JP2015088247A - Secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent capacity reduction of a secondary battery by suppressing fluctuation of a space between the outermost periphery of a negative electrode and a positive electrode.SOLUTION: A secondary battery 100 includes a wound body 3 formed by laminating and winding a positive electrode 34 and a negative electrode 32 each having a mixture layer on both sides of belt-like metal foil and having a metal foil exposed part where the metal foil is exposed at the end part of one long side of the metal foil with separators 33 and 35 interposed. The wound body has a flat shape including a pair of flat surface parts 3A and 3A, a metal foil exposed part 34b of the positive electrode 34 and a metal foil exposed part 32b of the negative electrode 32 are disposed on one side and the other side in a winding axis direction, the negative electrode 32 is used as the outermost peripheral electrode of the wound body 3, the outermost peripheral part of the negative electrode 32 is covered with the separators 33 and 35, and at least a part of portions forming the separators 33 and 35 and covering the outermost peripheral part of the negative electrode 32 is fixed by the metal foil exposed part 34b of the positive electrode 34.

Description

  The present invention relates to a secondary battery having a flat wound body in which a positive electrode and a negative electrode are stacked and wound.

  For example, a rectangular secondary battery used for in-vehicle use has a wound body in which a positive electrode and a negative electrode are stacked with a separator interposed therebetween. Since the wound body has a structure in which the positive electrode is sandwiched between two negative electrodes facing each other, the negative electrode is disposed outside the positive electrode at the outermost periphery. The separator is wound further outside the outermost peripheral portion of the negative electrode, and the end of the separator is protruded in the winding direction from the end of the end of the negative electrode. In order to prevent the winding body from loosening and slackening, an adhesive tape is stuck on the outermost periphery of the separator across the end portion of the separator to be rolled (Patent Document 1).

JP 2012-69290 A

  However, in the case of a wound body, the outermost negative electrode is only covered with a separator on the outer side, so that partial lifting may occur. When partial lifting occurs on the outermost negative electrode, the distance between the outermost negative electrode and the positive electrode on the inner side may fluctuate, which may cause a reduction in capacity.

  The present invention has been made in view of the above points, and the object of the present invention is to reduce the capacity by suppressing the variation in the distance between the outermost negative electrode of the wound body and the inner positive electrode. It is providing the secondary battery which can be prevented.

  The secondary battery of the present invention that solves the above problems has a metal foil exposed portion having a mixture layer on both sides of a strip-shaped metal foil, and the metal foil exposed at one end of one long side of the metal foil. A secondary battery including a wound body in which a positive electrode and a negative electrode are stacked and wound with a separator interposed therebetween, the wound body having a flat shape including a pair of flat surface portions, The metal foil exposed part of the positive electrode and the metal foil exposed part of the negative electrode are arranged on one side and the other side of the winding axis direction, the negative electrode is the outermost peripheral electrode of the wound body, The outermost peripheral portion is covered with the separator, and at least a part of the separator and the outermost peripheral portion of the negative electrode is fixed to the exposed metal foil portion of the positive electrode. .

  ADVANTAGE OF THE INVENTION According to this invention, the fluctuation | variation of the space | interval of the outermost peripheral part of a negative electrode and a positive electrode can be suppressed, and a capacity | capacitance fall can be prevented. Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

The external appearance perspective view of a square secondary battery. The disassembled perspective view of a square secondary battery. The expansion | deployment perspective view of a winding body. The figure explaining the structure of the winding body which concerns on 1st Embodiment. Sectional drawing which expanded the principal part by the side of the positive electrode foil exposure part of the winding body which concerns on 1st Embodiment. Sectional drawing which expanded the principal part by the side of the negative electrode foil exposure part of the winding body which concerns on 1st Embodiment. The figure explaining the tape stopper structure of the conventional winding body. The figure explaining the structure of the winding body which concerns on 2nd Embodiment. Sectional drawing which expanded the principal part by the side of the positive electrode foil exposure part of the winding body which concerns on 2nd Embodiment. Sectional drawing which expanded the principal part by the side of the negative electrode foil exposure part of the winding body which concerns on 2nd Embodiment.

