WO2025028066A1 - 正極活物質、正極、非水電解質二次電池、および正極活物質の製造方法 - Google Patents

正極活物質、正極、非水電解質二次電池、および正極活物質の製造方法 Download PDF

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WO2025028066A1
WO2025028066A1 PCT/JP2024/022715 JP2024022715W WO2025028066A1 WO 2025028066 A1 WO2025028066 A1 WO 2025028066A1 JP 2024022715 W JP2024022715 W JP 2024022715W WO 2025028066 A1 WO2025028066 A1 WO 2025028066A1
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positive electrode
active material
electrode active
lithium
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French (fr)
Japanese (ja)
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正悟 江崎
浩史 川田
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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 JP2025537727A priority patent/JPWO2025028066A1/ja
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • 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

  • This disclosure relates to a positive electrode active material, a positive electrode, a non-aqueous electrolyte secondary battery, and a method for producing a positive electrode active material.
  • the positive electrode active material has a significant effect on battery performance such as input/output characteristics, capacity, and durability, and therefore has been the subject of much research.
  • lithium transition metal composite oxides containing transition metal elements such as Ni and Mn are used as positive electrode active materials.
  • the type and amount of elements contained in the lithium transition metal composite oxide, as well as the crystal structure of the composite oxide have a significant effect on battery performance, and even slight changes in these physical properties may make it impossible to achieve the desired performance.
  • Patent Documents 1 to 6 disclose improvements to the crystal structure of positive electrode active materials of specific compositions with the aim of improving battery performance such as increasing capacity.
  • Non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries has expanded to include power sources for electric vehicles.
  • the positive electrode active materials in Patent Documents 1 to 6 do not take into consideration achieving both high capacity and excellent charge/discharge cycle characteristics and load characteristics, and there is still room for improvement.
  • a positive electrode active material is a positive electrode active material used in a non-aqueous electrolyte secondary battery, and has a crystal structure belonging to the space group R-3m, and is represented by the composition formula Li x Na y Ni 1-a-b Mn a X b O c , in which X is at least one selected from the group consisting of transition metal elements and typical elements other than Li, Na, Ni, and Mn, and 0.80 ⁇ x ⁇ 1.15, 0 ⁇ y ⁇ 0.20, 0.80 ⁇ x+y ⁇ 1.20, 0 ⁇ 1-a-b ⁇ 1, 0 ⁇ a ⁇ 1, 0 ⁇ b ⁇ 1, and c are values that satisfy electrical neutrality, and in a dQ/dV curve obtained when the non-aqueous electrolyte secondary battery is initially charged, the voltage has a peak in the range of 4.2V or more and 4.4V or less, and the half-width of the peak is 0.11V or less.
  • a method for producing a positive electrode active material is a method for producing a positive electrode active material for use in a non-aqueous electrolyte secondary battery, and includes the steps of: synthesizing a Na composite oxide represented by a composition formula Na e Ni 1-f- g Mn f X g O h (wherein X is at least one element selected from metal elements other than Li, Na, Ni, and Mn, and e ⁇ 1.15, 0 ⁇ 1-f-g ⁇ 1, 0 ⁇ f ⁇ 1, 0 ⁇ g ⁇ 1, and h is a value that satisfies electrical neutrality); and reacting the Na composite oxide with a lithium compound to exchange a portion of Na in the Na composite oxide for Li, wherein the lithium compound includes at least one selected from the group consisting of lithium hydroxide, lithium carbonate, and lithium hydrogen carbonate.
  • the positive electrode of one aspect of the present disclosure is characterized by including the above-mentioned positive electrode active material.
  • the nonaqueous electrolyte secondary battery which is one aspect of the present disclosure, is characterized by having the above-mentioned positive electrode, a negative electrode, and a nonaqueous electrolyte.
  • the positive electrode active material disclosed herein can improve the battery capacity, charge/discharge cycle characteristics, and load characteristics of non-aqueous electrolyte secondary batteries.
  • FIG. 1 is an axial cross-sectional view of a nonaqueous electrolyte secondary battery according to an embodiment of the present invention
  • FIG. 2 is a graph showing initial charge/discharge curves of nonaqueous electrolyte secondary batteries using the positive electrode active materials produced in the examples and comparative examples.
  • FIG. 4 is a graph showing dQ/dV curves of nonaqueous electrolyte secondary batteries using the positive electrode active materials produced in the examples and comparative examples.
  • a positive electrode active material represented by the composition formula Li x Na y Ni 1-a-b Mn a X b O c (wherein X is at least one selected from the group consisting of transition metal elements and typical elements other than Li, Na, Ni, and Mn, and 0.80 ⁇ x ⁇ 1.15, 0 ⁇ y ⁇ 0.20, 0.80 ⁇ x+y ⁇ 1.20, 0 ⁇ 1-a-b ⁇ 1, 0 ⁇ a ⁇ 1, 0 ⁇ b ⁇ 1, and c is a value that satisfies electrical neutrality) in the positive electrode, there is a relationship between the peak of the dQ/dV curve obtained at the time of the initial charge and the battery capacity.
  • a high capacity battery can be realized by having a peak in the voltage range of 4.2 V or more and 4.4 V or less in the dQ/dV curve obtained when the non-aqueous electrolyte secondary battery is initially charged. This is because, when the dQ/dV curve has a peak in the voltage range of 4.2 V or more and 4.4 V or less, a plateau region appears in the initial charge/discharge curve in which there is almost no change in voltage with respect to a certain change in capacity, as shown in Figure 2 in the Examples described later.
  • dQ/dV curve refers to a graph in which the horizontal axis indicates voltage and the vertical axis indicates dQ/dV, which is the value obtained by differentiating the battery capacity with respect to the voltage, during the initial charge of a nonaqueous electrolyte secondary battery.
