JP6504994B2 - Square storage element - Google Patents

Description

  The present invention relates to a square storage element.

  In a prismatic secondary battery such as a prismatic lithium ion secondary battery, a wound electrode group formed by overlapping and winding a strip-like positive electrode and a negative electrode with a separator interposed therebetween, and an electrolytic solution are accommodated in a rectangular container. . The uncoated portions of the positive electrode and the negative electrode are exposed from the separator at one side and the other side end of the wound electrode group in the winding axis direction, and the exposed uncoated portions are respectively a positive electrode current collector or It is welded to the negative electrode current collector. Such a structure enables a simple configuration, shortens the current passage to the electrode terminal and the positive and negative electrode current collectors, and reduces the connection resistance to obtain high output.

  In such a prismatic secondary battery, if a metal foreign matter is mixed into the battery, an internal short circuit may occur to cause a failure in the battery. As an example of this correspondence, the battery made into the structure covered with the insulation material which formed the winding electrode group in the bag shape is known. As the insulating material, a porous material having pores through which the electrolyte can flow is used. It is described that this structure can prevent an internal short circuit of the wound electrode group even when conductive foreign matter is mixed in the electrolytic solution when the electrolytic solution is injected from the liquid inlet of the battery lid.

JP, 2009-301892, A

  According to the technique described in Patent Document 1, foreign substances such as metal adhering to the surface or the like of the wound electrode group are accommodated in a bag-like porous film. Foreign matter contained in the bag-like porous film may be mixed with the electrolytic solution into the interior of the wound electrode group from the opening of the wound electrode group. This may cause a short circuit inside the wound electrode group, which may cause a battery failure such as a voltage drop.

  According to one aspect of the present invention, the prismatic storage element has a positive electrode, a negative electrode, and a separator, and one side edge of the positive electrode and the other side edge facing the one side edge of the negative electrode each have the above A wound electrode group which is laminated so as to have a foil exposed portion exposed from a separator, and wound so that the positive electrode, the negative electrode, and the separator have curved portions at both ends in a direction orthogonal to the winding axis direction. And a bonding member in which the one side edge of the positive electrode and the other side edge of the negative electrode are bundled and joined, and each of the positive electrode and the negative electrode includes at least the curved portion. An electrode foil gap communicating with the outside of the wound electrode group is formed at the center of the end face of the wound electrode group, and a porous film covering an opening communicating with the outside of the electrode foil gap is fixed to the wound electrode group .

  According to the present invention, it is possible to suppress that foreign substances adhering to the surface or the like of the wound electrode group are mixed in the electrode foil gap inside the curved portion of the wound electrode group.

BRIEF DESCRIPTION OF THE DRAWINGS The external appearance perspective view of the square secondary battery as Embodiment 1 of the square electrical storage element of this invention. FIG. 2 is an exploded perspective view of the prismatic secondary battery illustrated in FIG. 1; The disassembled perspective view of the square secondary battery illustrated by FIG. 2, The perspective view which shows the state which assembled | attached the battery cover. The disassembled perspective view which shows the state which expand | deployed a part of winding electrode group shown in figure by FIG. The external appearance perspective view which shows the state which fixed the porous film to the curved part in the negative electrode side of the winding electrode group. FIG. 6 is a detailed view of a region VI in FIG. 5; The external appearance perspective view which shows Embodiment 2 of this invention, and shows the state which fixed the porous film to the curved part in the negative electrode side of winding electrode group. FIG. 8 is a detailed view of a region VIII in FIG. 7;

-Embodiment 1-
Hereinafter, Embodiment 1 of the prismatic storage element of the present invention will be described with reference to FIGS. 1 to 6.
In the following, a lithium ion secondary battery is described as an example of the prismatic storage element.
FIG. 1 is an external perspective view of a prismatic secondary battery 100.
The prismatic secondary battery 100 includes the battery can 1 and the battery lid 6 and is formed in a flat shape. The battery can 1 has a pair of relatively wide side surfaces 1b having a relatively large area, a pair of narrow narrow side surfaces 1c having a relatively small area, and a bottom surface 1d. See FIG. 2).

