WO2015088252A1 - Materiau actif d'anode pour batterie au lithium-ion et procede de fabrication associe - Google Patents

Materiau actif d'anode pour batterie au lithium-ion et procede de fabrication associe Download PDF

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WO2015088252A1
WO2015088252A1 PCT/KR2014/012162 KR2014012162W WO2015088252A1 WO 2015088252 A1 WO2015088252 A1 WO 2015088252A1 KR 2014012162 W KR2014012162 W KR 2014012162W WO 2015088252 A1 WO2015088252 A1 WO 2015088252A1
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active material
silicon
fine particles
lithium ion
ion secondary
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PCT/KR2014/012162
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English (en)
Korean (ko)
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고바야시나오야
엔도모리노부
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삼성정밀화학 주식회사
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Priority claimed from JP2013255082A external-priority patent/JP6391237B2/ja
Priority claimed from JP2014236002A external-priority patent/JP2016100178A/ja
Priority claimed from JP2014236003A external-priority patent/JP2016100179A/ja
Application filed by 삼성정밀화학 주식회사 filed Critical 삼성정밀화학 주식회사
Priority to KR1020167015570A priority Critical patent/KR20160088338A/ko
Publication of WO2015088252A1 publication Critical patent/WO2015088252A1/fr

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/44—Methods for charging or discharging
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • 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 negative electrode active material for a lithium ion secondary battery, a method for producing a negative electrode active material for a lithium ion secondary battery, a method for charging a lithium ion secondary battery and a lithium ion secondary battery.
  • Carbon materials such as graphite are mainly used as a negative electrode material of the present lithium ion battery.
  • high capacity using graphite is mainly aimed at improving electrode density, but further high capacity has reached its limit.
  • As a next-generation material having a larger discharge capacity than graphite research and development on a silicon-based active material is in progress.
  • the silicon-based active material has a problem that the cycle life is shortened because it involves a lot of volume change when alloying with lithium.
  • the silicon-based active material may decompose the solvent when contacted with the solvent during the electrochemical reaction.
  • Solvent decomposition products are deposited on the silicon-based active material to prevent lithium ions from entering and exiting the silicon-based active material.
  • the silicon-based active material is broken by the volume change during charging and discharging, and a new side (the side where the solvent decomposition product is not deposited) appears, the part newly reacts with the solvent. And the charge and discharge cycle is repeated, the reaction is increased. This also shortens the cycle life.
  • Non-Patent Literature 1 causes the silicon-based active material, specifically, the silicon particles to be pulverized to coat the silicon material with the carbon material. According to the above technique, as the silicon particles are made into fine particles, the absolute amount of the volume change is reduced while the contact between the silicon fine particles and the solvent is suppressed by the carbon material, so that the cycle life can be improved.
  • Non-Patent Document 1 Journal of Power Sources 222 (2013) 400-409
  • silicon fine particles have a problem of being easy to oxidize in the atmosphere. Oxidized silicon fine particles, ie silicon oxide, inevitably react with lithium ions during initial charging. Therefore, more silicon oxide increases the irreversible capacity. In the technique disclosed in Non-Patent Document 1, the silicon particles were pulverized in the air, and thus, the silicon fine particles were exposed to the air during the pulverization. So this problem could not be solved.
  • the present invention has been made in view of the above problems, and an object of the present invention is to provide a new and improved lithium ion secondary battery capable of improving cycle life of a lithium ion secondary battery while maintaining a high discharge capacity of a silicon-based active material.
  • a negative electrode active material, a manufacturing method of a negative electrode active material for lithium ion secondary batteries, a lithium ion secondary battery, and the charging method of a lithium ion secondary battery are provided.
  • the negative electrode active material for lithium ion secondary batteries containing the silicon-based active material microparticles
  • fine-particles is provided.
  • the total mass of the said carbon material is 0.35-3.5 mass% with respect to the total mass of the said silicon type active material microparticles
  • the cycle life is particularly improved when the coating amount of the carbon material is within the above range.
  • the silicon crab active material fine particles may be polycrystalline.
  • the stress due to expansion and contraction of the silicon-based active material can be alleviated by the space formed inside the polycrystal.
  • the average particle diameter of a silicon type active material microparticle is 200 nm or less.
  • the cycle life is improved while the irreversible capacity of a lithium ion secondary battery is reduced.
  • the thickness of a carbon material is 2-20 nm.
  • the cycle life is improved while the irreversible capacity of a lithium ion secondary battery is reduced.
  • the first step of producing a dispersion solution in which silicon-based active material fine particles dispersed in the non-aqueous solvent by pulverizing the silicon-based active material in the non-aqueous solvent, and the organic material dissolved in the non-aqueous solvent is dispersed The negative electrode for lithium ion secondary batteries containing the 2nd process of manufacturing a mixed solution by melt
  • a method for producing an active material is provided.
  • the silicon-based active material fine particles are hard to be exposed to the atmosphere in the first to third processes, so that a negative electrode active material containing less silicon oxide can be produced.
  • the negative electrode active material is coated with a carbon material, the silicon-based active material fine particles are hardly exposed to the atmosphere during use of the negative electrode active material.
  • the irreversible capacity is reduced.
  • the high discharge capacity of the silicon-based active material can be maintained.
  • the negative electrode active material is assembled to the lithium ion secondary battery, direct contact between the silicon-based active material fine particles and the solvent can be suppressed.
  • the total mass of the carbon material is preferably 0.35 to 3.5 mass% with respect to the total mass of the silicon-based active material fine particles and the carbon material.
  • the cycle life is particularly improved when the coating amount of the carbon material is within the above range.
  • the average particle diameter of a silicon type active material microparticle is 200 nm or less here.
  • the cycle life is improved while the irreversible capacity of a lithium ion secondary battery is reduced.
  • the thickness of a carbon material is 2-20 nm.
  • the cycle life is improved while the irreversible capacity of a lithium ion secondary battery is reduced.
  • the organic material may be any one or more selected from the group consisting of hydroxy acids, monosaccharides and oligosaccharides.
  • the cycle life is improved while the irreversible capacity of a lithium ion secondary battery is reduced.
  • hydroxy acid may be any one or more selected from the group consisting of citric acid and glycolic acid.
  • the cycle life is improved while the irreversible capacity of a lithium ion secondary battery is reduced.
  • non-aqueous solvent may be any one or more selected from the group consisting of alcohols and ethers.
  • the cycle life is improved while the irreversible capacity of a lithium ion secondary battery is reduced.
  • Inert atmosphere may be composed of any one or more selected from the group consisting of argon and nitrogen.
  • the firing may be carried out in a temperature range of 500 ⁇ 800 °C.
  • the surface-modified fine particles having a silicon-based active material fine particles and a carbon material covering the surface of the silicon-based active material fine particles and lithium having hard carbon composited with the surface-modified fine particles
  • a negative active material for an ion secondary battery is provided.
  • the total mass of the said carbon material is 0.35-3.5 mass% with respect to the total mass of the said silicon-based active material fine particle and the said carbon material.
  • the silicon-based active material fine particles are coated with a carbon material, the silicon-based active material fine particles are hardly exposed to the atmosphere during the use of the surface modified fine particles. Therefore, the irreversible capacity of the negative electrode active material is reduced. In other words, the high discharge capacity of the silicon-based active material can be maintained. In addition, direct contact between the silicon-based active material fine particles and the solvent is suppressed. Therefore, the cycle life of the lithium ion secondary battery can be improved.
  • the surface modified fine particles are also introduced into the hard carbon as it is complexed with the hard carbon. Therefore, the stress due to expansion and contraction of the surface-modified fine particles is alleviated by the hard carbon, so the cycle life is improved in this respect. In addition, it is possible to introduce a large amount of surface-modified fine particles in the hard carbon to improve the theoretical capacity, that is, the discharge capacity of the negative electrode active material.
  • the silicon-based active material fine particles may have a cylindrical shape.
  • the hard carbon may be obtained by firing a solid starting material, and the total mass of the surface modified fine particles is preferably 50 to 80% by mass relative to the total mass of the hard carbon and the surface modified fine particles.
  • the irreversible capacity of a lithium ion secondary battery reduces, and the cycle life of a lithium ion secondary battery improves.
  • the starting material of the solid system may be any one or more selected from the group consisting of PVC, sucrose, gelatin and agar.
  • the hard carbon may be obtained by firing the starting material of the liquid system, and the total mass of the surface modified fine particles is preferably 75 to 90 mass% with respect to the total mass of the hard carbon and the surface modified fine particles.
  • the starting material of the liquid system is preferably any one selected from the group consisting of resol type phenol resins and furfuryl alcohol.
  • the axial length of the silicon-based active material fine particles is preferably 500 nm or less and the diameter is 50 nm or less.
  • the thickness of a carbon material is 2-20 nm.
  • the first step of producing a dispersion solution in which silicon-based active material fine particles dispersed in a non-aqueous solvent by pulverizing the silicon-based active material in a non-aqueous solvent, and the organic material dissolved in the non-aqueous solvent to the dispersion solution A second step of producing a mixed solution by dissolving; a third step of producing surface-modified fine particles coated with a carbon material on the surface of the silicon-based active material fine particles by firing the mixed solution under an inert atmosphere;
  • a method for producing a negative electrode active material for a lithium ion secondary battery comprising a fourth step of preparing a negative electrode active material by mixing a starting material of carbon and firing in an inert atmosphere.
  • the total mass of the said carbon material is 0.35-3.5 mass% with respect to the total mass of the said silicon-based active material fine particle and the said carbon material.
  • the silicon-based active material fine particles are hard to be exposed to the atmosphere in the first to third processes, and thus surface-modified fine particles having less silicon oxide can be produced.
  • the surface-modified fine particles are coated with a carbon material, the silicon-based active material fine particles are hardly exposed to the atmosphere during use of the surface-modified fine particles. Therefore, the irreversible capacity of the negative electrode active material is reduced. In other words, the high discharge capacity of the silicon-based active material can be maintained.
  • direct contact between the silicon-based active material fine particles and the solvent is suppressed. Therefore, the cycle life of the lithium ion secondary battery can be improved.
  • the surface modified fine particles are introduced into the hard carbon by complexing with the hard carbon.
  • the stress due to expansion and contraction of the surface-modified fine particles is alleviated by the hard carbon, so the cycle life is improved in this respect.
  • a large amount of surface-modified fine particles can be introduced into the hard carbon, thereby improving the theoretical capacity, that is, the discharge capacity of the negative electrode active material.
  • the silicon-based active material fine particles have a circumferential shape, it is possible to suppress the absolute amount of expansion shrinkage, particularly the absolute amount of expansion shrinkage in the direction perpendicular to the axial direction (diameter direction). This also improves cycle life.
  • At least one of the inert atmosphere of the third process and the fourth process may be composed of any one or more selected from the group consisting of argon and nitrogen.
  • the firing of the fourth process may be performed in a temperature range of 500 ⁇ 800 °C.
  • a lithium ion secondary battery comprising the negative electrode active material.
  • the metal lithium foil may be disposed on a part of the negative electrode current collector.
  • a charging method of a lithium ion secondary battery wherein the charging capacity of the lithium ion secondary battery is maintained at 70% or less of the theoretical capacity implemented by the silicon-based active material fine particles.
  • the cycle life of the lithium ion secondary battery can be improved while maintaining the high discharge capacity of the silicon-based active material.
  • FIG. 1 is a side cross-sectional view schematically showing the configuration of a lithium ion secondary battery according to an embodiment of the present invention.
  • FIG. 2 is a graph showing a correspondence relationship between firing temperature, initial efficiency, and cycle life.
  • 5 is a TEM photograph of a negative electrode active material.
  • Fig. 6 is a graph showing the theoretical capacities between the negative electrode active material of the present embodiment and the conventional negative electrode active material.
  • FIG. 7 is a graph showing a comparison between the charge capacity and the uncharged capacity of the negative electrode active material of the present embodiment and the conventional negative electrode active material.
  • FIG. 8 is a graph showing a correspondence relationship between a charge ratio of a silicon-based active material, discharge capacity, and cycle life of a lithium ion secondary battery.
  • FIG. 9 is a graph showing a correspondence relationship between firing temperature, initial efficiency, and cycle life in a fourth process.
  • FIG. 10 is a graph showing a correspondence relationship between Si / hard carbon ratio and cycle life.
  • Fig. 13 is a graph showing the correspondence relationship between the firing temperature, the initial efficiency, and the cycle life of the third process.
  • 15 is a STEM photograph of the silicon-based active material fine particles according to the present embodiment.
  • FIG. 16 is an enlarged view of FIG. 15.
  • Fig. 19 is a TEM photograph of single crystal silicon active material fine particles.
  • 20 is a graph showing a correspondence relationship between a charge ratio of a silicon-based active material, discharge capacity, and cycle life of a lithium ion secondary battery.
  • 21 is a graph showing a correspondence relationship between firing temperature, initial efficiency, and cycle life in a fourth process.
  • FIG. 23 is a graph showing a correspondence relationship between Si / hard carbon ratio and cycle life.
  • 24 is a graph showing the correspondence relationship between the discharge test environment temperature and the discharge capacity.
  • 25 is a graph showing the correspondence relationship between the firing temperature, the initial efficiency, and the cycle life of the third process.
  • Fig. 26 is a graph showing the correspondence relationship between the C / Si ratio of the surface modified fine particles, the initial efficiency, and the cycle life.
  • 27 is a graph showing the correspondence relationship between Si average particle diameter and cycle life.
  • 29 is a TEM photograph of single crystal silicon-based active material fine particles.
  • the silicon-based active material involves a large volume change when alloying with lithium. Therefore, when the silicon-based active material is used as the negative electrode active material of the lithium ion secondary battery, the negative electrode active material layer expands and contracts during charge and discharge, and as a result, the cycle life of the lithium ion secondary battery is shortened.
