WO2023068221A1 - Positive electrode active material for nonaqueous electrolyte secondary batteries, and nonaqueous electrolyte secondary battery - Google Patents

Positive electrode active material for nonaqueous electrolyte secondary batteries, and nonaqueous electrolyte secondary battery Download PDF

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WO2023068221A1
WO2023068221A1 PCT/JP2022/038573 JP2022038573W WO2023068221A1 WO 2023068221 A1 WO2023068221 A1 WO 2023068221A1 JP 2022038573 W JP2022038573 W JP 2022038573W WO 2023068221 A1 WO2023068221 A1 WO 2023068221A1
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positive electrode
active material
electrode active
electrolyte secondary
ratio
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PCT/JP2022/038573
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French (fr)
Japanese (ja)
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敏信 金井
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三洋電機株式会社
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—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
    • H01M4/50—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
    • 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 positive electrode active materials for non-aqueous electrolyte secondary batteries and non-aqueous electrolyte secondary batteries.
  • a non-aqueous electrolyte secondary battery has a positive electrode, a negative electrode, and a non-aqueous electrolyte, and charges and discharges by moving lithium ions etc. between the positive electrode and the negative electrode. Batteries are widely used.
  • Patent Document 1 at least one selected from a first positive electrode active material and a second positive electrode active material is included, and the first positive electrode active material has a general composition formula Li (1+a) Mn x Ni y Co (1-xyz) M z O 2 (where M is at least one element selected from the group consisting of Ti, Zr, Nb, Mo, W, Al, Si, Ga, Ge and Sn is represented by ⁇ 0.15 ⁇ a ⁇ 0.15, 0.1 ⁇ x ⁇ 0.5, 0.6 ⁇ x+y+z ⁇ 1.0, 0 ⁇ z ⁇ 0.1), and the second The positive electrode active material has a general composition formula Li (1-sb) Mg s Co (1-tu) Al t M' u O 2 (where M' is selected from the group consisting of Ti, Zr and Ge). is at least one element that is A non-aqueous electrolyte secondary battery using the active material obtained by the method is disclosed.
  • the composition of the secondary particles serving as the core is Li x1 Ni 1-y1-z1-w1 Co y1 Mn z1 M1 w1 O 2-v K v (1 ⁇ x1 ⁇ 1.3, 0 ⁇ y1 ⁇ 0.33, 0.2 ⁇ z1 ⁇ 0.33, 0 ⁇ w1 ⁇ 0.1, 0 ⁇ v ⁇ 0.05, and M1 is at least one metal selected from Al, Mg and K is at least one anion selected from F ⁇ , PO 4 3- ), the Li—Ni—Mn composite oxide having the composition Li x2 Ni 1-y2 on or near the surface of the secondary particles.
  • M2 is at least selected from Al, Mg, Zr, Ti
  • a non-aqueous electrolyte secondary battery using Li--Ni composite oxide particles for non-aqueous electrolyte secondary batteries coated with or having Li--Ni composite oxide (a type of metal) present therein is disclosed.
  • the present disclosure provides a direct current resistance of a non-aqueous electrolyte secondary battery even when a Ni-containing lithium composite oxide having a high ratio of the number of moles of Ni to the total number of moles of metal elements excluding lithium is used as a positive electrode active material. and suppress deterioration of charge-discharge cycle characteristics.
  • a positive electrode active material for a nonaqueous electrolyte secondary battery which is one aspect of the present disclosure, includes a first positive electrode active material and a second positive electrode active material, and the first positive electrode active material is a Ni-containing lithium composite oxide, , the ratio (B 1 /A 1 ) of the number of moles of Ni (B 1 ) to the total number of moles (A 1 ) of the metal elements excluding Li is 0.85 or more and 0.94 or less, and the metal elements excluding Li
  • the ratio (C 1 /A 1 ) of the number of moles of Li (C 1 ) to the total number of moles (A 1 ) of Li is 0.950 or more and 0.983 or less
  • the second positive electrode active material is a Ni-containing lithium composite an oxide, wherein the ratio of the number of moles of Ni (B 2 ) to the total number of moles of metal elements excluding Li (A 2 ) is 0.85 or more and 0.94 or less, and the total number of metal elements excluding Li is The ratio (
  • a non-aqueous electrolyte secondary battery includes a positive electrode, a negative electrode, and a non-aqueous electrolyte, and the positive electrode contains the positive electrode active material for a non-aqueous electrolyte secondary battery.
  • the non-aqueous electrolyte secondary battery even when a Ni-containing lithium composite oxide having a high ratio of the number of moles of Ni to the total number of moles of metal elements excluding lithium is used as the positive electrode active material, the non-aqueous electrolyte secondary battery It is possible to reduce the direct current resistance of the battery and suppress the deterioration of the charge-discharge cycle characteristics.
  • FIG. 1 is a cross-sectional view of a non-aqueous electrolyte secondary battery that is an example of an embodiment
  • FIG. 1 is a cross-sectional view of a non-aqueous electrolyte secondary battery that is an example of an embodiment.
  • the non-aqueous electrolyte secondary battery 10 shown in FIG. A battery case having insulating plates 18 and 19 arranged, and a case main body 16 and a sealing member 17 for accommodating the above members is provided.
  • the wound electrode body 14 another form of electrode body such as a stacked electrode body in which positive and negative electrodes are alternately stacked via a separator may be applied.
  • the battery case include cylindrical, square, coin-shaped, button-shaped metal cases, and resin cases formed by laminating resin sheets (so-called laminated type).
  • the case body 16 is, for example, a bottomed cylindrical metal container.
  • a gasket 28 is provided between the case body 16 and the sealing member 17 to ensure hermeticity inside the battery.
  • the case main body 16 has an overhanging portion 22 that supports the sealing member 17, for example, a portion of the side surface overhanging inward.
  • the projecting portion 22 is preferably annularly formed along the circumferential direction of the case body 16 and supports the sealing member 17 on the upper surface thereof.
  • the sealing body 17 has a structure in which a filter 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 to each other at their central portions, and an insulating member 25 is interposed between their peripheral edge portions.
  • the lower valve body 24 deforms and breaks so as to push the upper valve body 26 upward toward the cap 27, thereby breaking the lower valve body 24 and the upper valve.
  • the current path between bodies 26 is interrupted.
  • the upper valve body 26 is broken and the gas is discharged from the opening of the cap 27 .
  • the positive electrode lead 20 attached to the positive electrode 11 extends through the through hole of the insulating plate 18 toward the sealing member 17, and the negative electrode lead 21 attached to the negative electrode 12 is insulated. It extends to the bottom side of the case body 16 through the outside of the plate 19 .
  • the positive electrode lead 20 is connected to the lower surface of the filter 23, which is the bottom plate of the sealing member 17, by welding or the like, and the cap 27, which is the top plate of the sealing member 17 electrically connected to the filter 23, serves as a positive electrode terminal.
  • the negative lead 21 is connected to the inner surface of the bottom of the case body 16 by welding or the like, and the case body 16 serves as a negative terminal.
  • the positive electrode 11 includes a positive electrode current collector and a positive electrode mixture layer arranged on the positive electrode current collector. In addition, it is desirable that the positive electrode mixture layers are arranged on both sides of the positive electrode current collector.
  • the positive electrode current collector a foil of a metal such as aluminum or an aluminum alloy that is stable in the potential range of the positive electrode, or a film in which the metal is placed on the surface can be used.
  • the positive electrode current collector has a thickness of, for example, about 10 ⁇ m to 100 ⁇ m.
  • the positive electrode mixture layer includes a first positive electrode active material and a second positive electrode active material.
  • the positive electrode mixture layer preferably contains a binder in order to bind the positive electrode active materials together and ensure the mechanical strength of the positive electrode mixture layer.
  • the positive electrode mixture layer preferably contains a conductive material in that the conductivity of the layer can be improved.
  • a positive electrode mixture slurry containing a first positive electrode active material, a second positive electrode active material, a binder, a conductive material, and the like is prepared, and this positive electrode mixture slurry is applied on a positive electrode current collector and coated. After drying the film, it can be prepared by rolling the coating film.
  • the ratio (B 1 /A 1 ) of the number of moles of Ni (B 1 ) to the total number of moles (A 1 ) of metal elements excluding Li is 0.85 or more and 0.94 or less.
  • a Ni-containing lithium composite oxide in which the ratio (C 1 /A 1 ) of the number of moles (C 1 ) of Li to the total number of moles (A 1 ) of metal elements excluding Li is 0.950 or more and 0.983 or less be.
  • the ratio (B 2 /A 2 ) of the number of moles (B 2 ) of Ni to the total number of moles (A 2 ) of metal elements excluding Li is 0.85 or more and 0.94 or less.
  • Ni-containing lithium composite oxide having a ratio (C 2 /A 2 ) of the number of moles (C 2 ) of Li to the total number of moles (A 2 ) of metal elements excluding Li of 0.984 or more and 1.004 or less is.
  • the Ni-containing lithium composite oxide of the first positive electrode active material has the following general formula (1) in terms of reducing the direct current resistance of the non-aqueous electrolyte secondary battery or suppressing deterioration in charge-discharge cycle characteristics. It is preferably a Ni-containing lithium composite oxide represented by. LizNi1 -xyMxAlyO2 ( 1 ) where x, y and z are 0 ⁇ x ⁇ 0.15, 0 ⁇ y ⁇ 0.10, 0.85 ⁇ 1-xy ⁇ 0.94, 0.950 ⁇ z ⁇ 0.983 0.02 ⁇ x ⁇ 0.10, 0.03 ⁇ y ⁇ 0.07, 0.85 ⁇ 1-xy ⁇ 0.94, 0.970 ⁇ z ⁇ 0.983 is more preferable.
  • M is preferably at least one element selected from the group consisting of Co, W, Nb, Mg, Ti, Mn and Mo, and at least one element selected from Co, Mn and W is more preferably an element of
  • the Ni-containing lithium composite oxide of the second positive electrode active material has the following general formula (2) in terms of reducing the direct current resistance of the non-aqueous electrolyte secondary battery or suppressing deterioration in charge-discharge cycle characteristics. It is preferably a Ni-containing lithium composite oxide represented by. LizNi1 -xyMxAlyO2 ( 2 ) where x, y and z are 0 ⁇ x ⁇ 0.15, 0 ⁇ y ⁇ 0.10, 0.85 ⁇ 1-xy ⁇ 0.94, 0.984 ⁇ z ⁇ 1.004 0.02 ⁇ x ⁇ 0.10, 0.03 ⁇ y ⁇ 0.07, 0.85 ⁇ 1-xy ⁇ 0.94, 0.984 ⁇ z ⁇ 1.000 is more preferable.
  • M is preferably at least one element selected from the group consisting of Co, W, Nb, Mg, Ti, Mn and Mo, and at least one element selected from Co, Mn and W is more preferably an element of
  • the composition of the Ni-containing lithium composite oxide is measured by inductively coupled plasma (ICP) emission spectrometry.
