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WO2025069995A1 - Batterie secondaire à électrolyte non aqueux - Google Patents

Batterie secondaire à électrolyte non aqueux Download PDF

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Publication number
WO2025069995A1
WO2025069995A1 PCT/JP2024/032063 JP2024032063W WO2025069995A1 WO 2025069995 A1 WO2025069995 A1 WO 2025069995A1 JP 2024032063 W JP2024032063 W JP 2024032063W WO 2025069995 A1 WO2025069995 A1 WO 2025069995A1
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positive electrode
mass
active material
electrolyte secondary
secondary battery
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PCT/JP2024/032063
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English (en)
Japanese (ja)
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克彦 池谷
喜彦 池田
俊介 三谷
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パナソニックＩｐマネジメント株式会社
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Publication of WO2025069995A1 publication Critical patent/WO2025069995A1/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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • 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
    • 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

  • This disclosure relates to a non-aqueous electrolyte secondary battery.
  • the positive electrode active material which is a main component of a non-aqueous electrolyte secondary battery, has a large effect on battery performance such as the charge/discharge cycle characteristics, thermal stability, and output characteristics as well as the capacity of the battery, and therefore many studies have been conducted on the positive electrode active material.
  • Patent Document 1 discloses a non-aqueous electrolyte secondary battery using a lithium nickel cobalt composite oxide represented by the general formula LiNiCo (1-x-y) M1 y O 2 (wherein 0.65 ⁇ x ⁇ 0.90, 0.02 ⁇ y ⁇ 0.06, and M1 is at least one metal element selected from the group consisting of Al, Mg, Ti, Mn, and Zr) and a lithium cobalt composite oxide represented by the general formula LiCo (1-z) M2 z O 2 (wherein 0.005 ⁇ z ⁇ 0.03, and M2 is at least one metal element selected from the group consisting of Al, Mg, Ti, Mn, and Zr) as the positive electrode active material.
  • a lithium nickel cobalt composite oxide represented by the general formula LiNiCo (1-x-y) M1 y O 2 wherein 0.65 ⁇ x ⁇ 0.90, 0.02 ⁇ y ⁇ 0.06, and M1 is at least one metal element selected from the group consisting of Al, Mg, Ti, Mn, and Zr
  • lithium cobalt composite oxide (hereinafter sometimes referred to as "LCO") is used as the positive electrode active material of a non-aqueous electrolyte secondary battery, it is possible to increase the capacity by increasing the end-of-charge voltage.
  • LCO lithium cobalt composite oxide
  • the nonaqueous electrolyte secondary battery according to the present disclosure is a nonaqueous electrolyte secondary battery including a positive electrode, a negative electrode, and a nonaqueous electrolyte, the positive electrode having a positive electrode core and a positive electrode mixture layer provided on the positive electrode core, the positive electrode mixture layer including a positive electrode active material mainly composed of a lithium cobalt composite oxide having a layered crystal structure, carbon nanotubes, and carbon black, and the lithium cobalt composite oxide is a composite oxide represented by a general formula LiCo (1-w-x-y-z) AlwMgxTiyMnzO2 ( wherein 0.010 ⁇ w ⁇ 0.013, 0.003 ⁇ x ⁇ 0.006, 0.0004 ⁇ y ⁇ 0.0006, 0 ⁇ z ⁇ 0.0015).
  • the nonaqueous electrolyte secondary battery disclosed herein can improve charge/discharge cycle characteristics and thermal stability while increasing capacity.
  • FIG. 1 is a cross-sectional view of a nonaqueous electrolyte secondary battery according to an embodiment
  • non-aqueous electrolyte secondary batteries that use LCO-based composite oxides as the positive electrode active material
  • LCO-based composite oxides as the positive electrode active material
  • increasing the end-of-charge voltage causes crystal transition or decomposition of LCO, releasing oxygen from the crystal structure and promoting the oxidative decomposition reaction between the positive electrode active material and the electrolyte. This is thought to result in a large capacity loss during charge and discharge, and a decrease in thermal stability.
  • the present inventors have found that by using a specific composite oxide represented by the general formula LiCo (1-w-x-y-z) Al w Mg x Ti y Mn z O 2 (wherein 0.010 ⁇ w ⁇ 0.013, 0.003 ⁇ x ⁇ 0.006, 0.0004 ⁇ y ⁇ 0.0006, 0 ⁇ z ⁇ 0.0015) as the positive electrode active material and by using carbon nanotubes and carbon black in combination as the conductive agent, a good conductive path is formed in the positive electrode mixture layer, and excellent cycle characteristics and thermal stability are ensured even if the end-of-charge voltage of the battery is increased. Note that although carbon nanotubes are excellent as a conductive agent, sufficient effects cannot be obtained by using carbon nanotubes alone.
