WO2015015598A1 - Coating material for negative electrode active materials for lithium ion secondary batteries, negative electrode active material for lithium ion secondary batteries coated with said coating material, and lithium ion secondary battery using said negative electrode active material in negative electrode - Google Patents

Coating material for negative electrode active materials for lithium ion secondary batteries, negative electrode active material for lithium ion secondary batteries coated with said coating material, and lithium ion secondary battery using said negative electrode active material in negative electrode Download PDF

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WO2015015598A1
WO2015015598A1 PCT/JP2013/070763 JP2013070763W WO2015015598A1 WO 2015015598 A1 WO2015015598 A1 WO 2015015598A1 JP 2013070763 W JP2013070763 W JP 2013070763W WO 2015015598 A1 WO2015015598 A1 WO 2015015598A1
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negative electrode
electrode active
lithium ion
ion secondary
active material
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PCT/JP2013/070763
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French (fr)
Japanese (ja)
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紀雄 岩安
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株式会社日立製作所
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a coating material for a negative electrode active material for a lithium ion secondary battery, a negative electrode active material for a lithium ion secondary battery coated with the coating material, and a lithium ion secondary battery using the negative electrode active material as a negative electrode.
  • Patent Document 1 discloses a polymer electrolyte containing, as a matrix, a copolymer containing a polymer unit based on vinylidene fluoride and a polymer unit having —CF 2 COOLi or —CF 2 SO 3 Li in the side chain, and containing an organic solvent.
  • a lithium battery is disclosed.
  • Patent Document 2 discloses a lithium ion secondary battery in which a liquid containing lithium bis (oxalate) borate is in contact with the surface of an electrode.
  • An object of the present invention is to provide a novel coating material for a negative electrode active material of a lithium ion secondary battery that can reduce the irreversible capacity and reduce the battery resistance.
  • the covering material for a negative electrode active material for a lithium ion secondary battery is composed of a polymer represented by the chemical formula 1, wherein Z has a structure represented by the chemical formula 2, R 1 , R 2 , and R 3 each represent any of an alkyl group, a halogen group, and a hydrogen group; m 1 , n 1 , and n 2 each represent the number of repeating structural units; , A and B each represent a functional group containing a halogen element or hydrogen, at least one of A and B is a functional group containing a halogen element, and X is hydrogen, an alkali metal, and an alkaline earth metal. Represents either.
  • the covering material for a negative electrode active material for a lithium ion secondary battery includes a first monomer corresponding to a structural unit of a polymer represented by Chemical Formula 1, and a second monomer represented by Chemical Formulas 3-7.
  • At least one selected from the group consisting of a copolymer obtained by copolymerization wherein in Formula 1, Z has a structure represented by Formula 2, and R 1 , R 2 , and R 3 are each an alkyl group , A halogen group, and a hydrogen group, m 1 , n 1 , and n 2 each represent the number of repeating structural units, and in Chemical Formula 2, A and B are each a functional group containing a halogen element or Represents hydrogen, at least one of A and B is a functional group containing a halogen element, X represents any one of hydrogen, an alkali metal, and an alkaline earth metal; Y represents an alkali metal or hydrogen.
  • a coating material for a lithium ion secondary battery negative electrode active material capable of reducing irreversible capacity and battery resistance, and a lithium ion secondary battery negative electrode active material coated with the coating material can provide. Further, by using the negative electrode active material for the negative electrode, it is possible to provide a lithium ion secondary battery having a small irreversible capacity, a high capacity, a low battery resistance, and excellent output characteristics.
  • FIG. 1 is a cross-sectional view schematically showing a cross-sectional structure of a lithium ion secondary battery.
  • FIG. 2 is a diagram illustrating the synthesis of the monomer according to the embodiment of the present invention.
  • FIG. 3 is a table showing the composition of the coating material, the irreversible capacity of the negative electrode, and the direct current resistance of the battery in Examples and Comparative Examples of the present invention.
  • FIG. 1 is a diagram schematically showing the internal structure of a lithium ion battery.
  • a lithium ion battery 1 shown in FIG. 1 includes a positive electrode 10, a separator 11, a negative electrode 12, a battery container (battery can) 13, a positive electrode current collector tab 14, a negative electrode current collector tab 15, an inner lid 16, an internal pressure release valve 17, and a gasket 18. , A positive temperature coefficient (PTC) resistance element 19, a battery lid 20, and an axis 21.
  • the battery lid 20 is configured integrally with the inner lid 16, the internal pressure release valve 17, the gasket 18, and the PTC resistance element 19.
  • An electrode group composed of the separator 11 inserted between the positive electrode 10 and the negative electrode 12 is configured to be wound around an axis 21.
  • the electrode group may have various shapes such as a laminate of strip electrodes, a positive electrode 10 and a negative electrode 12 wound in an arbitrary shape such as a flat shape. it can.
  • the shape of the battery case 13 can be selected from shapes such as a cylindrical shape, a flat oval shape, a flat oval shape, and a square shape according to the shape of the electrode group.
  • the material of the battery container 13 is selected from materials that are corrosion resistant to the nonaqueous electrolyte, such as aluminum, stainless steel, and nickel-plated steel. Further, when the battery container 13 is electrically connected to the positive electrode 10 or the negative electrode 12, the material is not deteriorated due to corrosion of the battery container 13 or alloying with lithium ions in the portion in contact with the nonaqueous electrolyte. Thus, the material of the battery container 13 is selected.
  • the electrode group is housed in the battery container 13, the negative electrode current collecting tab 15 is connected to the inner wall of the battery container 13, and the positive electrode current collecting tab 14 is connected to the bottom surface of the battery lid 20.
  • the electrolytic solution is injected into the battery container interior 13. There are two methods for injecting the electrolytic solution: a method in which the battery lid 20 is opened and a direct injection into the electrode group, or a method in which injection is performed from an injection port installed in the battery lid 20. After injecting the electrolyte, the battery lid 20 is brought into close contact with the battery container 13 to seal the entire battery. If there is an electrolyte inlet, seal the inlet.
  • Known methods such as welding and caulking can be applied to the method of sealing the battery.
  • the positive electrode 10 is produced by applying a positive electrode mixture containing a positive electrode active material, a conductive agent, and a binder to the surface of the positive electrode current collector to form a positive electrode mixture layer.
  • Typical examples of the positive electrode active material include LiCoO 2 , LiNiO 2 , and LiMn 2 O 4 .
  • the size of the positive electrode active material particles is set to be equal to or less than the thickness of the positive electrode mixture layer formed by the positive electrode active material, the conductive agent, and the binder. When there are particles larger than the thickness of the positive electrode mixture layer in the positive electrode active material powder, it is preferable to remove the large particles in advance by sieving classification or wind classification.
  • the purpose of using the conductive agent is to supplement the electrical conductivity because the positive electrode active material is generally an oxide having a high electrical resistance.
  • a conductive agent carbon powder is generally used.
  • the positive electrode active material and the conductive agent are generally powders, and these powders can be attached to the surface of the positive electrode current collector in a bound state by mixing a binder.
  • an aluminum foil having a thickness of 10 to 100 ⁇ m, an aluminum perforated foil in which a large number of holes having a diameter of 0.1 to 10 mm are formed on an aluminum foil having a thickness of 10 to 100 ⁇ m, an expanded metal, a foam metal plate, or the like is used. be able to.
  • materials such as stainless steel and titanium are also applicable, and various materials, shapes, and manufacturing methods are applicable.
  • the positive electrode is formed by applying a positive electrode mixture slurry prepared by mixing a positive electrode active material, a conductive agent, and a binder in an organic solvent to the positive electrode current collector, then evaporating the organic solvent, and then press-molding by a roll press. Can be produced. Application methods such as a doctor blade method, a dipping method, and a spray method can be applied to the application of the positive electrode mixture slurry. It is also possible to stack the positive electrode mixture layer on the positive electrode current collector by performing the steps from application of the positive electrode mixture slurry to drying in a plurality of times.
  • the negative electrode is produced by applying a negative electrode mixture containing a negative electrode active material and a binder to the surface of the negative electrode current collector to form a negative electrode mixture layer.
  • a negative electrode active material an easily graphitized material obtained from natural graphite, petroleum coke, coal pitch coke, etc. is heat-treated at a high temperature of 2500 ° C. or higher, and mesophase carbon, amorphous carbon, carbon fiber, and lithium are alloyed.
  • Metal a material having a metal supported on the carbon particle surface, and the like are applicable.
  • the metal a single material selected from lithium, silver, aluminum, tin, silicon, indium, gallium, and magnesium, or an alloy material of these metals can be used.
  • lithium titanate can also be used.
  • the negative electrode active material is coated with a negative electrode active material coating material.
  • the coating amount with the negative electrode active material coating material is 0.01% by mass or more and 10% by mass or less, preferably 0.1% by mass or more and 5% by mass or less, more preferably, with respect to the mass of the negative electrode active material. It is 0.3 mass% or more and 3 mass% or less.
  • the covering material for a negative electrode active material according to the present invention is a polymer having a structural formula represented by Chemical Formula 1.
  • m 1 is the number of repeating structural units (the structural portion shown in parentheses in Chemical Formula 1).
  • Z is a site containing halogen and a site due to an ionic functional group such as a sulfo group (—SO 3 X), a carboxyl group (—COOX), a phosphate group (—O—PO (OX) 2 ), etc. It consists of.
  • a sulfo group is preferable from the viewpoint of reducing the resistance of the battery.
  • R 1 , R 2 , and R 3 each represent an alkyl group, a halogen group, or hydrogen.
  • n 1 and n 2 are the number of repeating structural units, respectively.
  • the structural unit having the repeating number n 1 is composed of a methylene group.
  • n 1 is preferably an integer of 0 or more and 20 or less.
  • a and B are each composed of a functional group containing hydrogen or hydrogen, and at least one of A and B is configured to contain halogen.
  • halogen fluorine or chlorine is preferable, and fluorine is more preferable.
  • the functional group containing fluorine as a halogen fluorine and CF 3 are preferable.
  • the functional group containing halogen is preferably adjacent to the sulfo group. That is, in Chemical Formula 2, it is preferable that B contains a functional group containing a halogen. From the viewpoint of reducing battery resistance, in Chemical Formula 2, n 2 is preferably an integer of 1 or more and 20 or less, and more preferably 1 or more and 10 or less.
  • the explanation regarding the halogen-containing functional group and the sulfo group is similarly applied to the case where the ionic functional group includes a carboxyl group or a phosphate group instead of the sulfo group in Chemical Formula 2.
  • Chemical Formula 8 to Chemical Formula 10 are shown.
  • the structure shown in Chemical Formula 8 has the best solubility in a solvent, and the workability when preparing the coating material is considered to be the best.
  • the structure represented by Chemical Formula 10 is not as soluble in the solvent as the structure represented by Chemical Formula 8, but has a large polarity because CF 3 is disposed adjacent to the sulfo group (ionic functional group). Since it is easy to move ions, the effect of reducing the resistance of the battery is considered to be greater.
  • the solubility in a solvent and the ease of ion transfer are considered to be intermediate.
  • the structural formulas of chemical formulas 8 to 10 show structures in which the values of n 1 and n 2 are both 1. However, if these values are within the above ranges, the same effect can be obtained.
  • a polymer having the structure of Chemical Formula 1 is produced by polymerizing a monomer as the structural unit.
  • the synthesis of the monomer will be described with reference to FIG. 2, taking as an example the case where the Z portion in Chemical Formula 1 has the structure shown in Chemical Formula 8.
  • the negative electrode active material coating material according to the present invention is produced by polymerizing the above monomers.
  • the polymerization may be any of conventionally known bulk polymerization, solution polymerization, and emulsion polymerization.
  • the polymerization method is not particularly limited, but radical polymerization is preferred.
  • a polymerization initiator may or may not be used, but a radical polymerization initiator is preferably used from the viewpoint of ease of work. In polymerization using a radical polymerization initiator, there is no problem in the normal temperature range and polymerization time.
  • the blending amount of the polymerization initiator is preferably in the range of 0.1% by mass to 20% by mass with respect to the mass of the compound to be polymerized, and in the range of 0.3% by mass to 5% by mass. More preferably.