  • ICP inductively coupled plasma
  • the mixing ratio of the first positive electrode active material and the second positive electrode active material is 95: 5 to 75 in mass ratio in terms of reducing the direct current resistance of the non-aqueous electrolyte secondary battery and suppressing deterioration of charge-discharge cycle characteristics. :25, preferably 90:10 to 80:20.
  • the total amount of the first positive electrode active material and the second positive electrode active material contained in the positive electrode mixture layer is preferably 80% by mass or more, preferably 90% by mass, with respect to the total mass of the positive electrode mixture layer. It is more preferable to be above.
  • the first positive electrode active material and the second positive electrode active material are composed of secondary particles that are aggregated primary particles.
  • the average particle size of the secondary particles of the first positive electrode active material and the average particle size of the secondary particles of the second positive electrode active material are, for example, 5 ⁇ m or more and 15 ⁇ m or less in terms of increasing the capacity of the non-aqueous electrolyte secondary battery. and more preferably 8 ⁇ m or more and 12 ⁇ m or less.
  • the average particle size of the secondary particles is the volume average particle size measured by the laser diffraction method, and means the median size at which the volume integrated value is 50% in the particle size distribution.
  • the average particle size of the secondary particles of the first positive electrode active material and the second positive electrode active material can be measured using, for example, a laser diffraction scattering particle size distribution analyzer (manufactured by HORIBA, Ltd.).
  • the average particle size of the primary particles of the first positive electrode active material and the average particle size of the primary particles of the second positive electrode active material should be 0.1 ⁇ m or more from the viewpoint of increasing the capacity of the non-aqueous electrolyte secondary battery. It is preferably 0 ⁇ m or less, more preferably 0.2 ⁇ m or more and 0.8 ⁇ m or less.
  • the average particle size of the primary particles of the first positive electrode active material and the second positive electrode active material is obtained by randomly selecting 100 primary particles in the SEM image of the first positive electrode active material and the second positive electrode active material, It is obtained by measuring the diameter of the circumscribed circle of and averaging the measured values.
  • the positive electrode mixture layer may contain a positive electrode active material other than the first positive electrode active material and the second positive electrode active material.
  • the positive electrode active material other than the first positive electrode active material and the second positive electrode active material is not particularly limited as long as it is a compound capable of reversibly intercalating and deintercalating lithium .
  • Ni-free Li composite oxides, Ni-containing lithium composite oxides having a smaller Ni content than the first positive electrode active material and the second positive electrode active material, and the like can be mentioned.
  • Carbon materials such as carbon black, acetylene black, ketjen black, and graphite can be exemplified as the conductive material contained in the positive electrode mixture layer. These may be used alone or in combination of two or more.
  • the content of the conductive material in the positive electrode mixture layer is, for example, preferably 0.5% by mass or more and 4% by mass or less, and more preferably 0.5% by mass or more and 1.5% by mass or less.
  • the binder contained in the positive electrode mixture layer includes fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resins, acrylic resins, polyolefin resins, styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC) or salts thereof, polyacrylic acid (PAA) or salts thereof (PAA-Na, PAA-K, etc., may also be partially neutralized salts), polyethylene oxide (PEO), polyvinyl alcohol (PVA) and the like. These may be used alone or in combination of two or more.
  • the content of the binder in the positive electrode mixture layer is, for example, preferably 0.5% by mass or more and 4% by mass or less, and more preferably 0.5% by mass or more and 1.5% by mass or less. .
  • the negative electrode 12 is composed of, for example, a negative electrode current collector and a negative electrode mixture layer formed on the current collector.
  • a negative electrode current collector a foil of a metal such as copper that is stable in the potential range of the negative electrode, a film having the metal on the surface layer, or the like can be used.
  • the negative electrode mixture layer includes, for example, a negative electrode active material, a binder, and the like.
  • a negative electrode mixture slurry containing a negative electrode active material, a binder, etc. is prepared, the negative electrode mixture slurry is applied on a negative electrode current collector, the coating film is dried, and then the coating film is applied. It can be produced by rolling.
  • the negative electrode active material is not particularly limited as long as it is a material capable of intercalating and deintercalating lithium ions.
  • Lithium alloys such as tin alloys, graphite, coke, carbon materials such as organic sintered bodies, metal oxides such as SnO 2 , SnO, TiO 2 and the like. These may be used singly or in combination of two or more.
  • the binder contained in the negative electrode mixture layer as in the case of the positive electrode, fluorine resin, PAN, polyimide resin, acrylic resin, polyolefin resin, SBR, CMC or its salt, PAA or its salt, Examples include PEO and PVA.
  • the negative electrode mixture layer may contain a conductive material as in the case of the positive electrode.
  • the separator 13 for example, a porous sheet or the like having ion permeability and insulation is used. Specific examples of porous sheets include microporous thin films, woven fabrics, and non-woven fabrics.
  • the separator 13 is made of, for example, polyolefin such as polyethylene or polypropylene, or cellulose.
  • the separator 13 may be a laminate having a cellulose fiber layer and a thermoplastic resin fiber layer such as polyolefin.
  • the separator 13 may be a multilayer separator including a polyethylene layer and a polypropylene layer, and may have a surface layer composed of an aramid resin or a surface layer containing an inorganic filler.
  • the non-aqueous electrolyte contains a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent.
  • the nonaqueous electrolyte is not limited to a liquid electrolyte (nonaqueous electrolyte), and may be a solid electrolyte using a gel polymer or the like.
  • non-aqueous solvents that can be used 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.
  • esters examples 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. , Ethyl propyl carbonate, methyl isopropyl carbonate and other chain carbonates, ⁇ -butyrolactone, ⁇ -valerolactone and other cyclic carboxylic acid esters, methyl acetate, ethyl acetate, propyl acetate, methyl propionate (MP), ethyl propionate, etc. and chain carboxylic acid esters of.
  • 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.
  • 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-cineol, 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, cycl
  • nitriles examples include acetonitrile, propionitrile, butyronitrile, valeronitrile, n-heptanirile, succinonitrile, glutaronitrile, adibonitrile, pimeronitrile, 1,2,3-propanetricarbonitrile, 1,3 , 5-pentanetricarbonitrile and the like.
  • 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
  • FEC fluoroethylene carbonate
  • FMP fluorinated chain carboxylates
  • electrolyte salts examples 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 4O7 , borates such as Li(B( C2O4 ) F2 ) , LiN( SO2CF3 ) 2 , LiN( ClF2l + 1SO2 )( CmF2m + 1SO2 ) ⁇ l , where m is an integer of 1 or more ⁇ . Electrolyte salts may be used singly or in combination of two or more. The concentration of the electrolyte
  • the composite oxide containing Ni, Co and Al and LiOH were mixed so that the total molar ratio of Li to Ni, Co and Al was 1.02:1.
  • the mixture was fired in an oxygen atmosphere at 740° C. for 3.5 hours to obtain Ni, Co and Al-containing lithium composite oxide A (Li 1.02 Ni 0.90 Co 0.05 Al 0.05 O 2 ).
  • Ni-, Co- and Al-containing lithium composite oxide B Li 1.05 Ni 0.90 Co 0.05 Al 0.05 O 2 .
  • the Ni-, Co- and Al-containing lithium composite oxide A was washed with water and dried. This was used as the first positive electrode active material.
  • the Ni-, Co- and Al-containing lithium composite oxide B was washed with water and dried to obtain a second positive electrode active material.
  • composition of the second positive electrode active material was analyzed by ICP and found to be Li 0.997 Ni 0.895 Co 0.048 Al 0.057 O 2 .
  • the first positive electrode active material (secondary particle average particle size: 11 ⁇ m) and the second positive electrode active material (secondary particle average particle size: 11 ⁇ m) were mixed at a mass ratio of 80:20.
  • NMP N-methyl-2-pyrrolidone
  • a non-aqueous electrolyte was prepared by dissolving LiPF 6 at a concentration of 1.0 mol/L in a mixed non-aqueous solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 3:7. got
  • a positive electrode lead was attached to the positive electrode prepared above, and a negative electrode lead was attached to the negative electrode prepared above.
  • a separator was placed between these two electrodes and spirally wound to produce a wound electrode assembly. After the electrode assembly and the non-aqueous electrolyte were arranged in an aluminum laminate outer package, the periphery of the outer package was heated and welded to obtain a non-aqueous electrolyte secondary battery.
  • Example 2 A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that the first positive electrode active material and the second positive electrode active material were mixed at a mass ratio of 85:15.
  • Example 1 A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that only the first positive electrode active material was used as the positive electrode active material.
  • Example 2 A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that only the second positive electrode active material was used as the positive electrode active material.
  • Example 3 A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that the first positive electrode active material and the second positive electrode active material were mixed at a mass ratio of 70:30.
  • Example 3 A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that the first positive electrode active material and the second positive electrode active material were mixed at a mass ratio of 95:5.
  • a non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1 using only the first positive electrode active material obtained above as a positive electrode active material.
  • Table 1 summarizes the results of DCR, initial capacity, and capacity retention rate in each example and each comparative example. However, these results represent the results of other examples and comparative examples as relative values, with the result of Comparative Example 1 as a reference (100).
  • the ratio (B 1 /A 1 ) of the number of moles (B 1 ) of Ni to the total number of moles (A 1 ) of the metal elements excluding Li is 0.85 or more and 0.94 or less, and the metal excluding Li
  • the ratio of the number of moles of Ni (B 2 ) to the total number of moles (A 2 ) of is 0.85 or more and 0.94 or less, and the number of moles of Li to the total number of moles (A 2 ) of the metal elements excluding Li

Abstract

This positive electrode active material for nonaqueous electrolyte secondary batteries includes a first positive electrode active material and a second positive electrode active material. The first positive electrode active material is a Ni-containing lithium composite oxide. The ratio (B1/A1) of the molar number (B1) of Ni with respect to the total molar number (A1) of metal elements excluding Li is 0.85-0.94 inclusive. The ratio (C1/A1) of the molar number (C1) of Li with respect to the total molar number (A1) of metal elements excluding Li is 0.950-0.983 inclusive. The second positive electrode active material is a Ni-containing lithium composite oxide. The ratio of the molar number (B2) of Ni with respect to the total molar number (A2) of metal elements excluding Li is 0.85-0.94 inclusive. The ratio (C2/A2) of the molar number (C2) of Li with respect to the total molar number (A2) of metal elements excluding Li is 0.984-1.004 inclusive. The mixing ratio of the first positive electrode active material to the second positive electrode active material is 95:5 to 75:25 by mass ratio.

Description

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Positive electrode active material for non-aqueous electrolyte secondary battery, and non-aqueous electrolyte secondary battery
　本開示は、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に関する。 The present disclosure relates to positive electrode active materials for non-aqueous electrolyte secondary batteries and non-aqueous electrolyte secondary batteries.