  • a cylindrical battery in which a wound electrode body 14 is housed in a cylindrical exterior can 16 with a bottom is exemplified, but the exterior can is not limited to a cylindrical exterior can and may be, for example, a rectangular exterior can (rectangular battery) or a coin-shaped exterior can (coin battery). It may also be an exterior (pouch battery) made of a laminate sheet including a metal layer and a resin layer.
  • the electrode body is not limited to a wound type and may be a laminated type electrode body in which multiple positive electrodes and multiple negative electrodes are alternately stacked with separators between them.
  • the nonaqueous electrolyte secondary battery 10 includes a wound electrode assembly 14, a nonaqueous electrolyte (not shown), and an exterior can 16 that contains the electrode assembly 14 and the nonaqueous electrolyte.
  • the electrode assembly 14 has a positive electrode 11, a negative electrode 12, and a separator 13, and has a wound structure in which the positive electrode 11 and the negative electrode 12 are wound in a spiral shape with the separator 13 interposed therebetween.
  • the exterior can 16 is a cylindrical metal container with a bottom that is open on one axial side, and the opening of the exterior can 16 is closed by a sealing body 17.
  • the sealing body 17 side of the battery is referred to as the top
  • the bottom side of the exterior can 16 is referred to as the bottom.
  • the positive electrode 11, negative electrode 12, and separator 13 that make up the electrode body 14 are all long, strip-shaped bodies that are wound in a spiral shape and stacked alternately in the radial direction of the electrode body 14.
  • the negative electrode 12 is formed to be slightly larger than the positive electrode 11 in order to prevent lithium precipitation. That is, the negative electrode 12 is formed to be longer in the longitudinal direction and width direction (short direction) than the positive electrode 11.
  • the separator 13 is formed to be at least slightly larger than the positive electrode 11, and for example, two separators 13 are arranged to sandwich the positive electrode 11.
  • the electrode body 14 has a positive electrode lead 20 connected to the positive electrode 11 by welding or the like, and a negative electrode lead 21 connected to the negative electrode 12 by welding or the like.
  • Insulating plates 18, 19 are arranged above and below the electrode body 14.
  • the positive electrode lead 20 passes through a through hole in the insulating plate 18 and extends toward the sealing body 17, and the negative electrode lead 21 passes outside the insulating plate 19 and extends toward the bottom side of the outer can 16.
  • the positive electrode lead 20 is connected to the underside of the internal terminal plate 23 of the sealing body 17 by welding or the like, and the cap 27, which is the top plate of the sealing body 17 and is electrically connected to the internal terminal plate 23, serves as the positive electrode terminal.
  • the negative electrode lead 21 is connected to the inner bottom surface of the outer can 16 by welding or the like, and the outer can 16 serves as the negative electrode terminal.
  • a gasket 28 is provided between the exterior can 16 and the sealing body 17 to ensure airtightness inside the battery.
  • the exterior can 16 has a grooved portion 22 formed with a portion of the side surface that protrudes inward to support the sealing body 17.
  • the grooved portion 22 is preferably formed in an annular shape along the circumferential direction of the exterior can 16, and supports the sealing body 17 on its upper surface.
  • the sealing body 17 is fixed to the top of the exterior can 16 by the grooved portion 22 and the open end of the exterior can 16 that is crimped against the sealing body 17.
  • the sealing body 17 has a structure in which, in order from the electrode body 14 side, an internal terminal plate 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a cap 27 are stacked.
  • Each member constituting the sealing body 17 has, for example, a disk or ring shape, and each member except for the insulating member 25 is electrically connected to each other.
  • the lower valve body 24 and the upper valve body 26 are connected at their respective centers, and the insulating member 25 is interposed between their respective peripheral edges.
  • the end-of-charge voltage of the nonaqueous electrolyte secondary battery 10 is preferably 4.3 V or higher.
  • the nonaqueous electrolyte secondary battery 10 can achieve excellent cycle characteristics and thermal stability while increasing the capacity of the battery by increasing the end-of-charge voltage.
  • the upper limit of the end-of-charge voltage is not particularly limited, but an example is 4.8 V.
  • the positive electrode 11, negative electrode 12, separator 13, and nonaqueous electrolyte that make up the nonaqueous electrolyte secondary battery 10 are described in detail below.
  • the positive electrode 11 has a positive electrode core and a positive electrode mixture layer provided on the positive electrode core.
  • a foil of a metal such as aluminum or an aluminum alloy that is stable in the potential range of the positive electrode 11, or a film having the metal disposed on the surface layer can be used.
