WO2012127548A1 - Electrode négative pour une batterie secondaire à lithium-ion et batterie secondaire à lithium-ion - Google Patents

Electrode négative pour une batterie secondaire à lithium-ion et batterie secondaire à lithium-ion Download PDF

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WO2012127548A1
WO2012127548A1 PCT/JP2011/006581 JP2011006581W WO2012127548A1 WO 2012127548 A1 WO2012127548 A1 WO 2012127548A1 JP 2011006581 W JP2011006581 W JP 2011006581W WO 2012127548 A1 WO2012127548 A1 WO 2012127548A1
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carbon particles
negative electrode
particles
carbon
lithium ion
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English (en)
Japanese (ja)
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慶一 高橋
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パナソニック株式会社
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • 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
    • 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 lithium ion secondary battery, and more particularly to improvement of a negative electrode for a lithium ion secondary battery using a graphite material as a negative electrode active material.
  • a lithium ion secondary battery (hereinafter also simply referred to as a battery) has a high operating voltage and energy density. For this reason, it is widely used as a driving power source for portable electronic devices such as mobile phones and notebook personal computers. For example, a power source for driving a portable electronic device is required to have excellent cycle characteristics that can maintain a capacity retention rate of 70% or more even when a charge / discharge cycle is repeated 500 times or more.
  • lithium-ion secondary batteries have been rapidly developed as power sources for driving hybrid vehicles and electric vehicles and power sources for power storage.
  • Lithium ion secondary batteries for such applications are required to have high input / output characteristics.
  • graphite particles having an amorphous or low-crystalline carbon material made of a non-graphitizable carbon material or the like on the surface have been proposed as a negative electrode active material for improving the input / output characteristics of a battery (Patent Documents 1 and 2).
  • the non-graphitizable carbon material has low orientation, and sites for inserting and extracting lithium ions are randomly located. Therefore, such graphite particles have high lithium ion acceptability.
  • Patent Document 3 discloses that a carbon material having a large particle size and a carbon material having a small particle size are mixed and used as a negative electrode active material for a lithium ion secondary battery.
  • a negative electrode active material containing artificial graphite having an average particle size D 50 of 15 to 50 ⁇ m as a main component and further containing artificial graphite particles having a particle size of 10 ⁇ m or less is disclosed. It is described that by controlling the particle size of the artificial graphite in the negative electrode active material, an increase in the internal resistance of the battery due to repeated charge / discharge can be suppressed, and deterioration of charge / discharge cycle characteristics can be suppressed.
  • Graphite particles having a low crystalline carbon material such as a non-graphitizable carbon material on the surface are more likely to raise the battery temperature during charge / discharge at a high current density than graphite particles not having a low crystalline carbon material on the surface. There was a trend. And when battery temperature rises, a charge capacity and cycling characteristics are reduced. Therefore, a battery using graphite particles having a low crystalline carbon material on the surface as a negative electrode active material is not suitable for long-term use such as a power source for driving a hybrid car or an electric vehicle.
  • the present invention improves cycle characteristics even when used under charge / discharge conditions at high current density by improving conductivity and heat conductivity. It aims at providing the lithium ion secondary battery which can suppress a fall.
  • One aspect of the present invention includes a core material and a negative electrode active material layer formed on the surface of the core material, and the negative electrode active material layer includes first carbon particles, second carbon particles, and a binder, wherein the first carbon particles have artificial graphite particles and amorphous carbon layer formed on the surface of the artificial graphite particles, the median diameter D 1 50 of the first carbon particles is 5 ⁇ 25 [mu] m, the first The two carbon particles are natural graphite particles, the median diameter D 2 50 of the second carbon particles is 0.2 to 10 ⁇ m, and satisfies D 1 50 > D 2 50, and is contained in the negative electrode active material layer.
  • the amount of the second carbon particles is 1 to 10 parts by mass with respect to 100 parts by mass of the first carbon particles.
  • the first carbon particles are artificial graphite particles having an amorphous carbon layer on the surface, and are high capacity negative electrode active materials having excellent input / output characteristics.
  • the amorphous carbon layer on the surface of the first carbon particles has lower conductivity than a carbon material having a high degree of graphitization.
