WO2024247746A1 - 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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WO2024247746A1
WO2024247746A1 PCT/JP2024/018129 JP2024018129W WO2024247746A1 WO 2024247746 A1 WO2024247746 A1 WO 2024247746A1 JP 2024018129 W JP2024018129 W JP 2024018129W WO 2024247746 A1 WO2024247746 A1 WO 2024247746A1
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positive electrode
active material
electrode active
composite oxide
transition metal
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English (en)
French (fr)
Japanese (ja)
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晃宏 河北
勝哉 井之上
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 CN202480032956.1A priority Critical patent/CN121336294A/zh
Priority to EP24815230.8A priority patent/EP4723226A1/en
Priority to JP2025523461A priority patent/JPWO2024247746A1/ja
Publication of WO2024247746A1 publication Critical patent/WO2024247746A1/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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • This disclosure relates to a positive electrode active material for a non-aqueous electrolyte secondary battery, and a non-aqueous electrolyte secondary battery.
  • Patent Document 1 discloses a non-aqueous electrolyte secondary battery that uses a lithium transition metal composite oxide with low-solubility Li salts scattered on the surface as the positive electrode active material, with the aim of reducing reaction resistance during storage at high temperatures.
  • Patent Document 1 In non-aqueous electrolyte secondary batteries, improving the initial charge/discharge efficiency is an important issue.
  • the technology described in Patent Document 1 does not consider improving the initial efficiency, and there is still room for improvement.
  • the purpose of this disclosure is to provide a positive electrode active material for non-aqueous electrolyte secondary batteries that enables improved initial efficiency.
  • a positive electrode active material for a nonaqueous electrolyte secondary battery comprises a lithium transition metal composite oxide and a sulfonic acid compound present on the surface of the lithium transition metal composite oxide, the lithium transition metal composite oxide being secondary particles having a layered structure and containing 75 mol % or more of Ni relative to the total number of moles of metal elements excluding Li, and characterized in that the Gini coefficient of SO3- on the secondary particle surface is 0.7 or less in an element concentration distribution on a cross section of the secondary particle measured using time-of-flight secondary ion mass spectrometry.
  • A is a Group 1 or Group 2 element
  • R is a hydrocarbon group
  • n is 1 or 2.
  • a positive electrode active material for a non-aqueous electrolyte secondary battery includes a lithium transition metal composite oxide and a sulfonic acid compound present on a surface of the lithium transition metal composite oxide, the lithium transition metal composite oxide having a layered structure and being secondary particles containing 75 mol % or more of Ni relative to the total number of moles of metal elements excluding Li, and characterized in that the Gini coefficient of SO3- within the secondary particles is 0.6 or less in an element concentration distribution on a cross section of the secondary particles measured using time-of-flight secondary ion mass spectrometry.
  • A is a Group 1 or Group 2 element
  • R is a hydrocarbon group
  • n is 1 or 2.
  • the nonaqueous electrolyte secondary battery comprises a positive electrode containing the above-mentioned positive electrode active material, a negative electrode, and a nonaqueous electrolyte, and is characterized in that the negative electrode contains S.
  • the positive electrode active material for a nonaqueous electrolyte secondary battery which is one aspect of the present disclosure, can improve the initial efficiency of the nonaqueous electrolyte secondary battery.
  • FIG. 1 is a longitudinal sectional view of a nonaqueous electrolyte secondary battery according to an embodiment of the present invention
  • the present inventors have found that by making a sulfonic acid compound present on the particle surface of a predetermined lithium transition metal oxide and uniformly dispersing the sulfonic acid compound until the Gini coefficient of the depth mapping intensity ratio distribution of SO 3- when analyzed by TOF-SIMS is 0.7 or less, the protective effect of the film containing the sulfonic acid compound is significantly exhibited, making it easier for Li + to be inserted/desorbed, and improving the initial efficiency.
  • a sulfonic acid compound present on the particle surface of a predetermined lithium transition metal oxide and uniformly dispersing the sulfonic acid compound until the Gini coefficient of the depth mapping intensity ratio distribution of SO 3- when analyzed by TOF-SIMS is 0.7 or less, the protective effect of the film containing the sulfonic acid compound is significantly exhibited, making it easier for Li + to be inserted/desorbed, and improving the initial efficiency.
  • a cylindrical battery in which a wound electrode body is housed in a cylindrical exterior body is exemplified, but the electrode body is not limited to the wound type, and may be a laminated type in which multiple positive electrodes and multiple negative electrodes are alternately stacked one by one with separators between them.
  • the exterior body is not limited to a cylindrical shape, and may be, for example, a square shape, a coin shape, etc., or a battery case made of a laminate sheet including a metal layer and a resin layer.
  • FIG. 1 is an axial cross-sectional view of a cylindrical secondary battery 10, which is an example of an embodiment.
  • the secondary battery 10 includes a wound electrode body 14, an electrolyte, and an exterior body 16 that contains the electrode body 14 and the electrolyte.
  • the electrode body 14 includes a positive electrode 11, a negative electrode 12, and a separator 13, and has a wound structure in which the positive electrode 11 and the negative electrode 12 are wound in a spiral shape with the separator 13 interposed therebetween.
  • the exterior body 16 is a cylindrical metal container with a bottom that is open on one axial side, and the opening of the exterior body 16 is closed by a sealing body 17.
  • the sealing body 17 side of the battery is referred to as the top
  • the bottom side of the exterior body 16 is referred to as the bottom.
  • the positive electrode 11, negative electrode 12, and separator 13 constituting the electrode body 14 are all rectangular, elongated bodies that are wound in a spiral shape in the longitudinal direction and are alternately stacked in the radial direction of the electrode body 14.
  • the separator 13 isolates the positive electrode 11 and the negative electrode 12 from each other.
  • the negative electrode 12 is formed to be slightly larger than the positive electrode 11 in order to prevent lithium precipitation. That is, the negative electrode 12 is formed to be longer in the longitudinal direction and the lateral direction than the positive electrode 11.
  • the two separators 13 are formed to be at least slightly larger than the positive electrode 11, and are arranged to sandwich the positive electrode 11, for example.
  • the electrode body 14 includes 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.
  • the longitudinal direction of the positive electrode 11 and the negative electrode 12 is the winding direction
  • the lateral direction of the positive electrode 11 and the negative electrode 12 is the axial direction. That is, the short-side end faces of the positive electrode 11 and the negative electrode 12 form the axial end faces of the electrode body 14.