  • the positive electrode mixture layer contains a positive electrode active material, a binder, and a conductive agent, and is preferably provided on both sides of the positive electrode core.
  • the positive electrode 11 can be produced, for example, by applying a slurry of a positive electrode mixture containing a positive electrode active material, a binder, and a conductive agent onto the positive electrode core, drying the coating, and then compressing it to form a positive electrode mixture layer on both sides of the positive electrode core.
  • the positive electrode active material is mainly composed of lithium cobalt composite oxide having a layered crystal structure.
  • the lithium cobalt composite oxide (hereinafter referred to as "LCO") constituting the main component of the positive electrode active material is a composite oxide represented by the general formula LiCo (1-w-x-y-z) Al w Mg x Ti y Mn z O 2 (wherein 0.010 ⁇ w ⁇ 0.013, 0.003 ⁇ x ⁇ 0.006, 0.0004 ⁇ y ⁇ 0.0006, 0 ⁇ z ⁇ 0.0015).
  • LCO is a composite oxide in which a predetermined amount of Al, Mg, and Ti are added to a composite oxide containing Li and Co as metal elements.
  • the content of Co in LCO is, for example, 97.8 mol% or more with respect to the total number of moles of elements excluding Li and O.
  • Mn is an optional component, the effect of improving cycle characteristics becomes more remarkable by adding Mn.
  • the main component of the positive electrode active material means the component with the highest mass ratio among the materials constituting the positive electrode active material.
  • the content of LCO is preferably 60 mass% or more, more preferably 70 mass% or more, of the mass of the positive electrode active material.
  • the positive electrode active material may be substantially composed of only LCO represented by the above general formula.
  • the composition of the positive electrode active material can be measured using an ICP optical emission spectrometer (iCAP6300, manufactured by Thermo Fisher Scientific).
  • the positive electrode mixture layer may contain, as a positive electrode active material, other lithium-containing composite oxides other than the LCO represented by the above general formula, as long as the object of the present disclosure is not impaired.
  • An example of the other lithium-containing composite oxide is a lithium cobalt composite oxide that does not substantially contain Al, Mg, or Ti, and is represented by the general formula LiCoO 2.
  • a composite oxide other than the lithium cobalt composite oxide may be used as long as the object of the present disclosure is not impaired.
  • LCO has a layered crystal structure.
  • Specific examples include a layered structure belonging to space group R-3m, or a layered structure belonging to space group C2/m.
  • the addition of Al, Mg, and Ti, especially Al and Mg, is thought to contribute greatly to the stabilization of such a crystal structure.
  • the crystal structure of the complex oxide can be measured using a powder X-ray diffractometer (Rigaku Corporation, RINT2200, Cu-K ⁇ source).
  • the volume-based median diameter (D50) of LCO is, for example, 5 ⁇ m or more and 50 ⁇ m or less, preferably 10 ⁇ m or more and 40 ⁇ m or less, and more preferably 15 ⁇ m or more and 30 ⁇ m or less.
  • LCO is, for example, a secondary particle formed by agglomeration of primary particles, and the D50 of LCO means the D50 of the secondary particles.
  • D50 means the particle size at which the cumulative frequency is 50% from the smallest particle size in the volume-based particle size distribution.
  • the particle size distribution of the complex oxide can be measured using a laser diffraction particle size distribution measuring device (for example, MT3000II manufactured by Microtrack Bell Co., Ltd.) with water as the dispersion medium.
  • the Al content in LCO is 1.0 mol% or more and 1.3 mol% or less, and more preferably 1.0 mol% or more and 1.2 mol% or less, based on the total number of moles of elements excluding Li and O. If the amount of Al added is within this range, the stability of the crystal structure is improved, and the cycle characteristics and thermal stability of the battery are improved. If the amount of Al added is less than 1.0 mol% or exceeds 1.3 mol%, no improvement effect on cycle characteristics, etc. is obtained, and capacity reduction is also significant. Note that even if the amount of Al added is within the above range, if Mg and Ti are not added, the above improvement effect is not obtained.
  • the Mg content in LCO is 0.3 mol% or more and 0.6 mol% or less, based on the total number of moles of elements excluding Li and O. If the amount of Mg added is within this range, the stability of the crystal structure is improved, and cycle characteristics and thermal stability are improved. If the amount of Mg added is less than 0.3 mol% or exceeds 0.6 mol%, no improvement in cycle characteristics etc. is obtained, and if too much Mg is added, the capacity will decrease significantly.
  • the Ti content in LCO is 0.04 mol% or more and 0.06 mol% or less, based on the total number of moles of elements excluding Li and O. If the amount of Ti added is within this range, it is believed that the material resistance can be reduced, and in particular the cycle characteristics are improved. If the amount of Ti added is less than 0.04 mol% or exceeds 0.06 mol%, no improvement in cycle characteristics, etc. can be obtained, and if the amount of Ti added is too large, the capacity decrease becomes significant.