  • the second carbon particles are natural graphite fine particles having high conductivity. This 2nd carbon particle is distribute
  • the first carbon particles having the specific median diameter D 1 50 and the second carbon particles having the median diameter D 2 50 as described above are blended in the above proportion, whereby the second carbon particles become the first carbon particles. It arrange
  • the conductive path between the first carbon particles is sufficiently formed, the resistance in the negative electrode is reduced, and the heat dissipation is improved.
  • the sphericity of the first carbon particles is preferably 80% or more so that the first carbon particles are not easily broken during rolling of the negative electrode active material layer.
  • the second carbon particles preferably have a BET specific surface area of 10 to 30 m 2 / g and are scaly or scaly from the viewpoint of excellent contact with the surface of the first carbon particles.
  • the graphitization degree of the second carbon particles is preferably 0.75 or more in order to further increase the conductivity of the negative electrode active material layer.
  • the median diameter D 2 50 of the second carbon particles is 10 to 50% of the median diameter D 1 50 of the first carbon particles, so that a conductive path between the first carbon particles is more easily formed. It is preferable from the point.
  • Another aspect of the present invention is a lithium ion secondary battery including the above-described negative electrode for a lithium ion secondary battery, a positive electrode, a separator interposed between the negative electrode and the positive electrode, and a nonaqueous electrolyte.
  • the negative electrode of the present invention it is possible to obtain a high-capacity lithium ion secondary battery that is excellent in input / output characteristics and suppressed in deterioration in cycle characteristics when used under charge / discharge conditions of high density current.
  • the negative electrode 10 for a lithium ion secondary battery includes a core material 11 and a negative electrode active material layer 12 formed on the surface of the core material 11.
  • the negative electrode active material layer 12 includes first carbon particles 13, second carbon particles 14, and a binder 15.
  • the core material 11 is not particularly limited as long as it can be used for the negative electrode of a lithium ion secondary battery. Specifically, for example, a metal foil or metal sheet made of copper, copper alloy, stainless steel, nickel or the like having a thickness in the range of 5 to 50 ⁇ m can be used.
  • the first carbon particles are particles having artificial graphite particles and amorphous carbon layer formed on its surface, the median diameter D 1 50 is 5 ⁇ 25 [mu] m. Note that the surface of the artificial graphite particles may be completely covered with the amorphous carbon layer or may be partially covered. The graphite portion contributes to increasing the capacity of the negative electrode, and the amorphous carbon layer on the surface contributes to maintaining high input / output characteristics and excellent compression resistance of the first carbon particles.
  • the amorphous carbon layer is indefinite and has many sites where lithium ions that play the same role as the edge surface of the carbon network surface can be inserted and removed.
  • the amorphous carbon layer can suppress the breakage of particles and the orientation of the carbon network surface that occur when natural graphite particles are used as the negative electrode active material. For this reason, the first carbon particles have a high breaking strength. That is, at the time of producing the negative electrode plate, since particle breakage during rolling can be suppressed, high-density filling is possible.
  • the amorphous carbon layer has low conductivity and tends to increase the internal resistance of the battery. For this reason, when charging / discharging is repeated at a high current density, the temperature of the battery is increased, and the charge / discharge characteristics tend to be reduced.
  • the second carbon particles are blended in order to improve the conductivity and heat dissipation of such an amorphous carbon layer.
  • a part of the graphite particle portion of the first carbon particle may be natural graphite. Further, at least a part of the graphite particle portion may be artificial graphite obtained by baking and graphitizing a carbon material that can be graphitized such as pitch and coke. Further, the graphite particles need not all be graphitized, and may include, for example, a carbon portion in the course of the graphitization process.
  • the amorphous carbon layer of the first carbon particles is formed on the surface of the graphite particles by a method described later.
  • the thickness of such an amorphous carbon layer is preferably 0.01 to 0.07 ⁇ m, more preferably 0.01 to 0.03 ⁇ m, from the viewpoint of suppressing an increase in irreversible capacity during the first charge / discharge.
  • the particle diameter of the first carbon particles is such that the median diameter D 1 50 (that is, the cumulative 50% diameter value in the volume-based particle size distribution) in the particle size distribution measurement by the diffraction scattering method is 5 to 25 ⁇ m, preferably 15 to 20 ⁇ m. is there.
  • the median diameter D 1 50 is less than 5 ⁇ m, the filling property is decreased, leading to a decrease in battery capacity. Also, when the median diameter D 1 50 exceeds 25 ⁇ m, the effect of improving the conductivity and heat conductivity of the second carbon particles is reduced.