　近年、高出力、高エネルギー密度の二次電池として、正極と、負極と、非水電解質とを備え、正極と負極との間でリチウムイオン等を移動させて充放電を行う非水電解質二次電池が広く利用されている。 In recent years, as a secondary battery with high output and high energy density, a non-aqueous electrolyte secondary battery has a positive electrode, a negative electrode, and a non-aqueous electrolyte, and charges and discharges by moving lithium ions etc. between the positive electrode and the negative electrode. Batteries are widely used.
　例えば、特許文献１には、第１の正極活物質及び第２の正極活物質から選ばれる少なくとも１種を含み、前記第１の正極活物質は、一般組成式Ｌｉ（１＋ａ）ＭｎｘＮｉｙＣｏ（１－ｘ－ｙ－ｚ）ＭｚＯ２（但し、Ｍは、Ｔｉ、Ｚｒ、Ｎｂ、Ｍｏ、Ｗ、Ａｌ、Ｓｉ、Ｇａ、Ｇｅ及びＳｎからなる群から選ばれる少なくとも１種の元素であり、－０．１５＜ａ＜０．１５、０．１＜ｘ≦０．５、０．６＜ｘ＋ｙ＋ｚ＜１．０、０≦ｚ≦０．１）で表され、前記第２の正極活物質は、一般組成式Ｌｉ（１－ｓ－ｂ）ＭｇｓＣｏ（１－ｔ－ｕ）ＡｌｔＭ’ｕＯ２（但し、Ｍ'は、Ｔｉ、Ｚｒ及びＧｅからなる群から選ばれる少なくとも１種の元素であり、０．０１≦ｓ＜０．１、０＜ｕ＜０．１、０．０１＜ｔ＋ｕ＜０．１、－０．０６≦ｂ＜０．０５）で表される活物質を使用した非水電解質二次電池が開示されている。 For example, in Patent Document 1, at least one selected from a first positive electrode active material and a second positive electrode active material is included, and the first positive electrode active material has a general composition formula Li (1+a) Mn x Ni y Co (1-xyz) M z O 2 (where M is at least one element selected from the group consisting of Ti, Zr, Nb, Mo, W, Al, Si, Ga, Ge and Sn is represented by −0.15<a<0.15, 0.1<x≦0.5, 0.6<x+y+z<1.0, 0≦z≦0.1), and the second The positive electrode active material has a general composition formula Li (1-sb) Mg s Co (1-tu) Al t M' u O 2 (where M' is selected from the group consisting of Ti, Zr and Ge). is at least one element that is A non-aqueous electrolyte secondary battery using the active material obtained by the method is disclosed.
　また、例えば、特許文献２には、核となる二次粒子の組成がＬｉｘ１Ｎｉ１－ｙ１－ｚ１－ｗ１Ｃｏｙ１Ｍｎｚ１Ｍ１ｗ１Ｏ２－ｖＫｖ（１＜ｘ１≦１．３、０≦ｙ１≦０．３３、０．２≦ｚ１≦０．３３、０≦ｗ１＜０．１、０≦ｖ≦０．０５であり、Ｍ１はＡｌ、Ｍｇから選ばれる少なくとも１種の金属及びＫはＦ－、ＰＯ４ ３－から選ばれる少なくとも１種のアニオン）であるＬｉ－Ｎｉ－Ｍｎ複合酸化物において、前記二次粒子の粒子表面若しくは表面近傍に、組成がＬｉｘ２Ｎｉ１－ｙ２－ｚ２Ｃｏｙ２Ｍ２ｚ２Ｏ２（０．９８≦ｘ２≦１．０５、０．１５≦ｙ２≦０．２、０≦ｚ２≦０．０５、Ｍ２はＡｌ、Ｍｇ、Ｚｒ、Ｔｉから選ばれる少なくとも１種の金属）であるＬｉ－Ｎｉ複合酸化物を被覆又は存在させた非水電解質二次電池用Ｌｉ－Ｎｉ複合酸化物粒子粉末を使用した非水電解質二次電池が開示されている。 Further, for example, in Patent Document 2, the composition of the secondary particles serving as the core is Li x1 Ni 1-y1-z1-w1 Co y1 Mn z1 M1 w1 O 2-v K v (1<x1≦1.3, 0 ≤ y1 ≤ 0.33, 0.2 ≤ z1 ≤ 0.33, 0 ≤ w1 < 0.1, 0 ≤ v ≤ 0.05, and M1 is at least one metal selected from Al, Mg and K is at least one anion selected from F − , PO 4 3- ), the Li—Ni—Mn composite oxide having the composition Li x2 Ni 1-y2 on or near the surface of the secondary particles. -z2 Co y2 M2 z2 O 2 (0.98 ≤ x2 ≤ 1.05, 0.15 ≤ y2 ≤ 0.2, 0 ≤ z2 ≤ 0.05, M2 is at least selected from Al, Mg, Zr, Ti A non-aqueous electrolyte secondary battery using Li--Ni composite oxide particles for non-aqueous electrolyte secondary batteries coated with or having Li--Ni composite oxide (a type of metal) present therein is disclosed.
特開２００８－２７００８６号公報JP 2008-270086 A 特開２０１０－０９２８４８号公報JP 2010-092848 A
　ところで、非水電解質二次電池の高容量化に伴い、電池構成材料である正極活物質の高容量化が求められている。正極活物質を高容量化するための手法としては、リチウムを除く金属元素の総モル数（Ａ）に対するＮｉのモル数（Ｂ）の比を高くしたＮｉ含有リチウム複合酸化物を用いること、例えば、Ｂ／Ａの比が０．８５以上のＮｉ含有リチウム複合酸化物を用いることが考えられる。しかし、Ｂ／Ａの比が高くなると、非水電解質二次電池の直流抵抗（ＤＣＲ）が上昇したり、充放電サイクル特性が低下したりする場合がある。 By the way, as the capacity of non-aqueous electrolyte secondary batteries increases, there is a demand for increasing the capacity of the positive electrode active material, which is a constituent material of the battery. As a method for increasing the capacity of the positive electrode active material, using a Ni-containing lithium composite oxide in which the ratio of the number of moles (B) of Ni to the total number of moles (A) of metal elements excluding lithium is increased, for example , B/A ratio of 0.85 or more. However, when the B/A ratio increases, the direct current resistance (DCR) of the non-aqueous electrolyte secondary battery may increase, or the charge/discharge cycle characteristics may deteriorate.
　そこで、本開示は、正極活物質としてリチウムを除く金属元素の総モル数に対するＮｉのモル数の比が高いＮｉ含有リチウム複合酸化物を用いた場合においても、非水電解質二次電池の直流抵抗を低減し、且つ充放電サイクル特性の低下を抑制することを目的とする。 Therefore, the present disclosure provides a direct current resistance of a non-aqueous electrolyte secondary battery even when a Ni-containing lithium composite oxide having a high ratio of the number of moles of Ni to the total number of moles of metal elements excluding lithium is used as a positive electrode active material. and suppress deterioration of charge-discharge cycle characteristics.
　本開示の一態様である非水電解質二次電池用正極活物質は、第１正極活物質と第２正極活物質を含み、前記第１正極活物質は、Ｎｉ含有リチウム複合酸化物であって、Ｌｉを除く金属元素の総モル数（Ａ１）に対するＮｉのモル数（Ｂ１）の比（Ｂ１／Ａ１）が０．８５以上０．９４以下であり、前記Ｌｉを除く金属元素の総モル数（Ａ１）に対するＬｉのモル数（Ｃ１）の比（Ｃ１／Ａ１）が０．９５０以上０．９８３以下であり、前記第２正極活物質は、Ｎｉ含有リチウム複合酸化物であって、Ｌｉを除く金属元素の総モル数（Ａ２）に対するＮｉのモル数（Ｂ２）の比が０．８５以上０．９４以下であり、前記Ｌｉを除く金属元素の総モル数（Ａ２）に対するＬｉのモル数（Ｃ２）の比（Ｃ２／Ａ２）が０．９８４以上１．００４以下であり、前記第１正極活物質と前記第２正極活物質の混合比は、質量比で９５：５～７５：２５であることを特徴とする。 A positive electrode active material for a nonaqueous electrolyte secondary battery, which is one aspect of the present disclosure, includes a first positive electrode active material and a second positive electrode active material, and the first positive electrode active material is a Ni-containing lithium composite oxide, , the ratio (B 1 /A 1 ) of the number of moles of Ni (B 1 ) to the total number of moles (A 1 ) of the metal elements excluding Li is 0.85 or more and 0.94 or less, and the metal elements excluding Li The ratio (C 1 /A 1 ) of the number of moles of Li (C 1 ) to the total number of moles (A 1 ) of Li is 0.950 or more and 0.983 or less, and the second positive electrode active material is a Ni-containing lithium composite an oxide, wherein the ratio of the number of moles of Ni (B 2 ) to the total number of moles of metal elements excluding Li (A 2 ) is 0.85 or more and 0.94 or less, and the total number of metal elements excluding Li is The ratio (C 2 /A 2 ) of the number of moles (C 2 ) of Li to the number of moles (A 2 ) is 0.984 or more and 1.004 or less, and the ratio of the first positive electrode active material and the second positive electrode active material The mixing ratio is characterized by a mass ratio of 95:5 to 75:25.
　本開示の一態様である非水電解質二次電池は、正極と、負極と、非水電解質とを備え、前記正極が上記非水電解質二次電池用正極活物質を含む。 A non-aqueous electrolyte secondary battery according to one aspect of the present disclosure includes a positive electrode, a negative electrode, and a non-aqueous electrolyte, and the positive electrode contains the positive electrode active material for a non-aqueous electrolyte secondary battery.
　本開示の一態様によれば、正極活物質としてリチウムを除く金属元素の総モル数に対するＮｉのモル数の比が高いＮｉ含有リチウム複合酸化物を用いた場合においても、非水電解質二次電池の直流抵抗を低減し、且つ充放電サイクル特性の低下を抑制することが可能となる。 According to one aspect of the present disclosure, even when a Ni-containing lithium composite oxide having a high ratio of the number of moles of Ni to the total number of moles of metal elements excluding lithium is used as the positive electrode active material, the non-aqueous electrolyte secondary battery It is possible to reduce the direct current resistance of the battery and suppress the deterioration of the charge-discharge cycle characteristics.
実施形態の一例である非水電解質二次電池の断面図である。1 is a cross-sectional view of a non-aqueous electrolyte secondary battery that is an example of an embodiment; FIG.
  以下、実施形態の一例について詳細に説明する。実施形態の説明で参照する図面は、模式的に記載されたものであり、図面に描画された構成要素の寸法比率などは、現物と異なる場合がある。また、本明細書において、「数値（１）～数値（２）」との記載は、数値（１）以上、数値（２）以下を意味する。 An example of an embodiment will be described in detail below. The drawings referred to in the description of the embodiments are schematic representations, and the dimensional ratios and the like of the components drawn in the drawings may differ from the actual product. Further, in this specification, the description of "numerical value (1) to numerical value (2)" means numerical value (1) or more and numerical value (2) or less.