  • LCO further contains Mn
  • the Mn content (z) in the general formula is preferably 0.0004 ⁇ z ⁇ 0.0015, and more preferably 0.0010 ⁇ z ⁇ 0.0015.
  • the amount of Mn added is 0.10 mol % or more and 0.15 mol % or less with respect to the total number of moles of elements excluding Li and O, it is believed that the material resistance can be effectively reduced. As a result, the improvement effect on the cycle characteristics and thermal stability of the battery becomes more significant, and the discharge characteristics in a low-temperature environment are also improved. Note that if the amount of Mn added is too large, for example, the cycle characteristics and the like may deteriorate and the capacity decrease may become more noticeable.
  • the LCO is manufactured, for example, through the following steps. (1) A first step of obtaining a composite hydroxide or composite oxide containing Co, Al, Mg, Ti, and Mn; (2) A second step of mixing the composite hydroxide or composite oxide with a lithium compound and calcining the mixture; and (3) A third step of washing the calcined product with water and drying the mixture.
  • an alkaline solution such as sodium hydroxide is dropped into a stirred solution of metal salts containing Co, Al, Mg, Ti, and Mn, and the pH is adjusted to the alkaline side, thereby precipitating (co-precipitating) a composite hydroxide.
  • the composite hydroxide may be fired at a lower temperature than the firing in the second step.
  • the composite hydroxide or composite oxide obtained in the first step is mixed with a lithium compound.
  • lithium compounds include Li2CO3 , LiOH, Li2O2 , Li2O , LiNO3 , LiNO2 , Li2SO4 , LiOH.H2O , LiH, and LiF.
  • the mixture in the second step is fired, for example, in an oxygen stream at a temperature of 500 °C or higher and 900°C or lower.
  • the firing temperature is preferably 600°C or higher and 800°C or lower.
  • the firing may be performed in two or more stages with different firing conditions.
  • the sintered product is washed with water to remove impurities such as excess Li, and the washed sintered product is dried. If necessary, the sintered product is crushed, classified, etc., and the D50 of the LCO is adjusted to the desired range.
  • the washed sintered product may be dried in a vacuum or in the air. An example of the drying temperature is 150°C or higher and 250°C or lower.
  • the positive electrode mixture layer contains a binder and two types of conductive agents.
  • binders contained in the positive electrode mixture layer include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide, acrylic resin, and polyolefin. These resins may be used in combination with cellulose derivatives such as carboxymethylcellulose (CMC) or a salt thereof, and polyethylene oxide (PEO).
  • the content of the binder is, for example, 0.5% by mass or more and 5% by mass or less with respect to the mass of the positive electrode mixture layer.
  • the positive electrode mixture layer contains carbon nanotubes (CNT) and carbon black (CB) as conductive agents.
  • CNT carbon nanotubes
  • CB carbon black
  • the use of CNT and CB in combination with the above positive electrode active material significantly improves the battery's cycle characteristics, output characteristics (load characteristics), and high-temperature storage characteristics. It is believed that the significant improvement in battery performance is due to the stabilizing effect of the crystal structure caused by the co-addition of Al, Mg, and Ti to the LCO-based composite oxide, and the suppression effect of resistance increase caused by the combined use of CNT and CB.
  • the conductive agent content is, for example, 0.5% by mass or more and 5% by mass or less relative to the mass of the positive electrode mixture layer.
  • CNTs are conductive carbon fibers with a tube outer diameter of several tens of nanometers or less, and have a large aspect ratio.
  • the aspect ratio of CNTs is the ratio of fiber length to fiber diameter.
  • the average aspect ratio of CNTs is preferably 20 times or more, and more preferably 50 times or more.
  • the fiber length refers to the length of a CNT when it is stretched in a straight line, and the fiber diameter refers to the length perpendicular to the fiber length direction.
  • the average fiber diameter of the CNTs is, for example, 20 nm or less, preferably 15 nm or less, and more preferably 10 nm or less.
  • the lower limit of the average fiber diameter of the CNTs is not particularly limited, but an example is 1 nm.
  • the average fiber diameter of the CNTs is determined by image analysis using a transmission electron microscope (TEM).
  • the average fiber diameter of the CNTs is determined by measuring the fiber diameters of 100 randomly selected CNTs and taking the arithmetic average of the measured values.
  • the average fiber length of the CNTs is, for example, 0.5 ⁇ m or more, and may be 1 ⁇ m or more.
  • the upper limit of the average fiber length of the CNTs is not particularly limited, but an example is 100 ⁇ m.
