WO2024047854A1 - リチウムイオン二次電池用正極及びリチウムイオン二次電池 - Google Patents

リチウムイオン二次電池用正極及びリチウムイオン二次電池 Download PDF

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Publication number
WO2024047854A1
WO2024047854A1 PCT/JP2022/033039 JP2022033039W WO2024047854A1 WO 2024047854 A1 WO2024047854 A1 WO 2024047854A1 JP 2022033039 W JP2022033039 W JP 2022033039W WO 2024047854 A1 WO2024047854 A1 WO 2024047854A1
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Prior art keywords
positive electrode
active material
material layer
layer
lithium ion
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PCT/JP2022/033039
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English (en)
French (fr)
Japanese (ja)
Inventor
章 稲葉
健 三木
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Vehicle Energy Japan Inc
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Vehicle Energy Japan Inc
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Priority to PCT/JP2022/033039 priority Critical patent/WO2024047854A1/ja
Priority to US18/998,120 priority patent/US20260031325A1/en
Priority to CN202280097551.7A priority patent/CN119487641A/zh
Priority to JP2024543737A priority patent/JPWO2024047854A1/ja
Priority to EP22957448.8A priority patent/EP4583185A4/en
Publication of WO2024047854A1 publication Critical patent/WO2024047854A1/ja
Anticipated expiration legal-status Critical
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—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
    • H01M4/52—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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • 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
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a positive electrode for a lithium ion secondary battery and a lithium ion secondary battery including the positive electrode.
  • Lithium ion secondary batteries having a positive electrode including a plurality of active material layers are conventionally known (see, for example, Patent Documents 1 and 2).
  • the positive electrode for a lithium ion secondary battery of the present invention includes a positive electrode current collector and a positive electrode active material layer laminated on the positive electrode current collector, and the positive electrode active material layer is laminated on the positive electrode current collector.
  • a positive electrode first active material layer laminated on the positive electrode first active material layer, and the positive electrode first active material layer is made of a lithium-containing composite containing Li and Ni.
  • the positive electrode second active material layer includes a positive electrode first active material whose main component is an oxide
  • the positive electrode second active material layer includes a positive electrode second active material whose main component is a lithium-containing composite oxide containing Li and Ni.
  • the mole fraction of Ni in the positive electrode second active material of the second active material layer is smaller than the Ni mole fraction in the positive electrode first active material of the positive electrode first active material layer.
  • the lithium ion secondary battery of the present invention is a lithium ion secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, and the positive electrode is the positive electrode for a lithium ion secondary battery of the present invention.
  • lithium ion secondary battery equipped with the positive electrode for lithium ion secondary batteries of the present invention both high energy density and long life can be achieved.
  • FIG. 1 is a schematic perspective view showing a battery 1 including an example positive electrode 110 according to an embodiment.
  • FIG. 2 is a schematic perspective view showing a charge/discharge body 100 of the battery 1 shown in FIG. 1.
  • FIG. 3 is a schematic perspective view showing a portion of the charge/discharge body 100 shown in FIG. 2 including a positive electrode tab 111b and a negative electrode tab 121b, with the positions of the side ends of the positive electrode 110, the negative electrode 120, and the separator 130 different.
  • FIG. 4 is a schematic side view showing the charge/discharge body 100 shown in FIG. 3.
  • FIG. FIG. 3 is a schematic enlarged view of a die head and a back roller used in manufacturing a positive electrode.
  • FIG. 6 is a schematic cross-sectional view of a positive electrode and a negative electrode of a separator-less battery including another positive electrode according to the embodiment.
  • FIG. 3 is a schematic enlarged cross-sectional view of the interface between the second positive active material layer and the positive electronic insulating layer of the positive active material layer of the positive electrode of another example according to the embodiment and the vicinity thereof.
  • the width direction X and depth direction Y of the battery 1 and the height direction Z changes.
  • Positive electrode for lithium ion secondary batteries may be abbreviated as “positive electrode.”
  • Lithium ion secondary battery is sometimes abbreviated as “battery”.
  • a battery 1 including an example of a positive electrode 110 according to the embodiment is a lithium ion secondary battery, and as shown in FIG. 200, and an external terminal 300 connected to the charge/discharge body 100 and attached to the container 200.
  • the charge/discharge body 100 has a positive electrode 110, a negative electrode 120, and a separator 130, as shown in FIGS. 2 to 4.
  • the separator 130 is impregnated with an electrolytic solution in which a supporting salt (electrolyte) is dissolved.
  • the charge/discharge body 100 has a positive electrode 110 formed in an elongated shape and a negative electrode 120 formed in an elongated shape, which are wound together with a separator 130 formed in an elongated shape interposed therebetween. It is rotated and composed.
  • the charging/discharging body 100 is formed into a rectangular parallelepiped shape with rounded ends when the constituent members are wound.
  • the positive electrode 110 is a positive electrode for a lithium ion secondary battery, and includes a positive electrode current collector 111 and a positive electrode active material layer 112 laminated on the positive electrode current collector 111, as shown in FIGS. 3 and 4. .
  • the cathode active material layer 112 includes a first cathode active material layer 113 laminated on the cathode current collector 111 and a second cathode active material layer 114 laminated on the first cathode active material layer 113 . That is, the positive electrode 110 includes a plurality of active material layers.
  • the positive electrode current collector 111 is formed in an elongated shape extending in the width direction X. As shown in FIGS. 3 and 4, the positive electrode current collector 111 includes a current collecting portion 111a and a positive electrode tab 111b.
  • the current collector 111a is elongated in the width direction X and is formed in a foil shape. As shown in FIGS. 3 and 4, the positive electrode tab 111b protrudes in the lateral direction (above the height direction Z) of the current collecting section 111a from the side edge 111c along the longitudinal direction of the current collecting section 111a. .
  • the positive electrode tab 111b is formed integrally with the current collector 111a. For example, one positive electrode tab 111b is formed in the current collector 111a.
  • the current collector 111a is formed of, for example, aluminum or an aluminum alloy, such as aluminum foil having a plate-like (sheet-like) shape.
  • the positive electrode first active material layer 113 is joined to the current collecting portion 111a of the positive electrode current collector 111.
  • the positive electrode first active material layer 113 may be formed on both sides of the current collector 111a.
  • the positive electrode first active material layer 113 faces, for example, the entire region along the transverse direction (height direction Z) of the current collector 111a.
  • the positive electrode second active material layer 114 is joined to the positive electrode first active material layer 113.
  • the positive electrode first active material layer 113 includes, as a positive electrode first active material, large-sized solid particles 113f and small-sized solid particles having a smaller median diameter (average particle size) than the large-sized solid particles 113f. Particles 113s.
  • the first positive electrode active material layer 113 generally corresponds to a positive electrode active material layer used in a battery electric vehicle (BEV).
  • the large-sized solid particles 113f are, for example, solid particles with a particle size of 8 ⁇ m or more and 20 ⁇ m or less.
  • the small-sized solid particles 113s are, for example, solid particles with a particle size of 2 ⁇ m or more and 6 ⁇ m or less.
  • the bulk density of the large-sized solid particles 113f is, for example, 2.5 g/cm 3 or more and 3.5 g/cm 3 or less. Further, the bulk density of the small-sized solid particles 113s is, for example, 1.4 g/cm 3 or more and 2.4 g/cm 3 or less.
  • the bulk density of solid particles refers to the density when a container with a constant volume is filled with solid particle powder and the internal volume is taken as the volume.
  • the large particle size solid particles 113f and the small particle size solid particles 113s have the same composition, and have the following general composition formula Li 1+X M A O 2 (1) (In the formula, X satisfies -0.15 ⁇ X ⁇ 0.15, and M A represents an element group containing at least one element selected from the group consisting of Mn and Al, Ni, and Co. ) It is a ternary lithium-containing composite oxide represented by Note that the small-sized solid particles 113s are preferably single crystals. This is because the single crystal solid particles 113s contribute to extending the life of the battery 1.
  • the positive electrode first active material layer 113 further includes, for example, a conductive additive 113c, a binder 113b, and the like.
  • a conductive additive 113c of the positive electrode first active material layer 113 carbon nanotubes are preferable. This is because the electronic conductivity of the positive electrode first active material layer 113 can be improved.