  • the coating material for negative electrode active material according to the present invention may be composed of a copolymer obtained by copolymerizing a monomer (main monomer) corresponding to the polymer represented by Chemical Formula 1 and another monomer (copolymerization monomer). Good.
  • a monomer having a structure represented by Chemical Formula 3 to Chemical Formula 7 is preferable.
  • Y represents an alkali metal or hydrogen, and is preferably an alkali metal from the viewpoint of electrochemical stability.
  • An improvement in irreversible capacity can be expected by using a negative electrode coating material made of a copolymer. Possible reasons for this are as follows. There is a possibility that the coating material with the polymer represented by Chemical Formula 1 may not necessarily have sufficient wettability with respect to the negative electrode active material. In such a case, there is a portion where the surface of the negative electrode active material cannot be covered with the coating material. It is considered a thing. In a portion that cannot be covered, it is conceivable that the negative electrode active material and the electrolytic solution are in direct contact with each other and the electrolytic solution is decomposed.
  • the wettability to the negative electrode active material is improved, and more part of the surface of the negative electrode active material is coated with the coating material Can be considered.
  • the effect of reducing the irreversible capacity by suppressing the decomposition of the electrolytic solution can be expected.
  • the monomers represented by the chemical formulas 3 to 7 the effect of improving the wettability with respect to the negative electrode active material is relatively large for the monomers represented by the chemical formulas 3 and 4, and the effects for the monomers represented by the chemical formulas 6 and 7 are relatively small. it is conceivable that.
  • the monomer represented by Formula 5 is considered to have an intermediate effect.
  • the present invention includes a mixture of a polymer represented by Chemical Formula 1 and at least one polymer obtained by polymerizing monomers represented by Chemical Formulas 3 to 7 as a negative electrode active material coating material.
  • the polymer structure may be any of a linear structure, a branched structure, a crosslinked structure, and a dendrimer structure. From the viewpoint of workability when coating the negative electrode active material, a polymer having a linear structure is preferable.
  • the polymerization mode for copolymerization is not particularly limited, and examples thereof include random copolymerization, alternating copolymerization, block copolymerization, and graft copolymerization.
  • the number average molecular weight of the polymer used as the negative electrode active material coating material according to the present invention is 1,000 or more and 5,000,000 or less, preferably 1,000 or more and 1,000,000 or less. By adjusting the number average molecular weight, aggregation of the negative electrode active material, which tends to occur when the negative electrode active material is coated, can be suppressed.
  • the “polymer” mentioned here includes a copolymer.
  • the composition ratio of the monomer (main monomer), which is the structural unit of the polymer represented by Chemical Formula 1, to the monomer (copolymerization monomer) to be copolymerized is x for the number of moles of the main monomer, and When y, 0 ⁇ x / (x + y) ⁇ 1, preferably 0.1 ⁇ x / (x + y) ⁇ 1, more preferably 0.25 ⁇ x / (x + y) ⁇ 0.75. is there.
  • a coating material for a negative electrode active material that has a smaller irreversible capacity and a low battery resistance can be provided.
  • the method for coating the negative electrode active material with the coating material is not particularly limited.
  • a negative electrode active material surface is prepared by preparing a solution in which a negative electrode active material coating material is dissolved in a solvent, mixing the negative electrode active material in the solution, and then evaporating the solvent. It is preferable to coat with.
  • the solvent is not particularly limited as long as the polymer dissolves well. Protic solvents such as water and ethanol, aprotic solvents such as N-methylpyrrolidone, nonpolar solvents such as toluene and hexane, and the like can be used.
  • the separator 11 is inserted between the positive electrode 10 and the negative electrode 12 to prevent the positive electrode 10 and the negative electrode 12 from being short-circuited.
  • a sheet made of a polyolefin polymer such as polyethylene or polypropylene, or a sheet having a two-layer structure in which a fluorine polymer sheet made of polyolefin polymer and tetrafluoropolyethylene is laminated is used. It is possible.
  • a sheet having a thin layer formed of a mixture of ceramic and binder on the surface may be used. Since the separator 11 needs to allow lithium ions to pass therethrough during charge / discharge of the battery, generally, a large number of fine pores having a diameter of 0.01 to 10 ⁇ m are provided so as to have a porosity of 20 to 90%. .
  • Electrode> As an electrolytic solution, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate or the like mixed with ethylene carbonate is used as a solvent, and lithium hexafluorophosphate (LiPF 6 ) or lithium borofluoride (LiBF 4 ) is used as an electrolyte in this solvent. ) Is generally used. However, there are no particular restrictions on the type of solvent or electrolyte, and the mixing ratio thereof, and electrolytes other than those described above can also be used.
  • non-aqueous solvents examples include propylene carbonate, ethylene carbonate, butylene carbonate, vinylene carbonate, ⁇ -butyrolactone, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane, 2-methyl Tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, methyl propionate, ethyl propionate, phosphate triester, trimethoxymethane, dioxolane, diethyl ether, sulfolane, 3-methyl-2-oxazolidinone, Tetrahydrofuran, 1,2-diethoxyethane, chloroethylene carbonate, fluoroethylene carbonate, chloropropylene carbonate, etc. . Solvents other than those described above may be used as long as they do not decompose in the positive electrode 10 or the negative electrode 12.
  • Nonaqueous electrolytes in which these lithium salts are dissolved in the above various nonaqueous solvents can be used.
  • An electrolyte other than the above may be used as long as it does not decompose in the positive electrode 10 or the negative electrode 12.
  • solid polymer electrolyte polymer electrolyte
  • ion conductive polymers such as polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, polyhexafluoropropylene, and polyethylene oxide can be used.
  • these solid polymer electrolytes there is an advantage that the separator 11 can be omitted.
  • An ionic liquid can also be used as the electrolyte.
  • the ionic liquid include 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI-BF4), a mixed salt of lithium salt LiN (SO 2 CF 3 ) 2 (LiTFSI), triglyme and tetraglyme, and a cyclic quaternary ammonium type.
  • EMI-BF4 1-ethyl-3-methylimidazolium tetrafluoroborate
  • LiTFSI lithium salt LiN (SO 2 CF 3 ) 2
  • triglyme and tetraglyme tetraglyme
  • a cyclic quaternary ammonium type LiN (SO 2 CF 3 ) 2
  • a combination that does not decompose in the positive electrode 10 or the negative electrode 12 can be selected from a cation (for example, N-methyl-N-propylpyrrolidinium) and an imide anion (for
  • Example 1 Preparation of coating material for negative electrode active material>
  • monomer A represented by Chemical Formula 11 and Tetrohydrofuran as a reaction solvent were added, AIBN (azoisobutylnitrile) was further added as a polymerization initiator, and heated at a temperature of 60 ° C. for 3 hours.
  • Polymer A was polymerized where the Z moiety had the structure of Formula 8.
  • the part of X in Chemical formula 8 was Li (lithium).
  • the concentration of the polymerization initiator was 4% by mass with respect to the mass of the monomer.
  • the polymer A corresponds to the coating material for a negative electrode active material according to the present invention.
  • the produced negative electrode was punched into a circle having a diameter of 15 mm to produce an evaluation electrode.
  • a separator was sandwiched between the evaluation electrode and the Li metal electrode, and the sample was inserted into the container, and an electrolytic solution was injected to prepare an evaluation cell.
  • the evaluation cell was charged at a current density of 0.72 mA / cm 2 to a preset lower limit voltage, and then discharged at a current density of 0.72 mA / cm 2 to a preset upper limit voltage.
  • the lower limit voltage was 0.01V, and the upper limit voltage was 1.5V.
  • the irreversible capacity was determined from the difference between the charge capacity and the discharge capacity obtained during charge / discharge.
  • the same electrode as the above evaluation electrode was produced.
  • a separator was sandwiched between the evaluation electrode as the negative electrode and the positive electrode and the battery was inserted into the battery container, and an electrolytic solution was injected into the battery container to produce an evaluation battery.
  • the positive electrode was produced by the following procedure.
  • LiCoO 2 as a positive electrode active material, graphite (SP270: manufactured by Nippon Graphite Industries) as a conductive agent, and polyvinylidene fluoride as a binder are mixed so as to have a mass ratio of 85: 7.5: 7.5.
  • N-methyl-2-pyrrolidone was added to adjust the viscosity to prepare a positive electrode mixture slurry.
  • This positive electrode mixture slurry was applied to the surface of an aluminum foil having a thickness of 20 ⁇ m by a doctor blade method, and then the solvent was evaporated and further pressed to produce a positive electrode.
  • the coating amount of the positive electrode mixture was 200 g / m 2 .
  • the battery for evaluation was charged at a current density of 0.72 mA / cm 2 to a preset upper limit voltage, and then discharged at a current density of 0.72 mA / cm 2 to a preset lower limit voltage.
  • the upper limit voltage was 4.2V
  • the lower limit voltage was 3.0V.
  • the discharge capacity obtained during discharge was taken as the initial capacity of the battery.
  • the battery was charged to 50% of the initial capacity, and the DC resistance at that time was measured.
  • Example 2 A coating material for a negative electrode active material was prepared by the following procedure. That is, the monomer B represented by the chemical formula 12 was polymerized by the same procedure as in Example 1 to polymerize the polymer B in which the Z portion in the chemical formula 1 has the structure of the chemical formula 9. Note that X in Chemical Formula 9 was Li. The coating amount of the coating material with respect to the mass of the negative electrode active material was 0.5 wt%. The irreversible capacity and DC resistance were measured by the same procedure as in Example 1 except that the above-described negative electrode active material coating material was used. Polymer B corresponds to the negative electrode active material coating material according to the present invention.
  • Example 3 A coating material for a negative electrode active material was prepared by the following procedure. That is, the monomer C represented by the chemical formula 13 was polymerized by the same procedure as in Example 1 to polymerize the polymer C in which the Z portion in the chemical formula 1 has the structure of the chemical formula 10. Note that X in Chemical Formula 10 was Li. The coating amount of the coating material with respect to the mass of the negative electrode active material was 0.5 wt%. The irreversible capacity and DC resistance were measured by the same procedure as in Example 1 except that the above-described negative electrode active material coating material was used. The polymer C corresponds to the negative electrode active material coating material according to the present invention.
  • Example 4 A coating material for a negative electrode active material was prepared by the following procedure. That is, the monomer A (main monomer) and the monomer shown in Chemical Formula 5 (copolymerization monomer) are mixed so as to have a molar ratio of 75:25, and then polymerized to copolymerize as a coating material for the negative electrode active material. Polymer D was synthesized. Note that the Y portion in Chemical Formula 5 was Li. The coating amount of the coating material with respect to the mass of the negative electrode active material was 0.5 wt%. The irreversible capacity and DC resistance were measured by the same procedure as in Example 1 except that the above-described negative electrode active material coating material was used.
  • Example 5 The irreversible capacity and direct current were the same as in Example 4 except that the copolymer A was prepared by setting the molar ratio of the monomer A (main monomer) and the monomer (copolymerized monomer) shown in Chemical Formula 5 to 50:50. Resistance was measured.
  • Example 6 The irreversible capacity and direct current were the same as in Example 4 except that the copolymer A was prepared by setting the molar ratio of the monomer A (main monomer) and the monomer (copolymerized monomer) shown in Chemical Formula 5 to 25:75. Resistance was measured.
  • the irreversible capacity is 25.4 mAhg ⁇ 1 in the comparative example, whereas in Examples 1 to 6, all are lower than 25 mAhg ⁇ 1 . From this, it can be seen that the irreversible capacity could be reduced by producing the negative electrode using the negative electrode active material whose surface was coated with the negative electrode active material coating material according to the present invention. In Examples 4 to 6, a low value lower than 24 mAhg ⁇ 1 was obtained. From this, it can be seen that the irreversible capacity could be further reduced by using the coating material made of a copolymer.
  • the direct current resistance was 11.5 ⁇ in the comparative example, whereas all of Examples 1 to 6 were less than 11 ⁇ , and the negative electrode active material whose surface was coated with the coating material for negative electrode active material according to the present invention. It can be seen that the battery resistance can be lowered by producing the negative electrode using the substance.
  • X in the chemical formulas 8 to 10 is Li in all examples, but the same effect can be obtained even when X is hydrogen or an alkali metal or alkaline earth metal other than Li. Is obtained.
  • the portion indicated by Y in the structures shown in the chemical formulas 3 to 7 is Li in any of the examples, but the same effect can be obtained even when Y is hydrogen or an alkali metal other than Li. can get.
  • a coating material for a negative electrode active material for a lithium ion secondary battery capable of reducing the irreversible capacity and the battery resistance, and a lithium ion secondary coated with the coating material can be provided.

