WO2024203506A1 - リチウムイオン電池 - Google Patents

リチウムイオン電池 Download PDF

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Publication number
WO2024203506A1
WO2024203506A1 PCT/JP2024/010442 JP2024010442W WO2024203506A1 WO 2024203506 A1 WO2024203506 A1 WO 2024203506A1 JP 2024010442 W JP2024010442 W JP 2024010442W WO 2024203506 A1 WO2024203506 A1 WO 2024203506A1
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WIPO (PCT)
Prior art keywords
positive electrode
negative electrode
separator
electrode layer
ion battery
Prior art date
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Ceased
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PCT/JP2024/010442
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English (en)
French (fr)
Japanese (ja)
Inventor
信博 森▲崎▼
幸信 由良
大祐 飯田
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NGK Insulators Ltd
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NGK Insulators Ltd
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Priority to JP2025510516A priority Critical patent/JPWO2024203506A1/ja
Publication of WO2024203506A1 publication Critical patent/WO2024203506A1/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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • 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
    • 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
    • H01M10/058—Construction or manufacture
    • 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
    • H01M10/058—Construction or manufacture
    • H01M10/0585—Construction or manufacture of accumulators having only flat construction elements, i.e. flat positive electrodes, flat negative electrodes and flat separators
    • 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
    • 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
    • H01M4/64—Carriers or collectors
    • 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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/431—Inorganic material
    • H01M50/434—Ceramics
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/46—Separators, membranes or diaphragms characterised by their combination with 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

  • This disclosure relates to lithium-ion batteries.
  • This application claims priority to Japanese Patent Application No. 2023-058368 and Japanese Patent Application No. 2023-058369, filed on March 31, 2023, and incorporates all of the contents of said Japanese Patent Application by reference.
  • a known lithium ion battery has a positive electrode layer made of a sintered body of lithium composite oxide, a negative electrode layer made of a sintered body containing titanium, and a ceramic separator disposed between the positive electrode layer and the negative electrode layer.
  • Patent Document 1 discloses a lithium ion battery that is made of an integrated sintered plate in which the positive electrode layer, ceramic separator, and negative electrode layer are bonded together, and that is impregnated with an electrolyte.
  • the lithium ion battery disclosed in Patent Document 1 has a ceramic separator made of MgO and glass as the separator.
  • Patent Document 2 discloses a lithium ion battery including a battery element in which a power generating sheet including a ceramic positive electrode layer, a ceramic separator, a ceramic negative electrode layer, and a ceramic insulating layer is wound into a roll.
  • the lithium ion battery of Patent Document 2 has a battery element wound into a roll as an integral sintered body, and is characterized by the spatial structure of the power generating sheet.
  • the separator is a microporous film made of ceramic such as MgO or Al2O3 , and may contain a glass component.
  • one of the objectives of the invention disclosed herein is to provide a lithium-ion battery that is less susceptible to deterioration even when pulse discharge is performed continuously over a short period of time at a large current.
  • a lithium ion battery includes an electrode, an electrolyte impregnated in the electrode, and an exterior body containing the electrode and the electrolyte.
  • the electrode includes a positive electrode layer, a negative electrode layer, and a separator disposed between the positive electrode layer and the negative electrode layer.
  • the positive electrode layer, the negative electrode layer, and the separator are sintered together to form an integrated sintered body.
  • the positive electrode active material contained in the positive electrode layer is lithium cobalt oxide, and the separator contains LiAlO2 .
  • the Li/Co ratio in the positive electrode layer and the Li/Al ratio in the separator satisfy 0.85 ⁇ (Li/Co)/(Li/Al) ⁇ 1.15.
  • the above lithium-ion battery provides a lithium-ion battery that is less susceptible to deterioration even when pulse discharge is performed continuously over a short period of time at a large current.
  • FIG. 1 is a schematic cross-sectional view showing a lithium ion battery according to the present disclosure.
  • FIG. 2 is a schematic cross-sectional perspective view showing a laminated portion included in a lithium ion battery according to the present disclosure.
  • FIG. 3 is a schematic perspective view showing a sintered body included in a lithium ion battery according to the present disclosure.
  • FIG. 4 is a schematic perspective view showing a sintered body included in a lithium ion battery according to the present disclosure.
  • FIG. 5 is a schematic diagram showing a part of a process for producing a sintered body included in a lithium ion battery according to the present disclosure.
  • FIG. 1 is a schematic cross-sectional view showing a lithium ion battery according to the present disclosure.
  • FIG. 2 is a schematic cross-sectional perspective view showing a laminated portion included in a lithium ion battery according to the present disclosure.
  • FIG. 3 is a schematic perspective view showing a sintered body included in a lithium i
  • FIG. 6 is a schematic diagram showing a part of a process for producing a sintered body included in a lithium ion battery according to the present disclosure.
  • FIG. 7 is a schematic diagram showing a part of a process for producing a sintered body included in a lithium ion battery according to the present disclosure.
  • FIG. 8 is a schematic perspective view showing the appearance of a lithium-ion battery according to the present disclosure.
  • a lithium ion battery according to the present disclosure includes an electrode, an electrolyte impregnated in the electrode, and an exterior body in which the electrode and the electrolyte are accommodated.
  • the electrode includes a positive electrode layer, a negative electrode layer, and a separator disposed between the positive electrode layer and the negative electrode layer.
  • the positive electrode layer, the negative electrode layer, and the separator are sintered together to form an integrated sintered body.
  • the positive electrode active material contained in the positive electrode layer is lithium cobalt oxide, and the separator contains LiAlO 2.
  • the Li/Co ratio in the positive electrode layer and the Li/Al ratio in the separator satisfy 0.85 ⁇ (Li/Co)/(Li/Al) ⁇ 1.15.
  • the composition of the positive electrode layer, negative electrode layer, separator, etc., which are elements that constitute the electrodes has been studied. Among them, the study was carried out under the concept of forming the separator with a ceramic material containing LiAlO 2. It was found that when the ratio of the Li/Co ratio in the positive electrode layer and the Li/Al ratio in the separator is within a certain range, even when a large current pulse discharge is performed continuously in a short time, a battery with little decrease in battery capacity and suppressed deterioration can be obtained.
  • the lithium-ion battery according to the present disclosure has the above-mentioned configuration, and the balance between the expansion and contraction of each layer when firing an integrated sintered body including the positive electrode layer and the separator is good, and the uniformity of the residual stress of each member of the completed integrated sintered body is good, thereby obtaining the effect according to the present disclosure.
