WO2018088311A1 - Negative electrode for non-aqueous-electrolyte-based electrochemical element, method for manufacturing said electrode, lithium-ion secondary cell, and method for manufacturing said cell - Google Patents

Negative electrode for non-aqueous-electrolyte-based electrochemical element, method for manufacturing said electrode, lithium-ion secondary cell, and method for manufacturing said cell Download PDF

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WO2018088311A1
WO2018088311A1 PCT/JP2017/039660 JP2017039660W WO2018088311A1 WO 2018088311 A1 WO2018088311 A1 WO 2018088311A1 JP 2017039660 W JP2017039660 W JP 2017039660W WO 2018088311 A1 WO2018088311 A1 WO 2018088311A1
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negative electrode
active material
mixture layer
positive electrode
electrode active
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PCT/JP2017/039660
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French (fr)
Japanese (ja)
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阿部　浩史
祐介 中村
春樹 上剃
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マクセルホールディングス株式会社
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Priority to JP2018550168A priority Critical patent/JPWO2018088311A1/en
Publication of WO2018088311A1 publication Critical patent/WO2018088311A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • 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
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    • 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
    • H—ELECTRICITY
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    • 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
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
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    • 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
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
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    • 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
    • H01M4/139—Processes of manufacture
    • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
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    • 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
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
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    • 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
    • H—ELECTRICITY
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    • 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
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/443—Particulate material
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    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • 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 negative electrode for a non-aqueous electrolyte based electrochemical device having excellent productivity and a method for producing the same, and a lithium ion secondary battery having the negative electrode and having excellent charge / discharge cycle characteristics and a method for producing the same. is there.
  • lithium ion secondary batteries have high voltage and high capacity, there are great expectations for their development. Particularly recently, improvements have been made not only to positive electrode active materials and negative electrode active materials involved in battery reactions and non-aqueous electrolytes, but also to binders used in positive electrodes and negative electrodes.
  • Patent Documents 1 and 2 by using a copolymer of vinyl alcohol and an alkali metal neutralized ethylenically unsaturated carboxylic acid as a binder for the negative electrode mixture layer, the negative electrode active material can be removed or the negative electrode composite can be removed. A technique for suppressing peeling of the agent layer from the current collector has been proposed.
  • a negative electrode active material has been used as a widely used graphite.
  • Li lithium
  • Si silicon
  • Sn titanium
  • high capacity negative electrode material a material that can accommodate more Li (lithium) such as low crystalline carbon, Si (silicon), Sn (tin), etc.
  • the negative electrode (negative electrode mixture layer) is doped with Li ions (pre-doping) to increase the proportion of Li that can travel between the positive electrode and the negative electrode during charge / discharge of the battery.
  • pre-doping Li ions into the negative electrode
  • Patent Documents 3 and 4 Such a pre-doping technique of Li ions into the negative electrode is described in Patent Documents 3 and 4 in addition to means for pre-doping Li ions into the negative electrode in the battery (hereinafter sometimes referred to as “in-system pre-doping”).
  • the negative electrode active material in the negative electrode mixture layer is doped with Li ions by pre-doping outside the system, the hardness of the negative electrode mixture layer increases and becomes brittle, so that the handleability is reduced compared to before doping with Li ions, This tends to reduce the productivity of the negative electrode, and there is room for improvement in this respect.
  • the negative electrode before doping with Li ions is wound into a roll shape
  • Li ions are doped while the negative electrode drawn from the roll is transported, and then wound into a roll shape again. It is also conceivable to dope Li ions continuously by the so-called roll-to-roll method.
  • the productivity of the negative electrode is particularly high. The decline tends to be noticeable.
  • the negative electrode active material is directly doped with Li ions, and the negative electrode is produced using this, the negative electrode mixture layer is likely to be brittle.
  • the productivity of the negative electrode may be reduced.
  • the hardness of the negative electrode mixture layer is increased by doping Li ions by pre-doping outside the system, the charge / discharge cycle characteristics of the lithium ion secondary battery are likely to be lowered, and there is room for improvement in this respect.
  • the present invention has been made in view of the above circumstances, and its object is to provide a negative electrode for a non-aqueous electrolyte based electrochemical device excellent in productivity, a method for producing the same, and the negative electrode, and charge / discharge cycle characteristics.
  • An excellent lithium ion secondary battery and a method for manufacturing the same are provided.
  • the negative electrode for a non-aqueous electrolyte based electrochemical device of the present invention that has achieved the above object has a negative electrode mixture layer containing a negative electrode active material and a binder, and the negative electrode mixture layer contains Li ions. It contains at least a doped negative electrode active material and a copolymer having a unit represented by the following formula (1) and a unit represented by the following formula (2) as the binder. It is a feature.
  • R is hydrogen or a methyl group
  • M ′ is an alkali metal element
  • the negative electrode for a non-aqueous electrolyte based electrochemical device of the present invention is a step of doping Li ions into the negative electrode active material in the negative electrode mixture layer of a negative electrode having a negative electrode mixture layer containing a negative electrode active material and a binder. It can manufacture by the manufacturing method (1) of this invention which has these.
  • the negative electrode for a non-aqueous electrolyte based electrochemical device of the present invention includes a step of producing a negative electrode having a negative electrode mixture layer containing a negative electrode active material doped with Li ions at least partially and a binder. It can also be produced by the production method (2) of the invention.
  • the lithium ion secondary battery of the present invention comprises a negative electrode, a positive electrode having a positive electrode mixture layer containing a positive electrode active material and a binder, a separator, and a nonaqueous electrolyte solution housed in an exterior body.
  • the negative electrode for an electrolyte-based electrochemical device is configured as the negative electrode.
  • the lithium ion secondary battery according to the present invention includes a step of assembling a lithium ion secondary battery using the negative electrode for a non-aqueous electrolyte based electrochemical device obtained by the production method (1) or (2). It can be manufactured by a manufacturing method.
  • a negative electrode for a non-aqueous electrolyte based electrochemical device having excellent productivity and a method for producing the same, and a lithium ion secondary battery having the negative electrode and having excellent charge / discharge cycle characteristics and a method for producing the same are disclosed. Can be provided.
  • the negative electrode for a non-aqueous electrolyte based electrochemical device of the present invention (hereinafter simply referred to as “negative electrode”) has a non-aqueous electrolyte such as a lithium ion secondary battery or a supercapacitor and is repeatedly charged and discharged. It is used for the negative electrode of a chemical element.
  • the negative electrode of the present invention has a negative electrode mixture layer containing a negative electrode active material and a binder.
  • the negative electrode mixture layer has a structure in which the negative electrode mixture layer is formed on one side or both sides of a current collector. At least a part of the negative electrode active material contained in the negative electrode mixture layer is doped with Li ions by pre-doping outside the system.
  • the negative electrode (the negative electrode mixture layer) in which the negative electrode active material in the negative electrode mixture layer is doped with Li ions by pre-doping outside the system has a large hardness and becomes brittle. Therefore, especially when performing pre-doping outside the system by a roll-to-roll method, the negative electrode mixture layer tends to collapse or peel from the negative electrode current collector when the negative electrode after Li ion doping is wound into a roll. Further, even when the roll-to-roll method is not adopted, for example, the negative electrode mixture layer containing a negative electrode active material previously doped with Li ions is obtained by performing pre-doping outside the system by the roll-to-roll method.
  • the negative electrode containing the negative electrode active material that has been pre-doped in this way is low in handleability as in the case of. For these reasons, there is a problem that productivity is low in the case of a negative electrode containing a negative electrode active material that is pre-doped outside and doped with Li ions.
  • the negative electrode active material that requires doping of Li ions has a large amount of expansion / contraction due to charging / discharging of the battery, and the negative electrode mixture layer containing this greatly expands / contracts along with charging / discharging of the battery.
  • an electrochemical element such as a lithium ion secondary battery using a negative electrode whose hardness of the negative electrode mixture layer is increased by pre-doping outside the system, the hard and brittle negative electrode mixture layer is defective due to a large volume change due to charge and discharge. Therefore, the capacity is likely to decrease due to repeated charge and discharge.
  • copolymer (A ) a copolymer having a unit represented by the above formula (1) and a unit represented by the above formula (2) in the binder of the negative electrode mixture layer [hereinafter referred to as “copolymer (A ) ”)].
  • the negative electrode mixture layer using the copolymer (A) as a binder has high flexibility and also improves the peel strength from the negative electrode current collector. In addition, defects in the negative electrode mixture layer hardly occur and the handleability is improved. Therefore, the negative electrode of the present invention has good productivity even if it contains a negative electrode active material that has undergone extra-predoping. And when manufacturing the negative electrode of this invention, even when it carries out out-of-system pre dope by a roll-to-roll method, since a defect part does not generate
  • the deterioration of the negative electrode mixture layer due to repeated charge and discharge can be suppressed. Charge / discharge cycle characteristics are improved.
  • the load characteristics of an electrochemical element such as a lithium ion secondary battery are also improved. This is thought to be because the negative electrode mixture layer using the copolymer (A) as a binder has a structure in which the nonaqueous electrolytic solution penetrates well inside.
  • the copolymer (A) as a binder it is possible to highly suppress the precipitation of Li on the negative electrode surface that may occur with the use of an electrochemical element.
  • carbon materials such as graphite, pyrolytic carbons, cokes, glassy carbons, fired bodies of organic polymer compounds, mesocarbon microbeads, carbon fibers, activated carbon; Si or Sn simple substance; Si or Sn-containing alloy; Si or Sn-containing oxide; As the negative electrode active material, only one of these may be used, or two or more may be used in combination.
  • a material containing Si and O as constituent elements a material containing Si and O as constituent elements (although the atomic ratio x of O with respect to Si is preferably 0.5 ⁇ x ⁇ 1.5 (hereinafter, this material may be referred to as “material S”).
  • Examples of the material S include materials containing Si and O as constituent elements and not containing Li as a constituent element, such as those represented by the composition formula SiO x (0.5 ⁇ x ⁇ 1.5). Can be mentioned.
  • the SiO x may contain Si microcrystal or amorphous phase.
  • the atomic ratio of Si and O is a ratio including Si microcrystal or amorphous phase Si. That is, the SiO x includes a structure in which Si (for example, microcrystalline Si) is dispersed in an amorphous SiO 2 matrix, and is dispersed in the amorphous SiO 2 .
  • the material S preferably constitutes a composite that is combined with a carbon material.
  • the surface of the material S is preferably coated with the carbon material.
  • a conductive material conductive aid
  • the material S and the conductive material in the negative electrode are electrically conductive. It is necessary to form an excellent conductive network by making good mixing and dispersion with the conductive material.
  • the conductive network in the negative electrode is better than when a material obtained by simply mixing the material S and a conductive material such as a carbon material is used. Formed.
  • Examples of the composite of the material S and the carbon material include a granulated body of the material S and the carbon material as well as the material S coated with the carbon material as described above.
  • a carbon material that can be used for forming a composite with the material S for example, low crystalline carbon, carbon nanotube, vapor grown carbon fiber, and the like are preferable.
  • the details of the carbon material include at least one selected from the group consisting of fibrous or coiled carbon materials, carbon black (including acetylene black and ketjen black), artificial graphite, graphitizable carbon, and non-graphitizable carbon.
  • a seed material is preferred.
  • a fibrous or coiled carbon material is preferable in that it easily forms a conductive network and has a large surface area.
  • Carbon black (including acetylene black and ketjen black), graphitizable carbon, and non-graphitizable carbon have high electrical conductivity and high liquid retention. Even if the particles expand and contract, it is preferable in that it has a property of easily maintaining contact with the particles.
  • a fibrous carbon material is particularly preferable as a material used when the composite with the material S is a granulated body.
  • the fibrous carbon material has a thin thread shape and high flexibility, so that it can follow the expansion and contraction of the material S that accompanies charging / discharging of the battery, and since the bulk density is large, This is because it can have many junctions.
  • the fibrous carbon include polyacrylonitrile (PAN) -based carbon fiber, pitch-based carbon fiber, vapor-grown carbon fiber, and carbon nanotube, and any of these may be used.
  • the ratio of the material S to the carbon material is preferably 3 parts by mass or more of the carbon material with respect to 100 parts by mass of the material S: 5 parts by mass or more. More preferably, it is more preferably 7 parts by mass or more, more preferably 20 parts by mass or less, and even more preferably 17 parts by mass or less.
  • Li ions when Li ions are doped, the charge / discharge cycle characteristics of the battery can be further improved by adjusting the ratio of the material S and the carbon material in the composite as described above. It becomes.
  • the composite of the material S and the carbon material can be obtained by, for example, the following method.
  • the particles of the material S and the hydrocarbon gas are heated in the gas phase, and are generated by thermal decomposition of the hydrocarbon gas. Carbon is deposited on the surface of the particles.
  • the hydrocarbon-based gas spreads to every corner of the particle of the material S, and a thin and uniform film (carbon) containing a conductive carbon material on the particle surface. Since the material covering layer) can be formed, the conductivity of the particles of the material S can be imparted with good uniformity with a small amount of carbon material.
  • the processing temperature (atmosphere temperature) of the CVD method varies depending on the type of hydrocarbon gas, but is usually 600 to 1200 ° C., and more preferably 700 ° C. It is preferable that it is above, and it is still more preferable that it is 800 degreeC or more. This is because the higher the treatment temperature, the less the remaining impurities, and the formation of a coating layer containing carbon having high conductivity.
  • liquid source of hydrocarbon gas toluene, benzene, xylene, mesitylene and the like can be used, but toluene that is easy to handle is particularly preferable.
  • a hydrocarbon-based gas can be obtained by vaporizing them (for example, bubbling with nitrogen gas).
  • methane gas, acetylene gas, etc. can also be used.
  • a dispersion liquid in which the material S is dispersed in a dispersion medium is prepared, sprayed and dried to obtain a granulated body including a plurality of particles.
  • ethanol or the like can be used as the dispersion medium. It is appropriate to spray the dispersion liquid in an atmosphere of 50 to 300 ° C.
  • a granulated body of the material S and the carbon material can be produced also by a granulating method by a mechanical method using a vibration type or planetary type ball mill or rod mill.
  • the average particle size of the material S is too small, the dispersibility of the material S may be reduced and the effects of the present invention may not be sufficiently obtained, and the material S has a large volume change associated with charging / discharging of the battery. If the average particle diameter is too large, the material S is likely to collapse due to expansion / contraction (this phenomenon leads to capacity degradation of the material S), and therefore it is preferably 0.1 ⁇ m or more and 10 ⁇ m or less.
  • the content of the composite in the total amount of the negative electrode active material contained in the negative electrode mixture layer is, for example, 5% by mass or more from the viewpoint of better ensuring the effect of increasing the battery capacity by using the composite. It is preferably 10% by mass or more, more preferably 20% by mass or more, and further preferably 50% by mass or more.
  • the suitable upper limit of content of the said composite in the negative electrode active material whole quantity which a negative mix layer contains is 100 mass%.
  • the content of the negative electrode active material in the negative electrode mixture layer (total content of all negative electrode active materials) is preferably 80 to 99.5% by mass.
  • the copolymer (A) used as a binder for the negative electrode mixture layer saponifies a copolymer obtained by polymerizing vinyl ester and at least one of acrylic acid ester and methacrylic acid ester as monomers. Can be obtained.
  • Examples of the vinyl ester for obtaining the copolymer (A) include vinyl acetate, vinyl propionate, and vinyl pivalate, and one or more of these can be used. Among these vinyl esters, vinyl acetate is more preferable.
  • copolymer of vinyl ester and at least one of acrylic acid ester and methacrylic acid ester for obtaining copolymer (A) is a unit derived from monomers other than vinyl ester, acrylic acid ester and methacrylic acid ester. You may have.
  • the copolymer of vinyl ester and at least one of acrylic acid ester and methacrylic acid ester is a suspension in which polymerization is performed in a state where these monomers are suspended in an aqueous solution containing a polymerization catalyst and a dispersant, for example.
  • Polymerization can be performed by a turbid polymerization method.
  • organic peroxides such as benzoyl peroxide and lauryl peroxide
  • azo compounds such as azobisisobutyronitrile and azobisdimethylvaleronitrile; and the like can be used.
  • the dispersant used in the suspension polymerization includes water-soluble polymers (polyvinyl alcohol, poly (meth) acrylic acid or a salt thereof, polyvinyl pyrrolidone, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, etc.), inorganic compounds (Calcium phosphate, magnesium silicate, etc.) can be used.
  • water-soluble polymers polyvinyl alcohol, poly (meth) acrylic acid or a salt thereof, polyvinyl pyrrolidone, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, etc.
  • inorganic compounds Calcium phosphate, magnesium silicate, etc.
  • the temperature at which suspension polymerization is performed may be about ⁇ 20 to + 20 ° C. with respect to the 10-hour half-life temperature of the polymerization catalyst, and the polymerization time may be several hours to several tens of hours.
  • Saponification of a copolymer of vinyl ester with at least one of acrylic acid ester and methacrylic acid ester uses an alkali (sodium hydroxide, potassium hydroxide, lithium hydroxide, etc.) containing an alkali metal, and is aqueous. It can be performed in a mixed solvent of an organic solvent and water. By this saponification, the unit derived from the vinyl ester becomes a unit in which a hydroxyl group is directly bonded to the main chain of the copolymer [that is, a unit represented by the above formula (1)].
  • alkali sodium hydroxide, potassium hydroxide, lithium hydroxide, etc.
  • the unit derived from at least one monomer is a unit in which an alkali metal salt (group) of a carboxyl group is directly bonded to the main chain of the copolymer [that is, a unit represented by the formula (2)]. Therefore, examples of M ′ in the formula (2) include sodium, potassium, and lithium.
  • aqueous organic solvent used for saponification examples include lower alcohols (such as methanol and ethanol), ketones (such as acetone and methyl ethyl ketone), and the like.
  • the use ratio of the aqueous organic solvent to water is preferably 3/7 to 8/2 in terms of mass ratio.
  • the temperature at the time of saponification may be 20 to 60 ° C., and the time at that time may be about several hours.
  • the saponified copolymer may be taken out from the reaction solution, washed and then dried.
  • the unit represented by the formula (1) of the copolymer (A) obtained through the saponification has a structure in which an unsaturated bond of vinyl alcohol is opened and polymerized
  • the unit represented by (2) is an acrylate or methacrylate (hereinafter referred to as “(meth) acrylate” collectively, and acrylic acid and methacrylic acid are collectively referred to as “(meth) A structure in which an unsaturated bond of “acrylic acid” is polymerized by opening.
  • the copolymer (A) uses vinyl alcohol or (meth) acrylate as a monomer and is not obtained by copolymerizing these, but for convenience, “vinyl alcohol and (meth) It may also be referred to as an acrylate salt [a copolymer of (meth) acrylic acid alkali metal neutralized product].
  • the composition ratio of the unit represented by the formula (1) and the unit represented by the formula (2) is the formula (1) when the total of these units is 100 mol%. Is preferably 5 mol% or more, more preferably 50 mol% or more, still more preferably 60 mol% or more, and preferably 95 mol% or less, and 90 mol%. The following is more preferable. That is, when the total of the unit represented by the formula (1) and the unit represented by the formula (2) is 100 mol%, the ratio of the unit represented by the formula (2) is 5 mol% or more. Is preferably 10 mol% or more, more preferably 95 mol% or less, more preferably 50 mol% or less, and still more preferably 40 mol% or less.
  • the content of the copolymer (A) in the negative electrode mixture layer is preferably 2% by mass or more, and more preferably 5% by mass or more, from the viewpoint of ensuring a good effect due to its use.
  • the content of the copolymer (A) in the negative electrode mixture layer is preferably 15% by mass or less, and more preferably 10% by mass or less.
  • binders used in the negative electrode mixture layer according to the negative electrode of a normal lithium ion secondary battery for example, styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC) ), Polyvinylidene fluoride (PVDF), and the like can also be used.
  • SBR styrene butadiene rubber
  • CMC carboxymethyl cellulose
  • PVDF Polyvinylidene fluoride
  • the content of the binder other than the copolymer (A) in the total amount of binder contained in the negative electrode mixture layer is preferably 50% by mass or less.
  • the negative electrode mixture layer may contain a conductive auxiliary as necessary.
  • conductive assistants to be included in the negative electrode mixture layer include graphites such as natural graphite (scaly graphite, etc.), artificial graphite and the like; acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black and the like.
  • -It is preferable to use carbon materials such as bon blacks; carbon fibers; and conductive fibers such as metal fibers; carbon fluorides; metal powders such as aluminum; zinc oxide; conductivity such as potassium titanate. Whiskers; conductive metal oxides such as titanium oxide; organic conductive materials such as polyphenylene derivatives; and the like can also be used.
  • the conductive assistant those exemplified above may be used singly or in combination of two or more.
  • the content of the conductive additive in the negative electrode mixture layer is preferably 10% by mass or less.
  • the negative electrode (negative electrode precursor) to be used for pre-doping outside the system in order to produce the negative electrode of the present invention by the production method (1) contains, for example, a negative electrode active material and a binder, and further, if necessary, a conductive aid.
  • the negative electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone (NMP) or water to prepare a paste-like or slurry-like negative electrode mixture-containing composition (however, the binder is dissolved in the solvent).
  • NMP N-methyl-2-pyrrolidone
  • the negative electrode to be used for pre-doping outside the system is not limited to those manufactured by the above method, but may be manufactured by other methods.
  • a negative electrode active material at least partly uses a negative electrode active material doped with Li ions by pre-doping outside the system
  • a binder Furthermore, if necessary, a negative electrode mixture containing a conductive auxiliary agent is dispersed in a solvent such as NMP or water to prepare a paste-like or slurry-like negative electrode mixture-containing composition (however, the binder is added to the solvent). It may be dissolved), and this may be applied to one or both sides of the current collector, dried, and then subjected to a pressing process such as a calendar process if necessary.
  • the negative electrode current collector a copper or nickel foil, a punching metal, a net, an expanded metal, or the like can be used, but a copper foil is usually used.
  • the upper limit of the thickness is preferably 30 ⁇ m, and the lower limit is 5 ⁇ m in order to ensure mechanical strength. Is desirable.
  • the thickness of the negative electrode mixture layer (when the negative electrode mixture layer is provided on both sides of the current collector, the thickness per side) is preferably 10 to 100 ⁇ m.
  • the extra-system pre-doping of the negative electrode active material can be performed, for example, by the following (i) or (ii).
  • In-system pre-doping method (i) A negative electrode manufactured using a negative electrode active material not doped with Li ions is used, and the negative electrode active material is doped with Li ions.
  • the doping of Li ions into the negative electrode active material in the negative electrode mixture layer of the negative electrode is performed by, for example, biphenyl, polycyclic aromatic compounds (anthracene, naphthalene) in a solvent such as tetrahydrofuran or diethyl ether. Etc.), and the negative electrode is immersed in a solution in which p-benzoquinone, metal Li, etc. are dissolved, and then washed with a solvent and dried [hereinafter referred to as “out-of-system pre-doping method (i-1)”. ].
  • the doping amount of Li ions at this time can be controlled by adjusting the amount of each component in the solution. For example, the molar ratio Li / M may be adjusted so as to satisfy the preferred value.
  • a negative electrode (working electrode) and a lithium metal foil (counter electrode, including a lithium alloy foil) are immersed in a nonaqueous electrolytic solution, and a current is passed between them.
  • the negative electrode active material in the negative electrode mixture layer can be doped with Li ions [hereinafter referred to as out-of-system pre-doping method (i-2)].
  • the non-aqueous electrolyte the same non-aqueous electrolyte for lithium ion secondary batteries (described in detail later) can be used.
  • the doping amount of Li ions at this time can be controlled by adjusting the current density per area of the negative electrode (negative electrode mixture layer) and the amount of electricity to be energized.
  • the molar ratio Li / M has the preferred value. Adjust to meet.
  • the negative electrode wound around a roll is pulled out and introduced into an electrolyte bath provided with a non-aqueous electrolyte and a lithium metal electrode, and the negative electrode in the electrolyte bath
  • a roll-to-roll method in which a negative electrode active material in a negative electrode mixture layer is doped with Li ions by energizing between the lithium metal electrode and the lithium metal electrode, and the subsequent negative electrode is wound into a roll shape.
  • FIG. 1 shows an explanatory diagram of a step of doping Li ions into a negative electrode active material in a negative electrode mixture layer of a negative electrode by a roll-to-roll method.
  • the negative electrode 2a is pulled out from the roll 20a around which the negative electrode 2a for use in doping Li ions is wound, and introduced into the electrolytic solution tank 101 for doping Li ions.
  • the electrolyte bath 101 has a non-aqueous electrolyte (not shown) and a lithium metal electrode 102, and can be energized by a power source 103 between the negative electrode 2 a passing through the electrolyte bath 101 and the lithium metal electrode 102. It is configured as follows.
  • the negative electrode mixture layer of the negative electrode 2a is energized between the negative electrode 2a and the lithium metal electrode 102 by the power source 103.
  • the negative electrode active material therein is doped with Li ions.
  • the negative electrode 2 after the Li-ion is doped into the negative electrode active material in the negative electrode mixture layer and passed through the electrolyte bath 101 is preferably washed and wound on a roll 20.
  • the negative electrode 2 can be cleaned, for example, by allowing the negative electrode 2 to pass through a cleaning tank 104 filled with a cleaning organic solvent, as shown in FIG.
  • the negative electrode 2 after passing through the cleaning tank 104 is wound around the roll 20 after passing through the drying means 105 and being dried.
  • the drying method in the drying means 105 is not particularly limited as long as the organic solvent adhering to the negative electrode 2 can be removed in the cleaning tank 104. For example, drying with warm air or an infrared heater, or in a dry inert gas Various methods such as drying through can be applied.
  • the electrolytic solution tank 101 shown in FIG. 1 is lithium metal so that the negative electrode mixture layer formed on both surfaces of the negative electrode current collector can be doped with Li ions simultaneously on the negative electrode mixture layers on both surfaces.
  • an electrolyte bath used only to dope Li ions into the negative electrode mixture layer of the negative electrode having a negative electrode mixture layer only on one side of the negative electrode current collector although two electrodes 102 are provided. It is only necessary to provide one lithium metal electrode only at a location facing the negative electrode mixture layer.
  • Out-of-system pre-doping method (ii) A negative electrode active material not doped with Li ions is directly doped with Li ions. In this case, by immersing a negative electrode active material (a negative electrode active material before Li ion doping) in place of the negative electrode in the solution in which the negative electrode described above in the description of the extra-system pre-doping method (i-1) is immersed.
  • the negative electrode active material can be doped with Li ions.
  • the negative electrode active material used for the production of the negative electrode is doped with Li ions by the extra-system pre-doping method (ii). Can do.
  • the ratio of the negative electrode active material doped with Li ions by the extra-system pre-doping method (ii) in the negative electrode active material used for the production of the negative electrode and the doping amount of Li ions into the negative electrode active material are, for example, the molar ratio Li / What is necessary is just to adjust so that M may satisfy
  • the negative electrode active material doped with Li ions by the extra-system pre-doping method (ii) preferably has a large acceptance amount of Li ions and a large irreversible capacity.
  • Li ions are added to a material containing Si and O as constituent elements. It is desirable to dope.
  • the negative electrode containing the negative electrode active material doped with Li ions by pre-doping outside the system is cut into a required size and used for the production of electrochemical elements such as lithium ion secondary batteries.
  • electrochemical elements such as lithium ion secondary batteries.
  • the negative electrode of the present invention is used as a negative electrode of an electrochemical element having a non-aqueous electrolyte and repeatedly charged and discharged, such as a lithium ion secondary battery and a super capacitor.
  • the application is a lithium ion secondary battery.
  • the lithium ion secondary battery using the negative electrode of the present invention is one in which the negative electrode, the positive electrode, the separator, and the non-aqueous electrolyte are accommodated in an outer package. is there.
  • a positive electrode according to a lithium ion secondary battery has a positive electrode mixture layer containing a positive electrode active material and a binder.
  • the positive electrode mixture layer has a structure formed on one side or both sides of a current collector. And those composed of a positive electrode mixture layer (positive electrode mixture molded body).
  • a metal oxide composed of Li and a metal M other than Li (Co, Ni, Mn, Fe, Mg, Al, etc.) is used.
  • lithium-containing composite oxides include lithium cobalt oxides such as LiCoO 2 ; lithium manganese oxides such as LiMnO 2 and Li 2 MnO 3 ; lithium nickel oxides such as LiNiO 2 ; LiCo 1-x NiO Lithium-containing composite oxide having a layered structure such as 2 ; Lithium-containing composite oxide having a spinel structure such as LiMn 2 O 4 and Li 4/3 Ti 5/3 O 4 ; Lithium-containing composite oxide having an olivine structure such as LiFePO 4 And oxides having the above-described oxide as a basic composition and substituted with various elements.
  • lithium cobalt oxide (lithium cobaltate) containing at least Co and at least one element M 1 selected from the group consisting of Mg, Zr, Ni, Mn, Ti, and Al. ) Is preferred.
  • the positive electrode material mixture layer more preferably contains a positive electrode material in which the surfaces of such lithium cobalt oxide particles are coated with an Al-containing oxide.
  • the lithium cobalt oxide is an element that includes Co, at least one element M 1 selected from the group consisting of Mg, Zr, Ni, Mn, Ti, and Al, and other elements that may further be contained.
  • group M a is represented by the composition formula LiM a O 2.
  • the element M 1 has an effect of increasing the stability of the lithium cobalt oxide in a high voltage region and suppressing the elution of Co ions, and the thermal stability of the lithium cobalt oxide. It also has the effect of increasing
  • the amount of the element M 1 is preferably such that the atomic ratio M 1 / Co with Co is 0.003 or more from the viewpoint of more effectively exerting the above action, and 0.008 or more. It is more preferable that
  • the amount of the element M 1 in the lithium cobalt oxide is preferably such that the atomic ratio M 1 / Co with Co is 0.06 or less, and more preferably 0.03 or less.
  • Zr adsorbs hydrogen fluoride that may be generated due to a fluorine-containing lithium salt (such as LiPF 6 ) contained in the non-aqueous electrolyte, and suppresses deterioration of the lithium cobaltate.
  • a fluorine-containing lithium salt such as LiPF 6
  • the lithium cobaltate is synthesized so as to also contain Zr
  • Zr oxide is deposited on the surface of the particles, and this Zr oxide adsorbs hydrogen fluoride. Therefore, deterioration of the lithium cobalt oxide due to hydrogen fluoride can be suppressed.
  • the positive electrode active material contains Zr
  • the load characteristics of the battery are improved.
  • the lithium cobalt oxide contained in the positive electrode material is two materials having different average particle diameters
  • the larger average particle diameter is lithium cobalt oxide (A)
  • the smaller average particle diameter is lithium cobalt oxide (B).
  • the load characteristics of the battery tend to deteriorate. Therefore, among the positive electrode active materials constituting the positive electrode material, it is preferable that lithium cobaltate (A) having a larger average particle diameter contains Zr.
  • lithium cobaltate (B) may contain Zr or may not contain it.
  • the amount of Zr is such that the atomic ratio Zr / Co with Co is preferably 0.0002 or more, more preferably 0.0003 or more, from the viewpoint of better exerting the above action. Is more preferable. However, if the amount of Zr in the lithium cobalt oxide is too large, the amount of other elements decreases, and there is a possibility that the effects of these elements cannot be sufficiently ensured. Therefore, the amount of Zr in the lithium cobaltate is preferably such that the atomic ratio Zr / Co with Co is 0.005 or less, and more preferably 0.001 or less.
  • the lithium cobalt oxide includes Li-containing compounds (such as lithium hydroxide and lithium carbonate), Co-containing compounds (such as cobalt oxide and cobalt sulfate), Mg-containing compounds (such as magnesium sulfate), and Zr-containing compounds (such as zirconium oxide).
  • Li-containing compounds such as lithium hydroxide and lithium carbonate
  • Co-containing compounds such as cobalt oxide and cobalt sulfate
  • Mg-containing compounds such as magnesium sulfate
  • Zr-containing compounds such as zirconium oxide
  • compounds containing elements M 1 oxides, hydroxides, sulfates, etc.
  • compounds containing elements M 1 oxides, hydroxides, sulfates, etc.
  • composite compound containing Co and the element M 1 (hydroxides, oxides, etc.) and the like and Li-containing compound are mixed and firing the raw material mixture It is preferable.
  • the firing condition of the raw material mixture for synthesizing the lithium cobaltate can be, for example, 800 to 1050 ° C. for 1 to 24 hours, but once the temperature is lower than the firing temperature (for example, 250 to 850 ° C.). It is preferable to preheat by heating and holding at that temperature, and then to raise the temperature to the firing temperature to advance the reaction. There is no particular limitation on the preheating time, but it is usually about 0.5 to 30 hours.
  • the atmosphere during firing can be an atmosphere containing oxygen (that is, in the air), a mixed atmosphere of an inert gas (such as argon, helium, or nitrogen) and oxygen gas, or an oxygen gas atmosphere.
  • the oxygen concentration (volume basis) is preferably 15% or more, and more preferably 18% or more.
  • the surface of the lithium cobalt oxide particles is coated with an Al-containing oxide (for example, 90 to 100% or more of the total area of the lithium cobalt oxide particle surface includes Al-containing oxides). Things are present).
  • Al-containing oxide covering the surface of the lithium cobalt oxide particles include Al 2 O 3 , AlOOH, LiAlO 2 , and LiCo 1-w Al w O 2 (where 0.5 ⁇ w ⁇ 1). Of these, only one of them may be used, or two or more of them may be used in combination.
  • the film formed of an Al-containing oxide that covers the surface of the lithium cobaltate constituting the positive electrode material may be a film containing such a component.
  • the average coating thickness of the Al-containing oxide according to the positive electrode material increases the resistance due to the inhibition of the Al-containing oxide in the positive and negative electrode active materials during charging and discharging of the battery according to the positive electrode material, From the viewpoint of further improving the charge / discharge cycle characteristics of the battery by suppressing Li deposition at the negative electrode and from the viewpoint of satisfactorily suppressing the reaction between the positive electrode active material according to the positive electrode material and the non-aqueous electrolyte, the thickness is 5 nm or more. It is preferable that the thickness is 15 nm or more.
  • the average coating of the Al-containing oxide according to the positive electrode material is preferably 50 nm or less, and more preferably 35 nm or less.