  • a sufficient diffusion path for lithium ions can be secured, it is possible to improve energy density in addition to cycle durability, lithium ion storage durability, and charge rate characteristics when battery 1 is repeatedly charged and discharged. This is because it can be done.
  • the content of the positive electrode first active material can be increased instead of reducing the content of the conductive additive in the positive electrode first active material layer 113.
  • the ratio of the weight of the positive electrode first active material to the total weight of the positive electrode first active material layer 113 is, for example, 94% by weight or more. It is preferably 99% by weight or less.
  • the ratio of the weight of the large particle size solid particles 113f to the weight of the positive electrode active first material in the positive electrode first active material layer 113 is preferably, for example, 60% by weight or more and 90% by weight or less.
  • the positive electrode second active material layer 114 includes hollow particles 114s (positive electrode second active material) as the positive electrode second active material.
  • the second positive electrode active material layer 114 generally corresponds to a positive electrode active material layer used in a hybrid electric vehicle (HEV).
  • HEV hybrid electric vehicle
  • the hollow particles 114s are, for example, hollow particles with a particle size of 3 ⁇ m or more and 7 ⁇ m or less.
  • the bulk density of the hollow particles 114s is, for example, 1.2 g/cm 3 or more and 2.0 g/cm 3 or less.
  • the bulk density of the hollow particles refers to the density when a container with a constant volume is filled with hollow particle powder and the internal volume is taken as the deposit.
  • the hollow particles 114s (positive electrode second active material) have the following general composition formula Li 1+P M B O 2 (2) (In the formula, P satisfies -0.15 ⁇ P ⁇ 0.15, and M B represents an element group containing at least one element selected from the group consisting of Mn and Al, Ni, and Co. ) It is a ternary lithium-containing composite oxide represented by
  • the positive electrode second active material layer 114 further includes a conductive additive 114c and a binder 114b.
  • the ratio of the weight of the positive electrode second active material to the total weight of the positive electrode second active material layer 114 is, for example, preferably 85% by weight or more and 96% by weight or less.
  • the mole fraction of Ni in the hollow particles 114s (positive electrode second active material) of the positive electrode second active material layer 114 is the same as that of the large-sized solid particles 113f (The mole fraction of Ni is smaller than the mole fraction of Ni in the positive electrode first active material).
  • the median diameter (average particle size) of the positive electrode second active material (hollow particles 114s) of the positive electrode second active material layer 114 is the same as that of the positive electrode first active material (large diameter) of the positive electrode first active material layer 113. It is smaller than the median diameter (average particle diameter) of particles containing both the solid particles 113f and the large solid particles 113f.
  • the median diameter (average particle diameter) of the positive electrode first active material (particles containing both the large particle size solid particles 113f and the large particle size solid particles 113f) of the positive electrode first active material layer 113 is, for example, 5.
  • the range is .6 ⁇ m or more and 18.6 ⁇ m or less.
  • the median diameter (average particle size) of the positive electrode second active material (hollow particles 114s) of the positive electrode second active material layer 114 is, for example, in the range of 3.0 ⁇ m or more and 8.0 ⁇ m or less.
  • the negative electrode 120 is a negative electrode for a lithium ion secondary battery, and includes a negative electrode current collector 121 and a negative electrode active material layer 122 laminated on the negative electrode current collector 121, as shown in FIGS. 3 and 4. .
  • the negative electrode current collector 121 is formed in an elongated shape extending in the width direction X. As shown in FIGS. 3 and 4, the negative electrode current collector 121 includes a current collecting portion 121a and a negative electrode tab 121b. The current collector 121a is elongated in the width direction X and is formed in a foil shape. As shown in FIG. 4, the current collecting portion 121a of the negative electrode 120 has a longer width in the transverse direction (height direction Z) than the current collecting portion 111a of the positive electrode 110. Within the range (from the upper end to the lower end in the height direction Z) along the width direction of the current collection portion 121a of the negative electrode 120, both ends ( from the upper end to the lower end in the height direction Z).
  • the negative electrode tab 121b protrudes in the lateral direction (above the height direction Z) of the current collecting section 121a from the side edge 121c along the longitudinal direction of the current collecting section 121a. .
  • the negative electrode tab 121b protrudes in the same direction (above the height direction Z) as the positive electrode tab 111b of the positive electrode 110 in a state where it is laminated with the positive electrode 110 via the separator 130.
  • the negative electrode tab 121b is separated from the positive electrode tab 111b of the positive electrode 110 in the width direction X in a state where the negative electrode tab 121b is laminated with the positive electrode 110 with the separator 130 in between.
  • the negative electrode tab 121b is formed integrally with the current collector 121a.
  • one negative electrode tab 121b is formed in the current collector 121a.
  • the current collector 121a is made of copper or a copper alloy, for example.
  • the negative electrode active material layer 122 is joined to the current collecting part 121a of the negative electrode current collector 121.
  • the negative electrode active material layer 122 may be formed on both sides of the current collector 121a.
  • the negative electrode active material layer 122 faces, for example, the entire region along the transverse direction (height direction Z) of the current collector 121a.
  • the negative electrode active material layer 122 includes a negative electrode active material.
  • the negative electrode active material is not particularly limited as long as it is a material that can intercalate and deintercalate lithium ions, but examples include natural graphite, artificial graphite, non-graphitizable carbon (hard carbon), easily graphitizable carbon (soft carbon), etc. Examples include carbon materials and graphite coated with amorphous carbon.
  • the negative electrode active material layer 122 further includes, for example, a conductive additive, a binder, and the like.
  • a conductive additive for example, the same material as the conductive agent 113c of the positive electrode first active material layer 113 is used.
  • the material for the binder of the negative electrode active material layer 122 for example, the same material as the binder 113b of the positive electrode first active material layer 113 is used.
  • the separator 130 has an insulating function of insulating between the positive electrode 110 and the negative electrode 120 and preventing short circuit between the positive electrode 110 and the negative electrode 120, and retains the non-aqueous electrolyte. It has a function. Separator 130 allows lithium ions to pass through the electrolyte. Separator 130 is formed into a long shape. As shown in FIG. 4, the separator 130 has a longer width in the transverse direction (height direction Z) than the current collecting section 111a of the positive electrode 110 and the current collecting section 121a of the negative electrode 120.
  • Both ends of the current collector 111a of the positive electrode 110 along the width direction are located within the range along the width direction of the separator 130 (from the top end to the bottom end in the height direction Z). However, both ends (from the upper end to the lower end in the height direction Z) along the width direction of the current collecting part 121a of the negative electrode 120 are located.
  • Separator 130 is made of porous material.
  • the separator 130 may be a porous sheet made of resin such as polyethylene (PE), polypropylene (PP), polyester, cellulose, or polyamide, or a laminated sheet thereof (for example, a three-layer structure of PP/PE/PP). sheets) are used.
  • a layer containing an inorganic material (for example, alumina particles, etc.) and a binder may be provided on one or both surfaces of the separator 130.
  • the electrolyte is impregnated into the separator 130 and is in contact with the positive electrode 110 and the negative electrode 120.
  • the electrolytic solution includes an organic solvent and a supporting salt (electrolyte), and may further include additives.
  • organic solvent for example, carbonate ester is used.
  • lithium salt is used as the supporting salt.
  • additives used include vinylene carbonate and fluoroethylene carbonate.
  • the container 200 houses the charge/discharge body 100.
  • Container 200 includes a case 201 and a lid 202.
  • the lid 202 is joined to the opening of the case 201 and seals the charge/discharge body 100 together with the case 201.
  • a charging/discharging body 100 sealed by a case 201 and a lid 202 is filled with an electrolyte.
  • the external terminal 300 includes a positive terminal 301 and a negative terminal 302.
  • the positive terminal 301 and the negative terminal 302 relay input and output of electric power between the charging/discharging body 100 and external equipment. Further, when a battery pack is configured using a plurality of batteries 1, one adjacent positive electrode terminal 301 and the other adjacent negative electrode terminal 302 are joined via a bus bar.
  • the positive electrode terminal 301 is connected to the positive electrode tab 111b indirectly or directly via a positive current collector plate.
  • the negative electrode terminal 302 is connected to the negative electrode tab 121b indirectly or directly via a negative electrode current collector plate.
