WO2023063303A1 - 正極複合活物質、リチウムイオン二次電池、及びリチウムイオン二次電池の製造方法 - Google Patents

正極複合活物質、リチウムイオン二次電池、及びリチウムイオン二次電池の製造方法 Download PDF

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WO2023063303A1
WO2023063303A1 PCT/JP2022/037846 JP2022037846W WO2023063303A1 WO 2023063303 A1 WO2023063303 A1 WO 2023063303A1 JP 2022037846 W JP2022037846 W JP 2022037846W WO 2023063303 A1 WO2023063303 A1 WO 2023063303A1
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active material
positive electrode
coating layer
lithium ion
oxide
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French (fr)
Japanese (ja)
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充康 今▲崎▼
剛 菊池
純一 今泉
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Kaneka Corp
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Kaneka Corp
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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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H—ELECTRICITY
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
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    • H01M4/00—Electrodes
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • H—ELECTRICITY
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    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to a positive electrode composite active material, a lithium ion secondary battery, and a method for manufacturing a lithium ion secondary battery.
  • Lithium-ion secondary batteries have been attracting attention as applications such as on-board power sources for electric vehicles, and there is a demand for higher energy densities.
  • positive electrode active materials for lithium ion secondary batteries include lithium nickel manganese oxide (hereinafter also referred to as LNMO) (eg, Patent Document 1).
  • LNMO lithium nickel manganese oxide
  • LNMO has an operating voltage of 4.7 V based on the deposition potential of lithium, which is higher than conventional lithium insertion materials (e.g., 4 V for lithium cobaltate) used as positive electrode active materials, and has a high energy density. It is expected that the
  • Patent Document 2 the surface of the positive electrode active material is covered with a solid electrolyte, and the surface of the positive electrode active material is not directly exposed to the non-aqueous electrolyte, thereby generating gas due to decomposition of the non-aqueous electrolyte on the positive electrode active material. has been proposed.
  • the present inventor emulated the positive electrode composite active material of Patent Literature 2 and made a prototype of a lithium ion secondary battery using a positive electrode composite active material in which the thickness of the solid electrolyte was reduced.
  • the thickness of the solid electrolyte is reduced, the increase in the resistance of the positive electrode composite active material due to the presence of the solid electrolyte is reduced, but the effect of suppressing gas generation is also reduced.
  • the quality of the positive electrode composite active material produced as a trial product varied in quality during the production process, resulting in a problem of poor yield.
  • the present invention covers the surface of the oxide active material with a coating layer, and can suppress the resistance loss due to the coating layer while suppressing the generation of gas due to the decomposition of the non-aqueous electrolyte as compared with the conventional method.
  • An object of the present invention is to provide a positive electrode composite active material and a lithium ion secondary battery.
  • Another object of the present invention is to provide a method for manufacturing a lithium ion secondary battery that can improve the yield and ensure a certain level of quality as compared with the conventional method.
  • the present inventors studied the relationship between the amount of gas generated and the resistance in the positive electrode composite active material, and found that the positive electrode composite active material in which the positive electrode active material was coated with a solid electrolyte showed a complex impedance plot. Unlike the waveform of the complex impedance plot of the positive electrode active material that does not cover the solid electrolyte, it was found that an arc attributed to the grain boundary resistance of the solid electrolyte was confirmed. That is, in the positive electrode active material that is not coated with a solid electrolyte, a complex impedance plot having one arc attributed to the charge transfer resistance of the positive electrode active material is confirmed in the frequency range of 0.1 Hz to 1 kHz.
  • the aspect derived based on the above findings is a positive electrode composite active material that constitutes a part of the positive electrode of a lithium ion secondary battery that uses a non-aqueous electrolyte as an electrolyte, comprising an oxide active material and the oxide It has a coating layer covering the surface of the active material, the coating layer has lithium ion conductivity, and the grain boundary resistance of the coating layer is 3 to 20 times the charge transfer resistance of the oxide active material. is a positive electrode composite active material.
  • the oxide active material is in contact with the non-aqueous electrolyte, and the generation of gas due to the decomposition of the non-aqueous electrolyte can be suppressed, and the resistance loss due to the coating layer can be suppressed compared to the conventional case.
  • the coating layer has a grain boundary resistance per unit weight of 0.2 ⁇ /g or more and 2 ⁇ /g or less.
  • the grain boundary resistance is small, the resistance loss can be suppressed.
  • a preferable aspect is that the thickness of the coating layer is 5 nm or more and 50 nm or less.
  • the generation of gas can be suppressed even if the thickness of the coating layer is thin.
  • the coating layer contains phosphorus.
  • the coating layer contains a lithium phosphate-based lithium ion conductive oxide.
  • the lithium ion conductive oxide contains a compound represented by the following formula (1).
  • the lithium ion conductive oxide contains a compound represented by formula (2) below.
