JP6563008B2 - Secondary battery - Google Patents

Description

  The present invention relates to a secondary battery including a wound electrode group.

  For example, secondary batteries with large capacity (Wh) have been developed as power sources for hybrid electric vehicles and pure electric vehicles, and in particular, prismatic lithium ion secondary batteries with high energy density (Wh / kg) are of interest. Has been. Such a secondary battery is configured, for example, by enclosing an electrode group, in which a positive electrode plate and a negative electrode plate are wound with a separator interposed therebetween, together with an electrolytic solution in a battery outer package (for example, Patent Document 1 below). See).

  In Patent Document 1, as one of the causes of the internal short circuit of the nonaqueous secondary battery, when the electrode group is wound in a spiral shape, the positional relationship between the electrode plate and the separator is shifted, and the electrode plate is exposed. Is described. In Patent Document 1, the electrode plate and the separator are overlapped and wound around the core, and then wound in a spiral shape. Only the part remains in the core, and therefore, the electrode plate in the vicinity thereof is not covered with the separator, or the central part of the electrode group protrudes from the wound body, and the body does not form the electrode group Etc. are described.

  Patent Document 1 includes a positive electrode plate and a negative electrode plate having different surface friction coefficients as means for solving the above problems, and the positive electrode plate and the negative electrode plate are wound through separators having different friction coefficients on both sides. A battery electrode group comprising: a separator having a large friction coefficient surface wound so as to contact a positive electrode plate and a negative electrode plate having a larger surface friction coefficient. An electrode group is disclosed. According to Patent Document 1, the above configuration suppresses the electrode plate from being exposed due to the displacement of the separator during the production of the electrode group, and suppresses the dropping of the mixture layer when the electrode group is formed into a flat shape. It is described that it is possible to suppress a short circuit.

JP 2013-89441 A

  6 and 9 of Patent Document 1, the battery electrode group of Patent Document 1 has a portion in which only the separator is wound on the innermost periphery. Since there is neither a positive electrode plate nor a negative electrode plate in this portion, it is impossible to obtain a frictional force due to contact between the separator having a large friction coefficient and the positive electrode plate and the negative electrode plate having the larger surface friction coefficient. Therefore, the battery electrode group of Patent Literature 1 cannot prevent the separator from being displaced at a portion where only the innermost separator is wound when the electrode group is pulled out from the core, for example.

  This invention is made | formed in view of the said subject, and it aims at providing the secondary battery which can prevent the shift | offset | difference of the innermost separator of a winding electrode group.

  In order to achieve the object, the secondary battery of the present invention is a secondary battery including a wound electrode group in which an electrode is wound with a separator interposed therebetween, and is more than a starting end portion in the winding direction of the electrode. A fixing portion for fixing at least a part of the separator wound around the inner periphery is provided.

  According to the secondary battery of the present invention, the separator of the wound electrode group is displaced by including the fixing portion that fixes at least a part of the separator wound on the inner periphery from the start end in the winding direction of the electrode. Can be prevented.

1 is an external perspective view of a secondary battery according to Embodiment 1 of the present invention. The disassembled perspective view of the secondary battery shown in FIG. The disassembled perspective view of the winding electrode group of the secondary battery shown in FIG. The expanded sectional view of the wound electrode group which follows the IV-IV line shown in FIG. The expanded sectional view which shows the state by which the wound electrode group shown in FIG. 4 was wound by the winding core. The expanded sectional view of the wound electrode group which follows the VI-VI line shown in FIG. FIG. 7 is an enlarged cross-sectional view corresponding to FIG. 6 and showing a first modification of the fixing portion according to the first embodiment. FIG. 7 is an enlarged cross-sectional view corresponding to FIG. 6 and showing a second modification of the fixing portion according to the first embodiment. FIG. 6 is an enlarged cross-sectional view corresponding to FIG. 4 and showing a third modification of the fixing portion according to the first embodiment. The expanded sectional view of the winding electrode group corresponded in FIG. 4 of the secondary battery which concerns on Embodiment 2 of this invention. The expanded sectional view which shows the modification 1 of the fixing | fixed part of the winding electrode group shown in FIG. The expanded sectional view which shows the modification 2 of the fixing | fixed part of the winding electrode group shown in FIG.

  Embodiments of a secondary battery of the present invention will be described below with reference to the drawings.

[Embodiment 1]
First, Embodiment 1 of the secondary battery of the present invention will be described. FIG. 1 is an external perspective view of a secondary battery 100 according to Embodiment 1 of the present invention. FIG. 2 is an exploded perspective view of the secondary battery 100 shown in FIG.

  The secondary battery 100 of the present embodiment is a prismatic lithium ion secondary battery having a large capacity and high energy density, which is used as a power source for, for example, a hybrid electric vehicle or a pure electric vehicle. Although details will be described later, the secondary battery 100 according to the present embodiment includes at least a part of the separators 33 and 34 wound around the inner periphery of the winding start end 32B of the negative electrode 32 of the wound electrode group 30. The greatest feature is that a fixing portion 50 (see FIG. 4) for fixing is provided.

  The secondary battery 100 of the present embodiment is mainly accommodated in a flat rectangular battery container 10, a positive electrode external terminal 20 </ b> A and a negative electrode external terminal 20 </ b> B provided outside the battery container 10, and the battery container 10. The wound electrode group 30 includes a positive electrode current collector plate 40A and a negative electrode current collector plate 40B that connect the wound electrode group 30 to the positive electrode external terminal 20A and the negative electrode external terminal 20B. The positive electrode external terminal 20A and the negative electrode external terminal 20B, the wound electrode group 30, and the positive electrode current collector plate 40A and the negative electrode current collector plate 40B are attached to the battery container 10 by the gasket 1, the insulating plate 2, and the insulating protective film 3. It is electrically insulated.