  • a positive terminal 301 and a negative terminal 302 are attached to the lid 202.
  • a battery including the example positive electrode according to the embodiment can be manufactured using techniques known in the technical field of the present invention, except for the method for manufacturing the positive electrode.
  • An example of the positive electrode 110 according to the embodiment can be manufactured, for example, as follows. First, materials included in the first positive electrode active material layer 113 (for example, a positive electrode active material, a conductive additive, a binder, etc.) are prepared. This material may be in powder form. Next, the materials are mixed and the resulting mixture is dispersed in a solvent (eg, N-methyl-2-pyrrolidone (NMP) and/or water) to obtain a positive electrode first slurry. Next, the positive electrode first slurry is applied to the surface (one side or both sides) of the positive electrode current collector 111 using a known technique, dried, and calendered if necessary to form the positive electrode first active material layer 113. Form.
  • a solvent eg, N-methyl-2-pyrrolidone (NMP) and/or water
  • materials included in the second positive electrode active material layer 114 are prepared. This material may be in powder form.
  • the materials are mixed and the resulting mixture is dispersed in a solvent (eg, N-methyl-2-pyrrolidone (NMP) and/or water) to obtain a second positive electrode slurry.
  • NMP N-methyl-2-pyrrolidone
  • the positive electrode second slurry is applied to the surface (one side or both sides) of the positive electrode first active material layer 113 by a known technique, dried, and calendered if necessary to form the positive electrode second active material layer 113.
  • the positive electrode 110 is obtained by the above manufacturing method. However, the positive electrode 110 is not limited to that manufactured by the above manufacturing method, and may be manufactured by other methods.
  • the positive electrode active material layer 112 includes a positive electrode first active material layer 113 laminated on the positive electrode current collector 111 and a positive electrode second active material layer laminated on the positive electrode first active material layer 113.
  • a material layer 114 is included.
  • an inert material containing nickel oxide (NiO) is formed. Since deterioration of the active material layer due to layer formation etc. can be suppressed, the durability of the battery 1 can be improved and the life of the battery 1 can be extended.
  • the battery 1 including the positive electrode 110 according to the embodiment can achieve both high energy density and long life.
  • a positive electrode for a lithium ion secondary battery includes a positive electrode current collector, and a positive electrode active material layer laminated on the positive electrode current collector, and the positive electrode active material layer is , a positive electrode first active material layer laminated on the positive electrode current collector, and a positive electrode second active material layer laminated on the positive electrode first active material layer.
  • the positive electrode first active material layer includes a positive electrode first active material.
  • the positive electrode first active material is composed of a lithium-containing composite oxide containing Li and Ni.
  • the lithium-containing composite oxide constituting the positive electrode first active material is not particularly limited as long as it contains Li and Ni, but it is preferably one containing Co in addition to Li and Ni.
  • Li In addition to Ni and Co, those containing at least one element selected from the group consisting of Mn and Al are preferable, and in particular, those having the following general composition formula Li 1+X M A O 2 (1) (In the formula, X satisfies -0.15 ⁇ X ⁇ 0.15, and M A represents an element group containing at least one element selected from the group consisting of Mn and Al, Ni, and Co. ) A ternary lithium-containing composite oxide represented by is preferred. Note that the value of X in general compositional formula (1) is determined by ICP analysis.
  • the ternary lithium-containing composite oxide represented by the above general compositional formula (1) has high thermal stability and stability in high potential conditions, and by applying this oxide, the safety of the battery 1 can be improved. It is possible to improve various battery characteristics.
  • All or part of the positive electrode first active material may be a single crystal. By using a single crystal positive electrode first active material with high purity and high uniformity, the life characteristics of the positive electrode first active material can be improved. Also. The cycle durability and lithium ion storage durability when the battery 1 is repeatedly charged and discharged can be improved.
  • the positive electrode first active material layer is not particularly limited as long as it contains the positive electrode first active material, but it is preferably one in which all or part of the positive electrode first active material is formed solidly. Compared to a hollow positive electrode first active material, a solid positive electrode first active material has excellent charging characteristics. Therefore, the energy density of the lithium ion secondary battery can be improved.
  • the positive electrode first active material layer includes large-sized solid particles and an average particle size (e.g., median diameter) of the large-sized solid particles. (D50)) is preferably small-diameter solid particles. This is because the packing density of the positive electrode active material in the first positive electrode active material layer can be improved, and the energy density of the battery can be increased.
  • the positive electrode first active material layer contains hollow particles as the positive electrode first active material, it is preferable that the positive electrode first active material contains more solid particles than hollow particles.
  • the positive electrode first active material layer includes, as the positive electrode first active material, particles having a smaller average particle size than the particles having the larger average particle size, in addition to particles having a larger average particle size. It is preferable that the particles having a small average particle size in the positive electrode first active material have a particle size sufficiently smaller than the particles having a large average particle size in the positive electrode first active material by 1/2 or less. It can be packed with high density and contributes to obtaining high battery performance.
  • the particles having a small average particle size in the positive electrode first active material have a larger average particle size than the particles having a small average particle size in the positive electrode second active material described later. This is because a highly filled electrode can be formed even if there are variations in the shape of particles having a large average particle size in the first positive electrode active material.
  • the particles with a small average particle size in the positive electrode first active material have substantially the same average particle size as the particles with a small average particle size in the positive electrode second active material, which will be described later. This is preferable because it makes it easier to manage raw materials and manufacturing. Particles having the same specifications can be used as the particles having a small average particle size in the positive electrode second active material and the particles having a small average particle size in the positive electrode first active material, which will be described later. Note that “substantially the same” can be defined as a difference in average particle size within 10%. This is because variations in particle size were taken into account.
  • the particles having a small average particle size in the positive electrode first active material have a smaller average particle size than the particles having a small average particle size in the positive electrode second active material described later. Since it can be placed in the interstices of various large particles, it can provide a battery with high energy density.
  • the positive electrode first active material layer is not particularly limited as long as it contains the positive electrode first active material, but for example, in addition to the positive electrode first active material, at least one type selected from the group consisting of a conductive additive, a binder, etc. Among these, those that further contain a conductive additive are preferred, and those that further include a conductive additive and a binder are particularly preferred.
  • a carbon-based material can be used as the material for the conductive additive of the positive electrode first active material layer.
  • crystalline carbon e.g., amorphous carbon, or a mixture thereof can be used.
  • crystalline carbon include natural graphite (eg, flaky graphite), artificial graphite, carbon fiber, or mixtures thereof.
  • amorphous carbon include carbon black (eg, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, or mixtures thereof).
  • Examples of carbon fibers include carbon nanotubes.
  • binder material for the positive electrode first active material layer examples include polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), polyethylene, polystyrene, polybutadiene, polyacrylonitrile, polyvinyl fluoride, polyfluorinated propylene, and polyfluorinated chloroprene. , butyl rubber, nitrile rubber, styrene butadiene rubber (SBR), polysulfide rubber, nitrocellulose, cyanoethylcellulose, various latexes, acrylic resins, or mixtures thereof can be used.
  • PVdF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • PTFE polyethylene
  • polystyrene polybutadiene
  • polyacrylonitrile polyvinyl fluoride
  • polyfluorinated propylene examples of the binder material for the positive electrode first active material
  • the ratio of the weight of the positive electrode first active material to the total weight of the positive electrode first active material layer is, for example, preferably 94% by weight or more and 99% by weight or less.
  • the thickness of one side of the positive electrode first active material layer in the stacking direction (for example, the depth direction Y in FIG. 4) (for example, the first thickness T1 in FIG. 4) is, for example, an average thickness of 5 ⁇ m or more and 500 ⁇ m or less.
  • the average thickness may be 10 ⁇ m or more and 300 ⁇ m or less.
  • the positive electrode second active material layer includes a positive electrode second active material.
  • the positive electrode second active material is composed of a lithium-containing composite oxide containing Li and Ni.
  • the lithium-containing composite oxide constituting the second positive electrode active material is not particularly limited as long as it contains Li and Ni, but it is preferably one containing Co in addition to Li and Ni.