  • the “average coating thickness of the Al-containing oxide” as used herein refers to a cross section of the positive electrode material obtained by processing by the focused ion beam method, observed at a magnification of 400,000 times using a transmission electron microscope, Of the positive electrode material particles existing in the field of view of 500 ⁇ 500 nm, particles having a cross-sectional size within the average particle diameter (d 50 ) ⁇ 5 ⁇ m of the positive electrode material are arbitrarily selected for 10 fields, and for each field, Al It means the average value (number average value) calculated for all thicknesses (thicknesses at 100 locations) obtained by measuring the thickness of the coating film of the contained oxide at 10 arbitrary locations.
  • the specific surface area of the positive electrode material is preferably 0.1 m 2 / g or more, more preferably 0.2 m 2 / g or more, and preferably 0.4 m 2 / g or less, More preferably, it is 0.3 m 2 / g or less.
  • the positive electrode material When the surface of the lithium cobalt oxide constituting the positive electrode material is coated with an Al-containing oxide or when Zr oxide is deposited on the surface of the lithium cobalt oxide particles, the positive electrode material is usually used. The surface becomes rough and the specific surface area increases. For this reason, the positive electrode material has a small specific surface area as described above if the properties of the Al-containing oxide film covering the surface of the lithium cobalt oxide particles are good in addition to a relatively large particle size. It is preferable because it is easy.
  • the said lithium cobaltate which the said positive electrode material contains one type may be sufficient, as above-mentioned, two materials from which an average particle diameter differs may be sufficient, and three or more from which an average particle diameter differs It may be a material.
  • the average particle diameter of the positive electrode material is preferably 10 to 35 ⁇ m.
  • the surface of lithium cobalt oxide (A) particles is coated with an Al-containing oxide, and the average particle diameter is 1
  • the positive electrode material (a) having a particle size of 40 ⁇ m and the surface of lithium cobalt oxide (B) particles are coated with an Al-containing oxide, the average particle diameter is 1 to 40 ⁇ m, and the positive electrode material (a)
  • the positive electrode material (b) having a small average particle diameter is included. More preferably, it is an embodiment comprising large particles [positive electrode material (a)] having an average particle diameter of 24 to 30 ⁇ m and small particles [positive electrode material (b)] having an average particle diameter of 4 to 8 ⁇ m.
  • the ratio of the positive electrode material (a) in the total amount of the positive electrode material is preferably 75 to 90% by mass.
  • the particle size distribution of the positive electrode material in the present specification means a particle size distribution obtained by a method for obtaining an integrated volume from particles having a small particle size distribution using a microtrack particle size distribution measuring apparatus “HRA9320” manufactured by Nikkiso Co., Ltd. .
  • the average particle diameter of the positive electrode material and other particles (such as the material S) in the present specification is the volume-based integrated fraction when the integrated volume is obtained from particles having a small particle size distribution using the above-described apparatus. Means the value of 50% diameter (d 50 ).
  • the following method can be employed.
  • a lithium hydroxide aqueous solution having a pH of 9 to 11 and a temperature of 60 to 80 ° C.
  • the lithium cobalt oxide particles are charged and dispersed by stirring, and Al (NO 3 ) 3 ⁇ 9H 2 O and Aqueous ammonia for suppressing fluctuations in pH is added dropwise to produce an Al (OH) 3 coprecipitate and adhere to the surface of the lithium cobalt oxide particles.
  • the lithium cobalt oxide particles to which the Al (OH) 3 coprecipitate is adhered are taken out from the reaction solution, washed, dried, and then heat-treated to form an Al-containing oxide on the surface of the lithium cobalt oxide particles.
  • a film is formed to form the positive electrode material.
  • the heat treatment of the lithium cobaltate particles to which the Al (OH) 3 coprecipitate is deposited is preferably performed in the air atmosphere, and the heat treatment temperature is 200 to 800 ° C. and the heat treatment time is 5 to 15 hours. preferable.
  • the Al-containing oxide as a main component constituting the coating is changed to Al 2 O 3 or AlOOH by adjusting the heat treatment temperature. Or LiAlO 2 or LiCo 1-w Al w O 2 (where 0.5 ⁇ w ⁇ 1).
  • the lithium nickelate is represented by the chemical formula LiM b O 2 when Ni, Co, and the element M 2 , and other elements that may further be contained, are combined into an element group M b .
  • Ni Ni of the total number of atoms in 100 mol% of the element group M 2, the amount of Co and the element M 2, respectively, expressed in s (mol%), t ( mol%) and u (mol%), 30 ⁇ s ⁇ 97, 0.5 ⁇ t ⁇ 40, 0.5 ⁇ u ⁇ 40 are preferable, and 70 ⁇ s ⁇ 97, 0.5 ⁇ t ⁇ 30, and 0.5 ⁇ u ⁇ 5 are more preferable. preferable.
  • the compound (oxide, hydroxide, sulfate, etc.) to be mixed can be mixed, and this raw material mixture can be fired.
  • Ni, complex compound containing a plurality of elements among the elements M b be contained if Co and the required (hydroxides, oxides, etc.), It is preferable to mix other raw material compounds (such as Li-containing compounds) and to fire this raw material mixture.
  • the firing conditions of the raw material mixture for synthesizing the lithium nickelate can also be set at, for example, 800 to 1050 ° C. for 1 to 24 hours, as in the case of the lithium cobaltate, but once lower than the firing temperature. It is preferable to heat up to a temperature (for example, 250 to 850 ° C.) and perform preliminary heating by holding at that temperature, and then raise the temperature to the firing temperature to advance the reaction. There is no particular limitation on the preheating time, but it is usually about 0.5 to 30 hours.
  • the atmosphere during firing can be an atmosphere containing oxygen (that is, in the air), a mixed atmosphere of an inert gas (such as argon, helium, or nitrogen) and oxygen gas, or an oxygen gas atmosphere.
  • the oxygen concentration (volume basis) is preferably 15% or more, and more preferably 18% or more.
  • the amount of the positive electrode material in a total of 100 mass% of the positive electrode material and the other positive electrode active material Is preferably 50% by mass or more, more preferably 80% by mass or more (that is, the amount of the other positive electrode active material used together with the positive electrode material is the same as that of the positive electrode material and the other positive electrode active material).
  • the total content is preferably 50% by mass or less, and more preferably 20% by mass or less. Since only the positive electrode material may be used as the positive electrode active material, the preferred upper limit of the amount of the positive electrode material in the total of 100% by mass of the positive electrode material and the other positive electrode active material is 100% by mass. is there.
  • the amount of the lithium nickelate in a total of 100% by mass of the positive electrode material and the lithium nickelate is preferably 5% by mass or more, and more preferably 10% by mass or more.
  • Conductive aids for the positive electrode mixture layer include natural graphite (such as flake graphite), graphite such as artificial graphite (graphitic carbon material); acetylene black, ketjen black, channel black, furnace black, lamp black, thermal Carbon materials such as carbon black such as black; carbon fiber; Also, PVDF, polytetrafluoroethylene (PTFE), vinylidene fluoride-chlorotrifluoroethylene copolymer [P (VDF-CTFE)], SBR, CMC, etc. are preferably used as the binder for the positive electrode mixture layer. It is done.
  • the positive electrode is prepared, for example, by preparing a paste-like or slurry-like positive electrode mixture-containing composition in which a positive electrode active material (such as the above-mentioned positive electrode material), a conductive additive and a binder are dispersed in a solvent such as NMP. May be dissolved in a solvent), and this is applied to one or both sides of the current collector, dried, and then subjected to a press treatment such as a calender treatment as necessary.
  • a positive electrode active material such as the above-mentioned positive electrode material
  • a conductive additive and a binder are dispersed in a solvent such as NMP. May be dissolved in a solvent), and this is applied to one or both sides of the current collector, dried, and then subjected to a press treatment such as a calender treatment as necessary.
  • the positive electrode is not limited to those manufactured by the above manufacturing method, and may be manufactured by other methods.
  • the positive electrode is produced by a method of pressing a positive electrode mixture containing a positive electrode active material, a conductive additive, a binder, and the like into a pellet shape. can do.
  • the current collector can be the same as that used for the positive electrode of a conventionally known lithium ion secondary battery, such as aluminum foil, punching metal, net, expanded metal, etc.
  • the thickness is preferably 5 to 30 ⁇ m.
  • the amount of the positive electrode active material is preferably 60 to 95% by mass, and the amount of the binder is 1 to 15% by mass.
  • the amount of the conductive auxiliary is preferably 3 to 20% by mass.
  • the thickness of the positive electrode mixture layer is preferably 30 to 150 ⁇ m.
  • the thickness is preferably 0.15 to 1 mm.
  • a negative electrode a negative electrode containing a negative electrode active material doped with Li ions by pre-doping outside the system
  • a positive electrode laminated body laminated via a separator, or this laminated body.
  • laminated body laminated via a separator, or this laminated body.
  • wound electrode body wound in a spiral shape.
  • the separator is preferably a porous film made of polyolefin such as polyethylene, polypropylene, ethylene-propylene copolymer; polyester such as polyethylene terephthalate or copolymer polyester; Note that the separator preferably has a property of closing the pores at 100 to 140 ° C. (that is, a shutdown function). Therefore, the separator has a melting point, that is, a thermoplastic resin having a melting temperature measured using a differential scanning calorimeter (DSC) of 100 to 140 ° C. as a component in accordance with JIS K 7121.
  • DSC differential scanning calorimeter
  • it is a single-layer porous film mainly composed of polyethylene or a laminated porous film comprising a porous film such as a laminated porous film in which 2 to 5 layers of polyethylene and polypropylene are laminated.
  • a resin having a melting point higher than that of polyethylene such as polyethylene and polypropylene is used by mixing or laminating, it is preferable that polyethylene is 30% by mass or more, and 50% by mass or more as a resin constituting the porous membrane. More preferred.
  • a resin porous membrane for example, a porous membrane composed of the above-mentioned exemplified thermoplastic resin used in a conventionally known lithium ion secondary battery or the like, that is, a solvent extraction method, a dry type Alternatively, an ion-permeable porous film manufactured by a wet stretching method or the like can be used.
  • the average pore diameter of the separator is preferably 0.01 ⁇ m or more, more preferably 0.05 ⁇ m or more, more preferably 1 ⁇ m or less, and even more preferably 0.5 ⁇ m or less.
  • a laminated separator having a porous film (I) mainly composed of a thermoplastic resin and a porous layer (II) mainly including a filler having a heat resistant temperature of 150 ° C. or higher may be used.
  • the separator has both shutdown characteristics, heat resistance (heat shrinkage resistance), and high mechanical strength.
  • the charge / discharge cycle characteristics of the battery are further improved by using the laminated separator. The reason for this is not clear, but the high mechanical strength of the laminated separator shows high resistance to negative electrode expansion / contraction associated with the battery charge / discharge cycle. It is presumed that this is because the adhesion between the positive electrodes can be maintained.
  • heat-resistant temperature is 150 ° C. or higher” means that deformation such as softening is not observed at least at 150 ° C.
  • the porous membrane (I) according to the separator is mainly for ensuring a shutdown function, and when the battery reaches or exceeds the melting point of the thermoplastic resin, which is the main component of the porous membrane (I), The thermoplastic resin related to the porous membrane (I) melts and closes the pores of the separator, and a shutdown that suppresses the progress of the electrochemical reaction occurs.
  • the thermoplastic resin that is the main component of the porous membrane (I) is preferably a resin having a melting point of 140 ° C. or lower, and specifically includes polyethylene.
  • a microporous membrane usually used as a battery separator or a dispersion containing polyethylene particles is applied to a substrate such as a nonwoven fabric and dried. Examples thereof include sheet-like materials such as those obtained.
  • the total volume of the constituent components of the porous membrane (I) [the total volume excluding the void portion. The same applies to the volume content of the constituent components of the porous membrane (I) and the porous layer (II) according to the separator.
  • the volume content of the resin whose main melting point is 140 ° C. or lower is 50% by volume or more, and more preferably 70% by volume or more.
  • the volume content of the resin having a melting point of 140 ° C. or lower is 100% by volume.
  • the porous layer (II) according to the separator has a function of preventing a short circuit due to direct contact between the positive electrode and the negative electrode even when the internal temperature of the battery rises, and has a heat resistance temperature of 150 ° C. or higher.
  • the function is secured by. That is, when the battery becomes high temperature, even if the porous membrane (I) shrinks, the porous layer (II) which does not easily shrink can cause the positive and negative electrodes directly when the separator is thermally shrunk. It is possible to prevent a short circuit due to the contact.
  • the heat-resistant porous layer (II) acts as a skeleton of the separator, thermal contraction of the porous membrane (I), that is, thermal contraction of the entire separator itself can be suppressed.
  • the filler related to the porous layer (II) has a heat resistant temperature of 150 ° C. or higher, is stable with respect to the non-aqueous electrolyte of the battery, and is electrochemically stable that is difficult to be oxidized and reduced within the battery operating voltage range.
  • Any inorganic particles or organic particles may be used as long as they are fine, but fine particles are preferable from the viewpoint of dispersion and the like, and inorganic oxide particles, more specifically, alumina, silica, and boehmite are preferable.
  • Alumina, silica, and boehmite have high oxidation resistance, and the particle size and shape can be adjusted to the desired numerical values, making it easy to control the porosity of the porous layer (II) with high accuracy. It becomes.
  • the filler whose heat-resistant temperature is 150 degreeC or more may use the thing of the said illustration individually by 1 type, and may use 2 or more types together, for example.
  • the phrase “containing a filler having a heat resistant temperature of 150 ° C. or higher as a main component” of the porous layer (II) means that 70% by volume or more of the filler is included in the total volume of the constituent components of the porous layer (II). is doing.
  • the amount of the filler in the porous layer (II) is preferably 80% by volume or more and more preferably 90% by volume or more in the total volume of the constituent components of the porous layer (II).
  • the porous layer (II) preferably contains an organic binder to bind the fillers or bind the porous layer (II) and the porous membrane (I).
  • the suitable upper limit of the amount of filler (B) in the porous layer (II) is, for example, 99% by volume in the total volume of the constituent components of the porous layer (II).
  • the amount of the filler (B) in the porous layer (II) is less than 70% by volume, for example, it is necessary to increase the amount of the organic binder in the porous layer (II).
  • the pores of the layer (II) are filled with the organic binder, and the function as a separator is lost, for example.
  • the fillers or the porous layer (II) and the porous film (I) can be bonded well, are electrochemically stable, and are used for an electrochemical element.
  • an electrochemical element There is no particular limitation as long as it is stable with respect to the non-aqueous electrolyte.
  • fluororesin such as PVDF
  • fluorororubber SBR
  • CMC hydroxyethyl cellulose
  • HEC hydroxyethyl cellulose
  • PVA polyvinyl alcohol
  • PVB polyvinyl butyral
  • PVP polyvinyl pyrrolidone
  • Poly N-vinylacetamide Cross-linked acrylic resin, polyurethane, epoxy resin and the like
  • These organic binders may be used alone or in combination of two or more.
  • the laminated separator is, for example, a composition for forming a porous layer (II) containing, in the porous membrane (I), the filler, an organic binder, and the like, and a solvent (an organic solvent such as water and ketones) ( It can be manufactured by applying a slurry, paste, etc.) and then drying at a predetermined temperature to form the porous layer (II).
  • a solvent an organic solvent such as water and ketones
  • the laminated separator may have one or more each of the porous membrane (I) and the porous layer (II). Specifically, the porous layer (II) is disposed only on one side of the porous membrane (I) to form the laminated separator. For example, the porous layer (II) is formed on both sides of the porous membrane (I). May be used as the laminated separator. However, if the number of layers of the multilayer separator is too large, it is not preferable because the thickness of the separator is increased, which may increase the internal resistance of the battery or decrease the energy density. Is preferably 5 layers or less.
  • the thickness of the separator (the laminated separator and other separators) is preferably 6 ⁇ m or more and more preferably 10 ⁇ m or more from the viewpoint of more reliably separating the positive electrode and the negative electrode. On the other hand, if the separator is too thick, the energy density of the battery may be lowered. Therefore, the thickness is preferably 50 ⁇ m or less, and more preferably 30 ⁇ m or less.
  • the thickness of the porous membrane (I) [the total thickness when a plurality of porous membranes (I) are present] is preferably 5 to 30 ⁇ m. Further, the thickness of the porous layer (II) [when there are a plurality of porous layers (II), the total thickness] is preferably 1 ⁇ m or more, more preferably 2 ⁇ m or more, and 4 ⁇ m or more. Further, it is preferably 20 ⁇ m or less, more preferably 10 ⁇ m or less, and further preferably 6 ⁇ m or less.
  • the porosity of the separator is preferably 30 to 70%.
  • the separator (the laminated separator and other separators) has an adhesive layer on one side or both sides thereof.
  • the separator and the electrode are integrated by the adhesive layer of the separator when forming the laminated electrode body or the wound electrode body, even if charging / discharging is repeated in a battery using such an electrode body, Since the shape change can be suppressed, the charge / discharge cycle characteristics of the battery are further improved. In the case of a battery using a flat wound electrode body having a flat cross section, the effect of improving the charge / discharge cycle characteristics by the adhesive layer is particularly remarkable.
  • the adhesive layer of the separator preferably contains an adhesive resin that exhibits adhesiveness when heated.
  • the separator and the electrode can be integrated by undergoing a step of pressing while heating the electrode body (heating press).
  • the minimum temperature at which the adhesiveness of the adhesive resin is expressed needs to be lower than the temperature at which shutdown occurs in the layers other than the adhesive layer in the separator. Specifically, the temperature is from 60 ° C to 120 ° C. Preferably there is. Further, when the separator is the laminated separator, the minimum temperature at which the adhesive resin exhibits adhesiveness needs to be lower than the melting point of the thermoplastic resin that is the main component of the porous membrane (I). .
  • the peel strength obtained when a peel test at 180 ° between the electrode (for example, the negative electrode) constituting the electrode body and the separator is carried out is preferable in the state before the hot press.
  • the electrode mixture layer (the positive electrode mixture layer and the negative electrode mixture layer) may peel from the current collector of the electrode, and the conductivity may be lowered.
  • the peel strength according to the peel test at ° is preferably 10 N / 20 mm or less after being hot pressed at a temperature of 60 to 120 ° C.
  • the peel strength at 180 ° between the electrode and the separator referred to in this specification is a value measured by the following method.
  • the separator and the electrode are each cut into a size of 5 cm in length and 2 cm in width, and the cut-out separator and the electrode are overlapped.
  • a test piece is prepared by hot-pressing a 2 cm ⁇ 2 cm region from one end. The end of the test piece on the side where the separator and electrode are not heated and pressed is opened, and the separator and the negative electrode are bent so that these angles are 180 °.
  • both the one end side of the separator opened at 180 ° of the test piece and the one end side of the electrode are gripped and pulled at a pulling speed of 10 mm / min. Measure the strength when peeled off.
  • the peel strength of the separator and the electrode before heating press was determined by preparing a test piece in the same manner as above except that the separator and electrode cut out as described above were stacked and pressed without heating. The peel test is performed in the same manner as described above.
  • the adhesive resin has almost no adhesiveness (stickiness) at room temperature (for example, 25 ° C), and the minimum temperature at which the adhesiveness is developed is less than the temperature at which the separator shuts down, preferably 60 ° C to 120 ° C. Those having tackiness are desirable.
  • the temperature of the heating press when integrating the separator and the electrode is more preferably 80 ° C. or more and 100 ° C. or less at which the thermal contraction of the separator does not occur significantly, and the adhesiveness of the adhesive resin is exhibited.
  • the minimum temperature is more preferably 80 ° C. or higher and 100 ° C. or lower.
  • the adhesive resin having a delayed tack property a resin that has almost no fluidity at room temperature, exhibits fluidity when heated, and has a property of being in close contact with a press is preferable.
  • a resin of a type that is solid at room temperature, melts by heating, and exhibits adhesiveness by a chemical reaction can also be used as the adhesive resin.
  • the adhesive resin preferably has a softening point in the range of 60 ° C. or higher and 120 ° C. or lower with the melting point, glass transition point and the like as indices.
  • the melting point and glass transition point of the adhesive resin can be measured, for example, by a method prescribed in JIS K 7121, and the softening point of the adhesive resin can be measured, for example, by a method prescribed in JIS K 7206.
  • adhesive resins include, for example, low density polyethylene (LDPE), poly- ⁇ -olefin [polypropylene (PP), polybutene-1, etc.], polyacrylate ester, ethylene-vinyl acetate copolymer. (EVA), ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-butyl acrylate copolymer (EBA), ethylene-methyl methacrylate copolymer (EMMA), ionomer resin Etc.
  • LDPE low density polyethylene
  • PP polypropylene
  • PP polybutene-1, etc.
  • EVA ethylene-vinyl acetate copolymer
  • EMA ethylene-methyl acrylate copolymer
  • EAA ethylene-ethyl acrylate copolymer
  • EBA ethylene-butyl acrylate copolymer
  • EMMA ethylene-methyl methacrylate copolymer
  • Each resin, or a resin having adhesiveness at room temperature such as SBR, nitrile rubber (NBR), fluorine rubber, or ethylene-propylene rubber, is used as a core, and the melting point and softening point are within the range of 60 ° C to 120 ° C
  • a resin having a core-shell structure with a resin as a shell as an adhesive resin.
  • various acrylic resins and polyurethane can be used for the shell.
  • the adhesive resin one-pack type polyurethane, epoxy resin, or the like that exhibits adhesiveness in a range of 60 ° C. or higher and 120 ° C. or lower can be used.
  • one of the above exemplified resins may be used alone, or two or more of them may be used in combination.
  • the location where the adhesive resin is present and the location where the adhesive resin is not present may be alternately formed in a groove shape, and the location where the adhesive resin such as a circle is not present in a plan view is not present.
  • a plurality may be formed continuously. In these cases, the locations where the adhesive resin is present may be regularly arranged or randomly arranged.
  • the area may be such that, for example, the peel strength at 180 ° after thermocompression bonding of the separator and the electrode is the above value, and depending on the type of adhesive resin used Specifically, the adhesive resin is preferably present in 10 to 60% of the surface area of the adhesive resin in plan view.
  • the basis weight of the adhesive resin improves the adhesion with the electrode.
  • the peel strength at 180 ° after the pressure bonding between the separator and the electrode is performed as described above. to adjust the value is preferably to 0.05 g / m 2 or more, and more preferably set to 0.1 g / m 2 or more.
  • the basis weight of the adhesive resin is too large in the presence of the adhesive resin, the electrode body becomes too thick, or the adhesive resin blocks the pores of the separator, and the movement of ions inside the battery is hindered. There is a risk. Therefore, the existing surface of the adhesive resin, the basis weight of the adhesive resin is preferably 1 g / m 2 or less, more preferably 0.5 g / m 2 or less.
  • the adhesive layer is composed of a porous film or a porous film (I) and a porous layer (II) using a composition for forming an adhesive layer (adhesive resin solution or emulsion) containing an adhesive resin and a solvent as a separator. ) And a step of applying to one side or both sides of the laminate.
  • non-aqueous electrolyte solution related to the lithium ion secondary battery for example, a solution prepared by dissolving a lithium salt in the following non-aqueous solvent can be used.
  • Non-aqueous solvents include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ⁇ -butyrolactone ( ⁇ -BL ), 1,2-dimethoxyethane (DME), tetrahydrofuran (THF), 2-methyltetrahydrofuran, dimethyl sulfoxide (DMSO), 1,3-dioxolane, formamide, dimethylformamide (DMF), dioxolane, acetonitrile, nitromethane, Methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivative, sulfolane, 3-methyl-2-oxazolidinone, propylene carbonate derivative, tetrahydrofuran derivative Aprotic organic solvents such as diethyl ether and 1,3-propane s
  • the lithium salt according to the non-aqueous electrolyte solution for example, LiClO 4, LiPF 6, LiBF 4, LiAsF 6, LiSbF 6, LiCF 3 SO 3, LiCF 3 CO 2, Li 2 C 2 F 4 (SO 3) 2, LiN (CF 3 SO 2 ) 2 , LiC (CF 3 SO 2 ) 3 , LiC n F 2n + 1 SO 3 (n ⁇ 2), LiN (RfOSO 2 ) 2 [where Rf is a fluoroalkyl group] At least one selected from the above.
  • the concentration of these lithium salts in the non-aqueous electrolyte is preferably 0.6 to 1.8 mol / l, and more preferably 0.9 to 1.6 mol / l.
  • Non-aqueous electrolytes include vinylene carbonate, vinyl ethylene carbonate, acid anhydride, sulfonic acid for the purpose of further improving the charge / discharge cycle characteristics of the battery and improving safety such as high temperature storage and overcharge prevention.
  • Additives such as esters, dinitriles, 1,3-propane sultone, diphenyl disulfide, cyclohexylbenzene, biphenyl, fluorobenzene, t-butylbenzene can also be added as appropriate.
  • non-aqueous electrolyte a gel (gel electrolyte) obtained by adding a known gelling agent such as a polymer can be used.
  • the form of the lithium ion secondary battery there is no particular limitation on the form of the lithium ion secondary battery.
  • any of a small cylindrical shape, a coin shape, a button shape, a flat shape, a square shape, a large size used for an electric vehicle, and the like may be used.
  • Some lithium ion secondary batteries having a negative electrode containing a negative electrode active material doped with Li ions perform Li ion doping to the negative electrode active material in the negative electrode mixture layer by in-system pre-doping. For example, by assembling a battery using an electrode (third electrode) having a Li supply source separately from the positive electrode and the negative electrode, and energizing the third electrode, the Li supply source in the negative electrode mixture layer in the battery Some negative electrode active materials are doped with Li ions. Therefore, in this type of battery, even when the doping of Li ions is completed, the third electrode in which a part of the Li supply source remains or all of it disappears remains in the battery.
  • the lithium ion secondary battery is assembled using a negative electrode containing a negative electrode active material previously doped with Li ions by pre-doping outside the system, a third electrode used (or used) for doping Li ions is provided inside. I don't have it.
  • the negative electrode active material in the negative electrode mixture layer of the negative electrode is doped with Li ions until the voltage reaches 2.0 V at a discharge current rate of 0.1 C.
  • the molar ratio (Li / M) between Li contained in the positive electrode active material and the metal M other than Li it is preferable to use a negative electrode in which the Li ion doping amount of the negative electrode active material in the negative electrode mixture layer is adjusted so that the molar ratio Li / M is 0.8 or more and 1.05 or less.
  • the molar ratio Li / M becomes smaller than the lower limit value.
  • the Li ions doped into the negative electrode active material by extra-predoping so that the molar ratio Li / M in the battery is 0.8 or more and 1.05 or less are irreversible when converted into the battery capacity.
  • the amount is equal to or less than the capacity.
  • the composition analysis of the positive electrode active material when discharged at a discharge current rate of 0.1 C until the voltage reaches 2.0 V can be performed using an ICP (Inductive Coupled Plasma) method as follows. First, 0.2 g of a positive electrode active material to be measured is collected and placed in a 100 mL container. Thereafter, 5 mL of pure water, 2 mL of aqua regia, and 10 mL of pure water are added in order and dissolved by heating. After cooling, the sample is further diluted 25 times with pure water, and calibrated using an ICP analyzer “ICP-757” manufactured by JARRELASH. The composition is analyzed by the line method. The composition amount can be derived from the obtained results. The molar ratio Li / M described in the examples described later is a value determined by this method.
  • the positive electrode active material for obtaining the molar ratio Li / M in this specification includes a positive electrode material in which the surface of the positive electrode active material particles is coated with a specific material (such as an Al-containing oxide).
  • a specific material such as an Al-containing oxide.
  • the amount of the metal contained in the specific material existing on the surface of the positive electrode material is also included in the amount of the metal M for obtaining the molar ratio Li / M.
  • Example 1 LiCo 0.9795 Mg 0.011 Zr 0.0005 Al 0.009 O 2 of lithium cobalt oxide (A1)
  • the positive electrode material (b1) is used, and the metal M other than Li at this time refers to Co, Mg, Zr, and Al. That is, after producing the lithium ion secondary battery, the battery after predetermined charge / discharge is disassembled, and the positive electrode material (mixture in this Example 1) is collected and analyzed from the positive electrode mixture layer to derive the molar ratio Li / M.
  • Example 1 ⁇ Production of negative electrode> A unit represented by the above formula (1) and a unit represented by the above formula (2), wherein R is hydrogen and M 'is potassium in the above formula (2). A copolymer (A) having a molar ratio of 6/4 to the unit represented by the formula (2) is dissolved in ion-exchanged water, and an aqueous solution having a copolymer (A) concentration of 8% by mass is obtained. Prepared.
  • a composite Si-1 in which the surface of SiO serving as the negative electrode active material was coated with a carbon material (average particle diameter was 5 ⁇ m, specific surface area was 8.8 m 2 / g, and the amount of carbon material in the composite was SiO 2 : 10 parts by mass with respect to 100 parts by mass) and carbon black were added and mixed by stirring to obtain a negative electrode mixture-containing paste.
  • the composition ratio (mass ratio) of negative electrode active material: carbon black: copolymer (A) in this paste was 90: 2: 8.
  • the negative electrode mixture-containing paste is unwound from a roll wound with a copper foil having a thickness of 10 ⁇ m, continuously applied to one side of the copper foil and dried to form a negative electrode mixture layer on one side of the copper foil,
  • the density of the negative electrode mixture layer was adjusted to 1.2 g / cm 3 by performing a press treatment, and then wound into a roll to obtain a negative electrode roll.
  • Li ion was doped to the negative electrode active material in a negative mix layer by the method (roll to roll method) shown in FIG.
  • the negative electrode 2a was pulled out from the negative electrode roll 20a, and LiPF 6 was dissolved at a concentration of 1 mol / l in a non-aqueous electrolyte (a mixed solvent of ethylene carbonate and diethyl carbonate in a volume ratio of 30:70), and vinylene carbonate: 4 mass. %, 4-fluoro-1,3-dioxolan-2-one: solution added in an amount of 5% by mass) and the electrolyte bath 101 provided with the lithium metal electrode 102.
  • a non-aqueous electrolyte a mixed solvent of ethylene carbonate and diethyl carbonate in a volume ratio of 30:70
  • vinylene carbonate 4 mass. %, 4-fluoro-1,3-dioxolan-2-one: solution added in an amount of 5% by mass
  • an electric current corresponding to 500 mAh / g per mass of the negative electrode active material is obtained between the negative electrode 2a and the lithium metal electrode 102 at a current density of 0.2 mA / cm 2 per area of the negative electrode.
  • the negative electrode active material in the negative electrode mixture layer was doped with Li ions by supplying an amount.
  • the negative electrode 2 after Li ion doping is washed in a washing tank 104 equipped with diethyl carbonate after passing through the electrolytic solution tank 101, further dried in a drying tank 105 filled with argon gas, and then wound around a roll 20. It was.
  • Li 2 CO 3 that is a Li-containing compound, Co 3 O 4 that is a Co-containing compound, Mg (OH) 2 that is a Mg-containing compound, ZrO 2 that is a Zr compound, and Al (OH that is an Al-containing compound 3 ) was mixed in a mortar at an appropriate mixing ratio, then solidified into a pellet, and baked in an air atmosphere (under atmospheric pressure) at 950 ° C. for 24 hours using an muffle furnace, and ICP (Inductive Coupled) Lithium cobaltate (A1) having a composition formula determined by the Plasma) method of LiCo 0.9795 Mg 0.011 Zr 0.0005 Al 0.009 O 2 was synthesized.
  • ICP Inductive Coupled Lithium cobaltate (A1) having a composition formula determined by the Plasma
  • the average particle diameter of the obtained positive electrode material (a1) was measured by the above method and found to be 27 ⁇ m.
  • Li 2 CO 3 that is a Li-containing compound, Co 3 O 4 that is a Co-containing compound, Mg (OH) 2 that is an Mg-containing compound, and Al (OH) 3 that is an Al-containing compound are appropriately mixed. After mixing in a mortar, the mixture was hardened into pellets, baked at 950 ° C. for 4 hours in an atmospheric atmosphere (under atmospheric pressure) using a muffle furnace, and the composition formula obtained by ICP method was LiCo 0.97. Mg 0.012 Al 0.009 O 2 lithium cobaltate (B1) was synthesized.
  • lithium cobalt oxide (B1) is added to 200 g of lithium hydroxide aqueous solution: 200 having a pH of 10 and a temperature of 70 ° C., and dispersed by stirring. 3) 3 ⁇ 9H 2 O: and 0.077 g, and ammonia water to suppress variation in pH, was added dropwise over 5 hours, to produce a Al (OH) 3 coprecipitate, the lithium cobaltate ( It was made to adhere to the surface of B1). Thereafter, the lithium cobaltate (B1) to which the Al (OH) 3 coprecipitate is adhered is taken out from the reaction solution, washed, dried, and then heat-treated at 400 ° C. for 10 hours in an air atmosphere. Then, an Al-containing oxide film was formed on the surface of the lithium cobalt oxide (B1) to obtain a positive electrode material (b1).
  • the average particle diameter of the obtained positive electrode material (b1) was measured by the above method and found to be 7 ⁇ m.
  • the positive electrode material (a1) and the positive electrode material (b1) were mixed at a mass ratio of 85:15 to obtain a positive electrode material (1) for battery preparation.
  • the average coating thickness of the Al-containing oxide on the surface of the obtained positive electrode material (1) was measured by the above method, it was 30 nm.
  • the composition of the film was confirmed by element mapping when measuring the average coating thickness, the main component was Al 2 O 3 .
  • the volume-based particle size distribution of the positive electrode material (1) was confirmed by the above method, the average particle diameter was 25 ⁇ m, and peak tops were observed at the respective average particle diameters of the positive electrode material (a1) and the positive electrode material (b1). Two peaks were observed with Moreover, it was 0.25 m ⁇ 2 > / g when the BET specific surface area of positive electrode material (1) was measured using the specific surface area measuring apparatus by a nitrogen adsorption method.
  • Positive electrode material (1) 96.5 parts by mass, NMP solution containing binder (P (VDF-CTFE) at a concentration of 10% by mass): 20 parts by mass, and acetylene black as a conductive auxiliary agent: 1.5 parts by mass Part was kneaded using a biaxial kneader, and NMP was added to adjust the viscosity to prepare a positive electrode mixture-containing paste. This paste is applied to one side of an aluminum foil having a thickness of 15 ⁇ m, vacuum-dried at 120 ° C. for 12 hours to form a positive electrode mixture layer on one side of the aluminum foil, and press treatment is performed to obtain a positive electrode. It was.