  • the graphitization degree of the first carbon particles is preferably 0.65 to 0.85, and more preferably 0.70 to 0.80.
  • the value (G) of the degree of graphitization was obtained by obtaining the value (a 3 ) of the 002 plane spacing d 002 obtained by XRD analysis of the carbon particles, and substituting this into the following equation.
  • the sphericity of the first carbon particles is preferably 80% or more, more preferably 85 to 95%. In this case, since the stress applied at the time of rolling or charging / discharging is made uniform, destruction of the first carbon particles can be suppressed.
  • the sphericity is represented by 4 ⁇ S / L 2 (where S is the area of the orthographic image of the first carbon particles, and L is the perimeter of the orthographic image) ⁇ 100 (%).
  • the average sphericity of 100 arbitrary first carbon particles is preferably in the above range.
  • the first carbon particles can be produced by the following method using, for example, natural graphite particles serving as the core of the particles and a carbon material that can be graphitized such as pitch and coke as raw materials.
  • grain surface is smooth and it is thought that many basal surfaces are exposed rather than the edge part of a carbon network surface. Since the basal surface does not contribute to occlusion and release of lithium ions, it is preferable that the surface pulverized with as little stress as possible has few basal surfaces.
  • the natural graphite particles are preferably pulverized so that the content ratio of particles of 5 ⁇ m or less is 3% by mass or less. Further, the value of the cumulative 50% diameter in the volume-based particle size distribution of the natural graphite particles (that is, the median diameter D 50 in the particle size distribution measurement by the diffraction scattering method) is 1.5 to 3 times the value of the cumulative 10% diameter.
  • the cumulative 90% diameter value is preferably 1.1 to 1.5 times the cumulative 50% diameter value.
  • the pitch is melted by heating the first precursor in an inert gas atmosphere at 600 to 1000 ° C., and subsequently maintained for a predetermined time. Thereby, the 2nd precursor by which the pitch was polymerized is obtained. Thereafter, the third precursor is obtained by heating the second precursor at 1100 to 1500 ° C. to carbonize the polymerization pitch.
  • the third precursor is heated at 2200 to 2800 ° C. in an inert gas atmosphere to obtain a lump of composite graphite particles obtained by graphitizing the carbonized polymerization pitch.
  • Graphitization can be confirmed, for example, by an increase in the sharpness of the peak in XRD.
  • the carbonization and graphitization described above are preferably performed in an inert atmosphere, for example, in an atmosphere containing at least one gas of nitrogen and argon.
  • the mass of composite graphite particles is pulverized and classified so as to have a desired average particle diameter. Since the above-mentioned lump of composite graphite particles has a discontinuous structure, it is easily pulverized. Therefore, even if the pulverization stress is relatively small, the particle size of the composite graphite particles can be easily controlled to a desired value. Further, since the pulverization stress can be reduced, the surface of the composite carbon particles is not excessively smooth, and a state having a certain degree of surface roughness is maintained. It is considered that the edge portion of the carbon network surface appears sufficiently on the surface of the composite carbon particle having such surface roughness.
  • lithium ions are quickly inserted during battery charging, and lithium ions are rapidly desorbed during discharging. That is, by using the first carbon particles including the composite graphite particles described above as the negative electrode active material, the charge acceptability of the negative electrode is improved.
  • the first carbon particles can be obtained by further forming an amorphous carbon layer on the surface of the composite graphite particles.
  • the method for forming the amorphous carbon layer on the surface of the composite graphite particles is not particularly limited, and a known gas phase method or liquid phase method can be used.
  • the amorphous carbon layer can be formed by reducing it to make it amorphous.
  • an amorphous carbon layer can also be formed on the surface of the composite graphite particles by heating the composite graphite particles in a reducing atmosphere such as acetylene gas or ethylene gas.
  • the proportion of the amorphous carbon layer in the first carbon particles is preferably 0.2 to 2.0% by mass, and more preferably 0.5 to 1.0% by mass.
  • the ratio of the amorphous carbon layer in the first carbon particles can be calculated from, for example, the ratio of the area of the amorphous carbon layer in the cross section of the whole particle by observing the cross section of the first carbon particle with an electron microscope. Specifically, the cross section of the first carbon particles may be observed with an electron microscope and obtained from the area ratio of the amorphous carbon layer in the cross section of the entire first carbon particles.