  • LiaAbDcPO4 ( 2 ) (In the above formula (2), a, b, and c satisfy 0.9 ⁇ a ⁇ 1.1, 0 ⁇ b ⁇ 1, 0 ⁇ c ⁇ 1, 0.9 ⁇ b + c ⁇ 1.1, and A is at least one selected from the group consisting of Co, Mn, Ni, Fe, Cu and Cr, and D is Mg, Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc and at least one selected from the group consisting of Y.)
  • the lithium ion conductive oxide includes a compound represented by (3) below and a compound represented by (4) below.
  • LiaAbDcPO4 ( 4 ) (In the above formula (4), a, b, and c satisfy 0.9 ⁇ a ⁇ 1.1, 0 ⁇ b ⁇ 1, 0 ⁇ c ⁇ 1, 0.9 ⁇ b + c ⁇ 1.1, and A is at least one selected from the group consisting of Co, Mn, Ni, Fe, Cu and Cr, and D is Mg, Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc and at least one selected from the group consisting of Y.)
  • the oxide active material contains a lithium manganese oxide having a spinel crystal structure.
  • One aspect of the present invention has a positive electrode, a non-aqueous electrolyte, and a negative electrode, wherein the positive electrode includes a positive electrode composite active material, and the positive electrode composite active material comprises an oxide active material and the oxide Having a coating layer covering the surface of the active material, the coating layer has lithium ion conductivity, and when charged to a charging depth of 50%, AC impedance is measured at a frequency of 0.1 Hz to 10 kHz and an amplitude of 10 mV, When calculating the Nyquist plot, at least two arcs are calculated, and among the two arcs, the diameter of the arc on the low frequency component side is 3 times or more and 20 times or less than the diameter of the arc on the high frequency component side. It is a lithium ion secondary battery.
  • the oxide active material is in contact with the non-aqueous electrolyte, and the generation of gas due to the decomposition of the non-aqueous electrolyte can be suppressed.
  • the negative electrode contains lithium titanate as a negative electrode active material.
  • One aspect of the present invention is a method for manufacturing a lithium ion secondary battery having a positive electrode having a positive electrode composite active material, a non-aqueous electrolyte, and a negative electrode, comprising: covering the surface of the oxide active material with a coating layer; An active material forming step of forming the positive electrode composite active material, a positive electrode forming step of applying the positive electrode composite active material to a current collector to form the positive electrode, and measuring the grain boundary resistance of the coating layer in the positive electrode.
  • a method for manufacturing a lithium ion secondary battery including a measurement step.
  • the amount of gas generated can be predicted by measuring the grain boundary resistance, so the yield can be improved and a certain level of quality can be ensured.
  • a preferred aspect includes a judgment step of judging the positive electrode as a non-defective product on the condition that the grain boundary resistance of the coating layer of the positive electrode falls within a predetermined range.
  • non-defective products can be determined, so the yield can be further improved.
  • one aspect of the present invention is to configure a part of the positive electrode of a lithium ion secondary battery using a non-aqueous electrolyte as an electrolyte, add a fine particle fluid to an oxide active material, grind it and oxidize it.
  • the grain boundary resistance of the coating layer is the grain boundary resistance of the coating layer when the coating layer is formed on the surface of the oxide active material by grinding an allowable limit amount of fine particle fluid with respect to the oxide active material. difference is within 5%, and the coating layer is formed by grinding fine particle fluid in an amount of 50% or less of the allowable limit amount with respect to the oxide active material. be.
  • the term "permissible limit amount” as used herein refers to the limit amount that can be maintained in the added state. That is, the allowable limit amount for the oxide active material means the limit amount that the oxide active material can hold.
  • the "average particle size” referred to here represents an arithmetic mean particle size and can be determined by various methods. For example, the "average particle size” may be obtained by direct observation with a microscope such as a transmission electron microscope (TEM) or a scanning electron microscope (SEM), or may be determined from the specific surface area by a specific surface area measuring method (BET method).
  • TEM transmission electron microscope
  • SEM scanning electron microscope
  • XRD X-ray diffraction
  • DLS dynamic light scattering method
  • LD laser diffraction/scattering method
  • the fine particle fluid even if the fine particle fluid is not added in an amount exceeding the allowable limit for the oxide active material, it is almost the same as when the allowable limit amount is added, and gas generation can be suppressed. Resistance loss due to the coating layer can be suppressed while suppressing gas generation due to decomposition of the aqueous electrolyte.
  • the fine particle fluid to be used can be reduced, costs can be reduced.
  • the positive electrode composite active material and the lithium ion secondary battery of the present invention it is possible to suppress the resistance loss due to the coating layer while suppressing the generation of gas due to the decomposition of the non-aqueous electrolyte as compared with the conventional case.
  • the method for manufacturing a lithium ion secondary battery of the present invention it is possible to improve the yield and ensure a certain level of quality.