  In the battery can 1, a wound electrode group 3 (see FIG. 2) is accommodated, and an opening 1 a of the battery can 1 is sealed by a battery cover 6. The battery cover 6 has a substantially rectangular flat plate shape, and is welded so as to close the upper opening 1 a of the battery can 1 so that the battery can 1 is sealed. The battery cover 6 is provided with a positive electrode external terminal 14 and a negative electrode external terminal 12. The wound electrode group 3 is charged via the positive electrode external terminal 14 and the negative electrode external terminal 12, and power is supplied to the external load. The gas discharge valve 10 is integrally provided on the battery lid 6, and when the pressure in the battery container constituted by the battery can 1 and the battery lid 6 rises, the gas discharge valve 10 is opened to discharge the gas from the inside. And the pressure in the battery container is reduced. Thereby, the safety of the prismatic secondary battery 100 is secured.

FIG. 2 is an exploded perspective view of the prismatic secondary battery shown in FIG. 1, and FIG. 3 is a disassembled perspective view of the prismatic secondary battery shown in FIG. It is a perspective view.
The battery can 1 of the prismatic secondary battery 100 is directed upward at the upper end of the rectangular bottom surface 1 d, the wide rectangular side surface 1 b and the narrow width side surface 1 c, and the wide side surface 1 b and the narrow width side surface 1 c rising from the bottom surface 1 d. And an open portion 1a. In the battery can 1, a wound electrode group 3 is accommodated via a protective film 2 made of an insulating material.

  The wound electrode group 3 is wound in a flat shape, and includes a pair of curved portions 3a and 3b having a semicircular cross section formed at both ends in a direction (y direction) orthogonal to the winding axis direction, and the pair And a pair of flat surfaces 3c formed continuously between the curved portions 3a and 3b. In the following description, the winding axis direction is the x direction shown in the drawing, and the direction orthogonal to the winding axis is the y direction shown in the drawing. In the wound electrode group 3, the battery can 1 with the curved portion 3 b downward while keeping both side portions in the winding axial direction (x direction) along the inner surface of the wide side 1 b and the inner surface of the narrow side 1 c of the battery can 1. It is inserted into the inside, and the upper curved portion 3 a side is disposed on the opening 1 a side of the battery can 1. In FIG. 3, the protective film 2 is folded and accommodated in the battery can 1.

  The positive electrode metal foil exposed portion 34 c (see also FIG. 4) of the wound electrode group 3 is electrically connected to the positive electrode external terminal 14 provided on the battery cover 6 via the positive electrode current collector plate 44. Further, the negative electrode metal foil exposed portion 32 c (see also FIG. 4) of the wound electrode group 3 is electrically connected to the negative electrode external terminal 12 provided on the battery lid 6 via the negative electrode current collector 24. Thus, power is supplied from the wound electrode group 3 to the external load via the positive electrode current collector plate 44 and the negative electrode current collector plate 24, and the wound electrode group 3 is provided via the positive electrode current collector plate 44 and the negative electrode current collector plate 24. Externally generated power is supplied and charged.

  A gasket 5 and an insulating plate 7 are provided on the battery lid 6 to electrically insulate the positive electrode current collector plate 44 and the negative electrode current collector plate 24 and the positive electrode external terminal 14 and the negative electrode external terminal 12 from the battery lid 6, respectively. ing. A liquid injection port 9 for injecting an electrolytic solution into the battery case is formed in the battery cover 6. After the electrolytic solution is injected from the liquid injection port 9 into the battery can 1, the liquid injection plug 11 is joined to the battery lid 6 by laser welding to seal the liquid injection port 9, and the prismatic secondary battery 100 is sealed.

Here, as a forming material of the positive electrode external terminal 14 and the positive electrode current collector plate 44, for example, an aluminum alloy can be mentioned, and as a forming material of the negative electrode external terminal 12 and the negative electrode collector plate 24, a copper alloy can be mentioned. Moreover, as a formation material of the insulating plate 7 and the gasket 5, the resin material which has insulation, such as a polybutylene terephthalate, a polyphenylene sulfide, a perfluoro alkoxy fluorine resin, etc. is mentioned, for example.

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 is applied as the electrolytic solution injected into the battery container. Can.