  The battery container 10, the positive electrode external terminal 20A, and the positive electrode current collector plate 40A can be made of, for example, an aluminum alloy. Moreover, the negative electrode external terminal 20B and the negative electrode current collector plate 40B can be made of, for example, a copper alloy. In addition, the gasket 1 and the insulating plate 2 can be made of an insulating resin material such as polybutylene terephthalate, polyphenylene sulfide, or perfluoroalkoxy fluororesin. The insulating protective film 3 can be manufactured by a sheet of a synthetic resin such as PP (polypropylene) or a plurality of film members.

  In the secondary battery 100 of the present embodiment, the positive electrode side and the negative electrode side, for example, the positive electrode external terminal 20A and the negative electrode external terminal 20B, and the positive electrode current collector plate 40A and the negative electrode current collector plate 40B are arranged in the width direction of the secondary battery 100. It has a configuration that is generally in contrast to the centerline at W. Therefore, in the following, regarding the configuration common to the positive electrode side and the negative electrode side, the positive electrode external terminal 20A and the negative electrode external terminal 20B are collectively referred to as the external terminal 20, and the positive electrode current collector plate 40A and the negative electrode current collector plate 40B are collectively illustrated. The current collector plate 40 will be described.

  The battery container 10 includes a flat bottomed rectangular tube-shaped battery can 11 having an opening 11 a at the top, and a rectangular flat battery cover 12 that seals the opening 11 a of the battery can 11. . The battery can 11 has a generally rectangular bottom surface 11b, a generally rectangular wide side surface 11c and a narrow side surface 11d rising vertically from the bottom surface 11b, and an upper portion is opened to have a generally rectangular opening 11a. The battery can 11 is welded and sealed so that the battery lid 12 closes the opening 11a in a state where the wound electrode group 30 is accommodated therein.

  The battery lid 12 has a substantially rectangular upper surface 12a with the width direction W of the secondary battery 100 as the longitudinal direction. A positive electrode external terminal 20A and a negative electrode external terminal 20B are provided at one end and the other end of the upper surface 12a of the battery lid 12 in the longitudinal direction. The battery lid 12 has through holes 12b through which the columnar connecting portions 22 of the external terminals 20 are inserted at one end and the other end in the longitudinal direction of the upper surface 12a, respectively. It is electrically insulated from the plate 40.

A gas discharge valve 13 and a liquid injection port 14 are provided at an intermediate portion in the longitudinal direction of the battery lid 12. The gas discharge valve 13 is provided integrally with the battery cover 12 by thinning the battery cover 12, for example, and is cleaved and discharges gas when the internal pressure of the battery container 10 exceeds a predetermined value. Then, the internal pressure of the battery container 10 is reduced to ensure the safety of the secondary battery 100. The liquid injection port 14 is used to inject an electrolytic solution into the battery container 10, and after the injection of the electrolytic solution, the liquid injection plug 15 is welded and sealed, for example, by laser welding. As the electrolytic solution to be injected into the battery container 10, for example, a nonaqueous electrolytic solution in which a lithium salt such as lithium hexafluorophosphate (LiPF ₆ ) is dissolved in a carbonic acid ester-based organic solvent such as ethylene carbonate is applied. be able to.

  The external terminal 20 has a weld joint 21 that is welded to a bus bar or the like, and a connection 22 that is connected to the current collector plate 40. The weld joint 21 has a rectangular parallelepiped block shape arranged outside the battery lid 12, the lower surface faces the upper surface of the battery lid 12, and the upper surface is parallel to the upper surface of the battery lid 12 at a predetermined height position. It has a configuration. The connection portion 22 protrudes from the lower surface of the weld joint portion 21 in a direction penetrating the battery lid 12 and has a cylindrical shape that can be inserted into the circular through hole 12 b of the battery lid 12.

  The current collector plate 40 is a rectangular plate-like base portion 41 disposed to face the lower surface of the battery lid 12, and is bent at a side end of the base portion 41 and is directed toward the bottom surface along the wide side surface 11 c of the battery can 11. A connecting end 42 extending in the direction. The base portion 41 of the current collector plate 40 has a through hole 43 through which the connection portion 22 of the external terminal 20 is inserted. The connection end portion 42 of the current collector plate 40 is overlapped with the foil exposed portions 31c and 32c at both ends in the winding axis direction of the wound electrode group 30 so as to overlap with each other, for example, by ultrasonic welding or resistance welding. It is joined to the exposed portions 31c and 32c and is electrically connected to the positive electrode 31 and the negative electrode 32 (see FIG. 3) constituting the wound electrode group 30.

  The connection portion 22 of the external terminal 20 is sequentially inserted into the through hole 1a of the gasket 1, the through hole 12b of the battery cover 12, the through hole 2a of the insulating plate 2, and the through hole 43 of the base 41 of the current collector plate 40. It crimps so that the front-end | tip which protruded in the lower surface of the base 41 of the electric board 40, ie, the surface on the opposite side to the battery cover 12, may expand. Accordingly, the external terminal 20 and the current collector plate 40 are integrally fixed to the battery lid 12 via the gasket 1 and the insulating plate 2, and the wound electrode group 30 is connected to the battery lid 12 via the current collector plate 40 and the insulating plate 2. Fixed to. Further, the external terminal 20 is electrically connected to the positive electrode 31 and the negative electrode 32 (see FIG. 3) constituting the wound electrode group 30 via the current collector plate 40.

  The wound electrode group 30 is covered with the insulating protective film 3 while being fixed to the battery lid 12 via the current collector plate 40 and the insulating plate 2, and is inserted into the battery can 11 from the opening 11 a of the battery can 11. The entire circumference of the battery lid 12 is joined to the entire circumference of the opening 11 a of the battery can 11 by, for example, laser welding, and enclosed in the battery container 10. Thereafter, an electrolytic solution is injected into the battery container 10 through the liquid injection port 14 of the battery lid 12, and a liquid injection plug 15 is joined to the liquid injection port 14 by, for example, laser welding to seal the battery container 10.