  • a cylindrical battery in which a wound electrode body 14 is housed in a cylindrical exterior body 16 with a bottom is exemplified as a nonaqueous electrolyte secondary battery, but the exterior body of the battery is not limited to a cylindrical exterior body.
  • the nonaqueous electrolyte secondary battery according to the present disclosure may be, for example, a prismatic battery with a prismatic exterior body, a coin battery with a coin-shaped exterior body, or a pouch-type battery with an exterior body composed of a laminate sheet including a metal layer and a resin layer.
  • the electrode body is not limited to a wound type, and may be a laminated type electrode body in which multiple positive electrodes and multiple negative electrodes are alternately stacked with separators interposed therebetween.
  • the design of the nonaqueous electrolyte secondary battery according to the present disclosure is not limited to the design of the exemplified nonaqueous electrolyte secondary battery, and a known nonaqueous electrolyte secondary battery design may be applied.
  • the nonaqueous electrolyte secondary battery 10 includes a wound electrode body 14, a nonaqueous electrolyte, and an exterior body 16 that contains the electrode body 14 and the nonaqueous 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 that constitute the electrode body 14 are all rectangular, elongated bodies that are spirally wound in the longitudinal direction and stacked alternately 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 two separators 13 are arranged, for example, to sandwich the positive electrode 11.
  • 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 transverse direction of the positive electrode 11 and the negative electrode 12 is the axial direction. That is, the transverse 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 a positive electrode core and a positive electrode mixture layer disposed on the positive electrode core.
  • a foil of a metal such as aluminum, an aluminum alloy, stainless steel, or titanium that is stable in the potential range of the positive electrode 11, or a film having such a metal disposed on the surface layer can be used.
  • the positive electrode mixture layer preferably contains a positive electrode active material, a conductive agent, and a binder, and is provided on both sides of the positive electrode core.
  • the positive electrode 11 can be produced, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, and a binder onto the positive electrode core, drying the coating, and then compressing it to form a positive electrode mixture layer on both sides of the positive electrode core.
  • Examples of the conductive agent contained in the positive electrode mixture layer include carbon black such as acetylene black and ketjen black, graphite, carbon nanotubes (CNT), carbon nanofibers, graphene, metal fibers, metal powders, conductive whiskers, etc.
  • the conductive agent may be used alone or in combination with multiple types.
  • the content of the conductive agent is not particularly limited, but is, for example, 0.1% by mass or more and 5% by mass or less with respect to the mass of the positive electrode mixture layer.
  • binder contained in the positive electrode mixture layer examples include fluorine-containing resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), olefin resins such as polyethylene, polypropylene, ethylene-propylene-isoprene copolymer, and ethylene-propylene-butadiene copolymer, and acrylic resins such as polyacrylonitrile (PAN), polyimide, polyamide, and ethylene-acrylic acid copolymer. These resins may also be used in combination with carboxymethylcellulose (CMC) or a salt thereof, polyethylene oxide (PEO), and the like.
  • CMC carboxymethylcellulose
  • PEO polyethylene oxide
  • One type of binder may be used alone, or multiple types may be used in combination.
  • the content of the binder is not particularly limited, but is, for example, 0.1% by mass or more and 5% by mass or less with respect to the mass of the positive electrode mixture layer.
  • the positive electrode active material is a lithium sodium transition metal composite oxide (hereinafter referred to as "Li-Na composite oxide”) that includes a crystal structure belonging to the space group R-3m and is represented by the composition formula Li x Na y Ni 1-a-b Mn a X b O c .
  • X is at least one selected from the group consisting of transition metal elements and typical elements other than Li, Na, Ni, and Mn, and 0.80 ⁇ x ⁇ 1.15, 0 ⁇ y ⁇ 0.20, 0.80 ⁇ x+y ⁇ 1.20, 0 ⁇ 1-a-b ⁇ 1, 0 ⁇ a ⁇ 1, 0 ⁇ b ⁇ 1, and c is a value that satisfies electrical neutrality.
  • the composite oxide that constitutes the positive electrode active material contains Li, Na, and Ni as essential elements, and preferably further contains Mn.
  • the contents of Li, Na, Ni, Mn and X contained in the positive electrode active material can be measured using an ICP emission spectrometer (for example, CIROS-120 manufactured by SPECTRO).
  • the molar ratio of Na (y) may be more than 0 and less than 0.2 (0 ⁇ y ⁇ 0.2), but is preferably 0.02 or more, more preferably 0.05 or more, and even more preferably 0.08 or more.
  • the molar ratio of Na (y) is 0.02 ⁇ y ⁇ 0.2, or 0.05 ⁇ y ⁇ 0.2, or 0.08 ⁇ y ⁇ 0.2, the half-width of the peak in the voltage range of 4.2V or more and 4.4V or less in the dQ/dV curve obtained upon initial charging becomes small. As a result, it becomes easy to achieve both excellent charge/discharge cycle characteristics and load characteristics while realizing high capacity.
  • the molar ratio (y) of Na is preferably 0.15 or less, more preferably 0.14 or less, and even more preferably 0.13 or less.
  • the molar ratio (y) of Na is 0 ⁇ y ⁇ 0.15, or 0 ⁇ y ⁇ 0.14, or 0 ⁇ y ⁇ 0.13, it is considered that the layered structure of the complex oxide is stabilized, and the improvement effect of the charge/discharge capacity and the initial charge/discharge efficiency becomes more remarkable.
  • the molar ratio (y) of Na exceeds 0.2, Na ions are extracted to the positive electrode during charging, and the extracted Na ions may be occluded in the negative electrode.
  • an example of a suitable range for the molar ratio (y) of Na is 0.02 ⁇ y ⁇ 0.15, or 0.05 ⁇ y ⁇ 0.14, or 0.06 ⁇ y ⁇ 0.13.
  • the molar ratio of Li (x) may be 0.80 or more and 1.15 or less (0.80 ⁇ x ⁇ 1.15), but is preferably 0.82 or more, more preferably 0.84 or more.
