WO2024053225A1 - 二次電池 - Google Patents

二次電池 Download PDF

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Publication number
WO2024053225A1
WO2024053225A1 PCT/JP2023/024445 JP2023024445W WO2024053225A1 WO 2024053225 A1 WO2024053225 A1 WO 2024053225A1 JP 2023024445 W JP2023024445 W JP 2023024445W WO 2024053225 A1 WO2024053225 A1 WO 2024053225A1
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WO
WIPO (PCT)
Prior art keywords
electrode
active material
material layer
battery element
negative electrode
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/JP2023/024445
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English (en)
French (fr)
Japanese (ja)
Inventor
大貴 西家
盛朗 奥野
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Murata Manufacturing Co Ltd
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Murata Manufacturing Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Murata Manufacturing Co Ltd filed Critical Murata Manufacturing Co Ltd
Priority to JP2024545460A priority Critical patent/JP7852726B2/ja
Publication of WO2024053225A1 publication Critical patent/WO2024053225A1/ja
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • H01M10/058—Construction or manufacture
    • H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
    • 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
    • H01M10/04—Construction or manufacture in general
    • 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
    • H01M10/04—Construction or manufacture in general
    • H01M10/0431—Cells with wound or folded electrodes
    • 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
    • H01M50/10—Primary casings; Jackets or wrappings
    • H01M50/102—Primary casings; Jackets or wrappings characterised by their shape or physical structure
    • H01M50/109—Primary casings; Jackets or wrappings characterised by their shape or physical structure of button or coin shape
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present disclosure relates to secondary batteries.
  • This secondary battery includes a positive electrode, a negative electrode, and an electrolyte housed inside an exterior member, and various studies have been made regarding the configuration of the secondary battery (see, for example, Patent Document 1).
  • Patent Document 1 describes a sealed power storage device that includes an electrode body in which a positive electrode body and a negative electrode body are laminated or wound with a separator in between, and an exterior case that houses the electrode body.
  • a secondary battery is a battery in which a first electrode and a second electrode are laminated with a separator interposed therebetween and are wound around a winding shaft extending in a first direction. It includes an element and an exterior member that houses the battery element.
  • the second electrode includes a second electrode current collector including an inner surface of the second electrode facing the winding axis and an outer surface of the second electrode opposite to the inner surface of the second electrode, and a second electrode provided on the inner surface of the second electrode. and a second electrode outer active material layer provided on the outer surface of the second electrode.
  • the area density of the second electrode outer active material layer is such that it faces the second electrode outer active material layer with the second electrode current collector in between.
  • the area density of the second electrode inner active material layer is larger than the area density of the second electrode inner active material layer.
  • a secondary battery is a battery in which a first electrode and a second electrode are laminated with a separator in between and are wound around a winding shaft extending in a first direction. It includes an element and an exterior member that houses the battery element.
  • the second electrode includes a second electrode current collector including an inner surface of the second electrode facing the winding axis and an outer surface of the second electrode opposite to the inner surface of the second electrode, and a second electrode provided on the inner surface of the second electrode. and a second electrode outer active material layer provided on the outer surface of the second electrode.
  • the area density of the second electrode outer active material layer is highest at the inner end of the battery element, and decreases as it approaches the outer end of the battery element from the inner end of the battery element.
  • the area density of the second electrode inner active material layer is lowest at the inner end of the battery element, and increases as it approaches the outer end of the battery element from the inner end of the battery element.
  • the first electrode in the relationship between the first electrode and the second electrode that face each other with the separator in between, the first electrode is The capacitance of the second electrode becomes larger than the capacitance. Therefore, it is possible to suppress the formation of precipitates accompanying the battery reaction, and it is possible to suppress the deterioration of battery performance. Therefore, it has high reliability.
  • FIG. 1 is a perspective view showing the configuration of a secondary battery as a first embodiment of the present disclosure.
  • FIG. 2 is a sectional view showing the configuration of the secondary battery shown in FIG. 1.
  • FIG. 3 is a cross-sectional view showing the configuration of the battery element shown in FIG. 2.
  • FIG. 4 is a cross-sectional view showing an example of the cross-sectional structure of the battery element shown in FIG. 2.
  • FIG. 5 is a developed view schematically showing a positive electrode and a negative electrode of the battery element shown in FIG.
  • FIG. 6 is a perspective view showing the structure of the outer can used in the manufacturing process of the secondary battery shown in FIG. FIG.
  • FIG. 7 is an explanatory diagram showing the relationship between the capacity of the positive electrode and the capacity of the negative electrode in the battery element shown in FIG. 2.
  • FIG. 8 is a developed view schematically showing a positive electrode and a negative electrode of a battery element of a secondary battery according to a second embodiment of the present disclosure.
  • FIG. 9 is an explanatory diagram showing the relationship between the capacity of the positive electrode and the capacity of the negative electrode in the battery element shown in FIG.
  • FIG. 10 is a developed view schematically showing a positive electrode and a negative electrode of a battery element of a secondary battery according to a third embodiment of the present disclosure.
  • FIG. 11 is an explanatory diagram showing the relationship between the capacity of the positive electrode and the capacity of the negative electrode in the battery element shown in FIG.
  • the secondary battery described here has a flat and columnar three-dimensional shape, and is called a so-called coin type or button type. As will be described later, this secondary battery has a pair of bottom portions facing each other and a side wall portion located between the pair of bottom portions. In this secondary battery, the height is smaller than the outer diameter.
  • the “outer diameter” here is the maximum diameter (maximum outer diameter) of the bottom. In this secondary battery, the maximum diameters of each of the pair of opposing bottom portions are substantially equal to each other.
  • the "height” here is the maximum distance from the upper surface of one bottom to the lower surface of the other bottom. In this embodiment, the direction in which the pair of bottoms face each other is defined as the height direction Z.
  • This secondary battery includes a positive electrode, a negative electrode, and an electrolyte.
  • the charging capacity of the negative electrode is larger than the discharge capacity of the positive electrode in order to prevent electrode reactants from depositing on the surface of the negative electrode during charging. That is, the electrochemical capacity per unit area of the negative electrode is set to be larger than the electrochemical capacity per unit area of the positive electrode.
  • the secondary battery of this embodiment is a secondary battery with high charging voltage specifications that can exhibit good cycle characteristics without reducing energy density even when charged at a high voltage of 4.38 V or higher. be.
  • the type of electrode reactant is not particularly limited, but specifically light metals such as alkali metals and alkaline earth metals.
  • Alkali metals include lithium, sodium and potassium
  • alkaline earth metals include beryllium, magnesium and calcium.
  • a secondary battery whose battery capacity is obtained by utilizing intercalation and desorption of lithium is a so-called lithium ion secondary battery.
  • lithium ion secondary battery lithium is intercalated and released in an ionic state.
  • FIG. 1 shows a perspective configuration of a secondary battery.
  • FIG. 2 shows a cross-sectional configuration of the secondary battery shown in FIG. 1.
  • FIG. 3 shows a cross-sectional configuration of the battery element 40 shown in FIG. 2. However, in FIG. 3, only a part of the cross-sectional structure of the battery element 40 is enlarged.
  • the secondary battery described here has a three-dimensional shape in which the height H is smaller than the outer diameter D, that is, a flat and columnar three-dimensional shape.
  • the three-dimensional shape of the secondary battery is flat and cylindrical.
  • the vertical direction of the paper plane in each of FIGS. 1 and 2 is defined as the height direction Z. Therefore, the height H means the dimension in the height direction Z of the secondary battery of this embodiment.
  • the outer diameter D means the dimension in the direction orthogonal to the height direction Z in the secondary battery of this embodiment.
  • the dimensions of the secondary battery are not particularly limited, but for example, the outer diameter D is 3 mm to 30 mm, and the height H is 0.5 mm to 70 mm.
  • the ratio of the outer diameter D to the height H (D/H) is larger than 1. That is, the outer diameter D is larger than the height H.
  • the upper limit of this ratio (D/H) is not particularly limited, but is preferably 25 or less.
  • this secondary battery includes an outer can 10, an external terminal 20, a battery element 40, and a positive electrode lead 51.
  • the secondary battery further includes a gasket 30, a negative electrode lead 52, a sealant 61, and insulating films 62, 63.
  • the exterior can 10 is a hollow exterior member that houses the battery element 40 and the like.
  • the outer can 10 is made of a conductive material.
  • the outer can 10 has a flat and substantially cylindrical three-dimensional shape in accordance with the flat and cylindrical three-dimensional shape of the secondary battery.
  • the exterior can 10 has a pair of bottoms M1 and M2 facing each other, and a side wall M3 located between the bottoms M1 and M2. That is, the side wall portion M3 connects the bottom portion M1 and the bottom portion M2 and surrounds the battery element 40.
  • the upper end of the side wall M3 is connected to the bottom M1.
  • a lower end portion of the side wall portion M3 is connected to the bottom portion M2.
  • the outer can 10 has a substantially cylindrical shape.
  • the planar shape of each of the bottom portions M1 and M2 is circular, and the surface of the side wall portion M3 is a convex curved surface.
  • the outer can 10 includes a storage section 11 and a lid section 12 that are welded to each other. That is, by welding the lid part 12 to the storage part 11, the internal space of the outer can 10 is sealed.
  • the bottom portion M1 constitutes the lid portion 12, and the bottom portion M2 and the side wall portion M3 together constitute the storage portion 11. Therefore, the outer edge of the lid portion 12 is welded to the upper end portion of the side wall portion M3.
  • the storage section 11 is a flat and cylindrical storage member that stores the battery element 40 and the like therein.
  • the storage section 11 has a hollow structure with an open upper end and a closed lower end. That is, the storage portion 11 has an opening 11K (FIG. 2) at the upper end as an insertion opening through which the battery element 40 can be inserted in the height direction Z.
  • the lid portion 12 is a substantially disc-shaped lid member that closes the opening 11K of the storage portion 11, and has a through hole 12K.