  • Insulating plates 18, 19 are arranged above and below the electrode body 14.
  • the positive electrode lead 20 passes through a through hole in the insulating plate 18 and extends toward the sealing body 17, and the negative electrode lead 21 passes outside the insulating plate 19 and extends toward the bottom side of the exterior body 16.
  • the positive electrode lead 20 is connected to the underside of the internal terminal plate 23 of the sealing body 17 by welding or the like, and the cap 27, which is the top plate of the sealing body 17 and is electrically connected to the internal terminal plate 23, serves as the positive electrode terminal.
  • the negative electrode lead 21 is connected to the inner bottom inner surface of the exterior body 16 by welding or the like, and the exterior body 16 serves as the negative electrode terminal.
  • a gasket 28 is provided between the exterior body 16 and the sealing body 17 to ensure airtightness inside the battery.
  • the exterior body 16 has a grooved portion 22 that supports the sealing body 17, with part of the side surface protruding inward.
  • the grooved portion 22 is preferably formed in an annular shape along the circumferential direction of the exterior body 16, and supports the sealing body 17 on its upper surface.
  • the sealing body 17 is fixed to the top of the exterior body 16 by the grooved portion 22 and the open end of the exterior body 16 that is crimped to the sealing body 17.
  • the sealing body 17 has a structure in which, in order from the electrode body 14 side, an internal terminal plate 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a cap 27 are stacked.
  • Each member constituting the sealing body 17 has, for example, a disk or ring shape, and each member except for the insulating member 25 is electrically connected to each other.
  • the lower valve body 24 and the upper valve body 26 are connected at their respective centers, and the insulating member 25 is interposed between their respective peripheral edges.
  • the positive electrode 11 has, for example, a positive electrode core and a positive electrode mixture layer formed on the surface of the positive electrode core.
  • the positive electrode mixture layer is preferably formed on both sides of the positive electrode core.
  • a foil of a metal stable in the potential range of the positive electrode 11, such as aluminum or an aluminum alloy, or a film having the metal disposed on the surface layer can be used.
  • the thickness of the positive electrode core is, for example, 10 ⁇ m or more and 30 ⁇ m or less.
  • the positive electrode mixture layer includes, for example, a positive electrode active material, a conductive agent, and a binder.
  • the thickness of the positive electrode mixture layer is, for example, 10 ⁇ m or more and 150 ⁇ m or less on one side of the positive electrode current collector.
  • the positive electrode 11 can be produced, for example, by applying a positive electrode mixture slurry including a positive electrode active material, a conductive agent, and a binder to the surface of the positive electrode current collector, drying the coating, and then rolling to form a positive electrode mixture layer on both sides of the positive electrode current collector.
  • the conductive agent contained in the positive electrode mixture layer may be, for example, carbon black (CB) such as acetylene black (AB) or ketjen black, carbon nanotubes (CNT), graphene, graphite, or other carbon-based materials. These may be used alone or in combination of two or more types.
  • CB carbon black
  • AB acetylene black
  • CNT carbon nanotubes
  • the content of the conductive agent in the positive electrode mixture layer is, for example, 0.1% by mass or more and 10% by mass or less with respect to the total mass of the positive electrode mixture layer.
  • binder contained in the positive electrode mixture layer examples include fluorine-based resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide-based resins, acrylic-based resins, and polyolefin-based resins. 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, 0.1% by mass or more and 10% by mass or less with respect to the total mass of the positive electrode mixture layer.
  • the positive electrode active material contained in the positive electrode mixture layer 31 includes particulate lithium transition metal composite oxide.
  • the lithium transition metal composite oxide particles include, for example, secondary particles formed by agglomeration of primary particles.
  • the particle size of the primary particles is, for example, 0.02 ⁇ m or more and 2 ⁇ m or less.
  • the particle size of the primary particles is measured as the diameter of a circumscribed circle in a particle image observed by a scanning electron microscope (SEM).
  • SEM scanning electron microscope
  • the average particle size of the secondary particles is, for example, 2 ⁇ m or more and 30 ⁇ m or less.
  • the average particle size means the volume-based median diameter (D50).
  • D50 means the particle size at which the cumulative frequency is 50% from the smallest particle size in the volume-based particle size distribution, and is also called the median diameter.
  • the particle size distribution of the secondary particles can be measured using a laser diffraction type particle size distribution measuring device (for example, MT3000II manufactured by Microtrack Bell Co., Ltd.)
  • the lithium transition metal composite oxide particles include, for example, single particles, or secondary particles formed by agglomeration of 2 to 1000 single particles.
  • the average particle size of the single particles is preferably 0.5 to 5 ⁇ m, more preferably 0.7 to 4 ⁇ m. Note that single particles function in the same way as secondary particles, and therefore, in the following, "secondary particles" includes single particles.
  • the lithium transition metal composite oxide has a layered structure.
  • the layered structure of the lithium transition metal composite oxide include a layered structure belonging to the space group R-3m and a layered structure belonging to the space group C2/m. From the viewpoint of high capacity and stability of the crystal structure, it is preferable that the lithium transition metal composite oxide has a layered structure belonging to the space group R-3m.
  • the layered structure of the lithium transition metal composite oxide may include a transition metal layer, a Li layer, and an oxygen layer.
  • the lithium transition metal composite oxide contains 75 mol% or more of Ni relative to the total number of moles of metal elements excluding Li. This allows for a high capacity battery.
  • the Ni content is, for example, 80 mol% or more and 98 mol% or less.
  • the lithium transition metal composite oxide may contain, in addition to Ni, one or more elements selected from the group consisting of Co, Al, and Mn.
  • the contents of Co, Al, and Mn in the lithium transition metal composite oxide are, for example, 0 mol% or more and 25 mol% or less, respectively, relative to the total number of moles of metal elements excluding Li.
  • the sum of the contents of Co, Al, and Mn is, for example, 0 mol% or more and 25 mol% or less.
  • the ratio of the metal element contained in the lithium transition metal composite oxide can be measured, for example, by an inductively coupled plasma atomic emission spectrometer (ICP-AES).