The positive electrode external terminal 14 and the negative electrode external terminal 12 have a welded joint portion welded to a bus bar or the like. The weld joint has a rectangular block shape projecting upward from the battery lid 6, and the lower surface faces the surface of the battery lid 6, and the upper surface is parallel to the battery lid 6 at a predetermined height position. Have.
The positive electrode connection portion 14a and the negative electrode connection portion 12a project from the lower surface of the positive electrode external terminal 14 and the negative electrode external terminal 12, respectively, and have cylindrical shapes whose tips can be inserted into the positive electrode side through hole 46 and the negative electrode side through hole 26 of the battery lid 6. Have. The positive electrode connection portion 14 a and the negative electrode connection portion 12 a penetrate the battery lid 6, respectively, and the battery can than the positive electrode current collector plate base 41 of the positive electrode current collector plate 44 and the negative electrode current collector plate base 21 of the negative electrode current collector plate 24. It protrudes toward the bottom 1d side of 1. The tips of the positive electrode connection portion 14a and the negative electrode connection portion 12a are crimped in this protruding state. As a result, the positive electrode external terminal 14 and the positive electrode current collector plate 44 and the negative electrode external terminal 12 and the negative electrode current collector plate 24 are integrally fixed to the battery cover 6. A gasket 5 is interposed between each of the positive electrode external terminal 14 and the negative electrode external terminal 12 and the battery cover 6. In addition, an insulating plate 7 is interposed between each of the positive electrode current collector plate 44 and the negative electrode current collector plate 24 and the battery cover 6. Thus, the positive electrode current collector plate 44 and the positive electrode external terminal 14 are insulated from the battery cover 6. Further, the negative electrode current collector 24 and the negative electrode external terminal 12 are insulated from the battery cover 6.

The positive electrode current collector plate 44 has a rectangular plate-like positive electrode current collector plate base 41 disposed to face the lower surface of the battery lid 6. In addition, the positive electrode current collector plate 44 is bent at the side end of the positive electrode current collector plate base 41 and extends along the wide side surface 1 b of the battery can 1 toward the bottom surface 1 d. Have. The positive electrode side connection end portion 42 is connected in a state of being superimposed on the positive electrode metal foil exposed portion 34 c of the wound electrode group 3 so as to face each other.
Similarly, the negative electrode current collector 24 has a rectangular plate-like negative electrode current collector base 21 disposed opposite to the lower surface of the battery lid 6. Further, the negative electrode current collector plate 24 is bent at the side end of the negative electrode current collector plate base 21 to extend the negative electrode side connection end 22 extending toward the bottom surface 1 d along the wide side surface 1 b of the battery can 1. Have. The negative electrode side connection end 22 is connected in a state where it is overlapped with the negative electrode metal foil exposed portion 32 c of the wound electrode group 3 so as to face each other.
In each of the positive electrode current collector plate base 41 and the negative electrode current collector plate base 21, a positive electrode side opening hole 43 and a negative electrode side opening hole 23 through which the positive electrode connection portion 14a and the negative electrode connection portion 12a are inserted are respectively formed.

  A protective film 2 is provided around the wound electrode group 3 with a direction along the flat surface 3 c of the wound electrode group 3 and a direction (y direction) orthogonal to the wound axis direction of the wound electrode group 3 as a central axis direction. Is wound. The protective film 2 is made of, for example, one sheet or a plurality of film members made of synthetic resin such as PP (polypropylene), and is parallel to the flat surface 3 c of the wound electrode group 3 and orthogonal to the winding axial direction It has a length such that the wound electrode group 3 can be wound with the direction (y direction) as the winding center.