  • Li In addition to Ni and Co, those containing at least one element selected from the group consisting of Mn and Al are preferable, and in particular, those having the following general composition formula Li 1+P M B O 2 (2) (In the formula, P satisfies -0.15 ⁇ P ⁇ 0.15, and M B represents an element group containing at least one element selected from the group consisting of Mn and Al, Ni, and Co. )
  • a ternary lithium-containing composite oxide represented by is preferred. Note that the P value of general compositional formula (2) is determined by ICP analysis.
  • the positive electrode second active material it is preferable that the whole or part of the material is formed hollow, as in the example according to the embodiment.
  • the electrolyte electrolytic solution
  • the electrolyte impregnates the voids of the hollow particles of the positive electrode second active material, thereby increasing the diffusion rate of lithium ions.
  • the resistance of the positive electrode active material layer can be improved and the resistance of the positive electrode active material layer can be reduced.
  • the ionic conductivity is increased, and a battery with high capacity and high output can be obtained.
  • the positive electrode second active material layer contains solid particles as the positive electrode second active material, it is preferable that the positive electrode second active material contains more hollow particles than solid particles.
  • the positive electrode second active material layer is not particularly limited as long as it contains the positive electrode second active material, but for example, in addition to the positive electrode second active material, at least one type selected from the group consisting of a conductive additive, a binder, etc. Among these, those that further contain a conductive additive are preferred, and those that further include a conductive additive and a binder are particularly preferred.
  • the material of the conductive additive of the positive electrode second active material layer is the same as the material of the conductive additive of the positive electrode first active material layer, so a description thereof will be omitted here.
  • the material of the binder of the second positive electrode active material layer is the same as the material of the binder of the first positive electrode active material layer, so a description thereof will be omitted here.
  • the ratio of the weight of the positive electrode second active material to the total weight of the positive electrode second active material layer is, for example, preferably 85% by weight or more and 96% by weight or less.
  • the mole fraction of Ni in the cathode second active material of the cathode second active material layer is the same as the Ni mole fraction in the cathode first active material of the cathode first active material layer. It is less than the mole fraction of Ni. That is, the mole fraction of Ni in the first active material of the positive electrode>the molar fraction of Ni in the second active material of the positive electrode is satisfied.
  • the positive electrode first active material is composed of a lithium-containing composite oxide represented by the above general compositional formula (1)
  • the positive electrode second active material is composed of a lithium-containing composite oxide represented by the above general compositional formula (2).
  • the mole fraction of Ni and the mole fraction of Co in all elements constituting the element group represented by M , and the molar fraction of at least one element selected from the group consisting of Mn and Al are respectively Y (0 ⁇ Y ⁇ 1), Z (0 ⁇ Z ⁇ 1), and 1-YZ, and the above general
  • the mole fractions are respectively Q (0 ⁇ Q ⁇ 1), R (0 ⁇ R ⁇ 1), and 1-QR, Y>Q is satisfied.
  • an inactive layer containing nickel oxide (NiO) can be formed. Since deterioration of the active material layer due to the formation of , etc. can be suppressed, the durability of the battery can be improved and the life of the battery can be extended. Further, nickel oxide is inactive in a lithium ion secondary battery and does not contribute to battery reactions.
  • the positive electrode first active material layer receives lithium ions through the positive electrode second active material layer, it has relatively less contact with the electrolytic solution compared to the positive electrode second active material layer.
  • the positive electrode first active material layer which is a high capacity layer, generates and grows less nickel oxide than the positive electrode second active material layer. Therefore, it is possible to improve cycle durability and lithium ion storage durability when the lithium ion secondary battery is repeatedly charged and discharged.
  • the above-mentioned values of Y and Z and the above-mentioned values of Q and R are determined by ICP analysis.
  • the positive electrode active material layer is not particularly limited as long as the mole fraction of Ni in the first active material of the positive electrode>mole fraction of Ni in the second active material of the positive electrode, but for example, if the mole fraction of Ni in the first active material of the positive electrode is 50 ⁇ It is preferable that the mole fraction ⁇ 96 and 25 ⁇ the mole fraction of Ni in the positive electrode second active material ⁇ 50 are satisfied.
  • the mole fraction of Ni in the first active material of the positive electrode is at least the lower limit of these ranges, and the mole fraction of Ni in the second active material of the positive electrode is less than the upper limit of these ranges, so that the energy density of the battery can be sufficiently increased.
  • the lithium-containing composite oxide constituting the positive electrode first active material of the positive electrode first active material layer further contains Co
  • the positive electrode second active material of the positive electrode second active material layer Preferably, the lithium-containing composite oxide constituting the substance further contains Co
  • the mole fraction of Co in the second positive electrode active material is greater than the mole fraction of Co in the first positive electrode active material. That is, it is preferable that the mole fraction of Co in the positive electrode first active material ⁇ the mole fraction of Co in the positive electrode second active material is satisfied.
  • a second positive electrode active material layer having a higher mole fraction of Co than that of the first positive electrode active material layer By arranging a second positive electrode active material layer having a higher mole fraction of Co than that of the first positive electrode active material layer on the separator side of the positive electrode active material layer, lithium ions can easily diffuse, and the positive electrode activity can be improved, especially at low temperatures. This is because the resistance of the material layer can be reduced, so the low-temperature output of the battery 1 can be improved. Furthermore, the positive electrode active material layer can suppress heat generation as well as suppress an increase in resistance.
  • the positive electrode active material layer preferably satisfies the mole fraction of Co in the first active material of the positive electrode ⁇ the molar fraction of Co in the second active material of the positive electrode, and in particular, for example, 0 ⁇ Co in the first active material of the positive electrode. It is preferable that the mole fraction of Co ⁇ 25 and 25 ⁇ the mole fraction of Co in the positive electrode second active material ⁇ 40 are satisfied. This is because when the mole fraction of Co in the second positive electrode active material is at least the lower limit of these ranges, the resistance at low temperatures of the positive electrode active material layer can be more effectively reduced.
  • the average particle size of the positive electrode second active material in the positive electrode second active material layer is smaller than the average particle size of the positive electrode first active material in the positive electrode first active material layer.
  • the average particle size of the positive electrode first active material of the positive electrode first active material layer is Mf [ ⁇ m] measured as the median diameter (D50)
  • the positive electrode second active material of the positive electrode second active material layer is When the average particle size of the active material is Ms [ ⁇ m] measured as the median diameter (D50), it is preferable that Mf>Ms be satisfied.
  • the diffusion path of lithium ions in the thickness direction of the positive electrode active material layer can be shortened, and the positive electrode active material This is because the resistance of the layer can be reduced.
  • the reaction area of the positive electrode active material per unit volume in the positive electrode active material layer is larger than that of the positive electrode second active material layer, which is a high input/output layer, compared to the positive electrode first active material layer, which is a high capacity layer. is relatively larger.
  • the positive electrode second active material layer which is a high input/output layer can relatively shorten the diffusion path of lithium ions. Therefore, the charging characteristics, particularly the rapid charging characteristics, of the lithium ion secondary battery can be improved.
  • the reaction area of the positive electrode active material per unit volume in the positive electrode active material layer is higher in the positive electrode first active material layer, which is a high capacity layer, than in the positive electrode second active material layer, which is a high input/output layer. becomes relatively small. Therefore, in the positive electrode first active material layer, which is a high capacity layer, it is possible to improve the cycle durability and the storage durability of lithium ions when the lithium ion secondary battery is repeatedly charged and discharged.
  • the median diameter (D50) is the diameter of particles when the integrated value is 50% in particle size distribution measurement measured by laser diffraction scattering particle size distribution measurement method.
  • the positive electrode active material layer preferably satisfies Mf>Ms, and particularly preferably satisfies 5.6 ⁇ m ⁇ Mf ⁇ 18.6 ⁇ m and 3.0 ⁇ m ⁇ Ms ⁇ 8.0 ⁇ m.
  • the positive electrode active material layer is preferably one in which the weight ratio of the conductive additive to the total weight of the positive electrode second active material layer is greater than the ratio of the weight of the conductive additive to the total weight of the positive electrode first active material layer.
  • the weight ratio of the conductive additive to the total weight of the positive electrode second active material layer is greater than the ratio of the weight of the conductive additive to the total weight of the positive electrode first active material layer.
  • the ratio of the weight of the conductive additive to the total weight of the positive electrode first active material layer is 0.5% by weight or more and 2% by weight or less, and the conductivity is based on the total weight of the positive electrode second active material layer.