  • FIG. 1 is a cross-sectional view conceptually showing a lithium ion secondary battery according to a first embodiment of the present invention
  • FIG. 2 shows Nyquist plots of lithium ion secondary batteries of Experimental Example 1 and Experimental Example 14 of the present invention, where (a) represents Experimental Example 1 and (b) represents Experimental Example 14.
  • FIG. FIG. 12 shows Nyquist plots of lithium ion secondary batteries of Experimental Examples 9 and 12 of the present invention, where (a) represents Experimental Example 9 and (b) represents Experimental Example 12.
  • FIG. 1 is an explanatory diagram showing the relationship between the grain boundary resistance, the amount of gas generated, and the initial capacity of lithium ion secondary batteries of Experimental Examples 1 to 14 of the present invention, and (a) is a graph showing the relationship of the amount of gas generated with respect to the grain boundary resistance. and (b) is a graph showing the relationship between the grain boundary resistance and the initial capacitance.
  • FIG. 1 is a model diagram of the reaction mechanism in the formation of the coating layer of the present invention, (a) to (c) showing the passage of time.
  • a lithium ion secondary battery 1 includes a positive electrode 2, a negative electrode 3, a non-aqueous electrolyte 5, and a separator 6, as shown in FIG. An external load 7 is connected.
  • the positive electrode 2 is formed by stacking a positive electrode composite active material layer 11 on a positive electrode current collector 10, and is an insertion electrode into which lithium ions can be inserted/extracted.
  • the positive electrode composite active material layer 11 contains a positive electrode composite active material 20, a conductive aid, and a binder.
  • the negative electrode 3 is formed by laminating a negative electrode active material layer 13 on a negative electrode current collector 12, and is an insertion electrode into which lithium ions can be inserted/extracted.
  • the negative electrode active material layer 13 contains a negative electrode active material 21, a conductive aid, and a binder.
  • the positive electrode composite active material 20 is a coated positive electrode active material in which the surface of the oxide active material 30 is coated with the coating layer 31 .
  • the oxide active material 30 is a lithium ion conductive active material, and has an average lithium desorption/insertion potential of 4.5 V or more with respect to the deposition potential of Li (also indicated as vs. Li + /Li)5. It is preferably 0 V or less. That is, the oxide active material 30 preferably has an operating potential of 4.5 V or more and 5.0 V or less based on lithium metal.
  • the potential of lithium ion insertion/extraction reaction (hereinafter also referred to as voltage) (vs. Li + /Li) is, for example, the charge/discharge of a half-cell using the oxide active material 30 as the working electrode and the lithium metal as the counter electrode.
  • the plateau with the lowest voltage value may be 4.5 V (vs. Li + /Li) or more, and the plateau with the highest voltage value is 5.0 V (vs. Li + / Li) or less.
  • the oxide active material 30 is not particularly limited, a spinel-type lithium manganese oxide represented by the following formula (1) is preferable.
  • x and y respectively satisfy 0 ⁇ x ⁇ 0.2 and 0 ⁇ y ⁇ 0.8
  • M is Al, Mg, Zn, Ni, Co, Fe, Ti, Cu, and Cr.
  • the oxide active material 30 may contain, for example, a trace amount of an element other than lithium and manganese, such as Ti, in addition to the lithium-manganese-based oxide.
  • the particle diameter of the oxide active material 30 is not particularly limited, but the median diameter d50 is preferably 5 ⁇ m or more, more preferably 10 ⁇ m or more, and even more preferably 20 ⁇ m or more. Within this range, the difference from the particle size of the coating layer 31 can be ensured, and the coating of the coating layer 31 is facilitated.
  • the median diameter d50 of the oxide active material 30 is preferably 100 ⁇ m or less, more preferably 80 ⁇ m or less, even more preferably 50 ⁇ m or less, and particularly preferably 30 ⁇ m or less.
  • the coating layer 31 is composed of a lithium ion conductive oxide containing phosphorus as an element, and is preferably composed of a positive electrode active material that functions alone as a positive electrode active material.
  • the lithium ion conductive oxide used in the coating layer 31 of the present embodiment is preferably a lithium phosphate-based lithium ion conductive oxide.
  • the crystal structure of the lithium phosphate-based lithium ion conductive oxide includes an inverse fluorite type, a NASICON type, a perovskite type, a garnet type, an olivine type, and the like, but is not particularly limited.
  • lithium phosphate-based lithium ion conductive oxide for example, a compound represented by the following formula (a) (hereinafter also referred to as LATP) can be used, particularly Li 1+p Al p Ti 2-p P 3 O 12 (which satisfies 0 ⁇ p ⁇ 1) is preferably used.
  • lithium phosphate-based lithium ion conductive oxide for example, a transition metal lithium phosphate having an olivine-type crystal structure and represented by the following formula (b) can be used. 4 is preferred.
  • LiaAbDcPO4 ( b ) (In the above formula (b), a, b, and c satisfy 0.9 ⁇ a ⁇ 1.1, 0 ⁇ b ⁇ 1, 0 ⁇ c ⁇ 1, 0.9 ⁇ b + c ⁇ 1.1, and A is at least one selected from the group consisting of Co, Mn, Ni, Fe, Cu and Cr, and D is Mg, Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc and at least one selected from the group consisting of Y.)
