WO2023008232A1 - 非水電解質二次電池用正極活物質及び非水電解質二次電池 - Google Patents

非水電解質二次電池用正極活物質及び非水電解質二次電池 Download PDF

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WO2023008232A1
WO2023008232A1 PCT/JP2022/027862 JP2022027862W WO2023008232A1 WO 2023008232 A1 WO2023008232 A1 WO 2023008232A1 JP 2022027862 W JP2022027862 W JP 2022027862W WO 2023008232 A1 WO2023008232 A1 WO 2023008232A1
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Prior art keywords
composite oxide
positive electrode
lithium
transition metal
electrolyte secondary
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English (en)
French (fr)
Japanese (ja)
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大造 地藤
毅 小笠原
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Panasonic Intellectual Property Management Co Ltd
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Panasonic Intellectual Property Management Co Ltd
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Priority to CN202280051044.XA priority Critical patent/CN117751469A/zh
Priority to US18/580,826 priority patent/US20240356019A1/en
Priority to JP2023538440A priority patent/JPWO2023008232A1/ja
Priority to EP22849295.5A priority patent/EP4379864A4/en
Publication of WO2023008232A1 publication Critical patent/WO2023008232A1/ja
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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
    • 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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • C01G53/40—Complex oxides containing nickel and at least one other metal element
    • C01G53/42—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—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
    • 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
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • 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
    • H01M4/48—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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/76—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by a space-group or by other symmetry indications
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
    • C01P2004/82—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/12—Surface area
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/40—Electric properties
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • 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 disclosure relates to a positive electrode active material for non-aqueous electrolyte secondary batteries and a non-aqueous electrolyte secondary battery using the positive electrode active material.
  • nonaqueous electrolyte secondary batteries in which charge and discharge are performed by moving Li ions or the like between a positive electrode and a negative electrode have been widely used, and in recent years, there has been a demand for further improvements in battery characteristics.
  • the negative electrode contains an irreversible negative electrode active material such as a Si-based material
  • the positive electrode contains Li 2 NiO 2 as a Li supplement, thereby supplying Li ions to the negative electrode during initial charging
  • a secondary battery that suppresses a decrease in capacity retention rate during initial charging and discharging has been disclosed.
  • Li 2 NiO 2 releases Li during the initial charge and changes to LiNiO 2 , and LiNiO 2 hardly contributes to subsequent charging and discharging. Therefore, if the amount of Li 2 NiO 2 contained in the positive electrode is too large, the battery capacity will become small. Therefore, the present inventors have made intensive studies and found that, depending on the form of Li 2 NiO 2 , it is possible to supply a sufficient amount of Li ions to the negative electrode while suppressing the amount of Li 2 NiO 2 contained in the positive electrode. I found what I can do. The technique of Patent Document 1 does not consider the optimum form of Li 2 NiO 2 and there is still room for improvement.
  • An object of the present disclosure is to provide a positive electrode active material capable of improving battery capacity.
  • a positive electrode active material for a non-aqueous electrolyte secondary battery which is one aspect of the present disclosure, has the general formula Li a Ni b M1 1-b O 2 (where 1.5 ⁇ a ⁇ 2.5, 0.95 ⁇ b ⁇ 1.00, M1 is at least one element selected from Cu, Sr, Ca, Nb, Si, and Al), and the first lithium-transition metal composite oxide
  • the object has voids inside, and the porosity of the first lithium-transition metal composite oxide is 2% to 10%.
  • a non-aqueous electrolyte secondary battery includes a positive electrode containing the positive electrode active material, a negative electrode, and a non-aqueous electrolyte.
  • the positive electrode active material according to the present disclosure it is possible to improve the battery capacity of the non-aqueous electrolyte secondary battery.
  • FIG. 1 is a cross-sectional view of a non-aqueous electrolyte secondary battery that is an example of an embodiment
  • FIG. It is a figure which expands and shows a part of cross section of the electrode body which is an example of embodiment.
  • BRIEF DESCRIPTION OF THE DRAWINGS It is the figure which represented typically the cross section of the 1st lithium transition metal oxide which is an example of embodiment.
  • Li 2 NiO 2 functions as a supplementary agent that supplies Li ions during initial charging.
  • Li 2 NiO 2 releases Li during the initial charge and changes to LiNiO 2 , and LiNiO 2 hardly contributes to subsequent charging and discharging. Therefore, if the amount of Li 2 NiO 2 contained in the positive electrode is too large, the battery capacity will become small.
  • the inventors of the present invention made intensive studies to solve the above problems, and found that the first lithium-transition metal composite oxide represented by the general formula Li a Ni b M1 1-b O 2 such as Li 2 NiO 2 is
  • the porosity is 2% to 10% while having voids inside, a sufficient amount of Li ions can be supplied to the negative electrode while suppressing the amount of Li 2 NiO 2 contained in the positive electrode. , the battery capacity is improved.
  • a cylindrical battery in which the wound electrode body 14 is housed in a cylindrical outer can 16 with a bottom is exemplified, but the outer casing of the battery is not limited to a cylindrical outer can. It may be an exterior can (square battery), a coin-shaped exterior can (coin-shaped battery), or an exterior body (laminate battery) composed of a laminate sheet including a metal layer and a resin layer. Further, the electrode body may be a laminated electrode body in which a plurality of positive electrodes and a plurality of negative electrodes are alternately laminated with separators interposed therebetween.
  • FIG. 1 is a diagram schematically showing a cross section of a non-aqueous electrolyte secondary battery 10 that is an example of an embodiment.
  • the non-aqueous electrolyte secondary battery 10 includes a wound electrode body 14, a non-aqueous electrolyte, and an outer can 16 that accommodates the electrode body 14 and the non-aqueous electrolyte.
  • the electrode body 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 spirally wound with the separator 13 interposed therebetween.
  • the outer can 16 is a bottomed cylindrical metal container that is open on one side in the axial direction. In the following description, for convenience of explanation, the side of the sealing member 17 of the battery will be referred to as the upper side, and the bottom side of the outer can 16 will be referred to as the lower side.
  • the positive electrode 11, the negative electrode 12, and the separator 13, which constitute the electrode assembly 14, are all strip-shaped elongated bodies, and are alternately laminated in the radial direction of the electrode assembly 14 by being spirally wound.
  • the negative electrode 12 is formed with a size one size larger than that of the positive electrode 11 in order to prevent deposition of lithium. That is, the negative electrode 12 is formed longer than the positive electrode 11 in the longitudinal direction and the width direction (transverse direction).
  • the separator 13 is formed to have a size at least one size larger than that of the positive electrode 11, and two separators 13 are arranged so as to sandwich the positive electrode 11 therebetween.
  • 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 and 19 are arranged above and below the electrode body 14, respectively.
  • the positive electrode lead 20 extends through the through hole of the insulating plate 18 toward the sealing member 17
  • the negative electrode lead 21 extends through the outside of the insulating plate 19 toward the bottom of the outer can 16 .
  • the positive electrode lead 20 is connected to the lower surface 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 electrically connected to the internal terminal plate 23, serves as the positive electrode terminal.