  • the weight ratio of the auxiliary agent is 0.8% by weight or more and 5% by weight or less.
  • the thickness of one side of the positive electrode second active material layer in the stacking direction (for example, the depth direction Y in FIG. 4) (for example, the second thickness T2 in FIG. 4) is, for example, an average thickness of 5 ⁇ m or more and 500 ⁇ m or less.
  • the average thickness may be 10 ⁇ m or more and 300 ⁇ m or less.
  • materials included in the first positive electrode active material layer are prepared.
  • the materials are mixed and the resulting mixture is dispersed in a solvent (eg, N-methyl-2-pyrrolidone (NMP) and/or water) to obtain a positive electrode first slurry.
  • materials included in the second positive electrode active material layer are prepared.
  • the materials are mixed and the resulting mixture is dispersed in a solvent (eg, N-methyl-2-pyrrolidone (NMP) and/or water) to obtain a second positive electrode slurry.
  • the first positive electrode slurry and the second positive electrode slurry are simultaneously applied onto the positive electrode current collector 34a.
  • the die head 50 includes an exit block 57, a three-dimensional shim 58, and an entry block 59.
  • a positive electrode second slurry manifold 52 and a positive electrode first slurry manifold 51 are provided inside the die head 50.
  • the second positive slurry and the first positive slurry are simultaneously discharged from each manifold 52 and 51 toward the positive current collector 34a that is being conveyed along the back roller 56. Thereby, a second positive slurry layer 33d and a first positive slurry layer 33b are formed.
  • the solvent contained in the first positive slurry layer 33b and the second positive slurry layer 33d is evaporated using a drying oven or the like, and the first positive slurry layer 33b and the second positive slurry layer 33d are dried.
  • a first positive active material layer (not shown) and a second positive active material layer (not shown) are formed on one surface of the positive current collector 34a.
  • the positive electrode current collector 34a, the positive electrode first active material layer, and the positive electrode second active material layer are pressed. Specifically, a laminate including the cathode current collector 34a, the cathode first active material layer, and the cathode second active material layer is sandwiched between rolls heated to 60 to 120° C. and pressure is applied. Thereafter, this laminate is slit to a predetermined width. Thereby, a positive electrode is obtained.
  • the positive electrode first active material layer (positive electrode first slurry layer 33b) is replaced by the positive electrode second active material layer (positive electrode first slurry layer 33b).
  • the interface on the second slurry layer 33d) side is not pressed by a roll.
  • the interface of the positive electrode second active material layer (positive electrode second slurry layer 33d) on the side opposite to the positive electrode first active material layer (positive electrode first slurry layer 33b) is pressed by a roll.
  • the positive electrode first active material layer which includes large particle size particles and small particle size particles whose average particle size is smaller than the large particle size particles, as the positive electrode first active material, the large particle size is damage to particles can be suppressed.
  • the second positive active material layer is laminated on the first positive active material layer (first positive slurry layer 33b).
  • the surface of the positive electrode second slurry layer 33d opposite to the positive electrode first active material layer (the positive electrode first slurry layer 33b) is roll pressed. This is preferable because it can improve the adhesion between the first positive active material layer and the second positive active material layer.
  • the surface of the positive electrode second active material layer (positive electrode second slurry layer 33d) facing the roll during roll pressing is lower than the surface of the positive electrode second active material layer (positive electrode second slurry layer 33d) and the positive electrode first active material layer (
  • the interface between the positive electrode first slurry layers 33b) can be formed to have larger irregularities, which is preferable because good adhesion and stable ionic conductivity can be obtained.
  • the lithium ion secondary battery according to the embodiment is a battery including a positive electrode, a negative electrode, and an electrolyte, and the positive electrode is the positive electrode for the lithium ion secondary battery according to the embodiment.
  • the lithium ion secondary battery is not limited to a battery that is installed in an electric vehicle and supplies power to a drive motor of the electric vehicle.
  • a lithium ion secondary battery can be applied to a battery installed in a portable electronic device such as a smartphone (registered trademark), or a battery installed in a stationary power generation device.
  • the lithium ion secondary battery according to the embodiment is not particularly limited, for example, as in an example according to the embodiment, the lithium ion secondary battery includes a charge/discharge body having a positive electrode, a negative electrode, and a separator, and the electrolyte is connected to the separator. It is impregnated with.
  • the lithium ion secondary battery according to the embodiment preferably includes an electrolytic solution in which the above electrolyte is dissolved.
  • the lithium ion secondary battery according to the embodiment is a battery including a solid electrolyte as an electrolyte, and includes a positive electrode, a negative electrode, and a solid electrolyte layer containing the solid electrolyte, and the solid electrolyte layer serves as the positive electrode. It may also include a charging/discharging body interposed between the negative electrode and the negative electrode.
  • a battery including such a solid electrolyte does not need to contain an electrolyte, so it can have high safety.
  • the positive electrode second active material layer including the positive electrode second active material having a smaller average particle size and a larger specific surface area than the positive electrode first active material layer Since it is placed on the solid electrolyte layer side, good ion conduction is achieved.
  • the interface between the positive electrode second active material layer and the solid electrolyte layer preferably has larger irregularities in the thickness direction than the interface of the solid electrolyte layer on the side opposite to the positive electrode second active material layer. It is preferable for lithium ion transfer because of its high adhesion.
  • solid electrolytes examples include sulfide-based solid electrolytes, such as Li 10 GeP 2 S 12 , Li 6 PS 5 Cl, Li 2 S-P 2 S 5 -based glass, and Li 2 S-SiS 2- based glass. , Li 2 S-P 2 S 5 -GeS 2- based glass, Li 2 S-B 2 S 3 -based glass, oxide-based solid electrolytes, such as Li 7 La 3 Zr 2 O 12 , LiLaTiO 3 , LiTi(PO 4 ) 3 , LiGe(PO 4 ) 3 , and complex hydride solid electrolytes, such as LiBH 4 -LiI, LiBH 4 -LiNH 2 , and mixtures of two or more thereof.
  • sulfide-based solid electrolytes such as Li 10 GeP 2 S 12 , Li 6 PS 5 Cl, Li 2 S-P 2 S 5 -based glass, and Li 2 S-SiS 2- based glass.
  • a battery may further include a positive electrode electronic insulating layer provided on the positive electrode and a negative electrode electronic insulating layer provided on the negative electrode instead of the separator.
  • the positive electrode 34 includes a positive electrode current collector 34a and a positive electrode current collector 34a.
  • a positive electrode active material layer 34b (positive electrode mixture layer) joined to both sides of the positive electrode active material layer 34b, a positive electrode first active material layer 34b1 joined to both sides of the positive electrode current collector 34a, and a positive electrode first active material layer 34b1 joined to both sides of the positive electrode current collector 34a.
  • the positive electrode second active material layer 34b2 is bonded to each of the first active material layers 34b1.
  • the positive electrode 34 further includes a positive electrode electronic insulating layer 34d bonded to each of the positive electrode second active material layers 34b2.
  • the negative electrode 32 includes a negative electrode current collector 32a, a negative electrode active material layer 32b (negative electrode mixture layer) bonded to both surfaces of the negative electrode current collector 32a, and a negative electrode electronic insulating layer bonded to each of the negative electrode active material layers 32b. 32d.
  • a portion (hereinafter referred to as “positive electrode current collector exposed portion”) 34c that is not covered with either the positive electrode active material layer 34b or the positive electrode electronic insulating layer 34d is provided at one end of the positive electrode current collector 34a.
  • the positive electrode current collector exposed portion 34c is provided at and near the end face of the winding group (not shown).
  • the positive electrode current collector exposed portion 34c faces and is electrically connected to a positive electrode side connection end (not shown) of a positive electrode current collector plate (not shown).
  • a portion 32c (hereinafter referred to as “negative electrode current collector exposed portion”) that is not covered with either the negative electrode active material layer 32b or the negative electrode electronic insulating layer 32d is provided at one end of the negative electrode current collector 32a. It will be done.
  • the negative electrode current collector exposed portion 32c is provided on the end face of the wound group and in the vicinity thereof.
  • the negative electrode current collector exposed portion 32c faces and is electrically connected to a negative electrode side connection end (not shown) of a negative electrode current collector plate (not shown).