  • the second carbon particles are natural graphite fine particles having a median diameter D 2 50 of 0.2 to 10 ⁇ m.
  • the second carbon particles are blended for the purpose of improving the conductivity and heat transfer of the first carbon particles. That is, the first carbon particles have an amorphous carbon layer on the particle surface, so that the surface conductivity is slightly lowered. In this case, a conductive path and a heat dissipation path between the first carbon particles can be ensured by filling the gaps between the first carbon particles with the second carbon particles having excellent conductivity and heat conductivity. As a result, an increase in the temperature of the negative electrode active material layer can be suppressed even during charge / discharge at a high current density.
  • the second carbon particles have a median diameter D 2 50 in the particle size distribution measurement by a diffraction scattering method of 0.2 to 10 ⁇ m, preferably 3 to 8 ⁇ m.
  • the median diameter D 2 50 of the second carbon particles is less than 0.2 ⁇ m, the second carbon particles tend to aggregate with each other, so that the formation of a conductive path that connects the first carbon particles becomes insufficient.
  • the median diameter D 2 50 of the second carbon particles exceeds 10 ⁇ m, the second carbon particles are difficult to be arranged in the gap between the first carbon particles, and a conductive path that connects the first carbon particles is formed. Becomes insufficient.
  • the median diameter D 2 50 of the second carbon particles is preferably 10 to 50%, more preferably 20 to 30% of the median diameter D 1 50 of the first carbon particles.
  • the second carbon particles are arranged in the gap between the first carbon particles. It is possible to form a large number of conductive paths that connect the first carbon particles.
  • the BET specific surface area of the second carbon particles is preferably 10 to 30 m 2 / g, more preferably 14 to 25 m 2 / g, and particularly preferably 15 to 25 m 2 / g.
  • the BET specific surface area of the second carbon particles is 10 to 30 m 2 / g, the effect of improving the conductivity of the negative electrode active material layer is good.
  • the second carbon particles are particularly preferably scaly or scaly natural graphite fine particles having a BET specific surface area of 10 to 30 m 2 / g.
  • a conductive path can be efficiently formed between the first carbon particles with a small amount.
  • the BET specific surface area in the above range, it is possible to suppress a decrease in the contact between the second carbon particles and between the first carbon particles and the second carbon particles due to the smooth surface of the second carbon particles. .
  • the particle diameter of the second carbon particles does not become too small, and aggregation between the second carbon particles can be suppressed.
  • the degree of graphitization of the second carbon particles is larger than that of the first carbon particles, preferably 0.75 or more, more preferably larger than 0.80 and not more than 0.90. Due to the high degree of graphitization of the second carbon particles, the conductivity of the second carbon particles is increased. For this reason, the effect which improves the electroconductivity of a negative electrode active material layer with the conductive path formed in the clearance gap between 1st carbon particles becomes large.
  • the content of the second carbon particles in the negative electrode active material layer is 1 to 10 parts by mass, preferably 2 to 5 parts by mass with respect to 100 parts by mass of the first carbon particles.
  • the second carbon particles can be efficiently arranged in the gap between the first carbon particles.
  • the content of the second carbon particles is less than 1 part by mass with respect to 100 parts by mass of the first carbon particles, the amount of the second carbon particles disposed in the gap between the first carbon particles is reduced, so that the conductive path As a result, the conductivity and heat conductivity of the negative electrode active material layer are lowered.
  • the content of the second carbon particles exceeds 10 parts by mass with respect to 100 parts by mass of the first carbon particles, the negative electrode filling ability is reduced, and the production yield of the negative electrode is reduced in a rolling process or the like. .
  • the average value of the BET specific surface area of the entire carbon particles, including the first carbon particles and the second carbon particles contained in the negative electrode active material layer, is preferably 2.5 to 5 m 2 / g, and preferably 3 to 4 m. 2 / g is more preferable.
  • the average value of the BET specific surface area is 2.5 to 5 m 2 / g, it is possible to achieve both excellent charge / discharge cycle characteristics and high input / output characteristics at a high level.
  • binder examples include polyolefin resins, fluororesins, and particulate binders having rubber elasticity.
  • polyolefin resin examples include polyethylene and polypropylene.
  • fluororesin examples include polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, and vinylidene fluoride-hexafluoropropylene copolymer.
  • particulate binder having rubber elasticity examples include a copolymer (SBR) containing a styrene unit and a butadiene unit.