  • the lithium transition metal composite oxide is produced through a first step of synthesizing a transition metal composite hydroxide containing Ni, Co, Mn, Al, etc., for example, by a coprecipitation method, a second step of heat-treating the composite hydroxide to obtain a transition metal composite oxide, and a third step of mixing the composite oxide with lithium hydroxide and firing the mixture.
  • the mixture is fired at a temperature of 650°C or higher.
  • the preferred firing temperature range is 650°C or higher and 1100°C or lower.
  • the firing is preferably carried out in an oxygen stream.
  • an excess of lithium source lithium hydroxide
  • a stoichiometric ratio of 1 to 1.1 times that of the composite oxide is preferred.
  • the particle size of the primary particles can be adjusted, and single particles can also be produced.
  • the particle size of the single particles can be increased by increasing the maximum temperature reached.
  • the positive electrode active material contains, in addition to a lithium transition metal composite oxide, a sulfonic acid compound represented by the following general formula I.
  • the sulfonic acid compound is present on the surface of the lithium transition metal composite oxide.
  • A is a Group 1 or Group 2 element
  • R is a hydrocarbon group
  • n is 1 or 2.
  • the Gini coefficient of SO 3- at the secondary particle surface may be 0.7 or less, preferably 0.6 or less, and more preferably 0.5 or less. This improves the initial efficiency. Since SO 3- is detected due to a sulfonic acid compound, the smaller the Gini coefficient of SO 3- at the secondary particle surface, the more uniformly the sulfonic acid compound is dispersed on the secondary particle surface.
  • the Gini coefficient of SO 3- at the secondary particle surface is, for example, 0.1 or more.
  • the Gini coefficient inside the secondary particle of SO 3- may be 0.6 or less, preferably 0.55 or less, and more preferably 0.5 or less. This improves the initial efficiency. Since SO 3- is detected due to a sulfonic acid compound, the smaller the Gini coefficient inside the secondary particle of SO 3- , the more uniformly the sulfonic acid compound is dispersed inside the secondary particle.
  • the Gini coefficient inside the secondary particle of SO 3- is, for example, 0.1 or more.
  • the Gini coefficient of the SO 3- secondary particle surface is twice the area enclosed between the diagonal and the Lorentz curve when the cumulative rate is expressed in order of intensity for the normalized intensity I SO3-_OUT of SO 3- on the secondary particle surface.
  • the Gini coefficient of the SO 3- secondary particle interior is twice the area enclosed between the diagonal and the Lorentz curve when the cumulative rate is expressed in order of intensity for the normalized intensity I SO3-_IN of SO 3- inside the secondary particle.
  • the Gini coefficient is 0 when completely uniform, and increases with decreasing uniformity.
  • the Gini coefficient of the SO 3- secondary particle interior may be smaller than the Gini coefficient of the SO 3- secondary particle surface, or may be equal to or greater than the Gini coefficient of the SO 3- secondary particle surface. When the Gini coefficient of the SO 3- secondary particle interior is equal to or greater than the Gini coefficient of the SO 3- secondary particle surface, the effect of the present application may be significantly exhibited.
  • the normalized intensity ratio of SO 3- is obtained by measurement under the following conditions using a time-of-flight secondary ion mass spectrometer (TOF-SIMS5 manufactured by IONTOF Corporation).
  • the image showing the concentration distribution of Ni and SO3- obtained by the above measurement is divided into 256 x 256 pixels, and the detection intensity of Ni and SO3- is calculated for each pixel. Furthermore, the ratio of the detection intensity of SO3- to the detection intensity of Ni is calculated as the normalized intensity of SO3-, I SO3- .
  • the range from the surface of the secondary particle recognized from the above image to 0.5 ⁇ m inside is defined as the surface of the secondary particle, and pixels included in the surface of this secondary particle (hereinafter referred to as surface pixels) are defined.
  • a set of I SO3- corresponding to each surface pixel is I SO3-_OUT .
  • the inside of the secondary particle surface defined above is defined as the interior of the secondary particle, and pixels included in the interior of this secondary particle (hereinafter referred to as internal pixels) are defined.
  • a set of I SO3- corresponding to each internal pixel is I SO3-_IN . From I SO3-_OUT and I SO3-_IN , the Gini coefficient of SO 3- on the secondary particle surface and the Gini coefficient of SO 3- inside the secondary particle are calculated.
  • the sample to be observed in cross section may be a sample in which a lithium transition metal composite oxide is embedded in a resin or the like, or may be a positive electrode mixture layer containing a lithium transition metal composite oxide.
  • A is preferably a Group 1 element, and more preferably Li. This allows the DC resistance to be further reduced.
  • n 1.
  • R is preferably an alkyl group.
  • R is more preferably an alkyl group having 5 or less carbon atoms, even more preferably an alkyl group having 3 or less carbon atoms, and particularly preferably a methyl group.
  • some of the hydrogens bonded to the carbons may be substituted with fluorine.
  • R not all of the hydrogens bonded to the carbons are substituted with fluorine. The smaller the molecular weight of R, the smaller the direct current resistance can be.
  • sulfonic acid compounds include lithium methanesulfonate, lithium ethanesulfonate, lithium propanesulfonate, sodium methanesulfonate, magnesium methanesulfonate, and lithium fluoromethanesulfonate.
  • the amount of the sulfonic acid compound contained in the positive electrode 11 is preferably 0.1% by mass or more and 1.5% by mass or less, and more preferably 0.25% by mass or more and 1.0% by mass or less, relative to the mass of the lithium transition metal composite oxide.
  • the presence of the sulfonic acid compound in the positive electrode 11 can be confirmed by Fourier transform infrared spectroscopy (FT-IR).
  • FT-IR Fourier transform infrared spectroscopy
  • the positive electrode 11 may have absorption peaks at at least one of the following positions: 1238 cm ⁇ 1 , 1175 cm ⁇ 1 , 1065 cm ⁇ 1 , and 785 cm ⁇ 1 .
  • the positive electrode 11 containing lithium methanesulfonate has absorption peaks near 1238 cm -1 , 1175 cm -1 , 1065 cm -1 , and 785 cm -1 .
  • the peaks near 1238 cm -1 , 1175 cm -1 , and 1065 cm -1 are absorption peaks due to SO stretching vibration derived from lithium methanesulfonate.
  • the peak near 785 cm -1 is an absorption peak due to CS stretching vibration derived from lithium methanesulfonate.