  • the positive electrode electronic insulating layer 34d and the negative electrode electronic insulating layer 32d have the function of preventing short circuit between the positive electrode active material layer 34b and the negative electrode active material layer 32b, and the function of preventing ions from occurring between the positive electrode active material layer 34b and the negative electrode active material layer 32b. It has the function of conducting.
  • the positive electrode electronic insulating layer 34d and the negative electrode electronic insulating layer 32d may be porous layers made of an electrically insulating (that is, electronically and ionically insulating) material. The porous layer can hold an electrolytic solution in its pores, and can conduct ions between the positive electrode active material layer 34b and the negative electrode active material layer 32b via this electrolytic solution.
  • the porous positive electrode electronic insulating layer 34d and negative electrode electronic insulating layer 32d may also have a function of buffering expansion and contraction of the positive electrode active material layer 34b and negative electrode active material layer 32b accompanying charging and discharging of the lithium ion secondary battery 100.
  • the expansion and contraction of the negative electrode active material layer 32b accompanying charging and discharging of the battery 1 is generally larger than the expansion and contraction of the positive electrode active material layer 34b. Therefore, in order to buffer the expansion and contraction of the larger negative electrode active material layer 32b, the negative electrode electronic insulating layer 32d may have a larger average pore diameter than the average pore diameter of the positive electrode electronic insulating layer 34d.
  • the average pore diameter of the positive electrode electronic insulating layer 34d and the negative electrode electronic insulating layer 32d means the average value of volume-based pore diameters measured by mercury porosimetry.
  • the total content of Na and Fe in the positive electronic insulating layer 34d and the negative electronic insulating layer 32d may be 300 ppm or less based on the weight of the positive electronic insulating layer 34d and the negative electronic insulating layer 32d.
  • the amount of each element contained in the positive electrode electronic insulating layer 34d and the negative electrode electronic insulating layer 32d can be measured by an ICP (Inductive Coupled Plasma) method.
  • the positive electronic insulating layer 34d may include positive electronic insulating particles, and the negative electronic insulating layer 32d may include negative electronic insulating particles.
  • the positive electrode electronically insulating particles and the negative electrode electronically insulating particles are collectively referred to as electronically insulating particles.
  • the electronically insulating particles may be electrically insulating particles. Examples of electrically insulating particles include ceramic particles.
  • Ceramic particles include alumina (Al 2 O 3 ), boehmite (Al 2 O trihydrate ), magnesia (MgO), zirconia (ZrO 2 ), titania (TiO 2 ), iron oxide, silica (SiO 2 ), and It may contain at least one selected from the group consisting of barium titanate (BaTiO 2 ), preferably at least one selected from the group consisting of alumina, boehmite, magnesia, zirconia, and titania.
  • the electronically insulating particles may have an average particle size within the range of 0.7-1.1 ⁇ m.
  • the average particle diameter of the electronic insulating particles is the arithmetic mean of the projected area circular diameters of 100 or more electronic insulating particles randomly selected based on microscopic images of the positive electrode electronic insulating layer 34d and the negative electrode electronic insulating layer 32d. It can be obtained by calculating.
  • the electronically insulating particles may contain at least one of 100 to 200 ppm Na, 50 to 100 ppm Fe, or 50 to 100 ppm Ca, based on the weight of the electronic insulating particles.
  • the positive electrode electronic insulating layer 34d and the negative electrode electronic insulating layer 32d may further include a binder.
  • the binder may be dispersed or dissolved in an aqueous or non-aqueous solvent such as N-methyl-2-pyrrolidone (NMP), such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), etc. , polyacrylic acid (PAA), and carboxymethylcellulose (CMC).
  • NMP N-methyl-2-pyrrolidone
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PAA polyacrylic acid
  • CMC carboxymethylcellulose
  • the positive electrode electronic insulating layer 34d and the negative electrode electronic insulating layer 32d may further contain a dispersant.
  • the dispersant may contain at least one selected from the group consisting of carboxylic acid compounds and phosphoric acid compounds.
  • the interface 34e between the positive electrode electronic insulating layer 34d and the positive electrode active material layer 34b (the second positive electrode active material layer 34b2) has an uneven shape, and the height of the unevenness is 2 ⁇ m or more, preferably in the range of 2 to 4 ⁇ m. It is within.
  • the interface 32e between the negative electrode electronic insulating layer 32d and the negative electrode active material layer 32b has an uneven shape, and the height of the unevenness is 2 ⁇ m or more, preferably within the range of 2 to 4 ⁇ m.
  • the positive electrode electronic insulating layer 34d Since the unevenness height of the interface 34e between the positive electrode electronic insulating layer 34d and the positive electrode active material layer 34b and the interface 32e between the negative electrode electronic insulating layer 32d and the negative electrode active material layer 32b is 2 ⁇ m or more, the positive electrode electronic insulating layer 34d The adhesion between the positive electrode active material layer 34b and the negative electrode electronic insulating layer 32d and the negative electrode active material layer 32b can be improved. Thereby, peeling of the positive electrode electronic insulating layer 34d and the negative electrode electronic insulating layer 32d from the positive electrode active material layer 34b and the negative electrode active material layer 32b can be prevented or reduced, respectively, and the reliability of the lithium ion secondary battery 100 can be improved. can be improved.
  • the height of the unevenness of the interface 34e between the positive electrode active material layer 34b (positive electrode second active material layer 34b2) and the positive electrode electronic insulating layer 34d is, for example, the height of the unevenness of the positive electrode second active material particles ( It can be controlled by the particle diameter of the positive electrode electronic insulating particles contained in the positive electrode second active material) and the positive electrode electronic insulating layer 34d. As shown in FIG. 7, the average particle diameter of the positive electrode second active material particles 34b2p (positive electrode second active material) contained in the positive electrode second active material layer 34b2 is the same as that of the positive electrode electronic insulating particles contained in the positive electrode electronic insulating layer 34d.
  • the positive electrode electronic insulating particles 34dp enter the gap between the positive electrode second active material particles 34b2p, and the interface 34e between the positive electrode second active material layer 34b2 and the positive electrode electronic insulating layer 34d It becomes an uneven shape.
  • spherical positive electrode second active material particles 34b2p having an average particle diameter within the range of 4.5 to 5.5 ⁇ m
  • positive electrode electronic insulating particles having an average particle diameter within the range of 0.7 to 1.1 ⁇ m.
  • the unevenness height of the interface 34e between the positive electrode active material layer 34b (positive electrode second active material layer 34b2) and the positive electrode electronic insulating layer 34d is set to 2 ⁇ m or more, preferably within the range of 2 to 4 ⁇ m. Can be done.
  • the unevenness height of the interface 32e between the negative electrode active material layer 32b and the negative electrode electronic insulating layer 32d is determined by the negative electrode active material particles (negative electrode active material) contained in the negative electrode active material layer 32b and the negative electrode contained in the negative electrode electronic insulating layer 32d. It can be controlled by the particle size of the electronically insulating particles. For example, by using scale negative electrode active material particles having an average particle size in the range of 9 to 11 ⁇ m and negative electrode electronic insulating particles having an average particle size in the range of 0.7 to 1.1 ⁇ m, negative electrode active material particles can be used.
  • the height of the unevenness at the interface 32e between the material layer 32b and the negative electronic insulating layer 32d can be set to 2 ⁇ m or more, preferably within the range of 2 to 4 ⁇ m.
  • the unevenness height of the interface 34e between the positive electrode electronic insulating layer 34d and the positive electrode active material layer 34b (positive electrode second active material layer 34b2) and the interface 32e between the negative electrode active material layer 32b and the negative electrode electronic insulating layer 32d is measured as follows.
  • a scanning electron microscope (SEM) is used to obtain cross-sectional SEM images of three arbitrary points on the positive electrode 34 or the negative electrode 32, and in each cross-sectional SEM image, a predetermined reference plane is obtained from ten or more arbitrary points on the interfaces 34e and 32e.
  • the thickness of the insulating layer 34d and the thickness of the negative electrode electronic insulating layer 32d are measured.
  • the standard deviation of the obtained distance values is defined as the unevenness height of the interfaces 34e and 32e.