  • the negative electrode lead 21 is connected to the inner surface of the bottom of the outer can 16 by welding or the like, and the outer can 16 serves as a negative electrode terminal.
  • the outer can 16 is a bottomed cylindrical metal container that is open on one side in the axial direction.
  • a gasket 28 is provided between the outer can 16 and the sealing member 17 to ensure hermeticity inside the battery and insulation between the outer can 16 and the sealing member 17 .
  • the outer can 16 is formed with a grooved portion 22 that supports the sealing member 17 and has a portion of the side surface projecting inward.
  • the grooved portion 22 is preferably annularly formed along the circumferential direction of the outer can 16 and supports the sealing member 17 on its upper surface.
  • the sealing member 17 is fixed to the upper portion of the outer can 16 by the grooved portion 22 and the open end of the outer can 16 that is crimped to the sealing member 17 .
  • the sealing body 17 has a structure in which an internal terminal plate 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a cap 27 are layered in order from the electrode body 14 side.
  • Each member constituting the sealing member 17 has, for example, a disk shape or a ring shape, and each member other than 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 central portions, and an insulating member 25 is interposed between their peripheral edge portions.
  • FIG. 2 is a schematic diagram showing an enlarged part of the cross section of the electrode assembly 14. As shown in FIG.
  • the positive electrode 11 has a positive electrode core 30 and a positive electrode mixture layer 31 formed on at least one surface of the positive electrode core 30 .
  • a foil of a metal such as aluminum or an aluminum alloy that is stable in the potential range of the positive electrode 11, a film having the metal on the surface layer, or the like can be used.
  • the positive electrode mixture layer 31 contains a positive electrode active material, a binder, and a conductive agent, and is preferably formed on both surfaces of the positive electrode core 30 .
  • a lithium-transition metal composite oxide is used as the positive electrode active material.
  • the positive electrode 11 is formed by applying a positive electrode mixture slurry containing a positive electrode active material, a binder, a conductive agent, and the like on a positive electrode core 30 , drying the coating film, and then compressing the positive electrode mixture layer 31 to form a positive electrode. It can be manufactured by forming on both sides of the core body 30 .
  • binder contained in the positive electrode mixture layer 31 examples include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide, acrylic resins, and polyolefins.
  • fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide, acrylic resins, and polyolefins.
  • these resins may be used in combination with cellulose derivatives such as carboxymethyl cellulose (CMC) or salts thereof, polyethylene oxide (PEO), and the like.
  • the content of the binder is preferably 0.1% by mass to 5% by mass, more preferably 0.5% by mass to 3% by mass, relative to the total mass of the positive electrode mixture layer 31 .
  • Examples of the conductive agent contained in the positive electrode mixture layer 31 include particulate conductive agents such as carbon black, acetylene black, ketjen black, graphite, vapor grown carbon fiber (VGCF), electrospun carbon fiber, polyacrylonitrile (PAN )-based carbon fiber, pitch-based carbon fiber, graphene, carbon nanotube (CNT), and other fibrous conductive agents.
  • the content of the conductive agent is preferably 0.01% by mass to 5% by mass, more preferably 0.05% by mass to 3% by mass, relative to the total mass of the positive electrode mixture layer 31 .
  • the positive electrode mixture layer 31 contains at least a first lithium-transition metal composite oxide.
  • the first lithium-transition metal composite oxide (hereinafter referred to as “composite oxide (A)”) has the general formula Li a Ni b M1 1-b O 2 (wherein 1.5 ⁇ a ⁇ 2.5, 0.95 ⁇ b ⁇ 1.00, and M1 is at least one element selected from Cu, Sr, Ca, Nb, Si, and Al).
  • Composite oxide (A) is, for example, Li 2 NiO 2 .
  • the positive electrode mixture layer 31 preferably further contains a second lithium-transition metal composite oxide (hereinafter referred to as “composite oxide (B)”).
  • composite oxide (B) has the general formula Li c Ni 2-cd M2 d O 2 (wherein 0 ⁇ c ⁇ 0.5, 0 ⁇ d ⁇ 0.5, M2 is at least Li and Ni excluding It is a composite oxide represented by one kind of metal element).
  • the coexistence of the composite oxides (A, B) in the positive electrode mixture layer 31 specifically suppresses an increase in resistance during the initial charge/discharge and at the initial stage of the cycle test.
  • the composite oxide (B) is thought to protect the particle surfaces of the composite oxide (A), effectively suppress deterioration of the particle surfaces, and suppress side reactions between the composite oxide (A) and the electrolyte. , and as a result, an increase in resistance is effectively suppressed.
  • the complex oxide (B) may be mixed with the complex oxide (A) by applying a strong shearing force or compressive force, and immobilized on the surface of the complex oxide (A).
  • the composite oxide (B) exhibits the above effects with the addition of a small amount, the amount of the composite oxide (B) added is within a preferable range from the viewpoint of efficiently suppressing an increase in resistance while maintaining a high capacity. exists.
  • the content of the composite oxide (B) is preferably 0.1% by mass to 20% by mass, more preferably 0.5% by mass to 20% by mass, based on the mass of the composite oxides (A, B). More preferably 1% by mass to 15% by mass, particularly preferably 2% by mass to 15% by mass. If the amount of the composite oxide (B) is within this range, the increase in resistance can be efficiently suppressed.
  • the positive electrode mixture layer 31 preferably further contains a third lithium-transition metal composite oxide (hereinafter referred to as "composite oxide (C)").
  • composite oxide (C) has the general formula Li x Ni 1-yz Co y M3 z O 2 (wherein 0.97 ⁇ x ⁇ 1.2, 0 ⁇ y ⁇ 0.2, 0 ⁇ z ⁇ 0.5 and M3 is at least one element selected from Mn, W, Mg, Mo, Nb, Ti, Si, Al and Zr).
  • the composite oxide (C) is added to the positive electrode mixture layer 31 in a larger amount than the composite oxides (A, B), for example, from the viewpoint of ensuring battery capacity.
  • the content of the composite oxides (A, B) is preferably 0.1% by mass to 15% by mass, more preferably 0.5% by mass to 15 mass %, more preferably 1 mass % to 15 mass %, particularly preferably 1 mass % to 10 mass %. If the amount of the composite oxides (A, B) is within this range, the Li ions that compensate for the irreversibility of the negative electrode 12 are sufficiently supplied from the positive electrode 11 during the initial charge, and the decrease in the capacity retention rate is suppressed. , the resistance increase is effectively suppressed.
  • a composite oxide other than the composite oxides (A, B, and C) (for example, a lithium-transition metal composite oxide that does not satisfy the above general formulas) is used within a range that does not impair the purpose of the present disclosure. things) may be included.
  • the composite oxides (A, B, C) are preferably contained in an amount of 50% by mass or more with respect to the total mass of the positive electrode mixture layer 31 .
  • the lower limit of the total content of the composite oxides (A, B, C) with respect to the total mass of the positive electrode mixture layer 31 is preferably 85% by mass or more, more preferably 90% by mass or more, and particularly 95% by mass or more. preferable.