  • the lithium ion battery may include a plurality of the positive electrode layers, a plurality of the negative electrode layers, and a separator disposed between the positive electrode layers and the negative electrode layers, and may be configured as an integrated sintered body in which the plurality of the positive electrode layers, the plurality of the negative electrode layers, and the separator are sintered together.
  • the effect of the present disclosure becomes clearer when the lithium ion battery has a multi-layered electrode including a plurality of positive electrode layers and a plurality of negative electrode layers.
  • the lithium ion battery may have a Li/Co ratio in the positive electrode layer of 0.9 to 1.21.
  • a lithium ion battery that is particularly effective according to the present disclosure can be obtained.
  • the lithium ion battery may have a Li/Al ratio in the separator of 0.9 to 1.20.
  • the Li/Al ratio in the separator is 0.9 to 1.20, a lithium ion battery that is particularly effective according to the present disclosure can be obtained.
  • the separator may contain LiAlO 2 and a metal oxide other than LiAlO 2.
  • the separator contains a different metal oxide in addition to LiAlO 2 , the electrode strength can be adjusted while maintaining the effects of the present disclosure.
  • the negative electrode layer may be composed of a titanium-containing sintered body.
  • a lithium ion battery including an integrated sintered body composed of the separator and the positive electrode layer is expected to have improved pulse cycle characteristics.
  • the electrode is provided with a negative electrode current collector layer in contact with the negative electrode layer, and the thickness of the negative electrode current collector layer may be 0.1 ⁇ m or more and 150 ⁇ m or less, and the thickness of the separator may be 1 ⁇ m or more and 50 ⁇ m or less.
  • FIG. 1 is a schematic cross-sectional view showing the structure of a lithium ion battery 10 according to an embodiment of the present disclosure.
  • FIG. 2 is a schematic cross-sectional perspective view showing a laminated portion 1 in a sintered body 9 included in the lithium ion battery 10.
  • FIG. 3 is a schematic perspective view showing a sintered body 9 included in the lithium ion battery 10. In this specification, the direction along the X-axis shown in FIGS.
  • the width direction of the laminated portion 1 to the sintered body 9 is referred to as the width direction of the laminated portion 1 to the sintered body 9, the direction along the Y-axis is referred to as the depth direction of the laminated portion 1 to the sintered body 9, and the direction along the Z-axis is referred to as the stacking direction or thickness direction of the laminated portion 1 to the sintered body 9.
  • the surface of the top layer in the stacking direction of the laminated portion 1 is referred to as the top surface
  • the surface of the bottom layer in the stacking direction is referred to as the bottom surface
  • the surfaces on which all the stacked layers are exposed are referred to as the front and back surfaces.
  • the front and back surfaces are parallel to the XZ plane.
  • the surfaces on which the stacked structure is exposed which extend between the front and back surfaces and extend along the depth direction are referred to as side surfaces.
  • the side surface is a surface parallel to the YZ plane.
  • Surfaces other than the top and bottom surfaces, that is, the front and back surfaces in addition to the side surfaces, may also be referred to as side surfaces.
  • the top surface, bottom surface, side surface, etc. are relative names used for convenience of explanation in this specification, and it is natural that the arrangement direction and use direction of the lithium ion battery are not limited to these directions.
  • the lithium ion battery 10 has an electrode 5 housed inside an exterior body 24.
  • the electrode 5 includes a sintered body 9, and a positive electrode current collector 14 and a negative electrode current collector 18 attached to both side surfaces of the sintered body 9, respectively.
  • the sintered body 9 includes a laminated portion 1 and an insulating portion 51 as an insulating ceramic portion extending to the periphery of the laminated portion 1.
  • the laminated portion 1 is formed by laminating a plurality of positive electrode layers 12, a plurality of negative electrode layers 16, and a separator 20.
  • the laminated portion 1 and the insulating portion 51 as a whole constitute the sintered body 9, which is a single integrated sintered body. Note that the electrode 5 shown in FIG.
  • the electrodes of the lithium ion battery according to the present disclosure are not limited to this form. That is, the electrodes of the lithium ion battery according to the present disclosure may be composed of one positive electrode layer, one negative electrode layer, and one separator layer.
  • the positive electrode layers 12 and the negative electrode layers 16 are alternately stacked in the lamination direction (Z-axis direction).
  • a separator 20 is interposed between the positive electrode layers 12 and the negative electrode layers 16.
  • the separator 20 separates the positive electrode layers 12 and the negative electrode layers 16 from each other.
  • the positive electrode layers 12 are made of a sintered body containing, for example, lithium cobalt oxide.
  • the negative electrode layers 16 are made of a sintered body containing, for example, titanium.
  • the separator 20 is made of ceramic.
  • the electrode 5 of the lithium ion battery 10 includes a positive electrode collector 14 arranged in contact with the sintered body 9 from the side to the bottom of the sintered body 9.
  • the lithium ion battery 10 also includes a negative electrode collector 18 arranged in contact with the sintered body 9 from the side to the top of the sintered body 9.
  • the positive electrode collector 14 and the negative electrode collector 18 may be metal foils such as aluminum foils.
  • the positive electrode collector 14 may be made of LiCoO 2 , which is a positive electrode active material constituting the positive electrode layer 12, or may be made of LiCoO 2.
  • the negative electrode collector 18 may be made of copper foil, silver foil, or silver.
  • a carbon layer (not shown) is preferably provided between the positive electrode collector 14 and the negative electrode collector 18 and the sintered body 9.
  • the carbon layer is preferably made of conductive carbon.
  • the carbon layer can be formed, for example, by applying a conductive carbon paste to the surface of a metal foil used as a collector.
  • the exterior body 24 has an enclosed space formed inside.
  • the electrodes 5 and electrolyte 22 are contained in this enclosed space.
  • the lithium-ion battery 10 has the electrolyte 22 sealed inside the exterior body 24.
  • the positive electrode layer 12, the negative electrode layer 16, and the separator 20 are impregnated with the electrolyte 22.
  • the exterior body 24 may be appropriately selected depending on the type of the lithium ion battery 10.
  • the exterior body 24 typically includes a positive electrode can 24a, a negative electrode can 24b, and a gasket 24c, and the positive electrode can 24a and the negative electrode can 24b are crimped via the gasket 24c to form a sealed space.