FIG. 4 is an exploded perspective view showing a state in which a part of the wound electrode group 3 is developed.
The wound electrode group 3 is configured by laminating the separators 33 and 35 between the negative electrode 32 and the positive electrode 34 and winding them in a flat shape. In the wound electrode group 3, the outermost electrode is the negative electrode 32, and the separators 33 and 35 are further wound on the outer peripheral side. The separators 33 and 35 have a role of insulating between the positive electrode 34 and the negative electrode 32.
The positive electrode 34 has a positive electrode mixture layer 34 b in which a positive electrode active material mixture is applied to both the front and back sides of a positive electrode metal foil 34 a which is a positive electrode current collector. A positive metal foil exposed portion 34c to which the positive electrode active material mixture is not applied is provided at one end of the positive electrode metal foil 34a in the width direction (x direction). The negative electrode 32 has a negative electrode mixture layer 32 b in which a negative electrode active material mixture is applied to both the front and back sides of a negative electrode metal foil 32 a which is a negative electrode current collector. At the other end of the negative electrode metal foil 32 a in the width direction (x direction), a negative electrode metal foil exposed portion 32 c to which the negative electrode active material mixture is not applied is provided. The positive electrode metal foil exposed portion 34c and the negative electrode metal foil exposed portion 32c are areas where the metal surfaces of the positive and negative electrode metal foils 34a and 32a are exposed, and are disposed at one side and the other side in the winding axis direction. It is wounded by

  The negative electrode mixture layer 32 b of the negative electrode 32 is larger in the width direction (x direction) than the positive electrode mixture layer 34 b of the positive electrode 34 so that the positive electrode mixture layer 34 b is always sandwiched between the negative electrode mixture layers 32 b. Is configured. The positive electrode metal foil exposed portion 34c and the negative electrode metal foil exposed portion 32c are respectively bundled and joined by welding or the like. The separators 33 and 35 are wider than the negative electrode mixture layer 32b in the width direction (x direction), but the separators 33 and 35 are stacked at the positions where the positive metal foil exposed portion 34c and the negative metal foil exposed portion 32c are exposed. Therefore, there is no hindrance when bundling and welding.

  With respect to 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 is added thereto as a dispersion solvent. -A negative electrode mixture was prepared by adding and kneading methyl pyrrolidone (hereinafter referred to as NMP). The negative electrode mixture was applied to both sides of a copper foil (negative electrode metal foil) having a thickness of 10 μm leaving a welded portion (negative electrode uncoated portion). Thereafter, the resultant was dried, pressed, and cut to obtain a negative electrode 32 having a thickness of 70 μm and a negative electrode active material-coated portion not including a copper foil.

  In the present embodiment, although the case of using amorphous carbon as the negative electrode active material is exemplified, the present invention is not limited to this, and natural graphite which can insert and desorb lithium ion, and various kinds of artificial graphite materials And carbonaceous materials such as coke, compounds such as Si and Sn (for example, SiO, TiSi 2 etc.), or composite materials thereof, and even in the form of particles thereof, scaly, spherical, fibrous, massive etc. It is not something to be done.

  For the positive electrode 34, 10 parts by weight of scaly 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 LiMn2O4) as a positive electrode active material, NMP was added as a dispersion solvent and kneaded to prepare a positive electrode mixture. The positive electrode mixture was applied to both sides of a 20 μm thick aluminum foil (positive electrode metal foil) leaving a welded portion (positive electrode uncoated portion). Thereafter, through drying, pressing, and cutting steps, a positive electrode active material coated portion having a thickness of 90 μm, which does not contain an aluminum foil, was obtained.

Further, in the present embodiment, the case of using lithium manganate as the positive electrode active material has been exemplified, but other lithium manganate having a spinel crystal structure, a lithium manganese composite oxide in which a part is substituted or doped with a metal element, Lithium cobaltate or lithium titanate having a crystal structure, or a lithium-metal composite oxide in which part of these is substituted or doped with a metal element may be used.
Further, in the present embodiment, the case of using PVDF as the binder of the coated portion in the positive electrode 34 and the negative electrode 32 is exemplified, but 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, polymers such as acrylic resins, and mixtures thereof It can be used.

  Further, as the shaft core (not shown), for example, one formed by winding a resin sheet having higher bending rigidity than any of the positive electrode metal foil 34a, the negative electrode metal foil 32a, and the separator 33 can be used.

The porous film 50 is fixed to both ends in the x direction of the curved portions 3 a and 3 b of the wound electrode group 3. Hereinafter, the fixing structure and function of the porous film 50 will be described. In addition, in FIG. 2, FIG. 3, the state before each porous film 50 is fixed to curved part 3a, 3b of the winding electrode group 3 is shown.
As illustrated in FIG. 4, the wound electrode group 3 has the separator 35, the negative electrode 32, the separator 33, and the positive electrode 34 stacked, and in a stacked state, the wound electrode group 3 has a flat shape around an axial core (not shown). It is configured by winding.