  • NMP solution containing binder P (VDF-CTFE) at a concentration of 10% by mass): 20 parts by mass
  • acetylene black as a conductive auxiliary agent 1.5 parts by mass Part was kneaded using a biaxial kneader, and NMP was added to adjust the viscosity to prepare a
  • FIG. 2 is a longitudinal sectional view schematically showing the coin-type lithium ion secondary battery of Example 1.
  • the positive electrode 1 is accommodated inside a metal outer can 4, and the negative electrode 2 is disposed thereon via a separator 3.
  • the negative electrode 2 is in contact with the inner surface of the metal sealing plate 5.
  • the layers of the positive electrode 1, the negative electrode 2, and the separator 3 are not shown separately, but the positive electrode 1 and the negative electrode 2 are opposed to each other with the positive electrode mixture layer and the negative electrode mixture layer through the separator 3.
  • the separator 3 is arranged so that the porous layer (II) is on the positive electrode 1 side.
  • a non-aqueous electrolyte (not shown) is injected into the lithium ion secondary battery 10.
  • the outer can 4 also serves as a positive electrode terminal
  • the sealing plate 5 also serves as a negative electrode terminal.
  • the opening part of the armored can 4 presses the resin-made annular packing 6 arrange
  • the peripheral edge and the inner peripheral surface of the opening end of the outer can 4 are pressed against each other and sealed. That is, in the coin-type lithium ion battery 10, a resin packing 6 is interposed between the positive electrode terminal (exterior can 4) and the negative electrode terminal (sealing plate 5), and is sealed by this packing 6.
  • Example 2 Artificial graphite having an average particle size of 22 ⁇ m: 50 mass% and composite Si-1: 50 mass% were mixed in a V-type blender for 12 hours to obtain a negative electrode active material.
  • a negative electrode mixture-containing paste was prepared in the same manner as in Example 1 except that this negative electrode active material was used, and a negative electrode roll was obtained in the same manner as in Example 1 except that this negative electrode mixture-containing paste was used.
  • the negative electrode active material in the negative electrode mixture layer of the negative electrode according to this negative electrode roll was doped with Li ions in the same manner as in Example 1 except that the amount of electricity passed was 250 mAh / g per negative electrode active material mass.
  • the coin-type lithium ion secondary battery was produced like Example 1 except having used this negative electrode.
  • Example 3 A negative electrode active material was obtained in the same manner as in Example 2 except that the ratio of the artificial graphite and the composite Si-1 in the negative electrode active material was 95% by mass of the artificial graphite and 5% by mass of the composite Si-1.
  • a negative electrode mixture-containing paste was prepared in the same manner as in Example 1 except that this negative electrode active material was used, and a negative electrode roll was obtained in the same manner as in Example 1 except that this negative electrode mixture-containing paste was used.
  • the negative electrode active material in the negative electrode mixture layer of the negative electrode related to the negative electrode roll was doped with Li ions in the same manner as in Example 1 except that the amount of electricity supplied was 50 mAh / g per mass of the negative electrode active material.
  • the coin-type lithium ion secondary battery was produced like Example 1 except having used this negative electrode.
  • Example 4 Scale A graphite powder: 97 parts by mass and silicon powder: 3 parts by mass were mixed by a mixing method involving compressive force and shear force to obtain a mixture A.
  • Mixture B was prepared by mixing 100 parts by mass of this mixture A and 3 parts by mass of non-graphitic carbon material by a mixing method involving compression force and shearing force. The mixture B was heated at 1000 ° C. for 1 hour in an inert atmosphere, and then crushed, and composite particles in which silicon sandwiched between the flaky graphite particles was fixed by amorphous carbon were obtained. Obtained.
  • a negative electrode mixture-containing paste was prepared in the same manner as in Example 1 except that this was used as the negative electrode active material, and a negative electrode roll was obtained in the same manner as in Example 1 except that this negative electrode mixture-containing paste was used.
  • the negative electrode active material in the negative electrode mixture layer of the negative electrode related to the negative electrode roll was doped with Li ions in the same manner as in Example 1 except that the amount of electricity supplied was 100 mAh / g per mass of the negative electrode active material.
  • the coin-type lithium ion secondary battery was produced like Example 1 except having used this negative electrode.
  • Example 5 A negative electrode mixture-containing paste was prepared in the same manner as in Example 1 except that the same artificial graphite as that used in Example 2 was used as the negative electrode active material, and Example 1 except that this negative electrode mixture-containing paste was used. Similarly, a negative electrode roll was obtained. The negative electrode active material in the negative electrode mixture layer of the negative electrode related to the negative electrode roll was doped with Li ions in the same manner as in Example 1 except that the amount of electricity passed was 30 mAh / g per mass of the negative electrode active material. And the coin-type lithium ion secondary battery was produced like Example 1 except having used this negative electrode.
  • Example 6 Artificial graphite same as that used in Example 2: 50% by mass; material Si-2 whose SiO surface is not coated with a carbon material (average particle size is 5 ⁇ m, specific surface area is 6.8 m 2 / g): 50 Mass% was mixed for 12 hours with a V-type blender to obtain a negative electrode active material.
  • a negative electrode mixture-containing paste was prepared in the same manner as in Example 1 except that this negative electrode active material was used, and a negative electrode roll was obtained in the same manner as in Example 1 except that this negative electrode mixture-containing paste was used.
  • the negative electrode active material in the negative electrode mixture layer of the negative electrode according to this negative electrode roll was doped with Li ions in the same manner as in Example 1 except that the amount of electricity passed was 250 mAh / g per negative electrode active material mass. And the coin-type lithium ion secondary battery was produced like Example 1 except having used this negative electrode.
  • Example 1 Coin-type lithium in the same manner as in Example 1 except that the same negative electrode as prepared in Example 1 (negative electrode before doping Li ions to the negative electrode active material in the negative electrode mixture layer) was used as it was. An ion secondary battery was produced.
  • Composite Si-1 negative electrode active material: 90 parts by mass, carbon black: 2 parts by mass, CMC: 1.5 parts by mass, and SBR: 6.5 parts by mass were mixed with ion-exchanged water, An agent-containing paste was prepared.
  • a negative electrode roll was produced in the same manner as in Example 1 except that this negative electrode mixture-containing paste was used. Lithium was added to the negative electrode active material in the negative electrode mixture layer of the negative electrode related to this negative electrode roll in the same manner as in Example 1. Doped with ions. And the coin-type lithium ion secondary battery was produced like Example 1 except having used this negative electrode.
  • the lithium ion secondary batteries (5 each) were charged at a constant current of up to 4.4V at a current value of 0.5C, and subsequently the current value was set at 0.02C at a constant voltage of 4.4V. Charged until it reached. Then, it discharged to 2.0V with the constant current of 0.2C, and calculated
  • Each battery was subjected to constant current-constant voltage charging and constant current discharging under the same conditions as those for the initial discharge capacity measurement, and the discharge capacity was determined. Then, a value obtained by dividing these discharge capacities by the initial discharge capacities was expressed as a percentage to obtain a capacity maintenance ratio, and an average value of 5 pieces was calculated for each.
  • Table 1 shows the configurations of the lithium ion secondary batteries of Examples and Comparative Examples and the evaluation results.
  • the capacity retention rate at the time of charge / discharge cycle characteristic evaluation is shown as a relative value when the value of the battery of Example 5 is 100.
  • the negative electrodes according to the lithium ion secondary batteries of Examples 1 to 6 using the copolymer (A) as the binder of the negative electrode mixture layer were prepared by adding Li to the negative electrode active material in the negative electrode mixture layer.
  • the negative electrode mixture layer did not fall off even when wound into a roll after ion doping, and the properties of the negative electrode mixture layer were good. Therefore, it can be said that these negative electrodes are excellent in productivity.
  • the lithium ion secondary batteries of Examples 1 to 6 had a high capacity retention rate when evaluating charge / discharge cycle characteristics, and had excellent charge / discharge cycle characteristics.
  • the negative electrode according to the battery of Comparative Example 2 using SBR, which is widely used in ordinary lithium ion secondary batteries, as the binder of the negative electrode mixture layer is Li to the negative electrode active material in the negative electrode mixture layer.
  • the negative electrode mixture layer dropped off when it was wound into a roll after ion doping. Since such a part cannot be used for a battery, it can be said that the manufactured negative electrode is inferior in productivity because the ratio of the part that can be used for battery manufacture becomes small.
  • the battery of Comparative Example 2 using this negative electrode and the battery of Comparative Example 1 using a negative electrode in which the negative electrode active material in the negative electrode mixture layer was not doped with Li were included in the charge / discharge cycle characteristics evaluation. The capacity retention rate was low, and the charge / discharge cycle characteristics were inferior.
  • Example 7 [Experimental example of a lithium ion secondary battery having a negative electrode containing a negative electrode active material doped with Li ions by an extra-system pre-doping method (ii)] (Example 7)
  • the same composite Si-1 as used in Example 1 was immersed in a solution of naphthalene and metallic Li dissolved in tetrahydrofuran. Thereafter, it was washed with diethyl carbonate and dried to obtain a composite Si-1 doped with Li ions.
  • a negative electrode mixture-containing paste was prepared in the same manner as Example 1 except that this Li ion-doped composite Si-1 was used, and a copper foil having a thickness of 10 ⁇ m was wound using this paste.
  • the rolled roll was unwound and continuously applied to one side of the copper foil and dried to form a negative electrode mixture layer on one side of the copper foil, and a press treatment was performed to make the density of the negative electrode mixture layer 1.2 g / cm 3.
  • the film was wound into a roll to obtain a negative electrode roll.
  • a coin-type lithium ion secondary battery was produced in the same manner as in Example 1 except that the negative electrode drawn from the negative electrode roll was cut into a predetermined shape and used, and was successfully produced.
  • molar ratio Li / M in the obtained coin-type lithium ion secondary battery was 0.94.
  • the negative electrode used for the lithium ion secondary battery of Example 7 when the negative electrode wound up in roll shape after preparation was checked for the presence or absence of the negative electrode mixture layer from the current collector, the negative electrode mixture layer The negative electrode mixture layer had good properties. Therefore, it can be said that this negative electrode is excellent in productivity.
  • the lithium ion secondary battery of the present invention can be applied to the same use as that of a conventionally known lithium ion secondary battery.

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Abstract

The present invention provides a negative electrode for non-aqueous-electrolyte-based electrochemical elements having excellent producibility, a method for manufacturing the negative electrode, a lithium-ion secondary cell that has the negative electrode and has excellent charge/discharge cycle characteristics, and a method for manufacturing the lithium-ion secondary cell. This negative electrode for non-aqueous-electrolyte-based electrochemical elements is characterized in that a negative electrode mixture layer: contains at least a negative electrode active material doped with Li ions; and contains, as a binder, a copolymer having a unit that contains a hydroxyl group and a unit that contains an alkali metal salt group of a carboxyl group. This lithium-ion secondary cell is characterized in that the negative electrode for non-aqueous-electrolyte-based electrochemical elements is formed as a negative electrode.

Description

非水電解液系電気化学素子用負極、その製造方法、リチウムイオン二次電池およびその製造方法Non-aqueous electrolyte-based electrochemical element negative electrode, method for producing the same, lithium ion secondary battery and method for producing the same
　本発明は、生産性に優れた非水電解液系電気化学素子用負極とその製造方法、および前記負極を有し、充放電サイクル特性に優れたリチウムイオン二次電池とその製造方法に関するものである。 The present invention relates to a negative electrode for a non-aqueous electrolyte based electrochemical device having excellent productivity and a method for producing the same, and a lithium ion secondary battery having the negative electrode and having excellent charge / discharge cycle characteristics and a method for producing the same. is there.
　リチウムイオン二次電池は、高電圧・高容量であることから、その発展に対して大きな期待が寄せられている。特に最近では、電池反応に関与する正極活物質や負極活物質、非水電解液のみならず、正極や負極で使用されるバインダについての改良も行われている。 Since lithium ion secondary batteries have high voltage and high capacity, there are great expectations for their development. Particularly recently, improvements have been made not only to positive electrode active materials and negative electrode active materials involved in battery reactions and non-aqueous electrolytes, but also to binders used in positive electrodes and negative electrodes.
　例えば、特許文献１、２には、ビニルアルコールとエチレン性不飽和カルボン酸アルカリ金属中和物との共重合体を負極合剤層のバインダに使用することで、負極活物質の脱落や負極合剤層の集電体からの剥離を抑制する技術が提案されている。 For example, in Patent Documents 1 and 2, by using a copolymer of vinyl alcohol and an alkali metal neutralized ethylenically unsaturated carboxylic acid as a binder for the negative electrode mixture layer, the negative electrode active material can be removed or the negative electrode composite can be removed. A technique for suppressing peeling of the agent layer from the current collector has been proposed.
　ところで、最近では、小型化および多機能化した携帯機器用のリチウムイオン二次電池について更なる高容量化が望まれており、これを受けて、負極活物質を、従来から汎用されている黒鉛から、低結晶性炭素、Ｓｉ（シリコン）、Ｓｎ（錫）などのように、より多くのＬｉ（リチウム）を収容可能な材料（以下、「高容量負極材料」ともいう）へ変更することも検討されている。 By the way, recently, a further increase in capacity has been desired for a lithium-ion secondary battery for portable devices that has been downsized and multifunctional, and in response to this, a negative electrode active material has been used as a widely used graphite. To a material that can accommodate more Li (lithium) such as low crystalline carbon, Si (silicon), Sn (tin), etc. (hereinafter also referred to as “high capacity negative electrode material”). It is being considered.
　ところが、高容量負極材料を用いて構成した電池では、一般に、充電によって正極から放出されたＬｉのうち、高容量負極材料に取り込まれて次の放電時に放出されずに残留するものの割合が大きく、電池が本来備えている容量を十分に引き出し得ないといった問題が生じやすい。 However, in a battery configured using a high-capacity negative electrode material, in general, among Li released from the positive electrode by charging, the ratio of those taken into the high-capacity negative electrode material and remaining without being discharged at the next discharge is large. There is a tendency that the capacity that the battery originally has cannot be drawn out sufficiently.
　このような電池の不可逆容量を小さくするために、負極（負極合剤層）にＬｉイオンをドープ（プレドープ）して、電池の充放電時に正極と負極との間を行き来できるＬｉの割合を高める技術も検討されている。こうした負極へのＬｉイオンのプレドープ技術としては、電池内で負極にＬｉイオンをプレドープ（以下、「系内プレドープ」という場合がある）する手段の他に、特許文献３、４に記載されているように、あらかじめＬｉイオンをプレドープした負極を用いて電池を組み立てる手段（以下、このような手段での負極へのＬｉイオンのプレドープを「系外プレドープ」という場合がある）も提案されている。 In order to reduce the irreversible capacity of such a battery, the negative electrode (negative electrode mixture layer) is doped with Li ions (pre-doping) to increase the proportion of Li that can travel between the positive electrode and the negative electrode during charge / discharge of the battery. Technology is also being considered. Such a pre-doping technique of Li ions into the negative electrode is described in Patent Documents 3 and 4 in addition to means for pre-doping Li ions into the negative electrode in the battery (hereinafter sometimes referred to as “in-system pre-doping”). Thus, means for assembling a battery using a negative electrode pre-doped with Li ions in advance (hereinafter, pre-doping of Li ions into the negative electrode by such means may be referred to as “outside pre-doping”) has also been proposed.
国際公開第２０１４／２０７９６７号International Publication No. 2014/207967 特開２０１５－８１４７号公報Japanese Patent Laying-Open No. 2015-8147 特開平１１－２８３６７０号公報JP 11-283670 A 特開２００８－９１１９１号公報JP 2008-91191 A
　ところが、系外プレドープによって負極合剤層中の負極活物質にＬｉイオンをドープすると、負極合剤層の硬度が増大して脆くなるため、Ｌｉイオンのドープ前に比べて取扱い性が低下し、これによって負極の生産性が低下しやすく、かかる点において改善の余地がある。 However, when the negative electrode active material in the negative electrode mixture layer is doped with Li ions by pre-doping outside the system, the hardness of the negative electrode mixture layer increases and becomes brittle, so that the handleability is reduced compared to before doping with Li ions, This tends to reduce the productivity of the negative electrode, and there is room for improvement in this respect.
　負極の生産性を考慮すると、例えば、Ｌｉイオンをドープする前の負極をロール状に巻き取り、そのロールから引き出した負極を搬送する途中にＬｉイオンのドープを行い、その後再度ロール状に巻き取る、いわゆるロール・トゥ・ロール法で連続的にＬｉイオンのドープを行うことも考えられる。しかし、Ｌｉイオンのドープによって負極合剤層が脆くなっていると、ロール状に巻き取り難くなるため、ロール・トゥ・ロール法による系外プレドープを採用した場合には、特に負極の生産性の低下が顕著となりやすい。更に、負極活物質に直接Ｌｉイオンをドープし、これを用いて負極を作製したときにも、負極合剤層が脆くなりやすく、このような負極を連続的に製造する場合などでは、例えば、ロール状に巻き取り難くなるなど、取扱い性が損なわれるため、負極の生産性が低下する虞がある。 Considering the productivity of the negative electrode, for example, the negative electrode before doping with Li ions is wound into a roll shape, Li ions are doped while the negative electrode drawn from the roll is transported, and then wound into a roll shape again. It is also conceivable to dope Li ions continuously by the so-called roll-to-roll method. However, if the negative electrode mixture layer becomes brittle due to the doping of Li ions, it becomes difficult to wind it into a roll. Therefore, when adopting an external pre-dope by the roll-to-roll method, the productivity of the negative electrode is particularly high. The decline tends to be noticeable. Furthermore, when the negative electrode active material is directly doped with Li ions, and the negative electrode is produced using this, the negative electrode mixture layer is likely to be brittle. In the case of continuously producing such a negative electrode, for example, Since handleability is impaired such as difficulty in winding in a roll shape, the productivity of the negative electrode may be reduced.
　また、系外プレドープによるＬｉイオンのドープによって負極合剤層の硬度が増大することで、リチウムイオン二次電池の充放電サイクル特性が低下しやすく、かかる点においても改善の余地がある。 In addition, since the hardness of the negative electrode mixture layer is increased by doping Li ions by pre-doping outside the system, the charge / discharge cycle characteristics of the lithium ion secondary battery are likely to be lowered, and there is room for improvement in this respect.
　本発明は、前記事情に鑑みてなされたものであり、その目的は、生産性に優れた非水電解液系電気化学素子用負極とその製造方法、および前記負極を有し、充放電サイクル特性に優れたリチウムイオン二次電池とその製造方法を提供することにある。 The present invention has been made in view of the above circumstances, and its object is to provide a negative electrode for a non-aqueous electrolyte based electrochemical device excellent in productivity, a method for producing the same, and the negative electrode, and charge / discharge cycle characteristics. An excellent lithium ion secondary battery and a method for manufacturing the same are provided.
　前記目的を達成し得た本発明の非水電解液系電気化学素子用負極は、負極活物質およびバインダを含有する負極合剤層を有しており、前記負極合剤層は、Ｌｉイオンがドープされてなる負極活物質を少なくとも含有し、かつ下記式（１）で表されるユニットと下記式（２）で表されるユニットとを有する共重合体を前記バインダとして含有していることを特徴とするものである。 The negative electrode for a non-aqueous electrolyte based electrochemical device of the present invention that has achieved the above object has a negative electrode mixture layer containing a negative electrode active material and a binder, and the negative electrode mixture layer contains Li ions. It contains at least a doped negative electrode active material and a copolymer having a unit represented by the following formula (1) and a unit represented by the following formula (2) as the binder. It is a feature.
Figure JPOXMLDOC01-appb-C000003
Figure JPOXMLDOC01-appb-C000003
Figure JPOXMLDOC01-appb-C000004
Figure JPOXMLDOC01-appb-C000004
　前記式（２）中、Ｒは水素またはメチル基であり、Ｍ’はアルカリ金属元素である。 In the formula (2), R is hydrogen or a methyl group, and M ′ is an alkali metal element.
　本発明の非水電解液系電気化学素子用負極は、負極活物質とバインダとを含有する負極合剤層を有する負極の、前記負極合剤層中の負極活物質にＬｉイオンをドープする工程を有する本発明の製造方法（１）によって製造することができる。 The negative electrode for a non-aqueous electrolyte based electrochemical device of the present invention is a step of doping Li ions into the negative electrode active material in the negative electrode mixture layer of a negative electrode having a negative electrode mixture layer containing a negative electrode active material and a binder. It can manufacture by the manufacturing method (1) of this invention which has these.
　更に、本発明の非水電解液系電気化学素子用負極は、少なくとも一部にＬｉイオンをドープした負極活物質と、バインダとを含有する負極合剤層を有する負極を作製する工程を有する本発明の製造方法（２）によっても製造することができる。 Furthermore, the negative electrode for a non-aqueous electrolyte based electrochemical device of the present invention includes a step of producing a negative electrode having a negative electrode mixture layer containing a negative electrode active material doped with Li ions at least partially and a binder. It can also be produced by the production method (2) of the invention.
　また、本発明のリチウムイオン二次電池は、負極、正極活物質およびバインダを含有する正極合剤層を有する正極、セパレータおよび非水電解液が外装体内に収容されてなり、本発明の非水電解液系電気化学素子用負極を前記負極として構成されたことを特徴とするものである。 In addition, the lithium ion secondary battery of the present invention comprises a negative electrode, a positive electrode having a positive electrode mixture layer containing a positive electrode active material and a binder, a separator, and a nonaqueous electrolyte solution housed in an exterior body. The negative electrode for an electrolyte-based electrochemical device is configured as the negative electrode.
　本発明のリチウムイオン二次電池は、前記製造方法（１）または（２）で得られた非水電解液系電気化学素子用負極を用いてリチウムイオン二次電池を組み立てる工程を有する本発明の製造方法によって製造することができる。 The lithium ion secondary battery according to the present invention includes a step of assembling a lithium ion secondary battery using the negative electrode for a non-aqueous electrolyte based electrochemical device obtained by the production method (1) or (2). It can be manufactured by a manufacturing method.
　本発明によれば、生産性に優れた非水電解液系電気化学素子用負極とその製造方法、および前記負極を有し、充放電サイクル特性に優れたリチウムイオン二次電池とその製造方法を提供することができる。 According to the present invention, a negative electrode for a non-aqueous electrolyte based electrochemical device having excellent productivity and a method for producing the same, and a lithium ion secondary battery having the negative electrode and having excellent charge / discharge cycle characteristics and a method for producing the same are disclosed. Can be provided.
ロール・トゥ・ロール法によって負極の負極合剤層中の負極活物質にＬｉイオンをドープする工程の説明図である。It is explanatory drawing of the process of doping Li ion to the negative electrode active material in the negative mix layer of a negative electrode by the roll-to-roll method. 本発明のリチウムイオン二次電池の一例を模式的に表す縦断面図である。It is a longitudinal cross-sectional view which represents typically an example of the lithium ion secondary battery of this invention.
　本発明の非水電解液系電気化学素子用負極（以下、単に「負極」という）は、リチウムイオン二次電池やスーパーキャパシタなとの、非水電解液を有し、充放電が繰り返される電気化学素子の負極に使用されるものである。そして、本発明の負極は、負極活物質およびバインダを含有する負極合剤層を有し、例えばこの負極合剤層が集電体の片面または両面に形成された構造を有しており、更に、負極合剤層が含有する負極活物質の少なくとも一部に系外プレドープによってＬｉイオンがドープされてなるものである。 The negative electrode for a non-aqueous electrolyte based electrochemical device of the present invention (hereinafter simply referred to as “negative electrode”) has a non-aqueous electrolyte such as a lithium ion secondary battery or a supercapacitor and is repeatedly charged and discharged. It is used for the negative electrode of a chemical element. The negative electrode of the present invention has a negative electrode mixture layer containing a negative electrode active material and a binder. For example, the negative electrode mixture layer has a structure in which the negative electrode mixture layer is formed on one side or both sides of a current collector. At least a part of the negative electrode active material contained in the negative electrode mixture layer is doped with Li ions by pre-doping outside the system.
　前記の通り、系外プレドープによって負極合剤層中の負極活物質にＬｉイオンをドープした負極（その負極合剤層）は硬度が大きく脆くなる。そのため、特にロール・トゥ・ロール法で系外プレドープを行う場合、Ｌｉイオンドープ後の負極をロール状に巻き取る際に負極合剤層が崩れたり、負極集電体から剥離したりしやすい。また、ロール・トゥ・ロール法を採用しない場合でも、例えばあらかじめＬｉイオンをドープした負極活物質を含有する負極合剤層は、ロール・トゥ・ロール法で系外プレドープを行って得られた負極の場合と同様に脆くなりやすく、このように系外プレドープを経た負極活物質を含有する負極は取り扱い性が低い。このような理由から、系外プレドープを行ってＬｉイオンをドープした負極活物質を含有する負極の場合、生産性が低いといった問題があった。 As described above, the negative electrode (the negative electrode mixture layer) in which the negative electrode active material in the negative electrode mixture layer is doped with Li ions by pre-doping outside the system has a large hardness and becomes brittle. Therefore, especially when performing pre-doping outside the system by a roll-to-roll method, the negative electrode mixture layer tends to collapse or peel from the negative electrode current collector when the negative electrode after Li ion doping is wound into a roll. Further, even when the roll-to-roll method is not adopted, for example, the negative electrode mixture layer containing a negative electrode active material previously doped with Li ions is obtained by performing pre-doping outside the system by the roll-to-roll method. The negative electrode containing the negative electrode active material that has been pre-doped in this way is low in handleability as in the case of. For these reasons, there is a problem that productivity is low in the case of a negative electrode containing a negative electrode active material that is pre-doped outside and doped with Li ions.
　また、Ｌｉイオンのドープを要するような負極活物質は、電池の充放電に伴う膨張・収縮量が大きく、これを含有する負極合剤層も電池の充放電に伴って大きく膨張・収縮するが、系外プレドープによって負極合剤層の硬度が増大した負極を用いたリチウムイオン二次電池などの電気化学素子においては、充放電によって大きく体積変化することで硬く脆い負極合剤層に欠陥が生じやすいため、充放電の繰り返しによる容量低下が生じやすい。 In addition, the negative electrode active material that requires doping of Li ions has a large amount of expansion / contraction due to charging / discharging of the battery, and the negative electrode mixture layer containing this greatly expands / contracts along with charging / discharging of the battery. In an electrochemical element such as a lithium ion secondary battery using a negative electrode whose hardness of the negative electrode mixture layer is increased by pre-doping outside the system, the hard and brittle negative electrode mixture layer is defective due to a large volume change due to charge and discharge. Therefore, the capacity is likely to decrease due to repeated charge and discharge.
　そこで、本発明の負極では、負極合剤層のバインダに、前記式（１）で表わされるユニットと前記式（２）で表わされるユニットとを有する共重合体〔以下、「共重合体（Ａ）」という〕を使用することとした。 Therefore, in the negative electrode of the present invention, a copolymer having a unit represented by the above formula (1) and a unit represented by the above formula (2) in the binder of the negative electrode mixture layer [hereinafter referred to as “copolymer (A ) ”)].
　共重合体（Ａ）をバインダに用いた負極合剤層は、可撓性が高くなり、また、負極集電体との剥離強度も向上するため、系外プレドープによってＬｉイオンをドープしても、負極合剤層の欠陥が生じ難く、その取扱い性が向上する。よって、本発明の負極は、系外プレドープを経た負極活物質を含有していても良好な生産性を有している。そして、本発明の負極を製造するにあたり、ロール・トゥ・ロール法によって系外プレドープを行った場合でも、欠陥部分が発生し難いため、これにより更に生産性を高めることができる。 The negative electrode mixture layer using the copolymer (A) as a binder has high flexibility and also improves the peel strength from the negative electrode current collector. In addition, defects in the negative electrode mixture layer hardly occur and the handleability is improved. Therefore, the negative electrode of the present invention has good productivity even if it contains a negative electrode active material that has undergone extra-predoping. And when manufacturing the negative electrode of this invention, even when it carries out out-of-system pre dope by a roll-to-roll method, since a defect part does not generate | occur | produce easily, productivity can be improved further by this.
　また、本発明の負極を用いて構成したリチウムイオン二次電池（本発明のリチウムイオン二次電池）などの電気化学素子においても、充放電の繰り返しによる負極合剤層の劣化を抑制できるため、充放電サイクル特性が向上する。 In addition, in an electrochemical element such as a lithium ion secondary battery (lithium ion secondary battery of the present invention) configured using the negative electrode of the present invention, the deterioration of the negative electrode mixture layer due to repeated charge and discharge can be suppressed. Charge / discharge cycle characteristics are improved.
　更に、共重合体（Ａ）を負極合剤層のバインダに使用することで、リチウムイオン二次電池などの電気化学素子の負荷特性も向上する。これは、共重合体（Ａ）をバインダに使用した負極合剤層では、内部に非水電解液が良好に浸透するような構造が形成されているためではないかと考えている。また、共重合体（Ａ）をバインダに使用することで、電気化学素子の使用に伴って生じる虞がある負極表面でのＬｉの析出も、高度に抑制できる。 Furthermore, by using the copolymer (A) as a binder for the negative electrode mixture layer, the load characteristics of an electrochemical element such as a lithium ion secondary battery are also improved. This is thought to be because the negative electrode mixture layer using the copolymer (A) as a binder has a structure in which the nonaqueous electrolytic solution penetrates well inside. In addition, by using the copolymer (A) as a binder, it is possible to highly suppress the precipitation of Li on the negative electrode surface that may occur with the use of an electrochemical element.
　負極合剤層に使用する負極活物質としては、黒鉛、熱分解炭素類、コークス類、ガラス状炭素類、有機高分子化合物の焼成体、メソカーボンマイクロビーズ、炭素繊維、活性炭などの炭素材料；ＳｉまたはＳｎの単体；ＳｉまたはＳｎを含む合金；ＳｉまたはＳｎを含む酸化物；などが挙げられる。負極活物質には、これらのうちの１種のみを用いてもよく、２種以上を併用してもよい。 As the negative electrode active material used for the negative electrode mixture layer, carbon materials such as graphite, pyrolytic carbons, cokes, glassy carbons, fired bodies of organic polymer compounds, mesocarbon microbeads, carbon fibers, activated carbon; Si or Sn simple substance; Si or Sn-containing alloy; Si or Sn-containing oxide; As the negative electrode active material, only one of these may be used, or two or more may be used in combination.
　このような負極活物質の中でも、本発明による効果がより顕著となることから、Ｌｉイオンの受け入れ量が大きくかつ不可逆容量が大きいものが望ましく、例えば、ＳｉとＯとを構成元素に含む材料（ただし、Ｓｉに対するＯの原子比ｘは、０．５≦ｘ≦１．５。以下、この材料を「材料Ｓ」という場合がある。）を使用することが好ましい。 Among such negative electrode active materials, since the effect of the present invention becomes more remarkable, it is desirable to have a large amount of Li ions accepted and a large irreversible capacity. For example, a material containing Si and O as constituent elements ( However, the atomic ratio x of O with respect to Si is preferably 0.5 ≦ x ≦ 1.5 (hereinafter, this material may be referred to as “material S”).
　前記材料Ｓとしては、ＳｉとＯとを構成元素に含む一方でＬｉを構成元素に含まない材料、例えば、組成式ＳｉＯｘ（０．５≦ｘ≦１．５）で表されるものなどが挙げられる。 Examples of the material S include materials containing Si and O as constituent elements and not containing Li as a constituent element, such as those represented by the composition formula SiO x (0.5 ≦ x ≦ 1.5). Can be mentioned.
　ＳｉＯｘは、Ｓｉの微結晶または非晶質相を含んでいてもよく、この場合、ＳｉとＯの原子比は、Ｓｉの微結晶または非晶質相のＳｉを含めた比率となる。すなわち、ＳｉＯｘには、非晶質のＳｉＯ２マトリックス中にＳｉ（例えば、微結晶Ｓｉ）が分散した構造のものが含まれ、この非晶質のＳｉＯ２と、その中に分散しているＳｉを合わせて、前記の原子比ｘが０．５≦ｘ≦１．５を満足していればよい。例えば、非晶質のＳｉＯ２マトリックス中にＳｉが分散した構造で、ＳｉＯ２とＳｉのモル比が１：１の材料の場合、ｘ＝１であるので、構造式としてはＳｉＯで表記される。このような構造の材料の場合、例えば、Ｘ線回折分析では、Ｓｉ（微結晶Ｓｉ）の存在に起因するピークが観察されない場合もあるが、透過型電子顕微鏡で観察すると、微細なＳｉの存在が確認できる。 The SiO x may contain Si microcrystal or amorphous phase. In this case, the atomic ratio of Si and O is a ratio including Si microcrystal or amorphous phase Si. That is, the SiO x includes a structure in which Si (for example, microcrystalline Si) is dispersed in an amorphous SiO 2 matrix, and is dispersed in the amorphous SiO 2 . In combination with Si, the atomic ratio x should satisfy 0.5 ≦ x ≦ 1.5. For example, in the case of a material in which Si is dispersed in an amorphous SiO 2 matrix and the material has a molar ratio of SiO 2 to Si of 1: 1, since x = 1, the structural formula is represented by SiO. . In the case of a material having such a structure, for example, in X-ray diffraction analysis, a peak due to the presence of Si (microcrystalline Si) may not be observed, but when observed with a transmission electron microscope, the presence of fine Si Can be confirmed.
　材料Ｓは、炭素材料と複合化した複合体を構成していることが好ましく、例えば、材料Ｓの表面が炭素材料で被覆されていることが望ましい。通常、材料Ｓは導電性が乏しいため、これを負極活物質として用いる際には、良好な電池特性確保の観点から、導電性材料（導電助剤）を使用し、負極内における材料Ｓと導電性材料との混合・分散を良好にして、優れた導電ネットワークを形成する必要がある。材料Ｓを炭素材料と複合化した複合体であれば、例えば、単に材料Ｓと炭素材料などの導電性材料とを混合して得られた材料を用いた場合よりも、負極における導電ネットワークが良好に形成される。 The material S preferably constitutes a composite that is combined with a carbon material. For example, the surface of the material S is preferably coated with the carbon material. In general, since the material S has poor conductivity, when using it as a negative electrode active material, a conductive material (conductive aid) is used from the viewpoint of securing good battery characteristics, and the material S and the conductive material in the negative electrode are electrically conductive. It is necessary to form an excellent conductive network by making good mixing and dispersion with the conductive material. In the case of a composite in which the material S is combined with a carbon material, for example, the conductive network in the negative electrode is better than when a material obtained by simply mixing the material S and a conductive material such as a carbon material is used. Formed.