  • the absorption peaks derived from the sulfonic acid compound can be identified, just as in the case of a positive electrode 11 containing lithium methanesulfonate.
  • the presence of the sulfonic acid compound in the positive electrode 11 can also be confirmed by ICP, atomic absorption spectrometry, X-ray photoelectron spectroscopy (XPS), synchrotron radiation XRD measurement, TOF-SIMS, etc.
  • a metal compound may be present on the surface of the lithium transition metal composite oxide.
  • the metal compound contains, for example, one or more metal elements selected from the group consisting of Sr, Ca, W, Zr, rare earth, and Al.
  • Sr-containing compound include SrO, Sr(OH) 2 , and SrCO 3.
  • Ca-containing compound include CaO, Ca(OH) 2 , and CaCO 3.
  • W-containing compound include WO 3.
  • Examples of the Al-containing compound include Al 2 O 3.
  • Examples of the Zr-containing compound include ZrO 2 , Zr(OH) 4 , Zr(CO 3 ) 2 , and Zr(SO 4 ) 2.4H 2 O.
  • the rare earth-containing compound examples include oxides, hydroxides, carbonates, sulfates, nitrates, and phosphates of rare earth.
  • the metal compound may contain a plurality of kinds of these metal elements, and examples thereof include SrAlO 4 and CaAlO 4.
  • the metal compound may further contain Li, and an example thereof is lithium tungstate.
  • a nonmetallic compound may be present on the surface of the lithium transition metal composite oxide.
  • the nonmetallic compound contains, for example, one or more nonmetallic elements selected from the group consisting of P and B.
  • An example of a compound containing P is Li3 - xHxPO4 (0 ⁇ x ⁇ 3 ).
  • An example of a compound containing B is H3BO3 , Li3BO3 , or Li2B4O7 .
  • the positive electrode active material can be prepared, for example, by adding a sulfonic acid solution to a lithium transition metal composite oxide and adhering the sulfonic acid compound to the surface of the lithium transition metal composite oxide (addition process).
  • the lithium transition metal composite oxide may be subjected to a washing process and a drying process.
  • the lithium transition metal composite oxide is washed with water and dehydrated to obtain a cake-like composition.
  • the washing and dehydration can be performed by known methods and under known conditions. They should be performed within a range in which lithium is not eluted from the lithium transition metal composite oxide and the battery characteristics are not deteriorated.
  • the positive electrode active material according to this embodiment is washed with water, there is little residual alkaline component.
  • the cake-like composition obtained in the washing step is dried to obtain a powder-like composition.
  • the drying step may be performed under a vacuum atmosphere.
  • the drying conditions are, for example, 150°C to 400°C and 0.5 hours to 15 hours.
  • a heat treatment may be performed after the drying step.
  • the heating temperature is, for example, 100°C to 450°C.
  • the heat treatment may be performed after the crushing step described below.
  • the powder composition obtained in the drying step can be pulverized to obtain single particles.
  • a jet mill or the like can be used for pulverization. Pulverization using a jet mill can be performed, for example, using a PJM-80 (manufactured by Nippon Pneumatic Co., Ltd.) under the following conditions. Compressed air consumption: 0.5 Nm3/ min Supply gas pressure: 0.53 MPa Processing capacity: 2000g/hour
  • a sulfonic acid compound and a sulfonic acid solution is added to the cake-like composition obtained in the washing step or the powder-like composition obtained in the drying step. This allows the sulfonic acid compound to adhere to the surface of the lithium transition metal composite oxide. It is preferable to add at least one of a sulfonic acid compound and a sulfonic acid solution to the cake-like composition.
  • the sulfonic acid compound may be in the form of a powder or a solution.
  • the sulfonic acid solution is, for example, a methanesulfonic acid solution obtained by dissolving methanesulfonic acid in water.
  • a Li compound or a Li compound solution may be added to the cake-like composition or the powder-like composition together with the sulfonic acid solution, or a mixed solution in which a sulfonic acid solution and a Li compound or a Li compound solution are mixed in advance may be added to the cake-like composition or the powder-like composition.
  • the Li compound is, for example, LiOH
  • the Li compound solution is, for example, a LiOH solution in which LiOH is dissolved in water.
  • the amount of the Li compound and the sulfonic acid solution added to the cake-like composition preferably satisfies the relationship of 0 ⁇ Li compound/sulfonic acid ⁇ 1.3 in molar ratio.
  • the amount of the sulfonic acid compound or sulfonic acid added is preferably 0.1% by mass to 1% by mass, more preferably 0.3% by mass to 0.8% by mass, relative to the mass of the lithium transition metal composite oxide.
  • the concentration of each of the sulfonic acid solution and the sulfonic acid compound solution is, for example, 0.5% by mass to 40% by mass.
  • the addition process may be performed during or after the washing process, during or after the drying process, and the timing of the addition process can be changed as appropriate.
  • the dispersibility of the sulfonic acid compound on the surface and inside of the lithium transition metal composite oxide is improved.
  • This mixing may be performed, for example, using a mixer at a rotation speed of 10 rpm to 100 rpm for 0.1 minutes to 60 minutes.
  • Metal compounds containing one or more metal elements selected from the group consisting of Sr, Ca, W, Zr, rare earth elements, and Al, and nonmetal compounds containing one or more nonmetal elements selected from the group consisting of P and B can be attached to the surface of the lithium transition metal composite oxide by adding raw materials of the metal compounds and nonmetal compounds during the synthesis process, after the synthesis process, during the cleaning process, after the cleaning process, during the drying process, after the drying process, or during the addition process.
  • Sr raw materials include Sr(OH) 2 , Sr(OH) 2.8H2O , SrO, SrCo3 , SrSO4 , Sr( NO3 ) 2 , SrCl2 , SrAlO4, etc.
  • Examples of Ca raw materials include Ca(OH) 2 , CaO, CaCO3 , CaSO4 , Ca( NO3 ) 2, CaCl2 , CaAlO4 , etc.
  • Examples of Zr raw materials include Zr(OH) 4 , ZrO 2 , Zr(CO 3 ) 2 , and Zr(SO 4 ) 2.4H 2 O.
  • Examples of rare earth raw materials include oxides, hydroxides, and carbonates of rare earths.