  • the coating layer 31 may be configured using two or more types of lithium ion conductive oxides, and the compound represented by the above formula (a) and the compound represented by the above formula (b) It may be composed of a compound.
  • the ratio of LATP to transition metal lithium phosphate is 2. /3 or more and 3/2 or less.
  • the particle size of the lithium ion conductive oxide constituting the coating layer 31 is preferably 10 nm or less in terms of BET specific surface area (dBET), more preferably 8 nm or less, and further preferably 6 nm or less. preferable. Within this range, the surface of the oxide active material 30 can be uniformly coated, and a dense coating layer 31 can be formed.
  • the average particle size calculated using the X-ray small angle scattering method is preferably 10 nm or less.
  • the median diameter d50 of the oxide active material 30 is preferably 100 or more and 10000 or less, more preferably 300 or more and 5000 when the BET specific surface area conversion diameter dBET of the lithium ion conductive oxide constituting the coating layer 31 is 1. It is more preferably 500 or more and 2000 or less, and particularly preferably 1000 or less. Within this range, the coating of the lithium ion conductive oxide on the oxide active material 30 is preferred over the aggregation of the lithium ion conductive oxides and the formation of aggregates of the oxide active material 30 and the lithium ion conductive oxide. becomes dominant, and the lithium ion conductive oxide can easily cover the surface of the oxide active material 30 to form the coating layer 31 .
  • the coating layer 31 is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 2 parts by mass or more with respect to 100 parts by mass of the oxide active material 30. .
  • the coating layer 31 is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 4 parts by mass or less with respect to 100 parts by mass of the oxide active material 30. .
  • the coating layer 31 constitutes a continuous layer that closely covers the surface shape of the oxide active material 30 .
  • the thickness of the coating layer 31 is preferably 5 nm or more and 50 nm or less, and more preferably 20 nm or less. Within this range, it is possible to suppress the amount of gas generated while suppressing resistance loss in the coating layer 31 .
  • the grain boundary resistance of the coating layer 31 is preferably three times or more, more preferably four times or more, the charge transfer resistance of the oxide active material 30 .
  • the grain boundary resistance of the coating layer 31 is preferably 20 times or less, more preferably 8 times or less, the charge transfer resistance of the oxide active material 30 .
  • the coating layer 31 is the coating layer 31 obtained when the coating layer 31 is formed on the surface of the oxide active material 30 by grinding a fine particle fluid described later that has an allowable limit amount of grain boundary resistance with respect to the oxide active material 30.
  • the difference from the grain boundary resistance of is preferably within 5%.
  • the coating layer 31 preferably has a grain boundary resistance per unit weight of 0.2 ⁇ /g or more and 2 ⁇ /g or less.
  • Lithium titanate is preferably used as the negative electrode active material 21 from the viewpoint that lithium deposition is less likely to occur and safety is improved.
  • lithium titanates lithium titanate having a spinel structure is particularly preferable for the negative electrode active material 21 because the expansion and contraction of the active material in the reaction of intercalation and deintercalation of lithium ions is small.
  • Lithium titanate may contain, for example, trace amounts of elements other than lithium and titanium, such as Nb.
  • the conductive aid is not particularly limited, but a carbon material is preferable.
  • the carbon material is preferably at least one selected from natural graphite, artificial graphite, vapor-grown carbon fiber, carbon nanotube, acetylene black, ketjen black, and furnace black.
  • the amount of the conductive aid contained in the positive electrode 2 is preferably 1 part by weight or more and 30 parts by weight or less with respect to 100 parts by weight of the positive electrode composite active material 20 .
  • the amount of the conductive aid contained in the negative electrode 3 is preferably 1 part by weight or more and 30 parts by weight or less with respect to 100 parts by weight of the negative electrode active material 21 .
  • the binder is not particularly limited, but for both the positive electrode 2 and the negative electrode 3, for example, from the group consisting of polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber, polyimide, and derivatives thereof At least one selected can be used.
  • PVdF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • styrene-butadiene rubber polyimide
  • derivatives thereof At least one selected can be used.
  • the binder is preferably dissolved or dispersed in a non-aqueous solvent or water for ease of production of the positive electrode 2 and the negative electrode 3 .
  • Non-aqueous solvents include, but are not limited to, N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, methyl acetate, ethyl acetate, and tetrahydrofuran.
  • NMP N-methyl-2-pyrrolidone
  • dimethylformamide dimethylacetamide
  • methyl ethyl ketone methyl acetate
  • ethyl acetate tetrahydrofuran.
  • a dispersant and a thickener may be added to these.
  • the amount of the binder contained in the positive electrode 2 is preferably 1 part by weight or more and 30 parts by weight or less with respect to 100 parts by weight of the positive electrode composite active material 20 .