  The present invention provides a positive electrode and a negative electrode having a mixture layer on both sides of a strip-shaped metal foil, and having a metal foil exposed portion where the metal foil is exposed at one end of the long side of the metal foil. A secondary battery comprising a wound body that is laminated and wound via a separator, wherein the wound body has a flat shape with a pair of flat surface portions, and one side and the other side in the winding axis direction A metal foil exposed portion of the positive electrode and a metal foil exposed portion of the negative electrode are disposed, the negative electrode is the outermost peripheral electrode of the wound body, and the outermost peripheral portion of the negative electrode is covered with the separator. The separator has a structure in which at least a part of a portion covering the outermost peripheral portion of the negative electrode is fixed to the exposed metal foil portion of the positive electrode.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In this embodiment, as an example of a secondary battery, a case of a prismatic lithium ion secondary battery (hereinafter referred to as a square secondary battery) mounted on a vehicle such as a hybrid vehicle or an electric vehicle will be described as an example. However, the present invention is not limited to the contents of the present embodiment, and can be applied to any battery having a wound body in which a positive electrode and a negative electrode are wound.

  FIG. 1 is an external perspective view of a prismatic secondary battery as an embodiment of a storage element, and FIG. 2 is an exploded perspective view showing the configuration of the prismatic secondary battery.

  As shown in FIG. 1, the prismatic secondary battery 100 includes a battery container including a battery can 1 and a battery lid 6. The material of the battery can 1 and the battery lid 6 is aluminum or an aluminum alloy. The battery can 1 is formed into a flat rectangular box shape having one end opened by performing deep drawing. The battery can 1 has a rectangular flat plate-like bottom surface 1d, a pair of wide side surfaces 1b provided on each of the pair of long side portions of the bottom surface 1d, and a pair of narrow width portions provided on each of the pair of short side portions of the bottom surface 1d. And a side surface 1c.

  The battery lid 6 has a rectangular flat plate shape and is laser-welded so as to close the opening of the battery can 1. That is, the battery lid 6 seals the opening of the battery can 1. A positive electrode external terminal 14 and a negative electrode external terminal 12 that are electrically connected to the positive electrode 34 and the negative electrode 32 (see FIG. 3) of the wound body 3 are disposed on the battery lid 6. A positive-side external insulator 24 and a negative-side external insulator 22 are arranged between the positive external terminal 14 and the battery cover 6 and between the negative external terminal 12 and the battery cover 6 to prevent short circuit. Yes.

  The positive external terminal 14 is provided with a flat bus bar welded portion 142, and the negative external terminal 12 is provided with a flat bus bar welded portion 152. When producing the assembled battery, the bus bar is connected to the positive electrode external terminal 14 and the bus bar is connected to the negative electrode external terminal 12 by welding the bus bar to the bus bar welding portions 142 and 152 so that they are welded.

  The battery lid 6 is provided with a gas discharge valve 10. The gas discharge valve 10 is formed by partially thinning the battery cover 6 by press working. The thin-walled member may be attached to the opening of the battery lid 6 by laser welding or the like, and the thin portion may be used as a gas discharge valve. The gas discharge valve 10 generates heat when the square secondary battery 100 generates heat due to an abnormality such as overcharge, and when the pressure in the battery container rises and reaches a predetermined pressure, the gas discharge valve 10 is opened and gas is discharged from the inside. By discharging, the pressure in the battery container is reduced.

  As shown in FIG. 2, the wound body 3 (see FIG. 3) held by the lid assembly 107 is accommodated in the battery can 1. The positive electrode current collector plate 180 joined to the positive electrode 34 (see FIG. 3) of the wound body 3, the negative electrode current collector plate 190 joined to the negative electrode 32 (see FIG. 3) of the wound body 3, and the wound body 3. Is housed in the battery can 1 while being covered with the insulating case 108. The material of the insulating case 108 is an insulating resin such as polypropylene, and the battery can 1 and the wound body 3 are electrically insulated. The lid assembly 107 referred to here is an assembly of the winding body 3, the positive current collector plate 180, the positive external terminal 14, the negative current collector 190, the negative external terminal 12, and the battery cover 6.

