WO2016174992A1 - Secondary battery - Google Patents

Secondary battery Download PDF

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Publication number
WO2016174992A1
WO2016174992A1 PCT/JP2016/060876 JP2016060876W WO2016174992A1 WO 2016174992 A1 WO2016174992 A1 WO 2016174992A1 JP 2016060876 W JP2016060876 W JP 2016060876W WO 2016174992 A1 WO2016174992 A1 WO 2016174992A1
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WO
WIPO (PCT)
Prior art keywords
secondary battery
elastic
separator
wound
negative electrode
Prior art date
Application number
PCT/JP2016/060876
Other languages
French (fr)
Japanese (ja)
Inventor
八木　陽心
直子 月森
拓是 森川
Original Assignee
日立オートモティブシステムズ株式会社
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Application filed by 日立オートモティブシステムズ株式会社 filed Critical 日立オートモティブシステムズ株式会社
Priority to JP2017515451A priority Critical patent/JPWO2016174992A1/en
Publication of WO2016174992A1 publication Critical patent/WO2016174992A1/en

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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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to a secondary battery.
  • the electrode material accommodated in the battery can expands and contracts with charge / discharge.
  • the electrode material expands, the gap in the electrode and the gap in the separator are crushed, and the electrolyte filled in that portion is pushed out of the electrode.
  • the extruded electrolyte cannot completely return to its original position when the electrode material contracts. For this reason, when charging and discharging are repeated, the electrolytic solution is gradually depleted. As a result, the movement of lithium ions in the electrolytic solution decreases or the ability to exchange with the active material decreases, so that the performance such as capacity and output decreases.
  • Patent Document 1 suppression of electrolyte depletion in the wound electrode group due to charge / discharge is insufficient, and there is room for improvement.
  • the secondary battery according to the present invention is a secondary battery having a wound electrode group in which an electrode and a separator are wound on an axial core, wherein the axial core is more rigid than a rigid body portion made of resin and the rigid body portion. And an elastic portion made of resin having a low rate, and the elastic portion is disposed between the innermost separator and the rigid body portion.
  • the cross-sectional schematic diagram which shows the structure of the secondary battery which concerns on 1st Embodiment.
  • the figure which shows an axial center.
  • (A) is a schematic enlarged cross-sectional view of a main part at the time of charging and discharging the wound electrode group according to the comparative example
  • (b) is a point at the time of charging and discharging of the wound electrode group according to the first embodiment.
  • FIG. The cross-sectional schematic diagram which shows the electrolyte solution in the secondary battery which concerns on a comparative example.
  • (A) is a perspective view which shows the axial center which concerns on 4th Embodiment.
  • the disassembled perspective view which shows the structure of the secondary battery which concerns on 5th Embodiment.
  • the cross-sectional schematic diagram which shows the internal structure of the secondary battery which concerns on 5th Embodiment.
  • FIG. 1 is a schematic cross-sectional view showing the configuration of the secondary battery 100 according to the first embodiment.
  • the secondary battery 100 includes a battery container, a wound electrode group 104 accommodated in the battery container, and an electrolytic solution.
  • the battery container is made of stainless steel, and has a bottomed cylindrical battery can 101 having one end opened, and a battery lid unit 120 that seals the opening.
  • the battery lid unit 120 side is described as the upper side of the secondary battery 100
  • the bottom surface side of the battery can 101 is described as the lower side of the secondary battery 100.
  • the wound electrode group 104 which is a charge / discharge element, has a positive electrode 141 and a negative electrode 142 with respect to the shaft core 109 via the first separator 143a and the second separator 143b. It is formed by winding around the rotation axis X.
  • the wound electrode group 104 according to the present embodiment is wound in a spiral shape to have a cylindrical shape. That is, the wound electrode group 104 is configured as a curved portion whose outer peripheral surface is curved over a 360-degree range around the winding axis X, that is, the entire circumference.
  • FIG. 2 is a view showing the shaft core 109.
  • FIG. 2A is a perspective view of the shaft core 109, and the elastic portion 108 is hatched for easy understanding.
  • FIG. 2B is a schematic cross-sectional view taken along a plane orthogonal to the central axis (winding axis X) of the shaft core 109.
  • FIG. 2C is a schematic cross-sectional view taken along a plane parallel to the central axis (winding axis X) of the shaft core 109 and including the central axis (winding axis X).
  • the shaft core 109 is formed in an elongated cylindrical shape (hollow columnar shape) having a hollow portion along the winding axis X direction.
  • the shaft core 109 has a cylindrical rigid body portion 107 and an elastic portion 108 provided so as to cover the outer peripheral surface of the rigid body portion 107.
  • the rigid portion 107 is made of a resin material such as polypropylene.
  • the elastic portion 108 has a cylindrical shape whose outer peripheral surface is a curved surface along the winding direction, and is made of a resin material as described below.
  • the resin material of the elastic portion 108 can be selected from open-cell polyethylene foam, polyethylene, fluororesin, and the like.
  • resin material of the elastic portion 108 urethane foam, butyl rubber, ethylene propylene rubber, or the like having organic electrolyte resistance can be selected.
  • a porous material as the material of the elastic portion 108, the elastic modulus of the elastic portion 108 can be further reduced, or the elastic portion 108 can be provided with liquid retention.
  • non-woven fabrics such as polyolefin fibers having resistance to organic solvents can be used as the material of the elastic portion 108.
  • the thickness of the elastic portion 108 is suitably about 0.05 mm to 2.0 mm in consideration of the amount of electrode expansion described later and the amount of contraction of the elastic portion 108.
  • a resin material having a compressive elastic modulus (Young's modulus) of about 1 to 40 MPa is used as the material of the elastic portion 108. Since the compression elastic modulus (Young's modulus) of the rigid body portion 107 is about 5000 MPa, the elastic modulus of the elastic portion 108 is sufficiently lower than the elastic modulus of the rigid body portion 107.
  • Both ends of the axis 109 in the winding axis X direction are not covered with the elastic portion 108 and are exposed portions where the rigid portion 107 is exposed.
  • FIG. 3 is a perspective view of a state in which a part of the wound electrode group 104 is cut
  • FIG. 4 is a plan view of a state in which the terminal side of the wound electrode group 104 is developed.
  • the positive electrode 141 is composed of, for example, a layer of a positive electrode active material mixture (hereinafter referred to as a positive electrode mixture) (Referred to as an agent layer 147).
  • the positive electrode mixture layer 147 is formed on the positive electrode foil 145 so that a positive electrode mixture untreated portion where the positive electrode foil 145 is exposed (hereinafter referred to as a positive electrode uncoated portion) is formed on one side edge of the positive electrode foil 145.
  • a positive electrode active material mixture is applied.
  • the positive electrode mixture layer 147 is kneaded by adding a conductive agent and a binder (binder) to the positive electrode active material, adding an organic dispersion solvent thereto, and applying the kneaded slurry to both the front and back surfaces of the positive electrode foil 145 with a predetermined width. It is formed through drying and pressing.
  • the positive electrode active material is a lithium-containing transition metal double oxide such as lithium manganate. A portion of the positive electrode uncoated portion is notched, and a plurality of positive electrode lead pieces (hereinafter referred to as positive electrode tabs 145t) are formed as shown in the figure.
  • a negative electrode active material mixture layer (hereinafter referred to as a negative electrode mixture layer 148) is formed on both front and back surfaces of a negative electrode foil 146 made of a rolled copper foil, a rolled copper alloy foil or the like having a thickness of about 10 ⁇ m. It has been done.
  • the negative electrode mixture layer 148 is formed on the negative electrode foil 146 so that a negative electrode mixture untreated portion where the negative electrode foil 146 is exposed (hereinafter referred to as a negative electrode uncoated portion) is formed on one side edge of the negative electrode foil 146. A negative electrode mixture is applied.
  • the negative electrode mixture layer 148 is prepared by adding a binder (binder) to the negative electrode active material and kneading, adding an organic dispersion solvent thereto, applying the kneaded slurry to both the front and back surfaces of the negative electrode foil 146 in a predetermined width, drying, Formed through press working.
  • the negative electrode active material is a carbon material such as natural graphite capable of reversibly occluding and releasing lithium ions, and various artificial graphite materials. A portion of the negative electrode uncoated portion is cut away, and a plurality of negative electrode lead pieces (hereinafter referred to as negative electrode tabs 146t) are formed as shown in the figure.
  • binder for example, polyvinylidene difluoride (PVDF) can be employed.
  • PVDF polyvinylidene difluoride
  • dispersion solvent any of a non-aqueous solvent and an aqueous solvent can be used.
  • the winding start side end portion of the negative electrode 142 is connected to the positive electrode 141 between the first separator 143a and the second separator 143b whose tip portions are welded to the shaft core 109, respectively. It is arranged and wound so as to be located inside the winding start side end.
  • the positive electrode uncoated portion and the negative electrode uncoated portion are disposed so as to be positioned on the side edges opposite to the width direction (direction orthogonal to the winding direction).
  • the width of the negative electrode mixture layer 148 is formed wider than the width of the positive electrode mixture layer 147.
  • the separator 143 has an insulating property and is made of a polyethylene microporous material through which lithium ions can pass, and has a thickness of about 25 ⁇ m.
  • the separator 143 has a compression elastic modulus (Young's modulus) of, for example, about 200 MPa, which is lower than the elastic modulus of the rigid body portion 107 of the shaft core 109 and higher than that of the elastic portion 108.
  • the elastic part 108 of the shaft core 109 described above is provided at a position facing the region in the winding axis X direction in the positive electrode mixture layer 147.
  • the length WE in the winding axis X direction of the elastic portion 108 is longer than the length WP in the winding axis X direction of the positive electrode mixture layer 147, and the upper end of the elastic portion 108 is at the positive electrode mixture.
  • the upper portion of the layer 147 is located above the upper end, and the lower end of the elastic portion 108 is located below the lower end of the positive electrode mixture layer 147. Therefore, when the direction (radial direction) orthogonal to the winding axis X is viewed from the winding axis X, the projection surface of the elastic portion 108 covers the entire projection surface of the positive electrode mixture layer 147.
  • the wound electrode group 104 is accommodated in the battery container so that the positive electrode tab 145t is disposed on the upper side and the negative electrode tab 146t is disposed on the lower side.
  • a groove 109a having a diameter larger than that of the hollow portion is formed on the inner periphery of the upper end portion of the shaft core 109, and a lower cylindrical portion 152 provided in a positive electrode current collecting ring 105 described later is press-fitted into the groove 109a.
  • a step portion 109b having a small outer diameter is formed on the outer periphery of the lower end portion of the shaft core 109, and this step portion 109b is formed in an opening of an inner peripheral cylindrical portion 162 provided in the negative electrode current collecting ring 106 described later. It is press-fitted.
  • the positive electrode current collecting ring 105 includes a disc-shaped base, a lower cylindrical portion 152 that protrudes from the center of the base toward the axis 109, and an upper cylindrical portion 151 that protrudes from the outer periphery of the base toward the battery lid 102. And have.
  • the plurality of positive electrode tabs 145t provided on the positive electrode 141 are deformed, overlapped, and connected to the outer peripheral surface of the upper cylindrical portion 151 of the positive electrode current collecting ring 105 by ultrasonic welding.
  • a positive electrode lead plate 159 (a part of the positive electrode current collecting member) is disposed between the positive electrode current collecting ring 105 and a battery lid unit 120 described later. One end of the positive electrode lead plate 159 is welded to the positive electrode current collecting ring 105, and the other end is welded to the case 122 constituting the lower surface of the battery lid unit 120.
  • the positive electrode lead plate 159 is a flexible conductive member configured by overlapping a plurality of aluminum ribbons (metal foils).
  • the negative electrode current collector ring 106 includes a disc-shaped base, an inner peripheral cylindrical portion 162 that protrudes from the center of the base toward the bottom of the battery can 101, and a bottom of the battery can 101 that protrudes from the outer periphery of the base. And an outer peripheral cylindrical portion 161.
  • the plurality of negative electrode tabs 146t provided on the negative electrode 142 are deformed, overlapped, and connected to the outer peripheral surface of the outer peripheral cylindrical portion 161 of the negative electrode current collecting ring 106 by ultrasonic welding.
  • a negative electrode lead plate 169 is disposed between the negative electrode current collecting ring 106 and the bottom of the battery can 101.
  • the negative electrode lead plate 169 has an inverted hat shape in cross section, a circular recess 169a that contacts the bottom of the battery can 101 below the shaft core 109, and an annular flange 169b that extends outward from the opening periphery of the circular recess 169a. It has.
  • the flange 169 b is welded to the negative electrode current collector ring 106, and the bottom of the circular recess 169 a is welded to the bottom of the battery can 101.
  • the battery lid unit 120 is fixed to the battery can 101 via an insulating gasket 129.
  • the battery lid unit 120 is fixed to the battery can 101 by caulking the upper end of the battery can 101 so as to sandwich the outer periphery of the battery lid unit 120.
  • the battery lid unit 120 includes a battery lid 102, a safety valve (gas discharge valve) 123, a valve pressing member 124, and a case 122.
  • the case 122 is made of an aluminum alloy and is disposed to face the positive electrode current collecting ring 105.
  • the case 122 is caulked so that the peripheral portion sandwiches the safety valve 123 and the battery lid 102, and holds the battery lid 102 and the safety valve 123.
  • the case 122 has a concave portion that is recessed toward the wound electrode group 104 at the center, and a valve pressing member 124 is disposed in the concave portion.
  • the valve pressing member 124 is disposed between the bottom plate of the concave portion of the case 122 and the safety valve 123, and supports the safety valve 123 from below.
  • Safety valve 123 is provided with a fragile part such as engraving. When the pressure in the battery container rises and reaches a predetermined pressure, the safety valve 123 reduces the pressure in the battery container by cleaving the fragile portion and releasing the gas generated inside the battery to the outside. . In order to discharge the gas generated inside the battery to the outside, one or more openings are formed in the bottom plate of the recess of the case 122, the positive electrode current collecting ring 105, and the battery cover 102, respectively.
  • the positive electrode 141 is electrically connected to the battery lid 102 via the positive electrode current collecting ring 105, the positive electrode lead plate 159, and the case 122. For this reason, the battery cover 102 functions as a positive electrode external output terminal.
  • the negative electrode 142 is electrically connected to the bottom of the battery can 101 via the negative electrode current collecting ring 106 and the negative electrode lead plate 169. For this reason, the bottom part of the battery can 101 functions as a negative electrode external output terminal.
  • a nonaqueous electrolyte solution (not shown) is injected into the secondary battery 100, and the wound electrode group 104 is infiltrated with the nonaqueous electrolyte solution.
  • the non-aqueous electrolyte for example, a solution obtained by dissolving lithium hexafluorophosphate (LiPF 6 ) at a rate of 1 mol / liter in a mixed organic solvent of ethylene carbonate (EC) and dimethyl carbonate (DEC) is used. be able to.
  • the assembly procedure of the secondary battery 100 according to this embodiment will be described.
  • a first separator 143a and a second separator 143b are prepared.
  • the innermost side edge portions of the first separator 143 a and the second separator 143 b are bonded to the shaft core 109.
  • the first separator 143a and the second separator 143b are wound around the shaft core one to several turns, the negative electrode 142 is sandwiched between the second separator 143b and the first separator 143a, and the shaft core 109 is wound at a predetermined angle. . Thereafter, the positive electrode 141 is sandwiched between the first separator 143a and the second separator 143b. In this state, the spiral wound electrode group 104 is manufactured by winding a predetermined number of turns.
  • the first separator 143a and the second separator 143b are wound on the innermost peripheral side, and the negative electrode 142, the first separator 143a, the positive electrode 141, and the second separator 143b are sequentially stacked on the outer side. Is done.
  • the first separator 143 a is in contact with the curved surface (outer peripheral surface) of the elastic portion 108 of the shaft core 109.
  • the second separator 143b is in contact with the outer peripheral surface of the first innermost separator 143a.
  • the negative electrode 142 is located outside the second separator 143b, and the first separator 143a is located outside the second separator 143b.
  • the positive electrode 141 is located outside the first separator 143a, and the second separator 143b is located outside the positive electrode 141.
  • the first separator 143a is wound so as to cover the negative electrode 142.
  • the outermost first separator 143a is stopped with a winding tape (not shown) so that the wound electrode group 104 is not unwound.
  • the separator 143 is interposed between the positive electrode 141 and the negative electrode 142, the positive electrode 141 and the negative electrode 142 are not in direct contact with each other.
  • the positive electrode tab 145t and the negative electrode tab 146t are arranged at both ends of the wound electrode group 104 opposite to each other.
  • the positive current collecting ring 105 and the negative current collecting ring 106 are fixed to both ends of the shaft core 109, respectively.
  • the positive electrode tab 145t is brought into close contact with the upper cylindrical portion 151 of the positive electrode current collecting ring 105, and ultrasonic welding is performed.
  • the negative electrode tab 146t is brought into close contact with the outer peripheral cylindrical portion 161 of the negative electrode current collecting ring 106 and ultrasonic welding is performed.
  • the negative electrode lead plate 169 is welded to the negative electrode current collecting ring 106 in advance.
  • the insulating sheet for example, a base material made of polyimide and a pressure-sensitive adhesive made of hexamethacrylate applied on one side thereof can be adopted.
  • the electrode group unit is made up of the battery can 101 so that the negative electrode current collection ring 106 side is arranged on the bottom side of the battery can 101 with the electrode group unit in which the positive and negative current collecting rings are fixed to the shaft core 109 of the wound electrode group 104. Insert into. At this time, an annular spacer 168 is disposed between the negative electrode current collector ring 106 and the bottom of the battery can 101.
  • the negative electrode lead plate 169 is welded to the battery container, and a predetermined amount of non-aqueous electrolyte is injected into the battery can 101 from the upper opening of the battery can 101.
  • a predetermined amount of electrolyte is injected into the battery can 101 from the upper opening of the battery can 101.
  • the inside of the battery container is decompressed and a predetermined amount of electrolyte is injected.
  • the electrolyte solution is impregnated throughout the wound electrode group 104.
  • the battery lid unit 120 and the upper end of the battery can 101 are caulked and fixed via the gasket 129.
  • the cylindrical secondary battery 100 is assembled.
  • the secondary battery 100 is completed by performing initial charge on the assembled secondary battery 100 to give a function as a battery.
  • the volume of the electrode material (for example, the negative electrode active material, the positive electrode active material, etc.) of the wound electrode group 104 expands and contracts with charge / discharge.
  • the electrode material expands, the gap in the electrode and the gap in the separator are crushed, and the electrolyte filled in that portion is pushed out of the electrode.
  • the extruded electrolyte cannot completely return to its original position when the electrode material contracts. For this reason, when charging and discharging are repeated, the electrolytic solution is gradually depleted. As a result, the movement of lithium ions in the electrolytic solution decreases or the ability to exchange with the active material decreases, so that the performance such as capacity and output decreases.
  • FIG. 5A is an enlarged schematic cross-sectional view of a main part when the wound electrode group 904 according to the comparative example is charged (right side in the figure) and discharged (left side in the figure).
  • the axial center 909 is configured by only the rigid body portion 107 and does not include the elastic portion 108.
  • the negative electrode active material greatly expands during charging.
  • the shaft core 909 is configured only by the rigid portion 107
  • the negative electrode mixture layer 148 expands radially inward of the wound electrode group 104. It is suppressed.
  • the compression elastic modulus (Young's modulus) of the positive electrode foil 145 is, for example, about 70 GPa
  • the compression elastic modulus (Young's modulus) of the negative electrode foil 146 is, for example, about 130 GPa
  • the compression modulus (Young's modulus) of the positive electrode mixture layer 147 is, for example, about 1 to 2 GPa
  • the compression modulus (Young's modulus) of the negative electrode mixture layer 148 is, for example, about 0.5 to 1 GPa. It is.
  • the positive electrode foil 145 and the negative electrode foil 146 have higher elastic modulus than the resin material, the positive electrode mixture layer 147, and the negative electrode mixture layer 148. That is, the positive electrode foil 145 and the negative electrode foil 146 have a property that it is difficult to stretch when the negative electrode mixture layer 148 expands. In this way, the positive electrode foil 145 and the negative electrode foil 146 which are not easily stretched are spirally wound around the shaft core 909 in a state where tension is applied during the winding operation, so that the negative electrode mixture layer 148 is wound on the wound electrode group 104. Expansion to the outside in the radial direction is also suppressed.