  • Examples of W raw materials include tungsten oxide (WO 3 ), lithium tungstate (Li 2 WO 4 , Li 4 WO 5 , Li 6 W 2 O 9 ), and the like. Note that a solution containing W may be used as the W raw material.
  • Al raw materials include Al 2 O 3 , Al(OH) 3 , and Al 2 (SO 4 ) 3 , but may also be Al derived from a lithium transition metal composite oxide.
  • P raw materials include Li 3-x H x PO 4 (0 ⁇ x ⁇ 3).
  • B raw material include H 3 BO 3 , Li 3 BO 3 , and Li 2 B 4 O 7. These compounds may be pulverized to appropriately change the particle size, or the water content, including hydrates, may be adjusted before use.
  • the positive electrode mixture layer may contain other positive electrode active materials in addition to the positive electrode active material of the present embodiment.
  • positive electrode active materials include a positive electrode active material containing a lithium transition metal composite oxide with a Ni content of less than 75 mol %, and a positive electrode active material in which no sulfonic acid compound is present on the surface of the lithium transition metal composite oxide.
  • the negative electrode 12 may have, for example, a negative electrode core and a negative electrode mixture layer formed on the surface of the negative electrode core, or a metal Li foil may be used as the negative electrode 12.
  • the negative electrode 12 may have a negative electrode core, and lithium metal may be deposited on the surface of the negative electrode core by charging.
  • the negative electrode mixture layer is preferably formed on both sides of the negative electrode core.
  • a foil of a metal stable in the potential range of the negative electrode 12, such as copper or a copper alloy, or a film in which the metal is disposed on the surface layer may be used.
  • the thickness of the negative electrode core is, for example, 5 ⁇ m or more and 30 ⁇ m or less.
  • the negative electrode mixture layer includes, for example, a negative electrode active material and a binder.
  • the thickness of the negative electrode mixture layer is, for example, 10 ⁇ m or more and 150 ⁇ m or less on one side of the negative electrode core.
  • the negative electrode 12 can be produced, for example, by applying a negative electrode mixture slurry containing a negative electrode active material, a binder, etc. to the surface of a negative electrode core body, drying the coating, and then rolling it to form a negative electrode mixture layer on both sides of the negative electrode core body.
  • the negative electrode active material contained in the negative electrode mixture layer is not particularly limited as long as it can reversibly absorb and release lithium ions, and generally carbon materials such as graphite are used.
  • Graphite may be any of natural graphite such as scaly graphite, lump graphite, and earthy graphite, lump artificial graphite, and artificial graphite such as graphitized mesophase carbon microbeads.
  • metals that are alloyed with Li such as Si and Sn, metal compounds containing Si and Sn, and lithium titanium composite oxides may be used as the negative electrode active material.
  • those provided with a carbon coating may be used.
  • Si-containing compound represented by SiO x (0.5 ⁇ x ⁇ 1.6) or a Si-containing compound in which fine particles of Si are dispersed in a lithium silicate phase represented by Li 2y SiO (2+y) (0 ⁇ y ⁇ 2) may be used in combination with graphite.
  • Binders contained in the negative electrode mixture layer include, for example, styrene butadiene rubber (SBR), nitrile butadiene rubber (NBR), carboxymethyl cellulose (CMC) or its salts, polyacrylic acid (PAA) or its salts (PAA-Na, PAA-K, etc., or it may be a partially neutralized salt), polyvinyl alcohol (PVA), etc. These may be used alone or in combination of two or more types.
  • SBR styrene butadiene rubber
  • NBR nitrile butadiene rubber
  • CMC carboxymethyl cellulose
  • PAA polyacrylic acid
  • PAA-Na polyacrylic acid
  • PAA-K polyvinyl alcohol
  • PVA polyvinyl alcohol
  • the negative electrode 12 preferably contains S. This further improves the initial efficiency. For example, by aging the secondary battery 10, a portion of the S contained in the positive electrode 11 can be transferred to the negative electrode 12.
  • the S content in the negative electrode 12 is, for example, 10 ppm by mass or more and 1000 ppm by mass or less with respect to the total mass of the negative electrode active material.
  • the S content in the negative electrode 12 can be measured, for example, by an inductively coupled plasma atomic emission spectrometer (ICP-AES).
  • ICP-AES inductively coupled plasma atomic emission spectrometer
  • the aging treatment can be performed, for example, by charging the battery at a constant current of 0.1 C to 0.5 C for 10 minutes to 60 minutes, and then storing the battery in a temperature environment of 40°C to 80°C for 10 hours to 20 hours.
  • a porous sheet having ion permeability and insulating properties is used for the separator 13.
  • the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric.
  • the material of the separator 13 is preferably a polyolefin such as polyethylene or polypropylene, or cellulose.
  • the separator 13 may have a single layer structure or a multi-layer structure.
  • a highly heat-resistant resin layer such as an aramid resin may be formed on the surface of the separator 13.
  • a filler layer containing an inorganic filler may be formed at the interface between the separator 13 and at least one of the positive electrode 11 and the negative electrode 12.
  • inorganic fillers include oxides and phosphate compounds containing metal elements such as Ti, Al, Si, and Mg.
  • the filler layer can be formed by applying a slurry containing the filler to the surface of the positive electrode 11, the negative electrode 12, or the separator 13.
  • Non-aqueous electrolyte has, for example, lithium ion conductivity.
  • the non-aqueous electrolyte may be a liquid electrolyte (electrolytic solution) or a solid electrolyte.
  • the liquid electrolyte contains, for example, a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent.
  • the non-aqueous solvent examples include esters, ethers, nitriles such as acetonitrile, amides such as dimethylformamide, and mixed solvents of two or more of these.
  • the non-aqueous solvent may contain a halogen-substituted product in which at least a portion of the hydrogen of these solvents is replaced with a halogen atom such as fluorine.
  • halogen-substituted product examples include fluorinated cyclic carbonates such as fluoroethylene carbonate (FEC), fluorinated chain carbonates, and fluorinated chain carboxylates such as methyl fluoropropionate (FMP).
  • FEC fluoroethylene carbonate
  • FMP fluorinated chain carboxylates
  • FEC fluoroethylene carbonate
  • FMP fluorinated chain carboxylates
  • esters examples include cyclic carbonate esters such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate; chain carbonate esters such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl propyl carbonate, ethyl propyl carbonate, and methyl isopropyl carbonate; cyclic carboxylate esters such as gamma-butyrolactone (GBL) and gamma-valerolactone (GVL); and chain carboxylate esters such as methyl acetate, ethyl acetate, propyl acetate, methyl propionate (MP), and ethyl propionate (EP).