  • the positive electrode can 24a and the negative electrode can 24b may be made of a metal such as stainless steel, but are not limited to these.
  • the gasket 24c may be an annular member made of an insulating resin such as polypropylene, polytetrafluoroethylene, PFA resin, or the like, but are not particularly limited to these.
  • the lithium ion battery 10 shown in FIG. 1 is in the form of a coin-type battery
  • the form of the lithium ion battery according to the present disclosure is not limited to a coin-type battery.
  • the exterior body is preferably a resin substrate, and the electrodes and electrolyte are embedded in the resin substrate.
  • the electrodes may be sandwiched between a pair of resin films.
  • the pair of resin films may be bonded together with an adhesive.
  • the pair of resin films may be heat-sealed to each other by a heat press.
  • a separator made of a solid electrolyte may be used as the separator, and may not contain an electrolyte.
  • FIG. 2 is a schematic cross-sectional perspective view showing a laminated portion 1 as a component of an electrode included in a lithium ion battery according to the present disclosure.
  • the laminated portion 1 is a laminated body in which a large number of layers are laminated.
  • FIG. 2 shows the laminated portion 1 having a rectangular parallelepiped shape, but the shape of the laminated portion 1 is not limited thereto. It is also preferable that a part of the periphery is formed in an arc shape according to a desired electrode shape, etc.
  • the rectangular parallelepiped shape has a rectangular parallelepiped shape whose outer shape is defined by a width W, a depth D, and a thickness T. Note that the rectangular parallelepiped shape does not only mean a rectangular parallelepiped in a mathematically accurate sense, but also includes a three-dimensional structure having a shape similar to a rectangular parallelepiped for design and manufacturing reasons.
  • the separator 20 is exposed on the upper and lower surfaces of the laminate 1. That is, the uppermost and lowermost layers of the laminate 1 are both layers of the separator 20.
  • the positive electrode layer 12 and the negative electrode layer 16 that face each other through the separator 20 form one cell.
  • Five cells are formed in the laminate 1 of FIG. 2.
  • the number of cells in the laminate included in the lithium ion battery according to the present disclosure is not limited as long as the effect of the invention is maintained, but the laminate may include, for example, 3 to 200 cells. In the lithium ion battery according to the present disclosure, the number of cells in the laminate may be one. That is, the laminate may have a configuration in which one positive electrode layer and one negative electrode layer face each other through a separator.
  • a plurality of positive electrode layers 12 and a plurality of negative electrode layers 16 are alternately laminated.
  • the positive electrode layers 12 and the negative electrode layers 16 constituting the laminate 1 are each in the shape of a quadrilateral plate.
  • the widths of the positive electrode layers 12 and the negative electrode layers 16 are both smaller than the width W of the laminate 1. In other words, the positive electrode layers 12 and the negative electrode layers 16 do not exist over the entire width W of the laminate 1.
  • the positive electrode layers 12 and the negative electrode layers 16 are arranged at positions offset from each other in the width direction, and each of the positive electrode layers 12 and the negative electrode layers 16 is exposed only on one of the first side surface s1 and the second side surface s2 that face each other in the laminate 1.
  • each of the multiple positive electrode layers 12 is exposed on the first side surface s1 of the laminate 1, but not on the second side surface s2.
  • the positive electrode layer 12 extends in the width direction from the side surface s1 to the middle of the width direction of the laminate 1, and the inner end surface 12e is the end in the width direction.
  • Each of the multiple negative electrode layers 16 is exposed on the second side surface s2 of the laminate 1, but not on the first side surface s1.
  • the negative electrode layer 16 extends in the width direction from the side surface s2 to the middle of the width direction of the laminate 1, with the inner end surface 16e being the end in the width direction.
  • the negative electrode layer 16 has a negative electrode collector layer 19 on one of its main surfaces or inside in the thickness direction, which contacts the negative electrode layer 16.
  • the negative electrode collector layer 19 may be provided inside the negative electrode layer 16 in the thickness direction.
  • the negative electrode collector layer 19 may also be formed so as to be exposed on one of the main surfaces of the negative electrode layer 16.
  • the negative electrode collector layer 19 is made of a material with excellent electrical conductivity.
  • a separator 20 is interposed between the positive electrode layer 12 and the negative electrode layer 16.
  • the separator 20 includes a first region 21, a second region 22, and a third region 23.
  • the first region 21 extends across the entire width W in the width direction of the laminated portion 1, and is interposed between the positive electrode layer 12 and the negative electrode layer 16 in the thickness direction of the laminated portion 1.
  • the second region 22 is a region that is at the same position as the positive electrode layer 12 in the thickness direction, is aligned with the positive electrode layer 12 in the width direction (X-axis direction), and extends between the inner end surface 12e of the positive electrode layer 12 and the side surface s2.
  • the second region 22 functions as an insulating layer that insulates between the positive electrode layer 12 and the side surface s2.
  • the third region 23 is at the same position as the negative electrode layer 16 in the thickness direction, is aligned with the negative electrode layer 16 in the width direction (X-axis direction), and is a region that extends between the inner end surface 16e of the negative electrode layer 16 and the side surface s1.
  • the third region 23 functions as an insulating layer that provides insulation between the negative electrode layer 16 and the side surface s1.
  • the first region 21, the second region 22, and the third region 23 are continuous without any boundaries.
  • the first region 21, the second region 22, and the third region 23 are regions that are partitioned for the sake of convenience of explanation, and in an actual electrode, it is preferable that the first region 21, the second region 22, and the third region 23 are an integral structure that is continuous throughout.
  • Fig. 3 is a schematic perspective view showing a sintered body 9 included in the lithium ion battery according to the present disclosure.
  • Fig. 3(a) shows the external appearance
  • Fig. 3(b) is a schematic view showing the configuration of layers included in the sintered body 9, including the inside.
  • the sintered body 9 includes the laminated portion 1 described above and an insulating layer 51 added in contact with the laminated portion 1.
  • the first side surface s1 of the periphery of the laminated portion 1 exposes the positive electrode layer 12 and the separator 20, and the negative electrode layer 16 is not exposed.
  • the second side surface s2 of the periphery of the laminated portion 1 exposes the negative electrode layer 16 and the separator 20, and the positive electrode layer 12 is not exposed.
  • the first side surface s1 and the second side surface s2 of the laminated portion 1 are exposed and form the surface of the sintered body 9.