Abstract

A coating material for negative electrode active materials for lithium ion secondary batteries, which is composed of a polymer that is represented by chemical formula (1). In chemical formula (1), Z has a structure that is represented by chemical formula (2); each of R1, R2 and R3 represents an alkyl group, a halogen group or a hydrogen group; and each of m1, n1 and n2 represents the number of repetition of each structural unit. In chemical formula (2), each of A and B represents a functional group containing a halogen element, or a hydrogen atom; A and/or B represents a functional group containing a halogen element; and X represents a hydrogen atom, an alkali metal atom or an alkaline earth metal atom.

Description

リチウムイオン二次電池負極活物質用被覆材、前記被覆材で被覆されたリチウムイオン二次電池負極活物質、および、前記負極活物質を負極に用いたリチウムイオン二次電池Lithium ion secondary battery negative electrode active material coating material, lithium ion secondary battery negative electrode active material coated with the coating material, and lithium ion secondary battery using the negative electrode active material as a negative electrode

　本発明は、リチウムイオン二次電池負極活物質用被覆材、前記被覆材で被覆されたリチウムイオン二次電池負極活物質、および、前記負極活物質を負極に用いたリチウムイオン二次電池に関する。
The present invention relates to a coating material for a negative electrode active material for a lithium ion secondary battery, a negative electrode active material for a lithium ion secondary battery coated with the coating material, and a lithium ion secondary battery using the negative electrode active material as a negative electrode.

　近年、リチウムイオン二次電池電極用被覆材料の開発が盛んに進められている。リチウムイオン二次電池の負極は、電解液に対する還元活性が高いために電解液を分解し易い。電解液が分解されると電池の不可逆容量が増加し、電池容量が低下するという問題が発生することが知られている。このような問題の発生を避けるため、負極活物質をポリマーで被覆して電池性能を向上させる試みがなされている。　
In recent years, coating materials for lithium ion secondary battery electrodes have been actively developed. Since the negative electrode of a lithium ion secondary battery has high reduction activity with respect to an electrolyte solution, the electrolyte solution is easily decomposed. It is known that when the electrolytic solution is decomposed, the irreversible capacity of the battery increases and the battery capacity decreases. In order to avoid such problems, attempts have been made to improve battery performance by coating a negative electrode active material with a polymer.
　特許文献１には、フッ化ビニリデンに基づく重合単位と側鎖に－ＣＦ2 ＣＯＯＬｉまたは－ＣＦ2 ＳＯ3 Ｌｉを有する重合単位とを含む共重合体をマトリックスとし、かつ有機溶媒を含有するポリマー電解質を有するリチウム電池について開示されている。特許文献２には、電極の表面に、リチウムビス（オキサレート）ボレートを含有する液体が接触されたリチウムイオン二次電池について開示されている。 Patent Document 1 discloses a polymer electrolyte containing, as a matrix, a copolymer containing a polymer unit based on vinylidene fluoride and a polymer unit having —CF 2 COOLi or —CF 2 SO 3 Li in the side chain, and containing an organic solvent. A lithium battery is disclosed. Patent Document 2 discloses a lithium ion secondary battery in which a liquid containing lithium bis (oxalate) borate is in contact with the surface of an electrode.
特開平１０－２８４１２８号公報JP-A-10-284128 特開２０１２－２０９１４５号公報JP 2012-209145 A

　しかし、特許文献１および２に開示されたポリマーで負極活物質を被覆すると、不可逆容量が増加するという問題が発生する。これは、前記ポリマーの電気化学的安定性が低いことが原因と考えられる。また、電池の抵抗が高くなり、出力特性が低下する問題も発生する。これは、前記ポリマーにより負極表面に形成されるSEI(Solid Electrolyte Interface)の抵抗が大きいことが原因と考えられる。　
However, when the negative electrode active material is coated with the polymers disclosed in Patent Documents 1 and 2, there arises a problem that the irreversible capacity increases. This is considered due to the low electrochemical stability of the polymer. In addition, there is a problem that the resistance of the battery increases and the output characteristics deteriorate. This is presumably because the resistance of SEI (Solid Electrolyte Interface) formed on the negative electrode surface by the polymer is large.

　本発明は、不可逆容量を小さく、かつ、電池抵抗を低くすることを可能とする、新規なリチウムイオン二次電池負極活物質用被覆材を提供することを目的とする。
An object of the present invention is to provide a novel coating material for a negative electrode active material of a lithium ion secondary battery that can reduce the irreversible capacity and reduce the battery resistance.

　本発明の第１の態様によると、リチウムイオン二次電池負極活物質用被覆材は、化学式１で表されるポリマーからなり、化学式１において、Ｚは化学式２で表される構造を有し、Ｒ１、Ｒ２、およびＲ３はそれぞれ、アルキル基、ハロゲン基、および水素基のいずれかを表わし、ｍ１、ｎ１、およびｎ２はそれぞれ、構造単位の繰り返し数を表わし、化学式２において、ＡおよびＢはそれぞれ、ハロゲン元素を含む官能基または水素を表わし、少なくともＡおよびＢのうちの一方はハロゲン元素を含む官能基であり、Ｘは、水素、アルカリ金属、およびアルカリ土類金属のいずれかを表わす。
Figure JPOXMLDOC01-appb-C000006
Figure JPOXMLDOC01-appb-C000007
 　本発明の第２の態様によると、リチウムイオン二次電池負極活物質用被覆材は、化学式１で表されるポリマーの構造単位に相当する第１モノマーと、化学式３～７に示す第２モノマーのうちの少なくとも１種と、を共重合させた共重合体からなり、化学式１において、Ｚは化学式２で表される構造を有し、Ｒ１、Ｒ２、およびＲ３はそれぞれ、アルキル基、ハロゲン基、および水素基のいずれかを表わし、ｍ１、ｎ１、およびｎ２はそれぞれ、構造単位の繰り返し数を表わし、化学式２において、ＡおよびＢはそれぞれ、ハロゲン元素を含む官能基または水素を表わし、少なくともＡおよびＢのうちの一方はハロゲン元素を含む官能基であり、Ｘは、水素、アルカリ金属、およびアルカリ土類金属のいずれかを表わし、化学式３～７において、Ｙはアルカリ金属または水素を表わす。
Figure JPOXMLDOC01-appb-C000008
According to the first aspect of the present invention, the covering material for a negative electrode active material for a lithium ion secondary battery is composed of a polymer represented by the chemical formula 1, wherein Z has a structure represented by the chemical formula 2, R 1 , R 2 , and R 3 each represent any of an alkyl group, a halogen group, and a hydrogen group; m 1 , n 1 , and n 2 each represent the number of repeating structural units; , A and B each represent a functional group containing a halogen element or hydrogen, at least one of A and B is a functional group containing a halogen element, and X is hydrogen, an alkali metal, and an alkaline earth metal. Represents either.
Figure JPOXMLDOC01-appb-C000006
Figure JPOXMLDOC01-appb-C000007
 According to the second aspect of the present invention, the covering material for a negative electrode active material for a lithium ion secondary battery includes a first monomer corresponding to a structural unit of a polymer represented by Chemical Formula 1, and a second monomer represented by Chemical Formulas 3-7. At least one selected from the group consisting of a copolymer obtained by copolymerization, wherein in Formula 1, Z has a structure represented by Formula 2, and R 1 , R 2 , and R 3 are each an alkyl group , A halogen group, and a hydrogen group, m 1 , n 1 , and n 2 each represent the number of repeating structural units, and in Chemical Formula 2, A and B are each a functional group containing a halogen element or Represents hydrogen, at least one of A and B is a functional group containing a halogen element, X represents any one of hydrogen, an alkali metal, and an alkaline earth metal; Y represents an alkali metal or hydrogen.
Figure JPOXMLDOC01-appb-C000008

　本発明によれば、不可逆容量を小さく、かつ、電池抵抗を低くすることが可能なリチウムイオン二次電池負極活物質用被覆材、および、前記被覆材で被覆したリチウムイオン二次電池負極活物質を提供できる。また、前記負極活物質を負極に用いることにより、不可逆容量が小さく高容量で、かつ電池抵抗が低く出力特性に優れたリチウムイオン二次電池を提供できる。
According to the present invention, a coating material for a lithium ion secondary battery negative electrode active material capable of reducing irreversible capacity and battery resistance, and a lithium ion secondary battery negative electrode active material coated with the coating material Can provide. Further, by using the negative electrode active material for the negative electrode, it is possible to provide a lithium ion secondary battery having a small irreversible capacity, a high capacity, a low battery resistance, and excellent output characteristics.

図１は、リチウムイオン二次電池の断面構造を模式的に示す断面図である。FIG. 1 is a cross-sectional view schematically showing a cross-sectional structure of a lithium ion secondary battery. 図２は、本発明の実施の形態に係るモノマーの合成を説明する図である。FIG. 2 is a diagram illustrating the synthesis of the monomer according to the embodiment of the present invention. 図３は、本発明の実施例および比較例における被覆材の組成と、負極の不可逆容量および電池の直流抵抗を示す表である。FIG. 3 is a table showing the composition of the coating material, the irreversible capacity of the negative electrode, and the direct current resistance of the battery in Examples and Comparative Examples of the present invention.

　図１は、リチウムイオン電池の内部構造を模式的に表す図である。図１に示すリチウムイオン電池１は、正極１０、セパレータ１１、負極１２、電池容器（電池缶）１３、正極集電タブ１４、負極集電タブ１５、内蓋１６、内圧開放弁１７、ガスケット１８、正温度係数（Positive temperature coefficient；ＰＴＣ）抵抗素子１９、電池蓋２０、および軸心２１から構成される。電池蓋２０は、内蓋１６、内圧開放弁１７、ガスケット１８、およびＰＴＣ抵抗素子１９と一体に構成されている。正極１０と負極１２との間に挿入されたセパレータ１１からなる電極群は軸心２１に捲回されて構成される。軸心２１は、正極１０、セパレータ１１および負極１２を担持できるものであれば、公知のものを用いることができる。電極群は、図１に示した円筒形状の他に、短冊状電極を積層したもの、正極１０と負極１２を扁平状等の任意の形状に捲回したもの等、種々の形状にすることができる。電池容器１３の形状は、電極群の形状に合わせ、円筒形、偏平長円形状、扁平楕円形状、角形等の形状を選択できる。　
FIG. 1 is a diagram schematically showing the internal structure of a lithium ion battery. A lithium ion battery 1 shown in FIG. 1 includes a positive electrode 10, a separator 11, a negative electrode 12, a battery container (battery can) 13, a positive electrode current collector tab 14, a negative electrode current collector tab 15, an inner lid 16, an internal pressure release valve 17, and a gasket 18. , A positive temperature coefficient (PTC) resistance element 19, a battery lid 20, and an axis 21. The battery lid 20 is configured integrally with the inner lid 16, the internal pressure release valve 17, the gasket 18, and the PTC resistance element 19. An electrode group composed of the separator 11 inserted between the positive electrode 10 and the negative electrode 12 is configured to be wound around an axis 21. As the axis 21, a known one can be used as long as it can carry the positive electrode 10, the separator 11, and the negative electrode 12. In addition to the cylindrical shape shown in FIG. 1, the electrode group may have various shapes such as a laminate of strip electrodes, a positive electrode 10 and a negative electrode 12 wound in an arbitrary shape such as a flat shape. it can. The shape of the battery case 13 can be selected from shapes such as a cylindrical shape, a flat oval shape, a flat oval shape, and a square shape according to the shape of the electrode group.

　電池容器１３の材質は、アルミニウム、ステンレス鋼、ニッケルメッキ鋼製等、非水電解質に対して耐食性のある材料から選択される。また、電池容器１３を正極１０または負極１２に電気的に接続する場合は、非水電解質と接触している部分において、電池容器１３の腐食やリチウムイオンとの合金化による材料の変質が起こらないように、電池容器１３の材料の選定を行う。　
The material of the battery container 13 is selected from materials that are corrosion resistant to the nonaqueous electrolyte, such as aluminum, stainless steel, and nickel-plated steel. Further, when the battery container 13 is electrically connected to the positive electrode 10 or the negative electrode 12, the material is not deteriorated due to corrosion of the battery container 13 or alloying with lithium ions in the portion in contact with the nonaqueous electrolyte. Thus, the material of the battery container 13 is selected.