  • cyclic carbonate esters such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate
  • chain carbonate esters such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC
  • ethers examples include 1,3-dioxolane, 4-methyl-1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, propylene oxide, 1,2-butylene oxide, 1,3-dioxane, 1,4-dioxane, 1,3,5-trioxane, furan, 2-methylfuran, 1,8-cineole, cyclic ethers such as crown ethers, 1,2-dimethoxyethane, diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, dihexyl ether, ethyl vinyl ether, butyl vinyl ether, methylphenyl ether, Examples of such chain ethers include ethyl phenyl ether, ethyl phenyl ether, butyl phenyl ether, pentyl phenyl ether, methoxytoluene,
  • the electrolyte salt is preferably a lithium salt.
  • the lithium salt include LiClO4 , LiBF4, LiPF6 , LiAlCl4 , LiSbF6 , LiSCN , LiCF3SO3 , LiCF3CO2 , LiAsF6 , LiB10Cl10 , lower aliphatic lithium carboxylate, LiCl, LiBr, LiI, phosphates, borates, and imide salts.
  • the phosphates include lithium difluorophosphate ( LiPO2F2 ) , lithium difluorobis(oxalato ) phosphate (LiDFBOP), and lithium tetrafluoro(oxalato)phosphate.
  • borates examples include lithium bis(oxalato)borate (LiBOB), and lithium difluoro(oxalato)borate (LiDFOB).
  • imide salt lithium bisfluorosulfonylimide (LiN(FSO 2 ) 2 ), lithium bistrifluoromethanesulfonate imide (LiN(CF 3 SO 2 ) 2 ), lithium trifluoromethanesulfonate nonafluorobutanesulfonate imide (LiN(CF 3 SO 2 )(C 4 F 9 SO 2 )), lithium bispentafluoroethanesulfonate imide (LiN(C 2 F 5 SO 2 ) 2 ), etc. are used.
  • the concentration of the lithium salt may be, for example, 4 mol or less per 1 L of nonaqueous solvent, may be 3 mol or less, preferably 1.8 mol or less, and more preferably 0.8 mol or more and 1.8 mol or less.
  • the non-aqueous electrolyte may contain an additive.
  • the additive include unsaturated carbonate esters, acid anhydrides, phenol compounds, benzene compounds, nitrile compounds, isocyanate compounds, sultone compounds, sulfate compounds, borate ester compounds, phosphate ester compounds, and phosphite ester compounds.
  • unsaturated cyclic carbonates examples include vinylene carbonate, 4-methylvinylene carbonate, 4,5-dimethylvinylene carbonate, 4-ethylvinylene carbonate, 4,5-diethylvinylene carbonate, 4-propylvinylene carbonate, 4,5-dipropylvinylene carbonate, 4-phenylvinylene carbonate, 4,5-diphenylvinylene carbonate, vinylethylene carbonate, and divinylethylene carbonate.
  • One type of unsaturated cyclic carbonate may be used alone, or two or more types may be used in combination. In the unsaturated cyclic carbonate, some of the hydrogen atoms may be substituted with fluorine atoms.
  • the acid anhydride may be an anhydride in which multiple carboxylic acid molecules are condensed intermolecularly, but is preferably an acid anhydride of a polycarboxylic acid.
  • acid anhydrides of polycarboxylic acids include succinic anhydride, maleic anhydride, and phthalic anhydride.
  • Phenol compounds include, for example, phenol and hydroxytoluene.
  • Benzene compounds include, for example, fluorobenzene, hexafluorobenzene, and cyclohexylbenzene (CHB).
  • Nitrile compounds include adiponitrile, pimelonitrile, propionitrile, succinonitrile, etc.
  • Isocyanate compounds include methyl isocyanate (MIC), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), bisisocyanatomethylcyclohexane (BIMCH), etc.
  • Sultone compounds include propane sultone, propene sultone, etc.
  • Sulfate compounds include ethylene sulfate, ethylene sulfite, dimethyl sulfate, lithium fluorosulfate, etc.
  • Boron ester compounds include trimethyl borate, tris(trimethylsilyl)borate, etc.
  • Phosphate ester compounds include trimethyl phosphate, tris(trimethylsilyl)phosphate, etc.
  • Phosphite ester compounds include trimethyl phosphite, tris(trimethylsilyl)phosphite, etc.
  • the solid electrolyte for example, a solid or gel-like polymer electrolyte, an inorganic solid electrolyte, etc. can be used.
  • the inorganic solid electrolyte a material known in all-solid-state lithium ion secondary batteries, etc. (for example, an oxide-based solid electrolyte, a sulfide-based solid electrolyte, a halogen-based solid electrolyte, etc.) can be used.
  • the polymer electrolyte includes, for example, a lithium salt and a matrix polymer, or a non-aqueous solvent, a lithium salt, and a matrix polymer.
  • the matrix polymer for example, a polymer material that absorbs a non-aqueous solvent and gels is used.
  • the polymer material for example, a fluororesin, an acrylic resin, a polyether resin, etc. can be used.
  • Nickel-cobalt-aluminum composite hydroxide [ Ni0.90Co0.05Al0.05 ] (OH) 2 ) obtained by the coprecipitation method was baked at 500°C for 8 hours to synthesize a composite oxide containing Ni, Co, and Al.
  • This composite oxide was mixed with LiOH in a molar ratio of 1:1.02, and the mixture was baked at 800°C for 3 hours in an oxygen stream to obtain a lithium transition metal composite oxide.
  • the lithium transition metal composite oxide was in the form of secondary particles formed by agglomeration of primary particles.
  • FT-IR Fourier transform infrared spectroscopy
  • TOF-SIMS time-of-flight secondary ion mass spectrometry
  • the Gini coefficients on the surface and inside of the secondary particles of SO 3- were 0.39 and 0.52, respectively.
  • ICP-AES inductively coupled plasma atomic emission spectrometer
  • 92 parts by mass of the positive electrode active material, 5 parts by mass of acetylene black (AB), and 3 parts by mass of polyvinylidene fluoride (PVDF) were mixed, and an appropriate amount of N-methyl-2-pyrrolidone (NMP) was added to prepare a positive electrode mixture slurry.