  • SBR copolymer
  • the negative electrode active material layer may contain a thickener such as carboxymethyl cellulose and other various additives as optional components in addition to the first carbon particles, the second carbon particles, and the binder as essential components. Good.
  • the negative electrode active material layer 12 is prepared by applying the negative electrode mixture paste to one or both surfaces of the core material 11 and drying it. After forming the negative electrode mixture paste, the negative electrode active material layer 12 is generally rolled using a roller or the like. By rolling the negative electrode active material layer 12, the negative electrode 10 having a high packing density of the negative electrode active material and high strength can be obtained.
  • the above-mentioned first carbon particles are difficult to align. Therefore, even if the packing density of the negative electrode active material layer is increased to 1.6 to 1.8 g / cm 3 , good charge acceptability can be obtained. Thereby, it is possible to achieve both high energy density and high input / output characteristics in an excellent balance.
  • the packing density means the mass of the negative electrode active material layer per unit volume.
  • the total filling rate of the first carbon particles and the second carbon particles in the negative electrode active material layer is, for example, preferably 77% or more, more preferably 78 to 82% on a volume basis.
  • the first carbon particles, the second carbon particles, the binder, the thickener and other various additives contained as necessary, and the first carbon particles are mainly used. A gap formed between them, that is, a void portion is provided.
  • the total filling rate of the first carbon particles and the second carbon particles is 77% or more on a volume basis.
  • the porosity is 18% to 23%, preferably 20 to 22%.
  • the total filling rate on a volume basis is obtained by cutting the negative electrode active material layer in the thickness direction to form a cross section, processing the cross section with polishing and a cross polisher, obtaining a SIM image of the processed cross section, It can be obtained from the contrast of the SIM image using image software (ImageJ).
  • image software imageJ
  • the cross-section SIM image is binarized and a distribution map is acquired, the void portion is displayed as a black region. If the ratio of the area of the black region to the total cross-sectional area is calculated using image software, the porosity can be obtained.
  • the total mass content of the first carbon particles and the second carbon particles in the negative electrode active material layer is preferably 90 to 99% by mass, and more preferably 98 to 99% by mass.
  • the total content of the first carbon particles and the second carbon particles is preferably 1 to 10% by mass, and more preferably 1 to 2% by mass.
  • the capacity density of the negative electrode active material layer as a lithium ion secondary battery is 315 to 350 Ah / kg.
  • the theoretical capacity of graphite is 372 Ah / kg, but when general graphite is used as the negative electrode material, the capacity density of the negative electrode active material layer is designed to be 315 Ah / kg or more from the viewpoint of maintaining sufficient charge acceptance. It is difficult to do.
  • the present invention since the above carbon material particles are used, excellent charge acceptability can be obtained. Therefore, even if the capacity density of the negative electrode active material layer is increased to, for example, 315 to 350 Ah / kg, good charge acceptability can be obtained.
  • the capacity density of the negative electrode active material layer is determined by dividing the fully charged battery capacity by the mass of the carbon material particles contained in the negative electrode active material layer portion facing the positive electrode active material layer.
  • the lithium ion secondary battery 20 includes the above-described negative electrode 10 for a lithium ion secondary battery, a positive electrode 21, and a separator 22 interposed between the negative electrode 10 and the positive electrode 21.
  • the positive electrode 21 includes a positive electrode core material and a positive electrode active material layer attached to the surface thereof.
  • the positive electrode active material layer generally includes a positive electrode active material such as a lithium-containing composite oxide, a conductive agent such as carbon black, and a binder such as PTFE and polyvinylidene fluoride.
  • a positive electrode active material such as a lithium-containing composite oxide
  • a conductive agent such as carbon black
  • a binder such as PTFE and polyvinylidene fluoride.
  • known materials can be used without any particular limitation.
  • As the positive electrode core material a sheet of stainless steel, aluminum, titanium, or the like can be used.
  • the total thickness of the two positive electrode active material layers is preferably 50 to 250 ⁇ m. By setting the total thickness of the positive electrode active material layer to 50 ⁇ m or more, it becomes easy to obtain a sufficient capacity. By setting the total thickness of the positive electrode active material layer to 250 ⁇ m or less, the internal resistance of the battery can be easily reduced.
  • a known active material such as a lithium-containing composite oxide can be used without any particular limitation.