  • the through hole 12K is used as a connection path for connecting the battery element 40 and the external terminal 20 to each other.
  • the lid portion 12 is welded to the storage portion 11 at the opening portion 11K.
  • An external terminal 20 is attached to the lid portion 12 via a gasket 30. That is, the lid portion 12 supports the external terminal 20 via the gasket 30.
  • the external terminal 20 is attached to the lid portion 12 via a gasket 30 so as to close the through hole 12K.
  • the external terminal 20 is electrically insulated from the outer can 10.
  • the lid portion 12 is welded to the storage portion 11 as described above. As described above, the opening 11K is closed by the lid 12. Therefore, it is conceivable that it is not possible to confirm whether the storage section 11 has the opening 11K even by looking at the external appearance of the secondary battery.
  • the lid part 12 is bent so as to partially protrude along the height direction Z toward the inside of the storage part 11, and forms a recessed part 12H. That is, when viewed from the outside of the exterior can 10, the lid portion 12 has a shape that is partially recessed in the height direction Z toward the battery element 40 housed inside the exterior can 10.
  • the recessed portion 12H includes a through hole 12K penetrating in the height direction Z, a bottom portion 12HB surrounding the through hole 12K along a horizontal plane perpendicular to the height direction Z, and a wall portion erected along the outer edge of the bottom portion 12HB. 12HW.
  • the portion of the lid portion 12 other than the recessed portion 12H is a peripheral portion 12R.
  • the peripheral portion 12R has an annular shape and is provided so as to surround the recessed portion 12H in a horizontal plane perpendicular to the height direction Z of the secondary battery.
  • the peripheral portion 12R is a portion surrounding the recessed portion 12H and protruding away from the battery element 40 along the height direction Z. Therefore, in the height direction Z, the surface 12HS of the bottom portion 12HB of the recessed portion 12H is located at a lower position toward the inside of the storage portion 11 than the surface 12RS of the peripheral portion 12R. That is, in the height direction Z, the distance between the surface 12HS of the bottom 12HB of the recessed portion 12H and the battery element 40 is shorter than the distance between the surface 12RS of the peripheral portion 12R and the battery element 40.
  • the shape of the recess 12H in plan view that is, the shape defined by the outer edge of the recess 12H when the secondary battery is viewed from above, is not particularly limited.
  • the shape of the recessed portion 12H in plan view is approximately circular.
  • the inner diameter and depth of the recessed portion 12H are not particularly limited and can be set arbitrarily.
  • the height of the surface 20S of the external terminal 20 is lower than the height of the surface 12RS of the peripheral part 12R.
  • the depth of 12H is set.
  • the exterior can 10 is a can in which the housing portion 11 and the lid portion 12, which were physically separated from each other, are welded together, and is a so-called welded can.
  • the welded exterior can 10 is a physically integrated member as a whole, and therefore cannot be separated into the housing portion 11 and the lid portion 12 after the fact.
  • the exterior can 10 which is a welded can, is a so-called crimpless can, which is different from a crimp can formed using crimping. This is because the element space volume increases inside the outer can 10, so the energy density per unit volume increases.
  • This "element space volume” is the volume (effective volume) of the internal space of the exterior can 10 that can be used to house the battery element 40.
  • the exterior can 10 which is a welded can, does not have any parts that overlap each other, and does not have any parts where two or more members overlap each other.
  • Having no mutually folded portions means that a portion of the outer can 10 is not processed (folded) so as to be folded over each other. Furthermore, “there is no overlap between two or more members” means that the outer can 10 is physically one member after the completion of the secondary battery, so the outer can 10 is This means that it cannot be separated into two or more parts. In other words, the state of the outer can 10 in the completed secondary battery is not a state in which two or more members are assembled while overlapping each other so that they can be separated later.
  • the outer can 10 has electrical conductivity. Specifically, each of the storage section 11 and the lid section 12 has electrical conductivity.
  • the outer can 10 is electrically connected to the negative electrode 42 of the battery element 40 via the negative electrode lead 52. Therefore, the outer can 10 also serves as an external connection terminal for the negative electrode 42. Since the secondary battery of this embodiment does not need to be provided with an external connection terminal for the negative electrode 42 separately from the outer case 10, the element space volume due to the presence of the external connection terminal for the negative electrode 42 is reduced. Decrease is suppressed. This increases the element space volume, thereby increasing the energy density per unit volume.
  • the exterior can 10 is a metal can containing one or more types of conductive materials such as metal materials and alloy materials.
  • the conductive materials that make up the metal can include iron, copper, nickel, stainless steel, iron alloys, copper alloys, and nickel alloys.
  • the type of stainless steel is not particularly limited, but specific examples include SUS304 and SUS316.
  • the material for forming the storage portion 11 and the material for forming the lid portion 12 may be the same or different from each other.
  • the lid portion 12 is insulated from the external terminal 20 as an external connection terminal of the positive electrode 41 via a gasket 30. This is to prevent contact between the outer can 10, which is the external connection terminal of the negative electrode 42, and the external terminal 20, which is the external connection terminal of the positive electrode 41, that is, a short circuit.
  • the external terminal 20 is a connection terminal that is connected to an electronic device when the secondary battery is mounted on the electronic device. As described above, the external terminal 20 is attached to and supported by the lid 12 of the outer can 10. The external terminal 20 is provided at a position opposite to the bottom M2 when viewed from the lid portion 12 and overlaps the through hole 12K in the height direction Z.
  • the external terminal 20 is connected to the positive electrode 41 of the battery element 40 via the positive electrode lead 51. Therefore, the external terminal 20 functions as an external connection terminal for the positive electrode 41.
  • the secondary battery is connected to an electronic device via the external terminal 20 (terminal for external connection of the positive electrode 41) and the outer can 10 (terminal for external connection of the negative electrode 42). Therefore, the electronic device becomes operable using the secondary battery as a power source.
  • the external terminal 20 is a flat, substantially plate-shaped member that extends along a horizontal plane perpendicular to the height direction Z of the secondary battery, and is disposed inside the recess 12H with a gasket 30 interposed therebetween.
  • the external terminal 20 is insulated from the lid portion 12 via a gasket 30.
  • the position of the surface 20S of the external terminal 20 is lower toward the battery element 40 than the position of the surface 12RS of the peripheral part 12R of the outer can 10.
  • the external terminal 20 is housed inside the recess 12H so that the surface 20S, which is the upper end thereof, is recessed toward the battery element 40 rather than the surface 12RS.
  • the height of the secondary battery is smaller than that in the case where the external terminal 20 protrudes above the lid portion 12. Therefore, the energy density per unit volume of the secondary battery increases. Further, it is possible to prevent a short circuit between the outer can 10 and the external terminal 20 via another conductive member. Further, in the present embodiment, the peripheral portion of the external terminal 20 overlaps the bottom portion 12HB of the recessed portion 12H in the height direction Z. By having an overlapping portion between the external terminal 20 and the lid portion 12, the mechanical strength of the secondary battery as a whole can be improved.
  • the length of the overlapping portion of the external terminal 20 and the peripheral portion along the horizontal plane perpendicular to the height direction Z is preferably greater than the thickness of the external terminal 20 and greater than the thickness of the bottom portion 12HB.
  • the outer diameter of the external terminal 20 is smaller than the inner diameter of the recess 12H. Therefore, the outer edge 20T of the external terminal 20 is spaced apart from the lid portion 12.
  • the gasket 30 is arranged only in a part of the area between the external terminal 20 and the lid part 12 (the recessed part 12H). More specifically, if the gasket 30 were not present, the external terminal 20 and the lid portion 12 are arranged only at locations where they would come into contact with each other. However, the gasket 30 is preferably also provided between the inner wall surface of the wall portion 12HW of the recessed portion 12H and the outer edge 20T of the external terminal 20. Further, it is preferable that the lid portion 12 and the external terminal 20 are fixed to each other by a gasket 30.
  • the external terminal 20 includes one or more types of conductive materials such as metal materials and alloy materials, and the conductive materials include aluminum, aluminum alloy, and the like.
  • the external terminal 20 may be formed of a cladding material.
  • This cladding material includes an aluminum layer and a nickel layer in order from the side closer to the gasket 30, and in the cladding material, the aluminum layer and the nickel layer are roll-bonded to each other.
  • the gasket 30 is an insulating member disposed between the outer can 10 (lid 12) and the external terminal 20, as shown in FIG.
  • the external terminal 20 is fixed to the lid portion 12 via a gasket 30.
  • the gasket 30 has a ring-shaped planar shape with a through hole at a location corresponding to the through hole 12K.
  • the gasket 30 includes one or more types of insulating materials such as insulating polymer compounds, and the insulating materials are resins such as polypropylene and polyethylene.
  • the installation range of the gasket 30 is not particularly limited and can be set arbitrarily.
  • the gasket 30 is arranged in the gap between the upper surface of the lid section 12 and the lower surface of the external terminal 20 inside the recessed section 12H.
  • the gasket 30 may also be provided between the inner wall surface of the wall portion 12HW of the recessed portion 12H and the outer edge 20T of the external terminal 20. Further, it is preferable that the lid portion 12 and the external terminal 20 are fixed to each other by a gasket 30.
  • the battery element 40 is a power generating element that advances charging and discharging reactions, and is housed inside the outer can 10.
  • Battery element 40 includes a positive electrode 41 and a negative electrode 42.
  • the battery element 40 further includes a separator 43 and an electrolyte (not shown) that is a liquid electrolyte.
  • the center line PC shown in FIG. 2 is a line segment corresponding to the center of the battery element 40 in the direction along the outer diameter D of the secondary battery (exterior can 10). That is, the position P0 of the center line PC corresponds to the position of the center of the battery element 40.