  • the upper limit of the total content of the composite oxides (A, B, C) with respect to the total mass of the positive electrode mixture layer 31 is, for example, 99% by mass.
  • the composite oxide (A) has the general formula Li a Ni b M1 1-b O 2 (wherein 1.5 ⁇ a ⁇ 2.5, 0.95 ⁇ b ⁇ 1.00, M1 is at least one element selected from Cu, Sr, Ca, Nb, Si, and Al).
  • the content of the metal element M1 is less than the content of Li and Ni, and is 5 mol % or less with respect to the total molar amount of the metal elements excluding Li, and may be substantially 0 mol %.
  • the composition of the composite oxide (A) can be analyzed using ICP emission spectrometry.
  • the composite oxide (A) has voids inside, and the porosity of the composite oxide (A) is 2% to 10%. Thereby, the battery capacity of the non-aqueous electrolyte secondary battery 10 can be improved. Although the details of the mechanism are not clear, it is presumed that the complex oxide (A), which has internal voids, is likely to induce a crystal structure change during the initial charge, increasing the amount of released Li. . When the porosity of the composite oxide (A) is less than 2%, the crystal structure change of the composite oxide (A) cannot be induced, and the amount of released Li is not sufficient.
  • the porosity of the composite oxide (A) is more than 10%, the composite oxide (A) becomes bulky, and the effect of increasing the amount of released Li is offset by the decrease in the density of the positive electrode mixture layer 31.
  • the battery capacity hardly increases, and in some cases it decreases.
  • FIG. 3 is a diagram schematically showing a cross section of the composite oxide (A).
  • the composite oxide (A) is, for example, secondary particles 35 formed by aggregation of a plurality of primary particles.
  • the volume-based median diameter (D50) of the composite oxide (A) is preferably 1 ⁇ m to 15 ⁇ m, more preferably 1 ⁇ m to 10 ⁇ m. D50 means a particle size at which the cumulative frequency is 50% from the smaller particle size in the volume-based particle size distribution, and is also called median diameter.
  • the particle size distribution of the secondary particles of the composite oxide can be measured using a laser diffraction particle size distribution analyzer (eg MT3000II manufactured by Microtrack Bell Co., Ltd.) using water as a dispersion medium.
  • the particle size of the primary particles of the composite oxide (A) is, for example, 0.05 ⁇ m to 1 ⁇ m.
  • the particle size of the primary particles is measured as the diameter of the circumscribed circle in the cross-sectional image of the secondary particles observed with a scanning electron microscope (SEM).
  • SEM scanning electron microscope
  • the BET specific surface area of the composite oxide (A) is, for example, 0.5 m 2 /g to 2.5 m 2 /g.
  • the BET specific surface area is measured according to the BET method (nitrogen adsorption method) described in JIS R1626.
  • the secondary particles 35 shown in FIG. 3 have voids 37a, 37b, 37c, and 37d inside.
  • the voids 37a, 37b, and 37c are not connected to the outside of the secondary particles 35 and exist inside the secondary particles 35 in a closed state.
  • the gap 37d is connected to the outside at the outer edge of the secondary particle 35, but the width W1 at the outer edge of the secondary particle 35 and the maximum width W2 of the gap 37d in the direction parallel to the width W1 are equal to W1 /W2 ⁇ 0.9.
  • the recess 39 is connected to the outside at the outer edge of the secondary particle 35, and the relationship between the width W3 at the outer edge of the secondary particle 35 and the maximum width W4 of the recess 39 in the direction parallel to the width W3 is W3/W4. >0.9, so it is not a void.
  • the voids are present in the interior of the secondary particles 35 in a closed state, or are connected to the outside at the outer edges of the secondary particles 35 and have a width at the outer edges of the secondary particles 35.
  • W 0 and the maximum width W m of the gap in the direction parallel to the width WO satisfy the relationship W 0 /W m ⁇ 0.9.
  • the porosity of the composite oxide (A) can be calculated, for example, as follows.
  • ⁇ Method for calculating porosity of composite oxide (A)> Expose the cross section of the secondary particles 35 .
  • Examples of the method of exposing the cross section include a method of embedding the secondary particles 35 in resin, processing with an ion milling device (eg, IM4000PLUS manufactured by Hitachi High-Tech), and exposing the cross section of the secondary particles 35. .
  • An ion milling device eg, IM4000PLUS manufactured by Hitachi High-Tech
  • a backscattered electron image of the cross section of the exposed secondary particles 35 is taken using a scanning electron microscope (SEM).
  • Porosity void area/secondary particle cross section area x 100 (5)
  • Ten secondary particles 35 contained in the same composite oxide (A) are subjected to the above measurement, and the average porosity calculated for each of the ten secondary particles is calculated as the composite oxide (A ) porosity.
  • the composite oxide (A) supplies Li ions to the negative electrode 12 for compensating for the irreversibility of the negative electrode active material during initial charging, thereby suppressing a decrease in the capacity retention rate.
  • the composite oxide (A) releases Li during the initial charge and changes into highly active LiNiO 2 , for example. Due to the side reaction between LiNiO 2 and the electrolyte, deterioration of the composite oxide (A), deposition of decomposition reaction products on the negative electrode 12, etc. occur, and it is thought that the battery resistance increases. As a result, the increase in resistance is effectively suppressed.
  • the composite oxide (A) has, for example, a crystal structure belonging to the space group Immm at least before initial charge/discharge. Moreover, the composite oxide (A) has a composition represented by the general formula Li a Ni b M1 1-b O 2 (0.5 ⁇ a ⁇ 1.5) after the initial charge and discharge. The composite oxide (A) releases and absorbs Li to some extent during charge and discharge even after the initial charge and discharge, but in order to ensure the battery capacity, it is preferable to add the composite oxide (C). .
  • the composite oxide (A) may contain multiple types of composite oxides having similar compositions, and may contain compounds that do not satisfy the above general formula, such as Li 2 O and NiO.
  • the composite oxide (B) exists in the positive electrode mixture layer 31, for example, in a state surrounded by multiple composite oxides (A).
  • the particle surfaces of the composite oxides (A, B) are in contact with each other. In this case, it is considered that the interaction between the composite oxides (A, B) is more effectively expressed, and the effect of suppressing the resistance increase is enhanced.
  • the composite oxide (B) is not limited to being intentionally added, and may be mixed as a by-product of another composite oxide or an impurity of another positive electrode material.
  • the composite oxide (A) for example, a first step of mixing predetermined amounts of Li raw material and Ni raw material to obtain a mixture, and a second step of firing the mixture at 500 ° C. to 800 ° C. for 10 hours to 30 hours.
  • the raw material may be pulverized, and a raw material containing the metal element M1 may be added within the range satisfying the above general formula.
  • the mixture may be molded into pellets and then fired, or the pellets may be crushed after firing.
  • the baking in the second step is performed, for example, in an inert gas atmosphere such as nitrogen.
  • the method for adjusting the porosity of the composite oxide (A) is not particularly limited, but the porosity of the composite oxide (A) can be determined, for example, by the ratio of the Li raw material to the Ni raw material, the particle size and purity of the raw material, and the content of the metal element M1. It can be adjusted by adding amount, pellet density, firing profile and firing time.