　材料Ｓと炭素材料との複合体としては、前記のように、材料Ｓの表面を炭素材料で被覆したものの他、材料Ｓと炭素材料との造粒体などが挙げられる。 Examples of the composite of the material S and the carbon material include a granulated body of the material S and the carbon material as well as the material S coated with the carbon material as described above.
　材料Ｓとの複合体の形成に用い得る炭素材料としては、例えば、低結晶性炭素、カーボンナノチューブ、気相成長炭素繊維などが好ましいものとして挙げられる。 As a carbon material that can be used for forming a composite with the material S, for example, low crystalline carbon, carbon nanotube, vapor grown carbon fiber, and the like are preferable.
　炭素材料の詳細としては、繊維状またはコイル状の炭素材料、カーボンブラック（アセチレンブラック、ケッチェンブラックを含む。）、人造黒鉛、易黒鉛化炭素および難黒鉛化炭素よりなる群から選ばれる少なくとも１種の材料が好ましい。繊維状またはコイル状の炭素材料は、導電ネットワークを形成しやすく、かつ表面積の大きい点において好ましい。カーボンブラック（アセチレンブラック、ケッチェンブラックを含む。）、易黒鉛化炭素および難黒鉛化炭素は、高い電気伝導性、高い保液性を有しており、更に、電池の充放電によって材料Ｓの粒子が膨張・収縮しても、その粒子との接触を保持しやすい性質を有している点において好ましい。 The details of the carbon material include at least one selected from the group consisting of fibrous or coiled carbon materials, carbon black (including acetylene black and ketjen black), artificial graphite, graphitizable carbon, and non-graphitizable carbon. A seed material is preferred. A fibrous or coiled carbon material is preferable in that it easily forms a conductive network and has a large surface area. Carbon black (including acetylene black and ketjen black), graphitizable carbon, and non-graphitizable carbon have high electrical conductivity and high liquid retention. Even if the particles expand and contract, it is preferable in that it has a property of easily maintaining contact with the particles.
　前記例示の炭素材料の中でも、材料Ｓとの複合体が造粒体である場合に用いるものとしては、繊維状の炭素材料が特に好ましい。繊維状の炭素材料は、その形状が細い糸状であり柔軟性が高いために電池の充放電に伴う材料Ｓの膨張・収縮に追従でき、また、嵩密度が大きいために、材料Ｓの粒子と多くの接合点を持つことができるからである。繊維状の炭素としては、例えば、ポリアクリロニトリル（ＰＡＮ）系炭素繊維、ピッチ系炭素繊維、気相成長炭素繊維、カーボンナノチューブなどが挙げられ、これらの何れを用いてもよい。 Among the carbon materials exemplified above, a fibrous carbon material is particularly preferable as a material used when the composite with the material S is a granulated body. The fibrous carbon material has a thin thread shape and high flexibility, so that it can follow the expansion and contraction of the material S that accompanies charging / discharging of the battery, and since the bulk density is large, This is because it can have many junctions. Examples of the fibrous carbon include polyacrylonitrile (PAN) -based carbon fiber, pitch-based carbon fiber, vapor-grown carbon fiber, and carbon nanotube, and any of these may be used.
　材料Ｓと炭素材料との複合体において、材料Ｓと炭素材料との比率は、材料Ｓ：１００質量部に対して、炭素材料が、３質量部以上であることが好ましく、５質量部以上であることがより好ましく、７質量部以上であることが更に好ましく、また、２０質量部以下であることが好ましく、１７質量部以下であることがより好ましい。理由は定かではないが、Ｌｉイオンをドープした場合には、前記複合体における材料Ｓと炭素材料との比率を前記のように調整することで、電池の充放電サイクル特性を更に高めることが可能となる。 In the composite of the material S and the carbon material, the ratio of the material S to the carbon material is preferably 3 parts by mass or more of the carbon material with respect to 100 parts by mass of the material S: 5 parts by mass or more. More preferably, it is more preferably 7 parts by mass or more, more preferably 20 parts by mass or less, and even more preferably 17 parts by mass or less. The reason is not clear, but when Li ions are doped, the charge / discharge cycle characteristics of the battery can be further improved by adjusting the ratio of the material S and the carbon material in the composite as described above. It becomes.
　材料Ｓと炭素材料との複合体は、例えば下記の方法によって得ることができる。 The composite of the material S and the carbon material can be obtained by, for example, the following method.
　材料Ｓの表面を炭素材料で被覆して複合体とする場合には、例えば、材料Ｓの粒子と炭化水素系ガスとを気相中にて加熱して、炭化水素系ガスの熱分解により生じた炭素を、粒子の表面上に堆積させる。このように、気相成長（ＣＶＤ）法によれば、炭化水素系ガスが材料Ｓの粒子の隅々にまで行き渡り、粒子の表面に導電性を有する炭素材料を含む薄くて均一な皮膜（炭素材料被覆層）を形成できることから、少量の炭素材料によって材料Ｓの粒子に均一性よく導電性を付与できる。 When the surface of the material S is coated with a carbon material to form a composite, for example, the particles of the material S and the hydrocarbon gas are heated in the gas phase, and are generated by thermal decomposition of the hydrocarbon gas. Carbon is deposited on the surface of the particles. Thus, according to the vapor deposition (CVD) method, the hydrocarbon-based gas spreads to every corner of the particle of the material S, and a thin and uniform film (carbon) containing a conductive carbon material on the particle surface. Since the material covering layer) can be formed, the conductivity of the particles of the material S can be imparted with good uniformity with a small amount of carbon material.
　炭素材料で被覆された材料Ｓの製造において、ＣＶＤ法の処理温度（雰囲気温度）については、炭化水素系ガスの種類によっても異なるが、通常、６００～１２００℃が適当であり、中でも、７００℃以上であることが好ましく、８００℃以上であることが更に好ましい。処理温度が高い方が不純物の残存が少なく、かつ導電性の高い炭素を含む被覆層を形成できるからである。 In the production of the material S coated with the carbon material, the processing temperature (atmosphere temperature) of the CVD method varies depending on the type of hydrocarbon gas, but is usually 600 to 1200 ° C., and more preferably 700 ° C. It is preferable that it is above, and it is still more preferable that it is 800 degreeC or more. This is because the higher the treatment temperature, the less the remaining impurities, and the formation of a coating layer containing carbon having high conductivity.
　炭化水素系ガスの液体ソースとしては、トルエン、ベンゼン、キシレン、メシチレンなどを用いることができるが、取り扱いやすいトルエンが特に好ましい。これらを気化させる（例えば、窒素ガスでバブリングする）ことにより炭化水素系ガスを得ることができる。また、メタンガスやアセチレンガスなどを用いることもできる。  As the liquid source of hydrocarbon gas, toluene, benzene, xylene, mesitylene and the like can be used, but toluene that is easy to handle is particularly preferable. A hydrocarbon-based gas can be obtained by vaporizing them (for example, bubbling with nitrogen gas). Moreover, methane gas, acetylene gas, etc. can also be used.
　また、材料Ｓと炭素材料との造粒体を作製する場合には、材料Ｓが分散媒に分散した分散液を用意し、それを噴霧し乾燥して、複数の粒子を含む造粒体を作製する。分散媒としては、例えば、エタノールなどを用いることができる。分散液の噴霧は、通常、５０～３００℃の雰囲気内で行うことが適当である。前記の方法以外にも、振動型や遊星型のボールミルやロッドミルなどを用いた機械的な方法による造粒方法においても、材料Ｓと炭素材料との造粒体を作製することができる。 In addition, when producing a granulated body of the material S and the carbon material, a dispersion liquid in which the material S is dispersed in a dispersion medium is prepared, sprayed and dried to obtain a granulated body including a plurality of particles. Make it. For example, ethanol or the like can be used as the dispersion medium. It is appropriate to spray the dispersion liquid in an atmosphere of 50 to 300 ° C. In addition to the above method, a granulated body of the material S and the carbon material can be produced also by a granulating method by a mechanical method using a vibration type or planetary type ball mill or rod mill.
　材料Ｓの平均粒子径は、小さすぎると材料Ｓの分散性が低下して本発明の効果が十分に得られなくなる虞があることや、材料Ｓは電池の充放電に伴う体積変化が大きいため、平均粒子径が大きすぎると膨張・収縮による材料Ｓの崩壊が生じやすくなる（この現象は材料Ｓの容量劣化につながる）ことから、０．１μｍ以上１０μｍ以下であることが好ましい。 If the average particle size of the material S is too small, the dispersibility of the material S may be reduced and the effects of the present invention may not be sufficiently obtained, and the material S has a large volume change associated with charging / discharging of the battery. If the average particle diameter is too large, the material S is likely to collapse due to expansion / contraction (this phenomenon leads to capacity degradation of the material S), and therefore it is preferably 0.1 μm or more and 10 μm or less.
　負極合剤層が含有する負極活物質全量中の前記複合体の含有量は、例えば前記複合体を使用することによる電池の高容量化効果をより良好に確保する観点から、５質量％以上であることが好ましく、１０質量％以上であることが好ましく、２０質量％以上であることがより好ましく、５０質量％以上とすることが更に好ましい。なお、負極活物質には前記複合体のみを用いてもよいため、負極合剤層が含有する負極活物質全量中の前記複合体の含有量の好適上限値は１００質量％である。 The content of the composite in the total amount of the negative electrode active material contained in the negative electrode mixture layer is, for example, 5% by mass or more from the viewpoint of better ensuring the effect of increasing the battery capacity by using the composite. It is preferably 10% by mass or more, more preferably 20% by mass or more, and further preferably 50% by mass or more. In addition, since only the said composite may be used for a negative electrode active material, the suitable upper limit of content of the said composite in the negative electrode active material whole quantity which a negative mix layer contains is 100 mass%.
　負極合剤層における負極活物質の含有量（全負極活物質の合計含有量）は、８０～９９．５質量％であることが好ましい。 The content of the negative electrode active material in the negative electrode mixture layer (total content of all negative electrode active materials) is preferably 80 to 99.5% by mass.
　負極合剤層のバインダとして使用する共重合体（Ａ）は、ビニルエステルと、アクリル酸エステルおよびメタクリル酸エステルのうちの少なくとも一方とをモノマーとして重合して得られる共重合体を、ケン化することにより得ることができる。 The copolymer (A) used as a binder for the negative electrode mixture layer saponifies a copolymer obtained by polymerizing vinyl ester and at least one of acrylic acid ester and methacrylic acid ester as monomers. Can be obtained.
　共重合体（Ａ）を得るための前記ビニルエステルとしては、酢酸ビニル、プロピオン酸ビニル、ピバリン酸ビニルなどが挙げられ、これらのうちの１種または２種以上を用いることができる。これらのビニルエステルの中でも酢酸ビニルがより好ましい。 Examples of the vinyl ester for obtaining the copolymer (A) include vinyl acetate, vinyl propionate, and vinyl pivalate, and one or more of these can be used. Among these vinyl esters, vinyl acetate is more preferable.
　また、共重合体（Ａ）を得るためのビニルエステルとアクリル酸エステルおよびメタクリル酸エステルのうちの少なくとも一方との共重合体は、ビニルエステル、アクリル酸エステルおよびメタクリル酸エステル以外のモノマー由来のユニットを有していてもよい。 The copolymer of vinyl ester and at least one of acrylic acid ester and methacrylic acid ester for obtaining copolymer (A) is a unit derived from monomers other than vinyl ester, acrylic acid ester and methacrylic acid ester. You may have.
　ビニルエステルとアクリル酸エステルおよびメタクリル酸エステルのうちの少なくとも一方との共重合体は、例えば、重合触媒と分散剤とを含む水溶液中に、これらのモノマーを懸濁させた状態で重合を行う懸濁重合法によって重合することができる。この際の重合触媒には、ベンゾイルパーオキサイド、ラウリルパーオキサイドなどの有機過酸化物；アゾビスイソブチロニトリル、アゾビスジメチルバレロニトリルなどのアゾ化合物；などを使用することができる。また、懸濁重合の際の分散剤には、水溶性高分子〔ポリビニルアルコール、ポリ（メタ）アクリル酸またはその塩、ポリビニルピロリドン、メチルセルロース、カルボキシメチルセルロース、ヒドロキシエチルセルロース、ヒドロキシプロピルセルロースなど〕、無機化合物（リン酸カルシウム、ケイ酸マグネシウムなど）などを用いることができる。 The copolymer of vinyl ester and at least one of acrylic acid ester and methacrylic acid ester is a suspension in which polymerization is performed in a state where these monomers are suspended in an aqueous solution containing a polymerization catalyst and a dispersant, for example. Polymerization can be performed by a turbid polymerization method. As the polymerization catalyst at this time, organic peroxides such as benzoyl peroxide and lauryl peroxide; azo compounds such as azobisisobutyronitrile and azobisdimethylvaleronitrile; and the like can be used. In addition, the dispersant used in the suspension polymerization includes water-soluble polymers (polyvinyl alcohol, poly (meth) acrylic acid or a salt thereof, polyvinyl pyrrolidone, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, etc.), inorganic compounds (Calcium phosphate, magnesium silicate, etc.) can be used.
　懸濁重合を行う際の温度は、重合触媒の１０時間半減期温度に対して－２０～＋２０℃程度とすればよく、重合時間は数時間～数十時間とすればよい。 The temperature at which suspension polymerization is performed may be about −20 to + 20 ° C. with respect to the 10-hour half-life temperature of the polymerization catalyst, and the polymerization time may be several hours to several tens of hours.
　ビニルエステルとアクリル酸エステルおよびメタクリル酸エステルのうちの少なくとも一方との共重合体のケン化は、アルカリ金属を含有するアルカリ（水酸化ナトリウム、水酸化カリウム、水酸化リチウムなど）を使用し、水性有機溶媒と水との混合溶媒中で行うことができる。このケン化によって、ビニルエステル由来のユニットが、共重合体の主鎖に水酸基が直接結合したユニット〔すなわち、前記式（１）で表わされるユニット〕となり、アクリル酸エステルおよびメタクリル酸エステルのうちの少なくとも一方のモノマー由来のユニットが、共重合体の主鎖にカルボキシル基のアルカリ金属塩（基）が直接結合したユニット〔すなわち、前記式（２）で表わされるユニット〕となる。よって、前記式（２）におけるＭ’は、ナトリウム、カリウム、リチウムなどが挙げられる。 Saponification of a copolymer of vinyl ester with at least one of acrylic acid ester and methacrylic acid ester uses an alkali (sodium hydroxide, potassium hydroxide, lithium hydroxide, etc.) containing an alkali metal, and is aqueous. It can be performed in a mixed solvent of an organic solvent and water. By this saponification, the unit derived from the vinyl ester becomes a unit in which a hydroxyl group is directly bonded to the main chain of the copolymer [that is, a unit represented by the above formula (1)]. The unit derived from at least one monomer is a unit in which an alkali metal salt (group) of a carboxyl group is directly bonded to the main chain of the copolymer [that is, a unit represented by the formula (2)]. Therefore, examples of M ′ in the formula (2) include sodium, potassium, and lithium.
　ケン化に使用する水性有機溶媒としては、低級アルコール（メタノール、エタノールなど）、ケトン類（アセトン、メチルエチルケトンなど）などが挙げられる。水性有機溶媒と水との使用比率は、質量比で、３／７～８／２であることが好ましい。 Examples of the aqueous organic solvent used for saponification include lower alcohols (such as methanol and ethanol), ketones (such as acetone and methyl ethyl ketone), and the like. The use ratio of the aqueous organic solvent to water is preferably 3/7 to 8/2 in terms of mass ratio.
　ケン化の際の温度は２０～６０℃とすればよく、その際の時間は数時間程度とすればよい。 The temperature at the time of saponification may be 20 to 60 ° C., and the time at that time may be about several hours.
　ケン化後の共重合体は、反応液から取り出し、洗浄した後に乾燥すればよい。 The saponified copolymer may be taken out from the reaction solution, washed and then dried.
　前記のケン化を経て得られる共重合体（Ａ）の有する前記式（１）で表されるユニットは、ビニルアルコールの不飽和結合が開いて重合したような構造を有しており、また、前記（２）で表されるユニットは、アクリル酸塩やメタクリル酸塩〔以下、両者を纏めて「（メタ）アクリル酸塩」といい、アクリル酸とメタアクリル酸とを纏めて「（メタ）アクリル酸」という〕の不飽和結合が開いて重合したような構造を有している。よって、共重合体（Ａ）は、ビニルアルコールや（メタ）アクリル酸塩をモノマーに使用し、これらを共重合することで得られたものではなくても、便宜上、「ビニルアルコールと（メタ）アクリル酸塩〔（メタ）アクリル酸のアルカリ金属中和物〕との共重合体」と称される場合もある。 The unit represented by the formula (1) of the copolymer (A) obtained through the saponification has a structure in which an unsaturated bond of vinyl alcohol is opened and polymerized, The unit represented by (2) is an acrylate or methacrylate (hereinafter referred to as “(meth) acrylate” collectively, and acrylic acid and methacrylic acid are collectively referred to as “(meth) A structure in which an unsaturated bond of “acrylic acid” is polymerized by opening. Therefore, the copolymer (A) uses vinyl alcohol or (meth) acrylate as a monomer and is not obtained by copolymerizing these, but for convenience, “vinyl alcohol and (meth) It may also be referred to as an acrylate salt [a copolymer of (meth) acrylic acid alkali metal neutralized product].
　共重合体（Ａ）において、前記式（１）で表わされるユニットと前記式（２）で表わされるユニットとの組成比は、これらのユニットの合計を１００ｍｏｌ％としたとき、前記式（１）で表わされるユニットの割合が、５ｍｏｌ％以上であることが好ましく、５０ｍｏｌ％以上であることがより好ましく、６０ｍｏｌ％以上であることが更に好ましく、また、９５ｍｏｌ％以下であることが好ましく、９０ｍｏｌ％以下であることがより好ましい。すなわち、前記式（１）で表わされるユニットと前記式（２）で表わされるユニットとの合計を１００ｍｏｌ％としたとき、前記式（２）で表わされるユニットの割合が、５ｍｏｌ％以上であることが好ましく、１０ｍｏｌ％以上であることがより好ましく、また、９５ｍｏｌ％以下であることが好ましく、５０ｍｏｌ％以下であることがより好ましく、４０ｍｏｌ％以下であることが更に好ましい。 In the copolymer (A), the composition ratio of the unit represented by the formula (1) and the unit represented by the formula (2) is the formula (1) when the total of these units is 100 mol%. Is preferably 5 mol% or more, more preferably 50 mol% or more, still more preferably 60 mol% or more, and preferably 95 mol% or less, and 90 mol%. The following is more preferable. That is, when the total of the unit represented by the formula (1) and the unit represented by the formula (2) is 100 mol%, the ratio of the unit represented by the formula (2) is 5 mol% or more. Is preferably 10 mol% or more, more preferably 95 mol% or less, more preferably 50 mol% or less, and still more preferably 40 mol% or less.
　負極合剤層における共重合体（Ａ）の含有量は、その使用による効果を良好に確保する観点から、２質量％以上であることが好ましく、５質量％以上であることがより好ましい。ただし、負極合剤層中の共重合体（Ａ）の量が多すぎると、負極合剤層の密度の調整が困難となったり、電池の容量や負荷特性が低下したりする虞がある。よって、負極合剤層における共重合体（Ａ）の含有量は、１５質量％以下であることが好ましく、１０質量％以下であることがより好ましい。 The content of the copolymer (A) in the negative electrode mixture layer is preferably 2% by mass or more, and more preferably 5% by mass or more, from the viewpoint of ensuring a good effect due to its use. However, if the amount of the copolymer (A) in the negative electrode mixture layer is too large, it may be difficult to adjust the density of the negative electrode mixture layer, and the capacity and load characteristics of the battery may be reduced. Therefore, the content of the copolymer (A) in the negative electrode mixture layer is preferably 15% by mass or less, and more preferably 10% by mass or less.
　負極合剤層には、共重合体（Ａ）と共に、通常のリチウムイオン二次電池の負極に係る負極合剤層で使用されているバインダ、例えば、スチレンブタジエンゴム（ＳＢＲ）、カルボキシメチルセルロース（ＣＭＣ）、ポリフッ化ビニリデン（ＰＶＤＦ）なども使用することができる。ただし、負極合剤層が含有するバインダ全量中の、共重合体（Ａ）以外のバインダの含有量は、５０質量％以下とすることが好ましい。 In the negative electrode mixture layer, together with the copolymer (A), binders used in the negative electrode mixture layer according to the negative electrode of a normal lithium ion secondary battery, for example, styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC) ), Polyvinylidene fluoride (PVDF), and the like can also be used. However, the content of the binder other than the copolymer (A) in the total amount of binder contained in the negative electrode mixture layer is preferably 50% by mass or less.
　負極合剤層には、必要に応じて導電助剤を含有させることもできる。負極合剤層に含有させる導電助剤としては、天然黒鉛（鱗片状黒鉛など）、人造黒鉛などのグラファイト類；アセチレンブラック、ケッチェンブラック、チャンネルブラック、ファーネスブラック、ランプブラック、サーマルブラックなどのカ－ボンブラック類；炭素繊維；などの炭素材料を用いることが好ましく、また、金属繊維などの導電性繊維類；フッ化カーボン；アルミニウムなどの金属粉末類；酸化亜鉛；チタン酸カリウムなどの導電性ウィスカー類；酸化チタンなどの導電性金属酸化物；ポリフェニレン誘導体などの有機導電性材料；などを用いることもできる。導電助剤には、前記例示のものを１種単独で用いてもよく、２種以上を併用してもよい。 The negative electrode mixture layer may contain a conductive auxiliary as necessary. Examples of conductive assistants to be included in the negative electrode mixture layer include graphites such as natural graphite (scaly graphite, etc.), artificial graphite and the like; acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black and the like. -It is preferable to use carbon materials such as bon blacks; carbon fibers; and conductive fibers such as metal fibers; carbon fluorides; metal powders such as aluminum; zinc oxide; conductivity such as potassium titanate. Whiskers; conductive metal oxides such as titanium oxide; organic conductive materials such as polyphenylene derivatives; and the like can also be used. As the conductive assistant, those exemplified above may be used singly or in combination of two or more.
　負極合剤層に導電助剤を含有させる場合には、負極合剤層における導電助剤の含有量を１０質量％以下とすることが好ましい。 When the conductive additive is contained in the negative electrode mixture layer, the content of the conductive additive in the negative electrode mixture layer is preferably 10% by mass or less.
　前記製造方法（１）によって本発明の負極を製造するために系外プレドープに供する負極（負極前駆体）は、例えば、負極活物質およびバインダ、更には必要に応じて導電助剤などを含有する負極合剤を、Ｎ－メチル－２－ピロリドン（ＮＭＰ）や水などの溶剤に分散させてペースト状やスラリー状の負極合剤含有組成物を調製し（ただし、バインダは溶剤に溶解していてもよい）、これを集電体の片面または両面に塗布し、乾燥した後に、必要に応じてカレンダー処理などのプレス処理を施す工程を経て製造することができる。ただし、系外プレドープに供する負極は、前記の方法で製造されたものに限定される訳ではなく、他の方法で製造したものであってもよい。 The negative electrode (negative electrode precursor) to be used for pre-doping outside the system in order to produce the negative electrode of the present invention by the production method (1) contains, for example, a negative electrode active material and a binder, and further, if necessary, a conductive aid. The negative electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone (NMP) or water to prepare a paste-like or slurry-like negative electrode mixture-containing composition (however, the binder is dissolved in the solvent). Alternatively, after applying this to one or both sides of the current collector and drying, it can be produced through a step of applying a press treatment such as a calender treatment if necessary. However, the negative electrode to be used for pre-doping outside the system is not limited to those manufactured by the above method, but may be manufactured by other methods.
　また、前記製造方法（２）によって本発明の負極を製造するに際しては、例えば、負極活物質（少なくとも一部には、系外プレドープによってＬｉイオンをドープした負極活物質を使用する）およびバインダ、更には必要に応じて導電助剤などを含有する負極合剤を、ＮＭＰや水などの溶剤に分散させてペースト状やスラリー状の負極合剤含有組成物を調製し（ただし、バインダは溶剤に溶解していてもよい）、これを集電体の片面または両面に塗布し、乾燥した後に、必要に応じてカレンダー処理などのプレス処理を施すなどすればよい。 Further, when producing the negative electrode of the present invention by the production method (2), for example, a negative electrode active material (at least partly uses a negative electrode active material doped with Li ions by pre-doping outside the system) and a binder, Furthermore, if necessary, a negative electrode mixture containing a conductive auxiliary agent is dispersed in a solvent such as NMP or water to prepare a paste-like or slurry-like negative electrode mixture-containing composition (however, the binder is added to the solvent). It may be dissolved), and this may be applied to one or both sides of the current collector, dried, and then subjected to a pressing process such as a calendar process if necessary.
　負極の集電体としては、銅製やニッケル製の箔、パンチングメタル、網、エキスパンドメタルなどを用い得るが、通常、銅箔が用いられる。この負極集電体は、高エネルギー密度の電池を得るために負極全体の厚みを薄くする場合、厚みの上限は３０μｍであることが好ましく、機械的強度を確保するために下限は５μｍであることが望ましい。 As the negative electrode current collector, a copper or nickel foil, a punching metal, a net, an expanded metal, or the like can be used, but a copper foil is usually used. In the negative electrode current collector, when the thickness of the entire negative electrode is reduced in order to obtain a battery having a high energy density, the upper limit of the thickness is preferably 30 μm, and the lower limit is 5 μm in order to ensure mechanical strength. Is desirable.
　負極合剤層の厚み（集電体の両面に負極合剤層を有する場合には、片面あたりの厚み）は、１０～１００μｍであることが好ましい。 The thickness of the negative electrode mixture layer (when the negative electrode mixture layer is provided on both sides of the current collector, the thickness per side) is preferably 10 to 100 μm.
　負極活物質の系外プレドープは、例えば、以下の（ｉ）または（ｉｉ）によって行うことができる。 The extra-system pre-doping of the negative electrode active material can be performed, for example, by the following (i) or (ii).
系外プレドープ法（ｉ）
　Ｌｉイオンをドープしていない負極活物質を用いて製造した負極を使用し、その負極活物質にＬｉイオンをドープする。 In-system pre-doping method (i)
A negative electrode manufactured using a negative electrode active material not doped with Li ions is used, and the negative electrode active material is doped with Li ions.
　系外プレドープ法（ｉ）において、負極の負極合剤層中の負極活物質へのＬｉイオンのドープは、例えば、テトラヒドロフランやジエチルエーテルなどの溶媒に、ビフェニル、多環芳香族化合物（アントラセン、ナフタレンなど）、ｐ－ベンゾキノン、金属Ｌｉなどを溶解させた溶液中に、負極を浸漬し、その後溶剤で洗浄および乾燥させることで実施することができる〔以下、系外プレドープ法（ｉ－１）という〕。このときのＬｉイオンのドープ量は、前記溶液中の各成分量などの調整によって制御することができ、例えば前記モル比Ｌｉ／Ｍが前記好適値を満たすように調節すればよい。 In the extra-system pre-doping method (i), the doping of Li ions into the negative electrode active material in the negative electrode mixture layer of the negative electrode is performed by, for example, biphenyl, polycyclic aromatic compounds (anthracene, naphthalene) in a solvent such as tetrahydrofuran or diethyl ether. Etc.), and the negative electrode is immersed in a solution in which p-benzoquinone, metal Li, etc. are dissolved, and then washed with a solvent and dried [hereinafter referred to as “out-of-system pre-doping method (i-1)”. ]. The doping amount of Li ions at this time can be controlled by adjusting the amount of each component in the solution. For example, the molar ratio Li / M may be adjusted so as to satisfy the preferred value.
　また、系外プレドープ法（ｉ）では、負極（作用極）とリチウム金属箔（対極。リチウム合金箔を含む。）とを非水電解液中に浸漬し、これらの間に通電する方法によっても、負極合剤層中の負極活物質にＬｉイオンをドープすることができる〔以下、系外プレドープ法（ｉ－２）という〕。非水電解液には、リチウムイオン二次電池用の非水電解液（詳しくは後述する）と同じものが使用できる。このときのＬｉイオンのドープ量は、負極（負極合剤層）の面積当たりの電流密度や、通電する電気量の調整によって制御することができ、例えば前記モル比Ｌｉ／Ｍが前記好適値を満たすように調節すればよい。 Further, in the extra-system pre-doping method (i), a negative electrode (working electrode) and a lithium metal foil (counter electrode, including a lithium alloy foil) are immersed in a nonaqueous electrolytic solution, and a current is passed between them. In addition, the negative electrode active material in the negative electrode mixture layer can be doped with Li ions [hereinafter referred to as out-of-system pre-doping method (i-2)]. As the non-aqueous electrolyte, the same non-aqueous electrolyte for lithium ion secondary batteries (described in detail later) can be used. The doping amount of Li ions at this time can be controlled by adjusting the current density per area of the negative electrode (negative electrode mixture layer) and the amount of electricity to be energized. For example, the molar ratio Li / M has the preferred value. Adjust to meet.
　系外プレドープ法（ｉ－２）を行う場合、ロールに巻回した負極を引き出して、非水電解液およびリチウム金属極を備えた電解液槽内に導入し、前記電解液槽内で前記負極と前記リチウム金属極との間に通電することで負極合剤層中の負極活物質にＬｉイオンをドープし、その後の負極をロール状に巻き取るロール・トゥ・ロール法で実施することが好ましい。本発明の負極であれば、Ｌｉイオンのドープ後にロール状に巻き取っても負極合剤層に欠陥が生じ難いため、ロール・トゥ・ロール法の適用によって生産性をより高めることができる。 When performing the extra-system pre-doping method (i-2), the negative electrode wound around a roll is pulled out and introduced into an electrolyte bath provided with a non-aqueous electrolyte and a lithium metal electrode, and the negative electrode in the electrolyte bath It is preferable to carry out by a roll-to-roll method in which a negative electrode active material in a negative electrode mixture layer is doped with Li ions by energizing between the lithium metal electrode and the lithium metal electrode, and the subsequent negative electrode is wound into a roll shape. . If the negative electrode of the present invention is used, it is difficult for defects to occur in the negative electrode mixture layer even if it is wound into a roll after doping with Li ions. Therefore, productivity can be further improved by applying the roll-to-roll method.
　図１に、ロール・トゥ・ロール法によって負極の負極合剤層中の負極活物質にＬｉイオンをドープする工程の説明図を示す。まず、Ｌｉイオンのドープに供するための負極２ａを巻き取ったロール２０ａから負極２ａを引き出し、Ｌｉイオンをドープするための電解液槽１０１内へ導入する。電解液槽１０１は非水電解液（図示しない）とリチウム金属極１０２とを有しており、電解液槽１０１内を通過する負極２ａとリチウム金属極１０２との間に、電源１０３によって通電できるように構成されている。そして、電解液槽１０１内を負極２ａがリチウム金属層２０２と対向しつつ通過する際に、電源１０３によって負極２ａとリチウム金属極１０２との間に通電することで、負極２ａの負極合剤層中の負極活物質にＬｉイオンをドープする。 FIG. 1 shows an explanatory diagram of a step of doping Li ions into a negative electrode active material in a negative electrode mixture layer of a negative electrode by a roll-to-roll method. First, the negative electrode 2a is pulled out from the roll 20a around which the negative electrode 2a for use in doping Li ions is wound, and introduced into the electrolytic solution tank 101 for doping Li ions. The electrolyte bath 101 has a non-aqueous electrolyte (not shown) and a lithium metal electrode 102, and can be energized by a power source 103 between the negative electrode 2 a passing through the electrolyte bath 101 and the lithium metal electrode 102. It is configured as follows. When the negative electrode 2a passes through the electrolytic solution tank 101 while facing the lithium metal layer 202, the negative electrode mixture layer of the negative electrode 2a is energized between the negative electrode 2a and the lithium metal electrode 102 by the power source 103. The negative electrode active material therein is doped with Li ions.
　負極合剤層中の負極活物質にＬｉイオンをドープし、電解液槽１０１内を通過させた後の負極２は、好ましくは洗浄した後、ロール２０に巻き取る。負極２の洗浄は、例えば、図１に示すように、洗浄用の有機溶媒を満たした洗浄槽１０４に負極２を通過させることにより行うことができる。また、洗浄槽１０４を通過させた後の負極２は、乾燥手段１０５を通過させて乾燥させてからロール２０に巻き取ることが好ましい。乾燥手段１０５での乾燥方法については、特に制限はなく、洗浄槽１０４で負極２に付着した有機溶媒を除去できればよいが、例えば、温風や赤外線ヒーターによる乾燥、乾燥状態の不活性ガス内を通過させる乾燥などの各種方法を適用することができる。 The negative electrode 2 after the Li-ion is doped into the negative electrode active material in the negative electrode mixture layer and passed through the electrolyte bath 101 is preferably washed and wound on a roll 20. The negative electrode 2 can be cleaned, for example, by allowing the negative electrode 2 to pass through a cleaning tank 104 filled with a cleaning organic solvent, as shown in FIG. Moreover, it is preferable that the negative electrode 2 after passing through the cleaning tank 104 is wound around the roll 20 after passing through the drying means 105 and being dried. The drying method in the drying means 105 is not particularly limited as long as the organic solvent adhering to the negative electrode 2 can be removed in the cleaning tank 104. For example, drying with warm air or an infrared heater, or in a dry inert gas Various methods such as drying through can be applied.
　なお、図１に示す電解液槽１０１は、負極集電体の両面に負極合剤層が形成されている負極について、その両面の負極合剤層に同時にＬｉイオンをドープできるように、リチウム金属極１０２を２つ備えているが、負極集電体の片面のみに負極合剤層を有する負極の負極合剤層へＬｉイオンをドープすることのみに使用される電解液槽の場合には、その負極合剤層と対向する箇所にだけ１つのリチウム金属極を備えていればよい。 In addition, the electrolytic solution tank 101 shown in FIG. 1 is lithium metal so that the negative electrode mixture layer formed on both surfaces of the negative electrode current collector can be doped with Li ions simultaneously on the negative electrode mixture layers on both surfaces. In the case of an electrolyte bath used only to dope Li ions into the negative electrode mixture layer of the negative electrode having a negative electrode mixture layer only on one side of the negative electrode current collector, although two electrodes 102 are provided. It is only necessary to provide one lithium metal electrode only at a location facing the negative electrode mixture layer.