  • the average fiber length of the CNTs is determined by image analysis using a scanning electron microscope (SEM).
  • SEM scanning electron microscope
  • the average fiber length of the CNTs is determined by measuring the lengths of 100 randomly selected CNTs and taking the arithmetic average of the measured values.
  • the CNTs present in the positive electrode mixture layer may be in the form of a bundle of multiple CNTs. The above average fiber length is calculated using the length of a single CNT present in the bundle of CNTs.
  • the CNT may be either a single-walled CNT (SWCNT) or a multi-walled CNT (MWCNT), or SWCNT and MWCNT may be used in combination.
  • SWCNT has a structure in which one layer of graphite sheet is formed into a tube shape
  • MWCNT has a structure in which multiple graphite sheets are formed into a tube shape.
  • An example of MWCNT is a double-walled CNT having a double-walled structure.
  • An example of the BET specific surface area of CNT is 200 m 2 /g or more and 2000 m 2 /g or less. The BET specific surface area is measured according to the BET method (nitrogen adsorption method) described in JIS R1626.
  • the CNT content is preferably 0.05% by mass or more and 0.5% by mass or less, more preferably 0.1% by mass or more and 0.4% by mass or less, and particularly preferably 0.1% by mass or more and 0.3% by mass or less, relative to the mass of the positive electrode active material. Even a small amount of CNT forms a good conductive path in the positive electrode mixture layer, and the lower limit of the content is, for example, 0.01% by mass, and more preferably 0.05% by mass. If the CNT content is within this range, the effect of improving cycle characteristics, output characteristics, and high-temperature storage characteristics becomes more significant.
  • CB is a particulate conductive carbon material, examples of which include acetylene black and ketjen black.
  • the average particle size of CB is, for example, 50 nm or less. There is no particular limit to the lower limit of the average particle size, but one example is 1 nm.
  • CB is composed of primary particles called domains or particles, primary aggregates that are a collection of these primary particles, and secondary aggregates that are a collection of the primary aggregates.
  • the average particle size of CB means the average particle size of the primary particles.
  • the aspect ratio of the CB is, for example, 1.1 times or more and 2.5 times or less, or 1.2 times or more and 2.0 times or less.
  • the aspect ratio of the CB means the ratio of the major axis to the minor axis of the primary aggregate.
  • the average particle size of the CB is determined by image analysis using a TEM.
  • the average particle size of the CB is determined by randomly selecting 100 CBs, measuring the diameter of the circumscribed circle of the primary particle, and calculating the arithmetic average of the measured values.
  • the CB content is preferably 0.5% by mass or more and 1.5% by mass or less, more preferably 0.6% by mass or more and 1.2% by mass or less, and particularly preferably 0.7% by mass or more and 1.1% by mass or less, relative to the mass of the positive electrode active material.
  • the CB content is preferably greater than the CNT content. If the CB content is greater than the CNT content and the CB content is within this range, the effects of improving cycle characteristics, output characteristics, and high-temperature storage characteristics become more pronounced.
  • the negative electrode 12 has a negative electrode core and a negative electrode mixture layer provided on the negative electrode core.
  • a foil of a metal such as copper or a copper alloy that is stable in the potential range of the negative electrode 12, a film with the metal disposed on the surface layer, or the like can be used.
  • the negative electrode mixture layer contains a negative electrode active material, a binder, and if necessary, a conductive agent such as carbon nanotubes, and is preferably provided on both sides of the negative electrode core.
  • the negative electrode 12 can be produced, for example, by applying a negative electrode mixture slurry containing a negative electrode active material and a binder, etc., onto the negative electrode core, drying the coating, and then compressing it to form a negative electrode mixture layer on both sides of the negative electrode core.
  • the negative electrode mixture layer generally contains a carbon material that reversibly absorbs and releases lithium ions as the negative electrode active material.
  • a carbon material that reversibly absorbs and releases lithium ions as the negative electrode active material.
  • a suitable example of the carbon material is natural graphite such as scaly graphite, lump graphite, and earthy graphite, and artificial graphite such as lump artificial graphite (MAG) and graphitized mesophase carbon microbeads (MCMB).
  • an active material containing at least one of an element that alloys with Li, such as Si or Sn, and a material containing the element may be used as the negative electrode active material.
  • a suitable example of the active material is a Si-containing material in which Si fine particles are dispersed in a SiO 2 phase, a silicate phase such as lithium silicate, or an amorphous carbon phase.
  • Graphite and a Si-containing material may be used in combination as the negative electrode active material.
  • the binder contained in the negative electrode mixture layer can be fluororesin, PAN, polyimide, acrylic resin, polyolefin, etc., but it is preferable to use styrene-butadiene rubber (SBR).