　図１は、実施形態の一例である非水電解質二次電池の断面図である。図１に示す非水電解質二次電池１０は、正極１１及び負極１２がセパレータ１３を介して巻回されてなる巻回型の電極体１４と、非水電解質と、電極体１４の上下にそれぞれ配置された絶縁板１８，１９と、上記部材を収容するケース本体１６及び封口体１７を有する電池ケースと、を備える。なお、巻回型の電極体１４の代わりに、正極及び負極がセパレータを介して交互に積層されてなる積層型の電極体など、他の形態の電極体が適用されてもよい。また、電池ケースとしては、円筒形、角形、コイン形、ボタン形等の金属製ケース、樹脂シートをラミネートして形成された樹脂製ケース（所謂ラミネート型）などが例示できる。 FIG. 1 is a cross-sectional view of a non-aqueous electrolyte secondary battery that is an example of an embodiment. The non-aqueous electrolyte secondary battery 10 shown in FIG. A battery case having insulating plates 18 and 19 arranged, and a case main body 16 and a sealing member 17 for accommodating the above members is provided. Instead of the wound electrode body 14, another form of electrode body such as a stacked electrode body in which positive and negative electrodes are alternately stacked via a separator may be applied. Examples of the battery case include cylindrical, square, coin-shaped, button-shaped metal cases, and resin cases formed by laminating resin sheets (so-called laminated type).
　ケース本体１６は、例えば有底円筒形状の金属製容器である。ケース本体１６と封口体１７との間にはガスケット２８が設けられ、電池内部の密閉性が確保される。ケース本体１６は、例えば側面部の一部が内側に張出した、封口体１７を支持する張り出し部２２を有する。張り出し部２２は、ケース本体１６の周方向に沿って環状に形成されることが好ましく、その上面で封口体１７を支持する。 The case body 16 is, for example, a bottomed cylindrical metal container. A gasket 28 is provided between the case body 16 and the sealing member 17 to ensure hermeticity inside the battery. The case main body 16 has an overhanging portion 22 that supports the sealing member 17, for example, a portion of the side surface overhanging inward. The projecting portion 22 is preferably annularly formed along the circumferential direction of the case body 16 and supports the sealing member 17 on the upper surface thereof.
　封口体１７は、電極体１４側から順に、フィルタ２３、下弁体２４、絶縁部材２５、上弁体２６、及びキャップ２７が積層された構造を有する。封口体１７を構成する各部材は、例えば円板形状又はリング形状を有し、絶縁部材２５を除く各部材は互いに電気的に接続されている。下弁体２４と上弁体２６は各々の中央部で互いに接続され、各々の周縁部の間には絶縁部材２５が介在している。内部短絡等による発熱で非水電解質二次電池１０の内圧が上昇すると、例えば下弁体２４が上弁体２６をキャップ２７側に押し上げるように変形して破断し、下弁体２４と上弁体２６の間の電流経路が遮断される。さらに内圧が上昇すると、上弁体２６が破断し、キャップ２７の開口部からガスが排出される。 The sealing body 17 has a structure in which a filter 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 to each other at their central portions, and an insulating member 25 is interposed between their peripheral edge portions. When the internal pressure of the non-aqueous electrolyte secondary battery 10 rises due to heat generation due to an internal short circuit or the like, for example, the lower valve body 24 deforms and breaks so as to push the upper valve body 26 upward toward the cap 27, thereby breaking the lower valve body 24 and the upper valve. The current path between bodies 26 is interrupted. When the internal pressure further increases, the upper valve body 26 is broken and the gas is discharged from the opening of the cap 27 .
　図１に示す非水電解質二次電池１０では、正極１１に取り付けられた正極リード２０が絶縁板１８の貫通孔を通って封口体１７側に延び、負極１２に取り付けられた負極リード２１が絶縁板１９の外側を通ってケース本体１６の底部側に延びている。正極リード２０は封口体１７の底板であるフィルタ２３の下面に溶接等で接続され、フィルタ２３と電気的に接続された封口体１７の天板であるキャップ２７が正極端子となる。負極リード２１はケース本体１６の底部内面に溶接等で接続され、ケース本体１６が負極端子となる。 In the non-aqueous electrolyte secondary battery 10 shown in FIG. 1, the positive electrode lead 20 attached to the positive electrode 11 extends through the through hole of the insulating plate 18 toward the sealing member 17, and the negative electrode lead 21 attached to the negative electrode 12 is insulated. It extends to the bottom side of the case body 16 through the outside of the plate 19 . The positive electrode lead 20 is connected to the lower surface of the filter 23, which is the bottom plate of the sealing member 17, by welding or the like, and the cap 27, which is the top plate of the sealing member 17 electrically connected to the filter 23, serves as a positive electrode terminal. The negative lead 21 is connected to the inner surface of the bottom of the case body 16 by welding or the like, and the case body 16 serves as a negative terminal.
［正極］
　正極１１は、正極集電体と、正極集電体上に配置される正極合材層とを備える。なお、正極合材層は正極集電体の両面に配置されることが望ましい。 [Positive electrode]
The positive electrode 11 includes a positive electrode current collector and a positive electrode mixture layer arranged on the positive electrode current collector. In addition, it is desirable that the positive electrode mixture layers are arranged on both sides of the positive electrode current collector.
　正極集電体には、アルミニウムやアルミニウム合金などの正極の電位範囲で安定な金属の箔、当該金属を表層に配置したフィルム等を用いることができる。正極集電体は、例えば、１０μｍ～１００μｍ程度の厚みを有する。 For the positive electrode current collector, a foil of a metal such as aluminum or an aluminum alloy that is stable in the potential range of the positive electrode, or a film in which the metal is placed on the surface can be used. The positive electrode current collector has a thickness of, for example, about 10 μm to 100 μm.
　正極合材層は、第１正極活物質及び第２正極活物質を含む。正極合材層は、正極活物質同士を結着して正極合材層の機械的強度を確保する等の点で、結着材を含むことが好適である。また、正極合材層は、当該層の導電性を向上させることができる等の点で、導電材を含むことが好適である。 The positive electrode mixture layer includes a first positive electrode active material and a second positive electrode active material. The positive electrode mixture layer preferably contains a binder in order to bind the positive electrode active materials together and ensure the mechanical strength of the positive electrode mixture layer. In addition, the positive electrode mixture layer preferably contains a conductive material in that the conductivity of the layer can be improved.
　正極は、例えば、第１正極活物質、第２正極活物質、結着材、導電材等を含む正極合材スラリーを調整し、この正極合材スラリーを正極集電体上に塗布し、塗膜を乾燥させた後、この塗膜を圧延することにより作製できる。 For the positive electrode, for example, a positive electrode mixture slurry containing a first positive electrode active material, a second positive electrode active material, a binder, a conductive material, and the like is prepared, and this positive electrode mixture slurry is applied on a positive electrode current collector and coated. After drying the film, it can be prepared by rolling the coating film.
　第１正極活物質は、Ｌｉを除く金属元素の総モル数（Ａ１）に対するＮｉのモル数（Ｂ１）の比（Ｂ１／Ａ１）が、０．８５以上０．９４以下であり、Ｌｉを除く金属元素の総モル数（Ａ１）に対するＬｉのモル数（Ｃ１）の比（Ｃ１／Ａ１）が０．９５０以上０．９８３以下であるＮｉ含有リチウム複合酸化物である。また、第２正極活物質は、Ｌｉを除く金属元素の総モル数（Ａ２）に対するＮｉのモル数（Ｂ２）の比（Ｂ２／Ａ２）が０．８５以上０．９４以下であり、Ｌｉを除く金属元素の総モル数（Ａ２）に対するＬｉのモル数（Ｃ２）の比（Ｃ２／Ａ２）が０．９８４以上１．００４以下であるＮｉ含有リチウム複合酸化物である。これら２つのＮｉ含有リチウム複合酸化物を正極活物質として使用すること、及び第１正極活物質及び第２正極活物質の混合比を後述する比にすることにより、リチウムを除く金属元素の総モル数に対するＮｉのモル数の比が高いにも関わらず、非水電解質二次電池の直流抵抗を低減し、且つ充放電サイクル特性の低下を抑制することが可能となる。 In the first positive electrode active material, the ratio (B 1 /A 1 ) of the number of moles of Ni (B 1 ) to the total number of moles (A 1 ) of metal elements excluding Li is 0.85 or more and 0.94 or less. , a Ni-containing lithium composite oxide in which the ratio (C 1 /A 1 ) of the number of moles (C 1 ) of Li to the total number of moles (A 1 ) of metal elements excluding Li is 0.950 or more and 0.983 or less be. In the second positive electrode active material, the ratio (B 2 /A 2 ) of the number of moles (B 2 ) of Ni to the total number of moles (A 2 ) of metal elements excluding Li is 0.85 or more and 0.94 or less. Ni-containing lithium composite oxide having a ratio (C 2 /A 2 ) of the number of moles (C 2 ) of Li to the total number of moles (A 2 ) of metal elements excluding Li of 0.984 or more and 1.004 or less is. By using these two Ni-containing lithium composite oxides as the positive electrode active material, and by adjusting the mixing ratio of the first positive electrode active material and the second positive electrode active material to the ratio described later, the total moles of the metal elements excluding lithium Although the ratio of the number of moles of Ni to the number is high, it is possible to reduce the DC resistance of the non-aqueous electrolyte secondary battery and to suppress the deterioration of the charge-discharge cycle characteristics.
　第１正極活物質のＮｉ含有リチウム複合酸化物は、非水電解質二次電池の直流抵抗を低減すること又は充放電サイクル特性の低下を抑制すること等の点で、以下の一般式（１）で表されるＮｉ含有リチウム複合酸化物であることが好ましい。
　ＬｉｚＮｉ１－ｘ－ｙＭｘＡｌｙＯ２　　　　（１）
　式中、ｘ、ｙ、ｚは、０＜ｘ≦０．１５、０＜ｙ≦０．１０、０．８５≦１－ｘ－ｙ≦０．９４、０．９５０≦ｚ≦０．９８３を満たすことが好ましく、０．０２≦ｘ≦０．１０、０．０３≦ｙ≦０．０７、０．８５≦１－ｘ－ｙ≦０．９４、０．９７０≦ｚ≦０．９８３を満たすことがより好ましい。また、式中Ｍは、Ｃｏ、Ｗ、Ｎｂ、Ｍｇ、Ｔｉ、Ｍｎ及びＭｏからなる群から選択される少なくとも１種の元素であることが好ましく、Ｃｏ、Ｍｎ、及びＷから選ばれる少なくとも１種の元素であることがより好ましい。 The Ni-containing lithium composite oxide of the first positive electrode active material has the following general formula (1) in terms of reducing the direct current resistance of the non-aqueous electrolyte secondary battery or suppressing deterioration in charge-discharge cycle characteristics. It is preferably a Ni-containing lithium composite oxide represented by.