  The positive electrode external terminal 14 is electrically connected to the positive electrode 34 (see FIG. 3) of the wound body 3 through the positive electrode current collector plate 180, and the negative electrode external terminal 12 is connected through the negative electrode current collector plate 190. 3 negative electrodes 32 (see FIG. 3). For this reason, power is supplied to the external device via the positive external terminal 14 and the negative external terminal 12, or external generated power is supplied to the winding body 3 via the positive external terminal 14 and the negative external terminal 12 for charging. Is done.

  The positive current collector plate 180 includes a seat surface portion 181 connected to the positive electrode external terminal 14, a joint plane portion 183 connected to the positive electrode 34, and a plane portion 182 provided between the seat surface portion 181 and the joint plane portion 183. Have Similarly to the positive electrode current collector plate 180, the negative electrode current collector plate 190 includes a seat surface portion 191 connected to the negative electrode external terminal 12, a joint plane portion 193 connected to the negative electrode 32, and a seat surface portion 191 and a joint plane portion 193. It has a structure having a flat surface portion 192 provided therebetween.

As shown in FIG. 2, the battery lid 6 is provided with a liquid injection hole 9 for injecting an electrolytic solution into the battery container. The liquid injection hole 9 is sealed with a liquid injection stopper 11 after the electrolytic solution is injected. As the electrolytic solution, for example, a non-aqueous electrolytic solution in which a lithium salt such as lithium hexafluorophosphate (LiPF ₆ ) is dissolved in a carbonate-based organic solvent such as ethylene carbonate can be used.

  The structure of the wound body 3 will be described with reference to FIG. FIG. 3 is a perspective view showing the wound body, and shows a state where the winding end side of the wound body is unfolded.

  The wound body 3 that is a power generation element is configured by laminating a long positive electrode 34 and a negative electrode 32 with separators 33 and 35 interposed therebetween, and winding in a flat shape around the winding central axis W. Has a laminated structure.

  Each of the positive electrode 34 and the negative electrode 32 constituting the wound body 3 has a foil exposed portion in which a metal foil is exposed without applying an active material to one end of one long side, that is, one end in the width direction. 34b and 32b. The positive electrode 34 and the negative electrode 32 are overlapped so that the exposed foil portions 34b and 32b of the positive electrode 34 and the negative electrode 32 are opposite to each other in the width W direction, and are wound into a flat shape around a winding axis parallel to the width direction. . Thereby, a pair of flat flat surface portions 3A and 3A are formed on both sides of the wound body 3 in the thickness direction (arrow D direction), and the wound body 3 has a winding axis direction (arrow W direction) and a thickness. On both sides of the height direction (arrow H direction) which is a direction perpendicular to the vertical direction, a pair of curved surface portions 3B and 3B in which the positive electrode and the negative electrode laminated through the separators 33 and 35 are curved in an arc shape. Is formed.

  The positive electrode 34 has a positive electrode mixture layer 34a in which a positive electrode active material mixture is applied on both surfaces of a strip-like positive electrode foil (metal foil) that is a positive electrode current collector, and is provided at one end in the width direction of the positive electrode foil. Is provided with a positive electrode foil exposed portion 34b where no positive electrode active material mixture is applied. The negative electrode 32 has a negative electrode mixture layer 32a in which a negative electrode active material mixture is applied on both sides of a strip-like negative electrode foil (metal foil) that is a negative electrode current collector, and is provided at the other end in the width direction of the negative electrode foil. Is provided with a negative electrode foil exposed portion 32b where no negative electrode active material mixture is applied. The positive electrode foil exposed portion 34b and the negative electrode foil exposed portion 32b are regions where the metal surfaces of the positive electrode foil and the negative electrode foil are exposed, respectively, and one of the winding body 3 in the winding central axis direction (the width W direction in FIG. 3). It arrange | positions in the position of the side and the other side.

  Regarding the negative electrode 32, 10 parts by weight of polyvinylidene fluoride (hereinafter referred to as PVDF) is added as a binder to 100 parts by weight of amorphous carbon powder as a negative electrode active material, and N as a dispersion solvent. -A negative electrode mixture in which methylpyrrolidone (hereinafter referred to as NMP) was added and kneaded was prepared. This negative electrode mixture was applied to both surfaces of a 10 μm thick copper foil (negative electrode foil) leaving the welded portion (negative electrode foil exposed portion 32b). Then, the negative electrode 32 with a negative electrode active material application part thickness of 70 micrometers which does not contain copper foil was obtained through drying, a press, and a cutting process.