  • the negative electrode mixture layer 148 is suppressed from expanding radially inward and outward by the rigid portion 107, the positive foil 145, and the negative foil 146. For this reason, the negative electrode mixture layer 148 expands so as to crush the voids of the negative electrode mixture layer 148.
  • the separator 143 is interposed between the negative electrode mixture layer 148 and the rigid portion 107 or between the negative electrode mixture layer 148 and the positive electrode mixture layer 147, the negative electrode mixture layer 148 has a slight diameter. Expansion inward and outward is allowed. For this reason, when the negative mix layer 148 expand
  • the wound electrode group 104 is curved over the entire circumference, and a tensile force in the circumferential direction acts on the positive foil 145 and the negative foil 146.
  • a force pressed inward (winding axis X side) by the positive foil 145 and the negative foil 146 acts on the positive electrode mixture layer 147 and the negative electrode mixture layer 148.
  • This pressing force is more concentrated in a narrower range as the inner side of the wound electrode group 104 (winding axis X side) becomes larger.
  • the pressure acting on the positive electrode mixture layer 147 and the negative electrode mixture layer 148 increases as the winding center of the wound electrode group 104 is approached.
  • FIG. 6 is a schematic cross-sectional view showing an electrolytic solution in the secondary battery 900 according to the comparative example.
  • FIG. 6A shows a case where the secondary battery 900 is placed vertically, that is, the case where the secondary battery 900 is arranged so that the winding axis X is parallel to the vertical direction.
  • the liquid level WL of the electrolytic solution may be located below the positive and negative electrode layers of the wound electrode group 104 and the lower end surface of the separator.
  • the electrolytic solution pushed out from the wound electrode group 104 at the time of charging cannot return to the wound electrode group 104 at the time of discharging, and is gradually charged and discharged, thereby gradually winding the wound electrode group 104.
  • the electrolyte inside is depleted.
  • FIG. 6B shows the case where the secondary battery 900 is placed horizontally, that is, the case where the secondary battery 900 is arranged so that the winding axis X is parallel to the horizontal direction.
  • the liquid level WL of the electrolytic solution is located below the winding axis X as illustrated. For this reason, the extruded electrolyte cannot return into the wound electrode group 104 above the liquid level WL, and the electrolyte in the wound electrode group 104 is gradually gradually charged and discharged. Depleted.
  • the electrolytic solution is sucked into the wound electrode group 104 when the wound electrode group 104 contracts during discharge.
  • the electrolyte is completely removed at the lower part of the wound electrode group 104. You cannot return to position.
  • the electrolytic solution is gradually depleted, and the movement of lithium ions in the solution is reduced, and lithium ions are exchanged with the active material. Performance such as capacity and output is reduced because it becomes difficult.
  • FIG. 5 (b) is an enlarged schematic cross-sectional view of the main part of the wound electrode group 104 according to the first embodiment during charging (right side in the figure) and discharging (left side in the figure).
  • the elastic portion 108 having a lower elastic modulus than the negative electrode mixture layer 148 is compressed in the radial direction when the volume of the negative electrode active material during expansion is expanded. Therefore, the radial dimension of the negative electrode mixture layer 148 is enlarged as compared with the comparative example.
  • the force generated when the negative electrode mixture layer 148 expands can be absorbed. Therefore, in the present embodiment, the force acting to crush the voids in the negative electrode mixture layer 148 and the voids of the separator 143 is greater than that in the case where the shaft core 909 including only the rigid body portion 107 is used (comparative example). Can be reduced. For this reason, it becomes difficult to extrude the electrolyte solution filled in the voids, and the depletion of the electrolyte solution can be suppressed.
  • the shaft core 109 has a rigid portion 107 made of resin, and an elastic portion 108 made of resin having a lower elastic modulus than the rigid portion 107.
  • the elastic part 108 is disposed between the innermost separator 143 and the rigid part 107.
  • the expansion of the volume of the active material occurs when lithium ions are inserted into or desorbed from the active material where the positive electrode mixture layer 147 and the negative electrode mixture layer 148 are opposed to each other.
  • the negative electrode mixture layer 148 is made wider than the positive electrode mixture layer 147 so as to face the positive electrode mixture layer 147 in order to suppress lithium dendrid during charging.
  • a mixture layer 148 is disposed. That is, when the direction (radial direction) orthogonal to the winding axis X is viewed from the winding axis X, the projection surface of the negative electrode mixture layer 148 covers the entire projection surface of the positive electrode mixture layer 147.
  • the elastic portion 108 is provided at a position facing at least the region in the winding axis X direction of the wound electrode group 104 in the positive electrode mixture layer 147 of the positive electrode 141, the elastic portion 108 is provided. It is possible to effectively absorb the expansion of the electrode material and suppress the depletion of the electrolytic solution.
  • the elastic portion 108 has a curved surface along the winding direction of the wound electrode group 104, and the curved surface is in contact with the innermost separator 143. For this reason, it is possible to reduce the force acting so as to crush the gaps in the negative electrode mixture layer 148 and the gaps of the separator 143 uniformly along the winding direction, and the electrolyte depletion can be suppressed uniformly.
  • the elastic modulus of the elastic portion 108 is lower than any of the elastic modulus of the separator 143, the elastic modulus of the positive electrode mixture layer 147, and the elastic modulus of the negative electrode mixture layer 148. For this reason, it can suppress that each space
  • FIG. 7A is a view similar to FIG. 2A and is a perspective view showing an axis 209 according to the second embodiment.
  • FIG. 7B is a diagram similar to FIG. 1 and is a schematic cross-sectional view showing the configuration of the secondary battery 200 according to the second embodiment.
  • the projection surface of the elastic portion 108 covers the entire projection surface of the positive electrode mixture layer 147.
  • the elastic portion 108 is provided over the entire outer peripheral surface except for both axial ends of the rigid portion 107 (see FIGS. 1 to 4).
  • the shaft core 209 according to the second embodiment is provided with an elastic portion 208 at the center of the rigid body portion 207 in the winding axis X direction.
  • the elastic portion 208 is provided particularly in a portion where the electrolytic solution is easily depleted.
  • FIG. 8 is an enlarged schematic cross-sectional view showing the elastic part 208 fixed to the rigid body part 207.
  • 8A shows a state after the separator 143 and the electrode are wound around the shaft core 209
  • FIG. 8B shows the state before the separator 143 and the electrode are wound around the shaft core 209. Indicates the state.
  • a concave portion 207a is provided along the outer peripheral surface with a predetermined length in the winding axis X direction.
  • the rigid body portion 207 has a large-diameter portion 207l having an outer diameter (diameter) DL and a small-diameter portion 207s having an outer diameter (diameter) DS, and the outer peripheral surface of the small-diameter portion 207s covers the bottom surface of the recess 207a. It is composed.
  • the outer peripheral surface of the cylindrical elastic portion 208 is more radial than the large-diameter portion 207l of the rigid portion 207. Projects outward. That is, the outer diameter (diameter) DE of the elastic portion 208 is larger than the outer diameter (diameter) DL of the large-diameter portion 207l.
  • the elastic portion 208 is compressed radially inward, and the outer diameter (diameter) of the elastic portion 208 is compressed.
  • DE is substantially the same as the outer diameter (diameter) DL of the large diameter portion 207l.
  • the innermost separator 143 comes into direct contact with the outer peripheral surface of the large-diameter portion 207l of the rigid portion 207.
  • the elastic portion 208 is provided in the central portion where the electrolyte solution is easily depleted as compared with both ends of the rigid portion 207 in the winding axis X direction. Thereby, compared with 1st Embodiment, the material cost of the elastic part 208 can be reduced.
  • the rigid portion 207 is in direct contact with the innermost separator 143 at both ends in the winding axis X direction.
  • the elastic portion 208 is provided so as to protrude from the concave portion 207a of the rigid body portion 207 before the separator 143 and the electrode are wound around the shaft core 209. Thereby, in the recessed part 207a of the axial center 209, the elastic part 208 and the innermost periphery separator 143 can be made to contact in the case of charging / discharging.
  • the elastic portion 208 allows deformation of the wound electrode group 104 toward the inner peripheral side during charging and prevents the electrolyte from being pushed out of the wound electrode group 104.
  • the elastic part 208 spreads the innermost separator 143 outward in the radial direction by the elastic force of the elastic part 208 during discharge, thereby preventing the state where the separator 143 bites into the recess 207a.
  • FIG. 8C shows a comparative example.
  • the elastic portion 908 does not protrude outward from the opening surface of the recess 207a before the separator 143 and the electrode are wound around the shaft core 209. For this reason, as shown in FIG. 8C, the elastic portion 908 cannot give sufficient elastic force to the separator 143 at the time of discharge, and the separator 143 bites into the recess 207a. There is a risk of being maintained.
  • the elastic portion 208 exerts a larger elastic force than the comparative example toward the radially outer side with respect to the separator 143 during discharge. Can be granted. For this reason, according to this Embodiment, compared with a comparative example, shape retainability can be improved.
  • FIG. 9A is a view similar to FIG. 7A and is a perspective view showing an axis 309 according to the third embodiment.
  • an elastic portion 208 is provided at the central portion of the rigid body portion 207 in the winding axis X direction, and the outer peripheral surfaces of both ends of the rigid body portion 207 in the winding axis X direction are in direct contact with the separator 143. (See FIG. 7).
  • the shaft core 309 includes an exposed portion of the rigid portion 307 and a covering portion in which the rigid portion 307 is covered by the elastic portion 308.
  • the elastic portion 308 are alternately provided in the winding axis X direction. That is, a plurality of portions where the rigid portion 307 and the innermost separator 143 are in direct contact with each other are provided apart from each other in the winding axis X direction.
  • Each of the plurality of elastic portions 308 is provided in a belt shape over the entire circumference so as to be orthogonal to the winding axis X direction, and has a cylindrical shape.
  • FIG. 9B is a diagram showing a modification of the third embodiment, and is a schematic side view of the shaft core 309.
  • a plurality of belt-like elastic portions 308 may be provided apart from each other along the winding axis X direction so as to intersect the winding axis X direction at 45 degrees.
  • One band-like elastic portion 308 may be spirally wound around the rigid body portion 307.
  • FIG. 10A is a view similar to FIG. 9A, and is a perspective view showing an axis 409 according to the fourth embodiment.
  • FIG. 10B is a schematic cross-sectional view taken along a plane orthogonal to the central axis (winding axis X) of the shaft core 409.
  • a plurality of portions where the innermost separator 143 and the rigid body portion 307 are in direct contact with each other are formed apart from each other in the winding axis X direction (see FIG. 9A).
  • the portion where the innermost separator 143 (not shown in FIG. 10) and the rigid portion 407 are in direct contact is a cylindrical rigid portion 407.
  • a plurality are formed apart from each other. That is, in the shaft core 409 according to the fourth embodiment, the exposed portion of the rigid portion 407 and the covering portion formed by covering the rigid portion 407 with the elastic portion 408 are alternately provided in the circumferential direction of the rigid portion 407. ing.
  • FIG. 11 is an external perspective view of a secondary battery 500 according to the fifth embodiment
  • FIG. 12 is an exploded perspective view showing the configuration of the secondary battery 500 according to the fifth embodiment.
  • the secondary battery 500 has a flat rectangular parallelepiped shape, and includes a battery container including a battery can 501 and a battery lid 502.
  • the material of the battery can 501 and the battery lid 502 is aluminum or an aluminum alloy.
  • the battery can 501 accommodates a wound electrode group 504 held by the battery lid assembly 520.
  • the battery cover assembly 520 is formed by attaching the positive electrode external terminal 550 and the negative electrode external terminal 560, and the positive electrode current collector 505 and the negative electrode current collector 506 to the battery cover 502.
  • the battery can 501 is formed in a rectangular box shape with one end opened.
  • the wound electrode group 504 is accommodated in the battery can 501 while being covered with an insulating sheet (not shown).
  • the material of the insulating sheet (not shown) is an insulating resin such as polypropylene or polyethylene terephthalate. Thereby, the bottom and side surfaces of the battery can 501 and the wound electrode group 504 are electrically insulated.
  • the battery lid 502 has a rectangular flat plate shape and is laser-welded so as to close the opening of the battery can 501. That is, the battery lid 502 seals the battery can 501.
  • the battery lid 502 is provided with a liquid injection part 511.
  • the liquid injection part 511 has a liquid injection hole for injecting an electrolytic solution into the battery container. The liquid injection hole is sealed with a liquid injection plug after the electrolyte is injected.
  • a safety valve (gas discharge valve) 523 is recessed on the surface of the battery lid 502.
  • the safety valve 523 is formed by partially thinning the battery lid 502 by press work so that the degree of stress concentration during internal pressure action is relatively high.
  • the safety valve 523 is provided with a weak portion such as an engraving.
  • the battery lid 502 is provided with a positive external terminal 550 and a negative external terminal 560 that are electrically connected to the positive electrode 541 and the negative electrode 542 of the wound electrode group 504, respectively. .
  • the positive external terminal 550 and the negative external terminal 560 are connected to the positive current collector 505 and the negative current collector 506 disposed in the battery can 501 by caulking, respectively.
  • the positive electrode external terminal 550, the positive electrode current collector 505, the negative electrode external terminal 560, and the negative electrode current collector 506 are electrically insulated from the battery lid 502 by an insulating member.
  • the positive electrode external terminal 550 is electrically connected to the positive electrode 541 of the wound electrode group 504 via the positive electrode current collector 505, and the negative electrode external terminal 560 is connected to the negative electrode of the wound electrode group 504 via the negative electrode current collector 506. 542 is electrically connected. For this reason, electric power is supplied to the external load via the positive external terminal 550 and the negative external terminal 560. Alternatively, external generated power is supplied to the wound electrode group 504 through the positive external terminal 550 and the negative external terminal 560 and charged.
  • FIG. 13 is a perspective view and a schematic side view showing a wound electrode group 504 according to the fifth embodiment.
  • the vertical direction is defined based on the orientation of the secondary battery 500 in a vertically placed state, and the wound electrode group 504 will be described below.
  • the rigid portion 507 of the shaft core 509 is hatched for easy understanding.
  • the wound electrode group 504 is formed by winding a long positive electrode 541 and a negative electrode 542 in a flat shape around an axis 509 with a separator 143 interposed therebetween. It is a laminated structure.
  • the electrode and separator 143 is wound around the shaft core 509 by rotating the shaft core 509 about the winding axis X in a state where tension is applied to the electrode and separator 143.
  • Both end portions of the wound electrode group 504 in the width direction are respectively unmixed portions.
  • One end portion in the width direction of the wound electrode group 504 is a portion where an uncoated portion (exposed portion of the positive foil 145) where the positive electrode mixture layer 147 is not formed is laminated.
  • the other end portion in the width direction of the wound electrode group 504 is a portion where an uncoated portion (exposed portion of the negative electrode foil 146) where the negative electrode mixture layer 148 is not formed is laminated.
  • the laminate of the positive electrode uncoated portion and the laminate of the negative electrode uncoated portion are crushed in advance, respectively, and the positive electrode current collector 505 and the negative electrode current collector 506 of the battery lid assembly 520, respectively. And ultrasonically welded.
  • the outer shape of the wound electrode group 504 has a semicircular upper curved portion 514U provided in the upper end portion and a semicircular view in the side view provided in the lower end portion.
  • the flat shape is defined by the lower curved portion 514L and a rectangular parallelepiped flat portion 515P provided between the curved portions.
  • the upper bending portion 514U and the lower bending portion 514L have substantially the same configuration, and both are collectively referred to as a bending portion 514.
  • FIG. 14A is a perspective view showing an axis 509 according to the fifth embodiment
  • FIG. 14B is an enlarged schematic cross-sectional view showing an elastic part 508 provided on the long side part 509L
  • FIG. 15 is a schematic cross-sectional view showing the internal structure of the secondary battery 500 according to the fifth embodiment.
  • the shaft core 509 includes a rectangular flat plate-shaped rigid body portion 507 and two columnar elastic portions 508.
  • the rigid body portion 507 has a pair of long side portions 509L facing each other and a pair of short side portions 509S facing each other.
  • the pair of long side portions 509L extend in parallel to the winding axis X, and the pair of short side portions 509S extend perpendicular to the winding axis X.
  • an elastic portion 508 is provided in each of the pair of long side portions 509L.
  • the long side portion 509L has a concave surface 507a having a semicircular cross section.
  • the elastic portion 508 has a columnar shape, a semicircular portion on the rigid body portion 507 side is fitted to the concave surface 507a of the long side portion 509L, and an opposite semicircular portion protrudes outward from the opening surface of the concave surface 507a. .
  • the elastic portion 508 is disposed between the innermost separator 143 and the concave surface 507 a of the rigid portion 507 in the curved portion 514 of the wound electrode group 504, and is wound by the wound electrode group 504. It is pressed toward the axis X.
  • the secondary battery 500 includes the wound electrode group 504 wound in a flat spiral shape having the flat portion 515P and the curved portion 514.
  • the wound electrode group 504 wound in a flat spiral shape as described above, when the active material expands during charging and the electrode tries to expand, in addition to the expansion force of the electrode, the following is performed. Force acts on the metal foil.
  • the bending portion 514 having a larger curvature than the flat portion 515P has a larger tensile force in the circumferential direction acting on the metal foil (positive foil and negative foil) than the flat portion 515P.
  • the force acting so as to crush the gaps in the electrodes and separators constituting the curved part 514 is larger than the force acting so as to crush the gaps in the electrodes and separators constituting the flat part 515P. That is, in the curved portion 514, the electrolyte is more easily depleted than the flat portion 515P.
  • the elastic portion made of a resin material having a lower elastic modulus than the resin material constituting the rigid portion 507. 508 is arranged.
  • the elastic portion 508 since the elastic portion 508 is arranged in the curved portion 514 where the electrolyte solution is likely to be exhausted as in (1) described in the first embodiment, the active material The force generated by the expansion of the elastic portion 508 can be absorbed by the elastic portion 508 compressively deforming. Thereby, it can suppress that the space
  • a rectangular flat plate-like rigid body portion 507 having a higher elastic modulus than the elastic portion 508 is provided. Thereby, the deformation
  • FIG. 16 is a perspective view showing the shaft core according to the modification, and the elastic portions 508A, 508B, and 508C are hatched for easy understanding.
  • the elastic portion 508 of the fifth embodiment as shown in FIG. 16A, a cylindrical rigid body portion 597A and a central portion in the winding axis X direction of the rigid body portion 597A are provided.
  • An intermediate member 590A including the elastic portion 508A may be provided. According to such a modification, in addition to the same effects as the fifth embodiment, the same effects as the second embodiment are achieved.
  • Modification 2 In the fifth embodiment, an example in which the elastic portion 508 is formed in a columnar shape will be described.
  • the intermediate members 590A to 590C (hereinafter collectively referred to as the intermediate member 590) are circular.
  • the columnar example has been described, the present invention is not limited to this.
  • shape of the elastic portion 508 and the intermediate member 590 various shapes such as a semi-cylindrical shape (see FIG. 17A) and a rectangular column shape (see FIG. 17B) can be adopted.
  • the columnar shape, the semi-cylindrical shape, and the rectangular columnar shape are not limited to a complete columnar shape, a semi-cylindrical shape, and a rectangular columnar shape. Includes a columnar shape, a substantially semi-cylindrical shape, and a substantially rectangular columnar shape.
  • each elastic portion 108 is formed of a resin material lower than the elastic modulus of the resin material of the rigid portion 107.
  • the innermost elastic portion 108 is in direct contact with the rigid portion 107 and the outermost elastic portion 108 is in direct contact with the separator 143.
  • the outer peripheral surface of the elastic portion 208 protrudes radially outward from the opening surface of the recess 207a before the separator 143 and the electrode are wound around the shaft core 209.
  • the present invention is not limited to this.
  • the outer peripheral surface of the elastic portion 208 may be located radially inward from the opening surface of the recess 207a. It is sufficient that at least the wound innermost separator 143 is in contact with the elastic portion 208. From the viewpoint of improving shape retention, the outer peripheral surface of the elastic portion 208 is positioned on the opening surface of the recess 207a before the separator 143 and the electrode are wound around the shaft core 209, or the opening of the recess 207a. It is preferable that the outer peripheral surface of the elastic portion 208 be positioned radially outward from the surface.