  • the upper limit of the molar ratio of Li (x) is preferably 1.00, more preferably 0.95.
  • An example of a suitable range of the molar ratio of Li (x) is 0.80 ⁇ x ⁇ 1.00, 0.80 ⁇ x ⁇ 0.95, 0.82 ⁇ x ⁇ 1.15, 0.82 ⁇ x ⁇ 1.00, 0.82 ⁇ x ⁇ 0.95, 0.84 ⁇ x ⁇ 1.15, 0.84 ⁇ x ⁇ 1.00, or 0.84 ⁇ x ⁇ 0.95.
  • the molar ratio (x) of Li is within this range, the effects of improving the charge/discharge capacity and the initial charge/discharge efficiency become more significant.
  • the total molar ratio of Li and Na (x+y) may be more than 0.80 and 1.20 or less (0.80 ⁇ x+y ⁇ 1.20), but is preferably 0.85 or more, more preferably 0.90 or more, and even more preferably 0.95 or more.
  • the upper limit of the total molar ratio of Li and Na (x+y) is preferably 1.10, more preferably 1.05.
  • An example of a suitable range of the total molar ratio (x+y) of Li and Na is 0.80 ⁇ x+y ⁇ 1.10, 0.80 ⁇ x+y ⁇ 1.05, 0.85 ⁇ x+y ⁇ 1.20, 0.85 ⁇ x+y ⁇ 1.10, 0.85 ⁇ x+y ⁇ 1.05, 0.90 ⁇ x+y ⁇ 1.20, 0.90 ⁇ x+y ⁇ 1.10, 0.90 ⁇ x+y ⁇ 1.05, 0.95 ⁇ x+y ⁇ 1.20, 0.95 ⁇ x+y ⁇ 1.10, or 0.95 ⁇ x+y ⁇ 1.05. If the total molar ratio (x+y) of Li and Na is within this range, the improvement effect of the charge/discharge capacity and the initial charge/discharge efficiency becomes more remarkable.
  • the molar ratio of Ni (1-a-b) may be 1 or less (0 ⁇ 1-a-b ⁇ 1), but is preferably 0.82 or less, more preferably 0.70 or less.
  • the molar ratio of Ni (1-a-b) is preferably 0.30 or more, more preferably 0.40 or more. Therefore, an example of a suitable range of the molar ratio of Ni (1-a-b) is 0.30 ⁇ 1-a-b ⁇ 0.82, or 0.40 ⁇ 1-a-b ⁇ 0.70. In this case, the improvement effect of the charge-discharge capacity and the initial charge-discharge efficiency becomes more remarkable.
  • the positive electrode active material preferably contains Mn.
  • the molar ratio (a) of Mn is preferably 0.75 or less, more preferably 0.65 or less.
  • the molar ratio (a) of Mn is preferably 0.20 or more, more preferably 0.25 or more.
  • An example of a suitable range of the molar ratio (a) of Mn is 0.20 ⁇ a ⁇ 0.75, or 0.25 ⁇ a ⁇ 0.65. In this case, the improvement effect of the charge/discharge capacity and the initial charge/discharge efficiency becomes more remarkable.
  • X may be at least one element selected from Mg, Ca, Sr, Ba, Sn, Ti, Si, V, Cr, Fe, Cu, Zn, Bi, Sb, B, Ga, In, P, Zr, Hf, Nb, Ta, Mo, W, Co, and Al.
  • the molar ratio (b) of X is preferably 0.10 or less (0 ⁇ b ⁇ 0.10), more preferably 0.08 or less (0 ⁇ b ⁇ 0.08), and even more preferably 0.05 or less (0 ⁇ b ⁇ 0.05).
  • X is preferably at least one selected from Al, Co, and Zr, and among them, Al or Co is preferable.
  • Al is contained in the positive electrode active material
  • an example of a suitable range of the molar ratio (b) of Al is 0.005 ⁇ b ⁇ 0.025.
  • Co is contained in the positive electrode active material
  • an example of a suitable range of the molar ratio (b) of Co is 0.005 ⁇ b ⁇ 0.1.
  • the molar ratio of O (c) is a value that satisfies electrical neutrality.
  • the molar ratio of O (c) is a value that satisfies the valence of O in the positive electrode active material.
  • the layered rock salt structure has a structure in which oxygen is deficient.
  • the layered rock salt structure has an excess of oxygen.
  • the electron conductivity of the positive electrode active material is improved by oxygen deficiency, but if the oxygen deficiency increases, the crystal structure belonging to the space group R-3m cannot be maintained, which is thought to cause a decrease in charge/discharge capacity and cycle characteristics.
  • the electron conductivity of the positive electrode active material is improved by the presence of oxygen between the lattices, but if the amount of excess oxygen increases, the valence of Ni and Mn in the positive electrode active material increases, and it is thought that the charge capacity is greatly reduced. Therefore, for example, when the sum of the molar ratios of Ni, Mn, and X is 1, the molar ratio (c) of O is preferably 1.8 or more and 2.3 or less, more preferably 1.85 or more and 2.25 or less.
  • the oxygen amount of the positive electrode active material can be measured using an oxygen/nitrogen analyzer (e.g., EMGA-920 manufactured by Horiba, Ltd.).
  • the Li-Na composite oxide is, for example, a secondary particle formed by agglomeration of a plurality of primary particles.
  • An example of the volume-based median diameter (D50) of the Li-Na composite oxide is 1 ⁇ m or more and 30 ⁇ m or less, or 3 ⁇ m or more and 20 ⁇ m or less.
  • the D50 of the composite oxide is a particle size at which the volume integrated value is 50% in the particle size distribution measured by the laser diffraction scattering method.
  • the BET specific surface area of the Li-Na composite oxide is, for example, 0.1 m 2 /g or more and 10 m 2 /g or less, or 0.5 m 2 /g or more and 5 m 2 /g or less.