  • Specific examples include LiCoO 2 , LiNiO 2 and LiMn 2 O 4 having a spinel structure.
  • a part of the transition metal contained in the composite oxide can be substituted with another element.
  • a lithium nickel composite oxide in which a part of Ni element of LiNiO 2 is substituted with Co or other elements has charge / discharge cycle life characteristics and input / output characteristics at a high current density. Can be balanced.
  • a liquid electrolyte composed of a nonaqueous solvent and a lithium salt dissolved in the nonaqueous solvent is preferable.
  • the non-aqueous solvent include mixed solvents of cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate, and chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Further, ⁇ -butyrolactone, dimethoxyethane, and the like can be used.
  • lithium salts include inorganic lithium fluorides and lithium imide compounds. Examples of the inorganic lithium fluoride include LiPF 6 and LiBF 4, and examples of the lithium imide compound include LiN (CF 3 SO 2 ) 2 .
  • Examples of the separator 22 include polyolefin microporous membranes such as polypropylene and polyethylene, woven fabrics, and non-woven fabrics. Polyolefin is preferable from the viewpoint of improving the safety of the secondary battery because it is excellent in durability and has a shutdown function.
  • the lithium ion secondary battery 20 can be manufactured as follows. First, the wound electrode group 23 is formed by winding the negative electrode 10 and the positive electrode 21 with a separator 22 interposed therebetween. Next, the positive-side insulating plate 25 and the negative-side insulating plate 26 are attached to both ends of the wound electrode group 23, respectively. A positive electrode lead 27 and a negative electrode lead 28 are electrically connected to the positive electrode 21 and the negative electrode 10, respectively. Next, the wound electrode group 23 is accommodated in the battery case 24 and a non-aqueous electrolyte is injected. The amount of the nonaqueous electrolyte can be appropriately set according to the size of the wound electrode group 23 and the like.
  • a step 30 for receiving the sealing plate 29 is formed in the vicinity of the opening of the battery case 24, the sealing plate 29 is disposed on the step 30, and the opening end of the battery case 24 is placed on the peripheral edge of the sealing plate 29. Caulking. Thereby, the battery case 24 is sealed, and the cylindrical lithium ion secondary battery 20 can be obtained.
  • the lithium ion secondary battery can be applied to batteries of various shapes using a wound electrode group such as a square, a cylinder, and a flat shape.
  • the first carbon particles were produced as follows. First, natural graphite particles having an average particle size of 25 ⁇ m (manufactured by Kansai Thermochemical Co., Ltd.) are pulverized with a jet mill “Co-Jet” manufactured by Seishin Enterprise Co., Ltd., so that the particle size is reduced to 10 to 20 ⁇ m. It was adjusted.
  • the melted state was maintained in an argon atmosphere for 2 hours to obtain a second precursor containing a polymerization pitch.
  • the 3rd precursor containing the carbonized polymerization pitch was obtained by heating the 2nd precursor at 1200 degreeC for 1 hour in argon atmosphere.
  • the 3rd precursor was heated at 2800 degreeC in argon atmosphere, and the lump was obtained.
  • the obtained lump was pulverized and classified so that the average particle diameter (median diameter) was 22 ⁇ m, thereby obtaining composite graphite particles having natural graphite portions and artificial graphite portions in the particles.
  • an amorphous carbon layer was formed on at least a part of the surface of the composite graphite particles.
  • the 1st carbon particle which consists of composite carbon particle by which the composite graphite particle and the amorphous carbon layer which coat
  • the thickness of the amorphous carbon layer was 0.01 ⁇ m to 0.015 ⁇ m as measured with a transmission electron microscope (TEM).
  • Median diameter D 1 50 due to diffraction scattering method of the first carbon particles was 22 .mu.m.
  • the BET specific surface area was 3.2 m 2 / g, the degree of graphitization was 0.78, and the sphericity was 87%.
  • the obtained negative electrode mixture paste was applied to both sides of a copper foil having a thickness of 10 ⁇ m, and the coating film was dried. After drying, the copper foil and the coating film (negative electrode active material layer) of the negative electrode mixture paste formed on both surfaces thereof were rolled with a roller so that the total thickness was 160 ⁇ m. At this time, the total filling rate of the first carbon particles and the second carbon particles in the negative electrode active material layer after rolling is 78.6% on a volume basis, and the packing density of the negative electrode active material layer is 1.73 g / cm. It was 3 .