  • the positive electrode active material is a material capable of inserting and removing lithium ions, and a lithium transition metal composite oxide into which a sufficient amount of lithium ions has been inserted in advance may be used. Further, as the positive electrode active material, a material obtained by substituting or doping lithium in the crystal of the lithium transition metal composite oxide or a part of the transition metal with an element other than those may be used.
  • the crystal structure is not particularly limited, and may have any crystal structure of spinel, layered, or olivine.
  • the negative electrode active material a carbonaceous material such as amorphous carbon or coke in which lithium ions can be inserted and removed may be used.
  • SiO, Si alloy, and the like can also be cited as materials capable of inserting and removing lithium ions. A mixture of these materials may be used, and the mixing ratio is not limited.
  • the particle shape is not particularly limited, such as a scale shape, a spherical shape, a fiber shape, or a lump shape.
  • Binders include polytetrafluoroethylene (PTFE), polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene / butadiene rubber, polysulfide rubber, nitrocellulose, cyanoethyl cellulose, various latexes, acrylonitrile, vinyl fluoride, and fluoride.
  • PTFE polytetrafluoroethylene
  • Polyethylene polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene / butadiene rubber, polysulfide rubber, nitrocellulose, cyanoethyl cellulose, various latexes, acrylonitrile, vinyl fluoride, and fluoride.
  • Polymers such as vinylidene, propylene fluoride, and chloroprene fluoride, and mixtures thereof can be used.
  • a nonaqueous electrolyte solution is obtained by dissolving lithium hexafluorophosphate (LiPF 6 ) in a mixed solution of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC).
  • EC ethylene carbonate
  • DMC dimethyl carbonate
  • EMC ethyl methyl carbonate
  • the present invention is not limited to this. Any nonaqueous electrolytic solution in which a general lithium salt is used as an electrolyte and dissolved in an organic solvent may be used.
  • LiClO 4 , LiAsF 6 , LiBF 4 , LiB (C 6 H 5 ) 4 , CH 3 SO 3 Li, CF 3 SO 3 Li, or a mixture thereof can be used.
  • the organic solvent include propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, ⁇ -butyrolactone, tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, Diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propiontonyl, etc., or a mixed solvent of two or more of these may be used, and the mixing ratio is not limited.
  • the hollow columnar (cylindrical) rigid body portions 107, 207, 307, and 407 have been described as examples. However, a solid columnar rigid body portion or an elliptical columnar rigid body portion may be used.
  • the present invention can also be applied to a rigid part.
  • the columnar shape and the elliptical columnar shape are not limited to the complete columnar shape and the elliptical columnar shape, but are substantially the same, and include a substantially cylindrical shape and a substantially elliptical columnar shape that exhibit the effects of the present invention.
  • the rectangular flat plate-like rigid body portion 507 has been described as an example, but the present invention is not limited to this.
  • the present invention can also be applied to a flat elliptical columnar rigid body portion 507 (see FIG. 17C).
  • the rectangular flat plate shape and the flat elliptical columnar shape are not limited to the complete rectangular flat plate shape and the flat elliptical columnar shape, but are substantially the same and substantially the same as the rectangular flat plate shape or the substantially flat plate shape that exhibits the effect of the present invention. Includes a flat elliptical columnar shape.
  • the elastic portion 108 that covers substantially the entire cylindrical rigid body portion 107 has been described, and in the second embodiment, the elastic portion 208 that covers the central portion of the cylindrical rigid body portion 207 has been described.
  • the example in which the exposed portions of the cylindrical rigid body portions 307 and 407 and the covering portions covered by the elastic portions 308 and 408 are alternately arranged has been described.
  • the elastic portion is not limited to these shapes. Any configuration may be used as long as the elastic portion 108 is disposed on at least a part of the outer peripheral surface of the cylindrical rigid body portion 107. For example, a lattice shape (see FIG. 17D) or a matrix shape (see FIG. 17E). ).

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Abstract

In the present invention, the depletion of an electrolyte in a group of wound electrodes, as a result of charging/discharging, is mitigated. Provided is a secondary battery having a group of wound electrodes in which electrodes and separators are wound about a core. The core has a rigid body portion made of a resin, and an elastic portion made of a resin having a lower elastic modulus than that of the rigid body portion, the elastic portion being disposed between the innermost circumferential separator and the rigid body portion.

Description

二次電池Secondary battery
　本発明は、二次電池に関する。 The present invention relates to a secondary battery.
　リチウムイオン二次電池などの二次電池の電池内部では電池缶内に収容されている電極材料が充放電に伴って膨張・収縮する。電極材料が膨張した際、電極内の空隙やセパレータの空隙が潰され、その部分に満たされていた電解液が電極外へ押し出される。押し出された電解液は、電極材料が収縮した際に、完全に元の位置に戻ることができない。このため、充放電が繰り返されると徐々に電解液が枯渇する。その結果、電解液中のリチウムイオンの動きが低下したり、活物質との授受能力が低下したりするため、容量や出力などの性能が低下する。 In the battery of a secondary battery such as a lithium ion secondary battery, the electrode material accommodated in the battery can expands and contracts with charge / discharge. When the electrode material expands, the gap in the electrode and the gap in the separator are crushed, and the electrolyte filled in that portion is pushed out of the electrode. The extruded electrolyte cannot completely return to its original position when the electrode material contracts. For this reason, when charging and discharging are repeated, the electrolytic solution is gradually depleted. As a result, the movement of lithium ions in the electrolytic solution decreases or the ability to exchange with the active material decreases, so that the performance such as capacity and output decreases.
　電極材料の膨張・収縮に伴う電解液の枯渇を抑制する方法として、金属製の軸芯（放熱プレート）に捲回された捲回電極群（電極体）の捲回内周の内側に軽量で硬質なポリプロピレンからなる樹脂シートを設け、樹脂シートのクッション性により、捲回電極群の膨張・収縮を緩和する方法が知られている（特許文献１参照）。 As a method to suppress electrolyte depletion due to expansion and contraction of electrode material, it is lightweight inside the wound inner circumference of a wound electrode group (electrode body) wound around a metal shaft core (heat dissipation plate). A method is known in which a resin sheet made of hard polypropylene is provided, and the expansion / contraction of the wound electrode group is mitigated by the cushioning property of the resin sheet (see Patent Document 1).
特開２０１０－０５５８８７号公報JP 2010-055887 A
　しかしながら、特許文献１の構成では、充放電に伴う捲回電極群における電解液の枯渇の抑制が不十分であり、改善の余地があった。 However, in the configuration of Patent Document 1, suppression of electrolyte depletion in the wound electrode group due to charge / discharge is insufficient, and there is room for improvement.
　本発明に係る二次電池は、軸芯に電極およびセパレータを捲回した捲回電極群を有する二次電池であって、前記軸芯は、樹脂から成る剛体部と、前記剛体部よりも弾性率が低い樹脂から成る弾性部とを有し、前記弾性部は、最内周のセパレータと前記剛体部との間に配置されている。 The secondary battery according to the present invention is a secondary battery having a wound electrode group in which an electrode and a separator are wound on an axial core, wherein the axial core is more rigid than a rigid body portion made of resin and the rigid body portion. And an elastic portion made of resin having a low rate, and the elastic portion is disposed between the innermost separator and the rigid body portion.
　本発明によれば、充放電に伴う捲回電極群における電解液の枯渇を抑制することができる。 According to the present invention, it is possible to suppress the depletion of the electrolytic solution in the wound electrode group accompanying charge / discharge.
第１の実施の形態に係る二次電池の構成を示す断面模式図。The cross-sectional schematic diagram which shows the structure of the secondary battery which concerns on 1st Embodiment. 軸芯を示す図。The figure which shows an axial center. 捲回電極群の一部を切断した状態の斜視図。The perspective view of the state which cut a part of winding electrode group. 捲回電極群の終端側を展開した状態の平面図。The top view of the state which expand | deployed the terminal side of the winding electrode group. （ａ）は比較例に係る捲回電極群の充電時および放電時の要部拡大断面模式図、（ｂ）は第１の実施の形態に係る捲回電極群の充電時および放電時の要部拡大断面模式図。(A) is a schematic enlarged cross-sectional view of a main part at the time of charging and discharging the wound electrode group according to the comparative example, and (b) is a point at the time of charging and discharging of the wound electrode group according to the first embodiment. FIG. 比較例に係る二次電池内の電解液を示す断面模式図。The cross-sectional schematic diagram which shows the electrolyte solution in the secondary battery which concerns on a comparative example. 第２の実施の形態に係る軸芯の斜視図および二次電池の構成を示す断面模式図。The perspective view of the axial core which concerns on 2nd Embodiment, and the cross-sectional schematic diagram which shows the structure of a secondary battery. 剛体部に固定される弾性部を示す拡大断面模式図。The expanded cross-section schematic diagram which shows the elastic part fixed to a rigid body part. 第３の実施の形態に係る軸芯を示す斜視図および第３の実施の形態の変形例に係る軸芯を示す側面模式図。The perspective view which shows the axial center which concerns on 3rd Embodiment, and the side surface schematic diagram which shows the axial center which concerns on the modification of 3rd Embodiment. （ａ）は第４の実施の形態に係る軸芯を示す斜視図。（ｂ）は軸芯の中心軸（捲回軸Ｘ）に直交する平面で切断した断面模式図。(A) is a perspective view which shows the axial center which concerns on 4th Embodiment. (B) is the cross-sectional schematic diagram cut | disconnected by the plane orthogonal to the central axis (winding axis | shaft X) of an axial center. 第５の実施の形態に係る二次電池の外観斜視図。The external appearance perspective view of the secondary battery which concerns on 5th Embodiment. 第５の実施の形態に係る二次電池の構成を示す分解斜視図。The disassembled perspective view which shows the structure of the secondary battery which concerns on 5th Embodiment. 第５の実施の形態に係る捲回電極群を示す斜視図および側面模式図。The perspective view and side surface schematic diagram which show the winding electrode group which concerns on 5th Embodiment. 第５の実施の形態に係る軸芯を示す図。The figure which shows the axial center which concerns on 5th Embodiment. 第５の実施の形態に係る二次電池の内部構造を示す断面模式図。The cross-sectional schematic diagram which shows the internal structure of the secondary battery which concerns on 5th Embodiment. 変形例に係る軸芯を示す斜視図。The perspective view which shows the axial center which concerns on a modification. 変形例に係る軸芯を示す模式図。The schematic diagram which shows the axial center which concerns on a modification.
　以下、図面を参照して、本発明をリチウムイオン二次電池（以下、単に二次電池と記す）に適用した実施の形態について説明する。 Hereinafter, an embodiment in which the present invention is applied to a lithium ion secondary battery (hereinafter simply referred to as a secondary battery) will be described with reference to the drawings.
－第１の実施の形態－
　図１は、第１の実施の形態に係る二次電池１００の構成を示す断面模式図である。図１に示すように、二次電池１００は、電池容器、電池容器内に収容される捲回電極群１０４および電解液を備えている。電池容器は、ステンレス製であり、一端が開口された有底円筒状の電池缶１０１と、開口を封止する電池蓋ユニット１２０とを有している。以下、説明の便宜上、電池蓋ユニット１２０側を二次電池１００の上側、電池缶１０１の底面側を二次電池１００の下側として説明する。 -First embodiment-
FIG. 1 is a schematic cross-sectional view showing the configuration of the secondary battery 100 according to the first embodiment. As shown in FIG. 1, the secondary battery 100 includes a battery container, a wound electrode group 104 accommodated in the battery container, and an electrolytic solution. The battery container is made of stainless steel, and has a bottomed cylindrical battery can 101 having one end opened, and a battery lid unit 120 that seals the opening. Hereinafter, for convenience of explanation, the battery lid unit 120 side is described as the upper side of the secondary battery 100, and the bottom surface side of the battery can 101 is described as the lower side of the secondary battery 100.
　充放電要素である捲回電極群１０４は、軸芯１０９に対して、正極電極１４１と負極電極１４２とを第１セパレータ１４３ａおよび第２セパレータ１４３ｂを介して、軸芯１０９の中心軸である捲回軸Ｘを中心に捲回することによって形成される。本実施の形態に係る捲回電極群１０４は、渦巻き状に捲回されて、円筒形状とされている。つまり、捲回電極群１０４は、捲回軸Ｘ周りの３６０度の範囲、すなわち全周に亘って外周面が湾曲している湾曲部として構成されている。 The wound electrode group 104, which is a charge / discharge element, has a positive electrode 141 and a negative electrode 142 with respect to the shaft core 109 via the first separator 143a and the second separator 143b. It is formed by winding around the rotation axis X. The wound electrode group 104 according to the present embodiment is wound in a spiral shape to have a cylindrical shape. That is, the wound electrode group 104 is configured as a curved portion whose outer peripheral surface is curved over a 360-degree range around the winding axis X, that is, the entire circumference.
　図２は軸芯１０９を示す図である。図２（ａ）は軸芯１０９の斜視図であり、分かりやすいように弾性部１０８にハッチングを施している。図２（ｂ）は軸芯１０９の中心軸（捲回軸Ｘ）に直交する平面で切断した断面模式図である。図２（ｃ）は軸芯１０９の中心軸（捲回軸Ｘ）に平行、かつ中心軸（捲回軸Ｘ）を含む平面で切断した断面模式図である。 FIG. 2 is a view showing the shaft core 109. FIG. 2A is a perspective view of the shaft core 109, and the elastic portion 108 is hatched for easy understanding. FIG. 2B is a schematic cross-sectional view taken along a plane orthogonal to the central axis (winding axis X) of the shaft core 109. FIG. 2C is a schematic cross-sectional view taken along a plane parallel to the central axis (winding axis X) of the shaft core 109 and including the central axis (winding axis X).
　図２に示すように、軸芯１０９は、捲回軸Ｘ方向に沿う中空部を有する細長い円筒形状（中空円柱状）に形成されている。軸芯１０９は、円筒状の剛体部１０７と、剛体部１０７の外周面を覆うように設けられた弾性部１０８とを有している。剛体部１０７は、ポリプロピレンなどの樹脂材料から成る。弾性部１０８は、外周面が捲回方向に沿う湾曲面とされた円筒状であり、以下に示すような樹脂材料から成る。 As shown in FIG. 2, the shaft core 109 is formed in an elongated cylindrical shape (hollow columnar shape) having a hollow portion along the winding axis X direction. The shaft core 109 has a cylindrical rigid body portion 107 and an elastic portion 108 provided so as to cover the outer peripheral surface of the rigid body portion 107. The rigid portion 107 is made of a resin material such as polypropylene. The elastic portion 108 has a cylindrical shape whose outer peripheral surface is a curved surface along the winding direction, and is made of a resin material as described below.
　弾性部１０８の樹脂材料としては、連続気泡ポリエチレンフォーム、ポリエチレン、フッ素樹脂などから選択できる。その他、弾性部１０８の樹脂材料として、耐有機電解液性を有するウレタンフォームやブチルゴム、エチレンプロピレンゴムなどを選択することもできる。弾性部１０８の材料に多孔性材料を採用することで、弾性部１０８の弾性率をさらに低くしたり、弾性部１０８に保液性を持たせることもできる。さらに、耐有機溶剤性を持ったポリオレフィン繊維などの不織布等も弾性部１０８の材料として採用可能である。弾性部１０８の厚みとしては、後述する電極の膨張量を考慮し、かつ弾性部１０８の収縮量を考慮して、０．０５ｍｍ～２．０ｍｍ程度が適当である。 The resin material of the elastic portion 108 can be selected from open-cell polyethylene foam, polyethylene, fluororesin, and the like. In addition, as the resin material of the elastic portion 108, urethane foam, butyl rubber, ethylene propylene rubber, or the like having organic electrolyte resistance can be selected. By adopting a porous material as the material of the elastic portion 108, the elastic modulus of the elastic portion 108 can be further reduced, or the elastic portion 108 can be provided with liquid retention. Furthermore, non-woven fabrics such as polyolefin fibers having resistance to organic solvents can be used as the material of the elastic portion 108. The thickness of the elastic portion 108 is suitably about 0.05 mm to 2.0 mm in consideration of the amount of electrode expansion described later and the amount of contraction of the elastic portion 108.
　本実施の形態では、圧縮弾性率（ヤング率）が１～４０ＭＰａ程度の樹脂材料を弾性部１０８の材料として採用した。剛体部１０７の圧縮弾性率（ヤング率）は５０００ＭＰａ程度であるため、弾性部１０８の弾性率は剛体部１０７の弾性率に比べて十分に低い。 In this embodiment, a resin material having a compressive elastic modulus (Young's modulus) of about 1 to 40 MPa is used as the material of the elastic portion 108. Since the compression elastic modulus (Young's modulus) of the rigid body portion 107 is about 5000 MPa, the elastic modulus of the elastic portion 108 is sufficiently lower than the elastic modulus of the rigid body portion 107.
　軸芯１０９の捲回軸Ｘ方向（長手方向）の両端部は、弾性部１０８が被覆されておらず、剛体部１０７が露出した露出部とされている。 Both ends of the axis 109 in the winding axis X direction (longitudinal direction) are not covered with the elastic portion 108 and are exposed portions where the rigid portion 107 is exposed.
　図３は捲回電極群１０４の一部を切断した状態の斜視図であり、図４は捲回電極群１０４の終端側を展開した状態の平面図である。図３および図４に示すように、正極電極１４１は、たとえば、厚さ１５μｍ程度のアルミニウム箔やアルミニウム合金箔等からなる正極箔１４５の表裏両面に正極活物質合剤の層（以下、正極合剤層１４７と記す）が形成されたものである。正極合剤層１４７は、正極箔１４５の一側縁に、正極箔１４５が露出された正極合剤未処理部（以下、正極未塗工部と記す）が形成されるように正極箔１４５に正極活物質合剤が塗工されてなる。 FIG. 3 is a perspective view of a state in which a part of the wound electrode group 104 is cut, and FIG. 4 is a plan view of a state in which the terminal side of the wound electrode group 104 is developed. As shown in FIG. 3 and FIG. 4, the positive electrode 141 is composed of, for example, a layer of a positive electrode active material mixture (hereinafter referred to as a positive electrode mixture) (Referred to as an agent layer 147). The positive electrode mixture layer 147 is formed on the positive electrode foil 145 so that a positive electrode mixture untreated portion where the positive electrode foil 145 is exposed (hereinafter referred to as a positive electrode uncoated portion) is formed on one side edge of the positive electrode foil 145. A positive electrode active material mixture is applied.
　正極合剤層１４７は、正極活物質に導電剤および結着剤（バインダ）を加えて混練し、これに有機分散溶媒を添加、混練したスラリを正極箔１４５の表裏両面に所定幅で塗布し、乾燥、プレス加工を経て形成される。正極活物質は、マンガン酸リチウム等のリチウム含有遷移金属複酸化物である。正極未塗工部は、一部が切り欠かれて、図示するように正極リード片（以下、正極タブ１４５ｔと記す）が複数形成される。 The positive electrode mixture layer 147 is kneaded by adding a conductive agent and a binder (binder) to the positive electrode active material, adding an organic dispersion solvent thereto, and applying the kneaded slurry to both the front and back surfaces of the positive electrode foil 145 with a predetermined width. It is formed through drying and pressing. The positive electrode active material is a lithium-containing transition metal double oxide such as lithium manganate. A portion of the positive electrode uncoated portion is notched, and a plurality of positive electrode lead pieces (hereinafter referred to as positive electrode tabs 145t) are formed as shown in the figure.
　負極電極１４２は、たとえば、厚さ１０μｍ程度の圧延銅箔や圧延銅合金箔等からなる負極箔１４６の表裏両面に負極活物質合剤の層（以下、負極合剤層１４８と記す）が形成されたものである。負極合剤層１４８は、負極箔１４６の一側縁に、負極箔１４６が露出された負極合剤未処理部（以下、負極未塗工部と記す）が形成されるように負極箔１４６に負極合剤が塗工されてなる。 In the negative electrode 142, for example, a negative electrode active material mixture layer (hereinafter referred to as a negative electrode mixture layer 148) is formed on both front and back surfaces of a negative electrode foil 146 made of a rolled copper foil, a rolled copper alloy foil or the like having a thickness of about 10 μm. It has been done. The negative electrode mixture layer 148 is formed on the negative electrode foil 146 so that a negative electrode mixture untreated portion where the negative electrode foil 146 is exposed (hereinafter referred to as a negative electrode uncoated portion) is formed on one side edge of the negative electrode foil 146. A negative electrode mixture is applied.