  • the BET specific surface area of the composite oxide is measured according to the BET method (nitrogen adsorption method) described in JIS R1626. If the D50 and the BET specific surface area are within the range, it is easy to increase the capacity.
  • the positive electrode active material is mainly composed of the Li-Na composite oxide.
  • the main component means the component with the highest mass ratio among the components of the positive electrode active material.
  • the mixture layer of the positive electrode 11 may contain a composite oxide other than the Li-Na composite oxide as the positive electrode active material, but the content of the Li-Na composite oxide is preferably 50 mass% or more, and may be substantially 100 mass%.
  • a non-aqueous electrolyte secondary battery using the above Li-Na composite oxide as the positive electrode active material has a peak in the voltage range of 4.2 V or more and 4.4 V or less in the dQ/dV curve obtained upon initial charging, and the half-value width of the peak is 0.11 V or less.
  • the non-aqueous electrolyte secondary battery when the non-aqueous electrolyte secondary battery is initially charged refers to the case where the non-aqueous electrolyte secondary battery is initially charged, the non-aqueous electrolyte secondary battery being composed of a positive electrode containing a positive electrode active material made of Li-Na composite oxide, a negative electrode made of lithium metal foil, and a non-aqueous electrolyte, and the specific conditions are as described in the examples described later.
  • FIG. 2 and 3 show the initial charge/discharge curves and the dQ/dV curves obtained upon initial charging of a nonaqueous electrolyte secondary battery using the Li—Na composite oxide of this embodiment as the positive electrode active material.
  • Fig. 2 and Fig. 3 show the initial charge/discharge curves and the dQ/dV curves of a nonaqueous electrolyte secondary battery using the composite oxides synthesized in Example 1, Comparative Example 1, and Comparative Example 2 described below as the positive electrode active material.
  • Example 1 is represented by the composition formula Li0.851Na0.123Ni0.505Mn0.495O1.804
  • the composite oxides of Comparative Examples 1 and 2 are represented by the composition formula Li0.938Na0.0229Ni0.505Mn0.495O1.935 and Li1.00Ni0.500Mn0.500O2.000 , respectively .
  • the dQ/dV curve of the nonaqueous electrolyte secondary battery of Example 1 shows a convex peak at about 4.31 V.
  • the initial charge/discharge curve of the nonaqueous electrolyte secondary battery of Example 1 shows a plateau region at about 4.316 V where there is almost no change in voltage with respect to a certain change in capacity.
  • the half-width of the peak in the range of 4.2V or more and 4.4V or less may be 0.11V or less, but is preferably 0.08V or less, more preferably 0.06V or less, and even more preferably 0.04V or less. When the half-width is 0.08V or less, or 0.06V or less, or 0.04V or less, the effect of improving the charge/discharge cycle characteristics and the load characteristics is more significant.
  • the lower limit of the half-width of the peak in the range of 4.2V or more and 4.4V or less is not particularly limited, but is preferably 0.001V or more, and more preferably 0.005V. In this case, the effect of improving the charge/discharge cycle characteristics and the load characteristics is more significant.
  • the intensity of the peak appearing in the range of 4.2V or more and 4.4V or less is preferably greater than the intensity of the peak appearing in other ranges.
  • the intensity of the peak appearing in the range of 4.2V or more and 4.4V or less is maximum in the charge/discharge voltage range of 3V or more and 4.5V or less.
  • a peak (first peak) near 4.3V, a peak (second peak) near 3.8V, and a peak (third peak) near 3.7V appear.
  • the intensity of the first peak is I1
  • the intensity of the second peak is I2
  • the intensity of the third peak is I3
  • I1 > I2 and I1 > I3 it is preferable to satisfy I1 > I2 and I1 > I3 . In this case, the improvement effect of the charge/discharge cycle characteristics and the load characteristics is more remarkable.
  • the positive electrode active material which is an example of an embodiment, can be manufactured by the following method. Note that the manufacturing method described here is only one example, and the manufacturing method of the positive electrode active material is not limited to this method.
  • the Li-Na composite oxide is produced through a process of (1) mixing and calcining a sodium raw material and a nickel raw material to synthesize a Na composite oxide, and (2) reacting the Na composite oxide with a lithium compound to exchange a part of the Na in the Na composite oxide for Li.
  • a manganese raw material it is preferable to further add a manganese raw material, and a raw material containing an element X may be added, and a Na composite oxide is synthesized that is represented by the composition formula Na e Ni 1-f-g Mn f X g O h , where X is at least one element selected from metal elements other than Li, Na, Ni, and Mn, and e ⁇ 1.15, 0 ⁇ 1-f-g ⁇ 1, 0 ⁇ f ⁇ 1, 0 ⁇ g ⁇ 1, and h is a value that satisfies electrical neutrality.
  • the sodium raw material is at least one selected from the group consisting of metallic sodium and sodium compounds.
  • the sodium compound is not particularly limited as long as it contains Na, and examples thereof include acetates such as CH 3 COONa and CH 3 COONa.3H 2 O, nitrates such as NaNO 3 , sulfates such as Na 2 SO 4 , carbonates such as Na 2 CO 3 , hydrogen carbonates such as NaHCO 3 , hydroxides such as NaOH, and oxides such as Na 2 O and Na 2 O 2.
  • Na 2 CO 3 , NaHCO 3 , NaOH, and NaNO 3 are preferred.
  • the nickel raw material is at least one selected from the group consisting of metallic nickel and nickel compounds.
  • the nickel compound is not particularly limited as long as it contains Ni, and examples thereof include oxides such as NiO, hydroxides such as Ni(OH) 2 and NiOOH, nitrates such as NiNO 3 , carbonates such as NiCO 3 and Ni 4 CO 3 (OH) 6 (H 2 O) 4 , and sulfates such as NiSO 4. Among them, Ni(OH) 2 is preferred.