  • the battery element 40 is a so-called wound electrode body. That is, in the battery element 40, a positive electrode 41 and a negative electrode 42 are stacked on each other with a separator 43 in between. Furthermore, as shown in FIG. 4, the stacked positive electrode 41, negative electrode 42, and separator 43 are wound around the center line PC as the winding axis. The positive electrode 41 and the negative electrode 42 are wound while maintaining a state facing each other with a separator 43 in between. Therefore, a winding center space 40K is formed at the center of the battery element 40.
  • FIG. 4 shows an example of the configuration of the battery element 40 taken along a horizontal cross section orthogonal to the height direction Z. However, in FIG. 4, illustration of the separator 43 is omitted to ensure visibility.
  • the positive electrode 41, the negative electrode 42, and the separator 43 are wound such that the separator 43 is disposed at the outermost periphery of the wound electrode body and at the innermost periphery of the wound electrode body, respectively.
  • the number of turns of each of the positive electrode 41, the negative electrode 42, and the separator 43 is not particularly limited, and can be set arbitrarily.
  • the negative electrode 42 is arranged outside the positive electrode 41. That is, as shown in FIG. 4, the outermost positive electrode portion 41out located at the outermost periphery of the positive electrodes 41 included in the battery element 40 is the outermost negative electrode 41out located at the outermost periphery of the negative electrodes 42 included in the battery element 40.
  • the positive electrode outermost circumferential portion 41out is the outermost portion of the positive electrode 41 that corresponds to one circumference in the battery element 40.
  • the negative electrode outermost circumferential portion 42out is the outermost portion of the negative electrode 42 in the battery element 40, which corresponds to one circumference.
  • the negative electrode 42 is preferably disposed inside the positive electrode 41 at the innermost circumference of the battery element 40 . That is, as shown in FIG. 4, the innermost negative electrode portion 42in located at the innermost circumference of the negative electrodes 42 included in the battery element 40 is located at the innermost circumference of the positive electrodes 41 included in the battery element 40.
  • the positive electrode be located inside the innermost peripheral portion 41 inches of the positive electrode.
  • the positive electrode innermost circumferential portion 41in is the innermost portion of the positive electrode 41 that corresponds to one circumference in the battery element 40.
  • the negative electrode innermost circumferential portion 42in is the innermost portion of the negative electrode 42 in the battery element 40, which corresponds to one circumference.
  • the battery element 40 has a three-dimensional shape similar to the three-dimensional shape of the outer can 10. Specifically, the battery element 40 has a flat and substantially cylindrical three-dimensional shape. Compared to the case where the battery element 40 has a three-dimensional shape different from the three-dimensional shape of the outer can 10, when the battery element 40 is housed inside the outer can 10, a so-called dead space, a concrete In this case, a gap between the outer can 10 and the battery element 40 is less likely to occur. Therefore, the internal space of the outer can 10 is effectively utilized. As a result, the element space volume increases, and the energy density per unit volume of the secondary battery increases.
  • the positive electrode 41 is a first electrode used to advance the charge/discharge reaction, and includes a positive electrode current collector 41A and a positive electrode active material layer 41B, as shown in FIGS. 3 and 4.
  • the positive electrode current collector 41A has a pair of surfaces on which the positive electrode active material layer 41B is provided. More specifically, the positive electrode current collector 41A has a positive electrode current collector inner surface 41A1 facing the winding center side of the battery element 40, that is, position P0, and a positive electrode current collector inner surface 41A1 facing the opposite side to the winding center side of the battery element 40. That is, it includes the positive electrode current collector outer surface 41A2 on the opposite side of the positive electrode current collector inner surface 41A1.
  • the positive electrode current collector 41A includes a conductive material such as a metal material, and the metal material is aluminum or the like.
  • the positive electrode 41 includes, as a positive electrode active material layer 41B, a positive electrode inner active material layer 41B1 that covers at least a portion of the positive electrode current collector inner surface 41A1, and a positive electrode outer active material layer 41B2 that covers at least a portion of the positive electrode current collector outer surface 41A2. has.
  • the positive electrode inner active material layer 41B1 and the positive electrode outer active material layer 41B2 are made of the same constituent material and may have the same thickness. Note that in this specification, the positive electrode inner active material layer 41B1 and the positive electrode outer active material layer 41B2 may be collectively referred to as the positive electrode active material layer 41B without distinguishing them.
  • the positive electrode active material layer 41B includes one or more types of positive electrode active materials capable of intercalating and deintercalating lithium. Further, the positive electrode active material layer 41B may further contain a positive electrode binder, a positive electrode conductive agent, and the like.
  • the method for forming the positive electrode active material layer 41B is not particularly limited, specifically, a coating method is
  • the positive electrode active material contains a lithium compound.
  • This lithium compound is a general term for compounds containing lithium as a constituent element, and more specifically, it is a compound containing lithium and one or more types of transition metal elements as constituent elements. This is because high energy density can be obtained.
  • the lithium compound may further contain one or more of other elements (excluding lithium and transition metal elements).
  • the type of lithium compound is not particularly limited, but specific examples include oxides, phosphoric acid compounds, silicic acid compounds, and boric acid compounds. Specific examples of oxides include LiNiO 2 , LiCoO 2 and LiMn 2 O 4 , and specific examples of phosphoric acid compounds include LiFePO 4 and LiMnPO 4 .
  • the positive electrode binder contains one or more of synthetic rubber, polymer compounds, and the like.
  • the synthetic rubber is styrene-butadiene rubber
  • the polymer compound is polyvinylidene fluoride.
  • the positive electrode conductive agent contains one or more types of conductive materials such as carbon materials, and the carbon materials include graphite, carbon black, acetylene black, and Ketjen black.
  • the conductive material may be a metal material, a polymer compound, or the like.
  • the negative electrode 42 is a second electrode used to advance the charge/discharge reaction, and as shown in FIG. 3, includes a negative electrode current collector 42A and a negative electrode active material layer 42B.
  • the negative electrode current collector 42A has a pair of surfaces on which the negative electrode active material layer 42B is provided. More specifically, the negative electrode current collector 42A has an inner surface 42A1 of the negative electrode current collector facing the winding center side of the battery element 40, that is, position P0, and a negative electrode current collector inner surface 42A1 facing the opposite side to the winding center side of the battery element 40. That is, it includes the negative electrode current collector outer surface 42A2 on the opposite side of the negative electrode current collector inner surface 42A1.
  • the negative electrode current collector 42A includes a conductive material such as a metal material, and the metal material is copper or the like.
  • the negative electrode 42 includes, as a negative electrode active material layer 42B, a negative electrode inner active material layer 42B1 that covers at least a portion of the negative electrode current collector inner surface 42A1, and a negative electrode outer active material layer 42B2 that covers at least a portion of the negative electrode current collector outer surface 42A2. has. From the inner peripheral end 40E1 of the battery element 40 to the outer peripheral end 40E2 of the battery element 40, the areal density of the negative electrode outer active material layer 42B2 is larger than the areal density of the negative electrode inner active material layer 42B1. As an example, when the area density of the negative electrode outer active material layer 42B2 is 101.8%, the area density of the negative electrode inner active material layer 42B1 is 98.2%.
  • the negative electrode inner active material layer 42B1 and the negative electrode outer active material layer 42B2 are made of the same constituent material, and as shown in FIG.
  • the thickness T2 of the negative electrode outer active material layer 42B2 is thicker than the thickness T1 of the negative electrode inner active material layer 42B1 up to the outer peripheral side end 40E2 of the negative electrode 40.
  • FIG. 5 is a developed view schematically showing the positive electrode 41 and negative electrode 42 of the battery element 40. Note that the broken lines in FIG. 5 represent the negative electrode inner active material layer 42B1 and the negative electrode outer active material layer 42B2 when the thickness T1 and the thickness T2 are equal to each other.
  • the negative electrode inner active material layer 42B1 and the negative electrode outer active material layer 42B2 may be collectively referred to as the negative electrode active material layer 42B without distinguishing them.
  • the inner end 40E1 as used herein means the innermost end of the portion of the battery element 40 where the positive electrode active material layer 41B and the negative electrode active material layer 42B face each other.
  • the outer peripheral end 40E2 in this specification means the outermost end of the portion of the battery element 40 where the positive electrode active material layer 41B and the negative electrode active material layer 42B face each other.
  • the negative electrode active material layer 42B includes one or more types of negative electrode active materials capable of intercalating and deintercalating lithium. However, the negative electrode active material layer 42B may further contain a negative electrode binder, a negative electrode conductive agent, and the like. The details regarding each of the negative electrode binder and the negative electrode conductive agent are the same as the details regarding each of the positive electrode binder and the positive electrode conductive agent.
  • the method of forming the negative electrode active material layer 42B is not particularly limited, but specifically, any one of a coating method, a gas phase method, a liquid phase method, a thermal spraying method, a firing method (sintering method), or the like. There are two or more types.
  • the negative electrode active material contains one or both of a carbon material and a metal-based material. This is because high energy density can be obtained.
  • Carbon materials include easily graphitizable carbon, non-graphitizable carbon, and graphite (natural graphite and artificial graphite).
  • a metal-based material is a material that contains as a constituent element one or more of metal elements and metalloid elements that can form an alloy with lithium, and the metal elements and metalloid elements include silicon and metalloid elements. such as one or both of tin.
  • the metallic material may be a single substance, an alloy, a compound, a mixture of two or more thereof, or a material containing phases of two or more thereof. Specific examples of the metal-based materials include TiSi 2 and SiOx (0 ⁇ x ⁇ 2, or 0.2 ⁇ x ⁇ 1.4).
  • the height of the negative electrode 42 is greater than the height of the positive electrode 41. That is, the negative electrode 42 protrudes above the positive electrode 41 and also projects below the positive electrode 41. This is to prevent lithium released from the positive electrode 41 from being deposited.
  • This "height" is a dimension corresponding to the height H of the secondary battery described above, that is, a dimension in the vertical direction in each of FIGS. 1 and 2. The definition of height explained here is also the same hereafter.