  • the silicon-based active material decomposes the solvent when contacted with the solvent during the electrochemical reaction. Decomposition products of the solvent deposit on the silicon-based active material, thereby preventing lithium ions from entering and exiting the silicon-based active material.
  • the present inventors made the basis of suppressing the volume change of the negative electrode active material layer containing a silicon type active material (reducing the absolute value of volume change) by making a silicon type active material into fine particles similarly to the technique of the nonpatent literature 1 here.
  • the fine particles of the silicon-based active material have a problem of being easily oxidized by oxygen in the atmosphere.
  • the oxidized silicon-based active material ie, silicon oxide
  • the silicon-based active material since the silicon-based active material was pulverized in the air, the silicon-based active material was exposed to the air during the pulverization. Therefore, this problem could not be solved.
  • the silicon type active material is grind
  • the inventors found that by adding an organic substance dissolved in a nonaqueous solvent to a nonaqueous solvent in which silicon-based active material fine particles are dispersed, a mixed solution is produced and the mixed solution is baked in an inert atmosphere. By this treatment, the silicon-based active material fine particles are coated with the carbon material. Therefore, the silicon-based active material fine particles coated with the carbon material is inhibited from being oxidized by the carbon material.
  • the coating method of the carbon material according to the present embodiment can be implemented at a lower cost than the coating method disclosed in Non-Patent Document 1 (a method of coating the carbon material on the silicon fine particles by the chemical vapor phase method using acetylene gas).
  • the present inventors came up with using the silicon type active material microparticles
  • the silicon-based active material itself has low conductivity, it is difficult to introduce lithium ions into the negative electrode active material layer (layer including the negative electrode active material) when the silicon-based active material is used as the negative electrode active material.
  • the silicon-based active material is made into fine particles to improve the specific surface area of the negative electrode active material layer, and the surface of the silicon-based active material can be coated with a carbon material to improve the conductivity of the negative electrode active material. Therefore, lithium ions are easily introduced into the negative electrode active material layer. According to the present embodiment described above, it is possible to improve the cycle life of the lithium ion secondary battery at low cost while maintaining the high discharge capacity of the silicon-based active material.
  • the lithium ion secondary battery 10 includes a positive electrode 20, a negative electrode 30, and a separator layer 40.
  • the charge arrival voltage (redox potential) of the lithium ion secondary battery 10 is, for example, 4.3 V ( ⁇ s.Li / Li + ) or more and 5.0 V or less, particularly 4.5 V or more and 5.0 V or less.
  • the form of the lithium ion secondary battery 10 is not particularly limited. That is, the lithium ion secondary battery 10 may be any one of a cylindrical shape, a square shape, a laminate type, and a button type.
  • the positive electrode 20 includes a current collector 21 and a positive electrode active material layer 22.
  • the current collector 21 may be any conductor, and is composed of, for example, aluminum, stainless steel, nickel coated steel, or the like.
  • the positive electrode active material layer 22 may include at least a positive electrode active material and may further include a conductive agent and a binder.
  • the positive electrode active material is, for example, a solid solution oxide including lithium, but is not particularly limited as long as it is a material capable of electrochemically storing and releasing lithium ions.
  • Solid solution oxides include Li a Mn x Co y Ni z O 2 (1.150 ⁇ a ⁇ 1.430, 0.45 ⁇ x ⁇ 0.6, 0.10 ⁇ y ⁇ 0.15, 0.20 ⁇ z ⁇ 0.28), LiMn x Co y Ni z O 2 (0.3 ⁇ x ⁇ 0.85, 0.10 ⁇ y ⁇ 0.3, 0.10 ⁇ z ⁇ 0.3), and LiMn 1.5 Ni 0.5 O 4 .
  • the conductive agent is, for example, carbon black such as Ketjen black, acetylene black, natural graphite, artificial graphite, or the like, but is not particularly limited as long as it is for enhancing the conductivity of the positive electrode.
  • the binder is not particularly limited as long as the binder binds the positive electrode active material and the conductive agent onto the current collector 21.
  • the binder for example, polyimide, polyvinylidene fluoride, ethylene-propylene-diene terpolymer, styrene-butadiene rubber, acrylonitrile butadiene rubber (acrylonitrile-butadiene rubber), fluororubber, polyvinyl acetate, polymethylmethacrylate, polyethylene, cellulose nitrate, etc., but a positive electrode active material and a conductive agent Is not particularly limited as long as the binder is bound on the current collector 21.
  • the negative electrode 30 includes a current collector 31 and a negative electrode active material layer 32.
  • the current collector 31 is a conductor, and is preferably an electrochemically stable material that does not dissolve or is difficult to alloy with lithium, and is made of, for example, copper, stainless steel, nickel plated steel, or the like.
  • the negative electrode active material layer 32 includes a negative electrode active material and a binder.
  • silicon-based active material fine particles are coated with a carbon material.
  • the silicon-based active material is a material containing silicon (atoms) and capable of occluding and releasing lithium ions electrochemically.
  • fine-particles of a silicon compound, etc. are mentioned, for example.
  • the silicon compound is not particularly limited as long as it is used as a negative electrode active material of a lithium ion secondary battery.
  • a silicon compound etc. are mentioned, for example.
  • a silicon alloy Si-Ti-Ni alloy, Si-Al-Fe alloy, etc. are mentioned, for example.
  • the average particle diameter of the silicon-based active material fine particles is preferably as small as possible.
  • the average particle diameter of the silicon-based active material fine particles is preferably 200 nm or less, and even more preferably 100 nm or less. In the case where the average particle diameter of the silicon-based active material fine particles falls within these ranges, the cycle life is particularly improved.
  • an average particle diameter of a silicon type active material particle can be made into about 50-60 nm by making grinding time into 30 hours or more, for example.
  • the average particle diameter of the silicon-based active material particles is a diameter when the silicon-based active material particles are viewed in a spherical shape, and can be measured, for example, by a laser diffraction / scattering particle size distribution analyzer.
  • the particle size distribution of the silicon-based active material fine particles is measured by a laser diffraction / scattering particle size distribution analyzer and the average particle size arithmetic average value of the silicon-based active material fine particles is calculated based on the particle size distribution.
  • the carbon material is formed on the surface of the silicon-based active material fine particles by firing an organic material together with the silicon-based active material fine particles.
  • the carbon material contains carbon as a main component.
  • the thickness of a carbon material is not specifically limited, It is preferable to exist in the range of 2-20 nm. When the thickness of the carbon material exceeds 20 nm, lithium entry and exit of the silicon-based active material may be inhibited. When the thickness of the carbon material is less than 2 nm, the carbon material becomes difficult to suppress direct contact between the silicon-based active material and the electrolyte solution. However, the thickness of the carbon material can be measured by direct observation in the TEM or by argon etching by XPS. An example of a TEM is shown in FIG. Region A represents a silicon-based active material and region B represents a carbon material.
  • the total mass of a carbon material is 0.35-3.5 mass% with respect to the coating amount of a carbon material, ie, the total mass of a silicon type active material microparticle and a carbon material. This is because the cycle life is particularly improved when the coating amount of the carbon material becomes a value within the above range, as shown in Examples described later.
  • the coating amount of the carbon material can be measured, for example, by a differential thermal analyzer or the like.
  • the preferable coating amount of a carbon material is 0.7-1.75 mass%.
  • the silicon-based active material fine particles are coated with a carbon material, the silicon-based active material fine particles are hardly exposed to the atmosphere. Therefore, oxidation of the silicon-based active material fine particles is suppressed. This reduces the initial irreversible capacity.
  • direct contact between the silicon-based active material fine particles and the electrolyte solution is suppressed, decomposition of the solvent is suppressed. Thus, cycle life is improved.
  • the binder may be the same as the binder constituting the positive electrode active material layer 22.
  • carboxymethyl cellulose hereinafter, CMC
  • CMC carboxymethyl cellulose
  • content of the binder containing a thickener is 1 mass% or more and 10 mass% or less with respect to the gross mass of a negative electrode mixture. Battery content especially improves when content of the binder containing a thickener is these ranges.
  • the separator layer 40 includes a separator and an electrolyte solution.
  • the separator is not particularly limited, and any separator may be used as long as it is used as a separator of a lithium ion secondary battery.
  • As a separator it is preferable to use together or use a porous film, a nonwoven fabric, etc. which show the outstanding high rate discharge performance.
  • the resin constituting the separator include polyolefin resins represented by polyethylene, polypropylene, and the like, polyethylene terephthalate, polybutylene terephthalate, and the like.
  • polyester resin PVDF, vinylidene fluoride (VDF) -hexafluoropropylene (HFP) copolymer, vinylidene fluoride-perfluoro vinyl ether, vinylidene fluoride tetra Fluoroethylene (tetrafluoroethylene) copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-fluoroethylene copolymer, vinylidene fluoride-hexafluoroacetone copolymer, vinylidene fluoride- Ethylene copolymer, vinylidene fluoride-propylene copolymer, Vinylidene fluoride (trifluoro propylene) copolymer, vinylidene fluoride (tetrafluoroethylene) -hexafluoropropylene copolymer, vinylidene fluoride (ethylene) -tetrafluoroethylene copolymer Coalescence, etc. are
  • the nonaqueous electrolyte may be used without particular limitation as the same as the nonaqueous electrolyte used in lithium secondary batteries.
  • the nonaqueous electrolyte has a composition in which an electrolyte salt is contained in the nonaqueous solvent.
  • non-aqueous solvent for example, cyclic carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, chloroethylene carbonate and vinylene carbonate
  • Cyclic esters such as ⁇ -butyrolactone and ⁇ -valerolactone; dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate Chain carbonates; chain esters such as methyl formate, methyl acetate, butyric acid methyl; tetrahydrofuran or derivatives thereof; 1,3-dioxane , 1,4-dioxane, 1,2-dimethoxyethane, 1,4-dibutoxyethane, methyl diglyme, etc.
  • Ethers such as acetonitrile and benzonitrile
  • dioxolane or derivatives thereof ethylene sulfide, sulfolane, sultone ( sultone) or derivatives thereof, or a mixture of two or more thereof, and the like, but are not limited thereto.
  • the concentration of the electrolyte salt may be the same as the nonaqueous electrolyte used in the conventional lithium secondary battery, and there is no particular limitation.
  • concentration of about 0.8-1.5 mol / L can be used.
  • additives can be added to the nonaqueous electrolyte.
  • Such additives include negative electrode action additives, positive electrode action additives, ester additives, carbonate ester additives, sulfuric acid ester additives, phosphate ester additives, boric acid ester additives, acid anhydride additives, and electrolyte type additives. Additives etc. are mentioned. Any of these species may be added to the nonaqueous electrolyte, and a plurality of kinds of additives may be added to the nonaqueous electrolyte.
  • the positive electrode 20 is produced as follows. First, a slurry is formed by dispersing the mixture of the positive electrode active material, the conductive agent and the binder in the above ratio in a solvent (for example, N-methyl-2-pyrrolidone). Subsequently, the positive electrode active material layer 22 is formed by forming (for example, coating) and drying the slurry on the current collector 21.
  • the coating method is not particularly limited. As a coating method, the knife coater method, the gravure coater method, etc. can be considered, for example. Each following coating process is also performed by the same method. Then, the positive electrode active material layer 22 is pressed to a density within the above range by a press. Thereby, the positive electrode 20 is produced.
  • the cathode 30 is manufactured as follows. First, the manufacturing method of a negative electrode active material is demonstrated. The manufacturing method of a negative electrode active material is divided roughly into three processes below. In the first step, the silicon-based active material is pulverized in the non-aqueous solvent to prepare a dispersion solution in which the silicon-based active material fine particles are dispersed in the non-aqueous solvent. That is, in the first step, the silicon-based active material is granulated by wet pulverization of the silicon-based active material. According to this method, oxidation of a silicon type active material is suppressed at the time of grinding
  • non-aqueous solvent used for the wet grinding of the first step it is possible to suppress the reagglomeration of the silicon-based active material fine particles without reacting with the silicon-based active material, so that it is industrially economical and can dissolve the organic material which is the carbon source in the second step. It is preferable. In detail, alcohols, such as ethanol and methanol, an ether, etc. are preferable. These nonaqueous solvents may be used alone or in combination of two or more kinds thereof.
  • an apparatus used for the wet grinding of a 1st process For example, a ball mill apparatus, a planetary ball mill apparatus, a bead mill apparatus, etc. which use a media can be used. It is preferable to use an electrochemically inert ceramic material such as zirconium oxide, alumina, or the like for the media and the device container in order to reduce the influence of impurities as much as possible.
  • the media particle diameter (diameter) such as zirconium oxide or alumina is preferably small, and 50 to 100 ⁇ m or less is preferable.
  • a mixed solution is prepared by dissolving an organic substance dissolved in a nonaqueous solvent in a dispersion solution.
  • Organic materials which can be used in the second step can be dissolved in a nonaqueous solvent, and a material having a high content of carbon is preferable. By using such an organic substance, it is easy to form a dense carbon material film.
  • the content rate of carbon is 10.7-44.1 mass% with respect to the gross mass of an organic substance.
  • the content rate of oxygen the range of 16.7-63.1 mass% is preferable with respect to the gross mass of an organic substance.
  • hydroxy acid, monosaccharide, oligosaccharide, etc. are mentioned, for example.
  • Examples of the hydroxy acid include citric acid and glycolic acid.
  • monosaccharides erythritol, D-erythrulose, D-erythrose, D-threose, and D-arabinose , L-arabinose, D-xylulose, L-xylulose, D-xylose, D-lyxose ( D-lyxose, L-Lixose, D-ribulose, D-idose, D-quinoose, glucari gymd , D-digitoxose, D-cymarose, 2-deoxy D-glucose, L-fucose, D -D-psicose, D-fructose, L-rhamnose, L-Iduronic acid, D-glucuronic acid ), And the like.