  FIG. 3 is an exploded perspective view of the wound electrode group 30 of the secondary battery 100 shown in FIG. FIG. 4 is an enlarged cross-sectional view of the innermost peripheral portion of the wound electrode group 30 along the line IV-IV shown in FIG. FIG. 5 is an enlarged cross-sectional view showing a state where the wound electrode group 30 shown in FIG. 4 is wound around the core 60. FIG. 6 is an enlarged cross-sectional view of the wound electrode group 30 along the line VI-VI shown in FIG. 4 and 6 show a state where the core 60 shown in FIG. 5 is removed.

  The wound electrode group 30 is configured by winding the positive electrode 31 and the negative electrode 32 around the separators 33 and 34 wound on the innermost periphery with the separators 33 and 34 interposed therebetween. The separators 33 and 34 have a role of insulating between the positive electrode 31 and the negative electrode 32.

  As shown in FIGS. 4 to 6, the separators 33, 34 are wound around the core 60 before the positive electrode 31 and the negative electrode 32, and the separators 33, 34 are disposed on the innermost periphery of the wound electrode group 30. 34 is wound over more than one turn. Therefore, in the secondary battery 100 of the present embodiment, the separators 33 and 34 wound around the innermost periphery of the wound electrode group 30 are broadly defined in the winding direction R of the innermost negative electrode 32. The separators 33 and 34 wound around the inner peripheral side from the start end portion 32B are meant. In the present embodiment, the innermost separators 33 and 34 in the broad sense are referred to as leading edge portions 35 of the separators 33 and 34.

  Of the leading edge portions 35 of the separators 33, 34, when wound around the core 60, one turn in the winding direction R from the start end portion 33 </ b> B of the innermost separator 33 facing the outer surface of the core 60. The part up to this is the separator 33 wound around the innermost circumference in a narrow sense. The separator 33 wound around the innermost periphery in the narrow sense is referred to as an innermost peripheral portion 33 </ b> A of the separator 33. The innermost peripheral portion 33 </ b> A of the separator 33 faces the hollow portion 30 c formed at the center of the wound electrode group 30 after the winding core 60 is extracted from the wound electrode group 30.

  As described above, the secondary battery 100 of the present embodiment includes at least a part of the separators 33 and 34 wound around the inner periphery of the start end 32B in the winding direction R of the negative electrode 32 of the wound electrode group 30. The most characteristic feature is that a fixing portion 50 for fixing is provided. Further, in the secondary battery 100 of the present embodiment, the fixing portion 50 fixes the innermost peripheral portion 33A of the separator 33 to the separator 34 on the outer peripheral side, and the separator 34 is further connected to the negative electrode 32 or separator on the outer peripheral side. 33 is fixed. That is, the fixing portion 50 fixes the inner circumferential side separator 33 to the outer circumferential side separator 34 at the leading edge portion 35 of the separators 33 and 34. The fixing unit 50 is fixed to the negative electrode 32, and the leading end portion 35 of the separators 33 and 34 is fixed to the negative electrode 32.

  The material of the fixing part 50 is not particularly limited as long as the separators 33 and 34 can be fixed to at least one of the positive electrode 31 and the negative electrode 32. For example, an adhesive, an adhesive, or the positive electrode 31 and the negative electrode are used. The same material as the binder used for 32 can be used. As the adhesive, an acrylic adhesive is particularly preferable. For example, the fixed portion 50 can be formed by winding the separators 33 and 34 in a state where these materials are applied or arranged on at least one of the front and back surfaces of the separators 33 and 34. Further, a heat welding part in which at least a part of the separators 33 and 34 is melted and solidified may be used as the fixing part 50.

  In the secondary battery 100 of the present embodiment, the fixing portion 50 is provided between the separators 33 and 34 in the leading end portion 35 of the separators 33 and 34 including the innermost peripheral portion 33A of the separator 33. They are fixed to each other. The fixed portion 50 is provided between the separator 34 wound on the outermost side of the leading edge portions 35 of the separators 33, 34 and the negative electrode 32, and includes the innermost peripheral portion 33 </ b> A of the separator 33. The leading end portions 35 of 33 and 34 are fixed to the negative electrode 32.

  That is, in the secondary battery 100 of the present embodiment, the innermost peripheral portion 33A of the separator 33 of the wound electrode group 30 is connected to the negative electrode through the plurality of fixing portions 50 and the separators 33 and 34 of the leading end portion 35. 32 is fixed to the innermost peripheral portion 32A. Here, the innermost peripheral portion 32A of the negative electrode 32 means a portion from the winding start end portion 32B of the negative electrode 32 to a round of the winding core 60 or the hollow portion 30c in the winding direction R. More specifically, the fixing portion 50 fixes the leading end portion 35 of the separators 33 and 34 to the negative electrode mixture layer 32b of the innermost peripheral portion 32A of the negative electrode 32. Further, the plurality of fixing portions 50 are provided at positions overlapping each other in the stacking direction of the separators 33 and 34, that is, in the thickness direction of the separators 33 and 34.

  Further, in the secondary battery 100 of the present embodiment, as shown in FIG. 6, the fixing portion 50 is provided on the flat portion 30a of the wound electrode group 30, and is not provided on the curved portion 30b. Further, in the secondary battery 100 of the present embodiment, the fixing portion 50 has a width in the width direction W of the separators 33 and 34 orthogonal to the winding direction R of the separators 33 and 34 as shown in FIGS. It is provided over the entire width in the width direction W including the end portion in the direction W.

  Further, the start end portion 32B of the negative electrode 32 is disposed outside the leading end portion 35 of the separators 33 and 34, and is sandwiched between the separator 34 inside the negative electrode 32 and the separator 33 outside the negative electrode 32. The negative electrode 32 is wound around the core 60 shown in FIG. 5 over one or more turns together with the separator 34 on the inner side and the separator 33 on the outer side.