  • the separator 43 is an insulating porous film disposed between the positive electrode 41 and the negative electrode 42, as shown in FIGS. 2 and 3.
  • the separator 43 allows lithium ions to pass through while preventing a short circuit between the positive electrode 41 and the negative electrode 42 .
  • Separator 43 contains a high molecular compound such as polyethylene.
  • the height of the separator 43 is greater than the height of the negative electrode 42. That is, it is preferable that the separator 43 protrudes upwardly from the negative electrode 42 and downwardly from the negative electrode 42 .
  • the electrolytic solution is impregnated into each of the positive electrode 41, the negative electrode 42, and the separator 43, and contains a solvent and an electrolyte salt.
  • the solvent contains one or more types of nonaqueous solvents (organic solvents) such as carbonate ester compounds, carboxylic ester compounds, and lactone compounds, and contains the nonaqueous solvent.
  • the electrolyte is a so-called non-aqueous electrolyte.
  • the electrolyte salt contains one or more light metal salts such as lithium salts.
  • the positive electrode lead 51 is housed inside the outer can 10, as shown in FIG.
  • the positive electrode lead 51 is a connection wiring connected to the positive electrode 41 and the external terminal 20, respectively.
  • the secondary battery shown in FIG. 2 includes one positive electrode lead 51.
  • the secondary battery shown in FIG. may include two or more positive electrode leads 51.
  • the positive electrode lead 51 is connected to the upper end of the positive electrode 41. Specifically, the positive electrode lead 51 is connected to the upper end of the positive electrode current collector 41A. Further, the positive electrode lead 51 is connected to a part of the surface 20S of the external terminal 20 via a through hole 12K provided in the lid portion 12.
  • the method for connecting the positive electrode lead 51 is not particularly limited, but specifically, one or more of welding methods such as resistance welding and laser welding are used. The details regarding the welding method described here are also the same hereafter.
  • the positive electrode lead 51 includes a first portion 511, a second portion 512, and a folded portion 513.
  • the first portion 511 and the second portion 512 extend along a horizontal plane perpendicular to the height direction Z of the secondary battery. Further, the first portion 511 and the second portion 512 overlap each other in the height direction Z of the secondary battery with the sealant 61 interposed therebetween.
  • the folded portion 513 is curved so as to connect the first portion 511 and the second portion 512.
  • the first portion 511 and the second portion 512 are sandwiched between the battery element 40 and the recessed portion 12H of the lid portion 12 in the height direction Z of the secondary battery.
  • the positive electrode lead 51 is held by the lid 12 and the battery element 40 by extending along the lower surface of the lid 12 and the upper surface of the battery element 40, respectively. Therefore, the positive electrode lead 51 is fixed inside the outer can 10. Since the positive electrode lead 51 becomes difficult to move even when the secondary battery receives external forces such as vibrations and shocks, the positive electrode lead 51 becomes less likely to be damaged.
  • the damage to the positive electrode lead 51 includes the occurrence of a crack in the positive electrode lead 51, the cutting of the positive electrode lead 51, the falling off of the positive electrode lead 51 from the positive electrode 41, and the like.
  • a portion of the positive electrode lead 51 is sandwiched between the outer can 10 and the battery element 40 means that the positive electrode lead 51 is insulated from the outer can 10 and the battery element 40, but the positive electrode lead 51 is sandwiched between the outer can 10 and the battery element 40, respectively. Since the positive electrode lead 51 is held from above and below by the element 40, this means that the positive electrode lead 51 is difficult to move inside the outer can 10 even if the secondary battery is subjected to external forces such as vibrations and shocks. There is. The fact that the positive electrode lead 51 is difficult to move inside the outer can 10 means that the battery element 40 is also difficult to move inside the outer can 10 . Therefore, when the secondary battery is subjected to vibration or impact, it is possible to avoid problems such as unwinding of the battery element 40, which is a wound electrode body.
  • the positive electrode lead 51 bites into the battery element 40 due to being pressed by the battery element 40. More specifically, as described above, the height of the separator 43 is greater than the height of each of the positive electrode 41 and the negative electrode 42, so the positive electrode lead 51 bites into the upper end of the separator 43. is preferred. In this case, a depression is formed at the upper end of the separator 43 due to the pressure of the positive electrode lead 51. Since part or all of the positive electrode lead 51 is housed inside the recess, the positive electrode lead 51 is held by the separator 43 . This is because the positive electrode lead 51 becomes more difficult to move inside the outer can 10, so that the positive electrode lead 51 is less likely to be damaged.
  • the lid portion 12 includes the recess 12H, and a portion of the positive electrode lead 51 is sandwiched between the recess 12H and the battery element 40. That is, a portion of the positive electrode lead 51 is held by the recess 12H and the battery element 40 by extending along the lower surface of the recess 12H and the upper surface of the battery element 40, respectively. Since the positive electrode lead 51 is more easily held using the recessed portion 12H, the positive electrode lead 51 is less likely to be damaged.
  • a portion of the positive electrode lead 51 is insulated from the lid portion 12 and the negative electrode 42 via the separator 43, the sealant 61, and the insulating films 62, 63, respectively.
  • the height of the separator 43 is greater than the height of the negative electrode 42. As a result, a portion of the positive electrode lead 51 is separated from the negative electrode 42 via the separator 43 and is therefore insulated from the negative electrode 42 via the separator 43. This is because a short circuit between the positive electrode lead 51 and the negative electrode 42 is prevented.
  • the positive electrode lead 51 is surrounded by an insulating sealant 61. Thereby, a portion of the positive electrode lead 51 is insulated from each of the lid portion 12 and the negative electrode 42 via the sealant 61. This is because a short circuit between the positive electrode lead 51 and the lid portion 12 is prevented, and a short circuit between the positive electrode lead 51 and the negative electrode 42 is also prevented.
  • an insulating film 62 is arranged between the lid portion 12 and the positive electrode lead 51. As a result, a portion of the positive electrode lead 51 is insulated from the lid portion 12 via the insulating film 62. This is because a short circuit between the positive electrode lead 51 and the lid portion 12 is prevented.
  • an insulating film 63 is arranged between the battery element 40 and the positive electrode lead 51. Thereby, a portion of the positive electrode lead 51 is insulated from the negative electrode 42 via the insulating film 63. This is because a short circuit between the positive electrode lead 51 and the negative electrode 42 is prevented.
  • the details regarding the forming material of the positive electrode lead 51 are the same as the details regarding the forming material of the positive electrode current collector 41A. However, the material for forming the positive electrode lead 51 and the material for forming the positive electrode current collector 41A may be the same or different from each other.
  • the positive electrode lead 51 is connected to the positive electrode 41 in a region in front of the center line PC, that is, in a region to the right of the center line PC in FIG.
  • the positive electrode lead 51 has a folded portion 513 on the way toward the external terminal 20 in order to be connected to the external terminal 20 .
  • the folded portion 513 exists in a region further back than the center line PC, that is, in a region to the left of the center line PC in FIG.
  • the positive electrode lead 51 has a first portion 511 that extends from the point connected to the positive electrode 41 to the folded portion 513 through the center position P0.
  • the first portion 511 extends along the upper surface of the battery element 40 in a direction perpendicular to the height direction Z.
  • the positive electrode lead 51 has a second portion 512 as a portion on the way from the folded portion 513 to the location connected to the external terminal 20 .
  • the second portion 512 extends in a direction perpendicular to the height direction Z along the upper surface of the battery element 40 so as to cover the first portion 511 .
  • a portion of the positive electrode lead 51 is directed toward the external terminal 20 while being sandwiched between the lid portion 12 and the battery element 40 in both the area in front of the center line PC and the area behind the center line PC. It has been extended.
  • the area in front of the center line PC refers to the area when the battery element 40 is divided into two areas with the center line PC as a reference in the direction along the outer diameter D. , is one region where the connection point of the positive electrode lead 51 to the positive electrode 41 exists.
  • the "region in front of the center line PC” is the region to the right of the center line PC.
  • the "area behind the center line PC” is the other of the two areas mentioned above, and in FIG. It is an area.
  • the area behind the center line PC refers to the connection point of the positive electrode lead 51 to the positive electrode 41 when the battery element 40 is divided into two areas with the center line PC as a reference in the direction along the outer diameter D. This is the other area in which it does not exist.
  • connection position of the positive electrode lead 51 to the positive electrode 41 is not particularly limited and can be set arbitrarily. Among these, it is preferable that the positive electrode lead 51 is connected to the positive electrode 41 on the inner circumferential side of the positive electrode 41 rather than the outermost circumference thereof. This is because, unlike the case where the positive electrode lead 51 is connected to the positive electrode 41 at the outermost periphery of the positive electrode 41, corrosion of the outer can 10 caused by the rising of the electrolytic solution is prevented.
  • This "climbing up of the electrolyte” means that when the positive electrode lead 51 is placed close to the inner wall surface of the outer can 10, the electrolyte in the battery element 40 creeps up the positive electrode lead 51 inside the outer can 10. The goal is to reach the wall. When the electrolytic solution comes into contact with the outer can 10 due to "the rising of the electrolytic solution", a phenomenon occurs in which the outer can 10 is dissolved or discolored.
  • the positive electrode lead 51 is folded back one or more times between the positive electrode 41 and the external terminal 20, so it is folded over one or more times.
  • the number of times the positive electrode lead 51 is folded back is not particularly limited as long as it is one or more times.
  • the phrase "the positive electrode lead 51 is folded back" means that the extending direction of the positive electrode lead 51 changes in the middle so as to form an angle larger than 90°.
  • the folded portion of the positive electrode lead 51 preferably has a curved shape without being bent, like the folded portion 513.
  • FIG. 2 illustrates a case in which the positive electrode lead 51 includes one folded portion 513, it may include a plurality of folded portions 513.
  • the positive electrode lead 51 is folded back at a folded portion 513 on the way from the positive electrode 41 to the external terminal 20.