  • oligosaccharides isomaltose, rutinose and the like can be given.
  • the organic substance can use any one of
  • an organic substance 10 mass% or less is preferable with respect to the mass of a dispersion solution, 5 mass% or less is more preferable, and 2 mass% or less is more preferable.
  • the lower limit is not particularly limited as long as the parameters required for the carbon material are filled.
  • the mixed solution is baked in an inert atmosphere to coat the carbon material on the surface of the silicon-based active material fine particles. This produces a negative electrode active material.
  • Inert atmosphere here can be implemented by argon, nitrogen, etc., for example. These gases can be used alone or in combination.
  • the firing temperature considering the temperature at which carbonization of the organic material proceeds, 550 ° C. or more is preferable. Moreover, as for an upper limit temperature, 800 degrees C or less which generation of SiC by reaction of a silicon and carbon does not produce is preferable. The optimum temperature depends on the type of organic material used for firing.
  • a negative electrode active material is produced by the above process. As described above, in the second to third processes, the silicon-based active material fine particles are present in the nonaqueous solvent and thus are not exposed to the atmosphere. Therefore, oxidation at the time of baking is also suppressed.
  • the coating method of the carbon material by this embodiment can be implement
  • the same process as that of the positive electrode 20 is performed. That is, a slurry is formed by disperse
  • the negative electrode active material layer 32 is formed by forming (for example, coating) and drying the slurry on the current collector 31. Then, the negative electrode active material layer 32 is pressed by a press. As a result, the cathode 30 is produced.
  • the electrode structure is produced by placing the separator between the positive electrode 20 and the negative electrode 30.
  • the electrode structure is then processed into a desired shape (eg cylindrical, square, laminated, buttoned, etc.) and inserted into a container of that shape.
  • the electrolyte is impregnated into the pores in the separator by injecting the electrolyte solution of the composition into the vessel. Thereby, a lithium ion secondary battery is produced.
  • Example 1-1 a negative electrode active material was produced by the following steps.
  • Silicon particles having an average particle diameter of 25 ⁇ m are added in a proportion of 10% by mass based on the total mass of ethanol and silicon particles, and with a zirconium oxide beads having a diameter (particle diameter) of 50 ⁇ m, Rabostar mini manufactured by Ashiyawa Finetech Co., Ltd. (Labstar) LMZ015.
  • grains was measured using the laser diffraction / scattering type particle size distribution analyzer LA-920 by Horiba Corporation. Specifically, the particle size distribution was measured using the above apparatus, and the arithmetic mean value of the particle size was calculated based on the particle size distribution.
  • the input amount of zirconium oxide beads was 80 volume% with respect to the container volume.
  • the circumferential speed of the agitator was operated for 24 hours at 12 m / s. This produced the dispersion solution which the silicon type active material microparticles
  • the average particle diameter of the silicon-based active material fine particles was measured by the same method as that of the silicon particles, but the average particle diameter was 110 nm.
  • a mixed solution was prepared by adding and mixing 2 g of citric acid (2% by mass based on the total mass of the dispersion solution) with respect to 100 g of the dispersion solution prepared in the first step.
  • the mixed solution prepared in the second step was transferred to a ceramic crucible and installed in a quartz glass tube furnace. After argon gas was sufficiently flowed into the tube furnace at 500 cm 3 / min, the temperature inside the tube furnace was raised to 600 ° C. at a speed of 2.5 ° C./min. After that, the inside of the tube furnace was kept at 600 ° C. for 5 hours, and naturally cooled to reach room temperature, and then the crucible was taken out.
  • the negative electrode active material was produced by grind
  • the carbon material coating amount on the silicon-based active material was calculated as follows. That is, the weight loss of citric acid was measured using a differential thermal analyzer EXSTAR6000 manufactured by Seiko Instruments, Inc., and the carbonization rate of citric acid was calculated from the result, which was 3.57% by mass. And the mass% with respect to the total mass of the silicon type active material microparticles
  • the element of the thickness direction of the negative electrode active material was analyzed by analyzing the surface of the negative electrode active material with the X-ray photoelectron spectroscopy apparatus AXIS-ULTRA-DLD by a Kratos company. This measured the thickness of a carbon material. As a result, the thickness of the carbon material was measured at 3 nm.
  • the surface of the negative electrode active material was analyzed using a transmission electron microscope (TEM) JEOL-2010 FEF manufactured by Nippon Electronics Co., Ltd., and the thickness of the carbon material was 2 to 10 nm.
  • TEM transmission electron microscope
  • the mixed solution was produced by adding 40 mass parts of negative electrode active materials and 45 mass parts of graphite to the polyimide solution which added and melt
  • a lithium foil was prepared as a counter electrode, and an electrode structure was produced by laminating a lithium foil and a negative electrode through a polyethylene separator having a thickness of 20 ⁇ m.
  • the 2032 type coin battery was produced by adding 0.1 cm ⁇ 3> of 1M-LiPF6EC / DEC (1: 1) electrolyte solution to an electrode structure.
  • the battery was charged and discharged using a charge-discharge tester BTS2010 manufactured by Index Corporation. Charged and discharged at 0.05 C at 1 to 2 cycles, 0.1 C at 3 to 4 cycles, and then 0.5 C. Charging was carried out with a constant current constant voltage, discharge was made with a constant current, and the voltage range was 0.02-1.5V, and the test temperature was 25 degreeC.
  • initial efficiency was made into the charging / discharging efficiency (discharge amount / charge amount) of 1st cycle, and cycle life was made into the number of cycles when discharge capacity falls below 90% by charge / discharge at 0.5C.
  • Example 1-1 It processed similarly to Example 1-1 except having used the isomaltose of an oligosaccharide as an organic substance.
  • Example 1-1 It processed similarly to Example 1-1 except using erythritol of a monosaccharide as an organic substance.
  • Example 1-1 It processed similarly to Example 1-1 except using the silicon type active material microparticles
  • Example 1-1 to 3 and Comparative Example 1-1 are compared with Table 1, and are shown. However, in Table 1, the initial efficiency and cycle life of Examples 1-1 to 3 are shown by normalizing it by the comparative example 1-1.
  • Example 1-1 the initial efficiency of Example 1-1 (coating silicon material with fine particles of silicon-based active material) was 16 compared with that of Comparative Example 1-1 (without coating carbon material with silicon-based active materials fine particles).
  • the cycle life was improved by 2.7 times.
  • the silicon-based active material fine particles are coated by the carbon material as a reason for the improvement of the initial efficiency, and it can be considered that direct contact between the silicon-based active material fine particles and oxygen in the atmosphere is suppressed. That is, in Example 1-1, production of silicon oxide, which is a major factor of the initial irreversible capacity, was suppressed.
  • the reason why the cycle life is improved can be considered that the direct contact between the silicon-based active material fine particles and the solvent is suppressed by the carbon material.
  • Example 1-2, 1-3 and Example 1-1 the initial efficiency of Example 1-2 was better than the initial efficiency of Example 1-1.
  • the cycle life of Example 1-3 was better than the cycle life of Example 1-1.
  • Example 4 carried out Example 4 to confirm the correspondence between the firing temperature and the characteristics of the lithium ion secondary battery.
  • Example 1-4 it processed similarly to Example 1-1 except having changed the baking temperature in the 400-900 degreeC range in the 3rd process of Example 1-1.
  • the results are shown in FIG. 2 represents the firing temperature and the vertical axis represents the initial efficiency and cycle life.
  • initial stage efficiency and cycle life show the value normalized as the comparative example 1-1.
  • the initial efficiency was higher than Comparative Example 1-1 between 400 and 900 ° C
  • the cycle life was higher than Comparative Example 1-1 between 550 and 800 ° C. Therefore, it is preferable that baking temperature is 550-800 degreeC.
  • the reason why the cycle life and initial efficiency are lowered when the firing temperature is less than 400 ° C is that carbonization of the organic material is less likely to proceed at a lower firing temperature and the coating amount of the carbon material is lowered.
  • the firing temperature is 900 ° C, the initial efficiency and cycle life are greatly reduced.
  • generation of electrochemically inert SiC can be considered. In other words, it is thought that the reactivity with carbon is increased by making the silicon-based active material fine, and SiC is partially produced even at 900 ° C.
  • Example 1-5 in order to confirm the correspondence relationship of the mass% of a carbon material with the characteristic of a lithium ion secondary battery with respect to the coating amount of a carbon material, ie, the total mass of a silicon type active material particle and a carbon material.
  • it processed similarly to Example 1-1 except having changed the coating amount of the carbon material in the range of 0.07-6.7 mass% by changing the amount of citric acid addition in the 2nd process of Example 1-1.
  • the results are shown in FIG. 3 represents the coating amount of the carbon material (mass% of the carbon material, C / Si ratio to the total mass of the silicon-based active material fine particles and the carbon material), and the vertical axis represents the initial efficiency and the cycle life.
  • initial stage efficiency and cycle life show the value normalized as the comparative example 1-1.
  • the cycle life and initial efficiency are maximized when the carbon material coverage is 0.7-1.75 mass%.
  • the coating amount of the carbon material falls within this range, it is considered that the carbon material hardly inhibits the movement of lithium ions and the oxidation inhibiting effect of the silicon-based active material fine particles by the carbon material is maximized.
  • Example 1-6 performed Example 1-6 in order to confirm the correspondence relationship between the average particle diameter of a silicon type active material microparticle, and the characteristic of a lithium ion secondary battery.
  • it processed similarly to Example 1-1 except having changed the average particle diameter of the silicon type active material microparticles
  • the result is shown in FIG. 4, the horizontal axis represents the average particle diameter of the silicon-based active material fine particles, and the vertical axis represents the cycle life. However, cycle life shows the value normalized as the comparative example 1-1.
  • the cycle life fluctuated rapidly, especially around 200nm.
  • the graph shape is estimated to be maximized below 100nm. Accordingly, the average particle diameter is preferably 200 nm or less, and even more preferably 100 nm or less.
  • the average particle diameter can be selected in terms of cost and performance.
  • Example 1-7 This inventor performed the following Example 1-7 to confirm that the same effect is acquired also in other silicon type active material.
  • it processed similarly to Example 1-1 except having replaced the silicon of Example 1-1 with the silicon alloy (Si: Al: Fe 55: 29: 16 (mass ratio)).
  • fine-particles are hard to expose to air
  • the negative electrode active material is coated with a carbon material, so that the silicon-based active material fine particles are hardly exposed to the atmosphere during use of the negative electrode active material. Therefore, the irreversible capacity is reduced. In other words, the high discharge capacity of the silicon-based active material can be maintained.
  • the negative electrode active material is placed in a lithium ion secondary battery, direct contact between the silicon-based active material fine particles and the solvent is suppressed.
  • the 1st-3rd process can be implemented at low cost than the technique disclosed by the nonpatent literature 1. Therefore, the cycle life of the lithium ion secondary battery can be improved at low cost.
  • the average particle diameter of the silicon-based active material fine particles can be 200 nm or less. In this case, the irreversible capacity of the lithium ion secondary battery is reduced, and the cycle life is also improved.
  • the thickness of the carbon material can be 2 to 20 nm. In this case, the irreversible capacity of the lithium ion secondary battery is reduced, and the cycle life is also improved.
  • the organic material may be any one or more selected from the group consisting of hydroxy acids, monosaccharides and oligosaccharides, in which case the irreversible capacity of the lithium ion secondary battery is reduced while the cycle life is also improved.
  • the hydroxy acid may be any one or more selected from the group consisting of citric acid and glycolic acid.
  • the irreversible capacity of the lithium ion secondary battery is reduced while the cycle life is also improved.
  • non-aqueous solvent may be any one or more selected from the group consisting of alcohols and ethers, in which case the irreversible capacity of the lithium ion secondary battery is reduced while the cycle life is also improved.
  • the inert atmosphere may be composed of any one or more selected from the group consisting of argon and nitrogen, in which case the irreversible capacity of the lithium ion secondary battery is reduced while the cycle life is also improved.
  • baking can be performed within the temperature range of 550-800 degreeC, In this case, the irreversible capacity
  • the silicon type active material was grind
  • the inventors found that by adding an organic substance dissolved in a nonaqueous solvent to a nonaqueous solvent in which silicon-based active material fine particles are dispersed, a mixed solution is produced and the mixed solution is baked in an inert atmosphere. This treatment coats the silicon-based active material fine particles with a carbon material. Therefore, the silicon-based active material fine particles (hereinafter referred to as "surface modified fine particles”) coated with the carbon material are inhibited from being oxidized by the carbon material.
  • the silicon-based active material fine particles are present in the nonaqueous solvent, and thus are difficult to be exposed to the atmosphere. Therefore, oxidation during grinding and firing is also suppressed.
  • the coating method of the carbon material which concerns on this embodiment can be implement
  • the inventors further examined further suppressing the volume change of the negative electrode active material layer.
  • the silicon-based active material also had a problem of rapid deterioration when the charge up to full charge was repeated. Here, this inventor also examined this problem.
  • Hard carbon has a structure in which skeleton particles having the same layered structure as graphite are randomly arranged, and a plurality of gaps are formed between the skeleton particles. Therefore, in the hard carbon, a large number of spaces capable of absorbing stress due to expansion and contraction of the surface-modified fine particles, in particular, interlayer gaps of the skeleton particles and gaps between the skeleton particles are formed. Therefore, a large amount of surface-modified microparticles
  • the volume change of a negative electrode active material can be further suppressed by making surface modified microparticles
  • fine-particles further improve the theoretical capacity of a negative electrode active material.
  • the present inventors have investigated suppressing the volume change of the silicon-based active material fine particles themselves.
  • the present inventors paid attention to the cylindrical silicon-based active material fine particles as the silicon-based active material fine particles.
  • the length (ie, the diameter) in the direction perpendicular to the axial direction is shorter than the axial length.