  In the secondary battery 100 of the present embodiment, as shown in FIG. 6, the leading edge portion 35 of the separators 33, 34 is included in a portion including the start end portion 32 </ b> B of the negative electrode 32 positioned on the flat portion 30 a of the wound electrode group 30. The outermost separator 34 is fixed via a fixing portion 50. The fixed portion 50 is provided between the portion including the start end portion 32 </ b> B of the negative electrode 32 and the separators 33 and 34 of the leading end portion 35 overlapping in the thickness direction of the separators 33 and 34. As a result, in the flat portion 30a of the wound electrode group 30, the innermost peripheral portion 33A of the separator 33 includes a plurality of fixed portions 50 and separators 33 of the leading edge portion 35 in a portion including the start end portion 32B of the negative electrode 32. 34 is fixed.

  Furthermore, as shown in FIG. 5, the starting end portion 31 </ b> B of the positive electrode 31 is sandwiched between the separators 33 and 34 outside the negative electrode 32 wound for one or more rounds. The positive electrode 31 and the negative electrode 32 are wound around the core 60 over a plurality of circumferences with the separators 33 and 34 interposed therebetween. In the outermost peripheral portion of the wound electrode group 30, the negative electrode 32 is wound around the outer periphery of the positive electrode 31 via the separator 34 over one round, and the separators 33, 34 are further wound over the outer circumference over the round. Turned. The terminal portions of the separators 33 and 34 are fixed to the outermost separator 34 of the wound electrode group 30 with an adhesive tape.

The separators 33 and 34 include a base material 36 and a heat-resistant layer 37 provided on at least one surface of the base material 36. The base material 36 is comprised by the porous film which can let electrolyte solution pass, for example. As the porous film, for example, a porous film made of a polyolefin resin material can be used. As a resin material for the porous film, for example, polypropylene (PP), polyethylene (PE) or the like can be used.
The porous film may be a single-layer porous film or a laminated porous film in which a plurality of porous films made of the same or different materials are laminated.

The heat-resistant layer 37 is composed of a filler made of fine particles and a binder made of an inorganic or organic oxide. The heat-resistant layer 37 can be manufactured, for example, by applying a resin solution in which a filler and a binder are mixed to at least one surface of a substrate 36 such as a porous film and evaporating the solvent. As the filler, for example, fine particles such as alumina (Al ₂ O ₃ ) and silica (SiO ₂ ) can be used, and preferably have heat resistance and insulating properties. The filler may be inorganic nitride such as aluminum nitride or fine particles such as boehmite (alumina hydrate), and is not particularly limited as long as it has heat resistance and insulating properties. As the binder containing an inorganic or organic oxide, for example, an acrylic-based, polyolefin-based, fluororesin-based, or SBR-based resin material can be used.

  The positive electrode 31 has a positive electrode foil 31a that is a positive electrode current collector and a positive electrode mixture layer 31b made of a positive electrode active material mixture applied to both surfaces of the positive electrode foil 31a. One side of the positive electrode 31 in the width direction W is a foil exposed portion 31c where the positive electrode mixture layer 31b is not formed and the positive foil 31a is exposed. The positive electrode 31 is wound around the core 60 with the foil exposed portion 31 c disposed on the opposite side of the foil exposed portion 32 c of the negative electrode 32 and the axial direction of the core 60, that is, the winding axis direction.

  The positive electrode 31 is formed by, for example, applying a positive electrode active material mixture obtained by adding a conductive material, a binder, and a dispersion solvent to a positive electrode active material and kneading the positive electrode foil 31a on both sides except for one side in the width direction W. It can be produced by drying, pressing and cutting. As the positive electrode foil 31a, for example, an aluminum foil having a thickness of about 20 μm can be used. The thickness of the positive electrode mixture layer 31b not including the thickness of the positive electrode foil 31a is, for example, about 90 μm.

As a material of the positive electrode active material mixture, for example, 100 parts by weight of lithium manganate (chemical formula LiMn ₂ O ₄ ) is used as the positive electrode active material, 10 parts by weight of flaky graphite as the conductive material, and 10% by weight as the binder. Part of polyvinylidene fluoride (hereinafter referred to as PVDF) and N-methylpyrrolidone (hereinafter referred to as NMP) can be used as a dispersion solvent. The positive electrode active material is not limited to the above-described lithium manganate. For example, another lithium manganate having a spinel crystal structure, or a lithium manganese composite oxide partially substituted or doped with a metal element may be used. Further, as the positive electrode active material, lithium cobaltate or lithium titanate having a layered crystal structure, and a lithium-metal composite oxide obtained by substituting or doping a part thereof with a metal element may be used.

  The negative electrode 32 has a negative electrode foil 32a that is a negative electrode current collector, and a negative electrode mixture layer 32b made of a negative electrode active material mixture applied to both surfaces of the negative electrode foil 32a. One side of the negative electrode 32 in the width direction W is a foil exposed portion 32c where the negative electrode mixture layer 32b is not formed and the negative foil 32a is exposed. The negative electrode 32 is wound around the core 60, with the foil exposed portion 32 c thereof arranged on the opposite side of the foil exposed portion 31 c of the positive electrode 31 and the axial direction of the core 60, that is, the winding axis direction.

  The negative electrode 32 is prepared by, for example, applying a negative electrode active material mixture kneaded by adding a binder and a dispersion solvent to the negative electrode active material on both surfaces of the negative electrode foil 32a except for one side in the width direction W, drying, pressing It can be produced by cutting. As the negative electrode foil 32a, for example, a copper foil with a thickness of about 10 μm can be used. The thickness of the negative electrode mixture layer 32b not including the thickness of the negative electrode foil 32a is, for example, about 70 μm.

As a material for the negative electrode active material mixture, for example, 100 parts by weight of amorphous carbon powder as the negative electrode active material, 10 parts by weight of PVDF as the binder, and NMP as the dispersion solvent can be used. The negative electrode active material is not limited to the above-mentioned amorphous carbon, and natural graphite capable of inserting and removing lithium ions, various artificial graphite materials, carbonaceous materials such as coke, and compounds such as Si and Sn (for example, , SiO, TiSi ₂ or the like), or a composite material thereof.
The particle shape of the negative electrode active material is not particularly limited, and a particle shape such as a scale shape, a spherical shape, a fiber shape, or a lump shape can be appropriately selected.