  • the ratio of the Li raw material to the Ni raw material is small, the raw material particle size is large, the raw material purity is low, the amount of the metal element M1 added is large, and the pellet density is low within the range that does not interfere with the synthesis reaction of the composite oxidation part (A).
  • the porosity can be adjusted to be high.
  • Li raw materials include Li 2 CO 3 , LiOH, Li 2 O 2 , Li 2 O, LiNO 3 , LiNO 2 , Li 2 SO 4 , LiOH ⁇ H 2 O, LiH, and LiF.
  • Ni raw materials include NiO, Ni(OH) 2 , NiCO 3 , NiSO 4 , Ni(NO 3 ) 2 and the like.
  • M1 raw materials include oxides, hydroxides, carbonates, nitrates, and sulfates of M1. The mixing ratio of each raw material is adjusted so that the composition of the composite oxide (A) satisfies the above general formula. For example, Li 2 NiO 2 is obtained by mixing Li 2 O and NiO such that the molar ratio of Li to Ni is 2 to 2.1.
  • the composite oxide (A) may contain Li 2 O and NiO as described above. For example, when Li 2 O and NiO are used as raw materials, these may be included in the composite oxide (A) as unreacted components. Further, when the composite oxide (A) and N-methylpyrrolidone (NMP) were mixed at a mass ratio of 0.1:20, stirred and stored at room temperature for 24 hours, the amount of Li extracted into NMP was 100 ⁇ m. It is preferably mol/g or less. By this method, the amount of Li contained in the composite oxide (A) and present in a state that is easily extracted by NMP can be measured. If the amount of Li extracted into NMP exceeds 100 ⁇ mol/g, the properties of the positive electrode mixture slurry may deteriorate.
  • NMP N-methylpyrrolidone
  • the composite oxide (B) is Li c Ni 2-cd M2 d O 2 (where 0 ⁇ c ⁇ 0.5, 0 ⁇ d ⁇ 0.5, M2 is Li and Ni). at least one metal element excluding).
  • the content of the metal element M2 is preferably less than the content of Li and Ni, and is, for example, less than 10 mol % or less than 5 mol % with respect to the total molar amount of the metal elements.
  • Examples of the metal element M2 include at least one selected from Cu, Sr, Ca, Nb, Si, and Al.
  • Composite oxide (B) does not release or absorb Li during charging and discharging, and its composition does not change.
  • the composite oxide (A) that releases Li during the initial charge has high activity and may increase the resistance of the battery by reacting with the electrolyte. When used in combination with, the increase in battery resistance is specifically suppressed.
  • the composite oxide (B) protects the particle surface of the composite oxide (A), and the composite oxide (A ) and the electrolyte.
  • the composite oxide (B) may contain multiple types of composite oxides having similar compositions.
  • c in the above general formula is more preferably 0.1 ⁇ c ⁇ 0.5 or 0.2 ⁇ c ⁇ 0.4. If c is in the said range, a resistance rise will be suppressed more effectively.
  • the composition of the composite oxide (B) can be identified from the X-ray diffraction pattern and can be analyzed using ICP emission spectrometry.
  • the composite oxide (B) is, for example, a composite oxide having at least one diffraction peak with a peak top at a diffraction angle (2 ⁇ ) of 21.40° to 21.65° in synchrotron radiation X-ray diffraction (light energy 16 keV). is.
  • the X-ray diffraction pattern of the composite oxide (B) is obtained by a powder X-ray diffraction method under the following conditions using a synchrotron radiation facility (beamline BL5S2 at Aichi Synchrotron Light Center). Light energy; 16 keV Scan range; 10° to 90° Analysis optical system: Debye-Scherrer type
  • the obtained data is subjected to a peak search using identification analysis software PDXL (manufactured by Rigaku) to identify the composite oxide (B).
  • NiO has a peak at 21.36°, and as c in the above general formula increases, the peak shifts to the high angle side. If c in the above general formula is within the above range, a main peak exists at 21.40° to 21.65°.
  • Composite oxide (B) can be identified by matching with the JCPDS card including other peaks.
  • the composite oxide (B) is, for example, particles having a particle size smaller than that of the composite oxide (A), and is secondary particles formed by agglomeration of a plurality of primary particles.
  • D50 of the composite oxide (B) is preferably 1 ⁇ m to 15 ⁇ m, more preferably 1 ⁇ m to 10 ⁇ m, particularly preferably 2 ⁇ m to 7 ⁇ m.
  • the BET specific surface area of the composite oxide (B) is, for example, 0.5 m 2 /g to 2.5 m 2 /g.
  • the composite oxide (B) exists in the positive electrode mixture layer 31, for example, in a state surrounded by multiple composite oxides (A).
  • the particle surfaces of the composite oxides (A, B) are in contact with each other. In this case, it is considered that the interaction between the composite oxides (A, B) is more effectively expressed, and the effect of suppressing the resistance increase is enhanced.
  • the composite oxide (B) is not limited to being intentionally added, and may be mixed as a by-product of another composite oxide or an impurity of another positive electrode material.
  • the composite oxide (B) for example, a first step of mixing predetermined amounts of Li raw material and Ni raw material to obtain a mixture, and a second step of firing the mixture at 500 ° C. to 800 ° C. for 10 hours to 30 hours.
  • the raw material may be pulverized, and a raw material containing the metal element M2 may be added as long as the X-ray diffraction pattern of the composite oxide (B) satisfies the above conditions.
  • the mixture may be molded into pellets and then fired, or the pellets may be crushed after firing.
  • the firing in the second step is performed, for example, in air or in an oxygen atmosphere.
  • Li raw materials include Li 2 CO 3 , LiOH, Li 2 O 2 , Li 2 O, LiNO 3 , LiNO 2 , Li 2 SO 4 , LiOH ⁇ H 2 O, LiH, and LiF.
  • Ni raw materials include NiO, Ni(OH) 2 , NiCO 3 , NiSO 4 , Ni(NO 3 ) 2 and the like.
  • the mixing ratio of the Li raw material and the Ni raw material is, for example, such that the X-ray diffraction pattern of the composite oxide (B) satisfies the above conditions, and c in the above general formula satisfies the condition of 0 ⁇ c ⁇ 0.5. adjusted to meet
  • the composite oxide (C) has the general formula Li x Ni 1-yz Co y M3 z O 2 (wherein 0.97 ⁇ x ⁇ 1.2, 0 ⁇ y ⁇ 0.2, 0 ⁇ z ⁇ 0.5, M3 is at least one element selected from Mn, W, Mg, Mo, Nb, Ti, Si, Al and Zr), wherein Mn is an essential constituent element , W, Mg, Mo, Nb, Ti, Si, Al and Zr. Also, the composite oxide (C) preferably contains Co. However, since Co is particularly rare and expensive, the composite oxide (C) may be substantially Co-free.
  • the Co content is preferably 20 mol% or less, and 0.1 mol% to 10 mol%, relative to the total molar amount of the metal elements excluding Li. is more preferred, and 0.5 mol % to 5 mol % is particularly preferred.