  • the amount of the binder contained in the negative electrode 3 is preferably 1 part by weight or more and 30 parts by weight or less with respect to 100 parts by weight of the negative electrode active material 21 .
  • the current collectors 10 and 12 are not particularly limited, but are preferably made of aluminum or an aluminum alloy because they are stable under the positive electrode reaction atmosphere and the negative electrode reaction atmosphere, and are JIS standard 1030, 1050, 1085, 1N90, 1N99. High-purity aluminum represented by, for example, is more preferable.
  • the current collectors 10 and 12 may also be made of a metal other than aluminum (copper, SUS, nickel, titanium, and alloys thereof) coated with a metal that does not react with the potentials of the positive electrode 2 and negative electrode 3 .
  • the non-aqueous electrolytic solution 5 is not particularly limited, but may be a non-aqueous electrolytic solution in which a solute is dissolved in a non-aqueous solvent, a gel electrolyte in which a polymer is impregnated with a non-aqueous electrolytic solution in which a solute is dissolved in a non-aqueous solvent, or the like. can be used.
  • the non-aqueous solvent preferably contains a cyclic aprotic solvent and/or a chain aprotic solvent.
  • cyclic aprotic solvents include cyclic carbonates, cyclic esters, cyclic sulfones and cyclic ethers.
  • chain aprotic solvent a chain carbonate, a chain carboxylic acid ester, a chain ether, and a solvent generally used as a solvent for non-aqueous electrolytes, such as acetonitrile, may be used.
  • aprotic solvents include dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, ⁇ -butyl lactone, 1,2-dimethoxy Ethane, sulfolane, dioxolane, methyl propionate, and the like can be used. These solvents may be used singly or in combination of two or more kinds. is preferably used.
  • dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, dipropyl carbonate, and methyl propyl carbonate have high stability at high temperatures and high lithium conductivity at low temperatures. It is preferable to mix one or more of the chain carbonates exemplified in (1) with one or more of the cyclic compounds exemplified by ethylene carbonate, propylene carbonate, butylene carbonate, and ⁇ -butyl lactone.
  • Particularly preferred is a mixture of one or more chain carbonates exemplified by dimethyl carbonate, methylethyl carbonate and diethyl carbonate and one or more cyclic carbonates exemplified by ethylene carbonate, propylene carbonate and butylene carbonate.
  • the solute used in the non-aqueous electrolyte 5 is not particularly limited, but examples include LiClO 4 , LiBF 4 , LiPF 6 , LiAsF 6 , LiCF 3 SO 3 , LiBOB (Lithium Bis (Oxalato) Borate), LiN(SO 2 CF 3 ) 2 and the like are preferable because they are easily dissolved in a solvent.
  • the non-aqueous electrolyte 5 may further contain a vinyl group-containing cyclic siloxane such as 2,4,6,8-tetravinyl-2,4,6,8-tetramethylcyclotetrasiloxane (4VC4S) as an additive. good.
  • a vinyl group-containing cyclic siloxane such as 2,4,6,8-tetravinyl-2,4,6,8-tetramethylcyclotetrasiloxane (4VC4S) as an additive. good.
  • the non-aqueous electrolyte 5 may be included in the positive electrode 2, the negative electrode 3, and the separator 6 in advance, or after winding or laminating the separator 6 between the positive electrode 2 side and the negative electrode 3 side. may be added.
  • the separator 6 is placed between the positive electrode 2 and the negative electrode 3, and may have any structure as long as it is insulating and can contain the non-aqueous electrolytic solution 5. As shown in FIG.
  • the separator 6 is, for example, nylon, cellulose, polysulfone, polyethylene, polypropylene, polybutene, polyacrylonitrile, polyimide, polyamide, polyethylene terephthalate, polyvinyl alcohol, and woven fabrics, nonwoven fabrics, microporous membranes, etc. of composites of two or more thereof. is mentioned.
  • the separator 6 may contain various plasticizers, antioxidants, and flame retardants, or may be coated with metal oxide or the like.
  • the method for manufacturing the lithium ion secondary battery 1 of the present embodiment mainly includes an active material forming step for forming the positive electrode composite active material 20, a positive electrode forming step for forming the positive electrode 2, and a negative electrode forming step for forming the negative electrode 3. , and a secondary battery assembly process for assembling the positive electrode 2, the negative electrode 3, and the non-aqueous electrolyte 5.
  • the negative electrode forming process and the secondary battery assembling process are the same as the conventional processes, so the description is omitted. do.
  • a measurement step of measuring the grain boundary resistance of the positive electrode 2 after the secondary battery assembly step and a judgment step of judging quality are performed as necessary. implement.
  • the lithium ion conductive oxide is pulverized by a pulverizing device such as a ball mill to form lithium ion conductive oxide particles (pulverization step).
  • the lithium ion conductive oxide is a phosphorus-containing lithium ion conductive oxide similar to that of the coating layer 31 described above, and can be selected from materials similar to those of the coating layer 31 described above.