  • the manganese raw material is at least one selected from the group consisting of metallic manganese and manganese compounds.
  • the manganese compound is not particularly limited as long as it contains Mn, and examples thereof include oxides such as MnO, Mn2O3 , Mn3O4 , and MnO2, hydroxides such as Mn(OH) 2 and MnOOH, carbonates such as MnCO3 , nitrates such as Mn ( NO3 ) 2 , and sulfates such as MnSO4 .
  • Mn(OH) 2 is preferred.
  • the raw material containing element X at least one selected from the group consisting of element X and compounds of element X is used.
  • the compound containing element X is not particularly limited as long as it contains X, and examples thereof include oxides, hydroxides, carbonates, nitrates, and sulfates. Note that as the raw material for the Na composite oxide, a compound containing Ni and Mn, a compound containing Ni and X, a compound containing Mn and X, or a compound containing Ni, Mn, and X may be used.
  • the mixing ratio of the raw materials for the Na complex oxide may be set appropriately and is not particularly limited.
  • the molar ratio of Na in the mixture of raw materials for the Na complex oxide is e
  • the molar ratio of Ni is 1-f-g
  • the molar ratio of Mn is f
  • the molar ratio of element X is g
  • the ratios are set so that 0.90 ⁇ e ⁇ 1.15, 0.4 ⁇ 1-f-g ⁇ 0.82, 0.25 ⁇ f ⁇ 0.65, and 0.005 ⁇ g ⁇ 0.05.
  • the method for mixing the raw materials is not particularly limited as long as it can mix the raw materials uniformly, and mixing using a known mixer such as a mixer is an example.
  • the mixture of the raw materials is fired in a firing furnace in the air or in an oxygen stream.
  • the firing temperature is preferably 700°C or higher and 900°C or lower, and more preferably 750°C or higher and 850°C or lower.
  • the heating rate is preferably slow, for example, 0.3°C/min or higher and 5.0°C/min or lower, or 0.5°C/min or higher and 3.0°C/min or lower.
  • the firing time is preferably 20 hours or longer.
  • the firing time means the time from when the temperature of the firing furnace reaches the firing temperature to when the firing ends and cooling begins.
  • the fired product is, for example, rapidly cooled in the air by being removed from the firing furnace.
  • step (2) a part of the Na in the Na composite oxide is exchanged with Li. That is, it is necessary to exchange Li so that a predetermined amount of Na remains.
  • a suitable method of exchanging Na with Li includes a method of adding a molten salt of a lithium compound (hereinafter referred to as "lithium molten salt") to the Na composite oxide and heating it.
  • lithium hydroxide for example, at least one selected from the group consisting of lithium hydroxide, lithium carbonate, lithium hydrogen carbonate, lithium nitrate, lithium sulfate, lithium chloride, lithium iodide, and lithium bromide is used as the lithium molten salt, but it is preferable to use at least one selected from the group consisting of lithium hydroxide, lithium carbonate, and lithium hydrogen carbonate, and it is more preferable to use lithium hydroxide.
  • lithium hydroxide may be anhydrous or hydrated.
  • the molar ratio of lithium hydroxide to the total moles of the lithium molten salt is preferably 5 mol% or more, more preferably 25 mol% or more, even more preferably 50 mol% or more, and even more preferably 75 mol% or more.
  • the lithium molten salt may essentially be composed of only lithium hydroxide.
  • the mixing ratio of the Na composite oxide and the lithium molten salt can be set appropriately.
  • the mixing ratio of the Na composite oxide and the lithium molten salt is preferably such that the molar ratio (Li/Na) of Li in the lithium molten salt to Na in the Na composite oxide is 0.9 or more, more preferably 1.0 or more, and even more preferably 1.5 or more.
  • (Li/Na) is preferably 15 or less, preferably 10 or less, and even more preferably 8 or less.
  • the mixing ratio of the Na composite oxide and the lithium molten salt is preferably such that (Li/Na) is 0.9 or more and 15 or less, more preferably 1.0 or more and 10 or less, and even more preferably 1.5 or more and 8 or less.
  • the heating temperature in the Li exchange process is preferably 200°C or higher and 400°C or lower, and more preferably 250°C or higher and 350°C or lower. If the heating temperature exceeds 400°C, the reaction may proceed too rapidly, resulting in a non-uniform reaction. On the other hand, if the heating temperature is lower than 200°C, the reaction may not proceed sufficiently, and excess Na may remain.
  • the heating treatment time is set to 3 hours or higher and 10 hours or lower, for example, after the desired heating treatment temperature is reached by increasing the temperature at a rate of 3.0°C/min or higher and 8.0°C/min or lower. After the heating treatment, the material is cooled.
  • the cooling method is not particularly limited, and may be, for example, natural cooling (cooling in a furnace).
  • the resulting product is thoroughly washed with water, ethanol, or methanol, and then dried to obtain Li-Na composite oxide.
  • the atmosphere for drying after washing is either air or vacuum, and is not particularly limited. After washing, another heating treatment or another washing treatment may also be performed.
  • 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 precipitated on the surface of the negative electrode core by charging.
  • the negative electrode 12 has a negative electrode mixture layer, 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
  • a porous sheet having ion permeability and insulating properties is used for the separator 13.
  • the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric.
  • the material of the separator 13 is preferably a polyolefin such as polyethylene or polypropylene, or cellulose.
  • the separator 13 may have a single layer structure or a multi-layer structure.
  • a highly heat-resistant resin layer such as an aramid resin may be formed on the surface of the separator 13.
  • a filler layer containing an inorganic filler may be formed at the interface between the separator 13 and at least one of the positive electrode 11 and the negative electrode 12.
  • inorganic fillers include oxides and phosphate compounds containing metal elements such as Ti, Al, Si, and Mg.