In the present embodiment, the case where amorphous carbon is used as the negative electrode active material is exemplified, but the present invention is not limited to this. Natural graphite capable of inserting and removing lithium ions, and various artificial graphites It may be a carbonaceous material such as a material, coke, or a compound such as Si or Sn (for example, SiO, TiSi ₂ or the like), or a composite material thereof, and also in the particle shape, scale-like, spherical, fibrous, massive, There is no particular limitation.

Regarding the positive electrode 34, 10 parts by weight of flaky graphite as a conductive material and 10 parts by weight of PVDF as a binder are added to 100 parts by weight of lithium manganate (chemical formula LiMn ₂ O ₄ ) as a positive electrode active material. A positive electrode mixture was prepared by adding and kneading NMP as a dispersion solvent. This positive electrode material mixture was applied to both surfaces of an aluminum foil (positive electrode foil) having a thickness of 20 μm, leaving the welded portion (positive electrode foil exposed portion 34b). Thereafter, a positive electrode 34 having a thickness of 90 μm in the thickness of the positive electrode active material coating portion not including an aluminum foil was obtained through drying, pressing, and cutting processes.

  Further, in the present embodiment, the case where lithium manganate is used as the positive electrode active material is exemplified, but other lithium manganate having a spinel crystal structure or a lithium manganese composite oxide partially substituted or doped with a metal element or A lithium cobalt oxide or lithium titanate having a layered crystal structure, or a lithium-metal composite oxide in which a part thereof is substituted or doped with a metal element may be used.

  Moreover, in this Embodiment, although illustrated about the case where PVDF is used as the binder of the mixture layer application part in the positive electrode 34 and the negative electrode 32, polytetrafluoroethylene (PTFE), polyethylene, polystyrene, polybutadiene, butyl rubber , Nitrile rubber, styrene butadiene rubber, polysulfide rubber, nitrocellulose, cyanoethyl cellulose, various latexes, acrylonitrile, vinyl fluoride, vinylidene fluoride, propylene fluoride, chloroprene fluoride, acrylic resins, and mixtures thereof The body can be used.

  One end of each end of the wound body 3 in the width direction, that is, the center axis direction of the winding, is a foil laminated portion of the positive electrode 34, and the other is a foil laminated portion of the negative electrode 32. The foil laminated portion of the positive electrode 34 provided at one end is obtained by laminating a positive foil exposed portion 34b where the positive electrode mixture layer 34a is not formed. The foil laminated portion of the negative electrode 32 provided at the other end is obtained by laminating a negative foil exposed portion 32b where the negative electrode mixture layer 32a is not formed. The foil laminate portion of the positive electrode foil exposed portion 34b and the foil laminate portion of the negative electrode foil exposed portion 32b are respectively bundled in the thickness direction of the wound body 3, and the positive electrode current collector plate 180 and the negative electrode current collector of the lid assembly 107, respectively. Connected to the plate 190 by ultrasonic bonding to form an electrode assembly.

  The wound body 3 is electrically connected to the positive electrode external terminal 14 and the negative electrode external terminal 12 provided on the battery lid 6 via the current collector plates 180 and 190 in the positive electrode foil exposed portion 34b and the negative electrode foil exposed portion 32b. The battery case 1 is housed in a state covered with the insulating case 108. More specifically, the foil exposed portions 34b and 32b of the positive electrode and the negative electrode of the wound body 3 are bundled in the thickness direction on the flat surface portions 3A and 3A, respectively, to form the close contact portions 34c and 32c, and are fixed to the battery lid 6. The positive electrode current collector plate 180 and the negative electrode current collector plate 190 are joined by, for example, ultrasonic welding. As a result, in the flat surface portion 3A of the wound body 3, joint portions to the current collector plates 180 and 190 are formed in the foil exposed portions 34b and 32b. The wound body 3 supported and fixed to the battery lid 6 via the current collector plates 180 and 190 joined to the joint portion is inserted from the upper opening of the flat box-shaped battery can 1 and the flat surface portions 3A and 3A. Is accommodated in the battery can 1 so as to be parallel to the wide side surface 1 b of the battery can 1. Thereafter, the battery lid 6 is sealed and welded to the opening of the battery can 1, the electrolytic solution is injected into the battery can 1 from the liquid injection hole 9 provided in the battery lid 6, and the liquid injection plug 11 is injected into the liquid injection hole 9. Is sealed and welded by laser welding, whereby the secondary battery 100 is manufactured.