  • a laminated structure including a positive electrode layer, a negative electrode layer, and a separator appears on the third side surface s3 and the fourth side surface s4 of the periphery of the laminated portion 1.
  • the third side surface s3 and the fourth side surface s4 of the laminated portion 1 are covered with an insulating layer 51 as an insulating ceramic portion. That is, the third side surface s3 and the fourth side surface s4 of the laminated portion 1 are not exposed to the outside because they are covered with the insulating layer 51 in the sintered body 9.
  • the periphery of the laminated portion 1 means the surface of the laminated portion 1 located on the outer periphery, excluding the upper and lower surfaces in the lamination direction.
  • the insulating layer 51 is preferably provided so as to cover both the third side s3 and the fourth side s4 of the laminate 1, but may be provided so as to cover either the third side s3 or the fourth side s4. Also, it is preferable that the insulating layer 51 covers the entire surfaces of the third side s3 and the fourth side s4, but may be provided so as to cover only a portion of them.
  • the insulating layer 51 extends over at least a portion of the lamination direction of the third side s3 and the fourth side s4 so as to cover at least a portion of the layers constituting the laminate. Also, the insulating layer 51 is not a required component, and the sintered body 9 may be composed of only the laminate 1.
  • the sintered body 9 has a rectangular parallelepiped (square) shape, but the external shape of the sintered body is not limited to this.
  • it may be a cylinder (round) with sides, or a polygonal prism shape.
  • the insulating layer 51 may cover only a portion of the third side surface s3 and the fourth side surface s4, rather than covering the entire surfaces of the third side surface s3 and the fourth side surface s4.
  • the sintered body included in the lithium ion battery according to the present disclosure may be round, in addition to a square shape like the sintered body 9.
  • Figures 4(a) and 4(b) show a sintered body 91 having a shape in which a part of a cylinder has been cut off.
  • Figure 4(a) shows the appearance
  • Figure 4(b) is a schematic diagram showing the configuration of the layers included in the sintered body 91, including the inside. This shape is called "round”.
  • the sintered body 91 has a different shape from the sintered body 9, but has the same laminated structure as the sintered body 9.
  • the sintered body 91 includes a laminated section 11 and an insulating layer 511 arranged to cover the arc-shaped side surface of the laminated section 11.
  • the laminated section 11 has the same configuration as the laminated section 1, except for the difference in the external shape.
  • the sintered body 91 has a shape in which a part of a cylinder has been cut off parallel to a tangent line, and two opposing side surfaces s5 and s6 are formed.
  • the end surface of the separator 120 and the end surface of the positive electrode layer 112 are exposed on the side surface s5.
  • the negative electrode layer 116 is not exposed on side surface s5.
  • the end surface of the separator 120 and the end surface of the negative electrode layer 116 are exposed on side surface s6, which is the surface opposite side surface s5.
  • the positive electrode layer 112 is not exposed on side surface s6.
  • the positive electrode layer is composed of a sintered body of a lithium composite oxide containing lithium cobalt oxide as a positive electrode active material.
  • the positive electrode layer may not contain a binder or a conductive additive.
  • the lithium cobalt oxide may contain another metal (M) (when 0 ⁇ x ⁇ 0.05 in the general formula).
  • an LCO sintered body formed into a plate shape as a positive electrode layer for example, those disclosed in Japanese Patent No. 5587052 and International Publication No. 2017/146088 can be used.
  • Examples of the compound represented by the general formula LiCo1- xMxO2 (wherein 0 ⁇ x ⁇ 0.05 , M is one or more elements selected from the group consisting of Ti, Zr, Al, W, and Nb) include, in addition to LiCoO2 , LiCo0.95Al0.05O2 , LiCo0.95Ti0.05O2 , etc.
  • the lithium composite oxide constituting the positive electrode layer may contain, in addition to LiCo 1-x M x O 2 (wherein 0 ⁇ x ⁇ 0.05, M is one or more selected from the group consisting of Ti, Zr, Al, W, and Nb), one or more additive elements selected from Nb, Ti, W, Al, and Mg.
  • M is one or more selected from the group consisting of Ti, Zr, Al, W, and Nb
  • additive elements selected from Nb, Ti, W, Al, and Mg.
  • the amount of the additive element added to the entire positive electrode layer may be 5.0 wt % or less. In this specification, the amount added is indicated as the internal amount added unless otherwise specified.
  • the lithium cobalt oxide constituting the primary particles in the positive electrode layer may be Li x NiCoO 2 (lithium nickel cobalt oxide), Li x CoNiMnO 2 (lithium cobalt nickel manganese oxide), Li x CoMnO 2 (lithium cobalt manganese oxide), etc.
  • other lithium composite oxides may be included together with the lithium cobalt oxide. Examples of lithium composite oxides include oxides represented by Li x MO 2 (wherein 0.05 ⁇ x ⁇ 1.10, M is at least one transition metal, and M typically includes one or more of Ni and Mn).
  • the molar ratio of Li to Co in the positive electrode layer may be 0.9 to 1.21, and is preferably 1.0 to 1.1.
  • the Li/Co ratio is 0.9 or more, the resistance is low.
  • the Li/Co ratio is 1.21 or less, there is an advantage that little gas is generated.
  • the Li/Co ratio in the positive electrode layer can be calculated as follows. First, the positive electrode layer constituting the electrode is taken from the electrode of the lithium secondary battery. When multiple layers of positive electrode layers are included, the positive electrode layer located at the outermost part is taken.
  • the method of taking the positive electrode layer is not particularly limited as long as the composition of the positive electrode layer is maintained and the elution of a specific component (especially elution of Li) does not occur.
  • peeling of each layer constituting the electrode can be induced by applying a short-term thermal shock to the electrode, and the peeled positive electrode layer can be taken. For example, the thermal shock is performed by heating the electrode to 900°C at a heating rate of 600°C/hr and then quenching.
  • the peeled positive electrode layer is subjected to elemental analysis by ICP measurement. The Li/Co ratio is measured from the contents of Li and Co calculated based on the ICP measurement.
  • the average particle size of the multiple primary particles that make up the positive electrode layer is preferably 5 ⁇ m or less. More specifically, it is more preferably 2 ⁇ m or less.
  • the positive electrode layer may contain pores.
  • the electrolyte can penetrate into the sintered body when the sintered body is incorporated into a battery as a positive electrode layer, thereby improving the lithium ion conductivity.