　負極合剤層１４８は、負極活物質に結着剤（バインダ）を加えて混練し、これに有機分散溶媒を添加、混練したスラリを負極箔１４６の表裏両面に所定幅で塗布し、乾燥、プレス加工を経て形成される。負極活物質は、リチウムイオンを可逆に吸蔵、放出可能な天然黒鉛、人造の各種黒鉛材等の炭素材である。負極未塗工部は、一部が切り欠かれて、図示するように負極リード片（以下、負極タブ１４６ｔと記す）が複数形成される。 The negative electrode mixture layer 148 is prepared by adding a binder (binder) to the negative electrode active material and kneading, adding an organic dispersion solvent thereto, applying the kneaded slurry to both the front and back surfaces of the negative electrode foil 146 in a predetermined width, drying, Formed through press working. The negative electrode active material is a carbon material such as natural graphite capable of reversibly occluding and releasing lithium ions, and various artificial graphite materials. A portion of the negative electrode uncoated portion is cut away, and a plurality of negative electrode lead pieces (hereinafter referred to as negative electrode tabs 146t) are formed as shown in the figure.
　結着剤としては、たとえば、ポリビニリデンジフルオライド（ＰＶＤＦ）を採用できる。分散溶媒としては、非水溶媒および水溶媒のいずれも使用可能である。 As the binder, for example, polyvinylidene difluoride (PVDF) can be employed. As the dispersion solvent, any of a non-aqueous solvent and an aqueous solvent can be used.
　捲回電極群１０４を形成するには、軸芯１０９に先端部を溶着させた第１セパレータ１４３ａと第２セパレータ１４３ｂの間に、それぞれ、負極電極１４２の巻始め側端部を、正極電極１４１の巻始め側端部よりも内側に位置するように配置して捲回する。この場合、正極未塗工部と負極未塗工部とは、幅方向（捲回方向に直交する方向）の反対側の側縁に位置するように配置する。負極合剤層１４８の幅は、正極合剤層１４７の幅よりも広く形成されている。 In order to form the wound electrode group 104, the winding start side end portion of the negative electrode 142 is connected to the positive electrode 141 between the first separator 143a and the second separator 143b whose tip portions are welded to the shaft core 109, respectively. It is arranged and wound so as to be located inside the winding start side end. In this case, the positive electrode uncoated portion and the negative electrode uncoated portion are disposed so as to be positioned on the side edges opposite to the width direction (direction orthogonal to the winding direction). The width of the negative electrode mixture layer 148 is formed wider than the width of the positive electrode mixture layer 147.
　なお、第１セパレータ１４３ａおよび第２セパレータ１４３ｂは、同様の構成であるので、以下、総称してセパレータ１４３とも記す。セパレータ１４３は絶縁性を有し、リチウムイオンが通過可能なポリエチレン系微多孔質材料からなり、厚さは２５μｍ程度である。セパレータ１４３の圧縮弾性率（ヤング率）は、たとえば２００ＭＰａ程度であり、上述した軸芯１０９の剛体部１０７の弾性率よりも低く、弾性部１０８の弾性率よりも高い。 In addition, since the 1st separator 143a and the 2nd separator 143b are the same structures, hereafter, it generically describes also as the separator 143. The separator 143 has an insulating property and is made of a polyethylene microporous material through which lithium ions can pass, and has a thickness of about 25 μm. The separator 143 has a compression elastic modulus (Young's modulus) of, for example, about 200 MPa, which is lower than the elastic modulus of the rigid body portion 107 of the shaft core 109 and higher than that of the elastic portion 108.
　上述した軸芯１０９の弾性部１０８は、正極合剤層１４７における捲回軸Ｘ方向の領域に対向する位置に設けられている。図４に示すように、弾性部１０８の捲回軸Ｘ方向の長さＷＥは、正極合剤層１４７の捲回軸Ｘ方向の長さＷＰよりも長く、弾性部１０８の上端は正極合剤層１４７の上端よりも上方に位置し、弾性部１０８の下端は正極合剤層１４７の下端よりも下方に位置している。したがって、捲回軸Ｘから捲回軸Ｘと直交する方向（径方向）を見たときに、弾性部１０８の投影面は、正極合剤層１４７の投影面の全体を覆うことになる。 The elastic part 108 of the shaft core 109 described above is provided at a position facing the region in the winding axis X direction in the positive electrode mixture layer 147. As shown in FIG. 4, the length WE in the winding axis X direction of the elastic portion 108 is longer than the length WP in the winding axis X direction of the positive electrode mixture layer 147, and the upper end of the elastic portion 108 is at the positive electrode mixture. The upper portion of the layer 147 is located above the upper end, and the lower end of the elastic portion 108 is located below the lower end of the positive electrode mixture layer 147. Therefore, when the direction (radial direction) orthogonal to the winding axis X is viewed from the winding axis X, the projection surface of the elastic portion 108 covers the entire projection surface of the positive electrode mixture layer 147.
　図１を参照して、電池容器内の各構成部材について説明する。図１に示すように、上側に正極タブ１４５ｔが配置され、下側に負極タブ１４６ｔが配置されるように、捲回電極群１０４が電池容器内に収容される。 Referring to FIG. 1, each component in the battery container will be described. As shown in FIG. 1, the wound electrode group 104 is accommodated in the battery container so that the positive electrode tab 145t is disposed on the upper side and the negative electrode tab 146t is disposed on the lower side.
　軸芯１０９の上端部の内周には、中空部よりも径大の溝１０９ａが形成され、この溝１０９ａに後述の正極集電リング１０５に設けられた下部筒部１５２が圧入されている。軸芯１０９の下端部の外周には、外径が径小とされた段部１０９ｂが形成され、この段部１０９ｂが後述の負極集電リング１０６に設けられた内周筒部１６２の開口に圧入されている。 A groove 109a having a diameter larger than that of the hollow portion is formed on the inner periphery of the upper end portion of the shaft core 109, and a lower cylindrical portion 152 provided in a positive electrode current collecting ring 105 described later is press-fitted into the groove 109a. A step portion 109b having a small outer diameter is formed on the outer periphery of the lower end portion of the shaft core 109, and this step portion 109b is formed in an opening of an inner peripheral cylindrical portion 162 provided in the negative electrode current collecting ring 106 described later. It is press-fitted.
　正極集電リング１０５は、円板状の基部と、基部の中央部から軸芯１０９側に向かって突出する下部筒部１５２と、基部の外周縁から電池蓋１０２側に突出する上部筒部１５１とを有する。正極電極１４１に設けられた複数の正極タブ１４５ｔは、変形され、重なり合って、正極集電リング１０５の上部筒部１５１の外周面に超音波溶接により接続されている。 The positive electrode current collecting ring 105 includes a disc-shaped base, a lower cylindrical portion 152 that protrudes from the center of the base toward the axis 109, and an upper cylindrical portion 151 that protrudes from the outer periphery of the base toward the battery lid 102. And have. The plurality of positive electrode tabs 145t provided on the positive electrode 141 are deformed, overlapped, and connected to the outer peripheral surface of the upper cylindrical portion 151 of the positive electrode current collecting ring 105 by ultrasonic welding.
　正極集電リング１０５と後述の電池蓋ユニット１２０との間には、正極リード板１５９（正極集電部材の一部）が配置されている。正極リード板１５９は、一端が正極集電リング１０５に溶接され、他端が電池蓋ユニット１２０の下面を構成するケース１２２に溶接されている。正極リード板１５９は、複数枚のアルミニウム製のリボン（金属箔）が重ね合わされて構成されたフレキシブルな導電部材である。 A positive electrode lead plate 159 (a part of the positive electrode current collecting member) is disposed between the positive electrode current collecting ring 105 and a battery lid unit 120 described later. One end of the positive electrode lead plate 159 is welded to the positive electrode current collecting ring 105, and the other end is welded to the case 122 constituting the lower surface of the battery lid unit 120. The positive electrode lead plate 159 is a flexible conductive member configured by overlapping a plurality of aluminum ribbons (metal foils).
　負極集電リング１０６は、円板状の基部と、基部の中央部から電池缶１０１の底部側に向かって突出する内周筒部１６２と、基部の外周縁から電池缶１０１の底部側に突出する外周筒部１６１とを有する。負極電極１４２に設けられた複数の負極タブ１４６ｔは、変形され、重なり合って、負極集電リング１０６の外周筒部１６１の外周面に超音波溶接により接続されている。 The negative electrode current collector ring 106 includes a disc-shaped base, an inner peripheral cylindrical portion 162 that protrudes from the center of the base toward the bottom of the battery can 101, and a bottom of the battery can 101 that protrudes from the outer periphery of the base. And an outer peripheral cylindrical portion 161. The plurality of negative electrode tabs 146t provided on the negative electrode 142 are deformed, overlapped, and connected to the outer peripheral surface of the outer peripheral cylindrical portion 161 of the negative electrode current collecting ring 106 by ultrasonic welding.
　負極集電リング１０６と電池缶１０１の底部との間には、負極リード板１６９が配置されている。負極リード板１６９は、断面逆ハット状であり、軸芯１０９の下方で電池缶１０１の底部に接する円形凹部１６９ａと、円形凹部１６９ａの開口周縁から外方に延在する円環状のフランジ１６９ｂとを備えている。負極リード板１６９は、フランジ１６９ｂが負極集電リング１０６に溶接され、円形凹部１６９ａの底部が電池缶１０１の底部に溶接されている。 A negative electrode lead plate 169 is disposed between the negative electrode current collecting ring 106 and the bottom of the battery can 101. The negative electrode lead plate 169 has an inverted hat shape in cross section, a circular recess 169a that contacts the bottom of the battery can 101 below the shaft core 109, and an annular flange 169b that extends outward from the opening periphery of the circular recess 169a. It has. In the negative electrode lead plate 169, the flange 169 b is welded to the negative electrode current collector ring 106, and the bottom of the circular recess 169 a is welded to the bottom of the battery can 101.
　電池蓋ユニット１２０は、絶縁性を有するガスケット１２９を介して電池缶１０１に固定される。本実施の形態では、電池缶１０１の上端部が電池蓋ユニット１２０の外周部を挟むようにかしめられることで、電池蓋ユニット１２０が電池缶１０１に固定されている。 The battery lid unit 120 is fixed to the battery can 101 via an insulating gasket 129. In the present embodiment, the battery lid unit 120 is fixed to the battery can 101 by caulking the upper end of the battery can 101 so as to sandwich the outer periphery of the battery lid unit 120.
　電池蓋ユニット１２０は、電池蓋１０２と、安全弁（ガス排出弁）１２３と、弁押え部材１２４と、ケース１２２とを備えている。ケース１２２は、アルミニウム合金製であり、正極集電リング１０５に対向して配置されている。 The battery lid unit 120 includes a battery lid 102, a safety valve (gas discharge valve) 123, a valve pressing member 124, and a case 122. The case 122 is made of an aluminum alloy and is disposed to face the positive electrode current collecting ring 105.
　ケース１２２は、周縁部が安全弁１２３と電池蓋１０２とを挟むようにかしめられ、電池蓋１０２と安全弁１２３とを保持している。ケース１２２は、中心部に捲回電極群１０４側に窪んだ凹部を有しており、凹部には弁押え部材１２４が配置されている。弁押え部材１２４は、ケース１２２の凹部の底板と安全弁１２３との間に配置され、安全弁１２３を下側から支持している。 The case 122 is caulked so that the peripheral portion sandwiches the safety valve 123 and the battery lid 102, and holds the battery lid 102 and the safety valve 123. The case 122 has a concave portion that is recessed toward the wound electrode group 104 at the center, and a valve pressing member 124 is disposed in the concave portion. The valve pressing member 124 is disposed between the bottom plate of the concave portion of the case 122 and the safety valve 123, and supports the safety valve 123 from below.
　安全弁１２３には彫り込み等の脆弱部が設けられている。安全弁１２３は、電池容器内の圧力が上昇して所定圧力に達したときに、脆弱部が開裂して、電池内部で発生したガスを外部に放出することで、電池容器内の圧力を低減させる。電池内部で発生したガスを外部に排出するために、ケース１２２の凹部の底板や正極集電リング１０５、電池蓋１０２のそれぞれには１以上の開口が形成されている。 Safety valve 123 is provided with a fragile part such as engraving. When the pressure in the battery container rises and reaches a predetermined pressure, the safety valve 123 reduces the pressure in the battery container by cleaving the fragile portion and releasing the gas generated inside the battery to the outside. . In order to discharge the gas generated inside the battery to the outside, one or more openings are formed in the bottom plate of the recess of the case 122, the positive electrode current collecting ring 105, and the battery cover 102, respectively.
　正極電極１４１は、正極集電リング１０５、正極リード板１５９、ケース１２２を介して電池蓋１０２に電気的に接続されている。このため、電池蓋１０２が、正極外部出力端子として機能する。負極電極１４２は、負極集電リング１０６、負極リード板１６９を介して電池缶１０１の底部に電気的に接続されている。このため、電池缶１０１の底部が、負極外部出力端子として機能する。 The positive electrode 141 is electrically connected to the battery lid 102 via the positive electrode current collecting ring 105, the positive electrode lead plate 159, and the case 122. For this reason, the battery cover 102 functions as a positive electrode external output terminal. The negative electrode 142 is electrically connected to the bottom of the battery can 101 via the negative electrode current collecting ring 106 and the negative electrode lead plate 169. For this reason, the bottom part of the battery can 101 functions as a negative electrode external output terminal.
　二次電池１００内には、図示しない非水電解液が注液されており、捲回電極群１０４は非水電解液に浸潤されている。非水電解液には、たとえば、エチレンカーボネート（ＥＣ）とジメチルカーボネート（ＤＥＣ）との混合有機溶媒中に六フッ化リン酸リチウム（ＬｉＰＦ６）を１モル／リットルの割合で溶解したものを用いることができる。 A nonaqueous electrolyte solution (not shown) is injected into the secondary battery 100, and the wound electrode group 104 is infiltrated with the nonaqueous electrolyte solution. As the non-aqueous electrolyte, for example, a solution obtained by dissolving lithium hexafluorophosphate (LiPF 6 ) at a rate of 1 mol / liter in a mixed organic solvent of ethylene carbonate (EC) and dimethyl carbonate (DEC) is used. be able to.
　本実施形態に係る二次電池１００の組立手順について説明する。セパレータ１４３として、第１セパレータ１４３ａおよび第２セパレータ１４３ｂを準備する。第１セパレータ１４３ａおよび第２セパレータ１４３ｂの最も内側の側縁部を軸芯１０９に接着する。 The assembly procedure of the secondary battery 100 according to this embodiment will be described. As the separator 143, a first separator 143a and a second separator 143b are prepared. The innermost side edge portions of the first separator 143 a and the second separator 143 b are bonded to the shaft core 109.
　第１セパレータ１４３ａと第２セパレータ１４３ｂを軸芯１０９に１～数周捲回し、第２セパレータ１４３ｂと第１セパレータ１４３ａとの間に負極電極１４２を挟み込み、所定角度、軸芯１０９を捲回する。その後、第１セパレータ１４３ａと第２セパレータ１４３ｂとの間に正極電極１４１を挟み込む。この状態で、所定の巻数分、捲回して渦巻き状の捲回電極群１０４を作製する。 The first separator 143a and the second separator 143b are wound around the shaft core one to several turns, the negative electrode 142 is sandwiched between the second separator 143b and the first separator 143a, and the shaft core 109 is wound at a predetermined angle. . Thereafter, the positive electrode 141 is sandwiched between the first separator 143a and the second separator 143b. In this state, the spiral wound electrode group 104 is manufactured by winding a predetermined number of turns.
　図３に示すように、最内周側に第１セパレータ１４３ａおよび第２セパレータ１４３ｂが捲回され、その外側に、負極電極１４２、第１セパレータ１４３ａおよび正極電極１４１、第２セパレータ１４３ｂが順に積層される。 As shown in FIG. 3, the first separator 143a and the second separator 143b are wound on the innermost peripheral side, and the negative electrode 142, the first separator 143a, the positive electrode 141, and the second separator 143b are sequentially stacked on the outer side. Is done.
　すなわち、最内周において、第１セパレータ１４３ａが軸芯１０９の弾性部１０８の湾曲面（外周面）に接している。最内周側の第１セパレータ１４３ａの外周面には、第２セパレータ１４３ｂが接している。この第２セパレータ１４３ｂの外側には負極電極１４２が位置し、その外側に第１セパレータ１４３ａが位置している。この第１セパレータ１４３ａの外側には正極電極１４１が位置し、その外側に第２セパレータ１４３ｂが位置している。 That is, in the innermost periphery, the first separator 143 a is in contact with the curved surface (outer peripheral surface) of the elastic portion 108 of the shaft core 109. The second separator 143b is in contact with the outer peripheral surface of the first innermost separator 143a. The negative electrode 142 is located outside the second separator 143b, and the first separator 143a is located outside the second separator 143b. The positive electrode 141 is located outside the first separator 143a, and the second separator 143b is located outside the positive electrode 141.
　捲回電極群１０４の最外周では、負極電極１４２を覆うように第１セパレータ１４３ａが捲回されている。最外周の第１セパレータ１４３ａは、捲回電極群１０４が捲き解かれないように、巻き止めテープ（不図示）で止められる。 In the outermost periphery of the wound electrode group 104, the first separator 143a is wound so as to cover the negative electrode 142. The outermost first separator 143a is stopped with a winding tape (not shown) so that the wound electrode group 104 is not unwound.
　正極電極１４１と負極電極１４２との間には、セパレータ１４３が介在されているため、正極電極１４１と負極電極１４２とが直接接することは無い。なお、捲回の際、正極タブ１４５ｔおよび負極タブ１４６ｔが、それぞれ捲回電極群１０４の互いに反対側の両端に配置されるようにする。 Since the separator 143 is interposed between the positive electrode 141 and the negative electrode 142, the positive electrode 141 and the negative electrode 142 are not in direct contact with each other. In the winding, the positive electrode tab 145t and the negative electrode tab 146t are arranged at both ends of the wound electrode group 104 opposite to each other.
　正極集電リング１０５および負極集電リング１０６をそれぞれ軸芯１０９の両端部に固定する。正極タブ１４５ｔを正極集電リング１０５の上部筒部１５１に密着させて、超音波溶接する。負極タブ１４６ｔを負極集電リング１０６の外周筒部１６１に密着させて、超音波溶接する。なお、負極リード板１６９は、予め負極集電リング１０６に溶接されている。 The positive current collecting ring 105 and the negative current collecting ring 106 are fixed to both ends of the shaft core 109, respectively. The positive electrode tab 145t is brought into close contact with the upper cylindrical portion 151 of the positive electrode current collecting ring 105, and ultrasonic welding is performed. The negative electrode tab 146t is brought into close contact with the outer peripheral cylindrical portion 161 of the negative electrode current collecting ring 106 and ultrasonic welding is performed. The negative electrode lead plate 169 is welded to the negative electrode current collecting ring 106 in advance.
　捲回電極群１０４と電池容器とが直接接触しないように、絶縁シートを捲回電極群１０４の外周面を覆うように、１周以上巻く。絶縁シートには、たとえば、基材がポリイミドでその片面にヘキサメタアクリレートからなる粘着剤を塗布したものを採用できる。 Wrap the insulating sheet one or more times so as to cover the outer peripheral surface of the wound electrode group 104 so that the wound electrode group 104 and the battery container do not directly contact each other. As the insulating sheet, for example, a base material made of polyimide and a pressure-sensitive adhesive made of hexamethacrylate applied on one side thereof can be adopted.
　正負極集電リングが捲回電極群１０４の軸芯１０９に固定されてなる電極群ユニットを負極集電リング１０６側が電池缶１０１の底部側に配置されるように、電極群ユニットを電池缶１０１に挿入する。このとき、円環状のスペーサ１６８を負極集電リング１０６と電池缶１０１の底部との間に配置する。 The electrode group unit is made up of the battery can 101 so that the negative electrode current collection ring 106 side is arranged on the bottom side of the battery can 101 with the electrode group unit in which the positive and negative current collecting rings are fixed to the shaft core 109 of the wound electrode group 104. Insert into. At this time, an annular spacer 168 is disposed between the negative electrode current collector ring 106 and the bottom of the battery can 101.