  • the surface 34f of the positive electrode electronic insulating layer 34d and the surface 32f of the negative electrode electronic insulating layer 32d are surfaces facing each other, and may be sufficiently flat compared to the interfaces 34e and 32e.
  • the height of the unevenness on the surfaces 34f and 32f of the positive electronic insulating layer 34d and the negative electronic insulating layer 32d may be one-tenth or less of the height of the unevenness on the interfaces 34e and 32e, respectively.
  • the interface 34e between the positive electrode electronic insulating layer 34d and the positive electrode active material layer 34b has an uneven shape means "A positive electrode active material and an electronic insulating material are provided between the positive electrode electronic insulating layer 34d and the positive electrode active material layer 34b.” It can also be paraphrased as “having a positive electrode mixed layer containing the positive electrode mixture layer.” Similarly, “the interface 32e between the negative electrode electronic insulating layer 32d and the negative electrode active material layer 32b has an uneven shape” means that "the negative electrode active material and the electronic insulating layer 32d and the negative electrode active material layer 32b are It can be paraphrased as "having a negative electrode mixed layer containing a negative electrode material”.
  • the thickness of the positive electrode mixed layer is 2 ⁇ m or more, preferably within the range of 2 to 4 ⁇ m.
  • the thickness of the negative electrode mixed layer is 2 ⁇ m or more, preferably within the range of 2 to 4 ⁇ m.
  • the thickness of the positive electrode mixed layer and the negative electrode mixed layer is the same as the uneven height of the interfaces 34e and 32e between the positive electrode electronic insulating layer 34d and the negative electrode electronic insulating layer 32d and the positive electrode active material layer 34b and the negative electrode active material layer 32b described above. can be measured.
  • the positive electrode electronic insulating layer 34d and the negative electrode electronic insulating layer 32d may be in contact with each other.
  • the positive electrode electronic insulating layer 34d and the negative electrode electronic insulating layer 32d may be in contact with each other without being fixed to each other. Since the positive electrode electronic insulating layer 34d and the negative electrode electronic insulating layer 32d are not fixed to each other, stress caused by expansion and contraction of the negative electrode active material layer 32b and the positive electrode active material layer 34b accompanying charging and discharging of the lithium ion secondary battery 100 is alleviated.
  • peel strength of the positive electrode electronic insulating layer 34d with respect to the positive electrode active material layer 34b and the peel strength of the negative electrode electronic insulating layer 32d with respect to the negative electrode active material layer 32b are greater than the peel strength of the positive electrode electronic insulating layer 34d with respect to the negative electrode electronic insulating layer 32d. good. Peel strength can be measured, for example, by a 180° tape peel test based on JIS C 0806-3 1999.
  • the height of the unevenness of the interface 34e between the positive electrode active material layer 34b (the second positive electrode active material layer 34b2) and the positive electrode electronic insulating layer 34d is determined by, in addition to the particle diameters of the positive electrode active material particles and positive electrode electronic insulating particles described above,
  • the solvent of the positive electrode slurry (positive electrode second slurry) used for forming the positive electrode active material layer 34b (positive electrode second active material layer 34b2) by coating and the positive electrode electronic insulating material slurry used for forming the positive electrode electronic insulating layer 34d by coating It can also be controlled by the type, viscosity, etc.
  • the unevenness height of the interface 32e between the negative electrode active material layer 32b and the negative electrode electronic insulating layer 32d is also determined by the negative electrode slurry used for forming the negative electrode active material layer 32b by coating and the formation by coating the negative electrode electronic insulating layer 32d. It can be controlled by the type of solvent, viscosity, etc. of the negative electrode electronic insulating material slurry used.
  • the average pore diameter of the positive electrode electronic insulating layer 34d and the negative electrode electronic insulating layer 32d can be controlled by the particle size of the electronic insulating particles, the press pressure during press processing, etc. Specifically, the higher the press pressure, the smaller the average pore diameter, and the smaller the particle diameter of the electronic insulating particles, the smaller the average pore diameter.
  • the strength of the electronic insulating layer (the positive electronic insulating layer 34d and the negative electronic insulating layer 32d) is higher than that of the separator, so the safety of the battery is improved. is obtained.
  • such other examples of the battery 1 are particularly suitable for positive electrodes manufactured by the above-mentioned manufacturing method in which two-layer simultaneous coating is applied, or by the manufacturing method in which three-layer simultaneous coating is applied, which will be described later. By installing a cathode manufactured by this method, it is possible to contribute to the provision of batteries with high energy density and long life.
  • each of the positive electrode electronic insulating layer 34d and the negative electrode electronic insulating layer 32d is a solid electrolyte (i.e., an electronic insulating It is a layer containing ionically conductive and ionically conductive materials.
  • This modified battery does not need to contain an electrolyte, so it can have high safety.
  • the electronic insulating particles included in the positive electronic insulating layer 34d and the negative electronic insulating layer 32d may be solid electrolyte particles. Since the solid electrolyte can be well formed by press molding, in this case, it is not essential that the positive electrode electronic insulating layer 34d and the negative electrode electronic insulating layer 32d contain a binder and a dispersant.
  • At least one of the first cathode active material layer 34b1 and the second cathode active material layer 34b2 included in the cathode active material layer 34b contains, in addition to the active material, an optional binder, a conductive aid, and a dispersant, It may further contain a solid electrolyte. Thereby, the ion conductivity of at least one of the positive electrode first active material layer 34b1 and the positive electrode second active material layer 34b2 can be improved.
  • the negative electrode active material layer 32b may further contain a solid electrolyte in addition to the electrode active material, an optional binder, a conductive aid, and a dispersant. Thereby, the ion conductivity of the negative electrode active material layer 32b can be improved.
  • the battery 1 of the above modification does not need to contain an electrolytic solution, and the strength of the electronic insulating layers (positive electronic insulating layer 34d and negative electronic insulating layer 32d) is higher than that of the separator, so high safety can be achieved.
  • the battery 1 of such a modified example is particularly manufactured using a positive electrode manufactured using a manufacturing method that uses two layers of simultaneous coating as described above, or a manufacturing method that uses three layers of simultaneous coating that will be described later. By installing the manufactured positive electrode, it is possible to contribute to the provision of batteries with high energy density and long life.
  • Such a separator-less battery (lithium ion secondary battery) can be manufactured using techniques known in the technical field of the present invention, except for the manufacturing method of the positive electrode of the other example according to the embodiment.
  • the first positive active material layer 34b1 and the second positive active material layer 34b2 of the positive electrode active material layer 34b and the positive electronic insulating layer 34d are simultaneously coated as follows. It can be manufactured by
  • materials included in the first positive electrode active material layer 34b1 are prepared.
  • the materials are mixed and the resulting mixture is dispersed in a solvent (eg, N-methyl-2-pyrrolidone (NMP) and/or water) to obtain a positive electrode first slurry.
  • materials included in the second positive electrode active material layer 34b2 are prepared.
  • the materials are mixed and the resulting mixture is dispersed in a solvent (eg, N-methyl-2-pyrrolidone (NMP) and/or water) to obtain a second positive electrode slurry.
  • materials included in the positive electrode electronic insulating layer 34d are prepared.
  • the materials are mixed and the resulting mixture is dispersed in a solvent (eg, N-methyl-2-pyrrolidone (NMP) and/or water) to obtain a positive electrode electronic insulating material slurry.
  • a solvent eg, N-methyl-2-pyrrolidone (NMP) and/or water
  • the first positive electrode slurry, the second positive electrode slurry, and the positive electronic insulating material slurry are simultaneously applied onto the positive electrode current collector.
  • the positive electrode second slurry layer, the positive electrode first slurry layer, and the positive electrode electronic insulating material slurry layer are laminated in this order.
  • the solvent contained in the positive electrode second slurry layer, the positive electrode first slurry layer, and the positive electrode electronic insulating material slurry layer is evaporated using a drying oven or the like, and the positive electrode second slurry layer, the positive electrode first slurry layer, and the positive electrode Dry the electronic insulation slurry layer.
  • the first positive active material layer 34b1, the second positive active material layer 34b2, and the positive electronic insulating layer 34d are stacked in this order on one surface of the positive current collector 34a.
  • the positive electrode current collector 34a, the positive electrode first active material layer 34b1, the positive electrode second active material layer 34b2, and the positive electrode electronic insulating layer 34d are pressed.