  The binder used for the positive electrode mixture layer 31b and the negative electrode mixture layer 32b is not limited to PVDF. Examples of the binder include polytetrafluoroethylene (PTFE), polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene butadiene rubber, polysulfide rubber, nitrocellulose, cyanoethyl cellulose, various latexes, acrylonitrile, and vinyl fluoride. Polymers such as vinylidene fluoride, propylene fluoride, chloroprene fluoride, and acrylic resins, and mixtures thereof may be used.

  In the axial direction of the winding core 60 of the wound electrode group 30, that is, the winding axis direction, the width of the negative electrode mixture layer 32 b of the negative electrode 32 is wider than the width of the positive electrode mixture layer 31 b of the positive electrode 31. A negative electrode 32 is wound around the innermost and outermost circumferences of the wound electrode group 30. Accordingly, the positive electrode mixture layer 31b is sandwiched between the negative electrode mixture layer 32b from the start end portion to the end portion of the positive electrode 31.

  As described above, the wound electrode group 30 is manufactured by winding the positive electrode 31 and the negative electrode 32 around the flat core 60 with the separators 33 and 34 interposed therebetween. Accordingly, the wound electrode group 30 includes a flat portion 30a in which the positive electrode 31 and the negative electrode 32 are laminated flat, and a curved portion in which the positive electrode 31 and the negative electrode 32 are bent and laminated on both sides of the flat portion 30a. 30b. That is, the wound electrode group 30 has a pair of semicircular curved portions 30b at both ends of a flat portion 30a as viewed from the winding axis direction.

  The foil exposed portions 31c and 32c of the positive electrode 31 and the negative electrode 32 are respectively bundled by the flat portion 30a of the wound electrode group 30 and joined to the connection end portion 42 of the current collector plate 40 by, for example, ultrasonic pressure welding or resistance welding. Is done. Thus, the positive electrode external terminal 20A and the negative electrode external terminal 20B are electrically connected to the positive electrode 31 and the negative electrode 32 constituting the wound electrode group 30 via the positive electrode current collector plate 40A and the negative electrode current collector plate 40B, respectively. Connected. As a result, the wound electrode group 30 is inserted into the battery can 11 such that one curved portion 30 b is disposed to face the battery lid 12 and the winding axis direction is along the width direction W of the secondary battery 100. The other curved portion 30 b is disposed to face the bottom surface 11 b of the battery can 11.

  In addition, in the winding axis direction of the wound electrode group 30, the widths of the separators 33 and 34 are wider than the width of the negative electrode mixture layer 32b, but the foil exposed portions 31c and 32c of the positive electrode 31 and the negative electrode 32 are respectively The separators 33 and 34 protrude outward in the width direction W from the end portions in the width direction W. Therefore, the separators 33 and 34 do not hinder the foil exposed portions 31c and 32c when bundled and welded.

  The secondary battery 100 having such a configuration is used, for example, as an assembled battery in which a bus bar is welded to the upper surface of the weld joint 21 of the external terminal 20 and a plurality of secondary batteries 100 are connected in series. The secondary battery 100 is charged by, for example, storing power supplied from a power supply source such as a generator in the wound electrode group 30 via the external terminal 20 and the current collector plate 40. Further, the secondary battery 100 supplies the power stored in the wound electrode group 30 to a device that consumes power, such as a motor, via the current collector plate 40 and the external terminal 20.

  Hereinafter, the operation of the secondary battery 100 of the present embodiment will be described.

  In the secondary battery 100 of the present embodiment, as described above, the positive electrode 31 and the negative electrode 32 are wound around the separators 33 and 34 wound around the innermost periphery with the separators 33 and 34 interposed therebetween. A wound electrode group 30 is provided. When the wound electrode group 30 is manufactured, as shown in FIG. 5, the separators 33 and 34, the positive electrode 31, and the negative electrode 32 are wound around the winding core 60. Extracted from the wound electrode group 30.

  In the conventional battery electrode group described in Patent Document 1, there is no positive electrode plate or negative electrode plate in the portion where only the innermost separator is wound, and friction due to contact with the positive electrode plate or the negative electrode plate. I can't get power. Further, the portion where only the innermost separator of the electrode group is wound is not fixed, and the starting end portion is a free end. Therefore, when the conventional battery electrode group is pulled out of the core, the separator is displaced at the portion where only the innermost separator is wound, causing internal short-circuiting, or the body as an electrode group. May be lost.

  On the other hand, the secondary battery 100 of the present embodiment includes a fixing portion 50 that fixes at least a part of the separators 33 and 34 wound around the inner periphery of the start end portion 32B in the winding direction R of the negative electrode 32. ing. Therefore, when the secondary battery 100 of the present embodiment pulls out the core 60 from the wound electrode group 30, even when a frictional force is generated between the innermost peripheral portion 33A of the separator 33 and the core 60, The fixing portion 50 can prevent the separators 33 and 34 wound around the inner circumference from the start end portion 32B of the negative electrode 32.

  Further, in the secondary battery 100 of the present embodiment, the fixing portion 50 fixes the inner circumferential side separator 33 to the outer circumferential side separator 34 in the leading edge portion 35 of the separators 33 and 34. Thereby, the shift | offset | difference of the separators 33 and 34 wound by inner periphery rather than the start end part 32B of the negative electrode 32 by the fixing | fixed part 50 can be prevented, and the shift | offset | difference of 33 A of innermost peripheral parts of the separator 33 can be prevented. Further, in the secondary battery 100 of the present embodiment, the fixing portion 50 is fixed to the negative electrode 32. As described above, since the fixing portion 50 that fixes the separators 33 and 34 to the negative electrode 32 having higher rigidity than the separators 33 and 34 is provided, the separators 33 and 34 are prevented from being displaced due to the rigidity of the negative electrode 32. it can.