  • the porosity of the positive electrode layer is preferably 10 to 60%, more preferably 20 to 55%, and even more preferably 30 to 50%.
  • the porosity of the sintered body can be measured according to a known method.
  • the average pore diameter of the positive electrode layer is preferably 0.1 to 10.0 ⁇ m, more preferably 0.2 to 5.0 ⁇ m, and even more preferably 0.25 to 3.0 ⁇ m. Within the above range, localized stress concentration in large pores is suppressed, making it easier to release stress uniformly within the sintered body. In addition, the pores can more effectively improve lithium ion conductivity by allowing the electrolyte to penetrate inside.
  • the thickness of the positive electrode layer in the laminated portion is not particularly limited, but is preferably, for example, 1 to 400 ⁇ m, more preferably 5 to 300 ⁇ m, and even more preferably 10 to 200 ⁇ m. Within this range, electronic resistance is suppressed, and the resistance to the movement of Li ions contained in the electrolyte is also suppressed, making it possible to reduce battery resistance.
  • the separator is a microporous layer made of ceramic.
  • the separator contains LiAlO 2.
  • the separator is a sintered body containing LiAlO 2. Conventionally, LiAlO 2 has not been expected to be used as a separator in a multilayer laminated ceramic electrode.
  • the molar ratio of Li to Al (Li/Al ratio) in the separator may be 0.9 to 1.20, and is preferably 1.0 to 1.1.
  • Li/Al ratio is in the range of 1.0 to 1.20, there is an advantage in that the cycle characteristics are good.
  • the Li/Al ratio in the separator can be calculated as follows:
  • the separator that constitutes the electrode is extracted from the electrode of the lithium secondary battery.
  • the outermost separator is extracted.
  • the method for extracting the separator so long as the composition of the separator is maintained and no elution of specific components (particularly elution of Li) occurs.
  • peeling of each layer that constitutes the electrode can be induced by subjecting the electrode to a short-term thermal shock, and the peeled separator can be extracted.
  • the thermal shock is performed by heating the electrode to 900°C at a heating rate of 600°C/hr and then rapidly cooling it.
  • An elemental analysis is performed on the peeled separator by ICP measurement. The Li/Al ratio is measured from the Li and Al contents calculated based on the ICP measurement.
  • the separator may contain LiAlO2 and a metal oxide other than LiAlO2 .
  • the metal oxide other than LiAlO2 may specifically include one or more selected from the group consisting of MgO , Li2ZrO3 , ZrO2 , Al2O3 , Li3AlO4 , and LiAl5O8 .
  • the separator may also contain LiAlO2 and a compound other than a metal oxide.
  • the compound other than a metal oxide may include a nitride or carbide that is a ceramic material, specifically, for example, SiC , Si3N4 , AlN, etc.
  • the ratio of LiAlO 2 to the entire separator is preferably 50% by volume or more, more preferably 70% by volume or more. For example, it may contain about 30% by volume of a binding component such as glass.
  • the separator may be 100% by volume of LiAlO 2 , that is, the entire separator may be composed of LiAlO 2 except for unavoidable impurities.
  • the ratio of LiAlO 2 to the entire separator is 65% by volume or more, the effect of the present disclosure becomes clear.
  • the thickness of the separator in the laminated portion is not particularly limited, but is preferably, for example, 1 to 50 ⁇ m, and more preferably 2 to 30 ⁇ m.
  • the thickness of the separator here refers to the thickness of the region that separates the positive electrode layer and the negative electrode layer in the lamination direction (first region 21 shown in Figure 2).
  • the second region 22 and third region 23 of the separator 20 can be made to be the same thickness as the positive electrode layer and the negative electrode layer, respectively.
  • the porosity of the separator is not particularly limited, but can be, for example, about 30 to 70%, and is preferably about 40 to 60%.
  • the lithium ion battery disclosed herein has a Li/Co ratio in the positive electrode layer and a Li/Al ratio in the separator that satisfy 0.85 ⁇ (Li/Co)/(Li/Al) ⁇ 1.15. It is more preferable that (Li/Co)/(Li/Al) is 0.95 or more and 1.05 or less.
  • the values of (Li/Co) and (Li/Al) are measured and calculated by the method described above.
  • the value of (Li/Co) relative to (Li/Al) is calculated from the values of (Li/Co) and (Li/Al).
  • the negative electrode layer is, for example, composed of a plate-shaped sintered body containing a titanium-containing composition.
  • the negative electrode layer may be one that does not contain a binder or a conductive additive.
  • the titanium-containing sintered body preferably contains lithium titanate Li 4 Ti 5 O 12 (hereinafter, LTO) or niobium titanium composite oxide Nb 2 TiO 7 , and more preferably contains LTO.
  • LTO lithium titanate Li 4 Ti 5 O 12
  • Nb 2 TiO 7 niobium titanium composite oxide
  • LTO is not limited to a spinel structure.
  • a part of LTO may be replaced with other elements. Examples of other elements include Nb, Ta, W, Al, Mg, etc.
  • the LTO sintered body can be produced, for example, according to the method described in JP 2015-185337 A.
  • the transition metal element of the negative electrode layer is Ti.
  • the transition metal elements of the negative electrode layer are Nb and Ti.
  • the negative electrode layer has a structure in which a large number of primary particles are bonded together. These primary particles are preferably composed of LTO or Nb 2 TiO 7.
  • the negative electrode layer is composed of an integrated sintered body together with the positive electrode layer and the separator.
  • the thickness of the negative electrode layer is not particularly limited, but is preferably 1 to 400 ⁇ m, more preferably 2 to 150 ⁇ m, and even more preferably 5 to 100 ⁇ m.
  • the primary particle size which is the average particle size of the multiple primary particles that make up the negative electrode layer, is preferably 1.2 ⁇ m or less, more preferably 0.02 to 1.2 ⁇ m, and even more preferably 0.05 to 0.7 ⁇ m.
  • the negative electrode layer preferably contains pores. By containing pores, particularly open pores, when the negative electrode layer is incorporated into a battery, the electrolyte can penetrate into the inside, thereby improving the lithium ion conductivity.
  • the porosity of the negative electrode layer is preferably 20 to 60%, more preferably 30 to 55%, and even more preferably 35 to 50%.