LizNi1 -xyMxAlyO2 ( 1 )
where x, y and z are 0<x≤0.15, 0<y≤0.10, 0.85≤1-xy≤0.94, 0.950≤z≤0.983 0.02≤x≤0.10, 0.03≤y≤0.07, 0.85≤1-xy≤0.94, 0.970≤z≤0.983 is more preferable. In the formula, M is preferably at least one element selected from the group consisting of Co, W, Nb, Mg, Ti, Mn and Mo, and at least one element selected from Co, Mn and W is more preferably an element of
　第２正極活物質のＮｉ含有リチウム複合酸化物は、非水電解質二次電池の直流抵抗を低減すること又は充放電サイクル特性の低下を抑制すること等の点で、以下の一般式（２）で表されるＮｉ含有リチウム複合酸化物であることが好ましい。
　ＬｉｚＮｉ１－ｘ－ｙＭｘＡｌｙＯ２　　　　（２）
　式中、ｘ、ｙ、ｚは、０＜ｘ≦０．１５、０＜ｙ≦０．１０、０．８５≦１－ｘ－ｙ≦０．９４、０．９８４≦ｚ≦１．００４を満たすことが好ましく、０．０２≦ｘ≦０．１０、０．０３≦ｙ≦０．０７、０．８５≦１－ｘ－ｙ≦０．９４、０．９８４≦ｚ≦１．０００を満たすことがより好ましい。また、式中Ｍは、Ｃｏ、Ｗ、Ｎｂ、Ｍｇ、Ｔｉ、Ｍｎ及びＭｏからなる群から選択される少なくとも１種の元素であることが好ましく、Ｃｏ、Ｍｎ、及びＷから選ばれる少なくとも１種の元素であることがより好ましい。 The Ni-containing lithium composite oxide of the second positive electrode active material has the following general formula (2) in terms of reducing the direct current resistance of the non-aqueous electrolyte secondary battery or suppressing deterioration in charge-discharge cycle characteristics. It is preferably a Ni-containing lithium composite oxide represented by.
LizNi1 -xyMxAlyO2 ( 2 )
where x, y and z are 0<x≤0.15, 0<y≤0.10, 0.85≤1-xy≤0.94, 0.984≤z≤1.004 0.02 ≤ x ≤ 0.10, 0.03 ≤ y ≤ 0.07, 0.85 ≤ 1-xy ≤ 0.94, 0.984 ≤ z ≤ 1.000 is more preferable. In the formula, M is preferably at least one element selected from the group consisting of Co, W, Nb, Mg, Ti, Mn and Mo, and at least one element selected from Co, Mn and W is more preferably an element of
　Ｎｉ含有リチウム複合酸化物の組成は、誘導結合プラズマ（ＩＣＰ）発光分光分析により測定される。 The composition of the Ni-containing lithium composite oxide is measured by inductively coupled plasma (ICP) emission spectrometry.
　第１正極活物質と第２正極活物質の混合比は、非水電解質二次電池の直流抵抗を低減し、且つ充放電サイクル特性の低下を抑制する点で、質量比で９５：５～７５：２５の範囲であり、好ましくは９０：１０～８０：２０の範囲である。なお、正極合材層中に含まれる第１正極活物質と第２正極活物質の合計量は、正極合材層の総質量に対して、８０質量％以上であることが好ましく、９０質量％以上であることがより好ましい。 The mixing ratio of the first positive electrode active material and the second positive electrode active material is 95: 5 to 75 in mass ratio in terms of reducing the direct current resistance of the non-aqueous electrolyte secondary battery and suppressing deterioration of charge-discharge cycle characteristics. :25, preferably 90:10 to 80:20. The total amount of the first positive electrode active material and the second positive electrode active material contained in the positive electrode mixture layer is preferably 80% by mass or more, preferably 90% by mass, with respect to the total mass of the positive electrode mixture layer. It is more preferable to be above.
　第１正極活物質及び第２正極活物質は、一次粒子が凝集した二次粒子から構成される。第１正極活物質の二次粒子の平均粒径及び第２正極活物質の二次粒子の平均粒径は、例えば、非水電解質二次電池の高容量化等の点で、５μｍ以上１５μｍ以下であることが好ましく、８μｍ以上１２μｍ以下であることがより好ましい。ここで、二次粒子の平均粒径とは、レーザ回折法によって測定される体積平均粒径であって、粒子径分布において体積積算値が５０％となるメジアン径を意味する。第１正極活物質及び第２正極活物質の二次粒子の平均粒径は、例えば、レーザ回折散乱式粒度分布測定装置（株式会社堀場製作所製）を用いて測定できる。また、第１正極活物質の一次粒子の平均粒径及び第２正極活物質の一次粒子の平均粒径は、非水電解質二次電池の高容量化等の点で、０．１μｍ以上１．０μｍ以下であることが好ましく、０．２μｍ以上０．８μｍ以下であることがより好ましい。第１正極活物質及び第２正極活物質の一次粒子の平均粒径は、第１正極活物質や第２正極活物質のＳＥＭ画像において、１００個の一次粒子をランダムに選択し、当該各粒子の外接円の直径を測定して、測定値を平均化することで求められる。 The first positive electrode active material and the second positive electrode active material are composed of secondary particles that are aggregated primary particles. The average particle size of the secondary particles of the first positive electrode active material and the average particle size of the secondary particles of the second positive electrode active material are, for example, 5 μm or more and 15 μm or less in terms of increasing the capacity of the non-aqueous electrolyte secondary battery. and more preferably 8 μm or more and 12 μm or less. Here, the average particle size of the secondary particles is the volume average particle size measured by the laser diffraction method, and means the median size at which the volume integrated value is 50% in the particle size distribution. The average particle size of the secondary particles of the first positive electrode active material and the second positive electrode active material can be measured using, for example, a laser diffraction scattering particle size distribution analyzer (manufactured by HORIBA, Ltd.). In addition, the average particle size of the primary particles of the first positive electrode active material and the average particle size of the primary particles of the second positive electrode active material should be 0.1 μm or more from the viewpoint of increasing the capacity of the non-aqueous electrolyte secondary battery. It is preferably 0 μm or less, more preferably 0.2 μm or more and 0.8 μm or less. The average particle size of the primary particles of the first positive electrode active material and the second positive electrode active material is obtained by randomly selecting 100 primary particles in the SEM image of the first positive electrode active material and the second positive electrode active material, It is obtained by measuring the diameter of the circumscribed circle of and averaging the measured values.
　正極合材層には、第１正極活物質及び第２正極活物質以外の正極活物質が含有されていてもよい。第１正極活物質及び第２正極活物質以外の正極活物質としては、可逆的にリチウムを挿入・脱離可能な化合物であれば特に限定されず、例えば、ＬｉＭｎ２Ｏ４、ＬｉＣｏＯ２等のＮｉ非含有のＬｉ複合酸化物、第１正極活物質や第２正極活物質よりＮｉ含有量の少ないＮｉ含有リチウム複合酸化物等が挙げられる。 The positive electrode mixture layer may contain a positive electrode active material other than the first positive electrode active material and the second positive electrode active material. The positive electrode active material other than the first positive electrode active material and the second positive electrode active material is not particularly limited as long as it is a compound capable of reversibly intercalating and deintercalating lithium . Ni-free Li composite oxides, Ni-containing lithium composite oxides having a smaller Ni content than the first positive electrode active material and the second positive electrode active material, and the like can be mentioned.
　正極合材層に含まれる導電材としては、カーボンブラック、アセチレンブラック、ケッチェンブラック、黒鉛等の炭素材料が例示できる。これらは、単独で用いてもよく、２種類以上を組み合わせて用いてもよい。正極合材層中の導電材の含有量は、例えば、０．５質量％以上４質量％以下であることが好ましく、０．５質量％以上１．５質量％以下であることがより好ましい。 Carbon materials such as carbon black, acetylene black, ketjen black, and graphite can be exemplified as the conductive material contained in the positive electrode mixture layer. These may be used alone or in combination of two or more. The content of the conductive material in the positive electrode mixture layer is, for example, preferably 0.5% by mass or more and 4% by mass or less, and more preferably 0.5% by mass or more and 1.5% by mass or less.
　正極合材層に含まれる結着材としては、ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリフッ化ビニリデン（ＰＶｄＦ）等のフッ素樹脂、ポリアクリロニトリル（ＰＡＮ）、ポリイミド系樹脂、アクリル系樹脂、ポリオレフィン系樹脂、スチレン－ブタジエンゴム（ＳＢＲ）、カルボキシメチルセルロース（ＣＭＣ）又はその塩、ポリアクリル酸（ＰＡＡ）又はその塩（ＰＡＡ－Ｎａ、ＰＡＡ－Ｋ等、また部分中和型の塩であってもよい）、ポリエチレンオキシド（ＰＥＯ）、ポリビニルアルコール（ＰＶＡ）等が挙げられる。これらは、単独で用いてもよく、２種類以上を組み合わせて用いてもよい。正極合材層中の結着材の含有量は、例えば、０．５質量％以上４質量％以下であることが好ましく、０．５質量％以上１．５質量％以下であることがより好ましい。 The binder contained in the positive electrode mixture layer includes fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resins, acrylic resins, polyolefin resins, styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC) or salts thereof, polyacrylic acid (PAA) or salts thereof (PAA-Na, PAA-K, etc., may also be partially neutralized salts), polyethylene oxide (PEO), polyvinyl alcohol (PVA) and the like. These may be used alone or in combination of two or more. The content of the binder in the positive electrode mixture layer is, for example, preferably 0.5% by mass or more and 4% by mass or less, and more preferably 0.5% by mass or more and 1.5% by mass or less. .
［負極］
　負極１２は、例えば、負極集電体と、当該集電体上に形成された負極合材層とで構成される。負極集電体には、銅などの負極の電位範囲で安定な金属の箔、当該金属を表層に配置したフィルム等を用いることができる。負極合材層は、例えば、負極活物質及び結着材等を含む。負極は、例えば、負極活物質、結着材等を含む負極合材スラリーを調整し、この負極合材スラリーを負極集電体上に塗布し、塗膜を乾燥させた後、この塗膜を圧延することにより作製できる。 [Negative electrode]
The negative electrode 12 is composed of, for example, a negative electrode current collector and a negative electrode mixture layer formed on the current collector. As the negative electrode current collector, a foil of a metal such as copper that is stable in the potential range of the negative electrode, a film having the metal on the surface layer, or the like can be used. The negative electrode mixture layer includes, for example, a negative electrode active material, a binder, and the like. For the negative electrode, for example, a negative electrode mixture slurry containing a negative electrode active material, a binder, etc. is prepared, the negative electrode mixture slurry is applied on a negative electrode current collector, the coating film is dried, and then the coating film is applied. It can be produced by rolling.