　電池容器１３に電極群を収納し、電池容器１３の内壁に負極集電タブ１５を接続し、電池蓋２０の底面に正極集電タブ１４を接続する。電解液は電池容器内部１３に注入される。電解液の注入方法は、電池蓋２０を解放した状態にて電極群に直接注入する方法、あるいは、電池蓋２０に設置した注入口から注入する方法がある。電解液を注入した後、電池蓋２０を電池容器１３に密着させて電池全体を密閉する。電解液の注入口がある場合は注入口も密封する。電池を密閉する方法には、溶接、かしめ等公知の技術が適用できる。　
The electrode group is housed in the battery container 13, the negative electrode current collecting tab 15 is connected to the inner wall of the battery container 13, and the positive electrode current collecting tab 14 is connected to the bottom surface of the battery lid 20. The electrolytic solution is injected into the battery container interior 13. There are two methods for injecting the electrolytic solution: a method in which the battery lid 20 is opened and a direct injection into the electrode group, or a method in which injection is performed from an injection port installed in the battery lid 20. After injecting the electrolyte, the battery lid 20 is brought into close contact with the battery container 13 to seal the entire battery. If there is an electrolyte inlet, seal the inlet. Known methods such as welding and caulking can be applied to the method of sealing the battery.

＜正極＞
　正極１０は、正極集電体表面に、正極活物質、導電剤、およびバインダを含む正極合剤を塗布して正極合剤層を形成することで作製する。　
<Positive electrode>
The positive electrode 10 is produced by applying a positive electrode mixture containing a positive electrode active material, a conductive agent, and a binder to the surface of the positive electrode current collector to form a positive electrode mixture layer.

　正極活物質の材料としては、ＬｉＣｏＯ２、ＬｉＮｉＯ２、およびＬｉＭｎ２Ｏ４が代表例として挙げられる。これらの材料の他に、ＬｉＭｎＯ３、ＬｉＭｎ２Ｏ３、ＬｉＭｎＯ２、Ｌｉ４Ｍｎ５Ｏ１２、ＬｉＭｎ２－ＸＭｘＯ２（ただし、Ｍ＝Ｃｏ、Ｎｉ、Ｆｅ、Ｃｒ、Ｚｎ、Ｔｉからなる群から選ばれる少なくとも１種、ｘ＝０．０１～０．２）、Ｌｉ２Ｍｎ３ＭＯ８（ただし、Ｍ＝Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｚｎからなる群から選ばれる少なくとも１種）、Ｌｉ１－ｘＡｘＭｎ２Ｏ４（ただし、Ａ＝Ｍｇ、Ｂ、Ａｌ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｒ、Ｚｎ、Ｃａからなる群から選ばれる少なくとも１種、ｘ＝０．０１～０．１）、ＬｉＮｉ１－ｘＭｘＯ２（ただし、Ｍ＝Ｃｏ、Ｆｅ、Ｇａからなる群から選ばれる少なくとも１種、ｘ＝０．０１～０．２）、ＬｉＦｅＯ２、Ｆｅ２（ＳＯ４）３、ＬｉＣｏ１－ｘＭｘＯ２（ただし、Ｍ＝Ｎｉ、Ｆｅ、Ｍｎからなる群から選ばれる少なくとも１種、ｘ＝０．０１～０．２）、ＬｉＮｉ１－ｘＭｘＯ２（ただし、Ｍ＝Ｍｎ、Ｆｅ、Ｃｏ、Ａｌ、Ｇａ、Ｃａ、Ｍｇからなる群から選ばれる少なくとも１種、ｘ＝０．０１～０．２）、Ｆｅ（ＭｏＯ４）３、ＦｅＦ３、ＬｉＦｅＰＯ４、およびＬｉＭｎＰＯ４等を列挙することができる。　
Typical examples of the positive electrode active material include LiCoO 2 , LiNiO 2 , and LiMn 2 O 4 . In addition to these materials, LiMnO 3 , LiMn 2 O 3 , LiMnO 2 , Li 4 Mn 5 O 12 , LiMn 2−X MxO 2 (where M = Co, Ni, Fe, Cr, Zn, Ti) At least one selected from x, 0.01 to 0.2), Li 2 Mn 3 MO 8 (wherein M = at least one selected from the group consisting of Fe, Co, Ni, Cu, Zn), Li 1-x A x Mn 2 O 4 (where A = Mg, B, Al, Fe, Co, Ni, Cr, Zn, Ca, at least one selected from the group consisting of x = 0.01 to 0.1 ), LiNi 1-x M x O 2 (where M = Co, Fe, Ga, at least one selected from the group consisting of x = 0.01 to 0.2), LiFeO 2 , Fe 2 (SO 4 ) 3, LiCo 1-x M x 2 (where, M = Ni, Fe, at least one selected from the group consisting of Mn, x = 0.01 ~ 0.2) , LiNi 1-x M x O 2 ( however, M = Mn, Fe, Co , At least one selected from the group consisting of Al, Ga, Ca, Mg, x = 0.01 to 0.2), Fe (MoO 4 ) 3 , FeF 3 , LiFePO 4 , LiMnPO 4, etc. Can do.

　正極活物質の粒子の大きさは、正極活物質、導電剤、およびバインダにより形成される正極合剤層の厚さ以下になるように設定される。正極活物質の粉末中に正極合剤層厚さより大きな粒子がある場合には、予めふるい分級や風流分級等により、大きな粒子を除去することが好ましい。　
The size of the positive electrode active material particles is set to be equal to or less than the thickness of the positive electrode mixture layer formed by the positive electrode active material, the conductive agent, and the binder. When there are particles larger than the thickness of the positive electrode mixture layer in the positive electrode active material powder, it is preferable to remove the large particles in advance by sieving classification or wind classification.

　導電剤を用いる目的は、正極活物質は一般に電気抵抗が高い酸化物であるため、電気伝導性を補うことにある。導電剤としては、炭素粉末を用いるのが一般的である。正極活物質と導電剤とは一般に粉末であり、これらの粉末はバインダを混合することにより結着させた状態で正極集電体表面に付着させることができる。　
The purpose of using the conductive agent is to supplement the electrical conductivity because the positive electrode active material is generally an oxide having a high electrical resistance. As a conductive agent, carbon powder is generally used. The positive electrode active material and the conductive agent are generally powders, and these powders can be attached to the surface of the positive electrode current collector in a bound state by mixing a binder.

　正極集電体としては、厚さ１０～１００μｍのアルミニウム箔、厚さ１０～１００μｍのアルミニウム箔に直径０．１～１０ｍｍの孔を多数形成したアルミニウム穿孔箔、エキスパンドメタル、発泡金属板等を用いることができる。アルミニウムの他に、ステンレスやチタン等の材質も適用可能であり、多様な材質、形状、製造方法が適用可能である。　
As the positive electrode current collector, an aluminum foil having a thickness of 10 to 100 μm, an aluminum perforated foil in which a large number of holes having a diameter of 0.1 to 10 mm are formed on an aluminum foil having a thickness of 10 to 100 μm, an expanded metal, a foam metal plate, or the like is used. be able to. In addition to aluminum, materials such as stainless steel and titanium are also applicable, and various materials, shapes, and manufacturing methods are applicable.

　正極は、正極活物質、導電剤、バインダを有機溶媒に混合して調製された正極合剤スラリーを正極集電体に塗布した後、有機溶媒を蒸発させ、さらにロールプレスによって加圧成形することにより作製できる。正極合剤スラリーの塗布には、ドクターブレード法、ディッピング法、スプレー法等の塗布方法が適用できる。正極合剤スラリーの塗布から乾燥までを複数回に分けて行うことにより、正極合剤層を正極集電体に積層させることも可能である。
The positive electrode is formed by applying a positive electrode mixture slurry prepared by mixing a positive electrode active material, a conductive agent, and a binder in an organic solvent to the positive electrode current collector, then evaporating the organic solvent, and then press-molding by a roll press. Can be produced. Application methods such as a doctor blade method, a dipping method, and a spray method can be applied to the application of the positive electrode mixture slurry. It is also possible to stack the positive electrode mixture layer on the positive electrode current collector by performing the steps from application of the positive electrode mixture slurry to drying in a plurality of times.

＜負極＞
　負極は、負極集電体表面に、負極活物質とバインダを含む負極合剤を塗布して負極合剤層を形成することにより作製する。負極活物質としては、天然黒鉛、石油コークスや石炭ピッチコークス等から得られる易黒鉛化材料を２５００℃以上の高温で熱処理したもの、メソフェーズカーボン、非晶質炭素、炭素繊維、リチウムと合金化する金属、炭素粒子表面に金属を担持した材料等が適用可能である。金属としては、リチウム、銀、アルミニウム、スズ、ケイ素、インジウム、ガリウム、マグネシウムより選ばれた単一材料あるいはこれらの金属の合金材料を用いることが可能である。また、チタン酸リチウムを用いることもできる。　
<Negative electrode>
The negative electrode is produced by applying a negative electrode mixture containing a negative electrode active material and a binder to the surface of the negative electrode current collector to form a negative electrode mixture layer. As a negative electrode active material, an easily graphitized material obtained from natural graphite, petroleum coke, coal pitch coke, etc. is heat-treated at a high temperature of 2500 ° C. or higher, and mesophase carbon, amorphous carbon, carbon fiber, and lithium are alloyed. Metal, a material having a metal supported on the carbon particle surface, and the like are applicable. As the metal, a single material selected from lithium, silver, aluminum, tin, silicon, indium, gallium, and magnesium, or an alloy material of these metals can be used. Moreover, lithium titanate can also be used.

　負極活物質は負極活物質用被覆材で被覆される。負極活物質用被覆材による被覆量は、負極活物質の質量に対して ０．０１質量％以上かつ１０質量％以下であり、好ましくは０．１質量％以上かつ５質量％以下、より好ましくは０．３質量％以上かつ３質量％以下である。　
The negative electrode active material is coated with a negative electrode active material coating material. The coating amount with the negative electrode active material coating material is 0.01% by mass or more and 10% by mass or less, preferably 0.1% by mass or more and 5% by mass or less, more preferably, with respect to the mass of the negative electrode active material. It is 0.3 mass% or more and 3 mass% or less.