　負極リード板１６９を電池容器に溶接し、電池缶１０１の上部開口から非水電解液を電池缶１０１内に所定量注液する。注液作業では、たとえば電池容器内部を減圧し、所定量の電解液を注入する。所定時間が経過すると、捲回電極群１０４の内部全域に電解液が含浸される。その後、ガスケット１２９を介して電池蓋ユニット１２０と電池缶１０１の上端部とをかしめて固定する。これにより、円筒形の二次電池１００が組み立てられる。組み立てられた二次電池１００に初充電を行い電池としての機能を付与することによって、二次電池１００が完成する。 The negative electrode lead plate 169 is welded to the battery container, and a predetermined amount of non-aqueous electrolyte is injected into the battery can 101 from the upper opening of the battery can 101. In the liquid injection operation, for example, the inside of the battery container is decompressed and a predetermined amount of electrolyte is injected. When a predetermined time elapses, the electrolyte solution is impregnated throughout the wound electrode group 104. Thereafter, the battery lid unit 120 and the upper end of the battery can 101 are caulked and fixed via the gasket 129. Thereby, the cylindrical secondary battery 100 is assembled. The secondary battery 100 is completed by performing initial charge on the assembled secondary battery 100 to give a function as a battery.
　ところで、リチウムイオン二次電池では捲回電極群１０４が有する電極材料（たとえば負極活物質、正極活物質等）が充放電に伴ってその体積が膨張・収縮する。電極材料が膨張した際、電極内の空隙やセパレータの空隙が潰され、その部分に満たされていた電解液が電極外へ押し出される。押し出された電解液は、電極材料が収縮した際に、完全に元の位置に戻ることができない。このため、充放電が繰り返されると徐々に電解液が枯渇する。その結果、電解液中のリチウムイオンの動きが低下したり、活物質との授受能力が低下したりするため、容量や出力などの性能が低下する。 By the way, in the lithium ion secondary battery, the volume of the electrode material (for example, the negative electrode active material, the positive electrode active material, etc.) of the wound electrode group 104 expands and contracts with charge / discharge. When the electrode material expands, the gap in the electrode and the gap in the separator are crushed, and the electrolyte filled in that portion is pushed out of the electrode. The extruded electrolyte cannot completely return to its original position when the electrode material contracts. For this reason, when charging and discharging are repeated, the electrolytic solution is gradually depleted. As a result, the movement of lithium ions in the electrolytic solution decreases or the ability to exchange with the active material decreases, so that the performance such as capacity and output decreases.
　図５（ａ）を参照して捲回電極群１０４における液枯れのメカニズムを説明する。図中、白抜きの多角形および楕円により、負極活物質および正極活物質を模式的に表している。なお、以下の説明では、便宜上、正極合剤層１４７および負極合剤層１４８のうち、相対的に膨張率および収縮率の大きい負極合剤層１４８に着目して説明する。図５（ａ）は比較例に係る捲回電極群９０４の充電時（図示右側）および放電時（図示左側）の要部拡大断面模式図である。比較例に係る捲回電極群９０４は、軸芯９０９が剛体部１０７のみで構成され、弾性部１０８を備えていない。リチウムイオン二次電池は、充電時に負極活物質が大きく膨張する。しなしながら、図５（ａ）に示す比較例のように、軸芯９０９が剛体部１０７のみで構成されている場合、負極合剤層１４８が捲回電極群１０４の径方向内側へ膨張することが抑制される。 With reference to FIG. 5 (a), the mechanism of liquid withering in the wound electrode group 104 will be described. In the figure, the negative electrode active material and the positive electrode active material are schematically represented by white polygons and ellipses. In the following description, for the sake of convenience, the negative electrode mixture layer 148 having a relatively large expansion coefficient and shrinkage ratio among the positive electrode mixture layer 147 and the negative electrode mixture layer 148 will be described. FIG. 5A is an enlarged schematic cross-sectional view of a main part when the wound electrode group 904 according to the comparative example is charged (right side in the figure) and discharged (left side in the figure). In the wound electrode group 904 according to the comparative example, the axial center 909 is configured by only the rigid body portion 107 and does not include the elastic portion 108. In the lithium ion secondary battery, the negative electrode active material greatly expands during charging. However, as in the comparative example shown in FIG. 5A, when the shaft core 909 is configured only by the rigid portion 107, the negative electrode mixture layer 148 expands radially inward of the wound electrode group 104. It is suppressed.
　なお、正極箔１４５の圧縮弾性率（ヤング率）は、たとえば７０ＧＰａ程度であり、負極箔１４６の圧縮弾性率（ヤング率）は、たとえば１３０ＧＰａ程度である。これに対して、正極合剤層１４７の圧縮弾性率（ヤング率）は、たとえば１～２ＧＰａ程度であり、負極合剤層１４８の圧縮弾性率（ヤング率）は、たとえば０．５～１ＧＰａ程度である。 In addition, the compression elastic modulus (Young's modulus) of the positive electrode foil 145 is, for example, about 70 GPa, and the compression elastic modulus (Young's modulus) of the negative electrode foil 146 is, for example, about 130 GPa. In contrast, the compression modulus (Young's modulus) of the positive electrode mixture layer 147 is, for example, about 1 to 2 GPa, and the compression modulus (Young's modulus) of the negative electrode mixture layer 148 is, for example, about 0.5 to 1 GPa. It is.
　正極箔１４５および負極箔１４６は、樹脂材料や正極合剤層１４７、負極合剤層１４８に比べて弾性率が高い。つまり、正極箔１４５および負極箔１４６は、負極合剤層１４８が膨張する際に伸びにくい性質を有している。このように、伸びにくい正極箔１４５および負極箔１４６は、捲回作業時に張力が付与された状態で軸芯９０９に渦巻き状に捲回されるので、負極合剤層１４８が捲回電極群１０４の径方向外側へ膨張することも抑制される。 The positive electrode foil 145 and the negative electrode foil 146 have higher elastic modulus than the resin material, the positive electrode mixture layer 147, and the negative electrode mixture layer 148. That is, the positive electrode foil 145 and the negative electrode foil 146 have a property that it is difficult to stretch when the negative electrode mixture layer 148 expands. In this way, the positive electrode foil 145 and the negative electrode foil 146 which are not easily stretched are spirally wound around the shaft core 909 in a state where tension is applied during the winding operation, so that the negative electrode mixture layer 148 is wound on the wound electrode group 104. Expansion to the outside in the radial direction is also suppressed.
　上述のとおり、負極合剤層１４８は、剛体部１０７および正極箔１４５、負極箔１４６によって、径方向内側および外側への膨張が抑制される。このため、負極合剤層１４８は、負極合剤層１４８が有する空隙を潰すように膨張する。 As described above, the negative electrode mixture layer 148 is suppressed from expanding radially inward and outward by the rigid portion 107, the positive foil 145, and the negative foil 146. For this reason, the negative electrode mixture layer 148 expands so as to crush the voids of the negative electrode mixture layer 148.
　なお、負極合剤層１４８と剛体部１０７との間や、負極合剤層１４８と正極合剤層１４７との間にはセパレータ１４３が介在されているので、負極合剤層１４８は僅かに径方向内側および外側への膨張が許容されている。このため、負極合剤層１４８が膨張する際、セパレータ１４３が有する空隙も潰されることになる。 In addition, since the separator 143 is interposed between the negative electrode mixture layer 148 and the rigid portion 107 or between the negative electrode mixture layer 148 and the positive electrode mixture layer 147, the negative electrode mixture layer 148 has a slight diameter. Expansion inward and outward is allowed. For this reason, when the negative mix layer 148 expand | swells, the space | gap which the separator 143 has is also crushed.
　本実施の形態では、捲回電極群１０４が全周に亘って湾曲しており、正極箔１４５および負極箔１４６に対して周方向の引張力が作用する。その結果、正極合剤層１４７や負極合剤層１４８には、正極箔１４５や負極箔１４６によって内側（捲回軸Ｘ側）に押圧される力が作用する。この押圧力は、捲回電極群１０４の内側（捲回軸Ｘ側）になるほど、より狭い範囲に集中して作用することになる。つまり、正極合剤層１４７や負極合剤層１４８に対して作用する圧力は、捲回電極群１０４の捲回中心に近づくほど大きくなる。 In the present embodiment, the wound electrode group 104 is curved over the entire circumference, and a tensile force in the circumferential direction acts on the positive foil 145 and the negative foil 146. As a result, a force pressed inward (winding axis X side) by the positive foil 145 and the negative foil 146 acts on the positive electrode mixture layer 147 and the negative electrode mixture layer 148. This pressing force is more concentrated in a narrower range as the inner side of the wound electrode group 104 (winding axis X side) becomes larger. In other words, the pressure acting on the positive electrode mixture layer 147 and the negative electrode mixture layer 148 increases as the winding center of the wound electrode group 104 is approached.
　負極合剤層１４８内の空隙やセパレータ１４３の空隙が潰されると、空隙に満たされていた電解液が押し出される。空隙から押し出された電解液は、捲回軸Ｘ方向外側に向かって移動し、捲回電極群１０４の外部へ押し出される。図６は、比較例に係る二次電池９００内の電解液を示す断面模式図である。図６（ａ）は、二次電池９００を縦置きした場合、すなわち捲回軸Ｘが鉛直方向に平行となるように二次電池９００が配置された場合を示している。この場合、電解液の液面ＷＬが、捲回電極群１０４の正極、負極合剤層やセパレータの下端面よりも下側に位置する場合がある。 When the gap in the negative electrode mixture layer 148 or the gap of the separator 143 is crushed, the electrolyte filled in the gap is pushed out. The electrolytic solution pushed out from the gap moves outward in the winding axis X direction and is pushed out of the wound electrode group 104. FIG. 6 is a schematic cross-sectional view showing an electrolytic solution in the secondary battery 900 according to the comparative example. FIG. 6A shows a case where the secondary battery 900 is placed vertically, that is, the case where the secondary battery 900 is arranged so that the winding axis X is parallel to the vertical direction. In this case, the liquid level WL of the electrolytic solution may be located below the positive and negative electrode layers of the wound electrode group 104 and the lower end surface of the separator.
　このような場合、充電時に捲回電極群１０４から押し出された電解液は、放電時に捲回電極群１０４内に戻ることができず、充放電が繰り返されることで、徐々に捲回電極群１０４内の電解液が枯渇する。 In such a case, the electrolytic solution pushed out from the wound electrode group 104 at the time of charging cannot return to the wound electrode group 104 at the time of discharging, and is gradually charged and discharged, thereby gradually winding the wound electrode group 104. The electrolyte inside is depleted.
　なお、電解液の液面ＷＬが、捲回電極群１０４の正極、負極合剤層やセパレータの下端面よりも上側に位置した場合であっても、以下の理由（ｉ）（ｉｉ）により、電解液が捲回電極群１０４内に完全に元の位置に戻ることができない。（ｉ）放電時における収縮の際に、重力に抗して電解液が捲回電極群１０４内に吸い込まれることになる。（ｉｉ）膨張時にセパレータと正負極合剤層とが密着し、収縮時に密着された部分が剥がれずに密着状態が維持される部分が発生してしまうと、電解液が捲回電極群１０４内に戻る流路における抵抗が増加する。 In addition, even when the liquid level WL of the electrolytic solution is located above the positive electrode, the negative electrode mixture layer and the lower end surface of the separator of the wound electrode group 104, for the following reasons (i) and (ii), The electrolyte cannot completely return to the original position in the wound electrode group 104. (I) During contraction during discharge, the electrolyte is sucked into the wound electrode group 104 against gravity. (Ii) When the separator and the positive and negative electrode mixture layers are in close contact with each other during expansion, and a portion in which the close contact state is maintained without being peeled off during contraction occurs, the electrolyte solution is contained in the wound electrode group 104. The resistance in the flow path returning to increases.
　図６（ｂ）は、二次電池９００を横置きした場合、すなわち捲回軸Ｘが水平方向に平行となるように二次電池９００が配置された場合を示している。この例では、電解液の液面ＷＬは、図示するように、捲回軸Ｘよりも下側に位置している。このため、液面ＷＬよりも上側では、押し出された電解液が捲回電極群１０４内に戻ることができず、充放電が繰り返されることで、徐々に捲回電極群１０４内の電解液が枯渇する。 FIG. 6B shows the case where the secondary battery 900 is placed horizontally, that is, the case where the secondary battery 900 is arranged so that the winding axis X is parallel to the horizontal direction. In this example, the liquid level WL of the electrolytic solution is located below the winding axis X as illustrated. For this reason, the extruded electrolyte cannot return into the wound electrode group 104 above the liquid level WL, and the electrolyte in the wound electrode group 104 is gradually gradually charged and discharged. Depleted.
　捲回電極群１０４の下部では、放電時における捲回電極群１０４の収縮の際に、電解液が捲回電極群１０４内に吸い込まれる。しかしながら、上記（ｉｉ）と同様に、電解液が捲回電極群１０４内に戻る流路における抵抗が増加することに起因して、捲回電極群１０４の下部においても電解液が完全に元の位置に戻ることはできない。 In the lower part of the wound electrode group 104, the electrolytic solution is sucked into the wound electrode group 104 when the wound electrode group 104 contracts during discharge. However, as in (ii) above, due to the increase in resistance in the flow path where the electrolyte returns into the wound electrode group 104, the electrolyte is completely removed at the lower part of the wound electrode group 104. You cannot return to position.
　以上のとおり、比較例に係る二次電池９００では、充放電が繰り返されると徐々に電解液が枯渇し、液中のリチウムイオンの動きが低下したり、活物質とのリチウムイオンの授受がしにくくなったりするため、容量や出力などの性能が低下する。 As described above, in the secondary battery 900 according to the comparative example, when charging and discharging are repeated, the electrolytic solution is gradually depleted, and the movement of lithium ions in the solution is reduced, and lithium ions are exchanged with the active material. Performance such as capacity and output is reduced because it becomes difficult.
　これに対して、本実施の形態に係る二次電池１００では、上述したように、最内周のセパレータ１４３と剛体部１０７との間に、最内周のセパレータ１４３に接する弾性部１０８が配置されている。このため、本実施の形態では、比較例に比べて、液枯れが抑制される。図５（ｂ）を参照して本実施の形態における液枯れの抑制のメカニズムを説明する。図中、白抜きの多角形および楕円により、負極活物質および正極活物質を模式的に表している。図５（ｂ）は第１の実施の形態に係る捲回電極群１０４の充電時（図示右側）および放電時（図示左側）の要部拡大断面模式図である。 On the other hand, in the secondary battery 100 according to the present embodiment, as described above, the elastic portion 108 that is in contact with the innermost separator 143 is disposed between the innermost separator 143 and the rigid portion 107. Has been. For this reason, in this Embodiment, compared with a comparative example, liquid withering is suppressed. With reference to FIG.5 (b), the mechanism of suppression of the liquid withering in this Embodiment is demonstrated. In the figure, the negative electrode active material and the positive electrode active material are schematically represented by white polygons and ellipses. FIG. 5B is an enlarged schematic cross-sectional view of the main part of the wound electrode group 104 according to the first embodiment during charging (right side in the figure) and discharging (left side in the figure).
　図５（ｂ）に示すように、本実施の形態では、充電時の負極活物質の体積の膨張の際、負極合剤層１４８よりも弾性率が低い弾性部１０８が径方向に圧縮されるため、比較例に比べて負極合剤層１４８の径方向寸法が拡大される。 As shown in FIG. 5B, in the present embodiment, the elastic portion 108 having a lower elastic modulus than the negative electrode mixture layer 148 is compressed in the radial direction when the volume of the negative electrode active material during expansion is expanded. Therefore, the radial dimension of the negative electrode mixture layer 148 is enlarged as compared with the comparative example.
　軸芯１０９の弾性部１０８が、捲回電極群１０４の径方向内側に圧縮変形することにより、負極合剤層１４８が膨張する際に発生する力を吸収することができる。したがって、本実施の形態では、剛体部１０７のみからなる軸芯９０９を用いた場合（比較例）よりも、負極合剤層１４８内の空隙やセパレータ１４３の空隙を押し潰すように作用する力を減少させることができる。このため、空隙に満たされていた電解液が押し出されにくくなり、電解液の枯渇を抑制できる。 When the elastic part 108 of the shaft core 109 is compressed and deformed radially inward of the wound electrode group 104, the force generated when the negative electrode mixture layer 148 expands can be absorbed. Therefore, in the present embodiment, the force acting to crush the voids in the negative electrode mixture layer 148 and the voids of the separator 143 is greater than that in the case where the shaft core 909 including only the rigid body portion 107 is used (comparative example). Can be reduced. For this reason, it becomes difficult to extrude the electrolyte solution filled in the voids, and the depletion of the electrolyte solution can be suppressed.
　上述した実施の形態によれば、次の作用効果が得られる。
（１）軸芯１０９が樹脂から成る剛体部１０７と、剛体部１０７よりも弾性率が低い樹脂から成る弾性部１０８とを有している。弾性部１０８は、最内周のセパレータ１４３と剛体部１０７との間に配置されている。これにより、捲回電極群１０４を構成する電極材料内の空隙に満たされていた電解液が押し出されにくくなり、充放電に伴う捲回電極群１０４の電解液の枯渇を抑制することができる。したがって、リチウムイオンの動きや活物質とのリチウムイオンの授受が阻害されないため、容量や出力などの性能の低下を抑制できる。つまり、本実施の形態によれば、長寿命な二次電池を提供することができる。 According to the embodiment described above, the following operational effects can be obtained.
(1) The shaft core 109 has a rigid portion 107 made of resin, and an elastic portion 108 made of resin having a lower elastic modulus than the rigid portion 107. The elastic part 108 is disposed between the innermost separator 143 and the rigid part 107. Thereby, the electrolyte filled in the gaps in the electrode material constituting the wound electrode group 104 is hardly pushed out, and depletion of the electrolyte in the wound electrode group 104 due to charge / discharge can be suppressed. Therefore, the movement of lithium ions and the exchange of lithium ions with the active material are not hindered, so that a reduction in performance such as capacity and output can be suppressed. That is, according to the present embodiment, a long-life secondary battery can be provided.
（２）ところで、活物質の体積の膨張は、正極合剤層１４７と負極合剤層１４８が対向している場所で、リチウムイオンが活物質内に挿入または脱離することで起こる。一般にリチウムイオン二次電池では、充電時のリチウムデンドライド抑制のため、負極合剤層１４８の面積を正極合剤層１４７の面積よりも広くして、正極合剤層１４７に対向するように負極合剤層１４８が配置されている。つまり、捲回軸Ｘから捲回軸Ｘと直交する方向（径方向）を見たときに、負極合剤層１４８の投影面は正極合剤層１４７の投影面の全体を覆っている。 (2) By the way, the expansion of the volume of the active material occurs when lithium ions are inserted into or desorbed from the active material where the positive electrode mixture layer 147 and the negative electrode mixture layer 148 are opposed to each other. In general, in a lithium ion secondary battery, the negative electrode mixture layer 148 is made wider than the positive electrode mixture layer 147 so as to face the positive electrode mixture layer 147 in order to suppress lithium dendrid during charging. A mixture layer 148 is disposed. That is, when the direction (radial direction) orthogonal to the winding axis X is viewed from the winding axis X, the projection surface of the negative electrode mixture layer 148 covers the entire projection surface of the positive electrode mixture layer 147.
　本実施の形態では、弾性部１０８が、少なくとも正極電極１４１の正極合剤層１４７における捲回電極群１０４の捲回軸Ｘ方向の領域に対向する位置に設けられているので、弾性部１０８が電極材料の膨張を効果的に吸収して、電解液の枯渇を抑制することができる。 In the present embodiment, since the elastic portion 108 is provided at a position facing at least the region in the winding axis X direction of the wound electrode group 104 in the positive electrode mixture layer 147 of the positive electrode 141, the elastic portion 108 is provided. It is possible to effectively absorb the expansion of the electrode material and suppress the depletion of the electrolytic solution.