系外プレドープ法（ｉｉ）
　Ｌｉイオンをドープしていない負極活物質に、Ｌｉイオンを直接ドープする。この場合、系外プレドープ法（ｉ－１）の説明で先に記載した負極を浸漬する前記溶液中に、負極に代えて負極活物質（Ｌｉイオンドープ前の負極活物質）を浸漬することで、負極活物質にＬｉイオンをドープすることができる。 Out-of-system pre-doping method (ii)
A negative electrode active material not doped with Li ions is directly doped with Li ions. In this case, by immersing a negative electrode active material (a negative electrode active material before Li ion doping) in place of the negative electrode in the solution in which the negative electrode described above in the description of the extra-system pre-doping method (i-1) is immersed. The negative electrode active material can be doped with Li ions.
　この系外プレドープ法（ｉｉ）を採用する場合、負極の製造に使用する負極活物質には、その一部または全部に、系外プレドープ法（ｉｉ）によってＬｉイオンをドープしたものを使用することができる。負極の製造に使用する負極活物質中の、系外プレドープ法（ｉｉ）によってＬｉイオンをドープした負極活物質の割合や、負極活物質へのＬｉイオンのドープ量は、例えば前記モル比Ｌｉ／Ｍが前記好適値を満たすように調節すればよい。 When this extra-system pre-doping method (ii) is adopted, a part or all of the negative electrode active material used for the production of the negative electrode is doped with Li ions by the extra-system pre-doping method (ii). Can do. The ratio of the negative electrode active material doped with Li ions by the extra-system pre-doping method (ii) in the negative electrode active material used for the production of the negative electrode and the doping amount of Li ions into the negative electrode active material are, for example, the molar ratio Li / What is necessary is just to adjust so that M may satisfy | fill the said suitable value.
　系外プレドープ法（ｉｉ）でＬｉイオンをドープさせる負極活物質は、Ｌｉイオンの受け入れ量が大きくかつ不可逆容量が大きいものが望ましく、例えば、ＳｉとＯとを構成元素に含む材料にＬｉイオンをドープすることが望ましい。 The negative electrode active material doped with Li ions by the extra-system pre-doping method (ii) preferably has a large acceptance amount of Li ions and a large irreversible capacity. For example, Li ions are added to a material containing Si and O as constituent elements. It is desirable to dope.
　系外プレドープによってＬｉイオンをドープした負極活物質を含有している負極は、必要なサイズに切断するなどして、リチウムイオン二次電池などの電気化学素子の製造に供される。また、負極には、必要に応じて、リチウムイオン二次電池などの電気化学素子内の他の部材と電気的に接続するためのリード体を、常法に従って形成してもよい。 The negative electrode containing the negative electrode active material doped with Li ions by pre-doping outside the system is cut into a required size and used for the production of electrochemical elements such as lithium ion secondary batteries. Moreover, you may form the lead body for electrically connecting with the other member in electrochemical elements, such as a lithium ion secondary battery, according to a conventional method to a negative electrode as needed.
　本発明の負極は、前記の通り、リチウムイオン二次電池やスーパーキャパシタなどの、非水電解液を有し、かつ充放電が繰り返し行われる電気化学素子の負極として使用されるが、特に主要な用途は、リチウムイオン二次電池である。 As described above, the negative electrode of the present invention is used as a negative electrode of an electrochemical element having a non-aqueous electrolyte and repeatedly charged and discharged, such as a lithium ion secondary battery and a super capacitor. The application is a lithium ion secondary battery.
　本発明の負極を用いたリチウムイオン二次電池（本発明のリチウムイオン二次電池）は、前記負極と、正極と、セパレータと、非水電解液とが、外装体内に収容されてなるものである。 The lithium ion secondary battery using the negative electrode of the present invention (lithium ion secondary battery of the present invention) is one in which the negative electrode, the positive electrode, the separator, and the non-aqueous electrolyte are accommodated in an outer package. is there.
　リチウムイオン二次電池に係る正極は、正極活物質およびバインダを含有する正極合剤層を有するものであり、例えば、この正極合剤層が集電体の片面または両面に形成された構造を有するものや、正極合剤層で構成されたもの（正極合剤成形体）が挙げられる。 A positive electrode according to a lithium ion secondary battery has a positive electrode mixture layer containing a positive electrode active material and a binder. For example, the positive electrode mixture layer has a structure formed on one side or both sides of a current collector. And those composed of a positive electrode mixture layer (positive electrode mixture molded body).
　正極活物質には、ＬｉとＬｉ以外の金属Ｍ（Ｃｏ、Ｎｉ、Ｍｎ、Ｆｅ、Ｍｇ、Ａｌなど）とで構成される金属酸化物（リチウム含有複合酸化物）が使用される。このようなリチウム含有複合酸化物としては、例えば、ＬｉＣｏＯ２などのリチウムコバルト酸化物；ＬｉＭｎＯ２、Ｌｉ２ＭｎＯ３などのリチウムマンガン酸化物；ＬｉＮｉＯ２などのリチウムニッケル酸化物；ＬｉＣｏ１－ｘＮｉＯ２などの層状構造のリチウム含有複合酸化物；ＬｉＭｎ２Ｏ４、Ｌｉ４／３Ｔｉ５／３Ｏ４などのスピネル構造のリチウム含有複合酸化物；ＬｉＦｅＰＯ４などのオリビン構造のリチウム含有複合酸化物；前記の酸化物を基本組成とし各種元素で置換した酸化物；などが挙げられる。 As the positive electrode active material, a metal oxide (lithium-containing composite oxide) composed of Li and a metal M other than Li (Co, Ni, Mn, Fe, Mg, Al, etc.) is used. Examples of such lithium-containing composite oxides include lithium cobalt oxides such as LiCoO 2 ; lithium manganese oxides such as LiMnO 2 and Li 2 MnO 3 ; lithium nickel oxides such as LiNiO 2 ; LiCo 1-x NiO Lithium-containing composite oxide having a layered structure such as 2 ; Lithium-containing composite oxide having a spinel structure such as LiMn 2 O 4 and Li 4/3 Ti 5/3 O 4 ; Lithium-containing composite oxide having an olivine structure such as LiFePO 4 And oxides having the above-described oxide as a basic composition and substituted with various elements.
　このような正極活物質の中でも、Ｃｏと、Ｍｇ、Ｚｒ、Ｎｉ、Ｍｎ、ＴｉおよびＡｌよりなる群から選択される少なくとも１種の元素Ｍ１とを少なくとも含有するリチウムコバルト酸化物（コバルト酸リチウム）が好ましい。そして、正極合剤層は、このようなコバルト酸リチウムの粒子の表面がＡｌ含有酸化物で被覆されてなる正極材料を含有していることがより好ましい。前記の正極材料を使用した場合には、電池の充電時の正極での抵抗を大きくすることができるため、負極でのＬｉの析出が起こり難くなることから、負極合剤層中での前記複合体の割合を大きくしても、リチウムイオン二次電池の充放電サイクル特性をより高めることができる。 Among such positive electrode active materials, lithium cobalt oxide (lithium cobaltate) containing at least Co and at least one element M 1 selected from the group consisting of Mg, Zr, Ni, Mn, Ti, and Al. ) Is preferred. The positive electrode material mixture layer more preferably contains a positive electrode material in which the surfaces of such lithium cobalt oxide particles are coated with an Al-containing oxide. When the positive electrode material is used, since the resistance at the positive electrode during battery charging can be increased, it is difficult for Li to precipitate at the negative electrode, so the composite in the negative electrode mixture layer Even if the proportion of the body is increased, the charge / discharge cycle characteristics of the lithium ion secondary battery can be further improved.
　前記コバルト酸リチウムは、Ｃｏと、Ｍｇ、Ｚｒ、Ｎｉ、Ｍｎ、ＴｉおよびＡｌよりなる群から選択される少なくとも１種の元素Ｍ１と、更に含有してもよい他の元素とを纏めて元素群Ｍａとしたときに、組成式ＬｉＭａＯ２で表されるものである。 The lithium cobalt oxide is an element that includes Co, at least one element M 1 selected from the group consisting of Mg, Zr, Ni, Mn, Ti, and Al, and other elements that may further be contained. when the group M a, is represented by the composition formula LiM a O 2.
　前記コバルト酸リチウムにおいて、元素Ｍ１は、前記コバルト酸リチウムの高電圧領域での安定性を高め、Ｃｏイオンの溶出を抑制する作用を有しており、また、前記コバルト酸リチウムの熱安定性を高める作用も有している。 In the lithium cobalt oxide, the element M 1 has an effect of increasing the stability of the lithium cobalt oxide in a high voltage region and suppressing the elution of Co ions, and the thermal stability of the lithium cobalt oxide. It also has the effect of increasing
　前記コバルト酸リチウムにおいて、元素Ｍ１の量は、前記の作用をより有効に発揮させる観点から、Ｃｏとの原子比Ｍ１／Ｃｏが、０．００３以上であることが好ましく、０．００８以上であることがより好ましい。 In the lithium cobalt oxide, the amount of the element M 1 is preferably such that the atomic ratio M 1 / Co with Co is 0.003 or more from the viewpoint of more effectively exerting the above action, and 0.008 or more. It is more preferable that
　ただし、前記コバルト酸リチウム中の元素Ｍ１の量が多すぎると、Ｃｏの量が少なくなりすぎて、これらによる作用を十分に確保できない虞がある。よって、前記コバルト酸リチウムにおいて、元素Ｍ１の量は、Ｃｏとの原子比Ｍ１／Ｃｏが、０．０６以下であることが好ましく、０．０３以下であることがより好ましい。 However, when the amount of the element M 1 in the lithium cobalt oxide is too large, too small amounts of Co, there is a possibility can not be sufficient action by these. Therefore, in the lithium cobaltate, the amount of the element M 1 is preferably such that the atomic ratio M 1 / Co with Co is 0.06 or less, and more preferably 0.03 or less.
　前記コバルト酸リチウムにおいて、Ｚｒは、非水電解液中に含まれるフッ素含有リチウム塩（ＬｉＰＦ６など）が原因となって発生し得るフッ化水素を吸着し、コバルト酸リチウムの劣化を抑制する作用を有している。 In the lithium cobaltate, Zr adsorbs hydrogen fluoride that may be generated due to a fluorine-containing lithium salt (such as LiPF 6 ) contained in the non-aqueous electrolyte, and suppresses deterioration of the lithium cobaltate. have.
　リチウムイオン二次電池に使用される非水電解液中に若干の水分が不可避的に混入していたり、他の電池材料に水分が吸着していたりすると、非水電解液が含有するフッ素含有リチウム塩と反応してフッ化水素が生成する。電池内でフッ化水素が生成すると、その作用で正極活物質の劣化を引き起こしてしまう。 Fluorine-containing lithium contained in the non-aqueous electrolyte if some moisture is inevitably mixed in the non-aqueous electrolyte used in the lithium ion secondary battery or if moisture is adsorbed by other battery materials Reacts with salt to produce hydrogen fluoride. When hydrogen fluoride is generated in the battery, the action causes deterioration of the positive electrode active material.
　ところが、Ｚｒも含有するように前記コバルト酸リチウムを合成すると、その粒子の表面にＺｒ酸化物が析出し、このＺｒ酸化物がフッ化水素を吸着する。そのため、フッ化水素による前記コバルト酸リチウムの劣化を抑制することができる。 However, when the lithium cobaltate is synthesized so as to also contain Zr, Zr oxide is deposited on the surface of the particles, and this Zr oxide adsorbs hydrogen fluoride. Therefore, deterioration of the lithium cobalt oxide due to hydrogen fluoride can be suppressed.
　なお、正極活物質にＺｒを含有させると、電池の負荷特性が向上する。正極材料が含有する前記コバルト酸リチウムが、平均粒子径の異なる２つの材料である場合、平均粒子径が大きい方をコバルト酸リチウム（Ａ）、平均粒子径が小さい方をコバルト酸リチウム（Ｂ）とする。一般に、粒子径が大きい正極活物質を使用すると電池の負荷特性が低下する傾向にある。よって、前記正極材料を構成する正極活物質のうち、より平均粒子径が大きいコバルト酸リチウム（Ａ）にはＺｒを含有させることが好ましい。他方、コバルト酸リチウム（Ｂ）は、Ｚｒを含有していてもよく、含有していなくてもよい。 In addition, when the positive electrode active material contains Zr, the load characteristics of the battery are improved. When the lithium cobalt oxide contained in the positive electrode material is two materials having different average particle diameters, the larger average particle diameter is lithium cobalt oxide (A), and the smaller average particle diameter is lithium cobalt oxide (B). And In general, when a positive electrode active material having a large particle size is used, the load characteristics of the battery tend to deteriorate. Therefore, among the positive electrode active materials constituting the positive electrode material, it is preferable that lithium cobaltate (A) having a larger average particle diameter contains Zr. On the other hand, lithium cobaltate (B) may contain Zr or may not contain it.
　前記コバルト酸リチウムにおいて、Ｚｒの量は、前記の作用をより良好に発揮させる観点から、Ｃｏとの原子比Ｚｒ／Ｃｏが、０．０００２以上であることが好ましく、０．０００３以上であることがより好ましい。ただし、前記コバルト酸リチウム中のＺｒの量が多すぎると、他の元素の量が少なくなって、これらによる作用を十分に確保できない虞がある。よって、前記コバルト酸リチウムにおけるＺｒの量は、Ｃｏとの原子比Ｚｒ／Ｃｏが、０．００５以下であることが好ましく、０．００１以下であることがより好ましい。 In the lithium cobaltate, the amount of Zr is such that the atomic ratio Zr / Co with Co is preferably 0.0002 or more, more preferably 0.0003 or more, from the viewpoint of better exerting the above action. Is more preferable. However, if the amount of Zr in the lithium cobalt oxide is too large, the amount of other elements decreases, and there is a possibility that the effects of these elements cannot be sufficiently ensured. Therefore, the amount of Zr in the lithium cobaltate is preferably such that the atomic ratio Zr / Co with Co is 0.005 or less, and more preferably 0.001 or less.
　前記コバルト酸リチウムは、Ｌｉ含有化合物（水酸化リチウム、炭酸リチウムなど）、Ｃｏ含有化合物（酸化コバルト、硫酸コバルトなど）、およびＭｇ含有化合物（硫酸マグネシウムなど）、Ｚｒ含有化合物（酸化ジルコニウムなど）などの元素Ｍ１を含有する化合物（酸化物、水酸化物、硫酸塩など）を混合し、この原料混合物を焼成するなどして合成することができる。なお、より高い純度で前記コバルト酸リチウムを合成するには、Ｃｏおよび元素Ｍ１を含む複合化合物（水酸化物、酸化物など）とＬｉ含有化合物などとを混合し、この原料混合物を焼成することが好ましい。 The lithium cobalt oxide includes Li-containing compounds (such as lithium hydroxide and lithium carbonate), Co-containing compounds (such as cobalt oxide and cobalt sulfate), Mg-containing compounds (such as magnesium sulfate), and Zr-containing compounds (such as zirconium oxide). compounds containing elements M 1 (oxides, hydroxides, sulfates, etc.) can be mixed, synthesized, for example, by firing the raw material mixture. Incidentally, in synthesizing the lithium cobaltate with a higher purity, composite compound containing Co and the element M 1 (hydroxides, oxides, etc.) and the like and Li-containing compound are mixed and firing the raw material mixture It is preferable.
　前記コバルト酸リチウムを合成するための原料混合物の焼成条件は、例えば、８００～１０５０℃で１～２４時間とすることができるが、一旦焼成温度よりも低い温度（例えば、２５０～８５０℃）まで加熱し、その温度で保持することにより予備加熱を行い、その後に焼成温度まで昇温して反応を進行させることが好ましい。予備加熱の時間については特に制限はないが、通常、０．５～３０時間程度とすればよい。また、焼成時の雰囲気は、酸素を含む雰囲気（すなわち、大気中）、不活性ガス（アルゴン、ヘリウム、窒素など）と酸素ガスとの混合雰囲気、酸素ガス雰囲気などとすることができるが、その際の酸素濃度（体積基準）は、１５％以上であることが好ましく、１８％以上であることが好ましい。 The firing condition of the raw material mixture for synthesizing the lithium cobaltate can be, for example, 800 to 1050 ° C. for 1 to 24 hours, but once the temperature is lower than the firing temperature (for example, 250 to 850 ° C.). It is preferable to preheat by heating and holding at that temperature, and then to raise the temperature to the firing temperature to advance the reaction. There is no particular limitation on the preheating time, but it is usually about 0.5 to 30 hours. The atmosphere during firing can be an atmosphere containing oxygen (that is, in the air), a mixed atmosphere of an inert gas (such as argon, helium, or nitrogen) and oxygen gas, or an oxygen gas atmosphere. The oxygen concentration (volume basis) is preferably 15% or more, and more preferably 18% or more.
　前記正極材料においては、前記コバルト酸リチウムの粒子の表面がＡｌ含有酸化物で被覆されている（例えば、前記コバルト酸リチウムの粒子の表面の全面積中の９０～１００％以上に、Ａｌ含有酸化物が存在している）。前記コバルト酸リチウムの粒子の表面を被覆するＡｌ含有酸化物としては、Ａｌ２Ｏ３、ＡｌＯＯＨ、ＬｉＡｌＯ２、ＬｉＣｏ１－ｗＡｌｗＯ２（ただし、０．５＜ｗ＜１）などが挙げられ、これらのうちの１種のみを用いてもよく、２種以上を併用してもよい。なお、例えば後述する方法で前記コバルト酸リチウムの表面をＡｌ２Ｏ３で被覆した場合、Ａｌ２Ｏ３中に、前記コバルト酸リチウムから移行するＣｏやＬｉ、Ａｌなどの元素を含むＡｌ含有酸化物が一部混在する被膜が形成されるが、前記正極材料を構成する前記コバルト酸リチウムの表面を覆うＡｌ含有酸化物で形成された被膜は、このような成分を含む被膜であってもよい。 In the positive electrode material, the surface of the lithium cobalt oxide particles is coated with an Al-containing oxide (for example, 90 to 100% or more of the total area of the lithium cobalt oxide particle surface includes Al-containing oxides). Things are present). Examples of the Al-containing oxide covering the surface of the lithium cobalt oxide particles include Al 2 O 3 , AlOOH, LiAlO 2 , and LiCo 1-w Al w O 2 (where 0.5 <w <1). Of these, only one of them may be used, or two or more of them may be used in combination. For example, when the surface of the lithium cobalt oxide is coated with Al 2 O 3 by a method described later, an Al-containing oxide containing elements such as Co, Li, and Al transferred from the lithium cobalt oxide in the Al 2 O 3 Although a film in which a part is mixed is formed, the film formed of an Al-containing oxide that covers the surface of the lithium cobaltate constituting the positive electrode material may be a film containing such a component. .
　前記正極材料に係るＡｌ含有酸化物の平均被覆厚みは、前記正極材料に係る電池の充放電時における正極活物質でのリチウムイオンの出入りをＡｌ含有酸化物が阻害することによる抵抗を増加させ、負極でのＬｉ析出を抑制することによる電池の充放電サイクル特性をより向上させる観点と、前記正極材料に係る正極活物質と非水電解液との反応を良好に抑制する観点から、５ｎｍ以上であることが好ましく、１５ｎｍ以上であることがより好ましい。また、電池の充放電時における正極活物質でのリチウムイオンの出入りをＡｌ含有酸化物が阻害することによる電池の負荷特性低下を抑制する観点から、前記正極材料に係るＡｌ含有酸化物の平均被覆厚みは、５０ｎｍ以下であることが好ましく、３５ｎｍ以下であることがより好ましい。 The average coating thickness of the Al-containing oxide according to the positive electrode material increases the resistance due to the inhibition of the Al-containing oxide in the positive and negative electrode active materials during charging and discharging of the battery according to the positive electrode material, From the viewpoint of further improving the charge / discharge cycle characteristics of the battery by suppressing Li deposition at the negative electrode and from the viewpoint of satisfactorily suppressing the reaction between the positive electrode active material according to the positive electrode material and the non-aqueous electrolyte, the thickness is 5 nm or more. It is preferable that the thickness is 15 nm or more. In addition, from the viewpoint of suppressing deterioration of the load characteristics of the battery due to the Al-containing oxide inhibiting the lithium ion in and out of the positive electrode active material during charging and discharging of the battery, the average coating of the Al-containing oxide according to the positive electrode material The thickness is preferably 50 nm or less, and more preferably 35 nm or less.
　本明細書でいう「Ａｌ含有酸化物の平均被覆厚み」は、集束イオンビーム法により加工して得られた正極材料の断面を、透過型電子顕微鏡を用いて４０万倍の倍率で観察し、５００×５００ｎｍの視野に存在する正極材料粒子のうち、断面の大きさが正極材料の平均粒子径（ｄ５０）±５μｍ以内の粒子を１０視野分だけ任意に選択し、各視野ごとに、Ａｌ含有酸化物の被膜の厚みを任意の１０か所で測定し、全視野で得られた全ての厚み（１００箇所の厚み）について算出した平均値（数平均値）を意味している。 The “average coating thickness of the Al-containing oxide” as used herein refers to a cross section of the positive electrode material obtained by processing by the focused ion beam method, observed at a magnification of 400,000 times using a transmission electron microscope, Of the positive electrode material particles existing in the field of view of 500 × 500 nm, particles having a cross-sectional size within the average particle diameter (d 50 ) ± 5 μm of the positive electrode material are arbitrarily selected for 10 fields, and for each field, Al It means the average value (number average value) calculated for all thicknesses (thicknesses at 100 locations) obtained by measuring the thickness of the coating film of the contained oxide at 10 arbitrary locations.
　前記正極材料の比表面積は、０．１ｍ２／ｇ以上であることが好ましく、０．２ｍ２／ｇ以上であることがより好ましく、また、０．４ｍ２／ｇ以下であることが好ましく、０．３ｍ２／ｇ以下であることがより好ましい。正極材料の比表面積が前記の値にある場合には、電池の充放電時における抵抗をより増加させるため、電池の充放電サイクル特性が更に良好となる。 The specific surface area of the positive electrode material is preferably 0.1 m 2 / g or more, more preferably 0.2 m 2 / g or more, and preferably 0.4 m 2 / g or less, More preferably, it is 0.3 m 2 / g or less. When the specific surface area of the positive electrode material is in the above value, the resistance during charging / discharging of the battery is further increased, so that the charge / discharge cycle characteristics of the battery are further improved.
　なお、前記正極材料を構成する前記コバルト酸リチウムの表面をＡｌ含有酸化物で被覆したり、前記コバルト酸リチウム粒子の表面にＺｒ酸化物が析出するようにしたりした場合には、通常、正極材料の表面が粗くなって比表面積が増大する。そのため前記正極材料は、比較的大きな粒径とすることに加えて、前記コバルト酸リチウム粒子の表面を被覆するＡｌ含有酸化物の被膜の性状が良好であると、前記のような小さな比表面積となりやすいことから、好ましい。 When the surface of the lithium cobalt oxide constituting the positive electrode material is coated with an Al-containing oxide or when Zr oxide is deposited on the surface of the lithium cobalt oxide particles, the positive electrode material is usually used. The surface becomes rough and the specific surface area increases. For this reason, the positive electrode material has a small specific surface area as described above if the properties of the Al-containing oxide film covering the surface of the lithium cobalt oxide particles are good in addition to a relatively large particle size. It is preferable because it is easy.
　前記正極材料が含有する前記コバルト酸リチウムについては、１種類であってもよいし、上述したように平均粒子径が異なる２つの材料であってもよいし、平均粒子径が異なる３つ以上の材料であってもよい。 About the said lithium cobaltate which the said positive electrode material contains, one type may be sufficient, as above-mentioned, two materials from which an average particle diameter differs may be sufficient, and three or more from which an average particle diameter differs It may be a material.
　前記正極材料の比表面積を前記の値に調整するには、１種類の前記コバルト酸リチウムを使用する場合、前記正極材料の平均粒子径を１０～３５μｍとすることが好ましい。 In order to adjust the specific surface area of the positive electrode material to the above value, when one type of the lithium cobaltate is used, the average particle diameter of the positive electrode material is preferably 10 to 35 μm.
　前記正極材料が含有する前記コバルト酸リチウムに平均粒子径が異なる２つの材料を使用する場合、コバルト酸リチウム（Ａ）の粒子の表面がＡｌ含有酸化物で被覆されてなり、平均粒子径が１～４０μｍである正極材料（ａ）と、コバルト酸リチウム（Ｂ）の粒子の表面がＡｌ含有酸化物で被覆されてなり、平均粒子径が１～４０μｍであり、かつ正極材料（ａ）よりも平均粒子径が小さい正極材料（ｂ）とを少なくとも含んでいると好ましい。更に好ましくは、平均粒子径が２４～３０μｍの大粒子〔正極材料（ａ）〕と、平均粒子径が４～８μｍの小粒子〔正極材料（ｂ）〕とで構成されている態様である。そして、正極材料が、正極材料（ａ）と正極材料（ｂ）とを含んでいる場合、正極材料全量中での正極材料（ａ）の割合は、７５～９０質量％であることが好ましい。これによって比表面積の調整ができるだけではなく、正極合剤層のプレス処理において、大粒径の正極材料の隙間に小粒径の正極材料が入り込むことで、正極合剤層にかかる応力が全体に分散し、正極材料粒子の割れが良好に抑制されてＡｌ含有酸化物での被覆による作用をより良好に発揮することができる。 When two materials having different average particle diameters are used for the lithium cobalt oxide contained in the positive electrode material, the surface of lithium cobalt oxide (A) particles is coated with an Al-containing oxide, and the average particle diameter is 1 The positive electrode material (a) having a particle size of 40 μm and the surface of lithium cobalt oxide (B) particles are coated with an Al-containing oxide, the average particle diameter is 1 to 40 μm, and the positive electrode material (a) It is preferable that at least the positive electrode material (b) having a small average particle diameter is included. More preferably, it is an embodiment comprising large particles [positive electrode material (a)] having an average particle diameter of 24 to 30 μm and small particles [positive electrode material (b)] having an average particle diameter of 4 to 8 μm. When the positive electrode material contains the positive electrode material (a) and the positive electrode material (b), the ratio of the positive electrode material (a) in the total amount of the positive electrode material is preferably 75 to 90% by mass. As a result, not only can the specific surface area be adjusted, but also when the positive electrode mixture layer is pressed, the positive electrode material having a small particle size enters the gap between the positive electrode materials having a large particle size, so that the stress applied to the positive electrode mixture layer is entirely reduced. It is possible to disperse and to suppress the cracking of the positive electrode material particles satisfactorily, so that the action by the coating with the Al-containing oxide can be exhibited better.
　本明細書でいう正極材料の粒度分布は、日機装株式会社製マイクロトラック粒度分布測定装置「ＨＲＡ９３２０」を用いて、粒度分布の小さい粒子から積分体積を求める方法により得られる粒度分布を意味している。また、本明細書における正極材料や、その他の粒子（前記材料Ｓなど）の平均粒子径は、前記の装置を用いて、粒度分布の小さい粒子から積分体積を求める場合の体積基準の積算分率における５０％径の値（ｄ５０）を意味している。 The particle size distribution of the positive electrode material in the present specification means a particle size distribution obtained by a method for obtaining an integrated volume from particles having a small particle size distribution using a microtrack particle size distribution measuring apparatus “HRA9320” manufactured by Nikkiso Co., Ltd. . In addition, the average particle diameter of the positive electrode material and other particles (such as the material S) in the present specification is the volume-based integrated fraction when the integrated volume is obtained from particles having a small particle size distribution using the above-described apparatus. Means the value of 50% diameter (d 50 ).
　前記コバルト酸リチウム粒子の表面をＡｌ含有酸化物で被覆して前記正極材料とするには、例えば下記の方法が採用できる。ｐＨを９～１１とし、温度を６０～８０℃とした水酸化リチウム水溶液中に、前記コバルト酸リチウム粒子を投入し攪拌して分散させ、ここにＡｌ（ＮＯ３）３・９Ｈ２Ｏと、ｐＨの変動を抑えるためのアンモニア水とを滴下して、Ａｌ（ＯＨ）３共沈物を生成させ、前記コバルト酸リチウム粒子の表面に付着させる。その後、この反応液からＡｌ（ＯＨ）３共沈物が付着した前記コバルト酸リチウム粒子を取り出し、洗浄後、乾燥させた後に、熱処理して、前記コバルト酸リチウム粒子の表面にＡｌ含有酸化物の被膜を形成して、前記正極材料とする。Ａｌ（ＯＨ）３共沈物が付着した前記コバルト酸リチウム粒子の熱処理は大気雰囲気中で行うことが好ましく、また、熱処理温度を２００～８００℃とし、熱処理時間を５～１５時間とすることが好ましい。この方法で前記コバルト酸リチウム粒子の表面をＡｌ含有酸化物で被覆する場合、前記の熱処理温度の調整によって、被膜を構成する主成分となるＡｌ含有酸化物を、Ａｌ２Ｏ３としたり、ＡｌＯＯＨとしたり、ＬｉＡｌＯ２としたり、ＬｉＣｏ１－ｗＡｌｗＯ２（ただし、０．５＜ｗ＜１）としたりすることができる。 In order to coat the surface of the lithium cobalt oxide particles with an Al-containing oxide to form the positive electrode material, for example, the following method can be employed. In a lithium hydroxide aqueous solution having a pH of 9 to 11 and a temperature of 60 to 80 ° C., the lithium cobalt oxide particles are charged and dispersed by stirring, and Al (NO 3 ) 3 · 9H 2 O and Aqueous ammonia for suppressing fluctuations in pH is added dropwise to produce an Al (OH) 3 coprecipitate and adhere to the surface of the lithium cobalt oxide particles. Thereafter, the lithium cobalt oxide particles to which the Al (OH) 3 coprecipitate is adhered are taken out from the reaction solution, washed, dried, and then heat-treated to form an Al-containing oxide on the surface of the lithium cobalt oxide particles. A film is formed to form the positive electrode material. The heat treatment of the lithium cobaltate particles to which the Al (OH) 3 coprecipitate is deposited is preferably performed in the air atmosphere, and the heat treatment temperature is 200 to 800 ° C. and the heat treatment time is 5 to 15 hours. preferable. When the surface of the lithium cobalt oxide particles is coated with an Al-containing oxide by this method, the Al-containing oxide as a main component constituting the coating is changed to Al 2 O 3 or AlOOH by adjusting the heat treatment temperature. Or LiAlO 2 or LiCo 1-w Al w O 2 (where 0.5 <w <1).
　前記正極材料と、他の正極活物質とを使用する場合には、電池の連続充電特性がより向上すると共に、前記正極材料によるリチウムイオン二次電池の高温下での充放電サイクル特性や貯蔵特性を損なわないことから、前記他の正極活物質として、ＮｉおよびＣｏと、Ｍｇ、Ｍｎ、Ｂａ、Ｗ、Ｔｉ、Ｚｒ、ＭｏおよびＡｌよりなる群から選択される元素Ｍ２とを含有するニッケル酸リチウムを用いることが好ましい。 When the positive electrode material and another positive electrode active material are used, the continuous charge characteristics of the battery are further improved, and the charge / discharge cycle characteristics and storage characteristics of the lithium ion secondary battery using the positive electrode material at a high temperature Therefore, nickel acid containing Ni and Co and element M 2 selected from the group consisting of Mg, Mn, Ba, W, Ti, Zr, Mo, and Al as the other positive electrode active material It is preferable to use lithium.
　前記ニッケル酸リチウムは、Ｎｉ、Ｃｏおよび元素Ｍ２、並びに、更に含有してもよい他の元素を纏めて元素群Ｍｂとしたときに、化学式ＬｉＭｂＯ２で表されるものであり、元素群Ｍ２の全原子数１００ｍｏｌ％中のＮｉ、Ｃｏおよび元素Ｍ２の量を、それぞれ、ｓ（ｍｏｌ％）、ｔ（ｍｏｌ％）およびｕ（ｍｏｌ％）で表したとき、３０≦ｓ≦９７、０．５≦ｔ≦４０、０．５≦ｕ≦４０であることが好ましく、７０≦ｓ≦９７、０．５≦ｔ≦３０、０．５≦ｕ≦５であることがより好ましい。 The lithium nickelate is represented by the chemical formula LiM b O 2 when Ni, Co, and the element M 2 , and other elements that may further be contained, are combined into an element group M b . when Ni of the total number of atoms in 100 mol% of the element group M 2, the amount of Co and the element M 2, respectively, expressed in s (mol%), t ( mol%) and u (mol%), 30 ≦ s ≦ 97, 0.5 ≦ t ≦ 40, 0.5 ≦ u ≦ 40 are preferable, and 70 ≦ s ≦ 97, 0.5 ≦ t ≦ 30, and 0.5 ≦ u ≦ 5 are more preferable. preferable.
　前記ニッケル酸リチウムは、Ｌｉ含有化合物（水酸化リチウム、炭酸リチウムなど）、Ｎｉ含有化合物（硫酸ニッケルなど）、Ｃｏ含有化合物（硫酸コバルト、酸化コバルトなど）、および必要に応じて元素Ｍｂを含有する化合物（酸化物、水酸化物、硫酸塩など）を混合し、この原料混合物を焼成するなどして製造することができる。なお、より高い純度で前記ニッケル酸リチウムを合成するには、Ｎｉ、Ｃｏおよび必要に応じて含有させる元素Ｍｂのうちの複数の元素を含む複合化合物（水酸化物、酸化物など）と、他の原料化合物（Ｌｉ含有化合物など）とを混合し、この原料混合物を焼成することが好ましい。 The lithium nickelate, Li-containing compound (lithium hydroxide, etc. lithium carbonate), Ni-containing compound (such as nickel sulfate), Co-containing compound (cobalt sulfate, cobalt oxide, etc.), and containing the element M b as necessary The compound (oxide, hydroxide, sulfate, etc.) to be mixed can be mixed, and this raw material mixture can be fired. Incidentally, in synthesizing the lithium nickel oxide at a higher purity, Ni, complex compound containing a plurality of elements among the elements M b be contained if Co and the required (hydroxides, oxides, etc.), It is preferable to mix other raw material compounds (such as Li-containing compounds) and to fire this raw material mixture.