  • this inventor considered that the absolute amount of the volume change of a negative electrode active material can be made small by using cylindrical silicon type active material particle as a negative electrode active material.
  • the inventors of the present invention further improved the cycle life when the surface-modified fine particles were prepared using the cylindrical silicon-based active material fine particles and the negative electrode active material was prepared using the surface-modified fine particles and hard carbon. Details are described in the Examples.
  • FIG. 6 shows the theoretical capacity of the negative electrode active material in which silicon-based active material fine particles and hard carbon are mixed at a mass ratio of 7: 3, the theoretical capacity of the negative electrode active material in which silicon-based active material fine particles and graphite are mixed at a mass ratio of 2: 8, and graphite.
  • the theoretical capacity of the prepared negative electrode active material is compared and shown.
  • the silicon-based active material fine particles become fine particles of silicon.
  • the bar graph corresponding to the silicon-based active material shows the theoretical capacity implemented by the silicon-based active material among the theoretical capacities of the entire negative active material. The same applies to the bar graphs corresponding to graphite and hard carbon. Since hard carbon can introduce a large amount of fine particles of silicon, the negative electrode active material in which silicon-based active material fine particles and hard carbon are combined has a very large theoretical capacity.
  • graphite has a charge potential characteristic in which charging is first started when the charge potential is raised to a potential close to the lithium potential. Therefore, when the mixture of silicon-based active material fine particles and graphite is used as a negative electrode active material of a lithium ion secondary battery, the silicon-based active material fine particles are already in a fully charged state when charging of graphite is started. Therefore, the silicon-based active material fine particles deteriorate quickly.
  • hard carbon has a charging potential characteristic in which the charging capacity gradually rises with the increase of the charging potential. Therefore, when the surface modified fine particles and the hard carbon complexed with the surface modified fine particles are used as the negative electrode active material of the lithium ion secondary battery, the charge potential of the negative electrode active material, in particular, the charge capacity of the silicon active material fine particles is lower than the full charge by controlling the charging potential. Can be adjusted.
  • each negative electrode active material shown in FIG. 6 is compared and shown.
  • the negative electrode active material obtained by compounding silicon-based active material fine particles and hard carbon at a mass ratio of 7: 3 may be charged to the theoretical capacity of the negative electrode active material in which silicon-based active material fine particles and graphite were mixed at a mass ratio of 2: 8.
  • the charge capacity remains. That is, the silicon-based active material fine particles are not fully charged. Therefore, deterioration of a silicon type active material is suppressed and the cycle life improves further.
  • the silicon-based active material itself has low conductivity, it is difficult to introduce lithium ions into the negative electrode active material layer (layer including the negative electrode active material) when the silicon-based active material is used as the negative electrode active material.
  • the silicon-based active material is made into fine particles to improve the specific surface area of the negative electrode active material layer, and the surface of the silicon-based active material can be coated with a carbon material to improve the conductivity of the negative electrode active material.
  • the surface-modified fine particles are complexed with hard carbon to further improve the conductivity of the negative electrode active material. Therefore, lithium ions are easily introduced into the negative electrode active material layer.
  • propylene carbonate may be used as a solvent of the electrolyte by using a negative electrode active material in which surface-modified fine particles and hard carbon are combined.
  • a negative electrode active material in which surface-modified fine particles and hard carbon are combined.
  • the negative electrode active material becomes graphite
  • the lithium ion secondary battery which used graphite as a negative electrode active material what mixed solid ethylene carbonate with a low boiling point solvent at normal temperature is used as a solvent of electrolyte solution. Therefore, in such a lithium ion secondary battery, it is easy to solidify in the environment of cryogenic temperature (for example, -20 degrees C or less).
  • cryogenic temperature for example, -20 degrees C or less
  • propylene carbonate can be used as a solvent of electrolyte solution by using the negative electrode active material which surface-modified microparticles
  • Propylene carbonate is liquid at room temperature and hard to solidify even at cryogenic temperatures. Therefore, the lithium ion secondary battery using propylene carbonate as the solvent of the electrolyte solution can maintain the conductivity because it is difficult to solidify the electrolyte even in an extremely low temperature environment. That is, the lithium ion secondary battery can function as a battery. This low temperature is an important requirement for a wide range of application environment temperature ranges, such as electric vehicles.
  • the inventors have found that the negative electrode active material obtained by combining the surface-modified fine particles and the hard carbon is applied to a lithium ion secondary battery. Moreover, this inventor made the silicon-based active material microparticles
  • the configuration of the lithium ion secondary battery 10 according to the present embodiment will be described again with reference to FIG. 1, except for the description overlapping with the above description.
  • the negative electrode 30 includes a current collector 31 and a negative electrode active material layer 32.
  • the current collector 31 is a conductor and preferably a material which does not dissolve electrochemically stably or is difficult to alloy with lithium, and is made of, for example, copper, stainless steel, nickel plated steel, or the like.
  • the metallic lithium foil in a part of the current collector 31, for example, in a part where the electrode current collector terminal is welded to a part not facing the positive electrode active material layer 22.
  • metal lithium may be attached to the current collector 31 behind the negative electrode active material layer 32.
  • the metal lithium foil may be attached to an uncoated portion of the negative electrode active material layer 32 of the current collector 31.
  • the silicon-based active material fine particles have a columnar shape. For this reason, the silicon-based active material fine particles can suppress the absolute amount of the volume change, especially the volume change in the direction perpendicular to the axial direction (diameter direction). This also improves cycle life.
  • 15 and 16 show silicon-based active material fine particles X1 as an example of columnar silicon-based active material fine particles.
  • 15 and 16 are STEM photographs of the silicon-based active material fine particles (X1). 16 is an enlarged view of FIG. As a result of STEM observing silicon-based active material fine particles (X1) from all angles, the inventors obtained the same photograph as in FIG. That is, almost any of the STEM photographs showed the generally rectangular silicon-based active material fine particles (X1) shown in FIG. 15.
  • the silicon-based active material fine particles (X1) can be estimated in a columnar shape.
  • Fig. 17 shows silicon-based active material fine particles (X2) generally having ellipsoidal shape as silicon-based active material fine particles having a shape other than columnar shape.
  • 17 is a TEM photograph of silicon-based active material fine particles (X2).
  • the present inventors obtained TEM observation of silicon-based active material fine particles (X2) from all angles, and obtained the same photograph as in FIG. That is, in any TEM image, the generally oval-shaped silicon-based active material fine particles (X2) shown in FIG. 17 appeared.
  • the silicon-based active material fine particles (X2) can be estimated to have a substantially spheroidal shape. 17, the grid Y of the sample stage is also shown.
  • a silicon type active material microparticle is a polycrystal here.
  • the silicon-based active material fine particles become polycrystalline, the silicon-based active material fine particles have a large number of single crystal particles (domains), and spaces are formed between domains. Therefore, the stress caused by the volume change of the silicon-based active material fine particles is alleviated by this space. This also improves cycle life.
  • TEM image observation, XRD analysis, etc. are mentioned as a method of distinguishing microcrystalline silicon active material microparticles
  • 18 shows a TEM image of the polycrystalline silicon active material fine particles.
  • 19 shows a TEM photograph of the single crystal silicon active material fine particles.
  • the polycrystalline silicon active material fine particles have a plurality of single crystal particles therein.
  • the single crystal silicon-based active material fine particles are composed of almost single single crystal particles.
  • 18 is 800,000 times and FIG. 19 is 400,000 times.
  • the peak shape of the XRD due to such a structural difference.
  • the half width of the polycrystalline main peak (corresponding to the (111) plane) is 0.13 ° ⁇ 0.005 °
  • the half width of the single crystal main peak is within the range of 0.11 ° ⁇ 0.005 ° .
  • the silicon-based active material fine particles are preferably as small as possible, while the aspect ratio (axial length / diameter) is preferably as large as possible.
  • the axial length of the silicon-based active material fine particles is preferably 500 nm or less and the diameter is 50 nm or less.
  • the axial length is 350 nm or less and the diameter is more preferably 30 nm or less.
  • the cycle life is particularly improved when the axial length and diameter of the silicon-based active material fine particles are within these ranges.
  • the lower limit of the axial length and diameter of the silicon-based active material fine particles there is no particular limitation on the lower limit of the axial length and diameter of the silicon-based active material fine particles.
  • the lower limit of the axial length is preferably 50 nm and the lower limit of the diameter is 10 nm.
  • the length and diameter of the silicon-based active material fine particles can be reduced by lengthening the treatment time (milling time) by the bead mill.
  • the axial length and diameter of the silicon-based active material fine particles can be measured by STEM observation of the silicon-based active material fine particles.
  • the carbon material is formed on the surface of the silicon-based active material fine particles by firing an organic material together with the silicon-based active material fine particles.
  • the carbon material contains carbon as a main component.
  • the thickness of the carbon material is not particularly limited but is preferably in the range of 2 to 20 nm. When the thickness of the carbon material exceeds 20 nm, lithium entry and exit of the silicon-based active material may be inhibited. When the thickness of the carbon material is less than 2 nm, the carbon material becomes difficult to suppress direct contact between the silicon-based active material and the electrolyte solution. However, the thickness of the carbon material may be measured by direct observation in the TEM or by argon etching by XPS.
  • the total mass of a carbon material is 0.35-3.5 mass% with respect to the coating amount of a carbon material, ie, the total mass of a silicon type active material microparticle and a carbon material. This is because the cycle life is particularly improved when the coating amount of the carbon material becomes a value within this range, as shown in the examples below.
  • the coating amount of the carbon material can be measured, for example, by a differential thermal analyzer or the like.
  • the preferable coating amount of a carbon material is 0.7-1.75 mass%.
  • the silicon-based active material fine particles are coated with a carbon material, the silicon-based active material fine particles are hardly exposed to the atmosphere. Therefore, oxidation of the silicon-based active material fine particles is suppressed. This reduces the initial irreversible capacity.
  • direct contact between the silicon-based active material fine particles and the electrolyte solution is suppressed, decomposition of the solvent is suppressed. Thus, cycle life is improved.
  • the cycle life improves when the mass ratio of surface modified microparticles
  • This range depends on the starting material of the hard carbon.
  • the starting materials of the solid system include PVC, sucrose, gelatin and agar. Any one of these starting materials may be used, and plural kinds thereof may be used.
  • Resol type phenol resin, furfuryl alcohol, etc. are mentioned as a starting material of a liquid system here. Any one of these starting materials may be used, and plural kinds thereof may be used.
  • the hard carbon obtained as the starting material of the solid system has a larger proportion in the negative electrode active material than the hard carbon obtained as the starting material of the liquid system.
  • more hard carbon is needed to improve cycle life.
  • the following can be considered as the reason. That is, the starting material of the solid system is more difficult to mix with the surface modified fine particles than the starting material of the liquid system.
  • the hard carbon obtained as a starting material of a solid system is lower in homogeneity than the hard carbon obtained as a starting material of a liquid system, and it is hard to contact surface modified fine particles. For example, the contact area per unit mass is small.
  • the carbonization rate of the starting material may be considered as a secondary factor influencing the range of mass ratios in which the cycle life is improved.
  • the resol type phenol resin has a carbonization rate of about 28% by mass, while PVC is 10% by mass. The larger the carbonization rate of the starting material is, the larger the bulk density of the hard carbon is, so that the mass of hard carbon required to improve the cycle life becomes smaller.
  • Surface modified fine particles are compounded in hard carbon. Specifically, the surface-modified fine particles are introduced into the space in the hard carbon, that is, the interlayer gap between the skeleton particles and the gap between the skeleton particles. Complexation of the hard carbon with the surface modified fine particles is performed by mixing the starting material of the hard carbon with the surface modified fine particles and firing these mixtures. It mentions later in detail.
  • the nonaqueous electrolyte may be the same as the nonaqueous electrolyte used in lithium secondary batteries.
  • the nonaqueous electrolyte has a composition in which an electrolyte salt is contained in the nonaqueous solvent.
  • an electrolyte salt is contained in the nonaqueous solvent.
  • the non-aqueous solvent for example, cyclic carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, chloroethylene carbonate and vinylene carbonate ( esters; cyclic esters such as ⁇ -butyrolactone and ⁇ -valerolactone; dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and the like Chain carbonates; chain esters such as methyl formate, methyl acetate, butyric acid methyl, Tetrahydrofuran or derivatives thereof; 1,3-dioxane ), 1,4-dioxane, 1,2-dimethoxyethane, 1,4-d
  • Ethers such as acetonitrile and benzonitrile
  • dioxolane or derivatives thereof ethylene sulfide, sulfolane, sultone ( sultone) or a derivative thereof, or a mixture of two or more thereof, and the like, but are not limited thereto.
  • propylene carbonate can be used suitably.
  • the positive electrode 20 is produced as follows. First, a slurry is formed by dispersing a mixture of the positive electrode active material, the conductive agent, and the binder in the above ratio in a solvent (for example, N-methyl-2-pyrrolidone). Then, the slurry is collected in the current collector 21.
  • the positive electrode active material layer 22 is formed by forming (for example, coating) and drying on the phase.
  • the coating method is not particularly limited. As a coating method, the knife coater method, the gravure coater method, etc. can be considered, for example. Each following coating process is also performed by the same method. Next, the positive electrode active material layer 22 is pressed so as to have a density within the above range by a press. Thereby, the positive electrode 20 is produced.
  • the cathode 30 is manufactured as follows. First, the manufacturing method of a negative electrode active material is demonstrated. The production method of the negative electrode active material is roughly divided into the following four steps. In the first step, the silicon-based active material is pulverized in the non-aqueous solvent to prepare a dispersion solution in which the silicon-based active material fine particles are dispersed in the non-aqueous solvent. That is, in the first step, the silicon-based active material is granulated by wet pulverization of the silicon-based active material. According to the above method, oxidation of the silicon-based active material is suppressed at the time of grinding.