  • SBR styrene-butadiene rubber
  • the negative electrode mixture layer further contains CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol (PVA), etc.
  • PAA polyacrylic acid
  • PVA polyvinyl alcohol
  • a porous sheet having ion permeability and insulating properties is used for the separator 13.
  • the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric.
  • the material of the separator 13 is preferably a polyolefin such as polyethylene or polypropylene, or cellulose.
  • the separator 13 may have a single layer structure or a multi-layer structure.
  • a highly heat-resistant resin layer such as an aramid resin may be formed on the surface of the separator 13.
  • a filler layer containing an inorganic filler may be formed at the interface between the separator 13 and at least one of the positive electrode 11 and the negative electrode 12.
  • inorganic fillers include oxides and phosphate compounds containing metal elements such as Ti, Al, Si, and Mg.
  • the filler layer can be formed by applying a slurry containing the filler to the surface of the positive electrode 11, the negative electrode 12, or the separator 13.
  • Non-aqueous electrolyte has ion conductivity (for example, lithium ion conductivity).
  • the non-aqueous electrolyte may be a liquid electrolyte (electrolytic solution) or a solid electrolyte.
  • the liquid electrolyte contains, for example, a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent.
  • the non-aqueous solvent examples include esters, ethers, nitriles such as acetonitrile, amides such as dimethylformamide, and mixed solvents of two or more of these.
  • the non-aqueous solvent may contain a halogen-substituted product in which at least a portion of the hydrogen of these solvents is replaced with a halogen atom such as fluorine.
  • halogen-substituted product examples include fluorinated cyclic carbonates such as fluoroethylene carbonate (FEC), fluorinated chain carbonates, and fluorinated chain carboxylates such as methyl fluoropropionate (FMP).
  • FEC fluoroethylene carbonate
  • FMP fluorinated chain carboxylates
  • FEC fluoroethylene carbonate
  • FMP fluorinated chain carboxylates
  • esters examples include cyclic carbonate esters such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate; chain carbonate esters such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl propyl carbonate, ethyl propyl carbonate, and methyl isopropyl carbonate; cyclic carboxylate esters such as gamma-butyrolactone (GBL) and gamma-valerolactone (GVL); and chain carboxylate esters such as methyl acetate, ethyl acetate, propyl acetate, methyl propionate (MP), and ethyl propionate (EP).
  • cyclic carbonate esters such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate
  • chain carbonate esters such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC
  • ethers examples include 1,3-dioxolane, 4-methyl-1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, propylene oxide, 1,2-butylene oxide, 1,3-dioxane, 1,4-dioxane, 1,3,5-trioxane, furan, 2-methylfuran, 1,8-cineole, cyclic ethers such as crown ethers, 1,2-dimethoxyethane ethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, dihexyl ether, ethyl vinyl ether, butyl vinyl ether, methyl phenyl ether, Examples of such chain ethers include ethyl phenyl ether, ethyl phenyl ether, butyl phenyl ether, pentyl phenyl ether, methoxytoluene,
  • the electrolyte salt it is preferable to use a lithium salt.
  • concentration of the lithium salt is, for example, 0.5 mol or more and 3 mol or less per 1 L of non-aqueous solvent, and preferably 0.8 mol or more and 1.5 mol or less.
  • the lithium salt may be used alone or in combination with multiple types.
  • lithium salts examples include LiBF 4 , LiClO 4 , LiPF 6 , LiAsF 6 , LiSbF 6 , LiAlCl 4 , LiSCN, LiCF 3 SO 3 , LiCF 3 CO 2 , Li(P(C 2 O 4 )F 4 ), LiPF 6-x (CnF 2n+1 ) x (1 ⁇ x ⁇ 6, n is 1 or 2), LiB 10 Cl 10 , LiCl, LiBr, LiI, lithium chloroborane, lithium lower aliphatic carboxylate, Li[B(C 2 O 4 ) 2 ], Li 2 B 4 O 7 , and Li(B(C 2 O 4 )F 2 ), and imide salts such as lithium bisfluorosulfonylimide (LiN( FSO2 ) 2 ), lithium bistrifluoromethanesulfonyl imide ( LiN ( CF3SO2 ) 2 ), lithium trifluoromethanesulfonyl nonafluorobut
  • the solid electrolyte for example, a solid or gel-like polymer electrolyte, an inorganic solid electrolyte, etc. can be used.
  • the inorganic solid electrolyte a material known in all-solid-state lithium ion secondary batteries, etc. (for example, an oxide-based solid electrolyte, a sulfide-based solid electrolyte, a halogen-based solid electrolyte, etc.) can be used.