  • the average particle size of the lithium ion conductive oxide at this time is not particularly limited.
  • the average particle size of the lithium ion conductive oxide is preferably more than 0 nm and less than or equal to 10 nm. Within this range, the crystalline structure can be partially destroyed, the whole or part can be made amorphous, and a dense layer can be formed.
  • the average particle size of the lithium ion conductive oxide is preferably 20 nm or more and 100 nm or less in the case of transition metal lithium phosphate, for example. Within this range, it is possible to suppress peeling off due to agglomeration in the pulverized material forming step.
  • the lithium ion conductive oxide particles pulverized and micronized in a pulverization step are dispersed in a dispersion solvent to form a fine particle fluid (fine particle fluid forming step).
  • the dispersion solvent used at this time is preferably one or a plurality of alcohol solutions, and more preferably ethanol from the viewpoint of volatility and safety.
  • the particulate fluid formed at this time is a transparent sol in a sol state, and is an electrolytic sol having fluidity.
  • the oxide active material A coating layer 31 is formed on the surface of the oxide active material 30 by a mechanical coating method for mechanically contacting the material 30 and the lithium ion conductive oxide in the fine particle fluid.
  • the particulate fluid is ground into the oxide active material 30 by a grinding device such as a grinding mill to form a ground material (ground material forming step).
  • the treatment temperature in the grinding device is preferably 5° C. or higher and 130° C. or lower, more preferably 8° C. or higher and 80° C. or lower, and further preferably 10° C. or higher and 50° C. or lower.
  • the processing time in the grinding device at this time is preferably 5 minutes or more and 90 minutes or less, more preferably 10 minutes or more and 60 minutes or less.
  • the atmosphere in the grinding device is preferably an inert gas atmosphere or an air atmosphere.
  • the pulverized material is formed by pulverizing the particulate fluid in an amount equal to or less than 50% of the allowable limit amount with respect to the oxide active material 30 .
  • the ground material is heat-treated to remove the dispersion solvent from the ground material to form the positive electrode composite active material 20 (removal step).
  • the heat treatment temperature at this time is preferably over 50° C., more preferably 100° C. or higher, even more preferably 300° C. or higher, and particularly preferably 350° C. or higher. If the heat treatment temperature is lower than 50° C., the adhesion between the oxide active material 30 and the coating layer 31 is insufficient, so that the coating layer 31 may peel off during charging and discharging of the battery, leading to a decrease in the long-term reliability of the battery. be. On the other hand, if the heat treatment temperature is too high, the crystal structure of the coating layer 31 will change, the Li ion conductivity will decrease, and charging and discharging of the battery may not be performed normally. It is preferably less than 600° C., and more preferably 500° C.
  • the heat treatment time is preferably 30 minutes or longer, more preferably 1 hour or longer. Although the upper limit of the heat treatment time is not particularly limited, it is, for example, 3 hours or less.
  • the above is the active material forming step.
  • the positive electrode forming step is performed.
  • the positive electrode composite active material 20 obtained in the active material forming step is mixed with a conductive aid and a binder to prepare a positive electrode mixture, and the positive electrode mixture is applied to the positive electrode current collector 10 ( positive electrode coating step).
  • the positive electrode current collector 10 coated with the positive electrode mixture is dried to form the positive electrode 2 (positive electrode drying step).
  • the above is the positive electrode forming step.
  • the positive electrode 2 formed by the positive electrode forming process described above is assembled together with the negative electrode 3 formed by the negative electrode forming process and the non-aqueous electrolyte 5 in the same manner as in the prior art to complete the lithium ion secondary battery 1 .
  • the lithium ion secondary battery 1 formed by the above steps is subjected to AC impedance measurement as necessary to measure the grain boundary resistance of the coating layer 31 in the positive electrode 2 (measurement step). Then, it is confirmed whether or not the grain boundary resistance of the coating layer 31 falls within a predetermined range, and if it falls within a predetermined range, the lithium ion secondary battery 1 is determined to be non-defective. If not, the lithium ion secondary battery 1 is determined to be defective (determining step).
  • the predetermined range at this time is preferably a range in which the grain boundary resistance of the coating layer 31 is 3 times or more and 20 times or less the charge transfer resistance of the oxide active material 30 .
  • the AC impedance is plotted with the vertical axis representing the real number component and the horizontal axis representing the imaginary number component.
  • Calculation of the charge transfer resistance and the grain boundary resistance from the Nyquist plot is not particularly limited, but for example, they can be separated by performing fitting using an equivalent circuit in which at least two or more RC parallel circuits are connected in series. can be calculated by It should be noted that the grain boundary resistance of the coating layer 31 when the coating layer 31 is formed on the surface of the oxide active material 30 by grinding fine particle fluid having an allowable limit amount with respect to the oxide active material 30 is The quality criterion may be that the difference from the grain boundary resistance is within 5%.