  • the first portion 511 extends from a first position P1 other than the center position P0 of the outer can 10 in a horizontal plane perpendicular to the height direction of the secondary battery. It extends to a second position P2 on the opposite side from the first position P1 when viewed from the position.
  • the second portion 512 extends from the second position P2 toward the central position P0.
  • the overlapping portion of the first portion 511 and the second portion 512 is a surplus portion. That is, it can be said that the positive electrode lead 51 has a length margin in its longitudinal direction.
  • the outer can 10 when forming the outer can 10 using the storage section 11 and the lid section 12 in the secondary battery manufacturing process, there is a margin for changing the attitude of the lid section 12 with respect to the storage section 11. .
  • the external forces are alleviated using the length margin of the positive electrode lead 51, so that the positive electrode lead 51 is less likely to be damaged.
  • the connection position of the positive electrode lead 51 to the positive electrode 41 can be changed arbitrarily without changing the length of the positive electrode lead 51.
  • the length of the positive electrode lead 51 (the entire length including the length margin) is not particularly limited and can be set arbitrarily.
  • the length of the positive electrode lead 51 is preferably at least half the outer diameter D of the outer can 10. This is because, regarding the length of the positive electrode lead 51, a length margin for standing the lid part 12 up against the storage part 11 is ensured, so that it becomes easier to stand the lid part 12 up against the storage part 11.
  • connection range of the positive electrode lead 51 to the external terminal 20 is not particularly limited.
  • the connection range of the positive electrode lead 51 to the external terminal 20 is sufficiently wide to prevent the positive electrode lead 51 from falling off from the external terminal 20, and narrow enough to provide a length margin for the positive electrode lead 51.
  • the connection range of the positive electrode lead 51 to the external terminal 20 is sufficiently narrow because the portion of the positive electrode lead 51 that is not connected to the external terminal 20 serves as a length margin. This is because it becomes sufficiently large.
  • the positive electrode lead 51 is provided separately from the positive electrode current collector 41A. However, since the positive electrode lead 51 is physically continuous with the positive electrode current collector 41A, it may be integrated with the positive electrode current collector 41A.
  • the negative electrode lead 52 is housed inside the outer can 10, as shown in FIG.
  • the negative electrode lead 52 is electrically connected to each of the negative electrode 42 and the outer can 10 (accommodating portion 11). Therefore, the storage portion 11 (bottom M2) is electrically connected to the negative electrode 42 via the negative electrode lead 52.
  • the secondary battery includes one negative electrode lead 52.
  • the secondary battery may include two or more negative electrode leads 52.
  • the negative electrode lead 52 is connected to the lower end of the negative electrode 42, and more specifically, to the lower end of the negative electrode current collector 42A. Further, the negative electrode lead 52 is connected to the bottom surface of the storage section 11.
  • the method for connecting the negative electrode lead 52 is not particularly limited, but specifically, one or more welding methods such as resistance welding and laser welding are used.
  • the details regarding the material for forming the negative electrode lead 52 are the same as the details regarding the material for forming the negative electrode current collector 42A. However, the material forming the negative electrode lead 52 and the material forming the negative electrode current collector 42A may be the same or different.
  • connection position of the negative electrode lead 52 to the negative electrode 42 is not particularly limited and can be set arbitrarily.
  • the negative electrode lead 52 is connected to the outermost peripheral portion of the negative electrode 42 that constitutes the wound electrode body.
  • the negative electrode lead 52 is provided separately from the negative electrode current collector 42A. However, since the negative electrode lead 52 is physically continuous with the negative electrode current collector 42A, it may be integrated with the negative electrode current collector 42A.
  • the sealant 61 is a first insulating member that covers the periphery of the positive electrode lead 51, as shown in FIG. It is constructed by attaching.
  • the sealant 61 covers the periphery of the intermediate portion of the positive electrode lead 51 in order to connect the positive electrode lead 51 to each of the positive electrode 41 and the external terminal 20.
  • the sealant 61 is not limited to having a tape-like structure, and may have a tube-like structure, for example.
  • the sealant 61 contains one or more types of insulating materials such as insulating polymer compounds, and the insulating material is polyimide or the like.
  • the insulating film 62 is an insulating member disposed between the lid part 12 and the battery element 40 in the height direction Z, as shown in FIG.
  • the insulating film 62 has a ring-shaped planar shape with an opening 62K in the height direction Z at a location corresponding to the through hole 12K.
  • the insulating film 62 may be adhered to the lid part 12 via an adhesive layer.
  • the insulating film 62 may include one or more types of insulating materials such as insulating polymer compounds.
  • the insulating material included in the insulating film 62 is polyimide or the like.
  • the insulating film 63 is an insulating member disposed between the battery element 40 and the positive electrode lead 51, as shown in FIG.
  • the insulating film 63 has a flat planar shape.
  • the insulating film 63 is arranged to shield the winding center space 40K and to cover the battery elements 40 around the winding center space 40K.
  • the details regarding the material for forming the insulating film 63 are the same as the details regarding the material for forming the insulating film 62. However, the forming material of the insulating film 63 and the forming material of the insulating film 62 may be the same or different.
  • the secondary battery may further include one or more types of other components.
  • the secondary battery is equipped with a safety valve mechanism.
  • This safety valve mechanism is configured to disconnect the electrical connection between the outer can 10 and the battery element 40 when the internal pressure of the outer can 10 reaches a certain level or higher.
  • the causes of the internal pressure of the outer can 10 reaching a certain level or higher include a short circuit occurring inside the secondary battery, and the secondary battery being heated from the outside.
  • the installation location of the safety valve mechanism is not particularly limited, but it is preferable that the safety valve mechanism is provided on either of the bottom portions M1 and M2, and the safety valve mechanism is preferably provided on the bottom portion M2 where the external terminal 20 is not attached. It is more preferable that
  • the secondary battery may include an insulator other than the insulating films 62 and 64 between the outer can 10 and the battery element 40.
  • This insulator includes one or more of an insulating film, an insulating sheet, and the like, and prevents a short circuit between the outer can 10 and the battery element 40.
  • the installation range of the insulator is not particularly limited and can be set arbitrarily.
  • the outer can 10 is provided with an opening valve.
  • This opening valve opens when the internal pressure of the outer can 10 reaches a certain level or higher, and thus releases the internal pressure.
  • the installation location of the open series valve is not particularly limited, but, like the installation location of the safety valve mechanism described above, either of the bottom portions M1 and M2 is preferred, and the bottom portion M2 is particularly preferred.
  • FIG. 6 shows a perspective configuration of the outer can 10 used in the manufacturing process of a secondary battery, and corresponds to FIG. 1.
  • FIG. 6 shows a state in which the lid 12 is separated from the storage part 11 before the lid part 12 is welded to the storage part 11.
  • FIGS. 1 to 5 will be referred to from time to time together with FIG. 6.
  • the storage portion 11 is a substantially vessel-shaped member in which a bottom portion M2 and a side wall portion M3 are integrated with each other, and has an opening portion 11K.
  • the lid part 12 is a substantially plate-shaped member corresponding to the bottom part M1, and the external terminal 20 is attached in advance to a recessed part 12H provided in the lid part 12 via a gasket 30.
  • the storage portion 11 may be formed by preparing a bottom portion M2 and a side wall portion M3 that are physically separated from each other, and welding the side wall portion M3 to the bottom portion M2.
  • a positive electrode mixture is prepared by mixing a positive electrode active material, a positive electrode binder, a positive electrode conductive agent, and the like.
  • a paste-like positive electrode mixture slurry is prepared by adding the prepared positive electrode mixture to an organic solvent or the like.
  • a positive electrode active material layer 41B is formed by applying a positive electrode mixture slurry to both surfaces of the positive electrode current collector 41A.
  • the positive electrode active material layer 41B is compression molded using a roll press or the like. In this case, the positive electrode active material layer 41B may be heated or compression molding may be repeated multiple times. In this way, the positive electrode 41 is manufactured.
  • the negative electrode 42 is manufactured by the same procedure as the positive electrode 41. Specifically, a negative electrode mixture formed by mixing a negative electrode active material, a negative electrode binder, a negative electrode conductive agent, etc. is poured into an organic solvent to prepare a paste-like negative electrode mixture slurry, and then the negative electrode current collector 42A is prepared. A negative electrode active material layer 42B is formed by applying a negative electrode mixture slurry to both surfaces of the negative electrode active material layer 42B. At this time, the thickness T2 of the negative electrode outer active material layer 42B2 covering the negative electrode current collector outer surface 42A2 is set to be thicker than the thickness T1 of the negative electrode inner active material layer 42B1 covering the negative electrode current collector inner surface 42A1. Thereafter, the negative electrode active material layer 42B is compression molded using a roll press machine or the like. Thereby, the negative electrode 42 is produced.
  • the positive electrode lead 51 whose periphery is covered with the sealant 61 is connected to the positive electrode 41 (positive electrode current collector 41A), and the negative electrode lead 52 is connected to the negative electrode 42 (negative electrode current collector 41A). Connect it to the electric body 42A).
  • the positive electrode 41 and the negative electrode 42 are laminated with the separator 43 in between, and then the laminated body including the positive electrode 41, the negative electrode 42, and the separator 43 is wound to form a wound body as shown in FIG. Create 40Z.
  • the wound body 40Z has the same configuration as the battery element 40, except that the positive electrode 41, the negative electrode 42, and the separator 43 are not impregnated with electrolyte.
  • illustration of each of the positive electrode lead 51 and the negative electrode lead 52 is omitted.
  • the wound body 40Z to which the positive electrode lead 51 and the negative electrode lead 52 are connected, is stored inside the storage section 11 through the opening 11K.
  • the negative electrode lead 52 is connected to the housing portion 11 using a welding method such as a resistance welding method.
  • the insulating film 63 is placed on the wound body 40Z.