  The positive electrode metal foil exposed portion 34c of the wound electrode group 3 is disposed between the positive electrode current collector plate 44 and the positive electrode side ribbon 40 (see FIG. 3), and is clamped by the positive electrode current collector plate 44 and the positive electrode side ribbon 40. In the state as it is, it joins by welding, such as ultrasonic welding and resistance welding, for example. Similarly, the negative electrode metal foil exposed portion 32 c of the wound electrode group 3 is disposed between the negative electrode current collector plate 24 and the negative electrode side ribbon 30 (see FIG. 3), and the negative electrode current collector plate 24 and the negative electrode side ribbon 30 In a state of being clamped by welding, welding is performed by welding such as ultrasonic welding or resistance welding. In addition, although mentioned later, when welding the positive electrode metal foil exposed part 34c of the wound electrode group 3, the positive electrode current collecting plate 44, and the positive electrode side ribbon 40, or the negative electrode metal foil exposed part 32c of the wound electrode group 3 and a negative electrode When welding the current collection board 24 and the negative electrode side ribbon 30, it carries out in the state to which the porous film 50 was being fixed to each of curved part 3a, 3b.

  The central region in the y direction of the negative electrode metal foil exposed portion 32c of the wound electrode group 3 is welded in a state of being pressed by the negative electrode current collector plate 24 and the negative electrode side ribbon 30, so after welding it is crushed Flat part. Curved portions 3a and 3b thicker than the thin flat portion are formed on both sides of the thin flat portion. In the axial core portions of the curved portions 3a and 3b, metal foil gaps are formed in which the opposing portions in the innermost periphery of the negative electrode metal foil 32a of the negative electrode 32 are separated. The metal foil gap communicates with the outside from the opening 61a (see FIGS. 2 and 3) of the side end face 61 of the curved portions 3a and 3b in the x direction. Similarly, since the central region in the y direction of positive electrode metal foil exposed portion 34c of wound electrode group 3 is welded in a state of being clamped by positive electrode current collector plate 44 and positive electrode side ribbon 40, after welding, It becomes a thin flat part crushed. Curved portions 3a and 3b thicker than the thin flat portion are formed on both sides of the thin flat portion. In the axial core portions of the curved portions 3a and 3b, metal foil gaps are formed in which the innermost circumferential portion of the positive electrode metal foil 34a of the positive electrode 34 is separated. Although not shown, the metal foil gap has an opening communicating with the side end surface of the curved portions 3a and 3b in the winding axial direction (x direction), similarly to the opening 61a on the negative electrode side.

Thus, in the axial core portions of the curved portions 3a and 3b, metal foils in which the innermost peripheral portion of the negative electrode metal foil 32a of the negative electrode 32 or the innermost peripheral portion of the positive electrode metal foil 34a of the positive electrode 34 are separated. A gap is formed. The metal foil gap communicates with the outside through the opening 61a of the side end face 61 of the curved portions 3a and 3b in the x direction.
As described above, a gap is formed between the wound metal foils on the outer side of the opening 61a formed at the center of the end surface of the curved portions 3a and 3b in the x-axis direction. These metal foil gaps serve as the inlet / outlet of the flow path through which the electrolytic solution flows through the internal members of the wound electrode group 3, that is, the positive electrode 34, the negative electrode 32, and the separators 33 and 35. If foreign matter is attached to any part of the wound electrode group 3, for example, the welded portion of the negative electrode current collector plate 24, the positive electrode current collector plate 44, the inside of the battery can 1, etc. Float in the metal foil gap and may be mixed into the interior of the wound electrode group 3. For example, when fine metal particles enter the interior of the wound electrode group 3 from the metal foil gap, the metal may cause a dissolution precipitation reaction to cause an internal short circuit between the positive electrode 34 and the negative electrode 32.
As described above, in order to prevent the internal short circuit of the wound electrode group 3 due to the conductive foreign matter, it is necessary to suppress the mixing of the conductive foreign matter into the metal foil gap.