  • the coating layer 31 uniformly covers the oxide active material 30, so the area in contact with the non-aqueous electrolyte 5 is reduced and gas generation can be suppressed. Further, even if the non-aqueous electrolyte 5 and the additive are partially decomposed, the decomposed product can fill the gaps in the coating of the coating layer 31 to form a good film, so further decomposition of the non-aqueous electrolyte 5 can be suppressed. It becomes possible.
  • the grain boundary resistance of the coating layer 31 is 3 times or more and 20 times or less than the charge transfer resistance of the oxide active material 30. It is possible to suppress the resistance loss due to the resistance of the coating layer 31 while suppressing the generation of gas due to the decomposition of 5 .
  • the coating layer 31 has a grain boundary resistance per unit weight of 0.2 ⁇ /g or more and 2 ⁇ /g or less, and since the grain boundary resistance is small, resistance loss is suppressed. can.
  • AC impedance measurement is performed in a state of charging to a charging depth of 50%, and when a Nyquist plot is calculated at a frequency of 0.1 Hz to 10 kHz and an amplitude of 10 mV, at least two Arcs are calculated, and the diameter of the arc on the low frequency component side of the two arcs is between 3 and 20 times the diameter of the arc on the high frequency component side. Therefore, it is possible to suppress the resistance loss due to the resistance of the coating layer 31 while suppressing the generation of gas due to the decomposition of the non-aqueous electrolyte 5 as compared with the conventional case.
  • the amount of gas generated can be predicted based on the grain boundary resistance of the coating layer 31 of the positive electrode 2, and the quality can be judged, so the yield can be improved.
  • the grain boundary resistance of the coating layer 31 grinds the allowable limit amount of the fine particle fluid to the surface of the oxide active material 30.
  • the difference from the grain boundary resistance of the coating layer 31 when the coating layer 31 is formed is within 5%, and the coating layer 31 has an amount of fine particle flow of 50% or less of the allowable limit amount with respect to the oxide active material 30 It is formed by grinding the body.
  • the grain boundary resistance of the coating layer 31 is within 5%
  • the coating layer 31 is formed of the particulate fluid in an amount of 50% or less of the allowable limit amount of the oxide active material 30 . Therefore, gas generation can be suppressed without adding the fine particle fluid to the oxide active material 30 in an amount exceeding the allowable limit. It is possible to suppress the resistance loss due to In addition, since the fine particle fluid to be used can be reduced, costs can be reduced.
  • the grain boundary resistance of the coating layer 31 in the positive electrode 2 was measured after the lithium ion secondary battery 1 was completed, but the present invention is not limited to this.
  • the quality of the positive electrode 2 may be determined by performing a measurement step of measuring the grain boundary resistance of the coating layer 31 in the positive electrode 2 after forming the positive electrode 2 by the positive electrode forming step.
  • each constituent member can be freely replaced or added between the embodiments.
  • Li1.3Al0.3Ti1.7 ( PO4 ) 3 (hereinafter also referred to as LATP) was prepared as a lithium ion conductive oxide.
  • a predetermined amount of Li 2 CO 3 , AlPO 4 , TiO 2 , NH 4 H 2 PO 4 and ethanol as a solvent were mixed as starting materials, and subjected to planetary ball mill treatment at 150 G for 3 hours using zirconia balls with a diameter of 3 mm. . After removing the zirconia balls from the treated mixture with a sieve, the mixture was dried at 120° C. to remove the ethanol. Thereafter, treatment was performed at 800° C. for 2 hours to obtain LATP powder.
  • a predetermined amount of ethanol as a solvent was mixed with the obtained LATP powder, and planetary ball milling was performed for 1 to 3 hours using zirconia balls with a diameter of 0.5 mm. After removing the zirconia balls from the treated mixture with a sieve, the mixture was dried at 120° C. to remove the ethanol. As a result, LATP fine powder having a dBET of 10 nm or less was obtained. Next, the LATP fine powder and ethanol were mixed to obtain a slurry (fine particle fluid) in which the LATP fine powder was dispersed in 16.4% by weight of ethanol.
  • LNMO Spinel-type lithium nickel manganate
  • a median diameter of 20 ⁇ m was used as the positive electrode active material.
  • 40 g of LNMO is put into a grinding mill (manufactured by Hosokawa Micron Corporation, product name: Nobilta) and rotated at 2600 rpm with a clearance of 0.6 mm and a rotor load power of 1.5 kW. was added in two batches so that the amount of added was 1.2% by weight.
  • the rotor rotation speed was maintained in the range of 2600 rpm to 3000 rpm, and the treatment was performed at room temperature for 10 minutes in an air atmosphere to obtain an LNMO surface-coated with LATP.
  • the resulting surface-coated LNMO was heat-treated at 350° C. for 1 hour to obtain a positive electrode composite active material.
  • a slurry was prepared in N-methyl-2-pyrrolidone (NMP).