（３）弾性部１０８は、捲回電極群１０４の捲回方向に沿う湾曲面を有し、湾曲面が最内周のセパレータ１４３に接している。このため、捲回方向に沿って均一に負極合剤層１４８内の空隙やセパレータ１４３の空隙を押し潰すように作用する力を減少させて、均一に電解液の枯渇を抑制できる。 (3) The elastic portion 108 has a curved surface along the winding direction of the wound electrode group 104, and the curved surface is in contact with the innermost separator 143. For this reason, it is possible to reduce the force acting so as to crush the gaps in the negative electrode mixture layer 148 and the gaps of the separator 143 uniformly along the winding direction, and the electrolyte depletion can be suppressed uniformly.
（４）弾性部１０８の弾性率は、セパレータ１４３の弾性率、正極合剤層１４７の弾性率および負極合剤層１４８の弾性率のいずれよりも低い。このため、セパレータ１４３、正極合剤層１４７および負極合剤層１４８のそれぞれの空隙が潰されることを抑制し、電解液の枯渇を効果的に抑制することができる。 (4) The elastic modulus of the elastic portion 108 is lower than any of the elastic modulus of the separator 143, the elastic modulus of the positive electrode mixture layer 147, and the elastic modulus of the negative electrode mixture layer 148. For this reason, it can suppress that each space | gap of the separator 143, the positive mix layer 147, and the negative mix layer 148 is crushed, and can suppress depletion of electrolyte solution effectively.
－第２の実施の形態－
　図７および図８を参照して第２の実施の形態に係る二次電池２００について説明する。図中、第１の実施の形態と同一または相当部分には同一符号を付し、相違点について主に説明する。図７（ａ）は、図２（ａ）と同様の図であり、第２の実施の形態に係る軸芯２０９を示す斜視図である。図７（ｂ）は、図１と同様の図であり、第２の実施の形態に係る二次電池２００の構成を示す断面模式図である。 -Second Embodiment-
A secondary battery 200 according to the second embodiment will be described with reference to FIGS. 7 and 8. In the figure, the same or corresponding parts as those in the first embodiment are denoted by the same reference numerals, and differences will be mainly described. FIG. 7A is a view similar to FIG. 2A and is a perspective view showing an axis 209 according to the second embodiment. FIG. 7B is a diagram similar to FIG. 1 and is a schematic cross-sectional view showing the configuration of the secondary battery 200 according to the second embodiment.
　第１の実施の形態では、捲回軸Ｘから捲回軸Ｘと直交する方向（径方向）を見たときに、弾性部１０８の投影面が正極合剤層１４７の投影面の全体を覆うように、弾性部１０８が剛体部１０７の軸方向両端部を除いて外周面の全体に亘って設けられていた（図１～図４参照）。 In the first embodiment, when the direction (radial direction) perpendicular to the winding axis X is viewed from the winding axis X, the projection surface of the elastic portion 108 covers the entire projection surface of the positive electrode mixture layer 147. As described above, the elastic portion 108 is provided over the entire outer peripheral surface except for both axial ends of the rigid portion 107 (see FIGS. 1 to 4).
　これに対して、第２の実施の形態に係る軸芯２０９は、剛体部２０７の捲回軸Ｘ方向の中央部に弾性部２０８が設けられている。弾性部２０８の捲回軸Ｘ方向の中央部では、捲回軸Ｘ方向の両端部に比べて、電解液が枯渇しやすい。このため、本実施の形態では、特に電解液が枯渇しやすい部分に弾性部２０８が設けられている。 On the other hand, the shaft core 209 according to the second embodiment is provided with an elastic portion 208 at the center of the rigid body portion 207 in the winding axis X direction. In the central portion of the elastic portion 208 in the winding axis X direction, the electrolyte is more easily depleted than at both ends in the winding axis X direction. For this reason, in the present embodiment, the elastic portion 208 is provided particularly in a portion where the electrolytic solution is easily depleted.
　図８は、剛体部２０７に固定される弾性部２０８を示す拡大断面模式図である。図８（ａ）は、セパレータ１４３および電極が軸芯２０９に捲回された後の状態を示しており、図８（ｂ）は、セパレータ１４３および電極が軸芯２０９に捲回される前の状態を示している。 FIG. 8 is an enlarged schematic cross-sectional view showing the elastic part 208 fixed to the rigid body part 207. 8A shows a state after the separator 143 and the electrode are wound around the shaft core 209, and FIG. 8B shows the state before the separator 143 and the electrode are wound around the shaft core 209. Indicates the state.
　剛体部２０７の外周面には、捲回軸Ｘ方向における所定長さで外周面に沿って凹部２０７ａが設けられている。換言すれば、剛体部２０７は、外径（直径）ＤＬの大径部２０７ｌと外径（直径）ＤＳの小径部２０７ｓとを有しており、小径部２０７ｓの外周面が凹部２０７ａの底面を構成している。 On the outer peripheral surface of the rigid body portion 207, a concave portion 207a is provided along the outer peripheral surface with a predetermined length in the winding axis X direction. In other words, the rigid body portion 207 has a large-diameter portion 207l having an outer diameter (diameter) DL and a small-diameter portion 207s having an outer diameter (diameter) DS, and the outer peripheral surface of the small-diameter portion 207s covers the bottom surface of the recess 207a. It is composed.
　図８（ｂ）に示すように、軸芯２０９にセパレータ１４３および電極が捲回される前の状態では、円筒状の弾性部２０８の外周面が剛体部２０７の大径部２０７ｌよりも径方向外側に突出している。つまり、大径部２０７ｌの外径（直径）ＤＬよりも弾性部２０８の外径（直径）ＤＥの方が大きい。 As shown in FIG. 8B, in the state before the separator 143 and the electrode are wound around the shaft core 209, the outer peripheral surface of the cylindrical elastic portion 208 is more radial than the large-diameter portion 207l of the rigid portion 207. Projects outward. That is, the outer diameter (diameter) DE of the elastic portion 208 is larger than the outer diameter (diameter) DL of the large-diameter portion 207l.
　図８（ａ）に示すように、軸芯２０９にセパレータ１４３および電極が捲回された後の状態では、弾性部２０８が径方向内側に向かって圧縮されて、弾性部２０８の外径（直径）ＤＥは、大径部２０７ｌの外径（直径）ＤＬと略同じになる。 As shown in FIG. 8A, in the state after the separator 143 and the electrode are wound around the shaft core 209, the elastic portion 208 is compressed radially inward, and the outer diameter (diameter) of the elastic portion 208 is compressed. ) DE is substantially the same as the outer diameter (diameter) DL of the large diameter portion 207l.
　弾性部２０８が圧縮されることで、最内周のセパレータ１４３が剛体部２０７の大径部２０７ｌの外周面に直接接する。 As the elastic portion 208 is compressed, the innermost separator 143 comes into direct contact with the outer peripheral surface of the large-diameter portion 207l of the rigid portion 207.
　このような第２の実施の形態によれば、第１の実施の形態の作用効果に加えて、次の作用効果を得ることができる。
（５）剛体部２０７の捲回軸Ｘ方向の両端部に比べて電解液が枯渇しやすい中央部に、弾性部２０８を設けた。これにより、第１の実施の形態に比べて、弾性部２０８の材料費を低減できる。
（６）捲回軸Ｘ方向の両端部では、剛体部２０７が直接、最内周のセパレータ１４３に接するようにした。剛体部２０７の一部をセパレータ１４３に直接接触させることで、軸芯２０９にセパレータ１４３および電極を捲回する際、セパレータ１４３および電極に適切な張力を付与できるので、セパレータ１４３や電極にしわが発生することを抑制できる。さらに、軸芯２０９の両端部において、充放電時の捲回電極群１０４の形状保持性を中央部に比べて向上できる。 According to such 2nd Embodiment, in addition to the effect of 1st Embodiment, the following effect can be obtained.
(5) The elastic portion 208 is provided in the central portion where the electrolyte solution is easily depleted as compared with both ends of the rigid portion 207 in the winding axis X direction. Thereby, compared with 1st Embodiment, the material cost of the elastic part 208 can be reduced.
(6) The rigid portion 207 is in direct contact with the innermost separator 143 at both ends in the winding axis X direction. By directly contacting a part of the rigid body portion 207 to the separator 143, when the separator 143 and the electrode are wound around the shaft core 209, an appropriate tension can be applied to the separator 143 and the electrode, so that the separator 143 and the electrode are wrinkled. Can be suppressed. Furthermore, the shape retainability of the wound electrode group 104 at the time of charging / discharging at both ends of the shaft core 209 can be improved as compared with the central portion.
（７）セパレータ１４３および電極を軸芯２０９に捲回する前の状態において、剛体部２０７の凹部２０７ａから突出するように弾性部２０８を設けた。これにより、軸芯２０９の凹部２０７ａにおいて、充放電の際に、弾性部２０８と最内周のセパレータ１４３とを接触させることができる。弾性部２０８は、充電時には捲回電極群１０４の内周側への変形を許容して電解液が捲回電極群１０４の外部へ押し出されることを防止する。弾性部２０８は、放電時には最内周のセパレータ１４３を弾性部２０８の弾性力により径方向外方に押し広げて、セパレータ１４３が凹部２０７ａ内に食い込んだ状態が維持されることを防止する。 (7) The elastic portion 208 is provided so as to protrude from the concave portion 207a of the rigid body portion 207 before the separator 143 and the electrode are wound around the shaft core 209. Thereby, in the recessed part 207a of the axial center 209, the elastic part 208 and the innermost periphery separator 143 can be made to contact in the case of charging / discharging. The elastic portion 208 allows deformation of the wound electrode group 104 toward the inner peripheral side during charging and prevents the electrolyte from being pushed out of the wound electrode group 104. The elastic part 208 spreads the innermost separator 143 outward in the radial direction by the elastic force of the elastic part 208 during discharge, thereby preventing the state where the separator 143 bites into the recess 207a.
　図８（ｃ）は、比較例を示す図である。比較例では、図示しないが、セパレータ１４３および電極を軸芯２０９に捲回する前の状態において、弾性部９０８が凹部２０７ａの開口面から外方に向かって突出していない。このため、図８（ｃ）に示すように、放電時において、弾性部９０８がセパレータ１４３に対して十分な弾性力を付与することができずに、セパレータ１４３が凹部２０７ａ内に食い込んだ状態が維持されてしまうおそれがある。 FIG. 8C shows a comparative example. In the comparative example, although not shown, the elastic portion 908 does not protrude outward from the opening surface of the recess 207a before the separator 143 and the electrode are wound around the shaft core 209. For this reason, as shown in FIG. 8C, the elastic portion 908 cannot give sufficient elastic force to the separator 143 at the time of discharge, and the separator 143 bites into the recess 207a. There is a risk of being maintained.
　これに対して、本実施の形態では、図８（ａ）に示すように、放電時において、弾性部２０８がセパレータ１４３に対して、径方向外側へ向かって、比較例よりも大きな弾性力を付与することができる。このため、本実施の形態によれば、比較例に比べて、形状保持性を向上できる。 On the other hand, in the present embodiment, as shown in FIG. 8A, the elastic portion 208 exerts a larger elastic force than the comparative example toward the radially outer side with respect to the separator 143 during discharge. Can be granted. For this reason, according to this Embodiment, compared with a comparative example, shape retainability can be improved.
－第３の実施の形態－
　図９を参照して第３の実施の形態に係る二次電池に用いられる軸芯３０９について説明する。図中、第２の実施の形態と同一または相当部分には同一符号を付し、相違点について主に説明する。図９（ａ）は、図７（ａ）と同様の図であり、第３の実施の形態に係る軸芯３０９を示す斜視図である。 -Third embodiment-
The shaft core 309 used for the secondary battery according to the third embodiment will be described with reference to FIG. In the figure, the same or corresponding parts as those of the second embodiment are denoted by the same reference numerals, and differences will mainly be described. FIG. 9A is a view similar to FIG. 7A and is a perspective view showing an axis 309 according to the third embodiment.
　第２の実施の形態では、剛体部２０７の捲回軸Ｘ方向の中央部に弾性部２０８を設けて、剛体部２０７の捲回軸Ｘ方向の両端部の外周面を直接、セパレータ１４３に接触させていた（図７参照）。 In the second embodiment, an elastic portion 208 is provided at the central portion of the rigid body portion 207 in the winding axis X direction, and the outer peripheral surfaces of both ends of the rigid body portion 207 in the winding axis X direction are in direct contact with the separator 143. (See FIG. 7).
　これに対して、第３の実施の形態に係る軸芯３０９は、図９（ａ）に示すように、剛体部３０７の露出部と、弾性部３０８により剛体部３０７が覆われて成る被覆部とが捲回軸Ｘ方向に交互に設けられている。つまり、剛体部３０７と最内周のセパレータ１４３とが直接接する部分が捲回軸Ｘ方向に離間して複数設けられている。複数の弾性部３０８は、それぞれ、捲回軸Ｘ方向と直交するように全周に亘って帯状に設けられ、円筒状を呈している。 On the other hand, as shown in FIG. 9A, the shaft core 309 according to the third embodiment includes an exposed portion of the rigid portion 307 and a covering portion in which the rigid portion 307 is covered by the elastic portion 308. Are alternately provided in the winding axis X direction. That is, a plurality of portions where the rigid portion 307 and the innermost separator 143 are in direct contact with each other are provided apart from each other in the winding axis X direction. Each of the plurality of elastic portions 308 is provided in a belt shape over the entire circumference so as to be orthogonal to the winding axis X direction, and has a cylindrical shape.
　なお、本実施の形態では、捲回軸Ｘ方向と直交する帯状の弾性部３０８が剛体部３０７に巻かれて円筒状を呈する例について説明したが、以下のように変形することもできる。図９（ｂ）は、第３の実施の形態の変形例について示す図であり、軸芯３０９の側面模式図である。図９（ｂ）に示すように、複数の帯状の弾性部３０８をそれぞれ捲回軸Ｘ方向と４５度で交差するように、捲回軸Ｘ方向に沿って離間して複数設けてもよい。１本の帯状の弾性部３０８を螺旋状に剛体部３０７に巻く構成としてもよい。 In the present embodiment, the example in which the belt-like elastic portion 308 perpendicular to the winding axis X direction is wound around the rigid portion 307 to form a cylindrical shape has been described. However, the present embodiment can be modified as follows. FIG. 9B is a diagram showing a modification of the third embodiment, and is a schematic side view of the shaft core 309. As shown in FIG. 9B, a plurality of belt-like elastic portions 308 may be provided apart from each other along the winding axis X direction so as to intersect the winding axis X direction at 45 degrees. One band-like elastic portion 308 may be spirally wound around the rigid body portion 307.
　このような第３の実施の形態によれば、第１の実施の形態で説明した（１）～（４）および第２の実施の形態で説明した（７）の作用効果に加えて、次の作用効果を奏する。
（８）最内周のセパレータ１４３と剛体部３０７とが直接接する部分が、捲回軸Ｘ方向に、離間して複数形成されている。これにより、捲回時の張力によって、セパレータ１４３および電極が軸芯３０９へ押し付けられる力が分散されるので、第２の実施の形態に比べて、捲回時における電極やセパレータ１４３の形状維持が容易である。 According to the third embodiment, in addition to the effects of (1) to (4) described in the first embodiment and (7) described in the second embodiment, Has the effect of.
(8) A plurality of portions where the innermost separator 143 and the rigid portion 307 are in direct contact with each other are formed apart from each other in the winding axis X direction. Accordingly, the force with which the separator 143 and the electrode are pressed against the shaft core 309 is dispersed by the tension at the time of winding, so that the shape of the electrode and the separator 143 at the time of winding can be maintained as compared with the second embodiment. Easy.
（９）最内周のセパレータ１４３と弾性部３０８とが直接接する部分が、捲回軸Ｘ方向に、離間して複数形成されている。これにより、充放電の際の体積膨張の力が分散して吸収されるので、第２の実施の形態に比べて、液枯れ防止の効果の向上を図ることができる。 (9) A plurality of portions where the innermost separator 143 and the elastic portion 308 are in direct contact with each other are formed apart from each other in the winding axis X direction. Thereby, since the force of volume expansion at the time of charging / discharging is disperse | distributed and absorbed, compared with 2nd Embodiment, the improvement of the effect of liquid dripping prevention can be aimed at.
－第４の実施の形態－
　図１０を参照して第４の実施の形態に係る二次電池に用いられる軸芯４０９について説明する。図中、第３の実施の形態と同一または相当部分には同一符号を付し、相違点について主に説明する。図１０（ａ）は、図９（ａ）と同様の図であり、第４の実施の形態に係る軸芯４０９を示す斜視図である。図１０（ｂ）は、軸芯４０９の中心軸（捲回軸Ｘ）に直交する平面で切断した断面模式図である。 -Fourth embodiment-
An axial core 409 used in the secondary battery according to the fourth embodiment will be described with reference to FIG. In the figure, the same or corresponding parts as those in the third embodiment are denoted by the same reference numerals, and differences will be mainly described. FIG. 10A is a view similar to FIG. 9A, and is a perspective view showing an axis 409 according to the fourth embodiment. FIG. 10B is a schematic cross-sectional view taken along a plane orthogonal to the central axis (winding axis X) of the shaft core 409.
　第３の実施の形態では、最内周のセパレータ１４３と剛体部３０７とが直接接する部分が、捲回軸Ｘ方向に、離間して複数形成されていた（図９（ａ）参照）。これに対して、第４の実施の形態では、図１０に示すように、最内周のセパレータ１４３（図１０において不図示）と剛体部４０７とが直接接する部分が、円筒状の剛体部４０７の周方向に、離間して複数形成されている。つまり、第４の実施の形態に係る軸芯４０９は、剛体部４０７の露出部と、弾性部４０８により剛体部４０７が覆われて成る被覆部とが剛体部４０７の周方向に交互に設けられている。 In the third embodiment, a plurality of portions where the innermost separator 143 and the rigid body portion 307 are in direct contact with each other are formed apart from each other in the winding axis X direction (see FIG. 9A). On the other hand, in the fourth embodiment, as shown in FIG. 10, the portion where the innermost separator 143 (not shown in FIG. 10) and the rigid portion 407 are in direct contact is a cylindrical rigid portion 407. In the circumferential direction, a plurality are formed apart from each other. That is, in the shaft core 409 according to the fourth embodiment, the exposed portion of the rigid portion 407 and the covering portion formed by covering the rigid portion 407 with the elastic portion 408 are alternately provided in the circumferential direction of the rigid portion 407. ing.
　第４の実施の形態に係る軸芯４０９は、捲回軸Ｘ方向に沿う溝が剛体部４０７の周方向に等間隔に設けられている。各溝には、帯状の弾性部４０８が嵌合されている。このような、第４の実施の形態によれば、第３の実施の形態と同様の作用効果を得ることができる。 In the shaft core 409 according to the fourth embodiment, grooves along the winding axis X direction are provided at equal intervals in the circumferential direction of the rigid portion 407. A belt-like elastic portion 408 is fitted in each groove. According to such 4th Embodiment, the effect similar to 3rd Embodiment can be acquired.
－第５の実施の形態－
　図１１～図１４を参照して第５の実施の形態に係る二次電池５００について説明する。図中、第１の実施の形態と同一または相当部分には同一符号を付し、相違点について主に説明する。図１１は第５の実施の形態に係る二次電池５００の外観斜視図であり、図１２は第５の実施の形態に係る二次電池５００の構成を示す分解斜視図である。 -Fifth embodiment-
A secondary battery 500 according to the fifth embodiment will be described with reference to FIGS. In the figure, the same or corresponding parts as those in the first embodiment are denoted by the same reference numerals, and differences will be mainly described. FIG. 11 is an external perspective view of a secondary battery 500 according to the fifth embodiment, and FIG. 12 is an exploded perspective view showing the configuration of the secondary battery 500 according to the fifth embodiment.
　第１～第４の実施の形態では、本発明を円筒形二次電池に適用した例について説明した。これに対して、第５の実施の形態では、本発明を角形二次電池に適用した例について説明する。 In the first to fourth embodiments, examples in which the present invention is applied to a cylindrical secondary battery have been described. In contrast, in the fifth embodiment, an example in which the present invention is applied to a prismatic secondary battery will be described.
　図１１に示すように、二次電池５００は、扁平な直方体形状であって、電池缶５０１と電池蓋５０２とからなる電池容器を備えている。電池缶５０１および電池蓋５０２の材質は、アルミニウムまたはアルミニウム合金などである。 As shown in FIG. 11, the secondary battery 500 has a flat rectangular parallelepiped shape, and includes a battery container including a battery can 501 and a battery lid 502. The material of the battery can 501 and the battery lid 502 is aluminum or an aluminum alloy.