FIG. 5 is an external perspective view showing the porous film fixed to the curved portion on the negative electrode side of the wound electrode group, and FIG. 6 is a detailed view of region VI in FIG.
As illustrated in FIG. 5, a porous film 50 is fixed to the negative electrode side ends of the curved portions 3 a and 3 b at the upper and lower ends of the wound electrode group 3. The porous film 50 is fixed to the outer peripheral surface of the curved portions 3a and 3b adjacent to the side end surface 61 and the side end surface 61 of the curved portion 3a or 3b. The opening 61 a formed in the side end surface 61 of the curved portion 3 a, 3 b is covered by the porous film 50. That is, the opening 61a in the axial core portion of the negative electrode metal foil 32a and the metal foil gap on the outer periphery thereof are sealed from the outside. The end of the porous film 50 covering the outer peripheral surface adjacent to the side end surface 61 of the curved portions 3a and 3b extends in the x direction to a position reaching the separator 33 or 35 (see FIG. 4).
Although not shown, the positive electrode side of the wound electrode group 3 is also similar to the negative electrode side, and the side end surfaces of the curved portions 3a and 3b at the upper and lower ends and the outer peripheral surface of the curved portions 3a and 3b adjacent to the side end surfaces. The porous film 50 is fixed to the

  The porous film 50 is formed of, for example, a resin such as polypropylene or polyethylene. The porous film 50 has a large number of pores for circulating the electrolytic solution. The average pore diameter of the porous film 50 is preferably equal to or less than the thickness of the separator. However, it is necessary to prevent the permeability of the electrolytic solution and the generated gas from being inhibited, and from this viewpoint, the average pore diameter of the porous film 50 is preferably about 0.1 μm or more.

The shape of the porous film 50 before fixing is a flat sheet-like member. The thickness of the sheet-like member is, for example, 20 to 50 μm, and the sheet-like member has flexibility. The central region of the porous film 50, which is a sheet-like member, is pressed against the side end surface 61 of the curved portions 3a and 3b to cover the opening 61a formed in the side end surface 61. And the peripheral part of the porous film 50 is bent along the outer peripheral surface of the side end surface 61 of curved part 3a, 3b.
In order to fix the porous film 50, for example, it is adhered to the wound electrode group 3 together with the porous film 50 by an insulating adhesive tape. Alternatively, the porous film 50 is welded to the outermost periphery of the separator 33 or 35. Alternatively, an adhesive is applied to one side of the porous film 50 and is adhered to the outermost periphery of the separators 33 and 35. It is also possible to adopt other fixing means, and it is not particularly limited to this fixing means. Any fixing means may be used as long as the electrode foil gap of the curved portions 3a and 3b of the wound electrode group 3 is fixed so as to close the outer periphery with the opening 61a communicating with the outside. In particular, since most of the foreign matter enters from the opening 61a, at least the porous film 50 may close the opening 61a.

  After the porous film 50 is fixed to each of the curved portions 3a and 3b of the wound electrode group 3, the positive electrode metal foil exposed portion 34c of the wound electrode group 3 and the positive current collector plate 44 and the positive electrode side ribbon 40 are welded Also, the negative electrode metal foil exposed portion 32c of the wound electrode group 3, the negative electrode current collector plate 24, and the negative electrode side ribbon 30 are welded. At this time, both ends in the y direction of each of the positive electrode side ribbon 40 and the negative electrode side ribbon 30 are disposed so as to overlap with the end portion 51 (see FIG. 6) of the porous film 50 and are welded in this state. That is, the porous film 50 is disposed on the outermost periphery of the negative electrode metal foil exposed portion 32 of the wound electrode group 3 or on the outermost periphery of the positive electrode metal foil exposed portion 34c of the wound electrode group 3 The negative electrode side ribbon 30 or the positive electrode side ribbon 40 is disposed on the negative electrode metal foil exposed portion 32 or the outermost peripheral portion of the positive electrode metal foil exposed portion 34c so as to overlap with a part of the end portion 51 of 50 and welding is performed.