  • the binder used was prepared in an N-methyl-2-pyrrolidone (NMP) solution having a solid concentration of 5% by weight, and NMP was further added to adjust the viscosity so as to facilitate the later-described coating.
  • the positive electrode was produced by vacuum drying at 170°C.
  • Two sheets of aluminum laminate films were prepared as exterior materials, and after forming a recess for the battery portion and a recess for the gas trapping portion by pressing, the electrode laminate was put therein.
  • the outer periphery leaving a space for non-aqueous electrolyte injection was heat-sealed at 180 ° C.
  • LNMO 30 g of LNMO is put into a grinding mill and rotated at 2600 rpm with a clearance of 0.6 mm and a rotor load power of 1.5 kW. I divided it into two times and put it in. After that, the rotor rotation speed was maintained in the range of 2600 rpm to 3000 rpm, and the treatment was performed at room temperature for 10 minutes in an air atmosphere to obtain an LNMO surface-coated with LFP. The resulting surface-coated LNMO was heat-treated at 350° C. for 1 hour to obtain a positive electrode composite active material.
  • a slurry was prepared in N-methyl-2-pyrrolidone (NMP).
  • the binder used was prepared in an N-methyl-2-pyrrolidone (NMP) solution having a solid concentration of 5% by weight, and NMP was further added to adjust the viscosity so as to facilitate the later-described coating.
  • the positive electrode was produced by vacuum drying at 170°C.
  • a slurry was prepared in N-methyl-2-pyrrolidone (NMP).
  • the binder used was prepared in an N-methyl-2-pyrrolidone (NMP) solution having a solid concentration of 5% by weight, and NMP was further added to adjust the viscosity so as to facilitate the later-described coating.
  • the positive electrode was produced by vacuum drying at 170°C.
  • the weight of the lithium ion secondary battery was measured with an electronic balance.
  • the weight in water was measured using a hydrometer (manufactured by Alpha Mirage Co., Ltd., product number: MDS-3000), and the buoyancy was calculated by taking the difference between these weights.
  • the volume of the lithium ion secondary battery was calculated by dividing this buoyancy by the density of water (1.0 g/cm 3 ).
  • the lithium ion secondary battery was connected to a charging/discharging device (HJ1005SD8, manufactured by Hokuto Denko Co., Ltd.) and cycled.
  • AC impedance measurement AC impedance measurement is performed by using a Solartron potentiostat and a frequency response analyzer, and by applying an AC wave with a voltage amplitude of 10 mV and a frequency of 0.1 Hz to 10 kHz to a lithium ion secondary battery charged to a charging depth of 50%. Impedance measurements were performed. Also, the Nyquist plot obtained by the AC impedance measurement was fitted using an equivalent circuit to evaluate the series resistance, the charge transfer resistance in the positive electrode composite active material, and the grain boundary resistance in the coating layer.
  • Figures 2, 3 and Table 1 show the results of gas generation amount measurement, initial capacity, and AC impedance measurement in Experimental Examples 1 to 14.
  • the grain boundary resistance is 3 times or more and 20 times or less than the charge transfer resistance of LNMO.
  • FIG. 4(a) shows the relationship between the grain boundary resistance and the amount of gas generated in Experimental Examples 1 to 14, and FIG. b).
  • the lithium ion secondary batteries of Experimental Examples 1 to 14 as shown in FIG. 4, there is a high correlation between the grain boundary resistance and the amount of gas generated, and between the grain boundary resistance and the initial capacity. As a result, the amount of gas generated decreased and the initial capacity decreased. That is, in FIG. 4(a), the grain boundary resistance and the amount of gas generated correspond approximately 1:1, and in FIG. 4(b), it was found that the grain boundary resistance and the initial capacity correspond approximately 1:1. .
  • the amount of gas generated decreased by covering the LNMO with a coating layer.
  • an arc corresponding to the grain boundary resistance of the coating layer appears in the impedance plot, and between the grain boundary resistance and the gas generation rate and between the grain boundary resistance and the initial capacity It was found to show a high correlation. It was suggested that by measuring the grain boundary resistance, it is possible to predict the amount of gas generation that may occur in the future. It was suggested that when the nano-sized LATP was coated in excess of the permissible amount, the coating layer was formed distortedly and became a uniform layer after the coating layer was peeled off. It was found that by using the grain boundary resistance of the coating layer added in excess of the allowable limit as a reference, it is possible to constantly form a coating layer of the same quality as the allowable limit amount.

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PCT/JP2022/037846 2021-10-14 2022-10-11 正極複合活物質、リチウムイオン二次電池、及びリチウムイオン二次電池の製造方法 Ceased WO2023063303A1 (ja)

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JP2020517049A (ja) * 2017-03-29 2020-06-11 ユニバシティ オブ メリーランド カレッジ パーク 固体ハイブリッド電解質、その作製方法、およびその使用
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JP7770356B2 (ja) 2023-06-08 2025-11-14 本田技研工業株式会社 全固体電池用正極スラリーの評価方法

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