  • the molar fraction of metal elements in the composite oxide can be measured by inductively coupled plasma (ICP) emission spectrometry.
  • the composite oxide (C) preferably has the highest Ni content among the metal elements other than Li.
  • the Ni content is preferably 50 mol % or more, more preferably 70 mol % or more, particularly preferably 80 mol % or more, relative to the total molar amount of metal elements excluding Li.
  • a suitable example of Ni content is 80 mol % to 97 mol %, or 85 mol % to 95 mol %. That is, a suitable example of (1-yz) indicating the Ni content in the above general formula is 0.80 ⁇ (1-yz) ⁇ 0.97, or 0.85 ⁇ (1-y- z) ⁇ 0.95.
  • a suitable example of the composite oxide (C) is, as described above, a composite oxide containing 80 mol% or more of Ni with respect to the total molar amount of metal elements excluding Li.
  • the Ni-rich composite oxide (C) has good compatibility with the composite oxide (B) and is effective in improving cycle characteristics.
  • x indicating the Li content is 0.8 ⁇ x ⁇ 1.2, or 0.97 ⁇ x ⁇ 1.2, and the composite oxide (C) has a molar ratio of Li to the transition metal More than one lithium-excess type composite oxide may be used.
  • the composite oxide (C) contains at least one metal element M3 selected from Mn, W, Mg, Mo, Nb, Ti, Si, Al and Zr.
  • the metal element M3 preferably contains at least one of Mn and Al.
  • the total content of the metal element M3 is preferably 50 mol% or less with respect to the total molar amount of the metal elements excluding Li, and is preferably 0.1 mol% to 20 mol%. It is more preferably 0.5 mol % to 10 mol %, and particularly preferably 1 mol % to 10 mol %.
  • the composite oxide (C) has, for example, a crystal structure belonging to the space group R-3m.
  • the composite oxide (C) has a layered structure including a transition metal layer, a Li layer and an oxygen layer.
  • the composite oxide (C) is, for example, secondary particles formed by aggregation of a plurality of primary particles.
  • D50 of the composite oxide (C) is preferably 3 ⁇ m to 20 ⁇ m, more preferably 5 ⁇ m to 15 ⁇ m.
  • the particle size of the primary particles of the composite oxide (C) is, for example, 0.05 ⁇ m to 1 ⁇ m.
  • the BET specific surface area of the composite oxide (C) is, for example, 0.2 m 2 /g to 2.0 m 2 /g.
  • the particle surface of the composite oxide (C) contains at least one selected from Sr, Ca, W, Mg, Nb, Al, B and Zr (hereinafter referred to as "metal element M4").
  • the compound may be fixed.
  • the M4 compound containing the metal element M4 may be scattered on the particle surface of the composite oxide (C), or may be present in a layer so as to cover the entire particle surface.
  • the thickness of the layer of M4 compound is, for example, 0.1 nm to 5 nm. It is believed that the M4 compound protects the surface of the composite oxide (C) and also protects the surface of the composite oxide (A, B). side reactions are suppressed.
  • M4 compounds are oxides, hydroxides, or carbonates. Specific examples of M4 compounds include SrO, CaO, Sr(OH) 2 , Ca(OH) 2 , SrCO 3 , CaCO 3 and the like.
  • the amount of the M4 compound is, for example, 0.05 mol % to 1.0 mol % in terms of the metal element M4 with respect to the total molar amount of the metal elements excluding Li constituting the composite oxide (C).
  • the presence of M4 compounds can be confirmed by energy dispersive X-ray spectroscopy (TEM-EDX). Also, the metal element M4 can be measured by ICP emission spectroscopic analysis of a solution in which the composite oxide (C) is dissolved in hydrofluoric nitric acid.
  • the composite oxide (C) is prepared by a first step of obtaining a composite oxide containing, for example, Ni, a metal element M3, etc., a second step of mixing the composite oxide and the Li raw material to obtain a mixture, and firing the mixture. It is manufactured through the third step.
  • a raw material containing the metal element M4 hereinafter referred to as "M4 raw material" may be added in the second step.
  • the composition, particle size, BET specific surface area, etc. of the composite oxide (C) and M4 compound can be adjusted by controlling the mixing ratio of raw materials, the firing conditions in the third step, and the like.
  • the first step for example, while stirring a solution of a metal salt containing a metal element such as Ni and a metal element M3, an alkaline solution such as sodium hydroxide is added dropwise, and the pH is adjusted to the alkaline side (eg, 8.5 to 12.5 ) to precipitate (coprecipitate) a composite hydroxide containing a metal element. Thereafter, by firing this composite hydroxide, a composite oxide containing Ni, metal element M3, and the like is obtained.
  • the firing temperature is not particularly limited, it is 300 to 600° C. as an example.
  • the composite oxide obtained in the first step, the Li raw material, and optionally the M4 raw material are mixed to obtain a mixture.
  • Li raw materials include Li 2 CO 3 , LiOH, Li 2 O 2 , Li 2 O, LiNO 3 , LiNO 2 , Li 2 SO 4 , LiOH ⁇ H 2 O, LiH, and LiF.
  • M4 raw materials include oxides, hydroxides, carbonates, nitrates, and sulfates of M4.
  • the mixing ratio of the composite oxide obtained in the first step and the Li raw material is adjusted, for example, so that the molar ratio of metal elements other than Li to Li is 1:0.98 to 1:1.22. .
  • the mixing ratio of the composite oxide and the M4 raw material is adjusted so that the molar ratio of metal elements excluding Li to M4 is 1:0.0005 to 1:0.01, for example.
  • the mixture obtained in the second step is fired at a predetermined temperature and time to obtain a fired product.
  • Firing of the mixture includes, for example, a first firing step of firing at a first heating rate to a first set temperature of 450 ° C. or higher and 680 ° C. or lower in a firing furnace under an oxygen stream, and after the first firing step, a firing furnace A second firing step of firing at a second heating rate to a second set temperature of over 680° C. and not more than 800° C. in an oxygen stream.
  • the first heating rate is 1.5° C./min to 5.5° C./min
  • the second heating rate is slower than the first heating rate and is 0.1° C./min to 3.5° C./min. good too. It should be noted that a plurality of heating rates may be set for each firing step.
  • the retention time of the first set temperature in the first firing step is preferably 0 to 5 hours, more preferably 0 to 3 hours.
  • the holding time of the set temperature is the time for maintaining the set temperature after reaching the set temperature.
  • the holding time of the second set temperature in the second firing step is preferably 1 hour to 10 hours, more preferably 1 hour to 5 hours.
  • Firing of the mixture is performed in an oxygen stream with an oxygen concentration of 60% or more, and the flow rate of the oxygen stream is 0.2 mL/min to 4 mL/min per 10 cm 3 of the firing furnace and 0.3 L/min or more per 1 kg of the mixture. good too.
  • the baked product may be washed with water, dehydrated and dried to remove impurities.
  • the M4 raw material is not added in the second step, and the M4 raw material is added in the third step, when the fired product is washed with water or dried.