　図１２に示すように、電池缶５０１には電池蓋組立体５２０に保持された捲回電極群５０４が収容されている。電池蓋組立体５２０は、正極外部端子５５０および負極外部端子５６０、ならびに正極集電体５０５および負極集電体５０６が電池蓋５０２に取り付けられることで形成される。 As shown in FIG. 12, the battery can 501 accommodates a wound electrode group 504 held by the battery lid assembly 520. The battery cover assembly 520 is formed by attaching the positive electrode external terminal 550 and the negative electrode external terminal 560, and the positive electrode current collector 505 and the negative electrode current collector 506 to the battery cover 502.
　電池缶５０１は一端が開口された矩形箱状に形成されている。捲回電極群５０４は絶縁シート（不図示）に覆われた状態で電池缶５０１に収容されている。絶縁シート（不図示）の材質は、ポリプロピレンやポリエチレンテレフタレート等の絶縁性を有する樹脂である。これにより、電池缶５０１の底面および側面と、捲回電極群５０４とは電気的に絶縁されている。 The battery can 501 is formed in a rectangular box shape with one end opened. The wound electrode group 504 is accommodated in the battery can 501 while being covered with an insulating sheet (not shown). The material of the insulating sheet (not shown) is an insulating resin such as polypropylene or polyethylene terephthalate. Thereby, the bottom and side surfaces of the battery can 501 and the wound electrode group 504 are electrically insulated.
　図１１および図１２に示すように、電池蓋５０２は、矩形平板状であって、電池缶５０１の開口を塞ぐようにレーザ溶接されている。つまり、電池蓋５０２は、電池缶５０１を封止している。電池蓋５０２には、注液部５１１が設けられている。注液部５１１には、電池容器内に電解液を注入するための注液孔が穿設されている。注液孔は、電解液注入後に注液栓によって封止される。 As shown in FIGS. 11 and 12, the battery lid 502 has a rectangular flat plate shape and is laser-welded so as to close the opening of the battery can 501. That is, the battery lid 502 seals the battery can 501. The battery lid 502 is provided with a liquid injection part 511. The liquid injection part 511 has a liquid injection hole for injecting an electrolytic solution into the battery container. The liquid injection hole is sealed with a liquid injection plug after the electrolyte is injected.
　電池蓋５０２の表面には、安全弁（ガス排出弁）５２３が凹設されている。安全弁５２３は、内圧作用時の応力集中度合が相対的に高くなるように、プレス加工によって電池蓋５０２を部分的に薄肉化することで形成されている。安全弁５２３には彫り込み等の脆弱部が設けられている。 A safety valve (gas discharge valve) 523 is recessed on the surface of the battery lid 502. The safety valve 523 is formed by partially thinning the battery lid 502 by press work so that the degree of stress concentration during internal pressure action is relatively high. The safety valve 523 is provided with a weak portion such as an engraving.
　図１２に示すように、電池蓋５０２には、捲回電極群５０４の正極電極５４１および負極電極５４２のそれぞれと電気的に接続された正極外部端子５５０および負極外部端子５６０が配設されている。 As shown in FIG. 12, the battery lid 502 is provided with a positive external terminal 550 and a negative external terminal 560 that are electrically connected to the positive electrode 541 and the negative electrode 542 of the wound electrode group 504, respectively. .
　正極外部端子５５０および負極外部端子５６０は、それぞれ電池缶５０１内に配設される正極集電体５０５および負極集電体５０６にかしめにより接続されている。なお、正極外部端子５５０、正極集電体５０５、負極外部端子５６０および負極集電体５０６は、それぞれ絶縁部材によって電池蓋５０２と電気的に絶縁されている。 The positive external terminal 550 and the negative external terminal 560 are connected to the positive current collector 505 and the negative current collector 506 disposed in the battery can 501 by caulking, respectively. The positive electrode external terminal 550, the positive electrode current collector 505, the negative electrode external terminal 560, and the negative electrode current collector 506 are electrically insulated from the battery lid 502 by an insulating member.
　正極外部端子５５０が正極集電体５０５を介して捲回電極群５０４の正極電極５４１に電気的に接続され、負極外部端子５６０が負極集電体５０６を介して捲回電極群５０４の負極電極５４２に電気的に接続されている。このため、正極外部端子５５０および負極外部端子５６０を介して外部負荷に電力が供給される。あるいは、正極外部端子５５０および負極外部端子５６０を介して外部発電電力が捲回電極群５０４に供給されて充電される。 The positive electrode external terminal 550 is electrically connected to the positive electrode 541 of the wound electrode group 504 via the positive electrode current collector 505, and the negative electrode external terminal 560 is connected to the negative electrode of the wound electrode group 504 via the negative electrode current collector 506. 542 is electrically connected. For this reason, electric power is supplied to the external load via the positive external terminal 550 and the negative external terminal 560. Alternatively, external generated power is supplied to the wound electrode group 504 through the positive external terminal 550 and the negative external terminal 560 and charged.
　図１３は、第５の実施の形態に係る捲回電極群５０４を示す斜視図および側面模式図である。便宜上、図１１に示すように、縦置きされた状態の二次電池５００の姿勢を基準に上下方向を規定し、以下、捲回電極群５０４について説明する。なお、図１３（ａ）では、分かりやすいように軸芯５０９の剛体部５０７にハッチングを施している。 FIG. 13 is a perspective view and a schematic side view showing a wound electrode group 504 according to the fifth embodiment. For convenience, as shown in FIG. 11, the vertical direction is defined based on the orientation of the secondary battery 500 in a vertically placed state, and the wound electrode group 504 will be described below. In FIG. 13A, the rigid portion 507 of the shaft core 509 is hatched for easy understanding.
　図１３（ａ）に示すように、捲回電極群５０４は、長尺状の正極電極５４１および負極電極５４２をセパレータ１４３を介在させて、軸芯５０９の周りに扁平形状に捲回することで積層構造とされている。なお、電極およびセパレータ１４３は、電極およびセパレータ１４３に対して張力を付与した状態で軸芯５０９を捲回軸Ｘを中心に回転させることで、軸芯５０９の周りに捲回される。 As shown in FIG. 13A, the wound electrode group 504 is formed by winding a long positive electrode 541 and a negative electrode 542 in a flat shape around an axis 509 with a separator 143 interposed therebetween. It is a laminated structure. The electrode and separator 143 is wound around the shaft core 509 by rotating the shaft core 509 about the winding axis X in a state where tension is applied to the electrode and separator 143.
　捲回電極群５０４の幅方向（捲回方向に直交する捲回軸Ｘ方向）の両端部は、それぞれ合剤未処理部とされている。捲回電極群５０４の幅方向の一端部は、正極合剤層１４７が形成されていない未塗工部（正極箔１４５の露出部）が積層された部分とされている。捲回電極群５０４の幅方向の他端部は、負極合剤層１４８が形成されていない未塗工部（負極箔１４６の露出部）が積層された部分とされている。正極未塗工部の積層体および負極未塗工部の積層体は、図１２に示すように、それぞれ予め押し潰され、それぞれ電池蓋組立体５２０の正極集電体５０５および負極集電体５０６と超音波溶接される。 Both end portions of the wound electrode group 504 in the width direction (winding axis X direction orthogonal to the winding direction) are respectively unmixed portions. One end portion in the width direction of the wound electrode group 504 is a portion where an uncoated portion (exposed portion of the positive foil 145) where the positive electrode mixture layer 147 is not formed is laminated. The other end portion in the width direction of the wound electrode group 504 is a portion where an uncoated portion (exposed portion of the negative electrode foil 146) where the negative electrode mixture layer 148 is not formed is laminated. As shown in FIG. 12, the laminate of the positive electrode uncoated portion and the laminate of the negative electrode uncoated portion are crushed in advance, respectively, and the positive electrode current collector 505 and the negative electrode current collector 506 of the battery lid assembly 520, respectively. And ultrasonically welded.
　図１３（ｂ）に示すように、捲回電極群５０４の外形形状は、上端部に設けられた側面視半円状の上部湾曲部５１４Ｕと、下端部に設けられた側面視半円状の下部湾曲部５１４Ｌと、両湾曲部の間に設けられた直方体形状の平坦部５１５Ｐとで規定される扁平形状とされている。なお、上部湾曲部５１４Ｕおよび下部湾曲部５１４Ｌは略同じ構成であり、両者を総称して湾曲部５１４とも記す。 As shown in FIG. 13B, the outer shape of the wound electrode group 504 has a semicircular upper curved portion 514U provided in the upper end portion and a semicircular view in the side view provided in the lower end portion. The flat shape is defined by the lower curved portion 514L and a rectangular parallelepiped flat portion 515P provided between the curved portions. The upper bending portion 514U and the lower bending portion 514L have substantially the same configuration, and both are collectively referred to as a bending portion 514.
　図１４（ａ）は第５の実施の形態に係る軸芯５０９を示す斜視図であり、図１４（ｂ）は長辺部５０９Ｌに設けられた弾性部５０８を示す拡大断面模式図である。図１５は、第５の実施の形態に係る二次電池５００の内部構造を示す断面模式図である。図１４（ａ）に示すように、軸芯５０９は、矩形平板状の剛体部５０７と、円柱状の弾性部５０８を２つ備えている。剛体部５０７は、互いに対向する一対の長辺部５０９Ｌと、互いに対向する一対の短辺部５０９Ｓとを有している。 FIG. 14A is a perspective view showing an axis 509 according to the fifth embodiment, and FIG. 14B is an enlarged schematic cross-sectional view showing an elastic part 508 provided on the long side part 509L. FIG. 15 is a schematic cross-sectional view showing the internal structure of the secondary battery 500 according to the fifth embodiment. As shown in FIG. 14A, the shaft core 509 includes a rectangular flat plate-shaped rigid body portion 507 and two columnar elastic portions 508. The rigid body portion 507 has a pair of long side portions 509L facing each other and a pair of short side portions 509S facing each other.
　一対の長辺部５０９Ｌは捲回軸Ｘに平行に延在し、一対の短辺部５０９Ｓは捲回軸Ｘに直交して延在している。第５の実施の形態では、一対の長辺部５０９Ｌのそれぞれに弾性部５０８が設けられている。 The pair of long side portions 509L extend in parallel to the winding axis X, and the pair of short side portions 509S extend perpendicular to the winding axis X. In the fifth embodiment, an elastic portion 508 is provided in each of the pair of long side portions 509L.
　図１４（ａ）および図１４（ｂ）に示すように、長辺部５０９Ｌは、断面半円弧状の凹面５０７ａを有している。弾性部５０８は、円柱状であり、剛体部５０７側の半円部分が長辺部５０９Ｌの凹面５０７ａに嵌合され、反対側の半円部分が凹面５０７ａの開口面から外方に突出している。 As shown in FIGS. 14 (a) and 14 (b), the long side portion 509L has a concave surface 507a having a semicircular cross section. The elastic portion 508 has a columnar shape, a semicircular portion on the rigid body portion 507 side is fitted to the concave surface 507a of the long side portion 509L, and an opposite semicircular portion protrudes outward from the opening surface of the concave surface 507a. .
　図１５に示すように、弾性部５０８は、捲回電極群５０４の湾曲部５１４における最内周のセパレータ１４３と剛体部５０７の凹面５０７ａとの間に配置され、捲回電極群５０４によって捲回軸Ｘに向かって押圧されている。 As shown in FIG. 15, the elastic portion 508 is disposed between the innermost separator 143 and the concave surface 507 a of the rigid portion 507 in the curved portion 514 of the wound electrode group 504, and is wound by the wound electrode group 504. It is pressed toward the axis X.
　このように、第５の実施の形態に係る二次電池５００は、平坦部５１５Ｐおよび湾曲部５１４を有する扁平渦巻き状に捲回された捲回電極群５０４を備えている。ところで、このように扁平渦巻き状に捲回された捲回電極群を備える二次電池では、充電時に活物質が膨張し、電極が膨張しようとした際、電極の膨張力の他に次のような力が金属箔に作用する。捲回電極群５０４において、平坦部５１５Ｐに比べて曲率が大きい湾曲部５１４では、金属箔（正極箔および負極箔）に対して作用する周方向への引張力が平坦部５１５Ｐに比べて大きい。 Thus, the secondary battery 500 according to the fifth embodiment includes the wound electrode group 504 wound in a flat spiral shape having the flat portion 515P and the curved portion 514. By the way, in the secondary battery including the wound electrode group wound in a flat spiral shape as described above, when the active material expands during charging and the electrode tries to expand, in addition to the expansion force of the electrode, the following is performed. Force acts on the metal foil. In the wound electrode group 504, the bending portion 514 having a larger curvature than the flat portion 515P has a larger tensile force in the circumferential direction acting on the metal foil (positive foil and negative foil) than the flat portion 515P.
　このため、湾曲部５１４を構成する電極やセパレータにおける空隙を潰すように作用する力は、平坦部５１５Ｐを構成する電極やセパレータにおける空隙を潰すように作用する力に比べて大きくなる。つまり、湾曲部５１４では、平坦部５１５Ｐに比べて電解液が枯渇しやすい。 For this reason, the force acting so as to crush the gaps in the electrodes and separators constituting the curved part 514 is larger than the force acting so as to crush the gaps in the electrodes and separators constituting the flat part 515P. That is, in the curved portion 514, the electrolyte is more easily depleted than the flat portion 515P.
　本実施の形態では、上述したように、湾曲部５１４における最内周のセパレータ１４３と剛体部５０７との間に、剛体部５０７を構成する樹脂材料よりも弾性率が低い樹脂材料から成る弾性部５０８が配置されている。 In the present embodiment, as described above, between the innermost separator 143 and the rigid portion 507 in the curved portion 514, the elastic portion made of a resin material having a lower elastic modulus than the resin material constituting the rigid portion 507. 508 is arranged.
　このような第５の実施の形態によれば、第１の実施の形態で説明した（１）と同様、電解液の枯渇が大きくなりやすい湾曲部５１４に弾性部５０８を配置したので、活物質の膨張により発生した力を弾性部５０８が圧縮変形することによって吸収することができる。これにより、電極の空隙やセパレータの空隙が潰されることを抑制し、充放電に伴う捲回電極群５０４の電解液の枯渇を抑制することができる。 According to the fifth embodiment, since the elastic portion 508 is arranged in the curved portion 514 where the electrolyte solution is likely to be exhausted as in (1) described in the first embodiment, the active material The force generated by the expansion of the elastic portion 508 can be absorbed by the elastic portion 508 compressively deforming. Thereby, it can suppress that the space | gap of an electrode and the space | gap of a separator are crushed, and can suppress the depletion of the electrolyte solution of the winding electrode group 504 accompanying charging / discharging.
　さらに、第５の実施の形態によれば、第１の実施の形態で説明した（２）～（４）に加えて、次の作用効果を得ることができる。
（１０）弾性部５０８よりも弾性率の高い矩形平板状の剛体部５０７を設けた。これにより、金属箔（正極箔および負極箔）に対して周方向に引張られる力が作用した場合の捲回電極群５０４の変形を抑制し、捲回電極群５０４の形状を保持することができる。 Furthermore, according to the fifth embodiment, in addition to (2) to (4) described in the first embodiment, the following operational effects can be obtained.
(10) A rectangular flat plate-like rigid body portion 507 having a higher elastic modulus than the elastic portion 508 is provided. Thereby, the deformation | transformation of the winding electrode group 504 when the force pulled in the circumferential direction with respect to metal foil (positive electrode foil and negative electrode foil) can be suppressed, and the shape of the winding electrode group 504 can be maintained. .
　次のような変形も本発明の範囲内であり、変形例の一つ、もしくは複数を上述の実施形態と組み合わせることも可能である。
（変形例１－１）
　図１６は、変形例に係る軸芯を示す斜視図であり、分かりやすいように弾性部５０８Ａ，５０８Ｂ，５０８Ｃにハッチングを施している。第５の実施の形態の弾性部５０８に代えて、図１６（ａ）に示すように、円柱状の剛体部５９７Ａと、剛体部５９７Ａにおける捲回軸Ｘ方向中央部を覆うように設けられた弾性部５０８Ａとから成る中間部材５９０Ａを設ける構成としてもよい。このような変形例によれば、第５の実施の形態と同様の作用効果に加え、第２の実施の形態と同様の作用効果を奏する。 The following modifications are also within the scope of the present invention, and one or a plurality of modifications can be combined with the above-described embodiment.
(Modification 1-1)
FIG. 16 is a perspective view showing the shaft core according to the modification, and the elastic portions 508A, 508B, and 508C are hatched for easy understanding. Instead of the elastic portion 508 of the fifth embodiment, as shown in FIG. 16A, a cylindrical rigid body portion 597A and a central portion in the winding axis X direction of the rigid body portion 597A are provided. An intermediate member 590A including the elastic portion 508A may be provided. According to such a modification, in addition to the same effects as the fifth embodiment, the same effects as the second embodiment are achieved.
（変形例１－２）
　変形例１－１の中間部材５９０Ａに代えて、図１６（ｂ）に示すように、剛体部５９７Ｂの露出部と、弾性部５０８Ｂによる被覆部とを捲回軸Ｘ方向に交互に設けた中間部材５９０Ｂを採用してもよい。換言すれば、最内周のセパレータ１４３と剛体部５９７Ａとが直接接する部分が、捲回軸Ｘ方向に離間して複数形成されていてもよい。このような変形例によれば、第５の実施の形態と同様の作用効果に加え、第３の実施の形態と同様の作用効果を奏する。 (Modification 1-2)
In place of the intermediate member 590A of the modified example 1-1, as shown in FIG. 16B, an intermediate portion in which the exposed portion of the rigid portion 597B and the covering portion by the elastic portion 508B are alternately provided in the winding axis X direction. The member 590B may be employed. In other words, a plurality of portions where the innermost separator 143 and the rigid body portion 597A are in direct contact with each other may be formed apart from each other in the winding axis X direction. According to such a modification, in addition to the same operational effects as the fifth embodiment, the same operational effects as the third embodiment are achieved.
（変形例１－３）
　変形例１－１の中間部材５９０Ａに代えて、図１６（ｃ）に示すように、剛体部５９７Ｃの露出部と、弾性部５０８Ｃによる被覆部とを円柱状の剛体部５９７Ｃの周方向に交互に設けた中間部材５９０Ｃを採用してもよい。換言すれば、最内周のセパレータ１４３と剛体部５９７Ｃとが直接接する部分が、剛体部５９７Ｃの周方向に離間して複数形成されていてもよい。このような変形例によれば、第５の実施の形態と同様の作用効果に加え、第４の実施の形態と同様の作用効果を奏する。 (Modification 1-3)
Instead of the intermediate member 590A of the modified example 1-1, as shown in FIG. 16C, the exposed portion of the rigid body portion 597C and the covering portion by the elastic portion 508C are alternately arranged in the circumferential direction of the cylindrical rigid body portion 597C. An intermediate member 590 </ b> C provided in the above may be employed. In other words, a plurality of portions where the innermost separator 143 and the rigid body portion 597C are in direct contact with each other may be formed apart from each other in the circumferential direction of the rigid body portion 597C. According to such a modification, in addition to the same operational effects as the fifth embodiment, the same operational effects as the fourth embodiment are exhibited.
（変形例２）
　第５の実施の形態では弾性部５０８を円柱状とする例について説明し、変形例１－１～１－３では、中間部材５９０Ａ～５９０Ｃ（以下、総称して中間部材５９０と記す）を円柱状とする例について説明したが、本発明はこれに限定されない。弾性部５０８や中間部材５９０の形状としては、たとえば、半円柱状（図１７（ａ）参照）、矩形柱状（図１７（ｂ）参照）など、種々の形状を採用することができる。なお、本明細書において、円柱状や半円柱状、矩形柱状とは、完全な円柱状や半円柱状、矩形柱状に限らず、これとほぼ同一で、本願発明の効果を奏するような略円柱状や略半円柱状、略矩形柱状を含む。 (Modification 2)
In the fifth embodiment, an example in which the elastic portion 508 is formed in a columnar shape will be described. In the modified examples 1-1 to 1-3, the intermediate members 590A to 590C (hereinafter collectively referred to as the intermediate member 590) are circular. Although the columnar example has been described, the present invention is not limited to this. As the shape of the elastic portion 508 and the intermediate member 590, various shapes such as a semi-cylindrical shape (see FIG. 17A) and a rectangular column shape (see FIG. 17B) can be adopted. In the present specification, the columnar shape, the semi-cylindrical shape, and the rectangular columnar shape are not limited to a complete columnar shape, a semi-cylindrical shape, and a rectangular columnar shape. Includes a columnar shape, a substantially semi-cylindrical shape, and a substantially rectangular columnar shape.