＜負極活物質用被覆材＞
　本発明に係る負極活物質用被覆材は、化学式１で表わされる構造式からなるポリマーである。化学式１において、ｍ１は構造単位（化学式１において（）内に示された構造部分）の繰り返し数である。化学式１において、Ｚはハロゲンを含む部位、および、スルホ基(-SO3X)、カルボキシル基（-COOX）、リン酸基(-O-PO(OX)2)等のイオン性官能基による部位とから構成される。イオン性官能基としては、電池の抵抗を下げる観点から、スルホ基が好ましい。スルホ基を用いることにより、リチウムイオンとの解離性を高くすることが可能となるため、電池抵抗の低減が図れるものと考えられる。Ｚがハロゲンを含む部位とスルホ基で構成された具体例を化学式２に示す。Ｘは水素、またはアルカリ金属、またはアルカリ土類金属により構成される。これらのうち、電池性能の観点からはアルカリ金属が好ましく、リチウムやナトリウムがより好ましい。化学式１において、Ｒ１、Ｒ２、およびＲ３は、それぞれ、アルキル基、ハロゲン基、および水素のいずれかを表わす。　
Figure JPOXMLDOC01-appb-C000009
Figure JPOXMLDOC01-appb-C000010
<Coating material for negative electrode active material>
The covering material for a negative electrode active material according to the present invention is a polymer having a structural formula represented by Chemical Formula 1. In Chemical Formula 1, m 1 is the number of repeating structural units (the structural portion shown in parentheses in Chemical Formula 1). In Chemical Formula 1, Z is a site containing halogen and a site due to an ionic functional group such as a sulfo group (—SO 3 X), a carboxyl group (—COOX), a phosphate group (—O—PO (OX) 2 ), etc. It consists of. As the ionic functional group, a sulfo group is preferable from the viewpoint of reducing the resistance of the battery. By using a sulfo group, it becomes possible to increase the dissociation property with lithium ions, so that it is considered that the battery resistance can be reduced. A specific example in which Z is composed of a halogen-containing moiety and a sulfo group is shown in Chemical Formula 2. X is composed of hydrogen, an alkali metal, or an alkaline earth metal. Of these, alkali metals are preferable from the viewpoint of battery performance, and lithium and sodium are more preferable. In Chemical Formula 1, R 1 , R 2 , and R 3 each represent an alkyl group, a halogen group, or hydrogen.
Figure JPOXMLDOC01-appb-C000009
Figure JPOXMLDOC01-appb-C000010

　化学式２において、ｎ１およびｎ２はそれぞれ構造単位の繰り返し数である。繰り返し数ｎ１の構造単位はメチレン基で構成される。ｎ１は０以上２０以下の整数であることが好ましい。繰り返し数ｎ２の構造単位において、ＡおよびＢはそれぞれ、ハロゲンを含む官能基または水素から構成され、少なくともＡおよびＢのうち、いずれか一方にはハロゲンが含まれるように構成される。ハロゲンとしては、フッ素または塩素が好ましく、フッ素がより好ましい。ハロゲンとしてフッ素を含む官能基としては、フッ素およびＣＦ３が好ましい。化学式２のＡおよびＢとして、これらの官能基を用いることで、スルホ基の電子密度が低減されてイオンの解離性が高まるため、電池抵抗を低減できると考えられる。ハロゲンを含む官能基はスルホ基に隣接していること好ましい。即ち、化学式２において、Ｂにハロゲンを含む官能基が含まれることが好ましい。電池抵抗を低下させる観点から、化学式２において、ｎ２は１以上２０以下の整数であることが好ましく、１以上１０以下であることがより好ましい。なお、上記のハロゲン含有官能基とスルホ基に関する説明は、化学式２において、イオン性官能基としてスルホ基の代わりにカルボキシル基またはリン酸基が含まれて構成される場合についても同様に当てはまる。　
In Chemical Formula 2, n 1 and n 2 are the number of repeating structural units, respectively. The structural unit having the repeating number n 1 is composed of a methylene group. n 1 is preferably an integer of 0 or more and 20 or less. In the structural unit having the repeating number n 2 , A and B are each composed of a functional group containing hydrogen or hydrogen, and at least one of A and B is configured to contain halogen. As the halogen, fluorine or chlorine is preferable, and fluorine is more preferable. As the functional group containing fluorine as a halogen, fluorine and CF 3 are preferable. By using these functional groups as A and B in Chemical Formula 2, it is considered that the electron resistance of the sulfo group is reduced and the ion dissociation property is increased, so that battery resistance can be reduced. The functional group containing halogen is preferably adjacent to the sulfo group. That is, in Chemical Formula 2, it is preferable that B contains a functional group containing a halogen. From the viewpoint of reducing battery resistance, in Chemical Formula 2, n 2 is preferably an integer of 1 or more and 20 or less, and more preferably 1 or more and 10 or less. The explanation regarding the halogen-containing functional group and the sulfo group is similarly applied to the case where the ionic functional group includes a carboxyl group or a phosphate group instead of the sulfo group in Chemical Formula 2.

　化学式２の構造例として、化学式８～化学式１０を示す。これらの中で、溶媒への溶解性が最も良好なのは化学式８に示される構造であり、被覆材を調製する際の作業性は最もよいと考えられる。一方、化学式１０に示される構造は、溶媒への溶解性は化学式８で示される構造には及ばないが、スルホ基（イオン性官能基）に隣接してＣＦ３が配置されるので極性が大きく、イオンを移動させ易いことから、電池の抵抗を低減する効果はより大きいと考えられる。化学式９で示される構造については、溶媒への溶解性およびイオン移動の容易性はそれぞれ中間的なものであると考えられる。なお、化学式８～１０の構造式においては、ｎ１およびｎ２の値がいずれも１である場合の構造を示しているが、これらの値は上記範囲であれば同様の効果が得られる。　
Figure JPOXMLDOC01-appb-C000011
As structural examples of Chemical Formula 2, Chemical Formula 8 to Chemical Formula 10 are shown. Among these, the structure shown in Chemical Formula 8 has the best solubility in a solvent, and the workability when preparing the coating material is considered to be the best. On the other hand, the structure represented by Chemical Formula 10 is not as soluble in the solvent as the structure represented by Chemical Formula 8, but has a large polarity because CF 3 is disposed adjacent to the sulfo group (ionic functional group). Since it is easy to move ions, the effect of reducing the resistance of the battery is considered to be greater. Regarding the structure represented by Chemical Formula 9, the solubility in a solvent and the ease of ion transfer are considered to be intermediate. Note that the structural formulas of chemical formulas 8 to 10 show structures in which the values of n 1 and n 2 are both 1. However, if these values are within the above ranges, the same effect can be obtained.
Figure JPOXMLDOC01-appb-C000011

　化学式１の構造を持つポリマーは、その構造単位であるモノマーを重合することで作製する。モノマーの合成について、化学式１のＺの部分が化学式８に示した構造である場合を例に、図２を用いて説明する。　
A polymer having the structure of Chemical Formula 1 is produced by polymerizing a monomer as the structural unit. The synthesis of the monomer will be described with reference to FIG. 2, taking as an example the case where the Z portion in Chemical Formula 1 has the structure shown in Chemical Formula 8.

　まず、溶媒としてのテトラヒドロフランに塩化アクリルと図２に示した構造のアルコールを混合し撹拌する。次に、重合が起こることを防ぐために窒素ガスを吹き込みながら５０ ℃まで昇温する。この状態で約３時間撹拌することで、両者が反応して化学式８の構造を有する合成物が得られる。反応の際には塩化水素が発生するので、塩化水素を排気しながら撹拌を行う。合成物は、シリカゲルを充填剤として用いたカラムクロマトグラフィーにより精製することで純度が高められ、化学式８に示すモノマーが調製される。なお、化学式９および１０に示すモノマーについても上記と同様な方法で合成できる。　
First, acrylic chloride and alcohol having the structure shown in FIG. 2 are mixed with tetrahydrofuran as a solvent and stirred. Next, the temperature is raised to 50 ° C. while blowing nitrogen gas in order to prevent polymerization from occurring. By stirring for about 3 hours in this state, both react to obtain a compound having the structure of Chemical Formula 8. Since hydrogen chloride is generated during the reaction, stirring is performed while evacuating the hydrogen chloride. The synthesized product is purified by column chromatography using silica gel as a filler, whereby the purity is increased, and a monomer represented by Formula 8 is prepared. The monomers represented by Chemical Formulas 9 and 10 can also be synthesized by the same method as described above.

（重合方法）
　本発明に係る負極活物質用被覆材は、上記モノマーを重合させて作製する。重合は、従来から知られている、バルク重合、溶液重合、乳化重合のいずれによってもよい。重合方法は特に限定はされないが、ラジカル重合が好ましい。重合に際して、重合開始剤は使用してもしなくても構わないが、作業の容易さの点からはラジカル重合開始剤を用いることが好ましい。ラジカル重合開始剤を用いた重合に際しては、通常の温度範囲と重合時間で問題ない。本実施形態においては、重合開始剤の配合量を、重合させる化合物の質量に対して０．１質量％から２０質量％の範囲とすることが好ましく、０．３質量％から５質量％の範囲とすることがより好ましい。　
(Polymerization method)
The negative electrode active material coating material according to the present invention is produced by polymerizing the above monomers. The polymerization may be any of conventionally known bulk polymerization, solution polymerization, and emulsion polymerization. The polymerization method is not particularly limited, but radical polymerization is preferred. In the polymerization, a polymerization initiator may or may not be used, but a radical polymerization initiator is preferably used from the viewpoint of ease of work. In polymerization using a radical polymerization initiator, there is no problem in the normal temperature range and polymerization time. In the present embodiment, the blending amount of the polymerization initiator is preferably in the range of 0.1% by mass to 20% by mass with respect to the mass of the compound to be polymerized, and in the range of 0.3% by mass to 5% by mass. More preferably.

　本発明に係る負極活物質用被覆材は、化学式１に示したポリマーに相当するモノマー（主モノマー）とそれ以外のモノマー（共重合モノマー）とを共重合させた共重合体からなるものとしてもよい。共重合モノマーとしては、化学式３から化学式７に示す構造を含むモノマーが好ましい。なお、化学式３～７において、Ｙはアルカリ金属または水素を表わし、電気化学的安定性の観点からは、アルカリ金属であることが好ましい。
The coating material for negative electrode active material according to the present invention may be composed of a copolymer obtained by copolymerizing a monomer (main monomer) corresponding to the polymer represented by Chemical Formula 1 and another monomer (copolymerization monomer). Good. As the copolymerization monomer, a monomer having a structure represented by Chemical Formula 3 to Chemical Formula 7 is preferable. In the chemical formulas 3 to 7, Y represents an alkali metal or hydrogen, and is preferably an alkali metal from the viewpoint of electrochemical stability.
Figure JPOXMLDOC01-appb-C000012
 　共重合体からなる負極用被覆材とすることで、不可逆容量の改善が期待できる。その理由として考えられることは次の通りである。化学式１に示したポリマーによる被覆材は負極活物質に対する濡れ性が必ずしも十分とは言えない可能性があり、そのような場合、負極活物質の表面を被覆材が被覆しきれない部分が存在するものと考えられる。被覆しきれない部分においては、負極活物質と電解液が直接接触して、電解液の分解が起こることが考えられる。共重合した場合に負極活物質に対する濡れ性を向上させるようなモノマーを用いることで、負極活物質に対する濡れ性が向上し、負極活物質の表面のより多くの部分が被覆材で被覆されることが考えられる。その結果、電解液の分解が抑制されて不可逆容量をより小さくする効果が期待できる。化学式３～７に示すモノマーの中で、負極活物質に対する濡れ性の改善効果は、化学式３、４に示すモノマーが相対的に大きく、化学式６、７に示すモノマーはこの効果は相対的に小さいと考えられる。化学式５に示すモノマーはこの効果が中間的であると考えられる。　
Figure JPOXMLDOC01-appb-C000012
 An improvement in irreversible capacity can be expected by using a negative electrode coating material made of a copolymer. Possible reasons for this are as follows. There is a possibility that the coating material with the polymer represented by Chemical Formula 1 may not necessarily have sufficient wettability with respect to the negative electrode active material. In such a case, there is a portion where the surface of the negative electrode active material cannot be covered with the coating material. It is considered a thing. In a portion that cannot be covered, it is conceivable that the negative electrode active material and the electrolytic solution are in direct contact with each other and the electrolytic solution is decomposed. By using a monomer that improves the wettability to the negative electrode active material when copolymerized, the wettability to the negative electrode active material is improved, and more part of the surface of the negative electrode active material is coated with the coating material Can be considered. As a result, the effect of reducing the irreversible capacity by suppressing the decomposition of the electrolytic solution can be expected. Among the monomers represented by the chemical formulas 3 to 7, the effect of improving the wettability with respect to the negative electrode active material is relatively large for the monomers represented by the chemical formulas 3 and 4, and the effects for the monomers represented by the chemical formulas 6 and 7 are relatively small. it is conceivable that. The monomer represented by Formula 5 is considered to have an intermediate effect.

　なお、化学式１に示すポリマーと、化学式３～７に示すモノマーをそれぞれ重合させて得たポリマーの少なくとも１種とを混合したものを負極活物質用被覆材とすることも本発明に含まれる。　
In addition, the present invention includes a mixture of a polymer represented by Chemical Formula 1 and at least one polymer obtained by polymerizing monomers represented by Chemical Formulas 3 to 7 as a negative electrode active material coating material.

（ポリマーの構造）
　本発明において、ポリマーの構造は、直鎖構造、枝分かれ構造、架橋構造、デンドリマー構造のいずれであってもよい。負極活物質を被覆する際の作業性の観点からは直鎖構造のポリマーが好ましい。また、共重合させる際の重合様式は特に制限されないが、ランダム共重合、交互共重合、ブロック共重合、グラフト共重合等が挙げられる。　
(Polymer structure)
In the present invention, the polymer structure may be any of a linear structure, a branched structure, a crosslinked structure, and a dendrimer structure. From the viewpoint of workability when coating the negative electrode active material, a polymer having a linear structure is preferable. In addition, the polymerization mode for copolymerization is not particularly limited, and examples thereof include random copolymerization, alternating copolymerization, block copolymerization, and graft copolymerization.

