC impedance method at 100 mHz increased by 0.58 ⁇ .
  • the high-frequency side negative charge transfer resistance Rct2 obtained by fitting to the circuit model is 0.24 ⁇ from 0.57 ⁇ to 0.81 ⁇ , and the low-frequency side positive charge transfer resistance Rct is 0.40 ⁇ to 0.76 ⁇ . It changed by 34 ⁇ .
  • the projection value ⁇ Rx is ⁇ 0.26 ⁇ .
  • the resistance is evaluated by the AC impedance method from 100 mHz to 300 kHz, and the relationship between ⁇ Rct and ⁇ Rct2 extracted by fitting the equivalent circuit shown in FIG. As shown in FIG. Despite changing the lithium salt concentration, electrolyte composition, additives, etc., ⁇ Rct and ⁇ Rct2 showed a strong negative correlation.
  • normalized values ⁇ Rc and ⁇ Ra can be obtained by projecting in a radiation direction from a point ( ⁇ Rct2, ⁇ Rct) onto a circle having a radius of 1 ⁇ centered on the origin and normalizing. Subsequently, as shown in FIG.
  • FIG. 6 shows a distribution of the change amount ⁇ Rall of the actual resistance value measured by the AC impedance method at 100 mHz.
  • -0.6 is the meaning of the average value of all evaluation data of various electrolytes, and it can be easily estimated that this value changes if it is classified for each electrolyte. For this reason, for example, it is considered that a value in the range from -1/3, which is approximately half the size, to -3, which is the reciprocal, can be taken as a value.
  • FIG. 5 shows that ⁇ Rall tends to be minimum when the horizontal axis is near zero. For example, in order to set ⁇ Rall to 1.7 ⁇ or less, the projection value ⁇ Rx needs to be between 0 ⁇ ⁇ 0.5 ⁇ . By setting ⁇ Rx between 0 ⁇ ⁇ 0.3 ⁇ , ⁇ Rall can be further reduced.
  • the cell is selected as a cell that is likely to become defective due to an abnormality, and ⁇ Rx is Those within a predetermined range can be selected as good products.
  • the technology of the present invention can also be used as a means for selecting a lithium ion secondary battery.
  • the selection method of the lithium ion secondary battery of the present invention is LiCoPO 4 , Li (Co 0.5 Mn 0.5 ) O 2 , Li (Li 0.2 M 0. it is suggested also effective in 3 Mn 0.5) O 2 cathode material or the like.

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Abstract

La présente invention concerne une batterie secondaire au lithium pourvue d'une électrode positive comprenant un matériau actif d'électrode positive, une électrode négative comprenant un matériau actif d'électrode négative, et une solution d'électrolyte comprenant un solvant d'électrolyte non aqueux. Sur un plan défini par deux axes orthogonaux dont l'un représente le changement de résistance au transfert de charge au niveau de l'électrode positive et l'autre représente le changement de résistance au transfert de charge au niveau de l'électrode négative, les points (ΔRct2, ΔRct) représentant le changement (ΔRct) de résistance au transfert de charge au niveau de l'électrode positive et le changement (ΔRct2) de résistance au transfert de charge au niveau de l'électrode négative avant et après application d'une contrainte prédéterminée sont projetés, dans la direction d'une ligne radiale, sur un cercle ayant pour centre l'origine et pour rayon 1Ω, et normalisés sous forme des points (ΔRa, ΔRc). Sur un plan défini par deux axes orthogonaux dont l'un représente le changement de résistance au transfert de charge au niveau de l'électrode positive après normalisation et l'autre représente le changement de résistance au transfert de charge au niveau de l'électrode négative après normalisation, les distances par rapport à l'origine des points obtenus par projection des points (ΔRa, ΔRc) perpendiculairement à une ligne passant par l'origine se situent dans une plage prédéterminée.
PCT/JP2013/084154 2012-12-26 2013-12-19 Batterie secondaire au lithium et son procédé de sélection WO2014103893A1 (fr)

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CN110611098A (zh) * 2019-10-23 2019-12-24 陕西煤业化工技术研究院有限责任公司 一种高放射状、高振实的镍钴铝酸锂前驱体及其制备方法
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