  • the through hole 12K is formed using a welding method such as resistance welding.
  • the positive electrode lead 51 is connected to the external terminal 20 via the terminal.
  • the wound body 40Z (positive electrode 41) stored inside the storage portion 11 and the external terminal 20 attached to the lid portion 12 are connected to each other via the positive electrode lead 51.
  • the electrolytic solution is injected into the storage section 11 through the opening 11K.
  • the lid 12 does not close the opening 11K, so the opening 11K can be accessed from the storage area.
  • the electrolytic solution can be easily injected into the inside of 11.
  • the wound body 40Z including the positive electrode 41, the negative electrode 42, and the separator 43 is impregnated with the electrolytic solution, and the battery element 40, which is a wound electrode body, is manufactured.
  • the opening 11K is closed using the lid 12, and then the lid 12 is attached to the storage part 11 using a welding method such as a laser welding method. to weld.
  • a welding method such as a laser welding method. to weld.
  • a portion of the positive electrode lead 51 is sandwiched between the lid portion 12 and the battery element 40, and the positive electrode lead 51 is bent in front of the connection location to the external terminal 20. so that a folded portion 513 is formed.
  • the outer can 10 is formed, and the battery element 40 and the like are housed inside the outer can 10, completing the assembly of the secondary battery.
  • the areal density of the negative electrode outer active material layer 42B2 from the inner peripheral side end 40E1 to the outer peripheral side end 40E2 is equal to the area density of the negative electrode inner active material layer 42B1. It is made to be larger than the areal density of . Therefore, in the relationship between the positive electrode 41 and the negative electrode 42 that face each other with the separator 43 in between, the capacity of the negative electrode 42 becomes larger than the capacity of the positive electrode 41.
  • the capacity of the negative electrode outer active material layer 42B2 is made larger than the capacity of the positive electrode inner active material layer 41B1. can do.
  • the secondary battery of this embodiment can suppress the formation of precipitates such as lithium metal accompanying battery reactions during charging, and can suppress deterioration in battery performance. Therefore, it has high reliability.
  • FIG. 7 is an explanatory diagram showing the relationship between the capacity of the positive electrode 41 and the capacity of the negative electrode 42 in the battery element 40.
  • the horizontal axis in FIG. 7 represents the element diameter d
  • the vertical axis in FIG. 7 represents N/P, which is the ratio of the negative electrode capacity N to the positive electrode capacity P.
  • the element diameter d is the distance from the center position P0 of the battery element 40 to an arbitrary position on the separator 43, as shown in FIG.
  • N/P represents the ratio of capacitance between the positive electrode active material layer 41B and the negative electrode active material layer 42B that face each other with the separator 43 in between at the position of the element diameter d.
  • N/P continuously changes depending on the element diameter d. More specifically, among the four curves shown in FIG. 7, two curves C7-1 and C7-2, in which N/P increases as the element diameter d increases, represent the relationship between the capacity of the positive electrode inner active material layer 41B1. It represents the capacity ratio Nout/Pin of the negative electrode outer active material layer 42B2. Of the two curves C7-1 and C7-2, the solid line C7-1 represents Nout/Pin of the secondary battery of this embodiment, and the broken line C7-2 represents the negative electrode outer active material layer.
  • 42B2 represents Nout/Pin of a secondary battery of a comparative example in which the areal density of 42B2 and the areal density of negative electrode inner active material layer 42B1 are substantially equal. Furthermore, among the four curves shown in FIG. 7, the two curves C7-3 and C7-4, in which N/P decreases as the element diameter d increases, are the negative electrode inner active material relative to the capacity of the positive electrode outer active material layer 41B2. It represents the capacitance ratio Nin/Pout of the material layer 42B1. Of the two curves C7-3 and C7-4, the solid line C7-3 represents Nin/Pout of the secondary battery of this embodiment, and the broken line C7-4 represents the negative electrode outer active material layer. 42B2 represents the Nin/Pout of a secondary battery of a comparative example in which the areal density of the negative electrode inner active material layer 42B1 is substantially equal to the areal density of the negative electrode inner active material layer 42B1.
  • Nout/Pin is particularly small in the region where the element diameter d is small, in the secondary battery of the comparative example, Nout/Pin is less than 1 in the region where the element diameter d ⁇ d1 (see curve C7-2). In that case, precipitates such as lithium metal are likely to be generated as a result of battery reactions, especially during charging at high voltages.
  • the decrease in Nout/Pin can be suppressed in the region where the element diameter d is small, and the Nout/Pin can be reduced by 1 or more in the region where the element diameter d ⁇ d0. (see curve C7-1). Therefore, in the secondary battery of this embodiment, it is possible to suppress the formation of precipitates such as lithium metal accompanying the battery reaction during charging, and it is possible to suppress the deterioration of battery performance. Further, according to the secondary battery of this embodiment, the deviation between Nout/Pin and Nin/Pout can be reduced from the inner circumferential end 40E1 to the outer circumferential end 40E2, and the cycle characteristics can be improved. It is advantageous for improvement.
  • a recess 12H is provided in the lid portion 12, and the external terminal 20 is arranged in the recess 12H. Therefore, the height of the secondary battery can be reduced while ensuring battery capacity.
  • the positive electrode lead can be used even in small secondary batteries that have large restrictions in terms of size. 51 is less likely to be damaged, a higher effect can be obtained in terms of physical durability.
  • the secondary battery is a lithium ion secondary battery, sufficient battery capacity can be stably obtained by utilizing lithium intercalation and desorption.
  • FIG. 8 is a developed view schematically showing a positive electrode 41 and a negative electrode 42 of a battery element 40A of a secondary battery according to a second embodiment of the present disclosure.
  • FIG. 8 corresponds to FIG. 5 showing a developed view of the battery element 40 of the secondary battery of the first embodiment.
  • the areal density of the negative electrode outer active material layer 42B2 is lower than that of the negative electrode inner active material layer 42B1 from the inner peripheral end 40E1 to the outer peripheral end 40E2. It is made to be larger than the areal density.
  • the negative electrode inner active material layer 42B1 and the negative electrode outer active material layer 42B2 are made of the same constituent material, and extend from the inner peripheral end 40E1 of the battery element 40 to the outer peripheral end 40E2 of the battery element 40.
  • the thickness T2 of the negative electrode outer active material layer 42B2 is made thicker than the thickness T1 of the negative electrode inner active material layer 42B1.
  • both the thickness T1 and the thickness T2 are made substantially constant in the longitudinal direction of the negative electrode 42 (the winding direction of the battery element 40).
  • the battery element 40A of the secondary battery according to the present embodiment shown in FIG. I'm trying to change.
  • the thickness T1 and the thickness T2 are each gradually changed.
  • the areal density of the negative electrode outer active material layer 42B2 in the entire battery element 40A is substantially equal to the areal density of the negative electrode inner active material layer 42B1 in the entire battery element 40A.
  • the constituent material of the negative electrode inner active material layer 42B1 and the constituent material of the negative electrode outer active material layer 42B2 are substantially the same, and the occupied area of the negative electrode inner active material layer 42B1 and the occupied area of the negative electrode outer active material layer 42B2 are substantially the same.
  • the weight of the negative electrode inner active material layer 42B1 and the weight of the negative electrode outer active material layer 42B2 are substantially equal. Note that the broken lines in FIG. 8 represent the negative electrode inner active material layer 42B1 and the negative electrode outer active material layer 42B2 when the thickness T1 and the thickness T2 are equal to each other.
  • the areal density of the negative electrode outer active material layer 42B2 at the inner peripheral end 40E1 of the battery element 40A is higher than the areal density of the negative electrode outer active material layer 42B2 at the outer peripheral end 40E2 of the battery element 40A. More specifically, in the example of FIG. 8, the areal density of the negative electrode outer active material layer 42B2 is highest at the inner end 40E1, and becomes lower as it approaches the outer end 40E2 from the inner end 40E1. There is. Furthermore, the negative electrode outer active material layer 42B2 is made of a substantially homogeneous constituent material, and the thickness T2 of the negative electrode outer active material layer 42B2 is thickest at the inner circumferential end 40E1 and starts from the inner circumferential end 40E1.
  • the areal density of the negative electrode inner active material layer 42B1 at the inner peripheral end 40E1 of the battery element 40A is higher than that of the negative electrode inner active material layer 42B1 at the outer peripheral end 40E2 of the battery element 40A. higher than areal density. More specifically, in the example of FIG. 8, the areal density of the negative electrode inner active material layer 42B1 is lowest at the inner end 40E1, and increases as it approaches the outer end 40E2 from the inner end 40E1. There is.
  • the negative electrode inner active material layer 42B1 is made of a substantially homogeneous constituent material, and the thickness T1 of the negative electrode inner active material layer 42B1 is the thinnest at the inner circumferential end 40E1 and starts from the inner circumferential end 40E1. It becomes thicker as it approaches the outer circumferential end 40E2, and is thickest at the outer circumferential end 40E2. That is, if the thickness of the negative electrode inner active material layer 42B1 at the inner peripheral end 40E1 is T1S, and the thickness of the negative electrode inner active material layer 42B1 at the outer peripheral end 40E2 is T1E, then the relationship T1S ⁇ T1E holds. be.
  • the secondary battery of this embodiment has substantially the same configuration as the secondary battery of the first embodiment, except for the above points.
  • the thickness T2 of the negative electrode outer active material layer 42B2 and the thickness T1 of the negative electrode inner active material layer 42B1 are measured from the inner peripheral side end 40E1 to the outer peripheral side end 40E2.
  • the method of manufacturing the secondary battery is the same as that of the first embodiment, except that the secondary battery is manufactured so that the value gradually changes.
  • the areal density of the negative electrode active material layer 42B gradually changes from the inner end 40E1 to the outer end 40E2.