（ポリマーの分子量）
　本発明に係る負極活物質用被覆材として用いるポリマーの数平均分子量は、1,000以上かつ5,000,000以下であり、好ましくは1,000以上かつ1,000,000以下である。数平均分子量を調整することにより負極活物質を被覆する際に起こりやすい、負極活物質の凝集を抑制することができる。なお、ここで言う「ポリマー」には共重合体も含まれる。　
(Molecular weight of polymer)
The number average molecular weight of the polymer used as the negative electrode active material coating material according to the present invention is 1,000 or more and 5,000,000 or less, preferably 1,000 or more and 1,000,000 or less. By adjusting the number average molecular weight, aggregation of the negative electrode active material, which tends to occur when the negative electrode active material is coated, can be suppressed. The “polymer” mentioned here includes a copolymer.

（共重合組成比）
　本発明において、化学式１で示すポリマーの構造単位であるモノマー（主モノマー）と共重合させるモノマー（共重合モノマー）との組成比は、 主モノマーのモル数をｘ、共重合モノマーのモル数をｙとした場合、０＜ｘ／（ｘ＋ｙ）≦１であり、好ましくは０．１≦ｘ／（ｘ＋ｙ）≦１であり、より好ましくは０．２５≦ｘ／（ｘ＋ｙ）≦０．７５である。主モノマーと共重合モノマーのモル比率を適当な範囲とすることにより、不可逆容量がより小さく、かつ、電池抵抗の低くすることが可能な負極活物質用被覆材が提供できる。　
(Copolymerization composition ratio)
In the present invention, the composition ratio of the monomer (main monomer), which is the structural unit of the polymer represented by Chemical Formula 1, to the monomer (copolymerization monomer) to be copolymerized is x for the number of moles of the main monomer, and When y, 0 <x / (x + y) ≦ 1, preferably 0.1 ≦ x / (x + y) ≦ 1, more preferably 0.25 ≦ x / (x + y) ≦ 0.75. is there. By setting the molar ratio of the main monomer and the copolymerization monomer to an appropriate range, a coating material for a negative electrode active material that has a smaller irreversible capacity and a low battery resistance can be provided.

　本発明に係る負極活物質用被覆材において、負極活物質に前記被覆材を被覆する方法については特に制限はない。コストの観点からは、負極活物質用被覆材を溶媒に溶解させた溶液を調製し、その溶液中に負極活物質を混合させた後、溶媒を蒸発させることで、負極活物質表面を被覆材により被覆することが好ましい。溶媒としては、ポリマーが良好に溶解すればよく、溶媒の種類には特に制限はない。水、エタノール等のプロトン性溶媒、Ｎ－メチルピロリドン等の非プロトン性溶媒、トルエン、ヘキサン等の非極性溶媒等を用いることができる。　
In the coating material for a negative electrode active material according to the present invention, the method for coating the negative electrode active material with the coating material is not particularly limited. From the viewpoint of cost, a negative electrode active material surface is prepared by preparing a solution in which a negative electrode active material coating material is dissolved in a solvent, mixing the negative electrode active material in the solution, and then evaporating the solvent. It is preferable to coat with. The solvent is not particularly limited as long as the polymer dissolves well. Protic solvents such as water and ethanol, aprotic solvents such as N-methylpyrrolidone, nonpolar solvents such as toluene and hexane, and the like can be used.

＜セパレータ＞　
　セパレータ１１は、正極１０および負極１２との間に挿入することで、正極１０と負極１２とが短絡することを防止する。セパレータの材料としては、ポリエチレン、ポリプロピレン等のポリオレフィン系高分子からなるシートや、ポリオレフィン系高分子と４フッ化ポリエチレン等からなるフッ素系高分子シートを積層させた２層構造のシート等を使用することが可能である。電池温度が高くなった場合にもセパレータが収縮しないようにするために、表面にセラミックスとバインダの混合物による薄い層を形成したシートを用いてもよい。セパレータ１１は、電池の充放電時にリチウムイオンを透過させる必要があるため、一般に直径が０．０１～１０μｍの多数の微細な孔が気孔率２０～９０％の範囲となるように設けられている。　
<Separator>
The separator 11 is inserted between the positive electrode 10 and the negative electrode 12 to prevent the positive electrode 10 and the negative electrode 12 from being short-circuited. As a material for the separator, a sheet made of a polyolefin polymer such as polyethylene or polypropylene, or a sheet having a two-layer structure in which a fluorine polymer sheet made of polyolefin polymer and tetrafluoropolyethylene is laminated is used. It is possible. In order to prevent the separator from contracting even when the battery temperature becomes high, a sheet having a thin layer formed of a mixture of ceramic and binder on the surface may be used. Since the separator 11 needs to allow lithium ions to pass therethrough during charge / discharge of the battery, generally, a large number of fine pores having a diameter of 0.01 to 10 μm are provided so as to have a porosity of 20 to 90%. .

＜電解質＞
　電解液としては、ジメチルカーボネート、ジエチルカーボネート、エチルメチルカーボネート等を、エチレンカーボネートに混合したものを溶媒として、この溶媒に電解質として六フッ化リン酸リチウム（ＬｉＰＦ６）、やホウフッ化リチウム（ＬｉＢＦ４）を溶解させたものが一般的に用いられる。ただし、溶媒や電解質の種類、それらの混合比には特に制限はなく、上記以外の電解液も利用可能である。　
<Electrolyte>
As an electrolytic solution, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate or the like mixed with ethylene carbonate is used as a solvent, and lithium hexafluorophosphate (LiPF 6 ) or lithium borofluoride (LiBF 4 ) is used as an electrolyte in this solvent. ) Is generally used. However, there are no particular restrictions on the type of solvent or electrolyte, and the mixing ratio thereof, and electrolytes other than those described above can also be used.

　電解液に使用可能な非水溶媒の例としては、プロピレンカーボネート、エチレンカーボネート、ブチレンカーボネート、ビニレンカーボネート、γ－ブチロラクトン、ジメチルカーボネート、ジエチルカーボネート、メチルエチルカーボネート、１、２－ジメトキシエタン、２－メチルテトラヒドロフラン、ジメチルスルフォキシド、１、３－ジオキソラン、ホルムアミド、ジメチルホルムアミド、プロピオン酸メチル、プロピオン酸エチル、リン酸トリエステル、トリメトキシメタン、ジオキソラン、ジエチルエーテル、スルホラン、３－メチル－２－オキサゾリジノン、テトラヒドロフラン、１、２－ジエトキシエタン、クロルエチレンカーボネート、フルオロエチレンカーボネート、またはクロルプロピレンカーボネート等が挙げられる。正極１０または負極１２において分解しない限り上記以外の溶媒を用いてもよい。　
Examples of non-aqueous solvents that can be used in the electrolyte include propylene carbonate, ethylene carbonate, butylene carbonate, vinylene carbonate, γ-butyrolactone, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane, 2-methyl Tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, methyl propionate, ethyl propionate, phosphate triester, trimethoxymethane, dioxolane, diethyl ether, sulfolane, 3-methyl-2-oxazolidinone, Tetrahydrofuran, 1,2-diethoxyethane, chloroethylene carbonate, fluoroethylene carbonate, chloropropylene carbonate, etc. . Solvents other than those described above may be used as long as they do not decompose in the positive electrode 10 or the negative electrode 12.

　電解質としては、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＣｌＯ４、ＬｉＣＦ３ＳＯ３、ＬｉＣＦ３ＣＯ２、ＬｉＡｓＦ６、ＬｉＳｂＦ６、リチウムトリフルオロメタンスルホンイミドに代表されるリチウムのイミド塩等、多種類のリチウム塩が使用可能である。これらのリチウム塩を上記各種の非水溶媒に溶解させた非水電解液を使用することができる。正極１０または負極１２において分解しない限り上記以外の電解質を用いてもよい。　
As the electrolyte, LiPF 6, LiBF 4, LiClO 4, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, imide salts such as lithium represented by lithium trifluoromethane sulfonimide, many kinds of lithium salt It can be used. Nonaqueous electrolytes in which these lithium salts are dissolved in the above various nonaqueous solvents can be used. An electrolyte other than the above may be used as long as it does not decompose in the positive electrode 10 or the negative electrode 12.

　固体高分子電解質（ポリマー電解質）としては、ポリエチレンオキシド、ポリアクリロニトリル、ポリフッ化ビニリデン、ポリメタクリル酸メチル、ポリヘキサフルオロプロピレン、ポリエチレンオキサイド等のイオン伝導性ポリマーを用いることができる。これらの固体高分子電解質を用いた場合には、セパレータ１１を省略することができるという利点がある。　
As the solid polymer electrolyte (polymer electrolyte), ion conductive polymers such as polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, polyhexafluoropropylene, and polyethylene oxide can be used. When these solid polymer electrolytes are used, there is an advantage that the separator 11 can be omitted.

　イオン性液体を電解液として用いることもできる。イオン性液体としては、例えば、1-ethyl-3-methylimidazolium tetrafluoroborate（ＥＭＩ－ＢＦ４）、リチウム塩ＬｉＮ（ＳＯ２ＣＦ３）２（ＬｉＴＦＳＩ）とトリグライムとテトラグライムとの混合錯体、環状四級アンモニウム系陽イオン（例えば、N-methyl-N-propylpyrrolidinium）、および、イミド系陰イオン（例えば、bis(fluorosulfonyl)imide）から、正極１０または負極１２において分解しないような組み合わせを選択して用いることができる。
An ionic liquid can also be used as the electrolyte. Examples of the ionic liquid include 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI-BF4), a mixed salt of lithium salt LiN (SO 2 CF 3 ) 2 (LiTFSI), triglyme and tetraglyme, and a cyclic quaternary ammonium type. A combination that does not decompose in the positive electrode 10 or the negative electrode 12 can be selected from a cation (for example, N-methyl-N-propylpyrrolidinium) and an imide anion (for example, bis (fluorosulfonyl) imide). .

（実施例１）
＜負極活物質用被覆材の作製＞
　反応容器内に化学式１１で示すモノマーＡと反応溶媒としてのテトロヒドロフランを投入し、さらに重合開始剤としてAIBN（アゾイソブチルニトリル）を加え、温度６０℃で３時間加熱することで、化学式１におけるＺの部分が化学式８の構造を有するポリマーＡを重合した。なお、化学式８におけるＸの部分はＬｉ（リチウム）とした。また、重合開始剤の濃度はモノマーの質量に対して４質量％とした。ポリマーＡは本発明に係る負極活物質用被覆材に相当するものである。
Example 1
<Preparation of coating material for negative electrode active material>
Into the reaction vessel, monomer A represented by Chemical Formula 11 and Tetrohydrofuran as a reaction solvent were added, AIBN (azoisobutylnitrile) was further added as a polymerization initiator, and heated at a temperature of 60 ° C. for 3 hours. Polymer A was polymerized where the Z moiety had the structure of Formula 8. In addition, the part of X in Chemical formula 8 was Li (lithium). The concentration of the polymerization initiator was 4% by mass with respect to the mass of the monomer. The polymer A corresponds to the coating material for a negative electrode active material according to the present invention.
Figure JPOXMLDOC01-appb-C000013
 ＜負極活物質用被覆材による負極活物質の被覆＞
　負極活物質用被覆材としての上記ポリマーＡを溶媒としての水に溶解させた溶液を調整し、その中に負極活物質としてのグラファイト粒子を投入して撹拌し混合させた後、水を蒸発させることにより、負極活物質としてのグラファイト粒子の表面を負極活物質用被覆材としてのポリマーＡで被覆した。負極活物質の質量に対する被覆材の被覆量は０．５ｗｔ％とした。　
Figure JPOXMLDOC01-appb-C000013
 <Coating of negative electrode active material with a coating material for negative electrode active material>
A solution in which the polymer A as a coating material for a negative electrode active material is dissolved in water as a solvent is prepared, and graphite particles as a negative electrode active material are put into the mixture, stirred and mixed, and then water is evaporated. By this, the surface of the graphite particle as a negative electrode active material was coat | covered with the polymer A as a coating material for negative electrode active materials. The coating amount of the coating material with respect to the mass of the negative electrode active material was 0.5 wt%.