  • the polymer electrolyte includes, for example, a lithium salt and a matrix polymer, or a non-aqueous solvent, a lithium salt, and a matrix polymer.
  • the matrix polymer for example, a polymer material that absorbs a non-aqueous solvent and gels is used.
  • the polymer material for example, a fluororesin, an acrylic resin, a polyether resin, etc. can be used.
  • Example 1 [Synthesis of positive electrode active material] A composite hydroxide containing Co, Al, Mg, Ti, and Mn obtained by coprecipitation and lithium hydroxide were mixed so that the molar ratio of the total amount of metal elements to Li was 1.0:1.03. The mixture was baked at 850°C for 20 hours under oxygen flow. The baked product was then washed with water and vacuum dried at 180°C for 2 hours to obtain a lithium cobalt composite oxide having a layered crystal structure, containing a predetermined amount of Al, Mg, Ti, and Mn, and having a D50 of about 26 ⁇ m. In Example 1, the lithium cobalt composite oxide is used as the positive electrode active material. It was confirmed by ICP that the composition of the positive electrode active material was LiCo 0.9821 Al 0.01 Mg 0.006 Ti 0.0004 Mn 0.0015 O 2. Table 1 shows the amount (mol%) of metal elements other than Li and Co added.
  • the positive electrode active material, carbon nanotubes (CNT), carbon black (CB), and polyvinylidene fluoride were mixed in a solid content mass ratio of 100:0.2:0.9:1.2, and N-methyl-2-pyrrolidone (NMP) was used as a dispersion medium to prepare a positive electrode mixture slurry.
  • NMP N-methyl-2-pyrrolidone
  • Multi-layered CNTs with an average fiber diameter of 8 nm and an average fiber length of 15 ⁇ m were used for the CNTs, and Ketjen Black with an average particle size of 30 nm was used for the CBs.
  • the positive electrode mixture slurry was applied onto a positive electrode core made of aluminum foil, the coating was dried and compressed, and then the positive electrode core was cut into a predetermined electrode size to obtain a positive electrode in which a positive electrode mixture layer was formed on both sides of the positive electrode core.
  • An aluminum lead was welded to the exposed part of the positive electrode core.
  • Graphite was used as the negative electrode active material.
  • the negative electrode active material, the sodium salt of CMC, and the dispersion of SBR were mixed in a solid content mass ratio of 97.8:1.2:1.2, and a negative electrode mixture slurry was prepared using water as a dispersion medium.
  • the negative electrode mixture slurry was applied onto a negative electrode core made of copper foil, the coating film was dried and rolled, and then the negative electrode core was cut into a predetermined electrode size to obtain a negative electrode in which a negative electrode mixture layer was formed on both sides of the negative electrode core.
  • a nickel lead was welded to the core exposed part of the negative electrode.
  • a non-aqueous electrolyte was prepared by dissolving LiPF6 at a concentration of 1.2 mol/L in a solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 30:70 (25° C.).
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • the positive electrode and the negative electrode were wound in a spiral shape with a separator interposed therebetween, and the wound body was pressed into a flat shape to obtain an electrode body.
  • the laminate sheet was processed to form an outer casing, and the electrode body and the non-aqueous electrolyte were housed in the outer casing in an inert atmosphere.
  • a non-aqueous electrolyte secondary battery having a length of 69 mm, a width of 56 mm, a thickness of 4.9 mm, and a rated capacity of 3150 mAh.
  • Examples 2 to 5 A nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 1, except that a lithium-cobalt composite oxide having the composition shown in Table 1 was used as the positive electrode active material.
  • Examples 6 and 7 A nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 2, except that the amounts of CNT and CB added were changed to those shown in Table 1.
  • Example 1 A nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 2, except that no CNT was added.
  • Example 2 A nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 2, except that CB was not added.
  • Example 3 A nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 1, except that no CNTs were added.
  • Example 4 A nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 1, except that CB was not added.
  • Example 5 A nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 1, except that a lithium-cobalt composite oxide having the composition shown in Table 1 was used as the positive electrode active material.
  • the nonaqueous electrolyte secondary batteries of the Examples and Comparative Examples were evaluated for cycle characteristics, discharge load characteristics, and high-temperature charge storage characteristics under the following conditions.
  • the evaluation results are shown in Table 1, along with the composition of the positive electrode active material and the amounts of CNT and CB added.
  • the battery was charged at a constant current of 0.7 C in a temperature environment of 23 ° C until the battery voltage reached 4.45 V, and then discharged at a constant current of 1.0 C-0.2 C until the battery voltage reached 3.0 V, and the recovery capacity was determined.
  • the batteries of the examples have higher capacity retention rates in cycle tests and superior cycle characteristics compared to the batteries of the comparative examples.