  Thus, when welding is performed after fixing the porous film 50 to each of the curved portions 3a and 3b of the wound electrode group 3, spattering of the metal that scatters at the time of welding corresponds to the curved portions 3a and 3b of the wound electrode group 3. The porous film 50 can be prevented from intruding into the electrode foil gap of the positive and negative electrodes. In addition, when welding is performed in a state where the negative electrode side ribbon 30 or the positive electrode side ribbon 40 is overlapped with a part of the end 51 of the porous film 50, the porous film 50 and the positive electrode side ribbon 40 or the porous film The occurrence of a gap between the negative electrode side ribbon 30 and the negative electrode side ribbon 30 is eliminated, and the suppression of the entry of foreign matter into the interior of the wound electrode group 3 becomes more reliable. In addition, alignment between the positive and negative electrode side ribbons 40 and 30 and the porous film 50 is facilitated, and the productivity is improved.

  However, the method is not limited to this method, and the positive electrode metal foil exposed portion 34c of the wound electrode group 3, the positive electrode current collector plate 44, and the positive electrode side ribbon 40 are welded, or the negative metal foil exposure of the wound electrode group 3 is exposed. After welding the portion 32c, the negative electrode current collector plate 24, and the negative electrode side ribbon 30, the porous film 50 may be fixed to the curved portions 3a and 3b.

  The assembly in which the wound electrode group 3, the porous film 50, and the battery lid 6 are all assembled is covered with an insulating cover, inserted into the battery can 1, and the upper surface of the battery can 1 and the battery lid 6 are laser welded. The square secondary battery 100 illustrated in FIG. 1 can be obtained by bonding at

According to the said Embodiment 1, there exist the following effects.
(1) In the wound electrode group 3 having a pair of curved portions 3a and 3b having a semicircular cross section formed at both ends in the direction (y direction) orthogonal to the winding axis direction, the axis of each curved portion 3a and 3b The porous film 50 covering the opening 61a communicating with the outside of the positive and negative electrode foil gaps formed in the core portion was fixed. For this reason, the inside of wound electrode group 3 from the opening 61a which the foreign substance adhering to the surface etc. of wound electrode group 3 communicates with the outside of the electrode foil gap of curved portions 3a and 3b of wound electrode group 3 Can be suppressed.

(2) The porous film 50 presses the central portion of the sheet-like film against the side end surface 61 of the curved portions 3a and 3b to cover at least the opening 61a formed in the side end surface 61. Etc. It can fix to curved part 3a, 3b by fixing means, such as. Therefore, the cost of parts is low, the fixing operation is easy, and the cost of assembly can be low.

(3) After fixing the porous film 50 to each of the curved portions 3a and 3b of the wound electrode group 3, the positive / negative metal foil exposed portions 34c and 32 of the wound electrode group 3 and the positive / negative current collector plate 44 and 42 and the positive and negative electrode side ribbons 40 and 30 are welded. Thereby, the porous film 50 can prevent the spatter of metal scattered during welding from entering the electrode foil gap between the positive and negative electrodes of the curved portions 3a and 3b of the wound electrode group 3.

(4) The both ends of each of the positive and negative electrode side ribbons 40 and 30 are disposed so as to overlap the end 51 of the porous film 50, and welding is performed in this state. As a result, no gap is generated between the porous film 50 and each of the positive and negative electrode side ribbons 30, and the suppression of the entry of foreign matter into the wound electrode group 3 becomes more reliable. In addition, alignment between the positive and negative electrode side ribbons 40 and 30 and the porous film 50 is facilitated, and the productivity is improved.

-Embodiment 2-
FIG. 7 is an external perspective view showing a state in which the porous film is fixed to the curved portion on the negative electrode side of the wound electrode group according to Embodiment 2 of the present invention, and FIG. 8 is a region VIII in FIG. FIG.
In the prismatic secondary battery 100 shown as the second embodiment, on the negative electrode side, the position of the end of the porous film 50 in the x direction is within the width of the negative metal foil exposed portion 32 c, and the end of the separator 33 is Not reached. That is, the porous film 50 on the negative electrode side covers only a part of the outermost periphery of the negative electrode metal foil exposed portion 32c. Similarly, although not shown, on the positive electrode side, the position of the end of the porous film 50 in the x direction is in the area of the width of the positive electrode metal foil exposed portion 34 c and does not reach the end of the separator 35. That is, the porous film 50 on the positive electrode side covers only a part of the outermost periphery of the positive electrode metal foil exposed portion 34c. The same fixing means as in Embodiment 1 can be used for fixing each porous film 50 to the wound electrode group 3.