　前記ニッケル酸リチウムを合成するための原料混合物の焼成条件も、前記コバルト酸リチウムの場合と同様に、例えば、８００～１０５０℃で１～２４時間とすることができるが、一旦焼成温度よりも低い温度（例えば、２５０～８５０℃）まで加熱し、その温度で保持することにより予備加熱を行い、その後に焼成温度まで昇温して反応を進行させることが好ましい。予備加熱の時間については特に制限はないが、通常、０．５～３０時間程度とすればよい。また、焼成時の雰囲気は、酸素を含む雰囲気（すなわち、大気中）、不活性ガス（アルゴン、ヘリウム、窒素など）と酸素ガスとの混合雰囲気、酸素ガス雰囲気などとすることができるが、その際の酸素濃度（体積基準）は、１５％以上であることが好ましく、１８％以上であることが好ましい。 The firing conditions of the raw material mixture for synthesizing the lithium nickelate can also be set at, for example, 800 to 1050 ° C. for 1 to 24 hours, as in the case of the lithium cobaltate, but once lower than the firing temperature. It is preferable to heat up to a temperature (for example, 250 to 850 ° C.) and perform preliminary heating by holding at that temperature, and then raise the temperature to the firing temperature to advance the reaction. There is no particular limitation on the preheating time, but it is usually about 0.5 to 30 hours. The atmosphere during firing can be an atmosphere containing oxygen (that is, in the air), a mixed atmosphere of an inert gas (such as argon, helium, or nitrogen) and oxygen gas, or an oxygen gas atmosphere. The oxygen concentration (volume basis) is preferably 15% or more, and more preferably 18% or more.
　正極活物質に前記正極材料と他の正極活物質（例えば前記ニッケル酸リチウム）とを使用する場合には、前記正極材料と他の正極活物質との合計１００質量％中の前記正極材料の量が、５０質量％以上であることが好ましく、８０質量％以上であることがより好ましい（すなわち、前記正極材料と共に使用される他の正極活物質の量が、前記正極材料と他の正極活物質との合計１００質量％中、５０質量％以下であることが好ましく、２０質量％以下であることがより好ましい）。なお、正極活物質には前記正極材料のみを用いてもよいため、前記正極材料と他の正極活物質との合計１００質量％中の前記正極材料の量の好適上限値は、１００質量％である。ただし、前記ニッケル酸リチウムの使用による電池の連続充電特性向上効果をより良好に確保するためには、前記正極材料と前記ニッケル酸リチウムとの合計１００質量％中の前記ニッケル酸リチウムの量が、５質量％以上であることが好ましく、１０質量％以上であることがより好ましい。 When the positive electrode material and another positive electrode active material (for example, the lithium nickelate) are used as the positive electrode active material, the amount of the positive electrode material in a total of 100 mass% of the positive electrode material and the other positive electrode active material Is preferably 50% by mass or more, more preferably 80% by mass or more (that is, the amount of the other positive electrode active material used together with the positive electrode material is the same as that of the positive electrode material and the other positive electrode active material). The total content is preferably 50% by mass or less, and more preferably 20% by mass or less. Since only the positive electrode material may be used as the positive electrode active material, the preferred upper limit of the amount of the positive electrode material in the total of 100% by mass of the positive electrode material and the other positive electrode active material is 100% by mass. is there. However, in order to better ensure the continuous charge characteristics improvement effect of the battery by using the lithium nickelate, the amount of the lithium nickelate in a total of 100% by mass of the positive electrode material and the lithium nickelate, It is preferably 5% by mass or more, and more preferably 10% by mass or more.
　正極合剤層に係る導電助剤としては、天然黒鉛（鱗片状黒鉛など）、人造黒鉛などの黒鉛（黒鉛質炭素材料）；アセチレンブラック、ケッチェンブラック、チャンネルブラック、ファーネスブラック、ランプブラック、サーマルブラックなどのカ－ボンブラック；炭素繊維；などの炭素材料などが挙げられる。また、正極合剤層に係るバインダには、ＰＶＤＦ、ポリテトラフルオロエチレン（ＰＴＦＥ）、フッ化ビニリデン－クロロトリフルオロエチレン共重合体〔Ｐ（ＶＤＦ－ＣＴＦＥ）〕、ＳＢＲ、ＣＭＣなどが好適に用いられる。 Conductive aids for the positive electrode mixture layer include natural graphite (such as flake graphite), graphite such as artificial graphite (graphitic carbon material); acetylene black, ketjen black, channel black, furnace black, lamp black, thermal Carbon materials such as carbon black such as black; carbon fiber; Also, PVDF, polytetrafluoroethylene (PTFE), vinylidene fluoride-chlorotrifluoroethylene copolymer [P (VDF-CTFE)], SBR, CMC, etc. are preferably used as the binder for the positive electrode mixture layer. It is done.
　正極は、例えば、正極活物質（前記正極材料など）、導電助剤およびバインダなどを、ＮＭＰなどの溶剤に分散させたペースト状やスラリー状の正極合剤含有組成物を調製し（ただし、バインダは溶剤に溶解していてもよい）、これを集電体の片面または両面に塗布し、乾燥した後に、必要に応じてカレンダー処理などのプレス処理を施す工程を経て製造される。 The positive electrode is prepared, for example, by preparing a paste-like or slurry-like positive electrode mixture-containing composition in which a positive electrode active material (such as the above-mentioned positive electrode material), a conductive additive and a binder are dispersed in a solvent such as NMP. May be dissolved in a solvent), and this is applied to one or both sides of the current collector, dried, and then subjected to a press treatment such as a calender treatment as necessary.
　ただし、正極は、前記の製造方法で製造されたものに限定される訳ではなく、他の方法で製造したものであってもよい。例えば、正極をペレット状の正極合剤成形体とする場合には、正極活物質、導電助剤およびバインダなどを含有する正極合剤をプレス処理してペレット状に成形する方法で、正極を製造することができる。 However, the positive electrode is not limited to those manufactured by the above manufacturing method, and may be manufactured by other methods. For example, when the positive electrode is formed into a pellet-like positive electrode mixture molded body, the positive electrode is produced by a method of pressing a positive electrode mixture containing a positive electrode active material, a conductive additive, a binder, and the like into a pellet shape. can do.
　集電体は、従来から知られているリチウムイオン二次電池の正極に使用されているものと同様のものが使用でき、例えば、アルミニウム製の箔、パンチングメタル、網、エキスパンドメタルなどがあげられ、厚みは５～３０μｍが好ましい。 The current collector can be the same as that used for the positive electrode of a conventionally known lithium ion secondary battery, such as aluminum foil, punching metal, net, expanded metal, etc. The thickness is preferably 5 to 30 μm.
　正極合剤層や正極合剤成形体の組成としては、正極活物質（前記正極材料を含む）の量が６０～９５質量％であることが好ましく、バインダの量が１～１５質量％であることが好ましく、導電助剤の量が３～２０質量％であることが好ましい。また、正極合剤層と集電体とを有する形態の正極の場合、正極合剤層の厚み（集電体の片面あたりの厚み）は、３０～１５０μｍであることが好ましい。他方、正極合剤成形体からなる正極の場合、その厚みは、０．１５～１ｍｍであることが好ましい。 As the composition of the positive electrode mixture layer and the positive electrode mixture molded body, the amount of the positive electrode active material (including the positive electrode material) is preferably 60 to 95% by mass, and the amount of the binder is 1 to 15% by mass. The amount of the conductive auxiliary is preferably 3 to 20% by mass. In the case of a positive electrode having a positive electrode mixture layer and a current collector, the thickness of the positive electrode mixture layer (thickness per one side of the current collector) is preferably 30 to 150 μm. On the other hand, in the case of a positive electrode comprising a positive electrode mixture molded body, the thickness is preferably 0.15 to 1 mm.
　リチウムイオン二次電池において、負極（系外プレドープによってＬｉイオンがドープされた負極活物質を含有する負極）と正極とは、セパレータを介して積層した積層体（積層電極体）や、この積層体を更に渦巻状に巻回した巻回体（巻回電極体）などの形態で使用される。 In a lithium ion secondary battery, a negative electrode (a negative electrode containing a negative electrode active material doped with Li ions by pre-doping outside the system) and a positive electrode are laminated body (laminated electrode body) laminated via a separator, or this laminated body. Is further used in the form of a wound body (wound electrode body) wound in a spiral shape.
　セパレータは、ポリエチレン、ポリプロピレン、エチレン－プロピレン共重合体などのポリオレフィン；ポリエチレンテレフタレートや共重合ポリエステルなどのポリエステル；などで構成された多孔質膜であることが好ましい。なお、セパレータは、１００～１４０℃において、その孔が閉塞する性質（すなわちシャットダウン機能）を有していることが好ましい。そのため、セパレータは、融点、すなわち、ＪＩＳ　Ｋ　７１２１の規定に準じて、示差走査熱量計（ＤＳＣ）を用いて測定される融解温度が、１００～１４０℃の熱可塑性樹脂を成分とするものがより好ましく、ポリエチレンを主成分とする単層の多孔質膜であるか、ポリエチレンとポリプロピレンとを２～５層積層した積層多孔質膜などの多孔質膜を構成要素とする積層多孔質膜であることが好ましい。ポリエチレンとポリプロピレンなどのポリエチレンより融点の高い樹脂を混合または積層して用いる場合には、多孔質膜を構成する樹脂としてポリエチレンが３０質量％以上であることが好ましく、５０質量％以上であることがより好ましい。 The separator is preferably a porous film made of polyolefin such as polyethylene, polypropylene, ethylene-propylene copolymer; polyester such as polyethylene terephthalate or copolymer polyester; Note that the separator preferably has a property of closing the pores at 100 to 140 ° C. (that is, a shutdown function). Therefore, the separator has a melting point, that is, a thermoplastic resin having a melting temperature measured using a differential scanning calorimeter (DSC) of 100 to 140 ° C. as a component in accordance with JIS K 7121. Preferably, it is a single-layer porous film mainly composed of polyethylene or a laminated porous film comprising a porous film such as a laminated porous film in which 2 to 5 layers of polyethylene and polypropylene are laminated. Is preferred. When a resin having a melting point higher than that of polyethylene such as polyethylene and polypropylene is used by mixing or laminating, it is preferable that polyethylene is 30% by mass or more, and 50% by mass or more as a resin constituting the porous membrane. More preferred.
　このような樹脂多孔質膜としては、例えば、従来から知られているリチウムイオン二次電池などで使用されている前記例示の熱可塑性樹脂で構成された多孔質膜、すなわち、溶剤抽出法、乾式または湿式延伸法などにより作製されたイオン透過性の多孔質膜を用いることができる。 As such a resin porous membrane, for example, a porous membrane composed of the above-mentioned exemplified thermoplastic resin used in a conventionally known lithium ion secondary battery or the like, that is, a solvent extraction method, a dry type Alternatively, an ion-permeable porous film manufactured by a wet stretching method or the like can be used.
　セパレータの平均孔径は、０．０１μｍ以上であることが好ましく、０．０５μｍ以上であることがより好ましく、また、１μｍ以下であることが好ましく、０．５μｍ以下であることがより好ましい。 The average pore diameter of the separator is preferably 0.01 μm or more, more preferably 0.05 μm or more, more preferably 1 μm or less, and even more preferably 0.5 μm or less.
　前記セパレータとして、熱可塑性樹脂を主体とする多孔質膜（Ｉ）と、耐熱温度が１５０℃以上のフィラーを主体として含む多孔質層（ＩＩ）とを有する積層型のセパレータを使用してもよい。前記セパレータは、シャットダウン特性と耐熱性（耐熱収縮性）および高い機械的強度とを兼ね備えている。また、積層型セパレータを用いることで、電池の充放電サイクル特性が更に向上する。その理由は定かではないが、積層型セパレータが有する高い機械的強度が、電池の充放電サイクルに伴う負極の膨張・収縮に対して高い耐性を示し、セパレータのよれを抑制して負極－セパレータ－正極間の密着性を保つことができることが理由であると推測される。 As the separator, a laminated separator having a porous film (I) mainly composed of a thermoplastic resin and a porous layer (II) mainly including a filler having a heat resistant temperature of 150 ° C. or higher may be used. . The separator has both shutdown characteristics, heat resistance (heat shrinkage resistance), and high mechanical strength. Moreover, the charge / discharge cycle characteristics of the battery are further improved by using the laminated separator. The reason for this is not clear, but the high mechanical strength of the laminated separator shows high resistance to negative electrode expansion / contraction associated with the battery charge / discharge cycle. It is presumed that this is because the adhesion between the positive electrodes can be maintained.
　本明細書において、「耐熱温度が１５０℃以上」とは、少なくとも１５０℃において軟化などの変形が見られないことを意味している。 In this specification, “heat-resistant temperature is 150 ° C. or higher” means that deformation such as softening is not observed at least at 150 ° C.
　セパレータに係る多孔質膜（Ｉ）は、主にシャットダウン機能を確保するためのものであり、電池が多孔質膜（Ｉ）の主体となる成分である熱可塑性樹脂の融点以上に達したときには、多孔質膜（Ｉ）に係る熱可塑性樹脂が溶融してセパレータの空孔を塞ぎ、電気化学反応の進行を抑制するシャットダウンを生じる。 The porous membrane (I) according to the separator is mainly for ensuring a shutdown function, and when the battery reaches or exceeds the melting point of the thermoplastic resin, which is the main component of the porous membrane (I), The thermoplastic resin related to the porous membrane (I) melts and closes the pores of the separator, and a shutdown that suppresses the progress of the electrochemical reaction occurs.
　多孔質膜（Ｉ）の主体となる熱可塑性樹脂としては、融点が１４０℃以下の樹脂が好ましく、具体的には、例えばポリエチレンが挙げられる。また、多孔質膜（Ｉ）の形態としては、電池用のセパレータとして通常用いられている微多孔膜や、不織布などの基材にポリエチレンの粒子を含む分散液を塗布し、乾燥するなどして得られるものなどのシート状物が挙げられる。ここで、多孔質膜（Ｉ）の構成成分の全体積中〔空孔部分を除く全体積。セパレータに係る多孔質膜（Ｉ）および多孔質層（ＩＩ）の構成成分の体積含有率に関して、以下同じ。〕において、主体となる融点が１４０℃以下の樹脂の体積含有率は、５０体積％以上であり、７０体積％以上であることがより好ましい。なお、例えば多孔質膜（Ｉ）を前記ポリエチレンの微多孔膜で形成する場合は、融点が１４０℃以下の樹脂の体積含有率が１００体積％となる。 The thermoplastic resin that is the main component of the porous membrane (I) is preferably a resin having a melting point of 140 ° C. or lower, and specifically includes polyethylene. In addition, as the form of the porous membrane (I), a microporous membrane usually used as a battery separator or a dispersion containing polyethylene particles is applied to a substrate such as a nonwoven fabric and dried. Examples thereof include sheet-like materials such as those obtained. Here, among the total volume of the constituent components of the porous membrane (I) [the total volume excluding the void portion. The same applies to the volume content of the constituent components of the porous membrane (I) and the porous layer (II) according to the separator. ], The volume content of the resin whose main melting point is 140 ° C. or lower is 50% by volume or more, and more preferably 70% by volume or more. For example, when the porous membrane (I) is formed of the polyethylene microporous membrane, the volume content of the resin having a melting point of 140 ° C. or lower is 100% by volume.
　セパレータに係る多孔質層（ＩＩ）は、電池の内部温度が上昇した際にも正極と負極との直接の接触による短絡を防止する機能を備えたものであり、耐熱温度が１５０℃以上のフィラーによって、その機能を確保している。すなわち、電池が高温となった場合には、たとえ多孔質膜（Ｉ）が収縮しても、収縮し難い多孔質層（ＩＩ）によって、セパレータが熱収縮した場合に発生し得る正負極の直接の接触による短絡を防止することができる。また、この耐熱性の多孔質層（ＩＩ）がセパレータの骨格として作用するため、多孔質膜（Ｉ）の熱収縮、すなわちセパレータ全体の熱収縮自体も抑制できる。 The porous layer (II) according to the separator has a function of preventing a short circuit due to direct contact between the positive electrode and the negative electrode even when the internal temperature of the battery rises, and has a heat resistance temperature of 150 ° C. or higher. The function is secured by. That is, when the battery becomes high temperature, even if the porous membrane (I) shrinks, the porous layer (II) which does not easily shrink can cause the positive and negative electrodes directly when the separator is thermally shrunk. It is possible to prevent a short circuit due to the contact. In addition, since the heat-resistant porous layer (II) acts as a skeleton of the separator, thermal contraction of the porous membrane (I), that is, thermal contraction of the entire separator itself can be suppressed.
　多孔質層（ＩＩ）に係るフィラーは、耐熱温度が１５０℃以上で、電池の有する非水電解液に対して安定であり、更に電池の作動電圧範囲において酸化還元され難い電気化学的に安定なものであれば無機粒子でも有機粒子でもよいが、分散などの点から微粒子であることが好ましく、また、無機酸化物粒子、より具体的には、アルミナ、シリカ、ベーマイトが好ましい。アルミナ、シリカ、ベーマイトは、耐酸化性が高く、粒径や形状を所望の数値などに調整することが可能であるため、多孔質層（ＩＩ）の空孔率を精度よく制御することが容易となる。なお、耐熱温度が１５０℃以上のフィラーは、例えば前記例示のものを１種単独で用いてもよく、２種以上を併用してもよい。 The filler related to the porous layer (II) has a heat resistant temperature of 150 ° C. or higher, is stable with respect to the non-aqueous electrolyte of the battery, and is electrochemically stable that is difficult to be oxidized and reduced within the battery operating voltage range. Any inorganic particles or organic particles may be used as long as they are fine, but fine particles are preferable from the viewpoint of dispersion and the like, and inorganic oxide particles, more specifically, alumina, silica, and boehmite are preferable. Alumina, silica, and boehmite have high oxidation resistance, and the particle size and shape can be adjusted to the desired numerical values, making it easy to control the porosity of the porous layer (II) with high accuracy. It becomes. In addition, the filler whose heat-resistant temperature is 150 degreeC or more may use the thing of the said illustration individually by 1 type, and may use 2 or more types together, for example.
　多孔質層（ＩＩ）の「耐熱温度が１５０℃以上のフィラーを主成分として含む」とは、多孔質層（ＩＩ）の構成成分の全体積中、前記フィラーを７０体積％以上含むことを意味している。多孔質層（ＩＩ）における前記フィラーの量は、多孔質層（ＩＩ）の構成成分の全体積中、８０体積％以上であることが好ましく、９０体積％以上であることがより好ましい。多孔質層（ＩＩ）中の前記フィラーを前記のように高含有量とすることで、セパレータ全体の熱収縮を良好に抑制して、高い耐熱性を付与することができる。 The phrase “containing a filler having a heat resistant temperature of 150 ° C. or higher as a main component” of the porous layer (II) means that 70% by volume or more of the filler is included in the total volume of the constituent components of the porous layer (II). is doing. The amount of the filler in the porous layer (II) is preferably 80% by volume or more and more preferably 90% by volume or more in the total volume of the constituent components of the porous layer (II). By making the said filler in porous layer (II) high content as mentioned above, the thermal contraction of the whole separator can be suppressed favorably and high heat resistance can be provided.
　また、多孔質層（ＩＩ）には、前記フィラー同士を結着したり多孔質層（ＩＩ）と多孔質膜（Ｉ）とを結着したりするために有機バインダを含有させることが好ましく、このような観点から、多孔質層（ＩＩ）におけるフィラー（Ｂ）量の好適上限値は、例えば、多孔質層（ＩＩ）の構成成分の全体積中、９９体積％である。なお、多孔質層（ＩＩ）におけるフィラー（Ｂ）の量を７０体積％未満とすると、例えば、多孔質層（ＩＩ）中の有機バインダ量を多くする必要が生じるが、その場合には多孔質層（ＩＩ）の空孔が有機バインダによって埋められてしまい、例えばセパレータとしての機能を喪失する虞がある。 The porous layer (II) preferably contains an organic binder to bind the fillers or bind the porous layer (II) and the porous membrane (I). From such a viewpoint, the suitable upper limit of the amount of filler (B) in the porous layer (II) is, for example, 99% by volume in the total volume of the constituent components of the porous layer (II). When the amount of the filler (B) in the porous layer (II) is less than 70% by volume, for example, it is necessary to increase the amount of the organic binder in the porous layer (II). There is a possibility that the pores of the layer (II) are filled with the organic binder, and the function as a separator is lost, for example.
　多孔質層（ＩＩ）に用いる有機バインダとしては、前記フィラー同士や多孔質層（ＩＩ）と多孔質膜（Ｉ）とを良好に接着でき、電気化学的に安定で、かつ電気化学素子用の非水電解液に対して安定であれば特に制限はない。具体的には、フッ素樹脂（ＰＶＤＦなど）、フッ素系ゴム、ＳＢＲ、ＣＭＣ、ヒドロキシエチルセルロース（ＨＥＣ）、ポリビニルアルコール（ＰＶＡ）、ポリビニルブチラール（ＰＶＢ）、ポリビニルピロリドン（ＰＶＰ）、ポリＮ－ビニルアセトアミド、架橋アクリル樹脂、ポリウレタン、エポキシ樹脂などが挙げられる。これらの有機バインダは１種単独で使用してもよく、２種以上を併用しても構わない。 As an organic binder used for the porous layer (II), the fillers or the porous layer (II) and the porous film (I) can be bonded well, are electrochemically stable, and are used for an electrochemical element. There is no particular limitation as long as it is stable with respect to the non-aqueous electrolyte. Specifically, fluororesin (such as PVDF), fluororubber, SBR, CMC, hydroxyethyl cellulose (HEC), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinyl pyrrolidone (PVP), poly N-vinylacetamide, Cross-linked acrylic resin, polyurethane, epoxy resin and the like can be mentioned. These organic binders may be used alone or in combination of two or more.
　前記積層型セパレータは、例えば、多孔質膜（Ｉ）に、前記フィラーや有機バインダなどと溶剤（水やケトン類などの有機溶剤など）とを含有する多孔質層（ＩＩ）形成用組成物（スラリー、ペーストなど）を塗布した後、所定の温度で乾燥して多孔質層（ＩＩ）を形成することによって製造することができる。 The laminated separator is, for example, a composition for forming a porous layer (II) containing, in the porous membrane (I), the filler, an organic binder, and the like, and a solvent (an organic solvent such as water and ketones) ( It can be manufactured by applying a slurry, paste, etc.) and then drying at a predetermined temperature to form the porous layer (II).
　前記積層型セパレータは、多孔質膜（Ｉ）と多孔質層（ＩＩ）とを、それぞれ１層ずつ有していてもよく、複数有していてもよい。具体的には、多孔質膜（Ｉ）の片面にのみ多孔質層（ＩＩ）を配置して前記積層型セパレータとする他、例えば、多孔質膜（Ｉ）の両面に多孔質層（ＩＩ）を配置して前記積層型セパレータとしてもよい。ただし、前記積層型セパレータの有する層数が多くなりすぎると、セパレータの厚みを増やして電池の内部抵抗の増加やエネルギー密度の低下を招く虞があるので好ましくなく、前記積層型セパレータ中の層数は５層以下であることが好ましい。 The laminated separator may have one or more each of the porous membrane (I) and the porous layer (II). Specifically, the porous layer (II) is disposed only on one side of the porous membrane (I) to form the laminated separator. For example, the porous layer (II) is formed on both sides of the porous membrane (I). May be used as the laminated separator. However, if the number of layers of the multilayer separator is too large, it is not preferable because the thickness of the separator is increased, which may increase the internal resistance of the battery or decrease the energy density. Is preferably 5 layers or less.
　セパレータ（前記積層型セパレータおよびそれ以外のセパレータ）の厚みは、正極と負極とをより確実に隔離する観点から、６μｍ以上であることが好ましく、１０μｍ以上であることがより好ましい。他方、セパレータが厚すぎると、電池のエネルギー密度が低下してしまうことがあるため、その厚みは、５０μｍ以下であることが好ましく、３０μｍ以下であることがより好ましい。 The thickness of the separator (the laminated separator and other separators) is preferably 6 μm or more and more preferably 10 μm or more from the viewpoint of more reliably separating the positive electrode and the negative electrode. On the other hand, if the separator is too thick, the energy density of the battery may be lowered. Therefore, the thickness is preferably 50 μm or less, and more preferably 30 μm or less.
　また、多孔質膜（Ｉ）の厚み〔多孔質膜（Ｉ）が複数存在する場合には、その総厚み〕は、５～３０μｍであることが好ましい。更に、多孔質層（ＩＩ）の厚み〔多孔質層（ＩＩ）が複数存在する場合には、その総厚み〕は、１μｍ以上であることが好ましく、２μｍ以上であることがより好ましく、４μｍ以上であることが更に好ましく、また、２０μｍ以下であることが好ましく、１０μｍ以下であることがより好ましく、６μｍ以下であることが更に好ましい。 Further, the thickness of the porous membrane (I) [the total thickness when a plurality of porous membranes (I) are present] is preferably 5 to 30 μm. Further, the thickness of the porous layer (II) [when there are a plurality of porous layers (II), the total thickness] is preferably 1 μm or more, more preferably 2 μm or more, and 4 μm or more. Further, it is preferably 20 μm or less, more preferably 10 μm or less, and further preferably 6 μm or less.
　セパレータ（前記積層型セパレータおよびそれ以外のセパレータ）の空孔率は、３０～７０％であることが好ましい。 The porosity of the separator (the laminated separator and other separators) is preferably 30 to 70%.
　また、セパレータ（前記積層型セパレータおよびそれ以外のセパレータ）は、その片面または両面に接着層を有していることが好ましい。積層電極体や巻回電極体の形成時に、セパレータの接着層によってセパレータと電極とを一体化させた場合には、このような電極体を用いた電池において充放電を繰り返しても、電極体の形状変化を抑制できるため、電池の充放電サイクル特性が更に向上する。横断面を扁平状に成形した扁平状巻回電極体を用いた電池の場合には、前記接着層による充放電サイクル特性の向上効果が特に顕著となる。 Further, it is preferable that the separator (the laminated separator and other separators) has an adhesive layer on one side or both sides thereof. When the separator and the electrode are integrated by the adhesive layer of the separator when forming the laminated electrode body or the wound electrode body, even if charging / discharging is repeated in a battery using such an electrode body, Since the shape change can be suppressed, the charge / discharge cycle characteristics of the battery are further improved. In the case of a battery using a flat wound electrode body having a flat cross section, the effect of improving the charge / discharge cycle characteristics by the adhesive layer is particularly remarkable.
　セパレータの接着層は、加熱することで接着性が発現する接着性樹脂を含有していることが好ましい。接着性樹脂を含有する接着層の場合は、電極体を加熱しながら押圧する工程（加熱プレス）を経ることでセパレータと電極とを一体化させることができる。接着性樹脂の接着性が発現する最低温度は、セパレータにおける接着層以外の層で、シャットダウンが発現する温度よりも低い温度である必要があるが、具体的には、６０℃以上１２０℃以下であることが好ましい。また、セパレータが前記積層型セパレータである場合、接着性樹脂の接着性が発現する最低温度は、多孔質膜（Ｉ）の主成分である熱可塑性樹脂の融点よりも低い温度である必要がある。 The adhesive layer of the separator preferably contains an adhesive resin that exhibits adhesiveness when heated. In the case of an adhesive layer containing an adhesive resin, the separator and the electrode can be integrated by undergoing a step of pressing while heating the electrode body (heating press). The minimum temperature at which the adhesiveness of the adhesive resin is expressed needs to be lower than the temperature at which shutdown occurs in the layers other than the adhesive layer in the separator. Specifically, the temperature is from 60 ° C to 120 ° C. Preferably there is. Further, when the separator is the laminated separator, the minimum temperature at which the adhesive resin exhibits adhesiveness needs to be lower than the melting point of the thermoplastic resin that is the main component of the porous membrane (I). .
　このような接着性樹脂を使用することで、セパレータと正極および／または負極とを加熱プレスして一体化する際に、セパレータの劣化を良好に抑制することができる。 By using such an adhesive resin, deterioration of the separator can be satisfactorily suppressed when the separator and the positive electrode and / or the negative electrode are integrated by heating and pressing.
　接着性樹脂は、その存在によって、電極体を構成する電極（例えば負極）とセパレータとの間の１８０°での剥離試験を実施した際に得られる剥離強度が、加熱プレス前の状態では、好ましくは０．０５Ｎ／２０ｍｍ以下、特に好ましくは０Ｎ／２０ｍｍ（全く接着力のない状態）であり、６０～１２０℃の温度で加熱プレスした後の状態では０．２Ｎ／２０ｍｍ以上となるディレードタック性を有していることが好ましい。 Due to the presence of the adhesive resin, the peel strength obtained when a peel test at 180 ° between the electrode (for example, the negative electrode) constituting the electrode body and the separator is carried out is preferable in the state before the hot press. Is 0.05 N / 20 mm or less, particularly preferably 0 N / 20 mm (a state having no adhesive force), and a delayed tack property of 0.2 N / 20 mm or more after being heated and pressed at a temperature of 60 to 120 ° C. It is preferable to have.
　ただし、前記剥離強度が強すぎると、電極の合剤層（正極合剤層および負極合剤層）が電極の集電体から剥離して、導電性が低下する虞があることから、前記１８０°での剥離試験による剥離強度は、６０～１２０℃の温度で加熱プレスした後の状態で１０Ｎ／２０ｍｍ以下であることが好ましい。 However, if the peel strength is too strong, the electrode mixture layer (the positive electrode mixture layer and the negative electrode mixture layer) may peel from the current collector of the electrode, and the conductivity may be lowered. The peel strength according to the peel test at ° is preferably 10 N / 20 mm or less after being hot pressed at a temperature of 60 to 120 ° C.
　なお、本明細書でいう電極とセパレータとの間の１８０°での剥離強度は、以下の方法により測定される値である。セパレータおよび電極を、それぞれ長さ５ｃｍ×幅２ｃｍのサイズに切り出し、切り出したセパレータと電極と重ねる。加熱プレスした後の状態の剥離強度を求める場合には、片端から２ｃｍ×２ｃｍの領域を加熱プレスして試験片を作製する。この試験片のセパレータと電極とを加熱プレスしていない側の端部を開き、セパレータと負極とを、これらの角度が１８０°になるように折り曲げる。その後、引張試験機を用い、試験片の１８０°に開いたセパレータの片端側と電極の片端側とを把持して、引張速度１０ｍｍ／ｍｉｎで引っ張り、セパレータと電極とを加熱プレスした領域で両者が剥離したときの強度を測定する。また、セパレータと電極との加熱プレス前の状態での剥離強度は、前記のように切り出した各セパレータと電極とを重ね、加熱をせずにプレスする以外は前記と同様に試験片を作製し、前記と同じ方法で剥離試験を行う。 In addition, the peel strength at 180 ° between the electrode and the separator referred to in this specification is a value measured by the following method. The separator and the electrode are each cut into a size of 5 cm in length and 2 cm in width, and the cut-out separator and the electrode are overlapped. When obtaining the peel strength in the state after being hot-pressed, a test piece is prepared by hot-pressing a 2 cm × 2 cm region from one end. The end of the test piece on the side where the separator and electrode are not heated and pressed is opened, and the separator and the negative electrode are bent so that these angles are 180 °. Thereafter, using a tensile tester, both the one end side of the separator opened at 180 ° of the test piece and the one end side of the electrode are gripped and pulled at a pulling speed of 10 mm / min. Measure the strength when peeled off. In addition, the peel strength of the separator and the electrode before heating press was determined by preparing a test piece in the same manner as above except that the separator and electrode cut out as described above were stacked and pressed without heating. The peel test is performed in the same manner as described above.
　よって、接着性樹脂は、室温（例えば２５℃）では接着性（粘着性）が殆どなく、かつ接着性の発現する最低温度がセパレータのシャットダウンする温度未満、好ましくは６０℃以上１２０℃以下といったディレードタック性を有するものが望ましい。なお、セパレータと電極とを一体化する際の加熱プレスの温度は、セパレータの熱収縮があまり顕著に生じない８０℃以上１００℃以下であることがより好ましく、接着性樹脂の接着性が発現する最低温度も、８０℃以上１００℃以下であることがより好ましい。 Therefore, the adhesive resin has almost no adhesiveness (stickiness) at room temperature (for example, 25 ° C), and the minimum temperature at which the adhesiveness is developed is less than the temperature at which the separator shuts down, preferably 60 ° C to 120 ° C. Those having tackiness are desirable. The temperature of the heating press when integrating the separator and the electrode is more preferably 80 ° C. or more and 100 ° C. or less at which the thermal contraction of the separator does not occur significantly, and the adhesiveness of the adhesive resin is exhibited. The minimum temperature is more preferably 80 ° C. or higher and 100 ° C. or lower.
　ディレードタック性を有する接着性樹脂としては、室温では流動性が殆どなく、加熱時に流動性を発揮し、プレスによって密着する特性を有する樹脂が好ましい。また、室温で固体であり、加熱することによって溶融し、化学反応によって接着性が発揮されるタイプの樹脂を接着性樹脂として用いることもできる。 As the adhesive resin having a delayed tack property, a resin that has almost no fluidity at room temperature, exhibits fluidity when heated, and has a property of being in close contact with a press is preferable. A resin of a type that is solid at room temperature, melts by heating, and exhibits adhesiveness by a chemical reaction can also be used as the adhesive resin.
　接着性樹脂は、融点、ガラス転移点などを指標とする軟化点が６０℃以上１２０℃以下の範囲内にあるものが好ましい。接着性樹脂の融点およびガラス転移点は、例えば、ＪＩＳ　Ｋ　７１２１に規定の方法によって、また、接着性樹脂の軟化点は、例えば、ＪＩＳ　Ｋ　７２０６に規定の方法によって、それぞれ測定することができる。 The adhesive resin preferably has a softening point in the range of 60 ° C. or higher and 120 ° C. or lower with the melting point, glass transition point and the like as indices. The melting point and glass transition point of the adhesive resin can be measured, for example, by a method prescribed in JIS K 7121, and the softening point of the adhesive resin can be measured, for example, by a method prescribed in JIS K 7206.