  • the filler layer can be formed by applying a slurry containing the filler to the surface of the positive electrode 11, the negative electrode 12, or the separator 13.
  • Non-aqueous electrolyte has ion conductivity (for example, lithium ion conductivity).
  • the non-aqueous electrolyte may be a liquid electrolyte (electrolytic solution) or a solid electrolyte.
  • the liquid electrolyte contains, for example, a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent.
  • the non-aqueous solvent examples include esters, ethers, nitriles such as acetonitrile, amides such as dimethylformamide, and mixed solvents of two or more of these.
  • the non-aqueous solvent may contain a halogen-substituted product in which at least a portion of the hydrogen of these solvents is replaced with a halogen atom such as fluorine.
  • halogen-substituted product examples include fluorinated cyclic carbonates such as fluoroethylene carbonate (FEC), fluorinated chain carbonates, and fluorinated chain carboxylates such as methyl fluoropropionate (FMP).
  • FEC fluoroethylene carbonate
  • FMP fluorinated chain carboxylates
  • FEC fluoroethylene carbonate
  • FMP fluorinated chain carboxylates
  • esters examples include cyclic carbonate esters such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate; chain carbonate esters such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl propyl carbonate, ethyl propyl carbonate, and methyl isopropyl carbonate; cyclic carboxylate esters such as gamma-butyrolactone (GBL) and gamma-valerolactone (GVL); and chain carboxylate esters such as methyl acetate, ethyl acetate, propyl acetate, methyl propionate (MP), and ethyl propionate (EP).
  • cyclic carbonate esters such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate
  • chain carbonate esters such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC
  • ethers examples include 1,3-dioxolane, 4-methyl-1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, propylene oxide, 1,2-butylene oxide, 1,3-dioxane, 1,4-dioxane, 1,3,5-trioxane, furan, 2-methylfuran, 1,8-cineole, cyclic ethers such as crown ethers, 1,2-dimethoxyethane ethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, dihexyl ether, ethyl vinyl ether, butyl vinyl ether, methyl phenyl ether, Examples of such chain ethers include ethyl phenyl ether, ethyl phenyl ether, butyl phenyl ether, pentyl phenyl ether, methoxytoluene,
  • the electrolyte salt 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).
  • 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.
  • Li-Na composite oxide was analyzed using an ICP optical emission spectrometer (CIROS-120 manufactured by SPECTRO) and an oxygen/nitrogen analyzer (EMGA-920 manufactured by HORIBA, Ltd. ), and it was confirmed that the Li-Na composite oxide was represented by the composition formula Li0.851Na0.123Ni0.505Mn0.495O1.804 .
  • the Li-Na composite oxide was used as the positive electrode active material.
  • the positive electrode active material, acetylene black, and polyvinylidene fluoride were mixed in a solid content mass ratio of 92:5:3, and N-methyl-2-pyrrolidone (NMP) was used as a dispersion medium to prepare a positive electrode mixture slurry.
  • NMP N-methyl-2-pyrrolidone
  • This positive electrode slurry was applied onto a positive electrode core made of aluminum foil, and after drying the coating, the coating was rolled with a rolling roller to obtain a positive electrode in which a positive electrode mixture layer was formed on the positive electrode core.
  • a non-aqueous electrolyte was prepared by dissolving lithium hexafluorophosphate (LiPF 6 ) in a mixed solvent prepared by mixing fluoroethylene carbonate (FEC) and methyl propionate (FMP) in a volume ratio of 1:3 to a concentration of 1 mol/L.
  • LiPF 6 lithium hexafluorophosphate
  • FEC fluoroethylene carbonate
  • FMP methyl propionate
  • test cell A lithium metal foil was used as the negative electrode, and the positive and negative electrodes were arranged to face each other with a separator interposed therebetween to form an electrode assembly.
  • This electrode assembly and the nonaqueous electrolyte were placed in a coin-shaped outer can, and the opening of the outer can was sealed with a gasket and a sealer to prepare a test cell (nonaqueous electrolyte secondary battery).
  • test cell was charged at a constant current of 0.2 C at 25° C. until the battery voltage reached 4.5 V, and then charged at a constant voltage of 4.5 V until the current value reached 0.02 C, and the charge capacity was determined. After a 20-minute break, the test cell was discharged at a constant current of 0.2 C until the battery voltage reached 2.5 V, and the discharge capacity was determined.
  • Figure 2 shows the initial charge/discharge curve of the test cell of Example 1
  • Figure 3 shows the dQ/dV curve during the initial charge/discharge of the test cell of Example 1.
  • the test cell prepared in Example 1 exhibits a plateau region with almost no voltage change near 4.316 V.
  • the test cell prepared in Example 1 exhibits a peak with a half-width of 0.026 V in the range of 4.2 V to 4.4 V in the dQ/dV curve.
  • the battery was charged at a constant current of 0.2 C until the battery voltage reached 4.5 V, and then was charged at a constant voltage of 4.5 V until the current value reached 0.02 C.
  • the battery was then discharged at a constant current of 0.2 C until the battery voltage reached 2.5 V, and the 0.2 C discharge capacity was measured.
  • Example 2 In the preparation of the positive electrode active material, a test cell was prepared and evaluated in the same manner as in Example 1, except that the lithium molten salt was changed. More specifically, in the preparation of the positive electrode active material, a lithium molten salt was used prepared by mixing lithium hydroxide, lithium nitrate, and lithium chloride in a molar ratio of 75:22:3. The composition formula of the Li-Na composite oxide prepared in Example 2 was Li 0.857 Na 0.114 Ni 0.505 Mn 0.495 O 1.926 . In the test cell prepared in Example 2, a plateau region appeared near 4.316 V in the charge/discharge curve. In addition, in the test cell prepared in Example 2, a peak with a half-width of 0.028 V was observed in the range of 4.2 V or more and 4.4 V or less in the dQ/dV curve.