（変形例３）
　上述した実施の形態、たとえば第１の実施の形態では、１層の弾性部１０８が直接最内周のセパレータ１４３に接する例について説明したが、本発明はこれに限定されない。弾性部１０８は複数層設けてもよい。この場合、各弾性部１０８は、いずれも剛体部１０７の樹脂材料の弾性率よりも低い樹脂材料で形成される。弾性部１０８を複数層設ける場合、最も内側の弾性部１０８が剛体部１０７に直接接触し、最も外側の弾性部１０８がセパレータ１４３に直接接触する。 (Modification 3)
In the above-described embodiment, for example, the first embodiment, the example in which the elastic layer 108 of one layer is in direct contact with the innermost separator 143 has been described, but the present invention is not limited to this. A plurality of elastic portions 108 may be provided. In this case, each elastic portion 108 is formed of a resin material lower than the elastic modulus of the resin material of the rigid portion 107. When a plurality of elastic portions 108 are provided, the innermost elastic portion 108 is in direct contact with the rigid portion 107 and the outermost elastic portion 108 is in direct contact with the separator 143.
（変形例４）
　第２の実施の形態では、軸芯２０９にセパレータ１４３および電極が捲回される前の状態において、凹部２０７ａの開口面から弾性部２０８の外周面が径方向外側に突出する例について説明したが本発明はこれに限定されない。凹部２０７ａの開口面よりも径方向内側に弾性部２０８の外周面が位置していてもよい。少なくとも、捲回された最内周のセパレータ１４３が弾性部２０８に接する構成であればよい。なお、形状保持性の向上の観点から、軸芯２０９にセパレータ１４３および電極が捲回される前の状態において、弾性部２０８の外周面を凹部２０７ａの開口面に位置させる、あるいは凹部２０７ａの開口面よりも径方向外側に弾性部２０８の外周面を位置させることが好ましい。 (Modification 4)
In the second embodiment, an example has been described in which the outer peripheral surface of the elastic portion 208 protrudes radially outward from the opening surface of the recess 207a before the separator 143 and the electrode are wound around the shaft core 209. The present invention is not limited to this. The outer peripheral surface of the elastic portion 208 may be located radially inward from the opening surface of the recess 207a. It is sufficient that at least the wound innermost separator 143 is in contact with the elastic portion 208. From the viewpoint of improving shape retention, the outer peripheral surface of the elastic portion 208 is positioned on the opening surface of the recess 207a before the separator 143 and the electrode are wound around the shaft core 209, or the opening of the recess 207a. It is preferable that the outer peripheral surface of the elastic portion 208 be positioned radially outward from the surface.
（変形例５）
　正極活物質としてマンガン酸リチウム、負極活物質として黒鉛をそれぞれ例示したが、本発明はこれに限定されない。正極活物質としては、リチウムイオンを挿入・脱離可能な材料であり、予め十分な量のリチウムイオンを挿入したリチウム遷移金属複合酸化物を用いればよい。また、正極活物質としては、リチウム遷移金属複合酸化物の結晶中のリチウムや遷移金属の一部をそれら以外の元素で置換あるいはドープした材料を使用してもよい。結晶構造についても特に制限はなく、スピネル系、層状系、オリビン系のいずれの結晶構造を有していてもよい。一方、負極活物質としては、リチウムイオンを挿入、脱離可能な非晶質炭素やコークスなどの炭素質材料等を用いてもよい。ＳｉＯやＳｉ合金などもリチウムイオンを挿入・脱離可能な材料として挙げられる。これらの材料を混合したものでもよく、混合配合比についても限定されない。粒子形状においても、鱗片状、球状、繊維状、塊状等、特に制限されるものではない。 (Modification 5)
Although lithium manganate was exemplified as the positive electrode active material and graphite was exemplified as the negative electrode active material, the present invention is not limited thereto. The positive electrode active material is a material capable of inserting and removing lithium ions, and a lithium transition metal composite oxide into which a sufficient amount of lithium ions has been inserted in advance may be used. Further, as the positive electrode active material, a material obtained by substituting or doping lithium in the crystal of the lithium transition metal composite oxide or a part of the transition metal with an element other than those may be used. The crystal structure is not particularly limited, and may have any crystal structure of spinel, layered, or olivine. On the other hand, as the negative electrode active material, a carbonaceous material such as amorphous carbon or coke in which lithium ions can be inserted and removed may be used. SiO, Si alloy, and the like can also be cited as materials capable of inserting and removing lithium ions. A mixture of these materials may be used, and the mixing ratio is not limited. The particle shape is not particularly limited, such as a scale shape, a spherical shape, a fiber shape, or a lump shape.
（変形例６）
　上述した実施の形態では、正負極活物質合剤の結着剤としてＰＶＤＦを用いる場合について例示したが、本発明はこれに限定されない。結着剤として、ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリエチレン、ポリスチレン、ポリブタジエン、ブチルゴム、ニトリルゴム、スチレン／ブタジエンゴム、多硫化ゴム、ニトロセルロース、シアノエチルセルロース、各種ラテックス、アクリロニトリル、フッ化ビニル、フッ化ビニリデン、フッ化プロピレン、フッ化クロロプレンなどの重合体およびこれらの混合体などを用いることができる。 (Modification 6)
In the embodiment described above, the case where PVDF is used as the binder of the positive and negative electrode active material mixture is exemplified, but the present invention is not limited to this. Binders include polytetrafluoroethylene (PTFE), polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene / butadiene rubber, polysulfide rubber, nitrocellulose, cyanoethyl cellulose, various latexes, acrylonitrile, vinyl fluoride, and fluoride. Polymers such as vinylidene, propylene fluoride, and chloroprene fluoride, and mixtures thereof can be used.
（変形例７）
　上述した実施の形態では、非水電解液として、エチレンカーボネート（ＥＣ）、ジメチルカーボネート（ＤＭＣ）、エチルメチルカーボネート（ＥＭＣ）の混合溶液中に六フッ化リン酸リチウム（ＬｉＰＦ６）を溶解した非水電解液を例示したが、本発明はこれに限定されない。一般的なリチウム塩を電解質とし、これを有機溶媒に溶解した非水電解液であればよい。たとえば、電解質としては、ＬｉＣｌＯ４、ＬｉＡｓＦ６、ＬｉＢＦ４、ＬｉＢ（Ｃ６Ｈ５）４、ＣＨ３ＳＯ３Ｌｉ、ＣＦ３ＳＯ３Ｌｉ等やこれらの混合物を用いることができる。また、有機溶媒としては、プロピレンカーボネート、エチレンカーボネート、１，２－ジメトキシエタン、１，２－ジエトキシエタン、γ－ブチロラクトン、テトラヒドロフラン、１，３－ジオキソラン、４－メチル－１，３－ジオキソラン、ジエチルエーテル、スルホラン、メチルスルホラン、アセトニトリル、プロピオニトニル等またはこれら２種類以上の混合溶媒を用いるようにしてもよく、混合配合比についても限定されない。 (Modification 7)
In the above-described embodiment, a nonaqueous electrolyte solution is obtained by dissolving lithium hexafluorophosphate (LiPF 6 ) in a mixed solution of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC). Although the water electrolyte was illustrated, the present invention is not limited to this. Any nonaqueous electrolytic solution in which a general lithium salt is used as an electrolyte and dissolved in an organic solvent may be used. For example, as the electrolyte, LiClO 4 , LiAsF 6 , LiBF 4 , LiB (C 6 H 5 ) 4 , CH 3 SO 3 Li, CF 3 SO 3 Li, or a mixture thereof can be used. Examples of the organic solvent include propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, Diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propiontonyl, etc., or a mixed solvent of two or more of these may be used, and the mixing ratio is not limited.
（変形例８－１）
　第１～第４の実施の形態では、中空円柱状（円筒状）の剛体部１０７，２０７，３０７，４０７を例に説明したが、中実円柱状の剛体部としてもよいし、楕円柱状の剛体部にも本発明を適用することができる。なお、本明細書において、円柱状や楕円柱状とは、完全な円柱状や楕円柱状に限らず、これとほぼ同一で、本願発明の効果を奏するような略円柱状や略楕円柱状を含む。 (Modification 8-1)
In the first to fourth embodiments, the hollow columnar (cylindrical) rigid body portions 107, 207, 307, and 407 have been described as examples. However, a solid columnar rigid body portion or an elliptical columnar rigid body portion may be used. The present invention can also be applied to a rigid part. In the present specification, the columnar shape and the elliptical columnar shape are not limited to the complete columnar shape and the elliptical columnar shape, but are substantially the same, and include a substantially cylindrical shape and a substantially elliptical columnar shape that exhibit the effects of the present invention.
（変形例８－２）
　第５の実施の形態では、矩形平板状の剛体部５０７を例に説明したが、本発明はこれに限定されない。扁平楕円柱状の剛体部５０７（図１７（ｃ）参照）にも本発明を適用することができる。なお、本明細書において、矩形平板状や扁平楕円柱状とは、完全な矩形平板状や扁平楕円柱状に限らず、これとほぼ同一で、本願発明の効果を奏するような略矩形平板状や略扁平楕円柱状を含む。 (Modification 8-2)
In the fifth embodiment, the rectangular flat plate-like rigid body portion 507 has been described as an example, but the present invention is not limited to this. The present invention can also be applied to a flat elliptical columnar rigid body portion 507 (see FIG. 17C). In the present specification, the rectangular flat plate shape and the flat elliptical columnar shape are not limited to the complete rectangular flat plate shape and the flat elliptical columnar shape, but are substantially the same and substantially the same as the rectangular flat plate shape or the substantially flat plate shape that exhibits the effect of the present invention. Includes a flat elliptical columnar shape.
（変形例９）
　第１の実施の形態では円柱状の剛体部１０７の略全体を覆う弾性部１０８について説明し、第２の実施の形態では円柱状の剛体部２０７の中央部を覆う弾性部２０８について説明した。第３および第４の実施の形態では、円柱状の剛体部３０７，４０７の露出部と弾性部３０８，４０８によって覆われる被覆部とが交互に配置される例について説明した。円筒形二次電池が備える軸芯において、弾性部はこれらの形状に限定されない。円柱状の剛体部１０７における外周面の少なくとも一部に弾性部１０８が配置されている構成であればよく、たとえば、格子状（図１７（ｄ）参照）やマトリクス状（図１７（ｅ）参照）に設けてもよい。 (Modification 9)
In the first embodiment, the elastic portion 108 that covers substantially the entire cylindrical rigid body portion 107 has been described, and in the second embodiment, the elastic portion 208 that covers the central portion of the cylindrical rigid body portion 207 has been described. In the third and fourth embodiments, the example in which the exposed portions of the cylindrical rigid body portions 307 and 407 and the covering portions covered by the elastic portions 308 and 408 are alternately arranged has been described. In the shaft core provided in the cylindrical secondary battery, the elastic portion is not limited to these shapes. Any configuration may be used as long as the elastic portion 108 is disposed on at least a part of the outer peripheral surface of the cylindrical rigid body portion 107. For example, a lattice shape (see FIG. 17D) or a matrix shape (see FIG. 17E). ).
（変形例１０）
　上述した実施の形態では、リチウムイオン二次電池を一例として説明したが、ニッケル水素電池など、その他の二次電池にも本発明を適用できる。 (Modification 10)
In the above-described embodiment, the lithium ion secondary battery has been described as an example, but the present invention can also be applied to other secondary batteries such as a nickel metal hydride battery.
　上記では、種々の実施の形態および変形例を説明したが、本発明はこれらの内容に限定されるものではない。本発明の技術的思想の範囲内で考えられるその他の態様も本発明の範囲内に含まれる。 Although various embodiments and modifications have been described above, the present invention is not limited to these contents. Other embodiments conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.
　１００　二次電池、１０１　電池缶、１０２　電池蓋、１０４　捲回電極群、１０５　正極集電リング、１０６　負極集電リング、１０７　剛体部、１０８　弾性部、１０９　軸芯、１０９ａ　溝、１０９ｂ　段部、１２０　電池蓋ユニット、１２２　ケース、１２３　安全弁、１２４　弁押え部材、１２９　ガスケット、１４１　正極電極、１４２　負極電極、１４３　セパレータ、１４３ａ　第１セパレータ、１４３ｂ　第２セパレータ、１４５　正極箔、１４５ｔ　正極タブ、１４６　負極箔、１４６ｔ　負極タブ、１４７　正極合剤層、１４８　負極合剤層、１５１　上部筒部、１５２　下部筒部、１５９　正極リード板、１６１　外周筒部、１６２　内周筒部、１６８　スペーサ、１６９　負極リード板、１６９ａ　円形凹部、１６９ｂ　フランジ、２００　二次電池、２０７　剛体部、２０７ａ　凹部、２０７ｌ　大径部、２０７ｓ　小径部、２０８　弾性部、２０９　軸芯、３０７　剛体部、３０８　弾性部、３０９　軸芯、４０７　剛体部、４０８　弾性部、４０９　軸芯、５００　二次電池、５０１　電池缶、５０２　電池蓋、５０４　捲回電極群、５０５　正極集電体、５０６　負極集電体、５０７　剛体部、５０７ａ　凹面、５０８　弾性部、５０９　軸芯、５０９Ｌ　長辺部、５０９Ｓ　短辺部、５１１　注液部、５１４　湾曲部、５１４Ｌ　下部湾曲部、５１４Ｕ　上部湾曲部、５１５Ｐ　平坦部、５２０　電池蓋組立体、５２３　安全弁、５４１　正極電極、５４２　負極電極、５５０　正極外部端子、５６０　負極外部端子、５９０　中間部材、５９７Ａ，５９７Ｂ，５９７Ｃ　剛体部、９００　二次電池、９０４　捲回電極群、９０８　弾性部、９０９　軸芯 100 secondary battery, 101 battery can, 102 battery lid, 104 wound electrode group, 105 positive current collecting ring, 106 negative current collecting ring, 107 rigid body part, 108 elastic part, 109 elastic core, 109 axis, 109a groove, 109b step part, 120 battery lid unit, 122 case, 123 safety valve, 124 valve retainer, 129 gasket, 141 positive electrode, 142 negative electrode, 143 separator, 143a first separator, 143b second separator, 145 positive electrode foil, 145t positive electrode tab, 146 negative electrode Foil, 146t negative electrode tab, 147 positive electrode mixture layer, 148 negative electrode mixture layer, 151 upper cylinder part, 152 lower cylinder part, 159 positive electrode lead plate, 161 outer cylinder part, 162 inner cylinder part, 168 spacer, 169 negative electrode lead Plate, 169a circular recess, 69b flange, 200 secondary battery, 207 rigid body part, 207a concave part, 207l large diameter part, 207s small diameter part, 208 elastic part, 209 axial core, 307 rigid body part, 308 elastic part, 309 axial core, 407 rigid body part, 408 elastic Part, 409 shaft core, 500 secondary battery, 501 battery can, 502 battery cover, 504 wound electrode group, 505 positive electrode current collector, 506 negative electrode current collector, 507 rigid body part, 507a concave surface, 508 elastic part, 509 shaft Core, 509L long side, 509S short side, 511 liquid injection part, 514 bending part, 514L lower bending part, 514U upper bending part, 515P flat part, 520 battery lid assembly, 523 safety valve, 541 positive electrode, 542 negative electrode Electrode, 550 positive external terminal, 560 negative external terminal, 590 intermediate member, 97A, 597B, 597C rigid unit, 900 battery, 904 wound electrode group, 908 elastic portion, 909 axial

Claims (10)

  1. 　軸芯に電極およびセパレータを捲回した捲回電極群を有する二次電池であって、
    　前記軸芯は、樹脂から成る剛体部と、前記剛体部よりも弾性率が低い樹脂から成る弾性部とを有し、
    　前記弾性部は、最内周のセパレータと前記剛体部との間に配置されている二次電池。     A secondary battery having a wound electrode group in which an electrode and a separator are wound on an axis;
    The shaft core has a rigid part made of resin and an elastic part made of resin having a lower elastic modulus than the rigid body part,
    The elastic part is a secondary battery disposed between the innermost separator and the rigid part.
  2. 　請求項１に記載の二次電池において、
    　前記弾性部は、捲回電極群の湾曲部における最内周のセパレータに接している二次電池。     The secondary battery according to claim 1,
    The elastic part is a secondary battery in contact with the innermost separator in the curved part of the wound electrode group.
  3. 　請求項２に記載の二次電池において、
    　前記電極は正極電極および負極電極であり、前記弾性部は、少なくとも前記正極電極の合剤層における前記捲回電極群の捲回軸方向の領域に対向する位置に設けられている二次電池。     The secondary battery according to claim 2,
    The said electrode is a positive electrode and a negative electrode, The said elastic part is a secondary battery provided in the position facing the area | region of the winding axis direction of the said winding electrode group in the mixture layer of the said positive electrode at least.
  4. 　請求項３に記載の二次電池において、
    　前記弾性部は、前記捲回電極群の捲回方向に沿う湾曲面を有し、前記湾曲面が前記最内周のセパレータに接している二次電池。     The secondary battery according to claim 3,
    The elastic portion has a curved surface along a winding direction of the wound electrode group, and the curved surface is in contact with the innermost separator.
  5. 　請求項４に記載の二次電池において、
    　前記剛体部は矩形平板状であり、
    　前記矩形平板状の剛体部において対向する一対の辺のそれぞれに前記弾性部が配置されている二次電池。     The secondary battery according to claim 4,
    The rigid part is a rectangular flat plate,
    A secondary battery in which the elastic portion is disposed on each of a pair of sides facing each other in the rectangular flat plate-like rigid body portion.
  6. 　請求項４に記載の二次電池において、
    　前記剛体部は円柱状であり、
    　前記円柱状の剛体部における外周面の少なくとも一部に前記弾性部が配置されている二次電池。     The secondary battery according to claim 4,
    The rigid part is cylindrical.
    A secondary battery in which the elastic portion is disposed on at least a part of an outer peripheral surface of the cylindrical rigid body portion.
  7. 　請求項５または６に記載の二次電池において、
    　前記捲回電極群の湾曲部における最内周のセパレータと前記剛体部とが直接接するように、前記剛体部の外周面の一部に前記弾性部が設けられている二次電池。     The secondary battery according to claim 5 or 6,
    The secondary battery in which the elastic portion is provided on a part of the outer peripheral surface of the rigid body portion so that the innermost separator in the curved portion of the wound electrode group and the rigid body portion are in direct contact with each other.
  8. 　請求項７に記載の二次電池において、
    　前記弾性部は、前記最内周のセパレータと前記剛体部とが直接接する部分が、前記捲回軸方向あるいは前記剛体部の周方向に、離間して複数形成されている二次電池。     The secondary battery according to claim 7,
    The elastic portion is a secondary battery in which a plurality of portions where the innermost separator and the rigid body portion are in direct contact are formed apart from each other in the winding axis direction or the circumferential direction of the rigid body portion.
  9. 　請求項７に記載の二次電池において、
    　前記弾性部は、前記剛体部における前記捲回電極群の捲回軸方向の中央部に配置され、前記剛体部における前記捲回軸方向の両端部の外周面は、前記最内周のセパレータに直接接している二次電池。     The secondary battery according to claim 7,
    The elastic portion is disposed at a central portion in the winding axis direction of the wound electrode group in the rigid body portion, and outer peripheral surfaces of both end portions in the winding axis direction of the rigid body portion are arranged on the innermost separator. Secondary battery in direct contact.
  10. 　請求項１ないし６のいずれか一項に記載の二次電池において、
    　前記弾性部の弾性率は、前記セパレータの弾性率および前記電極の合剤層の弾性率よりも低い二次電池。     The secondary battery according to any one of claims 1 to 6,
    The elastic modulus of the elastic portion is a secondary battery lower than the elastic modulus of the separator and the elastic modulus of the mixture layer of the electrode.
PCT/JP2016/060876 2015-04-28 2016-04-01 Secondary battery WO2016174992A1 (en)

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