  • NMP N-methyl-2-pyrrolidone
  • the positive electrode mixture slurry was applied to both sides of a positive electrode core made of aluminum foil, and after drying the coating, the coating was rolled with a rolling roller and cut to a predetermined electrode size to prepare a positive electrode.
  • an exposed portion in which the surface of the positive electrode core was exposed was provided in a part of the positive electrode.
  • Natural graphite was used as the negative electrode active material.
  • the negative electrode active material sodium carboxymethylcellulose (CMC-Na), styrene-butadiene rubber (SBR), and lithium methanesulfonate were mixed in an aqueous solution at a solid content mass ratio of 100:1:1:0.08 to prepare a negative electrode mixture slurry.
  • the negative electrode mixture slurry was applied to both sides of a negative electrode core made of copper foil, and after drying the coating film, the coating film was rolled with a rolling roller and cut into a predetermined electrode size to prepare a negative electrode.
  • an exposed portion was provided in which the surface of the negative electrode core was exposed in a part of the negative electrode.
  • the content of S in the negative electrode was measured by an ICP atomic emission spectrometer (ICP-AES), and was 250 ppm by mass with respect to the total mass of the negative electrode active material.
  • ICP-AES ICP atomic emission spectrometer
  • a non-aqueous electrolyte was prepared by dissolving lithium hexafluorophosphate (LiPF 6 ) in a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 3:3:4 to a concentration of 1.2 mol/L.
  • LiPF 6 lithium hexafluorophosphate
  • EMC ethyl methyl carbonate
  • DMC dimethyl carbonate
  • a positive electrode lead was attached to the exposed portion of the positive electrode, and a negative electrode lead was attached to the exposed portion of the negative electrode, and the positive and negative electrodes were spirally wound with a polyolefin separator interposed therebetween, and then pressed in the radial direction to produce a flat wound electrode body.
  • This electrode body was housed in an exterior body made of an aluminum laminate sheet, and the nonaqueous electrolyte was injected, and the opening of the exterior body was sealed to obtain a test cell.
  • Example 1-2 A test cell was produced and evaluated in the same manner as in Example 1-1, except that in the preparation of the positive electrode active material, the mixing time of the cake-like composition and the powdered lithium methanesulfonate was changed to 3 minutes.
  • Examples 1-3 to 1-6> In the preparation of the positive electrode active material, a lithium methanesulfonate solution in which lithium methanesulfonate was dissolved in pure water was added instead of powdered lithium methanesulfonate, and the amount of lithium methanesulfonate added and the mixing time of the cake-like composition and the powdered lithium methanesulfonate were changed as shown in Table 1. Test cells were prepared and evaluated in the same manner as in Example 1-1. It was confirmed by Fourier transform infrared spectroscopy (FT-IR) that lithium methanesulfonate was present on the surface of each positive electrode active material.
  • FT-IR Fourier transform infrared spectroscopy
  • Example 1-7 In the addition step of preparing the positive electrode active material, a solution containing methanesulfonic acid and LiOH dissolved in pure water in a molar ratio of 1:1 (hereinafter, methanesulfonic acid + LiOH solution) was added instead of powdered lithium methanesulfonate, and the amount of lithium methanesulfonate added to the total mass of the lithium transition metal composite oxide was 0.5% by mass. Except for this, a test cell was prepared and evaluated in the same manner as in Example 1-1.
  • methanesulfonic acid + LiOH solution a solution containing methanesulfonic acid and LiOH dissolved in pure water in a molar ratio of 1:1
  • the concentration of the added methanesulfonic acid + LiOH solution was 10% by mass, and the methanesulfonic acid + LiOH solution was added so that the amount of lithium methanesulfonate added was as described above. It was confirmed by Fourier transform infrared spectroscopy (FT-IR) that lithium methanesulfonate was present on the surface of the positive electrode active material.
  • FT-IR Fourier transform infrared spectroscopy
  • Example 1-8> In the addition step of preparing the positive electrode active material, a solution containing methanesulfonic acid and LiOH dissolved in pure water in a molar ratio of 1:1 (hereinafter, methanesulfonic acid + LiOH solution) was added instead of powdered lithium methanesulfonate, and the amount of lithium methanesulfonate added to the total mass of the lithium transition metal composite oxide was 0.5% by mass. Except for this, a test cell was prepared and evaluated in the same manner as in Example 1-2.
  • methanesulfonic acid + LiOH solution a solution containing methanesulfonic acid and LiOH dissolved in pure water in a molar ratio of 1:1
  • the concentration of the added methanesulfonic acid + LiOH solution was 10% by mass, and the methanesulfonic acid + LiOH solution was added so that the amount of lithium methanesulfonate added was as described above. It was confirmed by Fourier transform infrared spectroscopy (FT-IR) that lithium methanesulfonate was present on the surface of the positive electrode active material.
  • FT-IR Fourier transform infrared spectroscopy
  • Example 1-9 A test cell was prepared in the same manner as in Example 1-3, and then the initial efficiency was evaluated while carrying out an aging treatment as described below. After the evaluation, 250 ppm of S was detected in the negative electrode contained in the test cell relative to the total mass of the negative electrode active material. [Evaluation of initial efficiency during aging treatment] The test cell was charged at 0.2C for 30 minutes in a temperature environment of 25°C, and then stored at a temperature environment of 60°C for 15 hours. Thereafter, the test cell was charged again at a constant current of 0.2C in a temperature environment of 25°C until the battery voltage reached 4.2V, and then charged at a constant voltage of 4.2V until the current value reached 0.02C.
  • the test cell After standing for 1 hour, the test cell was discharged at a constant current of 0.2C until the battery voltage reached 2.5V.
  • the initial efficiency was calculated from the charge capacity and discharge capacity measured in the above charge and discharge by the following formula.
  • the charge capacity is the sum of the charge capacity when charged at 0.2C for 30 minutes, the charge capacity when charged at 0.2C until 4.2V, and the charge capacity when charged at 4.2V until 0.02C.
  • Initial efficiency discharge capacity / charge capacity
  • Example 1-10> A test cell was prepared in the same manner as in Example 1-4, and then the initial efficiency was evaluated while performing an aging treatment in the same manner as in Example 1-9. After the evaluation, 400 ppm of S was detected in the negative electrode contained in the test cell relative to the total mass of the negative electrode active material.