　このような接着性樹脂の具体例としては、例えば、低密度ポリエチレン（ＬＤＰＥ）、ポリ－α－オレフィン〔ポリプロピレン（ＰＰ）、ポリブテン－１など〕、ポリアクリル酸エステル、エチレン－酢酸ビニル共重合体（ＥＶＡ）、エチレン－メチルアクリレート共重合体（ＥＭＡ）、エチレン－エチルアクリレート共重合体（ＥＥＡ）、エチレン－ブチルアクリレート共重合体（ＥＢＡ）、エチレン－メチルメタクリレート共重合体（ＥＭＭＡ）、アイオノマー樹脂などが挙げられる。 Specific examples of such adhesive resins include, for example, low density polyethylene (LDPE), poly-α-olefin [polypropylene (PP), polybutene-1, etc.], polyacrylate ester, ethylene-vinyl acetate copolymer. (EVA), ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-butyl acrylate copolymer (EBA), ethylene-methyl methacrylate copolymer (EMMA), ionomer resin Etc.
　また、前記の各樹脂や、ＳＢＲ、ニトリルゴム（ＮＢＲ）、フッ素ゴム、エチレン－プロピレンゴムなどの室温で粘着性を示す樹脂をコアとし、融点や軟化点が６０℃以上１２０℃以下の範囲内にある樹脂をシェルとしたコアシェル構造の樹脂を接着性樹脂として用いることもできる。この場合、シェルには、各種アクリル樹脂やポリウレタンなどを用いることができる。更に、接着性樹脂には、一液型のポリウレタンやエポキシ樹脂などで、６０℃以上１２０℃以下の範囲内に接着性を示すものも用いることができる。 Each resin, or a resin having adhesiveness at room temperature, such as SBR, nitrile rubber (NBR), fluorine rubber, or ethylene-propylene rubber, is used as a core, and the melting point and softening point are within the range of 60 ° C to 120 ° C It is also possible to use a resin having a core-shell structure with a resin as a shell as an adhesive resin. In this case, various acrylic resins and polyurethane can be used for the shell. Further, as the adhesive resin, one-pack type polyurethane, epoxy resin, or the like that exhibits adhesiveness in a range of 60 ° C. or higher and 120 ° C. or lower can be used.
　接着性樹脂には、前記例示の樹脂を１種単独で使用してもよく、２種以上を併用してもよい。 As the adhesive resin, one of the above exemplified resins may be used alone, or two or more of them may be used in combination.
　なお、接着性樹脂で構成される実質的に空孔を含有しない接着層を形成した場合には、セパレータと一体化した電極の表面に、電池の有する非水電解液が接触し難くなる虞があることから、正極、負極およびセパレータにおける接着性樹脂の存在面においては、接着性樹脂の存在する箇所と、存在しない箇所とが形成されていることが好ましい。具体的には、例えば、接着性樹脂の存在箇所と、存在しない箇所とが、溝状に交互に形成されていてもよく、また、平面視で円形などの接着性樹脂の存在箇所が、不連続に複数形成されていてもよい。これらの場合、接着性樹脂の存在箇所は、規則的に配置されていてもランダムに配置されていてもよい。 When an adhesive layer made of an adhesive resin and containing substantially no pores is formed, there is a risk that the non-aqueous electrolyte of the battery will be difficult to contact the surface of the electrode integrated with the separator. For this reason, it is preferable that a portion where the adhesive resin exists and a portion where the adhesive resin does not exist are formed on the surface where the adhesive resin exists in the positive electrode, the negative electrode, and the separator. Specifically, for example, the location where the adhesive resin is present and the location where the adhesive resin is not present may be alternately formed in a groove shape, and the location where the adhesive resin such as a circle is not present in a plan view is not present. A plurality may be formed continuously. In these cases, the locations where the adhesive resin is present may be regularly arranged or randomly arranged.
　なお、正極、負極およびセパレータにおける接着性樹脂の存在面においては、接着性樹脂の存在する箇所と、存在しない箇所とを形成する場合、接着性樹脂の存在面における接着性樹脂の存在する箇所の面積（総面積）は、例えば、セパレータと電極とを加熱圧着した後のこれらの１８０°での剥離強度が、前記の値となるようにすればよく、使用する接着性樹脂の種類に応じて変動し得るが、具体的には、平面視で、接着性樹脂の存在面の面積のうち、１０～６０％に、接着性樹脂が存在していることが好ましい。 In addition, in the presence surface of the adhesive resin in the positive electrode, the negative electrode, and the separator, when forming the location where the adhesive resin is present and the location where the adhesive resin is not present, The area (total area) may be such that, for example, the peel strength at 180 ° after thermocompression bonding of the separator and the electrode is the above value, and depending on the type of adhesive resin used Specifically, the adhesive resin is preferably present in 10 to 60% of the surface area of the adhesive resin in plan view.
　また、接着性樹脂の存在面において、接着性樹脂の目付けは、電極との接着を良好にして、例えば、セパレータと電極とを加圧接着した後のこれらの１８０°での剥離強度を前記の値に調整するには、０．０５ｇ／ｍ２以上とすることが好ましく、０．１ｇ／ｍ２以上とすることがより好ましい。ただし、接着性樹脂の存在面において、接着性樹脂の目付けが大きすぎると、電極体が厚くなりすぎたり、接着性樹脂がセパレータの空孔を塞ぎ、電池内部でのイオンの移動が阻害されたりする虞がある。よって、接着性樹脂の存在面において、接着性樹脂の目付けは、１ｇ／ｍ２以下であることが好ましく、０．５ｇ／ｍ２以下であることがより好ましい。 Further, in the presence of the adhesive resin, the basis weight of the adhesive resin improves the adhesion with the electrode. For example, the peel strength at 180 ° after the pressure bonding between the separator and the electrode is performed as described above. to adjust the value is preferably to 0.05 g / m 2 or more, and more preferably set to 0.1 g / m 2 or more. However, if the basis weight of the adhesive resin is too large in the presence of the adhesive resin, the electrode body becomes too thick, or the adhesive resin blocks the pores of the separator, and the movement of ions inside the battery is hindered. There is a risk. Therefore, the existing surface of the adhesive resin, the basis weight of the adhesive resin is preferably 1 g / m 2 or less, more preferably 0.5 g / m 2 or less.
　接着層は、接着性樹脂および溶剤などを含む接着層形成用組成物（接着性樹脂の溶液またはエマルション）を、セパレータに使用する多孔質膜や、多孔質膜（Ｉ）と多孔質層（ＩＩ）との積層体の片面または両面に塗布する工程を経て形成することができる。 The adhesive layer is composed of a porous film or a porous film (I) and a porous layer (II) using a composition for forming an adhesive layer (adhesive resin solution or emulsion) containing an adhesive resin and a solvent as a separator. ) And a step of applying to one side or both sides of the laminate.
　リチウムイオン二次電池に係る非水電解液には、例えば、下記の非水系溶媒中に、リチウム塩を溶解させることで調製した溶液を用いることできる。 As the non-aqueous electrolyte solution related to the lithium ion secondary battery, for example, a solution prepared by dissolving a lithium salt in the following non-aqueous solvent can be used.
　非水系溶媒には、エチレンカーボネート（ＥＣ）、プロピレンカーボネート（ＰＣ）、ブチレンカーボネート（ＢＣ）、ジメチルカーボネート（ＤＭＣ）、ジエチルカーボネート（ＤＥＣ）、メチルエチルカーボネート（ＭＥＣ）、γ－ブチロラクトン（γ－ＢＬ）、１，２－ジメトキシエタン（ＤＭＥ）、テトラヒドロフラン（ＴＨＦ）、２－メチルテトラヒドロフラン、ジメチルスルフォキシド（ＤＭＳＯ）、１，３－ジオキソラン、ホルムアミド、ジメチルホルムアミド（ＤＭＦ）、ジオキソラン、アセトニトリル、ニトロメタン、蟻酸メチル、酢酸メチル、燐酸トリエステル、トリメトキシメタン、ジオキソラン誘導体、スルホラン、３－メチル－２－オキサゾリジノン、プロピレンカーボネート誘導体、テトラヒドロフラン誘導体、ジエチルエーテル、１，３－プロパンサルトンなどの非プロトン性有機溶媒を１種単独で、または２種以上を混合した混合溶媒として用いることができる。 Non-aqueous solvents include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), γ-butyrolactone (γ-BL ), 1,2-dimethoxyethane (DME), tetrahydrofuran (THF), 2-methyltetrahydrofuran, dimethyl sulfoxide (DMSO), 1,3-dioxolane, formamide, dimethylformamide (DMF), dioxolane, acetonitrile, nitromethane, Methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivative, sulfolane, 3-methyl-2-oxazolidinone, propylene carbonate derivative, tetrahydrofuran derivative Aprotic organic solvents such as diethyl ether and 1,3-propane sultone can be used singly or as a mixed solvent in which two or more are mixed.
　非水電解液に係るリチウム塩としては、例えば、ＬｉＣｌＯ４、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＡｓＦ６、ＬｉＳｂＦ６、ＬｉＣＦ３ＳＯ３、ＬｉＣＦ３ＣＯ２、Ｌｉ２Ｃ２Ｆ４（ＳＯ３）２、ＬｉＮ（ＣＦ３ＳＯ２）２、ＬｉＣ（ＣＦ３ＳＯ２）３、ＬｉＣｎＦ２ｎ＋１ＳＯ３（ｎ≧２）、ＬｉＮ（ＲｆＯＳＯ２）２〔ここでＲｆはフルオロアルキル基〕などのリチウム塩から選ばれる少なくとも１種が挙げられる。これらのリチウム塩の非水電解液中の濃度としては、０．６～１．８ｍｏｌ／ｌとすることが好ましく、０．９～１．６ｍｏｌ／ｌとすることがより好ましい。 The lithium salt according to the non-aqueous electrolyte solution, for example, LiClO 4, LiPF 6, LiBF 4, LiAsF 6, LiSbF 6, LiCF 3 SO 3, LiCF 3 CO 2, Li 2 C 2 F 4 (SO 3) 2, LiN (CF 3 SO 2 ) 2 , LiC (CF 3 SO 2 ) 3 , LiC n F 2n + 1 SO 3 (n ≧ 2), LiN (RfOSO 2 ) 2 [where Rf is a fluoroalkyl group] At least one selected from the above. The concentration of these lithium salts in the non-aqueous electrolyte is preferably 0.6 to 1.8 mol / l, and more preferably 0.9 to 1.6 mol / l.
　また、非水電解液には、電池の充放電サイクル特性の更なる改善や、高温貯蔵性や過充電防止などの安全性を向上させる目的で、ビニレンカーボネート、ビニルエチレンカーボネート、無水酸、スルホン酸エステル、ジニトリル、１，３－プロパンサルトン、ジフェニルジスルフィド、シクロヘキシルベンゼン、ビフェニル、フルオロベンゼン、ｔ－ブチルベンゼンなどの添加剤（これらの誘導体も含む）を適宜加えることもできる。 Non-aqueous electrolytes include vinylene carbonate, vinyl ethylene carbonate, acid anhydride, sulfonic acid for the purpose of further improving the charge / discharge cycle characteristics of the battery and improving safety such as high temperature storage and overcharge prevention. Additives (including these derivatives) such as esters, dinitriles, 1,3-propane sultone, diphenyl disulfide, cyclohexylbenzene, biphenyl, fluorobenzene, t-butylbenzene can also be added as appropriate.
　更に、非水電解液には、ポリマーなどの公知のゲル化剤を添加してゲル化したもの（ゲル状電解質）を用いることもできる。 Furthermore, as the non-aqueous electrolyte, a gel (gel electrolyte) obtained by adding a known gelling agent such as a polymer can be used.
　リチウムイオン二次電池の形態については、特に制限はない。例えば、小型の円筒型、コイン形、ボタン形、扁平形、角形、電気自動車などに用いる大型のものなど、いずれであってもよい。 There is no particular limitation on the form of the lithium ion secondary battery. For example, any of a small cylindrical shape, a coin shape, a button shape, a flat shape, a square shape, a large size used for an electric vehicle, and the like may be used.
　Ｌｉイオンをドープした負極活物質を含有する負極を有するリチウムイオン二次電池には、負極合剤層中の負極活物質へのＬｉイオンのドープを系内プレドープによって行うものもあり、この場合、例えば、正極および負極とは別にＬｉ供給源を有する電極（第３電極）を使用して電池を組み立て、この第３電極に通電することで、電池内で前記Ｌｉ供給源から負極合剤層中の負極活物質にＬｉイオンをドープするものがある。よって、この種の電池では、Ｌｉイオンのドープが終了した時点においても、Ｌｉ供給源の一部が残存するかまたは全部が消失した第３電極が電池内に残存しているが、本発明のリチウムイオン二次電池は、系外プレドープによってあらかじめＬｉイオンをドープした負極活物質を含有する負極を用いて組み立てるため、Ｌｉイオンのドープに利用される（または利用された）第３電極を内部に有しない。 Some lithium ion secondary batteries having a negative electrode containing a negative electrode active material doped with Li ions perform Li ion doping to the negative electrode active material in the negative electrode mixture layer by in-system pre-doping. For example, by assembling a battery using an electrode (third electrode) having a Li supply source separately from the positive electrode and the negative electrode, and energizing the third electrode, the Li supply source in the negative electrode mixture layer in the battery Some negative electrode active materials are doped with Li ions. Therefore, in this type of battery, even when the doping of Li ions is completed, the third electrode in which a part of the Li supply source remains or all of it disappears remains in the battery. Since the lithium ion secondary battery is assembled using a negative electrode containing a negative electrode active material previously doped with Li ions by pre-doping outside the system, a third electrode used (or used) for doping Li ions is provided inside. I don't have it.
　なお、リチウムイオン二次電池において、負極の負極合剤層中の負極活物質にＬｉイオンをドープしたものであることは、電池を０．１Ｃの放電電流レートで電圧が２．０Ｖに達するまで放電したときに、正極活物質に含まれるＬｉとＬｉ以外の金属Ｍとのモル比（Ｌｉ／Ｍ）によって把握することができる。リチウムイオン二次電池においては、モル比Ｌｉ／Ｍが０．８以上１．０５以下となるように負極合剤層中の負極活物質のＬｉイオンドープ量を調整した負極を用いることが好ましい。ちなみに、Ｌｉを含まない負極活物質を含有する負極合剤層中の前記負極活物質にＬｉイオンを系外プレドープ（および系内プレドープ）していない負極を有する電池においては、通常、モル比Ｌｉ／Ｍが前記下限値よりも小さくなる。 In the lithium ion secondary battery, the negative electrode active material in the negative electrode mixture layer of the negative electrode is doped with Li ions until the voltage reaches 2.0 V at a discharge current rate of 0.1 C. When discharged, it can be grasped by the molar ratio (Li / M) between Li contained in the positive electrode active material and the metal M other than Li. In the lithium ion secondary battery, it is preferable to use a negative electrode in which the Li ion doping amount of the negative electrode active material in the negative electrode mixture layer is adjusted so that the molar ratio Li / M is 0.8 or more and 1.05 or less. By the way, in a battery having a negative electrode in which the negative electrode active material in the negative electrode mixture layer containing a negative electrode active material not containing Li is not pre-doped (and pre-doped in the system) with Li ions, the molar ratio Li / M becomes smaller than the lower limit value.
　そして、電池にした時のモル比Ｌｉ／Ｍが０．８以上１．０５以下となるように負極活物質に系外プレドープによってドープするＬｉイオンは、電池容量に換算すると、負極活物質の不可逆容量と同一かまたはそれより少ない量である。 The Li ions doped into the negative electrode active material by extra-predoping so that the molar ratio Li / M in the battery is 0.8 or more and 1.05 or less are irreversible when converted into the battery capacity. The amount is equal to or less than the capacity.
　０．１Ｃの放電電流レートで電圧が２．０Ｖに達するまで放電した時の正極活物質の組成分析は、ＩＣＰ（Ｉｎｄｕｃｔｉｖｅ　Ｃｏｕｐｌｅｄ　Ｐｌａｓｍａ）法を用いて以下のように行うことができる。まず、測定対象となる正極活物質を０．２ｇ採取して１００ｍＬ容器に入れる。その後、純水５ｍＬ、王水２ｍＬ、純水１０ｍＬを順に加えて加熱溶解し、冷却後に更に純水で２５倍に希釈し、ＪＡＲＲＥＬＡＳＨ社製のＩＣＰ分析装置「ＩＣＰ－７５７」を用いて、検量線法により組成を分析する。得られた結果から、組成量を導くことができる。後述する実施例に記載のモル比Ｌｉ／Ｍは、この方法によって求めた値である。 The composition analysis of the positive electrode active material when discharged at a discharge current rate of 0.1 C until the voltage reaches 2.0 V can be performed using an ICP (Inductive Coupled Plasma) method as follows. First, 0.2 g of a positive electrode active material to be measured is collected and placed in a 100 mL container. Thereafter, 5 mL of pure water, 2 mL of aqua regia, and 10 mL of pure water are added in order and dissolved by heating. After cooling, the sample is further diluted 25 times with pure water, and calibrated using an ICP analyzer “ICP-757” manufactured by JARRELASH. The composition is analyzed by the line method. The composition amount can be derived from the obtained results. The molar ratio Li / M described in the examples described later is a value determined by this method.
　なお、本明細書でいうモル比Ｌｉ／Ｍを求める正極活物質には、前記の正極活物質粒子の表面を特定の材料（Ａｌ含有酸化物など）で被覆した正極材料も含まれ、この場合、前記正極材料の表面に存在する前記特定の材料に含まれる金属の量も、モル比Ｌｉ／Ｍを求めるための金属Ｍの量に含める。 Note that the positive electrode active material for obtaining the molar ratio Li / M in this specification includes a positive electrode material in which the surface of the positive electrode active material particles is coated with a specific material (such as an Al-containing oxide). The amount of the metal contained in the specific material existing on the surface of the positive electrode material is also included in the amount of the metal M for obtaining the molar ratio Li / M.
　ちなみに、モル比Ｌｉ／Ｍについて、後述する実施例１を例にとって説明すると、実施例１ではＬｉＣｏ０．９７９５Ｍｇ０．０１１Ｚｒ０．０００５Ａｌ０．００９Ｏ２のコバルト酸リチウム（Ａ１）の表面にＡｌ含有酸化物の被膜を形成した正極材料（ａ１）と、ＬｉＣｏ０．９７Ｍｇ０．０１２Ａｌ０．００９Ｏ２のコバルト酸リチウム（Ｂ１）の表面にＡｌ含有酸化物の被膜を形成した正極材料（ｂ１）とを用いているが、その際のＬｉ以外の金属Ｍとは、Ｃｏ、Ｍｇ、Ｚｒ、Ａｌのことを指す。つまり、リチウムイオン二次電池作製後、所定の充放電後の電池を分解し、正極合剤層から正極材料（この実施例１では混合物）を採取・分析し、モル比Ｌｉ／Ｍを導き出す。 Incidentally, the molar ratio Li / M will be described by taking Example 1 described later as an example. In Example 1, LiCo 0.9795 Mg 0.011 Zr 0.0005 Al 0.009 O 2 of lithium cobalt oxide (A1) The cathode material (a1) having an Al-containing oxide film formed on the surface and the LiCo 0.97 Mg 0.012 Al 0.009 O 2 lithium cobalt oxide (B1) surface formed with an Al-containing oxide film The positive electrode material (b1) is used, and the metal M other than Li at this time refers to Co, Mg, Zr, and Al. That is, after producing the lithium ion secondary battery, the battery after predetermined charge / discharge is disassembled, and the positive electrode material (mixture in this Example 1) is collected and analyzed from the positive electrode mixture layer to derive the molar ratio Li / M.
　系外プレドープによってＬｉイオンをドープした負極活物質を含有する負極を有し、かつそのＬｉイオンのドープの程度を、正極活物質における前記モル比Ｌｉ／Ｍが前記の範囲内となるように調整した負極を用いて組み立てた電池であれば、負極活物質の不可逆容量の低減に適正な量のＬｉイオンがドープされているため、例えばＬｉデンドライトの発生を抑制でき、この発生によって電池の微短絡が生じることを良好に抑えることができる。 Having a negative electrode containing a negative electrode active material doped with Li ions by pre-doping outside the system, and adjusting the degree of doping of the Li ions so that the molar ratio Li / M in the positive electrode active material is within the above range If the battery is assembled using the negative electrode, since it is doped with an appropriate amount of Li ions for reducing the irreversible capacity of the negative electrode active material, for example, the generation of Li dendrite can be suppressed, and this generation causes a short circuit of the battery. Can be suppressed satisfactorily.
　以下、実施例に基づいて本発明を詳細に述べる。ただし、下記実施例は、本発明を制
限するものではない。 Hereinafter, the present invention will be described in detail based on examples. However, the following examples do not limit the present invention.
（実施例１）
＜負極の作製＞
　前記式（１）で表わされるユニットおよび前記（２）式で表わされるユニットのみを有し、前記式（２）におけるＲが水素でＭ’がカリウムであり、前記式（１）で表わされるユニットと前記式（２）で表わされるユニットとのモル比が６／４である共重合体（Ａ）をイオン交換水に溶解し、共重合体（Ａ）の濃度が８質量％である水溶液を調製した。この水溶液に、負極活物質であるＳｉＯ表面を炭素材料で被覆した複合体Ｓｉ－１（平均粒径が５μｍ、比表面積が８．８ｍ２／ｇで、複合体における炭素材料の量が、ＳｉＯ：１００質量部に対して１０質量部）と、カーボンブラックとを加え、攪拌混合することで負極合剤含有ペーストを得た。なお、このペーストにおける負極活物質：カーボンブラック：共重合体（Ａ）の組成比（質量比）は、９０：２：８とした。 Example 1
<Production of negative electrode>
A unit represented by the above formula (1) and a unit represented by the above formula (2), wherein R is hydrogen and M 'is potassium in the above formula (2). A copolymer (A) having a molar ratio of 6/4 to the unit represented by the formula (2) is dissolved in ion-exchanged water, and an aqueous solution having a copolymer (A) concentration of 8% by mass is obtained. Prepared. In this aqueous solution, a composite Si-1 in which the surface of SiO serving as the negative electrode active material was coated with a carbon material (average particle diameter was 5 μm, specific surface area was 8.8 m 2 / g, and the amount of carbon material in the composite was SiO 2 : 10 parts by mass with respect to 100 parts by mass) and carbon black were added and mixed by stirring to obtain a negative electrode mixture-containing paste. The composition ratio (mass ratio) of negative electrode active material: carbon black: copolymer (A) in this paste was 90: 2: 8.
　前記負極合剤含有ペーストを、厚みが１０μｍである銅箔を巻回したロールを巻き出して銅箔の片面に連続塗布し乾燥を行って、銅箔の片面に負極合剤層を形成し、プレス処理を行って負極合剤層の密度を１．２ｇ／ｃｍ３に調整した後にロール状に巻き取って負極ロールを得た。 The negative electrode mixture-containing paste is unwound from a roll wound with a copper foil having a thickness of 10 μm, continuously applied to one side of the copper foil and dried to form a negative electrode mixture layer on one side of the copper foil, The density of the negative electrode mixture layer was adjusted to 1.2 g / cm 3 by performing a press treatment, and then wound into a roll to obtain a negative electrode roll.
　前記負極ロールから引き出した負極について、図１に示す方法（ロール・トゥ・ロール法）で負極合剤層中の負極活物質にＬｉイオンをドープした。前記負極ロール２０ａから負極２ａを引き出して、非水電解液（エチレンカーボネートとジエチルカーボネートとの体積比３０：７０の混合溶媒に、ＬｉＰＦ６を１ｍｏｌ／ｌの濃度で溶解させ、ビニレンカーボネート：４質量％、４－フルオロ－１，３－ジオキソラン－２－オン：５質量％となる量で添加した溶液）およびリチウム金属極１０２を備えた電解液槽１０１内を通過させた。そして、この電解液槽１０１内で負極２ａとリチウム金属極１０２との間に、負極の面積当たりにして０．２ｍＡ／ｃｍ２の電流密度で、負極活物質質量当たり５００ｍＡｈ／ｇに相当する電気量を通電して負極合剤層中の負極活物質にＬｉイオンをドープした。 About the negative electrode pulled out from the said negative electrode roll, Li ion was doped to the negative electrode active material in a negative mix layer by the method (roll to roll method) shown in FIG. The negative electrode 2a was pulled out from the negative electrode roll 20a, and LiPF 6 was dissolved at a concentration of 1 mol / l in a non-aqueous electrolyte (a mixed solvent of ethylene carbonate and diethyl carbonate in a volume ratio of 30:70), and vinylene carbonate: 4 mass. %, 4-fluoro-1,3-dioxolan-2-one: solution added in an amount of 5% by mass) and the electrolyte bath 101 provided with the lithium metal electrode 102. In the electrolyte bath 101, an electric current corresponding to 500 mAh / g per mass of the negative electrode active material is obtained between the negative electrode 2a and the lithium metal electrode 102 at a current density of 0.2 mA / cm 2 per area of the negative electrode. The negative electrode active material in the negative electrode mixture layer was doped with Li ions by supplying an amount.
　Ｌｉイオンドープ後の負極２は、電解液槽１０１の通過後にジエチルカーボネートを備えた洗浄槽１０４内で洗浄し、更にアルゴンガスを充填した乾燥槽１０５内で乾燥させた後に、ロール２０に巻き取った。 The negative electrode 2 after Li ion doping is washed in a washing tank 104 equipped with diethyl carbonate after passing through the electrolytic solution tank 101, further dried in a drying tank 105 filled with argon gas, and then wound around a roll 20. It was.
＜正極の作製＞
　Ｌｉ含有化合物であるＬｉ２ＣＯ３と、Ｃｏ含有化合物であるＣｏ３Ｏ４と、Ｍｇ含有化合物であるＭｇ（ＯＨ）２と、Ｚｒ化合物であるＺｒＯ２と、Ａｌ含有化合物であるＡｌ（ＯＨ）３とを適正な混合割合で乳鉢に入れて混合した後、ペレット状に固め、マッフル炉を用いて、大気雰囲気中（大気圧下）で、９５０℃で２４時間焼成し、ＩＣＰ（Ｉｎｄｕｃｔｉｖｅ　Ｃｏｕｐｌｅｄ　Ｐｌａｓｍａ）法で求めた組成式がＬｉＣｏ０．９７９５Ｍｇ０．０１１Ｚｒ０．０００５Ａｌ０．００９Ｏ２のコバルト酸リチウム（Ａ１）を合成した。 <Preparation of positive electrode>
Li 2 CO 3 that is a Li-containing compound, Co 3 O 4 that is a Co-containing compound, Mg (OH) 2 that is a Mg-containing compound, ZrO 2 that is a Zr compound, and Al (OH that is an Al-containing compound 3 ) was mixed in a mortar at an appropriate mixing ratio, then solidified into a pellet, and baked in an air atmosphere (under atmospheric pressure) at 950 ° C. for 24 hours using an muffle furnace, and ICP (Inductive Coupled) Lithium cobaltate (A1) having a composition formula determined by the Plasma) method of LiCo 0.9795 Mg 0.011 Zr 0.0005 Al 0.009 O 2 was synthesized.
　次に、ｐＨを１０とし、温度を７０℃とした水酸化リチウム水溶液：２００ｇ中に、前記コバルト酸リチウム（Ａ１）：１０ｇを投入し、攪拌して分散させた後、ここにＡｌ（ＮＯ３）３・９Ｈ２Ｏ：０．０１５４ｇと、ｐＨの変動を抑えるためのアンモニア水とを、５時間かけて滴下して、Ａｌ（ＯＨ）３共沈物を生成させ、前記コバルト酸リチウム（Ａ１）の表面に付着させた。その後、この反応液からＡｌ（ＯＨ）３共沈物が付着した前記コバルト酸リチウム（Ａ１）を取り出し、洗浄後、乾燥させた後に、大気雰囲気中で、４００℃の温度で１０時間熱処理することで、前記コバルト酸リチウム（Ａ１）の表面にＡｌ含有酸化物の被膜を形成して、正極材料（ａ１）を得た。 Next, 10 g of the lithium cobaltate (A1) is added to 200 g of a lithium hydroxide aqueous solution having a pH of 10 and a temperature of 70 ° C., and the mixture is stirred and dispersed. Then, Al (NO 3 ) is added thereto. ) 3 · 9H 2 O: and 0.0154G, and ammonia water to suppress variation in pH, was added dropwise over 5 hours, to produce a Al (OH) 3 coprecipitate, the lithium cobalt oxide (A1 ). Thereafter, the lithium cobalt oxide (A1) to which the Al (OH) 3 coprecipitate is adhered is taken out from the reaction solution, washed, dried, and then heat-treated at 400 ° C. for 10 hours in an air atmosphere. Thus, an Al-containing oxide film was formed on the surface of the lithium cobalt oxide (A1) to obtain a positive electrode material (a1).
　得られた正極材料（ａ１）について、前記の方法で平均粒子径を測定したところ、２７μｍであった。 The average particle diameter of the obtained positive electrode material (a1) was measured by the above method and found to be 27 μm.
　Ｌｉ含有化合物であるＬｉ２ＣＯ３と、Ｃｏ含有化合物であるＣｏ３Ｏ４と、Ｍｇ含有化合物であるＭｇ（ＯＨ）２と、Ａｌ含有化合物であるＡｌ（ＯＨ）３とを適正な混合割合で乳鉢に入れて混合した後、ペレット状に固め、マッフル炉を用いて、大気雰囲気中（大気圧下）で、９５０℃で４時間焼成し、ＩＣＰ法で求めた組成式がＬｉＣｏ０．９７Ｍｇ０．０１２Ａｌ０．００９Ｏ２のコバルト酸リチウム（Ｂ１）を合成した。 Li 2 CO 3 that is a Li-containing compound, Co 3 O 4 that is a Co-containing compound, Mg (OH) 2 that is an Mg-containing compound, and Al (OH) 3 that is an Al-containing compound are appropriately mixed. After mixing in a mortar, the mixture was hardened into pellets, baked at 950 ° C. for 4 hours in an atmospheric atmosphere (under atmospheric pressure) using a muffle furnace, and the composition formula obtained by ICP method was LiCo 0.97. Mg 0.012 Al 0.009 O 2 lithium cobaltate (B1) was synthesized.
　次に、ｐＨを１０とし、温度を７０℃とした水酸化リチウム水溶液：２００中ｇに、前記コバルト酸リチウム（Ｂ１）：１０ｇを投入し、攪拌して分散させた後、ここにＡｌ（ＮＯ３）３・９Ｈ２Ｏ：０．０７７ｇと、ｐＨの変動を抑えるためのアンモニア水とを、５時間かけて滴下して、Ａｌ（ＯＨ）３共沈物を生成させ、前記コバルト酸リチウム（Ｂ１）の表面に付着させた。その後、この反応液からＡｌ（ＯＨ）３共沈物が付着した前記コバルト酸リチウム（Ｂ１）を取り出し、洗浄後、乾燥させた後に、大気雰囲気中で、４００℃の温度で１０時間熱処理することで、前記コバルト酸リチウム（Ｂ１）の表面にＡｌ含有酸化物の被膜を形成して、正極材料（ｂ１）を得た。 Next, 10 g of the lithium cobalt oxide (B1) is added to 200 g of lithium hydroxide aqueous solution: 200 having a pH of 10 and a temperature of 70 ° C., and dispersed by stirring. 3) 3 · 9H 2 O: and 0.077 g, and ammonia water to suppress variation in pH, was added dropwise over 5 hours, to produce a Al (OH) 3 coprecipitate, the lithium cobaltate ( It was made to adhere to the surface of B1). Thereafter, the lithium cobaltate (B1) to which the Al (OH) 3 coprecipitate is adhered is taken out from the reaction solution, washed, dried, and then heat-treated at 400 ° C. for 10 hours in an air atmosphere. Then, an Al-containing oxide film was formed on the surface of the lithium cobalt oxide (B1) to obtain a positive electrode material (b1).
　得られた正極材料（ｂ１）について、前記の方法で平均粒子径を測定したところ、７μｍであった。 The average particle diameter of the obtained positive electrode material (b1) was measured by the above method and found to be 7 μm.
　そして、正極材料（ａ１）と正極材料（ｂ１）とを、質量比で８５：１５の割合で混合して、電池作製用の正極材料（１）を得た。得られた正極材料（１）の表面のＡｌ含有酸化物の平均被覆厚みを前記の方法で測定したところ、３０ｎｍであった。また、平均被覆厚みの測定の際に元素マッピングによって被膜の組成を確認したところ、主成分がＡｌ２Ｏ３であった。更に、正極材料（１）の体積基準の粒度分布を前記の方法で確認したところ、平均粒子径は２５μｍで、正極材料（ａ１）および正極材料（ｂ１）の各平均粒子径の箇所にピークトップを有する２つのピークが認められた。また、正極材料（１）のＢＥＴ比表面積を、窒素吸着法による比表面積測定装置を用いて測定したところ、０．２５ｍ２／ｇであった。 Then, the positive electrode material (a1) and the positive electrode material (b1) were mixed at a mass ratio of 85:15 to obtain a positive electrode material (1) for battery preparation. When the average coating thickness of the Al-containing oxide on the surface of the obtained positive electrode material (1) was measured by the above method, it was 30 nm. Moreover, when the composition of the film was confirmed by element mapping when measuring the average coating thickness, the main component was Al 2 O 3 . Furthermore, when the volume-based particle size distribution of the positive electrode material (1) was confirmed by the above method, the average particle diameter was 25 μm, and peak tops were observed at the respective average particle diameters of the positive electrode material (a1) and the positive electrode material (b1). Two peaks were observed with Moreover, it was 0.25 m < 2 > / g when the BET specific surface area of positive electrode material (1) was measured using the specific surface area measuring apparatus by a nitrogen adsorption method.
　正極材料（１）：９６．５質量部と、バインダであるＰ（ＶＤＦ－ＣＴＦＥ）を１０質量％の濃度で含むＮＭＰ溶液：２０質量部と、導電助剤であるアセチレンブラック：１．５質量部とを、二軸混練機を用いて混練し、更にＮＭＰを加えて粘度を調節して、正極合剤含有ペーストを調製した。このペーストを、厚みが１５μｍであるアルミニウム箔の片面に塗布し、１２０℃で１２時間の真空乾燥を行って、アルミニウム箔の片面に正極合剤層を形成し、プレス処理を行って正極を得た。 Positive electrode material (1): 96.5 parts by mass, NMP solution containing binder (P (VDF-CTFE) at a concentration of 10% by mass): 20 parts by mass, and acetylene black as a conductive auxiliary agent: 1.5 parts by mass Part was kneaded using a biaxial kneader, and NMP was added to adjust the viscosity to prepare a positive electrode mixture-containing paste. This paste is applied to one side of an aluminum foil having a thickness of 15 μm, vacuum-dried at 120 ° C. for 12 hours to form a positive electrode mixture layer on one side of the aluminum foil, and press treatment is performed to obtain a positive electrode. It was.