　負極活物質は、リチウムイオンを吸蔵・放出することが可能な材料であれば特に制限されるものではなく、例えば、金属リチウム、リチウム－アルミニウム合金、リチウム－鉛合金、リチウム－シリコン合金、リチウム－スズ合金等のリチウム合金、黒鉛、コークス、有機物焼成体等の炭素材料、ＳｎＯ２、ＳｎＯ、ＴｉＯ２等の金属酸化物等が挙げられる。これらは、１種単独でもよいし、２種以上を組み合わせて使用してもよい。 The negative electrode active material is not particularly limited as long as it is a material capable of intercalating and deintercalating lithium ions. Lithium alloys such as tin alloys, graphite, coke, carbon materials such as organic sintered bodies, metal oxides such as SnO 2 , SnO, TiO 2 and the like. These may be used singly or in combination of two or more.
　負極合材層に含まれる結着材としては、正極の場合と同様に、フッ素系樹脂、ＰＡＮ、ポリイミド系樹脂、アクリル系樹脂、ポリオレフィン系樹脂、ＳＢＲ、ＣＭＣ又はその塩、ＰＡＡ又はその塩、ＰＥＯ、ＰＶＡ等が挙げられる。なお、負極合材層は、正極の場合と同様に、導電材を含んでいてもよい As the binder contained in the negative electrode mixture layer, as in the case of the positive electrode, fluorine resin, PAN, polyimide resin, acrylic resin, polyolefin resin, SBR, CMC or its salt, PAA or its salt, Examples include PEO and PVA. Note that the negative electrode mixture layer may contain a conductive material as in the case of the positive electrode.
［セパレータ］
　セパレータ１３には、例えば、イオン透過性及び絶縁性を有する多孔性シート等が用いられる。多孔性シートの具体例としては、微多孔薄膜、織布、不織布等が挙げられる。セパレータ１３は、例えばポリエチレン、ポリプロピレン等のポリオレフィン、セルロースなどで構成される。セパレータ１３は、セルロース繊維層及びポリオレフィン等の熱可塑性樹脂繊維層を有する積層体であってもよい。また、セパレータ１３は、ポリエチレン層及びポリプロピレン層を含む多層セパレータであってもよく、アラミド樹脂で構成される表面層又は無機物フィラーを含有する表面層を有していてもよい。 [Separator]
For the separator 13, for example, a porous sheet or the like having ion permeability and insulation is used. Specific examples of porous sheets include microporous thin films, woven fabrics, and non-woven fabrics. The separator 13 is made of, for example, polyolefin such as polyethylene or polypropylene, or cellulose. The separator 13 may be a laminate having a cellulose fiber layer and a thermoplastic resin fiber layer such as polyolefin. Moreover, the separator 13 may be a multilayer separator including a polyethylene layer and a polypropylene layer, and may have a surface layer composed of an aramid resin or a surface layer containing an inorganic filler.
［非水電解質］
　非水電解質は、非水溶媒と、非水溶媒に溶解した電解質塩とを含む。非水電解質は、液体電解質（非水電解液）に限定されず、ゲル状ポリマー等を用いた固体電解質であってもよい。非水溶媒には、例えばエステル類、エーテル類、アセトニトリル等のニトリル類、ジメチルホルムアミド等のアミド類、及びこれらの２種以上の混合溶媒等を用いることができる。非水溶媒は、これら溶媒の水素の少なくとも一部をフッ素等のハロゲン原子で置換したハロゲン置換体を含有していてもよい。 [Non-aqueous electrolyte]
The non-aqueous electrolyte contains a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. The nonaqueous electrolyte is not limited to a liquid electrolyte (nonaqueous electrolyte), and may be a solid electrolyte using a gel polymer or the like. Examples of non-aqueous solvents that can be used 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.
　上記エステル類の例としては、エチレンカーボネート（ＥＣ）、プロピレンカーボネート（ＰＣ）、ブチレンカーボネート等の環状炭酸エステル、ジメチルカーボネート（ＤＭＣ）、エチルメチルカーボネート（ＥＭＣ）、ジエチルカーボネート（ＤＥＣ）、メチルプロピルカーボネート、エチルプロピルカーボネート、メチルイソプロピルカーボネート等の鎖状炭酸エステル、γ－ブチロラクトン、γ－バレロラクトン等の環状カルボン酸エステル、酢酸メチル、酢酸エチル、酢酸プロピル、プロピオン酸メチル（ＭＰ）、プロピオン酸エチル等の鎖状カルボン酸エステルなどが挙げられる。 Examples of the 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. , Ethyl propyl carbonate, methyl isopropyl carbonate and other chain carbonates, γ-butyrolactone, γ-valerolactone and other cyclic carboxylic acid esters, methyl acetate, ethyl acetate, propyl acetate, methyl propionate (MP), ethyl propionate, etc. and chain carboxylic acid esters of.
　上記エーテル類の例としては、１，３－ジオキソラン、４－メチル－１，３－ジオキソラン、テトラヒドロフラン、２－メチルテトラヒドロフラン、プロピレンオキシド、１，２－ブチレンオキシド、１，３－ジオキサン、１，４－ジオキサン、１，３，５－トリオキサン、フラン、２－メチルフラン、１，８－シネオール、クラウンエーテル等の環状エーテル、１，２－ジメトキシエタン、ジエチルエーテル、ジプロピルエーテル、ジイソプロピルエーテル、ジブチルエーテル、ジヘキシルエーテル、エチルビニルエーテル、ブチルビニルエーテル、メチルフェニルエーテル、エチルフェニルエーテル、ブチルフェニルエーテル、ペンチルフェニルエーテル、メトキシトルエン、ベンジルエチルエーテル、ジフェニルエーテル、ジベンジルエーテル、o－ジメトキシベンゼン、１，２－ジエトキシエタン、１，２－ジブトキシエタン、ジエチレングリコールジメチルエーテル、ジエチレングリコールジエチルエーテル、ジエチレングリコールジブチルエーテル、１，１－ジメトキシメタン、１，１－ジエトキシエタン、トリエチレングリコールジメチルエーテル、テトラエチレングリコールジメチルエーテル等の鎖状エーテル類などが挙げられる。 Examples of the above 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-cineol, 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, o-dimethoxybenzene, 1,2-diethoxy Chain ethers such as ethane, 1,2-dibutoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, 1,1-dimethoxymethane, 1,1-diethoxyethane, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether and the like.
　上記ニトリル類の例としては、アセトニトリル、プロピオニトリル、ブチロニトリル、バレロニトリル、ｎ－ヘプタニトリル、スクシノニトリル、グルタロニトリル、アジボニトリル、ピメロニトリル、１，２，３－プロパントリカルボニトリル、１，３，５－ペンタントリカルボニトリル等が挙げられる。 Examples of the above nitriles include acetonitrile, propionitrile, butyronitrile, valeronitrile, n-heptanirile, succinonitrile, glutaronitrile, adibonitrile, pimeronitrile, 1,2,3-propanetricarbonitrile, 1,3 , 5-pentanetricarbonitrile and the like.
　上記ハロゲン置換体の例としては、フルオロエチレンカーボネート（ＦＥＣ）等のフッ素化環状炭酸エステル、フッ素化鎖状炭酸エステル、フルオロプロピオン酸メチル（ＦＭＰ）等のフッ素化鎖状カルボン酸エステルなどが挙げられる。 Examples of the halogen-substituted compounds include fluorinated cyclic carbonates such as fluoroethylene carbonate (FEC), fluorinated chain carbonates, and fluorinated chain carboxylates such as methyl fluoropropionate (FMP). .
　電解質塩の例としては、ＬｉＢＦ４、ＬｉＣｌＯ４、ＬｉＰＦ６、ＬｉＡｓＦ６、ＬｉＳｂＦ６、ＬｉＡｌＣｌ４、ＬｉＳＣＮ、ＬｉＣＦ３ＳＯ３、ＬｉＣＦ３ＣＯ２、Ｌｉ（Ｐ(Ｃ２Ｏ４)Ｆ４）、ＬｉＰＦ６－ｘ（ＣｎＦ２ｎ＋１）ｘ（１＜ｘ＜６，ｎは１又は２）、ＬｉＢ１０Ｃｌ１０、ＬｉＣｌ、ＬｉＢｒ、ＬｉＩ、クロロボランリチウム、低級脂肪族カルボン酸リチウム、Ｌｉ２Ｂ４Ｏ７、Ｌｉ（Ｂ(Ｃ２Ｏ４)Ｆ２）等のホウ酸塩類、ＬｉＮ（ＳＯ２ＣＦ３）２、ＬｉＮ（ＣｌＦ２ｌ＋１ＳＯ２）（ＣｍＦ２ｍ＋１ＳＯ２）｛ｌ，ｍは１以上の整数｝等のイミド塩類などが挙げられる。電解質塩は、これらを１種単独で用いてもよいし、複数種を混合して用いてもよい。電解質塩の濃度は、例えば非水溶媒１Ｌ当り０．８～１．８モルである。 Examples of electrolyte 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 4O7 , borates such as Li(B( C2O4 ) F2 ) , LiN( SO2CF3 ) 2 , LiN( ClF2l + 1SO2 )( CmF2m + 1SO2 ) {l , where m is an integer of 1 or more}. Electrolyte salts may be used singly or in combination of two or more. The concentration of the electrolyte salt is, for example, 0.8 to 1.8 mol per 1 L of non-aqueous solvent.
　以下、実施例により本開示をさらに説明するが、本開示はこれらの実施例に限定されるものではない。 The present disclosure will be further described below with reference to examples, but the present disclosure is not limited to these examples.
＜実施例１＞
［正極活物質の合成］
　共沈法により得られた［Ｎｉ０．９０Ｃｏ０．０５Ａｌ０．０５］（ＯＨ）２で表される複合水酸化物を５００℃で２時間焼成し、Ｎｉ、Ｃｏ及びＡｌを含む複合酸化物（Ｎｉ０．９０Ｃｏ０．０５Ａｌ０．０５Ｏ２）を得た。 <Example 1>
[Synthesis of positive electrode active material]
A composite hydroxide represented by [Ni 0.90 Co 0.05 Al 0.05 ](OH) 2 obtained by a coprecipitation method was calcined at 500 ° C. for 2 hours to obtain a composite hydroxide containing Ni, Co and Al. An oxide (Ni 0.90 Co 0.05 Al 0.05 O 2 ) was obtained.
　上記Ｎｉ、Ｃｏ及びＡｌを含む複合酸化物とＬｉＯＨとを、Ｌｉと、Ｎｉ、Ｃｏ及びＡｌの総量のモル比が１．０２：１になるように混合した。当該混合物を酸素雰囲気中にて、７４０℃で３．５時間焼成して、Ｎｉ、Ｃｏ及びＡｌ含有リチウム複合酸化物Ａ（Ｌｉ１．０２Ｎｉ０．９０Ｃｏ０．０５Ａｌ０．０５Ｏ２）を得た。 The composite oxide containing Ni, Co and Al and LiOH were mixed so that the total molar ratio of Li to Ni, Co and Al was 1.02:1. The mixture was fired in an oxygen atmosphere at 740° C. for 3.5 hours to obtain Ni, Co and Al-containing lithium composite oxide A (Li 1.02 Ni 0.90 Co 0.05 Al 0.05 O 2 ).