  • Example 1-1 A test cell was prepared in the same manner as in Example 1-1, except that the cake-like composition and powdered lithium methanesulfonate were not mixed in the preparation of the positive electrode active material, and then the initial efficiency was evaluated while performing an aging treatment in the same manner as in Example 1-9. After the evaluation, 400 ppm of S was detected in the negative electrode contained in the test cell relative to the total mass of the negative electrode active material.
  • Example 1-2 A test cell was produced and evaluated in the same manner as in Example 1-1, except that the cake-like composition and powdered lithium methanesulfonate were not mixed in the preparation of the positive electrode active material.
  • Example 2-1> [Preparation of Positive Electrode Active Material] A nickel-manganese composite hydroxide ([ Ni0.80Mn0.20 ](OH) 2 ) obtained by the coprecipitation method was baked at 500°C for 8 hours to synthesize a composite oxide containing Ni and Mn. This composite oxide was mixed with LiOH in a molar ratio of 1:1.02, and the mixture was baked at 900°C for 10 hours in an oxygen stream to obtain a lithium transition metal composite oxide. The lithium transition metal composite oxide was in the form of single particles.
  • Example 2-1 a positive electrode active material of Example 2-1. It was confirmed by Fourier transform infrared spectroscopy (FT-IR) that lithium methanesulfonate was present on the surface of the positive electrode active material.
  • FT-IR Fourier transform infrared spectroscopy
  • the element concentration distribution in the cross section of the positive electrode active material was measured by time-of-flight secondary ion mass spectrometry (TOF-SIMS), and the Gini coefficient of SO 3- on the surface of the positive electrode active material was 0.39.
  • the positive electrode active material was measured by inductively coupled plasma atomic emission spectrometry (ICP-AES), and the elements shown in Table 2 were confirmed as elements other than Li and O.
  • ICP-AES inductively coupled plasma atomic emission spectrometry
  • a test cell was prepared using the positive electrode active material of Example 2-1 in the same manner as Example 1-1, and an evaluation was performed.
  • Examples 2-2 to 2-4> In the preparation of the positive electrode active material, test cells were prepared and evaluated in the same manner as in Example 2-1, except that the amount of lithium methanesulfonate solution added and the mixing time of the cake-like composition and the lithium methanesulfonate solution were changed as shown in Table 1. It was confirmed by Fourier transform infrared spectroscopy (FT-IR) that lithium methanesulfonate was present on the surface of each positive electrode active material.
  • FT-IR Fourier transform infrared spectroscopy
  • Example 2-1 A test cell was produced and evaluated in the same manner as in Example 2-1, except that in the addition step of producing the positive electrode active material, powdered lithium methanesulfonate was added instead of a lithium methanesulfonate solution in which lithium methanesulfonate was dissolved in pure water, and the cake-like composition and powdered lithium methanesulfonate were not mixed.
  • Tables 1 and 2 The evaluation results of the test cells of the examples and comparative examples are shown in Tables 1 and 2.
  • Table 1 the initial efficiencies of the test cells of Examples 1-1 to 1-10 and Comparative Example 1-1 are expressed relatively to the initial efficiency of the test cell of Comparative Example 1-2, which is set to 100.
  • Table 2 the initial efficiencies of the test cells of Examples 2-1 to 2-4 are expressed relatively to the initial efficiency of the test cell of Comparative Example 2-1, which is set to 100.
  • Tables 1 and 2 also show the Gini coefficients of SO 3- on the surface and inside of the lithium transition metal composite oxide particles, as well as the amount of lithium methanesulfonate added and the mixing time. Note that S was not detected from the negative electrodes of the test cells other than those of Examples 1-9.1-10 and Comparative Example 1-1.
  • the test cells of the examples all have improved initial efficiency compared to the test cells of the corresponding comparative examples. This tendency is particularly noticeable in the test cells that were subjected to aging treatment. Therefore, it can be seen that the initial efficiency is improved by having a sulfonic acid compound present on the particle surface of a specific lithium transition metal oxide and dispersing the sulfonic acid compound uniformly until the Gini coefficient of the depth mapping intensity ratio distribution of SO 3- in TOF-SIMS analysis is 0.7 or less.
  • Configuration 1 A positive electrode active material for a non-aqueous electrolyte secondary battery, comprising a lithium transition metal composite oxide and a sulfonic acid compound present on a surface of the lithium transition metal composite oxide,
  • the lithium transition metal composite oxide has a layered structure and is a secondary particle containing 75 mol % or more of Ni based on the total number of moles of metal elements excluding Li,
  • the positive electrode active material for a non-aqueous electrolyte secondary battery has a Gini coefficient of SO 3 ⁇ on the secondary particle surface of 0.7 or less.
  • a positive electrode active material for a non-aqueous electrolyte secondary battery comprising a lithium transition metal composite oxide and a sulfonic acid compound present on a surface of the lithium transition metal composite oxide,
  • the lithium transition metal composite oxide is a secondary particle having a layered structure and containing 75 mol % or more of Ni based on the total number of moles of metal elements excluding Li,
  • the positive electrode active material for a non-aqueous electrolyte secondary battery has a Gini coefficient of SO 3 ⁇ within the secondary particles of 0.6 or less.
  • Configuration 3 3. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein A is a Group 1 element.
  • Configuration 4 3. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein A is Li.
  • Configuration 5 5. The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein R is an alkyl group.
  • Configuration 6 5. The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein R is a methyl group.
  • Configuration 7 7. The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 6, wherein the amount of the sulfonic acid compound present on the surface of the lithium transition metal composite oxide is 0.1% by mass or more and 1.5% by mass or less, based on the mass of the lithium transition metal composite oxide.
  • Configuration 8 8. A positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 7 , which has an absorption peak in an infrared absorption spectrum at least at one or more positions near 1238 cm -1 , 1175 cm -1 , 1065 cm -1 and 785 cm -1 .
  • Configuration 9 A positive electrode including the positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of configurations 1 to 8, a negative electrode, and a non-aqueous electrolyte; The negative electrode contains S.
  • REFERENCE SIGNS LIST 10 secondary battery 11 positive electrode, 12 negative electrode, 13 separator, 14 electrode body, 16 exterior body, 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

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