  • the nonaqueous solvent used for the wet grinding of the first step does not react with the silicon-based active material and can suppress the reagglomeration of the silicon-based active material fine particles and is industrially economical, while dissolving the organic material which is the carbon source in the second step. It is desirable to be able to. In detail, alcohols, such as ethanol and methanol, an ether, etc. are preferable. These nonaqueous solvents may be used alone or in combination of two or more kinds thereof.
  • the apparatus used for the wet grinding of a 1st process can use the bead mill apparatus using media.
  • Particularly preferable bead mills include MSC mills (for example, MSC100 mills) manufactured by Nippon Coke Co., Ltd., and the like.
  • MSC mills for example, MSC100 mills
  • Such a bead mill apparatus can mildly pulverize a silicon-based active material as compared to other bead mill apparatuses, ball mill apparatuses, and the like.
  • the silicon-based active material is pulverized for a longer time than other bead mill devices. For this reason, the cylindrical silicon-based active material fine particles can be produced easily. It is also important to employ beads as small as possible to obtain fine particles.
  • the beads and the pulverized product need to be separated.
  • these methods were separated using the screen method or the gap method.
  • these methods cause the particles to reaggregate and become clogged.
  • pulverization to the extent required for this invention was not possible in the other mill.
  • the MSC mill employs a centrifugal rotor to separate the beads and the pulverized product by centrifugal force. This removes the restriction on the bead diameter that can be used in MSC mills. Therefore, the MSC mill is capable of finer grinding.
  • the circumferential silicon-based active material fine particles according to the present embodiment can be produced by pulverizing the silicon-based active material with an SC100 mill and then pulverizing with an MSC100 mill.
  • the axial length and diameter of a silicon type active material microparticle can be made small.
  • an electrochemically inert ceramic material for example, zirconium oxide, alumina, or the like, in the container of the media or the device in order to reduce the influence of impurities as much as possible.
  • the particle diameter (diameter) of media such as zirconium oxide or alumina is preferably small, and is preferably about 50 to 100 ⁇ m.
  • a mixed solution is prepared by dissolving an organic substance dissolved in a nonaqueous solvent in a dispersion solution.
  • the organic substance which can be used in a 2nd process is further soluble in a nonaqueous solvent, and the material with a high carbon content rate (carbonation rate) is preferable. It is because it is easy to form a dense carbon material film by using such an organic substance.
  • carbon content rate it is preferable that carbon content rate is 10.7-44.1 mass% with respect to the organic substance total mass.
  • the content of oxygen is preferably in the range of 16.7 to 63.1 mass% with respect to the total mass of organic matter.
  • hydroxy acid, monosaccharide, oligosaccharide, etc. are mentioned, for example.
  • hydroxy acid examples include citric acid and glycolic acid.
  • monosaccharides include erythritol, D-erythrulose, and D-erythrose. , D-threose, D-arabinose, L-arabinose, L-arabinose, D-xylulose, L-xylulose L-xylulose, D-xylose, D-lyxose, L-lyxose, D-ribulose, D-idose (D- idose), D-quinoboose, glucaric acid, D-digitoxose, D-cymarose, 2-deoxy D-glucose (2) -Deoxy-D-glucose, L-fucose, D-psicose, D-fructose, L-rhamnose, L- L-Iduronic acid, D-glucuronic acid, etc. are mentioned.
  • oligosaccharides isomaltose,
  • an organic substance 10 mass% or less is preferable with respect to the mass of a dispersion solution, 5 mass% or less is more preferable, and 2 mass% or less is more preferable.
  • the lower limit is not particularly limited as long as the parameter required for the carbon material is satisfied.
  • the mixed solution is baked in an inert atmosphere to coat the carbon material on the surface of the silicon-based active material fine particles. This produces surface modified microparticles
  • the inert atmosphere can be implemented by, for example, argon or nitrogen. These gases can be used alone or in combination.
  • the firing temperature 500 ° C. or more is preferable considering the temperature at which carbonization of the organic material proceeds. And as for an upper limit temperature, 800 degrees C or less which generation of SiC by reaction of a silicon and carbon does not generate
  • the optimum temperature depends on the type of organic material used for firing. Surface-modified microparticles
  • the coating method of the carbon material by this embodiment can be implement
  • a negative electrode active material is produced by combining hard carbon and surface modified fine particles. Complexation of the hard carbon with the surface modified fine particles is performed by mixing the starting material of the hard carbon with the surface modified fine particles and firing these mixtures.
  • the starting materials for hard carbon include phenol resin, PVC (polyvinyl chloride), furfurylalcohol, sucrose, gelatin, agar and the like. Only one species of these starting materials can be used and a plurality of types of starting materials can be used.
  • Resol type phenol resin, furfuryl alcohol, etc. are mentioned as a starting material of a liquid system here.
  • the mixing method may be either wet or dry.
  • An inert atmosphere can be implemented, for example by argon, nitrogen, etc. These gases can be used alone or in combination.
  • the firing temperature 500 ° C. or more is preferable in consideration of the temperature at which hard carbon is generated.
  • an upper limit temperature 800 degrees C or less which generation
  • a slurry is formed by disperse
  • the negative electrode active material layer 32 is formed by forming (for example, coating) and drying the slurry on the current collector 31.
  • the negative electrode active material layer 32 is pressed by a press. As a result, the cathode 30 is produced.
  • the separator is sandwiched between the positive electrode 20 and the negative electrode 30 to produce an electrode structure.
  • the electrode structure is then processed into a desired shape (eg, cylindrical, square, laminated, buttoned, etc.) and inserted into a container of that type.
  • the electrolyte is impregnated into the pores in the separator by injecting the electrolyte solution of the composition into the vessel. Thereby, a lithium ion secondary battery is produced.
  • the lithium ion secondary battery 10 As described above, in the lithium ion secondary battery 10 according to the present embodiment, a large amount of silicon-based active material fine particles can be used for the negative electrode active material, and the theoretical capacity of the negative electrode active material is very high.
  • the charging capacity of the lithium ion secondary battery is maintained at 70% or less of the theoretical capacity realized by the silicon-based active material fine particles, that is, the full charge amount of the silicon-based active material fine particles. As a result, deterioration of the silicon-based active material fine particles is suppressed, thereby improving cycle life.
  • Example 2-1 a negative electrode active material was produced by the following steps.
  • silicon particles metal silicon particles (SIE04PB) manufactured by High Purity Chemical Research Institute Co., Ltd. were prepared.
  • the average particle diameter of this silicon particle was 30 micrometers.
  • grains is a diameter when a silicon particle is regarded as a sphere, and it measured using the laser diffraction / scattering type particle size distribution analyzer LA-950 by Horiba Corporation. In detail, the particle size distribution was measured using this apparatus, and the arithmetic mean of particle size was computed based on the particle size distribution. The average particle diameter described below was also measured by this method.
  • the silicon particles were added to ethanol in a 10% by mass blend with respect to the total mass of ethanol and silicon particles, and charged into a SC100 mill manufactured by Nippon Coke Co., Ltd. together with zirconium oxide beads having a diameter (particle diameter) of 500 ⁇ m.
  • the input amount of zirconium oxide beads was 60 volume% with respect to the container volume. And the circumferential speed of the agitator was operated for 13 hours at 13 m / s. This obtained the ethanol dispersion liquid of a silicon particle.
  • the zirconium oxide beads were removed from the ethanol dispersion, and the ethanol dispersion after removing the zirconium oxide beads was introduced into a MSC100 mill manufactured by Nippon Coke Co., Ltd. together with the zirconium oxide beads having a diameter of 50 ⁇ m.
  • the input amount of zirconium oxide beads was 55 volume% with respect to the container volume. And the circumferential speed of the stirrer was operated for 20 hours as 13 m / s.
  • the silicon-based active material fine particles were observed with STEMHD-2700 manufactured by Hitachi High-Technology Co., Ltd. to obtain a STEM photograph shown in FIG. About 20 samples were extracted from the STEM photograph shown in FIG. 15 and the axial length of the sample was measured. As a result, the axial length was distributed in the range of 130 to 330 nm. On the other hand, each sample was enlarged and observed as shown in Fig. 16, and the diameter of the sample was measured. As a result, the maximum diameter was 30 nm.
  • a mixed solution was prepared by adding and mixing 2 g of citric acid (2% by mass based on the total mass of the dispersion solution) with respect to 100 g of the dispersion solution prepared in the first step.
  • the mixed solution produced in the second step was transferred to a ceramic crucible and placed in a quartz glass tube furnace. After argon gas was sufficiently flowed into the tube furnace at 500 cm 3 / min, the tube furnace was heated up to 600 ° C. at a speed of 2.5 ° C./min. Thereafter, the inside of the tube furnace was kept at 600 ° C. for 5 hours to naturally cool and the crucible was taken out after reaching room temperature.
  • the carbon material coating amount on the silicon-based active material is 2.4% by mass based on the carbonization rate obtained as a result of the above firing test with citric acid alone.
  • the weight loss of citric acid was measured using the differential thermal analyzer EXSTAR6000 manufactured by Seiko Instruments, Inc., and as a result, the coating amount of the carbon material was measured to be 2.3% by mass. As a result, both were found to have almost the same value.
  • the surface of the negative electrode active material was analyzed using STEMHD-2700 manufactured by Hitachi High-Technology Co., Ltd., and the thickness of the carbon material was 3 to 8 nm.
  • fine-particles and PVC were weighed so that mass ratio of surface-modified microparticles
  • the mixture obtained by this mixing was transferred to the ceramic crucible and installed in the quartz glass tube furnace. After argon gas was flowed at 500 cm 3 / min to be sufficiently substituted, the tube furnace was heated up to 600 ° C. at a speed of 2.5 ° C./min. Thereafter, the inside of the tube furnace was kept at 600 ° C for 3 hours to naturally cool and the crucible was taken out after reaching room temperature. The sample in the crucible was then ground by Menow induction. As a result, the surface-modified fine particles and the hard carbon were combined. That is, the negative electrode active material was produced.
  • the mixed solution was produced by adding 75 mass parts of negative electrode active materials and 10 mass parts of carbon black to the polyimide solution which added and dissolved N-methyl- 2-pyrrolidone with respect to 15 mass parts of polyimides. Then, a slurry was prepared by mixing the mixed solution with Agate mortar. And this slurry was apply
  • the electrode body was produced by preparing the thing which adhered lithium foil to the copper foil as a counter electrode, and laminating
  • 2032 type coin battery was produced by adding 0.1 cm ⁇ 3> of 1M-LiPF6EC / DEC (1: 1 volume ratio) electrolyte solution to an electrode structure.
  • the battery was charged and discharged using a charge-discharge tester BTS2010 manufactured by Index Co., Ltd. Charged and discharged at 0.05C for the 1st to 2nd cycles, 0.1C for the 3rd to 4th cycles, and then 0.5C. Charge was carried out by constant current constant voltage, discharge was carried out by constant current, and the charging capacity was 1000mAh / g, the discharge end voltage was 1.5V, and the test temperature was 25 degreeC.
  • the discharge efficiency initial efficiency and cycle life of the lithium ion secondary battery were measured.
  • the initial efficiency is the charge / discharge efficiency (discharge capacity / charge capacity) at the first cycle
  • the cycle life is the number of cycles when the discharge capacity is less than 90% of the discharge capacity at the fifth cycle by charge / discharge at 0.5C. did.
  • Example 2-1 It processed similarly to Example 2-1 except having set the processing time of the MSC100 mill of Example 2-1 to 10 hours.
  • the axial length of the obtained silicon-based active material fine particles was 300-480 nm, and the maximum value of diameter was 48 nm.
  • Example 2-1 It processed similarly to Example 2-1 except having set the processing time of the MSC100 mill of Example 2-1 to 5 hours.
  • the axial length of the obtained silicon-based active material fine particles was 550-700 nm, and the maximum value of diameter was 65 nm.
  • Example 2-1 It processed similarly to Example 2-1 except having set the processing time of the MSC100 mill of Example 2-1 to 1 hour.
  • the axial length of the obtained silicon-based active material fine particles was 720-850 nm, and the maximum value of diameter was 110 nm.
  • Example 2-5 it processed similarly to Example 2-1 except having used this single crystalline silicon particle instead of the metal silicon particle of Example 2-1.
  • the axial length of the obtained silicon-based active material fine particles was 150-290 nm, and the maximum value of the diameter was 32 nm.
  • the surface modified fine particles of Example 2-5 were observed using a transmission electron microscope (TEM) JEOL-2010 FEF manufactured by Nippon Electronics Co., Ltd., to obtain a TEM image shown in FIG.
  • TEM transmission electron microscope
  • Example 2-5 It processed similarly to Example 2-5 except having made MSC100 mill processing time of Example 2-5 into 5 hours.
  • the axial length of the obtained silicon-based active material fine particles was 570-680 nm, and the maximum value of diameter was 60 nm.
  • Example 2-7 the same procedure was followed as in Example 2-1 except that the polycrystalline silicon particles were used instead of the metal silicon particles of Example 2-1.
  • the axial length of the obtained silicon-based active material fine particles was 100-210 nm, and the maximum value of diameter was 25 nm.
  • fine-particles of Example 7 were observed using the transmission electron microscope (TEM) JEOL-2010 FEF by the Japan Electronics Corporation, and the TEM photograph shown in FIG. 18 was obtained.
  • TEM transmission electron microscope
  • Example 2-7 It processed similarly to Example 2-7 except having made MSC100 mill processing time of Example 2-7 into 5 hours.
  • the axial length of the obtained silicon-based active material fine particles was 520-640 nm, and the maximum diameter was 53 nm.