  4A and 4B are diagrams illustrating the configuration of the wound body, in which FIG. 4A is a front view, and FIG. 4B is a schematic diagram illustrating a cross section taken along line AA in FIG. FIG. 5 is a cross-sectional view taken along the line B-B shown in FIG. 4A and is an enlarged schematic cross-sectional view of the main part on the positive electrode foil exposed portion side of the wound body according to the present embodiment. FIG. 6 is a cross-sectional view taken along the line C-C shown in FIG. 4A, and is an enlarged schematic view showing a main part on the negative electrode foil exposed portion side of the wound body according to the present embodiment.

  In the wound body 3, the negative electrode 32 is the outermost peripheral electrode of the wound body 3, and the outermost peripheral portion of the negative electrode 32 is covered with a separator 33. In the present embodiment, as shown in FIG. 4 (a), the end portion 34e of the positive electrode 34 is disposed on one flat surface portion 3A, and the end portion of the positive electrode 34 is disposed on the same flat surface portion 3A. A winding end end portion 32 e of the negative electrode 32 is disposed so as to protrude from the winding direction 34 e, and the outer side of the positive electrode 34 is covered with the negative electrode 32. Further, on the same flat surface portion 3A, the winding end end portion 33e of the separator 33 is disposed so as to protrude from the winding end portion 32e of the negative electrode 32 in the winding direction, and the outer side of the negative electrode 32 is covered with the separator 33. It has been broken. An adhesive tape 40 is applied to the outermost periphery of the separator 33 so as to straddle the winding end portion 33e of the separator 33, and the winding body 3 is prevented from being loosened.

  Winding body 3 is part of separator 33 and covers the outermost peripheral portion of negative electrode 32, and is fixed to positive foil exposed portion 34b. In this embodiment, flat surface portion 3A of winding body 3; In 3A, the side end of the separator 33 on the positive electrode foil exposed portion 34b side is fixed to the positive electrode foil exposed portion 34b by an adhesive tape 42. As shown in FIG. 4B, the adhesive tape 42 is attached to each of the pair of flat surface portions 3A and 3A.

  As shown in FIG. 5, the positive foil exposed portion 34 b of the positive electrode 34 of the wound body 4 is bundled and adhered to the flat surface portions 3 </ b> A and 3 </ b> A of the wound body 3. One end of the adhesive tape 42 is fixed to the side end portion of the separator 33 covering the outermost peripheral portion of the negative electrode 32 on the flat surface portions 3A and 3A of the wound body 3, and the other end is a positive electrode. 34 is fixed to a position between the side end portion of the positive electrode mixture layer 34 a and the close contact portion 34 c of the positive electrode foil exposed portion 34 b of the positive electrode 34.

FIG. 7 is a diagram for explaining a conventional winding structure of a wound body.
In the conventional wound body 203, only the adhesive tape 240 is attached so as to straddle the winding end portion 33e of the separator 33 in order to prevent the loosening. In the case of the conventional wound body 203, the outermost peripheral portion of the negative electrode 32 is only held on the outer side by the separator 33, so that it easily floats away from the inner positive electrode 34, and the distance from the positive electrode 34 is increased. May fluctuate and decrease capacity.

  For example, in the outermost peripheral portion of the negative electrode 32, the side end on the negative electrode foil exposed portion 32b side, as shown in FIG. 6, the negative electrode foil exposed portion 32b is bundled and biased inward so that it is difficult to lift. The interval between the negative electrode and the positive electrode is not likely to fluctuate.

  However, in the outermost peripheral portion of the negative electrode 32, the side end portion on the positive electrode foil exposed portion 34b side is only located on the outer side of the separator 33, and the inner end like the side end portion on the negative electrode foil exposed portion 32b side. Is not energized. And since the winding body 3 has a flat shape, the curved surface portions 3B and 3B are easily tensioned and are urged toward the inside to be relatively difficult to lift, but the flat surface portions 3A and 3A. Since they are not biased toward the inside, as shown in FIG. That is, in the flat-shaped wound body 3, the flat surface portion of the outermost peripheral negative electrode is easily lifted because no inward force due to the tension component is applied unlike the curved surface portion.