  • the M4 compound may be fixed to the particle surfaces of the composite oxide (C) by performing heat treatment for 15 hours.
  • the negative electrode 12 has a negative electrode core 40 and a negative electrode mixture layer 41 formed on at least one surface of the negative electrode core 40 .
  • a foil of a metal such as copper or a copper alloy that is stable in the potential range of the negative electrode, a film in which the metal is arranged on the surface layer, or the like can be used.
  • the negative electrode mixture layer 41 contains a negative electrode active material and a binder, and is preferably formed on both surfaces of the negative electrode core 40 . Further, a conductive agent may be added to the negative electrode mixture layer 41 .
  • the negative electrode 12 is produced by applying a negative electrode mixture slurry containing a negative electrode active material, a binder, and the like on the negative electrode core 40 , drying the coating film, and then compressing the negative electrode mixture layer 41 onto the negative electrode core 40 . It can be manufactured by forming on both sides.
  • a carbon-based active material at least one selected from Si, Sn, Sb, Mg, and Ge (hereinafter referred to as “metal element M5”) and metal element M5 and at least one of the M5 compounds containing
  • the content of the metal element M5 and M5 compound is preferably 0.5% by mass to 30% by mass, more preferably 1% by mass to 15% by mass, relative to the total mass of the negative electrode active material.
  • a metal element M5 may be added to the negative electrode mixture layer 41, but preferably an M5 compound is added.
  • M5 compounds include SiC, SnO 2 , a silicon oxide phase and a first silicon material (SiO) containing Si dispersed in the silicon oxide phase, a lithium silicate phase and dispersed in the lithium silicate phase. and a third silicon material (Si—C) containing a carbon phase and Si dispersed in the carbon phase.
  • SiO, LSX, or Si—C is preferable.
  • Carbon-based active materials include, for example, natural graphite such as flake graphite, massive artificial graphite, and artificial graphite such as graphitized mesophase carbon microbeads.
  • the content of the carbon-based active material (graphite) is preferably 70% by mass to 99.5% by mass, more preferably 85% by mass to 99% by mass, relative to the mass of the negative electrode active material.
  • D50 of the carbon-based active material is preferably 1 ⁇ m to 20 ⁇ m, more preferably 2 ⁇ m to 15 ⁇ m.
  • SiO and LSX are particles whose D50 is smaller than that of graphite, for example.
  • D50 of SiO and LSX is more preferably 1 ⁇ m to 15 ⁇ m, more preferably 3 ⁇ m to 10 ⁇ m.
  • a conductive layer made of a highly conductive material may be formed on the surface of the SiO and LSX particles.
  • a suitable conductive layer is a carbon coating composed of a carbon material.
  • the thickness of the conductive layer is preferably 1 nm to 200 nm, more preferably 5 nm to 100 nm, in consideration of ensuring conductivity and diffusibility of Li ions into the particles.
  • SiO has a particle structure in which fine Si particles are dispersed in a silicon oxide phase.
  • Suitable SiO has a sea-island structure in which fine Si particles are substantially uniformly dispersed in an amorphous silicon oxide matrix, and is represented by the general formula SiO x (0 ⁇ x ⁇ 2).
  • the silicon oxide phase is composed of aggregates of particles finer than Si particles.
  • the content of Si particles is preferably 35% by mass to 75% by mass with respect to the total mass of SiO from the viewpoint of compatibility between battery capacity and cycle characteristics.
  • the average particle size of the Si particles dispersed in the silicon oxide phase is, for example, 500 nm or less, preferably 200 nm or less, or 50 nm or less before charging and discharging. After charging and discharging, it is, for example, 400 nm or less, or 100 nm or less.
  • the average particle size of Si particles is obtained by observing the cross section of SiO particles using a SEM or a transmission electron microscope (TEM) and calculating the average value of the longest diameters of 100 Si particles (LSX, Si—C also as well).
  • LSX has a particle structure in which fine Si particles are dispersed in the lithium silicate phase.
  • a suitable LSX has a sea-island structure in which fine Si particles are substantially uniformly dispersed in a lithium silicate matrix.
  • the lithium silicate phase is composed of aggregates of particles finer than Si particles.
  • the content of Si particles is preferably 35% by mass to 75% by mass with respect to the total mass of LSX.
  • the average particle size of the Si particles is, for example, 500 nm or less, preferably 200 nm or less, or 50 nm or less before charging and discharging.
  • the content of the main component is preferably more than 50% by mass with respect to the total mass of the lithium silicate phase, and 80% by mass or more is more preferred.
  • Si--C has a carbon phase and Si particles dispersed within the carbon phase.
  • the content of Si particles of suitable Si—C is preferably 30% by mass or more and 80% by mass or less, and preferably 35% by mass or more and 75% by mass or less in terms of increasing capacity. , 55% by mass or more and 70% by mass or less.
  • the average particle size of Si particles is generally 500 nm or less, preferably 200 nm or less, and more preferably 100 nm or less before charging and discharging. After charging and discharging, the thickness is preferably 400 nm or less, more preferably 100 nm or less.
  • the binder contained in the negative electrode mixture layer 41 similarly to the case of the positive electrode 11, fluorine resin, PAN, polyimide, acrylic resin, polyolefin, or the like can be used. It is preferable to use Moreover, the negative electrode mixture layer 41 preferably further contains CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol (PVA), or the like. Among them, it is preferable to use SBR together with CMC or its salt or PAA or its salt.
  • the content of the binder is, for example, 0.1% by mass to 5% by mass with respect to the mass of the negative electrode active material.
  • the separator 13 has a porous substrate 50 and a surface layer 51 formed on the surface of the substrate 50 facing the positive electrode 11 side.
  • the surface layer 51 is a layer containing inorganic particles and a binder.
  • the surface layer 51 may be formed on both sides of the substrate 50, but is preferably formed only on one side of the substrate 50 facing the positive electrode 11 from the viewpoint of increasing the capacity.
  • the separator 13 is a porous sheet interposed between the positive electrode 11 and the negative electrode 12 to prevent electrical contact between the two electrodes, and has ion permeability and insulation.
  • the porosity of the separator 13 is, for example, 30% to 70%. Note that the porosity of the separator 13 is determined by the porosity of the base material 50 .
  • the base material 50 is a resin porous sheet.
  • the thickness of the base material 50 is preferably 5 ⁇ m to 50 ⁇ m, more preferably 10 ⁇ m to 30 ⁇ m.
  • the resin constituting the base material 50 is not particularly limited, but specific examples include polyethylene, polypropylene, polyolefins such as copolymers of ethylene and ⁇ -olefin, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, polyether ether ketone, and polyimide. , fluororesin, cellulose, and the like.
  • the base material 50 may have a single-layer structure, or may have a laminated structure such as a three-layer structure of polyethylene/polypropylene/polyethylene.
  • the surface layer 51 is porous like the base material 50 and has ion permeability and insulating properties. Although the thickness of the surface layer 51 is not particularly limited, it is preferably thinner than the thickness of the substrate 50, for example, 0.5 ⁇ m to 10 ⁇ m, more preferably 1 ⁇ m to 6 ⁇ m.