  • Example 2-1 It processed similarly to Example 2-1 except having changed the 1st process of Example 2-1 as follows. That is, the silicon particles (metal silicon particles) of Example 2-1 were added to ethanol in a proportion of 10% by mass based on the total mass of ethanol and silicon particles, and a planetary ball mill made by FRITSCH with a zirconium oxide ball having a diameter (particle diameter) of 5 mm. It put in P-7 and operated for 5 hours at 800 rpm. The input amount of zirconium oxide balls was 50 volume% with respect to the volume of a container. This produced the dispersion solution which the silicon type active material microparticles
  • the silicon-based active material fine particles were observed with a transmission electron microscope (TEM) JEOL-2010 FEF manufactured by Nippon Electronics Co., Ltd. to obtain a TEM photograph shown in FIG.
  • the silicon-based active material fine particles in the TEM photograph were generally in the shape of an ellipsoid and were clearly different from the columnar shape.
  • the maximum length in the major axis direction and the maximum length in the minor axis direction of the silicon-based active material fine particles in the TEM photograph were measured to be 114 nm and 78 nm, respectively. Therefore, the aspect ratio of these lengths was clearly different from the present Example. That is, no cylindrical silicon-based active material fine particles as in the present embodiment were observed.
  • Example 2-1 to 2-8 the initial stage efficiency and cycle life with Comparative Example 2-1 are compared with Table 2, and are shown. However, in Table 2, the initial efficiency and cycle life of Examples 2-1 to 2-8 are standardized and shown in Example 2-4, Comparative Example 2-1, and the like.
  • Example 2-1 the columnar silicon-based active material fine particles were confirmed, whereas in Comparative Example 2-1, the columnar silicon-based active material fine particles were not confirmed.
  • Example 2-1 the columnar silicon-based active material fine particles were higher than in Comparative Example 2-1.
  • Example 2-3 As shown in Examples 2-2 to 4, the treatment time of the MSC100 mill was changed, but silicon-based active material fine particles of various sizes could be obtained. As a result of evaluating these under the same conditions, the initial efficiency was 1% in Example 2-3 (length 720 to 850 nm, maximum diameter of 110 nm) in Example 2-3 (length 550 to 700 nm, maximum diameter of 65 nm). The furnace cycle characteristic was an improvement of 7%.
  • Example 2-2 300-480 nm in length, the maximum value of diameter is 48 nm
  • Example 2-1 the length is 130-330 nm, At the maximum diameter of 30 nm
  • an initial efficiency of 3% and a cycle characteristic of 60% were recognized.
  • the axial length is preferably 500 nm or less
  • the diameter is preferably 50 nm or less.
  • Example 2-6 in which the length and diameter were long (570-680 nm in length and 60 nm in maximum diameter) Compared with this, the initial efficiency is improved by 4% and the cycle life is improved by 55%.
  • Example 2-7 of polycrystalline silicon (length is 100-210 nm, maximum diameter is 25 nm) is also compared to Example 2-8 (length is 520-640 nm, maximum diameter is 53 nm), initial efficiency is 7%, cycle Lifespan improved 75%. Comparing Example 2-5 and Example 2-7 with the same processing time in single crystal silicon and polycrystalline silicon, the polycrystalline silicon has a shorter length and a smaller diameter. As a result, the characteristic of Example 2-7 was better than Example 2-5. Therefore, it can be seen that the polycrystalline silicon-based active material fine particles are superior to the single-crystal silicon-based active material fine particles.
  • the polycrystalline silicon-based active material fine particles have a large number of single crystal regions (domains) therein and a space is formed between the domains. Each domain expands by alloying with lithium during charging, but it can be considered that the stress of the expansion is caused by the space between the domains.
  • a single macro domain is alloyed with lithium at the time of filling, but in the polycrystalline silicon-based active material fine particles, a plurality of minute domains are alloyed with lithium.
  • polycrystalline silicon-based active material fine particles expansion itself caused by alloying with lithium is also dispersed, and thus it can be considered that the expansion stress is alleviated. For this reason, it can be said that polycrystalline silicon-based active material fine particles are superior to single-crystal silicon-based active material fine particles.
  • Example 2-9 it processed similarly to Example 2-1 except having used the resol type phenol resin instead of PVC.
  • Example 2-1 It processed similarly to Example 2-1 except having used sucrose instead of PVC.
  • Example 2-1 The same treatment as in Example 2-1 was carried out except that gelatin was used instead of PVC.
  • Example 2-1 The same treatment as in Example 2-1 was carried out except that agar was used instead of PVC.
  • Example 2-1 It processed similarly to Example 2-1 except having changed PVC and using furfuryl alcohol.
  • Example 2-1 It processed similarly to Example 2-1 except having made the 4th process the following process. That is, the silicon-based active material fine particles and the artificial graphite were weighed so that the mass ratio of the silicon-based active material fine particles produced in the first step to the artificial graphite was 75:25, and these were mixed uniformly by menow induction. This mixture was used as a negative electrode active material.
  • Example 2-1, 2-9-13, and Comparative Examples 2-2-7 are shown compared with Table 3. However, in Table 3, the initial stage efficiency and cycle life of Example 2-1, 2-9-13 are normalized to Comparative Examples 2-2-7, and are shown.
  • Examples 2-1 and 2-9-13 had the characteristic better than Comparative Examples 2-2-7.
  • Example 2-1 since the surface-modified fine particles are complexed with hard carbon, expansion of the hard carbon and relaxation of conductivity can be expected.
  • the graphite of Comparative Example 2-2 was unable to absorb the stress caused by the expansion when silicon alloyed with lithium expanded the electrode. Therefore, it can be said that Example 2-1 improved the characteristic compared with Comparative Example 2-2 by this reason.
  • Example 2-9 to 13 instead of the PVC of Example 2-1, a composite material was produced using various carbon sources such as phenol resin and compared with 2-7 in Comparative Example 2-3. As a result, the same effects as in Example 2-1 using PVC were obtained.
  • Example 2-14 This inventor carried out Example 2-14 in order to confirm the correspondence of the charge capacity, discharge capacity, and cycle life of a lithium ion secondary battery.
  • the results are shown in FIG. 8 represents the charge ratio of the silicon-based active material (the charge capacity of the lithium ion secondary battery / theoretical capacity implemented by the silicon-based active material), and the vertical axis represents the discharge capacity and cycle life of the first cycle.
  • the discharge capacity was expressed by standardizing the discharge capacity when the charge ratio of the silicon-based active material is 20%.
  • the cycle life normalized the cycle life at the time of the filling ratio of a silicon type active material to 100%, and showed it.
  • the cycle life was greatly improved when the filling ratio of the silicon-based active material was 70% or less.
  • the discharge capacity was maintained at a higher level than artificial graphite, and this embodiment was carried out in view of both high discharge capacity (that is, reduction of irreversible capacity) and long cycle life. It can be seen that the shape is excellent.
  • Example 2-1 It processed similarly to Example 2-1 except having changed the baking temperature of the 4th process within the range of 400-900 degreeC.
  • the results are shown in FIG. 9 represents the firing temperature and the vertical axis represents the initial efficiency and cycle life. However, initial stage efficiency and cycle life were shown by normalizing the value at the baking temperature to 400 degreeC to 1.
  • both the initial efficiency and the cycle life were higher than the case of 400 ° C between 500 and 800 ° C. It may be considered that the lower the temperature is due to the effect that the carbonization progress of the carbon source of hard carbon becomes difficult to proceed.
  • the initial efficiency and cycle life deteriorate considerably at 900 degreeC, it can be considered that this is because of the bad effect by production
  • Example 2-16, 2-17 Carried out.
  • Example 2-16 it processed similarly to Example 2-1 except having changed the mass ratio of surface modified microparticles
  • the results are shown in FIG.
  • the horizontal axis in Fig. 10 represents the mass% of the surface modified fine particles (mass% relative to the total mass of the surface modified fine particles and the hard carbon) and the vertical axis represents the cycle life.
  • the cycle life was shown by normalizing the value to 1 when the surface-modified fine particles became 100% by mass.
  • the cycle life was increased when the mass ratio of the surface modified fine particles to the hard carbon became a value within the range of 50:50 to 80:20. Specifically, the cycle life for this range was 1.8 times greater than the cycle life when the mass% of the surface modified fine particles became 100%.
  • Example 2-17 the same process as in Example 2-9 was carried out except that the mass ratio of the surface-modified fine particles and hard carbon was changed within the range of 40:60 to 100: 0 in the fourth step.
  • the results are shown in FIG.
  • the horizontal axis in Fig. 11 represents the mass% of the surface modified fine particles (mass% relative to the total mass of the surface modified fine particles and the hard carbon) and the vertical axis represents the cycle life.
  • the cycle life was shown by normalizing the value to 1 when the mass% of the surface-modified fine particles became 100%.
  • the cycle life was increased when the mass ratio of the surface-modified fine particles to the hard carbon became a value within the range of 75:25 to 90:10. Specifically, the cycle life for this range was 1.8 times greater than the cycle life when the mass% of the surface modified fine particles became 100%.
  • Example 2-18 Except having changed the electrolyte solution of Example 2-1 into 1M-LiPF6PC / DEC (1: 1 volume ratio), it processed similarly to Example 2-1, and produced the battery.
  • Example 2-18 the charge of the 1st cycle was changed to 25 degreeC similarly to Example 2-1, and the environmental temperature of the battery was changed to 0-20, respectively, and it hold
  • Example 2-19 in order to confirm the correspondence between the baking temperature in the 3rd process, and the characteristic of a lithium ion secondary battery.
  • Example 2-19 it processed similarly to Example 2-1 except having changed the baking temperature in the range of 400-900 degreeC in the 3rd process of Example 2-1.
  • the results are shown in FIG.
  • Fig. 13 the horizontal axis represents firing temperature and the vertical axis represents initial efficiency and cycle life.
  • initial stage efficiency and cycle life show the value normalized by the following comparative example 2-8.
  • Example 8 It processed similarly to Example 2-19 except not having performed the 2nd and 3rd process of Example 2-1. That is, in Comparative Example 8, the surface of the silicon-based active material fine particles was not covered with a carbon material.
  • baking temperature is 500-800 degreeC.
  • the reason why the cycle life and initial efficiency are lowered when the firing temperature is lower than 500 ° C. is that carbonization of the organic material is less likely to proceed at a lower firing temperature and the coating amount of the carbon material is lowered.
  • the firing temperature is 900 ° C, the initial efficiency and cycle life are greatly reduced.
  • generation of electrochemically inert SiC can be considered. In other words, as the silicon-based active material is made into fine particles, the reactivity with carbon is increased, and SiC may be partially produced even at 900 ° C.
  • Example 2-20 in order to confirm the correspondence between the coating amount of the carbon material, that is, the mass% of the carbon material with respect to the total mass of the silicon-based active material fine particles and the carbon material and the characteristics of the lithium ion secondary battery. did.
  • it processed similarly to Example 2-1 except having changed the coating amount of carbon material in the range of 0.07-6.7 mass% by changing the addition amount of citric acid in the 2nd process of Example 2-1. .
  • the results are shown in FIG.
  • the cycle life and initial stage when the coating amount of the carbon material is 0.35 to 3.5% by mass are better than the comparative example 2-8, and the coating cycle of the carbon material is 0.7 to 1.75% by mass. Efficiency is maximized.
  • the coating amount of carbon material exceeds 3.5 mass%, it can be considered that it is because of the structure of a carbon material as a reason that cycling life and initial stage efficiency fall.
  • the carbon material covering the silicon-based active material fine particles is assumed to have a graphite structure, but since this structure is immature (in particular, there are many amorphous portions), the carbon material increases the amount of the lithium-based silicon-based active material particles by the carbon material. This is because the access of the person is rather hindered.
  • the cycle life and initial efficiency are maximized when the carbon material coating amount is 0.7-1.75 mass%.
  • the coating amount of the carbon material falls within this range, it is considered that the carbon material hardly inhibits the movement of lithium ions and the oxidation inhibiting effect of the silicon-based active material fine particles by the carbon material is maximized.
  • Example 2-21 This inventor performed the following Example 2-21 in order to confirm that the same effect is acquired also in other silicon type active material.
  • it processed similarly to Example 2-1 except having replaced the metal silicon of Example 2-1 with the polycrystalline silicon alloy (Si: Al: Fe 55: 29: 16 (mass ratio)).
  • fine-particles are hard to expose to air
  • the surface-modified fine particles are coated with a carbon material, the silicon-based active material fine particles are hardly exposed to the atmosphere during the use of the surface-modified fine particles. Therefore, the irreversible capacity of the negative electrode active material is reduced. In other words, it is possible to maintain a high discharge capacity of the silicon-based active material (that is, to realize a high initial efficiency). In addition, direct contact between the silicon-based active material fine particles and the solvent is suppressed.
  • the cycle life of the lithium ion secondary battery can be improved.
  • the surface modified fine particles are introduced into the hard carbon by complexing with the hard carbon. Therefore, the stress due to the volume change of the surface-modified fine particles is reduced by the hard carbon, so the cycle life is improved in this respect.
  • a large amount of surface-modified fine particles can be introduced into the hard carbon, thereby improving the theoretical capacity of the negative electrode active material, that is, the discharge capacity.
  • the silicon-based active material is circumferential, the absolute amount of volume change, particularly the absolute amount of volume change in the radial direction, can be reduced. In this embodiment as well, the cycle life is improved.
  • the hard carbon can be obtained by firing a solid starting material, and the total mass of the surface modified fine particles is preferably 50 to 80% by mass relative to the total mass of the hard carbon and the surface modified fine particles.
  • the irreversible capacity of the lithium ion secondary battery is reduced and the cycle life of the lithium ion secondary battery is improved.
  • the starting material of the solid system may be any one or more selected from the group consisting of PVC, sucrose, gelatin and agar. In this case, the irreversible capacity of the lithium ion secondary battery is reduced and the cycle life of the lithium ion secondary battery is improved.