  • the areal density of the negative electrode outer active material layer 42B2 at the inner peripheral end 40E1 of the battery element 40A is higher than the areal density of the negative electrode outer active material layer 42B2 at the outer peripheral end 40E2 of the battery element 40A. Therefore, similarly to the secondary battery of the first embodiment, in the relationship between the positive electrode 41 and the negative electrode 42 facing each other with the separator 43 in between, the capacity of the negative electrode 42 is larger than the capacity of the positive electrode 41.
  • the secondary battery of this embodiment can suppress the formation of precipitates such as lithium metal accompanying battery reactions during charging, and can suppress deterioration in battery performance. Therefore, it has high reliability.
  • FIG. 9 is an explanatory diagram showing the relationship between the capacity of the positive electrode 41 and the capacity of the negative electrode 42 in the battery element 40A of this embodiment, and corresponds to FIG. 7 described in the first embodiment.
  • the horizontal axis in FIG. 9 represents the element diameter d
  • the vertical axis in FIG. 9 represents N/P, which is the ratio of the negative electrode capacity N to the positive electrode capacity P.
  • N/P continuously changes depending on the element diameter d. More specifically, among the four curves shown in FIG.
  • two curves C9-1 and C9-2 represent the ratio Nout/Pin of the capacity of the negative electrode outer active material layer 42B2 to the capacity of the positive electrode inner active material layer 41B1. represents.
  • the solid line C9-1 represents Nout/Pin of the secondary battery of this embodiment
  • the broken line C9-2 represents the negative electrode outer active material layer.
  • 42B2 represents Nout/Pin of a secondary battery of a comparative example in which the areal density of the negative electrode inner active material layer 42B1 is substantially equal to the areal density of the negative electrode inner active material layer 42B1.
  • two curves C9-3 and C9-4 represent the ratio Nin/Pout of the capacity of the negative electrode inner active material layer 42B1 to the capacity of the positive electrode outer active material layer 41B2.
  • the solid line C9-3 represents Nin/Pout of the secondary battery of this embodiment
  • the broken line C9-4 represents the negative electrode outer active material layer.
  • 42B2 represents the Nin/Pout of a secondary battery of a comparative example in which the areal density of the negative electrode inner active material layer 42B1 is substantially equal to the areal density of the negative electrode inner active material layer 42B1.
  • Nout/Pin is less than 1 in the region where the element diameter d ⁇ d1, as shown by curve C9-2. Therefore, in a region where the element diameter d ⁇ d1, especially during charging at a high voltage, precipitates such as lithium metal are likely to be generated as a result of battery reactions, and battery performance is likely to deteriorate.
  • FIG. 10 is a developed view schematically showing a positive electrode 41 and a negative electrode 42 of a battery element 40B of a secondary battery according to a third embodiment of the present disclosure.
  • FIG. 10 corresponds to FIG. 8 showing a developed view of the battery element 40A of the secondary battery according to the second embodiment.
  • the areal density of the negative electrode outer active material layer 42B2 in the entire battery element 40B is lower than The area density is set to be larger than the area density of the active material layer 42B1. Note that the broken lines in FIG. 10 represent the negative electrode inner active material layer 42B1 and the negative electrode outer active material layer 42B2 when the thickness T1 and the thickness T2 are equal to each other.
  • the secondary battery of this embodiment has substantially the same configuration as the secondary battery of the second embodiment, except for the above points.
  • the areal density of the negative electrode outer active material layer 42B2 in the entire battery element 40B is larger than the areal density of the negative electrode inner active material layer 42B1 in the entire battery element 40B.
  • the method of manufacturing the secondary battery of the second embodiment is the same as that of the second embodiment except for the following.
  • the areal density of the negative electrode outer active material layer 42B2 in the entire battery element 40B is equal to the areal density of the negative electrode inner active material layer 42B1 in the entire battery element 40B.
  • the areal density of the negative electrode active material layer 42B gradually changes from the inner peripheral end 40E1 to the outer peripheral end 40E2. Therefore, similarly to the secondary battery of the first embodiment, in the relationship between the positive electrode 41 and the negative electrode 42 facing each other with the separator 43 in between, the capacity of the negative electrode 42 is larger than the capacity of the positive electrode 41.
  • the secondary battery of this embodiment can suppress the formation of precipitates such as lithium metal accompanying battery reactions during charging, and can suppress deterioration in battery performance. Therefore, it has high reliability.
  • FIG. 11 is an explanatory diagram showing the relationship between the capacity of the positive electrode 41 and the capacity of the negative electrode 42 in the battery element 40B of this embodiment, and corresponds to FIG. 7 described in the first embodiment.
  • the horizontal axis in FIG. 11 represents the element diameter d
  • the vertical axis in FIG. 11 represents N/P, which is the ratio of the negative electrode capacity N to the positive electrode capacity P.
  • N/P continuously changes depending on the element diameter d. More specifically, among the four curves shown in FIG.
  • two curves C11-1 and C11-2 represent the ratio Nout/Pin of the capacity of the negative electrode outer active material layer 42B2 to the capacity of the positive electrode inner active material layer 41B1. represents.
  • the solid line C11-1 represents Nout/Pin of the secondary battery of this embodiment
  • the broken line C11-2 represents the negative electrode outer active material layer.
  • 42B2 represents Nout/Pin of a secondary battery of a comparative example in which the areal density of 42B2 and the areal density of negative electrode inner active material layer 42B1 are substantially equal.
  • two curves C11-3 and C11-4 represent the ratio Nin/Pout of the capacity of the negative electrode inner active material layer 42B1 to the capacity of the positive electrode outer active material layer 41B2.
  • the solid line C11-3 represents Nin/Pout of the secondary battery of this embodiment
  • the broken line C11-4 represents the negative electrode outer active material layer.
  • 42B2 represents the Nin/Pout of a secondary battery of a comparative example in which the areal density of the negative electrode inner active material layer 42B1 is substantially equal to the areal density of the negative electrode inner active material layer 42B1.
  • Example 1 The secondary batteries (lithium ion secondary batteries) shown in FIGS. 1 to 5 were manufactured. Specifically, the areal density of the negative electrode outer active material layer 42B2 from the inner peripheral side end 40E1 of the battery element 40 to the outer peripheral side end 40E2 of the battery element 40 is set to the negative electrode inner active material layer as follows. A coin-shaped secondary battery having an area density higher than that of 42B1 was manufactured.
  • a positive electrode mixture was prepared by mixing 91 parts by mass of a positive electrode active material (LiCoO 2 ), 3 parts by mass of a positive electrode binder (polyvinylidene fluoride), and 6 parts by mass of a positive electrode conductive agent (graphite). . Subsequently, the positive electrode mixture was added to an organic solvent (N-methyl-2-pyrrolidone), and the organic solvent was stirred to prepare a paste-like positive electrode mixture slurry.
  • a positive electrode active material LiCoO 2
  • a positive electrode binder polyvinylidene fluoride
  • graphite a positive electrode conductive agent
  • a positive electrode mixture slurry is applied to both sides of the positive electrode current collector 41A (a strip-shaped aluminum foil having a thickness of 12 ⁇ m) using a coating device, and then the positive electrode mixture slurry is dried to form a positive electrode active material.
  • a material layer 41B was formed.
  • the thickness of the positive electrode inner active material layer 41B1 and the positive electrode outer active material layer 41B2 after compression molding were each 0.037 mm.
  • a negative electrode active material graphite
  • a negative electrode binder polyvinylidene fluoride
  • an organic solvent N-methyl-2-pyrrolidone
  • a positive electrode mixture slurry is applied to both sides of the negative electrode current collector 42A (a strip-shaped copper foil having a thickness of 15 ⁇ m) using a coating device, and then the negative electrode mixture slurry is dried to form a negative electrode active material.
  • a material layer 42B was formed.
  • the negative electrode outer active material layer 42B2 in the entire battery element 40 is The area density was 101.8%, and the area density of the negative electrode inner active material layer 42B1 in the entire battery element 40 was 98.2%.
  • the areal density of the negative electrode outer active material layer 42B2 and the areal density of the negative electrode inner active material layer 42B1 have no gradient in the longitudinal direction of the negative electrode 42, and are substantially constant.
  • the positive electrode 41 and the negative electrode 42 are laminated with each other via a separator 43 (a microporous polyethylene film having a thickness of 25 ⁇ m and a width of 4.0 mm), and then the positive electrode 41, the negative electrode 42, and the separator 43 are wound.
  • the wound body 40Z was stored inside the storage part 11.
  • the negative electrode lead 52 was welded to the housing portion 11 using a resistance welding method.
  • the electrolytic solution was injected into the inside of the storage part 11 through the opening 11K.
  • the wound body 40Z (the positive electrode 41, the negative electrode 42, and the separator 43) was impregnated with the electrolytic solution, so that the battery element 40 was manufactured.
  • the lid 12 was welded to the storage portion 11 using a laser welding method.
  • a folded part 513 is formed in a part of the positive electrode lead 51 so as to form a curved shape, and the folded part 513 is located in the peripheral part 12R.
  • the distance between the folded portion 513 and the inner surface of the side wall portion M3 was adjusted to be 0.5 mm.
  • constant current charging was performed with a current of 0.1C until the voltage reached 4.2V, and then constant voltage charging was performed with the voltage of 4.2V until the current reached 0.05C.
  • constant current discharge was performed at a current of 0.1C until the voltage reached 3.0V.
  • 0.1C is a current value that completely discharges the battery capacity (theoretical capacity) in 10 hours
  • 0.05C is a current value that completely discharges the battery capacity in 20 hours.
  • discharge test conditions (1) Implementation environment temperature: 23°C
  • Charging conditions Constant current and constant voltage (CC-CV) charging was performed. After charging to a voltage of 4.38V with a constant current of 0.5C, charging was performed with a constant voltage of 4.38V. The cutoff current was 0.025C.
  • Post-charge rest time 30 minutes
  • Discharge conditions Constant current (CC) discharge was performed at a constant current of 0.5C. The cutoff voltage was 3.0V.