  • the average pore diameter of the negative electrode layer is preferably 0.08 to 5.0 ⁇ m, more preferably 0.1 to 3.0 ⁇ m, and even more preferably 0.12 to 1.5 ⁇ m.
  • the negative electrode collector layer can be made of a material having excellent electrical conductivity.
  • the negative electrode collector layer preferably contains Ag (silver).
  • the negative electrode collector layer may further contain, in addition to Ag, one or more selected from the group consisting of Au (gold), Pt (platinum), Pd (palladium), Al (aluminum), Cu (copper) and Ni (nickel).
  • the content ratio of Ag in the negative electrode collector layer may be 30% or more, more preferably 50% or more, and even more preferably 100%. That is, the negative electrode collector layer 19 is preferably a layer made of Ag.
  • the thickness of the negative electrode collector layer is not particularly limited, but is preferably 0.1 to 60 ⁇ m, and more preferably 0.5 to 30 ⁇ m. It is also believed that when the relationship between the thickness of the negative electrode collector layer and the thickness of the separator is within a certain range, the diffusion of Ag contained in the negative electrode collector layer can be effectively suppressed.
  • the ratio of the thickness of the negative electrode collector layer (A) to the thickness of the separator (B) is preferably 0.1 ⁇ B/A ⁇ 50, and more preferably 0.15 ⁇ B/A ⁇ 30.
  • the insulating layer included in the sintered body covers the periphery of the laminated part, particularly the side surface other than the part where the internal electrode layer is drawn out.
  • the insulating layer is composed of insulating ceramic. Specifically, the same ceramic as that used as the separator can be used.
  • the insulating ceramic part preferably contains LiAlO 2 and is composed of LiAlO 2 and impurities.
  • the thickness w2 of the insulating layer see FIG.
  • 3(b)) is not particularly limited, but is preferably 1 ⁇ m to 1000 ⁇ m, for example, and more preferably 2 ⁇ m to 500 ⁇ m.
  • the insulating layer and the separator may be integrated during the sintering process, and the insulating layer and the separator may be an integrated region without a boundary in the sintered body.
  • the lithium ion battery includes an electrolyte.
  • the electrolyte is not particularly limited, and any electrolyte known as an electrolyte for lithium ion batteries can be used.
  • the solvent one or a combination of two or more selected from ethylene carbonate (EC), methyl ethyl carbonate (MEC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), propylene carbonate (PC) and ⁇ -butyrolactone (GBL) can be used.
  • a lithium salt compound such as lithium hexafluorophosphate (LiPF 6 ) or lithium borofluoride (LiBF 4 ) can be used.
  • the electrolyte 22 may further include at least one selected from vinylene carbonate (VC), fluoroethylene carbonate (FEC), vinyl ethylene carbonate (VEC), and lithium difluoro(oxalato)borate (LiDFOB) as an additive.
  • the concentration of the electrolyte in the electrolytic solution is preferably 0.5 to 4.0 mol/L, more preferably 0.6 to 3.0 mol/L, even more preferably 0.7 to 2.5 mol/L, and particularly preferably 0.8 to 2.0 mol/L.
  • a solid electrolyte or a polymer electrolyte can be used as the electrolyte.
  • the electrolyte is impregnated at least inside the pores of the separator.
  • the impregnation method examples include a method in which the electrolyte is melted and allowed to penetrate into the pores of the separator, and a method in which a compressed powder of the electrolyte is pressed against the separator.
  • FIG. 5 is a schematic diagram showing a process for preparing, stacking and pressing each sheet for constituting a laminate, among the steps for producing a sintered body.
  • the positive electrode green sheet 112, the negative electrode green sheet 116, and the separator green sheet 120 which are materials for forming the laminate, are prepared separately. Typically, a slurry containing the raw materials for each layer is first prepared, and then the prepared slurry is formed into a sheet on a resin film, thereby preparing the green sheets.
  • the negative electrode green sheet 116 may have a collector layer 119 formed on one of its main surfaces.
  • each sheet cut to a predetermined width is stacked in order to form a predetermined layer structure. Note that the layer structure is simply shown in the example of FIG. 5, but a unit U including the negative electrode green sheet 116, the separator green sheet 120, the positive electrode green sheet 112, and the separator green sheet 120 may be repeatedly stacked to form a multi-layer laminate.
  • each green sheet when stacking, each green sheet may be used alone in the thickness direction, or two or more of the same type of sheets may be stacked continuously in the thickness direction.
  • two negative electrode green sheets 116 having a current collector layer 119 on one side may be stacked.
  • the stacked sheets are integrated at the sintering stage, so that the sintered body becomes a single layer.
  • the positive electrode green sheet 112 and the negative electrode green sheet 116 are arranged to be shifted from each other in the width direction (X-axis direction). By arranging them in this manner, it is possible to obtain a configuration in which, of the pair of side surfaces in the laminate 1 ( Figure 2), the positive electrode layer 12 is exposed on one side surface and the negative electrode layer 16 is not exposed, and the negative electrode layer 16 is exposed on the other side surface and the positive electrode layer 12 is not exposed.
  • the green sheet laminate 101 is pressurized to bond the layers together.
  • the green sheets included in the green sheet laminate 101 can be bonded together by pressing. It is preferable to press the green sheet laminate 101 in the thickness direction (Z-axis direction).
  • the pressing method can be, for example, cold isostatic pressing (CIP), hot isostatic pressing (WIP), hydrostatic pressing, or the like, and is not particularly limited. Pressing may be performed while heating.
  • FIG. 6 shows a part of the process for manufacturing a rectangular sintered body in which each layer is formed into a quadrilateral and the entire body is a rectangular parallelepiped.
  • the cutting points c1 to c4 are indicated by thick lines. Referring to FIG. 6(1), first, both side surfaces of the green sheet laminate 101 are cut at the cutting points c1 and c2 so as to obtain a predetermined width.
  • the cutting point c1 is a position where the positive electrode green sheet 112 is cut but the negative electrode green sheet 116 is not cut.
  • the cutting point c2 is a position where the negative electrode green sheet 116 is cut but the positive electrode green sheet 112 is not cut.
  • the cutting points c3 and c4 are positions where only the separator green sheet 120 is cut but the positive electrode green sheet 112 and the negative electrode green sheet 116 are not cut.
  • degreasing and firing are performed to obtain an integrated sintered body 9 ( Figure 6 (2)) having an insulating ceramic portion on the periphery of the laminate. Degreasing and firing can be performed under known conditions and methods.