  • the hard carbon can be obtained by calcining the starting material of the liquid system, and the total mass of the surface modified fine particles is preferably 75 to 90% by mass relative to the total mass of the hard carbon and the surface modified fine particles. In this case, the irreversible capacity of the lithium ion secondary battery is reduced and the cycle life of the lithium ion secondary battery is improved.
  • the average particle diameter of the silicon-based active material fine particles may be 200 nm or less, in which case the irreversible capacity of the lithium ion secondary battery is reduced and the cycle life is also improved.
  • the carbon material may have a thickness of 2 to 20 nm, in which case the irreversible capacity of the lithium ion secondary battery is reduced, and the cycle life is also improved.
  • At least one of the inert atmosphere of the third process and the fourth process may be composed of any one or more selected from the group consisting of argon and nitrogen, in which case the irreversible capacity of the lithium ion secondary battery is reduced and the cycle life is also improved. do.
  • baking of a 4th process can be performed in the temperature range of 500-800 degreeC, In this case, the irreversible capacity
  • the metal lithium foil may be disposed in a part of the negative electrode current collector, for example, in a part where the electrode current collector terminal is welded, and a part not facing the positive electrode active material layer. In this case, the irreversible capacity of the lithium ion secondary battery is reduced, and the cycle life is also improved.
  • the charging capacity of the lithium ion secondary battery can be maintained at 70% or less of the theoretical capacity realized by the silicon-based active material fine particles. In this case, the irreversible capacity of the lithium ion secondary battery is reduced and the cycle life is also improved.
  • the organic material may be any one or more selected from the group consisting of hydroxy acids, monosaccharides and oligosaccharides, in which case the irreversible capacity of the lithium ion secondary battery is reduced and the cycle life is also improved.
  • the hydroxy acid may be any one or more selected from the group consisting of citric acid and glycolic acid, in which case the irreversible capacity of the lithium ion secondary battery is reduced and the cycle life is also improved.
  • non-aqueous solvent may be any one or more selected from the group consisting of alcohols and ethers, in which case the irreversible capacity of the lithium ion secondary battery is reduced and the cycle life is also improved.
  • baking of a 3rd process can be performed in the temperature range of 500-800 degreeC, In this case, the irreversible capacity
  • the inventors have found that a negative electrode active material obtained by complexing surface-modified fine particles and hard carbon is applied to a lithium ion secondary battery.
  • the present inventors also made the silicon-based active material fine particles constituting the surface-modified fine particles polycrystalline. According to this embodiment, it became possible to improve the cycle life of a lithium ion secondary battery at low cost, maintaining the high discharge capacity of a silicon type active material.
  • the lithium ion secondary battery of this embodiment can be used under a wider temperature range.
  • 28 shows a TEM image of the polycrystalline silicon active material fine particles.
  • 29 shows a TEM image of the single crystal silicon active material fine particles.
  • the polycrystalline silicon active material fine particles have a plurality of single crystal particles therein.
  • the single crystal silicon-based active material fine particles are composed of almost single single crystal particles. 28 is 800,000 times, while FIG. 29 is 400,000 times.
  • the difference in the structure can be seen in the peak shape of the XRD.
  • the half width of the polycrystalline main peak (corresponding to the (111) plane) is 0.13 ° ⁇ 0.005 ° It is a value within a range, and the half width of the single crystal main peak is a value within a range of 0.11 ° ⁇ 0.005 ° .
  • the average particle diameter of the silicon-based active material fine particles is preferably as small as possible. In the case where the silicon-based active material fine particles are alloyed with lithium in the negative electrode 30, the smaller the particle size of the silicon-based active material fine particles decreases the absolute value of expansion per particle. For this reason, expansion of the cathode 30 can be suppressed.
  • the average particle diameter of the silicon-based active material fine particles is preferably 200 nm or less, and even more preferably 100 nm or less. The cycle life is particularly improved when the average particle diameter of the silicon-based active material fine particles is within these ranges.
  • the average particle diameter of a silicon type active material fine particle it is preferable that it is 50-60 nm, for example. That is, it is possible to make an average particle diameter about 50-60 nm by making grinding
  • the average particle diameter of the silicon-based active material fine particles is a diameter when the silicon-based active material fine particles are regarded as spheres, and can be measured, for example, by a laser diffraction / scattering particle size distribution measuring device.
  • the particle size distribution of the silicon-based active material fine particles is measured by a laser diffraction / scattering particle size distribution analyzer, and an arithmetic mean value of the particle sizes of the silicon-based active material fine particles is calculated as the average particle diameter based on the particle size distribution.
  • Example 3-1 a negative electrode active material was produced by the following steps.
  • silicon particles polycrystalline silicon particles (Lot3775062) manufactured by High Purity Chemical Research Institute Co., Ltd. were prepared.
  • the half peak width of the main peak was 0.1317 ° .
  • the average particle diameter of the said silicon particle was 53 micrometers.
  • grains was measured using the laser diffraction / scattering type particle size distribution analyzer LA-950 by Horiba Corporation. In detail, the particle size distribution was measured using this apparatus, and the arithmetic mean of particle size was computed based on the particle size distribution. The average particle size described below was also measured by this method.
  • the silicon fine particles were added to ethanol in a proportion of 10% by mass based on the total mass of ethanol and silicon fine particles, and with a zirconium oxide beads having a diameter (particle diameter) of 50 ⁇ m, Leverstar mini (manufactured by Ashiyazawa Finetech) Labstar) was put into the LMZ015.
  • the input amount of zirconium oxide beads was 80 volume% with respect to the container volume.
  • the circumferential speed of the agitator was performed for 24 hours at 12 m / s. This produced the dispersion solution which the silicon type active material microparticles
  • the average particle diameter of the silicon-based active material fine particles was measured in the same manner as the silicon fine particles, and the average particle diameter was 97 nm.
  • a mixed solution was prepared by adding and mixing 2 g of citric acid (2% by mass based on the total mass of the dispersion solution) with respect to 100 g of the dispersion solution prepared in the first step.
  • the mixed solution produced in the second step was transferred to a ceramic crucible and placed in a quartz glass tube furnace. After argon gas was sufficiently flowed into the tube furnace at 500 cm 3 / min, the tube furnace was heated up to 600 ° C. at a speed of 2.5 ° C./min. Thereafter, the tube furnace was naturally cooled at 600 ° C. for 5 hours to reach room temperature, and then the crucible was taken out.
  • the coating amount of the carbon material on the silicon-based active material is 2.4% by mass based on the carbonization rate obtained from the results of the above firing experiment with citric acid alone.
  • the weight loss of citric acid was measured using the differential thermal analyzer EXSTAR6000 manufactured by Seiko Instruments, Inc., and the coating amount of the carbon material was measured, and the result was 2.3% by mass. Therefore, it was confirmed that both became almost the same value.
  • the surface of the negative electrode active material was analyzed using a transmission electron microscope (TEM) JEOL-2010 FEF manufactured by Nippon Electronics Co., Ltd., and the thickness of the carbon material was 3 to 8 nm. Further, the surface-modified fine particles were observed under the same microscope, and a TEM photograph shown in FIG. 28 was obtained.
  • TEM transmission electron microscope
  • the surface-modified fine particles and PVC were weighed so that the mass ratio of the surface-modified fine particles to the hard carbon was 65:35, and the mixture was uniformly mixed with the induction of menow. Then, the mixture obtained by the mixing was transferred to a ceramic crucible and installed in a quartz glass tube furnace. After argon gas was flowed at 500 cm 3 / min to be sufficiently substituted, the tube furnace was heated up to 600 ° C. at a speed of 2.5 ° C./min. Then, the crucible was taken out after natural cooling and reaching room temperature, maintaining the inside of a tube furnace at 600 degreeC for 3 hours. And the sample in the crucible was ground by menow induction. As a result, the surface-modified fine particles and the hard carbon were combined. That is, the negative electrode active material was produced.
  • the mixed solution was produced by adding 75 mass parts of negative electrode active materials and 10 mass parts of carbon black to the polyimide solution which added and melt
  • the electrode body was produced by preparing the thing which adhered lithium foil to the copper foil as a counter electrode, and laminating
  • 2032 type coin battery was produced by adding 0.1 cm ⁇ 3> of 1M-LiPF6EC / DEC (1: 1 volume ratio) electrolyte solution to an electrode structure.
  • the battery was charged and discharged using a charge / discharge tester BTS2010 manufactured by Index. Charged and discharged at 0.05C for the 1st to 2nd cycles, 0.1C for the 3rd to 4th cycles, and then 0.5C.
  • the charging was carried out with a constant current constant voltage, the discharge was made with a constant current, the charging capacity was 1000mAh / g, the discharge end voltage was 1.5V, and the test temperature was 25 ° C.
  • the discharge capacity, initial efficiency, and cycle life of the lithium ion secondary battery were measured.
  • the initial efficiency was defined as the charge / discharge efficiency (discharge capacity / charge capacity) at the 1st cycle, and the cycle life was charged and discharged at 0.5 C.
  • the cycle number was obtained when the discharge capacity at the 5th cycle of discharge capacity was lower than 90%.
  • Example 3-1 The same treatment as in Example 3-1 was carried out except that a sol type phenol resin was used instead of PVC.
  • Example 3-1 It processed similarly to Example 3-1 except having used sucrose instead of PVC.
  • Example 3-1 The same treatment as in Example 3-1 was carried out except that gelatin was used instead of PVC.
  • Example 3-1 The same treatment as in Example 3-1 was carried out except that agar was used instead of PVC.
  • Example 3-1 It processed similarly to Example 3-1 except having changed PVC and used furfuryl alcohol.
  • silicon particles single crystal silicon particles (Lot3775061) manufactured by High Purity Chemical Research Institute Co., Ltd. were prepared. After the analysis of silicon particles in a measurement condition of a speed reconsider 3 / minute, range of 5 ⁇ 90 réelle XRD, the full width at half maximum of the main peak was 0.1072 réelle. Moreover, the average particle diameter of this silicon particle was 48 micrometers.
  • the comparative example 3-1 it processed similarly to Example 3-1 except having used this single crystalline silicon particle instead of the polycrystalline silicon particle of Example 3-1. As a result of observing the surface-modified fine particles according to Comparative Example 3-1 under the same microscope, a TEM image shown in FIG. 29 was obtained.
  • Example 3-1 It processed similarly to Example 3-1 except having made the 4th process into the following process. That is, the silicon-based active material fine particles and the artificial graphite were weighed so as to have a mass ratio of the silicon-based active material fine particles produced in the first step to artificial graphite at 75:25, and these were uniformly mixed with menow induction. This mixture was used as a negative electrode active material.
  • Example 3-1 using polycrystalline silicon was able to improve the initial efficiency by 8% and improve the cycle life by 65% than Comparative Example 3-1 using single crystal silicon.
  • the polycrystalline silicon-based active material fine particles have a large number of single crystal regions (domains) therein and a space is formed between the domains.
  • each domain expands by alloying with lithium at the time of charge, it can be considered that the stress of the expansion is alleviated by the space between the domains.
  • a single macro domain is alloyed with lithium at the time of charging, while in the polycrystalline silicon-based active material, a small number of domains are alloyed with lithium.
  • Example 3-1 since the surface-modified fine particles are complexed with the hard carbon, it is also possible to reduce the expansion by the hard carbon and to secure the conductivity. For this reason, it can be said that Example 3-1 improves a characteristic than Comparative Example 3-1.
  • Example 3-1 was able to improve the initial efficiency by 18% and the lifespan by 2.5 times compared with Comparative Example 3-2 (having the negative electrode active material as a composite material of the polycrystalline silicon-based active material and graphite). It can be considered that the graphite of Comparative Example 3-2 cannot absorb the stress due to the expansion when silicon alloyed with lithium expands the electrode. For this reason, it can be said that cycle deterioration increased in the comparative example 3-2.
  • Example 3-2 to 6 composites were prepared using various carbon sources such as phenol resins in place of PVC of Example 3-1, and compared with those in Comparative Examples 3-3. As a result, the same effects as in Example 3-1 using PVC were obtained, and the initial efficiency was improved by 3 to 10% and the cycle life by 25 to 50%.
  • Example 3-7 This inventor carried out Example 3-7 in order to confirm the correspondence of the charge capacity, discharge capacity, and cycle life of a lithium ion secondary battery.
  • the result is shown in FIG.
  • the horizontal axis in Fig. 20 shows the charge ratio of the silicon-based active material (the theoretical capacity implemented by the lithium ion secondary battery's charge capacity / silicon-based active material), and the vertical axis shows the discharge capacity and cycle life of the first cycle.
  • the discharge capacity was expressed by standardizing the discharge capacity when the charge ratio of the silicon-based active material is 20%.
  • the cycle life was shown by normalizing the cycle life to 1 when the filling ratio of the silicon-based active material is 100%.
  • the cycle life was greatly improved when the filling ratio of the silicon-based active material was 70% or less.
  • the discharge capacity is maintained at a higher level than artificial graphite, and therefore, the present embodiment has been made in view of both high discharge capacity (that is, reduction of irreversible capacity) and long cycle life. It can be seen that it is excellent.
  • Example 3-1 It processed similarly to Example 3-1 except having changed the baking temperature of the 4th process within the range of 400-900 degreeC.
  • the results are shown in FIG. In Fig. 21, the horizontal axis represents firing temperature and the vertical axis represents initial efficiency and cycle life. However, initial stage efficiency and cycle life were shown by normalizing the value at the baking temperature to 400 degreeC to 1.
  • both the initial efficiency and the cycle life were higher than the case of 400 ° C between 500 and 800 ° C. If the temperature is lowered, it may be considered that the carbonization progress of the hard carbon carbon source is difficult to progress.
  • the initial efficiency and cycle life greatly fall at 900 ° C., it can be considered that this is due to the adverse effect of the production of electrochemically inert SiC. In other words, it is thought that SiC is produced even at 900 ° C by increasing the reactivity with carbon by miniaturizing silicon.