The other configuration of the second embodiment is the same as that of the first embodiment.
Therefore, also in the second embodiment, the same effects as in the first embodiment can be obtained.
In addition, in the second embodiment, the porous film 50 is disposed on the outermost periphery of the negative electrode metal foil exposed portion 32c or the positive electrode metal foil exposed portion 34c. Therefore, the height (position in the y direction) of the outer peripheral surface of the porous film 50 is substantially the same as the height of the outer peripheral surface of the outermost periphery of the separators 33 and 35 disposed on the negative electrode 32 or the positive electrode 34. It is also possible. As a result, although the structure in which the wound electrode group 3 is wound around the curved portions 3 a and 3 b of the wound electrode group 3, the height of the wound electrode group 3 in the y direction is not provided with the porous film 50. It can be made almost identical to the wound electrode group. That is, it has compatibility with the conventional wound electrode group.

  In the above embodiments, the porous film 50 covers the side end surfaces 61 of the curved portions 3a and 3b of the wound electrode group 3 and the outer peripheral surfaces of the curved portions 3a and 3b adjacent to the side end surfaces 61. Illustrated. However, as long as the porous film 50 is configured to cover the opening 61 a formed in the side end surface 61, only the side end surface 61 of the curved portions 3 a and 3 b of the wound electrode group 3 may be covered.

  In the above embodiments, the porous film 50 is illustrated as a structure in which a flat sheet member is deformed and fixed along the outer peripheral surface of the curved portions 3a and 3b. However, the porous film 50 may be formed in advance into a required shape by molding.

  The structure of the battery cover 6 and the respective members on the positive and negative sides attached to the battery cover 6 in the above embodiment are merely illustrated as an example, and can be appropriately changed and applied.

  In the above embodiments, the prismatic secondary battery 100 is illustrated as a lithium ion battery. However, the present invention is also applicable to the prismatic secondary battery 100 using a water-soluble electrolyte, such as a nickel hydrogen battery, a nickel cadmium battery, and a lead storage battery. Furthermore, the present invention is also applicable to capacitors such as lithium ion capacitors.

  Although various embodiments and modifications have been described above, the present invention is not limited to these contents. Other embodiments considered within the scope of the technical idea of the present invention are also included within the scope of the present invention.

3 wound electrode group 3a, 3b curved portion 24 negative electrode current collector plate 30 negative electrode side ribbon 32 negative electrode 32a negative electrode metal foil 32b negative electrode mixture layer 32c negative electrode metal foil exposed portion 33, 35 separator 34 positive electrode 34a positive metal foil 34b positive electrode Mixture layer 34c Cathode metal foil exposed portion 40 Cathode side ribbon 44 Cathode current collector plate 50 porous film 51 end 61 side end face 61a opening 100 square secondary battery

Claims (6)

It has a positive electrode, a negative electrode and a separator, and is laminated such that one side edge of the positive electrode and the other side edge opposite to the one side edge of the negative electrode have a foil exposed portion exposed from the separator A wound electrode group wound such that the positive electrode, the negative electrode, and the separator have curved portions at both ends in a direction orthogonal to the winding axis direction;
And a bonding member in which the one side edge of the positive electrode and the other side edge of the negative electrode are bundled and joined, respectively.
In each of the positive electrode and the negative electrode, an electrode foil gap communicating with the outside of the wound electrode group is formed at least at the center of the end face of the curved portion.
The square electrical storage element by which the porous film which covers the opening part connected to the exterior of the said electrode foil clearance gap is being fixed to the said winding electrode group. In the prismatic storage element of claim 1,
The square electric storage element by which the said porous film is being fixed to the side end surface of the said curved part. In the prismatic storage element of claim 1,
The square electricity storage element by which the said porous film is being fixed to the said foil exposed part of the outermost periphery of the said winding electrode group. In the prismatic storage element of claim 1,
The prismatic storage element in which the porous film is fixed to the separator at the outermost periphery of the wound electrode group. In the prismatic storage element of claim 1,
The prismatic storage element wherein an end of the porous film on the bonding member side is disposed between the bonding member and the positive electrode or the negative electrode. The prismatic storage element according to any one of claims 1 to 5,
The prismatic storage element in which the porous film is formed of a sheet-like member.

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