  • Figure 7 shows a green sheet laminate 911 for obtaining a round sintered body.
  • the green sheet laminate 911 is obtained by cutting out the positive electrode green sheet 112, the negative electrode green sheet 116, and the separator green sheet 120 into a circular shape using a punch or the like.
  • Figure 7 (1) is a schematic diagram showing the internal laminate structure of the green sheet laminate 911.
  • the positive electrode green sheet 112, the negative electrode green sheet 116, and the separator green sheet 120 constituting the respective layers of the green sheet laminate 911 can be the same as the various green sheets constituting the green sheet laminate 101, except for their different shapes.
  • the stacking order can also be the same as that of the green sheet laminate 101.
  • the positive electrode green sheet 112 and the negative electrode green sheet 116 included in the green sheet laminate 911 each have a shape in which a part of a circle has been cut away parallel to the tangent.
  • the positive electrode green sheet 112 and the negative electrode green sheet 116 are alternately stacked with circular separator green sheets 120 in between.
  • the positive electrode green sheet 112 and the negative electrode green sheet 116 are also arranged so that the cut areas are located on opposite sides of each other.
  • the separator green sheet 120 covers the entire periphery of the stacked portion.
  • the green sheet laminate 911 is cut.
  • the cut points c8 and c9 are indicated by thick lines.
  • the cut point c8 is a position where the negative electrode green sheet 116 does not overlap with the negative electrode green sheet 116 and where the positive electrode green sheet 112 is cut.
  • the cut point c8 is parallel to the cut portion of the negative electrode green sheet 116.
  • the cut point c9 is a position where the negative electrode green sheet 116 is cut and where the positive electrode green sheet 112 does not overlap with the positive electrode green sheet 112. In addition, the cut point c9 is parallel to the cut portion of the positive electrode green sheet 112.
  • a side s6 (FIG. 7(2)) is obtained in which the negative electrode green sheet 116 and the separator green sheet 120 are exposed on the cross section, and the positive electrode green sheet 112 is not exposed.
  • degreasing and sintering are performed, and an integrated sintered body 91 is obtained in which an insulating ceramic portion is formed on the periphery of the laminate.
  • collectors are attached to both sides of the sintered body.
  • a positive electrode collector 14 is attached to the first side s1 of the sintered body 9, and a negative electrode collector 18 is attached to the second side s2.
  • a conductive material such as aluminum foil, can be used for the positive electrode collector 14 and the negative electrode collector 18.
  • the positive electrode collector 14 is attached so as to cover the entire first side s1, and can be configured to extend to the lower surface of the sintered body 9.
  • the negative electrode collector 18 is attached so as to cover the entire second side s2, and can be configured to extend to the upper surface of the sintered body 9.
  • the sintered body 9 and the positive electrode collector 14, and the sintered body 9 and the negative electrode collector 18 can be bonded together using a conductive adhesive.
  • a conductive carbon paste can be used as the conductive adhesive.
  • the thickness of the conductive adhesive layer is not particularly limited as long as it exerts its effect as an adhesive layer and does not interfere with the effects of the invention, but it can be, for example, about 1 to 500 ⁇ m.
  • the electrodes obtained by the above manufacturing method can be placed inside an exterior body according to known methods and conditions, and an electrolyte can be sealed in to obtain a lithium-ion battery.
  • Examples and Comparative Examples The lithium ion battery according to the present disclosure will be described in more detail below with reference to examples and comparative examples.
  • Samples 1 to 5 are examples of the lithium ion battery according to the present disclosure.
  • Samples 6 and 7 are examples outside the scope of the lithium ion battery according to the present disclosure.
  • Example 1 A lithium ion battery was fabricated according to the methods described in 1 to 8 below.
  • Laminates Green sheets for each layer constituting the sintered body were prepared under the conditions and methods of (1) to (3).
  • the viscosity of the slurry was measured using a Brookfield LVT viscometer. The doctor blade method was used to form the slurry on a PET film.
  • LCO green sheet positive electrode green sheet
  • Co3O4 powder manufactured by Seido Chemical Industry Co., Ltd.
  • Li2CO3 powder manufactured by Honjo Chemical Co., Ltd.
  • the obtained powder was pulverized in a pot mill so that the volumetric D50 was 0.4 ⁇ m to obtain a powder consisting of LCO plate-like particles.
  • 10 parts by weight of a binder polyvinyl butyral: product number BM-2, manufactured by Sekisui Chemical Co., Ltd.
  • 2 parts by weight of a plasticizer DOP: Di (2-ethylhexyl) phthalate, manufactured by Kurogane Kasei Co., Ltd.
  • a dispersant product name Rheodol SP-O30, manufactured by Kao Corporation
  • LTO green sheet negative electrode green sheet
  • LTO powder volume standard D 50 particle size 0.6 ⁇ m, manufactured by Ishihara Sangyo Kaisha, Ltd.
  • binder polyvinyl butyral: product number BM-2, manufactured by Sekisui Chemical Co., Ltd.
  • plasticizer DOP: Di (2-ethylhexyl) phthalate, manufactured by Kurogane Kasei Co., Ltd.
  • dispersant product name Rheodol SP-O30, manufactured by Kao Corporation
  • the obtained negative electrode raw material mixture was stirred and degassed under reduced pressure, and the viscosity was adjusted to 4000 cP to prepare an LTO slurry.
  • the prepared slurry was formed into a sheet on a PET film to form an LTO green sheet.
  • the thickness of the negative electrode layer after firing was adjusted to 40 ⁇ m.
  • LiAlO 2 powder volume standard D 50 particle size 1.5 ⁇ m
  • 20 parts by weight of a binder polyvinyl butyral: product number BM-2, manufactured by Sekisui Chemical Co., Ltd.
  • 4 parts by weight of a plasticizer DOP: Di (2-ethylhexyl) phthalate, manufactured by Kurogane Kasei Co., Ltd.
  • a dispersant product name: Rheodol SP-O30, manufactured by Kao Corporation
  • the obtained raw material mixture was stirred under reduced pressure to degas and the viscosity was adjusted to 4000 cP to prepare a slurry.
  • the prepared slurry was formed into a sheet on a PET film to form a separator green sheet.
  • the thickness of the separator located between the positive electrode layer and the negative electrode layer was set to 30 ⁇ m after firing.