  • Example 3 In the preparation of the positive electrode active material, a test cell was prepared and evaluated in the same manner as in Example 1, except that the lithium molten salt was changed. More specifically, in the preparation of the positive electrode active material, a lithium molten salt was used prepared by mixing lithium hydroxide, lithium nitrate, and lithium chloride in a molar ratio of 50:44:6. The composition formula of the Li-Na composite oxide prepared in Example 3 was Li 0.875 Na 0.100 Ni 0.505 Mn 0.495 O 1.926 . In the test cell prepared in Example 3, a plateau region appeared near 4.320 V in the charge/discharge curve. In addition, in the test cell prepared in Example 3, a peak with a half-width of 0.025 V was observed in the range of 4.2 V or more and 4.4 V or less in the dQ/dV curve.
  • Example 4 In the preparation of the positive electrode active material, a test cell was prepared and evaluated in the same manner as in Example 1, except that the lithium molten salt was changed. More specifically, in the preparation of the positive electrode active material, a lithium molten salt was used prepared by mixing lithium hydroxide, lithium nitrate, and lithium chloride in a molar ratio of 25:66:9. The composition formula of the Li-Na composite oxide prepared in Example 4 was Li 0.882 Na 0.0831 Ni 0.506 Mn 0.494 O 1.837 . In the test cell prepared in Example 4, a plateau region appeared near 4.326 V in the charge/discharge curve. In addition, in the test cell prepared in Example 4, a peak with a half-width of 0.027 V was observed in the range of 4.2 V or more and 4.4 V or less in the dQ/dV curve.
  • Example 5 In the preparation of the positive electrode active material, the heating temperature of the lithium molten salt and the Na composite oxide was changed from 280 ° C. to 350 ° C., except that the test cell was prepared and evaluated in the same manner as in Example 1.
  • the composition formula of the Li-Na composite oxide prepared in Example 5 was Li 0.901 Na 0.0890 Ni 0.506 Mn 0.494 O 1.930 .
  • a plateau region appeared near 4.321 V in the charge/discharge curve.
  • a peak with a half-width of 0.028 V was observed in the range of 4.2 V or more and 4.4 V or less in the dQ/dV curve.
  • Example 6 In the preparation of the positive electrode active material, the heating temperature of the lithium molten salt and the Na composite oxide was changed from 280 ° C. to 350 ° C., except that the test cell was prepared and evaluated in the same manner as in Example 2.
  • the composition formula of the Li-Na composite oxide prepared in Example 6 was Li 0.897 Na 0.0861 Ni 0.505 Mn 0.495 O 1.859 .
  • a plateau region appeared near 4.321 V in the charge/discharge curve.
  • a peak with a half-width of 0.029 V was observed in the range of 4.2 V or more and 4.4 V or less in the dQ/dV curve.
  • Example 7 In the preparation of the positive electrode active material, the heating temperature of the lithium molten salt and the Na composite oxide was changed from 280 ° C. to 350 ° C., except that the test cell was prepared and evaluated in the same manner as in Example 3.
  • the composition formula of the Li-Na composite oxide prepared in Example 7 was Li 0.914 Na 0.0735 Ni 0.504 Mn 0.496 O 1.929 .
  • a plateau region appeared near 4.326 V in the charge/discharge curve.
  • a peak with a half-width of 0.035 V was observed in the range of 4.2 V or more and 4.4 V or less in the dQ/dV curve.
  • Example 8 In the preparation of the positive electrode active material, the heating temperature of the lithium molten salt and the Na composite oxide was changed from 280 ° C. to 350 ° C., except that the test cell was prepared and evaluated in the same manner as in Example 4.
  • the composition formula of the Li-Na composite oxide prepared in Example 8 was Li 0.915 Na 0.0652 Ni 0.506 Mn 0.494 O 1.861 .
  • a plateau region appeared near 4.331 V in the charge/discharge curve.
  • a peak with a half-width of 0.041 V was observed in the range of 4.2 V or more and 4.4 V or less in the dQ/dV curve.
  • the composition formula of the Li-Na composite oxide prepared in Comparative Example 1 was Li 0.938 Na 0.0229 Ni 0.505 Mn 0.495 O 1.935 .
  • FIG. 2 shows the initial charge/discharge curve of the test cell of Comparative Example 1, and FIG.
  • FIG. 3 shows the dQ/dV curve at the time of the initial charge/discharge of the test cell of Comparative Example 1.
  • a plateau region with almost no change in voltage is generated near 4.376 V.
  • the length of the plateau region is shorter than the length of the plateau region of Example 1.
  • a peak with a half-width of 0.115 V appears in the range of 4.2 V or more and 4.4 V or less.
  • FIG. 2 shows the initial charge/discharge curve of the test cell of Comparative Example 2
  • FIG. 3 shows the dQ / dV curve at the time of the initial charge/discharge of the test cell of Comparative Example 2.
  • the plateau region is not expressed in the initial charge/discharge curve of the test cell of Comparative Example 2.
  • no peak appears in the range of 4.2 V or more and 4.4 V or less.
  • Table 1 shows the charge capacity, discharge capacity, first load characteristic, second load characteristic, and capacity retention rate of the test cells of Examples 1 to 8 and Comparative Examples 1 and 2.
  • Table 1 also shows the composition of the composite oxide, the type of lithium molten salt, the potential at which the plateau region appears (plateau potential), the presence or absence of a peak in the range of 4.2 V or more and 4.4 V or less, and the half-value width of the peak.
  • the test cells of Examples 1 to 8 have improved capacity retention and load characteristics while realizing higher capacity compared to the test cells of Comparative Examples 1 and 2.
  • a positive electrode active material containing a predetermined amount of Na and controlling the half-width of the peak in the range of 4.2 V to 4.4 V to 0.11 V or less it is possible to improve the charge/discharge cycle characteristics and load characteristics while realizing a high capacity battery.