＜負極の作製＞
　ポリマーＡで被覆した負極活物質としてのグラファイトと、バインダとしてのポリフッ化ビニリデンとを、質量比が９５：５となるように混合して混合物を調製し、この混合物を溶媒としてのＮ－メチル－２－ピロリドンに投入して混合し、負極合剤スラリーを調製した。この負極合剤スラリーを、厚さ10 μｍの銅箔にドクターブレード法にて塗布した後、溶媒を蒸発させ、さらにプレスを行なって、負極合剤のかさ密度が１．５ ｇ／ｃｍ３で形成された負極を作製した。　
<Production of negative electrode>
Graphite as a negative electrode active material coated with polymer A and polyvinylidene fluoride as a binder were mixed at a mass ratio of 95: 5 to prepare a mixture, and this mixture was used as a solvent with N-methyl- The mixture was put into 2-pyrrolidone and mixed to prepare a negative electrode mixture slurry. After applying this negative electrode mixture slurry to a copper foil having a thickness of 10 μm by a doctor blade method, the solvent was evaporated, and further pressing was performed, so that the bulk density of the negative electrode mixture was 1.5 g / cm 3 . The formed negative electrode was produced.

＜負極の評価＞
　作製した負極を、直径１５ｍｍの円形に打ち抜いて評価用電極を作製した。評価用電極とＬｉ金属電極との間にセパレータを挟んで容器内に挿入し、電解液を注入して評価用セルを作製した。評価用セルを、予め設定した下限電圧まで電流密度０．７２ｍＡ／ｃｍ２で充電した後、予め設定した上限電圧まで電流密度０．７２ｍＡ／ｃｍ２で放電した。下限電圧は０．０１Ｖ、上限電圧は１．５Ｖとした。充放電時に得られた充電容量と放電容量の差から不可逆容量を求めた。　
<Evaluation of negative electrode>
The produced negative electrode was punched into a circle having a diameter of 15 mm to produce an evaluation electrode. A separator was sandwiched between the evaluation electrode and the Li metal electrode, and the sample was inserted into the container, and an electrolytic solution was injected to prepare an evaluation cell. The evaluation cell was charged at a current density of 0.72 mA / cm 2 to a preset lower limit voltage, and then discharged at a current density of 0.72 mA / cm 2 to a preset upper limit voltage. The lower limit voltage was 0.01V, and the upper limit voltage was 1.5V. The irreversible capacity was determined from the difference between the charge capacity and the discharge capacity obtained during charge / discharge.
＜電池の作製＞
　上記評価用電極と同じものを作製した。負極としての評価用電極と正極との間にセパレータを挟んで電池容器に挿入し、電池容器内に電解液を注入して評価用電池を作製した。なお、正極は次の手順で作製した。 <Production of battery>
The same electrode as the above evaluation electrode was produced. A separator was sandwiched between the evaluation electrode as the negative electrode and the positive electrode and the battery was inserted into the battery container, and an electrolytic solution was injected into the battery container to produce an evaluation battery. The positive electrode was produced by the following procedure.
　正極活物質としてＬｉＣｏＯ２、導電剤として黒鉛（ＳＰ２７０：日本黒鉛工業製）、バインダとしてポリフッ化ビニリデンを、質量比が８５：７．５：７．５の割合となるように混合し、溶媒としてのＮ－メチル－２－ピロリドンを加えて粘度を調整し、正極合剤スラリーを調製した。この正極合剤スラリーを、厚さ２０μｍのアルミニウム箔の表面にドクターブレード法により塗布した後、溶媒を蒸発させ、さらにプレスすることにより正極を作製した。正極合剤塗布量は２００ｇ／ｍ2 であった。 LiCoO 2 as a positive electrode active material, graphite (SP270: manufactured by Nippon Graphite Industries) as a conductive agent, and polyvinylidene fluoride as a binder are mixed so as to have a mass ratio of 85: 7.5: 7.5. N-methyl-2-pyrrolidone was added to adjust the viscosity to prepare a positive electrode mixture slurry. This positive electrode mixture slurry was applied to the surface of an aluminum foil having a thickness of 20 μm by a doctor blade method, and then the solvent was evaporated and further pressed to produce a positive electrode. The coating amount of the positive electrode mixture was 200 g / m 2 .

＜直流抵抗の評価方法＞
　評価用電池を、予め設定した上限電圧まで電流密度０．７２ｍＡ／ｃｍ２で充電した後、予め設定した下限電圧まで電流密度０．７２ｍＡ／ｃｍ２で放電した。上限電圧は４．２Ｖ、下限電圧は３．０Ｖとした。放電時に得られた放電容量を電池の初期容量とした。次に、初期容量の５０％まで充電し、その際の直流抵抗を測定した。　
<Evaluation method of DC resistance>
The battery for evaluation was charged at a current density of 0.72 mA / cm 2 to a preset upper limit voltage, and then discharged at a current density of 0.72 mA / cm 2 to a preset lower limit voltage. The upper limit voltage was 4.2V, and the lower limit voltage was 3.0V. The discharge capacity obtained during discharge was taken as the initial capacity of the battery. Next, the battery was charged to 50% of the initial capacity, and the DC resistance at that time was measured.

（実施例２）
　負極活物質用被覆材を次の手順で作製した。即ち、化学式１２で示すモノマーＢを、実施例１と同様の手順により重合させて、化学式１におけるＺの部分が化学式９の構造を有するポリマーＢを重合した。なお、化学式９におけるＸの部分はＬｉとした。負極活物質の質量に対する被覆材の被覆量は０．５ｗｔ％とした。上記の負極活物質用被覆材に変更した以外は、実施例１と同様の手順により、不可逆容量と直流抵抗を測定した。ポリマーＢは本発明に係る負極活物質用被覆材に相当するものである。
(Example 2)
A coating material for a negative electrode active material was prepared by the following procedure. That is, the monomer B represented by the chemical formula 12 was polymerized by the same procedure as in Example 1 to polymerize the polymer B in which the Z portion in the chemical formula 1 has the structure of the chemical formula 9. Note that X in Chemical Formula 9 was Li. The coating amount of the coating material with respect to the mass of the negative electrode active material was 0.5 wt%. The irreversible capacity and DC resistance were measured by the same procedure as in Example 1 except that the above-described negative electrode active material coating material was used. Polymer B corresponds to the negative electrode active material coating material according to the present invention.
Figure JPOXMLDOC01-appb-C000014
 （実施例３）
　負極活物質用被覆材を次の手順で作製した。即ち、化学式１３で示すモノマーＣを、実施例１と同様の手順により重合させて、化学式１におけるＺの部分が化学式１０の構造を有するポリマーＣを重合した。なお、化学式１０におけるＸの部分はＬｉとした。負極活物質の質量に対する被覆材の被覆量は０．５ｗｔ％とした。上記の負極活物質用被覆材に変更した以外は、実施例１と同様の手順により、不可逆容量と直流抵抗を測定した。ポリマーＣは本発明に係る負極活物質用被覆材に相当するものである。
Figure JPOXMLDOC01-appb-C000014
 Example 3
A coating material for a negative electrode active material was prepared by the following procedure. That is, the monomer C represented by the chemical formula 13 was polymerized by the same procedure as in Example 1 to polymerize the polymer C in which the Z portion in the chemical formula 1 has the structure of the chemical formula 10. Note that X in Chemical Formula 10 was Li. The coating amount of the coating material with respect to the mass of the negative electrode active material was 0.5 wt%. The irreversible capacity and DC resistance were measured by the same procedure as in Example 1 except that the above-described negative electrode active material coating material was used. The polymer C corresponds to the negative electrode active material coating material according to the present invention.
Figure JPOXMLDOC01-appb-C000015
 （実施例４）
　負極活物質用被覆材を次手順で作製した。即ち、モノマーＡ（主モノマー）と、化学式５に示したモノマー（共重合モノマー）を、７５：２５のモル比となるように混合した後、重合させて負極活物質用被覆材としての共重合ポリマーＤを合成した。なお、化学式５におけるＹの部分はＬｉとした。負極活物質の質量に対する被覆材の被覆量は０．５ｗｔ％とした。上記の負極活物質用被覆材に変更した以外は、実施例１と同様の手順により、不可逆容量と直流抵抗を測定した。　
Figure JPOXMLDOC01-appb-C000015
 Example 4
A coating material for a negative electrode active material was prepared by the following procedure. That is, the monomer A (main monomer) and the monomer shown in Chemical Formula 5 (copolymerization monomer) are mixed so as to have a molar ratio of 75:25, and then polymerized to copolymerize as a coating material for the negative electrode active material. Polymer D was synthesized. Note that the Y portion in Chemical Formula 5 was Li. The coating amount of the coating material with respect to the mass of the negative electrode active material was 0.5 wt%. The irreversible capacity and DC resistance were measured by the same procedure as in Example 1 except that the above-described negative electrode active material coating material was used.

（実施例５）
　モノマーＡ（主モノマー）と、化学式５に示したモノマー（共重合モノマー）とのモル比を５０：５０として共重合ポリマーＥとしたこと以外は、実施例４と同様の手順で不可逆容量と直流抵抗を測定した。　
(Example 5)
The irreversible capacity and direct current were the same as in Example 4 except that the copolymer A was prepared by setting the molar ratio of the monomer A (main monomer) and the monomer (copolymerized monomer) shown in Chemical Formula 5 to 50:50. Resistance was measured.

（実施例６）
　モノマーＡ（主モノマー）と、化学式５に示したモノマー（共重合モノマー）とのモル比を２５：７５として共重合ポリマーＦとしたこと以外は、実施例４と同様の手順で不可逆容量と直流抵抗を測定した。　
(Example 6)
The irreversible capacity and direct current were the same as in Example 4 except that the copolymer A was prepared by setting the molar ratio of the monomer A (main monomer) and the monomer (copolymerized monomer) shown in Chemical Formula 5 to 25:75. Resistance was measured.

　以上の説明した実施例１～６において求めた不可逆容量と直流抵抗の測定結果を図３の表に一覧表として示す。図３には、各実施例における負極活物質用被覆材の組成についても示す。　
The measurement results of the irreversible capacity and DC resistance obtained in Examples 1 to 6 described above are shown as a list in the table of FIG. In FIG. 3, it shows also about the composition of the coating material for negative electrode active materials in each Example.

（比較例）
　被覆材により被覆しない負極活物質を用いたこと以外は実施例１と同様の手順で不可逆容量と直流抵抗を測定した。測定結果を図３に示す。　
(Comparative example)
The irreversible capacity and DC resistance were measured in the same procedure as in Example 1 except that a negative electrode active material not covered with a coating material was used. The measurement results are shown in FIG.

　図３からわかる通り、不可逆容量に関して、比較例では２５．４ｍＡｈｇ－１であるのに対して、実施例１～６では、いずれも２５ｍＡｈｇ－１を下回っている。このことから、本発明に係る負極活物質用被覆材により表面を被覆した負極活物質を用いて負極を作製したことにより、不可逆容量を小さくできたことがわかる。また、実施例４～６では２４ｍＡｈｇ－１を下回る低い値が得られている。このことから、共重合体からなる被覆材を用いたことにより、不可逆容量をより一層小さくできたことがわかる。直流抵抗に関しては、比較例では１１．５Ωであるのに対して、実施例１～６では、いずれも１１Ωを下回っており、本発明に係る負極活物質用被覆材により表面を被覆した負極活物質を用いて負極を作製したことにより、電池抵抗を低くできたことがわかる。　
As can be seen from FIG. 3, the irreversible capacity is 25.4 mAhg −1 in the comparative example, whereas in Examples 1 to 6, all are lower than 25 mAhg −1 . From this, it can be seen that the irreversible capacity could be reduced by producing the negative electrode using the negative electrode active material whose surface was coated with the negative electrode active material coating material according to the present invention. In Examples 4 to 6, a low value lower than 24 mAhg −1 was obtained. From this, it can be seen that the irreversible capacity could be further reduced by using the coating material made of a copolymer. The direct current resistance was 11.5Ω in the comparative example, whereas all of Examples 1 to 6 were less than 11Ω, and the negative electrode active material whose surface was coated with the coating material for negative electrode active material according to the present invention. It can be seen that the battery resistance can be lowered by producing the negative electrode using the substance.
　なお、化学式８～１０におけるＸで示した部分について、いずれの実施例においてもＬｉとしたが、Ｘが水素の場合およびＬｉ以外のアルカリ金属やアルカリ土類金属の場合であっても同様の効果が得られる。また、化学式３～７に示した構造におけるＹで示した部分について、いずれの実施例においてもＬｉとしたが、Ｙが水素の場合およびＬｉ以外のアルカリ金属の場合であっても同様の効果が得られる。 In the examples, X in the chemical formulas 8 to 10 is Li in all examples, but the same effect can be obtained even when X is hydrogen or an alkali metal or alkaline earth metal other than Li. Is obtained. In addition, the portion indicated by Y in the structures shown in the chemical formulas 3 to 7 is Li in any of the examples, but the same effect can be obtained even when Y is hydrogen or an alkali metal other than Li. can get.
　以上説明した通り、本発明によれば、不可逆容量を小さく、かつ、電池抵抗を低くすることが可能なリチウムイオン二次電池負極活物質用被覆材、および、前記被覆材で被覆したリチウムイオン二次電池負極を提供できる。 As described above, according to the present invention, a coating material for a negative electrode active material for a lithium ion secondary battery capable of reducing the irreversible capacity and the battery resistance, and a lithium ion secondary coated with the coating material. A secondary battery negative electrode can be provided.