  • the surface layer 51 is in contact with the surface of the positive electrode mixture layer 31 and is preferably formed over substantially the entire area of one side of the substrate 50 .
  • the surface layer 51 can be formed, for example, by applying a slurry containing inorganic particles and a binder to the entire surface of the base material 50 and then drying the coating film.
  • the surface layer 51 is a layer containing inorganic particles as a main component.
  • the content of the inorganic particles is preferably 70% by mass or more, more preferably 80% by mass or more, relative to the total mass of the surface layer 51 .
  • a suitable range for the content of the inorganic particles is preferably 70% by mass to 99% by mass, more preferably 80% by mass to 98% by mass, and particularly preferably 85% by mass to 95% by mass.
  • the surface layer 51 has a function of suppressing damage to the separator 13 due to conductive foreign matter, deformation of the separator 13 during abnormal heat generation, and the like.
  • the surface layer 51 in contact with the positive electrode 11 suppresses a side reaction of the electrolyte in the positive electrode 11 by interacting with the composite oxide (B), and the provision of the surface layer 51 makes the cycle characteristics and storage characteristics of the battery unique. substantially improved.
  • Inorganic particles contained in the surface layer 51 include metal oxides, metal nitrides, metal fluorides, metal carbides, aluminum hydroxide (boehmite), metal hydroxides such as magnesium hydroxide, calcium carbonate, magnesium carbonate, and barium carbonate. and particles of metal sulfates such as calcium sulfate, magnesium sulfate, barium sulfate, and the like.
  • One type of inorganic particles may be used alone, or two or more types may be used in combination.
  • the D50 of the inorganic particles is preferably 0.01 ⁇ m to 10 ⁇ m, more preferably 0.05 ⁇ m to 5 ⁇ m.
  • metal oxides include aluminum oxide (alumina), titanium oxide, magnesium oxide, zirconium oxide, nickel oxide, silicon oxide, and manganese oxide.
  • metal nitrides are titanium nitride, boron nitride, aluminum nitride, magnesium nitride, silicon nitride, and the like.
  • metal fluorides are aluminum fluoride, lithium fluoride, sodium fluoride, magnesium fluoride, calcium fluoride, barium fluoride, and the like.
  • metal carbides are silicon carbide, boron carbide, titanium carbide, tungsten carbide, and the like. From the viewpoint of improving cycle characteristics and storage characteristics, an example of suitable inorganic particles is at least one selected from alumina, boehmite, and barium sulfate.
  • the binder contained in the surface layer 51 is not particularly limited as long as it can bond the inorganic particles together, can bond the inorganic particles to the substrate 50, and has electrolyte resistance.
  • the same kind of binder as used for the agent layer 31 and the negative electrode mixture layer 41 can be used. Specific examples include fluorine resins such as PVDF and PTFE, PAN, and acrylic resins. Moreover, you may use resin with high heat resistance like an aramid resin.
  • An example of a suitable binder includes at least one selected from aramid resins and acrylic resins.
  • the non-aqueous electrolyte contains a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent.
  • non-aqueous solvents examples include esters, ethers, nitriles such as acetonitrile, amides such as dimethylformamide, and mixed solvents of two or more thereof.
  • the non-aqueous solvent may contain a halogen-substituted product obtained by substituting at least part of the hydrogen atoms of these solvents with halogen atoms such as fluorine.
  • halogen-substituted compounds 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
  • the non-aqueous electrolyte is not limited to a liquid electrolyte, and may be a solid electrolyte.
  • the non-aqueous electrolyte contains a sulfonylimide salt as an electrolyte salt.
  • a non-aqueous electrolyte secondary battery 10 having a positive electrode 11 containing a composite oxide (A, B) or a composite oxide (A, B, C)
  • the positive electrode active It is thought that a good protective film is formed on the particle surface of the substance, side reactions of the electrolyte on the particle surface are suppressed, and the cycle characteristics are specifically improved.
  • the concentration of the sulfonylimide salt is preferably 0.05 mol/L to 2.5 mol/L, more preferably 0.1 mol/L to 2.0 mol/L, particularly preferably 0.1 mol/L to 1 .5 mol/L. If the content of the sulfonylimide salt is within this range, the cycle characteristics can be improved more effectively.
  • the sulfonylimide salt added to the non-aqueous electrolyte is preferably lithium sulfonylimide.
  • Lithium sulfonylimides include, for example, lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide, lithium bis(nonafluorobutanesulfonyl)imide, lithium bis(pentafluoroethanesulfonyl)imide (LIBETI), etc. is mentioned. Among them, at least one lithium sulfonylimide selected from LiFSI and lithium bis(trifluoromethanesulfonyl)imide is preferable.
  • the sulfonylimide salts may be used singly or in combination of two or more.
  • the non-aqueous electrolyte may further contain other lithium salts.
  • other lithium salts include LiBF4 , LiClO4, LiPF6 , LiAsF6 , LiSbF6 , LiAlCl4 , LiSCN , LiCF3SO3 , LiCF3CO2 , Li ( P ( C2O4 ) F4 ), LiPF 6-x (C n F 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 2 B 4 O 7 , Li(B(C 2 O 4 )F 2 ) and other borates.
  • Lithium sulfonylimide and the second lithium salt preferably coexist in the non-aqueous electrolyte.
  • the combination of LiFSI and LiPF6 is particularly preferred.
  • the concentration of lithium sulfonylimide is adjusted, for example, within the above range even when the second lithium salt is included.
  • the concentration of lithium sulfonylimide is 0.1 mol/L to 1.5 mol/L, and the total concentration of lithium salts is 1.5 mol/L to 2.5 mol/L.
  • the concentration of lithium sulfonylimide is, for example, 30% to 70% of the concentration of lithium salt contained in the non-aqueous electrolyte.
  • the non-aqueous electrolyte may contain additives such as vinylene carbonate (VC), ethylene sulfite (ES), cyclohexylbenzene (CHB), ortho-terphenyl (OTP), and propanesultone compounds.
  • VC vinylene carbonate
  • ES ethylene sulfite
  • CHB cyclohexylbenzene
  • OTP ortho-terphenyl
  • propanesultone compounds propanesultone compounds.
  • concentration of the additive is not particularly limited, one example is 0.1% by mass to 5% by mass.
  • esters and ethers are used as non-aqueous solvents.
  • esters include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC) and butylene carbonate, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl propyl carbonate, Chain carbonates such as ethyl propyl carbonate and methyl isopropyl carbonate, cyclic carboxylic acid esters such as ⁇ -butyrolactone (GBL) and ⁇ -valerolactone (GVL), methyl acetate, ethyl acetate, propyl acetate, methyl propionate (MP) , and chain carboxylic acid esters such as ethyl propionate (EP).