　また、上記Ｎｉ、Ｃｏ及びＡｌを含む複合酸化物とＬｉＯＨとを、Ｌｉと、Ｎｉ、Ｃｏ及びＡｌの総量のモル比が１．０５：１になるように混合した混合物を、酸素雰囲気中にて、７４０℃で３．５時間焼成して、Ｎｉ、Ｃｏ及びＡｌ含有リチウム複合酸化物Ｂ（Ｌｉ１．０５Ｎｉ０．９０Ｃｏ０．０５Ａｌ０．０５Ｏ２）を得た。 Further, a mixture obtained by mixing the composite oxide containing Ni, Co and Al and LiOH so that the total molar ratio of Li and the total amount of Ni, Co and Al is 1.05:1 is placed in an oxygen atmosphere. and sintered at 740° C. for 3.5 hours to obtain Ni-, Co- and Al-containing lithium composite oxide B (Li 1.05 Ni 0.90 Co 0.05 Al 0.05 O 2 ).
　上記Ｎｉ、Ｃｏ及びＡｌ含有リチウム複合酸化物Ａを水洗・乾燥した。これを第１正極活物質とした。また、上記Ｎｉ、Ｃｏ及びＡｌ含有リチウム複合酸化物Ｂを水洗・乾燥したものを第２正極活物質とした。 The Ni-, Co- and Al-containing lithium composite oxide A was washed with water and dried. This was used as the first positive electrode active material. The Ni-, Co- and Al-containing lithium composite oxide B was washed with water and dried to obtain a second positive electrode active material.
　第１正極活物質の組成をＩＣＰにより分析した結果、Ｌｉ０．９７３Ｎｉ０．８９５Ｃｏ０．０４８Ａｌ０．０５７Ｏ２であった。 As a result of analyzing the composition of the first positive electrode active material by ICP, it was Li 0.973 Ni 0.895 Co 0.048 Al 0.057 O 2 .
　また、第２正極活物質の組成をＩＣＰにより分析した結果、Ｌｉ０．９９７Ｎｉ０．８９５Ｃｏ０．０４８Ａｌ０．０５７Ｏ２であった。 Further, the composition of the second positive electrode active material was analyzed by ICP and found to be Li 0.997 Ni 0.895 Co 0.048 Al 0.057 O 2 .
［正極の作製］
　第１正極活物質（二次粒子の平均粒径：１１μｍ）と第２正極活物質（二次粒子の平均粒径：１１μｍ）を８０：２０の質量比で混合した。この混合した正極活物質と、導電材としてのカーボンブラックと、結着材としてのＰＶＤＦとを、質量比で１００：１：１となるように混合した後、Ｎ－メチル－２－ピロリドン（ＮＭＰ）を適量加えて、正極合材スラリーを調製した。このスラリーをアルミニウム箔からなる正極集電体の両面に塗布し、塗膜を乾燥した後、圧延ローラにより圧延することにより、正極集電体の両面に正極合材層が形成された正極を得た。 [Preparation of positive electrode]
The first positive electrode active material (secondary particle average particle size: 11 μm) and the second positive electrode active material (secondary particle average particle size: 11 μm) were mixed at a mass ratio of 80:20. After mixing the mixed positive electrode active material, carbon black as a conductive material, and PVDF as a binder in a mass ratio of 100:1:1, N-methyl-2-pyrrolidone (NMP ) was added in an appropriate amount to prepare a positive electrode mixture slurry. This slurry is applied to both sides of a positive electrode current collector made of aluminum foil, the coating film is dried, and then rolled by rolling rollers to obtain a positive electrode having positive electrode mixture layers formed on both sides of the positive electrode current collector. rice field.
［負極の作製］
　人造黒鉛と、結着材としてのＣＭＣ及びＳＢＲを、質量比で、１００：１：１となるように混合した後、水を適量加えて、負極合材スラリーを調製した。このスラリーを銅箔からなる負極集電体の両面に塗布し、塗膜を乾燥した後、圧延ローラにより圧延することにより、負極集電体の両面に負極合材層が形成された負極を得た。 [Preparation of negative electrode]
After mixing artificial graphite and CMC and SBR as binders at a mass ratio of 100:1:1, an appropriate amount of water was added to prepare a negative electrode mixture slurry. This slurry is applied to both sides of a negative electrode current collector made of copper foil, the coating film is dried, and then rolled with rolling rollers to obtain a negative electrode having negative electrode mixture layers formed on both sides of the negative electrode current collector. rice field.
［非水電解質の調製］
　エチレンカーボネート（ＥＣ）とエチルメチルカーボネート（ＥＭＣ）とを、３：７の体積比で混合した混合非水溶媒に、ＬｉＰＦ６を１．０モル／Ｌの濃度で溶解させることにより、非水電解質を得た。 [Preparation of non-aqueous electrolyte]
A non-aqueous electrolyte was prepared by dissolving LiPF 6 at a concentration of 1.0 mol/L in a mixed non-aqueous solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 3:7. got
［非水電解質二次電池の作製］
　上記作製した正極に正極リードを取り付け、上記作製した負極に負極リードを取り付けた。これら両極間にセパレータを配置して、渦巻状に巻回することにより、巻回型の電極体を作製した。電極体と上記非水電解質とをアルミニウム製のラミネートの外装体内に配置した後、外装体の周縁部を加熱して溶着することにより、非水電解質二次電池を得た。 [Production of non-aqueous electrolyte secondary battery]
A positive electrode lead was attached to the positive electrode prepared above, and a negative electrode lead was attached to the negative electrode prepared above. A separator was placed between these two electrodes and spirally wound to produce a wound electrode assembly. After the electrode assembly and the non-aqueous electrolyte were arranged in an aluminum laminate outer package, the periphery of the outer package was heated and welded to obtain a non-aqueous electrolyte secondary battery.
＜実施例２＞
　第１正極活物質と第２正極活物質を８５：１５の質量比で混合したこと以外は、実施例１と同様にして、非水電解質二次電池を作製した。 <Example 2>
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that the first positive electrode active material and the second positive electrode active material were mixed at a mass ratio of 85:15.
＜比較例１＞
　正極活物質として第１正極活物質のみを用いたこと以外は、実施例１と同様にして、非水電解質二次電池を作製した。 <Comparative Example 1>
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that only the first positive electrode active material was used as the positive electrode active material.
　＜比較例２＞
　正極活物質として第２正極活物質のみを用いたこと以外は、実施例１と同様にして、非水電解質二次電池を作製した。 <Comparative Example 2>
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that only the second positive electrode active material was used as the positive electrode active material.
　＜比較例３＞
　第１正極活物質と第２正極活物質を７０：３０の質量比で混合したこと以外は、実施例１と同様にして、非水電解質二次電池を作製した。 <Comparative Example 3>
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that the first positive electrode active material and the second positive electrode active material were mixed at a mass ratio of 70:30.
　＜実施例３＞
　第１正極活物質と第２正極活物質を９５：５の質量比で混合したこと以外は、実施例１と同様にして、非水電解質二次電池を作製した。 <Example 3>
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that the first positive electrode active material and the second positive electrode active material were mixed at a mass ratio of 95:5.
　＜比較例４＞
　上記Ｎｉ、Ｃｏ及びＡｌを含む複合酸化物とＬｉＯＨとを、Ｌｉと、Ｎｉ、Ｃｏ及びＡｌの総量のモル比が１．０００：１になるように混合した。当該混合物を酸素雰囲気中にて、７４０℃で３．５時間焼成して、Ｎｉ、Ｃｏ及びＡｌ含有リチウム複合酸化物Ｃ（Ｌｉ０．９９７Ｎｉ０．９０Ｃｏ０．０５０Ａｌ０．０５０Ｏ２）を得た。上記Ｎｉ、Ｃｏ及びＡｌ含有リチウム複合酸化物Ｃを水洗・乾燥した。これを第１正極活物質とした。第１正極活物質の組成をＩＣＰにより分析した結果、Ｌｉ０．９４５Ｎｉ０．９０Ｃｏ０．０４９Ａｌ０．０５１Ｏ２であった。 <Comparative Example 4>
The composite oxide containing Ni, Co and Al and LiOH were mixed so that the total molar ratio of Li to Ni, Co and Al was 1.000:1. The mixture was sintered in an oxygen atmosphere at 740° C. for 3.5 hours to obtain Ni, Co and Al-containing lithium composite oxide C (Li 0.997 Ni 0.90 Co 0.050 Al 0.050 O 2 ). The Ni-, Co- and Al-containing lithium composite oxide C was washed with water and dried. This was used as the first positive electrode active material. As a result of analyzing the composition of the first positive electrode active material by ICP, it was Li 0.945 Ni 0.90 Co 0.049 Al 0.051 O 2 .
　上記得られた第１正極活物質のみを正極活物質として用いて、実施例１と同様にして、非水電解質二次電池を作製した。 A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1 using only the first positive electrode active material obtained above as a positive electrode active material.
　＜比較例５＞
　上記Ｎｉ、Ｃｏ及びＡｌを含む複合酸化物とＬｉＯＨとを、Ｌｉと、Ｎｉ、Ｃｏ及びＡｌの総量のモル比が１．１２：１になるように混合した。当該混合物を酸素雰囲気中にて、７４０℃で３．５時間焼成して、Ｎｉ、Ｃｏ及びＡｌ含有リチウム複合酸化物Ｄ（Ｌｉ１．０９Ｎｉ０．９０Ｃｏ０．０５１Ａｌ０．０４９Ｏ２）を得た。上記Ｎｉ、Ｃｏ及びＡｌ含有リチウム複合酸化物Ｄを水洗・乾燥した。これを第２正極活物質とした。第２正極活物質の組成をＩＣＰにより分析した結果、Ｌｉ１．００６Ｎｉ０．８９５Ｃｏ０．０４９Ａｌ０．０５６Ｏ２であった。 <Comparative Example 5>
The composite oxide containing Ni, Co and Al and LiOH were mixed so that the total molar ratio of Li to Ni, Co and Al was 1.12:1. The mixture was fired in an oxygen atmosphere at 740° C. for 3.5 hours to obtain Ni, Co and Al-containing lithium composite oxide D (Li 1.09 Ni 0.90 Co 0.051 Al 0.049 O 2 ). The Ni-, Co- and Al-containing lithium composite oxide D was washed with water and dried. This was used as the second positive electrode active material. As a result of analyzing the composition of the second positive electrode active material by ICP, it was Li 1.006 Ni 0.895 Co 0.049 Al 0.056 O 2 .