  • a laminate in which the cathode current collector 34a, the cathode first active material layer 34b1, the cathode second active material layer 34b2, and the cathode electronic insulating layer 34d are stacked in this order is heated to 60 to 120°C. Place it between two rolls and apply pressure. Thereafter, this laminate is slit to a predetermined width. Thereby, a positive electrode is obtained.
  • the interface between each layer has unevenness. Strong adhesion provides high safety and reliability. Furthermore, if this manufacturing method is applied to the lithium ion secondary battery of the above modification, there is no need to include an electrolyte, and even higher safety and reliability can be obtained.
  • the positive electrode second active material layer 34b2 of the positive electrode first active material layer 34b1 (positive electrode first slurry layer)
  • the interface 34m on the (positive electrode second slurry layer) side is not pressed by a roll.
  • the surface 34f of the positive electrode electronic insulating layer 34d on the side opposite to the positive electrode second active material layer 34b2 is pressed with a roll.
  • the positive electrode first active material layer 34b1 containing large particle size particles and small particle size particles whose average particle size is smaller than the large particle size particles as the positive electrode first active material is rolled. It is possible to suppress damage to particles of a certain size.
  • the positive electrode electronic insulating layer 34d which is a coating layer laminated on the positive electrode second active material layer 34b2, is further The surface 34f opposite to the second active material layer 34b2 is roll pressed. This is preferable because the adhesion between the first positive electrode active material layer 34b1, the second positive active material layer 34b2, and the positive electronic insulating layer 34d (coating layer) can be improved.
  • the interface 34m between the active material layers 34b1 can be formed to have larger irregularities, which is preferable because it provides good adhesion and stable ionic conductivity.
  • the difference between the unevenness of the surface 34f of the positive electrode electronic insulating layer 34d and the unevenness of the interface 34m between the positive electrode second active material layer 34b2 and the positive electrode first active material layer 34b1 is more important than the difference between the positive electrode electronic insulating layer 34d and the positive electrode It is preferable that the difference between the unevenness of the interface 34e between the second active material layer 34b2 and the unevenness of the interface 34m between the positive electrode second active material layer 34b2 and the positive electrode first active material layer 34b1 is smaller.
  • PVdF polyvinylidene fluoride
  • a positive electrode active material, a conductive additive, and a binder were mixed at a weight ratio of 90:5:5.
  • NMP N-methyl-2-pyrrolidone
  • a 15 ⁇ m thick aluminum foil was prepared as a positive electrode current collector.
  • a positive electrode slurry was applied to both sides of the positive electrode current collector by a slot die coating method to form a positive electrode slurry layer. Then, the positive electrode slurry layer was dried and pressed. Thereby, a positive electrode (a positive electrode for a lithium ion secondary battery) in which positive electrode active material layers were formed on both sides of the positive electrode current collector was obtained.
  • Natural graphite coated with amorphous carbon was prepared as the negative electrode active material.
  • SBR styrene-butadiene rubber
  • CMC carboxymethyl cellulose
  • the negative electrode active material, binder, and dispersant were mixed at a weight ratio of 98:1:1. Ion-exchanged water was added to the resulting mixture to adjust the viscosity to obtain a negative electrode slurry.
  • a copper foil with a thickness of 10 ⁇ m was prepared as a negative electrode current collector.
  • a negative electrode slurry was applied to both sides of the negative electrode current collector by a slot die coating method to form a negative electrode slurry layer. Then, the negative electrode slurry layer was dried and pressed. Thereby, a negative electrode (negative electrode for lithium ion secondary battery) in which negative electrode active material layers were formed on both sides of the negative electrode current collector was obtained.
  • One separator, a negative electrode, another separator, and a positive electrode were stacked and wound in this order. Thereby, a wound group was produced. Further, ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed at a volume ratio of 1:2, and LiPF 6 was dissolved in the resulting mixed solution. Thereby, a 1.0 mol/L LiPF 6 solution was obtained as a non-aqueous electrolyte.
  • a lithium ion secondary battery was fabricated using a wound group and a non-aqueous electrolyte.
  • the lithium ion secondary battery was charged with a constant current of 0.2 CA until the battery voltage reached 4.2V, and then charged with a constant voltage of 4.2V. Charging was carried out for a total of 2.5 hours. After resting for 30 minutes, the lithium ion secondary battery was discharged at a constant current of 0.1 CA until the battery voltage reached 2.5 V, and the discharge capacity was determined. This discharge capacity was taken as the initial battery capacity.
  • a lithium ion secondary battery was charged using a constant current-constant voltage (CC-CV) method from 0% SOC to 50% SOC.
  • the charging current during constant current charging was 0.2 CA.
  • the lithium ion battery was discharged for 10 seconds at a constant current of 1 CA, and the voltage drop value due to discharge was measured.
  • similar constant current discharge was performed at discharge currents of 2CA and 3CA. The discharge current was plotted on the horizontal axis and the voltage drop value was plotted on the vertical axis, and the slope of the graph was taken as the initial DCR.
  • the lithium ion secondary battery was charged using a constant current-constant voltage (CC-CV) method from 0% SOC to 100% SOC. Then, the lithium ion secondary battery was stored in a constant temperature bath at 80° C. for 30 days. The lithium ion secondary battery was taken out of the 80° C. thermostat and discharged at a constant current of 1 CA until the battery voltage reached 2.8V.
  • CC-CV constant current-constant voltage
  • Capacity retention rate and DCR increase rate From the above measurement results, the capacity retention rate was determined by dividing the battery capacity after high temperature storage by the initial battery capacity. Further, the DCR increase rate was determined by dividing the DCR after high temperature storage by the initial DCR. The capacity retention rate and DCR increase rate of the lithium ion secondary batteries of each reference example are shown in Table 1 below.
  • the lithium ion secondary battery of Reference Example 1 in which the mole fraction of Ni in the positive electrode active material is low is different from the lithium ion secondary battery in Reference Example 2 in which the mole fraction of Ni in the positive electrode active material is high.
  • the capacity retention rate was higher and the DCR increase rate was lower. It is thought that one of the causes of the increase in DCR is the formation of an inactive layer.
  • an inert layer is generated on the separator side (the side far from the current collector).
  • an inert layer of the positive electrode can be formed. can be suppressed. As a result, it is possible to provide a battery with high energy density and long life by minimizing the hindrance to ion conduction while containing the desired amount of Ni in the electrode as a whole.
  • the present invention includes the following aspects.
  • a positive electrode comprising a positive electrode current collector, a positive electrode mixture layer provided on the positive electrode current collector, and a positive electrode electronic insulating layer provided on the positive electrode mixture layer;
  • a negative electrode comprising a negative electrode current collector, a negative electrode mixture layer provided on the negative electrode mixture layer, and a negative electrode electronic insulating layer provided on the negative electrode mixture layer; Equipped with The unevenness height of the interface between the positive electrode mixture layer and the positive electrode electronic insulating layer is 2 ⁇ m or more, A lithium ion secondary battery, wherein the unevenness height of the interface between the negative electrode mixture layer and the negative electrode electronic insulating layer is 2 ⁇ m or more.
  • [Section 2] Item 2.
  • 1 battery (lithium ion secondary battery), 100 charge/discharge body, 110 positive electrode (positive electrode for lithium ion secondary battery), 111 positive electrode current collector, 111a current collecting part, 111b positive electrode tab, 111c side edge, 112 positive electrode active material layer, 113 positive electrode first active material layer, 114 positive electrode second active material layer, 120 negative electrode, 121 negative electrode current collector, 121a current collector, 121b negative electrode tab, 121c side edge, 122 negative electrode active material layer, 130 separator, 200 container, 201 case, 202 lid, 300 external terminal, 301 positive terminal, 302 negative terminal, X width direction of battery 1, Y depth direction of battery 1, Z height direction of battery 1. All publications, patents, and patent applications cited herein are incorporated by reference in their entirety.

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PCT/JP2022/033039 2022-09-01 2022-09-01 リチウムイオン二次電池用正極及びリチウムイオン二次電池 Ceased WO2024047854A1 (ja)

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US18/998,120 US20260031325A1 (en) 2022-09-01 2022-09-01 Lithium ion secondary battery positive electrode and lithium ion secondary battery
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