  • the thickness of the separator (insulating layer) adjacent to the positive electrode layer was set to be the same as that of the positive electrode layer after firing, and the thickness of the separator (insulating layer) adjacent to the negative electrode layer was set to be the same as that of the negative electrode layer and the negative electrode current collector layer after firing.
  • the green sheets obtained in 1. were cut to be laminated. That is, the positive electrode green sheet and the negative electrode green sheet were each punched with a round puncher having a diameter of 15.5 mm to obtain circular green sheets. Furthermore, each circular green sheet was cut linearly at a position 2 mm from one point on the end face toward the center in parallel to the tangent at that point.
  • the cut laminate was heated from room temperature to 600° C. and degreased for 5 hours, then heated to 800° C. and held at that temperature for 10 minutes to be fired, and then cooled.
  • An aluminum foil serving as a positive electrode current collector was placed on the surface where the positive electrode and separator were exposed, with a conductive carbon paste interposed therebetween, and an aluminum foil serving as a negative electrode current collector was placed on the surface where the negative electrode and separator were exposed, with a conductive carbon paste interposed therebetween.
  • the Li/Co ratio in the positive electrode layer and the Li/Al ratio in the separator of the obtained laminated sintered body were measured and calculated.
  • the measurements were first performed by repeating thermal shock (rapid heating to 900°C and rapid cooling) until the layers constituting the laminated sintered body peeled off, separating each layer. After that, ICP was performed.
  • conductive carbon paste A binder (CMC: MAC350HC, manufactured by Nippon Paper Industries Co., Ltd.) was weighed out to 1.2 wt% in pure water and dissolved by stirring to obtain a 1.2 wt% CMC solution.
  • a carbon dispersion product number: BPW-229, manufactured by Nippon Graphite Co., Ltd.
  • a dispersant solution product number LB-300, manufactured by Showa Denko K.K.
  • the carbon dispersion, the dispersant solution, and the 1.2 wt% CMC solution were weighed out to 0.22:0.29:1, and mixed with a rotary mixer to prepare a conductive carbon paste.
  • the conductive carbon paste obtained in 5. was screen printed on the aluminum foil as a positive electrode current collector.
  • the positive electrode exposed surface of the laminated integral sintered body obtained in 4. was placed so as to be bonded within the undried printing pattern (the area where the conductive carbon paste was applied), and was lightly pressed with a finger, and then vacuum dried at 50 ° C for 60 minutes. In this way, the positive electrode exposed surface of the laminated integral sintered body and the positive electrode current collector were bonded via a conductive carbon adhesive layer.
  • the thickness of the conductive carbon adhesive layer was 30 ⁇ m.
  • LiPF6 LiPF6 was dissolved to a concentration of 1.5 mol/L in an organic solvent in which propylene carbonate (PC) and ⁇ -butyrolactone (GBL) were mixed in a volume ratio of 1:3.
  • PC propylene carbonate
  • GBL ⁇ -butyrolactone
  • Example 2 A lithium ion battery was produced in the same manner as in Sample 1, except that when the LCO green sheet was produced, Co3O4 powder and Li2CO3 powder were used so that the molar ratio of Li/Co was 1.00, and when the separator green sheet was produced, Li2CO3 powder and Al2O3 were used so that the molar ratio of Li/Al was 1.05.
  • Example 3 A lithium ion battery was produced in the same manner as in Sample 1, except that when the LCO green sheet was produced, Co3O4 powder and Li2CO3 powder were used so that the molar ratio of Li/Co was 0.90, and when the separator green sheet was produced, Li2CO3 powder and Al2O3 were used so that the molar ratio of Li/Al was 0.90.
  • Example 4 A lithium ion battery was produced in the same manner as in Sample 1, except that when the LCO green sheet was produced, Co3O4 powder and Li2CO3 powder were used so that the molar ratio of Li/Co was 1.05, and when the separator green sheet was produced, Li2CO3 powder and Al2O3 were used so that the molar ratio of Li/Al was 1.00.
  • Example 5 A lithium ion battery was produced in the same manner as in Sample 1, except that when the LCO green sheet was produced, Co3O4 powder and Li2CO3 powder were used so that the molar ratio of Li/Co was 1.21, and when the separator green sheet was produced, Li2CO3 powder and Al2O3 were used so that the molar ratio of Li/Al was 1.05.
  • Example 6 A lithium ion battery was produced in the same manner as in Sample 1, except that when the LCO green sheet was produced, Co3O4 powder and Li2CO3 powder were used so that the molar ratio of Li/Co was 1.00, and when the separator green sheet was produced, Li2CO3 powder and Al2O3 were used so that the molar ratio of Li/Al was 1.25.
  • Example 7 A lithium ion battery was produced in the same manner as in Sample 1, except that when the LCO green sheet was produced, Co3O4 powder and Li2CO3 powder were used so that the molar ratio of Li/Co was 1.25, and when the separator green sheet was produced, Li2CO3 powder and Al2O3 were used so that the molar ratio of Li/Al was 1.00.
  • Pulse charge-discharge cycle test The pulse cycle capacity retention rate (constant voltage charge cycle performance) of each of the lithium ion batteries of Samples 1 to 7 was measured by the following procedure. First, the initial capacity was measured by constant voltage charging at 2.7 V and then discharging at a discharge rate of 0.05 C. Then, a total of 100 charge-discharge cycles including 100 constant voltage charging at 2.7 V and discharging at 50 C for 0.5 seconds were performed. The charge-discharge cycles were performed in an environment of 25° C. Finally, the capacity after the cycle was measured by constant voltage charging at 2.7 V and then discharging at 0.05 C. The measured capacity after the cycle was divided by the initial capacity and multiplied by 100 to obtain the capacity retention rate (%).
  • the lithium ion batteries of samples 1 to 5 in which the (Li/Co)/(Li/Al) ratio was 0.85 or more and 1.15 or less, had a capacity retention rate of 86% to 98% after repeated pulse discharge at a large current (50C).
  • samples 2 to 4 in which the (Li/Co)/(Li/Al) ratio was 0.95 or more and 1.05 or less, had a capacity retention rate of 96% to 98%, which was extremely high.
  • sample 6 in which the (Li/Co)/(Li/Al) ratio was 0.80 had a capacity retention rate of 70%. Comparing samples 2 and 6, the Li/Co ratio in the positive electrode was the same, 1.00, but the capacity retention rates were significantly different.

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