[初期容量と直流抵抗（ＤＣＲ）の測定]
　各実施例及び各比較例の非水電解質二次電池を、２５℃の温度環境下、０．２Ｃの定電流で電池電圧が４．２Ｖになるまで定電流充電を行い、４．２Ｖで電流値が０．０１Ｃになるまで定電圧充電を行った。この時の容量を正極活物質質量当たりの容量に換算し、これを初期容量として算出した。１０分休止後、０．２Ｃの定電流で電池電圧が２．５Ｖになるまで定電流放電を行った。また、同条件で充電・休止後、１．０Ｃで１０秒放電し、その時に低下した電圧を電流値で割ることにより、ＤＣＲを求めた。 [Measurement of initial capacity and DC resistance (DCR)]
The non-aqueous electrolyte secondary battery of each example and each comparative example was subjected to constant current charging at a constant current of 0.2 C in a temperature environment of 25 ° C. until the battery voltage reached 4.2 V. Constant voltage charging was performed until the value reached 0.01C. The capacity at this time was converted into the capacity per mass of the positive electrode active material, which was calculated as the initial capacity. After resting for 10 minutes, constant current discharge was performed at a constant current of 0.2C until the battery voltage reached 2.5V. After charging and resting under the same conditions, the battery was discharged at 1.0 C for 10 seconds, and the DCR was obtained by dividing the voltage that dropped at that time by the current value.
[充放電サイクル特性の評価]
　各実施例及び各比較例の非水電解質二次電池を、２５℃の温度環境下、０．２Ｃの定電流で電池電圧が４．２Ｖになるまで定電流充電を行い、４．２Ｖで電流値が０．０１Ｃになるまで定電圧充電を行った。その後、０．２Ｃの定電流で電池電圧が２．５Ｖになるまで定電流放電を行った。この充放電サイクルを１００サイクル行い、下式により容量維持率を算出した。容量維持率が高いほど、充放電サイクル特性の低下が抑制されたことを示している。
容量維持率（％）＝（１００サイクル目の放電容量／１サイクル目の放電容量）×１００ [Evaluation of charge-discharge cycle characteristics]
The non-aqueous electrolyte secondary battery of each example and each comparative example was subjected to constant current charging at a constant current of 0.2 C in a temperature environment of 25 ° C. until the battery voltage reached 4.2 V. Constant voltage charging was performed until the value reached 0.01C. After that, constant current discharge was performed at a constant current of 0.2C until the battery voltage reached 2.5V. This charge/discharge cycle was repeated 100 times, and the capacity retention rate was calculated by the following formula. A higher capacity retention rate indicates that deterioration in charge-discharge cycle characteristics was suppressed.
Capacity retention rate (%) = (discharge capacity at 100th cycle/discharge capacity at 1st cycle) x 100
　表１に、各実施例及び各比較例におけるＤＣＲ、初期容量、容量維持率の結果をまとめた。但し、これらの結果は、比較例１の結果を基準（１００）として、他の実施例及び比較例の結果を相対値として表している。 Table 1 summarizes the results of DCR, initial capacity, and capacity retention rate in each example and each comparative example. However, these results represent the results of other examples and comparative examples as relative values, with the result of Comparative Example 1 as a reference (100).
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　実施例１～３はいずれも、比較例１と比べて、低いＤＣＲを示し、また、高い容量維持率を示した。比較例２～５は、比較例１と比べて、低いＤＣＲ及び高い容量維持率のいずれか一方しか満たさなかった。したがって、Ｌｉを除く金属元素の総モル数（Ａ１）に対するＮｉのモル数（Ｂ１）の比（Ｂ１／Ａ１）が０．８５以上０．９４以下であり、前記Ｌｉを除く金属元素の総モル数（Ａ１）に対するＬｉのモル数（Ｃ１）の比（Ｃ１／Ａ１）が０．９５０以上０．９８３以下である第１正極活物質と、Ｌｉを除く金属元素の総モル数（Ａ２）に対するＮｉのモル数（Ｂ２）の比が０．８５以上０．９４以下であり、前記Ｌｉを除く金属元素の総モル数（Ａ２）に対するＬｉのモル数（Ｃ２）の比（Ｃ２／Ａ２）が０．９８４以上１．００４以下である第２正極活物質とを含む正極活物質を用いること、及び第１正極活物質と第２正極活物質の混合比を質量比で９５：５～７５：２５とすることにより、非水電解質二次電池の直流抵抗の低減、及び充放電サイクル特性の低下抑制を図ることが可能となる。 All of Examples 1 to 3 exhibited a lower DCR and a higher capacity retention rate than Comparative Example 1. Compared to Comparative Example 1, Comparative Examples 2 to 5 satisfied only one of low DCR and high capacity retention rate. Therefore, the ratio (B 1 /A 1 ) of the number of moles (B 1 ) of Ni to the total number of moles (A 1 ) of the metal elements excluding Li is 0.85 or more and 0.94 or less, and the metal excluding Li A first positive electrode active material having a ratio (C 1 /A 1 ) of the number of moles (C 1 ) of Li to the total number of moles (A 1 ) of the elements (C 1 /A 1 ) of 0.950 or more and 0.983 or less, and a metal element other than Li The ratio of the number of moles of Ni (B 2 ) to the total number of moles (A 2 ) of is 0.85 or more and 0.94 or less, and the number of moles of Li to the total number of moles (A 2 ) of the metal elements excluding Li Using a positive electrode active material containing a second positive electrode active material having a ratio (C 2 /A 2 ) of (C 2 ) of 0.984 or more and 1.004 or less, and the first positive electrode active material and the second positive electrode active material By setting the mixing ratio of the substances to 95:5 to 75:25 in terms of mass ratio, it is possible to reduce the direct current resistance of the non-aqueous electrolyte secondary battery and suppress deterioration in charge-discharge cycle characteristics.
　１０　二次電池、１１　正極、１２　負極、１３　セパレータ、１４　電極体、１６　ケース本体、１７　封口体、１８　絶縁板、１８，１９　絶縁板、２０　正極リード、２１　負極リード、２２　張り出し部、２３　フィルタ、２４　下弁体、２５　絶縁部材、２６　上弁体、２７　キャップ、２８　ガスケット。 10 secondary battery, 11 positive electrode, 12 negative electrode, 13 separator, 14 electrode body, 16 case body, 17 sealing body, 18 insulating plate, 18, 19 insulating plate, 20 positive electrode lead, 21 negative electrode lead, 22 overhang, 23 filter , 24 lower valve body, 25 insulating member, 26 upper valve body, 27 cap, 28 gasket.

Claims (3)

  1. 　第１正極活物質と第２正極活物質を含み、
    　前記第１正極活物質は、Ｎｉ含有リチウム複合酸化物であって、Ｌｉを除く金属元素の総モル数（Ａ１）に対するＮｉのモル数（Ｂ１）の比（Ｂ１／Ａ１）が０．８５以上０．９４以下であり、前記Ｌｉを除く金属元素の総モル数（Ａ１）に対するＬｉのモル数（Ｃ１）の比（Ｃ１／Ａ１）が０．９５０以上０．９８３以下であり、
    　前記第２正極活物質は、Ｎｉ含有リチウム複合酸化物であって、Ｌｉを除く金属元素の総モル数（Ａ２）に対するＮｉのモル数（Ｂ２）の比が０．８５以上０．９４以下であり、前記Ｌｉを除く金属元素の総モル数（Ａ２）に対するＬｉのモル数（Ｃ２）の比（Ｃ２／Ａ２）が０．９８４以上１．００４以下であり、
    　前記第１正極活物質と前記第２正極活物質の混合比は、質量比で９５：５～７５：２５である、非水電解質二次電池用正極活物質。     including a first positive electrode active material and a second positive electrode active material,
    The first positive electrode active material is a Ni-containing lithium composite oxide, and the ratio (B 1 /A 1 ) of the number of moles (B 1 ) of Ni to the total number of moles (A 1 ) of metal elements excluding Li is 0.85 or more and 0.94 or less, and the ratio (C 1 /A 1 ) of the number of moles of Li (C 1 ) to the total number of moles (A 1 ) of the metal elements excluding Li is 0.950 or more and 0.95 or more. 983 or less,
    The second positive electrode active material is a Ni-containing lithium composite oxide, and the ratio of the number of moles (B 2 ) of Ni to the total number of moles (A 2 ) of metal elements excluding Li is 0.85 or more and 0.94. and the ratio (C 2 /A 2 ) of the number of moles of Li (C 2 ) to the total number of moles (A 2 ) of the metal elements excluding Li is 0.984 or more and 1.004 or less,
    A positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the mixing ratio of the first positive electrode active material and the second positive electrode active material is 95:5 to 75:25 in mass ratio.
  2. 　前記第１正極活物質は、一般式ＬｉｚＮｉ１－ｘ－ｙＭｘＡｌｙＯ２（０．０２≦ｘ≦０．１０、０．０３≦ｙ≦０．０７、０．８５≦１－ｘ－ｙ≦０．９４、０．９７０≦ｚ≦０．９８３、Ｍは、Ｃｏ、Ｗ、Ｎｂ、Ｍｇ、Ｔｉ、Ｍｎ及びＭｏからなる群から選択される少なくとも１種）で表され、
    　前記第２正極活物質は、一般式ＬｉｚＮｉ１－ｘ－ｙＭｘＡｌｙＯ２（０．０２≦ｘ≦０．１０、０．０３≦ｙ≦０．０７、０．８５≦１－ｘ－ｙ≦０．９４、０．９８４≦ｚ≦１．０００、Ｍは、Ｃｏ、Ｗ、Ｎｂ、Ｍｇ、Ｔｉ、Ｍｎ及びＭｏからなる群から選択される少なくとも１種）で表される、請求項１に記載の非水電解質二次電池用正極活物質。     The first positive electrode active material has the general formula LizNi1 -xyMxAlyO2 ( 0.02≤x≤0.10, 0.03≤y≤0.07 , 0.85≤1 -xy ≤ 0.94, 0.970 ≤ z ≤ 0.983, M is at least one selected from the group consisting of Co, W, Nb, Mg, Ti, Mn and Mo),
    The second positive electrode active material has the general formula LizNi1 -xyMxAlyO2 ( 0.02≤x≤0.10 , 0.03≤y≤0.07, 0.85≤1 -xy ≤ 0.94, 0.984 ≤ z ≤ 1.000, M is at least one selected from the group consisting of Co, W, Nb, Mg, Ti, Mn and Mo) The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1.
  3. 　正極、負極、及び非水電解質を含み、
    　前記正極は請求項１又は２に記載の非水電解質二次電池用正極活物質を含む、非水電解質二次電池。     including a positive electrode, a negative electrode, and a non-aqueous electrolyte;
    A non-aqueous electrolyte secondary battery, wherein the positive electrode comprises the positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 .
PCT/JP2022/038573 2021-10-20 2022-10-17 Positive electrode active material for nonaqueous electrolyte secondary batteries, and nonaqueous electrolyte secondary battery WO2023068221A1 (en)

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