  • the negative electrode thus obtained was cut so that it could be inserted into a battery case having a cylindrical shape 18650 (diameter 18.3 mm, length 65 mm).
  • the aluminum foil and the coating film (positive electrode active material layer) of the positive electrode mixture paste formed on both surfaces thereof were rolled with a roller so that the total thickness was 160 ⁇ m.
  • the positive electrode obtained in this way was cut so that its width could be inserted into a cylindrical 18650 battery case.
  • non-aqueous electrolyte Ethylene carbonate and methyl ethyl carbonate were mixed at a volume ratio of 1: 3. Furthermore, 2% by mass of vinylene carbonate, 2% by mass of vinylethylene carbonate, 5% by mass of fluorobenzene, and 5% by mass of phosphazene were mixed with respect to the total amount of the obtained mixed solvent. Next, a nonaqueous electrolyte was prepared by further dissolving LiPF 6 in the mixed solvent. The concentration of LiPF 6 was adjusted to 1.5 mol / L.
  • the prepared battery was charged and discharged three cycles. Charging / discharging was performed in an environment of 25 ° C., and constant current charging / discharging with a current value of 800 mA. The charge upper limit voltage was 4.2V, and the discharge lower limit voltage was 2.5V. The discharge capacity at the third cycle was taken as the initial capacity of the battery. Similarly, the initial capacity of the battery when constant current charging / discharging was performed at a current value of 1400 mA as the charging / discharging condition of the high-density current was also obtained. The results are shown in Table 1.
  • Examples 2 to 4> A negative electrode and a battery were produced in the same manner as in Example 1 except that the content ratio of the second carbon particles with respect to 100 parts by mass of the first carbon particles was changed from 4 to 10 parts by mass as shown in Table 1. The battery was evaluated in the same manner as in Example 1. The results are shown in Table 1.
  • Example 1 A negative electrode and a battery were produced in the same manner as in Example 1 except that the content ratio of the second carbon particles with respect to 100 parts by mass of the first carbon particles was 15 parts by mass. The battery was evaluated in the same manner as in Example 1. The results are shown in Table 1.
  • Example 2 A negative electrode and a battery were produced in the same manner as in Example 1 except that the second carbon particles were not contained in the negative electrode active material layer. The battery was evaluated in the same manner as in Example 1. The results are shown in Table 1.
  • Examples 5 to 7> A negative electrode and a battery were produced in the same manner as in Example 1 except that the BET specific surface area of the second carbon particles was changed as shown in Table 2. The battery was evaluated in the same manner as in Example 1. The results are shown in Table 2. Table 2 also shows the average value of the BET specific surface area of the second carbon particles and the BET specific surface area of the entire carbon particles including the first carbon particles and the second carbon particles.
  • the batteries of Examples 1 to 4 and Examples 5 to 7 according to the present invention having negative electrodes containing 1 to 10 parts by mass of the second carbon particles with respect to 100 parts by mass of the first carbon particles are as high as 1400 mAh. Even at the time of charge / discharge of the current density, the capacity retention rate after 500 cycles was maintained at 70% or more, and the maximum temperature reached was about 62 to 63 ° C. On the other hand, in the case of Comparative Example 2 in which the second carbon particles were not blended, the capacity retention rate after 500 cycles was significantly low at 33.2% at the time of charge / discharge at a high current density of 1400 mAh, The highest temperature reached was extremely high at 68.1 ° C.
  • capacitance maintenance factor fell to less than 70%, and the fall tendency in the case of a high current density of 1400 mA was especially large.
  • the batteries of Examples 6 and 7 using the second carbon particles having a BET specific surface area of 14.3 m 2 / g or 21.2 m 2 / g have the BET specific surface area of 4.8 m 2 / g. It can be seen that the capacity retention rate is significantly superior to the battery of Example 5 using two carbon particles.
  • the present invention is a negative electrode for a lithium ion secondary battery having high capacity and excellent input / output characteristics during charge / discharge at a high current density.