  • the batteries of the experimental examples also have superior load characteristics and high-temperature storage characteristics. In other words, the batteries of the examples can achieve high capacity by increasing the end-of-charge voltage while ensuring good charge-discharge cycle characteristics, output characteristics, and thermal stability.
  • Example 1 and Comparative Examples 3 and 4, and Example 2 and Comparative Examples 1 and 2 show that the use of CNT and CB together with the LCO represented by the above general formula significantly improves the cycle characteristics, output characteristics, and thermal stability. The improvement effect becomes even more remarkable when Mn is added in addition to Al, Mg, and Ti.
  • Configuration 1 A non-aqueous electrolyte secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the positive electrode has a positive electrode core and a positive electrode mixture layer provided on the positive electrode core, the positive electrode mixture layer includes a positive electrode active material mainly composed of a lithium cobalt composite oxide having a layered crystal structure, carbon nanotubes, and carbon black, and the lithium cobalt composite oxide is a composite oxide represented by a general formula LiCo (1-w-x-y-z) AlwMgxTiyMnzO2 ( wherein 0.010 ⁇ w ⁇ 0.013, 0.003 ⁇ x ⁇ 0.006, 0.0004 ⁇ y ⁇ 0.0006, 0 ⁇ z ⁇ 0.0015 ) .
  • LiCo (1-w-x-y-z) AlwMgxTiyMnzO2 wherein 0.010 ⁇ w ⁇ 0.013, 0.003 ⁇ x ⁇ 0.006, 0.0004 ⁇ y ⁇ 0.0006, 0 ⁇ z ⁇ 0.0015 .
  • Configuration 2 The nonaqueous electrolyte secondary battery according to configuration 1, wherein the content of the carbon nanotubes is 0.05% by mass or more and 0.5% by mass or less with respect to the mass of the positive electrode active material.
  • Configuration 3 The nonaqueous electrolyte secondary battery according to configuration 1 or 2, wherein the content of the carbon black is greater than the content of the carbon nanotubes and is 0.5 mass % or more and 1.5 mass % or less with respect to the mass of the positive electrode active material.
  • Configuration 4 The nonaqueous electrolyte secondary battery according to any one of configurations 1 to 3, wherein the lithium-cobalt composite oxide contains Mn, and the Mn content (z) in the general formula satisfies 0.0010 ⁇ z ⁇ 0.0015.

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Abstract

Une batterie secondaire à électrolyte non aqueux (10) comprend une électrode positive (11), une électrode négative (12) et un électrolyte non aqueux. Une couche de mélange d'électrode positive qui constitue l'électrode positive (11) comprend un matériau actif d'électrode positive qui est principalement composé d'un oxyde composite de lithium-cobalt ayant une structure cristalline en couches, un nanotube de carbone et un noir de carbone. L'oxyde composite de lithium cobalt est représenté par la formule généraleLiCo(1 – w – x – y − z)AlwMgxTiyMnzO2 (dans la formule, 0,010 ≤ w ≤ 0,013, 0,003 ≤ x ≤ 0,006, 0,0004 ≤ y ≤ 0,0006, et 0 ≤ z ≤ 0,0015).
PCT/JP2024/032063 2023-09-27 2024-09-06 Batterie secondaire à électrolyte non aqueux WO2025069995A1 (fr)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006009177A1 (fr) * 2004-07-20 2006-01-26 Seimi Chemical Co., Ltd. Matériau actif d’électrode positive pour batterie secondaire au lithium et procédé de fabrication dudit matériau
JP2008016267A (ja) * 2006-07-05 2008-01-24 Hitachi Maxell Ltd 非水電解液二次電池
JP2017021941A (ja) * 2015-07-09 2017-01-26 日立マクセル株式会社 非水電解質二次電池
WO2019216275A1 (fr) * 2018-05-08 2019-11-14 デンカ株式会社 Composition d'électrode positive pour accumulateur au lithium-ion, électrode positive pour accumulateur au lithium-ion et accumulateur au lithium-ion

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006009177A1 (fr) * 2004-07-20 2006-01-26 Seimi Chemical Co., Ltd. Matériau actif d’électrode positive pour batterie secondaire au lithium et procédé de fabrication dudit matériau
JP2008016267A (ja) * 2006-07-05 2008-01-24 Hitachi Maxell Ltd 非水電解液二次電池
JP2017021941A (ja) * 2015-07-09 2017-01-26 日立マクセル株式会社 非水電解質二次電池
WO2019216275A1 (fr) * 2018-05-08 2019-11-14 デンカ株式会社 Composition d'électrode positive pour accumulateur au lithium-ion, électrode positive pour accumulateur au lithium-ion et accumulateur au lithium-ion

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