  • the test cell of Comparative Example 1 has a higher capacity than the test cell of Comparative Example 2, but the load characteristics and capacity retention are worse than those of the test cells of the Examples.
  • the composition formula of the Li-Na composite oxide prepared in Example 9 was Li 0.883 Na 0.108 Ni 0.544 Mn 0.456 O 2. In the test cell prepared in Example 9, a plateau region appeared near 4.276 V in the charge/discharge curve. In addition, in the test cell prepared in Example 9, a peak with a half-width of 0.07 V was observed in the range of 4.2 V or more and 4.4 V or less in the dQ/dV curve.
  • the composition formula of the Li-Na composite oxide prepared in Example 10 was Li 0.897 Na 0.0944 Ni 0.596 Mn 0.404 O 2.
  • a plateau region appeared near 4.275 V in the charge/discharge curve.
  • a peak with a half-width of 0.07 V was observed in the range of 4.2 V or more and 4.4 V or less in the dQ/dV curve.
  • the composition formula of the Li-Na composite oxide prepared in Example 11 was Li 0.919 Na 0.0714 Ni 0.703 Mn 0.297 O 2.
  • a plateau region appeared near 4.236 V in the charge/discharge curve.
  • a peak with a half-width of 0.09 V was observed in the range of 4.2 V or more and 4.4 V or less in the dQ/dV curve.
  • Tables 2 to 4 show the composition of the composite oxide, the type of lithium molten salt, the potential at which the plateau region appears (plateau potential), the presence or absence of a peak in the range of 4.2 V or more and 4.4 V or less, and the half-value width of the peak.
  • the test cells of Examples 9 to 12 have higher capacities than the test cells of Comparative Examples 3 to 5.
  • a high capacity battery can be achieved by using a positive electrode active material containing a predetermined amount of Na and controlling the half-width of the peak in the range of 4.2 V to 4.4 V to 0.11 V or less.
  • the effects of the present disclosure are exerted even when the Ni content of the composite oxide increases.
  • Configuration 1 A positive electrode active material for use in a non-aqueous electrolyte secondary battery, the positive electrode active material having a crystal structure belonging to space group R-3m and represented by a composition formula Li x Na y Ni 1-a-b Mn a X b O c , in which X is at least one selected from the group consisting of transition metal elements and typical elements other than Li, Na, Ni, and Mn, 0.80 ⁇ x ⁇ 1.15, 0 ⁇ y ⁇ 0.20, 0.80 ⁇ x+y ⁇ 1.20, and c is a value satisfying electrical neutrality, and in a dQ/dV curve obtained when the non-aqueous electrolyte secondary battery is initially charged, the positive electrode active material has a peak in a voltage range of 4.2 V or more and 4.4 V or less, and the half width of the peak is 0.11 V or less.
  • Configuration 2 The positive electrode active material according to configuration 1, wherein the half-width of the peak is 0.08 V or less.
  • Aspect 3 The positive electrode active material according to aspect 1 or 2, wherein in the composition formula Li x Na y Ni 1-ab Mn a X b O c , the molar ratio of Na (y) is 0.02 ⁇ y ⁇ 0.15.
  • Aspect 4 The positive electrode active material according to any one of Aspects 1 to 3, wherein in the composition formula Li x Na y Ni 1-ab Mn a X b O c , the molar ratio of Na (y) is 0.06 ⁇ y ⁇ 0.13.
  • Aspect 5 The positive electrode active material according to any one of aspects 1 to 4, wherein in the composition formula Li x Na y Ni 1-a-b Mn a X b O c , the molar ratio of Ni (1-a-b) is 0.3 ⁇ 1-a-b ⁇ 0.7.
  • Structure 6 The positive electrode active material according to any one of structures 1 to 5 , wherein in the composition formula Li x Na y Ni 1-a-b Mn a X b O c, X is at least one selected from Mg, Ca, Sr, Ba, Sn, Ti, Si, V, Cr, Fe, Cu, Zn, Bi, Sb, B, Ga, In, P, Zr, Hf, Nb, Ta, Mo, W, Co, and Al.
  • Constitution 7 The positive electrode active material according to any one of constitutions 1 to 6, wherein in the composition formula Li x Na y Ni 1-ab Mn a X b O c , X is at least one selected from Al and Co.
  • Configuration 8 A method for producing a positive electrode active material for use in a non-aqueous electrolyte secondary battery, comprising: a step of synthesizing a Na composite oxide represented by a composition formula NaeNi1 -f-gMnfXgOh (wherein X is at least one element selected from metal elements other than Li, Na, Ni, and Mn, and e ⁇ 1.15, 0 ⁇ 1-f-g ⁇ 1, 0 ⁇ f ⁇ 1, 0 ⁇ g ⁇ 1, and h is a value that satisfies electrical neutrality); and a step of reacting the Na composite oxide with a lithium compound to exchange a part of Na in the Na composite oxide for Li, wherein the lithium compound includes at least one selected from the group consisting of lithium hydroxide, lithium carbonate
  • Configuration 9 A positive electrode comprising the positive electrode active material according to any one of configurations 1 to 7.
  • Aspect 10 A nonaqueous electrolyte secondary battery comprising the positive electrode according to aspect 9, a negative electrode, and a nonaqueous electrolyte.
  • nonaqueous electrolyte secondary battery 11 positive electrode, 12 negative electrode, 13 separator, 14 electrode body, 16 outer can, 17 sealing body, 18, 19 insulating plate, 20 positive electrode lead, 21 negative electrode lead, 22 grooved portion, 23 internal terminal plate, 24 lower valve body, 25 insulating member, 26 upper valve body, 27 cap, 28 gasket.

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PCT/JP2024/022715 2023-07-31 2024-06-24 正極活物質、正極、非水電解質二次電池、および正極活物質の製造方法 Pending WO2025028066A1 (ja)

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