  • the negative electrode of the present invention and the lithium ion secondary battery using this negative electrode are not only used as a driving power source in portable electronic devices such as mobile phones and notebook personal computers, but also as a driving power source in hybrid cars and electric vehicles, It can be suitably used as a power storage power source.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Composite Materials (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

L'invention concerne une batterie secondaire à lithium-ion, dans laquelle des particules de graphite artificiel à haute capacité ayant chacune une couche de carbone amorphe formée sur la surface de celles-ci sont utilisées comme matière active d'électrode négative, et dans laquelle la détérioration des propriétés de cycle pendant une utilisation dans des conditions de charge-décharge à une densité de courant élevée peuvent être empêchées par amélioration de la conductivité électrique et de propriétés de dissipation de chaleur. Ainsi, une électrode négative pour une batterie secondaire à lithium-ion comprend une matière centrale et une couche de matière active d'électrode négative formée sur la surface de la matière centrale, la couche de matière active d'électrode négative comprenant des premières particules de carbone, des secondes particules de carbone et un liant. Chacune des premières particules de carbone comprend une particule de graphite artificiel et une couche de carbone amorphe formée sur la surface de la particule de graphite artificiel. Les secondes particules de carbone sont des microparticules de graphite naturel. Les premières particules de carbone ont un diamètre médian (D1 50) de 5-25 μm, les secondes particules de carbone ont un diamètre médian (D2 50) de 0,2-10 μm, et D1 50 et D2 50 satisfont une relation représentée par l'équation D1 50 > D2 50. La quantité des secondes particules de carbone est de 1-10 parties en masse par rapport à 100 parties en masse des premières particules de carbone.
PCT/JP2011/006581 2011-03-18 2011-11-25 Electrode négative pour une batterie secondaire à lithium-ion et batterie secondaire à lithium-ion WO2012127548A1 (fr)

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CN103241731A (zh) * 2013-04-01 2013-08-14 东莞市凯金电池材料有限公司 二次锂离子电池用复合石墨材料的制备方法
JP2017069039A (ja) * 2015-09-30 2017-04-06 株式会社Ｇｓユアサ 蓄電素子用負極及び蓄電素子
EP3503267A1 (fr) * 2017-12-22 2019-06-26 Samsung SDI Co., Ltd. Matériau actif d'électrode négative pour batterie secondaire au lithium, électrode négative le comprenant et batterie secondaire au lithium comprenant l'électrode négative
CN111602274A (zh) * 2018-02-26 2020-08-28 株式会社Lg化学 锂二次电池用负极活性材料以及包含其的锂二次电池用负极和锂二次电池
CN115432698A (zh) * 2022-09-30 2022-12-06 贝特瑞新材料集团股份有限公司 碳素二次颗粒及其制备方法、人造石墨及其制备方法、锂离子电池负极材料和锂离子电池
JP2022554030A (ja) * 2020-04-30 2022-12-27 寧徳時代新能源科技股▲分▼有限公司 負極活性材料及びその製造方法、二次電池及び二次電池を含む装置
CN115810730A (zh) * 2022-11-15 2023-03-17 宁德时代新能源科技股份有限公司 负极活性物质、负极极片、二次电池及用电装置

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CN103241731A (zh) * 2013-04-01 2013-08-14 东莞市凯金电池材料有限公司 二次锂离子电池用复合石墨材料的制备方法
JP2017069039A (ja) * 2015-09-30 2017-04-06 株式会社Ｇｓユアサ 蓄電素子用負極及び蓄電素子
EP3503267A1 (fr) * 2017-12-22 2019-06-26 Samsung SDI Co., Ltd. Matériau actif d'électrode négative pour batterie secondaire au lithium, électrode négative le comprenant et batterie secondaire au lithium comprenant l'électrode négative
US11217783B2 (en) 2017-12-22 2022-01-04 Samsung Sdi Co., Ltd. Negative electrode active material for lithium secondary battery, negative electrode including the same, and lithium secondary battery including the negative electrode
CN111602274A (zh) * 2018-02-26 2020-08-28 株式会社Lg化学 锂二次电池用负极活性材料以及包含其的锂二次电池用负极和锂二次电池
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CN115432698A (zh) * 2022-09-30 2022-12-06 贝特瑞新材料集团股份有限公司 碳素二次颗粒及其制备方法、人造石墨及其制备方法、锂离子电池负极材料和锂离子电池
CN115432698B (zh) * 2022-09-30 2024-01-19 贝特瑞新材料集团股份有限公司 碳素二次颗粒及其制备方法、人造石墨及其制备方法、锂离子电池负极材料和锂离子电池
CN115810730A (zh) * 2022-11-15 2023-03-17 宁德时代新能源科技股份有限公司 负极活性物质、负极极片、二次电池及用电装置

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