  In particular, among the leading end portions 35 of the separators 33 and 34 wound around the innermost periphery of the wound electrode group 30, the innermost peripheral portion 33 </ b> A of the separator 33 facing the core 60 is used when the core 60 is extracted. The friction region RA is likely to be in contact with the winding core 60 and receive a frictional force. At least a part of the innermost peripheral portion 33A of the separator 33 that has such a friction region RA and is most likely to shift when the winding core 60 is pulled out is fixed to the negative electrode 32 via the fixing portion 50 and the separators 33 and 34. And fixing the innermost peripheral portion 33A of the separator 33 can be effectively prevented.

  Furthermore, in the secondary battery 100 of the present embodiment, as shown in FIG. 6, in the secondary battery 100, the starting end portion 33 </ b> B in the winding direction R of the leading end portion 35 of the separators 33 and 34 wound around the innermost periphery. , 34B. Since the start end portions 33B and 34B of the separators 33 and 34 are particularly likely to be displaced, by providing the fixing portion 50 at the start end portions 33B and 34B of the separators 33 and 34, the displacement of the separators 33 and 34 can be more effectively performed. Can be prevented. In particular, the start end portion 33B of the innermost peripheral portion 33A of the separator 33 is fixed to the negative electrode 32 through the fixing portion 50 and the separators 33 and 34, thereby preventing the displacement of the separators 33 and 34 more reliably. it can. Note that the innermost peripheral portion 32A of the negative electrode 32 to which the fixing portion 50 is fixed is an inactive region that does not face the positive electrode 31, and therefore the battery characteristics and the like by the fixing portion 50 are not affected.

  In the secondary battery 100 of the present embodiment, the wound electrode group 30 is formed into a flat shape having a flat portion 30a and a curved portion 30b, and the fixed portion 50 is provided on the flat portion 30a. The wound electrode group 30 wound in a flat shape around the core 60 is pressed to be formed into a flatter shape after the winding is completed after the winding is finished. Most of 30 becomes the flat part 30a. In this way, by providing the fixing portion 50 in the flat portion 30 a that occupies most of the wound electrode group 30, a sufficient area for fixing the innermost separators 33 and 34 to the negative electrode 32 can be secured. And the displacement of the separators 33 and 34 can be more reliably prevented.

  In the secondary battery 100 of the present embodiment, the fixing portion 50 is provided over the entire width of the separators 33 and 34 in the width direction W. As a result, a sufficient area for fixing the innermost separators 33 and 34 to the negative electrode 32 can be secured, and displacement of the separators 33 and 34 can be prevented more reliably.

  Moreover, when the fixing | fixed part 50 is the heat welding part which fuse | melted and solidified the separators 33 and 34, a part of separators 33 and 34 can be used as the fixing | fixed part 50, without adding a new member. it can. Moreover, when the fixing | fixed part 50 is an adhesive, it is not necessary to heat or dry the fixing | fixed part 50, shortening the time which manufactures the secondary battery 100, and improving productivity. It becomes possible. Further, when the fixing portion 50 is an adhesive, the separators 33 and 34 can be fixed to the negative electrode 32 more firmly than the adhesive.

  As described above, according to the secondary battery 100 of the present embodiment, at least a part of the separators 33 and 34 wound around the innermost periphery of the wound electrode group 30 is at least part of the positive electrode 31 and the negative electrode 32. By providing the fixing portion 50 that is fixed to one side, it is possible to prevent the separators 33 and 34 on the innermost periphery of the wound electrode group 30 from being displaced. Therefore, according to the secondary battery 100 of the present embodiment, the productivity and yield of the secondary battery 100 can be improved as compared with the conventional case, and an internal short circuit can be prevented more reliably.

  Hereinafter, Modification 1 to Modification 3 of the fixing unit 50 of the secondary battery 100 of the present embodiment will be described with reference to FIGS. 7 to 9.

(Modification 1)
FIG. 7 is an enlarged cross-sectional view corresponding to FIG. 6 illustrating Modification 1 of the fixing portion 50 of the secondary battery 100 of the present embodiment. In the present modified example, the fixing portion 50 includes the leading end portions 35 of the separators 33 and 34, and the start end portions 33B and 34B of the separators 33 and 34 and the start end portions 33B and 34B in the thickness direction of the separators 33 and 34. It is provided in a region overlapping with 34B. The width WR2 in the winding direction R of the fixing portion 50 provided on the front and back surfaces of the separator 34 adjacent to the outermost negative electrode 32 of the leading edge portion 35 of the separators 33 and 34 is the starting end portion of the separators 33 and 34. It is wider than the width WR1 in the winding direction R of the fixing portion 50 provided at 33B, 34B.

  As described above, when the start end portions 33B and 34B of the innermost separators 33 and 34 of the wound electrode group 30 become free ends, the innermost separators 33 and 34 are easily displaced. Accordingly, the start end portions 33B, 34B of the separators 33, 34 are fixed to the negative electrode 32 via the fixing portion 50 and the separators 33, 34, so that the displacement of the innermost separators 33, 34 of the wound electrode group 30 is increased. Can be prevented.

(Modification 2)
FIG. 8 is an enlarged cross-sectional view corresponding to FIG. 6 and showing a second modification of the fixing portion 50 of the secondary battery 100 of the present embodiment. In this modification, the fixing portion 50 is provided over one or more rounds in the winding direction R of the separators 33 and 34 from the start end portions 33B and 34B of the separators 33 and 34. Thereby, the area which fixes separator 33, 34 of the innermost periphery with respect to the negative electrode 32 can be expanded more, and it extends over one round or more of winding direction R from start-end part 33B, 34B of separator 33,34. Further, the displacement of the separators 33 and 34 can be prevented more reliably. In the present modification, the fixed portion 50 is provided on the curved portion 30 b of the wound electrode group 30. Thereby, the shift | offset | difference of the separators 33 and 34 of the curved part 30b with strong clamping | tightening compared with the flat part 30a of the winding electrode group 30 can be prevented reliably.

(Modification 3)
FIG. 9 is an enlarged cross-sectional view corresponding to FIG. 4 showing Modification 3 of the fixing portion 50 of the secondary battery 100 of the present embodiment. In the present modification, the fixing portion 50 is provided in a part of the width direction W of the separators 33 and 34 orthogonal to the winding direction R of the separators 33 and 34. More specifically, the fixing portion 50 is provided at the end of the separators 33 and 34 in the width direction W.