  In the case of a cylindrical wound body, since the outermost peripheral negative electrode is curved over the entire circumference, the inward force due to the component force of tension is applied over the entire circumference, and the problem of floating Does not occur. That is, the problem of lifting is a specific problem that occurs when the wound body 3 has a flat shape. Therefore, in the secondary battery using the conventional winding body 203 having a flat shape, the distance between the outermost negative electrode 32 and the positive electrode 34 varies on the flat surface portions 3A and 3A of the winding body 203, and the battery Reaction unevenness may occur and the capacity may decrease.

  On the other hand, in the present embodiment, as shown in FIG. 4, the flat surface portions 3A and 3A of the wound body 3 having a flat shape and the side end portion on the positive electrode foil exposed portion 34b side of the separator 33 are adhesive tape. 42 is fixed to the positive foil exposed portion 34 b of the positive electrode 34. In other words, the wound body 3 has the flat surface portions 3 </ b> A and 3 </ b> A of the wound body 3 and the side end portion on the positive electrode foil exposed portion 34 b side of the separator 33 covering the outermost peripheral portion of the negative electrode 32 is exposed to the positive foil of the positive electrode 34. It is fixed to the part 34b. Therefore, the positive electrode foil 34 b of the positive electrode 34 is bundled and welded to the current collector plate 180 to prevent the outermost peripheral portion of the negative electrode 32 from being lifted, and the fluctuation of the gap with the inner positive electrode 34 is suppressed. In addition, capacity reduction due to uneven battery reaction can be prevented.

  The adhesive tape 42 is attached to both the one flat surface portion 3A and the other flat surface portion 3A of the wound body 3, and is provided over the entire height direction of the flat surface portions 3A and 3A. The range to be fixed by the adhesive tape 42 may be at least a part of the flat surface portions 3A and 3A of the wound body 3, but it is preferably pasted over the entire height direction of the flat surface portions 3A and 3A. The lifting of the outermost peripheral portion can be prevented more reliably.

  In the present embodiment, the case where the adhesive tape 42 is attached to each of the pair of flat surface portions 3A and 3A of the separator 33 has been described as an example. However, the winding end portion 32e of the negative electrode 32 is disposed. The adhesive tape 42 may be attached only to the flat surface portion 3A. With such a configuration, at least the end portion 32e of the negative electrode 32 can be prevented from floating from the inner positive electrode 34.

  The timing at which the adhesive tape 42 is affixed to the wound body 3 may be when the wound body 3 is wound with a winding machine (not shown), or the positive foil exposed portion 34b and the negative foil exposed portion 32b are thick. It may be after compressing in the direction D and joining to the current collector plates 180 and 190. When affixed when the wound body 3 is manufactured, the adhesive tape 42 can be affixed by a winding machine, and the affixing operation can be simplified. In addition, in the case of being joined to the current collector plates 180 and 190, since the positive foil exposed portion 34b can be attached in a state of being fixed to the current collector plate, positioning is easy and reliable attachment is possible. .

[Second Embodiment]
FIG. 8 is a diagram illustrating the configuration of the wound body according to the present embodiment, FIG. 9 is an enlarged cross-sectional view of the main part of the wound body according to the present embodiment on the positive electrode foil exposed portion side, and FIG. These are the expanded sectional views of the principal part by the side of the negative electrode foil exposure part of the winding body which concerns on this Embodiment.

  What is characteristic in the present embodiment is that, instead of the adhesive tape 42, the separator is fixed to the positive electrode foil exposed portion 34b by heat welding. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 9, the separators 33, 35 face the positive electrode foil exposed portion 34 b of the positive electrode 34, with the side end portions on the positive electrode exposed portion 34 b side projecting sideward from the negative electrode 32. . The portions that sandwich the outermost peripheral portion of the negative electrode 32 and protrude to the side of the negative electrode 32 and overlap each other are thermally welded and fixed to the positive foil exposed portion 34b. The heat welding is performed, for example, by pressing a heater heated to a high temperature against the overlapping portions of the separators 33 and 35. The separators 33 and 35 are fixed to the positive electrode foil exposed portion 34b by exhibiting an anchor effect when the molten resin melted by heating enters the fine irregularities present on the surface of the positive electrode exposed portion 34b and solidifies.