  • the cycle capacity retention rate [%] was determined by conducting a charge/discharge cycle test under the following test conditions.
  • Minimum negative electrode potential (d ⁇ 4 mm) [mV] is the open circuit potential of the negative electrode 42 (based on lithium metal) measured in a region where the element diameter d is less than 4 mm in the battery element 40 of a fully charged secondary battery. It is.
  • the minimum negative electrode potential (d ⁇ 4mm) [mV] is the open circuit potential of the negative electrode 42 (lithium metal standard) measured in a region where the element diameter d is 4 mm or more among the battery elements 40 of a fully charged secondary battery. It is.
  • the discharge capacity was obtained by a discharge test based on the above-mentioned discharge test conditions, and on the assumption that the volume of the secondary battery was constant, the capacity increase rate was calculated based on the discharge capacity of Comparative Example 2 described later. It was determined as the energy density increase rate [%].
  • Example 2 A secondary battery of Example 2 was produced in the same manner as Example 1. However, the battery voltage during charging (charging voltage) in the charge/discharge cycle test was 4.45V. Except for this point, the secondary battery of Example 2 was evaluated in the same manner as the evaluation of the secondary battery of Example 1. The results are also shown in Table 1.
  • Example 3 The inner diameter of the winding center space 40K was 1.0 mm. Except for this point, the secondary battery of Example 3 was produced in the same manner as the secondary battery of Example 1, and the same evaluation as that of the secondary battery of Example 1 was performed. The results are also shown in Table 1.
  • Example 4 A secondary battery of Example 4 was produced in the same manner as Example 3. However, the battery voltage during charging (charging voltage) in the charge/discharge cycle test was 4.45V. Except for this point, the secondary battery of Example 4 was evaluated in the same manner as the evaluation of the secondary battery of Example 1. The results are also shown in Table 1.
  • Example 5 The inner diameter of the winding center space 40K was 1.0 mm. Further, as in the battery element 40B shown in FIG. 10, the thickness T1 of the negative electrode inner active material layer 42B1 gradually increases from the inner peripheral end 40E1 to the outer peripheral end 40E2, and the negative electrode outer active material layer The thickness T2 of the layer 42B2 was made to gradually become thinner. Furthermore, the battery voltage during charging (charging voltage) in the charge-discharge cycle test was set to 4.45V. Except for these points, the secondary battery of Example 5 was produced in the same manner as in Example 1, and the same evaluation as that of the secondary battery of Example 1 was performed. The results are also shown in Table 1.
  • the minimum value of the thickness T1 is 94% and the maximum value of the thickness T1 is 106%.
  • the minimum value of the thickness T2 is 94% and the maximum value of the thickness T2 is 106%.
  • Comparative example 2 A secondary battery of Comparative Example 2 was produced in the same manner as the secondary battery of Comparative Example 1 except that the inner diameter of the winding center space 40K was 4.0 mm. Furthermore, the battery voltage during charging (charging voltage) in the charge/discharge cycle test was 4.45V. Except for this point, the same evaluation as the secondary battery of Comparative Example 1 was performed. The results are also shown in Table 1.
  • Comparative example 3 A secondary battery of Comparative Example 3 was produced in the same manner as Comparative Example 1. However, the battery voltage during charging (charging voltage) in the charge/discharge cycle test was 4.45V. Except for this point, the secondary battery of Comparative Example 3 was evaluated in the same manner as the evaluation of the secondary battery of Comparative Example 1. The results are also shown in Table 1.
  • Example 1 and Example 3 where the charging voltage was 4.38V the cycle capacity retention rate is significantly improved compared to Comparative Example 1 where the charging voltage was also 4.38V.
  • the minimum negative electrode potential in the region where the element diameter d is less than 4 mm is significantly lower than the minimum negative electrode potential in the region where the element diameter d is 4 mm or more, whereas in Example 1 This is also because in Example 3, the minimum negative electrode potential did not decrease in the region where the element diameter d was less than 4 mm.
  • the capacity of the negative electrode outer active material layer 42B2 could be made larger than the capacity of the positive electrode inner active material layer 41B1 even in the region where the element diameter d of the battery element 40 was less than 4 mm. Conceivable.
  • the areal density of the negative electrode outer active material layer 42B2 from the inner peripheral side end 40E1 to the outer peripheral side end 40E2 is lower than the areal density of the negative electrode inner active material layer 42B1.
  • both the areal density of the negative electrode outer active material layer 42B2 and the areal density of the negative electrode inner active material layer 42B1 are made to gradually change from the inner peripheral end 40E1 to the outer peripheral end 40E2. It was confirmed that it is possible to further improve the cycle capacity retention rate.
  • the outer can is a welded can (crimpless can)
  • the structure of the outer can is not particularly limited, and may be a crimped crimp can.
  • a storage section and a lid section that are separated from each other are crimped together via a gasket.
  • the electrode reactant is not particularly limited.
  • the electrode reactants may be other alkali metals such as sodium and potassium, or alkaline earth metals such as beryllium, magnesium and calcium, as described above.
  • the electrode reactant may be other light metals such as aluminum.
  • the second electrode includes a second electrode current collector including a second electrode inner surface facing the winding axis side and a second electrode outer surface opposite to the second electrode inner surface; a second electrode inner active material layer provided on the surface, and a second electrode outer active material layer provided on the outer surface of the second electrode,
  • the areal density of the second electrode outer active material layer from the inner circumferential end of the battery element to the outer circumferential end of the battery element is such that the area density of the second electrode outer active material layer is equal to or smaller than the second electrode outer side with the second electrode current collector in between.
  • the area density of the second electrode inner active material layer facing the active material layer is greater than the area density of the secondary battery.
  • the areal density of the second electrode outer active material layer at the inner peripheral end of the battery element is higher than the areal density of the second electrode outer active material layer at the outer peripheral end of the battery element.
  • Secondary battery listed. ⁇ 3> The area density of the second electrode outer active material layer is highest at the inner end of the battery element, and decreases as it approaches the outer end of the battery element from the inner end of the battery element.
  • the thickness of the second electrode outer active material layer is the thickest at the inner end of the battery element, and becomes thinner as it approaches the outer end of the battery element from the inner end of the battery element.
  • the areal density of the second electrode inner active material layer at the inner peripheral end of the battery element is lower than the areal density of the second electrode inner active material layer at the outer peripheral end of the battery element.
  • ⁇ 6> The area density of the second electrode inner active material layer is lowest at the inner end of the battery element, and increases as it approaches the outer end of the battery element from the inner end of the battery element.
  • the thickness of the second electrode inner active material layer is the thinnest at the inner end of the battery element, and becomes thicker as it approaches the outer end of the battery element from the inner end of the battery element.
  • the second electrode includes a second electrode current collector including a second electrode inner surface facing the winding axis side and a second electrode outer surface opposite to the second electrode inner surface; a second electrode inner active material layer provided on the surface, and a second electrode outer active material layer provided on the outer surface of the second electrode,
  • the area density of the second electrode outer active material layer is highest at the inner end of the battery element, and decreases as it approaches from the inner end of the battery element to the outer end of the battery element,
  • the area density of the second electrode inner active material layer is lowest at the inner end of the battery element, and increases as it approaches the outer end of the battery element from the inner end of the battery element.
  • the thickness of the second electrode outer active material layer is the thickest at the inner end of the battery element, and becomes thinner as it approaches the outer end of the battery element from the inner end of the battery element.
  • the thickness of the second electrode inner active material layer is the thinnest at the inner end of the battery element, and becomes thicker as it approaches the outer end of the battery element from the inner end of the battery element. 8> or the secondary battery according to ⁇ 9>.
  • the outer diameter of the exterior member in a second direction perpendicular to the first direction is larger than the height of the exterior member in the first direction. battery.

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JP2007294111A (ja) * 2006-04-20 2007-11-08 Toshiba Battery Co Ltd 小型電池
JP2008262826A (ja) * 2007-04-12 2008-10-30 Hitachi Maxell Ltd コイン形非水電解液二次電池
JP2010027415A (ja) * 2008-07-22 2010-02-04 Sony Corp 二次電池
JP2011023131A (ja) * 2009-07-13 2011-02-03 Panasonic Corp 非水系二次電池用負極板およびこれを用いた非水系二次電池
JP2012128956A (ja) * 2010-12-13 2012-07-05 Sony Corp 二次電池、電池パック、電子機器、電動工具、電動車両および電力貯蔵システム
JP2013051125A (ja) * 2011-08-31 2013-03-14 Panasonic Corp 円筒形リチウムイオン二次電池
JP2015138729A (ja) * 2014-01-24 2015-07-30 トヨタ自動車株式会社 リチウムイオン二次電池
JP2017130317A (ja) * 2016-01-19 2017-07-27 トヨタ自動車株式会社 捲回電極体を有する非水電解液二次電池

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007294111A (ja) * 2006-04-20 2007-11-08 Toshiba Battery Co Ltd 小型電池
JP2008262826A (ja) * 2007-04-12 2008-10-30 Hitachi Maxell Ltd コイン形非水電解液二次電池
JP2010027415A (ja) * 2008-07-22 2010-02-04 Sony Corp 二次電池
JP2011023131A (ja) * 2009-07-13 2011-02-03 Panasonic Corp 非水系二次電池用負極板およびこれを用いた非水系二次電池
JP2012128956A (ja) * 2010-12-13 2012-07-05 Sony Corp 二次電池、電池パック、電子機器、電動工具、電動車両および電力貯蔵システム
JP2013051125A (ja) * 2011-08-31 2013-03-14 Panasonic Corp 円筒形リチウムイオン二次電池
JP2015138729A (ja) * 2014-01-24 2015-07-30 トヨタ自動車株式会社 リチウムイオン二次電池
JP2017130317A (ja) * 2016-01-19 2017-07-27 トヨタ自動車株式会社 捲回電極体を有する非水電解液二次電池

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