  Thus, by providing the fixing portion 50 in a part of the separators 33 and 34 in the width direction W, the negative electrode 32 having rigidity higher than that of the separators 33 and 34 prevents the separators 33 and 34 from being displaced in the width direction W. Is done. Therefore, the shift in the width direction W of the separators 33 and 34 can be prevented regardless of the direction in which the core 60 is pulled out. Moreover, compared with the case where the fixing | fixed part 50 is provided over the full width of the width direction W of the separators 33 and 34, the usage-amount of the material of the fixing | fixed part 50 can be reduced and it is advantageous in cost. The fixing portion 50 is provided at the end of the separators 33 and 34 in the width direction W, so that the fixing portion 50 is formed as compared with the case where the fixing portion 50 is provided in the center portion of the separators 33 and 34 in the width direction W. Can be easily.

  Modification 1 to Modification 3 of the fixing unit 50 described above can be applied in appropriate combination with the secondary battery 100 of Embodiment 1 described above.

[Embodiment 2]
Next, Embodiment 2 of the secondary battery of the present invention will be described with reference to FIGS. 1 to 3 and FIG. FIG. 10 is an enlarged cross-sectional view of the wound electrode group 30 corresponding to FIG. 4 of the secondary battery according to Embodiment 2 of the present invention.

  The secondary battery of the present embodiment is different from the secondary battery 100 described in the first embodiment in that the fixing portion is the adhesive tape 50A. Since the other points of the secondary battery of the present embodiment are the same as those of the secondary battery 100 of the above-described first embodiment, the same portions are denoted by the same reference numerals and description thereof is omitted.

  One end of the adhesive tape 50 </ b> A is affixed to the surface of the base material 36 facing the core 60 of the innermost peripheral portion 33 </ b> A of the separator 33, and the other end is wound outside the leading end portion 35 of the separators 33 and 34. The negative electrode 32 is affixed to the foil exposed portion 32c of the innermost peripheral portion 32A. Thereby, the adhesive tape 50A has at least a part of the separators 33 and 34 wound around the innermost periphery of the wound electrode group 30, more specifically, at least a part of the innermost peripheral part 33A of the separator 33. It is fixed to the negative electrode 32.

  In order to fix the separators 33 and 34 wound around the innermost circumference of the wound electrode group 30 by the adhesive tape 50A to the negative electrode 32, first, the adhesive tape 50A is fixed in the width direction W of the innermost circumference 33A of the separator 33. One end of the adhesive tape 50 </ b> A is affixed to the surface of the innermost peripheral portion 33 </ b> A of the separator 33 that faces the core 60 in a state of projecting from the end portion. In this state, as in the first embodiment, the positive electrode 31 and the negative electrode 32 are wound around the separators 33 and 34 wound on the innermost periphery with the separators 33 and 34 interposed therebetween. Thereby, the other end of the adhesive tape 50 </ b> A protruding from the end portion in the width direction W of the innermost peripheral portion 33 </ b> A of the separator 33 is attached to the foil exposed portion 32 c of the negative electrode 32.

  According to the secondary battery of the present embodiment, the innermost peripheral portion 33A of the separator 33 is fixed to the negative electrode 32 having higher rigidity than the separators 33 and 34, as in the secondary battery of the first embodiment. The same effects as those of the secondary battery 100 of the first embodiment can be obtained. That is, according to the secondary battery of this embodiment, the adhesive that fixes at least a part of the separators 33 and 34 wound around the innermost periphery of the wound electrode group 30 to at least one of the positive electrode 31 and the negative electrode 32. By providing the tape 50A, it is possible to prevent the separators 33 and 34 on the innermost periphery of the wound electrode group 30 from being displaced.

  The adhesive tape 50 </ b> A is provided at the end of the separators 33 and 34 in the width direction W. Therefore, the shift in the width direction W of the separators 33 and 34 can be prevented regardless of the direction in which the core 60 is pulled out. Further, by using the adhesive tape 50A, it is possible to fix the separators 33 and 34 to the negative electrode 32 simply by attaching the adhesive tape 50A, and the secondary battery can be easily manufactured.

  Further, the adhesive tape 50A similar to the adhesive tape that fixes the terminal portions of the separators 33 and 34 positioned at the end of winding of the wound electrode group 30 and the outermost separator 34 can be used as a fixing portion. This is also advantageous from the viewpoint of sharing the material of the secondary battery 100. The adhesive tape 50A is preferably attached to at least a part of the flat portion 30a of the wound electrode group 30, and more preferably attached to a region where the current collector plate 40 of the foil exposed portion 32c of the negative electrode 32 is not joined. preferable.

  Hereinafter, Modification 1 and Modification 2 of the adhesive tape 50 </ b> A that is a fixing portion of the secondary battery of the present embodiment will be described with reference to FIGS. 11 and 12.

(Modification 1)
FIG. 11 is an enlarged cross-sectional view corresponding to FIG. 10 showing Modification 1 of the adhesive tape 50A that is a fixing portion of the secondary battery of the present embodiment. In this modification, the adhesive tape 50A is attached to the surface on the base material 36 side, one end of which is opposed to the core 60 of the innermost peripheral portion 33A of the separator 33, and on the outer side of the innermost peripheral portion 32A of the negative electrode 32. It is affixed to the foil exposed portion 31c of the rotated positive electrode 31. Thereby, the adhesive tape 50A has at least a part of the separators 33 and 34 wound around the innermost periphery of the wound electrode group 30, more specifically, at least a part of the innermost peripheral part 33A of the separator 33. The positive electrode 31 is fixed.