　上記の通り、種々の実施の形態および変形例について説明したが、本発明はこれらの内容に限定されるものではない。本発明の技術的思想の範囲内で考えられるその他の態様も本発明の範囲内に含まれる。
As described above, various embodiments and modifications have been described, but the present invention is not limited to these contents. Other embodiments conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

１　リチウムイオン二次電池
１０　正極
１１　セパレータ
１２　負極
１３　電池容器
１４　正極集電タブ
１５　負極集電タブ
１６　内蓋
１７　内圧解放弁
１８　ガスケット
１９　正温度抵抗素子
DESCRIPTION OF SYMBOLS 1 Lithium ion secondary battery 10 Positive electrode 11 Separator 12 Negative electrode 13 Battery container 14 Positive electrode current collection tab 15 Negative electrode current collection tab 16 Inner lid 17 Internal pressure release valve 18 Gasket 19 Positive temperature resistance element

Claims (15)

  1. 　化学式１で表されるポリマーからなるリチウムイオン二次電池負極活物質用被覆材であって、
    Figure JPOXMLDOC01-appb-C000001
     　前記化学式１において、
    　　Ｚは化学式２で表される構造を有し、Ｒ１、Ｒ２、およびＲ３はそれぞれ、アルキル基、ハロゲン基、および水素基のいずれかを表わし、
    Figure JPOXMLDOC01-appb-C000002
     　　ｍ１、ｎ１、およびｎ２はそれぞれ、構造単位の繰り返し数を表わし、
    　前記化学式２において、
    　　ＡおよびＢはそれぞれ、ハロゲン元素を含む官能基または水素を表わし、少なくともＡおよびＢのうちの一方はハロゲン元素を含む官能基であり、
    　　Ｘは、水素、アルカリ金属、およびアルカリ土類金属のいずれかを表わすことを特徴とするリチウムイオン二次電池負極活物質用被覆材。     A covering material for a negative electrode active material for a lithium ion secondary battery comprising a polymer represented by Chemical Formula 1,
    Figure JPOXMLDOC01-appb-C000001
     In Formula 1,
    Z has a structure represented by Chemical Formula 2, and R 1 , R 2 , and R 3 each represent an alkyl group, a halogen group, or a hydrogen group,
    Figure JPOXMLDOC01-appb-C000002
     m 1 , n 1 , and n 2 each represent the number of repeating structural units;
    In Formula 2,
    A and B each represents a functional group containing a halogen element or hydrogen, and at least one of A and B is a functional group containing a halogen element;
    X is a covering material for a negative electrode active material for a lithium ion secondary battery, wherein X represents any one of hydrogen, an alkali metal, and an alkaline earth metal.
  2. 　請求項１に記載のリチウムイオン二次電池負極活物質用被覆材において、ｎ１は０以上かつ２０以下の整数であり、ｎ２は１以上２０以下の整数であることを特徴とするリチウムイオン二次電池負極活物質用被覆材。 In the lithium ion secondary battery negative electrode active material for dressing according to claim 1, n 1 is 0 or more and 20 or less an integer, n 2 is lithium ion, which is a 1 to 20 integer Covering material for secondary battery negative electrode active material.
  3. 　請求項１または２に記載のリチウムイオン二次電池負極活物質用被覆材において、
    　Ｘはリチウムであることを特徴とするリチウムイオン二次電池負極活物質用被覆材。     In the covering material for lithium ion secondary battery negative electrode active materials according to claim 1 or 2,
    A covering material for a negative electrode active material for a lithium ion secondary battery, wherein X is lithium.
  4. 　リチウムイオン二次電池負極活物質用被覆材であって、
    　前記被覆材は、化学式１で表されるポリマーの構造単位に相当する第１モノマーと、化学式３～７に示す第２モノマーのうちの少なくとも１種と、を共重合させた共重合体からなり、
    Figure JPOXMLDOC01-appb-C000003
    Figure JPOXMLDOC01-appb-C000004
     　前記化学式１において、
    　　Ｚは化学式２で表される構造を有し、Ｒ１、Ｒ２、およびＲ３はそれぞれ、アルキル基、ハロゲン基、および水素基のいずれかを表わし、
    Figure JPOXMLDOC01-appb-C000005
     　　ｍ１、ｎ１、およびｎ２はそれぞれ、構造単位の繰り返し数を表わし、
    　前記化学式２において、
    　　ＡおよびＢはそれぞれ、ハロゲン元素を含む官能基または水素を表わし、少なくともＡおよびＢのうちの一方はハロゲン元素を含む官能基であり、
    　　Ｘは、水素、アルカリ金属、およびアルカリ土類金属のいずれかを表わし、
    　前記化学式３～７において、Ｙはアルカリ金属または水素を表わすことを特徴とするリチウムイオン二次電池負極活物質用被覆材。     A covering material for a negative electrode active material of a lithium ion secondary battery,
    The coating material comprises a copolymer obtained by copolymerizing a first monomer corresponding to a structural unit of a polymer represented by Chemical Formula 1 and at least one of the second monomers represented by Chemical Formulas 3 to 7. ,
    Figure JPOXMLDOC01-appb-C000003
    Figure JPOXMLDOC01-appb-C000004
     In Formula 1,
    Z has a structure represented by Chemical Formula 2, and R 1 , R 2 , and R 3 each represent an alkyl group, a halogen group, or a hydrogen group,
    Figure JPOXMLDOC01-appb-C000005
     m 1 , n 1 , and n 2 each represent the number of repeating structural units;
    In Formula 2,
    A and B each represents a functional group containing a halogen element or hydrogen, and at least one of A and B is a functional group containing a halogen element;
    X represents any one of hydrogen, an alkali metal, and an alkaline earth metal,
    A covering material for a negative electrode active material for a lithium ion secondary battery, wherein Y in the chemical formulas 3 to 7 represents an alkali metal or hydrogen.
  5. 　請求項４に記載のリチウムイオン二次電池負極活物質用被覆材において、ｎ１は０以上かつ２０以下の整数であり、ｎ２は１以上２０以下の整数であることを特徴とするリチウムイオン二次電池負極活物質用被覆材。 The lithium ion secondary battery negative electrode active material coating material according to claim 4, wherein n 1 is an integer of 0 or more and 20 or less, and n 2 is an integer of 1 or more and 20 or less. Covering material for secondary battery negative electrode active material.
  6. 　請求項４または５に記載のリチウムイオン二次電池負極活物質用被覆材において、
    　Ｘはリチウムであることを特徴とするリチウムイオン二次電池負極活物質用被覆材。     In the covering material for lithium ion secondary battery negative electrode active materials according to claim 4 or 5,
    A covering material for a negative electrode active material for a lithium ion secondary battery, wherein X is lithium.
  7. 　請求項４～６のいずれか１項に記載のリチウムイオン二次電池負極活物質用被覆材において、
    　Ｙはリチウムまたはナトリウムであることを特徴とするリチウムイオン二次電池負極活物質用被覆材。     The lithium ion secondary battery negative electrode active material coating material according to any one of claims 4 to 6,
    A covering material for a negative electrode active material for a lithium ion secondary battery, wherein Y is lithium or sodium.
  8. 　請求項４～７のいずれか１項に記載のリチウムイオン二次電池負極活物質用被覆材において、
    　前記共重合体は、前記第１モノマーと前記第２モノマーのモル数をそれぞれ、ｘおよびｙとした場合、ｘ／（ｘ＋ｙ）の値が、０．１以上かつ１以下であることを特徴とするリチウムイオン二次電池負極活物質用被覆材。     The covering material for a negative electrode active material for a lithium ion secondary battery according to any one of claims 4 to 7,
    The copolymer is characterized in that the value of x / (x + y) is not less than 0.1 and not more than 1 when the number of moles of the first monomer and the second monomer is x and y, respectively. A covering material for a negative electrode active material for a lithium ion secondary battery.
  9. 　請求項８に記載のリチウムイオン二次電池負極活物質用被覆材において、
    　前記共重合体は、ｘ／（ｘ＋ｙ）の値が、０．２５以上かつ０．７５以下であることを特徴とするリチウムイオン二次電池負極活物質用被覆材。     In the covering material for lithium ion secondary battery negative electrode active materials according to claim 8,
    The said copolymer has a value of x / (x + y) being 0.25 or more and 0.75 or less, The covering material for lithium ion secondary battery negative electrode active materials characterized by the above-mentioned.
  10. 　請求項１～９のいずれか１項に記載のリチウムイオン二次電池負極活物質用被覆材において、
    　前記被覆材の数平均分子量は、１０００以上かつ５００００００以下であることを特徴とするリチウムイオン二次電池負極活物質用被覆材。     The lithium ion secondary battery negative electrode active material coating material according to any one of claims 1 to 9,
    The number average molecular weight of the said covering material is 1000 or more and 5 million or less, The covering material for lithium ion secondary battery negative electrode active materials characterized by the above-mentioned.
  11. 　請求項１０に記載のリチウムイオン二次電池負極活物質用被覆材において、
    　前記被覆材の数平均分子量は、１０００以上かつ１００００００以下であることを特徴とするリチウムイオン二次電池負極活物質用被覆材。     In the covering material for lithium ion secondary battery negative electrode active materials according to claim 10,
    The number average molecular weight of the said covering material is 1000 or more and 1 million or less, The covering material for lithium ion secondary battery negative electrode active materials characterized by the above-mentioned.
  12. リチウムイオン二次電池用負極活物質であって、
    　前記負極活物質は、請求項１～１１のいずれか１項に記載のリチウムイオン二次電池用負極活物質用被覆剤により表面が被覆されていることを特徴とするリチウムイオン二次電池用負極活物質。
    A negative electrode active material for a lithium ion secondary battery,
    A negative electrode for a lithium ion secondary battery, the surface of the negative electrode active material being coated with the coating agent for a negative electrode active material for a lithium ion secondary battery according to any one of claims 1 to 11. Active material.
  13. 　請求項１２に記載のリチウムイオン二次電池用負極活物質において、
    　前記負極活物質用被覆剤による前記負極活物質表面の被覆量は、前記負極活物質の質量に対して、０．０１質量％以上かつ１０質量％以下であることを特徴とするリチウムイオン二次電池用負極活物質。     The negative electrode active material for a lithium ion secondary battery according to claim 12,
    The covering amount of the negative electrode active material surface by the negative electrode active material coating agent is 0.01% by mass or more and 10% by mass or less based on the mass of the negative electrode active material. Negative electrode active material for batteries.
  14. 　請求項１２または１３に記載のリチウムイオン二次電池用負極活物質を負極に用いたリチウムイオン二次電池。 A lithium ion secondary battery using the negative electrode active material for a lithium ion secondary battery according to claim 12 or 13 as a negative electrode.
  15. 　請求項１４に記載のリチウムイオン二次電池を用いた電池システム。 A battery system using the lithium ion secondary battery according to claim 14.
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