＜セパレータの作製＞
　変性ポリブチルアクリレートの樹脂バインダ：３質量部と、ベーマイト粉末（平均粒径１μｍ）：９７質量部と、水：１００質量部とを混合し、多孔質層（ＩＩ）形成用スラリーを調製した。このスラリーを、厚さ１２μｍのリチウムイオン電池用ポリエチレン製微多孔膜〔多孔質層（Ｉ）〕の片面に塗布、乾燥をした。多孔質層（Ｉ）の片面にベーマイトを主体とした多孔質層（ＩＩ）を形成したセパレータを得た。なお、多孔質層（ＩＩ）の厚みは３μｍであった。 <Preparation of separator>
Modified polybutyl acrylate resin binder: 3 parts by mass, boehmite powder (average particle size 1 μm): 97 parts by mass, and water: 100 parts by mass were mixed to prepare a slurry for forming a porous layer (II). This slurry was applied to one side of a polyethylene microporous membrane [porous layer (I)] having a thickness of 12 μm and dried. A separator in which a porous layer (II) mainly composed of boehmite was formed on one surface of the porous layer (I) was obtained. The thickness of the porous layer (II) was 3 μm.
＜コイン形リチウムイオン二次電池の組み立て＞
　Ｌｉイオンドープ後の前記負極、前記正極および前記セパレータを、それぞれの直径が１７ｍｍ、１６ｍｍおよび１８ｍｍとなるように打ち抜いた。打ち抜いた負極、正極およびセパレータを、非水電解液（エチレンカーボネートとジエチルカーボネートとの体積比３０：７０の混合溶媒に、ＬｉＰＦ６を１ｍｏｌ／ｌの濃度で溶解させ、ビニレンカーボネート：４質量％、４－フルオロ－１，３－ジオキソラン－２－オン：５質量％、アジポニトリル：０．５質量％、および１，３－ジオキサン：０．５質量％となる量で添加した溶液）と共に電池容器内に封入して、直径２０ｍｍ、厚み１．６ｍｍで、図２に示す構造のコイン形リチウムイオン二次電池を作製した。 <Assembly of coin-type lithium ion secondary battery>
The negative electrode, the positive electrode, and the separator after Li ion doping were punched out so that their diameters were 17 mm, 16 mm, and 18 mm, respectively. Punched negative electrode, a positive electrode and the separator, the nonaqueous electrolytic solution (mixed at a volumetric ratio of 30:70 of ethylene carbonate and diethyl carbonate, LiPF 6 was dissolved at a concentration of 1 mol / l, vinylene carbonate: 4 mass%, 4-fluoro-1,3-dioxolan-2-one: 5% by mass, adiponitrile: 0.5% by mass, and 1,3-dioxane: 0.5% by mass. A coin-type lithium ion secondary battery having a diameter of 20 mm and a thickness of 1.6 mm and having a structure shown in FIG. 2 was produced.
　ここで、図２について説明すると、図２は、実施例１のコイン形リチウムイオン二次電池を模式的に表す縦断面図である。リチウムイオン二次電池１０においては、正極１が金属製の外装缶４の内側に収容され、その上にセパレータ３を介して負極２が配置されている。また、負極２は金属製の封口板５の内面と接触している。なお、図２では、正極１、負極２およびセパレータ３の各層を区別して示していないが、正極１と負極２とは、正極合剤層と負極合剤層とがセパレータ３を介して対向するように、かつセパレータ３は、その多孔質層（ＩＩ）が正極１側となるように配置されている。更に、リチウムイオン二次電池１０の内部には非水電解液（図示しない）が注入されている。 Here, FIG. 2 will be described. FIG. 2 is a longitudinal sectional view schematically showing the coin-type lithium ion secondary battery of Example 1. FIG. In the lithium ion secondary battery 10, the positive electrode 1 is accommodated inside a metal outer can 4, and the negative electrode 2 is disposed thereon via a separator 3. The negative electrode 2 is in contact with the inner surface of the metal sealing plate 5. In FIG. 2, the layers of the positive electrode 1, the negative electrode 2, and the separator 3 are not shown separately, but the positive electrode 1 and the negative electrode 2 are opposed to each other with the positive electrode mixture layer and the negative electrode mixture layer through the separator 3. Thus, the separator 3 is arranged so that the porous layer (II) is on the positive electrode 1 side. Further, a non-aqueous electrolyte (not shown) is injected into the lithium ion secondary battery 10.
　リチウムイオン二次電池１０において、外装缶４は正極端子を兼ねており、封口板５は負極端子を兼ねている。そして、外装缶４の開口部は、外装缶４の開口端部の内方への締め付けにより、封口板５の周縁部に配設した樹脂製で環状のパッキング６を押圧して封口板５の周縁部と外装缶４の開口端部の内周面とに圧接させて封口されている。すなわち、コイン形リチウムイオン電池１０は、正極端子（外装缶４）と負極端子（封口板５）との間に樹脂製のパッキング６が介在しており、このパッキング６によって封止されている。 In the lithium ion secondary battery 10, the outer can 4 also serves as a positive electrode terminal, and the sealing plate 5 also serves as a negative electrode terminal. And the opening part of the armored can 4 presses the resin-made annular packing 6 arrange | positioned in the peripheral part of the sealing board 5 by the inward fastening of the opening edge part of the armored can 4, and the sealing plate 5 The peripheral edge and the inner peripheral surface of the opening end of the outer can 4 are pressed against each other and sealed. That is, in the coin-type lithium ion battery 10, a resin packing 6 is interposed between the positive electrode terminal (exterior can 4) and the negative electrode terminal (sealing plate 5), and is sealed by this packing 6.
（実施例２）
　平均粒子径が２２μｍの人造黒鉛：５０質量％と複合体Ｓｉ－１：５０質量％とを、Ｖ型ブレンダーで１２時間混合して負極活物質を得た。この負極活物質を用いた以外は実施例１と同様にして負極合剤含有ペーストを調製し、この負極合剤含有ペーストを用いた以外は実施例１と同様にして負極ロールを得た。この負極ロールに係る負極の負極合剤層中の負極活物質に、通電電気量を負極活物質質量当たり２５０ｍＡｈ／ｇとした以外は、実施例１と同様にしてＬｉイオンをドープした。そして、この負極を用いた以外は、実施例１と同様にしてコイン形リチウムイオン二次電池を作製した。 (Example 2)
Artificial graphite having an average particle size of 22 μm: 50 mass% and composite Si-1: 50 mass% were mixed in a V-type blender for 12 hours to obtain a negative electrode active material. A negative electrode mixture-containing paste was prepared in the same manner as in Example 1 except that this negative electrode active material was used, and a negative electrode roll was obtained in the same manner as in Example 1 except that this negative electrode mixture-containing paste was used. The negative electrode active material in the negative electrode mixture layer of the negative electrode according to this negative electrode roll was doped with Li ions in the same manner as in Example 1 except that the amount of electricity passed was 250 mAh / g per negative electrode active material mass. And the coin-type lithium ion secondary battery was produced like Example 1 except having used this negative electrode.
（実施例３）
　負極活物質における人造黒鉛および複合体Ｓｉ－１の割合を、人造黒鉛：９５質量％とし、複合体Ｓｉ－１：５質量％とした以外は、実施例２と同様にして負極活物質を得、この負極活物質を用いた以外は実施例１と同様にして負極合剤含有ペーストを調製し、この負極合剤含有ペーストを用いた以外は実施例１と同様にして負極ロールを得た。この負極ロールに係る負極の負極合剤層中の負極活物質に、通電電気量を負極活物質質量当たり５０ｍＡｈ／ｇとした以外は、実施例１と同様にしてＬｉイオンをドープした。そして、この負極を用いた以外は、実施例１と同様にしてコイン形リチウムイオン二次電池を作製した。 (Example 3)
A negative electrode active material was obtained in the same manner as in Example 2 except that the ratio of the artificial graphite and the composite Si-1 in the negative electrode active material was 95% by mass of the artificial graphite and 5% by mass of the composite Si-1. A negative electrode mixture-containing paste was prepared in the same manner as in Example 1 except that this negative electrode active material was used, and a negative electrode roll was obtained in the same manner as in Example 1 except that this negative electrode mixture-containing paste was used. The negative electrode active material in the negative electrode mixture layer of the negative electrode related to the negative electrode roll was doped with Li ions in the same manner as in Example 1 except that the amount of electricity supplied was 50 mAh / g per mass of the negative electrode active material. And the coin-type lithium ion secondary battery was produced like Example 1 except having used this negative electrode.
（実施例４）
　鱗片状黒鉛粉末：９７質量部とケイ素粉末：３質量部とを、圧縮力とせん断力とを伴う混合方法によって混合して混合物Ａを得た。この混合物Ａ：１００質量部と非黒鉛質炭素材料：３質量部とを、圧縮力とせん断力とを伴う混合方法によって混合して混合物Ｂを調製した。前記の混合物Ｂを、非活性雰囲気下、１０００℃で１時間加熱した後、解砕処理を施し、鱗片状黒鉛粒子間に挟み込まれたケイ素が非晶質炭素によって固定化された複合化粒子を得た。これを負極活物質とした以外は実施例１と同様にして負極合剤含有ペーストを調製し、この負極合剤含有ペーストを用いた以外は実施例１と同様にして負極ロールを得た。この負極ロールに係る負極の負極合剤層中の負極活物質に、通電電気量を負極活物質質量当たり１００ｍＡｈ／ｇとした以外は、実施例１と同様にしてＬｉイオンをドープした。そして、この負極を用いた以外は、実施例１と同様にしてコイン形リチウムイオン二次電池を作製した。 Example 4
Scale A graphite powder: 97 parts by mass and silicon powder: 3 parts by mass were mixed by a mixing method involving compressive force and shear force to obtain a mixture A. Mixture B was prepared by mixing 100 parts by mass of this mixture A and 3 parts by mass of non-graphitic carbon material by a mixing method involving compression force and shearing force. The mixture B was heated at 1000 ° C. for 1 hour in an inert atmosphere, and then crushed, and composite particles in which silicon sandwiched between the flaky graphite particles was fixed by amorphous carbon were obtained. Obtained. A negative electrode mixture-containing paste was prepared in the same manner as in Example 1 except that this was used as the negative electrode active material, and a negative electrode roll was obtained in the same manner as in Example 1 except that this negative electrode mixture-containing paste was used. The negative electrode active material in the negative electrode mixture layer of the negative electrode related to the negative electrode roll was doped with Li ions in the same manner as in Example 1 except that the amount of electricity supplied was 100 mAh / g per mass of the negative electrode active material. And the coin-type lithium ion secondary battery was produced like Example 1 except having used this negative electrode.
（実施例５）
　実施例２で用いたものと同じ人造黒鉛を負極活物質とした以外は実施例１と同様にして負極合剤含有ペーストを調製し、この負極合剤含有ペーストを用いた以外は実施例１と同様にして負極ロールを得た。この負極ロールに係る負極の負極合剤層中の負極活物質に、通電電気量を負極活物質質量当たり３０ｍＡｈ／ｇとした以外は、実施例１と同様にしてＬｉイオンをドープした。そして、この負極を用いた以外は、実施例１と同様にしてコイン形リチウムイオン二次電池を作製した。 (Example 5)
A negative electrode mixture-containing paste was prepared in the same manner as in Example 1 except that the same artificial graphite as that used in Example 2 was used as the negative electrode active material, and Example 1 except that this negative electrode mixture-containing paste was used. Similarly, a negative electrode roll was obtained. The negative electrode active material in the negative electrode mixture layer of the negative electrode related to the negative electrode roll was doped with Li ions in the same manner as in Example 1 except that the amount of electricity passed was 30 mAh / g per mass of the negative electrode active material. And the coin-type lithium ion secondary battery was produced like Example 1 except having used this negative electrode.
（実施例６）
　実施例２で用いたものと同じ人造黒鉛：５０質量％と、ＳｉＯ表面を炭素材料で被覆していない材料Ｓｉ－２（平均粒径が５μｍ、比表面積が６．８ｍ２／ｇ）：５０質量％とを、Ｖ型ブレンダーで１２時間混合して負極活物質を得た。この負極活物質を用いた以外は実施例１と同様にして負極合剤含有ペーストを調製し、この負極合剤含有ペーストを用いた以外は実施例１と同様にして負極ロールを得た。この負極ロールに係る負極の負極合剤層中の負極活物質に、通電電気量を負極活物質質量当たり２５０ｍＡｈ／ｇとした以外は、実施例１と同様にしてＬｉイオンをドープした。そして、この負極を用いた以外は、実施例１と同様にしてコイン形リチウムイオン二次電池を作製した。 (Example 6)
Artificial graphite same as that used in Example 2: 50% by mass; material Si-2 whose SiO surface is not coated with a carbon material (average particle size is 5 μm, specific surface area is 6.8 m 2 / g): 50 Mass% was mixed for 12 hours with a V-type blender to obtain a negative electrode active material. A negative electrode mixture-containing paste was prepared in the same manner as in Example 1 except that this negative electrode active material was used, and a negative electrode roll was obtained in the same manner as in Example 1 except that this negative electrode mixture-containing paste was used. The negative electrode active material in the negative electrode mixture layer of the negative electrode according to this negative electrode roll was doped with Li ions in the same manner as in Example 1 except that the amount of electricity passed was 250 mAh / g per negative electrode active material mass. And the coin-type lithium ion secondary battery was produced like Example 1 except having used this negative electrode.
（比較例１）
　実施例１で作製したものと同じ負極（負極合剤層中の負極活物質へのＬｉイオンのドープ前の負極）を、そのまま負極として用いた以外は、実施例１と同様にしてコイン形リチウムイオン二次電池を作製した。 (Comparative Example 1)
Coin-type lithium in the same manner as in Example 1 except that the same negative electrode as prepared in Example 1 (negative electrode before doping Li ions to the negative electrode active material in the negative electrode mixture layer) was used as it was. An ion secondary battery was produced.
（比較例２）
　複合体Ｓｉ－１（負極活物質）：９０質量部、カーボンブラック：２質量部、ＣＭＣ：１．５質量部、およびＳＢＲ：６．５質量部を、イオン交換水と混合して、負極合剤含有ペーストを調製した。この負極合剤含有ペーストを用いた以外は実施例１と同様にして負極ロールを作製し、この負極ロールに係る負極の負極合剤層中の負極活物質に、実施例１と同様にしてＬｉイオンをドープした。そして、この負極を用いた以外は、実施例１と同様にしてコイン形リチウムイオン二次電池を作製した。 (Comparative Example 2)
Composite Si-1 (negative electrode active material): 90 parts by mass, carbon black: 2 parts by mass, CMC: 1.5 parts by mass, and SBR: 6.5 parts by mass were mixed with ion-exchanged water, An agent-containing paste was prepared. A negative electrode roll was produced in the same manner as in Example 1 except that this negative electrode mixture-containing paste was used. Lithium was added to the negative electrode active material in the negative electrode mixture layer of the negative electrode related to this negative electrode roll in the same manner as in Example 1. Doped with ions. And the coin-type lithium ion secondary battery was produced like Example 1 except having used this negative electrode.
　実施例および比較例のリチウムイオン二次電池およびこれらに係る負極について、下記の各評価を行った。 The following evaluations were performed on the lithium ion secondary batteries of Examples and Comparative Examples and the negative electrodes related thereto.
＜負極における負極合剤層の脱落の有無＞
　実施例１～６および比較例２のリチウムイオン二次電池に使用した負極について、負極合剤層中の負極活物質へＬｉイオンをドープした後にロール状に巻き取った負極の、負極合剤層の集電体からの脱落の有無を調べた。 <Presence or absence of removal of negative electrode mixture layer in negative electrode>
For the negative electrodes used in the lithium ion secondary batteries of Examples 1 to 6 and Comparative Example 2, the negative electrode mixture layer of the negative electrode wound into a roll after doping Li ions into the negative electrode active material in the negative electrode mixture layer The presence or absence of dropping from the current collector was examined.
＜充放電サイクル特性評価＞
　実施例１～６および比較例１、２のリチウムイオン二次電池の各５個を、０．５Ｃの電流値で４．４Ｖまで定電流充電し、引き続いて４．４Ｖの一定電圧で電流値が０．０２Ｃに到達するまで充電した。その後、０．２Ｃの定電流で２．０Ｖまで放電を行って、初回放電容量を求めた。 <Charge / discharge cycle characteristics evaluation>
Each of the five lithium ion secondary batteries of Examples 1 to 6 and Comparative Examples 1 and 2 was charged with a constant current of up to 4.4 V at a current value of 0.5 C, and then the current value at a constant voltage of 4.4 V. Until it reached 0.02C. Then, it discharged to 2.0V with the constant current of 0.2C, and calculated | required the initial discharge capacity.
　初回放電容量測定後のリチウムイオン二次電池（各５個）を、０．５Ｃの電流値で４．４Ｖまで定電流充電し、引き続いて４．４Ｖの一定電圧で電流値が０．０２Ｃに到達するまで充電した。その後、０．２Ｃの定電流で２．０Ｖまで放電を行って、初回放電容量を求めた。次に、各電池について、１Ｃの電流値で４．４Ｖまで定電流充電し、引き続いて４．４Ｖの定電圧で電流値が０．０５Ｃになるまで充電した後に、１Ｃの電流値で２．０Ｖまで放電する一連の操作を１サイクルとして、これを５００回サイクル実施した。そして、各電池について、初回放電容量測定時と同じ条件で定電流－定電圧充電および定電流放電を行って、放電容量を求めた。そして、これらの放電容量を初回放電容量で除した値を百分率で表して容量維持率を求め、それぞれ５個の平均値を算出した。 After the initial discharge capacity measurement, the lithium ion secondary batteries (5 each) were charged at a constant current of up to 4.4V at a current value of 0.5C, and subsequently the current value was set at 0.02C at a constant voltage of 4.4V. Charged until it reached. Then, it discharged to 2.0V with the constant current of 0.2C, and calculated | required the initial discharge capacity. Next, each battery was charged with a constant current up to 4.4 V at a current value of 1 C, subsequently charged with a constant voltage of 4.4 V until the current value reached 0.05 C, and then 2. with a current value of 1 C. A series of operations for discharging to 0 V was taken as one cycle, and this was repeated 500 times. Each battery was subjected to constant current-constant voltage charging and constant current discharging under the same conditions as those for the initial discharge capacity measurement, and the discharge capacity was determined. Then, a value obtained by dividing these discharge capacities by the initial discharge capacities was expressed as a percentage to obtain a capacity maintenance ratio, and an average value of 5 pieces was calculated for each.
　実施例および比較例のリチウムイオン二次電池の構成と前記の評価結果とを、表１に示す。なお、表１では、充放電サイクル特性評価時の容量維持率は、実施例５の電池の値を１００としたときの相対値で示す。 Table 1 shows the configurations of the lithium ion secondary batteries of Examples and Comparative Examples and the evaluation results. In Table 1, the capacity retention rate at the time of charge / discharge cycle characteristic evaluation is shown as a relative value when the value of the battery of Example 5 is 100.
Figure JPOXMLDOC01-appb-T000005
Figure JPOXMLDOC01-appb-T000005
　表１に示す通り、負極合剤層のバインダとして共重合体（Ａ）を用いた実施例１～６のリチウムイオン二次電池に係る負極は、負極合剤層中の負極活物質へのＬｉイオンのドープ後にロール状に巻き取っても負極合剤層の脱落が生じておらず、負極合剤層の性状が良好であった。よって、これらの負極は生産性が優れているといえる。また、実施例１～６のリチウムイオン二次電池は、充放電サイクル特性評価時の容量維持率が高く、優れた充放電サイクル特性を有していた。 As shown in Table 1, the negative electrodes according to the lithium ion secondary batteries of Examples 1 to 6 using the copolymer (A) as the binder of the negative electrode mixture layer were prepared by adding Li to the negative electrode active material in the negative electrode mixture layer. The negative electrode mixture layer did not fall off even when wound into a roll after ion doping, and the properties of the negative electrode mixture layer were good. Therefore, it can be said that these negative electrodes are excellent in productivity. In addition, the lithium ion secondary batteries of Examples 1 to 6 had a high capacity retention rate when evaluating charge / discharge cycle characteristics, and had excellent charge / discharge cycle characteristics.
　これに対し、負極合剤層のバインダに、通常のリチウムイオン二次電池で汎用されているＳＢＲを用いた比較例２の電池に係る負極は、負極合剤層中の負極活物質へのＬｉイオンのドープ後にロール状に巻き取った際に負極合剤層の脱落が生じた。このような箇所は電池に供することができないため、製造した負極は、電池の製造に使用可能な部分の割合が小さくなることから、その生産性が劣っているといえる。また、この負極を用いた比較例２の電池、および負極合剤層中の負極活物質へのＬｉイオンのドープを行わなかった負極を用いた比較例１の電池は、充放電サイクル特性評価時の容量維持率が低く、充放電サイクル特性が劣っていた。 On the other hand, the negative electrode according to the battery of Comparative Example 2 using SBR, which is widely used in ordinary lithium ion secondary batteries, as the binder of the negative electrode mixture layer, is Li to the negative electrode active material in the negative electrode mixture layer. The negative electrode mixture layer dropped off when it was wound into a roll after ion doping. Since such a part cannot be used for a battery, it can be said that the manufactured negative electrode is inferior in productivity because the ratio of the part that can be used for battery manufacture becomes small. In addition, the battery of Comparative Example 2 using this negative electrode and the battery of Comparative Example 1 using a negative electrode in which the negative electrode active material in the negative electrode mixture layer was not doped with Li were included in the charge / discharge cycle characteristics evaluation. The capacity retention rate was low, and the charge / discharge cycle characteristics were inferior.
〔系外プレドープ法（ｉｉ）によってＬｉイオンをドープした負極活物質を含有する負極を有するリチウムイオン二次電池の実験例〕
（実施例７）
　テトラヒドロフランにナフタレンおよび金属Ｌｉを溶解した溶液中に、実施例１で用いたものと同じ複合体Ｓｉ－１を浸漬させた。その後、ジエチルカーボネートで洗浄し、乾燥して、Ｌｉイオンをドープした複合体Ｓｉ－１を得た。このＬｉイオンをドープした複合体Ｓｉ－１を用いた以外は全て実施例１と同様にして、負極合剤含有ペーストを作製し、このペーストを用いて、厚みが１０μｍである銅箔を巻回したロールを巻き出して銅箔の片面に連続塗布し乾燥を行って、銅箔の片面に負極合剤層を形成し、プレス処理を行って負極合剤層の密度を１．２ｇ／ｃｍ３に調整した後にロール状に巻き取って負極ロールを得た。そして、この負極ロールから引き出した負極を所定形状に切断して使用した以外は、実施例１と同様にしてコイン形リチウムイオン二次電池を作製したところ、良好に作製することができた。なお、得られたコイン形リチウムイオン二次電池におけるモル比Ｌｉ／Ｍは、０．９４であった。 [Experimental example of a lithium ion secondary battery having a negative electrode containing a negative electrode active material doped with Li ions by an extra-system pre-doping method (ii)]
(Example 7)
The same composite Si-1 as used in Example 1 was immersed in a solution of naphthalene and metallic Li dissolved in tetrahydrofuran. Thereafter, it was washed with diethyl carbonate and dried to obtain a composite Si-1 doped with Li ions. A negative electrode mixture-containing paste was prepared in the same manner as Example 1 except that this Li ion-doped composite Si-1 was used, and a copper foil having a thickness of 10 μm was wound using this paste. The rolled roll was unwound and continuously applied to one side of the copper foil and dried to form a negative electrode mixture layer on one side of the copper foil, and a press treatment was performed to make the density of the negative electrode mixture layer 1.2 g / cm 3. After being adjusted, the film was wound into a roll to obtain a negative electrode roll. Then, a coin-type lithium ion secondary battery was produced in the same manner as in Example 1 except that the negative electrode drawn from the negative electrode roll was cut into a predetermined shape and used, and was successfully produced. In addition, molar ratio Li / M in the obtained coin-type lithium ion secondary battery was 0.94.
　また、実施例７のリチウムイオン二次電池に使用した負極について、作製後にロール状に巻き取った負極の、負極合剤層の集電体からの脱落の有無を調べたところ、負極合剤層の脱落が生じておらず、負極合剤層の性状が良好であった。よって、この負極は生産性が優れているといえる。 Moreover, about the negative electrode used for the lithium ion secondary battery of Example 7, when the negative electrode wound up in roll shape after preparation was checked for the presence or absence of the negative electrode mixture layer from the current collector, the negative electrode mixture layer The negative electrode mixture layer had good properties. Therefore, it can be said that this negative electrode is excellent in productivity.
　本発明は、その趣旨を逸脱しない範囲で、前記以外の形態としても実施が可能である。本出願に開示された実施形態は一例であって、本発明は、これらの実施形態には限定されない。本発明の範囲は、前記の明細書の記載よりも、添付されている請求の範囲の記載を優先して解釈され、請求の範囲と均等の範囲内での全ての変更は、請求の範囲に含まれる。 The present invention can be implemented in other forms as long as it does not depart from the spirit of the present invention. The embodiments disclosed in the present application are examples, and the present invention is not limited to these embodiments. The scope of the present invention is construed in preference to the description of the appended claims rather than the description of the above specification, and all modifications within the scope equivalent to the claims are construed in the scope of the claims. included.
　本発明のリチウムイオン二次電池は、従来から知られているリチウムイオン二次電池の用途と同じ用途に適用することができる。 The lithium ion secondary battery of the present invention can be applied to the same use as that of a conventionally known lithium ion secondary battery.
　　１　　正極
　　２　　負極
　　２ａ　Ｌｉイオンドープ前の負極
　　３　　セパレータ
　　４　　外装缶
　　５　　封口板
　　６　　樹脂製のパッキング
　１０　　リチウムイオン二次電池
　２０　　負極２を巻き取ったロール
　２０ａ　負極２ａを巻き取ったロール
１０１　　電解液槽
１０２　　リチウム金属極
１０３　　電源
１０４　　洗浄槽
１０５　　乾燥手段 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 2a Negative electrode before Li ion dope 3 Separator 4 Outer can 5 Sealing plate 6 Resin packing 10 Lithium ion secondary battery 20 Roll which wound negative electrode 2 20a Roll 101 which wound negative electrode 2a Electrolyte tank 102 Lithium metal electrode 103 Power supply 104 Washing tank 105 Drying means

Claims (12)

  1. 　負極活物質およびバインダを含有する負極合剤層を有する非水電解液系電気化学素子用負極であって、
    　前記負極合剤層は、Ｌｉイオンがドープされてなる負極活物質を少なくとも含有し、かつ下記式（１）で表されるユニットと下記式（２）で表されるユニットとを有する共重合体を前記バインダとして含有していることを特徴とする非水電解液系電気化学素子用負極。
    Figure JPOXMLDOC01-appb-C000001
    Figure JPOXMLDOC01-appb-C000002
     〔前記式（２）中、Ｒは水素またはメチル基であり、Ｍ’はアルカリ金属元素である。〕     A negative electrode for a non-aqueous electrolyte-based electrochemical device having a negative electrode mixture layer containing a negative electrode active material and a binder,
    The negative electrode mixture layer contains at least a negative electrode active material doped with Li ions and has a unit represented by the following formula (1) and a unit represented by the following formula (2). The negative electrode for non-aqueous-electrolyte type | system | group electrochemical elements characterized by including as a said binder.
    Figure JPOXMLDOC01-appb-C000001
    Figure JPOXMLDOC01-appb-C000002
     [In the formula (2), R is hydrogen or a methyl group, and M ′ is an alkali metal element. ]
  2. 　前記負極活物質として、Ｓｉを含む材料Ｓを含有している請求項１に記載の非水電解液系電気化学素子用負極。 The negative electrode for a non-aqueous electrolyte based electrochemical device according to claim 1, wherein the negative electrode active material contains a material S containing Si.
  3. 　前記材料Ｓとして、ＳｉＯｘ（ただし、０．５≦ｘ≦１．５）を含有している請求項２に記載の非水電解液系電気化学素子用負極。 The negative electrode for a non-aqueous electrolyte based electrochemical device according to claim 2, wherein the material S contains SiO x (where 0.5 ≦ x ≦ 1.5).
  4. 　前記ＳｉＯｘは炭素材料と複合体を構成している請求項３に記載の非水電解液系電気化学素子用負極。 The negative electrode for a non-aqueous electrolyte based electrochemical device according to claim 3, wherein the SiO x forms a composite with a carbon material.
  5. 　前記負極合剤層が含有する負極活物質全量中における前記複合体の含有量が、５質量％以上である請求項４に記載の非水電解液系電気化学素子用負極。 The negative electrode for a non-aqueous electrolyte based electrochemical device according to claim 4, wherein the content of the composite in the total amount of the negative electrode active material contained in the negative electrode mixture layer is 5% by mass or more.
  6. 　請求項１～５のいずれかに記載の非水電解液系電気化学素子用負極を製造する方法であって、
    　負極活物質とバインダとを含有する負極合剤層を有する負極の、前記負極合剤層中の負極活物質にＬｉイオンをドープする工程を有することを特徴とする非水電解液系電気化学素子用負極の製造方法。     A method for producing a negative electrode for a non-aqueous electrolyte based electrochemical device according to any one of claims 1 to 5,
    A non-aqueous electrolyte type electrochemical device comprising a step of doping a negative electrode active material in a negative electrode mixture layer of a negative electrode having a negative electrode mixture layer containing a negative electrode active material and a binder, with Li ions Manufacturing method for negative electrode.
  7. 　負極活物質とバインダとを含有する負極合剤層を有する負極を巻回したロールから前記負極を引き出して、非水電解液およびリチウム金属極を備えた電解液槽内に導入し、前記電解液槽内で前記負極と前記リチウム金属極との間に通電することで負極合剤層中の負極活物質にＬｉイオンをドープして非水電解液系電気化学素子用負極とし、Ｌｉイオンをドープした後の前記非水電解液系電気化学素子用負極をロール状に巻き取る工程を有する請求項６に記載の非水電解液系電気化学素子用負極の製造方法。 The negative electrode is drawn out from a roll wound with a negative electrode having a negative electrode mixture layer containing a negative electrode active material and a binder, and introduced into an electrolyte bath equipped with a non-aqueous electrolyte and a lithium metal electrode. Doping Li ions into the negative electrode active material in the negative electrode mixture layer by conducting current between the negative electrode and the lithium metal electrode in the tank to form a negative electrode for a non-aqueous electrolyte electrochemical device, and doping with Li ions The manufacturing method of the negative electrode for non-aqueous electrolyte type | system | group electrochemical elements of Claim 6 which has the process of winding up the said negative electrode for non-aqueous electrolyte type | system | group electrochemical elements after carrying out in roll shape.
  8. 　請求項１～５のいずれかに記載の非水電解液系電気化学素子用負極を製造する方法であって、
    　少なくとも一部にＬｉイオンをドープした負極活物質と、バインダとを含有する負極合剤層を有する負極を作製する工程を有することを特徴とする非水電解液系電気化学素子用負極の製造方法。     A method for producing a negative electrode for a non-aqueous electrolyte based electrochemical device according to any one of claims 1 to 5,
    A method for producing a negative electrode for a non-aqueous electrolyte based electrochemical device, comprising a step of producing a negative electrode having a negative electrode mixture layer containing a negative electrode active material at least partially doped with Li ions and a binder .
  9. 　負極、正極活物質およびバインダを含有する正極合剤層を有する正極、セパレータおよび非水電解液が外装体内に収容されてなるリチウムイオン二次電池であって、
    　請求項１～５のいずれかに記載の非水電解液系電気化学素子用負極を前記負極として構成されたことを特徴とするリチウムイオン二次電池。     A lithium ion secondary battery in which a negative electrode, a positive electrode having a positive electrode mixture layer containing a positive electrode active material and a binder, a separator, and a non-aqueous electrolyte are housed in an outer package,
    A lithium ion secondary battery comprising the negative electrode for a non-aqueous electrolyte based electrochemical device according to any one of claims 1 to 5 as the negative electrode.
  10. 　前記正極合剤層は、正極活物質の粒子の表面がＡｌ含有酸化物で被覆されてなる正極材料を含み、前記Ａｌ含有酸化物の平均被覆厚みが５～５０ｎｍであり、前記正極材料が含有する正極活物質は、Ｃｏと、Ｍｇ、Ｚｒ、Ｎｉ、Ｍｎ、ＴｉおよびＡｌよりなる群から選択される少なくとも１種の元素Ｍ１とを少なくとも含有するコバルト酸リチウムである請求項９に記載のリチウムイオン二次電池。 The positive electrode mixture layer includes a positive electrode material in which the surface of the positive electrode active material particles is coated with an Al-containing oxide, the average coating thickness of the Al-containing oxide is 5 to 50 nm, and the positive electrode material includes 10. The positive electrode active material to be used is lithium cobalt oxide containing at least Co and at least one element M 1 selected from the group consisting of Mg, Zr, Ni, Mn, Ti, and Al. Lithium ion secondary battery.
  11. 　前記セパレータは、熱可塑性樹脂を主体とする多孔質膜（Ｉ）と、耐熱温度が１５０℃以上のフィラーを主体として含む多孔質層（ＩＩ）とを有している請求項９または１０に記載のリチウムイオン二次電池。 11. The separator according to claim 9, wherein the separator has a porous film (I) mainly composed of a thermoplastic resin and a porous layer (II) mainly composed of a filler having a heat resistant temperature of 150 ° C. or more. Lithium ion secondary battery.
  12. 　請求項９～１１のいずれかに記載のリチウムイオン二次電池を製造する方法であって、
    　請求項６～８のいずれかに記載の製造方法によって得られた非水電解液系電気化学素子用負極を用いてリチウムイオン二次電池を組み立てる工程を有することを特徴とするリチウムイオン二次電池の製造方法。     A method for producing a lithium ion secondary battery according to any one of claims 9 to 11,
    A lithium ion secondary battery comprising a step of assembling a lithium ion secondary battery using the negative electrode for a non-aqueous electrolyte based electrochemical device obtained by the production method according to any one of claims 6 to 8. Manufacturing method.
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