  The method of applying the adhesive tape 50A to the positive electrode 31 is the same as that for applying the adhesive tape 50A to the negative electrode 32 described above, but the length of the adhesive tape 50A needs to be slightly longer. In addition, regardless of the winding axis direction in which the winding core 60 is extracted from the wound electrode group 30, the foil of the positive electrode 31 is disposed at the end in the direction in which the winding core 60 is pulled out or in the opposite direction. Either the exposed portion 31c or the foil exposed portion 32c of the negative electrode 32 is present. Therefore, the winding tape group structure for winding the wound electrode group 30 forms a fixing portion by the adhesive tape 50A at the end in the winding axis direction of the wound electrode group 30 where the adhesive tape 50A sticking mechanism is easily provided. can do.

(Modification 2)
FIG. 12 is an enlarged cross-sectional view corresponding to FIG. 10, illustrating a second modification of the adhesive tape 50 </ b> A that is a fixing portion of the secondary battery of the present embodiment. In FIG. 12, only the portion corresponding to the lower portion of the hollow portion 30c of the wound electrode group 30 shown in FIG. 10 is shown enlarged. In the present modification, the wound electrode group 30 has a rear collar portion 38 on which the separators 33 and 34 are wound over a plurality of circumferences on the outermost circumference.

  One end of the adhesive tape 50 </ b> A is affixed to the surface of the innermost peripheral portion 33 </ b> A of the separator 33 facing the core 60, and the other end is wound inside the rear flange portion 38 of the separators 33 and 34. The negative electrode 32 is affixed to the foil exposed portion 32c of the outermost peripheral portion 32C. Thereby, the adhesive tape 50A has at least a part of the separators 33 and 34 wound around the innermost periphery of the wound electrode group 30, more specifically, at least a part of the innermost peripheral part 33A of the separator 33. The negative electrode 32 is fixed to the outermost periphery 32C.

  In order to fix the separators 33 and 34 wound around the innermost periphery of the wound electrode group 30 by the adhesive tape 50A to the outermost peripheral portion 32C of the negative electrode 32, first, after the winding of the wound electrode group 30 is completed, The diameter of the winding core 60 is made smaller than the inner diameter of the wound electrode group 30. Then, a space is formed between the core 60 and the innermost peripheral portion 33A of the separator 33 of the leading end portion 35 of the wound electrode group 30, and the innermost peripheral portion 33A of the separator 33 and the outermost peripheral portion of the negative electrode 32 are formed. The foil exposed part 32c of 32C is clamped by the clamp mechanism holding the adhesive tape 50A.

  Thereby, one end of the adhesive tape 50A is attached to the innermost peripheral portion 33A of the separator 33, and the other end is attached to the foil exposed portion 32c of the outermost peripheral portion 32C of the negative electrode 32, and the wound electrode group is attached by the adhesive tape 50A. The separators 33 and 34 wound around the innermost periphery 30 are fixed to the outermost periphery 32 </ b> C of the negative electrode 32. The adhesive tape 50A is preferably attached to at least a part of the flat portion 30a of the wound electrode group 30, and more preferably attached to a region where the current collector plate 40 of the foil exposed portion 32c of the negative electrode 32 is not joined. preferable.

  According to the secondary battery including the adhesive tape 50A of the present modification, the same effects as those of the secondary battery of the second embodiment and the modification 1 described above can be obtained. Further, according to the secondary battery provided with the adhesive tape 50A of the present modification, the metal foreign matter between the positive electrode 31 of the wound electrode group 30 and the separators 33 and 34 in the actual use environment of the secondary battery. Mixing can be prevented, and voltage drop due to a short circuit phenomenon can be suppressed.

  The embodiment of the present invention has been described in detail with reference to the drawings, but the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention.

30 wound electrode group 30a flat portion 30b curved portion 31 positive electrode (electrode)
32 Negative electrode (electrode)
33 Separator 33B Start end 34 Separator 34B Start end 50 Fixed portion 50A Adhesive tape (fixed portion)
100 Secondary battery R Winding direction W Width direction

Claims (13)

A secondary battery comprising a wound electrode group in which the winding core is removed after winding the electrode around the winding core with a separator interposed therebetween,
The wound electrode group is formed into a flat shape having a flat portion in which the electrodes are laminated flat, and a curved portion in which the electrodes are bent and laminated on both sides of the flat portion,
A fixing portion for fixing at least a part of two overlapping separators wound on the inner periphery over one or more rounds from the starting end in the winding direction of the electrode;
The fixing portion, wherein with provided on the flat portion provided on the leading end in the winding direction of the two of the separator, that secure the overlapping said leading end of said two of said separator to said electrode Secondary battery.   The fixing portion fixes the separator on the inner peripheral side to the separator on the outer peripheral side in the leading end portion of the separator wound around the inner periphery from the start end portion of the electrode, and The secondary battery according to claim 1, wherein the secondary battery is fixed to the innermost peripheral portion of the electrode. The fixing portion fixes an end portion including the starting end portion of the electrode to the separator on the outermost periphery of the leading end portion, and the leading end portion overlaps the end portion of the electrode and the thickness direction of the separator. Provided between the separators,
The innermost peripheral portion of the separator in the flat portion is fixed to the end portion of the electrode via a plurality of the fixing portions and the separator of the leading edge portion. The secondary battery as described.   The secondary battery according to claim 3, wherein the fixing portion fixes the leading end portion to the mixture layer of the electrode.   The secondary battery according to claim 1, wherein the fixing portion is provided over one or more rounds in the winding direction from the starting end portion of the separator.   The secondary battery according to claim 1, wherein the fixing portion is provided in the bending portion.   The secondary battery according to any one of claims 1 to 6, wherein the fixing portion is provided in at least a part of a width direction of the separator perpendicular to a winding direction of the separator.   The secondary battery according to claim 7, wherein the fixing portion is provided over the entire width in the width direction.   The secondary battery according to claim 7, wherein the fixing portion is provided at an end in the width direction.   The secondary battery according to claim 9, wherein the fixing portion is an adhesive tape.   The secondary battery according to claim 7, wherein the fixing part is a heat welding part in which the separator is melted and solidified.   The secondary battery according to claim 7, wherein the fixing part is an adhesive.   The secondary battery according to claim 7, wherein the fixing part is an adhesive.

Images