  • Example 3-9 it processed similarly to Example 3-1 except having changed the mass ratio of surface-modified microparticles
  • the results are shown in FIG.
  • the horizontal axis in Fig. 22 represents the mass% of the surface modified fine particles (mass% relative to the total mass of the surface modified fine particles and the hard carbon), and the vertical axis represents the cycle life.
  • the cycle life was expressed by normalizing the value to 1 when the mass% of the surface-modified fine particles became 100%.
  • the cycle life is increased when the mass ratio of the surface modified fine particles to the hard carbon is within a range of 50:50 to 80:20. Specifically, the cycle life for this range was 1.8 times larger than the cycle life when the mass% of the surface modified fine particles became 100%.
  • Example 3-10 it processed similarly to Example 3-2 except having changed the mass ratio of surface-modified microparticles
  • the results are shown in FIG.
  • the horizontal axis in Fig. 23 represents the mass% of the surface modified fine particles (mass% relative to the total mass of the surface modified fine particles and the hard carbon), and the vertical axis represents the cycle life. However, the cycle life was expressed by normalizing the value to 1 when the mass% of the surface-modified fine particles became 100%.
  • the cycle life was increased when the mass ratio of the surface modified fine particles to the hard carbon became a value within the range of 75:25 to 90:10. Specifically, the cycle life for this range was 1.8 times larger than the cycle life when the mass% of the surface modified fine particles became 100%.
  • Example 3-11 A battery was produced in the same manner as in Example 3-1 except that the electrolyte solution of Example 3-1 was changed to 1M-LiPF6PC / DEC (1: 1 volume ratio).
  • Example 3-11 after charging the 1st cycle at 25 degreeC similarly to Example 3-1, the environmental temperature of the battery was changed to 0-20 and each hold
  • Example 3-11 using a PC it was found that the discharge capacity at low temperature was significantly increased compared with the battery of Example 3-1 using EC. It is thought that this is because the melting point does not freeze at -20 ° C and does not interfere with the movement of lithium ions at -55 ° C. On the other hand, since the melting point is 37 ° C. in EC, it is thought that by mixing with DEC having a low boiling point, it becomes solid at room temperature as the liquid or the temperature decreases, and the mobility of lithium ions is inhibited and it cannot be discharged. The use of this PC leads to the expansion of the available low temperature range, which can be a great advantage in applications such as electric vehicles.
  • Example 3-12 in order to confirm the correspondence between the baking temperature in a 3rd process, and the characteristic of a lithium ion secondary battery.
  • Example 3-12 it processed similarly to Example 3-1 except having changed the baking temperature within the range of 400-900 degreeC with respect to the 3rd process of Example 3-1.
  • the results are shown in FIG. 25, the horizontal axis represents firing temperature and the vertical axis represents initial efficiency and cycle life.
  • initial stage efficiency and cycle life show the value normalized by the following comparative example 3-8.
  • Example 3-8 It processed similarly to Example 3-12 except not having performed the 2nd and 3rd process of Example 3-1. That is, in Comparative Example 3-8, the surface of the silicon-based active material fine particles was not covered with a carbon material.
  • the initial efficiency was higher than the comparative example 3-8 between 500-800 degreeC
  • the cycle life was higher than the comparative example 3-8 between 500-800 degreeC. Therefore, it is preferable that baking temperature is 500-800 degreeC.
  • the reason why the cycle life and initial efficiency are lowered when the firing temperature is lower than 500 ° C. is that carbonization of the organic material is less likely to proceed at a lower firing temperature and the coating amount of the carbon material is lowered.
  • the firing temperature is 900 ° C, the initial efficiency and cycle life are greatly reduced. The reason for this can be considered to be an adverse effect due to the generation of electrochemically inert SiC. That is, as the silicon-based active material is made into fine particles, the reactivity with carbon increases, and thus SiC is partially produced even at 900 ° C.
  • Example 3-13 in order to confirm the correspondence relationship between the mass of the carbon material and the characteristics of the lithium ion secondary battery with respect to the coating amount of the carbon material, that is, the total mass of the silicon-based active material fine particles and the carbon material.
  • it processed similarly to Example 3-1 except having changed the coating amount of the carbon material in the range of 0.07-6.7 mass% by changing the addition amount of citric acid about the 2nd process of Example 3-1. The results are shown in FIG. The horizontal axis in Fig.
  • the cycle life and initial stage when the coating amount of the carbon material is 0.35 to 3.5% by mass are better than those of Comparative Example 3-8, and the cycle life and initial stage when the coating amount of the carbon material is 0.7 to 1.75% by mass. Efficiency is maximal.
  • the coating amount of carbon material exceeds 3.5 mass%, it can be said that it is based on the structure of a carbon material as a reason for the cycle life and initial stage efficiency falling.
  • the carbon material covering the silicon-based active material fine particles is assumed to have a graphite structure, but since this structure is immature (in particular, there are many amorphous portions), when the coating amount of the carbon material increases, This is because access to the active material fine particles is rather inhibited.
  • the cycle life and initial efficiency are maximized when the carbon material coating amount is 0.7-1.75 mass%.
  • the carbon material hardly inhibits the movement of lithium ions, and the oxidation inhibiting effect of the silicon-based active material fine particles by the carbon material is maximized.
  • Example 3-14 in order to confirm the correspondence relationship between the average particle diameter of a silicon type active material microparticle, and the characteristic of a lithium ion secondary battery.
  • it processed similarly to Example 3-1 except having changed the average particle diameter of the silicon type active material microparticles
  • the result is shown in FIG. 27, the horizontal axis represents the average particle diameter of the silicon-based active material fine particles, and the vertical axis represents the cycle life.
  • a cycle life shows the value normalized by the comparative example 3-8.
  • the cycle life fluctuated rapidly, especially around 200nm.
  • the shape of the graph is estimated to be maximized below 100nm. As for this, 200 nm or less is preferable and 100 nm or less of an average particle diameter is further more preferable.
  • the wet grinding method of Example 3-1 it is difficult to reaggregate or grind the particles, which requires a lot of time for grinding to 100 nm or less. Industrially, the average particle size can be selected in terms of cost and performance.
  • fine-particles are hard to be exposed to air
  • fine-particles with little silicon oxide can be produced.
  • the surface-modified fine particles are coated with a carbon material, the silicon-based active material fine particles are hardly exposed to the atmosphere during the use of the surface-modified fine particles.
  • the irreversible capacity of the negative electrode active material is reduced. In other words, it is possible to maintain a high discharge capacity of the silicon-based active material (that is, to realize a high initial efficiency).
  • direct contact between the silicon-based active material fine particles and the solvent is suppressed.
  • the surface modified fine particles are also introduced into the hard carbon by complexing with the hard carbon. Therefore, the stress due to expansion and contraction of the surface-modified fine particles is alleviated by the hard carbon, so the cycle life is improved in this respect.
  • a large amount of surface-modified fine particles can be introduced into the hard carbon, thereby improving the theoretical capacity, that is, the discharge capacity of the negative electrode active material.
  • the silicon-based active material is polycrystalline, it has a large number of single crystal particles (domains) and a space is formed between domains. Therefore, stress due to expansion and contraction of the silicon-based active material is alleviated by these spaces. This also improves cycle life.
  • the hard carbon can be obtained by firing a solid starting material, and the total mass of the surface modified fine particles is preferably 50 to 80% by mass relative to the total mass of the hard carbon and the surface modified fine particles.
  • the irreversible capacity of the lithium ion secondary battery is reduced and the cycle life of the lithium ion secondary battery is improved.
  • the starting material of the solid system may be any one or more selected from the group consisting of PVC, sucrose, gelatin and agar. In this case, the irreversible capacity of the lithium ion secondary battery is reduced, and the cycle life of the lithium ion secondary battery is improved.
  • Hard carbon can be obtained by calcining the starting material of the liquid system, and the total mass of the surface modified fine particles is preferably 75 to 90% by mass relative to the total mass of the hard carbon and the surface modified fine particles. In this case, the irreversible capacity of the lithium ion secondary battery is reduced and the cycle life of the lithium ion secondary battery is improved.
  • the average particle diameter of the silicon-based active material fine particles may be 200 nm or less, in which case the irreversible capacity of the lithium ion secondary battery is reduced, and the cycle life is also improved.
  • the carbon material may have a thickness of 2 to 20 nm, in which case the irreversible capacity of the lithium ion secondary battery is reduced, and the cycle life is also improved.
  • At least one of the inert atmosphere of the third process and the fourth process may be composed of any one or more selected from the group consisting of argon and nitrogen, in which case the irreversible capacity of the lithium ion secondary battery is reduced and the cycle life is also improved. do.
  • baking of a 4th process can be performed in the temperature range of 500-800 degreeC, In this case, the irreversible capacity
  • the metal lithium foil may be disposed in a portion of the negative electrode current collector, for example, a portion in which the electrode current collector terminal is welded, and a portion not facing the positive electrode active material layer. In this case, the irreversible capacity of the lithium ion secondary battery is reduced, and the cycle life is also improved.
  • the charging capacity of the lithium ion secondary battery can be maintained at 70% or less of the theoretical capacity implemented by the silicon-based active material fine particles, and in this case, the irreversible capacity of the lithium ion secondary battery is reduced and the cycle life is also improved.
  • the organic material may be any one or more selected from the group consisting of hydroxy acids, monosaccharides and oligosaccharides, in which case the irreversible capacity of the lithium ion secondary battery is reduced and the cycle life is also improved.
  • the hydroxy acid may be any one or more selected from the group consisting of citric acid and glycolic acid, in which case the irreversible capacity of the lithium ion secondary battery is reduced and the cycle life is also improved.
  • non-aqueous solvent may be any one or more selected from the group consisting of alcohols and ethers, in which case the irreversible capacity of the lithium ion secondary battery is reduced and the cycle life is also improved.
  • baking of a 3rd process can be performed in the temperature range of 500-800 degreeC, In this case, the irreversible capacity
  • lithium ion secondary battery 20 positive electrode

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Abstract

L'invention concerne un matériau actif d'anode pour batterie au lithium-ion, qui a été amélioré récemment en vue de renforcer la durée de vie d'une batterie au lithium-ion tout en maintenant la capacité élevée de décharge d'un matériau actif à base de silicium ; un procédé de fabrication du matériau actif d'anode pour batterie au lithium-ion ; une batterie au lithium-ion ; et un procédé de recharge de la batterie au lithium-ion. Selon un aspect, la présente invention concerne des particules de matériau actif à base de silicium ainsi qu'un matériau actif d'anode pour batterie au lithium-ion, dans lesquels la surface des particules du matériau actif à base de silicium est recouverte d'une matière carbonée.
PCT/KR2014/012162 2013-12-10 2014-12-10 Materiau actif d'anode pour batterie au lithium-ion et procede de fabrication associe WO2015088252A1 (fr)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109817908A (zh) * 2019-01-03 2019-05-28 欣旺达电子股份有限公司 硅碳复合材料及其制备方法、锂离子电池
CN109843799A (zh) * 2016-08-23 2019-06-04 奈克松有限公司 二次电池用硅类活性物质粒子及其制备方法
CN109923707A (zh) * 2016-10-19 2019-06-21 太克万株式会社 碳硅复合材料、负极、二次电池、碳硅复合材料制造方法

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11450849B2 (en) * 2018-06-15 2022-09-20 Umicore Active material powder for use in a negative electrode of a battery and a battery comprising such an active material powder

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH103920A (ja) * 1996-06-17 1998-01-06 Toshiba Corp リチウム二次電池及びその製造方法
KR20120087000A (ko) * 2011-01-27 2012-08-06 도레이첨단소재 주식회사 리튬 2차 전지용 음극재 및 이의 제조방법
KR20130004536A (ko) * 2011-06-30 2013-01-11 삼성에스디아이 주식회사 음극 활물질, 그 제조방법 및 이를 포함하는 리튬 전지
KR20130005102A (ko) * 2011-07-05 2013-01-15 울산대학교 산학협력단 실리콘-탄소 코어쉘을 이용한 리튬이차전지용 음극활물질 및 이의 제조방법

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH103920A (ja) * 1996-06-17 1998-01-06 Toshiba Corp リチウム二次電池及びその製造方法
KR20120087000A (ko) * 2011-01-27 2012-08-06 도레이첨단소재 주식회사 리튬 2차 전지용 음극재 및 이의 제조방법
KR20130004536A (ko) * 2011-06-30 2013-01-11 삼성에스디아이 주식회사 음극 활물질, 그 제조방법 및 이를 포함하는 리튬 전지
KR20130005102A (ko) * 2011-07-05 2013-01-15 울산대학교 산학협력단 실리콘-탄소 코어쉘을 이용한 리튬이차전지용 음극활물질 및 이의 제조방법

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
NG, SEE HOW ET AL.: "Amorphous carbon-coated silicon nanocomposites: a low- temperature synthesis via spray pyrolysis and their application as high- capacity anodes for lithium-ion batteries", THE JOURNAL OF PHYSICAL CHEMISTRY C, vol. 111, no. 29, 2007, pages 11131 - 11138 *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109843799A (zh) * 2016-08-23 2019-06-04 奈克松有限公司 二次电池用硅类活性物质粒子及其制备方法
CN109843799B (zh) * 2016-08-23 2022-10-14 奈克松有限公司 二次电池用硅类活性物质粒子及其制备方法
CN109923707A (zh) * 2016-10-19 2019-06-21 太克万株式会社 碳硅复合材料、负极、二次电池、碳硅复合材料制造方法
CN109923707B (zh) * 2016-10-19 2022-05-03 太克万株式会社 碳硅复合材料、负极、二次电池、碳硅复合材料制造方法
CN109817908A (zh) * 2019-01-03 2019-05-28 欣旺达电子股份有限公司 硅碳复合材料及其制备方法、锂离子电池

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