  As shown in FIG. 8A and FIG. 8B, the heat welded portion 44 is a flat foil portion 3A, 3A of the wound body 3 and the positive foil exposed portion of the separator 33 that covers the outermost peripheral portion of the negative electrode 32. It is provided along the side end on the 34b side. Therefore, the positive electrode foil 34 b of the positive electrode 34 is bundled and welded to the current collector plate 180 to prevent the outermost peripheral portion of the negative electrode 32 from being lifted, and the fluctuation of the gap with the inner positive electrode 34 is suppressed. In addition, capacity reduction due to uneven battery reaction can be prevented. According to the present embodiment, the adhesive tape 42 can be omitted as compared with the first embodiment described above, and the manufacturing cost can be reduced. Moreover, the operation | work which affixes the adhesive tape 42 can be abbreviate | omitted, and simplification of manufacture can be aimed at.

  The present invention is not limited to the contents of the above-described embodiments, and various modifications can be made without departing from the gist of the present invention. For example, in the first embodiment, the adhesive tape 42 is used, and in the second embodiment, the configuration in which the separators 33 and 35 are fixed to the positive electrode foil exposed portion 34b by heat welding has been described. However, the separators 33 and 35 are exposed to the positive electrode foil. Any member that can be fixed to the portion 34b may be used. For example, an adhesive glue may be used instead of the adhesive tape 42.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various designs can be made without departing from the spirit of the present invention described in the claims. It can be changed. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations described. Further, a part of the configuration of an embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of an embodiment. Furthermore, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

DESCRIPTION OF SYMBOLS 1 Battery can 3 Winding body 3A Flat surface part 3B Curved surface part 32 Negative electrode 32a Negative electrode mixture layer 32b Negative electrode foil exposed part 33, 35 Separator 34 Positive electrode 34a Positive electrode mixture layer 34b Positive electrode foil exposed part 40 Adhesive tape 42 Adhesive tape 44 Thermally welded part 100 square secondary battery

Claims (8)

Between the positive electrode and the negative electrode having a mixture layer on both sides of the strip-shaped metal foil, and having a metal foil exposed portion where the metal foil is exposed at one end of the long side of the metal foil, with a separator interposed therebetween A secondary battery comprising a wound body that is laminated and wound,
The wound body has a flat shape with a pair of flat surface portions, and the metal foil exposed portion of the positive electrode and the metal foil exposed portion of the negative electrode are disposed on one side and the other side in the winding axis direction, The negative electrode is the outermost peripheral electrode of the wound body, the outermost peripheral portion of the negative electrode is covered with the separator, and at least a part of the separator and the outermost peripheral portion of the negative electrode is covered with the positive electrode A secondary battery comprising a structure fixed to an exposed portion of a metal foil of an electrode.   2. The secondary battery according to claim 1, wherein in the wound body, a side end portion of the separator is fixed to a metal foil exposed portion of the positive electrode in at least a part of the pair of flat surface portions. .   The secondary battery according to claim 2, wherein the winding body has a side end portion of the separator fixed to a metal foil exposed portion of the positive electrode in each of the pair of flat surface portions.   4. The secondary battery according to claim 2, wherein in the wound body, a side end portion of the separator is fixed to a metal foil exposed portion of the positive electrode over the entire flat surface portion. .   The secondary battery according to claim 4, wherein a side end portion of the separator is fixed to an exposed portion of the metal foil of the positive electrode by an adhesive tape.   The secondary battery according to claim 4, wherein a side end portion of the separator is fixed to a metal foil exposed portion of the positive electrode by an adhesive glue.   The secondary battery according to claim 4, wherein a side end portion of the separator is thermally welded to a metal foil exposed portion of the positive electrode.   In the wound body, the side end portion of the separator that protrudes toward the metal foil exposed portion side of the positive electrode by sandwiching the outermost peripheral portion of the negative electrode from the inner peripheral side and the outer peripheral side is the metal foil of the positive electrode The secondary battery according to claim 7, wherein the secondary battery is thermally welded to the exposed portion.

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