  • EC ethylene carbonate
  • PC propylene carbonate
  • DMC dimethyl carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • ethers 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 ether, 1,2-dimethoxyethane, diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, Dihexyl ether, ethyl vinyl ether, butyl vinyl ether, methyl phenyl ether, ethyl phenyl ether, butyl phenyl ether, pentyl phenyl ether, methoxytoluene, benzyl ethyl ether, diphenyl ether, dibenzyl ether
  • a composite oxide (A1) containing Li 2 NiO 2 with a porosity of 2.2% was prepared by using Li 2 O and NiO as raw materials and sintering under the conditions adjusted as described above. After mixing the composite oxide (A1), acetylene black (AB), and polyvinylidene fluoride (PVDF) at a solid content mass ratio of 92:5:3, and adding an appropriate amount of N-methylpyrrolidone (NMP) , and kneaded to prepare a positive electrode mixture slurry.
  • NMP N-methylpyrrolidone
  • the positive electrode mixture slurry is applied to a positive electrode core made of aluminum foil, and after drying the coating film, the coating film is rolled using a rolling roller, cut into a predetermined electrode size, and applied to both sides of the positive electrode core.
  • a positive electrode on which a positive electrode mixture layer was formed was obtained.
  • an exposed portion where the surface of the positive electrode core was exposed was provided on a part of the positive electrode.
  • Composite oxide (A1) contained Li 2 NiO 2 as a main component and a small amount of Li 2 O and NiO, and was identified by an X-ray diffraction method to have a crystal structure belonging to the space group Immm. D50 of the composite oxide (A1) measured using MT3000II manufactured by Microtrack Bell Co., Ltd. using water as a dispersion medium was 10 ⁇ m.
  • LiPF 6 was dissolved at a concentration of 1 mol/L in a mixed solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 3:7 (25° C., 1 atm), A non-aqueous electrolyte was prepared.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • a Li foil cut into a predetermined size was used as the negative electrode.
  • An aluminum lead was attached to the exposed portion of the prepared positive electrode, and a nickel lead was attached to a predetermined position of the negative electrode.
  • This electrode assembly was housed in an exterior body, the prepared non-aqueous electrolyte was injected, and then the opening of the exterior body was sealed to obtain a test cell.
  • Example 2 A test cell was prepared in the same manner as in Example 1, except that a composite oxide (A2) containing Li 2 NiO 2 with a porosity of 3.6% was used instead of the composite oxide (A1) in the preparation of the positive electrode. made.
  • Example 3 A test cell was prepared in the same manner as in Example 1, except that a composite oxide (A3) containing Li 2 NiO 2 with a porosity of 4.8% was used instead of the composite oxide (A1) in the preparation of the positive electrode. made.
  • Example 4 A test cell was prepared in the same manner as in Example 1, except that a composite oxide (A4) containing Li 2 NiO 2 with a porosity of 6.4% was used instead of the composite oxide (A1) in the preparation of the positive electrode. made.
  • Example 5 A test cell was prepared in the same manner as in Example 1, except that a composite oxide (A5) containing Li 2 NiO 2 with a porosity of 8.2% was used instead of the composite oxide (A1) in the preparation of the positive electrode. made.
  • a test cell was prepared in the same manner as in Example 1, except that a composite oxide (A6) containing Li 2 NiO 2 with a porosity of 1.1% was used instead of the composite oxide (A1) in the preparation of the positive electrode. made.
  • the initial charge capacity was evaluated by the following method.
  • the evaluation results are shown in Table 1 together with the porosity of the composite oxide (A) used for the positive electrode.
  • the initial charge capacity shown in Table 1 is a relative value when the charge capacity of the test cell of the comparative example is used as a reference (100).
  • the test cells of the examples all have a larger initial charge capacity than the test cells of the comparative example.
  • a composite oxide with a porosity of 2% to 10% as the positive electrode active material, a sufficient amount of Li can be supplied to the negative electrode during initial charging, so the battery capacity can be improved.
  • a composite oxide (B1) was prepared as follows, and test cells of Examples 6 and 7 were produced using a mixture of the composite oxide (B1) and the composite oxide A as the positive electrode active material.
  • Example 6 A test cell was prepared in the same manner as in Example 1, except that a mixture of the composite oxides (A1, B1) at a mass ratio of 98:2 was used instead of the composite oxide (A1) in the preparation of the positive electrode. bottom.
  • Example 7 A test cell was prepared in the same manner as in Example 5, except that a mixture of the composite oxides (A6, B1) at a mass ratio of 98:2 was used instead of the composite oxide (A6) in the preparation of the positive electrode. made.
  • the resistance increase rate was evaluated by the following method.
  • the evaluation results are shown in Table 2 together with the configuration of the positive electrode.
  • the resistance increase rate shown in Table 2 is a relative value when the resistance increase rate of the test cell of Example 1 is used as a reference (100).
  • Resistance increase rate (resistance after 15 cycles - resistance after 1 cycle) / (resistance after 1 cycle) ⁇ Cycle test>
  • the test cell was charged at a constant current of 0.3C until the battery voltage reached 4.3V under a temperature environment of 25°C, and then charged at a constant voltage of 4.3V until the current value reached 0.02C. After that, constant current discharge was performed at 0.05C until the battery voltage reached 2.5V. This charge/discharge cycle was repeated 15 cycles.
  • the test cell of Example 6 has a lower increase in resistance after 15 cycles than the test cell of Example 1. That is, when the positive electrode containing the composite oxide (A1) and the composite oxide (B1) is used, an increase in resistance of the battery is specifically suppressed.
  • Example 5 showed a greater rise in resistance after 15 cycles than the test cell of Example 1.
  • the composite oxide (A5) with high porosity has a large charge capacity and contains a large amount of highly active LiNiO 2 , so side reactions with the electrolyte are likely to occur.
  • the reason for this is thought to be that the number of voids 37d that are present also increases, making it easier for side reactions to occur using these as active points.
  • the particle surface of the composite oxide (A5) which tends to cause side reactions, can be effectively protected. It is possible to keep the resistance increase at the same level.
  • non-aqueous electrolyte secondary battery 11 positive electrode 12 negative electrode 13 separator 14 electrode body 16 outer can 17 sealing body 18, 19 insulating plate 20 positive electrode lead 21 negative electrode lead 22 grooved portion 23 internal terminal Plate 24 Lower valve body 25 Insulating member 26 Upper valve body 27 Cap 28 Gasket 30 Positive electrode core 31 Positive electrode mixture layer 40 Negative electrode core 41 Negative electrode mixture layer

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JP2012004109A (ja) * 2010-06-13 2012-01-05 Samsung Sdi Co Ltd リチウム二次電池用正極活物質、その製造方法及びリチウム二次電池
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KR102646712B1 (ko) * 2017-11-22 2024-03-12 주식회사 엘지에너지솔루션 리튬 이차전지용 양극 첨가제의 제조방법
WO2019103574A2 (ko) * 2017-11-27 2019-05-31 주식회사 엘지화학 양극 첨가제, 이의 제조 방법, 이를 포함하는 양극 및 리튬 이차 전지
JP7617565B2 (ja) * 2019-04-26 2025-01-20 パナソニックＩｐマネジメント株式会社 二次電池用の正極活物質、及び二次電池
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JP2012004109A (ja) * 2010-06-13 2012-01-05 Samsung Sdi Co Ltd リチウム二次電池用正極活物質、その製造方法及びリチウム二次電池
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